Accumulation of CO2 in the atmosphere has triggered research on topics related to causes, effects, and solutions to potential problems associated with global warming. The present research was conducted to determine if grassland plant communities can be managed to promote sequestration of carbon in the soil, potentially mitigating the effects of increasing atmospheric CO2. The effects of shrub invasion or heavy livestock grazing on peak standing crop of phytomass, root mass and soil organic carbon content were therefore studied. These studies were complimented by a study of the decomposition rates of leaves and roots of snowberry and grasses. The effects of snowberry encroachment on peak standing crop of aboveground phytomass, and soil organic carbon content (SOC) were also studied. Total aboveground phytomass in the snowberry community was more than triple that of the ecotone and was 6-times greater than that of the grassland community. Similarly, the mass of large roots was greatest in the snowberry community (1.2 kg m-2, SE= 0.19), intermediate in the ecotone (0.5 kg m-2, SE= 0.08), and least in the grassland (0.1 kg m-2, SE= 0.04). Conversely, the mass of fine and medium roots was not different (P>0.05) among the three communities, averaging 0.7 kg m-2 in all communities (SE= 0.03, 0.07, 0.49 in snowberry, ecotone and grassland, respectively). Greater aboveground phytomass did not correspond with greater SOC in the snowberry community. Soil organic carbon in the upper 50 cm averaged 8.3 (SE= 0.7), 7.9 (SE= 1.0), and 7.9 (SE= 0.7) kg m-2 in snowberry, ecotone, and grassland communities, respectively. Peak standing crop of aboveground phytomass averaged 157 g m-2 (SE= 27) and 488 g m-2 (SE= 48) in grazed and ungrazed grassland, respectively. Conversely, grazing had no affect on root mass. The mass of fine roots averaged 0.9 kg m-2 (SE= 0.04) and 0.8 kg m-2 (SE= 0.06) in grazed and ungrazed grassland, respectively, while that of medium roots averaged 0.6 kg m-2 (SE= 0.07) in both grazing treatments. Total SOC in the upper 50 cm of soil was not affected (P>0.05) by livestock grazing, averaging 5.5 kg m-2 (SE= 0.7) in grazed and 6.8 kg m-2 (SE= 0.9) in ungrazed grassland. Livestock grazing also had no effect (P>0.05) on SOC at the 0-3, 3-10, 10-20, 20-30, and 30-40 cm depths. The SOC in fine- and coarse-textured soils averaged 7.6 kg m-2 (SE= 0.8) and 5.1 kg m-2 (SE=0.7), respectively. Differences existed between decomposition of roots and leaves for graminoids and snowberry. On a monthly basis decomposition was 0.6 to 0.8 % greater in leaves than roots. The decomposition of roots and leaves ranged from 2.2 to 5.0 % month-1. Decay rate constants for leaves ranged from 0.45 yr-1 (SE= 0.03) to 0.71 yr-1 (SE= 0.02) while those of roots ranged from 0.34 yr-1 (SE= 0.03) to 0.47 yr-1 (SE= 0.04). The decomposition of roots and leaves did not correspond with macroclimatic or regional climate data nor with initial C:N content of the plant material. In summary, invasion of snowberry into grassland does not appear to conflict with goals related to maintenance of SOC in Mixed Prairie. Current grazing management regimes also appear to be consistent with goals related to maintenance of existing SOC. Soil texture had a greater effect on SOC than management of the plant community. Decomposition of leaves and roots appeared to be controlled by many interacting factors such as plant organ type, collection year, study year (climate) and physical and/or chemical characteristics of the site.

