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Surface mining of the Athabasca Oil Sands of Canada is occurring at an unparalleled rate resulting in large scale disturbances over vast areas. Soil water availability for plants is one of the key issues faced when reclaiming the landscape. A factor which limits the soil water availability is soil water repellency (SWR). Soil water repellency is found on both natural and disturbed sites in this region and can cause reduced infiltration, reduced soil water storage, enhanced runoff, increased preferential flow, and reduced ecosystem productivity. Effective characterization of SWR, determination of the causes of SWR and understanding how it affects soil pores and water flow are important for environmental management. The main objective of this study is to examine the effect of SWR and fungal hydrophobicity on soil water dynamics in Athabasca Oil Sands. This was accomplished by determining the relationship between the measurement of severity and persistence of SWR and the critical water content (CWC) where SWR is greatest between different soils in the region. Examining how the water conducting porosity and soil pores are affected by SWR. Developing methods to quantify fungal strains that cause SWR and testing of these fungal strains for their ability to alter the SWR and infiltration into soil. Results show that a high severity (Contact angle) of repellency does not necessarily denote long persistence (Water Drop Penetration Time) or high CWC in soils from the region. A high severity of SWR in larger diameter pores decreased the water conducting porosity due to the larger pore contribution to the total liquid flux. The modified microscopy approach and the alcohol percentage test (APT) resulted in improved characterization of fungal hydrophobicity. Fungal strains were classified as hydrophilic, hydrophobic and chrono-amphililic based on their surface properties from these measurements. The surface property of selected fungi strains can alter the SWR in both a repellent and wettable soil and can also change the water infiltration rate. This research highlights the importance of characterization of SWR, the effects on water flow, and how fungal hydrophobicity can alter the SWR and infiltration. This will aid in improving our understanding of SWR and improve remediation efforts on water repellent soils in the Athabasca Oil Sands region.

Flocculation, the process whereby yeast cells attach in groups and sediment to the top or bottom of a fermenter, is industrially important in many fermentation batch operations. These batch operations include wine, distilled spirits, cider, bio-ethanol and production of commercial yeast metabolites. In the case of brewing yeast, it has been determined that flocculation occurs due to three forces called hydrophobic interactions, zymolectin binding and to a lesser extent, surface charge neutralization. This project sought to more closely study hydrophobic interactions and zymolectin binding. Earlier studies had shown that certain hydrophobic carboxylic acids, 3-OH oxylipins, formed in brewing yeast at flocculation onset. Therefore, these compounds showed potential as an indicator of overall cell surface hydrophobicity, and it was believed that flocculation level, cell surface hydrophobicity and oxylipin level would increase in unison in the yeast cell during brewing fermentations. During lab scale fermentations in shaker flasks and in a miniature fermentation assay setup, both flocculation level and cell surface hydrophobicity increased coincidently. However, 3-OH oxylipins could not be isolated from whole cells or cell wall isolates grown in the shaker flasks or whole cells grown in the miniature fermentation assay at detection limits approximated as 50 ng/0.5 g wet yeast. Due to their minute levels in brewing yeast cells, it was proposed that 3-OH oxylipins may mediate flocculation and aggregation via a quorum sensing mechanism instead of by increasing cell surface hydrophobicity. A disagreement exists in the literature where certain researchers believe zymolectin activity is induced, while others believe it is constitutive. The second part of this study attempted to address this by measuring zymolectin density during lab scale fermentations with a flow cytometer. Because of flow cytometry’s capacity for multiparametric analysis, large amounts of data were produced which gave information on not only zymolectin density, but also cell size and cellular complexity. Upon statistical analysis of the data, it was not possible to either refute or confirm the claim that zymolectin activity is induced or constitutive. However, the results suggested there could have been a population of cells with fewer zymolectins, and this certainly warrants further investigation. During the lab scale fermentations, cell size measured by a flow cytometer appeared to be correlated with manual measures of cell size. Furthermore, cell size tended towards uniformity during the fermentation which has also been observed in similar studies employing flow cytometry. Conversely, the cellular complexity of the yeast in this study did not change as in other studies by this may have been due either to strain differences or the methods used herein.

