Neste trabalho apresenta-se a modelagem de chamas difusivas na forma de jato, para baixo número de Mach e elevado número de Damköhler. O modelo é baseado na solução das equações na forma flamelet para a parte química e na fração de mistura para o fluxo. Este modelo descreve bem o comportamento de chamas difusivas, exceto na sua extremidade (ponta), onde geralmente surgem instabilidades. Resultados numéricos são apresentados para uma cinética química de uma e multietapas, utilizando a técnica LES (Large-Eddy Simulation) com o modelo de Smagorinsky para a viscosidade turbulenta. A discretização das equações governantes é feita em diferenças finitas, com a aplicação da técnica TVD (Total Variation Diminishing). Além disso, apresentamse mecanismos reduzidos multietapas para o metano, o metanol e o etanol, visando obter resultados realistas. A modelagem de chamas de metanol e etanol diferencia-se da modelagem de chamas de metano por ocorrer uma mudança de fase antes da combustão. Modela-se o efeito global das gotas usando uma descrição Lagrangeana que é incorporada à descrição Euleriana do escoamento, via termos fonte. Testes numéricos foram realizados para chamas difusivas de metano, metanol e etanol, e os resultados estão em concordância com os dados encontrados na literatura. / This work presents a model for a jet diffusion flame, for low Mach and high Damköhler numbers. The model is based on the solution of the flamelet equations for the chemistry and on the mixture fraction for the flow. This model describes well the behavior of diffusion flames, except at the flame tip, where instabilities can often occur. Numerical results are presented for an one-step and multi-step chemical kinetic models, using the LES (Large-Eddy Simulation) technique with the Smagorinsky model for the turbulent viscosity. The discretization of the governing equations follows the finite difference method, with the application of the TVD (Total Variation Diminishing) technique. Besides, multi-step reduced mechanisms for the methane, the methanol and the ethanol are employed, obtaining realistic results. The flame modeling of methanol and ethanol differs from the modeling of methane flames because of a phase change occurs before the combustion. The droplets global effect is modeled based on a Lagrangian description, which is incorporated into the Eulerian description of the flow through source terms. Numerical tests were carried out for methane, methanol and ethanol diffusion flames, and the results compare well with data in the literature.

Magister Scientiae - MSc / Fuel cells convert chemical energy from a fuel into electricity through chemical reaction with oxygen. This possesses some challenges like slow oxygen reduction reaction (ORR), overpotential, and methanol fuel cross over in a direct methanol fuel cell (DMFC). These challenges cause inefficiency and use of higher amounts of the expensive platinum catalyst.Several binary catalysts with better ORR activity have been reported. In this study we investigate the best catalyst with better ORR and MOR performances and lower over-potentials for PEMFC and DMFC applications by comparing the in-house catalysts (10%Pt/C, 20%Pt/C,30%Pt15%Ru/C, 40%Pt20%Ru/C, 30%PtCo/C, 20%Pt20%Cu/C and 20%PtSn/C) with the commercial platinum based catalysts (10%Pt/C, 20%Pt/C, 20%Pt10%Ru/C, 20%PtCo/C,20%PtCu/C and 20%PtSn/C) using the cyclic voltammetry and the rotating disk electrode to determine their oxygen reduction reaction and methanol tolerance. HRTEM and XRD techniques were used to determine their particle size, arrangement and the atomic composition. It was observed that the 20%Pt/C in-house catalyst gave the best ORR activity and higher methanol oxidation current peaks compared to others catalysts followed by 20%Pt10%Ru/C commercial catalyst. The 20%PtCo/C commercial, 30%PtCo/C in-house and 20%PtSn/C in-house catalysts were found to be the most methanol tolerant catalysts making them the best catalysts for ORR in DMFC. It was observed that the ORR activity of 20%PtCo/C commercial and 30%PtCo/C inhouse catalysts were enhanced when heat treated at 350 0C. From XRD and HRTEM studies, the particle sizes were between 2.72nm to 5.02nm with little agglomeration but after the heat treatment, the particles were nicely dispersed on the carbon support.

