VictorJuiz/thesis huggingface dataset:
Rational Design and Synthesis of sub-15 nm Upconverting Nanoparticles for Improved LRET Efficiency
Keywords: bioassay
core-shell
lifetime
LRET
nanomaterials
Upconverting nanoparticles

Herein, sub-15 nm β-NaGdF4:Yb@NaYF4:Yb,Tm@NaYF4 upconverting nanoparticles (UCNPs) were synthesized to improve efficiency in luminescence resonance energy transfer (LRET) with fluorescein in solution. Analysis of luminescence intensity and lifetime associated with blue emission channel of as-synthesized UCNPs reveal superior protection against solvent-related quenching as compared to conventional homogeneous core-shell UCNP constructs of similar size, composition, and shell thickness. The NaGdF4-NaYF4 core-shell design offered vibrational and spatial separation of sensitizer from solvent environment. Additionally, activators confined to a thin NaYF4 shell close to particle surface decrease the distance between energy donating centers and accepting fluorophore bound to particle surface. Consequently, core-shell-shell UCNP constructs demonstrate a two-fold improvement in sensitivity to fluorescein as compared to homogeneous core-shell constructs. The relatively high LRET efficiency (62±2%) presented in this work has yet to be reported in literature at particle sizes of
Upconversion nanoparticles coated with Alendronate and PEG-conjugated Alendronate
Keywords: Alendronate
Colloidal Stability
Optical Stability
Polyethylene Glycol
Surface Density
Upconvering Nanoparticles

Upconverting nanoparticles (UCNPs) have gained traction as diagnostic and imaging probes for biological applications due to their many unique optical properties. This thesis describes the exploration of alendronate and polyethylene glycol (PEG) surface chemistries to impart NaYF4:Yb3+ /Er3+@NaYF4 core shell UCNPs with the colloidal and optical stability required for biological applications upon transference into aqueous environments. Prior to evaluating colloidal and optical stability, NMR studies to confirm binding and surface coverage studies of alendronate and alendronate PEG 5kDa were conducted yielding ligand densities of 2.56 +/- 0.16 nm-2 and 0.085 +/- 0.02 nm-2 , respectively. Alendronate PEG 5kDa coated UCNPs demonstrated enhanced colloidal stability in comparison to alendronate coated UCNPs in 1X PBS buffer. Both alendronate and alendronate PEG coating led to a significant decrease in optical intensity of the main green emission peak at 537 nm by 84% and 93%, respectively.
The Robust Canadian Traveler Problem and Its Application to Robot Routing
Keywords: Canadian Traveler Problem
Path Planning
Planning Under Uncertainty

The stochastic Canadian Traveler Problem (CTP), which finds application in robot route selection under uncertainty, aims to find the traversal policy with the minimum expected cost. This thesis extends the stochastic CTP to what we call the Robust Canadian Traveler Problem (RCTP), in which the variability of the policy cost is also considered. An optimal algorithm and an approximate algorithm are then proposed to compute the policy that has a good balance of both mean and variation of the traversal cost. The benefit of the proposed framework versus traditional approaches is shown by doing simulations in randomly generated worlds as well as on a map of 5 km of paths built from robot field trials. Specifically, the RCTP framework is able to search for policy alternatives with significant lower worst-case cost and less computational time compared against the optimal CTP policy, but with little sacrifice on the expected cost.
Examining Representations of Relevant and Irrelevant Items in Visual Working Memory: An Analysis of Age-related Memory Differences
Keywords: Inhibitory Deficits
Memory
Neural Representations

The inhibitory deficit hypothesis suggests that older adults fail to suppress irrelevant information, resulting in impaired memory for task-relevant items and increased priming of distractors (Hasher et al., 1988). In contrast, younger adults seem to filter out extraneous information and ultimately remember target items better. We set out to explore these differences by investigating how relevant and irrelevant items are represented in the brain. Using a classifier trained on four image categories, we found that while younger adults were unaffected by the representational similarity of simultaneously presented categories, older adults actually performed better when category similarity was higher. This contradicted our hypothesis that greater representational similarity would result in increased interference between studied stimuli, adding strain to already weak inhibitory mechanisms and further impairing memory for targets in older adults. These surprising results may lead to fruitful new avenues of research and opportunities to build on existing theoretical frameworks.
Real-Time Data Acquisition System for Monitoring Focused Ultrasound Blood-Brain Barrier Opening
Keywords: Blood Brain Barrier
Data Acquisition System
Focused Ultrasound
FPGA
PCB
Ultrasound

