VictorJuiz/thesis huggingface dataset:
The Influence of Curvature on Mantle Convection featuring a Temperature-dependent Viscosity
Keywords: curvature
mantle convection
Mercury
secular cooling
stagnant-lid convection
viscosity

Convection in the silicate mantles or ice layers of terrestrial planets and moons is characterized by a strongly temperature-dependent viscosity. Mantle convection regime is first examined in 2D and 3D spherical geometry with varying mantle curvature (core-to-surface radii-ratio, f) and constant heating conditions and viscosity contrast across the mantle depth (ΔηT). The onset of the stagnant-lid regime occurs for different conditions for bodies with relatively small cores and relatively thin shells. Differences in mean temperature and flow fields observed between 2D and 3D geometry are amplified as relative core-size is decreased. This finding has implications for modelling the thermal evolution and evaluating heat extraction from the cores of small moons or dwarf planets. Next, I consider evolving conditions for a body the size of the Earth's Moon with f = 0.5. Typically, modelling methods employ a ΔηT that does not encompass the entire effective range of values for ductile flow. This may result in spurious changes in convective regime and overestimate heat extraction from the core. Improving upon conventional methods for viscosity modelling, I employ a novel constant-viscosity contrast modelling method that emulates a large effective viscosity contrast ΔηT = 10^10. With this adjustment, regime change is suppressed in the calculations tested. Moreover, the modelling approach I propose may be less computationally intensive and save resources. The generation of a magnetic field is associated with plate-tectonics because efficient heat extraction is required at the core-mantle boundary. However, the planet Mercury, which does not have plate-tectonics, features a magnetic field. The work presented concludes by investigating the evolution of the Mercurian mantle. I propose that an increased mantle thermal diffusivity due to an iron-poor composition results in a conducting mantle at present that is compatible with the heat extraction required by Mercury's magnetic field strength. The possibility of higher core heat extraction as follows a mantle transitioning from stagnant-lid convection to conduction may explain the origin of the Mercurian magnetic field.
Stressed, Sick, and Sad: A Transdiagnostic Investigation of the Translation of Stress into Depression through Neuroendoimmune Disruptions
Keywords: depression
HPA axis
neuroendoimmune
proinflammatory immune

Depression is a prevalent and disabling form of psychopathology that is frequently precipitated by experiences of stress. Disruptions in stress-sensitive biological systems, notably the immune system and hypothalamic-pituitary-adrenal axis, are strongly implicated in depression, and disturbances in these systems could reflect potential pathways through which experiences of stress are translated into depression. These systems, broadly subsumed within the neuroendoimmune system, may be highly responsive to stress and cognitive abilities related to stress management. To characterize the links between stress and depression and the potential influence of immune activity, the present study investigated the following: (1) the associations among perceived stress (across different time periods of life), proinflammatory immune markers, and depressive symptoms; (2) whether neuroendoimmune activity mediates the relationship between perceived stress and depressive symptoms; and (3) whether perceived stress and immune activity mediate the relationship between cognitive control and depressive symptoms. Fifty-nine medically healthy adult females with varying levels of depression participated in the study. Participants provided dimensional ratings of their depression symptoms and perceived life stress, and they completed a neuropsychological test of cognitive control. Plasma biomarkers of stress, including pro-inflammatory cytokines, C-reactive protein, and free cortisol, were assayed following a fasted morning blood draw. Consistent with hypotheses, both greater perceived stress and higher concentrations of the proinflammatory immune marker, interleukin-6 (IL-6), were associated with greater depressive symptoms. Although levels of IL-6 alone did not significantly mediate the relationship between perceived stress and depressive symptoms, when considered together, elevated concentrations of IL-6 and lower free cortisol mediated the relationship between severity of childhood stress and current depressive symptoms. Contrary to expectations, cognitive control was not significantly associated with stress, immune markers, or depression. The findings are interpreted in the context of a potentially long-term reduction in glucocorticoid tone triggered by early life stress that curbs cortisol output, produces chronic low-grade immune activation, and leads to depression vulnerability later in life. Overall, the study provides new insights into potential pathways among stress, the neuroendoimmune system, and depression, shedding light on how early life stress may be translated into depression in adulthood.
Interpersonal Perceptions of Mental Fatigue Vary with Willpower Theories
Keywords: attributions
excuses
lay theories
person perception
self-control
social support

