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Rayon, Municipio de Rayon, San Luis Potosi Collection particulière de Don Pedro Sanchez Orta. Têtes de figurines : a gauche, représentation vraissemblelement du dieu du vent; a droite tête d'aspect félin.

Hydrodynamic and sedimentary processes are studied in the English Channel, particularly in the southern Dover Straits, and in the Sea of Iroise and the bay of Douarnenez, with emphasis on the effects of spatial heterogeneity of bottom sediments, surface gravity waves via their interaction with current in the bottom boundary layer and wind. The heterogeneity of bottom sediments is ensured through the use of a new spatial interpolation procedure of granulometric distribution. The methodological approach combines and compares field measurements with numerical modelling. Modelling that couples 3D circulation model (COHERENS) and wave propagation model (SWAN), incorporates a set of non-cohesive polydispersive sediment transport equations, a bottom boundary layer wave-current interaction model and various parameterisations of bottom ripples (geometry, friction coefficient), and optimized computation of the near-bed deposition rate. Comparison of results with measurements in the Dover Straits highlights the interaction between the nearshore silty fine sands and the spatio-temporal variability of hydrodynamics under conditions of tide alone and in wind-generated surface gravity waves superimposed on tide. Modelling is then applied to the eastern and central English Channel. In the bay of Douarnenez, the local analysis aims at the modelling of respective effects of tidal currents alone, stormy waves superimposed on tidal currents and wind. Finally, a theoretical study of headland-associated sand bank is performed.; Les processus hydrodynamiques et sédimentaires subtidaux sont étudiés en Manche au niveau du détroit du Pas-de-Calais et de son littoral méridional, et de la Mer d'Iroise et de la Baie de Douarnenez, à travers diverses modalités d'influence de l'hétérogénéité spatiale des sédiments de fond, de la houle via son interaction avec le courant en couche limite de fond et du vent. Une procédure nouvelle d'interpolation spatiale des distributions granulométriques permet de respecter l'hétérogénéité du substrat. L'approche méthodologique combine et confronte mesures de terrain et modélisation numérique. La modélisation, couplant des codes de circulation 3D (COHERENS) et de propagation de houle (SWAN), incorpore des modules de transport sédimentaire non-cohésif multiclasse, un module spécifique d'interaction houle-courant et diverses paramétrisations liées aux rides sableuses de fond (géométrie, coefficient de frottement), ainsi qu'un calcul optimisé du dépôt à l'interface eau-sédiment. La comparaison des prédictions numériques aux mesures recueillies le long du littoral méridional du détroit du Pas-de-Calais montre les interactions entre la bande littorale de sables fins envasés et la variabilité spatio-temporelle de l'hydrodynamique en conditions de courant de marée seul et superposé à une houle de Nord. La modélisation est ensuite appliquée à l'ensemble de la Manche orientale et centrale. En Baie de Douarnenez, l'analyse locale débouche sur une modélisation des influences respectives des courants de marée seuls, d'une houle de tempête superposée aux courants de marée et du vent. Enfin, une étude théorique des effets d'un cap sur la formation des bancs en drapeau est présentée.

