Directional Fast Neutron Detection using a Time Projection Chamber (open access)

Directional Fast Neutron Detection using a Time Projection Chamber

None
Date: April 13, 2010
Creator: Bowden, N.; Heffner, M.; Carosi, G.; Cater, D.; O'Malley, P.; Mintz, J. et al.
Object Type: Article
System: The UNT Digital Library
Progress Towards Deployable Antineutrino Detectors for Reactor Safeguards (open access)

Progress Towards Deployable Antineutrino Detectors for Reactor Safeguards

Fission reactors emit large numbers of antineutrinos and this flux may be useful for the measurement of two quantities of interest for reactor safeguards: the reactor's power and plutonium inventory throughout its cycle. The high antineutrino flux and relatively low background rates means that simple cubic meter scale detectors at tens of meters standoff can record hundreds or thousands of antineutrino events per day. Such antineutrino detectors would add online, quasi-real-time bulk material accountancy to the set of reactor monitoring tools available to the IAEA and other safeguards agencies with minimal impact on reactor operations. Between 2003 and 2008, our LLNL/SNL collaboration successfully deployed several prototype safeguards detectors at a commercial reactor in order to test both the method and the practicality of its implementation in the field. Partially on the strength of the results obtained from these deployments, an Experts Meeting was convened by the IAEA Novel Technologies Group in 2008 to assess current antineutrino detection technology and examine how it might be incorporated into the safeguards regime. Here we present a summary of our previous deployments and discuss current work that seeks to provide expanded capabilities suggested by the Experts Panel, in particular aboveground detector operation.
Date: April 5, 2010
Creator: Bowden, N; Bernstein, A; Dazeley, S; Keefer, G; Reyna, D; Cabrera-Palmer, B et al.
Object Type: Article
System: The UNT Digital Library
Small Wind Turbine Testing Results from the National Renewable Energy Laboratory: Preprint (open access)

Small Wind Turbine Testing Results from the National Renewable Energy Laboratory: Preprint

In 2008, the U.S. Department of Energy's (DOE) National Renewable Energy Laboratory (NREL) began testing small wind turbines (SWTs) through the Independent Testing project. Using competitive solicitation, five SWTs were selected for testing at the National Wind Technology Center (NWTC). NREL's NWTC is accredited by the American Association of Laboratory Accreditation (A2LA) to conduct duration, power performance, safety and function, power quality, and noise tests to International Electrotechnical Commission (IEC) standards. Results of the tests conducted on each of the SWTs are or will be available to the public on the NREL website. The results could be used by their manufacturers in the certification of the turbines or state agencies to decide which turbines are eligible for state incentives.
Date: April 1, 2010
Creator: Bowen, A.; Huskey, A.; Link, H.; Sinclair, K.; Forsyth, T.; Jager, D. et al.
Object Type: Article
System: The UNT Digital Library
Probing the pairing symmetry of the iron pnictides with electronic Raman scattering (open access)

Probing the pairing symmetry of the iron pnictides with electronic Raman scattering

An important issue in the study of the iron-arsenic based superconductors is the symmetry of the superconducting gap, a problem complicated by multiple gaps on different Fermi surface sheets. Electronic Raman scattering is a flexible bulk probe which allows one in principle to determine gap magnitudes and test for gap nodes in different regions of the Brillouin zone by employing different photon polarization states. Here we calculate the clean Raman intensity for A{sub 1g}, B{sub 1g} and B{sub 2g} polarizations, and discuss the peak structures and low-energy power laws which might be expected for several popular models of the superconducting gap in these systems.
Date: April 29, 2010
Creator: Boyd, G.R.
Object Type: Article
System: The UNT Digital Library
Stardust and the Molecules of Life (Why are the Amino Acids Left-Handed?) (open access)

Stardust and the Molecules of Life (Why are the Amino Acids Left-Handed?)

