Conditions de mise en œuvre de la tomodensitométrie pour l’ étude d’ un couteau médiéval découvert en contexte préventif (diagnostic « Cœur de Ville » à Buzançais, Indre)

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Constraining the nature of the most extreme Galactic particle accelerator. H.E.S.S. observations of the microquasar V4641 Sgr

International audienceMicroquasars have emerged as promising candidates to explain the cosmic-ray flux at petaelectronvolt energies. LHAASO observations revealed V4641~Sgr as the most extreme example so far. Using $\approx$100~h of H.E.S.S. data, we performed a spectro-morphological study of the gamma-ray emission around V4641~Sgr. We employed HI and dedicated CO observations of the region to infer the target material for cosmic-ray interactions. We detected multi-TeV emission around V4641~Sgr with a high significance. The emission region is elongated. We found a power-law spectrum with an index $\approx$1.8, and together with results from other gamma-ray instruments, this reveals a spectral energy distribution that peaks at energies of $\approx$100~TeV for the first time. We found indications (3$σ$) of a two-component morphology, with indistinguishable spectral properties. The position of V4641~Sgr is inconsistent with the best-fit position of the single-component model and with the dip between the two components. We found no significant evidence of an energy-dependent morphology. No dense gas was found at any distance towards V4641~Sgr. The peak of the SED at $\approx$100~TeV identifies V4641~Sgr as a candidate cosmic-ray accelerator beyond the so-called knee. The absence of dense target gas places stringent energetic constraints on hadronic interpretations, however. The H.E.S.S. measurement requires an unusually hard ($\approx 1.5$) spectral index for the protons. A leptonic scenario faces fewer obstacles if the particle transport is fast enough to avoid losses and to reproduce the observed energy-independent morphology. The absence of bright \xray emission across the gamma-ray emission region requires a magnetic field strength $\lesssim3$~$μ$G, however. Our findings favour a leptonic origin of the gamma-ray emission. This conclusion does not exclude hadron acceleration in the V4641~Sgr system

Validation of a Compact and Tunable Continuous Gas-Flow Laser-Plasma Target for Electron Beam Production Above 150 MeV

International audienceThe present article reports on the generation of stable 50 pC low-divergence electron beams above 150 MeV from laser-driven wakefield acceleration using a continuous-flow gas target prototype tested at the 60 TW Salle Jaune facility at LOA. The gas target design is meant to be easily transported and integrated as an element of the beamline with a differential pumping system offering some 10$^{−4}$ mbar pressure in the rest of the line. A dedicated gas injection system allows for the control of the gas mixture concentration and gas pressure in two different regions of the target within the frame of controlled ionisation injection schemes. The measured electron beam parameters show the importance of gas density profiles and longitudinal gas mixture confinement

Theory-based evaluation of user participation in MedPrev, a digital preventive intervention in primary care in France

International audienceBackground Digital health interventions, particularly those delivered via mobile health, are transforming the way health prevention is provided. Evaluating user participation and its contribution to intervention outcomes is key to ensuring the effectiveness of an intervention. This study aims to identify conditions shaping user participation in MedPrev, a digital health intervention designed to deliver prevention in primary care. MethodsWe conducted a theory-driven qualitative study following the Consolidated Criteria for Reporting Qualitative Research (COREQ). A conceptual framework for user participation was developed prior to data collection, informed by a scoping review and co-creation workshops with stakeholders, which did not constitute data for the present study. Data collection then combined interviews with patients (n = 8) and health professionals (n = 5) with observations of MedPrev consultations (n = 10) across two French regions. Thematic analysis was performed using NVivo® software. Our findings were subsequently validated and refined through three deliberative workshops involving users, health professionals, and program designers (n = 19 participants). ResultsParticipation in MedPrev intervention is influenced by interdependent factors relating to professional and organizational settings, digital interventions, and user conditions. Three key themes emerged from the analysis: i) professional/organizational context, characterized by factors such as physician shortages, time constraints, and physician training in prevention; ii) intervention design elements, including technical barriers (e.g., web-based platform, login complexity) and lack of personalization; and iii) user factors, encompassing digital literacy, health literacy, and life circumstances. Conclusion User participation in digital health interventions is closely related to contextual factors.A systemic approach is essential in any attempt to address barriers related to adoption and usage, and to optimize the effectiveness of user participation in MedPrev and similar interventions. Recommendations include facilitating adoption, improving the feasibility of human intervention, personalizing the digital intervention, and strengthening hybrid follow-up approaches to combine digital and human interaction. Specific recommendations emphasize the value of hybrid models that combine digital innovations with human support to make digital preventive interventions effective and to ensure long-term engagement.</div

