The modulation of galactic cosmic ray (GCR) Carbon in a north-south asymmetrical heliosphere is studied, using a two-dimensional numerical model that contains a solar wind termination shock (TS), a heliosheath, as well as particle drifts and diffusive shock re-acceleration of GCRs. The asymmetry in the geometry of the heliosphere is incorporated in the model by assuming a significant dependence on heliolatitude of the thickness of the heliosheath. As a result, the model allows comparisons of modulation in the north and south hemispheres during both magnetic polarity cycles of the Sun, and from solar minimum to moderate maximum conditions. When comparing the computed spectra between polar angles of 55o (approximating the Voyager 1 direction) and 125o (approximating the Voyager 2 direction), it is found that at kinetic energies E < 1:0 GeV/nuc the effects of the assumed asymmetry in the geometry of the heliosphere on the modulated spectra are insignificant up to 60 AU from the Sun, but become increasingly more significant with larger radial distances to reach a maximum inside the heliosheath. In contrast, with E > 1:0 GeV/nuc, these effects remained insignificant throughout the heliosphere even very close to the heliopause (HP). However, when the enhancement of both polar and radial perpendicular diffusion coefficients off the equatorial plane is assumed to differ from heliographic pole to pole, reflecting different modulation conditions between the two hemispheres, major differences in the computed intensities between the two Voyager directions are obtained throughout the heliosphere. The model is further improved by incorporating new information about the HP location and the relevant heliopause spectrum for GCR Carbon at E < 200 MeV/nuc based on the recent Voyager 1 observations. When comparing the computed solutions at the Earth with ACE observations taken during different solar modulation conditions, it is found that it is possible for the level of modulation at the Earth, when solar activity changes from moderate maximum conditions to solar minimum conditions, to exceed the total modulation between the HP and the Earth during solar minimum periods. In the outer heliosphere, reasonable compatibility with the corresponding Voyager observations is established when drifts are scaled down to zero in the heliosheath in both polarity cycles. The effects of neglecting drifts in the heliosheath are found to be more significant than neglecting the enhancement of polar perpendicular diffusion. Theoretical expressions for the scattering function required for the reduction of the drift coefficient in modulation studies are illustrated and implemented in the numerical model. It is found that when this scattering function decreases rapidly over the poles, the computed A < 0 spectra are higher than the A > 0 spectra at all energies at Earth primarily because of drifts, which is unexpected from a classical drift modeling point of view. Scenarios of this function with strong decreases over the polar regions seem realistic at and beyond the TS, where the solar wind must have a larger latitudinal dependence. / PhD (Space Physics), North-West University, Potchefstroom Campus, 2015

Doctor of Philosophy / Department of Chemical Engineering / Keith L. Hohn / Catalytic partial oxidation (CPO) has received considerable interest recently both as a way to utilize remote natural gas resources and to provide H[subscript]2 for a fuel cell. Studies on the reactions at lower temperatures and transient conditions were performed, which can provide insights on the mechanism of CPO at high reactions, particularly on the role of the chemical and physical state of the noble metal catalyst. In this work, ignition of methane CPO on Pt/Al[subscript]2O[subscript]3 and Rh/Al[subscript]2O[subscript]3 catalysts and methanol CPO on Pt/Al[subscript]2O[subscript]3 catalysts were studied using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The ignition mechanism study of CH4 on Pt/Al[subscript]2O[subscript]3 showed that oxygen mainly covers the surface until ignition. Competition between the two reactants is assumed. The heat of adsorption of oxygen is a key factor for ignition of the methane partial oxidation reaction on Pt/Al[subscript]2O[subscript]3. The ignition mechanism on Rh/Al[subscript]2O[subscript]3 was found to be different from Pt/Al[subscript]2O[subscript]3. The oxidation state of the catalyst changed significantly as the temperature was raised towards the ignition. An oxidized rhodium state, Rh[superscript]n+, progressively formed as the temperature was increased while Rh[superscript]0 decreased. In addition, a greater amount of Rh[supercript]n+ was found when the oxygen concentration in the feed was higher. From these results, it is hypothesized that ignition of methane CPO on Rh/Al[subscript]2O[subscript]3 is related to the accumulation of the Rh[superscript]n+ state. Dissociation adsorption of methanol occurs on both Al2O3 and Pt/Al[subscript]2O[subscript]3. It is suggested that formate was one of the important intermediates in the reaction pathway. Oxygen species play a key role in the formation of formate on the catalysts, and it also affects the product composition. Formate mainly decomposed into CO, which is the dominant source for CO[subscript]2 production in the reactions at higher temperatures.

