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.

Multiple axon guidance pathways asymmetrically distribute axons in the ventral nerve cord of Caenorhabditis elegans

Author: 
Date created: 
2018-11-22
Abstract: 

Early during development neurons project small filamentous processes, axons and dendrites, that extend and eventually connect with other cells and tissues. These processes can grow over long distances and allow for transmission of information between cells. The proper functioning of our nervous system is dependent on these same processes correctly navigating to specific end targets. This is achieved through guidance cues in the environment which interact with receptors on the extending processes allowing them to be steered in the correct direction. Unfortunately, due to the high complexity of most vertebrate nervous systems our understanding of how axons and dendrites use these cues to navigate is still very limited. The aim of this thesis was to discover novel genes regulating axon guidance to shine additional light on how axons navigate during development. Normally axons of the ventral nerve cord in the nematode Caenorhabditis elegans are invariably sorted asymmetrically. Animals with mutations impacting function in individual axon guidance signaling pathways show no or only very low penetrance of disruption of VNC asymmetry. Here genetic screens successfully isolated four mutants in which asymmetry between major longitudinal axon tracts is disrupted. One of these four mutants include a novel allele of the gene col-99 which encodes a previously uncharacterized transmembrane collagen with vertebrate homologs. Detailed characterization of animals lacking COL-99 revealed widespread axon guidance defects impacting longitudinal and lateral axon navigation of a variety of neurons. Of the remaining three mutants two were found to be alleles of unc-52 and unc-34, both previously characterised for roles in axon guidance, while the final mutation remains unidentified. Disruption of any one signaling pathway does not lead to penetrant VNC asymmetry defects suggesting redundancy between parallel signaling pathways here. To better understand how signaling pathways of multiple guidance cues may converge to control guidance at choice points single mutants were crossed into a nid-1 null mutant background and VNC asymmetry phenotypes examined. Previously nid-1 was found to substantially enhance navigation defects of the VNC pioneering neuron AVG when crossed into mutants showing a low penetrance of AVG navigation defects. Double mutants with nid-1 saw defect penetrance significantly increase in several cases indicating parallel signaling pathways. Combination of mutants into triple and quadruple mutant strains showed that UNC-6, SAX-3, and COL-99 represent members of parallel signaling pathways acting redundantly to guide axons in establishment of asymmetry which in addition depends on basement membranes components, including EPI-1. Thus multiple axon guidance signaling pathways, acting in tandem, ensure correct guidance and segregation of axons at the anterior choice point of the VNC establishing VNC asymmetry.

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

The expression and regulation of lipid transport proteins in the desert locust, Schistocerca gregaria

Author: 
Date created: 
2018-11-19
Abstract: 

Lipids play a central role in insects, both for storage of nutrients and as an energy source during development and dispersal. Due to their low water solubility, special transport mechanisms are required for their efficient mobilization and utilization. In this thesis, I studied intra- and extracellular proteins involved in lipid transport in the desert locust, Schistocerca gregaria. Vitellogenins are very high-density lipoproteins produced by adult females and deposited into the developing eggs. Two different vitellogenins, named VG-A and VG-B, are expressed in locust fat body. Their complete cDNA transcripts of ~5.6 kb each have been sequenced, coding for two proteins of ~200 kDa each. VG-A and VG-B are co-expressed in similar amounts by mature females, commencing 11 days after adult eclosion, and continuing at high levels throughout the entire adult life. The expression of both proteins is dependent on the nuclear transcription factors Met or RXR, and knockdown of each of these proteins almost completely eliminates VG expression. A similar expression profile was observed in adult muscle for the cytosolic fatty acid binding protein FABP, albeit in both sexes. The direct knockdown of the strongly expressed FABP by RNA inference reduced its levels to less than 2% of what is normally found 3 weeks after adult eclosion. In a series of flight experiments, it was demonstrated that in the absence of FABP, insects are incapable of engaging in flight longer than 30 min; at this time, most carbohydrate resources have been depleted, and locusts normally switch to lipids as the sole fuel for muscle energy production. Short-term flight performance of FABP knockdown locusts was identical to control insects, suggesting that the lack of FABP does not interfere with carbohydrate metabolism. Moreover, the mobilization of lipids in the fat body and their transport by the major hemolymph lipoprotein lipophorin was indistinguishable from control animals. In contrast, knockdown of apolipophorin III, which is essential for lipid transport during flight, completely eliminated flight capability, even for short duration flights. Taken together, this thesis highlights the essential role of lipid transport proteins for locust reproduction and dispersal and identifies potential targets for insect control strategies.

