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Stability Of Plasma Configurations During Compression (open access)

Stability Of Plasma Configurations During Compression

Magnetized Target Fusion (MTF) efforts are based on calculations showing that the addition of a closed magnetic field reduces the driver pressure and rise time requirements for inertial confinement fusion by reducing thermal conductivity. Instabilities that result in convective bulk transport at the Alphen time scale are of particular concern since they are much faster than the implosion time. Such instabilities may occur during compression due to, for example, an increase in the plasma-magnetic pressure ratio {beta} or, in the case of a rotating plasma, spin-up due to angular momentum conservation. Details depend on the magnetic field topology and compression geometry. A hard core z pinch with purely azimuthal magnetic field can theoretically be made that relaxes into a wall supported diffuse profile satisfying the Kadomtsev criterion for the stability of m = 0 modes, which is theoretically preserved during cylindrical outer wall compression. The center conductor radius and current must also be large enough to keep the {beta} below stability limits to stabilize modes with m > 0. The stability of m > 0 modes actually improves during compression. A disadvantage of this geometry, though, is plasma contact with the solid boundaries. In addition to the risk of high …
Date: October 27, 2006
Creator: Ruden, E L & Hammer, J H
System: The UNT Digital Library
A Search for the B^0 to e^+ e^- \gamma and B^0 to \mu^+ \mu^- \gamma Decays (open access)

A Search for the B^0 to e^+ e^- \gamma and B^0 to \mu^+ \mu^- \gamma Decays

With the BABAR detector at the PEP-II asymmetric B Factory at SLAC, they present the first search for the decays B{sup 0} {yields} {ell}{sup +}{ell}{sup -}{gamma} ({ell} = e, {mu}). Using a data set of 292 fb{sup -1} collected at the {Upsilon}(4S) resonance, they find no significant signal and set the following branching fraction upper limits at 90% confidence level: {Beta}(B{sup 0} {yields} e{sup +}e{sup -}{gamma}) < 0.7 x 10{sup -7} and {Beta}(B{sup 0} {yields} {mu}{sup +}{mu}{sup -}{gamma}) < 3.4 x 10{sup -7}.
Date: September 27, 2006
Creator: Aubert, B.
System: The UNT Digital Library
X-ray Absorption Spectroscopy and Density Functional Theory Studies of [(H3buea)FeIII-X]n1 (X= S2-, O2-,OH-): Comparison of Bonding and Hydrogen Bonding in Oxo and Sulfido Complexes (open access)

X-ray Absorption Spectroscopy and Density Functional Theory Studies of [(H3buea)FeIII-X]n1 (X= S2-, O2-,OH-): Comparison of Bonding and Hydrogen Bonding in Oxo and Sulfido Complexes

Iron L-edge, iron K-edge, and sulfur K-edge X-ray absorption spectroscopy was performed on a series of compounds [Fe{sup III}H{sub 3}buea(X)]{sup n-} (X = S{sup 2-}, O{sup 2-}, OH{sup -}). The experimentally determined electronic structures were used to correlate to density functional theory calculations. Calculations supported by the data were then used to compare the metal-ligand bonding and to evaluate the effects of H-bonding in Fe{sup III}-O vs Fe{sup III-}S complexes. It was found that the Fe{sup III-}O bond, while less covalent, is stronger than the FeIII-S bond. This dominantly reflects the larger ionic contribution to the Fe{sup III-}O bond. The H-bonding energy (for three H-bonds) was estimated to be -25 kcal/mol for the oxo as compared to -12 kcal/mol for the sulfide ligand. This difference is attributed to the larger charge density on the oxo ligand resulting from the lower covalency of the Fe-O bond. These results were extended to consider an Fe{sup IV-}O complex with the same ligand environment. It was found that hydrogen bonding to Fe{sup IV-}O is less energetically favorable than that to Fe{sup III-}O, which reflects the highly covalent nature of the Fe{sup IV-}O bond.
Date: September 27, 2006
Creator: Dey, Abhishek; Hocking, Rosalie K.; /Stanford U., Chem. Dept.; Larsen, Peter; Borovik, Andrew S.; U., /Kansas et al.
System: The UNT Digital Library
Coherent Instabilities of ILC Damping Ring (open access)

