States

Hydrodynamic Modeling Analysis of Union Slough Restoration Project in Snohomish River, Washington (open access)

Hydrodynamic Modeling Analysis of Union Slough Restoration Project in Snohomish River, Washington

A modeling study was conducted to evaluate additional project design scenarios at the Union Slough restoration/mitigation site during low tide and to provide recommendations for finish-grade elevations to achieve desired drainage. This was accomplished using the Snohomish River hydrodynamic model developed previously by PNNL.
Date: December 20, 2010
Creator: Yang, Zhaoqing & Wang, Taiping
Object Type: Report
System: The UNT Digital Library
ALTERED STRUCTURE OF THE MN4CA CLUSTER IN THE OXYGEN EVOLVING COMPLEX OF PHOTOSYSTEM II BY A HISTIDINE LIGAND MUTATION (open access)

ALTERED STRUCTURE OF THE MN4CA CLUSTER IN THE OXYGEN EVOLVING COMPLEX OF PHOTOSYSTEM II BY A HISTIDINE LIGAND MUTATION

None
Date: January 20, 2011
Creator: Yano, Junko; Walker, Lee; Service, Rachel; Yachandra, Vittal & Debus, Richard
Object Type: Article
System: The UNT Digital Library
Double Photoionization of excited Lithium and Beryllium (open access)

Double Photoionization of excited Lithium and Beryllium

We present total, energy-sharing and triple differential cross sections for one-photon, double ionization of lithium and beryllium starting from aligned, excited P states. We employ a recently developed hybrid atomic orbital/ numerical grid method based on the finite-element discrete-variable representation and exterior complex scaling. Comparisons with calculated results for the ground-state atoms, as well as analogous results for ground-state and excited helium, serve to highlight important selection rules and show some interesting effects that relate to differences between inter- and intra-shell electron correlation.
Date: May 20, 2010
Creator: Yip, Frank L.; McCurdy, C. William & Rescigno, Thomas N.
Object Type: Article
System: The UNT Digital Library
Modeling Low-Platinum-Loading Effects in Fuel-Cell Catalyst Layers (open access)

Modeling Low-Platinum-Loading Effects in Fuel-Cell Catalyst Layers

The cathode catalyst layer within a proton-exchange-membrane fuel cell is the most complex and critical, yet least understood, layer within the cell. The exact method and equations for modeling this layer are still being revised and will be discussed in this paper, including a 0.8 reaction order, existence of Pt oxides, possible non-isopotential agglomerates, and the impact of a film resistance towards oxygen transport. While the former assumptions are relatively straightforward to understand and implement, the latter film resistance is shown to be critically important in explaining increased mass-transport limitations with low Pt-loading catalyst layers. Model results demonstrate agreement with experimental data that the increased oxygen flux and/or diffusion pathway through the film can substantially decrease performance. Also, some scale-up concepts from the agglomerate scale to the more macroscopic porous-electrode scale are discussed and the resulting optimization scenarios investigated.
Date: January 20, 2011
Creator: Yoon, Wonseok & Weber, Adam Z.
Object Type: Article
System: The UNT Digital Library
Nanoimaging to Prevent and Treat Alzheimer’s and Parkinson’s Diseases. Scientific/Technical report (open access)

Nanoimaging to Prevent and Treat Alzheimer’s and Parkinson’s Diseases. Scientific/Technical report

This project will develop innovative approaches to characterization of the very early stages of protein aggregation that eventually can be translated to the development of early diagnostic tools and efficient treatments for Alzheimer’s, Parkinson’s and Huntington’s diseases. Funding will be used to acquire nanoimaging technology for nanoscale imaging, manipulation and analysis of biomedical materials to develop treatments that will repair disabled proteins and cure diseases that result from protein malfunction, specifically Alzheimer’s and Parkinson’s diseases. Expected outcomes include tests for early diagnosis and therapeutic treatments for these devastating neurological diseases. To elucidate the mechanisms of protein misfolding, we will establish an extensive program of experimental studies using a broad arsenal of advanced nanoscale and traditional techniques that will be integrated with molecular-scale modeling of protein misfolding and the nucleation of aggregate structures. To identify intracellular machinery or/and multicomponent complexes critically involved in protein misfolding, we will characterize interactions between targeted proteins and specific intracellular components or metabolites that impact on protein conformational pathways leading to protein misfolding accompanied by formation of toxic aggregated morphologies. To design innovative nanotechnology tools for the control of intracellular protein misfolding and aggregation processes, we will develop a predictive molecular scale model for intracellular protein …
Date: December 20, 2012
Creator: Yuri L. Lyubchenko, PhD, DSc
Object Type: Report
System: The UNT Digital Library
Determination of the Azimuthal Asymmetry of Deuteron Photodisintegration in the Energy Region E{sub {gamma}} = 1.1 - 2.3 GeV (open access)

