VictorJuiz/thesis huggingface dataset:
Multiplication of Generalized Affine Grassmannian Slices and Comultiplication of Shifted Yangians
Keywords: Geometric representation theory

Given a semisimple algebraic group G, shifted Yangians are quantizations of certain generalized slices in G((t-1)). In this thesis, we work with these generalized slices and the shifted Yangians in the simply-laced case. Using a presentation of antidominantly shifted Yangians inspired by the work of Levendorskii, we show the existence of a family of comultiplication maps between shifted Yangians. We include a proof that these maps quantize natural multiplications of generalized slices. On the commutative level, we define a Hamiltonian action on generalized slices, and show a relationship between them via Hamiltonian reduction. This relationship is established by constructing an explicit inverse to a multiplication map between slices. Finally, we show that the above relationship lifts to the Yangian level.
Trends in the Frequency of Extreme Temperatures for Canadian Urban Centres from 1971 to 2000
Keywords: Canada
Climate Change
Extremes
Temperature
Trends
Urban Heat Island

Extreme temperature trends for Canadian urban centres during the latter portion of the 20th century were explored in four complementary research studies. The analysis used a novel methodology of frequency of extreme occurrences using extreme temperature records as the metric. A second methodological innovation, day-to-day temperature variability, was used to characterize climate stations as urban, rural and peri-urban. The first study examined extreme temperature seasonal trends for five stations in the Greater Toronto Area over a 30-year period. This analysis also completed a 50-year annual extreme temperature analysis for two of the stations. Statistically significant decreases in extreme minimum temperature counts annually and seasonally, in the spring and winter months, indicated localized urban heat islands were present. The second study characterized urban-rural station pairings for Vancouver, Edmonton, Montreal and Halifax using day-to-day temperature variability. A subset of the urban stations were identified as peri-urban using this analysis. The third study using these characterizations examined annual extreme temperature record counts for 14 stations across four urban centres in Canada. Urban and peri-urban stations had statistically significant decreasing extreme cold temperature record counts while rural stations tended not to. The coincident increase in minimum temperatures was indicative of urban heat island development. Montreal experienced statistically significant decreases at all stations that likely indicated an underlying localized climate change signal or nascent urbanization at the local rural station. Edmonton experienced an above average warm 1980s and thus net temporal trends in extreme temperature record counts were not evident. In the fourth study, the results of the frequency of occurrence analysis for Halifax were compared to standard climate extreme indicators. The comparison of the results determined that the frequency of occurrence methodology aligned with the more generally used climatic indicator findings. These studies have indicated that the extreme frequency of occurrence and day-to-day variability methodologies could be effectively used in climate data analysis. These studies have also shown that trends in extreme minimum temperatures have decreased more rapidly than extreme maximum temperatures have increased for multiple urban centres across Canada for the latter portion of the 20th century.
Small NGOs in Global Governance: Agenda Setting in the Governance of Biodiversity and Wildlife
Keywords: advocacy networks
agenda setting
civil society
conservation
global governance
nongovernmental organizations

International relations theories have conceptualized nongovernmental organizations (NGOs) as, inter alia, agenda setters for global governance. To date, existing research on NGO agenda setting has overwhelmingly focused on how advocacy is supplied by well-established, leading NGOs, but overlooked how and why advocacy is demanded in the first place. Contrary to the assumption that small NGOs are "bandwagoners," I argue that small NGOs substantially influence the variation of issue salience in a given issue area due to the interdependence of demand and supply in the advocacy market. Drawing on the insight of public opinion research, I argue that the demand for advocacy is concentrated in a small segment of the public, referred to as the issue public. Leading NGOs cannot target their advocacy to the issue public alone because they cannot maintain their social and economic resources with a small segment of the public. By contrast, small NGOs can frame their advocacy to resonate with the identities and shared values of the issue public. The stability of attention from the issue public legitimates small NGOs' agenda and allows them to exercise influence over policymakers with expert knowledge. The implications are important: the existing literature overestimates the agenda-setting power of leading NGOs while trivializing small NGOs' issue entrepreneurship. I evaluate my theory in the issue area of biodiversity and wildlife conservation to overcome a persistent problem in the study of NGO agenda setting: selection bias. As NGOs cannot advocate for non-existent species, all conservation issues are observable regardless of the outcome of advocacy work. Three empirical tests were conducted. First, I quantitatively explored the relationship between small NGOs and issue salience among Northern publics, leveraging the computational text analysis of 20,000 newspaper articles and 350,000 mission statements. Second, I analyzed the causal linkage between types of NGOs, locational issue characteristics, and their interaction with survey experiments in Canada, the United Kingdom, and Germany. Finally, I qualitatively investigated the recent case of issue emergence, pangolin (scaly anteater) conservation, through in-depth interviews. I conclude with the reviews of my overall findings and contributions and potential applications for future research.
Second Order Inference in Locally s=Stationary Time Series
Keywords: consistent estimate
convergence rate
local stationarity
long-run variance
threshold estimator
time series