A mechanism for creating and selecting amino acid chirality is identified, and subsequent chemical replication and galactic mixing that would populate the galaxy with the predominant species will be described. This involves: (1) the spin of the {sup 14}N in the amino acids, or in precursor molecules from which amino acids might be formed, coupling to the chirality of the molecules; (2) the neutrinos emitted from the supernova, together with magnetic field from the nascent neutron star or black hole from the supernova selectively destroying one orientation of the {sup 14}N, thereby selecting the chirality associated with the other {sup 14}N orientation; (3) amplification by chemical evolution, by which the molecules replicate on a relatively short timescale; and (4) galactic mixing on a longer timescale mixing the selected molecules throughout the galaxy.
Date: April 2, 2010
Creator: Boyd, Richard N.; Kajino, Toshitaka & Onaka, Takashi
Object Type: Article
System: The UNT Digital Library
The Cyber Science and Security Institute (open access)

The Cyber Science and Security Institute

None
Date: April 22, 2010
Creator: Brase, J M & Spain, C W
Object Type: Report
System: The UNT Digital Library
AdS/QCD, LIight-Front Holography, and the Non-perturbative Running Coupling (open access)

AdS/QCD, LIight-Front Holography, and the Non-perturbative Running Coupling

The combination of Anti-de Sitter space (AdS) methods with light-front (LF) holography provides a remarkably accurate first approximation for the spectra and wavefunctions of meson and baryon light-quark bound states. The resulting bound-state Hamiltonian equation of motion in QCD leads to relativistic light-front wave equations in terms of an invariant impact variable {zeta} which measures the separation of the quark and gluonic constituents within the hadron at equal light-front time. These equations of motion in physical space-time are equivalent to the equations of motion which describe the propagation of spin-J modes in anti-de Sitter (AdS) space. The eigenvalues give the hadronic spectrum, and the eigenmodes represent the probability distributions of the hadronic constituents at a given scale. A positive-sign confining dilaton background modifying AdS space gives a very good account of meson and baryon spectroscopy and form factors. The light-front holographic mapping of this model also leads to a non-perturbative effective coupling {alpha}{sub s}{sup Ads} (Q{sup 2}) which agrees with the effective charge defined by the Bjorken sum rule and lattice simulations. It displays a transition from perturbative to nonperturbative conformal regimes at a momentum scale {approx} 1 GeV. The resulting {beta}-function appears to capture the essential characteristics of the …
Date: April 29, 2010
Creator: Brodsky, Stanley J.; de Teramond, Guy & Deur, Alexandre
Object Type: Article
System: The UNT Digital Library
Overview of the 2009 Release of the Evaluated Nuclear Data Library (endl2009) (open access)

Overview of the 2009 Release of the Evaluated Nuclear Data Library (endl2009)

The Lawrence Livermore National Laboratory (LLNL) Physics Division has produced the next iteration of LLNL's evaluated nuclear database, ENDL2009. ENDL2009 is the second in a series of major ENDL library releases designed to support LLNL's current and future nuclear data needs. This library includes 585 distinct transport-ready evaluations in the neutron sub-library and many physics improvements for stockpile stewardship, attribution signatures, key radiochemical diagnostics and performance of conventional and hybrid fission/fusion reactors. In building this library, we adopted the best of the world's nuclear data efforts: 46% of the library is from the ENDF/B-VII.0 library, 10% is from the JENDL libraries and 8% from other libraries. The remaining 36% of the neutron sub-library and all of the charged-particle sub-libraries consist of new evaluations developed at LLNL for the ENDL2009 library. In addition, ENDL2009 supports new features such as energy-dependent Q values from fission, support for unresolved resonances and average momentum deposition. Finally, this release is our most highly tested release as we have strengthened our already rigorous testing regime by adding tests against LANL Activation Ratio Measurements and more than 1200 new critical assemblies. Our testing is now being incorporated into our development process and is serving to guide database …
Date: April 25, 2010
Creator: Brown, D. A.; Beck, B.; Descalle, M.; Hoffman, R.; Ormand, E.; Navratil, P. et al.
Object Type: Article
System: The UNT Digital Library
MEASUREMENTS OF PAST 14C LEVELS AND 13C/12C RATIOS IN THE SURFACE WATERS OF THE WORLD'S SUBPOLAR OCEANS. (open access)

MEASUREMENTS OF PAST 14C LEVELS AND 13C/12C RATIOS IN THE SURFACE WATERS OF THE WORLD'S SUBPOLAR OCEANS.

Under this project we have developed methods that allow the reconstruction of past {sup 14}C levels of the surface waters of the subpolar North Pacific Ocean by measuring the {sup 14}C contents of archived salmon scales. The overall goal of this research was to reduce of the uncertainty in the uptake of fossil CO{sub 2} by the oceans and thereby improve the quantification of the global carbon cycle and to elucidate the fate of anthropogenic CO{sub 2}. Ocean General Circulation Models (OGCMs), with their three dimensional global spatial coverage and temporal modeling capabilities, provide the best route to accurately calculating the total uptake of CO{sub 2} by the oceans and, hence, to achieving the desired reduction in uncertainty. {sup 14}C has played, and continues to play, a central role in the validation of the OGCMs calculations, particularly with respect to those model components which govern the uptake of CO{sub 2} from the atmosphere and the transport of this carbon within the oceans. Under this project, we have developed time-series records of the {sup 14}C levels of the surface waters of three areas of the subpolar North Pacific Ocean. As the previously available data on the time-history of oceanic surface water …
Date: April 22, 2010
Creator: Brown, T A
Object Type: Report
System: The UNT Digital Library
Unauthorized Aliens in the United States (open access)

