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Sample records for core junctions modelling

  1. A Cul-3-BTB ubiquitylation pathway regulates junctional levels and asymmetry of core planar polarity proteins

    PubMed Central

    Strutt, Helen; Searle, Elizabeth; Thomas-MacArthur, Victoria; Brookfield, Rosalind; Strutt, David

    2013-01-01

    The asymmetric localisation of core planar polarity proteins at apicolateral junctions is required to specify cell polarity in the plane of epithelia. This asymmetric distribution of the core proteins is proposed to require amplification of an initial asymmetry by feedback loops. In addition, generation of asymmetry appears to require the regulation of core protein levels, but the importance of such regulation and the underlying mechanisms is unknown. Here we show that ubiquitylation acts through more than one mechanism to control core protein levels in Drosophila, and that without this regulation cellular asymmetry is compromised. Levels of Dishevelled at junctions are regulated by a Cullin-3-Diablo/Kelch ubiquitin ligase complex, the activity of which is most likely controlled by neddylation. Furthermore, activity of the deubiquitylating enzyme Fat facets is required to maintain Flamingo levels at junctions. Notably, ubiquitylation does not alter the total cellular levels of Dishevelled or Flamingo, but only that of the junctional population. When junctional core protein levels are either increased or decreased by disruption of the ubiquitylation machinery, their asymmetric localisation is reduced and this leads to disruption of planar polarity at the tissue level. Loss of asymmetry by altered core protein levels can be explained by reference to feedback models for amplification of asymmetry. PMID:23487316

  2. Nanooptics of Plasmonic Nanomatryoshkas: Shrinking the Size of a Core-Shell Junction to Subnanometer.

    PubMed

    Lin, Li; Zapata, Mario; Xiong, Min; Liu, Zhonghui; Wang, Shanshan; Xu, Hong; Borisov, Andrei G; Gu, Hongchen; Nordlander, Peter; Aizpurua, Javier; Ye, Jian

    2015-10-14

    Quantum effects in plasmonic systems play an important role in defining the optical response of structures with subnanometer gaps. Electron tunneling across the gaps can occur, altering both the far-field optical response and the near-field confinement and enhancement. In this study, we experimentally and theoretically investigate plasmon coupling in gold "nanomatryoshka" (NM) nanoparticles with different core-shell separations. Plasmon coupling effects between the core and the shell become significant when their separation decreases to 15 nm. When their separation decreases to below 1 nm, the near- and far-field properties can no longer be described by classical approaches but require the inclusion of quantum mechanical effects such as electron transport through the self-assembled monolayer of molecular junction. In addition, surface-enhanced Raman scattering measurements indicate strong electron-transport induced charge transfer across the molecular junction. Our quantum modeling provides an estimate for the AC conductances of molecules in the junction. The insights acquired from this work pave the way for the development of novel quantum plasmonic devices and substrates for surface-enhanced Raman scattering. PMID:26375710

  3. Global Core Plasma Model

    NASA Technical Reports Server (NTRS)

    Gallagher, Dennis L.; Craven, P. D.; Comfort, R. H.

    1999-01-01

    Abstract. The Global Core Plasma Model (GCPM) provides, empirically derived, core plasma density as a function of geomagnetic and solar conditions throughout the inner magnetosphere. It is continuous in value and gradient and is composed of separate models for the ionosphere, the plasmasphere, the plasmapause, the trough, and the polar cap. The relative composition of plasmaspheric H+, He+, and O+ is included in the GCPM. A blunt plasmaspheric bulge and rotation of the bulge with changing geomagnetic conditions is included. The GCPM is an amalgam of density models, intended to serve as a framework for continued improvement as new measurements become available and are used to characterize core plasma density, composition, and temperature.

  4. Electrostatic Modeling of Vacuum Insulator Triple Junctions

    SciTech Connect

    Tully, L K; Goerz, D A; Houck, T L; Javedani, J B

    2006-10-25

    Triple junctions are often initiation points for insulator flashover in pulsed power devices. The two-dimensional finite-element TriComp [1] modeling software suite was utilized for its electrostatic field modeling package to investigate electric field behavior in the anode and cathode triple junctions of a high voltage vacuum-insulator interface. TriComp enables simple extraction of values from a macroscopic solution for use as boundary conditions in a subset solution. Electric fields computed with this zoom capability correlate with theoretical analysis of the anode and cathode triple junctions within submicron distances for nominal electrode spacing of 1.0 cm. This paper will discuss the iterative zoom process with TriComp finite-element software and the corresponding theoretical verification of the results.

  5. Coordinate transformation in the model of long Josephson junctions: geometrically equivalent Josephson junctions

    NASA Astrophysics Data System (ADS)

    Semerdzhieva, E. G.; Boyadzhiev, T. L.; Shukrinov, Yu. M.

    2005-10-01

    The transition from the model of a long Josephson junction of variable width to the model of a junction with a coordinate-dependent Josephson current amplitude is effected through a coordinate transformation. This establishes the correspondence between the classes of Josephson junctions of variable width and quasi-one-dimensional junctions with a variable thickness of the barrier layer. It is shown that for a junction of exponentially varying width the barrier layer of the equivalent quasi-one-dimensional junction has a distributed resistive inhomogeneity that acts as an attractor for magnetic flux vortices. The curve of the critical current versus magnetic field for a Josephson junction with a resistive microinhomogeneity is constructed with the aid of a numerical simulation, and a comparison is made with the critical curve of a junction of exponentially varying width. The possibility of replacing a distributed inhomogeneity in a Josephson junction by a local inhomogeneity at the end of the junction is thereby demonstrated; this can have certain advantages from a technological point of view.

  6. Model Building to Facilitate Understanding of Holliday Junction and Heteroduplex Formation, and Holliday Junction Resolution

    ERIC Educational Resources Information Center

    Selvarajah, Geeta; Selvarajah, Susila

    2016-01-01

    Students frequently expressed difficulty in understanding the molecular mechanisms involved in chromosomal recombination. Therefore, we explored alternative methods for presenting the two concepts of the double-strand break model: Holliday junction and heteroduplex formation, and Holliday junction resolution. In addition to a lecture and…

  7. Flexible Photodiodes Based on Nitride Core/Shell p–n Junction Nanowires

    PubMed Central

    2016-01-01

    A flexible nitride p-n photodiode is demonstrated. The device consists of a composite nanowire/polymer membrane transferred onto a flexible substrate. The active element for light sensing is a vertical array of core/shell p–n junction nanowires containing InGaN/GaN quantum wells grown by MOVPE. Electron/hole generation and transport in core/shell nanowires are modeled within nonequilibrium Green function formalism showing a good agreement with experimental results. Fully flexible transparent contacts based on a silver nanowire network are used for device fabrication, which allows bending the detector to a few millimeter curvature radius without damage. The detector shows a photoresponse at wavelengths shorter than 430 nm with a peak responsivity of 0.096 A/W at 370 nm under zero bias. The operation speed for a 0.3 × 0.3 cm2 detector patch was tested between 4 Hz and 2 kHz. The −3 dB cutoff was found to be ∼35 Hz, which is faster than the operation speed for typical photoconductive detectors and which is compatible with UV monitoring applications. PMID:27615556

  8. Global Core Plasma Model

    NASA Technical Reports Server (NTRS)

    Gallagher, Dennis L.; Craven, Paul D.; Comfort, Richard H.

    1999-01-01

    Over 40 years of ground and spacecraft plasmaspheric measurements have resulted in many statistical descriptions of plasmaspheric properties. In some cases, these properties have been represented as analytical descriptions that are valid for specific regions or conditions. For the most part, what has not been done is to extend regional empirical descriptions or models to the plasmasphere as a whole. In contrast, many related investigations depend on the use of representative plasmaspheric conditions throughout the inner magnetosphere. Wave propagation, involving the transport of energy through the magnetosphere, is strongly affected by thermal plasma density and its composition. Ring current collisional and wave particle losses also strongly depend on these quantities. Plasmaspheric also plays a secondary role in influencing radio signals from the Global Positioning System satellites. The Global Core Plasma Model (GCPM) is an attempt to assimilate previous empirical evidence and regional models for plasmaspheric density into a continuous, smooth model of thermal plasma density in the inner magnetosphere. In that spirit, the International Reference Ionosphere is currently used to complete the low altitude description of density and composition in the model. The models and measurements on which the GCPM is currently based and its relationship to IRI will be discussed.

  9. Metallic Electrode: Semiconducting Nanotube Junction Model

    NASA Technical Reports Server (NTRS)

    Yamada, Toshishige; Biegel, Bryon (Technical Monitor)

    2001-01-01

    A model is proposed for two observed current-voltage (I-V) patterns in an experiment with a scanning tunneling microscope tip and a carbon nanotube [Collins et al., Science 278, 100 ('97)]. We claim that there are two contact modes for a tip (metal) -nanotube semi conductor) junction depending whether the alignment of the metal and semiconductor band structure is (1) variable (vacuum-gap) or (2) fixed (touching) with V. With the tip grounded, the tunneling case in (1) would produce large dI/dV with V > 0, small dI/dV with V < 0, and I = 0 near V = 0 for an either n- or p-nanotube. However, the Schottky mechanism in (2) would result in forward current with V < 0 for an n-nanotube, while with V > 0 for an p-nanotube. The two observed I-V patterns are thus entirely explained by a tip-nanotube contact of the two types, where the nanotube must be n-type. We apply this picture to the source-drain I-V characteristics in a long nanotube-channel field-effect-transistor (Zhou et al., Appl. Phys. Lett. 76, 1597 ('00)], and show that two independent metal-semiconductor junctions connected in series are responsible for the observed behavior.

  10. Direct imaging of p-n junction in core-shell GaN wires.

    PubMed

    Tchoulfian, P; Donatini, F; Levy, F; Dussaigne, A; Ferret, P; Pernot, J

    2014-06-11

    While core-shell wire-based devices offer a promising path toward improved optoelectronic applications, their development is hampered by the present uncertainty about essential semiconductor properties along the three-dimensional (3D) buried p-n junction. Thanks to a cross-sectional approach, scanning electron beam probing techniques were employed here to obtain a nanoscale spatially resolved analysis of GaN core-shell wire p-n junctions grown by catalyst-free metal-organic vapor phase epitaxy on GaN and Si substrates. Both electron beam induced current (EBIC) and secondary electron voltage constrast (VC) were demonstrated to delineate the radial and axial junction existing in the 3D structure. The Mg dopant activation process in p-GaN shell was dynamically controlled by the ebeam exposure conditions and visualized thanks to EBIC mapping. EBIC measurements were shown to yield local minority carrier/exciton diffusion lengths on the p-side (∼57 nm) and the n-side (∼15 nm) as well as depletion width in the range 40-50 nm. Under reverse bias conditions, VC imaging provided electrostatic potential maps in the vicinity of the 3D junction from which acceptor Na and donor Nd doping levels were locally determined to be Na = 3 × 10(18) cm(-3) and Nd = 3.5 × 10(18) cm(-3) in both the axial and the radial junction. Results from EBIC and VC are in good agreement. This nanoscale approach provides essential guidance to the further development of core-shell wire devices.

  11. Models of the Earth's Core.

    PubMed

    Stevenson, D J

    1981-11-01

    Combined inferences from seismology, high-pressure experiment and theory, geomagnetism, fluid dynamics, and current views of terrestrial planetary evolution lead to models of the earth's core with the following properties. Core formation was contemporaneous with earth accretion; the core is not in chemical equilibrium with the mantle; the outer core is a fluid iron alloy containing significant quantities of lighter elements and is probably almost adiabatic and compositionally uniform; the more iron-rich inner solid core is a consequence of partial freezing of the outer core, and the energy release from this process sustains the earth's magnetic field; and the thermodynamic properties of the core are well constrained by the application of liquid-state theory to seismic and laboratory data. PMID:17839632

  12. DNA Three Way Junction Core Decorated with Amino Acids-Like Residues-Synthesis and Characterization.

    PubMed

    Addamiano, Claudia; Gerland, Béatrice; Payrastre, Corinne; Escudier, Jean-Marc

    2016-01-01

    Construction and physico-chemical behavior of DNA three way junction (3WJ) functionalized by protein-like residues (imidazole, alcohol and carboxylic acid) at unpaired positions at the core is described. One 5'-C(S)-propargyl-thymidine nucleotide was specifically incorporated on each strand to react through a post synthetic CuACC reaction with either protected imidazolyl-, hydroxyl- or carboxyl-azide. Structural impacts of 5'-C(S)-functionalization were investigated to evaluate how 3WJ flexibility/stability is affected. PMID:27563857

  13. Lunar magnetism. [primordial core model

    NASA Technical Reports Server (NTRS)

    Goldstein, M. L.

