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target developments for research and production of radionuclides at GIP ARRONAX
No full textInternational audienceTarget manufacturing methods are key for radionuclide production. On the one hand, thin targets are useful for research activities such as cross section measurements using the stacked foils technique or to develop new chemical separation schemes using radiotracer. On the other hand, thick targets are mandatory for cost effective production of large radionuclide quantities as needed for radiopharmaceuticals. At GIP ARRONAX [1], we are focusing our work on innovative radionuclides for nuclear medicine and as such, we have to develop and characterized our own targets using the most appropriate technique. Over the last 15 years, we have developed the following techniques for target preparation:ElectrodepositionRadiopharmaceuticals such as Cu-64, Cu-67 and Pb-203 are produced at GIP Arronax through irradiation of enriched target with light particles: Ni-64 for Cu-64, Zn-70 and Zn-68 for Cu-67 [2] [3] and Tl-205 for Pb-203 [4]. These enriched targets are manufactured by electrodeposition, which allows the preparation of both thin and thick layers.Deposition under vacuumNatural Bi targets are prepared by deposition under vacuum and subsequently irradiated with alpha particles to produce At-211, a promising α-emitter for targeted therapy. Thus technique allows for uniform thin or thick targets.Molecular plating and co-electrodepositionObtaining enriched lanthanide deposits suitable for irradiation using electrodeposition or vacuum deposition remains challenging. In the case of electrodeposition, very negative standard potentials prevent metallic deposition, while vacuum deposition gives low yields and is problematic due to the high cost of enriched lanthanides. Molecular plating offers an alternative, yielding well-adhering, non-metallic deposits that require additional characterization. This technique has proven effective for lanthanide targets. Co-electrodeposition has also been developed, in which insoluble oxides (e.g., Gd2O3) are trapped in a nickel deposit [5]. Although deposition yields are low, residual particles in solution can be recycled for further use. These approaches are particularly suited for preparing thin deposits.PelletizingPelletizing provides an efficient method for preparing thick targets when electrodeposition or vacuum deposition is not feasible. Materials investigated include RbCl for Sr-82 production, Gd2O3 for Tb-155 production and Mo for Ru-97 production.In this work, we intend to present an overview of the target manufacturing techniques currently applied at GIP Arronax, along with the characterization that have been developed to validate them and explain the choice of the most suitable method based on the physicochemical properties of each element.[1] F. Haddad et al., “ARRONAX, a high-energy and high-intensity cyclotron for nuclear medicine,” Eur J Nucl Med Mol Imaging, vol. 35, no. 7, pp. 1377–1387, 2008, doi: 10.1007/s00259-008-0802-5.[2] G. Pupillo et al., “New production cross sections for the theranostic radionuclide 67Cu,” Nucl Instrum Methods Phys Res B: Beam Interactions with Materials and Atoms, vol. 415, pp. 41–47, Jan. 2018, doi: 10.1016/j.nimb.2017.10.022.[3] E. Nigron et al., “Is 70Zn(d,x)67Cu the Best Way to Produce 67Cu for Medical Applications?,” Front. Med., vol. 8, 2021, doi: 10.3389/fmed.2021.674617.[4] T. Sounalet et al., “Manufacture of Tl targets by electrodeposition for the study of excitation functions of 203Pb,” EPJ Web Conf., vol. 285, p. 09001, 2023, doi: 10.1051/epjconf/202328509001.[5] Y. Wang et al., “Electrochemical co-deposition of Ni–Gd2O3 for composite thin targets preparation: Production of 155Tb as a case study,” Appl Radiat Isot, vol. 186, p. 110287, Aug. 2022, doi: 10.1016/j.apradiso.2022.110287
BeHAVE : Un générateur de données de recommandations de groupes
No full textInternational audiencePlusieurs stratégies ont été proposées pour recommander des éléments à des groupes d'utilisateurs. Toutefois, la comparaison de leurs performances demeure limitée par l'absence de datasets représentatifs capables de refléter la diversité des scénarios de recommandation de groupe. Pour pallier ce manque, cet article propose deux contributions : (1) une analyse empirique des corpus utilisés pour la recommandation de groupes. Cette analyse est axée sur l'adaptabilité des utilisateurs lorsqu'ils passent de préférences individuelles à des choix collectifs, ainsi que sur la diversité des éléments d'intérêt ; (2) BeHAVE, le premier générateur de données configurable pour la recommandation de groupes. Basé sur un graphe de connaissances décrivant les éléments à recommander et leur sémantique, BeHAVE (Mokhtari et Smits, 2025) permet de simuler des interactions de groupes en contrôlant des paramètres tels que l'adaptabilité de ses utilisateurs et la diversité des éléments avec lesquels ils interagissent. Les résultats expérimentaux montrent que BeHAVE ouvre la voie vers des évaluations réalistes et complètes de systèmes de recommandation de groupe
Comprehensive experimental analysis of pyrolytic gas composition from various lignocellulosic biomass
