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Regional depth-specific subchondral bone density measures in osteoarthritic and normal distal femora: in vivo precision and preliminary comparisons
Get PDFKnee osteoarthritis (OA) is a degenerative disease which affects the cartilage and underlying
bone of afflicted joints. OA can be diagnosed by clinical symptoms such as joint pain, stiffness
and swelling or radiographically according to the presence of key structural changes associated
with the disease. The investigation of subchondral bone is a growing topic of interest in the study
of OA, though its exact relationship with disease initiation and progression is currently not well
understood. Previous studies have investigated subchondral bone’s role in OA at the proximal
tibia and patella; however there is a paucity of research at the distal femur. Additionally, many of
the existing strategies to study subchondral bone in OA have relied on time-consuming manual
techniques, limiting their applicability in studies with large sample sizes. This highlights a need
for the development of automated techniques which assess subchondral bone at the distal femur.
The primary goal of this research was to develop an automated workflow capable of
precisely assessing regional density measures at the distal femur to differentiate between OA and
normal subjects. This resulted in the following objectives: 1) Develop an automated workflow
for assessing regional density measures at the distal femur; 2) determine precision errors of the
acquired density measures; and 3) compare distal femoral density measures between individuals
with and without knee OA.
Following the development of an automated workflow, in vivo precision (assessed via
root mean square coefficients of variation, CV%RMS) at the distal femur was assessed and ranged
from 1.6% to 3.6%. These results are consistent with the in vivo precision errors found at the
proximal tibia and patella, indicating they are suitable for investigating differences between OA
and normal distal femora.
For the comparison analysis, mean regional density measures were not found to differ
significantly between normal and OA distal femora; however, peak density clusters at depths of
2.5-5mm were found to be ~16% lower in OA distal femora.
Thesis results indicate that suitable precision can be obtained at the distal femur with
automated methods. Results also suggest that subchondral density patterns may differ in OA and
normal distal femora in complex ways, not necessarily detectable via regional analyses alone
EXPERIMENTAL AND THEORETICAL ANALYSIS OF THE ADVECTION OF HEAT AND SOLUTE IN NON-REACTIVE POROUS MEDIA
Get PDFOne of the first objectives of this project was to design and build an experiment that could measure the advection rates of heat and solute in a non-reactive porous medium. The second objective was to examine the continuum theories that relate to the transport of heat and solute in a non-reactive porous medium. Specifically, to verify that the velocity of solute is faster than the thermal velocity when the Peclet number is below 1 at the pore scale and that their advection rates are similar when the Peclet number is above 1 at the pore scale.
To simulate a non-reactive porous medium, sand, glass microspheres and expanded polystyrene were used. A liquid that contrasted the temperature and solute levels present in the cell, was supplied via a supply tank whose height was varied to create variable flow rates in a pressure-driven system. Changes in voltage, caused by changes in temperature and conductivity inside the porous medium, were recorded by a personal computer (PC) oscilloscope (a PicoScope); the sensors were electrodes and thermistors installed near the inlet and outlet of the cell containing the porous medium. The time between the inlet and outlet signals was used to determine the experimental velocity which was then compared to theoretical values. Experiments where the system was transitioned from a state of low to high resistivity were the most challenging in terms of obtaining good signal quality. A numerical model was introduced to assist in the analysis of the signal shape for these experiments.
Results are given for pore-scale Peclet numbers (Pe_pore) of less than and greater than 1. In experiments for Pe_pore < 1, the advection rates of solute were observed to be greater than heat which agrees with the theory that assumes heat equilibrates with its surroundings as it is advected with the fluid causing it to lag the solute. When the pore-scale Peclet number is greater than 1, the expectation was that the advection rates of heat and solute would be similar. In some cases, their velocities were similar while in others, the solutal velocity was faster than the thermal velocity. The difference was due to significant roles that thermal conductivity and volumetric heat capacity play in the transport of heat
CROP SEQUENCE AND NITROGEN APPLICATION RATE EFFECT PRODUCTIVITY, NITROGEN USE EFFICIENCY, AND SOIL CARBON A SEMI-ARID POTATO PRODUCTION SYSTEM
Get PDFPotato is the most valuable vegetable crop grown in Canada, with production reaching 4.78 Mt—accounting for 29% of all vegetable crop receipts—in 2015. However, potato is a demanding crop that requires large rates of fertilizer, intensive use of tillage and is susceptible to water stress. An important consideration, therefore, is whether crops grown in rotation with potatoes can improve the overall nitrogen use efficiency of the cropping sequence and help counterbalance the small organic matter inputs provided by the potatoes. Through the quantification and comparison of multiple soil parameters, yield and N2O emissions from three different potato cropping sequences with different rates of N, this research aimed to find a combination of crops and nitrogen rates to improve the environmental sustainability of the potato production. The analysis of active carbon and soil microbial communities confirmed the negative impact of tillage on soil organic matter. Furthermore, the increase in N rates increased potato crop biomass but did not increase yield, indicating that N was not the limiting factor for yield. The use of faba beans as preceding crops is an interesting option to improve soil residual N (SRN) and reduce the need for N application, however the rate of mineralization is unpredictable. The results indicated the importance of soil sampling to evaluate the SRN and manage N rates accordingly, for all the crops that require N application. This would not only improve the cost of potato production but also reduce N2O emissions due to overapplication of N, as was observed in this study where N2O emissions increased with the increase of N rates. This research provides a look into the effect of three different cropping sequences on SOM, yield and N2O emissions and potential areas for mitigation
What is the Optimal Rate and N2O Mitigation Policy for Nitrogen Application in Saskatchewan Canola?
