Submitted by Cláudia Bueno (claudiamoura18@gmail.com) on 2016-01-15T16:51:23Z No. of bitstreams: 2 Dissertação - Rafaela Souza Santos - 2015.pdf: 7723635 bytes, checksum: 89791ae5835c5b06e83c5e64b4a28bb5 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2016-01-18T09:08:35Z (GMT) No. of bitstreams: 2 Dissertação - Rafaela Souza Santos - 2015.pdf: 7723635 bytes, checksum: 89791ae5835c5b06e83c5e64b4a28bb5 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2016-01-18T09:08:35Z (GMT). No. of bitstreams: 2 Dissertação - Rafaela Souza Santos - 2015.pdf: 7723635 bytes, checksum: 89791ae5835c5b06e83c5e64b4a28bb5 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2015-02-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The issue of pollution is not new. The burning of biomass used for heat generation already was beginning to anthropogenic processes of air pollution. The pollutants are in the atmosphere in solid, liquid and gaseous state. The set of solid and liquid particles is called particulate matter (PM), and the other form the set of gaseous pollutants. The MP covers a range of 0.1-100 microns and varies greatly in size composition, emission sources and adverse effects on health. The gaseous compounds are formed mostly of volatile organic compounds (VOCs), which are organic compounds which are gaseous at room temperature. These pollutants can be emitted by natural and anthropogenic sources, among which stand out the combustion processes and soil dust resuspension by wind action. The city of Catalão - GO has grown greatly in recent years, mainly due to the arrival of mining in the city exploring the carbonatite complexes Catalão I and Catalão II. The aim of this study was to monitor the atmospheric air in a region of the city of Catalan through the sampling and analysis of PM and VOCs. Samples MP, which occurred every six days over a period of 24 hours, were carried out for TSP, PM10 and PM2,5 in HI-VOL samplers suitable for each particle size. Gravimetric analysis indicated that the measured concentrations are in accordance with the standards set by law. The elementary MP analysis was performed by EDXRF technique and indicated that the elements present are mostly from vehicle emissions and resuspended soil dust by the wind. Sampling was performed by VOCs microextraction technique of solid phase (SPME - solid phase microextraction) twice a week for 12 hours. The analysis of the sampled VOCs was performed by gas chromatography-mass spectrometry (GC / MS - gas chromatography mass spectrometry) in which the compounds were identified by comparison with a NIST library / MS (National Institute of Standards and Technology / Mass Spectral) present in the equipment. The identification of these compounds indicated a strong influence of vehicle emissions in the composition of atmospheric air. / A questão da poluição não é algo recente. A queima de biomassa utilizada para geração de calor já dava início aos processos antrópicos de poluição atmosférica. Os poluentes encontram-se na atmosfera nos estados sólido, líquido e gasoso. O conjunto das partículas sólidas e líquidas constitui o chamado material particulado (MP), e as demais formam o conjunto de poluentes gasosos. O MP abrange uma faixa de tamanho entre 0,1-100 e varia em tamanho, composição, fontes de emissão e efeitos adversos causados a saúde. Os compostos gasosos são formados em sua maioria pelos compostos orgânicos voláteis (COVs), que são compostos orgânicos que encontram-se no estado gasoso em temperatura ambiente. Esses poluentes podem ser lançados na atmosfera por fontes naturais e antrópicas, dentre as quais destacam-se os processos de combustão e ressuspensão da poeira do solo por ação dos ventos. A cidade de Catalão GO tem crescido bastante nos últimos anos, principalmente devido a chegada de mineradoras na cidade que exploram os complexos carbonatíticos de Catalão I e Catalão II. O objetivo deste trabalho foi realizar o monitoramento do ar atmosférico em uma região da cidade de Catalão pela amostragem e análise de MP e COVs. As amostragens de MP, que aconteceram a cada seis dias por um período de 24 horas, foram realizadas para PTS, MP10 e MP2,5 em amostradores de grande volume adequados para cada tamanho de partícula. A análise gravimétrica indicou que os as concentrações medidas estão de acordo com os padrões definidos pela legislação. A análise elementar do MP foi realizada pela técnica de EDXRF e indicou que os elementos presentes são, em sua maioria, provenientes da emissão veicular e poeira ressuspensa do solo pela ação dos ventos. A amostragem dos COVs foi realizada pela técnica de microextração por fase sólida (SPME do inglês solid phase microextraction), duas vezes por semana por 12 horas. A análise dos COVs amostrados foi realizada por cromatografia gasosa acoplada a espectrometria de massas (GC / MS - do inglês gas chromatography mass spectrometry) em que os compostos foram identificados por comparação com a biblioteca NIST / MS (Nacional Institute of Standard and Technology / Mass Spectral) presente no equipamento. A identificação desses compostos indicou uma forte influência das emissões veiculares na composição do ar atmosférico.

