<p>In this thesis, I combined comparative and experimental approaches to examine selection on reproductive traits and population differentiation in the insect-pollinated, self-incompatible, perennial herb <i>Primula farinosa</i>. More specifically, I (1) determined whether the effects of floral display and interactions with pollinators and seed predators, and plant reproductive success were frequency-dependent and affected by surrounding vegetation context, (2) examined the consequences of intermittent drought years on population dynamics using numerical simulations based on demographic data collected over seven years, (3) analyzed among-population differentiation in flowering phenology and reproductive allocation, and its relationship to soil-depth at the site of origin. </p><p>A field experiment suggested that conspicuous plants facilitate inconspicuous plants in terms of pollinator attraction, and that the facilitation effect is contingent on the height of the surrounding vegetation. Further experiments revealed that both mutualistic and antagonistic interactions can result in frequency-dependent selection on floral display. Among inconspicuous plants, both fruit initiation, and damage from seed predators increased with the proportion of the conspicuous morph. The relative strength of these effects, and therefore their net outcome on the relationship between morph ratio and seed production varied among years. </p><p>I combined information on vital rates and their relation to environmental conditions in simulations to predict future population viability in changing environments. Simulated stochastic population growth rate decreased with increasing frequency of drought years. </p><p>Reproductive allocation varied significantly among populations both in the field and in a common-garden experiment, but was correlated with soil depth at the site of origin only in the field. The results suggest that among-population variation in reproductive effort in the field mainly reflects plastic responses to environmental conditions, and that this plasticity may be adaptive. The common-garden experiment suggested that the study populations have diverged genetically in flowering time.</p>

As homeostatic organisms, rotifers have to use the mechanism to cope with nutrition unbalance in their food. The regulation of digestive enzyme activities as a possible physiological mechanism involved in maintaining of rotifer homeostasis was studied. This study further explored the effect of food quantity and quality on rotifer population growth rate and reproduction.

Submitted by Henrique Yu Jiunn Wang (henriqueyjw@gmail.com) on 2015-09-21T21:41:16Z No. of bitstreams: 1 Intervenções fiscais em uma economia monetária- um estudo do caso brasileiro.pdf: 13075665 bytes, checksum: 460672073307c2ae8ff746ee1b17f376 (MD5) / Rejected by Renata de Souza Nascimento (renata.souza@fgv.br), reason: Henrique, Será necessário fazer alguns ajustes na formatação das primeiras páginas de seu trabalho, pois não não está de acordo com as normas da ABNT. Encaminharemos as orientações por e-mail. Att on 2015-09-21T22:15:38Z (GMT) / Submitted by Henrique Yu Jiunn Wang (henriqueyjw@gmail.com) on 2015-09-21T23:15:53Z No. of bitstreams: 1 Intervenções fiscais em uma economia monetária- um estudo do caso brasileiro.pdf: 13079987 bytes, checksum: 7b8cba8ba1620901c7863edbd398d23c (MD5) / Approved for entry into archive by Renata de Souza Nascimento (renata.souza@fgv.br) on 2015-09-21T23:18:19Z (GMT) No. of bitstreams: 1 Intervenções fiscais em uma economia monetária- um estudo do caso brasileiro.pdf: 13079987 bytes, checksum: 7b8cba8ba1620901c7863edbd398d23c (MD5) / Made available in DSpace on 2015-09-22T13:56:45Z (GMT). No. of bitstreams: 1 Intervenções fiscais em uma economia monetária- um estudo do caso brasileiro.pdf: 13079987 bytes, checksum: 7b8cba8ba1620901c7863edbd398d23c (MD5) Previous issue date: 2015-08-25 / In this study, we consider an economy where the determination of fiscal and monetary policies are subject to the budget constraint of the government, seen as a consolidated agent that incorporates the executive and the central bank. We study how changes in the growth rate and composition of government liabilities (currency and governmental bonds) affect prices, interest rates, and economic activity. We are particularly interested in analyzing how these effects are affected by changes in the relative liquidity of government bonds. A central result of this work is that increases in the degree of liquidity of government bonds positively affect economic activity and the financing of public debt. We describe this last aspect with an example reflecting the case of the Brazilian economy. / Neste estudo consideramos uma economia onde a determinação das políticas fiscais e monetárias estão sujeitas à restrição orçamentária do governo, visto como um agente consolidado que incorpora o executivo e o banco central. Nós estudamos como mudanças na taxa de crescimento e na composição do passivo governamental (moeda e títulos) afetam preços, juros, e atividade econômica. Estamos particularmente interessados em analisar como estes efeitos são afetados por mudanças na liquidez relativa dos títulos públicos. Um resultado central deste trabalho é que aumentos no grau de liquidez dos títulos públicos afetam positivamente a atividade econômica e o financiamento da dívida pública. Descrevemos este último aspecto com um exemplo refletindo o caso da economia brasileira.

