Graduate Theses & Dissertations

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Archaeological Investigation of the North Group at Pacbitun, Belize
This thesis reports on the 2010 excavations of the North Group and Eastern Court at the ancient Lowland Maya site of Pacbitun. It provides a construction history of the architecture and an analysis of associated artifacts, burials, and caches. The archaeological investigations demonstrate that the seven structures (Strs. 34-40) of this restricted access plazuela group were built in the Early Classic period, and renewed in the Late Classic period. Based on analyses of artifacts (ceramics and lithics), skeletal and faunal remains, and intra- and inter-site comparisons, the North Group functioned as a secondary elite domestic residential group. Reconstruction suggests that the inhabitants here were not commoners; instead, the occupants probably were related to the ruling elite of Pacbitun. Some of the evidence includes the central location and elevation of the North Group, the presence of red painted plaster surfacing, a burial with multiple ceramic musical instruments, and multiple dedicatory caches with exotic goods (e.g., marine shell, jadeite, "Charlie Chaplin" figures). Author Keywords: Ancient Maya, ceramic musical instruments, Charlie Chaplin figurines, Pacbitun, North Group, Eastern Court, Belize River Valley, Belize, restrictive access plazuela group, secondary elite
Models of partitioning, uptake, and toxicity of neutral organic chemicals in fish
Models of partitioning, uptake, and toxicity of neutral organic chemicals in fish Alena Kathryn Davidson Celsie A novel dynamic fugacity model is developed that simulates the uptake of chemicals in fish by respiration as applies in aquatic toxicity tests. A physiologically based toxicokinetic model was developed which calculates the time-course of chemical distribution in four tissue compartments in fish, including metabolic biotransformation in the liver. Toxic endpoints are defined by fugacity reaching a 50% mortality value. The model is tested against empirical data for the uptake of pentachloroethane in rainbow trout and from naphthalene and trichlorobenzene in fathead minnows. The model was able to predict bioconcentration and toxicity within a factor of 2 of empirical data. The sensitivity to partition coefficients of computed whole-body concentration was also investigated. In addition to this model development three methods for predicting partition coefficients were evaluated: lipid-fraction, COSMOtherm estimation, and using Abraham parameters. The lipid fraction method produced accurate tissue-water partitioning values consistently for all tissues tested and is recommended for estimating these values. Results also suggest that quantum chemical methods hold promise for predicting the aquatic toxicity of chemicals based only on molecular structure. Author Keywords: COSMOtherm, fish model, fugacity, Partition coefficient, tissue-water, toxicokinetics
Near-Hand Effects and Recruitment of Visual-Tactile Bimodal Cells
Near-hand benefits are seen when individuals are able to process targets more quickly, accurately, and with greater precision when a hand is placed near, rather than far from a target. One possibility is that near-hand stimuli recruit visual-tactile bimodal cells. Research reports that placing a hand near a target delayed immediate saccade onset and speeded delayed saccade onset. Study 1 examined saccade onset to targets appearing near a real hand, a realistic fake hand, or a non-hand visual cue. Immediate saccades were facilitated and delayed saccades were slowed with a real hand in the display, in comparison to a fake hand and no-hand. To establish the link between near-hand effects and bimodal cells, Study 2 used repetitive transcranial magnetic stimulation (rTMS) to depress cortical activity in PMd. RTMS did not induce a reversal of interference induced by near-hand, congruent targets. However, a reversal of the hand effect was found in the stimulation group; a real hand in the display may delay immediate saccades and improve delayed saccades post-stimulation. This finding may double dissociate the effect of the real hand from the fake hand and may be inconsistent with the hypothesis that the hand is attracting attention. Author Keywords: multisensory integration, near-hand effects, PMd, premotor cortex, rTMS, visual-tactile bimodal neurons
regional comparison of the structure and function of benthic macroinvertebrate communities within Precambrian Shield and St. Lawrence lowland lakes in south-central Ontario
Benthic macroinvertebrtes (BMI) are functionally important in aquatic ecosystems; as such, knowledge of their community structure and function is critical for understanding these systems. BMI were sampled from ten lakes in each of two regions of south-central Ontario to investigate which chemical and physical variables could be shaping their community structure and function. Ten Precambrian Shield lakes in the Muskoka-Haliburton region, and ten St Lawrence lowland lakes in the Kawartha lakes region were sampled. These lakes are geologically and chemically distinct, creating natural chemical and physical gradients within and between both regions. Community function was assessed using stable isotope analysis to elucidate carbon transfer dynamics (δ13C) and food web interactions (δ15N). It was predicted that the BMI from Shield lakes would have a δ13C signature indicative of allochthonous carbon subsidies, whereas the lowland lake BMI signatures would reflect autochthonous production. Additionally, it was predicted that the food web length (measured in δ15N units) would be different in Shield and lowland lakes. Both of these predictions were supported; however, the data indicate that δ13C signatures are more likely influenced by catchment geology (represented by bicarbonate concentration) than the extent of allochthony. The best predictor of food web length was found to be region. To assess BMI community structure, taxonomic richness, %EPT (% Ephemeroptera, Plecoptera, Trichoptera; a water quality index), and distribution of functional feeding groups were examined. Based on