Ahluwalia, Monish-A Surface Complexation Model of Selenium Sorption Through Illite and Montmorillonite in PHREEQC (Dr. Shinya Nagasaki)
The Nuclear Waste Management Organization is developing a database to predict sorption for elements of interest on crystalline and sedimentary rocks for Deep Geological Repository (DGR) site selection, monitoring, and safety. Se(-II), a uranium fission product, is a key radionuclide of interest due to its long half-life and potential for migration through groundwater solutions. To predict interactions of selenium with groundwater environments, this thesis examines selenium speciation, solubility, and sorption. First, selenium speciation is analyzed in PhreePlot to determine relevant ions of importance with respect to two groundwater reference solutions: SR-270-PW (sedimentary) and CR-10 (crystalline). Then, the solubilities of these ions are modelled in PHREEQC with respect to redox potential, pH, and ionic strength to determine which ions have the greatest potential to migrate through a wide variety of groundwater environments. Finally, sorption is modelled in PHREEQC on illite and montmorillonite, key sedimentary components used in the construction in the DGR and found in the surrounding areas. This model is used to calculate sorption constants (KD) that describe sorption reactions and allow for predictive capacity for a wide range of soils. Overall, this thesis serves as an analysis of the interaction of selenium ions in sedimentary and crystalline environments to help better understand concerns with spent nuclear fuel management.
AlShenaiber, Leena-Exploring the Feasibility of Reducing the Consumption of Food Additives in the Diet of Adults with Obesity (Dr. Natalia McInnes)
Currently, Canada has over a 29% prevalence rate of obesity, which is defined by a body mass index (BMI) of 30 kg/m2 and above. The prevalence of obesity has been steadily increasing since the 1970s where the prevalence rate was less than 10%. A major obstacle in tackling this health issue is the complexity of its causes. However, it is well known that diet is a major contributing cause.
The role of food additives in promoting obesity is largely unknown. This five-month study explores the feasibility of reducing the consumption of food additives in the diet of obese adults. Eligible participants between the ages of 20 and 80 with a BMI of 30 and above were taught how to limit the exposure to the studied food additives in their diet. At 2 months of follow-up, interviews were conducted to explore participants’ perceptions on the dietary intervention and study conduction. Qualitative content analysis was used to analyze interview data. Overall, the results of this feasibility study will guide the design of future randomized controlled trials that will evaluate the impact of various food additives on body weight.
Balint, Liz-Understanding the Role of Bim in Macrophage Apoptosis and Atherosclerosis (Dr. Bernardo Trigatti)
Cardiovascular disease (CVD) is the leading cause of death worldwide. Atherosclerosis, the underlying cause of CVD, is an inflammatory disease characterized by sub-endothelial plaque formation within the arteries. Macrophages internalize accumulated lipoproteins in the sub-endothelium, but excessive uptake induces endoplasmic reticulum stress and results in apoptosis. Dead macrophages are ineffectively removed and form a necrotic core that increases plaque instability and can result in plaque rupture, causing myocardial infarction or stroke.
Bim is a proapoptotic protein implicated in macrophage apoptosis. Cre/lox recombination was used to develop a macrophage-specific Bim knockout (Bim mKO) to investigate the impact of reduced apoptosis on atherogenesis. Male LDLR-/- mice received bone marrow transplants from LyzMCre/Cre (control) or LyzMCre/CreBimfl/fl (Bim mKO) mice and were fed a 10-week high fat diet. Following 10 weeks, the heart, aorta, liver, spleen, and blood were collected.
Histological analysis of the aortic sinus did not demonstrate significant differences in plaque or necrotic core sizes between treatment groups. Cleaved caspase 3 staining demonstrated that apoptosis in atherosclerotic plaques decreased, but overall cell death, shown by staining for DNA strand breaks, did not change. This may suggest that these macrophages are dying through other pathways and may explain why there was no observed impact on atherogenesis. Interestingly, Bim mKO significantly increased atheroprotective high density lipoprotein levels, and may suggest that Bim plays an unexpected role in its homeostasis. Overall, decreasing macrophage apoptosis through bone marrow Bim mKO does not appear to impact atherogenesis in LDLR-/- mice fed a 10-week high fat diet.
Barker, Bronwyn-Combating Antimicrobial Resistance in Under-Resourced Hospital Settings (Dr. Jeffrey Pernica)
The spread of antimicrobial resistance amongst bacterial and fungal infections is a growing global concern. The effectiveness of international efforts to decelerate the spread vary according to the region. Under-resourced hospitals see a greater incidence of antimicrobial resistance and there is far less research and understanding on what widespread resistance is and the practitioners’ knowledge of resistance or prescription practices. Antibiograms are an important tool for curbing over-prescription rates that are frequently implemented in higher- and middle-income countries, to various degrees of success. Antibiograms serve as a way of communicating the efficacy of different antimicrobials on strains of bacteria isolated in a specific region, but they are often under-used. This thesis aims to investigate the prescribing practices of physicians in the Princess Marina Hospital of Botswana, while analyzing frequency and effectiveness of antibiograms in that setting. A quantitative survey was distributed to all physicians in the paediatric ward of the hospital, inquiring about the physician’s education and familiarity regarding antimicrobial resistance and antibiograms. The physicians were asked to respond to clinical vignettes using sample antibiograms. The survey has found that physicians are not well educated in antimicrobial resistance and antibiogram use, and that it impacts their prescription practices. There needs to be a better understanding around the importance of ethical prescription patterns in terms of antimicrobial resistance and how to use an antibiogram. This study has implications for how physicians and microbiologists can combat the growing problem of antimicrobial resistance in under-resourced settings.
Bider, Pascale-Relating turtle health to fecal contamination of freshwater turtle habitat in Southern Ontario (Dr. Pat Chow-Fraser)
In 2017, the first case of turtle ranavirus in Canada was confirmed in a snapping turtle from Cootes Paradise, a degraded coastal wetland in Southern Ontario. Ranavirus is a highly infectious and transmissible disease caused by viruses in the family Iridoviridae that affects ectotherms. Symptoms include lesions, inflammations, and tissue necrosis eventually leading to death. However, not all ectotherms affected by the virus exhibit symptoms of the disease. Some researchers speculate that symptoms could be aggravated if the sick animal is under stress due to anthropogenic disturbances, such as exposure to pathogens from fecal contamination. This study sought to identify and test the environmental pathways through which fecal contamination and exposure to pathogens may play a role in increased susceptibility of turtles to ranavirus in wetlands and ponds. This past summer, I collected 43 water samples in natural and created wetlands of Southern Ontario. Using a TECTA Pathogen Detection System (PDS), I analyzed the samples for presence of E. coli, an indicator of fecal contamination. The TECTA PDS uses fluorimetry to measure concentrations of E. coli metabolite and infer the number of colony forming units per 100 mL sample. I confirmed that levels of E. coli in Cootes Paradise Marsh are highest of all sites sampled and that rain events led to especially high E. coli concentrations in areas used for turtle nesting. This study highlights the importance of further investigating the effects of fecal contamination on turtle health, particularly in Cootes Paradise where pathogen loadings are especially elevated.
