ED Mathématiques et Informatique
Multivariate quantiles and regularized optimal transport
by Gauthier THURIN (IMB - Institut de Mathématiques de Bordeaux)
The defense will take place at 10h00 - Salle de conférences 351, cours de la Libération Batiment A33 33 405 TALENCE
in front of the jury composed of
- Jeremie BIGOT - Professeur - Université de Bordeaux - Directeur de these
- Davy PAINDAVEINE - Professeur - Université Libre de Bruxelles - Rapporteur
- Eustasio DEL BARRIO - Professor - Mathematics Research Institute at the University of Valladolid - Rapporteur
- Elena DI-BERNARDINO - Professeure - Université Côte d'Azur - Examinateur
- Francois-Xavier VIALARD - Professeur - Université Gustave Eiffel and INRIA Paris - Examinateur
- Bernard BERCU - Professeur - Université de Bordeaux - CoDirecteur de these
This thesis is concerned with the study of the Monge-Kantorovich quantile function. We first address the crucial question of its estimation, which amounts to solve an optimal transport problem. In particular, we try to take advantage of the knowledge of the reference distribution, that represents additional information compared with the usual algorithms, and which allows us to parameterize the transport potentials by their Fourier series. Doing so, entropic regularization provides two advantages: to build an efficient and convergent algorithm for solving the semi-dual version of our problem, and to obtain a smooth and monotonic empirical quantile function. These considerations are then extended to the study of spherical data, by replacing the Fourier series with spherical harmonics, and by generalizing the entropic map to this non-Euclidean setting. The second main purpose of this thesis is to define new notions of multivariate superquantiles and expected shortfalls, to complement the information provided by the quantiles. These functions characterize the law of a random vector, as well as convergence in distribution under certain assumptions, and have direct applications in multivariate risk analysis, to extend the traditional risk measures of Value-at-Risk and Conditional-Value-at-Risk.
ED Sciences de la Vie et de la Santé
Adaptive potential of Fusarium spp. to climate changes : representativeness, ecophysiology, interactions.
by Marie-Anne GARCIA (MycSA - Mycologie et Sécurité des Aliments)
The defense will take place at 9h00 - Amphithéâtre de l'Institut des Sciences de la Vigne et du Vin Institut des Sciences de la Vigne et du Vin, 210 Chemin de Leysotte, 33140 Villenave d'Ornon
in front of the jury composed of
- Marie FOULONGNE-ORIOL - Chargée de recherche - INRAE - Directeur de these
- Gaétan LE FLOCH - Professeur des universités - ESIAB - Rapporteur
- Matias PASQUALI - Associate Professor - Université de Milan - Rapporteur
- Anne-Lise BOIXEL - Ingénieure de recherche - Université Paris-Saclay - Examinateur
- Cécile ROBIN - Directrice de recherche - INRAE - Examinateur
- Michel HERNOULD - Professeur - Université de Bordeaux - Examinateur
Fusarium Head Blight (FHB) is one of the most devastating fungal diseases affecting cereals worldwide. This disease is caused by a complex of different fungal species, belonging to Fusarium genus, that coexist within the same host plant. Beyond the yield losses due to infection, Fusarium species are able to produce mycotoxins that are harmful for humans and animals health. Fusarium / wheat complex is in constant interaction with the environment where climatic factors and agricultural practices drive the dynamics of Fusarium populations and the associated mycotoxin risk. Therefore, studying the evolution of Fusarium species under changing environment is a key factor in predicting and controlling FHB. To better understand species dynamics and their adaptive potential in the context of climate changes, this work focuses on two main areas. On the one hand, changes in the occurrence of Fusarium species in France over the last 15 years were studied. A metabarcoding approach was used to characterize the distribution of Fusarium species in wheat samples, alongside the associated mycotoxin patterns. This study highlighted the spatio-temporal dynamics of Fusarium species and mycotoxins, using a large database to explore various agronomic and climatic factors. On the other hand, ecophysiological behaviours of Fusarium species were studied in response to combined temperature and water activity variations. Growth and mycotoxin production were measured in vitro, both in monocultures and in species in interaction.
