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Expanding the theory and applications of carbon dioxide and other modifier gases in differential mobility spectrometry
Full text linkThis thesis explores the mechanisms and applications of CO2 and other gases or solvents for modifying the nitrogen carrier gas in differential mobility spectrometry (DMS), a technique which separates ions moving in the carrier gas through an oscillating electric field before mass spectrometry (MS) detection. Investigations include what makes CO2 a “soft” gas, and by extension, how any other gas mixture will affect this “softness”. These insights are then extended to a variety of challenging analyses. For experimental work, ions were produced with electrospray ionization (ESI) before DMS separation, and their final identification with MS. Custom modifications were made to the DMS carrier gas system to enable the use of many gas mixtures. These analyses were supplemented with quantum chemical calculations using density functional theory (DFT). This work shows evidence that a range of fragile ions are commonly protected by CO2 through efficient energy transfer during collisions, contradicting a hypothesis that ion-CO2 clusters provide the protective mechanism. More generally, it is shown that the comparative “softness” of a gas mixture can be predicted by its viscosity. These insights are then applied to show evidence that chemical analyte multimer ions are produced during the ESI process, rather than via condensation during the free jet expansion process as ions enter the MS vacuum. Control of gas conditions also factors into investigations of how to enhance the isolation of unstable prototropic isomers (protomers), showing elimination of water from the analysis is a key concern. Novel gas mixtures are considered, using an N2 carrier gas with a solvent vapour as well as some gas modifier (like CO2), to enhance resolution for challenging samples, while linking this behaviour to existing theory. This work also describes the first evidence that Ne can be a particularly useful modifier gas for DMS separations. Together, this thesis gives new insights into how the gas composition in DMS-MS can improve its performance for the separation of fragile and/or difficult to resolve ions by allowing more informed design and control of experimental conditions to enable effective analysis of challenging analytes
Dynamics of Vitamin D Metabolites in Hospitalized Horses with Enterocolitis
Full text linkEquine typhlocolitis is a life-threatening condition characterized by an acute onset of diarrhea and electrolyte imbalances including hypocalcemia. Recent research on critically ill foals showed an altered vitamin D axis in association with hypocalcemia. Considering vitamin D is an important calcium homeostatic regulator, dysregulation of the vitamin D axis warrants further investigation in diarrheic horses. This study aimed to determine seasonal serum 25-hydroxyvitamin D (25[OH]D) concentrations in healthy horses located in Ontario, Canada and to investigate the serum concentration dynamics of 25(OH)D, 1,25-dihydroxyvitamin D (1,25[OH]2D; calcitriol), and parathyroid hormone (PTH) in hospitalized diarrheic adult horses during the first 72 h of admission and their association to non-survival. In healthy horses, seasonal 25(OH)D serum concentrations over a one-year period appeared to remain relatively constant. Serum 25(OH)D, 1,25(OH)₂D, and PTH concentrations were not significantly different between survivors and non-survivors on admission although 1,25(OH)₂D serum concentrations were significantly lower in the diarrheic group compared to healthy horses. During hospitalization, 25(OH)D concentrations significantly declined in non-survivors but remained stable or increased in survivors. Serum PTH concentrations were higher in non-survivors and decreased over time in all horses. This thesis highlights the complexity of the vitamin D axis assessment and the important role for vitamin D in homeostasis in critically ill adult horses
Investigation of the Immune Response of Goats to Gastrointestinal Nematode Infection under Ontario Grazing Conditions