Determination of the Azimuthal Asymmetry of Deuteron Photodisintegration in the Energy Region E{sub {gamma}} = 1.1 - 2.3 GeV

Deuteron photodisintegration is a benchmark process for the investigation of the role of quarks and gluons in nuclei. Existing theoretical models of this process describe the available cross sections with the same degree of success. Therefore, spin-dependent observables are crucial for a better understanding of the underlying dynamical mechanisms. However, data on the induced polarization (P{sub y}), along with the polarization transfers (C{sub x'} and C{sub z'} ), have been shown to be insensitive to differences between theoretical models. On the other hand, the beam-spin asymmetry {Sigma} is predicted to have a large sensitivity and is expected to help in identifying the energy at which the transition from the hadronic to the quark-gluon picture of the deuteron takes place. Here, the work done to determine the experimental values of the beam-spin asymmetry in deuteron photodisintegration for photon energies between 1.1 – 2.3 GeV is presented. The data were taken with the CLAS at the Thomas Jefferson National Accelerator Facility during the g13 experiment. Photons with linear polarization of ~80% were produced using the coherent bremsstrahlung facility in Hall B. The work done by the author to calibrate a specific detector system, select deuteron photodisintegration events, study the degree of photon …
Date: May 20, 2012
Creator: Zachariou, Nicholas
Object Type: Thesis or Dissertation
System: The UNT Digital Library
Comment on "Wall Forces Produced During ITER Disruptions" by H. R. Strauss, R. Paccagnella, and J. Breslau (PHYSICS OF PLASMAS 17, 082505 (2010) (open access)

Comment on "Wall Forces Produced During ITER Disruptions" by H. R. Strauss, R. Paccagnella, and J. Breslau (PHYSICS OF PLASMAS 17, 082505 (2010)

The paper by H.R. Strauss presents numerical simulations, which pretend to describe the disruption instability in ITER device. The simulations were performed with numerical code M3D, described in Ref.[7] of the paper.
Date: October 20, 2010
Creator: Zakharov, Leonid E.
Object Type: Report
System: The UNT Digital Library
Comment on "Wall Forces Produced During ITER Disruptions" by H. R. Strauss, R. Paccagnella, and J. Breslau (PHYSICS OF PLASMAS 17, 082505 (2010) (open access)

Comment on "Wall Forces Produced During ITER Disruptions" by H. R. Strauss, R. Paccagnella, and J. Breslau (PHYSICS OF PLASMAS 17, 082505 (2010)

The paper by H.R. Strauss presents numerical simulations, which pretend to describe the disruption instability in ITER device. The simulations were performed with numerical code M3D, described in Ref.[7] of the paper.
Date: October 20, 2010
Creator: Zakharov, Leonid E.
Object Type: Report
System: The UNT Digital Library
Design Of JET ELM Control Coils For Operation At 350 C (open access)

