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An arbuscular mycorrhizal fungus modifies the soil microbial community and nitrogen cycling during litter decomposition (open access)

An arbuscular mycorrhizal fungus modifies the soil microbial community and nitrogen cycling during litter decomposition

None
Date: April 30, 2012
Creator: Nuccio, E E; Hodge, A; Pett-Ridge, J; Herman, D J; Weber, P & Firestone, M K
System: The UNT Digital Library
Ceramic HEPA Filter Program (open access)

Ceramic HEPA Filter Program

Potential benefits of ceramic filters in nuclear facilities: (1) Short term benefit for DOE, NRC, and industry - (a) CalPoly HTTU provides unique testing capability to answer questions for DOE - High temperature testing of materials, components, filter, (b) Several DNFSB correspondences and presentations by DNFSB members have highlighted the need for HEPA filter R and D - DNFSB Recommendation 2009-2 highlighted a nuclear facility response to an evaluation basis earthquake followed by a fire (aka shake-n-bake) and CalPoly has capability for a shake-n-bake test; (2) Intermediate term benefit for DOE and industry - (a) Filtration for specialty applications, e.g., explosive applications at Nevada, (b) Spin-off technologies applicable to other commercial industries; and (3) Long term benefit for DOE, NRC, and industry - (a) Across industry, strong desire for better performance filter, (b) Engineering solution to safety problem will improve facility safety and decrease dependence on associated support systems, (c) Large potential life-cycle cost savings, and (d) Facilitates development and deployment of LLNL process innovations to allow continuous ventilation system operation during a fire.
Date: April 30, 2012
Creator: Mitchell, M A; Bergman, W; Haslam, J; Brown, E P; Sawyer, S; Beaulieu, R et al.
System: The UNT Digital Library
DIXI (Dilation x-ray imager) a new/faster gated x-ray imager for the NIF (open access)

DIXI (Dilation x-ray imager) a new/faster gated x-ray imager for the NIF

None
Date: April 30, 2012
Creator: Nagel, S. R.; Hilsabeck, T. J.; Bell, P. M.; Bradley, D. K.; Ayers, M. J.; Barrios, M. A. et al.
System: The UNT Digital Library
Efficient and Scalable Retrieval Techniques for Global File Properties (open access)

Efficient and Scalable Retrieval Techniques for Global File Properties

None
Date: April 30, 2012
Creator: Ahn, D H; Brim, M; de Supinski, B R; Gamblin, T; Lee, G L; LeGendre, M P et al.
System: The UNT Digital Library
High Bandwidth Differential Amplifier for Shock Experiments (open access)

High Bandwidth Differential Amplifier for Shock Experiments

We developed a high bandwidth differential amplifier for gas gun shock experiments/applications. The circuit has a bandwidth > 1 GHz, and is capable of measuring signals of ≤1.5 V with a common mode rejection of 250 V. Conductivity measurements of gas gun targets are measured by flowing high currents through the targets. The voltage is measured across the target using a technique similar to a four-point probe. Because of the design of the current source and load, the target voltage is approximately 250 V relative to ground. Since the expected voltage change in the target is < 1 V, the differential amplifier must have a large common mode rejection. High pass filters suppress internal ringing of operational amplifiers. Results of bench tests are shown.
Date: April 30, 2012
Creator: Ross, P. W., Tran, V., Chau, R.
System: The UNT Digital Library
Investigating the effects of proton exchange membrane fuel cell conditions on carbon supported platinum electrocatalyst composition and performance (open access)

Investigating the effects of proton exchange membrane fuel cell conditions on carbon supported platinum electrocatalyst composition and performance

Changes that carbon-supported platinum electrocatalysts undergo in a proton exchange membrane fuel cell environment were simulated by ex situ heat treatment of catalyst powder samples at 150 C and 100% relative humidity. In order to study modifications that are introduced to chemistry, morphology, and performance of electrocatalysts, XPS, HREELS and three-electrode rotating disk electrode experiments were performed. Before heat treatment, graphitic content varied by 20% among samples with different types of carbon supports, with distinct differences between bulk and surface compositions within each sample. Following the aging protocol, the bulk and surface chemistry of the samples were similar, with graphite content increasing or remaining constant and Pt-carbide decreasing for all samples. From the correlation of changes in chemical composition and losses in performance of the electrocatalysts, we conclude that relative distribution of Pt particles on graphitic and amorphous carbon is as important for electrocatalytic activity as the absolute amount of graphitic carbon present
Date: April 30, 2012
Creator: Patel, A.; Artyushkova, K.; Atanassov, P.; Colbow, V.; Dutta, M.; Harvey, D. et al.
System: The UNT Digital Library
Soft x-ray images of the Laser Entrance Hole of NIC Hohlraums (paper, HTPD2012) (open access)

