About MacSphere

MacSphere is McMaster University's Institutional Repository (IR). The purpose of an IR is to bring together all of a University's research under one umbrella, with an aim to preserve and provide access to that research. The research and scholarly output included in MacSphere has been selected and deposited by the individual university departments and centres on campus.

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Students wishing to deposit their PhD or Masters thesis, please follow the instructions outlined by the School of Graduate Studies.

Communities in MacSphere

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Recent Submissions

Stabilizing Effects of Prey Growth Delay in a Delayed Predator-Prey System
(2026) Lenz Gil, Konstantin
Approved Minutes: November 2025 Graduate Council
(2025) School of Graduate Studies
Colorful photovoltaics using thickness-modulated thin film optical filters
(2026) Bhattacharyya, Paramita
Colorful photovoltaics have long been appealing to consumers for applications such as rooftop, building-integrated, and electric vehicle-integrated solar cells, among others. Achieving vibrant colors involves reflecting specific wavelengths of visible light. But energy capture in the visible range is crucial, as it often provides optimal external quantum efficiency. Therefore, it is essential to enhance the reflection of solar irradiance to achieve color while minimizing photocurrent loss. Researchers have explored various bottom-up approaches, such as modulating the thickness of single or dual-layer antireflective coatings (ARCs) or adding layers to existing standard ARCs. However, this often leads to broader reflection peaks and substantial photocurrent loss. While photonic crystal structures and metasurfaces show promise for color rendering, they require significant development before mass production. We explored various design strategies to develop two innovative methods for optical filter design that enhance both aesthetic appeal and photovoltaic efficiency while using fewer layers. Our first method employs a top-down strategy utilizing OptiLayer and MATLAB to design optical filters consisting of 2-6 layers. This approach results in narrower reflection peaks and achieves optimal colors (blue, green, red) while maintaining a photocurrent loss of only 5-10%, a notable improvement over previously proposed solutions. We investigated various combinations of materials to identify the optimal range of material pairs for this specific application. Our designs were validated through fabrication with three material pairs and two deposition techniques (CVD and PVD), and feedback from our experimental understanding was incorporated into our design method to make it robust. Our second approach uses a custom MATLAB code to design an optimal filter based on selected layer numbers and materials, specified by the manufacturers. The thesis includes details on design methods, deposition and characterization techniques, comparisons of spectral responses, and images of the colors produced by the fabricated filters.
REFERRAL PATTERNS OF PRIMARY CARE PRACTICES IN ONTARIO
(2026) Rahman, Bahram; Costa, Andrew; Health Research Methodology
Background: Primary care physicians (PCPs) are critical to Ontario’s health care system, acting as the first point of contact for patients with the system. They play a critical role in facilitating referrals to specialists and laboratory services, as part of clinical decision-making to address patients’ health care needs. However, there is limited understanding of how different primary care practice models impact different aspects of referrals, such as rate of referrals to specialists, communication with specialists about their referrals, and rate of referrals to laboratory medicine services, particularly within the context of Ontario’s primary care reform. This thesis aimed to comprehensively study primary care physician referrals to specialists and laboratory services and examine the association between their practice model and referral rates to specialist services and laboratory medicine. Methods: This thesis includes three independent studies using quantitative observational research methods. Primary care physicians practicing comprehensive care were identified from health administrative databases, and their data was linked to physicians’ billing data (Ontario Health Insurance Plan), population-level patient experience survey data (Health Care Experience Survey) and other health administrative databases. Statistical analyses were conducted to examine the association between primary care physician’s practice models and referral rates to specialist and laboratory medicine services, adjusted for other physician, patient and practice-level factors. Results: The first study showed that primary care physician referrals to specialists vary by practice model and sex. Those in predominantly fee-for-service models referred fewer patients to specialists than those in Family Health Teams (FHTs), Ontario's largest team-based care model. The second study showed that while patients generally across all models reported a high level of information coordination between their primary care physician and specialist, patients rostered to predominantly fee-for-service models were more likely to report that the specialist did not receive the necessary medical information from their primary care physician. The third study found that primary care physicians in FHTs had a lower rate of referrals to laboratory services than those in other primary care practice models. Conclusion: Primary care physician practice models significantly influenced rates of referrals to specialists and laboratory medicine services. Primary care physicians in FHTs had lower referral rates for laboratory services and higher coordination of information with specialists, they had a higher referral rate to specialists and to different subspecialties. These findings emphasize the importance of considering the impact changes to primary care practice models could have on the utilization of specialist and laboratory medicine services as Ontario continues to reform the primary care system and expand team-based care models such as FHTs
Super-Earth Masses and Stellar Abundances from NIRPS Reveal Tentative Evidence for Water-Rich Formation around M Dwarfs
(2026) Weisserman, Drew
Tracing the compositional link between terrestrial super-Earths and their host stars provides clues to their dominant formation pathway. By constraining the stellar abundances of refractory elements, we can predict the core mass fractions (CMFs) of their super-Earths. The level of agreement between this prediction and the planet’s true CMF from their masses and radii can teach us about past formation processes, like mantle stripping and water-rich formation plus sequestration in the planet’s core. Here, we present the first results from the Near Infrared Planet Searcher’s (NIRPS) GTO CMF subprogram: an intensive radial velocity campaign to refine masses of transiting super-Earths and compute their host stellar abundances. We retrieve precise masses for three hot super- Earths around M dwarfs (GJ 1132 b, GJ 1252 b, and LTT 3780 b), calculating masses of 1.69 ± 0.15M⊕, 1.54 ± 0.18M⊕, and 2.34 ± 0.10M⊕ respectively. We measure the CMFs of these and five further hot super-Earths from the literature to 10-15% precision. We compare these to CMF predictions from measuring the Fe, Mg, and Si abundances of their host stars measured from the NIRPS spectra. We find that the CMFs of these planets are smaller than expected from their host stellar abundances, to a statistically significant degree. This discrepancy is suggestive of significant reservoirs of water, generally consistent with water mass fractions of ∼ 1%, sequestered inside the interiors of these planets.

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