VictorJuiz/thesis huggingface dataset:
Characteristics of Social Networks Relevant to Predictions of Social Influence

Understanding social influence and identifying influential members of a community is of interest to the designers and evaluators of various online services such as recommender systems in e-commerce or health promotion programs in healthcare. Various methods have been proposed for the identification of influentials in past research. However, there is limited research on the relationships between these different methods and the role of networks' topology on these relationships. The main goals of the research in this thesis were to study relationships between measures of network structure, and to characterize different types of network, where the properties of structural measures differ across the network types. Understanding the structure of social networks should lead to more useful and usable social network applications. In the research reported in this dissertation I began by examining the relationship between structural and behavioral measures of social influence, finding that they are relatively independent of each other in the two social networks that were examined. I then focused on social network centrality measures, which are structural measures commonly used to identify central and potentially influential members of a social network. Two new factors representing network topology properties were identified and a set of 62 real-world social networks were grouped into three different types based on their scores on those factors. Correlations amongst various structural influence measures, and the effect of network topology on structural measures of centrality, were also examined. A secondary goal of this research was to determine when approximations of computationally complex measures may be used to estimate social influence. Using the factors representing network topology, the correlation between the computationally complex measure of betweenness centrality and the computationally simpler measure of ego betweenness was found to vary depending on network topology, opening the way towards network topology-based selection of centrality-based measures of influence. The research findings presented in this thesis are offered as a first step towards improved methods of identifying influential members in very large social networks.

Keywords: centrality measures
ego betweenness
network structure measures
network topology
social networks
Advisor: Chignell, Mark
Contesting Migrant Labour: A Politics of Precarity on the Thai-Myanmar Border

The global proliferation of export processing zones, linking migrant labour to international markets and global supply chains, has established these sites as critical components of contemporary globalised capitalism. As regulatory enclaves of industrial production, export processing zones are marked by forms of population administration organised around the optimisation of low-waged, flexible labour. This dissertation is a study of the social construction of formal and informal labour regulation at one such regulatory enclave. It focuses on the Mae Sot Special Border Economic Zone in northwest Thailand, where some 200,000 plus Myanmar migrants have been engaged in highly precarious employment in garment and textile manufacturing, agriculture, and service work since the early 1990s. While formal state policy significantly impacts the on-the-ground regulation of migrant labour in Mae Sot, the local situation exhibits a variety of overlapping, formal and informal regulatory regimes. These multiple regimes of regulation are subject to continual processes of contestation, negotiation and compromise, with uncertain effects on Mae Sot's border capitalism. In order to trace these processes, I present ethnographic accounts of migrants engagement with various state and private actors, including the Mae Sot police, officials of the Thai government's Labour Protection Office, private passport companies, and non-governmental organisations. I further trace the emergence of migrant social formations, shaped by the particular conditions of low-waged, flexible labour as well as despotic employment practices and coercive policing. The dissertation concludes by following the organisational efforts of a group of migrants employed at one Mae Sot garment factory, as they seek to raise their wages and improve their working conditions over the course of a year. Throughout, I find that migrants' everyday practices and patterns of struggle are shaped both by the site's network of governmental rule and by the disciplinary powers of the local police.

Keywords: Governmentality
Industrialisation
Labour
Migration
Regulation
Advisor: Li, Tania
A Systematic Analysis of Intertwined Homomeric Proteins

Intertwined homomers are multimeric protein complexes, whereby identical subunits appear to exchange small segments or compact protein substructures (domains). Using a formal definition of intertwined homo-oligomers, we survey the Protein Data Bank for all such complexes. Results show that intertwining occurs in 13,442 (24%) of all surveyed structures. This thesis charts the landscape of intertwined proteins by examining their structural properties and classifying them accordingly. We define three primary categories to classify intertwined proteins, based on the structural nature of the exchanged element. S-type intertwined proteins exchange one contiguous chain segment and account for the majority of all intertwined homomers (72%). D-type intertwined proteins (10%) exchange structural domains. M-type intertwined proteins (18%) display complex swapping topologies that exchange multiple segments or domains. The studies presented in this thesis provide unique insights into the role of intertwining in homomeric association. For instance, intertwining promotes homomer formation for all three classes of intertwined proteins, particularly among the S-type class and smaller protein structures. Additionally, we found that intertwining provides some homomeric proteins with the ability to adopt different inter-subunit geometries, with minimal changes in the subunit-subunit interface. These changes in inter-subunit geometry were thoroughly investigated among D-type intertwined homomers and were found to be associated with a number of roles, such as DNA binding and functional regulation.

