VictorJuiz/thesis huggingface dataset:
Planetary Systems in Polarized Light: Debris Disk Observations and Instrumentation
Keywords: Data Reduction
Debris Disks
Exoplanets
Instrumentation
Polarimetry

Understanding planet formation is one of the major challenges of modern astronomy. Polarimetry is a powerful tool with which we can confront this challenge. In particular, polarimetric observations can be useful for imaging debris disks and characterizing exoplanet atmospheres. With that in mind, this thesis has been constructed with two main aspects: i) observational studies of two debris disk systems, Beta Pic and HD 157587, using the Gemini Planet Imager and ii) the characterization and testing of a new type of diffraction grating, called a polarization grating, that we plan to use for future observations of exoplanet atmospheres. The Gemini Planet Imager is a high-contrast imager that includes a polarimetry mode designed to image circumstellar disks. Here we detail the development of new data analysis techniques that reduce systematics and noise in processed GPI data. We apply these techniques to observations of the Beta Pic and HD 157587 debris disks and then fit each disk image to a geometric disk model. The Beta Pic disk model's morphology cannot be explained by interactions with the planet Beta Pic b, and the presence of a second planet could be invoked to explain the discrepancy. In the case of HD 157587, the disk model's geometric centre is offset from the location of the star, which could be explained by a perturbing planet. Characterization of the planets' interactions with their debris disks is a critical method to gain more information about these two systems. The second component of this thesis focuses on polarization gratings, thin film optical devices that can simultaneously act as polarizing beam splitters and as spectral dispersive elements. Moreover, they can be designed for high diffraction efficiency across a broad wavelength range. These features make polarization gratings useful for many types of astronomical observations. We have carried out laboratory and on-sky test observations using a polarization grating optimized for visible wavelengths. The laboratory tests confirm the expected diffraction efficiency and beam splitting capabilities of the grating. Our on-sky observations demonstrate the grating's ability to measure linear polarization fraction and position angle, and recover spectra in an astronomical setting. In the future we plan to use a near-infrared polarization grating to search for spectropolarimetric features in exoplanet atmospheres.
Event Typicality and Memory: Investigating How Prior Knowledge and Novelty Modulate Memory for Complex Events
Keywords: episodic memory
medial prefrontal cortex
medial temporal lobes
memory consolidation
schemas
semantic memory

A complex set of processes and brain regions work together in healthy adults, allowing them to create and recall memories of daily events. Additionally, the perception and recall of these events is shaped by factors such as novelty and congruence with prior knowledge (typicality). Despite a long history of research, studies on the neural underpinnings of the mnemonic effects of novelty and typicality rarely examine complex naturalistic event memories. Moreover, it is uncertain how these effects evolve over time, as memories are stabilized and transformed from acquisition to retention and retrieval. In this thesis I use naturalistic film clip stimuli, behavioural measures, and functional magnetic resonance imaging (fMRI) to explore the effects of both novelty and typicality on the neural substrates mediating memory, and examine how these effects evolve through encoding and retrieval over the course of a week. Behaviourally, I find that both typicality and novelty enhance memory for events, but that atypical events are recalled with more errors over time. With respect to the neural bases of memory, I demonstrate that the greatest differences based on event typicality are seen during encoding - when typicality is correlated with greater medial prefrontal cortex (mPFC) and parietal activation, while novelty is correlated with greater activation in the medial temporal lobes (MTLs) and posterior sensory cortices. During retrieval, however, such differences based on typicality are subtler, with retrieval supported by the MTLs, irrespective of event typicality, at all time points. Notwithstanding these overall neural similarities in the retrieval of all events, typical clips are associated with attenuated MTL activation during remote retrieval, indicating that recall dynamics may be influenced by event typicality over time. Furthermore, I provide evidence for differential functional connectivity of both the mPFC and MTLs during encoding and retrieval, based on event typicality. These results, which demonstrate how the neural substrates mediating narrative episodic memories are modulated by event typicality, are consistent with two complementary theories - Trace Transformation Theory and Schema Theory. Furthermore, they suggest, through mPFC and MTL functional connectivity, potential mechanisms by which typical and novel events may be differentially encoded and retrieved.
Thalamic Mechanisms Mediating the Sedating Effects of General Anesthesia
Keywords: Anesthesia
EEG
GABA type A receptors
Sleep
Thalamus

