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Generic Absoluteness in Set Theory
No full textIn this thesis, we describe the state of the field of generic absoluteness, that is, the study of which statements retain their truth value under any forced generic extension or series of generic extensions of , along with what large cardinal assumptions are necessary or sufficient to cause formulas to become generically absolute. We detail some of the tools used in generic absoluteness, such as homogeneously Suslin trees, direct limits of models, extenders, and the incredibly powerful Stationary Tower used for stationary tower forcing, along with the effect specific large cardinal properties have when combined with the stationary tower.
We describe various landmark generic absoluteness results including the following: Shoenfield's -Absoluteness theorem, which establishes that all statements retain their truth across all transitive models of containing . We also examine more advanced generic absoluteness results in the projective hierarchy, such as the equiconsistency projective absoluteness with the existence of \om-many strong cardinals, and that projective absoluteness follows from \om-many Woodin cardinals. Further up the hierarchy, we describe -absoluteness conditioned on , which states that assuming a proper class of measurable Woodin cardinals and holding in , if is a statement and is a generic filter for \p some partial order such that and , then if and only if . We also cover -absoluteness with generic , a generic form of Jensen's principle, and its relation to Neeman Games in -logic.
Furthermore, we cover the generic absoluteness properties of universally Baire sets, , such as a proper class of Woodin cardinals implying for and and any generic extension an elementary embedding such that and , along with the more recent axiom of Sealing, which seeks to 'seal' the truth of the universally Baire sets, along with examinations of the -powerset of , , such as Weak Sealing for , a strengthening of Sealing. We examine particular inner models of interest, such as Chang-like models and their unique generic absoluteness properties. Finally, we give proofs of the Shoenfield \bSigma_2^1 absoluteness theorem, and the fact that \bSigma^1_3 absoluteness follows from a class of measurable cardinals
Is Fiji’s Metabolism Built for Resilience? A Socio-Metabolic Risk Perspective.
No full textSmall Island Developing States (SIDS), despite contributing less than 1% of global greenhouse gas emissions, are among the most affected by the climate crisis. They face rising sea levels and climate-related economic losses averaging 2.1% of GDP, seven times the global average. This vulnerability is not limited to environmental exposure; it is further intensified by compounding factors such as a heavy reliance on external resources and limited material circularity. Most SIDS import over 60% of their food, and nearly all fossil fuels and construction materials, leaving them highly exposed to global supply chain disruptions and price fluctuations. To analyze this nexus of environmental and economic fragility, the Socio-Metabolic Risk (SMR) concept links a nation’s resilience to its material metabolism, its patterns of resource extraction, trade, consumption, and waste. SMR assesses risk across three pillars: secure resource access, circular material use, and equitable distribution of services. While pioneering studies have validated SMR's utility, applications remain limited to single-year snapshots. This leaves a critical gap, as a static view cannot capture the path-dependent dynamics, material lock-ins, and potential tipping points that evolve over time. Addressing this gap, this thesis uses Fiji as a case study to ask: Has the country’s material use from 2000 to 2022 mitigated or accumulated its SMR? To answer this, the study constructs the first multi-decadal (2000–2022), economy-wide material flow analysis (ew-MFA) mass balance account from a SMR lens, for a SIDS. Over two decades, Fiji underwent a profound metabolic transformation. Domestic biomass extraction, once the economy's cornerstone, fell by 42% (driven by a decline in the sugarcane industry), while biomass imports surged by 80%, eroding food self-sufficiency. Concurrently, imports of non-metallic minerals (e.g., cement, aggregates) increased more than fivefold (+436%), with surges for reconstruction following major cyclones like Cyclone Winston in 2016. Reliance on imported fossil fuels remained absolute, with total inflows growing by 26%. Fiji's overall import dependency climbed from 27% in 2000 to 46% in 2022. The analysis also shows a steady buildup of material assets, likely concentrated in hazard-prone coastal areas. This occurs within an overwhelmingly linear system, where material circularity is negligible and recycling practices are largely absent. The study concludes that Fiji’s development path has intensified its SMR, creating a material lock-in marked by growing reliance on imports and limited progress toward circular resource use. This creates a vicious cycle where climate shocks destroy vulnerable stocks, driving further import-heavy reconstruction that deepens vulnerability. By operationalizing SMR with a longitudinal dataset, this research provides a robust empirical foundation for evidence-based policy. The findings highlight the urgent need for interventions aligned with Fiji’s national development goals to strengthen the circular economy, accelerate the transition to renewable energy, promote local food systems, and enforce disaster-resilient 'build-back-better' standards. Ultimately, steering SIDS toward a more sustainable and resilient future requires a fundamental transformation of their resource use patterns
Defect Engineering of Titanium Dioxide Nanostructures: From Fundamentals to Applications
No full textTitanium dioxide (TiO2) is widely used in photocatalytic and photoelectrochemical applications due to its low cost, stability, and abundance. However, its wide band gap limits its light absorption to the ultraviolet region, and fast electron-hole recombination reduces its efficiency. Strategies to overcome these challenges include doping, heterojunction formation, and defect engineering.
