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Seminole Sentinel (Seminole, Tex.), Vol. 93, No. 77, Ed. 1 Wednesday, July 12, 2000
Semiweekly newspaper from Seminole, Texas that includes local, state, and national news along with advertising.
Date:
July 12, 2000
Creator:
Dow, M. Gene & Fisher, David
Object Type:
Newspaper
System:
The Portal to Texas History
SIAM Workshop: Focus on Diversity
The Fourth SlAM Graduate Student Focus on Diversity workshop was held on July 12, 2000 at the Westin Rio Mar Hotel in Rio Grande, Puerto Rico. The Department of Energy provided partial support for this event. The day-long workshop consisted of several different activities. The meeting opened with a discussion of some data collected by the American Mathematical Society on Ph.D.'s awarded in the U.S. to citizens and non-citizens, further classified as blacks, latinos, asians and native americans. The activity continued with nine technical talks by underrepresented minority graduate students, informal luncheon and pizza breaks to foster social interaction, and an evening forum chaired by Dr. Richard Tapia (Rice University) in which issues related to the participation of minorities in national meetings and proposal writing where discussed. These sessions were open to the entire SIAM community and served to highlight the progress, achievements, and aspirations of the workshop participants. The students attended as well the three SlAM plenary talks during the day and the community lecture in the evening. The activity had a lively participation of students and representatives from various academic institutions and sponsoring agencies. In particular, we had the participation of 24 undergraduate students from the Mathematics REU …
Date:
July 12, 2000
Creator:
unknown
Object Type:
Article
System:
The UNT Digital Library
Simple Simulations of DNA Condensation
Molecular dynamics simulations of a simple, bead-spring model of semiflexible polyelectrolytes such as DNA are performed. All charges are explicitly treated. Starting from extended, noncondensed conformations, condensed structures form in the simulations with tetravalent or trivalent counterions. No condensates form or are stable for divalent counterions. The mechanism by which condensates form is described. Briefly, condensation occurs because electrostatic interactions dominate entropy, and the favored Coulombic structure is a charge ordered state. Condensation is a generic phenomena and occurs for a variety of polyelectrolyte parameters. Toroids and rods are the condensate structures. Toroids form preferentially when the molecular stiffness is sufficiently strong.
Date:
July 12, 2000
Creator:
STEVENS,MARK J.
Object Type:
Article
System:
The UNT Digital Library
Simulating Retention in Gas-Liquid Chromatography: Benzene, Toluene, and Xylene Solutes
Accurate predictions of retention times, retention indices, and partition constants are a long sought-after goal for theoretical studies in chromatography. Although advances in computational chemistry have improved the understanding of molecular interactions, little attention has been focused on chromatography, let alone calculations of retention properties. Configurational-bias Monte Carlo simulations in the isobaric-isothermal Gibbs ensemble were used to investigate the partitioning of benzene, toluene, and the three xylene isomers between a squalane liquid phase and a helium vapor phase. The united-atom representation of the TraPPE (Transferable Potentials for Phase Equilibria) force field was used for all solutes and squalane. The Gibbs free energies of transfer and Kovats retention indices of the solutes were calculated directly from the partition constants (which were averaged over several independent simulations). While the calculated Kovats indices of benzene and toluene at T = 403 K are significantly higher than their experimental counterparts, much better agreement is found for the xylene isomers at T = 365 K.
Date:
July 12, 2000
Creator:
Wick, Collin D.; Martin, Marcus G.; Siepmann, J. Ilja & Schure, Mark R.
Object Type:
Article
System:
The UNT Digital Library
Small Column Ion Exchange Testing of Superlig 644 for Removal of 137Cs from Hanford Tank Waste Envelope A (Tank 241-AW-101)
The current BNFL Inc. flow sheet for the pretreatment of the Hanford High-Level tank wastes includes the use of Superlig{reg_sign} materials for the removal of {sup 137}Cs from the aqueous fraction of the waste. The Superlig materials applicable to cesium removal include the cesium selective Superlig 632 and Superlig 644. These materials have been developed and supplied by IBC Advanced Technologies, Inc., American Fork, UT. The work contained in this report involves testing the Superlig 644 ion exchange material in a small dual column system (15 mL each; L/D = 5.7). The sample processed was approximately 2.5 L of diluted waste [Na{sup +}] = 4.6M from Tank 241-AW-101 (Envelope A). This waste had been previously clarified in a single tube cross-flow filtration unit. All ion exchange process steps were tested including resin bed preparation, loading, feed displacement water rinse, elution and resin regeneration. During the initial run, the lag column did not perform as expected so that the {sup 137}Cs concentration in the effluent composite was above the LAW treatment limits. This required a second column run with the partially decontaminated feed that was conducted at a higher flow rate. A summary of performance measures for both runs is shown …
Date:
July 12, 2000
Creator:
Kurath, DE; Blanchard, DL & Bontha, JR
Object Type:
Report
System:
The UNT Digital Library
Stratospheric Ozone Depletion: Implementation Issues
For two decades, scientists have been warning that chlorofluorocarbons (CFCs) and halons (bromine-containing fluorocarbons) may deplete the stratospheric ozone shield that screens out some of the Sun's harmful ultraviolet rays and thus regulates the amounts which reach the Earth's surface. CFCs have been used as refrigerants, solvents, foam blowing agents, and outside the United States, as aerosol propellants; Halons are used primarily as firefighting agents. Increased radiation could result in an increase in skin cancers, suppression of the human immune system, and decreased productivity of terrestrial and aquatic organisms, including some commercially important crops.
