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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: A stochastic multi-scale model of stream-groundwater interaction in strongly heterogeneous porous medium and its application in southern Branch County, Michigan
Creator: Xinyu, Ye
Date: 2014
Collection: Electronic Theses & Dissertations
Description: In this paper, stream depletion is assessed by the approach of multi-scale geostatistics in stressed watershed, South Branch County, Michigan. The watershed is currently under large water demand and representative of the general failure to pass the online Water Withdrawal Assessment Tool. Due to the heterogeneity of porous medium and the high variability of hydrogeological parameters and scale, there is a deviation between field observations and simulated groundwater flow in those areas. The...
Show moreIn this paper, stream depletion is assessed by the approach of multi-scale geostatistics in stressed watershed, South Branch County, Michigan. The watershed is currently under large water demand and representative of the general failure to pass the online Water Withdrawal Assessment Tool. Due to the heterogeneity of porous medium and the high variability of hydrogeological parameters and scale, there is a deviation between field observations and simulated groundwater flow in those areas. The approach of multi-scale geostatistics model based on detailed lithological data and its application in numerical groundwater simulation can be used in stream depletion assessment. Specifically, the multi-scale transition probability geostatistics approach, supplemented with a 10m Digital Elevation Model, allows for a more realistic integration of heterogeneous medium into the development of correlated spatial variability of hydrogeological parameters at each spatial scale. This approach enables accurate simulation of complex hydrogeology, including vertical shift structural variation and aquifer thickness variations. Systematic hydrology models at the regional, local and site scale allows for simulations of integrated water budget analysis. These simulations are necessary to evaluate the water depletions of targeted streams and the surrounded protected area. The hydrology system is calibrated with the steady state water levels from 732 monitoring wells.The stability of transition probability geostatistics model depends on the distributions, the heterogeneity of simulated area and other factors. The results show that transition probability geostatistics model provides a reasonable distribution of materials in aquifer medium, improving numerical groundwater modeling in assessing water depletion in streams and venerable area.
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