title: Cutting Edge Honing With Non-Newtonian Fluids

contributor:
Koshy, Philip
Mechanical Engineering

subject:
Cutting Tool
Honing
Flow

abstract: Cutting tool edges are honed to an edge radius of about 15-30 micrometers for enhancing tool performance. During honing, defects left by prior manufacturing processes such as grinding and pressing are removed to achieve a higher quality edge. Recently, researchers have shown that tailoring the edge microgeometry to comprise an asymmetric shape and/or a gradient edge microgeometry is beneficial. Conventional edge honing processes such as brush honing and abrasive micro-blasting are limited in terms of reliably generating such geometries in a productive manner. To this end, this research explored the application of non-Newtonian aqueous suspensions of cornstarch and abrasives, for the edge honing of cutting tools. This thesis details the science, technology, characteristics and capabilities of this innovative process.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: Contextualizing functional status with comorbidities in prognosticating post-hospital discharge outcomes: a retrospective cohort study

contributor:
Costa, Andrew
Health Research Methodology

abstract:
Background
	Discharges from acute episodes of hospitalization are well recognized as periods where individuals are at high risk of poor outcomes including hospital and emergency re-presentation, death, and long-term care facility (LTCF) admission or wait listing for older adults.  As the population of Ontario ages and is at higher risk of these outcomes, efforts to prognosticate these risks to optimize care delivery have recognized demographics and medical morbidity have been well-associated with these events using large datasets.  The impact of individual patient function and capacity to carry out their activities of daily living (ADLs), however, is not as well understood despite being central to an individual’s ability to remain successfully within the community.  Recent efforts have allowed for the administrative collection of data concerning functional capacity to both demonstrate the functional characteristics of the acutely hospitalized adult and understand its impact on post-discharge outcomes.

Methods
	Using databases housed at the Institute for Clinical Evaluative Sciences (ICES), a retrospective cohort of all adults 65 years of age or older who underwent assessment of their ADLs in the Healthcare Outcomes for Better Information and Care (HOBIC) during acute hospital admissions between 2008 and 2016.  Individuals who were expected to return to hospital (e.g. due to chemotherapy or dialysis) or were receiving palliative care, as well as individuals assessed at hospitals who did not complete enough HOBIC assessments to provide reliable information were excluded.  Descriptive analysis was performed to understand the functional and medical characteristics of the cohort.  Multivariable logistic regression analysis was used to determine how demographics, comorbidities, previous health service use, and functional status were associated with hospital re-admission, emergency re-presentation, death, and LTCF admission or wait-listing at 180 days post-discharge.  Subgroup analysis was also performed across common comorbidities including chronic obstructive pulmonary disease, coronary artery disease, congestive heart failure, falls, delirium, and dementia.

Results
	An analytic cohort of 139 798 was constructed for whom 67.4% of admission HOBIC assessments and 56.7% of discharge assessments were complete.  With increasing age there was increasing functional disability as well as increasing burdens of congestive heart failure, delirium, dementia, and falls.  The majority of individuals who were admitted with some degree of functional impairment experienced an improvement during their admission.  Function and comorbidities were found to be equally and moderately associated with increased odds of experiencing ED re-presentation and re-hospitalization, though there was poor discriminability (AUROC 0.62, 95% confidence interval 0.62-0.63 and 0.64, 0.63 – 0.65 respectively).  For death and LTCF admission or wait listing, however, functional impairment had greater association than comorbidities, and there higher discriminability was seen (AUROC 0.84, 0.83-0.85 and 0.79, 0.79-0.80).  Functional impairment was also more highly associated with poor outcomes in those with chronic obstructive pulmonary disease and dementia.

Discussion
	This analysis demonstrates that administrative data can be used to assess function, and that function is of comparable importance to the studied outcomes as medical comorbidity.  It demonstrates that meaningful information concerning function can be derived from secondary data, though information gathered concerning function at admission appears to be of questionable reliability, and comorbidities are likely under-reported.  Overall, however, it suggests that future efforts to assess individual risks of post-discharge outcomes should consider functional status as equally important to other factors more extensively historically studied.

abstract: Thesis

abstract: Master of Health Sciences (MSc)


title: Understanding Device Performance of Blue Organic Light-Emitting Diodes with Fluorescent and Phosphorescent Emitters

contributor:
Mascher, Peter
Engineering Physics

abstract:
This thesis proposes blue organic light-emitting diodes (OLEDs) composed of fluorescent and phosphorescent emitting layers (EMLs) and the study was accomplished by engineering device architecture and dopant distribution in the EMLs. We investigated the electrical and optical properties when both types of emitters are applied as EMLs into a single device and determined the emission ratio and contribution between fluorescent and phosphorescent emitters by deconvoluting electroluminescent spectra with Gaussian fitting. The fluorescent EML is composed of 4,4 -bis(2,2 -diphenylvinyl)-1,1 –diphenyl (DPVBi) doped with 4,4'-bis(9-ethyl-3-carbazovinylene)-1,1'-biphenyl (BCzVBi) while Bis[2-(4,6-difluorophenyl)pyridinato-C2,N](picolinato)iridium(III) (FIrpic) is doped into 1,3-Bis(N-carbazolyl)benzene (mCP) for the phosphorescent EML.
Firstly, dual-EML blue OLEDs are introduced and differentiated by doping styles, doping concentration and device structure to study the operating principles and changes in the efficiency and color characteristic in blue OLEDs. When both types of EMLs are used, the predominant emission is phosphorescence and the relative intensity of fluorescent and phosphorescent emission is controlled by the fluorescent doping concentration. With the incorporation of a step-graded doping profile in the EMLs, the trend of device performance is indicative of the effect of the location of the non-doped area. Blue OLEDs with the step-controlled doping concentration showed higher device efficiency and strengthened emission from fluorescence compared to the uniformly doped devices.
Secondly, triple-EML blue OLEDs with the various combinations of EML host configurations were studied. The electroluminescent spectra of the devices were deconvoluted by Gaussian peak fitting to understand the origin of blue emission. The device performance is strongly influenced by the location of the n-type host material. Furthermore, effects of interlayer and EML thickness variation in devices were investigated to optimize device efficiency and color emission.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: Unstable Systems of Viscous and Elastic Polymer Thin Films

contributor:
Dalnoki-Veress, Kari
Physics and Astronomy

subject:
Physics
Soft matter

abstract:
The work presented in this thesis focuses on the study of viscous and elastic polymer thin films in initially unstable configurations. The systems are driven to flow viscously or deform elastically to minimize their free energy. Since these experiments take place on length scales at which gravity does not play a role, the physics is governed purely by surface tension and viscosity in the case of fluid films, or elasticity in the case of rigid films. It is also possible to combine hydrodynamics and elasticity, for example, a viscous film that flows in response to the bending energy of an elastic perturbation, or an elastic film deformed by the capillarity or flow of a fluid.
Viscous flow in thin polymer films is studied in a system which is free-standing in air, meaning it has two fluid-air interfaces. Cylindrical holes are formed part way through a nano-scale polymer film, creating an unstable geometry with dissimilar surface areas at the two interfaces. When heated above its glass transition temperature, surface tension drives the film to flow to minimize its total excess surface area. The evolution is first dominated by fast vertical flow, which equilibrates Laplace pressure through the film by forming symmetric holes at each interface. Slow horizontal flow then becomes dominant, which continually reduces excess surface area by filling in the holes. A novel atomic force microscopy method is developed to monitor the two interfaces of a film as they flow, allowing the total free energy evolution of the system to be measured. The results agree with a hydrodynamic model developed to describe both stages of flow.
Elastic instabilities, where a rigid film deforms in response to geometrical confinement, are studied in a free-standing bilayer system consisting of a thin film on a pre-strained elastic substrate. These instabilities include sinusoidal wrinkling of the capping film, or, since the entire bilayer is free-standing, global buckling, where the entire system deforms out-of-plane. The transition between wrinkling and buckling is found to depend on the thickness and moduli ratios of the films, as well as the pre-strain in the substrate. A simple model shows good agreement with experiments.
Finally, the interaction between elasticity and viscosity is studied by measuring the flow of a viscous fluid perturbation driven by the bending energy of a rigid capping film. The experimental scaling of the perturbation size is in agreement with the theoretical prediction in the large perturbation limit.

abstract: Thesis

abstract: Doctor of Science  (PhD)


title: Adaptive Lighting for Computer Vision

contributor:
Kitai, R.
Electrical Engineering

subject:
adaptive lighting
computer vision

abstract:
A system capable of adjusting a computer vision system to unpredictable ambient lighting has been designed and attached to a silhouette robot vision system. Its principle of operation is based on the generation and analysis of the distribution of light in one T.V. frame. Designed to be used in robot vision applications, high speed processing of data is achieved in the system to generate a histogram of grey levels in one frame time. An addressable RAM technique for this purpose is explained. The system obtains two threshold values from the histogram of grey levels and places them into a threshold logic unit. A silhouette
from a grey level picture is obtained as the result of the process. Adaptability of the system is performed by using different integration times in the read out of the visual transducer. The implementation of the system is based on a video rate histogram generator, a sensitivity control unit, a DMA circuit, an 86/12A microcomputer and a solid state T.V. camera. A graphics printer is used to print out results and a CRT terminal to communicate with the microcomputer. The custom hardware and software implementations
for the system are depicted in detail.

abstract: Thesis

abstract: Master of Engineering (ME)


title: Theoretical and Experimental Investigation for the Effect Strain on the Below Threshold Output of InGaAsP Diode Lasers

contributor:
Cassidy, Daniel
Engineering Physics

subject:
theoretical investigation
electrical investigation
strain effect
threshold output
InGaAsP diode
diode lasers

abstract: The effect of strain (stress) on the below threshold output of InGaAsP diode lasers has been investigated theoretically and experimentally. The degree of polarization (DOP) and the polarization- resolved spectral output (PRSO) were obtained as a function of the external stress applied to the device. A correlation between the DOP and the peak of the PRSO as a function of the stress was found. This correlation suggests that below threshold, DOP can be used to measure the strain in the active region of lasers. A model based on a strain modified Shockley matrix for the band calculation and a strain modified dipole moment for the optical emission has been constructed to bridge the correlation between the DOP and PRSO.

