Polycyclic aromatic hydrocarbons (PAH) are environmental pollutants that are present in air, food, and water. While PAH compounds are chemically inert and are sparingly soluble in aqueous solutions, in living cells they are metabolized to a variety of oxygenated derivatives, including the high mutagenic and tumorigenic diol epoxide derivatives. The diol epoxides of the sterically hindered fjord region compound benzo[c]phenanthrene (B[c]PhDE) are among the most powerful tumorigenic compounds in animal model test systems. In this project, site-specifically modified oligonucleotides containing single B[c]PhDE-N{sup 6}-dA lesions derived from the reactions of the 1S,2R,3R,4S and 1R,2S,3S,4R diol epoxides of B[c]PhDE with dA residues were synthesized. The replication of DNA catalyzed by a prokaryotic DNA polymerase (the exonuclease-free Klenow fragment E. Coli Po1 I) in the vicinity of the lesion at base-specific sites on B[c]PhDE-modified template strands was investigated in detail. The Michaelis-Menten parameters for the insertion of single deoxynucleotide triphosphates into growing DNA (primer) strands using the modified dA* and the bases just before and after the dA* residue as templates, depend markedly on the stereochemistry of the B[c]PhDE-modified dA residues. These observations provide novel insights into the mechanisms by which bulky PAH-DNA adducts affect normal DNA replication.

The objective of this quarter of study was to prepare fuel pellets containing PVC, newspaper and plastics to be co-fired with coal in the AFBC combustor. The Western Kentucky University atmospheric fluidized bed combustion system requires the fuel to fall from a bunker into a lock-hopper, and from there into a mixing box where the fuel is auger-fed under pressure into the bottom of the fluidized bed. The fuel must flow freely out of the bunker and through the lock- hopper for proper feeding into the combustor. In order for the fuel to continuously fall through these units and into the mixing box during combustion, the density of the fuel and the size of the particles must meet certain requirements. The particles must be no larger than 3/8 inches in diameter and must have a density approaching that of coal. Loose materials such as sawdust, shredded paper products and most shredded plastics do not feed properly in the WKU AFBC system. Bridging and blockage of feed chutes result, even with constant vibration of parts of the feed mechanism. It is not possible to run the AFBC system powered solely by these loose materials.

Gas core reactors can form the basis for advanced nuclear thermal propulsion (NTP) systems capable of providing specific impulse levels of more than 2,000 sec., but containment of the hot uranium plasma is a major problem. The initial phase of an experimental study of hydrodynamic confinement of the fuel cloud in a gas core fission reactor by means of an innovative application of a base injection stabilized recirculation bubble is presented. The development of the experimental facility, a simulated thrust chamber approximately 0.4 m in diameter and 1 m long, is described. The flow rate of propellant simulant (air) can be varied up to about 2 kg/sec and that of fuel simulant (air, air-sulfur hexafluoride) up to about 0.2 kg/sec. This scale leads to chamber Reynolds numbers on the same order of magnitude as those anticipated in a full-scale nuclear rocket engine. The experimental program introduced here is focused on determining the size, geometry, and stability of the recirculation region as a function of the bleed ratio, i.e. the ratio of the injected mass flux to the free stream mass flux. A concurrent CFD study is being carried out to aid in demonstrating that the proposed technique is practical.

Task 1: The technical paper, `Assessment of Foam Properties and Effectiveness in Mobility Reduction for C0{sub 2} Foam Floods,` was prepared and presented at the 1997 SPE International Symposium on Oilfield Chemistry. The paper covers five surfactants tested earlier for their foam properties. Work is progressing on evaluating surfactants and their foam properties under high pressure conditions by using a foam durability apparatus. Two surfactants, Witcolate 1259 and Witcolate 1276, were tested in this quarter and the new data were added into our existing database for correlation between foam properties in the bulk phase and in porous media. The new data support the earlier conclusion that foam stability and interfacial tension correlate with selective mobility reduction. Task 2: The changing permeability of the core during a series of foam tests is a significant factor in determining foam coreflood test parameters. A series of tests often requires hundreds of pore volumes of fluids to pass through the core. During this quarter, a new core was developed that should eliminate this problem and provide a constant base line. We ran a series of tests, which showed that this core has a constant permeability, as anticipated. We continued to examine procedures for history-matching …