VictorJuiz/thesis huggingface dataset:
The Associate Teacher in the Preservice Practicum
Keywords: associate teacher
practicum

This study explores the perspectives of associate teachers (also known as cooperating teachers, host teachers, mentor teachers) during the preservice practicum. The study was conducted over the span of one school year (2008-09) in one school district. Ten associate teachers consisting of primary, junior, and intermediate elementary teachers, who had been associate teachers during the 2008-2009 school year, were interviewed once for approximately one hour. Based upon the responses of the participants and related literature, the study reveals that overall associate teachers found the practicum experience to be positive. However, the varied responses also reveal that there is room for improvement. The findings indicate that the practicum experience would be greatly enhanced through allowing associate teachers more input into the preservice program, and increasing the collaboration amongst university supervisors, teacher candidates, and associate teachers. The findings also indicate that associate teachers seek a more defined and structured role description, which takes into account the reality of classrooms and their emotional work. Further, the study highlights the need for preservice programs to rebuild and promote professional practice that supports on-going learning for associate teachers. Suggestions for improvements in the preservice practicum are given as well as implications for future research. It is concluded that associate teachers need to be considered as real partners in preservice education, which can be achieved by preservice programs seeking programmatic coherence, rethinking institutional patterns and re-envisioning the role of associate teachers. It is suggested that a collaborative and innovative direction is required that takes into account the complex work of teachers and associate teachers.
Wavelength Conversion in Domain-disordered Quasi-phase Matching Superlattice Waveguides
Keywords: nonlinear optics
second-harmonic generation
difference frequency generation
optical Kerr effect
photonic integrated circuit
semiconductor
second-order optical nonlinearity
quasi-phase matching
parametric conversion
superlattice

This thesis examines second-order optical nonlinear wave mixing processes in domain-disordered quasi-phase matching waveguides and evaluates their potential use in compact, monolithically integrated wavelength conversion devices. The devices are based on a GaAs/AlGaAs superlattice-core waveguide structure with an improved design over previous generations. Quantum-well intermixing by ion-implantation is used to create the quasi-phase matching gratings in which the nonlinear susceptibility is periodically suppressed. Photoluminescence experiments showed a large band gap energy blue shift around 70 nm after intermixing. Measured two-photon absorption coefficients showed a significant polarization dependence and suppression of up to 80% after intermixing. Similar polarization dependencies and suppression were observed in three-photon absorption and nonlinear refraction. Advanced modeling of second-harmonic generation showed reductions of over 50% in efficiency due to linear losses alone. Self-phase modulation was found to be the dominant parasitic nonlinear effect on the conversion efficiency, with reductions of over 60%. Simulations of group velocity mismatch showed modest reductions in efficiency of less than 10%. Experiments on second-harmonic generation showed improvements in efficiency over previous generations due to low linear loss and improved intermixing. The improvements permitted demonstration of continuous wave second-harmonic generation for the first time in such structures with output power exceeding 1 µW. Also, Type-II phase matching was demonstrated for the first time. Saturation was observed as the power was increased, which, as predicted, was the result of self-phase modulation when using 2 ps pulses. By using 20 ps pulses instead, saturation effects were avoided. Thermo-optically induced bistability was observed in continuous wave experiments. Difference frequency generation was demonstrated with wavelengths from the optical C-band being converted to the L- and U-bands with continuous waves. Conversion for Type-I phase matching was demonstrated over 20 nm with signal and idler wavelengths being separated by over 100 nm. Type-II phase matched conversion was also observed. Using the experimental data for analysis, self-pumped conversion devices were found to require external amplification to reach practical output powers. Threshold pump powers for optical parametric oscillators were calculated to be impractically large. Proposed improvements to the device design are predicted to allow more practical operation of integrated conversion devices based on quasi-phase matching superlattice waveguides.
Design of a Novel Serum-free Monolayer Differentiation System for Murine Embryonic Stem Cell-derived Chondrocytes for Potential High-content Imaging Applications
Keywords: embryonic stem cells
chondrocytes
serum-free
monolayer

