3-D Model of Broadband Emission from Supernova Remnants Undergoing Non-linear Diffusive Shock Acceleration (open access)

3-D Model of Broadband Emission from Supernova Remnants Undergoing Non-linear Diffusive Shock Acceleration

We present a 3-dimensional model of supernova remnants (SNRs) where the hydrodynamical evolution of the remnant is modeled consistently with nonlinear diffusive shock acceleration occurring at the outer blast wave. The model includes particle escape and diffusion outside of the forward shock, and particle interactions with arbitrary distributions of external ambient material, such as molecular clouds. We include synchrotron emission and cooling, bremsstrahlung radiation, neutral pion production, inverse-Compton (IC), and Coulomb energy-loss. Boardband spectra have been calculated for typical parameters including dense regions of gas external to a 1000 year old SNR. In this paper, we describe the details of our model but do not attempt a detailed fit to any specific remnant. We also do not include magnetic field amplification (MFA), even though this effect may be important in some young remnants. In this first presentation of the model we don't attempt a detailed fit to any specific remnant. Our aim is to develop a flexible platform, which can be generalized to include effects such as MFA, and which can be easily adapted to various SNR environments, including Type Ia SNRs, which explode in a constant density medium, and Type II SNRs, which explode in a pre-supernova wind. When …
Date: July 2, 2008
Creator: Lee, Shiu-Hang; Kamae, Tuneyoshi & Ellison, Donald C.
Object Type: Article
System: The UNT Digital Library
Aerosols and clouds in chemical transport models and climate models. (open access)

Aerosols and clouds in chemical transport models and climate models.

Clouds exert major influences on both shortwave and longwave radiation as well as on the hydrological cycle. Accurate representation of clouds in climate models is a major unsolved problem because of high sensitivity of radiation and hydrology to cloud properties and processes, incomplete understanding of these processes, and the wide range of length scales over which these processes occur. Small changes in the amount, altitude, physical thickness, and/or microphysical properties of clouds due to human influences can exert changes in Earth's radiation budget that are comparable to the radiative forcing by anthropogenic greenhouse gases, thus either partly offsetting or enhancing the warming due to these gases. Because clouds form on aerosol particles, changes in the amount and/or composition of aerosols affect clouds in a variety of ways. The forcing of the radiation balance due to aerosol-cloud interactions (indirect aerosol effect) has large uncertainties because a variety of important processes are not well understood precluding their accurate representation in models.
Date: March 2, 2008
Creator: Lohmann,U. & Schwartz, S. E.
Object Type: Article
System: The UNT Digital Library
Afghanistan: Post-War Governance, Security, and U.S. Policy (open access)

Afghanistan: Post-War Governance, Security, and U.S. Policy

This report discusses Afghanistan's political transition, which was completed with the convening of a parliament in December 2005. Since then, insurgent threats to Afghanistan's government have escalated to the point that some experts are questioning the future of U.S. stabilization efforts.
Date: September 2, 2008
Creator: Katzman, Kenneth
Object Type: Report
System: The UNT Digital Library
AIDS in Africa (open access)

AIDS in Africa

This report discusses the AIDS issues in Africa and the Bush administration call to double U.S. international funding for AIDS.
Date: February 2, 2008
Creator: Cook, Nicolas
Object Type: Report
System: The UNT Digital Library
Alignment of the Pixel and SCT Modules for the 2004 ATLAS Combined Test Beam (open access)

Alignment of the Pixel and SCT Modules for the 2004 ATLAS Combined Test Beam

A small set of final prototypes of the ATLAS Inner Detector silicon tracking system(Pixel Detector and SemiConductor Tracker), were used to take data during the 2004 Combined Test Beam. Data were collected from runs with beams of different flavour (electrons, pions, muons and photons) with a momentum range of 2 to 180 GeV/c. Four independent methods were used to align the silicon modules. The corrections obtained were validated using the known momenta of the beam particles and were shown to yield consistent results among the different alignment approaches. From the residual distributions, it is concluded that the precision attained in the alignmentof the silicon modules is of the order of 5 mm in their most precise coordinate.
Date: June 2, 2008
Creator: Ahmad, A.; Andreazza, A.; Atkinson, T.; Baines, J.; Barr, A. J.; Beccherle, R. et al.
Object Type: Article
System: The UNT Digital Library
Ambient-temperature Conditioning as a Probe of Double-C Transformation Mechanisms in Pu-2.0 at. % Ga (open access)

Ambient-temperature Conditioning as a Probe of Double-C Transformation Mechanisms in Pu-2.0 at. % Ga