Coherent Instabilities of ILC Damping Ring

The paper presents the first attempt to estimates the ILC damping ring impedance and compare thresholds of the classical instabilities for several designs initially proposed for the DR. The work was carried out in the spring of 2006. Since then the choice of the DR is narrowed. Nevertheless, the analysis described may be useful for the next iterations of the beam stability. Overall, the conventional instabilities will have little impact on the ring performance provided the careful design of the ring minimizes the impedance below acceptable level indicated above. The only exception is the transverse CB instability. The longitudinal CB is less demanding. However, even the transverse CB instability would have threshold current above nominal provided the aperture in the wigglers is increased from 8 mm to 16 mm. The microwave instability needs more studies. Nevertheless, we should remember that the ILC DR is different from existing high-current machines at least in two respects: absence of the beam-beam tune spread stabilizing beams in colliders, and unusual strict requirements for low emittance. That may cause new problems such as bunch emittance dilution due to high-frequency wakes (BPMs, grooves), etc. Even if such a possibility exists, it probably universal for all machines …
Date: September 27, 2006
Creator: Heifets, S.; Stupakov, G. & Bane, K.
System: The UNT Digital Library
The Effect of Unheated Sections on Moisture Transport in the Emplacement Drift (open access)

The Effect of Unheated Sections on Moisture Transport in the Emplacement Drift

The goals of this study are: (1) to configure a thermal-hydrological, natural-ventilation model for simulating temperature, humidity, and condensate distributions in the coupled domains of in-drift airspace and near-field rockmass. Rokmass model: TOUGH2, in-drift model: MULTIFLUX (MF); (2) obtain meaningful results from the model for a practical application in which the beneficial effects of unheated drift sections are analyzed; and (3) study the sensitivity to the axial dispersion coefficient with the model.
Date: April 27, 2006
Creator: Danko, G.; Birkholzer, J. & Bahrami, D.
System: The UNT Digital Library
LOW AMPLITUDE SINGLE AND MULTIPLE SHOCK INITIATION EXPERIMENTS AND MODELING OF LX-04 (open access)

LOW AMPLITUDE SINGLE AND MULTIPLE SHOCK INITIATION EXPERIMENTS AND MODELING OF LX-04

Shock initiation experiments were performed on the plastic bonded explosive (PBX) LX-04 (85% HMX, 15% Viton binder) using single and multiple low amplitude shocks to obtain pressure history data for use in Ignition and Growth reactive flow modeling parameterization. A 100 mm diameter propellant driven gas gun was utilized to initiate the LX-04 explosive charges containing manganin piezoresistive pressure gauge packages placed between explosive discs. In the single shock experiments, the run distances to detonation at three shock pressures showed agreement with previously published data above 3 GPa. Even longer run distances to detonation were measured using 80 mm long by 145 mm diameter LX-04 charges impacted by low velocity projectiles from a 155 mm diameter gun. The minimum shock pressure required to cause low levels of exothermic reaction were determined for these large LX-04 charge dimensions. Multiple shocks were generated as double shocks by using a flyer plate with two materials and as reflected shocks by placing a high impedance material at the rear of the explosive charge. In both cases, the first shock pressure was not high enough to cause detonation of LX-04, and the second shock pressure, which would have been sufficient to cause detonation if generated …
Date: June 27, 2006
Creator: Vandersall, K S; Tarver, C M; Garcia, F; Chidester, S; Urtiew, P A & Forbes, J W
System: The UNT Digital Library
First Annual U.S. Department of Energy Office of Science JointGenome Institute User Meeting (open access)

First Annual U.S. Department of Energy Office of Science JointGenome Institute User Meeting

None
Date: March 27, 2006
Creator: unknown
System: The UNT Digital Library
Design and Use of a Novel Apparatus for Measuring Capsule Fill Hole Conductance (open access)

