Graduate Theses & Dissertations

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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 Clinical Usefulness of Three Tablet-Based Visuomotor Tasks to Evaluate Closed Head Injury
Evidence suggests that visuomotor system behaviour may be more sensitive to the prolonged effects of mild brain injuries than neuropsychological tests. We evaluated whether participants with a mild closed head injury (CHI) would show lingering visuomotor deficits, but not cognitive deficits, up to three years post-injury compared to participants with an orthopaedic injury and healthy controls. All three groups completed a tablet-based visuomotor assessment tool and a brief neuropsychological test battery. The CHI participants scored comparable to the control groups on the neuropsychological tests, but when assessed for visuomotor function requiring adjustment to a changing stimulus, CHI participants showed poorer performance than the control groups. Combined, these findings add to the evidence that CHI can lead to persistent visuomotor deficits that extend beyond those of neuropsychological tests. Therefore, visuomotor assessment should be included in brain injury and recovery evaluation, and this can be accomplished easily using tablet-based tasks. Author Keywords: closed head injury, neuropsychological assessment, recovery, tablet, traumatic brain injury, visuomotor
TESTING THE ROLE OF BIMODAL CELLS IN NEAR-HAND EFFECTS
We investigated whether hand-proximity effects arise from the recruitment of visual-tactile bimodal cells. In Experiment 1, we executed right-hand open-loop reaching movements to targets, presented either near or far from the resting left-hand, and after applying repetitive transcranial magnetic stimulation (rTMS) to suppress neuronal activity in the PMd and AIP, in Experiment 2. Results from Experiment 1, indicated that near-hand targets improved accuracy and reduced variability. In Experiment 2, suppressing PMd showed similar near-hand effects as above. In contrast, applying rTMS to AIP disrupted the representation of target location, indicating less accuracy and greater error. Near-hand proximity effects possibly arise from the recruitment of visual-tactile bimodal cells within the human AIP. Author Keywords: anterior intraparietal sulcus, peripersonal space, repetitive transcranial magnetic stimulation (rTMS), , rTMS, anterior intraparietal sulcus, AIP., visual-tactile bimodal neurons
Stability Properties of Disease Models under Economic Expectations
Comprehending the dynamics of infectious diseases is very important in formulating public health policies to tackling their prevalence. Mathematical epidemiology (ME) has played a very vital role in achieving the above. Nevertheless, classical mathematical epidemiological models do not explicitly model the behavioural responses of individuals in the presence of prevalence of these diseases. Economic epidemiology (EE) as a field has stepped in to fill this gap by integrating economic and mathematical concepts within one framework. This thesis investigated two issues in this area. The methods employed are the standard linear analysis of stability of dynamical systems and numerical simulation. Below are the investigations and the findings of this thesis: Firstly, an investigation into the stability properties of the equilibria of EE models is carried out. We investigated the stability properties of modified EE systems studied by Aadland et al. [6] by introducing a parametric quadratic utility function into the model, thus making it possible to model the maximum number of contacts made by rational individuals to be determined by a parameter. This parameter in particular influences the level of utility of rational individuals. We have shown that if rational individuals have a range of possible contacts to choose from, with the maximum of the number of contacts allowable for these individuals being dependent on a parameter, the variation in this parameter tends to affect the stability properties of the system. We also showed that under the assumption of permanent recovery for disease coupled with individuals observing or not observing their immunity, death and birth rates can affect the stability of the system. These parameters also have effect on the dynamics of the EE SIS system. Secondly, an EE model of syphilis infectivity among &ldquo men who have sex with men &rdquo (MSM) in detention centres is developed in an attempt at looking at the effect of behavioural responses on the disease dynamics among MSM. This was done by explicitly incorporating the interplay of the biology of the disease and the behaviour of the inmates. We investigated the stability properties of the system under rational expectations where