We compared open-site and below-canopy climatic conditions from 14 different sites in Switzerland based on LWF data (Long-term Forest Ecosystem Research). The 14 sites represent different locations, orientations and elevations, from the Jura Mountains to the southern side of the Alps, composed of deciduous, coniferous and mixed forests. Meteorological measurements were carried out under the canopy at the observation plots, and in open areas outside the forest plots. We analysed air temperature during summer 2003, in connection with the exceptionally high temperatures measured during that summer and during the 11-day August heat wave. From April to October 2003, there was a significant correlation between the absolute value of temperature and the difference between open-site and below-canopy temperature: the warmer the temperature, the stronger the impact of the forest. For maximum temperature, the difference was higher in deciduous and mixed forests, especially those with beech as the dominant tree species, compared to conifer forests. For minimum temperature, the discrepancy was higher in conifer forests but, generally, the north-oriented slopes showed greater differences than the other slopes. The results are similar for a decade period of temperature analysis between below-canopy and open-field, from 1998 to 2007. We also compared below-canopy and open-field data for minimum, maximum and daily mean temperature, relative humidity (RH), maximum and daily mean photosynthetically active radiation (PAR) and wind speed (m/s) from 1998 to 2007. We analysed the forest influence on local summer and winter climate according to the forest type (coniferous, mixed, deciduous), soil type, basal area (m2/ha) and tree height (m). In summer, deciduous and mixed forests generally have the strongest impact on daytime temperatures, from 3 to 5 K cooler under the canopy, with a higher RH, up to 17%. Coniferous forests have a moderating effect on night temperatures, from 1 to 4 K warmer below-canopy, with a lower HR, from 4 to 15% less humid under the canopy. In winter, the forest lowered the day-time temperatures, from 0.2 to 5K, accordingly to the orientation and the dominant specie, and generally increased night-time temperatures, up to 6.2 K in north-oriented conifer sites. The day-time RH was enhanced in all forest types compared to open-field, from 5 to 22%, except in an open Scots pine forest, and the night-time RH was generally reduced below-canopy, especially in coniferous stands, being up to 22% less humid below-canopy in pine forests. We applied the Heat Index (HI) and the NET (Net effective temperature) index to the open-field and below-canopy meteorological data (maximum temperature, relative humidity and wind speed) in order to determine the bioclimatic potential of the different forest stands in summer from 1998 to 2007, and more specifically during the summer 2003 heat wave. We applied the NET index and the Windchill index to determine the forest bioclimatic potential for human wellbeing during winter from 1998 to 2007. In summer, generally, the bioclimatic conditions were clearly more comfortable for humans in the forest than in open-field. When the conditions came out as very hot or requiring extreme caution in open-field, they were in the more comfortable zone in the deciduous and mixed forest at hill and mountain level. This was particularly evident during the exceptionally hot summer of 2003. In winter, bioclimatic conditions were also more comfortable below-canopy, mainly due to the forest effectively reducing wind speed. In order to cope with the likely increasing frequency and intensity of heat waves, our results show and quantify the role of forests in providing a cool shelter. The results are of particular value to urban areas, where forested parks could provide an important source of relief during heatwaves. It is therefore necessary to maintain and develop the accessibility of forested areas to city dwellers. Accordingly to our sample, the most efficient ecosystems for this purpose appear to be generally the deciduous and mixed forests and more specifically the beech and beech–silver fir stands. The opposite effect was seen in mugo pine and Scots pine forests, with warmer temperatures under the canopy compared to open-site.

[1] Evaluating long equatorial wave reflections at the Pacific western boundary has been a concern for many past studies in order to discuss whether the delayed action oscillator mechanism may indeed be at work to terminate El Nino events. In the present study, we investigate the respective contributions of Rossby wave reflection and wind forcing in the generation of interannual long equatorial Kelvin waves in the western Pacific Ocean using satellite data over the 1993–2001 period. The reflection efficiency of the western Pacific boundary (east of 165°E) is found to be about 80–90% of a perfect wall at interannual timescales. This result would suggest that the delayed action oscillator mechanism is indeed at work during that period. However, the wind contribution increases significantly from 145°E to 175°E and actually represents more than 80% of the Kelvin wave variance at 175°E. As a conclusion, although Rossby wave reflection is efficient and sufficient to theoretically terminate an El Nino event, easterly wind anomalies in the western Pacific during the mature phase of the 1997–1998 event mostly contribute to the upwelling Kelvin signal involved in the termination of the event confirming previous studies mainly based on other methods. If such a mechanism were found to be at work during other El Nino events, then the negative feedback mechanism of the delayed action oscillator mechanism would be a combination of easterly wind anomalies and wave reflection with a significant role played by easterly wind anomalies. Our result may support some aspects of the western Pacific oscillator paradigm.

L’objectiu d’aquest document és l’estudi de la instal•lació d’un parc eòlic al litoral català amb l’objectiu de generar electricitat mitjançant una font d’energia renovable com ara el vent. Es justificarà l’emplaçament escollit pel que fa la localització geogràfica tenint en compte tots els factors limitants existents ja siguin normatius, topogràfics, ambientals, marítims, etc. l’objectiu d’aquest document és l’estudi de la instal•lació d’un parc eòlic al litoral català amb l’objectiu de generar electricitat mitjançant una font d’energia renovable com ara el vent. Es justificarà l’emplaçament escollit pel que fa la localització geogràfica tenint en compte tots els factors limitants existents ja siguin normatius, topogràfics, ambientals, marítims, etc.