    1975-01-01

    It is shown, for a very simple model of the moon, that the existence of a primordial core magnetic field would give rise to a present day nonzero dipole external field. In the investigation a uniformly magnetized core embedded in a permeable mantle is considered. The significance of the obtained results for the conclusions reported by Runcorn (1975) is discussed. Comments provided by Runcorn to the discussion are also presented.

  14. The influence of the instabilities in modelling arteriovenous junction haemodynamics.

    PubMed

    Broderick, Stephen P; Houston, J Graeme; Walsh, Michael T

    2015-10-15

    The arteriovenous junction is characterised by high flow rates, large pressure difference and typically a palpable thrill or audible bruit, associated with turbulent flow. However, the arteriovenous junction is frequently studied with the assumption of streamline flow. This assumption is based on the Reynolds number calculation, although other factors can contribute to turbulent generation. In this study, the presence of instabilities is examined and the influencing factors discussed. This was performed using a pseudo-realistic geometry with adapted graft angles, vein diameter, outflow split ratio and graft inlet velocity values. Correlation was performed between steady and unsteady averaged simulation cases with correlation performance ranked. Overall the arteriovenous junction is capable of possessing highly disturbed flows, in which strict modelling requirements are necessary to capture such instabilities and avoid erroneous conclusions. Vein diameter and flow split ratio contribute to turbulent generation, thus Reynolds number cannot be used as a sole turbulent criterion in the arteriovenous junction. PMID:26315920

  15. Application of Core Dynamics Modeling to Core-Mantle Interactions

    NASA Technical Reports Server (NTRS)

    Kuang, Weijia

    2003-01-01

    Observations have demonstrated that length of day (LOD) variation on decadal time scales results from exchange of axial angular momentum between the solid mantle and the core. There are in general four core-mantle interaction mechanisms that couple the core and the mantle. Of which, three have been suggested likely the dominant coupling mechanism for the decadal core-mantle angular momentum exchange, namely, gravitational core-mantle coupling arising from density anomalies in the mantle and in the core (including the inner core), the electromagnetic coupling arising from Lorentz force in the electrically conducting lower mantle (e.g. D-layer), and the topographic coupling arising from non-hydrostatic pressure acting on the core-mantle boundary (CMB) topography. In the past decades, most effort has been on estimating the coupling torques from surface geomagnetic observations (kinematic approach), which has provided insights on the core dynamical processes. In the meantime, it also creates questions and concerns on approximations in the studies that may invalidate the corresponding conclusions. The most serious problem is perhaps the approximations that are inconsistent with dynamical processes in the core, such as inconsistencies between the core surface flow beneath the CMB and the CMB topography, and that between the D-layer electric conductivity and the approximations on toroidal field at the CMB. These inconsistencies can only be addressed with numerical core dynamics modeling. In the past few years, we applied our MoSST (Modular, Scalable, Self-consistent and Three-dimensional) core dynamics model to study core-mantle interactions together with geodynamo simulation, aiming at assessing the effect of the dynamical inconsistencies in the kinematic studies on core-mantle coupling torques. We focus on topographic and electromagnetic core-mantle couplings and find that, for the topographic coupling, the consistency between the core flow and the CMB topography is

  16. Haploinsufficiency for Core Exon Junction Complex Components Disrupts Embryonic Neurogenesis and Causes p53-Mediated Microcephaly.

    PubMed

    Mao, Hanqian; McMahon, John J; Tsai, Yi-Hsuan; Wang, Zefeng; Silver, Debra L

    2016-09-01

    The exon junction complex (EJC) is an RNA binding complex comprised of the core components Magoh, Rbm8a, and Eif4a3. Human mutations in EJC components cause neurodevelopmental pathologies. Further, mice heterozygous for either Magoh or Rbm8a exhibit aberrant neurogenesis and microcephaly. Yet despite the requirement of these genes for neurodevelopment, the pathogenic mechanisms linking EJC dysfunction to microcephaly remain poorly understood. Here we employ mouse genetics, transcriptomic and proteomic analyses to demonstrate that haploinsufficiency for each of the 3 core EJC components causes microcephaly via converging regulation of p53 signaling. Using a new conditional allele, we first show that Eif4a3 haploinsufficiency phenocopies aberrant neurogenesis and microcephaly of Magoh and Rbm8a mutant mice. Transcriptomic and proteomic analyses of embryonic brains at the onset of neurogenesis identifies common pathways altered in each of the 3 EJC mutants, including ribosome, proteasome, and p53 signaling components. We further demonstrate all 3 mutants exhibit defective splicing of RNA regulatory proteins, implying an EJC dependent RNA regulatory network that fine-tunes gene expression. Finally, we show that genetic ablation of one downstream pathway, p53, significantly rescues microcephaly of all 3 EJC mutants. This implicates p53 activation as a major node of neurodevelopmental pathogenesis following EJC impairment. Altogether our study reveals new mechanisms to help explain how EJC mutations influence neurogenesis and underlie neurodevelopmental disease. PMID:27618312

  17. Haploinsufficiency for Core Exon Junction Complex Components Disrupts Embryonic Neurogenesis and Causes p53-Mediated Microcephaly

    PubMed Central

    Wang, Zefeng; Silver, Debra L.

    2016-01-01

    The exon junction complex (EJC) is an RNA binding complex comprised of the core components Magoh, Rbm8a, and Eif4a3. Human mutations in EJC components cause neurodevelopmental pathologies. Further, mice heterozygous for either Magoh or Rbm8a exhibit aberrant neurogenesis and microcephaly. Yet despite the requirement of these genes for neurodevelopment, the pathogenic mechanisms linking EJC dysfunction to microcephaly remain poorly understood. Here we employ mouse genetics, transcriptomic and proteomic analyses to demonstrate that haploinsufficiency for each of the 3 core EJC components causes microcephaly via converging regulation of p53 signaling. Using a new conditional allele, we first show that Eif4a3 haploinsufficiency phenocopies aberrant neurogenesis and microcephaly of Magoh and Rbm8a mutant mice. Transcriptomic and proteomic analyses of embryonic brains at the onset of neurogenesis identifies common pathways altered in each of the 3 EJC mutants, including ribosome, proteasome, and p53 signaling components. We further demonstrate all 3 mutants exhibit defective splicing of RNA regulatory proteins, implying an EJC dependent RNA regulatory network that fine-tunes gene expression. Finally, we show that genetic ablation of one downstream pathway, p53, significantly rescues microcephaly of all 3 EJC mutants. This implicates p53 activation as a major node of neurodevelopmental pathogenesis following EJC impairment. Altogether our study reveals new mechanisms to help explain how EJC mutations influence neurogenesis and underlie neurodevelopmental disease. PMID:27618312

  18. A device model for the tandem junction solar cell

    NASA Technical Reports Server (NTRS)

    Matzen, W. T.; Chiang, S. Y.; Carbajal, B. G.

    1979-01-01

    A conceptual device model has been developed to explain operation of the tandem junction cell (TJC) when back contacts only are used. Operation and parameters of the cell are explained by transistor action. Experimental observations are presented which confirm that current is collected for carrier generation in the front uncontacted n(plus) region. The model should be useful as a guideline to optimize the TJC by application of transistor design principles.

  19. Extension of the ADC Charge-Collection Model to Include Multiple Junctions

    NASA Technical Reports Server (NTRS)

    Edmonds, Larry D.

    2011-01-01

    The ADC model is a charge-collection model derived for simple p-n junction silicon diodes having a single reverse-biased p-n junction at one end and an ideal substrate contact at the other end. The present paper extends the model to include multiple junctions, and the goal is to estimate how collected charge is shared by the different junctions.

  20. A Model for the Behavior of Magnetic Tunnel Junctions

    SciTech Connect

    Bryan John Baker

    2003-08-05

    A magnetic tunnel junction is a device that changes its electrical resistance with a change in an applied magnetic field. A typical junction consists of two magnetic electrodes separated by a nonmagnetic insulating layer. The magnetizations of the two electrodes can have two possible extreme configurations, parallel and antiparallel. The antiparallel configuration is observed to have the higher measured resistance and the parallel configuration has the lower resistance. To switch between these two configurations a magnetic field is applied to the device which is primarily used to change the orientation of the magnetization of one electrode usually called the free layer, although with sufficient high magnetic field the orientation of the magnetizations of both of the electrodes can be changed. The most commonly used models for describing and explaining the electronic behavior of tunnel junctions are the Simmons model and the Brinkman model. However, both of these models were designed for simple, spin independent tunneling. The Simmons model does not address the issue of applied magnetic fields nor does it address the form of the electronic band structure in the metallic electrodes, including the important factor of spin polarization. The Brinkman model is similar, the main difference between the two models being the shape of the tunneling barrier potential between the two electrodes. Therefore, the research conducted in this thesis has developed a new theoretical model that addresses these important issues starting from basic principles. The main features of the new model include: the development of equations for true spin dependent tunneling through the insulating barrier, the differences in the orientations of the electrode magnetizations on either side of the barrier, and the effects of the density of states function on the behavior of the junction. The present work has explored densities of states that are more realistic than the simplified free electron density

  1. Summary of mathematical models for a conventional and vertical junction photoconverter

    NASA Technical Reports Server (NTRS)

    Heinbockel, J. H.

    1986-01-01

    The geometry and computer programming for mathematical models of a one-dimensional conventional photoconverter, a one-dimensional vertical junction photoconverter, a three-dimensional conventinal photoconverter, and a three-dimensional vertical junction solar cell are discussed.

  2. The core legion object model

    SciTech Connect

    Lewis, M.; Grimshaw, A.

    1996-12-31

    The Legion project at the University of Virginia is an architecture for designing and building system services that provide the illusion of a single virtual machine to users, a virtual machine that provides secure shared object and shared name spaces, application adjustable fault-tolerance, improved response time, and greater throughput. Legion targets wide area assemblies of workstations, supercomputers, and parallel supercomputers, Legion tackles problems not solved by existing workstation based parallel processing tools; the system will enable fault-tolerance, wide area parallel processing, inter-operability, heterogeneity, a single global name space, protection, security, efficient scheduling, and comprehensive resource management. This paper describes the core Legion object model, which specifies the composition and functionality of Legion`s core objects-those objects that cooperate to create, locate, manage, and remove objects in the Legion system. The object model facilitates a flexible extensible implementation, provides a single global name space, grants site autonomy to participating organizations, and scales to millions of sites and trillions of objects.

  3. Inflow Models of Nearby Cores

    NASA Astrophysics Data System (ADS)

    De La Cruz, David; De Vries, C. H.; Arce, H. G.

    2012-01-01

    We obtained observations of nearby (d < 300 pc) isolated pre-stellar and Class 0 cores from the Caltech Submillimeter Observatory. The optically thick HCO+ J=3-2 rotational transition was observed in order to detect the blue-asymmetric infall signature often seen in pre-stellar cores. The asymmetric spectral line profiles were analyzed by using a 1-D radiative transfer model that assumes a uniform infall velocity and a realistic radial excitation profile. The model is able to reproduce the asymmetric line profile in most cases by varying only 5 physical cloud parameters. The analysis was used to obtain a reliable estimate of the infall rate. The sources presented here and observed in the HCO+ J=3-2 rotational transition were B228, CB130 SMM2, OPH MM 126, and RCRA SMM1A. Analysis of these spectra yielded some unexpected results. Our analysis did a good job at fitting the spectral lines in some sources while it performed poorly for others. We observed infall velocities ranging from -1.1, indicating expansion, to 0.4 km/s in these sources and found line center optical depths ranging from 0.03 to 520. The peak excitation temperature for the HCO+ J=3-2 transition was found to range from 3 to 57 K.