Some people, to varying degrees, believe that self-control becomes depleted with use. People with limited theories of willpower report that engaging in a strenuous mental activity causes them to be fatigued and unable to continue, while those with more nonlimited theorists report that they can do mental work without becoming depleted. Willpower theories may not only affect people’s own experiences of depletion, but may also affect their interpersonal perceptions and reactions. Chapter 2 first describes how people’s willpower theory affects their judgements of a target person based on knowledge of the target’s prior activity. A target who just engaged in an effortful activity (e.g., exam writing, working) is generally seen as less able (and fatigued) according to more a limited theorist, but the same target is seen as more able (and hardworking) according to a more non-limited theorist. These differing perceptions can affect partner selection (Chapter 2) and effort exertion during teamwork tasks (Chapter 3). In Chapters 4-6, I examine whether people are more compassionate or forgiving of a target’s self-control failure, if they perceive that target as potentially depleted due to prior mental exertion. Limited willpower theorists were no more likely to attribute a stranger’s poor exam grade to depletion (Chapter 4), but they did respond more compassionately to their romantic partners’ irritating behaviours when their partner was seen as potentially fatigued (Chapter 5). Seeing that limited willpower theorists were more in-tune to their partner’s potential depletion, Chapter 6 examines whether willpower theory affects people’s intentions to support their romantic partners in everyday life. This daily diary study found that limited theorists were more likely to see their partners as fatigued, but were also more likely to experience fatigue themselves – ultimately, limited willpower theorists were less likely to intend to provide support. Overall, this dissertation finds that self-theories of willpower can affect how people understand to and respond to the behaviour of others. However, while those with more limited willpower theories are more likely to perceive fatigue in other people, they are not necessarily more likely to respond with compensatory effort or additional support.
Fundamentals of Porphyrin-lipid J-aggregation in Nanomedicine
Keywords: bacteriochlorophyll
fluorescence
lipoprotein
liposome
photoacoustics
photothermal

Nanomedicine takes advantage of new, medically useful properties that arise from nanoscale control of material composition and structure. This thesis investigates a nanoscale photophysical phenomenon called J-aggregation within the context of porphyrin-lipid nanomedicine. Porphyrins are endogenous chromophores medically used as photosensitizers and optical imaging agents. Conjugating porphyrins to lipids enables their self-assembly into lipid nanoparticles. Interactions between porphyrins in the nanoparticle lipid membrane changes their photophysical properties. J-aggregation occurs when porphyrins are aligned head-to-tail and results in a dramatic red-shift in the absorption spectrum. Because J-aggregation relies on nanoscale dye–dye ordering it is sensitive to external stimuli that impact membrane structure, including temperature and interactions with biological species. In Chapter 1, porphyrin-lipid nanomedicine is first contextualized within the nanomedicine field. In Chapter 2, a background is provided on the mechanisms that alter the photophysical properties of dyes in nanomedicines and porphyrin J-aggregation is specifically reviewed. Chapter 3 examines the nanostructure-dependent photophysical properties of porphyrin-lipid aggregates in lipid membranes. Chapter 4 investigates the optical stability of J-aggregating porphyrin-lipid nanoparticles during exposure to serum proteins. Chapter 5 explores the potential utility of these J-nanoparticles for phototherapy and optical imaging applications. Lastly, Chapter 6 presents a discussion of new knowledge gained and potential future directions. From these fundamental studies, an assessment is provided of whether the unique nanostructure-dependent photophysical properties of J-nanoparticles are also potentially medically useful.
Activation and Stabilization of the Caspase-8 Survivalsome is Indispensable for Functional Toll-like Receptor 4 Dependent Signaling in Septic Neutrophils
Keywords: Apoptosis
Caspase-8
Inflammation
Neutrophil
Signalling
Toll-Like Receptor-4