Unauthorized Aliens in the United States

This report discusses the unauthorized immigrant (illegal alien) population in the United States, which is a key and controversial immigration issue.
Date: April 27, 2010
Creator: Bruno, Andorra
Object Type: Report
System: The UNT Digital Library
Switchable cell trapping using superparamagnetic beads (open access)

Switchable cell trapping using superparamagnetic beads

Ni{sub 81}Fe{sub 19} microwires are investigated as the basis of a switchable template for positioning magnetically-labeled neural Schwann cells. Magnetic transmission X-ray microscopy and micromagnetic modeling show that magnetic domain walls can be created or removed in zigzagged structures by an applied magnetic field. Schwann cells containing superparamagnetic beads are trapped by the field emanating from the domain walls. The design allows Schwann cells to be organized on a surface to form a connected network and then released from the surface if required. As aligned Schwann cells can guide nerve regeneration, this technique is of value for developing glial-neuronal co-culture models in the future treatment of peripheral nerve injuries.
Date: April 30, 2010
Creator: Bryan, M. T.; Smith, K. H.; Real, M. E.; Bashir, M. A.; Fry, P. W.; Fischer, P. et al.
Object Type: Article
System: The UNT Digital Library
The Endangered Species Act (ESA) in the 111th Congress: Conflicting Values and Difficult Choices (open access)

The Endangered Species Act (ESA) in the 111th Congress: Conflicting Values and Difficult Choices

The Endangered Species Act has been one of the more contentious environmental laws. This may stem from its strict substantive provisions, which can affect the use of both federal and nonfederal lands and resources. This report discusses oversight issues and legislation introduced in the 11th Congress to address Endangered Species Act implementation and management of endangered and threatened species.
Date: April 23, 2010
Creator: Buck, Eugene H.; Corn, M. Lynne; Sheikh, Pervaze A.; Meltz, Robert & Alexander, Kristina
Object Type: Report
System: The UNT Digital Library
Geochemical data reported by Paquay et al. do not refute Younger Dryas impact event (open access)

Geochemical data reported by Paquay et al. do not refute Younger Dryas impact event

None
Date: April 12, 2010
Creator: Bunch, T. E.; West, A.; Firestone, R. B.; Kennett, J. P.; Wittke, J. H.; Kinzie, C. R. et al.
Object Type: Article
System: The UNT Digital Library
Report on 238Pu(n,x) surrogate cross section measurement (open access)

Report on 238Pu(n,x) surrogate cross section measurement

The goal of this year's effort is to measure the {sup 238}Pu(n,f) and {sup 238}Pu(n,2n) cross section from 100 keV to 20 MeV. We designed a surrogate experiment that used the reaction {sup 239}Pu(a,a{prime}x) as a surrogate for {sup 238}Pu(n,x). The experiment was conducted using the STARS/LIBERACE experimental facility located at the 88 Inch Cyclotron at Lawrence Berkeley National Laboratory in January 2010. A description of the experiment and status of the data analysis is given. In order to obtain a reliable {sup 238}Pu(n,x) cross section we designed the experiment using the surrogate ratio technique. This technique allows one to measure a desired, unknown, cross section relative to a known cross section. In the present example, the {sup 238}Pu(n,x) cross section of interest is determined relative to the known {sup 235}U(n,x) cross section. To increase confidence in the results, and to reduce overall uncertainties, we are also determining the {sup 238}Pu(n,x) cross section relative to the known {sup 234}U(n,x) cross section. The compound nuclei of interest for this experiment were produced using inelastic alpha scattering. For example, {sup 236}U(a,a{prime}x) served as a surrogate for {sup 235}U(n,x); analogous reactions were considered for the other cross sections. Surrogate experiments determine the probabilities …
Date: April 2, 2010
Creator: Burke, J. T.; Ressler, J. J.; Henderson, R. A.; Scielzo, N. D.; Escher, J. E.; Thompson, I. J. et al.
Object Type: Report
System: The UNT Digital Library
High Pressure - High Temperature Polymorphism in Ta: Resolving an Ongoing Experimental Controversy (open access)