Cartilage defects have limited capacity for repair and are often replaced by fibrocartilage with inferior mechanical properties. To overcome the limitations of artificial joint replacement, high throughput screens (HTS) could be developed to identify molecules that stimulate differentiation and/or proliferation of articular cartilage for drug therapy or tissue engineering. Currently embryonic stem cells (ESCs) can differentiate into articular cartilage by forming aggregates (embryoid body (EB), pellet, micromass), which are difficult to image. I present a novel, single-step method of generating murine ESC (mESC)-derived chondrocytes in monolayer cultures in chemically defined conditions. Mesoderm induction was achieved in cultures supplemented with BMP4, Activin A or Wnt3a. Prolonged culture with sustained Activin A, TGFβ3 or BMP4 supplementation led to robust chondrogenic induction. A short pulse of Activin A or BMP4 also induced chondrogenesis efficiently while Wnt3a acted as a later inducer. Long-term supplementation with Activin A or with Activin A followed by TGFβ3 may specifically promote articular cartilage formation. Thus, I devised a serum-free (SF) culture system to generate ESC-derived chondrocytes without the establishment of 3D cultures or the aid of cell sorting. Cultures were governed by the same signaling pathways as 3D ESC differentiation systems and limb bud mesenchyme or articular cartilage explant cultures. I am also in the process of creating a Col2a1 promoter-controlled, Cre-inducible reporter cell line to be used in my SF culture system using the Multisite Gateway® cloning technology. ESCs undergoing chondrogenic differentiation can be identified and quantified in HTS via the expression of fluorescent proteins. In addition, this transgenic line can be used to isolate ESC-derived chondrocytes as well as their progeny via cell sorting or antibiotic selection for in-depth characterization. The modular design of my construct system allows transgenic lines to be generated using various promoters of chondrogenic marker genes to perform parallel HTS analyses.
Periodic Mesoporous Organosilica and Silica
Keywords: Porous Materials
thin films
Low dielectric constant
inorganic-organic hybrid

Periodic mesoporous material is a class of solids that possess periodically ordered pores with sizes of 2–50 nm. After a brief introduction to the synthesis, structure, property and function of periodic mesoporous materials in general in Chapter 1, a specific type of periodic mesoporous material, periodic mesoporous organosilica (PMO), is examined in detail in Chapter 2. Chapter 3 and Chapter 4 focus on the application of periodic mesoporous organosilica as low-dielectric-constant (low-k) insulating materials on semiconductor microprocessors. Specifically, Chapter 3 introduces a vapor-phase delivery technique, vacuum-assisted aerosol deposition, for the synthesis of PMO thin films; Chapter 4 studies one property crucial for the application of low-k PMO in detail—hydrophobicity. The focus of Chapter 5 turns to a novel sandwich-structured nanocomposite made of periodic mesoporous silica and graphene oxide. In Chapter 6, progress towards the synthesis of periodic mesoporous quartz is summarized. A conclusion and an outlook are given in Chapter 7.
Stigma Resistance: Exploring the Experiences of Young People at Risk for Psychosis Through Photo Elicitation
Keywords: early psychosis
adolescence
qualitative methods
photo elicitation
stigma