Soft x-ray images of the Laser Entrance Hole of NIC Hohlraums (paper, HTPD2012)

Hohlraums at the National Ignition Facility convert laser energy into a thermal x-radiation drive, which implodes the capsule, thus compressing the fuel. The x-radiation drive is measured with a low resolution, time-resolved x-ray spectrometer that views the hohlraum's laser entrance hole (LEH) at 37{sup o} to the hohlraum axis. This measurement has no spatial resolution. To convert this to the drive inside the hohlraum, the area and fraction of the measured x-radiation which comes from the region inside the hohlraum must be known. The size of the LEH is measured with the time integrated Static X-ray Imager (SXI) which view the LEH at 18{sup o} to the hohlraum axis. A soft x-ray image has been added to the SXI to measure the fraction of x-radiation inside the LEH's Clear Aperture in order to correct the measured radiation. A multilayer mirror plus filter selects an x-ray band centered at 870 eV, near the x-ray energy peak of a 300 eV blackbody. Results from this channel and corrections to the x-radiation drive are discussed.
Date: April 30, 2012
Creator: Schneider, M. B. & Meezan, N. B.
System: The UNT Digital Library
Modeling Responses of Naturally Fractured Geothermal Reservoir to Low-Pressure Stimulation (open access)

Modeling Responses of Naturally Fractured Geothermal Reservoir to Low-Pressure Stimulation

None
Date: April 27, 2012
Creator: Fu, P & Carrigan, C R
System: The UNT Digital Library
Beyond Mean-Field Calculation For Pairing Correlation (open access)

Beyond Mean-Field Calculation For Pairing Correlation

None
Date: April 26, 2012
Creator: Hupin, G & Lacroix, D
System: The UNT Digital Library
From self-organized to extended criticality (open access)

From self-organized to extended criticality

Article discussing the criticality of transition processes in neurophysiology.
Date: April 26, 2012
Creator: Lovecchio, Elisa; Allegrini, Paolo; Geneston, Elvis L.; West, Bruce J. & Grigolini, Paolo
System: The UNT Digital Library
General Relativistic Magnetohydrodynamic Simulations of Magnetically Choked Accretion Flows around Black Holes (open access)

General Relativistic Magnetohydrodynamic Simulations of Magnetically Choked Accretion Flows around Black Holes

Black hole (BH) accretion flows and jets are qualitatively affected by the presence of ordered magnetic fields. We study fully three-dimensional global general relativistic magnetohydrodynamic (MHD) simulations of radially extended and thick (height H to cylindrical radius R ratio of |H/R| {approx} 0.2-1) accretion flows around BHs with various dimensionless spins (a/M, with BH mass M) and with initially toroidally-dominated ({phi}-directed) and poloidally-dominated (R-z directed) magnetic fields. Firstly, for toroidal field models and BHs with high enough |a/M|, coherent large-scale (i.e. >> H) dipolar poloidal magnetic flux patches emerge, thread the BH, and generate transient relativistic jets. Secondly, for poloidal field models, poloidal magnetic flux readily accretes through the disk from large radii and builds-up to a natural saturation point near the BH. While models with |H/R| {approx} 1 and |a/M| {le} 0.5 do not launch jets due to quenching by mass infall, for sufficiently high |a/M| or low |H/R| the polar magnetic field compresses the inflow into a geometrically thin highly non-axisymmetric 'magnetically choked accretion flow' (MCAF) within which the standard linear magneto-rotational instability is suppressed. The condition of a highly-magnetized state over most of the horizon is optimal for the Blandford-Znajek mechanism that generates persistent relativistic jets with …
Date: April 26, 2012
Creator: McKinney, Jonathan C.; Tchekhovskoy, Alexander & Blandford, Roger D.
System: The UNT Digital Library
Integrated X-Ray Reflectivity Measurements for Elliptically Curved PET Crystals (open access)

