Theses, Dissertations, and other Required Graduate Degree Essays

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This collection contains digitized SFU theses except for those theses submitted within the last 12 months. If you cannot find the thesis you are looking for please search Recently Submitted Theses as it may be a recently submitted thesis and thus not yet available in Summit.

Thermal contact resistance between ceramic and metallic surfaces with applications in power electronics

Date created: 
2018-11-29
Abstract: 

In power electronic systems, aluminum oxide (alumina) is frequently used to electrically isolate high voltage devices mounted onto touch safe heat sinks for cooling. The thermal contact resistance (TCR) developed between the aluminum oxide and the metallic surfaces may significantly increase the thermal resistance between the heat generating device and the heat sink. In this thesis, the thermal contact resistance between ceramics and metals is explored analytically and experimentally. The TCR between polished ceramics and bead-blasted metals was first measured under uniform contact pressures (0.25 – 1.5 MPa) in both atmospheric and vacuum conditions. These results are compared with existing metallic surface TCR models to validate their use with metallic-ceramic surfaces. TCR measurements of as-fired, lapped and polished aluminum oxide in contact with machined, cast and anodized extruded aluminum surfaces with thermal interface materials (TIMs) are also presented.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Majid Bahrami
Department: 
Applied Sciences: School of Mechatronic Systems Engineering
Thesis type: 
(Thesis) M.A.Sc.

Physical modeling of local reaction conditions inside of cathode catalyst layer of polymer electrolyte fuel cells

Author: 
Date created: 
2018-12-06
Abstract: 

The foremost practical objective in research on polymer electrolyte fuel cells is to design catalyst layers with high performance at markedly reduced platinum loading. The overarching goal is thus to enhance the effectiveness factor of platinum utilization inside the cathode catalyst layer. This requires design modifications in fuel cell components, understanding of local reaction conditions inside the cathode catalyst layer, accounting for the impact of surface charging phenomena at pore walls on catalyst activity, as well as understanding water distribution and fluxes in porous electrode media and how the water balance affects all the aforementioned effects. As a contribution towards this objective, this thesis presents models to understand the local reaction conditions inside the cathode catalyst layer. This refers to rationalizing the oxygen and proton density in the cathode catalyst layer from the macroscopic level to the nanopore level. This work has been divided into three parts. The first part focuses on understanding of surface charging phenomena and catalytic activity in water-filled pores that are bounded on one side by an ionomer-skin layer. The model-based analysis reveals that the density of charged side chains at the ionomer shell exerts a pronounced impact on the surface charge density at the Pt surface and thereby on the activity of the pore for the oxygen reduction reaction. In the second part, we employed physical models of catalyst layer operation to analyze large sets of experimental performance data of fuel cells with gradually decreased Pt loading. The analysis reveals systematic variations in physical properties of cathode catalyst layers with Pt loading that can be consistently explained with a variation in the fuel cell water balance. A correlation exponent was introduced, which can be used to assess the design of a catalyst layer in terms of the propensity to flooding. The last part serves the need for a comprehensive water balance model as revealed by research described in the previous paragraph. We present a basic 1D +1D model to rationalize variations in water distribution and water fluxes in catalyst layers, diffusion media, and flow fields in response to changes in structure, composition and operating conditions. The model-based analysis consistently reproduces major trends in performance upon a systematic reduction in Pt loading. The tools and analyses provided in this thesis could thus inform strategies for minimizing the Pt loading without running into the water trap.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Michael Eikerling
Department: 
Science: Department of Chemistry
Thesis type: 
(Thesis) Ph.D.

EndoVision: A prototype robotic laparoscope and telementoring system allowing intuitive endoscopic visualization

Author: 
Date created: 
2018-12-14
Abstract: 

This project is for the development of a prototype system for endoscopic visualization for minimally invasive surgeries (MIS). The system will assist a surgeon in adjusting and maintaining the field of view (FOV) of an endoscopic system through head motions alone, relieving the need for hands-on adjustment of a camera scope. A surgeon would wear a head-mounted display (HMD) to visualize the area of interest. A market-ready device would include real-time web communication allowing remote surgeons to provide audio and visual feedback during a surgery. This medical device would reduce the number of medical staff needed for an MIS procedure, as well as providing surgeons with assistance from other medical professionals over the web, increasing the success rate of MIS procedures. Uses for this device include: Providing intuitive control of the surgical FOV, training of surgeons in MIS, and as a platform for real-time communication between surgeons at a distance.

