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
Origin of charge density at LaAlO3-on-SrTiO3 heterointerfacespossibility of intrinsic doping (open access)

Origin of charge density at LaAlO3-on-SrTiO3 heterointerfacespossibility of intrinsic doping

As discovered by Ohtomo et al., a large sheet charge density with high mobility exists at the interface between SrTiO{sub 3} and LaAlO{sub 3}. Based on transport, spectroscopic and oxygen-annealing experiments, we conclude that extrinsic defects in the form of oxygen vacancies introduced by the pulsed laser deposition process used by all researchers to date to make these samples is the source of the large carrier densities. Annealing experiments show a limiting carrier density. We also present a model that explains the high mobility based on carrier redistribution due to an increased dielectric constant.
Date: April 29, 2010
Creator: Siemons, W.
Object Type: Article
System: The UNT Digital Library
MEASUREMENTS OF DIRECT CP VIOLATION AND CONSTRAINT ON THE CKM TRIANGLE IN B->K*pi DECAYS (open access)

MEASUREMENTS OF DIRECT CP VIOLATION AND CONSTRAINT ON THE CKM TRIANGLE IN B->K*pi DECAYS

We constrain the apex of the Cabibbo-Kobayashi-Maskawa unitarity triangle with measurements of B {yields} K*{pi} amplitudes from analyses of B{sup 0} {yields} K{sup +}{pi}{sup -}{pi}{sup 0} and B{sup 0} {yields} K{sub S}{pi}{sup +}{pi}{sup -} decays. This constraint is consistent with the world average. The B{sup 0} {yields} K{sup +}{pi}{sup -}{pi}{sup 0} decay mode is reconstructed from a sample of 454 million B{sup 0}{bar B}{sup 0} events collected by the BABAR detector at SLAC. We measure direct CP violation in B{sup 0} {yields} K*{sup +}{pi}{sup -} decays at the level of 3{sigma} when measurements from both B{sup 0} {yields} K{sup +}{pi}{sup -}{pi}{sup 0} and B{sup 0} {yields} K{sub S}{pi}{sup +}{pi}{sup -} decays are combined.
Date: April 29, 2010
Creator: Wagner, Andrew Phillips
Object Type: Thesis or Dissertation
System: The UNT Digital Library
Quasi-zero dimensional CuB2O4: a resonant inelastic X-ray scattering case study (open access)

Quasi-zero dimensional CuB2O4: a resonant inelastic X-ray scattering case study

We explore the general phenomenology of resonant inelastic scattering (RIXS) using CuB{sub 2}O{sub 4}, a network of CuO{sub 4} plaquettes electronically isolated by B{sup +3} ions. Spectra show a small number of well-separated features, and we exploit the simple electronic structure to explore RIXS phenomenology by developing a calculation which allows for intermediate-state effects ignored in standard approaches. These effects are found to be non-negligible and good correspondence between our model and experiment leads to a simple picture of such phenomenology as the genesis of d {yields} d excitations at the K edge and intermediate-state interference effects.
Date: April 29, 2010
Creator: Hancock, J.N.
Object Type: Article
System: The UNT Digital Library
Introduction to Extra Dimensions (open access)

Introduction to Extra Dimensions

Extra dimensions provide a very useful tool in addressing a number of the fundamental problems faced by the Standard Model. The following provides a very basic introduction to this very broad subject area as given at the VIII School of the Gravitational and Mathematical Physics Division of the Mexican Physical Society in December 2009. Some prospects for extra dimensional searches at the 7 TeV LHC with {approx}1 fb{sup -1} of integrated luminosity are provided.
Date: April 29, 2010
Creator: Rizzo, Thomas G.
Object Type: Article
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
Kinetics of small particle activation in supersaturated vapors (open access)