The main objective of this diploma thesis is compare the production efficiency of special types of feed for African catfish in experimental conditions in a recirculating system with biological treatment of water. It was tested four different types of floating feed, differing in the proportion of main components, the chemical composition and determining - for catfish (CatCo GROWER - 12 EF, CatCo SELECT - 13 EF and CatCo GROWER - 13 EF), respectively salmonid fish species (Dibaq Trout Evolution). The primary outcome indicators was the growth rate, individual weight (and it's variability), feed conversion ratio, the cost of feed consumed per unit of growth and product quality, evaluated according the average dress-out percentage of skinless fillets, organoleptic assessment and chemical composition of flesh.

Made available in DSpace on 2014-12-17T14:33:08Z (GMT). No. of bitstreams: 1 LeideAPS_DISSERT.pdf: 986741 bytes, checksum: e18d4b42b9411720a51bd3f7786fa126 (MD5) Previous issue date: 2012-09-25 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / Cyanobacterial blooms are common in eutrophic reservoirs in Brazilian northeastern semi-arid. Given this reality, the present study aimed to analyze the effect of potentially toxic cyanobacterial blooms in Gargalheiras reservoir (semi-arid) on the cladocerans Ceriodaphnia dubia and Daphnia gessneri. In vitro chronic bioassays were performed with reservoir water dilutions from August/2011 to May/2012 and the following effects were evaluated on: intrinsic rate of population growth (r), reproductive parameters (age of first reproduction and fecundity per capita) and cladocerans movements. Phytoplankton was dominated by Cylindrospermopsis raciborskii and Planktothrix agardhii and saxitoxin and microcystin were detected in reservoir water. In most months C. dubia showed differences in r between control (absence of cyanobacteria) and treatments, and has shown negative effects on reproductive parameters. In all months paralysis of swimming movements was observed in C. dubia when both C. raciborskii and saxitoxin (cyanotoxin neurotoxic) were present in water. While C. dubia was sensitive to the reservoir water containing cyanobacteria, D. gessneri showed less intense negative effects in r and reproductive parameters. Furthermore, D. gessneri showed no paralysis of swimming movements. These results support the hypothesis in the literature that D. gessneri is resistant to the Cylindrospermopsis effects. The clone&#8223;s life history may be a key to understand the results. The C. dubia clone, isolated from eutrophicated environment, is in the lab for ten years and it is an exotic species in Brazil. D. gessneri is a common species in the country and this clone was isolated from the Gargalheiras reservoir (where there are constant blooms of potentially toxic cyanobacteria) a year ago. Perhaps the recent contact with cyanobacteria explain the higher resistance presented by this D. gessneri clone. In conclusion, the cladocerans studied have different levels of sensitivity to cyanobacteria, characterizing species-specific responses / Flora??es de cianobact?ras s?o frequentes em reservat?rios eutr?ficos do semi-?rido do nordeste brasileiro. Diante dessa realidade o presente trabalho objetivou analisar o efeito de flora??es de cianobact?rias potencialmente t?xicas do reservat?rio Gargalheiras (semi-?rido brasileiro) sobre os clad?ceros Ceriodaphnia dubia e Daphnia gessneri. Foram realizados ensaios cr?nicos in vitro com dilui??es de ?gua do reservat?rio de agosto/2011 a maio/2012 e foram avaliados efeitos sobre: taxa intr?nseca de crescimento populacional (r), par?metros