Graduate Theses & Dissertations

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Effects of Silver Nanoparticles on Lower Trophic Levels in Aquatic Ecosystems
Due to their effective antibacterial and antifungal properties, silver nanoparticles (AgNPs) have quickly become the most commonly used nanomaterial, with applications in industry, medicine and consumer products. This increased use of AgNPs over the past decade will inevitably result in an elevated release of nanoparticles into the environment, highlighting the importance of assessing the environmental impacts of these nanomaterials on aquatic ecosystems. Although numerous laboratory studies have already reported on the negative effects of AgNPs to freshwater organisms, only a handful of studies have investigated the impacts of environmentally relevant levels of AgNPs on whole communities under natural conditions. This thesis examines the effects of chronic AgNP exposure on natural freshwater littoral microcrustacean, benthic macroinvertebrate and pelagic zooplankton communities. To assess the responses of these communities to AgNPs, I focused on a solely field-based approach, combining a six-week mesocosm study with a three-year whole lake experiment at the IISD – Experimental Lakes Area (Ontario, Canada). Our mesocosm study tested the effects of AgNP concentration (low, medium and high dose), surface coating (citrate- and polyvinylpyrrolidone [PVP]-coated AgNPs), and type of exposure (chronic and pulsed addition) on benthic macroinvertebrates in fine and stony sediments. Relative abundances of metal-tolerant Chironomidae in fine sediments were highest in high dose PVP-AgNP treatments; however, no negative effects of AgNP exposure were seen on biodiversity metrics or overall community structure throughout the study. I observed similar results within the whole lake study that incorporated a long-term addition of low levels of AgNPs to an experimental lake. Mixed-effects models and multivariate methods revealed a decline in all species of the littoral microcrustacean family Chydoridae in the final year of the study within our experimental lake, suggesting that this taxon may be sensitive to AgNP exposure; however, these effects were fairly subtle and were not reflected in the overall composition of littoral communities. No other negative effects of AgNPs were observed on the pelagic zooplankton or benthic macroinvertebrate communities. My results demonstrate that environmentally relevant levels of AgNPs have little impact on natural freshwater microcrustacean and benthic macroinvertebrate communities. Instead, biodiversity metrics and community structure are primarily influenced by seasonal dynamics and nutrient concentrations across both lakes. This thesis highlights the importance of incorporating environmental conditions and the natural variability of communities when examining the potential risks posed by the release of AgNPs into the environment, as simplistic laboratory bioassays may not provide an adequate assessment of the long-term impacts of AgNPs on freshwater systems. Author Keywords: Benthic macroinvertebrates, IISD - Experimental Lakes Area, Littoral microcrustaceans, Silver nanoparticles, Whole lake experiment, Zooplankton
Who Cares? Examining associations between caregiving sensitivity and parent-peer attachment
Although years of research have established that attachment representations are not consistently transmitted from parent to child (also known as the transmission gap), the reasons for this gap remain relatively unknown. This transmission gap exists between parents and peers as well. The purpose of this thesis was to examine the role of caregiving sensitivity in the relationship between parent attachment and peer attachment and to test if caregiving sensitivity helps explains the relationship between parent attachment and peer attachment. This study found support for the transmission of attachment from parent to peers, but not that caregiving sensitivity explains this transmission. Results indicate that parenting caregiving sensitivity questionnaires are inconsistent in assessing the construct of sensitivity. Parenting caregiving sensitivity questionnaires also do not measure the same concepts as peer caregiving sensitivity questionnaires. These findings suggest that assessing caregiving sensitivity in parents differently may help close the transmission gap. Author Keywords: attachment, caregiving, parenting, peer, sensitivity
Support Vector Machines for Automated Galaxy Classification
