University of Saskatchewan Research Archive
Not a member yet
14369 research outputs found
Sort by
Gaseous Contaminant Transfer in Membrane Energy Exchangers
Get PDFMembrane-based air-to-air energy exchangers (M-AAEEs) reduce the energy required for conditioning building ventilation air by transferring heat and moisture between the building exhaust and ventilation air. However, M-AAEEs may also contaminate the ventilation air due to the transfer of contaminants from the stale exhaust air leaving the building to the fresh ventilation air being supplied to the building. It is important to quantify this transfer to assess its impact on indoor air quality. Hence, the main objective of this thesis is to quantify contaminant transfer in M-AAEEs using test methods available in the literature.
A test facility was developed, and experiments were performed to quantify the contaminant transfer for different air flow rates, pressure conditions, contaminants and membrane types. Contaminant transfer was quantified using a parameter called the exhaust contaminant transfer ratio (ECTR), which gives the fraction of the contaminants that transferred from the exhaust air to the ventilation air. Furthermore, a theoretical model was developed to predict contaminant transfer through the membranes. The results from the experiments and the theory were in good agreement within uncertainty limits. The experimental uncertainty in ECTR was between ± 0.5% and ± 2.7%.
Contaminants with lower molecular weight and smaller size (i.e., higher diffusivity) tend to have higher transfer through the membranes considered in this study. As a result, the inert tracer gas test, which is recommended in current energy exchanger standards to determine leakage in M-AEEs, may not represent the transfer of many common indoor contaminants. Moreover, the theoretical model presented in this study can be used to estimate contaminant transfer if the moisture transfer rate through the membrane is known
Effect of acute isometric handgrip exercise on vascular function in children and emerging adults with congenital heart disease
No full textThe abstract of this item is unavailable due to an embargo
Drowning Commuter Trains : The journey from budding hydrologist to flood forecaster
Get PDFCanada First Research Excellence FundNon-Peer ReviewedA young scientist's career choices are influenced by interactions with mentors, fellow students, and by exposure to societal impacts related to flooding
Investigating the role of host genetics and genomics in beef cow efficiency
Get PDFThe ability to utilize forage to produce vigorous offspring annually contributes to a beef cow’s lifetime efficiency. This study aimed to identify genetic and genomic variation associated with beef cow efficiency using a novel weighted percentile scoring system. Ninety-eight Black Angus cows were raised under extensive feeding management over two years and cow efficiency was determined using a scoring system based on back fat at calving, day within the calving season, and calf weaning weight represented as a function of cow body weight (adjusted for sex and age). Eighty-three of these cows were retained for genetic analysis. Five genes (LEP, NPY, CCKBR, GHRL, and GHR) were selected for a candidate gene study to identify variants associated with the efficiency phenotype. Three genome-wide association studies (GWAS) were conducted using differing subpopulations and phenotypic classifications, including the efficiency ranking phenotype and a qualitative efficiency phenotype (HD-Quantitative, HD-Qualitative, and FULL). Based on the GWAS, a positional candidate study was conducted for two genes: SNX29 and RITA1. Results of the GWAS identified regions on BTA 10, 17, 25, and 27 as loci suggestively associated with efficiency in the GWAS, despite associations not reaching significance (Bonferroni threshold). Sequencing of the candidate genes identified two SNP in GHR and 11 SNP in RITA1 significantly associated with cow efficiency. Further study of associated RITA1 SNP identified five associated SNP are non-synonymous, causing four amino acid substitutions. This study has identified genetic variation with potential functional consequences associated with efficiency. Further validation is needed to confirm these preliminary findings if these markers are to be used for selection of efficient beef cows
Investigating Salmonella CsgD - Mediated Bet-Hedging Using a Dual Reporter Strain
Get PDFNon-typhoidal Salmonella are a leading cause of foodborne illness. These bacteria cycle
between infecting hosts and persisting in nature as biofilms. The host to environment transition
of Salmonella is a critical stage in the transmission cycle that is not fully understood.
In non-typhoidal Salmonella bistable synthesis of the master biofilm regulator CsgD
results in a population of CsgD⁺ biofilm aggregates CsgD⁻ single cells. The single cells
synthesize the Salmonella pathogenicity island 1 type III secretion system (SPI-1 T3SS) which
is a major virulence factor for host cell invasion. We believe this population splitting is a bet hedging strategy to improve transmission, providing a way to cause disease immediately (single
cells) or after long time periods (aggregates). We hypothesize that Salmonella enterica serovar
Typhimurium (S. Typhimurium) differentiates into biofilm⁺ cells and SPI-1 T3SS⁺ cells in vivo.
