The transfer of neutral molecules, ions and ionic species from water to ethylene glycol and to propylene carbonate; descriptors for pyridinium cations (open access)

The transfer of neutral molecules, ions and ionic species from water to ethylene glycol and to propylene carbonate; descriptors for pyridinium cations

Article on the transfer of neutral molecules, ions and ionic species from water to ethylene glycol and to propylene carbonate and descriptors for pyridinium cations.
Date: June 29, 2010
Creator: Abraham, M. H. (Michael H.) & Acree, William E. (William Eugene)
System: The UNT Digital Library
The transverse momentum dependent distribution functions in the bag model (open access)

The transverse momentum dependent distribution functions in the bag model

Leading and subleading twist transverse momentum dependent parton distribution functions (TMDs) are studied in a quark model framework provided by the bag model. A complete set of relations among different TMDs is derived, and the question is discussed how model-(in)dependent such relations are. A connection of the pretzelosity distribution and quark orbital angular momentum is derived. Numerical results are presented, and applications for phenomenology discussed. In particular, it is shown that in the valence-x region the bag model supports a Gaussian Ansatz for the transverse momentum dependence of TMDs.
Date: January 29, 2010
Creator: Avakian, Harut; Efremov, Anatoly; Schweitzer, Peter & Yuan, Feng
System: The UNT Digital Library
Systematic reduction of sign errors in many-body calculations of atoms and molecules (open access)

Systematic reduction of sign errors in many-body calculations of atoms and molecules

None
Date: March 29, 2010
Creator: Bajdich, M.; Tiago, M. L.; Hood, R. Q.; Kent, P. R. & Reboredo, F. A.
System: The UNT Digital Library
On the Performance of an Algebraic MultigridSolver on Multicore Clusters (open access)

On the Performance of an Algebraic MultigridSolver on Multicore Clusters

Algebraic multigrid (AMG) solvers have proven to be extremely efficient on distributed-memory architectures. However, when executed on modern multicore cluster architectures, we face new challenges that can significantly harm AMG's performance. We discuss our experiences on such an architecture and present a set of techniques that help users to overcome the associated problems, including thread and process pinning and correct memory associations. We have implemented most of the techniques in a MultiCore SUPport library (MCSup), which helps to map OpenMP applications to multicore machines. We present results using both an MPI-only and a hybrid MPI/OpenMP model.
Date: April 29, 2010
Creator: Baker, A H; Schulz, M & Yang, U M
System: The UNT Digital Library
Fabrication and Test of 90-mm Nb3Sn Quadrupole Model Based on Dipole-type Collar (open access)

Fabrication and Test of 90-mm Nb3Sn Quadrupole Model Based on Dipole-type Collar

A series of 90-mm TQC quadrupole models with a collar-based mechanical structure has been fabricated and tested within the framework of the US-LHC Accelerator Research Program (LARP) using quadrupole-symmetric stainless steel collar laminations. This paper describes the design features, construction and test of TQC02Eb, the first TQC made with dipole-type collar and collaring techniques. Magnet test includes quench performance and field quality measurements at 4.5 and 1.9 K. Results of model performance for TQC quadrupoles based on dipole-type and quadrupole-type collars are compared and discussed.
Date: July 29, 2010
Creator: Bossert, R.; Andreev, N.; Chlachidze, G.; Kashikhin, V. S.; Kashikhin, V. V.; Lamm, M. J. et al.
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.
System: The UNT Digital Library
APPLICATIONS OF BIOTECHNOLOGY IN DEVELOPMENT OF BIOMATERIALS: NANOTECHNOLOGY AND BIOFILMS (open access)