reprodutivos (idade da primeira reprodu??o e fecundidade per capita) e movimenta??o dos clad?ceros. O fitopl?ncton foi dominado por Cylindrospermopsis raciborskii e Planktothrix agardhii e houve detec??o de saxitoxina e microcistina na ?gua do reservat?rio. Na maioria dos meses C. dubia apresentou diferen?a em r entre controle (aus?ncia de cianobact?rias) e tratamentos, al?m de ter apresentado efeitos negativos nos par?metros reprodutivos. Observou-se ainda um efeito de paralisia dos movimentos natat?rios de C. dubia em todos os meses, concomitante ? presen?a de C. raciborskii e saxitoxina (cianotoxina neurot?xica) na ?gua. Enquanto C. dubia apresentou-se sens?vel ? ?gua do reservat?rio contendo cianobact?rias, D. gessneri apresentou efeitos negativos menos intensos em r e nos par?metros reprodutivos. Al?m disso, esta esp?cie n?o teve os movimentos paralisados. Esses resultados apoiam a hip?tese levantada na literatura de que D. gessneri apresenta resist?ncia aos efeitos da Cylindrospermopsis. A hist?ria de vida dos clones pode ser uma chave para compreens?o dos resultados. O clone de C. dubia, isolado de ambiente eutrofizado, est? em laborat?rio h? dez anos e essa ? uma esp?cie ex?tica no Brasil. D. gessneri ? uma esp?cie comum no pa?s e este clone foi isolado h? um ano do reservat?rio Gargalheiras, onde h? constantes flora??es de cianobact?rias potencialmente t?xicas. A hip?tese mais prov?vel ? que o contato recente deste clone de D. gessneri com cianobact?rias tenha lhe conferido maior resist?ncia. Conclui-se que os clad?ceros estudados apresentam diferentes n?veis de sensibilidade ?s cianobact?rias, caracterizando respostas esp?cie-espec?ficas

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2017-02-20T13:51:05Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação CD Biblioetca Denise Moraes 2016 FINAL.pdf: 2561125 bytes, checksum: 30370d4b25d98afe00850c78927ba185 (MD5) / Made available in DSpace on 2017-02-20T13:51:05Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação CD Biblioetca Denise Moraes 2016 FINAL.pdf: 2561125 bytes, checksum: 30370d4b25d98afe00850c78927ba185 (MD5) Previous issue date: 2016-08-19 / FACEPE / O conhecimento dos parâmetros de crescimento e mortalidade em braquiúros é fundamental para a compreensão da sua dinâmica e para o manejo de suas populações. Neste sentido, foram estimados os parâmetros de crescimento e mortalidade para Cardisoma guanhumi Latreille, 1825 (guaiamum), uma espécie com elevada importância socioeconômica no nordeste brasileiro e atualmente considerada pelo Ministério do Meio Ambiente como Criticamente em Perigo de extinção. As amostragens foram efetuadas durante um ano, entre abril de 2015 a março de 2016, na margem superior do mangue do CMA/ICMBio/CEPENE na ilha de Itamaracá, Pernambuco, Brasil. Foram capturados, medidos e pesados 1078 indivíduos (572 machos e 506 fêmeas). Destes, 291 indivíduos foram marcados com microchips PIT ("Passive Integrated Transponder"), para determinação dos parâmetros de crescimento através dos incrementos de peso e tamanho e do crescimento individual. Para a análise dos dados, foram utilizados o método ELEFAN I (baseado na distribuição de frequência de largura de carapaça de 1078 indivíduos), inserido no pacote computacional Fisat II e através da função GrowthTraject (baseada em incrementos individuais de 291 indivíduos marcados com PITs, utilizando o pacote fishmethods (Ambiente de programação “R”). Os indivíduos de C.guanhumi apresentaram largura da carapaça entre 20,9 e 70,0 mm (média: 43,45 mm, desvio padrão: 8,53 mm, mediana: 44,05 mm) o peso total entre 4 e 162 g (média: 45,85 g, desvio padrão: 25,34 g, mediana: 44,0 