QSpace: Queen's Scholarship & Digital Collections
QSpace is an open access repository for scholarship and research produced at Queen's University. QSpace offers faculty, students, staff, and researchers a free and secure home to preserve and present their scholarship.
Recent Submissions
Item The History of Archaeological Work and Attitudes Towards Antiquities at Nineveh and Uruk(2024-10)Archaeology as a discipline is deeply connected and blurs into politics, colonialism, national identity and economic interests. The history of ancient regions and civilizations, such as that of Mesopotamia, can be studied with these themes in mind in order to understand how these civilizations evolved and the ways their cultural, social, and technological contributions have shaped aspects of the modern world. Many ancient Mesopotamian sites have been revealed since the emergence of archaeological exploration, including the two sites known as Nineveh and Uruk. Nineveh, (or Kouyunjik, the name it was known by during the Ottoman Empire period), was the largest city and capital of the Neo-Assyrian Empire (911 BC–609 BC, Nineveh as the capital from 705–612 BC). Uruk, also known as Warka, is an ancient Mesopotamian site in southern Iraq that has been the focus of archaeological exploration for over 165 years. These sites are a key point of reference for understanding the development of early urbanisation, writing, architecture, production, and social structure. Over nearly two centuries, changing politics, methods of archaeology and attitudes towards antiquities have affected the way these sites were handled. My major research paper focuses on those critical changes which reveal the evolution of archaeology from a Western-dominated affair to a more inclusive practice. In this paper, I will discuss and evaluate the history of archaeological work and attitudes towards antiquities at Nineveh and Uruk with an emphasis on the teams that excavated there, their methods of excavation, the conditions of the permits they were given, as well as the significant finds and their subsequent distribution. The analysis will be divided into historical time periods (from the Ottoman Empire period to Iraq after the US-led invasion of 2003) based on the modern history of this region. Governmental and professional policies are also explored in regard to antiquities laws, methods of archaeology and local versus foreign involvement.Item Investigating the Microstructural Stability of Nanocrystalline Oxide Dispersion-Strengthened Alloys under Proton Irradiation by X-ray Line Profile Analysis(2025-01-13)Nanocrystalline (NC) alloys contain unique defect structures compared to conventional Coarse-Grained (CG) alloys. NC alloys have smaller grains, and therefore higher Grain Boundary (GB) volume fraction, higher dislocation density and more ordered dislocation structures. Experimental and computational studies of NC alloys show improved resistance to degradation of material properties under irradiation due to increased point-defect (PD) sink densities. As a result, there is a reduced concentration of PDs available for clustering into higher-dimensional defects, which are chiefly responsible for the degradation of properties at the engineering scale. This work aims to experimentally validate the approach of limiting radiation damage by introducing pre-existing defect structures, as well as to gain a better understanding of the defect interactions that govern the thermodynamics and kinetics of irradiation-induced microstructural evolution. A Ni-based superalloy (Inconel 617, solution-annealed and aged) and two Oxide Dispersion-Strengthened (ODS) alloys, Ni and Fe-based (MA754 and MA957), are processed by High-Pressure Torsion (HPT), a form of Severe Plastic Deformation (SPD). Convolutional Multiple-Whole Profile (CMWP) analysis of high-resolution Xray diffraction (XRD) patterns reveals these sample to have dislocation densities on the order of 1016 m-2 and crystallite sizes of approximately 15 nm. Following low temperature (T < 0.35Tm) proton irradiation up to two displacements per atom (dpa), XRD experiments are repeated. Irradiation is found to cause partial annihilation of the dislocations created by HPT, with the mechanism of dislocation annihilation seemingly depending on crystal structure. Irradiation-induced grain growth, thought to be due to cascade-induced thermal spikes overlapping with grain boundaries, is observed in all samples. However, Inconel 617 exhibits “NC stability”, exemplified by a stable grain size with increasing dose – the greater NC stability of Inconel 617 agrees with earlier differential scanning calorimetry recrystallization experiments. XRD phase analysis suggests that the nanoscale oxide dispersions in MA754 and MA957 undergo ballistic dissolution due to low-temperature irradiation. Thus, they are unable to exert a Zener pinning force on mobile GBs to improve NC stability, nor can they serve as effective recombination sites for PDs, indicating that NC-ODS alloys do not show significant promise in the pursuit of material stability in extreme environments. The results suggest that NC stability is better approached by finetuning the alloy system to reduce GB energy. Finally, the irradiation-induced precipitation of α-Cr is found to occur in all Ni-based samples, with the effect being far more prevalent in MA754. Experimental evidence for radiation-induced segregation occurring concurrently with grain growth (previously investigated via phase-field models) is presented, with XRD revealing a grain size dependence on Cr concentration.Item Understanding likely responses of a low Arctic mesic tundra plant community to anticipated climate warming using long-term, climatically realistic soil nutrient enhancements.