Design Of JET ELM Control Coils For Operation At 350 C

A study has confirmed the feasibility of designing, fabricating and installing resonant magnetic field perturbation (RMP) coils in JET1 with the objective of controlling edge localized modes (ELM). A system of two rows of in-vessel coils, above the machine midplane, has been chosen as it not only can investigate the physics of and achieve the empirical criteria for ELM suppression, but also permits variation of the spectra allowing for comparison with other experiments. These coils present several engineering challenges. Conditions in JET necessitate the installation of these coils via remote handling, which will impose weight, dimensional and logistical limitations. And while the encased coils are designed to be conventionally wound and bonded, they will not have the usual benefit of active cooling. Accordingly, coil temperatures are expected to reach 350 C during bakeout as well as during plasma operations. These elevated temperatures are beyond the safe operating limits of conventional OFHC copper and the epoxies that bond and insulate the turns of typical coils. This has necessitated the use of an alternative copper alloy conductor C18150 (CuCrZr). More importantly, an alternative to epoxy had to be found. An R&D program was initiated to find the best available insulating and bonding …
Date: September 20, 2010
Creator: Zatz, I. J.; Brooks, A.; Cole, M.; Neilson, G. H.; Lowry, C.; Mardenfeld, M. et al.
Object Type: Article
System: The UNT Digital Library
3d segmentation of rodent brain structures using active volume model with shape priors; conference paper (open access)

3d segmentation of rodent brain structures using active volume model with shape priors; conference paper

N/A
Date: March 20, 2011
Creator: Zhang, Shaoting; Huang, J.; Uzunbas, M.; Shen, T.; Delis, F.; Volkow, N. D. et al.
Object Type: Article
System: The UNT Digital Library
Analysis of kicker noise induced beam emittance growth (open access)

Analysis of kicker noise induced beam emittance growth

Over the last few years, physicists have occasionally observed the presence of noise acting on the RHIC beams leading to emittance growth at high beam energies. While the noise was sporadic in the past, it became persistent during the Run-11 setup period. An investigation diagnosed the source as originating from the RHIC dump kicker system. Once identified the issue was quickly resolved. We report in this paper the investigation result, circuit analysis, measured and simulated waveforms, solutions, and future plans.
Date: May 20, 2012
Creator: Zhang, W.; Sandberg, J.; Ahrens, L.; Blacker, I. M.; Brennan, M.; Blaskiewicz, M. et al.
Object Type: Article
System: The UNT Digital Library
Analysis of beam loss induced abort kicker instability (open access)

Analysis of beam loss induced abort kicker instability

Through more than a decade of operation, we have noticed the phenomena of beam loss induced kicker instability in the RHIC beam abort systems. In this study, we analyze the short term beam loss before abort kicker pre-fire events and operation conditions before capacitor failures. Beam loss has caused capacitor failures and elevated radiation level concentrated at failed end of capacitor has been observed. We are interested in beam loss induced radiation and heat dissipation in large oil filled capacitors and beam triggered thyratron conduction. We hope the analysis result would lead to better protection of the abort systems and improved stability of the RHIC operation.
Date: May 20, 2012
Creator: Zhang, W.; Sandberg, J.; Ahrens, L.; Fischer, W.; Hahn, H.; Mi, J. et al.
Object Type: Article
System: The UNT Digital Library
Research and development of RHIC injection kicker upgrade with nano second FID pulse generator (open access)

Research and development of RHIC injection kicker upgrade with nano second FID pulse generator

Our recent effort to test a 50 kV, 1 kA, 50 ns pulse width, 10 ns pulse rise time FID pulse generator with a 250 ft transmission cable, resistive load, and existing RHIC injection kicker magnet has produced unparalleled results. This is the very first attempt to drive a high strength fast kicker magnet with a nano second high pulsed power (50 MVA) generator for large accelerator and colliders. The technology is impressive. We report here the result and future plan of RHIC Injection kicker upgrade.
Date: May 20, 2012
Creator: Zhang, W.; Sandberg, J.; Hahn, H.; Fischer, W.; Liaw, C. J.; Pai, C. et al.
Object Type: Article
System: The UNT Digital Library
High-temperature-oxidation-induced ordered structure in Inconel 939 superalloy exposed to oxy-combustion environments (open access)

High-temperature-oxidation-induced ordered structure in Inconel 939 superalloy exposed to oxy-combustion environments

