title: The roles of midwives in health systems

title: Understanding the roles of midwives in political and health systems

contributor:
Lavis, John N.
Health Policy

subject:
health systems
midwifery

abstract:
There is a lack of conceptual clarity regarding the drivers of midwives’ roles within health systems, which has contributed to the significant variability both within and across countries in whether, to what extent and how midwives are integrated in these systems. This dissertation incorporated a mix of methodological approaches to address this gap. First, a critical interpretive synthesis was used to develop a theoretical framework that identifies the different types of policy levers that would be required to enhance to roles of midwives within any given health system, and an exploratory network analysis was used to analyze relationships among the ‘health system arrangements’ part of the framework and to identify gaps in the literature. Second, a logistic regression was used to examine the correlates of birth-experience satisfaction – as a patient experience component of the health system ‘triple aim’ – among women receiving care from midwives, family physicians and/or obstetricians in Ontario’s health system. Third, an embedded single-case study design and Kingdon’s agenda setting and the 3i+E theoretical frameworks were used to qualitatively assess how and under what conditions the Ontario health system has assigned roles to midwives. The research chapters build on each other and make substantive, methodological and theoretical contributions. Specifically, insights gained from the theoretical framework informed variable selection and definition for the quantitative analysis and were tested in the embedded single-case study. Substantively, the dissertation provides a rich understanding of the roles of midwives in health systems through a mix of qualitative and quantitative research evidence, adding to the evidence base that policymakers can draw from when making decisions regarding midwifery care.
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Methodologically, the dissertation introduces a novel combination of a critical interpretive synthesis and exploratory network analysis. Lastly, the dissertation advances the theoretical understanding of the roles of midwives within health systems through a new theoretical framework.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)

abstract: Midwives who are educated and regulated according to international standards can play important roles in the provision of maternal and newborn care. Yet, there is significant variation within and across countries in whether, to what extent and how the profession has been integrated in most health systems. A lack of understanding regarding these roles likely contributes to this variation. This dissertation addresses gaps in understanding through: 1) a framework, which can be used as a tool by policymakers to identify policy levers that would be needed to enhance to roles of midwives within any given health system; 2) supportive quantitative evidence on birth-experience satisfaction among women in Ontario’s health system who received care from midwives; and 3) examining in two reform efforts why many women continue to experience unmet midwifery needs in Ontario’s health system even though the government is generally supportive of the profession.


title: EFFECTS OF PROBIOTIC SUPPLEMENTATION ON INDUCING   REMISSION TO DRUG-FREE NORMOGLYCEMIA IN ADULTS WITH PREDIABETES – STUDY DESIGN.

contributor: Clinical Epidemiology/Clinical Epidemiology & Biostatistics

subject:
study design
protocol
randomized controlled trial
diabetes
probiotics

abstract: Study design of a randomized-controlled trial investigating the effects of probiotic supplementation on induction of prediabetes remission to normoglycemia in adults with prediabetes.

abstract:
BACKGROUND: Patients with prediabetes are at a high risk of developing type 2 diabetes (T2D) and the current strategies to prevent the progression of prediabetes to T2D are difficult to implement at the population level. Recently, the role of gut microbiota has emerged as a possible link to metabolic disease. The modulation of the gut microbiota in individuals with prediabetes through probiotic supplementation may improve metabolic dysfunction and induce remission of prediabetes to normoglycemia.
OBJECTIVES: The primary objective of this trial is to determine the effect of 900 billion CFU/day of VSL#3®, a multi-strain probiotic supplement for 20 weeks, on induction of drug-free remission to normoglycemia (HbA1c<6.0%) in adults with prediabetes compared to placebo 20 weeks post-randomization.
METHODS: In a randomized, triple-blind, controlled multi-centre trial, 568 adults with prediabetes will undergo a 2-week run-in after which they will be randomly allocated to 20 weeks of either 900 billion CFUs of VSL#3® per day or placebo. Prediabetes remission will be measured using HbA1C at week 20 and 32. Change in insulin resistance (HOMA-IR), beta-cell function (HOMA-B), weight, BMI, waist circumference and fecal relative abundance of bacteria will be measured from baseline at week 20 and 32. Exploratory regression analyses will involve a multiple logistic regression model to assess whether the change in relative abundance of the Rosburia genus from baseline at week 20 is an independent predictor of drug-free prediabetes remission at week 20.
DISCUSSION: Individuals with prediabetes are at high risk of developing T2D and the induction of prediabetes remission would be important to patients and clinicians. The role of microbiota in metabolic processes presents the potential for therapeutic applications of probiotics. If successful, probiotics would offer a therapeutic option for reversing prediabetes to normoglycemia that is simple, cheap and easy to incorporate into standard clinical care.

abstract: Thesis

abstract: Master of Science (MSc)

abstract:
BACKGROUND: Patients with prediabetes are at a high risk of developing type 2 diabetes (T2D) and the current strategies to prevent the progression of prediabetes to T2D are difficult to apply at the population level. Recently, the role of gut bacteria has emerged as a possible link to metabolic disease. Changing the gut microbiota in people with prediabetes through probiotic supplements may improve metabolic function and result in remission of prediabetes to normal glucose control.
OBJECTIVES: The primary objective of this study is to determine the effect of VSL#3®, a probiotic supplement, for 20 weeks, on induction of drug-free remission to normal glucose control in adults with prediabetes compared to placebo, 20 weeks after randomization.
METHODS: In a randomized, triple-blind, controlled multi-centre trial, 568 adults with prediabetes will be randomly assigned to 20 weeks of either VSL#3® per day or placebo. Prediabetes remission will be measured using HbA1C at week 20 and 32. Change in insulin resistance (HOMA-IR), beta-cell function (HOMA-B), weight, BMI, waist circumference and fecal bacteria will be measured from baseline at week 20 and 32.
DISCUSSION: Individuals with prediabetes are at high risk of developing T2D and the induction of prediabetes remission would be important to patients and clinicians. The role of gut bacteria in metabolic health presents the potential for probiotics to be therapy options. If successful, probiotics would be simple, cheap and easy to incorporate into standard clinical care.


title: Three Essays on Health and Pension Economics

contributor:
Sweetman, Arthur
Economics

abstract:
This thesis comprises two essays in health economics and one on pension economics. The first two essays use the institutional changes (mainly physician payment changes) of primary care reform in Ontario to study the impact of financial incentives on physician behavior and continuity of care. Specifically, we focus on two major primary care physician/General Practitioner (GP) payment model transitions in the reform: from traditional fee-for-service (FFS) to the enhanced FFS (referred as the first transition), and from enhanced FFS to blended capitation (referred to as the second transition). The first essay uses the second transition as a quasi-natural experiment and explores how the payment structure in the blended capitation model influences the provision of health care services by GPs and their practice groups. The second essay uses the first and second transitions to examine the association between continuity of care and patient rostering that is incentivized by premiums and bonuses in the enhanced FFS and the blended capitation model. The last chapter diverges from this topic and addresses one aspect of social insurance, namely pensions in China; it assesses how internal migrants and locals differ in terms of the pension contributions they make and the benefits they receive under the national policies that were recently introduced to reduce the fragmentation of the pension operations.The first chapter examines the switch in physician payment system from FFS to the blended capitation-FFS model on GPs’ billing behavior within a group practice. There are multiple dimensions of payment blending in the blended capitation model: first, a blend of capitation for services inside the capitated basket, which are quite commonly employed and represent a large proportion of the services offered by GPs, and FFS for services outside the basket; second, a blend of capitation and less than full-cost FFS payment for services inside the capitated basket; third, a blend of different payment mechanisms for rostering and non-rostering patients funded under blended capitation or traditional FFS ; fourth, a blend of pay for performance, capitation and FFS (Sweetman and Buckley, 2014). We provide both a theoretical model examining the provision of care inside and outside the capitated basket and an associated econometric analysis using comprehensive administrative data, and the second transition in primary care reform as a quasi-natural experiment. We construct a panel of continuously rostered patient-GP pairs and employ a propensity score weighted difference-in-differences approach to identify the impact of a change in the GPs’ remuneration model on the shifting of services across payment categories which are created by multiple blending dimensions. Consistent with the theory presented, rostering GPs provide fewer capitated services and simultaneously more FFS services. Other GPs within the rostering group reduce service provision within the capitated basket, with no change in FFS services. All other GPs in Ontario have relative reductions, both inside and outside the basket, which is consistent with GPs concentrating their primary care with rostered patients as a result of the introduction of the capitation payment model.
	The second chapter examines the impact of rostering on continuity of care, as measured indirectly by various indices, from both patients' and GPs' perspectives. The empirical analysis consists of two transitions, and three payment models with different ‘levels’ of rostering: traditional FFS has no rostering; enhanced FFS is termed as ‘weak’ rostering; blended capitation is termed ‘strong’ rostering. Estimation using propensity score weighted difference-in-differences with fixed effects is used in both transitions to identify the impacts of different ‘levels’ of rostering. Our results show that the strong patient rostering indeed strengthens the bond between patients and GPs in the second transition. Furthermore, GPs in the blended capitation model can also be combined with interdisciplinary teams to form Family Health Teams (FHTs). The FHT model performs better than the blended capitation model alone in keeping rostered patients within the rostering practice. However, we don’t find a significant increase of the continuity of care indices in the first transition, which is probably due to the rostering incentives behind enhanced FFS.
	The third chapter examines how the recent reforms to improve pension portability affect the relative pension treatment of migrants compared to locals in China. Using simulation methods, we compare how residents who differ in terms of their hukou, a record of household residence registration, and in their productive characteristics and geographic locations are treated by the pension system in one municipality. Shenzhen in the province of Guangdong is chosen as a representative developed urban city in China. Our results show that, even after recent reforms, migrants fare poorly compared to locals with hukou; migrants who transfer to another urban pension plan are likely to experience larger reductions in benefits than migrants who retired and remained in Shenzhen; the least benefits go to migrants who have contributed to urban plans for less than 15 years and hence have coverage only under the County and Rural Residents’ Plan. We also find that the pension replacement rate is inversely associated with income level and positively associated with the age of retirement.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: Investigating the role of the pulmonary innate immune system in anti-tuberculosis immunity

