Archives ouvertes Hal IMT Atlantique
Not a member yet
20414 research outputs found
Sort by
A Hybrid Machine learning and Combinatorial Optimization method for the Design of Assembly Lines under Uncertainties
No full textNational audienc
Production Cross Section Measurements Of 111Ag With The Reaction natPd(α,x)
No full textInternational audienceThe radionuclides used in targeted radionuclide therapy emit charged particles, such as α, β- and Auger electron, that makes possible the delivery of a significant dose to the tumor cells while sparring the healthy tissues surrounding them. The radioisotope 111Ag (T1/2 = 7.45 days, Emax,β- = 1.04 MeV) is a β- emitter that is promising for this kind of application. Its low energy β- has a medium tissue penetration of average 1.8 mm which enables the targeting of medium tumors . Additionally, its γ rays at 245 keV (1.3 %) and 342 keV (6.7 %) are well suited for SPECT imaging which is helpful for monitoring more precisely the in vivo dose delivered. Several routes have been studied to produce 111Ag either with research reactors, cyclotrons, photonuclear reactions or on-line mass separators. The production cross sections of natPd(α,x)111Ag, one of the reactions for the alpha route, has only been measured by two teams. However, these measurements do not cover the whole region of the peak and what’s happening after it.Several measurements of the production cross sections of the natPd(α,x)111Ag reaction have been performed at the GIP ARRONAX with an alpha beam of 67.4 MeV to get experimental data above 40 MeV. The “stacked-foils” method has been used during our experiments. The intensity of the beam has been monitored through the natAl(α,x)22Na nuclear reactions. HPGe detectors were used to perform the γ-spectrometry of each foil: short acquisitions were done directly after the irradiation to measure short-lived radionuclides and longer acquisitions days after to measure 111Ag and the contaminants 105Ag, 106mAg and 110mAg. The analysis of the spectra was performed using multiple γ-rays for each radionuclide when possible
Inclusive and multiplicity-dependent pseudorapidity densities of charged particles in pp collisions at TeV
No full textInternational audienceThe distribution of the pseudorapidity density of primary charged particles () in 0 event class (events having at least one charged particle in 0 results follow a power-law scaling with the center-of-mass energy. These measurements provide a new reference for charged-particle production at the highest protonproton collision energy available at the LHC
Direct multi-model dark-matter search with gravitational-wave interferometers using data from the first part of the fourth LIGO-Virgo-KAGRA observing run
No full textInternational audienceGravitational-wave detectors can probe the existence of dark matter with exquisite sensitivity. Here, we perform a search for three kinds of dark matter -- dilatons (spin-0), dark photons (spin-1) and tensor bosons (spin-2) -- using three independent methods on the first part of the most recent data from the fourth observing run of LIGO--Virgo--KAGRA. Each form of dark matter could have interacted with different standard-model particles in the instruments, causing unique differential strains on the interferometers. While we do not find any evidence for a signal, we place the most stringent upper limits to-date on each of these models. For scalars with masses between eV that couple to photons or electrons, our constraints improve upon those from the third observing run by one order of magnitude, with the tightest limit of at a mass of . For vectors with masses between eV that couple to baryons, our constraints supersede those from MICROSCOPE and Eöt-Wash by one to two orders of magnitude, reaching a minimum of at a mass of eV. For tensors with masses of eV (the full mass range analyzed) that couple via a Yukawa interaction, our constraints surpass those from fifth-force experiments by four to five orders of magnitude, achieving a limit as low as at eV. Our results show that gravitational-wave interferometers have become frontiers for new physics and laboratories for direct multi-model dark-matter detection
Space-time evolution of particle emission in pPb collisions at TeV with 3D kaon femtoscopy
