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Invited Paper: Causal Mutual Byzantine Broadcast
No full textInternational audienceRecently, a new communication abstraction called Mutual Broadcast has been proposed for message-passing distributed systems where some processes may fail by crashing. It is a one-to-all broadcast abstraction providing an ordering property that allows it to be computationally equivalent to atomic registers. This paper proposes an adaptation of this abstraction, Causal Mutual Byzantine Broadcast (in short CMB-Broadcast) for message-passing systems where some processes may experience Byzantine faults. Byzantine faults are a more severe failure model compared to crash failures. A Byzantine process can behave arbitrarily. After defining this new communication abstraction, we show how it can be used to emulate atomic registers and also how it can be implemented using quorums and the famous Byzantine reliable broadcast abstraction of Bracha. We also prove a necessary condition on the size of the quorums
High Energy Particles Induced X-ray Emission (HE-PIXE) set-up optimisation to detect trace elements in silver coins
No full textInternational audiencePrevious research has traced the provenance of silver extracted from mines in South America (Mexico and Potosi) via trade between Spain and France during the 16th century. A new numismatic approach focusing on a corpus of silver coins minted in Nantes enables them to be selected for chemical composition analysis, enabling trace elements such as gold, mercury, and indium to be quantified.This presentation will show the progress of the experimental work carried out at ARRONAX cyclotron and will focus particularly on high-energy PIXE to detect traces of indium in silver-copper matrix probed with 68 MeV alphas beam. Setup was optimized to improve the detection limit down to few ppm and reach the average indium concentration in Potosi silver ore of 6.9±2.6 ppm.HE-PIXE non-destructive analyses where done with high energy HPGe X-ray detector. Experimental parameters like resolution, shielding, X-ray filters, geometry (distances, angles) and electronic settings were explored to find the best configuration for indium detection. As a result, the count rate, signal-to-noise ratio and detection limit were improved using reference materials. The aim was to distinguished natural indium from activation products.High count rates in the Ag Kα main pic about 6000 cps reduce irradiation time and provide enough statistic in In Kα line at 24.2 keV (Figure 1) with a dead time below 15% and good peak resolution. Also, first results show that irradiation time impact the production of Cd (Z+1) but not In (Z+2). Background noise was reduced using PMMA filter placed in front of the detector window to reduced low energy sum peaks in the area, improving S/N ratio. Assuming that indium nuclear production should be proportional to the silver content of the target, we found a difference between two Ag-Cu targets with 37 ppm and 65 ppm In. Meaning that natural In was detected within a few ppm. This results shows that high energy PIXE can be used to quantify traces elements in silver coins
Etude des bus SPI et I2C avec un analyseur logique très faible coût
No full textInternational audienceDans le cadre d'un cours du master « Capteurs Intelligents et qualité des Systèmes Electroniques », il était nécessaire de faire étudier expérimentalement les bus SPI et I2C. Pour ce faire, nous avons réalisé un travail expérimental utilisant un analyseur logique très faible cout associé à un logiciel libre et multiplateforme pour l'analyse des trames
Ultrafast probing of isotope-induced explicit symmetry breaking in ethylene
No full textInternational audienceSymmetry governs nature's law, yet many of the natural phenomena occur due to the breakdown of symmetry. Here, we show how isotope-induced inversion symmetry breaking influences ultrafast photoisomerization processes in ethylene. Using extreme ultraviolet pump-near infrared probe time-of-flight mass spectrometry, we find that replacing one of the carbon atoms in ethylene with a 13C isotope leads to twice-faster structural relaxation via ethylene-ethylidene isomerization in the photo-excited molecular cation. Advanced trajectory surface hopping calculations incorporating the nuclear symmetry of the molecular systems, reveal that it arises from the mixing of different normal modes in the isotope-substituted species, interactions otherwise forbidden by symmetry. Although the mixing does not alter the symmetry of the electronic Hamiltonian, it modifies that of the nuclear Hamiltonian, causing explicit symmetry breaking. This facilitates efficient intra-molecular vibrational energy redistribution, lowering the isomerization yield. Our findings offer opportunities to use isotope-induced nuclear symmetry breaking to control the outcome of light-molecule interactions across ultrafast timescales
The thermal axion production rate, precisely
No full textInternational audienceThe axion is a hypothetical particle first proposed by Peccei, Quinn, Weinberg and Wilczek to solve the strong CP problem. It was later realized that ultra-relativistic (or "hot") axions thermally produced in the early Universe can contribute measurably to the energy density of the Universe as dark radiation.The effective number of neutrinos Neff, parametrizing this dark radiation fraction of the energy density, has already been measured by experiments like Planck or ACT and will be determined to a greater degree of precision by future CMB telescopes like the Simons Observatory. Precise theoretical determinations of the axion contribution to Neff as a function of the axion-Standard Model couplings can be used to place constraints on those couplings.Specifically, this talk discusses new results obtained in the Kim-Shifman-Vainshtein-Zakharov (KSVZ) model where the axion only interacts with gluons, and the only parameter is the axion scale fPQ.I will show how the main source of theoretical uncertainty is the implementation of finite-temperature collective effects. Comparing three leading-order equivalent implementations of those thermal corrections allow us to quantify the uncertainty on the axion rate and -- through solving the Boltzmann equation -- on Neff.For a value of fPQ close to the current limit from astrophysical observations, we find that the axion contribution to Neff is around 0.0281, with a theoretical uncertainty of the order of 0.0003.We also critically examine previous determinations of the rate in the literature.The results presented in this talk are published in 2404.06113, written by myself and Jacopo Ghiglieri
