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Recent Submissions

Access status: Open Access ,
Investigation of loss of synchronism phenomenon in synchronous machines and protection using trajectory of relative speed
(2025-12-10) Samarawickrama, Kasun Chamara; Kordi, Behzad (Electrical and Computer Engineering); Hollaender, Hartmut (Civil Engineering); Tavares, Maria Cristina (University of Campinas); Rajapakse, Athula; Perera, Nuwan
The "loss of synchronism" condition in a synchronous machine is a critical state where the rotor fails to stay synchronized with the stator magnetic field. This can be caused by various factors, including system disturbances and power system instabilities. A machine undergoing a loss of synchronism may experiences torsional stresses, increased rotor iron currents and winding stresses in their mechanical systems. Synchronous machine loss of synchronism protection is employed to promptly disconnect a machine operating asynchronously to avoid damage or degradation. This thesis explores the loss of synchronism phenomenon in synchronous generators and introduces a novel loss of synchronism detection method based on the estimated relative speed of the rotor. The proposed algorithm utilizes readily available terminal voltage, current and machine parameters to estimate the rotor speed following a disturbance. It identifies loss of synchronism condition if the estimated relative speed tends to increase during a swing cycle. This method is computationally simple, easy to implement, and faster than impedance-based techniques under certain conditions. The sensitivity and security of this method is evaluated through time-domain simulations under various power system conditions. The performance of the proposed method is also compared against well established loss of synchronism protection schemes. The occurrence of loss of synchronism in synchronous condensers has not been extensively studied, primarily due to its rarity in traditional power systems. However, with the increasing integration of inverter-based resources and associated grid issues, synchronous condensers have become more common. The literature indicates a considerable gap in understanding the loss of synchronism phenomenon in synchronous condensers, particularly under conditions where inverter-based resources dominate the power grid. This thesis examines the loss of synchronism phenomenon in synchronous condensers, including theoretical analysis using phasor diagrams of realistic scenarios. It also investigates the distinction between loss of synchronism and the pole slipping phenomenon, which has led to failures in traditional impedance-based schemes. The proposed relative speed-based method is applied to synchronous condensers and its effectiveness is demonstrated in situations where traditional schemes have failed. Additionally, effectiveness of the proposed method in weak grids with a high penetration of inverter-based resources is analysed using a modified IEEE 39 bus system.
Access status: Open Access ,
Freshwater influence on the hydrography and dissolved CO2 of the Northeast
(2025-11-03) Willcox, Esdoorn; Wang, Feiyue (Environment and Geography); Hamme, Roberta (Environment and Geography); Fripiat, François (Université Libre de Bruxelles); Rysgaard, Søren; Galley, Ryan
The Northeast Greenland shelf and the associated fjords are an extremely dynamic Arctic environment. It is influenced by Arctic Ocean processes, the Greenland Ice Sheet, and the North Atlantic. In turn, any modifications that occur in the region are exported south, back into the North Atlantic. This thesis addresses some of the open questions in the region regarding regional water mass distribution, carbon dynamics, and fjord processes. The first research chapter presents an updated hydrography for the Northeast Greenland shelf, including observations from latitudes that were not included in previous work. We look at the sources for the water masses identified and find a clear link between the Polar Surface Water found on the Northeast Greenland shelf and the Laptev Sea region in the Siberian Arctic using geochemical tracers. The second research chapter is an investigation of the effect of the hydrographical configuration identified in the previous chapter on the carbon system. We determine that the region can act as a source of CO2 to the atmosphere rather than a sink, challenging the prior understanding of the Northeast Greenland shelf as a strong atmospheric CO2 sink. The third and last research chapter focuses on a mooring and novel automated stable water isotope sampler deployed, with a weather station, in a fjord linked to the Northeast Greenland shelf. After the maximum discharge occurs in autumn, driven by a change from along-shelf winds to piteraq, the salinity increases steadily. Nonetheless, the fjord remains stratified throughout winter between depths of 11 m and 50 m, even recovering after two high salinity events. This very stably stratified water column will be exported onto the shelf, where it will add to an already highly stratified surface water identified in the first research chapter.