contributor:
Xing, Zhou
Medical Sciences

subject:
Dendritic Cell
Delayed T cell response
Mycobacterium tuberculosis
Innate immune response
AdHuAg85A
IL-10

abstract: M.tb, the causative agent of pulmonary tuberculosis (TB) remains one of the leading causes of infectious disease-based death worldwide.  BCG, the only clinically approved TB vaccine, has been in use for almost a century to vaccinate against TB. Despite its success in protecting against disseminated forms of TB, it is unable to provide protection against pulmonary M.tb infection. Although there have been many recent efforts to enhance or replace BCG, our lack of understanding towards host immunity against M.tb has substantially hindered this goal. One aspect of pulmonary M.tb infection that remains poorly understood is the induction of Th1 immunity, which is substantially delayed in comparison to other pulmonary infections. This allows the bacteria to establish an infectious foothold within the host and impairs the ability of the host to clear the infection. Given the importance of the innate immune response in the induction of adaptive immunity, this delay in the establishment of Th1 immunity following pulmonary M.tb infection is likely due to a defect in the early innate immune response. However, the specific roles of this immune compartment in regards to T cell activation following pulmonary M.tb infection is still not well understood. As such, the scope of this thesis is to gain an increased understanding towards the role of the innate immune compartment in the generation of Th1 responses. Such insights will allow us to develop new strategies to improve upon future and existing TB vaccine design.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: TWIN SCREW WET AND DRY GRANULATION

contributor:
Thompson, Michael
Chemical Engineering

abstract:
Twin screw granulation has gained wide interest by pharmaceutical manufacturing and the industry is still trying to expand its application. This thesis will further explore this technique and try to develop a new granulation strategy based on similar machinery setups.
This thesis is firstly focused on twin screw wet granulation by investigating the function of conveying elements upstream and downstream of the kneading blocks and the wetting behavior of ingredients, with immediate released and controlled released formulations, separately. Granular properties were found to be sensitive to the pitch of downstream conveying elements where larger and irregular shaped particles were found when higher pitch was used. Although these findings are consistent with the theories of granule growth proposed by earlier studies, chunks were prone to be produced when complicated formulations including hydroxypropyl methylcellulose (HPMC) were used but can be surprisingly diminished by higher barrel temperature. This is believed to relate to the wetting behavior of ingredients. Higher temperature was found to reduce water absorption capacity, particularly for HPMC due to the gel layer formation, which is proposed as the dominant bridging mechanism for particle growth at lower temperature. This water uptake as a function of temperature enables process modification to ensure equivalent wetting behavior amongst ingredients for proper particle size control.
Stimulated by the difficulties brought by the water addition as above and the needs from industry, a novel granulation strategy has been developed within a twin screw granulator by heat assistance which is significantly different from dry granulation in a roller compactor or conventional hot melt granulation. In twin screw dry granulation, particle combination is caused by the melting/softening of polymer binders which  occurred exclusively in the kneading block driven by the heat generated from frictional, conductive and plastic dissipation. By limiting the heat exposure for formulations, this new method has advantages over hot melt granulation by protecting the ingredients from thermal degradation. For parameters, higher screw speed and lower feed rates enabled more of the feed particles to increase in temperature in the granulation zone and hence develop stronger and larger granules for a given screw pitch. Formulations including a polymer binder with lower molecular weight could be granulated at lower screw speed and binder content by comparing two grades of hydroxypropyl methylcellulose with different molecular weights, AFFINISOLTM HPMC HME 100LV and 4M. In addition, formulations with a higher binder content were likely to granulate under a broader range of operating conditions and ingredients with extremely low coefficients of friction could retard the particle agglomeration by greatly reducing frictional heat generation.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)

abstract: Granulation is an important process to obtain a particular product known as “granules” which can be an intermediate between powder formulations and medical tablets in pharmaceutical industry. This thesis will further explore this granulation method by looking at screw configuration and the influence of heat from differing sources. Since screws can be configured with different components (screw elements), the study on functions of individual elements made up the first study in this thesis. The first section focused on twin-screw wet granulation where water is added during the process. The second body of work examined why particles were able to grow into granules by discussing the wetting ability of powders which affected by temperature. Because of disadvantages brought out by using water, a novel ‘twin-screw dry granulation’ technique was developed in this thesis using a similar screw configuration to twin-screw hot melt granulation. For this new technique, initial powder materials could be granulated directly without water addition. The last two sections in this thesis cover the new mechanism of granule growth by this technique, studying the influences of material and process parameters in order to provide guidance to the industry on its use and future research needed.


title: Assessing Functional and Structural Connectivity in Former Professional Athletes

contributor:
Noseworthy, Michael
Biomedical Engineering

subject:
Concussion
Magnetic Resonance Imaging
Football
Diffusion Tensor Imaging
Functional Magnetic Resonance Imaging
White Matter
Chronic Traumatic Encephalopathy
Mild Traumatic Brain Injury

abstract: Recently there has been considerable attention directed towards the increased risk for head injuries that athletes face while participating in high impact sports. Furthermore, there is also heightened interest in the asymptomatic sport related sub-concussive blows, commonly experienced during play, that possibly lead to long term neurological deficits. Purpose: The goal of this study was to investigate retired professional athletes of the Canadian Football League with a history of sport-related concussions, using several advanced MRI methods. The ultimate goal being the identification of any potential synergistic effects between a history of sport-related concussions, and exacerbated cognitive decline later on in life. Materials and Methods: Twenty former professional athletes of the Canadian Football League were scanned using a GE Discovery MR750 3T MRI with a 32-channel RF-coil. Axial FSPGR-3D images were used to define rs-BOLD and DTI scans. Seed based network analysis of the DMN was performed on rs-BOLD data. Voxel-wise tensor fitting of DTI data provided the means for estimating several tensor metrics. Results were normalized through comparison with a database of healthy controls. Potential associations between functional connectivity, white matter integrity, and cortical thickness measures were correlated with retired athlete position and years of professional play. Results: We found widespread cortical thinning in retired CFL subjects, alongside significant increases in axial and mean diffusivity in the corona radiata and splenium and genu of the corpus callosum compared to controls. Seed based correlation analysis of the DMN network revealed interrupted connectivity in retired athletes. Athlete age, po- sition, and number of years played appear to be factors in overall core white matter microstructural integrity. Conclusions: When compared to an age and sex matched control population, differences were observed both in functional and structural con- nectivity, suggesting that even years after retiring the brains of these former athletes still exhibit signs of damage.

abstract: Thesis

abstract: Master of Applied Science (MASc)

abstract: Sport-related concussions affect millions of athletes on a yearly basis in the United States alone. Concussions are often accompanied by short-lived neurological impairments, such as confusion, headaches, dizziness, nausea and memory loss. In addition, there is the potential for development of long term mental health and cognitive impairment. The goal of this work was to identify any neurological changes present in retired athletes of the Canadian Football League, through the use of advanced magnetic resonance imaging techniques evaluating thickness of brain structures, changes in brain activity, and alterations in core microstructure of the brain. Analyzing the results of these techniques revealed changes in a number of brain regions within the retired professional athlete population. These results suggest that a career of high impact sports may lead to short term, in addition to long-term neurological consequences.


title: Design and Control of a Miniature Rotary Robot Joint

contributor:
Bone, Gary M.
Mechanical Engineering

subject: design, control, miniature, rotary robot, joint, power-to-weight, magnetic field, feedforward controller

abstract: Over the past 20 years research into miniature actuators has been increasing. In addition to having a compact geometry, desirable characteristics for miniature actuators include having a large power-to-weight ratio, fast response, fine resolution of movement and high power efficiency. In the first part of this thesis the design of a miniature rotary robot joint is presented. Two single acting miniature cylinders each with a bore diameter of 4 mm drive the joint using water as the hydraulic fluid. The cylinders are mated to a rack and pinion mechanism that converts the opposing linear motion of the cylinders shafts into rotation. Also within the design, a novel position sensor using magnetic field sensing technology is presented. Overall, the joint measures 11 mm wide x 8.8 mm high x 150 mm long. In the second part of this thesis a hydraulic servo positioning system is presented along with a novel valve modeling technique and two position control strategies. Four low-cost, 3-way on/off solenoid valves were used to control the flow of the water in and out of the cylinders. The two nonlinear position controllers employed were a position-velocity-acceleration plus model-based feedforward controller (PVA+FF) and a novel PVA + FF plus sliding mode controller. For experiments involving horizontal rotation of the joint while carrying no load the PVA +FF controller achieved a steady-state error of ± 0.77° or ± 0.06 mm in terms of rack position. The steady-state error produced by the PVA + FF plus sliding mode controller was ± 0.85° or ± 0.07 mm. The maximum tracking error produced by both controllers was 5° or 0.41 mm and occurred during the initial cycloidal rising portion of a 120° displacement. The root mean square error (RMSE) of the PVA + FF and PVA + FF plus sliding mode controllers were 42% and 54% less than that produced by a linear PVA controller. Both controllers were found to be robust to changes in payload. This was experimentally verified by adding masses of 6.5 g and 13.5 g to the end of the output link of the joint. By conducting similar experiments in the vertical direction it was found that the PVA + FF plus sliding mode controller was more robust, achieving on average a 30% reduction in RMSE compared to the FF + PVA controller.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: Three Essays in Bank Financial Reporting

