title: DEVELOPMENT OF CELL-BASED BIOSENSORS FOR BIOCIDE DETECTION APPLICATIONS IN WASTEWATER

contributor: Dr. David R. Latulippe, Dr. Carlos D. M. Filipe

abstract: Biocides, commonly used in industrial processes, are responsible for inhibiting a biologically mediated process in municipal wastewater treatment plants (WWTPs) known as nitrification. Testing wastewaters (WW) that contain biocides prior to their treatment at municipal WWTPs is critical; inhibition of nitrification may cause ammonia levels to exceed effluent limits and lead to the discharge of biocides and other chemical compounds into receiving waterways. The specific nitrification rate (SNR) batch test/nitrification inhibition test is considered the gold-standard test for this evaluation; however, it is cumbersome and requires approximately 4 hours to conduct. The focus of this thesis aims to address the critical need for the development of a rapid nitrification inhibition test by using bacteria as cell-based biosensors (CBBs). First, non-pathogenic E. coli and an off-the-shelf nucleic acid stain were used to detect three common biocides. Expanding on this work, six additional bacterial strains (nitrifying, non-nitrifying) as CBBs were selected and the combined response – a set of fluorescence signals (“fingerprint”) – were found to successfully predict the nitrification inhibition potential of real industrial wastewater samples. Furthermore, changes in bacteria concentration and salinity content were found useful in manipulating biocide detection sensitivity. Efforts were also focused on preserving E. coli: storage temperature, salinity content, and a sugar-based polymer, pullulan, were important to maintaining a high level of survival in solution format. The benefits of sugars (pullulan and trehalose) in a dry format were also investigated: a miniature (1 L) electrospinning system was used to create thin and instantly dissolvable E. coli-embedded films to detect biocides. Finally, a new technique of aerosolizing bacteria while electrospinning sugar fibers was found to be gentler at incorporating bacteria into electrospun films when compared to electrospinning alone. Thus, this new technique could serve as a promising method of preserving the bacterial strains used as CBBs to predict nitrification inhibition potential.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: Lateral Torsional Buckling Strength of Sinusoidal Corrugated Web Plate Girders

contributor:
Balomenos, Georgios
Civil Engineering

subject:
Corrugated Web Plate Girders
Sinusoidally Corrugated Web Profile
Lateral Torsional Buckling
Experimental Analysis

abstract: Corrugated web plate girders (CWPGs) have become an increasingly popular structural member in Canada in recent years. This is because of their economic efficiency over standard wide flange members. Although the flexural performance of such has been increasingly studied in recent years there is still advancements that can be made in their design. No research has been completed in Canada on the subject of lateral torsional buckling (LTB) strength and very minimal research has been published on sinusoidal CWPGs. In order to examine the LTB strength of a CWPG with a sinusoidally shaped web, nine specimens were loaded and failed in simply supported arrangement that favours lateral torsional buckling. Specimens were chosen to observe the difference in strength due to web thickness, web depth and variation in identical beams. All of the specimens recorded strengths that exceeded the theoretical design strengths confirming that the current design procedure is conservative. A trend of ultimate capacity increasing was observed with the increase of web thickness. The depth of the web had no significant effect on the torsional strength besides what is gained from the increased flange distance. An equivalent web thickness equation was formulated based on the results for the purpose of calculating LTB strength. To test the proposed equation a numerical analysis was run on a wider range of beams and compared with the testing results. It was determined the physical testing results can be effectively captured by the proposed equation among more than just the tested beams. Two additional analyses were prepared to lay the foundation for further investigation of the proposed equation. The first was a Monte Carlo simulation to test the risk of using the proposed equation which requires additional data. Secondly, a preliminary finite element analysis (FEA) model was developed and presented for future use to expand this research.

abstract: Thesis

abstract: Master of Applied Science (MASc)

abstract:
Corrugated web plate girders (CWPG) have grown in popularity due to their economic efficiency. No research has been presented in Canada and very minimal research has been published on the lateral torsional strength of CWPGs with sinusoidally corrugated webs.
This research studied the lateral torsional buckling (LTB) strength of CWPGs through the experimental testing of physical members and a new equation for the calculation of the LTB strength is proposed. This equation and design process was then numerically tested to determine its viability as a design process.


title: Experimental Investigation of Boiling Heat Transfer Under an Impinging Water Jet

contributor:
Hamed, Mohamed
Mechanical Engineering

subject:
Jet impingement boiling
Transition boiling
Bubble departure diameter
Mechanistic model

abstract: The current study is an experimental and analytical investigation of JIB within the nucleate and transition boiling regimes. This study focuses on studying JIB within the stagnation zone of a free water jet. An experimental setup has been designed and built at the Thermal Processing Laboratory (TPL) with the capability of carrying out boiling experiments at heat fluxes up to 12 MW/m2. The JIB  curves have been obtained under steady-state conditions for a wide range of jet conditions, higher than those considered during previous JIB studies. The effect of jet velocity, up to 3.8 m/s, and degree of subcooling, up to 49 °C, on the JIB curve has been studied. The results showed that both jet velocity and degree of subcooling have a weak effect on the nucleate boiling regime and significantly affect the transition boiling regime. Bubble dynamics under the impinging jet within the nucleate boiling regime and the stability of the vapor layer within the transition boiling regime have been investigated. An analytical mechanistic model, based on force balance and thermal balance equations, has been developed to predict the bubble growth rate and the BDD. The developed model was validated using current experimental data. The model gave a relative deviation of 17.8 %. Results of the mechanistic model within the stagnation zone showed that, amongst the three heat transfer mechanisms that affect bubble growth (i.e., the microlayer evaporation, the heat from the superheated layer, the convection heat loss to subcooled liquid),  the microlayer evaporation is the most significant contributor to the rate of bubble growth. The current work conducted within the transition boiling regime was focused on the determination of the total wall heat flux within the stagnation zone, both experimentally and analytically. Steady-state experiments have been carried out during which the vapor layer stability was examined. The vapor layer breakup frequency was measured using a fiber-optic probe. Experiments were conducted at a jet velocity of 1 m/s and degrees of subcooling between 11 and 49 ºC.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: Econometric Analyses of  Cardiac Arrest in Ontario, Canada

contributor:
Sweetman, Arthur
Economics

subject:
Health Economics
Econometrics

abstract:
Cardiac arrest is a major cause of mortality and morbidity including recurring cardiac events, cognitive impairments, and mental health issues. This thesis is on empirical analyses of cardiac arrest patients in Ontario, Canada using administrative health data sources.

Chapter 1 is a retrospective population surveillance study, which employs logistic regression analysis to examine short-term and long-term survival trends for adult patients in acute care hospitals. The 1-year adjusted odds ratio for initial successful resuscitation is 1.049 (95% CI: 1.022-1.076) when controlling for demographics, pre-admission comorbidities, and hospital of arrest. In stark contrast, there was no evidence of a trend in survival at discharge, 30 days, or 1 year. Results suggest further research into post-resuscitation care in Ontario care may be useful. However, we also find evidence of measurement error coding in successful resuscitation that is trending in magnitude in way that could bias trend estimates.

Chapter 2 takes a serious look at the nonclassical measurement error problem in resuscitation success coding identified in the previous chapter. We employ a combination of credible assumptions from within the partial identification econometrics literature to nonparametrically bound the trend is resuscitation while allowing misclassification rates to trend. We also develop a novel approach which weakly restricts asymmetry between false positive and negative rates. We find that restricting false positives and negative to be within 10% and 90% of misclassified observations, in combination with monotonicity assumptions is enough to identify a trend.

Chapter 3 follows survivors of cardiac arrest after discharge and investigates follow-up patterns in primary care. These patients remain at high risk of death, recurrence of cardiac events, cognitive impairment, and mental health issues. They may benefit from ongoing monitoring of cardiac risk factors, early mental health screening, and co-ordination of specialist care. This requires continuity of primary care. Primary care reforms in Ontario, Canada have led to the majority of general practitioners (GP) switching from fee-for-service remuneration to enhanced patient enrolment models, which encourage or require GPs to formally enroll most patients attached to their practice. To understand continuity of care across payment models, we use semi-parametric duration models to analyze time to first GP outpatient follow-up visit, distinguishing visits a patient’s own regular GP, and other GPs. We find enrolled patients visit their own (other) GP earlier (later) compared to patients whose regular GP is fee-for-service.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: Use of Machine Learning for Outlier Detection in Healthy Human Brain Magnetic Resonance Imaging (MRI) Diffusion Tensor (DT) Datasets

title: Outlier Detection in Brain MRI Diffusion Datasets

contributor:
Noseworthy, Michael
Biomedical Engineering

subject:
Outlier Detection
MRI
Machine learning
DTI

abstract:
Machine learning (ML) and deep learning (DL) are powerful techniques that allow for analysis and classification of large MRI datasets. With the growing accessibility of high-powered computing and large data storage, there has been an explosive interest in their uses for assisting clinical analysis and interpretation. Though these methods can provide insights into the data which are not possible through human analysis alone, they require significantly large datasets for training which can difficult for anyone (researcher and clinician) to obtain on their own. The growing use of publicly available, multi-site databases helps solve this problem. Inadvertently, however, these databases can sometimes contain outliers or incorrectly labeled data as the subjects may or may not have subclinical or underlying pathology unbeknownst to them or to those who did the data collection. Due to the outlier sensitivity of ML and DL techniques, inclusion of such data can lead to poor classification rates and subsequent low specificity and sensitivity. Thus, the focus of this work was to evaluate large brain MRI datasets, specifically diffusion tensor imaging (DTI), for the presence of anomalies and to validate and compare different methods of anomaly detection.

