Radioactive decay of nuclei via emission of ??-particles is studied using three different theoretical approaches, viz: the quasi-bound state wavefunction approach (QSWA), the superasymmetric ??ssion model (SAFM) and the semiclassical approximation (QCA). The half-lives of the radioactive nuclei, calculated using these methods, are compared with each other and with available experimental data. The resonance wavefunction is obtained by numerically integrating the Schrödinger equation with outgoing boundary conditions. The sensitivity of the calculated decay widths to two particular parameter sets of the Woods-Saxon (WS) optical potentials are studied. Double folding (DF) model calculations to obtain the bare ??-nucleus potential have been carried out with the Reid M3Y effective nucleon-nucleon (NN) interactions. The exchange part of the interaction was taken to be of zero-range pseudo-potential and the density dependence of the NN interaction is accounted for. The effectiveness of the method is demonstrated using both even-even and odd-mass spherical nuclei. / Physics / MSC (PHYSICS)

Austropuccinia psidii, the causal agent of myrtle rust, is a biotrophic pathogen, and therefore its growth and development depend on the host tissues. The uredospores of A. psidii infect Eucalyptus by engaging in close contact with the host surface and interacting with the leaf cuticle that provides important chemical and physical signals to trigger the infection process. Due to the inherent characteristics of the Eucalyptus cuticle, it was hypothesized that the preformed mechanism, comprised mostly by cuticular waxes, plays a crucial role in Eucalyptus resistance against A. psidii and its ability to modulate the expression of genes associated to the pathogenicity of A. psidii during the early stage of infection. In chapter 2, the cuticular waxes of Eucalyptus spp. were analyzed to determine their composition or structure and then correlated to susceptibility/resistance to Austropuccinia psidii. Twenty-one Eucalyptus spp. in the field were classified as resistant or susceptible. From these, the resistance/susceptibility level of six Eucalyptus spp. was evaluated in controlled conditions using qPCR, revealing that the pathogen can germinate on the eucalyptus surface of some species without multiplying in the host. CG-TOF-MS analysis detected 26 compounds in the Eucalyptus spp. cuticle and led to the discovery of the role of hexadecanoic acid in the susceptibility of E. grandis and E. phaeotricha to A. psidii. The scanning electron microscopy check revealed differences in A. psidii germination during host infection. It was found a correlation between epicuticular morphology and the resistance to A. psidii. In chapter 3, we investigated gene expression of A. psidii through bioassays in vitro containing cuticular waxes from E. grandis (E. g), E. urograndis (E. ug) and E. urophylla (E. u). Mineral oil (MO) treatment was used to all comparative analysis (negative control). The presence of cuticular waxes from E. g induced the expression of genes encoding proteins related to growth and colonization of A. psidii such as binding proteins (peptidylprolyl isomerase and ribosomal) and cell wall degrading proteins (beta-xylanase). However, other pathogenic proteins were repressed in presence of cuticular wax of E. g, for instance, triosephosphate isomerase, family 18 glycoside hydrolase, mitochondrial ATP carrier, and glutamine-dependent NAD synthetase. The E. ug x MO analysis resulted in DEGs associated with proteins related to membrane transporters and receptors, DNA repair and glycine dehydrogenase. As to the cuticular wax of E. u, it up-regulated the expression of genes encoding proteins associated with pheromone, cutinases, and prefoldin. Thus, for the first time, it was demonstrated a considerable interspecific variation in Eucalyptus species on the susceptibility to A. psidii and its correlation with cuticular waxes chemical compounds that seem to play a synergistic role as a preformed defense mechanism. We also demonstrated that Eucalyptus spp. cuticular waxes may modulate the A. psidii gene expression, suggesting the importance of early plant-pathogen molecular interaction to the development of myrtle rust. / Austropuccinia psidii é o agente causal da ferrugem das mirtáceas com crescimento biotrófico, ou seja, o patógeno depende dos tecidos do hospedeiro para crescer e se desenvolver. Os uredósporos de A. psidii infectam Eucalyptus por meio do contato inicial com a superfície do hospedeiro e também pela interação com a cutícula da folha que por sua vez fornece importantes sinais químicos e físicos capaz de desencadear o processo de infecção. Devido às características inerentes à cutícula de Eucalyptus, consideramos as hipóteses de que o mecanismo pré-formado, composto principalmente pelas ceras cuticulares, desempenha um papel crucial na resistência de Eucalyptus spp. contra A. psidii, e, também, é capaz de modular a expressão fúngica de genes associados a patogenicidade durante o estágio inicial de infecção de A. psidii. No capítulo 2, as ceras cuticulares de Eucalyptus spp. foram analisadas para determinar a composição/estrutura e sua correlação com suscetibilidade/resistência de A. psidii. Vinte e uma espécies de Eucalyptus foram classificadas em campo como resistentes ou suscetíveis. A análise de qPCR de seis Eucalyptus spp. revelou que o patógeno pode germinar na superfície de algumas espécies de eucaliptos sem se multiplicar no tecido hospedeiro. Foram identificados 26 compostos presentes na cutícula de Eucalyptus spp. e descobrimos o papel do ácido hexadecanóico na suscetibilidade de E. grandis e E. phaeotricha à ferrugem. Por meio da microscopia eletrônica de varredura encontramos uma correlação entre a morfologia epicuticular e a resistência contra A. psidii. No capítulo 3 para compreender a expressão gênica de A. psidii realizamos bioensaios (in vitro) contendo as ceras cuticulares de E. grandis (E. g), E. urograndis (E. ug) e E. urophylla (E. u). O tratamento com óleo mineral (MO) foi utilizado em todas as análises comparativas como controle negativo. A presença de ceras cuticulares de E. g induziu a expressão de genes que codificam proteínas relacionadas ao crescimento e colonização de A. psidii, como proteínas de ligação (peptidylprolyl isomerase e ribosomal) e proteínas de degradação da parede celular (beta xilanase). No entanto, outras proteínas patogênicas foram reprimidas na presença da cera cuticular de E. g, por exemplo, triosephosphate isomerase, family 18 glycoside hydrolase, mitochondrial ATP carrier e glutamine-dependent NAD synthetase. A análise de E. ug x MO resultou na ativação de proteínas associadas a transportadores e receptores de membrana, reparo de DNA e glycine dehydrogenase. Já a cera cuticular de E. u induziu a expressão de genes que codificam proteínas associadas a feromônios, cutinases e prefoldin. Pela primeira vez, está sendo apresentado a considerável variação interespecífica em espécies de Eucalyptus quanto à suscetibilidade a ferrugem, e, sua correlação com os compostos químicos de ceras cuticulares, os quais parecem ser um importante mecanismo de defesa pré-formado. Também foi revelado que as ceras cuticulares de Eucalyptus spp. são capazes de modular a expressão gênica de A. psidii, evidenciando o papel da interação molecular planta-patógeno precoce no desenvolvimento da ferrugem das mirtáceas.

