VictorJuiz/thesis huggingface dataset:
Effects of Transient Hydro-mechanical Cemented Paste Tailings Properties on One-dimensional Deposition Behaviour

When underground mining voids are filled with Cemented Paste Backfill (CPB) a dynamic interaction occurs between the hydrating CPB's engineering properties (hydraulic conductivity, stiffness and strength) and the fill rise rate, drainage conditions, and underground atmospheric conditions. These interactions are particularly important in the first 24 hours after a fill layer's placement in order to support continuous filling. Unfortunately, most previous studies started taking measurements at one day or more, missing this critical initial period. The work presented in this thesis obtains representative material properties at curing times as soon as 30 minutes. Four stages of hydraulic conductivity evolution are linked to corresponding stages of binder hydration at times from 30 minutes to 5 days, and it is shown conventional measurement methods could under-estimate initial hydraulic conductivity by an order of magnitude. Consolidation tests with virtually continuous loading rates simulated effective stress development onsets between 4 and 48 hours, at rates between 5 and 20 kPa/hr and final level of 400 kPa. In virtually continuous loading it is impossible to deconvolve the parameters controlling the ultimately achieved void ratio and stiffness, but a graphical technique is developed to aid preliminary design and determine likely void ratios that should be used in other laboratory tests for engineering properties. The hydraulic conductivity and consolidation element test results are then used to interpret results from four mesoscale laboratory experiments that simulate continuous backfilling. These tests demonstrate the importance of properly simulating the underground atmospheric conditions, and in placing the fill in the most continuous manner possible. For placement conditions that most closely simulate the actual placement conditions at the studied mine, it is found that virtually no self-weight consolidation occurs and thus the void ratios in the field and in the meso-scale experiments are essentially identical. Therefore, the effective stress path realized in the field will not lead to significant self-weight consolidation and the attendant strength gains that might otherwise occur.

Keywords: Cemented Paste Backfill
Column Experiments
Consolidation
Hydraulic Conductivity
Mine Tailings
Numerical Analyses
Advisor: Grabinsky, Murray
Approximate Inference in Variational Autoencoders

A deep latent variable model is a powerful tool for modelling complex distributions. However, in order to train this model, we must perform approximate inference of the latent variable. A variational autoencoder (VAE) is a framework for learning both the generative and inference models for a latent variable model. This thesis provides novel analyses, applications, and interpretations of approximate inference in VAEs. This thesis reviews many of the recent developments made to improve VAEs. One such improvement is the importance-weighted autoencoder. The standard interpretation of importance-weighted autoencoders is that they maximize a tighter lower bound on the marginal likelihood than the standard evidence lower bound. The first contribution of this thesis is to provide an alternative interpretation: that it optimizes the standard variational lower bound, but using a stochastic importance-weighted variational distribution. In order to improve approximate inference in VAEs, it is important to understand what causes inference to be suboptimal. Two important factors that determine the quality of approximate inference in VAEs are: a) whether the variational distribution is expressive enough to match the true posterior and b) the ability of the recognition network to produce good variational parameters for each datapoint. This thesis contributes to our understanding of approximate inference in VAEs by using these factors to diagnose suboptimal inference across a number of settings. Finally, we investigate the task of using a latent variable to learn a joint distribution over two data modalities: images and text. The contribution of this work is to develop a model for this task and analyze how to perform approximate inference in this model. Specifically, we identify a problem arising from the mismatch between the posteriors of each modality and we demonstrate how the problem can be largely addressed by modelling the aggregate of the image posteriors.

Keywords: Approximate Inference
Generative Modelling
Machine Learning
Variational Autoencoder
Advisor: Morris, Quaid
Duvenaud, David
The Electrophysiological Characterization of Duchenne Muscular Dystrophy Using 3D Human Bioengineered Skeletal Muscle Tissue and Neuromuscular Junctions

