University of Idaho Library Digital Initiatives
Not a member yet
54971 research outputs found
Sort by
Interspecific Interactions in the Zebra Chip Pathosystem: Identifying Host Plant Resistance, Vector Cold Tolerance, and Multipartite Interactions with Potato virus Y
No full textZebra chip (ZC) disease is a threat to the potato industry because it reduces production and quality of tubers. The pathogen is associated with the bacteria “Candidatus Liberibacter solanacearum” (Lso) that is transmitted by the potato psyllid Bactericera cockerelli Šulc (Hemiptera: Triozidae). Since its detection in the United States in 2000, studies have been conducted to address different aspects of the ZC pathosystem. Sources of resistance has been investigated but characterization of resistance has been studied based on the interaction between the potato psyllid and potato or based on ZC symptom severity in fresh tubers at harvest. Moreover most of those studies have been conducted under controlled conditions. However, there are still critical questions to address that are directly relevant to ZC management and epidemiology. The overall objective of this dissertation was to study interactions between the potato psyllid and a range of potato genotypes, Lso and host genotypes and the potato psyllid and Lso. Although host plant resistance has been proposed as an effective approach in integrated pest management (IPM) program to ZC, none of the commercial potato cultivars in the U.S. are known to be resistant or tolerant consistently. In the first chapter we present a literature review of the zebra chip pathosystem. In chapter second chapter we studied Lso development and ZC symptoms in eight selected potato genotypes in the field, and in the third chapter we evaluated the progress of Lso development and ZC symptom progress post-harvest. Potato genotypes from the A07781 family exhibited relative resistance and/or tolerance to ZC because they showed low susceptibility to Lso and expression of ZC symptoms at harvest and after storage. Therefore, they were proposed as potential source of resistance to ZC. The fourth chapter was aimed at studying the effect of cold temperatures on potato psyllid mortality in relation to their Lso status and the vector haplotype. Lso may promote its vector’s ability to acclimate to cold temperatures but it was not influenced by the potato psyllid genotype (haplotype). We also evaluated the effect of Lso on potato psyllid respiration and we have found that Lso affects the respiration of potato psyllids negatively. Finally, Potato virus Y (PVY) and Zebra Chip (ZC) pathosystems can coexist in within fields, and they affect the potato industry productivity. Monitoring of potato fields indicates that potato psyllids arrive later in the growing season, when PVY may be already established. The objective was to evaluate the impact of PVY on the ZC pathosystem. Pre-existing PVY infection did not affect Lso development, but it negatively impacted Lso vectors by reducing their oviposition. Therefore, PVY may limit the spread of Lso by affecting its vector. Findings from the present dissertation contribute to our understanding of the ZC pathosystem, and represent the first reported study of its interaction with another pathosystem (PVY) in potato host.doctoral, Ph.D., Plant, Soil and Entomological Sciences -- University of Idaho - College of Graduate Studies, 2019-0
Association of a high fat diet, gut microbiota and host interactions with enteric neuropathy and dysmotility in a mouse model of type two diabetes
No full textType 2 diabetes is associated with gut microbiota alterations and debilitating gastrointestinal illnesses caused by neuropathy of the enteric nervous system and smooth muscle dysfunction. However, the specific triggers of enteric neuropathy and muscle dysfunction, and the role of gut microbiota alterations are not fully understood. We studied the specific roles played by gut microbiota alterations in the development of enteric neuropathy using germ free and conventionally raised high fat mouse models. We then studied gut microbiota, myenteric inhibitory neurons and intestinal dysmotility in these mice using next generation sequencing, tissue culture, immunohistochemistry, transmission electron microscopy, ex vivo gastrointestinal motility assays and intracellular microelectrode recording in smooth muscle cells. Conventionally raised male mice became obese, and had impaired glucose tolerance and insulin resistance after 4 weeks of high fat diet (HFD) ingestion. Conventionally raised female mice were however resistant to the weight gain, impaired glucose tolerance, and insulin resistance induced by HFD ingestion even after 8 weeks. Despite these differences, after 8 weeks, conventionally raised male and female mice fed a HFD had slower intestinal propulsive motility. These mice had microbiota alterations marked by increased gram-positive Firmicutes and lower