Sepsis, defined as life-threatening organ dysfunction caused by a dysregulated host response to infection, is a complex, heterogenous, and redundant syndrome that is the leading cause of mortality in intensive care units worldwide. We investigated signalling mechanisms that mediate activation and termination of the response to infection by neutrophils – circulating white blood cells that are the primary agents of the early host response. While a failure of activation impairs antibacterial defenses, failure in terminating that response through a process called apoptosis contributes to systemic inflammation and tissue injury in septic patients. By investigating the intracellular biology that controls neutrophil activation and termination, we sought to identify potential targets to treat clinical sepsis. Using healthy human and septic patient neutrophils, we first showed the function of caspase-8, the apical caspase in the extrinsic cell death pathway, is modified by its phosphorylation. Caspase-8 tyrosine phosphorylation at tyrosine-380 established an anti-apoptotic signaling module we termed the survivalsome that promoted neutrophil III survival. Conversely, caspase-8 dephosphorylation at tyrosine-380 prevented survivalsome assembly and induced caspase-3 dependent neutrophil death. By inducing sepsis in a caspase-8 deficient mouse model, we demonstrated that in vivo caspase-8 deletion significantly reduces mortality, accelerates bacterial clearance, and limits lung injury. Serendipitously, we found an association between the variability of neutrophil response to lipopolysaccharide with caspase-8 variant expression. Neutrophils coexpressing both caspase-8 A and B isoforms demonstrated lower rates of apoptosis from baseline following lipopolysaccharide stimulation versus neutrophils expressing only A or B. Expression of caspase-8 isoforms further correlated with multiple organ dysfunction score and white blood cell count in septic patients. Since caspase-8 is phosphorylated in response to lipopolysaccharide, we investigated whether caspase-8 tyrosine phosphorylation at tyrosine-380 is required for functional Toll Like Receptor 4 (TLR-4) signal transduction. Using healthy human and septic neutrophils, we showed th ipopolysaccharide-induced TLR-4 activation increases caspase-8 tyrosine phosphorylation and MyD88 receptor-mediated signaling to trigger NF-B translocation and pro-inflammatory gene transcription. Finally, this PhD thesis uncovered a mechanism that stabilizes Src-induced caspase-8 tyrosine phosphorylation for phosphoinositide 3-kinase activation: heat shock protein 90 prevents ubiquitin-mediated degradation of caspase-8 and c-Src to prolong inflammatory neutrophil survival.
Understanding the Complexity of Falls and Fall Prevention for Wheelchair Users with Spinal Cord Injury across the Continuum of Care
Keywords: fall prevention
falls
spinal cord injury

Wheelchair users with spinal cord injury (SCI) are at a high risk for falls; however, our understanding of falls and fall prevention in this population remains limited. This thesis, which is comprised of four studies, aimed to advance knowledge in these areas by exploring: (1) the challenges faced by administrators when implementing fall prevention policies and practices in SCI rehabilitation centres, (2) the factors that influence falls/fall risk for wheelchair users with SCI, (3) the psychosocial impact of falls, and the risk of falling on the lives of wheelchair users with SCI, and (4) the perspectives of wheelchair users with SCI on fall circumstances and fall prevention strategies/interventions. Findings from the first qualitative study in this thesis revealed that administrators (n=10) faced challenges with the fall prevention policies/procedures (e.g. not SCI-specific), clinicians (e.g. variable staff adherence), and patients (e.g. balancing risk vs. rehabilitation progress). In study two, photo-elicitation interviews conducted with wheelchair users with SCI (n=12) revealed one overarching theme (i.e. individualized, dynamic, and complex fall risk factors) and four themes: (1) falls and fall risk caused by multiple interacting factors; (2) dynamic nature of fall risk; (3) single factors perceived to reduce falls and fall-related injuries; and, (4) fall prevention experiences and priorities). In study three, photo-elicitation interviews conducted with wheelchair users with SCI (n=12) revealed two themes: (1) varying concern about falling/impact of falls; and (2) fear, falling, and limitations impact daily activities, parenting, work, and leisure/recreation. In study four, thirty-two wheelchair users with SCI participated and more than half of these participants reported a fall over six months. Most fell indoors, in the afternoon, and while transferring or wheeling over uneven ground. Two main themes were identified in study four from a photovoice focus group discussion with wheelchair users with SCI (n=11): circumstances surrounding the falls and preferences for fall prevention strategies/interventions. Current fall prevention approaches fail to meet the complex, dynamic, and individualized fall prevention needs of wheelchair users with SCI, and the psychosocial consequences that could arise from a fall or risk of falling. This thesis advances knowledge to guide fall prevention initiatives for this population.
Culture, Institutions and Development in Africa
Keywords: agriculture
culture
development
institutions
security

In my dissertation I explore the economic development of Sub-Saharan Africa with a particular focus on the role played by institutions and culture. In the first chapter, The Fruits (and Vegetables) of Crime, I provide experimental evidence that weak institutions that are unable to provide full protection of farm output causes distortions to agricultural production and reduced output as well as imposing social costs through local disputes. In the second chapter, How Cultures Converge with Arthur Blouin, we show, using a novel empirical approach identifying loanwords among languages, that the rate and direction of cultural convergence is endogenous to economic incentives and is shaped by strategic decisions reflecting these incentives. Finally, in the third chapter, Pumps, Prosperity and Household Power with Jeremy Shapiro, we provide experimental evidence that distributing small-scale irrigation pumps to women in farming households is an effective intervention to increase incomes and empowerment of women, in a context where institutional capacity has long constrained the adoption of large-scale irrigation investments.
Targeting the Mitochondrial Peptidase Neurolysin in Acute Myeloid Leukemia
Keywords: AML
metabolism
NLN
respiratory chain supercomplexes