Accurate simulation of energy, water, and carbon fluxes exchanging between the land surface and the atmosphere is beneficial for improving terrestrial ecohydrological and climate predictions. We systematically assessed the Noah land surface model (LSM) with mutiparameterization options (Noah-MP) in simulating these fluxes and associated variations in terrestrial water storage (TWS) and snow cover fraction (SCF) against various reference products over 18 United States Geological Survey two-digital hydrological unit code regions of the continental United States (CONUS). In general, Noah-MP captures better the observed seasonal and interregional variability of net radiation, SCF, and runoff than other variables. With a dynamic vegetation model, it overestimates gross primary productivity by 40% and evapotranspiration (ET) by 22% over the whole CONUS domain; however, with a prescribed climatology of leaf area index, it greatly improves ET simulation with relative bias dropping to 4%. It accurately simulates regional TWS dynamics in most regions except those with large lakes or severely affected by irrigation and/or impoundments. Incorporating the lake water storage variations into the modeled TWS variations largely reduces the TWS simulation bias more obviously over the Great Lakes with model efficiency increasing from 0.18 to 0.76. Noah-MP simulates runoff well in most regions except an obvious overestimation (underestimation) in the Rio Grande and Lower Colorado (New England). Compared with North American Land Data Assimilation System Phase 2 (NLDAS-2) LSMs, Noah-MP shows a better ability to simulate runoff and a comparable skill in simulating R-n but a worse skill in simulating ET over most regions. This study suggests that future model developments should focus on improving the representations of vegetation dynamics, lake water storage dynamics, and human activities including irrigation and impoundments.

A exploração eficiente do paralelismo no nível de threads tem sido um desafio para os desenvolvedores de softwares. Como muitas aplicações não escalam com o número de núcleos, aumentar cegamente o número de threads pode não produzir os melhores resultados em desempenho ou energia. No entanto, a tarefa de escolher corretamente o número ideal de threads não é simples: muitas variáveis estão envolvidas (por exemplo, saturação do barramento off-chip e sobrecarga de sincronização de dados), que mudam de acordo com diferentes aspectos do sistema (por exemplo, conjunto de entrada, micro-arquitetura) e mesmo durante a execução da aplicação. Para abordar esse complexo cenário, esta tese apresenta Aurora. Ela é capaz de encontrar automaticamente, em tempo de execução e com o mínimo de sobrecarga, o número ideal de threads para cada região paralela da aplicação e se readaptar nos casos em que o comportamento de uma região muda durante a execução. Aurora trabalha com o OpenMP e é completamente transparente tanto para o programador quanto para o usuário final: dado um binário de uma aplicação OpenMP, Aurora o otimiza sem nenhuma transformação ou recompilação de código. Através da execução de quinze benchmarks conhecidos em quatro processadores multi-core, mostramos que Aurora melhora o trade-off entre desempenho e energia em até: 98% sobre a execução padrão do OpenMP; 86% sobre o recurso interno do OpenMP que ajusta dinamicamente o número de threads; e 91% quando comparado a uma emulação do feedback-driven threading. / Efficiently exploiting thread-level parallelism has been challenging for software developers. As many parallel applications do not scale with the number of cores, blindly increasing the number of threads may not produce the best results in performance or energy. However, the task of rightly choosing the ideal amount of threads is not straightforward: many variables are involved (e.g. off-chip bus saturation and overhead of datasynchronization), which will change according to different aspects of the system at hand (e.g., input set, micro-architecture) and even during execution. To address this complex scenario, this thesis presents Aurora. It is capable of automatically finding, at run-time and with minimum overhead, the optimal number of threads for each parallel region of the application and re-adapt in cases the behavior of a region changes during execution. Aurora works with OpenMP and is completely transparent to both designer and end-user: given an OpenMP application binary, Aurora optimizes it without any code transformation or recompilation. By executing fifteen well-known benchmarks on four multi-core processors, Aurora improves the trade-off between performance and energy by up to: 98% over the standard OpenMP execution; 86% over the built-in feature of OpenMP that dynamically adjusts the number of threads; and 91% over a feedback-driven threading emulation.