(2025-01-10)Tundra plant community composition and structure will be directly influenced by the particularly rapid climate warming currently occurring in the Arctic. Furthermore, increased soil microbial activity due to warming will enhance the supply of growth-limiting nutrients to plants and therefore influence plant community composition. In recent decades, vegetation composition has been shifting in many locations across the Low Arctic and shrubs are expanding their cover and range. Tundra greening and the associated reduction in albedo (reflectance) as well as the potential for widespread soil carbon losses to the atmosphere are expected to cause significant positive feedbacks to warming. Currently, we have a limited understanding of these feedbacks – and particularly of how climatically realistic increases in soil fertility will impact vegetation. Experimental warming significantly increased deciduous and evergreen shrub biomass after 14 years at the low Arctic Daring Lake site, and experiments with factorial large additions of nitrogen and phosphorus eliminating nutrient limitation have increased deciduous shrub growth there and at several other Arctic sites. While these high-level additions demonstrated species’ nutrient limitation regimes and established a dogma of nitrogen-limited plant growth in the tundra, they typically enhance soil nutrient availability far above expected what is expected with climate warming over coming decades. In this study, plant community aboveground biomass, and shoot growth measurements of Betula glandulosa were measured after 19 and 18 years, respectively, of factorial annual low-level nitrogen and phosphorus additions to simulate climatically realistic anticipated increases in soil fertility Corroborating results from high-level fertilization experiments, the low nitrogen addition significantly influenced some individual species’ biomass, and community composition. Furthermore, soil active layer depth was significantly correlated with community composition, positively with some species and negatively with others, suggesting an additional mechanism by which warming may significantly influence tundra plant communities. Finally, only birch shoot growth measurements from the sampling year corroborated known NP growth colimitation. Together, these responses to low-level factorial N x P additions improve our understanding of likely plant community shifts in response to future climate warming, and suggest scalar issues are critical, often overlooked factors needed to accurately predict patterns of future plant community change.Item Characterization of the Multifaceted Roles of sFRP1 in Melanoma: Investigations into WNT Signalling and Phenotypic Modulation(2025-01-10)Melanoma is an aggressive form of skin cancer that is commonly characterized by frequent metastasis and acquisition of therapeutic resistance. While early-stage treatment offers favourable outcomes, the prognosis for advanced disease remains poor. Recently, secreted Frizzled-Related Proteins (sFRPs) have been identified to exert nuanced roles in various cancers. For instance, the most well-studied of the family group, sFRP1, is strongly implicated as a tumour suppressor in colorectal cancer, though conversely, promotes tumour development in prostate cancer. Although its role is established in other cancers, the precise mechanism of sFRP1s contribution towards melanoma progression remains underexplored. Within our lab, preliminary evidence suggests that sFRP1 positively correlates with poor patient outcomes, including poor overall and distant metastasis free survival, and has found elevated expression of sFRP1 in metastases. As such, we hypothesized that sFRP1 promotes migratory and invasive phenotypes, while reducing proliferation, through modulation of Wnt signalling pathways. Results revealed distinct expression levels of sFRP1, Wnt ligands, and Wnt receptors across cell lines, indicative of unique environmental niches. Furthermore, sFRP1 demonstrated cell-line-specific effects over Wnt signalling mediators, likely driven by variations in local ligand-receptor availability, that further manifested as cell-line specific impacts over melanoma cell behaviours. Notably, sFRP1 decreased proliferation of cells cultured in non-adherent conditions, and decreased invasion, and migration in the B16F10 cell line. Intriguingly, preliminary data revealed that sFRP1 upregulates PD-L1 expression in B16F10 cells, representing the first reported association between sFRPs and immune checkpoint regulation in melanoma. These findings suggest a multifaceted role for sFRP1 in melanoma progression, including potential contributions to immune modulation, warranting further mechanistic exploration.Item A two-step quadrature-based variational calculation of ro-vibrational levels and wavefunctions of CO2 using a bisector-x molecule-fixed frame(Royal Society of Chemistry, 2024-04-25)In this paper, we propose a new two-step strategy for computing ro-vibrational energy levels and wavefunctions of a triatomic molecule and apply it to CO2. A two-step method [J. Tennyson and B. T. Sutcliffe, Mol. Phys., 1986, 58, 1067] uses a basis whose functions are products of K-dependent “vibrational” functions and symmetric top functions. K is the quantum number for the molecule-fixed z component of the angular momentum. For a linear molecule, a two-step method is efficient because the Hamiltonian used to compute the basis functions includes the largest coupling term. The most important distinguishing feature of the two-step method we propose is that it uses an associated Legendre basis and quadrature rather than a K-dependent discrete variable representation. This reduces the cost of the calculation and simplifies the method. We have computed ro-vibrational energy levels with J up to 100 for CO2, on an accurate available potential energy surface which is known as the AMES-2 PES and present a subset of those levels. We have converged most levels up to 20 000 cm−1 to 0.0001 cm−1.
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