A total of 1029 male and female subjects ages 22 to 35 were downloaded from a global imaging repository and divided into 6 cohorts depending on their age and sex. Care was made to minimize variance due to hardware and hence only data from a specific vendor (General Electric Healthcare) and MRI B0 field strength (i.e. 3 Tesla) were obtained. The raw DTI data (i.e. in this case DICOM images) was first preprocessed into scalar metrics (i.e. FA, RD, AD, MD) and warped to MNI152 T1 1mm  standardized space using the FMRIB software library (FSL).  Subsequently data was segmented into regions of interest (ROI) using the JHU DTI-based white-matter atlas and a mean was calculated for each ROI defined by that atlas. The ROI data was standardized and a Z-score, for each ROI over all subjects, was calculated. Four different algorithms were used for anomaly detection, including Z-score outlier detection, maximum likelihood estimator (MLE) and minimum covariance determinant (MCD) based Mahalanobis distance outlier detection, one-class support vector machine (OCSVM) outlier detection, and OCSVM novelty detection trained on MCD based Mahalanobis distance data.

The best outlier detector was found to be MCD based Mahalanobis distance, with the OCSVM novelty detector performing exceptionally well on the MCD based Mahalanobis distance data. From the results of this study, it is clear that these global databases contain outliers within their healthy control datasets, further reinforcing the need for the inclusion of outlier or novelty detection as part of the preprocessing pipeline for ML and DL related studies.

abstract: Thesis

abstract: Master of Applied Science (MASc)

abstract: Artificial intelligence (AI) refers to the ability of a computer or robot to mimic human traits such as problem solving or learning. Recently there has been an explosive interest in its uses for assisting in clinical analysis. However, successful use of these methods require a significantly large training set which can often contain outliers or incorrectly labeled data. Due to the sensitivity of these techniques to outliers, this often leads to poor classification rates as well as low specificity and sensitivity. The focus of this work was to evaluate different methods of outlier detection and investigate the presence of anomalies in large brain MRI datasets. The results of this study show that these large brain MRI datasets contain anomalies and provide a method best fit for identifying them.


title: A Vascular Graft On-a-Chip Platform for Assessing Thrombogenicity with Tuneable Flow and Surface Conditions

contributor:
Didar, Tohid
Biomedical Engineering

abstract: Key Words: Thrombosis, Vascular Graft, Microfluidics, Wall Shear Stress

abstract: Vascular grafts are essential for the management of cardiovascular disease. However, the lifesaving potential of these devices is undermined by thrombosis arising from material and flow interactions on the blood contacting surface. To combat this issue, the use of antithrombogenic coatings has emerged as a promising strategy for modulating blood and graft interaction in vivo. Although an important determinant of graft performance, hemodynamics are frequently overlooked in the in vitro testing of coatings and their translatability remains poorly understood. We address this limitation with a microscale platform that incorporates vascular prosthesis and coatings with tuneable flow and surface conditions in vitro. As a proof of concept, we use the platform to test the thrombogenic performance of a novel class of lubricant infused (LIS) and antibody lubricant infused (anti-CD34 LIS) coated ePTFE vascular grafts in the presence of arterial wall shear stress, with and without the presence of endothelial cells. Our findings suggest lubricant infused coated ePTFE vascular grafts are thromboresistant under flow and may have potential for in vivo arterial grafting applications. It is moreover apparent that the microscale properties of the device could be advantageous for the testing and translation of novel antithrombogenic coatings or blood contacting prosthesis in general.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: Thermal Contact Resistance Modeling in AA7075 Hot Stamping

contributor:
Jain, Mukesh K
Hamed, Mohamed S
Mechanical Engineering

subject:
Hot Stamping
Thermal Contact Resistance
AA7075

abstract:
Hot stamping and die quenching (HS/DQ) process of AA7075 aluminum alloy is one of attractive forming techniques for producing high strength automotive structural components to encounter their poor formability at room temperature. In this technique, quenching rate of this alloy is very crucial as it affects precipitation kinetics after artificial ageing of part formed, which in turn determines the final in-service mechanical properties and corrosion performance of part. Thermal contact resistance (TCR) between two solid surfaces is the main parameter that controls heat transfer between hot AA7075 sheet and cold steel dies, and thus affects quenching rate of part formed. Therefore, the final properties of automotive parts produced by hot stamping is indirectly influenced by TCR.
The common methods of determining TCR in HS/DQ are often impracticable as they require thermocouples to be inserted into complex-shaped stamping dies, punches and thin aluminum sheet (blank) to be formed. A potential mechanistic approach for determining TCR could be an attractive alternative due to its avoidance of embedded thermocouples into the tooling and blank. The mechanistic method emphasizes on physical mechanisms (roughness etc.) governing interfacial heat transfer between cold forming tools and hot blank.
The proposed work focuses on utilizing the mechanistic method to predict TCR between multiple cylindrical asperities on a nominally flat (and heated) AA7075 blank surface and a rigid, flat, asperity-free (and cold) steel die surface. The asperities were considered to deform elastoplastically, increasing contact area. Subsequently, TCR correlation as a function of temperature, contact load, and contact area was formulated. To validate the mechanistic model, a series of surface asperity flattening experiments using thermocouple-embedded AA7075 blank and polished stainless steel planar dies were carried out. Good agreement between mechanistic model predictions and experimental results in term of contact area and TCR as a function of contact load were observed.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: Preliminary Thermodynamics and Neutronics Analysis of Canadian Nuclear Battery

abstract:
The Canadian Nuclear BatteryTM (CNB) is a 2400 kWth (500 kWe) small modular
reactor (SMR) initially designed in the 1980s targeted at applications in remote locations
in Northern Canada [1]–[3]. The reactor uses potassium or sodium heat pipes as the
primary heat removal system which demonstrate passive cooling characteristics. Heat
pipes are metal pipes filled with working liquid and its vapour phase to transfer heat
from the heated area (evaporator section) to the cooled area (condenser section) through
phase change. Theoretical investigations are carried out to produce adequate information
for the effective utilization of the heat pipe design in the reactor. Steady-state and a
hypothetical double-power transient are simulated with STAR-CCM+ to understand
the thermodynamics of the core and the propagation of heat pipe failures in accidental
events. Preliminary neutronics calculations are carried out for the hypothetical double
power transient and 50% power setback transient to evaluate the neutronics and xenon
behaviours of the reactor. The purpose of the study is to provide first information about
the thermal and neutronics performances of CNB in the early stage of development.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: Investigating the Role of Estrogens on the Molecular Mechanisms Modulating Pancreatic Beta Cell Health and Cardiometabolic Disease

contributor:
Werstuck, Geoff
Chemical Biology

subject:
sex as a biological variable
pancreatic beta cells
atherosclerosis
estrogen

abstract: Sex-dependent differences in the prevalence of diabetes and cardiovascular diseases are well established. The objective of this project is to investigate the molecular mechanisms by which estrogen modulates chronic disease progression. Our lab, and others, have previously implicated endoplasmic reticulum (ER) stress in the development and progression of diabetes and cardiometabolic disease. We hypothesize that estrogens protect pancreatic beta cell health, and slow the progression of cardiometabolic disease, by modulating the unfolded protein response (UPR) in response to ER stress. Two distinct mouse models were used in these studies. The ApoE-/-Ins2+/Akita mouse model of hyperglycemia-induced atherosclerosis, in which females are significantly protected from hyperglycemia and atherosclerosis relative to males, and the TALLYHO/JngJ mouse model, in which females are protected from chronic hyperglycemia relative to males. We found that ovariectomy of female ApoE-/-Ins2+/Akita or TALLYHO/JngJ mice promoted chronic hyperglycemia. Supplementation with exogenous 17-beta estradiol significantly lowered blood glucose levels in ovariectomized ApoE-/-Ins2+/Akita mice and reduced atherosclerotic lesion development in both male and ovariectomized female mice. Pancreatic islets from sham operated ApoE-/-Ins2+/Akita female mice showed a significant increase in the expression of protective UPR factors and a decrease in pro-apoptotic factors, compared to males or ovariectomized females.  To determine if alleviating ER stress could moderate hyperglycemia, male and ovariectomized female TALLYHO/JngJ mice were treated with the chemical chaperone 4-phenylbutryic acid (4-PBA). We showed that 4-PBA treatment significantly lowered fasting blood glucose levels and improved glucose tolerance. The results of this thesis suggest that estrogens play a protective role in the maintenance of beta cell health and blood glucose regulation by activating the adaptive UPR. This mechanism may explain the protection observed in premenopausal women and may lead to the development of targeted therapies to treat diabetes and cardiometabolic diseases.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)

abstract: People who suffer from diabetes mellitus have a higher risk of developing heart attack and stroke compared to those who do not have diabetes. Moreover, the risk of heart attack and stroke is higher in men than in women. We still do not understand the underlying reasons for these differences. This thesis project has used unique mouse models that display many of the same sex differences in disease progression that we see in humans to study the pathways and mechanisms that promote diabetes development. Specifically, we examined the protective effects of estrogen towards the development of diabetes and cardiovascular disease and how this hormone affected specific cells and tissues. The results of these studies are important because they will provide more information regarding the effects of menopause and aging on chronic disease progression in women.