Interés del estudio: El virus de la rotura del color de la flor del Pelargonium (Pelargonium flower break virus, PFBV) (género Carmovirus, familia Tombusviridae) constituye uno de patógenos virales más frecuentes en geranio, una planta ornamental de gran interés para la industria floral. En los últimos años se ha registrado un aumento progresivo de las infecciones causadas por este patógeno, con un porcentaje de incidencia superior al 80% en regiones de Europa occidental y en algunas áreas de España. La información acerca de las relaciones estructura-función en las proteínas de este virus era prácticamente inexistente al inicio de este trabajo y bastante limitada para las proteínas equivalentes de muchos virus relacionados, de modo que la aportación de datos adicionales en este campo puede ser de gran utilidad para entender mejor el establecimiento de la infección y los mecanismos de interacción con el huésped de este virus y de otros equivalentes. Objetivos: Durante el desarrollo de esta Tesis Doctoral se han llevado a cabo análisis de las relaciones estructura-función de las proteínas que codifica el PFBV, centrándonos en aquellos productos virales con características atípicas o cuya función no está del todo clara dentro del grupo al cual pertenece el virus. Con ello se ha pretendido aportar nuevos datos al conocimiento del patógeno y, en general, del grupo al que pertenece. Elementos de la metodología a destacar: La realización de esta Tesis ha permitido la publicación de varios artículos de divulgación científica, aprobados por comités que han avalado convenientemente el uso de las metodologías empleadas. Resultados logrados: Con este trabajo se ha establecido la etapa del ciclo infeccioso en la que se encuentran involucradas las distintas proteínas del PFBV y se han analizado relaciones estructura-función en dichos productos. Asimismo, se han determinado algunas propiedades relevantes de proteínas implicadas en la replicación, así como de aquellas que asisten / Martínez Turiño, S. (2012). ANÁLISIS FUNCIONAL DE PROTEÍNAS CODIFICADAS POR EL VIRUS DE LA ROTURA DEL COLOR DE LA FLOR DEL PELARGONIUM [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/16807 / Palancia

Metals are essential nutrients for plant health, but not all metals are necessary and can sometimes be harmful towards plants depending on factors such as species, elemental composition in the soil and concentration of a metal. Iron (Fe), which is one of the most abundant metals in the earth’s crust is also one the most important nutrients for plant growth, as it is responsible for metabolism. Lead (Pb) has been widely outspoken to be a harmful pollutant to plants and has been shown in studies to have an impact on a plant’s physiology and morphology. The aim of this study is to analyze whether Pb and Fe influence the metal content of Garden cress (Lepidium sativum). A solution of Pb with the following concentrations; 2.4 g/L, 1.2 g/L, 0.48 g/L, 0.24 g/L, 0.12 g/L, 0.048 g/L and 0.024 g/L were used. Another solution of Fe with the following concentrations; 0.56 g/L, 0.28 g/L, 0.11 g/L, 0.056 g/L, 0.028 g/L, 0.011 g/L and 0.0056 g/L were also used. Then a combined solution of both Pb- and Fe solution were mixed with a volume ratio of 1:1 corresponding to the following concentrations of lead and iron, respectively; 0.024/0.0056 g/L, 0.048/0.0112 g/L, 0.12/0.028 g/L, 0.24/0.056 g/L, 0.48/0.112 g/L, 1.2/0.28 g/L were used. A total of 29 different metal contents were analyzed, which include; Aluminum (Al), silver (Ag), Barium (Ba), Beryllium (Be), Bismuth (Bi), Cadmium (Cd), Cobalt (Co), Copper (Cu), Fe, gallium (Ga), potassium (K), lithium (Li), magnesium (Mg), manganese (Mn), Molybdenum (Mo), sodium (Na), nickel (Ni), Pb, rubidium (Rb), selenium (Se), strontium (Sr), tellurium (Te), thallium (Tl), uranium (U), vanadium (V), zinc (Zn). Before initial analysis, microwave plasma atomic emission spectrometry (MP-AES) was applied with a test sample to evaluate if the acidified digestion method used with nitric acid and hydrogen peroxide was successful enough to be used for the original experiment. It was successful, so the cress samples underwent the same digestion method and were analyzed with inductive coupled plasma mass spectrometry (ICP-MS). The results showed that Pb overall decreased most metal contents, while Fe seemed to generally maintain a constant metal content of most metals. Fe fed cress seemed to grow the healthiest in appearance compared to Pb fed cress which grew the worst. Mixed solution Pb and Fe cress fed grew worse than Fe fed cress, but better than Pb fed cress. The growth quality was the worst with Pb fed and the best for controlled water fed cress. For mixed Pb and Fe solution fed cress the plants seemed to share similar qualities of both Pb- and Fe solution fed cress, with better growth capabilities than Pb fed cress, but worse than Fe fed cress. The high dilution factor during the sample preparation led to the fact that some trace and ultra-trace elements could not be determined, since their contents were below LOD or LOQ. Adapting the sample preparation procedure to these low concentrations would be a further improvement.

El objetivo de esta investigación fue evaluar ”in vitro” la actividad antibacteriana de dos pastas: 3 Mix-MP y Calen PMCC® como medicación intraconducto en un biofilm formado por 3 cepas: Porphyromona Gingivalis, Enterococcus Faecalis y Peptostreptococcus Anaerobius, presentes en Periodontis apical crónica; se utilizaron 32 piezas dentarias (premolares) a las cuales se les aplicó el mismo protocolo: fueron instrumentadas con sistema Mtwo hasta la lima 40.04, luego 22 piezas fueron seccionadas mesiodistalmente y 10 no seccionadas, fueron esterilizadas y contaminadas manteniéndolas en caldo BHI vitaminado por un lapso de 7 días. El proceso se dividió en 2 fases: en la primera fase se usaron 12 piezas seccionadas; a las que se les hizo el raspado en toda la superficie sembrándose en Agar Shaedler por 7 días; luego se realizaron 4 pozos de 5mm de diámetro por cada placa donde se colocaron las pastas de 3Mix-MP, Calen PMCC®, Hidróxido de calcio con suero fisiológico (control positivo) y glicerina (control negativo) dichas placas se incubaron por 7 días en anaerobiosis y se procedió a la lectura de los halo de inhición bacteriana. En la segunda fase siguiendo el protocolo anterior se usaron las 20 piezas restantes (10 seccionadas y 10 no seccionadas a las que se les colocó la pasta 3Mix-MP, la pasta Calen PMCC®, hidróxido de calcio con suero fisiológico (control positivo), se realizó el raspado y sembrado en agar shaedler manteniéndolo en anaerobiosis por 7 días para finalmente realizar la lectura de las unidades formadoras de colonias (ufc) presentes. El resultado observado con respecto a los halos de inhibición mostró que fue mayor para la pasta 3Mix - MP (40mm.) en comparación con la pasta Calen PMCC® (7mm.), con respecto a la lectura no se pudo recuperar colonias en las muestras de 3Mix-MP a diferencia de Calen PMCC® que se obtuvo 04 ufc.; concluyéndose que la pasta 3Mix-MP tiene mayor efecto antibacteriano como medicación intraconducto frente a la pasta Calen PMCC®. / Tesis

