Graduate Theses & Dissertations

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Fingerprinting of dissolved organic matter and copper ligands in the Canadian Arctic and North Pacific Ocean
Dissolved organic matter (DOM) in oceans provides nutrients and ultraviolet radiation protection to microbes. Some DOM compounds can chelate with metals, including copper, controlling their transport and bioavailability in marine systems. As copper functions as both a nutrient and toxicant, studies into the chemical structures of Cu-ligands is important, however currently limited. In this thesis, the chemical composition of total and Cu-binding DOM is investigated using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) in the Canadian Arctic and North Pacific. Chapter 2 reveals chemical differences in DOM composition between the southern and northern Canada Basin, revealing the influence of terrestrial and biological sources. Chapter 3 shows the uniqueness of Cu-binding ligands found in the Canadian Arctic and North Pacific Ocean. Studying the composition of DOM gives insight into the chemical diversity of marine DOM, helping to predict the effects of a changing climate on marine ecosystems. Author Keywords: biological, dissolved organic matter, fluorescence, immobilized metal-ion affinity chromatography, mass spectrometry, terrestrial
First Time…A Second Time
The purpose of the current study was to explore virginity loss experiences in lesbian, gay, and bisexual individuals (LGB), specifically those who have had both a sexual experience with a member of a different sex and a member of the same sex. This phenomenon is what the current study is defining as second virginity loss. Participants consisted of 645 LGB self-identified individuals, the sample was approximately half women (53%) and ages ranged from 18-65. Further, six semi-structured interviews were conducted to gain a clearer understanding of LGB individuals virginity loss experiences. Of the sample, approximately 60% of each sexual orientation reported having two sexual experiences they equated with virginity loss, one with a member of a different sex, and one with a member of the same sex. Analyses of both the qualitative and quantitative data were conducted in an attempt to gain an understanding in three main areas: (1) definitions of virginity loss, (2) virginity beliefs, and (3) motivations. It was found that LGB individuals continue to hold heteronormative definitions of virginity loss, i.e. penile-vaginal intercourse, though these definitions were found to be transitional in nature. LGB individuals also seem to hold more gift related beliefs toward their same-sex experience and more stigma related beliefs toward their different sex experience, however, as shown by previous research (Carpenter, 2001, 2002), most LGB individuals highly endorsed process beliefs. Finally, motivations for virginity loss were found to be consistent with two main themes: validation and drive. Overall, this research suggests that the LGB community has a fairly complicated relationship with virginity but certainly do not feel exempt from the concept or the pressures attached. The current study is the first to explore the phenomenon of second virginity loss in LGB individuals and should be used as a foundation for future research in both first sexual experience and LGB fields to build upon. Author Keywords: first sexual experience, LGB, mixed-methods, second virginity loss, virginity
Fish and invertebrate use of invasive Phragmites in a Great Lakes freshwater delta
Invasive Phragmites australis ssp. australis (herein “Phragmites”) has established and rapidly spread throughout many coastal areas of the Great Lakes. Known to displace native vegetation communities as it forms large, monotypic stands, Phragmites has a bad reputation when it comes to losses of biodiversity and habitat provision for wildlife. However, the extent to which Phragmites provides habitat for fish and invertebrates in coastal freshwater wetlands remains relatively unquantified. Thus, this study assessed whether fish assemblages and invertebrate communities in stands of Phragmites differ from those in stands of two native emergent vegetation communities, Typha spp. and Schoenoplectus spp. The findings showed significant differences in habitat variables among the vegetation communities in terms of water depth, macrophyte species richness, stem density and water quality. While abundance of the functional feeding group filterer-collectors was found to be significantly less in stands of Phragmites when compared to Schoenoplectus, no difference was observed in invertebrate taxa richness among vegetation communities. Lastly, no difference in fish assemblage or invertebrate community was detected when using multivariate analyses, implying that invasive Phragmites provides habitat that appears to be as valuable for fish and invertebrates as other emergent vegetation types in the St. Clair River Delta. The findings of this study will ultimately benefit the literature on invasive Phragmites and its role as fish habitat in freshwater wetlands, and aid management agencies in decisions regarding control of the invasive species. Author Keywords: aquatic invasive species, aquatic macroinvertebrates, freshwater fish, freshwater wetlands, nMDS, Phragmites
