Los Alamos, NM, United States
Los Alamos, NM, United States

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Van Laethem F.,U.S. National Institutes of Health | Tikhonova A.N.,U.S. National Institutes of Health | Tikhonova A.N.,New York University | Pobezinsky L.A.,U.S. National Institutes of Health | And 9 more authors.
Cell | Year: 2013

Thymic selection requires signaling by the protein tyrosine kinase Lck to generate T cells expressing αβ T cell antigen receptors (TCR). For reasons not understood, the thymus selects only αβTCR that are restricted by major histocompatibility complex (MHC)-encoded determinants. Here, we report that Lck proteins that were coreceptor associated promoted thymic selection of conventionally MHC-restricted TCR, but Lck proteins that were coreceptor free promoted thymic selection of MHC-independent TCR. Transgenic TCR with MHC-independent specificity for CD155 utilized coreceptor-free Lck to signal thymic selection in the absence of MHC, unlike any transgenic TCR previously described. Thus, the thymus can select either MHC-restricted or MHC-independent αβTCR depending on whether Lck is coreceptor associated or coreceptor free. We conclude that the intracellular state of Lck determines the specificity of thymic selection and that Lck association with coreceptor proteins during thymic selection is the mechanism by which MHC restriction is imposed on a randomly generated αβTCR repertoire. © 2013 Elsevier Inc.


Lewis A.C.,United States Naval Research Laboratory | Qidwai S.M.,United States Naval Research Laboratory | Geltmacher A.B.,Research Applications Corporation
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science | Year: 2010

Abstract: To determine statistically relevant microstructure-yield correlations in three-dimensional (3-D) microstructures, large volumes comprised of many grains must be studied. With the aim of limiting computational loads without reducing the fidelity of the volume being simulated, this work investigates the use of reduced constitutive parameters, specifically the number of available slip systems, to analyze initial plastic flow in the microstructure. This is performed by embedding a 3-D reconstruction of a single-phase beta-Ti microstructure in a finite element (FE) computational model and subjecting it to a number of loading conditions. Three separate singlecrystal plasticity formulations were used for each loading: reduced 12 slip systems (<111>{110} family), reduced 24 slip systems (<111>{110}+<111>{112} families), and full 48 slip systems (<111>{110}+<111>{112}+<111>{123} families). The analysis results show that the 24-slipsystem model accurately predicts the global stress-strain behavior and locations of initial yield under all loadings, with no more than 10 pct error in the spatial description of local state variables compared to the full 48-slip-system model. The 12-slip-system model generally follows the full model predictions and provides an even better cost improvement, but with errors in excess of 40 pct in local descriptions. Computational cost and data reduction are improved by 26 and 53 pct, respectively. © The Minerals, Metals & Materials Society and ASM International 2010.


Chae J.,Human Genome Research Institutes | Cho Y.-H.,U.S. National Institutes of Health | Lee G.-S.,Human Genome Research Institutes | Cheng J.,U.S. National Institutes of Health | And 4 more authors.
Immunity | Year: 2011

Missense mutations in the C-terminal B30.2 domain of pyrin cause familial Mediterranean fever (FMF), the most common Mendelian autoinflammatory disease. However, it remains controversial as to whether FMF is due to the loss of an inhibitor of inflammation or to the activity of a proinflammatory molecule. We generated both pyrin-deficient mice and " knockin" mice harboring mutant human B30.2 domains. Homozygous knockin, but not pyrin-deficient, mice exhibited spontaneous bone marrow-dependent inflammation similar to but more severe than human FMF. Caspase-1 was constitutively activated in knockin macrophages and active IL-1β was secreted when stimulated with lipopolysaccharide alone, which is also observed in FMF patients. The inflammatory phenotype of knockin mice was completely ablated by crossing with IL-1 receptor-deficient or adaptor molecule ASC-deficient mice, but not NLRP3-deficient mice. Thus, our data provide evidence for an ASC-dependent NLRP3-independent inflammasome in which gain-of-function pyrin mutations cause autoinflammatory disease. © 2011 Elsevier Inc.


