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Motivation in Early Psychosis: Temporal Dynamics, Activity Engagement, and Relationships with Socio-Environmental Factors
Get PDFMotivational impairment, considered one of the hallmark symptoms of psychotic disorders, is notably difficult to measure and treat. Much remains unknown about how motivation is experienced by individuals with psychosis. Recent empirical and theoretical work has suggested that the experience of motivation in psychosis is more complex and dynamic than previously believed, and has introduced the putative role of socio-environmental processes in the etiology and maintenance of motivational impairment.
This longitudinal ecological momentary assessment study was interested in examining internal and external factors related to motivation in the daily lives of young people with psychosis and investigate its associations with goal-directed behaviour. Forty-two participants with early psychosis and 49 community controls aged 18-36 answered questions related to motivation and activity engagement in up to five daily surveys for one week on their personal mobile devices, followed by a clinical assessment. Individuals with early psychosis had significantly lower ratings from controls on standard, retrospective measures of motivation-related constructs, but not on momentary measures. The experience of momentary motivation fluctuated significantly, and the temporal dynamics and intensity of motivation ratings across functional domains were similar between participants with early psychosis and controls. Interestingly, momentary motivation predicted the odds of productive activity engagement differently between the groups. While the odds of engaging in productive activity increased as momentary motivation increased in both groups, controls were still more likely to engage in goal-directed activity at low levels of motivation relative to participants with early psychosis. Material deprivation, a socio-economic variable, appeared to moderate the relationship between momentary motivation and goal-directed activity at a trend-level. In this case, higher levels of deprivation strengthened this relationship selectively in the early psychosis group. We introduce a novel theoretical construct of motivational reserve as a putative explanatory mechanism underlying some of the differences in the complex relationship between motivation and action observed in our findings. We conclude that momentary motivation manifests differently across individuals, time, and classes of activities and provide numerous future directions to further investigate the experience of motivation in psychosis, refine its measurement, and inform multidimensional and personalized approaches treatment for motivational impairment.Ph.D
Performance–Complexity–Latency Trade-offs of Concatenated Codes for High-Throughput Optical Communication Systems
Get PDFThis thesis explores the performance-complexity-latency trade-offs of concatenated coding systems for high-throughput optical communication systems. In particular, outer Reed--Solomon (RS) codes concatenated with inner Bose--Ray-Chaudhuri--Hocquenghem (BCH) codes are studied. The inner BCH codes are decoded using either a hard-decision (HD) or a soft-decision (SD) decoder, while the outer RS codes are decoded using an HD decoder only.
For the concatenated RS-HDBCH coding system, the binary symmetric channel model is assumed. For the concatenated RS-SDBCH coding system, the additive white Gaussian noise channel with four-level pulse amplitude modulation (PAM4) is assumed. Both bit-interleaved coded modulation (BICM) and multilevel coding (MLC) coded modulation architectures are considered in the case of RS-SDBCH.
For a fixed interleaving scheme between the outer RS and inner BCH codes, a generating function is used to describe the interaction between bit errors in the BCH codewords and symbol errors in the RS codewords. The generating function gives rise to computationally tractable analytical and semi-analytical formulas that accurately estimate the frame error rate arising at the output of the concatenated RS-BCH decoder, eliminating the need for time-consuming Monte Carlo simulation. These formulas are used to search a large space of codes to find those achieving good trade-offs of performance (measured by the gap to the hard-decision Shannon limit and PAM4-constrained Shannon limit in the case of RS-HDBCH and RS-SDBCH, respectively), complexity (measured by the number of elementary decoding operations per decoded information bit), and latency (measured by overall block length).
Finally, a hybrid soft/hard-decision iterative decoding scheme between the outer RS and inner BCH codes is considered. In this scheme, the inner BCH codes are decoded using an SD decoder only on the first decoding round, while an HD decoder is used for the subsequent decoding rounds. By allowing additional decoding iterations, the performance of rate-0.88 RS-BCH codes can be improved by up to 0.4 dB with only a modest increase in decoding complexity.Ph.D
Transport Properties of Hydrogels: From Fundamentals to Biomedical Applications
No full textControlling transport properties is essential for hydrogels used in biomedical applications. While progress has been made in tuning uniform pore sizes of hydrogels to control transport kinetics of molecules and nanoparticles, current approaches offer limited ability to regulate transport that is dynamic, environmentally responsive, and spatially directed. My Ph.D. research addressed these limitations by engineering hydrogels with stimulus-responsive pores, hierarchically structured pore networks, and anisotropic pore geometries.
