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Title: Aflatoxin levels in sunflower seeds, cakes, and crude oil sediments locally produced in Tanzania and potential phytochemicals for aflatoxin management
Creator: Mmongoyo, Juma Abdallah
Date: 2016
Collection: Electronic Theses & Dissertations
Description: This dissertation had two objectives. The first was to determine total aflatoxin concentrations in sunflower seeds, cakes and crude oil sediments from small-scale oil processors across Tanzania. The towns selected for sunflower sample collection included Mbeya, Iringa, Morogoro, Dodoma, Singida, Babati-Manyara and Karatu-Arusha. We collected a total of 232 samples: sunflower seed (n = 90), cake samples (n = 92) and crude sunflower oil sediments (n = 50) across two years, which were analyzed...
Show moreThis dissertation had two objectives. The first was to determine total aflatoxin concentrations in sunflower seeds, cakes and crude oil sediments from small-scale oil processors across Tanzania. The towns selected for sunflower sample collection included Mbeya, Iringa, Morogoro, Dodoma, Singida, Babati-Manyara and Karatu-Arusha. We collected a total of 232 samples: sunflower seed (n = 90), cake samples (n = 92) and crude sunflower oil sediments (n = 50) across two years, which were analyzed for total aflatoxin concentrations using a direct competitive enzyme-linked immunosorbent assay (ELISA). The aflatoxin surveillance performed in June-August 2014, indicated that the highest aflatoxin levels in sunflower seeds were from the towns of Babati-Manyara, Singida, and Dodoma. The aflatoxin levels in sunflower cakes were exceedingly high in Singida, Dodoma, and Mbeya. The surveillance performed in August-October 2015, indicated that the highest aflatoxin concentrations in sunflower seeds were from Mbeya, Singida, and Morogoro. Singida, Dodoma, and Morogoro had shown unacceptable aflatoxin levels in sunflower cakes. Aflatoxin levels in oil sediments were considerably lower in both years except Morogoro, which showed two oil sediments exceedingly contaminated (41.7 and 85.3 ng/g). Concerning risk assessment, Dodoma and Babati-Manyara showed dietary exposures of 25 and 21 ng/kg bw/day, respectively, for sunflower seed consumption in 2014. Liver cancer risks for these exposures were 0.9 and 0.8 cases per year per 100,000 individuals, respectively. Samples from Morogoro suggested dietary exposure of 24 ng/kg bw/day for sunflower seed consumption in 2015 that carried a risk of 0.9 cases per year per 100,000 individuals. Although the crude oil sediment data showed that crude oils were safe, the general results of aflatoxin levels in seeds and cakes particularly from Manyara, Singida, Dodoma and Morogoro, and crude oil sediments from Morogoro, indicate that there is a potential risk of exposure to aflatoxin through sunflower products and intervention strategies are required. Our second objective was to determine the anti-aflatoxigenic properties of compounds from a traditional medicinal plant D. mafiensis root bark against vegetative growth, sporulation and aflatoxin production by Aspergillus flavus and Aspergillus parasiticus. The bioactive compounds diosquinone (DQ) and 3-hydroxydiosquinone (3HDQ) were elucidated and identified using 1H- and 13C-NMR and LC-MS methods. Growth inhibition was determined by measuring the colony diameters of the molds in culture. Total aflatoxin was quantified by direct competitive enzyme-linked immunosorbent assay (ELISA). DQ showed weak potency against A. flavus and A. parasiticus vegetative growth (MIC50 >100 μg/mL), and 3HDQ demonstrated a strong potency against A. flavus (MIC50 = 14.9 μg/mL) and A. parasiticus (MIC50 = 39.1 μg/mL). Despite its weak potency against vegetative growth, DQ strongly reduced total aflatoxin production by A. flavus and A. parasiticus for over 90 %. Counterintuitively, 3HDQ stimulated aflatoxin production by A. flavus at lower doses but started to reduce aflatoxin production at the dose of 100 μg/mL. 3HDQ strongly reduced total aflatoxin production by A. parasiticus even at lower doses. In summary, DQ and 3HDQ could be used as natural fungicides to prevent mold growth and aflatoxin accumulation in food and feed.
