Browsing by Subject "Selenium"
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Item Advances in gamma-ray spectroscopy : compton suppression and gamma-gamma coincidence(2011-05) Horne, Steven Michael; Landsberger, Sheldon; Biegalski, StevenThis project aims to improve research in gamma-ray spectroscopy by using advanced detector systems. These systems are designed to reduce interference inherent in gamma-ray spectroscopy by rejecting Compton scattering events from high-energy gamma-rays, as well as look at cascading decays of gamma-rays through gamma-gamma coincidence counting. By combining these methods, one is able to lower detection limits for many elements than would otherwise be possible. This work also takes advantage of neutron activation analysis, which allows stable elements to be analyzed by activating them with neutrons, causing them to become unstable and decay with radioactive signatures. By analyzing these signatures, one is able to detect trace levels of elements with relatively small samples sizes (< 1g) and in a nondestructive manner.Item An evaluation of the role of organic selenium in immune function in cattle.(Texas Tech University, 2008-05) Covey, Tanya L.; Galyean, Michael L.; Wester, David B.; Defoor, Paul J.; Albin, Robert C.Selenium (Se) plays a vital antioxidant role as a constituent of glutathione peroxidase (GSH-Px). Newly received feedlot cattle are exposed to multiple factors that can lead to oxidative stress, including viral infection. The objective of the research conducted for this dissertation was to evaluate the effects of different Se sources on immune function (Exp. 1) of calves challenged with infectious bovine rhinotracheitis virus (IBRV) and on health and performance in a field study (Exp. 2). In Exp. 1, 24 Holstein steers (BW = 148.2 ± 2.79 kg) were assigned randomly to treatments, including: 1) Control = no supplemental Se; 2) Sel-Plex = 1 mg/(steer•d) of Se from Se yeast (Sel-Plex; Alltech Inc., Nicholasville, KY); or 3) Selenite = 5 mg/(steer•d) of Se from sodium selenite. The Se sources were fed for 28 d before steers were intranasally inoculated with IBRV (d 0) and continued through 21 d after the challenge. Treatments did not affect body weight (P > 0.05) or feed intake (P > 0.30) before or after the challenge. Whole blood Se concentrations were greater (P < 0.01) when Sel-Plex was fed than with the other two groups, but GSH-Px activity (P > 0.20) was not affected by treatment. Supplemental Se tended (P = 0.08) to increase IBRV titer values on d -14 but to decrease (P = 0.06) titers on d 21. Steers fed Sel-Plex tended (P = 0.08) to have lower rectal temperatures for 18 h before the challenge than steers fed selenite, but there were no other differences (P > 0.10) in rectal temperature. Serum interleukin-1b concentrations were lower overall (P = 0.02) and tumor necrosis factor-á concentrations 12 h after the challenge were greater (P = 0.04) in steers fed Sel-Plex than in those fed Selenite. In Exp. 2, crossbred newly received heifers (4 pens/treatment) were fed the same treatments as in Exp. 1, except that Selenite supplied 1 mg/(heifer•d). No differences (P > 0.10) among treatments were noted for performance or health during the 28-d study. Additional research is needed to clarify how providing Se in the form of Sel-Plex affects immune response to viral infections in cattle.Item Assembly of colloidal nanocrystals into phospholipid structures and photothermal materials(2012-08) Rasch, Michael; Korgel, Brian Allan, 1969-There has been growing interest in developing colloidal metal and semiconductor nanocrystals as biomedical imaging contrast agents and therapeutics, since light excitation can cause the nanocrystals to fluoresce or heat up. Recent advances in synthetic chemistry produced fluorescent 2-4 nm diameter silicon and 1-2 nm diaemeter CuInSSe nanocrystals, as well as 16 nm diameter copper selenide (Cu₂₋[subscript x]Se) nanocrystals exhibiting strong absorbance of near infrared light suitable for biomedical applications. However, the syntheses yield nanocrystals that are stabilized by an adsorbed layer of hydrocarbons, making the nanocrystals hydrophobic and non-dispersible in aqueous solution. Encapsulating these nanocrystals in amphiphilic polymer micelles enables the nanocrystals to disperse in water. Subsequently, the Si nanocrystals were injected into tissue to demonstrate fluorescence imaging, the photothermal transduction efficiency of copper selenide nanocrystals was characterized in water, and the copper selenide nanocrystals were used enhance the photothermal destruction of cancer cells in vitro. The polymer-encapsulated copper selenide nanocrystals were found to have higher photothermal transduction efficiency than 140 nm diameter Au nanoshells, which have been widely investigated for photothermal therapy. Combining the optical properties of metal and semiconductor nanocrystals with the drug-carrying capability of lipid vesicles has received attention lately since it may create a nanomaterial capable of performing simultaneous drug delivery, optical contrast enhancement, and photo-induced therapy. Hydrophobic, dodecanethiol-coated Au nanocrystals were dispersed in water with phosphatidylcholine lipids and characterized using cryo transmission electron microscopy. 