Access status: Open Access ,
Effects of density and linoleic acid exposure on the chemical profiles of cercarial echinostome parasites
(2026-01-12) Sehgal, Joshita; Aukema, Harold (Food and Human Nutritional Sciences); Ramey-Balci, Patricia (Biological Sciences); Detwiler, Jillian
For many 2- and 3-host life cycle trematode parasites, transmission between hosts requires the cercarial stage to emerge from the first intermediate host to infect a second intermediate host or a definitive host. As the role of chemicals in cercarial-host interactions has only been investigated in a few trematode species and in limited contexts, it is unclear if ecological factors affect the diversity of types and concentration of emissions. I investigated the influence of cercarial density and host exposure to linoleic acid on the oxylipin emissions of the trematode parasite, Echinostoma trivolvis lineage c. Using high performance liquid chromatography-tandem mass spectrometry, a total of 40 oxylipins were quantified from nine samples ranging from 363-1621 cercariae per 10 mL, with seven oxylipins being present in ≥75% of the samples. Neither the diversity of types of oxylipins nor their concentrations showed a monotonic relationship with cercarial density, and no linear trends were observed. Forty-seven oxylipins were quantified from four samples of cercariae that each originated from infected snails that were exposed or unexposed to linoleic acid (385-674 cercariae/10 mL and 470-640 cercariae/10 mL, respectively), with 29 oxylipins being quantified in ≥75% of the samples in the unexposed, exposed, or both groups. Among these, oxylipin concentrations between the groups did not differ. Although linoleic acid appeared to be higher in the tissues of exposed snails, this increase did not affect the chemical profiles of the cercariae themselves. My thesis is the first to demonstrate that cercariae of E. trivolvis lineage c emit oxylipins. In addition, this work is the first to test whether density and host diet influence the chemical emissions of echinostome cercariae. By understanding how ecological factors may influence oxylipin emissions of parasites, we can better understand how these chemicals shape patterns of infection, host-parasite dynamics, and ecosystem-level interactions.
Access status: Open Access ,
Enchanted green blue infrastructure
(2026-01-06) dos Santos Martins Macedo Alfonso, Vanessa; Thurmayr, Anna (Landscape Architecture); Prociuk, Shauna (City of Winnipeg); Straub, Dietmar
Enchanted Green Blue Infrastructure reimagines the post industrial corridor south of the Refinery District in Winnipeg, Manitoba as a living social ecological landscape. The project responds to a site shaped by industrial remnants, fragmented access, and overlooked ecological potential. By integrating water, landform, vegetation, and community use into a cohesive framework, the design transforms the corridor into an extension of both the Refinery District and the Awasisak Mēskanow Greenway. The practicum explores how green blue infrastructure can become more than a technical system by supporting biodiversity, enhancing stormwater performance, and creating a resilient foundation for future growth. At the same time, the design introduces community gardens, gathering spaces, play environments, and accessible pathways that foster cultural connection, learning, and a sense of belonging for surrounding residents. By working with existing conditions and strengthening natural systems, the project demonstrates how urban landscapes can reconnect people with the land while addressing functional, ecological, and social needs. Enchanted Green Blue Infrastructure positions the corridor as a meaningful place to inhabit, experience, and care for, illustrating how infrastructure can cultivate both environmental resilience and enriched community life.
Access status: Open Access ,
Advancing spatiotemporal individual-level modeling of infectious disease transmission dynamics
(2026-01-19) Abed, Amin; Romanescu, Razvan (Community and Global Health); Deardon, Rob (Community and Global Health); Moodie, Erica (McGill University); Torabi, Mahmoud; Mashreghi, Zeinab
This thesis advances spatiotemporal modeling of infectious disease transmission dynamics by addressing key limitations of the Geographically Dependent Individual-Level Model (GD-ILM) framework. These limitations include reinfection, seasonal transmission, and computational inefficiency for large-scale epidemics. This work is further supported by development of two R packages. In addition, spatiotemporal analyses of Gonorrhea data from Manitoba identify persistent hotspots for targeted interventions. First, the GD-ILM is extended within a Susceptible-Exposed-Infectious-Recovered-Susceptible framework to capture reinfection dynamics, enabling the model to estimate susceptibility to both primary infection and reinfection while preserving spatially explicit transmission patterns. Application to individual-level Tuberculosis data from Manitoba reveals significant regional and individual-level risk factors and produces fine-scale infection probability maps, providing actionable insights for public health intervention. Second, the GD-ILM is extended to incorporate seasonally varying transmission, capturing temporal fluctuations in infection risk due to environmental, behavioral, and pathogen-driven factors. Applied to Influenza data from Manitoba, the seasonal GD-ILM identifies high-risk regions and periods, demonstrating the importance of integrating temporal dynamics into spatial models, with simulations confirming the ability to recover spatiotemporal patterns. Parameter estimation in both extensions is performed using a likelihood-based Monte Carlo Expectation Conditional Maximization algorithm. Third, to overcome computational challenges posed by large-scale epidemics when using the GD-ILM framework, a stratified temporally-weighted Kernel Density Estimation-based Probability Proportional to Size sampling approach, combined with Stochastic Approximation Expectation Conditional Maximization, is developed, enabling efficient parameter estimation and real-time application, and is illustrated through simulations and COVID-19 data from Manitoba. Fourth, two R packages, "GDILM.SEIRS" and "SeasEpi", are developed and made publicly available on the Comprehensive R Archive Network (CRAN) to facilitate reproducibility and practical adoption of the proposed frameworks in future spatiotemporal individual-level modeling of infectious disease transmission dynamics. Finally, spatial, temporal, and spatiotemporal cluster detection analyses of Gonorrhea data from Manitoba identify persistent high-risk areas and time periods, guiding targeted public health interventions.