abstract: Thesis

abstract: Master of Engineering (ME)


title: Diffusion of Receptors on Macrophage Plasma Membranes

title: Characterizing the Lateral Diffusion of TLR2 and CD14 Receptors on Macrophage Plasma Membranes

contributor:
Moran-Mirabal, Jose
Bowdish, Dawn
Biomedical Engineering

subject: Macrophage, Receptor, Diffusion, Single Particle Tracking, Raster Image Correlation Spectroscopy, Surface Topography, Aging

abstract: Among the central constituents of the innate immune system are macrophages, which are known for phagocytosis or ‘eating’ foreign particles or pathogens. Macrophages express several cell-surface proteins including transmembrane and membrane-anchored receptors, which play a vital role in their response to pathogenic stimuli. The plasma membrane is a highly fluid and dynamic environment, which facilitates the diffusion of lipids and proteins within the plane of the membrane. This study aims to measure the lateral diffusion of two types of plasma membrane receptors on macrophages, toll-like receptor II (TLR2) and cluster of differentiation 14 (CD14), to answer three main research questions: 1) Which type of fluorescence-based microscopy techniques is best suited for measuring the lateral diffusion of TLR2 and CD14 on macrophage plasma membrane? 2) Does culturing macrophages on different surface topographies impact the diffusion of TLR2 in the plasma membrane and its pro-inflammatory response, along with morphological changes? 3) Does aging alter the lateral diffusion of TLR2 in the plasma membrane of macrophages? To date, a variety of fluorescence-based methods have been developed to study the dynamics of cell membrane constituents. These techniques are based on either ensemble or single particle measurements. We have used single particle tracking methods to track the mobility of fluorescently labeled membrane receptors on murine bone marrow-derived macrophages. Total internal reflection fluorescence microscopy (TIRF) was used to visualize and capture the dynamics in live cells. Using a custom routine algorithm we detected, localized, and tracked the particles to calculate their diffusion coefficient, extracted from the mean-squared displacement as the most common measure of diffusion. We also measured the diffusion coefficient using an ensemble-based technique known as Raster Image Correlation Spectroscopy (RICS) with a confocal laser-scanning microscope. The use of confocal eliminates the out-of-focus signal and enables measurements that are confined to a narrow plane in the cell. Also, the ability of RICS to separate the slow and immobile fractions of particles makes it possible to detect heterogeneities in diffusion. To our knowledge, this is the first study that has utilized both SPT and RICS to directly compare receptors’ diffusion in different membrane sections. Moreover, this is the first study that has examined the diffusion of receptors on macrophages adhered to different surface topographies, and the first that has investigated the receptors’ diffusion in young and old macrophages.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)

abstract: The immune system is highly dependent on a specialized subset of white blood cells known as macrophages that are capable of clearing damaged and dead cells as well as a wide range of invading micro-organisms. Specific receptor proteins present on the membrane of macrophages are involved in the recognition of particles and subsequent signaling to recruit other immune cells or to promote healing and wound repair. To date, a variety of fluorescence-based microscopy methods have been used to study the dynamics of cell membrane components. The mobility of several membrane receptors in macrophages has been studied using microscopy techniques, which have provided valuable insights into their function. However, there is still insufficient information about the behavior of two key receptors (TLR2 and CD14) that participate in signaling in response to bacterial products. This thesis aims to answer three major questions with regard to receptor mobility (i.e., diffusion) within macrophage membrane: 1) Which type of fluorescence-based microscopy technique is more suitable for measuring the mobility of TLR2 and CD14 receptors on macrophage membranes? 2) What is the impact of different surface topographies on TLR2 diffusion in adhered macrophages, as well as cell shape, and the ability of macrophages to internalize particles? 3) Does aging alter TLR2 mobility in the membrane of macrophages? The following chapters provide detailed answers to these questions. In brief, we have demonstrated that TLR2 and CD14 diffusion measurements in adhered macrophages highly depend on the membrane section chosen. In addition, our results show that micro- and nanostructured surface topographies alter the shape of adhered macrophages and yield higher bacteria internalization, while the diffusion of TLR2 is not changed. When comparing macrophages derived from young and old mice, we find similar diffusion rate of TLR2 in macrophages of the two age groups.


title: TOOL LIFE ENHANCEMENT OF COATED CARBIDE TOOLS USED FOR MILLING OF H13 TOOL STEEL

contributor:
Veldhuis, Stephen C.
Mechanical Engineering

subject: milling; multilayer; interlayer; WPC treatment, PVD coating, micro-mechanical property assessment.

abstract: Dry High speed and wet milling strategies have both been used to machine hardened die and mold H13 tool steel (HRC 45-58). The TiAlCrSiYN-based family of PVD coatings prepared with various architectures (mono-, multi- and multilayer with an TiAlCrN interlayer) were studied to evaluate the coating micro-mechanical properties that affect tool life during dry high-speed milling of H13 tool steel. A systematic design of varying TiAlCrN interlayer thickness within a multilayer coating structure was developed and its influence on coating properties and cutting performance was investigated. A comprehensive characterization of the coatings was performed using a transmission electron microscope (TEM), focused ion beam (FIB), scanning electron microscope (SEM), X-ray powder diffraction (XRD), room-temperature nanoindentation, a nano-impact, ramped load scratch and a repetitive load wear test. The incorporation of an interlayer into the multilayer coating structure was found to increase the crack propagation resistance (CPRs) to 5.8 compared to 1.9 for the multilayer and 1.6 for the monolayer coatings, which resulted in a 60% tool life increase. The wear test at a load of 1.5 N showed that although the 500nm interlayer exhibited the best coating adhesion, a decline in the H3/E2 ratio was observed to worsen the machining performance. An approximate 40% increase in the tool life was achieved with the 300 nm interlayer by obtaining a balance between mechanical and adhesion properties. To investigate the tool performance during the wet milling of hardened tool steels, the (AlCrN-TiAlN) bi-layer PVD coating was post-treated by WPC (Wide Peening Cleaning) at various pressures and times. Fatigue resistance of the coating following the application of post treatment was observed to improve as the micro-mechanical characteristics (such as H3/E2 ratio, yield stress) were increased. A deterioration in the coating’s adhesion with increasing WPC pressure was also observed as measured by wear test applying a load of 1 N. Through experimentation a balance between fatigue resistance and adhesion was found with tool life being improved by 35% at a WPC applied pressure of 0.2 MPa.

abstract: Dissertation

abstract: Doctor of Philosophy (PhD)

abstract: Over the last 50 years, PVD (physical vapor deposition) coatings have played an increasingly important role in manufacturing where tool cost takes up 3% of the total expenses of the production process. Optimization of these coatings can expedite production wherever machining is conducted under extreme cutting conditions and consequent high material removal rates. These considerations assert significant importance on conducting  research on PVD coating development specifically for milling of H13 tool steel, the material widely used in the mold and die industry. This research work seeks to enhance the micro-mechanical and adhesion properties of PVD coatings through architectural design and careful process development while relating desired properties to the high-performance milling of H13 tool steel.


title: SOCIAL DETERMINANTS OF HEALTH IN UTERINE CANCER PATIENTS IN ONTARIO: ASSOCIATION WITH DISEASE PRESENTATION AND OUTCOME

contributor:
Seow, Hsien
Health Research Methodology

subject:
social determinants of health
uterine cancer
cancer outcomes

abstract:
Objective: Delay in diagnosis and treatment of endometrial cancer may be associated with disease progression and impact management and outcomes. Social and cultural barriers influence recognition of symptoms and self-advocacy in seeking and complying with care. Associations between social determinants of health (SDH) and disease presentation, treatment and outcomes has been shown in some healthcare systems. Our objective was to investigate these in Ontario’s universal access system.
Methods: Endometrial cancer patients in Ontario diagnosed 2009-2017 were identified, and clinical, social and demographic information extracted from administrative databases. SDH were quantified using previously validated marginalization quintiles (material deprivation, residential instability and ethnic concentration). Associations between SDH, disease stage, treatment and outcome were explored using chi-square, log-rank and logistic regression.
Results: 19530 patients were identified. 73% of cancers were confined to the uterus. Stage distribution differed across marginalization quintiles (p<0.001) with advanced disease found more frequently in highly marginalized patients (highest vs lowest quintile): OR=1.28 (95% CI 1.14-1.45) for deprivation, OR=1.2 (95% CI 1.06-1.35) for residential instability and OR=1.3 (95% CI 1.15-1.46) for ethnic concentration (<0.0001)). Highly marginalized patients also had less timely surgery (p<0.0001). Overall survival was shorter in patients in high deprivation and residential instability quintiles (log rank p-value<0.0001) but not in high ethnic concentration quintiles, with HR=1.4 for deprivation (p<0.0001) and HR=1.53 for instability (p<0.0001) for the highest marginalization quintile. Survival differences persisted in more uniform cohorts of early (stage I) disease and endometrioid tumors and on multivariable analysis.
Conclusions: Marginalized populations diagnosed with uterine cancer present at more advanced stages, wait longer for surgery and have shorter overall survival. Associations of SDH with uterine cancer presentation and management in Ontario could shed light on the impact of these factors on disease trajectory, drive policies for patient advocacy and redistribution of resources and promote health equity in this population.

abstract: Thesis

abstract: Master of Public Health (MPH)

abstract:
Conditions in the social environment in which people are born, live and work are powerful influencers of health and well-being. In fact, these circumstances have also been called Social Determinants of Health (SDH). Cancer outcomes are one of the domains impacted by SDH.
In this study, we set out to investigate the association between SDH and uterine cancer outcomes in Ontario, Canada. We guessed that SDH may influence how soon patients with symptoms seek help from their doctors, how quickly their problem is investigated and how well they are able to undergo treatment.
We used a tool called the Ontario Marginalization Index to break down Ontario’s uterine cancer patient population into groups according to degree of social, financial and ethnic marginalization. We found that more marginalized patients tended to present to care with more advanced cancers, that they took longer to have surgery for their cancer and that their survival was worse. These findings suggest there is more work to be done to promote health equity in cancer care.


