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Electronic Structure and Oxidation State Changes in the Mn (4) Ca Cluster of Photosystem II (open access)

Electronic Structure and Oxidation State Changes in the Mn (4) Ca Cluster of Photosystem II

Oxygen-evolving complex (Mn{sub 4}Ca cluster) of Photosystem II cycles through five intermediate states (S{sub i}-states, i = 0-4) before a molecule of dioxygen is released. During the S-state transitions, electrons are extracted from the OEC, either from Mn or alternatively from a Mn ligand. The oxidation state of Mn is widely accepted as Mn{sub 4}(III{sub 2},IV{sub 2}) and Mn{sub 4}(III,IV{sub 3}) for S{sub 1} and S{sub 2} states, while it is still controversial for the S{sub 0} and S{sub 3} states. We used resonant inelastic X-ray scattering (RIXS) to study the electronic structure of Mn{sub 4}Ca complex in the OEC. The RIXS data yield two-dimensional plots that provide a significant advantage by obtaining both K-edge pre-edge and L-edge-like spectra (metal spin state) simultaneously. We have collected data from PSII samples in the each of the S-states and compared them with data from various inorganic Mn complexes. The spectral changes in the Mn 1s2p{sub 3/2} RIXS spectra between the S-states were compared to those of the oxides of Mn and coordination complexes. The results indicate strong covalency for the electronic configuration in the OEC, and we conclude that the electron is transferred from a strongly delocalized orbital, compared to those in …
Date: August 17, 2012
Creator: Yano, J.; Pushkar, Y.; Messinger, J.; Bergmann, U.; Glatzel, P. & Yachandra, V. K.
System: The UNT Digital Library
Thoughts on polarimetry for 3He beams at RHIC (open access)

Thoughts on polarimetry for 3He beams at RHIC

N/A
Date: September 17, 2012
Creator: Makdisi, Y.
System: The UNT Digital Library
A Compact Ring Design with Tunable Momentum Compaction (open access)

A Compact Ring Design with Tunable Momentum Compaction

A storage ring with tunable momentum compaction has the advantage in achieving different RMS bunch length with similar RF capacity, which is potentially useful for many applications, such as linear collider damping ring and predamping ring where injected beam has a large energy spread and a large transverse emittance. A tunable bunch length also makes the commissioning and fine tuning easier in manipulating the single bunch instabilities. In this paper, a compact ring design based on a supercell is presented, which achieves a tunable momentum compaction while maintaining a large dynamic aperture.
Date: May 17, 2012
Creator: Sun, Y.
System: The UNT Digital Library
Electron Anomalous Magnetic Moment in Basis Light-Front Quantization Approach (open access)

Electron Anomalous Magnetic Moment in Basis Light-Front Quantization Approach

We apply the Basis Light-Front Quantization (BLFQ) approach to the Hamiltonian field theory of Quantum Electrodynamics (QED) in free space. We solve for the mass eigenstates corresponding to an electron interacting with a single photon in light-front gauge. Based on the resulting non-perturbative ground state light-front amplitude we evaluate the electron anomalous magnetic moment. The numerical results from extrapolating to the infinite basis limit reproduce the perturbative Schwinger result with relative deviation less than 1.2%. We report significant improvements over previous works including the development of analytic methods for evaluating the vertex matrix elements of QED.
Date: February 17, 2012
Creator: Zhao, Xingbo; Honkanen, Heli; Maris, Pieter; Vary, James P. & Brodsky, Stanley J.
System: The UNT Digital Library
S-Band Sheet Beam Klystron Research and Development at SLAC (open access)

S-Band Sheet Beam Klystron Research and Development at SLAC

None
Date: December 17, 2012
Creator: Jensen, Aaron; Fazio, Michael V.; Haase, Andrew; Jongewaard, Erik N.; Martin, David W.; Neilson, Jeffrey et al.
System: The UNT Digital Library
Tailoring properties of carbon-nanotube-based foams by ion bombardment (open access)