Chou, Sommer-Screening natural products against Caenorhabditis elegans to find novel anthelmintic compounds (Dr. Gerry Wright and Dr. Lesley MacNeil)
Parasitic worm, or helminth, infections affect over one billion people worldwide and are especially prevalent in developing countries. The overall impact of helminthiases on human health is often neglected compared to more publicized parasitic diseases such as malaria. Nevertheless, the global burden from long-term cognitive and physical impairments that arise from helminth infections is indisputable. The already limited arsenal of anthelmintic compounds is also rapidly diminishing due to a rise in resistance. The lack of effective pharmaceutical remedies and severity of these conditions corroborates that more resources should be allocated towards novel anthelmintic discovery.
In the past, natural products have proven to be a rich source of clinically relevant therapeutics, as numerous anti-cancer and antibiotic compounds were derived from natural sources. Therefore, these should be further mined for compounds possessing anthelmintic activity.
Here, we describe a screening protocol using Caenorhabditis elegans, a non-pathogenic and free-living soil nematode, as a model organism for the identification of nematicides. This screen is designed such that compounds inducing paralysis, sterility, developmental delay, and death can be identified in the initial screen. Several natural product extracts produced by bacterial or fungal species in the Wright Actinomycete Collection (WAC) were tested against C. elegans. Thus far, we have identified three WAC strains that are producing inhibitors of worm development.
Coles, Victoria -Investigation and Synthesis of BAY 11-7082 and its Analogues as Novel Antimicrobials (Dr. Lori Burrows)
BAY 11-7082 is an anti-inflammatory compound with multiple targets, allowing it to display diverse biological activities. We recently found using a novel bacterial biofilm stimulation assay that this compound has potent antimicrobial activity against a broad spectrum of bacteria including multidrug resistant strains. Herein we report the synthesis of a series of structural analogues and their evaluation for both antimicrobial and anti-inflammatory potency. MLLB-1704 was found to have increased antimicrobial potency over BAY 11-7082 with comparable anti-inflammatory activity. The double bond and nitrile moieties were determined to be essential for the molecule’s antimicrobial activity while only the double bond was necessary for anti-inflammatory potency, indicating the two activities can be separated and likely occur via distinct mechanisms. Also discussed are our efforts to elucidate the molecules’ antimicrobial mechanism of action, which may occur through inhibition of bacterial protein tyrosine phosphatases. Ultimately, this scaffold represents an excellent starting point for the development of a potent antimicrobial with a novel mechanism of action.
Conant, Amory-Calcite raft use as a proxy for coastal karst aquifer conditions and evolution (Dr. Ed Reinhardt)
Calcite rafts, microcrystalline platelets of calcite that form on the surface of standing water bodies in caves, were investigated for their potential as a paleoenvironmental proxy. Six raft cores were collected from the extensive cave systems in Quintana Roo Province, Yucatan Peninsula, Mexico. Cores were scanned by high resolution x-ray fluorescence in addition to microscopy and isotopic analysis. Through a combination of fluid and matrix inclusions, calcite rafts demonstrate a clear ability to reflect geochemical properties of the host solution and record the evolution of a coastal cave aquifer. Trace elements common to the system (Sr, Cl, S, Ti, Al, Si, Fe, K) are captured consistently in raft material, allowing for paleoenvironmental reconstruction and interpretation. Raft material is particularly sensitive to variations in paleosalinity driven by the mixing of meteoric and saltwater masses through the Cl/Ca and Cl/Ti record. The Sr/Ca record may be related to raft morphology and changes in element sources, while silicate elements and isotope records supply additional information on aquifer evolution. Established trends and relationships in the raft record can be consistently observed both within and across sites, further establishing their viability as an archive of aquifer conditions. Precipitation at the air-water interface allows rafts to act as minimum water level indicators, and the frequency of the acicular polymorph can potentially help further refine past water depths. The established ability of calcite to record parameters of climate and aquifer conditions is thus a valuable tool when planning the management of critical karst and coastal water resources.
Coppens, Jarod-Limits to Silicon Solar Cell Efficiency due to Free Carrier Absorption (Dr. Rafael Kleiman)
At wavelengths above 1μm (near the bandgap of silicon), light has a much lower chance of being absorbed by solar cells which reduces their efficiency. To combat this. different light trapping techniques have been developed to improve solar cell efficiency in this range. These techniques refract light as it enters a solar cell, keeping it in the cell longer and increasing the chance of absorption. Light trapping is proven to be very useful in improving solar cell performance, however, at higher illumination free carrier absorption (FCA) could reduce its effectiveness. FCA occurs when already-excited carriers absorb more light but then quickly lose the additional energy through thermalization (heat). As illumination increases the number of light-generated carriers increases, creating more FCA. Increased FCA should decrease the average distance light travels in a cell as more light is absorbed by the free carriers. Therefore, it is hypothesized that light trapping effectiveness decreases in the near-bandgap range as illumination increases.
The Z-factor describes the average distance light travels in a cell and is the most common means of quantify light trapping. A solar simulator was constructed to measure the quantum efficiency (QE) of different cells under varying illumination levels, from which a cell’s Z-factor can be determined. It is expected that changes observed in a cell’s Z-factor will give insight as to how effective a cell’s respective light trapping method is at higher light levels.
Determining how Z changes under different lighting conditions will be used to quantify how light-induced FCA affects light trapping with increased illumination. A better understanding of how light trapping works at higher light levels will allow for further optimization, particularly for concentrator solar cells. Concentrator photovoltaics have the potential for much higher efficiencies and could help lead to increased renewable energy systems.
Craughwell, Meghan-Investigation into the genetic basis of melanin variation in Cryptococcus neoformans through backcrossing (Dr. Jianping Xu)
The human fungal pathogen Cryptococcus neoformans primarily affects immunocompromised individuals, causing cryptococcal infections. One important virulence factor of this fungal species is its ability to produce melanin, which effectively protects it against natural immune responses. Due to substantial intra-specific variation in the amount of melanin produced, melanin production has been classified as a polygenic trait with one known essential gene, LAC1. Further understanding of melanin production, beyond LAC1, may provide insight into the progression of cryptococcal infections and assist in elucidating possible targets for future treatment of this disease. This study initiates 50 sexual crosses using backcrossing techniques where offspring from a cross are repetitively mated back to a recurrent parent. With each backcross, the progeny become more similar to this parental strain, which allows for the isolation of melanin-related loci while limiting the effects of the genetic background on this trait. Melanin assays are used to quantify the amount of melanin produced by 50 collected progeny from each cross and to predict when the goal of only one melanin-related locus differing between parental strains is reached. From 50 matings, three crosses resulted with melanin assay observations showing two phenotypic groups among the progeny, suggesting the influence of only one locus. A further quantitative analysis statistically confirmed a decrease in phenotypic variation. The generation of these three strains allows for further investigation of the genetic architecture of melanin production and exploration into the additive, synergistic, or antagonistic effects that the three isolated loci have on each other through further crosses.