AR Data Ribbon: Break the Frame and Unroll Data in the Air

International audienceUnderstanding the difference between small and big values spanning over several orders of magnitude can be difficult. In this demo, we introduce a proof of concept named AR Data Ribbons, an augmented reality visualization scaled so that even smaller values are visible but requiring people to unroll the biggest values of a bar chart going beyond its frame. While the smallest values appear as classic bars on a 2D canvas, participants are invited to pick up a roll handle and to unroll ribbons representing the biggest values of the dataset. Ribbons are then unfolded in the space surrounding the participant until reaching the length corresponding to the data value. We hope our design could lead to a greater engagement, creative ribbon output patterns and better data understanding

Walks in the quadrant with interacting boundaries : genus zero case

The study of lattice walks restricted to the first quadrant has shed a lot of interest in the past twenty years. In particular, there has been an important effort to classify models of weighted walks with small steps with respect to the algebraic-differential nature of their generating function. The techniques that were developed in the course of this work are now applied to different extensions of those walks. One of these extensions, called walks with interacting boundaries, consists in accounting for the number of contacts of the walk with the axes, with motivation coming from statistical physics. These contacts are encoded as two additional parameters for the generating function, the Boltzmann weights. For one notable family of models, called genus zero models, we establish in this paper the complete classification of their generating function, for all real values of the parameters. We do this by adapting to this more general case a method due to Dreyfus, Hardouin, Roques and Singer, used in the former classification, and which consists in studying the rational solutions to a $q$-difference equation. In almost all cases, we show that the generating function is hypertranscendental, regardless of the values of the weights. In the remaining cases, we prove that specific algebraic relations between the Boltzmann weights make the generating function $\mathbb{N}$-algebraic or $\mathbb{N}$-rational, contrasting with the interaction-less case

Glycosyl modified nucleoside motifs for glycoconjugation of oligonucleotides

International audienceThis study presents a simple phosphoramidite-based strategy using glycosylated nucleoside phosphoramidites to efficiently synthesize a wide diversity of carbohydrate–oligonucleotide conjugates directly during solid-phase oligonucleotide assembly

De l'assimilation aux trajectoires individuelles : les Pondichériens depuis le fin du XIXe siècle

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Tailored Electrostriction in Self-Assembled Block Copolymers

International audienceElectrostrictive polymers are of practical interest for emerging applications, including capacitive sensors, micro-robotics, and mechanical energy harvesting, due to their low hysteresis and high deformability. However, their practical deployment is limited by a low electromechanical coupling coefficient. Developing polymeric materials with tunable electrostriction has remained a longstanding challenge. Herein, we address this limitation by harnessing block copolymer self-assembly to produce nanostructured electrostrictive films. Tunable electrostrictive coefficients were achieved by manipulating dielectric heterogeneities through the segregation behavior of methacrylate-type block copolymers, which consist of a poly(ionic liquid) block linked to an insulating mechanically robust block. The resulting electrostrictive response was found to strongly depend on the self-assembled morphology and its ordering quality. Solvent-annealed films with ionic blocks segregated into isolated spherical domains within an insulating matrix exhibited slightly lower electrostrictive coefficients but significantly reduced dielectric losses compared to as-cast films. In contrast, well-ordered lamellar morphologies yielded electrostrictive coefficients up to an order of magnitude higher than those of as-cast films over the measured frequency range. These findings demonstrate that block copolymer self-assembly is a powerful approach to precisely control the nanoscale architecture of electrostrictive polymers, offering a versatile strategy to enhance and tailor their electromechanical performance

Ultimate detection of lithium by LIBS in LiF atomic layers

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