Recent studies have shown that creating controlled defects in TiO2 can improve its optical and electrical properties. One promising defect engineering approach is laser based modification, which can precisely introduce defects into TiO2 structures without the use of high temperatures, pressures, or toxic chemicals. While laser processing has shown potential to enhance optical and electrical properties, the specific influence of laser parameters and defect locations on performance remains unclear. Additionally, hydrogen doping is known to introduce beneficial shallow states, yet in situ hydrogen doping during thin film growth has not been fully explored.
This research explores defect engineering of TiO2 nanostructures through controlled laser treatments and hydrogen doping to enhance their photocatalytic, photoelectrochemical, and electronic performance. Two different laser systems, femtosecond and nanosecond lasers, are used to systematically study the effects of laser parameters on defect formation, band structure modification, and performance improvement.
Femtosecond laser irradiation is applied to TiO@ nanoparticles to create localized surface defects without damaging the bulk structure or causing phase transformation. The introduction of oxygen vacancies and Ti3+ states result in improved photocatalytic activity under UV illumination by reducing electron-hole recombination and increasing surface active sites.
In contrast, nanosecond laser irradiation produces black TiO2 with significant band gap narrowing, phase transformation from anatase to rutile, and bulk defect formation. This material shows enhanced photocatalytic performance under visible light due to extended light absorption and modified electronic properties. The effect of defect location, i.e. surface versus bulk, on charge separation and recombination is also investigated, revealing that controlled surface defects promote better photoelectrochemical performance under UV light.
In addition, an in-situ hydrogen doping method is developed using plasma-assisted atomic layer deposition (PAALD) to produce hydrogen-doped TiO thin films. This approach introduces shallow defect states, modifies the electronic structure, and improves the electrical conductivity of TiO2. The doped films were integrated into metal-insulator-metal (MIM) diodes, where significant reductions in resistance and improvements in responsivity are achieved, showing their potential for high-frequency applications.
This work provides new insights into laser-based and deposition-based defect engineering strategies for TiO2, highlighting their potential to improve solar-driven processes and electronic device performance
Enhancing Social Learning in Humanoid Robots Taught by Non-Expert Human Teachers
No full textTools that assist with daily tasks are valuable. For example, with the aging population in Canada and worldwide, there is a growing demand for ways to help older adults perform daily activities independently. Socially intelligent robots can promote independence by assisting with routine tasks. While advanced robots may be capable of performing various specialized operations, it is not feasible for their designers to program them in advance to effectively carry out multi-step, complex tasks requiring high-level planning and coordination, `out of the box' in new environments and for users with diverse preferences. To successfully integrate into domestic environments, robots must learn new task knowledge from human users. Many of our own skills as human beings have been acquired through social learning, i.e., learning via observation of or interaction with others, throughout our lifetime. Social learning for robots enables the transfer of skills without the need for explicit programming, allowing users to teach robots via natural, intuitive, and interactive methods.
This thesis targets three key challenges in the social learning of robots: enabling non-expert humans to teach robots without external help, enabling robots to learn and perform multi-step tasks, and enabling robots to identify the most suitable teachers in their social learning.
The first phase of my research examines whether or not participants with no prior experience teaching a robot could become more proficient robot teachers through repeated human-robot teaching interactions. An experiment was conducted with twenty-eight participants who were asked to kinesthetically teach a Pepper robot various cleaning tasks across five repeated sessions. Analysis of the data revealed a diversity in non-experts' human-robot teaching styles in repeated interaction. Most participants significantly improved both the success rate and speed of their kinesthetic demonstrations after multiple rounds of teaching the robot.
