Les mycotoxines sont des métabolites secondaires des moisissures qui contaminentnaturellement de nombreuses denrées alimentaires, notamment les céréales. Certainesmycotoxines présentent des effets toxiques potentiellement dangereux pour l’homme à desdoses extrêmement faibles. Les objectifs de ce travail étaient d’évaluer in vitro : (1) la toxicitéde trois mycotoxines qualifiées d’émergentes : la beauvericine, l’enniatine B et lamoniliformine ; (2) les effets de mycotoxines testées simultanément : déoxynivalénol etbeauvericine, déoxynivalénol et fumonisine B1, déoxynivalénol et zéaralénone,déoxynivalénol et toxine T-2, toxine T-2 et zéaralénone, beauvericine et enniatine B. Lesétudes ont été réalisées sur des cellules humaines d’origine hématopoïétique, en raison de leurforte sensibilité connue à certaines mycotoxines majeures. La myélotoxicité a été évaluée surles progéniteurs hématopoïétiques granulo-monocytaires, érythrocytaires et plaquettaires.L’immunotoxicité a été évaluée sur les cellules dendritiques et les macrophages.Un effet cytotoxique a été observé pour les progéniteurs hématopoïétiques exposésaux toxines émergentes. Une inhibition de la différenciation des progéniteurs érythroïdes a éténotée en présence d’enniatine B ou de moniliformine. Une cytotoxicité a été mise en évidencepour les cellules immunitaires exposées à la beauvericine ou à l’enniatine B. L’exposition à lamoniliformine a provoqué une inhibition de la différenciation des monocytes en cellulesdendritiques ou en macrophages. Une inhibition de la capacité de maturation des cellulesdendritiques a été mise en évidence en présence de beauvericine ou d’enniatine B. Les travauxmenés en co-exposition ont montré des effets cytotoxiques principalement additifs sur lesprogéniteurs hématopoïétiques et sur les cellules dendritiques. Une synergie a été observéepour les progéniteurs hématopoïétiques exposés au déoxynivalénol et à la beauvericine. Unantagonisme a été noté pour les progéniteurs et pour les cellules dendritiques exposéssimultanément au déoxynivalénol et à la fumonisine B1.Ces travaux réalisés in vitro suggèrent que les mycotoxines émergentes pourraientprovoquer chez l’homme une diminution du nombre et un dysfonctionnement des celluleshématopoïétiques, avec pour conséquence l’induction de troubles hématologiques etimmunologiques. La présence concomitante de mycotoxines pourrait augmenter le risque demyélotoxicité et d’immunotoxicité chez l’homme. Des études in vivo devraient être menéesafin de compléter ces travaux. / Mycotoxins are secondary metabolites of fungi that are natural contaminants ofseveral commodities, in particular cereals. The main objectives of the thesis were to assess thein vitro toxicity of: (1) emerging mycotoxins beauvericin, enniatin b and moniliformin; (2)combinations of fusariotoxins known to co-contaminate cereals or food commodities:deoxynivalenol and beauvericin, deoxynivalenol and fumonisin B1, deoxynivalenol andzearalenone, deoxynivalenol and T-2, T-2 and zearalenone, beauvericin and enniatin B.Experiences have been done using human hematopoietic cells. Myelotoxicity has beenevaluated using clonogenic assays on granulo-monocytic, erythroid and megakaryocyticprogenitors. Immunotoxicity has been assessed on dendritic cells and macrophages.Emerging mycotoxins were cytotoxic for hematopoietic progenitors. Inhibition oferythroid differentiation has been observed in the presence of enniatin b or moniliformin.Beauvericin and enniatin B were cytotoxic for dendritic cells and macrophages. Thedifferentiation process of monocytes into immature dendritic cells or into macrophages wasdisturbed in the presence of moniliformin. Beauvericin and enniatin B have been shown tointeract with dendritic cells maturation process. Additive myelotoxic and immunotoxic effectswere observed for combination of deoxynivalenol and zearalenone, deoxynivalenol and T-2,T-2 and zearalenone, beauvericin and enniatin B. Co-exposure of granulo-monocyticprogenitors to deoxynivalenol and beauvericin resulted in synergic effects. Combination ofdeoxynivalenol and fumonisin B1 showed antagonist myelotoxic and immunotoxic effects.These in vitro results suggested that emerging mycotoxins could be responsible forhematological and immunological troubles on human in case of consumption of contaminatedcommodities. Simultaneous presence of mycotoxins in food commodities and diet may bemore toxic than the presence of one mycotoxin alone. In vivo studies should be performed totest these hypotheses.

