No description available.

<p>Microscale environments provide significant resolution and distortion challenges with respect to measurement techniques; however, with improvements to existing techniques, it is possible to gather relevant data to better understand the thermal and fluidic mechanisms at such small scales in evaporating droplets.</p> <p> </p> <p>Infrared thermography provides several unique challenges at small scales. A primary issue is that the low native resolution of traditional infrared cameras significantly hamper the collection of details of microscale features. Furthermore, surfaces exhibiting vastly different emissivities, results in inaccurate temperature measurements that can only be corrected with irradiance-based emissivity maps of the surface; however, due to the resolution limitations of infrared thermography, these emissivity maps can also display significant errors. These issues are overcome through the use of multi-frame super-resolution. The enhanced resolution allows for better capture of microscale features, therefore, enhancing the emissivity map. A quantitative error analysis of the system is conducted to quantify the feature size resolution improvement as well as the smoothing effect of super-resolution reconstruction. Furthermore, a sensitivity analysis is conducted to quantify the impact of registration uncertainty on the accuracy of the reconstruction. Finally, the improved emissivity map from super-resolution is demonstrated to show the increased accuracy over low-resolution mapping.</p> <p> </p> <p>When applied to water droplets, particularly on nonwetting surfaces, infrared thermography is confounded by the presence of nonuniform reflectivities due to the spherical curvature of the liquid-air interface. Thus, when measuring the temperature along the vertical axis of a water droplet, it is necessary to correct the reflection. Using a controlled background environment, in conjunction with the Fresnel equations, it is possible to correct the reflective effects on the interface and calculate the actual temperature profile. This allows for a better understanding of the governing mechanisms that determine the thermal transport within the droplet. While thermal conduction is the primary transport mechanism along the vertical axis of the droplet, it is determined that the temperature drop is partially dampened by the convective transport from the ambient air to the liquid interface. From this understanding revealed by the measurements, the vapor-diffusion-based model for evaporation was enhanced to better predict evaporation rates.</p> <p> </p> <p>Further exploration into the mechanisms behind droplet evaporation on nonwetting surfaces requires accurate knowledge of the internal flow behavior. In addition, the influence of the working fluid can have a significant impact on the governing mechanisms driving the flow and the magnitude of the flowrate. While water droplet evaporation has been shown to be governed by buoyancy-driven convection on nonwetting substrates, similar studies on organic liquid droplets are lacking. Particle image velocimetry is effective at generating a velocity flow field, but droplets introduce distortion due to the refraction from the spherical interface of the droplet. As such, velocity correction using a ray-tracing approach was conducted to correct the velocity magnitudes and direction. With the velocity measurements, the flow was determined to be surface-tension-driven and showed speeds that are an order of magnitude higher than those seen in buoyancy-driven flow in water droplets. This resulted in the discovery that advection plays a significant role in the transport within the droplet. As such, the vapor-diffusion-governed evaporation model was adjusted to show a dramatic improvement at predicting the temperature gradient along the vertical axis of the droplet.</p> <p> </p> <p>Armed with the knowledge of flow behavior inside droplets, it is expected that droplets with aqueous solutions should exhibit buoyancy-driven convection. The final part of this work, therefore, leverages this phenomenon to enhance mixing during reactions. Colorimetry is a technique that is widely utilized to measure the concentration of a desired sample within some liquid; the sample reacts with a reagent dye the color change is measured, usually through absorbance measurements. In particular, the Bradford assay is used to measure protein concentration by reacting the protein to a Coomassie^TM Brilliant Blue G-250. The absorbance of the dye increases, most significantly at the 590 nm wavelength, allowing for precise quantitation of the amount of protein in the solution. A droplet-based reaction chamber with buoyancy-enhanced mixing has the potential to speed up the measurement process by removing the need for a separate pre-mixing step. Furthermore, the reduced volume makes the process more efficient in terms of reactant usage. Experimental results of premixed solutions of protein sample and reagent dye show that the absorbance measurement through a droplet tracks strongly with the protein concentration. When the protein sample and dye reagent are mixed <i>in situ</i>, the complex interaction between the reactants, the mixing, and the adsorption of protein onto the substrate creates a unique temporal evolution in the measured absorbance of the droplet. The characteristic peaks and valleys of this evolution track strongly with concentration and provide the framework for measurement of concentration in a droplet-based system.</p> <p> </p> <p>This thesis extends knowledge about droplet thermal and fluidic behavior through enhanced measurement techniques. This knowledge is then leveraged in a novel application to create a simple, buoyancy-driven colorimetric reaction setup. Overall, this study contributes to the field of miniaturized, efficient reaction and measurement devices.</p>