title: Indigenous Masculinity, HIV Wellness and Disclosure

contributor:
Jackson, Randy
Social Work

subject:
Indigenous Health
Indigenous Men
Indigenous Masculinity
Indigenous Gender
Disclosure
HIV/AIDS

abstract:
Title: Indigenous Masculinity and HIV Disclosure
Aim/Objective: The goal of this this research project is to explore how self-regulation of a masculine identity is impacted by colonization in the context of HIV disclosure for Indigenous men. Specific objectives under this goal include the following: (1) Understanding Indigenous men’s ideas about Indigenous masculinity; (2) understanding how Indigenous men come to understand the impact of colonization on their masculine identity; and (3) understanding how colonization affects Indigenous men’s experience of HIV disclosure.
Methods: This project adopts an Indigenous directed process consistent with principles of community-based research (CBR) and driven by decolonizing and Indigenous methodologies. Following an examination of relevant literature, six Indigenous men living with HIV were interviewed to discuss the significance of Indigenous masculinity in the context of HIV wellness and HIV disclosure. The findings from the literature review and interviews were coded within NVivo qualitative analysis software to compare emerging themes.
Findings: Following a discussion of the several aspects of Indigenous masculinity, the participants described the hinderances of colonization and stigmatization in disrupting healthy practices and conceptualization of Indigenous masculinity. Throughout the journey of healing, a process of deconstructing western ideals was necessary towards developing a personal sense of Indigenous masculinity which aligned with their Indigenous identity. Upon successful negotiation of the relationship between Indigenous masculinity and HIV status, disclosure was used at various stages of the healing journey to affirm Indigenous masculinity, discover a personal sense of purpose, and to educate others.
Conclusion: The use of disclosure was found to be a vital component towards the development and practice of Indigenous masculinity. The findings of this project will be used to apply for future grants to design a service or intervention which provides Indigenous men living with HIV with a safe and healthy environment to practice Indigenous masculinity.

abstract: Thesis

abstract: Master of Social Work (MSW)


title: THE INTEGRATION OF CULTURAL SAFETY IN NURSING EDUCATION: AN INDIGENOUS INQUIRY OF NURSE EDUCATOR EXPERIENCES

contributor:
Wahoush, Olive
Nursing

subject: Cultural Safety, Nursing Education, Nurse Educators, Indigenous Health, Micro-Reconciliation

abstract: The objectives of this research were to (a) explore nursing educators' experiences of integrating cultural safety in nursing education, (b) describe the strategies that nurse educators use, and (c) identify the barriers and possible solutions to facilitate the integration of cultural safety into nursing education. Indigenous Research Methodology was used to gain insight into nurse educators' experiences of integrating cultural safety in nursing education. Conducted in Ontario with 15 participants from 11 of the 14 accredited SON across Ontario. Conversing and listening to personal stories was the primary knowledge-seeking method. A harmonized narrative and thematic approach were used to analyze the conversations and stories from nurse educators. The results demonstrated the current colonial structure of nursing education is incompatible with and a barrier to the integration of cultural safety. As a consequence, this study reveals more barriers than strategies for integration, which demonstrates the substantial need for leadership, resources, and institutional support to integrate cultural safety. Current approaches have amplified forms of structural violence experienced by Indigenous nurse educators. This form of violence has been labeled a sophisticated type of racism that manifests in ways such as tokenism and othering of Indigenous nurse educators. Information about barriers, challenges and successes experienced by study participants supports recommendations for the dismantling of colonial discourses that are pervasive in nursing education and a barrier to integration of cultural safety. This study of integrating cultural safety supported the problematic nature of decolonization and Indigenization approaches as solutions to ensure cultural safety. Micro-reconciliation was identified as a possible solution to promote successful integration of cultural safety in nursing education.

abstract: Thesis

abstract: Master of Science in Nursing (MSN)


title: THE DESIGN AND CHARACTERIZATION OF MICROPHYSIOLOGICAL PLATFORMS TO MODEL THE HUMAN PLACENTA

title: MICROPHYSIOLOGICAL MODELS OF THE HUMAN PLACENTA

contributor:
Raha, Sandeep
Medical Sciences

subject:
placenta
trophoblast
microphysiological
spheroid
cell culture
model
pregnancy
barrier

abstract: The human placenta facilitates many key functions during pregnancy, including uterine invasion, vascular remodeling, hormone secretion, immune regulation, and maternal-fetal exchange. Placental research, however, has been limited in part by the unrepresentative nature of traditional models. The objective of this doctoral thesis was to build and characterize novel, in vitro models that reintegrated important anatomical and environmental elements of the human placenta, thus enabling more physiologically-accurate assessments of placental function. In our first model, we manipulated the thickness of the extracellular matrix surface to promote the self-assembly of trophoblast cells into three-dimensional (3D) aggregates that exhibited increased genetic and functional markers of syncytial fusion. In our second model, we established a high-throughput platform to generate 3D trophoblast spheroids that underwent dynamic invasion and migration, expressed transcriptomic profiles redolent of the extravillous trophoblast phenotype, and responded to various drugs relevant to pregnancy. In our third model, we developed a trophoblast-endothelial co-culture model of the placental barrier that underwent syncytial fusion, exhibited size-specific barrier permeability, and functioned under physiologically-relevant oxygen tensions. In conclusion, our models may each serve as valuable tools for researchers, contribute to investigations of different aspects of placental biology, and aid in the screening of drugs and toxins for pregnancy.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)

abstract: The human placenta is an important organ that helps regulate the health of both the mother and fetus during pregnancy. Researchers have traditionally studied the placenta through the use of animals or isolated cells, but these have been criticized for not being similar enough to the human placenta. Our objective was to build models that better resembled the structure and environment experienced by the human placenta within the body, such that we could better study its function. During the course of my doctoral work, I built and analyzed three models of the human placenta using human cells that were grown in three dimensions, in multiple layers, and/or in a specific environment. Our first model demonstrated that placental cell behaviour and function can be controlled by altering the thickness of the surface we grew them on. Our second model grew placental cells in three-dimensions and mimicked the invasion process into the mother’s uterus during early pregnancy. Our third model grew placental cells with blood vessel cells to form the barrier that regulates the passage of all substances between the mother and fetus during pregnancy. We also tested the impact of low oxygen on the placental barrier’s formation and function. Overall, we discovered that placental cells could indeed function more similarly to how we expect them to in the body when we design platforms that better resemble their structure and environment. Our model development work provides new information about placental biology and may serve as valuable tools in research and drug development.


title: Numerical Integration of Stiff Differential-Algebraic Equations

contributor:
Nedialkov, Nedialko
Computational Engineering and Science

subject:
differential-algebraic equations
stiff

abstract:
Systems of differential-algebraic equations (DAEs) arise in many areas including electrical circuit simulation, chemical engineering, and robotics. The difficulty of solving a DAE is characterized by its index. For index-1 DAEs, there are several solvers, while a high-index DAE is numerically much more difficult to solve. The DAETS solver by Nedialkov and Pryce integrates numerically high-index DAEs. This solver is based on explicit Taylor series method and is efficient on non-stiff to mildly stiff problems, but can have severe stepsize
restrictions on highly stiff problems.
Hermite-Obreschkoff (HO) methods can be viewed as a generalization of Taylor series methods. The former have smaller error than the latter and can be A- or L- stable. In this thesis, we develop an implicit HO method for numerical solution of stiff high-index DAEs. Our method reduces a given DAE to a system of generally nonlinear equations and a constrained optimization problem. We employ Pryce’s structural analysis to determine the constraints of the problem and to organize the computations of higher-order Taylor coefficients (TCs) and their gradients. Then, we use automatic differentiation to compute these TCs and gradients, which are needed for evaluating the resulting system and its Jacobian.                                                                   We design an adaptive variable-stepsize and variable-order algorithm and implement it in C++ using literate programming. The theory and implementation are interwoven in this thesis, which can be verified for correctness by a human expert. We report numerical results on stiff DAEs illustrating the accuracy and performance of our method, and in particular, its ability to take large steps on stiff problems.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: GS-MBE Growth of Ga(ln)AsN Nitrides for Long Wavelength Semiconductor Lasers

contributor:
Thompson, David A.
Engineering Physics

subject:
semiconductor lasers
GS-MBE
Ga(ln)AsN
Ga(ln)AsN nitrides

abstract:
Quaternary GalnAsN containing a small amount of nitrogen (<2%) is a
potentially promising material for realizing long-wavelength emission lasers for
applications in optical communication systems. Such devices should have better high-temperature characteristics than conventional InGaAsP lasers due to an increase of the
conduction band offset. In this thesis, the GS-MBE growth of quaternary GalnAsN and
ternary GaAsN was carried out. Active N was produced by passing high purity nitrogen
gas into either an RF or an ECR plasma source. The RF plasma source was found to
produce better quality nitrides. Characterization techniques such as photoluminescence,
X-ray diffraction, TEM, SIMS, and Hall effect measurements were used to characterize
thick layers (e.g. 1 pm) and quantum wells of these nitride materials.
The concentration of N incorporated into GalnAs and GaAs is very dependent on
growth conditions and plasma conditions. The incorporation of a small amount of N into
compressively strained InGaAs reduces the strain and produces a red-shift of
photoluminescence peak. However, compared to N-free InGaAs materials, the optical
quality is dramatically degraded yielding reduced photoluminescence intensity and a
broadened FWHM of the PL peak. Hall effect measurements on un-doped, Si-doped, Bedoped thick GalnAsN layers indicate the presence of a high concentration of electron and
hole traps. The results of SIMS suggest that impurity H might be responsible for the deep
level defects formed. However, the nature of the defects is currently unknown. From
TEM observations and comparison to samples grown with a He-plasma instead of a Nplasma, spinodal decomposition and ion-induced damage in GalnAsN may produce
the reduced quality of materials, but these are not the major reasons responsible for the
dramatic degradation of optical quality.
Thermal annealing was found to be an effective method for significantly
improving the optical quality of GalnAsN with a low N concentration. Optimum
annealing conditions were obtained. Hall effect measurements on annealed samples
indicate that electron and hole traps are reduced but still present after anneal.

