title: Strategies For Improving Luminescence Properties of Glycothermally Synthesized Ce:YAG Nanophosphors

contributor:
Kitai, Adrian
Engineering Physics

subject: Ce:YAG Nanophosphors

abstract: Ce:YAG phosphors used in white LED backlit LCD displays suffer from two major issues: the phosphor powder is too large for next generation microLED display technology, and there is a lack of red in its emission spectrum. To address this, Ce:YAG based nanophosphors were synthesized using the glycothermal method. They were found to contain ~10x higher concentrations of octahedrally coordinated Al atoms compared to bulk Ce:YAG, confirmed by NMR spectroscopy. Photoluminescence and photostability were found to be enhanced with the growth of an intrinsic shell layer, made using a two-step growth process. Shell thickness was controlled by the addition of intrinsic precursor material as a ratio of the initial precursor concentration, denoted as the shell-to-seed ratio (SSR). The absorption spectra of Ce:YAG could be tuned up to 40 nm with the addition of Mg-Si pairs. An enhancement of Ce:YAG nanophosphor luminescence was seen when the reaction temperature was slightly elevated, attributed to increased precursor reactivity due to the higher kinetics of precursor ligand cleavage. The introduction of Mn2+ as a co-dopant was found to provide a red component to the Ce:YAG emission spectrum. XRD structural analysis indicated that Mn2+ should preferentially occupy the Y site, though the 594 nm emission characteristic of 4T1(4G)  6A1(6S) transitions in octahedral co-ordination was observed. Mn2+ atoms which occupy Al octahedral sites are well supported for luminescence due to the high density of octahedral sites present after gycothermal synthesis. Mn2+ emission was enhanced using Si4+ as a charge compensator, and further enhanced with the addition of an intrinsic shell layer. Non-radiative energy transfer of Ce to Mn2+ was observed, indicating that the parity allowed 5d  4f transition of Ce acts as an effective sensitizer for Mn2 luminescence. Glycothermal synthesis was found to preserve the luminescent trivalent and divalent oxidation states of Ce and Mn, respectively.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: Advanced electrode materials and fabrication of supercapacitors

contributor:
Zhitomirsky, Igor
Materials Science and Engineering

subject: supercapacitor electrode MXene Fe3O4

abstract:
Supercapacitors (SCs) have generated significant interest due to their advantages including lightweight, rapid charge-discharge, good rate capability and high cyclic stability. Electrodes are one of the most important factors influencing the performance of SCs. MXene is a promising candidate for supercapacitor electrodes, which is a relatively new material with formula Mn+1XnTx, where M is a transitional metal, X stands for C or N, and Tx is surface terminations. Due to its multi-layered structure, high surface area and rich redox chemistry, good electrochemical performance can be expected. To further enhance the conductivity of the MXene electrodes, multi-walled carbon nanotubes (MCNT) were applied as the conducting additive. The as-fabricated composite electrodes showed reduced resistance and enhanced electrochemical performance. Advanced co-dispersants such as cationic celestine blue (CCB) and anionic catechol violet (ACV) were employed to improve the dispersion of components.  CCB and ACV can adsorb strongly on the MXene and MCNT surface to form a homogenous suspension and thus improve the mixing between them. Another advanced dispersant 3,4,5-trihydroxybenzamide (THB) also showed adsorption on both MXene and MCNT particles, favored their dispersive mixing and improved electrochemical performance.
Iron oxides are promising materials for negative electrodes for supercapacitors. The attempt to combine highly capacitive Fe3O4 with MXene-MCNT composites proved the synergistic effect of individual components. Investigation of Zn-doped FeOOH as high active mass loading anode with MCNT as conducting additive allowed for enhanced performance. Zn-Fe double hydroxide materials are promising for the fabrication of advanced supercapacitor electrodes. A safe and neutral Na2SO4 electrolyte was was beneficial for the development of asymmetric devices with enlarged voltage window. For cathodes working in an overlapping window with Zn-FeOOH anode, polypyrrole coated carbon nanotube electrode was fabricated with a comparable capacitance. The advanced dopant eriochrome cyanine R (ECR) allowed for the uniform thickness of PPy coating on MCNT and enhanced charge transfer between PPy and MCNT was achieved. Enhanced capacitive properties of cathodes and anodes at high active mass loading working in complimentary voltage windows allowed for fabrication of high-performance supercapacitor, which was a promising device for practical applications.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)

abstract:
To reduce the consumption of fossil fuel and meet the surging demand of electric energy, intensive attention has been drawn to new energy storage device, such as capacitors, batteries and supercapacitors. Owing to their higher energy density compared with conventional capacitors and higher power density compared with batteries, supercapacitors are attracting tremendous research interest. The advantages of supercapacitors are fast charge-discharge rate, high power and energy density and excellent cyclic stability.
The objective of this work was to fabricate high-performance supercapacitor devices based on the development of advanced electrode materials. MXene and Fe-based composite materials were synthesized by conceptually new colloidal approach and some efficient dispersants were developed during the process. The enlarged voltage window and superior performance were recorded for asymmetric supercapacitors. The results presented in this work showed much more promising performance compared with that reported in the literature and paved the way for future research.


title: ENTERIC PARASITE INFECTION-INDUCED ALTERATION OF THE GUT MICROBIOTA REGULATES INTESTINAL GOBLET CELL BIOLOGY AND MUCIN PRODUCTION VIA TLR2 SIGNALLING

contributor:
Khan, Waliul
Medical Sciences

subject: Host-parasite-gut microbiota interactions

subject: T. muris infection

subject: Gut microbiota

subject: TLR2

abstract:
In the gastrointestinal (GI) tract, goblet cells are the major source of mucins, the
main structural components of the mucus layer, which functions as the front line of innate
defense. The GI tract contains trillions of commensal microbes, and these microbes can
manipulate mucin production by activating different signalling cascades initiated by
pattern recognition receptors (PRRs), including bacterial sensing Toll-like receptors
(TLRs). In addition, sterile α motif pointed domain-containing ETS transcription factor
(SPDEF) is a transcription factor that modulates goblet cell differentiation and positively
regulates mucin production. During helminth infections, due to the co-existence of
parasites and microbiota in close proximity of goblet cells in the gut, it is likely that
helminth-microbiota interactions play an important role in mucin production. Indeed,
goblet cell hyperplasia and increased mucin production are observed in many enteric
helminth infections, including Trichuris muris, and these processes play key roles in host
infection clearance. However, it should be noted that the role of microbiota within this
axis is not yet understood. Here, we hypothesize T. muris-induced altered microbiota
modulates goblet cell differentiation and mucin production via SPDEF-mediated
transcriptional regulation and TLR2 signalling.
C57BL/6 mice were gavaged with ~300 T. muris eggs. Mice were sacrificed 36
days post-infection. Microbiota from these T. muris-infected and non-infected mice were
transferred into two groups of germ-free (GF) mice. Microbiota analysis revealed that
treatments in both experiments (infection with T. muris and microbiota transfer from T.
muris-infected mice into GF mice) significantly account for the among-sample variations
in the composition of the gut microbiota between groups (p <= 0.001).
In GF mice, transfer of T. muris-infected microbiota significantly increased goblet
cell numbers and TLR2 expression as well as upregulated Muc2 expression compared to
MSc Thesis –Yousefi Y; McMaster University – Medical Sciences
v
GF mice with non-infected microbiota. Antibiotic-treated (ABX-treated) TLR2 knockout
(KO) mice after receiving microbiota from T. muris-infected mice showed significantly
decreased expression of Muc2 and Muc5ac compared to ABX-treated wild-type (WT)
mice receiving the same microbiota. To investigate whether SPDEF is a driving factor
for Muc2 production in response to T. muris microbiota stimulation, we next transferred
T. muris-infected microbiota into antibiotic-treated SPDEF KO and WT mice. We
observed a slight, though not significant, the influence of SPDEF on the stimulation of
mucin production by T. muris microbiota. These findings reveal important interactions
among parasites, resident microbiota, and host in relation to goblet cell response in the
gut. In addition, this study provides new information on TLR2-based innate signalling in
the regulation of goblet cell biology and mucin productio

abstract: Thesis

abstract: Master of Science (MSc)


title: On The Habitability Of An Impacted Young Earth: The effects of a post-impact, reducing atmosphere on Hadean Earth’s habitability

contributor:
Pudritz, Ralph
Physics and Astronomy

abstract: Atmospheres have an important role in determining whether a planet can both form and sustain life. In the case of early Earth under the faint young Sun, a heavy hydrogen- dominant atmosphere would have allowed for a temperate surface and the production of biomolecules necessary for life to form, such as HCN and H2CO. This heavy atmosphere is thought to have been delivered to Earth by a large impact or series of large impacts on Earth’s surface. In this work, we use a 1D radiative-convective equilibrium modelling code to obtain the thermal profiles for various post-impact atmospheres outlined by Zahnle et al. (2020). Our current results suggest that, in the work of Zahnle et al. (2020), early post-impact HCN yields were computed for atmospheres that are too hot for the necessary liquid surface water.

abstract: Thesis

abstract: Master of Science (MSc)


title: Simulations of Non-Enzymatic Template Directed RNA Replication

contributor:
Higgs, Paul
Biology

subject:
RNA world
non-enzymatic
RNA replication
simulations

abstract: The universal traits of cellular expression and replication in modern life point to the existence of an ancient RNA world. Leading up to the origin of life, this stage of evolution utilized RNA as the genetic material, and as a catalyst in the form of ribozymes. Although it is expected that a polymerase ribozyme was required for the efficient replication of RNA, it is also likely that the earliest form of replication took place under non-enzymatic conditions. There are several problems with the current scenarios depicting non-enzymatic RNA replication, thus we aim to examine them in more detail using computational models. We first consider the relationship between the thermodynamics of RNA base pairing and non-enzymatic nucleotide addition in an attempt to model the rate of primer extension. Our predicted rates reveal the model parameters to be too simple to produce reliably accurate results. For now, we should simply use available experimental rate data, until we have access to more data and less unknown parameters. Nevertheless, the model indicates that the primer extension rate does depend on thermodynamics of base pairing, and a more accurate model can be of great use when creating realistic complex models of RNA world scenarios. In chapter 3, we investigate non-enzymatic RNA replication under temperature cycling using computer simulations. When starting with a diverse mixture of sequences, partially matching sequences can reanneal in configurations that allow continued strand growth. This is in contrast to the case of having multiple copies of matching sequences, where reannealing occurs quickly upon cooling. We find that, starting with short oligomers, strands can grow over multiple cycles to produce long sequences over 100 nucleotides in length. The small strand extension per cycle does not produce replicates of any one specific sequence. This relates to the work done in chapter 4, where we look for the presence of a virtual circular genome within our simulations. In a virtual circle, short overlapping RNA sequences will make up a mutually catalytic set. Within the diversity of our simulation, virtual circles are rare, and require a specific level of starting mixture diversity along with no input of new sequences. Continued replication of the diverse sequence mixture and emergence of long strands may eventually lead to the creation of rolling circles and ribozymes.