In the integrated oxy-fuel combustion and turbine power generation system, turbine alloys are exposed to high temperature and an atmosphere comprised of steam, CO2 and O2. While surface and internal oxidation of the alloy takes place, the microstructure in the subsurface region also changes due to oxidation that results in the loss of the strengthening precipitates. In an earlier study of the oxidation of Inconel 939 Ni-based superalloy exposed to oxy-fuel combustion environment for up to 1000 hours, a high-temperature-oxidation-induced phase transformation in the sub-surface region was noticed and a two-phase region formed at the expense of strengthening γ' phase. While one of the two phases was identified as the Ni-matrix (γ solid solution, face-center-cubic) phase, the other product phase remained unidentified. In this study, the crystal structure of the unknown phase and its orientation relationship with the parent Ni-matrix phase was investigated through electron diffraction and high-resolution transmission electron microscopy. It was determined that the crystal structure of the unknown phase could be modeled as a ternary derivative of the ordered η-Ni3Ti phase (D024) structure with lattice parameters of a = 0.5092 nm and c = 0.8336 nm, α = 90º, β = 90º and γ = 120º.
Date: April 20, 2013
Creator: Zhu, Jingxi; Wise, Adam; Nuhfer, Thomas; Holcomb, Gordon R.; Jablonski, Paul D.; Sridhar, Seetharaman et al.
Object Type: Article
System: The UNT Digital Library
Bottomonium Studies at BaBar (open access)

Bottomonium Studies at BaBar

None
Date: June 20, 2013
Creator: Ziegler, Veronique
Object Type: Article
System: The UNT Digital Library
R&D Toward a Neutrino Factory and Muon Collider (open access)

R&D Toward a Neutrino Factory and Muon Collider

Significant progress has been made in recent years in R&D towards a neutrino factory and muon collider. The U.S. Muon Accelerator Program (MAP) has been formed recently to expedite the R&D efforts. This paper will review the U.S. MAP R&D programs for a neutrino factory and muon collider. Muon ionization cooling research is the key element of the program. The first muon ionization cooling demonstration experiment, MICE (Muon Ionization Cooling Experiment), is under construction now at RAL (Rutherford Appleton Laboratory) in the UK. The current status of MICE will be described.
Date: March 20, 2011
Creator: Zisman, Michael S.
Object Type: Article
System: The UNT Digital Library
Enhancing trappable antiproton populations through deceleration and frictional cooling (open access)

Enhancing trappable antiproton populations through deceleration and frictional cooling

CERN currently delivers antiprotons for trapping experiments with the Antiproton Decelerator (AD), which slows the antiprotons down to about 5 MeV.This energy is currently too high for direct trapping, and thick foils are used to slow down the beam to energies which can be trapped.To allow further deceleration to $\sim 100 \;\mbox{keV}$, CERN is initiating the construction of ELENA,consisting of a ring which will combine RF deceleration and electron cooling capabilities. We describe a simple frictionalcooling scheme that can serve to provide significantly improved trapping efficiency, either directly from the AD or first usinga standard deceleration mechanism (induction linac or RFQ). This scheme could be implemented in a short time.The device itself is short in length, uses accessible voltages, and at reasonable cost could serve in the interim beforeELENA becomes operational, or possibly in lieu of ELENA for some experiments. Simple theory and simulations provide a preliminary assessment of theconcept and its strengths and limitations, and highlight important areas for experimental studies, in particular to pin down the level of multiplescattering for low-energy antiprotons. We show that the frictional cooling scheme can provide a similar energy spectrum to that of ELENA,but with higher transverse emittances.
Date: March 20, 2012
Creator: Zolotorev, Max; Sessler, Andrew; Penn, Gregory; Wurtele, Jonathan S. & Charman, Andrew E.
Object Type: Article
System: The UNT Digital Library
2012 ATOMIC AND MOLECULAR INTERACTIONS GORDON RESEARCH CONFERENCE AND GORDON RESEARCH SEMINAR, JULY 15-20, 2012 (open access)