To study bet-hedging, I built a fluorescent reporter strain of S. Typhimurium that tracks
biofilm⁺ cells (green fluorescent protein) and SPI-1 T3SS⁺ cells (mCherry) simultaneously. I
quantified the number of cells that form in a biofilm flask model using confocal microscopy. S.
Typhimurium formed four cell populations: biofilm⁺ cells (49%), SPI-1 T3SS⁺ cells (26%),
biofilm and SPI-1 T3SS⁺ cells (2%), and non-fluorescent cells (23%). As SPI-1 is bistably
regulated, we think non-fluorescent cells are a SPI-1 T3SS⁻ population.
To determine if population splitting happens in vivo, I developed a model using
Caenorhabditis elegans. I evaluated survival of worms exposed to S. Typhimurium and
quantified Salmonella inside worms. Exposure to Salmonella shortened worm lifespan, and the
intestinal load of Salmonella increased over time. Worms infected with S. Typhimurium were
imaged by confocal microscopy. Both SPI-1 T3SS⁺ cells and biofilm⁺ cells were observed in the
intestine.
My MSc research has laid the groundwork for future studies on Salmonella bet-hedging
and host-pathogen interactions. The S. Typhimurium dual reporter strain provides a unique way
to study different Salmonella cell types in real-time and in more detail than before. Studying how
biofilm and virulent cells interact with the host immune system will aid in development of
Salmonella vaccines and will help us better understand the importance of bet-hedging for
Salmonella transmission
Developing spring wheat in the Noah-MP land surface model (v4.4) for growing season dynamics and responses to temperature stress
No full text© Author(s) 2023.
This work is distributed under the Creative Commons Attribution 4.0 License.
Published by Copernicus Publications on behalf of the European Geosciences Union.Global Institute for Water Security, University of Saskatchewan (Agricultural Water Futures grant); the Global Water Futures (Agricultural Water Futures grant); the National Institute of Food and Agriculture (grant no. 2015-67003-23460); the National Science Foundation (grant no. 1739705); and the National Oceanic and Atmospheric Administration (grant no. NA18OAR4590381).Peer ReviewedThe US Northern Great Plains and the Canadian Prairies are known as the world’s breadbaskets for their large spring wheat production and exports to the world. It is essential to accurately represent spring wheat growing dynamics and final yield and improve our ability to predict food production under climate change. This study attempts to incorporate spring wheat growth dynamics into the Noah-MP crop model for a long time period (13 years) and fine spatial scale (4 km). The study focuses on three aspects: (1) developing and calibrating the spring wheat model at a point scale, (2) applying a dynamic planting and harvest date to facilitate large-scale simulations, and (3) applying a temperature stress function to assess crop responses to heat stress amid extreme heat. Model results are evaluated using field observations, satellite leaf area index (LAI), and census data from Statistics Canada and the United States Department of Agriculture (USDA). Results suggest that incorporating a dynamic planting and harvest threshold can better constrain the growing season, especially the peak timing and magnitude of wheat LAI, as well as obtain realistic yield compared to prescribing a static province/state-level map. Results also demonstrate an evident control of heat stress upon wheat yield in three Canadian Prairies Provinces, which are reasonably captured in the new temperature stress function. This study has important implications in terms of estimating crop yields, modeling the land–atmosphere interactions in agricultural areas, and predicting crop growth responses to increasing temperatures amidst climate change
Digital Twins and Blockchain for IoT Management
Get PDFWe live in a data-driven world powered by sensors getting data from anywhere at any time. This advancement is possible thanks to the Internet of Things (IoT). IoT embeds common physical objects with heterogeneous sensing, actuating, and communication capabilities to collect data from the environment and people. These objects are generally known as things and exchange data with other things, entities, computational processes, and systems over the internet. Consequently, a web of devices and computational processes emerges involving billions of entities collecting, processing, and sharing data. As a result, we now have an internet of entities/things that process and produce data, an ever-growing volume that can easily exceed petabytes. Therefore, there is a need for novel management approaches to handle the previously unheard number of IoT devices, processes, and data streams.