Keywords: Homomeric Proteins
Intertwined Proteins
Structural Biology
Advisor: Wodak, Shoshana J
Parkinson, John
Mathematical models provide insight into the role of interneurons in hippocampal CA1 network theta rhythm generation

The theta rhythm, a network rhythm oscillating between 3-12 Hz, is one of the most prominent clocking mechanisms detected in the mammalian brain. These rhythms are recorded in the hippocampus during exploratory behaviour and R.E.M. sleep, and are associated with episodic memory and spatial navigation (Buzsรกki, 2002). A "classic" theta model predicts that pacemaker neurons in the medial septum drive the hippocampal rhythm. However, Goutagny et al. (2009) recently showed that the hippocampal formation possesses the necessary and sufficient circuitry to generate its own theta rhythm, implying that different subregions of the hippocampus can perform separate computational tasks simultaneously. Mathematical models have been used to investigate the possibility of independent hippocampal theta generators, but in general rely on a population of pacemaking interneurons to drive the system (Wulff et al., 2009; Rotstein et al., 2005; Tort et al., 2007), a mechanism that may not be physiologically relevant (Kispersky et al., 2012). In an attempt to understand the underlying dynamics of this rhythm, a number of experimentally constrained mathematical network models are developed with a focus on the CA1 hippocampus. We first describe the development of simple models of individual CA1 parvalbumin-positive (PV+) interneurons, oriens-lacunosum-moleculare (OLM) interneurons, and pyramidal cells (PYR), as derived from an intact, whole hippocampus preparation in vitro expressing population oscillations. These single cell models are used to construct thousands of network models, and we investigate the role of these different cell types in CA1 network oscillations. Networks of PV+ interneurons alone exhibited sharp transitions into coherent high frequency firing (> 100 Hz), providing insight into how these fast oscillations could become nested in theta rhythms. We predict that the dis-inhibitory effect of OLM cells on bistratified cell (BSC) to PYR interactions plays a critical role in the power of network theta oscillations. Additionally, our network models demonstrated that without a phasic drive, PYR network models alone could not exhibit coherent oscillations while maintaining sparse firing - a feature of our PYR recordings during theta. However, when PV+ cell networks were incorporated into the PYR networks, PYR sparsely fired, and network frequency and stability was increased. Thus, our experimentally constrained network models suggest that PV+ interneurons play a key role in the frequency and stability of network oscillations, and that OLM-BSC interactions may influence network theta power.

Keywords: Computational Neuroscience
Fast-Spiking Interneurons
Hippocampal Microcircuits
Hippocampal Oscillations
Network Models
Advisor: Skinner, Frances K
Content Management in Planet-Scale Video CDNs

Global video Content Distribution Networks (CDNs) serve a significant fraction of the entire Internet traffic through a global network of cache servers. Effective handling of the massive traffic at the edge is vital for the feasibility of these CDNs, which can otherwise incur significant monetary costs and resource overloads in the Internet. We study this problem from several angles. First, we design cache management algorithms for individual servers of these CDNs: an LRU-based baseline solution to address their unique requirements; a flexible ingress-efficient algorithm; a greedy offline cache aware of future requests to estimate the maximum possible efficiency; and an optimal offline cache (for limited scales). In addition, we study cross-server content management. We analyze how in the absence (impracticality) of cooperative caching, the knowledge of requests in other serving locations can lead to better caching decisions overall and reducing up to hundreds of Gbps of costly traffic. We call this practice cache coordination and design the proper mechanism for realizing it. Based on actual workload data from a large-scale, global video CDN, we first conduct a detailed analysis of the spatial correlation of video popularities---workload similarities---worldwide. We then analyze the effectiveness and feasibility of cache coordination and its scalability: from within a city to across countries. Furthermore, we study the problem of provisioning the right CDN server cluster to deploy in each location, a central problem for today's continuously expanding CDNs. We optimize the proper server count, peering bandwidth, and server configuration as the disk drives and the necessary SSD and/or RAM cache layers to sustain the intensive I/O load. The optimization framework carefully captures the interaction of cache layers inside each server, the interplay between egress/disk capacity and network bandwidth, storage drives' read/write constraints and their costs. Finally, we study the generic problem of large-scale message distribution in networked systems with minimum end-to-end latency. We develop a rich suite of algorithms for different message delivery requirements and application scenarios, with up to 60% reduction in delivery latency and support for several times larger scales compared to existing solutions.