Date:
July 12, 2000
Creator:
Parker, Larry
Object Type:
Report
System:
The UNT Digital Library
Tank Farm Waste Transfer Compatibility Program
The compatibility program described in this document formalizes the process for determining waste compatibility. The primary goal of the program is to ensure that sufficient controls are in place to prevent the formation of incompatible mixtures during future operations. The process described involves characterizing waste, comparing characteristics with criteria, resolving potential incompatibilities and documenting the process.
Date:
July 12, 2000
Creator:
FOWLER, K.D.
Object Type:
Report
System:
The UNT Digital Library
Task Technical and Quality Assurance Plan for the Characterization of the Tank 40H Samples
The High Level Waste Tank Farms store and process high-level liquid wastes from a number of sources including F- and H-Canyons and a recycle stream from the Defense Waste Processing Facility (DWPF). The deposition of sodium aluminosilicate along with sodium diuranate in the 242-16H evaporator system led to the removal of authorization to process High Level Waste containing DWPF recycle. Therefore, High Level Waste Engineering has requested SRTC to perform analysis of the contents of Tank 40H and associated transfers from sludge washing to ensure silicon levels are sufficiently low to allow processing of the supernate through the 3H Evaporator.
Date:
July 12, 2000
Creator:
Wilmarth, W.R.
Object Type:
Report
System:
The UNT Digital Library
Transferable Potentials for Phase Equilibria. 4. United-Atom Description of Linear and Branched Alkenes and Alkylbenzenes
The Transferable Potentials for Phase Equilibria-United Atom (TraPPE-UA) force field for hydrocarbons is extended to alkenes and alkylbenzenes by introducing the following pseudo-atoms: CH{sub 2}(sp{sup 2}), CH(sp{sup 2}), CH(aro), R-C(aro) for the link to aliphatic side chains, and C(aro) for the link of two benzene rings. In this united-atom force field, the nonbonded interactions of the hydrocarbon pseudo-atoms are solely governed by Lennard-Jones 12-6 potentials, and the Lennard-Jones well depth and size parameters for the new pseudo-atoms were determined by fitting to the single-component vapor-liquid phase equilibria of a few selected model compounds. Configurational-bias Monte Carlo simulations in the NVT version of the Gibbs ensemble were carried out to calculate the single-component vapor-liquid coexistence curves for ethene, propene, 1-butene, trans- and cis-2-butene. 2-methylpropene, 1,5-hexadiene, 1-octene, benzene, toluene, ethylbenzene, propylbenzene, isopropylbenzene, o-, m-, and p-xylene, and naphthalene. The phase diagrams for the binary mixtures of (supercritical) ethene/n-heptane and benzene/n-pentane were determined from simulations in the NpT Gibbs ensemble. Although the TraPPE-UA force field is rather simple and makes use of relatively few different pseudo-atoms, its performance, as judged by comparisons to other popular force fields and available experimental data, is very satisfactory.
Date:
July 12, 2000
Creator:
WICK,COLLIN D.; MARTIN,MARCUS G. & SIEPMANN,J. ILJA
Object Type:
Article
System:
The UNT Digital Library
Use of Imperfect Calibration for Seismic Location
Efforts to more effectively monitor nuclear explosions include the calibration of travel times along specific paths. Benchmark events are used to improve travel-time prediction by (1) improving models, (2) determining travel times empirically, or (3) using a hybrid approach. Even velocity models that are determined using geophysical analogy (i.e. models determined without the direct use of calibration data) require validation with calibration events. Ideally, the locations and origin times of calibration events would be perfectly known. However, the existing set of perfectly known events is spatially limited and many of these events occurred prior to the installation of current monitoring stations, thus limiting their usefulness. There are, however, large numbers of well (but not perfectly) located events that are spatially distributed, and many of these events may be used for calibration. Identifying the utility and limitations of the spatially distributed set of imperfect calibration data is of paramount importance to the calibration effort. In order to develop guidelines for calibration utility, we examine the uncertainty and correlation of location parameters under several network configurations that are commonly used to produce calibration-grade locations. We then map these calibration uncertainties through location procedures with network configurations that are likely in monitoring situations. …
Date:
July 12, 2000
Creator:
Myers, S C & Schultz, C A
Object Type:
Article
System:
The UNT Digital Library
Věstník (Temple, Tex.), Vol. 88, No. 27, Ed. 1 Wednesday, July 12, 2000
Weekly Czech and English language newspaper from Temple, Texas published as the official organ of the Slavonic Benevolent Order of the State of Texas that includes news of interest to members along with advertising.
Date:
July 12, 2000
Creator:
Vanicek, Brian
Object Type:
Newspaper
System:
The Portal to Texas History
The Wylie News (Wylie, Tex.), Vol. 54, No. 7, Ed. 1 Wednesday, July 12, 2000
Weekly newspaper from Wylie, Texas that includes local, state and national news along with advertising.
Date:
July 12, 2000
Creator:
Engbrock, Chad B.
Object Type:
Newspaper
System:
The Portal to Texas History