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Event-Driven Power-Law Relaxation in Weak Turbulence (open access)

Event-Driven Power-Law Relaxation in Weak Turbulence

This article discusses event-driven power-law relaxation in weak turbulence.
Date: January 5, 2009
Creator: Silvestri, Ludovico; Fronzoni, Leone; Grigolini, Paolo & Allegrini, Paolo
Object Type: Article
System: The UNT Digital Library
High Resolution Simulation of Beam Dynamics in Electron Linacs for Free Electron Lasers (open access)

High Resolution Simulation of Beam Dynamics in Electron Linacs for Free Electron Lasers

In this paper we report on large scale multi-physics simulation of beam dynamics in electron linacs for next generation free electron lasers (FELs). We describe key features of a parallel macroparticle simulation code including three-dimensional (3D) space-charge effects, short-range structure wake fields, longitudinal coherent synchrotron radiation (CSR) wake fields, and treatment of radiofrequency (RF) accelerating cavities using maps obtained from axial field profiles. A macroparticle up-sampling scheme is described that reduces the shot noise from an initial distribution with a smaller number of macroparticles while maintaining the global properties of the original distribution. We present a study of the microbunching instability which is a critical issue for future FELs due to its impact on beam quality at the end of the linac. Using parameters of a planned FEL linac at Lawrence Berkeley National Laboratory (LBNL), we show that a large number of macroparticles (beyond 100 million) is needed to control numerical shot noise that drives the microbunching instability. We also explore the effect of the longitudinal grid on simulation results. We show that acceptable results are obtained with around 2048 longitudinal grid points, and we discuss this in view of the spectral growth rate predicted from linear theory. As an …
Date: January 5, 2009
Creator: Ryne, R.D.; Venturini, M.; Zholents, A.A. & Qiang, J.
Object Type: Article
System: The UNT Digital Library
Zinc surface complexes on birnessite: A density functional theory study (open access)

Zinc surface complexes on birnessite: A density functional theory study

Biogeochemical cycling of zinc is strongly influenced by sorption on birnessite minerals (layer-type MnO2), which are found in diverse terrestrial and aquatic environments. Zinc has been observed to form both tetrahedral (Zn{sup IV}) and octahedral (Zn{sup VI}) triple-corner-sharing surface complexes (TCS) at Mn(IV) vacancy sites in hexagonal birnessite. The octahedral complex is expected to be similar to that of Zn in the Mn oxide mineral, chalcophanite (ZnMn{sub 3}O{sub 7} {center_dot} 3H{sub 2}O), but the reason for the occurrence of the four-coordinate Zn surface species remains unclear. We address this issue computationally using spin-polarized Density Functional Theory (DFT) to examine the Zn{sub IV}-TCS and Zn{sup VI}-TCS species. Structural parameters obtained by DFT geometry optimization were in excellent agreement with available experimental data on Zn-birnessites. Total energy, magnetic moments, and electron-overlap populations obtained by DFT for isolated Zn{sup IV}-TCS revealed that this species is stable in birnessite without a need for Mn(III) substitution in the octahedral sheet and that it is more effective in reducing undersaturation of surface O at a Mn vacancy than is Zn{sub VI}-TCS. Comparison between geometry-optimized ZnMn{sub 3}O{sub 7} {center_dot} 3H{sub 2}O (chalcophanite) and the hypothetical monohydrate mineral, ZnMn{sub 3}O{sub 7} {center_dot} H{sub 2}O, which contains only tetrahedral …
Date: January 5, 2009
Creator: Kwon, Kideok D.; Refson, Keith & Sposito, Garrison
Object Type: Article
System: The UNT Digital Library
Thermal Analysis for in-Tank Ion-Exchange Column Process (open access)

Thermal Analysis for in-Tank Ion-Exchange Column Process

High Level Waste (HLW) at the Savannah River Site (SRS) is stored in three forms: sludge, saltcake, and supernate. A small column ion-exchange (SCIX) process is being designed to treat dissolved saltcake waste before feeding it to the saltstone facility to be made into grout. The waste is caustic with high concentrations of various sodium salts and lower concentrations of radionuclides. Two cation exchange media being considered are a granular form of crystalline silicotitanate (CST) and a spherical form of resorcinol-formaldehyde (RF) resin. CST is an inorganic material highly selective for cesium that is not elutable. Through this process, radioactive cesium from the salt solution is absorbed into ion exchange media (either CST or RF) which is packed within a flow-through column. A packed column loaded with radioactive cesium generates significant heat from radiolytic decay. If engineering designs cannot handle this thermal load, hot spots may develop locally which could degrade the performance of the ion-exchange media. Performance degradation with regard to cesium removal has been observed between 50 and 80 C for CST [1] and at 65 C for RF resin [2]. In addition, the waste supernate solution will boil around 130 C. If the columns boiled dry, the …
Date: January 5, 2009
Creator: Lee, S. & Frank02 Smith, F.
Object Type: Article
System: The UNT Digital Library
Measurement of CP Content and Time-Dependent CP Violation in B0 --> D*+D*- Decays (open access)