  4. Models of human core transcriptional regulatory circuitries

    PubMed Central

    Saint-André, Violaine; Federation, Alexander J.; Lin, Charles Y.; Abraham, Brian J.; Reddy, Jessica; Lee, Tong Ihn; Bradner, James E.; Young, Richard A.

    2016-01-01

    A small set of core transcription factors (TFs) dominates control of the gene expression program in embryonic stem cells and other well-studied cellular models. These core TFs collectively regulate their own gene expression, thus forming an interconnected auto-regulatory loop that can be considered the core transcriptional regulatory circuitry (CRC) for that cell type. There is limited knowledge of core TFs, and thus models of core regulatory circuitry, for most cell types. We recently discovered that genes encoding known core TFs forming CRCs are driven by super-enhancers, which provides an opportunity to systematically predict CRCs in poorly studied cell types through super-enhancer mapping. Here, we use super-enhancer maps to generate CRC models for 75 human cell and tissue types. These core circuitry models should prove valuable for further investigating cell-type–specific transcriptional regulation in healthy and diseased cells. PMID:26843070

  5. Phase dynamics modeling of parallel stacks of Josephson junctions

    NASA Astrophysics Data System (ADS)

    Rahmonov, I. R.; Shukrinov, Yu. M.

    2014-11-01

    The phase dynamics of two parallel connected stacks of intrinsic Josephson junctions (JJs) in high temperature superconductors is numerically investigated. The calculations are based on the system of nonlinear differential equations obtained within the CCJJ + DC model, which allows one to determine the general current-voltage characteristic of the system, as well as each individual stack. The processes with increasing and decreasing base currents are studied. The features in the behavior of the current in each stack of the system due to the switching between the states with rotating and oscillating phases are analyzed.

  6. Doping GaP Core-Shell Nanowire pn-Junctions: A Study by Off-Axis Electron Holography.

    PubMed

    Yazdi, Sadegh; Berg, Alexander; Borgström, Magnus T; Kasama, Takeshi; Beleggia, Marco; Samuelson, Lars; Wagner, Jakob B

    2015-06-10

    The doping process in GaP core-shell nanowire pn-junctions using different precursors is evaluated by mapping the nanowires' electrostatic potential distribution by means of off-axis electron holography. Three precursors, triethyltin (TESn), ditertiarybutylselenide, and silane are investigated for n-type doping of nanowire shells; among them, TESn is shown to be the most efficient precursor. Off-axis electron holography reveals higher electrostatic potentials in the regions of nanowire cores grown by the vapor-liquid-solid (VLS) mechanism (axial growth) than the regions grown parasitically by the vapor-solid (VS) mechanism (radial growth), attributed to different incorporation efficiency between VLS and VS of unintentional p-type carbon doping originating from the trimethylgallium precursor. This study shows that off-axis electron holography of doped nanowires is unique in terms of the ability to map the electrostatic potential and thereby the active dopant distribution with high spatial resolution.

  7. Models and methods for in vitro testing of hepatic gap junctional communication

    PubMed Central

    Willebrords, Joost; Vinken, Mathieu

    2015-01-01

    Inherent to their pivotal roles in controlling all aspects of the liver cell life cycle, hepatocellular gap junctions are frequently disrupted upon impairment of the homeostatic balance, as occurs during liver toxicity. Hepatic gap junctions, which are mainly built up by connexin32, are specifically targeted by tumor promoters and epigenetic carcinogens. This renders inhibition of gap junction functionality a suitable indicator for the in vitro detection of nongenotoxic hepatocarcinogenicity. The establishment of a reliable liver gap junction inhibition assay for routine in vitro testing purposes requires a cellular system in which gap junctions are expressed at an in vivo-like level as well as an appropriate technique to probe gap junction activity. Both these models and methods are discussed in the current paper, thereby focusing on connexin32-based gap junctions. PMID:26420514

  8. A Model of Tight Junction Function In CNS Myelinated Axons

    PubMed Central

    Gow, Alexander; Devaux, Jerome

    2010-01-01

    The insulative properties of myelin sheaths in the central and peripheral nervous systems (CNS and PNS) are widely thought to derive from the high resistance and low capacitance of the constituent membranes. Although this view adequately accounts for myelin function in large diameter PNS fibers, it poorly reflects the behavior of small fibers that are prominent in many regions of the CNS. Herein, we develop a computational model to more accurately represent conduction in small fibers. By incorporating structural features that, hitherto, have not been simulated, we demonstrate that myelin tight junctions improve saltatory conduction by reducing current flow through the myelin, limiting axonal membrane depolarization and restraining the activation of ion channels beneath the myelin sheath. Accordingly, our simulations provide a novel view of myelin by which tight junctions minimize charging of the membrane capacitance and lower the membrane time constant to improve the speed and accuracy of transmission in small diameter fibers. This study establishes possible mechanisms whereby TJs affect conduction in the absence of overt perturbations to myelin architecture and may in part explain the tremor and gait abnormalities observed in Claudin 11-null mice. PMID:20102674

  9. Strains at the myotendinous junction predicted by a micromechanical model

    PubMed Central

    Sharafi, Bahar; Ames, Elizabeth G.; Holmes, Jeffrey W.; Blemker, Silvia S.

    2011-01-01

    The goal of this work was to create a finite element micromechanical model of the myotendinous junction (MTJ) to examine how the structure and mechanics of the MTJ affect the local micro-scale strains experienced by muscle fibers. We validated the model through comparisons with histological longitudinal sections of muscles fixed in slack and stretched positions. The model predicted deformations of the A-bands within the fiber near the MTJ that were similar to those measured from the histological sections. We then used the model to predict the dependence of local fiber strains on activation and the mechanical properties of the endomysium. The model predicted that peak micro-scale strains increase with activation and as the compliance of the endomysium decreases. Analysis of the models revealed that, in passive stretch, local fiber strains are governed by the difference of the mechanical properties between the fibers and the endomysium. In active stretch, strain distributions are governed by the difference in cross-sectional area along the length of the tapered region of the fiber near the MTJ. The endomysium provides passive resistance that balances the active forces and prevents the tapered region of the fiber from undergoing excessive strain. These model predictions lead to the following hypotheses: (i) the increased likelihood of injury during active lengthening of muscle fibers may be due to the increase in peak strain with activation and (ii) endomysium may play a role in protecting fibers from injury by reducing the strains within the fiber at the MTJ. PMID:21945569

  10. Molecular Motion of the Junction Points in Model Networks Prepared by Acyclic Triene Metathesis.

    PubMed

    da Silva, Lucas Caire; Bowers, Clifford R; Graf, Robert; Wagener, Kenneth B

    2016-03-01

    The junction dynamics in a selectively deuterated model polymer network containing junctions on every 21st chain carbon is studied by solid state (2) H echo NMR. Polymer networks are prepared via acyclic triene metathesis of deuteron-labeled symmetric trienes with deuteron probes precisely placed at the alpha carbon relative to the junction point. The effect of decreasing the cross-link density on the junction dynamics is studied by introduction of polybutadiene chains in-between junctions. The networks are characterized by swelling, gel content, and solid state (1) H MAS NMR. Line shape analysis of the (2) H quadrupolar echo spectra reveals that the degree of motion anisotropy and the distribution of motion correlation times depend on the cross-link density and structural heterogeneity of the polymer networks. A detailed model of the junction dynamics at different temperatures is proposed and explained in terms of the intermolecular cooperativity in densely-packed systems. PMID:26787457

  11. Negative differential resistance in GeSi core-shell transport junctions: the role of local sp(2) hybridization.

    PubMed

    Liu, Nuo; Zhang, Lei; Chen, Xiaobin; Kong, Xianghua; Zheng, Xiaohong; Guo, Hong

    2016-09-21

    We report a theoretical investigation of nonlinear quantum transport properties of Au/GeSi/Au junctions. For GeSi semiconducting core-shell structures brought into contact with Au electrodes, a very unusual behavior is that the tunneling transport is on-resonance right at equilibrium. This resonance is not due to the alignment of a quantum level in GeSi to the electrochemical potential of Au, but due to the alignment of very sharp DOS features - hot spots, localized at the two Au/GeSi interfaces of the device. An applied bias voltage shifts the hot spots relative to each other which gives rise to substantial negative differential resistance (NDR). The hot spots localized at the two interfaces were found to be due to the unbonded pz orbital of a sp(2) hybridized interface Si atom which is surrounded by three non-sp(2) hybridized neighbors. The mechanism of inducing hot spots and NDR by a local structure unit is not limited to the GeSi. The results suggest an interesting scheme for constructing NDR devices by orbital manipulation, to be more explicit, for example, by designing local structural units having unbonded orbitals at the interfaces between electrodes and the central region of the transport junction.

  12. Negative differential resistance in GeSi core-shell transport junctions: the role of local sp(2) hybridization.

    PubMed

    Liu, Nuo; Zhang, Lei; Chen, Xiaobin; Kong, Xianghua; Zheng, Xiaohong; Guo, Hong

    2016-09-21

    We report a theoretical investigation of nonlinear quantum transport properties of Au/GeSi/Au junctions. For GeSi semiconducting core-shell structures brought into contact with Au electrodes, a very unusual behavior is that the tunneling transport is on-resonance right at equilibrium. This resonance is not due to the alignment of a quantum level in GeSi to the electrochemical potential of Au, but due to the alignment of very sharp DOS features - hot spots, localized at the two Au/GeSi interfaces of the device. An applied bias voltage shifts the hot spots relative to each other which gives rise to substantial negative differential resistance (NDR). The hot spots localized at the two interfaces were found to be due to the unbonded pz orbital of a sp(2) hybridized interface Si atom which is surrounded by three non-sp(2) hybridized neighbors. The mechanism of inducing hot spots and NDR by a local structure unit is not limited to the GeSi. The results suggest an interesting scheme for constructing NDR devices by orbital manipulation, to be more explicit, for example, by designing local structural units having unbonded orbitals at the interfaces between electrodes and the central region of the transport junction. PMID:27546305

  13. Molecular Models for Conductance in Junctions and Electrochemical Electron Transfer

    NASA Astrophysics Data System (ADS)

    Mazinani, Shobeir Khezr Seddigh

    This thesis develops molecular models for electron transport in molecular junctions and intra-molecular electron transfer. The goal is to identify molecular descriptors that afford a substantial simplification of these electronic processes. First, the connection between static molecular polarizability and the molecular conductance is examined. A correlation emerges whereby the measured conductance of a tunneling junction decreases as a function of the calculated molecular polarizability for several systems, a result consistent with the idea of a molecule as a polarizable dielectric. A model based on a macroscopic extension of the Clausius-Mossotti equation to the molecular domain and Simmon's tunneling model is developed to explain this correlation. Despite the simplicity of the theory, it paves the way for further experimental, conceptual and theoretical developments in the use of molecular descriptors to describe both conductance and electron transfer. Second, the conductance of several biologically relevant, weakly bonded, hydrogen-bonded systems is systematically investigated. While there is no correlation between hydrogen bond strength and conductance, the results indicate a relation between the conductance and atomic polarizability of the hydrogen bond acceptor atom. The relevance of these results to electron transfer in biological systems is discussed. Hydrogen production and oxidation using catalysts inspired by hydrogenases provides a more sustainable alternative to the use of precious metals. To understand electrochemical and spectroscopic properties of a collection of Fe and Ni mimics of hydrogenases, high-level density functional theory calculations are described. The results, based on a detailed analysis of the energies, charges and molecular orbitals of these metal complexes, indicate the importance of geometric constraints imposed by the ligand on molecular properties such as acidity and electrocatalytic activity. Based on model calculations of

  14. Three-dimensional models of conventional and vertical junction laser-photovoltaic energy converters

    NASA Technical Reports Server (NTRS)

    Heinbockel, John H.; Walker, Gilbert H.