Integrated X-Ray Reflectivity Measurements for Elliptically Curved PET Crystals

Spectroscopy provides valuable information about the temperature and density of a compressed pellet in a plasma. Elliptically curved pentaerythritol (PET) crystals are used as components for spectrometers. Their elliptical geometry gives several advantages related to spectral energy range, source focus, and spectral image compression.[1] The crystal curvature increases the spectrometer throughput but at the cost of a loss in resolution. Four different crystals are used in a spectrometer at the National Ignition Facility (NIF) target chamber at Lawrence Livermore National Laboratory (LLNL). Figure 1 shows the arrangement of the elliptical PET crystals in the snout of a NIF target diagnostic shown in Figure 2. The spectrum from the crystals is captured by four image plates located behind the crystals. A typical mandrel, the darkened section, upon which the PET crystal is glued, is shown in Figure 3, which also shows the complete ellipse. There are four elliptical segment types, each having the same major axis but a different minor axis. The crystals are 150 mm long in the diffraction direction and 25.4 mm high. Two crystals of each type were calibrated. The throughput for each spectrometer is determined by the integrated reflectivity of the PET crystal.[1] The goal of this …
Date: April 26, 2012
Creator: Haugh, M. J.; Ross, P. W.; Regan, P. W.; Magoon, J.; Shoup, M. J.; Barrios, M. A. et al.
System: The UNT Digital Library
Searches for Leptonic B Decays at BaBar (open access)

Searches for Leptonic B Decays at BaBar

Measurements of the branching fractions of purely leptonic decays of B-mesons translate into constraints in the plane of the charged Higgs mass versus tan {beta} which are relatively insensitive to the particular theoretical model. Using the full BABAR dataset of 450 million B-decays we search for these decays. No significant signal is found in the decays into electrons or muons and we set upper limits on the branching fractions of the order of a 10{sup -6} at 90% confidence level. We measure the branching fraction of B {yields} {tau}{mu} to be (1.7 {+-} 0.6) x 10{sup -4}.
Date: April 25, 2012
Creator: Nelson, Silke
System: The UNT Digital Library
High Multiplicity Searches at the LHC Using Jet Masses (open access)

High Multiplicity Searches at the LHC Using Jet Masses

This article introduces a new class of searches for physics beyond the Standard Model that improves the sensitivity to signals with high jet multiplicity. The proposed searches gain access to high multiplicity signals by reclustering events into large-radius, or 'fat', jets and by requiring that each event has multiple massive jets. This technique is applied to supersymmetric scenarios in which gluinos are pair-produced and then subsequently decay to final states with either moderate quantities of missing energy or final states without missing energy. In each of these scenarios, the use of jet mass improves the estimated reach in gluino mass by 20% to 50% over current LHC searches.
Date: April 24, 2012
Creator: Hook, Anson; /SLAC /Stanford U., Appl. Phys. Dept.; Izaguirre, Eder; /SLAC /Stanford U., Phys. Dept.; Lisanti, Mariangela; U., /Princeton et al.
System: The UNT Digital Library
PEP-II Status and Outlook (open access)

PEP-II Status and Outlook

PEP-II/BABAR are presently in their second physics run. With machine and detector performance and reliability at an all-time high, almost 51 fb{sup -1} have been integrated by BABAR up to mid-October 2001. PEP-II luminosity has reached 4.4 x 10{sup 33} cm{sup -2} s{sup -1} and our highest monthly delivered luminosity has been above 6 pb{sup -1}, exceeding the performance parameters given in the PEP-II CDR by almost 50%. The increase compared to the first run in 2000 has been achieved by a combination of beam-current increase and beam-size decrease. In this paper we will summarize the PEP-II performance and the present limitations as well as our plans to further increase machine performance.
Date: April 24, 2012
Creator: Wienands, H. U.; Biagini, M. E.; Decker, F. J.; Donald, M. H.; Ecklund, S.; Fisher, A. et al.
System: The UNT Digital Library
AB INITIO STUDY OF ADVANCED METALLIC NUCLEAR FUELS FOR FAST BREEDER REACTORS (open access)

AB INITIO STUDY OF ADVANCED METALLIC NUCLEAR FUELS FOR FAST BREEDER REACTORS

Density-functional formalism is applied to study the ground state properties of {gamma}-U-Zr and {gamma}-U-Mo solid solutions. Calculated heats of formation are compared with CALPHAD assessments. We discuss how the heat of formation in both alloys correlates with the charge transfer between the alloy components. The decomposition curves for {gamma}-based U-Zr and U-Mo solid solutions are derived from Ising-type Monte Carlo simulations. We explore the idea of stabilization of the {delta}-UZr{sub 2} compound against the {alpha}-Zr (hcp) structure due to increase of Zr d-band occupancy by the addition of U to Zr. We discuss how the specific behavior of the electronic density of states in the vicinity of the Fermi level promotes the stabilization of the U{sub 2}Mo compound. The mechanism of possible Am redistribution in the U-Zr and U-Mo fuels is also discussed.
Date: April 23, 2012
Creator: Landa, A; Soderlind, P; Grabowski, B; Turchi, P A; Ruban, A V & Vitos, L
System: The UNT Digital Library
DEPOSITION VELOCITY ESTIMATION WITH THE GENII V2 SOFTWARE (open access)

