Dès lors que des éléments rayonnants sont placés à proximité les uns des autres, comme c'est le cas au sein des antennes réseaux à balayage électronique, des interactions électromagnétiques parasites se créent entre eux. Ces couplages se manifestent par une perturbation des répartitions de courants des sources du réseau. Leur impact dépend fortement de l'angle de dépointage du réseau mais est généralement néfaste, car ils modifient les caractéristiques du rayonnement des sources. Les différents objectifs de compacité et les spécifications de performances radioélectriques visés pour les radars aéroportées peuvent conduire à des structures qui supportent et favorisent ces phénomènes de couplages parasites, sous la forme d’ondes d’espace et de surface. Ces derniers peuvent aller jusqu'à entrainer l'impossibilité pour l'antenne de rayonner dans certaines directions et à certaines fréquences d’utilisation : on parle de directions aveugles. Ce phénomène limite de manière considérable le volume de dépointage opérationnel d'un système radar. La maîtrise du couplage entre les éléments rayonnants est donc l'une des problématiques essentielles du développement et du dimensionnement d'une antenne réseau. La recherche qui traite de ce sujet n'en est plus à ses débuts (les premiers radars à balayage électronique sont exploités depuis les années 50) mais reste toujours en attente de solutions innovantes permettant de mieux comprendre et maîtriser ces phénomènes. Dans cette thèse, plusieurs méthodes permettant de minimiser les effets du couplage dans les réseaux à balayage électroniques ont été investiguées. Les travaux s'orientent notamment autour du défi de réduire les conséquences des directions aveugles sans modifier la maille initiale du réseau d'antenne (contrainte iso-maille). / When radiating elements are located close to one another, as it is the case in electronically phased array antennas, parasitic electromagnetic interferences occur between them. The impact of these coupling mechanisms depends to a large extent on the scanning angle of the array, but is usually harmful, since it alters the radiating properties and the active input impedance of the sources. The compactness objectives and radioelectric performances required for airborne radars can lead to structures that support and foster these parasitic couplings, in the form of surface or space waves. In some cases, mutual coupling can even result in the impossibility for the array to radiate in certain directions and at certain frequencies. This phenomenon, referred to as scan blindness, significantly reduces the operating scan volume of a radar system. In that respect, the control of coupling mechanisms between radiating elements is a major issue when developing an array antenna and although the research that deals with this subject is no longer in its infancy, it is always pending for new and innovating solutions to master these phenomena. In this thesis, different solutions enabling to minimize the effect of couplings in phased arrays are investigated. The presented research revolves around the challenge of limiting scan blindness consequences without modifying the initial mesh of the array antenna.

Este trabalho visou ao desenvolvimento de antenas de ressoador dielétrico de banda dupla em frequências de micro-ondas por meio do estabelecimento de uma metodologia de projeto para as mesmas e da proposição de configurações inéditas de antenas desse tipo. Estudos realizados sobre antenas de ressoador dielétrico e sobre suas técnicas de projeto forneceram a base para a elaboração de um procedimento de projeto para antenas de banda dupla que explora a flexibilidade das antenas de ressoador dielétrico. Empregando-se esse procedimento de projeto, duas antenas com configurações originais foram desenvolvidas para operar em frequências de micro-ondas. Uma delas é uma antena de ressoador dielétrico cilíndrica sobre plano de terra, destinada a operar nas frequências centrais de 3,94 GHz e de 5,42 GHz, com diagrama de radiação direcional e polarização circular na primeira banda de operação e com diagrama de radiação omnidirecional e polarização linear na segunda. A outra antena consiste em uma antena de ressoador dielétrico cilíndrica sobre substrato dielétrico aterrado, cujas frequências centrais de operação são 3,99 GHz e 6,20 GHz, com diagrama de radiação direcional e polarização circular em ambas as bandas de operação. O projeto das duas antenas também levou a contribuições novas adicionais em alguns temas específicos relacionados: estruturas de excitação para antenas de ressoador dielétrico, circuitos acopladores híbridos de 90° de banda dupla, circuitos de alimentação para antenas de banda dupla e modelos matemáticos para o ressoador dielétrico cilíndrico isolado no espaço livre. Os comportamentos previstos teoricamente para as antenas projetadas são confirmados por meio de resultados obtidos por simulação eletromagnética e por medição experimental, o que indica a validade das hipóteses adotadas, das configurações de antena propostas e da metodologia de projeto concebida, demonstrando também a flexibilidade desta para variadas especificações de antena. Os avanços obtidos com este trabalho e as melhorias que podem ser efetuadas sobre o mesmo são identificados examinando-se resultados recentemente publicados na literatura técnica. Este trabalho foi realizado na forma de uma pesquisa de doutorado sanduíche, desenvolvida parcialmente na University of Houston sob a supervisão do Prof. Stuart A. Long. / This work aimed at the development of microwave dual-band dielectric resonator antennas by means of establishing a design methodology for them and of proposing novel configurations of this antenna type. Studies on dielectric resonator antennas and on their design techniques provided the ground for elaborating a design procedure for dual-band antennas that exploits the flexibility of dielectric resonator