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Title: Measurement invariance of a summative achievement assessment over time : is status really ready for growth
Creator: Viger, Steven Guy
Date: 2014
Collection: Electronic Theses & Dissertations
Description: The current study investigates the phenomenon of measurement invariance by examining the construct stability of a summative mathematics achievement instrument over time gleaned from an existing data set. In doing so, not only is the general question of measurement invariance of the particular instrument addressed, but also in the context of growth studies. The onus of the study as well as the results are presented in light of the current political context of large scale K-12 assessment and...
Show moreThe current study investigates the phenomenon of measurement invariance by examining the construct stability of a summative mathematics achievement instrument over time gleaned from an existing data set. In doing so, not only is the general question of measurement invariance of the particular instrument addressed, but also in the context of growth studies. The onus of the study as well as the results are presented in light of the current political context of large scale K-12 assessment and the shifting of emphasis from status to growth. As the reader will discover, great pressure is placed on results not necessarily intended to serve as the metric required by policy. The results and implications are framed in both measurement and practical contexts.
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Title: Factors to consider in the indoor environment when evaluating the risk of human health at the environmental detection limit
Creator: Herzog, Amanda Blair
Date: 2014
Collection: Electronic Theses & Dissertations
Description: Quantitative analysis of the limit of detection, sample recovery efficiency (SRE) and characterization of the microbial community are necessary parameters for accurate exposure assessment as part of the quantitative microbial risk assessment framework for indoor environments. To control and remediate an indoor environment from an outbreak, accidental or intentional release of pathogens can be a challenging task. Without understanding the situation in quantitative terms, determination of a...
Show moreQuantitative analysis of the limit of detection, sample recovery efficiency (SRE) and characterization of the microbial community are necessary parameters for accurate exposure assessment as part of the quantitative microbial risk assessment framework for indoor environments. To control and remediate an indoor environment from an outbreak, accidental or intentional release of pathogens can be a challenging task. Without understanding the situation in quantitative terms, determination of a site as safe or "clean" especially when a sample result is negative will be unachievable. The negative result may not establish zero risk and can be due to variability in the sampling or detection methods. The release of Bacillus anthracis in 2001, the numerous outbreaks from the food industry, hospital settings, and on university campuses have highlighted the lack of quantitative information. A review of the literature for the limits of detection of methods detecting B. anthracis provided a distribution to quantify the variability in the instrument limit of detection; however there were only a few articles on the environmental limit of detection. An exponential dose response model estimated the risk at the dose equal to the environmental limit of detection to determine the probability of death as high as 0.52. The SRE of bacteriophage P22 was evaluated at the environmental limit of detection and was most affected by sampling time, fomite surface area, wetting agent and relative humidity. After samples dried on the fomite (20 min), less than 3% was able to be recovered even though the bacteriophage P22 was still active on the fomite. Genetically characterizing the bacterial communities on touched and untouched fomites resulted in two unique bacterial communities. Touched fomites were more diverse and had a high presence of fecal indicators which demonstrated potential reservoirs for pathogens. This research will improve exposure assessment by indicating the risk and limitations at the environmental limit of detection, enhancement of sampling strategies and the role fomites have in the transmission of infectious diseases.
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Title: Designing a package for pharmaceutical tablets in relation to moisture and dissolution
Creator: Yoon, Seungyil
Date: 2003
Collection: Electronic Theses & Dissertations

Title: An interactionist approach to assessing personality in work contexts : construct validation of a predictor of customer service performance
Creator: Ployhart, Robert E.
