University of Idaho Library Digital Initiatives
Not a member yet
54971 research outputs found
Sort by
Experimental characterization of HTGR reactor cavity gas dynamics following a primary system rupture
No full textFor a High-Temperature Gas-cooled Reactor (HTGR), there is a probability that the helium pressure boundary (HPB) suffers a breach that could lead to the depressurization of the system. The helium is discharged into the cavity section of the vented low-pressure containment building, and the cavity is eventually vented under specific conditions. Under the postulated accident event, the nuclear reactor can undergo significant damage if air makes its way from the breach towards the reactor core. Even though the probability of such an event is very low, this scenario has gained the attention of regulators, plant designers, and operators because of the possible catastrophic consequences. The University of Idaho - Idaho Falls Campus designed and built a 1/20th scaled-down HTGR based on the preliminary design of the Gas Turbine Modular Helium Reactor to analyze the gas dynamics of helium-air interaction and venting of the air located within the reactor cavity following a break on the HPB. In this study, a sensitivity study is executed to analyze the air and helium concentration within the containment building as a result of a break in the HPB. This effort aims to shed light on the gas dynamics within the vented low-pressure containment of an HTGR during the accident, as mentioned above. Additionally, this study evaluates the system behavior under varying conditions to reduce the oxygen concentration at the location of the break to reduce the probability of air ingress. Some of the varying conditions evaluated are the time of active ventilation, break size and location, and ventilation location. The experimental results presented in this study indicate that an active ventilation time of 22 seconds allows the system to vent most of the air from the cavity section compared to 50, 65, and indefinitely time scales. Additionally, the experimental results indicate that leaving the ventilation duct system open for too long results in lower temperatures in the cavity section. The break size also influenced the oxygen concentration, where the system vents more air with small breaks than relatively large ones. The location and orientation of the break have little effect on the temperature and oxygen concentration measurements. Nonetheless, it did significantly influence the velocity of the gases being vented. The location of the ventilation system did significantly influence the oxygen concentration. The placement of the ventilation system near the bottom floor of the power conversion vessel (PCV) containment building results in a higher oxygen concentration in the cavity region of the reactor pressure vessel and a lower concentration in the PCV cavity region. Contrarily, a lower oxygen concentration in the pressure vessel cavity and higher in the PCV is the outcome when the ventilation duct is placed near the roof of the containment building of the PCV. Velocities as a result of the initial depressurization and natural circulation were recorded. Experimental results indicate that the velocities at the bottom of the axial cross-vessel are higher than at the top.doctoral, Ph.D., Mechanical Engineering -- University of Idaho - College of Graduate Studies, 2022-0
The Mechanisms of Chlamydial Cell-form Development
No full textChlamydiae are obligate intracellular Gram-negative bacteria that infect an array of eukaryotic hosts. Chlamydia trachomatis, a human-adapted species, is the global leading cause of bacterial sexually transmitted infections as well as trachoma, a preventable form of blindness. All Chlamydiae progress through an essential biphasic developmental cycle consisting of two primary cell forms. The elementary body, or EB, is the infectious, non-replicating, cell form. Whereas, the reticulate body, or RB, is non-infectious, but replication competent. The infectious cycle is initiated by the EB via pathogen-mediated endocytosis. Once inside the host, development occurs within a parasitophorous vacuole, termed the inclusion. Within the first 11 hours of infection, the nascent inclusion migrates to the microtubules organization center and the EB undergoes primary differentiation into the replicating RB. At approximately 20 hours post infection, a subset of RBs begins secondary differentiation back into infectious EBs. Secondary differentiation continues through the remainder of the infectious cycle until host cell lysis or inclusion extrusion releases the EBs into the environment to initiate subsequent rounds of infection. Although the ability to transition from EB-to-RB-to-EB is essential for chlamydial growth and proliferation, the mechanisms that regulate Chlamydia cell-form development remain largely unknown. This dissertation demonstrates the power of combining automated live-cell microscopy and cell-form specific