Graduate Theses & Dissertations

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Research and development of synthetic materials for presumptive testing in bloodstain pattern analysis
Chemical presumptive tests are used as the primary detection method for latent bloodstain evidence. This work focuses on developing a forensic blood substitute which mimics whole blood reactivity to a luminol solution commonly used in presumptive testing. Designing safe and accessible materials that mimic relevant properties of blood is a recognized research need in forensic science. Understanding the whole blood dynamics related to reactivity with presumptive testing chemicals is important for developing accurate analogues. Provided in this thesis is a quantitative and qualitative characterization of photoemission from the reaction of a luminol solution to ovine blood. Luminol reactivity of a horseradish peroxidase encapsulated sol-gel polymer was validated against this ovine blood standard. This material, the luminol-reactive forensic blood substitute, is a key deliverable of this research. An optimized protocol for implementing this technology as a reagent control test, and as a secondary school chemistry experiment are presented. This thesis outlines the research and development of a forensic blood substitute as it relates to presumptive testing in bloodstain pattern analysis. Author Keywords: bloodstain pattern analysis, forensic science, luminol, presumptive testing, secondary school education, sol-gel chemistry
Responses of Primary Producers and Grazers to Silver Nanoparticle Exposure
The increasing production and use of silver nanoparticles (AgNPs) raise concerns on environmental exposure and impact. A large scale in situ enclosure study was conducted at the Experimental Lakes Area to determine the effect of AgNPs on natural phytoplankton and zooplankton communities. This study investigated AgNPs of varying concentrations (4, 16 and 64 μg/L), dosing regimens (chronic vs. pulse), and capping agents (poly-vinyl pyrrolidone vs. citrate). Phytoplankton communities were influenced only by the natural limnological properties of the system signifying tolerance to AgNPs. Zooplankton community structure significantly changed with AgNP concentration and dosing regimen indicating AgNP sensitivity. A microcosm study investigating the effect of AgNPs and phosphorus-dosed periphyton before and after grazing by two benthic invertebrate species (snails and caddisfly larvae) showed reduced periphyton stoichiometry with AgNP exposure. Grazers foraged less on silver dosed periphyton indicating a preferential choice in food quality. Phosphorus reduced the detrimental effects of AgNPs across all conditions. These studies verify the need for in situ experimental designs to fully investigate the effects of AgNPs and their interaction with environmental factors, multiple species assemblages, and across trophic levels. Author Keywords: benthic invertebrate, Experimental Lakes Area, periphyton, phytoplankton, silver nanoparticles, zooplankton
Retrograde Amnesia of Fear Memories Following Pentylenetetrazol Kindling
Memories pertaining to fearful events are some of the most salient and long-lasting memories, as they are critical to the survival of an organism. Seizures induce aberrant changes within temporal lobe and limbic brain structures that are critical for supporting fear memories. Seizures can occur at any time; therefore, it is imperative that research address how seizures impact previously learned information. The present series of experiments demonstrate that pentylenetetrazol-kindling induces retention deficits of previously acquired context fear memories in male rats. Kindling induced subsequent fear learning deficits but did not impact spatial learning. Additionally, following kindling, volumetric increase was observed within the hippocampal subfield CA3, as well as increased neural activation within the hippocampal subfield CA1. The results of this work suggests that chronic seizures can alter the function of neural networks important for supporting and retrieving previously acquired memories. Author Keywords: amygdala, anterograde amnesia, context fear conditioning, hippocampus, retrograde amnesia, seizures
Risk of Mortality for the Semipalmated Plover (Charadrius semipalmatus) Throughout Its Life Cycle
Three long-term mark and recapture/resight data sets of individually marked Semipalmated Plovers (Charadrius semipalmatus) were analyzed using Cormack-Jolly- Seber models. Data came from two breeding populations (Churchill, Manitoba, Canada, n=982, and Egg Island, Alaska, USA, n=84) and one overwintering population (Cumberland Island, Georgia, USA, n=62). For Alaska and Georgia, time-invariant models were best-supported, giving annual survival estimates of 0.67 (95%C.I.: 0.58- 0.76) and 0.59 (95%C.I.: 0.49-0.67) respectively. Data from Manitoba supported a timedependent model: survival estimates varied from 1.00 to 0.36, with lowest estimates from recent years, supporting observations of local population decline. Seasonal survival analysis of the Georgia population indicated lower mortality during winter (monthly Φoverwinter: 0.959, 95%CI: 0.871-0.988; for 6 month period Φoverwinter: 0.780 (0.440-0.929)) than during combined breeding and migratory periods (monthly ΦBreeding+Migration: 0.879 (0.825-0.918); for 8 month ΦBreeding+Migration: 0356 (0.215-0.504)). I recommend, based on high resight rates, continued monitoring of survival of wintering populations, to determine potential range-wide population declines. Keywords: survival, longevity, mortality, shorebird, overwinter, breeding, migration, life cycle Author Keywords: life cycle, longevity, mortality, non-breeding, shorebird, survival
Robust assessment of changes in wild mammal occupancy and activity relative to livestock and human disturbance
