VictorJuiz/thesis huggingface dataset:
Dynamic adjustment of financial policy

Chapter 1 of this thesis uses a more robust market timing measure to test the relation between market timing and capital structure. A persistent impact of market timing on leverage is found. Moreover, the market timing measure is not a proxy for other firm characteristics, such as growth opportunities. This chapter also shows that equity issues at the IPO affect capital structure persistently, but equity issues in hot markets do not significantly reduce leverage more than those in cold markets. Though these results seem inconsistent with the static trade-off theory, we have to be cautious in rejecting the theory because the underlying capital structure will change after a firm goes public. Therefore, the firm may not need to rebalance away the effect of market timing IPO issues. To circumvent the bias against the trade-off theory when examining the IPO firms, chapter 2 studies capital structure adjustment mechanisms of firms that experience substantial changes in leverage. Adjustments appear to be asymmetric among firms with large increases and those with large decreases in debt ratios. The different adjustments are not due to differences in leverage targets or industry distributions between the samples. Speeds of adjustment are found to be affected by market timing opportunities. The persistence of equity market timing opportunities slows some firms' rebalancing process. Chapter 3 examines the relation between dividend smoothing and information asymmetry. Both the amount of the dividend payment and the extent of dividend smoothing are found to be negatively related to standard measures of information asymmetry. Firms with higher levels of asymmetric information are associated with lower dividend payments and also have a higher propensity to smooth their dividends. These results imply that a firm's information environment affects its dividend policy as indicated by Miller and Modigliani (1961).
Modelling of a nanowire array based photonic crystal cavity

We propose a new class of Photonic Crystal cavity - namely, nanowire array based band edge and band gap PC cavities. This concept combines the advantages of PCs for tight confinement of light, with nanowires demonstrated suitability for fabricating lasers. A model is developed and used to evaluate the optical properties of band edge cavities. Given appropriate conditions, the exact treatment can be reduced to simple formulae, which provide an excellent approximation for field patterns and frequency values. We find boundary orientations, for which the lifetime of the confined modes can be enhanced by orders of magnitude. In band gap and "PC-based heterostructures" cavities, energy confinement is even more efficient. An optical mode with a small volume, on the order of (lambda/n)3, can have quality factor (Q) as high as 4 x 104. The formulae and simulation results provide guidelines for designing a compact and tightly confined optical mode in these cavities.
A study of an ILU preconditioned multi-model formulation for compressible flows

This work examines a preconditioned multi-model formulation for three dimensional compressible flows. A finite volume based conservative discretization for the coupling of the full potential equation and the Euler equations is reviewed. The resulting nonlinear system is solved by a pseudo-transient Newton-Krylov method. The novelty in this thesis is the use of an incomplete LU factorization applied to precondition the linear system derived for the multi-model formulation at each Newton step. Computed solutions for subsonic and transonic flows around half of a NACA0012 airfoil extruded in 3D to demonstrate the feasibility of this method are presented. Results show that the ILU preconditioner significantly improves the linear convergence and therefore reduces the number of outer nonlinear iterations for the multi-model formulation.
Recursive partitioning methods for affected relative pair linkage analysis

Research in human genetics has recently focused on investigating complex diseases that may be controlled by both genetic and environmental factors, possibly interacting together. A recursive-partitioning (RP) algorithm has been developed for identifying subgroups of affected relative pairs demonstrating increased evidence for linkage, where subgroups are defined by pair-level or family-level covariates. After growing a full tree, optimal tree structures are identified through a tree pruning procedure and a final tree structure selection procedure by use of bootstrap algorithms. Simulation studies showed that power to detect linkage can increase in the presence of gene-environment interactions, depending on the magnitude of the interaction, and the RP linkage model correctly identifies covariates associated with disease genes in a large proportion of simulations. The RP linkage model was applied to a dataset of families with bipolar disorder where linkage regions on chromosome 18 have been previously identified. Using the RP model, several suggestive regions were found on chromosome 18, and associated environmental factors were detected. The RP model has the potential to identify previously unknown gene-environment interactions, and the practical utility and potential of this new methodology have been demonstrated. In addition, for multiple dependent affected relative pairs, a GEE linkage approach was proposed, and was compared to an analysis using the log-likelihood ratio (LLR) statistics from a likelihood ratio (LR) linkage model (Olson 1999) with significance thresholds set empirically. Properties of quasi-likelihood ratio statistics from the GEE linkage model were studied by simulations. In all the simulation studies, based on an empirical approach, the LLR statistics from the LR linkage model with an independence assumption had better power to detect linkage, and were recommended as goodness of split statistics for the RP linkage model.
A numerical investigation of airfoil boundary layer using large eddy simulations