Este trabalho centrou-se no desenvolvimento tecnológico e na caracterização de nanopartículas poliméricas (nanocápsulas ou nanoesferas) contendo melatonina, empregando diferentes composições, métodos de preparação e concentrações de melatonina. De uma maneira geral, as diferentes suspensões nanoparticuladas foram caracterizadas segundo a determinação dos teores totais de melatonina, a determinação das taxas de associação da melatonina aos nanocarreadores, a análise morfológica, a determinação dos diâmetros médios de partículas e polidispersões, além da determinação dos valores de potenciais zeta. As suspensões de nanocápsulas ou de nanoesferas foram preparadas pelos métodos de deposição interfacial ou de nanoprecipitação, respectivamente. Foram avaliadas as influências do tipo de polímero [Eudragit® S100, Eudragit® RS100, poli(ε-caprolactona) ou poli(lactideo)], de óleo (triglicerídeos dos ácidos cáprico e caprílico, óleo mineral ou Eutanol G®) e de tensoativos (polissorbato 80, poloxamer 188, monooleato de sorbitano, monoestearato de sorbitano ou lecitina) sobre as características físico-químicas das suspensões. Os resultados demonstraram que as nanopartículas apresentaram diâmetros inferiores a 350 nm, encapsulação parcial da melatonina e morfologia esférica. As suspensões de nanoesferas apresentaram eficiências de encapsulação similares, mas diâmetros inferiores às respectivas nanocápsulas. O tipo de polímero empregado influenciou nas taxas de associação da melatonina. De acordo com a maior eficiência de encapsulação (56 %), nanocápsulas preparadas com Eudragit S100® foram selecionadas para secagem por aspersão, empregando dióxido de silício coloidal (3 % m/V). As micropartículas nanorrevestidas obtidas apresentaram eficiência de encapsulação de 93 % e foram capazes de controlar a velocidade de liberação da melatonina, comparativamente ao fármaco puro. O estudo de estabilidade das suspensões de nanocápsulas, comparativamente à nanoemulsão e à nanodispersão dos tensoativos, mostrou que a composição dos sistemas e as condições de armazenamento influenciaram a estabilidade físico-química das formulações. Um delineamento fatorial 23 foi também realizado objetivando-se a comparação das características físicoquímicas de nanocápsulas de Eudragit RS100® contendo melatonina obtidas através de deposição interfacial ou de emulsificação-difusão. As taxas de associação da melatonina não foram influenciadas pela composição das formulações e nem pelo método de preparação empregado. Por outro lado, os diâmetros, as polidispersões, os potenciais zeta, os valores de pH e a estabilidade físico-química foram influenciados pelo método de preparação e/ou pela composição dos sistemas. As propriedades antioxidantes da melatonina associada a nanopartículas foram também avaliadas. Desta forma, experimentos in vitro de lipoperoxidação de microssomas hepáticos e de lipossomas de fosfatidilcolina, induzida pelo radical ascorbil, foram realizados. Nanocápsulas ou nanoesferas preparadas com Eudragit S100® foram selecionadas para o estudo, com base na maior eficiência de associação do fármaco. Nanoemulsão também foi testada para verificar a influência da presença do polímero. A presença da melatonina foi capaz de proteger os lipídios em comparação aos controles, com influência da formulação, da dose de melatonina e do modelo de membrana empregado. Apenas os nanocarreadores poliméricos (nanocápsulas ou nanoesferas revestidas com polissorbato 80) contendo melatonina foram capazes de aumentar significativamente a atividade antioxidante deste fármaco nos dois modelos de membrana empregados. Finalmente, nanocápsulas de Eudragit S100® revestidas com polissorbato 80 foram administradas, intraperitonealmente em camundongos sadios, e os efeitos antioxidantes agudos da melatonina in vivo foram avaliados no cérebro (córtex frontal e hipocampo) e no fígado. Os resultados demonstraram que as nanocápsulas contendo melatonina foram capazes de reduzir significativamente a lipoperoxidação no córtex, no hipocampo e no fígado, ao passo que a solução do fármaco não exerceu efeito significativo. O conjunto dos resultados demonstrou a viabilidade tecnológica da preparação de sistemas poliméricos nanoparticulados e microparticulados contendo melatonina, na forma de suspensão ou de pós, com potencial aplicação tanto no aumento da atividade antioxidante quanto no controle da liberação deste fármaco. / This work has been based on the development and characterization of the melatoninloaded polymeric nanoparticles (nanocapsules or nanospheres) employing different system compositions, methods of preparation and melatonin concentrations. In general, the different nanoparticle suspensions were characterized in terms of melatonin content and its association within the particles, morphology, mean size and polydispersity of the particles, as well as the zeta potentials. The nanocapsule or nanosphere suspensions were prepared by interfacial deposition or nanoprecipitation methods, respectively. The influences of the type of the polymer [Eudragit® S100, Eudragit® RS100, poly(ε-caprolactone) or poly(lactide)], of the oil nature (caprylic/capric triglyceride, mineral oil or Eutanol G®) and of the type of surfactants (polysorbate 80, poloxamer 188, sorbitan monooleate, sorbitan monostearate or lecithin) on the physicochemical characteristics of suspensions were evaluated. The results demonstrated that the nanoparticles presented mean size lower than 350 nm, partial encapsulation of melatonin and they were spherically shape. The nanosphere suspensions presented similar encapsulation efficiencies to nanocapsules, however, the former presented a lower mean size of particles. The type of polymer used in the formulations influenced the encapsulation efficiencies. The nanocapsules prepared with Eudragit S100® were selected to be spray-dried, using colloidal silicon dioxide (3 % w/v), due to the highest encapsulation efficiency (56 %). The nanoparticle-coated microparticles presented the encapsulation efficiency of 93 % and they controlled the release rate of melatonin when compared to the pure drug. The physicochemical stability evaluation of the melatonin-loaded nanocapsule suspensions compared to the nanoemulsion or the nanodispersion of surfactants showed that the composition of the melatonin-loaded system and the storage conditions influenced the physicochemical stability of the formulations. Melatonin-loaded Eudragit RS100®-nanocapsule suspensions prepared by interfacial deposition or by emulsification-diffusion techniques were also compared in terms of physicochemical characteristics using a 23 fatorial-design. The formulation composition or the preparation methods did not influence the encapsulation efficiencies. However, the mean size, polydispersity, zeta potential, pH and physicochemical stability were influenced by the formulation composition and/or by the preparation methods. The antioxidant properties of the melatonin-loaded nanoparticle suspensions were also evaluated. Hence, phosphatidylcoline liposomes or liver microsomes were used as model of the lipid membrane and in vitro lipid peroxidation was induced by free radical ascorbyl. The melatonin-loaded Eudragit S100® nanoparticles (nanocapsules and nanospheres) were selected to this study based on the highest encapsulation efficiencies. The nanoemulsion was also evaluated for studying the influence of the presence of the polymer The results demonstrated that the lipids were protected against peroxidation due to the presence of the melatonin, and this effect depended on the type of formulation, drug concentration and on the type of the membrane model. Only the melatonin-loaded polymeric nanocarriers (polysorbate 80-coated nanocapsules or nanospheres) were able to improve the antioxidant action of melatonin in both membrane model. Finally, the in vivo acute antioxidant capacities of melatonin-loaded polysorbate 80-coated Eudragit S100® nanocapsules in the brain (frontal cortex and hippocampus) and in the liver were compared to the effect of the drug solution, after 1 h of intraperitoneal administration in mice. It was verified that the melatonin-loaded nanocapsules significantly decreased the lipid peroxidation in the cortex, in the hippocampus and in the liver. On the other hand, the melatonin solution did not significantly decrease the lipid peroxidation. Briefly, the results demonstrated the technological viability of the preparation of melatonin-loaded polymeric nanoparticulated and microparticulated systems in the form of suspension or powder. These polymeric particulated systems presented potential applications in both to improve the antioxidant activity and to control the release profile of melatonin.

Radioactive decay of nuclei via emission of ??-particles is studied using three different theoretical approaches, viz: the quasi-bound state wavefunction approach (QSWA), the superasymmetric ??ssion model (SAFM) and the semiclassical approximation (QCA). The half-lives of the radioactive nuclei, calculated using these methods, are compared with each other and with available experimental data. The resonance wavefunction is obtained by numerically integrating the Schrödinger equation with outgoing boundary conditions. The sensitivity of the calculated decay widths to two particular parameter sets of the Woods-Saxon (WS) optical potentials are studied. Double folding (DF) model calculations to obtain the bare ??-nucleus potential have been carried out with the Reid M3Y effective nucleon-nucleon (NN) interactions. The exchange part of the interaction was taken to be of zero-range pseudo-potential and the density dependence of the NN interaction is accounted for. The effectiveness of the method is demonstrated using both even-even and odd-mass spherical nuclei. / Physics / MSC (PHYSICS)

Este trabalho centrou-se no desenvolvimento tecnológico e na caracterização de nanopartículas poliméricas (nanocápsulas ou nanoesferas) contendo melatonina, empregando diferentes composições, métodos de preparação e concentrações de melatonina. De uma maneira geral, as diferentes suspensões nanoparticuladas foram caracterizadas segundo a determinação dos teores totais de melatonina, a determinação das taxas de associação da melatonina aos nanocarreadores, a análise morfológica, a determinação dos diâmetros médios de partículas e polidispersões, além da determinação dos valores de potenciais zeta. As suspensões de nanocápsulas ou de nanoesferas foram preparadas pelos métodos de deposição interfacial ou de nanoprecipitação, respectivamente. Foram avaliadas as influências do tipo de polímero [Eudragit® S100, Eudragit® RS100, poli(ε-caprolactona) ou poli(lactideo)], de óleo (triglicerídeos dos ácidos cáprico e caprílico, óleo mineral ou Eutanol G®) e de tensoativos (polissorbato 80, poloxamer 188, monooleato de sorbitano, monoestearato de sorbitano ou lecitina) sobre as características físico-químicas das suspensões. Os resultados demonstraram que as nanopartículas apresentaram diâmetros inferiores a 350 nm, encapsulação parcial da melatonina e morfologia esférica. As suspensões de nanoesferas apresentaram eficiências de encapsulação similares, mas diâmetros inferiores às respectivas nanocápsulas. O tipo de polímero empregado influenciou nas taxas de associação da melatonina. De acordo com a maior eficiência de encapsulação (56 %), nanocápsulas preparadas com Eudragit S100® foram selecionadas para secagem por aspersão, empregando dióxido de silício coloidal (3 % m/V). As micropartículas nanorrevestidas obtidas apresentaram eficiência de encapsulação de 93 % e foram capazes de controlar a velocidade de liberação da melatonina, comparativamente ao fármaco puro. O estudo de estabilidade das suspensões de nanocápsulas, comparativamente à nanoemulsão