title: A Causal Model of Individual Responses to Community Mental Health Care

contributor:
Taylor, S.M.
Geography

subject: Geography Geography

abstract:
This study examines the causal processes underlying individual non-user responses to community mental health care. With the containing trend toward community-based delivery of mental health services in the United States and Canada it is essential to understand the response of non-users to potential mental health facilities near their home.

The analysis is based on a simple yet comprehensive conceptual model of the individual response process. The desirability of a future mental health facility near a person's home is regarded as primarily a function of attitudes toward that mentally ill and perceived mental health facility impacts. Attitudes toward the mentally ill are themselves regarded as a function of personal non-attitudinal characteristics. Facility impacts are viewed as a function of facility characteristics and characteristics of the local neighbourhood. The latter also influence facility desirability.

These relationships are stated in a causal model of the response process which is described by a set of nineteen hypotheses. Each hypothesis describes a specific relationship in the model. The empirical validity of the causal model and the hypotheses are tested using data collected in an extensive questionnaire survey of metropolitan Toronto, Ontario residents. Respondents were randomly chosen from census enumeration areas with and without existing mental health facilities. The sample was stratified by two levels of geographic location and three levels of social class.

The intervariable correlations and direct effects estimated by path analysis generally support the hypotheses, with some exceptions. Several neighbourhood variables were found to have non-significant effects on perceived mental health facility impacts and facility desirability. This was due to a mismatch in the units of analysis. Neighbourhood variables were measured at the census tract or enumeration area level and attitudes toward facilities were measured at the individual level. Awareness of a neighbourhood mental health facility did not significantly influence facility impacts or facility desirability.

Personal non-attitudinal factors were found to have significant effects on attitudes toward the mentally ill. Attitudes toward the mentally ill were, in turn, the most powerful predictor of perceived facility impacts. Completing the causal sequence, attitudes toward the mentally ill and perceived facility impacts exert strong antecedent influences on facility desirabilty.

Although the direct influence of neighbourhood factors on facility desirability is limited, their indirect effects via perceived facility impacts increases the total influence of several of these variables quite markedly. Facility impacts also act as an intervening variable for the influence of attitudes toward the mentally ill on facility desirability. Distance from home has a significant effect on facility desirability. Closer locations are viewed as less desirable rather than more undesirable.

A post hoc test of the specification assumptions underlying the structure of the causal model confirms the major relationships between attitudes toward the mentally ill, perceived facility impacts and facility desirability. Individual non-attitudinal factors are found to have pervasive influences on reactions to facilities. Hence, the intervening role of attitudes toward the mentally ill between personal factors and reactions to facilities is undermined.

Overall, the results indicate that personal non-attitudinal factors, attitudes toward the mentally-ill and perceived facility impacts exert significant direct influences on facility desirability. From a theoretical point of view, these findings constitute a significant advance, clarifying many of the questions and ambiguities characterising previous research. In terms of practical implications, the results suggest, among other things, that the widespread acceptance of community mental health care is dependent upon fostering, by means of public education campaigns, positive attitudes of non-users to the mentally ill and the facilities that serve them.

abstract: Doctor of Philosophy (PhD)


title: THE RELIABILITY AND VALIDITY OF THE PSFS IN PEOPLE WITH PD

contributor:
Letts, Lori
Paul Stratford, Laurie Wishart
Paul Stratford, Laurie Wishart
Rehabilitation Science

subject:
Parkinson Disease
Patient Specific Functional Scale
Patient Reported Outcome Measures
Measurement
Other Rehabilitation and Therapy
Other Rehabilitation and Therapy

abstract:
Objectives: To assess the reliability and validity of the Patient Specific Functional Scale when administered to people living with Parkinson’s Disease.

Methods and Materials: Twenty six people living with Parkinson’s Disease from Hamilton and Burlington were interviewed four times within a four month period. The participants answered the Movement Disorders Sponsored Unified Disease Rating Scale part II, the Parkinson’s Disease Questionnaire 39, and the Patient Specific Functional Scale. Reliability assessment addressed test-retest reliability and reliability of the change scores using Intraclass Correlation Coefficients. Validity assessment focused on convergent construct validity and longitudinal validity by correlating the Patient Specific Functional Scale with the other measures administered.

Results: The test retest reliability of the scores yielded by the PSFS was ICCpre= 0.72 (95%CI=0.47-0.86); ICCpost=0.83 (95%CI=0.66-0.92). The reliability of change scores was 0.50. In relation to the validity, no significant correlations were found between the Patient Specific Functional Scale and the other measures.

Conclusions: The PSFS yields reliable scores when it is administered to people living with PD. The Patient Specific Functional Scale does not target the same outcomes as the MDS-UPDRS part II and the PDQ-39. The PSFS does not detect change in functioning in people living with PD within a four month period.

abstract: Master of Science (MSc)


title: On Nietzsche's Genealogy of Cruelty

contributor:
Allen, Barry
Sciaraffa, Stefan
Ajzenstat, S.
Philosophy

subject:
Nietzsche
Cruelty
Genealogy
Palaeoanthropology
Ascetic
Pre-history
Continental Philosophy
Ethics and Political Philosophy
History of Philosophy
Philosophy
Philosophy of Science
Continental Philosophy

abstract: Unfortunately I have had bit of difficulty with setting up the page numbers appropriately. I have been unable to figure out how to make the preliminary part of document in Roman numerals while at the same time separating this from the main body of the text using Arabic numbers. My apologies, but I sincerely do not know how to resolve this frustrating problem. I can resolve this problem if I send you the preliminary part and main body as separate documents, but just not as one continuous document. Please contact me if this latter method is the way to go.

abstract: This thesis provides an expository account and critical analysis of Friedrich Nietzsche’s genealogical position on cruelty. Its primary engagement is with Nietzsche’s On The Genealogy of Morals, however, other works by this author are discussed when relevant. The general import of this thesis is threefold. First, it demonstrates Nietzsche’s genealogical account of cruelty, detailing its complex evolutionary progression and its various facets of influence. Second, this work identifies some authors who are critical of Nietzsche position on cruelty. These criticisms are identified and are then largely refuted on various grounds. Third, this thesis argues that an appropriate critical analysis of Nietzsche’s genealogical theorizing will be based on a cross-examination of his positions with current palaeoanthropological findings. The conclusion drawn from this analysis is that there is insufficient empirical evidence to substantiate Nietzsche’s accounts and his methodical approach to genealogical theorizing is, furthermore, untenable.


title: NEIGHBOURHOOD AND SOCIAL INFLUENCES ON PARTICIPATION IN EVERYDAY ACTIVITIES AMONG OLDER ADULTS WITH CHRONIC HEALTH CONDITIONS

contributor:
Law, Mary
Rehabilitation Science

subject:
older adults
chronic disease
human activities
residence characteristics
social environment
Medicine and Health Sciences
Medicine and Health Sciences

abstract:
Older adults with chronic health conditions experience limitations participating in everyday activities. Neighbourhood characteristics and social support can offset individual impairments and help to facilitate participation; however, gaps in this literature exist. This thesis presents the results of three studies that explore the influence of neighbourhood and social factors on participation in everyday activities among older adults with chronic health conditions. The first paper describes a scoping review of academic literature regarding neighbourhood influences on participation. The findings of the review indicated that neighbourhood economic status, amenities, problems, mobility barriers, cohesion, and safety may influence participation but the pathways through which this occurs are not clear.

The second paper uses findings from a cross-sectional survey (n=248) that examined the relationship between perceptions of neighbourhood characteristics and satisfaction with participation among older adults with chronic health conditions. Path analysis showed that fewer neighbourhood problems directly predict higher participation while higher neighbourhood cohesion and safety indirectly predict higher participation.

The third paper uses data from the same cross-sectional survey to examine the types of social support that most strongly predict satisfaction with participation. Regression analyses showed that participants who perceived greater tangible support and positive social interaction support had more satisfaction with participation than participants with lower levels of these types of support.

The findings in this thesis extend previous research by showing that neighbourhood characteristics influence participation even after accounting for social and individual factors. This research identified a potential pathway from neighbourhood characteristics to participation that includes neighbourhood cohesion and social support and established a link between positive social interaction support and participation. The findings in this thesis help to better understand neighbourhood and social influences on participation. These influences may be addressed through clinical or policy interventions to facilitate participation in older adults with chronic health conditions.

abstract: Doctor of Philosophy (PhD)


title: Connecting the Dots: Comparing SPH Simulations and Synthetic Observations of Star-forming Clumps in Molecular Clouds

contributor:
Sills, Alison
Wadsley, James
Wilson, Christine
Physics and Astronomy

subject: Star formation

subject: Molecular Clouds

subject: Simulations

subject: Synthetic Observations

subject: Stars, Interstellar Medium and the Galaxy

abstract: The gravitational collapse of a giant molecular cloud produces localized dense regions, called clumps, within which low-mass star formation is believed to occur. Recent studies have shown that limitations of current observing techniques make it difficult to correctly identify and measure properties of these clumps that reflect the true nature of the star-forming regions. In order to make a direct comparison with observations, we produced synthetic column density maps and a spectral-line cube from the simulated collapse of a large 5000 solar mass molecular cloud. The synthetic observations provide us with the means to study the formation of star-forming clumps and cores in our simulation using methods typically used by observers. Since we also have the full 3D simulation, we are able to provide a direct comparison of `observed' and `real' star-forming objects, highlighting any discrepancies in their physical properties, including the fraction of cores which are gravitationally bound. We have accomplished this by studying the global properties of the star-forming objects, in addition to performing a direct correlation of individual objects to determine the error in the observed mass estimates. By correlating the clumps found in the simulation to those found in the synthetic observations, we find that the properties of objects derived from the spectral-line data cube were more representative of the true physical properties of the clumps, due to effects of projection greatly impacting the estimates of clump properties derived from two-dimensional column density maps.

abstract: Master of Science (MSc)


title: The Characterization and Diagnosis of Late-Onset Psychotic Disorder: A prospective longitudinal case series

contributor:
Rosebush, Patricia
Mazurek, Michael
MacQueen, Glenda
Neuroscience

subject:
late-onset psychosis
late-onset schizophrenia
late-onset delusional disorder
diagnosis
validity
characterization
Psychiatric and Mental Health
Psychiatric and Mental Health

abstract:
There is considerable confusion regarding the diagnosis of patients presenting with non-affective psychosis in the absence of a dementia or secondary to a general medical condition in the fifth decade and beyond. A number of different terms, diagnostic criteria and age-cut-offs have been applied to this presentation posing a challenge to clinicians and researchers alike. Despite diagnostic inconsistencies and conceptual uncertainty, a remarkably consistent clinical picture has emerged. However, many questions still remain with regards to its underlying etiopathophysiological mechanisms, treatment and prognosis, including whether it is distinct from schizophrenia and whether it might be a prelude to cognitive deterioration. Currently there is no official diagnostic designation for patients who develop a primary psychosis in late life, with patients being typically diagnosed as either schizophrenia or delusional disorder, although the validity of such a distinction has been questioned.