The present study presents a numerical tool using large-eddy simulation (LES) to study the separated boundary-layer transition where the separation bubble is induced by a change of curvature of the surface on a NACA0025 airfoil. The unstructured Rannacher-Turek non-conforming rotated bilinear finite elements are used for spatial discretization. A consistent splitting method is employed so that at each time step four large linear systems are solved using an existing multigrid solver. A box filter based on the non-conforming elements is constructed. The scheme based on piecewise constant Smagorinsky coefficient allows a simple approach to the variable viscosity. The multigrid solver is modified so that all the filtering operations of LES were conducted on the finest mesh for different levels of multigrid cycles. Analyses of the different vortex structures in the near field of the boundary layer have been performed. The vortex merger and the entrainment of roll-up vortex were captured, which yielded an important hint to the related mechanisms of instability. The Kelvin-Helmholtz instability could be identified as the major source for the generation of the coherent vortices. Comparisons of the results between the numerical simulations and the experimental findings have provided further improvements required. The results are in excellent agreement with experimental results for the pressure distribution and the power spectrum density of velocity fluctuations.
In search of home on landscapes in transition: narratives of newcomer families' cross-cultural schooling experience

This is a study of newcomer families in search of home in Canada on landscapes in transition. My 3-year intensive fieldwork and 2-year follow up at Bay Street Community School, an inner-city school in Toronto, helped me develop a narrative understanding of linguistically and culturally diverse school life. Narrative methodology enables me to simultaneously study the cultural tensions and communications in the processes of cultural adaptation while appreciating the knowledge and values brought to Canada by new immigrants. I offer a concept of generational family narratives and use generational narratives as the lens to construct immigrant educational profiles of five families. I interpret these profiles as culturally and personally embedded expressions of Confucian philosophy and I make comparisons with Deweyian experiential philosophy. I explore the curricular significance of these family narratives by using Schwab's practical concept of curriculum. I found that Chinese families' notion of home is closely related to their notion of learning, which is deeply rooted in Confucian thought. Chinese grandparents' and parents' dedication to the family and their efforts and sacrifices for younger generations are, from the Confucian perspective, contributions to family harmony, and hence to the harmony and growth of society. Through the lens of generational narratives, my study reveals both hidden needs and special contributions. It also shows that Canadian society is constantly reshaped and reconstituted by newcomers' cultural interactions with and adaptation to the existing society. People thought of as the mainstream or those who have adapted to the mainstream need to see themselves as part of the adaptation process in the changing landscape. This reciprocity can help contribute to a society that is multicultural and inclusive for all. Generational narratives provide insights for cultivating 'we-consciousness' in diversity, a vision intended to embrace linguistically and culturally diverse school life in narrative unity: Confucian continuity of being and Deweyian continuity of knowing. The study calls for extended and expanded mutual we-ness in dialogues across civilizations in hopes of building a multidimensional bridge that can harmoniously connect ethnically, socially, culturally, and linguistically diverse people. Hence our children can grow up in positive multicultural harmony in diversity.
All transparent, laser-micromachined, lab-on-a-chip device for dielectrophoretic manipulation of micro- and nano-particles