Support Vector Machines (SVMs) are a deterministic, supervised machine learning algorithm that have been successfully applied to many areas of research. They are heavily grounded in mathematical theory and are effective at processing high-dimensional data. This thesis models a variety of galaxy classification tasks using SVMs and data from the Galaxy Zoo 2 project. SVM parameters were tuned in parallel using resources from Compute Canada, and a total of four experiments were completed to determine if invariance training and ensembles can be utilized to improve classification performance. It was found that SVMs performed well at many of the galaxy classification tasks examined, and the additional techniques explored did not provide a considerable improvement. Author Keywords: Compute Canada, Kernel, SDSS, SHARCNET, Support Vector Machine, SVM
third wheel
Population cycles are regular fluctuations in population densities, however, in recent years many cycles have begun to disappear. With Canada lynx this dampening has also been seen with decreasing latitude corresponding to an increase in prey diversity. My study investigates the role of alternate prey on the stability of the lynx-hare cycle by first comparing the functional responses of two sympatric but ecologically distinct predators on a primary and alternate prey. I then populated a three species predator-prey model to investigate the role of alternate prey on population stability. My results showed that alternate prey can promote stability, though they are unlikely to “stop the cycle”. Furthermore, stability offered by alternate prey is contingent on its ability to increase intraspecific competition. My study highlights that population cycles are not governed by a single factor and that future research needs to be cognizant of interactions between alternate prey and intraspecific competition. Author Keywords: alternate prey, Canis latrans, functional response, Lepus americanus, Lynx canadensis, Tamiasciurus hudsonicus
Modelling the Lanthanum Aluminate-Strontium Titanate Interface with a Modified Transverse Ising Model
In 2004 it was discovered that a two-dimensional electron gas (2DEG) forms at the interface between lanthanum aluminate (LAO) and strontium titanate (STO). This 2DEG exhibits a variety of electronic and magnetic phenomena, motivating intense research into its applicability to electronic devices. Over the years several models have been developed in theoretical exploration of this system. Here, the transverse Ising model is applied to the LAO/STO interface for the first time. It is shown that the model as it is traditionally formulated cannot accurately predict the structure of the electron density at the interface. I show that this can be fixed with a simple modification of the model, and discuss how this modification affects both the polarization distribution in ferroelectric thin films and the electron density at the LAO/STO interface. The importance of including the depolarizing field when modelling spatially inhomogeneous ferroelectric systems is also explored. Author Keywords: ferroelectric thin film, lanthanum aluminate, strontium titanate, transverse Ising model, two-dimensional electron gas
Assessing factors associated with wealth and health of Ontario workers after permanent work injury
I drew on Bourdieu’s theory of capital and theorized that different forms of economic, cultural and social capital which injured workers possessed and/or acquire over their disability trajectory may affect certain outcomes of permanent impairments. Using data from a cross-sectional survey of 494 Ontario workers with permanent impairments, I measured workers’ different indicators of capital in temporal order. Hierarchical regression analyses were used to test the unique association of workers’ individual characteristics, pre-injury capital, post-injury capital, and the outcomes of permanent impairments. The results show that factors related to individual characteristics, pre-injury and post-injury capital were associated with workers’ perceived health change, whereas pre-injury and post-injury capital were most relevant factors in explaining workers’ post-injury employment status and income recovery. When looking at the significance of individual predictors, post-injury variables were most relevant in understanding the outcomes of permanent impairment. The findings suggest that many workers faced economic and health disadvantages after permanent work injury. Author Keywords: Bourdieu, hierarchical regression, theory of capital, work-related disability, workers with permanent impairments
Reconceptualizing Immigration in Canada
