VictorJuiz/thesis huggingface dataset:
Energy Flow and Food Web Ecology along a Hydroperiod Gradient
Keywords: aquatic
stable isotopes
amphibians
invertebrates
disturbance
wetland

Identifying the ecological mechanisms that determine food web structure is critical for understanding the causes and consequences of diversity. The objective of this thesis was to identify the mechanisms structuring aquatic food webs across environmental gradients from a multi-level perspective (individual to ecosystem) using integrative methodology and field experiments to test classic ecological theory. My results demonstrate support for the dynamic constraints hypothesis, which predicts habitats with greater disturbance should have shorter food chains, but are not consistent with the ecosystem size hypothesis that predicts larger ecosystems have longer food chains. Insect and amphibian richness increased with increasing pond size and hydroperiod, indicating that insertion of new consumers into pond communities was driving variation in food-chain length. A multivariate analysis testing the influence of physicochemical variables on food-web characteristics revealed that hydroperiod and pond area had a strong influence on amphibian and invertebrate assemblages, trophic diversity and 15N range. Food-chain length did not respond strongly to any one variable, but instead responded weakly to multiple environmental variables, suggesting interacting influences on food-web structure. Conversely, the trophic niche of amphibian larvae was not influenced by pond hydroperiod, but did exhibit ontogenetic diet shifts. Populations of amphibian larvae with broader niche widths also had increased individual variation, supporting the niche variation hypothesis. In addition, I assessed whether species diversity influenced the magnitude of cross-habitat resource flow between aquatic and terrestrial habitats via emerging aquatic insects, metamorphosing amphibians, and litter deposition. Deposition into ponds far exceeded carbon exported via insect and amphibian emergences. We found a negative relationship between resource flux and the diversity of amphibians and insects, which contradicts the general pattern of positive biodiversity-ecosystem function relationships. My research strongly suggests environmental variation is a key process in shaping food-web structure and function and that multiple methodologies are needed to understand temporal and spatial dynamics of aquatic ecosystems.
Attentional Filtering in Young and Older Adulthood
Keywords: attention
aging
perception
neuroimaging

To date, research on cognitive aging has treated attention as a unitary resource that operates according to a single mechanism of top-down selection. However, contemporary theoretical models of attention propose that it is a distributed resource, embedded in distinct cortical subsystems, and operates in a manner that reflects the properties of those subsystems. For instance, perceptual attention is thought to originate in posterior sensory subsystems and filter competing unattended input prior to encoding, resulting in early selection of attended information. Executive attention, by contrast, is thought to originate in frontal control subsystems and filter unattended input after encoding, resulting in late selection of attended information. Guided by a distributed resource model, the work described here focuses on how healthy advanced aging influences early selection mechanisms embedded in posterior subsystems, perceptual encoding, and the relationship with frontal subsystems mediating late selection. To examine perceptual attention in isolation, object discrimination tasks were devised in which perceptual competition between repeated objects was manipulated while holding demand on executive control constant. Cortical mechanisms of early selection were probed using functional magnetic resonance imaging (fMRI) indices of neural response and adaptation. Evidence of an age-related impairment in early selection was detected across two fMRI experiments. Unlike young adults, unattended objects not only interfered with perceptual encoding in older adults, but were co-encoded along with the contents of attended input. Age impairments in early selection were also associated with greater reliance on frontally-mediated late selection resources, and, reduced functional connectivity with basal forebrain nuclei. In sum, the results indicate that with increasing age, frontal control subsystems become increasingly encumbered with compensatory redistribution of function from the perceptual cortices, possibly due to loss of central cholinergic integrity. Many well-described age-related deficits of executive attention may therefore represent a consequence of impaired early selection, rather than its cause.
The Effect of an Individualized Education Intervention versus Usual Care on Pain following Ambulatory Inguinal Hernia Repair
Keywords: Inguinal Hernia Repair
Pain
Ambulatory Surgery
Patient Education

