VictorJuiz/thesis huggingface dataset:
Essays in childhood obesity

This thesis aims to examine the various causes and consequences of childhood overweight and obesity in North America. In Chapter 2, I examine the issue of whether an increase in the mother's work intensity is associated with an increase in the risk of the child becoming overweight or obese for children in Canada. I also attempt to evaluate the causality of this relationship and the potential mechanisms that might facilitate this link. The results presented in this chapter are consistent with the idea that an increase in maternal work intensity in the earliest years of the child's life is associated with an increase in the risk of the child becoming overweight or obese later in childhood for children in Canada. In Chapter 3, I attempt to examine the consequences of childhood obesity outside of physical health outcomes for children in Canada and the United States. In particular, I look at whether weight affects school outcomes for pubescent children in Canada and the United States. I also examine the possible mechanisms behind this relationship. The results presented in this chapter suggest that there are potentially some differences between Canada and the U.S. in terms of how the child's weight affects his or her school performance. There is evidence to suggest that these differences do not appear to be primarily driven by differences in racial composition between the two countries. In Chapter 4, I examine the impact of household income on childhood weight status for children in the United States. In order to control for causality, I estimate various econometric models and implement an instrumental variable (IV) strategy based on exogenous changes in the tax code. The results presented in this suggest that although the prevalence of childhood obesity is higher in low-income families in the sample, household income might be acting mostly as a proxy for other unobserved characteristics that determine the child's weight status rather having a major direct causative role in determining the child's weight status for children in the United States.
Modelling of the nickel and cobalt kinetics during pressure acid leaching of laterites using Aspen Plus 11.1TM and OLI

The sulphuric acid pressure leaching process of lateritic ores employs an autoclave reactor operating at 230 to 270°C under vapour pressure. During this process, sulphuric acid selectively leaches nickel and cobalt values into the aqueous solution. The process has been commercially employed because it gives high nickel and cobalt extractions. In this thesis, the autoclave leaching process was simulated using commercial software, namely: Aspen Plus 11.1, Mathematica 5.0 and OLI. Kinetic parameters of acid-driven metal dissolution and precipitation reactions were determined from published experimental data using Mathematica 5.0. A dedicated thermodynamic database previously developed at the UofT was also used. Modelling accounted for hydrogen ion concentration at temperature as calculated by a full speciation via the OLI software. Mass balances were handled by Aspen Plus. It was found that the model gave very satisfactory predictions on nickel under industrial leaching conditions. Cobalt predictions fell below the experimental error for limonite leaching experiments.
Study of the paper fibre surface using atomic force microscopy

When wood fibres bond to form a paper sheet, it is their external surface which first comes into contact. The external surface and its properties thus play a very important role in determining the strength of the paper sheet. In this study, an atomic force microscope (AFM) was employed to probe the external surface of the fibre. AFM force curves obtained on never-dried pulp samples indicated the presence of a soft gelatinous fibrillar layer at the surface, the thickness of which was found to increase with beating. Transverse moduli of the gel layer and the cell wall were obtained by fitting the data to the Sneddon's model. Adhesion force measurements between an AFM tip functionalized with cellulose and fibre surfaces indicated that the degree of bonding improved with beating. The presence of a fibrillar layer at the surface was also seen in the total internal reflectance fluorescence microscopy images.
Phosphorylation of the N-methyl-D-Aspartate receptor in control and ischemic rat brain