No full textInternational audienceBiomass pyrolysis is a fundamental step in thermochemical conversion processes and represents a promising alternative source capable of producing multiple energy carriers. However, its complex reaction pathways make it hard to thoroughly understand it. Despite extensive research on biomass pyrolysis kinetics, most existing studies focus on overall devolatilization rather than individual volatile species. This study addresses this gap by investigating the evolution of major non-condensable gas species produced during the slow pyrolysis of five lignocellulosic biomass (Wood Mix, Wood Waste, Pine Bark, Palm Fiber, and Lavender Straw) using a model-based kinetic approach, supported by experimental data. The pyrolysis experiments are conducted in a laboratory-scale batch reactor under inert conditions at different heating rates and temperatures. The effects of heating rate and temperature on gas evolution profiles and FTIR spectra are analyzed. Results confirm that gas release is closely linked to the progressive thermal degradation of biomass constituents, while no systematic correlation was found between biomass physicochemical properties and kinetic parameters. The obtained kinetic parameters showed good agreement with the thermal decomposition of lignocellulosic components within tested temperatures range. The n th order single reaction model provided good agreement with experimental data for all feedstock (R² > 0.99), supporting the reliability of the proposed gas evolution reaction fitting scheme. Apparent activation energies (20 -110 kJ.mol -1 ) and reaction order (1.0 -2.5) vary depending on gas species and biomass type. These findings demonstrate that a simplified kinetic framework can successfully contribute to a better quantitative understanding of non-condensable gas evolution during biomass pyrolysis
Constraints on gravitational waves from the 2024 Vela pulsar glitch
No full textInternational audienceAmong known neutron stars, the Vela pulsar is one of the best targets for gravitational-wave searches. It is also one of the most prolific in terms of glitches, sudden frequency changes in a pulsar's rotation. Such glitches could cause a variety of transient gravitational-wave signals. Here we search for signals associated with a Vela glitch on 29 April 2024 in data of the two LIGO detectors from the fourth LIGO--Virgo--KAGRA observing run. We search both for seconds-scale burst-like emission, primarily from fundamental (f-)mode oscillations, and for longer quasi-monochromatic transients up to four months in duration, primarily from quasi-static quadrupolar deformations. We find no significant detection candidates, but for the first time we set direct observational upper limits on gravitational strain amplitude that are stricter than what can be indirectly inferred from the overall glitch energy scale. We discuss the short- and long-duration observational constraints in the context of specific emission models. These results demonstrate the potential of gravitational-wave probes of glitching pulsars as detector sensitivity continues to improve
Energy and momentum dependence of the soft-axion interaction rate
No full textInternational audienceAxions coupled to thermal non-Abelian gauge fields may have cosmological significance. As the heat bath defines a frame, its influence depends separately on energy and momentum. A light-like momentum () is relevant for the axion contribution to the effective number of light neutrinos, , whereas a vanishing momentum () plays a role for warm natural inflation or ultralight dark matter, and has been employed in lattice estimates (both classical and quantum-statistical) of the strong sphaleron rate. Focussing on soft energies (), we carry out an HTL computation to show how the domains and interpolate to each other. We then compare with lattice data at , and connect our analysis to NLO computations at . Assembling the current best input, we re-investigate light QCD axion decoupling dynamics at MeV, showing that efficient interactions in the ultrasoft domain increase from to at GeV
Majorization-Minimization Networks for Inverse Problems: An Application to EEG Imaging
No full textInverse problems are often ill-posed and require optimization schemes with strong stability and convergence guarantees. While learning-based approaches such as deep unrolling and meta-learning achieve strong empirical performance, they typically lack explicit control over descent and curvature, limiting robustness. We propose a learned Majorization-Minimization (MM) framework for inverse problems within a bilevel optimization setting. Instead of learning a full optimizer, we learn a structured curvature majorant that governs each MM step while preserving classical MM descent guarantees. The majorant is parameterized by a lightweight recurrent neural network and explicitly constrained to satisfy valid MM conditions. For cosine-similarity losses, we derive explicit curvature bounds yielding diagonal majorants. When analytic bounds are unavailable, we rely on efficient Hessian-vector product-based spectral estimation to automatically upper-bound local curvature without forming the Hessian explicitly. Experiments on EEG source imaging demonstrate improved accuracy, stability, and cross-dataset generalization over deep-unrolled and meta-learning baselines
Search for planetary-mass ultra-compact binaries using data from the first part of the LIGO--Virgo--KAGRA fourth observing run
