108 Matching Results

Search Results

Advanced search parameters have been applied.

PLUTONIUM FINISHING PLANT (PFP) GENERALIZED GEOMETRY HOLDUP CALCULATIONS & TOTAL MEASUREMENT UNCERTAINTY

Description: A collimated portable gamma-ray detector will be used to quantify the plutonium content of items that can be approximated as a point, line, or area geometry with respect to the detector. These items can include ducts, piping, glove boxes, isolated equipment inside of gloveboxes, and HEPA filters. The Generalized Geometry Holdup (GGH) model is used for the reduction of counting data. This document specifies the calculations to reduce counting data into contained plutonium and the associated total measurement uncertainty.
Date: February 1, 2005
Creator: BD, KEELE
Partner: UNT Libraries Government Documents Department

Lensless x-ray imaging in reflection geometry

Description: Lensless X-ray imaging techniques such as coherent diffraction imaging and ptychography, and Fourier transform holography can provide time-resolved, diffraction-limited images. Nearly all examples of these techniques have focused on transmission geometry, restricting the samples and reciprocal spaces that can be investigated. We report a lensless X-ray technique developed for imaging in Bragg and small-angle scattering geometries, which may also find application in transmission geometries. We demonstrate this by imaging a nanofabricated pseudorandom binary structure in small-angle reflection geometry. The technique can be used with extended objects, places no restriction on sample size, and requires no additional sample masking. The realization of X-ray lensless imaging in reflection geometry opens up the possibility of single-shot imaging of surfaces in thin films, buried interfaces in magnetic multilayers, organic photovoltaic and field-effect transistor devices, or Bragg planes in a single crystal.
Date: February 3, 2011
Creator: Roy, S.; Parks, D.H.; Seu, K.A.; Turner, J.J.; Chao, W.; Anderson, E.H. et al.
Partner: UNT Libraries Government Documents Department

Coordinateendonucleolytic 5' and 3' trimming of terminally blocked blunt DNA double-strand break ends by Artemis nuclease and DNA-dependent protein kinase

Description: Previous work showed that, in the presence of DNA-PK, Artemis slowly trims 3'-phosphoglycolate-terminated blunt ends. To examine the trimming reaction in more detail, long internally labeled DNA substrates were treated with Artemis. In the absence of DNA-PK, Artemis catalyzed extensive 5' {yields} 3' exonucleolytic resection of double-stranded DNA. This resection required a 5'-phosphate but did not require ATP, and was accompanied by endonucleolytic cleavage of the resulting 3' overhang. In the presence of DNA-PK, Artemis-mediated trimming was more limited, was ATP-dependent, and did not require a 5'-phosphate. For a blunt end with either a 3'-phosphoglycolate or 3'-hydroxyl terminus, endonucleolytic trimming of 2-4 nucleotides from the 3'-terminal strand was accompanied by trimming of 6 nucleotides from the 5'-terminal strand. The results suggest that autophosphorylated DNA-PK suppresses the exonuclease activity of Artemis toward blunt-ended DNA, and promotes slow and limited endonucleolytic trimming of the 5'-terminal strand, resulting in short 3' overhangs that are trimmed endonucleolytically. Thus, Artemis and DNA-PK can convert terminally blocked DNA ends of diverse geometry and chemical structure to a form suitable for polymerase mediated patching and ligation, with minimal loss of terminal sequence. Such processing could account for the very small deletions often found at DNA double-strand break repair sites.
Date: February 18, 2008
Creator: Povirk, Lawrence; Yannone, Steven M.; Khan, Imran S.; Zhou, Rui-Zhe; Zhou, Tong; Valerie, Kristoffer et al.
Partner: UNT Libraries Government Documents Department

Three-dimensional lithographically-defined organotypic tissue arrays for quantitative analysis of morphogenesis and neoplastic progression

