IsaMill is a stirred type mill used in mineral industry for fine and ultra-fine grinding. The difficulty in obtaining the internal flow information in the mill by experimental techniques has prevented the development of the fundamental understanding of the flow and generating general methods for reliable scale-up and optimized design and control parameters. This difficulty can be effectively overcome by numerical simulation based on discrete element method (DEM). In this work a DEM model was developed to study particle flow in a simplified IsaMill. The DEM model was validated by comparing the simulated results of the flow pattern, mixing pattern and power draw with those measured from a same scale lab mill. Spatial distributions of microdynamic variables related to flow and force structure such as local porosity, particle interaction forces, collision velocity and collision frequency have been analyzed. Among the materials properties of particles, it is shown that by decreasing particle/particle sliding friction coefficient, the particle flow becomes more vigorous which is useful to grinding performance. Restitution coefficient does not affect the particle flow significantly. A too low or too high particle density could decrease grinding efficiency. Although grinding medium size affects the flow, its selection may depend on the particle size of the products. Among the operational variables considered, the results show that fill volume and mill speed proved to be important factors in IsaMil process. Increase of fill volume or mill speed increases the interaction between particles and agitating discs which results in a more vigorous motion of the particles. Among the mill properties, particle/stirrer sliding friction plays a major role in energy transfer from stirrer to particles. Although there exists a minimum collision energy as particle/stirrer sliding friction increases, large particle/stirrer sliding friction may improve grinding performance as it has both large collision frequency and collision energy. However, that improvement is only up to a critical particle/disc sliding friction beyond which only input energy increases with little improvement on collision frequency and collision energy. Reducing the distance between stirrers or increasing the size of disc holes improves high energy transfer from discs to particles, leading to high collision frequency and collision energy. Among the different stirrer types, the energy transfer is more effective when disc holes are present. Pin stirrer shows increased collision energy and collision frequency which also result in a high power draw. Using the DEM results, a wear model has been developed to predict the wear pattern of the discs. This model can be used to predict the evolution of the disc wear with the time. It is shown that energy transfer from discs to particles are increased when discs are worn out. An attempt has also been made to analyze the microdynamic properties of the mill for different sizes. It is shown that specific power consumption and impact energy are correlated regardless of the mill size and mill speed.

IsaMill is a stirred type mill used in mineral industry for fine and ultra-fine grinding. The difficulty in obtaining the internal flow information in the mill by experimental techniques has prevented the development of the fundamental understanding of the flow and generating general methods for reliable scale-up and optimized design and control parameters. This difficulty can be effectively overcome by numerical simulation based on discrete element method (DEM). In this work a DEM model was developed to study particle flow in a simplified IsaMill. The DEM model was validated by comparing the simulated results of the flow pattern, mixing pattern and power draw with those measured from a same scale lab mill. Spatial distributions of microdynamic variables related to flow and force structure such as local porosity, particle interaction forces, collision velocity and collision frequency have been analyzed. Among the materials properties of particles, it is shown that by decreasing particle/particle sliding friction coefficient, the particle flow becomes more vigorous which is useful to grinding performance. Restitution coefficient does not affect the particle flow significantly. A too low or too high particle density could decrease grinding efficiency. Although grinding medium size affects the flow, its selection may depend on the particle size of the products. Among the operational variables considered, the results show that fill volume and mill speed proved to be important factors in IsaMil process. Increase of fill volume or mill speed increases the interaction between particles and agitating discs which results in a more vigorous motion of the particles. Among the mill properties, particle/stirrer sliding friction plays a major role in energy transfer from stirrer to particles. Although there exists a minimum collision energy as particle/stirrer sliding friction increases, large particle/stirrer sliding friction may improve grinding performance as it has both large collision frequency and collision energy. However, that improvement is only up to a critical particle/disc sliding friction beyond which only input energy increases with little improvement on collision frequency and collision energy. Reducing the distance between stirrers or increasing the size of disc holes improves high energy transfer from discs to particles, leading to high collision frequency and collision energy. Among the different stirrer types, the energy transfer is more effective when disc holes are present. Pin stirrer shows increased collision energy and collision frequency which also result in a high power draw. Using the DEM results, a wear model has been developed to predict the wear pattern of the discs. This model can be used to predict the evolution of the disc wear with the time. It is shown that energy transfer from discs to particles are increased when discs are worn out. An attempt has also been made to analyze the microdynamic properties of the mill for different sizes. It is shown that specific power consumption and impact energy are correlated regardless of the mill size and mill speed.