abstract: Thesis

abstract: Master of Engineering (ME)


title: Understanding How Motivation Impacts Learning Through Mind Wandering

contributor:
Kim, Joseph A.
Shore, David I.
Psychology

subject:
mind wandering
learning
attention
motivation

abstract: The current thesis intersects cognition and education to study the mental experience of mind wandering and its consequences. This research examines attention and memory using materials, methodologies, and research questions drawn from authentic classroom environments. The overarching question driving this thesis centres on when and why students mind wander during lectures, and how we can reduce its negative impact on learning. The hypothesis underpinning all the presented research proposes that stronger motivation reduces mind wandering, thus improving learning outcomes. The current thesis examines how three different motivational manipulations affect reports of intentional mind wandering—when participants deliberately choose to redirect their attention away from the lecture—and unintentional mind wandering—when participants find their attention to be off-task despite their best efforts to stay focused. Quizzing, monetary rewards, and time-based rewards affected mind wandering reports, particularly reports of intentional mind wandering. Although, throughout this thesis, there was no direct impact on learning, there was consistent evidence of a negative correlation between mind wandering reports and learning. Based on these findings, this thesis discusses implications for the enterprise of mind wandering research, principles of motivation to leverage in education, and pedagogies to improve the classroom learning experience.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)

abstract: Our minds wander multiple times a day—during work, school, leisure time, meals, and countless other activities. When mind wandering occurs during lectures, it negatively impacts our ability to learn information. If we are motivated, we are likely to learn more, and some researchers have suggested that this happens because we are better able to pay attention while learning. The research presented in this thesis used three reward types in an attempt to reduce two types of mind wandering (intentional vs. spontaneous) and, therefore, produce better learning. This thesis demonstrated that outside rewards can increase motivation, and that these changes in motivation appear to affect intentional mind wandering more than spontaneous mind wandering. Reducing mind wandering by properly motivating our students should promote better learning; as educators, effective lectures must play that role for students.


title: Mechanisms By Which Glucose Lowering Therapies Reduce Obesity And Atherosclerosis

contributor:
Steinberg, Gregory, R
Health Sciences

subject: Diabetes Obesity Atherosclerosis AMPK

abstract: The incidence of obesity, type 2 diabetes and cardiovascular disease (CVD) is increasing at alarming rates worldwide. Obesity is associated with a chronic nutrient surplus that contributes to chronic low-grade inflammation, ectopic lipid deposition and insulin resistance. Insulin resistance is an important factor contributing to the development of both type 2 diabetes and CVD.  Therefore, therapies that can address multiple aspects of cardio-metabolic diseases could have significant clinical utility to reduce morbidity and mortality associated with these conditions. Several distinct glucose lowering therapies have been developed, targeting unique molecular targets. Interestingly, three district glucose lowering therapies, metformin, canagliflozin and salsalate have been shown to potently activate the central energy regulating enzyme, AMP activated protein kinase (AMPK). Activation of AMPK has been shown to be important for regulating fatty acid and cholesterol synthesis, fatty acid oxidation, glucose homeostasis, inflammation and whole-body energy expenditure. Therefore, the objective of this thesis was to examine the effects of metformin, canagliflozin and salsalate, on obesity, atherosclerosis, hepatic lipid metabolism, and macrophage inflammatory signalling and to delineate the mechanism(s) by which these changes occur. In this thesis we show that metformin reduces obesity through a circulating hormone GDF15, and that AMPK is not required for metformin induced GDF15 secretion. Additionally, we show that canagliflozin reduces hepatic cholesterol synthesis and macrophage IL1-1β secretion through mechanisms requiring AMPKβ1. Lastly, we show that salsalate reduces atherosclerosis in a manner dependent on macrophage AMPK β1 and this is associated with reduced macrophage proliferation in vitro and in vivo. These insights into the mechanisms by which these glucose lowering therapies elicit beneficial effects on obesity and atherosclerosis further our understanding of the potential use of these agents for treatments beyond improved glycemic control. Furthermore, this evidence can direct future drug development or drug combinations to more effectively treat multiple aspects of these common chronic diseases that affect over a billion people worldwide.

abstract: Thesis

abstract: Doctor of Philosophy (Medical Science)


title: Polymer Functionalization of Single-Walled Carbon Nanotubes through Covalent Methods

contributor:
Adronov, Alex
Chemistry

subject:
Carbon Nanotubes
Single-walled carbon nanotubes
Functinalization

abstract:
The discovery of nanotubes with unique mechanical, electrical, and
thermal properties has led to their use in the development of the next generation
of composite materials. However, their poor solubility and dispersion properties
in any organic and aqueous solvents limits their potential applications.
In order to improve their solubility, single-walled carbon nanotubes
(SWNTs) were functionalized along their sidewalls with phenol groups using a
1,3-di^polar cycloaddition reaction. These phenols could be further derivatized
with 2-bromoisobutyryl bromide, resulting in the attachment of atom transfer
radical polymerization initiators to the sidewalls of the nanotubes. These
initiators were found to be active in the polymerization of methyl methacrylate
and t-butyl acrylate from the surface of the nanotubes. However, the
polymerizations were not controlled, leading to the production of high molecular
weight polymeric grafts with relatively large polydispersities. The resulting
polymer carrying nanotubes were analyzed by IR, Raman spectroscopy, solid-state NMR, DSC, TEM, and AFM. The nanotubes functionalized with
poly(methyl methacrylate) were found to be insoluble in organic solvents, such as
THF and CH2CI2. However, the dispersion property of SWNTs in the polymer matrix
was improved dramatically.
Another monomer t-butyl acrylate (t-BuA) was also polymerized using
the same macroinitiators. It was found that the SWNTs functionalized with t-BuA
iii were soluble in a variety of organic solvents. The t-butyl groups of these
appended polymers could also be removed to produce nanotubes functionalized
with poly (acrylic acid), resulting in nanocomposites that are soluble in aqueous
solutions.
In addition, polystyrene (PS) which was prepared by stable free radical
polymerization, was used to functionalize SWNTs through the radical coupling
reaction. IR, NMR, TEM, and AFM confirmed that this polystyrene was
covalently bonded to the SWNTs. It was also found that the resulting PS-SWNTs
composites were quite soluble in organic solvents, such as THF and CH2C12.

abstract: Thesis

abstract: Master of Science (MSc)


title: The Effects of Septal, Thalamic, and Tegmental Lesions on Locomotor Activity in the Hooded Rat

contributor:
Vanderwolf, C.H.
Psychology

subject:
Hooded rat
Locomotor activity
septal lesions
thalamic lesions
tegmental lesions

abstract: Animals with one of septal, medial thalamic or tegmental reticular formation lesions were compared on three measures of spontaneous activity (a brief test in a novel maze and seven-day tests in running wheels or photocells cages) and on active avoidance learning. Wheel running was depressed by all the lesions (especially septal and tegmental lesions) while locomotion in the maze and photocell cages was unaffected. Avoidance learning was depressed by septal and thalamic lesions but not by tegmental lesions. These results are discussed in terms of the hypothesis that these brain structures form part of systems which facilitate or inhibit somatomotor activity.

abstract: Thesis

abstract: Master of Arts (MA)


title: Towards Automating Code Reviews

contributor:
Sekerinski, Emil
Software Engineering

subject:
machine learning
code reviews

abstract: Existing software engineering tools have proved useful in automating some aspects of the code review process, from uncovering defects to refactoring code. However, given that software teams still spend large amounts of time performing code reviews despite the use of such tools, much more research remains to be carried out in this area. This dissertation present two major contributions to this field. First, we perform a text classification experiment over thirty thousand GitHub review comments to understand what code reviewers typically discuss in reviews. Next, in an attempt to offer an innovative, data-driven approach to automating code reviews, we leverage probabilistic models of source code and graph embedding techniques to perform human-like code inspections. Our experimental results indicate that the proposed algorithm is able to emulate human-like code inspection behaviour in code reviews with a macro f1-score of 62%, representing an impressive contribution towards the relatively unexplored research domain of automated code reviewing tools.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: The Relationship Between Gut Microbiota and Metabolites in the Expression of Generalized Anxiety Disorder

contributor: Medical Sciences (Division of Physiology/Pharmacology)

subject:
anxiety
depression
generalized anxiety disorder
major depression
gut microbiota
microbiome
bacteria
metabolism
metabolomics
neurotransmitters
trace amines
dopamine
acetylcholine
octopamine
germ-free
mouse
behaviour
emotion
beta defensin
Illumina
hippocampus
amygdala
olfactory bulb
BDNF
GDNF
neurotrophins
immunofluorescence
nanostring
genes
CCR2
Cnlp
Nfkb1
immune
cecum
brain
psychiatric

abstract:
Anxiety disorders are the most prevalent psychiatric conditions within primary
care, affecting up to 29% of people across their lifetime. Generalized Anxiety disorder
(GAD) is frequently comorbid with Major Depressive Disorder (MDD), resulting in
greater functional impairment. Gut microbiota have been shown to modulate brain
chemistry and function, possibly also playing a role in the genesis of anxiety. Bacteria are
also able to produce, or interact with the host metabolism of neuroactive substances,
including classical neurotransmitters and trace amines, like octopamine, which although
found in trace concentrations in the mammalian brain, can affect CNS function.
Specifically, trace amines can affect catecholamine release, reuptake and biosynthesis,
and modulate dopamine and serotonin metabolism.
We investigated whether microbiota from patients with GAD with no signs of immune activation can alter behaviour in gnotobiotic mice and whether this is accompanied by changes in metabolites within the gastrointestinal tract.
Germ-free NIH Swiss mice (n=35) were colonized with microbiota from either a
GAD patient (n=18) with severe anxiety, comorbid depression, and low serum and fecal
octopamine, or an age and sex-matched healthy control (HC) (n=17). Three weeks post-
colonization, mouse behaviour was assessed by standard psychometric tests. Emotionality
z-scores were calculated to provide a robust integrated behavioural assessment.
Microbiota profiles were assessed by 16S rRNA based Illumina, fecal β-defensin-3 level
was measured by ELISA. After sacrifice, mouse brain BDNF and GDNF expression was assessed by immunofluorescence, and gene expression in the hippocampus, amygdala,
and olfactory bulbs was assessed by Nanostring. Stool and cecum metabolites were
measured in all colonized mice by multisegment injection-capillary electrophoresis-mass
spectrometry (MSI-CE-MS).
There were no differences in fecal β-defensin levels between mice colonized with
GAD microbiota as compared to mice colonized with HC microbiota. However, GAD
mice exhibited greater anxiety and depressive-like behavior compared to HC mice in the
digging and tail suspensions tests. Behavioural z-scoring across all six standard
psychometric tests showed a significant increase in group emotionality score means of
GAD-colonized mice compared to HC-colonized mice. Mice colonized with microbiota
from a GAD patient had distinct bacterial profiles from mice colonized with HC
microbiota. Compared to HC mice, GAD mice had lower levels of dopamine, octopamine
and acetylcholine in cecum contents. Furthermore, GAD mice had higher expression of
BDNF in the amygdala, lower expression of BDNF in the hippocampus, and lower
expression of GDNF in the midbrain. GAD mice also had lower expression of CCR2 in
the hippocampus, higher Cnlp/CAMP in the amygdala and olfactory bulb, and higher
Nfkb1 in the olfactory bulb compared to HC mice.
Our results suggest that microbiota from a selected patient with GAD has the
ability to induce anxiety and depressive-like behavior, by mechanisms independent of
immune system, likely by altered production of biogenic amines and neurotransmitters.