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The plasma drifts or electric fields and their structures in the ionosphere affect the accuracy of the present-day space-based systems. For the first time, we have used ionospheric plasma drift data from Jicamarca radar measurements to study the climatology of altitudinal variations of vertical and zonal plasma drifts in low latitudes during daytime. We used data from 1998 to 2014 to derive these climatological values in bimonthly bins from 150 km to 600 km. For the vertical plasma drifts, we observed the drifts increasing with altitudes in the morning and slowly changing to drifts decreasing with altitude in the afternoon hours. The drifts change mostly linearly from E- to F-region altitudes except in the morning hours of May-June when the gradients are very small. The zonal drifts show a highly nonlinear increase in the westward drifts at the lower altitudes and then increase slowly at the higher altitudes. We see a break in the slopes at lower altitudes during the morning hours of March-April and May-June. The E-region zonal drifts, unlike vertical drifts, show a very large variability compared to F-region drifts. We also explored the altitudinal profiles of vertical drifts during late afternoon and evening hours when the electrodynamic properties in the ionosphere change rapidly. For the first time using drifts up to 2000 km, we have shown the drifts increase and decrease below and above the F-region peak before becoming height independent. These structures arise to satisfy the curl-free condition of electric fields in low latitudes. The altitudinal gradients of vertical drifts are balanced by a time derivative of the zonal drifts to satisfy the curl-free condition of electric fields. We have shown how these structures evolve with local time around the dusk sector and change with solar flux. During solar minimum, the peak region can go well below 200 km. The present-day electric field models do not incorporate these gradients, particularly in the evening sectors when they change very rapidly. Very often their results do not match with the observations. Including these gradients along with proper magnetic field models will improve the model results and accuracy of our navigation, communication, and positioning systems.

NOx storage and reduction activities of Pt/BaO/CexZr1-xO2 (x= 1, 0.75, 0.5, 0.25, 0) catalysts were investigated by transient reaction analysis and Diffuse Reflectance Infrared Fourier Tramsform Spectroscopy (DRIFTS). Pt/BaO/Al2O3 catalyst was used as reference catalyst. Ce-Zr mixed oxides were synthesized by means of Pechini Method. Pechini method is a sol-gel like method based on mixing the related mixed oxide precursors with an &amp / #945 / -hydroxy carboxylic acid. 10% BaO (w/w) and 1% Pt (w/w) were deposited on synthesized mixed oxide and reference alumina support via incipient wetness impregnation. Prepared catalysts were characterized by BET, XRD and in-situ DRIFTS. Pt/BaO/CexZr1-xO2 catalysts (x= 0.75, 0.5, 0.25) exhibited higher surface than pure ceria and zirconia supported catalysts and highest surface was observed for Pt/BaO/Ce0.5Zr0.5O2. The reducibility of catalysts was tested by Temperature Programmed Reduction (TPR). It was observed that the reducibility of Pt/BaO/CexZr1-xO2 catalysts increases with incorporation of Zr into ceria lattice. Pt/BaO/Ce0.25Zr0.75O2 showed the highest reducibility. The Pt dispersions of catalysts were determined by CO chemisorption. The highest Pt disperison was observed in the presence of Pt/BaO/Ce0.5Zr0.5O2 catalyst. NOx storage and reduction efficiency of the catalysts were determined by transient reaction analysis in a home-built setup at 350oC. The reaction results revealed that all catalysts exhibit similar NOX storage and reduction performance. The NOX storage performances of all catalysts were differentiated via in-situ DRIFTS analysis. Pt/BaO/CexZr1-xO2 (x= 0.75, 0.5, 0.25) catalysts revealed higher performance than the ceria and zirconia supported catalysts. Pt/BaO/Ce0.5Zr0.5O2 catalyst absorbed highest amount of NO on the surface in the form of nitrate. The reduction behaviours of catalysts also were investigated by in-situ DRIFTS. It was observed that nitrates and nitrites were completely removed from the surface after reduction by H2 at 300oC.

