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.

Numerical simulations of a multiscale model for maple sap exudation

Date created: 
2017-03-24
Abstract: 

Sap exudation refers to the process whereby trees such as sugar maple (Acer saccharum) and red maple (Acer rubrum) generate elevated stem pressure, which permits maple sap to be harvested as a viable agricultural product. There exists a vast literature on sap exudation and various hypotheses regarding the physical and biological mechanisms for in- ternal pressure generation in trees but very limited mathematical modeling work. Here, we perform a careful parametric study of a model for sap exudation recently published by Graf et al. [J R Soc Interface 12:20150665, 2015] which consists of a nonlinear system of differential equations obtained by homogenizing the equations governing phase change and sap transport at the cellular level. We focus on the influence of realistic daily temperature oscillations on the resulting stem pressure and draw comparisons with experimental mea- surements on red and sugar maple saplings taken during the sap harvest season. This study demonstrates the limitations and capabilities of our model in terms of capturing realistic exudation behaviour.

Document type: 
Thesis
File(s): 
Senior supervisor: 
John Stockie
Department: 
Science: Department of Mathematics
Thesis type: 
(Thesis) M.Sc.

Optical Dating Studies of southeastern Patagonian Sand Wedges in Chile and Argentina

Peer reviewed: 
No, item is not peer reviewed.
Date created: 
2016-04-18
Abstract: 

The purpose of this study was to establish a suitable single aliquot regenerative dose (SAR) optical dating protocol for K-feldspar sediments in southeast Patagonia using radiocarbon-dated Holocene dune sediments at Lago Arturo. The established protocol was then applied to sand wedge sediments found in the region in order to date periods of permafrost and to provide limiting ages on glaciation. The suitable SAR protocol incorporates a 200oC/10 s preheat for both the additive-dose and test dose measurements, a hot (290oC) bleach step at the end of each SAR cycle to reduce recuperation, and measurement of the stimulated luminescence at 50oC. A select number of sand wedges found throughout the region were dated using the established protocol. Those that yielded reliable ages date to the last glaciation. Some sand wedges provided older optical ages, however, more testing is required to determine if these ages are accurate.

Document type: 
Thesis
File(s): 
Senior supervisor: 
John Clague
Olav Lian
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) M.Sc.

The speed of life in sharks and rays: methods, patterns, and data-poor applications

Date created: 
2017-04-11
Abstract: 

Since the theory of evolution by natural selection was first postulated, biologists have noted that life histories evolve following broad patterns across all organisms. Understanding the mechanisms causing these relationships is the central focus of life history theory; these insights can also be used to better estimate the biology and extinction risk of data-poor species. Sharks, rays, and chimaeras (class Chondrichthyes) are an ideal taxon to explore these relationships as they have evolved a broad range of life history strategies. In this thesis, I focus on two key time-related life history parameters that are often used as a measure of productivity: growth coefficient k, which is estimated from the von Bertalanffy growth function (VBGF), and maximum intrinsic rate of population increase rmax, estimated by simplifying the Euler-Lotka equation. I begin by clarifying two methodological problems regarding the estimation of growth and productivity. I first show that fixing the y-intercept in the VBGF, a common approach in chondrichthyan age and growth studies, often causes considerable bias in growth coefficient estimates, and recommend using the three-parameter VBGF instead. I then point out an important omission in a method commonly used for estimating r max in chondrichthyans and clarify the correct way to estimate it. Next I explore the effect of uncertainty on the estimation of r max and show that species with low annual reproductive outputs are bound to have very low productivities, thus focus should be placed into accurately estimating litter sizes, breeding intervals, and the variability of these traits. As an example of how these insights can be applied, I better estimate growth and productivity for a data sparse species of conservation concern, the Spinetail Devil Ray (Mobula japanica), and show it has a much lower somatic growth rate than previously thought and one of the lowest productivities among chondrichthyans. Finally, I show that productivity in chondrichthyans varies with temperature as well as depth, and that the scaling of this relationship changes with temperature according to the expectation from Bergman’s rule. My thesis demonstrates that simple insights from life history theory can further our knowledge on the broad patterns that shape the evolution of life histories we see today, which can be used to inform management of data-poor species.