Measurement of CP Content and Time-Dependent CP Violation in B0 --> D*+D*- Decays

This dissertation presents the measurement of the Cp-odd fraction and time-dependent CP violation parameters for the B{sup 0} {yields} D*{sup +} D*{sup -} decay. These results are based on the full BABAR dataset of (467 {+-} 5) x 10{sup 6} B{bar B} pairs collected at the PEP-II B Factory at the Stanford Linear Accelerator Center. An angular analysis finds that the CP-odd fraction of the B{sup 0} {yields} D*{sup +} D*{sup -} decay is R{sub {perpendicular}} = 0.158 {+-} 0.028 {+-} 0.006, where the first uncertainty is statistical, and the second is systematic. A fit to the flavor-tagged, time-dependent, angular decay rate yields C{sub +} = 0.02 {+-} 0.12 {+-} 0.02; C{sub {perpendicular}} = 0.41 {+-} 0.50 {+-} 0.08; S{sub +} = -0.76 {+-} 0.16 {+-} 0.04; S{sub {perpendicular}} = -1.81 {+-} 0.71 {+-} 0.16, for the CP-odd ({perpendicular}) and CP-even (+) contributions. Constraining these two contributions to be the same results in C = 0.047 {+-} 0.091 {+-} 0.019; S = -0.71 {+-} 0.16 {+-} 0.03. These measurements are consistent with the Standard Model and with measurements of sin2{beta} from B{sup 0} {yields} (c{bar c})K{sup 0} decays.
Date: January 5, 2009
Creator: Anderson, Jacob M.
Object Type: Thesis or Dissertation
System: The UNT Digital Library
Functional Interfaces in Polymer-Based Bulk Heterojunction Solar Cells: Establishment of a Cluster for Interdisciplinary Research and Training (open access)

Functional Interfaces in Polymer-Based Bulk Heterojunction Solar Cells: Establishment of a Cluster for Interdisciplinary Research and Training

Remarkable scientific progress has been demonstrated toward the creation of a low cost (“printable”) solar cell technology by the interdisciplinary group at UC Santa Barbara. Multi-layer architectures were implemented with clean interfaces were demonstrated; the various interfaces are sharp; there is no evidence of inter-layer mixing. This is indeed remarkable since each of these layers was processed from solution. The use of “Processing Additives” such as the alkanedithiols was demonstrated to increase the power conversion efficiency of BHJ solar cells by a factor of two. Equally important, the mechanism by which these Processing Additives function has been identified.
Date: January 5, 2009
Creator: Heeger, Alan J & Nguyen, Thuc-Quyen
Object Type: Report
System: The UNT Digital Library
Casework in a Congressional Office: Background, Rules, Laws, and Resources (open access)

Casework in a Congressional Office: Background, Rules, Laws, and Resources

This report discusses House and Senate rules and guidelines, laws, and regulations affecting congressional casework, as well as the role of caseworkers.
Date: January 5, 2009
Creator: Petersen, R. Eric
Object Type: Report
System: The UNT Digital Library
Education of Individuals with Disabilities: The Individuals with Disabilities Education Act (IDEA), Section 504 of the Rehabilitation Act, and the Americans with Disabilities Act (ADA) (open access)

Education of Individuals with Disabilities: The Individuals with Disabilities Education Act (IDEA), Section 504 of the Rehabilitation Act, and the Americans with Disabilities Act (ADA)

This report will examine the similarities and differences in the IDEA, Section 504, and ADA coverage of education including the implications of the ADA Amendments Act of 2008.
Date: January 5, 2009
Creator: Jones, Nancy Lee & Toland, Carol J.
Object Type: Report
System: The UNT Digital Library
Quest for Environmentally-Benign Ligands for Actinide Separations: Thermodynamic, Spectroscopic, and Structural Characterization of U(VI) Complexes with Oxa-Diamide and Related Ligands (open access)

Quest for Environmentally-Benign Ligands for Actinide Separations: Thermodynamic, Spectroscopic, and Structural Characterization of U(VI) Complexes with Oxa-Diamide and Related Ligands

