VictorJuiz/thesis huggingface dataset:
Formation, Characteristics and Electrocatalytic Properties of Nanoporous Metals Formed by Dealloying of Ternary-noble Alloys

Nanoporous metals formed by electrochemical dealloying of silver from Ag-Au-Pt alloys, with 77 at.% silver and platinum contents of 1, 2 and 3 at.%, have been studied. The presence of platinum, which is immobile relative to gold, refine the ligament size and stabilized the nanostructure against coarsening, even under experimental conditions that would be expected to promote coarsening (e.g., exposure to high temperature, longer dealloying times). By adding only 1 at.% Pt to the alloy precursor, the ligament/pore size was reduced by 50% with respect to that in nanoporous gold (NPG), which was formed on a Ag-Au alloy with the same silver content as ternary alloys. A further decrease in the ligament size was observed by increasing the platinum content of the precursor; however, most of the improvement occurred with 1 at.% Pt. The adsorbate-induced surface segregation of platinum was also investigated for these nanoporous metals. By exposing freshly-dealloyed nanostructures to moderate temperatures in the presence of air, platinum segregated to the ligament surface; in contrast, in an inert atmosphere (Ar-H2), platinum mostly reverted to the bulk of the ligaments. This thermally activated process was thermodynamically driven by the interaction between platinum and oxygen; however, at the desorption temperature of oxygen, platinum de-segregated from the surface. Moreover, the co-segregation of platinum and oxygen hindered the thermal coarsening of the ligaments. Finally, the electrocatalytic abilities of these nanostructures were studied towards methanol and ethanol electro-oxidation, in alkaline and acidic media, showing significantly improved response in comparison to that observed in NPG. The synergistic effect between gold and platinum atoms and the smaller feature size of the nanostructures were directly associated with this behaviour. In alkaline electrolyte, the nanostructure formed on the alloy with 1 at.% Pt showed higher catalytic response than the other two ternary nanostructures, which could be associated with the platinum/gold ratio on the surface of the structure. In acidic electrolyte, the nanostructure with the highest platinum content displayed the highest electrocatalytic response. Furthermore, the presence of platinum changed the selectivity of both reactions: the concentrations of carbonate produced increased by increasing the platinum content in the alloy precursor.

Keywords: Dealloying
Electrocatalysis
Platinum
Surface segregation
Ternary-noble precursors
Advisor: Roger, C Newman
Fabrication and Optimization of Ni Superalloy Inconel 600 Microtruss Materials

Microtruss materials are multifunctional cellular hybrids composed of an interconnected arrangement of internal struts that can offer enhanced strength and stiffness at low densities. This study looks at the potential of Ni-based superalloys as microtruss materials. The potential of using the in-situ plastic strain imparted during stretch forming to grain boundary engineer the internal struts of Inconel 600 (IN600) cellular hybrids was also explored. In order to examine this question, a combination of experimental and finite element (FE) methods were employed. The non-uniform plastic deformation imparted to the microtruss struts during fabrication was modeled by FE and the local changes in grain boundary character in the fabricated trusses were mapped by electron backscattered diffraction.This study also examined the distribution of plastic strain over the microtruss architecture. A mechanical press with various pin geometries was employed to experimentally validate the FE models. Standard pin geometry results in substantially non-uniform plastic strain, which limits the maximum formability of the starting sheet material. Importantly, pins designed with tapers and spheres were shown to impart plastic strain along the entire length of the microtruss. This opened up possibility of new design strategies for facilitating grain boundary engineering over the entire truss. It may also present opportunities for enhancing the energy absorption performance of microtruss materials.Finally, this study examined the mechanical properties of IN600 microtrusses, in particular focusing on the significance of strut end constraints in determining the overall mechanical performance. While it is straightforward to analytically determine the inelastic buckling resistance of plastically deformed struts, there is no simple way to determine the rotational end constraint of the struts deformed to varying truss angles. It was seen that end constraint rigidity k could be determined using a FE-based bifurcation analysis and the value of k was architecture dependent.