Document type: 
Graduating extended essay / Research project
File(s): 
Senior supervisor: 
Andrew Rawicz
Department: 
Applied Sciences: School of Engineering Science
Thesis type: 
(Project) M.Eng.

Expanding the organocatalyzed α-chlorination-aldol reaction

Author: 
Date created: 
2018-12-14
Abstract: 

Organocatalysis, while still a relatively new field in organic chemistry, now plays an indispensable role in organic synthesis. Transformations not accessible by classical synthetic methods are now not only routine, but mild, high yielding and increasingly sophisticated in what they can achieve. One such reaction is the α-chlorination-aldol reaction developed by the Britton group in 2013. This reaction has been demonstrated to provide access to stereochemically rich chlorohydrins from readily available and achiral starting materials. The reaction has found extensive utility in the concise synthesis of imino-cyclitols and carbohydrate analogues. In this thesis a more general approach to the tandem α-chlorination-aldol with different electrophiles or ketones is investigated. Within, we show that azodicarboxylates can be used as electrophiles to functionalize aldehydes prior to submission to an aldol reaction. These aminated aldol adducts are further investigated for their utility in synthesizing imino-cyclitols, and their ability to form cyclic, polyhydroxylated hydrazones. As well, new substrates are investigated for their propensity to engage in an α-chlorination-aldol reaction. Four new substrates are demonstrated to form the corresponding chlorinated aldol adducts in moderate yields and high enantioselectivity. Furthermore, we demonstrate that these new aldol adducts can provide access to novel, natural product-like scaffolds.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Robert A. Britton
Department: 
Science: Department of Chemistry
Thesis type: 
(Thesis) M.Sc.

Applications of numerical linear algebra to protein structural analysis: the case of methionine-aromatic motifs

Author: 
Date created: 
2018-12-07
Abstract: 

Linear algebraic algorithms uncovered a preponderance of protein methionine residues interacting with two or more aromatic residues. The average geometric relationship between transition metals and methionine-aromatic interactions in PDB crystal structures was assessed with a nearest neighbours-like algorithm (“Met-aromatic”) developed for finding and classifying methionine-aromatic interactions. Here, we assumed that a methionine could interact with one to six midpoints between aromatic carbon atoms in any of phenylalanine, tyrosine, and tryptophan; an integer we termed “Order of Interaction.” Serendipitously, an oversight in Met-aromatic led to the discovery of a significant number of interactions of order exceeding VI, suggesting a large number of methionine residues interacting with two or more aromatics. This was termed the “Bridging Interaction.” Herein, the methioninearomatic and bridging interactions are discussed in light of their possible redox roles.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Jeff Warren
Department: 
Science: Department of Chemistry
Thesis type: 
(Thesis) M.Sc.

Nonmedical prescription opioid initiation, ongoing use, and related overdose among people who use drugs in Vancouver, Canada

Author: 
Date created: 
2018-12-12
Abstract: 