The zero-noise limit of differential equations with singular coefficients is investigated for the first time in the case when the noise is a general alpha-stable process. It is proved that extremal solutions are selected and the probability of selection is computed. Detailed analysis of the characteristic function of an exit time form on the half-line is performed, with a suitable decomposition in small and large jumps adapted to the singular drift.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / Clavulanic acid (AC) and amoxicillin (AMO) drugs are used in association and they are commercialized in Brazil as antibiotic agent. The simultaneous determination of these drugs is, usually, carried out by high performance liquid chromatography (HPLC). In the present study a methodology for simultaneous determination of AC and AMO was developed using Fourier transform mid infrared technique coupled with attenuated total reflectance (FTIR/ATR) and diffuse reflectance (DRIFTS). Nineteen commercial samples and 17 synthetic samples (28 samples for calibration set and 8 samples for prevision set) were used. Calibration models were developed using partial least squares (PLS) and interval partial least squares (iPLS), synergy partial least squares (siPLS) and backward interval partial least squares (biPLS) were used as variable selection methods. Multiplicative scatter correction (MSC) and the data centered in the media produced the best models. A relative standard error of prediction (RSEP) of 3.58% (root mean square error of prediction RMSEP = 6.17 mg g-1) for AC and RSEP of 5.12% (RMSEP = 33.58 mg g-1) for AMO was obtained after interval selection using biPLS algorithm for FTIR/ATR. For DRIFTS 4.98% (RMSEP = 8.44 mg g-1) and 4.75% (RMSEP = 23.31 mg g-1) RSEP values were obtained for AC and AMO, respectively, after selection of better intervals by siPLS. Results obtained by the proposed methodology were compared with those using the methodology by HPLC and no significant differences were obtained. Therefore, results using FTIR/ATR and DRIFTS techniques combined to multivariate analysis methods were suitable for the simultaneous determination of AC and AMO in commercial pharmaceuticals products. / Os fármacos ácido clavulânico (AC) e amoxicilina (AMO) são utilizados em associação e são comercializados no Brasil como agentes antibióticos. A determinação simultânea destes fármacos é, normalmente, realizada por cromatografia a líquido de alta eficiência (HPLC, do inglês high performance liquid chromatography). O presente estudo teve por objetivo a determinação simultânea de AC e AMO utilizando técnicas de espectroscopia de reflexão no infravermelho médio (FTIR/ATR e DRIFTS) combinadas com métodos de análise multivariada. Utilizaramse 19 amostras comerciais e 17 amostras sintéticas (28 amostras para o conjunto de calibração e 8 amostras para o conjunto previsão). Obtiveram-se modelos de calibração por mínimos quadrados parciais (PLS) e seleção de variáveis através dos algoritmos por mínimos quadrados parciais por intervalo (iPLS), por sinergismo (siPLS) e por exclusão (biPLS). Os melhores modelos foram obtidos através da utilização do pré-processamento centrado na média e do tratamento de correção do espalhamento de luz (MSC). Utilizando os dados obtidos por FTIR/ATR o modelo que apresentou melhor capacidade preditiva foi aquele que utilizou o algoritmo biPLS, fornecendo um erro padrão de predição relativo (RSEP) de 3,58% (raiz quadrada do erro médio de previsão - RMSEP = 6,17 mg g-1) para AC e RSEP de 5,12% (RMSEP = 33,58 mg g-1) para AMO. Quando utilizados os dados obtidos por DRIFTS, os melhores modelos foram os que utilizaram o algoritmo siPLS, produzindo RSEP de 4,98% (RMSEP = 8,44 mg g-1) para AC e RSEP de 4,75% (RMSEP = 23,31 mg g-1) para AMO. Os resultados de ambas as metodologias propostas foram comparados com os valores obtidos pela metodologia de referência por HPLC, não se verificando diferença significativa entre seus valores. Desta forma, os resultados mostraram que as técnicas de FTIR/ATR e DRIFTS associadas aos métodos de regressão multivariados permitiram a obtenção de modelos apropriados para a determinação simultânea de AC e AMO em formulações farmacêuticas.