abstract: Thesis

abstract: Master of Science (MSc)

abstract: The origin of biological life can be traced back by looking at the common themes between modern cellular processes. The role of RNA polymers seems to be of great importance, making us believe that an RNA world existed leading up to life’s origin. During this time, RNA would act as both a genetic material and a catalyst. To examine this theory in more detail, we use computational modeling to recreate and explore the various potential chemistries and conditions on the early Earth. Specifically, we explore the problems that exist for the replication and production of RNA polymers. Our results can be used to guide future theoretical and experimental research of the RNA world.


title: Exploring barriers and facilitators to surgical referrals for neonates with congenital anomalies

title: Improving surgical referrals for neonates in LLMICs

contributor:
Cameron, Brian
Global Health

subject:
congenital anomaly
neonate(s)
surgery
referral
low and low-middle income countries
global health

abstract: Systematic Review

abstract: Advancements in medicine have resulted in decreased neonatal mortality and morbidity associated with congenital anomalies (CA). Unfortunately, the advantages of these developments have been confined to high-income countries (HICs), demonstrated by the comparatively high incidence of congenital anomalies in low and low-middle-income countries (LLMICs). Evidence suggests that neonates in LLMICs encounter considerably more barriers to care than those in HICs due to a malfunctioning referral system and poorly implemented health policies that hinder the timely provision of care. As many CA are now accepted as surgically treatable, the purpose of this study was to understand what inhibits the success of a neonate from obtaining surgery in LLMICs and how that could be improved. Seven databases were searched in this systematic review to identify articles on neonates with surgically treatable CA. A total of 370 studies were identified for screening; 16 were included in the final analysis. Studies were screened and selected individually by two researchers based on the research question, and all disagreements were resolved jointly. Studies were reviewed for factors affecting the delivery of surgical treatment and were then coded as a barrier or a facilitator. Barriers to care were identified in every study, and suggested facilitators were offered by the authors, but these facilitators were not tested in the studies. This study contributes to the literature by providing additional detail on what is known about the surgical referral system in LLMICs. The study findings will inform policymakers and local governments of the realities faced by neonates and their caregivers while navigating through the surgical referral system and establish the need for alternate policy implementation strategies.

abstract: Thesis

abstract: Master of Science (MSc)

abstract: Congenital anomalies (CA) have been identified as a significant contributor to the global burden of disease, accounting for 25.3-38.8 million disability-adjusted life-years worldwide.  Many CA have been classified as surgically treatable however, approximately 295,000 neonates die annually due to these conditions. As 94% of CA occur in low- and low- middle-income countries (LLMICs), this study aims to elucidate any barriers and facilitators that may influence accessing surgical treatment. A systematic review has been selected to synthesize the literature regarding what is known about accessing surgery for neonates with CA in LLMICs.


title: The Characterization of CD8+ T Cells as a Potential Mechanism of Disease in Immune Thrombocytopenia

contributor:
Nazy, Ishac
Arnold, Donald
Kelton, John
Medical Sciences

subject:
immune thrombocytopenia
platelets
cd8+ t cells
autoimmunity

abstract: Immune thrombocytopenia (ITP) is an autoimmune bleeding disorder characterized by a low platelet count (less than 100 x 10^9 platelets/L) and an increased risk of bleeding. ITP is difficult to diagnose and manage due to the deficiencies in our understanding of the pathophysiological mechanisms leading to thrombocytopenia. Anti-platelet autoantibodies are believed to be the primary mechanism of thrombocytopenia in ITP. In this thesis, I demonstrate that autoantibodies can only be detected in half of all ITP patients; therefore, other mechanisms should be investigated. CD8+ T cells have been implicated as a mechanism of disease in ITP, but platelet-specific CD8+ T cells have yet to be identified. I have characterized CD8+ T cells in ITP patients and found that platelet-specific CD8+ T cells can be detected in ITP patients. These platelet-specific CD8+ T cells can also be detected in healthy individuals, so they are not specific to ITP. However, regulatory defects were observed in ITP patients and CD8+ T cell activity was elevated in ITP patients relative to healthy individuals and thrombocytopenic non-ITP patients. Investigating whether platelet-specific CD8+ T cells can actively participate in platelet destruction and underproduction will be an essential step towards better understanding the role of CD8+ T cells as a disease mechanism in ITP, which will lead to improvements in the management of ITP.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)

abstract: Platelets are small blood cells that are involved in minimizing blood loss at the site of a wound by forming a plug. In a disease called immune thrombocytopenia (ITP), patients have a low platelet count, which can result in bleeding. The bleeding symptoms of ITP decrease the quality of life for ITP patients and can be life-threatening in rare cases. It is believed that ITP is caused by proteins produced by the immune system called antibodies. I found that the antibodies that cause ITP can only be detected in half of all ITP patients. Therefore, there are probably additional causes of ITP. It is suspected that CD8+ T cells might cause ITP in some patients. CD8+ T cells are part of the immune system and they typically destroy other cells that are cancerous or infected by viruses. CD8+ T cells might also destroy healthy cells, like platelets. My goal was to characterize CD8+ T cells in order to determine their role in ITP. I found that CD8+ T cells from ITP patients can target platelets, and that healthy people have these CD8+ T cells as well. In regard to CD8+ T cells that target platelets, the difference between ITP patients and healthy people appears to be related to immune system regulation and CD8+ T cell activity. In the future, we should focus on understanding how platelet-specific CD8+ T cells can cause a low platelet count in order to improve the clinical management of ITP.


title: DYNAMICS OF ENTANGLED PAIR OF SPIN-1/2 PARTICLES IN THE PRESENCE OF RANDOM MAGNETIC FIELDS

creator: PYDIMARRI, VENKATA SATYA SURYA PHANEENDRA

contributor:
FIELD, TIMOTHY R.
Computational Engineering and Science

subject:
ENTANGLEMENT
QUANTUM COMMUNICATION PROTOCOLS
SPIN
NMR
RANDOM MAGNETIC FIELDS
STOCHASTIC DIFFERENTIAL EQUATIONS
PAIR OF SPINS
RELAXATION

abstract: Quantum communication protocols require maximally entangled state of pair of qubits (spin-1/2 states in this context) to be shared between sender and the receiver. The entangled qubits lose entanglement because of random magnetic field disturbances. The dynamics in the form of joint density matrix of random pure entangled state provide the steady (joint) state and the associated timescales (time taken by the pair to reach the steady state) providing a scope in future to quantify the effective utilization of quantum communication protocols.

abstract: The dynamics of an identical pair of entangled spin-1/2 particles, both subjected to the identical, independent, correlated random magnetic fields is studied. The dynamics of the pure joint state of the pair is derived using stochastic calculus. In case of identical fields, an ensemble of such pure states are combined using the modified spin joint density  matrix and the joint relaxation time is obtained for the pair of spin-1/2 particles. These dynamics can be interpreted as special kind of correlations involving the spatial components of the Bloch polarization vectors of the constituent entangled spin-1/2 particles. In case of independent random magnetic fields, the dynamics are obtained by considering a pure joint state of entangled spin-1/2 particles. The disentanglement time defined as the time taken for the particles to become disentangled, is obtained. In case of correlated random magnetic fields, the dynamics of a maximally entangled pair of spin-1/2 particles are derived in terms of the joint density matrix of the entangled pair from which the steady state density matrix and the associated timescale for it to be reached are obtained. The asymptotic density matrix in this case represents a state of (partial) disentanglement. In other words, there is a persistent entanglement in case of correlated field disturbances.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)

abstract: Maximally entangled pair of quantum bits (in the form of spin-1/2 states) lose entanglement either partially or completely depending upon the nature of random magnetic field disturbances around them (correlated/independent/identical fields). The dynamics of entangled states (in the form of density matrix of a random pure state) in the presence of random magnetic fields are obtained using the ideas of stochastic calculus to understand the steady state of the pair and the associated timescales to be reached.


title: Application of Data-Driven Modeling Techniques to Wastewater Treatment Processes

contributor:
Mhaskar, Prashant
Chemical Engineering

subject: wastewater treatment

subject: secondary clarifier

subject: clarifier failure

subject: subspace identification

subject: state-space

subject: partial least squares discriminant analysis (PLS-DA)

subject: classification

abstract:
Wastewater treatment plants (WWTPs) face increasingly stringent effluent quality constraints as a result of rising environmental concerns. Efficient operation of the secondary clarification process is essential to be able to meet these strict regulations. Treatment plants can benefit greatly from making better use of available resources through improved automation and implementing more process systems engineering techniques to enhance plant performance. As such, the primary objective of this research is to utilize data-driven modeling techniques to obtain a representative model of a simplified secondary clarification unit in a WWTP.

First, a deterministic subspace-based identification approach is used to estimate a linear state-space model of the secondary clarification process that can accurately predict process dynamics, with the ultimate objective of motivating the use of the subspace model in a model predictive control (MPC) framework for closed-loop control of the clarification process. To this end, a low-order subspace model which relates a set of typical measured outputs from a secondary clarifier to a set of typical inputs is identified and subsequently validated on simulated data obtained via Hydromantis's WWTP simulation software, GPS-X. Results illustrate that the subspace model is able to approximate the nonlinear process behaviour well and can effectively predict the dynamic output trajectory for various candidate input profiles, thus establishing its candidacy for use in MPC.