Sunnybrook Hospital’s Focused Ultrasound Lab has designed a new 256 element hemisphere dome for the purpose of blood brain barrier (BBB) disruption. This dome requires a receiver system that can digitize reflected ultrasonic pulses in order to determine the safety of the treatment and modify transmission settings in a closed feedback manner. Current commercial receiver systems do not address this problem in a cost effective manner. In order to address this issue a 32 channel, with the capability to expand to 256 channels, data acquisition system was designed to capture subharmonic reflections from ultrasonic pulses generated during blood brain barrier opening therapy. All channels of this device were characterized and a single channel was used to determine if inertial cavitation could be detected. The results indicate that the device is capable of detecting this and can be incorporated into a blood brain barrier disruption machine for monitoring purposes.
A Field Study of Exterior Airtightness Testing in Five Multi-Unit Residential Buildings
Keywords: Air Leakage
Airtightness
Blower Door
Exterior Airtightness
Multi-Unit Residential Buildings
MURB

The airtightness of a multi-unit residential building (MURB) enclosure is an important factor when considering energy consumption. There is limited data available on the airtightness of MURBs. The complexity of the MURB geometry complicate standard testing procedures; this is especially true when measuring the isolated exterior enclosure airtightness where the adjacent zones must be taken into consideration. This thesis explored three alternative suite-based methods from the literature used to measure the isolated exterior pressure boundary leakage. A field study took place in five MURBs where the goal was to compare the results from these methods to pressure neutralization test results. Of the three testing methods, the testing method that used adjacent pressure differentials in its calculation was the most similar. Ideally, these results and lessons learned will aid future researchers in developing airtightness testing methods and standards for conducting efficient and accurate tests.
Separate mesolimbic dopaminergic pathways mediate the opposing motivational effects of acute caffeine
Keywords: caffeine
core
dopamine
nucleus accumbens
shell
ventral tegmental area

Caffeine is the most commonly consumed psychoactive drug in the world, yet little is known about the neural substrates that underlie its rewarding and aversive properties. Using male Wistar rats in a place conditioning procedure, we showed that systemic caffeine at a low intraperitoneal dose of 2 mg/kg (or 100μM injected directly into the rostral, but not caudal, ventral tegmental area) induced reward. By contrast, high doses of systemic caffeine (10 and 30 mg/kg) produced aversions that were not recapitulated by a caffeine analog restricted to the periphery. We demonstrated that pharmacological blockade of dopamine receptors using α-flupenthixol injected into the nucleus accumbens shell, but not core, blocked caffeine reward. Conversely, α-flupenthixol injected into the nucleus accumbens core, but not shell, blocked caffeine aversions. Thus, our findings reveal two dopamine-dependent and functionally dissociable mechanisms for processing caffeine motivation that are segregated between nucleus accumbens subregions.
Impact Studies of Containment Ring during Blade Shed in Turbofan Engines
Keywords: Aircraft
Blade-Out
FBO
Turbofan

The catastrophic failure of fan blades in turbofan engines, referred to as fan blade-out (FBO), can cause severe damage to aircraft and result in fatal incidents. Recent accidents indicate that the protective containment structures (rings) used to limit the consequences of such failures may be inadequate. Accordingly, this study involves the design and analysis of a novel containment ring using dynamic nonlinear finite element (FE) simulations of ballistic impacts and FBO events, and the development of a novel instrumented test rig to calibrate the finite element simulations and study blade-out in turbofan engines. The predictions of the finite element method reveal that Kevlar is suitable for use in containment structures and that the optimal multilayered target has an exposed aluminum foam surface with a Kevlar fabric backing. This is confirmed in the containment of blade-out with a single trailing blade and fully bladed fan disk.
Late Cenozoic reconstructions of precipitation isotopes and climate in continental Alaska and Yukon
Keywords: Climate
Hydrogen isotope
Leaf wax
Pliocene
Subarctic
Tephra

