VictorJuiz/thesis huggingface dataset:
A Bayesian Approach to Factor Analysis via Comparing Prior and Posterior Concentration

We consider a factor analysis model that arises as some distribution form known up to first and second moments. We propose a new Bayesian approach to determine if any latent factors exist and the number of factors. As opposed to current Bayesian methodology for factor analysis, our approach only requires the specification of a prior for the mean vector and the variance matrix for the manifest variables. We compare the concentration of the prior and posterior about the various subsets of parameter space specified by the hypothesized factor structures. We consider two priors here, one is conjugate type and the other is based on the correlation factorization of the covariance matrix. A computational problem associated with the use of the second prior is solved by the use of importance sampling for the posterior analysis. If the data does not lead to a substantial increase in the concentration about the relevant subset, of the posterior compared to the prior, then we have evidence against the hypothesized factor structure. The hypothesis is assessed by computing the observed relative surprise. This results in a considerable simplification of the problem, especially with respect to the elicitation of the prior.

Advisor: Evans, Michael
Experimental Constraints on Lithium Exchange between Clinopyroxene, Olivine and Aqueous Fluid at High Pressures and Temperatures

Clinopyroxene, olivine, plagioclase and hydrous fluid lithium partition coefficients have been measured between 800-1100oC at 1 GPa. Clinopyroxene-fluid partitioning is a function of temperature (ln DLicpx/fluid = -7.3 (+0.5) + 7.0 (+0.7) * 1000/T) and appears to increase with increasing pyroxene Al2O3 content. Olivine-fluid partitioning of lithium is a function of temperature (ln DLiol/fluid = -6.0 (+2.0) + 6.5 (+2.0) * 1000/T) and appears to be sensitive to olivine Mg/Fe content. Anorthite-fluid lithium partitioning is a function of feldspar composition, similar to the partitioning of other cations in the feldspar-fluid system. Isotopic fractionation between clinopyroxene and fluid, Licpx-fluid, has been measured between 900-1100oC and ranges from -0.3 to -3.4 ‰ (±1.4 ‰). Lithium diffusion has been measured in clinopyroxene at 800-1000oC and in olivine at 1000oC. The lithium diffusion coefficient is independent of the diffusion gradient as values are the same if the flux of lithium is into or out of the crystal and ranges from -15.19 ± 2.86 m2/s at 800oC to -11.97 ± 0.86 m2/s at 1000oC. Lithium diffusion in olivine was found to be two orders of magnitude slower than for clinopyroxene at similar conditions. Closure temperatures calculated for lithium diffusion in clinopyroxene range from ~400 to ~600oC. These results demonstrate that lithium equilibration between fluids and minerals is instantaneous, on a geological timescales. The confirmation of instantaneous equilibration, combined with min-fluid partition coefficients and values for Licpx-fluid, permits quantitative modeling of the evolution of lithium concentration and isotopic composition in slab-derived fluids during transport to the arc melt source. Our results indicate that fluids migrating by porous flow will rapidly exchange lithium with the mantle, effectively buffering the fluid composition close to ambient mantle values, and rapidly attenuating the slab lithium signature. Fluid transport mechanisms involving fracture flow are required to maintain a slab-like lithium signature (both elemental and isotopic) from the slab to the melt source of island arc basalts. This study demonstrates that mineral-fluid equilibration is rapid, and as a result the lithium content of minerals can only reliably represent chemical exchange in the very latest stages of the sample’s history.

Keywords: lithium
isotopic fractionation
partitioning
clinopyroxene
olivine
fluids
Advisor: Brenan, James
Textual Community and Linguistic Distance in Early England

This dissertation examines the function of textual communities in England from the early Middle Ages until the early modern period, exploring the ways in which cultures and communities are formed through textual activities other than writing itself. I open by discussing the characteristics of a textual community in order to establish a new understanding of the term. I argue that a textual community is fundamentally based on activity carried out in books and that perceptions of linguistic distance stimulate this activity. Chapter 1 investigates Bede (c. 673–735) and his interest in multilingualism, coupled with his exploration of the boundaries between the written and spoken forms of English. Picking up on an element of Bede's work, I argue in Chapter 2 that Alfred (r. 871–899) and his grandson Æthelstan (r. 924/5–939) found new ways to make textuality the defining quality of the emerging West Saxon kingdom. In Chapter 3, I focus on the intralingual distance in the textual community surrounding the works of Ælfric (c. 950–1010) and Wulfstan (d. 1023). I also discuss the role of contemporary or near-contemporary manuscript use in forming a textual community at the intersection of ecclesiastical and political power. In Chapter 4, I examine the activities of a textual community in the West Midlands in the twelfth and thirteenth centuries. By glossing Old English texts and rethinking English orthography, this textual community both renewed the work of Anglo-Saxon writers and enabled the activity I discuss in Chapter 5. Chapter 5 argues for a more constructive rationalization of the curatorial and editorial activities of Matthew Parker (1504–1575) than has been presented hitherto. I argue that Parker's cavalier methods of conserving and editing his books in fact represent responses to the textual models he found in those manuscripts. An appendix presents the text and translation of the preface to Parker's edition of Asser's Life of King Alfred. I close with a discussion of the production and use of books, followed by an illustration of the ongoing importance of textual community in England by highlighting the layers of use in a single manuscript (Oxford, Bodleian Library, MS Hatton 20) that links together the chapters of this dissertation.

