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Applying Science and Technology to Combat WMD Terrorism (open access)

Applying Science and Technology to Combat WMD Terrorism

Lawrence Livermore National Laboratory (LLNL) is developing and fielding advanced strategies that dramatically improve the nation's capabilities to prevent, prepare for, detect, and respond to terrorist use of chemical, biological, radiological, nuclear, and explosive (CBRNE) weapons. The science, technology, and integrated systems we provide are informed by and developed with key partners and end users. LLNL's long-standing role as one of the two principle U.S. nuclear weapons design laboratories has led to significant resident expertise for health effects of exposure to radiation, radiation detection technologies, characterization of radioisotopes, and assessment and response capabilities for terrorist nuclear weapons use. This paper provides brief overviews of a number of technologies developed at LLNL that are being used to address national security needs to confront the growing threats of CBRNE terrorism.
Date: May 4, 2006
Creator: Wuest, C. R.; Werne, R. W.; Colston, B. W. & Hartmann-Siantar, C. L.
System: The UNT Digital Library
Behavior of Uranium (VI) during HEDPA Leaching for Aluminum Dissolution in Tank Waste Sludges (open access)

Behavior of Uranium (VI) during HEDPA Leaching for Aluminum Dissolution in Tank Waste Sludges

Batch adsorption/dissolution experiments were conducted toexamine the interactions between 233U(VI) and a synthetic aluminumoxyhydroxide (boehmite, g-AlOOH) in 1.0M NaCl suspensions containing1-hydroxyethane-1,1-diphosphonic acid (HEDPA). In the pH range 4 to 9,complexation of Al(III) by HEDPA significantly enhanced dissolution ofboehmite. This phenomenon was especially pronounced in the neutral pHregion where the solubility of aluminum, in the absence of complexants,is limited by the formation of sparsely soluble aluminum hydroxides. Athigh pH levels, dissolution of synthetic boehmite was inhibited by HEDPA,likely due to sorption of Al(III)/HEDPA complexes. Addition of HEDPA toequilibrated U(VI)-synthetic boehmite suspensions yielded an increase inthe aqueous phase uranium concentration. The concentration of uraniumcontinually increased over 59 days. Partitioning of uranium between thesolid and aqueous phase was found to correlate well with HEDPApartitioning.
Date: January 4, 2006
Creator: Powell, Brian A.; Rao, Linfeng; Nash, Kenneth L. & Martin, Leigh
System: The UNT Digital Library
Black Hole Entropy and Fourie-Mukai Transform (open access)

Black Hole Entropy and Fourie-Mukai Transform

We propose a microscopic CFT description of magnetically charged black holes in IIA compactifications on elliptic fibrations based on the Fourier-Mukai transform. The physical derivation of this model involves a chain of string duality transformations including the 4D/5D black hole correspondence. We compute the asymptotic behavior of the microstate degeneracy in a certain limit of large charges and show that it agrees with the macroscopic entropy formula. An interesting aspect of this setup is that the attractor points are situated deep in a hybrid phase of the quantum Kaehler moduli space.
Date: December 4, 2006
Creator: Bena, Iosif; /Saclay; Diaconescu, Duiliu-Emanuel; /Rutgers U., Piscataway; Florea, Bogdan & /Stanford U., Phys. Dept. /SLAC
System: The UNT Digital Library
Booming Plutons: Source of microearthquakes in South Carolina (open access)

Booming Plutons: Source of microearthquakes in South Carolina

None
Date: January 4, 2006
Creator: Stevenson, Donald
System: The UNT Digital Library
Brief History of Ffag Accelerators. (open access)

Brief History of Ffag Accelerators.