Keywords: Cellular materials
End constraint rigidity
Increasing formability
Optimization of properties of cellular materials
Pin design for increased formability
Plastic strain distribution
Advisor: Glenn, D Hibbard
Joint Three-flavour Oscillation Analysis of Muon Neutrino Disappearance and Electron Neutrino Appearance in the T2K Neutrino Beam

The Tokai to Kamioka (T2K) experiment is a long-baseline neutrino oscillation experiment based in Japan. An off-axis, high purity muon neutrino beam is produced at the Japan Proton Accelerator Research Complex by colliding a proton beam with a graphite target. The neutrinos are detected at a near detector complex (ND280), situated 280 m from the neutrino production target, and the Super-Kamiokande (SK) far detector at 295 km. This thesis first outlines current knowledge and challenges in the physics of neutrinos, then describes the T2K beam and detectors, including a novel optical transition radiation monitor for precisely measuring the proton beam in order to determine the neutrino beam direction. A framework for evaluating the uncertainties in neutrino interactions and pion hadronic interactions in ND280 and SK is presented. A new SK event reconstruction algorithm is described and the SK detector systematic errors are evaluated based on atmospheric neutrino and cosmic ray muon data. These developments are used in a Markov Chain Monte Carlo neutrino oscillation analysis of the T2K Run 1-4 data corresponding to 0.657 x 10^21 protons on target. The analysis simultaneously considers the 2013 ND280 muon neutrino samples, and SK single muon and single electron samples, producing a measurement of muon neutrino disappearance and muon neutrino to electron neutrino appearance. Estimates of the PMNS oscillation parameters and Bayesian credible intervals are determined. Recent measurements from reactor neutrino experiments are combined with the T2K data resulting in exclusion regions for the CP violating phase parameter.

Keywords: neutrino
oscillation
OTR monitor
pion interactions
Super-Kamiokande
T2K
Advisor: John, F Martin
Aboriginal Student Persistence and Success in Ontario Colleges

This study relies on a mixed method research approach with a focus on qualitative research including open-ended, semi-structured interviews at Aboriginal Resource Centres in three colleges in Ontario. Interviews were conducted with 31 participants engaged with Aboriginal Resource Centres, including Aboriginal students, staff and Elders. Participants spoke about their interactions with the Ontario college system including their positive and negative experiences. The research process is also informed by an in-depth analysis of various studies and reports regarding Aboriginal peoples, education and enrolment statistics from the 24 Ontario colleges. The overall data analysis and interpretation includes insight from all of these data sources. The research is guided by a two-eyed seeing approach (Iwama, Marshall, Marshall, Barlett, 2009) that respects a combination of Western and Aboriginal worldviews; however, a concerted effort has been made to honour Indigenous paradigms thus, at times, this minimizes the inclusion of traditional Euro-centric views and methodology. Nevertheless, parallels were drawn between Euro-centric student development and engagement theories and Indigenous paradigms to provide insight into how postsecondary institutions can support Aboriginal students and create a safe and welcoming environment on campus for all Aboriginal peoples. An Ojibwe Anishinabe Elder recognized by her community provided guidance throughout the research process. She allies with students connecting them to traditional protocols and shares authentic Indigenous teachings. Further, to respect the place of Aboriginal voices, a collection of Elder reflections describes a vision for Aboriginal education, and specifically postsecondary education.The conclusions drawn from the study suggest that many colleges in Canada, and Ontario, are helping Aboriginal students obtain a postsecondary credential. Colleges are creating a supportive and welcoming environment and Aboriginal Resource Centres are helping students connect with their communities, institutions and Aboriginal cultures. In spite of this success, many Aboriginal students do not reach postsecondary education. Many Aboriginal students are not engaging with these centres and Aboriginal peoples continue to experience racism on campus. The findings indicate that true collaboration and meaningful consultation with Aboriginal communities is needed to "Indigenize" the campuses.

Keywords: Aboriginal
Aboriginal student enrollment
Aboriginal student success
College
Indigenous education
native education
Advisor: Charles, Pascal
Device-to-Device Assisted Cooperative Communications

In a cooperative communications scenario, wireless devices assist each other in their transmissions or receptions. This cooperation has been shown to improve the communication reliability while increasing the efficiency of the spectrum usage.In this thesis, we study how a device, which may be idle otherwise, can be leveraged to increase the spectral efficiency of the wireless system. First, we consider a two-user case where a secondary user perceives the environment and adapts its behaviour in a way that it does not degrade the performance of a primary user (also known as the "cognitive radio"). Moreover, we consider a multi-user case where single antenna devices can be clustered together to virtually form a more sophisticated device that can perform beamforming.In the two-user cognitive radio, under the half-duplex assumption and collision avoidance model, the primary and secondary instantaneous data rates are derived as a function of the power allocation factor by the secondary user. Also, the performance of various cooperative schemes including decode-and-forward and amplify-and-forward is investigated.The two-user case is further extended to the multi-user case where the problems of clustering (of the source device with a subset of perhaps idle devices) and beamforming are separated and studied. For the clustering problem, a simple and agnostic greedy algorithm is shown to perform optimal. Also, two beamforming techniques are proposed: firstly, a selfish beam- forming using the feedback channel, and secondly a coordinated beamforming (also known as interference alignment) using the reciprocal channel.