Description: Here we describe a simple micromolding method to construct three-dimensional arrays of organotypic epithelial tissue structures that approximate in vivo histology. An elastomeric stamp containing an array of posts of defined geometry and spacing is used to mold microscale cavities into the surface of type I collagen gels. Epithelial cells are seeded into the cavities and covered with a second layer of collagen. The cells reorganize into hollow tissues corresponding to the geometry of the cavities. Patterned tissue arrays can be produced in 3-4 h and will undergo morphogenesis over the following one to three days. The protocol can easily be adapted to study a variety of tissues and aspects of normal and neoplastic development.
Date: February 13, 2008
Creator: Nelson, Celeste M.; Inman, Jamie L. & Bissell, Mina J.
Partner: UNT Libraries Government Documents Department

Surprising Coordination Geometry Differences in Ce(IV)- and Pu(IV)-Maltol Complexes

Description: As part of a study to characterize the detailed coordination behavior of Pu(IV), single crystal X-ray diffraction structures have been determined for Pu(IV) and Ce(IV) complexes with the naturally-occurring ligand maltol (3-hydroxy-2-methyl-pyran-4-one) and its derivative bromomaltol (5-bromo-3-hydroxy-2-methyl-pyran-4-one). Although Ce(IV) is generally accepted as a structural analog for Pu(IV), and the maltol complexes of these two metals are isostructural, the corresponding bromomaltol complexes are strikingly different with respect to ligand orientation about the metal ion: All complexes exhibit trigonal dodecahedral coordination geometry but the Ce(IV)-bromomaltol complex displays an uncommon ligand arrangement not mirrored in the Pu(IV) complex, although the two metal species are generally accepted to be structural analogs.
Date: February 12, 2008
Creator: Laboratory, Lawrence Berkeley National; Raymond, Kenneth; Szigethy, Geza; Xu, Jide; Gorden, Anne E.V.; Teat, Simon J. et al.
Partner: UNT Libraries Government Documents Department

Femtosecond electron and x-ray generation by laser andplasma-based sources

Description: The generation of ultra-short x-rays by Thomson scattering intense laser pulses from electron beams is discussed, including recent experimental results and methods for enhancing the x-ray flux. A high flux of x-rays in a femtosecond pulse requires the generation of femtosecond electron bunches and a head-on Thomson scattering geometry. The generation of ultrashort electron bunches in a plasma-based accelerator with an injection technique that uses two colliding laser pulses is discussed. Simulations indicate the bunches as short as a few fs can be produced. Conversion of the fs electron pulse to a fs x-ray pulse can be accomplished by Bremsstrahlung or Thomson scattering.
Date: February 1, 2000
Creator: Esarey, E. & Leemans, W.P.
Partner: UNT Libraries Government Documents Department

Assessment of the sources of error affecting the quantitative accuracy of SPECT imaging in small animals

Description: Small animal SPECT imaging systems have multiple potential applications in biomedical research. Whereas SPECT data are commonly interpreted qualitatively in a clinical setting, the ability to accurately quantify measurements will increase the utility of the SPECT data for laboratory measurements involving small animals. In this work, we assess the effect of photon attenuation, scatter and partial volume errors on the quantitative accuracy of small animal SPECT measurements, first with Monte Carlo simulation and then confirmed with experimental measurements. The simulations modeled the imaging geometry of a commercially available small animal SPECT system. We simulated the imaging of a radioactive source within a cylinder of water, and reconstructed the projection data using iterative reconstruction algorithms. The size of the source and the size of the surrounding cylinder were varied to evaluate the effects of photon attenuation and scatter on quantitative accuracy. We found that photon attenuation can reduce the measured concentration of radioactivity in a volume of interest in the center of a rat-sized cylinder of water by up to 50percent when imaging with iodine-125, and up to 25percent when imaging with technetium-99m. When imaging with iodine-125, the scatter-to-primary ratio can reach up to approximately 30percent, and can cause overestimation of the radioactivity concentration when reconstructing data with attenuation correction. We varied the size of the source to evaluate partial volume errors, which we found to be a strong function of the size of the volume of interest and the spatial resolution. These errors can result in large (>50percent) changes in the measured amount of radioactivity. The simulation results were compared with and found to agree with experimental measurements. The inclusion of attenuation correction in the reconstruction algorithm improved quantitative accuracy. We also found that an improvement of the spatial resolution through the use of resolution recovery techniques (i.e. modeling the ...
Date: February 15, 2008
Creator: Joint Graduate Group in Bioengineering, University of California, San Francisco and University of California, Berkeley; Department of Radiology, University of California; Gullberg, Grant T; Hwang, Andrew B.; Franc, Benjamin L.; Gullberg, Grant T. et al.
Partner: UNT Libraries Government Documents Department