The gallium-stabilized Pu-2.0 at. % Ga alloy undergoes a partial or incomplete low-temperature martensitic transformation from the metastable {delta} phase to the gallium-containing, monoclinic {alpha}{prime} phase near -100 C. This transformation has been shown to occur isothermally and it displays anomalous double-C kinetics in a time-temperature-transformation (TTT) diagram, where two nose temperatures anchoring an upper- and lower-C describe minima in the time for the initiation of transformation. The underlying mechanisms responsible for the double-C behavior are currently unresolved, although recent experiments suggest that a conditioning treatment--wherein, following an anneal at 375 C, the sample is held at a sub-anneal temperature for a period of time--significantly influences the upper-C of the TTT diagram. As such, elucidating the effects of the conditioning treatment upon the {delta} {yields} {alpha}{prime} transformation can provide valuable insights into the fundamental mechanisms governing the double-C kinetics of the transition. Following a high-temperature anneal, a differential scanning calorimeter (DSC) was used to establish an optimal conditioning curve that depicts the amount of {alpha}{prime} formed during the transformation as a function of conditioning temperature for a specified time. With the optimal conditioning curve as a baseline, the DSC was used to explore the circumstances under which the effects of …
Date: April 2, 2008
Creator: Jeffries, J R; Blobaum, K M; Wall, M A & Schwartz, A J
Object Type: Article
System: The UNT Digital Library
Angular Distributions in the Decays B to K*l+l- (open access)

Angular Distributions in the Decays B to K*l+l-

The authors use a sample of 384 million B{bar B} events collected with the BABAR detector at the PEP-II e{sup +}e{sup -} collider to study angular distributions in the rare decays B {yields} K*{ell}{sup +}{ell}{sup -}, where {ell}{sup +}{ell}{sup -} is either e{sup +}e{sup -} or {mu}{sup +}{mu}{sup -}. For low dilepton invariant masses, m{sub {ell}{ell}} < 2.5 GeV/c{sup 2}, they measure a lepton forward-backward asymmetry {Alpha}{sub FB} = 0.24{sub -0.23}{sup +0.18} {+-} 0.05 and K* longitudinal polarization F{sub L} = 0.35 {+-} 0.16 {+-} 0.04. For m{sub {ell}{ell}} > 3.2 GeV/c{sup 2}, they measure {Alpha}{sub FB} = 0.76{sub -0.32}{sup +0.52} {+-} 0.07 and F{sub L} = 0.71{sub -0.22}{sup 0.20} {+-} 0.04.
Date: May 2, 2008
Creator: Collaboration, The BABAR & Aubert, B.
Object Type: Article
System: The UNT Digital Library
Anisotropic x ray magnetic linear dichroism - Its importance for the analysis of soft x ray spectra of magnetic oxides (open access)

Anisotropic x ray magnetic linear dichroism - Its importance for the analysis of soft x ray spectra of magnetic oxides

Using spectroscopic information for x ray magnetometry and magnetic microscopy requires detailed theoretical understanding of spectral shape and magnitude of dichroism signals. We have shown unambiguously that--contrary to common belief--spectral shape and magnitude of x ray magnetic linear dichroism (XMLD) are not only determined by the relative orientation of magnetic moments and x ray polarization, but also their orientations relative to the crystallographic axes must be taken into account for accurate interpretation of XMLD data.
Date: July 2, 2008
Creator: van der Laan, G. & Arenholz, Elke
Object Type: Article
System: The UNT Digital Library
Aqueous Ln(III) Luminescence Agents Derived from a Tasty Precursor (open access)

Aqueous Ln(III) Luminescence Agents Derived from a Tasty Precursor

The synthesis, aqueous stability and photophysical properties are reported for a novel tetradentate ligand derived from maltol, a commonly used flavor enhancer. In aqueous solution, this chelate forms stable complexes with Ln(III) cations, and sensitized emission was observed from Eu(III), Yb(III), and Nd(III). A comparison with recently reported and structurally analogous ligands reveals a slightly higher basicity but lower complex stability with Eu(III) [pEu = 14.7 (1)]. A very poor metal centered quantum yield with Eu(III) was observed ({Phi}{sub tot} = 0.04%), which can be rationalized by the similar energy of the ligand triplet state and the Eu(III) {sup 5}D{sub 0} emissive level. Instead, sensitized emission from the Yb(III) and Nd(III) cations was observed, which emit in the Near Infra-Red (NIR).
Date: June 2, 2008
Creator: Jocher, C. J.; Moore, E. G.; Pierce, J. D. & Raymond, K. N.
Object Type: Article
System: The UNT Digital Library
Aquifer Testing Recommendations for Supporting Phase II of the T Area Technetium-99 Data Objectives Process (open access)

