Estimativas sobre alterações climáticas globais têm aumentando a demanda por estudos sobre propriedades dos solos relativamente secos e limitações impostas à absorção de água pelas plantas em condições de escassez hídrica. Neste estudo, fatores que influenciam a retenção da água no solo e o murchamento de plantas foram avaliados com base no conceito de equilíbrio da água no solo. Objetivou-se com este estudo: (i) avaliar a confiabilidade de medições do conteúdo de água no solo sob altas sucções matriciais em câmaras de pressão, usando como referência a técnica de ponto de orvalho (ii) avaliar as interações entre espécies de plantas e solos com diferentes classes texturais no ponto de murcha permanente (iii) investigar as relações entre equilíbrio hidráulico da água no solo e murchamento de plantas a partir do conceito de corte hidráulico. Para tanto, um experimento para avaliar a influência dos tipos de solos e espécies de plantas, no ponto de murcha permanente foi conduzido em casa de vegetação da Escola Superior de Agricultura \"Luiz de Queiroz\" da Universidade de São Paulo, Piracicaba, São Paulo. Avaliou-se o murchamento de plantas de girassol (Helianthus annuus L.), milho (Zea mays L.) e soja (Glycine max L.). Os solos utilizados no estudo foram coletados na camada superficial (0-10 cm) em quatro áreas, selecionadas com o objetivo de obter classes texturais contrastantes, localizadas no município de Piracicaba, São Paulo, Brasil. Sub-amostras foram utilizadas para determinação da distribuição do tamanho de partículas e atributos químicos. Amostras indeformadas foram coletadas para a determinação da curva de retenção da água no solo pela técnica de câmaras de pressão. Adicionalmente, amostras deformadas foram utilizadas para determinação das características de retenção da água no solo pela técnica do ponto de orvalho em altos valores de sucções matriciais. Os dados de retenção de água no solo foram ajustados a modelos empíricos para estimativas da sucção matricial e conteúdo de água relacionada à água em equilíbrio hidráulico (água residual). Foram observadas similaridades nas determinações das características de retenção da água no solo entre as técnicas de câmaras de pressão e ponto de orvalho, sugerindo a boa drenagem das amostras de solo em câmaras de pressão. Interações significativas foram observadas entre os tipos de solos e espécies de plantas no ponto de murcha permanente, indicando que o movimento de água no contínuo solo-planta-atmosfera foi dependente de resistências relacionadas tanto ao solo quanto às plantas. Ou seja, tanto à capacidade do solo em transportar água até raízes, quanto à habilidade das plantas em absorver a água transportada, assim como, aos processos de regulação de água que ocorrem nas plantas. A abordagem baseada no conteúdo de água residual para o intervalo de sucções matriciais de 0 a 15.000 hPa não foi adequada para ilustrar a condição de equilíbrio hidráulico da água no solo, definidos pelo corte hidráulico, e relações com as sucções matriciais em ocorre o murchamento de plantas. / Estimates about climate changes have increased the demand for studies of the properties of relatively dry soil and limitations on the plants water uptake in conditions of water scarcity. In this study, factors influencing the soil water retention and wilting plants were evaluated based on the concept of soil water equilibrium. The objectives of this study were: (i) to evaluate the reliability measurements of the soil water retention on pressure plate apparatus at high matric suctions using as reference the dew point meter (ii) to evaluate the interactions between soil types and plant species at permanent wilting point (iii) investigate the relationship between the hydraulic equilibrium of soil water and the plant wilting based on the hydraulic cut-off concept. A pot experiment to evaluate the effect of plant and soil types at permanent wilting point was carried out in a greenhouse at the Agricultural\'s College \"Luiz de Queiroz\" from University of São Paulo in Piracicaba, São Paulo, Brazil. Soil samples were collected at the topsoil (0-10 cm) from four different locations around the city of Piracicaba, São Paulo, Brazil. Subsamples were taken to determine the particle size distribution and chemical analysis. To determine soil water retention curve 30 soil samples were collected with undisturbed soil cores. The soils were selected to have a range of texture and organic carbon content. The wilting was evaluated using plants of sunflower (Helianthus annuus L.), maize (Zea mays L.) and soybean (Glycine max L.). The soil water retention data were fitted to the empirical models for estimating the matric suction and water content related soil water at hydraulic equilibrium (residual water content). Similar soil water content were observed for measurements at pressure plate apparatus and dew point meter, suggesting good drainage of the soil samples in pressure plate apparatus for the dry range of soil water retention curve. Significant interactions were observed between soil types and plant species at permanent wilting point, indicating that the water movement in the soil-plant-atmosphere continuum was dependent of resistances related to soil and the plants properties. The approach based on the residual water content for the matric suctions from 0 to 15,000 hPa was not adequate to illustrate the hydraulic equilibrium of the soil water defined by the cut-hydraulic and relations with the matric suction at wilting plants.

