The ability to observe temperature variations inside the human body may help in detecting the presence of medical anomalies. Abnormal changes in physiological parameters (such as metabolic and blood perfusion rates) cause localized tissue temperature change. If the anatomical information of an observed tissue region is known, then a nominal temperature profile can be created using the nominal physiological parameters. Temperature-varying radiation emitted from the human body can be captured using microwave radiometry and compared to the expected radiation from nominal temperature profiles to detect anomalies. Microwave radiometry is a passive system with the ability to capture radiation from tissue up to several centimeters deep into the body. Our proposed method is to use microwave radiometry in conjunction with another imaging modality (such as ultrasound) that can provide the anatomical information needed to generate nominal profiles and improve detection of temperature anomalies. An inference framework is developed for using the nominal temperature profiles and radiometric weighting functions obtained from electromagnetic simulation software, to detect and estimate the location of temperature anomalies. The effects on inference performance of random and systematic deviations from nominal tissue parameter values in normal tissue are discussed and analyzed.

Le matériau BiFeO3 (BFO) est le sujet de très nombreuses études fondamentales dans le domaine des matériaux multiferroïques. Cet intérêt est du au fait que cet oxyde présente deux ordres à longue distance à la température ambiante : ferroélectricité et antiferromagnétisme de type G (ce dernier est aussi non colinéaire avec la présence de faible ferromagnétisme ainsi qu’une modulation de spin de type cycloïdale possédant une longueur d’onde de 620 angstrœm). Il est alors possible d’étudier les comportements de couplage entre les propriétés électrique et magnétique. Ce travail concerne principalement la synthèse, les structures haute température, et les propriétés physiques (électronique et magnétique principalement) du matériau BiFeO3 ayant subi des recuits de différentes pressions partielles d’oxygène. La première étape de ce travail concerne l’étude de la synthèse afin de déterminer le protocole optimal de réalisation des céramiques. Les recuits sous atmosphère ont eu pour but de modifier la stœchiométrie en oxygène du matériau, afin d’affecter ses propriétés physiques. Des modifications de faible amplitude de certaines propriétés ont été détectées, mais à l’inverse, la température de Néel et la température de Curie ne sont pas affectées.Concernant la nature des structures haute température, les phases beta et gamma, sujettes à de nombreuses controverses dans la littérature, ont été étudiées par diffraction des rayons X et analyse DSC sur BFO pur ou avec excès de bismuth. Cet excès a permis de stabiliser la phase gamma entre 940 et 950°C, en évitant sa décomposition. Pour compléter ce travail sur BFO en phase pure, nous avons dopé des céramiques avec 10 % de Zr4+ pour étudier le comportement structurale à haute température, ainsi que les propriétés magnétiques et électriques de cette nouvelle composition. Enfin, des simulations numériques sur le composé stœchiométrique, lacunaire en bismuth ou en oxygène ont été réalisées pour comprendre les évolutions structurale, électronique et magnétique du matériau suite aux recuits. La dernière partie est une étude sur le comportement basse température de BFO pur sous différentes formes : nanotubes, céramiques et monocristaux. Nous avons analysé le comportement électrique (impédance, pyroélectricité, RPE et électrostriction), magnétique (aimantation en fonction de la température et du champ magnétique) et structurale (rayon X en thêta-2thêta et rasant, DSC, microRaman et résonance d’ultrasons). Suite à ces études, trois températures sont observées comme présentant un comportement particulier : 140 et 200 K, qui semblent liées par de nombreuses techniques d’analyses et ressortent comme étant une transition à la surface de BFO, mais aussi 180 K où nous avons un écart à la linéarité de la dilatation thermique et un effet d’électrostriction. / BiFeO3 material is the subject of number fundamental studies in multiferroic materials. This interest is mainly cause by the existence of two long range order at room temperature : ferroelectricity and G type antiferromagnetism (this one is also no collinear with the presence of a weak ferromagnetism, and a cycloidal spin modulation with a wave length of 620 angstrom). So, it is possible to study coupling behaviour between electrical and magnetic properties.This work is mainly about the synthesis, high temperature structures, and physical properties (principally electronic and magnetic one) in BFO material after sintering it under different oxygen partial pressure. The first step of this work is about the synthesis study in order