L’étude anthropologique des conceptions locales des phénomènes météorologiques est un point de vue privilégié pour s’interroger sur les définitions du climat fréquemment utilisées quand on fait référence aux communautés dites non occidentales. Dans ce texte, nous proposons de comprendre la relation entre les communautés rurales paysannes et autochtones de la région sud des Andes et le tourbillon de vent dans leur vie quotidienne. En nous basant sur notre propre expérience ethnographique et sur la littérature existante et locale, nous cherchons comment appréhender ce lien diffus mais constant entre le tourbillon et certaines entités malfaisantes, comme le diablo (diable)., The anthropological study of the local meteorological conceptions is a privileged point of view to question climate definitions often used when referencing the called non-western communities. In this work we attempt to understand the relationship between peasant and indigenous communities from south Andean regions and the whirlwind in their daily life. Based on our own ethnographic experience, historical and local literature, we try to apprehend this diffuse but constant link between whirlwind and some harmful entities, as the diablo (devil)., El estudio antropológico de las concepciones locales de los fenómenos meteorológicos es un punto de vista privilegiado para cuestionar las definiciones del clima que con frecuencia se reproducen cuando se hace referencia a las comunidades denominados como «no occidentales». En este texto, exploramos cómo las comunidades rurales campesinas e indígenas de la región sur de los Andes sitúan el remolino de viento en su universo cotidiano. Basándonos en nuestra experiencia etnográfica y en las referencias bibliográficas sobre la región, buscamos comprender la relación constante entre el remolino y ciertas entidades de potencias nocivas, verbigracia el diablo.

This paper presents a model of the Stokes emission vector from the ocean surface. The ocean surface is described as an ensemble of facets with Cox and Munk's (1954) Gram-Charlier slope distribution. The study discusses the impact of different up-wind and cross-wind rms slopes, skewness, peakedness, foam cover models and atmospheric effects on the azimuthal variation of the Stokes vector, as well as the limitations of the model. Simulation results compare favorably, both in mean value and azimuthal dependence, with SSM/I data at 53° incidence angle and with JPL's WINDRAD measurements at incidence angles from 30° to 65°, and at wind speeds from 2.5 to 11 m/s.

En la present tesina s’ha realitzat una recerca de tipologies i tecnologies actuals en el referent a estructures flotants i l’adaptació d’aquestes en l’estudi del comportament estàtic d’una torre flotant de suport per aerogeneradors construïda amb formigó. L’actual tendència en el marc global de les energies és un augment de la presència de les fonts d’energia renovable enfront les no renovables. Aquest fet, conjuntament amb la gran evolució en els últims anys de l’eficiència de la tecnologia de l’aprofitament de l’energia eòlica per a la producció d’electricitat, ha obert l’interès per la creació de nous grans parcs eòlics. Com a solució a la problemàtica, tant de caire mediambiental com de rebuig social pel seu impacte visual, que presenta la construcció d’aquestes infraestructures, en molts països es plantegen la seva construcció en el mar, en zones allunyades de la costa i que en la majoria de casos no permeten la fixació dels elements de suport al fons marí degut a les profunditats existents. Fins el dia d’avui s’han portat a terme alguns prototips, especialment al nord d’Europa, d’elements flotants per al suport d’aerogeneradors, tots ells dissenyats en acer i en fase de proves actualment. A mode d’innovació en el coneixement previ, en aquesta tesina s’ha considerat com a material de construcció el formigó, analitzant des d’un punt de vista estàtic el comportament d’una estructura flotant de tipus cilíndric de formigó enfront unes accions tipus. S’ha realitzat un estudi de flotabilitat d’aquest tipus d’estructures on s’observa les condicions de flotabilitat i estabilitat en funció de les seves dimensions i pes de llastrat, obtenint ordres de magnitud de les dimensions bàsiques, a partir de les quals es pot iniciar un anàlisi més acurat. El càlcul estructural s’ha realitzat mitjançant un model de càlcul estàtic no lineal de segon ordre, on les condicions de contorn de la interacció de l’estructura amb l’aigua s’han imposat en base a diferents hipòtesi que han permès simular de forma aproximada la resposta estructural d’un element d’aquest tipus amb models de càlcul estàndard. Finalment s’ha realitzat un predimensionament de l’estructura on s’ha definit l’acer passiu necessari així com una proposta de posttesat de l’estructura. En base als resultats obtinguts es dedueix que la construcció d’aquestes estructures amb formigó és viable tècnicament, tot i que cal adoptar nous models de càlcul més avançat per tal de continuar la recerca en aquest tema.