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

Impacts of a new Greenway on older adult mobility: A mixed-methods analysis in Vancouver, BC

Author: 
Date created: 
2017-04-19
Abstract: 

Our population is aging, and life expectancies are increasing globally. One strategy to promote healthy aging is by creating environments that support physical activity. Using a natural experiment study design, this dissertation takes a mixed-methods approach to capture the impacts of a built environment intervention aimed to increase active transportation among community-dwelling older adults. We captured location-specific travel and physical activity using accelerometers and GPS monitors one year before and after the Comox-Helmcken Greenway was developed, and measured change in weekly transportation-related activity, specific activity along the Greenway, and activity along a comparison corridor. Secondly, we interviewed a subset of these older adults to capture their perceptions of the Greenway. We found no change in weekly physical activity levels, but a decrease in the number of trips along the Greenway. Our interview data suggests this may result from confusion of messaging, the steep slope, and a lack of destinations.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Meghan Winters
Department: 
Health Sciences: Faculty of Health Sciences
Thesis type: 
(Thesis) M.Sc.

Enabling choice: Addressing barriers to abortion services in rural British Columbia

Date created: 
2017-04-19
Abstract: 

Induced abortion is an extremely common procedure in Canada; 1 in 3 Canadian women terminate at least one pregnancy in their life time. It is a medically necessary service, but women living in rural communities in British Columbia face extreme barriers when accessing abortion services. Women face extra-legal barriers related to distance, cost, a lack of rural health care professionals, and a lack of health care facility resources. This study seeks to examine existing interventions in BC and other jurisdictions, and synthesize existing research to compile a complete list of policy options. Following a full evaluation of these options to better understand effectiveness and tradeoffs, the study culminates with a list of priorities for action. The final recommendations first address flaws in existing policies for short term more immediate interventions, and secondly, introduce new initiatives for longer term success.

Document type: 
Graduating extended essay / Research project
File(s): 
Senior supervisor: 
John Richards
Department: 
Arts & Social Sciences: School of Public Policy
Thesis type: 
(Project) M.P.P.

On assistance, can work: The unrealized employment potential in Vancouver’s Downtown Eastside

Date created: 
2017-03-30
Abstract: 

Vancouver’s Downtown Eastside (DTES) neighborhood is home to around 2400 welfare recipients, many of whom can and want to work, but experience barriers in doing so. Many engage in a continuum of income generating activities that creates pathways from informal work to traditional employment. Currently there is inadequate movement along the continuum due to multiple systemic barriers. To understand these barriers, I undertake a qualitative thematic analysis of primary interview data with welfare recipients, representatives from community organizations/social enterprises in the DTES, and social policy experts. Using a series of evaluative criteria, I combine primary research findings with the literature to assess five policy options. I recommend a combination of these options to reduce administrative barriers, recognize the income generation continuum, and increase the financial incentive to work. This recommendation is designed to facilitate movement along the continuum and enhance economic security and well-being for DTES welfare recipients.

Document type: 
Graduating extended essay / Research project
File(s): 
Senior supervisor: 
Kora DeBeck
Department: 
Arts & Social Sciences: School of Public Policy
Thesis type: 
(Project) M.P.P.

Attracting talent to Vancouver's tech sector: Policy options for future growth

Date created: 
2017-04-07
Abstract: 

In BC’s shift toward a knowledge-based economy, growth in the tech sector and the ability of start-ups to evolve into globally competitive companies is vital for BC’s future economic viability. Vancouver is a leading centre for tech growth in BC, and an increasing number of firms are doing business in the city. Vancouver is also home to three “tech unicorns” – start-ups valued over $1B – in Hootsuite, Avigilon, and Slack, all of which have helped legitimize the city’s brand as a viable destination to do business. However, the sector faces a dire problem of finding adequate talent supply to fill over 2,000 immediate vacancies and 15,500 vacancies over the next five years in tech, specifically at the executive level. This capstone evaluates policy options using criteria and measures, and recommends changes to Canada’s Temporary Foreign Worker Program and immediate action on Vancouver’s housing affordability to ultimately increase tech talent supply.

Document type: 
Graduating extended essay / Research project
File(s): 
Senior supervisor: 
Josh Gordon
Department: 
Arts & Social Sciences: School of Public Policy
Thesis type: 
(Project) M.P.P.