antennas. By employing this design procedure, two antennas with original configurations have been developed for operation at microwave frequencies. One of them is a cylindrical dielectric resonator antenna on a ground plane, intended for operation at the center frequencies of 3.94 GHz and 5.42 GHz, with a directional radiation pattern and circular polarization in the first operating band and with an omnidirectional radiation pattern and linear polarization in the second one. The other antenna consists of a cylindrical dielectric resonator antenna on a grounded dielectric substrate, whose operating center frequencies are 3.99 GHz and 6.20 GHz, with a directional radiation pattern and circular polarization in both operating bands. The design of the two antennas also led to additional new contributions in some related specific subjects: excitation structures for dielectric resonator antennas, dual-band 90°-hybrid couplers, feeding circuits for dual-band antennas, and mathematical models for the cylindrical dielectric resonator isolated in free space. The behaviors theoretically expected for the designed antennas are confirmed by means of results obtained from electromagnetic simulation and from experimental measurements, which indicates the validity of the assumed hypotheses, of the proposed antenna configurations and of the conceived design methodology, also demonstrating the flexibility of the latter for various antenna specifications. The advances obtained with this work and the improvements that can be made on it are identified by examining results recently published in the technical literature. This work was carried out as a sandwich doctoral research, developed at the University of Houston under the supervision of Prof. Stuart A. Long.

O aquecimento por micro-ondas (MO) é uma tecnologia emergente para o processamento térmico contínuo de alimentos líquidos. A taxa d aquecimento e a profundidade de penetração das MO dependem das propriedades dielétricas (PD) do alimento (permissividade elétrica relativa e fator de perda dielétrica ). As PD de água de coco verde e de sucos de frutas cítricas (laranja, limão e tangerina) foram estudadas empregando a técnica de cabo coaxial. As medições foram realizadas em 101 frequências na faixa de 500 MHz até 3000 MHz e em temperaturas entre 0 °C e 90 °C, o que permitiu estudar o efeito da frequência e da temperatura. A profundidade de penetração foi calculada com uma expressão derivada das equações de Maxwell para eletromagnetismo. O trabalho experimental começou com as PD de: água de coco verde simulada, água destilada, solução de açúcares e sais da água de coco verde e água de coco verde natural. Resultados foram comparados para avaliar a contribuição de cada componente (água, açúcares e sais). PD de sucos de diferentes variedades de laranjas, tangerinas e limões, assim como misturas de sucos de duas variedades de laranja, foram também avaliadas. A condutividade elétrica das amostras foi medida nas diferentes temperaturas e o seu efeito sobre o fator de perda foi analisado. Os resultados foram comparados nas frequências comerciais de 915 MHz e 2450 MHz. O comportamento dielétrico das amostras estudadas foi caracterizado por dois mecanismos principais: a condução iônica de sais dissolvidos e a rotação dipolar da molécula de água, os quais têm predominância variável dependendo da frequência e da temperatura. A permissividade elétrica relativa de todas as amostras decresceu com o incremento da temperatura e da frequência, enquanto que o comportamento do fator de perda com a temperatura e frequência foi determinado pela composição. Os sais apresentaram maior efeito que os açúcares sobre as PD da água de coco verde. A profundidade de penetração foi maior na frequência de 915 MHz, associada com o aumento no comprimento de onda. Correlações polinomiais foram ajustadas nas frequências comerciais para representar a dependência com a temperatura. / Microwave (MW) heating is an emergent technology for thermal processing of liquid food products. Heating rate and MW penetration depth depending on dielectric properties (DP) of food material (relative electrical permittivity () and dielectric loss factor ()). DP for green coconut water (GCW) and citrus fruits juices (orange, tangerine and lemon) were studied by open-ended coaxial line probe technique. The measurements were carried out for frequencies between 500 MHz and 3000 MHz at 101 points in this range and temperatures from 0 °C to 90 °C, which allowed studying temperature and frequency effect. The power penetration depth was calculated using an expression derived from the Maxwell equations for electromagnetism. Experimental work started with DP measurement for: simulated (GCW), distilled water, sugars and salts solutions of (GCW) and natural (GCW). Results were compared in order to evaluate the each component contribution (water, sugars and salts). DP for juices from different orange, tangerine and lemon varieties as well as mixtures of orange juice from two varieties, were also evaluated. Electrical conductivity was measured and its effect on dielectric loss factor was analyzed. Obtained results were compared at commercial frequencies of 915 MHz and 2450 MHz. Dielectric behavior of studied samples was characterized by two main mechanisms: ionic conduction of dissolved salts and dipole rotation of water molecules, which presented variable predominance, depending on frequency and temperature. Relative electrical permittivity decreased with increase on both temperature and frequency for all tested samples, whereas dielectric loss factor behavior with temperature and frequency was determined by composition. Salts showed higher effect than sugars on dielectric properties of GCW. Penetration depth was higher at 915 MHz, associated to increasing wave length. Polynomial correlations for DP were adjusted at commercial frequencies in order to illustrate the temperature dependence.

