Comparison of a:Si and c:Si Photovoltaic Cells in Southern Minnesota

Historically all energy has been gathered from the sun. It should come as no surprise that after two centuries of heavy fossil fuel use, the energy economy of the future is returning to utilize the sun. In particular, Minnesota adopted an aggressive plan in 2007 to increase the amount of energy generated from renewable sources. Photovoltaic cells offer an avenue away from fossil fuels. While not the only types of photovoltaic cells, amorphous silicon and crystalline silicon offer two attractive options. This study compares performances of the two solar cell types by monitoring current and voltage characteristics over an extended time period. In conjunction with solar irradiance, atmospheric pressure, and temperature data obtained from the WALTER Weather Station here on the MSU campus, a photovoltaic cell comparison is made between these two types. Brief energy and economic summaries are presented

PENTAVALENT ACTINYL CATION-CATION COMPLEXES IN AQUEOUS AND NON-AQUEOUS MEDIA

A primary component of advanced nuclear fuel cycles is the separation of trivalent lanthanides from trivalent minor actinides. Due to similar chemistries of these two groups this separation is a challenging task. Redox-based separation schemes remain an attractive option for reprocessing efforts and can be highly effective in separating cations in solution based on changes in oxidation state. Unlike lanthanides, americium (Am) may exist in several higher oxidation states (Am4+, AmO2+, AmO22+). However, stabilization of higher oxidation states of americium (+5, +6) is challenging in solution media, however, complexation of cations can improve redox stability. The cation-cation complex is one such complexation event that may be able to satisfactorily stabilize the upper oxidation states of Am. In addition, the solution conditions (i.e. high ionic strengths and high metal ion concentrations) for reprocessing of used nuclear fuel are such that cation-cation complexation is thermodynamically favorable and understanding the role of these complexes remains an important avenue of research.The actinyl-actinyl complex was first reported more than 50 years ago and since then has seen a little more than two dozen publications. These publications have primarily focused on proving the existence of the complex and determining its structural features with the goal of possibly understanding the mechanism of complexation. There have been both high ionic strength aqueous and non-aqueous reports of complexes, with little work done to determine the details of complex formation.The focus of this dissertation was to identify components and conditions that promote cation-cation complex formation in the solution phase. A series of experiments were devised to probe various aspects of this solution chemistry and to ascertain the role each of these aspects may play in complex formation. The aspects considered included water activity, ionic strength, water structure, complexing media, and the identity of the actinyl ligand and the metal center. Electrochemical, spectrophotometric, and computational techniques were used to probe the aspects mentioned above. As an overall note, the cation-cation complexation arises from the combined effect of many contributions to free energy and this phenomenon appears to be more complicated than a purely electrostatic interaction

Fundamental Studies and Potential Applications of Cloud Point Extraction

Separation of the components of nuclear fuel provides an interesting and complicated separation challenge as the trivalent lanthanides and actinides must be separated from each other. The difficulties of this separation have prompted exploration of novel separation techniques such as cloud point extraction (CPE). CPE is an aqueous separation technique that utilizes a surfactant, in place of an organic solvent, for phase separation. The technique has shown utility for transition metal separations and some applicability to lanthanide separation. While numerous separation schemes have been demonstrated with CPE, very little fundamental research has been done to expand understanding of the mechanism of extraction and phase separation in the system. Current CPE systems have been developed using a "trial and error" approach with no insight into how to improve the separation.The focus of this dissertation is to develop a better fundamental understanding of the mechanism of extraction in CPE systems, as a means of improving separation system design. To achieve this goal a CPE system for lanthanide and actinide separation was designed and studied. The influence of electrolytes on the extraction behavior and system behavior has been examined. Additionally the influence of the surfactant on metal ligand complexation is examined using potentiometric titrations, uv-visible spectroscopy, and fluorescence spectroscopy. These studies when combined helped give insight into a seemingly simple extraction system, showing CPE is in fact much more complicated. The goal of these studies is to provide a better understanding of the CPE system to facilitate improved system design

Effect of Molecular Size on the Sorption of Hydrophobic Compounds with Dissolved Organic Matter

Synthetic hydrophobic organic compounds are a source of pollution in natural waters and can have effects on biological organisms. Dissolved organic matter (DOM) is found within aqueous systems, and hydrophobic organic compounds undergo a sorption process to DOM. Understanding this sorption process is important in determining the environmental transport of these hydrophobic compounds and their bioavailability. A series of probe molecules that absorb visible light were used in an attempt to identify the different properties of hydrophobic species that promote sorption to DOM. An HPLC equipped with a size-exclusion chromatography column was used as a means to partition the prepared aqueous solutions. UV-Vis spectroscopy was used to detect the quantities of probe molecules that eluted from the column

Population, Oil Consumption, and Carrying Capacity

In this work, I studied the relation between the population and oil consumption from the years 1980 to 2004. While one would expect oil consumption to increase with population growth, I examined a stronger hypothesis. I hypothesized that oil consumption is proportional to population. To understand the true nature of this proportionality, a number of representative countries were chosen and examined from around the world. As a general trend, the total world population has been on the rise with a corresponding rise in oil consumption. Of particular interest is the country of North Korea for which, following the decline of the Soviet Union, there was a rapid decrease in oil consumption. If oil consumption is proportional to population, and the oil consumption falls, so will the population. In fact, there was a famine in North Korea during the mid 1990\u27s in which 2.5 million people died. My work has determined that oil consumption and population are proportional for most of the representative countries

Trading house for the Omahaws

Trading house for the Omahaws by P. Sarpy, Belle Vue. May 16, 1851. From the journal of Swiss artist Rudolph Freiderich Kurtz of Bern. From 1846-1852, Kurtz toured the western trading posts of the great fur companies of the Mississippi and Missouri Rivers