chemistry it was expected that the Shield lakes would be more speciose, and of greater water quality (relatively lower nutrient levels). These predictions were rejected; since there were no significant regional differences in taxonomic richness or biologically inferred water quality (%EPT). However, sediment size was found to best explain the variability in both metrics, with greater richness and %EPT found at sites with medium and small substrates than those with large substrates. Significant regional differences were found in the distribution of functional feeding groups. Most notably, there were significantly greater proportions of scrapers and shredders in the lowland and Shield lakes, respectively. Based on the feeding mechanisms of these invertebrates it can be inferred that allochthonous subsidies are likely of greater importance to Shield lake BMI communities than those of the lowland lakes; supporting the carbon transfer prediction. These findings provide insight about the structure and function of BMI communities from two dominant lake types in Ontario, and could be useful when determining how future chemical and physical changes will impact these communities. Author Keywords: benthic macroinvertebrates, community function, community structure, Precambrian Shield, stable isotopes, St. Lawrence lowlands
CO2 dynamics of tundra ponds in the low-Arctic Northwest Territories, Canada
Extensive research has gone into measuring changes to the carbon storage capacity of Arctic terrestrial environments as well as large water bodies in order to determine a carbon budget for many regions across the Arctic. Inland Arctic waters such as small lakes and ponds are often excluded from these carbon budgets, however a handful of studies have demonstrated that they can often be significant sources of carbon to the atmosphere. This study investigated the CO2 cycling of tundra ponds in the Daring Lake area, Northwest Territories, Canada (64°52'N, 111°35'W), to determine the role ponds have in the local carbon cycle. Floating chambers, nondispersive infrared (NDIR) sensors and headspace samples were used to estimate carbon fluxes from four selected local ponds. Multiple environmental, chemical and meteorological parameters were also monitored for the duration of the study, which took place during the snow free season of 2013. Average CO2 emissions for the two-month growing season ranged from approximately -0.0035 g CO2-C m-2 d-1 to 0.12 g CO2-C m-2 d-1. The losses of CO2 from the water bodies in the Daring Lake area were approximately 2-7% of the CO2 uptake over vegetated terrestrial tundra during the same two-month period. Results from this study indicated that the production of CO2 in tundra ponds was positively influenced by both increases in air temperature, and the delivery of carbon from their catchments. The relationship found between temperature and carbon emissions suggests that warming Arctic temperatures have the potential to increase carbon emissions from ponds in the future. The findings in this study did not include ebullition gas emissions nor plant mediated transport, therefore these findings are likely underestimates of the total carbon emissions from water bodies in the Daring Lake area. This study emphasizes the need for more research on inland waters in order to improve our understanding of the total impact these waters may have on the Arctic's atmospheric CO2 concentrations now and in the future. Author Keywords: Arctic, Arctic Ponds, Carbon dioxide, Carbon Fluxes, Climate Change, NDIR sensor
Assessing the population genetic structure of the endangered Cucumber tree (Magnolia acuminata) in southwestern Ontario using nuclear and chloroplast genetic markers.
Magnolia acuminata (Cucumber tree) is the only native Magnolia in Canada, where it is both federally and provincially listed as endangered.Magnolia acuminata in Canada can be found inhabiting pockets of Carolinian forest within Norfolk and Niagara regions of southwestern Ontario. Using a combination of nuclear and chloroplast markers, this study assessed the genetic diversity and differentiation of M. acuminata in Canada, compared to samples from the core distribution of this species across the United States. Analyses revealed evidence of barriers to dispersal and gene flow among Ontario populations, although genetic diversity remains high and is in fact comparable to levels of diversity estimated across the much broader range of M. acuminata in the USA. When examining temporal differences in genetic diversity, our study found that seedlings were far fewer than mature trees in Ontario, and in one site in particular, diversity was lower in seedlings than that of the adult trees. This study raises concern regarding the future viability of M. acuminata in Ontario, and conservation managers should factor in the need to maintain genetic diversity in young trees for the long-term sustainability of M. acuminata in Ontario. Author Keywords: conservation genetics, cpDNA, forest fragmentation, Magnolia acuminata, microsatellites, population genetic structure
Barriers and Facilitators to Indigenous Knowledge Incorporation in Policy Making
The inclusion and application of Indigenous Knowledge (IK) has become a central and often demanded element of policy making involving Indigenous peoples. However, there are very few examples that exist in the literature and elsewhere that show how IK can be effectively integrated into decisions, policies, and programs. In response to these challenges, this research explored what processes are used to incorporate IK into policy and their effectiveness through the development of a framework that sought to identify critical factors related to IK inclusion. The framework was then applied to evaluate IK incorporation opportunities in the Nunatsiavut case, focusing on the development of the Nunatsiavut Government's Environmental Protection Act. The case study analysis was used to test and provide adaptations to the initial framework. This research identifies the importance of governance structures and processes, community participation and engagement approaches, and IK research and support programming in enhancing opportunities for IK to be integrated and reflected in policy outcomes. The Nunatsiavut case largely supported, but in some cases challenged critical factors of IK incorporation identified in the framework. The findings of this study are valuable for policy and decision makers (both Indigenous and non-Indigenous) regarding approaches and programs that can assist and support IK inclusion into policy processes and decisions. Author Keywords: environmental assessment, Indigenous Knowledge, Inuit Knowledge, Nunatsiavut, policy, self-government