Mason R.J.,Research Applications Corporation | Kirkpatrick R.C.,Research Applications Corporation | Faehl R.J.,Research Applications Corporation
Physics of Plasmas | Year: 2014

We report on numerical studies of real viscous effects on the implosion characteristics of imploded DT micro-targets. We use the implicit ePLAS code to perform 2D simulations of spherical and slightly ellipsoidal DT shells on DT gas filled ∼40 μm diameter voids. Before their final implosions the shells have been nearly adiabatically compressed up to 102 or 103 g/cm3 densities. While the use of conventional artificial viscosity can lead to high central densities for initially spherical shells, we find that a real physical viscosity from ion-ion collisions can give a high (>20 keV) central temperature but severely reduced central density (<200 g/cm 3), while the elliptical shells evidence p = 2 distortion of the heated central fuel region. These results suggest that the general use of artificial viscosities in Inertial Confinement Fusion (ICF) modeling may have lead to overly optimistic yields for current NIF targets and that polar direct drive with more energy for the imploding capsule may be needed for ultimate ICF success. © 2014 AIP Publishing LLC.


McCafferty E.,Research Applications Corporation
Electrochimica Acta | Year: 2010

The potential of zero charge of oxide-covered metals (Epzc) is shown to be linear function of the isoelectric point of the oxide film (pHpzc). The linearity is displayed for 14 different metals having n-type semiconductor oxide films and for three metals having p-type semiconductor oxide films. Using experimental values from the literature, the slope of the linear plot of Epzc vs. pHpzc is observed to be -0.142 V for n-type oxides and -0.115 V for p-type oxides. The theoretical slope is -0.120 V, which is derived in this communication. © 2009.


McCafferty E.,Research Applications Corporation
Journal of Applied Electrochemistry | Year: 2010

The free energy change is calculated for the interaction of 19 different oxyanions (metalates) with iron (steel) or aluminum surfaces. The oxyanions considered here are those of the transition metals in the fourth through sixth periods of the periodic table. The oxyanions which produce more negative values of ΔG o (per mole of oxyanion) than that of chromate (CrO 4-2) are permanganate (MnO4-), nickelate (NiO4-2), ruthenate (RuO4- or RuO4-2), and rhodate (RhO4-2). The oxyanions which produce values of ΔG o (per mole of oxyanion) similar to CrO4-2 are osmate (OsO 4-2), and iridate (IrO4-2). © 2009 Naval Research Laboratory, Washington DC.


McCafferty E.,Research Applications Corporation
Electrochimica Acta | Year: 2010

Expressions are derived to calculate the equilibrium oxidation-reduction potentials for the Al+3/Al, Cu+2/Cu, and Zn+2/Zn systems in small-scale electrolytes. The geometrical system consists of a droplet of electrolyte resting on a flat metal plate, and the metal is considered to be immersed in a solution of its own ions. When the radius of the drop is allowed to vary, both the size of the electrolyte and the size of the active metal beneath the droplet change simultaneously. The total free energy change for the system consists of both electrochemical and surface chemical contributions. The interfacial free energy for the solid/liquid interface has been estimated from the Girifalco-Good expression or from spreading pressure considerations. When the droplet becomes sufficiently small in radius, the surface chemical contributions become significant, and the calculated redox potential changes from its normal value to more negative values as the size of the system decreases. The magnitude of this effect depends on the particular system. For 2 M Cu+2, the calculated redox potential for a 0.8 nm radius droplet is 0.259 V more negative than for the bulk electrolyte. The effect is much smaller for aluminum and zinc. In all three systems, calculated redox potentials approach values for the bulk solution for droplet radii of about 10 nm. © 2010 Elsevier Ltd. All rights reserved.