Kinetics of small particle activation in supersaturated vapors

We examine the nucleated (with barrier) activation of perfectly wetting (zero contact angle) particles ranging from bulk size down to one nanometer. Thermodynamic properties of the particles, coated with liquid layers of varying thickness and surrounded by vapor, are analyzed. Nano-size particles are predicted to activate at relative humidity below the Kelvin curve on crossing a nucleation barrier, located at a critical liquid layer thickness such that the total particle size (core + liquid layer) equals the Kelvin radius (Fig. 1). This barrier vanishes precisely as the critical layer thickness approaches the thin layer limit and the Kelvin radius equals the radius of the particle itself. These considerations are similar to those included in Fletcher's theory (Fletcher, 1958) however the present analysis differs in several important respects. Firstly, where Fletcher used the classical prefactor-exponent form for the nucleation rate, requiring separate estimation of the kinetic prefactor, we solve a diffusion-drift equation that is equivalent to including the full Becker-Doering (BD) multi-state kinetics of condensation/evaporation along the growth coordinate. We also determine the mean first passage time (MFPT) for barrier crossing (Wedekind et al., 2007), which is shown to provide a generalization of BD nucleation kinetics especially useful for barrier heights …
Date: August 29, 2010
Creator: McGraw, R. & Wang, J.
Object Type: Article
System: The UNT Digital Library
Russian Contract Procurement Document (open access)

Russian Contract Procurement Document

This contract supports the enhancement of physical protection or nuclear material control and accounting systems at institutes or enterprises of the newly independent states under the material protection control and accounting (MPC&A) program. The contract is entered into pursuant to the MPC&A Program, a gratuitous technical assistance program, in accordance with the bilateral Agreements between the Russian Federation and the United States of America concerning the Safe and Secure Transportation, Storage and Destruction of Weapons and the Prevention of Weapons Proliferation of June 1992, as extended and amended by Protocol signed of June 1999, Agreement between the Government of the Russian Federation regarding Cooperation in the Area of Nuclear Materials Physical Protection, Control and Accounting of October 1999 and the Russian Federation law of May 1999 on the taxation exemption of gratuitous technical assistance with Russian Federation under registration No.DOE001000.
Date: March 29, 2010
Creator: Tobin, J G
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
Evaluation of Fish Passage Conditions for Juvenile Salmonids Using Sensor Fish at Detroit Dam, Oregon (open access)

Evaluation of Fish Passage Conditions for Juvenile Salmonids Using Sensor Fish at Detroit Dam, Oregon

Fish passage conditions through two spillways at Detroit Dam on the North Santiam River in Oregon were evaluated by Pacific Northwest National Laboratory for the U.S. Army Corps of Engineers (USACE), Portland District, using Sensor Fish devices. The objective of the study was to describe and compare passage exposure conditions through Spillbay 3 and Spillbay 6 at 1.5- and 3.5-ft gate openings, identifying potential fish injury regions of the routes. The study was performed in July 2009, concurrent with HI-Z balloon-tag studies by Normandeau Associates, Inc. Sensor Fish and live fish were deployed at elevations approximately 3 ft above structure at depths determined using a computational fluid dynamics model. Data collected were analyzed to estimate 1) exposure conditions, particularly exposure to severe collision and shear events by passage route sub-regions; 2) differences in passage conditions between passage routes; and 3) relationships to live-fish injury and mortality data estimates.
Date: January 29, 2010
Creator: Duncan, Joanne P.
Object Type: Report
System: The UNT Digital Library
Radiation Protection Studies for LCLS Tune Up Dump (open access)