Orientador: Carlos Eduardo Vergani / Banca: Ana Lucia Machado / Banca: Wander José da Silva / Resumo: Infecções causadas por bactérias resistentes a antibióticos são consideradas causa principal de mortalidade entre indivíduos imunocomprometidos e aproximadamente 50 % destas infecções tem sido relacionadas ao Staphylococcus aureus resistente à meticilina (MRSA). Estes microrganismos, quando presentes no biofilme das próteses dentarias, podem se dispersar nas secreções salivares e se disseminar pelo trato respiratório, causando pneumonia aspirativa. Assim, o presente estudo comparou a efetividade do hipoclorito de sódio a 1 %, digluconato de clorexidina a 2 % e irradiação por micro-ondas na desinfecção de próteses totais e corpos-de-prova circulares de resina acrílica para base de prótese (10 x 2 mm) contaminados com MRSA. Para isso, 36 próteses totais simuladas e 36 corpos-de-prova circulares foram confeccionados, esterilizados, inoculados com MRSA (107 ufc/mL) e incubados a 37 °C (por 24 e 48 h, respectivamente). Após incubação, próteses totais e corpos-de-prova foram distribuídos em 4 grupos de estudo (n=9): GC - não foi realizado nenhum método de desinfecção; GH - foi realizada a imersão em solução de hipoclorito de sódio a 1 % por 10 min; GCl -foi realizada a imersão em solução de digluconato de clorexidina a 2 % por 10 min; GM - foi realizada a desinfecção por irradiação em forno de micro-ondas a 650 W por 3 min. A efetividade dos procedimentos de desinfecção foi avaliada por meio de quantificação de colônias viáveis e da viabilidade celular. Para a quantificação de colônias viáveis, alíquotas de 25 μL da solução resultante das diluições seriadas (10-3 a 10-6 para GC e 100 a 10-3 para os grupos experimentais) foram semeadas em placas de Petri em duplicata e todas as placas foram incubadas por 48 h a 37 °C. As colônias foram quantificadas em ufc/mL. Para verificar a efetividade da desinfecção por micro-ondas em longo prazo... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Infections caused by antibiotic-resistant bacteria have been recognized as a predominant risk factor for mortality in elderly patients and approximately 50 % of these infections have been related to methicillin-resistant Staphylococcus aureus (MRSA). This microorganism, when present in the denture biofilm, can be released into the oral fluids and aspirated into the lower respiratory tract, thus causing infections such as aspiration pneumonia. The present study compared the efficacy of 1 % sodium hypochlorite, 2 % chlorhexidine gluconate, and microwave irradiation in disinfecting simulated complete dentures and circular specimens of acrylic resin denture base material (10 x 2 mm) contaminated with MRSA. Thirty-six dentures and 36 specimens were made, sterilized, inoculated with MRSA (107 cfu/mL), and incubated at 37 °C (for 24 and 48 h, respectively). After incubation, dentures and specimens were divided into 4 groups of study (n=9): PC - positive control, consisting of dentures and specimens not disinfected; HY - soaking in 1 % sodium hypochlorite solution for 10 min; CHL - soaking in 2 % chlorhexidine gluconate solution for 10 min; and MW - irradiating by microwave for 3 min at 650W. The effectiveness of the disinfection procedures was assessed cell viability (quantification of viable cells and XTT reduction method). For quantification procedures, aliquots of suspensions were plated at dilutions (10-3 to 10-6 for PC and 100 to 10-3 for experimental groups) and incubated (37 °C/48 h). Colonies counts (cfu/mL) were quantified. Dentures disinfected were also incubated at 37 °C for 7 days to verify the long-term effectiveness of disinfection. The viability of cells in each group of specimens was evaluated by XTT reduction method. The results showed that all dentures and specimens from the PC groups showed substantial microbial growth. No evidence of microbial growth was observed... (Complete abstract click electronic access below) / Mestre