Filtration performance of mineral concentrate is mainly controlled by solid particle size and surface hydrophobicity. Filtration of coarser particles with more hydrophobic surfaces produces better filtration performance characterized by higher filtration rate (U) and lower final moisture content (FMC) in the final cake. Some filtration aids could improve filtration performance by flocculating solid particles and enhancing surface hydrophobicity. For the mineral concentrate used in this study, many filtration aids tested could only improve either U or FMC: one type was effective in improving U, and another type was effective in improving FMC. The combination of the two types of filtration aids at certain dosages could achieve better filtration performance than the optimum performance achieved by each individual filtration aid. Based on the experimental results, the working mechanism of filtration aids behind the filtration behavior was explored to deepen the understanding of the chemical-enhanced filtration of Cu/Ni concentrate. / Chemical Engineering

abstract: This paper presents a theoretical model for evaluating flashover performance of insulators under contaminated conditions. The model introduces several new features when compared with existing models such as, the formation of dry bands, variations in insulator geometry and surface wettability. The electric field distribution obtained from software for 3-Dimensional models along with form factor are used to determine the dimensions of the dry bands and the onset of arcing. The model draws heavily from experimental measurements of flashover voltage and surface resistance under wet conditions of porcelain and composite insulators. The model illustrates the dominant role played by the insulator shape and housing material on the flashover performance. / Dissertation/Thesis / M.S. Electrical Engineering 2012

Les ELISA (Enzyme-Linked ImmunoSorbent Assay) sont une des technologies analytiques les plus utilisées dans la recherche et les applications biomédicales. Leur production nécessite la construction de films d’anticorps sur des surfaces constituées le plus souvent de polystyrène. La haute hydrophobie du polystyrène assure une adhésion forte et spontanée des anticorps permettant ainsi d’y construire facilement une monocouche d’anticorps. L’amélioration des ELISA passe certainement par l’amélioration et la compréhension des mécanismes physico-chimiques à l’œuvre lors de l’immobilisation des anticorps sur le polystyrène. Dans ce but, ce travail présente un essai de théorisation appuyé par des simulations numériques et des estimations expérimentales par microscopie à force atomique (AFM) et ELISA. En faisant référence à l’effet hydrophobe, la thermodynamique des processus irréversibles permet premièrement d’expliciter les raisons de l’adhésion des anticorps sur le polystyrène. Deuxièmement, des simulations numériques dans le cadre du modèle des additions séquentielles aléatoires (RSA) montrent la façon dont peuvent se saturer les surfaces en favorisant certaines orientations d’anticorps recherchées dans le cadre de l’ELISA. Finalement, l’amélioration du modèle RSA en un modèle RSA+R tenant compte des changements d’orientations par relaxation des anticorps illustre le lien entre les conditions de dépôt et la structure de la monocouche obtenue. Ces éléments semblent corroborés par l’expérience / ELISA (Enzyme-Linked ImmunoSorbent Assay) are widely used analytical technologies in research and biomedical fields. Their implementation require to build antibodies thin films onto predominantly composed polystyrene surfaces. The high hydrophobicity of polystyrene ensures spontaneous and strong antibodies adhesion allowing to easily build antibodies monolayers. ELISA improvements lie most probably throughout improvements and comprehension of physico-chemical mecanisms on which antibodies immobilization on polystyrene are relied. In this way, our work explains a therozation essay emphasized by numerical modelling and experimental estimations by atomic force microscopy (AFM) and ELISA. Keeping in mind the so-called hydrophobic effect, thermodynamics of irrversible processes allows in a first time explaining reasons of antibodies adhesion on polystyrene. In a second time, numerical modelling in the field of random sequential additions model (RSA) show a way of surfaces saturation involving a strong trend to favor some antibodies orientations expected for ELISA. Finally, a RSA improvement in a RSA+R model taking into account orientational changes by the way of relaxation shows a link between deposition conditions and obtained monolayer structure. Such results seem to be strongly correlated with experimental facts