Inguinal hernia repair (IHR) is a common ambulatory surgery procedure performed in Canada, after which many patients experience moderate to severe pain. Limited research has been found that examines interventions to reduce pain following ambulatory surgery, and none specifically for patients undergoing IHR. This trial evaluated the effectiveness of an individualized Hernia Repair Education Intervention (HREI) for patients following this ambulatory surgery. Participants (N= 82) were randomized to either the intervention or usual care group pre-operatively in the pre-admission clinic. The HREI included a booklet about managing pain and face-to-face session to discuss its content, and two telephone support calls (before surgery and 24 hours after surgery). The primary outcome was WORST 24 hour pain intensity on movement on post-operative day 2. Secondary outcomes included pain intensity at rest and movement, pain–related interference with activities, pain quality, analgesics taken, and adverse effects at post-operative days 2 and 7. At day 2, the intervention group reported significantly lower scores for all pain intensity outcomes, including WORST 24hr pain on movement (t (df) = 4.7 (73), p< 0.001), WORST 24 hr pain at rest (t (df) = 3.8 (73), p < 0.001), pain NOW at rest (t (df) = 3.3 (73), p = 0.001) and on movement (t (df) = 3.4 (73), p = 0.001). Also on day 2, pain-related interference scores for the intervention group were lower than the usual care group but not significantly different with the bonferroini correction (t (df) = 2.1 (73), p=0.04). The intervention group took significantly fewer opioids on day 2 (t (df) = 3.0 (73), p=0.004). Although there were no differences in any of the pain or interference outcomes on day 7, 36% (n=26) of the total sample reported moderate-severe pain at day 7. Constipation was the adverse effect identified most often, by both groups, on both days 2 and 7.This intervention was effective at post-operative day 2 but revisions need to be made to the intervention to assess for outcomes over a longer period of time.
Thermodynamic Studies of Halogen Bonding in Solution and Application to Anion Recognition
Keywords: Halogen bonding
anion receptor
solvent effect
molecular recognition
halide receptor
mesitylene

Halogen bonding (XB), the interaction between electron deficient halogen compounds and electron donors, is an established non-covalent interaction in the solid and gaseous phases. Understanding of XB in the solution phase is limited. This thesis describes experimental studies of XB interactions in solution, and the application of XB interactions in anion recognition. Chapter 1 is a brief review of current understanding of XB interaction: theoretical models, studies of XB in solid and gaseous phases and examples in biological systems are discussed. At the end of this chapter, halogen bonding in the solution phase is discussed, along with applications of halogen bonding in organic syntheses. In chapter 2, linear free energy relationships involving the thermodynamics of halogen bonding of substituted iodoaromatics are studied. The utility of substituent constants and calculated molecular electrostatic potential values as metrics of halogen bond donor ability are discussed. Density Functional Theory (DFT) calculations are shown to have useful predictive values for trends in halogen bond strength for a range of donor-acceptor pairs. Chapter 3 describes the development of new multidentate anion receptors based on halogen bonding. Bidentate and tridentate receptors were found to exhibit significantly higher binding constants than simple monodentate donors. These receptors show selectivity for halide anions over oxyanions. Using 19F NMR spectra at different temperature, the enthalpies and entropies of anion bindings for monodentate and tridentate receptors were determined. The results indicate a positive entropy contribution to anion binding for both mono and tridentate receptors in acetone solvent. Finally in chapter 4, some mesitylene based receptors with 3-halopyridinium and 2-iodobenzimidazolium donors are introduced. The receptors perform halide anion recognition in aqueous solvent system through charge-assisted XB interactions. These findings can allude to utility in organic synthesis, supramolecular chemistry and drug design.
"Caring" Global Policy? Sex Trafficking and Feminist International Ethics
Keywords: ethic of care
feminist ethics
sex trafficking
global governance