ED Sciences et environnements
Optimisation of copper phytoextraction in vineyard soils
by Pierre EON (ISPA - Interaction Sol-Plante-Atmosphère)
The defense will take place at 14h00 - Salle Conférence ISPA 71 Avenue Edouard Bourlaux, Villenave d'Ornon Bâtiment C1
in front of the jury composed of
- Mathieu PéDROT - Maître de conférences - Université de Rennes - Examinateur
- Stéphanie SAYEN - Professeure - Université de Reims Champagne Ardenne - Examinateur
- Eva SCHRECK - Maîtresse de conférences - Université Toulouse III Paul Sabatier - Rapporteur
- Domenico MORABITO - Professeur - Université d'Orléans - Rapporteur
Copper (Cu) is widely used as a fungicide in viticulture, through foliar application, to prevent downy mildew in vines. A portion of Cu is leached into the soil during rainfall, and the repeated use of these fungicides has led to an accumulation of copper in vineyard soils (up to several hundreds of mg kg-1 in some soils). This accumulation can have harmful conse-quences for the functioning of vineyard ecosystems over the long term. Alongside the search for alternatives to the use of copper, it is necessary to provide remediation solutions to reduce its accumulation and/or its potential harmful effects. Phytoextraction is an inexpensive, non-polluting solution that can be used to remediate large areas in situ. For these reasons, it is already widely used for some trace metals. However, the conditions favorable to phytoextraction are not satisfied in the case of Cu in a vineyard context. There are no plants recognized as Cu hyperaccumulators, and Cu availability in vineyard soils is moderate. As a result, Cu phytoextraction yields struggle to reach around 100 g Cu ha-1 year-1. Firstly, the aim of this thesis was to assess the sensitivity of a panel of plants to Cu contamination, in order to find one or more plants that respond positively to an increase in Cu phytoavailability and can accumulate a large quantity of copper in their aerial parts without any loss of biomass. The second objective of this thesis was to evaluate the effects of aerated compost tea (ACT) on copper dynamics in vineyard soils. These liquids resulting from the infusion of compost in water and are rich in soluble humic substances (SHS) which have the ability to mobilize and complex the Cu present in the soil. The genericity and durability of these effects will be determined on vineyard soils with contrasting physico-chemical properties. The potential risk of Cu being transferred downwards as a result of this mobilization will also be investigated. Finally, the combination of these two objectives aimed to set up a cultural itinerary to achieve an extraction yield of 1 kg Cu ha-1 year-1. Several plant species were characterized as responding to an increase in Cu concentration. Plants exhibit efficient strategies for combating copper contamination, and only a few species were adversely affected. However, no species accumulated more than 50 mg Cu kg-1 in its aerial parts, and plants capable of accumulating several hundred mg Cu kg-1 are needed for their use in Cu phytoextraction to be considered. The SHS contained in ACT have made it possible to increase the mobility of Cu, as well as its bioavailability in vineyard soils. The efficiency of Cu mobilization by ACT depends on the affinity of Cu for the SHS they contain, and the degree to which their addition increases the concentration of SHS in the soil pore water. Although the effects of adding ACT persist over time, they diminish as the SHS bind to the solid phases and are degraded by soil micro-organisms. Isotopic measurements showed that mobilization was limited to the first few centimeters of soil and that the risk of copper in-depth transfer was relatively low. Trials carried out under realistic conditions enabled us to almost triple the phytoextraction yield by adding ACT, confirming the beneficial effect of ACT on plant growth and Cu phytoavailability. However, Cu extraction yields varied between 25 and 165 g Cu ha-1 year-1, which remains low compared with the target of 1000 g Cu ha-1 year-1. These results show that the SHS contained in ACT can mobilize Cu without any risk of in-depth transfer, but the absence of Cu-hyperaccumulating plants limits the use of phytoextraction to mitigate contamination of vineyard soils.