reporter strains to monitor chlamydial developmental dynamics in active infections. Computational models were developed to test multiple chlamydial developmental hypotheses, explore cell-form subpopulation dynamics, and guide in vivo experiments. The data from these experiments suggests that Chlamydia is not only responding to an intrinsic developmental signal, but that cell-form differentiation is a multi step process consisting of both cell division dependent (RB-to-IB asymmetric production) and independent (IB-to-EB direct maturation) mechanisms. Lastly, to elucidate the genes involved in RB-to-EB differentiation we developed a mutagenesis screen using automated live-cell microscopy and a dual cell-form specific chlamydial reporter strain.doctoral, Ph.D., Biological Sciences -- University of Idaho - College of Graduate Studies, 2022-0
Navigating Information Spaces Through a Novel Immersive 3D Audio Interface
No full textScreen readers, braille displays, and voice-activated personal assistants (VAPAs) are the most common accessibility technologies aiding blind users in computer navigation tasks. However, several usability and performance issues have been identified with each method. Screen readers are constrained by high cognitive workloads (Theofanos & Redish, 2003), a loss of graphical information (Harper et al., 2006; Leuthold et al., 2008), and overall inefficiency (Lazar et al., 2007). Braille displays are often costly, and braille literacy has dropped drastically since the 1950s (National Federation of the Blind, 2009). VAPAs cannot handle complex tasks (Abdolrahmani et al., 2018) and force the user to spend a significant amount of time correcting misunderstood text (Azenkot & Lee, 2013). In the context of menu navigation, the current project analyzed the potential of a novel 3D audio interface to be a viable alternative to a conventional screen reader. Participants were tasked with navigating menu structures of varying depth and breadth to select a target item with three different interface styles (3D audio, screen reader, and visual). Results indicated the 3D audio interface was significantly slower, more error prone, and subjectively less-usable than the screen reader. However, the 3D audio interface showed larger performance improvements over the course of the experiment than did either the screen reader or visual interfaces, potentially indicating that more practice with this interface could eventually yield performance advantages over a screen reader.masters, M.S., Psychology & Communication -- University of Idaho - College of Graduate Studies, 2022-0
NUTRITIONAL APPROACHES TO MITIGATE THE IRON TOXICITY IN RAINBOW TROUT AND CATFISH
No full textCatfish (Ictalurus punctatus) and rainbow trout (Oncorhynchus mykiss) are the leading fish food in the United States. Iron (Fe) is an essential element for fish; however, a higher dose could exert toxic effects on fish. Vitamin C is a reducing agent that helps in facilitating iron uptake in the gut. Bentonite clay acts as a chelating agent. Our study investigated the effect of dietary supplementation of vitamin C and bentonite in mitigating the iron toxicity in catfish and trout. Vitamin C study: Catfish were exposed with/without iron (9.5 mg/L Fe3+ in water) and fed 3 diets [control, low vitamin-C (143 ppm), and high vitamin-C (573 ppm)] for 8 weeks. Results showed that fish growth was lower in iron exposed compared to non-exposed groups. Supplementations of vitamin C increased the growth rate, reduced oxidative stress, and mitigate the organs damages under iron-exposed conditions. Bentonite study: Six diets [0% bentonite (Con), 2% bentonite (LB), 4% bentonite (HB), 0.25% iron as FeSO4 (Fe), Fe+2% bentonite (LBFe), and Fe+4% bentonite (HBFe) were fed to trout for 8 weeks. Significantly lower fish growth was observed when fed Fe compared to control, however bentonite supplementation improved the growth. Oxidative status was enhanced in LBFe and HBFe groups compared to the Fe group. The liver showed infiltration with inflammatory cells and necrosis in Fe and HB groups whereas the LBFe group appears to be normal. Bentonite and Vitamin C study: Seven diets [500 ppm vitamin-C (Con), 0.25% iron as FeSO4 (Fe)+ Vitamin-C(500ppm) (ConFe), 2% bentonite, 0.25% iron as FeSO4 (Fe) (BenFe), Fe+1500 ppm Vitamin-C (MVCFe), Fe+2% bentonite + 1500 ppm Vitamin-C (MVCBenFe), Fe+3000 ppm Vitamin-C (HVCFe), and Fe+2% bentonite + 3000 ppm Vitamin-C (HVCBenFe) were fed to trout for 10 weeks. The result indicated that the supplementation of bentonite, vitamin C ,or in combination exposed to a higher dietary iron augmented (p doctoral, Ph.D., Animal, Vet & Food Sciences -- University of Idaho - College of Graduate Studies, 2022-1
Ecological factors Driving Aspen (Populus tremuloides Michx.) Stand Stability in a Semi-Arid Montane Region of the Intermountain West