contributor:
Jin, Justin
Business

abstract:
This thesis investigates three important issues on bank financial reporting quality: 1) the impact of banks’ retail versus wholesale funding structure on their earnings quality, 2) the implications of economic and monetary policy uncertainty for banks’ earnings opacity, and 3) the relationship between banks’ bad time history and accounting conservatism.
In the first essay, we examine the implications of banks’ funding strategies for banks’ earnings quality. We find that banks’ greater reliance on retail deposits over wholesale funds is negatively and significantly associated with the magnitude of earnings management through discretionary loan loss provisions, the likelihood of meeting-or-beating earnings benchmark, and the extent of income smoothing through loan loss provisions. This finding is consistent with the arguments that retail deposits are relatively more stable and information-insensitive, represent a more conservative business model, and attract more intensive monitoring from the Federal Deposit Insurance Corporation (FDIC) than wholesale funds, thereby improving banks’ financial reporting quality.
In the second essay, we investigate whether economic and monetary policy uncertainties affect banks’ earnings opacity. When economic and monetary policies are relatively uncertain, it is easier for bank managers to distort financial information, as unpredictable policy changes make assessing the existence and impact of hidden “adverse news” more difficult for investors and creditors. Policy uncertainty also increases the fluctuation in banks’ earnings and cash flows, providing additional incentives for bank managers to engage in earnings management. Our results show that uncertainty in economic and monetary policy is associated with greater magnitude of discretionary loan loss provisions, higher likelihood of just meeting-or-beating the prior year’s earnings, and lower levels of accounting conservatism, suggesting that economic and monetary policy uncertainties lead to higher banks’ earnings opacity.
In the third essay, we examine the impact of banks’ bad times on the conservatism of accounting policy. Specifically, we investigate two types of bad times: banks’ own past experiences of undercapitalization and their experiences of witnessing the failures of other banks in state-wide and county-wide crises. We find that both types of banks’ bad times are positively related to timelier recognition of earnings decreases versus earnings increases in accounting income. We also find that following exposure to bad times, banks increase their allowance for loan losses. Collectively, our results suggest that bank-specific bad times and macro-level banking crises lead to greater bank accounting conservatism. These findings support the arguments that banks exposed to past crises overweight their bad time history, and become more cautious and pessimistic about their future earnings performance and loan quality.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: Design and Synthesis of Novel Small Molecule Antimicrobials

contributor:
McNulty, James
Chemical Biology

subject:
organic chemistry
chemical biology

abstract:
Antimicrobial resistance is a significant threat to global health, and it is necessary
to identify new drugs and drug targets for pathogenic bacteria, parasites, viruses, and
fungi. Novel small molecules with antimicrobial activity may be discovered in the lab
through chemical synthesis or from nature as secondary metabolites. This thesis describes
our efforts to synthesize and identify antiparasitic and antiviral small molecules. The
preparation of 3-diarylether quinolines with 5 μM activity against the parasite T. gondii,
through a novel TFA-catalysed Povarov reaction using enol ethers as carbonyl surrogates
is described. Libraries of quinazolinone and dihydroquinazolinone derivatives have been
prepared through a multicomponent synthetic route. Structure activity relationship
analysis allowed for differentiation of the antiparasitic pharmacophore from the antiviral
pharmacophore, as well as the identification of compounds with single digit micromolar
activity against both T. gondii and Herpes Simplex Virus 1. This work also details the
design and synthesis of B-ring aza-analogs of bioactive Amaryllidaceae alkaloids in just 5
steps from chiral pool reagents. Aza-substitution of the B-ring eliminated antiviral
activity, and this modification may also affect anticancer activity. Analysis of several
natural product sources has also identified novel small molecules. Isolation of metabolites
from Xylaria polymorpha identified three novel polyketide derivatives with unknown
biological activity. The alkaloid candicine was found to be the primary polar metabolite
from Ficus benjamina latex, as well as a potent inhibitor of murine cytomegalovirus. By
identifying the mechanisms of action of these bioactive small molecules, we may identify
targets for further drug development.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)

abstract:
There is a need to discover new antimicrobial drugs to combat drug-resistant
infections. We are trying to find new molecules that can prevent the growth of parasites
and viruses by developing and using novel chemical reactions, as well as by isolating new
products from plants and fungi. This text describes a new way to make quinolines, a type
of molecule found in many drugs. A molecule prepared by this method inhibited the
parasite T. gondii at low concentrations. We have also identified quinazolinones,
molecules that can be rapidly assembled by combining three components, which inhibit
parasites and viruses. The thesis also includes a faster way to make derivatives of an
antiviral molecule from daffodils, which can help determine which parts of the molecule
are important for antiviral activity. We have also identified new molecules from the
fungus Xylaria polymorpha and an antiviral compound from the Ficus benjamina tree.


title: EVALUATING THE ASSOCIATION BETWEEN PROGRESSION-FREE SURVIVAL AND HEALTH-RELATED QUALITY OF LIFE IN CANCER.

contributor:
Xie, Feng
Guyatt, Gordon
Thabane, Lehana
Brundage, Michael
Health Research Methodology

abstract:
Background: In oncology, progression-free survival (PFS) is a surrogate outcome
measure and trial end point, which is increasingly being used to determine the efficacy
and implementation in patient care of new drugs. The goal of patient-centred cancer care
is to extend overall survival (OS) or improve health-related quality of life (HRQoL),
however, drugs with PFS benefit are more commonly being approved for use in the
absence of OS, when patient benefit would have to arise from improved HRQoL. The
association between PFS and HRQoL in oncology has been poorly studied, and this
association remains unknown. The objective of this thesis was to thoroughly evaluate the
PFS-HRQoL association in oncology.
Methods: We published a protocol outlining the design of a highly comprehensive
systematic review, and a new analytical approach to optimally explore the PFS-HRQoL
association from published oncology randomized controlled trials (RCTs). We recruited
an international team of reviewers to conduct the systematic review across three HRQoL
domains, and performed a quantitative analysis to find the PFS-HRQoL association in
oncology. We examined our database of eligible RCTs for methodological issues through
a descriptive exploration of risk of bias, to further inform on the design and conduct of
future RCTs.
Results: We failed to find an association between PFS and HRQoL in the absence of OS
in oncology. Very few published oncology RCTs measure and report HRQoL
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information, and among those that do, design and conduct issues related to blinding, and
especially attrition are common.
Conclusion: Oncology RCTs must either be adequately powered for OS, or designed to
properly measure HRQoL, so patients can receive treatments offering benefit in one of
these two patient-centered outcomes, and not solely based on PFS. There is a lack of high
quality RCTs informing on the PFS-HRQoL association, and more of these types of trials
are needed in the future for further analysis to confirm our findings.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: Interference Management in Wireless LAN Mesh Networks Using Free-Space Optical Links

contributor:
Todd, Terence C.
Electrical and Computer Engineering

subject: interference management, wireless LAN Mesh networks, free-space, optical links, radio frequency

abstract:
 Wireless LAN mesh networks (WMNs) are a cost effective way of deploying wireless LAN (WLAN) coverage over extended areas. As WMNs become more populated, scalability issues may arise due to the co-channel interference which is inherent in publicly available RF (radio frequency) channels. This co-channel interference can severely degrade network capacity and link reliability and may eventually make it impossible to operate with the frequency channels for which the network was originally designed. In this thesis, this problem is addressed by selectively installing supplementary free-space optical (FSO) links when RF link performance has deteriorated. The frequency assignment problem is solved using a heuristic technique based on a genetic algorithm. In order to determine the quality of the results, the proposed algorithm is compared with a lower bound solution obtained using an Integer Linear Programming (ILP) formulation.

 Another advantage of FSO links is that they may reduce node power consumption compared with conventional RF links. This may be an important consideration in cases where power consumption at the nodes is important, such as in solar powered mesh networks. Power consumption estimates of RF and FSO links are obtained and compared for different data rates. This data is then used along with historical solar insolation data to estimate the solar panel and battery sizes required to guarantee a
given node outage probability. The results show that no extra provisioning is required for replacing the deployed wireless nodes with new FSO links.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: Haptic-Enabled Collaborative Virtual Environments for Skills Training

contributor:
Sirouspour, Shahin
Electrical and Computer Engineering

subject: haptic-enabled, collaborative, virtual environments, skills training, nonlinear model

abstract:
 Many manual tasks such as those in surgical applications require a high degree of motor skills that can only be gained through extensive training. This thesis is concerned with the design and control of collaborative training virtual environments with haptic feedback for skills training. The term "collaborative training" refers to a scheme in which the trainee and the trainer operate in a shared virtual environment. They collaboratively carry out the intended tasks using a shared "virtual tool". In order to enhance the trainee's motor skills, the conventional visual feedback will be augmented by force feedback providing the feel of the task environment as well as active guidance by the expert trainer.

 First, a set of psychophysics experiments are designed to investigate the usefulness of haptic-enabled collaborative virtual environments for motor skills training. Eighteen volunteers randomly divided between two training and control groups have participated in the experiments. The training group would undergo a number of collaborative training sessions with active help from the trainer whereas the control group would try the task on their own to achieve a set of stated goals. Each of the experiments is designed with specific performance objectives in mind, including trajectory tracking and task completion time. The results of the psychophysics
experiments confirm that, when visual feedback is partially impaired, haptic-enabled collaborative training improves learning of a trajectory tracking task. In all the experimental scenarios tested, the results showed improvements in temporal response after receiving training.