The second phase introduces a novel, biologically inspired imitation approach enabling robots to understand and perform complex tasks using high-level programs that incorporate sequential regularities between sub-goals that a robot can recognize and achieve. To learn a new task, the system processes demonstrations to identify multiple possible arrangements of sub-goals that achieve the overall task goal. For task execution, the robot determines the optimal sequence of actions by evaluating the available sequences based on user-defined criteria, through mental simulation of the real task. This learning architecture was implemented on an iCub humanoid robot, and its effectiveness was evaluated across multiple scenarios.
In the third phase, I propose an attribute for identifying the most suitable teachers for a robot: human teachers’ awareness of and attention to the robot’s limitations and capabilities. I investigate the impact of this attribute on robot learning outcomes in an experiment with seventy-two participants who taught three physical tasks to an iCub humanoid robot. Teachers’ awareness of the robot’s visual limitations and learning capabilities was manipulated by offering the robot’s visual perspective and by placing participants in the robot’s position when labelling actions in demonstrations. Participants who could see the robot’s vision output paid increased attention to ensuring that task objects in their demonstrations were visible to the robot. This emphasis on attention resulted in improved learning outcomes for the robot, as indicated by lower perception error rates and higher learning scores. I also propose a metric for robots to estimate the potential for receiving high-quality demonstrations from particular human teachers.
These findings demonstrate the feasibility of non-experts adapting to robot teaching through repeated exposure to human-robot teaching tasks, without formal training or external intervention, and also contribute to understanding factors in human teachers that lead to better learning outcomes for robots. Furthermore, I propose a robot learning approach that accommodates variations in human teaching styles, enabling robots to perform tasks with greater flexibility and efficiency. Together, these contributions advance the development of multifunctional and adaptable robots capable of operating autonomously and safely in human environments to assist individuals in various daily activities
Fabrication of High Aspect Ratio Atomic Force Microscope Tips Using Silicon and Diamond
No full textAtomic Force Microscope (AFM) is in a family of microscopy called Scanning Probe Microscope (SPM) which also includes Scanning Tunneling Microscope (STM). AFM has become a standard characterization tool for surface topography measurements in most microfabrication. However, in order to obtain accurate representation of high aspect ratio structures such as trenches, the AFM tip must be capable of reaching the bottom of such a trench. This requires the AFM tip to have a high aspect ratio as well as sharp apex. Additionally, for application which require contact with the surface the AFM tip must have very high wear resistance, which is typically obtained using diamond AFM tips . In this work we have designed several methods to obtain high aspect ratio diamond and silicon AFM tips with sharp apex.
Chapter 3 and 4 discuss two methods to obtain high aspect ratio diamond tip with silicon base. We have used ultra-nanocrystalline diamond grown on silicon wafer and have fabricated diamond AFM tips using Reactive Ion Etching. In the first method we use O2/CHF3 gas to etch patterned diamond with shrinking mask. Next, we use pseudo-Bosch etching to fabricate high aspect ratio silicon pillars under the diamond tip. With this method we are able to obtain aspect ratio close to 10 and tip apex of less than 25 nm. In the second method we are able to obtain even smaller apex by fabricating the silicon base first before the fabrication of diamond apex using O2/C4F8 plasma. This method allows for aspect ratio of 7.5 and apex diameter close to 10 nm.
Chapter 5 and 6 focus on the fabrication of silicon AFM tips. In chapter 5 we use (111) oriented silicon wafers, which are first dry etched to form pillars. Next, the sample is etched in alkaline solution using either TMAH or surfactant added TMAH. We have tested two non-ionic surfactants and have obtained aspect ratio close to 14 and tip apex of less than 10 nm without oxidation sharpening when 1000 ppm Triton X-405 is added to 25 wt% TMAH. We have also studied the effect of surfactant composition and concentration on silicon etching.
