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The dynamical behavior of classifier systems

Description: Classifier systems are quite complicated, in terms of both their components and behavior. This complexity is understandable given the wide spectrum of activity they are intended to model. Unfortunately, the complexity of these systems also makes it difficult to understand them analytically. Previous analysis has focused on specific components of the classifier system, for example, the genetic algorithm or the bucket brigade. The lack of a unified theory has led users of these systems to rely on ad hoc methods for choosing representations and parameter settings. Recent results (Riolo, 1988) indicate that classifier systems can be very sensitive to particular encodings and parameter choices. In this paper, we propose a methodology for studying the interactions among various components of the classifier system architecture.
Date: February 10, 1989
Creator: Forrest, S. & Miller, J.H.
Partner: UNT Libraries Government Documents Department

Emergent behaviors of classifier systems

Description: This paper discusses some examples of emergent behavior in classifier systems, describes some recently developed methods for studying them based on dynamical systems theory, and presents some initial results produced by the methodology. The goal of this work is to find techniques for noticing when interesting emergent behaviors of classifier systems emerge, to study how such behaviors might emerge over time, and make suggestions for designing classifier systems that exhibit preferred behaviors. 20 refs., 1 fig.
Date: January 1, 1989
Creator: Forrest, S. & Miller, J.H.
Partner: UNT Libraries Government Documents Department

Modeling the dose-response relationship for cytotoxicity of human cells exposed to chemical carcinogens. [N-acetoxy-2-acetylaminofluorene]

Description: Compounds like N-acetoxy-2-acetylaminofluorene (N-AcO-AAF) result from the in vivo reduction of nitrate derivatives of benzo(..cap alpha..)pyrene. The dose-response relationship for survival of cloning ability in human fibroblasts exposed to N-AcO-AAF is being investigated to obtain a better understanding of the carcinogenic potential of coal-related air pollutants. A model is presented which correlates the survival of normal human fibroblasts after exposure to N-AcO-AAF with the rate of excision of carcinogen residues bound to DNA. The model predicts that the survival of normal cells, S/sub N/, is related to the survival of repair deficient cells, S/sub XPA/, by the equation 1n(S/sub N/) = 1n(S/sub XPA/) (1-f) where f is the fraction of potentially lethal damage repaired in the normal cell at a given dose of carcinogen. The rate of excision of AAF residues from the DNA of confluent human fibroblasts was measured over the same dose range as the survival studies. This information together with the dose-response relationship for survival of normal and repair deficient cells permits a determination of the mean number of adducts required to produce a potentially lethal lesion and the effective time available for repair. The model can be used to predict the mean lifetime of carcinogen residues on the DNA of partially repair deficient cells and the effect of recovery on the survival of normal cells. Extensions of the model to account for shoulders on the dose-response relationship curves are also discussed.
Date: September 1, 1980
Creator: Miller, J.H. & Heflich, R.H.
Partner: UNT Libraries Government Documents Department

Lanthanide extraction with 2,5-dimethyl-2-hydroxyhexanoic acid

Description: This research is concerned with the solvent extraction into chloroform of the lanthanides, using 2,5-dimethyl-2-hydroxyhexanoic acid (DMHHA). This acid is the first ..cap alpha..-hydroxy aliphatic acid to be studied as an extracting agent for the lanthanides. The chloroform-water DMHHA partition constant was determined to be 1.0 (at 0.1 M ionic strength and 25/sup 0/C). The acid dimerizes in chloroform with a constant of 56. The light lanthanides can be extracted into chloroform by forming complexes with the DMHHA anions. The extracted metal species is highly aggregated. This extraction has a solubility limit which increases with the addition of unionized acid. The resultant extract is also highly aggregated. At unionized acid-to-metal ratios greater than one, extractions first occur followed by the slow precipitation of the lanthanide. At the tracer level, neodymium is extracted primarily as NdA/sub 3/(HA)/sub 5/ and (NdA/sub 3/)/sub 2/(HA)/sub q/. Very small amounts of (NdA/sub 3/)/sub 2/ and other metal aggregates are also present. The heavy lanthanides do not extract from solutions of DMHHA and its potassium salt, but form aqueous emulsions and precipitates. In the presence of the organic soluble tetrabutylammonium ion the heavy lanthanides can be extracted, presumably as ion pairs. The stability constants of the light lanthanides and DMHHA were determined. The separation factors obtained from DMHHA extractions of the light lanthanides were also investigated and found to be comparable to those obtained employing normal aliphatic carboxylic acid.
Date: December 1, 1977
Creator: Miller, J. H.
Partner: UNT Libraries Government Documents Department