McCafferty E.,Research Applications Corporation
Journal of the Electrochemical Society | Year: 2010

The pitting corrosion of aluminum is modeled as a queueing process in which chloride ions (customers or units) enter the passive film and are serviced (form an emerging pit) at certain sites (servers) at the oxide/metal interface. X-ray photoelectron spectroscopy (XPS) data show that chloride ions penetrate the passive film on aluminum and are considered to lie in a queue. The servicing (or processing) stage includes chloride-assisted localized dissolution of aluminum, development of local acidity within the emerging pit, and buildup of chloride ions within the developing pit. The arrival rate (λ) of chloride ions is determined from quantitative XPS intensity data. The servicing rate (μ) has been determined from anodic polarization curves and also from Scully's criterion for stable pit growth. The following queueing characteristic parameters have been calculated: the number of units (Lq) in the queue, the number of units (L) in the system (queue plus server), the average time (Wq) a unit spends in the queue, and the average time (W) a unit spends in the system (queue and server). This is done for the following queueing systems: single queue with a single server, single queue with multiple servers, and multiple queues with single or multiple servers. A long time (W) in the system corresponds to a low rate for the ongoing corrosion reaction. The time (W) that a unit spends in the system is maximized for (i) a decrease in the number of servers, (ii) a decrease in the servicing rate μ, (iii) a decrease in the number of queues, or (iv) an increase in the arrival rate (up to λ=μ). © 2010 The Electrochemical Society.


Grant
Agency: Department of Energy | Branch: | Program: SBIR | Phase: Phase I | Award Amount: 150.00K | Year: 2011

High energy density laboratory plasmas (HEDLP) present unique opportunities for the extraction of clean energy from Fusion. Intense lasers and particle beams can create and interact with such plasmas, potentially yielding sufficient energy to satisfy all our national needs. However, few models are available to help aid the scientific community in the study and optimization of such interactions. This project will further enhance and disseminate the computer code, ePLAS, for the early understanding and control of Ignition in HEDLP for Fusion energy. ePLAS is a unique simulation code that tracks the transport of laser light to a target, the absorption of that light resulting in the generation and transport of hot electrons, and the heating and flow dynamics of the background plasma. It uses an implicit electromagnetic field-solving method to greatly reduce computing demands, so that useful target interaction studies can often be completed in 15 minutes on a portable 2.1 GHz PC. ePLAS permits the rapid scoping of calculations for the optimization of laser target interactions aimed at fusion. Recent efforts have initiated the use of analytic equations of state (EOS), K-alpha image rendering graphics, allocatable memory for source-free usage, and adaption to the latest Mac and Linux Operating Systems. The speed and utility of ePLAS are unequaled in the HEDLP simulation community. This project will work to enhance, test, document, and distribute an improved ePLAS for economical HEDLP community use: 1) for hot electron interactions - RAC will evaluate the effects of its new EOSs on target heating, 2) for fast ion driven studies - it will compare fluid and particle models for the ions and initiate the simultaneous use of both ion models in the code, 3) for shock ignition - it will study long time scale, 500 ps hot electron deposition, and 4) for improved utility - it will enable 64-bit W7 OS computing. RACs efforts will also include: a) the creation of an improved online manual, b) the initiation of a new GUI interface for input, c) additions to the codes present IDL Virtual Machine applications for visualization, d) the early exploration of shared memory multi-core parallelization, and e) preparation of a publication detailing current ePLAS features. Commercial Applications and Other Benefits: Implicit/hybrid plasma simulation codes are not generally available in industry or academia. ePLAS has been granted EAR99 export control status, permitting export without a license to most foreign countries. Beta-test versions of ePLAS have been granted to several Universities and commercial users. RAC will explore low cost code distribution for students and researchers via the company site: http://www.researchapplicationscorp.com


Grant
Agency: Department of Energy | Branch: | Program: SBIR | Phase: Phase I | Award Amount: 100.00K | Year: 2010

Fusion power is needed to meet the world

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