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Across land, sea, and mountains: sulphate aerosol sources and transport dynamics over the northern Apennines
No full textInternational audienceIn this study, we combine aerosol observations with high-resolution Eulerian (WRF-CHIMERE) and Lagrangian (FLEXPART) modelling to investigate the source regions, emission sources, transport pathways, and chemical transformation of sulphate aerosols at the high-altitude Monte Cimone station during July 2017. Our analysis shows that marine air masses are linked to higher levels of sulphate at Monte Cimone. In particular, the sea plays a dominant role in enhancing the oxidation of sulphur dioxide (SO2) into sulphate due to prolonged exposure to elevated hydroxyl radical (OH) concentrations over the sea. At the same time, sensitivity simulations reveal that industrial emissions contribute significantly to sulphate levels at Monte Cimone, even when air masses have spent a long time travelling over the sea. Furthermore, examination of vertical atmospheric dynamics indicates that free tropospheric air masses favour higher concentrations of sulphuric acid likely due to lower condensation sink (CS) conditions in the free troposphere (FT). In contrast, boundary layer conditions were found to enhance the transport of dimethyl sulphide (DMS) oxidation products, meaning that, over the Mediterranean Sea, DMS and its oxidation products do not reach the FT efficiently. Our results highlight the complex interaction between marine and terrestrial sources, atmospheric chemistry, and transport mechanisms in shaping sulphate aerosol levels at high-altitude sites. They also provide valuable insights into sulphate sources and transport processes over large geographical area
Lifecycle Wages and Human Capital Investments: Selection and Missing Data
No full textInternational audienceWe derive wage equations with individual specific coefficients from a structural model of human capital investment over the life cycle. This model allows for interruptions in labour market participation and deals with missing data and attrition problems. We propose a new framework that deals with missingness at random and is based on factor decompositions that allow for flexible control of selection. Our approach leads to an interactive effect wage specification, which we estimate using long administrative panel data on male wages in the private sector in France. A structural function approach shows that interruptions negatively affect average wages. Interestingly, they also negatively affect the inter-decile range of wages after twenty years. This is only partly due to the fact that interruptions are endogenous
Adaptive stratified Monte Carlo using decision trees
No full textInternational audienceIt has been known for a long time that stratification is one possible strategy to obtain higher convergence rates for the Monte Carlo estimation of integrals over the hyper-cube [0,1]8 of dimension . However, stratified estimators such as Haber's are not practical as grows, as they require k evaluations for some k≥2. We propose an adaptive stratification strategy, where the strata are derived from a decision tree applied to a preliminary sample. We show that this strategy leads to higher convergence rates, that is, the corresponding estimators converge at rate (N-1/2r) for some r > 0 for certain classes of functions. Empirically, we show through numerical experiments that the method may improve on standard Monte Carlo even when is large
Convolutions on partially regular recurrent lattices
No full textInternational audiencePartially regular recurrent lattices, are k-space grids that we propose, which consist of a central regular region that is extended using a recurrence relation, resulting in an asymptotically logarithmic lattice structure. Such a lattice can be used to model the turbulent cascade over a very large range of scales covered by the recurrent part, while keeping the large scale eddies mainly in the regular part. Here we propose a novel pseudo-spectral algorithm for computing the convolutions over such a lattice, using an overlapping partition of its different parts, using the fact that the interactions in the recurrent part of the lattice are limited, in each direction, to a small number of elements linked through the recurrence relation. We compare the results with a full grid, dense, fast Fourier transform (fft) based convolution, where the nonexistent elements on the full grid are set to zero, and show that the difference remains within a few orders of the machine precision. The algorithm in two dimensions uses one fft for the regular grid, and bunch of smaller ffts for the rest of the points, either elongated to match the length of the regular part of the grid in one dimension or even smaller ffts (typically) to include the interactions between recurrent parts of the lattice. The algorithm can be trivially generalized to arbitrary number of dimensions
Strategies for Quasi‐2D Integration in Perovskite p‐i‐n Solar Cells
