VictorJuiz/thesis huggingface dataset:
Existence, Uniqueness, Concavity and Geometry of the Monopolist?s Problem Facing Consumers with Nonlinear Price Preferences

A monopolist wishes to maximize her profits by finding an optimal price menu. After she announces a menu of products and prices, each agent will choose to buy that product which maximizes his utility, if positive. The principal's profits are the sum of the net earnings produced by each product sold. These are determined by the costs of production and the distribution of products sold, which in turn are based on the distribution of anonymous agents and the choices they make in response to the principal's price menu. In this thesis, two existence results will be provided, assuming each agent's disutility is a strictly increasing but not necessarily affine (i.e., quasilinear) function of the price paid. This has been an open problem for several decades before the first multi-dimensional result obtained here and independently by Nöldeke and Samuelson in 2015. Additionally, a necessary and sufficient condition for the convexity or concavity of this principal's (bilevel) optimization problem is investigated. Concavity when present, makes the problem more amenable to computational and theoretical analysis; it is key to obtaining uniqueness and stability results for the principal's strategy in particular. Even in the quasilinear case, our analysis goes beyond previous work by addressing convexity as well as concavity, by establishing conditions which are not only sufficient but necessary, and by requiring fewer hypotheses on the agents' preferences. Moreover, the analytic and geometric interpretations of a specific condition relevant to the concavity of the problem have been explored. Finally, various examples are given to explain the interaction between preferences of agents' utility and monopolist's profit which ensure statements equivalent to the concavity of the principal-agent problem. In particular, an example with quasilinear preferences on n-dimensional hyperbolic spaces is given with explicit solutions to show uniqueness without concavity. Similar results on spherical and Euclidean spaces are also provided. Additionally, the solutions of hyperbolic and spherical cases converge to those of Euclidean spaces as curvature goes to 0.

Advisor: McCann, Robert J
Metagenomic investigation of Dehalococcoidia used for bioremediation of groundwater and soil contaminated with chlorinated ethenes and ethanes

Chlorinated aliphatic hydrocarbons (CAHs) such as vinyl chloride (VC) and perchloroethene (PCE) are persistent, toxic groundwater and soil pollutants. Bioremediation using mixed microbial cultures such as KB-1 and WBC-2 has proven to be a technically viable and economically feasible remediation strategy. These cultures include members of the Dehalococcoides and Dehalogenimonas, genera from the class Dehalococcoidia, who use reductive dehalogenase enzymes (RDases) to dechlorinate CAHs in an obligatory respiratory process. Metagenomic DNA sequencing was conducted on the KB-1 and WBC-2 enrichment cultures to describe the diversity of microorganisms living in the cultures, and to close genomes of key organisms. Ten new complete genomes of Dehalococcoidia are presented here. Their reductive dehalogenase genes and their evolutionary history are described. Dehalococcoides mccartyi in KB-1 was used as an example to study mobile DNA, with a particular focus on the possible exchange of reductive dehalogenase genes. Extrachromosomal circular elements were discovered in D. mccartyi, and found to replicate in a circular intermediate state separate from the genome. Simultaneously, the VC reductase gene (vcrA)-containing genomic island was also found to periodically replicate in a circular intermediate state. Twelve new prophages and their interaction with CRISPR systems carried by D. mccartyi were described. Additionally, a reductive dehalogenase from Dehalogenimonas was identified and biochemically characterized using a combination of blue-native polyacrylamide gel electrophoresis followed by enzymatic assays and peptide sequencing. In summary, this work has nearly doubled the number of Dehalococcoidia genomes available in NCBI, has led to the discovery of new dehalogenases, new types of mobile DNA, and has begun to elucidate a mechanism for lateral gene transfer in D. mccartyi. Together this knowledge will help better manage contaminated sites and design more effective bioremediation approaches.

Keywords: Bioremediation
Dehalococcoides mccartyi
Dehalogenimonas
reductive dehalogenases
Advisor: Edwards, Elizabeth A
Excavating the Imagination: The Arabic Afterlife of Aristotle's Phantasia