>Magister Scientiae - MSc / The purpose of this study was to develop a high performance-lower cost catalyst to be applied in Direct Methanol Fuel Cells (DMFC). The study also aimed to prepare plurimetallic supported platinum (Pt), platinum-ruthenium (PtRu), platinum-ruthenium-vanadium (PtRuV) and platinum ruthenium-vanadium-iron (PtRuVFe) upon multi-walled carbon nanotube (MWCNT) as well as upon multiwalled carbon nanotube-titanium oxide (MWCNT/TiO2) supports. Platinum is very active but prone to poisoning by carbon monoxide (CO), which may be present in the fuel used in fuel cells. The focus on the use of methanol was because of its better reaction kinetics, and better performance in direct methanol fuel cells (DMFC) better than proton exchange membrane fuel cell (PEMFC). When Pt is alloyed with another platinum group metals (PGM) the alloying decreases the over-potential for reactions critical in the fuel cells. Proton exchange membrane fuel cell (PEMFC) performance may be improved at low metal loading, when supported pluri-metallic catalysts are applied since the trimetallic catalysts may promote high catalyst utilisation. In practice, DMFC require electrodes with a Pt loading to achieve acceptance fuel cell (FC) power performance. The aim of this study was therefore the reduction of the catalyst loading through further improvement of mass activity of Pt based catalysts by partial substitution of the noble metal/metals, and the use of a carbon support that will provide high surface area, good electrical conductivity and high stability. MWCNT supported pluri-metallic (PtRuVFe,) and bimetallic (PtRu) nanoparticles possessed characteristic of increased surface area, improved electron transfer rate, enhance electro-catalytic activity and promoted stability.

Eletrocatalisadores baseados em Pd/C, PdCu/C, PdNi/C e PdAg/C foram produzidos pelo método de micro-ondas para serem utilizados como cátodo na célula a combustível alcalina na ausência e presença de álcool. Este método se mostrou bastante efetivo para a produção dos materiais, uma vez que as partículas apresentaram boa dispersão no suporte de carbono e produziram eletrocatalisadores com tamanho de partícula em torno de 3,5 nm, de acordo com as análises de DRX e MET. A partir das voltametrias cíclicas observa-se que para os eletrocatalisadores de PdCu/C e PdNi/C quanto maior a quantidade de Cu ou Ni, respectivamente, maior a área ativa do material estudado. Análises de disco anel rotatório foram realizadas nos eletrocatalisadores demonstrando que, independente da composição estudada, a quantidade produzida de peróxido foi de no máximo 4%. Estes dados corroboram com as inclinação das retas nas análises de Koutecky-Levich, uma vez que em ambos os casos a RRO ocorre via 4 elétrons. Análises de estabilidade dos materiais demonstraram que todos eles mantiveram ou melhoraram seu desempenho diante da RRO, quando se compara os dados obtidos antes e depois de 1000 ciclos voltamétricos. Testes de tolerância ao metanol e etanol foram realizados em meia célula com todas as composições de eletrocatalisadores produzidos. Na presença tanto de metanol quanto de etanol as composições atômica de 50:50, para todos os materiais estudados, foram as que demonstraram menor influência da presença do álcool durante a varredura linear da RRO. Nas medidas realizadas em célula unitária, com relação à tolerância ao metanol durante a RRO, o eletrocatalisador que demonstrou melhor desempenho foi o PdAg/C 70:30 enquanto que na presença de etanol o eletrocatalisador que demonstrou melhor desempenho foi o PdNi/C 70:30. / Pd/C, PdCu/C, PdNi/C and PdAg/C electrocatalysts were produced by microwave method to be used as cathode in alkaline fuel cell in the absence and presence of alcohol. This method showed to be effective for the materials production, the particles exhibited good dispersion in carbon support and it produced electrocatalysts with a particle size of about 3.5 nm, according to XRD and TEM analysis. In cyclic voltammetry is observed that PdCu/C and PdNi/C electrocatalysts has higher active area with higher amount of Cu and Ni, respectively. Rotating ring disk analysis in the electrocatalysts showed that the amount of peroxide produced was at most 4%. This data is similar to Koutecky-Levich analysis, once for both the ORR occurs via 4 electrons. Materials stability analysis showed that they kept or improve performance in ORR, comparing the data before and after 1000 voltammetric cycles. Tolerance tests in methanol and ethanol were performed in a half cell in all electrocatalysts compositions. In presence of methanol and ethanol the compositions 50:50, to all materials studied, showed less influence in the presence of alcohol in ORR linear scan. In alkaline fuel cell PdAg/C 70:30 showed better performance for ORR in presence of methanol and PdNi/C 70:30 showed better performance for ORR in ethanol presence.