we showed that: (1) Behavioural responses to the prevalence of the disease affect the stability of the system. Therefore, public health policies have the tendency of putting the system on indeterminate paths if rational MSM have complete knowledge of the laws governing the motion of the disease states as well as a complete understanding on how others behave in the system when faced with risk-benefit trade-offs. (2) The prevalence of the disease in the long run is influenced by incentives that drive the utility of the MSM inmates. (3) The interplay between the dynamics of the biology of the disease and the behavioural responses of rational MSM tends to put the system at equilibrium quickly as compared to its counterpart (that is when the system is solely dependent on the biology of the disease) when subjected to small perturbation. Author Keywords: economic and mathematical epidemiology models, explosive path, indeterminate-path stability, numerical solution, health gap, saddle-path stability, syphilis,
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
Cytokinin biosynthesis, signaling and translocation during the formation of tumors in the Ustilago maydis-Zea mays pathosystem
Cytokinins (CKs) are hormones that promote cell division. During the formation of tumors in the Ustilago maydis-Zea mays pathosystem, the levels of CKs are elevated. Although CK levels are increased, the origins of these CKs have not been determined and it is unclear as to whether they promote the formation of tumors. To determine this, we measured the CK levels, identified CK biosynthetic genes as well as CK signaling genes and measured the transcript levels during pathogenesis. By correlating the transcript levels to the CK levels, our results suggest that increased biosynthesis and signaling of CKs occur in both organisms. The increase in CK biosynthesis by the pathosystem could lead to an increase in CK signaling via CK translocation and promote tumor formation. Taken together, these suggest that CK biosynthesis, signaling and translocation play a significant role during the formation of tumors in the Ustilago maydis-Zea mays pathosystem. Author Keywords: Biosynthesis, Cytokinins, Signaling, Translocation, Ustilago maydis, Zea mays
Hydrological and Flooding Effects on Stream Nutrient Levels
Stream solutes are strongly linked to hydrology, and as such, we sought to better understand how hydrology, particularly flooding, influences nitrogen (N) and phosphorus (P) levels. We used a long-term dataset of monthly water quality samples for many Ontario, Canada, catchments to assess the effects of landscape variables, such as land use and physiography, on the export of nutrients during floods, and to characterize overall concentration-discharge patterns. In general, we found that landscape variables could partially explain the export variation in flood waters, but that the importance of specific variables depended on flood characteristics. We also found that overall concentration-discharge relationships for N and P C were positive, but non-linear, with greater concentrations on the rising limb of the hydrograph depending on the nutrient. With these results, we have identified general patterns between nutrients and hydrology, which will be helpful for managing the ecological effects of flooding. Author Keywords: C-Q relationships, Discharge, Export, Flooding, Nutrients, Thresholds
Distribution of Cluster Fly Species (Pollenia, spp. Diptera
This thesis looks at the genus Pollenia: historically where they were first introduced into Canada and spatially, where they are found now. This project involved me identifying 2211 files, sorted from the 3 years of field specimens obtained in 2011, 2012, 2013. P. pediculata was the most abundant and widespread, yielding 1272 specimens out of 2211, and it was found in all provinces sampled. The previous understanding of all Pollenia specimens as being P. rudis appears to be incorrect both in terms of actual number of species – which is known – and how prevalent it is. P. rudis comprised only 20% of the entire collection. The least common was P. griseotomentosa, occurring as 45 of 2211, or 2%. I found new eight first provincial records: four species in Alberta (P. angustigena, P. labialis, P. rudis, P. vagabunda) , one species for Saskatchewan (P. pediculata), two for New Brunswick (P. griseotomentosa, P. labialis), and one for Nova Scotia (P. labialis). P. labialis was new to three provinces, the other species to one province each. Author Keywords: Calliphoridae, Canada, Cluster Fly, Distribution, Pollenia, Provincial Records
Assessment of an adult lake sturgeon translocation (Acipenser fulvescens) reintroduction effort in a fragmented river system