L’hydrogène peut être utilisé (et est utilisé depuis peu) comme un vecteur d’énergie propre. Il permet la transition du monde énergétique actuel, basé sur les énergies fossiles, vers le monde énergétique futur basé sur les énergies renouvelables et l’hydrogène. Cette transition ne sera envisageable que lorsque les problématiques liées à la production en masse de l’hydrogène et à son stockage seront résolues.L’objectif de ce travail de thèse est de produire l’hydrogène à partir de matériaux à base de magnésium en utilisant deux méthodes : (i) l’hydrolyse et (ii) la méthode micro-ondes.Notre premier objectif était d’élaborer des matériaux pour lesquels le phénomène de passivation du magnésium serait limité et présenteraient ainsi des rendements de production d’hydrogène optimaux. Le broyage mécanique à haute énergie est utilisé pour élaborer les différents composites à base de magnésium ou de son hydrure (Mg – 10 % en masse Additifs) afin d’accentuer la corrosion de ces derniers. Nous avons essentiellement focalisé nos efforts sur l’effet des additifs (i.e. Métaux de transition, Carbone et Oxydes) sur la réaction d’hydrolyse. Les tests d’hydrolyse ont été effectués dans une solution contenant 35 g/L NaCl (i.e. eau de mer). Notre stratégie, pour la résolution des problèmes de cinétique d’absorption/désorption (très lentes même à haute température (i.e. 350°C)), est basée essentiellement sur l’application de l’énergie micro-ondes. Notre deuxième objectif est donc l’utilisation des micro-ondes pour déshydrurer plus rapidement l’hydrure de magnésium (MgH2 – C) grâce à une élévation de température très rapide par rapport au procédé conventionnel. On a traité l’effet des irradiations micro-ondes sur la cinétique de désorption de mélange MgH2 – C, la morphologie et les propriétés de la poudre après un traitement micro-ondes. D’autre part, nous avons présenté une perspective possible de l’application des micro-ondes : la production de fines poudres de titane à partir de son hydrure. / A drastic reduction of emissions requires a partial or a full phase-out of fossil fuels and switch to renewable based energy production. Hydrogen appears to be a potential candidate to replace hydrocarbon fuels for producing clean energy. In this context, production and storage of hydrogen is one of the key challenges in developing the hydrogen economy.The objective of this thesis is to produce hydrogen from Mg-based materials using (i) hydrolysis and (ii) microwaves methods.The first aim of this thesis is to elaborate Mg-based materials with good hydrolysis kinetics and high yield of hydrogen generation (i.e. reducing the formation of the passivation layer on magnesium). For this study, we focalize essentially on the effect of various additives (Transition metals, Carbon or Oxides) on the hydrolysis reaction of Mg-based materials. The mixtures were prepared by ball milling. Chloride solution (3.5 wt. % NaCl, i.e. sea water) was used as reaction medium to beneficiate of chloride ions effect. Our strategy, to solve the problems related to the low absorption/desorption kinetics (even at high temperature (i.e. 350°C) of Mg-based materials, is based on microwaves energy application. Our second goal for this thesis is to investigate the dehydriding reaction of magnesium hydride catalyzed by carbon (i.e.MgH2 – C) under microwave irradiations. We have studied the effects of microwaves on the kinetics of hydrogen desorption, the morphology and sorption properties of Mg powder after microwave treatment. On the other hand, we have presented another microwaves application which appears very promising: production of fine titanium powder from titanium hydride.