APPLICATIONS OF BIOTECHNOLOGY IN DEVELOPMENT OF BIOMATERIALS: NANOTECHNOLOGY AND BIOFILMS

Biotechnology is the application of biological techniques to develop new tools and products for medicine and industry. Due to various properties including chemical stability, biocompatibility, and specific activity, e.g. antimicrobial properties, many new and novel materials are being investigated for use in biosensing, drug delivery, hemodialysis, and other medical applications. Many of these materials are less than 100 nanometers in size. Nanotechnology is the engineering discipline encompassing designing, producing, testing, and using structures and devices less than 100 nanometers. One of the challenges associated with biomaterials is microbial contamination that can lead to infections. In recent work we have examined the functionalization of nanoporous biomaterials and antimicrobial activities of nanocrystalline diamond materials. In vitro testing has revealed little antimicrobial activity against Pseudomonas fluorescens bacteria and associated biofilm formation that enhances recalcitrance to antimicrobial agents including disinfectants and antibiotics. Laser scanning confocal microscopy studies further demonstrated properties and characteristics of the material with regard to biofilm formation.
Date: November 29, 2010
Creator: Brigmon, R.; Berry, T. & Narayan, R.
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
System: The UNT Digital Library
Algebraic Multigrid for Linear Systems Obtained by Explicit Element Reduction (open access)

Algebraic Multigrid for Linear Systems Obtained by Explicit Element Reduction

None
Date: June 29, 2010
Creator: Brunner, T. A. & Kolev, T. V.
System: The UNT Digital Library
In situ spectroscopic detection of SMSI effect in a Ni/CeO2 system: hydrogen-induced burial and dig out of metallic nickel (open access)

In situ spectroscopic detection of SMSI effect in a Ni/CeO2 system: hydrogen-induced burial and dig out of metallic nickel

In situ APPES technique demonstrates that the strong metal support interaction effect (SMSI) in the Ni-ceria system is associated with the decoration and burial of metallic particles by the partially reduced support, a phenomenon reversible by evacuation at high temperature of the previously absorbed hydrogen.
Date: June 29, 2010
Creator: Caballero, Alfonso; Holgado, Juan P.; Gonzalez-delaCruz, Victor M.; Habas, Susan e.; Herranz, Tirma & Salmeron, Miquel
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
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
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.
System: The UNT Digital Library
Certification of Superconducting Solenoid-Based Focusing Lenses (open access)

Certification of Superconducting Solenoid-Based Focusing Lenses

The first production focusing lens for the HINS beam line at Fermilab has been assembled into a cryostat and tested. A total of 5 devices will be tested before they are installed in the low energy section of the HINS beam line, which uses copper Crossbar-H (CH) style RF cavities. One of the tested CH-section lens assemblies includes a pair of weak orthogonal steering dipoles nested within a strong focusing solenoid, and has six vapor cooled power leads. The other device has only the strong focusing solenoid, and utilizes a single pair of HTS power leads. The production test program is designed to measure the thermal performance of the cryostat, minimum cooling requirements for the HTS leads, quench performance of all superconducting components, and precise determination of the magnetic axis and field angles. Results and future plans for the first production device tests are presented.
Date: July 29, 2010
Creator: DiMarco, E.Joseph; Hemmati, Ali M.; Orris, Darryl F.; Page, Thomas M.; Rabehl, Roger H.; Tartaglia, Michael A. et al.
System: The UNT Digital Library
Service-Learning in Disaster Recovery: Rebuilding the Mississippi Gulf Coast (open access)

Service-Learning in Disaster Recovery: Rebuilding the Mississippi Gulf Coast

This article describes a course in the City and Regional Planning program at the Ohio State University.
Date: July 29, 2010
Creator: Evans-Cowley, Jennifer
System: The UNT Digital Library
EFFECTS OF RADIATION ON ESTABLISHED FORENSIC EVIDENCE CONTAINMENT METHODS (open access)

EFFECTS OF RADIATION ON ESTABLISHED FORENSIC EVIDENCE CONTAINMENT METHODS

The Federal Bureau of Investigation (FBI) Laboratory is currently exploring needs and protocols for the storage of evidentiary items contaminated with radioactive material. While a large body of knowledge on the behavior of storage polymers in radiation fields exists, this knowledge has not been applied to the field of forensics and maintaining evidentiary integrity. The focus of this research was to evaluate the behavior of several traditional evidentiary containment polymers when exposed to significant alpha, beta, gamma, neutron and mixed radiation sources. Doses were designed to simulate exposures possible during storage of materials. Several products were found to be poorly suited for use in this specific application based on standardized mechanical testing results. Remaining products were determined to warrant further investigation for the storage of radiologically contaminated evidence.
Date: November 29, 2010
Creator: Ferguson, C.; Duff, M.; Clark, E. & Chapman, G.
System: The UNT Digital Library
Standing-wave excited soft x-ray photoemission microscopy: application to Co microdot magnetic arrays (open access)

