Faculty of Graduate Studies Online Theses

Permanent URI for this collectionhttps://hdl.handle.net/10222/11163

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Access status: Open Access ,
Deep Learning for Field-Based Cereal Phenomics
(2026-05-29) Ravichandran, Prabahar; Yes; Doctor of Philosophy; Department of Mechanical Engineering; Not Applicable; Dr. Hao Gan; Yes; Dr. Clifton Johnston; Dr. Vasantha Rupasinghe; Dr. Ya-Jun Pan; Dr. Young Ki Chang
Plant phenomics has become a critical bottleneck in crop improvement, as the capacity to generate high-quality phenotypic data has not kept pace with advances in genotyping. This thesis integrates deep learning into cereal phenomics through end-to-end, non-destructive pipelines that combine proximal and remote sensing with modern neural network architectures. Near-infrared spectroscopy (NIRS) coupled with convolutional neural networks (CNNs) is applied to rice for predicting amylose content, chalkiness, grain dimensions, and grain shape. Visible to near-infrared (VIS-NIR) hyperspectral imaging is investigated for wheat grain phenotyping using grain-level patches and one-, two-, and three-dimensional CNN architectures, where reformulating cultivar-independent prediction as a classification task improves robustness for moisture and protein. For field-based phenotyping, a deep learning framework estimates rice blast severity from canopy-level images acquired in the Universal Blast Nursery (UBN), and foundation and instance segmentation models are fine-tuned to delineate breeding plots from uncrewed aerial vehicle (UAV) imagery, supporting reliable plot-level trait extraction. The work also treats phenomics models as production systems: pipelines are containerised and deployed across workstations, high-performance computing, and cloud platforms, with systematic evaluation of inference latency and system-level bottlenecks. Together, these contributions demonstrate that deep learning can convert plant phenomics from a limiting factor into a scalable, decision-ready component of modern cereal breeding programs.
Access status: Embargo ,
Terrain-Adaptive Compensation for Rover Wheel-Slip with Controllers Selected by Quality Diversity
(2026-05-29) Grant, Jasper; Yes; Master of Applied Science; Department of Electrical & Computer Engineering; Not Applicable; n/a; Not Applicable; Jason Gu; Hany El Naggar; Mae Seto
Wheel-slip in planetary rovers creates localization error, wasted power, worn tires and occasionally, mission failure. While wheel-slip estimation and sensing has advanced, active online compensation for wheel-slip has received less attention. Existing approaches use real-time terrain measurements or respond to proprioceptive feedback with only adjusted wheel speeds and torques. Therefore, there is potential to improve proprioceptive-only strategies by not only leveraging wheel speeds, but also potentially steering angles and active suspension, to actively respond to slip. A solution which uses these additional inputs is not confined to conventional driving and can consider unconventional gaits such as ``walking” or ``inch worm” style locomotion. Unconventional gaits can increase the range of navigable slopes beyond limits established by previous rovers. Despite their improved performance, unconventional gaits still rely on terrain parameter knowledge. Existing physics-based models also require knowledge of the soil properties of the navigated terrain. A proposed two-stage offline then online learning framework generates wheel-slip compensation controllers that are not confined to conventional gaits and iterates until a controller is identified to be high-performing on the terrain considered without directly sensing the terrain parameters. Results of this adaptation successfully converge on controllers that perform well on the simulated terrain. This contribution includes a software framework to evaluate and validate rover wheel-slip compensation solutions on realistic deformable terrain. Future work will trial this system on a rover model on real terrain.