Complexation of U(VI) with N,N,N{prime},N{prime}-tetramethyl-3-oxa-glutaramide (TMOGA) and N,N-dimethyl-3-oxa-glutaramic acid (DMOGA) was studied in comparison with their dicarboxylate analog, oxydiacetic acid (ODA). Thermodynamic parameters, including stability constants, enthalpy and entropy of complexation, were determined by spectrophotometry, potentiometry and calorimetry. Single-crystal X-ray diffractometry, EXAFS spectroscopy, FT-IR absorption and laser-induced luminescence spectroscopy were used to obtain structural information on the U(VI) complexes. Like ODA, TMOGA and DMOGA form tridentate U(VI) complexes, with three oxygen atoms (the amide, ether and/or carboxylate oxygen) coordinating to the linear UO{sub 2}{sup 2+} cation via the equatorial plane. The stability constants, enthalpy and entropy of complexation all decrease in the order ODA > DMOGA > TMOGA, showing that the complexation is entropy driven and the substitution of a carboxylate group with an amide group reduces the strength of complexation with U(VI) due to the decrease in the entropy of complexation. The trend in the thermodynamic stability of the complexes correlates very well with the structural and spectroscopic data obtained by single crystal XRD, FT-IR and laser-induced luminescence spectroscopy.
Date: January 5, 2009
Creator: Source, Advanced Light; Tian, Guoxin; Rao, Linfeng; Teat, Simon J. & Liu, Guokui
Object Type: Article
System: The UNT Digital Library
Complexation of Gluconate with Uranium(VI) in Acidic Solutions: Thermodynamic Study with Structural Analysis (open access)

Complexation of Gluconate with Uranium(VI) in Acidic Solutions: Thermodynamic Study with Structural Analysis

Within the pC{sub H} range of 2.5 to 4.2, gluconate forms three uranyl complexes UO{sub 2}(GH{sub 4}){sup +}, UO{sub 2}(GH{sub 3})(aq), and UO{sub 2}(GH{sub 3})(GH{sub 4}){sup -}, through the following reactions: (1) UO{sub 2}{sup 2+} + GH{sub 4}{sup -} = UO{sub 2}(GH{sub 4}){sup +}, (2) UO{sub 2}{sup 2+} + GH{sub 4}{sup -} = UO{sub 2}(GH{sub 3})(aq) + H{sup +}, and (3) UO{sub 2}{sup 2+} + 2GH{sub 4}{sup -} = UO{sub 2}(GH{sub 3})(GH{sub 4}){sup -} + H{sup +}. Complexes were inferred from potentiometric, calorimetric, NMR, and EXAFS studies. Correspondingly, the stability constants and enthalpies were determined to be log {Beta}{sub 1} = 2.2 {+-} 0.3 and {Delta}H{sub 1} = 7.5 {+-} 1.3 kJ mol{sup -1} for reaction (1), log {Beta}{sub 2} = -(0.38 {+-} 0.05) and {Delta}H{sub 2} = 15.4 {+-} 0.3 kJ mol{sup -1} for reaction (2), and log {Beta}{sub 3} = 1.3 {+-} 0.2 and {Delta}H{sub 3} = 14.6 {+-} 0.3 kJ mol{sup -1} for reaction (3), at I = 1.0 M NaClO{sub 4} and t = 25 C. The UO{sub 2}(GH{sub 4}){sup +} complex forms through the bidentate carboxylate binding to U(VI). In the UO{sub 2}(GH{sub 3})(aq) complex, hydroxyl-deprotonated gluconate (GH{sub 3}{sup 2-}) coordinates to U(VI) through the …
Date: January 5, 2009
Creator: Zhang, Zhicheng; Helms, G.; Clark, S. B.; Tian, Guoxin; Zanonato, PierLuigi & Rao, Linfeng
Object Type: Article
System: The UNT Digital Library
Soft inertial microfluidics for high throughput separation of bacteria from human blood cells (open access)

Soft inertial microfluidics for high throughput separation of bacteria from human blood cells