No full textInternational audienceWe present a search for gravitational waves from inspiraling, planetary-mass ultra-compact binaries using data from the first part of the fourth observing run of LIGO, Virgo and KAGRA. Finding no evidence of such systems, we determine the maximum distance reach for such objects and their merger rate densities, independently of how they could have formed. Then, we identify classes of primordial black-hole mass distributions for which these rate limits can be translated into relevant constraints on the mass distribution of primordial black holes, assuming that they compose all of dark matter, in the mass range . Our constraints are consistent with existing microlensing results in the planetary-mass range, and provide a complementary probe to sub-solar mass objects
Coexistence of shapes and octupole correlation in <math><mmultiscripts><mi>Kr</mi><mprescripts/><none/><mn>82</mn></mmultiscripts></math>
No full textInternational audienceLow- and intermediate-spin negative-parity band structures have been investigated in the Kr82 nucleus using the fusion-evaporation reaction Ge76 (Be9, 3n) at ELab≈31 MeV. Lifetimes of the states of interest in Kr82 have been measured using the Doppler shift attenuation method with the help of the Indian National Gamma Array, and the parity of the states has been confirmed from polarization measurements. The deduced B(M1) and B(E2) values from the lifetime measurements in comparison with the particle rotor model and the total Routhian surfaces calculations reveal that the bands DB1 and DB2 are based on the collective oblate and prolate deformed core, respectively. The enhanced electric dipole strengths, B(E1)s, and dipole moments, |D0|s, for the parity-changing transitions connecting the negative-parity bands DB1 and DB2 to the ground-state positive-parity band QB1 ensure the octupole correlation in Kr82
Interhemispheric and Latitudinal Variability of Ionospheric Disturbances During the 19-20 December 2015 Geomagnetic Storm: Insights from the South American Sector
No full textInternational audienceThis study investigates the response of the South American ionosphere to the December 19-20, 2015, geomagnetic storm using multi-instrument satellite and ground-based data. An interplanetary shock triggered prompt penetration electric fields (PPEFs) during the storm's initial phase, initiating rapid DP2 currents and significant equatorial electrojet (EEJ) fluctuations, particularly in Jicamarca, Peru. Our analysis shows that dayside field-aligned currents (FACs) are the primary drivers of the observed DP2 fluctuations. The South Atlantic Magnetic Anomaly (SAMA) also induced a westward geomagnetic gradient-induced current at the equatorward boundary, which suppressed the EEJ current at São Luiz during the magnetically quiet period. During the storm's main phase, eastward PPEFs enhanced ionospheric irregularities at several Global Positioning Satellite (GPS) stations: Sao Luiz (14.8%), Cuiaba (11.4%), and Jatai (15.5%) in Brazil; Tucuma (33.6%) and Rio Grande (33.2%) in Argentina; and all Peruvian GPS stations (5.8 -57.6%), with Arequipa showing the highest percentage. Conversely, irregularities were inhibited at Eusebio (-31.5%), São José dos Campos (-11.8%), and Campo Grande (-4.8%) in Brazil, and Rosario (-9.4%) and Villegas (-0.8%) in Argentina, relative to a magnetically quiet day, which was attributed to the interplay between westward disturbance dynamo electric fields (DDEF) and PPEF. Joule heating, peaking at 14:35 UT on 20 December drove equatorward disturbance winds that generated the DDEF and modulated irregularities during the recovery phase. Westward DDEF suppressed post-sunset irregularities across most Brazilian and Argentine stations (-50.2% to -10.1%), but slightly enhanced post-midnight ionospheric irregularities at Cuiabá (+4.3%) and Tucuma (+21.1%). All Peruvian stations recorded post-midnight enhancements (+14.8% to +136.7%), with Arequipa showing the highest increase. We quantified the delayed magnetic response of the disturbance dynamo (Ddyn) relative to Joule heating, revealing propagation delays of approximately 6, 8.5, and 8.2 h in Brazil, Argentina, and Peru, respectively. Ddyn exhibited strong spatiotemporal variability, including spatial anomalies associated with the SAMA. The Peruvian sector dominated the Ddyn power (59.0%), followed by Brazil (35.1%) and Argentina (5.9%). Evidence of interhemispheric FAC asymmetry, attributed to seasonal variability, was also observed. These findings significantly advance our understanding of storm-time lowlatitude electrodynamics and their regional variability
Multiplicity dependence of f(980) production in pp collisions at TeV
No full textInternational audienceThe dependence of f(980) production on the final-state charged-particle multiplicity is reported for proton-proton (pp) collisions at the centre-of-mass energy, TeV. The production of f(980) is measured with the ALICE detector via the f decay channel in a midrapidity region of . The evolution of the integrated yields and mean transverse momentum of f(980) as a function of charged-particle multiplicity measured in pp at TeV follows the trends observed in pp at TeV and in proton-lead (p-Pb) collisions at TeV. Particle yield ratios of f(980) to and K(892) are found to decrease with increasing charged-particle multiplicity. These particle ratios are compared with calculations from the canonical statistical thermal model as a function of charged-particle multiplicity. The thermal model calculations provide a better description of the decreasing trend of particle ratios when no strange or antistrange quark composition for f(980) is assumed, which suggests that the tetraquark interpretation of the f(980) is disfavored