Reduction of pertechnetate by acetohydroxamic acid: Formation of [TcNO(AHA)2(H2O)]+ and implications for the UREX process.

Description: Reductive nitrosylation and complexation of ammonium pertechnetate by acetohydroxamic acid has been achieved in aqueous nitric and perchloric acid solutions. The kinetics of the reaction depend on the relative concentrations of the reaction components and are accelerated at higher temperatures. The reaction does not occur unless conditions are acidic. Analysis of the x-ray absorption fine structure spectroscopic data is consistent with a pseudo-octahedral geometry with the linear Tc-N-O bond typical of technetium nitrosyl compounds, and electron spin resonance spectroscopy is consistent with a the d{sup 5} Tc(II) nitrosyl complex. The nitrosyl source is generally AHA, but may be augmented by products of reaction with nitric acid. The resulting low-valency trans-aquonitrosyl(diacetohydroxamic)-technetium(II) complex (1) is highly soluble in water, extremely hydrophilic, and is not extracted by tri-n-butylphosphate in a dodecane diluent. Its extraction properties are not pH-dependent; titration studies indicate a single species from pH 4.5 down to -0.6 (calculated). This molecule is resistant to oxidation by H{sub 2}O{sub 2}, even at high pH, and can undergo substitution to form other technetium nitrosyl complexes. The formation of 1 may strongly impact the fate of technetium in the nuclear fuel cycle.
Date: February 26, 2008
Creator: 1Harry Reid Center for Environmental Studies, Nuclear Science and Technology Division, University of Nevada, Las Vegas, Las Vegas, NV, 89154-4006; Gong, Cynthia-May S; Poineau, Frederic; Lukens, Wayne W & Czerwinski, Kenneth R.
Partner: UNT Libraries Government Documents Department

A LIQUID XENON RADIOISOTOPE CAMERA

Description: The increasing availability of short lived gamma and positron emitting isotopes, coupled with the importance of dynamical studies and better imaging, has generated the need for an improved {gamma}-ray camera. The authors discuss a new type of {gamma}-ray camera which makes use of electron avalanches in liquid xenon. A configuration currently under development is shown in Figure 1. The successful operation of a liquid xenon proportional counter was recently reported. The liquid xenon camera promises better spatial resolution and higher counting rate than the existing NaI(Tl) scintillation camera. The spatial resolution for {gamma} rays is in principle limited only by the range of photoelectrons in liquid xenon, which is < 0.2 mm for energies < 1 MeV. A counting rate of 10{sup 6} C/s or more appears possible. As a result of the better resolution and high counting rate capability, the definition of the picture is improved. In addition, the high counting rate capability makes possible dynamic studies which were previously unfeasible. Although they expect the energy resolution with liquid xenon to be superior to that of NaI, the preliminary measurements show 17% FWHM for 279 keV {gamma}'s. Improvements are expected by using better geometry and smoother wire.
Date: February 1, 1972
Creator: Zaklad, Haim.; Derenzo, Stephen E.; Muller, Richard A.; Smadja,Gerard.; Smits, Robert G. & Alvarez, Luis W.
Partner: UNT Libraries Government Documents Department