DEPOSITION VELOCITY ESTIMATION WITH THE GENII V2 SOFTWARE

In 2010, the Department of Energy (DOE) Chief of Nuclear Safety and Office of Health, Safety and Security (HSS), with the support of industry experts in atmospheric sciences and accident dose consequences analysis, performed detailed analyses of the basis for the dry deposition velocity (DV) values used in the MACCS2 computer code. As a result of these analyses, DOE concluded that the historically used default DV values of 1 centimeter/second (cm/s) for unfiltered/unmitigated releases and 0.1 cm/s for filtered/mitigated releases may not be reasonably conservative for all DOE sites and accident scenarios. HSS recently issued Safety Bulletin 2011-02, Accident Analysis Parameter Update, recommending the use of the newly developed default DV, 0.1 cm/s for an unmitigated/unfiltered release. Alternatively site specific DV values can be developed using GENII version 2 (GENII v2) computer code. Key input parameters for calculating DV values include surface roughness, maximum wind speed for calm, particle size, particle density and meteorological data (wind speed and stability class). This paper will include reasonably conservative inputs, and a truncated parametric study. In lieu of the highly-conservative recommended DV value (0.1cm/s) for unmitigated/unfiltered release, GENII v2 has been used to justify estimated 95th percentile DV values. Also presented here are …
Date: April 23, 2012
Creator: Hutchins, H.
System: The UNT Digital Library
PHOTOINDUCED CURRENTS IN CDZNTE CRYSTALS AS A FUNCTION OF ILLUMINATION WAVELENGTH (open access)

PHOTOINDUCED CURRENTS IN CDZNTE CRYSTALS AS A FUNCTION OF ILLUMINATION WAVELENGTH

We report variations in the currents of CdZnTe semiconductor crystals during exposure to a series of light emitting diodes of various wavelengths ranging from 470 to 950 nm. The changes in the steady-state current of one CdZnTe crystal with and without illumination along with the time dependence of the illumination effects are discussed. Analysis of the de-trapping and transient bulk currents during and after optical excitation yield insight into the behaviour of charge traps within the crystal. Similar behaviour is observed for illumination of a second CdZnTe crystal suggesting that the overall illumination effects are not crystal dependent.
Date: April 23, 2012
Creator: Teague, L.; Washington, A. & Duff, M.
System: The UNT Digital Library
2012 SINGLE MOLECULE APPROACHES TO BIOLOGY GORDON RESEARCH CONFERENCE (JULY 15-20, 2012 - MOUNT SNOW RESORT, WEST DOVER VT) (open access)

2012 SINGLE MOLECULE APPROACHES TO BIOLOGY GORDON RESEARCH CONFERENCE (JULY 15-20, 2012 - MOUNT SNOW RESORT, WEST DOVER VT)

Single molecule techniques are rapidly occupying a central role in biological research at all levels. This transition was made possible by the availability and dissemination of robust techniques that use fluorescence and force probes to track the conformation of molecules one at a time, in vitro as well as in live cells. Single-molecule approaches have changed the way many biological problems are studied. These novel techniques provide previously unobtainable data on fundamental biochemical processes that are essential for all forms of life. The ability of single-molecule approaches to avoid ensemble averaging and to capture transient intermediates and heterogeneous behavior renders them particularly powerful in elucidating mechanisms of the molecular systems that underpin the functioning of living cells. Hence, our conference seeks to disseminate the implementation and use of single molecule techniques in the pursuit of new biological knowledge. Topics covered include: Molecular Motors on the Move; Origin And Fate Of Proteins; Physical Principles Of Life; Molecules and Super-resolution Microscopy; Nanoswitches In Action; Active Motion Or Random Diffusion?; Building Blocks Of Living Cells; From Molecular Mechanics To Physiology; Tug-of-war: Force Spectroscopy Of Single Proteins.
Date: April 20, 2012
Creator: Fernandez, Julio
System: The UNT Digital Library
Assessment and Mitigation of Diagnostic-Generated Electromagnetic Interference at the National Ignition Facility (open access)

Assessment and Mitigation of Diagnostic-Generated Electromagnetic Interference at the National Ignition Facility