Keywords: Anglo-Saxon
England
manuscript
book history
Latin
Old English
medieval
early modern
Advisor: Orchard, Andy
Development of Neuronal Responses to Frequency-modulated Tones in Chinchilla Auditory Cortex

A central issue in auditory research is how the auditory brain encodes complex stimuli. However, the process by which the auditory cortex interprets complex sounds during development and the extent to which cortical organization can be manipulated by complex stimulation is still undetermined. We have addressed this gap in the following three studies. First, we characterized the responses of cortical neurons in adult chinchillas to frequency-modulated (FM) stimulation. Next, we asked whether FM coding at the cortical level is innate or if its development is influenced by normal postnatal environmental experience. Finally, we investigated the effect of sustained neonatal FM sweep exposure on the development of cortical responses to tonal and FM stimuli. In our adult study, results indicated that >90% of sampled neurons were responsive to FM sweeps. The population preference was for upward FM sweeps and for medium to fast speeds ( 0.3 kHz/ms). Three types of temporal response patterns were observed: a single peak at sweep onset/offset (‘onset’) and a single peak (‘late’) or multiple peaks (‘burst’) during the sweep. ‘Late’ units expressed the highest direction and speed selectivity; ‘onset’ units were selective only for direction and ‘burst’ units were selective for neither direction nor speed. In our developmental study, our results showed a significant developmental increase in FM direction selectivity. However, FM speed selectivity appeared to be established early in development. In our developmental plasticity study, we hypothesized that constant FM exposure would increase the proportion of auditory neurons that are selectively responsive to the conditioning FM sweep. However, our results showed that while tonal response latencies increased after the exposure period, the conditioning stimulus had minimal effect on the FM direction preferences of cortical neurons and decreased overall neuronal FM speed selectivity. In conclusion, we suggest that chinchilla auditory cortical neurons are not uniquely activated by FM sounds but that FM responses are largely predictable based on how changing frequency stimuli interact with the receptive fields of these neurons. We also propose that the development of FM direction sensitivity is experience-independent and that perhaps normal acoustic experience is required to maintain FM speed tuning.

Keywords: FM sweeps
development
direction selectivity
acoustic exposure
speed selectivity
conditioning
Advisor: Harrison, Robert
Mechanism of Helicobacter pylori Induced Gastric Cancer: Role of the Signal Transducer and Activator of Transcription Pathway

Infection with the gut-pathogen Helicobacter pylori is the single, most important risk factor in the development of gastric cancer. Although there is a rising incidence in mortality resulting from this malignancy, the exact mechanism underlying the initiation and progression of bacterial-induced gastric tumorigenesis is still not completely understood. Several studies implicate the activation of the Signal Transducer and Activator of Transcription 3 (STAT3) signaling pathway as a cellular trigger for promoting carcinogenes. In this thesis, I studied the role of the STAT3 signaling pathway in H. pylori mediated tumorigenesis, and attempted to delineate mechanisms involved. I have found that H. pylori activates the STAT3 signaling pathway both in vitro and in vivo, to promote carcinogenesis. Pivotal for H. pylori mediated STAT3 activation are the bacterial effector protein CagA and host receptor components, the gp130 and the IL-6αR subunits. Further investigation into the mechanism of STAT3 induction identified a key role for cholesterol-enriched membrane lipid rafts. Bacterial invasion and CagA injection into host cells was also dependent on lipid raft integrity. Co-fractionation via the use of sucrose gradients, which permits the isolation of lipid rafts, identified H. pylori CagA to be associated with these membrane microdomains. CagA, once injected into the cell, appears to interact with the inner leaflet of the host plasma membrane via a charge association that either directly or indirectly anchors it to the negatively charged anionic lipids in the cytoplasmic membrane. In addition, janus kinases were recruited to rafts upon H. pylori infection. In this thesis, I present a dynamic model of STAT3 activation, which requires the interaction of lipid raft associated proteins, H. pylori CagA and recruited JAKs with non-lipid raft receptor components to support STAT3 signaling. This study is significant since it provides insight into the possible mechanisms by which H. pylori induces gastric cancer and furthermore, it facilitates the development of novel therapeutic targets directed against bacterial induced carcinogenesis.