Aquifer Testing Recommendations for Supporting Phase II of the T Area Technetium-99 Data Objectives Process

Aquifer characterization needs are currently being assessed to optimize pump-and-treat remedial strategies within the 200-ZP-1 operable unit, specifically for the immediate area of the 241-T Tank Farm. This report provides a general discussion of the six identified hydrologic test methods for possible subsequent characterization within the 241-T Tank Farm area and details for implementing the large-scale recovery test after terminating pumping at the 241-Tank Farm extraction well locations.
Date: April 2, 2008
Creator: Spane, Frank A.
Object Type: Report
System: The UNT Digital Library
ARCHITECTURE OF A CHARGE-TRANSFER STATE REGULATING LIGHT HARVESTING IN A PLANT ANTENNA PROTEIN (open access)

ARCHITECTURE OF A CHARGE-TRANSFER STATE REGULATING LIGHT HARVESTING IN A PLANT ANTENNA PROTEIN

Energy-dependent quenching of excess absorbed light energy (qE) is a vital mechanism for regulating photosynthetic light harvesting in higher plants. All of the physiological characteristics of qE have been positively correlated with charge-transfer between coupled chlorophyll and zeaxanthin molecules in the light-harvesting antenna of photosystem II (PSII). In this work, we present evidence for charge-transfer quenching in all three of the individual minor antenna complexes of PSII (CP29, CP26, and CP24), and we conclude that charge-transfer quenching in CP29 involves a de-localized state of an excitonically coupled chlorophyll dimer. We propose that reversible conformational changes in CP29 can `tune? the electronic coupling between the chlorophylls in this dimer, thereby modulating the energy of the chlorophylls-zeaxanthin charge-transfer state and switching on and off the charge-transfer quenching during qE.
Date: April 2, 2008
Creator: Fleming, Graham; Ahn, Tae Kyu; Avenson, Thomas J.; Ballottari, Matteo; Cheng, Yuan-Chung; Niyogi, Krishna K. et al.
Object Type: Article
System: The UNT Digital Library
Arctic National Wildlife Refuge (ANWR): Votes and Legislative Actions, 95th Congress to 110th Congress (open access)

Arctic National Wildlife Refuge (ANWR): Votes and Legislative Actions, 95th Congress to 110th Congress

This report provides a summary of legislative attempts to address issues of energy development and preservation in the Refuge from the 95th Congress through the 110th Congress, with emphasis on the 108th through 110th Congresses.
Date: September 2, 2008
Creator: Corn, M. L. & Roberts, Beth A.
Object Type: Report
System: The UNT Digital Library
The Army Corps of Engineers’ Nationwide Permits Program: Issues and Regulatory Developments (open access)

The Army Corps of Engineers’ Nationwide Permits Program: Issues and Regulatory Developments

This report contains the issues and regulatory developments of the Army Corps of engineers' nationwide permits program.
Date: April 2, 2008
Creator: Copeland, Claudia
Object Type: Report
System: The UNT Digital Library
Babel Fortran 2003 Binding for Structured Data Types (open access)

Babel Fortran 2003 Binding for Structured Data Types

Babel is a tool aimed at the high-performance computing community that addresses the need for mixing programming languages (Java, Python, C, C++, Fortran 90, FORTRAN 77) in order to leverage the specific benefits of those languages. Scientific codes often rely on structured data types (structs, derived data types) to encapsulate data, and Babel has been lacking in this type of support until recently. We present a new language binding that focuses on their interoperability of C/C++ with Fortran 2003. The new binding builds on the existing Fortran 90 infrastructure by using the iso-c-binding module defined in the Fortran 2003 standard as the basis for C/C++ interoperability. We present the technical approach for the new binding and discuss our initial experiences in applying the binding in FACETS (Framework Application for Core-Edge Transport Simulations) to integrate C++ with legacy Fortran codes.
Date: May 2, 2008
Creator: Muszala, S; Epperly, T & Wang, N
Object Type: Article
System: The UNT Digital Library
beta 1 integrin inhibition dramatically enhances radiotherapy efficacy in human breast cancer xenografts (open access)

beta 1 integrin inhibition dramatically enhances radiotherapy efficacy in human breast cancer xenografts