Depuis les années 1990, l'aulne glutineux, espèce clé des ripisylves, est affecté par un oomycète qui cause son dépérissement : Phytophthora alni subsp. alni (Paa). La genèse de Paa est liée à un événement d'hybridation interspécifique entre deux espèces proches, improprement nommées P. alni subsp. uniformis (Pau) et P. alni subsp. multiformis (Pam), car initialement considérées comme des variants de Paa. L'objectif de cette thèse était d'identifier les facteurs ayant pu jouer un rôle dans l'émergence de la maladie en Europe. Par une approche de génétique des populations, nous avons montré que Pau est une espèce invasive en Europe, probablement originaire d'Amérique du Nord. Après son introduction, l'hybridation de Pau avec Pam serait l'un des facteurs essentiels de l'apparition de Paa. Nos résultats confirment que Paa aurait été généré suite à des hybridations récurrentes, qui ont structuré géographiquement les populations en Europe. L'analyse de la variabilité génétique de Paa, révélée par des marqueurs microsatellites, a toutefois montré un faible polymorphisme, avec un génotype dominant largement répandu en Europe. Par ailleurs grâce à la modélisation, nos résultats ont établi que le dépérissement du houppier des aulnes est lié à la température. En particulier l'incidence de la maladie augmente lors des hivers doux, qui pourraient favoriser la survie du mycélium de Paa, celui-ci ne présentant pas de structure de survie hivernale (chlamydospores ou oospores). La température estivale joue également un rôle, plus complexe à interpréter. On constate en effet que l'incidence de la maladie diminue avec l'augmentation des températures estivales, mais ce phénomène pourrait dépendre d'autres facteurs tels que l'état physiologique des arbres ou le type de communautés microbiologiques présentes dans les sols. Inversement, le phénomène de guérison des arbres est favorisé par des températures hivernales basses et par des températures estivales élevées. L'émergence de la maladie ne peut pas être expliquée par le changement climatique. Cependant, une augmentation des températures hivernales dans le futur dans le cadre du changement climatique aggraverait très probablement l'épidémie / Since the early 1990's alder decline caused by the oomycete Phytophthora alni subsp. alni (Paa) is one of the most important threats to riparian ecosystems in Europe. The emergence of Paa is related to an interspecific hybridization event between two related species -initially considered as Paa variants- misnamed as Phytophthora alni subsp. uniformis (Pau) and Phytophthora alni subsp. multiformis (Pam). The objective of this thesis was to identify the factors that may have contributed to the emergence of the disease in Europe. Following a population genetics approach we showed that Pau is likely to be an invasive species in Europe, probably native to North America. Its introduction would have enabled hybridization with Pam and, consequently be a major cause on the emergence of Paa. Our results confirm that Paa has arisen from several hybridization events, which have geographically structured its European populations. Paa's genetic variability, revealed by microsatellite markers, showed low levels of polymorphism, with a dominant genotype scattered throughout Europe. In addition, a modelling approach revealed that alders' crown decline is linked to temperature. In particular, the disease incidence increases during mild winters which favours mycelium survival as Paa does not produce resistant spores (chlamydospores or oospores). The effect of summer temperatures is more complex to explain. Disease incidence decreases when summer temperatures are higher, but this phenomenon can also be linked to the physiological conditions of trees or changes in soil microbiological communities. Conversely, tree recovery is favoured by lower winter and higher summer temperatures. Climate change does not explain the emergence of the disease. However, increases in winter temperatures du to climate change may strengthen the epidemic

A closer look at innovation for and from emerging markets respectively developing economies reveals that a variety of different terms and concepts related to this type of innovation exist. The goal of my conceptual paper is to present a comprehensive overview of related terms and concepts and to suggest theoretical based classification criteria in order to differentiate them. After a first investigation in relation to innovation for and from emerging markets the keywords ‘reverse’, ‘frugal’, ‘jugaad’, and ‘bottom of the pyramid / bottom of pyramid / bop’ were identified and used for searching the database of Google Scholar. For further investigation only texts were considered with at least eight various terms. 19 different texts were identified which classified for a further analysis. As results 33 identified terms in relation to innovation for and from emerging markets, various spellings and synonyms and references with at least two mentions in the identified texts are presented. As theoretical based classification criteria ‘market orientation’, ‘determinants’ (of innovation for and from emerging market)’, ‘nature’ (of innovation for and from emerging markets), sophistication’, ‘sustainability’, ‘novelty’ and ‘innovator type’ were identified.