Flavohemoglobin expression in Giardia intestinalis exposed to nitrosative stress
The parasitic protist Giardia intestinalis lacks most heme proteins yet encodes a flavohemoglobin (gFlHb) that converts nitric oxide to nitrate and likely protects the cell from nitrosative stress. In this work an antibody raised against gFlHb was used to examine both changes in gFlHb expression levels and intracellular localization in Giardia in response to nitrosative stress. Giardia trophozoites exposed to stressors which either directly release nitric oxide (diethyltriamine NONOate, 1 mM) or are sources of other reactive nitrogen intermediates (sodium nitrite 20 mM or S-nitrosoglutathione, 1 or 5 mM) exhibited a 2 to 9-fold increase of gFlHb after 24 hours. Increased expression levels of gFlHb were detectable by 8 hours in S-nitrosoglutathione and diethyltriamine-NONOate-treated trophozoites, and by 12 hours after sodium nitrite exposure; these differences were likely due to differences in the rates of release of RNS from these compounds. In addition to a band of the expected size for gFlHb (52 kDa), western blots detected a second, higher molecular weight band (72 kDa) with comparable or higher intensity upon treatment with these RNS donors, which is consistent with sumoylation of gFlHb. Immunofluorescence microscopy of Giardia trophozoites detected gFlHb diffused throughout the cytoplasm and more punctuated staining along the cell membrane and between the nuclei. The punctuated staining may be due to the association of gFlHb with either peripheral vacuoles or basal bodies. Author Keywords: Flavohemoglobin, Giardia intestinalis, Nitrosative stress
Forest Roost Use by Little Brown Bats (Myotis lucifugus) in Ontario
Roosts offer bats protection from predators, shelter from external environmental conditions, and a space where sociality, mating, and the rearing of young can occur. However, knowledge gaps still remain for many forest roosting species, such as the little brown bat (Myotis lucifugus) surrounding what roosts are selected, and what variables are influential at differing scales of selection. As a species-at-risk, identifying and predicting roost habitat selection may aid conservation and management. I identified forest roosts in a previously unexamined area of this species’ range using radio-telemetry, and measured tree-scale characteristics of located roosts. I then used a logistic model selection process with stand-scale variables to predict roost presence across forest stands. Height of trees in a given stand was the best predictor of roost presence - which may be linked to solar exposure and other thermal benefits. I then examined roost-level variables effecting the abundance of roosting bats in an artificial roosting environment (bat boxes). I found that temperature and social effects were both significant predictors of bat abundance, with warmer minimum temperatures in the box having a positive effect. These results suggest maternal bats may select roosts with higher minimum temperatures, likely due to the energetic benefits that may be gained over the course of reproduction. Author Keywords: forest roost, habitat selection, little brown bat, Myotic lucifugus, roost choice, stand selection
Fractionation of Mercury Isotopes in an Aqueous Environment
Fractionation of mercury isotopes in an aqueous environment: Chemical Oxidation Dimitri Stathopoulos The study of fractionation patterns for the stable isotopes of mercury is a growing field. The potential for stable isotopes to trace mercury through the environment from pollution sources to sinks make the subject interesting to geochemists and useful to a wider audience. The purpose of this study is to measure the fractionation of mercury as it is oxidized in an aqueous medium. Samples in this study are prepared by chemically oxidizing different proportions of elemental mercury using four different oxidants. The oxidized portion is then separated from the elemental portion and an analysis of the isotope ratios for both portions is performed using a multicollector inductively coupled plasma mass spectrometer MC-ICP/MS. These isotope