A mighty bulwark: three visions of the Lake Texoma and Denison Dam project

Thesis (M.A.)--University of Oklahoma, 1994.Includes bibliographical references

Two-fluid model for a rotating trapped Fermi gas in the BCS phase

We investigate the dynamical properties of a superfluid gas of trapped fermionic atoms in the BCS phase. As a simple example we consider the reaction of the gas to a slow rotation of the trap. It is shown that the currents generated by the rotation can be understood within a two-fluid model similar to the one used in the theory of superconductors, but with a position dependent ratio of normal and superfluid densities. The rather general result of this paper is that already at very low temperatures, far below the critical one, an important normal-fluid component appears in the outer regions of the gas. This renders the experimental observation of superfluidity effects more difficult and indicates that reliable theoretical predictions concerning other dynamical properties, like the frequencies of collective modes, can only be made by taking into account temperature effects.Comment: 6 pages, 4 figure

BEC-BCS Crossover and the Liquid-Gas Phase Transition in Hot and Dense Nuclear Matter

The effect of nucleon-nucleon correlations in symmetric nuclear matter at finite temperature is studied beyond BCS theory. Starting from a Hartree-Fock description of nuclear matter with the Gogny effective interaction, we add correlations corresponding to the formation of preformed pairs and scattering states above the superfluid critical temperature within the in-medium T-matrix approach, which is analogous to the Nozieres-Schmitt-Rink theory. We calculate the critical temperature for a BEC superfluid of deuterons, of a BCS superfluid of nucleons, and in the crossover between these limits. The effect of the correlations on thermodynamic properties (equation of state, energy, entropy) and the liquid-gas phase transition is discussed. Our results show that nucleon-nucleon correlations beyond BCS play an important role for the properties of nuclear matter, especially in the low-density region.Comment: 11 pages, 12 figures; v2: minor modifications of the text, references adde

Coupling of hydrodynamics and quasiparticle motion in collective modes of superfluid trapped Fermi gases

At finite temperature, the hydrodynamic collective modes of superfluid trapped Fermi gases are coupled to the motion of the normal component, which in the BCS limit behaves like a collisionless normal Fermi gas. The coupling between the superfluid and the normal components is treated in the framework of a semiclassical transport theory for the quasiparticle distribution function, combined with a hydrodynamic equation for the collective motion of the superfluid component. We develop a numerical test-particle method for solving these equations in the linear response regime. As a first application we study the temperature dependence of the collective quadrupole mode of a Fermi gas in a spherical trap. The coupling between the superfluid collective motion and the quasiparticles leads to a rather strong damping of the hydrodynamic mode already at very low temperatures. At higher temperatures the spectrum has a two-peak structure, the second peak corresponding to the quadrupole mode in the normal phase.Comment: 14 pages; v2: major changes (effect of Hartree field included

Defining Tucker Act Jurisdiction After Bowen v. Massachusetts

Part I of this Article summarizes the relevant provisions of the Tucker Act, and examines courts\u27 interpretations of whether a district court had jurisdiction over a claim when a potential judgment exceeded $10,000. This Article suggests that, over time, traditional Tucker Act jurisdiction has been distorted by the appearance of a new kind of plaintiff\u27 seeking structural reform rather than the kinds of compensation envisioned by the Act. This Article also suggests that Tucker Act jurisdiction has been distorted by two congressional actions: the creation of the judgment fund; and amendments to the Administrative Procedure Act. These congressional actions could be construed to extend district court jurisdiction over claims for money damages. As a result, the distinction between Tucker and non- Tucker Act remedies has been blurred. Part II of this Article explicates the case law before and after the passage of the APA and its relevant amendments. This Article notes how, in the 1980\u27s, the Department of Justice (DOJ) began to assert that state suits against the Federal Government seeking reimbursement of grant-in-aid funds should be treated as Tucker Act claims and tried in the United States Claims Court, rather than as non-Tucker Act claims to be tried in the district courts. Although the DOJ achieved some measure of success, Judge Bork, in a masterful display of judicial legerdemain, offered alternative reasoning which became the basis for the Bowen decision. This alternative was superficially attractive but intrinsically false and created the impression that Bowen had diminished the traditional jurisdiction of the Claims Court and Court of Appeals for the Federal Circuit. Part III discusses and analyzes the Bowen case, outlining its procedural history, and highlighting the United States Supreme Court\u27s efforts to distinguish Bowen from the run of the mill Tucker Act suits. In part IV, this Article offers alternative interpretations of the Bowen ruling. Finally, part V of this Article advances the preferred solution and suggests how the Bowen decision can be reconciled with a century of case law, thereby avoiding the kind of judicial nihilism evidenced in this Article\u27s introductory quotation

Exploring the Impact of and Perceptions about Interactive, Self-Explaining Environments in Molecular-Level Animations

This mixed-method study investigates the effects of interactivity in animations of a molecular-level process and explores perceptions about the animated learning tool used. Treatments were based on principles of cognitive psychology designed to study the main effects of treatment and spatial ability and their interaction. Results with students (n = 189) showed that science majors scored higher than non-science majors in retention measures (i.e., structure and function) but not in transfer. Significant main effects were found for treatment in function questions and spatial ability in structure questions. There was a significant interaction between treatment and spatial ability in structure questions. Additionally, in this study participants believed the key and the motion of ions and molecules were the most helpful parts of the animation. This study shows that students perceive the animations as being supportive of their learning, suggesting that animations do have a role in science classrooms

Pair-Breaking in Rotating Fermi Gases

We study the pair-breaking effect of rotation on a cold Fermi gas in the BCS-BEC crossover region. In the framework of BCS theory, which is supposed to be qualitatively correct at zero temperature, we find that in a trap rotating around a symmetry axis, three regions have to be distinguished: (A) a region near the rotational axis where the superfluid stays at rest and where no pairs are broken, (B) a region where the pairs are progressively broken with increasing distance from the rotational axis, resulting in an increasing rotational current, and (C) a normal-fluid region where all pairs are broken and which rotates like a rigid body. Due to region B, density and current do not exhibit any discontinuities.Comment: 4 pages, 2 figures; v2: discussion clarified, typos corrected, one reference adde

Enhanced protein immobilization on polymers - a plasma surface activation study

Over the last years, polymers have gained great attention as substrate material, because of the possibility to produce low-cost sensors in a high-throughput manner or for rapid prototyping and the wide variety of polymeric materials available with different features (like transparency, flexibility, stretchability, etc.). For almost all biosensing applications, the interaction between biomolecules (for example, antibodies, proteins or enzymes) and the employed substrate surface is highly important. In order to realize an effective biomolecule immobilization on polymers, different surface activation techniques, including chemical and physical methods, exist. Among them, plasma treatment offers an easy, fast and effective activation of the surfaces by micro/nanotexturing and generating functional groups (including carboxylic acids, amines, esters, aldehydes or hydroxyl groups). Hence, here we present a systematic and comprehensive plasma activation study of various polymeric surfaces by optimizing different parameters, including power, time, substrate temperature and gas composition. Thereby, the highest immobilization efficiency along with a homogenous biomolecule distribution is achieved with a 5-min plasma treatment under a gas composition of 50% oxygen and nitrogen, at a power of 1000 W and a substrate temperature of 80 C. These results are also confirmed by different surface characterization methods, including SEM, XPS and contact angle measurements