Flatness-based control for generalized synchronization of chaotic systems with large dissipation and dimension mismatch
No full textInternational audienceA flat control law is based on the structural analysis of a controlled system, allowing optimal placement of sensors and actuators. Once designed, any desired dynamics can be imposed onto the system. When the target dynamics comes from a system structurally different from the controlled one, generalized synchronization can be achieved, provided the control gain is sufficiently large. As the gain increases, various relationships emerge between the drive and response systems, depending on differences in their dimensions and dissipation rates. The principal contribution of this work lies in the exploration of drive-response system pairs with varying dimensions (ranging from 2 to 4) and dissipation levels, including combinations of dissipative and conservative systems. We identify several types of generalized synchronization, using a classification based on the thickness of the resulting Lissajous curves and the lack of conjugacy between the first-return maps of the drive and response systems
Towards teleconsultations in the metaverse: design and preliminary study of an immersive teleclinic for neuro-psychological assessment
No full textInternational audienceVirtual Reality (VR) and Metaverse technologies open new avenues for telemedicine, particularly for teleconsultations. Our goal is to explore how these remote medical interactions can take place within immersive teleclinics. Neuropsychological testing in VR is especially promising for diagnosing and monitoring cognitive disorders. This study presents our overall approach to immersive teleclinics and the development of a social VR platform for conducting such assessments. The application enables clinicians to perform remote testing sessions that begin in a virtual waiting room and continue with a combination of clinician-guided desk-based tasks and independent test activities. Clinicians can monitor patient performance in real time through dedicated dashboards. We evaluated the system with healthy participants (pseudo-patients) and clinicians using standard measures of usability (SUS), presence (MPS), and acceptability (UTAUTQ). Initial results indicated good usability, a strong sense of presence, and high acceptability among pseudo-patients. Clinicians were more hesitant, citing usability issues, uncertainty about the clinical validity of VR-based tests, and concerns about avatar quality for psychological interviews. We discuss our design choices, the potential of our prototype for remote cognitive assessment, and broader lessons learned for teleclinics in the Metaverse. While challenges remain, our work highlights the promise of such immersive teleclinics for future medical practice
Boosting Handwritten Mathematical Expression Recognition through Contextual Reasoning with Vision Large Language Models (vLLMs)
No full textInternational audienceHandwritten Mathematical Expression Recognition (HMER) has traditionally relied on dedicated models specifically designed for this task. With the emergence of Vision Large Language Models (vLLMs), we investigate their potential for HMER tasks. This paper presents a comprehensive benchmark study evaluating various state-of-the-art vLLMs on the CROHME dataset. We develop an experimental pipeline that includes language model inference, cleaning and conversion to structural graphs, and evaluation using graph-based metrics. Our experiments explore two prompting strategies: without context (image-to-text only) and with context (image-to-text with surrounding contextual information). Results show that while vLLMs demonstrate promising capabilities, dedicated models still outperform general-purpose vLLMs on HMER tasks. We analyze the performance gaps and discuss future directions for improving vLLM-based mathematical expression recognition.</div
Age‐Related Differences in Jumping and Sprinting Performance and Force Production Capacities in Young Soccer Players
No full textInternational audienceThe purpose of this study was to evaluate the evolution of jump and sprint force-production capacities with maturation in young soccer players. One hundred sixteen young elite male soccer players aged 11-17 years were assigned to six different groups according to their maturity status. The force-velocity (F-V) profiles in jumping and sprinting performances were compared among groups. The results show a significant, progressive, and linear improvement in the majority of F-V profile determinants of jumping and sprinting performances in parallel with maturation. When comparisons were carried out between consecutive groups, significant differences between PHV-1 and PHV groups in H max (p < 0.05), H 60 (p < 0.05), VT-F0 (p < 0.05), and VT-P max (p <0.05) were observed but disappeared when these variables were expressed relative to body mass. Regarding the F-V profile determinants of sprinting performance, we observed significantly shorter sprint times in PHV compared to PHV-1 and in PHV+2 in comparison with the PHV+1 group. These between-group differences were associated with significant greater HZT-F0 kg -1 (p < 0.05) and HZT-P max kg -1 (p < 0.001). However, significantly more negative value of HZT-Sfv kg -1 was observed in PHV-1 compared to PHV-2 (p < 0.05), in PHV+1 in comparison with PHV (p < 0.05) and in PHV+3 when compared to the PHV+2 group (p < 0.05). Thus, these findings revealed an alternation of accelerated periods of development in force and velocity qualities, expressing sprinting performance, with maturation during the physical development process of young soccer players. Trainers and coaches should be aware of the distinct mechanical characteristics related to each maturity stage and design specific programs accordingly.</div