Access status: Open Access ,
Artificial Neural Network Applications for Investigating Microwave Radiative Transfer in Polar Environments
(2026-06-02) Henschel, Colleen; Not Applicable; Doctor of Philosophy; Department of Physics & Atmospheric Science; Not Applicable; Dr. Randy Scharien; Not Applicable; Dr. Thomas Trappenberg; Dr. Glen Lesins; Dr. Thomas J. Duck
Accurate retrievals of surface and atmospheric parameters in polar regions are essential for climate monitoring, yet these environments pose unique challenges for remote sensing. Snow and ice exhibit strong spatial and temporal variability in properties such as depth, density, and grain size, leading to large variations in microwave penetration depth which complicates the interpretation of passive microwave satellite observations. This variability, combined with limited in situ observations, makes polar regions particularly difficult to characterize using traditional retrieval methods. This thesis explores whether Artificial Neural Networks (ANNs) can improve retrievals of geophysical parameters from passive microwave observations made by the Advanced Technology Microwave Sounder (ATMS), while also using these retrievals to investigate the physical properties of snow and ice. The study develops and validates two ANN-based retrieval approaches: a single-pixel Multi-Layer Perceptron (MLP) model and an image-to-image Swin-UNet model, which incorporates spatial context. Both models are trained using RTTOV-simulated brightness temperatures and validated against independent ground-based datasets, including measurements made by radiosondes, pyrgeometers, and ice mass balance buoys. The single-pixel retrievals demonstrate strong agreement with in situ observations for atmospheric profiles, emissivities, and frequency-dependent effective surface temperatures, while the image-to-image model further improves spatial coherence and retrieval stability by exploiting spatial structure in satellite swaths. Comparisons with ERA5 show that these ANN approaches often achieve comparable performance using this single-instrument retrieval, while also providing additional surface information in the effective surface temperatures and effective emissivities at lower frequencies. Finally, the retrieved effective surface temperatures and emissivities are compared to physics-based radiative transfer simulations using the Improved Born Approximation (IBA) and the Snow Microwave Radiative Transfer (SMRT) model. These comparisons demonstrate that the ANN retrievals encode physically meaningful information about snow. In particular, the 23.8 GHz effective surface temperature can be used as a proxy for the snow-ice interface temperature for snow-covered ice, while the 183.3 GHz effective surface temperature provides a reasonable approximation for the snow-air interface temperature, thereby providing estimates of the snow temperature gradients. Additionally, the retrieved emissivities can be used to interpret surface and snowpack conditions, where their frequency-dependent behaviour reflects physical changes in the surface state, providing qualitative indicators of evolving snow and ice surface conditions. By capturing the physical relationships between microwave emissions and snow properties, these ANN-based retrievals open new avenues for monitoring polar environments and refining our understanding of their role in the Earth’s climate system.
Access status: Open Access ,
Comprehensive Study of LFP and LMFP/Graphite Lithium-ion Batteries
(2026-06-02) Yue, Meng; Not Applicable; Doctor of Philosophy; Department of Physics & Atmospheric Science; Not Applicable; Dr. Karim Zaghib; Yes; Dr. Michael Metzger; Dr. Penghao Xiao; Dr. Jeff Dahn
Although phosphate-based cathodes are valued for their safety and low cost, their lifetime remains limited by capacity fade associated with lithium inventory loss and transition-metal dissolution. This thesis integrates the author’s published and unpublished work to investigate the degradation of LFP/graphite and LMFP/graphite lithium-ion cells. Electrochemical, physical, and chemical techniques, including cycling tests, impedance spectroscopy, X-ray fluorescence, and liquid-phase NMR, were used to study degradation at elevated temperatures. The results show that cell degradation is strongly influenced by electrolyte additives, salt chemistry, electrolyte quantity, and residual N-methyl pyrrolidone from electrode manufacturing. Increasing vinylene carbonate (VC) suppresses Fe deposition on graphite and improves the lifetime of LFP/graphite cells. In contrast, higher VC content accelerates Mn deposition in LMFP/graphite cells, highlighting the greater complexity of transition-metal dissolution in LMFP systems and the need for further electrolyte optimization to extend cell lifetime.
Access status: Embargo ,
Using fats and combined anti-methanogenic feeding strategies to modulate the dairy microbiome and reduce enteric methane emissions
(2026-05-29) Foster, Jacob; Not Applicable; Master of Science; Department of Animal Sciences and Aquaculture; Received; Dr Anne Laarman; No; Dr Natalie Diether; Dr Rhea Lumactud; Dr Stephnanie Collins; Dr Renée Petri
As the Canadian diary industry aims to achieve net-zero emissions by 2050, anti-methanogenic feeding strategies are needed to reduce enteric methane. This research utilized two approaches to investigate how dietary strategies influence rumen microbial communities and fermentation characteristics associated with methanogenesis. Experiment one used a linseed-based product (LP) and a semi-continuous in vitro model to test increasing dietary inclusion levels of LP. Addition of LP did not reduce methane production or alter fermentation dynamics or microbial populations. Experiment two used an in vivo approach to assess the addition of cultivated red seaweed in TMR diets. Seaweed inclusion did not affect rumen pH or overall microbial diversity. However, there were differences in beta diversity and relative abundances. Likewise, methane was reduced with the addition of cultivated seaweed to TMR diet. Using both in vitro and in vivo methods provides insight into how dietary strategies can reduce emissions from the dairy industry.
