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

CONSTELLATION SHAPING FOR WIRELESS OPTICAL INTENSITY CHANNELS
(2026) Parham Kazemi
As the demand for high-speed, power-efficient optical communication systems continues to grow, constellation shaping has emerged as a key technique for improving spectral efficiency or transmission reliability. This thesis investigates the application of constellation shaping in indoor visible light communication systems operating in high signal-to-noise ratio (SNR) regimes and employing intensity modulation/direct detection (IM/DD) optical channels, which provide a cost-effective alternative to coherent optical communication. Unlike conventional schemes based on equiprobable signaling, constellation shaping modifies the probability distribution of transmitted symbols to reduce the average transmission power and approach channel capacity while maintaining a fixed data rate. Two primary approaches for approaching the channel capacity are investigated: geometric constellation shaping (GCS) and probabilistic constellation shaping (PCS). GCS involves selecting signal points from a multidimensional lattice code while confining them within an optimal shaping region, thereby inducing a Maxwell–Boltzmann (MB) distribution, which maximizes entropy under non-negativity and average power constraints. In contrast, PCS directly assigns the MB distribution to a lower-dimensional constellation. Theoretical analysis demonstrates that both approaches achieve the same ultimate shaping gain at the expense of an increased constellation expansion ratio (CER) and peak-to-average power ratio (PAPR), thereby validating their effectiveness for IM/DD optical channels. This thesis extends prior work by generalizing the dimensionality of the constituent constellations. Although increasing the dimensionality introduces a trade-off that enables higher data rates at the expense of reduced shaping gain, an analytical framework is developed to evaluate these trade-offs in practical IM/DD systems. In addition, shaping codes originally developed for coherent optical systems, such as constant composition distribution matching (CCDM) and enumerative sphere shaping (ESS), are adapted to the constraints of IM/DD channels. In particular, enumerative cone shaping (ECS), which is a modification of ESS tailored to IM/DD channels, is fully implemented for both one-dimensional PAM constellations and three-dimensional raised-QAM constellations, achieving approximately 92\% and 89\% of the theoretical shaping gain, respectively. By contrast, CCDM is formulated analytically without a full implementation. The results of this thesis provide valuable insights for the design of band-limited indoor optical wireless communication systems, particularly visible light communication (VLC) systems, which represent a promising complementary solution to traditional radio-frequency (RF) systems in addressing the growing global demand for higher data rates.
Case Management: Towards Developing Principles to Interrupt the Effects of Cumulative Disadvantage in Later Life
(2026) Birchall, Elizabeth M.
The growing, diverse population of older adults in Canada will require a range of services to address their varied needs. Some older adults are aging with limited personal and practical resources, resulting in later years marked by poor health, difficulty accessing resources and bodies that are old before their time. Many of these older adults are accessing health and social care resources and receiving case management services. This study explores the ability of case management to interrupt the effect of cumulative disadvantage and improve aging. Principles have been developed to support the design, delivery, and evaluation of existing case management programs to provide redress for the effects of cumulative disadvantage and to improve the aging experience. This study is qualitative, informed by a critical theory and interpretivist perspective. A theoretical framework of cumulative inequality (CI) theory and paradigmatic life course approach informed the development of the research design, which employed narrative inquiry. The research was conducted in community agencies in Toronto, Ontario. The study’s findings show that case management can mitigate the effects of accumulated disadvantage and improve the aging experience. The principles developed are that case management must 1) address practical needs, 2) include emotional support, 3) continuity between workers is important, 4) people’s connections to their families and their social supports, as defined by them, are very important and should be given priority in casework, and 5) be realistic and compassionate about what is possible. Further research building on these principles could develop an evidenced based, critically informed model of case management for older adults aging with limited resources resulting from recent or limited accumulation and from structural accumulation of disadvantage.
An Economic Impact Analysis of the 2025 St. George Apple Fest in Brant County
(Prepared by the McMaster Research Shop for St. George Apple Fest, 2026-01) Cheetu, Shruti; Koptev, Egor; Mahajan, Arnav; Monkman, Eliott; Johnson, Sonia
The St. George Apple Fest is an annual event that attracts thousands of visitors and contributes to Brant County’s economy. This report evaluates the 2025 festival’s economic impact to provide organizers with reliable data to support funding, sponsorships, and municipal reporting.
INVESTIGATING THE NEURAL MECHANISMS AND THERAPEUTIC EFFECTS OF FMRI- AND EEG-BASED NEUROFEEDBACK IN POST-TRAUMATIC STRESS DISORDER
(2026) Jonathan Lieberman
Post-traumatic stress disorder (PTSD) is a prevalent and debilitating condition that often develops following trauma. Concerningly, many individuals struggle to tolerate or fully respond to existing first-line treatments. Although PTSD is associated with widespread disruptions in brain function—including hyperactivity and altered connectivity in regions such as the amygdala and posterior cingulate cortex (PCC) during both rest and trauma-related processing—this rapidly expanding neurobiological understanding has yet to be fully translated into clinical care. This dissertation investigates neurofeedback, a non-invasive method that provides real-time information about neural activity to support targeted self-regulation, as a neurobiologically informed adjunctive intervention for PTSD. Across a series of studies, it examines the therapeutic effects and underlying neural mechanisms of both functional magnetic resonance imaging (fMRI)- and electroencephalography (EEG)-based neurofeedback, the two predominant neurofeedback modalities. The findings demonstrate that individuals can learn to modulate PTSD-associated neural alterations and achieve meaningful reductions in symptoms following neurofeedback training. In addition, this work delineates the neural mechanisms associated with several distinct neurofeedback protocols and evaluates key methodological factors that shape both neural and therapeutic outcomes. Together, these studies advance a mechanistic understanding of how neurofeedback exerts its therapeutic effects in PTSD and provide empirical support for its use as a promising adjunctive treatment.
TRABECULAR BONE TEXTURE IN RADIOGRAPHS OF THE KNEE
(2005) Patrick Emond
Tibio-femoral osteoarthritis (OA) accelerates the degeneration of cartilage which alters the biomechanical environment surrounding the joint. As stresses applied to the proximal tibia increase, subchondral cancellous bone remodels itself in response to biomechanical changes. In order to detect the changes in subchondral trabecular bone, radiographic texture in regions of interest (ROI) in the medial and lateral compartment of the proximal tibia were examined. Dominant knees of 151 subjects were radiographed using the fixed flexion technique. Two radiologists independently graded each radiograph accord ing to Kellgren-Lawrence (KL) scoring. Two ROIs were selected to contain a representative sample of the trabecular pattern in the tibia. Run-length and trabecular strut analysis were applied to measure several indices of ra diographic texture. Aggregate reproducibility of the indices were assessed by analysing duplicate radiographs of 12 patients acquired 1-week apart. In general the reproducibility of the run-length indices were < 5% compared to those derives from strut analysis (< 10%). There was strong evidence of structural change in trabecular bone pattern in groups of subjects with differing Kellgren-Lawrence (KL) scores. For example, the difference in bone surface (p<0.05), bone volume (p<0.0001), trabecular spacing (p<0.005) and connectivity index (p<0.05) were statistically significant between subjects with KL scores of 4 and <1. In subjects with moderate osteoarthritis (KL=2,3), there was a non-significant trend to have greater apparent bone surface and bone volume, reduced trabecular spacing and greater connectivity as identified by strut analysis. It was found that structural change in trabecular bone can be identified by computer-aided analysis of radiographs of osteoarthritic knees. However, this change could not be identified in non-severe OA without greater statistical power.

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