Advisor: Liang, Ben
Differential Omission Rates: Exploring Factors that Influence Omission Rates in a Large-scale Pan-Canadian Assessment

This study explored why students simply skip selected response questions when they do not know the answer, especially when there is no penalty for incorrectly guessing? This question was examined with respect to omissions in selected response items in the 2010 Pan-Canadian Assessment Program (PCAP) Mathematics Assessment. The goal of this study was to explore how student, teacher, school, and cultural factors affect the rates of omission and how these factors help to explain differential patterns of omissions among provinces and between French- and English-speaking students, which may, in turn, lead to corresponding differences in group achievement scores. Multilevel modeling (HLM) was used to examine factors that predicted whether a student would omit one or more items. This analysis provides a statistical description of omission rates as they vary over the parts of the test, for different item types, and compares French- and English-speaking students from each of the three provinces using both their test booklets and the background questionnaires. In addition to differences in students' omission behaviour among the provinces and, between linguistic populations, the study explores how instructional, cultural, and psychological variables may influence students' omission behaviour. There were differences in omission rates between French- and English-speaking students in New Brunswick, but no longer in Ontario or Québec. Two factors were identified as significant in explaining omissions: the students' test-taking strategy for selected response items and their level of confidence in the subject. A measure of students' Locus of Control was not a significant predictor for any population nor was risk tolerance.

Keywords: Factors affecting omission rates
Locus of Control
Omissions of selected response items
Advisor: Wolfe, Richard
Stochastic Integer Programming: Decomposition Methods and Industrial Applications

Many practical problems from industry that contain uncertain demands, costs and other quantities are challenging to solve. Stochastic Mixed Integer Programs (SMIPs) have become an emerging tool to incorporate uncertainty in optimization problems. The stochastic and mixed integer nature of SMIPs makes them very challenging to solve. Decomposition methods have been developed to solve various practical problems modeled as large-scale SMIPs. In the thesis, we propose a scenario-wise decomposition method, the Dynamic Dual Decomposition method (D3 method), to decompose large-scale SMIPs in order to solve practical facility location problems more efficiently. The Lagrangian bounds are dynamically determined. We also consider alternative ways to represent non-anticipativity conditions to improve computational performance. The D3 method efficiently solved moderate and large sized instances whose deterministic equivalent problem could not be solved or solved much slower by a state-of-the-art commercial solver. Three-stage models are also studied and solved by the D3 method, which is found to be effective as well. We combine the D3 method and Column Generation approach to solve a stochastic version of the set packing problem. The proposed method is quite effective in numerical experiments and outperforms the commercial solver dramatically in most cases. We study the sensitivity of different density of patterns and find our proposed method is more robust than solving the whole problem by the commercial solver or by implementing the conventional column generation method directly. We use the D3 method as a framework and combine it with Benders Decomposition Method (BDM) to solve the Stochastic Multi-plant Facility Location Problem. The mathematical formulation of the model is a two-stage SMIP problem with integer first stage variables and mixed integer second stage variables. The integer variables in both stages cause the large-scale SMIP model to be intractable. Some strategies for accelerating BDM have been developed in solving scenario subproblems which are decomposed by D3 method. We develop the aggregation method to aggregate scenarios in solving decomposed Benders Dual subproblems and approximate the solution of the original problems. Our computational experiments on benchmark data and randomly generated data shows that the proposed method can solve large-sized problems more efficiently than conventional Benders Decomposition or a commercial solver. The computational comparisons also show that the aggregation method can reduce the number of scenarios in large problems and obtain approximately optimal solutions in much shorter computational time.

Advisor: Chan, Timothy
Activity of Anticancer Drugs in Relation to the Tumour Microenvironment and Potential to Inhibit Repopulation and Enhance Therapeutic Outcome