Tailoring properties of carbon-nanotube-based foams by ion bombardment

None
Date: May 17, 2012
Creator: Charnvanichborikarn, S.; Shin, S. J.; Worsley, M. A. & Kucheyev, S. O.
System: The UNT Digital Library
VEGETATION COVER ANALYSIS OF HAZARDOUS WASTE SITES IN UTAH AND ARIZONA USING HYPERSPECTRAL REMOTE SENSING (open access)

VEGETATION COVER ANALYSIS OF HAZARDOUS WASTE SITES IN UTAH AND ARIZONA USING HYPERSPECTRAL REMOTE SENSING

Remote sensing technology can provide a cost-effective tool for monitoring hazardous waste sites. This study investigated the usability of HyMap airborne hyperspectral remote sensing data (126 bands at 2.3 x 2.3 m spatial resolution) to characterize the vegetation at U.S. Department of Energy uranium processing sites near Monticello, Utah and Monument Valley, Arizona. Grass and shrub species were mixed on an engineered disposal cell cover at the Monticello site while shrub species were dominant in the phytoremediation plantings at the Monument Valley site. The specific objectives of this study were to: (1) estimate leaf-area-index (LAI) of the vegetation using three different methods (i.e., vegetation indices, red-edge positioning (REP), and machine learning regression trees), and (2) map the vegetation cover using machine learning decision trees based on either the scaled reflectance data or mixture tuned matched filtering (MTMF)-derived metrics and vegetation indices. Regression trees resulted in the best calibration performance of LAI estimation (R{sup 2} > 0.80). The use of REPs failed to accurately predict LAI (R{sup 2} < 0.2). The use of the MTMF-derived metrics (matched filter scores and infeasibility) and a range of vegetation indices in decision trees improved the vegetation mapping when compared to the decision tree classification …
Date: January 17, 2012
Creator: Serrato, M.; Jungho, I.; Jensen, J.; Jensen, R.; Gladden, J. & Waugh, J.
System: The UNT Digital Library
A Note on Neutron Capture Correlation Signals, Backgrounds, and Efficiencies (open access)

A Note on Neutron Capture Correlation Signals, Backgrounds, and Efficiencies

None
Date: January 17, 2012
Creator: Bowden, N; Dazeley, S & Sweany, M
System: The UNT Digital Library
Search for Lepton-Number Violating Processes in B+ to h- l+ l+ Decays (open access)

Search for Lepton-Number Violating Processes in B+ to h- l+ l+ Decays

We have searched for the lepton-number violating processes B{sup +} {yields} h{sup -}{ell}{sup +}{ell}{sup +} with h{sup -} = K{sup -}/{pi}{sup -} and {ell}{sup +} = e{sup +}/{mu}{sup +}, using a sample of 471 {+-} 3 million B{bar B} events collected with the BABAR detector at the PEP-II e{sup +}e{sup -} collider at the SLAC National Accelerator Laboratory. We find no evidence for these decays and place 90% confidence level upper limits on their branching fractions B (B{sup +} {yields} {pi}{sup -}e{sup +}e{sup +}) < 2.3 x 10{sup -8}, {Beta}(B{sup +} {yields} K{sup -}e{sup +}e{sup +}) < 3.0 x 10{sup -8}, {Beta}(B{sup +} {yields} {pi}{sup -}{mu}{sup +}{mu}{sup +}) < 10.7 x 10{sup -8}, and {Beta}(B{sup +} {yields} K{sup -}{mu}{sup +}{mu}{sup +}) < 6.7 x 10{sup -8}.
Date: May 17, 2012
Creator: Lees, J.P.
System: The UNT Digital Library
CORROSION ISSUES ASSOCIATED WITH AUSTENITIC STAINLESS STEEL COMPONENTS USED IN NUCLEAR MATERIALS EXTRACTION AND SEPARATION PROCESSES (open access)

CORROSION ISSUES ASSOCIATED WITH AUSTENITIC STAINLESS STEEL COMPONENTS USED IN NUCLEAR MATERIALS EXTRACTION AND SEPARATION PROCESSES