Antiproton Interaction Cross Sections

Description: Using the 1.19-Bev/c antiproton beam recently discovered at the Berkeley Bevatron of the University of California, we have measured the attenuation cross section in beryllium and copper. These cross sections are compared to attenuation measurements made with the same geometry using positive protons of the same incident energy (497 MeV).
Date: February 27, 1956
Creator: Chamberlain, Owen; Keller, Donald V.; Segre, Emilio; Steiner,Herbert M.; Wiegand, Clyde & Ypsilantis, Tom
Partner: UNT Libraries Government Documents Department

The effects of realistic pancake solenoids on particle transport

Description: Solenoids are widely used to transport or focus particle beams. Usually, they are assumed as being ideal solenoids with a high axial-symmetry magnetic field. Using the Vector Field Opera program, we modeled asymmetrical solenoids with realistic geometry defects, caused by finite conductor and current jumpers. Their multipole magnetic components were analyzed with the Fourier fit method; we present some possible optimized methods for them. We also discuss the effects of 'realistic' solenoids on low energy particle transport. The finding in this paper may be applicable to some lower energy particle transport system design.
Date: February 1, 2011
Creator: Gu, X.; Okamura, M.; Pikin, A.; Fischer, W. & Luo, Y.
Partner: UNT Libraries Government Documents Department

Cygnus Diverter Switch Analysis

Description: The Cygnus Dual Beam Radiographic Facility consists of two 2.25-MV, 60-kA, 50-ns x-ray sources fielded in an underground laboratory at the Nevada Test Site. The tests performed in this laboratory involve study of the dynamic properties of plutonium and are called subcritical experiments. From end-to-end, the Cygnus machines utilize the following components: Marx generator, water-filled pulse-forming line (PFL), waterfilled coaxial transmission line (WTL), 3-cell inductive voltage adder (IVA), and rod-pinch diode. The upstream WTL interface to the PFL is via a radial insulator with coaxial geometry. The downstream WTL terminates in a manifold where the center conductor splits into three lines which individually connect to each of the IVA cell inputs. There is an impedance mismatch at this juncture. It is a concern that a reflected pulse due to anomalous behavior in the IVA or diode might initiate breakdown upon arrival at the upstream PFL/WTL insulator. Therefore near the beginning of the WTL a radial diverter switch is installed to protect the insulator from over voltage and breakdown. The diverter has adjustable gap spacing, and an in-line aqueous-solution (sodium thiosulfate) resistor array for energy dissipation. There are capacitive voltage probes at both ends of the WTL and on the diverter switch. These voltage signals will be analyzed to determine diverter performance. Using this analysis the usefulness of the diverter switch will be evaluated.
Date: February 1, 2008
Creator: G. Corrow, M. Hansen, D. Henderson, C. Mitton et al.
Partner: UNT Libraries Government Documents Department

Cygnus Performance in Subcritical Experiments

Description: The Cygnus Dual Beam Radiographic Facility consists of two identical radiographic sources with the following specifications: 4-rad dose at 1 m, 1-mm spot size, 50-ns pulse length, 2.25-MeV endpoint energy. The facility is located in an underground tunnel complex at the Nevada Test Site. Here SubCritical Experiments (SCEs) are performed to study the dynamic properties of plutonium. The Cygnus sources were developed as a primary diagnostic for these tests. Since SCEs are single-shot, high-value events - reliability and reproducibility are key issues. Enhanced reliability involves minimization of failure modes through design, inspection, and testing. Many unique hardware and operational features were incorporated into Cygnus to insure reliability. Enhanced reproducibility involves normalization of shot-to-shot output also through design, inspection, and testing. The first SCE to utilize Cygnus, Armando, was executed on May 25, 2004. A year later, April - May 2005, calibrations using a plutonium step wedge were performed. The results from this series were used for more precise interpretation of the Armando data. In the period February - May 2007 Cygnus was fielded on Thermos, which is a series of small-sample plutonium shots using a one-dimensional geometry. Pulsed power research generally dictates frequent change in hardware configuration. Conversely, SCE applications have typically required constant machine settings. Therefore, while operating during the past four years we have accumulated a large database for evaluation of machine performance under highly consistent operating conditions. Through analysis of this database Cygnus reliability and reproducibility on Armando, Step Wedge, and Thermos is presented.
Date: February 1, 2008
Creator: G. Corrow, M. Hansen, D. Henderson, S. Lutz, C. Mitton, et al.
Partner: UNT Libraries Government Documents Department

ELLIPTIC FLOW, INITIAL ECCENTRICITY AND ELLIPTIC FLOW FLUCTUATIONS IN HEAVY ION COLLISIONS AT RHIC.