This thesis presents late Cenozoic reconstructions of hydrogen isotope ratios in mean annual precipitation (dDMAP) from fossil plant waxes (n-C28 alkanoic acids) and hydrated volcanic glass shards in tephra that are archived in sediments in south-east Alaska and central Yukon. The leaf wax dDMAP estimates, spanning 6.2 to 2.8 Ma, are negative compared to modern which is unexpected for a warmer-than-modern climate as indicated by other proxies. Tephra-dDMAP estimates spanning 6.7 to 0.025 Ma are consistent with North Pacific sea surface temperatures, documenting low dDMAP values during the latest Miocene, peak values during high pCO2 warm intervals (~5 and 3 Ma), and transition to the lowest values on record in the Late Pleistocene. The difference in trends between the two dDMAP reconstructions most likely owes to an inappropriate net-fractionation assumption associated with the leaf wax proxy which remains one of the largest uncertainties in fossil leaf wax derived paleoclimate reconstructions.
GABA: a Potential Agent of Beta-Cell Proliferation
Keywords: Beta-cell mass
Cell proliferation
GABA
Glucose tolerance
Metabolism
Pre-diabetes

Studies have shown that GABA can increase the β-cell mass and improve glucose tolerance in normal and STZ treated mouse models. Herein we explored the applicability of GABA to a pre-diabetes setting. We showed that 10 weeks of GABA administration via drinking water ad libitum to normal CD1 mice stimulated almost a 2-fold increase in β-cell mass. Inhibition of the GABAA receptor abolished ex-vivo GABA-induced increase in Ki-67+ staining in β-cells. Additionally, the OCR and MMP were unchanged with GABA treatment suggestive of no effect of GABA on cellular metabolism which is linked to the GABA shunt. Lastly, the HFD-induced pre-diabetic CD1 mice treated with GABA prior to and after pre-diabetes onset did not show an enhancement in the β-cell mass, glucose tolerance or insulin sensitivity. Thus, GABA may increase β-cell mass in normoglycemic CD1 mice, potentially through the GABAA receptor, but it does not reverse or prevent pre-diabetes.
Exploring Extended Producer Responsibility: Waste Tyres as a Resource for Job Creation in South Africa?
Keywords: Employment
Extended Producer Responsibility (EPR)
Integration of Informal Sector
South Africa
Waste Management
Waste Management Policy

Extended producer responsibility (EPR) has emerged globally as a means to shift the increasing costs of waste management of end-of-life products onto the producer. This research focused on an EPR scheme for waste tyres that was legislated by the South African government in 2012. While sharing many similarities with other EPR schemes, the South African program was unique in its focus on creating employment. More specifically, in response to the injustices of South Africa’s apartheid there was a focus on the upliftment of previously disadvantaged individuals. Based on semi-structured interviews with actors from various roles in the waste tyre system, this research investigated how the EPR affected employment and whether EPR can be used to create jobs. The EPR scheme for waste tyres in South Africa was found to have increased employment, however, potential challenges with using EPR as a tool for job creation were identified.
Vacant Land to Park Transformations as a Catalyst for Neighbourhood Change and Gentrification in Toronto, Ontario
Keywords: brownfields
community engagement
gentrification
neighbourhood change
parks
vacant land

Given the lack of vacant land in the City of Toronto, the redevelopment of available land tends to be highly contested. Stakeholders may advocate for the land to be developed as a park in order to increase social, economic and environmental services provided to residents, both at the neighbourhood scale and city-wide. However, concerns have emerged related to “green gentrification,” which is the exclusion or displacement of vulnerable populations through the creation of green amenities in marginalized neighbourhoods. Using a case study approach to three vacant land to park transformations, this thesis examines how neighbourhood change and gentrification are perceived by actors engaged in the park development process. Using historical analysis, stakeholder interviews, resident surveys and quantitative data analysis, this thesis reveals how the potential for park developments to accelerate gentrification is complex and highly politicized, and perceived more strongly on the ground than it is reflected in changes in quantitative data.
Corrosion of Electrodeposited Nanocrystalline Nickel-Iron (Ni-Fe) Alloys in Neutral and Alkaline Sulphate Environments
Keywords: Corrosion
Electrochemistry
Electrodeposition
Nanomaterials
Nickel
Nickel-Iron Alloys