Daniel, Tanya-An investigation of bee communities in urban Hamilton (Dr. Chad Harvey)
As human populations increase, many rural regions have transformed into suburban or metropolitan neighbourhoods. This process of urbanization has resulted in habitat loss, which restricts nesting areas and food sources for pollinators. As a result, a pollinator corridor primarily composed of community and local gardens was implemented by Environment Hamilton and Hamilton Naturalists’ Club, known as the Hamilton Pollinators Paradise Project. This project’s objective is to preserve pollinator populations by mitigating habitat loss regardless of the urban environment. These gardens also provide ecological services such as air purification, water flow mitigation, and climate regulation. Since bees play an essential role in sustaining modern crops and maintaining the green spaces in cities, an investigation of Hamilton bee communities provides insight into the potential of ecologically-aware initiatives that are integrated throughout urban areas. Over the summer of 2018, bee collection occurred at eight community gardens throughout Hamilton. Bees were sampled once a week from May to August using a pan trapping method. Bees were then identified to genus and by sex. The data underwent Canonical Correspondence Analysis in R. The results were analyzed for associations between bee genera and multiple variables (average daily temperature, humidity, community garden site) and discussed. This information assists urban ecologists with how types of community gardens can impact bee populations and communities. Furthermore, investigating bee presence in urban gardens provide an opportunity for the general public to be educated about local types of pollinators. Overall, this investigation aids in effective conservation and management of urban ecosystem services.
Doan, Alexi-Rumour Has It: Investigating the Intersection Between Contemporary Disease & Social Media (Dr. Chad Harvey)
Social media has become the foremost source of news, even to disseminate important information regarding outbreaks of disease. The unique landscape of social media newsfeeds, however, situates verified, truthful information alongside unverified rumours. Given that fatal disease outbreaks could potentially inspire secondary psychosocial sub-epidemics of fear, stigmatization, and extreme moralization, it is imperative that the public receives only truthful information from respectable sources. Accordingly, the present research gathered a corpus of 300 Twitter tweets from personal and news accounts pertaining to three case studies of modern disease: the Zika Virus Outbreak (ZVO), HIV/AIDS, and the Emirates Flight 203 Outbreak (EFO). All tweets were screened for five global variables – the presence of a rumour, rumour debunking, rumour spreading, sensationalizing, and political bias – as well as four case study-specific factors – mentioning Vanilla Ice (EFO), mentioning Prince Harry (HIV), debunking stigma (HIV), and perpetuating stigma (HIV). Screening data was then analyzed using stepwise generalized linear models, and significant results were further assessed using Tukey’s Honestly Significant Difference. Notably, personal discourse was significantly more likely than news discourse to both contain and spread rumours. Further, a significant interaction was identified between type of discourse and case study on sensationalizing behavior. Cohesively, the present results indicate that the way disease events are framed on social media is contingent on who is disseminating them. Future research pertaining to this topic should incorporate measurements of virality, or automated tweet collection and analysis software.
Fraschetti, Ariana-Development of an MRI-Compatible Cyclic Loading Device for Articular Cartilage Property Assessment (Dr. Cheryl Quenneville)
Osteoarthritis (OA) is an extremely common and disabling degenerative disease. It is characterized by articular cartilage loss in diarthrodial joints without the ability to repair itself, and is most commonly found in major weight-bearing joints. There is currently no cure, only symptomatic treatments and treatments reducing the rate of progression. To better understand OA development, this thesis aimed to assist in the completion of a magnetic resonance imaging (MRI)-compatible device, capable of applying cyclic loading to a whole porcine stifle (knee) joint ex vivo. The novelty of its MRI-compatibility will allow for the correlation of information from MRI on the cartilage response to loading with the mechanical response of all joint components. To quantify the load-strain relationship of the cartilage response, an MRI-compatible load cell was calibrated with the use of Instron testing equipment to measure its strain response to external loading. Cyclic loading tests at 500 cycles were conducted to establish a strain-load relationship, as well as two creep tests to determine the hysteresis, determining the viability of the cell for this purpose. As well, potting cups and the other components were constructed and assembled together with a potted specimen, and an MR image of it was acquired to ensure its MRI-compatibility. Moving forward, this apparatus can be used for cartilage property assessment and OA monitoring, directly mapping the material and morphological properties of articular cartilage under cyclic loading. Further advancements as a result will aid in understanding how OA develops and potential treatment modalities.
Garnett, Jacqueline-A linear analysis of pliopithecoid dental morphology (Dr. Chad T. Harvey)
Pliopithecoidea are an extinct group of catarrhine primates that occupied Eurasia during the Miocene. While their placement within the larger Primates order is well-classified, the phylogenetic and taxonomic relationships between pliopithecoid species are currently unresolved. This study sought to quantify the 2-D differences in tooth morphology between pliopithecoid species to determine whether these measurements were sufficiently able to differentiate between groups. We photographed the occlusal surface of the second (M/2) and third (M/3) lower molars from various Pliopithecoid, Propliopithecoid, and Parapithecoid species. ImageJ was used to record linear, angular, and area measurements. Variables were analyzed through a combination of univariate and multivariate statistical techniques, including principal component analyses and linear discriminate analyses (LDA) using PAST software. For both M/2 and M/3 analyses, the first two principal components accounted for approximately 85% of the total variance between specimens, largely relating to overall shape and cusp position. Species-level distinctions were observed among taxa, whereas great overlap was found at the family-level. Despite this overlap in variation, LDAs show that these 2-D dental measurements can reliably be used to classify samples into a priori groups. As such, we assert that linear measurements of pliopithecoid dentition are sufficient to elucidate morphological differences between pliopithecoid species on multiple scales. These results will assist in dental character selection which can then be used to inform pliopithecoid phylogenetic and biogeographic theory. This will ultimately broaden our comprehension of the factors that impacted Eurasian primates during the Miocene, information which will extend to our understanding of emerging hominoids.
Graham, Katie-The Characterization of Liquid-Liquid Phase Separation in a Spinocerebellar Ataxia Type I Model (Dr. Ray Truant)
Spinocerebellar ataxia type I (SCA1) is a neurodegenerative disease caused by an expansion of glutamine residues within the ataxin-1 protein. Ataxin-1 is a nuclear protein with unknown function, although it is known to have the ability to bind RNA. RNA-binding proteins, such as ataxin-1, require mechanisms to localize RNA interactions within the nucleus. One such mechanism is liquid-liquid phase separation (LLPS), whereby RNA-binding proteins undergo a phase transition in the nucleus. This forms a membraneless, dynamic liquid droplet, which assists in concentrating the RNA-binding protein interactions. Due to preliminary evidence suggesting ataxin-1 undergoes LLPS, as well as the implications of LLPS in other neurodegenerative disorders, we aimed to characterize LLPS in a SCA1 model.
Ataxin-1 forms distinct nuclear inclusions when transfected and over expressed in human cells, which appear similar to liquid droplets formed by other LLPS proteins. To characterize ataxin-1 nuclear inclusions as liquid droplets, live-cell imaging was used to analyze the liquid-like properties of both wild type and disease-causing (mutant) ataxin-1. We show that both wild type and mutant ataxin-1 nuclear inclusions are mobile and can coalesce. Further analyses suggestthat mutant ataxin-1 is more mobile between nuclear inclusions compared to wild type ataxin-1. This implies that mutant ataxin-1 is more liquid-like than wild type ataxin-1. Examining differences in LLPS properties of wild type and mutant ataxin-1 could provide insight into SCA1 pathogenic mechanisms, although further characterization is required.