Description: We present measurements of elliptic flow and event-by-event fluctuations established by the PHOBOS experiment. Elliptic flow scaled by participant eccentricity is found to be similar for both systems when collisions with the same number of participants or the same particle area density are compared. The agreement of elliptic flow between Au+Au and Cu+Cu collisions provides evidence that the matter is created in the initial stage of relativistic heavy ion collisions with transverse granularity similar to that of the participant nucleons. The event-by-event fluctuation results reveal that the initial collision geometry is translated into the final state azimuthal particle distribution, leading to an event-by-event proportionality between the observed elliptic flow and initial eccentricity.
Date: February 19, 2007
Creator: NOUICER,R.; ALVER, B.; BACK, B.B.; BAKER, M.D.; BALLINTIJN, M.; BARTON, D.S. et al.
Partner: UNT Libraries Government Documents Department

Experiments with planar inductive ion source meant for creation ofH+ Beams

Description: In this article the effect of different engineering parameters of an rf-driven ion sources with external spiral antenna and quartz disk rf-window are studied. Paper consists of three main topics: The effect of source geometry on the operation gas pressure, the effect of source materials and magnetic confinement on extracted current density and ion species and the effect of different antenna geometries on the extracted current density. The operation gas pressure as a function of the plasma chamber diameter, was studied. This was done with three cylindrical plasma chambers with different inner diameters. The chamber materials were studied using two materials, aluminum and alumina (AlO{sub 2}). The removable 14 magnet multicusp confinement arrangement enabled us to compare the effects of the two wall materials with and without the magnetic confinement. Highest proton fraction of {approx} 8% at 2000 W of rf-power and at pressure of 1.3 Pa was measured using AlO{sub 2} plasma chamber and no multicusp confinement. For all the compared ion sources at 1000W of rf-power, source with multicusp confinement and AlO2 plasma chamber yields highest current density of 82.7 mA/cm{sup 2} at operation pressure of 4 Pa. From the same source highest measured current density of 143 mA/cm{sup 2} at 1.3 Pa and 2200W of rf-power was achieved. Multicusp confinement increased the maximum extracted current up to factor of two. Plasma production with different antenna geometries was also studied. Antenna tests were performed using same source geometry as in source material study with AlO{sub 2} plasma chamber and multicusp confinement. The highest current density was achieved with 4.5 loop solenoid antenna with 6 cm diameter. Slightly lower current density with lower pressure was achieved using tightly wound 3 loop spiral antenna with 3.3 cm ID and 6 cm OD.
Date: February 7, 2007
Creator: Vainionpaa, J.H.; Kalvas, T.; Hahto, S.K. & Reijonen, J.
Partner: UNT Libraries Government Documents Department

Wind River Watershed Restoration Project; Underwood Conservation District, Annual Report 2002-2003.