Alterations in thalamic activity are associated with electrocortical patterns that characterize non-rapid eye movement (non-REM) sleep and general anesthetic-induced sedation and loss-of-consciousness. Both non-REM sleep and general anesthesia are states that are characterized by increased inhibitory Îł aminobutyric acid (GABA)-ergic signaling in the thalamus. There are three forms of GABA type A (GABAA) receptor-mediated inhibition that have been identified in thalamocortical neurons: (1) phasic inhibition mediated by the transient activation of synaptic GABAA receptors, (2) tonic inhibition mediated by the prolonged activation of extrasynaptic GABAA receptors, and (3) spillover inhibition mediated by the transient activation of extrasynaptic GABAA receptors. The separate impact of each of these forms of thalamic GABAergic inhibition on electrocortical activity is unclear and such an understanding would assist in elucidating the thalamic mechanisms mediating the changes in electrocortical activity that signal sedation and loss-of-consciousness. The experiments presented in this thesis identify the electrocortical effects of enhanced thalamic GABAA receptor-mediated tonic and spillover inhibition in vivo. The electrocortical changes elicited by a prototypic GABAA receptor-targeting general anesthetic agent when it is administered directly into the thalamus are characterized and compared to the effects identified with separate manipulations of GABAA receptor-mediated inhibition. These studies show that enhanced thalamic tonic inhibition in mice promotes electrocortical patterns associated with deep non-REM sleep. Specifically, enhanced GABAA receptor-mediated tonic inhibition in the thalamus elicits a state-independent increase in 1-4 Hz electrocortical activity and a decrease in sleep spindle-like oscillations. These effects were altered by blockade of thalamic T-type Ca2+ channels. Importantly, microperfusion of the general anesthetic etomidate into the thalamus elicits changes in electrocortical activity that are distinct form those associated with enhanced thalamic tonic inhibition. Moreover, the action of etomidate at the thalamus is sufficient to elicit an electrocortical signature associated with anesthetic-induced loss-of-consciousness, but only during non-REM sleep. Finally, enhanced GABAA receptor-mediated spillover inhibition in the thalamus fully recapitulates the electrocortical effects identified with etomidate at the thalamus. Together, the findings of this thesis indicate that alterations in thalamic spillover inhibition could underlie the changes in electrocortical activity that signal anesthetic-induced loss-of-consciousness.
Perfect Timing: Acquisition of the Spanish Present Perfect in a Francophone Context
Keywords: bilingual language acquisition
cross-linguistic influence
heritage language acquisition
Present Perfect
tense
aspect
and mood

Perfect Timing: Acquisition of the Spanish Present Perfect in a Francophone Context Joanne Markle LaMontagne Doctor of Philosophy Department of Spanish and Portuguese University of Toronto 2016 Abstract This thesis explores the possible role of cognate (similar) morphological forms and semantics in a model of cross-linguistic influence in bilingual language acquisition. Much of the previous research on the question of what counts as similarity and overlap in different languages, as a condition on language influence, has focused on syntactic structures (e.g., Hulk Müller, 2000; Strik Pérez-Leroux, 2011; Unsworth, 2003; Yip Matthews, 2000, 2007, 2009). Verbal morphemes and their corresponding semantics, however, have not been investigated before as conditions on language influence. Some of the work on this area has examined the role of shared semantic features related to Tense in bilingual children growing up in a language contact situation in Quechua and Spanish (e.g., Sánchez, 2004). Morphological similarity, however, has not been explicitly tested as to whether it determines language influence. This dissertation investigates whether cognate morphological forms and semantics (i.e., semantic features) are determinants of language influence, and whether quantitative and/or qualitative differences between monolingual and bilingual children occur. I present an experimental study that tests the grammatical knowledge of Spanish tense-aspect-mood and copula selection in Spanish heritage children growing up in a Canadian Francophone context. Four semantic contrasts are tested (e.g., Preterite/Present Perfect, Preterite/Imperfect, Subjunctive/Indicative, and ser/estar), all of which have shown sensitivity to bilingual effects such as language transfer, incomplete acquisition, and attrition. Such effects have been attested in studies on child and adult Spanish heritage language acquisition (e.g., Cuza, 2008, 2010; Cuza Miller, 2015; Miller Cuza, 2013; Montrul, 2002b; Montrul Slabakova, 2002, 2003; Silva-Corvalán, 1994, 2003). In order to examine the subtle, yet important, differences between the Spanish and French tense-aspect-mood systems, a contrastive analysis as in Cowper’s (2005) feature geometry analysis for features of Inflection is adopted. Results from a receptive vocabulary and a sentence imitation task show that while monolingual children outperform heritage children, the latter also show growth and development despite prolonged contact with French. This trend is also confirmed in the contextualized preference-based elicitation task, the main task chosen for this study. Language influence from French to Spanish occurs in heritage children, specifically overextension of certain verbal forms and feature reassembly, but no effect of form similarity (i.e., a cognate boost) is found.
Creative Producers and Gender Relations: A Field Analysis of Two Grassroots Music Scenes
Keywords: Cultural and symbolic capital
Cultural valuation
Fields of cultural production
Gender and creative careers
Gender and habitus
Gender and organizations

