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Validation of a Commercial Ultrasonic Real-Time Location System for Providing Position Constraints in Low-Cost Indoor Photogrammetric Reconstruction
No full textIndoor 3D reconstruction for building documentation faces a fundamental challenge: creating accurate, properly scaled digital models without relying on extensive ground control point (GCP) networks or specialized surveying expertise. This research investigates whether commercial ultrasonic real-time location systems (RTLS) can provide sufficiently accurate camera position constraints to eliminate GCPs in smartphone-based indoor photogrammetry while maintaining architectural documentation accuracy requirements (2–5 cm).
The ZeroKey Quantum RTLS was validated through three progressive experimental phases using tripod-mounted data collection under controlled conditions. Repeatability assessment established optimal data collection protocols – a 1-second sliding window threshold-based approach following brief settling – and quantified measurement precision: the root mean square (RMS) position precisions were 1.6 mm (X), 1.7 mm (Y), and 1.1 mm (Z), and the RMS orientation precisions were 0.08° (ω), 0.09° (ϕ), and 0.07° (κ).
Sparse reconstruction of signalized targets evaluated both position-only and combined position-and-orientation constraints. Position-only constraints demonstrated superior performance through 100% bundle adjustment convergence reliability and lower random errors, achieving inter-target distance RMS errors of 2.0–3.3 mm compared to terrestrial laser scan reference data after correcting for systematic scale errors. Critically, this systematic bias could be addressed using minimal ground control – as few as two GCPs – rather than extensive networks. Dense reconstruction of a complex indoor environment met the 2–5 cm accuracy requirements, achieving 11.6 mm RMS check point error while delivering 64% reduction in total processing time by eliminating manual GCP identification in images.
The research establishes that commercial ultrasonic RTLS can successfully replace extensive GCP networks for indoor photogrammetric reconstruction while maintaining architectural documentation accuracy, providing a foundation for future work transitioning to handheld operation. The proprietary nature of the RTLS represents the primary limitation, preventing investigation of systematic error sources
Air-Sea CO2 Exchange and Carbon Dynamics in Foxe Basin: Findings from a 2023 Oceanographic Survey
No full textThe ocean plays an important role in climate by removing large amounts of carbon dioxide (CO2) from the atmosphere through air-sea gas exchange. This process is particularly important in polar oceans, where sea-ice formation releases brine to the water column below and can create dense waters that sink and sequester dissolved carbon into deep waters. Foxe Basin, an inland sea north of Hudson Bay between Baffin Island and Melville Peninsula, is an ideal location to study this process as it is one of the few known places in Canada where sea-ice-driven deep water formation occurs consistently. A synoptic survey took place in Foxe Basin aboard the research icebreaker CCGS Amundsen in October 2023. Findings indicate that Foxe Basin was a weak sink for atmospheric CO2 during fall with a mean pCO2 of 396 ± 19 µatm and air-sea CO2 flux (FCO2) of -1.9 ± 2.1 mmol m⁻² day⁻¹. High pCO2 and positive FCO2 were associated with water column mixing and upwelling along the shelf break and Foxe Peninsula, while high pCO2 near Hall Beach reflected meteoric water input. Deep water bearing the signature of sea-ice brine formation (high salinity, low temperatures) and enriched in dissolved inorganic carbon (DIC) and total alkalinity (TA) was observed in Foxe Channel. A carbon budget attributed the 160 µmol kg⁻¹ enrichment in DIC between the surface and deep water to brine rejection (72%), respiration (24%), and gas exchange (4%). TA:DIC ratios showed no evidence that ikaite retention in sea ice affected bottom water carbonate chemistry. This thesis provides some of the first estimates of CO2 concentrations and carbon export in Foxe Basin, offering exciting insights into Arctic carbon cycling. This work highlights that sea-ice processes in Foxe Basin are particularly important for carbon export to deep water, making Foxe Basin an ideal location to study the role of sea ice in carbon export. These findings establish a foundation for future research necessary to achieve a comprehensive understanding of the basin's carbon dynamics
Stochastic Actor-Oriented Models of Functional and Structural Human Brain Networks in Aging