title: EXPERIMENTAL AND ANALYTICAL STUDIES ON THE EVALUATION OF ELASTOMERIC BRIDGE BEARINGS

contributor:
Balomenos, Georgios
Konstantinidis, Dimitrios
Civil Engineering

abstract:
Elastomeric bridge bearings (composed of alternating rubber layers and steel laminates surrounded by a rubber cover all around) have been historically introduced between the girder and the pier or abutment to accommodate service-level movements and rotations. During a seismic event, these bearings can also experience deformation demands that are considerably larger than the service-level demands. The manufacturing process of these bearings involves compression molding during which imperfections such as vertically misaligned, rotationally misaligned, and bent steel laminates might develop. The current quality control procedures for bearings involve costly, time-consuming, destructive tests on sample bearings. Therefore, there is a need for an efficient, nondestructive methodology for quality control testing of bearings. In addition, these bearings are a key component of the bridge, and thus the effects of manufacturing imperfections on different aspects of the bearing’s performance must be understood and quantified.
In the first phase of this research, an efficient vision-based assessment methodology was developed for the nondestructive identification of the internal structure of elastomeric bridge bearings and their potential imperfections. The developed methodology requires the application of three-dimensional digital image correlation (3D-DIC) and relies on the local extrema forming in displacement and strain fields on the vertical sides of compressed bearings. In the next two phases, extensive nonlinear 3D FEA studies were undertaken to evaluate the effects of imperfections on the behavior of bearings under maximum service loading and under large lateral displacements resulting from seismic actions. Based on the FEAs results, imperfections are not expected to trigger shear delamination in bearings and their increased vertical deflections due to imperfections would be also minimal. However, imperfections can appreciably increase the tensile stresses in the laminates and lead to greater extents of plasticity in them. In the third phase of this research, the examined bearings were subjected to simultaneous axial loading and five cycles of lateral displacements with increasing amplitudes, up to 200% of their total rubber thickness. It was found that imperfections do not cause a considerable difference in the overall deformed shape of bearings but can expedite the rollover of bearings in lower shear strains and increase their risks of instability. Although all the examined bearings exhibited fairly stable hysteretic response, their effective lateral stiffness and lateral force could increase up to 18% and 40%, respectively, due to imperfections. Imperfections could also increase damage measured using a plastic-energy-based damage factor by up to more than five times for bearings subjected to the five-cycle displacement protocol. However, the yielded laminates in all examined bearings under maximum service loading or cyclic lateral displacement were far from fracturing. The increase of plastic damage during a strong earthquake and due to imperfections is not expected to cause immediate failure of bearings, provided that no or limited plastic damage occurs prior to that and under the service-level condition.
The proposed nondestructive methodology can be adopted by departments/ministries of transportation as an alternative to the current destructive approaches for quality control of elastomeric bearings. For bearings subjected to maximum service loading, the use of sufficiently thick laminates (e.g., 4-mm-thick) is suggested to prevent plastic damage to the laminates, and thus alleviate concerns about the service-level performance of the bearings. Considering the risks of rollover, instability, and spread of plastic damage in the laminates under cyclic loading, slender bearings with laminate thicknesses of 2 mm, or less, and slender bearings in which the majority of laminates feature relatively large rotational misalignments (in the order of 0.025 rad, or more) should be avoided.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: A Comprehensive Analysis of Mortality due to COVID-19 in Long-Term Care

title: Mortality due to COVID-19 in Canadian Long-Term Care

contributor:
Grignon, Michel
Health and Aging

subject:
Long-Term Care
COVID-19 Mortality

abstract: The long-term care (LTC) sector in Canada has experienced high numbers of COVID-19 deaths. However, there is a paucity of data on the impact of COVID-19 in LTC by different socio- demographic variables and in LTC homes within different regions. Additionally, the question remains as to how exactly and by how much the pandemic has impacted mortality in LTC in comparison to previous years’ mortality. Ranges for expected mortality by sex, province, and age, for the 2020-21 fiscal year were determined by creating forecasts and confidence intervals based on mortality trends in the preceding four fiscal years. These ranges were then compared to the actual mortality data in 2020-21. Comparisons between expected ranges and actual data were also conducted for the number of active residents, admissions, and discharges in LTC by sex, province, and age. Further, mortality ratios were created and studied by sex, province, age, and health region/authority/local health integration network. Overall, the number of deaths in LTC in Canada increased beyond the expected ranges in quarter one and three of 2020-21, and the patterns in death ratios were similar. Increases were exceptional in comparison to the peaks in deaths in previous years for specific variables, but not all variables. Most commonly, the number of active residents and admissions decreased in 2020-21 and the number of discharges from LTC did not change in quarter one and three and decreased in quarter two and four. However, importantly, these trends also varied across variables. This was the first study to comprehensively examine mortality due to COVID-19 in LTC overall, and by multiple socio- demographic variables while elucidating the complexity in the study of mortality in LTC. Further research is required to concretely understand mortality in LTC by different variables and regions.

abstract: Thesis

abstract: Master of Arts (MA)

abstract: This study examined mortality due to COVID-19 from April 2020 to March 2021 in Canadian long-term care (LTC) homes by sex, age, province, and health region. Ranges of predicted values for mortality were created from mortality data from previous years and then compared with actual mortality. The number of active residents, admissions, and discharges were also examined by sex, age, and province to factor for changes in the population at risk. Overall, mortality increased in some quarters (April-June 2020 and October-December 2020) but was not always exceptional, as similar mortality rates had been observed in the four years prior to the pandemic. Also, the increase in mortality was seen mostly among younger residents (65 to 85); mortality remaining stable for the 85+. Further research is still required to better understand mortality in LTC by regional characteristics.


title: Monocyte Covalent Immune Recruiters: Tools to Modulate Synthetic Immune Recognition

contributor:
Rullo, Anthony
Chemical Biology

subject:
immunotherapeutic
protein labelling
immune recruitment
peptide synthesis

abstract: Immune recruiters are small molecule immunotherapeutics which redirect endogenous components of the immune system to target cells to elicit anti-cancer responses. Current immune recruiters made in the Rullo Lab are heterobispecific molecules which bind receptors on cancer cells and ligand-specific antibodies. Upon antibody binding, a proximity-induced covalent reaction with nearby nucleophilic residues installs a targeting ligand onto the protein. The resultant antibody conjugate then facilitates cancer killing through immune cell recruitment. Covalency circumvents limited binding affinity of the ligand•antibody complex, however antibody•immune receptor affinity remains an issue. This thesis presents an alternative immune recruiting strategy through direct engagement of effector immune cells; monocyte covalent immune recruiters (mCIRs). mCIRs utilize a monocyte specific peptide (cp33) to bind CD64, an activating receptor on monocytes. By incorporating a sulfonyl fluoride electrophile onto the N-terminus of cp33, selective covalent labelling of CD64 was achieved within 24 h. Furthermore, mCIRs demonstrated enhanced monocyte function relative to antibody recruiting platforms. However, these constructs have demonstrated that the order of addition to the target receptor then to CD64 is critical for bridging the two species. As a result, the effect of covalency on complex simplification and monocyte function has yet to be determined. Despite this, mCIRs represent a covalent immune recruitment strategy with the potential to address shortcomings of antibody-based therapeutics.

abstract: Thesis

abstract: Master of Science (MSc)


title: ADVANCES IN REAL-TIME QUANTITATIVE NEAR-FIELD MICROWAVE IMAGING FOR BREAST CANCER DETECTION

title: QUANTITATIVE MICROWAVE IMAGING FOR BREAST CANCER DETECTION

contributor:
Nikolova, Natalia K.
Bandler, John W.
Electrical and Computer Engineering

subject:
holography
breast cancer
imaging
microwave
quantitative microwave holography
phantom
Born
Rytov
filtering
inverse problems
near field
range migration
synthetic aperture radar (SAR)

abstract: Microwave imaging finds numerous applications involving optically obscured targets. One particular area is breast cancer detection, since microwave technology promises fast low-cost image reconstruction without the use of harmful radiation typical of X-ray mammography. However, the success of microwave imaging is hindered by a critical issue, the complex nature of near-field electromagnetic scattering in tissue. To overcome this, specialized image reconstruction algorithms alongside sensitive measurement hardware are required. In this work, real-time near-field microwave imaging algorithms known as quantitative microwave holography and scattered power mapping are explored. They are experimentally demonstrated to identify potential tumor regions in tissue phantoms. Alongside this development, quality control techniques for evaluating microwave hardware are also described. Two new methods for improving the image reconstruction quality are also presented. First, a novel technique, which combines two commonly used mathematical approximations of scattering (the Born and Rytov approximations), is demonstrated yielding improved image reconstructions due to the complimentary nature of the approximations. Second, a range migration algorithm is introduced which enables near-field refocusing of a point-spread function (PSF), which is critical for algorithms that rely on measured PSFs to perform image reconstruction.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)

abstract: Breast cancer remains as one of the highest causes of cancer-related deaths in women in Canada. Though X-ray mammography remains the gold standard for regular breast cancer screening, its use of harmful radiation, painful breast compression, and radiologist dependent evaluation remain as detracting factors for its use. Over the past 40 years, researchers have been exploring the use of microwave technology in place of X-ray mammography. Microwave radiation, used at power levels similar to that of a cellphone, has been demonstrated successfully in simulations of breast scans. However, in experimental evaluations with breast phantoms, the complex scattering path of the radiation through tissue complicates image reconstruction. In this thesis, methods of improving the accuracy of microwave algorithms are explored, alongside new breast phantom structures that replicate well the electrical properties of tissue. The results of this work demonstrate the flexibility of microwave imaging, and the adversities that still need to be overcome for it to begin seeing clinical use.


title: Microstructural and mineralogical analysis of greenschist-facies deformation in the eastern Yukon-Tanana terrane, Yukon, Canada

publisher: School of Earth, Environment and Society

subject: Yukon, geology, mineralogy, Yukon-Tanana terrane

abstract:
The Yukon-Tanana terrane of the northern Canadian Cordillera experienced multiple episodes of mafic-intermediate volcanism during the Paleozoic, followed by polyphase deformation during its accretion to the North American continent. This study seeks to analyse the deformation history of a heterolithic greenschist unit that is exposed near the Boswell River in south-central Yukon. This greenschist unit, which is coincident with an aeromagnetic high, includes thinly layered intervals that exhibit centimeter to meter-scale folds and crenulations.
Using an oriented greenschist facies sample collected from a meter-scale fold during field mapping, a detailed microstructural approach was applied to determine the number and nature of deformation events recorded in the area. Subsequent petrographic analysis was conducted to identify the minerals present and establish the temperature during deformation. Observations show that the main mineral phases are quartz-muscovite-chlorite, in addition to a variety of sulphide minerals, some of which show compositional zonation. A fracture runs through the slide, bearing crushed mica along one border, possibly indicative of shear. Based on these observations, it was established that the sample records at least three distinct stages of deformation. To further constrain the deformation history, use of a scanning electron microscope (SEM) was employed to link the observations to the larger-scale tectonic evolution of the area.