    1988-01-01

    Three-dimensional models of both conventional planar junction and vertical junction photovoltaic energy converters have been constructed. The models are a set of linear partial differential equations and take into account many photoconverter design parameters. The model is applied to Si photoconverters; however, the model may be used with other semiconductors. When used with a Nd laser, the conversion efficiency of the Si vertical junction photoconverter is 47 percent, whereas the efficiency for the conventional planar Si photoconverter is only 17 percent. A parametric study of the Si vertical junction photoconverter is then done in order to describe the optimum converter for use with the 1.06-micron Nd laser. The efficiency of this optimized vertical junction converter is 44 percent at 1 kW/sq cm.

  15. Mechanisms and Geochemical Models of Core Formation

    NASA Astrophysics Data System (ADS)

    David Rubie; Seth Andrew Jacobson

    2016-03-01

    The formation of the Earth's core is a consequence of planetary accretion and processes in the Earth's interior. The mechanical process of planetary differentiation is likely to occur in large, if not global, magma oceans created by the collisions of planetary embryos. Metal-silicate segregation in magma oceans occurs rapidly and efficiently unlike grain scale percolation according to laboratory experiments and calculations. Geochemical models of the core formation process as planetary accretion proceeds are becoming increasingly realistic. Single stage and continuous core formation models have evolved into multi-stage models that are couple to the output of dynamical models of the giant impact phase of planet formation. The models that are most successful in matching the chemical composition of the Earth's mantle, based on experimentally-derived element partition coefficients, show that the temperature and pressure of metal-silicate equilibration must increase as a function of time and mass accreted and so must the oxygen fugacity of the equilibrating material. The latter can occur if silicon partitions into the core and through the late delivery of oxidized material. Coupled dynamical accretion and multi-stage core formation models predict the evolving mantle and core compositions of all the terrestrial planets simultaneously and also place strong constraints on the bulk compositions and oxidation states of primitive bodies in the protoplanetary disk.

  16. Quantum interference in thermoelectric molecular junctions: A toy model perspective

    SciTech Connect

    Nozaki, Daijiro E-mail: research@nano.tu-dresden.de; Avdoshenko, Stas M.; Sevinçli, Hâldun; Cuniberti, Gianaurelio

    2014-08-21

    Quantum interference (QI) phenomena between electronic states in molecular circuits offer a new opportunity to design new types of molecular devices such as molecular sensors, interferometers, and thermoelectric devices. Controlling the QI effect is a key challenge for such applications. For the development of single molecular devices employing QI effects, a systematic study of the relationship between electronic structure and the quantum interference is needed. In order to uncover the essential topological requirements for the appearance of QI effects and the relationship between the QI-affected line shape of the transmission spectra and the electronic structures, we consider a homogeneous toy model where all on-site energies are identical and model four types of molecular junctions due to their topological connectivities. We systematically analyze their transmission spectra, density of states, and thermoelectric properties. Even without the degree of freedom for on-site energies an asymmetric Fano peak could be realized in the homogeneous systems with the cyclic configuration. We also calculate the thermoelectric properties of the model systems with and without fluctuation of on-site energies. Even under the fluctuation of the on-site energies, the finite thermoelectrics are preserved for the Fano resonance, thus cyclic configuration is promising for thermoelectric applications. This result also suggests the possibility to detect the cyclic configuration in the homogeneous systems and the presence of the QI features from thermoelectric measurements.

  17. Processor core model for quantum computing.

    PubMed

    Yung, Man-Hong; Benjamin, Simon C; Bose, Sougato

    2006-06-01

    We describe an architecture based on a processing "core," where multiple qubits interact perpetually, and a separate "store," where qubits exist in isolation. Computation consists of single qubit operations, swaps between the store and the core, and free evolution of the core. This enables computation using physical systems where the entangling interactions are "always on." Alternatively, for switchable systems, our model constitutes a prescription for optimizing many-qubit gates. We discuss implementations of the quantum Fourier transform, Hamiltonian simulation, and quantum error correction.

  18. Modeling in the Common Core State Standards

    ERIC Educational Resources Information Center

    Tam, Kai Chung

    2011-01-01

    The inclusion of modeling and applications into the mathematics curriculum has proven to be a challenging task over the last fifty years. The Common Core State Standards (CCSS) has made mathematical modeling both one of its Standards for Mathematical Practice and one of its Conceptual Categories. This article discusses the need for mathematical…

  19. Summary of mathematical models for a conventional and vertical junction photoconverter. Progress report, 1 March-30 June 1986

    SciTech Connect

    Heinbockel, J.H.

    1986-06-01

    The geometry and computer programming for mathematical models of a one-dimensional conventional photoconverter, a one-dimensional vertical junction photoconverter, a three-dimensional conventinal photoconverter, and a three-dimensional vertical junction solar cell are discussed.

  20. Geodynamo Modeling of Core-Mantle Interactions

    NASA Technical Reports Server (NTRS)

    Kuang, Wei-Jia; Chao, Benjamin F.; Smith, David E. (Technical Monitor)

    2001-01-01

    Angular momentum exchange between the Earth's mantle and core influences the Earth's rotation on time scales of decades and longer, in particular in the length of day (LOD) which have been measured with progressively increasing accuracy for the last two centuries. There are four possible coupling mechanisms for transferring the axial angular momentum across the core-mantle boundary (CMB): viscous, magnetic, topography, and gravitational torques. Here we use our scalable, modularized, fully dynamic geodynamo model for the core to assess the importance of these torques. This numerical model, as an extension of the Kuang-Bloxham model that has successfully simulated the generation of the Earth's magnetic field, is used to obtain numerical results in various physical conditions in terms of specific parameterization consistent with the dynamical processes in the fluid outer core. The results show that depending on the electrical conductivity of the lower mantle and the amplitude of the boundary topography at CMB, both magnetic and topographic couplings can contribute significantly to the angular momentum exchange. This implies that the core-mantle interactions are far more complex than has been assumed and that there is unlikely a single dominant coupling mechanism for the observed decadal LOD variation.

  1. A model for ballistic transport across locally gated graphene bipolar junctions.

    PubMed

    Nguyen, Nhung T T; To, D Quang; Nguyen, V Lien

    2014-01-01

    An alternative model of Gaussian-type potential is suggested, which allows us to describe the transport properties of the locally gated graphene bipolar junctions in all possible charge density regimes, including a smooth transition between the regimes. Using this model we systematically study the transmission probability, the resistances, the current-voltage characteristics, and the shot noise for ballistic graphene bipolar junctions of different top gate lengths under largely varying gate voltages. Obtained results on the one hand show multifarious manifestations of the Klein tunneling and the interference effects, and on the other hand describe well typical experimental data on the junction resistances.

  2. Model For Dense Molecular Cloud Cores

    NASA Technical Reports Server (NTRS)

    Doty, Steven D.; Neufeld, David A.

    1997-01-01

    We present a detailed theoretical model for the thermal balance, chemistry, and radiative transfer within quiescent dense molecular cloud cores that contain a central protostar. In the interior of such cores, we expect the dust and gas temperatures to be well coupled, while in the outer regions CO rotational emissions dominate the gas cooling and the predicted gas temperature lies significantly below the dust temperature. Large spatial variations in the gas temperature are expected to affect the gas phase chemistry dramatically; in particular, the predicted water abundance varies by more than a factor of 1000 within cloud cores that contain luminous protostars. Based upon our predictions for the thermal and chemical structure of cloud cores, we have constructed self-consistent radiative transfer models to compute the line strengths and line profiles for transitions of (12)CO, (13)CO, C(18)O, ortho- and para-H2(16)O, ortho- and para-H2(18)O, and O I. We carried out a general parameter study to determine the dependence of the model predictions upon the parameters assumed for the source. We expect many of the far-infrared and submillimeter rotational transitions of water to be detectable either in emission or absorption with the use of the Infrared Space Observatory (ISO) and the Submillimeter Wave Astronomy Satellite. Quiescent, radiatively heated hot cores are expected to show low-gain maser emission in the 183 GHz 3(sub 13)-2(sub 20) water line, such as has been observed toward several hot core regions using ground-based telescopes. We predict the (3)P(sub l) - (3)P(sub 2) fine-structure transition of atomic oxygen near 63 micron to be in strong absorption against the continuum for many sources. Our model can also account successfully for recent ISO observations of absorption in rovibrational transitions of water toward the source AFGL 2591.

  3. Enhanced Core Noise Modeling for Turbofan Engines

    NASA Technical Reports Server (NTRS)

    Stone, James R.; Krejsa, Eugene A.; Clark, Bruce J.

    2011-01-01

    This report describes work performed by MTC Technologies (MTCT) for NASA Glenn Research Center (GRC) under Contract NAS3-00178, Task Order No. 15. MTCT previously developed a first-generation empirical model that correlates the core/combustion noise of four GE engines, the CF6, CF34, CFM56, and GE90 for General Electric (GE) under Contract No. 200-1X-14W53048, in support of GRC Contract NAS3-01135. MTCT has demonstrated in earlier noise modeling efforts that the improvement of predictive modeling is greatly enhanced by an iterative approach, so in support of NASA's Quiet Aircraft Technology Project, GRC sponsored this effort to improve the model. Since the noise data available for correlation are total engine noise spectra, it is total engine noise that must be predicted. Since the scope of this effort was not sufficient to explore fan and turbine noise, the most meaningful comparisons must be restricted to frequencies below the blade passage frequency. Below the blade passage frequency and at relatively high power settings jet noise is expected to be the dominant source, and comparisons are shown that demonstrate the accuracy of the jet noise model recently developed by MTCT for NASA under Contract NAS3-00178, Task Order No. 10. At lower power settings the core noise became most apparent, and these data corrected for the contribution of jet noise were then used to establish the characteristics of core noise. There is clearly more than one spectral range where core noise is evident, so the spectral approach developed by von Glahn and Krejsa in 1982 wherein four spectral regions overlap, was used in the GE effort. Further analysis indicates that the two higher frequency components, which are often somewhat masked by turbomachinery noise, can be treated as one component, and it is on that basis that the current model is formulated. The frequency scaling relationships are improved and are now based on combustor and core nozzle geometries. In conjunction with the Task

  4. Mucin-type core 1 glycans regulate the localization of neuromuscular junctions and establishment of muscle cell architecture in Drosophila.

    PubMed

    Itoh, Kazuyoshi; Akimoto, Yoshihiro; Fuwa, Takashi J; Sato, Chikara; Komatsu, Akira; Nishihara, Shoko

    2016-04-01

    T antigen (Galβ1-3GalNAcα1-Ser/Thr), a core 1 mucin-type O-glycan structure, is synthesized by Drosophila core 1 β1,3-galactosyltrasferase 1 (dC1GalT1) and is expressed in various tissues. We previously reported that dC1GalT1 synthesizes T antigen expressed in hemocytes, lymph glands, and the central nervous system (CNS) and that dC1GalT1 mutant larvae display decreased numbers of circulating hemocytes and excessive differentiation of hematopoietic stem cells in lymph glands. dC1GalT1 mutant larvae have also been shown to have morphological defects in the CNS. However, the functions of T antigen in other tissues remain largely unknown. In this study, we found that glycans contributed to the localization of neuromuscular junction (NMJ) boutons. In dC1GalT1 mutant larvae, NMJs were ectopically formed in the cleft between muscles 6 and 7 and connected with these two muscles. dC1GalT1 synthesized T antigen, which was expressed at NMJs. In addition, we determined the function of mucin-type O-glycans in muscle cells. In dC1GalT1 mutant muscles, myofibers and basement membranes were disorganized. Moreover, ultrastructural defects in NMJs and accumulation of large endosome-like structures within both NMJ boutons and muscle cells were observed in dC1GalT1 mutants. Taken together, these results demonstrated that mucin-type O-glycans synthesized by dC1GalT1 were involved in the localization of NMJ boutons, synaptogenesis of NMJs, establishment of muscle cell architecture, and endocytosis. PMID:26896591

  5. Formation and stability of ridge-ridge-ridge triple junctions in rheologically realistic lithosphere model

    NASA Astrophysics Data System (ADS)

    Gerya, Taras; Burov, Evgueni

    2015-04-01

    -branch junction formation and evolution by using high-resolution 3D numerical mechanical experiments that take into account realistic thermo-rheological structure and rheology of the lithosphere. We find that two major types of quadruple and triple junctions are formed under bi-directional or multidirectional far-field stress field: (i) plate rifting junctions are formed by the initial plate fragmentation and can be subsequently re-arranged into (ii) oceanic spreading junctions controlled by the new oceanic crust accretion. In particular, we document initial formation and destabilization of quadruple R-R-R-R junctions as initial plate rifting structures under bi-directional extension. In most cases, quadruple plate rifting junctions rapidly (typically within 1-2 Myr) evolve towards formation of two diverging triple oceanic spreading junctions connected by a linear spreading center lengthening with time. This configuration remains stable over long time scales. However, under certain conditions, quadruple junctions may also remain relatively stable. Asymmetric stretching results in various configurations, for example formation of "T-junctions" with trans-extensional components and combination of fast and slow spreading ridges. Combined with plume impingement, this scenario evolves in realistic patterns closely resembling observed plate dynamics. In particular, opening of the Red Sea and of the Afar rift system find a logical explanation within a single model. Numerical experiments also suggest that several existing oceanic spreading junctions form as the result of plate motions rearrangements after which only one of two plates spreading along the ridge become subjected to bi-directional spreading.