abstract: Transmission voltages worldwide are increasing to accommodate higher power transfer from power generators to load centers. Insulator dimensions cannot increase linearly with the voltage, as supporting structures become too tall and heavy. Therefore, it is necessary to optimize the insulator design considering all operating conditions including dry, wet and contaminated. In order to design insulators suitably, a better understanding of the insulator flashover is required, as it is a serious issue regarding the safe operation of power systems. However, it is not always feasible to conduct field and laboratory studies due to limited time and money. The desire to accurately predict the performance of insulator flashovers requires mathematical models. Dynamic models are more appropriate than static models in terms of the instantaneous variation of arc parameters. In this dissertation, a dynamic model including conditions for arc dynamics, arc re-ignition and arc motion with AC supply is first developed. For an AC power source, it is important to consider the equivalent shunt capacitance in addition to the short circuit current when evaluating pollution test results. By including the power source in dynamic models, the effects of source parameters on the leakage current waveform, the voltage drop and the flashover voltage were systematically investigated. It has been observed that for the same insulator under the same pollution level, there is a large difference among these flashover performances in high voltage laboratories and real power systems. Source strength is believed to be responsible for this discrepancy. Investigations of test source strength were conducted in this work in order to study its impact on different types of insulators with a variety of geometries. Traditional deterministic models which have been developed so far can only predict whether an insulator would flashover or withstand. In practice, insulator flashover is a statistical process, given that both pollution severity and flashover voltage are probabilistic variables. A probability approach to predict the insulator flashover likelihood is presented based on the newly developed dynamic model. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2016

During the last decades, K. pneumoniae has emerged as one of the most clinically significant pathogens, especially due to the high prevalence of strains producing extended spectrum β-lactamases (ESBL) and carbapenemases. The therapeutic options to treat these infections are constrained not only by this enzyme production, but also by the regular ability to form biofilms. The development of K. pneumoniae biofilms on the host tissue eventually protect the microorganisms from the action of antimicrobial agents and from the immune response, apart from driving the expression of virulence factors. Thus, the aim of this study was to detect mechanisms of resistance, adhesive properties and ability of multi-resistant K. pneumoniae clinical isolates to form biofilms. In the first stage of the study, 33 strains of K. pneumoniae with reduced susceptibility to carbapenems were isolated. By using phenotypic tests, 10 samples positive for the modified Hodge test were detected, suggesting the production of carbapenemases, and 2 strains manifested positivity for the synergic test with boronic acid, suggesting the production of KPC. When employing molecular techniques, such as polymerase chain reaction, the gene blaKPC was not detected, characterizing failure on the phenotypic detection of KPC. In the second stage of the study, 14 strains of multi-resistant K. pneumoniae were analyzed in order to verify the ability of biofilm formation, as well as adhesive/aggregative properties. Most of the strains analyzed presented low affinity to p-xylene, suggesting hydrophilic character, aside from strong affinity to the basic solvent ethyl acetate indicating acidic surface characteristics. It was also verified that the strains studied manifested high ability of biofilm formation and important adhesion in epithelial cells. The combination of all the characteristics studied may contribute to the survival of K. pneumoniae in the host and in the environment, as