9441 research outputs found
Sort by
Self-Exciting Point Processes in Real Estate
Get PDFThis thesis introduces a novel approach to analyzing residential property sales through the lens of stochastic processes by employing point processes. Herein, property sales are treated as point patterns, using self-exciting point process models and a variety of statistical tools to uncover underlying patterns in the data. Key findings include the identification and explanation of clustering in both space and time, and the efficacy of a temporal Hawkes process with a sinusoidal background in predicting home sale occurrences. The temporal analysis starts by employing the state of art techniques for time series data like regression, autoregressive, and autoregressive integrated moving average (ARIMA) models, extending into more sophisticated point process models with self-excitation features. Spatial analysis delves into clustering and dispersion patterns within specific geographic boundaries, utilizing homogeneous and inhomogeneous processes with covariate analysis to describe these patterns. Further, the spatiotemporal exploration sets a precedent for future comprehensive models in this domain. This exploratory research establishes a foundation for further investigation into the dynamic field of real estate analytics under the framework of point processes
The effects of warmer temperatures on the physiology of invasive sea lamprey and imperiled populations of lake sturgeon in the Laurentian Great Lakes
Get PDFInvasive sea lamprey (Petromyzon marinus) contributed to massive declines in fisheries in the Laurentian Great Lakes due to their parasitism of large-bodied salmonid fishes in the 20th century. Chemical control measures, which involve the application of 3-trifluoromethyl-4-nitrophenol (TFM) into rivers containing larval sea lamprey, were successfully implemented approximately 60 years ago to control populations. Recently, however, it was discovered that TFM tolerance increases in sea lamprey with a rise in temperature for reasons which are incompletely understood. Nor is it understood how sea lamprey will respond to warmer temperatures due to climate change, which could affect their distribution in the Great Lakes. Warming waters could also jeopardize lake sturgeon (Acipenser fulvescens) conservation efforts by compromising their physiological capacity to forage, reproduce and evade predators. The goal of this thesis was to:
(i) Determine how the physiological performance of larval and juvenile sea lamprey is affected by warmer temperatures, and how it could influence their distribution in the Great Lakes.
(ii) Ascertain how warmer temperatures affect the physiological performance capacity of juvenile (young of the year; YOY) lake sturgeon in comparison to larval sea lamprey, which occupy similar habitat in the sturgeon’s early life stages.
To determine how warmer waters affected physiological performance, intermittent closed system respirometry was used to construct thermal performance curves in which O2 consumption (ṀO2) measurements were used to calculate standard metabolic rate (SMR) and maximum metabolic rate (MMR) of larval and juvenile sea lamprey, and YOY lake sturgeon, over a range of water temperatures. Aerobic metabolic scope (AMS = MMR – SMR) was then calculated at each temperature tested and used to calculate the thermal optima (Topt) and thermal breadth (Tbr) of the animals. The Topt of larval sea lamprey were 24.6, 25.4 and 26.2°C at acclimation temperatures of 6, 13 and 21°C, with a wide Tbr of 11.9°C (16.9-28.8°C), 10.9°C (18.5-29.4°C) and 10.9°C (19.8-30.7°C). Maximal AMS was highest in larvae acclimated to 13ºC, averaging 11.2 umol O2 g-1 h-1, and lowest at 8.1 umol O2 g-1 h-1 at an acclimation temperature of 21ºC. The Topt could not be calculated for juvenile sea lamprey because their maximal AMS (14.3 umol O2 g-1 h-1) was observed at the highest temperature tested (25°C), suggesting a surprisingly high thermal tolerance. Lake sturgeon were slightly less thermally robust, with a Topt of 22.8°C, but a higher maximal AMS of 14.8 umol O2 g-1 h-1, and Tbr of 11.7°C (range = 15.8 - 27.5°C). In conclusion, the relatively high Topt and wide Tbr of sea lamprey could have been a key adaptation the enabled them to successfully invade and occupy the Great Lakes. However, projected warming of rivers and streams could now result in reduced larval sea lamprey populations in some regions of the Great Lakes where water temperatures are already near their Topt. Conversely, lake-dwelling juvenile sea lamprey populations may benefit from warmer lake temperatures, which could promote growth and increased time to feed. Lake sturgeon populations could also be threatened by warming rivers as water temperatures approach or exceed their Topt, consequentially forcing them to migrate to less optimal habitats where food resources and protection from predators could be limited. The potential need to use higher amounts of lampricide in warmer waters to control sea lamprey, and the possible effects on lake sturgeon requires further investigation
Erwinia amylovora Phage Therapy: Biocontrol Formulation, Receptor Identification, Resistance Mechanisms
Get PDFFire blight is known as a disease of Rosaceae and it displays infection symptoms in about 200 species in 40 rosaceous genera. The most economically important crops that are affected by fire blight are apples and pears. Fire blight can cause severe outbreaks and a single fire blight outbreak can disrupt orchard production for years. The bacterium that causes this disease is indigenous in North America, and according to Statistics Canada, economic losses in apples and pears were valued at an estimated $4 million in 2005, which is approximately 5% of the total production. In addition, production costs can increase substantially during a fire blight spread because labor costs for diligent and regular pruning trips through the orchard are required.
