Metals

Sharks comprise a large portion of bycatch in pelagic longline fisheries worldwide. Lanthanide metals have been proposed as shark repellents. This study quantified the normalized voltage of lanthanide metals in seawater and found that there was no difference in normalized voltage among the six tested metals. Temperature and salinity had a significant effect on lanthanide normalized voltage. The output at 18ºC was significantly greater than at both 12 and 24ºC. The normalized voltage was significantly greater in freshwater than brackish or seawater. The dissolution rate for the lanthanides varied from -1.6 to -0.2g/h. As the metals dissolved the voltage remained constant. In a behavioral assay, neodymium was ineffective at repelling bonnethead sharks (Sphyrna tiburo) tested individually and in groups, and lemon sharks (Negaprion brevirostris) in groups. Due to high cost, fast dissolution rates, and lack of deterrent effects, lanthanide metals are not recommended for use in mitigating shark bycatch.

Stable and metastable phases of Fe and Al and structural anomalies of Zn and Cd have been studied by epitaxial Bain path (EBP) and minimum path (MNP) first-principles procedures, based on finding equilibrium structures from minimizing the Gibbs free energy G with respect to structure at a given hydrostatic pressure p and temperature T . The main accomplishments are as follows. (1) This dissertation illustrates the effectiveness of the MNP procedure for finding stable and metastable phases of an element by studying four Bravais phases of Fe including body-centered tetragonal (bct), body-centered cubic (bcc), face-centered cubic (fcc) and rhombohedral (rh) phases. The determination of absolute stability using MNP is new; MNP finds all the elastic constants cjj of a given state and the eigenvalues of the elastic constants matrix, which determine the absolute stability of the state.

Gold is a highly prized metal whose ore deposits are continually being mined and depleted. With the increasing scarcity of continental gold ores, gold miners and scientist are turning to the sea as one alternate source of this precious metal. But the problem arises in determining which parts of the ocean to mine. Ideally the area with the greatest concentration of gold would be the best place to start but determining an accurate concentration of gold in a sample of seawater is difficult for various reasons. The main reason being gold's extremely low concentration in seawater, averaging at about13 [sic] parts per trillion. This study deals with detecting trace amounts of gold in seawater. The first step in the analysis involves pre-concentrating gold in seawater using an ion exchange resin, Chelexª -100, and optimizing the experimental conditions. Then the chromatographic fractions are analyzed using a graphite furnace atomic absorption spectrometer. The results from several trials are presented in this study.