14277 research outputs found
Sort by
Degradation modelling and performance prediction of proton exchange membrane electrolyzers for wind-to-hydrogen systems
No full textThe integration of proton exchange membrane electrolyzers with intermittent renewable energy sources, particularly wind power, presents both opportunities and challenges for green hydrogen production. In this thesis, a novel degradation model is presented to investigate chemical degradation and operational performance of proton exchange membrane electrolyzers under intermittent renewable energy inputs, with a particular focus on wind integration. Three complementary modelling approaches are employed: long-term continuous and intermittent operation simulations of an electrolyzer, Rayleigh-distributed and real wind data simulations of a 2.8 MW system, and a validated SimulinkTM model for wind integration. Across the three studies presented, a clear picture emerges of the complex interplay between electrolyzer loading, membrane degradation, and hydrogen production.
Intermittent operation can more than double the rate of fluoride release compared to continuous operation, with rapid cycling initially increasing degradation before reaching a quasi-steady state. Specifically, continuous operation at full capacity resulted in a membrane lifetime of approximately 9.4 years, compared to only four years under intermittent operation. Frequent partial load operation and prolonged OFF periods intensify degradation due to the electrolyzer operating at open-circuit voltage conditions.
Rayleigh-distributed wind speed simulations at average velocities of 6, 8, and 10 ms-1 revealed that moderate wind conditions (8 ms-1) achieved near-maximum hydrogen output (?280,000 kg/year) while significantly minimizing membrane degradation (with the membrane thinning by 9.6 ?m). Dynamic simulations show that higher capacity ratios maximize hydrogen production (up to 269,768 kg), yet they experience the highest absolute degradation. However, efficiency quantified by hydrogen produced per membrane loss is lowest when capacity is fully matched. Faradaic efficiency analyses confirm that part-load and full-load cycling strongly influence electrochemical performance, emphasizing the need for operational strategies that minimize frequent voltage transients.
Finally, system-level sensitivity analyses revealed that electrolyzer design parameters, including temperature, membrane thickness, and exchange current density, significantly affect hydrogen production and efficiency. Higher operating temperatures and thinner membranes reduce cell voltage and enhance output, while elevated exchange current densities improve efficiency by reducing activation overpotentials. Pressure effects were minimal, suggesting that thermal and electrochemical control are the dominant levers for optimizing proton exchange membrane performance under variable renewable supply.
Collectively, these studies demonstrate that maximizing hydrogen productivity from wind-integrated proton exchange membrane electrolyzers requires careful attention to both system sizing and operational strategy. Achieving a balance between durability and output is essential: excessive cycling or poor load matching can rapidly accelerate membrane degradation, whereas optimal sizing and load distribution can deliver near-maximum hydrogen yield while preserving membrane integrity. The findings provide actionable guidance for designing resilient, high-performance electrolyzer systems for renewable hydrogen production and establish a foundation for future work integrating degradation modeling with techno-economic optimization
Analysis of the endocannabinoid system and potential effects of anti-seizure medications in chemical and genetic models of epilepsy
No full textEpilepsy is understood as a condition of variable origins which produces excessive neuronal firing, seizures and associated co-morbidities in the patient. Current treatments for seizures can produce undesirable side effects and have a relatively high rate of failure. Therefore, it is necessary to examine new drugs, including the recently legalized cannabis, and its impacts on epileptic behaviours. Such analyses can be accomplished using the D. rerio (zebrafish) model organism which has been previously used to examine seizure-like behaviours and associated drug treatments in the past. Phytocannabinoids, specific therapeutic compounds originating from cannabis known to reduce seizing in conditions such as Dravet Syndrome, are examined using a chemically-induced model, alongside a CRISPR mutant line targeting kcnq3, which is linked to childhood epilepsy disorders. As well, an examination of novel anti-epileptic drugs Alogabat and Darigabat was performed using behavioural tracking techniques. Investigations of specific receptor interactions in the brain�s endocannabinoid system, which is linked to neuroprotection, are performed using D. rerio specimens, alongside investigation of changes in concentration of endocannabinoid molecules before and after drug treatment and seizure induction using a novel UHPLC-MS/MS method. Finally, a brief investigation of the ability of multi-electrode array technologies to identify neurological activity before and after anti-epileptic drug application to the subject was performed. Overall, this investigation seeks to portray multiple approaches to epilepsy examinations using the D. rerio model organism, while also identifying additional treatments for this condition