Greenblat, Leeor-Numerical and analytical exploration of the semi-discrete massive Thirring system (Dr. Dmitry Pelinovsky)
The massive Thirring system is a completely integrable system of nonlinear partial differential equations in (1+1) dimensions. Computational approaches to understanding the solutions of this system require that the spatial variable be discretized. In a recent paper, Joshi and Pelinovsky (2019) obtain an integrable semi-discretization of the massive Thirring system in laboratory coordinates. In this thesis, we use von Neumann stability analysis to demonstrate that while explicit methods of numerically solving this system are unconditionally unstable, there are alternative, neutrally stable, semi-implicit schemes that are available. In pursuit of numerical solutions to this system, we generate a scheme that begins with initial data and inverts two finite difference equations before using a semi-implicit solver to find the solution at the next time step. Despite the unconditional stability of this implicit solver, the error between the numerical and exact solution grows with each iteration, preventing the acquisition of stable numerical solutions.
Houpt, Noah-Physiological and behavioural effects of simulated tide conditions on toadfish males (Dr. Sigal Balshine)
The choice of where to build a nest is influenced both by the needs of the offspring and the costs that parents experience when nesting at a certain location. Some fishes, including the plainfin midshipman (Porichthys notatus) fish, nest and rear their young in a particularly extreme and abiotically dynamic environment – the rocky intertidal zone. Nesting in intertidal zones may speed up the development of plainfin midshipman eggs, but exposes parents to frequent bouts of aquatic hypoxia and air exposure when the tides recede. We investigated the physiological costs and mitigating strategies demonstrated by guarder plainfin midshipman males in response to normoxic water, water with declining oxygen levels, or air exposure for six hours. We also tested for physiological and behavioural strategies that could mitigate these costs. Air exposed fish showed the greatest physiological disturbance based on plasma and tissue metabolites, although glycogen content did not vary in any tissue with exposure. Male plainfin midshipman may draw upon O2 stores from their swim bladders during bouts of environmental hypoxia, as we found that swim bladder oxygen content decreased during air exposure. In a second experiment, we found that plainfin midshipman males performed surface respiration more frequently when exposed to hypoxia than when exposed to normoxia. Our results illustrate the costs of nesting intertidally, but these fish rely on a suite of physiological and behavioural coping mechanisms that mitigate some of the costs of providing parental care in a fluctuating and harsh breeding environment.
Johnstone, Graham-Structural and Magnetic Properties of Mott-Insulator Ca (Dr. Graeme Luke)
Dr. Graeme Luke, The rapid advance of smaller, more efficient electronic technology is supported by the pursuit of emergent quantum mechanical descriptions of electrical conductivity and insulation. One promising class of materials with a suite of applications are the Mott-insulators. These materials are defined by their ability to transition between a conducting phase and an insulating phase by changing parameters such as temperature or pressure. Ca2RuO4 is a particularly noteworthy Mott-insulator because it is capable of transitioning from insulator to a conducting metal under an applied electric current.
A drawback of this material, however, is its tendency to self-fracture and shatter into ~mm3 size crystals as its structure distorts when it cools below TMIT=357K. This makes Ca2RuO4 difficult to work with for experimental inquiry and applications. Recent literature has presented a solution to this problem by introducing a slight (1%) substitution impurity of titanium in place of ruthenium.
This purpose of this project was to grow large scale samples of Ca2Ru1-xTixO4 (x=0.01) and investigate its structure using X-ray powder diffraction. Data fitting using Fullprof software showed that the crystals we synthesized had a 60% purity orthorhombic Ca2Ru1-xTixO4phase that was consistent with other structural information available for the Ti-doped variant. Characteristic measurements of the magnetic susceptibility were also performed to obtain a more descriptive profile of this crystal’s properties.
Future investigations of Ca2Ru1-xTixO4 which test the current induced Mott-transition could gauge its viability for commercial applications to solid state electronics in the form of memory-resistors and field-effect transistors.
Kawamoto, Cory-Assessing the Physical and Genetic Responses of the Eutrema Salsugineum to Phosphate Starvation (Dr. Weretilnyk)
Phosphate (Pi) is an essential, albeit limiting nutrient required for plant growth. The use of fertilizers leads to ecological repercussions. Plants have evolved physical and genetic adaptations to cope with phosphate starvation, therefore studying them may lead to the development of more resilient crops to nutrient stress. The Eutrema Salsuigenium (Eutrema), a small flowering plant is a relative of the Arabidopsis Thaliana and is a model for nutrient stress. Two ecotypes of Eutrema have been well studied. The Yukon is native to low phosphate soils while the Shandong is native to high phosphate soils. Comparing the responses of these two plants to phosphate starvation is ideal for studying these adaptive mechanisms. Inbred Yukon and Shandong seedlings were surface sterilized, germinated on Murashige and Skoog media, then placed on media containing 0 mM Pi or 0.5 mM Pi. Primary and lateral root lengths were taken at 0, 7, and 12 days. At day 12, RNA was extracted, then converted to cDNA by established methods. CDNA was RT-PCR amplified using primers specific for the IPS2 long non-coding RNA then analyzed on a 1.5% agarose gel. Two-Way ANOVA determined that plant ecotype and phosphate starvation significantly affected primary root and lateral root lengths (p<0.05). One-way ANOVA determined that phosphate starvation affected primary root and lateral root lengths within each ecotype (p<0.05). Multivariate analysis determined that plant ecotype and phosphate starvation significantly impacted the relationship between primary and lateral root length. The expression of IPS2, which is a long-non coding RNAs involved in phosphate homeostasis will be determined.,
Kim, Noel-Self-concept trajectories in children with epilepsy (Dr. Gabriel Ronen)
Self-concept refers to knowledge about the selfâ€”about our beliefs, personality, physical characteristics, abilities, values, goals, and roles. This knowledge is important because it shapes our thoughts, feelings, and behaviour. Children with epilepsy may shape their self-concept around their condition. Thus, it is important to better understand self-concept in this population, how it changes over time, and what factors affect it. The purpose of this study was to evaluate the trajectories of self-concept in children with epilepsy, as well as to identify determinants of these trajectories. Children with epilepsy completed three assessments of self-concept over 28 months. Data was also collected on demographic and seizure information, child depression, parent mood, perceived stigma of epilepsy, and child participation. The slope and intercept of self-concept trajectories were derived. Several independent variables were then assessed for their effect on self-concept trajectories. Self-concept was found to decrease significantly over time, with large variability between individuals. Factors that affected these trajectories included child age, child depression, perceived stigma of epilepsy, and parental mood. Seizure severity, gender, and child participation did not have a significant effect on self-concept. These findings suggest that self-concept worsens over the course of childhood years. Furthermore, this may be impacted by their age, depression, perception of stigma, and parents’ mood. Clinicians should be aware of these negative trajectories in self-concept in children with epilepsy. They may also target their depression symptoms, perception of stigma, or parents’ mood to improve self-concept.
