This dissertation addresses atomic-level structure and related properties of the (100) surfaces of Vanadium and Niobium. The primary motivation of the surface structure experiments is based on an observation by P.J. Feibelman [[superscript 3,4]] that ab-initio calculations of surface relaxation (interplanar separation of near-surface planes) exhibit significant and consistent deviation from corresponding experimental relaxation values obtained through LEED crystallography. The deviation is much larger than the accepted accuracy of both the theoretical and experimental techniques. Resolving this dilemma is the primary objective for this systematic investigation of multilayer relaxation at transition metal surfaces. This research also addresses important secondary issues. Closely related to the surface relaxation issue for Nb(100) are experiments that provide an experimentallydetermined structural basis for the "sub-surface valve" model that has been proposed to explain the novel hydrogen uptake kinetics in Niobium. Definitive experiments that address the longstanding search for ferromagnetic order at the surface of V(100) is another important issue.

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Introduction In order to address the increasing demand for Fluorine-18 and the rising cost per mL of 18O enriched water, IBA developed improvements to their 18F- production systems. For this new design we started from scratch, with the main objectives of reducing the required enriched water volume and improving the cooling of the insert. A better cooling allows increasing the target current and thus the produced activity. Finally, we aimed to reduce the number of parts and improve the design of auxiliary components. Material and Methods Six Niobium conical inserts with different target chamber volumes were machined and tested. Only 4 of these were selected to create the new range of IBA 18F− targets shown in TABLE 1. The new Niobium target inserts have a complex shape with drilled channels on the outside of the chamber and a deep channel next to the beam strike area (FIG. 1, green circle) to ensure efficient cooling. The 18O water inlet lines are now directly inserted in the Niobium body (FIG. 1, blue circle) to improve 18F- quality (no more contact with small o-rings). In operation, a 35µm Havar® target window is used. All tests were performed using IBA Cyclone® 18 cyclotron. The targets were filled with different volumes of enriched 18O water (enrichment > 92 %) and irradiated with 18 MeV protons on target with beam currents up to 145 μA for 30 to 150 minutes, while the internal pressure rise of the target was recorded. For each target, a pressure-current curve was plotted and an optimum balance between target water fill volume, pressure and current has been determined, which maximises available activity after two hours, in each case. Results and Conclusion Radionuclidic impurities were measured and more than 100 FDG syntheses on various synthesizers confirmed the effectiveness of the new design. Increasing the current up to 145µA in Conical 16, the production reached 18 Ci in 2 hours, single beam, with a target pressure under 43 bar. Today, the use of these new targets for daily commercial production is increasing within the IBA Cyclone® installed base.

Research into molecular electronics has exploded in recent years due to a proliferation of new and exciting techniques for producing atomic level structures (e-beam lithography, self-assembled monolayers, etc.); coupling these techniques with the ability to accurately manipulate atomic systems (such as with Scanning Tunneling Microscopes (STM), Atomic Force Microscopes (AFM), or Mechanically Controllable Break Junctions (MCBJ)) opens the possibility to create novel quantum coherent devices for both engineering applications, as well as research into fundamental physics. Along these lines, presented here is a series of experiments on superconducting point contacts which were aimed at understanding the dynamics of coupling superconducting effects to the mechanical degrees of freedom of a nanowire. In addition, another series of experiments presented here explore the nature of charge transport at high biases in superconducting point contacts. Specifically, an investigation of point contacts at high voltage biases revealed a suppression of one component of the total current, which is explained through a phenomenological model.

Thesis(M.S.)--Auburn University, 2006. / Abstract. Vita. Includes bibliographic references.

Thesis (M.Ch.E.)--University of Delaware, 2008. / Principal faculty advisors: Mark A. Barteau and Douglas J. Buttrey, Dept. of Chemical Engineering. Includes bibliographical references.

Thesis (Ph. D.)--University of Oregon, 2004. / On t.p. "m̲" and "n̲" are subscript. Typescript. Includes vita and abstract. Includes bibliographical references (leaves 147-153). Also available for download via the World Wide Web; free to University of Oregon users.

Thesis (M.S.)--University of Texas at El Paso, 2009. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.