A mesoscale evaluation is performed to determine the impacts of climate change on terrestrial hydrological components and the Net Irrigation Water Requirement (NIWR) throughout the Chesapeake Bay watershed in the mid-Atlantic region of the United States. The Noah-MP land surface model is calibrated and evaluated against the observed datasets of United States Geological Survey (USGS) streamflow gages, actual evapotranspiration from USGS Simplified Surface Energy Balance (SSEBop) Model and soil moisture from Soil Analysis Climate Network (SCAN). Six best performing Global Climate Models (GCM) based on Multivariate Adaptive Constructed Analogs (MACA) scheme are included for two future scenarios (RCP 4.5 and RCP 8.5), to assess the change in water balance components, change in NIWR for two dominant crops (corn and soybeans) and uncertainty in GCM projections. Using these long-term simulations, the flood inundation maps are developed for future scenarios along the Susquehanna River including the City of Harrisburg in Pennsylvania. The HEC-RAS 2D model is calibrated and evaluated against the high-water marks from major historical flood events and the stage-discharge relationship of the available USGS streamgages. Finally, the impacts of climate change are assessed on flood inundation depth and extent by comparing a 30-yr and 100-yr flood event based on the historical and future (scenario-based) peak discharge estimates at the USGS streamgages. Interestingly, flood inundation extent and severity predicted by the model along the Susquehanna River near Harrisburg is expected to rise in the future climate scenarios due to the greater frequency of extreme events increasing total precipitation. / Master of Science / Climate change is inevitable due to increased greenhouse gas emissions, with impacts varying in space and time significantly throughout the globe. The impacts are strongly driven by the change in precipitation and temperature which affect the control of the movement of water on the surface of the Earth. These changes in the water cycle require an understanding of hydrological components like streamflow, soil moisture, and evapotranspiration. Development of long-term climate models and computational hydrological models (based on mathematical equations and governed by laws of physics) has helped us in understanding this climate variability in space and time. This study performs a long-term simulation using the datasets from six different climate models to analyze the change in terrestrial hydrological components for the entire Chesapeake Bay watershed in the mid-Atlantic region of the United States. The simulations provide an understanding of the interplay between various land surface processes due to climate change and can help determine future water availability and consumption. To illustrate the usefulness of such long-term simulations, the crop water requirement is quantified for the dominant crops in Chesapeake Bay watershed to project water availability and support the development of mitigation strategies. Flood inundation maps are also developed for a section of Susquehanna River near the City of Harrisburg in south-central Pennsylvania using the streamflow from long-term simulations. The flood inundation depth and extent for major flood events such as Tropical Storm Agnes (1972) and Tropical Storm Lee (2011) are compared along the Susquehanna River, which can aid in managing flood operations, reduce the future flood damages and prioritize the mitigation efforts for endangered communities near the City of Harrisburg.