O objetivo do presente estudo foi determinar as concentrações de testosterona no pêlo de cães domésticos, testar dois protocolos diferentes de extração hormonal, comparar os níveis séricos e avaliar as possíveis diferenças de concentração de testosterona no pêlo de acordo com: o sexo; animais castrados e inteiros; região de colheita; tipo e tempo de armazenamento do extrato e coloração da pelagem. Foram utilizados 31 animais adultos, sendo 25 machos e 6 fêmeas, da raça poodle provenientes de canis particulares. O pêlo foi colhido com auxílio de tesoura ou máquina de tosa e armazenados em temperatura ambiente, juntamente com colheita da amostra de sangue. Os protocolos de extração utlizaram 3mL de metanol como solvente por 2 ou 48 horas, os extratos foram secos em ar comprimido, ressuspendidos e armazenados na geladeira ou freezer por até 30 dias. As concentrações foram determinadas por radioimunensaio (RIE). Os testes estatísticos foram realizados utilizando-se o programa computadorizado Statistical Analysis System (SAS). Os resultados mostraram que é possível determinar as concentrações do hormônio testosterona no pêlo de cães. Os dois protocolos de extração de testosterona no pêlo demonstraram-se eficientes, porém o segundo apresenta maior recuperação hormonal do que o primeiro. É possível determinar as concentrações do hormônio testosterona no pêlo de cães. Não há correlação positiva entre os níveis hormonais de testosterona encontrados no sangue e no pêlo. Há diferença estatística significativa entre as concentrações de testosterona no pêlo de acordo com o sexo: entre fêmeas e machos inteiros (p=0,0074) e entre fêmeas e machos (castrados e inteiros) (p=0,0042). Não há diferença entre fêmeas e machos castrados (p=0,3610). Não há diferença significativa das concentrações de testosterona no pêlo entre animais machos inteiros ou castrados. Não há diferença estatística significativa das concentrações de testosterona no pêlo entre as regiões de colheita da amostra (cabeça, corpo ou membros), pois em todos os animais há correlação positiva entre essas áreas. Não há diferença significativa das concentrações de testosterona no pêlo de acordo com a coloração da pelagem (branca, cinza, marrom e preta). Não há diferença estatística significativa das concentrações de testosterona no armazenamento do extrato do pêlo ressuspendido por até 30 dias na geladeira ou freezer. / The objective of the present study was to determine the concentrations of testosterone in domestic dogs hair, to test two different protocols of hormonal extraction, to compare the levels and in accordance with to evaluate the possible differences of hair concentration of testosterone: the sex; castrated and intact animals; sampling areas; type and time of storage of the extract and hair color. 31 adult animals had been used, being 25 males and 6 females, of the poodle breeds proceeding from particular kennels. The hair was cut with of scissors help or machine and keep in ambient temperature, together with of the sample of blood. The extraction protocols added 3mL of methanol as solvent for 2 or 48 hours, the extracts were dried in compressed air, added in assay buffer and stored in the refrigerator or to freezer for up to 30 days. The concentrations had been determined by radioimmunoassay (RIA). The statistical tests were performed using the computer program Statistical Analysis System (SAS). The results had shown that it is possible to determine the concentrations of testosterone in dogs hair. The two protocols of extraction of testosterone in the hair had been demonstrated efficient, however as it presents greater hormonal recovery of what the first one. The sex has difference significant statistics in accordance with testosterone concentrations in the hair: between females and intact males (p=0,0074) and between females and males (castrated and intact) (p=0,0042). It does not have difference between females and castrated males (p=0,3610). It does not have significant difference of the concentrations of testosterone in the hair between intact or castrated male. It does not have difference significant statistics of the concentrations of testosterone in the hair in the sampling areas (head, body or members), therefore has positive correlation between these areas. The hair color does not have significant difference with concentrations of testosterone in the coat (white, gray, brown and black). It does not have difference significant statistics of the concentrations of testosterone in the storage of the extract added in assay buffer for up to 30 days in the refrigerator or freezer.

Thesis (M.Sc. (Biochemistry) -- University of Limpopo, 2018 / Dicerocaryum senecioides is a plant widely used as a nutritional source. It is used also for treatment of measles, wounds and to facilitate birth in domestic animal and humans in many parts of southern Africa (Mampuru et al., 2012). Findings in our laboratory have shown that a dichloromethane fraction of D. senecioides possesses antiinflammatory properties in human t-lymphocytes (Madiga, 2009), while the methanol crude extract possesses anti-proliferative and proapoptotic properties against Jurkat T cancer cells (Mphahlele, 2008). In this study, the probable anti-cancer effect of D. senecioides crude methanol leaf extract was investigated on cervical HeLa cancer cells. Dried powdered leaves of D. senecioides were extracted with absolute methanol to obtain a crude extract. To assess the cytotoxicity effect of the extract, KMST-6 and HeLa cell cultures were exposed to various extract concentrations (0 to 600 µg/ml) for 24 and 48 hours and subjected to the MTT assay. The results showed the extract to have no significant increase in the viability inhibition of HeLa cells at all tested concentrations after 24 hours of treatment. However, treatment with 400, 500 and 600 µg/ml of the extract for 48 hours revealed significantly increased HeLa cell viability inhibition. Furthermore, the extract showed to have no effect on the viability of normal human fibroblast KMST-6 cells at concentrations below 600 µg/ml, after 24 and 48 hours of treatment, thus showing selective cytotoxicity of the extract. To determine the mode of cell death associated with the increase in HeLa cell viability inhibition, the Hoechst 33258 nuclear staining assay and inverted light microscopy were employed. The data proposed apoptosis as the mode of cell death associated with the inhibition of HeLa cell viability. This was evidenced by changes in cell morphology such as the loss of HeLa cell radial extensions, cell shrinkage, as well as nuclear morphological features such as chromatin condensation. Apoptosis induction was further confirmed by the annexin-V/PI and multicaspase assays, using flow cytometry. The results showed an increase in the percentage of cells stained with annexin-V/PI, as well as increased caspase activity in extract-treated HeLa cells. To elucidate proapoptotic mechanisms of the extract, Western blotting analysis as well as the human apoptosis antibody array kit were used. This was to measure the expression profile of a number of apoptosis regulatory proteins. The results demonstrated modulation of some anti- and pro-apoptotic proteins, as well as the release of mitochondrial proteins required xiii for initiation of apoptosis, in the cytoplasm. The D. senecioides extract showed to have no effect on the cell division cycle of HeLa cells as determined by the PI staining assay. In conclusion, D. senecioides crude methanol leaf extract induced some degree of apoptosis in cervical HeLa cancer cells via the intrinsic apoptosis pathway. This was by modulating some of the members of the Bcl-2 family of proteins, which, facilitated the release of cytochrome C and activation of a caspase cascade. / South African Medical Research Council (SAMRC)

