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Temporal analysis and gravity-informed marine traffic forecasting for non-indigenous species risk assessment through ballast water
No full textNon-indigenous species (NIS) spreading through ballast water and establishing themselves
in the new environment threaten biodiversity and marine ecosystems. Ballast
water risk assessment (BWRA) models estimate the risk for NIS introduction by ballast
water, and the environmental similarity between water source and destination
locations is important in these models. Previous BWRA models rely on annual-scale
environmental data and potentially neglect seasonal variability in the environmental
factors. This research investigates the impact of incorporating monthly-scale environmental
data on the evaluation of environmental similarity between source and
recipient locations. The statistical comparison reveals that using monthly-scale data
generally results in smaller environmental distances across all regions, indicating a
higher risk of NIS invasions into Canadian waters than previously estimated with annual
data. In addition, this work introduces a novel physics-inspired framework to
forecast maritime shipping traffic, enhancing the assessment of NIS spread through
global transportation networks. Integrating graph analysis, the gravity model, and the
self-attention mechanism from the Transformers, this framework outperforms existing
methods, achieving an 89% accuracy for discriminating existing and non-existing shipping
trajectories and an 84.8% accuracy in estimating the number of vessels
owing
between port areas. This represents more than 10% improvement over the traditional
deep-gravity model and nearly 50% improvement over the machine learning regressional
models, offering a more accurate tool to identify high-risk invasion pathways
and prioritize ballast water management in the future.Includes bibliographical references (pages 79-91
Determining the acceptability and preliminary impact of a digital resource hub among people living with chronic pain
No full textThe Power Over Pain Portal (POP) is a digital platform which provides people living with pain (PLWP) flexible access to chronic pain self-management resources. Using a mixed-methods design, the present study aimed to evaluate patient perceptions of acceptability and usability of POP, and patient outcomes among PLWP awaiting a first visit at a tertiary care pain clinic. Measures assessing acceptability, usability, and impact of POP included validated surveys completed at baseline and 3-months after using POP, and information gathered through interviews. Forty-one participants completed follow-up surveys. Nine participants completed interviews. There was a reduction in pain interference (Mdiff = -.66, SD = 1.78; p = .024) and belief in a medical cure (Mdiff = -.49, SD = 1.42, p = .033) after using POP for 3-months. POP was accepted among PLWP (M = 21.68, SD = 5.07; Ninterview = 5) and met expectations of usability (M = 70.56, SD = 20.95; Ninterview = 4). Participants also endorsed the use of POP among PLWP (Ninterview = 4). Some participants indicated POP was overwhelming (Ninterview = 4) and some resources were difficult to find (Ninterview = 3), indicating that changes could be made to improve ease of use. Finally, participants’ impression of change during the three month period was a slight deterioration in their condition (M = 3.53, SD = 1.36).Includes bibliographical references (pages 63-73
Clinical outcomes among patients with affective and non-affective psychosis and the role of substance use
No full textSubstance use is common among individuals experiencing psychosis and has important implications for clinical outcomes, symptomatic course, and treatment considerations. While research has largely focused efforts towards understanding the impact of cannabis in this population, insufficient attention has been paid towards alcohol in the existing literature. In addition, conclusions about the impact of substance use on patients with psychosis may be limited given that most research includes patients with affective and non-affective psychosis. There is some debate in the literature regarding the clinical utility of this dichotomy and further exploration is warranted. The aims of the current study were to: 1) examine the differences and similarities between patients with affective and non-affective psychosis; and 2) investigate whether substance use differentially impacts patients diagnosed with affective or non-affective psychosis. Patients were recruited from an early psychosis intervention program in St. John’s, NL and were diagnosed with either schizophrenia or bipolar disorder. Patients’ clinical characteristics (i.e., substance use, positive symptoms, overall functioning, illness severity, and overall improvement) were assessed at three time points: admission, 12 and 24 months. A significant interaction between diagnostic group and time was found and suggested that patients with schizophrenia tended to show greater levels of improvement over the course of 24 months compared to patients with bipolar disorder. Further, patients with schizophrenia who abused cannabis tended to improve over the same time while patients with bipolar disorder who abused cannabis tended to show a decline. The interaction between diagnostic group and time was not significant for positive symptoms, overall functioning, or illness severity. Patients with bipolar disorder were also rated as having higher overall levels of global functioning and lower levels of illness severity compared to patients with schizophrenia. Lastly, alcohol abuse was a significant
predictor of various clinical outcomes, including overall functioning and illness severity. The current study highlights the clinical utility of the dichotomy between affective and non-affective psychosis, and the need to further examine the impact of substance use, particularly alcohol, in this population.Includes bibliographical references (pages 69-92
Multiple imputation in censored quantile regression
No full textQuantile regression is a natural extension to the traditional linear regression. Instead
of modeling the conditional mean of the response variable, quantile regression models
the conditional quantiles of the response. With properly selected quantiles, the
quantile regression model provides a better understanding of the relationship between
the response and the covariates comparing with the traditional regression models Recently
this method is introduced to the area of survival analysis, where censoring is
a natural characteristic of the data. To address the challenges posed by censored
data, especially the specification issue at high quantiles, we propose a novel approach
that employs multiple imputations of censored observations using the Buckley-James
method, originally developed in the framework of classical quantile regression analysis.