mechanistic analysis of density dependence in algal population dynamics
Population density regulation is a fundamental principle in ecology, however there remain several unknowns regarding the functional expression of density dependence. One prominent view is that the patterns by which density dependence is expressed are largely fixed across a species, irrespective of environmental conditions. Our study investigated the expression of density dependence in Chlamydomonas reinhartti grown under a gradient of nutrient densities, and hypothesized that the relationship between per capita growth rate (pgr) and population density would vary from concave-up to concave-down as nutrients became less limiting. Contrary to prediction, we found that the relationship between a population's pgr and density became increasingly concave-up as nutrient levels increased. Our results suggest that density dependence is strongly variable depending on exogenous and endogenous processes acting on the population, implying that expression of density regulation depends extensively on local conditions. Population growth suppression may be attributable to environments with high intraspecific competition. Additional work should reveal the mechanisms influencing how the expression of density dependence varies across populations through space and time. Author Keywords: Chlamydomonas reinhartti, density dependence, logistic model, population dynamics, single species growth, theta-logistic equation
Maya Exploitation of Animal Resources during the Middle Preclassic Period
This study examines the foraging strategies of animal resource exploitation during the Middle Preclassic period (900-300 BC) at the ancient Maya site of Pacbitun, Belize. The faunal remains analyzed in this study were recovered from various domestic structures associated with the production of shell artifacts. Detailed taphonomic analyses have revealed that the Pacbitun faunal remains were particularly affected by weathering and density-mediated attrition. White-tailed deer was the prey most frequently acquired by the Middle Preclassic Maya of Pacbitun, followed by other lower-ranked artiodactyls. A variety of less profitable prey were sometimes included in the diet breadth. Using the central place forager prey choice model as a framework, the analysis of diet breadth, habitat use, and carcass transport patterns suggests that most animal resources were acquired from terrestrial habitats, at short distances from the site. Complete carcasses of large game appear to have been frequently transported to the site, where they were exploited for their meat and marrow. Comparisons with other Middle Preclassic faunal assemblages indicate significant differences in terms of taxonomic composition, with an emphasis on the procurement of fish and turtles. It is suggested that the Middle Preclassic Maya adopted foraging strategies focusing on the exploitation of local habitats, with occasional use of exotic resources. Author Keywords: Animal, Belize, Foraging, Maya, Subsistence, Zooarchaeology
Effects of Silver Nanoparticles on Lake Bacterioplankton
Silver nanoparticles (AgNP) released into aquatic environments could threaten natural bacterial communities and ecosystem services they provide. We examined natural lake bacterioplankton communities' responses to different exposures (pulse vs chronic) and types (citrate and PVP) of AgNPs at realistic environmental conditions using a mesocosm study at the Experimental Lakes Area. An in situ bioassay examined interactions between AgNPs and phosphorus loading. Bacterial communities exposed to high AgNP concentrations regardless of exposure or capping agent type accumulated silver. We observed increases in community production during additions of polyvinylpyrrolidone (PVP) -capped AgNPs and that site and nutrient-specific conditions are important to AgNPs toxicology in aquatic systems. Toxicological effects of AgNP are attenuated in natural conditions and differ from results from laboratory studies of AgNP toxicity. Our results demonstrate more studies are needed to fully assess the risk posed by these novel chemicals to the environment. This work could be useful in forming risk assessment policies which are largely based on lab studies and typically demonstrate strong toxic effects. Author Keywords: bacterial production, bacterioplankton communities, ecological stoichiometry, Experimental Lakes Area, mesocosms, silver nanoparticles
EXAMINING DREAMS, DREAM CONTENT, AND MEANING OF DREAMS IN BEREAVEMENT
Dreams that occur in bereavement have been mainly overlooked in the psychological literature. This study focuses on the most memorable dreams of the bereaved that contain imagery of the deceased. There were 52 participants who completed the study via email. The main goal of the study was to investigate the occurrence of common themes in the dreams that have the deceased as a character. It was hypothesized that the most memorable dreams are memorable because they positively influenced the dreamers waking life grief process, which was partially supported. Furthermore, it was expected that that the most memorable dreams will have a greater frequency of positive elements and a lower frequency of negative elements than the normative data on dreams, which was partially supported. These findings support past research on dreaming of the deceased and expand the impact that these types of dreams can have on the grief process. Author Keywords: bereavement, deceased imagery, dream content, dreams, grief
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

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Format: 2023/12/09