VictorJuiz/thesis huggingface dataset:
The Dynamic Interaction of Mantle Compositional Heterogeneities at the Surface and the Core-Mantle Boundary
Keywords: Large Low Shear Velocity Province (LLSVP)
Mantle Composition
Supercontinent Cycle
Tectonic Plates
Thermochemical Convection
Tracer Method

The Earth's D'' layer, the lowermost 200-300 km of the mantle, is perhaps as rich in chemical, phase and structural heterogeneity as the lithosphere. For instance, tomography studies show the existence of Large Low Shear Velocity Provinces (LLSVPs) extending through D'' beneath Africa and the Pacific that may be compositionally distinct. Of particular interest is the potential interaction between compositional heterogeneity in D'' and the mobility of tectonic plates. This is explored using the convection code MC3D featuring compositional variations, dynamically evolving tectonic plates and continents. To model compositional variations, the tracer ratio method was programmed into MC3D and benchmarked. Plates are modeled using a force-balance method. Also, subroutines were programmed into MC3D that allow tracers to track plate and continent boundary positions. A suite of approximately 40 calculations is used to analyze the effect of introducing a compositionally dense layer into a vigorously convecting mantle initially characterized by mobile-lid tectonics. Subsequent to the introduction of the dense layer, surface mobility is monitored. It was found that upwelling vigor tends to decrease as either the enriched material volume or density is increased, which is accompanied by a reduced rate of surface rupturing. Consequently, long-term surface mobility ceases if either the volume or density of the enriched material is increased beyond a threshold. Another suite of models is used to analyze the effect of introducing a compositionally dense layer into the D'' region of a mantle featuring mobile-lid convection with continents. Subsequently, the supercontinent cycle frequency is monitored for a range of oceanic and continental yield strengths. In calculations featuring a uniform D'' composition, upwelling positions can remain fixed in position over billions of years. However, calculations featuring enriched material exhibited upwellings with substantial lateral movement. It was found that supercontinent aggregation was hindered by the presence of fixed upwellings. Consequently, supercontinent cycle frequency increased in the presence of enriched material. In addition, it was found that the compositionally dense material formed into one or two large provinces for the majority of the time in all calculations featuring compositional variations, similar to the present-day structure of Earth's LLSVPs.
Pricing and Matching in the Sharing Economy
Keywords: Matching
Pricing
Sharing economy

We study operational problems related to the sharing economy. Sharing economy platforms such as Uber offer the crowdsourced suppliers a wage for providing services/goods, and charge the customers a price for using them. In Chapter 2, we study the fixed commission rate contract practiced by many sharing economy platforms. We show that by using the optimal flat-commission contract, the platform achieves at least 75% of the optimal profit of the first-best benchmark, in which the platform freely chooses the price and wage under various market conditions. In Chapter 3, we consider a platform's problem of dynamically matching random demand and supply of heterogeneous types in a periodic-review fashion. The platform decides the optimal matching policy to maximize the total discounted rewards minus costs. We provide sufficient and robustly necessary conditions only on matching rewards such that the optimal matching policy follows a priority hierarchy among possible matching pairs. In Chapter 4, we study the dynamic matching problem in Chapter 3 under two specific forms of reward structures. First, we consider the problem with horizontally differentiated supply and demand types. In that problem, supply and demand types locate on a unidirectional circle. The unit matching reward between a supply type j and a demand type i is a decreasing function with respect to the unidirectional distance from the location of j to that of i on the circle. We then study the problem with vertically differentiated supply and demand types, for which we impose a reward structure in which types have â qualityâ differences. For both cases, we apply the results in Chapter 3 to characterize the optimal matching policy. In Chapter 5, we study the pricing behaviors of two agents under incentives generated from social comparison. We demonstrate how opposite-directional social comparisons interact with demand variability to change competitive behaviors. In particular, we show that the stronger the behind aversion behavior, the more intense the price competition, and that there is a threshold on the market variability above which price competition is more alleviated and below which price competition is more intensified, when the agents exhibit stronger ahead-seeking behavior.
The Effects of Social Context on Physiological Covariation
Keywords: affiliation
autonomic nervous system
meditation
physiological covariation

