Theses, Dissertations, and other Required Graduate Degree Essays

Convergent-margin basins (CMBs) are rich in broadly coeval detrital zircon (DZ) owing to the proximity of active magmatic belts. Consequently, DZ geochronology can be employed to assess the utility of stratigraphic frameworks developed for these basins. This study uses DZ data to assess the utility of lithostratigraphy developed for the Cretaceous-aged lower Nanaimo Group in the Georgia Basin, Canada. Results show that the basal lithostratigraphic unit of the Nanaimo Group, the Comox Formation, comprises strata that are neither time correlative nor genetically related. The three lithostratigraphic units directly overlying the Comox Formation (Haslam, Extension, and Protection formations) comprise strata with similar genetic affinities, indicating that deposition of these units was not entirely sequential, and contemporaneous in some locales. Further, sediment provenance evolved through time, which the existing lithostratigraphic framework does not reflect. This work demonstrates that DZ geochronology can effectively test the utility of stratigraphic frameworks in CMBs.

Climate change is altering historic patterns of temperature and precipitation worldwide with significant implications for the abiotic and biotic dynamics of river ecosystems. Flowing downhill, precipitation aggregates into creeks, streams and eventually rivers, forming a branching network over the landscape architecturally similar to the branches, limbs and trunk of a tree. Linking disparate locations, these river networks integrate the varied expressions of climate within a watershed. Thus, the river network offers a framework for understanding how spatial patterns of climate are organized and become manifest in rivers. By considering the river network's structuring of climate and landscape interactions, we might better understand how climate and land-use change impact river ecosystems and more clearly identify particularly vulnerable biota. In chapter 2, I examine how river networks dampen signals of climate change in hydrologic flow by integrating varied flow trends from upstream. I demonstrate that by integrating a diverse climate portfolio, the network accumulates changing flow regimes of different volatility, direction and magnitude, such that on average downstream climate change trends are moderated. In chapter 3, I consider the match-mismatch potential of juvenile salmon migrating towards the springtime zooplankton resource pulse in the estuary. I show that populations further from, and whose climate is more dissimilar to, the estuary, are more likely to miss the peak zooplankton bloom. These findings suggest migratory distance influences phenological mismatch risk among populations. My fourth chapter develops an unsupervised machine learning method for cleaning stream temperature data to facilitate big data studies. In chapter 5, I gathered temperature data at over 100 locations throughout a watershed the size of Ireland, over 4 years at 2-hour intervals resulting in over 1 million data points. These data informed a spatial stream network model that quantified how landscape features and river connectivity control seasonal temperature dynamics. These temperature dynamics across space and time revealed that different adult salmon migrations have very different exposures to warm temperatures. Collectively, these findings illustrate that river networks: 1. integrate and dampen signals of climate change, 2. structure phenological match-mismatch patterns and 3. organize thermal exposure potential of biota.

Formalization of knowledge is an important aspect of reasoning about change. We review how knowledge is formalized in the Situation Calculus (a logical formalism for reasoning about action and change) and discuss the problems that occur when unexecutable actions (those actions whose preconditions are not met at the time of execution) are involved. We then provide a generalized framework that addresses these problems by tracing back source of the problem to the answer provided to the Frame Problem in the Situation Calculus. We develop a more generalized form for Successor Sate Axioms based on the new account of the solution to the Frame Problem and show how this solves the problems related to involvement of unexecutable actions.

Over the past decades, Chinese art collectors have drawn worldwide attention to their active acquisitions of artworks in both domestic and international art markets. On the one hand, the development of Chinese modern art and contemporary art has been accompanied by anxiety and uncertainty since the beginning of China’s search for modernity. On the other hand, with China’s reopening to the outside world, particularly concerning its economy, the rapid development of China’s art market and involvement in the international art market have brought China to the spotlight of the international art world. Hence, the impacts of the dynamic art market driven by Chinese art collectors in China on shaping the development of contemporary Chinese art and the perceptions of contemporary Chinese art domestically and internationally is worth exploring.

Gender nonconforming and trans youth experience high rates of bullying and victimization, placing them at risk for serious mental health challenges. Caregiver support is one of the most significant protective factors in this population, and parenting interventions that promote understanding and acceptance are needed to support the well-being of teens and their families. Connect (Moretti & Braber, 2013), a group attachment-based intervention for caregivers, has been shown to promote attachment security within the parent-teen relationship, increase caregiver sense of efficacy, and reduce teen emotional problems for up to two years post-treatment. During this strength-focused program, caregivers learn to “step back” in their interactions, to “step into” their teen’s shoes, and to better understand and respond to their teen’s attachment needs. This study examines the acceptance, uptake, and caregiver satisfaction of an adapted version of Connect which addresses the unique attachment related challenges and concerns of caregivers of trans and gender nonconforming youth. Adaptations were completed in consultation with a panel of mental health professionals to address relevant themes expressed by these families and to modify experiential learning content. Participants in the first three groups were 20 caregivers of 16 gender nonconforming youth (ages 12 - 18). On average, caregivers attended 9.2 sessions of the ten-week program and on questionnaires completed post intervention, reported feeling respected, safe, and welcomed in the group. They indicated that learning about attachment was helpful in enhancing their understanding of their teen and their understanding of themselves as parents. Caregivers also rated the group as helpful in increasing their understanding of their teen’s gender journey. During clinical interviews, caregivers reported feeling more confident in parenting and being able to empathize with their teen more easily. Common themes in group discussions related to gender included: coming out, finding support, affirming pronouns/names, medical transition, parental reactions (e.g. confusion, isolation, acceptance, grief), and concerns about safety and mental health. Qualitative analyses of group skills revealed that across sessions, caregivers demonstrated an increased capacity to “step back” and reflect on their teen’s experience and their own. Findings support the usefulness of this intervention, and feedback has informed further revisions of the program with the goal of co-creating a safe, helpful, gender-affirming intervention. Clinical implications and next steps are discussed.