title: Predicting Interfacial Characteristics during Powder Bed Fusion Process

contributor:
Phillion, André
Materials Science and Engineering

subject:
Powder Bed Fusion Process
Rapid Solidification
Cells
Dendrites

abstract: Powder bed fusion (PBF) is a metal additive manufacturing process that is increasingly used in the aerospace and medical industry to build complex parts directly from computer-aided design. Due to the presence of large temperature gradients and rapid cooling rates during the processing, the PBF process is assumed to follow a rapid solidification processing route. However, the extent of deviation of the solid-liquid interface from equilibrium as a function of processing conditions has not been studied in detail for the PBF process. In this thesis, a numerical model is developed to study the interfacial characteristics as a function of processing conditions to characterize if the PBF process exhibits rapid solidification or not. The model is based on the work of Hunt et al. [1, 2, 3] and is capable of simulating cellular and dendritic growth at both low and high interface velocities. The developed model accounts for the various undercooling such as constitutional and curvature undercooling, the variation of the liquidus temperature with composition, and the partition coefficient and diffusion coefficient with temperature. Moreover, the variation of the partition coefficient and the liquidus slope with the growth velocity has also been considered in the developed model. The model is used to predict the range of primary cellular/dendritic spacing for a given set of input parameters. In addition to this, the tip undercooling, tip Péclet number and spacing Péclet numbers have also been estimated using the model to quantify the extent of deviation of the solid-liquid interface from equilibrium. A good qualitative agreement between the predicted values from the numerical model and the analytical KGT model is achieved. This new model can be used to understand the relationship between the processing conditions, material system and interfacial characteristics during the PBF process, and thus improve microstructural development during PBF processing.

abstract: Thesis

abstract: Master of Science in Materials Science and Engineering (MSMSE)


title: Investigating Adaptive Regulatory Evolution of Intracellular Arginine Metabolism in Salmonella Typhimurium

title: Investigating Arginine Metabolism in Salmonella Typhimurium

contributor:
Coombes, Brian K.
Biochemistry and Biomedical Sciences

subject:
Salmonella
bacterial pathogenesis
bacterial metabolism
host-pathogen interactions

abstract: Salmonella enterica is a facultative intracellular pathogen capable of eliciting severe, systemic disease necessitating antibiotic intervention. Systemic infection is facilitated by intracellular replication within host immune cells, which is enabled by complex regulatory networks governed by two-component systems (TCSs). Intracellular-active TCSs sense antimicrobial chemical cues in the microenvironment and respond adaptively through transcriptional regulation to support intracellular survival. SsrA/SsrB and PhoQ/PhoP are two essential TCSs that elicit a robust defense against host immunity by regulating clusters of virulence genes and integrating novel targets to support regulon expansion and enhance pathogenicity. Metabolic adaptation is critical to bacterial survival and can initiate host-pathogen interactions that influence infection outcome. Further, mitigation of host immunity by manipulation of arginine metabolism has been documented in intracellular pathogens. Herein, I investigated TCS-mediated regulatory evolution pertaining to arginine metabolism, hypothesizing that adaptations to metabolic regulation might confer a fitness advantage to Salmonella replicating intracellularly. I explored intracellular regulation of de novo biosynthesis and extracellular import of arginine, establishing PhoP-mediated regulation of arginine transport. I determined that arginine transport contributes to bacterial fitness in macrophages and began to investigate the mechanism by which arginine importation enriches for intracellular replication. This work informs on evolutionary mechanisms that serve to enhance virulence in Salmonella and provides further insight into our understanding of the intracellular lifestyle of infection.

abstract: Thesis

abstract: Master of Science (MSc)

abstract: Salmonella enterica is an intestinal pathogen that survives within host immune cells and causes systemic disease. These bacteria replicate within antimicrobial cells by using sensory networks to detect harmful immune factors and respond adaptively by eliciting change in gene expression to defend against immune-based killing. The amino acid arginine is an important component of host immunity, as well as bacterial antimicrobial defenses; therefore, I hypothesized that bacterial metabolism might be adapted to the host immune cell environment in order to mitigate arginine-dependent antimicrobial activity. Here, I establish that arginine metabolism is controlled by intracellular-specific sensory networks, and demonstrate that this regulation is important for bacterial survival. This work provides evidence for the importance of this amino acid in Salmonella infection, which informs on our overall understanding of systemic disease.


title: When "the words don't fit you": Reflections on Madness and Nonsense

contributor:
Jeffery, Donaldson
English

subject:
Mad Studies
Nonsense Literature
Poststructural feminism
Deleuze

abstract: Divided into three substantial chapters, this dissertation centres on the interconnections of madness and nonsense. In particular, the introduction analyzes theories on nonsense literature, and the binaric logics that separately structure the discursive fields of these two phenomena. In this section, there is also a deconstruction of the problematics of analyzing nonsense as a literary technique without the influence of mad studies. The first chapter then moves to take on the figure of the Western serial killer, and the hermeneutic projects that the media takes on when reporting on his “senseless” crimes. Arguing that the labelling of the serial killer’s crimes as “nonsensical” demonstrates a particular aesthetic that works to associate madness with danger, disease, fear, and hatred within the public imaginary, this dissertation offers an analysis through a reading of Lynn Crosbie’s Paul’s Case. In the final chapter, this dissertation employs Margaret Atwood’s Surfacing and Emma Donoghue’s The Wonder to consider nonsensical madness within the context of feminine subjectivity. Considering autotheory as a feminist hermeneutic practice then leads into the author’s own experiences as a mad person. This dissertation aims to consider how to engage with nonsensically mad feminine texts, and the ethics of the hermeneutics of mad reading-projects.

abstract: Dissertation

abstract: Doctor of Philosophy (PhD)

abstract: Why do we deem certain groups of people nonsensical? Why is nonsense considered the ‘mother-tongue’ of madness? This dissertation attempts to unfold some of the dimensions of these questions through an historical taxonomy of madness and nonsense as separate yet connected phenomena; an analysis of the media and popular categorization of the Western serial killer; and feminine people deemed ‘mad’ via hysteria. Using their own experiences of madness, the author asks how we can possibly read mad articulations when they are often chalked up to nonsense, as well as the sociopolitical implications of this configuration of nonsense and madness.


title: Coming of Age in the Roman Empire

title: Exploring the Social and Physical Transformations of Adulescentia (Adolescence)

contributor:
Brickley, Megan
Prowse, Tracy
Anthropology

subject:
bioarchaeology
Roman Empire
stable isotopes
social age

abstract:
In modern populations, adolescence is recognized as a pivotal part of the life course, but bioarchaeologists have not yet widely considered the experiences of adolescents in the past. This research investigates the biological and social changes during Roman adulescentia for individuals buried at Isola Sacra (1st-4th centuries CE; Italy) and Lisieux-Michelet (4-5th centuries CE; France).
To investigate biological changes, this thesis identifies osteological indicators of pubertal timing and peptide analysis to assess biological sex for pre-pubertal individuals (n=264). Results demonstrate that adulescentia experienced an extended period of puberty, from nine to 20 years of age; menarche occurred around 15 years of age. Comparisons between the two archaeological sites demonstrate similar patterns of pubertal timing, suggesting similar exposure to Early Life Stress.
To investigate the social changes, this research uses stable isotope analysis of incremental dentine sections in teeth, to investigate dietary change between childhood, adolescence, and adulthood. Incorporating literary sources, observed changes in diet are contextualized in relation to expected social age changes for middle-class individuals within the Roman Empire. At both sites, females exhibit a gradual dietary transition, reflecting a gradual social age change, or that diet is not an appropriate proxy for social age changes for women. For males, changing dietary patterns correspond with the beginning of adulescentia, when these young men took on new roles within their communities and underwent pubertal development.
This research demonstrates that adulescentia was an extended period of biological and social change for males and females, which took on different forms depending on one’s sex/gender and social position. This research also demonstrates how investigations of adolescence can permit a more holistic interpretation of this transitional period of the life course and exposes the transitional experiences of these individuals as they come of age in the Roman Empire.

abstract: Dissertation

abstract: Candidate in Philosophy

abstract: There are kids, and there are adults, but what about those in-between? When does one become the other? These are the questions driving this doctoral research, and in applying them to the Roman Empire, I examine patterns of puberty and changes in diet, to better understand when children started to look like and eat like adults in their communities. This research demonstrates that adulescentia (i.e., adolescence) was a period of extended biological development, with puberty occurring between 9 and 20 years of age. Changes in diet, however, occurred in different ways for males and females, and across space and time within the Roman Empire, suggesting that there was not a singular experience or definition of adulescentia, but that lived experiences were more variable and nuanced than ancient literary sources suggest.


title: On the Asymptotic Plateau Problem in Hyperbolic Space

contributor:
Lu, Siyuan
Mathematics and Statistics

subject:
Hypersurfaces in Hyperbolic Space
Fully Non-linear Elliptic Equations
Plateau Problem

abstract: We are concerned with the so-called asymptotic Plateau problem in hyperbolic space. That is, to prove the existence of hypersurfaces in hyperbolic space whose principal curvatures satisfy a general curvature relation and has a precribed asymptotic boundary at infinity. In this thesis, by following the method of Bo Guan, Joel Spruck and their collaborators, we solve the problem with the aid of an additional assumption. In particular, our result applies to hypersurfaces whose principal curvatures lie in the k-th Garding cone and has constant (k,k-1) curvature quotient.