 The second part of the thesis is devoted to the development of a general control framework for the coordination of the users in haptic-enabled collaborative virtual
environments. The haptic interface control design is separated from the virtual environment
simulation in order to provide more versatility in control strategies for both impedance and admittance-type virtual environments. Adaptive nonlinear controllers are proposed that establish desired linear-time-invariant and/or nonlinear static mappings amongst the users and the virtual task environment positions and forces. These controllers account for the nonlinear model of haptic devices and can handle uncertainties in the haptic devices, the users, and the virtual environment dynamics. First, the tracking behavior of the system is shown via a Lyapunov analysis. Then using a priori known bounds on user and environment
parameters, the robust stability of the system is analyzed by employing the Nyquist envelops of interval plants and an off-axis circle criterion. The robust stability analysis provides bounds on the parameter of the linear and nonlinear mappings within which the stability of the system is guaranteed, for all possible system parameters with their a priori given bounds. Experiments carried out with two similar Quanser twin-pantograph haptic devices confirm the effectiveness of the proposed controllers in achieving the performance and stability objectives.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: SUBSTANCE USE DISORDERS AMONG EMERGING AND YOUNG ADULTS: AN EPIDEMIOLOGICAL STUDY

contributor:
Ferro, Mark A
Health Research Methodology

subject:
alcohol use disorder
drug use disorder
emerging adults

abstract:
Objectives:
We investigated the prevalence of substance use disorders among emerging adults and quantified the extent to which emerging adults, compared to young adults, are at increased odds for substance use disorders.
Methods:
Data come from the 2012 Canadian Community Health Survey – Mental Health (CCHS-MH). Respondents were 15–39 years of age (n=9228) and were categorized as: early emerging adults (15-22 years); late emerging adults (23-29 years); and, young adults (30-39 years). Substance use disorders (alcohol or drug abuse/dependence) were measured using the Composite International Diagnostic Interview 3.0. The prevalence of substance use disorders was compared across age groups using design-based χ2 analyses. Odds ratios (OR) and 95% confidence intervals (CI) were computed from logistic regression models adjusting for sociodemographic and health covariates. All analyses were weighted to maintain representativeness of the study sample to the Canadian population.
Results:
The prevalence of alcohol use disorder was 8.0%, 6.6%, and 2.7% for early emerging adults, late emerging adults, and young adults respectively. For drug use disorder, the prevalence was 6.4%, 3.6%, and 1.3%. Compared to young adults, early and late emerging adults were more likely to report substance use disorders (p<0.01). The prevalence of drug use disorder was higher among early versus late emerging adults (χ2=119.8, p=0.01). Among all age groups, males were more likely to report alcohol or drug use disorders (p≤0.01 for all). After covariate adjustment, early and late emerging adults had greater odds of reporting alcohol (OR=3.2, 95% CI=2.2-4.9 and OR=2.4, 95% CI=1.6-3.4, respectively) or drug (OR=4.2, 95% CI=2.5-7.0 and OR=2.5, 95% CI=1.6-4.1, respectively) use disorders compared to young adults.
Conclusion:
Emerging adulthood represents an important developmental period in which individuals are at increased odds of reporting substance use disorders. This finding has implications for the provision of screening and treatment of substance use disorders as these individuals transition from the pediatric to adult healthcare system.

abstract: Thesis

abstract: Master of Health Sciences (MSc)


title: On Modelling the Atmospheres of Potentially-Habitable Super-Earths

contributor:
Pudritz, Ralph
Physics and Astronomy

subject:
atmosphere
super-earths
radiative transfer
atmospheric composition
exoplanet
atmospheric modelling
radiative-convective
habitability

abstract:
Atmospheres play an important role in the habitability of a planet, so understanding and modelling them is an important step in the search for life on other planets.

This thesis presents a 1D frequency-dependent radiative-convective code that was written to help determine the temperature-pressure structure of potentially-habitable exoplanets. This code pairs with a chemistry model to determine the chemical composition of these planets' atmospheres.

This code is applied to the planets in the TRAPPIST-1 system. The initial atmospheric compositions of the TRAPPIST-1 planets are determined through planet formation history and considered for both outgassed and accreted atmospheres. An interesting result is found when running these initial atmospheric compositions through the chemistry model: when the atmosphere equilibrates, it can change its C/O ratio from equal to that found in the accreted or outgassed volatiles to something lower, because, in temperate conditions, CO$_2$ is favoured over CO. This has the consequence that observed C/O ratios in terrestrial atmospheres cannot be relied on to infer the C/O ratio of the protoplanetary disc in which the planet formed.

The initial results of atmospheric modelling for TRAPPIST-1 planets indicate that these planets are likely to have relatively warmer upper atmospheres due to the fact that their host star emits primarily in the infrared, and a portion of this radiation is then absorbed as it enters the top of the atmosphere. These initial results have not been seen in previous work.

These initial results are the beginning of a database of potential atmospheres on the TRAPPIST-1 planets. It is hoped that these atmospheres can be compared with observations from future observing missions like the James Webb Space Telescope to help constrain the surface conditions of these potentially-habitable planets and ultimately, to help in the search for life.

abstract: Thesis

abstract: Master of Science (MSc)


title: Landscape-level strategies for conservation of imperiled freshwater turtles

title: Landscape-level conservation of freshwater turtles

contributor:
Chow-Fraser, Patricia
Biology

abstract:
In Ontario, 7 of the 8 native species of freshwater turtles are listed as at-risk. Protection of species-at-risk requires delineation and identification of their critical habitat to enable the proposal of conservation strategies. Because of pre-existing development and limited resources for conservation, it is difficult to protect land required for species’ survival especially when faced with multiple threats such as habitat loss, degradation, and fragmentation, invasive species, and a changing climate. To improve conservation strategies, we must understand how turtle populations use a variety of different landscapes at a range of spatial scales.
 The goals of this thesis were to develop and assess landscape-level conservation strategies for imperiled freshwater turtles. I first determined that Blanding's turtles (Emydoidea blandingii) require inland and coastal wetlands, a suitable upland matrix and connecting corridors. Since turtles overwinter for majority of the year, I determined suitable thermal parameters of occupied sites, revealing suitable water temperatures range from 0.44° C to 3.68° C and slowly decline throughout the overwintering period. Using a landscape-level approach, my models support that habitat in Georgian Bay is in good condition; 64% of evaluated islands support habitat for Blanding’s turtles and majority of surveyed coastal wetlands support eastern musk turtles (Sternotherus odoratus). In particular, coastal wetlands with higher proportions of forest cover, lower densities of roads, buildings, and docks, and more variable bathymetric slopes provide more suitable habitat. In addition to anthropogenic stressors, invasive species pose a threat to turtles and their habitat. I provided the first quantitative evidence of the negative consequences of Phragmites australis invasion on availability of habitat for turtles. Since roads are a ubiquitous feature in our landscape, I evaluated strategies aimed at limiting their negative effects on at-risk reptiles. A decade-long dataset of road mortality reveals the ineffectiveness of partial fencing as a mitigation strategy. I recommend emphasis on fence integrity and continuity, limiting impact of edge effects, and conducting a comprehensive monitoring program. Finally, long-term changes in a protected landscape are evaluated and results indicate habitat succession and invasive species can negatively affect habitat suitability, and protection of land alone does not necessarily equate to protection of sensitive herpetofauna. My research integrates geographic information systems and remote sensing to advance our understanding of landscape requirements for turtles and will inform future conservation strategies aimed at mitigating threats to imperiled freshwater turtles.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)

abstract: Turtles are one of the most endangered taxonomic groups, with as many as 1 in 2 species at risk of extinction. Although turtles are one of the oldest groups of animals in the world, anthropogenic impacts causing habitat loss and degradation have led to population declines. The goals of this thesis were to develop and assess landscape-level conservation strategies for imperiled freshwater turtles. I analyzed habitat selection by an imperiled freshwater turtle and determined suitable thermal characteristics of critical overwintering habitat. At the landscape-scale, I modeled habitat suitability and occupancy for at-risk turtles. My research reveals the negative effects of invasive species and the ineffectiveness of partial fencing as a strategy to mitigate reptile road mortality. Lastly, I discuss the implications of habitat succession on reptile habitat and the need for management when protection of land alone does not equate to protection of sensitive species. My research advances our understanding of landscape requirements for turtles and will inform future conservation strategies for imperiled freshwater turtles.


title: Refining the tectonic and magmatic history of the SW Grenville Province

contributor:
Dickin, Alan
Geography and Earth Sciences

subject:
Precambrian Geology
Grenville Province
Central Metasedimentary Belt

abstract:
The largest structural trend of the major lithotectonic boundaries in the Grenville Province is located in Ontario where all lithotectonic belts are deflected around Georgian Bay, termed the Big Bend.  The thesis will explore some questions related to the formation of this structural feature such as; how the geometry of Grenville aged thrusting contributed to the Big Bend and what conditions led to the formation of the pre-Grenvillian Central Metasedimentary Belt whose geometrical shape may have controlled the development of the Big Bend.
First, the geometrical properties of the major lithotectonic boundaries are explored using a three-dimensional model in SketchUp. SketchUp was designed to visualize three-dimensional 1:1 scale real-world structures in Cartesian space. By utilizing refined isotope and geologic surface boundaries accompanied with seismic surveys a three-dimensional tectonic framework of the SW Grenville Province has been constructed.  The three-dimensional model of the Grenville Front, Allochthon Boundary Thrust and Central Metasedimentary Belt boundary provides a visual understanding of how the thrust geometry was superimposed from the top-down, eventually producing the Big Bend.
Second, 60 new Nd isotope analyses are presented for plutonic orthogneisses from the Central Metasedimentary Belt (CMB), Grenville Province.  The CMB has been identified as a back-arc aulacogen with blocks of rifted crustal basement (>1.35GaTDM) in a juvenile matrix of lavas, intrusions and supracrustal sequences (1.35GaTDM). The Grimsthorpe domain is located in the center of the CMB in Ontario and contains large batholiths that exhibit older crustal formation ages known as the Weslemkoon and Elzevir batholiths.  The presented Nd isotope analyses identify domains with older crustal formation ages separated by thin salients with younger crustal formation ages inside the Weslemkoon batholith.  The intricate geometry of the isotope boundaries within the Weslemkoon batholith suggest that the Laurentian crustal basement was incorporated in the rift and later broken-up by rift related transtension.  Continental rift and rifted-arc settings of the Danakil Depression and Gulf of California are explored as modern analogues along with rifted continental fragments known as the Danakil block and Isla Tiburon respectively.
Last, the Queensborough mafic-ultramafic complex (QC) is reviewed.  The QC is located at the southern end of the Elzevir batholith.  The QC was interpreted as a back-arc ophiolite based on REE ratios and MORB normalized spidergrams which were argued to be comparable to modern back-arc basalts.  Upon review of the published major and trace element ratios there is a mantle component that is problematical to explain with a back-arc tectonic scenario.  The geochemistry suggests that the QC could be partially derived from a mantle plume.  The current tectonic models contend this part of Laurentia formed only from subduction related magmatism but based on the trace element data a plume may have been involved as well.
The evidence presented supports the identification of the CMB as a failed continental rift and that the failed continental rift created an embayment in Laurentia which governed ductile deformation during Grenvillian orogenic events leading to the formation of the Big Bend.