A quimiluminescência derivada da decomposição induzida de 1,2-dioxetanos e do sistema peróxi-oxalato pode ser explicada através do mecanismo de luminescência iniciada por troca de elétron - CIEEL (\"Chemically Initiated Electron Exchange Luminescence\"). Esta proposta supõe uma transferência de elétron seguida de uma retrotransferência, que pode ocorrer de forma intra ou intermolecular, dependendo do sistema. A etapa de quimiexcitação do sistema peróxi-oxalato envolve uma retro-transferência de elétron intermolecular, da qual participam dois radicais-íons - um deles postulado como o dióxido de carbono radical-anion. Por outro lado, não existe consenso a respeito da via de retro-transferência de elétron na decomposição induzida de 1,2-dioxetanos, que pode ocorrer de forma intra ou intermolecular. Neste trabalho são apresentadas as sínteses de sete 1,2-dioxetanos, os resultados obtidos na investigação da via de quimiexcitação proposta no mecanismo CIEEL para a decomposição induzida de 1,2-dioxetanos e para o sistema peróxi-oxalato e a aplicação da quimiluminescência do luminol em matriz polimérica de poli(vinilpirrolidona) para a calibração de luminômetros de microplacas. Verificou-se, através do estudo do efeito da viscosidade do solvente sobre os rendimentos quânticos singlete na decomposição induzida de 1,2-dioxetanos, uma dependência entre a eficiência de quimiexcitação e o efeito da cavidade de solvente, que foi racionalizada em termos de um modelo difusional e friccional. Estes resultados, associados a cálculos teóricos, tomaram possível postular um mecanismo intramolecular modificado para a decomposição induzida de 1,2-dioxetanos. No sistema peróxi-oxalato foi realizada uma tentativa de detecção direta do dióxido de carbono ânion-radical através de medidas do sinal de ressonância paramagnética de elétron do aduto formado entre α-fenil-N-tert-butilnitrona (PBN), um spin trap, e o radical-anion. Apesar da leve discrepância entre as constantes de acoplamento do sinal observado em relação aos valores relatados na literatura para o aduto PBN-CO2, a caracterização foi realizada preliminarmente através de espectroscopia de massas com injeção direta. Finalmente, foi desenvolvido um sistema para calibração de luminômetros de microplacas, baseado na quimiluminescência de luminol em matriz polimérica, que pode ser utilizado - adicionalmente - na quantificação de peróxido de hidrogênio, em concentrações µmol-1, e agentes redutores com potencial anti-radicalar e antioxidante. / The chemiluminescence resulting from induced decomposition of 1,2-dioxetanes and the peroxyoxalate system can be explained by the Chemically Initiated Electron Exchange Luminescence - CIEEL mechanism. This hypothesis postulates an electron transfer followed by a bond cleavage or rearrangement and back electron transfer which can occur in a intra or intermolecular way, depending on the system. The chemiexcitation step in the peroxyoxalate system involves an intermolecular back electron transfer, in which two radical ions participates - one of them is assumed to be carbon dioxide radical anion. However, there is no consensus about the back electron transfer path in the induced decomposition of 1,2-dioxetanes, which Can occur in an intra or intermolecular way. This work reports the synthesis of seven 1,2-dioxetane derivatives, the results obtained in the investigation of the chemiexcitation path proposed by the CIEEL mechanism for the induced decomposition of 1,2-dioxetanes and for the peroxyoxalate system, and the application of poly(vinylpirrolidone) supported luminol chemiluminescence in the development of a rnicroplate luminometer calibration method. It was possible to confirm, by the study of solvent viscosity effect on singlet quantum yields in induced 1,2-dioxetane decomposition, a dependence between chemiexcitation efficiency and the solvent cavity effect, which was rationalized based on a diffusional and frictional model. These results, together with theoretical calculations, allow us to postulate a modified intermolecular chemiexcitation mechanism for the induced decomposition of 1,2-dioxetanes. An attempt to detect directly the carbon di oxide radical anion in the peroxyoxalate system was made based on the electron paramagnetic resonance detection of the α-phenyl-N-tert-butylnitrone (PBN)-CO2 adduct. Despite small discrepancies between the observed and the previously reported hyperfine coupling constant values, the adduct characterization was confirmed by direct injection mass spectrometry. Finally, a microplate luminometer light intensity calibration system, based on polymeric matrix-supported luminal, was developed. This method can be used also to determine hydrogen peroxide at µ mol-1 concentration and to quantify reducing agents with antiradical and antioxidant potential.

