Prévision hydrologique à court terme par réseaux de neurones artificiels pour différentes combinaisons, spatialisations et sources des intrants.

Le potentiel de l’utilisation des réseaux de neurones artificiels en prévision hydrologique à court terme (un à sept jours à l’avance) a été démontré dans plusieurs études. Toutefois, les exemples d’utilisation en opérationnel restent limités et la compréhension de l’intérêt de plusieurs variables d’intrants au modèle pas encore entièrement déterminée. Le rôle de la spatialisation des intrants dans ce type de modèle n’est pas connu. Cette thèse examine le rôle de différents intrants, de leur discrétisation spatiale à un modèle de prévision hydrologique à court terme. Elle vise également à confronter différentes sources de données utilisées comme intrants au modèle. Le modèle de réseaux de neurones développé est un modèle à rétropropagation avec une couche cachée à six neurones. Quatre bassins versants situés en Nouvelle Angleterre (Androscoggin et Susquehanna) ou dans le sud du Québec (Au saumon et Magog) servent de cas d’étude pour faire la prévision durant l’été, défini du 1er mai au 31 octobre. Le modèle de prévision hydrologique vise à prévoir le débit au pas de temps journalier. Au minimum une variable météorologique et une variable d’état sont utilisées comme intrants au modèle ; la variable d’état est aussi mise à jour à chaque pas de temps en étant une sortie du modèle. Deux environnements de travail sont exploités. L’environnement virtuel sert à identifier les variables d’intrants et la spatialisation les plus pertinentes pour la prévision hydrologique à court terme sur les bassins à l’étude. Le modèle hydrologique à base physique HYDROTEL est utilisé pour générer des séries de pseudo-observations hydrométéorologiques sur chaque site d’étude. Les expériences menées dans cet environnement virtuel révèlent que la meilleure configuration d’intrants utilise la température, la précipitation, l’humidité du sol en surface et le débit. De plus, elles révèlent que les modèles global et spatialisé ont des résultats équivalents. Basé sur les résultats obtenus en environnement virtuel, l’environnement réel utilise des données d’observations pour le débit et l’humidité et des données de réanalyses de température et de précipitation pour la météo. Les résultats montrent un réel potentiel dans l’utilisation d’un réseau de mesure in situ de l’humidité au sol pour faire de la prévision hydrologique. En revanche, la qualité des prévisions est très réduite pour les faibles débits

On the energetics of a two-layer baroclinic flow

The formation, evolution and co-existence of jets and vortices in turbulent planetary atmospheres is examined using a two-layer quasi-geostrophic β -channel shallow-water model. The study in particular focuses on the vertical structure of jets. Following Panetta & Held (J. Atmos. Sci., vol. 45 (22), 1988, pp. 3354–3365), a vertical shear arising from latitudinal heating variations is imposed on the flow and maintained by thermal damping. Idealised convection between the upper and lower layers is implemented by adding cyclonic/anti-cyclonic pairs, called hetons, to the flow, though the qualitative flow evolution is evidently not sensitive to this or other small-scale stochastic forcing. A very wide range of simulations have been conducted. A characteristic simulation which exhibits alternation between two different phases, quiescent and turbulent, is examined in detail. We study the energy transfers between different components and modes, and find the classical picture of barotropic/baroclinic energy transfers to be too simplistic. We also discuss the dependence on thermal damping and on the imposed vertical shear. Both have a strong influence on the flow evolution. Thermal damping is a major factor affecting the stability of the flow while vertical shear controls the number of jets in the domain, qualitatively through the Rhines scale LRh = √U/β.PostprintPeer reviewe

On the emergence and evolution of jets and vortices in turbulent planetary atmospheres