Design and Use of a Novel Apparatus for Measuring Capsule Fill Hole Conductance

Description and results of a novel apparatus for determining the flow conductance through a laser drilled hole in a spherical shell for inertial confinement fusion experiments are described. The instrument monitors the pressure of an enclosed volume containing the laser pressure drilled capsule as air bleeds through the hole into the shell. From these measurements one obtains the conductance of the fill hole. This system has proven to be a valuable tool for verifying the conduct conductance into the capsule in a timely and nondestructive manner.
Date: November 27, 2006
Creator: Seugling, R M; Nederbragt, W W; Klingmann, J L; Edson, S; Reynolds, J & Cook, R
System: The UNT Digital Library
The San Joaquin Valley Westside Perspective (open access)

The San Joaquin Valley Westside Perspective

Salt management has been a challenge to westside farmerssince the rapid expansion of irrigated agriculture in the 1900 s. Thesoils in this area are naturally salt-affected having formed from marinesedimentary rocks rich in sea salts rendering the shallow groundwater,and drainage return flows discharging into the lower reaches of the SanJoaquin River, saline. Salinity problems are affected by the importedwater supply from Delta where the Sacramento and San Joaquin Riverscombine. Water quality objectives on salinity and boron have been inplace for decades to protect beneficial uses of the river. However it wasthe selenium-induced avian toxicity that occurred in the evaporationponds of Kesterson Reservoir (the terminal reservoir of a planned but notcompleted San Joaquin Basin Master Drain) that changed public attitudesabout agricultural drainage and initiated a steady stream ofenvironmental legislation directed at reducing non-point source pollutionof the River. Annual and monthly selenium load restrictions and salinityand boron Total Maximum Daily Loads (TMDLs) are the most recent of thesepolicy initiatives. Failure by both State and Federal water agencies toconstruct a Master Drain facility serving mostly west-side irrigatedagriculture has constrained these agencies to consider only In-Valleysolutions to ongoing drainage problems. For the Westlands subarea, whichhas no surface irrigation drainage outlet to the San Joaquin …
Date: March 27, 2006
Creator: Quinn, Nigel W.T.; Linneman, J. Christopher & Tanji, Kenneth K.
System: The UNT Digital Library
Implementation of Localized Corrosion in the Performance Assessment Model for Yucca Mountain (open access)

Implementation of Localized Corrosion in the Performance Assessment Model for Yucca Mountain

None
Date: April 27, 2006
Creator: Jain, Vivek; Sevougian, S. David; Mattie, Patrick D.; Mon, Kevin G. & MacKinnon, Robert J.
System: The UNT Digital Library
Reduction of Thermal Conductivity in Wafer-Bonded Silicon (open access)

Reduction of Thermal Conductivity in Wafer-Bonded Silicon

Blocks of silicon up to 3-mm thick have been formed by directly bonding stacks of thin wafer chips. These stacks showed significant reductions in the thermal conductivity in the bonding direction. In each sample, the wafer chips were obtained by polishing a commercial wafer to as thin as 36 {micro}m, followed by dicing. Stacks whose starting wafers were patterned with shallow dots showed greater reductions in thermal conductivity. Diluted-HF treatment of wafer chips prior to bonding led to the largest reduction of the effective thermal conductivity, by approximately a factor of 50. Theoretical modeling based on restricted conduction through the contacting dots and some conduction across the planar nanometer air gaps yielded fair agreement for samples fabricated without the HF treatment.
Date: November 27, 2006
Creator: Liau, ZL; Danielson, LR; Fourspring, PM; Hu, L; Chen, G & Turner, GW
System: The UNT Digital Library
Dynamic Wildfire Risk Mapping: Challenges and Solutions (open access)

Dynamic Wildfire Risk Mapping: Challenges and Solutions

None
Date: July 27, 2006
Creator: Goldstein, N; Moritz, M & Kearns, F
System: The UNT Digital Library
On the Nature of Variations in Density and Composition within TATB-based Plastic Bonded Explosives (open access)

On the Nature of Variations in Density and Composition within TATB-based Plastic Bonded Explosives