The following prospective longitudinal study sets out to characterize the largest known group of patients (n=102) with first-episode, late-onset (>age 40) psychotic disorder on demographic, clinical, treatment and prognostic variables. Given that one of the most contentious issues in the characterization of these patients has been that of diagnostic classification, we examined whether the currently nosological distinction of schizophrenia (SCZ) from delusional disorder (DD) has validity and/or utility. Patients were classified as either SCZ (n=47) or DD (n=55) according to DSM-IV criteria, and were then compared on a number of validators proposed as part of the DSM-V development process. As predicted, there were no significant differences between the two groups. In conclusion, our analysis did not find the current diagnostic distinction of SCZ from DD in the late-onset population to be valid and/or useful. We recommend the use of the more general diagnostic term, “Late-Onset Psychotic Disorder”, to refer to all patients who develop a primary psychosis in their forties or beyond.

abstract: Master of Science (MSc)


title: ACCESSIBILITY AND BUILT ENVIRONMENT EFFECTS ON TRANSIT USE

contributor:
Paez, Antonio
Darren Scott, Pavlos Kanaroglou
Darren Scott, Pavlos Kanaroglou
Geography

subject:
Accessibility
Built Environment
Transit Modal Share
Spatial Filter
Walkability Audit
Site Selection
Urban Studies and Planning
Urban Studies and Planning

abstract: A critical factor in transit mode share analysis is the level of accessibility to transit services. The objective of this study is to investigate the relationships between accessibility and the built environment, and the use of transit. To do so, the proportion of transit users is modeled as a function of socio-economic characteristics, transit level of service, and built environment characteristics. While accessibility to transit has been the object of previous research, accessibility by transit is a factor that has received only limited attention in prior transit modal share research. The case study is the city of Hamilton, and the geographic unit of analysis is the Dissemination Area. A logistic model for proportions with a spatial filter (for spatial autocorrelation) and an over-dispersion parameter is found to provide the best fit and statistical properties. The results of analysis at the meso-scale show that accessibility by transit contributes positively to usage of transit. The possibility that factors at the micro-scale may also influence use of transit, suggests the development of a methodology, based on the use of spatial filtering, to systematically select walkability audit sites. The proposed methodology is demonstrated by means of a case study of neighborhoods in Hamilton. Statistical analysis of walkability audit information shows that the proposed selection strategy can be used to better target limited resources for field-based work, and produce valuable insights into the micro-level factors that may affect transit use.

abstract: Master of Arts (MA)


title: Functional analysis of Pso2 reveals a novel DNA hairpin endonuclease activity: Implications for interstrand crosslink repair

contributor:
Junop, Murray
Alba Guarne, Paul Berti
Alba Guarne, Paul Berti
Biochemistry

subject:
DNA Repair
interstrand crosslinks
Pso2
DNA hairpin.
Biochemistry
Biochemistry

abstract:
DNA interstrand crosslinks provide a challenge for repair machinery given that both strands contain the lesion. Cells have evolved a sophisticated mechanism to overcome this, by recruiting proteins from several repair pathways. One protein thought to function solely in interstrand-crosslinking repair is Pso2. Pso2 deficient cells display sensitivity towards ICL agents and accumulate DNA double strand breaks upon exposure. However, Pso2 is not required for repair of DNA double strand breaks generated by other means, suggesting that these particular breaks are unique requiring Pso2 processing for successful repair. To identify what characteristics these breaks possess and what role Pso2 plays in processing theses breaks, a thorough in vivo and in vitro characterization of Pso2 was conducted.

Pso2 was found to be a 5’-exonuclease independent of DNA structure and length but completely dependent on a 5’-phosphate. Pso2 also displayed structure-specific DNA hairpin-opening activity at the 3’ end two nucleotides from the apex. This activity was required for repair of genomic DNA capped by hairpin structures in the absence of ICL inducing agents as well those generated in response to ICL damage. The constitutively active DNA hairpin endonuclease β-CASP domain of Artemis was able to partially restore the DNA hairpin-opening deficiency and suppress the ICL defect in a pso2 null strain. This suggests that Pso2 acts as an endonuclease in ICL repair and that DNA hairpins may be an encountered intermediate, leading to further understanding of how this unique protein function in ICL repair as well as the repair mechanism itself.

abstract: Doctor of Science  (PhD)


title: MODELING OF ARCHING UNREINFORCED MASONRY WALLS SUBJECTED TO BLAST LOADINGS

contributor:
El-Dakhakhni, Wael
Civil Engineering

subject:
arching
masonry
blast
finite element modeling
LS-DYNA
contact
Structural Engineering
Structural Engineering

abstract: Masonry is one of the most commonly used materials in building construction throughout the world. Unreinforced masonry (URM) walls typically have very low flexural capacities and tend to posses brittle failure modes. Due to brittle nature of URM walls, it is critical to predict the behaviour of the wall when exposed to extreme out of plane loadings such as blast loads. An effective way to enhance the ability of unreinforced masonry walls to withstand blast loads and consequently to limit the amount of wall damage is imposing arching mechanism on the wall. Since carrying out physical experiments to study the response of URM walls subjected to blast load is both dangerous and expensive, finite element modeling has become more attractive to researchers. In this research, an unreinforced one-way arching wall is simulated using the finite element program LS-DYNA and its behaviour subjected blast loading is studied. The model is constructed based on the data recorded earlier during a physical blast experiment. Close agreement was observed between the numerical and experimental results which validated the developed model. A sensitivity study is then performed where the influence of variation of some input parameters such as mortar strength, coefficients of friction, scaled distance, boundary condition, wall height and the effect of two-way arching action on the wall’s response is evaluated. The most influential parameters in this study found to be the scaled distance, wall height and two-way arching action. Smaller scaled distances result in high deflection and as the scaled distance increases the maximum deflection decreases. The wall height also significantly affect the wall’s response to blast loads, i.e. the taller the wall the larger the maximum displacement. It is also concluded that two-way arching action can significantly reduce the wall’s maximum deflection.

abstract: Master of Applied Science (MASc)


title: Deletion Analysis of the Sinorhizobium meliloti Genome

contributor:
Finan, T.M.
Elliot, Marie
Golding, Brian
Biology

subject:
Sinorhizobium meliloti
Flp/FRT recombination system
megaplasmids
essential genes
toxin antitoxin systems
Molecular genetics
Molecular genetics

abstract: The Sinorhizobium meliloti genome consists of 6204 predicted protein-coding regions of which approximately 2000 are proteins of unknown function (PUFs). To identify functions of S. meliloti PUFs, we employed the FRT/Flp recombination system to delete large gene clusters and then screened for phenotypes. Large-scale deletions have been mainly used to define minimal gene sets that contain only those genes that are essential and sufficient to sustain a functioning cell. To adapt FRT/Flp for use in S. meliloti, we used an already constructed pTH1522-derived integration gene library of the S. meliloti genome (pTH1522 carries a single FRT site). A second FRT site was inserted at defined locations in the genome through integration of a second plasmid (pTH1937) that also carries a single FRT site. Here we outline how this Flp/FRT system was used to delete defined regions and hence generate multiple gene knock-out mutants. This system was used to delete 32 and 56 defined regions from the 1340 Kb pSymA and 1678 Kb pSymB megaplasmid, respectively. The structures of the resulting megaplasmid deletion mutants were confirmed by PCR analysis. Carbohydrate and nitrogen utilization phenotypes were associated with the deletion of specific regions. Deleting large, regions of the genome helped us to identify phenotypes such as inability to grow on minimal media with fucose, maltotriose, maltitol, trehalose, palatinose, lactulose and galactosamine as sole carbon source. For several FRT-flanked regions, few or no recombinants were recovered which suggested the presence of essential genes. Through this strategy, two essential genes tRNAarg and engA located on the pSymB and three toxin/antitoxin-like systems, sma0471/sma0473, sma2105 and sma2230/sma2231 on pSymA megaplasmid were identified.

abstract: Doctor of Philosophy (PhD)


title: Prima Luce: Roman Perspectives on the Salutatio

contributor:
Eilers, Claude
Haley, Evan W.
Beckmann, Martin
Classics

subject: Roman Republic

subject: Roman Empire

subject: Roman social history

subject: Latin epigraphy

subject: Identity and status in Rome

subject: Ancient History, Greek and Roman through Late Antiquity

subject: Other Classics

subject: Social History

abstract:
The aim of this thesis is to explore the Roman salutatio. The morning ritual was reiterated daily throughout the Republic and Empire, and was a fundamental facet of Roman interactions between citizens of varying status. This thesis moves beyond the traditional interpretation of the ritual as a manifestation of Roman patronage, and rather examines the asymmetrical social relationships that existed at the salutatio within the context of the applicable socio-political ideologies of the Republic and Empire. As a ritual that was enacted on a daily basis for centuries, the salutatio is a useful conduit to understand the complexities of social interaction in Roman society.

Much of the traditional scholarship on the salutatio has interpreted the salutator/salutatee relationship essentially as a system of social acquiescence, where the salutatee was able to accrue significant social esteem, and the salutator was merely a humble cliens or social inferior. This thesis dissects the abundant, yet fleeting references to the social practice in the ancient sources to analyze how participation in the salutatio impacted individual social status within the greater Roman collective, which was inherently hierarchical. The sources consequently suggest that the ritual was not a system of social subordination, but was rather an accepted behavioural practice which served as a mechanism to promote or establish a distinct ‘Roman-ness’ within the collective Roman identity, irrespective of status. This study furthermore considers influences which prompted significant adaptations of the salutatio over time, which consequently illuminates greater complexities of the Roman social structure.