abstract: Thesis

abstract: Master of Science (MSc)


title: The Effects of the Intensity of the Unconditioned Stimulus on the Acquisition and Extinction of the Conditioned Emotional Response

title: The Effects of US Intensity on the Conditioned Emotional Response

contributor:
Kamin, L. J.
Psychology

subject:
unconditioned stimulus
conditioned emotional response

abstract: The effects of intensity of the unconditioned stimulus (US) on the acquisition and extinction of the conditioned emotional response (CER) in rats were investigated. The US intensities studied were 0.28, 0.49, 0.85, 1.55, and 2.91 ma. Both acquisition and extinction of the CER were found to be monotonic functions of US intensity, with the higher US intensities producing more rapid acquisition and more resistance to extinction. The lowest shock intensity failed to produce suppression. The 0.49 ma. subjects typically showed a partial recovery of normal operant behavior after development of a fairly profound CER. The results were interpreted as consistent wth the supposition that the CER is acquired in accordance with Pavlovian laws of classical conditioning.

abstract: Thesis

abstract: Master of Arts (MA)


title: Growth and Cathofoluminescence of Zns:Mn Thin Films

subject: ZnS:Mn cathodoluminescence

abstract: A novel technique of incorporating dopants in a thin film was designed. It was successfully used to dope ZnS thin films with Mn. Cathodoluminescent (CL) properties of these Mn activated ZnS films were studied. For a constant accelerating potential and beam current density, the CL emission intensity was found to increase with Mn content up to -2 wt% Mn. A further increase in the Mn content lead to a decrease in the CL intensity. The optimum Mn content is different than that for electroluminescence (-0.7 wt%) and photoluminescence (-1.6 wt%). Emission spectra of ZnS:Mn with a higher Mn content (> 1.64 wt%) show an additional red band besides the usual 580 nm yellow band. The relative intensity of the red band to the yellow band increases with the Mn content. The phenomenon of concentration quenching and the red emission seem to be interrelated; an attempt has been made to explain the physical basis behind these phenomena. Coverage of rough ceramic substrates by ZnS thin films deposited by vacuum evaporation and atomic layer epitaxy (ALE) has been investigated. The results suggest a uniform coverage in the case of ALE deposited films, while those deposited by vacuum evaporation show a shadowing effect.

abstract: Thesis

abstract: Master of Engineering (ME)


title: Material Properties from Miniature Punch Test and Finite Element Analysis

contributor:
Metzger, Don
Mechanical Engineering

subject:
material properties
miniature punch test

abstract: The Punch test provides a technique for the determination of material properties from small specimens. Using the rectangular specimen, the test can be used to control the orientation of the cracking plane which was not possible in the ball punch on a circular disk design. A three dimensional quarter finite element model was formulated to simulate the punch test for 150°C and 300°C tests performed on So8 steel. The comparison of predicted and measured load-deflection and stress-strain curves showed good agreement between FE model and tests. A user interface, which allows for routine application, with the necessary postprocessing capabilities was developed and tested for the purpose of simulating miniature punch tests and estimating stress-strain data from measured load curves.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: Optical Waveguide Interconnects in Optoelectronic Matrix Switches

contributor:
Jessop, Paul
Engineering Physics

subject:
optical waveguide
optoelectronic matrix switch

abstract: The speed and simplicity of the metal-semiconductor-metal (MSM) detector has made it a prime candidate for use in integrated optoelectronic circuits. While in most applications the optical input is coupled in through the top surface of the device, it is also possible to distribute the optical signal by means of transparent waveguides that are located below the absorbing detector layer. By controlling the degree of coupling between the waveguide and detector layers the detectors can be made to act as optical taps. The optical signal can thus be shared among a series of detectors as required in optoelectronic switching applications. We have made a series of simple ridge waveguides, each with a number of MSM structures designed for the characterization of absorption, responsivity and frequency response. A 4x4 optoelectronic switch was also fabricated and analyzed. We show that balancing the switch is accomplished by tailoring the absorption coefficient in the detector region so that all detectors absorb equal amounts of optical power.

abstract: Thesis

abstract: Master of Engineering (ME)


title: The Effect of Contingency on Expectation of Reward in Selective Learning

contributor:
Jenkins, H. M.
Carment, D. W.
Psychology

subject:
contingency
expectation of reward
selective learning

abstract:
The experiment was designed to study the effect of conditionality on the growth and decline of expectancy scores during acquisition and extinction The results revealed that
conditionality affects the growth of expectation during acquisition for both direct and vicarious tasks but has no effect on variation scores, Percentage of reinforcement
is also effective, the expectancy scores for the 100% reward groups rising to a higher level in acquisition and dropping off more rapidly in extinction than for the 50% reward groups,
Problems arising from the differential effect of conditionality on expectancy scores and variation indices, and from differential expectancy levels at the end of acquisition were discussed,

abstract: Thesis

abstract: Master of Arts (MA)


title: The Effect of Fins on Vortex Shedding

contributor:
Ziada, Samir
Weaver, David
Mechanical Engineering

subject:
fins
vortex shedding

abstract:
An experimental study in air has been performed to determine what effect fins have on the flow over circular cylinders. The tubes under investigation included one bare tube and three segmented-finned tubes of different fin densities with the same root diameter as the bare tube. The tests were performed at two Reynolds numbers (2.61 x 104 and 4.98 x 104) and two downstream distances (2.5 & 5 diameters) and involved the use of hotwire anemometry. Measurements of mean and fluctuating velocities were taken across the wake as well as two-point fluctuating velocity correlations.
It was discovered that the use of fins can result in significant differences. Fins cause larger mean velocity deficits in the wake profiles and significant shape differences in the total turbulence intensity profiles. Fins also increase the strength of vortex shedding, contrary to what would be expected, and increase the number of harmonic frequency peaks in the frequency spectra as three harmonic peaks were observed for the bare tube, while as many as ten were seen for the densest finned tube.
Correlation length measurements, and thus radiated sound intensity, proved to be inconclusive. It was discovered that correlation length changed with angular rotation suggesting that this phenomenon needs to be investigated further before making any comparisons.
Based on the differences seen with increased fin density, it is thought that there may be a critical fin density which causes fundamental changes in the cylinder wake. Also, during the course of this investigation, it was concluded that while the use of an effective diameter, De, proved adequate in collapsing the finned tube data, this approximation could be improved.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: Concentration Quenching Mechanism in ZnS:Mn

contributor:
Kitai, A. H.
Cassidy, D. T.
Materials Science and Engineering

subject:
concentration quenching mechanism
ZnS:Mn

abstract: In this thesis photoluminescence measurements were made on ZnS:Mn thin-films with different concentration of Mn in order to observe the phenomenon of concentration quenching. A mathematical model, based on migration of energy among Mn centres and subsequent transfer to traps, is proposed to explain it. Probability of energy transfer to traps is considered independent of Mn concentration. It is consistent with experimental evidence reported in literature. Using this model we can give physical interpretation to the empirical decay-law for luminescence of Mn centres n(t) =n(0)exp[ - (t/r)a ] , where j and a change with Mn concentration. We are able to quantify the probability of energy loss to traps using Dexter's equation for dipole-dipole transfer. It is suggested that energy loss to the traps can be influenced by growth technique.

abstract: Thesis

abstract: Master of Engineering (ME)


title: Modeling of Extensional Behaviour of Polymers

contributor:
Vlachopoulus, J.
Koziey, B.
Civil Engineering

subject:
extensive behaviour
polymer

abstract: The use of polymeric materials in the manufacturing industry has vastly increased since the 1950’s. Because of the large amounts of material involved in modern processing operations, attempts have been made over the years to numerically simulate the processes, in the hope of optimizing operating parameters. However, in contrast to other, more traditional materials such as steel or glass, there is not a well understood connection between the microscopic structure and the (highly non-linear) macroscopic physical response of polymers. Because of this lack of microscopic cause - macroscopic effect knowledge, many descriptions of the physical response of polymers are largely phenomenological ones; that is, the equations used to model the stress/strain response make no attempt to convey information about the microscopic structure of the material. In the present work, five constitutive equations - Mooney-Rivlin, Ogden, G’Sell Two-term Polynomial and K-BKZ - are used to model the stress/strain response of two different polymers commonly used in thermoforming and blowmolding operations, ABS and HDPE, to uniaxial elongation and equibiaxial extension. The models are compared to experimental stress/strain data obtained from an industrial source, and the applicability of their predictions are investigated with regards to variations in strain, strain rate and temperature. Lastly, since the vast majority of real processes involve biaxial, not uniaxial, deformations, the ability of the models to predict equibiaxial response using parameters fit solely to uniaxial data is considered, in order to investigate the possibility of being able to forego the need for expensive, difficult biaxial tests.