the organization of microorganisms in biofilms complicates the pharmacological treatment and favors its spread and multi-resistance. / Durante as últimas décadas, a Klebsiella pneumoniae tem emergido como um dos patógenos mais importantes clinicamente, especialmente em função da alta prevalência de amostras produtoras de beta-lactamases de espectro estendido (ESBL) e carbapenemases. As opções terapêuticas para o tratamento destas infecções são limitadas não somente por esta produção enzimática, mas também pela frequente capacidade de formação de biofilmes. O estabelecimento de biofilmes de K. pneumoniae sobre tecidos do hospedeiro acaba por proteger os microrganismos da ação de agentes antimicrobianos e da resposta imunológica, além de conduzir a expressão de determinantes de virulência. Neste sentido, o objetivo deste trabalho foi detectar mecanismos de resistência, propriedades adesivas e capacidade de formação de biofilmes de isolados clínicos de K. pneumoniae multirresistentes. Na primeira fase deste estudo, foram isoladas 33 isolados clínicos de K. pneumoniae com perfil de sensibilidade reduzida aos carbapenêmicos. Através de testes fenotípicos foram detectadas 10 amostras que apresentaram positividade para o teste modificado de Hodge (MHT) sugerindo produção de carbapenemases e duas amostras que apresentaram positividade para o teste sinérgico com ácido borônico (AB), indicando produção de KPC (Klebsiella pneumoniae carbapenemase). Quando utilizado ferramentas moleculares, como a reação em cadeia da polymerase, não foi detectado o gene blaKPC, caracterizando desta forma uma falha na detecção fenotípica de KPC. Na segunda fase deste estudo, foram analisadas 14 amostras de K. pneumoniae multirresistentes a fim de verificar a capacidade de formação de biofilmes, bem como propriedades adesivas/agregativas. A maioria das isolados clínicos analisadas apresentaram baixa afinidade ao xileno, sugerindo um caráter hidrofílico, além de alta afinidade ao solvente básico acetato de etila indicando características superficiais ácidas. Foi verificado ainda que os isolados clínicos estudados apresentaram alta capacidade de formação de biofilme e importante adesão em células epiteliais. As combinações de todas estas características estudadas podem contribuir para a sobrevivência de K. pneumoniae no hospedeiro e no ambiente, pois a organização dos microrganismos em biofilme dificulta o tratamento farmacológico e favorece a sua disseminação e multirresistência.

A produção de filmes biodegradáveis à base de amido representa um desafio tecnológico, pois estas matrizes são altamente sensíveis à água. Neste sentido, as pesquisas estão sendo realizadas a fim de melhorar as caraterísticas de hidrofobicidade sem afetar a integridade estrutural das matrizes. Dentre os compostos comumente empregados para melhorar as características de filmes biodegradáveis, pode-se mencionar os óleos e ácidos graxos. O óleo de sementes de melancia apresenta alto potencial de aplicação em matrizes filmogênicas, pois além da possibilidade de melhorar as propriedades de barreira, apresenta compostos fitoquímicos com atividade antioxidante, que podem conferir um caráter ativo aos materiais produzidos. Neste contexto, o objetivo deste trabalho foi desenvolver e caracterizar filmes à base de amido modificado de mandioca e óleo de sementes de melancia. O óleo de sementes de melancia foi extraído por batelada com etanol pressurizado, sob diferentes temperaturas de extração (40, 60 e 80°C) e diferentes comprimentos de leito de extração (L1 = 4,2 cm, L2 = 9,8 cm e L3 = 15,8 cm). A cinética de extração foi matematicamente descrita utilizando-se o modelo de Peleg e os óleos caraterizados quanto à atividade antioxidante. Posteriormente foram testados quatro amidos modificados de mandioca (amido reticulado, AR; amido acetilado, AA; amido não modificado, ANM e amido duplamente modificado, AAR) com a finalidade de selecionar o que apresentasse melhores caraterísticas na produção de filmes quanto ao caráter hidrofóbico. Os filmes foram produzidos pela técnica de casting, utilizando - se concentrações fixas de amido e sorbitol (4 e 1,2 g/100g de solução filmogênica, respectivamente). O caráter hidrofóbico das matrizes foi avaliado pela determinação da solubilidade, grau de inchamento, permeabilidade ao vapor de água e ângulo de contato. Adicionalmente, foram produzidas emulsões através da técnica de Pickering, com diferentes concentrações de óleo e amido e