This dissertation uses a comparative case study of two grassroots music scenes—the folk music and heavy metal scenes in Toronto—to examine gender relations among cultural producers. I collect data using semi-structured interviews with 63 field actors, 70 instances of participant-observation, and discourse analysis of key public texts. Building on Bourdieu’s field theory, I argue that gender organizes fields of cultural production, including (1) the field’s economy of symbolic capital (2) the connection between field and habitus and (3) the spaces where musicians develop the embodied cultural capital required for music careers. The first paper shows that field organization impacts the extent to which field members’ gendered dispositions produce symbolic capital, or reputation. Two features of cultural fields shape whether symbolic capital is gendered: the degree to which symbolic capital is institutionalized, and the level of symbolic boundary-drawing in the field. The metal field’s low institutionalization of symbolic capital and high boundaries foreground gender as a basis of symbolic capital, while the folk field’s high institutionalization of symbolic capital and low boundary-drawing reduce the extent to which gender matters. The second paper situates gender as central to relationship between field and habitus. Participants in the metal field develop a metalhead habitus that privileges gendered practices centered on individual dominance and status competition, while the folkie habitus encourages gendered practices centered on caring, emotionality, and community-building. These gendered habitus support different working conventions: volunteer-based non-profit organizations in folk, and individual entrepreneurship in metal. The gendered habitus also supports different stylistic conventions: guitar virtuosity in the metal field, and participatory music-making in folk. The third paper finds gendered access to the learning spaces where musicians develop performance capital, a form of embodied cultural capital denoting the instrumental and interpersonal skills required to perform music. Folk’s learning spaces are largely public and do not require social networks for access, while heavy metal’s learning spaces are private and centered on male-dominated friendship networks from which women are often excluded. These different learning spaces creates gendered patterns of access to the embodied cultural capital required to develop a music career.
Energy Expenditure in the Opera Singer in Rehearsal and Performance
Keywords: energy expenditure
heart rate
indirect calorimetry
professional opera singers
submaximal VO2 test

Energy expenditure in professional classical opera singers is a field of study that has remained untouched until now. The purpose of this dissertation is to discover the most appropriate and accurate manner of assessing the number of calories a professional classical opera singer burns in the course of an aria, both in rehearsal and performance. Methods were developed for laboratory (Phase 1) and field testing of energy expenditure in six subjects during the rehearsal (Phase 2) and performance (Phase 3) of a staged opera aria. In Phase 1, a sub maximal VO2 treadmill test was administered using indirect calorimetry (gas exchange information using a Moxus Metabolic Cart). Additionally, heart rate information (using a Polar heart rate monitor and receiver) and perceived exertion information (using the Borg Rating of Perceived Exertion, or RPE) were collected. In the field, heart rate information was collected during the rehearsal and performance of the staged opera aria (Phases 2 and 3). Both rehearsal and performance were video recorded to track movement. Using the heart rate information and the Borg RPE information from the field testing, and the gas exchange information from the laboratory testing, reasonable estimations were made regarding the number of calories burned during the rehearsal and performance of a staged opera aria. For the six subjects, the average length of the staged aria was 2:50 minutes. The average heart rate for rehearsal (Phase 2) was 128 bpm, and average energy expenditure during this phase was 22.5 calories. The average heart rate for performance (Phase 3) was 138 bpm, and average energy expenditure during this phase was 28.5 calories. Further estimations were made for the approximate energy expenditure of a classical opera singer performing an entire role.
Brain Uptake and Metabolism of Eicosapentaenoic Acid in Rodents
Keywords: Beta-oxidation
Eicosapentaenoic acid
Fatty acid metabolism
Fatty acid uptake
Kinetic modeling

Omega-3 polyunsaturated fatty acids (n-3 PUFA) are currently being investigated as a potential therapy in mood disorders including depressive disorder and bipolar disorder. Clinical trials that used relatively pure EPA were more effective in alleviating depressive symptoms compared to relatively pure DHA supplementations. However, this poses a potential paradox as EPA levels in the brain are 250 to 300-fold lower than DHA, a finding consistent across mammals. The large difference in brain EPA and DHA levels may be explained by either selective differences in their uptake or metabolism upon entry into the brain. Based on the literature, EPA and DHA can passively diffuse across the blood-brain barrier at similar rate suggesting that the uptake of n-3 PUFA into the brain is non-selective. Therefore, I hypothesize that the difference between EPA and DHA concentrations might be explained by metabolic differences which are yet to be elucidated. First, we characterized the difference in EPA and DHA β-oxidation via in situ cerebral perfusion. We found that EPA was 2.5-fold more readily β-oxidized than DHA. Upon in vivo kinetic modeling in the rat, we observed a 3-fold lower esterification and 154-fold lower recycling of EPA in brain phospholipids as compared to DHA. This corresponded to a 7-fold increase in EPA loss from brain phospholipids compared to DHA in the rat brain. Moreover, upon inhibiting mitochondrial fatty acid β-oxidation, we observed a further reduction in EPA recycling and increased EPA elongation to n-3 docosapentaenoic acid (n-3 DPA) suggesting multiple redundant pathways are present to maintain low levels of EPA in the brain. In conclusion, the low levels of EPA in brain phospholipids, as compared to DHA, are maintained by increased β-oxidation, decreased esterification, increased conversion to n-3 DPA, decreased recycling and increased loss.
Chemical Genetic Interrogation of Strigolactone Receptors in Arabidopsis thaliana and Striga hermonthica
Keywords: Arabidopsis genetics
Chemical biology
Chemical genetics
Chemical screening
Parasitic plants
Plant hormones