1.8 nm diameter Au nanocrystals completely load the bilayer of unsaturated lipid vesicles when the vesicles contain residual chloroform, and without chloroform the nanocrystals do not incorporate into the vesicle bilayer. 1.8 nm Au nanocrystals dispersed in water with saturated lipids to form lipid-coated nanocrystal agglomerates, which sometimes adhered to vesicles, and the shape of the agglomerates varied from linear nanocrystal chains, to flat sheets, to spherical clusters as the lipid fatty acid length was increased from 12 to 18 carbons. Including squalene formed lipid-stabilized emulsion droplets which were fully loaded with the Au nanocrystals. Results with 4.1 nm Au and 2-3 nm diameter Si nanocrystals were similar, but these nanocrystals could not completely load the bilayers of unsaturated lipids.Item Automated test input generation and test execution for websites(2015-12) Nagarajan, Sarvesh Velore; Khurshid, Sarfraz; Barber, SuzanneThis report presents a framework for automating test input generation, test execution and validation of websites. The framework leverages popular libraries available for the Java language to perform functions such as interacting with a website, parsing the content of a webpage and writing unit tests. Formal methods for software verification are incorporated using Java Pathfinder (JPF), a model checker built using Java. A working prototype of this framework has been created and tested on a sample website built as part of the work presented in this report. The framework presented in this report can provide full round-trip coverage of user interactions with a website validating website front-end as well as backend execution paths. How this testing framework can be run as part of a continuous integration solution is also presented in this report and has been prototyped. The framework presented in this report can be applied to a variety of real-world websites that involve user interaction.Item Bioavailability of selenium from different meat assessed in selenium-deficient rats(Texas Tech University, 1995-05) Wen, Hong YuanNot availableItem Biological availability of selenium from sodium selenite, monoselenodiacetic acid, selenomethionine, and selenium yeast for glutathione peroxidase(Texas Tech University, 1980-05) Wang, Cheng ShengNot availableItem Cytotoxicity of Selenocyanobiotin Against MDA-MB-231 Breast Cancer Cells(2008-12) Tsai, I-Huei; Spallholz, Julian E.; Roman-Shriver, Carmen; Boylan, Lee M.Numerous selenium compounds have demonstrated their ability to act as a chemotherapeutic agent through their pro-oxidative activity in cancer therapy in vitro. However, one major problem in cancer therapy is tumor drug specificity. Previous studies have shown that the membrane bound folate receptors (FR) and biotin receptors (BR) are over expressed in numerous cancer cells but not in normal cells. The present study was aimed to determine whether a selenium-biotin conjugate can be internalized via a BR-overexpressing human breast cancer cell line, MDA-MB-231. It was observed that MDA-MB-231 cells treated with 1, 5, 10, and 20 µM of selenocyanobiotin (SeCN-biotin) after 24-, 72-, and 120-hour treatment resulted in inhibition of cell proliferation and cell death as determined by the [methyl-tritium] DNA thymidine incorporation assay. The experimental results provide support for the hypothesis that SeCN-biotin could penetrate into BR-over-expressing cancer cells and inhibit DNA synthesis in a time- and dose-dependent manner in vitro.Item Effect of selenium, riboflavin, and vitamin E on oxygen radical production and cytotoxic activity of peritoneal macrophages of Balb/c mice(Texas Tech University, 1994-05) Kang, ChunranIn nutrition science, we learn that many foods that are healthful in reasonable portions can also lead to ill health when eaten in excess. One can eat too much of almost anything. For example, vitamin A as retinol, when consumed in excess, has toxic effects, however, this vitamin is also clearly an essential nutrient for vision (Olson, 1984). When we realize that water is the most essential of the nutrients, since we cannot survive much longer than three days without it, then consider that without oxygen human beings will live less than a few minutes. However, at any level of dietary supplementation meeting essential requirements, oxygen is both toxic and carcinogenic. In this context oxygen demonstrates major toxicity and carcinogenicity at the same levels which are