Koniar, Helena-Mobility of Capicua in Live Fly Embryos (Dr. Cecile Fradin)
Capicua (CIC) is a protein that acts as a transcription repressor in developing tissues. The class of CIC proteins is well conserved among metazoan organisms and has been associated with human diseases, including cancer and neurodegeneration. In Drosophila melanogaster, CIC is essential for early embryogenesis because of its function in the Torso pathway, which controls the specifications of terminal regions in the fly embryo. Previous studies have identified that CIC functions through the repression of genes involved in RTK-pathways, however, CIC’s molecular interactions are not well understood and require further investigation. To examine CIC’s mobility at physicological conditions, we measured the diffusion of CIC using Fluorescent Correlation Spectroscopy (FCS) in live fly embryos that express a fusion protein of CIC and superfolder Green Fluorescent Protein (GFP). FCS experiments were conducted in the nuclei and cytoplasm, for various nuclear cycles, and at different positions along the anterior-posterior axis in several embryos. It was found that the best fitting model was a two-component 3D diffusion model, in which one species of CIC is rapidly diffusing (~30 µm2/s) and the remaining fraction is diffusing very slowly (~0.8 µm2/s). This suggests that when CIC binds to its DNA targets it diffuses very slowly and when it is unbound it diffuses freely until it finds a new target. This study provides new information on the CIC’s dynamics in a living organism and better informs us on its molecular interactions as a transcriptional repressor.
Lefebvre, Michele-Reconsidering the metacognitive model of depression using an adaptationist perspective to rumination (Dr. Paul W. Andrews)
The metacognitive model of depression attributes the development and maintenance of depression to the beliefs individuals hold about rumination. Empirical support for this model has proven somewhat inconsistent and necessitates further research. Since individuals with depression often believe rumination is helpful, a novel approach could involve merging its relevant predictions with the evolutionary analytical rumination hypothesis (ARH), which views depressive rumination as an adaptive cognitive process. Specifically, depressive symptoms promote causal analysis of the problems that triggered the episode (CA), followed by an analysis of possible solutions to the problems (PSA), which then exerts negative feedback onto depressive symptoms. The aim of this study was to explore the relevance of positive and negative metacognitive beliefs about rumination (PMBR and NMBR, respectively) in the context of the ARH. A sample of 352 undergraduate students from McMaster University completed self-reported questionnaires assessing depression severity, analytical rumination, and metacognitions. NMBR and PMBR were both positively correlated with depression and CA, but only PMBR was correlated with PSA. In addition, when NMBR was added to the cyclical model described above, it inhibited CA (p<.001); when PMBR was added to the cyclical model, it promoted CA (p=.07). These results suggest that depressive rumination is promoted by PMBR and inhibited by NMBR. This study has implications for better understanding the mechanisms involved in depression, which can ultimately aid in improving early intervention and treatment modalities for those in need.
Liu, Aileen-The role of Pseudomonas aeruginosa accessory genes tfpY and tfpZ in bacteriophage defenses (Dr. Lori Burrows)
Pseudomonas aeruginosa (Pa) is an opportunistic pathogen that is a major causative agent of hospital-acquired infections. Pa have long filaments on the cell surface known as type IV pili (T4P), which are virulence factors. Tail proteins on bacteriophages have evolved to recognize T4P as receptors, therefore, taking advantage of T4P as a phage receptor could be used as a therapeutic against antibiotic resistant strains of Pa. Bacteria have also evolved a number of phage defense mechanisms which can make Pa resistant to phage therapy. We analyzed a library of pilus-specific phages to characterize a novel phage defense system in Group III and Group V Pa pilins to determine if accessory genes tfpX and tfpY are involved in anti-phage defenses. We identified six phages that showed a decrease in bacterial cell death when TfpY and TfpZ were present compared to when the proteins were absent. Pa subcultures with and without tfpX and tfpY were challenged with our phages and optical density (OD) tests revealed that bacterial growth was higher in strains with the accessory genes compared to when the genes were absent. Twitching assays revealed that the number of surface pili decreased when the accessory genes were removed, suggesting TfpY and TfpZ may be involved in changing the structure of the pili to prevent phage adsorption. Our tests reveal that accessory genes tfpX and tfpY play a role in evading phage infection, which should be considered when making or adjuvants against multi-drug resistant Pa.
Macklai, Sabrina – Surveillance of Cannabis Use in Urine by Multisegment Injection-Capillary Electrophoresis-Electrospray Ionization-Triple Quadrupole-Mass Spectrometry (MSI-CE-ESI-QQQ-MS)
In October of 2018, the Canadian federal government legalized recreational cannabis. This newfound widespread availability of cannabis led to many researchers studying the public health effect of cannabis, namely determining its therapeutic potential and negative drawbacks.
One way to approach this is through studying cannabis metabolism. The most routinely screened-for metabolites of cannabis, referred to as cannabinoids, are Δ9-tetrahydrocannabinol and cannabidiol. These are known for their psychoactive and therapeutic properties respectively. By studying the concentrations of these metabolites in cannabis users’ urine, we can determine how metabolism differs per individual.
The gold standard for cannabis screening is urine screening using tandem liquid chromatography-mass spectrometry. However, the gold standard is flawed in that the immunoassay has issues with bias and the confirmatory test, while sensitive, requires hours to run multiple samples with extensive sample preparation.
Herein, we proposed a novel screening platform for cannabis surveillance in urine that allows for targeted analysis of metabolites and a higher throughput. This platform is multi-segment injection-capillary electrophoresis-electrospray ionization-triple quadrupole-mass spectrometry (MSI-CE-ESI-QQQ-MS). Results reveal that MSI-CE-ESI-QQQ-MS can confidently detect cannabinoids at the confirmatory level (25 ng/mL). As this new interface does not require enzyme deconjugation and also employs multi-segment injection, it can achieve a turnover of three minutes per sample.
Thus, this newly created platform can be used to screen for cannabis use for a wide variety of purposes. Beyond advancing our understanding of cannabis metabolism, this platform is ideal for use in workplace drug testing and other situations where rapid and reliable results are required.
MacLean, Connor-Evaluating Social Media Communications within the Faculty of Science (Dr. Maureen MacDonald)
In the age of rapidly changing communication trends, many companies, organizations, and groups are facing challenges in adapting to the evolving landscape of social media. The leadership of the Faculty of Science at McMaster University is keenly aware of this trend but lacks an informed strategy on how to respond. The purpose of this study was to examine the social media communication preferences and motivations of undergraduate students in the Faculty of Science. The Faculty will thereby determine how to most effectively utilize social media to ensure higher student engagement and effective information delivery. Data was collected through a variety of methods, including a survey and social media analytics of current McMaster University social media accounts. During the course of the two-week data collection period, the survey received 443 total responses. Of these responses, 307 of them were completed responses that were submitted by full-time undergraduate students within the Faculty of Science. In general, Instagram was found to be the most predominantly used social media platform. While many students have other social media accounts, none are used as intensively as Instagram, mainly for entertainment, time-passing, and social interaction purposes. Trends in social media usage vary somewhat by the academic level of the respondents, including the motivations for using each social media platform, and the most frequently used social media platform. It is recommended that the Faculty of Science create Instagram and Facebook accounts, develop a social media strategy, and implement a new Digital Media position to enhance communication with undergraduate students.