Keywords: gastric cancer
Helicobacter pylori
Advisor: Jones, Nicola L.
Falling Back into Teaching: A Triptych of Teachers' Motiviations, Decision and Consequences

You can always fall back into teaching. This thesis explores the meaning of this statement as it pertains to teachers’ motivations related to their careers, the decisions they make in both their daily work and their professional goals, and the consequences of those decisions. I investigate why teachers choose to teach. What are the reasons that lead teachers to ‘fall back’ into teaching? Upon beginning their career, what do these teachers experience during their daily work in the classroom? How do they negotiate how they feel with what they do? Falling back into teaching is an arts-informed thesis. I am an artist and a researcher who communicates in text and images. I combine autobiographical writing and the language of art, the elements of design, to explain my academic and artistic journey. The thesis employs the metaphor of a triptych, a three-paneled painting that has been and continues to be used specifically by visual artists. The left panel encompasses the introduction; a definition of 'fallback', an explanation of arts-informed inquiry as a method for researching fallback, and a first meeting with my parents and me who inform the thesis. The middle panel follows my research process in understanding 'fallback' using the elements of design: line, shape, space, colour, value and texture. The final panel provides a reflection on the process and a response to those who have read and relate to 'fallback'.

Keywords: teacher education
teacher attitudes
Advisor: Kooy, Mary
A Cross-species Examination of Cholinergic Influences on Feature Binding: Implications for Attention and Learning

Feature binding refers to the fundamental challenge of the brain to integrate sensory information registered by distinct brain regions to form a unified neural representation of a stimulus. While the human cognitive literature has established that attentional processes in a frontoparietal cortical network support feature binding, the neurochemical contributions to this attentional process remain unknown. Using systemic administration of the cholinergic muscarinic receptor antagonist scopolamine and a digging-based rat feature binding task that used both odor and texture stimuli, it was demonstrated that blockade of acetylcholine (ACh) at the muscarinic receptors impaired rats’ ability to feature bind at encoding, and it was proposed that ACh may support the attentional processes necessary for feature binding (Botly & De Rosa, 2007). This series of experiments further investigated a role for ACh and the cholinergic basal forebrain (BF) in feature binding. In Experiment 1, a cross-species experimental design was employed in which rats under the systemic influence of scopolamine and human participants under divided-attention performed comparable feature binding tasks using odor stimuli for rats and coloured-shape visual stimuli for humans. Given the comparable performance impairments demonstrated by both species, Experiment 1 suggested that ACh acting at muscarinic receptors supports the attentional processes necessary for feature binding at encoding. Experiments 2-4 investigated the functional neuroanatomy of feature binding using bilateral quisqualic acid excitotoxic (Experiment 2) and 192 IgG-saporin cholinergic immunotoxic (Experiments 3 and 4) brain lesions that were assessed for completeness using histological and immunohistological analyses. Using the crossmodal digging-based rat feature binding task, Experiment 2 revealed that the nucleus basalis magnocellularis (NBM) of the BF is critically involved in feature binding, and Experiment 3 revealed that cholinergic neurons in the NBM are necessary for feature binding at encoding. Lastly, in Experiment 4, rats performed visual search, the standard test of feature binding in humans, with touchscreen-equipped operant chambers. Here it was also revealed that cholinergic neurons in the NBM of the BF are critical for efficient visual search. Taken together, these behavioural, pharmacological, and brain-lesion findings have provided insights into the neurochemical contributions to the fundamental attentional process of feature binding.

Keywords: behavioral neuroscience
acetylcholine
feature binding
attention
learning
basal forebrain
nucleus basalis magnocellularis
Advisor: Rosa, Eve De
The Development of Nurse-patient Relationship Scales in Chronic Care

Quality of life and well-being of patients living in chronic care (CC) are determined to a considerable extent by the relationships these patients have with nursing personnel caring for them. Given the importance of these relationships, there is an absence of empirical research and measurement tools to assess these relationships from a patient’s perspective. The purpose of this study was to develop and test valid and reliable instruments to determine what qualities of the humanistic relationships between cognitively competent patients and nursing personnel in CC settings were most important to patients and what they experience most. A conceptual framework based on the Humanistic Nursing Theory by Paterson and Zderad (1976) served as a foundation to develop two scales; the Humanistic Relationship Importance Scale (HRIS) assessed what attributes of the relationship are most important, and the Humanistic Relationship Experience Scale (HRES) assessed what attributes of the relationship are experienced. Sixty-nine content relevant items based on six dimensions of the Paterson and Zderad theory were developed and tested for content validity resulting in the deletion of 20 items. Forty patients completed the now 49-item scales to establish their initial internal consistency reliability, test-retest reliability and construct validity. Another 25 items were deleted in the process. The 24-item scales were completed by 249 patients in five CC facilities and the results subjected to a iii principal axis analysis (PAA). An oblique rotation resulted in a five factor solution labeled: relational availability, promoting quality of daily life, recognizing and supporting choice, forming connections, and supporting human uniqueness. This was a simplification of the original six dimensions of the Paterson and Zderad theory. A PAA of the 24-item HRES resulted in a one factor solution labeled humanistic connection. Reliability testing of the factors resulted in the deletion of one more item and an HRIS with a Cronbach′s alpha of .87 indicating strong internal reliability and an HRES with a Cronbach′s alpha of .98 suggesting some redundancy of items. Relational availability was rated as the most important factor in the nurse-patient relationship although all factors were important to patients. The mean score of the HRES indicated that patients experience a moderate level of humanistic connection in terms of frequency and intensity with nurses who generally care for them. Findings of this study have contributed to a better understanding of the nurse-patient relationship, and support the care, research, and theoretical knowledge of nurses and patients in these environments.