This thesis ultimately presents the salutatio as a Republican ritual which was monopolized by the emperor after the substantial socio-political shift that ensued from the political modification of Republic to Empire. The ritual of the salutatio is therefore a manifestation of the instabilities of the Roman social structure.

abstract: Master of Arts (MA)


title: Spatial Structure, Spatial Interaction, and Distance-Decay Parameters

contributor:
Webber, M.J.
Geography

subject: Geography Geography

abstract:
One result of calibrating a spatial interaction model using interaction data specific to an origin i is to produce an estimate of the distance-decay parameter specific to that origin (βᵢ). A correct interpretation of βᵢ is important since it is frequently used as a descriptive statistic of the spatial system under investigation and as a parameter for predicting unknown interactions.

The traditional and still commonly-accepted interpretation of βᵢ is that it is a purely behavioural measure of the relationship between distance and interaction from an origin, ceteris paribus. The distance-decay parameter is assumed to measure the rate of decline of interaction between centres as the distance separating the centres increases. However, when a set of origin-specific, distance-decay parameters, {βᵢ}, is mapped, there is usually a marked spatial pattern to the values; accessible origins have less-negative values while inaccessible origins have more-negative values. As a result, several studies have recently attempted to reinterpret βᵢ in terms of the spatial structure of the system under investigation. These attempts have not gained general acceptance, however, and no sound theory has been posited to explain how spatial structure can determine βᵢ.

This thesis demonstrates that a strong relationship between spatial structure and βᵢ exists and that the present interpretation of such parameters is wrong. Spatial structure can determine βᵢ in two ways: one is a calibration-specific effect (to which existing literature has unsuccessfully alluded) and the second is a calibration-independent effect which until now has been unrecoginized. The former results from multicollinearity in unconstrained interaction models and from the presence of balancing factors in constrained interaction models. The latter is a result of model mis-specification: the accessibility of a destination is shown to be an important explanatory variable of the volume of interaction into the destination. Theoretical and empirical evidence is given that the more accessible is a destination to other destinations, the less attractive it is for interaction, ceteris paribus. This relationship is not measured in present spatial interaction models and when it is, the exaggerated spatial variation of distance-decay parameters disappears and the parameters can be interpreted as purely behavioural measures. When the effect of spatial structure is not taken into account, βᵢ is shown to be primarily an index of accessibility and not a behavioural parameter.

Thus, current spatial interaction models are mis-specified. A new type of spatial interaction model is presented which is correctly specified and which removes the spatial structure bias from distance-decay parameter estimates.

abstract: Doctor of Philosophy (PhD)


title: Simulating Protostellar Evolution and Radiative Feedback in the Cluster Environment

contributor:
Pudritz, Ralph E.
Wadsley, James
Wilson, Christine D.
Physics and Astronomy

subject: star formation

subject: molecular clouds

subject: HII regions

subject: protostellar evolution

subject: pre-main-sequence stars

subject: numerical simulation

abstract: Stars form in clusters amidst complex and coupled physical phenomena. Among the most important of these is radiative feedback, which heats the surrounding gas to suppress the formation of many low-mass stars. In simulations of star formation, pre-main-sequence modeling has often been neglected and stars are assumed to have the radii and luminosities of zero-age main sequence stars. We challenge this approach by developing and integrating a one-zone protostellar evolution model for FLASH and using it to regulate the radiation output of forming stars. The impact of accurate pre-main-sequence models is less ionizing radiation and less heating during the early stages of star formation. For stars modeled in isolation, the effect of protostellar modeling resulted in ultracompact HII regions that formed slower than in the ZAMS case, but also responded to transitions in the star itself. The HII region was seen to collapse and subsequently be rebuilt as the star underwent a swelling of its radius in response to changes in stellar structure and nuclear burning. This is an important effect that has been missed in previous simulations. It implies that observed variations in HII regions may signal changes in the stars themselves, if these variation can be disentangled from other environmental effects seen in the chaotic cluster environment.

abstract: Master of Science (MSc)


title: Pseudomonas aeruginosa Major Pseudopilin XcpT is Incorporated into The Type IV Pilus Under Native Conditions

contributor:
Burrows, Lori
Junop, Murray
Brown, Eric
Biochemistry

subject:
Pseudomonas aeruginosa
Type IV pili
Type II secretion
Pseudopilin
Bacterial Infections and Mycoses
Bacteriology
Biochemistry
Molecular Biology
Pathogenic Microbiology
Respiratory Tract Diseases
Bacterial Infections and Mycoses

abstract:
Retractable surface appendages Type IV pili (T4P) are one of the major virulence determinants in the opportunistic pathogen Pseudomonas aeruginosa (Pa), that is the leading cause of mortality in CF patients. T4P are heteropolymers composed of the major-pilin subunit PilA and the less-abundant minor pilins (MPs), FimU/PilV/W/X/E. Pilins share high sequence and structural similarity with pseudopilins (XcpT/U/V/W/X), that are proposed to form a periplasmic-structure in the evolutionarily related Type II secretion system (T2SS). Similar to T4P system, the T2SS is a multi-subunit complex that spans the inner (IM) and the outer (OM) membranes. It involves a two-step process facilitating the secretion of toxins into the extracellular milieu from the periplasm.

Using immunogold TEM analysis and Western blot we identified, under native conditions, the major pseudopilin of T2SS XcpT, is incorporated into the T4P appendage, thus appearing on the surface. This is in contrast to previous studies reporting, the otherwise periplasmic structure, the pseudopilus appears on the surface only upon over-expression of XcpT. Further, we identified this incorporation is strictly dependent on PilA expression, such that levels of surface-XcpT co-varied with the levels of surface-PilA. However, XcpT incorporation into the T4P fiber did not affect T4P-mediated twitching motility or T2SS-mediated elastase secretion. Based on these observations we proposed two explanations. Firstly, given the similarity between XcpT and type IV pilins, it is possible the pseudopilin is recognized by the T4P machinery and therefore is incorporated into the pilus. Secondly, since XcpT incorporation does not affect T4P-mediated motility, it may affect other properties of T4P, such adherence during biofilm formation, previously associated with surface-exposed pseudopilus. In addition, we also identified enhanced expression of fimU and pilX MPs drastically increased elastase secretion, through a yet to be discovered mechanism. Regardless, our results present an alternative role of both minor pilins and XcpT in their non-native systems suggesting there is more overlap between the T4P and T2S systems than previously appreciated. Further exploration of this overlap will aid in the study of the two systems in Pa, as well as in other pathogens.

abstract: Master of Science (MSc)


title: Acoustic emission spikes at workpiece edges in grinding: Origin and applications

contributor:
Koshy, Philip
Mechanical Engineering

subject:
grinding
acoustic emission
contact length
grinding burn
Manufacturing
Manufacturing

abstract: Unexplained acoustic emission spikes have been reported to occur at the workpiece entry and exit in interrupted machining operations, most notably during grinding. These AE spikes have yet to be fully explained in terms of their cause, or interpreted to yield useful information regarding the grinding process. This thesis research hence focuses on investigating this phenomenon. What started as a curiosity-driven project has resulted in an experimental technique to measure the actual contact length between the workpiece and the grinding wheel, as well as a technique for detecting grinding burn, which are of remarkable practical significance.

abstract: Master of Applied Science (MASc)


title: INVESTIGATIONS OF THE INTERACTIONS BETWEEN K+ AND Tl+ IN CHIRONOMUS RIPARIUS LARVAE

contributor:
O`Donnell, Michael
Wood, Chris
Wood, Chris
Biology

subject: Thallium

subject: Potassium

subject: Chironomus riparius

subject: Tl2+-selective microelectrodes

subject: Tl tolerance

subject: ion transport

subject: SIET

subject: Biology

subject: Other Pharmacology, Toxicology and Environmental Health

subject: Other Physiology

subject: Toxicology

subject: Biology

abstract: Tl+ is thought to be toxic to cells due to ionic mimicry of K+. The aims of this study were two-fold. First, to identify whether K+ and Tl+ were interacting in isolated guts, whole animals and tissues in Chironomus riparius, and second, to determine the strategies of Tl+ tolerance. C. riparius. were very tolerant towards Tl+ with a 48-hr LC50 of 723 μmol l-1. The Scanning Ion-selective Technique (SIET) allowed us to identify the caecae, AMG and PMG as the major K+-transporting regions of isolated guts. Evidence for an interaction was based on the finding that Tl+ was transported in the same directions at these segments (and others), and that 50 μmol l-1 Tl+ decreased K+ flux at the AMG and PMG. In addition, exposure to Tl+ prior to flux measurements had significant effects on net K+ transport by the gut. Measurements of Tl+ and K+ concentrations in the whole animal, gut and hemolymph by Atomic Absorption Spectroscopy (AAS) indicated that Tl+ uptake was saturable in the whole animal and gut, and non-saturable in the hemolymph. Together with the SIET measurements, the AAS data suggests that high levels of Tl+ can perturb K+ transport and homeostasis. The absorption of Tl+ from the gut to hemolymph, measured by SIET, was confirmed by hemolymph measurements of Tl+ using AAS. This indicated that Tl+ gains access to the hemolymph and that sensitive tissues (such as the nervous system) are thus exposed. However, survival of C. riparius at these concentrations implies efficient mechanisms for detoxification of Tl+. This tolerance may involve sequestration in the gut, metal-binding proteins and increased secretion by the anal papillae and MTs. In addition, loss of K+ from the muscle may prevent hypokalemia in the hemolymph and gut.

abstract: Master of Science (MSc)


title: Latent Variable Methods: Case Studies in the Food Industry

contributor:
MacGregor, John F.
Chemical Engineering

subject:
latent variable methods
food industry
reformulation
product development
PLS
PCA
NIR
Agriculture
Multivariate Analysis
Other Food Science
Process Control and Systems
Agriculture

abstract:
Accommodating changing consumer tastes, nutritional targets, competitive pressures and government regulations is an ongoing task in the food industry. Product development projects tend to have competing goals and more potential solutions than can be examined efficiently. However, existing databases or spreadsheets containing formulas, ingredient properties, and product characteristics can be exploited using latent variable methods to confront difficult formulation issues. Using these methods, a product developer can target specific final product properties and systematically determine new recipes that will best meet the development objectives.