Made available in DSpace on 2014-08-20T14:25:49Z (GMT). No. of bitstreams: 1 dissertacao_clovis_correa.pdf: 19288418 bytes, checksum: 98a82fd638a44d647e5b27b37e7a8288 (MD5) Previous issue date: 2010-02-26 / This work presents the study of atmospheric conditions associated the occurrence of Hurricane Catarina and two study cases. The Catarina occurred in March 2004 and reached the coast of southern Brazil.The other case studies correspond to cut-off lows that occurred in May 2005 and September 2008. It was used the WRF model, version 3.0, to obtain the meteorological fields during the period of occurrence of these events and images of the geostationary satellite GOES-12 and QuikSCAT. For Hurricane Catarina, data from surface meteorological stations were also analyzed. Initially, the study cases consisted of cut-off lows preceded by extratropical cyclones in the South Atlantic Ocean. When they shut the western flow, they occurred at the interface of different patterns of vertical variation of horizontal wind in the layer between 850-200hPa and showed closed cyclonic circulation at middle levels. At high levels, it was observed bifurcation of the jet with a trough quasi-stationnary near the southern coast of Brazil. The observed atmospheric blocking together with the thermodynamic and kinematic configurations of each case contributed to the occurrence of tropical transition and subsequent formation of Hurricane Catarina, in March 2004, while the other cut-off lows dissipated. / Neste trabalho é feito o estudo sobre as condições atmosféricas associadas à ocorrência do furacão Catarina e a dois casos de estudo. O Catarina ocorreu em março de 2004 e atingiu o litoral da região sul do Brasil. Os outros casos de estudo correspondem a baixas desprendidas que ocorreram em maio de 2005 e setembro de 2008. Foi utilizado o modelo WRF, versão 3.0, para a obtenção dos campos meteorológicos durante o período de ocorrência destes eventos e imagens do satélite geoestacionário GOES-12 e do QuikSCAT. Para o furacão Catarina, foram também analisados dados de estações meteorológicas de superfície. Os casos de estudo, inicialmente, corresponderam a baixas desprendidas precedidas por ciclones extratropicais no Oceano Atlântico Sul. Ao se isolarem do escoamento de oeste, ocorreram na interface de padrões distintos de variação vertical do vento horizontal na camada entre 850-200hPa e apresentaram circulação ciclônica fechada em níveis médios. Em altos níveis, foi observada bifurcação do jato com um cavado quase estacionário nas proximidades da costa sul do Brasil. Os bloqueios atmosféricos observados, juntamente com as configurações cinemáticas e termodinâmicas de cada caso, contribuíram para a ocorrência da transição tropical e posterior formação do furacão Catarina, em março de 2004, enquanto que as outras baixas desprendidas se dissiparam.

In this thesis, we propose a novel architecture for hybrid radio frequency (RF)/free–space optics (FSO) wireless systems. Hybrid RF/FSO systems are attractive since the RF and FSO sub–systems are affected differently by weather and fading phenomena. We give a thorough introduction to the RF and FSO technology, respectively. The state of the art of hybrid RF/FSO systems is reviewed. We show that a hybrid system robust to different weather conditions is obtained by joint bit–interleaved coded modulation (BICM) of the bit streams transmitted over the RF and FSO sub–channels. An asymptotic performance analysis reveals that a properly designed convolutional code can exploit the diversity offered by the independent sub–channels. Furthermore, we develop code design and power assignment criteria and provide an efficient code search procedure. The cut–off rate of the proposed hybrid system is also derived and compared to that of hybrid systems with perfect channel state information at the transmitter. Simulation results show that hybrid RF/FSO systems with BICM outperform previously proposed hybrid systems employing a simple repetition code and selection diversity. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

Submitted work engages in suggestion of frequency-selection filters with usage of more active elements of the MCMI (Multi-Output Current Mirror and inverter). The preamble of thesis is applied to theory of frequency-selection filters and possible usage of them. The projected circuit layouts with the active elements are discussed in terms of the impact of parasitic properties of the real models. The part of thesis is numerical suggestion of found solutions, their simulation in suitable program.

