The complex interactions at the interfaces of minerals, microbes, and metals drive the cycling of iron and the fate and transport of metal(loid)s in contaminated systems. The former uranium mine near Ronneburg, Germany is one such system, where slightly acidic mine drainage crossing a steep redox gradient (groundwater outflow into a stream) forms and transforms iron (oxy)hydroxide nanoparticles. These particles interact with toxic metal(loid)s in water and sediments. Iron oxidizing and reducing bacteria also play a role in these processes. Biogeochemical reactions are influenced by nanoscale properties, and thus it is critical to probe environmental samples with appropriate techniques such as analytical transmission electron microscopy (TEM). This dissertation presents two studies on the iron (oxy)hydroxide mineral nanoparticles found in the Ronneburg mine drainage system. The first study uses TEM in conjunction with bulk analytical techniques to demonstrate the complexity of iron (oxy)hydroxide transformations at the steep redox gradient, and the partitioning of metal(loid)s within those mineral phases. An important result was the identification of Zn-bearing green rust platelets in the anoxic outflow water. Green rust minerals have only been identified in nature a handful of times, and we believe this work to be only the second to examine naturally occurring green rust using high resolution TEM (HR-TEM). Downstream of the outflow, aggregates of poorly crystalline iron oxide spheroids co-precipitated with amorphous silica formed and settled to the stream bed, where they aged to form nanoparticulate goethite and sequestered metals such as As and Zn. However, significant concentrations of Zn and Ni remained in the dissolved/nano (< 0.1 um) water fraction and continued downstream. The second study demonstrates that natural green rust nanoparticles and their synthetic analogs can be complex polycrystalline phases composed of crystallites only a few nanometers in size, and often include nano-regions of amorphous material. In addition to the typical pseudo-hexagonal platelet morphology, green rust nanorods were synthesized, which has not previously been reported. This work has important implications for the reactivity of green rust with biogeochemical interfaces in natural, anthropogenic, and industrial systems. A third study, presented in the appendix, characterizes the bacterial community at the Ronneburg mine drainage site and highlights iron oxidizers such as Gallionella sp., in particular those that form stalks of iron oxide nanoparticles. These biogenic stalks also contribute to the uptake of metal contaminants in water and sediments. The science of iron cycling is complex. It requires field-based exploration to enrich the contributions made by experimental, laboratory and modeling studies. This dissertation adds another chapter in the search for filling in missing pieces of this interconnected system. / Ph. D.

Heterogeneous reactions between mineral dust aerosols and gas phase volatile organic compounds have the potential to impact important atmospheric chemical processes. However, little is known about the uptake and reactivity of volatile organic compounds on particulates found in the environment. A Knudsen cell was designed and constructed for providing precise measurement of reaction probabilities within these systems. The instrument was validated through a series of experiments. After validating the Knudsen cell against several key benchmarks, the instrument was used to measure the uptake coefficient for ethanol on particulate silicon dioxide. The uptake coefficient of ethanol on silicon dioxide, a common compound in mineral dust aerosols, was determined to be 7 x 10-7. Therefore, uptake of ethanol on silicon dioxide would be competitive with the loss of other volatile organic compounds on silicon dioxide, which show similar rates of uptake. The Knudsen cell was validated and measured the uptake of ethanol on silicon dioxide, and future work with the Knudsen cell will study the uptake of chemical warfare agent simulants on metal oxides. / Master of Science