In chapter 6, we have developed two method to fabricate tetrahedral AFM tips using a combination of dry and wet anisotropic etching. The first method uses SOI wafer coated with LPCVD nitride. After patterning the silicon is dry etched to form trenches which are then oxidized. Next, the LPCVD nitride is removed to exposed un-oxidized silicon that is anisotropically etched in 25 wt% TMAH to form AFM tips with one side perpendicular to the edge of the cantilever surface. In the second method we remove the need of LPCVD nitride which may not be readily available. In this method, after fabrication of trenches, the entire silicon surface is oxidized along with trench sidewalls. However, before anisotropic wet etching, the surface oxide is selectively removed using angled ion milling. Careful recipe optimization is done in order to fully remove the surface oxide while the oxide on the trench sidewalls remain unharmed. After wet anisotropic etching, this method allows for fabrication of silicon tips with apex as low as 60 nm before oxidation sharpening
Combining High-Level-Synthesis and Register-Transfer Level Design for Programmable Hardware
No full textAs network speeds continue to grow to hundreds of Gbps and beyond, offloading transport-layer functionality to programmable Network Interface Cards (NICs) has gained traction for improving performance and enabling higher-level offloads. FPGAs on NICs offer low latency and high throughput but are notoriously difficult to program. To reduce developer effort for hardware transport, prior works propose hardware architectures with reusable fixed-function modules for common transport data structures and operations, and programmable modules for protocol-specific operations. However, they either still require intricate Verilog programming for their programmable modules or are tied to specific protocols or pipeline abstractions.
In this work, we explore the design of a programmable hardware architecture for transport, called HTraP, that (1) offers a simple, intuitive programming interface without requiring detailed understanding of the rest of the architecture for effective programming, and (2) supports a broad range of transport protocols with varying levels of complexity. HTrap has one main programmable module that can be programmed to capture the core protocol logic in simple C code that is amenable to automated, efficient hardware generation with HLS. The generated hardware can then plug into the rest of HTraP which implements complex transport operations through a protocol-agnostic interface
Are We on the Same Track? Using Lived Experiences to Understand the Complex Impacts of New Transportation Investment
No full textNorth American planning is now emphasizing more integrated approaches that centre new transportation infrastructure in larger urban redevelopment approaches, such as transit-oriented development. Research demonstrates numerous measurable land-use and economic benefits associated with planning that prioritizes density, vibrancy, and accessibility through public transit and active transit infrastructure. But planners and policymakers lack insight into the mobility benefits and potential consequences for the original community and particularly, deeply marginalized residents. Importantly, these planning approaches are using transportation infrastructure as much more than a tool for improved transportation, and thus the implications also extend beyond travel.
As a response, this dissertation challenges the inherent benefit of large-scale transportation investment by providing a series of counternarratives to current understanding of the impact of new transportation on a community and its residents. This is done through lived experience data, which this dissertation argues is necessary for acquiring a comprehensive understanding of how these planning projects bring about change. Currently, implications of new transportation on individual mobility and on community transformation are underexplored. Using a mobility justice lens, this research interrogates unique dimensions of the impact and divide for residents and stakeholders navigating new active transportation, such as bike lanes, and new transit, such as light rail.
Using the Region of Waterloo as a study area, this dissertation provides three unique case studies that centre lived experiences and perspectives from different stakeholders, with a particular emphasis on deeply marginalized residents. Three sets of semi-structured interviews were conducted: the first with 22 key stakeholders (planners, politicians, etc.) who were involved in the development of the region’s ION light rail transit (LRT) project and have in-depth knowledge about its planning and political economy. Second, 22 realtors and developers working in the region were interviewed, as they have a strong sense of the regional market and associated trends. Finally, 20 deeply marginalized Region of Waterloo residents were interviewed, as they have experienced this change firsthand and are the most impacted by it. Waterloo Region presents as a particularly salient case study, as it is the smallest North American region to operate an LRT. Further, the arrival of the LRT came with a fundamental reorganization of the previously strong bus transit network. This means all regional ridership has been impacted by the LRT, whether residents use the LRT or not.
Findings are presented through three empirical manuscripts. The first manuscript demonstrates the divide between perceived project goals and ridership experience from community members who are navigating the integration of a new transit system. These findings highlight conflict between expert opinions and community needs, arguing that while appearances have improved, the ridership experience has actually declined for some. The second manuscript finds that opinions of transportation can be influenced by positionality, both physically and professionally, as suburban residents and realtors struggle to see themselves, or their needs, in new active and public transit. The final manuscript provides a holistic vantage of the interconnectedness of transportation and other social, political, and economic constraints. Through interviews with deeply marginalized residents, this manuscript finds that transportation investment has cascading impacts that disproportionately affect equity-deserving groups in visible and invisible ways.