Access status: Open Access ,
DESIGN AND CONSTRUCTION OF GENETIC CIRCUITS FOR ENGINEERING METHYL SELECTIVE DNA BINDING DOMAINS
(2026-05-29) Cucksey, Jordan; Not Applicable; Master of Science; Department of Biochemistry & Molecular Biology; Not Applicable; na; Not Applicable; Dr. K. Vanya Ewart; Dr. Barbara Karten; Dr. James M. Kramer; Dr. James Davey
DNA methylation is a crucial epigenetic modification that modifies protein-DNA interactions and regulates many essential processes in prokaryotes and eukaryotes. Control over DNA methylation has applications in disease characterization and treatment, memory-based genetic circuits, and cellular reprogramming. However, current approaches to studying and modifying DNA methylation lack the ability to selectively target methylated sequence-specific DNA. Furthermore, the conventional protein engineering workflow for designing DNA-binding proteins with methyl-selective, sequence-specific DNA recognition relies on inefficient multi-step screening processes. To address these limitations, a genetic circuit is proposed as a high-throughput selection platform for engineering sequence-specific, methylation-selective DNA-binding domains. The pCD plasmid was designed to present a helix-turn-helix repressor library with both methylated and unmethylated operators, and to integrate methylation-selective DNA recognition into an output that could be interrogated by GFP screening and kanamycin resistance selection. The pCD plasmid was successfully constructed using PCR-based DNA assembly of modular circuit components. Kanamycin growth results supported the use of kanamycin resistance as a selection marker to evaluate the binding specificity of engineered DNA-binding domains. The initial failure to establish circuit controls suggested the incorporation of a non-functional repressor construct, Rz. A simplified plasmid, pAD.02, was designed to further investigate the interaction between RZ and the corresponding operator, ZZ. RZ variants, XSN, XAN, XKR, and KSX were paired with TTA, TGT, GAC, and CGG operators, respectively, based on previously characterized LacI DNA-binding-domain operator interactions. These interactions were assessed across the proximal, core, and distal operator positions and revealed that the established LacI DNA-binding domain-operator pairings are not fully compatible within the RZ architecture. In total, 14 functional RZ-ZZ operator pairings were identified and can be incorporated as regulatory components in pCD. Overall, this work advances the development of a genetic circuit-based screening and selection platform for engineering methyl-selective DNA-binding proteins and suggests that surrounding structural features may influence DNA binding domain-operator interactions.
Access status: Open Access ,
Current measurements in the Drake Passage
(1972) Foster, Leslie Alexander; Not Applicable; Master of Science; Department of Oceanography; Not Applicable; unknown; Not Applicable; Dr. D. J. Lawrence; R.R. Lively; C.R. Mann
As part of the Hudson 'TO Expedition, an array of 12 current meters was moored in the Drake Passage near longitude 68° W for 10 days in February, 1970. A hydrographic section was run across the passage at the beginning and end of the mooring period. The geostrophic currents using assumed levels of no motion gave results similar to past studies. The current meter records indicated that a minimum velocity is found in the middle of the water column and they also showed the presence of a semi-diurnal tidal component. The best compromise between the current meter data and the hydrographic data is a variable level of no motion with a net transport qf 5 sverdrups toward the west, but because of lack of current meter data at the convergence zone, an unambiguous transport figure could not be determined.
Access status: Open Access ,
Suburban infill : an intervention for Gaborone's pedestrianways
(2008) Othogile, Helen Goabaone; Not Applicable; Master of Architecture; School of Architecture; Not Applicable; Jacques Rousseau; Not Applicable; Peter Sassenroth; Niall Savage
The thesis explores the potential benefits and possibilities of infill interventions within Gaborone's existing pedestrianways. The city was designed and laid out by European planners during the time of the Protectorate at the height of the Garden City movement, to become the new administrative capital for the newly independent Botswana. The resultant pedestrianways are an imported urban model that literally got "lost in translation" and as a result, the pedestrianways remain highly underutilized and could rightly be considered as wasted spaces in the city. Through a historical understanding and critical analysis, the thesis identifies why the pedestrianways are not working; how people are using them; and how the city could begin to redevelop them into meaningful and sustainable spaces.