Date: 1999
Collection: Electronic Theses & Dissertations

Title: High-precision mass measurement of N = Z = 34 nuclides for RP-process simulations and developments for the LEBIT facility
Creator: Savory, Joshua J.
Date: 2009
Collection: Electronic Theses & Dissertations

Title: Minimum distance measurement errors model fitting
Creator: Song, Weixing
Date: 2006
Collection: Electronic Theses & Dissertations

Title: The validity of a non-invasive method of maturity estimation and intrinsic risk factors for injury in youth football players : analysis of the 2002 and 2003 seasons
Creator: Dompier, Thomas Patrick
Date: 2005
Collection: Electronic Theses & Dissertations

Title: Detecting segregation in bituminous pavements and relating its effect to performance
Creator: Chang, Chieh-Min
Date: 2000
Collection: Electronic Theses & Dissertations

Title: Shock and vibration in the rail environment : trailor-on-flat car and container-in-well car
Creator: Goodwin, Daniel Lee
Date: 1988
Collection: Electronic Theses & Dissertations

Title: Relationship among motor skill development, aerobic capacity, body composition, and perceived competence of fourth grade school children
Creator: Kelly, Sheila Kathleen
Date: 2010
Collection: Electronic Theses & Dissertations

Title: Applied econometric studies in air quality and education
Creator: Khawand, Christopher
Date: 2016
Collection: Electronic Theses & Dissertations
Description: "This dissertation is comprised of three standalone chapters loosely organized around a causal inference theme. It addresses empirical questions in environmental quality and education, while also offering some methodological insight in each chapter." -- Abstract.

Title: Precision measurements in 20f beta decay
Creator: Hughes, Maximilian Nathan
Date: 2019
Collection: Electronic Theses & Dissertations
Description: The beta decay of 20F is an attractive low-energy probe for new physics. A parameter in beta decay highly sensitive to interactions beyond the standard model is the Fierz term. Since 20F is a Gamow-Teller decay, the Fierz term corresponds to tensor couplings in weak interactions. A beta spectrum shape measurement was done to measure the Fierz term in 20F. The analysis is not yet completed but a preliminary result is presented here. The current value of the Fierz term obtained is 0:0021 0...
Show moreThe beta decay of 20F is an attractive low-energy probe for new physics. A parameter in beta decay highly sensitive to interactions beyond the standard model is the Fierz term. Since 20F is a Gamow-Teller decay, the Fierz term corresponds to tensor couplings in weak interactions. A beta spectrum shape measurement was done to measure the Fierz term in 20F. The analysis is not yet completed but a preliminary result is presented here. The current value of the Fierz term obtained is 0:0021 0:0051stat 0:0084sys.In addition to the shape measurement, a half-life measurement was done. Previous measurements were inconsistent. The half-life was measured as 11:0011 0:0069stat 0:0030sys s. This is the most precise measurement of the half-life of 20F, and is 17 standard deviations away from the previously adopted value. This result has been conrmed by an additional measurement from another group using a dierent technique.
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Title: A time to forget : circadian and cognitive costs of nocturnal activity for a diurnal brain
Creator: Martin-Fairey, Carmel Annette
Date: 2014
Collection: Electronic Theses & Dissertations
Description: A TIME TO FORGET: CIRCADIAN AND COGNITIVE COSTS OF NOCTURNAL ACTIVITY FOR A DIURNAL BRAIN.ByCarmel Annette Martin-FaireyEntrainment of circadian rhythms to the day-night cycle serves to maintain appropriate relationships between behavioral and physiological processes and the external environment. In today's 24hour society, the newly attained capability to be active around the clock has challenged the body's ability to maintain entrainment to the day-night cycle. Humans, who are chronically...