Subsequently, a framework for forecasting the occurrence of sludge bulking--and consequently clarification failure--based on an engineered interaction variable that aims to capture the relationship between key input variables is proposed. Partial least squares discriminant analysis (PLS-DA) is used to discriminate between process conditions associated with clarification failure versus effective clarification. Preliminary results show that PLS-DA models augmented with the interaction variable demonstrate improved predictions and higher classification accuracy.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: Resilience Quantification Approaches of Low Impact Development (LID) Practices Using Analytical and Continuous Simulation Models

title: Resilience Quantification of Low Impact Development (LID) Practices

contributor:
Hassini, Sonia
Civil Engineering

subject:
Stormwater Management
Low Impact Development
Bibliometric Analysis
Research Cluster
Resilience
Reliability
Robustness
Rapidity
Serviceability

abstract: Implementing optimal Low Impact Development (LID) practices has grown in popularity as a means of mitigating the adverse effects of urbanization and climate change. As such incorporating aspects of resilience for optimal LID design has become paramount. This study focuses on identifying the current LID optimization strategies and associated research gaps as well as assessing whether a quantitative approach to measure LID resilience exists. To do so, a systematic and bibliometric literature review on LIDs optimization and resilience is first conducted, based on which resilience, climate change, and uncertainty are recognised as hotspot keywords. The review also showed that no LID resilience quantification technique was available. Based on the latter outcome and to facilitate LID’s optimal design in future, this research proposes a new resilience quantification approach of LID by developing set of equations using Analytical Probabilistic Approach (APA) and continuous simulation approach using SWMM. The equations consider LID’s functionality and assess resilience using three indices: robustness, rapidity and serviceability. A new overall resilience index (the product of robustness and serviceability) and reliability index (the product of volumetric, occurrence, and temporal reliability) are proposed using different area ratios between contributing catchment and LID area to assure a resilient and safe LID system. LID costing tool of the Sustainable Technologies Evaluation Program (STEP) is subsequently utilized to estimate the capital cost of LID. Finally, a user-oriented design guideline is proposed for a cost-effective, resilient, and reliable LID system. Although this study adopts bioretention (BR) as a demonstration of the approach utility, the developed approach is applicable to any form of LID practices.

abstract: Thesis

abstract: Master of Applied Science (MASc)

abstract: There is a critical need to develop and implement optimal low-impact development (LID) practices in the field of stormwater management to mitigate the adverse effects of urbanization and climate change. This thesis is focused on developing quantitative resilient measurement approach of LID designs. A comprehensive literature review is first carried out, focusing on identifying various optimization methodologies, relevant gaps, and resilience assessment techniques. Subsequently, a novel resilience evaluation approach is developed, using bioretention (BR). By constructing a new reliability index, the entire BR system's reliability can also be assessed. Finally, a cost-effective, resilient and reliable design guideline for BR system is proposed. Although bioretention (BR) is used as an example in this study, the developed approach opens the gate to quantify the resilience of all types of LID practices.


title: VULNERABILITY ASSESSMENT AND RESILIENCE ENHANCEMENT OF CRITICAL INFRASTRUCTURE NETWORKS

contributor:
Tait, Michael
El-Dakhakhni, Wael
Civil Engineering

subject:
Vulnerability Analysis
Complex Network Theory
Robustness
Centrality Measures
Dynamic Cascade Failure
Power Infrastructure Networks

abstract:
Modern societies are fully dependent on critical infrastructures networks to support the economy, security, and prosperity. Energy infrastructure network is of paramount importance to our societies. As a pillar of the economy, it is necessary that energy infrastructure networks continue to operate safely and be resilient to provide reliable power to other critical infrastructure networks. Nonetheless, frequent large-scale blackouts in recent years have highlighted the vulnerability in the power grids, where disruptions can trigger cascading failures causing a catastrophic regional-level blackout. Such catastrophic blackouts call for a systemic risk assessment approach whereby the entire network/system is assessed against such failures considering the dynamic power flow within. However, the lack of detailed data combining both topological and functional information, and the computational resources typically required for large-scale modelling, considering also operational corrective actions, have impeded large-scale resilience studies.
 In this respect, the research in the present dissertation focuses on investigating, analyzing, and evaluating the vulnerability of power grid infrastructure networks in an effort to enhance their resilience. Through a Complex Network Theory (CNT) lens, the power grid robustness has been evaluated against random and targeted attacks through evaluating a family of centrality measures. The results shows that CNT models provide a quick and potential indication to identify key network components, which support regulators and operators in making informed decisions to maintain and upgrade the network, constrained by the tolerable risk and allocated financial resources.
Furthermore, a dynamic Cascade Failure Model (CFM) has been employed to develop a Physical Flow-Based Model (PFBM). The CFM considers the operational corrective actions in case of failure to rebalance the supply and demand (i.e., dispatch and load shedding). The CFM was subsequently utilized to construct a grid vulnerability map function of the Link Vulnerability Index (LVI), which can be used to rank the line maintenance priority.  In addition, a Node Importance Index (NII) has been developed for power substations ranking according to the resulting cascade failure size. The results from CNT and CFM approaches were compared to address the impact of considering the physical behavior of the power grid. The comparison results indicate that relying solely on CNT topology-based model could result in erroneous conclusions pertaining to the grid behavior. Moving forward, a systemic risk mitigation strategy based on the Intentional Controlled Islanding (ICI) approach has been introduced to suppress the failure propagation. The proposed mitigation strategy integrated the operation- with structure-guided strategies has shown excellent capabilities in terms of enhancing the network robustness and minimizing the possibility of catastrophic large-scale blackouts.  This research demonstrates the model application on a real large-scale network with data ranging from low to high voltage. In the future, the CFM model can be integrated with other critical infrastructure network systems to establish a network-of-networks interaction model for assessing the systemic risk throughout and between multiple network layers. Understanding the interdependence between different networks will provide stakeholders with insight on enhancing resilience and support policymakers in making informed decisions pertaining to the tolerable systemic risk level to take reliable actions under abnormal conditions.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: Diarrhea during critical illness

contributor:
Cook, Deborah
Health Research Methodology

subject:
Diarrhea
Critical Illness
Intensive Care Unit
Epidemiology
Mortality
C. Difficle

abstract:
Diarrhea is common during critical illness; however, the etiology, definitions, incidence and risk factors for diarrhea and its impact on patient important outcomes require further investigation.  There are many possible etiologies of diarrhea, including iatrogenic causes such as laxative medications, often administered as part of bowel protocols, as well as Clostriodiodes difficile associated diarrhea (CDAD).
This thesis includes 6 chapters that address the knowledge gaps in the literature regarding the epidemiology of diarrhea in the intensive care unit (ICU), the impact of bowel protocols on diarrhea, and CDAD in critically ill adults.
Chapter 1 provides an introduction to gaps in the literature that are addressed by the studies included in this thesis.
Chapter 2 outlines the methodology used to inform the protocol for the Diarrhea, Incidence, Consequences and Epidemiology in the Intensive Care Unit (DICE-ICU) Study.
Chapter 3 reports on the findings of DICE-ICU including the incidence, risk factors, definitions, and outcomes of patients who develop diarrhea in the ICU.
Chapter 4 provides a content analysis of bowel protocols used in multiple ICUs.
Chapter 5 summarizes a nested cohort study addressing the incidence, prevalence, timing, treatments, and outcomes of CDAD in critically ill patients enrolled in the PROSPECT Trial.
Chapter 6 summarizes the work and discusses the strengths and limitations, implications and conclusions presented in this PhD thesis.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: COMPARING THE EFFECTS OF NET AND DMPA ON SUSCEPTIBILITY TO HSV-2 INFECTION AND EFFECTS ON IMMUNE CELLS

contributor:
Kaushic, Charu
Gillgrass, Amy
Medicine

subject:
HSV-2
Norethisterone
Depot medroxyprogesterone acetate
Hormonal contraceptives

abstract:
Background:
HSV-2 was estimated to infect 491 million people worldwide, with women disproportionately affected by HSV-2. Understanding factors that influence susceptibility to HSV-2 in women is important in preventing infections. Through various studies, the progestin-based contraceptive DMPA exhibited immunosuppressive effects, and has shown increased susceptibility to HIV and HSV-2. Studies comparing DMPA to other contraceptives like NET suggest that NET may be safer. In vivo NET effects have not been characterized thoroughly to better understand the effect of NET on susceptibility to HSV-2. Therefore, this study aimed to compare the effects of NET and DMPA in mouse models that affect susceptibility to HSV-2.  We hypothesized that NET treated mice will have decreased susceptibility to HSV-2 compared to DMPA but elevated compared to normal mice.
Method of study:
Ovariectomized mice were treated with DMPA (2mg) and NET (2 mg injections, 2.5 mg pellets or 5 mg pellets) for 10 days and intravaginally immunized with HSV-2 TK-, then intravaginally challenged with WT HSV-2 ~4-7 weeks later. Primary intravaginal WT HSV-2 challenges were conducted in ovariectomized and normal mice after 10 days of DMPA and NET treatment. Viral titers, pathology and survival were examined. Mucus production in the vagina was investigated through immunohistology. Effects of hormones on immune cells were explored in the lymph nodes, spleens, and vaginal tracts through flow cytometry.
Results:
Increased mucus was consistently observed in the vaginal tracts of mice after treatment with NET 2.5 mg and 5 mg treated mice, but not with DMPA Therefore, NET treated mice displayed reduced viral shedding and delayed pathology compared to DMPA treated mice. No significant changes occurred in immune cells analyzed post DMPA and NET treatment, although there were trends of increased T cells in progestin treated mice. However, more experiments need to be conducted to confirm observed trends.
Conclusion:
NET treatment in mice results in mucus production in the vaginal tract, a potential mechanism impeding intravaginal HSV-2 infection and could be applied to other STIs. This provides insight into protective effects of NET compared to DMPA allowing women to make informed decisions regarding hormonal contraceptives.