This dissertation consists of two essays. First essay investigates Fortune 500 companies that implemented Six Sigma. Since the 1980s, industrial organizations have adopted practices such as Six Sigma to maintain and enhance competitiveness. The purpose of this study is to look at the long run stock price and the operating performance of Fortune 500 companies that were identified to have implemented Six Sigma compared to the overall market performance as well as the performance of industry and size matched firms. Even though our sample firms improved several variables after implementing Six Sigma, their operating performances were not quite close to the performances of the matching firms. After implementing Six Sigma, compared to the industry and size matched firms, the only variable that improved out of 14 variables we looked at, is the growth in staff levels. The findings may contribute to understanding the reasons that underlie the so-called jobless recovery. Second essay investigates the real estate price indices in 19 emerging markets. The main objectives of the central banks are not necessarily in line with the goals for asset prices, particularly house prices; however house price changes can have important implications for economic activity and inflation. The consequences of excess changes in house prices also should be watched carefully by central banks and other government agencies that regulate financial institutions for the purpose of financial stability. This essay searches for a link between house prices, broad money, private credit and the macro-economy among 19 emerging markets. We are also trying to explain which variables predict the emerging markets real estate index returns. Our results show that money market rate, growth in GDP and CPI as well as log of private credit and money supply have significant predictive power on growth in real estate price indices a quarter ahead. We also show that there is multidirectional causality among all of the variables. A unique data is being used for the emerging markets real estate price indexes in this study. The data is provided by aDubaibased private company which offers emerging markets real estate information to its customers.

Since the opening of formerly closed markets in Eastern Europe and China in the early 1990s, numerous firms have sought to capture the growth opportunities prevailing in the virgin but institutionally distant business networks in these countries. I claim that the entry process into an institutionally distant business network has been realised when the entering firm has reached an insidership position in the network. To advance this idea, the thesis introduces the overlooked medium-sized multinational exporter (MME) and answers the following overarching research questions: (I) how do MMEs establish insidership positions in institutionally distant business networks, and (II) what critical abilities are developed by MMEs in the process of entering an institutionally distant business network? To answer these questions, qualitative and quantitative methods have sequentially been mixed to first give an in-depth understanding of the empirical field, and second to verify and generalise some of the most central tentative findings. Empirically, the study reports from a case study of eight firms in the Baltic Sea Region and from an on-site survey of 203 Swedish firms with experience of entries in Eastern Europe and/or China. Five individual essays are presented—all designed to reflect different aspects of the institutionally distant network entry process. The findings are condensed in the cover of the thesis, where it is claimed that an insidership position is reached through three main phases: the Scouting phase, the Qualifying phase and the Shielding phase. Furthermore, it is found that that the most critical abilities developed through the institutionally distant network entry process is local experience-based knowledge of high specificity. It is shown that previous experiences, generated in different business networks in mature markets, are not useful in the network entry process in immature markets. As a consequence, there is reason to believe that the entering firm needs to develop unlearning abilities to replace obsolete or misleading experience.

