VictorJuiz/thesis huggingface dataset:
Development of Deep-level Photo-thermal Spectroscopy and Photo-Carrier Radiometry for the Characterization of Semi-insulating Gallium Arsenide (SI-GaAs)
Keywords: DLPTS
PCR
SI-GaAs
Photo-thermal

Semi-insulating gallium arsenide (SI-GaAs) has gained great interest in recent years due to its wide application in optoelectronic devices and high-speed integrated circuits. An important feature of SI-GaAs is the high density of deep-level defect states, which control the electrical properties of the substrate by compensating the shallow defects. Over the years, deep-level transient spectroscopy (DLTS) and its variations have been the most effective tools employed for the characterization of deep-level defects. However, most of these techniques require a contact probe and tend to be quite restrictive in their applications’ scope. In this thesis deep-level photo-thermal spectroscopy (DLPTS), an all-optical rate-window-based technique, is presented as a novel noncontact technique for the characterization of deep-level defects in SI-GaAs. The signal-generation mechanism for DLPTS is the super-bandgap excitation of carriers, and the sub-bandgap detection of the defect’s thermal-emission process. Combined with the rate-window detection utilizing lock-in amplifiers, DLPTS measurements are performed in three different modalities: temperature-scan, pulse-rate scan, and time-scan. This work demonstrates that each mode provides unique information about the defect configuration, and, in combination, the modes offer a powerful tool for the study of defect properties and optoelectronic processes in SI-GaAs. A hierarchical carrier-emission theory is proposed to explain the thermal broadening (nonexponentiality) in photo-thermal spectra. The model is studied comparatively with the Gaussian distribution of activation energies, and their similarities demonstrate an ergodic equivalence of random energy distribution and the constrained hierarchical emission process. In addition, a rate-window gated photo-carrier radiometry (PCR) technique is developed. The original diffusion-based PCR theory is modified to reflect the signal domination by trap emission and capture rates in the absence of diffusion. Defect luminescence is collected and analyzed using photo-thermal temperature spectra and resonant detection combined with frequency scans. The study results in the identification of five radiative defect states and the defect-photoluminescence quantum efficiency.
Novel Metallic States at Low Temperatures in Strongly Correlated Systems
Keywords: Quantum Criticality
Non-Fermi Liquid

This thesis describes experiments carried out on two novel strongly correlated electron systems. The first, FeCrAs, is a new material that has not been studied before, while the second, Sr3Ru2O7, has been previously shown to have a very novel so-called ‘nematic’ phase around the metamagnetic quantum critical end point (QCEP). For these studies, a new variation on an established method for measuring the field dependence of susceptibility in a BeCu clamp cell has been developed, and is described, as is a relaxation heat capacity cell that works from 4 K down to 300 mK. A method of growing stoichiometric crystals of the hexagonal iron-pnictide FeCrAs has been developed, and transport and thermodynamic measurements carried out. The in-plane resistivity shows an unusual “non-metallic” dependence on temperature T, rising continuously with decreasing T from ∼800 K to below 100 mK. The c-axis resistivity is similar, except for a sharp drop upon entry into an antiferromagnetic state at T_N ∼ 125 K. Below 10 K the resistivity follows a non-Fermi-liquid power law, ρ(T) = ρ_0 − AT^x with x < 1, while the specific heat shows Fermi liquid behaviour with a large Sommerfeld coefficient, γ ∼ 30 mJ/molK^2. The high temperature properties are reminiscent of those of the parent compounds of the new layered iron-pnictide superconductors, however the T → 0 K properties suggest a new class of non-Fermi liquid. The metamagnetic critical end point temperature T^∗ in Sr3Ru2O7 as a function of hydrostatic pressure with H//ab has been studied using the ac susceptibility. It is found that T^∗ falls monotonically with increasing pressure, going to zero at Pc = 14±0.3 kbar. One sign of the nematic phase observed in the field-angle tuning, i.e. T^∗ rises as the novel phase emerges, has not been seen in our study. However, we see a slope change in T^∗ vs P at ∼12.8 kbar, and a shoulder at the upper field side of the peak in χ′ from ∼12.8 kbar to ∼16.7 kbar. These new features indicate that some new physics sets in near the pressure-tuned QCEP.
Tumor Initiating Cells in Mesenchymal Neoplasms
Keywords: Tumor Initiating Cell
Mesenchymal Neoplasms