No full textThe human brain is a complex and dynamical system that changes throughout the lifetime. Non-invasive imaging techniques, including magnetic resonance imaging (MRI), allow for the measurement of large-scale functional and structural connectivity networks in the brain. Beyond trends, the dynamics across long timescales are still poorly understood. Our research aims to address the question of these long-term dynamics by carefully adapting and applying the stochastic actor-oriented model to brain networks derived from MRI data in an aging population. The resulting models of network change suggest that the brain is promoting modularity, local efficiency, and short-range connectivity during aging with more adaptive functional networks compared to structural networks. Differences between individuals with and without cognitive impairment suggest a disruption in the maintenance of key brain topology in the progression of cognitive impairment with age. These results are modulated by subnetwork and sex differences that contribute further to the emerging picture of long-term dynamics in aging
Zero Trust Continuous Authentication Models and Automated Policy Formulation
No full textContinuous authentication mitigates threats such as session hijacking, insider attacks, and privilege abuse by continuously validating user behaviour throughout an active session. Applying Zero Trust principles, this thesis develops Zero Trust Continuous Authentication (ZTCA) as a family of four formally specified access control models for user-facing software applications. Each model provides increasingly expressive ways to characterize expected access patterns using directed graphs. Deploying a ZTCA model requires the authoring of policies that balance security and usability. To ease the challenge of developing such policies, we study the problem of automatically generating ZTCA policies from declarative usability and security requirements. We introduce a novel equivalence-based SAT encoding that represents policy structure as an equivalence relation over resources, enabling automated policy synthesis using modern SAT solvers. Empirical evaluation shows that this encoding approach is significantly faster and substantially more efficient than a competing encoding approach previously published in the literature. Building on these foundations, the thesis introduces an adaptive extension of ZTCA that enhances enforcement without altering the underlying policy graph. The adaptive model adjusts authentication penalties based on recent behavioural signals—such as risky access patterns and authentication outcomes—providing stronger responses during high-risk periods while preserving usability during benign activity. A simulation framework is developed to compare adaptive and non-adaptive enforcement under identical conditions. Experimental results show that the adaptive mechanism limits risky behaviour earlier, concentrates authentication where it is most needed, and maintains a similar authentication burden for legitimate users. Together, these contributions provide a formal foundation, automated synthesis method, and adaptive enforcement layer for continuous, Zero Trust–aligned authentication in user-facing applications
Ultra-early Gamma Knife stereotactic radiosurgery for trigeminal neuralgia (URGEnt-TN): study protocol for a single-center, two-arm, parallel group design, pragmatic, noninferiority, phase II, randomized controlled trial with intention-to-treat analysis for pre-refractory GK-SRS in classical or idiopathic TN
No full textAbstract Background Trigeminal neuralgia (TN) is a chronic, often debilitating neuropathic facial pain condition. First-line treatment is medical therapy, with carbamazepine (CBZ) being the gold standard. Surgery, including stereotactic radiosurgery in particular with Gamma Knife (GK-SRS), is usually considered when medical management fails, which occurs in >50% of patients. While surgery can provide long-term relief, prolonged disease duration before intervention is linked to a reduced response rate. A highly precise type of radiation therapy, GK-SRS is a non-invasive management option in TN, with a low risk of serious complications and fewer bothersome side effects compared to medical therapy. Evidence supports the safety and efficacy of GK-SRS in medically refractory TN, with published data suggesting that earlier intervention (within 3 years of pain onset) leads to improved long-term outcomes. However, the safety and efficacy of ultra-early GK-SRS—administered soon after TN diagnosis and before medical refractoriness—have not been examined. We hypothesize that ultra-early GK-SRS will yield superior long-term pain relief compared to ongoing medical management while also having a lower incidence of treatment-related adverse events (AEs). Methods We will perform a single-center, two-arm, randomized, controlled, parallel group design, pragmatic, noninferiority, phase II trial of ultra-early GK-SRS for TN in participants who will be treated before they have developed a medically refractory state and within 2 years of diagnosed TN per study neurologist. Eighty participants will be randomized 1:1 to either GK-SRS (intervention arm) or ongoing medical management (non-intervention/control arm). Crossover from the non-intervention/control arm to the intervention arm will be permitted. An intention-to-treat analysis will be conducted. The primary outcome will be the proportion of participants with satisfactory pain control at 2 years by the Barrow Neurological Institute Facial Pain Scale. Discussion This trial aims to test ultra-early GK-SRS as a first-line option in TN, based on a sound rationale for offering GK-SRS prior to failure of medical therapy. If validated, ultra-early GK-SRS will represent a paradigm shift in TN management leading to improved long-term pain control free from adverse medication-related side effects. Trial registration ClinicalTrials.gov NCT06949436. Registered on April 28, 2025