This dissertation focuses on the afterlife of Aristotle’s work on the imagination, specifically in the work of al-Farabi, Ibn Rushd, and Maimonides. Drawing on previous scholarship that has investigated the philosophical and psychological role of the imagination in Aristotle, this dissertation considers the role that Aristotle’s Rhetoric had to play in later Arabic readings of Aristotle. This dissertation demonstrates that it wasthe rich life of Aristotle’s Rhetoric in the Arabic world that lead to a slow-burning association of imagination and politics. For al-Farabi, Ibn Rushd, and Maimonides, the imagination is the psychological feature of human beings that make us susceptible to persuasive speech. Since the images of imagination in human beings are restrained and directed by the rational faculty, they can also be directed, although not restrained, by the power of persuasive speech. The imagination allows human beings to imagine the world differently from the way it is, but at the same time it is not intrinsically capable of ascertaining which future or change is good. But human reason, with its deliberative powers, allows us to distinguish between persuasion based on emotional triggers and habitual desires and the truly remarkable innovations that can stem only from the partnership between imagination and reason. In thought the evolution of the idea of the imagination was linked with an appreciation of Rhetoric, absent in the Latin world, which manifested in concerns about persuasion, manipulation, reactionary potential of the imagination. They turn to reason as a bulwark against the power of desire and anger, and therefore the means by which we can avoid being led entirely by our emotions and the images that they invoke.

Keywords: al-Farabi
Arabic philosophy
Aristotle
Ibn Rushd
Imagination
Maimonides
Advisor: Green, Kenneth H
Scalable Inference in Hardware Verification and Social Graph Reasoning

With the growing abundance of raw data and the increasing processing power of parallel computing systems, various industries nowadays embrace data mining and are rapidly replacing traditional methods with machine learning solutions. One area that is currently undergoing such transition is the semiconductor industry. In this domain several problems call for data-driven solutions, with failure triage being one of the most prominent. Failure triage is an emerging regression verification problem where the goal is to sort through thousands of hardware failures in order to characterize and prioritize them before they are analyzed in detail and fixed. This preprocessing step is critical in deciding how resources (i.e., engineering effort) will be allocated in fixing these failure. Today, industries assign these decisions to expert engineers. Such manual approaches are unsustainable long-term with design complexity on the rise and verification data becoming more and more sensitive to human interpretation. In the first part of this thesis we show that existing inference methods can be employed towards automating failure triage. Experiments demonstrate that the proposed inference methods can make correct decisions at various triage stages with at least 80% average accuracy, and only a 6.5% runtime overhead when used in modern debugging flows. In contrast to the semiconductor industry, a long thread of work based on data mining has already been established in the social media analytics sector, with applications ranging from sentiment analysis to community detection and viral marketing. In the second part, we study one of the dominant problems in computational social science, known as influence maximization. The problem relates to identifying a subset of a population that can spread information over a social network in a maximal way. We address influence maximization in the continuous-time domain, where the propagation of influence between members of the population obeys stochastic transmission times. Maximizing influence in the continuous-time domain is generally intractable and, therefore, the process calls for approximations. This dissertation proposes novel approximation algorithms that are specifically tailored for parallel computing, and that achieve between 5x-85x performance improvements over the state-of-the-art.

Keywords: GPU
Influence maximization
RTL
Triage
Verification
Advisor: Veneris, Andreas
The Role of Infections in the Etiology of Childhood Acute Lymphoblastic Leukemia

Childhood acute lymphoblastic leukemia (ALL) is the most common childhood cancer. However, the etiology of childhood ALL is uncertain. An infectious trigger for ALL is hypothesized based on evidence from biological and epidemiologic studies. The goal of the dissertation was to assess the relationship between prior infections and the development of childhood ALL. In a systematic review and meta-analysis, no overall relationship between prior infections and childhood ALL could be identified (odds ratio, OR=1.10, 95% confidence interval, CI 0.95-1.28). The systematic review showed most studies that used self-reported data to measure infections were susceptible to recall bias. Thus, administrative data may be particularly useful in furthering our understanding of the infectious etiology of ALL. Using electronic medical records as the reference standard, a study was conducted to assess the criterion validity of administrative databases to identify infectious syndromes in children aged 0-18 years from Ontario, Canada. Administrative billings codes for an infection (respiratory, skin and soft tissue, gastrointestinal, urinary tract or otitis externa) demonstrated moderate sensitivity (0.74, 95%CI 0.70-0.77), and high specificity (0.95, 95%CI 0.93-0.96), positive predictive value (0.87, 95%CI 0.84-0.90), and negative predictive value (0.88, 95%CI 0.86-0.89). Finally, the association between prior infections and the development of childhood ALL, using health administrative data, was conducted applying the findings from the validation study to define and measure infections. Overall, having >2 infections per year increased odds of ALL by 43% compared to children with ≤0.25 infections per year in Ontario. Infections occurring between 1 to 1.5 years of life may be a critical period as having an infection in this window increased the odds of ALL by 20%. Certain infections such as respiratory and invasive infections may be more important than other infections in the development of ALL. The accumulated insights from each study was used to inform subsequent objectives, resulting in a unified dissertation that found infections have a role in the etiology of childhood ALL. Future work should extend the empirical study investigate the critical period between 1 to 1.5 years by collecting detailed infection data and other exposures that begin around this period.