{beta}1 integrin signaling has been shown to mediate cellular resistance to apoptosis after exposure to ionizing radiation (IR). Other signaling molecules that increase resistance include Akt, which promotes cell survival downstream of {beta}1 integrin signaling. We showed previously that {beta}1 integrin inhibitory antibodies, AIIB2, enhance apoptosis and decrease growth in human breast cancer cells in 3 dimensional laminin-rich extracellular matrix (3D lrECM) cultures and in vivo. Here we asked whether AIIB2 could synergize with IR to modify Akt-mediated IR resistance. We used 3D lrECM cultures to test the optimal combination of AIIB2 with IR treatment of two breast cancer cell lines, MCF-7 and HMT3522-T4-2, as well as T4-2 myr-Akt breast cancer colonies or HMT3522-S-1, which form normal organotypic structures in 3D lrECM. Colonies were assayed for apoptosis and {beta}1 integrin/Akt signaling pathways were evaluated using western blot. In addition, mice bearing MCF-7 xenografts were used to validate the findings in 3D lrECM. We report that AIIB2 increased apoptosis optimally post-IR by down regulating Akt in breast cancer colonies in 3D lrECM. In vivo, addition of AIIB2 after IR significantly enhanced tumor growth inhibition and apoptosis compared to either treatment alone. Remarkably, the degree of tumor growth inhibition using AIIB2 plus …
Date: June 2, 2008
Creator: Park, Catherine C.; Park, Catherine C.; Zhang, Hui J.; Yao, Evelyn S.; Park, Chong J. & Bissell, Mina J.
Object Type: Article
System: The UNT Digital Library
A Bremsstrahlung Spectrometer using k-edge and Differential Filters with Image plate dosimeters (open access)

A Bremsstrahlung Spectrometer using k-edge and Differential Filters with Image plate dosimeters

A Bremsstrahlung spectrometer using k-edge and differential filtering has been used with Image Plate dosimeters to measure the x-ray fluence from short-pulse laser/target interactions. An electron spectrometer in front of the Bremsstrahlung spectrometer deflects electrons from the x-ray line of sight and simultaneously measures the electron spectrum. The response functions were modeled with the Monte Carlo code Integrated Tiger Series 3.0 and the dosimeters calibrated with radioactive sources. Electron distributions with slope temperatures in the MeV range are inferred from the Bremsstrahlung spectra.
Date: May 2, 2008
Creator: Chen, C.; Mackinnon, A.; Beg, F.; Chen, H.; Key, M.; King, J. A. et al.
Object Type: Article
System: The UNT Digital Library
Burma-U.S. Relations (open access)

Burma-U.S. Relations

This report provides an overview of United States policy towards Burma. The report discusses Burma - U.S. relations and the political situation in Burma.
Date: June 2, 2008
Creator: Niksch, Larry A.
Object Type: Report
System: The UNT Digital Library
Caution -- Beam Crossing Ahead (open access)

Caution -- Beam Crossing Ahead

There are times when a laser beam needs to cross between tables or even go from one room to another. This presents an interesting traffic-flow and safety challenge to both the laser safety officer and laser user. Fortunately it is a challenge that has several solutions But the simplest solution may not be the best one. For example, the simplest way to get a beam from one optical table to another is just to put a sturdy tube around it. That's a permanent solution, and it completely contains the laser beam. While this is laser safe, there can be egress issues if it blocks a walkway. One comment this author often hears is, 'We can just duck under the tube.' The fire marshal, as well as the laser safety officer, might have issues with this. Especially in the case of a darkened lab, a blocked walkway can present a hazard of its own. One good solution is to transport the beam from Point A to Point B through a fiberoptic cable, when that is possible. One should easily be able to run the fiber up and over any walkway or down through a conduit on the floor. An important concern …
Date: April 2, 2008
Creator: Barat, Kenneth L.
Object Type: Article
System: The UNT Digital Library
Chemical Kinetic Modeling of Hydrogen Combustion Limits (open access)