Gram-negative Bacteroidetes. In addition, they had fewer numbers of neurons per ganglion, lower numbers of myenteric inhibitory neurons, and axonal damage including swelling and loss of cytoskeletal filaments. HFD ingestion also impaired inhibitory neuromuscular transmission in both genders. To determine the role of HFD-microbiota-host interactions in HFD-induced enteric neuropathy and dysmotility, filtrates of luminal contents from the ileum and cecum (hereafter, ileocecal supernatants) of both conventionally raised male and female HFD fed mice were superfused into the lumen of isolated intestinal segments or applied on cultured duodenal or distal colon muscularis preparations. Ileocecal supernatants inhibited intestinal propulsive motility and muscularis contractions. We then used solid phase extraction to separate ileocecal supernatants into water-soluble and methanol (20%, 50% and 100%) soluble fractions and tested them in motility assays. Like the ileocecal supernatants, the water fraction from HFD mice inhibited intestinal propulsive motility and blocked muscularis contractions. HFD Supernatants and water fractions also caused loss of myenteric nitrergic neurons and inflammation. They damaged smooth muscle and impaired neuromuscular transmission in cultured muscularis preparations. Supernatants and water fractions blocked the discharge of spontaneous slow waves and action potentials, the electrical activities underlying contractions of smooth muscle cells. These effects matched the effect of HFD ingestion on the excitability of smooth muscle cells in distal colon. To determine the role of an intact gut microbiota in the development of enteric neuropathy, we used a germ free HFD mouse model. We found that compared to conventionally raised mice, HFD ingestion did not reduce the number of myenteric inhibitory neurons in the duodenum of germ free mice. HFD also induced alterations in the cecum of conventionally raised mice, which led to increased gram-positive bacteria. Subsequent studies revealed that lipoteichoic acid from gram-positive bacteria induced a loss of myenteric nitrergic neurons associated with oxidative stress and inflammation. Taken together, these studies provide new evidence to support the hypothesis that diet-microbiota-host interactions play a crucial role in the development of enteric neuropathy and dysmotility in a high fat diet mouse model of type 2 diabetes.doctoral, Ph.D., Biology -- University of Idaho - College of Graduate Studies, 2019-0
Examining the Grit, Optimism, Locus of Control, and Self-Efficacy of Student Leaders in Idaho’s Career and Technical Student Organizations
No full textCareer and technical education (CTE) is supported through federal funding and requires these programs to provide students with opportunities to engage in career and technical education student organizations. These organizations provide students with opportunities to engage in leadership through formal and non-formal roles and develop deeper understand for the course content through competitive events. This study is descriptive-relational in nature and examines four non-cognitive factors in a population of CTSO student leaders. In this study, grit, optimism, locus of control, and self-efficacy are described for the population and these factors are examined for differences based on the population’s demographics. The results indicate differences between grit and organization, locus of control and gender, and self-efficacy and gender. The authors make recommendations for future research and practice as it relates to CTSO student leaders and non-cognitive factors.masters, M.S., Agricultural Education & 4H Youth Development -- University of Idaho - College of Graduate Studies, 2019-0
Using Medium and Large-Sized Mammals as Indicator Species to Measure Connectivity and Large Infrastructure Impacts in Costa Rica
No full textConservation of biodiversity in all its forms, genetics, species and ecosystems, is essential to maintain the resilience of ecosystems and the stability of their functions and services. Over the past two centuries ecosystems are being changed, mainly associated to human-related impacts, global forest cover is being lost at a rate of 0.6% per year and extinction of species are occurring at a much higher rate than in most previous periods. Additionally, many protected areas are not enough to guarantee the long-term survival of species that require large extents to sustain viable populations. Thus, connectivity between protected or natural areas through dispersal or biological corridors is crucial for the conservation of wide-ranging species and biodiversity in general. Moreover, low genetic diversity and reduced gene flow may decrease the ability of a species to survive by reducing its ability to adapt to environmental changes or human-related threats, decreasing fitness and increasing genetic drift. Therefore, measuring genetic diversity