The Impact of an Oxygen Dopant in an ideal Bi_2Sr_2CaCu_2O_8 delta Crystal (open access)

The Impact of an Oxygen Dopant in an ideal Bi_2Sr_2CaCu_2O_8 delta Crystal

Recent scanning tunneling microscopy studies have shown that local nanoscale pairing inhomogenities are correlated with interstitial oxygen dopants in Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}}. Combining electrostatic and cluster calculations, in this paper the impact of a dopant on the local Madelung and charge transfer energies, magnetic exchange J, Zhang-Rice mobility, and interactions with the lattice is investigated. It is found that electrostatic modifications locally increases the charge transfer energy and slightly suppresses J. It is further shown that coupling to c-axis phonons is strongly modified near the dopant. The combined effects of electrostatic modifications and coupling to the lattice yield broadened spectral features, reduced charge gap energies, and a sizable local increase of J. This implies a strong local interplay between antiferromagnetism, polarons, and superconducting pairing.
Date: May 4, 2010
Creator: Johnston, S.
Object Type: Article
System: The UNT Digital Library
U.S. Trade and Investment Relationship with Sub-Saharan Africa: The African Growth and Opportunity Act (open access)

U.S. Trade and Investment Relationship with Sub-Saharan Africa: The African Growth and Opportunity Act

This report presents perspectives on African economic trends and provides an overview of U.S. trade and investment flows with sub-Saharan Africa (SSA). It discusses the provisions of the African Growth and Opportunity Act (AGOA) and the changes that have occurred since its enactment. It concludes with a brief discussion of issues of congressional interest.
Date: February 4, 2010
Creator: Jones, Vivian C.
Object Type: Report
System: The UNT Digital Library
Size Effect of Ruthenium Nanoparticles in Catalytic Carbon Monoxide Oxidation (open access)

Size Effect of Ruthenium Nanoparticles in Catalytic Carbon Monoxide Oxidation

Carbon monoxide oxidation over ruthenium catalysts has shown an unusual catalytic behavior. Here we report a particle size effect on CO oxidation over Ru nanoparticle (NP) catalysts. Uniform Ru NPs with a tunable particle size from 2 to 6 nm were synthesized by a polyol reduction of Ru(acac){sub 3} precursor in the presence of poly(vinylpyrrolidone) stabilizer. The measurement of catalytic activity of CO oxidation over two-dimensional Ru NPs arrays under oxidizing reaction conditions (40 Torr CO and 100 Torr O{sub 2}) showed an activity dependence on the Ru NP size. The CO oxidation activity increases with NP size, and the 6 nm Ru NP catalyst shows 8-fold higher activity than the 2 nm catalysts. The results gained from this study will provide the scientific basis for future design of Ru-based oxidation catalysts.
Date: April 4, 2010
Creator: Joo, Sang Hoon; Park, Jeong Y.; Renzas, J. Russell; Butcher, Derek R.; Huang, Wenyu & Somorjai, Gabor A.
Object Type: Article
System: The UNT Digital Library
Agriculture in Pending U.S. Free Trade Agreements with Colombia, Panama, and South Korea (open access)

Agriculture in Pending U.S. Free Trade Agreements with Colombia, Panama, and South Korea

This report discusses pending U.S. free trade agreements (FTAs) with South Korea, Colombia, and Panama. The bills to implement these agreements will now be debated under trade promotion authority, or fast-track rules, designed to expedite congressional consideration. The report includes an overview of agricultural issues regarding FTAs and pending FTA partners, as well as a closer breakdown of the specific issues for each of the countries.
Date: February 4, 2010
Creator: Jurenas, Remy
Object Type: Report
System: The UNT Digital Library
MULTI-KEV X-RAY YIELDS FROM HIGH-Z GAS TARGETS FIELDED AT OMEGA (open access)