Colleagues of mine have asked me few times why we have today so much interest in Fixed-Field Alternating-Gradient (FFAG) accelerators when these were invented a long time ago, and have always been ignored since then. I try here to give a reply with a short history of FFAG accelerators, at least as I know it. I take also the opportunity to clarify few definitions.
Date: December 4, 2006
Creator: Ruggiero, A.
System: The UNT Digital Library
A Cartesian embedded boundary method for hyperbolic conservation laws (open access)

A Cartesian embedded boundary method for hyperbolic conservation laws

The authors develop an embedded boundary finite difference technique for solving the compressible two- or three-dimensional Euler equations in complex geometries on a Cartesian grid. The method is second order accurate with an explicit time step determined by the grid size away from the boundary. Slope limiters are used on the embedded boundary to avoid non-physical oscillations near shock waves. They show computed examples of supersonic flow past a cylinder and compare with results computed on a body fitted grid. Furthermore, they discuss the implementation of the method for thin geometries, and show computed examples of transonic flow past an airfoil.
Date: December 4, 2006
Creator: Sjogreen, B & Petersson, N A
System: The UNT Digital Library
Comments on the paper 'A novel 3D wavelet-based filter forvisualizing features in noisy biological data', by Moss et al. (open access)

Comments on the paper 'A novel 3D wavelet-based filter forvisualizing features in noisy biological data', by Moss et al.

Moss et al.(2005) describe, in a recent paper, a filter thatthey use to detect lines. We noticed that the wavelet on which thisfilter is based is a difference of uniform filters. This filter is anapproximation to the second derivative operator, which is commonlyimplemented as the Laplace of Gaussian (or Marr-Hildreth) operator (Marr&Hildreth, 1980; Jahne, 2002), Figure 1. We have compared Moss'filter with 1) the Laplace of Gaussian operator, 2) an approximation ofthe Laplace of Gaussian using uniform filters, and 3) a few common noisereduction filters. The Laplace-like operators detect lines by suppressingimage features both larger and smaller than the filter size. The noisereduction filters only suppress image features smaller than the filtersize. By estimating the signal to noise ratio (SNR) and mean squaredifference (MSD) of the filtered results, we found that the filterproposed by Moss et al. does not outperform the Laplace of Gaussianoperator. We also found that for images with extreme noise content, linedetection filters perform better than the noise reduction filters whentrying to enhance line structures. In less extreme cases of noise, thestandard noise reduction filters perform significantly better than boththe Laplace of Gaussian and Moss' filter.
Date: February 4, 2006
Creator: Luengo Hendriks, Cris L. & Knowles, David W.
System: The UNT Digital Library
Complexation of actinides with derivatives of oxydiaceticacid (open access)

Complexation of actinides with derivatives of oxydiaceticacid

Complexation of Np(V), U(VI) and Nd(III) with dimethyl-3-oxa-glutaramic acid (DMOGA) and tetramethyl-3-oxa-glutaramide (TMOGA) was studied in comparison with the complexation with oxydiacetic acid (ODA). Stability constants and enthalpy of complexation were determined by potentiometry, spectrophotometry and calorimetry. Thermodynamic parameters, in conjunction with structural information of solid compounds, indicate that DMOGA and TMOGA form tridentate complexes with the ether-oxygen participating in bonding with actinide/lanthanide ions. The trends in the stability constants, enthalpy and entropy of complexation are discussed in terms of the difference in the hydration of the amide groups and carboxylate groups and the difference in the charge density of the metal ions.
Date: January 4, 2006
Creator: Rao, Linfeng & Tian, Guoxin
System: The UNT Digital Library
Coordination of 1,4-Diazabutadiene Ligands to Decamethylytterbocene: Additional Examples of Spin Coupling in Ytterbocene Complexes (open access)

Coordination of 1,4-Diazabutadiene Ligands to Decamethylytterbocene: Additional Examples of Spin Coupling in Ytterbocene Complexes