Access status: Embargo ,
CHARACTERIZING BENTHIC AND PLANKTONIC CYANOBACTERIA DYNAMICS IN KEJIMKUJIK NATIONAL PARK
(2026-05-20) Macdonald, Sarah; Not Applicable; Master of Applied Science; Department of Civil and Resource Engineering; Not Applicable; n/a; Not Applicable; Dr. Daniel G. Beach; Dr. Janice Lawrence; Dr. Lauren Somers; Dr. Rob Jamieson
Kejimkujik National Park and National Historic Site contains over 46 pristine lakes and several interconnected rivers and streams, providing habitat for wildlife and recreational activities. Cyanobacteria are an increasing concern in Atlantic Canada due to their association with numerous canine mortalities. This study is the first to exclusively investigate cyanobacteria dynamics within the park. Planktonic cyanobacteria communities were assessed in 18 lakes and did not dominate microbial communities, although their occurrence followed distinct environmental thresholds. Cyanobacteria were more commonly detected in lakes with total phosphorus <12 μg/L, total organic carbon <10 mg/L, and pH levels > 5.5. Benthic cyanobacteria communities were assessed in two brooks and one lake and were a dominant component of the biofilm. Low-level anatoxins (<120 ng/g) and microcystins (<220 ng/g) were detected in biofilm samples. These findings improve our understanding of cyanobacteria communities as well as their toxin production in minimally impacted systems in Atlantic Canada.
Access status: Embargo ,
DEVELOPMENT AND EVALUATION OF SULFORAPHANE-RICH BROCCOLI OINTMENT FOR ATOPIC DERMATITIS MANAGEMENT IN BALB/C MICE
(2026-05-14) Chaturvedi, Chandrika; No; Master of Science; Department of Plant, Food and Environmental Sciences; Received; n/a; No; Dr. Yunfei Jiang; Dr. Carman A. Giacomantonio; Dr. H.P. Vasantha Rupasinghe
This study investigated broccoli (Brassica oleracea) as a sustainable source of bioactive phytochemicals and its potential application in atopic dermatitis (AD). Ultrasound-assisted ethanol extraction (25% ethanol, 41°C, 32 min) yielded optimal total glucosinolate content (36.6 mg sinigrin equivalence/g DW) and sulforaphane content (0.38 mg/g DW), demonstrating strong antioxidant and anti-elastase activity. In the 2,4-dinitrochlorobenzene (DNCB)-induced BALB/c mouse model, AD-like symptoms were successfully established, confirmed by elevated serum IgE and dermatitis scores. Topical application of 15% broccoli head (BH) and broccoli sprout (BS) extracts significantly reduced dermatitis scores, epidermal thickness, and serum IgE levels. The 15% BS ointment further decreased serum CCL11 levels, consistent with its approximately 17.5-fold higher sulforaphane content. Serum cytokines showed no significant changes, indicating that therapeutic effects were primarily localized within the skin. These findings support broccoli-derived extract ointments as promising natural topical agents for AD management and functional cosmeceutical development.
Access status: Open Access ,
Traduire dans le domaine des technologies transformatrices: enjeux et difficultés, théorie et méthodologie
(2026-05-12) Toukam, Dieudonné; Not Applicable; Doctor of Philosophy; Department of French; Not Applicable; Patrick Drouin; Not Applicable; Raymond Mopoho; René Tondji-Simen; Jasmina Milićević; Yannick Marchand
This doctoral thesis aims to study the specialized language of disruptive technologies (Big Data, Artificial Intelligence, and Blockchain), their terminology, and the challenges and opportunities related to English-French translation in this field. In order to familiarize linguists and translators with this specialized discourse and provide them with a reliable terminological resource, we built 5-million-word text corpus hosted by Sketch Engine, and adopted an ECL-augmented lexicosemantic approach, with the Explanatory Combinatorial Lexicology (ECL) enriching terminology by leveraging the Government Pattern for describing the syntactic cooccurrence of terms, Lexical Functions for describing the lexical relationships of terms, and a more rigorous methodology for formulating lexicographic definitions. We then created an English-French glossary (the GLOTECHT, also available online) based on our corpus and a fine-tuned methodology. Finally, we tackled translation challenges, as well as issues regarding semantic taxonomic classification, lexicographic definitions, neology, polysemy, etc.