Current approaches to sex trafficking appear to be neither very successful in stopping sex trafficking nor, more importantly, very effective in helping those women for whom it is intended. Rather, the overwhelming focus on the issue of prostitution obscures the more fundamental issue of providing relevant assistant to trafficked women. The theoretical debates among academics and feminist activists do not delve sufficiently deep enough into this issue, while the policy discussions and the resulting international policy reflect the moral positions of abolitionist activists and policy-makers regarding the unacceptability of prostitution as a legitimate income-generating activity— a debate that is distinct from the issue of sex trafficking. I will argue that existing national anti-sex trafficking policies in India and Nepal, the regional policy for the South Asian Association for Regional Co-operation, and the United Nations Trafficking Protocol are ineffective because they reflect an association of sex trafficking with prostitution. A more effective policy would dissociate sex trafficking from moral judgments about prostitution. This can be accomplished by applying a feminist ethic of care as a methodology and as a political practice. Trafficked women emerge from a context of complex life histories and decision-making processes. Anti-sex trafficking governance structures are meant to provide care for trafficked women. As a methodology, an ethic of care would employ a critical moral ethnography to distill the experiences and articulated needs of trafficked women in order to show whether this is being accomplished and, if not, why. As a political practice, it can use the information that its methodology necessitates to provide guidance on how these governance structures might best be designed to provide care for trafficked women.
Special Cycles on Shimura Curves and the Shimura Lift
Keywords: Number theory
Arithmetic geometry
Modular forms
Kudla programme

The main results of this thesis describe a relationship between two families of arithmetic divisors on an integral model of a Shimura curve. The first family, studied by Kudla, Rapoport and Yang, parametrizes abelian surfaces with specified endomorphism structure. The second family is comprised of pullbacks of arithmetic cycles on integral models of Shimura varieties associated to unitary groups of signature (1,1). In the thesis, we construct these families of cycles, and describe their relationship, which is expressed in terms of the ``Shimura lift", a classical tool in the theory of modular forms of half-integral weight. This relations can be viewed as further evidence for the modularity of generating series of arithmetic "special cycles" for U(1,1), and fits broadly into Kudla's programme for unitary groups.
The Role of Language in the Development of Epistemic Concepts
Keywords: implicit false belief
language
theory of mind
epistemic concepts
preschool

This thesis examines the effects of linguistic input on the development of children’s epistemic concepts. It draws upon two fundamental questions in the field of cognitive development: (a) whether distinctions between automatic and controlled forms of cognitive processing are indicative of underlying conceptual differences, and (b) whether language is critical to the process of concept development. To establish the background of the current research, a summary of how these theoretical questions have been addressed in other fields of cognitive psychology is first provided (Chapter 1). These questions are then re- examined within the specific domain of epistemic concept development (Chapter 2). Changes in false-belief processing that occur between infancy and the early preschool years are discussed in relation to two competing theories of false-belief development. A framework to explain how language promotes children’s transition between automatic and controlled forms of processing is then provided. It is suggested that language facilitates change by both reducing the cognitive demands associated with controlled response tasks as well as assisting with the formation of robust epistemic representations. An empirical study that was designed to examine the effects of epistemic language (i.e., verbs and syntax) on children’s automatic and controlled processing of belief is then described (Chapters 3 to 5). Eighty-four children (Mage = 3;5 years), who initially failed elicited measures of false-belief, were trained with visual contexts of true- and false-belief. The critical manipulation across three conditions was the linguistic input presented in conjunction with these contexts. Children heard narrations that contained either (a) the description of an agent’s actions without an epistemic verb, (b) a familiar epistemic verb (thinks) across both contexts, or (c) the familiar epistemic verb in contexts of true-belief and a novel epistemic verb (gorps) in contexts of false-belief. Results demonstrated a significant advantage for children who were trained with epistemic verbs on spontaneous measures of false-belief (i.e., anticipatory gaze). Significant effects of epistemic verb exposure were also demonstrated in novel contexts of belief induction. Implications of these findings are discussed in relation to theories that make distinct predictions about the role of language in epistemic concept development (Chapter 6).
An Examination of the Population Health Implications of Voluntary Food Fortification and Nutrition-related Marketing Practices in Canada.
Keywords: Nutrition Marketing
Nutrition Labelling
Food Fortification
Discretionary Fortification
Tolerable Upper Intake Level
Nutrition Policy
Vitamins
Minerals
Canada
Canadian Community Health Survey (CCHS)
NHANES