MULTI-KEV X-RAY YIELDS FROM HIGH-Z GAS TARGETS FIELDED AT OMEGA

The authors report on modeling of x-ray yield from gas-filled targets shot at the OMEGA laser facility. The OMEGA targets were 1.8 mm long, 1.95 mm in diameter Be cans filled with either a 50:50 Ar:Xe mixture, pure Ar, pure Kr or pure Xe at {approx} 1 atm. The OMEGA experiments heated the gas with 20 kJ of 3{omega} ({approx} 350 nm) laser energy delivered in a 1 ns square pulse. the emitted x-ray flux was monitored with the x-ray diode based DANTE instruments in the sub-keV range. Two-dimensional x-ray images (for energies 3-5 keV) of the targets were recorded with gated x-ray detectors. The x-ray spectra were recorded with the HENWAY crystal spectrometer at OMEGA. Predictions are 2D r-z cylindrical with DCA NLTE atomic physics. Models generally: (1) underpredict the Xe L-shell yields; (2) overpredict the Ar K-shell yields; (3) correctly predict the Xe thermal yields; and (4) greatly underpredict the Ar thermal yields. However, there are spreads within the data, e.g. the DMX Ar K-shell yields are correctly predicted. The predicted thermal yields show strong angular dependence.
Date: November 4, 2010
Creator: Kane, J O; Fournier, K B; May, M J; Colvin, J D; Thomas, C A; Marrs, R E et al.
Object Type: Article
System: The UNT Digital Library
DISTRIBUTION AND RANGE OF RADIONUCLIDE SORPTIOIN COEFFICIENTS IN A SAVANNAH RIVER SITE SUBSURFACE: STOCHASTIC MODELING CONSIDERATIONS - 10259 (open access)

DISTRIBUTION AND RANGE OF RADIONUCLIDE SORPTIOIN COEFFICIENTS IN A SAVANNAH RIVER SITE SUBSURFACE: STOCHASTIC MODELING CONSIDERATIONS - 10259

The uncertainty associated with the sorption coefficient, or K{sub d} value, is one of the key uncertainties in estimating risk associated with burying low-level nuclear waste in the subsurface. The objective of this study was to measure >648 K{sub d} values and provide a measure of the range and distribution (normal or log-normal) of radionuclide K{sub d} values appropriate for the E-Area disposal site, within the Savannah River Site, near Aiken South Carolina. The 95% confidence level for the mean K{sub d} was twice the mean in the Aquifer Zone (18-30.5 m depth), equal to the mean for the Upper Vadose Zone (3.3-10 m depth), and half the mean for the Lower Vadose Zone (3.3-18 m depth). The distribution of K{sub d} values was log normal in the Upper Vadose Zone and Aquifer Zone, and normal in the Lower Vadose Zone. To our knowledge, this is the first report of natural radionuclide K{sub d} variability in the literature. Using ranges and distribution coefficients that are specific to the hydrostratigraphic unit improved model accuracy and reduced model uncertainty. Unfortunately, extension of these conclusions to other sites is likely not appropriate given that each site has its own sources of hydrogeological variability. …
Date: January 4, 2010
Creator: Kaplan, D.
Object Type: Article
System: The UNT Digital Library
Iran Sanctions (open access)

Iran Sanctions

This report focuses on the United States' relationship with Iran and how the Obama Administration is handling prior administrations' economic sanctions against Iran. The Obama Administration's policy approach toward Iran has contrasted with the Bush Administration's by attempting to couple the imposition of sanctions to an active and direct U.S. effort to negotiate with Iran on the nuclear issue.
Date: May 4, 2010
Creator: Katzman, Kenneth
Object Type: Report
System: The UNT Digital Library
Iraq: Politics, Elections, and Benchmarks (open access)

Iraq: Politics, Elections, and Benchmarks

Iraq's political system, the result of a U.S.-supported election process, has been increasingly characterized by peaceful competition, as well as by attempts to form cross-sectarian alliances. However, ethnic and factional infighting continues, sometimes involving the questionable use of key levers of power and legal institutions. This report discusses the current political climate of Iraq and also explores speculations as to what will happen after U.S. troops completely withdraw from the region at the end of 2011.
Date: October 4, 2010
Creator: Katzman, Kenneth
Object Type: Report
System: The UNT Digital Library
A Hybrid Monte Carlo-Deterministic Method for Global Binary Stochastic Medium Transport Problems (open access)

A Hybrid Monte Carlo-Deterministic Method for Global Binary Stochastic Medium Transport Problems