Physiological covariation – shared patterns of autonomic physiology between people – has been documented within all social relationships and predicts a variety of interpersonal outcomes. At a basic level, however, there remains uncertainty about how much “social experience” is needed for physiological covariation to occur. The present research addressed this issue by manipulating various facets common to social experiences. Study 1 manipulated social versus nonsocial engagement during cooperative and competitive tasks and examined whether physiological covariation predicts measures of affiliation. Across social contexts, partners exhibited physiological covariation in the sympathetic (SNS) and the parasympathetic (PNS) branches of the autonomic nervous system (ANS). However, whether partners exhibited shared increases versus decreases in autonomic activity differed by social context. Moreover, SNS covariation predicted measures of affiliation and appeared to be predominantly influenced by social processes. Conversely, PNS covariation did not predict measures of affiliation and occurred due to the procedural influences of the task. Studies 2 and 3 addressed, for the first time, what happens when the minimum requirement of two people is exceeded. Specifically, in a quasi-experimental field study (Study 2) and in an experimental paradigm (Study 3), I examined whether group size predicts physiological covariation during a group-based meditation comprised of a guided meditation followed by a silent meditation. I also explored the relationship between physiological covariation and familiarity. Across studies, group size predicted physiological covariation in SNS and PNS activity over time. How group size exerted its influence, however, depended on the branch of the ANS and the period of the meditation in which physiological covariation was observed. Among experienced meditators, large groups exhibited SNS covariation during the guided meditation, whereas small groups displayed PNS covariation. Among inexperienced meditators, both large and small groups displayed physiological covariation across the ANS. However, large groups exhibited shared decreases in PNS activity whereas small groups displayed shared increases. During silent meditation, the patterns of physiological covariation exhibited by large and small groups were also inconsistent across studies. Furthermore, familiarity predicted physiological covariation, but only in Study 3. The implications for physiological covariation research, the development of social relationships, and group dynamics are discussed.
Selective Transformations of Unprotected Carbohydrates Using Organoboron Compounds to Modulate Hydroxyl Reactivity
Keywords: activation
borinic acids
boronic acids
carbohydrates
protection
regioselective

Regioselective glycosylation of unprotected glycoside substrates has emerged as an attractive strategy for streamlining the synthesis of oligosaccharide targets. However, differentiation of multiple potentially reactive hydroxyl (OH) groups is not always straightforward. The use of small organic molecules to enforce regiocontrol in glycosylation reactions by enhancing the differences in reactivity of carbohydrate OH groups or by altering the innate regioselectivity of the substrate is a useful strategy. The work presented in this thesis describes how the interactions between carbohydrates and organoboron compounds can be used to promote selective transformations of unprotected glycosyl acceptors. Chapter 1 describes how organoboron-promoted regioselective glycosylation reactions can be used to streamline the synthesis of oligosaccharide targets by minimizing protection/deprotection steps. An initial regioselective glycosylation allows differentiation of the remaining OH groups of the disaccharide-derived diols, enabling further selective transformations through substrate controlled processes. Chapter 2 describes the development of a protocol for the regioselective protection of carbohydrate derivatives using boronic acids as temporary blocking groups which can be recovered/recycled. Boronic ester formation with carbohydrate-derived diols attenuates the nucleophilicity of the boron-bound alkoxides, permitting selective functionalization of free OH groups. Chapter 3 describes a novel boronic acid-mediated sequential functionalization protocol. Exploitation of the complementary reactivity of tricoordinate (protecting group) and tetracoordinate (activating group) boronate complexes allows multiple bond-forming reactions to be carried out without the need to isolate intermediate compounds. This allows the production of highly functionalized glycoside products directly from unprotected starting materials. In Chapter 4, strategies for the selective activation of 1,2- or 1,3-cis-diol groups are presented. The interaction between the glycosyl acceptor and the boronic- or borinic acid enables selective activation of one of the two diol groups. This chapter also describes how tuning the properties of a borinic acid catalyst can alter the regiochemical outcome of glycosylation reactions.
Novel Oncogenic Roles of Neuropilin-1 in Pancreatic Adenocarcinoma and its Relevance as a Therapeutic Target
Keywords: Chemoresistance
Neuropilin
Pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC), the most common type of pancreatic cancer, is a prominent cause of cancer mortality in Canada, with the lowest five-year survival rate. Recent evidence suggests that cellular processes such as endothelial-to-mesenchymal transition (EndMT), epithelial-to-mesenchymal transition (EMT), and autophagy when aberrantly upregulated, are unifying mechanisms of chemoresistance in PDAC. Apart from being involved in numerous cancer-initiating and promoting events, angiogenic co-receptor neuropilin-1 (NRP-1) is a mediator of TGFβ signaling, which remains the primary signaling mechanism regulating EndMT, EMT and autophagy. Overexpression of NRP-1 and transforming growth factor β (TGFβ) signaling is well-documented in PDAC. We investigated the role of NRP-1 in regulating EndMT, EMT and autophagy in pancreatic cancer. We observed a significant association between NRP-1 levels, EndMT, EMT and autophagy markers’ expression in human PDAC tissue obtained from a clinically relevant orthotopic model of PDAC in athymic rats. Knockdown of NRP-1 inhibited, while overexpression of NRP-1 promoted EndMT and associated fibrosis, respectively, through modulation of TGFβ signaling and Slug expression in endothelial cells. Moreover, in human pancreatic cancer cell lines and their chemoresistant forms, knockdown of NRP-1 inhibited, while overexpression of NRP-1 promoted EMT and associated invasiveness, respectively, via modulation of TGFβ signaling and SNAIL expression. Finally, NRP-1 knockdown inhibited autophagy, while NRP-1 overexpression activated autophagy by repressing mTOR activation in human pancreatic cancer cell lines. NRP-1 was also able to regulate autophagy induced by nutrient starvation and chemotherapy stress and subsequently, affect cancer cell survival. Together, these results suggest that anti-NRP-1 therapy could potentially overcome chemoresistance in PDAC and may emerge as an adjuvant therapy to existing chemotherapy strategies.
Human Optic Nerve Head Glial Cell Activation Following Biomechanical Compression
Keywords: Astrocyte
Compression
Glaucoma
Lamina Cribrosa
Neurodegeneration
Reactive Glial Cells