Ces travaux ont pour contexte de participer à l’optimisation les cycles de décontamination des salles propres en utilisant un nouveau système de décontamination. Le principe de ce système est de décontaminer un volume par condensation de vapeur de peroxyde d’hydrogène sur toutes les parois intérieures du volume. Différents modèles de condensation et d’évaporation pariétaux ont été étudiés, développés et implémentés dans un code CFD, en incluant des modèles simples ainsi que des modèles plus complexes prenant en compte la forme de la phase liquide pariétale. En parallèle, afin de valider les modèles, un dispositif expérimental d’isolateur pour la décontamination a été utilisé afin de créer une base de données expérimentale de condensation de vapeur. Enfin, la validation de ce modèle numérique a été réalisée en comparant les résultats numériques fournis par le modèle développé dans une reproduction numérique de l’isolateur expérimental avec les résultats des expérimentations. / The context of this work is to contribute to the optimization of clean room decontamination cycles by using a new decontamination system. The concept of this system is to decontaminate a volume by condensing hydrogen peroxide vapour on all the inner walls of the volume. Different models of wall condensation and evaporation have been studied, developed and implemented in a CFD code, including simple models as well as more complex models taking into account the shape of the liquid phase at the wall. In parallel, in order to validate the models, an experimental isolator device for decontamination was used to create an experimental steam condensation database. Finally, the validation of this numerical model was carried out by comparing the numerical results provided by the model developed in a digital reproduction of the experimental isolator with the results of the experiments.

As fosfolipases A2 secretadas (sFLA2) de veneno de serpente apresentam homologia estrutural e funcional com as sFLA2s do GIIA de mamíferos, cujos níveis estão elevados em doenças inflamatórias, como a aterosclerose. Nesta doença, as células de músculo liso vascular (CMLVs) acumulam corpúsculos lipídicos (CLs) e se diferenciam em células espumosas. Porém, o papel das sFLA2s neste fenômeno não é conhecido. Neste estudo foram avaliados os efeitos das FLA2 MT-III, cataliticamente ativa, e da BthTx-II, sem atividade catalítica, em CMLVs, com ênfase na formação de CLs e a participação de fatores da homeostasia lipídica. Os resultados obtidos demonstraram que a MT-III e a BthTx-II induziram a formação de CMLVs espumosas. Para tanto, estas enzimas recrutaram diferentes fatores envolvidos na síntese e acúmulo de lipídios. Nesta condição, os CLs constituem um local de síntese de prostaglandinas. Ainda, a MT-III induziu a diferenciação de CMLVs para fenótipo e função de macrófagos. A atividade catalítica não é relevante para a formação de CLs induzida por FLA2s. / Bothrops snake venom secreted phospholipases A2 (sPLA2s) share structural and functional features with mammalian GIIA sPLA2s, which are highly expressed during inflammatory diseases, such as atherosclerosis. In this disease, vascular smooth muscle cells (VSMCs) are loaded with lipid droplets (LDs) differentiating into foam cells. However, the role of these enzymes in this process is still unknown. In this study the effects of snake venom PLA2s MT-III with catalytic activity and BthTx-II, devoid of catalytic activity in VSMCs, with focus on LDs formation and mechanisms involved were investigated. Results here obtained show that both MT-III and BthTx-II induce formation of foam VSMCs and recruit distinct factors of synthesis and storage of lipids in these cells. In this condition, LDs constitute sites for synthesis of prostaglandins. Moreover, MT-III showed the ability to modulate VSMCs functions, leading them to a phenotipic switch to macrophage-like cells. In addition, the catalytic activity is not relevant to sPLA2-induced LDs formation.