No full textInternational audienceThe measurement of three-dimensional femtoscopic correlations between identical charged kaons (KK) produced in pPb collisions at center-of-mass energy per nucleon pair TeV with ALICE at the LHC is presented for the first time. This measurement, supplementary to those in pp and PbPb collisions, allows understanding the particle-production mechanisms at different charged-particle multiplicities and provides information on the dynamics of the source of particles created in pPb collisions, for which a general consensus does not yet exist. It is shown that the measured source sizes increase with charged-particle multiplicity and decrease with increasing pair transverse momentum. These trends for KK are similar to the ones observed earlier in identical charged-pion and KK correlations in PbPb collisions at various energies and in correlations in pPb collisions at TeV. At comparable multiplicity, the source sizes measured in pPb collisions agree within uncertainties with those observed in pp collisions, and there is an indication that they are smaller than those observed in PbPb collisions. The obtained results are also compared with predictions from the hadronic interaction model EPOS~3, which tends to underestimate the source size for the most central collisions and agrees with the data for semicentral and peripheral events. Furthermore, the time of maximal emission for kaons is extracted. It turns out to be comparable with the value obtained in highly peripheral PbPb collisions at the same energy, indicating that the kaon emission evolution is similar to that in pPb collisions
Structure preserving adversarial diffusion for unpaired medical image synthesis
No full textInternational audienc
Probing Earth's Missing Potassium using the Unique Antimatter Signature of Geoneutrinos
No full textInternational audienceThe formation of the Earth remains an epoch with mysterious puzzles extending to our still incomplete understanding of the planet's potential origin and bulk composition. Direct confirmation of the Earth's internal heat engine was accomplished by the successful observation of geoneutrinos originating from uranium (U) and thorium (Th) progenies, manifestations of the planet's natural radioactivity dominated by potassium (40K) and the decay chains of uranium (238U) and thorium (232Th). This radiogenic energy output is critical to planetary dynamics and must be accurately measured for a complete understanding of the overall heat budget and thermal history of the Earth. Detecting geoneutrinos remains the only direct probe to do so and constitutes a challenging objective in modern neutrino physics. In particular, the intriguing potassium geoneutrinos have never been observed and thus far have been considered impractical to measure. We propose here a novel approach for potassium geoneutrino detection using the unique antimatter signature of antineutrinos to reduce the otherwise overwhelming backgrounds to observing this rarest signal. The proposed detection framework relies on the innovative LiquidO detection technique to enable positron (e+) identification and antineutrino interactions with ideal isotope targets identified here for the first time. We also provide the complete experimental methodology to yield the first potassium geoneutrino discovery
An inquiry into Search Engine Neutrality: the case of movements against police violence in France and the U.S.
No full textInternational audienceThe digital transformation has revolutionized information consumption, with search engines playing a pivotal role in shaping user access to diverse media. Employing algorithms, these engines influence content visibility and aggregate news sources, significantly molding public opinion. As gatekeepers of information, search engines impact media outlet visibility, affecting online traffic, revenue, and journalistic diversity. In breaking news and societal issues, search engines expedite information dissemination, influencing initial narratives. Understanding their role is crucial for transparency and user access to diverse information. Focusing on movements against police violence, our paper conducts a comparative analysis across 12 search engines for terms "Black Lives Matter" and "Justice pour Adama". Our innovative methodology identifies biases in information diversity, providing insights into the dynamics shaping visibility of societal issues.</div
Recent Advances In Nantes Around The ARRONAX Facility
No full textInternational audienceIntroductionApplications of radiations for health is a long story that have started soon after the discovery of radioactivity. Nowadays, radiations are used in oncology (external radiation, targeted therapies, SPECT, PET), neurology and cardiology. Since 2013, a new wave of applications in nuclear medicine has started, focused on therapeutic agent and the so-called theranostics approach [1]. This has resulted in the approval of several new products such as177Lu-DOTATATE for neuroendocrine tumors in 2018 and 177Lu-PSMA for metastatic prostate cancers in 2021. Almost at the same time, alternative ways of dose delivery were investigated in external radiotherapy, the so-called spatial dose fractionation (SFRT) and ultra-high dose-rate (UHDR, “FLASH” effect). All these aspects are at the heart of the research program conducted in Nantes around the ARRONAX facilities and its accelerators.Description of the ProjectGIP ARRONAX is hosting a high energy high intensity multiparticle cyclotron (C70XP). It allows access to a wide variety of beam in terms of projectiles (p, d, alpha), of incident energies (up to 