Our method not only ensures consistent estimators of the model parameters, but also
achieves asymptotically normality when the sample size approaches infinity. Notably,
it overcomes the limitations of traditional censored quantile regression, particularly
in estimating extreme quantiles. Extensive simulation studies demonstrate the efficacy
of our approach. Additionally, we apply our method to a Health Maintenance
Organization (HMO) dataset as an illustration.Includes bibliographical references (pages 40-43
The effects of altered expression of clueless on ageing and neurodegeneration in Drosophila melanogaster
No full textMitochondrial dysfunction is linked to the pathology of age-related and neurodegenerative disease, including Parkinson disease and amyotrophic lateral sclerosis. Preservation of mitochondrial function is determined by the interconnected processes governing mitochondrial homeostasis: fission, fusion, trafficking, mitophagy, and biogenesis. The Drosophila melanogaster protein Clueless and its mammalian homologue CLUH are cytoplasmic RNA-binding proteins essential for mitochondrial function that may influence all of these processes. Clueless and its homologues may act as master regulators of mitochondrial homeostasis to control these processes in response to environmental cues including stress-response signalling. The effects of altered expression of clueless in Drosophila melanogaster dopaminergic and motor neurons on ageing and neurodegeneration were examined through lifespan and climbing assays. In humans, dopaminergic neuron degeneration causes Parkinson disease, and motor neurons degeneration causes amyotrophic lateral sclerosis. Inhibited clueless expression in Drosophila melanogaster dopaminergic and motor neurons reduced early-life climbing ability, and inhibited clueless expression in motor neurons caused impaired lifespan and a more rapidly progressive loss of climbing ability with age. Inhibited expression of clueless in motor neurons therefore causes age-related disease in this model organism. RNAi-mediated clueless suppression in motor neurons is a promising novel model for investigation of the role of mitochondrial dysfunction in the pathology of amyotrophic lateral sclerosis.Includes bibliographical references (pages 75-96
The deepwater volcaniclastic Mistaken Point Formation in the northeastern Avalon Peninsula: facies, architecture, and detrital (U-PB) zircon provenance
No full textThe Mistaken Point Formation (MPF) is a ~400 m-thick late Neoproterozoic siliciclastic-volcaniclastic unit that crops out in the Avalon Zone of Newfoundland Appalanchians and is recognized as one of the world's leading Ediacaran fossil-bearing deep-water successions. The MPF sits at the top of a thick sequence of volcaniclastic submarine fan strata within the Conception Group. These layers were deposited during the transition from a fore-arc or back-arc basin to a potentially foreland basin. Thus, MPF strata can provide insight into whether the basin transformation may have influenced important aspects of the sedimentary environment during the deposition of the MPF. Detailed stratigraphic, petrographic, and facies analysis were integrated, supporting a submarine fan depositional system with two lobe complexes: MPF1 and MPF2. Stratal stacking patterns indicate a “back stepping” lobe abandonment. Examination of facies reveals the presence of ponded turbidites and stratification resembling HCS, which document the gradual confinement of the basin over time. Paleocurrent measurements demonstrate a slight variation in sediment routing directions from S-SE to S-SW. MPF1 detrital zircon ages define a unimodal peak at ca. 650 Ma consisting mostly of Ediacaran to Cryogenian, subordinate peak of Mesoproterozoic and Paleoproterozoic ages, whereas the overlying MPF2 depicts a polymodal distribution with peaks at ca. 600 and 580 Ma comprising mostly Ediacaran ages, less Cryogenian than MPF1, and Mesoproterozoic ages. This research emphasizes the development of the MPF submarine fan system as it undergoes basin transformations. This transformation plays a crucial role in enhancing our understanding of paleogeographic reconstructions of submarine fans. It also provides valuable insights into the evolution of the basin and tectonic processes of Ediacaran strata in the northeastern Avalon Peninsula.Includes bibliographical references (pages 74-92
Microplastic and dispersed oil co-contaminants in the simulated marine environment: formation, transport, and fate
No full textMicroplastics (MPs) and oil spills are two major concerns in the marine
environment with negative effects on marine ecosystems. Each year, more than 700
million liters of oil enter oceans from thousands of oil spills during oil extraction,
transportation, and consumption. Chemical dispersants are widely adopted as oil spill
treating agents to break oil into tiny droplets and facilitate their biodegradation.
Dispersant efficiency could be affected by mixing energy, seawater salinity, dispersant-to-oil volumetric ratio (DOR), and suspended particles such as minerals. However, there is
extremely limited information on how MPs affect oil dispersion as well as dispersed oil
transport and transformation although MPs are frequently detected in oil-polluted oceans.