We developed a new approach to separate bacteria from human blood cells based on soft inertial force induced migration with flow defined curved and focused sample flow inside a microfluidic device. This approach relies on a combination of an asymmetrical sheath flow and proper channel geometry to generate a soft inertial force on the sample fluid in the curved and focused sample flow segment to deflect larger particles away while the smaller ones are kept on or near the original flow streamline. The curved and focused sample flow and inertial effect were visualized and verified using a fluorescent dye primed in the device. First the particle behavior was studied in detail using 9.9 and 1.0 {micro}m particles with a polymer-based prototype. The prototype device is compact with an active size of 3 mm{sup 2}. The soft inertial effect and deflection distance were proportional to the fluid Reynolds number (Re) and particle Reynolds number (Re{sub p}), respectively. We successfully demonstrated separation of bacteria (Escherichia coli) from human red blood cells at high cell concentrations (above 10{sup 8}/mL), using a sample flow rate of up to 18 {micro}L/min. This resulted in at least a 300-fold enrichment of bacteria at a wide range …
Date: January 5, 2009
Creator: Wu, Zhigang; Willing, Ben; Bjerketorp, Joakim; Jansson, Janet K. & Hjort, Klas
Object Type: Article
System: The UNT Digital Library
Goddard rattler-jamming mechanism for quantifying pressure dependence of elastic moduli of grain packs (open access)

Goddard rattler-jamming mechanism for quantifying pressure dependence of elastic moduli of grain packs

An analysis is presented to show how it is possible for unconsolidated granular packings to obey overall non-Hertzian pressure dependence due to the imperfect and random spatial arrangements of the grains in these packs. With imperfect arrangement, some gaps that remain between grains can be closed by strains applied to the grain packing. As these gaps are closed, former rattler grains become jammed and new stress-bearing contacts are created that increase the elastic stiffness of the packing. By allowing for such a mechanism, detailed analytical expressions are obtained for increases in bulk modulus of a random packing of grains with increasing stress and strain. Only isotropic stress and strain are considered in this analysis. The model is shown to give a favorable fit to laboratory data on variations in bulk modulus due to variations in applied pressure for bead packs.
Date: January 5, 2009
Creator: Pride, Steven R. & Berryman, James G.
Object Type: Article
System: The UNT Digital Library
The role of parallel heat transport in the relation between upstream scrape-off layer widths and target heat flux width in H-mode plasmas of NSTX. (open access)

The role of parallel heat transport in the relation between upstream scrape-off layer widths and target heat flux width in H-mode plasmas of NSTX.

The physics of parallel heat transport was tested in the Scrape-off Layer (SOL) plasma of the National Spherical Torus Experiment (NSTX) [M. Ono, et al., Nucl. Fusion 40, 557 (2000) and S. M. Kaye, et al., Nucl. Fusion 45, S168 (2005)] tokamak by comparing the upstream electron temperature (T{sub e}) and density (n{sub e}) profiles measured by the mid-plane reciprocating probe to the heat flux (q{sub {perpendicular}}) profile at the divertor plate measured by an infrared (IR) camera. It is found that electron conduction explains the near SOL width data reasonably well while the far SOL, which is in the sheath limited regime, requires an ion heat flux profile broader than the electron one to be consistent with the experimental data. The measured plasma parameters indicate that the SOL energy transport should be in the conduction-limited regime for R-R{sub sep} (radial distance from the separatrix location) < 2-3 cm. The SOL energy transport should transition to the sheath-limited regime for R-R{sub sep} > 2-3cm. The T{sub e}, n{sub e}, and q{sub {perpendicular}} profiles are better described by an offset exponential function instead of a simple exponential. The conventional relation between mid plane electron temperature decay length ({lambda}{sub Te}) and target …
Date: January 5, 2009
Creator: Ahn, J W; Boedo, J A; Maingi, R & Soukhanovskii, V A
Object Type: Article
System: The UNT Digital Library
Biofuels Incentives: A Summary of Federal Programs (open access)

Biofuels Incentives: A Summary of Federal Programs

This report outlines federal programs that provide direct or indirect incentives for biofuels. For each program described, the report provides details including administering agency, authorizing statue(s), annual funding, and expiration date.
Date: January 5, 2009
Creator: Yacobucci, Brent D.
Object Type: Report
System: The UNT Digital Library
Africa Command: U.S. Strategic Interests and the Role of the U.S. Military in Africa (open access)

Africa Command: U.S. Strategic Interests and the Role of the U.S. Military in Africa

This report provides information on U.S. Africa Command or (AFRICOM), including AFRICOM's mission, structure, interagency coordination, and its basing and manpower requirements. The report also gives a broad overview of U.S. strategic interests in Africa and the role of U.S. military efforts on the continent as they pertain to the creation of Africa Command.
Date: January 5, 2009
Creator: Ploch, Lauren
Object Type: Report
System: The UNT Digital Library
Trade Adjustment Assistance for Firms: Economic, Program, and Policy Issues (open access)