Get PDFThis thesis examines privately and socially optimal nitrogen (N) fertilizer rates for Canola production in Saskatchewan. In 2018 nitrous oxide (N2O) emissions from agricultural soils accounted for approximately 42% (in CO2eq) of all Canadian agricultural greenhouse gas emissions. In 2020 the Government of Canada set a national target of reducing absolute levels of GHG emissions from fertilizer application by 30% from 2020 levels by the year 2030. Canola is the largest N using crop in Canada and therefore optimizing N fertilizer use in this crop is of great importance. A canola production function is estimated using a large (n = 47,059) producer-reported data set from Saskatchewan Crop Insurance Corporation on field-level canola management over the years 2011-2019 and a wide variety of spatial and climatic conditions. The estimated implied canola N response curve was combined with price information and previous estimates for direct N2O emissions to estimate the marginal abatement cost curves and compare the observed applied N fertilizer rates to the estimated privately optimal rates and socially optimal rates. The results of this study support the previous findings of a nearly flat pay-off function for N fertilizer in crop production. On average, Saskatchewan canola producers do not appear to be overapplying nitrogen relative to the estimated privately optimal N rate. Regulation to reduce nitrogen fertilizer application rates by 30% from the privately optimal rate were found to result in net social welfare losses for canola cropping systems in Saskatchewan. When applying a N2O tax using the highest carbon price in the Canadian governments’ schedule of $170/t CO2eq for 2030, N rates are estimated to be reduced from the privately optimal rate by only 12.3% – 14.6% in the black soil zone and 6.12% – 6.92% in the brown soil zone. Given the heterogeneity in emissions factors across ecoregions and nitrogen management practices, focusing on the 4R’s of Nutrient Stewardship, agronomic research, and extension to improve N management and optimize fertilizer use are better opportunities to reduce emissions as opposed to a uniform mandatory reduction in N rates
Creating a New Standard for Human Body Sizing
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Evaluation of Yield and Agronomic Performance of Leafed and Semi-leafless Pea Blends
No full textThe abstract of this item is unavailable due to an embargo
EXAMINATION OF THE EFFECTIVENESS OF PROVISION OF FUNCTIONAL AMINO ACIDS TO ENHANCE ROBUSTNESS IN ENTERIC CHALLENGED PIGS
Get PDFThe predisposition of weaned pigs to enteric pathogens may increase if high protein (HP) diets, particularly from plant based (PB) sources, are fed. Growth performance and immune status of diseased pigs may be improved by supplementation with functional amino acids (FAA), including Threonine (Thr), Methionine (Met) and Tryptophan (Trp). The beneficial effects of FAA supplementation may be more advantageous in susceptible categories such as low birth weight (LBW) pigs. Therefore, this thesis evaluated the independent effect of FAA supplementation in Salmonella Typhimurium (ST)-challenged pigs and its interaction with dietary protein content and source, and with pig birth weight. The impact of adaptation period to FAA before a ST challenge was also evaluated. A disease challenge study revealed improved growth performance and immune status of ST-challenged pigs fed diets with supplemented with FAA, specifically Thr, Met, and Trp at 120% of requirements for growth, regardless of dietary protein content (low protein; LP [16%] vs. HP [20%]). The beneficial effects of FAA were associated with improved intestinal health and antioxidant defense, despite a lack of effect on ST presence in lymphoid tissues. In a subsequent ST-challenge study, a longer adaptation period (i.e., 2 weeks) to the same FAA-supplemented diets further enhanced gut health and suppressed ST intestinal colonization, despite no effect on ST presence in lymphoid tissues. Furthermore, antioxidant defense measurements were improved by FAA intake, but not adaptation period, which may be attributed to the dynamic sulfur amino acid (SAA) metabolism. Using intestinal samples from the first two studies, a third study provided evidence that the effects of FAA supplementation in ST-challenged pigs previously reported may be associated with or mediated by intestinal alkaline phosphatase (IAP) activity. Interestingly, there was a lack of effect of FAA adaptation period on IAP activity, which may suggest that amino acid (AA) intake, rather than length of feeding, is more important to the regulation of antioxidant balance. To investigate possible carryover effects of FAA supplementation, two follow-up disease challenge studies were conducted. The first one showed that FAA supplementation during nursery (e.g., 31 d post-weaning) improved growth performance, suppressed ST shedding, and reduced