Access status: Open Access ,
S-acylation of ATGL at Cys15: mechanism of activation and its relationship to ABHD5 coactivation
(2026-05-06) Afshari, Arezoo; Not Applicable; Master of Science; Department of Pathology; Not Applicable; Dr. Graham Dellaire; Not Applicable; Dr. Neale Ridgway; Dr. Barbara Karten; Dr. Gregory D. Fairn
Adipose triglyceride lipase (ATGL) catalyzes the first and rate-limiting step of triacylglycerol hydrolysis and is therefore a central regulator of lipid droplet catabolism in hepatocytes. Recent work identified S-acylation of ATGL at Cys15 as essential for lipase activity and lipid droplet homeostasis, but the mechanism by which this modification supports ATGL function remained unresolved. In particular, it was unknown whether Cys15 S-acylation influences ATGL activation through its major coactivator, α/β-hydrolase domain-containing protein 5 (ABHD5), and whether the requirement at Cys15 reflects a chemically specific need for cysteine modification or a more general requirement for local hydrophobicity. This thesis investigated the role of Cys15 S-acylation in ATGL activation and its relationship to ABHD5 coactivation. First, the effect of the S-acylation-deficient mutant C15S on ATGL interaction with and coactivation by ABHD5 was examined using confocal microscopy, co-immunoprecipitation, fluorescence lifetime imaging microscopy–Förster resonance energy transfer (FLIM-FRET), and cell-free lipase assays. Second, hydrophobic substitutions at Cys15 (C15F, C15L, and C15W) were tested to determine whether local hydrophobicity could partially substitute for S-acylation. Third, a preliminary microscopybased screen of candidate acyl-protein thioesterases was performed to identify potential negative regulators of ATGL deacylation. C15S retained localization to lipid droplets and co-immunoprecipitated with ABHD5, indicating that loss of S-acylation did not abolish association between the two proteins. However, FLIM-FRET showed that C15S did not exhibit the same degree of close-range proximity to ABHD5 observed for wild-type ATGL. Wild-type ATGL showed robust ABHD5-dependent activation, whereas C15S exhibited only weak stimulation, indicating that Cys15 S-acylation is required for full catalytic activation. Hydrophobic substitutions preserved lipid droplet localization and reduced lipid droplet retention relative to C15S, consistent with partial functional rescue. C15F mutant particularly restored FRETdetectable proximity to ABHD5 and partially recovered lipase activity, supporting the idea that hydrophobicity at position 15 contributes to ATGL activation, although it does not fully replace the effect of S-acylation. Finally, the thioesterase screen did not identify an obvious candidate regulator under the conditions tested. Together, these findings support a model in which Cys15 S-acylation promotes ATGL activation not by controlling lipid droplet targeting, but by enabling a productive functional relationship with ABHD5 and by contributing local hydrophobic character near the Nterminal catalytic region. This work refines the mechanistic understanding of ATGL regulation in hepatocytes and provides new insight into how defective ATGL activation may contribute to hepatic lipid accumulation and steatotic liver disease.
Access status: Embargo ,
DESIGN, DEVELOPMENT, AND EVALUATION OF A NOVEL HYDRAULIC SPRAY SYSTEM FOR MACHINE VISION-BASED REAL-TIME TARGET APPLICATION OF PESTICIDES ON BOOM SPRAYERS
(2026-04-30) Maambo, Humphrey; Not Applicable; Doctor of Philosophy; Faculty of Agriculture; Not Applicable; Mohamed Khelifi; Not Applicable; Travis J. Esau; Yves Leclerc; Madan Avulapati; Ahmad Al-Mallahi
A novel spraying mechanism assembly designed for machine vision–based, real time target application of pesticides on self propelled boom sprayers was developed and evaluated. The research addressed key limitations in modern precision spraying – such as nozzle valve actuation latency, boom pressure instability, and spray accuracy at higher ground speeds. The study investigates how 3D spray nozzles and a controller area network (CAN)–based feed forward pressure stabilization system can enhance timing accuracy and spraying at prescribed application rate. A comprehensive experimental investigation was conducted to characterize and optimize spray atomization parameters, including droplet size, velocity, breakup behaviour, spray coverage, and collision outcomes, across system pressures ranging from 275 to 482 kPa. Results show that 3D nozzles generate backward inclined spray patterns that effectively compensate for mechanical nozzle valve latency during real-time operation. A system pressure of 275 kPa emerged as the optimal pressure due to coarser droplets, minimized drift risk, favourable droplet coalescence, and reduced pumping power requirements. A CAN compatible feed forward pressure stabilization technique was developed to regulate boom pressure in anticipation of nozzle activation events, outperforming