Initiation of insensitive high explosives is affected by porosity in the 100 nm to micron size range. It is also recognized that as-pressed plastic bonded explosives (PBX) are heterogeneous in composition and density at much coarser length scale (10 microns-100 microns). However, variations in density and composition of these explosives have been poorly characterized. Here, we characterize the natural variations in composition and density of TATB-based PBX LX-17 with synchrotron radiation tomography and ultra small angle x-ray scattering. Large scale variations in composition occur as a result of binder enrichment at the prill particle boundaries. The pore fraction is twice as high in the prill particle as in the boundary. The pore distribution is bimodal, with small pores of 50-100 nm in radius and a broader distribution of pores in the 0.5-1.5 micron size range. The higher pore density within the prill particle is attributed to contact asperities between the crystallites that might inhibit complete consolidation and binder infiltration.
Date: June 27, 2006
Creator: Kinney, J H; Willey, T M & Overturf, G
System: The UNT Digital Library
The dynamics of diluted Ho spin ice Ho2-xYxTi2O7 studied byneutron spin echo spectroscopy (open access)

The dynamics of diluted Ho spin ice Ho2-xYxTi2O7 studied byneutron spin echo spectroscopy

We have studied the spin relaxation in diluted spin ice Ho{sub 2-x} Y{sub x} Ti{sub 2}O{sub 7} by means of neutron spin echo spectroscopy. Remarkably, the geometrical frustration is not relieved by doping with non-magnetic Y, and the dynamics of the freezing is unaltered in the spin echo time window up to x {approx_equal} 1.6. At higher doping with non-magnetic Y (x {ge} 1.6) a new relaxation process at relatively high temperature (up to at least T {approx_equal} 55 K) appears which is more than 10 times faster than the thermally activated main relaxation process. We find evidence that over the whole range of composition all Ho spins participate in the dynamics. These results are compared to a.c. susceptibility measurements of the diluted Ho and Dy spin ice systems. X-ray absorption fine structure (EXAFS) spectra and x-ray diffraction show that the samples are structurally well ordered.
Date: February 27, 2006
Creator: Ehlers, G.; Gardner, J. S.; Booth, C. H.; Daniel, M.; Kam, K. C.; Cheetham, A. K. et al.
System: The UNT Digital Library
New Tools for the site-specific attachment of proteins to surface (open access)

New Tools for the site-specific attachment of proteins to surface

Protein microarrays in which proteins are immobilized to a solid surface are ideal reagents for high-throughput experiments that require very small amounts of analyte. Such protein microarrays (''protein chips'') can be used very efficiently to analyze all kind of protein interactions en masse. Although a variety of methods are available for attaching proteins on solid surfaces. Most of them rely on non-specific adsorption methods or on the reaction of chemical groups within proteins (mainly, amino and carboxylic acid groups) with complementary reactive groups. In both cases the protein is attached to the surface in random orientations. The use of recombinant affinity tags addresses the orientation issue, however in most of the cases the interaction of the tags are reversible (e.g., glutathione S-transferase, maltose binding protein and poly-His) and, hence, are not stable over the course of subsequent assays or require large mediator proteins (e.g., biotin-avidin and antigen antibody). The key for the covalent attachment of a protein to a solid support with a total control over the orientation is to introduce two unique and mutually reactive groups on both the protein and the surface. The reaction between these two groups should be highly selective thus behaving like a molecular ''velcro''.
Date: June 27, 2006
Creator: Kwon, Y; Coleman, M A & Camarero, J A
System: The UNT Digital Library
Black Hole Production at the LHC by Standard Model Bulk Fields in the Randall-Sundrum Model. (open access)

Black Hole Production at the LHC by Standard Model Bulk Fields in the Randall-Sundrum Model.

We consider the production of black holes at the LHC in the Randall-Sundrum (RS) model through the collisions of Standard Model(SM) fields in the bulk. In comparison to the previously studied case where the SM fields are all confined to the TeV brane, we find substantial suppressions to the corresponding collider cross sections for all initial states, i.e., gg, qq and gq, where q represents a light quark or anti-quark which lie close to the Planck brane. For b quarks, which are closer to the TeV brane, this suppression effect is somewhat weaker though b quark contributions to the cross section are already quite small due to their relatively small parton densities. Semi-quantitatively, we find that the overall black hole cross section is reduced by roughly two orders of magnitude in comparison to the traditional TeV brane localized RS model with the exact value being sensitive to the detailed localizations of the light SM fermions in the bulk.
Date: November 27, 2006
Creator: Rizzo, Thomas G.
System: The UNT Digital Library
EVALUATION OF ORGANIC VAPOR RELEASE FROM CEMENT-BASED WASTE FORMS (open access)

