Thesis (M.S.)--Texas State University--San Marcos, 2008. / Vita. Includes bibliographical references (leaves 61-63). Also available on microfilm.

Thesis (M.S.)--Texas State University--San Marcos, 2009. / Vita. Appendices: leaves 38-39. Includes bibliographical references (leaves 40-41). Also available on microfilm.

Táto práca sa zameriava problematiku interakcie ibuprofénu s pôdnym systémom. Popísané sú jeho základné vlastnosti, správanie a faktory ovplyvňujúce toto správanie. Vo všeobecnosti najvplyvnejšími faktormi je prítomnosť pôdnej organickej hmoty v pôde a pH. Ibuprofén patrí do skupiny nesteroidných protizápalových liečiv. Patrí medzi ľahko dostupné a vysoko konzumované liečivá. Toto prispieva k jeho narastajúcemu transportu a kontaminácii životného prostredia. Jeho prítomnosť v životnom prostredí môže pôsobiť negatívne na živé organizmy. V experimentálnej časti bol preskúmaný vplyv pôdnej organickej hmoty a pH na sorpciu a desorpciu ibuprofénu. Použité boli tri pôdy získané z odlišných regiónov Českej republiky. V rámci procesu sorpcie a desorpcie boli použité koncentrácie v rozmedzí 1 až 10 mg/l. Vplyv pH na sorpciu a desorpciu bol preskúmaný použitím koncentrácie ibuprofénu 10 mg/l a Britton-Robinsonovho pufru s pH 3, 7 a 10. Detekcia ibuprofénu v jednotlivých vzorkách bola uskutočnená pomocou UV-VIS spektrometrie a kvapalinovej chromatografie s hmotnostne spektrometrickou detekciou.

In this dissertation I examine the properties and origins of the most energetic component of Mercury's atmosphere and how it couples to the planet's magnetosphere and space environment. Mercury' s atmosphere consists of particles liberated from its surface that follow ballistic, collisionless trajectories under the influence of gravity and solar radiation pressure. This tenuous atmosphere can be classified as an exosphere where the exobase boundary is the planet's surface. To explain how this exosphere is sustained, a number of theories have been presented: (1) thermal evaporation from the hot surface; (2) photo-desorption of surface materials by UV solar radiation; (3) sputtering by plasma surface interactions; and (4) vaporization of the surface by micro-meteorite impacts. Using a 3-dimensional numerical model, I determine the role each source has in populating the exosphere. New observations of Mercury's escaping atmosphere are presented using novel imaging techniques in which sodium acts as a tracer to identify atmospheric sources. I discuss the implications of these measurements for our understanding of the physical processes at work in the exosphere, and provide a foundation for modeling such processes. For the first time, this work quantifies the variability in the loss of Mercury's sodium as a seasonal effect. My observations show that atmospheric escape can, at times, exceed 10^24 Na atoms s^-1, nearly twice the highest rate previously reported. By forward modeling Mercury's atmospheric escape, I place new constraints on the source properties and eliminate the prevailing theory that the escaping tail is sputtered from the surface by solar wind ions. The MESSENGER spacecraft has recently discovered that sodium is distributed unevenly over the surface and that the magnetosphere is offset from the planet's center. Using the first model to include these effects, I demonstrate the magnetosphere's influence upon exospheric sources by simulating asymmetries observed in the escaping atmosphere. I conclude that the exosphere is sustained by a combination of micro-meteorite impact vaporization and photo-desorption that is locally enhanced by precipitating ions.