Cette étude concerne la simulation numérique directe d'ondes interfaciales séparant deux fluides incompressibles. Le modèle utilisé repose sur l'équation de Navier-Stokes et un suivi d'interface de type Volume Of Fluid (VOF). La résolution de cette équation nécessite d'inverser une équation de type Poisson, et pour cela, on a recours à une méthode multigrille. L'une des principales limitations de cette méthode est le rapport des masses volumiques des deux fluides. Nous nous proposons donc d'étudier l'influence de ce paramètre sur le comportement de l'algorithme. Le problème d'une onde interfaciale stationnaire est alors considéré pour différentes valeurs du rapport des masses volumiques.

The standard of living of the purse seine fishers operating in the northern coast of the Java Island is closely related to scad resources. Scads landings of the semi-industrial purse-seine fishery were analyzed using Seasonal Auto Regressive Integrated Moving Average (SARIMA) techniques. Several models were found to be suitable for describing the temporal fishery pattern and for forecasting the landings two years ahead. Forecasts were matched to actual data. It appears that such models can describe and forecast the dynamics of the scads fishery in the Java Sea. Until now, such results are difficult to predict owing to the strong influence of the year to year changes in the monsoon regime. Forecasting is more reliable with neritic species such as #Decapterus russellii$, since their spatial distribution in the Java Sea is relatively independent of the monsoon variability. On the contrary, oceanic species such as #Decapterus macrosoma$ are more difficult to forecast as their distribution is closely related to the environmental changes. In that case, transfer function models including environmental parameters would be more appropriate. (Résumé d'auteur)

En la actualidad, el cambio climático es un problema que afecta mucho al planeta. Hay diversos estudios realizados sobre como el cambio climático afecta al viento estudiando cómo puede afectar en un futuro. En este trabajo se analizará el impacto del viento sobre la operatividad portuaria, en concreto en el puerto de Tarragona comparando situaciones presentes y futuras. Para poder realizar el estudio se utilizan datos del viento modelados. Una vez se tienen los datos se deben analizar, mirando la dirección predominante del viento, los máximos valores de la velocidad anuales, los valores repetidos y el número de repeticiones. Una vez analizado los datos, se obtiene la probabilidad de excedencia de forma empírica y mediante el ajuste de Weibull para las dos situaciones y para climas medios y climas extremos. Una vez realizados los cálculos anteriores, con los parámetros obtenidos se calcula los períodos de retorno. Para calcular la inoperatividad se han utilizado directamente los datos del viento modelado y a partir de las limitaciones del viento para ciertas actividades que vienen regidas por la R.O.M se obtienen las horas de inoperatividad. Al final, se llega a la conclusión que el cambio climático no afecta mucho a lo que el viento se refiere. Aunque sí que aumenta la inoperatividad no superan los límites recomendados. Nowadays, climate change is a problem that is affecting the planet. There are several studies done on how climate change affects the wind studying how it can affect in a future situation This work will analyze the impact of the wind on the port operation, specifically in the port of Tarragona comparing present and future situations. Modeling wind data is used to perform the study. Once the data are given, it´s time to analyse them by looking at the prevailing wind direction, the maximum annual velocity values, the repeated values and the number of repetitions of each. Once the data are analyzed, the probability of exceedance is obtained empirically and by the Weibull adjustment for the two situations and for average climates and extreme climates. Once the previous calculations have been made, the return periods are calculated with the parameters obtained. In order to calculate the inoperativity, the data of the modeled wind have been used directly and from the limitations of the wind for certain activities that are governed by the R.O.M, the hours of inoperability are obtained. In the end, it is concluded that climate change does not affect much of what the wind refers to. Although it does increase inoperability do not exceed the recommended limits.