g). Não houve diferenças significativas, em tamanho médio e peso médio, entre machos e fêmeas. Os parâmetros de crescimento estimados com a função GrowthTraject para 130 incrementos (machos e fêmeas) foram: Linf (tamanho assintótico) = 108,03 mm (largura da carapaça); K (coeficiente de crescimento) = 0,145 ano-1. A Mortalidade total (Z) da população, estimada pelo método Length – converted Catch Curve (pacote FISAT II) usando os parâmetros de crescimento do GrowthTraject foi de = 2,39 ano-1. Não ocorrem capturas comerciais nesta área fechada, portanto, este valor equivale à mortalidade total e natural (Z=M). A idade dos indivíduos capturados variou de 1,49 anos (20,9mm) a 7,02 anos (70,0mm). O recrutamento, calculado no pacote FISAT II e estimado através da presença de juvenis, mostrou-se contínuo durante todo o ano. Os métodos de análises de frequência e comprimento inseridos no pacote FISAT (Bhattacharya, ELEFAN I e Shepherd’s) não foram capazes de determinar os parâmetros de crescimento, provavelmente devido ao crescimento lento e recrutamento contínuo durante todo ano. O tamanho total da população no manguezal do CMA foi estimado em 1262 indivíduos (+- 401ind.), baseado nos dados de marcação e recaptura. / Knowledge on the growth parameters and mortality in brachyuran is fundamental to the understanding of the dynamics and management of their populations. Growth and mortality parameters were estimated for Cardisoma guanhumi Latreille, 1825 (locally known as”guaiamum”), a species with high socio-economic importance in northeastern Brazil and currently considered by the Ministry of the Environment as Critically Endangered of Extinction. The samples were taken over one year, from April 2015 to March 2016, at the upper margin of a small, isolated mangrove patch at CMA-ICMBio-CEPENE on Itamaracá Island, Pernambuco, Brazil. A total of 1078 individuals (572 males and 506 females) were captured, measured and weighed. Of these, 291 individuals were marked with PIT tags (Passive Integrated Transponder tags), as to determine the growth parameters through the analysis of the increments in weight and size and individual growth. For the data analysis, we used the ELEFAN I method (based on the frequency distribution of carapace width 1078 individuals), inserted into the computer package FISAT II and through the GrowthTraject function (based on individual increments of 291 individuals marked with PIT tags, using the fishmethods package ("R” Environment). C. guanhumi showed carapace widths between 20.9 and 70.0 mm (mean: 43,45 mm, standard deviation: 8,53 mm, median: 44,05 mm) and total weight between 4 and 162 g (mean: 45,85 g, standard deviation: 25,34 g, median: 44,0 g). There were no significant differences in average size and average weight between males and females. Growth parameters estimated with the fishmethods package, based on 130 increments (males and females), were: L∞ (asymptotic carapace width) = 108.03 mm; K (coefficient growth) = 0.145 y-1. Total mortality (Z) of the population, estimated through the Length-converted catch Curve method (FISAT II package), using the fishmethods growth parameters, was 2.39 y-1. Since this is a restricted area without regular commercial catches, so this value is roughly equivalent to the total and natural mortality (Z = M). The age of the individuals captured ranged from 1.49 years (20,9 mm) to 7.02 years (70,0 mm). Recruitment, calculated in FISAT II package and estimated by the presence of juveniles, showed to be continuous throughout the year. The methods of length-frequency analysis inserted in the FISAT package (Bhattachary of protective measures for this species.