One approach involved designing a hydrogel with thermally responsive pore size. This was achieved by crosslinking aldehyde-modified cellulose nanocrystals with a chitosan-graft-poly(N-isopropylacrylamide) copolymer. Heating the gel above its volume phase transition temperature triggered an increase in pore size due to the collapse of grafted polymer chains, enabling release of encapsulated liposomes larger than the initial pores, without compromising the hydrogel’s structural or mechanical integrity.
A second approach developed a hierarchical network assembled from positively charged nanogels. These nanogels, formed via ionic crosslinking of quaternary-ammonium-functionalized chitosan, retained strong positive charges under physiological conditions and scavenged negatively charged biomolecules through electrostatic interactions. Uptake of oligodeoxynucleotides depended on nanogel charge density and pore size, which respectively governed surface adsorption and interior absorption. When assembled into a colloidal gel, nanometer-scale intra-nanogel pores and submicron inter-nanogel pores enabled staged uptake and release of competitively binding molecules. Using oligodeoxynucleotides and epidermal growth factor, I demonstrated control over the timescales of dynamic exchange relevant to chronic wound treatment.
The third approach focused on a hydrogel composed of cellulose nanocrystals and gelatin methacryloyl with an aligned fibrous structure. This hydrogel was fabricated via extrusion-based three-dimensional printing, enabling control over fiber orientation without altering matrix composition. Diffusion- and advection-driven transport experiments under physiologically relevant flow conditions showed that structural anisotropy enhanced nanoparticle movement along the fiber alignment and hindered it across the fibers, mimicking directional transport in biological tissues.
Collectively, my Ph.D. research established correlation between pore structure and transport behavior in these structurally complex hydrogels, advancing the understanding of hydrogel transport properties and supporting the development of hydrogels for biomedical and broader engineering applications.Ph.D
Exploring the experiences, aspirations, and identities of Chinese women graduate students in research psychology programs
Get PDFThis study investigates the experiences, aspirations, and perceptions of Chinese women graduate students in research psychology programs, asking: (1) What are the experiences of Chinese women in research psychology graduate programs?, (2) What are their professional aspirations and perceptions of their future employment?, and (3) How do their experiences, aspirations, and perceptions relate to their social identities? Three Chinese women from research psychology graduate programs in Ontario, Canada, were interviewed three times each. Thematic analysis of the interviews, informed by the capabilities approach and intersectionality, revealed the interplay of personal, social, and structural factors as shaped by the participants’ multiple, intersectional identities in determining their experiences, aspirations, and perceptions. This study serves as a stepping stone for future research and institutional practices to advance equity for Asian women and other marginalized academics in the discipline.M.A
Molecular Phylogeny and Evolution of Black Widow Spiders (Latrodectus, Theridiidae)
Get PDFUnderstanding links between species diversity and underlying genetic variation provides insight into histories of evolutionary change. My work examines genetic diversity among the widow spiders (genus Latrodectus) across development, across populations, and across species. The widow spiders (Theridiidae) have been the subject of fascination for more than 200 years, and are notorious for their extreme sexual behaviours and potent venom. I first tested hypotheses about sex-specific differences in the importance of visual opsins across development in an Australian widow (Latrodectus hasselti). Using transcriptomics, I identified three visual opsins and showed that two of them KO1 and KO2 had significant expression in males at sexual maturity, but not females. This aligns with the prediction that increased male mobility at sexual maturity increases the importance of photoreception. I then turned to the puzzling taxonomic status of western widows (Latrodectus hesperus) in which divergence in behaviour and morphology among broadly distributed populations suggests cryptic variation. Using a multi-gene approach (COI, 16S, and 28S) and sampling from 40 locations I show evidence of minimally three putative species that are geographically defined and genetically distinct. Finally, at the broadest level of analysis, I used mitochondrial and nuclear DNA (COI, 16S, 28S) to revisit evolutionary relationships across Latrodectus. Thirty of 34 recognized Latrodectus were included with topotypic specimens for most of the 80 available names. An alignment of 387 individuals included 115 new specimens from 25 countries. I confirmed the monophyly of Latrodectus and confirm robust support for two clades (geometricus- and mactans-) with geographic distributions largely corresponding with evolutionary relationships. A new species from Peru is identified, and inferences are made about consolidation of some species as synonyms and the re-establishment of other species names as valid. This broader taxon sampling confirms L. hesperus as a cryptic species complex, suggesting four (rather than three) cryptic species. Intriguingly, L. mactans may also be a cryptic species complex. Overall, this thesis provides significant new information about the molecular basis of the diversity seen within and across species of Latrodectus spiders, providing an important tool for a wide range of future comparative research.Ph.D