Orientador: Ana Cláudia Pavarina / Banca: Eunice Teresinha Giampaolo / Banca: Marco Antonio Compagnoni / Banca: Cristina Kurachi / Banca: Karin Hermana Neppelenbroek / Resumo: As próteses removíveis estão em contato direto com os tecidos bucais, saliva e sangue e, ao serem removidas da cavidade bucal do paciente, podem estar contaminadas com micro-organismos patogênicos. Esses micro-organismos podem ser transmitidos aos técnicos de laboratório por contato direto ou pelos aerossóis produzidos durante o desgaste ou o polimento de próteses contaminadas. Neste caso, os micro-organismos podem ser disseminados pelo ambiente, desencadeando infecção cruzada. Assim, para prevenir a contaminação cruzada, todas as próteses devem ser desinfetadas ao serem enviadas ao laboratório e ao retornarem ao consultório. Com base nessas considerações, o presente estudo avaliou a efetividade clínica da irradiação por micro-ondas e da terapia fotodinâmica (PDT) para desinfecção de próteses totais superiores. Para os procedimentos de irradiação por micro-ondas, amostras de biofilme das próteses foram coletadas de 30 pacientes, os quais foram divididos aleatoriamente em dois grupos experimentais com 15 indivíduos cada: Grupo 1 - as próteses foram expostas às micro-ondas durante 3 minutos (650 W), Grupo 2 - as próteses foram expostas às micro-ondas durante 2 minutos (650 W). Para os tratamentos com PDT, amostras de biofilme das próteses foram coletadas de 60 pacientes, os quais foram divididos aleatoriamente em quatro grupos experimentais (n = 15 cada): Grupos I e II - as próteses foram borrifadas com 50 mg/L e 100 mg/L do Photogem® em suspensão, respectivamente; Grupos III e IV - as próteses foram tratadas com 50 mg/L e 100 mg/L de Photogem® em gel, respectivamente. Após 30 minutos de pré-irradiação, todas as 60 próteses foram expostas à luz de LED azul com potência de 37,5 J/cm2 (26 minutos). Amostras das próteses foram obtidas utilizando-se swab estéril antes (nas superfícies do lado esquerdo) e após (nas superfícies do lado direito)... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Prosthetic appliances that have been in contact with oral tissues, saliva and blood can be contaminated with pathogenic microorganisms when they are removed from the patient's mouth. These microorganisms can be transmitted to laboratory staff through direct contact with the infected denture or from aerosols that will be formed when the surfaces are ground or polished. In this case, microorganisms with varying degrees of virulence can be spread and disseminated into the air, leading to cross-infection. In order to prevent microbial cross-contamination among denture patients, all dental prostheses must be disinfected on entering and again on leaving the laboratory. Therefore, this investigation evaluated the clinical effectiveness of microwave irradiation and photodynamic therapy (PDT) on the inactivation of microorganisms present on complete dentures. For microwave irradiation procedures, biofilm samples were collected from dentures of 30 patients, who were randomly divided into two experimental groups of 15 subjects each: Group 1 - patients had their maxillary denture microwaved for 3 minutes (650 W); Group 2 - patients had their maxillary denture microwaved for 2 minutes (650 W). For PDT treatments, biofilm samples were collected from dentures of 60 patients, who were randomly divided into four experimental groups (n = 15 each): Groups I and II - patients had their maxillary denture sprayed with 50 mg/L and 100 mg/L of Photogem® suspension, respectively; Groups III and IV - patients had their maxillary denture treated with 50 mg/L and 100 mg/L of Photogem® gel, respectively. After 30 minutes of pre-irradiation, all sixty dentures were exposure to blue LED light at 37.5 J/cm2 (26 minutes). Denture samples were taken with sterile cotton swabs, before (left side surfaces) and after (right side surfaces) microwave irradiation and PDT procedures. All microbial material was diluted... (Complete abstract click electronic access below) / Doutor

Orientador: Carlos Eduardo Vergani / Banca: Ana Lúcia Machado / Banca: Mônica Campos Serra / Resumo: Amostras de esmalte provenientes de dentes extraídos, de origem humana ou bovina, são amplamente utilizadas em estudos realizados in vitro e in situ. Esses dentes são considerados uma fonte em potencial de microorganismos patogênicos e devem ser esterilizados, antes da sua utilização nas pesquisas, para prevenir a ocorrência de infecções cruzadas. No entanto, o processo de esterilização do esmalte não deve alterar a sua integridade estrutural. O presente estudo teve como objetivo avaliar a efetividade da irradiação por microondas na esterilização do esmalte bovino, assim como o efeito deste método sobre a microdureza superficial e resistência à desmineralização do esmalte bovino. Dezoito incisivos bovinos foram utilizados para a obtenção de quarenta amostras de esmalte, divididas