No full textIn the western United States Populus tremuloides Michx., hereafter referred to as aspen, is considered an important forest cover type because of its contribution to local and regional biodiversity, as well as its use for habitat and food for a variety of large and small mammals, songbirds, and game birds. These critical ecosystem services provided by aspen have made many ecologists and resource managers concerned with recent trends of aspen decline across the western U.S. Many ecologists have for decades predicted a trajectory of disappearance while more recently others have suggested that aspen persistence is contingent on local disturbance regimes, management, and or geographical location. The greatest threats to aspen persistence in the West have been identified by researchers as competition with succeeding conifers, browsing by ungulates, and acute drought. In this dissertation, I investigate the relationship between aspen persistence and regeneration ecology with these identified threats focusing primarily on drought and soil moisture but accounting for successional conifer density and browsing pressure. My efforts focus on aspen stands in the Caribou-Targhee National Forest (CNF). In chapter 2, I explore the importance of precipitation as a proxy for potential soil moisture limitation on aspen growth across the CNF using dendrochronological methods. Specifically, I applied a new dendrochronological technique, Blue Intensity (BI), for the extraction of a climate signal in aspen latewood to explore the importance of mid-summer precipitation on aspen growth. Blue intensity is an effective and inexpensive proxy for wood density that has been found to correlate more accurately with climate factors (precipitation, temperature) than ring width, especially in latewood. The results of this analysis showed a positive correlation between mid-summer precipitation and latewood density that supports the first part of my hypothesis; aspen growing on sites with expected soil moisture limitations will produce a climate signal that correlates with precipitation; and the second part of my hypothesis that this signal reveals latewood development is driven by and dependent on soil moisture availability based on precipitation. From these results I conclude that late season growth for aspen on exposed high elevation sites is dependent on precipitation and growth is thus limited by soil moisture availability. In Chapter 3, I investigate the relationship between soil moisture availability and aspen stand persistence by comparing the structure, composition, and regeneration densities of nine aspen stands with nine paired upland aspen stands. Considering the numerous studies published in the last two decades that show evidence of drought being the main inciting factor of aspen decline on xeric sites, I hypothesized that the proximity to perennial streams will lead to higher soil moisture availability and thus increase the probability of aspen persistence on the Caribou-Targhee National Forest landscape. My results for this study partially supported my hypothesis that riparian areas support aspen stands that show evidence of a higher probability of persistence relative to upland aspen stands. The most compelling evidence comes from the significantly higher aspen regeneration densities at the seedling layer (1m height) aspen regeneration densities were still considerably higher in the riparian areas than in the upland areas but this difference was not significant. In this study I used the term “seedling layer” and “sapling layer” to refer to aspen regeneration in different height classes and did not differentiate between regeneration originating from seed versus regeneration originating from suckering. Building off of the results in chapter 3 of significant differences in the density of aspen in the regeneration layer between riparian and upland aspen stands, in chapter 5 I developed a model path analysis using structural equation modeling to explore the relative impacts and interactions of physiographic and ecological factors that affect aspen regeneration densities. Before any analysis of the direct factors influencing soil moisture availability on aspen regeneration, it was important to characterize the clonal diversity of each site. To do this, in chapter 4 I used a traditional approach, with modern techniques, based upon leaf morphology to determine the clonal diversity on each site to be used in a structural equation model (SEM). Overall, I found that there were differences in mean clonal diversity between riparian and upland aspen stands, with riparian stands tending to have higher clonal diversity. The results of the SEM analysis (chapter 5) support my hypothesis that factors affecting soil moisture availability have the strongest effect on regeneration. Specifically, the exogenous factor with the strongest direct effect on aspen regeneration was incident radiation (heatload), and the endogenous factor with the strongest direct effect on regeneration was the percent cover of competitive plant species. Overall, the results of each chapter support my global hypothesis that factors reducing soil moisture availability and increasing site susceptibility to drought have a negative effect on aspen growth and regeneration. My results, however, also emphasize that context is important in determining the collective effect of these factors. Thus, proper assessment of aspen vulnerability in the West requires analyses at multiple scales that can incorporate the relative weights and interactions of elements influencing aspen persistence.doctoral, Ph.D., Natural Resources -- University of Idaho - College of Graduate Studies, 2022-0