Le but de ce travail est de tester une approche multi-traceurs permettant de caractériser l'origine (éléments majeurs, Sr, Br, 87Sr/86Sr, δ18O, δ2H) et les temps de résidence (3H/3He, CFC, SF6) des eaux, pour identifier l'origine et évaluer le devenir des contaminants dans une nappe alluviale superficielle et peu profonde, la nappe de la Vistrenque. Les molécules étudiées sont les triazines, le métolachlore, le diuron, la carbamazépine, le sulfaméthoxazole, le diclofénac et l'ibuprofène. L'aquifère étudié est alimenté par une recharge directe, occasionnant le lessivage des pesticides des sols, et une recharge latérale provenant de l'aquifère karstique adjacent entraînant une dilution des eaux de la nappe en triazines. Localement, une contribution des eaux de surface (cours d'eau locaux, eau importée du Rhône) à la recharge de la nappe est mise en évidence entraînant également une dilution des eaux de la nappe en triazines mais au contraire une contamination en COE, quoique, en faibles concentrations. Les âges apparents des eaux alluviales échantillonnées, déterminés principalement par le couple 3H/3He, varient entre 1.4 et 22 ans. Le couplage de l'âge des eaux à leurs teneurs en triazines montre une persistance de ces molécules dans le milieu souterrain, et une atténuation de leur signal d'entrée soulignant l'efficacité de leur interdiction en 2003. Finalement, les eaux de la nappe alluviale montrent des rapports de dégradation des triazines variant entre 0,3 pour les eaux influencées par les eaux de surface et 4,8 pour celles montrant des âges apparents de 22 ans, suggérant une augmentation de ce rapport avec le temps de transfert des pesticides dans le système. / The aim of this work is to test a multi-tracer approach allowing the characterization of groundwater origin and residence time in a shallow alluvial aquifer, the Vistrenque aquifer, in order to identify the origin and the fate of contaminants therein. The selected compounds for the study are triazines, metolachlor, diuron, carbamazepine, sulfamethoxazole, diclofenac, and ibuprofen. The studied aquifer is mainly fed by 1) a direct recharge inducing pesticides leaching from soil layers and unsaturated zone and 2) by a lateral recharge from the karst adjacent aquifer, which induces triazines dilution in the alluvial aquifer. A local contribution of surface water (local streams and imported Rhône River water) was evidenced in the alluvial groundwater inducing also triazines dilution but EOCs contamination nevertheless at low concentrations. The apparent age of the alluvial groundwater samples varies between 1.4 and 22 years. Linking groundwater age to triazines contents allowed to highlight, first, the persistence of these compounds in the alluvial groundwater and, second, the decreasing of their input signal in relatively recent groundwater samples in accordance with their forbidding in 2003. Finally, the Vistrenque alluvial groundwater showed triazines degradation ratios varying from 0.3 for groundwater influenced by surface water infiltration to 4.8 for groundwater characterized by relatively older apparent residence time on the order of 22 years. This suggests an increasing ratio with the transfer time of these compounds in the alluvial aquifer system.