One-dimension (1D) nanostructures such as wires, rods, belts and tubes have become the focus of intensive researches for investigating structure-property relationships and related scientific and technological applications. Few-walled carbon nanotubes (FWNTs), a special type of small diameter multi-walled carbon nanotubes with superb structural perfection, are first discovered in our laboratory and systemically studied in this dissertation, including the synthesis by chemical vapor deposition (CVD) method, the purification and their applications. Moreover, iron phosphide nanorods/nanowires with controlled structures have been synthesized in solution phase and their magnetic properties have been investigated. The first parts of this dissertation are mainly focused on the studies of FWNTs synthesized by CVD method using binary catalyst Co (or Fe) with Mo (or W) supported on MgO made by modified combustion method. The structures of as-grown FWNTs can be controlled by three basic growth parameters: temperature, catalyst composition and carbon feeding rate. It is found that the as-grown FWNT materials prepared from W-containing catalysts are much more easily purified than those from Mo-containing catalysts. Both raw and purified FWNTs show enhanced electron field emission characteristics compared to other current commercial nanotubes. The highly pure FWNTs are then used to prepare composite materials with polymers and noble metal nanocrystals. Furthermore, the structures of FWNTs are attempted to be controlled by adjusting the growth parameters of carbon monoxide CVD. Highly pure DWNTs (over 95%) are obtained and well characterized by TEM, Raman and fluorescence spectrum. The optical properties of DWNTs and their application in bio-imaging are primarily investigated. In addition, conducing films are fabricated using highly pure FWNTs and the relationship between the structure and the conductivity is surveyed and further possible improvements are discussed. The second parts of this dissertation describe a solution-phase route for the preparation of single-crystalline iron phosphide nanorods and nanowires. The mixture of trioctylphosphine oxide (TOPO) and trioctylphosphine (TOP) which are commonly used as the solvents for semiconductor nanocrystal synthesis is not entirely inert. TOP serves as phosphor source and reacts with Fe precursors to generate iron phosphide nanostructures with large aspect ratios. In addition, the morphology of the produced iron phosphide structures can be controlled by the ratio of TOPO/TOP. A possible growth mechanism is discussed. / Dissertation

In a carbon-constrained economy, the decision making process for selecting carbon reducing technologies for existing single power plants, portfolios of power plants, or new power plant technologies must incorporate the monetary impact of reducing CO2 emissions. Cost of electricity and the monetary impacts of reducing criteria pollutants primarily drive power plant decisions. For example, a gas turbine power plant may upgrade its combustion system to a Dry Low NOx combustor if regulations require or provide incentives for reduced NOx emissions. Similarly, in a carbon-constrained economy, the CO2 emissions strategy selected may impact the operating profile and or equipment of the power plant. Given the wide array of CO2 mitigation strategies available for power plants, robust guidelines are needed to consistently compare varying strategies. The purpose of this study is to provide guidelines for comparing currently available and near-term CO2 mitigation strategies, while also providing guidelines for comparing new low CO2 emission technologies. Furthermore, the issue of making a decision for a portfolio of power plants versus a single plant will be explored along with fuel price sensitivity and CO2 credit trading.

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This thesis seeks to investigate the adsorption capabilities of activated carbon and carbon nanotubes. The adsorption of methanol on both of these substances was tested for their application in a solar based refrigeration cycle. Research on carbon nanotubes and their growth has been carried out for applications in the semiconductor industry. Enough focus has not been given to the use of nanotubes for refrigeration purposes. Adsorption refrigerators have been designed with the energy source being solar energy. Various adsorbent/adsorbate pairs have been tested in literature. The present work focuses on carbon nanotubes because theoretically, nanotubes should be able to adsorb better than activated carbon due to their high surface to volume ratios and hence a higher number of adsorption sites available for methanol to adsorb. The amount of adsorption of methanol on nanotubes depends on whether the end caps of the nanotubes are open or closed and also on the hydrophilic nature of the nanotubes. Nanotubes with ends closed are supposed to adsorb less than the nanotubes with their ends opened. The ends of carbon nanotubes can be blocked because of iron and other impurities. In this project, nanotubes are annealed under high vacuum to open the end caps. The hydrophobic nature of the nanotubes is corrected by treating them with concentrated nitric acid. The hydrophobic nature of the nanotubes is corrected by treating them with concentrated nitric acid. The acid treated nanotubes are used to obtain adsorption data at different temperatures. The adsorption of methanol on activated carbon, pristine and treated carbon nanotubes is measured at different temperatures. Electron microscopy is used to validate that annealing the nanotubes at high temperature under vacuum opens the end caps of the nanotubes. Finally, a matrix of nanotubes and carbon powder is prepared with different concentrations. The mixture is tested for adsorption of methanol. It is observed that the carbon nanotubes, pristine or treated, do not perform better than activated carbon. However, performance seems to increase when mixtures of activated carbon and carbon nanotubes are used as adsorbent. Also, it is found that mixtures containing annealed nanotubes perform better than mixtures with pristine nanotubes. Kinetics of the adsorption process is calculated for the different adsorbents used, which is used to explain the increase in the amount of methanol adsorbed for the activated carbon-carbon nanotube mixture.

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