Latent variable methods in reformulation are demonstrated for a product line of frozen muffin batters used in the food service industry. A particular attribute is to be minimized while maintaining the taste, texture, and appearance of the original products, but the minimization is difficult because the attribute in question is not well understood. Initially, existing data is used to develop a partial least squares (PLS) model, which identifies areas for further testing. Design of experiments (DOE) in the latent variable space generates new data that is used to augment the model. An optimization algorithm makes use of the updated model to produce recipes for four different products, and a significant reduction of the target attribute is achieved in all cases.

Latent variable methods are also applied to a difficult classification problem in oat milling. Process monitoring involves manually classifying and counting the oats and hulls in the product streams of groats; a task that is time-consuming and therefore infrequent. A solution based on near infrared (NIR) imaging and PLS-discriminant analysis (PLS-DA) is investigated and found to be feasible. The PLS-DA model, built using mixed-cultivar samples, effectively separates the oats and groats into two classes. The model is validated using samples of three pure cultivars with varying moistures and growing conditions.

abstract: Master of Applied Science (MASc)


title: AMPA Receptor Trafficking: A Mechanism of Excitatory Synaptic Plasticity

contributor:
Murphy, Kathryn
Neuroscience

subject:
cortical development
synaptic plasticity
critical period
Neurosciences
Neurosciences

abstract:
Trafficking of the glutamatergic AMPA receptors (AMPARs) has been implicated in synaptic plasticity regulation, including long-term potentiation, long-term depression, and synaptic scaling. Two proteins, GRIP for stabilization at the synapse and PICK for internalization, are involved in trafficking GluR2-containing AMPARs in and out of the synapse. In this thesis, I addressed the changes in the mechanisms of AMPAR trafficking by characterizing the developmental trajectories of GluR2, the phosphorylated form pGluR2, GRIP, and PICK and comparing expression in visual vs. frontal cortex. I found significant differences between cortical areas in the developmental trajectories of GluR2 and pGluR2. In visual cortex, expression levels exhibited smooth developmental increases. In frontal cortex, GluR2 and pGluR2 rose to an exuberant expression between P18 and P35. Developmental trajectories for GRIP and PICK showed smooth increases that were consistent across cortical areas. Furthermore, looking at the correlation between the surface components (GluR2 and GRIP) and internalized components (pGluR2 and PICK), I found that the development of AMPAR trafficking components is tightly regulated across the cortex.

In this thesis, I also looked at AMPAR expression in adult cortex. Fluoxetine has previously been reported to induce a juvenile like state of plasticity in visual cortex and this plasticity was assessed through monocular deprivation. My results indicated that fluoxetine administration was not associated with significant changes in AMPAR expression levels. However, monocular deprivation induced significant upregulation in expression levels of all four proteins. These results imply the presence of AMPAR-mediated plasticity in the adult brain.

abstract: Master of Science (MSc)


title: STRUCTURE, COMPOSITION AND PERFORMANCE OF SURFACE FILMS ON AZ ALLOYS AS A FUNCTION OF pH AND ALLOYED ALUMINUM CONCENTRATION

contributor:
Kish, Joey
Materials Science and Engineering

subject:
corrosion
magnesium alloys
STEM
surface films
passivity
Structural Materials
Structural Materials

abstract:
This thesis presents an investigation into the structure, composition and performance of naturally formed surface films on AZ alloys as a function of pH and alloyed Al concentration. STEM verified the film structure was bi-layer, consisting of an inner barrier layer, which was visibly deteriorated, and an outer porous layer. EDS SmartMaps™ coupled with the Inca™ software package determined the inner barrier layer was predominantly composed of MgO, whereas the outer layer was primarily Mg(OH)2. However, both layers appeared to posses mixed oxide/hydroxide components according to ToF-SIMS analysis.

Environmental pH had the largest effect on the structure and composition of the surface film. The near-neutral sample showed significant breakdown within the inner layer, which was attributed to natural hydration of MgO to Mg(OH)2. This favourable hydration reaction is slower in alkaline environments and as such, the stability of the inner barrier layers of the pH 14 samples were noticeably improved. The effect of alloyed Al concentration was less significant however; increased enrichment of Al into the surface film structure appeared to cause a reduction in the thickness of the corrosion film itself.

Drastic differences in corrosion performance were observed between the near-neutral and alkaline environments. Significantly better corrosion resistance to anodic dissolution was present in the alkaline environment coupled with a noticeably lower corrosion rate. The absence of breakdown potentials along with the presence of mass transport controlled anodic kinetics signified that the improved stability of the inner barrier layer was responsible for improved corrosion performance. In contrast, severe pitting and a narrow range of anodic stability were present for the near-neutral samples where the inner barrier layer was significantly compromised. This deterioration was deemed responsible for accelerated cathodic kinetics as well as minimal impedance to aggressive Cl- ions from initiating wide scale electrochemical breakdown of the surface film.

abstract: Master of Applied Science (MASc)


title: Characterizing the Quaternary Hydrostratigraphy of Buried Valleys using Multi-Parameter Borehole Geophysics, Georgetown, Ontario

contributor:
Boyce, Joe
Geography and Earth Sciences

subject:
borehole geophysics
buried bedrock valleys
Georgetown Ontario
principal component analysis
hydrostratigraphy
lithologic classification
Geophysics and Seismology
Geophysics and Seismology

abstract:
In 2009, the Regional Municipality of Halton and McMaster University initiated a 2-year collaborative study (Georgetown Aquifer Characterization Study-GACS) of the groundwater resource potential of Quaternary sediments near Georgetown, Ontario. As part of that study, this thesis investigated the Quaternary infill stratigraphy of the Middle Sixteen Mile Creek (MSMC) and Cedarvale (CV) buried valley systems using newly acquired core and borehole geophysical data. Multi-parameter geophysical log suites (natural gamma, EM conductivity, resistivity, magnetic susceptibility, full-waveform sonic, caliper) were acquired in 16 new boreholes (16 m to 55 m depth), pre-existing monitoring wells and from archival data. Characteristic log responses (electrofacies) were identified and correlated with core to produce a detailed subsurface model of a 20-km2 area to the southwest of Georgetown. Nine distinctive lithostratgraphic units were identified and their geometry mapped across the study area as structure contour and isochore thickness maps. The subsurface model shows that the CV valley truncates the Late Wisconsin MSMC stratigraphy along a channelized erosional unconformity and is a younger (post-glacial?) sediment-hosted valley system. Model results demonstrate the high level of stratigraphic heterogeneity and complexity that is inherent in bedrock valley systems and provides a geological framework for understanding groundwater resource availability.

Principal component analysis (PCA) was applied to selected log suites to evaluate the potential for objective lithologic classification using log data. Gamma, resistivity and conductivity logs were most useful for lithologic typing, while p-wave velocity and resistivity logs were more diagnostic of compact diamict units. Cross plots of the first and second principal components of log parameters discriminated silts and clays/shales from sand/gravel and diamict lithofacies. The results show that PCA is a viable method for predicting subsurface lithology in un-cored boreholes and can assist in the identification of hydrostratigraphic units.

abstract: Master of Science (MSc)


title: Analysis of Subglacial Deposits and Landforms in Southern Ontario Using Sedimentology and Geomatics

contributor:
Eyles, Carolyn H.
Geography and Earth Sciences

subject:
geomatics
sedimentology
geographic information systems
drumlin
geomorphometry
subglacial deformation
Geology
Geology

abstract:
This research utilizes sedimentology and geomatics to investigate relationships between sediment types, landforms and former glacial movement in southern Ontario, Canada. The research integrates qualitative field observations of sedimentary successions with quantitative assessment of landforms, specifically drumlins, using Geographic Information Systems (GIS). A detailed sedimentological analysis of late Quaternary sediments exposed in Vineland Quarry, Ontario identifies glaciolacustrine deposits which were subsequently overridden and deformed by glacial ice. The gradual transition from undisturbed, laminated sediment to increasingly deformed sediment and structureless diamict exposed at Vineland is consistent with theoretical models of subglacial deformation and suggests that the succession records a single episode of ice advance across the Vineland region.

The second component of this research is presented within two research papers that explore a computational methodology within GIS which allows identification of drumlins and their morphological characteristics from existing topographic digital data. The two studies examine the form and spatial distribution of drumlins within the Arran, Galt and Guelph drumlin fields and from a portion of the Peterborough drumlin field. Drumlins and their morphological characteristics, such as elongation ratio and long axis orientation, are identified and documented using a computer-based process that allows direct comparison of forms within and between individual drumlin fields. The computer-based spatial analysis shows that drumlins are not randomly distributed across the regions, but show distinct patterns of clustering. Drumlins with particular morphological characteristics also show a clustered distribution that may be related to spatial changes in sediment thickness, duration of ice cover, and the direction of ice movement. The ability to consistently identify and characterize drumlin morphology and distribution allows objective and systematic comparison of these landforms both within and between drumlin fields and will enhance understanding of the spatial controls on the development of these enigmatic landforms.

abstract: Doctor of Philosophy (PhD)


title: Inhibition of Notch signaling targets breast tumor initiating cells

contributor:
Hassell, John
Mossman, Karen
Mossman, Karen
Biochemistry

subject: cancer

subject: mammary gland

subject: Notch

subject: gamma-secretase

subject: stem cells

subject: Biochemistry, Biophysics, and Structural Biology

abstract: The cancer stem cell hypothesis claims that only a small subpopulation of cells within a tumor is responsible for tumor growth, recurrence after treatment and metastasis. These cells have been termed tumor-initiating cells or cancer stem cells and are functionally defined by their capacity to elicit the growth of tumors in immune-compromised animals that recapitulate the cellularity of the tumor from which they were isolated. Several reports demonstrate that tumor-initiating cells are resistant to most current treatments. Hence, novel therapies for breast cancer should be developed that specifically target these tumorigenic cells. The Notch signaling pathway is hyperactive in human breast cancer as well as in mouse mammary tumor-initiating cells. In this study, I have found that inhibitors of the pathway target breast tumor-initiating cells from various breast cancer subtypes and may provide a novel therapy for breast cancer. MRK-003, a gamma-secretase inhibitor that blocks Notch signaling, inhibited the self-renewal of breast tumor-initiating cells in vitro and reduced tumor growth in xenograft models. MRK-003 inhibited proliferation of tumor cells within xenografts and induced their apoptosis and differentiation towards the myoepithelial lineage. Expression of the Notch pathway antagonists led to similar outcome in human breast tumor cell lines. Notably, tumors in MRK-003 treated mice were devoid of tumor initiating cells, suggesting that inhibitors of Notch signaling may lead to durable cancer cures. These findings suggest that GSIs target breast tumor-initiating cells and may prove to be effective novel anti breast cancer drugs.

