HAL-Université de Bretagne Occidentale
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Connecting the Atlantic Meridional Overturning Circulation to the Southern Ocean Following the Closure of Equatorial Seaways During the Cenozoic
No full textInternational audienceAbstract Global ocean circulation regulates climate and has undergone significant changes over the Cenozoic. Today, the Atlantic Meridional Overturning Circulation (AMOC) is driven by North Atlantic Deep Water (NADW) formation and Southern Ocean upwelling. By contrast, during the middle Eocene to early Oligocene (48–28 Ma), a restricted Drake Passage was limiting the northern Ekman transport, while a circum‐equatorial current sustained by trade winds promoted low‐latitude upwelling. Our set of simulations with the IPSL‐CM5A2 model reveals that this paleogeographic setting favored proto‐NADW upwelling at low latitudes, confining the AMOC to the Northern Hemisphere. Consequently, the role of southern westerly winds was limited, and the northward heat transport was weaker than in the modern ocean
Learning Human Rhythmic Movements: Adaptive CPGs for Synchronized Virtual Agents
No full textInternational audienceThis paper presents a real-time framework for enabling a virtual agent to learn and synchronize with rhythmic human gestures using bio-inspired control. Each joint-axis of the agent is controlled by a Central Pattern Generator (CPG), a small network of adaptive Hopf oscillators, which continuously learns amplitude, frequency, phase, and offset from streaming motion-capture input. The pipeline maps Kinect V2 skeleton data to a normalized avatar representation, computes per-frame error signals, and updates 75 parallel CPGs at 30\,Hz, allowing fast convergence and real-time operation. Evaluated on a set of ten 60-second rhythmic gestures performed by a professional dancer, the system demonstrates that the CPGs quickly adapt to the human motion and can autonomously reproduce the learned trajectories after the learning process is frozen. This approach provides a compact and interpretable mechanism for sensory–motor coupling between human and virtual agent, with potential applications in creative co-dancing, interactive systems, and motor rehabilitation
Urbanisme et architecture de Narbonne : un reflet des fonctions portuaires de la ville ?
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Higher-order 2D lattices with long-range interactions and their nonlocal continua
No full textInternational audienceThis paper presents the formulation of two-dimensional (2D) square elastic lattices consisting of point-like material particles and incorporating central and angular (non-central) short- and long-range interactions of arbitrary order p . Each particle is assumed to interact with all other particles of the discrete medium along arbitrary directions. At the first-order asymptotic limit, these lattices converge to simple linear elastic continua. The lattice parameters are calibrated such that the asymptotic continuum behaves as a homogeneous, linear elastic, isotropic medium with a free Poisson’s ratio under both plane stress and plane strain conditions. When higher-order terms are retained in the asymptotic expansion, the discrete medium is shown to correspond to higher-order gradient elasticity or, equivalently, at the desired order, to a nonlocal elastic continuum. The exact wave dispersion properties of the generalized lattice with long-range interactions are investigated, with particular emphasis on the role of the discrete kernel. It is demonstrated that, for kernels with monotonically decreasing influence functions, the wave dispersion curves in the first Brillouin zone are monotonic for any interaction order p . We give a first proof from the analytical determination of the roots of the group velocity function, up to p = 5 interactions. Another proof is presented, whatever the number p of interactions, by expressing this gradient function through the Dirichlet kernel. Finally, the paper provides a calibration of nonlocal elasticity models to reproduce the wave dispersion characteristics of the higher-order lattice with long-range interactions. For both isotropic and anisotropic nonlocal models, the characteristic length scales are shown to depend on the interaction order and the shape of the discrete kernel
Airbnb and Returns to Housing Capital: Evidence on Inequality from Administrative Data
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Extreme Mediterranean rainfall impact on sedimentary routing systems: what can we learn from Storm Alex using in situ detrital 10Be?
