Woody plants are encroaching into a karst savanna on the Edwards Plateau in central Texas, but their impact on hydrology is unclear because of high variability in soil depth and uncertainties about shallow and deep root contributions to water uptake, and water dynamics in rocky soil. The overall objectives of this study are to quantify contributions of shallow and deep roots to water uptake, and to quantify the impact of rock on soil hydraulic properties and water storage. A study was conducted in a karst savanna with ~50% woody cover to monitor spatial and temporal variations in soil moisture and root water uptake with neutron probe and time-domain reflectometry measurements. Bulk density was measured using gamma densitometry. Measurements were made to a depth of 1.6 m in a 25 m  25 m grid (5 m node spacing). The results showed that rock created high spatial variability in water storage. Water storage capacity in the measurement grid ranged from 185 to 401 mm, and coupled with heterogeneous distribution of trees led to high spatial variability in root water uptake. Most of the water uptake came from the upper 1 m of the soil profile, but 10% came from below 1.6 m. This indicated that roots had access to water stored within the bedrock, possibly in soil pockets. Statistical analysis showed that spatial distribution of θ was significantly correlated with rock distribution in the profile. Laboratory evaporation measurements showed that Small volume fractions of rock can increase evaporation from soils by slowing upward movement of water, thereby maintaining capillary connectivity to the surface for a longer period of time. Two simulation models, van Genuchten (VG) and Durner, were compared with the data from evaporation experiments. Results showed that the Durner model was more appropriate than the VG model for describing water retention and hydraulic conductivity of rocky soils.

<p>Selective serotonin re-uptake inhibitors (SSRIs) are a new class of antidepressants used mainly for the treatment of depression and other forms of related disorders. There are a number of side effects associated with these drugs which include loss of weight, sexual dysfunction, nervousness and nausea. A fast and reliable detection method such as biosensing for the determination of the SSRIs metabolic profile is therefore essential for the appropriate dosing of these drugs. Biosensors for the determination of the SSRIs biotransformation were prepared with cytochrome P450 (2D6) isoenzyme and poly (anilinonapthalene sulfonic acid) film electrochemically deposited on gold.</p>

Magister Scientiae - MSc / Selective serotonin re-uptake inhibitors (SSRIs) are a new class of antidepressants used mainly for the treatment of depression and other forms of related disorders. There are a number of side effects associated with these drugs which include loss of weight, sexual dysfunction, nervousness and nausea. A fast and reliable detection method such as biosensing for the determination of the SSRIs metabolic profile is therefore essential for the appropriate dosing of these drugs. Biosensors for the determination of the SSRIs biotransformation were prepared with cytochrome P450 (2D6) isoenzyme and poly (anilinonapthalene sulfonic acid) film electrochemically deposited on gold. / South Africa

Master of Science / Department of Agronomy / Dorivar A. Ruiz Diaz Suarez / An effective nutrient management plan is essential for optimum wheat (Triticum aestivum) yields. The objectives of the first study were to: i.) evaluate changes in concentration of nitrogen (N), phosphorus (P), potassium (K), sulfur (S), copper (Cu), manganese (Mn), and zinc (Zn), within separate plant parts, throughout the growing season, ii.) evaluate the uptake pattern and redistribution of each of these nutrients within the plant throughout the season, and iii.) evaluate the impact of micronutrient and S fertilization on concentration and uptake of nutrients and the potential use of fertilization for biofortification. Three locations were established and sampled every 7 to 10 days during the spring. Samples were divided into leaf, stem, head, spike and grain fractions and analyzed for nutrient concentration. Concentration levels tended to decrease throughout the season in non-grain plant fractions and stay relatively constant in the grain. Harvest grain concentration of Zn was significantly higher with micronutrient fertilization at all locations, suggesting the possibility of Zn biofortification through fertilization. S, Cu, and Zn showed nutrient accumulation increases in all plant fractions until the time period around anthesis (Feekes 10.5.1), at which point leaf and stem fractions decreased in total accumulation while nutrients were remobilized to the grain. N, P, K and Mn showed a similar trend although timing of remobilization varied between locations and treatments. The objectives of the second study were to i.) evaluate the interaction of wheat grazing management and soil and fertilizer N requirements with emphasis on dual purpose wheat, ii.) assess the use of NDVI sensors for N management and forage quantity assessment in wheat grazing systems, and iii.) evaluate forage quality and quantity interactions with N management. Three locations were established and fertilized with N application rates of 0, 34, 67, and 101 kg ha⁻¹ in the fall, followed by simulated grazing. Spring topdress applications were made at rates of 0 and 90 kg ha⁻¹, or a sensor based rate. The impact of grazing on grain production varied by location. NDVI readings correlated with biomass at two of three locations and N recommendations using NDVI sensors resulted in significantly lower N rates and similar yield results to high N application rates. Forage dry matter and N concentration increased with higher N rates.

The increasingly stringent environmental regulations worldwide demand the use of efficient methods for air purification. Moreover, the alarming effect of greenhouse gases on the world climate requires the removal and sequestration of large quantities of anthropogenic carbon dioxide (CO2). This work is contributed towards the development of efficient, amine-containing, lamellar structured silica adsorbents for CO2 removal. Seven different materials were prepared by impregnation of various amounts of PEI, over as synthesized, or partially extracted or calcined lamellar silica. Materials were characterized by powder XRD and SEM. CO2 adsorption capacity was measured by thermogravimetry. The effects of PEI loading, temperature, CO2 partial pressure and surface alkyl chains were investigated. PEI seems to be dispersed better in a consistent surface alkyl chain network, leading to enhanced CO2 uptake. VB-13, the material with 50 wt% of PEI, recorded the highest CO2 uptake at 75 °C, in the presence of both 15% CO2/N2 and 100% CO2 with values of 3.02 and 3.50 mmol/g respectively. The optimum temperature for CO2 uptake was found to be 75 °C for samples with high PEI loading. Moreover, higher uptake was recorded in the presence of 100% CO2 versus 15% CO2/N2 for all temperatures. Another objective of this study was to investigate the effect of humidity on the CO2 adsorption process. In that case use of the column-breakthrough technique coupled with mass spectrometry to discriminate between CO2 and water was considered. Complete understanding of the technique and the different effects of moisture on CO2 adsorption over amine-containing materials, namely promotion of CO2 uptake and stabilization of the adsorbent, were achieved, based on a thorough scrutiny of the literature. Nonetheless, because of the Covid-19 pandemic and several technical issues, some experiments could not be undertaken.