abstract: Doctor of Philosophy (PhD)


title: The Absorption Spectrum of Carbonyl Selenide

contributor:
King, G.W.
Chemistry

subject: Chemistry Chemistry

abstract: The absorption spectrum of gas-phase carbonyl selenide (OCSe) in the infrared, ultraviolet and vacuum ultraviolet regions of the electromagnetic spectrum has been recorded under high resolution. A method of synthesis of the compound, which has been used in the preparation of selenium-isotope OCSe, has been described. A description of a novel light source, the emission continuum produced by which is suitable for absorption sepctroscopy of the ultraviolet and vacuum ultraviolet spectral regions, has been included. The ground state fundamental vibrational frequencies of carbonyl selenide have been determined. The spectrum in the ultraviolet and vacuum ultravioelt regions has been assigned to correspond to seventeen electronic transitions of OCSe. Vibrational analyses have been accomplished for each of these, and the symmetries and electron configurations of the excited electronic states have been assigned. The ionization potential of OCSe has been measured. The majority of these transitions have been shown to be Rydberg in nature, Quantum-mechanical calculations have been performed to predict the term values for Rydberg series members and to aid the analysis of the spectrum. The spin-orbit coupling in Rydberg states of OCSe has been shown to be intermediate between the cases (A,S) and (Ωc,ω) and to tend to the latter case as the ionization limit is approached. Some details of the spectra of the isoelectronic molecules OCS and CS2 have been included to support the analysis of the OCSe spectrum.

abstract: Doctor of Philosophy (PhD)


title: Studies on Dispersion and Turbulence in Liquid Flows

contributor:
Latto, B.
Mechanical Engineering

subject:
Mechanical Engineering
Mechanical Engineering

abstract:
This thesis describes an experimental study of the dispersion and turbulence of Newtonian fluids and dilute aqueous solutions of a drag reducing polymer, Reten 423, when ejected from a thin wall slot or point source into either developing or fully developed turbulent internal water flow at relatively high Reynolds numbers.

Two small water tunnels with injection facilities were constructed in which concentration and energy spectra measurements were made using a spectrophotometer and a Laser Doppler Anemometer. The investigation was carried out with a maximum flow velocity of the order of 4.5 m/s for various injection flow rates and with injection concentrations in the range 0 to 1000 w.p.p.m.

It was found that the dispersion rate for polymer solutions is reduced when compared to Newtonian diffusion. It was also observed that the velocity profiles for developing flows with polymer injection are fuller than those for water alone. Furthermore, there was no noticeable change in energy spectrum for low polymer concentration. However, for high injection concentration there was an increase of the energy within the low frequency end of the spectrum and a reduction of energy for the high frequency end of the spectrum.

Correlations for the concentration profiles, diffusion boundary layer growth, maximum concentration and eddy diffusivity are presented. The results indicate that a universal diffusion correlation exists which represents the data for both Newtonian and polymer solutions.

A very interesting phenomenon was observed for hetrogeneous polymer flow fields in which the sampling rate had an effect on the measured polymer solution concentration. The apparent concentration on the measured concentration approached the correct value when the sampling velocity approached that for the main stream, i.e. the isokinetic condition. This phenomenon is important and should be taken into consideration, for example, when using sampling techniques to obtain concentration profiles in nonhomogeneous polymer solution flow fields.

abstract: Doctor of Philosophy (PhD)


title: LOOSELY CULTIVATING DISCIPLINE: FROM ZERO TOLERANCE TO PROGRESSIVE DISCIPLINE IN AN ONTARIO SCHOOL BOARD

contributor:
Davies, Scott
Aurini, Janice
McKerrow, Mark
Sociology

subject: Education

subject: Inequality

subject: Policy

subject: Cultural Capital Theory

subject: Organizational Theory

subject: Educational Assessment, Evaluation, and Research

abstract: This study explores connections between school discipline policies and educational inequality by examining the implementation of “Progressive Discipline” (PD) in an Ontario school board. By using positive reinforcements, preventions, and early and ongoing interventions, PD has replaced more punitive “zero tolerance” approaches as the official approach to student discipline in provincial public schools. This study poses two broad research questions that are guided by prominent theories of school organization and family-school relations: i) Given prevailing schooling practices, how is PD actually implemented, ii) can PD compensate for student inequalities in exposure to cultural orientations demanded by schools. To address these questions, this study draws on 36 qualitative interviews with key actors in several schools, and has two key findings. First, despite the official shift from zero tolerance to PD, student discipline continues to be managed by schools and individual school-based actors along a continuum, with some becoming more progressive, while others remaining more punitive. Thus, this policy evolution has involved a shift from a tighter to a more “loosely coupled” form of organization. But despite this variation, school-based actors are gradually embracing PD, since more progressive perspectives on student discipline appear to resonate with many educators and administrators. Second, the shift to PD is creating new forms of cultural practices in schools, and these practices are generating considerable variations in the outcomes of discipline processes. Building on these findings, this study concludes that progressive discipline policy has the potential to serve as a mechanism of “cultural mobility” and partially compensate for students’ unequal exposure to the values, behaviours and skill sets that are needed to comply with schools’ standards of behaviour.

abstract: Master of Arts (MA)


title: Mechanisms of Weight Gain in Major Depressive Disorder Patients Taking Serotonin Reuptake Inhibitors

contributor:
Taylor, Valerie H.
Morrison, Katherine
Morrison, Katherine
Neuroscience

subject:
Depression
Obesity
Weight Gain
Antidepressant
SSRI
Adipokines
Psychiatric and Mental Health
Psychiatric and Mental Health

abstract: Individuals with mood disorders are particularly vulnerable to weight gain, due in part to an illness symptom profile that impacts appetite and energy and the iatrogenic weight-gain effects associated with psychotropic medications. The exact physiological mechanisms through which medication causes weight gain have yet to be clearly elucidated. The studies comprising this thesis examine changes in caloric consumption, physical activity and basal metabolic rate (BMR) in depressive disorder (MDD) patients starting on selective serotonin reuptake inhibitors (SSRIs). Since both depression and obesity have been linked to inflammation, we also monitored changes in cytokines and adipokines throughout treatment. In our sample, we observed a mean weight gain from baseline, prior to medication, to 6 months after the initiation of pharmacotherapy. We note that this weight gain is not likely due to increased caloric consumption, but could be related to the proportions of macronutrients being consumed and expended, as well as physical activity level. We also observed changes in adipokines and cytokines that are reflective of pharmacotherapy and not weight gain, even in the absence of clinical improvement. Collectively these studies have begun to shed light on the mechanisms involved in the weight gain experienced by MDD patients being treated with SSRI antidepressants. A better understanding of these mechanisms will lead to better management of the adverse metabolic side effects associated with psychotropic medication, and will improve patient compliance.

abstract: Master of Science (MSc)


title: Empowering Ontario Public Health Nurses to Address the Causes of Poverty: A Qualitative Descriptive Study

contributor:
Sword, Wendy
Valaitis, Ruta
Ciliska, Donna
Nursing

subject:
public health nurses
health units
empowerment
poverty
socio-political activity
social determinants of health
Health Services Research
Nursing
Public Health
Public Health and Community Nursing
Health Services Research

abstract: Research has demonstrated repeatedly that income and income distribution are powerful determinants of health. While Ontario public health units are mandated to promote health and reduce health inequities, they have done little to help eliminate poverty, instead focusing on individual behaviours such as smoking, diet, and physical activity – an approach likely to worsen health inequities, rather than mend them. Public health nurses (PHNs) across Canada recognize poverty as a powerful determinant of health, yet have expressed challenges in their ability to take meaningful action to address it (Cohen, 2006b; Reutter & Ford, 1996). The study sought insight into how Ontario public health units can strengthen PHNs socio-political efforts to address the causes of poverty. A qualitative descriptive design was used to explore PHNs’ views, while an Appreciative Inquiry approach was used to draw on participants’ successful past experiences in addressing the causes of poverty and their thoughts for the future. Organizational factors thought to empower PHNs’ socio-political efforts to address the causes of poverty were identified using Kanter’s Structural Theory of Power in Organizations as a starting conceptual framework. Fifteen PHNs participated in face-to-face or telephone interviews. Qualitative content analysis was used to describe participants’ affirmative experiences, empowering organizational attributes, and desired actions and supports for the future. Three overall themes emerged with respect to empowering organizational attributes: authorities within the health unit ‘permit and provide’, active associates ‘help each other out’, and external allies ‘contribute and collaborate’. Factors beyond the health unit that would support anti-poverty work were also identified. Findings suggested that action to address the causes of poverty is within the reach of PHNs, and is consistent with their role and the public health mandate, but requires leadership support and political buy-in in order to maximize its effectiveness.

abstract: Master of Science (MSc)


title: Digital Equalization of Fiber-Optic Transmission System Impairments

contributor:
Kumar, Shiva
X. Li,  W.P. Huang
X. Li,  W.P. Huang
Electrical and Computer Engineering

subject:
DSP
Coherent
QPSK
Optical
Adaptive Equalizer
Ting Luo
Digital Communications and Networking
Signal Processing
Systems and Communications
Digital Communications and Networking

abstract:
In the past half century, numerous improvements have been achieved to make fiber-optic communication systems overweigh other traditional transmission systems such as electrical coaxial systems in many applications. However, the physical features including fiber losses, chromatic dispersion, polarization mode dispersion, laser phase noise, and nonlinear effect still post a huge obstruction in fiber-optic communication system. In the past two decades, along with the evolution of digital signal processing system, digital approach to compensate these effects become a more simple and inexpensive solution.