70 MeV for p and alpha) and of intensities (from a thousand of particles per second up to several hundreds of µA). Several upgrades have been made since the installation of the machine to enlarge its capacity. In 2017, a radiopharmacy have been setup in collaboration with the Nantes University hospital to allow dose productions for clinical trials [2], in 2019, a pulsing system have been developed and installed [3]. In 2025, an internal target system has been installed to allow access to variable energies for our alpha beam and in parallel, a biomedical cyclotron (KIUBE-180) equipped with a beam line and target station connected to the existing rabbit system, is being commissioned.ConclusionsThese developments allow the ARRONAX facility to better fulfil its missions that are to support research in nuclear medicine by providing non-conventional radionuclides and radiopharmaceuticals for clinical trials and also support research in related fields: radiotherapy and radiobiology, radiolysis, physics, ion beam analysis, mass separation through the SMILES project, detector testing… This presentation will show the broad spectra of research activities conducted in the facility and its current status.References[1] Srivastava, S. C. (2012). Paving the Way to Personalized Medicine: Production of Some Promising Theragnostic Radionuclides at Brookhaven National Laboratory. Seminar in Nuclear Medicine, volume 42 (issue 3), 151-163.https://doi.org/10.1053/j.semnuclmed.2011.12.004[2] Bourgeois, M. et al (2020). ARRONAX Cyclotron: Setting up of In-House Hospital Radiopharmacy. BioMed Research International, 1572841, 6 pages. https://doi.org/10.1155/2020/1572841[3] Poirier, F. et al (2019). The pulsing chopper-based system of the ARRONAX C70XP cyclotron. JACoW Publishing, ISBN: 978-3-95450-208-0. https://doi.org/10.18429/JACoW-IPAC2019-TUPTS00
Segmentation en EEG néotanal — Apprentissage sur des représentations temps-fréquence
No full textNational audienceL’électroencéphalogramme (EEG) est utilisée en routine clinique pour le diagnostic et le suivi des nouveau-nés, notamment en cas de suspicion d’encéphalopathie anoxo-ischémique (HIE). L’interprétation de l’EEG pour la prise en charge du patient nécessite de localiser des figures physiologiques et/ou pathologiques dans le signal. Ceci nécessite un expert formé, disponible immédiatement et pendant toute la période de suivi. La conception d’outils semi-automatiques de détection / segmentation de motifs est ainsi un enjeu majeur pour améliorer les temps de diagnostic et d’intervention.L’apprentissage profond ouvre la voie au développement de tels outils. Néanmoins, dans le contexte clinique considéré, les motifs recherchés sont très peu nombreux dans des données de grande taille. L’utilisation brute du signal sous forme de série temporelle a fait l’objet d’une étude précédente qui a notamment montré les limites d’une telle approche (1). Nous explorons, dans ce travail, une stratégie alternative qui consiste à représenter les donnéesEEG dans un paradigme temps-fréquence. Nous étudions notamment dans quelle mesure ce changement de représentation est à même de permettre une segmentation efficace de motifs en EEG.Le signal EEG est subdivisé en fenêtres indépendantes de 2 560 points (10 secondes). Une transformée de Pseudo Wigner-Ville lissée (2) (avec un fenêtrage de Hamming en temps et en fréquence : 51 points en temps, 101 en fréquence) est appliquée pour extraire le module du spectre. Les images obtenues sont tronquées pour conserver l’information fréquentielle de 0 à 32 Hz, et sous-échantillonnées pour aboutir à une dimension de 256×32. Seules les fenêtres contenant une annotation de motif (encoche frontale, pointe, dysrythmie lente antérieure) sont utilisées. Les instants correspondant à une encoche frontale sont marqués comme cas positif, les autres comme cas négatifs. Chaque canal du signal EEG est considéré indépendamment.Nous proposons une architecture similaire à U-Net (3), adaptée pour la segmentation d’images de spectre temps-fréquence. Chaque étape implémente une Depthwise Separable Convolution 2D (4) (à padding égal), suivi d’une couche de max-pooling, et d’un sous-échantillonnage. La fonction de perte Focal Loss (5) est utilisée. Les signaux EEG sont issus de l’étude ancillaire LyTONEPAL (6), pour des patients ayant souffert d’une HIE sévère à modérée, dans leurs 6 premières heures de vie. L’étude est multi-centrique. Le montage utilisé dans tous les cas est le même, en référence bipolaire, longitudinal. Le signal est échantillonné à 256 Hz (un filtre passe-bas à 30 Hz est appliqué).La validation expérimentale de notre modèle sur les données EEG montre que l’information relative aux encoches frontales dans le signal brut est utilisable dans la représentation temps-fréquence pour la segmentation (67,16% AUC). La nature différente des modes de données invite à une comparaison plus précise entre série temporelle et de représentation spectrale