Critical research and advanced technology (CRT) support project

A critical technology base for utility and industrial gas turbines by planning the use of coal-derived fuels was studied. Development tasks were included in the following areas: (1) Combustion - investigate the combustion of coal-derived fuels and methods to minimize the conversion of fuel-bound nitrogen to NOx; (2) materials - understand and minimize hot corrosion; (3) system studies - integrate and focus the technological efforts. A literature survey of coal-derived fuels was completed and a NOx emissions model was developed. Flametube tests of a two-stage (rich-lean) combustor defined optimum equivalence ratios for minimizing NOx emissions. Sector combustor tests demonstrated variable air control to optimize equivalence ratios over a wide load range and steam cooling of the primary zone liner. The catalytic combustion of coal-derived fuels was demonstrated. The combustion of coal-derived gases is very promising. A hot-corrosion life prediction model was formulated and verified with laboratory testing of doped fuels. Fuel additives to control sulfur corrosion were studied. The intermittent application of barium proved effective. Advanced thermal barrier coatings were developed and tested. Coating failure modes were identified and new material formulations and fabrication parameters were specified. System studies in support of the thermal barrier coating development were accomplished

Nuclear Reaction Rates in a Plasma

The problem of determining the effects of the surrounding plasma on nuclear reaction rates in stars is formulated ab initio, using the techniques of quantum statistical mechanics. We derive a result that expresses the complete effects of Coulomb barrier penetration and of the influence of the surrounding plasma in terms of matrix elements of well defined operators. We find that possible "dynamical screening" effects that have been discussed in the literature are absent. The form of our results suggests that an approach that relies on numerical calculations of the correlation functions in a classical Coulomb gas, followed by construction of an effective two body potential and a quantum barrier penetration calculation, will miss physics that is as important as the physics that it includes.Comment: 66 pages, revtex, Errors Fixed, Explanation Adde

Single-electron transport through the vortex core levels in clean superconductors

We develop a microscopic theory of single-electron transport in N-S-N hybrid structures in the presence of applied magnetic field introducing vortex lines in a superconductor layer. We show that vortex cores in a thick and clean superconducting layer are similar to mesoscopic conducting channels where the bound core states play the role of transverse modes. The transport through not very thick layers is governed by another mechanism, namely by resonance tunneling via vortex core levels. We apply our method to calculation of the thermal conductance along the magnetic field.Comment: 4 pages, 1 figur

Andreev Reflections in Micrometer-Scale Normal-Insulator-Superconductor Tunnel Junctions

Understanding the subgap behavior of Normal-Insulator-Superconductor (NIS) tunnel junctions is important in order to be able to accurately model the thermal properties of the junctions. Hekking and Nazarov developed a theory in which NIS subgap current in thin-film structures can be modeled by multiple Andreev reflections. In their theory, the current due to Andreev reflections depends on the junction area and the junction resistance area product. We have measured the current due to Andreev reflections in NIS tunnel junctions for various junction sizes and junction resistance area products and found that the multiple reflection theory is in agreement with our data

Repair of anomalous origin of the left coronary artery in the infant and small child

Anomalous origin of the left coronary artery from the pulmonary artery is associated with myocardial infarction, left ventricular dysfunction, mitral valve dysfunction and, occasionally, intracardiac congenital abnormalities. A technique that utilizes a flap of the anterior wall of the pulmonary artery to serve as a neocoronary artery to direct aortic flow from a created aortopulinonary window to the pulmonary artery orifice of the anomalous left coronary artery was used in five patients aged 2.5 months to 4.75 years. Two patients were less than 4 months of age at operation. There was one death 2 days after operation and one late death. The two youngest patients required mitral valve replacement. Two of the three surviving patients are well at follow-up at 7 to 44 months. One patient has been lost to follow-up study. One patient had postoperative catheterization which showed an intact repair. The pulmonary artery neocor-onary procedure is applicable to infants and small patients with anomalous origin of the left coronary artery from the pulmonary artery

1986 Update of Agronomic and Animal Performance of Different Tall Fescue Varieties

The objective of the tall fescue breeding program at the University of Kentucky is the development of varieties characterized by superior nutritive value (including reduced levels of perloline and loline alkaloids), minimal infestation of the fungal endophyte, Acremonium coenophialum), higher palatability, improved disease resistance, and wider adaptation through the derivation of intergeneric and interspecific hybrids of ryegrass and tall fescue species. Kentucky 31, Kenwell, and Kenhy were varieties released from this breeding program. Johnstone tall fescue, developed cooperatively by the Kentucky Agricultural Experiment Station and USDA-ARS, is the most recently released variety. It is characterized as having low levels of perloline alkaloid and the fungal endophyte (Acremonium coenophialum) and improved forage quality during summer. Ample Johnstone seed should be available to meet demand during 1986