Trade Adjustment Assistance for Firms: Economic, Program, and Policy Issues

None
Date: January 5, 2009
Creator: unknown
Object Type: Report
System: The UNT Digital Library
GSE Regulatory Reform: Frequently Asked Questions (open access)

GSE Regulatory Reform: Frequently Asked Questions

This report summarizes the most frequently asked questions regarding GSE regulatory reform. It also discusses about who currently regulates Fannie Mae, Freddie Mac, and the FHL Banks?
Date: January 5, 2009
Creator: Weiss, N. Eric
Object Type: Report
System: The UNT Digital Library
Authority of the Senate to Exclude and Not Seat a Senator-Elect or Senator-Designate (open access)

Authority of the Senate to Exclude and Not Seat a Senator-Elect or Senator-Designate

This report is about the Authority of the Senate to exclude and not seat a Senator-elect or Senator-Designate.
Date: January 5, 2009
Creator: Maskell, Jack
Object Type: Report
System: The UNT Digital Library
The Express-Star (Chickasha, Okla.), Ed. 1 Monday, January 5, 2009 (open access)

The Express-Star (Chickasha, Okla.), Ed. 1 Monday, January 5, 2009

Daily newspaper from Chickasha, Oklahoma that includes local, state, and national news along with advertising.
Date: January 5, 2009
Creator: unknown
Object Type: Newspaper
System: The Gateway to Oklahoma History
Sapulpa Daily Herald (Sapulpa, Okla.), Vol. 94, No. 95, Ed. 1 Monday, January 5, 2009 (open access)

Sapulpa Daily Herald (Sapulpa, Okla.), Vol. 94, No. 95, Ed. 1 Monday, January 5, 2009

Daily newspaper from Sapulpa, Oklahoma that includes local, state, and national news along with advertising.
Date: January 5, 2009
Creator: Shance, Brenda
Object Type: Newspaper
System: The Gateway to Oklahoma History
Zimbabwe: 2008 Elections and Implications for U.S. Policy (open access)

Zimbabwe: 2008 Elections and Implications for U.S. Policy

This report provides an overview of Zimbabwe's March 2008 elections. The report discusses the power-sharing agreement, the transitional government, cholera outbreak, international reactions, and U.S. policy on Zimbabwe.
Date: January 5, 2009
Creator: Ploch, Lauren
Object Type: Report
System: The UNT Digital Library
Sweetwater Reporter (Sweetwater, Tex.), Vol. 111, No. 42, Ed. 1 Monday, January 5, 2009 (open access)

Sweetwater Reporter (Sweetwater, Tex.), Vol. 111, No. 42, Ed. 1 Monday, January 5, 2009

Daily newspaper from Sweetwater, Texas that includes local, state, and national news along with advertising.
Date: January 5, 2009
Creator: Rodriguez, Tatiana
Object Type: Newspaper
System: The Portal to Texas History
The Baytown Sun (Baytown, Tex.), Vol. 89, No. 5, Ed. 1 Monday, January 5, 2009 (open access)

The Baytown Sun (Baytown, Tex.), Vol. 89, No. 5, Ed. 1 Monday, January 5, 2009

Daily newspaper from Baytown, Texas that includes local, state, and national news along with advertising.
Date: January 5, 2009
Creator: Clements, Clifford E.
Object Type: Newspaper
System: The Portal to Texas History
Solenoid-free Plasma Start-up in NSTX using Transient CHI (open access)

Solenoid-free Plasma Start-up in NSTX using Transient CHI

Experiments in NSTX have now demonstrated the coupling of toroidal plasmas produced by the technique of Coaxial Helicity Injection (CHI) to inductive sustainment and ramp-up of the toroidal plasma current. In these discharges, the central Ohmic transformer was used to apply an inductive loop voltage to discharges with a toroidal current of about 100 kA created by CHI. The coupled discharges have ramped up to >700 kA and transitioned into an H-mode demonstrating compatibility of this startup method with conventional operation. The electron temperature in the coupled discharges reached over 800 eV and the resulting plasma had low inductance, which is preferred for long-pulse high performance discharges. These results from NSTX in combination with the previously obtained record 160 kA non-inductively-generated startup currents in an ST or tokamak in NSTX demonstrate that CHI is a viable solenoid-free plasma startup method for future STs and tokamaks.
Date: January 5, 2009
Creator: Raman, R.; Jarboe, T.; Nelson, B.; Mueller, D. & Soukhanovskii, V. A.
Object Type: Article
System: The UNT Digital Library