Electromagnetic interference (EMI) is an ever-present challenge at laser facilities such as the National Ignition Facility (NIF). The major source of EMI at such facilities is laser-target interaction that can generate intense electromagnetic fields within, and outside of, the laser target chamber. In addition, the diagnostics themselves can be a source of EMI, even interfering with themselves. In this paper we describe EMI generated by ARIANE and DIXI, present measurements, and discuss effects of the diagnostic-generated EMI on ARIANE's CCD and on a PMT nearby DIXI. Finally we present some of the efforts we have made to mitigate the effects of diagnostic-generated EMI on NIF diagnostics.
Date: April 20, 2012
Creator: Brown, C. G.; Ayers, M. J.; Felker, B.; Ferguson, W.; Holder, J P; Nagel, S. R. et al.
System: The UNT Digital Library
Combination of CDF and D0 Measurements of the $W$ Boson Helicity in Top Quark Decays (open access)

Combination of CDF and D0 Measurements of the $W$ Boson Helicity in Top Quark Decays

This report talks about Combination of CDF and D0 Measurements of the $W$ Boson Helicity in Top Quark Decays
Date: April 20, 2012
Creator: Aaltonen, T
System: The UNT Digital Library
Saturation of the Two-Plasmon Decay Instability in Long-Scale-Length Plasmas Relevant to Direct-Drive Inertial Confinement Fusion (open access)

Saturation of the Two-Plasmon Decay Instability in Long-Scale-Length Plasmas Relevant to Direct-Drive Inertial Confinement Fusion

Measurements of the hot-electron generation by the two-plasmon-decay instability are made in plasmas relevant to direct-drive inertial confinement fusion. Density-scale lengths of 400 {micro}m at n{sub cr}/4 in planar CH targets allowed the two-plasmon-decay instability to be driven to saturation for vacuum intensities above ~3.5 x 10{sup 14} W cm{sup -2}. In the saturated regime, ~1% of the laser energy is converted to hot electrons. The hot-electron temperature is measured to increase rapidly from 25 to 90 keV as the laser beam intensity is increased from 2 to 7 x 10{sup 14} W cm{sup -2}. This increase in the hot-electron temperature is compared with predictions from nonlinear Zakharov models.
Date: April 20, 2012
Creator: Yaakobi, B.; Hu, S. X.; Chang, P.-Y.; Craxton, R. S.; Edgell, D. H.; Follett, R. et al.
System: The UNT Digital Library
Fully Integrated Applications of Thin Films on Low Temperature Cofired Ceramic (LTCC) (open access)

Fully Integrated Applications of Thin Films on Low Temperature Cofired Ceramic (LTCC)

Thin film multilayers have previously been introduced on multilayer low temperature cofired ceramic (LTCC), as well as initial thin film capacitors on LTCC. The ruggedness of a multipurpose Ti-Cu-Pt-Au stack for connectivity and RF conductivity has continued to benefit fabrication and reliability in state of-the-art modules, while the capacitors have followed the traditional Metal-Insulator-Metal (MIM) style. The full integration of thin film passives with thin film connectivity traces is presented. Certain passives, such as capacitors, require specifically tailored and separately patterned thin film (multi-)layers, including a dielectric. Different capacitance values are achieved by variation of both the insulator layer thickness and the active area of the capacitor. Other passives, such as filters, require only the conductor - a single thin film multilayer. This can be patterned from the same connectivity thin film material (Ti-Cu-Pt-Au), or a specially tailored thin film material (e.g. Ti-Cu-Au) can be deposited. Both versions are described, including process and integration details. Examples are discussed, ranging from patterning for maximum tolerances, to space and performance-optimized designs. Cross-sectional issues associated with integration are also highlighted in the discussion.
Date: April 19, 2012
Creator: Wolf, Ambrose; Peterson, Ken; O'Keefe, Matt; Huebner, Wayne & Kuhn, Bill
System: The UNT Digital Library
Search for Bbar to Lambda_c+ X l- nu Decays in Events with a Fully Reconstructed B Meson (open access)

Search for Bbar to Lambda_c+ X l- nu Decays in Events with a Fully Reconstructed B Meson

We present a search for semileptonic B decays to the charmed baryon {Lambda}{sub c}{sup +} based on 420 fb{sup -1} of data collected at the {Upsilon}(4S) resonance with the BABAR detector at the PEP-II e{sup +}e{sup -} storage rings. By fully reconstructing the recoiling B in a hadronic decay mode, we reduce non-B backgrounds and determine the flavor of the signal B. We statistically correct the flavor for the effect of the B{sup 0} mixing. We obtain a 90% confidence level upper limit of {Beta}({bar B} {yields} {Lambda}{sub c}{sup +} X{ell}{sup -} {bar {nu}}{sub {ell}})/{Beta}({bar B} {yields} {Lambda}{sub c}{sup +} X) < 3.5%.
Date: April 19, 2012
Creator: Lees, J. P.; Poireau, V.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Martinelli, M. et al.
System: The UNT Digital Library