Strigolactones are a class of terpenoid plant hormones that regulate various areas of plant growth and development. They are best known as suppressors of axillary growth, but have also been implicated in areas as diverse as leaf shape, hypocotyl length, and seed germination. However, parasitic plants of the genera Striga, Orobanche, and Phelipanche have evolved to use strigolactones released from host plant roots as a cue for germination and parasitism. Because these parasitic plants cause billion-dollar yield losses in the developing world each year, considerable research efforts have been dedicated towards understanding the mechanism of strigolactone perception. The alpha/beta hydrolase HTL is the receptor for strigolactones in the seed. HTL interacts with effector proteins to elicit a strigolactone response. HTL-dependent signaling leads to increased germination and reduced hypocotyl length. We decided to use a chemical genetic approach to both probe HTLs while also developing Striga control technologies. Separately, we screened approximately 4000 compounds from a chemical library to identify small molecules that could be agonists and antagonists for Arabidopsis thaliana HTL. We were able to show that many of the compounds we isolated from the chemical screen were able to directly bind to HTL, and their action was specific to strigolactone signaling. These compounds were also able to stimulate Striga hermonthica germination, showing they have promise as leads for Striga control technology development. In order to identify new genes involved in strigolactone signaling, we screened a collection of overexpression lines for the ability to resist the effects of an HTL antagonist on germination. We found that the overexpression of the splicing factor U2AF35B was sufficient to suppress the effect of an antagonist on germination, and could partially suppress phenotypes associated with loss-of-function alleles of HTL. This suggests that U2AF35B plays a role in strigolactone signaling at or downstream of HTL.
Neural Substrates of Parkinson's Disease
Keywords: Cognition
Motor
MRI
Neuroinflammation
Parkinson's disease
PET

Parkinson’s disease is characterized by selective degeneration of dopaminergic neurons in the substantia nigra, the presence of Lewy bodies and Lewy neurites containing alpha synuclein ag-gregates in such neurons, and neuroinflammation mediated by the activation of microglia and astrocytes. These pathological changes collectively contribute to the cardinal motor symptoms of Parkinson’s disease such as resting tremor, bradykinesia, rigidity, and postural instability. In ad-dition, dysfunction of non-dopaminergic neurons such as serotonergic, noradrenergic, and cho-linergic neurons, the Lewy pathology, and neuroinflammation outside of the nigro-striatal re-gions are thought to play a major role in non-motor symptoms of Parkinson’s disease such as psychiat¬ric problems, cognitive dysfunction including dementia, autonomic symptoms, and rap-id-eye movement sleep disorder. Therefore, Parkinson’s disease is a multisystem disease, affect-ing diffuse area of brain and producing various symptoms. Current trends toward use of data driven analytic methods can facilitate to expand our knowledge about Parkinson’s disease be-yond the classic basal ganglia motor model and DA dysfunction. The general aim of this thesis is to investigate a whole brain in vivo to further understand the complex neural substrates of the disease using multimodal neuroimaging tools and techniques. This thesis has shed light on the cortical and subcortical structural and functional brain changes underpinning for the clinical manifestations in Parkinson’s disease. Changes in gray and white matter as well as functional changes were evident using magnetic resonance imaging (MRI). Gray matter and functional changes occurred in the frontal cortex while white matter changes occurred more diffuse area of the brain including bilateral frontal and temporal regions and left parietal and occipital regions as well as subcortical white matter tracts. These changes were also associated with motor and cog-nitive dysfunction, suggesting that structural MRI and diffusion tensor imaging as well as resting functional MRI may be promising as in vivo biomarkers for Parkinson’s disease. Our investiga-tion of neuroinflammation using Positron Emission Tomography and an improved second gener-ation radioligand did not find any changes in the striatum of patients with Parkinson’s disease. However, demonstrated gray matter, white matter, and functional changes warrant further inves-tigations of neuroinflammation in extra-striatal and white matter regions.