The paramagnetic 1:1 coordination complexes of (C5Me5)2Yb with a series of diazabutadiene ligands, RN=C(R')C(R')=NR, where R= CMe3, CHMe2, adamantyl, p-tolyl, p-anisyl, and mesityl when R'=H, and R= p-anisyl when R'= Me, have been prepared. The complexes are paramagnetic, but their magnetic moments are less than expected for the two uncoupled spin carriers, (C5Me5)2Yb(III, 4f13) and the diazabutadiene radical anions (S=1/2), which implies exchange coupling between the spins. The variable temperature 1H NMR spectra show that rotation about the R-N bond is hindered and these barriers are estimated. The barriers are largely determined by steric effects but electronic effects are not unimportant.
Date: November 4, 2006
Creator: Andersen, Richard; Walter, Marc D.; Berg, David J. & Andersen, Richard A.
System: The UNT Digital Library
DEVELOPING AN OPTIMIZED PROCESS STRATEGY FOR ACID CLEANING OF THE SAVANNAH RIVERSITE HLW TANKS (open access)

DEVELOPING AN OPTIMIZED PROCESS STRATEGY FOR ACID CLEANING OF THE SAVANNAH RIVERSITE HLW TANKS

At the Savannah River Site (SRS), there remains approximately 35 million gallons of High Level Waste (HLW) that was mostly created from Purex and SRS H-Area Modified (HM) nuclear fuel cycles. The waste is contained in approximately forty-nine tanks fabricated from commercially available carbon steel. In order to minimize general corrosion, the waste is maintained as very-alkaline solution. The very-alkaline chemistry has caused hydrated metal oxides to precipitate and form a sludge heel. Over the years, the sludge waste has aged, with some forming a hardened crust. To aid in the removal of the sludge heels from select tanks for closure the use of oxalic acid to dissolve the sludge is being investigated. Developing an optimized process strategy based on laboratory analyses would be prohibitively costly. This research, therefore, demonstrates that a chemical equilibrium based software program can be used to develop an optimized process strategy for oxalic acid cleaning of the HLW tanks based on estimating resultant chemistries, minimizing resultant oxalates sent to the evaporator, and minimizing resultant solids sent to the Defense Waste Processing Facility (DWPF).
Date: December 4, 2006
Creator: Ketusky, E
System: The UNT Digital Library
Distinguishing Monosaccharide Stereo- and Structural Isomers with ToF-SIMS and Multivariate Statistical Analysis (open access)

Distinguishing Monosaccharide Stereo- and Structural Isomers with ToF-SIMS and Multivariate Statistical Analysis

Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) is utilized to examine the mass spectra and fragmentation patterns of seven isomeric monosaccharides. Multivariate statistical analysis techniques, including principal component analysis (PCA), allow discrimination of the extremely similar mass spectra of stereoisomers. Furthermore, PCA identifies those fragment peaks which vary significantly between spectra. Heavy isotope studies confirm that these peaks are indeed sugar fragments, allow identification of the fragments, and provide clues to the fragmentation pathways. Excellent reproducibility is shown by multiple experiments performed over time and on separate samples. This study demonstrates the combined selectivity and discrimination power of ToF-SIMS and PCA, and suggests new applications of the technique including differentiation of subtle chemical changes in biological samples that may provide insights into cellular processes, disease progress, and disease diagnosis.
Date: May 4, 2006
Creator: Berman, E. F.; Kulp, K. S.; Knize, M. G.; Wu, L.; Nelson, E. J.; Nelson, D. O. et al.
System: The UNT Digital Library
DOPING AND BOND LENGTH CONTRIBUTIONS TO Mn K-EDGE SHIFT IN La1-xSrxMnO3 AND THEIR CORRELATION WITH ELECTRICAL TRANSPORT BEHAVIOUR. (open access)

DOPING AND BOND LENGTH CONTRIBUTIONS TO Mn K-EDGE SHIFT IN La1-xSrxMnO3 AND THEIR CORRELATION WITH ELECTRICAL TRANSPORT BEHAVIOUR.