to optimize the protocol of ceramic formation. The sintering under atmosphere are done in order to change the oxygen stoichiometry of BFO, we expected to affect this physical properties. We saw some weak modifications of few properties, but Néel and Curie temperature are not altered.Concerning the nature of BFO high temperature structure, beta and gamma phase, which are subject of number controversies in literature, were studied with X-rays and DSC analysis, in pure or in bismuth excess phase. This excess leads to stabilize the gamma phase between 940 and 950°C, and avoid decomposition. To complete this work on pure phase BFO, we doped ceramic with 10 % of Zr4+ in order to study the high temperature structural behaviour, electrical and magnetic properties of this new composition. At last, numerical simulation on the stoichiometric, bismuth or oxygen lacunar system are done to understand structural, electrical and magnetic evolution after the sintering.The last part is a study on behaviour of pure phase BFO at low temperature with different form : nanotube, ceramic and single crystal. We analysed electrical (impedance, pyroelectricity, EPR and electrostriction), magnetic (magnetization function of temperature and magnetic field) and structural comportment (X-rays in theta-2theta and grazing incidence, DSC, microRaman and ultrasonic resonance). It reveals that tree temperature show a specific behaviour : 140 and 200 K, which are link by several analysis technical and seems to be a surface transition (skin effect) in BFO, but also 180 K where we found a non constant evolution in the thermal dilatation, and an electrostriction effect.

The need to consider groundwater and surface water as a single resource has fostered the interest of the scientific community on the interactions between surface water and groundwater. The region below and alongside rivers where surface hydrology and subsurface hydrology concur is the hyporheic zone. This is the region where water exchange determines many biogeochemical and ecological processes of great impact on the functioning of rivers. However, the complex processes taking place in the hyporheic zone require a multidisciplinary approach. The combination of innovative point and distributed techniques originally developed in separated disciplines is of great advantage for the indirect identification of water exchange in the hyporheic zone. Distributed techniques using temperature as a tracer such as fiber-optic distributed temperature sensing can identify the different components of groundwater-surface water interactions based on their spatial and temporal thermal patterns at the sediment-water interface. In particular, groundwater, interflow discharge and local hyporheic exchange flows can be differentiated based on the distinct size, duration and sign of the temperature anomalies. The scale range and resolution of fiber-optic distributed temperature sensing are well complemented by geophysics providing subsurface structures with a similar resolution and scale. Thus, the use of fiber-optic distributed temperature sensing to trace flux patterns supported by the exploration of subsurface structures with geophysics enables spatial and temporal investigation of groundwater-surface water interactions with an unprecedented level of accuracy and resolution. In contrast to the aforementioned methods that can be used for pattern identification at the interface, other methods such as point techniques are required to quantify hyporheic exchange fluxes. In the present PhD thesis, point methods based on hydraulic gradients and thermal profiles are used to quantify hyporheic exchange flows. However, both methods are one-dimensional methods and assume that only vertical flow occurs while the reality is much more complex. The study evaluates the accuracy of the available methods and the factors that impact their reliability. The applied methods allow not only to quantify hyporheic exchange flows but they are also the basis for an interpretation of the sediment layering in the hyporheic zone. For upscaling of the previous results three-dimensional modelling of flow and heat transport in the hyporheic zone combines pattern identification and quantification of fluxes into a single framework. Modelling can evaluate the influence of factors governing groundwater-surface water interactions as well as assess the impact of multiple aspects of model design and calibration of high impact on the reliability of the simulations. But more importantly, this modelling approach enables accurate estimation of water exchange at any location of the domain with unparalleled resolution. Despite the challenges in 3D modelling of the hyporheic zone and in the integration of point and distributed data in models, the benefits should encourage the hyporheic community to adopt an integrative approach comprising from the measurement to the upscaling of hyporheic processes.