The discovery that it is possible to identify an individual before the onset of first episode psychosis and that treatment may prevent or delay onset have led to a proliferation of early intervention clinics designed to intervene before symptoms of psychosis have fully appeared. Early intervention has generated considerable debate, given the risks associated with intervening and that the majority of those identified will never develop full-blown psychosis. Despite potential stigmatizing effects, little is known about young people’s views regarding the favourable and/or adverse consequences of early intervention. This research examines the experiences and meaning of illness in young people identified as being at ultra high risk for psychosis and participating in a psychological intervention program. Specifically, the study uses photo elicitation to explore how participants construct and interpret their experiences, and the impact an at risk label has on their sense of self, identity, and social relationships. Five young people were invited to photograph their daily experiences at home, at school, and in the community. The participants and I then analyzed the photographs together in a photo elicitation interview. I further analyzed the visual and textual data from an interactionist perspective, exploring the concept of stigma and its relationship to young people’s experiences. Visual and narrative data revealed that young people reject their at risk status and redefine their experiences to fit with more acceptable and familiar notions of health. Participants are conscious of the stigma associated with psychosis and actively undertake strategies of resistance to avoid stigmatization and uphold a normal self conception and social impression. Photo elicitation provided insight and understanding into the experiences of young people at risk for psychosis that were not available through more traditional methods. The results from this study support the call for a reconsideration of the psychosis risk paradigm. There is a need to increase awareness about the power of diagnostic information and the labeling process. Non-specialized settings such as schools and community health centres may offer more appropriate environments for mental health monitoring and intervention.
The Role of ShcA Phosphotyrosine Signaling in the Myocardium
Keywords: adaptor protein
cardiovascular

Tyrosine kinases (TK) are important for cardiac function, but their downstream targets in the adult heart have yet to be established. The ShcA docking protein binds specific phosphotyrosine (pTyr) sites on activated TKs through its N-terminal PTB and C-terminal SH2 domains and stimulates downstream pathways through motifs such as pTyr sites in its central CH1 region. To explore the role of this TK scaffold in the adult heart, we generated a myocardial-specific knockout of murine ShcA (ShcA CKO). Such mice developed a dilated cardiomyopathy phenotype involving impaired systolic function with enhanced cardiomyocyte contractility. This uncoupling of global heart and intrinsic myocyte functions was associated with altered perimysial collagen and extracellular matrix complicance properties, suggesting disruption of mechanical coupling. In vivo dissection of ShcA signaling properties revealed that selective inactivation of the PTB domain in the myocardium had effects resembling those seen in ShcA CKO mice, while disruption of the SH2 domain caused a less severe cardiac phenotype. Downstream signaling through the CH1 pTyr sites was dispensable for baseline cardiac function, but necessary to prevent adverse remodeling after hemodynamic overload. Therefore, ShcA mediates pTyr signaling in the adult heart through multiple distinct signaling elements that control myocardial functions and response to stresses.
Evaluating T-cell Immunity in HCV/HIV Co-infection
Keywords: Immunology
Infectious Disease

Due to shared routes of transmission, co-infection with Hepatitis C (HCV) and Human Immuno-deficiency Virus (HIV) has become prevalent worldwide, with approximately one-third of all HIV-infected individuals and about 10% of all HCV infected individuals in North America being co-infected with the other virus (1). Recent advances in HIV treatment have increased the life expectancy of HIV-infected patients, resulting in HCV-associated disease to develop into a major cause of morbidity and mortality among the co-infected population. HIV is consistently shown to have a negative effect on different aspects of HCV disease, from increased HCV RNA levels (2) to aggravated liver fibrosis and more rapid progression to cirrhosis and end-stage liver disease (3). The host immune responses play a major role in not only controlling HCV infection, but also in causing hepatic inflammation and damage. Despite major advances in the understanding of the pathogenesis of these two infections, the mechanisms underlying the role of immune responses in more rapid progression of HCV disease in HCV/HIV co-infection is not quite clear. This thesis is generated based on an investigation to understand why HIV infection worsens HCV pathogenesis. This question is addressed throughout this thesis from different immunological aspects, with a focus on the function of T-cells. I have demonstrated that in HCV/HIV co-infection, functional HIV-specific T-cells accumulate in the liver and produce an array of cytokines, including INF- and TNF-, which may represent a bystander role for HIV in the aggravation of HCV-induced liver damage. My data also demonstrate that co-expression of two defined T-cell exhaustion markers, Tim-3 and PD-1 may play a significant role in HCV-specific T-cell dysfunction, in the setting of HIV co-infection. Both total and HCV-specific peripheral T-cells co-express Tim-3 and PD-1 in significantly higher frequencies, compared to HCV mono-infection. In co-infection, HCV-specific CD8+ T-cells showed greater frequencies of Tim-3/PD-1 dual-expression than those being HIV-specific, indicating a greater degree of exhaustion in the former. Additionally, I demonstrated that some HIV mono-infected individuals may contain CD8+ T-cells that cross-recognize two defined HLA-A2-restricted epitopes within the HIV and HCV proteome, the HIV-Gag: SLYNTVATL and HCV-NS5b: ALYDVVSKL. This T-cell cross-reactivity was further elaborated in the context of HCV/HIV co-infection, demonstrating that degeneracy of HIV-specific T-cells may play a role in the immuno-pathology of co-infection. Altogether, these data could be integrated into the foundation of potential mechanisms involved in the immunopathogenesis of HCV/HIV co-infection, and be applied to further investigation in basic science and clinical studies in this field.
A Chinese Civil Society in the Making? Civic Perceptions and Civic Participation of University Students in an Era of Massification
Keywords: Civil Society
Higher Education
Civic Perceptions
Civic Participation
Citizenship Education
University Students
Middle-Class
China