ratios are measured against the preoxidation isotope ratio to determine what if any change has occurred. From the findings of this work, it is now known chemical oxidation causes both mass dependent and mass independent fractionation. Mass dependent fractionation causes an enrichment of the heavier isotopes in the oxidized portion while the opposite is true for the elemental portion. Mass independent fractionation occurred only in the odd isotopes and causes a depletion of odd isotopes in the oxidized portion and enrichment in the elemental portion. These trends were found to be true for all oxidants tested as the pattern of fractionation does not change with varying oxidants. Author Keywords: Isotope, Mass Dependent, Mass Independent, Mercury, Oxidation
Framework for Testing Time Series Interpolators
The spectrum of a given time series is a characteristic function describing its frequency properties. Spectrum estimation methods require time series data to be contiguous in order for robust estimators to retain their performance. This poses a fundamental challenge, especially when considering real-world scientific data that is often plagued by missing values, and/or irregularly recorded measurements. One area of research devoted to this problem seeks to repair the original time series through interpolation. There are several algorithms that have proven successful for the interpolation of considerably large gaps of missing data, but most are only valid for use on stationary time series: processes whose statistical properties are time-invariant, which is not a common property of real-world data. The Hybrid Wiener interpolator is a method that was designed for repairing nonstationary data, rendering it suitable for spectrum estimation. This thesis work presents a computational framework designed for conducting systematic testing on the statistical performance of this method in light of changes to gap structure and departures from the stationarity assumption. A comprehensive audit of the Hybrid Wiener Interpolator against other state-of-the art algorithms will also be explored. Author Keywords: applied statistics, hybrid wiener interpolator, imputation, interpolation, R statistical software, time series
Fraud Detection in Financial Businesses Using Data Mining Approaches
The purpose of this research is to apply four methods on two data sets, a Synthetic dataset and a Real-World dataset, and compare the results to each other with the intention of arriving at methods to prevent fraud. Methods used include Logistic Regression, Isolation Forest, Ensemble Method and Generative Adversarial Networks. Results show that all four models achieve accuracies between 91% and 99% except Isolation Forest gave 69% accuracy for the Synthetic dataset. The four models detect fraud well when built on a training set and tested with a test set. Logistic Regression achieves good results with less computational eorts. Isolation Forest achieve lower results accuracies when the data is sparse and not preprocessed correctly. Ensemble Models achieve the highest accuracy for both datasets. GAN achieves good results but overts if a big number of epochs was used. Future work could incorporate other classiers. Author Keywords: Ensemble Method, GAN, Isolation forest, Logistic Regression, Outliers
Frog Virus 3
Understanding the maintenance and spread of invasive diseases is critical in evaluating threats to biodiversity and how to best minimize their impact, which can by done by monitoring disease occurrences across time and space. I sought to apply existing and upcoming molecular tools to assess fluctuations in both presence and strain variation of frog virus 3 (FV3), a species of Ranavirus, across Canadian waterbodies. I explored the temporal patterns and spatial distribution of ranavirus presence across multiple months and seasons using environmental DNA techniques. Results indicate that ranavirus was present in approximately 72.5% of waterbodies sampled on a fine geographical scale (<10km between sites, 7,150 km2), with higher detection rates in later summer months than earlier. I then explored the sequence variability at the major capsid protein gene (MCP) and putative virulence gene (vIF-2α) of FV3 samples from Ontario, Alberta, and the Northwest Territories, with the premise of understanding pathogen movement across the landscape. However, a lack of genetic diversity was found across regions, likely due to a lack of informative variation at the chosen genetic markers or lack of mutation. Instead, I found a novel FV3-like ranavirus and evidence for a recombinant between FV3 and a ranavirus of another lineage. This thesis provides a deeper understanding into the spatio-temporal distribution of FV3, with an idea of how widespread and threatening ranaviruses are to amphibian diversity. Keywords: ranavirus, frog virus 3, amphibians, environmental DNA, phylogenetics, wildlife disease, disease surveillance, major capsid protein, vIF-2α Author Keywords: amphibians, environmental DNA, frog virus 3, phylogenetics, ranavirus, wildlife disease