Systemic Neglect in the Ontario Child Welfare System: An Analysis of Youth Testimonies from the 2012 Youth Leaving Care Hearings in Ontario
Get PDFThis research examines and incorporates the themes from youth narratives in My Real-Life Book: Report from the Youth Leaving Care Hearings in Ontario (2012). Employing and engaging with the voices of those directly impacted by the child welfare system (CWS), namely youth in care (YICs), former youth in care (FYICs), and adoptees, this research offers an important alternate narrative to dominant public discourses that problematize children and youth in care. Using a social justice education lens that engages with an integrated scaffolded framework applying critical race theory (CRT), anti-racist feminist theory, and the concepts of Foucault and Bourdieu, this dissertation examines YIC/FYIC/Adoptees’ narratives to expose how systemic power imbalances impact youth through institutional neglect. The analysis of the youths’ narratives along with the researcher’s themes from the literature review, reveals the impacts of institutional practices devoid of meaningful, purposeful youth participation in decision-making, the lack of stability, and the life-long impacts of mandated care purported to protect children and youth. Critical discourse analysis is applied to analyze youth narratives to expose implicit and explicit realities contextualized within broader historical and socio-political frameworks that shape the experiences of YICs. This research also includes current public perspectives offered by key stakeholders, such as child advocates, social workers, health and mental health advocates, educators, criminal justice researchers and housing advocates. Thus, the study provides an important perspective on and understanding of how interconnected institutions maintain structural disparities in access to opportunities. The findings and analysis accentuate the potential for youth voices to transform the CWS by challenging dominant structural hierarchies and existing practices that are no longer helpful to youth in care. This work advocates for and contributes to the current research, highlighting the critical need for meaningfully collaborative policies and practices toward institutional reform with input from youth who are directly impacted by interconnected systems. Finally, this research aims to intensify the plea for a genuine, empathetic, equitable, and humane CWS that fosters youth agency, autonomy, and dignity.
Keywords: Youth in care; child welfare system; critical race theory; systemic power imbalances; critical discourse analysis; Bourdieu; Foucault.Ph.D
Effects of Centromedian Thalamic Deep Brain Stimulation on Glutamate GABA in the Cntnap2-KO Mouse Model of Epilepsy
Get PDFDeep brain stimulation (DBS) of the centromedian nucleus of the thalamus (CM) is a promising treatment for a subset of individuals with drug-resistant epilepsy. However, the effects of CM-DBS on neurotransmitters involved in excitatory/inhibitory balance, such as glutamate and GABA, are unknown.Here, I studied the effects of CM-DBS on glutamate and GABA levels in healthy (C57BL/6J) and epilepsy (Cntnap2KO) mouse models. At baseline, Cntnap2KO mice had lower striatal Glu/GABA ratios in comparison to healthy mice. CM-DBS led to increases in striatal glutamate levels and hippocampal GABA levels. Additionally, I analyzed neurotransmitters from a network perspective. Inter-regional neurotransmitter correlations involving the striatum were weaker in Cntnap2KO mice compared to healthy mice, and CM-DBS reversed the direction of these correlations. These findings provide initial insights into mechanisms involving glutamate/GABA neurotransmission that potentially underlie the anti-seizure effects of CM-DBS.M.Sc
“Becoming what I want to be”: A Grounded Theory of Professional Identity Development through Reflection and Relationships in Work-integrated Learning
Get PDFAlthough work-integrated learning (WIL) has received considerable investment from the Canadian Government and is regarded as a panacea for incorporating students into the workforce, scholars have argued that more explicit curriculum and reflection related to professional identity development is needed. Reflection is well-established in WIL curriculum, predominantly through graded written reflection assignments, but there is preliminary evidence that assessed reflections may be performative. Using a constructivist grounded theory approach, drawing on semi-structured interviews with undergraduate WIL students and instructors and discourse analysis of students’ reflection assignments and course syllabi, this study addressed the question: How is professional identity developed through reflection in WIL curriculum? Through theoretical sampling, the importance of relationships in WIL emerged as a recurring pattern. Findings are reported across patterns of professional identity, reflection, and relationships. Students and instructors