EVALUATION OF ORGANIC VAPOR RELEASE FROM CEMENT-BASED WASTE FORMS

A cement based waste form was evaluated to determine the rates at which various organics were released during heating caused by the cementitious heat-of-hydration reaction. Saltstone is a cement-based waste form for the disposal of low-level salt solution. Samples were prepared with either Isopar{reg_sign} L, a long straight chained hydrocarbon, or (Cs,K) tetraphenylborate, a solid that, upon heating, decomposes to benzene and other aromatic compounds. The saltstone samples were heated over a range of temperatures. Periodically, sample headspaces were purged and the organic constituents were captured on carbon beds and analyzed. Isopar{reg_sign} L was released from the saltstone in a direct relationship to temperature. An equation was developed to correlate the release rate of Isopar{reg_sign} L from the saltstone to the temperature at which the samples were cured. The release of benzene was more complex and relied on both the decomposition of the tetraphenylborate as well as the transport of the manufactured benzene through the curing saltstone. Additional testing with saltstone prepared with different surface area/volume also was performed.
Date: September 27, 2006
Creator: Cozzi, A; Jack Zamecnik, J & Russell Eibling, R
System: The UNT Digital Library
Benchmark Calculation Of Inclusive Responses In The Four-Body Nuclear System (open access)

Benchmark Calculation Of Inclusive Responses In The Four-Body Nuclear System

This paper reports on a recent benchmark calculation in the four-nucleon system, aimed at investigating the reliability of the no-core shell model (NCSM) approach to the description of inclusive response functions via the Lorentz integral transform (LIT) method.
Date: September 27, 2006
Creator: Quaglioni, S.; Stetcu, I.; Bacca, S.; Barrett, B. R.; Johnson, C. W.; Navratil, P. et al.
System: The UNT Digital Library
Multiple Quantum NMR Investigations of Structure- Property Relationships in Synthetic and Aged Silicone Elastomers (open access)

Multiple Quantum NMR Investigations of Structure- Property Relationships in Synthetic and Aged Silicone Elastomers

Complex engineering elastomeric materials are often characterized by a complex network structure obtained by crosslinking network chains with multiple chain lengths. Further, these networks are commonly filled with thixotropic reinforcing agents such as SiO{sub 2} or carbon black. Degradation of such materials often occurs via mechanisms that alter the fundamental network structure. In order to understand the effects of modifications of network structure and filler-polymer interaction on component performance, a series of model compounds have been studied by {sup 1}H multiple quantum NMR analysis and traditional mechanical property assessments. The {sup 1}H NMR data provides insight into the distribution of segmental dynamics that reveals insight into the changes in mechanical properties.
Date: September 27, 2006
Creator: Maxwell, R.; Gjersing, E.; Chinn, S.; Herberg, J.; Eastwood, E.; Bowen, D. et al.
System: The UNT Digital Library
Scrape-Off Layer Transport and Deposition Studies in DIII-D (open access)

Scrape-Off Layer Transport and Deposition Studies in DIII-D

Trace {sup 13}CH{sub 4} injection experiments into the main scrape-off layer of low density L-mode and high-density H-mode plasmas have been performed in the DIII-D tokamak [Luxon{_}NF02] to mimic the transport and deposition of carbon arising from a main chamber sputtering source. These experiments indicated entrainment of the injected carbon in plasma flow in the main SOL, and transport toward the inner divertor. Ex-situ surface analysis showed enhanced {sup 13}C surface concentration at the corner formed by the divertor floor and the angled target plate of the inner divertor in L-mode; in H-mode, both at the corner and along the surface bounding the private flux region inboard of the outer strike point. Interpretative modeling was made consistent with these experimental results by imposing a parallel carbon ion flow in the main SOL toward the inner target, and a radial pinch toward the separatrix. Predictive modeling carried out to better understand the underlying plasma transport processes suggests that the deuterium flow in the main SOL is related to the degree of detachment of the inner divertor leg. These simulations show that carbon ions are entrained with the deuteron flow in the main SOL via frictional coupling, but higher charge state carbon …
Date: October 27, 2006
Creator: Groth, M.; Allen, S.; Boedo, J.; Brooks, N.; Elder, J.; Fenstermacher, M. et al.
System: The UNT Digital Library
Bulk Properties of Iron Isotopes (open access)

