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Etude de la dégradation des sédiments cimentés par de la glace générés au cours de glissements de terrain et produisant des molards
No full textIn this thesis, I aim to broaden the understanding of geomorphological features known as permafrost molards - conical mounds of loose debris that can be found in landslide deposits in periglacial environments. If ground ice degrades in mountain slopes due to current climate change trends this can result in more frequent slope failures. Since molards are proposed to originate from ice-cemented blocks of debris being transported within the landslide material and degrade into conical mounds over time, they indicate the presence of an area of discontinuous permafrost at the level of the detachment zone. To better understand the physical processes leading to the formation of molards and how these processes determine the final molard shape, I studied the degradation of ice-cemented blocks under controlled laboratory conditions. To investigate the molards’ distribution within the landslide deposits, their individual shape parameters and their material composition, I studied seven molard landslides. I found that the initial block’s fracture surfaces, material composition, and the location of its degradation determine the resulting molards’ shape and size. The dominant degradation process of the initial ice-cemented block depends on the complexity of the degrading material, especially the content of the fine material and ice content which then determines the final morphology. By degrading initial CO2 and H2O ice-cemented blocks of sediment under martian pressure, I find that molards can also form by sublimation processes, therefore supporting the reports of molard candidates on other planetary bodies.Dans cette thèse, j'ai eu pour objectif d'élargir la compréhension d’objets géomorphologiques appelés molards - des monticules coniques de débris rocheux que l'on peut trouver dans les dépôts suite à un glissement de terrain en environnement périglaciaire. Si la glace présente dans les versants montagneux se dégrade en raison des tendances actuelles du changement climatique, le déclenchement de ruptures de versant risque d'être plus fréquents. Les molards proviendraient de morceaux de pergélisol cimentés par la glace et transportés par le glissement de terrain, qui se dégradent en monticules coniques au cours du temps. Ils sont susceptibles d’indiquer la présence d'une zone de pergélisol discontinu au niveau de la zone de rupture. Pour mieux comprendre les processus physiques qui conduisent à la formation des molards et la manière dont ces processus déterminent la forme finale des molards, j'ai étudié la dégradation de blocs débris rocheux cimentés par de la glace dans des conditions de laboratoire contrôlées. Pour étudier la répartition des molards dans les dépôts de glissement de terrain, leurs paramètres de forme individuels et leur composition lithologique, j'ai étudié in-situ sept glissements de terrain présentant des molards. J'ai constaté que les surfaces de rupture du bloc initial, la composition du matériau et le lieu de sa dégradation déterminent la forme et la taille des molards qui en résultent. Le processus de dégradation dominant du bloc initial cimenté par la glace dépend de la complexité du bloc gelé en cours de dégradation, en particulier de la teneur en matériau fin et de la teneur en glace, qui déterminent ensuite la morphologie finale. En dégradant des blocs initiaux de sédiments cimentés par la glace de CO2 et de H2O sous pression martienne, je constate que les molards peuvent également se former par des processus de sublimation, ce qui corrobore les rapports faisant état de candidats molards sur d'autres corps planétaires
Ecosystem Services provided by streams to adjacent agricultural terrestrial ecosystems
No full textInternational audienceStreams are traditionally viewed as receptacles rather than sources of energy with regard to nutrient and energy cycles. For a long time, terrestrial-aquatic interactions have focused on studying the impact of terrestrial ecosystems on aquatic ecosystems, but more and more studies are highlighting the role of aquatic ecosystems on terrestrial ecosystems. Numerous studies have shown that freshwater ecosystems are an important source of energy for the terrestrial environment, mainly through the emergence of winged aquatic insects, recognized as providing nutritional subsidies to terrestrial consumers. They represent a substantial source of fertilization for soils and an important resource for terrestrial organisms. Plants near wetlands where food webs contain fewer insect predators or flying insects receive more pollinator visits and are less pollen limited. Thus, dense hydrographic networks could suggest a strong impact in terms of ecosystem services in adjacent terrestrial ecosystems. The objective of our project is to evaluate three ecosystem services provided by aquatic insects in adjacent agricultural environments following a gradient of agricultural intensification and to analyze their impacts in terms of integration in the management policies of the