The N-methyl-D-aspartate (NMDA) receptor is a Ca2+/Na+ channel that is regulated by phosphorylation. In this thesis, it was demonstrated that Src-family protein tyrosine kinases (Src) phosphorylate the rodent NMDA receptor subunits NR2A and NR2B. Tryptic peptide mapping identified seven and five major tyrosine-phosphorylated peptides derived from NR2A and NR2B respectively, but phosphorylation of NR2B by endogenous postsynaptic density (PSD) tyrosine kinases yielded only three tyrosine-phosphorylated tryptic peptides, two of which corresponded to Src phosphorylation sites, and one of which was novel. Y1472 of NR2B was identified as a phosphorylation site for intrinsic PSD tyrosine kinases, including Src. Following a transient (15 minutes) global ischemic episode produced by the four-vessel occlusion procedure, phosphorylation of several PSD proteins, including NR2B on Y1472, NR2A, and NR1 on S890, S896 and S897, was enhanced relative to shams. The ability of intrinsic PSD tyrosine kinases to phosphorylate the NMDA receptor increased following ischemia. The levels of PSD-associated protein kinases, including gp145TrkB, activated PKC and PYK2, were elevated at early times [0 minute (TrkB) and 15 minutes (PKC and PYK2)] after the ischemic event. Although an increase in PSD-associated Src was delayed for between 20 minutes and 6 hours, activated Src was present in the PSD by as early as 15 minutes. Phosphorylation of NR2A and NR2B by exogenous Src was dependent upon initial binding of the kinase to PSDs via its SH2-domain. The in vitro binding of NR2A and NR2B to the SH2-domain of Src increased after ischemia and 6 hours of reperfusion. Inhibition of PKC reduced the ischemia-induced activation of PKC, PYK2 and Src in PSDs, and diminished the increase in tyrosine phosphorylation of NR2A and NR2B. Together, these results contribute to our understanding of the basic mechanisms that underlie ischemia-induced increases in tyrosine phosphorylation of the NMDA receptor.
Finite element analysis of an implanted femoral retrograde intramedullary nail

Intramedullary nails are routinely used in the treatment of fractures of the femur. While their effectiveness has been demonstrated clinically, a number of complications, including bone refracture and implant failure, persist. This thesis presents novel three-dimensional finite element (FE) models, at four stages of gait, of: (i) a realistic femur analogue known as third generation composite bone, and (ii) a system consisting of an intramedullary nail implanted in the femur of (i). A comparison of experimentally measured strains on the surface of the femur with those predicted by the FE model revealed good agreement. The models were then used to identify implant/bone load sharing patterns, areas of stress concentration in both the intramedullary nail and the bone, and possible stress shielding when statically locked by one or two screws at either end. The results of this study can be used to guide future implant design and surgical procedure.
Effect of dopamine depletion on D1 receptor binding in rat brain ; and metabolism studies of D1 agonist R-[11C]KF 82957 and phosphodiesterase-4 inhibitor R-[11C}rolipram

In theory, contrary to DA D1 antagonist SCH 23390, D 1 agonist SKF 82957 is expected to bind selectively to D1 HIGH in vivo. Phosphodiesterase-4 (PDE4) plays a role in controlling cAMP levels, disturbances of which have been linked to depression. The objectives of this project are to utilize R-[ 11C]SKF 82957 and [11C]SCH 23390 to assess changes in D1 receptors, and determine the levels of unchanged PDE4 inhibitor R-[11C]rolipram after treatments reducing endogenous DA, and affecting cAMP levels, respectively. We hypothesized that the proportion of D1HIGH will increase following DA depletion, with no production of metabolites, and that unchanged R-[ 11C]rolipram plasma levels will remain unchanged following drug treatment. Results suggest that only AMPT is able to increase the proportion of D 1HIGH, although a metabolite is detected in rat brain. Levels of unchanged R-[11C]rolipram are significantly affected by maprotiline and thioperamide, although a general upward trend is visible for several other drugs.
Student teachers and their journey: a reflective ethnography

