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 Photoinduced Spontaneous Surface Relief Gratings In Azo Glass Material(2025-02-07)This work investigates the formation of surface relief gratings (SRGs) on an azobenzene thin film when irradiated with a 532nm laser. The formation of linear gratings is created when exposed to a linearly polarized light, with the gratings formed parallel to the lights polarization. Adjusting the orientation of the lights polarization will result in a matching grating in the same direction. The growth of the SRGs is monitored by following the intensity of the first node via pass-through diffraction. The intensity pattern shows two operating functions over time, one which is actue and one which is longer. In attempt to obtain chirality from an isotropic beam, the azobenzene sample was rotated during growth period to obtain non-uniform, globule shaped structures which indicate non-symmetric properties. The SRGs formed are observed and studied through atomic force microsocpy, in which the grating pitch, orientation and overall structure can be observed. The resulting formations from rotating the sample at incidence, does in fact show varying degrees of anisotropy, however they do not show any clear or certain chiral features.Item Heterogeneous Approaches to Secure Discrete-Event Systems(2025-02-07)In the architectures of current networked systems, multiple components are potential targets under multiple types of attacks. Thus, this thesis proposes heterogeneous approaches to design secure controllers by employing three security notions in discrete-event systems (DES): secret protection, opacity, and actuator/sensor attacks. First, this thesis extends secret protection in DES from monolithic systems consisting only of one agent to distributed systems comprising more than one agent. The work presented in the thesis was motivated by the architecture of distributed databases and access control. The thesis addresses a problem of protecting secret information against intruders, supposing that secret information is separated into pieces and stored in local agents. The thesis approaches this problem by ensuring that at least one piece of distributed secret information is secured by a prescribed number of protections, preventing intruders from retrieving entire secret information. Next, this thesis tackles a problem of securing secret information in the system under two common attack types: eavesdropping and infiltration, by employing the existing methodologies of degree of opacity and secret protection. Given a prescription of required security levels against eavesdropping and infiltration for each secret in the system, the thesis develops algorithms to determine which event transitions in the system should be concealed and which ones should be protected. The main challenge in this problem is a constraint that transitions cannot be protected if they are concealed, and vice versa, modelling a limitation of practical security mechanisms. Finally, this thesis addresses the setting where all actuators and sensors in the system are subject to attack, called indefinite attacks. This setting captures a practical situation in which system designers do not know potential attack targets a priori. The thesis shows not only that even one sensor attack can make it impossible to find a supervisor that is resilient against indefinite actuator attacks, but also that sensor attacks can be prevented by disabling actuators equipped with sensors which the attacker targets. Taking these new challenges into account, the thesis proposes an extended methodology to compute a partial-observation supervisor which provides prescribed resilience against both indefinite actuator attacks and indefinite sensor attacks.Item Art and Waste in Panniqtuuq (Pangnirtung), Nunavut.(2025-02-07)The Art and Waste in Panniqtuuq Exhibition explores the ways Inuit Nunangat is a site where differing ideologies, epistemologies and cosmologies collide, and hegemonic assumptions marginalize Inuit ways of knowing and being (Zahara & Hird, 2016). Inuit have identified waste as a serious environmental, social and health threat. This collaborative, participatory community project interrogates the concept of waste (broadly defined as both tangible and intangible) in Panniqtuuq and asks who decides what is waste and who is responsible for the myriad of waste-related issues. An ad hoc collective of Inuit artists has produced art to animate personal and collective stories about their lived experiences to provide a counter-narrative to prevailing beliefs about Inuit and waste. I have created an installation - made of waste about waste from my perspective as a PhD candidate, waste researcher, and cis-gendered, white settler Canadian. I reversed my scholarly gaze and used research-creation to interrogate historical processes and deeply rooted white settler-colonialist assumptions, including those I have internalized and benefited from, linking these to barriers to Inuit sovereignty and rights to a healthy and safe environment. The portfolio of related work culminates in knowledge mobilization through public scholarship - a co-created touring art exhibition and critical accompanying pedagogical texts to raise awareness, encourage dialogue and call for