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This thesis aims mainly at investigating the potential oxidizing abilities and possible applications of the UV/Chlorine process as an Advanced Oxidation Process (AOP). Several organic compounds were used and added into the samples as challenging radical scavengers to investigate the possibilities of the UV/Chlorine process being used in the water and wastewater treatment industry. The UV/H2O2 process was selected as a reference, and experiments were carried out parallel; the results obtained earlier in the UV/Chlorine process were compared to those of the UV/H2O2 process. Methanol was added into active chlorine solutions at both pH 5 and 10. The quantum yields for the degradation of active chlorine were calculated after the samples had been exposed to UV. Also the production of OH radicals was calculated by determining the generation of formaldehyde. The OH radical yield factors, which are significant in evaluating AOPs, were calculated both in the UV/Chlorine and the UV/H2O2 processes. In addition to methanol, para-chlorobenzoic acid (pCBA) and cyclohexanoic acid (CHA) were added to active chlorine solutions and to H2O2 solutions. The first-order reaction rate constants for the oxidation of pCBA and CHA using the UV/Chlorine process were calculated and compared to those of the UV/H2O2 process. This allowed an evaluation of whether or not the UV/Chlorine process might be efficient for the treatment of contaminated water samples containing pCBA and/or CHA. Finally the thesis comes to a general conclusion about the efficiency of the UV/Chlorine process compared to that of the UV/H2O2 process. / Environmental Engineering

Vehicles powered by fuel cells are from an environmentalaspect superior to the traditional automobile using internalcombustion of gasoline. Power systems which are based upon fuelcell technology require hydrogen for operation. The ideal fuelcell vehicle would operate on pure hydrogen stored on-board.However, storing hydrogen on-board the vehicle is currently notfeasible for technical reasons. The hydrogen can be generatedon-board using a liquid hydrogen carrier such as methanol andgasoline. The objective of the work presented in this thesiswas to develop a catalytic hydrogen generator for automotiveapplications using methanol as the hydrogen carrier. The first part of this work gives an introduction to thefield of methanol reforming and the properties of a fuel cellbased power system. Paper I reviews the catalytic materials andprocesses available for producing hydrogen from methanol. The second part of this thesis consists of an experimentalinvestigation of the influence of the catalyst composition,materials and process parameters on the activity andselectivity for the production of hydrogen from methanol. InPapers II-IV the influence of the support, carrier andoperational parameters is studied. In Paper V an investigationof the catalytic properties is performed in an attempt tocorrelate material properties with performance of differentcatalysts. In the third part of the thesis an investigation isperformed to elucidate whether it is possible to utilizeoxidation of liquid methanol as a heat source for an automotivereformer. In the study which is presented in Paper VI a largeseries of catalytic materials are tested and we were able tominimize the noble metal content making the system more costefficient. In the final part of this thesis the reformer prototypedeveloped in the project is evaluated. The reformer which wasconstructed for serving a 5 kWe fuel cell had a highperformance with near 100 % methanol conversion and COconcentrations below 1 vol% in the product stream. The resultsof this part are presented in Paper VII. <b>Keywords:</b>methanol, fuel cell, vehicle, catalyst,copper, hydrogen, on-board, steam reforming, partial oxidation,combined reforming, oxidative steam reforming, auto-thermalreforming, zinc, zirconium, chromium, aluminium oxide,manganese, characterization, temperature programmed reduction,X-ray diffraction, chemisorption, carbon monoxide, poisoning,reformer.