Description: The goal of the Wind River project is to preserve, protect and restore Wind River steelhead. In March, 1998, the National Marine Fisheries Service listed the steelhead of the lower Columbia as 'threatened' under the Endangered Species Act. In 1997, the Washington Department of Fish and Wildlife rated the status of the Wind River summer run steelhead as critical. Due to the status of this stock, the Wind River summer steelhead have the highest priority for recovery and restoration in the state of Washington's Lower Columbia Steelhead Conservation Initiative. The Wind River Project includes four cooperating agencies. Those are the Underwood Conservation District (UCD), United States Geological Service (USGS), US Forest Service (USFS), and Washington State Department of Fish & Wildlife (WDFW). Tasks include monitoring steelhead populations (USGS and WDFW), Coordinating a Watershed Committee and Technical Advisory Group (UCD), evaluating physical habitat conditions (USFS and UCD), assessing watershed health (all), reducing road sediments sources (USFS), rehabilitating riparian corridors, floodplains, and channel geometry (UCD, USFS), evaluate removal of Hemlock Dam (USFS), and promote local watershed stewardship (UCD, USFS). UCD's major efforts have included coordination of the Wind River Watershed Committee and Technical Advisory Committee (TAC), water temperature and water chemistry monitoring, riparian habitat improvement projects, and educational activities. Our coordination work enables the local Watershed Committee and TAC to function and provide essential input to Agencies, and our habitat improvement work focuses on riparian revegetation. Water chemistry and temperature data collection provide information for monitoring watershed conditions and fish habitat, and are comparable with data gathered in previous years. Water chemistry information collected on Trout Creek should, with 2 years data, determine whether pH levels make conditions favorable for a fish parasite, Heteropolaria lwoffi. Educational activities further the likelihood that future generations will continue to understand and enjoy the presence of ...
Date: February 1, 2004
Creator: White, Jim
Partner: UNT Libraries Government Documents Department

Black Hole Attractors and Pure Spinors

Description: We construct black hole attractor solutions for a wide class of N = 2 compactifications. The analysis is carried out in ten dimensions and makes crucial use of pure spinor techniques. This formalism can accommodate non-Kaehler manifolds as well as compactifications with flux, in addition to the usual Calabi-Yau case. At the attractor point, the charges fix the moduli according to {Sigma}f{sub k} = Im(C{Phi}), where {Phi} is a pure spinor of odd (even) chirality in IIB (A). For IIB on a Calabi-Yau, {Phi} = {Omega} and the equation reduces to the usual one. Methods in generalized complex geometry can be used to study solutions to the attractor equation.
Date: February 21, 2006
Creator: Hsu, Jonathan P.; Maloney, Alexander & Tomasiello, Alessandro
Partner: UNT Libraries Government Documents Department

The Non-BPS Black Hole Attractor Equation

Description: We study the attractor mechanism for extremal non-BPS black holes with an infinite throat near horizon geometry, developing, as we do so, a physical argument as to why such a mechanism does not exist in non-extremal cases. We present a detailed derivation of the non-supersymmetric attractor equation. This equation defines the stabilization of moduli near the black hole horizon: the fixed moduli take values specified by electric and magnetic charges corresponding to the fluxes in a Calabi Yau compactification of string theory. They also define the so-called double-extremal solutions. In some examples, studied previously by Tripathy and Trivedi, we solve the equation and show that the moduli are fixed at values which may also be derived from the critical points of the black hole potential.
Date: February 8, 2006
Creator: Kollosh, R
Partner: UNT Libraries Government Documents Department