required for support of life. Oxygen toxicity can cause many cellular dysfunctions, including deactivation of essential enzymes by oxidation, with primary effect on the oxidation of cysteine thiols producing disulfides. It also involve effects of cellular mediators and secretions (Huber and Drath, 1981), and lipid peroxidation (Allen et al., 1973). The toxicity of lipid peroxides by disruption of the cellular membrane is the primary mediators of oxygen toxicity. Therefore, the basic schemata for lipid peroxidation functions as follows.Item Effect of vitamin E supplementation on plasma lipids and oxidized low-density lipoprotein in hypercholesterolemic rats(Texas Tech University, 1997-08) Shankar, PadminiCoronary artery disease is the leading cause of death in the United States. A major risk factor for atherosclerosis is elevated levels of semm cholesterol, particularly lowdensity lipoprotein (LDL) cholesterol in the blood. It has become increasingly evident that LDL must undergo oxidative modification before giving rise to foam cells, one of the earliest stages in the development of atherosclerosis. Micronutrient antioxidants can protect LDL from oxidation and can thus delay or prevent the development of fatty streaks in the arterial wall. The purpose of the present study was to determine the effect of graded doses of vitamin E and selenium on plasma total cholesterol, high-density lipoprotein (HDL) cholesterol, triglycerides and oxidized LDL cholesterol in rats fed control and cholesterol/cholic acid (l%)/0.3%)) enriched diets for five months. Eighty-two female Fischer rats were randomly assigned to seven treatment groups and fed experimental diets containing vitamin E supplementation ranging from 60 mg/kg basal diet (adequate level) to 2400 mg (high level). Six groups of rats were given adequate levels of selenium (0.2 mg/kg diet) and one group was given excess (4,0 mg/kg) selenium. At the end of the study period there was progressive weight gain in all the animals, but the vitamin E deficient group and the selenium excess group consistently showed lower weight gain compared to other treatment groups. Plasma lipids were elevated in all the treatment groups fed cholesterol. A positive association between HDL levels and increasing levels of vitamin E supplementation was noted. The liver weights of animals fed cholesterol were higher than that of the control group. Determination of total plasma oxidation based on malondialdehyde (MDA) formation showed that there was decreased formation of MDA at high levels of vitamin E supplementation. There was a positive association between increasing amoimts of dietary vitamin E supplementation and plasma a-tocopherol levels with the highest concentration found in the treatment group fed the highest amount of vitamin E. The oxidation kinetics of LDL based on the thiobarbituric acid reacting substances assay and conjugated diene assay revealed that the treatment group fed high levels of vitamin E had prolonged lag phase of oxidation compared to the other treatment groups. High levels of vitamin E supplementation did not produce any adverse effects in the rats.Item EVALUATION AND INHIBITION OF BIOFILM ATTACHMENT TO MEMBRANE SURFACES IN WATER AND WASTEWATER TREATMENT SYSTEMS(2010-12) Low, Darryl; Morse, Audra; Hamood, Abdul N.; Reid, Ted W.; Song, LianfaAs engineers’ understanding of the biological treatment systems in water and wastewater systems increased, advanced technologies have emerged. These included combining biological systems with other treatment systems such as membrane technologies. The overall objective of this research was to evaluate the impacts of bacterial attachment to membranes during treatment operations and propose an antimicrobial coating to maximize membrane performance. Membranes from a small scale, membrane aerated biological unit were removed and analyzed for continued performance after an extended operational period. Afterwards, a selenium based antimicrobial coating was developed to prevent microbial attachment without harming membrane performance. This coating was applied to reverse osmosis membranes and the coating’s efficacy to prevent biofilm growth on the reverse osmosis membrane surface was investigated. Ultimately, the selenium coating displayed a strong inhibition against bacterial attachment and biofilm formation. Selenium’s capability to catalytically generate superoxide molecules was effective in damaging bacterial cell membranes resulting in lysis. Both Gram positive (S. aureus) and Gram negative (E. coli) bacteria showed high susceptibility to the superoxide attack. Attachment utilizing the selenocystamine molecule via peptide bond to a modified membrane surface was selected as the desired attachment method. Selenocystamine allowed for the RO membrane to maintain its higj permeate flux without overly diminishing membrane rejection. Attachment