Martin, Sonya-How does Bicoid find its target on DNA? (Dr. Cecile Fradin)
Morphogens are molecules that can aid in cell differentiation, an important process for embryo development. In the Drosophila melanogaster embryo, the Bicoid (Bcd) protein acts as a morphogen and forms an exponential concentration gradient along the anterior-posterior axis. Bcd exerts its effect by acting as a transcription factor for important marker genes involved in pattern development in D. melanogaster. Interestingly, Bcd triggers precise gene expression in three minutes. This fact makes us ask the question: how can Bcd finds its target genes on the genome so quickly?
The goal of my project was to express and fluorescently label Bcd. Due to the instability of full-length Bcd, I worked on Bcd’s DNA binding domain, or homeodomain (Bcdhd).
The bcd homeodomain (bcdhd) gene, as well as a cysteine point mutation of the gene (bcdhd-c), were successfully cloned into an expression vector. In future imaging experiments, Bcdhd will act as a control for the functionality of the protein whereas Bcdhd-c can be functionalized to attach a fluorophore. Although Bcdhd was found to be rather insoluble and difficult to purify, various attempts resulted in finding optimal expression and purification conditions.
Once Bcdhd and Bcdhd-c are successfully purified they can be used in single particle imaging experiments to elucidate the search mechanism of Bcd for its target genes.
Nicole Zhang-Evolution of Interferon Regulatory Factor in bats indicates virus-host interaction (Dr. G. B. Golding and Dr. Dawn D.E. Bowdish)
Bats belong to a special group of mammals that have been reservoir for several viral epidemics. They are observed to have little inflammation response when pathogens ensue. The transcription factor family IRFs often have a large impact on the organisms’ response to viral infections, cancer and immunological triggers. By generating maximum likelihood phylogenetic trees of the bats along with other mammals, we found that they have variation in selection pressure. IRF3, IRF7 and IRF9 were positively selected, meaning new functions are promoted while the rest of the IRFs are under purifying selection. From site by site analysis, we formed further hypothesis on the selection site functions and the possible outcomes. Similarly, for ultra-conserved residues, we formed hypothesis on their respective conservation reason.
Norman, Bryce-Vortices in Bosonic Dark Matter (Dr. Cliff Burgess)
Dark matter is one of the biggest mysteries of modern day physics. Dark matter is a hypothetical type of matter that does not interact with light, but does interact gravitationally. There is an outstanding amount of evidence to support the existence of dark matter and many different theories to describe it, however, there has yet to be experimental detection of dark matter. Therefore, it is important to continue to look for new theories of dark matter in order to guide us towards detecting it. This thesis explores possible effective field theories for dark matter, including the novel idea of a superfluid bosonic dark matter. The rotation of dark matter in spiral galaxies would cause vortices to appear in the superfluid. This could mediate a force to give the behaviour that we commonly see in spiral galaxies, and lead to properties like the Tully-Fisher relation. This investigation has ruled out several different dark matter theories and developed constraints for the superfluid bosonic dark matter. This model has promise to explain properties of both galaxies and larger structures, such as galaxy clusters. Further development of this model could lead to the experimental detection of dark matter.
Pavic, Sarah-Assessing drug use among undergraduate students: Aligning campus services with student needs (Dr. Nikol Piskuric)
Canada is grappling with an ever-growing opioid epidemic which is characterized by increasing rates of opioid poisoning and death. In Ontario, the rates of opioid-related poisoning and death are among the highest in our city, Hamilton. Thus, we wondered whether students at McMaster University were affected by the opioid epidemic. However, in our attempts to find information about drug use at McMaster, we discovered these data did not exist. Therefore, we set out to perform a comprehensive study of drug use by McMaster undergraduate students.
The purpose of this study was to determine the types of drugs used by undergraduate students at McMaster, as well as the prevalence of drug use. Data on students’ drug use behaviours over the past 12 months were collected through an online survey. Of 1086 survey respondents, 72.4% reported using alcohol and 45.6% reported using cannabis. Illicit drugs were used less frequently; in particular, only 4.2% reported the use of opioids. Of those, 41.3% reported problems related to their use of drugs, though only 21.1% sought help for a drug problem.
In addition to quantifying drug use, respondents were asked to provide suggestions of how McMaster could help students with substance use issues. Ultimately, the results of this study were used to propose an action plan for McMaster to reduce the harms associated with drug use. The three main components of this plan include: increasing awareness of drug use and related consequences, increasing support and advertisement of services, and reducing stigma associated with drug use.
Saunders, Jacob-Direct Metal Laser Sintering Process Monitoring with a High-Speed Camera (Dr. Qiyin Fang)
Additive manufacturing (3D printing) has rapidly garnered interest around the globe due to its ability to create customised parts with complex internal structures. Consequently, build quality is of utmost importance and is the focus of much research. In the case of powder-bed fusion by direct metal laser sintering (DMLS), inconsistencies in laser beam size, speed, and power can result in defects such as lack of fusion, balling, and over-exposure. Detection of these imperfections post-construction can be inefficient and costly. In an effort to eventually improve the quality of DMLS builds, this project attempts to establish a method of non-contact process monitoring. This is done with a visible spectrum high-speed (2000 fps) camera and by monitoring parts printed with H13 tool steel on an EOS M280 DMLS machine. Spatial calibration of approximately 118 μm/pixel was achieved and the imaging setup allowed for qualitative analysis of the printing process. With the implementation of a longpass filter, analysis in the near-infrared regime was possible and provided information regarding the melt region dimensions. The melt pool itself was sometimes obscured, possibly due to cold spatters and/or plasma shielding. A Kalman filter particle-tracking method was verified by reconstructing the melt pool velocity and was subsequently used to obtain spatter number and a wide range of spatter velocities. Improved understanding of the relationships between these parameters and defects would provide a foundation for developing feedback control mechanisms that could significantly improve build quality.
Sharpe, Isobel-Measuring Sugar-Containing Beverage Intake Among Young Children: Comparing a Food Frequency Questionnaire with a 24-hour Dietary Recall for Food Administration for Parents (Dr. Laura Anderson)
Dr. Laura Anderson, Childhood obesity and its associated health outcomes pose a serious public health issue. One likely contributor to weight gain among children is the consumption of sugar-containing beverages (SCBs). To further understand and monitor the relationship between childhood SCB consumption and weight, it is important to use accurate and efficient instruments to measure beverage intake. However, the measurement of beverage intake in epidemiologic studies is challenging. While food frequency questionnaires (FFQs) are often used for this purpose due to their short length and ease of administration, they are not always accurate when compared to more comprehensive methods such as 24-hour dietary recalls. The objective of this study was to evaluate the accuracy of using a FFQ compared to using a 24-hour dietary recall to assess parent-reported consumption of SCBs among young children. A cross-sectional study was conducted on children four years of age and older from the TARGet Kids! primary care research network in Toronto. Descriptive statistics were used to characterize the study sample. To assess the relationship between the FFQ and 24-hour dietary recall, the correlation between different beverage types was measured. Preliminary results suggest moderate correlation between the FFQ and 24-hour dietary recall. If comparable to the 24-hour recall, the FFQ can be used to inform interventions for decreasing SCB intake among children, ultimately helping to reduce childhood obesity.