abstract: Thesis

abstract: Master of Science (MSc)


title: The Path to Measles Elimination in the United States

contributor:
Earn, David
Mathematics

subject: measles elimination eradication modeling epidemiology

abstract:
The eradication of infectious diseases has been of key interest for many years.
While the World Health Organization (WHO) and other health organizations
typically track the progress of disease eradication based on whether regions
are meeting their eradication targets, being able to quantify and/or visually
track the eradication of a disease could prove beneficial. This thesis creates the
“canonical path” to the elimination of measles in the United States (US), using
similar methods as defined by Graham et al. [1]. We build on preliminary work
conducted to fulfill the requirements of an Honours Bachelor of Science in Integrated
Science at McMaster University, and the analysis conducted by Graham
et al. [1], through the investigation of the sensitivity of the path to changes in
its definition, as well how the path changes when we change the characteristics
of the disease. This thesis demonstrates the ability to use a canonical path on
a smaller, country-level scale, by using United States (US) state level data to
create the US canonical path. We also determine the model structures necessary
to simulate the canonical path, which suggests that the canonical path
method is most useful for eradicable diseases for which we have ample knowledge
of the disease, including the natural history of infection and vaccination.
We also predict how the path is affected by the pattern of seasonality and by
the natural history of infection. Overall, the analysis suggests that the more
this method is implemented for other countries that have eliminated measles or
for other diseases for which we have achieved elimination, we may gain insight
of the successes and failures of elimination strategies. This knowledge could
help the WHO and other organizations improve their disease elimination and
eradication strategies in the future.

abstract: Thesis

abstract: Master of Science (MSc)


title: The Impact of Gendered Organizations on Worker Well-Being

contributor:
Young, Marisa
Sociology

subject:
work
gender
mental health

abstract: The ways in which paid work influences mental health and well-being is a topic of great interest to researchers focused on the social determinants of health. A primary focus in the literature has included the various conditions of work that can have both positive or negative effects on the mental health and well-being of workers. However, this perspective tends to disassociate the worker from the larger organizational context in which they are embedded. My dissertation addresses this limitation by examining the ways in which the organization and the workplace intersect to influence worker mental health and well-being through a gendered lens. Using data from the 2005 American Work Stress and Health survey, results from my research suggest that the gendered nature of organizations may matter more for worker mental health and well-being than work conditions or individual-level gender. Findings also suggest that this is dependent on both the occupation and workplace, and that consequences of the gendered organization can manifest in day-to-day interactions between workers.

abstract: Dissertation

abstract: Doctor of Philosophy (PhD)


title: Effects of several defects on the electroluminescence of 4H-SiC

contributor:
Kitai, Adrian
Materials Science and Engineering

subject: 4H-SiC, defects, EL

abstract: Silicon carbide is known for its potential in high power, high radiation and high temperature applications. It is also one of the first materials observed with phenomenon of electroluminescence. Depending on the mechanism of recombination, carriers inside silicon carbide recombine and release photons at different wavelengths. As one of the third-generation semiconductors, many studies focus on the effects of defects on silicon carbide device stability and performance. Especially for defects like stacking faults, which can be generated either during fabrication or induced by current under forward bias, can cause severe device degradation and limits the use of silicon carbide. By testing electroluminescence of silicon carbide, one can analyses the recombination event and identify the defects that trapped carriers, as each recombination mechanism would be shown as a unique emission peak on the sample EL spectra. In addition to the as-grown and recombination-induced defects, the changes of spectrum due to stress and chemical etching indicate the influence of external factors to the defects that are either existed prior to the external forces or that were induced during the testing. Such analysis could be helpful to understand the defect generation mechanism, reduce the density of the defects and to create innovative ideas for future applications. A general introduction to silicon carbide will be given in Chapter 1 with some detailed description of silicon carbide defect generation and characterization mechanisms in Chapter 2. In Chapters 3 and 4, the focus is to analyse the external effects to the spectrum of 4H silicon carbide, like chemical etching and mechanical stress. Before giving the conclusion in Chapter 6, Chapter 5 will be focusing on analysing the effect of external forces on the silicon carbide with stacking faults existed prior to the testing.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: Efficient Implementation & Application of Maximal String Covering Algorithm

title: MAXIMAL COVER ALGORITHM IMPLEMENTATION

contributor:
Smyth, William F.
Mhaskar, Neerja
Computing and Software

subject:
String
Maximal Cover
Repeats
MAXCOVER
protein sequence
pattern matching
NE repeat
MUMmer

abstract:
This thesis describes the development and application of the new software MAXCOVER that computes maximal covers and non-extendible repeats (a.k.a. “maximal repeats”).

A string is a finite array x[1..n] of elements chosen from a set of totally ordered symbols called an alphabet. A repeat is a substring that occurs at least twice in x. A repeat is left/right extendible if every occurrence is preceded/followed by the same symbol; otherwise, it is non-left/non-right extendible (NLE/NRE). A non-extendible (NE) repeat is both NLE and NRE. A repeat covers a position i if x[i] lies within the repeat. A maximal cover (a.k.a. “optimal cover”) is a repeat that covers the most positions in x.

For simplicity, we first describe a quadratic O(n2) implementation of MAXCOVER to compute all maximal covers of a given string based on the pseudocode given in [1]. Then, we consider the logarithmic O(n log n) pseudocode in [1], in which we identify several errors. We leave a complete correction and implementation for future work. Instead, we propose two improved quadratic algorithms that, shown through experiments, will execute in linear time for the average case.

We perform a benchmark evaluation of MAXCOVER’s performance and demonstrate its value to biologists in the protein context [2]. To do so, we develop an extension of MAXCOVER for the closely related task of computing NE repeats. Then, we compare MAXCOVER to the repeat-match feature of the well-known MUMmer software [3] (600+ citations). We determine that MAXCOVER is an order-of-magnitude faster than MUMmer with much lower space requirements. We also show that MAXCOVER produces a more compact, exact, and user-friendly output that specifies the repeats.

Availability: Open source code, binaries, and test data are available on Github at https://github.com/hollykoponen/MAXCOVER. Currently runs on Linux, untested on other OS.

abstract: Thesis

abstract: Master of Science (MSc)

abstract:
This thesis deals with a simple yet essential data structure called a string, a sequence of symbols drawn from an alphabet. For example, a DNA sequence is a string comprised of four letters.

We describe a new software called MAXCOVER that identifies maximal covers of a given string x (a repeating substring that ‘covers’ the most positions in x). This software is based on the algorithms in [1]. We propose two new algorithms that perform faster in practice.

We also extended MAXCOVER for the closely related task of computing non-extendible repeats. We compare this extension to the well-known MUMmer software (600+ citations). We find that MAXCOVER is many times faster than MUMmer with much lower space requirements and produces a more compact, exact and user-friendly output.


title: Anomaly Detection in Videos Based on Unsupervised Learning

contributor:
He, Wenbo
Computing and Software

abstract:
Anomaly detection for videos serves an important role in real-world applications. There are two types of anomaly detection for videos: anomalous video detection and anomalous event detection. Anomalous video detection is related to organizing video resources, which enables video-sharing platforms or public sectors to focus on the entire video belonging to the certain category; anomalous event detection in videos is applicable in the scenarios like monitoring in smart homes, smart cities and Internet of Things, which allows surveillance cameras to upload events of interest only so as to suppress the network traffic and reduce storage space in the cloud.

The two types of anomaly detection for videos are challenging. Due to the unavailability of abnormal samples, it is a cumbersome task to train an end-to-end deep supervised learning model. Meanwhile, video data representation is challenging because of the unstructured scheme of video contents. In this paper, we propose different methods for the two tasks.
For anomalous video detection, we propose a LSTM-autoencoder-based adversarial learning model (“VidAnomaly”) without abnormal samples in the training stage. LSTM-autoencoder learns the temporal dependence of the input sequence and reconstructs the input sequence for adversarial learning. In the inference stage, for a given input abnormal sample, the model poorly reconstructs the sample and the reconstruction error would be high because the proposed model is trained merely on normal samples and its parameters are only suitable for reconstructing normal samples. Based on the high reconstruction error, we detect abnormal samples.
For anomalous event detection in videos, we propose Onsite Event Detection (OED), a system that enables real-time event detection on edge. OED first trains a transformer-based autoencoder to learn the spatial-temporal representation of video data observed recently. Then it gains the ability to differentiate eccentric data patterns of events from routine. OED also features an updating strategy that adapts to the changing environment dynamically. As such, OED is capable of continuously detecting events of interest in video streams.