Glaucoma is the most prevalent neurodegenerative disease and the worldâ s second leading cause of blindness resulting from the slow and painless neuropathy of the optic nerve head, and death of the retinal ganglion cells. While very little is known about the onset and pathology of the disease, activated astrocytes are found in the optic nerve heads of early glaucoma patients. Activation of glial cells, including astrocytes, is known to be associated with several neurodegenerative diseases and believed to contribute to their pathophysiology. Glial cell activation has successfully been induced using biomechanical stretch, which was predicted to be experienced by the lamina cribrosa under elevated intra ocular pressure conditions. However, biomechanical compression was also predicted to be even more prevalent, although no good models existed to replicate this condition in vitro. It is for this reason that I have developed a novel model for replicating cellular compression by compressing the medium to which cells adhere in an equi-axial manner. Through careful calibration this model uses a device that is capable of generating specific and consistent amounts of compression by pre-stretching a sylastic membrane upon which cells are then seeded and cultured. The membranes are then removed from the device allowing them to return to their un-stretched state and compressing all cells that are attached. In this research I show how the model was designed and calibrated as well as its usefulness as an in vitro model for glial cell activation using biomechanical compression on human astrocytes and lamina cribrosa glial cells. Using advanced proteomic techniques, nearly 350 unique proteins of interest were observed to be regulated as a result of activation giving us significant insight into the pathways and networks involved in this process. Of particular interest are PEA15, RhoA, IL6, MMP2, HSP90, and FLNB. This model was also successfully used to target and block the actin stress fibre formation pathway, which is normally present in activated astrocytes. The results presented in this research give a powerful new model for examining the effects of cellular compression. It also provides insight into the networks and pathways associated with glial cell activation allowing us to better understand its role in the pathophysiology of glaucoma. This information will assist in efforts to understand the disease and develop better methods for detection, treatment and potential cure for this debilitating disease.
Aging and the Early Visual Pathways
Keywords: Aging
Perception
Vision
Visual Pathways

The role of aging on cognitive decline has been looked at with a great deal of interest over the past few decades. To a large extent, the aging literature has focused heavily on the impact of aging on memory and cognitive resources, and one area of literature that remains underdeveloped has been the role on how aging affects the cognitive processes of vision. More specifically â does aging change the activity and mutually inhibitory processes of the magnocellular (M) and parvocellular (P) pathways? In order to test how aging affects these two visual pathways, I implemented techniques known to hinder or bolster the M-pathway in younger adults with older adults. In Experiment 1, I tested if the inhibition of the M-pathway with a pulsed pedestal design also occurs with older adults. In this task, I had younger and older adults perceive low and high spatial frequency Gabors with either a pulsed or steady visual pedestal. In Experiment 2, I examined if the connection between the M-pathway and action processing found in younger adults changes with age. In Experiment 3, I examined the connection between object-based attention and the two visual pathways. Across the first three experiments, older adults showed a greater deficit to the M-pathway in the pulsed pedestal condition than younger adults. In Experiment 4, I examined if placing the hands proximal to visual images, which facilitates M-pathway processing in younger adults, also occurs in older adults. Here I found that older adults showed the opposite effect; greater advantage for low spatial frequency Gabors compared to younger adults when the hands were proximal. The data across all four experiments suggest that older adults may have noisier visual pathways, with larger deficits when the M-pathway is inhibited and larger benefits when the M-pathway is bolstered.
Nonlinear Dynamics of the Cosmic Neutrino Background
Keywords: Cosmology
Neutrinos