abstract: Thesis

abstract: Master of Engineering (ME)


title: CW Mid-Infrared NH3 Lasers

contributor:
Reid, J
Jessop, P. E.
Physics

subject:
CW
NH3 lasers
mid-infrared

abstract:
This thesis describes a series of experiments that were undertaken to extend the limits of output power and wavelength coverage of optically pumped mid-infrared lasers. Initially, two new cw Raman
lasers operating at wavelengths of 11.5 and 12.5 pm were developed. Maximum output powers of 650 add 150 mW were produced, with pump powers of 11 and 3.3 W, respectively. The effect of the pump offset on the output power was then determined by measuring the efficiency of an NH3 laser pumped at frequency offsets of 94 and 274 MHz. In lasers ope rating in pure NH3 the larger pump offset required a greater pump intensity to reach threshold, but efficiency increased with pump offset. Higher NH3 pressures could be used at larger pump offsets and the improved efficiency was attributed to reduced saturation effects at the higher operating pressures. Experiments carried out with NH3 inversion lasers have greatly increased the output powers available at a large number of wavelengths in the 10 to 14 um range. In a buffered NH3 mixture, the sR(5,0) transition was pumped on resonance. Collisions with either N2 or Ar buffer gases were effective in thermalizing the rotational populations in the v2=1 vibrational level and producing gain on a wide range of frequencies. Output powers as large as 3.5 W on a single Tine and greater than 5 W multi-line were produced, at efficiencies of 20 and 30 % respectively. The number of lasing wavelengths increased substantially, as more than forty ortho-NH3 transitions were observed to lase in a grating-tuned cavity. The optical pumping technique was then used for the first time to produce line-tunable lasing on para-NH3 transitions. The sR(5,1) transition was pumped near resonance and 24 para-transitions were observed to lase. In total, lasing was achieved on 65 different transitions in 14NHg, with wave lengths of 10.3 to 13.8 pm.

abstract: Thesis

abstract: Master of Science (MS)


title: A New Penalty Stiffness Treatment for Master-Slave Contact Surfaces

subject:
penalty
stiffness treatment
master-slave
contact surface

abstract: Finite element simulation of contact/impact problems using the penalty method is a well-established capability. The automatic penalty stiffness provides an easy way to implement the contact analysis. However, this way in which the penalty stiffness is associated with the material property and geometry of the master surface can lead to inappropriate distributions of contact pressure at edges or mesh transitions, or even cause much numerical noise. A new method of defining the penalty stiffness, which is associated with geometry of the slave surface, the reference penetration and reference contact pressure, is developed to consistently relate forces on contacting nodes with the contact pressure. This technique is successfully applied to several examples as the clamping simulation during the punch test and the rolling process. The results of such applications of new contact stiffness model demonstrate the effectiveness of such a model in avoiding the stress edge effect and the accompanying numerical noise. As an alternative approach to define the penalty stiffness, this new model provides another option for the contact analysis and gives the users more possibilities to control the contact performance.

abstract: Thesis

abstract: Master of Engineering (ME)


title: Shear Deformation in Thin Polymer Films as a Probe of Entanglement in Confined Systems

contributor:
Dalnoki-Veress, Kari
Materials Science and Engineering

subject:
shear deformation zone
thin polymer films

abstract: We present the results of our study of the shear deformation zone in free-standing thin polymer films as a probe of entanglement in confined systems. A stretching system was used to uniaxially strain thin polystyrene (PS) films. Atomic force microscopy was used to measure the thicknesses of the shear deformation zone (SDZ), hc, and the film thicknesses h. The maximum extension ratio 2 - h/hc, was measured as a function of film thickness. The results show that A increases with the decreasing film thickness which implies an increase in the entanglement molecular weight in confinement. The same experiments were carried out for thin PS film with different molecular weights. A tentative model was developed to explain the experimental results and found to be in good agreement with the data. More exciting is the fact that the model predicts a scaling dependence on the polymer molecular weight which was also observed.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: Thermal Stability and Phase Equilibrium of Au/PT Multilayers formed by Repeated Cold Rolling

contributor:
Purdy
Brooks
Materials Science and Engineering

subject:
thermal stability
phase equilibrium
au/Pt multilayer
repeated cold rolling

abstract:
Multilayers provide an ideal tool to study thermodynamics of heterogeneous systems far from equilibrium. In this study, synthesis, characterization, thermal stability and phase equilibrium of multilayers are investigated based on Au-Pt system. Au-50%Pt multilayers were first formed by repeated rolling and folding. The microstructure was investigated by x-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). These methods revealed that the process reduced layer thicknesses to below 30nm. However, delaminating and non-uniform spacings were also observed in some regions. To get well- welded and regular multilayers, the experiment was redesigned. The improved approach, involving repeated cutting, stacking, annealing and cold rolling, has yielded uniform multilayers with interlamellar spacings as low as 6nm. XRD demonstrated the formation of a homogeneous solid solution during cold rolling at room temperature. TEM suggested that the multilayers were discontinuously homogenized via steady state motion of boundaries. The reason for the solid solution formation is that the stored interface energy is higher than the energy barrier for solid solution formation. The solid solution is unstable. It decomposes into Au and Pt after heating to 500°C at 50°C/min by differential scanning calorimetry (DSC). The phase diagram is strongly modified in the nanometer range when we take into
account of interface energy. The grain size dependent phase diagram model of Au-Pt
system shows that the melting points of Au and Pt can be lowered more than 300K if the
average grain size is reduced to 10nm. The melting temperature of Au/Pt multilayers has been studied with theoretical and experimental approaches. High speed laser heating was used to minimize any modification of the multilayer structure prior to melting. The qualitative experimental
results are shown to be in agreement with expectations.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: Semiconductor Laser Diode Gain Switching Techniques and Laser Diode Equivalent Circuit Modelling in Spice

contributor:
Conn, D. R.
Electrical and Computer Engineering

subject:
semiconductor laser diode
circuit modelling in SPICE

abstract: In developing a compact electro-optic sampling system for industrial use it is desirable to utilize a semiconductor laser diode as the light source since these devices are compact and economical. This thesis investigates several novel laser driver techniques for generating extremely short optical gain switched pulses from a semiconductor laser diode. These techniques include a novel bias control scheme in which the bias to a semiconductor laser diode, that is being driven with a step recovery diode pulse generator circuit, is turned on and off in order to switch the gain switched optical pulses on and off as desired. The second technique involves a mono-cycle scheme that allows a step recovery diode pulse generator circuit, which is customarily driven by a fixed frequency oscillator, to be driven by a mono-cycle pulse train of variable repetition rate. An equivalent circuit model of a laser diode based on the mono-mode rate equations is discussed and implemented in SPICE for the purpose of studying the interaction of the laser driver circuit electronics and the laser diode. The laser diode equivalent circuit is benchmarked against analytical solutions of the rate equations. A qualitative agreement between the measurements of the laser diode optical and terminal voltage responses and the SPICE simulations of the laser diode equivalent circuit model are demonstrated.

abstract: Thesis

abstract: Master of Engineering (ME)


title: The Effect of Certain Nutrients on Ascospore Formation in Saccharomuces cerevisiae Meyen

subject:
effect of nutrients
ascospore formation
saccharomyces verevisiae

abstract:
Thesis
Master of Science (MS)


title: Sorption of Sulfate on Iron Oxide Minerals: Hematite and Goethite

contributor:
Kramer, James
Geology

subject:
sorption
iron oxide mineral
hematite
goethite

abstract: The influence of sulfate on terrestrial and aquatic ecosystems depends on the mobility of the sulfate anion in soils. This mobility is determined by several factors, one being the types and amounts of soil constituents. In this study, several iron oxide/hydroxide minerals were evaluated for sulfate sorption characteristics.Hematite and goethite were synthesized and positively identified using x-ray diffraction, mossbauer spectroscopy and scanning electron microscopy. Mineral surfaces were characterized using surface area and zero point of charge measurements, infrared spectroscopy and thermal analyses. Neutron activation and x-ray fluorescence were used to look for impurities. Samples were compared to a natural hematite sample and a synthetic jarosite. Sorption experiments, conducted on mineral suspensions in KNO3 media at room temperature, considered the variables time, ionic strength, solid:solution ratio, pH and sulfate concentration. Sorption was initiated by a fast reaction, followed by a longer, slower one which reached an apparent equilibrium in 24 hours. Sorption was unaffected by sol id:solution ratio and decreased with ionic strength at pH 5 for goethite only. Sorption increased with increasing sulfate concentration and decreasing pH. A sorption maximum was reached by a I 1 minerals except synthetic hematite. Under optimum pH and [SO4]. approximately half of the mineral surface is covered by su1 fate ions. Sulfate was sorbed irreversibly. Only a fraction of sorbed sulfate can be desorbed, an amount which increases with pH. Thermal analyses indicate sulfate to be strongly bonded. The presence of four infrared bands on sulfate treated surfaces indicate direct coordination of the anion to the iron cation. The above evidence, including irreversibility of sorption, supports inner sphere complexing of sulfate. Sulfate sorption on iron oxide/hydroxide minerals is thus a combination of nonspecific electrostatic attraction and mono - multi ligand exchange (including binuclear bridging) which act under different system conditions to form the basis of sulfate sorption behavior. The present observations are important in model ling of environmental systems, such as in the Direct Delayed Response Program Model, due to the significance of irreversibility of sulfate sorption on model assumptions.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: Resistance to Extinction and Rate of Lever-Pulling in Human Subjects as a Function of: (1) Number of Correct Acquisition Trials and Percentage of Reinforcement, and (2) Number of Reinforcements and Percentage of Reinforcement

contributor:
Carment, D. W.
Psychology

subject:
resistance to extinction
lever pulling
human subject

abstract: Two experiments were carried out. The first study was designed to investigate the effects of percentage of reinforcement and the number of correct acquisition trials, when combined, on the number of responses to extinction and rate of lever-pulling of human subjects. The second study was designed to investigate the effects off percentage of reinforcement combined with number of reinforcements on the same dependent variables. Analysis of the data revealed: (1) resistance to extinction in both experiments, was inversely related to the percentage of reinforcement; (2) resistance to extinction was inversely related to the number of reinforcements but was not affected by the number of correct acquisition trials; (3) the mean rate of responding was inversely related to the number of reinforcements but was not affected by either percentage of reinforcement or number of correct acquisition trials; and (4) the number of responses per unit of time increased during acquisition and decreased during extinction in both studies. The results were discussed in relation to theories stemming from previous partial reinforcement studies.