Duchenne muscular dystrophy (DMD) is the most severe and common form of inherited muscular disease, affecting 1 in 3,500 boys. Patients with DMD experience progressive muscle weakness, where most children with DMD are subject to a wheelchair by age 13 and eventual fatality occurs during their third decade of life. More than 25 years ago, mutations in the Dystrophin gene were found to cause DMD. Dystrophin is an important cytoplasmic protein in the Dystrophin-associated glycoprotein complex (DGC) that underlies the plasma membrane of skeletal muscle. The lack of Dystrophin in the DGC causes muscle cells to be susceptible to muscle membrane damage. My view is that there is a problem with skeletal muscle homeostasis in DMD, where the balance between muscle damage and muscle repair strongly favours damage. One area of DMD research which appears understudied is the pathophysiology of the DMD neuromuscular junction (NMJ). In this thesis, I use a 3D culture system to model skeletal muscle and the neuromuscular junction, using immortalized muscle cell lines from healthy and DMD patient biopsies, as well as human embryonic stem cell (hESC) derived motor neurons. The findings of my thesis provide a comprehensive analysis of muscle cell physiological of healthy and DMD skeletal muscle tissue, and provide preliminary synaptic physiological data for in vitro NMJ. The results lead me to conclude that DMD muscle alone-constructs as well as DMD NMJ co-cultures have a more positive resting membrane potential, and a lower muscle membrane resistance when compared to healthy muscle and healthy muscle co-cultures. DMD muscle alone-constructs were unable to achieve muscle excitability, and all DMD co-cultures had varying recordings of spontaneous muscle excitability. Furthermore, DMD muscle membrane fragility is an aspect that can be studied further using my 3D muscle culture system. All together my thesis provides the first comprehensive analysis of muscle cell physiology of engineered muscle, and I provide the first report of a human NMJ that shows successful innervation seen through synaptic physiological recordings. The results of my research contribute to the basic biological role of dystrophin, and provides a characterized 3D muscle culture system that could be used for disease modeling and drug screening.

Keywords: bioengineered
Duchenne muscular dystrophy
electrophysiology
Muscle
Neuromuscular junction
Advisor: Stewart, Bryan A
Logical Form and the Limits of Thought

What is the relation of logic to thinking? My dissertation offers a new argument for the claim that logic is constitutive of thinking in the following sense: representational activity counts as thinking only if it manifests sensitivity to logical rules. In short, thinking has to be minimally logical. An account of thinking has to allow for our freedom to question or revise our commitments – even seemingly obvious conceptual connections – without loss of understanding. This freedom, I argue, requires that thinkers have general abilities to respond to support and tension among their thoughts. And these abilities are constituted by following logical rules. So thinkers have to follow logical rules. But there isn’t just one correct logic for thinking. I show that my view is consistent with logical pluralism: there are a range of correct logics, any one of which a thinker might follow. A logic for thinking does, however, have to contain certain minimal principles: Modus Ponens and Non-Contradiction, and perhaps others. We follow logical rules by exercising logical capacities, which display a distinctive first-person/third-person asymmetry: a subject can find the instances of a rule compelling without seeing them as instances of a rule. As a result, there are two limits on illogical thinking. First, thinkers have to tend to find instances of logical rules compelling. Second, thinkers can’t think in obviously illogical ways. So thinking has to be logical – but not perfectly so. When we try to think, but fail, we produce nonsense. But our failures to think are often subjectively indistinguishable from thinking. To explain how this occurs, I offer an account of nonsense. To be under the illusion that some nonsense makes sense is to enter a pretence that the nonsense is meaningful. Our use of nonsense within the pretence relies on the role of logical form in understanding. Finally, while the normativity of logic doesn’t fall directly out of logical constitutivism, it’s possible to build an attractive account of logical normativity which has logical constitutivism as an integral part. I argue that thinking is necessary for human flourishing, and that this is the source of logical normativity.

Keywords: Nonsense
Normativity of logic
Philosophy of logic
Rule-following
Theory of understanding
Thinking
Advisor: Rattan, Gurpreet
Interracial Couples and Parenting: An Exploration of Interracial Couples’ Experiences with Parenting Mixed-race Children in the Greater Toronto Area