North American freshwater fishes are declining rapidly due to habitat fragmentation, degradation, and loss. In some cases, translocations can be used to reverse local extirpations by releasing species in suitable habitats that are no longer naturally accessible. Lake sturgeon (Acipenser fulvescens) experienced historical overharvest across their distribution, leading to endangered species listings and subsequent protection and recovery efforts. Despite harvest and habitat protections, many populations do not appear to be recovering, which has been attributed to habitat alteration and fragmentation by dams. In 2002, 51 adult lake sturgeon from the Mattagami River, Ontario, Canada were translocated 340 km upstream to a fragmented 35 km stretch of the river between two hydroelectric generating stations, where sturgeon were considered extirpated. This study assessed the translocation effort using telemetry (movement), demographics and genetic data. Within the first year, a portion of the radio-tagged translocated individuals dispersed out of the release area, and released radio-tagged individuals used different areas than individuals radio-tagged ten years later. Catches of juvenile lake sturgeon have increased over time, with 150 juveniles caught within the duration of this study. The reintroduced population had similar genetic diversity as the source population, with a marked reduction in effective population size (Ne). The results indicate that the reintroduction effort was successful, with evidence of successful spawning and the presence of juvenile lake sturgeon within the reintroduction site. Overall, the results suggest adult translocations may be a useful tool for re-establishing other extirpated lake sturgeon populations. Author Keywords: conservation, endangered species, lake sturgeon, reintroduction, telemetry, translocation
multi-faceted approach to evaluating the detection probability of an elusive snake (Sistrurus catenatus)
Many rare and elusive species have low detection probabilities, thereby imposing unique challenges to monitoring and conservation. Here, we assess the detection probability of the Eastern Massasauga (Sistrurus catenatus) in contrast to a more common and conspicuous species, the Eastern Gartersnake (Thamnophis sirtalis). We found that patterns of detection probability differed between species, wherein S. catenatus was detected less often and under a more specific set of sampling conditions. Correspondingly, detection trials with S. catenatus found a high non-detection rate, while detection trials with artificial models suggest that regional differences in detection probability are driven by variation in population density and habitat use. Our results suggest that current monitoring efforts are not sufficient, and that S. catenatus is frequently undetected. Accordingly, we highlight the importance of species-specific monitoring protocols when monitoring rare and elusive species, and recommend a multi-faceted approach that estimates detection probability and identifies species-specific challenges to monitoring. Author Keywords: detection probability, elusive species, monitoring programs, non-detection, S. catenatus, snakes
role of Cln5 in autophagy, using a Dictyostelium discoideum model of Batten disease
This thesis investigated the role of the neuronal ceroid lipofuscinosis protein, Cln5, during autophagy. This was accomplished by performing well-established assays in a Dictyostelium cln5 knockout model (cln5-). In this study, cln5- cells displayed a reduced maximum cell density during growth and impaired cell proliferation in autophagy-stimulating media. cln5- cells had an increased number of autophagic puncta (autophagosomes and lysosomes), suggesting that autophagy is induced when cln5 is absent. cln5- cells displayed increased amounts of ubiquitin-positive proteins but had no change in proteasome protein abundance. During the development of cln5- cells, fruiting bodies developed precociously and cln5- slug size was reduced. Lastly, when cln5- cells were developed on water agar containing ammonium chloride (NH4Cl), a lysosomotropic agent, the formation of multicellular structures was impaired, and the small slug phenotype was exaggerated. In summary, these results indicate that Cln5 plays a role in autophagy in Dictyostelium. The cellular processes that regulate autophagy in Dictyostelium are similar to those that regulate the process in mammalian cells. Thus, this research provides insight into the undefined pathological mechanism of CLN5 disease and could identify cellular pathways for targeted therapeutics. Author Keywords: Autophagy, Batten disease, Cln5, Dictyostelium discoideum, NCL
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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Format: 2021/01/19