Catalytic activity of nuclease P1: Experiment and theory

Description: Nuclease P1 from Penicillium citrinum is a zinc dependent glyco-enzyme that recognizes single stranded DNA and RNA as substrates and hydrolyzes the phosphate ester bond. Nuclease Pl seems to recognize particular conformations of the phosphodiester backbone and shows significant variation in the rate of hydrolytic activity depending upon which nucleosides are coupled by the phosphodiester bond. The efficiency of nuclease Pl in hydrolyzing the phosphodiester bonds of a substrate can be altered by modifications to one of the substrate bases induced by ionizing radiation or oxidative stress. Measurements have been made of the effect of several radiation induced lesions on the catalytic rate of nuclease Pl. A model of the structure of the enzyme has been constructed in order to better understand the binding and activity of this enzyme on various ssDNA substrates.
Date: October 1, 1994
Creator: Miller, J.H.; Falcone, J.M.; Shibata, M. & Box, H.C.
Partner: UNT Libraries Government Documents Department

Conceptual Process for the Manufacture of Low-Enriched Uranium/Molybdenum Fuel for the High Flux Isotope Reactor

Description: The U.S. nonproliferation policy 'to minimize, and to the extent possible, eliminate the use of HEU in civil nuclear programs throughout the world' has resulted in the conversion (or scheduled conversion) of many of the U.S. research reactors from high-enriched uranium (HEU) to low-enriched uranium (LEU). A foil fuel appears to offer the best option for using a LEU fuel in the High Flux Isotope Reactor (HFIR) without degrading the performance of the reactor. The purpose of this document is to outline a proposed conceptual fabrication process flow sheet for a new, foil-type, 19.75%-enriched fuel for HFIR. The preparation of the flow sheet allows a better understanding of the costs of infrastructure modifications, operating costs, and implementation schedule issues associated with the fabrication of LEU fuel for HFIR. Preparation of a reference flow sheet is one of the first planning steps needed in the development of a new manufacturing capacity for low enriched fuels for U.S. research and test reactors. The flow sheet can be used to develop a work breakdown structure (WBS), a critical path schedule, and identify development needs. The reference flow sheet presented in this report is specifically for production of LEU foil fuel for the HFIR. The need for an overall reference flow sheet for production of fuel for all High Performance Research Reactors (HPRR) has been identified by the national program office. This report could provide a starting point for the development of such a reference flow sheet for a foil-based fuel for all HPRRs. The reference flow sheet presented is based on processes currently being developed by the national program for the LEU foil fuel when available, processes used historically in the manufacture of other nuclear fuels and materials, and processes used in other manufacturing industries producing a product configuration similar to the form ...
Date: September 30, 2007
Creator: Sease, J.D.; Primm, R.T. III & Miller, J.H.
Partner: UNT Libraries Government Documents Department

Development of high-activity {sup 252}Cf sources for neutron brachytherapy

Description: The Gershenson Radiation Oncology Center of Wayne State University (WSU), Detroit, Michigan, is using {sup 252}Cf medical sources for neutron brachytherapy. These sources are based on a 20-year-old design containing {le} 30 {micro}g {sup 252}Cf in the form of a cermet wire of Cf{sub 2}O{sub 3} in a palladium matrix. The Radiochemical Engineering Development Center (REDC) of Oak Ridge National Laboratory has been asked to develop tiny high-activity {sup 252}Cf neutron sources for use with remote afterloading equipment to reduce treatment times and dose to clinical personnel and to expedite treatment of brain and other tumors. To date, the REDC has demonstrated that {sup 252}Cf loadings can be greatly increased in cermet wires much smaller than before. Equipment designed for hot cell fabrication of these wires is being tested. A parallel program is under way to relicense the existing source design for fabrication at the REDC.
Date: October 1, 1996
Creator: Martin, R.C.; Laxson, R.R.; Miller, J.H.; Wierzbicki, J.G.; Rivard, M.J. & Marsh, D.L.
Partner: UNT Libraries Government Documents Department

Mechanism involved in trichloroethylene-induced liver cancer: Importance to environmental cleanup. 1998 annual progress report