The experimental Mn K-edge x-ray absorption spectra of La{sub 1-x}Sr{sub x}MnO{sub 3}, x = 0 - 0.7 are compared with the band structure calculations using spin polarized density functional theory. It is explicitly shown that there is a correspondence between the inflection point on the absorption edge and the center of gravity of the unoccupied Mn 4p-band. This correspondence has been used to separate the doping and size contributions to edge shift due to variation in number of electrons in valence band and Mn-O bond lengths, respectively when Sr is doped into LaMnO{sub 3}. Such separation is helpful to find the localization behavior of charge carriers and to understand the observed transport properties and type of charge carrier participating in the conduction process in these compounds.
Date: December 4, 2006
Creator: Pandey, S. K.; Khalid, S.; Bindu, R.; Kumar, A. & Pimpale, A. V.
System: The UNT Digital Library
Effect of Substrate Surface Defects and Te Dopant Concentration on Crystalline Quality and Electrical Characteristics of AlGaAsSb Epitaxial Layers (open access)

Effect of Substrate Surface Defects and Te Dopant Concentration on Crystalline Quality and Electrical Characteristics of AlGaAsSb Epitaxial Layers

The influence of GaSb substrate surface defects such as native oxides on the crystalline quality of epitaxial layers was investigated using transmission electron microscopy (TEM). Cross sectional TEM imaging showed that there are discrete defects at the GaSb-substrate/epilayer interface. Secondary ion mass spectroscopy (SIMS) results revealed high oxygen concentration at the interface, indicating that the defects are likely oxides and presumed to be native oxides since other impurities were not detected. High resolution TEM micrographs showed that the subsequent growth of the epilayer continues beyond the defects without any additional defect generation or propagation. Tellurium doped AlGaAsSb epitaxial layers were grown lattice-matched on GaSb substrates and lattice-mismatched on semi-insulating GaAs substrates by organometallic vapor phase epitaxy. Secondary ion mass spectroscopy and Hall data showed that the ratio of carrier concentration to Te concentration decreases significantly when the carrier concentration increases from 2.5 x 10{sup 17} cm{sup -3} to 6.5 x 10{sup 17} cm{sup -3}. TEM imaging showed that the material with heavily doped Te generates a high density (about 10{sup 8} cm{sup 2}) of planar defects (stacking fault) located on (111) planes. Most of the Te-related defects originate at the GaSb buffer layer/AlGaAsSb epilayer interface. In addition, discrete precipitates were …
Date: January 4, 2006
Creator: Ehsani, H; Lewis, N; Nichols, G; Danielson, L; Dashiell, M; Shellenbarger, Z et al.
System: The UNT Digital Library
Effects of Temporal Wind Patterns on the Value of Wind-GeneratedElectricity at Different Sites in California and the Northwest (open access)

Effects of Temporal Wind Patterns on the Value of Wind-GeneratedElectricity at Different Sites in California and the Northwest

Wind power production varies on a diurnal and seasonal basis. In this paper, we use wind speed data from three different sources to assess the effects of wind timing on the value of electric power from potential wind farm locations in California and the Northwestern United States. By ''value'', we refer to either the contribution of wind power to meeting the electric system's peak loads, or the financial value of wind power in electricity markets. Sites for wind power projects are often screened or compared based on the annual average power production that would be expected from wind turbines at each site (Baban and Parry 2001; Brower et al. 2004; Jangamshetti and Rau 2001; Nielsen et al. 2002; Roy 2002; Schwartz 1999). However, at many locations, variations in wind speeds during the day and year are correlated with variations in the electric power system's load and wholesale market prices (Burton et al. 2001; Carlin 1983; Kennedy and Rogers 2003; Man Bae and Devine 1978; Sezgen et al. 1998); this correlation may raise or lower the value of wind power generated at each location. A number of previous reports address this issue somewhat indirectly by studying the contribution of individual wind …
Date: August 4, 2006
Creator: Fripp, Matthias & Wiser, Ryan
System: The UNT Digital Library
Environmental Cracking of Corrosion Resistant Alloys in the Chemical Process Industry - A Review (open access)

Environmental Cracking of Corrosion Resistant Alloys in the Chemical Process Industry - A Review

