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Multivariate distributional modeling of low, moderate, and large intensities without threshold selection steps
No full textIn fields such as hydrology and climatology, modelling the entire distribution of positive data is essential, as stakeholders require insights into the full range of values, from low to extreme. Traditional approaches often segment the distribution into separate regions, which introduces subjectivity and limits coherence. This is especially true when dealing with multivariate data. In line with multivariate extreme value theory, this paper presents a unified, threshold-free framework for modelling marginal behaviours and dependence structures based on an extended generalized Pareto distribution (EGPD). We propose decomposing multivariate data into radial and angular components. The radial component is modelled using a semi-parametric EGPD and the angular distribution is permitted to vary conditionally. This approach allows for sufficiently flexible dependence modelling. The hierarchical structure of the model facilitates the inference process. First, we combine classical maximum likelihood estimation (MLE) methods with semi-parametric approaches based on Bernstein polynomials to estimate the distribution of the radial component. Then, we use multivariate regression techniques to estimate the angular component's parameters. The model is evaluated through synthetic simulations and applied to hydrological datasets to exemplify its capacity to capture heavy-tailed marginals and complex multivariate dependencies without threshold specification
Experimental and numerical studies of the collapse of dense clouds induced by Herbig–Haro stellar jets
No full textInternational audienceThis study investigates the influence of Herbig–Haro jets on initiating star formation in dense environments. When molecular clouds are nearing gravitational instability, the impact of a protostellar jet could provide the impetus needed to catalyze star formation. A high-energy-density experiment was carried out at the LULI2000 laser facility, where a supersonic jet generated by a nanosecond laser was used to compress a foam or plastic ball, mimicking the interaction of a Herbig–Haro jet with a molecular cloud. Simulations using the 3D radiation hydrodynamics code TROLL provided comprehensive data for analyzing ball compression and calculating jet characteristics. After applying scaling laws, similarities between stellar and experimental jets were explored. Diagnostic simulations—including density gradient, emission, and X-ray radiographies—showed strong agreement with experimental data. The results of the experiment, supported by simulations, demonstrate that the impact of a protostellar jet on a molecular cloud could reduce the Bonnor–Ebert mass by approximately 9%, thereby initiating collapse
A Study of the Hall Effect on Doped and Undoped Praseodymium Nickelate Perovskite Thin Films and the Impact of the Reduction Process
No full textInternational audiencePrNiO3 and Pr0.8Sr0.2NiO3 epitaxial thin films were deposited by pulsed laser deposition (PLD) on different substrates and studied for Hall effect and resistivity behavior. Conductive behavior is observed in the doped composition, and a normal Hall effect allows to determine charge carrier’s density and mobility. The doped compositions show a high concentration of charge carriers (≈1023 cm−3 at 300 K), and it appears that they can be controlled by the strains. Sr doping enhances the transport properties, leading to a transition from semiconducting to metallic behavior. The impact of the reduction process on charge carrier concentration and mobility is also studied
Measurements of electroweak production of a photon in association with two jets in proton-proton collisions at = 13 TeV
No full textInternational audienceThe first observation of electroweak production of a photon in association with two forward jets in proton-proton collisions is presented. The measurement uses data recorded by the CMS experiment at the LHC during 20162018 at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb. The analysis is performed in a region enriched in photon production via vector boson fusion, with a requirement on the transverse momentum of the photon to exceed 200 GeV. The cross section is measured to be 202 fb, at a significance with respect to the null hypothesis that exceeds five standard deviations. This is in agreement with the standard model prediction of 177 fb. Differential cross sections are measured as a function of various observables. Limits are set on dimension-6 effective field theory operators that contribute to the WW interaction. The observed 95% confidence intervals for the corresponding Warsaw basis Wilson coefficients and are [0.11, 0.16] and [1.6, 1.5], respectively
Author Correction: Striking convergent selection history of wheat and barley and its potential for breeding
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Contributions of connectional pathways to shaping Alzheimer’s disease pathologies
No full textInternational audienceFour important imaging biomarkers of Alzheimer's disease, namely grey matter atrophy, glucose hypometabolism and amyloid-β and tau deposition, follow stereotypical spatial distributions shaped by the brain network of structural and functional connections. In this case-control study, we combined several predictors reflecting various possible mechanisms of spreading through structural and functional pathways to predict the topography of the four biomarkers in amyloid-positive patients while controlling for the effect of spatial distance along the cortex. For each biomarker, we quantified the relative contribution of each predictor to the variance explained by the model. We also compared the contribution between apolipoprotein E-ɛ4 carriers and non-carriers. We found that topological proximity to areas of maximal pathology through the functional connectome explained significant parts of variance for all biomarkers and that functional pathways totalized more than 30% of contributions for hypometabolism and amyloid load. By contrast, atrophy and tau load were mainly predicted by structural pathways, with major contributions from inter-regional diffusion. The ɛ4 allele modulated contributions to the four biomarkers in a way consistent with compromised brain connectomics in carriers. Our approach can be used to assess the contribution of concurrent mechanisms in other neurodegenerative diseases and the possible modifying impact of relevant factors on this contribution.</div
Machine learning-based tungsten spectroscopy analysis in the WEST tokamak
No full textInternational audienceThis article presents a machine learning approach to tungsten spectroscopy analysis using measurements performed in WEST tokamak plasmas. We developed a Random Forest algorithm to predict the maximum electron temperature (Temax) based on 45–65 Å tungsten brightness spectra measured along a mobile line of sight. The model achieves prediction errors typically below 5% across a broad temperature range (0.5–4 keV). Feature importance analysis highlights both physically meaningful wavelengths and others that, despite lacking direct interpretability, improve prediction stability and accuracy. In addition, a principal component analysis is conducted to investigate the relation between spectral variance and Temax unraveling that unaccounted-for parameters influence the spectral shape. Combined with the wavelength importance analysis, this study could potentially inform atomic structure and collisional-radiative models to better understand the tungsten spectral emission
Paleoproteomics reveals chromoblastomycosis as possible cause of King of France Louis XIV's death (1715)
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L-shell photoionisation cross sections in the S+, S2+, S3+ isonuclear sequence
No full textInternational audienceWe present absolute L-shell photoionisation cross sections for the S + , S 2+ , S 3+ ions. The cross sections were obtained using the monochromatised photon beam delivered by the SOLEIL synchrotron source coupled with an ion beam extracted from an electron cyclotron resonance source (ECRIS) in the merged dual-beam configuration. The cross sections for single, double and triple ionisation were measured and combined to generate total photoionisation cross sections. For each of the S + , S 2+ and S 3+ ions, the photon energy regions corresponding to the excitation and ionisation of a 2p or a 2s electron (∼175-230 eV) were investigated. The experimental results are interpreted with the help of multiconfigurational Dirac-Fock (MCDF) and Breit-Pauli R-Matrix (BPRM) or Dirac R-Matrix (DARC) theoretical calculations. The former generates photoabsorption cross sections from eigenenergies and eigenfunctions obtained by solving variationally the multiconfiguration Dirac Hamiltonian while the latter calculate cross sections for photon scattering by atoms. The cross sectional spectra feature rich resonance structures with narrow natural widths (typically 100 meV) due to 2p → nd excitations below and up to the 2p thresholds. This behaviour is consistent with the large number of inner-shell states based on correlation and spin–orbit mixed configurations having three open subshells. Strong and wide (typically ∼1 eV) Rydberg series of resonances due to 2s → np excitations dominate above the 2p threshold