Cette thèse consiste à étudier l'organisation du système de contrôle des voies métaboliques des bactéries afin de dégager des propriétés systémiques révélant son fonctionnement. Dans un premier temps, nous montrons que le contrôle des voies métaboliques est hautement structuré et peut se décomposer en modules fortement découplés en régime stationnaire. Ces modules possèdent des propriétés mathématiques remarquables ayant des conséquences importantes en biologie. Cette décomposition, basée intrinsèquement sur la vision système de l'Automatique, offre un cadre théorique formel général d'analyse du contrôle des voies métaboliques qui s'est révélé effectif pour analyser des données expérimentales. dans un deuxième temps, nous nous intéressons aux raisons possibles de l'émergence de cette structure de contrôle similaire. Nous identifions un ensemble de contraintes structurelles agissant au niveau de la répartition d'une ressource commune, les protéines, entre les processus cellulaires. Respecter ces contraintes pour un taux de croissance donné conduit à formaliser et résoudre un problème d'optimisation convexe non différentiable, que nous appelons Resource balance Analysis. Ce problème d'optimisation se résout numériquement à l'échelle de la bactérie grâce à un problème de Programmation Linéaire équivalent. plusieurs propriétés sont déduites de l'analyse théorique du critère obtenu. Tout d'abord, le taux de croissance est structurellement limité par la répartition d'une quantité finie de protéines entre les voies métaboliques et les ribosomes. Ensuite, l'émergence des modules dans les voies métaboliques provient d'une politique générale d'économie en protéines chez la bactérie pour gagner du taux de croissance. Certaines stratégies de transport bien connues comme la répression catabolique ou la substitution de transporteurs haute/basse affinités sont prédites par notre méthode et peuvent alors être interprétées comme le moyen de maximiser la croissance tout en minimisant l'investissement en protéines. / This thesis consist in studying the organization of the control system of metabolic pathways of bacteria to identify systemic properties revealing its operation. At first, we show that control of metabolic pathways is highly structured and can be decomposed into modules strongly decoupled in steady-state. These modules are defined by their singular mathematical properties having important implications in biology. This decomposition, based inherently on the system outlook of automatic control, offers a formal theoretical analysis of general control of metabolic pathways, which has been effective in analysing experimental data. In a second step, we consider the possible reasons for the emergence of this modular control structure. We identify a set of structural constraints acting at the distribution of a common resourc, the proteins between cellular processes. Satisfying these constraints for a given growth rate leads to formalize and to solve a non-differentiable convex optimization problem, that we call Resource Balance Analysis. This optimization problem is solved numerically at the scale of the bacteria through an equivalent linear programming problem. Several properties are derived from theoretical analysis of the obtained criterion. Firts, the growth rate is structurally limited by the distribution of a finite amount of proteines between the metabolic pathways and the ribosomes. Second, the emergence of modules in metabolic pathways arises from a policy of economy in proteins in the bacterium to increase the growth rate. Some well known transport strategies such as catabolite repression of the substitution between low/highaffinity transporters are predicted by our methods and could consequently be interpretd as ways to maximize growth while minimizing investment in proteins.