abstract: Thesis

abstract: Master of Science in Medical Sciences (MSMS)


title: Developing and Utilizing a Next-Generation Humanized Mouse Model for Investigating HIV and Tuberculosis

contributor:
Gillgrass, Amy
Medical Sciences

subject:
HIV
TB
Humanized mice
Co-infection

abstract: Infection & Immunity

abstract:
Currently, there are 38 million people living with human immunodeficiency virus (HIV-1)
worldwide and there were 680,000 HIV-related deaths in 2020 alone. The greatest cause of
mortality in people living with HIV (PLHIV) is infection with opportunistic pathogens such
as tuberculosis (TB), which accounts for one third of HIV-related deaths. PLHIV are 20
times more susceptible to TB and co-infection leads to significantly worsened outcomes in
terms of both diseases. Humanized mouse (hu-mouse) models, which possess human
immune cells for HIV to infect, have been useful for HIV research. Our aim is to create hu- mouse models of HIV, TB and co-infection to investigate disease progression, immune
responses, therapeutics, prevention and vaccination. NOD-Rag1null-IL2rgnull (NRG) mice are highly immunocompromised mice that are traditionally used to generate hu-mouse models. We are also developing NRG mice that are transgenic for human HLA-DR4 and HLA-A2 (DRAG-A2) and similar mice have been reported to have improved immune responses. NRG and DRAG-A2 mice were humanized with hematopoietic stem cells obtained from human umbilical cord blood. DRAG-A2 mice had significantly higher engraftment success rates (defined as the percentage of mice with >10% hCD45+) as well as higher overall CD45+ leukocyte, CD4+ T cell, CD19+ B cell and CD14+ monocyte reconstitution in the blood compared to huNRGs. huNRG mice were permissive to infection with JR-CSF or NL4.3-Bal-Env HIV-1 intravaginally or systemically. huDRAG-A2 mice were also infected intravaginally with NL4.3-Bal-Env HIV-1. huDRAG-A2 mice, but not huNRGs, produced HIV-specific IgG, indicating improved immune responses. huNRG mice were infected intranasally with mCherry-Erdman, YFP-H37Rv or H37Rv Mtb. huDRAG-A2 mice were also infected with H37Rv. Human immune cell involvement
and human-like granuloma formation was observed using flow cytometry and immunohistopathology. These findings show that the DRAG-A2 model may be optimal for
investigating HIV, TB and co-infection, which continue to be serious global health concerns.

abstract: Thesis

abstract: Master of Science (MSc)

abstract:
Human immunodeficiency virus (HIV) and tuberculosis (TB) are infectious diseases that
affect millions of people worldwide every year. The greatest cause of death in people living
with HIV is co-infection with TB and HIV-positive individuals are much more likely to get
TB. Humanized mouse (hu-mouse) models possess human immune cells for HIV to infect
and are useful for studying HIV. Our goal is to create hu-mouse models of HIV, TB and
HIV/TB co-infection that will allow us to study how these diseases interact. We are
currently developing a traditional hu-mouse model (known as NRG), as well as an
improved next-generation model (known as DRAG-A2) with a more functional immune
system. Both models have been successfully infected with HIV or TB. Only DRAG-A2
mice were able to make antibodies against HIV. The improved DRAG-A2 model will
enable future studies on HIV, TB and co-infection, which continue to be understudied
global problems.


title: Variable Selection Methods for Model-based Clustering and Application to High-dimensional Data

contributor:
McNicholas, Sharon
Jeganathan, Pratheepa
Mathematics and Statistics

subject: Clustering Statistics

abstract: Clustering helps in understanding the natural grouping and internal structure of data. Model-based clustering considers each cluster as a component in a mixture model. As the data dimensionality and complexity increase, model-based clustering tends to over-parametrize results. Thus, it is important to select a subset of critical variables instead of using all the variables for clustering. This study considers two variable selection methods for model-based clustering on real world high-dimensional data; variable selection for clustering and classification (VSCC) and variable selection for model-based clustering (clustvarsel). For simplicity, Gaussian mixture models were applied. Three criteria are used to compare the clustering accuracy and efficiency, which are the adjusted rand index (ARI), mis-clustering error, and performance time (in seconds).

abstract: Thesis

abstract: Master of Science (MSc)


title: Family-Managed Home Care in Ontario for Families with Technology-Dependent Children

title: Family-Managed Home Care

contributor:
Butt, Michelle
Jack, Susan
Carter, Nancy
Nursing

subject:
family-managed home care
technology-dependent children
home care nursing

abstract:
Background: Advances in technology have led to an increasing number of CMC-technology dependent children being discharged from hospital to their home communities. Families with CMC-technology dependent children require home care nursing services established prior to discharge. The Family-Managed Home Care model is used by some families to acquire these nursing services.
Aim: The study purpose was to explore how families with CMC-technology dependent children describe their use of and experiences with using the Family-Managed Home Care model to coordinate nursing care.
Methods: Thorne’s interpretive description method was used. Virtual, in-depth, semi-structured interviews were conducted with nine parents of CMC-technology dependent children. Data was analyzed using Braun and Clarke’s reflexive thematic analysis.
Results: Parents of CMC-technology dependent children using the Family-Managed Home Care model became their child’s care manager. The process of managing the child’s care occurs in three interrelated and overlapping phases: (1) transitioning home, (2) building the home care team, and (3) partnering to provide care. Control was identified as a central concept that underpinned each step in the overarching process of managing the child’s care. Parents value the control provided by the Family-Managed Home Care model as this alleviated some stress, anxiety, and uncertainty in caring for a CMC-technology dependent child at home.
Conclusion: Parents using this model of home care require enhanced support from LHINs and health care providers. Increasing health care provider knowledge of the Family-Managed Home Care model is needed to further support parents. Improved organization of discharges and policy changes are needed.

abstract: Thesis

abstract: Master of Science (MSc)

abstract: Family-Managed Home Care is a self-directed home care model parents of children with medical complexities that are technology dependent (CMC-technology dependent children) utilize to implement home care nursing services. The consistent presence of home care nurses is vital to preserve family functioning and ensure the safety of the CMC-technology dependent child. This study’s purpose was to understand how parents of CMC-technology dependent children use and describe their experiences of coordinating nursing care under the Family-Managed Home Care model. Nine parents were interviewed. Findings indicated that in the process of managing the child’s care (1) transitioning home is overwhelming, (2) parents take on the role of becoming their child’s care manager, (3) parental control is a valuable aspect of using Family-Managed Home Care, and (4) enhanced support is needed for parents using this home care model. Findings can be used to improve support for families using the Family-Managed Home Care model.


title: Maternal Diet and Asthma in Children

contributor:
de Souza, Russell
Medical Sciences

subject:
nutrition
maternal nutrition
asthma
recurrent wheeze
mediterranean diet

abstract: This thesis consists of three manuscripts, which are presented in chapters 2, 3 and 4. The first manuscript (chapter 2) is a protocol for systematic review which outlines the steps used to systematically analyze the literature with regards to the primary objective of reviewing available evidence. The second manuscript (chapter 3) is the presentation of systematic review and meta-analysis in the form of a manuscript to be submitted for peer-review by fall 2020. The third manuscript (chapter 4) summarizes an analysis of CHILD study data that assesses the association of dietary patterns with infant wheeze and asthma through age 3. In chapter 5, the thesis concludes by summarizing study limitations, epidemiological implications, clinical relevance of these findings and future directions. Appendices are also included to highlight research methodology and describe comprehensively all data analyses.

abstract: Thesis

abstract: Master of Science (MSc)

abstract: This paper-based thesis includes my graduate research work to satisfy the requirements for a masters in science (M.Sc.) degree in the Medical Sciences department. The focus of this thesis is to contribute an important study of the role of maternal and infant nutrition in the development of asthma and wheeze in children. My research findings are presented as original manuscripts of a systematic review protocol, systematic review, and a primary analysis of data collected as part of the CHILD longitudinal birth cohort study. At present, the first 2 manuscripts are under review by scientific journals; and the third will be submitted for peer-review in October 2021.


title: Studying cellulose nanostructure through fluorescence labeling and advanced microscopy techniques

contributor:
Moran-Mirabal, Jose
Chemistry and Chemical Biology

subject: Cellulose, super-resolution fluorescence microscopy, correlative imaging

abstract:
As the major component of the plant cell wall, cellulose is produced by all plant species at an
annual rate of over a hundred billion tonnes, making it the most abundant biopolymer on
Earth. The hierarchical assembly of cellulose glucan chains into crystalline fibrils, bundles
and higher-order networks endows cellulose with its high mechanical strength, but makes it
challenging to breakdown and produce cellulose-based nanomaterials and renewable
biofuels. In order to fully leverage the potential of cellulose as a sustainable resource, it is
important to study the supramolecular structure and hydrolysis of this biomaterial from the
nano- to the microscale.
In this thesis, we develop new chemical strategies for fluorescently labeling cellulose
and employ advanced imaging techniques to study its supramolecular structure at the singlefibril
level. The developed labeling method provides a simple and efficient route for
fluorescently tagging cellulose nanomaterials with commercially available dyes, yielding
high degrees of labeling without altering the native properties of the nanocelluloses. This
allowed the preparation of samples that were optimal for super-resolution fluorescence
microscopy (SRFM), which was used to provide for the first time, a direct visualization of
periodic disorder along the crystalline structure of individual cellulose fibrils. The
alternating disordered and crystalline structure observed in SFRM was corroborated with
time-lapsed acid hydrolysis experiments to propose a mechanism for the acid hydrolysis of
cellulose fibrils. To gain insight on the ultrastructural origin of these regions, we applied a
correlative super-resolution light and electron microscopy (SR-CLEM) workflow and
observed that the disordered regions were associated nanostructural defects present along
cellulose fibrils. Overall, the findings presented in this work provide significant
advancements in our understanding of the hierarchical structure and depolymerization of
cellulose, which will be useful for the development of new and efficient ways of breaking
down this polymer for the production of renewable nanomaterials and bio-based products
like biofuels and bioplastics.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)

abstract:
In this dissertation, we have studied in unprecedented detail the structure of cellulose – a
polymer that is found in every plant. As the main structural component of the plant cell wall,
cellulose endows trees with their strength and resilience while storing sunlight energy in its
chemical bonds. Since plant biomass represents eighty percent of all living matter on Earth,
cellulose is an abundant resource that can be used to produce sustainable and
environmentally benign nanomaterials and bioproducts, like biofuels and bioplastics. Our
ability to use cellulose as a renewable source of structural materials and energy is intimately
linked to our capacity to break apart its tight structural packing. Deconstructing cellulose
into various forms demands that we understand the multi-level organization of its structure
and the susceptible regions within it. To gain this information, in this thesis we develop new
labeling methods and apply state-of-the-art microscopy tools to directly visualize the
arrangement of cellulose fibrils at the nanoscale (comparable to 1/10,000 the width of a
human hair) and study their breakdown by acid treatment. The findings presented in this
work furthers our fundamental understanding of the natural structure of cellulose, which
has important implications on the development of industrial strategies to break down this
abundant and renewable biomaterial.