MENVSC / Department of Geography and Geo-Information Sciences / Out of all rain-producing weather systems, cut-off lows (COLs) are linked with the occurrence of high impact rainfall and in some cases short-lived floods which can last for 24 hours over South Africa. This study examined the characteristics associated with the present occurrence of the severe COL systems over South Africa from 2011 to 2017. The accuracy of the 4.4 km Unified Model (UM) which is currently in use for simulating areas of deep moist convection in South Africa was evaluated. The UM simulated geopotential height at 500 hPa as well as the associated 24 hours precipitation which were compared against the daily fields of geopotential height and 6-hourly precipitation from the European Centre for Medium-Range Weather Forecasts (ECMWF). COL events were categorized and analyzed according to the associated surface circulation patterns at 850 hPa. The seasonal distribution and duration of the systems over northern (10°E-33°E //22°-32°S) and southern (10°E-33°E //32°-35°S) regions of the study area were also analyzed. Results show COL systems shifting with season towards the north eastern parts of the country, with an increased number of events during the austral winter season during the study period. Systems which lasted for long time were observed during the austral winter and spring seasons. The UM tends to simulate areas of heavy precipitation accurately with poor simulation during the initial stages of the systems. The UM provided a more realistic-looking closed geopotential height and rainfall fields for systems which are coupled with a cold front at the surface. Application of the knowledge about the evolution in the characteristics of COL events from this study can improve the operational forecasting of these weather systems over the country. / NRF

In this dissertation, we use finite element method together with other numerical techniques to study advanced electron devices. We study the radiation properties in electron waveguide structure with multi-step discontinuities and soft wall lateral confinement. Radiation mechanism and conditions are examined by numerical simulation of dispersion relations and transport properties. The study of geometry variations shows its significant impact on the radiation intensity and direction. In particular, the periodic corrugation structure exhibits strong directional radiation. This interesting feature may be useful to design a nano-scale transmitter, a communication device for future nano-scale system. Non-quasi-static effects in AC characteristics of carbon nanotube field-effect transistors are examined by solving a full time-dependent, open-boundary Schrödinger equation. The non-quasi-static characteristics, such as the finite channel charging time, and the dependence of small signal transconductance and gate capacitance on the frequency, are explored. The validity of the widely used quasi-static approximation is examined. The results show that the quasi-static approximation overestimates the transconductance and gate capacitance at high frequencies, but gives a more accurate value for the intrinsic cut-off frequency over a wide range of bias conditions. The influence of metal interconnect resistance on the performance of vertical and lateral power MOSFETs is studied. Vertical MOSFETs in a D2PAK and DirectFET package, and lateral MOSFETs in power IC and flip chip are investigated as the case studies. The impact of various layout patterns and material properties on RDS(on) will provide useful guidelines for practical vertical and lateral power MOSFETs design.

No description available.

No description available.