Keywords: Cache coordination
Content distribution network
Overlay multicast
Server provisioning
Video caching
Advisor: Jacobsen, Hans-Arno
Pricing and Hedging of Variable Annuities on Mixed Funds under Levy Processes

Variable annuities (VAs) are deferred annuities whose future benefits are linked to the performance of a portfolio of securities during the deferment period. The VA policyholders can benefit from favorable movements in financial markets and are simultaneously protected against adverse events. As a result, variable annuities have options and option-like features embedded in their contracts. In this thesis, we consider pricing and hedging of such embedded options when the underlying reference portfolio is a mixed fund consisting of a bond index and a stock index. The bond index and the stock index are both assumed to follow exponential Levy processes while the risk-free interest rate is modeled by an Ornstein-Uhlenbeck process. As a key mathematical result, we solve the valuation partial-integro differential equation in semi-analytic closed-form using Fourier transform method. In our numerical illustrations, variance gamma processes are considered and calibrated to financial data and their parameters are estimated under the real world and risk neutral probability measures. The formulae are then used to value the minimal rate of return guarantee when the underlying Levy drivers are variance gamma processes. Our numerical results indicate that the method is fast, accurate and relatively straight-forward to implement. The sensitivities of the fair management fee with respect to different model parameters are also examined. In addition to determining the fair management fee, effective hedging strategies are crucial for insurance companies to prevent potentially large losses. Here, since jump risk and mortality risk result in an incomplete market, the usual dynamic hedging strategies are not applicable. We propose instead to resort to mean variance and local risk minimization hedging. By applying this technique, we are able to obtain semi-analytical closed-form hedging positions when using the mixed fund and an option on the mixed fund to hedge. Our numerical results show the advantage of local risk minimization over delta and delta-gamma hedging methods. Finally three common types of unit-linked life insurance: (i) pure endowment; (ii) term insurance; and (iii) endowment insurance; are used to demonstrate the efficiency of local risk minimization trading strategies.

Keywords: Fourier transform
Levy process
Local risk minimization
Mix funds
Variable annuities
Advisor: Lin, Xiaodong Sheldon
Jaimungal, Sebastian
Anthropogenic Impacts on Multihabitat Species and Applications for Conservation

Anthropogenic impacts are apparent in all ecosystems, threatening the persistence of biodiversity everywhere on Earth. Species' responses to these impacts depend largely on their biology and ecology, and therefore all species are not equally impacted. Species with particular life histories, such as long generation times, specific habitat requirements, small geographic ranges, or poor dispersal potential, are more at risk because they are unable to respond positively in the face of anthropogenic threats. With respect to habitat preferences, the more specific a species' needs, the higher the threat because even a small loss of habitat can lead to local extinctions, meaning that species requiring multiple habitats that are spatially adjacent might be even more at risk of extinction than those that do not. This need for multiple, adjacent habitats, is a common life history strategy, yet how anthropogenic impacts affect these species is currently understudied. Furthermore, the adjacency requirements of these species' habitats are rarely incorporated into conservation tools intended to inform conservation practitioners. To address these gaps in conservation science, in this thesis, I focus on a common group of species that require multiple habitats, Odonata, and investigate the influence of anthropogenic recreation, landuse change, and climate change on their diversity and community composition as larvae and as adults. I then incorporate adjacent habitat requirements into species distribution models and migration simulations. Overall, I find that: (1) anthropogenic impacts from recreation, landuse change, and climate change do affect the diversity and community composition of odonata, generally resulting in reduced diversity of specialist species; (2) adults and larvae respond differently to anthropogenic pressures, likely because they utilize distinct habitats, or the same habitats in different manners; and (3) incorporating adjacent habitats into species distribution models and migration simulations leads to more restrictive, but potentially more realistic, range expansion predictions of one species of Odonata in a fragmented landscape in southern Ontario.

Keywords: aquatic
Climate Change
Conservation
Dragonfly
Ecology
Odonata
Advisor: Fortin, Marie-JosĂŠe
Mathematical Explanation in Science

Inspired by indispensability arguments originating from Quine, mathematical realists such as Alan Baker argue that since mathematics plays a key explanatory role in our best scientific theories, then the very same reasons which convince us to be scientific realists should lead us to be mathematical realists as well. Baker's enhanced indispensability arguments (EIA) makes use of inference to the best explanation (IBE) to deliver the realist conclusion. Mathematical nominalists have resisted this argument by asserting that there is no such thing as a genuine mathematical explanation (GME) where the mathematics is playing an indispensable explanatory role. In this dissertation I will argue that the nominalist is incorrect and that GMEs do, in fact, exist. My methodology will be to develop a set of criteria that clearly defines a GME which the nominalist would gladly accept. From there, a new example of a GME will be advanced that satisfies all of the criteria. To solidify this result, I will show that Strevens' kairetic account of scientific explanation clearly points to mathematics playing an indispensable explanatory role in our supposed examples of GME. While this all bodes well for mathematical realism, I will further argue that the EIA still does not lead to mathematical realism. Baker assumes that using IBE to infer the existence of mathematical objects is unproblematic. I will challenge this assumption, and without IBE the EIA does not deliver. By no means does this result block the realist project. Ultimately, I believe that freeing ourselves from the yoke of traditional indispensability arguments and focussing on how it is that mathematics can explain physical facts explain will advance the realist position even further.