title: MECHANISMS OF VENOUS THROMBUS STABILITY

contributor: Medical Sciences (Blood and Cardiovascular)

subject:
Deep Vein Thrombosis
Pulmonary Embolism
Thrombus Stability
Mouse Model

abstract:
Whether a patient presents with deep vein thrombosis (DVT) or pulmonary embolism (PE) varies based on clinical factors. Patients with factor V Leiden (FVL) typically present with DVT while cancer patients present with PE. The biological mechanisms that determine DVT stability in the progression of DVT to PE are not known.
	Thus, little is known about the mechanism of thrombus stability, the factors involved, or the effect of anticoagulants on embolization and PE burden. In order to answer these questions, we first need to (i) develop a mouse model to evaluate DVT stability and its relationship with PE burden when treated with anticoagulants, (ii) determine if anticoagulants, by inhibiting thrombin, require FXIII to decrease thrombus stability, (iii) determine the effects of attenuating fibrinolysis, using epsilon aminocaproic acid (ε-ACA or EACA), supplemental FXIII and α2-AP, on clot stability and (iv) utilize our model to explain the FVL paradox.
	For our thrombus stability model, the femoral vein of C57BL/6, FXIII deficient (FXIII-/-), FVL heterozygous, or FVL homozygous female mice was subjected to ferric chloride (FeCl3) injury to initiate a non-occlusive thrombus. Treatment with saline, dalteparin, dabigatran, EACA or FXIII was administered 12 minutes after thrombus formation. Intravital videomicroscopy recorded the thrombus sizes and embolic events leaving the thrombus for 2 hours. Lungs were harvested, sectioned and stained for the presence of PE.
	Total and large embolic events were highest after dabigatran treatment compared to saline or dalteparin in wild-type (WT) mice. Variations in amounts of embolic events were not attributed to variations in thrombus size since thrombus size was similar between the groups. The number of emboli per lung slice was higher in dabigatran-treated mice. Large embolic events correlated positively with the number of emboli per lung slice independent of treatment. Dabigatran treatment in FXIII-/- mice did not alter embolization patterns suggesting that FXIII is required for dabigatran to decrease thrombus stability.
	EACA increases thrombus size significantly and therefore would not be a feasible alternative to IVC filters, as it will increase DVT size. FXIII marginally increased thrombus size. Treatment with FXIII decreases total and large embolic events in saline-, dalteparin- or dabigatran-treated mice, similar to EACA-treated mice. The number of emboli per lung slice was reduced after treatment with FXIII and EACA compared to non-treated mice. PE burden was not significantly different between FXIII anticoagulated mice or EACA-treated mice. The large embolic events correlate positively with PE burden.
	FVL heterozygous and homozygous mice had significantly reduced embolization and thrombus size grew significantly over time, this contrasted with WT mice, where thrombus size remained similar to the initial injury. PE burden was significantly reduced in the FVL mice compared to WT.
	Collectively, these data shows that we have successfully developed a mouse model of acute venous thrombus stability that can quantify emboli and PE burden. Consistent with clinical data, dabigatran, a DTI, was shown to acutely decrease thrombus stability and increase PE burden compared to LMWH or saline; an effect that was FXIII-dependent. Also, attenuating fibrinolysis with EACA, but not FXIII, increases thrombus size; but both increase DVT stability and decrease PE burden. Supplementing α2-AP did not alter thrombus stability. This suggests that administration of FXIII may be a better treatment option for DVT patients who are bleeding than EACA, since EACA may increase DVT size. Lastly, our model can explain the FVL paradox. Those with FVL have stable thrombus formation leading to an increased incidence of symptomatic DVT and a decreased risk of PE.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: Unified Nonlinear Optimization-Based Sensorless Control for Switched Reluctance Machine Drives

contributor:
Emadi, Ali
Electrical and Computer Engineering

subject:
Switched reluctance machine
Position sensorless control
Nonlinear optimization

abstract:
Rotor position estimation of switched reluctance machines (SRMs) is the main focus of this work. Rotor position sensors are a crucial component of optimal motor controls. Fail-safe operation and system cost reduction have been extensively researched and implemented in industry and academia. Position sensorless control on switched reluctance machines introduces a new challenge due to high nonlinearity under different operating conditions.

A comprehensive review of SRM analytical modeling is presented, detailing each technique's main advantages and drawbacks. A least square-based analytical model (LSA) is proposed, which provides a simpler implementation and improved performance when compared to the methods commonly used in the literature. A literature review of rotor position sensor technology, position sensor fail modes, and position sensorless control is presented, providing a good roadmap of potential development and current limitations of the current technology. A wide speed range sensorless control is usually required when considering fail-safe techniques, fail detection methods, and low-cost applications. A unified nonlinear optimization-based sensorless control is proposed in this thesis, where a single method is used for startup, low and high speeds, with reduced memory allocation where a look-up table is not required, optimal transient response due to the elimination of a phase-locked-loop (PLL), and robustness against parameter variation. The method is validated at a wide speed range and torque conditions, thus showing the performance against conventional methods.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: IMPACT OF PETROLEUM RELATED COMPOUNDS ON MESENCHYMAL STEM CELL DERIVED PROGENITOR CELLS

contributor: Medical Sciences (Division of Physiology/Pharmacology)

subject:
Metabolism
Bone
Adipose Tissue
Adipocyte
Osteoblast
Naphthenic Acid
Oil Sands
Toxicology

abstract: There is concern over the impact that petroleum related compounds (PRCs) associated with mining activity in the Athabasca Oil Sands Region (AOSR) are having on local wildlife.  With the increase in oil sands mining activity in the AOSR there has been a corresponding decline in the fertility of indicator species in the AOSR.  One of the primary sources of PRCs in the environment is oil sands process affected water (OSPW), which is stored in tailings ponds. Several PRCs, including naphthenic acid fraction components (NAFC), have endocrine disrupting effects, which may, in part, explain reduced fertility in indicator species.  For example, male North American river otters (Lontra canadensis) living in areas impacted by mining activity have lower baculum strength those unaffected by mining activity.  Weaker baculums are associated with increases in fracture rates and reduced fertility.  Baculum strength is maintained throughout life by bone remodeling, a process that requires the differentiation of osteoblasts.  NAFCs can impact several pathways integral to the development and path selection of mesenchymal stem cells into osteoblasts or adipocytes.  Therefore, the objective of this thesis was to test the hypothesis that NAFCs inhibit osteoblast differentiation and induce adipocyte differentiation from progenitor cells.  We exposed osteoblast progenitor cells and adipocyte progenitor cells to NAFCs.  We demonstrated that NAFCs inhibit osteoblast differentiation and activate the glucocorticoid receptor pathway.  We also found that NAFCs do not induce adipogenesis in adipocyte precursor cells.  Lastly, we showed that NAFCs are PPARγ ligands that inhibit the expression of PPARγ associated genes.  These insights into the effects of NAFCs on osteoblast and adipocyte progenitor cells suggest NAFCs may contribute to lower baculum strength and impaired adipose tissue function of animals living in the AOSR.  These effects my reduce the fertility and population of wildlife in the AOSR.

abstract: Thesis

abstract: Master of Science (MSc)

abstract: There is concern that chemicals from oil sands mining in the Athabasca oil sands region are hurting the reproductive health of animals in the wild.  Some of these animals, including bears, wolves, and river otters, need a bone in their penis called a baculum to reproduce.  Studies have shown that some chemicals, including those from mining activity can make the baculum bone weaker.  For bone to stay strong, bone cells always need to be developing to fix the bone tissue.  The goal of our study was to find how chemicals from mining activity can affect the development of bone cells.  We found that a group of chemicals that come from oil sands mining called naphthenic acid fraction components (NAFCs) stop bone cells from developing and making new bone.  We also know that having more fat cells in bone is associated with weaker bones.  We also looked at whether NAFCs could increase the development of fat cells.  However, NAFCs did not increase the development of fat cells.  Together, this research shows that NAFCs can make bones like the baculum weaker by slowing the development of new bone, but not by increasing fat cells.  Our research suggests that exposure to NAFCs may make baculums weaker which may be bad for the reproductive health of animals living near oil sands mining activity.


title: English Rehearsal Plays: Theatre, Politics, and "Theatrical Politics", 1660-1800

contributor:
Walmsley, Peter
English and Cultural Studies

abstract: This dissertation contributes to Restoration and eighteenth-century studies by advancing the first critical examination of rehearsal plays as a distinct subgenre of dramatic comedy. I examine the development of the genre alongside major changes to production practices and acting techniques during this period to argue that rehearsal plays’ burlesque subversions of contemporary drama and dramatic conventions satirically enact problematic political and theatrical successions from the Exclusion Crisis of the 1680s to the representation of Shakespearean tragedies in the 1780s. More than simply plays about other plays, rehearsal plays superimpose critical spectators whose dialectical engagements with the embedded burlesque expose a shift in the relationship between actors, authors, and audiences as the London patent theatres emerge from civic institutions of courtly pastime into civil enterprises of commercial entertainment. This dissertation has two aims. First, I chart adaptations of "The Rehearsal" by George Villiers, 2nd duke of Buckingham through the eighteenth century to show how this satire on Restoration courtiers and court drama is continually readapted into an oppositional satire on contemporary politicians and mock-heroic burlesque of contemporary tragedians. Second, I examine the changing dramatic structure of several eighteenth-century rehearsal plays to show how the genre flourishes in response to a rapid expansion of the theatrical marketplace during this period. Drawing upon a vast archive of playbills, performance reviews, and theatrical ephemera, this study examines some of the most celebrated Restoration and eighteenth-century rehearsal plays, and offers theatre historians an expanded understanding of some major playwrights and performers including Henry Fielding, Catherine Clive, David Garrick, and Richard Brinsley Sheridan.