Tumours have a disorganized and convoluted vasculature. Tumour cells that reside close to patent blood vessels are nourished by oxygen and other nutrients and are rapidly proliferating while distally located cells slowly proliferating. Anticancer drugs must be delivered in adequate (toxic) concentrations to all tumour cells to be effective, and it is therefore important to study their distribution of activity in tumours. In order to assess the distribution of anticancer agents in tumours using immuno-histochemistry (IHC) and fluorescence imaging, drugs must be either inherently fluorescent or have antibodies that recognize their activity. As the vast majority of anticancer drugs fulfill neither of these criteria, the first objective of this thesis was to develop techniques to assess the pharmacodynamic activity of anticancer drugs in relation to distance from vasculature and hypoxic regions using biomarkers that could be recognized by antibodies using IHC. I found that GH2AX , a biomarker of DNA damage was activated in as little as 10 minutes following treatment. In addition, changes in biomarkers of apoptosis (cleaved caspase -3 or -6) and cell proliferation (Ki-67) could be used to determine drug activity at 24 hours following drug treatment. The second objective of this thesis addressed the ability of a novel hypoxia activated pro-drug, TH-302, used alone or with chemotherapy (doxorubicin or docetaxel) to modify the distribution of biomarkers in relation to blood vessels and regions of hypoxia. It was found that TH-302 increased DNA damage and apoptosis not only in hypoxic regions but also in vascularized areas and this effect was augmented through the addition of chemotherapy. TH-302 increased growth delay due to chemotherapy of human tumour xenografts, consistent with complementary effects of the drugs in different regions of the tumour microenvironment.The third objective of this thesis was to study changes in the tumour microenvironment after chemotherapy. I injected into tumour-bearing mice two markers of hypoxia, EF5 and pimonidazole, with a variable interval between injections. I studied the effects of chemotherapy alone on repopulation of hypoxic tumour cells and the ability of TH-302 to inhibit repopulation. It was found that (i) reoxygenation of previously hypoxic cells and repopulation of the tumour from them occurs after chemotherapy, and (ii) TH-302 was able to reduce tumour cell reoxygenation and repopulation. This supports the potential of TH-302 to increase therapeutic effects of chemotherapy. The work presented in this thesis highlights the importance of the tumour microenvironment and its ability to impact the distribution of anticancer drugs to cells.

Keywords: Anticancer Drugs
Drug Distribution
Hypoxia
Hypoxia-activated prodrugs
Repopulation
Tumour Microenvironment
Advisor: Tannock, F Ian
Arvo Pärt's Serial and Tintinnabuli Works: A continuum of process

The music of Estonian composer Arvo Pärt has received wide recognition globally, making him one the world's most often performed living composers. In 1968, Pärt entered a self-imposed period of compositional silence and study. Before 1968 Pärt composed using an atonal, serial language. When he reemerged musically, in 1976, it was with an entirely new language he calls tintinnabuli. For good reason most scholarship acknowledges Pärt's years of silence as a great divide between two disparate periods of his writing. This study, however, makes an explicit link in the method of composition between his serial music and the triadic, tonal music of the his early years using the tintinnabuli language. It also reveals the extent to which his music has evolved since the codification of tintinnabuli procedures in the early 1980s. Once again, it is shown that Pärt's primary method of composition remains controlled by pre-compositional designs. Once set, these pre-compositional rules play out, predictably following their prescribed procedure. Recognizing this important parallel acknowledgesthat his music is not of disparate schools, but rather, is a continuum of compositional method. Complete musical analyses of important Pärt works, Credo (1968), Passio (1982) and Como cierva sedienta (1998), contained in this study reveal that although the musical language has entirely changed, the processes with which Pärt composes unite the work of a composer. Smaller, seminal works including Perpetuum mobile (1963), Solfegio (1964), Collage über B-A-C-H (1964), Cantus in memoriam Benjamin Britten (1977), Summa (1977), The Beatitudes (1989), Triodion (1998), Nunc dimittis (2000), and I am the true vine (1996) are also addressed in relation to the development of Pärt's oeuvre.

Keywords: analysis
Arvo Pärt
Como cierva sedienta
Credo
Passio
tintinnabuli
Advisor: Apfelstadt, Hilary
Promoting Interactions in Preschoolers with Autism Spectrum Disorder via Peer-mediated Intervention.

The purpose of this dissertation is to develop and examine the efficacy of a social skills intervention program that was delivered to preschoolers with Autism Spectrum Disorder (ASD) via typically-developing peers. According to the Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM 5; American Psychiatric Association, 2013), one of the defining characteristics of ASD is a marked impairment in social interaction. Children with ASD often lack the ability to use social cues and frequently fail to develop peer relationships that are appropriate to their developmental level. In this model, a speech language pathologist and three early childhood educators trained typically- developing peers to engage children with ASD in play. Three preschool children with ASD and six peers participated in five social skills training sessions followed by 12 implementation sessions (six sessions for each peer). The peer intervention took place in early childhood classrooms during play sessions with blocks and play dough. A single-subject multiple baseline design across subjects was used to determine the effects of the intervention. All three children with ASD demonstrated significant gains in the number and length of their interactions with peers, and in their responses and initiations with peers. Gains were maintained over time. In addition, generalization of the skills learnt was measured by collecting data with an untrained peer. The results provided preliminary evidence supporting this model of intervention. Treatment fidelity and social validation measures are documented. Limitations are acknowledged, future research is suggested, and implications are drawn.Keywords: autism spectrum disorder, peer-mediated intervention, social interaction, preschoolers, single subject design.

Keywords: autism spectrum disorder
peer-mediated intervention
preschoolers
single subject design
social interaction
Advisor: Luigi, E Girolametto