Show moreA TIME TO FORGET: CIRCADIAN AND COGNITIVE COSTS OF NOCTURNAL ACTIVITY FOR A DIURNAL BRAIN.ByCarmel Annette Martin-FaireyEntrainment of circadian rhythms to the day-night cycle serves to maintain appropriate relationships between behavioral and physiological processes and the external environment. In today's 24hour society, the newly attained capability to be active around the clock has challenged the body's ability to maintain entrainment to the day-night cycle. Humans, who are chronically active at night, have a higher risk for physiological and psychological pathologies, including a reduction in cognitive abilities. Investigations to improve our understanding of the neural underpinnings of the pathologies associated with nocturnal activity in humans have been stunted by the lack of a diurnal animal model and by the use of forced-activity paradigms. The experiments in this dissertation address these issues with the use of a diurnal mammalian model, the grass rat (Arvicanthis niloticus), that has the propensity to shift voluntarily its activity to match that of a nocturnal mammal.In the first set of experiments, the adoption of a nocturnal profile by grass rats resulted in a phase reversal of the rhythmic expression of clock genes in the hypothalamic paraventricular nucleus, but with no disruption of the nocturnal rise in plasma melatonin levels. These differences in the phase of clock gene expression, but not in the nocturnal rise in melatonin, indicate that nocturnal activity in a diurnal species is disruptive of some rhythmic processes, while others appear insensitive to such disruptions. In the second set of experiments, the Morris water maze (MWM) was used to investigate the optimal phase of retention for a hippocampal dependent task in sedentary diurnal grass rats. The rhythmic expression of plasticity gene products in areas important for learning and memory was also monitored. The optimal phase for long-term retention of a hippocampal task was found to be out of phase with that of the nocturnal lab rat. No time-of-testing effects were found for the acquisition curve or for short-term retention of the task, as previously reported for nocturnal lab rats. Plasticity gene product rhythms showed peak expression during the light phase in grass rats, while peak expression for nocturnal lab rats has been reported to occur in the dark phase. In the third set of experiments, the night-active grass rat was utilized as a model for understanding the cognitive deficits associated with nocturnal activity in humans. While the overall learning curve for the MWM did not show time-of-training or chronotype differences, the night active grass rat exhibited dramatic deficits in both short-and long-term retention. There was a chronotype difference in the phase of the rhythm of hippocampal expression of only one of two plasticity gene products. In the hippocampus cFOS expression was affected by chronotype only in the CA1. These observations indicate that nocturnal activity disrupts the circadian regulation of key hippocampal functions. Thus, circadian desynchrony in the hippocampus may be responsible for the cognitive deficits seen in humans who choose to be active at night. Taken together the present work links voluntary activity during the rest phase in a diurnal species to physiological and cognitive pathologies, and argues against the claim that mammalian chronotype is a completely malleable trait of the circadian system.
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Title: Landscape carbon measurement in systems of trees outside of forests : the case of agroforestry systems in rural savannas of Senegal
Creator: Dieng, Moussa
Date: 2015
Collection: Electronic Theses & Dissertations
Description: Monitoring forest cover changes and carbon content at regional and global level by using remote sensing has advanced significantly for closed humid tropical forests, and several methods have been developed. On the other hand monitoring of cover and carbon for semi-arid savannas and woodlands has been under-studied, and more methods are needed. Further, for systems of Trees Outside of Forests in semi-arid regions, monitoring of cover and carbon has not advanced at all, and new methods are...