Electrochemical behaviour of electrodeposited nanocrystalline nickel (Ni) and nickel-iron (Ni-Fe) alloys was assessed in comparison to their conventional polycrystalline counterparts. Alloys of similar composition (Ni, 85Ni-15Fe, 80Ni-20Fe, and 45Ni-55Fe), were investigated to better understand the relationship between grain refinement and alloying on corrosion behaviour. Potentiodynamic polarization tests were conducted in neutral (pH 7) and alkaline (pH 10) sulphate environments. Compared to their polycrystalline counterparts, significant increases in critical current density (icrit), passivation potential (Epass), and passive current densities (ipass) were observed for the nanocrystalline materials in neutral solution. These differences in corrosion behaviour were attributed to the effect of sulphur as a result of a necessary additive in the electrodeposition process more so than the effect of grain refinement. In alkaline medium, no significant effect of grain refinement on the corrosion behaviour was observed. This was attributed to the high OH- concentration, favouring passive film formation.
Organic Photovoltaics Based on Solution Cast Polymers and Boron Subphthalocyanines – Hybrid Device Architectures Enabling Novel Material Combinations
Keywords: Clean Energy
Organic Photovoltaics
Phthalocyanine
Solar Cells

Solution-cast films of crystalline electron donating poly(3,3”’-didodecylquaterthiophene) (PQT-12) were studied in pseudo-planar heterojunction (PPHJ) organic photovoltaic devices (OPVs) paired with boron subphthalocyanine (BsubPc) as the electron acceptor layer, and the effects of crystallinity domain size and layer thickness were investigated. Annealed, 10-20 nm films of intermediate-sized crystals were 40% more efficient than un-annealed PQT-12 layers and had comparable efficiency to their fullerene-based BHJ counterparts, demonstrating the ability of polymer|BsubPc PPHJ OPVs to accommodate highly crystalline polymers with a tendency to phase segregate and create devices with favorable electrical properties. These polymer|BsubPc PPHJs were further studied with the new amorphous copolymer electron donating material PBTZT-stat-BDTT-8. While optimized PPHJ devices of PBTZT-stat-BDTT-8|BsubPc had substantially lower efficiency than PBTZT-stat-BDTT-8|fullerene BHJs (which were free of morphological problems), they demonstrated comparable performance to their BHJ equivalents due to ideal morphology, presenting a pathway forward for OPV design of otherwise phase segregating polymer|BsubPc pairings.
Investigating Pattern Separation in the Medial Temporal Lobe through the Parametric Manipulation of Item Similarity
Keywords: fMRI
Medial Temporal Lobe
Pattern separation
Similarity

Pattern separation is the essential ability to create separate memory representations for overlapping events. This process is accomplished by magnifying the dissimilarity between memories. Computational models posit that the degree to which memories become separated varies as a function of the similarity between them. However, there is little human evidence to support this claim. Using fMRI, we recorded from participants as they performed an explicit memory task in which we manipulated the similarity between study and test items. Our analysis revealed that manipulating similarity did not reliably influence the degree to which memories were separated. We instead found that pattern separation was related to how confident participants were when making decisions related to memory. The implications of this finding, however, remain unclear with future studies needed to interpret them. These results suggest that trial-wise confidence ratings might be a truer measure of mnemonic “similarity” than our group-average similarity measures.
Application of the Indicator Amino Acid Oxidation Technique to Determine the Protein Quality of Indian Wheat by Studying the Metabolic Availability of Lysine in Healthy Young Adult Men
Keywords: Amino Acid
Bioavailability
Lysine
Protein
Protein Quality
Wheat