Geology of the Waste Treatment Plant Seismic Boreholes

Description: In 2006, DOE-ORP initiated the Seismic Boreholes Project (SBP) to emplace boreholes at the Waste Treatment Plant (WTP) site in order to obtain direct Vs measurements and other physical property measurements in Columbia River basalt and interbedded sediments of the Ellensburg Formation. The goal was to reduce the uncertainty in the response spectra and seismic design basis, and potentially recover design margin for the WTP. The characterization effort within the deep boreholes included 1) downhole measurements of the velocity properties of the suprabasalt, basalt, and sedimentary interbed sequences, 2) downhole measurements of the density of the subsurface basalt and sediments, and 3) confirmation of the geometry of the contact between the various basalt and interbedded sediments through examination of retrieved core from the corehole and data collected through geophysical logging of each borehole. This report describes the results of the geologic studies from three mud-rotary boreholes and one cored borehole at the WTP. All four boreholes penetrated the entire Saddle Mountains Basalt and the upper part of the Wanapum Basalt where thick sedimentary interbeds occur between the lava flows. The basalt flows penetrated in Saddle Mountains Basalt included the Umatilla Member, Esquatzel Member, Pomona Member and the Elephant Mountain Member. The underlying Priest Rapids Member of the Wanapum Basalt was also penetrated. The Ellensburg Formation sediments consist of the Mabton Interbed, the Cold Creek Interbed, the Selah Interbed and the Rattlesnake Ridge Interbed; the Byron Interbed occurs between two flows of the Priest Rapids Member. The Mabton Interbed marks the contact between the Wanapum and Saddle Mountains Basalts. The thicknesses of the basalts and interbedded sediments were within expected limits. However, a small reverse fault was found in the Pomona Member flow top. This fault has three periods of movement and less than 15 feet of repeated section. Most of ...
Date: February 28, 2007
Creator: Barnett, D. BRENT; Bjornstad, Bruce N.; Fecht, Karl R.; Lanigan, David C.; Reidel, Steve & Rust, Colleen F.
Partner: UNT Libraries Government Documents Department

FY05 LDRD Final ReportNanomaterials for Radiation Detection

Description: We have demonstrated that it is possible to enhance current radiation detection capability by manipulating the materials at the nano level. Fabrication of three-dimensional (3-D) nanomaterial composite for radiation detection has great potential benefits over current semiconductor- and scintillation-based technologies because of the precise control of material-radiation interaction and modulation of signal output. It is also a significant leap beyond current 2-D nanotechnology. Moreover, since we are building the materials using a combination of top-down and bottom-up approaches, this strategy to make radiation detection materials can provide significant improvement to radiation-detection technologies, which are currently based on difficult-to-control bulk crystal growth techniques. We are applying this strategy to tackle two important areas in radiation detection: gamma-rays and neutrons. In gamma-ray detection, our first goal is to employ nanomaterials in the form of quantum-dot-based mixed matrices or nanoporous semiconductors to achieve scintillation output several times over that from NaI(Tl) crystals. In neutron detection, we are constructing a 3-D structure using a doped nanowire ''forest'' supported by a boron matrix and evaluating the detection efficiency of different device geometry with simulation.
Date: February 6, 2006
Creator: Wang, T F; Letant, S E; Nikolic, R J & Chueng, C L
Partner: UNT Libraries Government Documents Department

A Maximally Supersymmetric Kondo Model

Description: We study the maximally supersymmetric Kondo model obtained by adding a fermionic impurity to N = 4 supersymmetric Yang-Mills theory. While the original Kondo problem describes a defect interacting with a free Fermi liquid of itinerant electrons, here the ambient theory is an interacting CFT, and this introduces qualitatively new features into the system. The model arises in string theory by considering the intersection of a stack of M D5-branes with a stack of N D3-branes, at a point in the D3 worldvolume. We analyze the theory holographically, and propose a dictionary between the Kondo problem and antisymmetric Wilson loops in N = 4 SYM. We perform an explicit calculation of the D5 fluctuations in the D3 geometry and determine the spectrum of defect operators. This establishes the stability of the Kondo fixed point together with its basic thermodynamic properties. Known supergravity solutions for Wilson loops allow us to go beyond the probe approximation: the D5s disappear and are replaced by three-form flux piercing a new topologically non-trivial S3 in the corrected geometry. This describes the Kondo model in terms of a geometric transition. A dual matrix model reflects the basic properties of the corrected gravity solution in its eigenvalue distribution.
Date: February 17, 2012
Creator: Harrison, Sarah; Kachru, Shamit; Torroba, Gonzalo & /Stanford U., Phys. Dept. /SLAC
Partner: UNT Libraries Government Documents Department

Lightning arrestor connector lead magnesium niobate qualification pellet test procedures.