Background: The prevalence and harms associated with nonmedical prescription opioid use (NMPOU) have risen in Canada, and the prevailing policy response has restricted the supply of prescription opioids (POs) and promoted more responsible patient behaviour. Despite this quick action to address NMPOU, there are key knowledge gaps related to NMPOU initiation, ongoing use, and associated harms among people who use illegal street drugs (PWUD). Objectives: (i) conduct a systematized review of the extant literature related to NMPOU, (ii) identify the prevalence and correlates associated with NMPOU-related initiation trajectories and engaging in recent NMPOU, and (iii) investigate the impact of acquiring POs from physicians for the purposes of NMPOU. Methods: Multiple databases were systematically searched for extant literature on NMPOU. For the empirical studies, data were derived from the Vancouver Drug Users Study, which is an open prospective cohort study of youth and adult PWUD in Vancouver, Canada. Utilizing cross-sectional and longitudinal regression techniques and various sub-samples, I assessed the relationship between various risk factors and the following outcomes: engaging in recent NMPOU, initiating NMPOU before illegal street drugs (vs. after), initiating NMPOU using a physician prescription, and recent non-fatal overdose. Results: The review found some consistent indicators of risk related to NMPOU and gaps in knowledge related to NMPOU among hidden populations. In the empirical analyses, engaging in NMPOU was associated with a higher risk profile regardless of age and sex, and initiating NMPOU before illegal street drugs was also linked with a higher risk profile when compared with those who never engaged in NMPOU. Initiating NMPOU with a physician prescription was not a key indicator of high-intensity substance use or socio-structural vulnerability and acquiring POs using a physician prescription was not associated with recent non-fatal overdose. Conclusions: The results indicate that engaging in NMPOU is associated with a higher risk profile; however, NMPOU-related initiation trajectories and acquisition source do not appear to be a meaningful target for policy solutions or interventions. This dissertation provides some evidence for developing unique strategies to address ongoing NMPOU among younger and older PWUD that includes opioid agonist treatment and income generation opportunities.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Will Small
Robert Hogg
Department: 
Health Sciences: Faculty of Health Sciences
Thesis type: 
(Thesis) Ph.D.

FMG based continuous finger movement prediction toward partial hand prosthesis control

Date created: 
2018-12-10
Abstract: 

Partial hand amputation forms more than 90% of all the upper limb amputations. To improve the quality of life for partial hand amputees different prosthesis options, including externally-powered prosthesis, have been investigated. This work is exploring Force Myography (FMG) as a technique for regressing grasping movement accompanied by wrist position variations. This study can lay the groundwork for a future investigation of FMG as a technique for controlling externally-powered prostheses continuously. Ten able-bodied participants performed three hand movements while their wrist was fixed in one of the six predefined positions. Two approaches were examined for estimating grasping: (i) one regression model, trained on data from all wrist positions and hand movements; (ii) a classifier that identified the wrist position followed by a separate regression model for each wrist position. Both approaches presented similar performance while the first approach was more than two times faster. The results indicate the potential of FMG to regress grasping movement, accompanied by wrist position variations.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Carlo Menon
Department: 
Applied Sciences: School of Engineering Science
Thesis type: 
(Thesis) M.A.Sc.

Non-lethal human-shark interactions and their ecological consequences

Date created: 
2018-10-31
Abstract: 

Collapses of predator populations, caused mainly by unsustainable fishing, have been documented in many marine ecosystems. Predators are thought to play critical roles in marine environments where, through direct predation and fear effects, they can shape demographic processes and community structure. My thesis focusses on the effects of two non-lethal anthropogenic impacts on sharks: prey depletion and shark provisioning tourism. Using stable isotopes and a time series of shark vertebrae, I first examine the historical isotope ecology of seven shark species from the southwest Indian Ocean. Two species with generalist diets showed no change over two decades in δ15N or δ13C signatures. Large individuals of five primarily piscivorous species exhibited isotope signatures that deviate from historical baselines, suggesting long-term changes in diet and/or foraging strategy. Next, I measure the effects of tourism-related provisioning on the trophic signatures and movement patterns of Caribbean reef sharks Carcharhinus perezi in the Bahamas. Combining stable isotope analyses, acoustic telemetry and direct observations, I show that individual sharks that are provisioned more frequently have elevated δ15N signatures, but similar residency and movement patterns to un-provisioned conspecifics, suggesting that their broader ecological roles are not affected by long-term provisioning. Finally, I use the gradient of shark abundance generated by provisioning for ecotourism to reveal the wider coral reef community corollaries of reef shark presence. Benthic community structure varied across this gradient, with less macroalgae and more turf algae at sites with more sharks. Herbivorous parrotfish were abundant but fed less selectively and consumed more macroalgae at sites with more sharks, suggesting that fear effects may drive the patterns observed. Teleost fish biomass was almost twice as high near the provisioning site than further away, a pattern driven by fisher avoidance of areas of more sharks. Effective shark conservation may thus deliver broad cascading benefits to coral reef communities. While most marine predator declines are due to direct fishing mortality, my thesis evokes additional mechanisms by which anthropogenic activities may drive change in predator populations and their communities.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Isabelle Côté
Department: 
Science: Biological Sciences Department
Thesis type: 
(Thesis) Ph.D.