We evaluate our approaches on different datasets in various scenarios (anomalous video detection and anomalous event detection in videos). The experimental results show that our approaches are effective and superior to other methods.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: Development of Data-Driven Models for Membrane Fouling Prediction at Wastewater Treatment Plants

contributor:
Li, Zoe (Zhong)
Baetz, Brian
Civil Engineering

subject: Membrane fouling, membrane bioreactor, wastewater treatment plant, uncertainty analysis, transmembrane pressure, random forest, long-short term memory, artificial neural network

abstract: Membrane bioreactors (MBRs) have proven to be an extremely effective wastewater treatment process combining ultrafiltration with biological processes to produce high-quality effluent. However, one of the major drawbacks to this technology is membrane fouling – an inevitable process that reduces permeate production and increases operating costs. The prediction of membrane fouling in MBRs is important because it can provide decision support to wastewater treatment plant (WWTP) operators. Currently, mechanistic models are often used to estimate transmembrane pressure (TMP), which is an indicator of membrane fouling, but their performance is not always satisfactory. In this research, existing mechanistic and data-driven models used for membrane fouling are investigated. Data-driven machine learning techniques consisting of random forest (RF), artificial neural network (ANN), and long-short term memory network (LSTM) are used to build models to predict transmembrane pressure (TMP) at various stages of the MBR production cycle. The models are built with 4 years of high-resolution data from a confidential full-scale municipal WWTP. The model performances are examined using statistical measures such as coefficient of determination (R2), root mean squared error, mean absolute percentage error, and mean squared error. The results show that all models provide reliable predictions while the RF models have the best predictive accuracy when compared to the ANN and LSTM models. The corresponding R2 values for RF when predicting before, during, and after back pulse TMP are 0.996, 0.927, and 0.996, respectively. Model uncertainty (including hyperparameter and algorithm uncertainty) is quantified to determine the impact of hyperparameter tuning and the variance of extreme predictions caused by algorithm choice. The ANN models are most impacted by hyperparameter tuning and have the highest variability when predicting extreme values within each model’s respective hyperparameter range.  The proposed models can be useful tools in providing decision support to WWTP operators employing fouling mitigation strategies, which can potentially lead to better operation of WWTPs and reduced costs.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: OPTIMIZATION OF LASER POWDER BED FUSION PROCESS  IN INCONEL 625 TOWARDS PRODUCTIVITY

contributor:
Elbestawi, Mohamed
Mechanical Engineering

subject:
Additive Manufacturing
Laser Powder Bed Fusion
Inconel 625
Process Optimization
Powder Layer Thickness
Density
Hardness
Productivity

abstract:
Laser Powder Bed Fusion (L-PBF) is a metal additive manufacturing technique that uses a laser beam as a heat source to melt metal powder selectively. Because of the process small layer thicknesses,  laser beam diameter, and powder particle size, L-PBF allows the fabrication of novel geometries and complex internal structures with enhanced properties. However, the main disadvantages of the L-PBF process are high costs and a lengthy production time. As a result, shortening the manufacturing process while maintaining comparable properties is exceptionally beneficial.

Inconel 625 (IN625) is a nickel-based superalloy becoming  increasingly popular in marine, petroleum, nuclear, and aerospace applications. However, the properties of IN625 parts produced by casting or forging are challenging to control due to their low thermal conductivity, high strength and work hardening rate, and  high chemical complexity. Furthermore, IN625 alloy is regarded as a difficult-to-machine material. As a result, it is worthwhile to seek new technologies to manufacture complex-shaped IN625 parts with high dimensional accuracy. IN625 alloy is known for its excellent weldability and high resistance to hot cracking; thus, IN625 alloy appears to be a promising candidate for additive manufacturing.

This thesis presents an experimentally focused study on optimizing L-PBF processing parameters in IN625 superalloy to increase process productivity while maintaining high material density and hardness. This study had four stages: preliminary, exploratory, modelling, and optimization. The first stage was devoted to conducting a literature review and determining the initial processing parameters. The second stage concentrated on determining the process window, for  which single tracks were printed with two high levels of laser power (300, 400 W), five levels of scan speed (500, 700, 900, 1100, 1300 mm/s), and five levels of powder layer thickness (30, 60, 90, 120, 150 µm). Then, the process window was defined after investigating the top views and cross-sections of the tracks. Stage 3 involved printing 48 cubes (10 × 10 × 10 mm^3) with a laser power of 400 W, scan speeds of  (700, 900, 1100, 1300 m/s), layer thicknesses of (60, 90, 120, 150 µm), and overlap percentages of (10, 30, 50%). As a result, the density of cubes was measured, and a statistical multiple regression analysis was used to predict it. Stage 4 involved estimating four sets of ideal processing parameters (based on statistical modelling of relative density) and printing 24 cubes (10 × 10 × 10 mm^3), six samples for each set. Finally, the relative density, hardness, and productivity of the  samples were assessed, and a trade-off was determined.

Even with the thickest powder layer of 150 µm (highest process productivity), samples with a mean relative density greater than 99% (i.e., 99.31% by Archimedes principle and 99.82% by image analysis) were printed. These findings are consistent with previously published results for L-PBF IN625 samples manufactured with smaller layer thicknesses ranging from 20 to 40 µm while maintaining  comparable material hardness. The findings of this study are noteworthy because IN625 parts can be printed with higher powder layer thicknesses (less production time) while retaining similar material properties to those published with typical layer thicknesses ranging from 20 to 40 µm. Reduced production time due to optimized processing parameters can lead to significant energy and cost savings.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: Accounting for water levels when using water quality to assess the health of Great Lakes coastal marshes

contributor:
Chow-Fraser, Patricia
Biology

abstract: Coastal marshes are at the unique interface between land and lake water, which are home to unique wildlife. There are numerous freshwater coastal marshes along the Great Lakes coast that each have distinct geomorphologies which are home to different vegetation and fauna communities. The determination of coastal marsh health conditions is a necessity to assess influences of environmental stressors such as human-induced disturbances upstream of wetlands. Water quality indices (WQIs) are used to indicate the impacts of watershed alterations on the health of coastal marshes. It typically uses nutrient and sediment variables in the water column to assess to relate that to marsh health conditions. As coastal marshes are subjected to the constant fluctuation of water levels, it was found to be a significant factor that impacted WQI scores, likely due to the dilution effect. With increasing water levels, WQI scores also generally increased which indicated improved wetland health. Thus, it is a confounding variable against land-use and land-cover (LULC) alterations within the watershed. This study is the first to evaluate the dilution effect by relating the change of WQI scores to the change in wetland volume and wetland area. As well, it is the first to test the confounding effects of varying watershed coverage in LULC, long-term lake level ranges, and the hydrogeomorphology of coastal wetlands.

abstract: Thesis

abstract: Master of Science (MSc)


title: Multibody Dynamics Problems in Natural Coordinates: Theory, Implementation and Simulation

contributor:
Nedialkov, Ned
Computational Engineering and Science

subject:
multibody
Lagrangian
natural coordinates
automatic differentiation

abstract:
We present a framework for modeling multibody systems based on the method of natural coordinates and Lagrange's equation of the first kind,
resulting in a system of Differential-Algebraic Equations (DAEs). The
C++ package  DAETS (DAEs by Taylor Series), a robust high-index DAE solver, is utilized to solve the models. The simulation process is straightforward, with no need to derive  equations of motion directly. Instead, the user supplies a  Lagrangian, kinematic constraints, and if applicable, a  dissipation function and external forces. A corresponding system of DAEs is formed by computing the required derivatives via automatic differentiation. DAETS primarily uses Cartesian coordinates as variables, eliminating angles and the associated trigonometric functions, which results in simplified models. Furthermore, DAETS provides direct access to the position/velocity data of any desired points or vectors as output, facilitating post-processing tasks, such as visualization. The main focus of this thesis is on establishing the viability of our framework through case studies. We simulate seven multibody systems and compare our results with those of reference models developed in the Simulink environment of MATLAB. A detailed account of the modeling process is given for each system, demonstrating the ease and intuitiveness of our approach. We also provide, from both DAETS and Simulink, the time history plots of several position coordinates to allow for direct comparison. Finally, we compute two types of errors over time. Our findings show that the results of DAETS match those of the reference models under different error tolerances for the studied systems, indicating that our framework is capable of simulating a wide variety of mechanisms with a superb degree of accuracy.

abstract: Thesis

abstract: Master of Science (MSc)


title: Determining the Molecular Function of a Translesion DNA Synthesis Complex

contributor:
Andres, Sara
Biochemistry and Biomedical Sciences

subject:
bacteria
DNA damage
DNA repair
polymerase
DNA binding
structural biology

abstract:
Translesion DNA Synthesis (TLS) is a mechanism that promotes DNA damage tolerance during DNA replication using an error-prone DNA polymerase complex. The complex is comprised of the ImuA, ImuB, and ImuC proteins that are found in approximately one-third of bacteria, including high priority antimicrobial resistant pathogens, such as Pseudomonas aeruginosa. Previous in vivo studies have shown that TLS increases beneficial bacterial mutations as the error-prone DNA polymerase, ImuC, lacks proof-reading activity. However, how ImuA and ImuB proteins contribute to the polymerase mechanism is unknown. Thus, the goal of this study is to characterize the TLS proteins in vitro to determine how ImuA and ImuB associate with ImuC to promote error- prone replication.
ImuA and ImuBNΔ34 were successfully purified for biochemical characterization from the homolog Myxococcus xanthus. Using size-exclusion chromatography coupled to multi-angle light scattering, both ImuA and ImuBNΔ34 are trimers in solution. Each protein also binds DNA independently as assessed by fluorescence polarization. Interestingly, both proteins bind ssDNA and a 3’ overhang substrate mimicking the DNA replication intermediate with the highest affinity. DNA binding assays further confirm these proteins can form a DNA-ImuA-ImuBNΔ34 complex. Using bacterial two-hybrid assays, the ImuA- ImuB interaction occurs in the C-terminal region of both proteins. Overall, these results suggest that ImuA and ImuB may recruit and stabilize ImuC on DNA for replication past damaged DNA, providing the first insights into the ImuA and ImuB molecular mechanism.