Acute myeloid leukemia (AML) cells and stem cells have unique mitochondrial characteristics with an increased reliance on oxidative phosphorylation (OXPHOS). Through a genetic screen to find novel mitochondrial targets in AML, we identified the mitochondrial peptidase, neurolysin (NLN). NLN is a metallopeptidase whose mitochondrial function is not well understood and whose role in AML has not been reported. We analyzed the expression of NLN in AML cells and normal hematopoietic cells. NLN gene expression was enhanced in 41% of AML samples and overexpression was confirmed by immunoblotting. Next, we assessed the effects of knocking down NLN in AML cell lines. NLN knockdown reduced AML growth by up to 70%, clonogenic growth by up to 80%, and engraftment into mouse marrow by 90%. We next identified NLN’s mitochondrial interactors by BioID-MS. NLN interacted extensively with the respiratory chain and NLN knockdown reduced OXPHOS. Moreover, NLN knockdown impaired the formation of respiratory chain supercomplexes (RCS), which promote efficient oxidative metabolism. RCS have not been previously studied in leukemia. We found that RCS assembly was increased in a subset of AML patients compared to normal hematopoietic cells and positively correlated with NLN protein expression (R2 = 0.80, p
Quantum Homomorphic Encryption: Implementation and Applications
Keywords: Cryptography
Homomorphic Encryption
Metrology
Super-resolution imaging

As the field of quantum information as a whole continues to see sustained and rapid progress, two sub- disciplines distinguish themselves as having had particularly noteworthy recent developments: quantum cryptography and quantum metrology. Of late, quantum cryptography has had a renaissance of sorts as techniques in classical post-quantum cryptography (i.e. classical schemes believed to be robust against attacks by a quantum computer) mature, making it possible to construct more elaborate and flexible quantum+classical schemes. A particularly interesting offshoot is the construction of quantum homomorphic encryption (QHE) which allows anyone in possession of a ciphertext to perform an arbitrary computation directly without having to decrypt beforehand. We describe the construction and experimental implementation of a QHE scheme which, unlike previous schemes that have focused on the use-case of delegating computation to an untrusted party, is flexible enough to serve as a primitive for much wider gamut of cryptographic applications. In quantum metrology, the gradual but continued adoption of rigorous analyses and bounds borrowed from classical statistics increasingly puts claims of quantum metrological advantage on more solid footing. Recently, an exciting insight stemming from these systematic analyses is that the Rayleigh criterion, long seen as a fundamental resolution limit in imaging with finite-sized optics, is not so fundamental after all. Leveraging this realization, in this thesis we describe the construction and implementation of a set of measurements (nicknamed “SPLICE”) that outperforms traditional imaging in its ability to resolve two arbitrary point sources separated along a known axis.
Management Going Concern Disclosure
Keywords: Accounting Standards
Corporate Failure
Going Concern
Management Disclosure
Textual Analysis

An entity’s ability to continue as a going concern (GC), or the ability to fulfill obligations when they become due, is one of the key concerns of businesses, investors, and policymakers. My dissertation provides a comprehensive study of management GC disclosures and generates insights that are timely and highly policy-relevant. Chapter one examines management GC disclosures after the implementation of ASU 2014-15, a new accounting standard issued by the FASB requiring management to evaluate GC uncertainties quarterly and to provide disclosures in the notes to the financial statements. I first show that the market reacts negatively to such disclosures overall. More importantly, by employing highly detailed textual analysis to extract and categorize mitigation-plan discussions, I find that certain types of management mitigation plans are interpreted positively by investors, thereby alleviating the negative market reactions. These plans include selling assets, increasing liquidity through debt, equity, and grants, and revenue-enhancing strategies. Further, I demonstrate that management GC disclosures are associated with corporate failures and that mitigation-plan discussions can indicate firms’ future viability. Chapter two focuses on management strategic behavior related to avoiding GC disclosures. Managers contemplate potential consequences to decide whether to disclose GC uncertainties. Chapter two explores how to separate “strategic firms” - companies with substantial doubt in GC but whose managers do not provide adequate disclosures - from “truthful firms.” Employing a linguistic model built based on textual features extracted from the Q sections of conference calls for distressed firms, I demonstrate that the strategic executives talk longer and in a less negative tone. The strategic executives are more likely to use deceptive language and to mention non-GAAP measures and macroeconomic information and are less likely to discuss litigation and liquidity matters. I further extend the linguistic model to the non-distressed sample and predict the strategic scores indicating whether firms have GC uncertainties but withhold such disclosures. I find that the strategic firms are less likely to mention the word “going concern” in the financial reports and tend to increase their leverage after a new GC standard - ASU 2014-15 - was issued by the FASB.