To facilitate single cell analysis for proteins and offer biological investigation, an accurate, dynamic, powerful, and easily integrated cell manipulation device is a necessity. This project demonstrates an integrated device to perform cell motion manipulation as part of a micro-total-analysis system for analyzing cytokine regulated gene expressions. The design, modeling, fabrication, and testing of a dielectrophoresis micro- and nano-particle trap, containing electrically conductive electrodes made of ITO, retaining the optical transparency, is successfully accomplished. The three novelties of this project are: (1) the first characterization of F2-laser ablation of ITO, (2) the first analytical study of the effect of femtosecond laser pulse repetition rate on ITO etching efficiency, and (3) the first demonstration of dielectrophoresis force generated by ITO electrodes in a 2D octuple configuration.
Design of minimalist Max proteins in yeast systems

Minimalist Max proteins were designed to bind E-box (5'-CACGTG), targeted by oncoprotein c-Myc. Several strategies were employed to generate minimalist Max derivatives that retain E-box binding function. One strategy involved conversion of the native MaxbHLHZ (basic/helix-loop-helix/leucine zipper) into a bHLH-like structure. Hybrids of the Max basic region and E47 HLH domain were fused to generate Max derivatives that retained DNA-binding function without the leucine zipper. These hybrids bind to the E-box site as strongly as does the native MaxbHLHZ and are capable of inhibiting native MaxbHLHZ's binding to E-box. Such hybrids between two different transcriptional activator families, bHLHZ and bHLH, have not been reported in the literature. Another strategy to generate minimalist Max derivatives involved conversion of native MaxbHLHZ into a bZIP-like structure. Two approaches were pursued: one was a functional hybrid between the basic region of Max and the leucine zipper of C/EBP, a bZIP protein. The other was to simplify the MaxbHLHZ directly by mutations and deletions in the Max HLHZ domain. In both studies, we performed in vivo library selection. The bZIP-like construct MM10 was uncovered after one round of selection. Several constructs---including MaxbH 1-FPAM-H2Z, MaxbH 1-RIRV-H2Z and MaxbH 1-GCEI-H2Z---showed weak binding as well, and further characterization is being performed on these mutants. Yeast one-hybrid and two-hybrid systems were used in all these studies to assay protein-DNA binding. We also improved the yeast one-hybrid system (Y1H) by incorporating homologous recombination and electroporation. These improvements give high transformation efficiencies, and we are able to screen quickly a library of ge;106 transformants per round of selection. Thus, the improved Y1H is useful for in vivo selection, and even directed evolution, experiments. Our minimalist design strategy reduces the structural complexity of native Max. The successful design of Max(E47) provides a scaffold for further exploration of the relationship between protein structure and DNA-binding function and further development of molecules that control c-Myc's aberrant activity.
Simulations of transport and bioremediation of volatile organic compounds in the subsurface

In this study, the Compsim model was used to simulate two previously conducted experiments: a two-dimensional laboratory experiment of vapour transport in sand and a three-dimensional pilot scale study of biodegradation of toluene under nutrient-limited conditions. The former was performed to investigate the influential factors on vapour transport in sand under various conditions such as single and multi-component, water content, infiltration, and soil vapour extraction. The latter was conducted to study the activities of microorganisms during aerobic biodegradation under varied nitrate conditions associated with bioventing. In the above simulations, the model exhibited good ability to represent the vapour transport processes such as gas phase advection, diffusion, density-driven flow, interfacial mass transfer, adsorption, valotilization, and biodegradation under various conditions. The simulation results also accurately illustrated the characteristics of soil vapour extraction and closely predicted the gas phase oxygen, carbon dioxide and toluene concentrations during the bioventing processes.
Global view and genetic dissection of genes in sister chromatid cohesion