In the Sahel, wind erosion occurs particularly in cultivated fields. This work was leaded at Banizoumbou in Niger where wind erosion fluxes have been measured for six years. The aims of this study was i) to monitor crop residues cover on traditional field and to quantify its influence on wind erosion ii) to characterize the impacts of soils crusting on erosion flux, iii) to characterize the impact of herbaceous strips on wind flux. Results showed that crop residues efficiently prevent cultivated fields from wind erosion during the dry season (January to April) and considerably reduce erosion fluxes at the beginning of the rainy season (May to July). Under a minimal crop residues cover rate of about 100 Kg.ha-1, soil losses by wind erosion would dramatically increase and favoured the development of erosion crust. These crusts lead to supply limitation of particles by wind and thus decreased wind erosion fluxes. In addition, herbaceous strips have also contributed to reduce soil lost by wind erosion on the bare soil. But they didn’t avoid soil crusting., En el Sahel, la erosión eólica se desarrolla particularmente sobre las superficies cultivadas. Este estudio tiene come objetivo: 1) cuantificar los residuos de cultivo en los campos tradicionales para determinar sus impactos sobre la intensidad de los flujos de erosión eólica; 2) determinar el papel de la erosión eólica en el desarrollo de las costras de erosión; 3) probar el papel que podrían jugar acondicionamientos de tipo franjas herbáceas de contorno sobre suelos desnudos muy sensibles. Seis años de medidas de flujos de erosión eólica se realizaron a Banizoumbou en el suroeste de Níger. Permitieron mostrar que los residuos de cultivo protegen la superficie de los campos de la erosión eólica durante la estación seca (enero – abril) y la disminuyen significativamente (más de tres veces) al principio de la estación lluviosa (mayo – julio). Sin embargo, debajo de un umbral de 100 kg.ha-1 de recubrimiento por los residuos de cultivo, la erosión eólica interviene durante todas las estaciones, fomentando el desarrollo de las costras de erosión. Estas pueden modificar los flujos de erosión eólica limitando el stock de partículas movilizadas. De otra manera, las franjas herbáceas de contorno contribuyeron a bajar los flujos de erosión eólica sobre los suelos desnudos pero no evitaron el desarrollo de las costras., Au Sahel, l'érosion éolienne se développe particulièrement sur les surfaces cultivées. La présente étude vise : 1) à quantifier les résidus de culture sur les champs traditionnels pour en déterminer leurs impacts sur l'intensité des flux d'érosion éolienne ; 2) à déterminer le rôle de l'érosion éolienne dans le développement des croûtes d'érosion d'horizon B et à déterminer en retour l'impact de cet encroû-tement sur le flux d'érosion éolienne ; 3) à tester le rôle que pourraient jouer des aménagements de type bandes enherbées sur des sols nus très sensibles. Six années de mesures de flux d'érosion éolienne ont été entreprises à Banizoumbou dans le sud-ouest du Niger. Celles-ci ont permis de montrer que les résidus de culture protègent la surface des champs de l'érosion éolienne pendant la saison sèche (janvier-avril) et la diminuent significativement (de plus de 3 fois) au début de la saison des pluies (mai-juillet). Cependant, en dessous d'un seuil de 100 kg.ha-1 de recouvrement par les résidus de culture, l'érosion éolienne intervient pendant toutes les saisons, favorisant du coup le développement des croûtes d'érosion. Celles-ci peuvent modifier les flux d'érosion éolienne en limitant le stock de particules mobilisables. Par ailleurs, les bandes enherbées ont contribué à baisser les flux d'érosion éolienne sur les sols nus, mais n'ont pas évité le dévelop-pement des croûtes. mots clés Sahel, érosion éolienne, résidus de culture, croûtes d'érosion, champs cultivés.