Collectively, these findings demonstrate the inherent bias that individuals and groups bring to conversations of transportation. Residents, stakeholders, and experts bring their own lived experiences that can prevent them from fully acknowledging or understanding oppositional opinions from individuals with vastly different experiences than their own. Essentially, this work stresses the importance of acknowledging, incorporating, and collecting diverse experiences and perspectives from as many groups as possible in the planning of new transportation. These perspectives can then be used to inform transportation systems that are beneficial for residents and the community at large. This research is valuable for theory as it contributes to the further theorization of mobility justice in planning research while addressing a growing gap in the way planners consider transportation’s complex impacts. It further provides numerous recommendations for planning practice, including integrating more diverse perspectives into all stages of the planning process, partnering with community organizations to ensure equity-deserving groups have access to the planning process, and reflecting on the role that transportation is meant to play within a community
Partial C*-dynamical systems and the ideal structure of partial reduced crossed products
No full textIn this thesis, we study C*-algebras stemming from partial C*-dynamical systems. We develop equivariant injective envelopes associated to such systems, which allow us to obtain canonical connections to enveloping actions as well as results on the ideal structure of partial crossed products.
We extend the theory of equivariant injective envelopes pioneered by Hamana in the 1980s to partial C*-dynamical systems. To do so, we introduce the category of generalized unital partial actions by allowing for partial *-automorphisms acting on families of special hereditary subalgebras. Utilizing properties of injective envelopes and the notion of an injective unitization of partial C*-dynamical systems, we argue that it suffices to consider unital objects in our category. This also allows us to connect our theory to Abadie’s notion of enveloping actions leading to a canonical relationship of their G-injective envelopes.
Utilizing properties of injective envelopes, we introduce novel non-triviality conditions for partial *-automorphisms inspired by global C*-dynamics. We contrast this notion with existing conditions in the literature. Lastly, we study a non-commutative generalization of stabilizer subgroups for pseudo-Glimm ideals. In particular, we show that for Glimm ideals in the G-injective envelope, these stabilizer subgroups are in fact amenable — a result which is crucial for our main theorems regarding the ideal structure of partial reduced crossed products.
Finally, our main application of the theory of G-injective envelopes is a characterization of the ideal intersection property for partial C*-dynamical systems subject to a cohomological condition as a generalization of the result for global group actions. To state this generalization, we utilize the dynamical conditions introduced previously and generalize the notion of equivariant pseudo-expectations to partial C*-dynamical systems. We also give a sufficient intrinsic condition in terms of non-commutative uniformly recurrent partial subsystems utilizing pseudo-Glimm ideals. As a consequence of our results, we obtain a full characterization of the ideal intersection property for partial actions on commutative C*-algebras in terms of freeness of the partial action on the spectrum of the G-injective envelope
Unfettering the Voices of Palestinian Women: Counterstorytelling Against Dehumanization, Suppression, and Genocide
No full textMy thesis uses the opportunity and its platform to amplify the voices of Palestinian women while Palestine is enduring a holocaust by the settler-colonial regime known as ‘israel.’ I have chosen to read the life writing of four Palestinian women to provide a historical survey that contextualizes Palestine—whose people and voice has long been dehumanized and suppressed within western cultural and political spaces. These women, who include Fadwa Tuqan, Leila Khaled, Bisan Owda and Jenan Matari, participate in an overall objective towards counterstorytelling for the purpose of social justice for Palestine, Palestinians, and Palestinian women. I believe it is necessary to understand the circumstances and context of the Palestinian reality in order to recognize the depth of the propagandic nature of the dominant western narrative and locates the necessity of counterstorytelling which dismantles hegemonic narratives, highlights double standards, and strives for the liberation of Palestine.
In the Introduction I include: my positionality while introducing background information to help situate the reader in discourse of Palestinian feminist liberation, the culture of resistance which has developed historically in Palestine, an introduction of my voices and offer a brief history of Palestinian women’s activism and popular resistance.