O desafio para amenizar a degradação do meio ambiente, principalmente referente às mudanças climáticas, tem levado a um aumento no interesse em mecanismos que incentivem o desenvolvimento e a adoção de tecnologias verdes. Uma dessas tecnologias refere-se à exploração de energia por meio da radiação solar. Por meio de patentes sobre energia fotovoltaica (PV) classificadas no IPC Green Inventory e depositadas entre 1998, esta pesquisa tem como objetivo compreender se as organizações proprietárias das tecnologias PV emergentes as desenvolvem por meio de cooperação tecnológica. A identificação das tecnologias emergentes ocorre por meio da análise de rotas tecnológicas bem como na observação da cooperação tecnológica entre titulares de patentes PV obtidas utilizando a metodologia de análise de redes sociais. Assim, foi possível descrever o perfil dos titulares das patentes PV, identificar as rotas e as tecnologias mais emergentes e promissoras e ainda mapear/caracterizar as redes de cooperação formada pelos titulares dessas patentes. Os resultados permitiram constatar que as organizações detentoras das principais patentes PV priorizam os seus desenvolvimentos exclusivamente nas suas áreas internas de P&D, abrindo mão de vantagens amplamente discutidas na literatura sobre a cooperação tecnológica. Também se concluiu que a indústria PV é predominante fechada, com relações de cooperação prioritárias entre organizações de mesma nacionalidade, organizações japonesas e americanas são as maiores influenciadoras nessas redes de cooperação e a base tecnológica para as tecnologias PV mais emergentes estão concentrados nos escritórios em patentes dos Estados Unidos e Japão. Além disso, a China tem evoluído exponencialmente na produção de patentes PV, mas ainda não se destaca como principal influenciador no desenvolvimento de inovações PV e as rotas tecnológicas também denotam um perfil de desenvolvimento não-colaborativo, com foco em criação interna ou aquisição de pesquisadores independentes. Os resultados também permitiram constatar o papel insignificante do Brasil no desenvolvimento de tecnologias PV. Apesar da crescente evolução nos últimos anos, os esforços têm sido tímidos e focados no fomento à geração de energia PV e não no desenvolvimento deste tipo de tecnologia. Apesar deste contexto, um conjunto de recomendações é dado para alavancar o potencial de desenvolvimento de tecnologias PV pelo Brasil com base em lições de países como China, Estados Unidos e Japão. Estes resultados também podem auxiliar pesquisadores, empresas e/ou universidades na identificação de tecnologias emergentes para a indústria PV. Além disso, pode apoiar nas decisões estratégicas sobre P&D, na priorização de investimentos, na identificação de potenciais parcerias (ou concorrentes) para desenvolvimento tecnológico e colaborar na definição de políticas públicas pautadas no fomento ao desenvolvimento e uso de energia PV / The challenge of mitigating the environment degradation, especially issues related to climate change, has led to an increase in interest in mechanisms that encourage development and adoption of green technologies. So, fostering innovation and development of green technologies becomes necessary for environmental and business sustainability. One of them, based on renewable and non-polluting resources, refers to the exploitation of energy through solar radiation called photovoltaic (PV). Through PV energy patents classified in the IPC Green Inventory and applied from 1998 to 2017 in the world\'s leading patent offices, this research aims to understand if assignees of emerging PV technologies develop them through technological cooperation. The identification of emerging technologies occurs using analysis of technological routes as well as the observation of technological cooperation between PV assignees is designed by analysis of social networks. Thus, it was possible to describe the profile of PV patents assignees, identify the technological routes and most promising and emerging PV technologies, and characterize technological cooperation between PV assignees. The findings pointed out that the organizations that own main PV patents prioritize their development exclusively in their internal R&D areas, leaving aside the widely discussed advantages of technological cooperation. It was also concluded that PV industry is predominantly closed in a collaborative point of view, prioritize relations between organizations of the same nationality, Japanese and American organizations are the major influencers in the cooperation networks of PV assignees and technological base of the most emerging technologies are concentrated in patent offices in the USA and Japan. In addition, China has evolved exponentially in PV patents production but still does not stand out as the main influencer in the development of PV innovations and the technological