abstract: Thesis

abstract: Master of Science (MSc)


title: The effect of brief intermittent stair climbing exercise on glycemic control in people with type 2 diabetes

contributor:
Gibala, Martin J.
Kinesiology

subject: Continuous glucose monitoring, type 2 diabetes, postprandial hyperglycemia, stair climbing

abstract: Physical activity is important for the management and treatment of type 2 diabetes (T2D). Interval exercise training has been shown to improve glycemic control in people with T2D; however, studies have generally utilized high volume protocols and/or specialized equipment that limit translation to a “real world” setting. The present proof-of-concept study examined the efficacy of brief, intermittent stair climbing exercise to improve indices of glycemic control in adults with T2D, using continuous glucose monitoring (CGM) under controlled dietary conditions. Each session involved 3 x 60-s bouts of vigorously ascending and slowly descending a single flight of stairs. This was set within a 10-min period, which otherwise involved walking for a warm-up, cool-down and recovery in between bouts. Data are reported for n=5 participants (52 ± 18 y, BMI: 31 ± 5 kg/m2, HbA1c: 6.6 ± 0.7 %; mean ± SD) who performed 18 training sessions over 6 weeks. Mean 24-h glucose and time spent in hyperglycemia (> 10 mmol/L) were unchanged after an acute session of stair climbing (p=0.38 and p=0.42, respectively) or after 6 weeks of training (p=0.15 and p=0.47, respectively). Measures of glycemic variability were improved in the 24-h period following a single session of stair climbing, based on reductions in the mean amplitude of glycemic excursions (MAGE) (4.4 ± 1.5 vs. 3.5 ± 1.0 mmol/L, p =0.02) and the standard deviation (SD) around the mean (1.7 ± 0.5 vs. 1.4 ± 0.5 mmol/L, p=0.02). There was a meal-specific improvement in postprandial hyperglycemia after training, with the incremental area under the curve (iAUC) of the lunchtime meal reduced by 36 ± 42 % (p=0.01). These preliminary results demonstrate the feasibility of stair climbing as a physical activity option for people with T2D, although the acute and chronic effects of this training on indices of glycemic control remain equivocal.

abstract: Thesis

abstract: Master of Science in Kinesiology

abstract: Physical activity is important for the management of type 2 diabetes (T2D). Interval training, which involves alternating periods of relatively intense exercise and recovery, can improve blood sugar control in adults with T2D. This has largely been shown in laboratory settings using specialized equipment and protocols that may not be practical or time-efficient. This small, proof-of-concept study examined whether brief, intermittent stair climbing exercise could improve blood sugar control in people with T2D. Average blood sugar measured over 24 hours was unchanged after a single bout of stair climbing and after 18 sessions of training performed over 6 weeks. However, stair-climbing exercise reduced blood sugar fluctuations in response to specific meals. These preliminary findings suggest that interval stair climbing is a feasible exercise option for adults with T2D, but the precise effects on blood sugar control remain to be clarified.


title: THE RELATIONSHIP BETWEEN SOCIAL COGNITION DEFICITS AND VIOLENCE IN INDIVIDUALS DIAGNOSED WITH A PSYCHOTIC DISORDER

contributor:
Moulden, Heather
Neuroscience

abstract: Understanding the intentions of other people is critical for navigating the complex social interactions within our environment. Individuals with schizophrenia demonstrate difficulty relating to and recognizing the feelings, thoughts, and intentions of others – a construct known as social cognition. While many studies have investigated social cognition deficits in patients with schizophrenia, few have explored how these problems may contribute to social behaviour in this group, and violence specifically. Individuals diagnosed with schizophrenia show specific deficits when asked to take the perspective of another person, and perhaps this may account for findings that this same group is more likely to commit a criminal act, including interpersonal violence, compared to the general population. The present study aims to test the hypothesis that social cognitive deficits may be related to violence by evaluating various aspects of neuropsychological functioning, and social cognition specifically, in individuals diagnosed with a psychotic disorder. Twenty-two participants, 12 violent and 10 non-violent, completed a battery of psychometric tests that assessed neuropsychological functioning, emotion recognition ability, theory of mind ability, and attribution style. Although no significant group differences were found between the violent and non-violent participants, two interesting findings emerged. First, explaining social transgressions as a joke was a theme that emerged only in the violent group. Second, there was no relationship between one’s accuracy and confidence regarding emotion recognition performance in this group. These trends signal potential explanations for violence in this group, with respect to misinterpretation, and specifically how this is related to psychotic content.

abstract: Thesis

abstract: Master of Science (MSc)


title: BPAF-Induced Adipogenesis in 3T3-L1 Cells: Role of Peripheral Serotonin Signaling

contributor: Medical Sciences (Division of Physiology/Pharmacology)

abstract: There is evidence that synthetic chemicals in our environment called, obesogens, may play an important role in the global obesity epidemic. Bisphenol A (BPA) is one of the most studied obesogens. Due to concerns surrounding the use of BPA, BPA structural analogues are being used as substitutes in consumer products. However, there is currently little information available regarding their effects on pathways important for the development of obesity. Interestingly, serotonin (5-HT) signaling in peripheral tissues plays an important role in regulating metabolic homeostasis. Moreover, BPA has been shown to alter 5-HT signaling in the central nervous system. Therefore, the objective of this study was to determine the effects of BPA analogues on adipogenesis and elucidate whether their obesogenic effects involve peripheral 5-HT signaling. 3T3-L1 preadipocytes were treated with 10 μM BPA or four commonly used BPA analogues during differentiation. Lipid accumulation was assessed by Oil Red O staining. Adipogenic markers and genes important for 5-HT synthesis/metabolism were subsequently examined following treatment with BPA and the structural analogue bisphenol AF (BPAF). The roles of tryptophan hydroxylase 1 (TPH1) and monoamine oxidase (MAO), in addition to glucocorticoid receptor (GR) signaling were also evaluated. Treatment with 10 μM BPAF and Bisphenol S (BPS) significantly increased lipid accumulation in differentiated 3T3-L1 cells. 10 μM BPAF significantly increased adipogenic gene markers, as well as GR gene transcripts. Moreover, BPAF induced adipogenesis in the absence of the synthetic glucocorticoid dexamethasone. Further, although BPAF significantly increased Tph1 mRNA levels, blocking its activity with para- chlorophenylalanine (pCPA), did not block the adipogenic effects of BPAF. However, co- treatment with the MAO inhibitor, phenelzine, significantly decreased lipid accumulation and peroxisome proliferator activated receptor gamma (Pparg) expression. Therefore, these data demonstrate that BPAF may act as an obesogen and suggests that its action might be mediated, in part, by altered 5-HT signaling.

abstract: Thesis

abstract: Master of Science (MSc)


title: The "what" and "how" questions of the healthy immigrant effect: Psychosocial resources and demands as pathways to mental health risks

contributor:
Denton, Margaret
Sociology

subject: immigrants, mental health, social support, interpersonal stress, health behavior

abstract: Current research identifies gender, age, and ethnic patterns for the healthy immigrant effect related to mental health, but little research explores what determines immigrants’ mental health and how mental health deterioration occurs. This dissertation investigates the ‘what’ and the ‘how’ questions by applying the Social Determinants of Health (SDOH) Perspective and the Stress Process Model. To answer the ‘what’ question, this dissertation draws on the SDOH framework to examine potential social determinants—in the form of structural conditions, behavioral risks and psychosocial demands—affecting long-term immigrants’ lower mental health status. To approach the ‘how’ question, it employs the Stress Process Model to investigate the differential exposure to behavioral risks and psychosocial demands between recent and long-term immigrants. The analysis of the data from the Canadian Community Health Survey-Mental Health 2012 and the General Social Survey-Social Identity 2013 indicates that structural conditions, behavioral risks, and psychosocial demands co-influence immigrants' mental health to some extent. Behavioral risks have independent contributions to mental health, but the contributions are small. Psychosocial resources and demands, however, have the greatest impact on mental health. An examination of the relationships between length of migration and psychosocial resources indicates that, compared to recent immigrants, long-term immigrants are in the state of 'high support and high strain,’ and the differences in these psychosocial resources and demands translate into mental health differences (the so-called healthy immigrant effect) between long-term and recent immigrants.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: Adiposity in childhood brain tumors: prevalence, predictors, and current management strategies