of selenium to membrane surfaces may be a valuable technology to allow for continuous performance even in the harsh operating conditions present in biological reactors.Item Mechanism of the reaction of thiols with selenite(Texas Tech University, 1980-05) Pan, Shu-tehAlthough selenium has now been shown to be required entirely apart from its interaction with vitamin E, the action of its prevention of deficiency diseases in animals is very intimately connected with that of vitamin E. Studies have indicated that vitamin E may be carried by a seleno-lipoprotein fraction associated with serum y-globulin. Thus one biological role of selenium appears to lie in a selenium-containing compound which acts as a carrier of vitamin E and which may function in the absorption, retention and prevention of destruction of d-ct-tocopherol, and perhaps in its transfer across cell membranes, thereby enhancing its biological activity in the blood and perhaps in the cells throughout the body.Item Mechanisms involved in selenium toxicity and modulation of NK cell function by selenium compounds(Texas Tech University, 1998-05) Davis, Randall L.The trace element selenium (Se) was first found to be toxic in 1934 in livestock that consumed native vegetation grown in seleniferous soils of the western United States (Franke, 1934). In 1957, Schwarz and Foltz confirmed that Se was an essential nutrient for laboratory rats and over the next decade it was identified as an essential nutrient for other mammalian species (Oldfield, 1981). Since this time, Se has been confirmed as an intregal component of several enzymes and other biologically important proteins(Wendel, 1992) as well as essential for optimal immune function (Turner and Finch, 1991). Se has also been noted as possessing cancer chemopreventive activity (Schrauzer, 1992; Patterson and Levander, 1997). The cytotoxic activity of Se has been demonstrated in vitro in several tumor cell models including mouse leukemic L1210 cells (Lu et al., 1994), HT29 human colonic carcinoma cells (Stewart et al., 1997) aind human mammary tumor cells (Yan et al., 1991). Additionally, Se supplementation has been shown to reduce tumor incidence in animal models (El-Bayoumy, 1991) and in human clinical trials (Clark et al, 1996). It has been suggested that the mechanisms involved in Se toxicity and the cancer chemopreventive activity of Se are related (Spallholz, 1994). However, the mechanisms involved have yet to be elucidated. There are a substantial amount of data that suggest that Se toxicity and the cancer chemopreventive activity of Se are both the result of the interactions between Se with thiols (Painter, 1941; Ganther, 1968). The cancer chemopreventive activity of Se has also been linked to the ability of Se supplementation to modulate immunocompetence, in particular the enhancement of natural killer (NK) cell function (Schrauzer, 1992).Item New selenium antimicrobials and material coating against bacteria and bacterial biofilms(Texas Tech University, 2008-05) Tran, Phat; Fralick, Joe A.; Reid, Ted W.; Hamood, Abdul N.; Spallholz, Julian E.; Kennedy, Ronald C.; Birney, David M.This Dissertation discusses the development of covalent selenium containing antimicrobials which targets a bacterium and the development of a cellulose bandage material that contains selenium and blocks biofilm formation. Both the antimicrobials and the cellulose bandage employ the redox property of selenium that produces O2• − (superoxide). Phase I: Selenium containing antimicrobials Purpose: To produce selenium labeled peptides and phage that can selectively bind to the surface of the pathogenic bacteria Yersinia pestis and inactivate it through the generation of superoxide radicals on its surface. Results: 1. Specific phage and peptides for a given bacterium can be obtained from peptide displayed phage library. 2. Selenium was covalently attached phage and peptides that target a specific site on a bacterial without affecting their binding ability. 3. These selenium labeled phage and peptides at micromolar concentration killed targeted bacteria that are resistant to the phage and peptides without selenium, at 10 ìM concentration. 4. These selenium labeled phage and peptides do not kill non-targeted bacteria. These results suggest a novel approach for the development of an antibacterial agent that can target a specific bacterial pathogen for destruction. Phase 2: Selenium containing antimicrobial bandage Purpose: To develop a selenium-based antimicrobial coating for cellulose materials that will prevent bacterial attachment and colonization, that could lead to bacterial biofilm formation and related infections. Results: 1. Selenium can be covalently attached to cellulose. 