This paper illustrated the magnitude of the systems, structures and components used at the Savannah River Site for nuclear materials extraction and separation processes. Corrosion issues, including stress corrosion cracking, pitting, crevice corrosion and other corrosion induced degradation processes are discussed and corrosion mitigation strategies such as a chloride exclusion program and corrosion release testing are also discussed.
Date: December 17, 2012
Creator: Mickalonis, J.; Louthan, M. & Sindelar, R.
System: The UNT Digital Library
Limits on Large Extra Dimensions Based on Observations of Neutron Stars with the Fermi-LAT (open access)

Limits on Large Extra Dimensions Based on Observations of Neutron Stars with the Fermi-LAT

We present limits for the compactification scale in the theory of Large Extra Dimensions (LED) proposed by Arkani-Hamed, Dimopoulos, and Dvali. We use 11 months of data from the Fermi Large Area Telescope (Fermi-LAT) to set gamma ray flux limits for 6 gamma-ray faint neutron stars (NS). To set limits on LED we use the model of Hannestad and Raffelt (HR) that calculates the Kaluza-Klein (KK) graviton production in supernova cores and the large fraction subsequently gravitationally bound around the resulting NS. The predicted decay of the bound KK gravitons to {gamma}{gamma} should contribute to the flux from NSs. Considering 2 to 7 extra dimensions of the same size in the context of the HR model, we use Monte Carlo techniques to calculate the expected differential flux of gamma-rays arising from these KK gravitons, including the effects of the age of the NS, graviton orbit, and absorption of gamma-rays in the magnetosphere of the NS. We compare our Monte Carlo-based differential flux to the experimental differential flux using maximum likelihood techniques to obtain our limits on LED. Our limits are more restrictive than past EGRET-based optimistic limits that do not include these important corrections. Additionally, our limits are more stringent …
Date: August 17, 2012
Creator: Ajello, M.; Baldini, L.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R. et al.
System: The UNT Digital Library
A New Green's Function for the Wake Potential Calculation of the SLAC S-band Constant Gradient Accelerating Section (open access)

A New Green's Function for the Wake Potential Calculation of the SLAC S-band Constant Gradient Accelerating Section

The behavior of the longitudinal wake fields excited by a very short bunch in the SLAC S-band constant gradient accelerating structures has been studied. Wake potential calculations were performed for a bunch length of 10 microns using the author's code to obtain a numerical solution of Maxwell's equations in the time domain. We have calculated six accelerating sections in the series (60-ft) to find the stationary solution. While analyzing the computational results we have found a new formula for the Green's function. Wake potentials, which are calculated using this Green's function are in amazingly good agreement with numerical results over a wide range of bunch lengths. The Green's function simplifies the wake potential calculations and can be easily incorporated into the tracking codes. This is very useful for beam dynamics studies of the linear accelerators of LCLS and FACET.
Date: February 17, 2012
Creator: Novokhatski, A,
System: The UNT Digital Library
Kirchhoff's Integral Representation and a Cavity Wake Potential (open access)

Kirchhoff's Integral Representation and a Cavity Wake Potential

A method is proposed for the calculation of the short-range wake field potentials of an ultra-relativistic bunch passing near some irregularities in a beam pipe. The method is based on the space-time domain integration of Maxwell's equations using Kirchhoff's formulation. We demonstrate this method on two cases where we obtain the wake potentials for the energy loss of a bunch traversing an iris-collimator in a beam pipe and for a cavity. Likewise, formulas are derived for Green's functions that describe the transverse force action of wake fields. Simple formulas for the total energy loss of a bunch with a Gaussian charge density distribution are derived as well. The derived estimates are compared with computer results and predictions of other models.
Date: February 17, 2012
Creator: Novokhatski, Alexander
System: The UNT Digital Library
Calculation of spin resonance harmonics in an accelerator with snakes (open access)

Calculation of spin resonance harmonics in an accelerator with snakes

N/A
Date: September 17, 2012
Creator: Ptitsyn, V. & Khalil, N.
System: The UNT Digital Library
Single Phase Melt Processed Powellite (Ba,Ca) MoO{sub 4} For The Immobilization Of Mo-Rich Nuclear Waste (open access)

Single Phase Melt Processed Powellite (Ba,Ca) MoO{sub 4} For The Immobilization Of Mo-Rich Nuclear Waste