and population structure is vital to quantify biodiversity at an evolutionary significant unit (i.e. populations with high genetic or ecological distinction) level. Medium and large-sized mammals play an important role in the ecosystems where they occur, but are also subject to several threats. Given, their high habitat requirements in terms of food and extent of area some medium and large-sized mammals are at higher risk of extinction than other species. This makes them especially vulnerable to habitat alterations and human related pressures. Consequently, medium and large-sized mammals can be monitored and used as indicator species to test for connectivity between protected or core areas, and assess the impacts of human activities (e.g. large infrastructure projects) on wildlife. This research intended to use medium and large-sized mammals to evaluate the condition of a critical link of the Mesoamerican Biological Corridor (MBC) in Costa Rica. Also, we intended to measure the impacts of a hydroelectric reservoir on the mammal community in this corridor. Rather than using single species analyses, we used hierarchical community occupancy models in a Bayesian framework. This, not only allowed for the use of data of rare species, but we believed helped produce stronger inferences on the status of the landscape in terms of biodiversity. Our results suggest that the status of this critical link with respect to medium and large-sized mammals is precarious. Furthermore, we were able to measure the impacts of the reservoir on medium and large mammals’ occupancy by including a dynamic component and comparing results in three time periods: before the flooding of the reservoir, immediately after the completion of the flooding of the reservoir, and approximately one year after the flooding of the reservoir. We found considerable changes in medium and large-sized mammals’ occupancy before and after the filling of the reservoir. In this work we also evaluated genetic diversity and population structure of ocelots (Leopardus pardalis) Costa Rica, and compared the genetic diversity of Costa Rican ocelots with that of jaguars (Panthera onca) and pumas (Puma concolor) in the country, and with ocelots in Belize. We found relatively high levels of genetic diversity for ocelots in Costa Rica and no patterns of genetic substructure, suggesting high levels of gene flow throughout the country and no strong barriers to movement. Additionally, genetic diversity of Costa Rican ocelots was higher than that of jaguars and pumas, and levels of genetic diversity were slightly higher in Costa Rican ocelots when compared to their counterparts in Belize, confirming the south to north decrease in genetic diversity reported in other studies for the species. We believe the community approaches implemented here can be used to monitor biodiversity and measure the effects of infrastructure in general on wildlife, help avoid impacts, and plan proper mitigation actions. Our study also provides critical baseline information to understand what is the status of the ocelot populations in the country.doctoral, Ph.D., Natural Resources -- University of Idaho - College of Graduate Studies, 2019-1
Visioning Place-Based Resource Recovery: the Twin Falls, Idaho Water Resource Recovery Facility
No full textn/amasters, M.S., Civil Engineering -- University of Idaho - College of Graduate Studies, 2019-0
Manipulation of Mechanical Properties of WAAM Deposited ER70S-6 Through Active Cooling
No full textBy employing active cooling methods with a steel-depositing wire-arc additive manufacturing (WAAM) system we have shown the hardness and yield strength of prints can be manipulated on-the-fly. The purpose of this research was to determine the scope of influence active cooling can have on the mechanical properties of WAAM printed steel. Active cooling is achieved by applying coolant onto deposited material continuously and directly behind the molten puddle. Tensile specimens are cut from thin walls of stacked single width passes. Tensile and hardness tests show the yield strength of ER70S-6 can increase up to 90 KSI and 10 HRC points respectively.masters, M.S., Mechanical Engineering -- University of Idaho - College of Graduate Studies, 2019-0
Using nutritional-landscape models to predict pregnancy rates of elk across broad spatial scales
