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Spreading properties of the Fisher--KPP equation when the intrinsic growth rate is maximal in a moving patch of bounded size
No full textInternational audienceThis paper is concerned with spreading properties of space-time heterogeneous Fisher–KPP equations in one space dimension. We focus on the case of everywhere favorable environment with three different zones, a left half-line with slow or intermediate growth, a central patch with fast growth and a right half-line with slow or intermediate growth. The central patch moves at various speeds. The behavior of the front changes drastically depending on the speed of the central patch. Among other things, intriguing phenomena such as nonlocal pulling and locking may occur, which would make the behavior of the front further complicated. The problem we discuss here is closely related to questions in biomathematical modelling. By considering several special cases, we illustrate the remarkable diversity of possible behaviors. In particular, when the central patch has constant size and constant speed, we provide a complete set of explicit formulas for the spreading speed
Enhanced propene oxidation over yttrium-doped cryptomelane MnO<sub>2</sub> catalysts: synergistic effects of structural modification and oxygen mobility
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A mesoscale Eulerian numerical method for short-range repulsion in interfacial dynamics
No full textInternational audienceThe dynamics of bubble and droplet coalescence and repulsion are critical in a variety of natural and industrial multiphase systems. Their direct numerical simulation (DNS) remains challenging due to the multiscale nature of interfacial interactions. This study presents a mesoscale numerical approach that incorporates a repulsive disjoining pressure into an Eulerian framework to model near-contact interactions without explicitly resolving nanoscale forces. The method computes interfacial distances through a transport equation, enabling efficient and scalable implementation across parallel computing architectures. Unlike traditional marker-based or interface-tracking methods, the approach is independant of the number of bubbles or droplets in the domain. The method is validated on representative test cases, including droplet collisions and static foam networks, and is shown to accurately capture both dynamic inertial effects and quasi-static configurations. Notably, it enables DNS of wet foams with reduced liquid fractions compared to conventional level-set methods where repulsive interactions are not accounted for. This approach lays the foundation for simulating more realistic foam structures and analyzing destabilization phenomena such as drainage and coarsening, thus contributing to the predictive modeling of complex gas-liquid systems
Opportunities from energy-loss near-edge fine structure analysis to track chemical and structural damage in zircon
No full textInternational audienceZircon (ZrSiO4) is the oldest-known mineral of Earth and an ubiquitous silicate in geochronology. More specifically, the accumulation of alpha decay damage in zircon over time significantly affects its physical and chemical properties, and can lead to a disturbance of the ages measured in this mineral. Therefore, analytical tools that enable comprehensive structural and chemical information at the nanoscale in this compound are highly sought after. In this context, we explore the electron energy-loss fine structures resulting from the excitation of O1s and Si2p core electrons in zircon, which are interpreted from ab initio calculations in a single-particle framework. An excellent agreement is obtained between the experimental and calculated fine structures, emphasizing the large distortion of the final electronic states induced by the core-hole potential. The O-K edge is particularly rich in information, with intense peaks dominated by O2p - Zr4d and O2p - Si3sp hybrids. This work suggests that the near-edge structures from the O1s and Si2p excitations accessible from electron energy-loss spectroscopy or X-ray absorption spectroscopy could be used as tools to follow, interpret and understand structural and chemical modifications in zircon subject to natural radiation damage. We illustrate the potential of this approach through the evolution of near-edge fine structures in a zircon sample that exhibits a locally amorphized zone formed by ultrafast laser excitation
Tailoring nanometric vanadium dioxide morphology to tune thermochromic optical properties
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Counteracting effects of eutrophication on the photochemical reactivity of dissolved organic matter in reservoirs
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A Scaled Poisson Bayesian Model for Viral Epidemic Monitoring
No full textInternational audienceMonitoring an ongoing epidemic requires accurate, trustworthy and easy to use tools, capable of handling low quality data. Extending existing epidemiological models quantifying the propagation intensity via a time-varying reproduction number, this work proposes a scaled Poisson model, accounting for large intrinsic variability in infection counts. The associated scaled likelihood is plugged into a Bayesian model with a quasi-noninformative prior. A carefully designed Markov Chain Monte Carlo algorithm yields a point estimate and credibility intervals of the reproduction number. The accuracy and robustness to model misspecification and to scale parameter selection of the proposed estimator is demonstrated through intensive numerical experiments on COVID-19 case counts in different countries and during various phases of the pandemic
Fusion of C+Si at deep sub-barrier energies
No full textInternational audienceThe existence of fusion hindrance is not well established in light heavy-ion systems. Studying slightly heavier cases allows extrapolating the trend to light systems of astrophysical interest. Fusion of 12C + 28Si has been measured down to deep sub-barrier energies, using 28Si beams from the XTU Tandem accelerator of LNL on thin 12C targets. The fusion-evaporation residues were detected by a detector telescope following an electrostatic beam separator, and coincidences between the gamma-ray array AGATA and segmented silicon detectors DSSD were performed, where the evaporated light charged particles were identified by pulse shape analysis. Fusion cross sections have been obtained in the wide range 150 mb-42 nb. Coupled-channel (CC) calculations using a Woods-Saxon potential reproduce the data above 0.1 mb. Below that, hindrance shows up and the CC results overestimate the cross sections which get close to the one-dimensional potential tunnelling limit. This suggests that the coupling strengths gradually vanish, as predicted by the adiabatic model. The hindrance threshold follows a recently updated phenomenological systematics
Non-verbal predication in Old Zamuco
No full textInternational audienceThis chapter describes non-verbal predication in †Old Zamuco, the language that gave its name to the Zamucoan family (southeastern Bolivia, northern Paraguay). Old Zamuco is the most conservative Zamucoan language, which is also reflected in non-verbal predication. After introducing Old Zamuco and its main features, the chapter is organized according to the semantic types of non-verbal predication: identity and inclusion predication, adverbial predication, existential predication, possessive predication, quantification and ostension. It then addresses the interaction of non-verbal predication with word classes, negation, TAM features and complex constructions