em dois grupos (n=20): controle (não-irradiados) e irradiados por microondas (3 minutos a 650 W). As amostras do grupo irradiado foram imersas, individualmente, em 200 mL de água destilada e submetidas à irradiação por microondas por 3 minutos a 650 W. Em seguida, ambos os grupos tiveram suas amostras imersas individualmente em tubos estéreis contendo 10 mL caldo BHI (Brain Heart Infusion), os quais foram incubados por 7 dias a 37°C, sob condições de aerobiose e anaerobiose. Após a incubação, o desenvolvimento de microorganismos foi verificado pela presença de turvação do meio de cultura. Em seguida, foram realizadas diluições seriadas (10-2 a 10-5), plaqueamento em meio ágar sangue e incubação em condições de aerobiose e anaerobiose, durante 48 h e 7 dias, respectivamente. Os valores de unidades formadoras de colônias foram calculados. Para a avaliação das propriedades do esmalte, outras 18 amostras de esmalte (4 x 4 mm) foram preparadas, individualmente embutidas em resina acrílica, seqüencialmente polidas e, então, seccionadas em duas metades, sendo uma das metades... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Enamel samples from bovine or human teeth are routinely used for in vitro and in situ caries research. These enamel samples need to be sterilized before they can be used in intra-oral appliances and the sterilization method must not affect the structural integrity of the tooth. The aim of this study was to evaluate the effectiveness of microwave irradiation on bovine enamel sterilization, as well as it's effect on the surface microhardness and resistance to demineralization of bovine enamel. Eighteen bovine incisors were used to produce forty enamel samples, divided in two groups (n = 20): control (nonirradiated) and microwave irradiated (3 minutes at 650 W). Microwaving samples were individually immersed in 200 mL of distilled water and submitted to irradiation at 650 W for 3 minutes. Following the microwaving, specimens from both groups were added individually to 10 mL of Brain Heart Infusion broth in sterile test tubes, which were incubated at 37°C for 7 days under aerobic and anaerobic conditions. After 7 days incubation, those test tubes in which turbidity was observed were considered to contain growing microorganisms. Dilutions of 10-2 to 10-5 were performed on blood agar plates, which were incubated aerobically and anaerobically for growth for up to 48 h and 7 days, respectively. After incubation, the numbers of colonyforming units were calculated. For the properties of enamel analysis, other 18 bovine enamel samples (4 x 4 mm) were prepared, embedded in acrylic resin, serially polished and sliced into two halves: one of the fragments was reserved as control while the other was microwaved in 200 mL of distilled water for 3 minutes at 650 W. Hardness measurements were conducted using a Microhardness tester with a Knoop diamond. Five indentations were performed under a load of 25 gf for 05 seconds. For the resistance to demineralization analysis, the groups were submitted... (Complete abstract click electronic access below) / Mestre

Ce travail vise l'étude de l'oxydation catalytique des Composés Organiques Volatils (COVs). L'objectif principal est de trouver des matériaux catalytiques qui sont des alternatives aux métaux nobles très onéreux. La recherche des matériaux catalytiques actifs, sélectifs, stables dans le temps et à base de métaux de transition est abordée. Afin d'améliorer les performances catalytiques des métaux de transition, la dispersion de l'espèce métallique doit être optimisée en utilisant une méthode de synthèse adéquate. Les différents solides préparés ont été caractérisés par différentes techniques physico-chimiques : la Diffraction des Rayons X (DRX), les Analyses Thermiques (ATD/ATG), la Spectroscopie Infrarouge (IR), la Réduction en Température Programmée (H₂-RTP), la Microscopie Electronique à Balayage (MEB), la Spectroscopie de Photoélectrons induits par rayons X (SPX)...De plus, les oxydes obtenus ont été testés dans les réactions d'oxydation totale du COV propène. En premier lieu, nous avons focalisé notre travail sur la préparation d'une série d'oxydes mixtes Co-Mg/Al-Fe par voie hydrotalcite afin d'obtenir des propriétés intéressantes en catalyse hétérogène. Cette étude consiste surtout à évaluer la substitution des cations bivalents et trivalents. Il s'est avéré que le solide contenant à la fois du cobalt et du fer (CoFe) possède l'activité catalytique la plus élevée. L'intérêt de la voie hydrotalcite par rapport à d'autres méthodes de synthèse, telles que la méthode classique et le mélange mécanique des oxydes a été mis en évidence. En second lieu, l'utilisation des irradiations micro-ondes lors de la synthèse des matériaux hydrotalcites a été également étudiée comme une méthode de synthèse non-conventionnelle. Un effet bénéfique a été observé avec l'utilisation des micro-ondes dû principalement à des surfaces spécifiques