e à nanodispersão dos tensoativos, mostrou que a composição dos sistemas e as condições de armazenamento influenciaram a estabilidade físico-química das formulações. Um delineamento fatorial 23 foi também realizado objetivando-se a comparação das características físicoquímicas de nanocápsulas de Eudragit RS100® contendo melatonina obtidas através de deposição interfacial ou de emulsificação-difusão. As taxas de associação da melatonina não foram influenciadas pela composição das formulações e nem pelo método de preparação empregado. Por outro lado, os diâmetros, as polidispersões, os potenciais zeta, os valores de pH e a estabilidade físico-química foram influenciados pelo método de preparação e/ou pela composição dos sistemas. As propriedades antioxidantes da melatonina associada a nanopartículas foram também avaliadas. Desta forma, experimentos in vitro de lipoperoxidação de microssomas hepáticos e de lipossomas de fosfatidilcolina, induzida pelo radical ascorbil, foram realizados. Nanocápsulas ou nanoesferas preparadas com Eudragit S100® foram selecionadas para o estudo, com base na maior eficiência de associação do fármaco. Nanoemulsão também foi testada para verificar a influência da presença do polímero. A presença da melatonina foi capaz de proteger os lipídios em comparação aos controles, com influência da formulação, da dose de melatonina e do modelo de membrana empregado. Apenas os nanocarreadores poliméricos (nanocápsulas ou nanoesferas revestidas com polissorbato 80) contendo melatonina foram capazes de aumentar significativamente a atividade antioxidante deste fármaco nos dois modelos de membrana empregados. Finalmente, nanocápsulas de Eudragit S100® revestidas com polissorbato 80 foram administradas, intraperitonealmente em camundongos sadios, e os efeitos antioxidantes agudos da melatonina in vivo foram avaliados no cérebro (córtex frontal e hipocampo) e no fígado. Os resultados demonstraram que as nanocápsulas contendo melatonina foram capazes de reduzir significativamente a lipoperoxidação no córtex, no hipocampo e no fígado, ao passo que a solução do fármaco não exerceu efeito significativo. O conjunto dos resultados demonstrou a viabilidade tecnológica da preparação de sistemas poliméricos nanoparticulados e microparticulados contendo melatonina, na forma de suspensão ou de pós, com potencial aplicação tanto no aumento da atividade antioxidante quanto no controle da liberação deste fármaco. / This work has been based on the development and characterization of the melatoninloaded polymeric nanoparticles (nanocapsules or nanospheres) employing different system compositions, methods of preparation and melatonin concentrations. In general, the different nanoparticle suspensions were characterized in terms of melatonin content and its association within the particles, morphology, mean size and polydispersity of the particles, as well as the zeta potentials. The nanocapsule or nanosphere suspensions were prepared by interfacial deposition or nanoprecipitation methods, respectively. The influences of the type of the polymer [Eudragit® S100, Eudragit® RS100, poly(ε-caprolactone) or poly(lactide)], of the oil nature (caprylic/capric triglyceride, mineral oil or Eutanol G®) and of the type of surfactants (polysorbate 80, poloxamer 188, sorbitan monooleate, sorbitan monostearate or lecithin) on the physicochemical characteristics of suspensions were evaluated. The results demonstrated that the nanoparticles presented mean size lower than 350 nm, partial encapsulation of melatonin and they were spherically shape. The nanosphere suspensions presented similar encapsulation efficiencies to nanocapsules, however, the former presented a lower mean size of particles. The type of polymer used in the formulations influenced the encapsulation efficiencies. The nanocapsules prepared with Eudragit S100® were selected to be spray-dried, using colloidal silicon dioxide (3 % w/v), due to the highest encapsulation efficiency (56 %). The nanoparticle-coated microparticles presented the encapsulation efficiency of 93 % and they controlled the release rate of melatonin when compared to the pure drug. The physicochemical stability evaluation of the melatonin-loaded nanocapsule suspensions compared to the nanoemulsion or the nanodispersion of surfactants showed that the composition of the melatonin-loaded system and the storage conditions influenced the physicochemical stability of the formulations. Melatonin-loaded Eudragit RS100®-nanocapsule suspensions prepared by interfacial deposition or by emulsification-diffusion techniques were also compared in terms of physicochemical characteristics using a 23 fatorial-design. The formulation composition or the preparation methods did not influence the encapsulation efficiencies. However, the mean size, polydispersity, zeta potential, pH and physicochemical stability were influenced by the formulation composition and/or by the preparation methods. The antioxidant properties of the melatonin-loaded nanoparticle suspensions were also evaluated. Hence, phosphatidylcoline liposomes or liver microsomes were used as model of the lipid membrane and in vitro lipid peroxidation was induced by free radical ascorbyl. The melatonin-loaded Eudragit S100® nanoparticles (nanocapsules and nanospheres) were selected to this study based on the highest encapsulation efficiencies. The nanoemulsion was also evaluated for studying the influence of the presence of the polymer The results demonstrated that the lipids were protected against peroxidation due to the presence of the melatonin, and this effect depended on the type of formulation, drug concentration and on the type of the membrane model. Only the melatonin-loaded polymeric nanocarriers (polysorbate 80-coated nanocapsules or nanospheres) were able to improve the antioxidant action of melatonin in both membrane model. Finally, the in vivo acute antioxidant capacities of melatonin-loaded polysorbate 80-coated Eudragit S100® nanocapsules in the brain (frontal cortex and hippocampus) and in the liver were compared to the effect of the drug solution, after 1 h of intraperitoneal administration in mice. It was verified that the melatonin-loaded nanocapsules significantly decreased the lipid peroxidation in the cortex, in the hippocampus and in the liver. On the other hand, the melatonin solution did not significantly decrease the lipid peroxidation. Briefly, the results demonstrated the technological viability of the preparation of melatonin-loaded polymeric nanoparticulated and microparticulated systems in the form of suspension or powder. These polymeric particulated systems presented potential applications in both to improve the antioxidant activity and to control the release profile of melatonin.