conceptualized professional identity as internal or external, and in follow-up interviews, students articulated professional identity as a merging of their internal personal identity with their more external professional one. Reflection played an important role in generating, deepening, and documenting learning, but students also curated their reflections by excluding or enhancing details. Students gave compelling examples of when they reflected dialogically through relationships, finding that sharing ideas with others without worrying about how their thoughts were being documented deepened their reflection. Relationships emerged as an essential part of students’ WIL experience and professional identity development. Their role in teaching and learning, trust and support, and being part of a community, as well as the absence of relationships spanned both course and workplace contexts. Based on the patterns emerging from the data, a theory of professional identity development through reflection and relationships in WIL curriculum is proposed. The theory is contextualized in the broader literatures of WIL, professional identity development, reflection, and relational approaches. While reflection is widely recognized as an essential part of WIL, it is argued that relationships also play a key role. Suggestions for application of the theory are explored to strengthen reflection and relationships in WIL. The study’s limitations are discussed, as well as possible directions for future study.Ph.D
Investigating Scintillation Screen Properties and Associations
Get PDFRadio waves from pulsars are scattered along multiple paths by ionized structures in the interstellar medium, causing pulsars to scintillate. Emission on the typical scales of these structures, a few AU, is not resolved with current interferometers, so we cannot directly connect the scintillation with observations of the interstellar medium. This thesis investigates associations between the discrete structures that cause scintillation, known as screens, and larger scale structures observed through emission in the interstellar medium.
Scintillation screens are typically elongated, so we first compared the direction of elongation of screens with elongated features seen in the interstellar medium. In this work, we found that scintillation screens and cold, neutral hydrogen filaments are more aligned than expected by chance. This suggests that the hydrogen and screens are being aligned by a shared mechanism and/or the hydrogen filaments have a self-similar density structure on scales from parsecs to sub-AU. The significance of this finding relies on the precision of our measurements of both scintillation screen and hydrogen filament orientations. In the remaining sections of my thesis, we used interferometric techniques to improve the precision of some scintillation screens and hydrogen filaments.
Using very long baseline interferometry (VLBI), we measured the screens of PSR B1133+16. This is the first measurement of screen properties for a pulsar with multiple scintillation arcs done using VLBI. With VLBI it is possible to measure screen orientations precisely with only one observation, so we may more quickly increase the number of scintillation screens with measured orientations.
With interferometry, we imaged neutral hydrogen emission towards ten pulsars. Unfortunately, these images did not have sufficient quality to improve filament orientation measurements. However, we found that the neutral hydrogen emission structures were fully resolved at scales of ~4 arcminutes, so the likelihood of chance alignment between hydrogen filaments and scintillation screens is unlikely to change for observations at higher resolution than 4 arcminutes.Ph.D
Endometriosis in Carriers of a Pathogenic Variant in BRCA1 or BRCA2: A Descriptive Analysis of a Large Multicentral BRCA Carrier Cohort
Get PDF<b>Background:</b> Endometriosis affects an estimated 10% of reproductive-aged women and is associated with increased ovarian cancer risk. While <i>BRCA1/2</i> mutations are established risk factors for ovarian cancer, their association with endometriosis remains unclear. This study aimed to characterize the prevalence and clinical features of endometriosis within a large cohort of <i>BRCA</i> mutation carriers. <b>Methods:</b> A descriptive analysis was conducted using data from a multi-center longitudinal cohort of women with pathogenic BRCA variants. Reproductive history and related factors were collected through self-reported questionnaires and compared. <b>Results:</b> Among 16,950 <i>BRCA</i> carriers, the prevalence of endometriosis was 2.4%. Compared to <i>BRCA</i> carriers without endometriosis, those with endometriosis were more likely to carry a <i>BRCA2</i> mutation, have post-secondary education, and experience earlier menarche. <i>BRCA</i> carriers with endometriosis had a lower ovarian cancer prevalence than those without (10% vs. 15%, <i>p</i> &lt; 0.001). <b>Conclusions:</b> This is the first study of this scale to report the prevalence of endometriosis among <i>BRCA</i> mutation carriers, which was lower than previously reported in the general population. The association between endometriosis and ovarian cancer does not appear to be generalizable to this population. Further prospective studies are warranted to clarify this association among <i>BRCA</i> mutation carriers