In second-order statistical inference, an interval estimate of autocorrelation is a convenient reporting form of a popular dependence measure. Construction of such a confidence band usually requires the estimation of long-run variance (LRV), a limiting variance in the central limit theorem. It is also a fundamental part of heteroscedasticity and autocorrelation-consistent (HAC) estimates for the variance of regression coefficients. For stationary processes, these questions are well investigated. However, real phenomena require non-stationary processes for modeling. The local-stationary model allows for the adaptation of the estimate from a stationary time series. In 2015 [Zha15], Zhao proposed a confidence band construction for local autocorrelation, based on non-linear filters over i.i.d. innovations. However, this result depended on an unknown LRV of the unobserved process, based on the lagged product ratio of the original time series. We managed to construct an estimate of the lacking quantity, to prove its consistency and inclusion in Zhao’s extreme value theorem for autocorrelation. Simulations confirmed the validity of the estimate and the asymptotic coverage probability of the band. As well, an LRV estimator, based on thresholding technique, was experimentally investigated. Its performance was measured against the industry-standard benchmark.
What Happens when the Uber Tailpipe Smoke Clears: An Examination of the Impacts of Ride-hailing in Canada
Keywords: Emerging transportation technologies
Ride-hailing
Shared mobility
Sustainable transportation
Transportation policies
Uber

Despite starting as a more convenient way to hail taxis, ride-hailing services (e.g. Uber and Lyft) have rapidly evolved into much more with the introduction of their peer-to-peer services in 2014. By no longer confining their algorithms to matching passengers with taxis, and allowing private vehicle owners to also serve as drivers, ride-hailing companies drastically expanded their pool of available drivers and experienced monumental growth in the process. Ride-hailing services have now become ubiquitous in the urban mobility landscape of cities worldwide, and have rapidly positioned themselves among the most valuable companies within the transportation sector. Yet, despite their growing role within cities, the impacts of this mode remain contested and largely misunderstood. The purpose of this dissertation is to explore several of the key impacts of ride-hailing on existing transportation systems and their users within the Greater Toronto Area and assess whether policies should be developed to encourage or deter its usage. In Chapter 2, I identify potentially marginalized groups – both socioeconomically and spatially – that may be excluded from ride-hailing, and define improvements to the data collection process that must take place to ensure ride-hailing limits transport inequalities. I further expose how the benefits of this mode may not be distributed equally in Chapter 3 by exploring the socioeconomic and trip characteristics of ride-hailing users. In Chapter 4, I show that ride-hailing behaves both as a substitute and supplement to transit, and demonstrate the need to consider trips individually. Chapter 5 focuses on shared ride-hailing services, and identifies factors that influence the matching propensity and detour penalty associated with shared trips. Lastly, Chapter 6 is my attempt to partake in the broader ride-hailing regulation discussion, as I caution against the premature legalization of this service. Together, the results of this research substantially improve our understanding of the many ways in which ride-hailing services impact our cities, and offer a practical contribution to policymakers seeking to properly regulate this service.
Pattern Scaling Methods for Understanding the Response to Polar Sea Ice Loss in Coupled Earth System Models
Keywords: climate
polar climate
sea ice