Crystalline and glass composite materials are currently being investigated for the immobilization of combined High Level Waste (HLW) streams resulting from potential commercial fuel reprocessing scenarios. Several of these potential waste streams contain elevated levels of transition metal elements such as molybdenum (Mo). Molybdenum has limited solubility in typical silicate glasses used for nuclear waste immobilization. Under certain chemical and controlled cooling conditions, a powellite (Ba,Ca)MoO{sub 4} crystalline structure can be formed by reaction with alkaline earth elements. In this study, single phase BaMoO{sub 4} and CaMoO{sub 4} were formed from carbonate and oxide precursors demonstrating the viability of Mo incorporation into glass, crystalline or glass composite materials by a melt and crystallization process. X-ray diffraction, photoluminescence, and Raman spectroscopy indicated a long range ordered crystalline structure. In-situ electron irradiation studies indicated that both CaMoO{sub 4} and BaMoO{sub 4} powellite phases exhibit radiation stability up to 1000 years at anticipated doses with a crystalline to amorphous transition observed after 1 X 10{sup 13} Gy. Aqueous durability determined from product consistency tests (PCT) showed low normalized release rates for Ba, Ca, and Mo (<0.05 g/m{sup 2}).
Date: September 17, 2012
Creator: Brinkman, Kyle; Marra, James; Fox, Kevin; Reppert, Jason; Crum, Jarrod & Tang, Ming
System: The UNT Digital Library
Fermi-LAT Observation of Supernova Remnant S147 (open access)

Fermi-LAT Observation of Supernova Remnant S147

We present an analysis of gamma-ray data obtained with the Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope in the region around SNR S147 (G180.0-1.7). A spatially extended gamma-ray source detected in an energy range of 0.2-10 GeV is found to coincide with SNR S147. We confirm its spatial extension at >5{sigma} confidence level. The gamma-ray flux is (3.8 {+-} 0.6) x 10{sup -8} photons cm{sup -2} s{sup -1}, corresponding to a luminosity of 1.3 x 10{sup 34} (d/1.3 kpc){sup 2} erg s{sup -1} in this energy range. The gamma-ray emission exhibits a possible spatial correlation with prominent H{alpha} filaments of S147. There is no indication that the gamma-ray emission comes from the associated pulsar PSR J0538+2817. The gamma-ray spectrum integrated over the remnant is likely dominated by the decay of neutral {pi} mesons produced through the proton-proton collisions in the filaments. Reacceleration of pre-existing CRs and subsequent adiabatic compression in the filaments is sufficient to provide the required energy density of high-energy protons.
Date: August 17, 2012
Creator: Katsuta, J.; Uchiyama, Y.; Tanaka, T.; Tajima, H.; Bechtol, K.; Funk, S. et al.
System: The UNT Digital Library
Evaluation of Historical Beryllium Abundance in Soils, Airborne Particulates and Facilities at Lawrence Livermore National Laboratory (open access)

Evaluation of Historical Beryllium Abundance in Soils, Airborne Particulates and Facilities at Lawrence Livermore National Laboratory

None
Date: April 17, 2012
Creator: Sutton, M.; Bibby, R. K.; Eppich, G. R.; Lee, S.; Lindvall, R. E.; Wilson, K. et al.
System: The UNT Digital Library
Passive Imaging of Warhead-Like Configurations Using Cosmic-Ray Muons (open access)

Passive Imaging of Warhead-Like Configurations Using Cosmic-Ray Muons

Cosmic-Muon-Based Interrogation has untapped potential for national security. This presentation describes muons-based passive interrogation techniques.
Date: July 17, 2012
Creator: Schwellenbach, D.
System: The UNT Digital Library
Oxy-Combustion Environment Characterization: Fire- and Steam-Side Corrosion in Advanced Combustion (open access)

Oxy-Combustion Environment Characterization: Fire- and Steam-Side Corrosion in Advanced Combustion

None
Date: April 17, 2012
Creator: Holcomb, G. R.; Tylczak, J.; Meier, G. H.; Lutz, B. S.; Yanar, N. M.; Pettit, F. S. et al.
System: The UNT Digital Library
Integrating The Non-Electrical Worker Into The Electrical Safety Program (open access)