2. Di-(Se-AAEMA) coated cellulose, at 0.1% and 0.2% selenium concentrations, completely inhibited Staphylococcus aureus and Pseudomonas aeruginosa biofilm formation respectively. After soaking in Phosphate Buffered Saline for a week, these selenium labeled cellulose discs still retained their antibacterial activity. A toxicology study on these same discs showed no indication of toxicity as exhibited by mammalian cell cultures exposed to the soaking solutions of 0.2% and 0.1% selenium coated cellulose discs. Moreover, selenium treated discs reduced already established P. aeruginosa biofilms. In contrast to the parent strain, colony biofilms formed by a P. aeruginosa sodA (a superoxide dismutase) mutant was significantly reduced at 0.05% selenium indicating that the effect depends on oxygen radicals. This study demonstrates the ability to produce a new wound dressing using selenium that resists biofilm formation.Item Pilot-Scale Demonstration of hZVI Process for Treating Flue Gas Desulfurization Wastewater at Plant Wansley, Carrollton, GA(2011-12-06) Peddi, Phani 1987-The hybrid Zero Valent Iron (hZVI) process is a novel chemical treatment platform that has shown great potential in our previous bench-scale tests for removing selenium, mercury and other pollutants from Flue Gas Desulfurization (FGD) wastewater. This integrated treatment system employs new iron chemistry to create highly reactive mixture of Fe^0, iron oxides (FeOx) and various forms of Fe (II) for the chemical transformation and mineralization of various heavy metals in water. To further evaluate and develop the hZVI technology, a pilot-scale demonstration had been conducted to continuously treat 1-2 gpm of the FGD wastewater for five months at Plant Wansley, a coal-fired power plant of Georgia Power. This demonstrated that the scaled-up system was capable of reducing the total selenium (of which most was selenate) in the FGD wastewater from over 2500 ppb to below 10 ppb and total mercury from over 100 ppb to below 0.01 ppb. This hZVI system reduced other toxic metals like Arsenic (III and V), Chromium (VI), Cadmium (II), Lead (II) and Copper (II) from ppm level to ppb level in a very short reaction time. The chemical consumption was estimated to be approximately 0.2-0.4 kg of ZVI per 1 m^3 of FGD water treated, which suggested the process economics could be very competitive. The success of the pilot test shows that the system is scalable for commercial application. The operational experience and knowledge gained from this field test could provide guidance to further improvement of technology for full scale applications. The hZVI technology can be commercialized to provide a cost-effective and reliable solution to the FGD wastewater and other metal-contaminated waste streams in various industries. This technology has the potential to help industries meet the most stringent environmental regulations for heavy metals and nutrients in wastewater treatment.Item Regulation and Function of Apoer2 and Vidlr in the Central Nervous and Reproductive Systems(2009-06-15) Bowen, Irene Masiulis; Herz, JoachimThe LDL receptor gene family is an evolutionarily ancient family of membrane spanning proteins composed of a diverse collection of receptors that share common domains and mediate a variety of organismal functions. Members of this family, Apoer2 and Vldlr, are highly similar receptors and are both involved in the Reelin signaling pathway. This pathway controls neuronal migration and organization of the brain during development as well as synaptic function in adulthood. Although both receptors partially compensate for one another during Reelin signaling, the generation of knockin mutant animals has allowed us to begin to uncover the unique and independent functions of these receptors that have not yet been explored. For example, a single amino acid mutation in Vldlr determines binding of the Pafah1b complex to the cytoplasmic tail of the receptor. Mice expressing this L838R mutation were created using ES cell homologous recombination techniques and will be useful in exploring the effects of the mutation in brain development and synaptic function in vivo. Vldlr independent functions that are unique to Apoer2 have been explored in more depth. These include binding of scaffolding proteins PSD95 and JIPs to an alternatively spliced exon within the cytoplasmic tail of Apoer2, which is not found in any other LDLR family member. This exon has been shown to mediate increased LTP induction after Reelin stimulation. Apoer2 knockin animals, expressing splice variants lacking another alternatively spliced exon encoding the O-linked sugar domain, show receptor stabilization through the inhibition of Apoer2 proteolytic processing. This causes increased Apoer2 levels in both the brain and testis. While lack of exon 16 has no known consequences in the testis, it does cause disrupted synaptic transmission and defective LTP induction after reelin stimulation in the brain. Apoer2 was recently found to be involved in selenium uptake into the testis