Running out of Thread: Securing Bangladeshi ready-made garment factory safety given the looming cut-off for the Accord and the Alliance

Date created: 
2017-03-24
Abstract: 

In response to the tragic Rana Plaza building collapse in 2013, Western clothing brands launched initiatives to inspect their Bangladeshi ready-made garment (RMG) supplier factories and remediate violations of global electrical, fire, and structural standards. The Bangladesh Accord on Fire and Building Safety (Accord) and the Alliance for Bangladesh Worker Safety (Alliance) are scheduled to end in June, 2018. While significant progress has been made in the remediation of electrical and fire deficiencies, inspection data from the Accord show that about half of identified structural problems remain unsolved, including a large portion of structural repairs over two years past their deadlines. As brands have taken temporary responsibility for safety in much of the sector, this report considers policy options available to them given the near-impossibility that complete remediation will occur by the initiatives’ deadline. Recommendations for decreasing the risk of death or injury borne by Bangladeshi RMG workers are provided.

Document type: 
Graduating extended essay / Research project
File(s): 
Senior supervisor: 
John Richards
Department: 
Arts & Social Sciences: School of Public Policy
Thesis type: 
(Project) M.P.P.

Color Constancy for RGB and Multispectral Images

Author: 
Date created: 
2017-04-03
Abstract: 

The problem of inferring the light color for a scene is called Illuminant Estimation. This step forms the first task in many workflows in the larger task of discounting the effect of the color of the illuminant, which is called Color Constancy. Illuminant Estimation is typically used as a pre-processing step in many computer vision tasks. In this thesis, we tackle this problem for both RGB and multispectral images. First, for RGB images we extend a moments based method in several ways: firstly by replacing the standard expectation value, the mean, considering moments that are based on a Minkowski p-norm; and then secondly by going over to a float value for the parameter p and carrying out a nonlinear optimization on this parameter; and finally by considering a different expectation value, generated by using the geometric mean. We show that these strategies can drive down the median and maximum error of illuminant estimates. And then for multispectral images, we formulate a multiple-illuminants estimation problem as a Conditional Random Field (CRF) optimization task over local estimations. We then improve local illuminant estimation by incorporating spatial information in each local patch.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Mark S. Drew
Ze-Nian Li
Department: 
Applied Sciences: School of Computing Science
Thesis type: 
(Thesis) M.Sc.

Localization and assembly of the Vibrio cholerae type IV pilus secretin channel

Date created: 
2017-04-12
Abstract: 

Type 4 pili (T4P) are filamentous structures found on the surfaces of many Gram-negative bacteria, including Vibrio cholerae. The V. cholerae T4P are the toxin-coregulated pili (TCP), which mediate bacterial aggregation and exoprotein secretion, critical functions in colonization of the human intestine to cause the diarrheal disease cholera. TCP assemble at the inner membrane (IM), grow through a multiprotein conduit in the periplasm and through a secretin channel in the outer membrane (OM). The multimeric secretin channel is formed by secretin subunits, which are translocated across the IM by the Sec apparatus, and in most T4P systems, are transported to the OM with the help of a lipoprotein co-chaperone. In the V. cholerae TCP the secretin subunit itself, TcpC, is a lipoprotein, and its putative co-chaperone, TcpQ, is non-lipidated. Here we use mutagenesis, cellular fractionation and functional assays to investigate secretin channel assembly in V. cholerae. TcpC must be co-expressed with TcpQ to complement a ΔtcpC mutant in an assay of pilus functions, but the reciprocal is not true. TcpQ is necessary for pilus assembly but not for localization of TcpC to the outer membrane, demonstrating that TcpQ is not a co-chaperone for TcpC. The periplasmic domain of TcpC can be expressed on its own, localizes to the outer membrane, and localizes TcpQ at the outer membrane as well, provided TcpC is lipidated. When the periplasmic domain of TcpC is unlipidated it gets degraded and TcpQ accumulates in the periplasm, suggesting that the periplasmic domain of TcpC interacts with TcpQ and localizes it to the outer membrane via its lipid moiety. Our results lead to a model whereby TcpC Cys1 is lipidated at the IM by the Lgt machinery and transported to the OM in complex with TcpQ. TcpC inserts into the OM at two points: via its C-terminal portion, which forms a β-barrel channel with TcpC C-terminal domains of other secretin subunits, and via lipid moiety in its N-terminal domain, which interacts with TcpQ to link the OM channel to periplasmic pilus conduit.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Lisa Craig
Department: 
Science: Department of Molecular Biology and Biochemistry
Thesis type: 
(Thesis) M.Sc.