Integrating The Non-Electrical Worker Into The Electrical Safety Program

The intent of this paper is to demonstrate an electrical safety program that incorporates all workers into the program, not just the electrical workers. It is largely in response to a paper presented at the 2012 ESW by Lanny Floyd entitled "Facilitating Application of Electrical Safety Best Practices to "Other" Workers" which requested all attendees to review their electrical safety program to assure that non-electrical workers were protected as well as electrical workers. The referenced paper indicated that roughly 50% of electrical incidents involve workers whose primary function is not electrical in nature. It also encouraged all to "address electrical safety for all workers and not just workers whose job responsibilities involve working on or near energized electrical circuits." In this paper, a program which includes specific briefings to non-electrical workers as well as to workers who may need to perform their normal activities in proximity to energized electrical conductors is presented. The program uses a targeted approach to specific areas such as welding, excavating, rigging, chart reading, switching, cord and plug equipment and several other general areas to point out hazards that may exist and how to avoid them. NFPA 70E-2004 was incorporated into the program several years ago …
Date: August 17, 2012
Creator: Mills, T. David & McAlhaney, John H.
System: The UNT Digital Library
Fermi-LAT and Suzaku Observations of the Radio Galaxy Centaurus B (open access)

Fermi-LAT and Suzaku Observations of the Radio Galaxy Centaurus B

CentaurusB is a nearby radio galaxy positioned in the Southern hemisphere close to the Galactic plane. Here we present a detailed analysis of about 43 months accumulation of Fermi-LAT data and of newly acquired Suzaku X-ray data for Centaurus B. The source is detected at GeV photon energies, although we cannot completely exclude the possibility that it is an artifact due to incorrect modeling of the bright Galactic diffuse emission in the region. The LAT image provides a weak hint of a spatial extension of the {gamma} rays along the radio lobes, which is consistent with the lack of source variability in the GeV range. We note that the extension cannot be established statistically due to the low number of the photons. Surprisingly, we do not detect any diffuse emission of the lobes at X-ray frequencies, with the provided upper limit only marginally consistent with the previously claimed ASCA flux. The broad-band modeling shows that the observed {gamma}-ray flux of the source may be produced within the lobes, if the diffuse non-thermal X-ray emission component is not significantly below the derived Suzaku upper limit. This association would imply that efficient in-situ acceleration of the ultrarelativistic particles is occurring and that …
Date: August 17, 2012
Creator: Katsuta, Junichiro; Tanaka, Y. T.; Stawarz, L.; O'Sullivan, S. P.; Cheung, C. C.; Kataoka, J. et al.
System: The UNT Digital Library
Improvements to High-Speed Monitoring of Events in Extreme Environments Using Fiber-optic Bragg Sensors (open access)

Improvements to High-Speed Monitoring of Events in Extreme Environments Using Fiber-optic Bragg Sensors

None
Date: February 17, 2012
Creator: Benterou, J J & Udd, E
System: The UNT Digital Library
Acceleration and transportation of multiple ion species at EBIS-based preinjector (open access)

Acceleration and transportation of multiple ion species at EBIS-based preinjector

N/A
Date: September 17, 2012
Creator: Raparia, D.
System: The UNT Digital Library
New Insights into the EMC Effect (open access)

New Insights into the EMC Effect

Deep-inelastic scattering cross section ratios plotted as a function of the Bjorken scaling variable, xB, show an unexpected structure indicating that partonic structure in nuclei is different than in free nucleons. This phenomenon is commonly referred to as the EMC effect. Recent Jefferson Lab experimental data showed that the slope of the EMC effect in the 0.3 < xB > 0.7 region scales as the local nuclear density rather than the average nuclear density. This result lead to the comparison of xB>1 short-range correlation plateaus, also a local density effect, to the magnitude of the EMC effect slopes and a clear linear relation was found. In this talk, I will discuss the EMC effect and the short-range correlation plateaus and what this phenomenological relationship between the two implies.
Date: August 17, 2012
Creator: Higinbotham, Douglas
System: The UNT Digital Library