Show moreMonitoring forest cover changes and carbon content at regional and global level by using remote sensing has advanced significantly for closed humid tropical forests, and several methods have been developed. On the other hand monitoring of cover and carbon for semi-arid savannas and woodlands has been under-studied, and more methods are needed. Further, for systems of Trees Outside of Forests in semi-arid regions, monitoring of cover and carbon has not advanced at all, and new methods are needed. In this dissertation, I developed methods for remote sensing-assisted carbon measurement and monitoring in semi-arid landscapes of Trees Outside of Forests (TOF) which include:- Plantation and Agroforestry systems- Other trees on farms: planted trees- Other trees on farms: remnant savanna trees In this study, remote sensing satellite techniques were used to estimate carbon at a landscape level in savanna systems. Remote sensing tree crown projection area (CPA) was used as a proxy to predict tree diameter at breast height (DBH). A relationship was established between remote sensing based crown projection area (CPA) and the field-based DBH. Both simple linear and non-linear regression analysis were applied to the Sokone and Karang sites in Senegal. The linear function presents a higher coefficient of determination (R2) in both sites with respectively R2= 0.71 and R2= 0.79 for Sokone and Karang sites. The non-linear model shows R-squared values ranged between 0.61 and 0.77 for Sokone and Karang sites respectively. The regression equations derived from the relationship between remote sensing-based crown projection area (CPA) and the field-based DBH are used to predict the DBH of all trees within the study area knowing their crown projection area from remote sensing. A general allometric equation that uses DBH as a parameter to calculate biomass and carbon per tree was used in this study. My findings show that:(1) A model that uses remote-sensing assisted landscape-scale carbon stock measurement has promise;(2) The relationship between CPA detected from remote sensing and allometric scaling is something that can be refined but seems to be a workable approach and these refinements would include an improved relationship model using non-linear relationships, developing a local allometric equation using destructive sampling, and specific parameters for the savanna or tree type/species and explore the use of automated detection. This study's findings will be useful for the Senegalese government and others with savanna systems. With 1,043,000 ha of savanna systems and trees outside of forests (TOF), my findings could be an important step for integrating TOF into the natural resource management scheme for carbon stock estimation and the reduction of greenhouse gas emissions in the forestry sector. The use of remote sensing will lower the costs of field sampling based methods in highly patchy woodland and TOF landscapes and increase the opportunity for small holders and communities of small holders to be engaged in carbon mitigation projects. My findings show that, with a minimum training, they will be able to do the tree measurements in their own farms.
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Title: Investigating blood flow and antibiotic dosing using traditional microfluidics and novel 3D printed devices
Creator: Meisel, Jayda Erkal
Date: 2015
Collection: Electronic Theses & Dissertations
Description: Over the last 25 years, it has been established that the red blood cell (RBC) is a major determinant in blood flow, which it can modulate through release of adenosine triphosphate (ATP). Although RBCs store intracellular ATP in mM concentrations, measurements indicate that the cells release nM concentrations when stimulated by deformation, hypoxia (lowered oxygen tension), or incubation with pharmacological stimuli such as hydroxyurea (HU), which is the only approved drug for treatment of...