abstract: For the past 30 years wildlife biologists have debated the need of pronghorn antelope (Antilocapra americana) to drink freestanding water (free water). Some have suggested that pronghorn may feed at night to increase preformed water (plant moisture) intake, thus decreasing their dependence on free water. Pronghorn diet composition and nutrient intake is integral to understanding water available to pronghorn through preformed and metabolic sources. The dual purpose of this study was to determine plant composition of pronghorn diets, and to examine whether night feeding provides a water allocation advantage by testing for differences between day and night and modeling free water requirements during biologically critical seasons and years of different precipitation. I determined species composition, selected nutrients, and moisture content of American pronghorn diets on Perry Mesa, Arizona in March, May, June and August of 2008 and 2009. I used microhistological analysis of fecal samples to determine percent plant composition of pronghorn diets. I used forage samples to evaluate the nutrient composition of those diets for moisture, crude protein and structural carbohydrates, and to calculate metabolic water. I used calculations proposed by Fox et al. (2000) to model free water requirements and modified the equations to reflect increased requirements for lactation. Diet analysis revealed that pronghorn used between 67% and 99% forbs and suggested fair range conditions. Preformed water was not significantly different between night and day. Night feeding appeared to be of marginal advantage, providing an average potential 9% preformed water increase in 2008, and 3% in 2009. The model indicated that neither male nor female pronghorn could meet their water requirements from preformed and metabolic water during any time period, season or year. The average free water requirements for females ranged from 0.67 L/animal/day (SE 0.06) in March, 2008 to 3.12 L/animal/day (SE 0.02) in June, 2009. The model showed that American pronghorn on Perry Mesa require access to free water during biological stress periods. / Dissertation/Thesis / M.S. Applied Biological Sciences 2012

Este trabalho centrou-se no desenvolvimento tecnológico e na caracterização de nanopartículas poliméricas (nanocápsulas ou nanoesferas) contendo melatonina, empregando diferentes composições, métodos de preparação e concentrações de melatonina. De uma maneira geral, as diferentes suspensões nanoparticuladas foram caracterizadas segundo a determinação dos teores totais de melatonina, a determinação das taxas de associação da melatonina aos nanocarreadores, a análise morfológica, a determinação dos diâmetros médios de partículas e polidispersões, além da determinação dos valores de potenciais zeta. As suspensões de nanocápsulas ou de nanoesferas foram preparadas pelos métodos de deposição interfacial ou de nanoprecipitação, respectivamente. Foram avaliadas as influências do tipo de polímero [Eudragit® S100, Eudragit® RS100, poli(ε-caprolactona) ou poli(lactideo)], de óleo (triglicerídeos dos ácidos cáprico e caprílico, óleo mineral ou Eutanol G®) e de tensoativos (polissorbato 80, poloxamer 188, monooleato de sorbitano, monoestearato de sorbitano ou lecitina) sobre as características físico-químicas das suspensões. Os resultados demonstraram que as nanopartículas apresentaram diâmetros inferiores a 350 nm, encapsulação parcial da melatonina e morfologia esférica. As suspensões de nanoesferas apresentaram eficiências de encapsulação similares, mas diâmetros inferiores às respectivas nanocápsulas. O tipo de polímero empregado influenciou nas taxas de associação da melatonina. De acordo com a maior eficiência de encapsulação (56 %), nanocápsulas preparadas com Eudragit S100® foram selecionadas para secagem por aspersão, empregando dióxido de silício coloidal (3 % m/V). As micropartículas nanorrevestidas obtidas apresentaram eficiência de encapsulação de 93 % e foram capazes de controlar a velocidade de liberação da melatonina, comparativamente ao fármaco puro. O estudo de estabilidade das suspensões de nanocápsulas, comparativamente à nanoemulsão e à nanodispersão dos tensoativos, mostrou que a composição dos sistemas e as condições de armazenamento influenciaram a estabilidade físico-química das formulações. Um delineamento fatorial 23 foi também realizado objetivando-se a comparação das características físicoquímicas de nanocápsulas de Eudragit RS100® contendo melatonina obtidas através de deposição interfacial ou de emulsificação-difusão. As taxas de associação da melatonina não foram influenciadas pela composição das formulações e nem pelo método de preparação empregado. Por outro lado, os diâmetros, as polidispersões, os potenciais zeta, os valores de pH e a estabilidade físico-química foram influenciados pelo método de preparação e/ou pela composição dos sistemas. As propriedades antioxidantes da melatonina associada a nanopartículas foram também avaliadas. Desta forma, experimentos in vitro