Anthropogenic activities such as human activity and livestock grazing are responsible for the global rise in disturbance impacts on wildlife and may underlie regional changes in biodiversity and ecosystem dynamics. Few studies have tried to disentangle the effects of different anthropogenic activities on wildlife behaviour, leaving a major gap in our understanding of conservation and management needs in disturbed areas. Human activity and livestock grazing are increasing in spread and intensity worldwide, thereby imposing pressure on both wildlife and natural areas. In this thesis, I used a camera trapping and occupancy modeling framework to assess whether human presence and livestock grazing had different impacts on site occupancy and activity of 10 wild mammal species, and how responses differed across taxa. Specifically, I predicted that all species would be sensitive to disturbance, but the type and intensity of the response would depend on disturbance type. I detected different responses to each disturbance type across species, but response type (displacement, activity change, crepuscularity) was not associated with species characteristics such as body. Importantly, disturbance intensity had a strong effect on wildlife activity levels, with many species exhibiting marked reductions in activity at high human or livestock disturbance intensity. It remains unclear whether all species’ responses are a direct consequence of disturbance versus indirect outcomes of shifts in behaviour of other species in the wildlife community (i.e., disturbance-related changes in prey activity may affect predator activity). Although on the whole disturbance intensity and effect sizes tended to be relatively low in this study, responses were exhibited across all species, implying that disturbance responses may be universal in wild mammals and largely underestimated. Ultimately, my work offers a template for the robust assessment of disturbance impacts on wildlife and provides new avenues for future research to deepen our understanding of wildlife sensitivity to anthropogenic activities. Author Keywords: activity, anthropogenic disturbance, human activity, livestock, occupancy, wildlife
Role of Media in Shaping Perceptions of HIV and Affecting Engagement in HIV Care
Media has had a significant influence on how individuals living with and at risk of Human Immunodeficiency Virus (HIV) care for their health. This research builds on previous research to explore the link between HIV related media messaging and HIV related health behaviours using a mixed methods approach. To investigate the access to and perceptions of HIV related media, a sample of 129 individuals took part in an online survey and 13 were assessed in follow up semi-structured interviews. People living with HIV, people at risk of HIV, and participants not in those groups differed on a number of HIV media access variables, including the amount of time spent interacting with HIV related media, how they accessed it, and its perceived effects on their HIV related attitudes and behaviours. Interviews explored these differences more, finding that while current HIV related media is less stigmatizing and more factual than the past, most current HIV related media is distributed via social media and is accessed by a relatively small group of HIV specialist viewers. The history of HIV related media continues to play an important role in determining perceptions of HIV related media. Implications of this study will inform strategies for the communication of HIV health messages. Author Keywords: AIDS, HIV, Media and Health, Mixed Methodology, Social Determinants of Health, Social Media
Role of Multiple Nights of Sleep in the Consolidation of an Engaging and Complex Motor Learning Task
The present study examined the role of multiple nights of sleep in the consolidation of a complex motor learning task. Participants were 24 Trent undergraduates, 12 in the learning group (Mage = 20.33, SD = 1.87, 10 female) and 12 in the control group (Mage = 21.92, SD = 3.42, 7 female). Participants underwent 5 consecutive nights of polysomnographic recordings, with a Rock Band learning session on the third night. A series of 2(group)x4(night) ANOVAs were performed on the sleep variables. Interactions were found in the number of spindles detected at Pz, F(333) = 9.19, p <.01, and in the density of spindles detected at Pz, F(3,33) = 4.06, p <.05. The pattern of changes from baseline was significantly different between the two groups; spindles increased in the learning group and decreased in the control group. The novel finding was that spindle number/density remained elevated at the third post-learning night of sleep. Author Keywords: Motor Learning, Procedural Memory, Sleep, Sleep Spindles
SARS-CoV-2 Protein-based Detection Using Localized Surface Plasmon Resonance
During the COVID-19 pandemic, nucleic acid and antibody-based testing methods were heavily relied upon, but can be costly, time-consuming and exhibit high false -negative and -positive rates. Thus, alternative strategies are needed. Viral antigens such as the SARS-CoV-2 spike (S) glycoprotein are critical in the function of the virus and useful as diagnostic biomarkers for viral infections. For biosensing applications, aptamers are suitable high-affinity and cost-effective binding partners for their specific targets. Using localized surface plasmon resonance (LSPR), real-time, rapid acquisition of results can be achieved, essential for improving the efficacy of a sensor. Herein, LSPR aptamer sensors were fabricated for the detection of the SARS-CoV-2 protein. Data indicate that the best performing aptasensor was the streptavidin-biotin sensor, while the current gold aptasensor exhibited lower sensitivity and the fabrication of the carboxyl aptasensor was unsuccessful. The S1 aptamer selectively bound the S1 protein with high binding affinity. Excellent shelf-life stability, reusability, and high recovery in complex matrices was also maintained. Additionally, a receptor binding domain (RBD) functionalized sensor was fabricated to examine the interactions with angiotensin converting enzyme 2 (ACE2), for future assessment of inhibitors used in drug therapies. Overall, LSPR has been demonstrated as a viable tool for measuring SARS-CoV-2 related aptamer-protein and protein-protein interactions, and this strategy may be applied to other viral or non-viral antigen targets. Author Keywords: Antigen-based Detection, Coronavirus, COVID-19, Inhibition, Localized Surface Plasmon Resonance, SARS-CoV-2
