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Mechanisms underlying morphological changes in recorded electrical signals by micro-anatomical arrhythmogenic substrates
No full textAimArrhythmogenic substrates responsible for lethal ventricular arrhythmias may be too small to be detected by commonly used medical imaging. However, they may still alter the morphology of electrical signals, allowing their detection and/or inference of their arrhythmogenesis. The aim of the study is to understand how micro-anatomical arrhythmogenic substrates (µAASs) give rise to pathological morphologies in the traces of recorded electrical signals. Methods and resultsEleven human biventricular models with a µAAS were created by varying the location of the µAAS and the volume of weakly coupled myocardium surrounding it. Electrograms (EGMs) and body surface potential maps (BSPMs) were simulated from the biventricular models under sinus activation within a torso. Sinus activation was achieved through either stimulating the His-Purkinje network or early activation sites (EAS).EGMs and BSPMs simulated in ventricular models with and without a µAAS were compared. A qualitative analysis showed that under sinus beat, EGMs from epicardial electrodes had more pronounced morphological changes than those from endocardial electrodes. Also, sinus activation through the His-Purkinje network resulted in EGMs with more pronounced morphological changes than sinus activation through EAS. All ventricular models with a µAAS caused morphological changes in BSPM but only one resulted in changes large enough to be distinguishable from noise. These changes were restricted to the torso area around the sternum. ConclusionsThe electrophysiological and structural properties of a substrate are more important for its effects on traces of measured electrical signal tracings than its size or location. µAASs significantly change BSPMs in regions closest to the heart.</div
Fermi-LAT detections of novae V1723 Sco and V6598 Sgr
No full textInternational audienceContext. Numerous classical novae have been observed to emit γ-rays (E > 100 MeV) detected by the Fermi-LAT. The prevailing hypothesis attributes this emission to the interaction of accelerated particles within shocks in the nova ejecta. However, the lack of non-thermal X-ray detection coincident with the γ-rays remains a challenge to this theory. Methods. We performed similar analyses of the Fermi-LAT data for both novae to determine the duration, localization, and spectral properties of the γ-ray emission. These results were compared with optical data from the AAVSO database and X-ray observations from NuSTAR, available for V1723 Sco 2024 only, to infer the nature of the accelerated particles. Finally, we used a physical emission model to extract key parameters related to particle acceleration. Results. V1723 Sco 2024 was found to be a very bright γ-ray source with an emission duration of 15 days allowing us to constrain the spectral index and the total energy of accelerated protons. Despite early NuSTAR observations, no non-thermal X-ray emission was detected simultaneously with the γ-rays. However, unexpected γ-ray and thermal hard X-ray emission were observed more than 40 days after the nova outburst, suggesting that particle acceleration can occur even several weeks post-eruption. V6598 Sgr 2023, on the other hand, was detected by the Fermi-LAT at a significance level of 4σover just two days, one of the shortest γ-ray emission durations ever recorded, coinciding with a rapid decline in optical brightness. Finally, the high ratio of γ-ray to optical luminosities and γ-ray to X-ray luminosities for both novae, as well as the curvature of the γ-ray spectrum of V1723 Sco below 500 MeV, are all more consistent with the hadronic than the leptonic scenario for γ-ray generation in novae
Linear and nonlinear crystal optics: phenomenology, symmetries, and angular distributions
No full textInternational audienceThis book provides both theoretical foundations and practical insights into linear and nonlinear crystal optics. It bridges the fundamental principles of light-crystal interactions with advanced applications in optics. Linear and Nonlinear Crystal Optics offers a thorough exploration of electric susceptibility—the cornerstone of optical properties through electric constitutive relations and Maxwell’s equations. Key features include comprehensive tensor representations, detailed angular distributions of optical parameters, complete mathematical demonstrations, and original research insights developed over decades. The book covers essential topics including phenomenological introduction to light-matter coupling, mathematical background in orientation and thermodynamic symmetries, electric susceptibility and field tensors, polarization calculations, linear optical effects linked to the real and imaginary parts of the refractive index, and both second-order and third-order interactions. Each chapter concludes with a summary and references, providing readers with clear learning pathways and resources for further exploration. This book is ideal for advanced undergraduate students, graduate students, and researchers in physics, optical engineering, materials science, and crystallography. It serves as an essential reference for professionals working in fields requiring deep understanding of crystal optics, including photonics, laser technology, telecommunications, and materials characterizatio
A record of Late Pleistocene environmental conditions at the transition from central to southern Europe from the Baix loess paleosol sequence (Rhône Rift Valley, SE France)