Keywords: Humanistic Nursing Theory
Measurement
Advisor: Pringle, Dorothy
McGilton, Katherine Simone
Imagined Futures and Unintended Consequences: An Environmental History of Toronto's Don River Valley

This dissertation explores human interactions with Toronto’s Don River Valley from the late eighteenth century to the present, focusing on the period of intense urbanization and industrialization between 1880 and 1940. Its concentration on the urban fringe generates new perspectives on the social and environmental consequences of urban development. From its position on the margins, the Don performed vital functions for the urban economy as a provider of raw materials and a sink for wastes. Insights derived from the intersections between social and environmental history are at the heart of this project. The dissertation begins by documenting the industrial history of the river and its transformation from a central provider in the lives of early Toronto residents to a polluted periphery in the latter half of the nineteenth century. An analysis of the valley’s related function as a repository for human “undesirables” reveals connections between the processes that identified certain individuals as deficient “others” and similar imperatives at work in classifying difficult or unpredictable environments as “waste spaces.” Efforts to “reclaim” and improve the river are the subject of the remaining chapters. A series of initiatives between 1870 and 1930 aimed at reconfiguring the lower Don as an efficient corridor for transportation and industrial development reveal in their shortcomings and unintended consequences a failure to accommodate dynamic and often unpredictable ecological processes. Reclamations of a different kind are explored in the conservation movement of the twentieth century, through which the valley emerges as a valuable public amenity. The dissertation concludes by investigating how the valley’s history informs current plans to “renaturalize” the river mouth. Throughout, the Don functions as an autonomous and causal force in the city’s history. On this small river on the urban fringe, nature and society worked in mutually constitutive ways to shape and reshape the metropolis.

Keywords: Don River
Toronto
pollution
urbanization
homelessness
improvement
conservation
19th century
20th century
Advisor: Sandwell, Ruth W.
Radiated Electric and Magnetic Fields Caused by Lightning Return Strokes to the Toronto CN Tower

In the present PhD work, three sophisticated models based on the "Engineering" modeling approach have been utilized to conveniently describe and thoroughly analyze details of Lightning events at the CN Tower. Both the CN Tower and the Lightning Channel are represented by a number of connected in series Transmission Line sections in order to account for the variations in the shape of the tower and for plasma processes that take place within the Lightning Channel. A sum of two Heidler functions is used to describe the "uncontaminated" Return Stroke current, which is injected at the attachment point between the CN Tower and the Lightning Channel. Reflections and refractions at all points of mismatched impedances are considered until their contribution becomes less than 1% of the originally injected current wave. In the proposed models, the problem with the current discontinuity at the Lightning Channel front, commonly taken care of by introducing a "turn-on" term when computing radiation fields, is uniquely treated by introducing reflected and transmitted components. For the first time, variable speed of propagation of the Return Stroke current front has been considered and its influence upon the predicted current distributions along the whole Lightning Channel path and upon the radiated distant fields analyzed. Furthermore, as another novelty, computation of the electromagnetic field is accomplished in Cartesian Coordinates. This fact permits to relax the requirement on the verticality of the Lightning Channel, normally imposed in Cylindrical Coordinates. Therefore, it becomes possible to study without difficulty the influence of a slanted Lightning Channel upon the surrounding electromagnetic field. Since the proposed sophisticated Five-Section Model has the capability to represent very closely the structure of the CN Tower and to emulate faithfully the shape of, as well as physical processes within the Lightning Channel, it is believed to have the potential of truthfully reproducing observed fields. The developed modeling approach can be easily adapted to study the anticipated radiated fields at tall structures even before construction.

Keywords: Return Stroke
Engineering Model
CN Tower
Five-Section Model
Variable Return Stroke Speed
Electric Field
Magnetic Field
Cartesian Coordinates
Advisor: Janischewskyj, Wasyl
Iravani, Mohammad Reza