No full textInternational audienceUnderstanding how extreme meteorological events influence sediment transport is critical for predicting landscape evolution under a changing climate. Detrital cosmogenic 10Be can provide insights into sediment dynamics following extreme rainfall, but high-resolution datasets tracking 10Be variations before and after a storm, alongside long-term records, remain rare.The Var catchment (French Southern Alps) presents a unique case study, as its 10Be signal was well-documented before the October 2020 Storm Alex (>500 mm of rainfall/24 h), which triggered flash floods, mobilized large sediment volumes, and formed a 10 km-long sediment plume in the Mediterranean Sea. We compare 10Be concentrations in river sediments collected pre-storm (2016–2018), and at +7 days, +21 days, +4 months, and +7 months post-storm. We also use a historical offshore sample and contextualize these results with a 75 ka-long 10Be record from deep-sea sediment cores.At the Var outlet, 10Be concentrations initially increased by ∼25 % at +7 and +21 days, attributed to the mobilization of 10Be-rich sediments from the upstream Var and Tinée sub-catchments. Concentrations returned to pre-storm levels within four months, primarily due to dilution with 10Be-poor sediments from the Vésubie sub-catchment fluvioglacial terraces. While short-term 10Be fluctuations at the Var outlet reflect complex sediment sourcing, our comparison with the 0–75 ka record confirms that major glaciation events and potential anthropic influences remain distinguishable, demonstrating that 10Be is a robust proxy of denudation changes, even when extreme events are involved
GATE 10 Monte Carlo particle transport simulation: II. Architecture and innovations
No full textInternational audienceOver the past years, we have developed GATE version 10, a major re-implementation of the long-standing Geant4-based Monte Carlo application for particle and radiation transport simulation in medical physics. This release introduces many new features and significant improvements, most notably a Python-based user interface replacing the legacy static input files. The new functionality of GATE version 10 is described in the part 1 companion paper (Sarrutet al2025 arXiv:2507.09842). The development brought significant challenges. In this paper, we present the solutions that we have developed to overcome these challenges. In particular, we present a modular design that robustly manages the core components of a simulation: particle sources, geometry, physics processes, and data acquisition. The architecture consists of integrated C++ and Python codes. This framework allows for the precise, time-aware generation of primary particles, a critical requirement for accurately modeling positron emission tomography, radionuclide therapies, or prompt-gamma timing systems. We present how GATE 10 handles complex Geant4 physics settings while exposing a simple interface to the user. Furthermore, we describe the methodological solutions that facilitate the seamless integration of advanced physics models and variance reduction techniques. The architecture supports sophisticated scoring of physical quantities (such as Linear Energy Transfer and Relative Biological Effectiveness) and is designed for multithreaded execution. The new user interface allows researchers to script complex simulation workflows and directly couple external tools, such as artificial intelligence models for source generation or detector response. By detailing these architectural innovations, we demonstrate how GATE 10 provides a more powerful and flexible tool for research and innovation in medical physics. This paper is not intended to be a developer guide. Its purpose is to share with the research community in-depth explanations of our development effort that made the new GATE 10 possible
Convergence of higher derivatives of random polynomials with independent roots
No full textLet be a probability measure on , and let be the random polynomial whose zeros are sampled independently from . We study the asymptotic distribution of zeros of high-order derivatives of . We show that, for large classes of measures , the empirical distribution of zeros of the -th derivative converges back to for all derivative orders . This includes all discrete measures and a broad family of measures satisfying a mild dimension-nondegeneracy condition. We further establish a robustness result showing that, for arbitrary , even after adding a vanishing proportion of roots drawn from a dimension-nondegenerate perturbation, the derivative zero measures still converge back to . These results break the previously known logarithmic barrier on the order of differentiation and demonstrate that the limiting root distribution is preserved under differentiation of order growing nearly linearly with the degree
Using Mixed-clay Sediment Gravity Flow Rheology as an Indicator for Flow Velocity and Runout Distance
No full textInternational audienceIt is important to determine whether the dynamics of mixed-clay sediment gravity flows (SGFs) can be predicted from their dominant clay type, because natural SGF deposits can contain mixtures of clay minerals of different cohesive strength, and latitudinal zonation in clay mineral production may influence depositional patterns in mud-rich submarine fans. The present lock-exchange experiments produced high-density SGFs carrying different proportions of strongly cohesive bentonite clay and weakly cohesive kaolinite clay with a fixed 20% volumetric concentration. Head velocity and runout distance of the flows decreased, and starting suspension yield stress increased, as the bentonite fraction increased beyond 20%. However, for bentonite fractions ≤20%, the initial suspensions had lower yield stresses and the flows were more mobile than the pure kaolinite flow, implying that small bentonite fractions reduce the cohesive strength of the suspensions. Predictive equations for the yield stress, head velocity, and runout distance of mixed-clay flows, based on yield stresses of pure-clay constituents, indicate minimal interaction between the constituents for bentonite fractions ≤20%. However, for bentonite fractions >20%, the equations demonstrate an increasingly nonlinear interaction. These results suggest natural SGF dynamics and deposits may be sensitive to the most cohesive clay rather than the dominant clay