Smith, Jeneva -The Neural Correlates of Effort-Based Decision-Making in Cannabis Use Disorder (Dr. Iris Balodis)
Approximately 43% of Canadians have used cannabis at least once and approximately 9% of people who use cannabis develop cannabis use disorder (CUD). Cannabis use is linked with amotivational symptoms but no studies have examined the neural correlates of effort-based decision-making in CUD. The purpose of this research was to examine the neural response underlying components of cost-benefit decision-making in CUD and determine if the severity of participants’ CUD was associated with this neural response. In this pilot project, participants with CUD completed many intake assessments, including the Cannabis Use Disorder Identification Test â€“ Revised (CUDIT-R), which was used to determine the severity of their CUD. The participants then completed a modified version of the Effort Expenditure for Rewards Task (EEfRT) during functional magnetic resonance imaging. To examine which brain regions encoded the choice of whether to complete work for a reward, we contrasted the blood oxygen level dependent (BOLD) signal following the first cue versus the second cue on the EEfRT. This contrast was correlated with the CUDIT-R scores to explore relationships with CUD severity. We expect that there will be increased BOLD activity in several brain regions, including the ventral striatum, anterior insula and dorsal anterior cingulate cortex, following presentation of both cues. As well, we expect BOLD activity in these areas to be inversely related to CUDIT-R scores. This research will elucidate the effects of chronic cannabis use on effort-based decision-making in the brain, which can be utilized in developing targeted CUD treatments focusing on improving motivation.
Sreerangan, Pooja-Comparing Movement Measures in Toddlers with Actical and ActiGraph Accelerometers (Dr. Joyce Obeid and Dr. Sara King-Dowling)
Background: Accelerometers are considered to be the most promising tool for measuring movement in children aged 0 to 5 years. However, existing accelerometers use brand-specific proprietary activity counts to quantify movement, making it difficult to directly compare data between monitors. Studies are now shifting towards the usage of raw acceleration to measure movement, but it is currently unknown how this data will compare between different accelerometers. Therefore, the objective of this study is to determine how measures of movement in toddlers differ between two commonly used accelerometers, ActiGraph and Actical.
Methods: Healthy toddlers aged 12 to 35 months were recruited to participate in a play session. Participants were fitted with both ActiGraph and Actical accelerometers on a waistband worn over their right hip. The play session consisted of simple sedentary and active toddler-appropriate games. Participants also wore the accelerometers at home for 7 days, and caregivers were instructed to only remove the accelerometers while sleeping or when accelerometers may come into contact with water.
Results: We hypothesize that raw accelerations will differ between ActiGraph and Actical because of differences in how their sensors detect accelerations. However, the ranking of total activity counts in participants will not differ between accelerometers. Discussion: The results of this study can be used to better understand how to measure movement levels in toddlers, and eventually determine optimal physical activity levels for this population.
Swing, Megan-Sm-Nd Isotope Mapping of the Ottawa-Bonnechere Graben within the Grenville Province (Dr. Alan Dickin)
The Ottawa-Bonnechere Graben (OBG) and the Grenville Province (GP) are major crustal features that intersect along the border of Ontario and Quebec. The OBG was formed during a rifting event approximately 600 million years ago, creating a complex, seismically active normal fault system. The OBG can be found cross-cutting the GP, which is the youngest component of the Canadian Shield. The GP formed during a major mountain building event known as the Grenville orogeny caused by a continental collision approximately 1100 million years ago. While these geological features have been studied extensively as separate entities, the possibility of these structures interacting is high. One issue is the Chalk River nuclear waste facility, which is in the area and could be threatened by seismic activity. The region could provide valuable insight into how the formation of the OBG has altered the structure of the GP.
This study examined the relationship between the OBG and the GP using Samarium-Neodymium isotope dating to determine crustal formation ages. Rock samples collected southeast of Algonquin Park were analyzed. The resulting ages could be separated based on the structural divisions of the GP which were used to map faulted blocks of crust. Samples furthest northeast were found to be influenced by the OBG, with multiple blocks of downfaulted crust, while samples further southwest were unaffected. This research is crucial to finding the extent at which the OBG has altered the Earth’s crust on a local scale and how likely the area is to experience earthquakes.
Takahashi, Monica-Epidemiology of visits to the emergency department across Ontario for diagnosis related to the eye and its adnexa (Dr. Kourosh Sabri)
Throughout North America, visits to Emergency Departments (ED) have been on the rise, leading to ED crowding. In fact, this is the most serious issue facing EDs in the developed world, and it is becoming more dire. In fact, there exists a growing body of evidence suggesting that ED crowding has adverse effects on clinically important outcomes and compromises quality of care of patients. In the United States, it is known that EDs provide a large amount of ocular care for non-urgent conditions. However, it is currently unclear how many of the ocular-related visits to EDs across Ontario are for urgent reasons.
The current study examined data collected from the Canadian Institute for Health Information (CIHI) on ocular-related ED visits across Ontario between 2012-2016 with the aim of determining the number of ocular-related visits that were for urgent reason. The data was categorized into different age groups and summary statistics were used to gain information on data demographics. Additionally, a Chi-squared test of independence was used to determine factors that significantly impacted presenting to the ED with an urgent versus a nonurgent diagnosis.
The study found that the most common ocular-related reason for ED visit, making up over 40% of the total visits each year, was conjunctivitis. Since conjunctivitis is a nonurgent diagnosis, this shows that a large portion of the visits to EDs were for nonemergent reasons.,
Tam, Audrey-A Test of Olfactory Sex Discrimination in Big Brown Bats (Eptesicus fuscus) (Dr. Paul Faure)
Effective communication is essential for the maintenance of cohesion in bat colonies, which can contain thousands of individuals. Several studies have shown that odour cues can provide information about the species, colony membership, and identity of a bat; however, the extent to which these odour cues can convey information about sex remains unclear. Because big brown bats (Eptesicus fuscus) live in mixed gender colonies during mating season, the ability to differentiate between sexes is necessary to locate a mate. The present study aims to examine whether E. fuscus can discriminate between sexes using only olfactory information.
Adult E. fuscus were recorded moving freely within a maze that contained scents obtained from a male and a female of the same species. One group of subjects was habituated to the maze prior to experimental trials, whereas a second group was not habituated prior to the experiment. The exploratory behaviour of the bats in the maze and the proportion of time spent near each scent were used as indicators of preference toward the odour of a particular sex.
Results provided no evidence that E. fuscus were able to discriminate between sexes using olfaction, as both male and female test bats did not show a preference for the scent of one sex over the other. Interestingly, non-habituated animals explored the maze to a greater degree and were more likely to approach a stimulus scent than those that had been habituated. This finding has important implications for the design of future behavioural studies involving bats.