A large variety of corrosion resistant alloys are used regularly in the chemical process industry (CPI). The most common family of alloys include the iron (Fe)-based stainless steels, nickel (Ni) alloys and titanium (Ti) alloys. There also other corrosion resistant alloys but their family of alloys is not as large as for the three groups mentioned above. All ranges of corrosive environments can be found in the CPI, from caustic solutions to hot acidic environments, from highly reducing to highly oxidizing. Stainless steels are ubiquitous since numerous types of stainless steels exist, each type tailored for specific applications. In general, stainless steels suffer stress corrosion cracking (SCC) in hot chloride environments while high Ni alloys are practically immune to this type of attack. High nickel alloys are also resistant to caustic cracking. Ti alloys find application in highly oxidizing solutions. Solutions containing fluoride ions, especially acid, seem to be aggressive to almost all corrosion resistant alloys.
Date: December 4, 2006
Creator: Rebak, R B
System: The UNT Digital Library
Gauge - Mediated Supersymmetry Breaking in String Compactifications (open access)

Gauge - Mediated Supersymmetry Breaking in String Compactifications

We provide string theory examples where a toy model of a SUSY GUT or the MSSM is embedded in a compactification along with a gauge sector which dynamically breaks supersymmetry. We argue that by changing microscopic details of the model (such as precise choices of flux), one can arrange for the dominant mediation mechanism transmitting SUSY breaking to the Standard Model to be either gravity mediation or gauge mediation. Systematic improvement of such examples may lead to top-down models incorporating a solution to the SUSY flavor problem.
Date: January 4, 2006
Creator: Diaconescu, Duiliu-Emanuel; /Rutgers U., Piscataway; Florea, Bogdan; Kachru, Shamit; Svrcek, Peter & /Stanford U., Phys. Dept. /SLAC
System: The UNT Digital Library
GeV electron beams from a cm-scale accelerator (open access)

GeV electron beams from a cm-scale accelerator

GeV electron accelerators are essential to synchrotron radiation facilities and free electron lasers, and as modules for high-energy particle physics. Radio frequency based accelerators are limited to relatively low accelerating fields (10-50 MV/m) and hence require tens to hundreds of meters to reach the multi-GeV beam energies needed to drive radiation sources, and many kilometers to generate particle energies of interest to the frontiers of high-energy physics.Laser wakefield accelerators (LWFA) in which particles are accelerated by the field of a plasma wave driven by an intense laser pulse produce electric fields several orders of magnitude stronger (10-100 GV/m) and so offer the potential of very compact devices. However, until now it has not been possible to maintain the required laser intensity, and hence acceleration, over the several centimeters needed to reach GeV energies.For this reason laser-driven accelerators have to date been limited to the 100 MeV scale. Contrary to predictions that PW-class lasers would be needed to reach GeV energies, here we demonstrate production of a high-quality electron beam with 1 GeV energy by channeling a 40 TW peak power laser pulse in a 3.3 cm long gas-filled capillary discharge waveguide. We anticipate that laser-plasma accelerators based on capillary discharge …
Date: May 4, 2006
Creator: Leemans, W. P.; Nagler, B.; Gonsalves, A. J.; Toth, C.; Nakamura, K.; Geddes, C. G. R. et al.
System: The UNT Digital Library
The Influence of Composition upon Surface Degradation and Stress Corrosion Cracking of the Ni-Cr-Mo Alloys in Wet Hydrofluoric Acid (open access)

The Influence of Composition upon Surface Degradation and Stress Corrosion Cracking of the Ni-Cr-Mo Alloys in Wet Hydrofluoric Acid