Understanding how nitrifiers react when exposed to low DO conditions could provide a greater understanding of low DO operations in full-scale biological wastewater treatment. Previous methods to observe nitrifier oxygen kinetics do exist in literature, however they are inefficient and labor intensive. Other more efficient methods require the use of selective inhibitors, which alter the characteristics of the biomass. This study developed a time and labor efficient respirometric method to distinctly measure oxygen half-saturation coefficients for both ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) without the use of selective inhibitors. By eliminating the use of inhibitory substances, representative biomass characteristics were maintained throughout the tests. The developed method, called the declining DO method, consisted of using a high-speed dissolved oxygen (DO) probe to measure relative oxygen uptake rates (OUR) within a batch reactor when varying substrates (ammonia and nitrite) were present in excess within the system. A forward model was developed based on Monod kinetics to simultaneously fit Monod curves to the experimental OUR data. These curves were fit by solving for optimum oxygen kinetic parameters representing endogenous respiration, NOB, and AOB. An inverse model using Markov chain Monte Carlo analysis was applied to the results found in the forward model to provide statistical validation of the proposed respirometric method. A separate method, called the substrate utilization rate test, was conducted in parallel with the declining DO tests to compare and verify oxygen half-saturation coefficient results. Parallel tests were conducted using biomass samples from three different Hampton Roads Sanitation District (HRSD) full-scale facilities. Operating conditions between the three HRSD facilities were considered when performing parallel testing, including averages for DO, solids retention time (SRT), and floc size. Average floc size was found to have a significant effect on the observed oxygen half-saturation values. Observed trends for the KO values estimated using the two methods remained consistent throughout all tests, where KO,NOB was always lower than KO,AOB. The comparison of the two methods highlighted some faults associated with the substrate utilization rate test, which is commonly used in literature to observe nitrifier oxygen kinetics. The declining DO method appeared to be more resistant to potential experimental error and required less than half the time compared to the substrate utilization rate test. The development of the declining DO method without the use of selective inhibitors provided a more time and labor efficient technique for estimating apparent KO values for NOB and AOB without sacrificing biomass characteristics representative of the full-scale treatment process. Biomass samples collected from variable treatment process conditions yielded consistent parallel test results, providing further evidence that the proposed declining DO method can be a robust and reliable technique for distinctly measuring apparent oxygen half-saturation values for NOB and AOB. / Master of Science / Wastewater treatment operations utilizing biological nitrogen removal (BNR) require a continuous supply of oxygen for aerobic processes. Energy costs associated with aeration generally accounts for at least 50% of the total energy consumption at conventional activated sludge wastewater treatment facilities. Operating aerobic zones at low average dissolved oxygen (DO) concentrations could be an effective way to significantly reduce aeration costs as well as material costs associated with BNR treatment processes. This study developed a method to measure oxygen kinetics for the two groups of autotrophic bacteria responsible for performing nitrogen removal. The method consisted of measuring relative oxygen uptake rates (OUR) within a batch reactor when varying substrates were available. This method is unique from previously developed techniques in that the use of selective inhibitors was not included, meaning the characteristics of the wastewater were largely unchanged and therefore better represent biomass conditions within the full-scale process. The results of the proposed method were verified using an alternate method for estimating oxygen kinetics. These two methods were conducted in parallel using biomass samples from several full-scale Hampton Roads Sanitation District wastewater treatment facilities utilizing a variety of process designs and operating conditions. Consistent results obtained between the two methods suggested the proposed method is an effective technique for distinctly measuring nitrifier oxygen kinetics.

The excessive use of fossil fuels, industrialization, and growing populations have increased environmental pollution, global warming, and global energy demands (Dimitriadis & Bezergianni, 2017). Due to these problems, a new alternative energy source must be used. Biomass conversion to liquid transportation fuels is a major category of renewable energy, with various waste biomasses as leading candidates (Dimitriadis & Bezergianni, 2017). Multiple thermo-chemical conversion (TCC) technologies exist to convert biomass into fuels with one of the most promising methods being hydrothermal liquefaction (HTL). The main benefit of HTL is that it does not require that the biomass be dried before processing which would be a fuel- and cost-intensive process (Grande et al., 2021; SundarRajan et al., 2021). However, HTL produces toxic solid, gaseous, and aqueous byproducts. The hydrothermal liquefaction aqueous-phase byproduct (HTL-AP) is thought to be the factor limiting commercial viability of the HTL process, particularly because some of the constituents have inhibitory effects on nitrifying bacteria (Macêdo et al., 2023). There are existing treatment technologies for HTL-AP such as anaerobic digestion, wet air oxidation (WAO), and more. The simplest treatment method at a wastewater treatment plant (WWTP) using HTL for sludge disposal would be to return the HTL-AP to the v headworks to be treated alongside standard wastewater flow (MBE, 2019). However, the inhibitory effects may cause the WWTP to not meet ammonia regulations, if relevant. In this project, four 3.5-L bench-scale aerated reactors were built to simulate conventional activated sludge wastewater treatment to develop methods to determine the long-term effects of HTL-AP on nitrification. Two reactors were controls fed only synthetic wastewater, and two reactors were fed synthetic wastewater with a small dilution of HTL-AP, called AP reactors. Two different doses of hydrothermal liquefaction aqueous phase (HTL-AP) were tested on long-operated activated sludge systems. A 275x dilution factor (DF) of HTL-AP was tested for 132 days and a 2750x DF was tested for 23 days. The weekly nitrogen data (total ammonia nitrogen, nitrate, and nitrite) suggested that both doses inhibited nitrification in the bench-scale activated sludge systems. Additionally, the nitrifying bacteria did not adapt over time to be able to nitrify the wastewater with HTL-AP. During the first experiment with a 275x DF, no nitrate was detected in the AP reactors (/L NO3 - -N) and nitrite was sparsely detected. The control reactors had low concentrations of nitrate of around 3-8 mg/L NO3 - -N and high concentrations of nitrite, typically around 10-40 mg/L NO2 - -N. Therefore, the AP reactors were performing minimal nitrification, if any, while the control reactors were primarily performing partial nitrification. Before implementing the 2750x DF of HTL-AP, all reactors were emptied, cleaned, and restarted with nitrifying mixed liquor from the San Luis Obispo Water Resource Recovery Facility membrane bioreactor (SLO WRRF MBR). By the end of the 23 days of HTL-AP exposure at a 2750x DF, the treatment reactors had a sharper nitrate decline with final NO3 - -N concentrations around 1 mg/L compared to about 5-7 mg/L vi NO3 - -N in the control reactors. At this time, nitrite concentrations were not considerable in any reactor. Because nitrification was not ideal even in the control reactors, future work is advised, including stabilizing the solids retention time and changing the synthetic wastewater formula to support higher concentrations of treatment bacteria. Some methods for the specific oxygen uptake rate (SOUR) test that are not explicitly or extensively outlined in ISO 8192 (ISO, 2007) were examined. First, a 10- minute trial duration was deemed sufficient compared to 20 minutes (R 2>0.99 in either case and Preliminary SOUR tests using the correct methods found that raw HTL-AP doses of 50x, 125x, and 250x dilution factors (DF’s) inhibited nitrification by about 80 to 105% in nitrifying sludge from the SLO WRRF MBR. Raw HTL-AP doses of 500x and 1000x DF’s did not inhibit nitrification respiration rates. From a SOUR test on this same sludge but on a different day, HTL-AP pretreated by wet air oxidation (WAO) had near-zero vii (neg. 0.9%) inhibition on nitrification respiration rates at a 250x DF compared to the 66% nitrification inhibition found in raw HTL-AP at this 250x DF on this testing date.