Dissolved organic matter of the spring bloom in the Labrador Sea; chracterized using optical properties and parallel factor analysis
No full textThe dynamics of dissolved organic matter (DOM) during the decline of annual spring phytoplankton bloom in the Labrador Sea in May/June 2022 were investigated using fluorescence spectroscopy coupled with parallel factor analysis (PARAFAC). Samples from two short term bioassays aimed to investigate phytoplankton production of DOM under varying temperature and nutrient conditions. Three series of biodegradation assays were used to investigate the microbial transformations of DOM over a six-month time period. Fluorescence data from both experiments of a five component PARAFAC model was validated and used alongside dissolved organic carbon and total dissolved nitrogen data to gain insight into the DOM dynamics. The PARAFAC model was compared to other models using the OpenFluor database and found that all components had been found in previous studies. Of the five components C1, C4, and C5 have been associated with more refractory DOM while C2 and C3 have been linked to freshly produced, more labile DOM and microbial activity. For the bioassay experiments, there were no distinctive trends in temperature or nutrient conditions that could be used to indicate how changing climate conditions may affect DOM production by phytoplankton. Biodegradation data had slight trends between the series for C1 and C2 but no overall trends across components. The lack of trends in both experiments was largely attributed to the bloom composition being dominated by Phaeocystis spp. which primarily releases polysaccharides which are unable to fluoresce. This data provides a basis into future DOM analysis during the spring bloom in this region and highlights a need of additional analysis techniques for phaeocystis blooms
Spatial analyses of the risk of cumulative impacts of mining on Canadian rivers and communities using hydrological connectivity and discharge-related indices
No full textCanada's vast freshwater systems are increasingly threatened by the cumulative impacts of industrial activities, particularly mining. Recent national investments in the extraction of critical elements, which are primarily driven by Canada's transition to clean energy, are expected to amplify these pressures. In this study, we endeavour to understand the cumulative impact of current mining activities on Canada's river system at a large scale. We develop and apply geospatial methodologies to evaluate how active mining operations affect river systems across the country and compare how these impacts are distributed between Indigenous and urban communities.
Two novel indices were created: the Hydrologic Connectivity Cumulative Vulnerability Index (HCCVI), which identifies rivers affected by cumulative impacts by highlighting river reaches where impacts from multiple upstream mine types converge, and the Discharge-Adjusted Cumulative Vulnerability Index (DACVI), which adjusts cumulative upstream mining impacts in a river reach by the river discharge, which account for the ability of the river reach to buffer the cumulative stress.
The HCCVI and DACVI indices were used to compare the spatial exposure of Indigenous and urban communities to hydrologically impacted river reaches, using proximity analysis and statistical testing.
Findings from HCCVI showed no statistically significant difference in proximity between Indigenous and urban communities, although a higher percentage of Indigenous communities were located within 5 km of impacted rivers. In contrast, DACVI analysis revealed that urban communities have significantly higher average impact values; however, a notable portion of Indigenous communities also fall within moderate or high DACVI impact thresholds. Stratified DACVI analysis by mine type provided additional insights: urban communities were more exposed to rivers affected by coal mining, while Indigenous communities were more commonly situated near oil sands-impacted rivers.
These findings underscore both group-level and localized environmental justice concerns and call for more nuanced, equity-driven approaches to cumulative impact assessment. Recommendations include incorporating empirical water quality data, accounting for anthropogenic flow modifications in future analysis, and supporting Indigenous-led environmental monitoring
Modeling of x-ray diffraction spectra of asphalt binders in condensed matter physics
No full textAsphalt binders from 20 samples were obtained from Canada (Ontario and Alberta), the
USA (Montana), and Venezuela. Thin-film samples, each measuring about (lmm), were
heated at a temperature of 150 °C for 10 minutes on glass slides. The X-ray diffraction
(XRD) patterns were obtained with monochromatic Cu K" radiation (40kV and 40mA)
on a Rigaku DMax 2200V-PC. Profile-fitting performed utilizing Pseudo-Voigt and
Pearson VII functions (Linear background, Exponent = 2.0 and Lorentzian =1.0) over
the ranges 5° to 35° and 60° to 110° = 2#.