Tweedle, Adam-Microclimatic Contrasts Between High- and Low-Density Monospecific Stands of Garlic Mustard in the Winter (Dr. Susan Dudley & Dr. Chad Harvey)
Garlic mustard (A.petiolata) is an invasive wintergreen biennial forb originating from Eurasia which has dominated the understories of forests ranging across Southern Canada and the Atlantic coast of the United States of America. The current management practices of A.petiolata are labour intensive and require multiple generations to exhaust the seed bank, due to the high fecundity and the seeds ability to become dormant for extended periods. The species also produces glucosionlates, allelopathic compounds that inhibit mycorrhizal fungi function. During winter months, A.petiolata retains the ability to photosynthesize, achieving maximum rate of photosynthesis in late winter and early spring when light is able to penetrate to the forest floor easily due to the lack of canopy. Studying garlic mustard microclimate during winter months provides an opportunity to see how the plant density affects the region on a small scale, potentially creating ideal conditions for garlic mustard population proliferation and longevity. Sites were selected in the McMaster Forest, pairing quadrats of high- and low-density garlic mustard populations. Temperature and light sensors were used to determine under leaf temperatures as well as environmental radiation to determine the variation between the high- and low-density sites and the environmental conditions. There was no significance in between the temperature of high- and low-density plots, indicating other environmental factors may work with temperature to create temperature variation.
Vitali, Elias-Carrier Diffusion Imaging of a Thin Silicon Solar Cell (Dr. Rafael Kleiman)
As the demand and necessity for more reliable renewable energy sources increases, more research is needed to ensure that new products which reach the market are as efficient as they can be. Photovoltaics research focuses on characterizing and improving the efficiency of solar cells. A major source of valuable information in photovoltaics research is the charge-carrier lifetime, a measure of how quickly the charge carriers recombine and stop producing electrical energy. We employ a new technique to measure the carrier lifetime, by direct imaging of the solar cell in action. An IR camera was used to image a thin Silicon sample illuminated by a 532 nm laser, in turn releasing charge carriers radially outwards. Our goal was to capture the diffusion of charge carriers and use the camera to analyze the minute temperature differences created on the sample as a result. By modulating the laser, we can look at the effect of varying frequencies on the amplitude of the signal produced by the diffusing charge carriers. Fitting a known relation to this allows us to extract the lifetime from the direct imaging of the cell. Using this technique, we were able to measure a lifetime of ~20 µs, which is well within the range for the sample used.
Wynn, Gabriella -Developing a Synthetic Distal Tibiofibular Syndesmosis for the Advancement of Orthopaedic Research (Dr. Cheryl Quenneville)
Ankle fractures are common injuries that often have a less than ideal prognosis. Surgical techniques to realign displaced bone fragment have become an increasingly prevalent treatment option for many types of severe ankle fractures. However, the incidence of posttraumatic osteoarthritis suggests that research is still needed in fixation techniques. While the tibia is often the model of choice to analyze fracture treatment options ex vivo, it is not the only consideration in ankle fractures; the fibula, ligaments, and interosseous membrane all play vital roles in the stability of an ankle joint. Thus, there is a need to consider fracture treatment techniques on the entire distal tibiofibular syndesmosis. Considering the limitations of cadaveric specimens, composite bones have been created in an attempt to adequately model the mechanical properties of real systems in orthopaedic studies. Previous validation studies have suggested that artificial tibiae mimic natural human tibiae fairly well. This project aims to extend the validation to synthetic fibulas and ligaments. Quasi-static loading tests were conducted to determine the stiffness of the aforementioned components and compare them to human values. A suitable surrogate ligament was identified, and the best methods to attach the ligament to the bone was determined by testing the fixation strength of different adhesives. An artificial distal tibia-fibula system was assembled, with the ligaments holding the bones together, and was tested under quasi-static loading conditions to again measure the construct stiffness. This model has the potential to enhance orthopaedic research and assist surgeons in implementing proper fracture fixation techniques.
Yachouh, Joshua-Professor Perspectives on Educational Development (John Maclachlan)
Within post-secondary education (PSE) institutions, professors hold a variety of roles. Universities expect their faculty members to be capable not only as researchers, but also within their teaching and service roles. Many professors may struggle to balance conflicting professional responsibilities; consequently, certain duties may take precedence over others. It is often the case that professors feel their institutions value excellence in research as compared to excellence in teaching.
This study aims to explore the educational development experiences of instructors within the uniquely structured Integrated Sciences program at McMaster University and explore opportunities for the institution to better adapt educational development across faculties and departments. Semi-structured interviews were conducted with seven instructors who were asked about their experiences in educational development within and outside the Integrated Sciences program and opportunities for enhancing education across the university. Following coding and thematic analysis, major interview themes included BuildingMacPherson-department relationships, Rewarding teaching, Risk-taking in Teaching, Developing Communities of Practice, and aLack of Time The results of this study suggest that academic departments can benefit from a flexible and up-front approach to educational development with potential for collaboration with the MacPherson Institute. Additionally, this study furthers the notion that promotion and tenure policies must continue evolving to more appropriately reward and assess teaching and that encouraging collaborative teaching efforts within and between departments can provide for uniquely beneficial development opportunities for instructors. Through implementing such efforts, institutions can apply tried and true methods for informally and formally advancing educational development.
Yeung, Jonas -Electrochemical pH monitoring of a neuronal cell culture in a microfluidic device (Dr. Ravi Selvaganapathy)
Extracellular pH monitoring is a useful indicator of neuronal cell health. Metabolic acidosis often occurs in neurodegenerative diseases as impaired metabolism due to oxidative stress result in lactic acid accumulation. One approach is to probe an electrochemical pH sensor into a well plate. This is limited as H+ metabolites are quickly diluted in the buffered media. In an effort to detect changes in extracellular pH, we measure the pH in cells within a microfluidic chip; a microfluidic format enables the integration of electrodes in the immediate vicinity of the cells with low volumes and minimal mixing, thus optimizing conditions for pH monitoring. A tungsten pH wire electrode was characterized with a sub-Nernstian slope in the physiological pH range. The tungsten and Ag/AgCl reference electrodes were implemented into a microfluidic chip. The Q7Q7 neuronal cells were grown with 70-80% confluency in a poly-l-lysine coated microfluidic chip. Cells in the microfluidic device were administered varying concentrations of paraquat (0, 4, 8 nM) to induce cell death and mitochondria disfunction. Potentiometric measurements were obtained at varying timepoints for each concentration.
Yu, Brian-Phosphate starvation in Eutrema salsugineum (Dr. Elizabeth Weretilnyk)
Soil phosphate levels commonly restrict crop productivity. Furthermore, crops are unable to take up much of the phosphate supplied by fertilizers, and rock phosphate, the natural resource that phosphate is derived from, is being rapidly depleted. The Yukon ecotype of Eutrema salsugineum is extremely hardy with respect to phosphate use efficiency; however, the mechanisms, biochemical pathways, and genes responsible for its high phosphate use efficiency remain undetermined. To this end, Eutrema plants were grown at different phosphate regimes and collected from their native environment in the Yukon. Plants had their biomass and phenotypes were recorded. RNA was extracted from the frozen plant tissue and used for the synthesis of cDNA. PCR was used to examine the expression levels of a phosphate induced lncRNA. This allowed for comparison of phosphate starvation in wild plants compared to cabinet-grown plants. Results will help to elucidate the similarities between wild and cabinet-grown plants and if cabinet conditions effectively mirror those of wild plants. These results may also help to reveal any epigenetic effects of plants grown in cabinet conditions. Phosphate content of plants was also determined to see if there was any difference in the amount of phosphate in the plants or where it is being sequestered. These findings aid in determining the root of Eutrema’s high phosphate use efficiency.