The 2004 Canadian Community Health Survey (CCHS) revealed many indicators of poor diet quality in Canada which, together with the high rates of obesity and diet-related chronic disease, suggest that shifts in dietary patterns are urgently needed. Given the widespread promotion of foods on the basis of nutrition and health, the aim of this work was to explore the population health implications of voluntary food fortification and nutrition-related marketing in Canada. Using the CCHS, the potential impact of a proposed discretionary food fortification policy on nutrient inadequacies and excesses was examined, in addition to the relationship between consumption of foods eligible to be fortified under this policy and indicators of dietary quality. To better understand the potential risk associated with liberal fortification practices, the National Health and Nutrition Examination Survey (2007-08) was used to examine potential for risk of excess associated with voluntarily fortified food consumption in the US, where these practices have long been permitted. The results suggest that proposed changes to voluntary fortification may reduce inadequacy and increase excess, and may reinforce poor diet patterns. Excessive nutrient intakes were also found to be associated with consumption of voluntarily fortified foods in the US, particularly among children. Therefore, there appears to be real potential for risk associated with voluntary fortification practices in Canada. The extent, nature, and population health implications of nutrition marketing in Canada was examined, using a survey of front-of-package nutrition-related marketing on foods within three large grocery stores in Toronto. Nutrition-related marketing was found on 41% of all foods surveyed, and was widely found on highly processed, often fortified foods. References to nutrients of public health concern (e.g. sodium, vitamin D) were infrequently found. Overall, this practice provides limited nutritional guidance. Current directions in nutrition policy in Canada should be re-evaluated, to ensure that they support healthy diet patterns.
Disulfide Bond Formation: Identifying Roles of PDI Family Thiol Oxidoreductases and ER Oxidant Pathways
Keywords: Protein Disulfide Isomerase
Endoplasmic reticulum
biogenesis & biodegradation
protein folding
chaperone
disulfide bonds

Protein disulfide isomerases (PDIs) catalyze the oxidation and isomerization of disulfide bonds in proteins passing through the endoplasmic reticulum (ER). Although as many as 20 enzymes are classified as PDI family members, their relative contributions to protein folding have remained an open question. Additionally, Ero1 has been characterized as the ER oxidase that transfers oxidizing equivalents from oxygen to PDI enzymes. However, knockout mice lacking the mammalian Ero1 isoforms, Ero1Lα and Ero1Lβ, are viable, and the role of other potential ER oxidases in maintaining an oxidative ER environment is now an important issue. By systematic depletion of ER PDI family members and potential ER oxidases and assessment of disulfide bond formation of secreted endogenous substrates, I have outlined the functional relationships among some of these enzymes. PDI family member depletion revealed that PDI, although not essential for complete disulfide bond formation in client proteins, is the most significant catalyst of oxidative folding. In comparison, ERp57 acts preferentially on glycosylated substrates, ERp72 functions in a more supplementary capacity, and P5 has no detectable role in formation of disulfide bonds for the substrates assayed. Initially, no impact of depletion of Ero1 was observed under steady state conditions, suggesting that other oxidase systems are working in parallel to support normal disulfide bond formation. Subsequent experiments incorporating a reductive challenge revealed that Ero1 depletion produces the strongest delay in re-oxidation of the ER and oxidation of substrate. Depletion of two other potential ER oxidases, peroxiredoxin 4 (PRDX4) and Vitamin K epoxide reductase (VKOR), showed more modest effects. Upon co-depletion of Ero1 and other oxidases, additive effects were observed, culminating in cell death following combined removal of Ero1, PRDX4, and VKOR activities. These studies affirm the predominant roles of Ero1 in ER oxidation processes and, for the first time, establish VKOR as a significant contributor to disulfide bond formation.
Leukocyte Structural Adaptations in Response to Hemodynamic Forces: Tension Transmitted Through VLA-4 Activates Upstream Rap1, PI3K, and Rac-Dependent Actin Polymerization
Keywords: leukocyte
shear stress
actin polymerization
adhesion