Erwinia amylovora is the causal agent of the contagious fire blight disease. This bacterium can infect different parts of the tree, such as blossoms, shoots, vascular tissues, rootstock crowns, and fruits. The bacterial ooze that occurs during infection consists of a high population of E. amylovora found within self-produced exopolysaccharides and the ooze is the main source for the spread of infection between plants. Once on a host, the pathogen spreads systemically after entering through natural openings (nectarthodes, stomata) or wounds. Depending on the plant part affected, disease symptoms develop as blossom blight, shoot blight or rootstock blight.
Streptomycin is considered the most effective bactericide against E. amylovora. However, the emerging resistance of E. amylovora to streptomycin raises the need for novel management measures. In addition, using antibiotics in agriculture is under critical analysis due to concerns that spray-drifted antibiotics greatly impact the environment and soil, including microorganisms that act as reservoirs of genes for antibiotic resistance that could ultimately have an impact on clinical medicine. Alternatively, the application of antagonistic bacteria as biocontrol agents can significantly reduce the epiphytic growth of E. amylovora. The effectiveness of these agents is based on combined modes of action, e.g. site exclusion, nutrient competition, and antibiotic production. Pantoea agglomerans represents one of these antagonistic biocontrol agents due to antibiosis and its superior growth rate on blossoms as an epiphytic bacterium. Bacteriophages have also been used as a biocontrol agent on other plants to control bacterial pathogens and the first bacteriophage product was registered with the U.S. Environmental Protection Agency in 2005 by OmniLytics Inc.. A few phage formulations are now commercially available in the United States for agricultural applications, such as AgriPhage-Fire Blight for apple and pear tree treatment, as well as AgriPhage-Citrus Canker for orange and grapefruit treatment.
While successes have been noted for the use of antagonistic bacteria and bacteriophage as biocontrol agents, E. amylovora remains an agricultural problem, so further development and combination of alternative techniques are needed to mitigate the spread and destruction caused by this pathogen. With this in mind, the ultimate goal of this thesis was to develop an efficient E. amylovora phage therapy method that relies on a phage-carrier system (i.e., P. agglomerans infected with E. amylovora phages). The initial part of this research was to develop an economical production protocol for the phage-carrier system. Using spray drying, an improved survival method for carrier (P. agglomerans) and phage-carrier (P. agglomerans infected with E. amylovora phages) production was developed. The results showed good efficacy of the spray-dried carrier and phage-carrier products to reduce E. amylovora growth with about 4.5 log reductions in bacterial count on treated pear discs and ≥90% of P. agglomerans cell viability after the spray drying procedure.
Given that improvements in biocontrol formulations and effectiveness are always being sought, a second aim of this thesis research was to understand better the dynamic interactions between E. amylovora, P. agglomerans, and E. amylovora phages. With the use of various bacterial surface receptor isolations and phage trial analyses, the receptors for two E. amylovora phages, phiEa21-4 and phiEa46-1-A1, were identified. These cumulative results showed that lipopolysaccharide (LPS) and OmpA are the receptors for these phages on E. amylovora, but that only OmpA serves as a receptor on P. agglomerans. Previous work demonstrated that the pathogenicity of E. amylovora to host plants is strictly dependent on a functional type III secretion system, amylovoran, and LPS. While LPS was further highlighted as a phage receptor in our work, the importance of OmpA has now also been established as important for phages across bacterial species.
While understanding phage receptors was necessary, we also explored the development of phage resistance mechanism(s) in E. amylovora to ultimately provide a foundation for how our phage therapy product may be adapted/enhanced in the future. Studying phage resistance in E. amylovora was achieved by generating a bacteriophage-insensitive mutant (B6-2) against phiEa46-1-A1. The B6-2 strain was compared with the parent E. amylovora D7 strain on phenotypic, genomic, and transcriptomic levels. Analysis of this combined data revealed that an insertion mutation in the rcsB gene (confirmed by genetic sequencing) is the main driving force for phage resistance development. In the transcriptomic data, there was downregulation of amylovoran, LPS, and OmpA genes, suggesting that receptor adaptions have occurred as a phage resistance mechanism in strain B6-2. These changes were paralleled by transcriptomic changes in the levels of the rcsA and rcsB genes, which further reflects their roles as a part of the Rcs two-component phosphorelay system that regulates genes in the EPS, LPS and OmpA pathways.
Additionally, there was upregulation of putative retron Ec48, which may act as a second-line abortive antiphage mechanism. On the phenotypic level, strain B6-2 had an altered metabolism of nitrogen sources and an increased sensitivity to streptomycin. This decrease in antibiotic resistance when phage resistance increases is considered as significant given that streptomycin is the primary antibiotic used to treat fire blight. In combination, this data provides a solid foundation to have a better understanding of the development of phage resistance in E. amylovora and how this may impact its pathogenicity and antibiotic resistance.