bacterial translocation to spleen in pigs placed onto a common grower diet and subsequently challenged with ST. However, the positive effects were observed particularly in normal birth weight (NBW), but not LBW pigs, which had aggravated gastrointestinal dysfunction, oxidative stress, and systemic commitment of the immune system. In the second study, pigs previously fed a PB feeding program in the nursery period (e.g., 31 days) had increased susceptibility to a subsequent ST challenge, particularly with increased bacterial colonization in the intestine, shedding, and diarrhea, compared to pigs fed animal-based (AB) protein sources. Conversely, supplementing PB, but not AB, nursery diets with FAA attenuated the negative effects of the subsequent ST challenge, despite a lack of effect of FAA supplementation on systemic markers of acute-phase responses and antioxidant balance. In summary, FAA supplementation and adaptation period is a valuable strategy to improve growth performance and immune status of ST-challenged pigs. The positive effects are more pronounced in NBW pigs and PB diets, regardless of dietary protein content
Foraging Ecology of the Feral Horses of Sable Island
Get PDFA foundational theory in the field of density-dependent foraging ecology is that of the Ideal Free Distribution, or IFD. The problem of pattern and scale in ecology has also received much attention. However, less is known of how IFD might scale in space and time. My thesis primarily focuses on expanding on previous research using IFD as a null model of intraspecific competition to describe the distribution and abundance of individuals within a landscape by testing for potential drivers of IFD-departure at the small scale. As the only terrestrial mammal of Sable Island, Nova Scotia, the island’s feral horses be studied without confounding effects of predation risk or inter-specific competition. I used the fitness proxy of hourly net energetic gain to build on previous research at the sub-population level and coarse-scaled habitat occupancy (Objective 1). Additionally, I explored how gastro-intestinal parasites might influence outward energetics of horses (Objective 2) and examined short-term (summer) patterns of resource selection in relation to energy content specific to vegetation communities (Objective 3). In 2018, I carried out a study on a focal group of 67 females, quantifying their instantaneous and daily energy intake rates, energy expenditures, parasite loads from strongyle fecal egg counts (FECs), and observed use of vegetation communities. When considering the extent of the whole island, horses did not select for communities based on energetic value but those potentially linked to water availability. However, western horses (high water availability, conspecific density, and FEC) had a higher rate of net energy intake (kJ/hr) than did those in the east there being a negative relationship in energy intake and FEC. The gradient I observed in net energy intake therefore indicates departure from IFD for short-term foraging behaviour using this currency. While IFD-departure at the large scale is known from heterogeneity in annual population growth rates, my research sheds light on fine-scale decisions and their constraints. I conclude that such constraints on behaviour and fitness at the level of the individual resulting in heterogeneity of net energetic gain across the population are likely foundational to the processes from which patterns at larger ecological scales emerge
Confronting the Ugly Truth: The (Un)Making of a 'Good' White Teacher on the Canadian Prairies
Get PDFThrough this autoethnographic inquiry into the writing of poststructural, critical race, and critical whiteness scholars, I sought understanding of the social and political forces that made me as a ‘good’ white female teacher on the Canadian prairies and the consequences of performing this subject role over four decades of teaching within the public education system. I visualized this inquiry as a puzzle whose interconnected pieces I was compelled to identify and understand as part of my exploration as to whether I could (un)make my constructed subject identity and performance as a ‘good’ white female teacher. I needed to understand both the role I filled so well, according to the expectations of the system I served, and the harmful consequences of that invested performativity so that I could explore possibilities for conscious identity (re)construction and performativity. My research findings point to significant and grave consequences for everyone involved, including Indigenous students, students of colour, white students, and me. My research also points the way to hope and agency on this personal and critically introspective journey of truth and reconciliation
Predicting biomolecule-disease associations based on machine learning approaches
No full textThe abstract of this item is unavailable due to an embargo