The number of interracial couples in Canada continues to rise, particularly in metropolitan regions such as the Greater Toronto Area (GTA) with a consequent increase in the number of mixed-race children. The importance of fostering positive racial identities in mixed-race children is well documented. However, there is little research investigating the processes through which interracial couples parent their children together or how they make meaning of their parenting experiences. To address this deficiency, the purpose of the current study was to explore the joint experiences of six interracial couples who were negotiating the parenting process of their school-aged mixed-race children. By employing interpretative phenomenological analysis, in-depth interviews were used to generate descriptions of the interracial couples’ experiences across three relationship phases (i) courtship and early stages of the interracial relationship, (ii) becoming parents and early parenting experiences, and (iii) experiences with co-parenting school-aged mixed-race children. Across these relationship phases, this analysis yielded three core transecting themes that reflected the experiences of jointly parenting mixed-race children. First, participants described how relationship and parenting experiences led to transformative racial identity experiences, both as individuals and couples. Second, experiences with their racially different partner, their mixed-race children, and the external world, led to the realization of their unique experience as interracial couples and mixed-race families in the context of a racially stratified society. Third, in terms of parenting, all six couples described the process through which they framed their interracial status as a strength for their mixed-race children, referencing the benefits of dual racial exposure. Parenting had clear impacts on the racial identity formation processes of the six interracial couples which manifested differently across different phases of their interracial relationship. Generally, the needs of mixed-race families are unique and in the context of a rapidly shifting sociopolitical climate, the perspectives of these families need to be understood to ensure the provision of culturally sensitive and competent practice and pedagogy. Although the findings of this study are an important contribution, more extensive research is needed to further understand the strengths and needs of interracial partners and their journeys of parenting their mixed-race children.

Keywords: interracial couples
mixed-race identity
parenting
Advisor: Moodley, Roy
“We’re really trying, and I know it’s not enough”: Settler Anti-pipeline Activists and the Turn to Frontline Solidarity with Indigenous Peoples

The logics and worldviews of settler environmentalism perpetuate settler colonialism and white supremacy; settler environmentalism has consistently failed to work in relation to Indigenous peoples in a good way. This research engages with the efforts of settler anti-pipeline activists in Canada to solve these problems of environmentalism by turning to frontline solidarity. Frontline solidarity relies on systems of power; the framework hinges on a solidarity group making use of their privileges to support the struggles of a frontline group while simultaneously attempting to de-emphasize this privilege through, for example, following frontline leadership. Frontline solidarity does not solve settler environmentalism; it does not enable settler environmentalists to become the “good ally.” However, this framework at times enabled settler anti-pipeline activists to productively support Indigenous-led legal battles and land defence. Separating the goal of stopping pipelines from the goal of supporting Indigenous self-determination has the potential to clarify roles for settlers on Indigenous land. Layered onto the contradictions of frontline solidarity, many of the settler activists worked at environmental organizations and were funded to stop pipelines through a collective campaign. Like frontline solidarity, philanthropy hinges on white settler power and fails to address systemic injustices. The organizational requirements of funded campaign engagement and the campaign absorbing solidarity goals into an “outreach” model worked primarily to maintain settler power. At the same time, the flexibility of campaign networks provided opportunities for relationships and learning between settler activists and Indigenous peoples; while not themselves decolonizing, the relationships provide an opening to work together against climate change and colonial power. Settler anti-pipeline activists are steeped in multiple oppressive systems and were at times “called out” for racist or colonial actions. Narratives of Indigenous trauma and white fragility led to the creation of a feeling rule in which settler activists did not allow themselves to feel the pain these callouts caused. This contributed to burnout and limited opportunities for learning and healing. This dissertation contributes to the literatures on solidarity, social movements, critical philanthropy, and politics of emotion. As an activist researcher, I am also motivated to contribute to the transformation of my own movement.

Keywords: activism
critical philanthropy
environmentalism
feeling rules
solidarity
whiteness
Advisor: Restoule, Jean-Paul
Vibratory Communication in the Black Widow Spider, Latrodectus hesperus (Araneae: Theridiidae)

Several studies have described vibration producing behaviours across many web-building spiders, and vibratory communication is thought to play an integral role during male-female interactions. Despite the presumed ubiquity of vibratory communication in this group of spiders, very little is known about the characteristics and functions of the signals involved, how signals are produced and transmitted through webs, or how vibrations are perceived. In this thesis, I used the western black widow spider, Latrodectus hesperus, as my focal organism, to investigate the details of vibratory communication from sender to the receiver. My results show that male L. hesperus courtship vibration signals comprise three distinct components (abdominal tremulation, bounce and web plucks), each produced using different signal production mechanism. Larger males produced bounce and web pluck signals with high power, which suggests that these signals may carry information about male traits. I found that during the early phase of courtship, males produced these different signal components haphazardly, with little temporal organization among the individual components (unstructured signaling). However, during the later phase of courtship, as males approach females, males intermittently organized signal components into a stereotyped temporal sequence (structured signaling). I tested the importance of these composite multicomponent signals, and found that males that displayed these structured signals more often were more likely to successfully copulate and copulate sooner. Vibrations arriving at the females are transmitted through the legs. My results show that the more distal joints of the legs (i.e. tarsus-metatarsus joint) move more to higher frequencies, and more proximal joints are tuned to lower frequencies. This suggests that female leg-joints play an important role in segregating vibration frequencies, and this may have important implications for prey/mate discrimination, as well as vibration source localization. These results show that L. hesperus males employ multiple signal components during courtship, and provide novel insights into emergent signal complexities in a web-building spider, previously thought to be ‘simple’ signalers. Additionally, the spider body mechanics can play a key role in influence vibration perception.