High Pressure - High Temperature Polymorphism in Ta: Resolving an Ongoing Experimental Controversy

Phase diagrams of refractory metals remain essentially unknown. Moreover, there is an ongoing controversy over the high pressure (P) melting temperatures of these metals: results of diamond anvil cell (DAC) and shock wave experiments differ by at least a factor of two. From an extensive ab initio study on tantalum we discovered that the body-centered cubic phase, its physical phase at ambient conditions, transforms to another solid phase, possibly hexagonal omega phase, at high temperature (T). Hence the sample motion observed in DAC experiments is not due to melting but internal stresses accompanying a solid-solid transformation, as explained in more detail in our work. In view of our results on tantalum and previous work on molybdenum, as well as other published data, it is highly plausible that high-PT polymorphism is a general feature of Groups V and VI refractory metals.
Date: April 7, 2010
Creator: Burkovsky, L.; Chen, S. P.; Preston, D. L.; Belonoshko, A. B.; Rosengren, A.; Mikhaylushkin, A. S. et al.
Object Type: Article
System: The UNT Digital Library
Transcript of Commission on Wartime Contracting in Iraq & Afghanistan Hearing: April 19, 2010 (open access)

Transcript of Commission on Wartime Contracting in Iraq & Afghanistan Hearing: April 19, 2010

Transcript of a public hearing held by the Commission on Wartime Contracting in Iraq & Afghanistan held April 19, 2010 in Washington, D.C. This hearing includes testimony from two panels of witnesses representing governmental agencies and contractors on improving the federal government's oversight on service contracts in Southwest Asia operations.
Date: April 19, 2010
Creator: CQ Transcriptions
Object Type: Text
System: The UNT Digital Library
A Southern Sky Survey with Fermi LAT and ASKAP (open access)

A Southern Sky Survey with Fermi LAT and ASKAP

We present the prospects for a future joint gamma-ray and radio survey of southern hemisphere sources using the Fermi Large Area Telescope (LAT) and the upcoming Australian Square Kilometre Array Pathfinder (ASKAP) radio telescope. ASKAP is a next generation radio telescope designed to perform surveys at GHz frequencies at a much higher survey speed than previous radio telescopes, and is scheduled to start engineering observations in 2011. The survey capabilities of both Fermi LAT and ASKAP are described, and the planned science surveys for ASKAP are summarized. We give some expected details of the Variable and Slow Transient (VAST) survey using ASKAP, which will search for transients on timescales from 5 seconds to years. Some observational properties of faint and transient sources seen at gamma-ray and radio wavelengths are summarized, and prospects and strategies for using ASKAP survey data for LAT source counterpart identification are summarized.
Date: April 29, 2010
Creator: Cameron, Robert A. & /SLAC /KIPAC, Menlo Park
Object Type: Article
System: The UNT Digital Library
Juvenile Salmon Acoustic Telemetry System Transmitter Downsize Assessment (open access)

Juvenile Salmon Acoustic Telemetry System Transmitter Downsize Assessment

At the request of the U.S. Army Corps of Engineers, Portland District, researchers from Pacific Northwest National Laboratory investigated the use of an application-specific integrated circuit (ASIC) to reduce the weight and volume of Juvenile Salmon Acoustic Telemetry System (JSATS) transmitters while retaining current functionality. Review of the design of current JSATS transmitters identified components that could be replaced by an ASIC while retaining the function of the current transmitter and offering opportunities to extend function if desired. ASIC design alternatives were identified that could meet transmitter weight and volume targets of 200 mg and 100 mm3. If alternatives to the cylindrical batteries used in current JSATS transmitters can be identified, it could be possible to implant ASIC-based JSATS transmitters by injection rather than surgery. Using criteria for the size of fish suitable for surgical implantation of current JSATS transmitters, it was concluded that fish as small as 70 mm in length could be implanted with an ASIC-based transmitter, particularly if implantation by injection became feasible.
Date: April 30, 2010
Creator: Carlson, Thomas J. & Myjak, Mitchell J.
Object Type: Report
System: The UNT Digital Library
Permissible Securities Activities of Commercial Banks Under the Glass-Steagall Act (GSA) and the Gramm-Leach-Bliley Act (GLBA) (open access)

Permissible Securities Activities of Commercial Banks Under the Glass-Steagall Act (GSA) and the Gramm-Leach-Bliley Act (GLBA)

