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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Recent Submissions

Exploring the Extrinsic Motivators and Strategies That Drive Immigrants, Newcomers, and Refugees in Western Countries to Engage and Sustain Participation in Physical Activity and Healthy Active Living: A Scoping Review
(2025) Moradkhan, Fatemeh Matin
Research shows that immigrants and refugees are at a higher risk for physical inactivity; however, there is no comprehensive synthesis that investigates the extrinsic motivators that can drive immigrants, newcomers and refugees that come from different backgrounds, and live in Western countries to engage and sustain their participation in physical activities. This scoping review investigates the extrinsic motivators that influence and facilitate the participation of immigrants, newcomers and refugees in Western countries to engage in physical activity and sustain a healthy active lifestyle. The methodology used for conducting this scoping review is based on the Arksey & O’ Mally (2005) framework. The results show that challenges such as time constraints, high costs, safety, and cultural expectations are closely linked and can discourage participation. However, with the right community programs, interventions and supportive policies, these challenges and barriers can be transformed into motivators to encourage regular physical activity among this population. Overall, the study highlights the importance of focusing on community needs and culturally sensitive approaches rather than on individual choices to help immigrants, newcomers and refugees stay active and healthy.
Synthesis and Characterization of Electron-Rich Inhibitors of the α-Carboxyketose Synthases DAHPS And NeuB
(2025) Brzezinski, Weronika
Antibiotic resistance is a growing global health crisis, creating an urgent need for new antibiotics. The α-carboxyketose synthase (αCKS) family, which includes 3-deoxy-Darabinoheptulosonate 7-phosphate synthase (DAHPS), N-acetylneuraminate synthase (NeuB), and 3-deoxy-D-mannooctulosonate 8-phosphate synthase (KDO8PS), offers attractive targets for antibiotic development because these enzymes are essential for bacterial virulence but are absent from mammalian pathways. Although several αCKS inhibitors have been described, none have advanced to clinical application. This work applied a fragment-based and inhibitor-in-pieces approach to design and assess electron-rich and oxime-derived molecules as inhibitors of DAHPS and NeuB. Eleven compounds were synthesized or obtained, and inhibition constants (Ki) were determined. Several compounds showed strong activity, including Me-OPD, which inhibited DAHPS with nanomolar potency (Ki = 7.7 × 10⁻¹⁰ M), making it the tightest-binding small molecule reported for this enzyme. Clear structure-activity trends emerged: DAHPS favored compact, strongly electronwithdrawing substituents, whereas NeuB tolerated bulkier or more polar oxime variants. The inhibitor fragment N-hydroxyalanine (NHA) showed DAHP oxime-like binding behaviour, especially in the presence of glycerol 3-phosphate (Gro3P), indicating its potential to future fulllength inhibitor designs. This work expands the range of αCKS inhibitors and defines structural features explaining DAHPS and NeuB selectivity, providing a better basis for developing more potent and potentially cell-permeable antibacterial candidates.
Performance characterization of the defect-enabled all-silicon avalanche photodiode at telecommunication wavelengths
(2025) Xie, Yanran
Although silicon forms the foundation of the traditional microelectronics industry, the growing demand for higher data transmission capacity and lower energy consumption is propelling the advancement of a complementary technology - Silicon Photonics. It delivers exceptional scalability and power efficiency while enabling low-cost production by leveraging CMOS fabrication facilities and processes. This work describes research on the performance of a fully-integrated, one-material photodetector solution for the Silicon Photonics platform, designed for operation at telecommunication wavelengths, specifically 1550 nm. Following a introductory chapter to place this work into context, Chapter 2 provides a theoretical background of photodetectors and absorption mechanism in silicon. Chapter 3 studies the introduction of defects into silicon waveguides to improve the photodetector efficiency in converting optical signals at 1550 nm. The fabricated devices achieved multiplication gains up to M=35, with gain-bandwidth products reaching 230 GHz, and responsivity as high as 13 A/W. Chapter 4 explores the noise characteristics of these devices and provides a detailed analysis of noise behavior under different operating conditions. The excess noise factor measurements confirmed low-noise avalanche performance with an effective k-value of 0.1, attributed to the dominance of electron-driven carrier multiplication. In Chapter 5, the high-power performance of the detector operating in avalanche mode is studied, particularly the device linearity under high optical power and high electrical RF power input. The device shows one of the highest bandwidth-power product amongst waveguide photodetectors. Chapter 6 conducts a thorough study of the temperature dependency behaviour of the silicon photodetector using integrated on-chip micro-heaters, and experimentally demonstrates an enhanced performance in device sensitivity and noise reduction at elevated temperature relative to room temperature operation. This thesis concludes with Chapter 7, in which a summary of the findings is provided, and suggestion for future work is made.
Competing Magnetic Correlations on the Triangular Lattice
(2025) Huang, Hsiao-Yuan (Symphony)
ErMgGaO4 is a quantum antiferromagnet wherein pseudospin 1/2, Er3+ degrees of freedom decorate two-dimensional triangular planes separated by disordered nonmagnetic bilayers of Mg2+ and Ga3+. Its sister compound, YbMgGaO4, has attracted much interest as a quantum spin liquid ground state candidate, although the presence of the disordered Mg-Ga bilayers add complexity to this description. In contrast to YbMgGaO4, ErMgGaO4 shows a clear spin glass transition near Tg around 2 K, which is about 1/3 of its Curie-Weiss temperature. We have carried out new inelastic neutron scattering measurements on powder ErMgGaO4 samples, which show the frozen elastic component of the scattering to develop below Tg. The frozen (elastic) and fluctuating (inelastic) spin correlations are analysed separately, using a combination of linear spin wave theory and Warren line shape analysis. These are consistent with fluctuating 120◦ spin correlations at all temperatures, and the development of competing stripy static correlations below Tg.
MAPPING AND CHARACTERIZATION OF A DOMAIN IN THE HERPES SIMPLEX VIRUS VHS PROTEIN THAT INTERACTS WITH VP16
(1996-07) Johanna Ursula Schmelter
The herpes simplex virus has devised mechanisms to manipulate and apprehend the cell’s inherent processes for its own efficient replication. Two proteins brought into the cell upon infection are partially responsible for this action; VP16, a transactivator of immediate-early genes, and vhs, which is responsible for the shutoff of host protein synthesis and the degradation of host and viral mRNAs. The virus therefore, must be capable of integrating strategic means of temporal gene expression controls to effectively progress through its lytic cycle. Recent Studies have shown that vhs and VP16 interact with one another (Smibert et al., 1994), suggesting that this association might directly link their corresponding regulation. The project described herein was concerned with identifying regions of vhs required for interaction with VP16. Through the construction of deletion mutants and analysis of protein-protein interactions in vivo and in vitro, a minimal region of vhs spanning residues 310 to 330, was identified as being sufficient for mediating a selective interaction between these two proteins. This region was further characterized by the generation of 13 mutants; each of which were then analyzed by the yeast two hybrid system and in vitro solid-phase capture assays to identify requirements for association with VP16. The tryptophan residue at position 321 was discovered to be essential for maintaining this interaction. Mutating this residue to alanine rendered the two proteins completely incapable of associating with one another. Furthermore, additional residues located close to this residue affected complex formation in vitro, suggesting that these residues might constitute part of the binding interface and aid in stabilizing the interaction. Thus, the isolation of mutants which disrupt and abate the vhs and VP16 complex should facilitate further research identifying the functional significance of this interaction and the consequences when this interaction is abrogated.

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