Standing-wave excited soft x-ray photoemission microscopy: application to Co microdot magnetic arrays

We demonstrate the addition of depth resolution to the usual two-dimensional images in photoelectron emission microscopy (PEEM), with application to a square array of circular magnetic Co microdots. The method is based on excitation with soft x-ray standing-waves generated by Bragg reflection from a multilayer mirror substrate. Standing wave is moved vertically through sample simply by varying the photon energy around the Bragg condition. Depth-resolved PEEM images were obtained for all of the observed elements. Photoemission intensities as functions of photon energy were compared to x-ray optical calculations in order to quantitatively derive the depth-resolved film structure of the sample.
Date: October 29, 2010
Creator: Gray, Alexander; Kronast, Florian; Papp, Christian; Yang, See-Hun; Cramm, Stefan; Krug, Ingo P. et al.
System: The UNT Digital Library
Analysis Efforts Supporting NSTX Upgrades (open access)

Analysis Efforts Supporting NSTX Upgrades

The National Spherical Torus Experiment (NSTX) is a low aspect ratio, spherical torus (ST) configuration device which is located at Princeton Plasma Physics Laboratory (PPPL) This device is presently being updated to enhance its physics by doubling the TF field to 1 Tesla and increasing the plasma current to 2 Mega-amperes. The upgrades include a replacement of the centerstack and addition of a second neutral beam. The upgrade analyses have two missions. The first is to support design of new components, principally the centerstack, the second is to qualify existing NSTX components for higher loads, which will increase by a factor of four. Cost efficiency was a design goal for new equipment qualification, and reanalysis of the existing components. Showing that older components can sustain the increased loads has been a challenging effort in which designs had to be developed that would limit loading on weaker components, and would minimize the extent of modifications needed. Two areas representing this effort have been chosen to describe in more details: analysis of the current distribution in the new TF inner legs, and, second, analysis of the out-of-plane support of the existing TF outer legs.
Date: November 29, 2010
Creator: H.Zhang, P. Titus, P. Rogoff, A.Zolfaghari, D. Mangra, M. Smith
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.
System: The UNT Digital Library
Enzyme-Like Catalysis of the Nazarov Cyclization by Supramolecular Encapsulation (open access)

Enzyme-Like Catalysis of the Nazarov Cyclization by Supramolecular Encapsulation

A primary goal in the design and synthesis of molecular hosts has been the selective recognition and binding of a variety of guests using non-covalent interactions. Supramolecular catalysis, which is the application of such hosts towards catalysis, has much in common with many enzymatic reactions, chiefly the use of both spatially appropriate binding pockets and precisely oriented functional groups to recognize and activate specific substrate molecules. Although there are now many examples which demonstrate how selective encapsulation in a host cavity can enhance the reactivity of a bound guest, all have failed to reach the degree of increased reactivity typical of enzymes. We now report the catalysis of the Nazarov cyclization by a self-assembled coordination cage, a carbon-carbon bond-forming reaction which proceeds under mild, aqueous conditions. The acceleration in this system is over a million-fold, and represents the first example of supramolecular catalysis that achieves the level of rate enhancement comparable to that observed in several enzymes. We explain the unprecedented degree of rate increase as due to the combination of (a) preorganization of the encapsulated substrate molecule, (b) stabilization of the transition state of the cyclization by constrictive binding, and (c) increase in the basicity of the complexed alcohol …
Date: March 29, 2010
Creator: Hastings, Courtney; Pluth, Michael; Bergman, Robert & Raymond, Kenneth
System: The UNT Digital Library
Gamma Spectrum from Neutron Capture on Tungsten Isotopes (open access)