In Chapter One I analyze and compare two Palestinian women’s autobiographies, Tuqan’s A Mountainous Journey: An Autobiography and Khaled’s My People Shall Live: Autobiography of a revolutionary by Leila Khaled as told to George Hajjar which are read through a Critical Race Theory (CRT) and feminist lens. Tuqan’s autobiography provides an emotional and poetic description of conservative patriarchy as her foremost oppressor as she lived through the imperial British Mandate, the growing zionist threat/invasion, the Nakba and Naksa. Khaled’s autobiography is written much closer to counterstorytelling as she presents the suppressed history and brutality of imperialism and zionism against Palestinians. She completes her counterstory by using her personal narrative as a central structure from which to tell the collective story of Palestine.
In Chapter Two I first illustrate how Palestine/Palestinians are being silenced through habitual media and social media censorship. After illustrating the pro-‘israel’ bias of western media/institutions/politics I present the voices of Bisan Owda and Jenan Matari as examples of digital counterstorytelling and analyze how they challenge the dominant western narrative. While Owda is literally surviving a genocide she manages to share her own personal stories as well as those in Gaza also trying to survive the holocaust. Matari, a storyteller from the diaspora, uses her platform to illustrate the vile depravity of ‘israeli’ society while simultaneously amplifying the voices of Palestinians in her homeland.
In the conclusion I include the results of a survey on the concept of “auditioning for humanity,” addressing the October 9th “ceasefire,” and the need to remain vigilant by following the lead of Palestinians as they alone must determine when justice has been applied in a Free Palestine
Micro-Calorimeter X-Ray Spectroscopy of Galaxy Clusters using the XRISM X-Ray Observatory
No full textGalaxy clusters are some of the most massive objects in the universe, yet the evolution of these objects, particularly with regards to the heating and cooling of the intracluster medium, still has many unknowns. With the launch of the new X-ray imaging and spectroscopy mission, XRISM, galaxy clusters can now be studied with higher precision. This data can reveal a plethora of new information about the dynamics of the atmospheres of these clusters, which can be used to develop a better understanding of the evolution of galaxy clusters.
In this thesis, I present analysis of X-ray spectroscopic data of the Perseus, Hydra A, and Cygnus A clusters obtained with XRISM Resolve. We apply spectral modeling techniques to the data to derive gas temperature, metal abundance, velocity dispersion, and bulk velocity to develop a further understanding of the dynamics of the intracluster medium in these galaxy clusters.
I present spectral analysis of the five XRISM Resolve pointings of the Perseus cluster, binned into a radial profile. We measure radial profiles of temperature, metal abundances, velocity dispersion, and bulk velocities up to kpc from the cluster center with single temperature models. While the temperature and abundance profiles are consistent with typical cool core clusters, the velocity dispersions suggest a relatively quiescent state for the intracluster medium, with only up to km s dispersion in the central kpc. We interpret this velocity dispersion to be due to turbulence. The dispersion profile suggests that the jets and bubbles may be driving turbulence in the core, but also that the core may be under-heated. We find evidence for a second temperature component in the inner kpc, that is cooler ( keV) and has a significantly higher velocity dispersion of km s. We interpret the cooler component to be sloshing gas from a merger or gas being churned by the jets and bubbles.
I present spectral analysis of the full-FOV XRISM Resolve data of the Hydra A cluster, measuring temperature, velocity dispersion, and bulk velocity with a single temperature model. Despite Hydra A's high jet power, we find a remarkably low velocity dispersion of km s, and a small velocity offset of km s between the gas and the central galaxy. We interpret this velocity dispersion to be due to turbulence, which may suggest that the relationship between the jet power and the velocity structure of the intracluster medium is less significant than expected. However, further analysis of the outer regions of the cluster is needed to fully understand the dynamics of the gas in Hydra A.
Finally, I present spectral analysis of the full-FOV XRISM Resolve data of the Cygnus A cluster, measuring temperature, metal abundances, velocity dispersion, and bulk velocity with a single temperature model. We measure a relatively higher velocity dispersion of km s with a bulk velocity of km s with respect to the central galaxy. These velocities likely reflect a combination of both turbulence in the gas and motion of the cocoon shock. We find some evidence for a second temperature component, that is cooler ( keV) and broader ( km s), with a bulk velocity of km s. The second component may be necessary for fitting asymmetric features in the prominent emission lines of the spectrum. However, the large uncertainties of the model fit along with other uncertainties suggest that this component may not be significant