Vitamin D has been connected with increased intramyocellular lipid (IMCL) mitochondrial function in skeletal muscle. It is also shown to prevent lipotoxicity in several tissues, but this has not yet been examined in skeletal muscle. Perilipin 2 (PLIN2), a lipid droplet protein upregulated with vitamin D treatment, is integral to managing IMCL capacity and lipid oxidation in skeletal muscle. Increased lipid storage and oxidation is associated with increased tolerance to a hyperlipidic environment and resistance to lipotoxicity. Therefore, I hypothesized that vitamin D increases β-oxidation and lipid turnover though a PLIN2 mediated mechanism, thereby preventing lipotoxicity. This hypothesis was divided into two specific aims: 1) Characterize the effect of vitamin D and PLIN2 on lipid turnover and β-oxidation in mature myotubes, and 2) Determine the role of vitamin D and PLIN2 in regulating key markers of lipotoxicity. To address these aims, cells were treated with or without vitamin D, palmitate, and PLIN2 siRNA in an eight group, 2x2x2 design. Key experiments included quantitative real time polymerase chain reaction for markers of lipid accumulation, lipolysis, and lipotoxicity; Seahorse oxygen consumption assay; 14C-palmitate oxidation assay; and analyses of lipid accumulation and profile. Failure of the palmitate treatment to produce a reliable model for lipotoxicity resulted in negative data for Aim 2 of this dissertation and a focus on vitamin D and PLIN2 knockdown treatments as a four group, 2x2 model. Aim 1 showed that vitamin D reliably increases markers of lipolysis and lipid accumulation. Most of these markers were in turn decreased after PLIN2 knockdown, and DGAT2 exhibited an interaction effect between the two treatments. Contrary to our hypothesis and some published research, PLIN2 knockdown did not prevent lipid accumulation. Vitamin D increased oxygen consumption, especially consumption driven by mitochondrial complex II. PLIN2 knockdown decreased oxygen consumption and demonstrated an interaction effect specific to mitochondrial complex II. Data in this dissertation show that vitamin D increases mitochondrial function, and these effects are at least in part accomplished through a PLIN2 mediated mechanism. However, this work lacks the data required to make specific claims regarding β-oxidation and lipid turnover. This research is some of the first to show that PLIN2 knockdown carries negative impacts for skeletal muscle mitochondria and makes valuable contributions to general knowledge of how vitamin D and lipid storage impact muscle health and function. This ultimately provides additional evidence to advocate for vitamin D supplementation as a means of improving musculoskeletal health and function. Future research should investigate how vitamin D and PLIN2 impact markers of lipotoxicity in skeletal muscle.

In this thesis investigations are carried out on two research topics in context to spray drying. The first research topic is the production of dried particles having uniform characteristics. The second research topic is the development of new applications of the reaction engineering approach which, in recent times, has emerged as an effective tool to formulate drying kinetics models. The reaction engineering approach is also implemented to simulate the drying of monodisperse droplets corresponding to the experimental work in the first research topic. Manufacturing micron- and nano-sized particles having uniform characteristics has recently become a popular research area due to the unique functionalities of these kinds of particles in biomedical, drug delivery, functional foods, nutraceuticals, cosmetics and other valuable applications. Spray drying has been a common and economical route to produce dried particles. A typical characteristic of spray dried products is the existence of a significant variation in particle properties such as size and morphology. One possible idea to restrict this product non-uniformity is to achieve a good control over the droplet’s behaviour and characteristics inside the drying chamber. The current thesis has investigated an innovative spray drying technique, i.e. a single stream drying approach in order to restrict product non-uniformity. In this drying approach, identical sized droplets having vertical trajectories are dried under controlled gas flow conditions. The piezoelectricity-driven monodisperse droplet generator is used as the atomizer to disperse liquid droplets. A prototype single stream dryer was assembled based on the single stream drying approach using various components designed in the laboratory and several parts purchased from the market. Experiments were carried out using aqueous lactose solutions as a model system in order to check the practicability of manufacturing uniform-sized spherical particles. Preliminary results were found to be positive and reported in this thesis. Mathematical models on the drying of monodisperse droplets were developed in order to predict important droplet and gas parameter profiles during single stream drying. These models serve as a platform for design, optimization and scale-up purposes. Several important advantages and drawbacks of single stream drying are also reported. Problems encountered during the experimental work and future recommendations are presented in detail so that a more robust and effective drying research tool can be developed in future. Recently the reaction engineering approach (REA) has emerged as a simple and reliable technique to characterize the drying of various food and dairy materials. In this thesis two new applications of the REA are described for the first time in context to convective drying of aqueous droplets. The REA is used in this study to formulate the drying kinetics model for the drying of aqueous sucrose and maltodextrin (DE6) droplets. The effect of initial moisture content was explicitly demonstrated. The development of a new ‘composite’ REA which aimed to model the drying of aqueous droplets containing multiple solutes has been described. The composite REA was found to be suitable to characterize the drying behaviour of aqueous sucrose-maltodextrin mixtures of different proportions. The second new application of the REA is the development of a procedure to estimate surface properties of aqueous droplets during drying. In literature various droplet characteristics such as surface moisture contents were normally estimated using the diffusion-based drying kinetics model or the receding interface model. Surface moisture content and surface glass transition temperature profiles were evaluated here using a lumped-parameter model (REA) during the drying of aqueous sucrose, maltodextrin (DE6) and their mixtures. The same experimental data used for the development of the composite REA were used to yield predictions. The procedure was found to be useful in estimating surface moisture contents and understanding the stickiness behaviour of sugar droplets during drying. During the formulation of the REA-based drying kinetics model in this thesis, the assumption of uniform temperature within droplets was used. In most studies published in literature the uniform temperature assumption was justified by calculating the heat-transfer Biot numbers at the beginning and end of drying. However, the conventional Biot number concept does not take into account the evaporation effect and therefore would not be suitable to drying scenarios. In this thesis, a new approximation procedure is developed to estimate surface-centre temperature differences within materials following the entire drying process. This new procedure was helpful to check the extent of temperature non-uniformity within skim milk droplets under isothermal laboratory conditions as well as industrial spray drying conditions. Both conventional and drying-based Biot numbers are calculated and compared. Predictions showed that temperature gradients within the droplets were negligible during the drying of suspended droplets under laboratory drying conditions (slow drying), whilst the gradients were small and existed only for a short drying period for small droplets under industrial spray drying conditions (fast drying). Furthermore, it was observed that the maximum temperature gradient within the droplets did not exist at the starting or end points of the drying process, and therefore the estimation of Biot numbers at the starting and end point does not reflect temperature non-uniformity under drying conditions. This is a significant theoretical development in the area.