Submitted by isabela.moljf@hotmail.com (isabela.moljf@hotmail.com) on 2017-05-26T13:54:03Z No. of bitstreams: 1 felipesiqueirapacheco.pdf: 3385187 bytes, checksum: 228543ccc9eb6937fa28ce63234bf0c4 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-05-26T15:11:47Z (GMT) No. of bitstreams: 1 felipesiqueirapacheco.pdf: 3385187 bytes, checksum: 228543ccc9eb6937fa28ce63234bf0c4 (MD5) / Made available in DSpace on 2017-05-26T15:11:47Z (GMT). No. of bitstreams: 1 felipesiqueirapacheco.pdf: 3385187 bytes, checksum: 228543ccc9eb6937fa28ce63234bf0c4 (MD5) Previous issue date: 2009-09-22 / Os processos físicos, químicos e biológicos que ocorrem nos ambientes aquáticos estão fortemente acoplados aos processos hidrodinamicos. O conhecimento dos processos responsáveis pela dispersão horizontal e vertical são pontos importantes para a compreensão da ciclagem de nutriente, dispersão de substâncias, produtividade primária e outros processos ecológicos. Apesar da importância, poucos estudos desta natureza são realizados em sistemas aquáticos continentais brasileiros, embora estes já tenham sido realizados em outros países. Durantes anos, os derivadores lagrangianos vem sendo utilizado na área da oceanografia, a fim de entender as correntes de águas marítimas. Este trabalho propôs: (1) o desenvolvimento de um derivador lagrangiano adaptado às condições de ecossistemas continentais; (2) desenvolvimento da cadeia de termistores, tendo em vista a aquisição de dados sobre a estrutura termal vertical, auxiliares para o presente estudo; (3) fazer uso do derivador para entender processos biogeoquímicos e; (4) entender o comportamento das correntes de densidades e a influencia da operação da usina para o padrão de circulação dos reservatórios. O trabalho foi realizado no reservatório APM Manso, localizado próximo a cidade de Cuiabá, Mato Grosso. Nossos estudos mostraram: (1) o vento determinou grande parte dos movimentos ocorridos nos primeiros metros da coluna d`água. (2) as turbinas influenciaram no padrão das correntes tanto diretamente (sucção pela turbina), quanto indiretamente (pela corrente de retorno). (3) movimentos advectivos foram predominantes na região intermediária do reservatório, indicando que pequenas variações temporais na condição inicial da dinâmica podem ser igualmente importantes a pequenas variações espaciais. (4) a diminuição da velocidade do rio ao entrar no reservatório pode causar mistura de águas profundas com águas superficiais, regida pela instabilidade de Kelvin-Helmholtz, proporcionando aumento da densidade fitoplanquitônica. / Physical, chemical and biological processes that occur in aquatic ecosystems are strongly dependent of hydrodynamic. Process responsible for horizontal and vertical dispersion are important points for the comprehension of nutrient cycle, substances dispersion, primary productivity and others ecological process. In despite of many studies have been done in others country, few studies were made in continental Brazilian aquatic ecosystems. During many years, lagrangian drifters have been used in oceanography to understand ocean water current. The purpose of this work was: (1) development of the lagrangian drifters adapted to continental ecosystems; (2) development of termistor chain to understand the vertical thermal structure; (3) use of drifters to understand biochemical process and; (4) understand the density currents and the influence of the dam to the water circulation in the reservoir. Experiments were carried out in APM Manso reservoir, located near Cuiaba city, Mato Grosso. Our studies showed: (1) most of movements in the surface layer were wind induced; (2) current was influenced by turbines suction (direct influence) and by return current from the dam (indirect influence); (3) advective ovements were predominant in intermediary region of the reservoir. It indicates that small temporal variation in the initial condition could be as important as small spatial variation; (4) the interaction among river and reservoir water engendered the Kelvin-Helmholtz instability. It causes vertical mixing of deep water that can increase phytoplankton density.

A Neogene contourite depositional system was identified and mapped along the DeSoto Slope in the northeastern Gulf of Mexico, U.S.A. A series of drift deposits comprising the larger contourite depositional system were interpreted from a 2-D industry seismic data set. The now subsurface drift deposits are adjacent to the anomalous seabed feature, the DeSoto Canyon, and these data suggest contourite deposition and ocean currents are in integral part of the canyon’s depositional history. The contourite depositional system is underlain by an extensive, middle Miocene aged, erosional unconformity formed by ocean currents. The timing of this erosional surface is in alignment with the widely accepted premise that the Miocene represented a transitional period in Gulf of Mexico basin circulation. The discovery of this contourite depositional system adds to an established list of Miocene-aged features pointing to the onset of enhanced Loop Current circulation in the Neogene Gulf of Mexico.

No description available.