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No description available.

No description available.

No description available.

Nitrogen is an essential constituent and building unit of all living organisms, and the primary limiting nutrient on our planet such that its cycle widely depends on the diverse nitrogen-transforming microorganisms, such as denitrifiers. Oxygen minimum zones or hypoxic aquatic ecosystems account for 30-50% of all nitrogen denitrification and under dynamic transformation imbalance, of measure dependent variable modularity, little is known about discrete shifts in denitrification competition by various microorganisms of divergent metabolism; or the Fe (II) – Fe (III) redox linking process. Novel nitrate dependent Fe (II) oxidizing bacteria as rapid denitrifier and iron oxidizer can significantly oxidize various iron minerals (magnetite and ferrous mono sulfide). Evidence of nitrate dependent Fe (II) oxidation by the bacterium P. ferrooxidans sp. MAI-1 could shed light as a novel competitor at microaerophilic (<2.0mg/L DO, -100 – +100 mV) interfacial competition with cyanobacteria Microcystis aeruginosa corollary to ecosystem eutrophication and concomitant microcystin production, with the goal of abating a toxic cyanobacterial bloom. Nitrate Dependent Iron Oxidizing Bacteria (NDFe(II)OB) showed rapid nitrate reduction (>25 mg/L NO2, day 7) and consequent bright-orange iron oxides. Saturation indices (day 1 and 8 SI = log (IAP/Ksp), showed non exclusive vivianite formation i.e., 3.80 and 0.44-0.55, respectively, with near complete oxidation by day 8, significantly abating logarithmic growth over a fourteen day period (p>0.01). N-N dichotomies are not purely exclusive, as terminal PO4 competition differed by ~0.1 mg/L after a 15 day period, with approximately one five hundred times more N-nitrogen loss compared to P-phosphorus loss difference. Early logarithmic cyanobacteria cell counts under the presence of the competitor decreased by >20% by day 18 of growth. This is consistent with the classical view that under primary metabolite exhaustion, interspecific competition should lead to competitive exclusion and not niche differentiation.

Typewritten Bibiography: leaves 209-222.

Hydroxylamine nitrate (HAN), an important agent for the nuclear industry and the U.S. Army, has been involved in several costly incidents. To prevent similar incidents, the study of HAN safe storage and handling boundary has become extremely important for industries. However, HAN decomposition involves complicated reaction pathways due to its autocatalytic behavior and therefore presents a challenge for definition of safe boundaries of HAN storage and handling. This research focused on HAN decomposition behavior under various conditions and proposed isothermal aging testing and kinetic-based simulation to determine safety boundaries for HAN storage and handling. Specifically, HAN decomposition in the presence of glass, titanium, stainless steel with titanium, or stainless steel was examined in an Automatic Pressure Tracking Adiabatic Calorimeter (APTAC). n-th order kinetics was used for initial reaction rate estimation. Because stainless steel is a commonly used material for HAN containers, isothermal aging tests were conducted in a stainless steel cell to determine the maximum safe storage time of HAN. Moreover, by changing thermal inertia, data for HAN decomposition in the stainless steel cell were examined and the experimental results were simulated by the Thermal Safety Software package. This work offers useful guidance for industries that manufacture, handle, and store HAN. The experimental data acquired not only can help with aspects of process safety design, including emergency relief systems, process control, and process equipment selection, but also is a useful reference for the associated theoretical study of autocatalytic decomposition behavior.

Organic nitrates such as glyceryl trinitrate (GTN) are commonly used to treat myocardial ischemia and congestive heart failure. GTN is proposed to act as a prodrug that requires bioactivation for pharmacological activity. However, continuous administration results in tolerance development, limiting its clinical usefulness. Aldehyde dehydrogenase 2 (ALDH2) has been proposed to be the primary enzyme responsible for GTN bioactivation, and ALDH2 inactivation has been proposed as the sole basis of nitrate tolerance. In the present study, we utilized an in vivo GTN tolerance model to investigate the role of ALDH2 in GTN bioactivation and tolerance. We assessed changes in ALDH2 protein, mRNA and activity levels in rat blood vessels during chronic GTN exposure (0.4 mg/hr for 6, 12, 24 and 48 hr) in relation to changes in vasodilator responses to GTN. A time-dependent decrease in both ALDH2 expression and activity occurred (80% in tolerant veins and 30% in tolerant arteries after 48 hrs exposure to GTN), concomitant with decreased vasodilator responses to GTN. However, after a 24 hr drug-free period following 48 hr GTN exposure, the vasodilator responses to GTN had returned to control values, whereas ALDH2 expression and activity were still markedly depressed. The dissociation between reduced ALDH2 activity and expression, and the duration of the impaired vasodilator responses to GTN in nitrate-tolerant blood vessels, suggest factors other than changes in ALDH2-mediated GTN bioactivation contribute to nitrate tolerance. / Thesis (Master, Pharmacology & Toxicology) -- Queen's University, 2008-10-03 16:14:49.313

No description available.

Due to the complexity of nitrogen dynamics in the soil, tracer techniques are employed to estimate the fate and transport of nitrate in agricultural fields. This study was conducted to examine effects of N fertilization and landscape position on two-dimensional redistribution of bromide in a hummocky landscape, and to identify the landscape position with the greatest potential for solute loss using a dual application of Br- and 15N. The field data on Br- transport was also simulated using the HYDRUS models. The study was carried out near Brandon, Manitoba in 2007 and 2008, using two separate plots denoted as Site-2007 and Site-2008, respectively. The field plot was delineated into three landscape positions as upper (UPP), middle (MID) and lower (LOW) slope. Each landscape position received labelled K15NO3 at the rates of 0, 90 and 135 kg N ha-1, and KBr at the rate of 200 kg Br- ha-1. Site-2007 was seeded to canola while Site-2008 had winter wheat. Soil samples were taken in the fall and the following spring and were analyzed for Br-, NO3-N, total N, and isotope N ratio. Nitrogen fertilization reduced the downward movement of Br- in the soil profile, resulting in a greater lateral movement of Br- compared to the unfertilized plots. The greatest vertical and lateral movement of Br- occurred at the LOW slope. In the dual-tracer experiment, the smallest amounts of Br-, 15N, and NO3-N were measured in the soil at the LOW slope, while the greatest amounts were at the MID slope; indicating that solute loss was: LOW > UPP > MID. In the absence of crop uptake, Br- transport was identical to that of 15N. The simulation study showed that HYDRUS-1D model was inadequate to describe solute transport in the landscape, as HYDRUS-2D/3D reproduced the field data better than HYDRUS-1D. However, the 2D model did not reflect effects of landscape position and N fertility on Br- transport. Overall, the study confirmed the “Campbell hypothesis” which states that proper N fertilization reduces nitrate leaching. The field experiment and model simulation both showed that downward movement is the main pathway of solute loss in the landscape.