and brain. Through the use of various Apoer2 intracellular domain mutant mice, a differentiation was made between the Apoer2 functional domains involved in cell signaling and the function of the receptor in selenium endocytosis. Further use of the aforementioned knockin mouse lines will help uncover previously unexplored functions of Vldlr and Apoer2 and advance our understanding of their potential involvement in neurological diseases such as Alzheimer's disease.Item Removal of Selenium from Wastewater using ZVI and Hybrid ZVI/Iron Oxide Process(2012-12-20) Yang, ZhenSelenium (Se), often in form of selenocyanate (SeCN-), which present in some of refinery process wastewater known as stripped sour water. As Se discharge is increasingly regulated, the industry struggles to find a cost-effective technology for SeCN- treatment. Zero-valent iron (ZVI) technology, with some successes in remediating toxic-metal contaminated groundwater remediation, emerges as a potential solution for addressing SeCN- problem. In this study, bench scale tests were conducted to investigate the removal of SeCN- from wastewater with ZVI. The removal efficiency was evaluated by a series of tests under different conditions such as initial pH, various ions, ZVI particle size, dissolved oxygen (DO) and iron oxide. Results showed that SeCN- was effectively removed from wastewater with ZVI and Fe(II) filings when the water pH was controlled at approximately 6 with sufficient DO. The further evaluate of treating SeCN- using hybrid zero valet iron (hZVI) system has also been conducted in this study. The hZVI system process is a novel chemical treatment that has shown valuable potential for removing several heavy metals from wastewater. This study concluded that at bench scale, the removal efficiency of SeCN- in the wastewater is over 99% with 2-steps of hZVI reactors and a HRT of 12 hours. In essence, this study concluded that ZVI is a highly valuable potential cost-effective treatment for SeCN- removal from wastewater and the results from bench scale hZVI system can be effectively used to scale up the system to serve the industrial needs in the future.Item Rising selenium levels at Truscott Brine Lake, Truscott, Texas: hazardous or harmless to the avian community?(Texas Tech University, 1999-08) Wrinkle, Lisa G.Selenium (Se) occurs naturally as a trace element in most soils and rock and is an essential micronutrient that is important in several biological processes. However, excess amounts of selenium can be toxic, especially to wildlife. Selenium toxicity in animals results from drinking water or consuming plants or animals in places where contaminated water has entered the food chain. Biomagnification of selenium in the aquatic food chain can dramatically increase the dietary concentrations of the element available to fish and birds that consume aquatic organisms. Consequently, a small increase in waterbome selenium will yield a disproportionately large increase in selenium levels offish and wildlife. Concentrations of selenium in water may not be toxic, but biomagnification may cause toxicity in higher trophic levels.Item Sorption of Arsenic, Mercury, Selenium onto Nanostructured Adsorbent Media and Stabilization via Surface Reactions(2011-02-22) Han, Dong SukThe overall goal of this study is to evaluate the ability of novel nanostructured adsorbent media (NTAs, iron sulfides (FeS2 and FeS)) to remove arsenic, selenium and mercury from ash and scrubber pond effluents. The NTAs aim to enhance arsenic removal from solution compared to conventional adsorbents. The iron sulfides are expected to produce stable residuals for ultimate disposal after removing As, Se and Hg from solution, so that removal of these compounds from wastewaters will not result in contamination of soils and groundwaters. Methods for reliably and economically producing these materials were developed. The synthesized NTAs and iron sulfides were characterized by surface analysis techniques such as XRD, FT-IR, SEM-EDS, TEM, XPS, AFM and N2-adsorption. These analyses indicated that Ti(25)-SBA-15 has highly ordered hexagonal mesopores, MT has interparticle mesopores, pyrite (FeS2) forms crystalline, nonporous rectangular nanoparticles (<500 nm), and mackinawite (FeS) forms amorphous, nonporous nanoparticles (<100 nm). Kinetic and equilibrium tests for As(III, V) removal were conducted with NTAs over a range of pH (4, 7, 9.5). The rates of arsenic uptake were very fast and followed a bi-phasic sorption pattern, where sorption was fast for the first 10 minutes, and then slowed and was almost completed within 200 minutes. Distinct sorption maxima for As(III) removal were observed between pH 7 and pH 9.5 for MT and between pH 4 and pH 7 for Ti(25)-SBA-15. The amount of As(V) adsorbed generally decreased as pH increased. In addition, a surface complexation model (SCM) based on the diffuse