Made available in DSpace on 2016-04-26T20:29:59Z (GMT). No. of bitstreams: 1 Giovane Serra Azul Guimaraes.pdf: 730625 bytes, checksum: d4dd129083baab843b61e1c545515e99 (MD5) Previous issue date: 2009-11-10 / The theme of this work was chosen owing to its importance, since it is a crucial collective issue as it refers to health insurance contracts, which involve the fundamental rights pointed out in the provisions of Brazilian Constitution, being the only public service therein expressly defined. The central aim of the present dissertation is firstly to demonstrate that collective contracts of health insurance involve a consumption relationship and that they have social relevance, which establishes the special standing of prosecutors in defending consumer s diffuse, collective and homogenous individual interests, and secondly, to analyze the available means of defending consumers both in administrative and judicial proceedings. It is also intended to demonstrate that the Supplementary Health National Agency is responsible for inspecting all the aspects of the aforementioned health insurance plans, including price readjustment, in spite of the still existing controversies. In order to reach the outlined objectives, legislation, doctrine and previous judicial decisions were investigated, including a detailed study of the Brazilian Health Insurance Law / O tema do presente trabalho foi determinado em razão da relevância que apresenta, tendo em vista tratar-se de assunto de grande interesse da coletividade, por se referir aos contratos de planos de saúde, que envolvem direitos fundamentais previstos na Constituição, tratando-se do único serviço de relevância pública definido expressamente na Carta Magna. Visa-se demonstrar que os contratos coletivos de planos de saúde envolvem relação de consumo, e que apresentam relevância social, determinante da atuação do Ministério Público, como legitimado extraordinário, na defesa dos interesses difusos, coletivos e individuais homogêneos dos consumidores, abordando-se também os meios disponíveis, na esfera administrativa e judicial, para essa defesa. Objetiva-se ainda demonstrar que a Agência Nacional de Saúde Suplementar, ANS, tem atribuição e o dever de agir na fiscalização e controle de todos os aspectos deste mencionados planos, inclusive no que se refere a reajustes de preços, não obstante às controvérsias ainda existentes. Para se chegar aos objetivos traçados, foram pesquisados aspectos doutrinários, legais e jurisprudenciais, com minucioso estudo dos dispositivos da Lei dos Planos de Saúde, LPS

This study took place in Malawi, south eastern Africa. Metal contamination of water and soil is a threat to the environment and human health and is a serious concern in many countries including Malawi. Blantyre is the city of commerce where most of the industry is located along the banks of the main rivers. Some of the industries produce wastewater, which due to poor access to wastewater treatment plants, is discharged without treatment into the environment. A match factory in Blantyre uses chromium as a colouring agent for match heads and very high concentrations of chromium(VI) have been measured downstream the factory with concentrations up to 56 mg/l, which is much higher than the WHO guidelines of 0.05 mg/l.  Chromium(VI) mainly occurs as chromate CrO42- and dichromate Cr2O72- ions. They are both toxic and carcinogenic and can cause mutations and chromosomal aberrations.   The aim of the study was to evaluate the efficiency of Granular Ferric Hydroxide (GFH) in adsorbing and removing chromium from an aqueous phase. Wastewater was collected from the match factory and by optimizing relevant parameters the removal efficiency was maximized. The parameters optimized were pH, dosage and contact time and the effect of initial concentration. After respective experiment, all samples were analysed for chromium using microwave plasma atomic emission spectroscopy (MP-AES).   The optimum pH was chosen to 8.0, the dosage to 17.4 g GFH/l and the contact time to 2 hours for a 95% removal of total chromium in undiluted wastewater. The removal efficiency of the GFH was 2.84 mg Cr/g GFH. To implement wastewater purification with GFH a number of practical issues have to be taken into consideration. Above all, a sufficient stirring method has to be devised as the removal efficiency is much affected by improper stirring. / Denna studie genomfördes i Malawi, sydöstra Afrika. Metallföroreningar i vatten och mark är ett stort problem i många länder, inklusive Malawi. Landets centrum för industri och handel ligger i Blantyre där de flesta av industrierna ligger längs med floderna. En del industrier genererar utsläppsvatten och på grund av dålig tillgång till vattenreningsteknik och vattenreningsanläggningar släpps mycket av det förorenade vattnet obehandlat ut i naturen. En tändsticksfabrik i Blantyre använder kromsalter för att färga tändstickshuvudena röda och höga koncentrationer av sexvärt krom har uppmätts nedströms fabriken. De uppmätta koncentrationerna var upp till 56 mg/l vilket är betydligt högre än WHO:s riktvärde på 0,05 mg/l. Sexvärt krom förekommer som kromat CrO42- och dikromat Cr2O72- joner vilka båda är mycket toxiska och cancerframkallande och därmed ett hot mot miljö och människor. Syftet med studien var att undersöka om granulära järnoxider (GFH) kunde användas som en adsorbent för att rena utsläppsvatten från kromater. Utsläppsvatten hämtades från tändsticksfabriken och genom att optimera relevanta parametrar kunde GFHns adsorbtionseffektivitet maximeras. Parametrarna som optimerades var pH, dos, kontakttid och initialkoncentration. Efter respektive experiment mättes kromkoncentrationen med mikrovågsplasma atomemissionsspektroskopi (MP-AES) Det optimala pH-värdet valdes till 8.0, dosen till 17.4 g GFH/l med en kontakttid på 2 timmar för en 95.3% reningsgrad på outspätt utsläppsvatten. Adsorptionseffektiviteten på GFHn var 2.84 mg Cr/g GFH. För att implementera vattenrening med GFH behöver flera praktiska aspekter tas med i beaktning. Framförallt är det viktigt med en bra omrörning för att GFHn ska kunna adsorbera effektivt.