Access status: Open Access ,
Evaluation of the Canadian CRA tool in caries-free children <6yrs
(2025-12-03) Bray, Hayley; Schroth, Robert
Introduction: The Canadian Caries Risk Assessment (CRA) Tool is a six-item screening tool used to identify risk level for future caries development in children <6 years. The purpose of this study was to determine whether baseline CRA tool scores in caries-free children <6 years of age can predict future caries development. Methods: Baseline and follow-up CRA tool scores were obtained as part of routine care from preschool children attending three publicly funded dental clinics in Winnipeg. Data for this study were restricted to children who were caries-free at baseline. Charts of children who had returned for follow-up one year later were then reviewed to determine the proportion developing caries, as evidenced by new carious lesions (including white spot lesions). Statistical analyses included descriptive statistics along with bivariate analyses. A p value ≤ 0.05 was significant. Results: A total of 145 children were caries-free at baseline, of which, 96 returned and had completed follow-up data. The mean total CRA score significantly increased from baseline to follow-up (1.9 ± 1.0 vs. 2.4 ± 1.9, p = 0.005). While not statistically significant, not brushing teeth twice daily (OR = 1.89, 95% CI = 0.72-4.90, p = 0.19) and low family income (OR = 1.73, 95% CI = 0.65-4.57, p = 0.27) were the strongest indicators of caries development by follow-up. The CRA tool was found to have a sensitivity and specificity for baseline CRA rating and the development of new caries at follow-up of 30.4% and 75.3%, respectively, indicating a low sensitivity but high specificity. Conclusions: The CRA tool has a high potential of identifying low risk children who truly do not develop future caries. This research emphasizes the use of CRA tools in preventive pediatric dentistry to improve children’s oral health and maintain a caries-free state.
Access status: Open Access ,
Genetic control of melanin production in the polyextremotolerant fungus Exophiala dermatitidis
(2026-01-04) Chhoker, Kamaldeep; Belmonte, Mark (Biological Sciences); Whyard, Steve (Biological Sciences); Gerstein, Aleeza (Microbiology); Kronstad, Jim (University of British Columbia; Harris, Steven; Hausner, Georg
Exophiala dermatitidis is a polymorphic black yeast found in various habitats such as soil, leaf litter and man-made environments including sinks, dishwashers and saunas. E. dermatitidis is also an opportunistic pathogen of humans where it can cause phaeohyphomycosis and skin infections. 1,8-DHN melanin found in E. dermatitidis has been shown to provide various functions that range from protection against cellular damage to conversion of visible UV energy into heat. Although the E. dermatitidis genome sequence has revealed the presence of genes responsible for production of melanin via three different pathways, relatively little is known about the relative contribution of these pathways to melanization. The aim of this study was to address this issue by using an unbiased genetic approach to determine which pathways are essential for melanin production. To this end, albino mutants lacking the ability to produce melanin were obtained using UV irradiation. Based on genome re-sequencing and SNVs analysis, all the albino mutants showed variants in the PKS1 gene including mutations ranging from missense base substitutions to frameshifts and short deletions. When grown on different carbon sources, some albino mutants were able to recover melanin production. Ultimately, comparative transcriptomics was used as a tool to examine differentially expressed genes when the various albino mutants were grown on different carbon sources. Transcriptomics analysis allowed us to investigate the expression of alternative genes/pathways that can promote the recovery of melanin production in the conditional albino mutants.
Access status: Open Access ,
Fault tolerant Euclidean K-Centers
(2025-12-16) Rahimzad Lamey, Sahar; Miller, Avery (Computer Science); Thulasiram, Ruppa (Computer Science); Durocher, Stephane; Li, Pak Ching
The Euclidean k -center problem is a fundamental question in computational geometry and facility location. Given a set P of n points in Rd, the goal is to choose a set F of k center points such that the maximum distance from any point in P to its nearest center in F is minimized. Geometrically, this corresponds to covering all points in P with k balls of minimal radius. We study a natural generalization known as the ℓ-fault-tolerant Euclidean k - center problem, which introduces a robustness parameter ℓ ≤ k. In this variant, each point in P must be covered by at least ℓ of the k balls, or equivalently, its distance to the ℓth nearest center in F must be minimized. This captures scenarios where redundancy is required for fault tolerance or load balancing. Our contributions include an exact O(n log n)-time algorithm for solving the problem in one dimension (R), where a linear order among points can be exploited. In two dimensions (R2), we prove that the problem becomes NP-hard. Nevertheless, we present an O(nk/ℓ)-time algorithm that computes a 2-approximation, offering an efficient and practical solution with provable guarantees.