To the best of our knowledge, this study represents the first time XRD spectra modeling
that has employed Generalized Fermi Function (GFF) in asphalt binders. Using these
functions, analysis of the broadening of diffraction Peaks on the asphalt thin-film was
analytically simulated and measured. In these simulations, two key parameters were
used (exponent=2.0 and Lorentzian = 1.0). The results of our study indicate a clear
correlation amongst the Pseudo-Voigt and Pearson VII. However, a poor correlation
was found with the GFF model. Additionally, the integral width (known as the full
width at half maximum, or FWHM) of the diffraction Peaks were employed to
approximate the experimental X-ray line profiles from the samples used. The two major
factors which are closely related to aging tendencies under low temperatures are
identified in the asphalt binder samples, using XRD of thin films. Based on these results,
it is clear that asphalt pavement easily cracks in cold climates, while rutting is an
ongoing issue in hot climates. Our results indicate that, in order to enhance the durability
and overall performance of asphalt pavements, we need to have adequate understanding
on a microscopic level, the composition and structure pertaining to the asphalt binders
Role of AI for corrective feedback in ESL academic writing
No full textCorrective feedback (CF) is a pedagogical process of developing English as a Second Language (ESL) academic writing for non-native English-speaking (NNES) students. Given that ESL academic writing entails grammatical accuracy, coherent structure, and scholarly discourse, the importance of the feedback mechanism rises remarkably. The emergence of artificial intelligence (AI) has revolutionized ESL education all around the world with its prompt and reliable feedback. However, enigmas remain about the ability of AI to challenge higher-order writing skills and adapt to the individual needs of the ESL learners. This qualitative study aimed to explore the role of AI feedback in developing the academic writing skills of NNES graduate students at Memorial University of Newfoundland in Canada. The study used an anonymous questionnaire survey and direct interviews with the participants to collect necessary data. The survey data were analyzed using a descriptive statistics approach. The interview data were presented through thematic analysis. The findings reveal that AI feedback significantly improves grammatical accuracy and structural coherence in NNES students' academic writings, though its efficacy diminishes for advanced writing aspects such as research-based assignments. Participants also expressed their concerns about losing personal writing competency due to over-reliance on AI feedback tools and AI's negative impact on the environment through excessive water consumption for data centers' cooling systems. Such results inform ongoing discussions about AI feedback by highlighting both the potential and limitations of AI tools for CF in ESL academic contexts. The study concludes by advocating a hybrid approach for CF, incorporating the technical balance of AI with the profound knowledge of humans and addressing both competence and pedagogical substance
Learning through the experts' eyes: an eye-movement modelling example based training intervention in an air traffic control decision making task
No full textThis study explored the effectiveness of Eye Movement Modeling Examples (EMME) as a training intervention for novices performing an air traffic control (ATC) decision-making task.
Nineteen participants were randomly assigned to either an implicit (visual-only) or explicit (visual-audio) training group. Participants completed a pre-test and post-test, with eye-tracking
technology capturing gaze behaviour (fixations, saccades) alongside performance measures (accuracy, response time). Linear and negative binomial mixed models assessed changes over
time and between groups.
Results showed no significant interaction effects for accuracy or gaze behaviour between
training modalities. However, response time, number of fixations, and number of saccades significantly decreased from pre- to post-test in both groups, suggesting improved visual processing efficiency. The implicit group demonstrated significantly longer fixation durations,
indicating greater cognitive effort.
While explicit verbal instruction did not enhance performance, overall reductions in gaze metrics suggest EMME may foster perceptual-cognitive refinement even in brief interventions.
These findings support early-stage learning effects showing improved visual search patterns and
faster response time. The study underscores EMMEs promise in training visual decision making
in complex environments and highlights the need for longitudinal, mixed-methods, and area-ofinterest focused future research
Spatial and temporal variability in lipid profiles in phytoplankton and Arctic cod (Boreogadus said) in the Canadian Arctic
No full textThe identification and characterization of energy flow in marine ecosystems is key to estimating how vulnerable ecosystems, such as the Arctic, will respond to climate change. Chapter 1 reviews energy and essential nutrient flow within two levels of the Canadian Arctic food web: phytoplankton and Arctic cod (Boreogadus saida). Chapter 2 investigates phytoplankton lipid and fatty acid profiles from across the Canadian Arctic. Across both 2019 and 2021, simulated oceanographic groups defined as oceanic, based on higher salinity, higher phosphate, and higher oxygen saturation levels were more likely to be more positively correlated with the sum of phytoplankton ?3 fatty acids. In all organisms, higher concentrations of ?3 fatty acids generally indicative of better overall health and condition.