contributor:
Samaan, M. Constantine
Medical Sciences

subject:
pediatric brain tumor
survivorship
obesity
adiposity

abstract:
Introduction: The increased survival rates of children with brain tumors is the result of decades of advancement in diagnostic and therapeutic approaches, but brought the adverse long-term effects of the treatments and tumors on these children into focus. Survivors of childhood brain tumors (SCBT) are at an increased risk of cardiometabolic disorders and premature mortality. Obesity and excess adiposity are well-established risk factor for cardiometabolic risk in the general population, but its contribution to these outcomes in survivors is unknown. More recently, adiposity has emerged as a more robust predictor of cardiometabolic risk than body mass index, the most clinically used measure of obesity. The current thesis pursued four objectives: 1) to determine the prevalence of obesity and excess adiposity in SCBT 2) to explore adiposity and its determinants in SCBT 3) to investigate the determinants of obesity in SCBT and 4) to identify potentially effective interventions to manage obesity in SCBT.
Methods: Systematic reviews and meta-analyses were used to evaluate the prevalence and interventions for overweight and obesity in SCBT while the determinants of adiposity and obesity were explored using primary data and regression analyses. General health information and brain tumors information were collected with standardized questionnaires and review of medical records. The overweight or obesity status of subjects was determined by body mass index (BMI), and adiposity profile was evaluated using percent body fat (%FM), waist-to-hip ratio (WHR) and waist-to-height ratio (WHtR).
Results: The results show no difference between the overweight and obesity rates in SCBT and non-cancer controls. However, SCBT have higher total and central adiposity. Birth weight is found to be a predictor of future BMI in SCBT, while a higher total adiposity in SCBT is predicted by having supratentorial tumors and receiving radiotherapy. Lastly, not enough evidence is available to conclude the effectiveness of lifestyle interventions, pharmacotherapy, and bariatric surgery on managing obesity in SCBT.
Conclusions: Obesity, determined by BMI, is not enough to determine cardiometabolic risks in SCBT. Total and central adiposity should be measured as well to identify high-risk group. Special attention should be paid to SCBT with high birth weight, supratentorial tumors, and having received radiotherapy. Lastly, more randomized controlled trials are needed to provide high-quality evidence to determine the effectiveness of interventions to manage obesity and improve outcomes in SCBT.

abstract: Thesis

abstract: Master of Science (MSc)

abstract:
Brain tumors are the most common solid tumors in children. The survival rates among children with brain tumors have increased significantly over the past four decades due to advances in early detection and treatment. However, these children are at increased risk of heart disease and type 2 diabetes, and early death. Evidence has suggested obesity and excess body fat as main reasons for cardiometabolic disorders in the general population, but it is not known if obesity and excess body fat contribute to diabetes and heart disease in survivors. Therefore, the current thesis aims to explore obesity and adiposity, their predictors and any existing treatments available to survivors of childhood brain tumors (SCBT) to see if outcomes can be improved.
	The results show that while survivors of childhood brain tumors have similar overweight and obesity rates to the general population when measured by the most common clinical measure, called body mass index (BMI), they in fact have higher fat mass. Furthermore, we identified birth weight as a predictor of obesity while the location of the tumors and receiving radiation therapy as predictors of the fat mass in SCBT. The results also show the lack of current effective interventions to manage obesity in SCBT. This data is critical to consider in the design and implementation of strategies to reduce heat disease and diabetes in survivors to improve their quality of life and lifespan.


title: A Multipronged Approach in Targeting Clostridium difficile: Multiple Domain Selection for Aptamer Isolation

contributor:
Li, Yingfu
Biochemistry and Biomedical Sciences

subject:
Aptamer
SELEX
Nucleic Acids
DNA
C. difficile
Multiple Domain Selection
MDS
DnaK
Hsp70

abstract: Clostridium difficile, the causative agent of C. difficile infection (CDI), causes hundreds of thousands of hospital-acquired infections in the United States and Canada annually. Furthermore, the prevalence and severity of CDI has been on the rise in developed countries, especially with the appearance of “hypervirulent” strains. Detection of CDI is thus of great importance. Traditional detection methods can be time consuming or lack the desired sensitivity. On the other hand, aptamers pose great prospects as diagnostic and therapeutic agents. Aptamers are nucleic acid ligands with molecular recognition capabilities rivaling those of antibodies. They are obtained by a process of in vitro selection known as systematic evolution of ligands by exponential enrichment (SELEX). However, the current approach may result in aptamers that experience non-specific binding in complex or biological samples. Here, we propose a multiple domain selection (MDS) method for aptamer isolation. This method utilizes independent selections on separate components of a single target in order to obtain uniquely specific aptamers. The aptamers can then be unified into a heterobivalent construct able to recognize two sites on one target. We hypothesize the combined aptamer would result in greater affinity and specificity for the target, resulting in greatly increased aptamer utility in current and future applications. In the current study, we have cloned and purified full length C. difficile DnaK as well as the N-terminal domain (NTD) and C-terminal domain (CTD) of the protein. MDS was performed on each target and the resulting aptamers were combined into a heterobivalent construct. The construct resulted in an approximately 100-fold affinity increase relative to the single aptamer for DnaK, and could detect much smaller quantities of target. Although it experienced low level recognition of high concentrations of purified E. coli DnaK, there was no detectable non-specific binding in several biological samples.

abstract: Thesis

abstract: Master of Science (MSc)


title: Characterization of surface plasmon resonances in metallic planar nanostructures by electron energy loss spectroscopy

contributor:
Botton, Gianluigi A.
Materials Science and Engineering

subject: Surface Plasmons, electron microscopy, EELS, Coupling, planar nanostructures

abstract: Surface plasmon resonances at the nanoscale hold great potential for applications in many areas, and the characterization of plasmonic nanostructures plays a critical role in the realization of these applications. Electron energy loss spectroscopy (EELS) has emerged as a powerful characterization tool to study the response of plasmonic nanostructures due to its high spatial-resolution and the capability to probe bright as well as dark plasmonic modes. The main limiting factor of EELS is the energy resolution. However, in this thesis, we overcome this limitation using a combination of electron monochromation and the use of the Richardson-Lucy algorithm. We show that the algorithm could be used to obtain effective energy resolutions up to 10 meV. Using EELS we analyze the resonances of planar nanostructures, and we found that the supported resonances can be described as edge and cavity or film modes, behaving as 1D and 2D modes respectively. We also demonstrate that edge modes are unaffected by the presence of bends up to the critical angle of 90◦ where the modes start self-interacting producing large energy shifts. The interaction of plasmon resonances is also studied, and we show that the coupling can be reduced to three behaviors: coupling through the edge, coupling through a corner, and non-coupling. We propose a method to control the coupling through the edge in offset nanowires, by tuning the nodal alignment and spectral overlap of the edge modes. Finally, we analyze the plasmon modes supported by Koch snowflake fractal antennas, and we demonstrate that modes present in the fractals are formed by the edge modes supported by their characteristic edges. This thesis provides a complete picture of the surface plasmon resonances supported by planar nanostructures and demonstrates the ability of EELS to probe and image a wide variety of plasmonic resonances.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: An Investigation Into The Flow In Candu Fan Nozzles

contributor:
Novog, David
Engineering Physics

subject: Candu

abstract:
The moderator within the CANDU calandria vessel is an important element of the reactor serving various operational and safety functions. A validated computational fluid dynamics model to simulate the fluid within the calandria vessel is required to predict how it would behave in different situations. Given is high level of complexity (flow from complicated inlets inlet, outlet, volumetric heating, flows around fuel channels, etc…) validation typically proceeds from separate effect studies for each component as well as integral validation where all complex phenomena are included.  This work is focused on the separate effect studies aimed at phenomena relevant to the inlets of Pickering A.

A scaled down model of the Pickering CANDU moderator inlet nozzle was constructed and used to verify simulations done on the same nozzle. Physical measurements were taken using a PIV laser system on the scaled down nozzle. Seven measurements planes were taken on two of the outlets of the nozzle at two different flowrates (0.2 kg/s and 0.1 kg/s).  Given a single PIV measurement plane contains approximately 1000 velocity points this represents approximately 28000 new velocity measurements for CFD validation.  A CAD model of the nozzle was imported into STAR-CCM+ CFD software to perform the simulations. The simulations used the k-ω SST turbulence model and were performed using the same flowrates as in the experiments. The k- model was also used as a comparison for the k- SST model. The same locations were used in calculations for the seven measurement planes so that the same areas could be compared for the models employed.

The CFD results were found to agree qualitatively with the measured ones but no quantitative comparisons should be made with care. Additional investigation is required for a more comprehensive comparison. While both, measured and calculated results, showed similar velocity distributions, the velocities values differed by varying degrees. In particular, the simulations did not show the same jet expansion as the physical measurements indicated. There is not enough data from the measurement planes to determine if the flow in the physical experiments are more diffuse and the velocity field gradients are lower than obtained in the current study. With large portions of the nozzle unobserved by the measurement planes, it cannot be concluded that there are no other peaks or large velocity gradient regions in between the planes. For future work it would be beneficial to have a larger model of the nozzle for better gradient resolution, as well as using a measuring system that allows for more precise data collection. Different turbulence models and measurements further away from the nozzle should also be used to determine which would be best in a larger simulation.

abstract: Thesis

abstract: Master of Applied Science (MASc)

abstract:
In order to create accurate simulations moderator flow in a calandria vessel, simulations of smaller components must first be verified. The moderator inlet fan nozzle found in the Pickering CANDU calandria vessel has complicated geometry which can be difficult to model using CFD. Simulations were performed on a scaled down version of the nozzle and physical experiments were performed on a constructed model.