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

3D visual-inertial odometry and autonomous mobile robot exploration with learned map prediction

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

2D and 3D scene reconstruction are important topics in the field of robotics and computer vision. Mobile robots require a model of the environment to perform navigational tasks, and model acquisition is a useful application in itself . This thesis presents a) A 3D odometry and mapping system producing metric scale map and pose estimates using a minimal sensor-suite b) An autonomous ground robot for 2D mapping of an unknown environment using learned map prediction. The first application proposes a direct visual-inertial odometry method working with a monocular camera. This system builds upon the state-of-the-art in direct vision-only odometry. It demonstrates superior system robustness and camera tracking accuracy compared to the original method. Furthermore, the system is able to produce a 3D map in metric scale, addressing the well known scale ambiguity inherent in monocular SLAM systems.The second application demonstrates an autonomous ground robot capable of exploring unknown indoor environments for reconstructing their 2D maps. This method combines the strengths of traditional information-theoretic approaches towards solving this problem and more recent deep learning techniques. Specifically, it employs a state-of-the-art generative neural network to predict unknown regions of a partially explored map, and uses the prediction to enhance the exploration in an information-theoretic manner. The system is evaluated against traditional methods in simulation using floor plans of real buildings and demonstrates advantage in terms of exploration efficiency. We retain an advantage over end-to-end learned exploration methods in that the robot's behavior is easily explicable in terms of the predicted map.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Ping Tan
Richard Vaughan
Department: 
Applied Sciences: School of Computing Science
Thesis type: 
(Thesis) M.Sc.

How Iceland Writers Retreat markets itself as an international writers event

Author: 
Date created: 
2018-12-10
Abstract: 

The first Iceland Writers Retreat (IWR) was held in 2014. It has since grown to be an annual event that boasts participants from around the globe, who travel to Iceland to learn from internationally renowned faculty, immerse themselves in the literary traditions of Iceland, and explore an unforgettable setting. This report outlines and examines Iceland Writers Retreat marketing efforts, particularly online. Further, it historicizes the beginning and inspirations of IWR, and delineates IWR’s role within both the landscape of international writing events and the liminal space it occupies between the Icelandic tourism industry and cultural sphere. It aims to outline marketing best practices that can be useful not only to other writing retreats and events, but also to any cultural organization that is moving their marketing efforts primarily online. Finally, it attempts to highlight opportunities for IWR to continue to grow their audience—both online and at the event.

Document type: 
Graduating extended essay / Research project
File(s): 
Senior supervisor: 
Leanne Johnson
Department: 
Communication, Art & Technology: Publishing Program
Thesis type: 
(Project) M.Pub.

Cell towers and the ambient population: A spatial analysis of disaggregated property crime in Vancouver, BC

Author: 
Date created: 
2018-12-10
Abstract: 

The current study employs a new measure of the ambient population, constructed using cell tower location data from OpenCellID, to compare residential and ambient population-based crime rates in Vancouver, BC. Five disaggregated property crime types are examined at the dissemination area level. Findings demonstrate striking differences in the spatial patterns of crime rates constructed using these two different measures of the population at risk. Multivariate results from spatial error models also highlight the substantial impact that the use of a theoretically-informed crime rate denominator can have on Pseudo R2 values, variable retention, and trends in significant relationships. Implications for theory testing and policy are discussed.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Martin Andresen
Department: 
Arts & Social Sciences: School of Criminology
Thesis type: 
(Thesis) M.A.

Game theoretic models of clear versus plain speech

Author: 
Date created: 
2018-11-27
Abstract: 

Clear speech is a speaking style intended to improve the comprehension of the hearer, which is usually due to the external noise, less ideal listening conditions, or the speaker is intended to be more intelligible. Clear speech, which exhibits increased duration, pitch, amplitude, and more exaggerated articulation, consumes more energy in order to improve the likelihood of accurate communication. To strike a balance between the cost of clear speech and the improvement it brings, we use game theory to model the phenomenon of clear speech. The conventions that speakers and hearers use to communicate are considered as equilibria in the communication game, and we need to make predictions of how the equilibria changes under the different circumstances. How our models correspond to what is experimentally observed, and what predictions are made for experimental results are discussed in the thesis. In the basic model, we study the case where the speaker has to send one of two messages equally likely in one-dimensional acoustic space. Next, we make a further discussion of the basic model in a priori probability of the sent message, the number of messages, and the conflicts between clearness and comprehensibility. The third contribution of this thesis is to extend the one-dimensional acoustic space to two dimensions, by introducing uncontrastive and contrastive features.