Keywords: administrative data
Childhood acute lymphoblastic leukemia
etiology
Infections
systematic review and meta analysis
validation
Advisor: Pole, Jason D
Sung, Lillian
A Heuristic Approach to Explore: Value of Perfect Information

How do consumers choose in a dynamic stochastic environment when they face uncertainty about the return from their choice? The classical solution to this problem is to assume consumers use dynamic programming to obtain the optimal decision rule. However, this approach has two drawbacks. First, it is computationally very expensive to implement because it requires solving a dynamic programming problem with a continuous state space. Second, a decision maker is assumed to behave “as if” she optimally processes information regardless of its cognitive tractability. To address these two issues, we propose a new heuristic decision process called Value of Perfect Information (VPI), which extends the idea first proposed by Howard (1966) in the engineering literature. This approach provides an intuitive and computationally tractable way to capture the value of exploring uncertain alternatives. Intuitively, in VPI, a decision maker investigates a subset of information which is expected by her to improve her myopic decision outcome. We argue that our VPI approach provides a “fast and frugal” way to balance the trade-off between exploration versus exploitation. More specifically, the VPI approach only involves ranking the alternatives and computing a one-dimensional integration to obtain the expected future value of exploration. In terms of computational costs, we show that the VPI approach is significantly simpler than the standard dynamic programming approach, making it a very practical learning model for consumers to employ. Also, the VPI approach captures asymmetric switching patterns with respect to price promotions in the data. Using individual-level scanner data, we find evidence that our VPI approach is able to capture consumers' choice well.

Keywords: Bellman Equation
Exploration-Exploitation Tradeoff
Forward-looking Behavior
Heuristics
Multi-armed bandit
Value of Perfect Information
Advisor: Ching, Andrew T
Moorthy, Sridhar
Alexander Invariants of Tangles via Expansions

This thesis consists of two parts. In the main part of the thesis we introduce an extension of the Alexander polynomial to tangles, known as Γ-calculus or Gassner calculus, which has appeared in [BNS13, Hal16] and various talks by Prof Bar-Natan. Our main object of study is w-tangles, which we describe using the language of meta-monoids (see [BNS13, BN15a, Hal16]). There is a map from usual tangles to w-tangles and so an invariant of w-tangles induces an invariant of usual tangles. Using the language of Γ-calculus, we rederive certain important properties of the Alexander polynomial, most notably the Fox-Milnor condition on the Alexander polynomials of ribbon knots [Lic97, FM66]. We argue that our proof has some potential for generalization which may help tackle the slice-ribbon conjecture. In a sense this thesis is an extension of [BNS13]. In the second part of the thesis, we study the associated graded space of w-tangles, which is the space of arrow diagrams [BND16, BND14]. We describe an expansion of w-tangles, i.e. a map from w-tangles to its associated graded space. The concept of expansions is inspired by the Taylor expansions, and w-tangles have a much simpler expansion than usual tangles (for usual tangles an expansion is given by the Kontsevich integral [Oht02]). There is a relationship between arrow diagrams and Lie algebras. Using the expansion of w-tangles we recover Γ-calculus by choosing a particular Lie algebra, namely the two-dimensional non-abelian Lie algebra. We give a commutative diagram that summarizes the spaces and maps involved. The second part of the thesis is more or less independent of the first part.

Keywords: Alexander Polynomials
Fox Milnor
Gamma Calculus
Knots
Ribbon
Tangles
Advisor: Bar-Natan, Dror
Falls in Community-dwelling Older Adults with Cancer: Impact on Cancer Treatment, Circumstances, Assessment, Management, and Reporting

Falls are major health issues among older adults and even more so in older cancer patients due to cancer and its treatment. Knowledge on circumstances surrounding falls and fear of falling is vital for understanding how various factors may precipitate falls and for informing development of effective interventions to prevent falls in this population. Delays in cancer treatment caused by fall injuries may have significant implications on disease trajectory and patient outcomes. However, a systematic review found gaps in knowledge in terms of how falls impact cancer treatment in this population. The aim of this research was to explore the circumstances of falls and fear of falling in community-dwelling older adults with cancer, as well as to examine how falls are assessed, reported, and managed in outpatient oncology clinics, and how falls might impact cancer treatment in this population. A cross-sectional study using a convergent-parallel mixed-methods design was conducted at the Princess Margaret Cancer Centre in Toronto, Canada. Data were collected by self-reported survey, chart review, and open-ended interviews. One hundred older adults (aged >=65) and 14 oncologists participated in this study. Falls were not commonly reported by patients to their oncologists (43%), and were rarely assessed by oncologists (7%). One in twenty who fall appears to lead to change in cancer management. However, falls were not commonly reported by patients nor prioritized by oncologists. Older patients perceived falls as minor incidents not worth mentioning (57%). When a fall was reported, oncologists’ actions included determining cause of falls (64%), asking circumstances of falls (36%), and referrals (29%). Oncologists indicated that the majority of older patients were not forthcoming in reporting falls. Circumstances of falls seem to be similar to those in the general geriatric population. This research shows that incorporating routine fall assessment in oncology clinic appointments may help identify those at risk for falls so that timely interventions can be triggered. Additionally, strategies for fall prevention and management used in the general geriatric population can potentially benefit this population as well. Attention may be warranted regarding medication review, health-teaching on fall safety, home evaluation, and referral for balance training.