The results found that the simulations predicted similar velocity distributions, but generally with higher peak velocity values than the physical experiments. However additional measurement locations would be needed to give a more comprehensive comparison. Going forward with the larger simulations, to better determine the best model to use for the nozzle, a larger version should be used with different turbulence models and measurement locations.


title: Surface Functionalized Cellulose Nanocrystals for Synthetic Latex Property Modification

contributor:
Cranston, Emily
Chemical Engineering

subject:
cellulose nanocrystals
synthetic latex
polymer chemistry
polymer grafting

abstract:
The objective of this thesis is to incorporate cellulose nanocrystals (CNCs) into polymer latexes prepared using various emulsion polymerization methods. CNCs are a promising new class of renewable materials with unique properties including nanoscale dimensions, a high aspect ratio, low density, and high strength. They show significant promise to enhance the properties of existing materials, but challenges often arise due to incompatibility and processing difficulties. This work investigates novel surface modification routes to improve the compatibility of CNCs with emulsion polymerization components, and aims to control the location and function of CNCs in latex systems in order to modify latex properties.
Three approaches to incorporate CNCs into polymer latexes are presented: (1) exploiting CNC-surfactant interactions in order to promote CNCs as Pickering stabilizers or as “passive” additives in the water phase, (2) enhancing the surface activity of CNCs by adsorbing the surface active biopolymer methyl cellulose (MC) to act as Pickering co-stabilizers, or (3) hydrophobic modification of CNCs through polymer grafting in order to provide improved compatibility between CNCs and the monomer/polymer phase to incorporate CNCs into the latex core.
First, the interactions between CNCs and surfactants were studied in suspension and at surfaces and the CNC-surfactant combinations were used to stabilize miniemulsion polymerization of methyl methacrylate (MMA), a model system used in this work. Oppositely charged CNCs and surfactants showed improved stability as Pickering stabilizers and the ability to co-stabilize the monomer/polymer-water interface. When like-charged CNCs and surfactants were used, the poly(methyl methacrylate) (PMMA) polymer particles were stabilized by surfactant only, while the CNCs remained in the water phase. Next, in order to avoid the use of surfactants, CNCs were coated with MC to provide improved surface activity. MC-coated CNCs were effectively used as Pickering stabilizers in the microsuspension polymerization of MMA, where a double morphology of PMMA particles was observed, and the morphology could be tuned based on the ratio of CNC to MC used. Finally, CNCs were modified with hydrophobic polymer via two different “grafting from” methods: free radical polymerization and atom transfer radical polymerization (ATRP). Free radical polymer grafting from CNCs resulted in polymer-grafted CNCs but the method lacked control over polymer graft length and graft density. To overcome this, CNCs were modified via surface initiated ATRP where considerably higher amounts of polymer were grafted from the CNCs in short reaction times and with simple purification steps. Furthermore, polymer-grafted CNCs were added to the monomer phase of the miniemulsion polymerization of MMA and latexes with CNCs inside the hydrophobic polymer particle core were prepared. Given the difficulties in characterizing polymer grafted CNCs, a novel solution state NMR method was used, whereby the modified CNCs were dissolved in ionic liquids and the polymer grafts were cleaved and collected to determine graft length and graft density.
Overall, this work provides three approaches for the preparation of nanocomposite latexes with CNCs using PMMA as a model system. The results presented here may expand the use of CNCs in latex products such as adhesives, paints, coatings, and cosmetics.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)

abstract: This research aims to prepare polymer latexes with tailorable properties using renewably-sourced particles and nanotechnology. Latexes are polymer particles dispersed in water, typically on the order of a few hundred to thousand nanometers (where a “nanometer” is one billionth of a meter), and are used in products such as adhesives, paints, and coatings. The field of nanotechnology takes advantage of nanomaterials where unique properties stem from the small size and high surface-area-to-volume ratio. In this work, we use cellulose, the most abundant natural polymer on earth, in the form of cellulose nanocrystals (CNCs).  These nanoparticles are extracted from pulp, cotton, and other natural resources to yield nanometer-sized rigid rod-like particles. CNCs have recently gained attention in research and the media because of their new industrial production and “safe nanomaterial” designation in Canada. In this work, CNCs were chemically modified by the attachment of new molecules or by coating them with polymers and were subsequently added during the synthesis of the polymer latex. Incorporating CNCs imparted new properties and the ability to control latex size, shape, and surface topography. CNCs are also expected to improve the overall mechanical strength of the latex, and may enhance the stickiness of adhesive latexes in particular, leading to products that are more environmentally friendly and that show improved performance.


title: Co-performer Communication and Audience Perception of Musical Performances

contributor:
Schutz, Michael
Psychology

subject:
Music Performance
Joint Action
Nonverbal Communication
Granger Causality

abstract:
A music performance is an exciting environment for studying joint action and
nonverbal communication. This thesis utilized music ensemble performances to study nonverbal communication occurring from two different perspectives. We examined bi-directional communication between co-performers and uni-directional communication of the musicians to the participants. The first paper (Chapter 2) used statistical measures (i.e., Granger causality analysis) to quantify head movements as a measure of joint action during a musical performance. We observed a change in direction and magnitude of information flow between co-performers based on the availability of visual and auditory cues. We wanted to extend this line of research to see how audience perception of the performances may change due to the auditory and visual manipulations of the performers. The second paper (Chapter 3) examines participant ratings of expression, cohesion, and general liking of the performance when presented with audio-visual, audio-only, and visual-only stimuli. These ratings not only show which sensory modality allows for the highest sensitivity to performer manipulations, but also provide insight into how musicians change their performances to communicate to the audience. My aim was to create a cohesive examination of co-performer communication and observer perception of musical performances.

abstract: Thesis

abstract: Master of Science (MSc)


title: Population Structure and Molecular Epidemiology of the Fungal Pathogen Aspergillus fumigatus at Global and Local Scales

contributor:
Xu, Jianping
Biology

subject:
Aspergillosis
Aspergillus fumigatus
Hamilton
Cameroon

abstract: Aspergillus fumigatus is an opportunistic fungus known to cause a group of life-threatening infections collectively known as aspergillosis. In this thesis, multilocus sequence and microsatellite markers, among others, were used to study global and local A. fumigatus population structures. We examined the roles of sexual and asexual reproduction in the initiation of azole resistance globally. Furthermore, we investigated the origin of multi-triazole resistance in India and whether the use of fungicides on farms propagates resistance in environmental strains of clinical importance in Hamilton, Ontario. We characterized for the first time the A. fumigatus population in Cameroon while concomitantly screening for environmental resistance. Our results showed that sexual reproduction plays a key role in the development of triazole resistance globally. We found that multi-triazole resistance in India has multiple origins, which include mutational, recombinational and exotic origins. Our results provided little to no evidence that azole fungicides are the origin, or increase the frequency of triazole resistance in clinical A. fumigatus in Hamilton. Additionally, we identified a significantly unique A. fumigatus population in Cameroon. Our findings will potentially contribute towards developing effective long-term management strategies against aspergillosis.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)

abstract: Aspergillus fumigatus is a mold capable of causing severe infection in humans. Infections caused by A. fumigatus can often be treated using antifungals. However, there have been several reported cases of treatment failure around the world over the last two decades. Generally speaking, treatment failure in patients is often associated with antifungal resistance in A. fumigatus. My thesis aims at better understanding the distribution and investigating the origin of resistance in A. fumigatus at both global and local levels. Here, we analyze A. fumigatus strains from 15 countries, including strains from Hamilton, Ontario. Our findings will potentially contribute towards establishing effective long-term management strategies against A. fumigatus infections locally and globally.


title: Active Disturbance Estimation and Compensation for Improving Diesel Aftertreatment Performance

contributor:
YAN, FENGJUN
Mechanical Engineering

subject:
Active Disturbance
Diesel aftertreatment systems
estimation
Control

abstract:
Diesel engines are widely used in automotive sector due to their high fuel efficiency, distinguished durability and great reliability. However, NOx and particulate matters (PM) are main concerns of the Diesel engines due to their lean burn conditions. To reduce these emissions, Diesel engines are usually coupled with state-of-the-art Diesel aftertreatment systems including a Diesel Oxidation Catalyst (DOC), a Diesel Particulate Filter (DPF), and a Selective Catalytic Reduction system (SCR). With increasingly stringent regulations, the estimation and control strategies of Diesel after-treatment systems for NOx and PM reduction are becoming more and more critical and challenging, especially under transient conditions with unknown system dynamics including disturbances and model uncertainties. To address these problems, this thesis focuses on advanced strategies based on disturbance estimation and compensation for improving the performance of Diesel after-treatment systems.

Urea injection and ammonia storage ratio are critical for the SCR system to achieve high NOx reduction efficiency and low NH3 slip. Nevertheless, unknown system dynamics including input (urea injection) disturbances and model uncertainties of SCR system make it challenging to achieve high NOx reduction efficiency and low NH3 slip. To deal with these obstacles, Paper 1, Paper 2 and Paper 3 (Chapter 2, 3, and 4 respectively) proposed active disturbance estimation and compensation methods for enhancing the SCR performance. Paper 1 (Chapter 2) introduces two different methods to accurately detect urea injection and correct for urea dosing control. Paper 2 (Chapter 3) depicts a robust Nonlinear Disturbance Observer (robust NDO) to effectively estimate the ammonia storage ratio in a cost-effective way. Paper 3 (Chapter 4) presents a compound control strategies based on active disturbance rejection control (ADRC) to precisely keep NH3 slip low and achieve high NOx reduction efficiency.