routes also denote a profile of non-collaborative development, with focus on internal creation or acquisition of independent researchers. The results also allowed us to verify the insignificant role of Brazil in the development of PV technologies. Despite the growing trend in recent years, efforts have been timid and focused on fostering PV power generation and not on the development of this type of technology. Despite this context, a set of recommendations is given to leverage the potential for development of PV technologies by Brazil based on lessons from countries such as China, the United States and Japan. These results may assist researchers, companies and universities to identify emerging technologies in the PV industry. In addition, it can support strategic decisions on R&D, prioritize investments, identify potential partnerships (or competitors) for technological development and collaborate in the definition of public policies based on development and use of PV solar energy

La recherche porte sur le sentiment identitaire professionnel des débutants infirmiers. Elle interroge le vécu subjectif des débuts professionnels et éclaire les rapports entre les dynamiques identitaires (Kaddouri, 2006) en jeu dans cette transition (Guichard, 2007) et l’émergence de la professionnalité. La méthodologie qualitative dans le cadre d’une approche psychophénoménologique (Vermersch, 2012), permet de questionner la logique personnelle du sujet dans ces moments (Mouchet, 2014), en mobilisant principalement les concepts de sentiment identitaire (Erikson, 1968 ; Allport, 1970 ; Tap, 1988) et de professionnalité émergente (Jorro, 2011). L’étude longitudinale s’appuie sur des entretiens compréhensifs (Kaufmann, 2014), d’explicitation (Vermersch, 1994) avec décryptage de sens (Faingold, 1998, 2011) et d’explicitation biographique (Lesourd, 2009). Les résultats mettent en évidence l’émergence d’un sentiment identitaire professionnel nécessaire à la construction de la professionnalité émergente spécifique des débutants infirmiers, et pourraient être pris en compte pour repenser leur accompagnement. / The doctoral research focuses on nursing beginners’professional identity feeling. It questions subjective experience about starting and enlightens the relations between identity dynamics (Kaddouri, 2006) during this transition (Guichard, 2007) and the emergence of the beginner’s professionalism. The qualitative methodology, in a psychophenomenology approach (Vermersch, 2012), questions personal subject logic in these moments (Mouchet, 2014) ; it mainly relies on concepts of identity feeling (Erikson, 1968; Allport, 1970; Tap, 1988) and emerging professionalism (Jorro, 2011).The longitudinal study is based on comprehensive interviews (Kaufmann, 2014), elicitation interviews (Vermersch, 1994) completed with the decryption of meanings (Faingold, 2011) and biographical interviews combined with elicitation (Lesourd, 2009).The results reveal a professional identity feeling which emerges among the beginners, and which is useful to develop their specific emerging beginning professionalism, and help to reconsider the professional accompaniment.

O interesse por técnicas analíticas que ofereçam a sensibilidade adequada, que sejam econômicas, ambientalmente corretas e capazes de processar rapidamente um grande número de amostras de diferentes complexidades é cada vez maior. Nesse aspecto, a utilização da LC no modo multidimensional é alternativa promissora, especialmente quando estratégias de extração e pré-concentração em fase sólida acopladas de forma on-line com a separação são exploradas, tanto em escala convencional quanto em escala miniaturizada. A ocorrência ambiental de contaminantes emergentes (EDCs) e seus impactos nas formas de vida aquática e terrestre têm sido motivo de preocupação. A quantificação desses analitos no ambiente exige métodos com limites de detecção (LDs) muito baixos, fazendo das estratégias column switching, com a inerente pré-concentração on-line, pertinentes para satisfazer as exigências na determinação desses compostos. Nesse cenário, o desenvolvimento e avaliação de estratégias column switching para determinação de contaminantes emergentes em amostras de interesse ambiental como aplicação modelo no estudo comparativo entre as escalas convencional e miniaturizada se faz impactante. Várias estratégias abrangendo column switching capilar e convencional foram investigadas. Colunas extratoras preenchidas com fases comerciais foram avaliadas, e tiveram seu desempenho testado no acoplamento com diversas colunas analíticas. Métodos em column switching capilar e convencional foram desenvolvidos e validados, tendo sido avaliadas as principais figuras de mérito. Os LQs atingidos em CS-UHPLC-ESI-MS/MS variaram de 0,001 ng mL-1 (BP e BzP) a 0,1 ng mL-1 (E3, E2 e EE2); para o método CS-cLC-ESI-MS/MS, os LQs foram