  6. Josephson junction devices: Model quantum mechanical systems and medical applications

    NASA Astrophysics Data System (ADS)

    Chen, Josephine

    In this dissertation, three experiments using Josephson junction devices are described. In Part I, the effect of dissipation on tunneling between charge states in a superconducting single-electron transistor (sSET) was studied. The sSET was fabricated on top of a semi-conductor heterostructure with a two-dimensional electron gas (2DEG) imbedded beneath the surface. The 2DEG acted as a dissipative ground plane. The sheet resistance of the 2DEG could be varied in situ by applying a large voltage to a gate on the back of the substrate. The zero-bias conductance of the sSET was observed to increase with increasing temperature and 2DEG resistance. Some qualitative but not quantitative agreement was found with theoretical calculations of the functional dependence of the conductance on temperature and 2DEG resistance. Part II describes a series of experiments performed on magnesium diboride point-contact junctions. The pressure between the MgB2 tip and base pieces could be adjusted to form junctions with different characteristics. With light pressure applied between the two pieces, quasiparticle tunneling in superconductor-insulator-superconductor junctions was measured. From these data, a superconducting gap of approximately 2 meV and a critical temperature of 29 K were estimated. Increasing the pressure between the MgB2 pieces formed junctions with superconductor-normal metal-superconductor characteristics. We used these junctions to form MgB2 superconducting quantum interference devices (SQUIDS). Noise levels as low as 35 fT/Hz1/2 and 4 muphi 0/Hz1/2 at 1 kHz were measured. In Part III, we used a SQUID-based instrument to acquire magnetocardiograms (MCG), the magnetic field signal measured from the human heart. We measured 51 healthy volunteers and 11 cardiac patients both at rest and after treadmill exercise. We found age and sex related differences in the MCG of the healthy volunteers that suggest that these factors should be considered when evaluating the MCG for

  7. Modeling of Memristive and Memcapacitive Behaviors in Metal-Oxide Junctions

    PubMed Central

    Mohamed, M. G. A.; Kim, HyungWon; Cho, Tae-Won

    2015-01-01

    Memristive behavior has been clearly addressed through growth and shrinkage of thin filaments in metal-oxide junctions. Capacitance change has also been observed, raising the possibility of using them as memcapacitors. Therefore, this paper proves that metal-oxide junctions can behave as a memcapacitor element by analyzing its characteristics and modeling its memristive and memcapacitive behaviors. We develop two behavioral modeling techniques: charge-dependent memcapacitor model and voltage-dependent memcapacitor model. A new physical model for metal-oxide junctions is presented based on conducting filaments variations, and its effect on device capacitance and resistance. In this model, we apply the exponential nature of growth and shrinkage of thin filaments and use Simmons' tunneling equation to calculate the tunneling current. Simulation results show how the variations of practical device parameters can change the device behavior. They clarify the basic conditions for building a memcapacitor device with negligible change in resistance. PMID:25705717

  8. Osmotic forces and gap junctions in spreading depression: a computational model

    NASA Technical Reports Server (NTRS)

    Shapiro, B. E.

    2001-01-01

    In a computational model of spreading depression (SD), ionic movement through a neuronal syncytium of cells connected by gap junctions is described electrodiffusively. Simulations predict that SD will not occur unless cells are allowed to expand in response to osmotic pressure gradients and K+ is allowed to move through gap junctions. SD waves of [K+]out approximately 25 to approximately 60 mM moving at approximately 2 to approximately 18 mm/min are predicted over the range of parametric values reported in gray matter, with extracellular space decreasing up to approximately 50%. Predicted waveform shape is qualitatively similar to laboratory reports. The delayed-rectifier, NMDA, BK, and Na+ currents are predicted to facilitate SD, while SK and A-type K+ currents and glial activity impede SD. These predictions are consonant with recent findings that gap junction poisons block SD and support the theories that cytosolic diffusion via gap junctions and osmotic forces are important mechanisms underlying SD.

  9. Hepatic immunohistochemical localization of the tight junction protein ZO-1 in rat models of cholestasis.

    PubMed Central

    Anderson, J. M.; Glade, J. L.; Stevenson, B. R.; Boyer, J. L.; Mooseker, M. S.

    1989-01-01

    Structural alterations in hepatocyte tight junctions accompanying cholestasis were investigated using immunolocalization of ZO-1, the first known protein component of the tight junction. Disruption in the paracellular barrier function of the tight junction has been proposed to allow reflux of bile into the blood. Cholestasis was induced in 210 to 235 g male Sprague-Dawley rats either by five consecutive daily subcutaneous injections of 17-alpha-ethinyl estradiol (0.5 mg/kg/d in propylene glycol) or ligation of the common bile duct for 72 hours. The structural organization of the tight junction was assessed in each model by indirect immunofluorescent and immunoperoxidase staining for ZO-1 on frozen sections of liver and compared with controls. In control, sham-operated, and estradiol-injected animals, ZO-1 localizes in a uniform continuous manner along the margins of the canaliculi. In contrast, bile duct ligation results in the appearance of numerous discontinuities in ZO-1 staining accompanied by dilation or collapse of the lumenal space. Tissue content of the ZO-1 protein, as determined by quantitative immunoblotting, was unaffected in either cholestatic model compared with controls. These findings indicate that the molecular organization of the tight junction can be assessed from immunostaining patterns of ZO-1 in frozen sections of cholestatic livers. Under these experimental conditions, the organization of the tight junction at the level of the ZO-1 protein is altered by bile duct obstruction but not by ethinyl estradiol. Images Figure 1 Figure 2 PMID:2719075

  10. Equidistance of branch structure in capacitively coupled Josephson junctions model with diffusion current

    NASA Astrophysics Data System (ADS)

    Shukrinov, Yu. M.; Mahfouzi, F.; Seidel, P.

    2006-11-01

    Branch structure in current-voltage characteristics of intrinsic Josephson junctions of HTSC is studied in the framework of two models: capacitively coupled Josephson junctions (CCJJ) model and CCJJ model with diffusion current (CCJJ + DC). We investigate the coupling dependence of the branch’s slopes and demonstrate that the equidistance of the branch structure in CCJJ model is broken at enough small values of coupling parameter (at α ≪ 1). We show that the inclusion of diffusion in the tunneling current through intrinsic Josephson junctions might restore the equidistance of the branch structure. Change of the current-voltage characteristics in CCJJ + DC model under variation of the coupling and McCumber parameters and effect of boundary conditions on the branch structure is analyzed.

  11. Peculiarities of phase dynamics of coupled Josephson junctions in CCJJ and CCJJ+DC models

    NASA Astrophysics Data System (ADS)

    Shukrinov, Y. U. M.; Rahmonov, I. R.; Demery, M. E. L.

    2010-11-01

    The phase dynamics of the coupled Josephson junctions in the framework of CCJJ and CCJJ+DC models is studied. The current voltage characteristics (CVC) are numerically calculated for the stacks with different number of junctions at different model parameters. We manifest the difference of these models for the branching at I = Ic and in the hysteretic region. The essential difference is observed in the breakpoint region, where the longitudinal plasma wave is created. We discuss the main features of both models, related with the role of the diffusion current between the superconducting layers.

  12. Modeling and theoretical efficiency of a silicon nanowire based thermoelectric junction with area enhancement

    NASA Astrophysics Data System (ADS)

    Seong, M.; Sadhu, J. S.; Ma, J.; Ghossoub, M. G.; Sinha, S.

    2012-06-01

    Recent experimental work suggests that individual silicon nanowires with rough surfaces possess a thermoelectric figure of merit as high as 0.6 near room temperature. This paper addresses the possibility of using an array of such nanowires in a thermoelectric junction for generation. Employing a model of frequency dependent phonon boundary scattering, we estimate the effective thermal conductivity of the array and investigate heat flow through the junction. We show that charge transport is largely unaffected by the roughness scales considered. Enhancing the area for heat exchange at an individual 200 μm × 200 μm p-n junction yields significant temperature differences across the junction leading to power >0.6 mW and efficiency >1.5% for a junction with effective thermal conductivity <5 W/mK, when the source and sink are at 450 K and 300 K, respectively. We show that relatively short nanowires of ˜50 μm length are sufficient for obtaining peak power and reasonable efficiency. This substantially reduces the challenge of engineering low resistivity electrical contacts that critically affect power and efficiency. This paper provides insight into how fundamental transport in relation to bulk heat transfer and charge transport, affects the performance of thermoelectric junctions based on nanostructured materials.

  13. Modeling and theoretical efficiency of a silicon nanowire based thermoelectric junction with area enhancement

    SciTech Connect

    Seong, M; Sadhu, JS; Ma, J; Ghossoub, MG; Sinha, S

    2012-06-15

    Recent experimental work suggests that individual silicon nanowires with rough surfaces possess a thermoelectric figure of merit as high as 0.6 near room temperature. This paper addresses the possibility of using an array of such nanowires in a thermoelectric junction for generation. Employing a model of frequency dependent phonon boundary scattering, we estimate the effective thermal conductivity of the array and investigate heat flow through the junction. We show that charge transport is largely unaffected by the roughness scales considered. Enhancing the area for heat exchange at an individual 200 mu m x 200 mu m p-n junction yields significant temperature differences across the junction leading to power >0.6 mW and efficiency >1.5% for a junction with effective thermal conductivity <5 W/mK, when the source and sink are at 450 K and 300 K, respectively. We show that relatively short nanowires of similar to 50 mu m length are sufficient for obtaining peak power and reasonable efficiency. This substantially reduces the challenge of engineering low resistivity electrical contacts that critically affect power and efficiency. This paper provides insight into how fundamental transport in relation to bulk heat transfer and charge transport, affects the performance of thermoelectric junctions based on nanostructured materials. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4728189

  14. From cusps to cores: a stochastic model

    NASA Astrophysics Data System (ADS)

    El-Zant, Amr A.; Freundlich, Jonathan; Combes, Françoise

    2016-09-01

    The cold dark matter model of structure formation faces apparent problems on galactic scales. Several threads point to excessive halo concentration, including central densities that rise too steeply with decreasing radius. Yet, random fluctuations in the gaseous component can `heat' the centres of haloes, decreasing their densities. We present a theoretical model deriving this effect from first principles: stochastic variations in the gas density are converted into potential fluctuations that act on the dark matter; the associated force correlation function is calculated and the corresponding stochastic equation solved. Assuming a power-law spectrum of fluctuations with maximal and minimal cutoff scales, we derive the velocity dispersion imparted to the halo particles and the relevant relaxation time. We further perform numerical simulations, with fluctuations realized as a Gaussian random field, which confirm the formation of a core within a time-scale comparable to that derived analytically. Non-radial collective modes enhance the energy transport process that erases the cusp, though the parametrizations of the analytical model persist. In our model, the dominant contribution to the dynamical coupling driving the cusp-core transformation comes from the largest scale fluctuations. Yet, the efficiency of the transformation is independent of the value of the largest scale and depends weakly (linearly) on the power-law exponent; it effectively depends on two parameters: the gas mass fraction and the normalization of the power spectrum. This suggests that cusp-core transformations observed in hydrodynamic simulations of galaxy formation may be understood and parametrized in simple terms, the physical and numerical complexities of the various implementations notwithstanding.