Together with the current antibiotic resistance crisis, bacterial persistence appears to play an increasingly important role in the frequent failure of antibiotic treatments. Persister cells are rare bacteria that transiently become drug tolerant, allowing them to survive lethal concentrations of bactericidal antibiotics. Upon antibiotic removal, persister cells are able to resume growth and give rise to a new bacterial population as sensitive to the antibiotic as the original population. Interest in persister cells seriously increased in the past few years as these phenotypic variants were shown to be involved in the recalcitrance of chronic infections, such as tuberculosis and pneumonia and in the well-known biofilm tolerance to antibiotics. Persistence has therefore been extensively studied throughout the last decade, which led to the discovery of large variety of different molecular mechanisms involved in persisters formation. However, the specific physiology of bacterial persisters remains elusive up to now, mainly because of the transient nature and the low frequencies of persister cells in growing bacterial cultures. This work aims to gain a better understanding of the physiology of Escherichia coli persisters by combining population analyses with single-cell observations.In the first part of this thesis, we developed an experimental method allowing for measuring persistence with increased reproducibility. The method was further refined, which allowed us to observe four distinct phases in the ofloxacin time-kill curve, suggesting the existence of a tolerance continuum at the population level at treatment time. Characterization of these four phases notably revealed that the growth rate and the intrinsic antibiotic susceptibility of the strain define the number of surviving cells at the onset of the persistence phase, while persister cells survival mainly relies on active stress responses (SOS and stringent responses in particular).We next investigated the molecular mechanisms underlying the well-known correlation between persistence and the growth rate. Interestingly, we showed that the growth rate determines the number of survival cells at the onset of the persistent phase, whereas it does not affect the death rate of persister cells during antibiotic treatment. Furthermore, slow growth was shown to influence survival to ofloxacin independently of the replication rate, thereby suggesting that target inactivation solely cannot explain this correlation. However, our preliminary data indicate that ppGpp induction upon ofloxacin exposure substantially increases in slow growing bacterial populations, supporting a model in which slow growth would allow bacteria to respond faster to the antibiotic treatment, thereby generating more persisters than fast growing bacterial populations.Finally, both population and single-cell analyses were performed to assess the influence of the SOS response on persistence to ofloxacin. Firstly, population analyses revealed that the SOS response is required for survival of both sensitive and persister cells, but only during recovery, after ofloxacin removal, presumably allowing cells to induce SOS-dependent DNA repair pathways, required to deal with the accumulated ofloxacin-induced DNA lesions. The SOS response therefore appears as a good target for anti-persisters strategies, as shown by the 100-fold decrease in persistence upon co-treatment of a bacterial population with an SOS-inhibitor and ofloxacin. Secondly, single-cell analyses revealed that persister cells sustain similar DNA damages than sensitive cells upon ofloxacin treatment and induce SulA- and SOS-independent filamentation upon antibiotic removal, probably reflecting the presence of remaining cleaved complexes, formed during ofloxacin exposure. Importantly, we showed filamentation to occur in persister cells upon ampicillin treatment as well, thereby suggesting these filaments to be part of a more general survival pathway, which molecular basis remains unknown. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

La ressource forestière en Guyane occupe une place maîtresse au sein de la région et est encore majoritairement préservée, mais la filière bois parvient difficilement à valoriser la biodiversité locale en raison de l’hétérogénéité de la ressource. Identifier les essences à planter demain représente aujourd’hui un enjeu à la fois environnemental, économique et social pour la Guyane. Bagassa guianensis Aubl. et Cordia alliodora (Ruiz & Pav.) Oken. vont à l’encontre des modèles usuels en associant vitesse de croissance et qualité du bois et sont identifiées comme prometteuses pour la plantation. Dans un premier temps, l’étude de la dynamique de croissance des deux espèces révèle un modèle écologique singulier, à la fois pionnières et longévives. La variabilité de l’infradensité dans l’arbre est l’élément clé qui permet un tel développement, favorisant une croissance rapide dans les premières années tout en assurant la longévité de l’individu. Dans une seconde partie, l’analyse d’un large panel de propriétés du bois (retrait, module, durabilité) en lien avec le développement de l’arbre confirme les qualités technologiques des deux espèces et permet l’émergence de résultats novateurs tels que le rôle des extractibles sur le retrait, le contrôle de la croissance grâce aux variations d’infradensité, l’évolution des traits foliaires au cours de l’ontogénie ou encore la mise en place de contrefil dans l’arbre pour assurer son maintien. La connaissance acquise vis-à-vis du mode de développement de ces deux espèces et des facteurs influençant la qualité de leur bois permet aujourd’hui de définir avec plus de précision le cadre d’un projet de plantation et les conditions de son succès. Les résultats de cette étude permettent finalement d’orienter la recherche de nouvelles espèces d’avenir pour la plantation en Guyane. / The forests of French Guiana occupy a central part of the region’s potential resource base, but as yet remain almost completely unexploited. This stems from the forestry industry struggling to valorize wood stocks of a high diversity with an extremely heterogeneous distribution. Indeed, identifying essences for future propagation is an issue of both environmental and socio-economic importance for the region. Bagassa guianensis Aubl. and Cordia alliodora (Ruiz & Pav.) Oken. go against conventional models, in that they display the life history characteristics of rapid growth and wood of high quality, and thus are species of high potential for future plantations. Firstly, our study of growth characteristics reveals a defined strategy half way between long-lived species and pioneer species. It is the variability of basic density of wood which is a key trait allowing for such a development, favoring rapid growth in initial years whilst allowing for tree longevity. Secondly, the analysis of a range of wood properties (shrinkage, modulus of elasticity, durability) in relation to tree growth confirms the technologic quality of the two species. It also enables the emergence of new results like the effect of extractives on wood stability, the control of growth as a result of basic density variation, the evolution of leaf traits throughout tree development or the improvement of trunk maintenance thanks to interlocked grain. The knowledge gained in relation to the developmental traits of these two species, and to the quality of their wood allows for the elaboration of plantation projects and what will be required for their success. The results of this study can orientate future studies on novel species for commercialization in French Guiana.