This thesis investigates the formation and evolution of jets and vortices in turbulent planetary atmospheres using a dual approach of high-resolution numerical simulations and novel laboratory experiments. A two-layer quasi-geostrophic beta-channel shallow water model is used for the numerical study. As in Panetta (1988), a vertical shear is implemented to represent a spatially-mean latitudinal temperature gradient, which is partially maintained by thermal relaxation. Baroclinic instabilities work to erode the temperature gradient, while thermal relaxation acts to restore it. As the basic state vertical shear is unstable, the thermal relaxation cannot lead to a full recovery, thus modifying subsequent instabilities and leading to rich nonlinear dynamical behaviour. First, we consider flow over a flat bottom, and model convective motions like those thought to occur on Jupiter by pairs of cyclones/anti-cyclones or ‘hetons’ as in Thomson (2016). We thereby obtain predominantly baroclinic jets, oscillating between quiescent phases, when jets are zonal and the energy is nearly stationary, and turbulent phases, when the flow loses its zonality, vortices pinch off from the meandering jets, and zonal energy components drop while eddy energy components increase. These turbulent phases typically last for a thermal relaxation period. The impacts of vertical shear (baroclinicity), thermal relaxation and heton forcing are comprehensively investigated by considering the energy transfers occurring between kinetic and potential energy, their barotropic and baroclinic parts as well as their zonal and eddy parts. This leads to a rethinking of the classic paradigm of energy transfer presented by Salmon (1982), as this paradigm is too simplistic to explain the results found. Then, we consider the effect of large-scale bottom topography, as a first approach to understanding the role of topography in jet and vortex formation. We use the same model as in the first study but include a linearly sloping topography which has the advantage of being characterised by a single parameter, the slope. We omit the heton forcing and instead perturb the flow with a small amplitude Rossby wave initially. The main effect of heton forcing is actually to act as a kind of damping: energy fluctuations are consistently less extreme than when no forcing is used. A linear stability analysis is carried out to motivate a series of nonlinear simulations investigating the effect of topography, in particular, differences from the flat bottom case previously examined. We find that destabilising topography makes the jets more dynamic. In the experimental part, a two-layer salt-stratified fluid is used in a rotating tank with a differentially rotating lid to generate the shear across the interface. We consider a baroclinically unstable front in the regime of amplitude vacillation, which is found to be characterised by the sequential emergence and disappearance of a large-scale vortex. Analysing two similar experiments at the limit of geostrophy, with different Rossby numbers Ro=0.4 and Ro=0.6, shows surprisingly different behaviours, with a baroclinic dipole for small, and a barotropic vortex for the large Rossby number. The small-scale wave activity is explored using different methods, and the results suggest small, spontaneously arising inertia-gravity waves preceding the emergence of the vortex which stirs the interface, thus having an impact on the mixing between the two layers. The recovery period of the amplitude vacillation, as well as the intensity of the vortex, increases with the Rossby number. For further research on fronts at two-layer immiscible interfaces, a very accurate novel optical method has been developed to detect the height and slope, based on the refractive laws of optics. The associated theoretical equations are solved numerically and validated in various idealised situations

Evaluation des pratiques de biosécurité en filière avicole dans le département des Landes dans le contexte des crises d’influenza

Les crises récentes d’influenza aviaire hautement pathogène de 2016 et 2017 ont sévèrement touché les filières avicoles françaises, révélant d’importante failles dans les mesures de biosécurité appliquées en élevage. L’attention portée à ces mesures a été renforcée suite à l’arrêté ministériel du 8 février 2016, et aux inspections officielles réalisées en élevage par les services de l’Etat. Dans ce contexte, une analyse épidémiologique a été conduite à partir des données des inspections biosécurité conduites par la DDPP des Landes, département particulièrement touché par les épizooties d’influenza. L’analyse de données issues de 472 visites met en lumière l’hétérogénéité de l’observance des mesures face aux exigences réglementaires. De plus, une régression logistique multivariée a permis de mettre en évidence trois facteurs ayant un effet significatif (p-value <0,05) sur le statut influenza aviaire des élevages. La présence de non-conformité concernant des éléments du plan de biosécurité (OR = 2,33 [I.C. 1,24-4,38]) ainsi que la définition et la délimitation des zones du plan (OR = 1,89 [0,95 – 3,80]) constituent des facteurs de risques. A l’inverse et de manière contre-intuitive, la non-conformité des pratiques de conservation des cadavres est associée à un risque réduit d’infection par l’influenza hautement pathogène (OR = 0,31 [0,12 - 0,78]

Célestin Montcocol, 1879-1981 - Notice biographique

Le nom de Montcocol évoque à la fois la figure du grand entrepreneur disparu en 1981 et l’entreprise de travaux souterrains et de voies ferrées qui a participé jusqu’à ce jour à toutes les étapes du développement des réseaux souterrains de Paris. On ne peut séparer les deux ; en 1900, année de la mise en service de la première ligne du métro, l’ingénieur débutant Célestin Montcocol fait partie de l’équipe de Fulgence Bienvenüe ; l’entreprise qu’il crée quelques années plus tard est restée fam..

Excess mortality related to the August 2003 heat wave in France.