  15. Mathematical modeling of intrinsic Josephson junctions with capacitive and inductive couplings

    NASA Astrophysics Data System (ADS)

    Rahmonov, I. R.; Shukrinov, Yu M.; Zemlyanaya, E. V.; Sarhadov, I.; Andreeva, O.

    2012-11-01

    We investigate the current voltage characteristics (CVC) of intrinsic Josephson junctions (IJJ) with two types of couplings between junctions: capacitive and inductive. The IJJ model is described by a system of coupled sine-Gordon equations which is solved numerically by the 4th order Runge-Kutta method. The method of numerical simulation and numerical results are presented. The magnetic field distribution is calculated as the function of coordinate and time at different values of the bias current. The influence of model parameters on the CVC is studied. The behavior of the IJJ in dependence on coupling parameters is discussed.

  16. Uncovering Divergence of Rice Exon Junction Complex Core Heterodimer Gene Duplication Reveals Their Essential Role in Growth, Development, and Reproduction.

    PubMed

    Gong, Pichang; He, Chaoying

    2014-05-12

    The exon junction complex (EJC) plays important developmental roles in animals; however, its role in plants is not well known. Here, we show various aspects of the divergence of each duplicated MAGO NASHI (MAGO) and Y14 gene pair in rice (Oryza sativa) encoding the putative EJC core subunits that form the obligate MAGO-Y14 heterodimers. OsMAGO1, OsMAGO2, and OsY14a were constitutively expressed in all tissues, while OsY14b was predominantly expressed in embryonic tissues. OsMAGO2 and OsY14b were more sensitive to different stresses than OsMAGO1 and OsY14a, and their encoded protein pair shared 93.8% and 46.9% sequence identity, respectively. Single MAGO down-regulation in rice did not lead to any phenotypic variation; however, double gene knockdowns generated short rice plants with abnormal flowers, and the stamens of these flowers showed inhibited degradation and absorption of both endothecium and tapetum, suggesting that OsMAGO1 and OsMAGO2 were functionally redundant. OsY14a knockdowns phenocopied OsMAGO1OsMAGO2 mutants, while down-regulation of OsY14b failed to induce plantlets, suggesting the functional specialization of OsY14b in embryogenesis. OsMAGO1OsMAGO2OsY14a triple down-regulation enhanced the phenotypes of OsMAGO1OsMAGO2 and OsY14a down-regulated mutants, indicating that they exert developmental roles in the MAGO-Y14 heterodimerization mode. Modified gene expression was noted in the altered developmental pathways in these knockdowns, and the transcript splicing of UNDEVELOPED TAPETUM1 (OsUDT1), a key regulator in stamen development, was uniquely abnormal. Concomitantly, MAGO and Y14 selectively bound to the OsUDT1 premessenger RNA, suggesting that rice EJC subunits regulate splicing. Our work provides novel insights into the function of the EJC locus in growth, development, and reproduction in angiosperms and suggests a role for these genes in the adaptive evolution of cereals.

  17. Modified pressure loss model for T-junctions of engine exhaust manifold

    NASA Astrophysics Data System (ADS)

    Wang, Wenhui; Lu, Xiaolu; Cui, Yi; Deng, Kangyao

    2014-11-01

    The T-junction model of engine exhaust manifolds significantly influences the simulation precision of the pressure wave and mass flow rate in the intake and exhaust manifolds of diesel engines. Current studies have focused on constant pressure models, constant static pressure models and pressure loss models. However, low model precision is a common disadvantage when simulating engine exhaust manifolds, particularly for turbocharged systems. To study the performance of junction flow, a cold wind tunnel experiment with high velocities at the junction of a diesel exhaust manifold is performed, and the variation in the pressure loss in the T-junction under different flow conditions is obtained. Despite the trend of the calculated total pressure loss coefficient, which is obtained by using the original pressure loss model and is the same as that obtained from the experimental results, large differences exist between the calculated and experimental values. Furthermore, the deviation becomes larger as the flow velocity increases. By improving the Vazsonyi formula considering the flow velocity and introducing the distribution function, a modified pressure loss model is established, which is suitable for a higher velocity range. Then, the new model is adopted to solve one-dimensional, unsteady flow in a D6114 turbocharged diesel engine. The calculated values are compared with the measured data, and the result shows that the simulation accuracy of the pressure wave before the turbine is improved by 4.3% with the modified pressure loss model because gas compressibility is considered when the flow velocities are high. The research results provide valuable information for further junction flow research, particularly the correction of the boundary condition in one-dimensional simulation models.

  18. Synchronization of coupled rotators: Josephson junction ladders and the Kuramoto model

    NASA Astrophysics Data System (ADS)

    Daniels, B. C.; Trees, B. R.

    2002-10-01

    We show that the resistively shunted junction (RSJ) equations describing a ladder array of overdamped, critical-current disordered Josephson junctions that are current-biased along the rungs of the ladder can be mapped onto a Kuramoto model with nearest-neighbor, sinusoidal couplings. This result is obtained by an averaging method, in which the fast dynamics of the RSJ equations are integrated out, leaving the dynamics which describe the time scale over which neighboring junctions along the rungs of the ladder phase and frequency synchronize. We quantify the degree of frequency synchronization of the rung junctions by calculating the standard deviation of their time-averaged voltages, σ_ω, and the phase synchronization is quantified by calculating the time average of the modulus of the Kuramoto order parameter, < |r|>. We test the results of our averaging process by comparing the values of σ_ω and < |r|> for the original RSJ equations and our averaged equations. We find excellent agreement for DC bias currents of I_B/< I_c>agt 3, where < I_c> is the average critical current of the rung junctions, and critical current disorders of up to 10%. We also study the effects of thermal noise on the synchronization properties of the overdamped ladder. Finally, we find that including the effects of junction capacitance can lead to a discontinuous synchronization transition as the strength of the coupling between neighboring junctions is smoothly varied. This project was supported by the Ohio Wesleyan University Summer Research Program which was funded in part by the McGregor Fund.

  19. c-Jun N-terminal kinase mediates disassembly of apical junctions in model intestinal epithelia.

    PubMed

    Naydenov, Nayden G; Hopkins, Ann M; Ivanov, Andrei I

    2009-07-01

    Dynamic remodeling of intercellular junctions is a critical determinant of epithelial barrier function in both physiological and pathophysiological states. While the disassembly of epithelial tight junctions (TJ) and adherens junctions (AJ) has been well-described in response to pathogens and other external stressors, the role of stress-related signaling in TJ/AJ regulation remains poorly understood. The aim of this study was to define the role of stress-activated c-Jun N-terminal kinase (JNK) in disruption of intercellular junctions in model intestinal epithelia. We show that rapid AJ/TJ disassembly triggered by extracellular calcium depletion of T84 and SK-CO15 cell monolayers was accompanied by activation (phosphorylation) of JNK, and prevented by pharmacological inhibitors of JNK. The opposite process, TJ/AJ reassembly, was accelerated by JNK inhibition and suppressed by the JNK activator anisomycin. JNK1 but not JNK2 was found to colocalize with intercellular junctions, and siRNA-mediated downregulation of JNK1 attenuated the TJ/AJ disruption caused by calcium depletion. JNK inhibition also blocked formation of characteristic contractile F-actin rings in calcium-depleted epithelial cells, suggesting that JNK regulates junctions by remodeling the actin cytoskeleton. In this role JNK acts downstream of the actin-reorganizing Rho-dependent kinase (ROCK), since ROCK inhibition abrogated JNK phosphorylation and TJ/AJ disassembly after calcium depletion. Furthermore, JNK acts upstream of F-actin-membrane linker proteins of the ERM (ezrin-radixin-moesin) family, but in a complex relationship yet to be fully elucidated. Taken together, our findings suggest a novel role for JNK in the signaling pathway that links ROCK and F-actin remodeling during disassembly of epithelial junctions.

  20. Models of Isotopic Fractionation in Prestellar Cores

    NASA Technical Reports Server (NTRS)

    Charnley, Steven B.

    2012-01-01

    Anomalously fractionated isotopic material is found in many primitive Solar System objects, such as meteorites and comets. It is thought, in some cases, to trace interstellar matter that was incorporated into the Solar Nebula without undergoing significant processing. We will present the results of models of the nitrogen, oxygen, and carbon fractionation chemistry in dense molecular clouds, particularly in cores where substantial freeze-out of molecules on to dust has occurred. The range of fractionation ratios expected in different interstellar molecules will be discussed and compared to the ratios measured in molecular clouds, comets and meteoritic material. These studies make several predictions that can be tested in the near future by high-resolution molecular line observations with ALMA.

  1. Models of Isotopic Fractionation in Prestellar Cores

    NASA Technical Reports Server (NTRS)

    Charnley, Steven B.; Cordiner, Martin A.

    2011-01-01

    Anomalously fractionated isotopic material is found in many primitive Solar System objects, such as meteorites and comets. It is thought, in some cases, to trace interstellar matter that was incorporated into the Solar Nebula without undergoing significant processing. We will present the results of models of the nitrogen, oxygen, and carbon fractionation chemistry in dense molecular clouds, particularly in cores where substantial freeze-out of molecules on to dust has occurred. The range of fractionation ratios expected in different interstellar molecules will be discussed and compared to the ratios measured in molecular clouds, comets and meteoritic material. These studies make several predictions that can be tested in the near future by high-resolution molecular line observations with ALMA.

  2. No-Core Shell Model and Reactions

    SciTech Connect

    Navratil, P; Ormand, W E; Caurier, E; Bertulani, C

    2005-04-29

    There has been a significant progress in ab initio approaches to the structure of light nuclei. Starting from realistic two- and three-nucleon interactions the ab initio no-core shell model (NCSM) can predict low-lying levels in p-shell nuclei. It is a challenging task to extend ab initio methods to describe nuclear reactions. In this contribution, we present a brief overview of the NCSM with examples of recent applications as well as the first steps taken toward nuclear reaction applications. In particular, we discuss cross section calculations of p+{sup 6}Li and {sup 6}He+p scattering as well as a calculation of the astrophysically important {sup 7}Be(p, {gamma}){sup 8}B S-factor.

  3. No-Core Shell Model and Reactions

    SciTech Connect

    Navratil, Petr; Ormand, W. Erich; Caurier, Etienne; Bertulani, Carlos

    2005-10-14

    There has been a significant progress in ab initio approaches to the structure of light nuclei. Starting from realistic two- and three-nucleon interactions the ab initio no-core shell model (NCSM) can predict low-lying levels in p-shell nuclei. It is a challenging task to extend ab initio methods to describe nuclear reactions. In this contribution, we present a brief overview of the NCSM with examples of recent applications as well as the first steps taken toward nuclear reaction applications. In particular, we discuss cross section calculations of p+6Li and 6He+p scattering as well as a calculation of the astrophysically important 7Be(p,{gamma})8B S-factor.

  4. Vector spin modeling for magnetic tunnel junctions with voltage dependent effects

    SciTech Connect

    Manipatruni, Sasikanth Nikonov, Dmitri E.; Young, Ian A.