Chapter 3 investigates the condition of both juvenile and immature Arctic cod in the Canadian Arctic. Fish condition was lower in the Chukchi and East Beaufort Shelf region compared to fish from the Canadian Arctic Archipelago, North Water Polynya, and Baffin Bay. Chapter 4 investigates the effects of temperature and food ration on adult Arctic cod energetic condition and essential fatty acid condition through a laboratory experiment. Adult Arctic cod were held at three temperatures (0, 3, and 8?C) for 12 weeks, and fish were fed either a low (1% fish dry weight/day) or high (4% fish dry weight/day) rations. Their specific growth rates, hepatosomatic indices, gonadosomatic indices, lipid profiles, and female gonad histological indices were compared. Total lipids also remained higher in the 3?C compared to the other two temperature treatments, while the condition metric in females, triacylglycerol:sterol, was also higher at 3?C at the most advanced stage of gonad maturity compared to females exposed to 0?C. Chapter 5 then synthesizes Chapters 2, 3, and 4, using total lipids, lipid classes, and fatty acids to investigate the current state of phytoplankton and Arctic cod health in the Canadian Arctic. The results provide an overall assessment of energetic condition for two key organisms of the Arctic food web across a broad region of the Arctic
Development of a golden hour guideline for a level 2+ NICU
No full textBackground and Purpose: The golden hour (GH) is used to describe the time during which
stabilization efforts of critically ill patients should be completed for the best possible patient outcomes. The purpose of this practicum was to develop a GH guideline and supplementary
resources for the Neonatal Intensive Care Unit (NICU) at the Queen Elizabeth Hospital in
Charlottetown, PE. The need for the GH guideline was identified following a recent reduction in
the accepted gestational age to 29+0/7 weeks, with plans to reduce it further to 28+0/7 weeks.
GH practices can improve neonatal health care by enhancing thermoregulation, glycemic control,
and cardiorespiratory stability. These are accomplished through pre-birth preparation, Neonatal Resuscitation Guidelines, and NICU admission practices. A GH guideline can help direct and
organize the NICU healthcare team to ensure consistent, evidence-based care, leading to higherquality care and improved patient outcomes.
Methods and Results: I completed a literature review, an environmental scan of GH resources available across Canada, and consultations with multidisciplinary local NICU team members.
These methods helped identify the potential impact of a GH guideline, the resources required to
support families, and the educational needs of NICU team members for its implementation.
These methods also assisted in gathering, organizing, and refining the GH guideline content based on the literature and existing NICU practices. Using the gathered data, I created a GH guideline and a parent handout. I also created a presentation and simulation to disseminate the GH guideline
Remote effect of local hypoxia/ischemia in the heart during myocardial infarction
No full textIschemic ventricular tachycardia (VT) occurs 48-72 hours after myocardial infarction (MI; heart attack) occasionally resulting in sudden cardiac death. The cardiac specific Sarco-(endo)plasmic reticulum (SR) calcium ATPase (SERCA2) is thought to be responsible for these arrhythmias. Replacement of normal SERCA2a sub-isoform by SERCA2b, a more efficient Ca²⁺ uptake pump not expressed in healthy conditions, is hypothesized to explain increased release of Ca²⁺ by SR, initiating post-MI tachycardias. This arrhythmogenic change of SERCA2 appeared in left ventricle (LV), at the MI location, and in other healthy heart regions. This observation suggests hypoxic/ischemic cells in LV release biochemicals changing SERCA2 expression affecting all cardiac regions when released into circulation. This hypothetical remote effect was tested by developing an assay mimicking hypoxic/ischemic MI conditions using Sprague Dawley rat ventricular myocytes. A preparation of cardiac cells was exposed in culture to hypoxia/ischemia (preparation #1). A second preparation of healthy normoxic cardiomyocytes (preparation #2) were incubated with media from preparation #1. After 3 days, healthy cells from preparation #2 exhibited typical arrhythmogenic characteristics compared to hypoxic/ischemic cells of preparation #1. The remote effect of substance(s) X produced by hypoxic/ischemic cells was evident in preparation #2 by measuring spontaneous contractile and Ca²⁺ activity in cultured cardiomyocytes