Dithiocarbamate-mediated nickel(II) uptake was studied in five cell lines: 1) cultured human B-lymphoblasts, 2) rabbit alveolar macrophages, 3) human peripheral lymphocytes, 4) human erythrocytes and 5) human polymorphonuclear leukocytes. Two different incubation protocols were employed: concurrent incubation of nickel(II) with the ligand, and sequential incubation of ligand followed by nickel(II) incubation. The effects of various experimental parameters such as ligand concentration, cell number and available nickel(II) concentration on nickel (II) uptake were examined for most of the above cell types. During concurrent incubations, the effect of ligand concentration on nickel (II) was maximum at 10⁻⁶ M sodium diethyldithiocarbamate (DDC) or ammonium pyrrolidinedithiocarbamate (APDC) for all cell types (except polymorphonuclear leukocytes). Enhanced uptake was evident at higher concentrations (≥ 10⁻³ M DDC or APDC) for sequential incubations. By contrast, ammonium dithiocarbamate (AD) had no enhancing effect on nickel(II) uptake in either protocol (tested only for human peripheral lymphocytes and human erythrocytes). Distribution studies indicated that enhanced cytosolic uptake of nickel(II) occurred for 10⁻⁷ - 10⁻⁵ M DDC. The observed effects on nickel (II) uptake of ligand concentration, Ni² concenration and cell number were interpreted on the basis of an 'Equilibrium Model' with several possible pathways. The nickel(II) uptake data were consistent with the possibility that ligand uptake precedes metal-ion uptake. The latter process may well involve the protonated form of the dithiocarbamate as an ionophore. As a means of enhancing cell-associated nickel(II), peripheral lymphocytes from nickel-sensitized and non-sensitized individuals were pretreated with APDC in veronal buffer. The transforming ability of these cells were then studied by use of a lymphocyte transformation (proliferation) test. This approach was not successful in enhancing the response to nickel (II) because of the inherent toxicities of the veronal buffer and APDC. / Thesis / Master of Science (MS)

Interactions of engineered nanomaterials (ENMs) with environmental interfaces have become a critical aspect of environmental health and safety evaluations. Carbon fullerene (C₆₀) has emerged at the forefront of nanoscale research and applications due to its unique properties. Although there are concerns associated with the harmful effects of fullerene towards living organisms, the mechanisms of fullerene toxicity are still under debate. A first step toward assessing these mechanisms requires evaluation of the bio-accumulation and bio-uptake of fullerene through lipid membranes which serve as biological barriers in cells. In this dissertation, partitioning of fullerene between water and lipid membranes and cellular uptake of fullerene were investigated to assess bioavailability of this nanoparticle. Traditional methods to estimate the equilibrium partitioning of molecular level chemicals between water and lipid membranes (K[subscript lipw]) cannot be applied to measure K[subscript lipw] of nanoparticles due to the large size of nanoparticle aggregates. In this study, we developed an in vitro method to estimate K[subscript lipw] of fullerene using solid supported lipid membranes (SSLMs) with various membrane compositions. K[subscript lipw] of fullerene increased with increasing acyl chain length and K[subscript lipw] values were higher after creating phase separation in ternary lipid membranes compared to pre-phase separation. In addition, the partitioning values (K[subscript lipw]) were found to depend on the lipid head charges. These results suggest that the lipid membrane composition can be a critical factor for assessing bioaccumulation of fullerene. Evaluation of the partitioning thermodynamics of fullerene demonstrated that the partitioning mechanism of fullerene is different from that of molecular level chemicals. It is generally acknowledged that molecular level chemicals partition into the hydrophobic center of lipid membranes (i.e., absorption), however, the partitioning mechanism of fullerene is a combination of adsorption on the lipid membrane surface and absorption. Caco-2 cellular uptake of fullerene nanoparticles was investigated using an in vitro method developed in this study to distinguish between active and passive transport across cell membranes. Energy dependent endocytosis is hypothesized to be the main cellular transport mechanism based on an observed temperature dependence of cellular uptake and evidence for saturation of the active sites of transport during cellular uptake of fullerene. Metabolic inhibitors decreased the mass of fullerene taken up by the cells, which supports an active transport mechanism of fullerene through the cell membranes. To evaluate bioavilability of fullerene under environmentally relevant conditions, the effects of humic acid and fetal bovine serum (FBS) on the lipid accumulation and cellular uptake were also investigated. Humic acid and FBS changed the surface characteristics of fullerene. The presence of FBS significantly decreased lipid accumulation of fullerene presumably due to higher steric hinderance of FBS coated fullerene as well as the changes in surface energy, water solubility, and lipid solubility of charged FBS coated fullerene relative to that of bare fullerene. Both humic acid and FBS also effectively lowered the cellular uptake of fullerene. These results imply that natural organic matter and biomolecules in natural aquatic and biological environments have significant effects on the bioavilability of fullerene nanoparticles / text

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