In this thesis, we discuss digital equalization techniques to mitigate the fiber-optic transmission impairments. We explain the methodology in our implementation of this simulation tool. Several major parts of such digital compensation scheme, such as laser phase noise estimator, fixed chromatic dispersion compensator, and adaptive equalizer, are discussed. Two different types of adaptive equalizer algorithm are also compared and discussed. Our results show that the digital compensation scheme using least mean square (LMS) algorithm can perfectly compensate all linear distortion effects, and laser phase noise compensator is optional in this scheme. Our result also shows that the digital compensation scheme using constant modulus algorithm (CMA) has about 3~4db power penalty compare to LMS algorithm. CMA algorithm has its advantage that it is capable of blind detection and self-recovery, but the laser phase noise compensator is not optional in this scheme. A digital compensation scheme which combines CMA and LMS algorithm would be a perfect receiver scheme for future work.

abstract: Master of Applied Science (MASc)


title: COMBATING INTRINSIC ANTIBIOTIC RESISTANCE IN GRAM-NEGATIVE BACTERIA

contributor:
Wright, Gerard
Lori Burrows, Eric Brown
Lori Burrows, Eric Brown
Biochemistry

subject:
High-throughput screening
enzymology
GmhA
GmhB
lipopolysaccharide
Gram-negative bacteria
Enzymes and Coenzymes
Medical Biochemistry
Enzymes and Coenzymes

abstract: The current rise in multi-drug resistant Gram-negative bacterial infections is of particularconcern. Gram-negative pathogens are difficult to treat due to their intrinsic resistome.The outer membrane (OM) of Gram-negative bacteria serves as a permeability barrier tomany antibiotics, due in large part to the lipopolysaccharide (LPS) component that isunique to these organisms, and in addition to, the OM is lined with a number of multidrugresistant efflux pumps. As the clinical effectiveness of first line therapies declines inthe face of this resistance, novel strategies to discover new antibiotics are required. Theidentification of new antibiotic targets is one method currently being applied to meet thischallenge. This work examines the permeability barrier of Escherichia coli as a possibletarget for antibiotic adjuvants. A structure-function analysis of GmhA and GmhB, whichcatalyze the first and third conserved steps in LPS ADP-heptose biosynthesis, wasperformed. The active site residues of each of these enzymes were identified viacrystallographic, mutagenic, and kinetic analyses. Potential mechanisms have beenproposed, offering insight into the function of these potential adjuvant targets. In addition,a whole screen of E. coli was performed to identify compounds that potentiatenovobiocin, an antibiotic with limited activity against Gram-negative pathogens due toOM permeability. Four small molecules were found that were able to synergize withnovobiocin. One of these, A22, is known to alter bacterial cell shape, suggesting a newpathway for antibiotic adjuvants to combat Gram-negative infection. Together, thesestudies highlight the varied targets available for novel therapeutic strategies.

abstract: Doctor of Philosophy (PhD)


title: New Worlds of Words: Vladimir Nabokov's Fairy Tales

contributor:
Sigman, Joseph
English

subject:
English Language and Literature
English Language and Literature

abstract: It was Vladimir Nabokov's contention that all fictional works are fantastic in nature, and that any novel can be considered a type of fairy tale. Emphasizing that aspect of his own fiction are the numerous allusions to tales such as "Cinderella" and Alice's Adventures in Wonderland that appear in his texts. Nabokov's novels portray characters who transform their lives into illusory fantasies. Ultimately, characters like Humbert Humbert, Van, and Kinbote are themselves artist-figures, who turn reality into fantasy through the process of writing.

abstract: Master of Arts (MA)


title: Real Time Sorting of Plastic Recyclables Using an FPGA based SVM

contributor:
Capson, David
Schuurman, Derek
Electrical and Computer Engineering

subject: FPGA

subject: Computer Vision

subject: Machine Learning

subject: SVM

subject: Recycling

subject: Signal Processing

subject: VLSI and circuits, Embedded and Hardware Systems

subject: Signal Processing

abstract: The amount of recyclable material being processed worldwide is increasing. There is a demand for new technologies that can quickly sort these materials for maxi-mum purity while maintaining high throughput. This thesis proposes a method toautomatically sort two materials: Polycoat containers and Polyethylene terephtha-late (PET) bottles. This method utilizes a visible light camera and does not relyon Near-Infrared spectrometry. A high-speed method to automatically locate re-gions that likely contain these materials within the image and remove them from thebackground is presented. These regions are merged into whole containers and are classified as either a Polycoat container or PET bottle. This is accomplished using alinear support vector machine (SVM) trained on the histogram of pixel intensities. Anovel graph theoretic based region growing technique is proposed and experimental results are provided to characterize the system. The proposed method obtained a93% recognition rate while running in real-time on an FPGA.

abstract: Master of Applied Science (MASc)


title: TECHNOLOGY AND SOCIAL NETWORKING DURING LECTURE

contributor:
Lewchuk, Wayne
Premji, Stephanie
Storey, Robert
Work and Society

subject:
History
Work
Preindustrialization
Industrialization
Multitasking
Technology
Social Networking
Work, Economy and Organizations
Work, Economy and Organizations

abstract: This study examines issues arising from the popular use of technology and social networking in the classroom during lecture and its effect on student grades. Data were collected in a first year social science course. Findings of a general survey show that the use of technology and social networking during lecture is a popular form for multitasking with little impact on grades up to a certain threshold. Addressing this issue, this paper puts forth a broad historical overview of the use of leisure activities by workers during preindustrialization and industrialized capitalism. Through an examination of multitasking during lectures, this paper will assess the extent to which social norms of time discipline may be changing and the impacts this could have on the future of work organization. Activity theory is one method of guiding research in order to incorporate these multitasking activities into teaching and learning paradigms and policies for use in the classroom.

abstract: Master of Arts (MA)


title: Impact of intestinal microbial composition on the regulation of immunoglobulin E

contributor:
McCoy, Kathy
Macpherson, Andrew
Kahn, Waliul
Medicine

subject:
Immunoglubulin E
immune dysregulation
microflora
germ-free
gnotobiotic
Immunity
Immunology and Infectious Disease
Immunity

abstract:
We are all born germ-free. Soon after birth, microbes colonize our body’s surfaces, with the intestine housing the highest density of microbes on earth. Most of us remain blissfully unaware of this co-existence because inflammatory responses to the indigenous microbes are normally not triggered. Nonetheless, intestinal microbes are true educators of our immune system, which is exemplified by the immature immune system observed in germ-free animals. Accumulating evidence suggests that microbial exposure and/or composition impacts on immune regulation. As an example, isotype switch to immunoglobulin E (IgE) is normally very tightly regulated such that in healthy individuals and mice, serum levels are maintained at very low levels. In contrast, total serum IgE levels are elevated in germ-free mice, indicating that in the absence of microbes the regulatory pathway that maintains IgE at basal levels is disrupted. We hypothesize that in the absence of stimuli from the resident intestinal bacteria the immune system does not receive adequate educational signals. We showed that in germ-free mice class switch recombination (CSR) to IgE occurred at intestinal mucosal lymphoid sites a few weeks after birth. IgE levels then remained at elevated levels throughout life, even when intestinal bacteria were introduced after weaning. In the first part of this thesis, the mechanisms involved in this hygiene-induced IgE were investigateted. In a second part, the immunoregulatory role of commensal bacteria was extended to a model of autoimmunity.

Collectively these results demonstrate a new dimension of the impact of intestinal symbionts on the immune system: they dictate baseline immune system regulation. Elucidating the mechanisms whereby microbes induce immunoregulatory pathways may give insights into the increasing prevalence of allergic- and autoimmune diseases.

abstract: Doctor of Philosophy (PhD)


title: Travel Preferences and Choices of University Students and the Role of Active Travel

contributor:
Paez, Antonio
Geography and Earth Sciences

subject:
active transportation
utility
commuting
cycling
Human Geography
Physical and Environmental Geography
Urban Studies and Planning
Human Geography

abstract:
The increased focus on the importance of active travel within a community to improved social, economic and environmental sustainability has facilitated discussion and questions about how to best encourage those who take a personal automobile to switch to an active mode of travel. In attempting to answer this question, it is first important to understand that there are a variety of factors that impact an individual’s decision to take a certain mode of transportation. This study attempts to determine which factors have the largest impact on students’ decisions to take an active mode of transportation within a university setting.

Through investigation of socio-demographic and attitudinal variables of university students, a comparison of ideal versus actual commute time was modeled. Regression analysis was applied to test the relationship between the ratio of ideal to actual commute time and the individual’s socio-demographic variables and attitudinal scores. Research using discrete choice analysis further provided more detailed evidence of specific factors affecting student’s decision to choose an active mode of travel based on the level of utility they obtained by each mode as a function of attitudes, the built environment and socio-demographic variables.