de lipoperoxidação de microssomas hepáticos e de lipossomas de fosfatidilcolina, induzida pelo radical ascorbil, foram realizados. Nanocápsulas ou nanoesferas preparadas com Eudragit S100® foram selecionadas para o estudo, com base na maior eficiência de associação do fármaco. Nanoemulsão também foi testada para verificar a influência da presença do polímero. A presença da melatonina foi capaz de proteger os lipídios em comparação aos controles, com influência da formulação, da dose de melatonina e do modelo de membrana empregado. Apenas os nanocarreadores poliméricos (nanocápsulas ou nanoesferas revestidas com polissorbato 80) contendo melatonina foram capazes de aumentar significativamente a atividade antioxidante deste fármaco nos dois modelos de membrana empregados. Finalmente, nanocápsulas de Eudragit S100® revestidas com polissorbato 80 foram administradas, intraperitonealmente em camundongos sadios, e os efeitos antioxidantes agudos da melatonina in vivo foram avaliados no cérebro (córtex frontal e hipocampo) e no fígado. Os resultados demonstraram que as nanocápsulas contendo melatonina foram capazes de reduzir significativamente a lipoperoxidação no córtex, no hipocampo e no fígado, ao passo que a solução do fármaco não exerceu efeito significativo. O conjunto dos resultados demonstrou a viabilidade tecnológica da preparação de sistemas poliméricos nanoparticulados e microparticulados contendo melatonina, na forma de suspensão ou de pós, com potencial aplicação tanto no aumento da atividade antioxidante quanto no controle da liberação deste fármaco. / This work has been based on the development and characterization of the melatoninloaded polymeric nanoparticles (nanocapsules or nanospheres) employing different system compositions, methods of preparation and melatonin concentrations. In general, the different nanoparticle suspensions were characterized in terms of melatonin content and its association within the particles, morphology, mean size and polydispersity of the particles, as well as the zeta potentials. The nanocapsule or nanosphere suspensions were prepared by interfacial deposition or nanoprecipitation methods, respectively. The influences of the type of the polymer [Eudragit® S100, Eudragit® RS100, poly(ε-caprolactone) or poly(lactide)], of the oil nature (caprylic/capric triglyceride, mineral oil or Eutanol G®) and of the type of surfactants (polysorbate 80, poloxamer 188, sorbitan monooleate, sorbitan monostearate or lecithin) on the physicochemical characteristics of suspensions were evaluated. The results demonstrated that the nanoparticles presented mean size lower than 350 nm, partial encapsulation of melatonin and they were spherically shape. The nanosphere suspensions presented similar encapsulation efficiencies to nanocapsules, however, the former presented a lower mean size of particles. The type of polymer used in the formulations influenced the encapsulation efficiencies. The nanocapsules prepared with Eudragit S100® were selected to be spray-dried, using colloidal silicon dioxide (3 % w/v), due to the highest encapsulation efficiency (56 %). The nanoparticle-coated microparticles presented the encapsulation efficiency of 93 % and they controlled the release rate of melatonin when compared to the pure drug. The physicochemical stability evaluation of the melatonin-loaded nanocapsule suspensions compared to the nanoemulsion or the nanodispersion of surfactants showed that the composition of the melatonin-loaded system and the storage conditions influenced the physicochemical stability of the formulations. Melatonin-loaded Eudragit RS100®-nanocapsule suspensions prepared by interfacial deposition or by emulsification-diffusion techniques were also compared in terms of physicochemical characteristics using a 23 fatorial-design. The formulation composition or the preparation methods did not influence the encapsulation efficiencies. However, the mean size, polydispersity, zeta potential, pH and physicochemical stability were influenced by the formulation composition and/or by the preparation methods. The antioxidant properties of the melatonin-loaded nanoparticle suspensions were also evaluated. Hence, phosphatidylcoline liposomes or liver microsomes were used as model of the lipid membrane and in vitro lipid peroxidation was induced by free radical ascorbyl. The melatonin-loaded Eudragit S100® nanoparticles (nanocapsules and nanospheres) were selected to this study based on the highest encapsulation efficiencies. The nanoemulsion was also evaluated for studying the influence of the presence of the polymer The results demonstrated that the lipids were protected against peroxidation due to the presence of the melatonin, and this effect depended on the type of formulation, drug concentration and on the type of the membrane model. Only the melatonin-loaded polymeric nanocarriers (polysorbate 80-coated nanocapsules or nanospheres) were able to improve the antioxidant action of melatonin in both membrane model. Finally, the in vivo acute antioxidant capacities of melatonin-loaded polysorbate 80-coated Eudragit S100® nanocapsules in the brain (frontal cortex and hippocampus) and in the liver were compared to the effect of the drug solution, after 1 h of intraperitoneal administration in mice. It was verified that the melatonin-loaded nanocapsules significantly decreased the lipid peroxidation in the cortex, in the hippocampus and in the liver. On the other hand, the melatonin solution did not significantly decrease the lipid peroxidation. Briefly, the results demonstrated the technological viability of the preparation of melatonin-loaded polymeric nanoparticulated and microparticulated systems in the form of suspension or powder. These polymeric particulated systems presented potential applications in both to improve the antioxidant activity and to control the release profile of melatonin.

