From Dark Matter to the Earth's Deep Interior: There and Back Again

This thesis is a two-way transfer of knowledge between cosmology and seismology, aiming to substantially advance imaging methods and uncertainty quantification in both fields. I develop a method using wavelets to simulate the uncertainty in a set of existing global seismic tomography images to assess the robustness of mantle plume-like structures. Several plumes are identified, including one that is rarely discussed in the seismological literature. I present a new classification of the most likely deep mantle plumes from my automated method, potentially resolving past discrepancies between deep mantle plumes inferred by visual analysis of tomography models and other geophysical data. Following on from this, I create new images of the upper-most mantle and their associated uncertainties using a sparsity-promoting wavelet prior and an advanced probabilistic inversion scheme. These new images exhibit the expected tectonic features such as plate boundaries and continental cratons. Importantly, the uncertainties obtained are physically reasonable and informative, in that they reflect the heterogenous data distribution and also highlight artefacts due to an incomplete forward model. These inversions are a first step towards building a fully probabilistic upper-mantle model in a sparse wavelet basis. I then apply the same advanced probabilistic method to the problem of full-sky cosmological mass-mapping. However, this is severely limited by the computational complexity of high-resolution spherical harmonic transforms. In response to this, I use, for the first time in cosmology, a trans-dimensional algorithm to build galaxy cluster-scale mass-maps. This new approach performs better than the standard mass-mapping method, with the added benefit that uncertainties are naturally recovered. With more accurate mass-maps and uncertainties, this method will be a valuable tool for cosmological inference with the new high-resolution data expected from upcoming galaxy surveys, potentially providing new insights into the interactions of dark matter particles in colliding galaxy cluster systems

A short note on rank-2 relaxation for waveform inversion

This note is a first attempt to perform waveform inversion by utilizing recent developments in semidefinite relaxations for polynomial equations to mitigate non-convexity. The approach consists in reformulating the inverse problem as a set of constraints on a low-rank moment matrix in a higher-dimensional space. While this idea has mostly been a theoretical curiosity so far, the novelty of this note is the suggestion that a modified adjoint-state method enables algorithmic scalability of the relaxed formulation to standard 2D community models in geophysical imaging. Numerical experiments show that the new formulation leads to a modest increase in the basin of attraction of least-squares waveform inversion.TOTAL (Firm)Belgian National Foundation for Scientific ResearchMIT International Science and Technology InitiativesUnited States. Air Force. Office of Scientific ResearchUnited States. Office of Naval ResearchNational Science Foundation (U.S.

On the impact of the vertical resolution on chemistry-transport modelling

International audienceThis paper presents a sensitivity analysis of the modelling of air pollutant concentrations in the surface layer with the WRF/CHIMERE models. The influence of the vertical resolution near the surface is studied. The simulations are carried out over two periods (winter and summer 2009) over the Paris area. Three model configurations are used: (i) the CHIMERE mesh used for the PREVAIR forecast (8 levels from 995 to 500 hPa), (ii) a mesh refined along the whole vertical axis (20 levels from 995 to 500 hPa) and (iii) a mesh with a refinement near the surface (9 levels from 999 to 500 hPa). The results are discussed in terms of differences on surface concentrations between the reference case and an improved resolution. Adding a point close to the surface appears to be important mainly for high nocturnal concentrations in very stable boundary layers. Refining the vertical mesh, with 20 levels instead of 8, enables to model new structures in the well mixed boundary layer, but with a moderate impact at the surface. It is shown that the different model configurations lead to changes of a few mu g m(-3) at most, showing that the vertical mesh is not the most sensitive factor in chemistry-transport modelling when results are compared to surface measurements. This finding validates the fact that a simplified vertical mesh is suitable for air quality forecasting even if an improved vertical resolution close to the ground is important to take into account the urban increment

Investor Behavioral Anomalies in Wartime Uncertainty: The Case of North Kivu in DRC