abstract: Dissertation

abstract: Doctor of Philosophy (PhD)


title: Caustics and Flags of Chaos in Quantum Many-Body Systems

contributor:
O'Dell, Duncan
Physics and Astronomy

subject: quantum caustic many-body chaos singularity catastrophe correlator OTOC

abstract:
We explore the dynamics of integrable and chaotic quantum many-body systems with
a focus on universal structures known as caustics, which are a type of singularity
categorized by catastrophe theory.
Papers I and II study light cones in quantum spin chains, which we show are
caustics and therefore inherits specific functional forms. For integrable systems, the
edge of the cone is a fold catastrophe, making the wavefunction locally of Airy form.
We also identify the cusp catastrophe in the XY model, thus the secondary light cone
is a Pearcey function. Vortex pairs appear in the dynamics, are sensitive to phase
transitions, and permit the extraction of critical scaling exponents. In paper II we use
a Gaussian wavefront form to distinguish integrable and chaotic models. Writing the
wavefront as exp[−m(x)(x − vt)2 + b(x)t], the scaling of coefficients m(x) and b(x) is
the diagnostic. The local Airy function description in free models leads to a power-law
∼ x^{−n/3} scaling, while for the chaotic case the scaling is exponential ∼ e^{−cx}.
In Paper III, we study the function Fn(t) = <(A(t)B)^n>, a generalization of the
four-point out-of-time ordered correlator (OTOC) F2(t), for an integrable system and
show that the function Fn(t) can be recast as the return amplitude of an effective time dependent chaotic system, exhibiting signals of chaos such as a positive Lyapunov
exponent, spectral statistics consistent with random matrix theory, and relaxation.
In Paper IV we perform a comprehensive investigation of caustics in many-body
systems in (1+1)- and (2+1)-dimensional Fock space and time. We show how a
hierarchy of caustics appear in the dynamics of many-body models, using two- and
three-mode Bose-Hubbard models as guiding systems. We show that, in the case of
the trimer, high dimensional caustics appear and are organized by the catastrophe
X9.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: Neutron Scattering Studies of the Family of High Temperature Superconducting Cuprates $La_{1.6-x}Nd_{0.4}Sr_xCuO_4$

contributor:
Gaulin, Bruce
Physics and Astronomy

subject: Superconductivity

abstract:
High TC superconductivity is regarded as one of the most challenging problems in the physical sciences of the 20th century. The ultimate goal is to create room temperature superconductors that have the potential to revolutionize many aspects of modern technology. The La-214 family of the cuprate high TC superconductors is comprised of single layers of CuO2 planes, and the original high TC superconductor was from this family. As such these copper oxides have been of great topical interest for 35 years since their discovery. This family displays a complex phase diagram with magnetism, charge order, an enigmatic pseudogap phase all intertwined with superconductivity. Neutron scattering famously first observed so-called stripe order phases by observing incommensurate elastic peaks centered
around (π, π) positions in reciprocal space in the Nd-LSCO member of this family in 1995. Since then, many related studies of stripe ordered phases have been carried out on different branches of the La-214 family, including LBCO, LSCO, and Nd-LSCO.
This thesis presents a comprehensive study of a series of La1.6−xNd0.4SrxCuO4 (Nd-LSCO) crystals, from their synthesis and single crystal growth, to their advanced characterization using elastic and inelastic neutron scattering techniques. The thesis begins with a detailed description of the methods of materials synthesis and single crystal growth and the related characterization of the materials synthesized. It then moves on to explore the evolution of magnetic order and low energy excitations at various Sr doping levels from x = 0.12 to 0.26 in Nd-LSCO single crystals. These data show that spin stripe magnetic order persists beyond the putative quantum critical point associated with the pseudogap phase, and extends
at least as far as the end of superconductivity. The behaviour of the associated dynamic spin stripes in these materials is also investigated with modern neutron spectroscopic methods, and these are also found to be pervasive across this range of doping. The implications of these data and their analysis are discussed and a new phase diagram is proposed which shows strong correlations between superconductivity and parallel spin stripe order and fluctuations.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: DELINEATION AND ANALYSIS OF ACTIVE GEOMORPHOLOGICAL PROCESSES USING HIGH RESOLUTION SPATIAL SURVEYS

contributor:
Eyles, Carolyn
Geography and Earth Sciences

subject:
Quaternary geomorphology
Structure from Motion
Close-range photogrammetry
Erosion
Niagara Escarpment

abstract:
The past few decades have seen rapid improvement in technologies related to remote sensing, specifically in digital photogrammetry and the use of unmanned aerial vehicles (UAVs). This has presented new opportunities to collect imagery at both a high temporal and spatial resolution to create detailed digital elevation models (DEMs) and investigate small-scale geomorphological features and their development over time. The high-resolution capacity of this methodology is well-suited to the study of a variety of terrains in which many critical geomorphological features are low relief and difficult or impossible to delineate using traditional remote sensing datasets. This study utilizes UAV-based imagery collection and data analysis, in conjunction with sedimentological analysis, of two study sites in Iceland and southern Ontario. The primary objective of this work is to explore the utility of integrating high-resolution spatial surveys with more traditional field techniques to identify geomorphological features, interpret their depositional origin, and quantify temporal changes in their form.
The first study was completed on the forefields of Öldufellsjökull and western Sléttjökull, two surge-type outlet glaciers of the Mýrdalsjökull Ice Cap in southeast Iceland. Glacial deposits are important sources of paleoclimatic information but not all deposits are formed by processes that reflect the overall climatic conditions of a region; surge-type (fast-flowing) glaciers undergo periodic episodes of rapid ice movement, often unrelated to ambient climatic conditions. Remotely sensed data and field investigations were combined to complete a landsystem analysis of the forefields at each of Öldufellsjökull and western Sléttjökull, and an unmanned aerial vehicle (UAV) was used to collect high-resolution imagery of areas of particular interest. The forefields of Öldufellsjökull and western Sléttjökull, lack many of the characteristics typical of surge-type landsystems and instead are more similar to the active temperate landsystem common in Iceland. The identification of landforms considered to be diagnostic of surge-type glacier behaviour was only possible through a targeted high-resolution UAV survey suggesting that small-scale diagnostic landforms may be overlooked in many investigations.
The second study area focused on the Niagara Escarpment in Hamilton, Ontario, a major landform resulting from extensive glacial and fluvial erosion of Paleozoic sedimentary rocks during the late Quaternary. In Hamilton, the Niagara Escarpment is a steep faced cuesta composed of Ordovician and Silurian sedimentary rocks. Recent rockfalls onto roads crossing the escarpment have raised serious concerns about its stability. To address these concerns, and to provide more information on erosional processes active along the escarpment in Hamilton, a comprehensive study of the Niagara Escarpment was completed including the collection of multi-temporal photogrammetric surveys of select rock faces, and detailed sedimentological and fracture analysis. A comprehensive lithological investigation was completed of all accessible rock outcrops in Hamilton to identify areas most likely to experience erosion based on site characteristics. A second component of this investigation was to evaluate the utility of using high-resolution imagery combined with Structure from Motion (SfM) software to detect temporal changes on the escarpment face. A staged erosion study was conducted in which lithological blocks of a known size were removed from the escarpment face at a selected site, to determine the lower limits of detection of erosion using this methodology. The study found that the location of block removal (erosion) was consistently identified, but the calculated volume of blocks removed was less accurately determined, differing by an average of 175% from the known volume of the block. A further study using this same methodology tested its ability to identify areas of natural loss (erosion) from the escarpment face. Based on multiple surveys taken 14 months apart at a selected study site, approximately one third of the area of interest experienced either loss (erosion) or gain (deposition) of material. There appear to be clear connections between lithology, density of fracturing, and the location of material loss (erosion); areas of the outcrop characterised by interbedded shales, and those areas exposing densely fractured sandstone or dolostone, were most likely to erode. The lithological characteristics of the Niagara Escarpment, including the strength of individual stratigraphic units, their vertical arrangement, and their density of fracturing, as well as climatic and hydrological factors (e.g., groundwater flow, location of surficial water features, mean annual temperature, mean annual precipitation etc.), all contribute to the amount and types of erosion active on the exposed rock face.
The studies reported in this thesis have integrated high-resolution, close-range imagery with traditional field techniques to explore the characteristics and development of geomorphological forms in different terrain types. In each of the studies, the importance of collecting high-resolution imagery (<10 cm) to map geomorphological features of various scales is highlighted.