abstract: Thesis

abstract: Master of Arts (MA)


title: CHARGE-SHIFTING POLYCATIONS FOR BIOMATERIAL APPLICATIONS

contributor:
Stöver, Harald D. H.
Chemistry and Chemical Biology

abstract:
Polycations are used extensively in a wide range of applications from enhanced oil recovery, wastewater treatment, and to biomaterials for delivery of therapeutics. This thesis focuses on the design, synthesis, and study of polycations towards improving the cyto- and immuno- compatibility in polyelectrolyte-based biomaterial applications. Alginate-based polyelectrolyte encapsulation and DNA delivery were chosen as applications to demonstrate the properties of the polycations developed, as a proof of concept.
	The work in this thesis represents significant contributions to the field, in particular, in the study of polymers based on N,N-(dimethylamino)ethyl acrylate (DMAEA) as charge-shifting polycations where it provides an in-depth study of the hydrolysis of PDMAEA that probes the mechanism of its unique reactivity.
	The hydrolysis of polymers of DMAEA was found to be highly pH dependent and sensitive to various neighboring groups on its pendent side chain, polymer backbone, and of comonomers. The effects were hypothesized to be due to a combination of interactions including hydrogen-bonding, steric hinderance, as well as ionic, hydrophilic, and hydrophobic interactions. These studies led to the synthesis of polycations with various rates of hydrolysis, with half-lives ranging from years to minutes. As these esters hydrolyze, the polymers have the potential to undergo transitions in net charge from cationic to zwitterionic, followed by anionic, due to the formation of carboxylate groups. Hence, the polymers are known as “charge-shifting” polycations in the field.
	As a proof of concept, charge-shifting polycations based on DMAEA were studied in alginate-based polyelectrolyte materials for encapsulation. Copolymers of DMAEA and 3-aminopropyl methacrylamide (APM), called PAD copolymers, were used as coating materials with polyanionic calcium alginate hydrogel capsules. The charge-shifting ability was confirmed as the coatings were shown to degrade over time due to disruption of electrostatic interactions. It was further demonstrated that covalent cross-linking could preserve the structural integrity of the membrane coating. Electrophoretic mobility measurements of PAD coated microspheres confirmed the shift in net surface charge from cationic to anionic with progressive hydrolysis.
	The charge-shifting ability of PAD copolymers was then tested for improving cytocompatibility as DNA delivery agents. PAD copolymers were shown to condense 60bp DNA to form polyplexes with very high cellular uptake efficiency in comparison to the gold standard polycation in the field, branched polyethylenimine (PEI). Cells exposed to PAD copolymers with the greatest charge-shifting ability were shown to have improved viabilities relative to non-charge-shifting polycations. This was attributed to the reduction of cytotoxic cationic charge of the polymer with progressive DMAEA hydrolysis.
The results described in this thesis provide fundamental structure–function information to help design and develop new polymers and materials with tunable properties towards biomaterial applications.

abstract: Dissertation

abstract: Doctor of Philosophy (PhD)


title: The satellite cell response following 10-weeks of resistance exercise and multi-ingredient supplementation in young men and women

contributor:
Parise, Gianni
Kinesiology

subject:
Muscle
Stem cell
Exercise
Supplementation

abstract: Skeletal muscle stem cells, known as satellite cells (SC), are essential for skeletal muscle regeneration/repair and have been linked to muscle hypertrophy in humans. There is a consensus within the literature that SC activate and proliferate in response to external stimuli, such as mechanical damage or exercise. However, the effect of nutritional supplementation in conjunction with exercise on SC function is not fully understood.  This may, in part, be due to varying responses of individuals to specific nutritional ingredients. Therefore, this study examined the efficacy of a multicomponent supplement containing whey protein isolate, leucine, creatine monohydrate, calcium citrate, and vitamin D, all of which have independently been shown to confer beneficial effects to skeletal muscle mass or function. Accordingly, when considering individual variability, a multicomponent nutritional strategy, when combined with resistance exercise, may be more likely to produce an augmented response compared to isolated supplements. Healthy, young males and females (18-26 y; ± 0.55) were randomly assigned to a multi-ingredient supplement (MIS)(n=13, 7M) or collagen peptide (CP)(n = 13, 6M) group. Participants performed a whole-body linear resistance-training program 4 times a week for 10-weeks. Skeletal muscle biopsies were obtained from the vastus lateralis pre and post 10 weeks of resistance training. Additionally, biopsies were obtained following an acute bout of damaging eccentric exercise prior to and following the 10 weeks of training.  Thus, this design provided a resting and an acute damage response (48-hours post damage) before and after 10-weeks of resistance exercise and supplementation. Training resulted in an 83% and 40% increase in the basal SC population for mixed fibres in the MIS and CP group (P < 0.05), respectively, with no group differences. No effect of time or group was found for acute SC proliferation. However, when collapsing groups, a 635% increase was observed in the relative delta SC activation following 10 weeks (P < 0.05). Also, similar increases were observed in both groups for myonuclear accretion and myonuclear domain (P < 0.05). The MIS group had a 16% larger increase in type II CSA compared to the CP group (P < 0.05). Irrespective of supplementation, our findings suggest 10-weeks of resistance exercise is capable of increasing the basal SC population, SC activation, myonuclear accretion, and myonuclear domain. Furthermore, consuming a MIS lead to superior increases in type II CSA, compared to the CP group.

abstract: Thesis

abstract: Master of Science (MSc)

abstract: Skeletal muscle stem cells, known as satellite cells (SC), are essential for skeletal muscle regeneration/repair and have been linked to muscle hypertrophy in humans. SC activate and proliferate in response to external stimuli, such as mechanical damage or exercise. However, the effect of nutritional supplementation in conjunction with exercise on SC biology is not fully understood.  This may, in part, be due to varying responses by individuals to specific nutritional ingredients. In this regard, multi-ingredient supplementation (MIS) has been implemented with the intention of eliciting a maximal adaptive response across all participants. Therefore, this study examined the efficacy of a multicomponent supplement containing whey protein isolate, leucine, creatine monohydrate, calcium citrate, and vitamin D, all of which have independently been shown to confer beneficial effects for skeletal muscle mass or function. Our findings suggest 10-weeks of resistance exercise is capable of increasing the basal SC population, SC activation, myonuclear accretion, and myonuclear domain. Nutritional Supplementation had no further effect. Importantly, however, consuming a MIS lead to greater increases in type II CSA, when compared to a control supplement.


title: The Effect of Contingency on Expectation of Renewal in Selective Learning

contributor:
Jenkins, H.M.
Carment, D.W.
Psychology

subject:
contingency
reward
selective learning
expectation of reward

abstract:
The experiment was designed to study the effect of conditionality on the growth and decline of expectancy scores during acquisition and extinction The results revealed that conditionality affects the growth of expectation during acquisition for both direct and vicarious tasks but has no effect on variation scores, Percentage of reinforcement is also effective, the expectancy scores for the 100% reward groups rising to a higher level in acquisition and dropping
off more rapidly in extinction than for the 50% reward groups. Problems arising from the differential effect of conditionality on expectancy scores and variation indices, and
from differential expectancy levels at the end of acquisition were discussed.

abstract: Thesis

abstract: Master of Arts (MA)


title: Studies on Thorium 3-Methyl-8-Hydroxyquinolate

contributor:
Graham, R.P.
Chemistry

subject: Thorium 3-Methyl-8-hydroxyquinolate

abstract: Thorium is shown to react with 3-methyl-8-hydroxyquinoline in the molar ratio 1:5, but isolation of the pure anhydrous compound requires special precautions. Thermogravimetry and differential thermal analysis of the compound indicate, amongst other things, the existence of a thorium 3-methyl-8-hydroxyquinolate of 1:4 stoichiometry. The pH dependence of the precipitation of thorium 3-methyl-8-hydroxyquinolate is determined, and correlated theoretically, with data for thorium 2-methyl-8-hydroxyquinolate. Thermal and other studies on thorium 8-hydroxyquinolate emphasize its anticipated similarity to the 3-methyl-8-hydroxyquinolate, and its differences from the 2-methyl compound. The precipitation of at least two compounds of thorium and 8-hydroxyquinoline is demonstrated. 3-Methyl-8-hydroxyquinoline is established as a sensitive reagent for determining thorium by both bromometric and polarographic methods with good precision and accuracy.

abstract: Thesis

abstract: Master of Science (MS)


title: The Effect of Tone on Tachistoscopic Word Recognition

contributor:
Newbigging, P.L.
Psychology

subject: Tachiatoscopic word recognition

abstract: Three experiences investigated auditory-visual interaction and the role of a visual fixation point in tachistoscopic word recognition. The results showed that when a 60db. or 90 db. tone preceded the presentation of the word by two, four, or eight seconds, different effects on the recognition threshold were obtained only for the two-second interval. In this case, the 90 db. group had significantly higher thresholds than did the 60db. group. Other results showed that a 60db. tone facilitated recognition to the same extent as a fixation point. It was concluded that a tone of moderate intensity and occurring a brief interval before the presentation of the word facilitate word recognition, whereas a more intense tone produces a disruptive effect.

abstract: Thesis

abstract: Master of Arts (MA)


title: Levels in 153Eu and 155Eu Populated by the Beta Decay and (3He,d) Reactions

contributor:
Johns, M. W.
Physics

subject: 153Eu

subject: 155Eu

subject: beta decay

subject: 3He,d reaction

abstract: Thirty-one excited levels in 153Eu and thirty-four in 155Eu have been located by means of the (3He,d) and beta decay reactions. The energies, intensities, and decay scheme classifications of forty-four gamma rays in 153Eu and fifty-two in 155Eu have been measured by means of singles and coincidence experiments using NaI and Ge(Li) detectors. Angular distribution studies of the reaction deuterons have been made a number of levels have neen assigned unique l values. An interpretation of the level schemes in terms of the Nilsson model have been attempted.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: The Desugn of MACPAC - A Graphics Subroutine Library Based on a Design Philosophy for the Next Generation of Graphics Packages

contributor:
Ryan, P. J.
Computation

subject:
graphics
subroutine library
design philosophy
next generation

abstract: This paper presents the design of a graphics subroutine library, MacPac, as a contribution to the development of a standard for future graphics packages. The need for a new graphics standard, and hence the motivation for the development of MacPac, is illustrated through a detailed discussion of existing graphics standards and systems. MacPac is based on a design philosophy developed by Mark Green for the next generation of graphics packages. It addresses the hardware and software ideas of the 80's, incorporating and building upon the valuable and tested ideas of a number of existing graphics systems. The design languages used in the development of MacPac were created by Mark Green for the design of user interfaces. This work examines the effectiveness of these languages in the design of a graphics system.