Guincho is known as the windiest beach of Portugal, ideal for nautical activities, such as windsurfing and kitesurfing. The main goals of this study are to explore the wind characteristics in Guincho and to compare the synoptic forecasts accessible to the public with actually occurring weather conditions. We used meteorological data, synoptical information, forecasts and field observations during the summers of 2009 and 2010. A sample of 124 days with good conditions for windsurfing were selected and classified into different groups. Within each group, the wind measured (and indirectly observed) in Guincho was compared to the results of the Global Forecast System (GFS). This analysis led to a useful classification allowing interpretation of GFS surface wind forecasts available to surfers at Guincho. We conclude that global weather models do not accurately forecast the wind, particularly due to model resolution and parameterisations, which do not detail local phenomena., O vento como recurso para práticas náuticas recreativas. O caso da praia do Guincho. A praia do Guincho, conhecida como a mais ventosa de Portugal, é ideal para a prática de windsurf e kitesurf. O principal objectivo deste estudo é explorar as características do vento no Guincho, comparando-as com as previsões me‑ teorológicas, acessíveis ao público. Usaram-se dados meteorológicos, informações si‑ nópticas, previsões e observações de terreno feitas nos verões de 2009 e 2010. Foi utili‑ zada uma amostra de 124 dias, com boas condições para a prática de windsurf, a qual foi classificada em diferentes grupos. Dentro de cada grupo foi medida a intensidade do vento (também observada indirectamente), tendo sido depois comparados com os resul‑ tados do modelo americano de previsão (Global Forecast System – GFS). Esta análise conduziu a uma classificação, que é útil para interpretar as previsões do GFS acessíveis a quem pratica surf no Guincho. Chegou-se à conclusão de que os modelos de previsão não são suficientemente rigorosos para dar conta das condições de vento, porque a resolução e o tipo de parametrização dos modelos não atende às características particulares dos locais., Le Vent, une ressource pour les activités nautiques récréatives: Le cas de guincho. La plage de Guincho, qui est connue pour être la plus ventée du Portugal, est un lieu idéal pour la pratique de la planche à voile et du kitesurf. L’objectif de cette étude est d’établir les caractéristiques du vent à Guincho et leur lien avec la situation synoptique. Elle est basée sur des données météorologiques (information synoptique, pré‑ visions et observations sur le terrain), obtenues pendant les étés 2009 et 2010. On a analysé un échantillon de 124 jours ayant des conditions adéquates pour la pratique de la planche à voile. Ils ont été analysés et classés par similarité en différents groupes. Pour chacun d’eux, la vitesse et la direction du vent ont été comparées aux données de prévision du modèle américain Global Forecast System (GFS), ce qui a permis d’établir une classification utile pour interpréter ladite prévision, facilement accessible aux pratiquants d’activités nautiques à Guincho. On en conclut que les modèles globaux de prévision sont insuffisamment précis et rigoureux, parce que leur résolution et leur paramétrisation ne détaillent pas assez les caractéristiques locales.

L’estudi de l’acció del vent sobre edificis complexes (estadis, torres de gran altura...) requereix sovint una precisió superior a l'obtinguda mitjançant l’aplicació directa de les normatives (Eurocodi 1-4) i avui dia s’està generalitzant l’ús d’assajos en un túnel de vent sobre una maqueta de l’edifici. Aquests assajos, però, donen “masses” resultats en el sentit que els enginyers encarregats de fer la verificació de la estructura disposen d’un temps limitat i només solen explotar una part molt reduïda de tota la informació disponible per mitjà de simplificacions. Aquesta tesina vol proposar un mètode per a treure el màxim profit a totes les dades de l’assaig en túnel de vent amb l’objectiu de crear un sistema de càrregues a aplicar al model d’elements finits de la estructura que sigui el més pròxim al que realment actuarà sobre la estructura (separació de les càrregues de pressió del vent de les càrregues dinàmiques). De la mateixa manera, s’implementarà el mètode a SCILAB (MATLAB) amb l’objectiu d’automatitzar-lo el màxim possible i es verificarà amb la seva aplicació a l’estudi de l'efecte del vent a la Tour Majunga a la Défense (Paris).

Acoustic tomography aims at recovering the unknown parameters that describe a field of interest by studying the physical characteristics of sound propagating through the considered field. The tomographic approach is appealing in that it is non-invasive and allows to obtain a significantly larger amount of data compared to the classical one-sensor one-measurement setup. It has, however, two major drawbacks which may limit its applicability in a practical setting: the methods by which the tomographic data are acquired and then converted to the field values are computationally intensive and often ill-conditioned. This thesis specifically addresses these two shortcomings by proposing novel acoustic tomography algorithms for signal acquisition and field reconstruction. The first part of our exposition deals with some theoretical aspects of the tomographic sampling problems and associated reconstruction schemes for scalar and vector tomography. We show that the classical time-of-flight measurements are not sufficient for full vector field reconstruction. As a solution, an additional set of measurements is proposed. The main advantage of the proposed set is that it can be directly computed from acoustic measurements. It thus avoids the need for extra measuring devices. We then describe three novel reconstruction methods that are conceptually quite different. The first one is based on quadratic optimization and does not require any a priori information. The second method builds upon the notion of sparsity in order to increase the reconstruction accuracy when little data is available. The third approach views tomographic reconstruction as a parametric estimation problem and solves it using recent sampling results on non-bandlimited signals. The proposed methods are compared and their respective advantages are outlined. The second part of our work is dedicated to the application of the proposed algorithms to three practical problems: breast cancer detection, thermal therapy monitoring, and temperature monitoring in the atmosphere. We address the problem of breast cancer detection by computing a map of sound speed in breast tissue. A noteworthy contribution of this thesis is the development of a signal processing technique that significantly reduces the artifacts that arise in very inhomogeneous and absorbent tissue. Temperature monitoring during thermal therapies is then considered. We show how some of our algorithms allow for an increased spatial resolution and propose ways to reduce the computational complexity. Finally, we demonstrate the feasibility of tomographic temperature monitoring in the atmosphere using a custom-built laboratory-scale experiment. In particular, we discuss various practical aspects of time-of-flight measurement using cheap, off-the-shelf sensing devices.