Show moreOver the last 25 years, it has been established that the red blood cell (RBC) is a major determinant in blood flow, which it can modulate through release of adenosine triphosphate (ATP). Although RBCs store intracellular ATP in mM concentrations, measurements indicate that the cells release nM concentrations when stimulated by deformation, hypoxia (lowered oxygen tension), or incubation with pharmacological stimuli such as hydroxyurea (HU), which is the only approved drug for treatment of sickle cell disease. Upon release, RBC-derived ATP can induce vessel dilation via activation of endothelial cell nitric oxide synthase (eNOS) to produce nitric oxide (NO). To probe the fate of increased ATP release from human RBCs incubated with the drug hydroxyurea, a traditional soft polymer platform was utilized to facilitate measurement of cell-to-cell communication between RBCs and a cultured endothelium. This device contained an array of micron-scale channels through which RBC samples were pumped. The sample flow was separated from a detection well by a porous polycarbonate membrane. Stimulated ATP released from the RBCs diffused across the membrane to the detection wells and was measured using the luciferin-luciferase chemiluminescence assay, integrated with a plate reader for detection. RBCs incubated with 100 uM of HU released on average 2.06 ± 0.37 times more ATP relative to the control sample. Through the use of various inhibitors, this increase in ATP release was subsequently demonstrated to depend on RBC deformability, RBC NOS activity, and the cystic fibrosis transmembrane conductance regulator protein (CFTR). The fate of the measured RBC-derived ATP was also investigated by probing ATP signalling to an adjacent cultured endothelium.ATP release from RBCs increases in response to hypoxia, or lowered oxygen tension; however, the dependence of RBC ATP release on oxygen tension has not been investigated. To enable measurement of RBC ATP release and oxygen tension in a flowing stream of RBCs, a 3D printed device was designed to accomodate commercial transwell inserts for ATP measurements, as well as threaded Clark-type electrodes for amperometric oxygen measurements. The device consisted of a channel 2 mm wide and 0.5 mm in height with two ports for analyte detection and one threaded port for an electrode. The Clark-type electrode was fabricated from gold and silver wires secured into a finger tight fitting. Oxygen standards and RBC samples were prepared using air and argon purged buffers. Using the 3D printed device, RBC ATP release and oxygen tension were measured simultaneously from prepared RBC samples. Relative to controls, RBC ATP release increased significantly in response to systematically lowered oxygen tension with a maximum increase of 2.38 ± 0.43 fold more ATP when exposed to 5.35 ± 0.12 ppm oxygen. ATP release saturated, i.e., was not significantly different, at lower oxygen tensions. This increase in ATP release was inhibited by incubating RBCs with the cell stiffening agent, diamide. The dependence of hypoxic RBC ATP release on the conformation of heme in hemoglobin (Hb) is demonstrated by converting measured oxygen tensions to Hb saturation.The 3D printed platforms presented herein were also utilized as in vitro tools to model pharmacokinetic dosing profiles, specifically with applications for studying antibiotic resistance. The World Health Organization, Centers for Disease Control, and the White House have issued reports that outline strategies to combat antibiotic resistance. The Spence lab has developed a 3D printed device to mimic in vivo drug dosing profiles on an in vitro platform for applications in drug discovery. This 3D printed diffusion-based dynamic dosing device mimics the dosing capabilities of the hollow fiber chamber reactor (HFCR). The in vitro 3D printed device contains 6 ports to house commercial polyester transwell membrane inserts (0.4 micron) and in house fabricated 0.2 micron pore size inserts (polyester), which can be loaded with a sample of Escherichia coli. Chemically competent, kanamycin resistant E. coli were dosed with the DNA gyrase and topoisomerase IV inhibitor levofloxacin, which reached a maximum concentration (Cmax) of 21.0 ± 5.7 uM (0.4 micron pore size) and 68.0 ± 7.1 uM (0.2 micron pore size) of levofloxacin in approximately 1 hour. After dosing, the viability of the bacteria samples was measured using standard plating methods.
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Title: Placement of phasor measurement units : optimization approaches and applications
Creator: Almasabi, Saleh
Date: 2019
Collection: Electronic Theses & Dissertations
Description: "Phasor measurement units (PMUs) provide measurements with high precision at a high resolution (up to 50 samples per second). These measurements are synchronized and time-stamped using the Global Positioning System. Despite these advantages, the industry has been slow in adopting PMU technology due to the high cost of installing PMUs. Therefore, PMU locations must be judiciously selected through optimal placement of PMUs (OPP), which enables the minimization of installation cost. This...