Chemical Kinetic Modeling of Hydrogen Combustion Limits

A detailed chemical kinetic model is used to explore the flammability and detonability of hydrogen mixtures. In the case of flammability, a detailed chemical kinetic mechanism for hydrogen is coupled to the CHEMKIN Premix code to compute premixed, laminar flame speeds. The detailed chemical kinetic model reproduces flame speeds in the literature over a range of equivalence ratios, pressures and reactant temperatures. A series of calculation were performed to assess the key parameters determining the flammability of hydrogen mixtures. Increased reactant temperature was found to greatly increase the flame speed and the flammability of the mixture. The effect of added diluents was assessed. Addition of water and carbon dioxide were found to reduce the flame speed and thus the flammability of a hydrogen mixture approximately equally well and much more than the addition of nitrogen. The detailed chemical kinetic model was used to explore the detonability of hydrogen mixtures. A Zeldovich-von Neumann-Doring (ZND) detonation model coupled with detailed chemical kinetics was used to model the detonation. The effectiveness on different diluents was assessed in reducing the detonability of a hydrogen mixture. Carbon dioxide was found to be most effective in reducing the detonability followed by water and nitrogen. The chemical …
Date: April 2, 2008
Creator: Pitz, W J & Westbrook, C K
Object Type: Report
System: The UNT Digital Library
Chemistrty with Ultracold Molecules (open access)

Chemistrty with Ultracold Molecules

This report contains information about slowing and cooling molecules via a counter-rotating supersonic nozzle
Date: December 2, 2008
Creator: Herschbach, Dudley R.
Object Type: Report
System: The UNT Digital Library
China's Top-1000 Energy-Consuming Enterprises Program:Reducing Energy Consumption of the 1000 Largest Industrial Enterprises in China (open access)

China's Top-1000 Energy-Consuming Enterprises Program:Reducing Energy Consumption of the 1000 Largest Industrial Enterprises in China

In 2005, the Chinese government announced an ambitious goal of reducing energy consumption per unit of GDP by 20% between 2005 and 2010. One of the key initiatives for realizing this goal is the Top-1000 Energy-Consuming Enterprises program. The energy consumption of these 1000 enterprises accounted for 33% of national and 47% of industrial energy usage in 2004. Under the Top-1000 program, 2010 energy consumption targets were determined for each enterprise. The objective of this paper is to evaluate the program design and initial results, given limited information and data, in order to understand the possible implications of its success in terms of energy and carbon dioxide emissions reductions and to recommend future program modifications based on international experience with similar target-setting agreement programs. Even though the Top-1000 Program was designed and implemented rapidly, it appears that--depending upon the GDP growth rate--it could contribute to somewhere between approximately 10% and 25% of the savings required to support China's efforts to meet a 20% reduction in energy use per unit of GDP by 2010.
Date: June 2, 2008
Creator: Price, Lynn; Price, Lynn; Wang, Xuejun & Yun, Jiang
Object Type: Report
System: The UNT Digital Library
China's Holdings of U.S. Securities: Implications for the U.S. Economy (open access)

China's Holdings of U.S. Securities: Implications for the U.S. Economy

This report examines the importance to the U.S. economy of China's investment in U.S. securities, as well as U.S. concerns over the possibility that China might unload a large share of those holdings, including the likelihood that this would occur, and the potential implications such action could have for the U.S. economy. The report concludes that a large sell-off of Chinese Treasury securities holdings could negatively affect the U.S. economy, at least in the short-run. As a result, such a move could diminish U.S. demand for Chinese products and thus could lower China's economic growth as well.
Date: October 2, 2008
Creator: Morrison, Wayne M. & Labonte, Marc
Object Type: Report
System: The UNT Digital Library
Cleanup Verification Package for the 118-F-6 Burial Ground (open access)

Cleanup Verification Package for the 118-F-6 Burial Ground

This cleanup verification package documents completion of remedial action for the 118-F-6 Burial Ground located in the 100-FR-2 Operable Unit of the 100-F Area on the Hanford Site. The trenches received waste from the 100-F Experimental Animal Farm, including animal manure, animal carcasses, laboratory waste, plastic, cardboard, metal, and concrete debris as well as a railroad tank car.
Date: October 2, 2008
Creator: Sulloway, H. M.
Object Type: Report
System: The UNT Digital Library
Climate Change: Design Approaches for a Greenhouse Gas Reduction Program (open access)

Climate Change: Design Approaches for a Greenhouse Gas Reduction Program

This report explores strategies to control greenhouse gas (GHG) emissions and options to address the cost issue in four parts. First, the basic economic tradeoff between controlling the quantity of GHG emissions and the program's compliance costs is introduced and explained. Second, the five dimensions of the cost issue that have arisen so far in the climate change debate are identified and discussed. Third, a representative sample of proposed approaches to address cost concerns is compared and analyzed according to the five cost dimensions identified previously. Finally, the proposed options are summarized and opportunities to combine or merge different approaches are analyzed.
Date: June 2, 2008
Creator: Parker, Larry
Object Type: Report
System: The UNT Digital Library