abstract: Gene manipulation techniques, such as RNA interference (RNAi), offer a powerful method for elucidating gene function and discovery of novel therapeutic targets in a high-throughput fashion. In addition, RNAi is rapidly being adopted for treatment of neurological disorders, such as Alzheimer's disease (AD), Parkinson's disease, etc. However, a major challenge in both of the aforementioned applications is the efficient delivery of siRNA molecules, plasmids or transcription factors to primary cells such as neurons. A majority of the current non-viral techniques, including chemical transfection, bulk electroporation and sonoporation fail to deliver with adequate efficiencies and the required spatial and temporal control. In this study, a novel optically transparent biochip is presented that can (a) transfect populations of primary and secondary cells in 2D culture (b) readily scale to realize high-throughput transfections using microscale electroporation and (c) transfect targeted cells in culture with spatial and temporal control. In this study, delivery of genetic payloads of different sizes and molecular characteristics, such as GFP plasmids and siRNA molecules, to precisely targeted locations in primary hippocampal and HeLa cell cultures is demonstrated. In addition to spatio-temporally controlled transfection, the biochip also allowed simultaneous assessment of a) electrical activity of neurons, b) specific proteins using fluorescent immunohistochemistry, and c) sub-cellular structures. Functional silencing of GAPDH in HeLa cells using siRNA demonstrated a 52% reduction in the GAPDH levels. In situ assessment of actin filaments post electroporation indicated a sustained disruption in actin filaments in electroporated cells for up to two hours. Assessment of neural spike activity pre- and post-electroporation indicated a varying response to electroporation. The microarray based nature of the biochip enables multiple independent experiments on the same culture, thereby decreasing culture-to-culture variability, increasing experimental throughput and allowing cell-cell interaction studies. Further development of this technology will provide a cost-effective platform for performing high-throughput genetic screens. / Dissertation/Thesis / Ph.D. Bioengineering 2012

This dissertation examines how Sikh women who survived the anti-Sikh massacre in 1984 in Delhi, India, cope with the long-term legacies of violence and trauma amid the backdrop of the urban space of the city. After the assassination of then Prime Minister Indira Gandhi by her Sikh bodyguards, approximately thirty-five hundred Sikh men were killed in October and November 1984. Many of the survivors, Sikh widows and their families, were relocated shortly after to the “Widow Colony,” a designated slum also known as Tilak Vihar, within the boundary of Tilak Nagar in West Delhi, as a means of rehabilitation and compensation. The work arises from fieldwork carried out between December 2012 and March 2014. I begin by discussing in depth the space of the Widow Colony and its relation to the rest of the city of Delhi. I then analyze the events of the 1984 massacre through the narratives of Sikh widows and how they remember their experiences of violence. I discuss how violence can have long-term ramifications for everyday life in arenas such as kinship networks, economic stability, health and wellness, and social life. These experiences are further amplified by gender, caste, and class. I also examine the impact of the stigma of widowhood in this community. This research seeks to interrogate how memories of violence inform, and are constituted by, embodied, affective practices carried out in a gendered space produced by the state. I argue that Sikh widows cope with long-term trauma by creating new forms of sociality and memory through their everyday lives and religious practices in the Widow Colony. The memory of the 1984 violence figures heavily among the Sikh diaspora. Thus, I also explore the relationship between the Widow Colony and Sikhs in the transnational arena. / Arts, Faculty of / Anthropology, Department of / Graduate