Global deep-penetration transport problems are difficult to solve using traditional Monte Carlo techniques. In these problems, the scalar flux distribution is desired at all points in the spatial domain (global nature), and the scalar flux typically drops by several orders of magnitude across the problem (deep-penetration nature). As a result, few particle histories may reach certain regions of the domain, producing a relatively large variance in tallies in those regions. Implicit capture (also known as survival biasing or absorption suppression) can be used to increase the efficiency of the Monte Carlo transport algorithm to some degree. A hybrid Monte Carlo-deterministic technique has previously been developed by Cooper and Larsen to reduce variance in global problems by distributing particles more evenly throughout the spatial domain. This hybrid method uses an approximate deterministic estimate of the forward scalar flux distribution to automatically generate weight windows for the Monte Carlo transport simulation, avoiding the necessity for the code user to specify the weight window parameters. In a binary stochastic medium, the material properties at a given spatial location are known only statistically. The most common approach to solving particle transport problems involving binary stochastic media is to use the atomic mix (AM) approximation …
Date: March 4, 2010
Creator: Keady, K P & Brantley, P
Object Type: Article
System: The UNT Digital Library
U.S. Nuclear Cooperation with India: Issues for Congress (open access)

U.S. Nuclear Cooperation with India: Issues for Congress

This report discusses the United States' relationship with India as it relates to nuclear arsenals and nuclear nonproliferation policies. The report includes background information on India's nuclear history and nuclear weapons-specific U.S. legislation.
Date: February 4, 2010
Creator: Kerr, Paul K.
Object Type: Report
System: The UNT Digital Library
Nuclear Cooperation with Other Countries: A Primer (open access)

Nuclear Cooperation with Other Countries: A Primer

This report discusses section 123 of the Atomic Energy Act (AEA), the specific requirements of which must be met in order for the United States to engage in civilian nuclear cooperation with other states. The AEA also provides for exemptions to these requirements, export control licensing procedures, and criteria for terminating cooperation.
Date: January 4, 2010
Creator: Kerr, Paul K. & Nikitin, Mary Beth
Object Type: Report
System: The UNT Digital Library
Staffing for Adequate Fire and Emergency Response: The SAFER Grant Program (open access)

Staffing for Adequate Fire and Emergency Response: The SAFER Grant Program

This report discusses Staffing for Adequate Fire and Emergency Response (SAFER) Act, which was enacted by the 108th Congress as Section 1057 of the FY2004 National Defense Authorization Act (P.L. 108-136). It includes background of the SAFER Act, appropriations from FY2010-FY2011, reauthorization of the program in the House and Senate, and information about program implementation.
Date: July 4, 2010
Creator: Kruger, Lennard G.
Object Type: Report
System: The UNT Digital Library
HEAVY ION FUSION SCIENCE VIRTUAL NATIONAL LABORATORY 1ST QUARTER 2010 MILESTONE REPORT:  Simulations of fast correction of chromatic aberrations to establish physics specifications for implementation on NDCX-1 and NDCX-2 (open access)

HEAVY ION FUSION SCIENCE VIRTUAL NATIONAL LABORATORY 1ST QUARTER 2010 MILESTONE REPORT: Simulations of fast correction of chromatic aberrations to establish physics specifications for implementation on NDCX-1 and NDCX-2

This milestone has been accomplished. The Heavy Ion Fusion Science Virtual National Laboratory has completed simulations of a fast correction scheme to compensate for chromatic and time-dependent defocusing effects in the transport of ion beams to the target plane in the NDCX-1 facility. Physics specifications for implementation in NDCX-1 and NDCX-2 have been established. This milestone has been accomplished. The Heavy Ion Fusion Science Virtual National Laboratory has completed simulations of a fast correction scheme to compensate for chromatic and time-dependent defocusing effects in the transport of ion beams to the target plane in the NDCX-1 facility. Physics specifications for implementation in NDCX-1 and NDCX-2 have been established. Focal spot differences at the target plane between the compressed and uncompressed regions of the beam pulse have been modeled and measured on NDCX-1. Time-dependent focusing and energy sweep from the induction bunching module are seen to increase the compressed pulse spot size at the target plane by factors of two or more, with corresponding scaled reduction in the peak intensity and fluence on target. A time-varying beam envelope correction lens has been suggested to remove the time-varying aberration. An Einzel (axisymmetric electric) lens system has been analyzed and optimized for general …
Date: January 4, 2010
Creator: LIDIA, S.M.; LUND, S.M. & SEIDL, P.A.
Object Type: Report
System: The UNT Digital Library
The Economic Implications of the Long-Term Federal Budget Outlook (open access)