Objectives: From August 1st to 20th, 2003, the mean maximum temperature in France exceeded the seasonal norm by 11-12 degrees C on nine consecutive days. A major increase in mortality was then observed, which main epidemiological features are described herein. Methods: The number of deaths observed from August to November 2003 in France was compared to those expected on the basis of the mortality rates observed from 2000 to 2002 and the 2003 population estimates. Results: From August 1st to 20th, 2003, 15,000 excess deaths were observed. From 35 years age, the excess mortality was marked and increased with age. It was 15% higher in women than in men of comparable age as of age 45 years. Excess mortality at home and in retirement institutions was greater than that in hospitals. The mortality of widowed, single and divorced subjects was greater than that of married people. Deaths directly related to heat, heatstroke, hyperthermia and dehydration increased massively. Cardiovascular diseases, ill-defined morbid disorders, respiratory diseases and nervous system diseases also markedly contributed to the excess mortality. The geographic variations in mortality showed a clear age-dependent relationship with the number of very hot days. No harvesting effect was observed. Conclusions: Heat waves must be considered as a threat to European populations living in climates that are currently temperate. While the elderly and people living alone are particularly vulnerable to heat waves, no segment of the population may be considered protected from the risks associated with heat waves

Using vital statistics to estimate the population-level impact of osteoporotic fractures on mortality based on death certificates, with an application to France (2000-2004)

Abstract Background We developed a methodology using vital statistics to estimate the impact of osteoporotic fractures on the mortality of an entire population, and applied it to France for the period 2000-2004. Methods Current definitions of osteoporotic fractures were reviewed and their components identified. We used the International Classification of Diseases with national vital statistics data for the French adult population and performed cross-classifications between various components: age, sex, I-code (site) and E-code (mechanism of fracture). This methodology allowed identification of appropriate thresholds and categorization for each pertinent component. Results 2,625,743 death certificates were analyzed, 2.2% of which carried a mention of fracture. Hip fractures represented 55% of all deaths from fracture. Both sexes showed a similar pattern of mortality rates for all fracture sites, the rate increased with age from the age of 70 years. The E-high-energy code (present in 12% of death certificates with fractures) was found to be useful to rule-out non-osteoporotic fractures, and to correct the overestimation of mortality rates. Using this methodology, the crude number of deaths associated with fractures was estimated to be 57,753 and the number associated with osteoporotic fractures 46,849 (1.85% and 1.78% of all deaths, respectively). Conclusion Osteoporotic fractures have a significant impact on overall population mortality.</p

Immune and Genetic Signatures of Breast Carcinomas Triggering Anti-Yo-Associated Paraneoplastic Cerebellar Degeneration

BACKGROUND AND OBJECTIVES: Paraneoplastic cerebellar degeneration (PCD) with anti-Yo antibodies is a cancer-related autoimmune disease directed against neural antigens expressed by tumor cells. A putative trigger of the immune tolerance breakdown is genetic alteration of Yo antigens. We aimed to identify the tumors' genetic and immune specificities involved in Yo-PCD pathogenesis. METHODS: Using clinicopathologic data, immunofluorescence (IF) imaging, and whole-transcriptome analysis, 22 breast cancers (BCs) associated with Yo-PCD were characterized in terms of oncologic characteristics, genetic alteration of Yo antigens, differential gene expression profiles, and morphofunctional specificities of their in situ antitumor immunity by comparing them with matched control BCs. RESULTS: Yo-PCD BCs were invasive carcinoma of no special type, which early metastasized to lymph nodes. They overexpressed human epidermal growth factor receptor 2 (HER2) but were hormone receptor negative. All Yo-PCD BCs carried at least 1 genetic alteration (variation or gain in copy number) on CDR2L, encoding the main Yo antigen that was found aberrantly overexpressed in Yo-PCD BCs. Analysis of the differentially expressed genes found 615 upregulated and 54 downregulated genes in Yo-PCD BCs compared with HER2-driven control BCs without PCD. Ontology enrichment analysis found significantly upregulated adaptive immune response pathways in Yo-PCD BCs. IF imaging confirmed an intense immune infiltration with an overwhelming predominance of immunoglobulin G-plasma cells. DISCUSSION: These data confirm the role of genetic alterations of Yo antigens in triggering the immune tolerance breakdown but also outline a specific biomolecular profile in Yo-PCD BCs, suggesting a cancer-specific pathogenesis