maiores, variando entre 0,008 ng mL-1 (BP e BzP) a 0,8 ng mL-1 (E3, E2 e EE2). A linearidade dos métodos foi atestada avaliando-se os gráficos de resíduos, coeficiente de determinação e aplicando-se ponderações quando pertinente. A exatidão e a precisão foram investigadas, apresentando valores dentro dos critérios de aceitação. Por fim, os métodos foram aplicados em amostras ambientais aquosas coletadas em São Carlos - SP, mostrando que os métodos são adequados ao fim a que se destinam. / The interest in analytical techniques that offer adequate sensitivity, that are economical, environmentally friendly and capable of rapidly processing many samples of different complexities is increasing. In this regard, the use of LC in the multidimensional mode is a promising alternative, especially when solid phase extraction and preconcentration strategies coupled online with the separation are explored, both on a conventional scale and on a miniaturized scale. The environmental occurrence of emerging pollutants (EDCs) and their impacts on aquatic and terrestrial life forms have been of concern. Quantification of these analytes in the environment requires methods with very low detection limits (LDs), making column switching strategies with the inherent preconcentration online relevant to satisfy the requirements in determining these compounds. In this scenario, the development and evaluation of column switching strategies for the determination of emerging contaminants in samples of environmental interest as an application model in the comparative study between conventional and miniaturized scales is striking. Several strategies covering capillary and conventional column switching were investigated. Extraction columns filled with commercial phases were evaluated, and their performance was tested in the coupling with several analytical columns. Methods in capillary and conventional column switching modes were developed and validated, and the main figures of merit were evaluated. The LQs reached in CS-UHPLC-ESI-MS / MS ranged from 0.001 ng mL-1 (BP and BzP) to 0.1 ng mL-1 (E3, E2 and EE2); for the CS-cLC-ESI-MS / MS method, the LQs were higher, ranging from 0.008 ng mL-1 (BP and BzP) to 0.8 ng mL-1 (E3, E2 and EE2). The linearity of the methods was attested by evaluating the residual plots, coefficient of determination and applying weighted calibration when needed. Accuracy and precision were investigated, presenting values within the acceptance criteria. Finally, the methods were applied in samples collected in São Carlos - SP, showing that the methods are suitable for the purpose.

La rencontre entre une couche limite laminaire se développant sur une plaque plane sous une surface libre et un obstacle rectangulaire émergent mène à l’apparition d’une zone de recirculation complexe appelée tourbillon en fer à cheval à l’amont de l’obstacle. Cette zone de recirculation est composée d’un certain nombre de vortex s’enroulant autour de l’obstacle et pouvant présenter des dynamiques variées. Le but de ce travail est de réaliser une étude expérimentale paramétrique du tourbillon en fer à cheval laminaire et faiblement turbulent. Les mesures sont réalisées par PIV et par trajectographies et des méthodes de détection basés sur la décomposition modale (POD) et la détection des points critiques sont utilisées afin de faciliter l’étude de la dynamique tourbillonnaire. Ce manuscrit se propose de : (i) Déterminer l’évolution des caractéristiques du tourbillon en fer à cheval en fonction des paramètres adimensionnels de l’écoulement. (ii) Mettre en place une typologie des différentes dynamiques exhibées. (iii) Déterminer les mécanismes à l’origine de l’apparition de ces différentes dynamiques à l’aide d’un modèle conceptuel. (iv) Et finalement, étudier l’influence de la longueur de l’obstacle sur le tourbillon en fer à cheval. / A laminar boundary layer developing under a free-surface and interacting with an emerging obstacle lead to the creation of a complex recirculation zone called horseshoe vortex upstream from the obstacle. This recirculation zone is composed of a given number of vortices wrapping around the obstacle with various kind of dynamics. The aim of this work is to perform an experimental parametric study of the laminar, and slightly turbulent horseshoe vortex. Measurements are obtained by PIV and trajectographies and detection method based on modal decomposition (POD) and critical points are used to ease the study of the vortex dynamics. This manuscript intends to : (i) Explain the horseshoe vortex main characteristics evolution with the non-dimensional parameters of the flow. (ii) Define a typology of the different observed vortex dynamics. (iii) Identify the physical mechanisms at the origin of those dynamics through the use of a conceptual model. (iv) And finally, show the influence of the obstacle length on the horseshoe vortex.