The results obtained from this study contribute insight and support for initiatives aimed to increasing active modes of travel by students in university settings. Recommendations are provided that can be adopted at the institutional and municipal level of both policy and planning to increase uptake of active modes of travel.

abstract: Master of Arts (MA)


title: A Unified Approach to Generalized Network Sensitivities with Applications to Power System Analysis and Planning

contributor:
Bandler, John W.
Electrical Engineering

subject:
Electrical and Electronics
Electrical and Electronics

abstract: This thesis presents a new methodology for describing adjoint network approaches to sensitivity calculations performed in various power system analysis and planning studies. Difficulties observed by previous workers regarding the exact modelling of some power network elements are overcome by proper techniques employed with special complex notation. A generalized version of the Tellegen's theorem-based approach is developed which provides the required sensitivities based on the exact a.c. load flow model for any chosen set of real and/or complex variables of practical interest. A theoretical consistency study is performed to allow proper modelling of adjoint elements for direct treatment of general complex functions. A simplified version with many desirable features is described for real function sensitivities. It employs a simple adjoint network. General sensitivity expressions common to all relevant power system studies are derived and tabulated. A new method for solving the load flow problem using Tellegen's theorem is described with several advantages claimed. A special elimination technique is used to describe the Newton-Raphson method for load flow solution in a compact complex mode. A complex version of the Lagrange multiplier approach is developed and applied to allow a general number of complex dependent variables to be defined in a particular problem. A generalized version of the class of methods of sensitivity calculations which exploit the Jacobian matrix of the load flow analysis in formulating the adjoint equations is developed. Generalized sensitivity expressions common to different modes of formulating power flow equations, e.g., cartesian and polar, are derived and tabulated for direct programming use. A unified comprehensive comparison between the Lagrange multiplier and Tellegen's theorem approaches to sensitivity calculations in electrical networks is presented.

abstract: Doctor of Philosophy (PhD)


title: Marine Geophysical and Geomorphic Survey of Submerged Bronze Age Shorelines and Anchorage SItes at Kalamianos (Korphos, Greece)

subject:
Kalamianos
Mycenaean Harbour
Magnetic Gradient
Coastal Subsidence
beachrock
Bronze Age
Geomorphology
Geophysics and Seismology
Tectonics and Structure
Geomorphology

abstract:
The modern coastline provides few clues as to the ancient harbour configuration since Kalamianos has been partially submerged by > 6 m of relative sea-level rise since the Early Helladic. In 2009, a detailed marine geophysical survey and underwater diver search was conducted in the inshore waters to identify potential anchorage sites and to examine evidence for coastal subsidence. Single-beam bathymetry and magnetic gradiometer data were acquired and integrated within a detailed digital bathymetric model (DBM).

The DBM revealed two submerged beachrock platforms (BR-1, BR-2) paralleling the modern shoreline and a submerged isthmus connecting the mainland with small island 200 m offshore. The BR-1 platform (3.5-3.7 m depth) contained abundant Late Helladic (LH; 1300-1190 BC) pottery sherds (30-50%) and wood charcoal fragments.14C dating of the extracted charcoal yielded an AMS 14C uncalibrated age of 3250±40 BP, consistent with the LH ceramics. The BR-2 platform (5.8-5.9 m depth) contained less pottery (<20%) and included well-preserved fragments of Early Helladic (EH) jars.

The beachrock elevations and 14C and pottery ages were used to reconstruct a sea level curve and a series of paleogeographic maps of the EH to LH shorelines. The presence of abundant pottery and wood charcoal in the BR-1 beachrock indicates that shipping activity during the LH was focused at the south end of the site in a western harbour basin. This is supported by magnetic gradiometer results, which identified several magnetic anomalies in the western harbour basin. These were investigated by diver search and found to be concentrations of ship ballast stones (mainly andesite) and clay pottery.

abstract: Master of Science (MSc)


title: Translating Adolf Muschg: Two Short Stories

contributor:
Chapple, Gerald
German

subject:
German Language and Literature
Other German Language and Literature
German Language and Literature

abstract: Certain Swiss authors, such as Gottfried Keller, Robert Walser, Friedrich Durrenmatt, and Max Frisch, are more frequently translated into English than others. To this day, Adolf Muschg has belonged to the latter; his texts have been translated, but into Eastern European languages rather than English. I decided to translate him because his prose appeals to a wide audience and deserves to be introduced to English-speaking readers. Muschg has concerned himself with literature and its related fields for many years. Contemporary Swiss and international issues are directly confronted in his writings, where he also analyzes the individual's relationships with culture and society. Not only does he use a variety of themes, but also an array of narrative techniques and structural elements. Diversity is extremely important when considering a text for translation, because the more diverse the author's writing style is, the more interesting and challenging the translation task will be. After having read a selection of Muschg's short prose, the stories "Besuch in der Schweiz II and "Wullschleger Country" caught my interest, because of the similarities In themes. The central figures in both stories come from different backgrounds: Swiss and German in the first; Swiss and Thai in the second. Thus Switzerland is observed from the perspective of natives and foreigners; by employing these opposing points of view Muschg can also voice his criticism of the respective culture and society. Adolf Muschg's texts challenge the translator due to the cultural contexts of his themes and the structural variety of his style; I attempted to consistently incooperate these aspects in my translations. In addition, by discussing the difficulties associated with these aspects in a detailed commentary, it becomes evident how much the translation process has to rely on interpretation, or else not every textual element is accounted for.

abstract: Master of Arts (MA)


title: Party Democracy and the Selection of National Party Leaders in Canada

contributor:
March, Roman R.
Political Science

subject:
Political Science
Political Science

abstract: This study examines the nature of internal decision making in the two major political parties in Canada as it relates to leadership selection. The thesis argues that, as essentially electoral-competitive (cadre-style) organizations, the Liberals and Conservatives do not rigidly adhere to democratic principles in the selection of their leaders. To support this contention, an examination of the representativeness, openness and the extent of membership control in the leadership selection process is undertaken in order to determine what factors facilitate and restrict intra-party democracy. The thesis also offers an analysis of motivational factors affecting delegate preference in order to test the validity of the winnability thesis, i.e., that the candidate perceived as the best vote-getter for the party is selected as leader regardless of his experience or loyalty to the party organization. In conclusion, it is argued that the Liberals and Conservatives, although primarily oriented towards electoral activity, should be understood as more than mere electoral machines unconcerned with internal democracy. Rather, the parties have displayed a steady, though as yet incomplete, movement towards a more open and democratic leadership selection process involving grassroots participation.

abstract: Master of Arts (MA)


title: LEVEL STRUCTURE OF 30S AND THE 29P(p, gamma)30S THERMONUCLEAR REACTION RATE

contributor:
Chen, Alan A.
Physics and Astronomy

subject:
Nuclear Astrophysics
Nuclear Reactions
Experiment
Nova Nucleosynthesis
Nuclear
Nuclear

abstract:
In order to determine the parent stellar sites for the presolar grains of potential nova origin, it is crucial to know the rates of the thermonuclear reactions which affect the Si production and destruction in novae. One such reaction is the 29P(p, gamma)30S. This reaction also influences type I X-ray bursts. The energy generation and nucleosynthesis in the burst, along with its duration and light-curve structure, are very sensitive to the reaction flow through a few waiting-point nuclei along the rp- and ap-process paths. In particular, network calculations show that the waiting-point nucleus 30S (t1/2 = 1175.9(17) ms) is critical.

The structure of proton-unbound 30S states strongly determines the thermonuclear 29P(p, gamma)30S reaction rate at temperatures characteristic of explosive hydrogen burning in classical novae and type I X-ray bursts (0.1 ≤ T ≤ 1.3 GK). Specifically, the rate had been previously predicted to be dominated by two low-lying, unobserved, Jpi = 3+ and 2+ levels in the Ex = 4.7 to 4.8 MeV region.

The 3+ resonance was observed a few years ago via a 32S(p, t)30S measurement. However, the 2+ resonance remained unobserved. To search for it, we have performed a higher energy resolution charged-particle spectroscopy and an in-beam gamma-ray spectroscopy to investigate the level structure of 30S above the proton threshold via the 32S(p, t)30S and 28Si(3He, n-gamma)30S reactions, respectively.

In this work we provide a description of the experimental setup, data analysis and results of both experiments. Moreover, we have calculated the 29P(p, gamma)30S reaction rate via the state-of-the-art Monte Carlo technique, and have investigated the impact of this updated rate on the abundances of elements synthesized in novae, including those of silicon isotopes.

abstract: Doctor of Philosophy (PhD)


title: PRENATAL CARE IN TWO NUNAVUT COMMUNITIES: THE BARRIERS, FACILITATORS AND MOTIVATORS TO UTILIZING CARE

contributor:
Bourgeault, Ivy
Health Research Methodology

subject:
Arviat
Rankin Inlet
Health Services
Remote
Health Services Research
Health Services Research

abstract:
Objective: Despite the known benefits of prenatal care, not all women access it equally. Evidence suggests women in Nunavut utilize prenatal care less than in any other jurisdiction in Canada and there is an absence of literature that explains why. This study seeks to improve our understanding of the factors influencing utilization of prenatal care for women in Nunavut by exploring the barriers, facilitators and motivators to utilization.

Methods: A qualitative, descriptive approach was used. Community collaboration informed the research process. Data were analyzed from 21 semi-structured interviews conducted with pregnant and postpartum women and maternity care providers in two Nunavut communities. Using a socioecological model of health services utilization and inductive content analysis, transcribed interviews were analysed to determine the factors that influence prenatal care utilization.

Findings: Utilization of prenatal care was influenced by personal, situational and system-related barriers, facilitators and motivators. Personal and situational barriers, facilitators and motivators to care were similar among women from both communities. System-related barriers and facilitators, related to the model of prenatal care and its delivery, differed between the two communities with barriers including language, appointment scheduling and waiting times.