Access status: Open Access ,
Blood metabolomes and molecular markers of cellular aging in wild fish
(2026-01-20) Wiens, Lilian Maria; Jeffries, Ken (Biological Sciences); Tomy, Gregg (Chemistry); Rennie, Michael (Biological Sciences); Eliason, Erika (UC Santa Barbara); Treberg, Jason
My work studies stress and aging physiology of wild fish using biochemical methods. The species used are two North-American temperate fish: Sander vitreus, walleye, and Salvelinus namaycush, lake trout, both species being upper-level predators of high ecological and economic importance. While using biochemical measurements is common in fish laboratory models, my thesis uses these techniques to gain insight into the biology of fishes in the wild with focus on possible environmental stress and the effect of biological aging. In my first research chapter, I determined by non-lethal sampling the whole blood metabolomic profile of S. vitreus from Winnipeg Lake to test for regional differences in metabolites across this population. Results show different blood metabolite patterns across the Southern versus the Northen basin of Lake Winnipeg. Northern S. vitreus exhibit higher concentrations of essential and branched-chain amino acids and metabolites of specific amino acid catabolism pathways, relative to Southern caught specimens. The pattern of amino acid metabolites in Northern S. vitreus may indicate heavier reliance on protein catabolism relative to the Southern fishes. Conversely, higher concentration of long-chain acylcarnitines in some Southern fish suggests higher reliance on β-oxidation for energy supply during spawning. My second research chapter investigated if patterns of changing metabolites with age in mammals may also be found in blood metabolites of Lake Winnipeg S. vitreus as they age in the wild. Results show amino acids, including essential, branched-chained and some non-essential amino acids, correlate positively with chronological age, while some medium and short-chained acyl-carnitines decrease with age. These results are similar to age-related patterns in mammals. The third research chapter investigated cellular senescence in wild-caught S. namaycush, using two common markers of aging associated with physiological decline, relative telomere length and lipofuscin accumulation. Results show no correlation of these aging markers with age in S. namaycush, in three tissues, heart, liver and red blood cells. These findings show that lipofuscin accumulation and relative telomere length data do not support increasing cellular senescence with age in this species and may represent negligible senescence in S. namaycush.
Access status: Open Access ,
The effects of nitrogen availability on plant species in the boreal tundra ecotone
(2025-09-09) Cummins, Gold; Klymiuk, Az (Biological Sciences); Worley, Anne (Biological Sciences); Markham, John
In high latitude biomes, increasing temperatures due to climate change are predicted to increase nutrient availability. Given the boreal region is dominated by plant and fungal species that are adapted to surviving in low nutrient soil, an increase in nutrients like nitrogen may cause a variety of responses in mycorrhizae fungi and their host plants. I found that several plant species responded to three years of 10 – 100 kg ha-1 nitrogen addition by changing their leaf N isotope ratios, morphology and physiology. However, these changes showed no obvious correspondence with mycorrhizal status. Although ectomycorrhizal fungi slow down the mineralization rates of nitrogen, and help to immobilize nitrogen, both ectomycorrhizal host plants, Picea glauca (Moench) Voss, and Dryas integrifolia Vahl, increased in total chlorophyll ∂15N while lowering the C:N ratio within their tissue due to fertilizer. The ericoid host plants (Ledum decumbens (Aiton) Lodd. ex. Steud, Vaccinium uliginosum L., and Empetrum nigrum L.) all responded differently from one another and did not respond to nitrogen unlike the ectomycorrhizal host plants. These results suggest that mycorrhizal types do not predict how boreal plant species will take up and utilize inorganic nitrogen. In some regions, climate change has resulted in boreal forests range expanding northwards, especially with a northward shift of coniferous trees. Northward range expansion for conifers on the tundra may involve the establishment and expansion of tree islands: clusters of conifers that create microhabitats on their leeward side. While we predicted these microhabitats would benefit conifer establishment and survival, we did not find this. After planting P. glauca and Pinus banksiana Lamb, seed around tree islands near Churchill, Manitoba, I found higher germination further away from the tree islands and on the windward side.