Keywords: Explanation
Indispensability
Inference to the best explanation
Mathematical Explanation
Naturalism
Realism
Advisor: Brown, James R
Geologic Record of Intraplate Seismicity in Southern Ontario

This thesis contributes to an understanding of intracratonic seismicity in eastern North America by presenting geological evidence for past earthquake activity within disturbed rocks and sediments (`seismites') in Southern Ontario. A major impediment to understanding modern day earthquake risk is the limited historic record of earthquake activity (early seventeenth century) and an instrumental record of short duration (typically

Keywords: co-seismic deformation
Intraplate Earthquakes
lake sediments
Precambrian Structures
Seismites
sub bottom profiling
Advisor: Eyles, Nicholas
An Ultrasound Contrast Agent Microbubble in a Microvessel: A Numerical Approach

The blood brain barrier (BBB), a selective barrier separating blood from the parenchyma of the central nervous system, restricts more than 98% of neurotherapeutics from traveling into the brain. Focused ultrasound (FUS) exposure combined with circulating microbubbles is an emerging technique capable of safely opening the BBB locally, transiently, and non-invasively, enabling targeted drug delivery in the brain. However, the mechanisms of the microbubble-vessel interactions central to this process are not fully understood. In this thesis, a comprehensive numerical model of a microbubble within a microvessel was developed aiming to shed light on bubble-vessel interactions, vessel wall mechanical stresses and acoustic emissions during FUS-induced BBB opening. An upward shift in the bubble's resonance frequency relative to unbound bubbles was calculated, whose magnitude was dependent on the vessel elasticity. The synergistic effects of acoustic frequency and vessel elasticity on wall stresses were investigated. Vessel wall stresses were found to be maximal when the bubble was driven above resonance. The numerical model was validated with ex vivo high-speed optical imaging experiments. Resultant amplitudes of bubble oscillation were within 15% of corresponding experimental measurements. Vessel wall stresses calculated during bubble compression (and vascular invagination) were larger than those during bubble expansion, implying that vascular damage could occur during this phase. The acoustic emissions from the ultrasound-stimulated microbubble were calculated, and their correlation with the vessel wall stresses was investigated. The normalized second harmonic decreased as a function of pressure until reaching a minimum, "transition point", after which point it was found to increase. The second and fourth harmonics of confined bubbles at this point were larger than those of unbound bubbles. Above the transition point, stresses induced by larger bubbles increased with a steeper slope. The results presented in this thesis could help in enhancing contrast imaging strategies, understanding bubble-vessel interactions, and optimizing ultrasound pulse parameters to maximize vessel wall stresses to improve drug delivery efficacy. Furthermore, the calculated acoustic emissions could provide feedback to online monitoring techniques and enable calibration of in vivo pressures.

Keywords: Acoustic Emissions
Blood-Brain Barrier
Finite-Element Analysis
Focused Ultrasound
Ultrasound Contrast Agent
Vessel Wall Stresses
Advisor: Hynynen, Kullervo
COST-EFFECTIVENESS OF PRESSURE ULCER PREVENTION AND CALIBRATION ANALYSIS OF DECISION-ANALYTIC MODELS

Pressure ulcers are common in the very ill, the elderly, and immobile or neurologically compromised individuals. In Ontario, the estimated prevalence is approximately 15% among hospital patients. Affected patients experience pain and reduced quality of life. The burden of pressure ulcers in Canada is estimated to exceed $1 billion annually, or approximately one-eighth the total health care cost of cardiovascular diseases in Canada. Current guidelines recommend early prevention to reduce the burden of pressure ulcers but the economic evidence supporting these recommendations is limited. This thesis reports on studies evaluating the cost effectiveness of strategies to prevent pressure ulcers in targeted high-risk patients. In order to conduct the cost-effectiveness analysis, it was necessary to resolve calibration issues in the decision-analytic model that simulates the natural history of pressure ulcers. Model calibration is the practice of comparing projected data from a decision model with corresponding observed data in order to determine unknown model parameters. A literature review was conducted to provide an inventory of methods for the calibration of decision models and categorize these methods according to their methodological approaches. The first study describes the development of a two-stage random search algorithm for model calibration. The second study reports on the cost-effectiveness analysis of strategies to prevent pressure ulcers in elderly patients seeking help in the emergency departments. The third study describes the cost-effectiveness analysis of strategies to prevent pressure ulcers originating intra-operatively in surgical patients. Results from the first study show that the proposed two-stage random search algorithm is suitable for routine calibration of moderately complex decision models. Results from the cost-effectiveness studies show that the evaluated prevention strategies are more cost-effective than current practice. The economic evidence supports the implementation of these early prevention strategies to reduce the burden of pressure ulcers in high-risk patients.

Keywords: calibration
cost-effectiveness
decision analytic model
pressure ulcer
prevention
validation
Advisor: Krahn, Murray