No full textUnderstanding how the choices made by individal herbivores as they navigate heterogeneous landscapes scale up to influence population performance is critical for accurately forecasting population trajectories. In recent decades, elk (Cervus canadensis) populations in Idaho have exhibited considerable variation in multiple vital rates, including pregnancy. Because elk populations that are not resource limited typically display high pregnancy rates (>80%), and several populations in Idaho regularly fall below this threshold, there is concern that habitat quality may be limiting the productivity of those populations. Nutritional condition is a primary driver of reproductive success in female herbivores, and thus poor habitat quality, suboptimal use of the nutritional landscape by elk, or a combination of both could cause depressed pregnancy rates. The goal of our research was to develop a series of linked dynamic models for predicting a) spatiotemporal variation in the nutritional landscapes available to elk in seven distinct populations in Idaho and b) interannual variation in pregnancy rates of those populations as a function of the overall quality and abundance of forage resources available to them and/or how they used those resources. Regression models for explaining spatiotemporal variation in usable forage biomass (biomass of forage that met or exceeded requirements for a female elk at peak lactation) generally performed well in each of our three study areas, with adjusted R2 values ranging from 0.26 to 0.61. High-quality foraging habitat was most abundant during summer in the Teton and Diamond Creek elk zones, and was least abundant in the Beaverhead and Sawtooth elk zones. This trend was similar during the fall, with the Teton and South Fork of the Clearwater elk zones supporting the most high-quality habitat, and the Beaverhead and Sawtooth zones supporting the least high-quality habitat. Differing patterns of habitat use were observed among the four elk populations for which we had simultaneous GPS-collar and pregnancy data. Elk in the Diamond Creek and Sawtooth zones appeared to utilize the nutritional landscape sub-optimally (i.e., locations used by elk had less high-quality forage than random locations on the landscape), particularly during summer (June 1 – July 31), whereas elk in the South Fork of the Clearwater used high-quality foraging habitat in greater proportion than it was available. Our top model for relating pregnancy rates of elk to the nutritional landscape explained 60% of the variation in pregnancy rates among 18 elk-population-years. Our top model for relating pregnancy of elk to how they used the nutritional landscape explained 75% of the variation in pregnancy rates among 10 population-years. Variation in pregnancy rates was positively related to both the maximum value of usable forage biomass and the degree of heterogeneity in the nutritional landscape across elk management zones in Idaho. This supports our hypothesis that pregnancy is mediated by habitat quality, and provides additional empirical evidence of a fundamental link between the nutritional landscape in summer and fall and population performance of elk.masters, M.S., Natural Resources -- University of Idaho - College of Graduate Studies, 2019-0
Conceptual Design of the Advanced Test Reactor Non-Destructive Examination System
No full textThe Advanced Test Reactor is one of the most capable research reactors in the world. Despite its world-class irradiative capabilities, on-site post-irradiation examination is limited to temporary, program-specific non-destructive examination needs, or non-existent altogether. Currently, fueled experiments and other fissile material are stored in the adjacent canal for cooling prior to shipment for comprehensive post-irradiation, reinsertion or disposal. This presents an opportunity for poolside post-irradiation examination to collect intermediate information about irradiated specimens only possible shortly after removal from the reactor. Idaho National Laboratory has funded the conceptual design of the Advanced Test Reactor Non-Destructive Examination System (ANDES), which conducts non-destructive post-irradiation examination on multiple types of specimens to assist reactor operations and further nuclear materials research. This thesis presents a design methodology driven by stakeholder and facility requirements for formulating the ANDES conceptual design. The individual subsystems of the ANDES conceptual design are discussed in detail, including enhanced videography and poolside gamma spectroscopy. Challenges and opportunities facing the development and deployment of ANDES are also discussed. If fully developed and deployed, the combined ANDES capabilities would provide an unparalleled post-irradiation examination approach for advancing nuclear energy science and technology.masters, M.S., Mechanical Engineering -- University of Idaho - College of Graduate Studies, 2019-0
Understanding the surface-atmosphere interactions on Titan