In conclusion, this research has provided a number of substantial advancements with phage therapy involving E. amylovora. Essential improvements in the formulation of a biocontrol agent that takes advantage of two alternate treatments (i.e., antagonistic bacteria and phage) have been developed and can now be tested in field trials. Recognizing that target phytopathogenic bacteria can develop resistance to the phage treatments, this study has proactively identified key phage receptors on E. amylovora and carrier cells and provided a sound basis for understanding the role of the Rcs system in receptor alterations that can lead to phage resistance. Ultimately, this work will lead to the continued improvement and applicability of phage therapy using a phage-carrier biopesticide system to mitigate the spread and damage caused by E. amylovora and fire blight
From Zombie to Martyr: The Short Military Service of Private Hector Sylvestre
Get PDFThis article outlines the brief military service of Private Hector Sylvestre, a young Franco-Ontarien paratrooper executed by the SS. His career began as a conscript in the Active Army, serving nine months prior to enlisting in the Canadian Active Service Force. From this point forward he made a series of fateful decisions, which ultimately led to his death as a member of the French Resistance. His path from Zombie to “martyr” is unique for a Canadian soldier during the Second World War
Review of “Bombs and Barbed Wire: Stories of Acadian Airmen and Prisoners of War, 1939-1945” by Ronald Cormier and “The Captain Was a Doctor: The Long War and Uneasy Peace of POW John Reid” by Jonathon Reid
Get PDFReview of Bombs and Barbed Wire: Stories of Acadian Airmen and Prisoners of War, 1939-1945 by Ronald Cormier and The Captain Was a Doctor: The Long War and Uneasy Peace of POW John Reid by Jonathon Reid
Review of “Varsity’s Soldiers: The University of Toronto Contingent of the Canadian Officers’ Training Corps, 1914-1968” by Eric McGeer
Get PDFReview of Varsity’s Soldiers: The University of Toronto Contingent of the Canadian Officers’ Training Corps, 1914-1968 by Eric McGee
Variation in mainland Northwest Territories late-winter muskox (Ovibos moschatus) density estimations and habitat associations above and below treeline.
Get PDFThe Arctic and Sub-Arctic ecosystems are seeing accelerated changes in temperature, landcover, and consequently species abundance and distributions. Reliable distributions, and associated population density estimates, are essential for effective conservation and management efforts. Growing concerns from northern communities regarding the relationship between muskox and declining caribou populations strengthens the need for updated information on muskox populations within mainland Northwest Territories (NWT). The first objective for my research was to quantify and map updated winter estimates of abundance, density, and distribution of muskoxen within three recent survey regions located in mainland NWT, using a multiple covariate distance sampling method (MCDS), paired with density surface modelling (DSM). My second objective was to explore spatial and social predictors of muskox habitat associations to help infer the extent and potential causes of their contemporary southward expansion across mainland NWT. I tested two competing hypotheses that drive ungulate distributions generally across large spatial and temporal scales of high habitat heterogeneity, as encompassed by the study regions investigated here; muskox density and distribution may be driven by the nutritional landscape where environmental covariates representing high forage quality best predict muskox occurrence. Alternatively, muskox density and distribution may be driven by a predatory landscape, where environmental covariates that support antipredator grouping behaviours best predict muskox occurrence. Through my analyses I infer muskox populations are stable in northern regions (the Sahtú and Beaufort Delta regions) and growing in southern regions (the East Arm region) of mainland NWT; range expansion of muskoxen appears to be continuing southward beyond their historical boundary. I showed varying support for both hypotheses. Muskox density was best predicted by nutritionally important environmental covariates but muskox distribution did not uphold my nutritional hypothesis, while group size was often correlated with land cover that supports antipredator grouping behaviours. However, weak, and inconsistent results across all regions suggest that unmeasured environmental conditions that occur similarly in all regions may also influence muskox occurrence and grouping behaviours. Snow depth and predator occurrence may be important considerations for future investigation. I suggest continued and expanded aerial survey efforts and additional environmental data collected at finer spatial grains may help to inform future muskox density and distribution analyses across mainland NWT
Review of Statesmen, Strategists & Diplomats: Canadian Prime Ministers and the Making of Foreign Policy edited by Patrice Dutil and Friends and Enemies: Essays in Canada’s Foreign Relations by J.L. Granatstein
Get PDFReview of Statesmen, Strategists & Diplomats: Canadian Prime Ministers and the Making of Foreign Policy edited by Patrice Dutil and Friends and Enemies: Essays in Canada’s Foreign Relations by J.L. Granatstei
Review of Warriors and Warships: Conflict on the Great Lakes and the Legacy of Point Frederick by Robert D. Banks
Get PDFReview of Warriors and Warships: Conflict on the Great Lakes and the Legacy of Point Frederick by Robert D. Bank