No full textInternational audienceUntil recently, bulky ammonium cations, or 2D cations, one of the most promising avenues for interface passivation, have been applied almost exclusively to the p‐type interface of the n‐i‐p architecture. As the perovskite photovoltaics community gradually moves toward the inverse architecture (p‐i‐n), the question of whether to integrate 3D/2D interfaces at the interface between perovskite and the N‐type contact layer is only natural. By comparing different integration strategies, this work highlights the importance of solvent engineering and additive strategies to integrate quasi‐2D perovskite in p‐i‐n devices. It is demonstrated that these strategies enable almost complete conversion of lead iodide (PbI 2 ) excess through its conversion to quasi‐2D phases, result in a quasi‐Fermi level splitting (QFLS) gain of up to 40 meV, and promote the emergence of quasi‐2D phases of higher dimensions, which are less detrimental to electron extraction. Increasing device efficiency and stability using 2D cations, however, remains a challenge for the p‐i‐n architecture due to the quasi‐2D phases’ intrinsic properties and interfacial mechanical stress at the nanoscale. It is anticipated that, to take full advantage of quasi‐2D perovskites’ superior stability and passivating power, one needs to gain control over the homogeneity, thickness, and phase of the low‐dimensionality layer
Improved phenomenology of transition distribution amplitudes
No full textInternational audienceTo study cross sections and polarization asymmetries for the processes and in the backward region, we develop a flexible phenomenological model for nucleon-to-pion transition distribution amplitudes ( TDAs), which are used in the QCD collinear factorization description of the scattering amplitudes. Our model is based on the two-component factorized Ansatz for the corresponding spectral densities, quadruple distribution. It takes into account the constraints for TDAs arising from the threshold pion production theorem and also includes a forward limit contribution that can be fitted to experimental data. We examine the sensitivity of observable predictions to various modelling assumptions
Tunability of ice supersaturation in the upper troposphere and lower stratosphere in the LMDZ atmospheric model
No full textModeling the Coupled and Decoupled states of Polar Boundary-Layer Mixed-Phase Clouds
No full textInternational audienceRepresenting mixed-phase clouds (MPCs) is a long-standing challenge for climate models, with major consequences regarding the simulation of radiative fluxes at high-latitudes and uncertainties in future cryosphere melting estimates. Low-level boundary-layer MPCs that prevail at high-latitudes can be either coupled or decoupled to the surface, which modulates their dynamical and microphysical properties. This study leverages a recent physically-based parameterization of phase partitioning considering an explicit coupling between microphysics and subgrid-scale dynamics and involving direct interactions between the cloud and turbulent diffusion schemes. This parameterization makes it possible to capture the structure of the decoupled state of polar boundary-layer MPCs – with a supercooled liquid dominated cloud-top sitting on top of precipitating ice crystals – in single column simulations with the LMDZ Atmospheric General Circulation Model. The positive feedback loop involving cloud-top radiative cooling induced by supercooled liquid droplets, subsequent buoyancy production of turbulence as well as the supercooled liquid water production associated with turbulence, is captured by the model. However, the liquid and cloud ice water path remain slightly underestimated which may be due to an underestimation of the net upward water flux from low layers. The paper further shows that accounting for the detrainment of shallow convective plume's air when diagnosing the in-cloud supersaturation makes it possible to capture the overall vertical structure of surface-coupled clouds, with realistic liquid and ice water contents. A parameteric sensitivity analysis further shows the importance of properly calibrating the parameter controling the supercooled liquid water production term by subgrid turbulence
Automated Nanosecond Plasma Jets for Targeted Medical Treatments
No full textInternational audienceCold atmospheric plasma (CAP) has emerged as a transformative tool in medicine, with applications ranging from selective cancer cell inactivation to the acceleration of wound healing. The therapeutic effects of CAP are largely mediated by reactive oxygen and nitrogen species (ROS/RNS), whose precise composition and concentration must be tightly controlled for safe and effective treatment. However, in many current systems, human handling introduces variability that compromises treatment reproducibility and limit accurate estimation of introduction of reactive species onto a treated surface.This study addresses the need for standardization in plasma-based therapies by implementing a modified computer numerical control (CNC) plasma treatment platform to automate and precisely control exposure parameters. By removing human variability, this system enables reproducible treatment conditions across multiple experimental sessions. To better understand the chemistry at the point of application, preliminary diagnostics were performed using fiber-enhanced spontaneous Raman backscattering.Our preliminary results suggest that reactive species profiles can be accurately defined along with the plasma plume with minimal invasiveness. Furthermore, the use of hollow core fiber allows for significant enhanced signalling effects due to its ability to increase the interaction length between the probing light source and the gas sample. As such, this work lays the groundwork for developing standardized plasma treatment protocols supported by real-time diagnostics. Ongoing and future studies will focus on integrating more advanced optical techniques and correlating plasma chemistry with biological effects to further improve the reliability and effectiveness of plasma-based medical interventions
Modeling of N2-H2 DC discharges for ammonia production
No full textInternational audienceIn this work we present the on-going validation of a kinetic model for nitrogen-hydrogen plasmas, highlighting the significance of plasma-surface interactions in ammonia production