Despite the clonal origins of tumors, the majority of neoplasms are composed of a heterogeneous population of cells. The origins of this phenotype these cells have the potential to get can be associated with cancer stem cells or tumor initiating cells have the potential to self-renew and to differentiate giving rise to all cell types compromising a heterogeneous malignancy. These cells are clinically important as they preferentially give rise to tumors and are therefore hypothesized to account for the longevity and recurrence of neoplastic lesions. Cancer stem cells have been identified from a broad range of hematopoietic, neural and epithelia tumors; however, their function in mesenchymal neoplasms is less well defined. Using the side population assay, we identified a subpopulation of cells within mesenchymal neoplasms, referred to as side population cells, which are enhanced for tumor initiating potential. Importantly, we show a correlation between the percentage of side population cells and tumor grade suggesting clinical prognostic value as the proportion of side population cells may be a predictor of patient outcome. Interestingly side population cells show distinct molecular features when compared to non-side population cells and manipulation of these molecular mechanisms reduces the ability of side population cells to initiate tumor formation in osteosarcoma cell lines. In conjunction with these experiments, we also sought to determine the cellular origins of the mesenchymal neoplasm, aggressive fibromatosis. Using mouse models we show the influence of a mesenchymal precursor cells in the development of this malignancy. These results identify important biological features of mesenchymal neoplasms from which the development of targeted treatment strategies can begin.
Time-varying Phononic Crystals
Keywords: acoustics
phononic crystals
time-varying
wave propagation
periodic materials
ultrasound

The primary objective of this thesis was to gain a deeper understanding of acoustic wave propagation in phononic crystals, particularly those that include materials whose properties can be varied periodically in time. This research was accomplished in three ways. First, a 2D phononic crystal was designed, created, and characterized. Its properties closely matched those determined through simulation. The crystal demonstrated band gaps, dispersion, and negative refraction. It served as a means of elucidating the practicalities of phononic crystal design and construction and as a physical verification of their more interesting properties. Next, the transmission matrix method for analyzing 1D phononic crystals was extended to include the effects of time-varying material parameters. The method was then used to provide a closed-form solution for the case of periodically time-varying material parameters. Some intriguing results from the use of the extended method include dramatically altered transmission properties and parametric amplification. New insights can be gained from the governing equations and have helped to identify the conditions that lead to parametric amplification in these structures. Finally, 2D multiple scattering theory was modified to analyze scatterers with time-varying material parameters. It is shown to be highly compatible with existing multiple scattering theories. It allows the total scattered field from a 2D time-varying phononic crystal to be determined. It was shown that time-varying material parameters significantly affect the phononic crystal transmission spectrum, and this was used to switch an incident monochromatic wave. Parametric amplification can occur under certain circumstances, and this effect was investigated using the closed-form solutions provided by the new 1D method. The complexity of the extended methods grows logarithmically as opposed linearly with existing methods, resulting in superior computational complexity for large numbers of scatterers. Also, since both extended methods provide analytic solutions, they may give further insights into the factors that govern the behaviour of time-varying phononic crystals. These extended methods may now be used to design an active phononic crystal that could demonstrate new or enhanced properties.
A Mixed Biosensing Film Composed of Oligonucleotides and Poly (2-hydroxyethyl methacrylate) Brushes to Enhance Selectivity for Detection of Single Nucleotide Polymorphisms
Keywords: DNA
biosensor
single nucleotide polymorphisms
mixed film
surface characterization
poly(2-hydroxyethyl methacrylate)

This work has explored the capability of a mixed film composed of oligonucleotides and oligomers to improve the selectivity for the detection of fully complementary oligonucleotide targets in comparison to partially complementary targets which have one and three base-pair mismatched sites. The intention was to introduce a “matrix isolation” effect on oligonucleotide probe molecules by surrounding the probes with oligomers, thereby reducing oligonucleotide-to-oligonucleotide and/or oligonucleotide-to-surface interactions. This resulted in a more homogeneous environment for probes, thereby minimizing the dispersity of energetics associated with formation of double-stranded hybrids. The mixed film was constructed by immobilizing pre-synthesized oligonucleotides onto a mixed aminosilane layer and then growing the oligomer portion by surface-initiated atom transfer radical polymerization (ATRP) of 2-hydroxy methacrylate (PHEMA). The performance of the mixed film was compared to films composed of only oligonucleotides in a series of hybridization and melt curve experiments. Surface characterization techniques were used to confirm the growth of the oligomer portion as well as the presence of both oligonucleotides and oligomer components. Polyatomic bismuth cluster ions as sources for time-of-flight secondary ion mass spectrometry experiments could detect both components of the mixed film at a high sensitivity even though the oligomer portion was at least 200-fold in excess. At the various ionic strengths investigated, the mixed films were found to increase the selectivity for fully complementary targets over mismatched targets by increasing the sharpness of melt curves and melting temperature differences (delta Tm) by 2- to 3-fold, and by reducing non-specific adsorption. This resulted in improved resolution between the melt curves of fully and partially complementary targets. A fluorescence lifetime investigation of the Cy3 emission demonstrated that Cy3-labeled oligonucleotide probes experienced a more rigid microenvironment in the mixed films. These experiments demonstrated that a mixed film composed of oligonucleotides and PHEMA can be prepared on silica-based substrates, and that they can improve the selectivity for SNP discrimination compared to conventional oligonucleotide films.
The Plant Transcriptome and Its Response to Envrionmental Stimuli
Keywords: Drought
R2R3-MYB
Diurnal
Arabidopsis
Hybrid poplar
Populus
Genomics
Microarray