Successful field waterflood is a crucial prerequisite for improving the performance before EOR methods, such as ASP, SP, and P flooding, are applied in the field. Excess water production is a major problem in mature waterflooded oil fields that leads to early well abandonment and unrecoverable hydrocarbon. Gel treatments at the injection and production wells to preferentially plug the thief zones are cost-effective methods to improve sweep efficiency in reservoirs and reduce excess water production during hydrocarbon recovery. There are extensive experimental studies performed by some researchers in the past to investigate the performance of gels in conformance control and decreasing water production in mature waterflooded reservoirs, but no substantial modeling work has been done to simulate these experiments and predict the results for large field cases. We developed a novel, 3-dimensional chemical compositional and robust general reservoir simulator (UTGEL) to model gel treatment processes. The simulator has the capability to model different types of microgels, such as preformed particle gels (PPG), thermally active polymers (TAP), pH-sensitive microgels, and colloidal dispersion gels (CDG). The simulator has been validated for gel flooding using laboratory and field scale data. The simulator helps to design and optimize the flowing gel injection for conformance control processes in larger field cases. The gel rheology, adsorption, resistance factor and residual resistance factor with salinity effect, gel viscosity, gel kinetics, and swelling ratio were implemented in UTGEL. Several simulation case studies in fractured and heterogeneous reservoirs were performed to illustrate the effect of gel on production behavior and water control. Laboratory results of homogeneous and heterogeneous sandpacks, and Berea sandstone corefloods were used to validate the PPG transport models. Simulations of different heterogeneous field cases were performed and the results showed that PPG can improve the oil recovery by 5-10% OOIP compared to waterflood. For recovery from fractured reservoirs by waterflooding, injected water will flow easily through fractures and most part of reservoir oil will remain in matrix blocks unrecovered. Recovery from these reservoirs depends on matrix permeability, wettability, fracture intensity, temperature, pressure, and fluid properties. Chemical processes such as polymer flooding (P), surfactant/polymer (SP) flooding and alkali/surfactant/polymer (ASP) flooding are being used to enhance reservoir energy and increase the recovery. Chemical flooding has much broader range of applicability than in the past. These include high temperature reservoirs, formations with extreme salinity and hardness, naturally fractured carbonates, and sandstone reservoirs with heavy and viscous crude oils. The recovery from fractured carbonate reservoirs is frequently considered to be dominated by spontaneous imbibition. Therefore, any chemical process which can enhance the rate of imbibition has to be studied carefully. Wettability alteration using chemicals such as surfactant and alkali has been studied by many researchers in the past years and is recognized as one of the most effective recovery methods in fractured carbonate reservoirs. Injected surfactant will alter the wettability of matrix blocks from oil-wet to water-wet and also reduce the interfacial tension to ultra-low values and consequently more oil will be recovered by spontaneous co-current or counter-current imbibition depending on the dominant recovery mechanism. Accurate and reliable up-scaling of chemical enhanced oil recovery processes (CEOR) are among the most important issues in reservoir simulation. The important challenges in up-scaling CEOR processes are predictability of developed dimensionless numbers and also considering all the required mechanisms including wettability alteration and interfacial tension reduction. Thus, developing new dimensionless numbers with improved predictability at larger scales is of utmost importance in CEOR processes. There are some scaling groups developed in the past for either imbibition or coreflood experiments but none of them were predictive because all the physics related to chemical EOR processes (interfacial tension reduction and wettability alteration) were not included. Furthermore, most of commercial reservoir simulators do not have the capability to model imbibition tests due to lack of some physics, such as surfactant molecular diffusion. The modeling of imbibition cell tests can aid to understand the mechanisms behind wettability alteration and consequently aid in up-scaling the process. Also, modeling coreflood experiments for fractured vuggy carbonates is challenging. Different approaches of random permeability distribution and explicit fractures were used to model the experiments which demonstrate the validity and ranges of applicability of upscaled procedures, and also indicate the importance of viscous and capillary forces in larger scales. The simulation models were then used to predict the recovery response times for larger cores.