conventional feedback based systems by reducing pressure deviations by up to 63% and shortening pressure settling times by up to 5.7 fold. The system was prototyped on a 60 nozzle target spraying boom as an add-on system and validated through laboratory and field experiments, including tests on artificial and real Colorado potato beetle (CPB) targets. Field results demonstrated accurate real time actuation, consistent droplet placement, and practical integration of machine vision detection with hydraulic and electronic control subsystems. Overall, the research establishes an effective, scalable framework for deploying real time, target specific pesticide application technology that reduces chemical use, improves timing accuracy, and advances the feasibility of precision pest management in commercial agriculture
Access status: Embargo ,
Testing Implicit Safety Science Assumptions in Maritime Waterway Risk Control Options: An Empirical Analysis of PAWSA Reports
(2026-04-29) Adeli, Mehdi; Not Applicable; Master of Science; Department of Industrial Engineering; Not Applicable; n/a; Not Applicable; Dr. Jakub Montewka; Dr. Ron Pelot; Dr. Floris Goerlandt
Maritime waterway safety remains a critical concern due to the severe human, environmental, and economic consequences of shipping accidents. The Ports and Waterways Safety Assessment (PAWSA) method relies on expert judgment to propose and evaluate Risk Control Options (RCOs), including their perceived Risk Reduction Effectiveness (RRE). This thesis analyzes an empirical dataset of 50 unique RCOs extracted from 21 PAWSA reports (2016–2023) using content analysis and a tailored Strength-of-Evidence (SoE) framework. Results show substantial variation in RRE and SoE, with many RCOs lacking strong empirical support and only a small subset demonstrating both high effectiveness and strong evidence. Further analyses examine RCOs across actor groups, hierarchy of controls, and risk management phases. Findings indicate that expert judgments only partially align with common safety science assumptions. This study contributes to understanding how expert judgment reflects underlying safety concepts and supports more evidence-informed decision-making in maritime risk management.
Access status: Embargo ,
DRINKING WATER TREATMENT ADAPTATION FOR LEAD CORROSION CONTROL UNDER CLIMATE-DRIVEN WATER QUALITY CHANGE
(2026-04-30) Hood, Kalli; Not Applicable; Doctor of Philosophy; Department of Civil and Resource Engineering; Not Applicable; Dr. Kelsey Pieper; Yes; Dr. Heather Murphy; Dr. Amina Stoddart; Dr. Graham Gagnon
Lead in drinking water remains a public health concern worth mitigating. Drinking water treatment and distributed water chemistry are key determinants of lead release. Gradual and acute climate-driven changes in source water quality, treatment technology and regulatory targets create new challenges for corrosion control related to natural organic matter, coagulant selection, inorganic compounds, and excess product in wastewater. The goal of this work was to investigate how drinking water treatment adaptation influences lead corrosion control with an emphasis on organic matter and treatment strategies for enhanced removal, orthophosphate-based corrosion inhibitors, trade-offs with sequestration, and the feasibility of zinc-reduction. Pilot- and bench-scale studies in combination with time-series modelling and screening-level exposure projections were used to evaluate lead response to environmental events and experimental treatments. Following an extreme precipitation event, natural organic matter increased in source water and was associated with a prolonged elevation in total lead in a model distribution system and projected increases to short-term exposure risk. Enhanced organic matter removal via granular activated carbon improved lead control in a bench-scale reactor of galvanic lead solder. Equivalent total organic carbon removal was achieved at lower product doses of a chloride-based (polyaluminum chloride) coagulant relative to sulfate- based (alum), but was linked with increased galvanic lead corrosion. Orthophosphate- silicate may be an alternative to blended phosphate for systems needing to manage discolouration due to high iron/manganese, though risks of increased dissolved lead must be considered. In low-alkalinity water, reducing zinc in orthophosphate inhibitors may be feasible without compromising lead or cement corrosion, but may result in small increases in copper. These reductions could offer a more sustainable option with lower burden for wastewater treatment. This work demonstrated shifts in source water quality and treatment processes like coagulation, filtration, corrosion inhibitors and sequestrants can be protective or destabilizing for lead control and infrastructure maintenance. Utilities should consider whole-system trade-offs in lead control, treatment performance, and downstream sustainability during process adaptation or redesign.