Upper Carboniferous Hvitland Peninsula Formation, NW Ellesmere Island, Sverdrup Basin (Arctic Canada, Nunavut)
No full textThe Hvitland Peninsula formation is a stratigraphic unit of the Sverdrup Basin (Arctic Canada) that has been poorly defined and inconsistently mapped on Ellesmere and Axel Heiberg islands. To end stratigraphic misunderstanding, it should be defined as a unit of carbonate rocks lying above evaporites and/or carbonates of the Otto Fiord Formation and overlain by mudrocks of the Hare Fiord Formation. The Hvitland Peninsula formation on Hvitland Peninsula and in the Blue Mountains on northwestern Ellesmere Island is part of an unconformity-bounded early Moscovian sequence. It comprises carbonate buildups (reefs) that grew during the last phase of orthogonal rifting in the Sverdrup Basin. An earlier Serpukhovian rifting phase created fault-bounded half-graben depressions that accumulated coarse clastic material; a later Bashkirian phase along the same structures led to marine evaporite and carbonate deposition. Renewed early Moscovian rifting was accompanied by a major marine transgression that led to accumulation of deep-water fine-grained material surrounding a variety of offshore carbonate buildups, including thick and laterally extensive banks of coalesced reefs—the Hvitland Peninsula formation. The early Moscovian reef system grew rapidly due to highly productive microbial communities in a deep- and cold-water environment, with each mound building as an autochthonous lime mud factory with 100–600 m of vertical development. Accessory shallower facies indicate the mounds built up into very shallow water just below sea level. Stratal stacking patterns and vertical facies trends indicate the mounds are mostly progradational coalesced structures that developed through at least three shallowing-upward cycles. The reefs are complex carbonate bodies, displaying an alveolar configuration in map view, and variably dipping internal surfaces in profile views, indicating both vertical aggradation and lateral progradation. The top of the reefs is locally truncated by a sharp erosion surface that cut at very high angle through the pre-existing reefs. The mounds were pervasively affected by early diagenetic processes during and immediately following deposition, including pervasive submarine radiaxial cementation, neptunian fracturing, and karst-related dissolution and brecciation. The Hvitland Peninsula reefs rank as some of the most prolific Pennsylvanian (Late Carboniferous) buildups in the world. Their disappearance prior to the onset of late Moscovian–Kasimovian sedimentation reflects the end of rifting in the Sverdrup Basin and a global shift from a calcite sea to an aragonite sea
A Critical Public Health Analysis of Private Donor Naming in Canadian Public Universities’ Public Health Programs
No full textBackground. Under neoliberal capitalism, public health academic programs in Canadian public universities accept private philanthropic funding in exchange for naming rights. Because public health is grounded in equity, social justice and collective well-being, such naming carries important ethical implications for the field, yet this practice remains largely under-studied. Objectives. This study has two objectives: first, to map the frequency and patterns of private donor naming in public health academic programs in Canadian public universities; and second, to critically analyze this phenomenon by examining donors’ sources of wealth and contrasting these findings with the stated values of public health. The study is theoretically grounded in political economy of health and commercial determinants of health frameworks. Methods. I conducted an explanatory sequential mixed methods study. First, I reviewed publicly available materials to identify all Canadian public universities offering public health programs and the subset with programs named after private donors. Second, I conducted an instrumental case study focusing on the social identities of the donors and the sectors through which they accumulated their wealth. Findings. Of 31 Canadian public universities offering public health programs, four (13%) had donor-named programs. These programs were linked to five private donors, all of whom were cisgender, heterosexual white men. The donors’ wealth came from mining, oil and gas, financial services, and real estate sectors – all of which are industries associated with social, environmental, and health harms that disproportionately affect structurally marginalized populations. The political economy of health framework illuminates that neoliberal policies support these industries, concentrating wealth and power among elites while increasing vulnerability for marginalized groups; while the commercial determinants of health framework demonstrates that these sectors’ activities generate preventable health harms. Conclusions. These findings highlight a fundamental tension: associating public health programs with donors whose wealth is rooted in industries that produce health harms contradicts, and thus risks undermining, the field’s core values