The protein quality (PQ) of wheat, limiting in Lysine (Lys), is understudied in humans. Wheat and pulse mixed diet (MD) improves PQ but data on combination ratio (CR) is lacking. We aimed to 1)determine the PQ of wheat (bread) by assessing the metabolic availability (MA) of Lys and 2)determine the effect of bread and lentil stew as a MD on PQ by using the indicator amino acid oxidation method repeated measures design in 5 healthy adult males. Based on the slope-ratio principles, L-[1-13C] phenylalanine oxidation (Pheox) to 13CO2 in response to graded Lys intakes fed as crystalline amino acid (reference protein), wheat (test protein), and wheat complemented with lentil (MD) provided the MA and MD effectiveness. Despite being of limiting concentration, the MA of Lys in yeast-leavened bread is 90%. Complementation with lentils reduced Pheox i.e. augmented MD Lys content. We recommend a CR of 2:1 bread to lentil protein.
Site Logistics Planning for High Rise Building Construction on Congested Downtown Sites
Keywords: congested buildings
construction
construction site
decision-making
logistics
Project management

Construction planning for tall buildings becomes more complex with small land parcels in urban cores, fast-paced schedules and a growing number of domains involved in decision-making. This research consists of evaluating the literature regarding construction planning techniques, decision-making models, constraints in the current construction industry and holding interviews with domain experts to summarize their implicit knowledge regarding construction site logistics planning. It was found that there is no existing tool that adequately optimizes a construction site plan as all research is carried out in isolation, only optimizing a certain piece of equipment or operation. In this research, a multi-domain decision-making tool was developed to assist project planners in site planning on complex construction projects so multiple domain decisions and impacts are simultaneously realized, and a framework for construction site planning that can be applied to the industry was introduced.
Modular Hip Design Failure: A Forensic Investigation of the Incidence of Liner Dissociation in the Pinnacle-Marathon Acetabular System
Keywords: Dissociation
Failure Analysis
Forensic Investigation
Hip Arthroplasty
Ultra-High Molecular Weight PE

The DePuy Pinnacle hip replacement, with Marathon crosslinked ultra-high molecular weight polyethylene liner, was identified as a design with a higher risk of dissociation. The purpose of this study was to identify key features of dissociation failures and analyze those features for evidence of failure mechanisms. A study of 68 dissociation cases revealed such features to be: migration of the liner out of the acetabular shell, deformation of the liner rim, shearing of the locking tabs, and burnishing of the femoral head and acetabular shell. Cases of extreme deformation exhibited fracture through the rim of the liner. Scanning electron microscopy of several liners revealed evidence of fatigue. The failure mechanisms are likely fatigue wear, coupled with impingement – occurring concurrently or consequentially. The key factors which contributed to these mechanisms are component positioning and insufficiencies in the liner locking mechanisms.
The Development of Learning Across Levels of Abstraction
Keywords: Abstraction
Category learning
Development
Gist
Memory

When we learn about the world around us, we not only process what makes items unique, we also notice consistencies across items. However, it is unknown how learning at these two levels of abstraction interact. Might there be a trade-off in learning? Moreover, given children’s different cognitive abilities, do they experience a similar trade-off? Finally, are irrelevant features still processed, just in a more superficial manner? We explored these questions using a categorization task followed by a surprise recognition test in adults and children. Results suggest that adults do show a trade-off in learning. However, children’s memory scores were too low to make any definitive conclusions. Lastly, both adults and children noticed consistencies in the irrelevant features, and this knowledge also traded-off with category learning in adults and moderately in children. These data point to a fundamental cognitive process in which learning comes at a cost, at least in adults.
Effects of Aging on Concrete Containment Structures: An Investigation of Shrinkage and Leakage
Keywords: Concrete
Leakage
Shrinkage

While historically used for infrastructure such as buildings, bridges, dams, and roadways, concrete is also a vital component for the storage of energy – especially sources of renewable energy such as natural gas or nuclear. For these applications, the leak-tightness of concrete walls is important and is linked with effects of aging. Most research investigating the leak tightness of concrete structures is outdated and was performed without aging in mind. Additionally, while a large set of experiments have researched the effects of relative humidity on aging, very few have dealt with humidity levels below 40%. This thesis investigates the effects of very dry climates on the shrinkage of concrete and develops an experimental program for analyzing leakage of air through cracks in concrete walls that may develop due to aging processes.