In 2010, Statham, Haegeli, et al. (2018) introduced the Conceptual Model of Avalanche Hazard (CMAH) to improve transparency and consistency of avalanche bulletin production in North America. However, since the CMAH has no explicit link to the avalanche danger scale, forecasters must rely on their own judgment to assign danger ratings, which can lead to inconsistencies in public avalanche risk communication. My research aims to address this missing link by exploring the relationship between avalanche hazard assessments and danger rating assignments in public avalanche bulletins. Using conditional inference trees, key decision rules and components of the CMAH influencing danger rating assignments are extracted. While the analysis offers insights into the assignment rules, it also highlights substantial variability that cannot be explained by components of the CMAH. The results from this study offer a foundation for critically reviewing existing forecasting practices and developing evidence-based decision aids to increase danger rating consistency.

The ElectroMagnetic Mass Analyzer EMMA is a vacuum mode recoil mass spectrometer that is capable of horizontally dispersing reaction recoils according to their mass/charge ratio at its focal plane station. The recoils enter into two consecutive gas-filled proportional counters, one that detects their positions and the other to measure their energy loss per unit length as well as the residual energy so that the recoils may be uniquely identified. EMMA was designed to exhibit excellent beam suppression so that reaction channels that are weakly populated may be extracted from the unreacted beam and high-yield background channels. EMMA has undergone several commissioning tests to determine how it performs compared to its design specifications. This thesis covers a subset of the tests which involved using a radioactive alpha source as well as accelerated ion beam backscattering to determine its energy/charge and angular acceptances as well as its mass/charge dispersion and acceptance as part of the commissioning of the spectrometer.

A strong understanding of regional variation in structure and composition of old-growth floodplain forests and ecosystem drivers is critical for improving riparian old-growth management. We reviewed the literature to develop a framework to evaluate these and the relative roles of climate, disturbance, other drivers and their interactions. We then examined forest structure from 17 plots across ~11° of latitude along the northern Pacific Coastal Temperate Rainforest (PCTR). Mean annual temperature and precipitation were the most influential drivers of stand structure. Several flood proxies correlated with structural attributes suggesting that hydrological disturbance is a key driver of structure, likely driving greater variability among floodplain stands than upland stands. Northern plots showed slower stand development compared to southern plots, differences in structure suggest a need to re-evaluate sub-regional boundaries of the PCTR. Delineating sub-regional boundaries are important for monitoring and predicting how climate change will affect these forests and their disturbance regimes.

Micro-scale energy storage devices have been developed for the demand of required energy autonomy of the portable and small-scale electronics. One main drawback in realization of micro-scale energy storage devices is limited areal capacitance due to low material loading per unit area on the substrate. 3-D electrodes with high aspect ratio could be promising strategy to overcome this, resulting in higher device performance. Specially, 3D printing technology offers numerous advantages to generate 3D electrodes for energy storage devices, which includes time-saving, cost-effective manufacturing, and realization of tailorable complex electrode designs. In this thesis, novel hierarchical 3D designs were printed by photo-curable 3D printing. Photo-curable resins with conductive fillers were optimized for conductive 3D electrode formation. Finally, energy storage devices with the hierarchical 3D electrodes have been demonstrated for the application of micro-supercapacitors (MSCs). The fabricated 3D hierarchical electrodes demonstrated low electrical resistance to be used as feasible MSCs electrodes. Energy storage from redox reactions was demonstrated in 3D architecture electrodes designed with mechanically durable 3D octet trusses.

Motivated by the breast cancer survivorship research program at BC Cancer Agency, this dissertation develops statistical approaches to analyzing right-censored multivariate event time data. Following the background and motivation of the research, we introduce the framework of the dissertation, and provide a literature review and a list of the research questions. A description of the motivating study data is then given together with a preliminary analysis before presenting the proposed approaches as follows. We consider firstly estimation of the joint survivor function of multiple event times when the observations are subject to informative censoring due to a terminating event. We formulate the potential dependence of the multiple event times with the time to the terminating event by the Archimedean copulas. This may account for the informative censoring and, at the same time, allow to adapt the commonly used two-step procedure for estimating the joint distribution of the multiple event times under a copula model. We propose an easy-to-implement pseudo-likelihood based estimation procedure under the model, which reduces computational intensity compared to its MLE counterpart. A more flexible approach is then proposed to handling informative censoring with particular attention to observations on bivariate event time potentially censored by a terminating event. We formulate the correlation of the bivariate event time with the censoring time by embedding the bivariate event time distribution in a bivariate copula model. This yields the convenience of inference under the conventional copula model. At the same time, the proposed model is more flexible, and thus potentially more appropriate in many practical situations than modeling the event times and the associated censoring time jointly by a single multivariate copula. Adapting the commonly used two-stage estimation procedure under a copula model, we develop an easy-to-implement estimator for the joint survivor function of the two event times. A by-product of the proposed approaches is an estimator for the marginal distribution of a single event time with semicompeting-risks data. Further, we extend the approach to regression settings to explore covariate effects in either parametric or nonparametric forms. In particular, adjusting for some covariates, we compare two populations based on an event time with observations subject to informative censoring. We conduct both asymptotic and simulation studies to examine the consistency, efficiency, and robustness of the proposed approaches. The breast cancer program that motivated this research is employed to illustrate the methodological development throughout the dissertation.