territories. Five sites located along a gradient of agricultural intensification and in different agricultural contexts where agricultural practices are informed, were selected within three Zones Ateliers from the French Long Term Socio-Ecological Research network. On each site, a headwater stream and its adjacent landscape (1 Km²) will be monitored at the same time (spring and summer) with 13 protocols. The first work package focuses on three ecosystem services provided and mediated by emerging aquatic insects (soil fertilization, pollination and crop pest control). These ecosystem services cannot be studied without an accurate quantification of biodiversity of streams (i.e. emerging aquatic insects and aquatic vegetation), riparian habitats (floral diversity, emerging aquatic insects and terrestrial predators), adjacent agricultural areas (i.e. emerging aquatic insects, terrestrial predators and type of crops) and the quantification of biological flux between aquatic and terrestrial environment. The second WP focuses on the governance of riparian areas. Its objective is to study the history of the governance of French riparian areas, to examine current management practices and their associated representations. This WP will also address recent improvements in the governance of these areas and aims to increase the adoption of ecologically responsible practices by stakeholders. The last WP aims to map Essential Biodiversity Variables (EBVs) of streams and floodplains with high-resolution data and remote sensing techniques and artificial intelligence modelling approach to estimate the respective contribution of various drivers (e.g. landscape features and their arrangement including 3D modelling) . This information is crucial for understanding and linking WP1 and WP2 (i.e. explaining ecosystem services distribution in relation with anthropogenic practices and land uses). Preliminary results suggested a possible important role of aquatic insects in fertilization but a relatively small contribution to direct pollination. We have also highlighted a succession of major changes in river management over the last 100 years, which have profoundly altered the functioning of aquatic ecosystems. However, headwater and riparian habitats are rarely considered in social sciences and limit our ability to integrate their specificities or to mitigate conflicts among users and managers. Ongoing research based a previous discussions with stakeholders, has highlighted that our project should help us to better quantify, in a spatially explicit manner, the relative contribution of freshwaters to ecosystem services in agricultural landscapes, and to better identify leverage points for integrating our results into agricultural practices and environmental management
Crust (unified) tool for equation-of-state reconstruction (CUTER) v2
No full textInternational audienceThe equation of state (EoS) is a needed input to determine the neutron-star global properties and to relate them. It is thus important to provide thermodynamically consistent and unified EoSs to avoid possible biases in the analyses coming from the use of inconsistent EoSs. We propose a numerical tool, CUTER, allowing the user to consistently match a nuclear-physics informed crust to an arbitrary higher density EoS. We present here the second version of this tool, CUTER v2. Two functionalities are available with the CUTER v2 tool, allowing the user to reconstruct either the whole (outer and inner) crust, or the outer crust only. We show that the code, that has been tested and validated for use by the astrophysical community, is able to efficiently perform both tasks, allowing the computation of neutron-star global properties in a consistent way
Le grillage américain en Normandie, des pistes d'aviation à la ferme.
No full textInternational audienceLes campagnes normandes présentent de nombreuses traces de réutilisation de matériels issus du Débarquement. Un des plus remarquables et répandu, est un treillis métallique appelé communément « grillage américain ». Appelé dans la nomenclature militaire alliée Square Mesh Track ou SMT (piste en grillage à maille carrée), ce treillis métallique soudé fut un produit purement britannique. Il fut conçu comme matériau de revêtement de sol pour l’établissement de pistes d’aviation temporaires, en remplacement de grillages de première génération, trop peu solides pour supporter le poids croissant des avions. Adopté dans l’urgence par les forces aériennes alliées comme matériau de transition, il fut posé dans le sud de l’Angleterre sur les terrains d’aviation avancés, puis en Normandie sur près de cinquante aérodromes et enfin, ponctuellement dans l’Europe libérée.Dès la fin de la bataille de Normandie, ces terrains d’aviation furent démantelés et les cultivateurs des environs se procurèrent les matériaux abandonnés par les Alliés. Une partie des 20.000 tonnes de grillage américain laissé sur le terrain fut ainsi réutilisé pour clôturer des champs, faire des portails ou des objets de la ferme
Use of mortality tables by level of deprivation in the study of social inequalities in cancer survival