La résistance partielle aux agents pathogènes représente une source importante pour l'amélioration des plantes. Cependant les mécanismes moléculaires sous-jacents à ce type de résistance sont encore mal connus. L'interaction entre le riz et le champignon Magnaporthe oryzae est un modèle de choix pour ce type d'analyse, de nombreuses ressources génétiques et outils d'analyse fonctionnelle étant disponibles. Chez le riz, hormis le gène Pi21 qui contrôle la résistance partielle, aucune information biologique et fonctionnelle ne permet d'expliquer cette forme de résistance. En amont de ce travail de thèse, le phénomène de défense préformée a récemment été identifié ; il est défini par la corrélation entre l'expression des gènes liés à la défense avant infection et la résistance partielle à M. oryzae. L'identification de régulateurs de la résistance partielle et des défenses préformées a été l'objectif de cette thèse. Deux stratégies ont été adoptées. Une étude du transcriptome visant à sélectionner et caractériser des gènes candidats sur la base de leur profil d'expression constitutive a été réalisée. Une méthode de sélection par « guilt-by-association » s'est avérée efficace pour identifier des gènes impliqués dans la résistance de la plante. Les gènes AGO18, Z-BED, HSF23 et CaMBP ont été identifiés comme des régulateurs positifs des défenses de la plante. Les gènes HSF23 et CaMBP contrôlent l'expression constitutive des gènes liés à la défense mais leur sur-expression modifie la croissance des plantes. La sur-expression des gènes Z-BED et AGO18 n'a entraîné aucune modification de la croissance de la plante mais une augmentation de la résistance à M. oryzae, sans modification apparente de l'expression des gènes de défense testés. Le gène Z-BED code pour un facteur de transcription putatif dont on peut faire l'hypothèse qu'il contrôle un ensemble encore inconnu de l'arsenal de défense. Le gène AGO18 code pour une protéine argonaute potentiellement impliquée dans l'extinction de gène via la méthylation de la chromatine. Enfin le gène OB-fold est un régulateur négatif des défenses de la plante dont les cibles, potentiellement des ARN, restent à identifier.La deuxième approche a consisté en une détection de loci contrôlant la densité de lésions causées par M. oryzae. Une zone du génome, PRM1, contrôle ce phénotype, confère une résistance à un spectre de souches relativement large, semble contrôler l'expression de gènes de défense avant et au cours de l'infection, et enfin semble ralentir la croissance du champignon avant pénétration. Cette approche sans a priori renforce l'hypothèse que l'expression des gènes de défense avant infection est associée à la résistance partielle du riz à M. oryzae.De plus amples investigations seront nécessaires pour relier les phénotypes de résistance partielle tels que l'inhibition de la croissance pré-pénétration et la densité de lésions entre eux d'une part et d'autre part à l'expression des gènes de défenses avant infection / Partial resistance to pathogens is a major source for plant breeding. However, the molecular mechanisms underlying this type of resistance are still poorly understood. The interaction between rice and the fungus Magnaporthe oryzae is a model of choice for this type of analysis, many genetic and functional analysis tools being available. In rice, except for the Pi21 gene that controls partial resistance, no biological and functional information can explain this form of resistance. Prior to this thesis, the phenomenon of preformed defense has recently been identified; it is defined by the correlation between the expression of genes related to defense before infection and partial resistance to M. oryzae. Identification of partial resistance and preformed defense regulators has been the objective of this thesis. Two strategies were adopted.A transcriptome analysis to select and characterize candidate genes based on their constitutive expression pattern was performed. A method of selection by "guilt-by-association" has been effective in identifying genes involved in plant resistance. The genes AGO18, Z-BED, HSF23 and CaMBP were identified as positive regulators of plant defenses. The genes HSF23 and CaMBP control the constitutive expression of defense related genes, but their over-expression modifies plant growth. Over-expression of Z-BED and AGO18 genes does not affect plant growth but increases the resistance to M. oryzae, without apparent change in the expression of the defense genes tested. The Z-BED gene encodes for a putative transcription factor that likely controls an unknown set of the defense arsenal. The AGO18 gene encodes an Argonaute protein potentially involved in gene silencing via chromatin methylation. Finally the OB-fold gene is a negative plant defense regulator, and its hypothetical RNA targets remain to be identified.The second approach consisted of detection of loci controlling the lesions density caused by M. oryzae. A region of the genome, PRM1, controls this phenotype, confers resistance to a relatively wide range of isolates, appears to control the expression of defense genes before and during the infection, and finally seems to inhibit the growth of the fungus before penetration. This approach without a priori supports the hypothesis that the expression of defense genes before infection is associated with partial resistance of rice to M. oryzae.Further investigations are needed to link the resistance phenotypes such as partial inhibition of fungal growth pre-penetration and density of these lesions on the one hand, and the defense gene expression before infection on the other hand.

Magister Scientiae Dentium - MSc(Dent) / The treatment objectives in the restoration of an endodontically treated tooth are maximum retention of post and core and to create a design in which the tooth is preserved when the restoration fails. The ferrule effect in root treated teeth requiring cast post and core has been studied extensively and has been shown to greatly improve fracture resistance (Gluskin et al 1995, Libman & Nicholls, 1995. Hemmings et al, 1991. Barkhordar et al, 1989. Rosen & Partida-Rivera, 1986). Studies have also shown that in the case of cast post and core, the longer the ferrule, the greater the fracture resistance (Libman and Nicholls, 1995). The use of the new bonding agents, composite resin cements and core materials, have led to a more conservative approach to post and core restorations. However few studies have considered the effect of different ferrule designs on prefabricated post and composite core systems (Volwiler et al 1989, Al Hazaimeh and Gutteridge 2001). There is little information as to whether the ferrule is of additional value in providing reinforcement in these restorations. This study investigated the effects of different ferrule designs on the fracture resistance of teeth incorporating prefabricated posts and composite cores. In addition teeth restored with a composite core but with no prefabricated post were included in the study to assess the necessity of a post in the restoration of endodonticallytreated teeth. Sixty extracted maxillary incisors (centrals and laterals) and carunes were randomly assigned into three groups and restored. Two groups had a prefabricated post and composite core with varying ferrule designs. A third group had a core with composite packed into the root canal but no post. All teeth were restored with cast crowns to simulate the clinical situation. A Zwick universal testing machine was used to apply compressive loads progressively on the restored teeth until failure occurred as a result of either root, tooth or post fracture. Failure loads, modes of fracture, post and core systems and tooth preparation were recorded and statistically analysed. The results showed no significant difference in the amount of force needed to break the teeth in the different groups irrespective of whether the teeth had a ferrule or not. They also showed no significant difference in the amount of force needed to break the teeth in the different groups irrespective of whether the teeth had a post or not.