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Les femmes et l’hérésie de sorcellerie démonolâtre : une association en construction à la fin du Moyen Âge
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Can subfossil insects complement pedoanthracology in reconstructing the past trajectories of old-growth forests? A study case from the Northern Central Pyrenees (France)
No full textInternational audienceThe presence of insect remains preserved in soils has the potential to serve as a complementary proxy to charcoal, facilitating the reconstruction of Holocene forest trajectories at high spatial resolution. Six pits were dug at three old-growth forest sites (two per site) in the Central Pyrenees (France). Insect remains and charcoal were collected in each soil layer, following the pedoanthracological method usually conducted in similar mountain contexts. Radiocarbon dating was performed on a selection of both insects and charcoal, and a time-since-death index was developed to evaluate the degradation stage and relative age of the insect remains. Insect remains were present in most layers, but were more abundant in the upper ones, as with charcoal. Whereas radiocarbon dating did not work on individual insect remains, the time-since-death index showed a consistent relationship between increasing degradation and increasing depth. Saproxylic beetles, which are key indicators of the maturity of old-growth forests, were poorly preserved in the soils studied, but some of the other beetles identified at genus or species level provided useful information on past forest openness
Heat Kernels and Resummations: the Spinor Case
No full textInternational audienceAmong the available perturbative approaches in quantum field theory, heat kernel techniques provide a powerful and geometrically transparent framework for computing effective actions in nontrivial backgrounds. In this work, resummation patterns within the heat kernel expansion are examined as a means of systematically extracting nonperturbative information. Building upon previous results for Yukawa interactions and scalar quantum electrodynamics, we extend the analysis to spinor fields, demonstrating that a recently conjectured resummation structure continues to hold. The resulting formulation yields a compact expression that resums invariants constructed from the electromagnetic tensor and its spinorial couplings, while preserving agreement with known proper-time coefficients. Beyond its immediate computational utility, the framework offers a unified perspective on the emergence of nonperturbative effects (such as Schwinger pair creation) in relation to perturbative heat kernel data, and provides a basis for future extensions to curved spacetimes and non-Abelian gauge theories
Hydrolytic weakening controls Jurassic to early Cretaceous mylonitisation in the basement of the Pyrenees
No full textInternational audienceThe age of the mylonite belts in the basement rocks of the Pyrenees is a subject of debate in the structural geology and petrology communities because of its potential implication on the regional tectono-thermal history and on the tectonic evolution of SW Europe. Here we address when and how mylonitisation took place in two key areas of the Eastern Pyrenees, where shear zones are associated with Giant Quartz Veins (GQVs). We conducted zircon U-Pb and muscovite 40 Ar/ 39 Ar dating coupled with structural, textural, and crystallographic preferred orientation (CPO) analyses of mylonites from the Cap de Creus and Canigó Massifs. U-Pb zircon dating of a dacite porphyry dyke crosscut by GQVs and mylonitic bands yields a maximum shear zone and GQV formation age of ca. 292 ± 3 Ma. 40 Ar/ 39 Ar analyses of muscovite within mylonitised GQVs yield initial crystallisation ages between ca. 164 and 188 Ma, as well as younger recrystallisation ages of ca. 110-118 Ma. A qualitative assessment of the GQV history is inferred from stepheating spectra of muscovite and quartz CPOs. The results indicate that GQV formation and mylonitisation were coupled, coeval, and long-lasting processes that took place from early Jurassic to early Cretaceous times. A comparative evaluation of quartz CPOs reveals inconsistencies regarding the strain distribution, quartz slip systems activity, and deformation temperatures depending on the deformed rock type. Quartz mylonites have stronger CPOs dominated by basal <a>, prism <a> or prism <c> slip systems, whilst phyllonites and granite mylonites show weaker fabrics mostly dominated by mixed <a> slip. This apparently suggests higher deformation temperatures in quartz mylonites than those inferred from more reliable proxies, such as mineral assemblages, brittle behaviour of K-feldspar, and fluid inclusion data. We suggest that the water-weakening effect caused by coeval formation and deformation of GQVs enabled easier dislocation glide and creep, allowing strain localisation and transitions between slip systems at lower temperatures than commonly inferred due to enhanced ductility. U-Pb zircon dating further suggests the existence of an early Carboniferous (ca. 332 ± 4 Ma; Visean) magmatic episode in the Pyrenees, in agreement with a cyclic, rather than a progressive, geodynamic history of the region during Variscan times.The present work challenges classical interpretations stating that Pyrenean mylonite belts developed during the retrograde stages of the Variscan Orogeny, highlighting that the structural evolution of this region during Mesozoic times deserves further investigation. Results have implications for interpreting deformation localisation mechanisms and conditions in crustal rocks, for the formation mechanisms of GQVs in worldwide orogenic belts, and for the tectono-thermal history of the Pyrenees since late-Variscan times.</div
Tensor-based higher-order multivariate singular spectrum analysis and applications to multichannel biomedical signal analysis