Integrated Technology for Large-Scale Underground Hydrogen Storage in Porous Media
No full textGlobal efforts toward low-carbon energy have increased the demand for large-scale hydrogen storage. Such storage is needed to balance the fluctuation of renewable energy supply and demand. Among different options, Underground Hydrogen Storage (UHS) in porous media provides large capacity, good safety, and economic potential. However, compared with Underground Gas Storage (UGS) , UHS still faces key challenges. The small molecular size, low viscosity, and high diffusivity of hydrogen lead to complex flow behavior, unstable cushion gas performance, and strong water invasion. This study builds an integrated framework that connects basic mechanisms with engineering practice for large-scale UHS. First, the feasibility of converting UGS to hydrogen storage is analyzed, showing advantages in construction, geological stability, and operation. Second, compositional and molecular simulations are developed to study how depth affects hydrogen storage performance under different pressure and temperature conditions. Third, pore-network and numerical simulations are used to examine the mechanisms and selection of cushion gases, including natural gas, nitrogen, carbon dioxide, and air. The results show that CO₂ improves hydrogen recovery by reducing interfacial tension and stabilizing pressure, while nitrogen offers higher gas purity with moderate cost benefits. To reduce water invasion and increase the working gas volume, this study introduces a new gel-barrier technology. This technology is modeled using coupled mass, energy, and reaction equations. Simulation results show that gel barriers can block water pathways, keep the storage pressure stable, and raise hydrogen recovery by 10–25% in water-bearing reservoirs. A techno-economic analysis based on a capital cost, an operating cost, net present value, and an internal rate of return confirms that combining cushion gas with gel barriers is technically reliable and economically feasible for field use. Overall, this research builds a unified framework that links theory and engineering for safe and efficient underground hydrogen storage in porous media. The findings provide scientific support and practical guidance for future UHS projects in porous media
Physical activity, quality of life, and mental health amongst Canadian children and youth with disabilities
No full textPhysical activity provides numerous health-related benefits across populations. Despite this, children and youth with disabilities (CYD, ages 5-24 years) face stigma, discrimination, and other barriers that exclude them from physical activity participation and negatively affect their mental health and quality of life. Fortunately, adapted physical activity camps/programs provide opportunities for CYD to be active in an inclusive environment. While much of the available literature examines the amount of physical activity required for benefits, a newer concept that has emerged is the quality of physical activity participation. Moreover, there is a lack of quantitative examination of factors influencing quality of life for CYD, along with exploring how physical activity experiences may shape mental health. To address these gaps, we conducted two research studies amongst Canadian CYD. The first study is a cross-sectional study in which we explored the associations between quality of life with demographic characteristics (e.g., age, sex, impairment type), quantity of physical activity, and quality of physical activity. Our sample included 51 CYD and we demonstrate an association between having a physical impairment and reporting more quality of life problems. CYD who reported having a positive physical activity participation experience also report fewer quality of life problems. We found no associations between quality of life and sex, age, nor amount of physical activity. The second study (chapter 4) was a qualitative exploration including 12 youth with disabilities (ages 15-24 years) to discuss how their physical activity participation has shaped their mental health. Mental health was largely influenced by connection: connection to a fellowship within adapted programs, connections to realizing their capabilities and developing their confidence and competence, and connections to their emotional regulation and resilience. Each of these interconnected subthemes played a critical role in promoting many aspects of their mental health (e.g., relieving stress, promoting self-efficacy). In conclusion, physical activity experiences appeared to play a significant role not only on quality of life, but also specifically on shaping mental health. Future research should continue to explore ways to improve participation experiences amongst CYD so that they may reap the benefits of physical activity throughout their lives