Radiation Protection Studies for LCLS Tune Up Dump

The Linac Coherent Light Source (LCLS) at the Stanford Linear Accelerator Center is a pioneer fourth generation hard x-ray free electron laser that shall start to deliver laser pulses in 2009. Among other components of LCLS that present radiation protection concerns, the tune up dump (tdund) is of special interest because it also constitutes an issue for machine protection, as it is placed close to radiation sensitive components, like electronic devices and permanent magnets in the undulators. This paper first introduces the stopper of tdund looking at the heat load, and then it describes the shielding around the dump necessary to maintain the prompt and residual dose within design values. Next, preliminary comparisons of the magnetization loss in a dedicated on-site magnet irradiation experiment with FLUKA simulations serve to characterize the magnetic response to radiation of magnets like those of LCLS. The previous knowledge, together with the limit for the allowed demagnetization, are used to estimate the lifetime of the undulator. Further simulations provide guidelines on which lifetime can be expected for an electronic device placed at a given distance of tdund.
Date: April 29, 2010
Creator: Santana-Leitner, M.; Fass, A.; Mao, S.; Nuhn, H. D.; Roesler, S.; Rokni, S. et al.
Object Type: Article
System: The UNT Digital Library
A momentum-dependent perspective on quasiparticleinterference in Bi2Sr2CaCu2O_8+delta (open access)

A momentum-dependent perspective on quasiparticleinterference in Bi2Sr2CaCu2O_8+delta

Angle Resolved Photoemission Spectroscopy (ARPES) probes the momentum-space electronic structure of materials, and provides invaluable information about the high-temperature superconducting cuprates. Likewise, cuprates real-space, inhomogeneous electronic structure is elucidated by Scanning Tunneling Spectroscopy (STS). Recently, STS has exploited quasiparticle interference (QPI) - wave-like electrons scattering off impurities to produce periodic interference patterns - to infer properties of the QP in momentum-space. Surprisingly, some interference peaks in Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} (Bi-2212) are absent beyond the antiferromagnetic (AF) zone boundary, implying the dominance of particular scattering process. Here, we show that ARPES sees no evidence of quasiparticle (QP) extinction: QP-like peaks are measured everywhere on the Fermi surface, evolving smoothly across the AF zone boundary. This apparent contradiction stems from different natures of single-particle (ARPES) and two-particle (STS) processes underlying these probes. Using a simple model, we demonstrate extinction of QPI without implying the loss of QP beyond the AF zone boundary.
Date: April 29, 2010
Creator: Vishik, I. M.
Object Type: Article
System: The UNT Digital Library
Evidence for weak electronic correlations in Fe-pnictides (open access)

Evidence for weak electronic correlations in Fe-pnictides

Using x-ray absorption and resonant inelastic x-ray scattering, charge dynamics at and near the Fe L edges is investigated in Fe pnictide materials, and contrasted to that measured in other Fe compounds. It is shown that the XAS and RIXS spectra for 122 and 1111 Fe pnictides are each qualitatively similar to Fe metal. Cluster diagonalization, multiplet, and density-functional calculations show that Coulomb correlations are much smaller than in the cuprates, highlighting the role of Fe metallicity and strong covalency in these materials. Best agreement with experiment is obtained using Hubbard parameters U {approx}< 2eV and J {approx} 0.8eV.
Date: April 29, 2010
Creator: Yang, W.L.
Object Type: Article
System: The UNT Digital Library
DETERMINING THE EFFECTS OF RADIATION ON AGING CONCRETE STRUCTURES OF NUCLEAR REACTORS (open access)

DETERMINING THE EFFECTS OF RADIATION ON AGING CONCRETE STRUCTURES OF NUCLEAR REACTORS

The U.S. Department of Energy Office of Environmental Management (DOE-EM) is responsible for the Decontamination and Decommissioning (D&D) of nuclear facilities throughout the DOE Complex. Some of these facilities will be completely dismantled, while others will be partially dismantled and the remaining structure will be stabilized with cementitious fill materials. The latter is a process known as In-Situ Decommissioning (ISD). The ISD decision process requires a detailed understanding of the existing facility conditions, and operational history. System information and material properties are need for aged nuclear facilities. This literature review investigated the properties of aged concrete structures affected by radiation. In particular, this review addresses the Savannah River Site (SRS) isotope production nuclear reactors. The concrete in the reactors at SRS was not seriously damaged by the levels of radiation exposure. Loss of composite compressive strength was the most common effect of radiation induced damage documented at nuclear power plants.
Date: January 29, 2010
Creator: Serrato, M.
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
Regulation of Yersina pestis Virulence by AI-2 Mediated Quorum Sensing (open access)