Chinese higher education has achieved a remarkable expansion in recent years but few studies have examined the civic perceptions and civic participation of contemporary university students. This study aims to fill the gap in the existing literature by accomplishing four main goals: first, to investigate how students view citizenship, civic issues, and civil society; second, to examine how they participate in civic activities, both on and off campus; third, to understand how their civic attitudes and behaviours are being influenced by society, university and family, also by such factors as formal citizenship education curricula, informal educational experiences and the mass media; and fourth, to analyze the impact of higher education expansion on civil society in China. This study adopted a mixed methods approach, and combined findings from a large-scale national student survey across 12 universities and 34 face to face interviews conducted in 3 selected institutions among the 12 that were surveyed. The conceptual framework drew upon social capital theory and both ecological and cognitive psychological theories to generate two analytic frameworks for analyzing the quantitative and qualitative data. The major findings were: (1) university students demonstrated strong patriotism, and a serious commitment to social justice and civic participation, which was partly the result of the distinctive form of citizenship education they received in the Chinese context; (2) half of the survey participants were found to be inactive participants in civic activities, which showed a disconnect between their civic attitudes and civic behaviours; (3) higher socio-economic status (SES) was associated with more active civic participation; (4) the mass media, especially the Internet was found to have a profound impact on students’ civic perceptions; (5) interview participants in the three qualitative case institutions revealed distinctive patterns of civic engagement, which confirmed the importance of university environment, policy, history and culture on student civic participation and citizenship development. This study has made a significant contribution to the existing literature on citizenship issues in contemporary Chinese universities. It has also added to current knowledge on trends of civil society development and the democratization process in China, from the perspective of university students.
Essays on Dynamic Contracts: Microfoundation and Macroeconomic Implications
Keywords: Macroeconomics
Dynamic Contracts
Incentives