Show more"Phasor measurement units (PMUs) provide measurements with high precision at a high resolution (up to 50 samples per second). These measurements are synchronized and time-stamped using the Global Positioning System. Despite these advantages, the industry has been slow in adopting PMU technology due to the high cost of installing PMUs. Therefore, PMU locations must be judiciously selected through optimal placement of PMUs (OPP), which enables the minimization of installation cost. This dissertation examines the OPP problem from several perspectives. First, the OPP problem definition is re-examined since most OPP literature associates the PMU installation cost with the PMU unit. Most techniques in the literature have proposed to minimize the number of PMUs while considering the complete observability of the system. However, PMUs require sufficient infrastructure to be in place before they can perform most of their intended functions. Therefore, the OPP problem should be reformulated to include the supporting infrastructure of PMUs. The proposed OPP formulation is implemented by using a bi-level framework. This framework can accommodate different varieties of OPP, such as single-stage, multistage, and application-based approaches. Moreover, the proposed framework achieves the optimal solution with the maximum observability in the case of multiple optima. Second, this dissertation examines application-based OPP approaches, where specific technical benefits are prioritized over the cost of the OPP. Three applications are proposed. The first application is a fault-tolerance based OPP approach, where the network fault-tolerance is enhanced by deploying PMUs to the vulnerable elements in the network. In the second application, a voltage stability criterion is developed and proposed, where the critical buses are identified and prioritized for PMU allocation. The third application addresses false data injection attacks (FDIAs), where the system topology is used by the adversary to bypass the bad data detection of state estimators. The proposed OPP approach enhances bad data detection against FDIAs by utilizing the PMUs as authenticators for each other."--Pages ii-iii.
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Title: Understanding observed sea lamprey marking rates of lake trout in the Great Lakes
Creator: Adams, Jean V.
Date: 2020
Collection: Electronic Theses & Dissertations
Description: Sea lampreys (Petromyzon marinus), native to the north Atlantic Ocean, invaded the Laurentian Great Lakes in the early 1900s. By the mid-1900s native lake trout (Salvelinus namaycush) populations, that once supported commercial harvests of millions of pounds, were decimated, due in part to the sea lamprey invasion. In response to this decimation, a treaty was struck between Canada and the United States in 1954, creating the Great Lakes Fishery Commission (Commission), whose job it is to...
Show moreSea lampreys (Petromyzon marinus), native to the north Atlantic Ocean, invaded the Laurentian Great Lakes in the early 1900s. By the mid-1900s native lake trout (Salvelinus namaycush) populations, that once supported commercial harvests of millions of pounds, were decimated, due in part to the sea lamprey invasion. In response to this decimation, a treaty was struck between Canada and the United States in 1954, creating the Great Lakes Fishery Commission (Commission), whose job it is to control sea lampreys. The Commission implemented a control program that greatly reduced Great Lakes sea lamprey populations. Control continues on an annual basis; when control is relaxed, sea lampreys bounce right back, setting back fishery and ecosystem recovery by decades. Fishery managers and the Commission prioritize monitoring sea lamprey populations, to keep them in check, and to tailor and prioritize spending according to fishery needs on each lake. Annual indices of lake trout abundance, sea lamprey abundance, and sea lamprey-induced marking rates on lake trout are used to monitor success of past efforts and direct future efforts of sea lamprey control. A mark (or wound) on a host fish is an indication that a sea lamprey has attached to and potentially fed on host fish. Marking rates on lake trout are presumed to be largely driven by abundances of sea lampreys and lake trout. Occasionally, marking rates increase when they are expected to decrease (or vice versa), leaving decision makers puzzled about the true status of sea lamprey control in the Great Lakes.I investigated three possible reasons for these occasional inconsistencies in the status metrics: measurement error in each metric, survivor bias in marking rates, and alternative hosts. Inclusion of measurement error alone did not reproduce observed inconsistency rates, implying that a simple predator-prey model (a Type II functional response) lacked some important components. With survivor bias, the sea lamprey attack rate and sea lamprey-induced mortality rate were well indexed by Type A (piercing) marking rates if annual lethality rates were relatively constant. Other studies have demonstrated evidence of a relatively constant lethality rate, so survival bias is likely not a major contributor to observed inconsistencies. In Lake Ontario, sea lampreys exhibited a strong preference for lake trout, but switched to Chinook salmon when relative abundance of lake trout was low. Host switching impedes using a marking rate focused only on lake trout as an index of sea lamprey attacks. I also developed stock-recruitment relations for sea lampreys. I used a lake-specific adult-to-adult stock recruitment model to quantify how lampricide treatment effort reduced sea lamprey recruitment.This work eliminates measurement error as a primary cause of observed inconsistencies in sea lamprey status metrics and diminishes concern about survivor bias in Type A marking rates. Although I demonstrated that the presence of alternative hosts can affect sea lamprey-induced marking rates on lake trout, further research into this and other mechanisms contributing to variability in the status metrics is needed.