Gamma Spectrum from Neutron Capture on Tungsten Isotopes

An evaluation of thermal neutron capture on the stable tungsten isotopes is presented, with preliminary results for the compound systems 183;184;185;187W. The evaluation procedure compares the g-ray cross-section data collected at the Budapest reactor, with Monte Carlo simulations of g-ray emission following the thermal neutron-capture process. The statistical-decay code DICEBOX was used for the Monte Carlo simulations. The evaluation yields new gamma rays in 185W and the confirmation of spins in 187W, raising the number of levels below which the level schemes are considered complete, thus increasing the number of levels that can be used in neutron data libraries.
Date: April 29, 2010
Creator: Hurst, Aaron; Summers, Neil; Sleaford, Brad; Firestone, Richard B; Belgya, T. & Revay, Z.S.
System: The UNT Digital Library
PyMercury: Interactive Python for the Mercury Monte Carlo Particle Transport Code (open access)

PyMercury: Interactive Python for the Mercury Monte Carlo Particle Transport Code

Monte Carlo particle transport applications are often written in low-level languages (C/C++) for optimal performance on clusters and supercomputers. However, this development approach often sacrifices straightforward usability and testing in the interest of fast application performance. To improve usability, some high-performance computing applications employ mixed-language programming with high-level and low-level languages. In this study, we consider the benefits of incorporating an interactive Python interface into a Monte Carlo application. With PyMercury, a new Python extension to the Mercury general-purpose Monte Carlo particle transport code, we improve application usability without diminishing performance. In two case studies, we illustrate how PyMercury improves usability and simplifies testing and validation in a Monte Carlo application. In short, PyMercury demonstrates the value of interactive Python for Monte Carlo particle transport applications. In the future, we expect interactive Python to play an increasingly significant role in Monte Carlo usage and testing.
Date: November 29, 2010
Creator: Iandola, F N; O'Brien, M J & Procassini, R J
System: The UNT Digital Library
Twist-three Fragmentation Function Contribution to the Single Spin Asymmetry in pp Collisions (open access)

Twist-three Fragmentation Function Contribution to the Single Spin Asymmetry in pp Collisions

We study the twist-three fragmentation function contribution to the single transverse spin asymmetries in inclusive hadron production in pp collisions, pp->h+X. In particular, we evaluate the so-called derivative contribution which dominates the spin asymmetry in the forward direction of the polarized proton. With certain parametrizations for the twist-three fragmentation function, we estimate its contribution to the asymmetry of pi0 production at RHIC energy. We find that the contribution is sizable and might be responsible for the big difference between the asymmetries in eta and pi0 productions observed by the STAR collaboration at RHIC.
Date: January 29, 2010
Creator: Kang, Zhong-Bo; Yuan, Feng & Zhou, Jian
System: The UNT Digital Library
Subsurface Mobile Plutonium Speciation:  Sampling Artifacts for Groundwater Colloids (open access)

Subsurface Mobile Plutonium Speciation: Sampling Artifacts for Groundwater Colloids

A recent review found several conflicting conclusions regarding colloid-facilitated transport of radionuclides in groundwater and noted that colloids can both facilitate and retard transport. Given these contrasting conclusions and the profound implications even trace concentrations of plutonium (Pu) have on the calculated risk posed to human health, it is important that the methodology used to sample groundwater colloids be free of artifacts. The objective of this study was: (1) to conduct a field study and measure Pu speciation, ({sup 239}Pu and {sup 240}Pu for reduced-Pu{sub aq}, oxidized-Pu{sub aq}, reduced-Pu{sub colloid}, and oxidized-Pu{sub colloid}), in a Savannah River Site (SRS) aquifer along a pH gradient in F-Area, (2) to determine the impact of pumping rate on Pu concentration, Pu speciation, and Pu isotopic ratios, (3) determine the impact of delayed sample processing (as opposed to processing directly from the well).
Date: June 29, 2010
Creator: Kaplan, D. & Buesseler, K.
System: The UNT Digital Library