The Economic Implications of the Long-Term Federal Budget Outlook

This report analyzes the long-run path of the federal budget. The United States is projected to undergo a demographic shift as the aging of the baby boomers causes an unprecedented increase in the fraction of the population that is retired. Coupled with rising life expectancy, this means, under current policy, a steady increase in the portion of the population that is both out of the workforce and receiving social insurance benefits from the government.
Date: January 4, 2010
Creator: Labonte, Marc
Object Type: Report
System: The UNT Digital Library
Measurement of the Branching Fraction for D8+ rarr tau+nu_tau and Extraction of the Decay Constant f_D_s (open access)

Measurement of the Branching Fraction for D8+ rarr tau+nu_tau and Extraction of the Decay Constant f_D_s

The branching fraction for the decay D{sub s}{sup +} {yields} {tau}{sup +}{nu}{sub {tau}} with {tau}{sup +} {yields} e{sup +}{bar {nu}}{sub {tau}}, is measured using a data sample corresponding to an integrated luminosity of 427 fb{sup -1} collected at center of mass energies near 10.58 GeV with the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} collider at SLAC. In the process e{sup +}e{sup -} {yields} c{bar c} {yields} D*{sub s}{sup +} {bar D}{sub TAG}{bar K}X, the D*{sub s}{sup +} meson is reconstructed as a missing particle, and the subsequent decay D*{sub s}{sup +} {yields} D{sub s}{sup +}{gamma} yields an inclusive D{sub s}{sup +} data sample. Here {bar D}{sub TAG} refers to a fully reconstructed hadronic {bar D} decay, {bar K} is a K{sup -} or {bar K}{sup 0}, and X stands for any number of charged or neutral pions. The decay D{sub s}{sup +} {yields} K{sub S}{sup 0}K{sup +} is isolated also, and from ratio of event yields and known branching fractions, {Beta}(D{sub s}{sup +} {yields} {tau}{sup +}{nu}{sub {tau}}) = (4.5 {+-} 0.5 {+-} 0.4 {+-} 0.3)% is determined. The pseudoscalar decay constant is extracted to be f{sub D{sub s}} = (233 {+-} 13 {+-} 10 {+-} 7) MeV, …
Date: June 4, 2010
Creator: Lees, J. P.; Poireau, V.; Prencipe, E.; Tisserand, V.; Garra Tico, J.; Grauges, E. et al.
Object Type: Report
System: The UNT Digital Library
The FY2011 Federal Budget (open access)

The FY2011 Federal Budget

This report provides an historical overview of the budget trends through the most recently completed fiscal year (2009). It discusses major budgetary challenges over the past several fiscal years given the current economic conditions and provides an in-depth discussion of the FY2011 budget process. Finally, it provides context for the issues facing the country's federal budget over the long term. This report will be updated as events warrant.
Date: August 4, 2010
Creator: Levit, Mindy R.
Object Type: Report
System: The UNT Digital Library
Momentum Transfer by Laser Ablation of Irregularly Shaped Space Debris (open access)

Momentum Transfer by Laser Ablation of Irregularly Shaped Space Debris

Proposals for ground-based laser remediation of space debris rely on the creation of appropriately directed ablation-driven impulses to either divert the fragment or drive it into an orbit with a perigee allowing atmospheric capture. For a spherical fragment, the ablation impulse is a function of the orbital parameters and the laser engagement angle. If, however, the target is irregularly shaped and arbitrarily oriented, new impulse effects come into play. Here we present an analysis of some of these effects.
Date: February 4, 2010
Creator: Liedahl, D A; Libby, S B & Rubenchik, A
Object Type: Article
System: The UNT Digital Library
Prediction of epigenetically regulated genes in breast cancer cell lines (open access)