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Title: Microbial succession on the lake sturgeon egg surface : mechanisms shaping the microbial community assembly during succession and the effect of microbial successional processes on host life history traits
Creator: Fujimoto, Masanori
Date: 2012
Collection: Electronic Theses & Dissertations
Description: Microbial community assemblages have been studied in a variety of hosts and environments. However, to date, most of the studies conducted on microbial community structure have been observational in nature. As a result, the underlying mechanisms shaping microbial community assembly at a given place and time remain largely unknown. In this study, we were particularly interested in understanding how a microbial community develops on animal hosts. As soon as eggs or neonatal organisms are exposed...
Show moreMicrobial community assemblages have been studied in a variety of hosts and environments. However, to date, most of the studies conducted on microbial community structure have been observational in nature. As a result, the underlying mechanisms shaping microbial community assembly at a given place and time remain largely unknown. In this study, we were particularly interested in understanding how a microbial community develops on animal hosts. As soon as eggs or neonatal organisms are exposed to environments, microbes colonize surfaces of eggs or the epithelium of host tissues and establish a microbial community. Such a process involving initial colonization and subsequent sequential changes in species composition is called "succession". Microbial succession is a complex process with the number of different factors involved including initial stochastic arrival of microbes at an open space via dispersal, attachment / colonization at the space, subsequent community sorting via adaptation, and continuous dispersal from neighboring spaces. In this study, we examined microbial succession on the egg surface of the Lake Sturgeon, a threatened fish species inhabiting in the Great Lakes. We sought to understand the role of both host factors (e.g. innate immunity, egg chemistry) and various environmental factors (e.g. aquatic microbes, stream flow rate and temperature) in influencing the formation of microbial communities on the egg surfaces over the course of the egg incubation period. We also sought to evaluate the effect of different microbial successional processes on host life history traits, including egg mortality and larval size at hatch. These topics were important for this system because dams constructed in the Lake Sturgeon's spawning streams can alter environmental factors such as aquatic microbes, stream flow rate, and temperature, which may in turn affect the life history of the sturgeon. To achieve these objectives, we adopted an integrative approach, which relied on manipulation of environmental factors including aquatic microbial community, aquatic microbial quantity, stream flow rate, and temperature. We also employed a combination of various analytical techniques, including 16S rRNA gene pyrosequencing, 16S rRNA based T-RFLP, 16S rRNA clone library, 16S rRNA based quantitative PCR, light and fluorescence microscopy, and culture methods. We found that egg microbial communities were distinct from source water microbial communities. Host eggs shaped egg-associated microbial communities within 60 minutes of fertilization, selecting for and against certain microbial species. In addition, the egg surface microbial communities were not constant but rather dynamic, as we observed directional changes of microbial communities along with egg developmental stages. Egg-associated microbial communities also varied with the environmental variables they were exposed to during incubation, including temperature, flow rate, and aquatic microbial community. These differences in the egg-associated microbial community composition affected host life history traits including egg mortality and larvae size at hatch. We also identified a key set of microbial species that significantly improved egg survival and could be used for probiotic treatment in this threatened fish species in the future. This study was the first microbial succession study conducted on fish eggs. Our results highlight the complexity of host-microbe-environment interactions. This study has implications for managing threatened host populations such as the Lake Sturgeon inhabiting human-altered rivers, since it demonstrates the potential effect of dams (which alter aquatic microbes and temperature) on downstream host-microbe interactions.
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Title: A new method for the visualization and measurement of ultrasonic fields
Creator: Bennett, Grant S.
Date: 1952
Collection: Electronic Theses & Dissertations

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