During inflammation, leukocytes modulate α4β1(VLA-4) integrin avidity in order to rapidly stabilize nascent adhesive contacts to VCAM-1-expressing endothelial cells and resist detachment forces imparted by the flowing blood. Linkage to the actin cytoskeleton is critical for integrin function, yet the exact role of the actin cytoskeleton in leukocyte adhesion stabilization under conditions of fluid flow remains poorly understood. We modeled leukocyte (U937 cell, mouse lymphocyte and human monocyte) arrest and adhesion stabilization through the use of a parallel plate flow chamber and visualized cells by phase contrast or fluorescent confocal microscopy. Live cell imaging with Lifeact-transfected U937 cells revealed that mechanical forces imparted by fluid flow induced formation of upstream tension-bearing anchors attached to the VCAM-1-coated surface. Scanning electron microscopy confirmed that flow-induced mechanical force culminates in the formation of structures that anchor monocyte adhesion. These structures are critical for adhesion stabilization, since disruption of actin polymerization dramatically inhibited VLA-4-dependent resistance to detachment, but did not affect VLA-4 expression, affinity modulation, and clustering or constitutive linkage to F-actin. Transfection of dominant-negative constructs and inhibition of kinase function or expression revealed key signaling steps required for upstream actin polymerization and adhesion stabilization. Rap1 was shown to be critical for resistance to flow-induced detachment and accumulated in its GTP form at the sites of anchor formation. A key mediator of force-induced Rac activation and actin polymerization is PI3K. Live cell imaging revealed accumulation of PIP3 within tension-bearing anchors and blockade of PI3K or deficiency of PI3Kγ isoform reproduced the adhesion defect produced by inhibition of actin polymerization. Thus, rapid signaling and structural adaptations enable leukocytes to stabilize adhesion and resist detachment forces; these included activation of Rap1, phosphoinositide 3-kinase γ-isoform and Rac, but not Cdc42.
Unprotected Aziridine Aldehydes in Isocyanide-based Multicomponent Reactions
Keywords: multicomponent reaction
isocyanide
aziridine aldehyde
cyclic peptide
fluorescence
ligation

While unprotected amino aldehydes are typically not isolable due to imine formation and consequent polymerization, stable unprotected aziridine aldehydes are useful and available reagents. Moreover, reversible hemiacetal and hemiaminal formation enable these compounds to reveal both their electrophilic and nucleophilic functional groups. This exceptional arrangement allows for aziridine aldehyde dimers to participate in and disrupt the mechanisms of an array of well-known organic reactions, including isocyanide-based multicomponent reactions. The scope and selectivity patterns of aziridine aldehyde induced amino acid or peptide macrocyclization have been investigated. A small library of constrained tri-, tetra-, and penta-peptide macrocycles – representing the most difficult cyclic peptides to synthesize – has been prepared. The scope of aziridine aldehyde participation in multicomponent reactions was also expanded to Ugi and Passerini reactions that do not employ tethered amine and acid functional groups. In order to facilitate cellular imaging of peptide macrocycles a fluorescent isocyanide reagent was prepared and applied to prepare mitochondrial targeting macrocycles. Thioester isocyanide reagents were synthesized to enable rapid assembly of cycle-tail peptides through ligation technology.