Prediction of epigenetically regulated genes in breast cancer cell lines

Methylation of CpG islands within the DNA promoter regions is one mechanism that leads to aberrant gene expression in cancer. In particular, the abnormal methylation of CpG islands may silence associated genes. Therefore, using high-throughput microarrays to measure CpG island methylation will lead to better understanding of tumor pathobiology and progression, while revealing potentially new biomarkers. We have examined a recently developed high-throughput technology for measuring genome-wide methylation patterns called mTACL. Here, we propose a computational pipeline for integrating gene expression and CpG island methylation profles to identify epigenetically regulated genes for a panel of 45 breast cancer cell lines, which is widely used in the Integrative Cancer Biology Program (ICBP). The pipeline (i) reduces the dimensionality of the methylation data, (ii) associates the reduced methylation data with gene expression data, and (iii) ranks methylation-expression associations according to their epigenetic regulation. Dimensionality reduction is performed in two steps: (i) methylation sites are grouped across the genome to identify regions of interest, and (ii) methylation profles are clustered within each region. Associations between the clustered methylation and the gene expression data sets generate candidate matches within a fxed neighborhood around each gene. Finally, the methylation-expression associations are ranked through a logistic …
Date: May 4, 2010
Creator: Loss, Leandro A; Sadanandam, Anguraj; Durinck, Steffen; Nautiyal, Shivani; Flaucher, Diane; Carlton, Victoria EH et al.
Object Type: Article
System: The UNT Digital Library
Laos: Background and U.S. Relations (open access)

Laos: Background and U.S. Relations

This report provides and overview of the political and economical situation in Laos, and discusses the U.S. assistance programs and human rights and humanitarian issues.
Date: January 4, 2010
Creator: Lum, Thomas
Object Type: Report
System: The UNT Digital Library
Atomistic Simulations of Chemical Reactivity of TATB Under Thermal and Shock Conditions (open access)

Atomistic Simulations of Chemical Reactivity of TATB Under Thermal and Shock Conditions

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Date: March 4, 2010
Creator: Manaa, M. R.; Reed, E. J. & Fried, L. E.
Object Type: Article
System: The UNT Digital Library
Membership of the 111th Congress: A Profile (open access)

Membership of the 111th Congress: A Profile

This report presents a profile of the membership of the 111th Congress. Statistical information is included on selected characteristics of Members, including data on party affiliation, average age and length of service, occupation, religious affiliation, gender, ethnicity, foreign births, and military service.
Date: February 4, 2010
Creator: Manning, Jennifer E.
Object Type: Report
System: The UNT Digital Library
GAO Bid Protests: An Overview of Timeframes and Procedures (open access)

GAO Bid Protests: An Overview of Timeframes and Procedures

Protests of high-profile awards and reports that the number of protests is increasing have recently prompted congressional and public interest in bid protests, particularly bid protests filed with the Government Accountability Office (GAO). This report is one of two providing Congress with background on the GAO bid-protest process. It provides an overview of the timeframes and procedures in a GAO bid protest, including several issues enumerated in the report's introduction.
Date: October 4, 2010
Creator: Manuel, Kate M. & Schwartz, Moshe
Object Type: Report
System: The UNT Digital Library
The 2009 Asia Pacific Economic Cooperation (APEC) Meetings and U.S. Trade Policy in Asia (open access)

The 2009 Asia Pacific Economic Cooperation (APEC) Meetings and U.S. Trade Policy in Asia

This report discusses the Asia Pacific Economic Cooperation forum (APEC) approach to trade liberalization, results of the 2009 meetings in Singapore, APEC and U.S. trade policy in Asia as well as other issues regarding APEC.
Date: February 4, 2010
Creator: Martin, Michael F.
Object Type: Report
System: The UNT Digital Library
Burma's 2010 Elections: Implications of the New Constitution and Election Laws (open access)

Burma's 2010 Elections: Implications of the New Constitution and Election Laws

This report provides background information on social and political situation in Burma and it discusses the 1990 parliamentary election.
Date: June 4, 2010
Creator: Martin, Michael F.
Object Type: Report
System: The UNT Digital Library