abstract: Thesis

abstract: Master of Science (MSc)


title: Effect of Solutionizing Heat Treatment and Hot Uniaxial Tensile Deformation on Ductility and Subsequent Age-hardening Characteristics of AA7075 Aluminum Sheet

contributor:
Jain, Mukesh
Zurob, Hatem
Mechanical Engineering

abstract:
Aluminum alloy AA7075 in sheet form has been extensively used in the past for structural applications due to its higher strength to weight ratio compared to the other aluminum structural alloys. In recent years, it has attracted much interest in the automotive industry for making parts by hot stamping due to its higher potential for weight reduction and albeit its poor room temperature formability compared to the other softer lower strength aluminum alloys. Hot stamping involves heating the blank to the solution heat treatment (SHT) temperature, followed by hot stamping and in-die quenching to generate a supersaturated solid solute (SSSS). The formed part is then artificially aged to achieve a T6 peak-strength. The hot deformation behavior and final strength of AA7075 sheet is dictated by the microstructural evolution, during hot stamping, which in turn is governed by the pre-forming heat treatment variables such as cooling rate, holding time and intermediate deformation temperature.
In the present work, the pre-forming heat treatment variables were systematically varied using a dilatometer based mechanical test system to establish a comprehensive understanding of the effect of process variables on microstructural evolution and corresponding mechanical properties of AA7075 in uniaxial tensile mode, and under solutionized and non-solutionized conditions. The relationships between formability (including strain heterogeneity, strain localization, void damage and fracture) and microstructural and texture characteristics (during and post deformation) of this alloy were investigated using in-situ uniaxial tension, ex-situ SEM (SEM-EBSD and SEM-fractography), X-ray diffraction and X-ray computed tomography methods under solutionized and non-solutionized conditions. Further, the effect of hot stamping process variables along with a typical pre-strain value on artificial aging response was also investigated. The solutionized samples performed better than the non-solutionized samples when deformed at 400 °C and showed considerably higher elongation compared to 300 °C. The non-solutionized samples at 450 °C produced better elongation compared to the solutionized samples. It was found that the arrangement of precipitates with respect to the grain boundaries played a critical role in plasticity, flow localization, damage development and fracture at the various deformation temperatures.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: Intergenerational Relations in Later Life: Theory, Co-Housing, and Social Dynamics

contributor:
Grenier, Amanda
Health and Aging

subject: Intergenerational Learning, Contemporary Dynamics, Theoretical Frameworks, Intergenerationality, Intergenerational Landscapes; Co-housing; Ageism

abstract: With the rise of intergenerational programming (e.g., intergenerational co-housing) across Canada and a demographic shift whereby the number of people 65 years and over is expected to almost double from 13.2% to 24.5% by 2036, mechanisms supporting intergenerational relations are crucial. Intergenerational landscapes (IL) is a term I use to describe all that is across, between, and within generational cohorts. The conceptual understandings of intergenerational landscapes and how they could be beneficial (or detrimental) in later life require revisiting in gerontological research. This dissertation uses a multi-method qualitative design to examine conceptual frameworks, experienced relations, and contemporary dynamics of IL. I am investigating IL at diverse locations of experience emphasizing the voices of both older and younger people. This includes, a conceptual review of intergenerational knowledge (Paper One), the intersections of intergenerational dynamics in a co-housing setting (Paper Two), and an autoethnographic account of managing an intergenerational co-housing project (Paper Three). This dissertation focuses on conceptual models, how paradigms of IL are reproduced in practice, and how contemporary dynamics are experienced in a Canadian context. This thesis aims to initiate a meaningful dialogue on how current theorizing requires revisiting, given the contemporary landscape. This thesis supports the advancement of academic knowledge, programming, and public policy in aging research.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)

abstract: The aim of this thesis is to understand how contemporary conditions, such as population aging, may influence intergenerational relations. In this dissertation, I examine conceptual understandings, social influences, and people’s experiences of intergenerational co-housing. In the first section of this dissertation, I suggest a new language to discuss the 'intergenerational’ and highlight the importance of critical gerontological perspectives. I then examine how participants of an intergenerational co-housing program experience their living arrangement against a backdrop of contemporary change through a critical realist lens. I then turn to an autoethnographic account of managing an intergenerational co-housing project that sheds light on features of contemporary society that impact intergenerational realities. Finally, this research suggests ways to better discuss and debate intergenerational ideas and how they are related to aging, the field of gerontology, and older people.


title: Design for Additive Manufacturing of high performance heat exchangers

contributor:
Elbestawi, Mo
Mechanical Engineering

subject:
Additive Manufacturing
Heat Exchangers
Laser Powder Bed Fusion
Intercooler
Charge air cooler
Gyroid

abstract:
Heat exchangers are integral parts for thermal management and find countless applications
in automotive, aerospace, energy, nuclear power plants, HVAC, etc. Due to
intensive research & development and technological advancements in manufacturing
technologies, there is an increasing rise in demand for high-performance heat exchangers.
In the automotive and aerospace industries, heat exchangers are expected
to deliver better thermal efficiency and improve the system’s overall functionality in
which they are installed by saving space and being lightweight. Additive Manufacturing
(AM) is a ground-breaking and promising technology that offers avenues of
opportunities to manufacture parts that were almost impossible to be produced with
conventional manufacturing and can improve part performance with lightweight and
compact designs. Laser-Based Powder Bed Fusion (LPBF), one of the well-known
AM techniques, provides freedom to design complex geometries and fabricate them
in a layer-by-layer fashion by exposing a high-density laser on a vertically moving
powder bed.
The study focuses on the application of AM in re-designing heat exchangers under
given design requirements using LPBF. It includes exploring Triply Periodic Minimal
Surfaces (TPMS) based structures such as gyroid and realizing them as heat exchanger
core. Computational gyroid-based heat exchanger core models were designed and
analyzed for thermal and fluid dynamics characteristics. A parametric study and
analysis based on gyroid TPMS network type, periodic length, thickness, aspect ratio,
and functional grading were carried out to optimize heat exchanger performance as
per design conditions and validate their manufacturability using LPBF. Successful
printable designs were further used to develop and manufacture prototypes.
The study concludes with a comparison between additively manufactured gyroid-based
design and conventional shell-and-tube design based on the thermal performance
from CFD analysis and the weight of prototypes. It was found that the thermal
performance from CFD analysis showed an 18.96% improvement, whereas weight
was reduced by 14.8% for the gyroid-based design as compared to the conventional shell-and-tube design.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: Genetic and Chemical Targeting of the Gram-Negative Outer Membrane to Potentiate Large-Scaffold Antibiotics

title: GENETIC AND CHEMICAL TARGETING OF THE OUTER MEMBRANE

contributor:
Brown, Eric
Biochemistry and Biomedical Sciences

subject:
outer membrane
antibiotics

abstract: The outer membrane (OM) is a formidable barrier that has made antibiotic drug discovery in Gram-negatives exceedingly difficult. Many antibiotics which are effective against Gram-positive bacteria cannot permeate the Gram-negative OM to reach their intracellular targets. Thus, it is important to explore unconventional approaches to overcome the intrinsic resistance conferred by the OM. Herein, we used both genetic and chemical means to compromise OM integrity to potentiate the activity of large-scaffold antibiotics against Escherichia coli. First, we mapped the genetic interaction network of OM biosynthetic genes using synthetic genetic arrays (SGAs) to reveal permeability determinants of the E. coli OM. This led to the creation of a publicly accessible dataset of ~155,400 double deletion strains with growth data in the presence of the large-scaffold antibiotics rifampicin and vancomycin. Investigations of a subset of synthetic sick interactions revealed connectivity in the context of permeability between lipopolysaccharide (LPS) inner core biosynthetic genes and an enigmatic gene involved in enterobacterial common antigen (ECA) regulation. Second, we leveraged a chemical screening platform based on the observation that disruption of the E. coli OM leads to antagonism of vancomycin activity at cold temperatures to uncover molecules that potentiate Gram-positive-targeting antibiotics at 37 ºC. Two of these compounds, liproxstatin-1 and MAC-0568743, were characterized to bind to LPS and disrupt OM integrity specifically without impacting the inner membrane (IM). Third, we performed genetic and chemical screening to unearth targets capable of potentiating the activity of Gram-positive-targeting antibiotics against E. coli. This validated the OM as a valuable target for antibiotic adjuvants and led to the discovery of two membrane active compounds and an inhibitor of lipid A biosynthesis. Overall, this thesis emphasizes the importance of elucidating biological factors contributing to OM permeability and the attractiveness of the OM as a target for antibiotic potentiators.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: MORPHOLOGICAL AND IDENTITY PRIMING IN WORD LEARNING AND TEXT READING AS A WINDOW INTO THE MENTAL LEXICON

contributor:
Kuperman, Victor
Humanities

subject:
reading
word learning
morphological priming
corpus-based research
eye-tracking

abstract:
This thesis examines the influence of morphological and identity priming to understand how repetition influences word recognition and novel word learning in first (L1) and second (L2) language adults. The following questions are addressed: How does morphological relatedness between repeated words influence (i) word recognition in natural reading and (ii) novel word learning? (iii) What interactions exist between word repetition and selective attention in novel word learning?
Chapter 2 addresses question (i), finding little evidence of morphological priming effects (i.e., faster recognition of a word following a morphologically related word) in L2 reading, and none in L1. The effects of identity priming were ubiquitous in both groups.
Chapter 3 examines question (ii) for L1 readers. Low-frequency base words (e.g., caltrop) and novel complex forms (e.g., caltroper) of those bases were primed by two repetitions of identical forms or alternate forms. Learning performance was consistently as good or better after identity priming than after morphological priming. However, orthographic and semantic learning for base forms was stronger in the morphological priming condition.
Chapter 4 examines question (iii). Attention was manipulated by delivering attention-inducing instructions, while the control group received no instructions. Exposure was manipulated by embedding novel words either 2, 4, or 8 times. The presence of instruction led to a short-lived speed-up in eye-movements and faster recognition of novel words. Critically, L1 learners reached optimal performance in the post-tests earlier (after 4 exposures), while L2 learners’ performance continued to improve through more exposures.
Overall, this thesis shows that morphological priming facilitated L2 visual word recognition and L1 novel word learning when a complex form is a prime, and the base form is a target. We discuss reasons for this asymmetric effect and these results in the framework of the theories of word learning and morphological processing.