caraterizadas quanto à estabilidade, tamanho de partículas e polidispersidade. A emulsão com maior estabilidade foi incorporada na formulação de filmes à base de AR em concentrações de 0 a 0,5 g de óleo na emulsão/100 g de solução filmogênica. Todos os filmes foram caracterizados quanto às propriedades mecânicas, microscopia, espectroscopia de infravermelho (FTIR), difração de raios X, cor, solubilidade, inchamento, permeabilidade ao vapor de água e ângulo de contato. Os resultados da extração de óleos mostraram rendimentos superiores sob temperaturas de 80°C e melhor atividade antioxidante a 60°C. O modelo de Peleg apresentou um bom ajuste, observando-se coeficientes de correlação altos (R2 > 0,90). A caraterização dos filmes produzidos com diferentes amidos modificados mostrou que o AR formou matrizes com maior ângulo de contato, menor grau de inchamento e maior resistência mecânica. As emulsões com maior de estabilidade foram produzidas com altas concentrações de óleo e amido (15 e 12 g/100 g de emulsão, respectivamente). Os filmes produzidos com incorporação de óleo na forma de emulsão Pickering apresentaram caráter mais hidrofóbico, sendo também alteradas as caraterísticas estruturais com o aumento da concentração de óleo. Os filmes produzidos com a incorporação de óleo em forma de emulsão apresentaram conteúdos de fenólicos totais de 0,19 a 5,68 mg equivalente de ácido gálico/100g de filmes. No entanto, os filmes não apresentaram atividade antioxidante frente ao radical DPPH•. / The production of biodegradable films based on starch represents a technological challenge because these matrices are highly sensitive to water. In this sense, the research is being carried out in order to improve the characteristics of hydrophobicity without affecting the structural integrity of the matrices. Among the compounds commonly used to improve the characteristics of biodegradable films, the oils and fatty acids can be highlighted. The oil of the watermelon seeds presents high potential of application in filmogenic matrices because in addition to the possibility of improving the barrier properties, it presents phytochemical compounds with antioxidant activity, which can impart an active characteristic to the produced materials. In this context, the objective of this work was to develop and characterize films based on modified cassava starch and watermelon oil. The watermelon oil was extracted in batches with pressurized ethanol under different extraction temperatures (40, 60, and 80°C) and different extraction bed lengths (L1 = 4.2 cm, L2 = 9.8 cm, and L3 = 15.8 cm). The kinetics of extraction were mathematically described using the Peleg model and the oils characterized for antioxidant activity. Four modified starches of cassava (reticulated starch, AR, acetylated starch, AA, unmodified starch, ANM, and doubly modified starch, AAR) were then tested in order to select the material with the best hydrophobic characteristics. The films were produced by the casting technique, using fixed concentrations of starch and sorbitol (4 and 1.2 g/100 g of film-forming solution, respectively). The hydrophobic characteristic of the matrices was evaluated by determining the solubility, degree of swelling, permeability to water vapor, and contact angle. In addition, emulsions were produced using the Pickering technique with different concentrations of oil and starch and then, characterized for stability, particle size, and polydispersity. The results of the extraction showed higher yields under temperatures of 80°C and better antioxidant activity at 60°C. The Peleg model presented a good fit, observing high correlation coefficients (R2> 0.90). The characterization of the films produced with different modified starches showed that AR formed matrices with higher contact angle, lower degree of swelling, and higher mechanical resistance. Emulsions with the highest degree of stability were produced with high concentrations of oil and starch (15 and 12 g/100 g of emulsion, respectively). The films produced with oil incorporation in the form of Pickering emulsion presented a more hydrophobic characteristic, and the structural characteristics were also altered with the increase of oil concentration. The films produced with the incorporation of oil in emulsion form presented total phenolic contents of 0.19 to 5.68 mg of gallic acid equivalent/100 g of films. However, the films did not present antioxidant activity against the DPPH• radical.