Functional Genetic Diversity in American Mink (Neovison vison)
The release of domestic organisms to the wild is considered a threat to biodiversity because the introduction of domestic genes through interbreeding can negatively impact wild conspecifics via outbreeding and local extinction. In North America, captive American mink (Neovison vison) are frequently escaping into the wild, yet the impact of these events on the functional genetic diversity of wild mink populations is unclear. I characterized domestic and wild mink in Ontario at 17 trinucleotide microsatellites located in functional genes thought to be associated with traits affected by domestication. I found low functional genetic diversity, as only 4 of 17 genes were variable and of those four there was little evidence of allele frequency differences between domestic and wild mink. Using redundancy analysis and a spatial analysis of principal components on the four variable loci (AR, ATN1, IGF-1, and TOB1) I found no evidence to suggest domestic release events are affecting functional genetic diversity of free-ranging mink at the set of markers assessed. Author Keywords: American mink, domestication, functional gene, introgression, Neovison vison
Functional Investigation of A Ustilago maydis Xylose Metabolism Gene and its Antisense Transcripts
Ustilago maydis is a biotrophic fungal plant pathogen that causes ‘common smut of corn’ disease. During infection, U. maydis develops a metabolic dependency on its host, relying on uptake of the carbon molecules provided within Zea mays tissues. The research presented indicated a requirement for metabolism of the pentose sugar D-xylose through functional investigation of a U. maydis xylitol dehydrogenase (uxm1), an enzyme involved in the bioconversion of D-xylose. This work is the first to outline the importance of pentose metabolism during biotrophic plant pathogenesis, as U. maydis haploid cells lacking this gene were impaired in their ability to cause disease and grow on medium containing only D-xylose. This thesis also explored the possibility that expression of this carbon-related gene is controlled by antisense RNAs (asRNAs), endogenous molecules with complementarity to mRNAs. Previous investigation of U. maydis asRNAs identified some that are exclusively expressed in the dormant teliospore, suggesting they have a functional role within this cell-type. A subset of these asRNAs at the uxm1 locus were investigated, with the purpose of identifying the mechanism(s) by which they influence U. maydis pathogenesis. This investigation involved the creation and functional analysis of a series of U. maydis deletion and expression strains. Together, these findings provided additional knowledge regarding the possible functions of U. maydis asRNAs, and their involvement in controlling important cellular processes, such as carbon metabolism and pathogenesis. Author Keywords: antisense transcripts, fungal carbon metabolism, non-coding RNAs, pathogenesis, Ustilago maydis, xylitol dehydrogenase
Functional Variation within Middle Paleolithic Ground Stone Tools
In the southern Levant, ground stone tools (GST) provide insight into early plant food exploitation, butchery, and cognition. Outside of these examples, GST evidence is scarce, particularly for the Middle Paleolithic. An extensive assemblage of GST recovered from Nesher Ramla, an open-air hunting camp in Israel, presents the unique opportunity to study the role of GST within Middle Paleolithic behaviour. Use-wear and residue analysis, together with replication experiments are employed to investigate GST function within a specific period of site use by focusing on GST from the Upper Sequence (Units I-II) which reflects a trend of decreasing site-use intensity. The results indicate that GST were employed for bone breaking and knapping during the final phases of occupation while comparison with Unit V suggests longer occupations involved more diverse and extensive use of GST. GST at open-air sites are also proposed to represent a strategy for intensive exploitation of location-specific resources. Author Keywords: Ground Stone Tools, Hammerstones, Middle Paleolithic, Residue Analysis, southern Levant, Use-Wear Analysis

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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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