No full textInternational audienceLoess-paleosol sequences (LPSs) provide valuable archives of Quaternary paleoenvironments. Here we present new data from the Baix LPS, comprising the entire Late Pleistocene. The Baix LPS is located at the western edge of the Rhône Rift Valley, France, in the transition zone from the presently temperate to the Mediterranean region of Europe. This LPS provides a missing link between the analyzed LPSs in the presently temperate regions farther north and those in the Mediterranean region. Reddish Btg horizons of a Stagnic Luvisol at the base of the Baix LPS represent the remains of an MIS 5 pedocomplex formed under warm and, at least temporarily, relatively moist conditions. Two brown Bw horizons of truncated Cambisols have been preserved in the overlying MIS 5a/4 to MIS 3 deposits. The upper Bw horizon is associated with large carbonate nodules, indicating that considerable amounts of calcium carbonate were leached from a former MIS 3 Cambisol and accumulated in the underlying loess unit. This truncated MIS 3 Cambisol is very similar to the MIS 3 paleosol remains in the LPS Collias that we investigated 87 km farther south in the present Mediterranean climate. No paleosols were observed in the late MIS 2 deposits
A propos du statut d’un ministre d’un culte non-statutaire en Alsace-Moselle au regard du droit du travail
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Clinical and Organizational Determinants of a Frequently Delayed Diagnosis of Ocular Syphilis in a French Referral Center
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Le bon représentant: Une comparaison européenne des conceptions citoyennes du système politique
No full textInternational audienceCe livre étudie la variété des conceptions des citoyens européens sur leur système politique, c’est-à-dire leurs visions et leurs évaluations sur deux questions : qui doit gouverner et que doit faire le gouvernement ? Il étudie leurs conceptions du « bon » système politique, identifie leurs différentes visions, reconstruit les discours idéaux-typiques associés à ces attentes alternatives et analyse leurs fondements normatifs. L’ouvrage prête une attention toute particulière aux caractéristiques nationales et individuelles qui structurent ces différents discours, et s’appuie sur un dispositif empirique original : une comparaison entre la Belgique, la France et l’Italie à partir d’une grande enquête et de plus d’une centaine d’entretiens. Ce livre s’inscrit dans un agenda de recherche dynamique sur les préférences des citoyens sur la manière dont doivent être prises les décisions politiques et s’interroge sur leurs positionnements sur la démocratie représentative et ses alternatives, autant d’enjeux d’une actualité particulière dans un contexte marqué par la multiplication des expérimentations démocratiques mais aussi la remise en cause de ses principes. Il démontre le caractère hybride, ambivalent et conflictuel des préférences citoyennes, mais aussi l'impossible dépassement de la représentation politique et l’existence d’une série de conceptions alternatives du « bon représentant » liées au contexte national et aux inégalités sociales et politiques
Mechanosensing and Sphingolipid-Docking Mediate Lipopeptide-Induced Immunity in <i>Arabidopsis</i>
No full textBacteria-derived lipopeptides are immunogenic triggers of host defenses in metazoans and plants. Root-associated rhizobacteria produce cyclic lipopeptides that activate systemically induced resistance (IR) against microbial infection in various plants. How these molecules are perceived by plant cells remains elusive. Here, we reveal that immunity activation in Arabidopsis thaliana by the lipopeptide elicitor surfactin is mediated by docking into specific sphingolipid-enriched domains and relies on host membrane deformation and subsequent activation of mechanosensitive ion channels. This mechanism leads to host defense potentiation and resistance to the necrotroph B. cinerea but is distinct from host pattern recognition receptor-mediated immune activation and reminiscent of damage-induced plant immunity. Main TextLipopeptides (LPs) represent a prominent and structurally heterogeneous class of molecules among the broad spectrum of small specialized metabolites synthesized by bacteria. Besides serving key functions for the ecological fitness of the producer (motility, biofilm formation, colonization, nutrient acquisition, or antagonism towards competing neighbors), some LPs also act as triggers of immune responses that restrict pathogen infection of metazoans and plants 1,2 . The vast majority of LPs formed by plant-associated bacteria are comprised of a partly or fully cyclized oligopeptide linked to a single fatty acid chain. Some of these cyclic lipopeptides (CLP) formed by beneficial species belonging to the Pseudomonas and Bacillus genera are potent elicitors of immune responses in the host plant leading to a systemically induced resistance (IR) against infection by microbial pathogens 2,3 .</div
Government polling in times of crises: when capacity meets incentives
No full textInternational audienceHow do governments mobilise public opinion in times of crises? While recent research examines the factors that determine the intensity of government polling at different points in the electoral cycle and the different representational logics behind this activity, empirical evidence on the more qualitative aspect of government polling is still lacking. What types of policy issues are covered in government polls? Understanding governments as actors in the production of public opinion, not just passive consumers, we examine the selection of issues in government polls. We present evidence from Germany, mobilising an original database of all poll questions directly commissioned by the German federal government during the 18th and 19th legislative periods (2013–2021). Using a conditional logit approach, we analyse how the character of the policy domain to which an issue belongs affects the likelihood that some issues are covered by government polls. Our results show that while motivations to ask questions about a particular issue are shaped by constraints (institutional, financial and political) on the government's ability to act in this area, incentives related to the salience of the issue can shift the focus of government polls to issues where they have less room for manoeuvre