abstract: Dissertation

abstract: Candidate in Philosophy


title: Development of Deposition-Controlled Printhead for Printing Multifunctional Devices

contributor:
Selvaganapathy, Ravi
Mechanical Engineering

subject:
Multimaterial 3D-printing
Silicone elastomer
Graded materials
Microfluidics
Fast Switching
Soft robotics
Passive mechanical control system
nonplanar surfaces

abstract: 3D printing technology, which has its origins in rapid prototyping, is increasingly used to build functional devices. Although 3D printing technology has been well developed for thermoplastic polymers and metals, it is still in the research phase for soft polymeric materials such as silicones. Silicones are an industrially vital polymer characterized by a broad spectrum of chemical and physical properties for several smart applications, including on skin printing, smart sensors, multigradient material, and soft actuators. Extrusion-based multimaterial printing is one of the 3D printing techniques that have been adapted due to its compatibility to process silicone-based materials for constructing various functional devices. However, there are several challenges such as achieving on the fly mixing at low Reynolds numbers regime, achieving fast switching while using Newtonian/non-Newtonian inks, and achieving multimaterial printing on nonplanar surfaces. The development of suitable and robust printheads that are able to tackle those challenges can expand the application of this technology to a wide range of fields. In this thesis, several deposition-controlled printhead designs have been created for 3D printing multifunctional devices using an understanding of microfluidics. The established printhead can be controlled to formulate different multigradient structures through on the fly mixing during the material printing. Moreover, the developed printhead can be adapted to print multi viscous inks with high switching rates up to 50 Hz. Through the developed system, the printhead was able to track topologies in real-time, allowing objects to be printed over complex substrates. These new capabilities were applied to fabricate functional structures in order to demonstrate the potential of the developed printhead approaches that can be used in various applications, including smart sensors, soft robotics and multigradient objects.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)

abstract: 3D printing techniques, such as extrusion-based multimaterial printing, have recently been utilized to process silicones due to their versatility in different smart applications, including multigradient material and soft actuators. Although it represents significant progress, there are still several challenges, including the proper mixing during printing with a laminar flow regime, the fast switching between different inks, and the printing over complex topographies. Therefore, various printhead designs have been developed in this thesis to tackle these challenges. In particular, a mixer printhead has been designed to allow mixing during printing for building multigradient objects. Also, a scalable printhead has been developed to allow fast switching for creating pixelated structures. Finally, a simple mechanical system has achieved multimaterial printing over various nonplanar surfaces. To the best of the author's knowledge, the developed printheads can be used in many fields, such as soft robotics and smart devices.


title: On the Modeling and Suppression of Electromagnetic Interference Emissions of Power Converters

contributor:
Emadi, Ali
Bilgin, Berker
Electrical and Computer Engineering

abstract:
Electromagnetic interference (EMI) issues are associated with high-speed switching of power converters. EMI modeling is an essential tool to study and control the EMI emission, enabling more efficient solutions. A comprehensive review and comparison of different modeling approaches for conducted emissions are provided in this paper, which can be used as a design guideline for engineers. Electromagnetic compatibility (EMC) measurement devices and testing procedures are also reviewed for power converter applications. This overview would help the reader to obtain a better understanding of the EMC testing procedure, requirements, and the EMC measurement devices.
Afterwards, conducted emissions in a three-phase inverter fed motor drive is studied. A physics-based model is derived for each part of the system using a device characterization tool, a finite element analysis tool, and impedance curve fitting tools. An improved universal equivalent circuit is proposed to model the induction motor in the entire frequency range. A balanced approach regarding the accuracy and simplicity of the model is considered through the model extraction. Furthermore, common mode and differential mode emissions are studied, and two equivalent circuits are extracted.

Spread spectrum modulation techniques have been proven to be an effective solution to suppress the conducted electromagnetic emissions of power converters.
Various modulation methods are investigated for an active neutral point clamped (ANPC) inverter. The effect of EMI receiver and intermediate filter bandwidth is also considered in the modeling. Furthermore, a new unified model is proposed for an active neutral point clamped inverter based on the existing equivalent circuit models for common mode (CM) EMI and the developed DM model. In another approach to reduce the EMI emissions, a new hybrid CBPWM strategy is proposed that not only eliminates the neutral point voltage oscillations but also reduces the common mode voltage (CMV) by half. Furthermore, the harmonic content of the output voltage is reduced by adjusting the modulation waves based on the location of the reference vector in the space vector diagram. An active neutral point voltage controller is also presented and applied in order to maintain the performance of the modulation strategy under the NPV perturbations. Modeling and simulation results are validated by experimental results.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: The Role of Biomechanical Cues in Mechanotransduction and Breast Cancer Metastasis

contributor:
Geng, Fei
Mechanical Engineering

subject:
Mechanotransduction
Biomechanical
Breast cancer
Metastasis
Stiffness
Yes-Associated-Protein

abstract: Breast cancer metastasis to the brain is one of the most lethal forms of metastases. Metastasis is regarded as a non-random process governed by several biomechanical factors including tissue stiffness. As brain tissue is ultrasoft and extremely heterogeneous compared to breast cancer primary sites; how are breast cancer cells able to colonize the vastly different microenvironment of the brain? As a key protein of the Hippo pathway, YAP is regarded as a mechanotransducer that is sensitive to changes in substrate stiffness. Its biochemical activity is intertwined with Piezo1, a mechanosensitive ion channel activated through plasma membrane deformation. To impact cellular function, YAP enters the nucleus and binds to the TEAD transcription domain triggering downstream expression of proteins involved in cell motility, wound healing, and metastasis. In this work, triple-negative breast cancers (TNBC) were shown to experience greater migration rates on stiff surfaces compared to soft PDMS substrates. Concurrently, cells showed YAP nuclear localization in a stiffness dependent manner. Then, mechanical characterization of human brain tissue was performed to characterize the stiffness heterogeneity in the brain associated with region specific metastasis. Five to six regions of the brain from two different patients showed similar patterns of stiffness heterogeneity with the anterior regions being generally stiffer than posterior regions. As Piezo1 is directly linked with detecting changes in biomechanical stimuli, it was used as a readout of surface stiffness to examine if cells in the brain could detect different regional stiffnesses. Comparisons of grey and white matter showed no significant difference in Piezo1 expression. As a drug screening framework, molecular dynamic simulations were performed to evaluate drug efficacy on well-characterized inflammatory mediators that are implicated in metastasis. These findings contribute to understanding the gap in knowledge surrounding the interplay between tissue stiffness and YAP mechanotransduction in the context of breast-to-brain metastasis.

abstract: Thesis

abstract: Master of Applied Science (MASc)

abstract: Breast cancer is the most common cause of cancer related deaths in women particularly when it spreads to the brain. The brain is composed of many different sub-locations comprised of different proteins that can change the tissue’s stiffness. Breast cancer can detect these changes and become more aggressive in its growth using a combination of proteins such as yes associated protein (YAP) and Piezo1. How these proteins interact in the context of breast to brain cancer metastasis however is poorly understood. This project examined the effects of surface stiffness, on YAP, and Piezo1 activity to understand how breast cancer and brain cells react to changes in surface stiffness. Results showed that on stiff surfaces YAP activity affects cancer cell migration. Also, human brain tissue was found to vary in stiffness depending on the region examined. Future investigations may shed light on therapies that could take advantage of learnings in this area to better target the spread of breast cancer.


title: Evaluation of Safety Transients in Helical Coil Steam Generators with RELAP5-3D Code

contributor: Engineering Physics and Nuclear Engineering

subject:
small modular reactors
safety analysis
nuscale
helical coil steam generators
relap5

abstract:
Around the world, countries are increasingly considering carbon-free energy generation
options as the threat of climate change grows. Small modular reactor designs,
promising such carbon-free energy generation, are thriving worldwide with novel and
innovative technologies that improve safety as well as economic performance. Canada
is also considering small modular reactors (SMRs) as a means of achieving net zero
carbon emissions by 2050.
Some of these reactor designs utilize pressurized water for cooling and moderator.
Reactors with pressurized water have been subjected to steam generator tube ruptures
in the past, and a detailed investigation into the possible consequences of such incidents
in SMRs should be conducted.
In this research, a model for one of the newer designs, the NuScale Integrated Small
Modular Reactor, was developed with the RELAP5-3D code for assessing safety related
transients. The NuScale Small Modular Reactor incorporates helical coil steam
generators within its reactor pressure vessel, which are more efficient in terms of heat
transfer than the U-tube steam generators that are widely used in nuclear reactors.
In the first part of the research, a detailed model is created and used to obtain steady
state conditions with parameters collected from NuScale’s Final Safety Analysis Report
(FSAR). The Steam Generator Tube Rupture event is analyzed in the second part
of the work. Slight differences in the broken and intact steam generator pressures as
well as decay heat removal system flow rates are seen in the comparison of reference
values and calculated results. Among the reasons for those differences could be that
the correlations used by the RELAP5-3D code for heat transfer coefficient and pressure
drop in the helical coil steam generators are different than those of the NuScale proprietary
code NRELAP5, with which the analyses have been performed in the FSAR.
Also, post-dryout heat transfer at the exit of helical coil steam generators and evaporator
sections could cause differences in the outlet conditions of the steam, resulting in
different mass flow rates as well.
The final section of the research simulates a comparable but more severe tube rupture
incident without the availability of decay heat removal systems in order to assess
the reactor’s emergency core cooling system reaction. Passive decay heat removal systems
are crucial components for removing heat after reactor shutdown through heat
exchangers that are submerged in the reactor pool and connected to steam generators
by a closed loop. The containment pressures, the containment wall temperatures, and
the peak fuel clad temperatures are considered to be the key design constraints that
must be observed.
Future work on this subject could include modifying the source code, adding specific
correlations for helical coil steam generators, and comparing the results, as well
as quantifying uncertainties in the SGTR event. Main parameters in the quantification
of uncertainties would be reactor power, single phase and two-phase discharge coefficients
from the break, trip signals and delays as well as break size and location.

abstract: Thesis

abstract: Master of Applied Science (MASc)