Graduate Theses & Dissertations

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Self-Organizing Maps and Galaxy Evolution
Artificial Neural Networks (ANN) have been applied to many areas of research. These techniques use a series of object attributes and can be trained to recognize different classes of objects. The Self-Organizing Map (SOM) is an unsupervised machine learning technique which has been shown to be successful in the mapping of high-dimensional data into a 2D representation referred to as a map. These maps are easier to interpret and aid in the classification of data. In this work, the existing algorithms for the SOM have been extended to generate 3D maps. The higher dimensionality of the map provides for more information to be made available to the interpretation of classifications. The effectiveness of the implementation was verified using three separate standard datasets. Results from these investigations supported the expectation that a 3D SOM would result in a more effective classifier. The 3D SOM algorithm was then applied to an analysis of galaxy morphology classifications. It is postulated that the morphology of a galaxy relates directly to how it will evolve over time. In this work, the Spectral Energy Distribution (SED) will be used as a source for galaxy attributes. The SED data was extracted from the NASA Extragalactic Database (NED). The data was grouped into sample sets of matching frequencies and the 3D SOM application was applied as a morphological classifier. It was shown that the SOMs created were effective as an unsupervised machine learning technique to classify galaxies based solely on their SED. Morphological predictions for a number of galaxies were shown to be in agreement with classifications obtained from new observations in NED. Author Keywords: Galaxy Morphology, Multi-wavelength, parallel, Self-Organizing Maps
Sensitivity of Forest Soils to Acidic Deposition Downwind of an Aluminum Smelter, Kitimat, B.C.
Maximum permitted SO2 emissions from an aluminum smelter in Kitimat, B.C., increased after modernization in 2015. An increase in acidic deposition can potentially acidify forest soils. Monitoring was conducted at two long-term soil monitoring plots at near (7 km) and far (41 km) sites downwind from the smelter. Change in soil properties was assessed between 2015 and 2018: for the near plot, there was significant decrease in pH and exchange acidity; far plot soils exhibited significant decrease of base cations and exchange acidity in the 0–5 cm layer only. The average total SO42- deposition at near and far plots were estimated to be between 8.2–12.1 and 6.7–7.4 kg/ha/yr, respectively. It was concluded no soil acidification was detected. Observed changes were attributed to measured differences in organic matter, likely influenced by sampling difficulty and measurement process discrepancies. Estimated SO42- deposition levels pose no risk to soil base cation depletion. Author Keywords: acid forest soils, acidic deposition, aluminum smelter, exchangeable base cations, long-term monitoring, minimum detectable change
Sex-Specific Graphs
Sex-specific genetic structure is a commonly observed pattern among vertebrate species. Facing differential selective pressures, individuals may adopt sex-specific life historical traits that ultimately shape genetic variation among populations. Although differential dispersal dynamics are commonly detected in the literature, few studies have investigated the potential effect of sex-specific functional connectivity on genetic structure. The recent uses of Graph Theory in landscape genetics have demonstrated network capacities to describe complex system behaviors where network topology intuitively represents genetic interaction among sub-units. By implementing a sex-specific network approach, our results suggest that Sex-Specific Graphs (SSG) are sensitive to differential male and female dispersal dynamics of a fisher (Martes pennanti) metapopulation in southern Ontario. Our analyses based on SSG topologies supported the hypothesis of male-biased dispersal. Furthermore, we demonstrated that the effect of the landscape, identified at the population-level, could be partitioned among sex-specific strata. We found that female connectivity was negatively affected by snow depth, while being neutral for males. Our findings underlined the potential of conducting sex-specific analysis by identifying landscape elements that promotes or impedes functional connectivity of wildlife populations, which sometimes remains cryptic when studied at the population level. We propose that SSG approach would be applicable to other vagile species where differential sex-specific processes are expected to occur. Author Keywords: genetic structure, Landscape Genetics, Martes pennanti, Population Graph, sex-biased dispersal, Sex-Specific Graphs
Sexting and Satisfaction