This thesis examines the particle capture, fibre wetting and droplet flow processes within wet filters collecting solid and liquid aerosols and within filters collecting only liquid aerosols. The processes involved in this type of filtration were examined through a series of experiments and models developed to describe the behaviour of fibre/liquid systems. This work can be summarized in 4 categories: (1) The bounce and immediate re-entrainment of liquid and solid monodisperse aerosols under a stable filtration regime (pre cake formation) by wet and dry fibrous filters. In this work it was found that the solid particles generally exhibited a lower fractional filtration efficiency than liquid particles (of the same size), although this difference decreased in the smaller size fractions. However, for the wet filtration regime (each fibre of the filter was coated by a film of water), no significant difference in filtration efficiency was detectable between solid and liquid aerosols. Either the bounce effect of the particles is inhibited by the liquid film, or the filtration conditions in the wet filter are so different that the aerosol properties are less significant with respect to capture. (2) A microscopic study of the effect of fibre orientation on the fibre wetting process and flow of liquid droplets along filter fibres when subjected to airflow and gravity forces was conducted. The flow of the liquid collected by the fibres was observed and measured using a specially developed micro-cell, detailed in the thesis. The experimental results were compared to a theoretical model developed to describe the flow of droplets on fibres. The theory and experimental results showed a good agreement. A sensitivity analysis of the model was performed which showed the droplet radius to be the most significant parameter. The model has the potential to improve filter self-cleaning and minimise water use. (3) An experimental study of the capture of solid and liquid (oil) aerosols on fibrous filters wetted with water. Variable quantities of liquid irrigation were used, and the possibility for subsequent fibre regeneration after clogging or drying was also studied. It was found that self-cleaning (removal of solid aerosols by water) occurred even under heavily dust-laden conditions, and post evaporation of water. With the collection of oil aerosols on fibres wetted with water, a predominance of the barrel shaped droplet on the fibre was observed, with oil droplets displacing water droplets (if the oil and fibre combination created a barrel shaped droplet), creating various compound droplets of oil and water not previously reported in literature. (4) An extensive experimental investigation of the wetting processes of fibre/liquid systems during air filtration (when drag and gravitational forces are acting) has shown many important features, including droplet extension, oscillatory motion, and detachment from fibres as airflow velocity increases. The droplet oscillation is believed to be induced by the onset of the transition from laminar to turbulent flow as droplet size increases. To model such oscillation it was necessary to create a new conceptual model to account for the forces both inducing and preventing such oscillation. The agreement between the model and experimental results is satisfactory for both the radial and transverse oscillations.