abstract: Dissertation

abstract: Doctor of Science  (PhD)


title: Solid state phosphate sensor technologies for environmental and medical diagnostics

contributor:
Selvaganapathy, P. Ravi
Biomedical Engineering

subject:
Solid state sensors
Phosphate sensor
Chemiresistive sensors
Potentiometry
Electrical pretreatment

abstract:
Phosphorus is needed by living organism including humans and plants, to survive. Imbalance in phosphate concentration in human body can result in numerous diseases or disorders while excess phosphorus levels in water bodies like lakes, and rivers, are responsible for the rise in incidence of algal bloom across world. Current commercial phosphate monitoring systems are dominated by colorimetric measurements while electrochemical sensors including potentiometric, amperometric and voltammetric sensors are still in the research phase. Electrochemical sensors require stable reference electrodes for reliable measurements that pose challenges for miniaturization.
Solid state potentiometric sensors are widely explored due to their rapid response, easy fabrication and simple electronic measurement system. However, the sensor miniaturization is dependent both on the working and reference electrode. Metal electrodes like cobalt offers advantages such as reagent-free detection, easy to miniaturize but the sensitivity of zero-current potentiometric sensors is limited by the theoretical Nernstian limit and cobalt sensors also require chemical pretreatment in standard solution before measurement.
Here, an in situ electrical pretreatment method is proposed to eliminate the need of chemical pretreatment and enhance the sensitivity of cobalt electrodes to -91.4 mV/ decade of phosphate concentration. However, this electrode still needs a reference electrode for reliable measurements.
Therefore, this study has demonstrated a chemiresistive sensing platform for solid state detection of phosphate using both enzyme and enzyme-free methods. A rapid prototyping method was developed to pattern the thin metal films (~100 nm thickness) using a bench top plotter cutter. The method was used to fabricate thin gold film contact electrodes for chemiresistors. The thin gold leaf contact electrodes exhibited low-noise and offered a robust, rapid and reproducible manufacturing process for chemiresistors. The chemiresistive sensor showed a wide measuring range (0.5 ppm to 500 ppm) for hydrogen peroxide detection. The sensor was deposited with glucose oxidase to demonstrate the application of the sensor for peroxidase assays to detect glucose in standard buffer solution and human pooled plasma. Phosphate also is detected using pyruvate oxidase in presence of pyruvate to generate hydrogen peroxide as the detectable molecule. Finally, metal phthalocyanines were used to perform enzyme-free phosphate measurements.
This work demonstrated the sensor technologies which could be used for in-field phosphate monitoring to prevent algal bloom and it also provides phosphate monitoring methods for rapid detection in medical diagnostics for early diagnosis for diseases like chronic kidney disease and to improve the patient’s outcomes for such diseases.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)

abstract:
Phosphorus is an essential element for the survival of living beings including humans and plants because it is needed in multiple physiological pathways and functions like cellular signalling, energy storage, metabolism and maintenance. Therefore, phosphate in the human body is strictly regulated and in disease conditions like chronic kidney disease, and metabolic disorders. It can increase or decrease resulting in ailments and worsening of diseases.
Phosphorus is also extensively used in the agricultural field to improve the growth and crop yield. Excess phosphorus from these fertilizers can enter our water sources via agricultural water run-offs leading to the increasing incidences of algal bloom across world.
Current phosphorus measuring systems require chemicals which generates toxic waste, needs manual sample collection and transport, and have narrow measuring ranges. There is an urgent need for sensors which would eliminate the need of sample collection and processing, do not require toxic chemicals and could work over a wide detection range. This study presents two solid-state sensor technologies which would simplify the phosphate detection for both environmental and medical diagnostics samples.


title: SELF-INSCRIPTION OF COMPLEX, FUNCTIONAL 3-D STRUCTURES WITH SELF-TRAPPED LIGHT BEAMS

abstract: The behavior and dynamics of light waves in soft light-responsive polymers were studied. We used the properties of these beams to develop three routes to functional 3-D structures which would be impossible to fabricate through conventional lithography. The method to obtain functional 3-D structures, known as Prismatic 3-D printing, exploits the fact the divergence of beams can be controlled through the rate of photopolymerization which is intensity-dependent, to rapidly 3-D objects. Here, we employ segmentation algorithms to deconstruct a mesh of the desired object into prisms, which are then inscribed in a single step by self-trapped beams to generate a wide range of complex architectures within seconds. Such prisms can be assembled in situ or as a form of post-processing. Each of these prismatic elements has a higher refractive index than their surroundings and they are also continuous along the propagation front direction. These two properties make each prismatic element light-guiding. Taking advantage of this function obtained through our method, remote-controllable waveguide architectures including planar slab waveguide, individual and small arrays of cylindrical waveguides as well as long-range waveguide lattices (>10 000 cm-2) made of electroactive hydrogels were printed using self-trapped beams. By applying and varying external electric fields, we can then dynamically control the bending, angular orientation and rotation (up to 360o) of these pliant light-guiding structures. Reminiscent of the camouflaging techniques of certain marine creatures, this allows precise, remote control of the waveguided light output. Finally, we examined the propagation dynamics and structures inscribed by vortex beams in photopolymerizable systems and showed that they elicited rotation along their propagation paths and ultimately collapsed into self-trapped filaments. The sense of rotation was commensurate with the topological charge of the vortex while the rotation rate was proportional to the intensity of the beam output.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: Thulium doped tellurium oxide amplifiers and lasers integrated on silicon and silicon  nitride photonic platforms

contributor:
D. B. Bradley, Jonathon
P. Knights, Andrew
Engineering Physics

subject: Silicon Photonics

subject: Integrated optics

subject: Rare earth doped silicon waveguide lasers

subject: Silicon nitride waveguide lasers and amplifiers

subject: On-chip silicon lasers

subject: Tellurium oxide

abstract:
Silicon photonics (SiP) has evolved into a mature platform for cost-effective low power
compact integrated photonic microsystems for many applications. There is a looming
capacity crunch for telecommunications infrastructure to overcome the data-hungry future,
driven by streaming and the exponential increase in data traffic from consumer-driven
products. To increase data capacity, researchers are now looking at the wavelength window
of the thulium-doped fiber amplifier (TDFA), centered near 2 µm as an attractive new
transmission window for optical communications, motivated by the demonstrations of low loss, low nonlinearity, and high bandwidth transmission. Large-scale implementation of
SiP telecommunication infrastructure will require light sources (lasers) and amplifiers to
generate signals and boost transmitted and/or received signals, respectively. Silicon (Si)
and silicon nitride (Si3N4) have become the leading photonic integrated circuit (PIC)
material platforms, due to their low-cost and wafer-scale production of high-performance
circuits. Silicon does however have a number of limitations as a photonic material,
including that it is not an ideal light-emitting/amplifying material. This proposed research
pertains to the fabrication of on-chip silicon and silicon nitride lasers and amplifiers to be
used in a newly accessible optical communications window of the TDFA band, which is a
significant step towards compact PICs for the telecommunication networks. Tellurium
oxide (TeO2) is an interesting host material due to its large linear and non-linear refractive
indices, low material losses and large rare-earth dopant solubility showing good
performance for compact low-loss waveguides and on-chip light sources and amplifiers.
Chapter 1 provides an overview of silicon photonics in the context of particularly rare
earth lasers and amplifiers, operating at extended wavelengths enabled by the Thulium
doped fiber amplifier. Chapter 2 presents a theoretical performance of waveguides and
microresonators as the efficient structure for laser and amplifiers applications designed for
optimized use in Erbium and Thulium doped fiber amplifier wavelength bands. Then
spectroscopic study thulium (Tm3+) has been studied as the rare earth element for Thulium
doped fiber amplifier wavelength bands. Chapter 3 presents an experimental study of
TeO2:Tm3+ coated Si3N4 waveguide amplifiers with internal net gains of up to 15 dB total
in a 5-cm long spiral waveguide. Chapter 4 provides a study of TeO2:Tm3+
-coated Si3N4 waveguide lasers with up to 16 mW double-sided on-chip output power. Chapter 5 presents an experimental study of low loss and high-quality factor silicon microring resonators coated with TeO2 for active, passive, and nonlinear applications. Chapter 6 represents the first demonstration of an integrated rare-earth silicon laser, with high performance, including single-mode emission, a lasing threshold of 4 mW, and bidirectional on-chip output powers of around 1 mW. Further results with a different design are presented
showing lasers with more than 2 mW of double-sided on-chip output power, threshold
pump powers of < 1 mW and lasing at wavelengths over a range of > 100 nm. Importantly,
a simple, low-cost design was used which is compatible with silicon photonics foundry
processes and enables wafer scale integration of such lasers in SiP PICs using robust
materials. Chapter 7 summarizes the thesis and provides paths for future work.

abstract: Dissertation

abstract: Doctor of Engineering (DEng)


title: Investigating the Efficacy of Non-Ionic Surfactants as Compatibilizing Agents for Polyethylene-Polyamide Sintered Polymer Blends

contributor:
Thompson, Michael
Vlachopoulos, John
Chemical Engineering

abstract: A novel strategy was considered in this work to improve the physical properties of rotationally molded parts formed using a thermodynamically immiscible physical blend of high-density polyethylene (HDPE) and polyamide 11 (PA11). Morphology of the melted system of the two polymers dry-mixed in the mold was dictated by the selected non-ionic surface-active agents. Through a preliminary evaluation of numerous non-ionic surfactants, Span 85 and Tween 20 showed the most promise at concentrations between 0.1 - 1.0 wt% for influencing how the two polymers spread over the mold surface in a uniaxial rotational molding unit; the two surfactants demonstrated favourable interparticle cohesion at 235 °C and were chosen on the basis of investigating the hydrophilic-lipophilic balance (HLB) as a predictive metric for polymer migration during rotomolding. For a comparison to a more traditional (and expensive) approach of preparing a molded part with blends of these two polymers, extrusion-mixed blends were first compounded using a twin-screw extruder, pelletized, ground, and finally rotomolded. The good compatibility of the two constituent polymers with Tween 20 was demonstrated by decreasing zero-shear viscosities with increasing surfactant concentration. In the molded samples, porosity for 50/50 dry-mixed blends increased at low concentrations of Tween 20, but ultimately the surfactant demonstrated its beneficial nature on sintering with a downward trend observed in porosity with increasing surfactant concentration; molded samples with 1.0 wt% Tween 20 showed a 1% improvement in porosity relative to uncoated blends, whereas 1.0 wt% Span 85 coated blends showed an undesirable increase in porosity instead. Similar trends were observed for 75/25 dry-mixed blends, except that the porosities for all Tween 20 concentrations were lower than those of uncoated blends. Low porosities were observed for all extrusion-mixed blends (with or without 1.0 wt% Tween 20) relative to the dry-mixed blends. As more favourable results for this new approach, Tween 20 coated dry-mixed blends showed an increase in impact strengths for both blend ratios, whereas extrusion-mixed blends showed a drastic decrease instead. Conversely, the inverse trend was found with flexural strengths. The results were reconciled through morphological analysis of the molded samples which demonstrated that a moderate degree of polymer migration occurred (i.e. aggregation of PA11 at the wall boundaries and HDPE near the centre) in the presence of the surfactant for 50/50 dry-mixed blends, whereas observations for the 75/25 blends were inconclusive. Therefore, based on the observations for density/porosity, impact strength, flexural strength, and morphology (i.e. polymer migration) modifying the blend-ratio, mixing strategy, and surfactant concentration for rotomolded HDPE-PA11 physical blends enables us to reliably predict and control the polyblends’ resultant properties and cater them to meet the requirements of a wide range of unique and specific use-case scenarios.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: Purpose Built Exergame Design

