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Plasma dynamics of an Al plasma in AlTi or AlAu mixtures heated by the PICO2000 ultra-intense laser pulse
No full textInternational audienceThe rapid cooling dynamics of thin solid foils heated by an ultra-intense (∼1018 Wcm−2) picosecond laser pulse are experimentally studied using three independent diagnostics based on a time-integrated and time-resolved x-ray emission spectroscopy as well as 2D x-ray imaging. Targets consist of plastic foils with buried Al, Al42Ti58, or Al85Au15 layers, where Al emission lines are used to infer the plasma conditions. Our measurements indicate that the Al K-shell emission occurs over a shorter duration and from a narrower region in AlTi or AlAu mixtures compared to pure Al samples, and that the average temperature is lower when increasing the atomic number of the high-Z element in the mixture. The TROLL radiation hydrodynamics code, coupled with the SAPHyR collisional radiative model, is used to infer the plasma heating conditions. This numerical platform has been able to consistently simulate the experimental results from the three diagnostics, allowing us to bypass the use of expensive PIC simulations. 2D simulations clearly show the importance of taking into account the particular 2D shape of the energy deposition, according to the measured radial laser intensity profile. The satisfactory agreement between simulations and measurements suggests that, for the relatively long laser pulse considered (∼1.3 ps), the target bulk is primarily heated through direct collisions with fast electrons. Furthermore, simulations indicate that significant radiative cooling is observed in AlAu targets
Joint neutrino oscillation analysis from the T2K and NOvA experiments
No full textInternational audienceThe landmark discovery that neutrinos have mass and can change type (or "flavor") as they propagate -- a process called neutrino oscillation -- has opened up a rich array of theoretical and experimental questions being actively pursued today. Neutrino oscillation remains the most powerful experimental tool for addressing many of these questions, including whether neutrinos violate charge-parity (CP) symmetry, which has possible connections to the unexplained preponderance of matter over antimatter in the universe. Oscillation measurements also probe the mass-squared differences between the different neutrino mass states (), whether there are two light states and a heavier one (normal ordering) or vice versa (inverted ordering), and the structure of neutrino mass and flavor mixing. Here, we carry out the first joint analysis of data sets from NOvA and T2K, the two currently operating long-baseline neutrino oscillation experiments (hundreds of kilometers of neutrino travel distance), taking advantage of our complementary experimental designs and setting new constraints on several neutrino sector parameters. This analysis provides new precision on the mass difference, finding in the normal (inverted) ordering, as well as a interval on of in the normal (inverted) ordering. The data show no strong preference for either mass ordering, but notably if inverted ordering were assumed true within the three-flavor mixing paradigm, then our results would provide evidence of CP symmetry violation in the lepton sector
C. Favre - Dynamical degree 3: Summer School 2025 - Cremona Group
No full textDynamical degrees were introduced by Russakovskii and Shiffman in 1997. They measure the growth of preimages of subvarieties of a fixed dominant rational map of a projective variety, and control many dynamical features of this map. In this first set of lectures, we shall define dynamical degrees using positivity properties of divisor classes, and explain how to compute them in low dimension and in some significant examples
The transformation of complex product industries: The case of the space industry
No full textInternational audienc
Hybrid stochastic-structural modelling of particle-laden turbulent flows based on wavelet reconstruction
No full textReduced-order modelling and simulation of turbulent particle-laden flows is required in numerous configurations, where the whole spectrum of turbulent scales through DNS is out of reach. Whereas structural or stochastic models have be derived in order to provide a synthetic turbulent model for the non-resolved scales of the gaseous flow field, reproducing preferential concentration is challenging because it requires capturing both spatial and temporal correlations. We present a novel reduced-order framework that overcomes this limitation by combining wavelet-based structural modelling with stochastic evolution. Using compactly supported divergence-free wavelets within a multiresolution analysis, the method provides direct control over spatial structures and correlations of synthetic multiscale velocity fields. In particular, a dedicated procedure enables to enforce a prescribed turbulent energy spectrum despite the nonlocal contribution in Fourier space of the wavelet basis functions. The stochastic evolution of wavelet coefficients further ensures consistent temporal correlations. The proposed framework is evaluated in homogeneous isotropic turbulence under a fully reduced setting, where all turbulent scales must be provided by the model. Resultsshow that it accurately reproduces preferential concentration across a wide range of Stokes numbers, achieving closer agreement with DNS data than classical Fourierbased kinematic simulations. This establishes a versatile and physically consistent turbulence model that combines structural fidelity with stochastic dynamics, offering a new tool to investigate particle–turbulence interactions.</p
Sensitivity Analysis of Emissions Markets: A Discrete-Time Radner Equilibrium Approach
No full textEmissions markets play a crucial role in reducing pollution by encouraging firms to minimize costs.However, their structure heavily relies on the decisions of policymakers, on the future economic activities, and on the availability of abatement technologies.This study examines how changes in regulatory standards, firms' abatement costs, and emissions levels affect allowance prices and firms' efforts to reduce emissions. This is done in a Radner equilibrium framework encompassing inter-temporal decision-making, uncertainty, and a comprehensive assessment of the market dynamics and outcomes.The results of this research have the potential to assist policymakers in enhancing the structure and efficiency of emissions trading systems, through an in-depth comprehension of the reactions of market stakeholders towards different market situations
Removing Behavioral Barriers to Energy Renovation: A Discrete Choice Experiment