While field experiences are deeply entrenched elements in Bachelor of Education programs, the theoretical basis for fieldwork is still underemphasized in the literature (Guyton and McIntyre, 1990). This study focuses on following questions: What does the process of learning to teach do to teacher candidates, and teacher educators? What do student teachers learn during practice teaching sessions? What possibilities, tensions, and challenges do pre-service teachers experience in the field during practicum; and how can Bachelor of Education programs offer effective teacher development programs to prepare student teachers for these experiences? This study will follow six student teachers through university and field experiences during the 2000–2001 academic year. It will focus on their expectations and experiences within their first and second practicum placements. Objectives include: (1) What are the most important lived experiences of practice teaching and their consequences? (2) What program features do teacher candidates feel inhibit classroom practice teaching? (3) What do preservice teacher candidates believe is needed in the academic program that will help teacher candidates in their classroom practice? The research is conducted using qualitative data collection methods. Specifically, as the researcher, I used a reflexive ethnographic methodology to study the teaching journey of 6 elementary education student teachers and myself. While this dissertation focuses primarily on the experiences of six students it also “unearths” and “unravels” the researcher's own autobiographical journey as a teacher educator. It is this focus on “their journey” and “mine,” that the study is described as a reflexive ethnography by virtue of the autobiographical journal entries of the researcher that appear alongside the narratives of the participants. The complexities of the dialogic qualities of teaching and learning can never be underestimated with a study ending with what appears to be a “complete” list of “recommendations” and fewer questions concerning about becoming a teacher than when the study was first conceived. This study invites the reader to see learning to teach as a continuous process that seeks no final answers, inasmuch as it seeks out new possibilities for preservice teacher education.

Keywords: Student teachers
Student teaching, Training of
Teachers, Training of
The activation of beta-catenin and TCF-dependent signaling during wound repair

Cutaneous wound healing involves inflammatory, proliferative, and remodeling phases. During the proliferative phase, fibroblasts accumulate in the dermis where they synthesize matrix. These fibroblasts share cytologic similarity with cells in fibroproliferative processes. One such process, aggressive fibromatosis, a monoclonal neoplasm of fibroblast origin, arises from the activation of beta-catenin mediated TCF-dependent signaling in which beta-catenin protein translocates to the nucleus where it complexes with TCF transcription factors, activating target genes involved in cellular proliferation. Here we show that fibroblasts involved in wound healing undergo a similar, but transient beta-catenin elevation and transcriptional activation during the proliferative phase. Moreover, wounds in conditionally stabilized beta-catenin-overexpressing mice are larger and have a higher proportion of proliferating fibroblasts compared to control mice, suggesting that beta-catenin modulates dermal fibroblast activity during the proliferative phase of cutaneous wound healing, and that its overexpression can lead to excessive scar formation. We also demonstrate that growth factors liberated during the initial inflammatory phase of wound healing trigger activation of beta-catenin-mediated TCF-dependent signaling during the subsequent proliferative phase. EGF and TGF-beta1 most potently increase beta-catenin protein levels and transcriptional activity, whereas beta-catenin mRNA expression is unaffected. Furthermore, this increase is attributed to the inactivation of GSK-3beta, a kinase important for beta-catenin destabilization. To examine this relationship in-vivo, subcutaneous injection of EGF or TGF-beta1 prior to wounding of TCF reporter mice resulted in larger scars and significant TCF activity. Knockout of smad3, a TGF-beta1 signaling intermediate, attenuated elevation of beta-catenin protein level and transcriptional activity in wounds. However, wounds from mice harboring a mutation in the EGF receptor exhibited only a slight reduction in beta-catenin expression and transactivation ability. Thus, smad3-dependent TGF-beta1, and to a lesser extent EGF signaling, play important roles in regulating beta-catenin-mediated TCF dependent signaling during the proliferative phase of repair. Our results suggest that beta-catenin acts during the proliferative phase of wound healing to integrate signals from initial phase growth factors into the expression of genes important during the later, remodeling phase. beta-catenin plays a central role in regulating mesenchymal cells during repair and may be an appealing therapeutic target for the specific control of aberrant repair.
Factors That Affect the Decisions of Racial/Ethnic Minorities to Enter and Stay in Teaching and the Implications for School Boards' Teacher Recruitment and Retention Policies