plus élevées et à une meilleure réductibilité des espèces oxydes. En outre, cette étude vise également la mise au point de cette nouvelle méthode. De ce fait, l'optimisation de la température, durée et puissance des irradiations micro-ondes a été effectuée sur le solide CoFe, afin de montrer l'influence de chaque paramètre sur les propriétés physico-chimiques des matériaux. En troisième lieu, la synthèse d'une série de catalyseurs par voie hydrotalcite avec différentes teneurs en Co²⁺ et Fe³⁺ a été effectuée. L'influence du rapport molaire sur la structure hydrotalcite a été montrée. Une comparaison entre ces solides et ceux préparés par la méthode micro-ondes a été également abordée. / This work aims to study the catalytic oxidation of Volatile Organic Compounds (VOCs). The main objective is to find catalytic materials that are alternatives to very expensive noble metals. The search for transition metal based catalysts is investigated. Furthermore, to improve the catalytic performance of the transition metals, their dispersion must be optimized using an adequate synthetic method. The various prepared solids were characterized by different physicochemical techniques : X-ray Diffraction (XRD), Thermal Analysis (TDA/TGA), Infrared Spectroscopy (IR), Temperature Programmed Reduction by hydrogen (H₂-TPR), Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS)...Moreover, the obtained oxides were tested in the total oxidation of the VOC propene. Firstly, we focused our work on the preparation of a series of Co/Fe hydrotalcites -like samples by the traditional co-precipitation method. This study consists mainly of evaluating the substitution of bivalent and trivalent cations. It has been found that the solid containing both cobalt and iron (CoFe) has the highest catalytic activity. The interest of the hydrotalcite route compared to other methods of synthesis, such as the classical method and the mechanical mixing of oxides was put into evidence. Secondly, the use of microwave irradiation during the synthesis of hydrotalcite materials has also been studied as an unconventional method of synthesis. A beneficial effect has been observed with the use of microwaves due mainly to higher specific surface areas and better reducibility of the oxide species. In addition, an optimization of the temperature, duration, and power of the microwave irradiations was carried out on the CoFe solid, in order to show the influence of each parameter on the physico-chemical properties of the materials. Thirdly, the synthesis of a series of hydrotalcite catalysts with different ratio of Co²⁺ and Fe³⁺ was carried out. The influence of the molar ratio on the hydrotalcite structure has been shown. A comparison between these solids and those prepared by the microwave method was also discussed.

Sustainable chemical processes are becoming increasingly important in all fields of synthetic chemistry. Catalysis can play an important role in developing environmentally benign chemical processes, and transition metals have an important role to play in the area of green chemistry. In particular, palladium(II) catalysis includes many key features for successful green chemistry methods, as demonstrated by a number of eco-friendly oxidation reactions catalyzed by palladium(II). The aim of the work presented in this thesis was to develop novel and greener palladium(II)-catalyzed coupling reactions. In striving to achieve this aim, the first open-vessel, room-temperature palladium(II)-catalyzed oxidative Heck reaction, using oxygen from the air as the reoxidant of palladium, was developed. In a further investigation of the palladium(II)-catalyzed oxidative Heck reaction, base-free conditions for the transformation were identified and suitable conditions for microwave-assisted oxidative Heck reactions were established. A convenient and low-cost palladium(II)-catalyzed method for the synthesis of styrene derivatives, by coupling arylboranes with vinyl acetate, was developed. The reaction mechanism was studied using ESI-MS, which enabled the detection of cationic palladium intermediates in ongoing productive reactions, and a plausible catalytic cycle was proposed. In an attempt to make the oxidative Heck and the styrene synthesis reactions more attractive from an industrial point of view, conditions for continuous flow synthesis were identified. The results were generally good and rapid synthesis of the desired products was obtained. The first palladium(II)-catalyzed C–P bond-forming Hirao-type reaction, employing arylboranes instead of the commonly used aryl halides, was developed. An ESI-MS study was performed, and a plausible catalytic pathway was suggested. Finally, a novel method for synthesizing aryl ketones from benzoic acids and nitriles, via palladium(II)-catalyzed decarboxylation of the benzoic acids, was established. Further, the reaction mechanism was studied by ESI-MS and a plausible catalytic route presented.