Full text linkGastrointestinal nematodes (GINs) constrain small ruminant health and productivity in Ontario. Conventional control of GINs relies on repeated anthelmintic use; however, escalating anthelmintic resistance necessitates investigation of potential immunologic control. This thesis examines mucosal responses of Ontario goats to GIN parasitism by characterizing salivary antibody responses to carbohydrate larval antigen (CarLA) and associations with age, GIN species, and farm management practices. In addition, storage conditions suitable for short-term fecal storage during shipment from farms to diagnostic centres were validated. Fecal samples suspended in water or sealed in airtight bags at 4 °C or 20 °C were assessed over 72 hours, during which fecal egg counts (FECs) did not differ significantly (p > 0.70). End-of-season salivary anti-CarLA IgA and IgG were quantified in two grazing seasons (2023–2024) in female kids (2 years), and tested in models of GIN FECs collected four times from June to October each year. Goats in all age groups developed detectable salivary antibodies. Adults exhibited the highest IgA and IgG titres and negative associations between FECs and salivary antibodies in mid-summer (IgG, 2024 p < 0.1) and early fall (IgA, 2023 p < 0.1; IgG, 2024 p < 0.05). Significant (p < 0.05) negative relationships between IgA and FEC were present in fall 2023 and spring 2024 in kids and spring 2024 in yearlings. At the herd level, ITS-2 rDNA nemabiome metabarcoding identified Haemonchus contortus and Trichostrongylus colubriformis as the predominant species across all farms. In 2024 only, farms with higher H. contortus proportions exhibited a negative relationship between anti-CarLA IgA and FEC at FECs < 1009 epg, with IgG trending similarly. Goats on farms using FAMACHA scoring (OR = 0.37, CI 0.16–0.85) or co-pastured with pigs/poultry (OR = 0.07, CI 0.01–0.60) had reduced odds of IgA ≥ 0.501 U/mL. Collectively, these findings demonstrate that Ontario goats develop measurable salivary anti-CarLA antibodies that increase with age. Although negative antibody–FEC relationships were identified, variation occurred by isotype, age group, and sampling time point. Future prospective studies are needed to refine anti-CarLA testing in Ontario goats
Assessing spatial and behavioural risk factors associated with the occurrence of zoonotic agents in lemurs
Full text linkPrevious research shows lemurs are exposed to zoonotic agents. Factors influencing exposure are poorly understood. This study was conducted on two groups of both Propithecus coquereli (PC) and Eulemur fulvus (EF); one of each living near and far from a community (N=4) in Ankarafantsika National Park. I used focal animal sampling and quadrat sampling to measure behavioural and spatial risks for parasitism. Fecal samples were analyzed microscopically.
I found no significant differences in behavioural risks across groups, or in spatial risk exposure between near and far groups. I found significantly higher spatial risk exposure and increased diversity of parasites in EF vs. PC. I recorded home range invasions in the PC-Far group and identified clinical signs in one invader, indicating intergroup encounters may influence local disease dynamics. Future studies are needed to determine statistical significance of the differences in parasitism between the two species and to further characterize local land-use
Mechanisms of Social Learning in Female Mice: The Roles of Estrogens and Muscarinic Acetylcholine Signaling
Full text linkSocial learning is a common, adaptive learning strategy in animals and humans, in which an individual acquires information or skills from another in their social group. Despite its importance to human and animal learning, social learning has received relatively little research attention, and we thus are only beginning to understand the neurobiological mechanisms underlying this type of cognition. In this thesis, I investigated the roles of the rapid effects of estrogens and the effects of acetylcholine signaling at muscarinic receptors in short- and long-term memory for socially learned information using the Social Transmission of Food Preferences (STFP) task in mice, in which an observer mouse preferentially consumes a novel food that they had previously smelled on the breath of a conspecific demonstrator mouse. Estradiol rapidly (within 45 minutes) and activation of the G protein-coupled estrogen receptor 1 (GPER1) with the agonist G1 facilitate short-term STFP memory on the STFP when administered systemically. The first part of this thesis focuses on the brain regions in which estrogens may act to facilitate social learning. We therefore infused estradiol into the dorsal hippocampus and basolateral amygdala of female ovariectomized (OVX) mice. Second, we investigated muscarinic acetylcholine signaling as a possible downstream mechanism of estradiol and G1’s rapid facilitatory effects. We tested this by co-administering doses of estradiol or G1 previously found to facilitate STFP memory with a subeffective dose of the muscarinic receptor antagonist scopolamine before testing short-term STFP memory. Finally, we sought to determine which muscarinic receptor subtypes mediate the impairing effects of scopolamine on the STFP. We first tested the effects of scopolamine on long-term STFP memory in ovariectomized and gonadally intact female mice. We then tested the effects of the M1 antagonist dicyclomine and the M2 antagonist AF-DX 116 on long-term STFP memory. Through these investigations, we found that while estradiol did not facilitate short-term STFP memory when infused into the hippocampus or basolateral amygdala, it may facilitate short-term memory by enhancing acetylcholine at muscarinic receptors. Lastly, we found that muscarinic receptor signaling is also necessary for long-term STFP memory in gonadally intact female mice and that the M1 receptor subtype is one of the muscarinic receptors mediating this effect