This study examines the underlying reasons for the shortage of racial/ethnic minority teachers in Canada and presents strategies to address the issue. The data are based on interviews with 125 African-, Chinese-, and Portuguese-Canadian subjects, which include elementary and high school students, teachers-in-training, and teachers, each representing a different stage of the teaching pipeline. The study found that racial minorities reject or select teaching based on a combination of intertwining personal, family/cultural and institutional factors. Some of the same structural barriers may appear in various forms for different groups and span several stages of the teaching pipeline. Also racism, sexism and classism were found to intersect to impede minority youth from teaching. The three racial/ethnic groups cited both different and similar factors. The major barriers to teaching were: (1) an exclusionary Euro-centric learning environment in the pre-university and university stages which tend to disengage Black Canadians from school; (2) among Chinese-Canadians, parental emphasis on numerical skills and de-emphasis on language skills, and pressure to choose higher status, higher paying careers; (3) parental low priority on education and expectations for early employment among Portuguese-Canadians. The primary motivating factors to become teachers were: (1) a strong desire to reform the educational system (mainly for African-Canadians); (2) parental support for post-secondary education (mainly for Portuguese-Canadians); (3) interest in working with children; (4) exposure to teaching-related experience; & (5) teacher support to excel in school and/or to consider teaching as a career. Policy implications for recruiting more racial/ethnic minority teachers include: (1) making the school environment more inclusive; (2) intervening at elementary grades before the student's career path is set; (3) customizing outreach strategies for different communities and subgroups within the communities; (4) paying attention to conditions that have facilitated minority youth to overcome barriers to teaching; (5) focusing on the inner motivation of minority youth to teach; (6) providing more teaching-related experiences for minority students; (7) increasing teachers' awareness that they are influential in shaping minority students' future career choices; (8) exploring unconventional sources of teacher recruitment; (9) having the various stakeholders cooperate; & (10) monitoring the representation of minority teachers through on-going data collection.

Keywords: Minority teachers, Canada
Educational anthropology
Discrimination in higher education, Canada
Race relations in school management, Canada
Teachers, Training of
Teachers, Canada
Sex discrimination in education, Canada
Cultural relativism
Synthesis-structure-property relationships in AA6061 periodic cellular materials

Periodic cellular materials (PCMs) can have high specific strengths and stiffness at low density, making them an attractive materials design option. Micro-truss PCMs can be fabricated through simple sheet forming operations of perforated starting materials. This study is divided into two parts: formability and mechanical testing. Square-punched AA6061 perforated sheets were subjected to a range of treatments: solutionizing (W), artificial ageing at 205C (T6), and full annealing (O). The range of attainable pyramidal architectures is presented for each condition. Fully annealed sheets provide the greatest formability but would require a post-fabrication solutionizing treatment to benefit from the AA6061's precipitation hardening capabilities. Conversely, fabrication from the W temper allows the post-forming strain hardening to be used as a microstructural design tool. Mechanical testing showed that thermomechanically treated (T8) samples generally show improved mechanical properties, combining both work-hardening from the micro-truss fabrication and precipitation hardening.
A 4PAM/2PAM coaxial cable driver targeting 40Gb/s in 0.13mum CMOS

The main contribution of this thesis work is the design of a coaxial cable driver with Pulse-Width Modulation Pre-Emphasis (PWM-PE) and 4PAM/2PAM signaling. The high-speed Current Mode Logic (CML) design approach discussed in this thesis enabled the circuit to operate up to 32.5Gb/s and 16.25Gb/s in 4PAM and 2PAM modes in a 0.13mum CMOS technology. Features such as adjustable duty-cycle (50-75%) and output amplitude controls (0.4-1.2Vpp per side) are successfully designed and tested. The transmitter compensated a maximum of 30.3dB of cable loss at 16.25Gb/s in 2PAM and 8.9dB at 32.5Gb/s in 4PAM. The design occupies an area of 1.71mm x 1.83mm, and consumes a total of 1.578W.
The role and mechanisms of double negative regulatory T cells in the prevention of cardiac xenograft rejection