    2014-05-07

    Integration and co-design of CMOS and spin transfer devices requires accurate vector spin conduction modeling of magnetic tunnel junction (MTJ) devices. A physically realistic model of the MTJ should comprehend the spin torque dynamics of nanomagnet interacting with an injected vector spin current and the voltage dependent spin torque. Vector spin modeling allows for calculation of 3 component spin currents and potentials along with the charge currents/potentials in non-collinear magnetic systems. Here, we show 4-component vector spin conduction modeling of magnetic tunnel junction devices coupled with spin transfer torque in the nanomagnet. Nanomagnet dynamics, voltage dependent spin transport, and thermal noise are comprehended in a self-consistent fashion. We show comparison of the model with experimental magnetoresistance (MR) of MTJs and voltage degradation of MR with voltage. Proposed model enables MTJ circuit design that comprehends voltage dependent spin torque effects, switching error rates, spin degradation, and back hopping effects.

  5. Multiscale modelling of nucleosome core particle aggregation

    NASA Astrophysics Data System (ADS)

    Lyubartsev, Alexander P.; Korolev, Nikolay; Fan, Yanping; Nordenskiöld, Lars

    2015-02-01

    The nucleosome core particle (NCP) is the basic building block of chromatin. Under the influence of multivalent cations, isolated mononucleosomes exhibit a rich phase behaviour forming various columnar phases with characteristic NCP-NCP stacking. NCP stacking is also a regular element of chromatin structure in vivo. Understanding the mechanism of nucleosome stacking and the conditions leading to self-assembly of NCPs is still incomplete. Due to the complexity of the system and the need to describe electrostatics properly by including the explicit mobile ions, novel modelling approaches based on coarse-grained (CG) methods at the multiscale level becomes a necessity. In this work we present a multiscale CG computer simulation approach to modelling interactions and self-assembly of solutions of NCPs induced by the presence of multivalent cations. Starting from continuum simulations including explicit three-valent cobalt(III)hexammine (CoHex3+) counterions and 20 NCPs, based on a previously developed advanced CG NCP model with one bead per amino acid and five beads per two DNA base pair unit (Fan et al 2013 PLoS One 8 e54228), we use the inverse Monte Carlo method to calculate effective interaction potentials for a ‘super-CG’ NCP model consisting of seven beads for each NCP. These interaction potentials are used in large-scale simulations of up to 5000 NCPs, modelling self-assembly induced by CoHex3+. The systems of ‘super-CG’ NCPs form a single large cluster of stacked NCPs without long-range order in agreement with experimental data for NCPs precipitated by the three-valent polyamine, spermidine3+.

  6. Multiscale modelling of nucleosome core particle aggregation.

    PubMed

    Lyubartsev, Alexander P; Korolev, Nikolay; Fan, Yanping; Nordenskiöld, Lars

    2015-02-18

    The nucleosome core particle (NCP) is the basic building block of chromatin. Under the influence of multivalent cations, isolated mononucleosomes exhibit a rich phase behaviour forming various columnar phases with characteristic NCP-NCP stacking. NCP stacking is also a regular element of chromatin structure in vivo. Understanding the mechanism of nucleosome stacking and the conditions leading to self-assembly of NCPs is still incomplete. Due to the complexity of the system and the need to describe electrostatics properly by including the explicit mobile ions, novel modelling approaches based on coarse-grained (CG) methods at the multiscale level becomes a necessity. In this work we present a multiscale CG computer simulation approach to modelling interactions and self-assembly of solutions of NCPs induced by the presence of multivalent cations. Starting from continuum simulations including explicit three-valent cobalt(III)hexammine (CoHex(3+)) counterions and 20 NCPs, based on a previously developed advanced CG NCP model with one bead per amino acid and five beads per two DNA base pair unit (Fan et al 2013 PLoS One 8 e54228), we use the inverse Monte Carlo method to calculate effective interaction potentials for a 'super-CG' NCP model consisting of seven beads for each NCP. These interaction potentials are used in large-scale simulations of up to 5000 NCPs, modelling self-assembly induced by CoHex(3+). The systems of 'super-CG' NCPs form a single large cluster of stacked NCPs without long-range order in agreement with experimental data for NCPs precipitated by the three-valent polyamine, spermidine(3+).

  7. Modeling the time-dependent transient radiation response of semiconductor junctions

    NASA Astrophysics Data System (ADS)

    Wunsch, T. F.; Axness, C. L.

    1992-12-01

    Analytical one-dimensional time-dependent photocurrent models are developed from new solutions to the ambipolar transport equation. The p-n junction model incorporates the effects of an electric field in the quasi-neutral region, finite diode length, and an arbitrary generation function g = f(x,t). It provides improved accuracy over the Wirth-Rogers and Enlow-Alexander models. An approximate photocurrent solution for p-n-n(+), n-p-p(+), and p-i-n diode junctions is developed considering high-injection effects. Comparison with experimental data shows that a single set of physical parameters is adequate to characterize the model with respect to dose rate, pulse width, and geometry.

  8. Feynman's and Ohta's Models of a Josephson Junction

    ERIC Educational Resources Information Center

    De Luca, R.

    2012-01-01

    The Josephson equations are derived by means of the weakly coupled two-level quantum system model given by Feynman. Adopting a simplified version of Ohta's model, starting from Feynman's model, the strict voltage-frequency Josephson relation is derived. The contribution of Ohta's approach to the comprehension of the additional term given by the…

  9. Physical model of the contact resistivity of metal-graphene junctions

    SciTech Connect

    Chaves, Ferney A. Jiménez, David; Cummings, Aron W.; Roche, Stephan

    2014-04-28

    While graphene-based technology shows great promise for a variety of electronic applications, including radio-frequency devices, the resistance of the metal-graphene contact is a technological bottleneck for the realization of viable graphene electronics. One of the most important factors in determining the resistance of a metal-graphene junction is the contact resistivity. Despite the large number of experimental works that exist in the literature measuring the contact resistivity, a simple model of it is still lacking. In this paper, we present a comprehensive physical model for the contact resistivity of these junctions, based on the Bardeen Transfer Hamiltonian method. This model unveils the role played by different electrical and physical parameters in determining the specific contact resistivity, such as the chemical potential of interaction, the work metal-graphene function difference, and the insulator thickness between the metal and graphene. In addition, our model reveals that the contact resistivity is strongly dependent on the bias voltage across the metal-graphene junction. This model is applicable to a wide variety of graphene-based electronic devices and thus is useful for understanding how to optimize the contact resistance in these systems.

  10. Structural modeling of sandwich structures with lightweight cellular cores

    NASA Astrophysics Data System (ADS)

    Liu, T.; Deng, Z. C.; Lu, T. J.

    2007-10-01

    An effective single layered finite element (FE) computational model is proposed to predict the structural behavior of lightweight sandwich panels having two dimensional (2D) prismatic or three dimensional (3D) truss cores. Three different types of cellular core topology are considered: pyramidal truss core (3D), Kagome truss core (3D) and corrugated core (2D), representing three kinds of material anisotropy: orthotropic, monoclinic and general anisotropic. A homogenization technique is developed to obtain the homogenized macroscopic stiffness properties of the cellular core. In comparison with the results obtained by using detailed FE model, the single layered computational model can give acceptable predictions for both the static and dynamic behaviors of orthotropic truss core sandwich panels. However, for non-orthotropic 3D truss cores, the predictions are not so well. For both static and dynamic behaviors of a 2D corrugated core sandwich panel, the predictions derived by the single layered computational model is generally acceptable when the size of the unit cell varies within a certain range, with the predictions for moderately strong or strong corrugated cores more accurate than those for weak cores.

  11. Opto-electronic modeling of light emission from avalanche-mode silicon p+n junctions

    NASA Astrophysics Data System (ADS)

    Dutta, Satadal; Hueting, Raymond J. E.; Annema, Anne-Johan; Qi, Lin; Nanver, Lis K.; Schmitz, Jurriaan

    2015-09-01

    This work presents the modeling of light emission from silicon based p+n junctions operating in avalanche breakdown. We revisit the photon emission process under the influence of relatively high electric fields in a reverse biased junction ( > 10 5 V/cm). The photon emission rate is described as a function of the electron temperature T e , which is computed from the spatial distribution of the electric field. The light emission spectra lie around the visible spectral range ( λ ˜ 300-850 nm), where the peak wavelength and the optical intensity are both doping level dependent. It is theoretically derived that a specific minimum geometrical width ( ˜ 170 nm) of the active region of avalanche is required, corresponding to a breakdown voltage of ˜5 V, below which the rate of photon emission in the desired spectrum drops. The derived model is validated using experimental data obtained from ultra-shallow p+n junctions with low absorption through a nm-thin p+ region and surface coverage of solely 3 nm of pure boron. We observe a peak in the emission spectra near 580 nm and 650 nm for diodes with breakdown voltages 7 V and 14 V, respectively, consistent with our model.

  12. Ab Initio No-Core Shell Model

    SciTech Connect

    Barrett, B R; Navratil, P; Vary, J P

    2011-04-11

    and NNN interactions, characterized by the order of the expansion retained (e.g. 'next-to-next-to leading order' is NNLO), provide a high-quality fit to the NN data and the A = 3 ground-state (g.s.) properties. The derivations of NN, NNN, etc. interactions within meson-exchange and {chi}EFT are well-established but are not subjects of this review. Our focus is solution of the non-relativistic quantum many-body Hamiltonian that includes these interactions using our no core shell model (NCSM) formalism. In the next section we will briefly outline the NCSM formalism and then present applications, results and extensions in later sections.

  13. Mathematical modeling of gap junction coupling and electrical activity in human β-cells

    NASA Astrophysics Data System (ADS)

    Loppini, Alessandro; Braun, Matthias; Filippi, Simonetta; Gram Pedersen, Morten

    2015-12-01

    Coordinated insulin secretion is controlled by electrical coupling of pancreatic β-cells due to connexin-36 gap junctions. Gap junction coupling not only synchronizes the heterogeneous β-cell population, but can also modify the electrical behavior of the cells. These phenomena have been widely studied with mathematical models based on data from mouse β-cells. However, it is now known that human β-cell electrophysiology shows important differences to its rodent counterpart, and although human pancreatic islets express connexin-36 and show evidence of β-cell coupling, these aspects have been little investigated in human β-cells. Here we investigate theoretically, the gap junction coupling strength required for synchronizing electrical activity in a small cluster of cells simulated with a recent mathematical model of human β-cell electrophysiology. We find a lower limit for the coupling strength of approximately 20 pS (i.e., normalized to cell size, ˜2 pS pF-1) below which spiking electrical activity is asynchronous. To confront this theoretical lower bound with data, we use our model to estimate from an experimental patch clamp recording that the coupling strength is approximately 100-200 pS (10-20 pS pF-1), similar to previous estimates in mouse β-cells. We then investigate the role of gap junction coupling in synchronizing and modifying other forms of electrical activity in human β-cell clusters. We find that electrical coupling can prolong the period of rapid bursting electrical activity, and synchronize metabolically driven slow bursting, in particular when the metabolic oscillators are in phase. Our results show that realistic coupling conductances are sufficient to promote synchrony in small clusters of human β-cells as observed experimentally, and provide motivation for further detailed studies of electrical coupling in human pancreatic islets.

  14. Tucker core consistency for validation of restricted Tucker3 models.

    PubMed

    Kompany-Zareh, Mohsen; Akhlaghi, Yousef; Bro, Rasmus

    2012-04-20

    In Tucker3 analysis of three-way data array obtained from a chemical or biological system, it is sometimes possible to use a priori knowledge about the system to specify what is called a restricted Tucker3 model. Often, the restricted Tucker3 model is characterized by having some elements of the core forced to zero. As a simple example, an F-component PARAFAC model can be seen as a restricted (F, F, F) Tucker3 model in which only superdiagonal elements of the core are allowed to be nonzero. The core consistency diagnostic was previously introduced by Bro and Kiers for determining the proper number of components in PARAFAC analysis. In the current study, this diagnostic is extended to other restricted Tucker3 models to validate the appropriateness of the applied constraints. The new diagnostic is named Tucker core consistency (TuckCorCon). When the dimensionality and the pattern of the restricted core is valid, the simple core of restricted Tucker3 model and a corresponding unrestricted core will be similar and in this case the TuckCorCon will be close to maximum (100%). A simulated chemical equilibrium data set and two experimental data sets were used to evaluate the applicability of the TuckCorCon to decide about the appropriateness of dimensionality and pattern of the core nonzero elements in the restricted Tucker3 models.