abstract: Thesis

abstract: Master of Science (MS)


title: Investigation of Two Polarimetric Optical Strain Sensors

contributor:
Jessop, Paul
Engineering Physics

subject:
polarimetric optical strain sensor
optical strain sensor

abstract: This thesis presents a theoretical description and experimental testing of two polarimetric fiber-optic strain sensors. 'The first .of these is an intrinsic sensor in which a single mode optical fiber acts as the sensing element. This sensor exhibited low strain sensitivity and high cross-sensitivity to temperature. The second sensor was of the extrinsic type, A single polarization maintaining fiber was used to deliver and collect light from the sensing element, which a was piece of photoelastic sheet PS-1. This type of sensor exhibited large dynamic range of 1:1350, resolution of 0.59ps, and strain sensitivity of the normalized signal of0.00219pe+1.

abstract: Thesis

abstract: Master of Engineering (ME)


title: InGaAsP/GaAs Quantum Well Lasers: Material Properties, Laser Design and Fabrication, Ultrashort-Pulse External-Cavity Operation

contributor:
Haugen, H. K.
Mascher, P.
Engineering Physics

subject: InGaAsP quantum well laser

subject: GaAs Quantum well laser

subject: material properties

subject: laser design

subject: ultrashort pulse external cavity operation

abstract:
A detailed characterization of the Ini-xGaxAsyP1-j, quaternary material system lattice matched to GaAs, grown by gas source Molecular Beam Epitixy (MBE) has been performed. Photoluminescence, X-ray diffraction and Transmission Electron Microscopy (TEM) were used to study the lateral composition modulation (LCM) which was observed in this material system. Optimization of the growth process and the substrate orientation resulted in a significant reduction of the LCM. Additionally, a comprehensive analysis of the optical constants was performed which resulted in the first publication of wavelength and composition dependent index of refraction data for this material system. The combination of growth optimization and index of refraction data lead to the demonstration of efficient, low threshold operation of InGaAsP/GaAs based multiple quantum well lasers.
In order to efficiently couple the above laser diodes to an external cavity to facilitate the generation of ultrashort pulses, antireflection facet coatings were required. As such, optical interference filters have been fabricated using a plasma enhanced chemical vapor deposition system, based on the SiOxNy material system. High quality antireflection facet coatings, suitable for application to the InGaAsP/GaAs diode lasers have been designed and fabricated, resulting in modal reflectivities of 1-2 x 10-4.
Finally, an ultrashort-pulse external-cavity diode laser system was designed and manufactured which allowed the laser diode to be wavelength tuned and emit mode-locked ultrashort optical pulses. Pulses with sub 2 ps duration and greater than 1 mW average output power have been achieved. A study of the novel application of an asymmetric quantum well structure to the generation of ultrashort optical pulses has been proposed
and initiated.

abstract: Thesis

abstract: Doctor of Philosophy (PhD)


title: Interactions of Well-Defined, Pyrene-Functionalized Diblock Copolymers with Single-Walled Carbon Nanotubes

contributor:
Adronov, Alex
Chemistry

subject:
diblock copolymer
single-walled carbon nanotube

abstract:
Since their discovery in 1991, carbon nanotubes, and especially single walled carbon nanotubes (SWNTs), have attracted significant attention due to their unique structural, mechanical, and electronic characteristics. Although many potential applications for carbon nanotubes have been suggested, several key obstacles currently preclude their practical commercial applications. One of these is their lack of solubility and processability. In order to address this issue, a number of covalent and non-covalent nanotube functionalization techniques have recently been reported in the literature. These methods allow for the manipulation of nanotube properties, such as their solubility, through the attachment of various chemical moieties. Although most of these methods involve covalent attachment of structures to either the ends or sidewalls of SWNTs, several examples of non- covalent functionalization have also been reported. Pyrene, with its flat and
aromatic structure, has been shown to form strong pi-pi stacking interactions with the surface of SWNTs. With this in mind, we explored several methods towards SWNT solubilization with diblock copolymers through non-covalent polymer- nanotube interactions. Living free radical polymerizations (SFRP, ATRP) were employed to produce diblock copolymers with narrow polydispersity. Commercial and synthetic monomers with different functionalities could be utilized to produce polymers with varying properties. Specifically, we used polymers such as polystyrene, poly(methyl methacrylate), poly(t-butyl acrylate) and poly(acrylic acid) as one block of our diblock copolymers. The second block was composed of synthetic pyrene-functionalized monomers mixed with different amounts of monomers that match the composition of the first block. It was found that, upon mixing these diblock copolymers with insoluble nanotubes in various solvents, the nanotubes were partially solubilized through pi-pi stacking with the pyrene- containing blocks.

abstract: Thesis

abstract: Master of Science (MS)


title: Functionalization of Single-Walled Carbon Nanotubes with Coumarin-Labeled Polymers

subject:
single walled carbon nanotubes
coumarin-labeled polymer

abstract: Single-walled carbon nanotubes (SWNTs) are a new class of materials that have recently attracted a great deal of interest because of their unique structural, mechanical, and electronic properties. Also, SWNTs have a high potential for a number of technological applications, including molecular electronics, emissive devices, and photovoltaic devices. To fully utilize their unique properties, control of the solubility, processibility, and functionality of SWNTs is required. Therefore chemical functionalization of SWNTs using a variety of methods, in either covalent or noncovalent manner, has been developed to produce soluble nanotube composites coupled with various chemical moieties. To explore the possibility of making potential soluble nanotube-based materials for solar cells, SWNTs were functionalized with organic chromophore-labeled polymers via a radical coupling process. The organic chromophore was used to absorb light to produce photo-induced electrons, while the polymer chains were used for improving the solubility of SWNTs. These novel chromophore-labeled polymers were made by stable free radical polymerization (SFRP), either using a synthetic chromophore-functionalized styrenic monomer or by derivatizing well-defined polystyrenes. Specifically, the chromophores employed in this investigation were commercially available 7-hydroxycoumarin and coumarin-343. In order to carry out fluorescence studies of SWNT-coumarin composites systematically, various factors were probed by (1) altering polystyrene lengths between the SWNT and the coumarin; (2) changing the distribution of coumarins along the polymer chain, in the form of either a block or random copolymer; (3) placing single coumarins on the surface of SWNTs. All of these resulting polymer functionalized SWNTs were found to be soluble in certain organic solvents such as CHCl3. Different absorption behaviors have been observed for SWNTs functionalized with 7-hydroxycoumarin containing copolymers. Fluorescence was still observable for all of these composites, and the pi-pi interactions between coumarins and nanotubes were believed to be responsible for the broadening of emission bands of the resulting composites.

abstract: Thesis

abstract: Master of Science (MS)


title: Bragg Grating Integrated on Silicon-on-Insulator Waveguide

subject:
Bragg grating
Silicon-on-Insulator

abstract:
This thesis details the design, fabrication and measurement of an integrated optical Bragg grating filter, operating at a free space wavelength of 1532 nm, based on silicon-on-insulator (SOI) ridge waveguide.
Grating-based integrated devices can interact with optical signals in photonic integrated circuits (PIC) in such a way as to selectively transmit, reflect or detect the signals that are resonant with these devices. Channel filters can access one channel of a wavelength division multiplexed signal without disturbing the other channels and are therefore important elements in WDM communications. Resonator filters are attractive candidates because they can potentially realize the narrowest linewidth for a given device size. Device models for this kind of device are developed by using the MATLAB programming language. Coupled mode theory (CMT) for filters, and the effective index method (EIM) which reduces a three dimensional (3D) analysis into two dimensions is used as modeling theoretical background. Computer modeling identifies the effect of device structure on the performance of the devices, and is also used to predict the output characteristics of this kind of device. This provides an understanding of device physics and operation, and a basis for comparison with experimental results. A common fabrication sequence for integrated optical Bragg grating filters based on SOI ridge waveguides is designed, developed and demonstrated. This includes the photomask for optical ridged waveguide, interferometic lithography for grating pattern and high accuracy RIE etching. This work demonstrates Bragg grating as a technology for realizing PIC in SOI material system, and presents the technology required to design, fabricate, characterize, and model these integrated devices.

abstract: Thesis

abstract: Master of Applied Science (MASc)


title: Modeling of Flow Mode-Transition of Natural Convection in Inclined Cavities

contributor:
Hamed, Mohamed
Mechanical Engineering

subject:
flow mode-transition
natural convection
inclined cavities

abstract: Steady two-dimensional natural convection in air-filled, regular and irregular inclined enclosures has been investigated numerically. The effect of various configurations of bidirectional temperature gradients on mode transition of thermal convection inside the cavity has been investigated. Numerical treatment of temperature discontinuity at the comer points of the cavity and its effect on the calculated Nusselt number has been discussed. Rayleigh numbers range between 103 and 104, aspect ratio (width/height) =1,2,4, and angle of inclination in the range between 0 and 90°. While the cavity bottom and top walls were kept at constant temperatures at Th (heated) and at Tc (cooled), respectively, thermal conditions of end walls were varied. In addition to the base case of insulated end walls, seven different configurations of thermal conditions of the two side walls have been studied. Results show that numerically predicted heat transfer rates strongly depend on the numerical treatment of temperature discontinuities at cavity comer points. Results also indicate that thermal conditions of cavity end walls have a significant effect on mode-transition of thermal convection flows; and hence, on heat transfer effectiveness inside the cavity, and on the Hysteresis phenomenon occurred as the cavity angle of inclination varied from zero (horizontal position) to 90 ° (vertical position) and back to zero. The effect of curved bottom is carried out by replacing flat bottom of the cavity with a curved one. Only insulated end walls were discussed in curved case. Results indicated that heat transfer rate and mode transition are strongly dependent on the height of curvature of the bottom wall, which offers more flexibility in controlling flow mode-transition, and hence, effectiveness of heat transfer inside the cavity.

abstract: Thesis

abstract: Master of Applied Science (MASc)