Synthesis and Development of a Series of Peptide Based Zwitterionic Cross-Linkers
No full textZwitterionic polymeric hydrogels (polyampholytes) have shown promise as functional biomaterial platforms with resistance to nonspecific protein adsorption (non-biofouling) and as controlled release drug delivery materials. However, there are few zwitterionic cross-linkers to complement these materials and provide a fully zwitterionic material. To date, available zwitterionic cross-linkers have been limited to carboxybetaine or sulfobetaine acrylate/methacrylates and only one of these has been tested in vivo. Peptides offer a highly adaptable zwitterionic scaffold to imbed a series of desired functions. To investigate this hypothesis a simple N-Ser-Ser-C dimethacrylate cross-linker was synthesized. This novel cross-linker was incorporated into a polyampholyte hydrogel, and its physical properties and biocompatibility were compared against a polyampholyte hydrogel synthesized with an EG-based cross-linker to reveal increased non-fouling performance while promoting enhanced cellular adhesion to fibrinogen delivered from the hydrogel over commercial polyethylene glycol (PEG) cross-linkers. Therefore, these results suggest that the S-S cross-linker will demonstrate superior future performance for in vivo applications Continuing, a library of serine and lysine-based zwitterionic dimethacrylamide and mixed methacrylate/ methacrylamide zwitterionic dipeptide cross-linkers (Lys-Lys, Ser-Lys, Lys-Ser) have been developed to provide a tunable polymer platform that retains the desired non-fouling properties. Moreover, this strategy was employed to build tripeptide zwitterionic cross-linkers to extend the distance between the zwitterionic components, another key feature not amenable in the carboxy- or sulfobetaine based cross-linkers. Peptide-based cross-linkers can be synthesized following an ‘outside-in’ approach and the key to this route is the selective protection strategy of both N and C termini, peptide coupling, and semi-orthogonal protection and deprotection strategy. It has been hypothesized that molecular-level control over the length, charge spacing, charge density, and sidechains will lead to fully tunable polymer hydrogels for directed biomaterial scaffolds.doctoral, Ph.D., Chemistry -- University of Idaho - College of Graduate Studies, 2022-0
Creep Fatigue Crack Growth and Creep Crack Growth Behavior of P92 at Elevated Temperature
No full textHigh chromium heat resistant steels are commonly used for boiler components that are operated around 600ºC in ultra-supercritical (USC) thermal power plants. This study focuses on the creep fatigue crack growth, creep crack growth and creep brittle or ductile behavior of ASME P92 steel at 650ºC. All specimens were machined from a header pipe in a homogeneous fashion. A side groove analysis was performed to determine the best side groove percentage to use for a uniform crack front propagation which found a 10% total side groove to be the best percentage. The study showed that for creep fatigue crack growth tests the contour integral (Ct)avg correlated the three tests with hold times of 60 s better than the stress intensity factor K. The creep crack growth tests showed similar results with the contour integral C* being a better crack tip parameter to characterize the data rather than the stress intensity factor K. The creep crack growth tests behaved in a creep ductile manner according to the load line displacement ratio and the non-dimensional crack velocity analyses.masters, M.S., Mechanical Engineering -- University of Idaho - College of Graduate Studies, 2022-1
Novel Security Models for IoT-Fog-Cloud Architectures in a Real-World Environment