L’obésité est un problème de santé publique reconnu. Dans la dernière décennie l’obésité abdominale (OA) a été considérée comme une maladie métabolique qui contribue davantage au risque de diabète et de maladies cardiovasculaires que l’obésité générale définie par l’indice de masse corporelle. Toutefois, dans les populations d’origine africaine, la relation entre l’OA et les autres biomarqueurs de risque cardiométabolique (RCM) demeure obscure à cause du manque d’études chez ces populations et de l’absence de valeurs-seuils spécifiques pour juger d’une OA. Cette étude visait à comparer la prévalence des biomarqueurs de RCM (OA, hypertension artérielle, hyperglycémie, dyslipidémie, résistance à l'insuline et inflammation pré-clinique) chez les Béninois de Cotonou et les Haïtiens de Port-au-Prince (PAP), à étudier l’association de l’OA avec les autres biomarqueurs de RCM, à documenter le rôle du niveau socio-économique (NSE) et du mode de vie dans cette association et à ’identifier les indicateurs anthropométriques de l’OA -tour de taille (TT) et le ratio TT/hauteur (TT/H)- et les seuils qui prédisent le mieux le RCM à Cotonou et à PAP. Il s’est agi d’une analyse de données transversales chez 452 adultes (52 % hommes) apparemment en bonne santé, âgés de 25 à 60 ans, avec 200 sujets vivant à Cotonou (Bénin) et 252 sujets à PAP (Haïti). Les biomarqueurs de RCM considérés étaient : le syndrome métabolique (SMet) d’après les critères harmonisés de 2009 et ses composantes individuelles - une OA à partir d’un TT ≥ 94cm chez les hommes et ≥ 80cm chez les femmes, une hypertension, une dyslipidémie et une hyperglycémie; la résistance à l’insuline définie chez l’ensemble des sujets de l’étude à partir du 75e centile de l’Homeostasis Model Assessment (HOMA-IR); un ratio d’athérogénicité élevé (Cholestérol sérique total/HDL-Cholestérol); et l’inflammation pré-clinique mesurée à partir d’un niveau de protéine C-réactive ultrasensible (PCRus) entre 3 et 10 mg/l. Le ratio TT/H était aussi considéré pour définir l’OA à partir d’un seuil de 0,5. Les données sur les habitudes alimentaires, la consommation d’alcool, le tabagisme, les caractéristiques sociodémographiques et les conditions socio-économiques incluant le niveau d’éducation et un proxy du revenu (basé sur l’analyse par composante principale des biens et des possessions) ont été recueillies au moyen d’un questionnaire. Sur la base de données de fréquence de consommation d’aliments occidentaux, urbains et traditionnels, des schémas alimentaires des sujets de chaque ville ont été identifiés par analyse typologique. La validité et les valeurs-seuils de TT et du ratio TT/H prédictives du RCM ont été définies à partir des courbes ROC (Receiver Operating Characteristics). Le SMet était présent chez 21,5 % et 16,1 % des participants, respectivement à Cotonou et à PAP. La prévalence d’OA était élevée à Cotonou (52,5 %) qu’à PAP (36%), avec une prévalence plus élevée chez les femmes que chez les hommes. Le profil lipidique sérique était plus athérogène à PAP avec 89,3 % d’HDL-c bas à PAP contre 79,7 % à Cotonou et un ratio CT/HDL-c élevé de 73,4 % à PAP contre 42 % à Cotonou. Les valeurs-seuils spécifiques de TT et du TT/H étaient respectivement 94 cm et 0,59 chez les femmes et 80 cm et 0,50 chez les hommes. Les analyses multivariées de l’OA avec les biomarqueurs de RCM les plus fortement prévalents dans ces deux populations montraient que l’OA était associée à un risque accru de résistance à l’insuline, d’athérogénicité et de tension artérielle élevée et ceci, indépendamment des facteurs socio-économiques et du mode de vie. Deux schémas alimentaires ont émergé, transitionnel et traditionnel, dans chaque ville, mais ceux-ci ne se révélaient pas associés aux biomarqueurs de RCM bien qu’ils soient en lien avec les variables socio-économiques. La présente étude confirme la présence de plusieurs biomarqueurs de RCM chez des sujets apparemment sains. En outre, l’OA est un élément clé du RCM dans ces deux populations. Les seuils actuels de TT devraient être reconsidérés éventuellement à la lumière d’études de plus grande envergure, afin de mieux définir l’OA chez les Noirs africains ou d’origine africaine, ce qui permettra une surveillance épidémiologique plus adéquate des biomarqueurs de RCM. / Obesity is recognized as a major public health problem. In the last decade abdominal obesity (AO) was considered as a metabolic disorder which further contributes to the risk of diabetes and cardiovascular disease than the general obesity defined by body mass index. However, in African origin population groups, the relationship between AO and other cardiometabolic risk (CMR) biomarkers remained unclear because of the lack of studies in these population groups and the lack of specific cut-off values to define AO. This study aimed to compare the prevalence of CMR biomarkers (OA, hypertension, hyperglycemia, dyslipidemia, insulin resistance and subclinical inflammation) in Beninese from Cotonou and Haitians from Port-au-Prince (PAP), to assess the association between AO and other CMR biomarkers in relation to Cotonou and PAP participants’ socioeconomic and lifestyle parameters and to define anthropometric indicators of AO -waist circumference (WC) and waist-to-height ratio (WHtR)- and specific thresholds that best predict the CMR in both Cotonou and PAP. The cross-sectional study included 452 apparently healthy adults (52 % men), aged 25-60 years, 200 subjects from Cotonou (Benin) and 252 subjects from PAP (Haiti). The CMR biomarkers were: the metabolic syndrome (MetS) according to the harmonized criteria of 2009, its individual components - AO defined by a WC ≥ 94cm in men and ≥ 80 cm in women, hypertension, dyslipidemia and hyperglycemia - Insulin resistance was set at the 75th centile of Homeostasis Model Assessment (HOMA-IR) for the whole sample of subjects. High atherogenicity index (total serum cholesterol/HDL-Cholesterol), subclinical inflammation according to high-sensitivity C-reactive protein (hsCRP) concentration between 3 to 10 mg/L was also assessed. WHtR from a cut-off point of 0.5 was also considered to assess AO. Data on dietary habits, alcohol consumption, tobacco, sociodemographic and socioeconomic status, including education level and a proxy of income (based on principal component analysis of property and possessions) were documented by a questionnaire. Dietary patterns were generated from Western, urban and traditional food frequency in each city by cluster analysis. Receiver Operating Characteristic (ROC) curves were used to assess the performance of specific WC and WHtR cut-offs to predict the CMR. MetS was present in 21.5 % and 16.1 % of participants in Cotonou and PAP respectively. AO was higher in Cotonou (52.5 %) than in PAP (36 %) with higher prevalence in women than in men. The serum lipid profile was more atherogenic in PAP with 89.3 % of low HDL-C in PAP comparing to 79.7 % in Cotonou and high seum TC / HDL-C ratio of 73.4 % in PAP versus 42 % in Cotonou. The specific WC and WHtR cut-off values were respectively 94 cm and 0.59 in women and 80cm and 0.50 in men. Multivariate analysis of AO with the most prevalent CMR biomarkers in these two population groups showed that AO was associated with increased risk of insulin resistance, high atherogenic index and high blood pressure, irrespective of socioeconomic and lifestyle factors. Two dietary patterns were defined: transitional and traditional in each city, but these were not associated with the CMR biomarkers although they were related to socioeconomic variables. This study confirms the presence of several CMR biomarkers in apparently healthy subjects. Additionally, AO was a key element of the CMR in both population groups. However, current WC thresholds should be reconsidered in light of larger studies to better define AO among Black African groups, which will improve the epidemiological surveillance of the CMR biomarkers.