This thesis challenges the contemporary framework of immigration in Canada. Despite Canada’s effort to promote cultural diversity and multicultural citizenship, immigration policy in the last decade has moved towards a model of cultural assimilation. The recent Bill—Strengthening Canadian Citizenship Act—devalues non-European cultures and hinders the successful integration for new immigrants. The problem of contemporary immigration in Canada lies in the narrow and exclusive understanding of immigration. That is, the current immigration framework is rooted in Eurocentrism, which draws exclusively from the economic and cultural values of the West. The Eurocentric understanding of migration not only hinders the successful integration for new immigrants, but it also hinders economic growth and weakens the social cohesion of Canada. For this reason, this thesis offers an alternative framework for understanding immigration. I focus on Chinese migration in Canada and take an interdisciplinary and a conceptual approach in order to present an inclusive understanding of Chinese migration. In particular, I apply the idea of "connected histories" to the context of immigration, and I demonstrate that immigration is a complex and interconnected phenomenon which cannot be reduced to the narratives of economics and ‘Canadian values.’ Instead, immigration should be understood as a process of transnational interactions because it not only allows us to understand benefits that transnational interactions would bring to immigrants, their country of origin and Canada, but it also recognizes different values and the agency of immigrants. Author Keywords: Bill C-24, Chinese Canadians, Eurocentrism, Immigration, Multicultrualism, Transnational
effects of Dissolved Organic Matter (DOM) sources on Pb2+, Zn2+ and Cd2+ binding
Metal binding to dissolved organic matter (DOM) determines metal speciation and strongly influences potential toxicity. The understanding of this process, however, is challenged by DOM source variation, which is not always considered by most existing metal speciation models. Source determines the molecular structure of DOM, including metal binding functional groups. This study has experimentally showed that the allochthonous-dominant DOM (i.e. more aromatic and humic) consistently has higher level of Pb binding than the autochthonous-dominant DOM (i.e. more aliphatic and proteinaceous) by more than two orders of magnitude. This source-discrimination, however, is less noticeable for Zn and Cd, although variation still exceeds a factor of four for both metals. The results indicate that metal binding is source-dependent, but the dependency is metal-specific. Accordingly, metal speciation models, such as the Windermere Humic Aqueous Model (WHAM), needs to consider DOM source variations. The WHAM input of active fraction of DOM participating in metal binding (f) is sensitive to DOM source. The commonly-used f = 0.65 substantially overestimated the Pb and Zn binding to autochthonous-dominant DOM, indicating f needs to be adjusted specifically. The optimal f value (fopt) linearly correlates with optical indexes, showing a potential to estimate fopt using simple absorbance and/or fluorescence measurements. Other DOM properties not optically-characterized may be also important to determine fopt, such as thiol, which shows strong affinity to most toxic metals and whose concentrations are appreciably high in natural waters (< 0.1 to 400 nmol L-1). Other analytical techniques rather than Cathodic Stripping Voltammetry (CSV) are required to accurately quantify thiol concentration for DOM with concentration > 1 mg L-1. To better explain the DOM-source effects, the conditional affinity spectrum (CAS) was calculated using a Fully Optimized ContinUous Spectrum (FOCUS) method. This method not only provides satisfactory goodness-of-fit, but also unique CAS solution. The allochthonous-dominant DOM consistently shows higher Pb affinity than autochthonous-dominant DOM. This source-discrimination is not clearly observed for Zn and Cd. Neither the variability of affinity nor capacity can be fully explained by the variability of individual DOM properties, indicating multiple properties may involve simultaneously. Together, the results help improve WHAM prediction of metal speciation, and consequently, benefit geochemical modelling of metal speciation, such as Biotic Ligand Model for predicting metal toxicity. Author Keywords: Dissolved organic matter, Metal binding, Source, Windermere Humic Aqueous Model
All I've Found is Pain and Terror
This thesis is concerned with how specific aesthetic elements function in various contemporary texts to distort, obscure, or illuminate the immoral actions and behaviours being represented. This thesis applies the moral status philosophy of Mary Anne Warren, along with the moral philosophy of Emmanuel Lévinas and Zygmunt Bauman. Close reading and critical analysis are supported by Michele Aaron’s theory of spectatorship. The sublime is explored in Dexter (2006) and Batman: The Dark Knight Returns (1986), the uncanny in Battlestar Galactica (2003) and Westworld (2016), and the abject in The Walking Dead (2003) and World War Z (2006). The intentions of this project are to conduct a formal examination of the relationship between audience and text as it is filtered through aesthetic representation and moral frameworks. This thesis argues that aesthetic effects must be understood in connection to morality for active consumers to engage with these texts as sites for ethical consideration. Author Keywords: aesthetic theory, moral status philosophy, Popular fiction, spectatorship, The Walking Dead, Westworld