No full textThe emergence of the Internet of things (IoT) has generated demand for computation performed at the ‘edge’ of the network. With companies being increasingly challenged to collect and send data collected from IoT devices to the cloud, this increases the need for fog computing. Fog computing is an intermediate computing layer that has emerged to address the latency issues of cloud-based Internet of things (IoT) environments. As a result, new forms of security and privacy threats are emerging. These threats are mainly due to the huge number of sensors, as well as the enormous amount of data generated in IoT environments that needs to be processed in real time. These sensors send data to the cloud through the fog computing layer, creating an additional layer of vulnerabilities. In addition, the cloud by nature is vulnerable because cloud services can be located in different geographical locations and provided by multiple service providers. Moreover, cloud services can be hybrid and public, which exposes them to risks due to their infinite number of anonymous users. This research proposed two architectures of cloud-based IoT environments and three analysis methods. The two proposed architectures are evaluated based on the three analysis methods to show the efficacy of the fog layer in different experiments in a real-world environment by examining performance metrics on the cloud and fog layers using different numbers of IoT devices. To overcome the security challenges between the IoT layer and fog layer and, thus, meet the security requirements, this research also proposed a fine-grained data access control model based on the attribute-based encryption of the IoT–Fog–Cloud architecture to limit the access to sensor data and meet the authorization requirements. In addition, this research proposed a blockchain-based certificate model for the IoT–Fog–Cloud architecture to authenticate IoT devices to fog devices and meet the authentication requirements. We evaluated the performance of the two proposed security models using AWS cloud metrics to determine their efficiency in real-life experiments of the IoT–Fog–Cloud architecture.doctoral, Ph.D., Computer Science -- University of Idaho - College of Graduate Studies, 2022-0
Impact of Nitrogen Stabilizer on Nitrogen Cycling, Nitrifying Organisms, and Winter Wheat Yield and Quality in High Rainfall Zones of Northern Idaho
No full textNitrogen loss to the environment has been a constant problem for growers and timing of nitrogen (N)fertilizer application can be challenging due to seasonal precipitation in northern Idaho. Nitrogen fertilizer is especially vulnerable to loss through leaching, runoff and volatilization when applied in the fall. Prevention of nitrogen loss through the winter is crucial to supply winter wheat (Triticum aestivum L.) planted in the fall with sufficient nutrients. One solution to minimize nitrogen loss is the use of nitrogen stabilizers with the application of nitrogen fertilizers. The stabilizers slow down nitrate (NO3-) leaching by inhibiting the process of nitrification by nitrifying bacteria and archaea. However, improved crop performance after the application of nitrogen stabilizers has been variable, and little work has been done in the Pacific Northwest. Additionally, there is uncertainty in how nitrification inhibitors might influence nitrifying organisms. Therefore, experimental plots were established in Cottonwood and Cavendish, Idaho during the 2019-2020 and 2020-2021 growing seasons to test the efficacy of nitrogen stabilizers in the high rainfall zone of northern Idaho. Two wheat cultivars soft white winter wheat LCS Hulk and the hard red winter wheat LSC Jet were studied in separate trials with five urea ammonium nitrate (UAN, 32-0-0) fertilizer rates (0, 56, 112, 168, and 224 kg/ha) applied with and without the nitrification inhibitor Instinct® II (Corteva Agriscience, USA). Soil samples were taken at four dates during the growing season to monitor ammonium and nitrate soil concentrations: November after planting, March, May, and September after harvest. Agronomic measurements that were taken include yield and postharvest quality as well as monitoring populations of bacteria and archaea and soil nitrate and ammonium. Soil samples collected from both locations indicated that the nitrogen stabilizer helped to retain ammonium in the soil and decreased the concentration of nitrate in the top 15 cm and 30 cm of soil, with differences being most obvious in November and March. Most agronomic measurements were not influenced by nitrogen stabilizer application. There as not a significant impact on yield. For only the hard red winter wheat at Cavendish there was a small, but significant decrease in test weight and increase in grain protein in plots treated with Instinct® II compared to plots without Instinct® II. Nitrifying archaeal populations did not respond to nitrogen stabilizer treatment, nor were they impacted by nitrogen fertilizer rate. However, bacterial populations were significantly decreased in the Instinct® II treated soils in the spring. Populations of ammonia-oxidizing bacteria did significantly increase with increasing nitrogen fertilizer rates. The results from this research help to further understand nitrogen stabilizer efficacy on winter wheat in rainfed areas of Idaho as well as its effect on nitrifying microorganisms’ populations. This information will aid decision making for growers looking to improve their nitrogen use efficiency and crop quality while not harming their soil health.masters, M.S., Plant Sciences -- University of Idaho - College of Graduate Studies, 2022-0