urgent action in response to the historical, present and imagined future of waste in Panniqtuuq, integral to Canada’s commitment to Truth and Reconciliation.Item From Microalgae to Sustainable Plastics: Preparing Protein Aggregates from Algal Biomass(2025-02-07)This thesis investigates the extraction and purification of proteins from microalgae, specifically spirulina and chlorella, and their self-assembly into amyloid-like aggregates as building blocks towards the development of sustainable bioplastic materials. In response to growing environmental concerns over traditional plastics, amyloid fibers – highly organized protein aggregates – offer a potential alternative due to their structural stability, functional versatility, and sustainability. Although amyloid fibers have been prepared from animal- and plant-based protein sources, microalgae protein-derived amyloid fibers remain largely unexplored. Given their high protein content and the current industrial production of microalgae, spirulina and chlorella present an untapped resource for the development of such materials. Protein extraction and purification from spirulina and chlorella was performed using a pH shifting method, which is well-documented as an efficient, facile, and high-throughput protein extraction technique. Amyloid-like aggregation was induced under acidic conditions and elevated temperature, whereby spirulina proteins formed beta-sheet-rich structures with the typical fiber-like morphology, while chlorella proteins predominantly aggregated into non-fibrillar, spherical/annular structures. This difference in structural morphology underscores the importance of both protein purity and composition between sources. Protein aggregation is investigated in detail through Thioflavin T fluorescence, Fourier-Transform Infrared and circular dichroism spectroscopies, dynamic light scattering, zeta potential measurements, and atomic force microscopy imaging. Despite their morphological differences, both microalgal protein aggregates exhibit impressive stability across a wide pH range, persisting up to pH 11 before disassembly at pH 12, making them promising candidates for robust sustainable applications. Preliminary investigations incorporating model amyloid fibers into crude spirulina biomass revealed minimal improvement in mechanical strength, attributed to poor component mixing, underscoring the importance of processing in composite formation. In short, this work underscores the feasibility of transforming microalgae proteins into stable aggregates with complex morphologies, and highlights the importance of biomass source, protein purity, and composition on the aggregation process. Our findings contribute to the growing and exceedingly important field of bio-based and biodegradable materials, and offer insights into the fundamental principles governing amyloid fiber formation. We anticipate that these efforts will lead to the formation of high-performance, tunable bioplastics which can be used for a variety of different applications.Item Indigenous/state relations and the "making" of surplus populations in the mixed economy of Northern Canada(Elsevier, 2021-11)Grounded in an analysis of the mixed economy of the Northwest Territories (NWT), Canada, this article examines the contemporary relationship between surplus populations and colonial capitalist accumulation of new spaces. The functioning of the reserve surplus population requires that the unwaged, or under-waged, want, or need, wage labour. Thus, like all capitalist relations, a reserve surplus population is predicated on the separation of workers from their means of subsistence: what Marx calls “primitive” accumulation. Traditionally the home of the Dene and Inuit, and now home to approximately equal parts Indigenous (primarily Dene, Inuit and Métis) and non-Indigenous residents, the NWT mixed economy is a set of social relations that combine subsistence and social reproduction, wherein labour is oriented toward the daily and intergenerational wellbeing of the collective rather than the profit of the individual, with capitalist production. With a focus on the diamond industry, this article traces the shifting Canadian State approach to Indigenous labour in this space across time and the state policies and extractive projects that have both “made” Indigenous labour surplus and rhetorically justified their existence through evocations of regional unemployment and imagined dependency. In so doing, the paper identifies a move from the welfare-state era, wherein the state structured northern Indigenous “dependency”, to the neoliberal era, wherein dependency became a problem to be solved through increased Indigenous incorporation into capitalist wage labour. The northern diamond mining industry, responding to both Indigenous demands for land recognition and neoliberal imperatives for lean operations, exemplifies this latter approach. Highlights •Mixed economies challenge the assumption that people need capitalist labour. •Canadian government is newly invested in incorporating Indigenous wage labour. •Diamond mines target Indigenous workers as marker of “responsible extraction”. •The mixed economy resists dispossession by northern extractive capital.
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