Yes / Introduction: Oral anticoagulant therapy choices for patients with atrial fibrillation (AF) expanded in the last decade with the introduction of direct oral anticoagulants (DOAC). However, the implementation of DOACs was slow and varied across different health economies in England. There is limited evidence on the patient role in the uptake of new medicines, including DOACs, apart from considering their demographic and clinical characteristics. Hence, this study aimed to address the gap by exploring the view of patients with AF on factors affecting DOAC use. Methods: A qualitative study using semi-structured interviews was conducted in three health economies in the North of England. Adult patients (>18 years) diagnosed with non-valvular AF, prescribed an oral anticoagulant (vitamin K antagonist or DOAC), and able to give written consent were recruited. Data were collected between August 2018 and April 2019. Audio recorded interviews were transcribed verbatim and analyzed using the framework method. Results: Four themes with eleven subthemes discussed identified factors affecting the use of DOACs. They were linked to limited healthcare financial and workforce resources, patient involvement in decision-making, patient knowledge about DOACs, safety concerns about oral anticoagulants, and oral anticoagulant therapy impact on patients' daily lives. Lack of a) opportunities to voice patient preferences and b) information on available therapy options resulted in some patients experiencing difficulties with the prescribed therapy. This was reported to cause negative impact on their daily lives, adherence, and overall satisfaction with the therapy. Conclusion: Greater patient involvement in decision-making could prevent and resolve difficulties encountered by some patients and potentially improve outcomes plus increase the uptake of DOACs. / Pharmacy Research UK (PRUK-2018-GA-1-KM) and Leeds Teaching Hospitals NHS Trust

A quantitative and descriptive type of study design was followed using structured self-administered questionnaires distributed among 84 conveniently selected male adolescent learners from Nanogang Community Junior Secondary School (NCJSS) in Gaborone. The purpose of this study was to describe factors that influence the uptake of safe male circumcision (SMC) as a human immune-deficiency virus (HIV) prevention strategy among male adolescent learners. The study findings show that protection from HIV and other sexually transmitted infections (STIs) was found to be the main reason for adolescent learners undergoing male circumcision (MC) (p<.01). Reasons such as maintenance of genital hygiene, culture, religion, and the enhancement of sexual pleasure were not found to be significant factors. Misconceptions such as the belief that girls do not like circumcised partners were found to be the main reason for adolescent learners not undergoing MC (p<.05). A number of factors which were claimed in previous studies to be obstacles for the uptake of MC, such as surgical complications, peer pressure, stigma, and discrimination, were not found to be major obstacles / Health Studies / M.A. (Public Health)