Un réseau sans fil multi-saut est un ensemble d’entités mobiles et/ou fixes formant un réseau dynamique temporaire avec ou sans l’aide de toute administration centralisée. Cette particularité rend le routage problématique en cas d’instabilité des éléments qui composent les communications non directes. Afin de palier ces problèmes, de nouvelles formes de routage sont utilisées comme le routage multi-chemin (MC). Le routage MC permet d’envoyer les données sur des chemins multiples et semble être une solution efficace pour ces réseaux. Le but de cette thèse est d’étudier les techniques de routage MC dans un contexte sans fil multi-saut en vue d’obtenir de meilleures performances. Nous avons choisi pour notre étude une extension MC du protocole OLSR, appelée MP-OLSR. Nous évaluons ses performances sous divers scénarios sous NS-2. Ces tests d’évaluation nous ont amenés à mettre en ´evidence deux problèmes dans MP-OLSR : la réactivité du protocole de routage MC suite à des ruptures de route et la stratégie de répartition des données sur les chemins multiples. Nous avons étudié la réactivité de tels mécanismes dans MP-OLSR. Nous avons proposé trois nouvelles techniques de réparation de pannes qui diminuent les temps de rétablissement d’une route et réduisent le taux de perte des flux transmis. Nous proposons aussi un mécanisme qui détecte la dégradation de la qualité des liens durant le transfert d’un trafic de données. Les informations déduites de ce mécanisme servent à adapter la proportion de trafic à affecter à chaque chemin selon les conditions réseaux. Cette nouvelle variante du protocole MP-OLSR est évaluée par simulation. / Wireless multi-hop networks consist of a collection of mobile and/or fixed nodes which dynamically exchange data with (or without) reliance on a (any) centralized administration. They are by definition self-organized. The frequent topological changes make multi-hop routing a crucial issue for these networks. To overcome these problems, new forms of routing schemes are used as the multipath routing (MP). MP routing uses multiple paths to send data and can be regarded as an effective solution for these networks. The purpose of this PhD thesis is to study the MP routing techniques in a wirelessmulti-hop context for better performance. We choose for our study a MP extension of OLSR, called MP-OLSR. We evaluate its performance under various scenarios in NS-2. These tests have led us to highlight two problems in MP-OLSR : the long recovery delays when facing network failure situations and the allocation strategy of data on multiple paths. We define and seek to evaluate the latency introduced by both protocols OLSR and MP-OLSR to find a new path after a link failure. We propose three new different recovery schemes and accordingly extend these original protocols in order to decrease theexpected latency and reduce the packet loss rate of transmitted flow. We also propose a mechanism which is able to detect the deterioration of the link quality during the transfer of data traffic. The information derived from this mechanism is used to adjust the proportion of traffic to be assigned to each path according to network conditions. This new version of MP-OLSR protocol is evaluated by simulation.