The relationship between an organism’s genome, developmental stage, and environment is complex. The aim of the research presented herein was to provide experimental evidence to contribute to the annotation of the P. trichocarpa genome and to test two major hypotheses addressing the interaction between drought and time of day in A. thaliana and in two hybrid Populus clones. In order to generate data to address these aims, three separate experiments were undertaken. First, all members of the R2R3-MYB family of transcription factors in the P. trichocarpa genome were characterised by phylogenetic analysis and their transcript accumulation patterns across a range of tissues and organs were assessed using whole genome poplar microarrays. Results of this analysis indicated that expansion and diversification of the R2R3-MYB family may have contributed to phenotypic innovation in the Populus lineage. Second, drought-responsive transcriptome adjustments of two hybrid poplar clones, DN34 (P. deltoides X P. nigra) and NM6 (P. nigra X P. maxiomowiczii) were assessed for time-of-day and genotype dependent patterns. For each genotype, each of four time points was characterised by discrete sets of drought-responsive genes. Furthermore, while a number of genes were identified that were responsive to drought in both genotypes, a much larger number of genotype-dependent, drought-responsive transcriptome changes were detected. Finally, the drought-responsive transcriptome adjustments A. thaliana plants were assessed for time-of-day dependent accumulation patterns. Results of this analysis indicate that time-of-day-dependent differences in the drought response were manifest as changes of different magnitudes for a conserved set of genes across the four time points measured. These results emphasise the complex interplay of a plant’s genome, developmental stage, and environment in shaping the observed transcriptome.
Structural Metaphor: An Exploration of the Subjective Experience of Psycho-analytic Essence
Keywords: Psychoanalysis
Subjectivity
Structural Metaphor
Delicate Empiricism
Clinical Practice
Qualitative Research
Phenomenology
Interviews

In this study the subjective experience of psycho-analytic essence is approached through an examination of conscious and unconscious representations of self-in-work (Dreyfus, 1991). The study begins with an heuristic identified as the psycho-analytic moment, a transitory self-state arising in the course of conducting a psycho-analysis and felt to correspond to occasions of right, expert, good or exemplary therapeutic practice. The study advances to an examination of the lived experience of clinical psycho-analysis through a set of structured and unstructured interviews with two psycho-analysts. The study’s general approach incorporates a revised version of Goethe’s delicate empiricism as adapted by Hoffman (1989). The methods for interviewing participants and for analyzing transcripts were designed to access unconscious communications regarding subjective experience. Interview procedures combined phenomenological and free-associative narrative techniques: Procedures for transcript analysis were developed from literary studies, psycholinguistics, psycho-analysis and grounded theory. The analysis of participants’ utterance led to the hypothesis that an unconscious configuration of inference and memory gives shape to the subjective experience of composite elements of psycho- analytic practice. This hypothesized coherence of unconscious memory and process structures is identified as a structural metaphor. The structural metaphor is posited to underwrite the verisimilitude of lived experience, personal idiom and aesthetic within the clinical encounter. Thus, the structural metaphor is hypothesized to shape not only the psycho-analyst’s representations of his or her way of being-in-work and linguistic deportment within the interview setting, but to also shape the subjective experience of psycho-analytic practice. Thus reconsidered, the psycho-analytic moment is viewed as an existential moment in the ongoing phenomenology of lived experience, occasioned by a convergence of unconscious identity and experience within the clinical field. This existential moment is taken to be indicative of the presence of something essential about self, work or self-in-work, as a result of a set of psychological, affective and visceral factors that arise in this moment of convergence. However, the psycho-analytic moment is assigned little epistemic value in identifying properties of psycho-analysis as a discipline or a practice, instead reflecting the structural metaphor that underlies the experience of that practice.
Political Learning and the Pathways to Political Engagement
Keywords: Canadian politics
political behaviour