Bulk Properties of Iron Isotopes

Nuclear level densities and radiative strength functions (RSF) in {sup 56}Fe and {sup 57}Fe were measured using the {sup 57}Fe({sup 3}He,{alpha}{gamma}) and {sup 57}Fe({sup 3}He, {sup 3}He{prime}{gamma}) reactions, respectively, at Oslo Cyclotron Laboratory. A low-energy enhancement in the RSF below 4 MeV energy was observed. This finding cannot be explained by common theoretical models. In a second experiment, two-step cascade intensities with soft primary transitions from the {sup 56}Fe(n,2{gamma}) reaction were measured. The agreement between the two experiments confirms the low-energy enhancement in the RSF. In a third experiment, the neutron evaporation spectrum from the {sup 55}Mn(dn,N){sup 56}Fe reaction was measured at 7-MeV deuteron energy at John Edwards Accelerator Laboratory at Ohio University. Comparison of the level density of {sup 56}Fe obtained from the first and third experiments gives an overall good agreement. Furthermore, observed enhancement for soft {gamma} rays is supported by the last experiment.
Date: July 27, 2006
Creator: Algin, E.; Schiller, A.; Voinov, A.; Agvannluvsan, U.; Belgya, T.; Bernstein, L. et al.
System: The UNT Digital Library
Magnetic Resonance Based Diagnostics for Polymer Production and Surveillance (open access)

Magnetic Resonance Based Diagnostics for Polymer Production and Surveillance

In an effort to develop a magnetic resonance based diagnostic tool to be used for polymer production and surveillance, we have investigated the use of magnetic resonance imaging (MRI) and unilateral relaxometry. MRI provides a spatial map of the polymer, which can be correlated to the structure heterogeneity. Though highly detailed information can be obtained with MRI, the high equipment cost and expertise required to operate the system makes it a poor choice for a production setting. Unilateral relaxometry via the NMR MOUSE provides rapid, inexpensive polymer screening, useful in the development in new polymer parts or to identify potentially defective components. The NMR ProFiler (originally called the NMR MOUSE) was procured by Kansas City originally for production support of the W80 LEP with future applications as a surveillance diagnostic. A robotic autosampler has been designed allowing the detection of several components without the need for any human interaction. A summary of the qualification experiments and results to date from the ProFiler and the robotic unit will be presented.
Date: September 27, 2006
Creator: Chinn, S; Herberg, J; Gjersing, E; Cook, A; Sawvel, A M; Maxwell, R et al.
System: The UNT Digital Library
Finite Elements approach for Density Functional Theory calculations on locally refined meshes (open access)

Finite Elements approach for Density Functional Theory calculations on locally refined meshes

We present a quadratic Finite Elements approach to discretize the Kohn-Sham equations on structured non-uniform meshes. A multigrid FAC preconditioner is proposed to iteratively solve the equations by an accelerated steepest descent scheme. The method was implemented using SAMRAI, a parallel software infrastructure for general AMR applications. Examples of applications to small nanoclusters calculations are presented.
Date: March 27, 2006
Creator: Fattebert, J; Hornung, R D & Wissink, A M
System: The UNT Digital Library
Freezing Kinetics in Overcompressed Water (open access)

Freezing Kinetics in Overcompressed Water

We report high pressure dynamic compression experiments of liquid water along a quasi-adiabatic path leading to the formation of ice VII. We observe dynamic features resembling Van der Waals loops and find that liquid water is compacted to a metastable state close to the ice density before the onset of crystallization. By analyzing the characteristic kinetic time scale involved we estimate the nucleation barrier and conclude that liquid water has been compressed to a high pressure state close to its thermodynamic stability limit.
Date: September 27, 2006
Creator: Bastea, Marina; Bastea, Sorin; Reaugh, John & Reisman, David
System: The UNT Digital Library