This report explains the extent to which commercial banks, their subsidiaries, and affiliates were able to engage in securities activities, including securities underwriting, dealing, and brokerage, under the authorities of the Glass-Steagall Act (GSA) and other pre-GLBA (Gramm-Leach-Bliley Act) banking laws, most notably the Bank Holding Company Act of 1956 (BHCA; 70 Stat. 133). It also discusses how the volume and scope of these securities activities expanded over time, and how the GLBA changed the GSA construct by facilitating affiliations among commercial banks and securities firms..
Date: April 12, 2010
Creator: Carpenter, David H. & Murphy, M. Maureen
Object Type: Report
System: The UNT Digital Library
A Discussion of Reversible and Irreversible Sorption for Sr, Cs, Np, and Pu (open access)

A Discussion of Reversible and Irreversible Sorption for Sr, Cs, Np, and Pu

None
Date: April 30, 2010
Creator: Carroll, S.; Tinnacher, R.; Kersting, A. & Zavarin, M.
Object Type: Report
System: The UNT Digital Library
Limits on tau lepton flavor violating decays in three charged leptons (open access)

Limits on tau lepton flavor violating decays in three charged leptons

A search for the neutrinoless, lepton-flavor violating decay of the {tau} lepton into three charged leptons has been performed using an integrated luminosity of 468 fb{sup -1} collected with the BABAR detector at the PEP-II collider. In all six decay modes considered, the numbers of events found in data are compatible with the background expectations. Upper limits on the branching fractions are set in the range (1.8-3.3) x 10{sup -8} at 90% confidence level.
Date: April 29, 2010
Creator: Cervelli, Alberto
Object Type: Article
System: The UNT Digital Library
Finite temperature spin-dynamics and phase transitions in spin-orbital models (open access)

Finite temperature spin-dynamics and phase transitions in spin-orbital models

We study finite temperature properties of a generic spin-orbital model relevant to transition metal compounds, having coupled quantum Heisenberg-spin and Ising-orbital degrees of freedom. The model system undergoes a phase transition, consistent with that of a 2D Ising model, to an orbitally ordered state at a temperature set by short-range magnetic order. At low temperatures the orbital degrees of freedom freeze-out and the model maps onto a quantum Heisenberg model. The onset of orbital excitations causes a rapid scrambling of the spin spectral weight away from coherent spin-waves, which leads to a sharp increase in uniform magnetic susceptibility just below the phase transition, reminiscent of the observed behavior in the Fe-pnictide materials.
Date: April 29, 2010
Creator: Chen, C. C.
Object Type: Article
System: The UNT Digital Library
Large-scale Relativistic Configuration-interaction Calculations for the 2s-2p and 3s-3p Transition Energies of Xenon Ions (open access)

Large-scale Relativistic Configuration-interaction Calculations for the 2s-2p and 3s-3p Transition Energies of Xenon Ions

None
Date: April 13, 2010
Creator: Chen, M H & Cheng, K T
Object Type: Article
System: The UNT Digital Library
SECONDARY ELECTRON TRAJECTORIES IN HIGH-GRADIENT VACUUM INSULATORS WITH FAST HIGH-VOLTAGE PULSES (open access)

SECONDARY ELECTRON TRAJECTORIES IN HIGH-GRADIENT VACUUM INSULATORS WITH FAST HIGH-VOLTAGE PULSES

Vacuum insulators composed of alternating layers of metal and dielectric, known as high-gradient insulators (HGIs), have been shown to withstand higher electric fields than conventional insulators. Primary or secondary electrons (emitted from the insulator surface) can be deflected by magnetic fields from external sources, the high-current electron beam, the conduction current in the transmission line, or the displacement current in the insulator. These electrons are deflected either toward or away from the insulator surface and this affects the performance of the vacuum insulator. This paper shows the effects of displacement current from short voltage pulses on the performance of high gradient insulators. Generally, vacuum insulator failure is due to surface flashover, initiated by electrons emitted from a triple junction. These electrons strike the insulator surface thus producing secondary electrons, and can lead to a subsequent electron cascade along the surface. The displacement current in the insulator can deflect electrons either toward or away from the insulator surface, and affects the performance of the vacuum insulator when the insulator is subjected to a fast high-voltage pulse. Vacuum insulators composed of alternating layers of metal and dielectric, known as high-gradient insulators (HGIs), have been shown to withstand higher electric fields than conventional …
Date: April 21, 2010
Creator: Chen, Y.; Blackfield, D.; Nelson, S. D. & Poole, B.
Object Type: Article
System: The UNT Digital Library