The response to polar sea ice loss is separated, using dedicated coupled modelling experiments and multi-parameter pattern scaling, from the response to tropical warming and from general greenhouse warming. In the first chapter, the motivation for this work is presented with an overview of the existing literature and knowledge gaps. The second chapter presents a cross-comparison of the atmospheric near-surface sensitivity of two coupled models to Arctic sea ice loss and to low-latitude warming. The models agree well with more similarities found in the sensitivity to sea ice loss than to low-latitude warming. Warming and moistening of the Arctic, a dipole of sea level pressure between Eurasia and North America, and an equatorward shift in 850 hPa winds is found to scale with sea ice loss. In the third chapter, a larger pool of coupled experiments are used that largely confirm the results of the previous chapter. This chapter also covers the sensitivities of the zonal mean atmospheric circulation. Two-parameter pattern scaling of the surface ocean is carried out for the first time, and, unlike the atmosphere, the sensitivity to low-latitude warming is more robust than to sea ice loss. The subpolar North Atlantic is found to be a region of poor inter-model agreement due to complex dynamics and non-linearities, but qualitatively consistent signals can be found in response to sea ice loss; deep water formation decreases in the Labrador Sea and the meridional overturning circulation weakens. In the fourth chapter, the focus is expanded to include the impacts of Antarctic sea ice loss. New simulations are carried out to assess the response to sea ice loss in either hemisphere separately or coincidentally under different albedo parameter settings. Contrary to expectations, the response to Antarctic sea ice loss, mediated by tropical warming, is non-negligible in the Northern Hemisphere. With these new simulations, three-parameter pattern scaling is derived and we simultaneously compute the sensitivities to Arctic sea ice loss, Antarctic sea ice loss, and tropical warming, with a focus on the Northern Hemisphere's response. Finally in the fifth chapter, the results are summarized and remaining knowledge gaps are highlighted alongside suggestions for future work.
Suboptimal Immune Restoration in People Living with HIV
Keywords: Clinical Trials
HIV
Immunologic Non-Response
Inflammation
Probiotics

Despite antiretroviral treatment (ART), people living with HIV continue to have a reduced life expectancy compared to the general population. During HIV infection, non-AIDS health burdens, such as cardiovascular or liver disease, are explained only in part by lifestyle factors, and are thought to be driven in part by chronic systemic immune activation. Moreover, immunologic non-responder (INR) individuals are a subset of people living with HIV who, despite virally suppressive ART, do not achieve optimal CD4+ T cell numbers in blood (typically to >350 cells/mm3); these individuals are at increased risk of adverse health events, and are a worthy target of interventional studies, including those of popular alternative therapies. First, I hypothesized that HIV-positive INR individuals would have increased peripheral CD8+ T cell activation, as measured as percent co-expression of HLA-DR and CD-38, a combination of markers that is linked to disease progression in untreated HIV infection. In a cross-sectional study I confirmed that INR individuals had elevated peripheral CD8 activation and also increased CD4+ T cell activation, measured by the percent expression of HLA-DR. Using validated markers as an outcome, I next assessed whether a complementary therapy intervention reduces these parameters. In a randomized, double-blinded, placebo-controlled phase 2b clinical trial, I assessed whether 48 weeks of probiotic supplementation reduced systemic immune activation in the INR context. Not only was no reduction observed in association with probiotic supplementation on CD8+ T cell activation, but in fact CD4+ T cell activation actually increased in the active drug arm. Finally, I assessed whether probiotic supplementation improved markers of gut immune function. Nested in part within the clinical trial, a predefined mucosal sub-study observed no changes associated with probiotic supplementation in gut T cell function or subset composition. Nevertheless, INR individuals had a unique gut immunopathologic profile, including, surprisingly, an upward skewing in the Th17 cell proportion and an increase in the Th17/Treg ratio. These findings emphasize not only that systemic immune activation during HIV-associated suboptimal immune restoration is a persistent problem, and that probiotic therapeutics are unlikely to confer a benefit, but also that gut immunopathology in INR individuals remains insufficiently understood.
Quadratic Poisson Brackets and co-Higgs Fields
Keywords: co-Higgs fields
Poisson brackets

This thesis is devoted to studying the geometry of holomorphic Poisson brackets on complex manifolds. We concentrate on the case when the underlying manifold admits a structure of a vector bundle, and the Poisson bracket is invariant under the dilation action of the multiplicative group of the field of complex numbers. We call such a Poisson bracket quadratic, and associate to it a Higgs type tensor, which we call a co-Higgs field. We study the interplay between these two geometric structures. A parallel theory is developed for Poisson brackets on projective bundles. Using the classical tool of the spectral correspondence available for co-Higgs fields, we construct many new examples of Poisson brackets, and provide new classification results in low dimensional cases. Most notably, we provide a classification of Poisson brackets on rank two projective bundles over the Riemann sphere, under a mild restriction on the underlying co-Higgs field.
Structural Insights into AAA+ Unfoldases and Associated Proteases
Keywords: ATPase
CryoEM
NMR
Protease
Protein
Unfolding

