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Bifurcation of gravity-capillary Stokes waves with constant vorticity
No full textInternational audienc
A Cahn--Hilliard--Willmore phase field model for non-oriented interfaces
No full textInternational audienceWe investigate a new phase field model for representing non-oriented interfaces, approximating their area and simulating their area-minimizing flow. Our contribution is related to the approach proposed in arXiv:2105.09627 that involves ad hoc neural networks. We show here that, instead of neural networks, similar results can be obtained using a more standard variational approach that combines a Cahn-Hilliard-type functional involving an appropriate non-smooth potential and a Willmore-type stabilization energy. We show some properties of this phase field model in dimension and, for radially symmetric functions, in arbitrary dimension. We propose a simple numerical scheme to approximate its -gradient flow. We illustrate numerically that the new flow approximates fairly well the mean curvature flow of codimension or interfaces in dimensions and
Effects of loading processes on contact forces when simulating static seating with a finite element human body model
No full textInternational audienceSeat interface forces, particularly shear forces, play an essential role in predicting the risk of pressure ulcers and seating discomfort. When a finite element human body model (HBM) is used for static seating simulation, the most common loading method is to put the model in a position close to the desired final posture and then ‘drop’ it from just above the seat by applying the gravity (DROP). This does not represent how people sit in a seat. In addition, high coefficients of friction (COF) are often used to prevent sliding, which may lead to unrealistically high tangential forces. This study aims to investigate the effects of the loading process and the COF on seating simulations with a HBM. We propose a new loading approach called ‘drop and rotate’ (D&R) to better mimic people sitting on a seat. With the trunk more flexed than the desired posture, the model is dropped to establish the contact between the buttocks and thighs, and the seat pan first, and then between the back and the backrest by rotating the hip. Simulations were performed using a recently developed and validated adult male model in two different seat configurations. Results show that the proposed D&R method was less sensitive to COF and gave a better prediction of contact forces, especially on the seat pan. However, its computational time is higher than the DROP method. The study highlights the importance of the loading process when simulating static seating
Hydrodynamic limit for an open facilitated exclusion process with slow and fast boundaries
No full text44 pagesInternational audienceWe study the symmetric facilitated exclusion process (FEP) on the finite one-dimensional lattice {1, . . . , N − 1} when put in contact with boundary reservoirs, whose action is subject to an additional kinetic constraint in order to enforce ergodicity, and whose speed is of order N^{−θ} for some parameter θ. We derive its hydrodynamic limit as N goes to infinity, in the diffusive space-time scaling, when the initial density profile is supercritical. More precisely, the macroscopic density of particles evolves in the bulk according to a fast diffusion equation as in the periodic case, which is now subject to boundary conditions that can be of Dirichlet, Robin or Neumann type depending on the parameter θ. In the Dirichlet case, the FEP exhibits a very peculiar behaviour: unlike for the classical SSEP, and due to the two-phased nature of FEP, the reservoirs impose boundary densities which do not coincide with their equilibrium densities. The proof is based on the classical entropy method, but requires significant adaptations to account for the FEP’s non-product stationary states and to deal with the non-equilibrium settin
Search for nonresonant new physics signals in high-mass dilepton events produced in association with b-tagged jets in proton-proton collisions at = 13 TeV
No full textInternational audienceA search for nonresonant new physics phenomena in high-mass dilepton events produced in association with b-tagged jets is performed using proton-proton collision data collected in 20162018 by the CMS experiment at the CERN LHC, at a center-of-mass energy of 13 TeV corresponding to an integrated luminosity of 138 fb. The analysis considers two effective field theory models with dimension-six operators; involving four-fermion contact interactions between two leptons (, electrons or muons) and b or s quarks (bb and bs). Two lepton flavor combinations (ee and ) are required and events are classified as having 0, 1, and 2 b-tagged jets in the final state. No significant excess is observed over the standard model backgrounds. Upper limits are set on the production cross section of the new physics signals. These translate into lower limits on the energy scale of 6.9 to 9.0 TeV in the bb model, depending on model parameters, and on the ratio of energy scale and effective coupling, , of 2.0 to 2.6 TeV in the bs model. The latter represent the most stringent limits on this model to date. Lepton flavor universality is also tested by comparing the dielectron and dimuon mass spectra for different b-tagged jet multiplicities. No significant deviation from the standard model expectation of unity is observed
Euclid Quick Data Release (Q1). A probabilistic classification of quenched galaxies