Advances in fluorogenic RNA aptamer systems for live cell imaging: Towards orthogonality and multicolour applications

Author: 
Date created: 
2018-10-25
Abstract: 

Recent developments in the field of RNA biology continue to demonstrate the importance of RNA in regulating cellular processes. However, directly imaging biologically important RNAs has been hindered by a lack of live cell fluorescent tools. As such, aptamers that bind and enhance the brightness of fluorogenic dyes are promising tools to improve fluorescent RNA imaging. The Unrau laboratory developed RNA Mango I, a small, 39-nt aptamer that binds to a modified thiazole orange fluorophore (TO1-Biotin) with nanomolar affinity. This binding is accompanied by an 1,100-fold increase in its green channel fluorescence. To further improve the Mango aptamers, in collaboration with the Ryckelynck laboratory, we used microfluidics-based selection methods to isolate three brighter, high affinity RNA Mango fluorogenic aptamers (Mango II, III and IV). Together with the Rueda laboratory, we show that these new Mangos can accurately image the sub-cellular localization of three small non-coding RNAs in fixed and live mammalian cells. These new Mangos are unique in structure. Unlike Mango I and II, Mango III rigidly connects its ligand binding core to an external helix. As the Spinach/Broccoli aptamer family, which binds GFP-like chromophores (DFHBI, DFHBI-1T), also share this property, the Broccoli/DFHBI-1T aptamer complex was used as a FRET donor paired with the far red-shifted Mango III/YO3-Biotin complex as a FRET acceptor. Interestingly, the high affinity Mango I, II, III aptamers can discriminate between TO1/YO3-Biotin and DFHBI/DFHBI-1T by at least a 102-fold difference in affinity. In contrast, Spinach binds many fluorophores indiscriminately and weaker. With this, concentrations could be determined to obtain appropriate binding for Mango III/YO3-Biotin and Broccoli/DFHBI-1T when in the same system. FRET efficiency was measured using an RNA duplex of variable length between the two aptamers. FRET signal depended on the length of the duplex, and oscillated in intensity precisely with the predicted twist of the helix, demonstrating strong orientation dependence. While this pair of aptamers enable in vitro FRET studies, there are no truly orthogonal fluorescent aptamer systems. To that end, I discuss an in vitro selection to develop orthogonal aptamers for a red fluorophore, TO3-Biotin, that can potentially be paired with existing Mango aptamers.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Peter Unrau
Department: 
Science: Department of Molecular Biology and Biochemistry
Thesis type: 
(Thesis) Ph.D.

Sedimentological and ichnological characterization of small- and large-scale channel IHS in the Middle McMurray Formation of the Central-C area, McMurray Sub-Basin, Alberta

Author: 
Date created: 
2018-12-11
Abstract: 

The Lower Cretaceous McMurray Formation is interpreted as a brackish-water, tidally influenced estuarine complex. The study area encompasses Townships 90-95, Ranges 10-14W4 in northeast Alberta. Facies analysis of 41 cored wells led to the identification and differentiation of large- and small-scale lateral accretion IHS associated with tidal-fluvial channels. Five sedimentary facies are assembled into four recurring facies associations to characterize these channel systems. Sedimentological and ichnological characteristics point to elevated physico-chemical stress in most large-scale channel successions, interpreted to be the consequence of carrying the bulk of the fluvial discharge through these trunk channel systems. By contrast, small-scale channels display less evidence of physico-chemical stress indicating they carried little fluvial flow. Abandoned channel deposits likewise show reduced paleoenvironmental stress. This study suggests that the deposits of small-scale channels and abandoned channels are the most suitable for assessing the degree of marine influence in the study area.

Document type: 
Thesis
Senior supervisor: 
James MacEachern
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) M.Sc.