contributor:
Carette, Jacques
Computing and Software

subject:
Software Engineering
Virtual Reality
Video Game Design
Exergaming
Exercise-based Video Game Design

abstract: Patients with end-stage renal disease that undergo dialysis treatment, visit a hospital on average 3 times a week. Such involved treatment means the patients lead very sedentary lifestyles. The sedentary lifestyle in turn makes the patient less capable and willing to participate in physical activity, worsening the patient’s overall health-related quality of life. Video games, more specifically exercise-based games, are an existing solution played by many across the world. It offers entertainment and while providing the player a means of exercising. An exercise based game played during treatment may potentially lead to a more active and healthy patient. This thesis explores the design of an exercise-based game for the patients that are required to play, similar to the circumstances the patients that the research project, Cyclescapes is being made for. We will learn the design considerations for making the challenges in an exercise based game for an audience that requires it and how to keep the player engaged and moving with respect to their own personal abilities and fitness levels. We then apply the knowledge in the design and creation of Cyclescapes, providing the patients with end-stage renal disease a safe and entertaining player experience that can challenge their physical fitness and improve their health related quality of life.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: Integrated Rotor Air Cooling System Design in Axial Flux Permanent Magnet Machines for Aerospace Applications

contributor:
Emadi, Ali
Mechanical Engineering

subject:
Axial-flux permanent magnet machines
Aerospace Electrification
CFD
Rotor Cooling
Thermal Management
Turbomachinery

abstract: A Thesis Submitted to the School of Graduate Studies in Partial Fulfillment of the Requirements for the Degree of Master of Applied Science in Mechanical Engineering

abstract: In the wake of the rising global demand for more electric transportation, aerospace electrification is becoming a highly active research area as commercial fully electric aircrafts are becoming a reality. The transportation electrification industry is challenged to develop powerful, safe, and compact-sized machines that can replace fossil fuel powered engines in aircrafts. Axial Flux Permanent Magnets (AFPM) machines are currently being intensively developed as a great candidate for this purpose due to their inherently higher power density compared to other machine electric machines topologies. The efforts of further increasing AFPM machines power density add more thermal challenges as intensive cooling is required at a relatively small machine package to avoid machine failure. One of the most concerning failure modes in these machines is power output reduction due to overheating of the rotor-mounted permanent magnets or even complete failure due to irreversible demagnetization. This research discusses the design process of an integrated rotor air cooling system for a 100 kW AFPM machine designed for an electric aircraft propulsion system. The embedded cooling system allows the rotor to be self-cooled at a sufficient cooling rate while minimizing the impact on machine efficiency due to windage power losses. The presented design process includes several stages of cooling enhancement including the addition and fine-tuning of rotor fan blades and rotor vents design. These enhancements are done by studying the air flow over the rotor surfaces in conjunction with heat transfer through Conjugate Heat Transfer (CHT) Computational Fluid Dynamics (CFD) analyses. In an initial study, different rotors with different combinations of rotor cooling features are studied and their thermal performance is compared. The results show that using rotor embedded fan blades in throughflow ventilated rotor geometry offers the best performance balance, achieving sufficient rotor cooling rate within a reasonable increase of windage power loss. A parametric study is performed to improve the rotor blade geometry for a higher ratio of heat transfer to windage losses. Another study is performed where the rotor and the enclosure geometries are fine-tuned simultaneously to reduce the negative effect on rotor heat transfer imposed by the enclosure. The final geometry of the rotor enclosure assembly is generated based on the research results and the design is integrated into the final machine prototype to be tested.

abstract: Thesis

abstract: Master of Applied Science (MASc)

abstract: Axial-flux permanent magnets (AFPM) machines are gaining the transportation electrification industy attention as a greener alternative to combustion engines in aircraft propulsion systems due to their high power and torque density. The intense endeavors of the current research to further improve AFPM machines power densities brings thermal design challenges to ensure the safe operation of the machine. Rotor permanent magnets failure due to demagnetization as a result of overheating can impose a great risk to the machine operation and safety. Accordingly, special attention should be paid to rotor thermal management. This research discusses the design process of an integrated rotor air cooling system for an AFPM machine designed for an electric aircraft. The machine mechanical and thermal design parameters are used to set an initial rotor design with different rotor cooling features based on literature findings. Rotor fan blades and air vents are selected as the main rotor cooling features for the design. Several design iterations are then made to fine-tune the rotor geometry targeting low operating temperature of the permanent magnets at a low cost of windage losses. The thermal performance of the different designs is assessed and compared to each other using conjugate heat transfer (CHT) computational fluid dynamics (CFD) analyses. Safe operating temperature of the magnets is achieved at an acceptable windage losses value with the final design, and it is selected for prototyping.


title: Coating Development for High-Speed Turning of Stainless Steel Addressing Combined Wear Mechanism

contributor:
Veldhuis, Stephen C.
Mechanical Engineering

abstract:
Austenitic stainless steel 304 (SS304) is one of the most widely used materials for aerospace, vehicle accessories, medical equipment, and ship parts. One of the reasons is that this material provides corrosion resistance and mechanical properties because of its chemical composition of predominantly chromium (Cr) and nickel (Ni). However, austenitic stainless steels have a high tendency to work-hardening and low thermal conductivity. This results in machining problems such as high cutting forces, unstable chip formation, and rapid tool failure. In addition, the work-hardening intensifies the frictional force at the tool-chip interface, which leads to a high localized temperature and causes diffusion and oxidation at the tool-workpiece interface.
    The aim of the current research was to develop novel compositions of adaptive PVD coatings for turning stainless steel, thereby cutting production costs, and improving product quality. The focus of this research was on a new generation of self-adaptive PVD coating designs and the use of these features to address machining issues during the cutting of stainless-steel material. It was found that during the high-speed turning of SS304, a complex combination of oxidation/diffusion wear mechanisms resulted in crater formation whereas abrasion/attrition led to flank wear. Therefore, the coating was designed and investigated with consideration of the dominant tool wear mechanisms, mechanical properties, and the tribological characteristics that were present in the cutting zone.
    In this research, different PVD and chemical vapour deposition (CVD) coating systems were studied for the semi-finish turning of SS304; monolayer AlTiN PVD coatings were investigated for the high-speed and ultra-high-speed turning of SS304 under various cooling conditions. Based on the research, a novel self-adaptive bilayer AlTiN PVD coating was developed and applied for the ultra-high-speed turning of SS304. The properties and performance of these coatings were comprehensively studied using X-Ray diffraction (XRD), scanning electron microscopy (SEM), nanomechanical indentation, scratch tests, optical 3D microscopy, tool wear studies, and tribological characterization. In addition, a chip cross-section analysis and surface integrity of the machined workpiece material were performed to study the machinability of SS304. The AlTiN PVD coating with the Al/Ti ratio of 60/40 was found to possess a favourable combination of tribological and micro-mechanical properties, and a novel self-adaptive bilayer AlTiN PVD coating was designed based on these findings. Tool life results have shown that the self-adaptive, bilayer AlTiN PVD coating improves tool life by over 1.3 - 4.6 times compared to the commercially available coatings.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: MOLECULAR GENETIC ANALYSIS OF THE AXIN HOMOLOG PRY-1 IN REGULATING DEVELOPMENTAL AND POST-DEVELOPMENTAL PROCESSES IN CAENORHABDITIS ELEGANS

contributor:
Gupta, Bhagwati
Biology

subject: Aging, Lipid metabolism, WNT, PRY-1, Axin, stress response

abstract:
My Ph.D. research project in the Bhagwati Gupta lab focuses on understanding the mechanism by which the Axin family of scaffolding proteins functions to regulate biological processes in multicellular eukaryotes. Towards this, I am using the nematode (worm) Caenorhabditis elegans as an animal model to investigate the role of one of the Axin homologs, PRY-1. Studies in various model systems and humans have shown that the Axin family of proteins plays crucial roles during cell proliferation, cell differentiation, and organ formation. Such a role of Axin depends on the negative regulation of the WNT signaling cascade. Consistent with these, alterations in Axin function are associated with developmental abnormalities and age-associated diseases such as axis duplication, neuroectodermal defect, and muscle degeneration.
As a scaffolding protein, Axin family members bind to and recruit multiple protein partners that are both WNT dependent and independent. However, how Axin interacts with these factors to regulate molecular events is not well understood. While some Axin-interacting factors have been identified, many more remain to be discovered. My project deals with the identification and functional characterization of pry-1/Axin interactors in C. elegans.
The key findings of my Ph.D. research are published in five peer-reviewed papers. Collectively, the results demonstrate that PRY-1 is necessary to regulate lipid metabolism, stress response, muscle health, and aging. I have shown that PRY-1 utilizes multiple pathways to control these diverse processes. Specifically, PRY-1 functions via the SREBP transcription factor homolog SBP-1 to regulate yolk lipoprotein expression to promote lipid synthesis. The analysis of pry-1’s role in aging and muscle health has revealed its interactions with the energy sensor AMPK homolog AAK-2, thereby affecting the function of the Insulin/IGF1 signaling (IIS) transcriptional regulator DAF-16/FOXO. Moreover, I have identified several mRNA genes and microRNAs that function downstream of PRY-1/Axin signaling to either suppress or enhance pry-1 mutant defects. All these novel interactors have mammalian homologs. Altogether, these findings form the basis to pursue future work to investigate the conserved mechanism of Axin signaling and hold the potential for effective intervention to delay aging and age-associated muscle deterioration.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)