This thesis thus focuses on the interaction between MPs and crude oil in the
presence of chemical dispersants and the formation, transport, and fate of MP-oil-dispersant agglomerates (MODAs) in the marine environment. It includes the following
objectives: 1) to conduct a viewpoint to summarize the knowledge gaps regarding MP and
crude oil interactions; 2) to explore the interaction between MPs and crude oil in the
presence of dispersants under diverse conditions (MP concentration, aging degree, and
DOR); 3) to reveal MODA formation mechanism under various MP sizes using the
surface free energy minimization principle, and evaluate the impacts of MODAs on oil
dispersion under different ocean conditions (seawater salinity and mixing energy); 4) to
evaluate the transport of MODAs in seawater layers (surface and column) under various
conditions (MP size, crude oil type, seawater salinity, and mineral concentration), and
predict the sinking velocity of MODAs; and 5) to investigate the degradation efficiency of
ii
dispersed oil in the presence of biofilm-developed MPs (B-MPs) in seawater layers, and
uncover the degradation mechanism. This thesis reported the existence of MODAs in the
marine environment for the first time and revealed the formation of two types of MODAs.
It suggested a transport model (Rubey’s equation) for MODA sinking velocity prediction
and demonstrated that minerals could enhance the downward transport of MODAs. The
combined effects of oil evaporation, B-MODA formation, and biodegradation (EBB
effects) were proposed for the first time to explain the degradation mechanisms of
dispersed oil. This thesis established a comprehensive framework for exploring the MP
and oil co-contaminants in marine environments. Findings would guide decision-making
on oil spill response strategies and operations in the presence of MPs and contribute to
marine MP and oil pollution control.Includes bibliographical references (pages 208-232
Advanced highly reliable DC-DC power electronics converters for battery charging systems
No full textThe thesis focuses on the development and analysis of advanced DC-DC
converters, incorporating coupled inductors and interleaved PWM switching schemes
to enhance efficiency and compactness. The proposed converters address key
challenges in power conversion, including minimizing current ripples, reducing filter
inductor size, and improving overall reliability. By leveraging high-frequency
operation, these converters achieve smaller passive components and eliminate reverse
recovery issues associated with MOSFET body diodes, enabling high-efficiency
performance. A family of non-isolated converters was designed with features such as
the doubling of effective switching frequency, common ground between input and
output terminals, and the elimination of short-circuit risks. Furthermore, a novel
single-phase non-isolated buck converter prototype demonstrated low current ripples
and enhanced efficiency. Additionally, an isolated DC-DC buck converter was
developed for renewable energy applications, incorporating phase-shift interleaving
to reduce voltage stress and further optimize inductor size. The experimental results
validate the proposed converters, showcasing their potential to significantly improve
efficiency, reliability, and size for energy storage and electric vehicle battery charging
systems.Includes bibliographical reference
A Comparative Study of Preparation Methods, Weighting Agents, and Temperature on Quality of E-M Compatible Borehole Imaging Fluid
No full textImaging fluids plays a crucial role in mitigating the impact of borehole groundwater on borehole E-M imaging results. Such fluid must possess specific characteristics such as low conductivity to minimize electromagnetic wave attenuation, appropriate dielectric permittivity to prevent signal ringing at the fluid-wellbore boundary, higher density than water for settlement at the bottom hole, and long-term stability throughout the imaging process. This study meticulously examines the influence of agitation and temperature on the quality of oil-based imaging fluids, comparing two major preparation methods with distinct grain sizes of the weighting agent. One is the conventional method involving a critical heating step of the emulsifier in 20% of the imaging fluid liquid base, while the second involves dissolving the emulsifier in the liquid base by agitation. Evaluation of the produced fluids encompasses considerations of their stability over time, settlement in various water temperatures, and rheological properties. The results of these experiments reveal the pros and cons of the agitation process compared to the conventional method, weighting agent grain size, and temperature on the overall quality of the produced imaging fluid
Assessing the Technical and Economic Viability of Galvanizing Snow Crab (Chionoecetes opilio) Traps
No full textCommercial harvesting of snow crabs (Chionoecetes opilio) began in Newfoundland and Labrador, Canada, in 1967. Today, the fishery consists of 2188 active fishing licenses and has grown into the province’s most economically valuable fishery. Snow crabs are captured using conical traps consisting of a mild carbon steel frame, hard plastic entry funnel and a jacket of polyethylene netting. The frames of these traps corrode over time, which is expedited by being deployed in marine environments and stored on land near the ocean when not in use. As a result, there is interest within the community to increase the longevity of crab traps. One solution is to galvanize the steel frames prior to installing the funnel and netting. However, before harvesters transition to galvanized traps, two questions must be answered. Will the use of galvanized steel negatively impact catch rates? Will the life cycle of a crab trap be extended sufficiently to justify the additional cost of galvanizing? This study employed a generalized linear mixed model to evaluate the catch of legal-sized male crabs (CPUE) during the commercial fishery as a function of three trap frame treatments (old traditional, new traditional and new galvanized). We also assessed the economic viability of galvanizing trap frames by evaluating the life cycle cost (LCC) of traditional and galvanized traps to the harvester. The LCC was calculated over a range of inflation (0–6%) and discount (3–20%) rates. Our results found no significant difference in CPUE between new traps (traditional vs. galvanized) and concluded that except during instances of very high discount rates (12.9–19.9%), it is economically favourable to galvanize crab trap frames