This thesis addresses two central questions: How in the long run do Canadian citizens learn about politics? And how does long term experience with politics influence democratic political engagement? The theoretical framework employed in this study makes four basic assumptions about citizens: they are intendedly rational, they use cognitive shortcuts, they are adaptive, and they often face deep uncertainty about the political world. These core assumptions generate a broad set of expectations about how long term experience with politics systematically affects citizen behaviour. This evidence indicates that years of accumulated experience with Canadian politics fundamentally shapes the political outlooks and behaviours of Canadian citizens. Political experience affects whether citizens vote, whether they get the requisite political information that helps them to make reasoned political judgments, and how different considerations enter into their vote choices. Moreover, and despite their different backgrounds, long term experience with Canadian politics influences democratic political engagement among Canadian born citizens and immigrant Canadians in strikingly similar ways.
A Scattering-based Approach to the Design, Analysis, and Experimental Verification of Magnetic Metamaterials Made from Dielectrics
Keywords: metamaterials
effective media
multiple scattering
magnetic permeability
silicon carbide
negative permeability
negative index
Mie theory
nanofabrication
nanochemistry
infrared spectroscopy

The design, modeling, fabrication, and validation of an optical magnetic response in dielectric-based metamaterials are studied. These metamaterials consist of either periodic or random arrays of dielectric particle inclusions, which may be spheres, coated spheres, or completely randomly shaped. It is demonstrated that because of the simple particle shapes and dielectric materials, these metamaterials are quite easy and feasible to implement in a bulk, three-dimensional sample, and the response is isotropic. This in is contrast to other predominant designs of optical metamaterials, which are planar and anisotropic arrays of complicated metallic fishnet or split-ring resonator structures, which require stringent tolerances and sophisticated assembly. It is shown that SiC is one of many materials from which such infrared magnetic metamaterials can be constructed. A simple SiC powder is used to verify these claims. The milled micropowder of crystalline SiC is comprised of particles of random shapes and sizes. A model of the electromagnetic response of such powders is developed, whereby the induced magnetic dipole response is modeled by equivalently-sized spheres of SiC, whereas the electric dipole response is modeled by a continuous distribution of ellipsoidal particles. Infrared spectroscopic measurements and numerical calculations are performed, verifying both the magnetic and electric response of the powder. A alternate approach is also described, where uniform SiC microspheres are fabricated using more sophisticated nanochemical techniques. In the final portion of the dissertation, the mutual near-field coupling between ideal magnetic dipoles induced in dielectric spheres is studied. This is implemented for microwave frequencies using large permittivity ceramic spheres. An approximate coupled dipole model of the multiple scattering among the spheres is developed, and a transition matrix method is implemented to calculate the exact scattering by the clusters. Experimental measurements are performed, confirming the two models. The results for pairs, chains, and rings of spheres indicates that the magnetic dipole modes hybridize in analogy to atomic bonding. A notable result is that certain hybridized magnetic dipole modes may have a net electric dipole moment. The similarity to atomic and molecular bonding should prove useful in conceptualizing and designing more sophisticated metamaterials.
The Impact of Adverse Events on Hospital Outcomes and Sensitvity of Cost Estimates to Diagnostic Coding Variation
Keywords: patient safety
outcomes
adverse events
hospital costs

Previous research has established a consensus that in-hospital adverse events are ubiquitous, cause significant harm to patients, and have important financial consequences. However, information on the extent, consequences and costs of adverse events in Canada is limited. For example, there is, as yet, no published study that has investigated the costs of adverse events in a Canadian context. This dissertation aims to redress this situation by providing Ontario-based estimates of the impact of eleven nursing sensitive adverse events on cost, death, readmission, and ambulatory care use within 90 days after hospitalization. This dissertation also aims to contribute more broadly to the patient safety literature by quantifying the impact of diagnostic coding error in administrative data on estimates of the excess costs attributable to adverse events. Given the increasing importance of these estimates in Canada and elsewhere for hospital payment policy and for assessments of the business case for patient safety, this is an important gap in the literature. Each of the adverse events was associated with positive excess costs, ranging from $29,501 (metabolic derangement) to $66,412 (pressure ulcers). Extrapolation from the study hospitals yielded a provincial estimate of $481 million in annual excess costs attributable to the adverse events, which represents 2.8 percent of Ontario’s total hospital expenditures. Several of the adverse events were also associated with significant excess rates of death, readmission, and ambulatory care use. These results suggest that there are economic as well as ethical reasons to improve patient safety in Ontario hospitals. Estimates of adverse event costs were highly sensitive to coding error. The excess cost of adverse events is likely to be significantly underestimated if the error is ignored. This finding, coupled with the observation that the likelihood of error is ignored in most studies, suggests that previous assessments of the business case for patient safety may have been biased against the cost effectiveness of patient safety improvements. Furthermore, the observed extent of institutional level variation in adverse event coding indicates that administrative data are an inadequate basis for adverse event payment policies or for public reporting of adverse event rates.