At least two of the three neutrino species are known to be massive, but their exact masses are currently unknown. Cosmic neutrinos decoupled from the rest of the primordial plasma early on when the Universe was over a billion times hotter than it is today. These relic particles, which have cooled and are now non-relativistic, constitute the Cosmic Neutrino Background and permeate the Universe. While they are not observable directly, their presence can be inferred by measuring the suppression of the matter power spectrum. This suppression is a linear effect caused by the large thermal velocities of neutrinos, which prevent them from collapsing gravitationally on small scales. Unfortunately, it is difficult to measure because of degeneracies with other cosmological parameters and biases arising from the fact that we typically observe point-like galaxies rather than a continous matter field. It is therefore important to look for new effects beyond linear suppression that may be more sensitive to neutrinos. This thesis contributes to the understanding of the nonlinear dynamics of the cosmological neutrino background in the following ways: (i) the development of a new injection scheme for neutrinos in cosmological N-body simulations which circumvents many issues associated with simulating neutrinos at large redshifts, (ii) the numerical study of the relative velocity field between cold dark matter and neutrinos including its reconstruction from density fields, (iii) the theoretical description of neutrinos as a dispersive fluid and its use in modelling the nonlinear evolution of the neutrino density power spectrum, (iv) the derivation of the dipole correlation function using linear response which allows for the Fermi-Dirac velocity distribution to be properly included, and (v) the numerical study and detection of the dipole correlation function in the TianNu simulation. In totality, this thesis is a comprehensive study of neutrino density and velocity fields that may lead to a new technique for constraining neutrino properties via the dipole correlation function.
Listening, Learning and Relationships: An Investigation of How Principals Facilitate Student Voice
Keywords: Principal Leadership
Relationships in Education
Student Empowerment
Student Engagement
Student Voice

The idea that students should play a greater role in their educational experience has emerged with fervor over the past twenty years. The importance of consulting students about their views of school and learning is not only progressively more accepted, it is becoming inscribed within policies and directives. Student voice is defined as pedagogies in which youth have the opportunity to influence decisions that will shape their lives and those of their peers inside and outside of school settings. The research shows an abundance of benefits that consulting students offers to both the students themselves and to schools. Lacking in the literature is research specifically examining the role of the school administrator in student voice initiatives. This qualitative study sought to investigate the experiences of elementary administrators who were committed to student voice. Twelve administrators from a variety of school boards in Ontario were interviewed about their experiences facilitating student voice. It was found that participants used similar strategies, and experienced comparable supports and constraints. When examining the external constraints, a richer picture emerged, which led to the examination of the student experience using a spectrum of student voice proposed by Toshalis and Nakkula (2012). Based on this, four participants were examined in further detail because they were the only administrators who experienced student voice within the classroom domain. The importance of bringing student voice into the classroom domain is discussed. The role relationships play in student voice was highlighted; parents, teachers, administrators, and of course students all impact student voice initiatives. In order for partnerships to happen, various stakeholders need to play a role, and thus suggestions are offered. Recommendations have been made for teaching the necessary skills to students, professional development for staff, parent involvement, suggestions for boards and Ministry and the necessity for developing the climate of the school. When relationships are at their best, it is more likely that student voice will meaningfully occur in both the school and the classroom domains.
Mining for the Future: Dynamics of Artisanal Gold Mining Practice and Governance in the Balan-Bakama (Mande, Mali)
Keywords: Africa
Extractive Industries
Gold
Mali
Mining
Modernity

This dissertation examines the social organization of artisanal gold mining in the Balan-Bakama, a zone of the Mande area of southern Mali (West-Africa). Based on fieldwork conducted primarily in 2010-11 I show how villagers and specifically their male and female mining authorities govern mining sites in the territory of their village. Unlike many artisanal mines that are described in the literature as enclaves disconnected from surrounding communities, Balan-Bakama artisanal mines are part of a locally placed extractive economy. Most inhabitants of the Balan-Bakama are both subsistence farmers and artisanal gold miners (at home or as seasonal migrants). These livelihood activities had traditionally been bound to the rainy season and dry season respectively. With a steadily rising gold price, women miners were increasingly engaged in rainy season surface mining while men mined using the new hard-rock mining technique. With placer mining, these techniques form the set of three artisanal mining techniques applied in the Balan-Bakama. In Mande, gold is categorized as owned by bush spirits who control the uncivilized space beyond villagersâ fields. In order to be able to mine safely and successfully, communities and individual miners are obliged to convince bush spirits to share their gold with humans and to refrain from causing accidents. People are able to gain access to gold through sacrifices, by following the rules of mining sites and by avoiding conflict. If local miners are successful, they will be joined by seasonal migrant miners. In an area characterized by high rural-urban migration but some rural-rural migration, village communities try manipulate migration patterns by stimulating mining to retain young men. Hoping to expand the village in order to achieve a locally defined modernity and form a closer connection to regional centers villagers work to attract informal miners and industrial mining corporations.