Enhancing Safety and Composting Processes in the Compost Bedded Pack Barn (CBP) Model: The Role of Beneficial Microbial Additives
No full textDairy housing systems significantly influence cow health, hygiene, and productivity, with bedding quality affecting udder cleanliness, milk quality, and milk safety. Compost bedded pack barns (CBPs) offer a loose housing system that improves cow comfort while supporting active composting. However, optimizing composting efficiency and controlling mastitis pathogens that threaten milk safety remain challenges. This study evaluated the effects of microbial inoculants, Bacillus velezensis (LL-11) and the commercial conditioner Manure Pro (MP), on composting dynamics and pathogen survival in a CBP model. MP treatment maintained higher temperatures than the control and single-strain treatments. Cellulose content decreased significantly from Week 0 to Week 5 in the MP group, while lignin increased over time in the control but remained relatively stable with MP. Mastitis-related Escherichia coli and Klebsiella pneumoniae were eliminated within one week, and Streptococcus uberis declined below detection within 24 h. Overall, CBP systems limited pathogen persistence and improved composting efficiency.Dairy Farmers of CanadaDairy Farmers of OntarioNatural Sciences and Engineering Research Council of Canada2026-12-0
Computational Methods for Particle Reactivity and Sensor-Based Monitoring in Enhanced Rock Weathering
Full text linkEnhanced rock weathering (ERW) is a promising carbon dioxide removal strategy, yet its large-scale deployment is constrained by uncertainties in particle reactivity and the field-scale monitoring. This thesis introduces a dual computational framework addressing these gaps. First, an image-based pipeline that quantifies mineral reactivity through high-resolution EPMA analysis, defining the exposed reactive perimeter ratio (ERPR) and simulating dissolution via a Shrinking core model. Second, a sensor-driven data pipeline that integrates multiple soils measurements (volumetric water content, electrical conductivity) with rainfall forcing, applying rigorous quality control, temporal harmonization, and unsupervised clustering (K-means, DBSCAN) to detect hydrological–geochemical response regimes. The results strongly reveal that Depth-dependent behavior where shallow layers exhibit rapid dissolution pulses but deep layers act as long-term verification zones. By coupling particle-scale geometry with field-scale sensing, this research advances the mechanistic understanding and provides a reproducible foundation for monitoring, reporting, and verification (MRV) in ERW systems
Space, Place and Power: A Case Study of Highly Skilled Talent and Governance Dynamics in The Bruce County Energy Sector
Full text linkThis research presents a case study on how Bruce County has transitioned into a highly specialized rural economy through its strategic alignment with the nuclear energy sector, centrally anchored by Bruce Power. The deliberate spatial clustering of industry stakeholders, specialized supplier networks and supportive institutional frameworks exemplifies Porter’s (1990) Diamond Framework, while also aligning with contemporary theories on regional governance systems and cluster development. Municipal planning and policy priorities, infrastructure investments and workforce development have become increasingly tailored towards meeting the specific operational needs of Bruce Power, illustrating the profound spatial and economic reconfiguration occurring within this rural setting through sectoral specialization and coordinated partnership with other actors. Interview data underscores that Bruce County’s ability to attract and retain highly skilled professionals is closely connected to its status and reputation as a center of an energy sector, focused on nuclear power operations. However, this research also reveals stratification within the skilled migration experience. While highly skilled workers, who are specialized and globally mobile professionals, are actively recruited, long-term residents and individuals employed in sectors that are not related to energy in Bruce County face limited access to equivalent economic opportunities
