The purpose of using chemical nitrification inhibitors is to delay the oxidation of ammoniacal fertilizers during the early part of the growing season in order to minimize N losses prior to the period of maximum crop uptake. Since NH₄⁺ is electrostatically attracted to soil particles, leaching losses would be minimized, and denitrification losses could not occur in the absence of NO₃⁻. Thus, smaller amounts of fertilizer N would be required, resulting in lower inputs of money and energy as well as less potential for environmental pollution. A study (Chapter Two) was initiated in the fall of 1977 to determine if ATC could minimize overwinter losses of fall-applied N. Urea (200 kg N/ha) with or without a 1% coating: of ATC (4-amino-l,2,4-triazole) was banded or broadcast onto a silt soil on November 8, when the soil temperature at 10 cm depth was 1.9°C. The soil was sampled to a depth of 90 cm at approximately one month intervals until April, and NH₄⁺ and NO₃⁻ were determined. In the banded plots, some nitrification occurred prior to January, but from this date unti1 March there was very little change in soil NH₄⁺ levels. Overall, from December to April, there were 70 and 48% decreases in the 0-15 cm plots without and with ATC, respectively. In all the broadcast plots, regardless of ATC treatment, nitrification proceeded steadily throughout the sampling period, with 93 and 85% decreases from the December 0-15 cm NH₄⁺ levels in the non-ATC and ATC plots, respectively. It is concluded that ATC is partially effective in minimizing N losses when applied in the fall as a band with urea, but when broadcast there is no effect on nitrification. Leaching of the water-soluble ATC was the likely cause of its poor effectiveness. Significant leaching of urea from the zone of application was also found to occur during the first month following its application. A laboratory study (Chapter Three) was conducted to determine the influence of the nitrification inhibitors ATC and N-Serve [2-chloro-6-(trichloromethyl)-pyridine] on urea hydrolysis in a silt soil at 2 and 12°C. There was no delay of ureolysis caused by the presence of these chemicals, even at 20 times the recommended application rate. At 2°C the rate of hydrolysis was about half that at 12°C, with 21 and 7 days being required for complete hydrolysis at 2 and 12°C, respectively. These results suggest that leaching of urea may occur following its application to a cold soil during periods of heavy precipitation as was found in the winter nitrification study (Chapter Two). A series of field experiments (Chapter Four) was conducted with silage corn (Zea mays L.) to compare the effectiveness of the nitrification inhibitors ATC and N-Serve in a loamy sand and a silt. Urea was coated with the inhibitors at a rate of 1% of active ingredient per weight of N and applied as a band or broadcast in the spring of 1977 and 1978. Neither inhibitor significantly affected nitrification when applied as a broadcast treatment to either soil. In the silt, both inhibitors were equally effective in delaying nitrification when banded, whereas in the loamy sand ATC was much more effective than N-Serve. The effectiveness of N-Serve persisted much longer in the silt (86 days) than in the loamy sand (23 days). This suggested that volatilization of N-Serve severely limited its effectiveness in the loamy sand. There was no significant improvement in crop yields or N content due to inhibitor treatment in either soil. / Land and Food Systems, Faculty of / Graduate

Alzheimer’s disease (AD) is neuropathologically characterized by excessive beta -amyloid (Abeta)plaques and neurofibrillary tangles composed of hyperphosphorylated tau in the brain. Although the etiology of genetic cases of AD has been attributed to mutations in presenilin and amyloid precursor protein (APP) genes, in most sporadic cases of AD, the etiology is still unknown and various predisposing factors could contribute to the pathology of AD. Predominant among these possible predisposing factors that have been implicated in AD are age, hypertension, traumatic brain injury, diabetes, chronic neuroinflammation, alteration in calcium levels and oxidative stress. Since both inflammation and altered calcium levels are implicated in the pathogenesis of AD, we wanted to study the effect of altered levels of calcium on inflammation and the subsequent effect of selective calcium channel blockers on the production of pro-inflammatory cytokines and chemokines. Our hypothesis is that Abeta depending on it conformation, may contribute to altered levels of intracellular calcium in neurons and glial cells. We wanted to determine which conformation of Abeta was most pathogenic in terms of increasing inflammation and calcium influx and further elucidate the possibility of a link between altered calcium levels and inflammation. In addition, we wanted to test whether calcium channel blockers could inhibit the inflammation mediated by the most pathogenic form of Abeta by antagonizing the calcium influx triggered by Abeta. Our results in human glial and neuronal cells demonstrate that the high molecular weight oligomers are the most potent at stimulating the release of pro-inflammatory cytokines IL-6 and IL-8 as well as increasing intracellular levels of calcium compared to other conformations of Abeta. Further, L-type calcium channel blockers and calmodulin kinase inhibitors are able to significantly reduce the levels of IL-6 and IL-8. These results suggest that Abeta induced alteration of intracellular calcium levels contributes to its pro-inflammatory effect.

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This document only includes an excerpt of the corresponding thesis or dissertation. To request a digital scan of the full text, please contact the Ruth Lilly Medical Library's Interlibrary Loan Department (rlmlill@iu.edu).

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Corrosion is one of the most complicated and costly problems facing drinking water utilities. Corrosion of iron pipes can lead to economic losses and customer complaints, while lead corrosion poses a serious health risk. This work first synthesizes nearly 100 years of iron corrosion research to provide the water industry with an updated understanding of factors that influence iron pipe corrosion including water quality and composition, flow conditions, biological activity, and corrosion inhibitors. Potential impacts of upcoming regulations on iron corrosion are also considered. Next, a four-year study is presented that evaluated the effect of water quality and phosphate inhibitors on the corrosion of iron pipes under extended stagnant water conditions. Surprisingly, many of the water quality parameters traditionally thought to influence iron corrosion were not controlling under these "worst case" stagnant conditions. Moreover, addition of phosphate inhibitors often had either no statistically significant effect or actually increased iron concentration, scale build-up and overall weight loss. Temperature is often overlooked when corrosion of distribution systems pipes is considered. Temperature impacts many parameters that are critical to pipe corrosion including physical properties of the solution, thermodynamic and physical properties of corrosion scale, chemical rates, and biological activity. Moreover, variations in temperature and temperature gradients may give rise to new corrosion phenomena worthy of consideration by water treatment personnel. In laboratory experiments, cast iron samples at 5°C had 23% more weight loss, ten times higher iron release to water, and twice as much tuberculation compared to samples at 25°C. For lead corrosion, hexametaphosphate inhibitors were proven to increase release of both particulate and soluble lead to drinking water by 200 - 3500% over a wide range of water qualities when compared to orthophosphate, effectively ending a long term debate as to their impacts. Utilities should consider these adverse effects whenever polyphosphate is used to prevent scaling or iron precipitation. / Ph. D.