No full textInternational audienceInvestigating the drivers of the quenching of star formation in galaxies is key to understanding their evolution. The Euclid mission will provide rich spatial and spectral data from optical to infrared wavelengths for millions of galaxies, enabling precise measurements of their star formation histories. Using the first Euclid Quick Data Release (Q1), we developed a probabilistic classification framework, that combines the average specific star-formation rate () inferred over two timescales ( yr), to categorize galaxies as `Ageing' (secularly evolving), `Quenched' (recently halted star formation), or `Retired' (dominated by old stars). We validated this methodology using synthetic observations from the IllustrisTNG simulation. Two classification methods were employed: a probabilistic approach, integrating posterior distributions, and a model-driven method optimizing sample purity and completeness using IllustrisTNG. At and , we obtain Euclid class fractions of 68-72%, 8-17%, and 14-19% for Ageing, Quenched, and Retired populations, respectively, consistent with previous studies. The evolution with redshift shows increasing/decreasing fraction of Ageing/Retired galaxies. The fraction of quenched systems shows a weaker dependence on stellar mass and redshift, varying between 5% and 15%. We analysed the mass-size-metallicity relation for each population. Ageing galaxies generally exhibit disc morphologies and low metallicities. Retired galaxies show compact structures and enhanced chemical enrichment, while Quenched galaxies form an intermediate population, more compact and chemically evolved than Ageing systems. This work demonstrates Euclid's great potential for elucidating the physical nature of the quenching mechanisms that govern galaxy evolution
Euclid Quick Data Release (Q1). First detections from the galaxy cluster workflow
No full textInternational audienceThe first survey data release by the Euclid mission covers approximately in the Euclid Deep Fields to the same depth as the Euclid Wide Survey. This paper showcases, for the first time, the performance of cluster finders on Euclid data and presents examples of validated clusters in the Quick Release 1 (Q1) imaging data. We identify clusters using two algorithms (AMICO and PZWav) implemented in the Euclid cluster-detection pipeline. We explore the internal consistency of detections from the two codes, and cross-match detections with known clusters from other surveys using external multi-wavelength and spectroscopic data sets. This enables assessment of the Euclid photometric redshift accuracy and also of systematics such as mis-centring between the optical cluster centre and centres based on X-ray and/or Sunyaev--Zeldovich observations. We report 426 joint PZWav and AMICO-detected clusters with high signal-to-noise ratios over the full Q1 area in the redshift range . The chosen redshift and signal-to-noise thresholds are motivated by the photometric quality of the early Euclid data. We provide richness estimates for each of the Euclid-detected clusters and show its correlation with various external cluster mass proxies. Out of the full sample, 77 systems are potentially new to the literature. Overall, the Q1 cluster catalogue demonstrates a successful validation of the workflow ahead of the Euclid Data Release 1, based on the consistency of internal and external properties of Euclid-detected clusters
Language and Screen-Based Multimodal Communication
No full textCollection online "Social Sciences"The main objective of this article is to explore how language and languaging are impacted by the mediatization of digital technologies. First we point to the main characteristics of screen-based communication, that is multimodality, interactivity, mobility, relationship to time and technogenres. Then we address three current research issues: multilingualism and translations, discrimination and hate speech, and automatic processing of languages in large language models
Local specialists' experience and skills in animal behaviour studies: insights from wild chimpanzee field assistants
No full textInternational audienceThe study of wild animal behaviour and cognition has greatly benefited from the foundational work of local specialists (LSs), particularly field assistants. In primate research, long-term studies rely on accurate identification and tracking of individuals—a skill often honed by LSs and passed on to international specialists (ISs). Despite growing recognition in publications, LSs' scientific contributions often remain undervalued. Here, we show that LSs at the Budongo Conservation Field Station (Uganda) reliably extract acoustic information (caller identity, sex and age, call components and production context) from long-distance pant hoot calls produced by wild chimpanzees. Importantly, LSs significantly outperform ISs at identifying individuals (LS accuracy = 50% (95% confidence interval (CI): 45–56%); IS accuracy = 8% (95% CI: 5–11%)), an important skill for recognizing and locating individuals in dense forests. LSs' performance was positively associated with duration of working experience. Given the limited field time of ISs (typically 1–2 years), LSs' expertise and longer commitment (mean 16.75 years) represent an essential yet underacknowledged scientific resource. Our study highlights LSs' critical role in ethological research—not only enhancing skills and data quality, but also potentially helping address both ethical (e.g. community involvement) and environmental (e.g. travel carbon footprint) challenges linked to fieldwork in remote locations