Access status: Open Access ,
Microfluidic Systems for Long-Term and High Spatiotemporal In Situ Total Alkalinity Measurement in Marine Environments
(2026-04-30) Motahari, Shahrooz; Yes; Doctor of Philosophy; Department of Electrical & Computer Engineering; Not Applicable; Dr. Adrian M. Nightingale; Yes; Dr. Michael Freund; Dr. Ghada Koleilat; Dr. Vincent Sieben
Atmospheric carbon dioxide (CO₂) levels continue to rise, altering the global carbon cycle and driving ocean acidification. The ocean absorbs a large fraction of emitted CO₂, making accurate measurement of marine carbonate chemistry essential. Total alkalinity (TA) is a key parameter of the carbonate system because it controls seawater buffering capacity, playing a critical role in carbon uptake and air–sea CO₂ exchange. However, most TA measurements are still performed in laboratories using discrete water samples, limiting sampling frequency and spatial coverage in dynamic marine environments. This thesis presents the first field deployment of a microfluidic Lab-on-Chip (LoC) TA analyzer during an Ocean Alkalinity Enhancement trial in Halifax Harbour. The system performed closed-cell, multi-point spectrophotometric titrations in a stop-flow configuration using integrated syringe pumps, solenoid valves, and on-chip optical absorbance cells. Over 40 days, the analyzer completed 314 TA measurements and 52 onboard certified reference material (CRM) measurements, generating approximately 3,300 optical readings. This autonomous in situ platform demonstrated high-resolution monitoring of alkalinity variability that is difficult to achieve with traditional bottle sampling. To improve performance for long-term autonomous deployment, two design advancements were developed. First, a compact Dean-flow micromixer was designed and experimentally validated to enhance mixing while reducing channel length and internal volume relative to the original ~300 µL stop-flow mixer. The design was modeled using COMSOL Multiphysics and validated through bench-top TA measurements of certified reference materials. Second, the first reported droplet-based LoC TA sensor was developed. The system performs multi-point spectrophotometric titrations in segmented flow, where each droplet represents a titration point. Superhydrophobic surface modification of PMMA channels enabled stable droplet formation. This droplet architecture significantly reduces sample and reagent consumption while increasing sampling frequency, making it well suited for long-term, high-spatiotemporal-resolution carbonate monitoring in marine environments. Overall, this work demonstrates that microfluidic Lab-on-Chip systems provide an efficient and practical solution for autonomous, high spatiotemporal, total alkalinity monitoring in marine environments.
Access status: Open Access ,
Understanding Optimism: Winston Churchill and the Evolution of British Strategic Bombing Warfare Against Germany, 1914-1941
(2026-04-30) Wang, Yufan; Not Applicable; Master of Arts; Department of History; Not Applicable; na; Not Applicable; Paul Doerr; Gregory Hanlon; Denis Kozlov
This thesis examines the origins, evolution and early effectiveness of British strategic bombing warfare against Germany from 1914 to 1941. It traces the intellectual and institutional foundations of air power, from the creation of the Royal Air Force, which included the Independent Force and later Bomber Command. The treatise situates British air policy within the broader framework of interwar grand strategy, highlighting the expectations that bombers could deter enemies and deliver decisive results. Particular emphasis is placed on Winston Churchill, whose support for strategic bombing reflected both strategic calculation and personal inclination towards offensive actions. The work evaluates the limited effectiveness of strategic bombing from both British and German perspectives. Although early results fell short of expectations, British optimism and continued investment were not irrational given contemporary theorical and technological constraints. Ultimately, effective inter-service cooperation is more important than over reliance on single magic weapon in winning a war.
Access status: Embargo ,
CHEMICAL MODIFICATION APPROACHES IN ORGANOMETAL HALIDE PEROVSKITE MATERIALS AND SOLAR CELLS
(2026-04-30) Abdelmageed, Ghada; Yes; Doctor of Philosophy; Department of Process Engineering and Applied Science; Not Applicable; Dr Bryan Koivisto; Yes; Dr Suzanne Budge; Dr Mita Dasog; Dr Ghada Koleilat
Metal halide perovskites are promising for future photovoltaics due to their optical absorption, carrier diffusion, and tunable bandgaps. Despite efficiency gains, instability and defects remain barriers. This thesis explores chemical modifications, additive engineering, and surface passivation to improve their optoelectronic properties and stability. First, the study examined how film formation and surface chemistry affect passivation by linking deposition techniques to the results. Oleic acid was used as a hydrophobic ligand for the surface passivation of MAPbI3 films prepared by different deposition techniques. Our findings showed that the success of surface treatments depends heavily on film morphology, and that customized passivation strategies notably improve resistance to humidity and stability. Next, we explored additive engineering through sulfur-based molecular engineering with thiazoline to boost crystallization, passivate halide vacancies, and enhance interfacial charge extraction. Strong Pb–S bonds lowered trap densities, increased carrier lifetimes, and led to high-performance devices with over 22% efficiency and better stability under humid and illuminated conditions. Finally, we synergistically combined additive engineering and surface passivation techniques by using carbamide-based additives to improve crystallization and reduce defect density in the bulk and 2D capping layer, passivating surface defects. These treatments resulted in significant improvements in charge-carrier lifetimes and recombination dynamics, emphasizing the importance of controlling defect formation during film growth. Overall, this research shows that incorporating specific chemical modifications into both the bulk and interfaces of perovskite films is an effective strategy to reduce recombination losses and improve environmental stability. By elucidating the connections between molecular design, film formation, and device physics, this thesis provides a detailed framework for creating high-efficiency, durable perovskite solar cells and supporting their development toward scalable, practical use.