Adsorption and desorption of picloram (4-amino-3,5,6-trichloropicolinic acid) in soils was studied utilizing both batch technique and soil columns. The five soils from the states of Utah and California ranged from 0.6 to 18.7 percent in organic matter content, 5 to 21 percent in sesquioxides and 6.45 to 7.55 in pH. In batch studies, the factors affecting picloram adsorption-desorption included time, soil type, organic matter, herbicide concentration, temperature, pH, and inorganic electrolytes. The soils adsorbed 10.8 to 58.2 percent of the added picloram from 0.05 to 10,0 ppm of picloram aqueous solutions. Adsorption was highly correlated with organic matter (r • 0.99), pH (r •- 0.98), and aesquioxides content (r • 0.96) of the soils, Adsorption was significantly correlated with cation exchange capacity of the soils at the 0.05 level. Equilibration timo rongod from 4 to 120 hours. An incraaa in the temperature from 17.7 C to 25 C cauaad 1ncroaa•d adsorptin; raising the temperature further resulted in a decrease in adsorption. The adsorption followed the Freundlich model, but not the Langmuir, Tempkin, or B.E.T. models. Adsorption was inversely related to induced pH changes from pH 3.6 to pH 9.2. From 41.0 to 71.8 percent of the initially adsorbed picloram could be eluted with two successive extractions of deionized water from the three soils at 25 C. The desorption thereafter was slow. No evidence was found of picloram precipitation with the addition of inorganic electrolytes in aqueous solutions without soil. Divalent inorganic cations were , generally, more effective in increasing adsorption than monovalent cations. Studies of the effect of CaC12 concentrations (from 5 to 500 me/ 1) on picloram adsorption by four soils suggested an exchange type reaction, picloram acting as a cation. These interpretations were not conclusive. Column studies with two of the soils, at 1.0 and 10.0 ppm picloram concentrations and in the natural state as well as after calcium saturation, corrobated the findings of batch studies; inorganic salts did impede picloram movement in soils, presumably by increasing picloram adsorption. Applicability of a mathematical model, based on chromatographic theory, to predict picloram movement in two soils was tested. The model overestimated adsorption. However, when a lower retardation factor was used, the prediction was reasonable on the adsorption side of the herbicide distribution curve, but not the desorption side. This suggested that a distribution coefficient, based on its change with soil depth, may improve the predictability of the model.

No description available.

Scanning probe microscopy techniques were used to investigate the desorption of hydrogen passivated silicon to form SiO2 etch masks The application of the etch masks were planned on being used to manufacture silicon nanowires. Low concentration hydrofluoric acid was used to passivate the surface. The surface was selectively depassivated by SPM techniques. Scanning tunneling microscopy (STM) and atomic force microscopy (AFM) were used to create the masks. The STM system used was found to desorb hydrogen from the surface faster than the STM could image and was considered incapable in the configuration investigated. This led to the use of atomic force microscopy (AFM). Using a conductive tip in contact mode, lithography on the passivated surface was performed. The topography of the lithography was compared to similar works and found to be similar in size. The width was found to be 80nm and the thickness 1nm. The depassivated layers were confirmed to be oxide through electronic force microscopy (EFM). Finally, voltages were swept with the tip in contact with the surface to find the bandgap of the oxide. It was found that the voltage sweeps were severely modifying the tip along with producing inconsistent desorption thicknesses ranging from 0.2 to 12nm. Despite the results from the voltage sweeps, the lithography procedure performed using the AFM was found to be successful.

No description available.

No description available.

In the past, water treatment plants have stopped the application of pre-filter oxidants to create a bioactive filtration process to remove soluble Mn. After the cessation of pre-filter oxidants, a Mn desorption phenomenon was seen where effluent Mn exceeds influent Mn concentrations. The reason for the sudden increase in effluent Mn was not known, but it was hypothesized that Mn-reducing bacteria on the filter media play a substantial role in this phenomenon. The primary goal of this research was to assess the role of Mn-reducing microorganisms in the desorption of MnOx(s) from coated filters once pre-filtration chlorine ceased. A secondary objective included the development of a molecular detection method for Mn-reducing microorganisms in laboratory and environmental samples. Bench-scale filter column studies were completed to investigate the impacts of Mn-reducing microbial populations on desorption of Mn from MnOx(s) coatings. Secondarily, the effects of influent carbon loading and MnOx(s) age on Mn desorption were investigated. In situ vial assays were created to gain insight into the impacts of MnOx(s) age on Mn reducing microorganism bioavailability. Lastly, a qPCR detection method was developed that targeted the mtrB gene. Results determined that microbially mediated Mn desorption was possible when sufficient numbers of Mn-reducing microorganisms were present on the MnOx(s) surface and that those organisms contributed to the Mn desorption phenomenon. qPCR detection methods were able to show a greater number of Mn-reducing microorganisms in studies where Mn desorption was observed. Lastly, MnOx(s) age was shown to play an important, but unexplained, role in bioavailability. / Master of Science