DOC thermal management is critical to effectively burn the soot during DPF regeneration (PM reduction). But unknown system dynamics including DOC inlet emissions and model uncertainties make it difficult for DOC mean temperature estimation and DOC outlet temperature control during DPF regeneration. To deal with these challenges, Paper 4 and Paper 5 (Chapter 5 and 6 respectively) developed active disturbance estimation and compensation strategies for improving DOC thermal management during DPF regeneration. Paper 4 (Chapter 5) introduces a robust filter based on Smooth Variable Structure Filter (SVSF) with augmented disturbance states to estimate the mean temperature of DOC. Paper 5 (Chapter 6) presents a composite controller combining a feedforward controller and an modified Active Disturbance Rejection Controller (mADRC) with time delay compensation for the DOC outlet temperature control.

The proposed methods in the 5 papers are either validated by the calibrated GT-power model or experiments with Diesel after-treatment systems.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: The Comintern and the Communist Parties of South Africa, Canada, and Australia on Questions of Imperialism, Nationality and Race, 1919-1943

contributor:
McDonald, Tracy
History

subject:
Communism
Comintern
Race
Anti-Imperialism
Self-Determination
Soviet Union
Communist Party of Canada
Communist Party of Australia
Communist Party of South Africa

abstract: In 1919, the Bolshevik Party of Russia formed the Communist International (Comintern) to lead the international communist movement. As part of its efforts, it maintained a strong commitment to supporting colonial liberation, self-determination of nations, and racial equality. Many scholars of the Comintern and the Soviet Union assume that Moscow demanded firm discipline of all member parties and these parties largely followed its lead. But the Comintern was not as monolithic as is often presumed. Colonial affairs frequently were overlooked and European Communist Parties often skirted their commitment to supporting their colonial counterparts. Individual communists took it upon themselves to promote anti-imperialism or racial equality, but their efforts were frequently hampered by the tactical shifts of the Comintern and eventually, the erosion of Moscow’s interest. Frequently, the prioritization of certain issues in the Comintern proved to be the most important factor in determining Comintern interference in member parties. This dissertation includes the first comparative analysis of the Communist Parties of South Africa, Canada and Australia on issues of anti-imperialism, nationality, and race. In comparing these parties, this study explores the limits of Moscow’s control of other Communist Parties, while detailing the similarities and differences in the efforts of these three parties to combat imperialism, support colonial liberation, and fight for national rights and racial equality. This dissertation is the first to detail the Canadian and Australian communism’s efforts, sometimes on their own initiative, on anti-imperialism, nationality and racial equality during the interwar period, to provide new conclusions about Comintern intervention in South Africa, and to highlight the prioritization of the Comintern as each party sees Moscow’s intervention on these issues to very different degrees.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)

abstract: In 1919, the Bolshevik Party of Russia created the Communist International, an organization to lead communist parties throughout the world. Through this body, the Bolsheviks and international communists promoted colonial liberation, racial equality, and self-determination of nations. This dissertation uses the examples of the Communist Parties of South Africa, Canada, and Australia to show that each party dealt with these issues differently, saw different levels of intervention from the Communist International, and the severity of this intervention is directly tied to the priorities of the Soviet Union and the Communist International. Also included in this study is a comparative analysis of the tactics of all three parties, including the efforts of individual communists in each nation in developing platforms unique to the local conditions they were facing.


title: Spontaneous Edge Current in Chiral Superconductors with High Chirality

contributor:
Kallin, Catherine
Physics and Astronomy

subject:
Chiral Superconductor
Edge Current
Meissner Screening
Rough Surface

abstract:
We study the spontaneous edge current of chiral superconductors with high chirality both in the absence and presence of Meissner screening. We compute the edge current from a self-consistent solution to a set of coupled equations: quasiclassical Eilenberger equation, superconducting gap equation, and Maxwell equation.
We find that the spatial dependent chiral edge current is largely suppressed and has more nodes for higher chirality pairings.
In the absence of Meissner screening, the integrated current at T=0 is zero for all higher chirality pairings; while it is substantial for chiral p-wave. This conclusion is consistent with previous studies.
In contrast, at finite T, the integrated current is non-zero even for higher chiral pairings. It turns out that the spatial varying order parameter is crucial to understand this finite T behavior of the edge current.
When Meissner screening is included, the magnitude of the edge currents is reduced for all chiral pairings; however, the reduction is much weaker in higher chirality cases. We conclude that the Meissner effect is not that important for higher chiral pairings.
We also consider the effect of the rough surface on the edge current. The edge current of even chiral pairings is inverted by the strong surface roughness; however, that of the odd chiral pairings is not. The sub-dominant order parameters, induced by the surface, are the key to understanding this current inversion.

abstract: Thesis

abstract: Master of Science (MSc)


title: Advances in Quantitative Microwave Holography

contributor:
Nikolova, Natalia
Bandler, John
Electrical and Computer Engineering

subject:
microwave imaging
electromagnetics
algorithms
diagnostics

abstract:
Microwave imaging has been used to observe optically obscured targets for over 40 years.
 Recently, there has been a push towards developing a microwave imaging technology for use in medical diagnostics.
 Microwave imaging technology has several advantages over current imaging modalities, including use of nonionizing radiation, and compact inexpensive electronics. However, no microwave diagnostic technology exists yet for clinical use. This is due to complications in estimating the complex near-field scattering of the microwave radiation. Recently, advancements in a direct inversion algorithm known as microwave holography have adapted it to operate on near-field measurements. This method, with simulations, has demonstrated the ability to estimate the relative permittivity of the imaged structures. The purpose of this work is to develop quantitative microwave holography for use in tissue imaging. In addition to the previous version of quantitative microwave holography using the Born approximation, a new version of the method using Rytov's approximation is derived, expanding the versatility of the algorithm. Filtering strategies are also developed to enhance the image-reconstruction quality. However, nonphysical permittivity values are still generated. One possible solution is a constrained optimization strategy, which is derived and implemented. Finally, experimental studies demonstrate the ability of quantitative microwave holography to produce reconstructions of several tissue phantoms.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: Triaxial Behaviour of Layered Soil at Small Strain Level

contributor:
Guo, Peijun
Stolle, Dieter
Civil Engineering

subject:
Layered soil
Triaxial behaviour
K0-compression test

abstract:
The purpose of this study was to analyze the anisotropic behaviour of layered soil at small strain level. This thesis comprised experimental, numerical, and theoretical aspects and provided an insight to the concept of the ‘equivalent’ homogeneous cross-anisotropic material indicating that the layered soil can be replaced by an equivalent transversely isotropic material under certain conditions.
In the experimental program, this study extended Vaid’s work (1971) to conduct K0-compression tests in a rigid triaxial cell with a flexible lateral boundary for the determination of the K0-value of normally consolidated soil. The error induced by the compliance of the cell-water system that always existed in the previous study was successively eliminated by attaching a compliance correction system (i.e., GDS controller) to the triaxial cell. Three stress path tests (i.e., the K0-compression test, the plane strain compression test, and the hydrostatic pressure compression test) were conducted consecutively in a rigid triaxial cell for a layered soil specimen to determine the elastic cross-anisotropic properties of the equivalent homogeneous material. The applicability of the proposed approach was demonstrated by conducting the tests on two types of soil (i.e., the homogeneous soil and the layered soil).
A three-parameter constitutive equation for describing the soil’s cross-anisotropic elastic behaviour was modified in a basic FEM program. Based on the material properties determined by the experimental study as an input, numerical simulations (i.e., the numerical K0-test) using FEM were conducted to compare numerical results with the test results.
In the theoretical part, this study made use of the Reuss and the Voigt approximations and proposed a simple, yet physically meaningful, approach to determine the equivalent cross-anisotropic elastic properties of a multilayered medium. To simplify the exposition, a multilayered medium with two constituent materials that were both isotropic was examined.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: Stream thermal regimes within an alpine discontinuous permafrost catchment, southern Yukon Territory

contributor:
Carey, Sean, K.
Earth and Environmental Sciences

subject:
Hydrology
Groundwater
Temperature
Streams
Energy balance

abstract: MSc. Thesis, Ryan L. Rolick

abstract: Stream temperature, which influences many biogeochemical processes, is controlled by the exchange of water and energy across the stream surface, banks, and bed. A stream’s thermal sensitivity is its sensitivity to changes in air temperature and is increasingly important with projected warming in northern regions. As the thermal dynamics in permafrost underlain headwater streams are poorly documented, this study examines the thermal signals of two neighboring alpine streams (Granger Creek, GC and Buckbrush Creek, BB) within the Wolf Creek Research Basin (WCRB), Yukon Territory, and quantifies the dominant energy fluxes through an energy budget approach. A 1950 m study reach was established in each stream where water temperature, vertical streambed temperature, and stream discharge were measured. Distinct thermal heterogeneity is observed in each stream, with areas of persistent temperature decrease along their lengths, minimal downstream increase in stream temperature in GC, and an overall decrease in downstream temperature in BB. These observations are indicative of focused groundwater upwelling, low thermal sensitivity, and an increasing downstream influence of groundwater. This is inferred from increases in specific conductivity (2 μS/cm – 20 μS/cm) at locations of temperature decrease, and patterns in low (high) mean air-water linear regression slope (intercept) values. With distance downstream, regression slope (intercept) in GC went from 0.37 (1.2 ̊C) upstream to 0.33 (2.6 ̊C) at the outlet. Similarly, in BB regression slope (intercept) went from 0.37 (2.1 ̊C) upstream to 0.24 (3.3 ̊C) downstream. These patterns also indicate an overall lower thermal sensitivity and greater groundwater influence across the study reach of BB. Downwelling is observed at locations of vertical temperature profiles in each stream through efficient downward propagation of the diel temperature signal into the streambed, indicating hyporheic exchange. The energy balance indicates a large unaccounted for sink in BB, further denoting a larger groundwater influence in its study reach. These findings highlight the importance for continued study of thermal regimes and the complicated interconnections between heat exchange processes in alpine catchments in permafrost regions.

abstract: Thesis

abstract: Master of Science (MSc)