Ring-shaped unfoldases of the AAA+ (ATPases Associated with a variety of cellular Activities) su- perfamily are responsible for the dismantling or remodelling of various protein complexes in the cell. These hexameric enzymes utilize energy from ATP hydrolysis to unfold client proteins, often passing them to proteases to be recycled into their amino acid components. Investigating the interplay between AAA+ motors, proteases, and substrates is key to understanding protein homeostasis in the cell. To investigate these systems, a combined structural approach using single particle electron cryomicroscopy (cryo-EM) and Nuclear Magnetic Resonance (NMR) spectroscopy was taken. Utilizing these approaches enabled structural insights into the archaeal Cdc48 system from Thermoplasma acidophilum, as well as the bacterial ClpP systems from Staphyloccoccus aureus, Mycobacterium tuberculosis, and Neisseria meningitidis. Our results illustrate several mechanisms of allosteric control, as well as protein-protein interactions that are important for proper function.
The Free Energy of Spherical Vector Spin Glasses
Keywords: free energy
Parisi formula
spherical models
spin glasses
vector spins

We study a class of vector spin models with configurations restricted to subsets of the sphere. We will prove a constrained free energy formula for these models. This formula defines a large deviations principle for the limiting distribution of the overlaps under the asymptotic Gibbs measure. The thesis builds on the mathematical results used to prove free energy formulas for the classical Sherrington–Kirkpatrick spin glass, spherical spin models, and vector spin glass models. The free energy formula proved in this thesis are true generalizations of the classical results, in the sense that these vector spin formulas restricted to one dimension coincide with the known results for classical models. The first contribution of this thesis is a variational formula for contrained copies of classical spherical spin glasses sampled at different temperatures. The free energy for multiple systems of spherical spin glasses with constrained overlaps was first studied by Panchenko and Talagrand. They proved an upper bound of the constrained free energy using Guerra’s interpolation. In this thesis, we prove this upper bound is sharp. Our approach combines the ideas of the Aizenman–Sims–Starr scheme and the synchronization mechanism used in the vector spin models. We derive a vector version of the Aizenman–Sims–Starr scheme for spherical spin glass and use the synchronization property of arrays obeying the overlap-matrix form of the Ghirlanda–Guerra identities to prove the matching lower bound. The second contribution of this thesis is the simplification of this variational formula to the form originally discovered for the classical spherical spin glass model by Crisanti and Sommers. In particular, we prove the analogue of the Crisanti–Sommers variational formula for spherical spin glasses with vector spins. This formula is derived from the discrete Parisi variational formula for the limit of the free energy of constrained copies of spherical spin glasses. In vector spin models, the variations of the functional order parameters must preserve the monotonicity of matrix paths which introduces a new challenge in contrast to the derivation of the classical Crisanti–Sommers formula.
Basing Clinical Decision on GRADE recommendations: Implications for Practice and Lessons Learned about Evidence
Keywords: clinical practice guidelines
Evidence based medicine
GRADE

The Grading of Recommendations Assessment, Development and Evaluation (GRADE) framework was developed as an evidence based approach to translating research evidence to clinical practice through recommendations. GRADE has become widely adopted by key healthcare stakeholders, and thus, recommendations derived using the framework have important implications on the care people receive, worldwide. The main activities of GRADE are: 1) assessing the quality/certainty of evidence, and 2) making a recommendation about how to manage the care of a patient with a specified disease or health condition. The assessment of evidence quality/certainty is based on a hierarchy of evidence, similar to that made popular by the Evidence Based Medicine (EBM) movement. In making a recommendation, users of the framework are to consider several factors, including quality of evidence, resource implications, and values and preferences of “typical” patients. Recommendations carry with them instruction on how to engage the patient in the clinical encounter. Despite its popularity and several modifications to the framework, GRADE has received little scrutiny regarding its structure and usefulness. When examined, several problems for patient care in the clinical encounter become apparent, stemming from a lack of a clear and justified theoretical and empirical basis. These problems pertain to GRADE’s narrow view on evidence, emphasis on average effects (both therapeutic effect estimates and patient “values and preferences”) derived from populations, and apparent promotion of paternalism. The result is one cannot know whether the use of GRADE is helpful or harmful for patient care. An examination of GRADE reveals several lessons for clinical decision making. First, judgment is unavoidable – even the framework relies on judgment of its users in assessing the quality and relevance of information as evidence and weighing that with other considerations. Second, a wide view on evidence may be necessary to understand what will help the patient. Finally, knowledge generation and its use for clinical practice is ultimately a social activity, one that is best facilitated through a process of deliberation. Thus, I put forward the thesis that clinical decisions require judgment, a broad view on evidence, and deliberation, something that cannot be replaced by a procedural framework.