Background Deep-sea hydrothermal vent animals occupy patchy and ephemeral habitats supported by chemosynthetic primary production. Volcanic and tectonic activities controlling the turnover of these habitats contribute to demographic instability that erodes genetic variation within and among colonies of these animals. We examined DNA sequences from one mitochondrial and three nuclear gene loci to assess genetic diversity in the siboglinid tubeworm, Riftia pachyptila, a widely distributed constituent of vents along the East Pacific Rise and Galápagos Rift. Results Genetic differentiation (F ST ) among populations increased with geographical distances, as expected under a linear stepping-stone model of dispersal. Low levels of DNA sequence diversity occurred at all four loci, allowing us to exclude the hypothesis that an idiosyncratic selective sweep eliminated mitochondrial diversity alone. Total gene diversity declined with tectonic spreading rates. The southernmost populations, which are subjected to superfast spreading rates and high probabilities of extinction, are relatively homogenous genetically. Conclusions Compared to other vent species, DNA sequence diversity is extremely low in R. pachyptila. Though its dispersal abilities appear to be effective, the low diversity, particularly in southern hemisphere populations, is consistent with frequent local extinction and (re)colonization events.

Un type de fouet, en forme de gourdin pourvu d'une double laniere de cuir, a ete identifie dans les scenes et dans la statuaire, et confronte a un exemplaire de manche en bois. Les sources temoignent de l'utilisation de ce fouet par le gardien dans les bâtiments institutionnels, le marin nfw sur les bateaux et le laboureur dans les scenes d'agriculture.

Variations of the zonal pressure gradient (ZPG) and the Equatorial Undercurrent (EUC) are described in the equatorial Atlantic Ocean (between 34° 30′W and 6°30′E) as observed during eight pairs of Programme Francais Ocean et Climate dans l'Atlantique Equatorial cruises between October 1982 and August 1984. In 1982 and 1983 the annual cycle of weak trades early in the year, followed by comparatively strong and sustained trades, were relatively normal. In the boreal winter of 1984, the extent of the collapse of the trade winds was exceptional, and consequences were observed in the upper layers of the ocean along the equator. The 20°C isotherm depth, representative of the thermocline depth, was unusually deep along the equator in the Gulf of Guinea. A near-zero value of the ZPG was observed from the Greenwich meridian westward. An eastward surface current, separated from the EUC by a layer of reduced velocity, was observed over much the same fetch. West of 10°W the maximum velocity of the EUC showed very little seasonal variation, usually between 70 and 80 cm s−1, except in the boreal fall of 1983 when it exceeded 100 cm s−1. During this period (in both 1983 and 1984) the EUC transport at 23°W reached 25 × 106 m3 s−1, or twice its annual average, which derived not only from the increase in speed but also for a deepening of the current to below 100 m. It was also the season when the ZPG was strongest and has a similar amplitude at both the surface and 50 dbar relative to 500 dbar. The seasonal variations of the EUC in the Gulf of Guinea were even more pronounced. During the boreal summer and fall, the current weakened, while the local ZPG reversed direction compared to the west. The stronger penetration of the EUC into the gulf occurred in the alternate seasons when there was no local reversal in the eastward acting ZPG force. The large changes in the oceanic and atmospheric circulation during the 1983–1984 period are hypothesized to be related to the suppression of the coastal period are hypothesized to be related to the suppression of the coastal Benguela upwelling along the Namibia coast. This Atlantic equivalent to El Nino occurred 1 year after the exceptionally strong event in the Pacific.