Sexting was explored in relation to cohabitation status, general and sexual communication, as well as the anxious and avoidant dimensions of attachment. The present study was focused the distinction between lifetime and recent sexting, in an attempt to more accurately assess the relationships between the examined factors and sexting behaviours. Individuals in long-distance relationships were more likely to report recently sexting and engaged more frequently than those in cohabitating relationships, but did not differ in their levels of sexual satisfaction. Recent sexters reported higher levels of sexual communication compared to lifetime sexters, and sexual communication was positively, though weakly, correlated with sexting frequency. The present study was unable to support a predictive relationship between recent sexting and levels of attachment anxiety or avoidance. These results highlight the importance of exploring the context in which sexting occurs, as well as distinguishing between lifetime and recent sexters in future sexting research. Author Keywords: Attachment, Long Distance Relationship, Recent Sexting, Satisfaction, Sexting, Sexual Communication
Sextual Consent
The purpose of the current study was to explore the relationships between sexting, perceptions of sexual consent, and nonconsensual sexual experiences (NSEs). Participants consisted of 100 community members and 851 undergraduate students enrolled at Trent University. It was found that males were more likely than females to interpret ambiguous sexual scenarios as consensual, but consent perceptions were not influenced by sexting. When examining past personal experiences, males interpreted received sext messages as an indicator of consent significantly more than females, while females were more likely to interpret received messages as more harassing. NSEs were significantly related to sexting behaviours: those who engage in sexting were more likely to also have experienced a NSE, and 20.5% of participants in the current study reported having experienced a NSE with a consensual sexting partner. The current study has important implications for the future of sexting research, practice, and policy. Author Keywords: nonconsensual sexual experiences, sexting, sexual assault, sexual consent, sexual harassment
Sexual Dimporphism and Population Dynamics of Sub-Arctic Breding Dunlin (Calidris alpina hudsonia) near Churchill, Manitoba, Canada
Around the world, many populations of migratory shorebirds appear to be declining. Conservation strategies to reverse declining trends rely on, among other information, a firm understanding of breeding ground population dynamics. From 2010 to 2014, I studied a breeding population of Dunlin (Calidris alpina hudsonia) near Churchill, Manitoba using mark-recapture methods. I found that females were significantly larger than males. I subsequently developed an equation based on morphological features that successfully classified 87.1% of females and 92.6% of males, sexed using molecular techniques. Using program MARK, I quantified the annual apparent survival of adults (± SE) within the breeding population (0.82 ± 0.063 for males, 0.73 ± 0.12 for females). Transient adults made up a significant percentage of the female population (32%, P = 0.011), but non-significant in the male population (12%, P > 0.05). Re-sight rate was high for both sexes, and ranged from 0.86-0.90 per year. Sex, year, and nest initiation date were the factors that had the greatest influence on annual returns. There was no significant difference in mean inter-annual nest site distance between sexes (male: 82.01 ± 13.42 m, female: 208.38 ± 55.88 m, P > 0.05). The high survival estimates obtained in this study suggest that the breeding population is stable and may not be contributing to suspected population declines within the subspecies. Author Keywords: demography, discriminant function analysis, mark-recapture, sexual size dimorphism, survival
Sexual consent
How one identifies their nonconsensual sexual experiences (NSE) and cognitively integrates the experience into their sexual schemas may affect how individuals perceive and negotiate sexual consent. Previous research has demonstrated that both the method of quantifying NSEs and the labels used to describe NSEs yield different results in psychosexual outcomes associated with NSEs. The current study assessed differences in subjectively and behaviourally quantified NSEs, as well as the role of cognitive and affective appraisals of sexuality and sexual interactions, on sexual consent attitudes. While behaviourally measured NSE history did not significantly influence sexual consent attitudes, the subjective identification of NSEs with various labels did influence attitudes toward sexual consent. Cognitive appraisals of rape and affective appraisals of sexuality also significantly predicted sexual consent attitudes. Implications for future research and NSE prevention are discussed. Keywords: Nonconsensual sexual experiences, sexual consent, quantifying NSEs, affective sexuality, cognitive sexuality Author Keywords: identification, nonconsensual sexual experiences, rape, sexual affectivity, sexual assault, sexual consent
Shorebird Habitat Use and Foraging Ecology on Bulls Island, South Carolina During the Non-Breeding Season