2012 ATOMIC AND MOLECULAR INTERACTIONS GORDON RESEARCH CONFERENCE AND GORDON RESEARCH SEMINAR, JULY 15-20, 2012

At the 2012 Atomic and Molecular Interactions Gordon Conference, there will be talks in several broadly defined and partially overlapping areas:  Intramolecular and single-collision reaction dynamics;  Photophysics and photochemistry of excited states;  Clusters, aerosols and solvation;  Interactions at interfaces;  Conformations and folding of large molecules;  Interactions under extreme conditions of temperature and pressure. The theme of the Gordon Research Seminar on Atomic & Molecular Interactions, in keeping with the tradition of the Atomic and Molecular Interactions Gordon Research Conference, is far-reaching and involves fundamental research in the gas and condensed phases along with application of these ideas to practical chemical fields. The oral presentations, which will contain a combination of both experiment and theory, will focus on four broad categories:  Ultrafast Phenomena;  Excited States, Photoelectrons, and Photoions;  Chemical Reaction Dynamics;  Biomolecules and Clusters.
Date: July 20, 2012
Creator: Zwier, Timothy
Object Type: Article
System: The UNT Digital Library
Light-front Holography - A New Approach to Relativistic Hadron Dynamics and Nonperturbative QCD (open access)

Light-front Holography - A New Approach to Relativistic Hadron Dynamics and Nonperturbative QCD

The holographic mapping of gravity in AdS space to QCD, quantized at fixed light-front time, provides a precise relation between the bound-state amplitudes in the fifth dimension of AdS space and the boost-invariant light-front wavefunctions describing the internal structure of hadrons in physical space-time. In particular, the elastic and transition form factors of the pion and the nucleons are well described in this framework. The light-front AdS/QCD holographic approach thus gives a frame-independent first approximation of the color-confining dynamics, spectroscopy, and excitation spectra of relativistic light-quark bound states in QCD. More generally, we show that the valence Fock-state wavefunctions of the eigensolutions of the light-front QCD Hamiltonian satisfy a single-variable relativistic equation of motion, analogous to the nonrelativistic radial Schroedinger equation, with an effective confining potential which systematically incorporates the effects of higher quark and gluon Fock states. The proposed method to compute the effective interaction thus resembles the two-particle-irreducible functional techniques used in quantum field theory.
Date: June 20, 2012
Creator: de Teramond, Guy F. & Brodsky, Stanley J.
Object Type: Article
System: The UNT Digital Library
Hadronic form factor models and spectroscopy within the gauge/gravity correspondence (open access)

Hadronic form factor models and spectroscopy within the gauge/gravity correspondence

We show that the nonperturbative light-front dynamics of relativistic hadronic bound states has a dual semiclassical gravity description on a higher dimensional warped AdS space in the limit of zero quark masses. This mapping of AdS gravity theory to the boundary quantum field theory, quantized at fixed light-front time, allows one to establish a precise relation between holographic wave functions in AdS space and the light-front wavefunctions describing the internal structure of hadrons. The resulting AdS/QCD model gives a remarkably good accounting of the spectrum, elastic and transition form factors of the light-quark hadrons in terms of one parameter, the QCD gap scale. The light-front holographic approach described here thus provides a frame-independent first approximation to the light-front Hamiltonian problem for QCD. This article is based on lectures at the Niccolo Cabeo International School of Hadronic Physics, Ferrara, Italy, May 2011.
Date: March 20, 2012
Creator: de Teramond, Guy F.; U., /Costa Rica & Brodsky, Stanley J.
Object Type: Article
System: The UNT Digital Library
Final Report (open access)

Final Report

The goal of this project was to quantify organic aerosol precursor concentrations in an urban environment and to measure suitable organic photoproduct species that can act as tracers of photochemical processing to identify the occurrence and rate of secondary organic aerosol formation. Field measurements were made as part of the ASR field program Carbonaceous Aerosols and Radiative Effects Study (CARES) in June 2010. What is new in our approach is the measurement for the total concentration of long chain alkanes (>C10) and heavier alkyl substituted aromatics associated with diesel exhaust gas phase organic compound emissions. A method to measure these so called intermediate volatility organic compounds (IVOCs) was developed by modifying a proton transfer reaction mass spectrometer instrument to perform both volatile organic compound (VOC) and IVOC analysis by thermal desorption from a Tenax adsorbent trap (TD-PTR-MS). Lab and field results show that the TD-PTR-MS technique can measure long chain alkanes associated with diesel engine emissions and thus provide a novel means to measure these compounds to better understand the impact of vehicle emissions on secondary organic aerosol formation.
Date: August 20, 2012
Creator: unknown
Object Type: Report
System: The UNT Digital Library