Conclusion: System-related barriers reduced access to prenatal care for women in one Nunavut community. Access may be improved in communities with low utilization by revising the current model of prenatal care to reflect care delivered in communities where care providers have dedicated prenatal care roles.

abstract: Master of Science (MSc)


title: THE INFLUENCE OF HOST STRESS ON THE GASTROINTESTINAL TRACT AND THE MICROBIOTA

contributor:
Collins, Stephen M
Verdu, Elena
Verdu, Elena
Medical Sciences

subject: Irritable bowel syndrome; gastrointestinal; intestinal microbiota; anxiety and depression; psychological stress; motility

subject: Digestive, Oral, and Skin Physiology

subject: Digestive, Oral, and Skin Physiology

abstract: Stress is known to play an important role in the natural history of gastrointestinal diseases, and functional disorders in particular. In health, activation of the stress response serves to maintain homeostasis in response to harmful stimuli. However, prolonged activation of the stress response can become maladaptive and contribute to the initiation and maintenance of symptoms in disorders such as irritable bowel syndrome (IBS). The mechanisms underlying this detrimental effect are unclear. This thesis investigates this relationship by examining the influence of 10 days of water avoidance stress on a murine model of acute bacterial gastroenteritis; a known trigger in a subset of IBS patients. Results indicate that stress can increase the level of the stress hormone norepinephrine in the gut. However, the overall influence of host stress during infection proves to be beneficial in this model, with decreased colonic inflammation and earlier clearance of the pathogen. Next, we utilized the olfactory bulbectomy (OBx) model of depression comorbid anxiety, which shows a heightened stress response, to examine mechanism underlying stress-mediated susceptibility in a more chronic setting. OBx resulted in increased neural activity and motility in the gut, and a change in composition of gut microbiota. These responses were not accompanied by changes in gut permeability or immune activation. Thus stress alters the habitat of commensal bacteria via a neurally mediated change in colonic motility. These results have bearing on the ability of stress to alter the microbiota: a feature of functional GI disorders.

abstract: Doctor of Philosophy (Medical Science)


title: Opportunistic Vehicular Assisted Ferrying in Energy Efficient Wireless Mesh Networks

contributor:
Todd, Terence D.
Zhao, Dongmei
Electrical and Computer Engineering

subject:
Wireless Mesh Networks (WMNs)
Delay Tolerant Networks (DTNs)
Routing
Energy efficiency
Mobility
WSNs
Electrical and Electronics
Electrical and Electronics

abstract: Wireless mesh networks are widely used for various communication purposes and are often deployed in a broad range of outdoor applications. In cases where the deployment area is outside the reach of fixed infrastructure, energy efficient operation of the mesh nodes is very important. Many approaches have been explored to find energy efficient network solutions for these types of scenarios. This thesisproposes power saving mechanisms where the mesh network nodes opportunistically access coexistent vehicular networks. This is referred to as Opportunistic Vehicle Assisted Ferrying (OVAF). The history of using moving particles for message carrying can be found in research on intermittently connected networks. However, this approachhas never been considered with fully connected networks. Two different models are presented to model the OVAFmechanism: \textbf{a}. \emph{A flow based model}, and \textbf{b}. \emph{Apacket based model}. For each model an analytic lower bound isobtained by formulating a linear integer optimization with differentcost functions. Heuristics, which simplify the complexity of theproblem, are then developed for eachmodel. Arriving vehicles and generated packets are also modeled asrandom processes under various scenarios using different parameters.Results are presented which demonstrate the superiority of the OVAFrouting method compared to conventional multihop forwarding (Up to $60\%$increase in energy saving).

abstract: Master of Applied Science (MASc)


title: Assessment of Bone Geometry in Postmenopausal Women with Osteoporosis of the Spine Before and After a 6 Month Aquatic Exercise Program

contributor:
MacIntyre, Norma J
Stratford, Paul
Webber, Colin
Rehabilitation Science

subject:
hydrotherapy
vertebral fracture
DXA
pQCT
reliability
vertebral morphometry
osteoporosis
Physical Therapy
Physical Therapy

abstract:
Background: Increased physical activity has a modest effect on the spatial distribution of bone mineral. The risks and benefits of exercise for women with osteoporosis at high risk to fracture are not known. The decompression of aquatic exercise is an option to increase exercise compliance. The dual energy absorptiometry (DXA) vertebral fracture assessment (VFA) images 2D bone geometry however measurement properties have not been established for this outcome.

Purpose: To determine relative and absolute intra-rater reliability of DXA-based vertebral height (VH) measures and to assess the feasibility of investigating bone outcomes in women with established osteoporosis before and after a 6 month aquatic exercise program.

Methods: DXA VFA scans of 32 women over 60 years old were analyzed on 2 occasions, 4 weeks apart. Relative reliability, intraclass correlation coefficient (95% CI) and absolute reliability, standard error of measurement (95% CI) were estimated for visible anterior, middle and posterior VHs from T4 to L4. Women with osteoporosis at high risk to fracture (clinical practice guidelines used) were recruited from two osteoporosis clinics. Feasibility of recruitment, adherence to the exercise, adherence to the assessment protocols (DXA, pQCT, physical performance measures), safety and retention were assessed.

Results: Intra-rater reliability ICC >0.87 (0.74, 0.94) and SEM <1.17 from T10 to L4. Recruitment of 9 women in 10 weeks; average adherence 68%; pQCT data loss 46%; 1 fracture after class; retention 89% at 12 months.

Conclusion: Further study of measurement properties of VH and protocols for recruitment, data management and safety are required.

abstract: Master of Science Rehabilitation Science (MSc)


title: YTTERBIUM-DOPED FIBER AMPLIFIERS: COMPUTER MODELING OF AMPLIFIER SYSTEMS AND A PRELIMINARY ELETRON MICROSCOPY STUDY OF SINGLE YTTERBIUM ATOMS IN DOPED OPTICAL FIBERS

contributor:
Haugen, Harold K.
Engineering Physics

subject:
Ytterbium
fiber
amplifier
single atom
Computational Engineering
Engineering Physics
Engineering Science and Materials
Optics
Computational Engineering

abstract:
Ytterbium-doped optical fibers have extensive applications in high-power fiber lasers, optical amplifiers, and amplified spontaneous emission light sources. In this thesis two sub-projects associated with ytterbium doped fibers are discussed.

Numerical simulations have been used to model high-repetition rate ultrafast ytterbium-doped fiber amplifier systems assuming continuous-wave input signals under variable situations, such as one-sided and two-sided pumping. Different system configurations are also developed, such as a single-stage amplification system, a two-stage amplification system and a separated amplification system, providing alternative choices for experiments and applications. The simulation results are compared with experimental data and the simulation results from some other software. The influence of nonlinear effects in the fiber is also very briefly discussed in this thesis.

In a second research activity, the distribution of ytterbium atoms is being investigated in a range of double-clad ytterbium-doped fibers. Using aberration-corrected electron microscopy, ytterbium atoms are directly observed from the wedge-shaped specimen, which was prepared from ytterbium-doped optical fibers by tripod polishing combined with ion milling. Challenges related to sample preparation and the interpretations of images are discussed, but the approach shows great potential to investigate the doping behaviors down to atomic scale in the fibers. The work is expected to help reveal mechanisms affecting the performance for the doped fibers, such as photodarkening which is potentially associated with clustering effects.

abstract: Master of Applied Science (MASc)


title: Experimental Evaluation of Bone Drilling using Ultrashort Pulsed Laser Ablation

contributor:
Fang, Qiyin
Hayward, Joseph E.
Haugen, Harold K.
Medical Physics

subject:
Laser ablation
femtosecond
bone
ultrafast material processing
incubation
Bioimaging and biomedical optics
Bioimaging and biomedical optics

abstract:
Mechanical oscillating drills and saws are used in orthopaedic surgery to cut bone and develop screw-holes; however, their use causes friction resulting in significant thermal damage. Ultrashort pulsed lasers appear well-suited to replace traditional tools as they have the ability to efficiently remove bone tissue while causing only minimal collateral damage. Laser ablation also has the added advantages of: (i) no mechanical vibration; (ii) minimal invasiveness; and (iii) small focus spot size. In this thesis work, we experimentally investigated a few key aspects of ultrashort laser ablation of bone tissue.

The ablation threshold of unaltered bone was measured using the D2 technique and found to range from 1.66 J/cm2 ± 0.87 J/cm2 to 2.37 J/cm2 ± 0.78 J/cm2 depending on incident pulse number. The reduction in ablation threshold with pulse number was an indication of an incubation effect. Using a power law model, the incubation coefficient, ζ, was measured to be 0.89 ± 0.03.

The effect of specific laser parameters and drilling protocols on ablation efficiency was also characterized. For ultrashort pulses (≤10 ps), the removal rate was found to be inversely related to the pulse duration; however, irradiation with 5-10 ps pulses were also shown to result in significant tissue removal. With a pulse repetition rate of 1 kHz, the removal rate was observed to be highest when ablating with 50-100 pulses per spot.

Larger volumes (>1 mm3) of bone tissue were removed using laser scanning procedures. A series of scanned concentric circles produced a structure ~2.4 mm deep; however, ablated side-lobes were present at oblique angles to the incident beam. A two-layer structure subsequently produced no side-lobes. The ablative precision in trabecular bone was observed to be less than cortical bone. Using mimicked Nd:YAG laser parameters, cylindrical drilling produced craters significantly less deep than those achieved with a typical Ti:Sapphire configuration. The ability to drill large-scale holes using low average pulse energies and optimized scanning procedures will alleviate the stringent requirements for optical components in clinical practice.

abstract: Master of Science (MSc)


title: A Study of an Adaptive Control Constraint System for Milling

contributor:
Tlusty, J.
Mechanical Engineering

subject:
Mechanical Engineering
Mechanical Engineering

abstract:
This thesis deals with an adaptive control constraint system for end milling with constant force. The control criterion is to hold the force acting on the cutter at a value safely below the force which would break the cutter. This criterion is applicable to finish milling of complex shapes, typically of die cavities. The controlled variable is the command feed rate.

Two other constraints were considered for the adaptive control system, namely: chatter and overload of the cutting edge.

The work presented in this thesis was based on a homemade Computer Numerical Control (CNC) and Adaptive Control (A/C) System consisting of an NC retrofitted No. 4 vertical milling machine and an HP 2100A minicomputer.

The operating characteristics of this system were examined both experimentally and by digital computer simulation. The analytical analysis of the A/C system concentrated on its behaviour as a servomechanism, i.e. mainly with respect to the speed of its response to step inputs and to its stability. In this analysis both the Laplace transform approach as well as a numerical simulation (State-Space approach) were used.

In order to improve the system response to collision or step changes in cutting loads caused by abrupt changes in work surface contact area, special action strategies are presented. These strategies are allowed to operate for a limited time during impact before the system switches back to a slower acting (lower gain) strategy. This leads to improved reaction time whilst maintaining system stability.

The A/C experiments were conducted using two different types of dynamometers for the on-line measurement of cutting force. Two different workpiece materials were used: Al. Alloy (95 BHN) and steel AISI 1020 (155 BHN). High Speed Steel end mills were used in all experiments.

An experimental investigation of the chatter constraint was also carried out as well as a review of the basic features of the phenomenon of cutting edge overload.

It is shown that the flexibility of the end milling cutters is beneficial in attenuating the overload in a sudden transient situation and it is also beneficial in attenuating chatter. These benefits are obtained for a certain range of diameters and lengths of cutters. Within this range constraints on feed rate for edge overload must be considered and outside of this range the chatter constraint has to be included.

abstract: Doctor of Philosophy (PhD)