This thesis consists of three chapters pertaining to issues of long-term relationships in labour markets. In Chapter 1, I analyze a model of a two-period advice game. The decision maker chooses to retain or replace the advisor after the first period depending on the first period events. Even though the decision maker and the advisor have identical preferences, this potential replacement creates incentive for the advisor to avoid telling the truth. I show the condition under which the decision maker can find a random retention rule that induces a truthful report from the advisor, and I characterize an optimal retention rule that maximizes the decision maker's expected payoff. In Chapter 2, I propose a search theoretic model of optimal employment contract under repeated moral hazard. The model integrates two important attributes of the labour market: workers' work incentive on the job and their mobility in the labour market. Even though all workers and firms are ex ante homogeneous, these two factors jointly generate (1) wages and productivity that increase with worker's tenure and (2) endogenous dynamic heterogeneity of the labour productivity of the match. The interaction of these factors provides novel implications for wage dispersion, labour mobility, and the business cycle behaviour of macroeconomic variables. Lastly, in Chapter 3, I quantitatively assess wage dispersion and business cycle implications of the model developed in Chapter 2. In terms of wage dispersion, the model with on-the-job search with wage-tenure contracts seems to accommodate sizable frictional wage dispersion. The model, however, generates very small productivity difference among workers, and shows weak evidence that the productivity difference generated by the endogenous variations in incentives is responsible for frictional wage dispersion. In terms of business cycle implications, workers' endogenous effort choice first amplifies the effect of productivity shock on unemployment rate. Second, responses of workers to productivity shocks generate marked difference between the effects of temporary productivity shock and that of permanent shock. Third, the analysis shows the importance of the distributional effect on macroeconomic variables during the transitory periods after a shock.
Data Processing Techniques on Modern Hardware Architectures
Keywords: novel hardware
query processing
chip multiprocessors
energy efficiency
flash storage
databases

The last decade has been characterized by radical changes in the computing landscape. We have witnessed the advent of multi-core processors, flash-based storage systems and the proliferation of scale out architectures, such as map-reduce-based systems and massively parallel databases. Although data management systems have embraced modern hardware technologies to some extent, they have not realized their full potential. The goal of this thesis is two-fold. Primarily, it demonstrates the staggering potential for performance improvement offered by modern hardware architectures and, then, proposes how data management systems must alter in order to realize this potential. Additionally, this thesis demonstrates that utilizing modern hardware architectures is important both for performance and energy-efficiency. Towards this goal, we propose query processing and indexing techniques for chip multiprocessors and we analyze the trade-offs of executing complex database queries on modern processor technologies. Subsequently, we propose query processing methods tailored to flash-based storage systems. Finally, we analyze the power consumption of database systems and we reveal opportunities for improving their energy efficiency.
Arginine Synthesis in Humans
Keywords: Amino acids

Arginine synthesis is a complex, age-dependant process involving multiple precursors and enzymes, and the interorgan transfer of substrates. The objectives of this thesis were to elucidate arginine synthesis from enteral precursors in newborn infants and in healthy adults using stable isotope methodology. In the first, of four studies, I validated the use of a non-invasive methodology using urinary amino acids for stable isotope studies of arginine synthesis and demonstrated a known, but under-recognised, problem with D-amino acid contamination of tracers. Implementing chiral chromatography, this issue was further investigated using samples from previous studies in our laboratory with several different isotopes. I demonstrated the novel finding that the impact of D-amino acids is dependent on the tracer used, and also on the age of the subject. In the second study, I used a multi-tracer design to assess arginine synthesis from enteral proline or glutamate in healthy preterm infants. Labeled arginine (M+2), proline (M+1) and glutamate (M+3) were given enterally to fifteen stable, growing preterm infants (gestational age at birth 30-35 weeks) at 1-3 weeks’ postnatal age. I found only arginine synthesis from proline, with no synthesis from glutamate. I conclude that enteral proline is the major contributor to arginine synthesis in vivo in human preterm infants. In the third study, I measured arginine synthesis from enteral proline in adults. I have demonstrated that enteral proline contributes significantly, ~25%, to newly synthesised arginine. In the fourth study, I used two glutamine tracers, 1-13C and 2-15N, to determine if glutamine is a carbon or nitrogen donor for arginine. I showed that enteral glutamine contributes ~50% of the carbon skeleton for arginine and that the 2-15N tracer significantly overestimates arginine synthesis, with the labeled N being transferred through transamination from pyrroline-5-carboxylate (to ornithine, rather than directly from glutamate to pyrroline-5-carboxylate. In conclusion, proline is the sole precursor for arginine in human neonates and combines with glutamaine as the dietary precusor in adults. As a precussor for arginine, though, glutamine’s main role is in provision of nitrogen independent of the carbon skeleton.