Description: 'The objective of this project is to develop critical data for changing risk-based clean-up standards for trichloroethylene (TCE). The project is organized around two interrelated tasks: Task 1 addresses the tumorigenic and dosimetry issues for the metabolites of TCE that produce liver cancer in mice, dichloroacetate (DCA) and trichloroacetate (TCA). Early work had suggested that TCA was primarily responsible for TCE-induced liver tumors, but several, more mechanistic observations suggest that DCA may play a prominent role. This task is aimed at determining the basis for the selection hypothesis and seeks to prove that this mode of action is responsible for TCE-induced tumors. This project will supply the basic dose-response data from which low-dose extrapolations would be made. Task 2 seeks specific evidence that TCA and DCA are capable of promoting the growth of spontaneously initiated cells from mouse liver, in vitro. The data provide the clearest evidence that both metabolites act by a mechanism of selection rather than mutation. These data are necessary to select between a linear (i.e. no threshold) and non-linear low-dose extrapolation model. As of May of 1998, this research has identified two plausible modes of action by which TCE produces liver tumors in mice. These modes of action do not require the compounds to be mutagenic. The bulk of the experimental evidence suggests that neither TCE nor the two hepatocarcinogenic metabolites of TCE are mutagenic. The results from the colony formation assay clearly establish that both of these metabolites cause colony growth from initiated cells that occur spontaneously in the liver of B 6 C 3 F 1 mice, although the phenotypes of the colonies differ in the same manner as tumors differ, in vivo. In the case of DCA, a second mechanism may occur at a lower dose involving the release of insulin. This observation ...
Date: June 1, 1998
Creator: Bull, R.J.; Thrall, B.D.; Sasser, L.B.; Miller, J.H. & Schultz, I.R.
Partner: UNT Libraries Government Documents Department

Free-radical yield in proton irradiation of oriented DNA: Relationship to energy transfer along DNA chains

Description: Spatial patterns of energy deposition on the nanometer scale are currently believed to be a major factor in determining the biological effectiveness of ionizing radiation. If the most common precursors of biologically significant lesions are clusters of ionization in or near DNA, then intramolecular energy and charge transfer along DNA chains could be very important in lesion development. This paper describes investigations of these phenomena through model calculations and measurements of radical yields in oriented DNA exposed to proton irradiation.
Date: October 1, 1991
Creator: Miller, J.H.; Frasco, D.L.; Ye, M. (Pacific Northwest Lab., Richland, WA (United States)); Swenberg, C.E.; Myers, L.S. Jr. (Armed Forces Radiobiology Research Inst., Bethesda, MD (United States)) & Rupprecht, A. (Stockholm Univ. (Sweden))
Partner: UNT Libraries Government Documents Department

Chemical vapor infiltration of TiB[sub 2] composites

Description: Efficiency of the Hall-Heroult electrolytic reduction of aluminum can be substantially improved by the use of a TiB[sub 2] cathode surface. The use of TiB[sub 2], however, has been hampered by the brittle nature of the material and the grain-boundary attack of sintering-aid phases by molten aluminum. In the current work, TiB[sub 2] is toughened through the use of reinforcing fibers, with chemical vapor infiltration (CVI) used to produce pure TiB[sub 2]. It has been observed, however, that the formation of TiB[sub 2] from chloride precursors at fabrication temperatures below 900 to 1000[degrees]C alloys the retention of destructive levels of chlorine in the material. At higher fabrication temperatures and under appropriate infiltration conditions, as determined from the use of a process model, a TIB[sub 2]THORNEL P-25 fiber composite, 45 mm in diam and 6 mm thick, has been fabricated in 20 h. The material has been demonstrated to be stable in molten aluminum in short-duration tests.
Date: January 1, 1993
Creator: Besmann, T.M.; Miller, J.H.; Cooley, K.C.; Lowden, R.A. (Oak Ridge National Lab., TN (United States)) & Starr, T.L. (Georgia Tech Research Inst., Atlanta, GA (United States))
Partner: UNT Libraries Government Documents Department

Manipulation hardware for microgravity research

Description: The establishment of permanent low earth orbit occupation on the Space Station Freedom will present new opportunities for the introduction of productive flexible automation systems into the microgravity environment of space. The need for robust and reliable robotic systems to support experimental activities normally intended by astronauts will assume great importance. Many experimental modules on the space station are expected to require robotic systems for ongoing experimental operations. When implementing these systems, care must be taken not to introduce deleterious effects on the experiments or on the space station itself. It is important to minimize the acceleration effects on the experimental items being handled while also minimizing manipulator base reaction effects on adjacent experiments and on the space station structure. NASA Lewis Research Center has been performing research on these manipulator applications, focusing on improving the basic manipulator hardware, as well as developing improved manipulator control algorithms. By utilizing the modular manipulator concepts developed during the Laboratory Telerobotic Manipulator program, Oak Ridge National Laboratory has developed an experimental testbed system called the Microgravity Manipulator, incorporating two pitch-yaw modular positioners to provide a 4 dof experimental manipulator arm. A key feature in the design for microgravity manipulation research was the use of traction drives for torque transmission in the modular pitch-yaw differentials.
Date: January 1, 1990
Creator: Herndon, J.N.; Glassell, R.L.; Butler, P.L.; Williams, D.M. (Oak Ridge National Lab., TN (USA)); Rohn, D.A. (National Aeronautics and Space Administration, Cleveland, OH (USA). Lewis Research Center) & Miller, J.H. (Sverdrup Technology, Inc., Brook Park, OH (USA))
Partner: UNT Libraries Government Documents Department