No full textInternational audienceBackground: Previous studies have reported lower net survival probabilities for socioeconomically deprived patients, using non-deprivation specific lifetables. Not accounting for the social gradient in background mortality could potentially overestimate the effect of deprivation on net survival. The aim of this study was to estimate the impact of taking into account the social gradient of expected mortality in the general population on the study of the social gradient of survival of people with cancer.Methods: French cancer registry data was analyzed, with 190,902 incident cases of nineteen cancer sites between 2013 and 2015. Deprivation was measured using the European deprivation index (EDI). Net survival was estimated thanks to additive models with French lifetables stratified on deprivation level with the EDI, using the non-parametric Pohar-perme method and flexible excess hazard modelling with multidimensional penalized splines, firstly with non-specific lifetables then with the deprivation specific-lifetables.Results: A significant effect of EDI on excess mortality hazard (EMH) remained when using the deprivation-specific lifetables for colorectal, lung cancer and melanoma in both sexes, and esophagus, bladder, head and neck and liver cancer for men, and breast, cervix and uterine cancer for women. The only site where the effect of EDI on EMH was no longer significant when using deprivation-specific lifetables was prostate cancer.Conclusions: The use of deprivation-specific lifetables confirms the existence of a social gradient in cancer survival, indicating that these inequalities do not result from inequalities in background mortality. Development of such deprivation-specific lifetables for future years is crucial to understand mechanisms of social inequalities and work towards reducing the social burden
Conception de Liquides Ioniques Biosourcés (LIBIOS) des nouveaux solvants verts
No full textInternational audienceConception de Liquides Ioniques Biosourcés (LIBIOS) des nouveaux solvants vert
Deep Reinforcement Learning Based Defense System for Electric Vehicle Charging Stations
No full textInternational audienceThe widespread adoption of Electric Vehicles (EVs) requires an efficient charging infrastructure. Using data connection-based charging equipment, smart charging, and vehicle-to-grid (V2G) charging technologies allow electric vehicles to connect to the electrical grid. This enables the exchange of information and instructions. However, this ecosystem is susceptible to physical or cyberattacks, just like any other cyber-physical system. In this paper, we investigate load-altering (LA) attacks that impact the functionality of the smart grid. We propose a two-phase strategy to avoid, detect, and mitigate attacks. Our first step is scheduling charging station operations to normalize system utilization to avert future simultaneous attacks. Therefore, a distributed Deep Reinforcement Learning (DRL) model is used to establish the ON/OFF status of each charging station. To maintain the system's power stability during the charging process, the system uses an event-based method to respond to the abrupt change in charging/discharging behavior. To detect attacks, a second multi-agent deep-reinforcement learning model is created. This enables the system to recognize and neutralize the effects of LA attacks on the power grid. After the compromised entities are located, they are isolated and the demands of certain backup charging stations either completely or partially replace the canceled power demands. The performance study shows that the suggested strategy minimizes the impact of LA attacks and delivers good results in terms of detection accuracy.</div
Plastiques : des flux insaisissables, pour une ambition performative de la circularité
No full textInternational audienceLes matières plastiques présentent des propriétés uniques de résistance et de légèreté à de faibles coûts qui ont entrainé leur omniprésence dans nos vies. Cette consommation, en forte croissance depuis les années 1950, pose une difficulté, car elle est corrélée à une production de déchets plastiques en constante augmentation mettant sous pression les systèmes de gestion et conduisant à des millions de tonnes de déchets rejetés. Face à cette pollution massive, la chaîne de valeur économique des plastiques est touchée par des dysfonctionnements techniques, réglementaires et de maîtrise des flux. Une injonction est alors lancée pour circulariser les flux, laissant entendre que le problème est en passe d’être réglé, alors que sur le terrain, le recyclage reste minime. Lorsque 5 599 kt de produits plastiques sont utilisés en 2018 en France, seulement 622 kt sont réellement recyclés. L’économie circulaire du plastique se révèle donc être plus performative qu’effective, tout en venant justifier la perpétuation d’une croissance de la consommation. Cet article s’attache à identifier le métabolisme français du plastique et à en analyser le fonctionnement. En s’appuyant sur une analyse des bilans matières et sur leur représentation par les différents acteurs, l’illusion performative de l’économie circulaire sera mise en évidence