Description: Enhanced knowledge preservation for DOE DP technical component activities has recently received much attention. As part of this recent knowledge preservation effort, improved documentation of the sample preparation and electrical testing procedures for lead magnesium niobate--lead titanate (PMN/PT) qualification pellets was completed. The qualification pellets are fabricated from the same parent powders used to produce PMN/PT lightning arrestor connector (LAC) granules at HWF&T. In our report, the procedures for fired pellet surface preparation, electrode deposition, electrical testing and data recording are described. The dielectric measurements described in our report are an information only test. Technical reasons for selecting the electrode material, electrode size and geometry are presented. The electrical testing is based on measuring the dielectric constant and dissipation factor of the pellet during cooling from 280 C to 220 C. The most important data are the temperature for which the peak dielectric constant occurs (Curie Point temperature) and the peak dielectric constant magnitude. We determined that the peak dielectric constant for our procedure would be that measured at 1 kHz at the Curie Point. Both the peak dielectric constant and the Curie point parameters provide semi-quantitative information concerning the chemical and microstructural homogeneity of the parent material used for the production of PMN/PT granules for LACs. Finally, we have proposed flag limits for the dielectric data for the pellets. Specifically, if the temperature of the peak dielectric constant falls outside the range of 250 C {+-} 30 C we propose that a flag limit be imposed that will initiate communication between production agency and design agency personnel. If the peak dielectric constant measured falls outside the range 25,000 {+-} 10,000 we also propose that a flag limit be imposed.
Date: February 1, 2009
Creator: Tuohig, W. (Honeywell FM&T, Kansas City, MO); Mahoney, Patrick A.; Tuttle, Bruce Andrew & Wheeler, Jill Susanne
Partner: UNT Libraries Government Documents Department

In-situ monitoring of surface post-processing in large aperture fused silica optics with Optical Coherence Tomography

Description: Optical Coherence Tomography is explored as a method to image laser-damage sites located on the surface of large aperture fused silica optics during post-processing via CO{sub 2} laser ablation. The signal analysis for image acquisition was adapted to meet the sensitivity requirements for this application. A long-working distance geometry was employed to allow imaging through the opposite surface of the 5-cm thick optic. The experimental results demonstrate the potential of OCT for remote monitoring of transparent material processing applications.
Date: February 8, 2008
Creator: Guss, G M; Bass, I l; Hackel, R P; Mailhiot, C & Demos, S G
Partner: UNT Libraries Government Documents Department

Modeling and simulation of blast-induced, early-time intracranial wave physics leading to traumatic brain injury.

Description: The objective of this modeling and simulation study was to establish the role of stress wave interactions in the genesis of traumatic brain injury (TBI) from exposure to explosive blast. A high resolution (1 mm{sup 3} voxels), 5 material model of the human head was created by segmentation of color cryosections from the Visible Human Female dataset. Tissue material properties were assigned from literature values. The model was inserted into the shock physics wave code, CTH, and subjected to a simulated blast wave of 1.3 MPa (13 bars) peak pressure from anterior, posterior and lateral directions. Three dimensional plots of maximum pressure, volumetric tension, and deviatoric (shear) stress demonstrated significant differences related to the incident blast geometry. In particular, the calculations revealed focal brain regions of elevated pressure and deviatoric (shear) stress within the first 2 milliseconds of blast exposure. Calculated maximum levels of 15 KPa deviatoric, 3.3 MPa pressure, and 0.8 MPa volumetric tension were observed before the onset of significant head accelerations. Over a 2 msec time course, the head model moved only 1 mm in response to the blast loading. Doubling the blast strength changed the resulting intracranial stress magnitudes but not their distribution. We conclude that stress localization, due to early time wave interactions, may contribute to the development of multifocal axonal injury underlying TBI. We propose that a contribution to traumatic brain injury from blast exposure, and most likely blunt impact, can occur on a time scale shorter than previous model predictions and before the onset of linear or rotational accelerations traditionally associated with the development of TBI.
Date: February 1, 2008
Creator: Ford, Corey C. (University of New Mexico, Albuquerque, NM) & Taylor, Paul Allen
Partner: UNT Libraries Government Documents Department