layer model (DLM) was used to predict arsenic adsorption envelopes by NTAs under various environmental conditions. The SCM for As(III, V) adsorption by NTAs demonstrated the role of mono- and bidentate surface complexes in arsenic adsorption. A batch reactor system was employed in an anaerobic chamber to conduct experiments to characterize both the removal of As, Se, Hg from solution and their subsequent reactions with iron sulfides. Experiment variables for removal experiments included: contaminant valence state (As(V), As(III), Se(VI), Se(IV), Hg(II)); adsorbent/reactant type (FeS, FeS2); adsorbent/reactant concentration; pH (7, 8, 9, 10); and competing ion (SO42-) concentration (0, 1, 10 mM). Experimental variables for reaction experiments were reaction time (up to 30 days) at pH 8 and oxidation states of contaminants. In addition, the stability of iron sulfides (FeS2, FeS) combined with target compounds was investigated by measuring the ability of the target compounds to resist release to the aqueous phase after removal. These experiments showed that iron sulfides were good adsorbent/reactants for target contaminants in spite of the presence of sulfate. This was particularly true at intermediate concentrations of target compounds. The experiments also demonstrated that iron sulfides interacted with target contaminants in such a way to improve their resistance to being released back to solution as pH was changed. Therefore, this study demonstrates the ability of novel nanostructured adsorbent media to remove arsenic, selenium and mercury from ash and scrubber pond effluents and the ability of iron sulfides to produce residuals that are stable when disposed in landfills.Item Studies of trialkylphosphine-carbon disulfide adducts and chalcogenide phosphorus cages(Texas Tech University, 1989-05) Ettel, Mary L.Item The amelioration of arsenic toxicity in Fischer 344 rats supplemented with selenite in the diet(Texas Tech University, 2002-08) Henderson, Lora SuzannePrior to the early 1970s, the people in rural areas of Bangladesh and West Bengal, India, where sanitary drinking water is scarce, had no ahemative to drinking severely polluted surface water (Henry 1990). During the 1970s, United Nations Intemational Children's Fund (UNICEF) fimded the digging of tube wells, which were to supply clean drinking water to the people from underground sources (Guha Mazumder 1998). In 1993, 10-20 years after the first wells were dug, people began developing unusual symptoms: hyperpigmentation of the skin on unexposed areas of the body, thickening of the pahns of the hands and soles of the feet, skin lesions (both malignant and benign), and ahered hver, nerve, gastrointestinal, and/or lung fiinction (Guha Mazumder 1998). These symptoms are all characteristic of chronic arsenic (As) toxicity. Testing water samples from the tube wells determined the water contained levels of As from less than 3 ppb, which is virtuaUy arsenic free, to over 1000 ppm (Chowdhury 2000), well above the tolerable hmits set by World Heahh Organization (WHO) (50 ppb) (Smith 2000). It has been estimated that 120 milhon people in Bangladesh and West Bengal have been exposed to unsafe levels (greater than or equal to 50 ppb) of As as a result of obtaining it in the drinking water from these wells (Chowdhury 2000). Attempting to alleviate the situation, WHO has ftinded many research projects (Anstiss 2001), mcluding those designed to remove As from the water, cheaply and effectively, as well as projects aimed at counteracting As toxicity in vivo. In the past, research has shown that As may amehorate selenium (Se) toxicity (Levander 1966b); As may act synergistically with Se (Obermeyer 1971); or Se may counteract As toxicity (Babich 1989). The objective of this study was to determine if Se counteracts As toxicity in rats. The first phase of research was designed to detennine two effects: the tolerable upper limit (TUL) of As as 50% arsenite/ 50% arsenate in Fischer 344 rats and the effects of dietary Se supplementation on As toxicity. Fourteen groups of 6 rats were given 0, 25, 50, 100, 150, 175, or 200 ppm As in the water and 0.2 or lOppm Se in the food. After evaluating the data from the first phase, a second phase was conducted to determine a level of Se suitable for amehorating As toxicity in rats at the TUL (50 ppm). Nine groups of 6 rats were given 0 or 50 ppm As in the drinking water and either 0, 0.2, 1.25, 2.5, or 5ppm Se in their food. The Se deficient diet (0 ppm Se) was introduced to mimic a potential Se deficient diet in Bangladesh or West Bengal (J. SpaUholz, personal communication, March 27, 2002). This study provides insight into the effects of Se supplementation on As toxicity, as well as demonstrates the TUL of As in rats. Once analyzed and summarized, the results of this study will be beneficial to those conducting ftirther research in As toxicity.