Keywords: biomechanics
Black widow spider
Multicomponent signal
Signal structure
Signaling mechanisms
Vibratory communication
Advisor: Mason, Andrew C
From Here To: Everyday Wayfinding in the Age of Digital Maps

These days, navigation is often associated with “asking” Google Maps for directions. Over one billion people per month use Google Maps and Google estimates that one-in-three mobile searches are location-related. What do spatial information practices look like in these everyday information contexts? To explore this question of street-level wayfinding, I used exploratory performance-based and drawing-based research. I approached people in the streets of Toronto, New York, Amsterdam and London, and asked for directions, requesting they draw directional instructions for me. In total, I collected 220 sets of drawings, corresponding observational fieldnotes, and 20 interviews. Following collection, I used visual grounded theory and situational analysis to assess the data from the interdisciplinary theoretical perspective of everyday life information seeking and critical information studies research. Findings show the complexity of everyday wayfinding, negotiated through the tacit and material forms of technological interventions, urban configurations, and information affects. I present the findings through a qualitative account of these modalities at play on the ground. The empirical findings build a theoretical framework to evaluate Google Maps’ affordances and discursive framings. In addition to establishing a critical information framework, my work contributes methodologically to the study of spontaneous and ad-hoc drawings in information studies. My research follows a trajectory of emerging critical internet scholarship in information studies, positioned in the context of everyday information practices.

Keywords: arts-based research
critical information studies
digital maps
everyday information practice
visual grounded theory
wayfinding
Advisor: Hartel, Jenna
Summary Measures for Quantifying the Extent of Visit Irregularity in Longitudinal Data

A common feature of observational longitudinal data is variability in the timings of visits across individuals. Irregular visits merit careful scrutiny as they can be associated with the outcome trajectory and lead to biased results if not properly addressed. Similar to missing data, exploring the extent of irregularity is important because it can help determine whether specialized methods for irregular data are needed. However, there are currently no measures for quantifying the extent of irregularity. This thesis proposes visual and numerical measures of irregularity which are based on bins constructed across the study duration. To visually assess the extent of irregularity, the bin widths are varied and the mean proportions of individuals with 0, 1, and >1 visits per bin are plotted. With perfect repeated measures, the mean proportions of individuals with 1 visit per bin are 1, and the mean proportions of individuals with 0 and >1 visits per bin are 0. Missingness leads to individuals with 0 visits per bin while irregularity leads to both individuals with >1 visit per bin and individuals with 0 visits per bin. To numerically assess the extent of irregularity, we use the area under the curve (AUC) of the mean proportions of individuals with 0 visits per bin plotted against the mean proportions of individuals with >1 visit per bin. To be an effective measure of irregularity, the AUC should increase with increasing irregularity, be intuitive, and be invariant to sample size and follow-up length. Ideally, the AUC should be invariant to missingness, but the AUC increases as the level of missingness increases due to increased proportions of individuals with 0 visits per bin. To allow judgement solely on irregularity and not missingness, likelihood-based estimation will be used to derive an AUC assuming no missingness. Simulation results demonstrate that the AUC increases with increasing irregularity and is invariant to sample size and the number of scheduled measurement occasions. Overall, these measures can lead to an improved quality of statistical analyses by informing the modelling approach. Health administrative data are increasingly available, but are susceptible to irregular visit timings. It is thus crucial to assess the extent of irregularity to inform the need for specialized methods for irregular data that minimize the potential for biased results.

Keywords: Inverse-Intensity Weighted Generalized Estimating Equations
Irregular Visits
Longitudinal Data
Missing Data
Repeated Measures
Summary Measures
Advisor: Pullenayegum, Eleanor M