Regulation of Yersina pestis Virulence by AI-2 Mediated Quorum Sensing

The proposed research was motivated by an interest in understanding Y. pestis virulence mechanisms and bacteria cell-cell communication. It is expected that a greater understanding of virulence mechanisms will ultimately lead to biothreat countermeasures and novel therapeutics. Y. pestis is the etiological agent of plague, the most devastating disease in human history. Y. pestis infection has a high mortality rate and a short incubation before mortality. There is no widely available and effective vaccine for Y. pestis and multi-drug resistant strains are emerging. Y. pestis is a recognized biothreat agent based on the wide distribution of the bacteria in research laboratories around the world and on the knowledge that methods exist to produce and aerosolize large amounts of bacteria. We hypothesized that cell-cell communication via signaling molecules, or quorum sensing, by Y. pestis is important for the regulation of virulence factor gene expression during host invasion, though a causative link had never been established. Quorum sensing is a mode of intercellular communication which enables orchestration of gene expression for many bacteria as a function of population density and available evidence suggests there may be a link between quorum sensing and regulation of Y. pesits virulence. Several pathogenic bacteria have been …
Date: March 29, 2010
Creator: Segelke, B; Hok, S; Lao, V; Corzett, M & Garcia, E
Object Type: Report
System: The UNT Digital Library
Science and Technology Review September 2010 (open access)

Science and Technology Review September 2010

None
Date: July 29, 2010
Creator: Blobaum, K. J.
Object Type: Report
System: The UNT Digital Library
YEAST METABOLIC FLUX MEASUREMENT BY ACCELERATOR MASS SPECTROMETRY (open access)

YEAST METABOLIC FLUX MEASUREMENT BY ACCELERATOR MASS SPECTROMETRY

None
Date: July 29, 2010
Creator: Stewart, B J; Navid, A; Turteltaub, K & Bench, G
Object Type: Article
System: The UNT Digital Library
Designing small catalysts for CO2 capture (open access)

Designing small catalysts for CO2 capture

None
Date: August 29, 2010
Creator: Wong, S. E.; Lau, E. Y.; Satcher, J. H.; Aines, R. D. & Lightstone, F. C.
Object Type: Article
System: The UNT Digital Library
Searching for Optimal Mitigation Geometries for Multilayer High Reflector Coatings (open access)

Searching for Optimal Mitigation Geometries for Multilayer High Reflector Coatings

None
Date: July 29, 2010
Creator: Qiu, S R; Wolfe, J E; Monterrosa, A M; Feit, M D; Pistor, T V & Stolz, C J
Object Type: Article
System: The UNT Digital Library
In Situ Transmission Electron Microscopy Observations of Rapid Solidification of Aluminum Thin Films (open access)

In Situ Transmission Electron Microscopy Observations of Rapid Solidification of Aluminum Thin Films

None
Date: June 29, 2010
Creator: Kulovits, A; Wiezorek, J M; LaGrange, T; Reed, B W & Campbell, G H
Object Type: Article
System: The UNT Digital Library
An estimate of collisional beam scattering during final focus in NDCX-II (open access)

An estimate of collisional beam scattering during final focus in NDCX-II

None
Date: March 29, 2010
Creator: Cohen, R H
Object Type: Report
System: The UNT Digital Library
Size-dependent Si Nanowire Mechanics are Invariant to Changes in the Surface State (open access)

Size-dependent Si Nanowire Mechanics are Invariant to Changes in the Surface State

None
Date: December 29, 2010
Creator: Lee, B & Rudd, R E
Object Type: Article
System: The UNT Digital Library
Application of solution techniques to rapid growth of organic crystals (open access)

Application of solution techniques to rapid growth of organic crystals

None
Date: June 29, 2010
Creator: Zaitseva, N.; Carman, L.; Glenn, A.; Newby, J.; Faust, M.; Hamel, S. et al.
Object Type: Article
System: The UNT Digital Library