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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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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.
Russian Nuclear Submarine Reactors: Applications for Civilian Power Generation
(1997-08) Marshall, Sean
As the worldwide demand for power increases, alternative sources of energy must be examined. Recently, in the former Soviet Union, a method of meeting the increasing demand for electricity was suggested: the nuclear reactors from decommissioned submarines could be adapted for use as civilian power stations in remote areas. Due to similarities between modern nuclear power plants and the reactors developed for submarines, this conversion should not pose any great engineering difficulties. However, it is important to examine the performance records of the Russian nuclear submarine fleet in terms of reliability and safety of these reactors to determine their suitability for use as power generating plants. By studying the known reactor accidents on board Russian nuclear vessels and making assumptions about their use based on the operation of nuclear submarines in other countries, an approximate probability of an accident resulting in core melting of 1 X 10=3 per reactor per year can be calculated for the Russian fleet. This number is at least one, and possibly two orders of magnitude higher than the average accepted probability for civilian reactors in use today around the world. Given this difference, the conversion of older submarine reactors into power generating plants does not appear to be an acceptable course of action. However, recent changes in the concept of nuclear safety in Russia has led not only to safer nuclear propulsion reactors, but also to the creation of a new breed of low-powered reactors. Both the new submarine reactors and their low-powered cousins may be capable of meeting the future demand for electricity in remote areas of Russia.
A Hybrid Computer Simulation of the U-Tube Dynamics in Two-Phase Control Absorbers for Nuclear Reactors
(1975-09) Kwok, K.K.
This report presents the development of a mathematical model describing the dynamic behaviour of a two-phase (gas and liquid) control absorber. This new type of absorber, invented in Italy, is being developed at the Reactor Control Branch of the Chalk River Nuclear Laboratories, Atomic Energy of Canada Ltd., for possible use in future CANDU nuclear reactors. The purpose of the mathematical model is: (1) to provide a tool for evaluating experimental data from a two-phase absorber test rig. (2) for use in larger simulations to investigate the controllability of future CANDU power plants. The mathematical model of the two-phase absorber presented here includes the U-tube dynamics, return line dynamics, gas line dynamics and liquid line dynamics. However, only the U-tube model has been implemented on the Hybrid Simulator. It is based on the conservation laws (mass, energy and momentum) using cross sectional averaged variables. A continuous space discrete time scheme is used to solve the void propagation equation. The U-tube model has been tested with perturbations in both time and frequency domains. However, the remainder of the simulation needs to be implemented on a hybrid computer to provide the parameters for direct comparisons with experimental data from the two-phase absorber test rig.
Sex Differences in the Innate Immune Response to Pneumococcal Pneumonia
(2025) Zhao, Kevin
Men are more likely to acquire and die from pneumonia compared to women, however the mechanism underlying this phenomenon is not yet fully understood. Thus, we explored sex differences in the innate immune system and immune response to Streptococcus pneumoniae infection (the most common bacterial cause of pneumonia). Female mice had greater survival compared to males after low- but not high-dose S. pneumoniae infection. RNAseq analysis of their lungs 6 hrs post infection (p.i.) revealed that chemokine signaling was differentially expressed during infection by sex. Using flow cytometry, we found that female mice had a stronger monocytic response while males had a neutrophilic response. Females had greater bone marrow monocyte progenitor counts at 18 hrs p.i. while males had more bone marrow neutrophils. Female bone marrow monocytes also had higher CCR2 expression at this time. Female mice recruited more monocytes to their lungs and had higher interstitial macrophage levels after infection, while males had more rapid neutrophil recruitment. Female lungs also had higher local inflammation after infection, but that males had higher persistent systemic inflammation after infection. Female monocytes and macrophages produced more tumor necrosis factor (TNF) after low- but not high-dose pneumococcal stimulation. Although male monocytes and macrophages had higher TNFR and TLR2 expression, male macrophages also had higher levels of NF-κB negative regulator expression (A20, Otulin, Cyld, Cezanne), perhaps explaining their depressed cytokine production. Monocyte depletion during infection diminished the female survival advantage, suggesting that monocyte recruitment is protective during infection. During aging, we highlighted how female mice appear to exhibit more dramatic changes in peripheral monocyte counts, bone marrow progenitor frequencies, bone marrow monocyte CCR2 expression. Furthermore, aging may increase baseline lung inflammation and monocyte TNF production after pathogenic stimulus in females but not males. Our findings highlight how biological sex impacts the murine immune system, and especially on monocytes.

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