This dissertation focuses on solutions for IoT management using decentralized technologies. A massive number of IoT devices interact with software and hardware components and are owned by different people. Therefore, there is a need for decentralized management. Blockchain is a capable and promising distributed ledger technology with features to support decentralized systems with large numbers of devices. People should not have to interact with these devices or data streams directly. Therefore, there is a need to abstract access to these components. Digital twins are software artifacts that can abstract an object, a process, or a system to enable communication between the physical and digital worlds. Fog/edge computing is the alternative to the cloud to provide services with less latency. This research uses blockchain technology, digital twins, and fog/edge computing for IoT management. The systems developed in this dissertation enable configuration, self-management, zero-trust management, and data streaming view provisioning from a fog/edge layer. In this way, this massive number of things and the data they produce are managed through services distributed across nodes close to them, providing access and configuration security and privacy protection
The effect of selected rest break activities on reaction time, balance, and perceived discomfort after one hour of simulated occupational whole-body vibration exposure in healthy adults
Get PDFCopyright statement: This is an Open Access article distributed under the terms of the creative commons Attribution license (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The terms on which this article has been published allow the posting of the Accepted Manuscript in a repository by the author(s) or with their consent.This work was supported by Agrivita Canada, Mitacs Accelerate, University of Saskatchewan College of Medicine Research Award, University of Saskatchewan College of Medicine MPT Research Project Funding, and WorkSafeBC Ralph McGinn Postdoctoral Fellowship. The funding sources had no involvement in study design, data collection, analysis and interpretation of data, writing the manuscript, and decision to submit the article for publication.Peer ReviewedBackground & Objective
Negative health effects from occupational whole-body vibration (WBV) exposure during machinery operation include alterations in proprioception, vestibular function, reaction time, stress, motor response, and decrements in musculoskeletal health. To reduce WBV exposure during machinery operation, it may be possible to incorporate short rest break activities throughout the day. This study aims to determine if there are intervention activities that can minimize decrements in cognitive, proprioceptive, and musculoskeletal effects related to WBV exposure during machine operation.
Materials & Methods
Eleven healthy adults participated in four 1-hour sessions of ecologically valid WBV exposure followed by one of four 5-minute activities: sitting, walking, 2 minutes of gaze stabilization exercise (GSE) coupled with 3 minutes of trunk mobility exercise (GSE+MOBIL), or 2 minutes of GSE coupled with a 3-minute walk (GSE+WALK). Baseline and post-activity measurements (rating of perceived discomfort, balance and postural sway measurements, 5-minute psychomotor vigilance task test) were submitted to a paired t-test to determine the effect of WBV exposure and activities on physical, cognitive, and sensorimotor systems and to a repeated measures ANOVA to determine any differences across activities.
Results
We observed degradation of the slowest 10% reaction speed outcomes between baseline and post-activity after walking (7.3%, p<0.05) and sitting (8.6%, p<0.05) but not after GSE+MOBIL or GSE+WALK activities. Slowest 10% reaction speeds after GSE+MOBIL activity was faster than all other activities. Rating of perceived discomfort was higher after SIT and WALK activities. There were no notable differences in balance outcomes.
Conclusion
When compared to sitting for 5 minutes, an activity including GSE and an active component, such as walking or trunk mobility exercises, resulted in maintenance of reaction time after WBV exposure. If confirmed in occupational environments, GSE may provide a simple, rapid, effective, and inexpensive means to protect against decrements in reaction time after WBV exposure
Characterization of an Inductively-Coupled Plasma Immersion Ion Implantation System
No full textThe field of materials processing has been one of the most important driving forces behind technological advancements in the last several decades. Surface modification by ion implantation, deposition or etching has benefited products ranging from integrated circuit chips, solar panels, diodes, biomaterials, television screens, and heavy-duty industrial tools. The initial approach, termed conventional beamline ion implantation (CBII), involved generating ions in a separate chamber and extracting, directing and accelerating them toward the object targeted for treatment. This line-of-sight process required a complex system of object manipulation, making uniform surface treatment a lengthy process for any object that is not small and simple in shape.
Plasma immersion ion implantation, or PIII, was developed in the 1980's as an alternative to CBII. PIII operates by immersing the target directly in the source of ions, i.e. the plasma. Then, negative-polarity high voltage (HV) pulses are applied to the target, creating a strong electric field between the bulk plasma and the target surface, or a sheath. This sheath develops perpendicularly to the surface, extracting ions from the source and directing them into the surface. This approach allows independent control of ion fluence, which depends on the density of the plasma generated, and incident ion energy, which is determined by the magnitude of the applied HV pulse. The dosage tends to be highly uniform for any object shape and can be completed much more quickly than with CBII. Furthermore, this process avoids the more complex elements of ion translation and object manipulation of CBII. PIII, therefore, has gained popularity in materials science, particularly for large or irregularly shaped objects.
It should be clear, based on the description of this process, that HV sheaths are a fundamental aspect of PIII. Most industrial applications of PIII, though, rely on a simplified model of HV sheath dynamics and empirical recipes of operational parameters (e.g. power and pressure). This can lead to material waste and an unpredictable and inconsistent ion implantation depth and dose. In order to improve process control and efficiency, developing a comprehensive HV sheath model based on experimental data is critical. However, the relationship between the sheath and the bulk reservoir of ions is highly non-linear, making the derivation of a self-consistent solution to the governing equations complex. Direct measurements of plasma parameters during processing are also difficult to obtain. This is due to the high time-resolution required to measure evolving plasma dynamics during the HV pulses, as well as the high spatial-resolution necessary to investigate the often sub-centimetre sheath lengths. As a result, many consequential characteristics of ion implantation are neglected and second-order physical phenomena that may have a large impact on the overall process efficiency go undetected.