At concentrations below 60%, wet hydrofluoric acid (HF) is extremely corrosive to steels, stainless steels and reactive metals, such as titanium, zirconium, and tantalum. In fact, only a few metallic materials will withstand wet HF at temperatures above ambient. Among these are the nickel-copper (Ni-Cu) and nickel-chromium-molybdenum (Ni-Cr-Mo) alloys. Previous work has shown that, even with these materials, there are complicating factors. For example, under certain conditions, internal attack and stress corrosion cracking (SCC) are possible with the Ni-Cr-Mo alloys, and the Ni-Cu materials can suffer intergranular attack when exposed to wet HF vapors. The purpose of this work was to study further the response of the Ni-Cr-Mo alloys to HF, in particular their external corrosion rates, susceptibility to internal attack and susceptibility to HF-induced SCC, as a function of alloy composition. As a side experiment, one of the alloys was tested in two microstructural conditions, i.e. solution annealed (the usual condition for materials of this type) and long-range ordered (this being a means of strengthening the alloy in question). The study of external corrosion rates over wide ranges of concentration and temperature revealed a strong beneficial influence of molybdenum content. However, tungsten, which is used as a partial replacement …
Date: December 4, 2006
Creator: Crook, P; Meck, N S & Rebak, R B
System: The UNT Digital Library
Large melting point hysteresis of Ge nanocrystals embedded inSiO2 (open access)

Large melting point hysteresis of Ge nanocrystals embedded inSiO2

The melting behavior of Ge nanocrystals embedded within SiO{sub 2} is evaluated using in situ transmission electron microscopy. The observed melting point hysteresis is large ({+-} 17%) and nearly symmetric about the bulk melting point. This hysteresis is modeled successfully using classical nucleation theory without the need to invoke epitaxy.
Date: May 4, 2006
Creator: Xu, Q.; Sharp, I. D.; Yuan, C. W.; Yi, D. O.; Liao, C. Y.; Glaeser, A. M. et al.
System: The UNT Digital Library
LSST Detector Module and Raft Assembly Metrology Concepts (open access)

LSST Detector Module and Raft Assembly Metrology Concepts

None
Date: May 4, 2006
Creator: Takacs, P. Z.; O'Connor, P.; Radeka, V.; Mahler, G.; Frank. J. & Geary, J.
System: The UNT Digital Library
Molecular cytogenetic characterization of a human thyroid cancercell line (open access)

Molecular cytogenetic characterization of a human thyroid cancercell line

The incidence of papillary thyroid carcinoma (PTC) increases significantly after exposure of the head and neck region to ionizing radiation, yet we know neither the steps involved in malignant transformation of thyroid epithelium nor the specific carcinogenic mode of action of radiation. Such increased tumor frequency became most evident in children after the 1986 nuclear accident in Chernobyl, Ukraine. In the twelve years following the accident, the average incidence of childhood PTCs (chPTC) increased over one hundred-fold compared to the rate of about 1 tumor incidence per 10{sup 6} children per year prior to 1986. To study the etiology of radiation-induced thyroid cancer, we formed an international consortium to investigate chromosomal changes and altered gene expression in cases of post-Chernobyl chPTC. Our approach is based on karyotyping of primary cultures established from chPTC specimens, establishment of cell lines and studies of genotype-phenotype relationships through high resolution chromosome analysis, DNA/cDNA micro-array studies, and mouse xenografts that test for tumorigenicity. Here, we report the application of fluorescence in situ hybridization (FISH)-based techniques for the molecular cytogenetic characterization of a highly tumorigenic chPTC cell line, S48TK, and its subclones. Using chromosome 9 rearrangements as an example, we describe a new approach termed ''BAC-FISH'' …
Date: January 4, 2006
Creator: Weier, Heinz-Ulrich G.; Tuton, Tiffany B.; Ito, Yuko; Chu, LisaW.; Lu, Chung-Mei; Baumgartner, Adolf et al.
System: The UNT Digital Library
Multipole (E1, M1, E2, M2, E3, M3) transition wavelengths and rates between 3l-15l' excited and ground states in nickel-like ions (open access)

Multipole (E1, M1, E2, M2, E3, M3) transition wavelengths and rates between 3l-15l' excited and ground states in nickel-like ions