The replication and transmission of genetic information from generation to generation is central to every organism. Accomplishment of this daunting task relies on the integrated action of a number of cellular processes in DNA dynamics: DNA replication, DNA repair, checkpoint pathways, chromosome structure, chromosome segregation and others. By extensively applying synthetic genetic array analysis, a genetic interaction network in DNA dynamics was created. This genetic network identified functionally related genes and was able to predict the functions of novel genes. In addition, this genetic network provides a global picture elucidating the relationships among different pathways and different cellular processes in DNA dynamics. I explored a subset of genetic interactions and discovered that the deletion mutation of SRS2 and genes in the establishment of sister chromatid cohesion result in synthetic lethality due to improper homologous recombination (HR). However, cohesion defects were not corrected by deleting the HR pathway, and cells maintained their viability in the presence of cohesion defects as long as excessive HR was controlled. I proposed a model suggesting that sister chromatid cohesion is required for the proper completion of homologous recombination repair. I also created a sub-network of genetic interactions involving genes required for sister chromatid cohesion. This sub-network identified a number of novel cohesion genes and linked sister chromatid cohesion with various aspects of DNA dynamics, suggesting that sister chromatid cohesion plays a critical role in DNA dynamics. In addition, extensive genetic interactions were uncovered among cohesion genes, indicating the presence of parallel pathways. By performing epistatic cohesion analysis, two cohesion pathways were defined: one is composed of Tof1/Csm3 complex together with Ctf4 and Chl1; the other one is composed of Ctf18 complex (Ctf18, Ctf8 and Dcc1) along with Mrc1. Both cohesion pathways are required for the establishment but not maintenance of sister chromatid cohesion.
Mutations in Smad2 and Smad4 associated with human cancer disrupt TGF[Beta] signal transduction

Transforming Growth Factor β (TGFβ) has a potent antiproliferative effect on epithelial cells and it is thought to play important role in cancer development. Biological signals for TGFβ are transduced through transmembrane serine/threonine kinase receptors and a family of intracellular mediators known as Smads. Smad2 and Smad4 are important for transcriptional and antiproliferative responses to TGFβ and their inactivation in human cancers indicates that they are tumor suppressors. A missense mutation at a conserved arginine residue in the MH1 domain of both Smad2 and Smad4 has been identified in colorectal and pancreatic cancers, respectively. However, the mechanism whereby this mutation interferes with Smad activity was uncertain. We provide evidence that these mutations do not directly disrupt activation of Smads, including receptor-mediated phosphorylation of Smad2, Smad2/Smad4 heteromeric complex formation and Smad nuclear translocation. However, they target the Smads for accelerated degradation through ubiquitin-proteasome pathway involving UbcH5 family of ubiquitin conjugating enzymes. Although at this point we have not been able to identify any recognizable E3 ligase that may target the MH1 mutant Smads for degradation, we have isolated several Smad-interacting proteins that may play an important role in Smad-mediated signal transduction, transcriptional regulation or tumorigenesis. Additionally, we examined the mechanism of disruption of TGFβ signaling by Smad4(Δexon 5–6), a Smad4 splice isoform originally found in TGFβ-resistant breast cancer cell line. We show that Smad4(Δexon 5–6) can still heteromerize with receptor-activated Smad2. Deletion of exon 5–6 does not perturb the DNA binding ability of Smad4 or formation of a transcriptional activation complex composed of Smad2/Smad4 and transcription factor FAST. However, Smad4(Δexon 5–6) displays a decrease in transcriptional activation of TGFβ-responsive genes and is unable to functionally interact with the transcriptional activator MSG1. Together, our studies demonstrate that whereas the arginine mutations in the MH1 domains of Smad2 and Smad4 target the Smads for proteasomal degradation, deletion of exons 5–6 in Smad4 results in a loss of functional interactions of Smad4 with a transcriptional activator MSG1. Both of these alterations lead to a loss of cellular responses to TGFβ's antiproliferative effect and thus may promote tumorigenesis.
The role of C-terminial SRC kinase (Csk) in the regulation of N-methyl-D-aspartate receptors