A quantitative and descriptive type of study design was followed using structured self-administered questionnaires distributed among 84 conveniently selected male adolescent learners from Nanogang Community Junior Secondary School (NCJSS) in Gaborone. The purpose of this study was to describe factors that influence the uptake of safe male circumcision (SMC) as a human immune-deficiency virus (HIV) prevention strategy among male adolescent learners. The study findings show that protection from HIV and other sexually transmitted infections (STIs) was found to be the main reason for adolescent learners undergoing male circumcision (MC) (p<.01). Reasons such as maintenance of genital hygiene, culture, religion, and the enhancement of sexual pleasure were not found to be significant factors. Misconceptions such as the belief that girls do not like circumcised partners were found to be the main reason for adolescent learners not undergoing MC (p<.05). A number of factors which were claimed in previous studies to be obstacles for the uptake of MC, such as surgical complications, peer pressure, stigma, and discrimination, were not found to be major obstacles / Health Studies / M.A. (Public Health)

This PhD research relates to the design, fabrication, characterization, and optimization of on-chip electrochemical microelectrode arrays (MEAs) for measurement of transient concentrations and gradients, focusing on fast transients and physiological applications. In particular, this work presents the determination of kinetic mechanisms taking place at an active interface (either physiological or non-physiological) in contact with a liquid phase using the MEA device to simultaneously estimate the concentration and gradient of the analyte of interest at the surface of the active interface. The design approach of the MEA device and the corresponding measurement methodology to acquire reliable concentration information is discussed. The ability of the MEA device to measure fast (i.e., in sub-second time scale) transient gradients is demonstrated experimentally using a controllable diffusion-reaction system which mimics the consumption of hydrogen peroxide by a 2D cell culture. The proposed MEA device and measurement methodology meet effectively most of the requirements for physiological applications and as a demonstration of this, two physiological applications are presented. In one application, the MEA device was tailored to measure the hydrogen peroxide uptake rate of human astrocytes and glioblastoma multiforme cells in 2D cell culture as a function of hydrogen peroxide concentration at the cell surface; the results allowed to quantitatively determine the uptake kinetics mechanisms which are well-described by linear and Michaelis-Menten expressions, in agreement with the literature. In the other application, further customization of the MEA device was realized to study the glucose uptake kinetics of human bronchial epithelial and small cell lung cancer cells, these latter with and without DDX5 gene knockdown; the results allowed to distinguish mechanistic differences in the glucose uptake kinetics among the three cell lines. These results were complemented with measurements of glycolytic and respiration rates to obtain a bigger picture of the glucose metabolism of the three cell lines. Finally, additional applications, both physiological and non-physiological, are proposed for the developed MEA device.

No description available.

Mesoporous materials constitute a promising class of nanomaterials for a number of applications due to their tunable pore structure. The synthesis of most mesoporous materials involves a surfactant liquid crystal structure to form the pores. As well as the many advantages associated with this method of synthesis, there are disadvantages such as high production costs and a substantial environmental impact which limit the possibilities for large scale production. Therefore there is a need for other synthesis routes. The aim of the work described herein was to contribute to this field by developing a synthesis route that does not rely on surfactants for pore formation. A mesoporous magnesium carbonate material was therefore formed by self-assemblage of the particles around carbon dioxide gas bubbles, which functioned as pore templates. It was also possible to vary the pore diameter between 3 and 20 nm. The biocompatibility of the formed magnesium carbonate material was evaluated in terms of in vitro cytotoxicity and hemocompatibility, in vivo skin irritation and acute systemic toxicity. The results from the in vitro cytotoxicity, in vivo skin irritation and acute systemic toxicity test using a polar extraction vehicle showed that the material was non-toxic. While signs of toxicity were observed in the acute systemic toxicity test using a non-polar solvent, this was attributed to injection of particles rather than toxic leachables. In the in vitro hemocompatibility test, no hemolytic activity was found with material concentrations of up to 1 mg/ml. It was further shown that the material had anticoagulant properties and induced moderate activation of the complement system. The anticoagulant properties were ascribed to uptake of Ca2+. Finally, the ability of the material to increase the dissolution rate of the poorly soluble drug itraconazole was analyzed.  Itraconazole was dissolved up to 23 times faster from the magnesium carbonate pores than when the free drug was used. The release rate from the delivery vehicle was dependent on the pore diameter. The work presented herein is expected to be useful for the development of alternative synthesis routes for mesoporous materials and also for encouraging the development of biomedical applications for these materials.