A relativistic many-body method is developed to calculate energy and transition rates for multipole transitions in many-electron ions. This method is based on relativistic many-body perturbation theory (RMBPT), agrees with MCDF calculations in lowest-order, includes all second-order correlation corrections and includes corrections from negative energy states. Reduced matrix elements, oscillator strengths, and transition rates are calculated for electric-multipole (dipole (E1), quadrupole (E2), and octupole (E3)) and magnetic-multipole (dipole (M1), quadrupole (M2), and octupole (M3)) transitions between 3l{sup -1}5l{prime} excited and ground states in Ni-like ions with nuclear charges ranging from Z = 30 to 100. The calculations start from a 1s{sup 2}s{sup 2}2p{sup 6}3s{sup 2}3p{sup 6}3d{sup 10} Dirac-Fock potential. First-order perturbation theory is used to obtain intermediate-coupling coefficients, and second-order RMBPT is used to determine the matrix elements. A detailed discussion of the various contributions to the dipole matrix elements and energy levels is given for nickel-like tungsten (Z = 74). The contributions from negative-energy states are included in the second order E1, M1, E2, M2, E3 and M3 matrix elements. The resulting transition energies and transition rates are compared with experimental values and with results from other recent calculations. These atomic data are important in modeling of M-shell radiation …
Date: May 4, 2006
Creator: Safronova, U I; Safronova, A S & Beiersdorfer, P
System: The UNT Digital Library
Noise Studies of Externally Dispersed Interferometry for Doppler Velocimetry (open access)

Noise Studies of Externally Dispersed Interferometry for Doppler Velocimetry

Externally Dispersed Interferometry (EDI) is the series combination of a fixed-delay field-widened Michelson interferometer with a dispersive spectrograph. This combination boosts the spectrograph performance for both Doppler velocimetry and high resolution spectroscopy. The interferometer creates a periodic comb that multiplies against the input spectrum to create moire fringes, which are recorded in combination with the regular spectrum. Both regular and high-frequency spectral components can be recovered from the data--the moire component carries additional information that increases the signal to noise for velocimetry and spectroscopy. Here we present simulations and theoretical studies of the photon limited Doppler velocity noise in an EDI. We used a model spectrum of a 1600K temperature star. For several rotational blurring velocities 0, 7.5, 15 and 25 km/s we calculated the dimensionless Doppler quality index (Q) versus wavenumber v. This is the normalized RMS of the derivative of the spectrum and is proportional to the photon-limited Doppler signal to noise ratio.
Date: May 4, 2006
Creator: Erskine, D. J.; Edelstein, J.; Lloyd, J. & Muirhead, P.
System: The UNT Digital Library
De Novo Ultrascale Atomistic Simulations On High-End Parallel Supercomputers (open access)

De Novo Ultrascale Atomistic Simulations On High-End Parallel Supercomputers

We present a de novo hierarchical simulation framework for first-principles based predictive simulations of materials and their validation on high-end parallel supercomputers and geographically distributed clusters. In this framework, high-end chemically reactive and non-reactive molecular dynamics (MD) simulations explore a wide solution space to discover microscopic mechanisms that govern macroscopic material properties, into which highly accurate quantum mechanical (QM) simulations are embedded to validate the discovered mechanisms and quantify the uncertainty of the solution. The framework includes an embedded divide-and-conquer (EDC) algorithmic framework for the design of linear-scaling simulation algorithms with minimal bandwidth complexity and tight error control. The EDC framework also enables adaptive hierarchical simulation with automated model transitioning assisted by graph-based event tracking. A tunable hierarchical cellular decomposition parallelization framework then maps the O(N) EDC algorithms onto Petaflops computers, while achieving performance tunability through a hierarchy of parameterized cell data/computation structures, as well as its implementation using hybrid Grid remote procedure call + message passing + threads programming. High-end computing platforms such as IBM BlueGene/L, SGI Altix 3000 and the NSF TeraGrid provide an excellent test grounds for the framework. On these platforms, we have achieved unprecedented scales of quantum-mechanically accurate and well validated, chemically reactive atomistic simulations--1.06 …
Date: September 4, 2006
Creator: Nakano, A.; Kalia, R. K.; Nomura, K.; Sharma, A.; Vashishta, P.; Shimojo, F. et al.
System: The UNT Digital Library