Nuclear-based hydrogen production via thermochemical water decomposition using a copper-chlorine cycle consists of a series of chemical reactions that split water into hydrogen and oxygen. This is accomplished through reactions involving intermediate copper and chlorine compounds, which act as catalysts that are recycled in the process. In this thesis, analytical and numerical solutions are developed to predict the behaviour of aqueous cupric chloride droplets in a solution undergoing spray-drying in the Cu-Cl cycle. The aqueous CuCl2 is present as a slurry within the cycle, which will later generate oxygen and hydrogen as a net result. The efficiency of the cycle can be increased by utilizing low-grade waste heat from any industrial source or nuclear power plant to assist in the drying process. There are many different methods employed in industry for drying of solutions. Each method has its own advantages and disadvantages, depending on the application and conditions. In this thesis, analytical correlations of heat and mass transfer are developed for the aqueous solution, subject to various drying conditions. The analysis is performed for moist air in contact with a sprayed aqueous solution of CuCl2(2H2O). Validation of the model is performed by comparisons with experimental results obtained from a Niro-spray dryer for CuCl2 and previous experimental and theoretical data for different fluids, on the basis of non-dimensional analysis. / UOIT

This thesis develops analytical and numerical solutions that predict behavior of Cupric-Chloride droplets undergoing spraying and drying processes. Cupric-Chloride (CuCl2) is present as molten salt and slurry within the Copper-Chlorine thermo-chemical cycle for generation of hydrogen. Utilizing low-grade heat from nuclear or industrial sources to assist drying of Cupric-Chloride can increase efficiency of the overall process. Analytical correlations for heat and mass transfer are developed and applied to the analysis of a solution of Cupric-Chloride, subject to various drying conditions. The study provides new information on effects of different concentrations of water in CuCl2 slurry drying at low air temperatures. / UOIT

<p>The <italic>Chlamydiaceae</italic> are Gram-negative, obligate intracellular bacteria that are significant pathogens of humans and animals. Intracellularly, the bacteria reside in a membrane-bound vacuole, called the inclusion, from which they manipulate host processes to create a niche optimal for survival and propagation. Acquisition of host-derived lipids is essential for chlamydial growth, yet the source of lipids and mechanisms of trafficking to the inclusion are not well-established. The inclusion avoids interaction with several classical membrane and lipid transport pathways. In a functional genomic screen to identify host modulating chlamydial proteins, our lab identified cytosolic lipid droplets (LDs) as potential target organelles of <italic>Chlamydia</italic>. LDs are postulated to function in many cellular processes, such as lipid metabolism and transport, membrane trafficking, and cell signaling; therefore, we hypothesized that LDs may be important for <italic>Chlamydia</italic> pathogenesis as a source of lipids or as a platform for regulating other cellular functions. Here, we characterize the interaction between eukaryotic LDs and the chlamydial inclusion.</p><p> We find that LDs are recruited to the <italic>Chlamydia</italic> inclusion, chlamydial infection disrupts neutral lipid homeostasis, and pharmacological prevention of LD formation inhibits chlamydial replication. <italic>Chlamydia</italic> produces proteins (Ldas) that localize with LDs in yeast and mammalian cells when transiently expressed and are exported out of the inclusion to peripheral lipid-rich structures during infection. By electron microscopy and live cell imaging, we observe the translocation of intact LDs into the <italic>Chlamydia</italic> inclusion lumen. Biochemical and microscopic analysis of LDs from infected cells reveals that LD translocation may occur at specialized subregions of the inclusion membrane. The <italic>Chlamydia</italic> Lda3 protein is implicated in LD tethering to the inclusion membrane, and displacement of the protective coat protein, ADRP, from LD surfaces. This phenomenon could provide access for lipases to the LD core for utilization by the replicating bacteria. Additionally, the functional domains of Lda3 involved in binding to LD and inclusion membranes are identified. </p><p> In these studies, we identify eukaryotic lipid droplets (LDs) as a novel target organelle important for <italic>Chlamydia</italic> pathogenesis and describe a unique mechanism of whole organelle sequestration not previously observed for bacterial pathogens. These results represent a fundamental shift in our understanding of host interactions with the chlamydial inclusion, and may represent a new area for research in the field of cellular microbiology.</p> / Dissertation