SPAF-network with Saturating Pretraining Neurons
In this work, various aspects of neural networks, pre-trained with denoising autoencoders (DAE) are explored. To saturate neurons more quickly for feature learning in DAE, an activation function that offers higher gradients is introduced. Moreover, the introduction of sparsity functions applied to the hidden layer representations is studied. More importantly, a technique that swaps the activation functions of fully trained DAE to logistic functions is studied, networks trained using this technique are reffered to as SPAF-networks. For evaluation, the popular MNIST dataset as well as all \(3\) sub-datasets of the Chars74k dataset are used for classification purposes. The SPAF-network is also analyzed for the features it learns with a logistic, ReLU and a custom activation function. Lastly future roadmap is proposed for enhancements to the SPAF-network. Author Keywords: Artificial Neural Network, AutoEncoder, Machine Learning, Neural Networks, SPAF network, Unsupervised Learning
Scarring, sex assignment, and sex-specific sociality of Indo-Pacific humpback dolphins (Sousa chinensis) in the Pearl River Estuary and eastern Taiwan Strait
The Pearl River Estuary (PRE) and eastern Taiwan Strait (ETS) populations of Indo-Pacific humpback dolphins (Sousa chinensis) contain ~600 and 100 catalogued individuals, respectively. Population demography is important for conservation actions but few animals have been sexed by conventional methods. Longitudinal analysis of tooth-rake scars on dorsal fins showed scars disappear within 7 months; sexing adults by scarring is likely not impacted by juvenile scarring. Using dorsal fin photographs, sex assigned for 87% of catalogued PRE adults (n=300) and for 93% of ETS adults (n=60), using scars hypothesized from male-male competition, was in concordance with sex assigned by DNA, calf association, and ventral photographs. Scarring was higher in presumed males than females and in PRE females than ETS females. Female:male sex ratios were 3:2 (PRE) and 2:1 (ETS), though this likely results from biases in photo-identification methods. Social analysis with presumed sexes showed strong female-female associations in both populations but stronger female-male and male-male associations in PRE. These results support sex differentiation by scarring, which was a non-invasive approach, and sex assignment for many PRE and ETS individuals. Author Keywords: Indo-Pacific humpback dolphins, photo-identification, scarring, sex differentiation, sexes, social structure
Scripted Sexual Beliefs and Behaviours
Sexual script theory suggests that sexual behaviours have social meaning, and that individuals perceive certain behaviours as normative and expected. Previous research has indicated that there is a common belief in a cultural sexual script for (hetero)sexual behaviour sequences (CSSHS). Study 1 compared perceived norms with behaviours in first ever penile-vaginal intercourse (PVI) sex events, as well as first and recent events with most recent partners. Many participants reported the CSSHS as typical, but few reported personal experiences that followed the CSSHS. Script adherence was not strongly related to physical pleasure. Study 2 found that committed relationships predicted greater female pleasure in first ever PVI sex. This link was mediated by communication during sexual activity. Results are discussed in the context of sexual script theory. Findings suggest that common scripted assumptions regarding PVI sex events should be reviewed for their value and representation of norms. Author Keywords: female pleasure, first sexual experiences, penile-vaginal intercourse, perceived norms, sexual behaviours, sexual script theory
Seasonal habitat use and movement of native brook trout (Salvelinus fontinalis) in urban headwater streams
Coldwater streams are becoming increasingly impacted due to urbanization. Using environmental surveys, mark-recapture and telemetry, I assessed factors influencing seasonal brook trout (Salvelinus fontinalis) habitat use and movement in urban headwater streams in central Ontario between 2017-18. Generalized additive models were used to assess which habitat variables best explained seasonal yearling and older brook trout abundance, while generalized least squares models were used to assess overall trends in radio-tagged brook trout movement. My research demonstrated dynamic patterns in habitat use and movement by urban stream-dwelling brook trout. Yearlings were primarily influenced by water quality (stream temperature, conductivity), while older brook trout were most strongly influenced by stream morphology (depth, undercut bank). Movement occurred disproportionately around the spawning season and was more limited in the smaller, more altered stream. These findings may be used to inform fisheries managers on crucial timing and location of brook trout habitat refugia within urbanized environments. Author Keywords: Brook trout, coldwater stream, groundwater, habitat use, radiotelemetry, urbanization

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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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