Ce travail porte sur l'étude expérimentale et numérique de jets coaxiaux de rapports de vitesses débitantes intérieure/extérieure) inférieurs à l’unité, présentant une rotation dans le jet annulaire. Dans un premier temps, des visualisations par tomographie laser ont été réalisées dans les plans méridien et transversaux permettant une description tridimensionnelle de l'écoulement. Pour différents nombres de Reynolds, de rapport de vitesses et de nombre de Swirl, un inventaire des modes dominants a pu être établi. Les champs instantanés de vitesses ont ensuite été mesurés par Vélocimétrie par Imagerie de Particules (PIV). Les résultats de mesures de vitesses longitudinales et azimutales moyennées en temps sont présentés. Une comparaison avec les structures observées par tomographie est proposée. Une décomposition de Fourier a été effectuée permettant d'identifier les modes dominants ainsi que leur position dans la direction radiale. L'approche expérimentale a été suivie par une analyse de stabilité linéaire. Une attention particulière est portée sur l'état de base stationnaire reconstruit à partir des profils de vitesses mesurées par PIV à la sortie du jet. Étant donné que l'écoulement est non parallèle, une approche globale de la stabilité est utilisée. L'étude de la stabilité est basée sur la résolution numérique des équations de Navier-Stokes par des méthodes pseudo-spectrales. L'objectif de cette analyse est de retrouver la carte en mode de Fourier azimutaux observée expérimentalement. Nous nous sommes donc intéressés au taux de croissance le plus élevé de la perturbation pour chaque mode azimutal ainsi qu'à la nature convective/ absolue des modes. Pour finir, une com / This work concerns the experimental and numerical study of coaxial jets with outer to inner velocity ratio lower than unity, presenting a rotation in the annular jet. At first, flow visualizations by tomography laser were used in the meridian and transverse plans in order to provide a spatial description of the flow. For various values of the nondimensional parameters : numbers of Reynolds, outer to inner velocity ratio and Swirl number, an inventory of the dominant modes was be established. Instantaneous velocity fields were then measured by Particle lmaging Velocimetry (PIV). The results of longitudinal and azimuthal time-averaged Velocity fields are presented. A comparison with the structures observed by tomography is proposed. A Fourier decomposition was made allowing to identify the dominant modes as well as their position in the radial direction. Experimental investigation was followed by a linear stability analysis. Special attention is paid to the steady base-flow solution reconstructed from the velocity profiles measured by PIV at the end of the nozzle. Given that the is not parallel, a global approach was used. Study of the stability is based on the numerical solution of the incompressible Navier-Stokes equations with pseudo-spectral methods. The objective of this analysis is to the map of azimuthal Fourier modes observed experimentally. We were thus interested in the most amplified growth rate of the disturbance for every azimuthal mode as well as in the absolute/convective nature of the modes. To conclude, a comparison of the results obtained in both numerical and experimental approaches is proposed.