Browsing by Subject "Sodium"
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Item External sulfate attack of concrete : an accelerated test method, mechanisms, and mitigation techniques(2016-05) Aguayo Jr., Federico Macias; Folliard, Kevin J.; Thomas, Michael D.A.; Fowler, David; Juenger, Maria C.G.; Wheat, HarovelSulfate attack of concrete is perhaps the least understood of the major durability mechanisms plaguing reinforced concrete infrastructures. Many studies have attempted to better understand the underlying mechanisms in which the various modes of deterioration by sulfate attack manifest; however, several controversies still exist. Moreover, ASTM C 1012 (2012), which is the most commonly referred standardized laboratory test method to determine sulfate resistance of blended portland cement mixtures, does not always link well to field performance and may take up to 18 months to complete. The research program presented in this dissertation investigates various issues pertaining to the mechanisms, testing methods, and factors influencing external sulfate attack. The primary focus of this research study was to investigate and propose a reliable, and innovative accelerated test method to evaluate the sulfate performance using concrete specimens. The research program was divided into the following four key components: (1) design a method that can obtain results within a reasonable timeframe (less than six months); (2) design a method that uses concrete specimens and thus links more closely to field performance; (3) develop a better understanding on the role and mechanisms of sulfate attack on concrete through a comprehensive research program including field and laboratory investigations; and (4) investigate the use of calcium sulfate (gypsum) used as an additive to mitigate the potential of sulfate attack in blended portland cement mixtures using high-calcium fly ash. The findings in this dissertation led to the development of a potential accelerated test method for determining sulfate resistance by vacuum impregnating concrete (or mortar) samples with sulfate solution to accelerate the ingress and onset of chemical reactions between the hydrated cement paste and sulfate ion (SO42-). The effects of binder type, water-to-cementitious ratio (w/cm), curing regime, sulfate type and concentration are examined. In comparison to the conventional ASTM C 1012 method, results showed a higher rate of expansion with significant distress observed in samples subjected to the accelerated test method and placed in a 5% Na2SO4 solution. Similar trends, but at a relatively lower expansion rate, were also observed in samples placed in a 0.89% Na2SO4 solution. Physical measurements, chemical analysis and microstructural studies were performed periodically on the specimens.Item Formation of complexes of potassium and sodium cations with dicyclohexano-18-crown-6, dibenzo-18-crown-6 and cyclohexano-15-crown-5 over a temperature range of 2° to 38°C(Texas Tech University, 1980-08) Mehta, Bharatkumar G.The percent extraction of potassium and sodium ions from aqueous solution has been measured for DC18C6, DB18C6 and C15C5 dissolved in methylene chloride as a function of temperature. The percent extraction was found to decrease as the temperature increased. For the binary mixture of potassium and sodium ions, synergestic effects appeared. These synergestic effects become pronounced as the temperature increases Also distribution coefficients were measured and observed to follow the same behavior with temperature. Selectivity for DC18C6 and DB18C6 is higher at room temperature (25°-30°C) for potassium over sodium ions Initial concentrations were kept constant during the whole course of experiment, only the effects of ions, ring size, and ring structure were investigated.Item Plate Waste in Elementary-School Lunches: A Focus on Food Pairings, Shortfall Nutrients, Potatoes and Sodium(2014-12-08) Destefano, Megan KElementary-school students have been found to waste a large amount of food served to them at school while consuming items high in sodium. This has led to decreased intake of calories, and the shortfall nutrients, fiber, potassium and calcium. There are many potential solutions to this problem including appropriate pairing of entr?e and vegetable and providing items that are well accepted and naturally low in sodium. Plate waste studies were conducted to analyze waste, consumption, nutrient intake, and nutrient loss in elementary-school lunches based on the entr?e and vegetable selection. Pairing of the entr?e and vegetable was analyzed, as well as consumption of the different vegetable products and their associated intake of calories and three of the shortfall nutrients, fiber, potassium, and calcium. The research found that there is an association between entr?e and vegetable pairing. Four of these pairings provided over 1000 milligrams of sodium. Potato products provided the highest average amount of calories at an average of 65.7, as well as the high average amount of calcium at 31.45 milligrams. Average waste for potato products was under 70% for each type of potato product, with tater tots having the lowest average amount of waste. This data could be used to assist in school menu preparation that might decrease waste in elementary school lunches, as well as increase consumption of crucial micronutrients potassium and calcium, as well as calories and fiber. This data can also be used to analyze which items are high in sodium in order to reduce the consumption of sodium.Item Radio Frequency Plasma as an Excitation Source for the Quantitative Study of Sodium and Potassium in Minerals(Texas Tech University, 1965-08) Pulte, Leo RobertNot Available.Item ROLE OF AGE-ASSOCIATED OXIDATIVE STRESS IN ALTERED RENAL D1 AND AT1 RECEPTOR FUNCTIONS AND HYPERTENSION(2012-04-19) Chugh, Gaurav; Lokhandwala, Mustafa F.; Asghar, Mohammad; Hussain, Tahir; Prince, Randall A.; Shek, EugeneBlood pressure (BP) and oxidative stress increase with aging. Renal dopamine D1 (D1R) and angiotensin AT1 (AT1R) receptors by maintaining sodium homeostasis regulate blood pressure. Impaired D1R and exaggerated AT1R functions in the kidneys contribute to hypertension in animal models, which also exhibit oxidative stress. However, the role of oxidative stress in age-related hypertension has not been studied. In this study, we hypothesized that age-associated increase in oxidative stress by altering renal D1R and AT1R functions cause high BP in aging. To test this hypothesis, we measured oxidative stress, BP, and D1 and AT1 receptor functions in adult (3-month) and old (21-month) Fischer 344 X Brown Norway F1 (FBN) rats supplemented without/with antioxidant tempol. We found age-related increases in oxidative stress and blood pressure; which were reduced with tempol treatment in old FBN rats. D1R and AT1R functions were determined by measuring diuretic and natriuretic responses to SKF-38393 (D1R agonist) and candesartan (AT1 receptor antagonist) respectively. Natriuresis in response to D1R activation was impaired in old rats, suggesting an age-associated decline in D1R function in old FBN rats. Increase in G protein coupled receptor kinase (GRK) expression/activity is associated with reduced D1R-G protein coupling and function in humans and animal models with hypertension. We found age-associated increase in GRK-4 levels accompanied with D1R-G protein uncoupling in the renal proximal tubules of old FBN rats. Tempol treatment reduced GRK-4 levels and restored D1R-G protein coupling in these old rats. Natriuretic and diuretic responses to candesartan; however, were exaggerated in old rats, suggesting an age-associated increase in renal AT1R function in old FBN rats. Age-related increases in angiotensin II-mediated G protein coupling leading to exaggerated Na,K-ATPase activity may have caused increased renal AT1R function observed in old FBN rats. Tempol treatment restored angiotensin II-mediated G protein coupling and Na,K-ATPase response and thus reduced candesartan-mediated natriuresis and diuresis in old FBN rats. Our results demonstrate that both diminished renal D1R and exaggerated AT1R functions are associated with high BP in old FBN rats. Furthermore, oxidative stress may cause altered renal D1R and AT1R functions and high BP in these old rats.Item Sodium-Dependent Transport in Chromatium Vinosum(Texas Tech University, 1981-08) Pettitt, Cynthia AnnNot Available.Item The effects of sodium bicarbonate on the growth of Neisseria gonorrhoeae.(Texas Tech University, 1975-05) Talley, Richard SterlingNot available