After combining the CPT1, SARF2, and greed and grievances dynamical systems, and the overreactions models, we conducted a questionnaire survey with a sample of 921 investors from North Kivu in the DRC, of which 879 (95%) were in the service sector. The evaluation of the risk taken by investors is carried out at two levels. At the first level, it is assessed according to an informational asymmetry focused on estimating probabilities describing the outlook for results over three years (from 2014 to 2016). At the second level, the analysis describes the investors’ attitude regarding their level of profit expectation as an endogenous variable of heuristic optimization, cognitive bias, and self-expressive bias. The results show that the anomalies described in the interactive behavior of N-K investors during wartime uncertainty stem from a plurality of attitudes reflecting an ambiguity of choices dominated by a sub-reaction at the base of reluctance and a loss of opportunity in the market

Pollution atmosphérique et climat

National audienceClimate change and air quality are closely related: through the policy measures implemented to mitigate these major environmental threats but also through the geophysical processes that drive them. We designed, developed and implemented a comprehensive regional air quality and climate modelling system to investigate future air quality in Europe taking into account the combined pressure of future climate change and long range transport. Using the prospective scenarios of the last generation of pathways for both climate change (emissions of well mixed greenhouse gases) and air pollutants, we can provide a quantitative view into the possible future air quality in Europe. We find that ozone pollution will decrease substantially under the most stringent scenario but the efforts of the air quality legislation will be adversely compensated by the penalty of global warming and long range transport for the business as usual scenario. For particulate matter, the projected reduction of emissions efficiently reduces exposure levels.Changement climatique et qualité de l'air sont intimement liés : à travers les politiques de gestion mises en oeuvre pour atténuer ces menaces environnementales majeures mais aussi à travers les processus géophysiques qui les gouvernent. Afin de pouvoir étudier l'évolution de la pollution atmosphérique en Europe en prenant en compte l'influence conjointe du changement climatique et du transport à longue distance, nous avons conçu, développé et mis en oeuvre un système complet de modélisation régionale du climat et de la qualité de l'air. En utilisant des scénarios prospectifs de dernière génération relatifs au changement climatique (émissions de gaz à effet de serre) mais aussi pour les polluants à courte durée de vie, nous avons pu proposer une quantification de l'évolution future de la qualité de l'air en Europe. D'après le scénario le plus volontariste, la pollution liée à l'ozone sera réduite de manière substantielle mais les efforts positifs induits par les politiques de gestion de la qualité de l'air seront contrebalancés par le changement climatique et le transport à longue distance pour le scénario statu-quo. En ce qui concerne les particules, les réductions d'émissions futures réduiront de manière efficace les niveaux d'exposition

Evaluation of the chimere model at high resolution over Europe : focus on urban area

International audienc

Population screening for liver fibrosis: Toward early diagnosis and intervention for chronic liver diseases

Population screening; Liver fibrosis; Early diagnosisCribratge de població; Fibrosi hepàtica; Diagnòstic precoçCribado de población; Fibrosis hepática; Diagnóstico precozCirrhosis, highly prevalent worldwide, develops after years of hepatic inflammation triggering progressive fibrosis. Currently, the main etiologies of cirrhosis are non-alcoholic fatty liver disease and alcohol-related liver disease, although chronic hepatitis B and C infections are still major etiological factors in some areas of the world. Recent studies have shown that liver fibrosis can be assessed with relatively high accuracy noninvasively by serological tests, transient elastography, and radiological methods. These modalities may be utilized for screening for liver fibrosis in at-risk populations. Thus far, a limited number of population-based studies using noninvasive tests in different areas of the world indicate that a significant percentage of subjects without known liver disease (around 5% in general populations and a higher rate −18% to 27%-in populations with risk factors for liver disease) have significant undetected liver fibrosis or established cirrhosis. Larger international studies are required to show the harms and benefits before concluding that screening for liver fibrosis should be applied to populations at risk for chronic liver diseases. Screening for liver fibrosis has the potential for changing the current approach from diagnosing chronic liver diseases late when patients have already developed complications of cirrhosis to diagnosing liver fibrosis in asymptomatic subjects providing the opportunity of preventing disease progression.LiverScreen Consortium and the European Commission under the H20/20 program (847989); AGAUR (2017SGR-01281); Centro de Investigacion Biomedica en Enfermedades Hepaticas y Digestivas; Fundación de Investigación Sanitaria, cofunded by Instituto Carlos III–Subdirección General de Evaluación and the European Regional Development Fund (PI18/01330, PI18/00662, and PI18/00862); and Gilead’s Investigator–sponsored research program (IN-ES-989-5309