The N-methyl-D-aspartate receptor (NMDAR) is a major subtype of glutamate receptor that mediates excitatory synaptic transmission in the central nervous system (CNS) and is required for inducing functional plasticity at many synapses. Up-regulation of NMDAR by Src family kinases (SFKs) is a critical mechanism underlying a variety of neuronal functions, and this regulation is controlled by the convergence of many signaling pathways on SFKs. It has been documented that protein tyrosine phosphatase alpha (PTPalpha), which activates SFKs by selectively dephosphorylating the phosphorylated C-tail tyrosine (Tyr527 in chicken c-Src), associates with NMDARs by binding to postsynaptic density 95 (PSD-95), and plays important roles in the initiation and maintenance of NMDAR up-regulation by SFKs. Here, I report that C-terminal Src kinase (Csk), which specifically phosphorylates the regulatory C-tail tyrosine of SFKs and thereby inhibits their kinase activity, targets NMDARs through direct and indirect associations with C-termini of NR2 and NR1 subunits, respectively. As Src activity increases, both associations are enhanced. In vitro pull-down assays show that Csk binds to a peptide corresponding to the C-tail of NR2A through multiple binding sites, but fails to bind to a peptide corresponding to the C-tail of NR1. The Csk-NR2A C-tail interaction can be significantly reduced by the mutation of the Src homology 2 (SH2) domain of Csk or by dephosphorylation of the NR2A C-tail, suggesting the involvement of the classical SH2-phosphotyrosine binding. Furthermore, Csk attenuates the phosphorylation of NR2A subunit mediated by wild-type Src, but not by the mutant Src in which the C-tail tyrosine phosphorylation is blocked. Applying recombinant Csk into hippocampal neurons cultured from embryos or isolated acutely from adult rats inhibits NMDAR-mediated whole-cell currents, and this effect can be occluded by pre-inhibition of SFKs, indicating that Csk down-regulates NMDAR activity via depression of SFKs. Finally, blocking Csk SH2 domain interaction significantly potentiates excitatory synaptic transmission and occludes the tetanic stimulation-induced long-term potentiation (LTP), whereas increasing intracellular Csk inhibits the induction of LTP at Schaffer collateral-CA1 synapses. Thus, it is the first demonstration that Csk dynamically targets NMDARs and negatively regulates NMDAR tyrosine phosphorylation, channel activity and synaptic plasticity.
Investigating the shear characteristics of high performance fiber reinforced concrete

Six reinforced PVA-ECC concrete panels were tested under conditions of in-plane pure shear in Toronto, as part of a joint research project between the Department of Civil Engineering of University of Toronto and Kajima Technical Research Institute in Japan. The performance of reinforced PVA-ECC concrete panels with regards to such variables as reinforcement ratios, loading conditions and mechanical properties of reinforcement was observed. The data gathered increased the small existing database of such elements subjected to pure shear. Once the test data accuracy was verified and validated, the stress-strain relationships of reinforced PVA-ECC concrete panels were determined and the pure shear capacity and ductility was investigated. From the analysis performed was found that the MCFT underestimates PVA-ECC concrete behavior both in terms of shear strength and ductility. Two improved models were proposed, MMCFT and MMCFTnocrack. The latter was found to significantly improve the MCFT prediction of PVA-ECC concrete behavior.
Glucose-inhibition of glucagon secretion via PI3K/Akt-dependent pathway

Little is known about the mechanisms underlying the inhibition of glucagon secretion from pancreatic alpha-cells, while lack of this suppression is an important contributor to diabetic hyperglycemia. It is known that glucose can inhibit glucagon secretion through GABA and insulin released from the pancreatic beta-cells. As GABAA receptors (GABAAR) expressed in the alpha-cells possess consensus phosphorylation sites for Akt, an effector downstream of PI3-kinase (PI3K) in the insulin-signalling pathway, one mechanism for the glucose-inhibition of glucagon secretion has been hypothesized to be via the insulin-PI3K-Akt-GABA/GABAAR pathway. In glucagon-secreting cell-lines and islets isolated from rats and human, co-treatment with wortmannin (PI3K-specific blocker) or bicuculline (GABA AR antagonist) significantly reversed the insulin/GABA-inhibition of glucagon secretion in high-glucose conditions. Alterations of cellular Akt activity affected both basal and insulin-suppressed glucagon secretion in the presence of GABA. Furthermore, activation of insulin receptors and Akt was reduced in cells with insulin resistance, which completely abolished the insulin- and GABA-mediated suppression of glucagon release. These results present a novel mechanism by which glucose suppresses glucagon secretion.