Access status: Open Access ,
Extreme Water Level Predictions on the Nova Scotian Coastline using a Bayesian Hierarchical Model
(2026-04-29) Sarhan, Fatma; Not Applicable; Master of Science; Department of Mathematics & Statistics - Statistics Division; Not Applicable; n/a; Not Applicable; Dr. Bruce Smith; Dr. Edward Susko; Dr. Orla Murphy; Dr. Jonathan Jalbert
The modelling of extreme coastal water levels is crucial when it comes to flood risk preparations, management, and defense design in Nova Scotia. Given the increasing frequency of flooding events in this region, it is essential to estimate their potential magnitude to mitigate their potentially devastating consequences. In extreme value analysis, return levels are quantifications of risk and represent the level that is expected to be exceeded once on average in a given time period. The challenge is that these extreme events are rare, and the data are limited and often incomplete. To address this challenge, a Bayesian hierarchical extreme value model is developed where information on extreme events is shared spatially across locations. By incorporating atmospheric covariates as physical drivers of extreme water levels, this research aims to establish a well informed Bayesian Hierarchical Model that enhances estimation precision and enables return level predictions for ungauged locations across the Nova Scotian coastline.
Access status: Open Access ,
Improving Lifetime of Lithium-Ion Cells with Electrolyte Additives
(2026-04-30) Azam, Saad; Not Applicable; Doctor of Philosophy; Department of Chemistry; Not Applicable; Betar Gallant; Not Applicable; Michael Metzger; Alex Speed; Michael Freund; Jeff Dahn
Lithium-ion batteries are the dominant technology for electric vehicles and grid energy storage, yet improvements in lifetime across wide voltage and temperature ranges remain essential for next-generation applications. Electrolyte additives improve cell lifetime by modifying the electrode–electrolyte interphases, which govern degradation processes including lithium inventory loss, transition metal dissolution, impedance growth, and electrolyte decomposition. In this work, nearly 25 novel additives and more than 100 additive combinations were evaluated in lithium-ion pouch cells containing layered oxide cathodes (LiNixMnyCozO2 or NMC) and olivine cathodes (LiFePO4 or LFP). Cells were tested under demanding conditions including high voltage operation up to 4.4 V and elevated temperatures up to 70 °C. For LFP/graphite cells cycled at 70 °C, 4% vinylene carbonate (VC) emerged as an effective additive formulation. The improved performance is attributed to residual VC in the electrolyte, which suppresses the formation of lithium alkoxide species that promote Fe dissolution from the LFP positive electrode and accelerate solid electrolyte interphase growth and lithium inventory loss. While cells containing 4% VC achieved about 1500 cycles at 70 °C, they failed at room temperature due to the formation of a highly resistive negative electrode surface impedance. To overcome this limitation, a novel additive, bis(1,3,2-dioxathiolane-2,2-dioxide) (bis-DTD), was synthesized by the author and investigated as a co-additive with lower VC concentrations. In LFP/graphite cells, the combination of 2% VC + 2% bis-DTD delivered a lifetime at 70 °C comparable to that obtained with 4% VC, while maintaining stable cycling at room temperature due to lower charge transfer resistance. This formulation enables LFP/graphite cells to operate over a wider temperature range. Bis-DTD also dramatically improved lifetime of LiNi0.65Mn0.3Co0.05O2/graphite pouch cells cycled to 4.4 V, where electrolytes containing 2% bis-DTD retained more than 80% capacity after over 2500 cycles at 40 °C and over 5000 cycles at 20 °C. In sodium-ion cells using layered oxide cathodes paired with hard carbon, bis-DTD improved capacity retention to more than 92% after about 1100 cycles at 40 °C. This single electrolyte additive has demonstrated significant lifetime improvements across diverse lithium-ion and sodium-ion chemistries, highlighting the potential of rational electrolyte additive design for next-generation energy storage systems.

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