No full textWith a thick atmosphere, a methane-based hydrological cycle, stable bodies of standing uid at its surface, and many active surface processes, Saturn's largest moon Titan is surprisingly Earth-like. Methane rain on Saturn's moon Titan makes it the only place, other than Earth, where rain interacts with the surface. Looking at Titan is like looking back in time to understand the evolution of present day Earth from early-Earth. This thesis combines several studies related to Titan's hydrologic system, particularly the ways uid interacts with the surface of Titan. Understanding this atmosphere|surface interaction is of great importance to understand Titan's meteorology and evolution. Follwing an introduction about the discovery and need to study Titan, chapter 2 addresses the possible reasons behind Ontario Lacus being the solo lake in the south pole of Titan. In chapter 3 we discuss our novell `wet-sidewalk' observation. Basically if ground gets wetted, and illuminated by the Sun at right geometries we get this broad specular re ection (glint) that's super-bright. That we've seen one near Titan's north pole means that it's rained there now coincident with north polar summer, and furthermore we've got a new technique for monitoring when and where rainfall occurs across Titan's surface. It is extremely dicult to detect rainfall events on Titan due to its thick atmospheric haze and very limited opportunities to view the surface (and its changes). Our wet-sidewalk observation using VIMS |Visual and Infrared Mapping Spectrometer, on the north pole of Titan is the rst of its kind i.e using broad surface re ection and the delayed north polar activity. Hence this observation and the rainfall discovery on the north pole is of extreme importance to understand Titan's climate. While the presence of a hydrological cycle might help explain how the depressions on Titan's surface are lled with liquid methane, the formation mechanisms of the depressions still remain a mystery at the end of Cassini in 2017. We address this question using a morphometric measurement methodology (EFDA|Elliptical Fourier Descriptor Analysis) to quantify the shapes of Titan's lakes in Chapter 4. We nd that the major variation in the shapes of lakes on Titan are from circular to elliptical followed by longer lakes with asymmetry along their long axis and longer lakes with asymmetry along their short axis. Also, smaller lakes on Titan are more circular indicating that probably lakes are initially formed by a punch but evolve to get bigger with more complexities in their shoreline. We then conclude the thesis by stating our future work about expanding the morphometric analyses to more lakes on Titan and nding more 'wet-side walk' like features on Titan's north pole.doctoral, Ph.D., Physics -- University of Idaho - College of Graduate Studies, 2019-0
The Effect of Leaf Litter Legacies and Nutrient Additions on Microbial Function
No full textMicroorganisms are integral to ecosystem carbon and nutrient cycling, yet we still lack a holistic understanding of the roles microorganisms play in these ecosystem processes. This thesis explores the role microbial communities play in leaf litter decomposition, as well as how micronutrient additions influence the function of microbial communities. The way that microbes decompose litter can be assessed via the indexes of home-field advantage and functional breadth. Often, past studies have focused on home-field advantage and ignored functional breadth as it is believed that the two are interchangeable. We performed a full factorial leaf litter by soil mesocosm experiment to compare how different microbial communities decompose substrates. We found an unimodal relationship between home-field advantage and functional breadth, as well as several other correlated variables that may help explain the presence or absence of these indexes in other scenarios. This unimodal relationship suggests that these two indexes, while related to each other are not ultimately the same, and should each be considered carefully in future studies. There is relatively little known about how micronutrients influence microbial communities, compared to the influence of macronutrients. In order to study the influence of micronutrients on microbial communities, we added micro- and macronutient fertilizer inputs to field soils and measured differences in microbial function (i.e., carbon mineralization, substrate-induced respiration, catabolic response profiles). We found that microbial communities responded to the addition of multiple types of fertilizer, rather than just one single type. This response to different nutrients suggests there is a possible colimitation of nutrients. Understanding how microbial communities regulate decomposition and nutrient cycling is a fundamental question for soil scientists. This work on the relationship between home-field advantage and functional breadth provides insight into a key component of the decomposition process. Similarly, this research on how macronutrients and micronutrients influence microbes shines light on what factors regulate microbial community assembly and diversity. Combined this work provides important insight into the roles and importance of microbial communities in global carbon cycling and ecosystem function.masters, M.S., Plant, Soil and Entomological Sciences -- University of Idaho - College of Graduate Studies, 2019-1