No full textInternational audienceSingular spectrum analysis (SSA) is a nonparametric spectral estimation method that decomposes time series signals into interpretable components. With the rise of big time series, the demand for effective and scalable SSA techniques has become increasingly urgent. In this paper, we propose a novel multiway extension of SSA, called higher-order multivariate SSA (HO-MSSA), specifically designed for multivariate and multichannel time series signal analysis via tensor decomposition. HO-MSSA utilizes time-delay embedding and tensor singular value decomposition to transform multichannel time series signals into trajectory tensors, which are then decomposed into elementary components in the Fourier domain, rather than the time domain as in traditional SSA methods. These components are grouped into disjoint subsets using spectral clustering, enabling the reconstruction of the underlying source signals. Experimental results demonstrate that HO-MSSA outperforms state-of-the-art SSA methods in various biomedical applications, including electromyography (EMG), electrocardiography (ECG), and electroencephalogram (EEG) signals
Le serment politique comme régulation ou comme contestation de l’ordre public au Moyen-Âge
No full textInternational audienceAu cours du Moyen Âge, bien qu’il ait été utilisé pour renforcer les liens sociaux et politiques, le serment a été source de contestations religieuses et vecteur de désordre social. Consciente de ces enjeux politiques, l’Église s’est efforcée de contrôler son potentiel créatif et émancipateur. En dépit de ses efforts, la parole jurée s’est largement affranchie de son contrôle, jouant alternativement un rôle de préservation ou de subversion des institutions
EMG-to-torque models for exoskeleton assistance: a framework for the evaluation of in situ calibration
No full textInternational audienceIn the field of robotic exoskeleton control, it is critical to accurately predict the intention of the user. While surface electromyography (EMG) holds the potential for such precision, current limitations arise from the absence of robust EMG-to-torque model calibration procedures and a universally accepted model. This paper introduces a practical framework for calibrating and evaluating upper-limb EMG-to-torque models, accompanied by a novel nonlinear model. The framework includes an in situ procedure that involves generating calibration trajectories and subsequently evaluating them using standardized criteria. A comprehensive assessment on a dataset with 17 participants, encompassing single-joint and multi-joint conditions, suggests that the novel model outperforms the others in terms of accuracy while conserving computational efficiency. This contribution introduces an efficient model and establishes a versatile framework for EMG-to-torque model calibration and evaluation, complemented by a dataset made available. This further lays the groundwork for future advancements in EMG-based exoskeleton control and human intent detection
Subdiffusive fractional limit of a jump-renewal equation
No full textIn this paper, we consider an age-structured jump model that arises as a description of continuous time random walks with infinite mean waiting time between jumps. We prove that under a suitable rescaling, this equation converges in the long time large scale limit to a time fractional subdiffusion equation
Fourchette et fricassée : socioanalyse d’une préparation de repas
No full textInternational audienceInspired by the approach to the ordinary developed by Yvette Delsaut, this article offers a socio-analysis of a meal preparation carried out in June 2024 by the author with her mother, Yolande Aucher (born in 1943 in Algeria), as part of an Authorization to Direct Research (HDR). The approach mobilizes various sources, such as photographic observation, verbatim reports, family archives, personal memories and even direct interviews. The examination of the case studied highlights a culinary practice which goes beyond the simple necessity of food to become a creative act, a vector of meaning and support for the autonomy of an active elderly person.En s’inspirant de l’approche de l’ordinaire développée par Yvette Delsaut, cet article propose une socioanalyse d’une préparation de repas effectuée en juin 2024 par l’auteur avec sa mère, Yolande Aucher (née en 1943 en Algérie), dans le cadre d’une Habilitation à diriger des recherches (HDR). La démarche mobilise diverses sources, telles que l’observation photographique, les verbatims, les archives familiales, les souvenirs personnels ou encore les entretiens directs. L’examen du cas étudié met en évidence une pratique culinaire qui dépasse la simple nécessité alimentaire pour devenir acte créatif, vecteur de sens et soutien à l’autonomie d’une personne âgée active
A window on the amalgamation of Western Gondwana: Geological history of the Ouaddaï massif (E. Chad)
No full textInternational audienceThe Saharan metacraton was assembled during pre-Neoproterozoic to Neoproterozoic times and was strongly remobilised during the Pan African orogeny. The Ouaddaï massif in eastern Chad represents the core of the Saharan metacraton, yet its geological history remains poorly documented. In this study, we combine of field observations, petrological analysis of metamorphic rocks, and geochemical and geochronological constraints to reconstruct the tectono-metamorphic evolution of the Ouaddaï massif. The study area is dominated by collision-related plutonic rocks and migmatitic gneisses, within which inliers of older basement occur. Geochemical data indicate a transition from active-margin to collisional magmatism, with a compositional evolution from diorite to granite. This suite is cross-cut by syenogranites and alkaline granites with shoshonitic affinities, interpreted as post-collisional granitoids derived from tonalitic rocks to sedimentary protoliths. Geochronological data (U-Pb on zircon and monazite) point to a ca. 1000 Ma age for orthogneisses inliers. Granitoids of the Ouaddaï massif record emplacement ages from 620 to 590 Ma, coeval with high-temperature metamorphism characterized by peak pressure–temperature conditions of 1.2 GPa and 850 °C (mafic granulite) and around 0.8 GPa and 700 °C (sillimanite-garnet bearing migmatites). Integrating our new results with regional data, we discuss the existence and geodynamic evolution of the Saharan Metacraton. Our findings emphasize the significance of the Saharan Metacraton as a key region for understanding the extensive reworking of cratonic lithosphere during both a Tonian magmatic phase prior and the assembly of Gondwan