Many conventional plasma diagnostics and their data acquisition methods common in industrial PIII chambers cannot provide this resolution, and cannot measure ion properties with great detail, if at all. Furthermore, alternatives are often costly and have not been thoroughly researched. The goal of the experimental work performed and presented in this thesis, therefore, is to characterize plasma dynamics during HV ion implantation with greater temporal and spatial detail. The former is achieved by applying a time-resolved data acquisition technique to Langmuir probe measurements. This revealed a perturbation in plasma properties, i.e. density, temperature and potential, that occurs in the bulk plasma far beyond the length of the HV sheath. This phenomena was unexpected because standard models assume that the sheath and the bulk plasma are de-coupled. However, the most extensive experimental work was constructing a laser-induced fluorescence (LIF) apparatus and collecting spectroscopic measurements of ion properties. Due to a number of factors such as complexity and cost, this is one of very few LIF diagnostics implemented for PIII characterization. In addition to the millimetre-length spatial resolution it provides, LIF measures ion temperature and directed velocity with unparalleled precision. Direct measurements of these ion characteristics are critical to developing a more complete and accurate predictive model of PIII processing. For example, by including direct measurements of ion impact energy gained across the sheath in the model, more precise deposition profiles may be reached more efficiently. As this is a newly built apparatus, the data acquisition, processing and error analysis routine is thoroughly documented to ensure these initial results are accurate. These results are then found to be overall consistent with theory and previously published research
THORIUM SPECIATION IN SYNTHETIC ANHYDRITE, PLACER ILMENITE CONCENTRATE, AND TITANIA SLAG: IMPLICATIONS FOR THORIUM GEOCHEMICAL BEHAVIOR, SEQUESTRATION, AND BENEFICIATION
No full textUnderstanding thorium speciation and distribution in ore minerals and related materials is of critical importance so that the thorium fuel cycle can be sourced as byproducts from metallurgical processes. The objective of this dissertation is to study thorium-bearing species in selected ore minerals and their metallurgical products, and the uptake mechanisms of thorium into these materials. Gaining an understanding of thorium in these materials will improve both thorium extraction and sequestration methods.
Conditions present in the Sulfuric Acid Roasting Method for rare-earth element (REE) mineral processing were simulated to synthesize thorium-bearing anhydrite. Synchrotron ThLIII-edge X-ray absorption spectroscopy (XAS) reveals that lattice-bound Th in anhydrite, via the substitution Th4++1O2–iCa2+-1 with an interstitial O2– ion, can account for at least 1780 ppm Th in anhydrite produced in relevant experimental conditions. Ilmenite concentrate from the Mandena deposit, Madagascar, used to produce titania slag, contains 133 ppm Th and 12.8 ppm U. Our data show that monazite-(Ce), mainly as discrete grains, accounts for ~55% of thorium in the Mandena ilmenite concentrates. Thorianite hosting the remaining thorium at ~45% is revealed by synchrotron ThLIII edge XAS and is correlated with the degree of ilmenite alteration. Titania slag produced from the Mandena ilmenite concentrate contains an average of 170 ppm Th and 16 ppm U. Our data collectively demonstrate that 95.37% of Th in the Rio Tinto Chloride Slag (RTCS) is hosted by a Th-REE-Ti-silicate phase, containing up to 9.24 wt% ThO2 with an empirical formula of (Ti1.37Ca0.79Ce0.72Th0.36La0.31Nd0.30Pr0.08Ba0.03K0.02Y0.01U0.01)□(Ti1.41Al0.27
Fe2+0.11 Mn0.08 Mg0.07Nb0.03Zr0.03)(Ti1.91□0.09)(Si3.05Ti0.95)O22. This Th-REE-Ti-silicate occurs as acicular (<0.3 μm ⨯ 12 μm) or tabular (<5 μm ⨯ 15 μm) crystals in association with an aluminosilicate glass as infillings either in interstitial to or along fractures of the main Ti-Fe-oxides of the sassite-ferropseudobrookite solid solution series, formed most likely during the quenching stage of the titania slag.
The viability of using primary ores and metallurgy products is evaluated based on their production tonnage, thorium concentration, and speciation. Hypothetically, if the global energy demand was met using only liquid fluoride thorium reactors, the cumulative thorium produced by the three mineral processing facilities studied would be sufficient to meet that global energy demand