Dominating Hyperplane Regularization for Multivariate Count Models with Structured Penalties
Full text linkCompositional data are common in many ecological and biological applications, including bioinformatics, microbiology, and ecology. For example, in biology, one might examine bacterial counts in the gut, whereas in ecology, one might study benthic macroinvertebrate counts in a river. Because the relative abundances of taxa are important indicators of ecosystem health, it is critical to understand the factors that influence these counts. This thesis focuses on methods for associating covariates (e.g., diet, lifestyle) with multivariate count outcomes, such as bacterial abundances in the human gut. In particular, the overarching goals of this thesis are to enhance multivariate count models through introducing stable optimization methods and effective coefficient selection. The first part of this thesis proposes Dominating Hyperplane Regularization (DHR), based on the majorization minimization framework, for models regularized with the sparse group lasso penalty. In multivariate count models, we estimate a matrix of coefficients, with rows corresponding to covariates and columns corresponding to count outcomes (i.e., taxa). In this setting, the coefficients for a given covariate across all outcomes can naturally be treated as a group. Although the sparse group lasso penalty groups coefficients and makes them non-separable, the DHR approach enables independent, column-wise univariate regressions to efficiently solve the optimization problem. Furthermore, we demonstrate the utility of this approach for generalized linear models as well. The second part of this thesis extends the DHR framework to a more complex multivariate count model: the regularized Dirichlet-Tree Multinomial (DTM) regression model, which incorporates taxonomic tree information. Applying DHR in this context enables the introduction of more intricate tree-guided penalty functions for the DTM regression model, allowing the model to leverage known relationships among taxa. In particular, we propose two novel tree-guided penalty functions: the tree-guided SGL, and the tree-guided hierarchical lasso for DTM regression. All methods are evaluated through simulation and demonstrated on real world data
Condemnation and Control: Ambition in Scotland, 1550–1625
Full text linkThis dissertation examines ambition as an historically contingent moral and political category, not a transhistorical psychological trait. In early modern Scotland, ambition functioned as a charge through which claims to authority were evaluated, contested, and disciplined. Across sermons, political treatises, didactic literature, and polemical print, ambition named not aspiration as such, but the pursuit of authority perceived as illegitimate—unsanctioned by divine order, social hierarchy, or communal consent. To be accused of ambition was to be positioned as a destabilizing figure whose desires threatened both political order and moral coherence. The dissertation argues that ambition operated as a cultural technology of governance. It translated anxieties about rebellion, social mobility, and contested sovereignty into a moralized language of vice that rendered overreach intelligible, condemnable, and punishable. Ambition was not understood as a private motive but as a relational judgment: it cohered only when recognized and affirmed by others, and its force lay in its capacity to recast structural conflict as personal moral failure. Methodologically, the study combines close rhetorical analysis with a digital humanities approach designed to recover ambition’s semantic field from within early modern discourse. Drawing on a curated corpus of 225 texts demonstrably available to Scottish readers, it applies Latent Semantic Analysis to trace patterns of lexical proximity and co-occurrence. These patterns reveal ambition’s consistent association with pride, avarice, treason, and covetousness, while also exposing contested overlaps with honour, virtue, and glory, sites where the boundaries between legitimate and illegitimate authority were actively negotiated. Structured around three analytic problems—definition, condemnation, and control—the dissertation shows how ambition was gendered in moral discourse, neutralized in institutional judgment, and managed through a repertoire of disciplinary practices including reputational sabotage, warding, treason prosecution, and remission. Together, these mechanisms constrained challenges to authority without producing martyrs, allowing the state to suppress dissent while preserving the appearance of moral and political order. Ambition thus emerges not as a marginal vice, but as a central concept through which early modern Scots articulated, defended, and enforced the limits of power