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

Activity monitor reliability and validity in community-dwelling older adults

Author: 
Date created: 
2018-11-20
Abstract: 

Monitoring older adult physical activity is central to surveillance of individual and population health as well as delivery and evaluation of health promotion programs, and it requires reliable and valid measurement tools. I investigated step count test-retest reliability and criterion validity across consumer-grade activity monitors in community-dwelling older adults with and without self-reported mobility limitations during over-ground walking (n = 36; mean 71.4 years). I evaluated six activity monitors (Fitbit Charge, Fitbit One, Garmin vívofit 2, Jawbone UP2, Misfit Shine, and New-Lifestyles NL-1000) during two 100-step walks, one continuous 400-metre walk, and one interrupted 400-metre walk. On average, all monitors undercounted steps. Step counts from hip-worn monitors generally exhibited better reliability and validity than from wrist-worn monitors. Mobility status did not affect monitor step count errors, but interruptions to walking negatively impacted criterion validity. The hip-worn Fitbit One was the only monitor with sufficiently high test-retest reliability and criterion validity.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Dawn Mackey
Department: 
Science: Department of Biomedical Physiology and Kinesiology
Thesis type: 
(Thesis) M.Sc.

The role of the editor: The case of Springer

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

Springer, as one of the largest commercial academic publishers, merged with Nature in 2015, and now has a new name: Springer Nature. The merger combines strength of two publishers, with strong book publishing plus strong journal publishing in one publisher. However, the merger does not affect the working modes of the editors at Springer or Nature. Different from the in-house editors at Nature who are handing peer-reviewing process of every article, what are the responsibilities of the editors at Springer? What skills should the editors at Springer have? How can one be a qualified editor at Springer? Facing the new trends in publishing, including big data, open access policies, information exposure, competitive markets, among others, what challenges are awaiting these editors? In particular, in the fast-growing Chinese market, with its enormous output of scientific documents, how can editors based in China work to address this challenge? This report describes the role of editors at Springer regarding the Chinese market, from skills to experiences and from opportunities to challenges.

Document type: 
Graduating extended essay / Research project
File(s): 
Senior supervisor: 
John Maxwell
Department: 
Communication, Art & Technology: Publishing Program
Thesis type: 
(Project) M.Pub.

Applying self-attention neural networks for sentiment analysis classification and time-series regression tasks

Date created: 
2018-11-26
Abstract: 

Many machine learning tasks are structured as sequence modeling problems, predominantly dealing with text and data with a time dimension. It is thus very important to have a model that is good at capturing both short range and long range dependencies across sequence steps. Many approaches have been used over the past few decades, with various neural network architectures becoming the standard in recent years. The main neural network architecture types that have been applied are recurrent neural networks (RNNs) and convolutional neural neworks (CNNs). In this work, we explore a new type of neural network architecture, self-attention networks (SANs), by testing on sequence modeling tasks of sentiment analysis classification and time-series regression. First we perform a detailed comparison between simple SANs, RNNs, and CNNs on six sentiment analysis datasets, where we demonstrate SANs achieving higher classification accuracy while having other better model characteristics over RNNs such as faster training and inference times, lower number of trainable parameters, and consuming less memory during training. Next we propose a more complex self-attention based architecture called ESSAN and use it to achieve state-of-the-art (SOTA) results on the Stanford Sentiment Treebank fine-grained sentiment analysis dataset. Finally, we apply our ESSAN architectures for the regression task of multivariate time-series prediction. Our preliminary results show that ESSAN once again achieves SOTA results, beating previous SOTA RNN with attention architectures.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Fred Popowich
Department: 
Applied Sciences: School of Computing Science
Thesis type: 
(Thesis) M.Sc.

Testing the ability of in-vitro depletion rates to assess the biotransformation rate and bioconcentration factor of hydrophobic chemicals in rainbow trout (Oncorhynchus mykiss)

Date created: 
2018-12-03
Abstract: 

The objective of this study was to test the ability of in-vitro biotransformation rates to predict in-vivo biotransformation rates and BCFs to ultimately improve chemical bioaccumulation assessment. In-vitro biotransformation rates of hydrophobic chemicals pyrene, methoxychlor, cyclohexyl salicylate, and 2,6 dimethyldecane were determined using a rainbow trout liver S9 preparation and then input into two in-vitro-in-vivo extrapolation (IVIVE) models to estimate in-vivo biotransformation rates (kMET) and modelled BCFs. Comparisons of in-vitro derived kMET values using both IVIVE models were in reasonable agreement when compared to in-vivo derived kMET values for pyrene and methoxychlor. Estimated BCFs from this study for pyrene, methoxychlor, and cyclohexyl salicylate were also in good agreement with estimated BCFs from previous studies using in-vitro biotransformation rates as inputs to IVIVE models, but were significantly higher compared to empirical BCFs. This indicates the potential usefulness of in-vitro biotransformation assays and IVIVE models for estimating kMET and BCFs, however kMET values from IVIVE models and BCF estimates should only be considered a conservative estimate at this time due to the uncertainty (i.e. extrahepatic metabolism) associated with these models and the further work required to fine-tune these models.

Document type: 
Graduating extended essay / Research project
File(s): 
Senior supervisor: 
Frank Gobas
Department: 
Science: Biological Sciences Department
Thesis type: 
(Project) M.E.T.