Spore forming organisms are a health threat to humans and other animals in part due to a remarkable resistance to UV irradiation. This resistance results from two events: first, the formation of a unique thymine dimer, 5-thyminyl-5,6-dihydrothymine (spore photoproduct, or SP) upon UV irradiation; and more importantly, the rapid and specific repair of this DNA photoproduct to two thymines by spore photoproduct lyase (SP lyase). Understanding the molecular basis of this radical-mediated DNA repair will ultimately allow for a better understanding of how to address the health risks caused by spore forming bacteria. SP lyase requires S-adenosyl-L-methionine and a [4Fe-4S]¹+/²+ cluster to perform its catalysis. Presented in this work is a characterization of Clostridium acetobutylicm SP lyase and its ability to repair stereochemically defined dinucleoside and dinucleotide synthetic substrates. Careful synthesis and characterization followed by assays monitored by HPLC indicate SP lyase repairs only the 5R isomer of SP with an activity of 0.4 nmol/min/mg (dinucleoside substrate) and 7.1 nmol/min/mg (dinucleotide substrate). These results support the longstanding theory of SP formation by dimerization of adjacent thymines in double-helical DNA. Kinetic and mechanistic studies were pursued to further elucidate the mechanism of SP repair. Upon pre-reducing SP lyase, the specific activity increased nearly 4-fold to 1.29 μmol/min/mg. Mechanistic studies utilizing [C-6-³H] SP DNA as the substrate revealed a primary tritium kinetic isotope effect of 16.1, indicating a rate determining step during the repair reaction. These results suggest nonstereospecific SP formation regarding the C-6 position and subsequent stereospecific abstraction of the C-6 H atom by SP lyase. Mossbauer and Fe/S K-edge X-ray absorption studies of anaerobically prepared SP lyase aided in further characterization of the [4Fe-4S] cluster and its interaction with SAM. The Fe K-edge EXAFS provide evidence for a slight cluster distortion upon interacting with SAM as a new spectral feature indicative of longer Fe-Fe distances is observed. The Fe K-edge XANES provide further support that SAM is not undergoing reductive cleavage in the presence of reduced SP lyase. Our XAS studies may provide new insights into the mechanism by which radical SAM enzymes initiate their diverse catalysis. 'Co-authored by Tilak Chandra, Egidijus Zilinskas, Eric M. Shepard, William E. Broderick, Joan B. Broderick, Shourjo Ghose, Jeffrey M. Buis, David J. Gardenghi, BoiHanh Huynh, and Robert K. Szilagyi.'

This study investigated the financial sustainability of electricity Mini-grids in Uganda. The challenges of sustainability of Mini-grids were recognised by Tenenbaum Bernard, Greacen Chris, Siyambalapitiya Tilak (2014) as well as Payen, Bordeleau and Young (2016), with a focus on developing countries, particularly in Asia. There is, however, no literature that was found on similar challenges in Uganda. The specific objectives of this study were to examine the profitability, liquidity, efficiency and operational sustainability of Mini-grids in Uganda. The study focused on four Mini-grids as case studies: Ferdsult Engineering Services Limited (FESL), Bundibugyo Energy Cooperative Society (BECS), Kilembe Investments Limited (KIL) and West Nile Rural Electrification Company (WENRECO). The research objective was addressed by analysing audited financial reports for the respective Mini-grids from 2010 to 2015 and other operational information published by the electricity regulator. The study established that Mini-grids in Uganda were not financially sustainable despite having steady growth in sales revenue and customer numbers. The main factors that affected the sustainability of Mini-grids include a higher growth rate in operational and maintenance costs compared to the sales revenue. In addition, operational efficiency challenges were observed, including energy losses, imprudent financial management practices and poor liquidity. These shortfalls consequently showed that the Mini-grids are not financially sustainable. Despite the fact that Mini-grids are not financially sustainable in Uganda, their benefits go beyond electricity provision. The other benefits of Mini-grids are socio-economic in nature, including support for health services and enhancement of economic activities and the livelihoods of the poor. The socio-economic benefits from access to electricity in these rural areas may far outweigh the financial limitations observed. It is therefore important that Mini-grids continue to get the necessary support until such a time as they become sustainable. It is recommended that the Government of Uganda should provide financial and operational support through subsidies or other support systems to ensure continuity of the Mini-grids and, ultimately, their financial sustainability in the medium term in order to enhance access to electricity and the knock- on benefits that come with this access. In this regard, governance and technical skills enhancement remain key in order for these -grids to move forward. Further research should establish the optimal size and internal operational parameters that will ensure the sustainability of the Mini-grids, the amount of government subsidy required and the time it would prudently take to attain sustainability.