We have previously identified peripheral alphabetaTCR+CD3 +CD4-CD8- double negative (DN) T cells as a distinct Treg subset. DN Tregs obtained from allograft-tolerant mice can suppress/kill anti-donor T cells in vitro in an antigen specific manner and prolong donor-specific allograft survival in recipient mice following adoptive transfer. In this thesis, I studied the role of DN Tregs in the prevention of organ xenograft rejection. I used a rat-to-mouse cardiac xenotransplantation model, in which CD4+ T cells play a critical role in rejecting xenografts since CD4+ T cell-deficient (CD4-/- ) mice failed to reject rat hearts. I demonstrate that a combination treatment of pretransplant donor lymphocyte infusion (DLI) and a short course of anti-CD4 depleting mAb, but not anti-CD4 mAb alone, induced permanent rat-heart survival in wild type mice. Adoptive transfer CD4+ T cells from DLI/anti-CD4-treated xenograft-accepted mice can induce rejection of rat hearts in CD4-/- mice, indicating the presence of functional anti-donor CD4 + T cells in xenograft-accepted mice. Interestingly, the number of DN Tregs was significantly increased in the secondary lymphoid organs of DLI/anti-CD4-treated xenografted mice when compared to that of anti-CD4-alone treated recipients. DN Tregs isolated from the secondary lymphoid organs of DLI/anti-CD4-, but not anti-CD4-, treated xenografted mice could suppress the in vitro proliferation of anti-donor CD4+ T cells in an antigen-specific manner. In addition, when the number and phenotype of graft-infiltrating cells were compared between anti-CD4- and DLI/anti-CD4-treated groups, I observed a significant increase in both the number and suppressive activity of DN Tregs in the xenografts of DLI/anti-lCD4-treated mice. Thus, DN Tregs may be involved in controlling anti-xenograft CD4+ T cell responses in both secondary lymphoid organs and xenografts. Furthermore, adoptive transfer DN Tregs from xenograft-accepted mice significantly inhibited the in vivo proliferation and cytokine production of transferred naive CD4+ T cells, and prevented transferred CD4+ T cell-mediated rejection of rat cardiac xenografts in CD4-/- mice. These data provide in vivo evidence that DN Tregs are able to control anti-xenograft CD4+ T cell responses. Taken together, I have shown that suppression of anti-donor CD4+ T cells by DN Tregs contributes to the maintenance of xenograft survival.
Femtosecond laser direct writing of optical directional couplers inside bulk glass

A high repetition rate femtosecond fiber laser was applied to fabricate broadband directional couplers inside borosilicate glass for general power splitting application in the 1250 to 1650-nm wavelength telecom spectrum. The broadband response was optimized over the 4100-nrn bandwidth by examining the spectral response of the straight interaction region and the bent transition region separately. The spectral responses of the laser-written couplers were well-represented by coupled mode theory, permitting simple design and implementation of broadband couplers for bulk 3D optical circuit integration. Broadband directional couplers with various coupling ratio were fabricated. High spatial finesse of the femtosecond-laser writing technique enabled close placement (6 mum) of adjacent waveguides that underpinned the wavelength-flattened broadband responses.
Ultra-fast and high-effienciency DC/DC conversion for data processing circuits

Powering next-generation microprocessors requires high-efficiency high-performance DC/DC converters with extremely low-voltage high-current fast-transient-response output. To address these challenges, comprehensive studies are carried out. A zero-voltage-switching quasi-square-wave (ZVS-QSW) buck converter with fixed-frequency peak-current-mode (PCM) control was developed. Targeting at integration with deep sub-micron commercial CMOS process using a minimum number of external components, a series of innovations for power conversion technology were examined. This includes a current-conveyor-based Sense-FET scheme for current sensing, and fast “adaptive” dead time control using Delay-Locked-Loop-like Dead-Time-Locked Loops (DTLLs) for accurate soft-switching realization. These solutions collectively minimize switching losses thus maximize power converting efficiency at high switching frequencies, lower EMI noise and voltage stress on power device, while providing ultra-fast transient response and the convenience for paralleling multi-phase DC/DC converters. The design was simulated with a 3.3V input and a 1.3V 10A nominal output for conceptual demonstration purposes. The basic electrical parameters are scalable for various applications.