Keywords: aging
Cancer
falls
geriatrics
Advisor: Puts, Martine
Behavioural Foundations of Elite Politics: How Individual-Level Characteristics Shape the Decision Making of Elected Politicians

What kind of decisions makers are elected politicians? Do they exhibit the same cognitive biases and choice anomalies that plague the reasoning of everyday citizens? Do they acquire some degree of expertise that makes their decision making systematically different? And what explains differences between different groups of politicians in how they confront policy problems and other in-office challenges? This dissertation consists of five papers that attempt to provide empirical answers for these questions from an individual-level behavioural perspective. These papers use evidence derived principally from in-person and online experiments conducted with hundreds of incumbent politicians and thousands of citizens in four countries. I find that politicians are equally susceptible as citizens to a series of policy-critical choice anomalies, including equivalency framing effects, the status-quo bias, escalation of commitment in face of sunk costs, and discounting future payoffs. In some cases they exhibit certain biases even more strongly than non-elites. I further document systematic differences between politicians in these domains, in ways that are directly tied to being held politically accountable and to the nature of their elected office: representatives who are more overconfident regarding their likelihood of being re-elected exhibit stronger risk-seeking behaviour; local officials who report an interest in future office-holding are strongly responsive to accountability cues, resulting in greater willingness to take risks, while those who are uninterested in re-election exhibit no behaviour change; and female and male politicians respond in opposite ways to being held publicly accountable, with men being significantly more likely to abandon policy choices presented as the status quo, and women becoming more entrenched in it. Finally, I use a formal model to analyze the implication of heterogeneity among elected officials in their capacity to engage in strategic reasoning in the context of elite frame production. Together, the papers in this dissertation provide an empirically-grounded and nuanced set of insights on elite decision making in politics that question the adequacy of numerous influential political science models and theories, which have either been relying on untested assumptions regarding elite behaviour, or have overlooked them altogether.

Keywords: Accountability
Behaviour
Bias
Decision making
Experiments
Politicians
Advisor: Loewen, Peter J
Using Network Theory to Manage Knowledge from Unstructured Data in Construction Projects: Application to a Collaborative Analysis of the Energy Consumption in the Construction of Oil and Gas Facilities

This research provides an approach to capture the knowledge in unstructured data related to the energy consumption in the construction of oil and gas projects. Because of the challenges of this industry in managing knowledge more efficiently, this work is relevant for planning/assessments during the construction of future projects. As a starting point, a concept map, which organizes thirty-four construction activities, systems, and factors that influence energy consumption during the construction, is presented. This concept map is a simplified taxonomy that guarantees consistency across different projects. As such, three case studies of oil and gas projects are conducted based on semi-structured interviews to design the respective concept networks. The method represents the concepts in the form of a network. The nodes of the network are the thirty-four concepts, and a tie is defined whenever there is a relationship between two concepts that impact the energy consumption in the construction stage. Network analysis is used to retrieve the knowledge, which is contextualized in the case-based projects. Then, the networks of the three cases are compared with a baseline, which was developed using an expert survey. With the survey focusing on the experts' general knowledge, blockmodeling is used to capture knowledge constructs in each case network. The research is evaluated using a test with one of the case studies and a system as an online interface for collaboration. The results collected from a questionnaire and a focus group with the participants of the test indicate that the proposed approach is satisfactory. Although this study is not an energy assessment, each project has its unique, contextual network; therefore, comparing them with the network of future projects constitutes a valuable source of knowledge. This work also highlights the importance of supporting collaboration between project team members to study and decide on the plans to manage/reduce energy consumption during the construction phase in oil and gas facilities. While the energy savings are smaller than the upstream and operation phases, it has received much less attention. It is also a phase with much more subjective and contextualized knowledge – making the use of case-based analyses more suitable.

Keywords: blockmodeling
construction management
energy use
knowledge retrieval and representation
network analysis
unstructured data
Advisor: El-Diraby, Tamer E.