Recent declines in North American shorebird populations could be linked to habitat loss on the non-breeding grounds. Sea-level rise and increased frequency of coastal storms are causing significant erosion of barrier islands, thereby threatening shorebirds who rely on shoreline habitats for foraging. I conducted shorebird surveys on Bulls Island, South Carolina in the winters of 2018 and 2019 and examined habitat selection and foraging behaviour in Dunlin (Calidris alpina), Sanderling (Calidris alba), Semipalmated Plovers (Charadrius semipalmatus), and Piping Plovers (Charadrius melodus). Area, tidal stage, and invertebrate prey availability were important determinants of shorebird abundance, behaviour, and distribution. My study highlights the importance of Bulls Island’s habitat heterogeneity to supporting a diverse community of non-breeding shorebirds. Considering both the high rate of erosion and the increased frequency of disturbance along the shoreline of the island, intertidal habitats should be monitored to predict negative effects of changes in habitat composition and area on non-breeding shorebirds. Author Keywords: foraging behaviour, habitat loss, habitat selection, invertebrate prey, non-breeding, shorebirds
Short photoperiod lowers visceral adiposity and shifts the molecular clock in Peromyscus leucopus
The length of photoperiod can alter circadian rhythms and change fat depot mass whencombined with environmental temperatures below thermoneutral. To isolate photoperiod effects, we compared the effects of long and short photoperiod exposure at thermoneutrality in photoperiod sensitive, F1 generation adult male white-footed mice (P. leucopus). Mice were housed in long-day or short-day photoperiod conditions at thermoneutrality for 4 weeks. Short photoperiod decreased vWAT mass without changing body weight, scWAT or iBAT mass, or calorie consumption. Short photoperiod increased Adrβ3 and Lpl mRNA expression in vWAT with no change in Ucp1, Pgc1a or Hsl. vWAT Per1, Per2 and Nr1d1 mRNA expression were aligned to the onset of dark and food intake, while Bmal1 and Clock were misaligned. These findings suggest that short photoperiod per se can decrease visceral fat accumulation, without activating thermogenesis, reinforcing that environmental photoperiod should be considered when researching cause and prevention of obesity. Author Keywords: adiposity, circadian rhythm, clock genes, obesity, Peromyscus, photoperiod
Sinc-Collocation Difference Methods for Solving the Gross-Pitaevskii Equation
The time-dependent Gross-Pitaevskii Equation, describing the movement of parti- cles in quantum mechanics, may not be solved analytically due to its inherent non- linearity. Hence numerical methods are of importance to approximate the solution. This study develops a discrete scheme in time and space to simulate the solution defined in a finite domain by using the Crank-Nicolson difference method and Sinc Collocation Methods (SCM), respectively. In theory and practice, the time discretiz- ing system decays errors in the second-order of accuracy, and SCMs are decaying errors exponentially. A new SCM with a unique boundary treatment is proposed and compared with the original SCM and other similar numerical techniques in time costs and numerical errors. As a result, the new SCM decays errors faster than the original one. Also, to attain the same accuracy, the new SCM interpolates fewer nodes than the original SCM, which saves computational costs. The new SCM is capable of approximating partial differential equations under different boundary con- ditions, which can be extensively applied in fitting theory. Author Keywords: Crank-Nicolson difference method, Gross-Pitaevskii Equation, Sinc-Collocation methods
Smote and Performance Measures for Machine Learning Applied to Real-Time Bidding
In the context of Real-Time Bidding (RTB) the machine learning problems of imbalanced classes and model selection are investigated. Synthetic Minority Oversampling Technique (SMOTE) is commonly used to combat imbalanced classes but a shortcoming is identified. Use of a distance threshold is identified as a solution and testing in a live RTB environment shows significant improvement. For model selection, the statistical measure Critical Success Index (CSI) is modified to add emphasis on recall. This new measure (CSI-R) is empirically compared with other measures such as accuracy, lift, efficiency, true skill score, Heidke's skill score and Gilbert's skill score. In all cases CSI-R is shown to provide better application to the RTB industry. Author Keywords: imbalanced classes, machine learning, online advertising, performance measures, real-time bidding, SMOTE
Social Anxiety and Emotional Competence
Prior research has examined social anxiety, emotional competence (EC) and life adjustment (i.e., loneliness and life satisfaction) using cross-sectional designs, although there is limited information on their association over time. The present study examined the impact of social anxiety on life adjustment and assessed if EC could mediate this relationship from young to middle adulthood. University students (N = 283) completed self-report measures at two time points: in first year university and 15 years later. The results accord with previous research demonstrating the stability and slight decrease of social anxiety over time. Social anxiety in young adulthood was a robust predictor of loneliness in middle adulthood, and a weak predictor of life dissatisfaction for men. Mediation analyses revealed that social anxiety was indirectly associated with interpersonal adjustment via EC, especially the intrapersonal EC domain. Social anxiety requires early intervention and EC may help to prevent later social anxiety and maladjustment. Author Keywords: emotional intelligence, life adjustment, social anxiety

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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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