La résistance aux antibiotiques est un enjeu de santé publique mondiale. L'alimentation est une des voies de contamination des bactéries résistantes aux antibiotiques entre l'environnement et l'Homme. Toutefois, les données concernant les bactéries résistantes aux antibiotiques dans les produits aquatiques sont rares. L'objectif de ces travaux a été d'étudier la flore bactérienne et sa résistance aux antibiotiques dans les produits de la pêche et de l'aquaculture. Dans un premier temps, la flore bactérienne mésophile cultivable a été isolée de 9 matrices différentes puis identifiée par la technique MALDI-TOF et/ou du séquençage de différents gènes de ménage. Au final, 1882 isolats bactériens ont été obtenus, et 150 espèces et 57 genres bactériens ont été identifiés. Dans un deuxième temps, nous avons étudié la résistance aux antibiotiques des genres bactériens les plus fréquemment isolés de ces produits. La résistance aux antibiotiques des genres Enterococcus, Staphylococcus, Exiguobacterium, Pseudomonas, Vibrio et Proteus a donc été étudiée. Au total, 46% des isolats étaient résistants aux antibiotiques et 3% étaient multi-résistants. Les crevettes étaient le produit dans lequel le plus de souches résistantes aux antibiotiques ont été identifiée. Et dans un troisième temps, la résistance aux antibiotiques d'une collection de souche de Vibrio parahaemolyticus, espèce bactérienne pathogène alimentaire pour l'homme, a été étudiée. Concernant V. parahaemolyticus, 15% des souches étaient résistantes et 3% des souches étaient multi-résistantes. Une souche, 16-B3PA-006, isolées de crevettes importées d'Asie du Sud-Est produisait une carbapénèmase NDM-1 et était résistante à 5 classes d'antibiotiques. / Antimicrobial resistance is a threat to global public health. Human can be contaminated by antibiotic resistant bacteria through food. However, data on antimicrobial resistant bacteria in seafood are scarce. The aim of this thesis was to study seafood bacterial flora and its antimicrobial resistance. First, mesophilic flora was obtained from 9 matrixes and MALDI-TOF and housekeeping genes sequencing technics were used to identify isolates. Antimicrobial resistance of most frequently bacteria were tested. In total, 1882 isolates were obtained and 150 bacterial species and 57 genera were identified. Enterococcus, Staphylococcus, Exiguobacterium, Pseudomonas, Vibrio and Proteus were most frequently isolated and their antimicrobial resistance was studied. Antibiotic resistant bacteria accounted for 46% of isolates and multidrug resistant bacteria accounted for 3% of isolates. Antimicrobial resistant bacteria were mostly isolated from shrimps. On a side study, antimicrobial resistance of a V.parahaemolyticus strain collection isolated from seafood was characterized. Antimicrobial resistant strains accounted for 15% and multi-drug resistant bacteria accounted for 3%. A NDM-1-producing multidrug resistant strain, 16-B3PA-006 was identified from shrimps imported from South-East Asia.