Emerging Dynamic Social Learning Theory of a Learning Community of Practice
In current knowledge-based economy, knowledge might be viewed as the most valuable organizational resource in sustaining any organization. Organizational knowledge originates from cognitive learning by individuals situated within organizations. In organizational learning, situated learning of knowledge by individuals is shared to create sustainable organizational competency. Yet, there is inadequate research to understand how situated learning operates as a social learning system within Community of Practice (‘CoP’). Through a case study of a multi-level, non-profit CoP in Ontario, Canada, this qualitative explanatory research contributes to the extant literature by building a unique theoretical framework that provides conceptual insights on linkages between organizational knowledge, social learning system, and organizational competency, in sustaining the organizational CoP. Using Straussian grounded theory methodology, qualitative primary data from in-depth interviews, participant observations, and documents were triangulated and analysed abductively to reveal an emerging dynamic knowledge-based social learning theory towards explaining how situated learning sustains this learning CoP. Author Keywords: Community of Practice, Grounded Theory, Organizational Knowledge, Organizational Learning, Organizational Sustainability, Situated Learning
On the Cyberflaneur
This thesis is a critical response to Evgeny Morozov’s article proclaiming the death of the cyberflâneur. Suspicious of the superficiality of his argument, I developed a practico-theoretical project to prove that the cyberflâneur is not dead but alive – or, if it were dead, to rescue it from its grave and bring it back to life. In the course of my response to Morozov, I develop a theoretical foundation that allows me to continue thinking about the concept and practice of the cyberflâneur in the context of the Internet. In doing so, I rely on Gilles Deleuze and Felix Guattari’s “Treatise on Nomadology: The War Machine” (2011), in combination with a history of the tradition of wandering. We are living in a postmodern-posthuman era driven by the chaotic and confusing forces that are manifested through the Internet. As such, it is no longer enough to be concerned with opening the space where we live, move and think; we cannot retreat to nature, we can’t escape society. However, I see potential in the Internet. The Internet, as a physical and material network, can be actualized as an apparatus of capture. It operates as a medium for accelerating or limiting speed, or as an apparatus for the control of the transmission of information. I develop the cyberflâneur as an aesthetic figure that reveals the Internet’s potential. If these revelations happen to be transmitted, then everyday life can again become an object of dispute, rather than unmeditated habituation. Author Keywords: Cyberflâneur, Everyday Life, Internet, Nomadology, Research-creation, Wandering
“It's like getting a new car without the manual”
This study explored teacher infusion of Indigenous curriculum content through interviews with ten non-Indigenous teachers of social studies and history. The interviews centered on teacher perceptions of preparedness to implement Ontario’s recent TRC curriculum revisions, which include more about the contributions, histories, cultures, and perspectives of Indigenous peoples. A brief analysis of Ontario’s First Nation, Métis, and Inuit Education Policy Framework is included, alongside critiques of the Eurocentrism at the heart of education systems. The interviews revealed that many of the teachers were committed to Indigenous education and learning more, but they felt unprepared and lacked resources to teach Indigenous curriculum content with confidence. This study highlighted the critical role of settler teachers in Indigenous education and the importance of teachers undertaking settler unsettling in order to be effective and appropriate in Indigenous curriculum delivery. Individual changes must occur alongside educational system decolonization with a particular focus on teacher preparation. Author Keywords: cognitive imperialism, Indigenous Education, Ontario, settler educator, settler unsettling, TRC curriculum

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Graduate student theses produced at Trent University. You may also browse theses and dissertations by year, program, or author.

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1973 - 2033
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Format: 2023/03/27

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