No full textThrough a discrete choice experiment conducted among French homeowners, we determine whether easing financial constraints through two financing programmes (third-party financing and Energy Efficient Mortgages) leads to an increase in the adoption rate of energy-efficient renovations. We examine whether the introduction of a contractual mechanism that intrinsically promotes trust between the parties (one-stop-shop) can increase the adoption rate.Among other things, our study reveals certain preferences among households with regard to financing energy-efficient home renovations and assesses certain cognitive biases. We find that both financing programmes increase the probability of choosing an energy renovation over the opt-out option. Nevertheless, participants exposed to the mortgage programme have a preference for the status quo (not renovating), unlike those exposed to third-party financing.With the latter financing programme, the effectiveness of the work seems guaranteed, unlike with the mortgage. This explains why the group offered the energy-efficient mortgage is more inclined to choose renovation scenarios that include an administrative facilitator, highlighting the importance of procedural support and risk transfer in the decision-making process.</p
Ultrafast photooxidation of semireduced flavin in fatty acid photodecarboxylase
No full textInternational audienceThe initial photoproduct of the natural photoenzyme fatty acid photodecarboxylase involves the flavin anion radical flavin adenine dinucleotide (FAD •– ). Using spectrally resolved ultrafast transient absorption spectroscopy, we demonstrate that FAD •– photoexcitation in the absence of substrate leads to the formation of the oxidized flavin FAD ox (the resting state in the catalytic cycle) within 100 femtoseconds. While this feature is similar to that occurring in flavoprotein oxidases, the ensuing photocycle is more complex. Upon excitation at the lowest-energy transition, the ejected electron is initially captured as a hydrated electron ( e – H ) before transferring to a secondary acceptor in 2.5 picoseconds and returning to the flavin in 37 picoseconds. This implies that e – H can be generated within a protein environment, an unprecedented finding. This assessment is supported by molecular dynamics simulations showing an expansion of the flavin-binding pocket without substrate, allowing water molecules to fill the void. Our results may pave the way to developing unconventional photocatalytic processes
SpeCT: A state-of-the-art tool to calculate correlated-k tables and continua of CO2-H2O-N2 gas mixtures
No full textInternational audienceA key challenge in modeling (exo)planetary atmospheres lies in generating extensive opacity datasets that cover the wide variety of possible atmospheric composition, pressure, and temperature conditions. This critical step requires specific knowledge and can be considerably time-consuming. To circumvent this issue, most available codes approximate the total opacity by summing the contributions of individual molecular species during the radiative transfer calculation. This approach neglects inter-species interactions, which can be an issue for precisely estimating the climate of planets. To produce accurate opacity data, such as correlated-k tables, χ factor corrections of the far wings of the line profile are required. We propose an update of the χ factors of CO2 absorption lines that are relevant for terrestrial planets (pure CO2, CO2-N2, and CO2-H2O). These new factors are already implemented in an original user-friendly open-source tool, named SpeCT, designed to calculate high-resolution spectra. This tool produces correlated-k tables for mixtures made of H2O, CO2, and N2, and accounts for inter-species broadening. In order to facilitate future updates of these χ factors, we also provide a review of all the relevant laboratory measurements available in the literature for the considered mixtures. Finally, we provide in this work eight different correlated-k tables and continua for pure CO2, CO2-N2, CO2-H2O, and CO2-H2O-N2 mixtures based on the MT_CKD formalism (for H2O), and calculated using SpeCT. These opacity data can be used to study various planets and atmospheric conditions, such as Earth’s paleo-climates, Mars, Venus, Magma ocean exoplanets, and telluric exoplanets
Development of a rabbit model of uterine rupture after caesarean section, Histological, biomechanical and polarimetric analysis of the uterine tissue
No full textInternational audienceUterine rupture is a major complication of caesarean section (CS) associated with a high foetal and maternal morbidity. The objective is to develop an in-vivo model of uterus healing and rupture after CS in order to analyse histological phenomena controlling scarring tissue development and potential cause of defects. Eighteen pregnant primiparous female rabbits were bred naturally. At caesarean, after 28 days of gestation, foetuses were either extracted through a longitudinal incision in one of the uterine horns (“CS horn”) or via a short incision at the tip of the contralateral horn (“control horn”). The uterine horns were sutured by single layer, all by the same surgeon. They were mated again 14 days later and euthanized at G28. Genital tracts were collected for histological, biomechanical and polarimetric analyses. Macroscopically, 2/18 presented a dehiscence and 1/18 a spontaneous rupture. The mean thickness of the scarred area was significantly lower 0.9 mm [0.7-1.4] that the non-scarring area on CS horns 2.2 [1.6-2.3] or control horns 2 [1.5-2.3] (p<0.0001). The scar zone was statistically more fibrous (p<0.0001), containing fewer vessels (p=0.03) and oestrogen (p<0.001) and progesterone receptors (p<0.0001). After balloon inflation, ruptured occurred in the scar zone in 8 out of 17 cases (47%). Polarimetry revealed that the scar zone was statistically inhomogeneous (73%). Multifactorial analysis allowed to identify groups with poor uterine healing and less resistant to rupture (balloon inflation) mostly in case of thin myometrium in the scar and a group with strong resistant to rupture and correct healing characteristics. Lay summary Caesarean section rates are rising across the world. When a caesarean section is carried out, it can lead to scarring on the uterus that can affect its resistance to pressure. During the next pregnancy, the uterus can tear, increasing risks to the mother and baby. We carried out caesarean sections in a rabbit, allowing us to analyse the scar on the uterus, the healing and tissue resistance. The scarred part of the uterus was statistically thinner, more fibrous and contained fewer vessels and hormone receptors than the area without scarring. Under similar conditions, poor healing was observed in some animals, reducing resistance in following pregnancies. These results suggest that individual and genetic factor have an effect on healing after a caesarean section. This study may enable us to improve our knowledge and management care for patients who have a caesarean section in order to reduce complications