  15. A model of dopant diffusion through a strongly correlated p-n junction

    NASA Astrophysics Data System (ADS)

    Wieteska, Jedrzej; Brierley, Richard; Guzman-Verri, Gian; Moller, Gunnar; Littlewood, Peter; Littlewood group Collaboration

    The diffusion of charged ions in a solid depends on an equation of state that balances diffusive and screened electrostatic forces, and is well understood in the case of conventional semiconductors and metals. In the case of a strongly-correlated material, the physics is different, and expected to be relevant, for example, in Li-ion battery cathodes. We propose a model of dopant ion motion through a strongly correlated p-n junction. Our approach is to consider diffusive (Nernst-Planck) dynamics of dopants under screened electrostatic interactions computed within a mean-field (Thomas-Fermi) approximation. Dopant profiles as function of time are calculated for a p-n junction held at constant voltage. In the case where filling levels are near a correlation-induced gap, Mott insulating regions can form at the p-n interface and their dynamics is studied.

  16. Behavioural model of Spin Torque Transfer Magnetic Tunnel Junction, Using Verilog-A

    NASA Astrophysics Data System (ADS)

    Garg, Rishubh; Kumar, Deepak; Jindal, Navneet; Negi, Nandita; Ahuja, Chetna

    2012-11-01

    A novel simple and efficient model of Spin Torque Transfer Magnetic Tunnel Junction (STT-MTJ) is presented. The model is implemented using Verilog-A. The model accurately emulates the main properties of an STT-MTJ which includes Tunnel Magneto resistance Ratio (TMR), its dependence on the voltage bias and the Critical switching current. The novelty of the model lies in the fact that the voltage dependence of TMR has been modeled using a single equation dividing it into three different operating regions. A register based on the model is also developed. The model can be used for faster simulations of hybrid Magnetic CMOS circuits and in various other wide range of applications. The models were verified using Synopsys Hspice 2010.

  17. Important issues facing model-based approaches to tunneling transport in molecular junctions

    NASA Astrophysics Data System (ADS)

    Bâldea, Ioan

    Extensive studies on thin films indicated a generic cubic current-voltage $I-V$ dependence as a salient feature of charge transport by tunneling. A quick glance at $I-V$ data for molecular junctions suggests a qualitatively similar behavior. This would render model-based studies almost irrelevant, since, whatever the model, its parameters can always be adjusted to fit symmetric (asymmetric) $I-V$ curves characterized by two (three) expansion coefficients. Here, we systematically examine popular models based on tunneling barrier or tight-binding pictures and demonstrate that, for a quantitative description at biases of interest ($V$ slightly higher than the transition voltage $V_t$), cubic expansions do not suffice. A detailed collection of analytical formulae as well as their conditions of applicability are presented to facilitate experimentalists colleagues to process and interpret their experimental data by obtained by measuring currents in molecular junctions. We discuss in detail the limits of applicability of the various models and emphasize that uncritically adjusting model parameters to experiment may be unjustified because the values deduced in this way may fall in ranges rendering a specific model invalid or incompatible to ab initio estimates. We exemplify with the benchmark case of oligophenylene-based junctions, for which results of ab initio quantum chemical calculations are also reported. As a specific issue, we address the impact of the spatial potential profile and show that it is not notable up to biases V somewhat larger than V_t, unlike at higher biases, where it may be responsible for negative differential resistance effects.

  18. Human alveolar epithelial cells expressing tight junctions to model the air-blood barrier.

    PubMed

    Kuehn, Anna; Kletting, Stephanie; de Souza Carvalho-Wodarz, Cristiane; Repnik, Urska; Griffiths, Gareth; Fischer, Ulrike; Meese, Eckart; Huwer, Hanno; Wirth, Dagmar; May, Tobias; Schneider-Daum, Nicole; Lehr, Claus-Michael

    2016-01-01

    This paper describes a new human alveolar epithelial cell line (hAELVi - human Alveolar Epithelial Lentivirus immortalized) with type I-like characteristics and functional tight junctions, suitable to model the air-blood barrier of the peripheral lung. Primary human alveolar epithelial cells were immortalized by a novel regimen, grown as monolayers on permeable filter supports and characterized morphologically, biochemically and biophysically. hAELVi cells maintain the capacity to form tight intercellular junctions, with high trans-epithelial electrical resistance (> 1000 Ω*cm²). The cells could be kept in culture over several days, up to passage 75, under liquid-liquid as well as air-liquid conditions. Ultrastructural analysis and real time PCR revealed type I-like cell properties, such as the presence of caveolae, expression of caveolin-1, and absence of surfactant protein C. Accounting for the barrier properties, inter-digitations sealed with tight junctions and desmosomes were also observed. Low permeability of the hydrophilic marker sodium fluorescein confirmed the suitability of hAELVi cells for in vitro transport studies across the alveolar epithelium. These results suggest that hAELVi cells reflect the essential features of the air-blood barrier, as needed for an alternative to animal testing to study absorption and toxicity of inhaled drugs, chemicals and nanomaterials. PMID:26985677

  19. Adaptive Phase-Field Modeling of Anisotropic Wetting with Line Tension at the Triple Junction.

    PubMed

    Yeh, S Y; Lan, C W

    2015-09-01

    Line tension could affect the contact angle at triple junction, especially in micro- to nanoscale wetting. We have developed an adaptive phase-field model to consider the line tension quantitatively. This model is coupled to the smoothed boundary method for treating the contact line with the solid phase, while the volume constraint is imposed. Our calculated contact angles are in good agreement with the modified Young's equation. Further examples are illustrated for the anisotropic wetting on hydrophilic/hydrophobic stripes and rectangular grooves.

  20. Modeling of Schottky Barrier Modulation due to Oxidation at Metallic Electrode and Semiconducting Carbon Nanotube Junction

    NASA Technical Reports Server (NTRS)

    Yamada, Toshishige; Biegel, Bryan (Technical Monitor)

    2003-01-01

    A model is proposed for the previously reported lower Schottky barrier for holes PHI (sub bH) in air than in vacuum at a metallic electrode - semiconducting carbon nanotube (CNT) junction. We assume that there is a transition region between the electrode and the CNT, and an appreciable potential can drop there. The role of the oxidation is to increase this potential drop with negatively charged oxygen molecules on the CNT, leading to lower PHI(sub Bh) after oxidation. The mechanism prevails in both p- and n-CNTs, and the model consistently explains the key experimental findings.

  1. A semi-analytic dynamical friction model for cored galaxies

    NASA Astrophysics Data System (ADS)

    Petts, J. A.; Read, J. I.; Gualandris, A.

    2016-11-01

    We present a dynamical friction model based on Chandrasekhar's formula that reproduces the fast inspiral and stalling experienced by satellites orbiting galaxies with a large constant density core. We show that the fast inspiral phase does not owe to resonance. Rather, it owes to the background velocity distribution function for the constant density core being dissimilar from the usually assumed Maxwellian distribution. Using the correct background velocity distribution function and our semi-analytic model from previous work, we are able to correctly reproduce the infall rate in both cored and cusped potentials. However, in the case of large cores, our model is no longer able to correctly capture core-stalling. We show that this stalling owes to the tidal radius of the satellite approaching the size of the core. By switching off dynamical friction when rt(r) = r (where rt is the tidal radius at the satellite's position), we arrive at a model which reproduces the N-body results remarkably well. Since the tidal radius can be very large for constant density background distributions, our model recovers the result that stalling can occur for Ms/Menc ≪ 1, where Ms and Menc are the mass of the satellite and the enclosed galaxy mass, respectively. Finally, we include the contribution to dynamical friction that comes from stars moving faster than the satellite. This next-to-leading order effect becomes the dominant driver of inspiral near the core region, prior to stalling.

  2. A semi-analytic dynamical friction model for cored galaxies

    NASA Astrophysics Data System (ADS)

    Petts, J. A.; Read, J. I.; Gualandris, A.

    2016-08-01

    We present a dynamical friction model based on Chandrasekhar's formula that reproduces the fast inspiral and stalling experienced by satellites orbiting galaxies with a large constant density core. We show that the fast inspiral phase does not owe to resonance. Rather, it owes to the background velocity distribution function for the constant density core being dissimilar from the usually-assumed Maxwellian distribution. Using the correct background velocity distribution function and the semi-analytic model from Petts et al. (2015), we are able to correctly reproduce the infall rate in both cored and cusped potentials. However, in the case of large cores, our model is no longer able to correctly capture core-stalling. We show that this stalling owes to the tidal radius of the satellite approaching the size of the core. By switching off dynamical friction when rt(r) = r (where rt is the tidal radius at the satellite's position) we arrive at a model which reproduces the N-body results remarkably well. Since the tidal radius can be very large for constant density background distributions, our model recovers the result that stalling can occur for Ms/Menc ≪ 1, where Ms and Menc are the mass of the satellite and the enclosed galaxy mass, respectively. Finally, we include the contribution to dynamical friction that comes from stars moving faster than the satellite. This next-to-leading order effect becomes the dominant driver of inspiral near the core region, prior to stalling.

  3. A seismologically consistent compositional model of Earth's core.

    PubMed

    Badro, James; Côté, Alexander S; Brodholt, John P

    2014-05-27

    Earth's core is less dense than iron, and therefore it must contain "light elements," such as S, Si, O, or C. We use ab initio molecular dynamics to calculate the density and bulk sound velocity in liquid metal alloys at the pressure and temperature conditions of Earth's outer core. We compare the velocity and density for any composition in the (Fe-Ni, C, O, Si, S) system to radial seismological models and find a range of compositional models that fit the seismological data. We find no oxygen-free composition that fits the seismological data, and therefore our results indicate that oxygen is always required in the outer core. An oxygen-rich core is a strong indication of high-pressure and high-temperature conditions of core differentiation in a deep magma ocean with an FeO concentration (oxygen fugacity) higher than that of the present-day mantle. PMID:24821817

  4. A seismologically consistent compositional model of Earth's core.

    PubMed

    Badro, James; Côté, Alexander S; Brodholt, John P

    2014-05-27

    Earth's core is less dense than iron, and therefore it must contain "light elements," such as S, Si, O, or C. We use ab initio molecular dynamics to calculate the density and bulk sound velocity in liquid metal alloys at the pressure and temperature conditions of Earth's outer core. We compare the velocity and density for any composition in the (Fe-Ni, C, O, Si, S) system to radial seismological models and find a range of compositional models that fit the seismological data. We find no oxygen-free composition that fits the seismological data, and therefore our results indicate that oxygen is always required in the outer core. An oxygen-rich core is a strong indication of high-pressure and high-temperature conditions of core differentiation in a deep magma ocean with an FeO concentration (oxygen fugacity) higher than that of the present-day mantle.

  5. Model-Form Uncertainty Quantification in RANS Simulation of Wing-Body Junction Flow

    NASA Astrophysics Data System (ADS)

    Wu, Jinlong; Wang, Jianxun; Xiao, Heng

    2015-11-01

    Junction flow, known as one of the remaining challenges for computational aerodynamics, occurs when a boundary layer encounters an obstacle mounted on the surface. Previous studies have shown that the RANS models are not capable to provide satisfactory prediction. In this work, a novel open-box, physics-informed Bayesian framework is used to quantify the model-form uncertainties in RANS simulation of junction flow. The first objective is to correct the bias in RANS prediction, by utilizing several observation data. The second one is to quantify the model-form uncertainties, which can enable risk-informed decision-making. To begin with a standard RANS simulation, which is performed on a 3:2 elliptic nose and NACA0020 tail cylinder, uncertainties with empirical prior knowledge and physical constraints are directly injected into the Reynolds stresses term, and the unbiased knowledge from observation data is incorporated by an iterative ensemble Kalman method. Current results show that the bias in the quantities of interest (QoIs) of the RANS prediction, e.g., mean velocity, turbulent kinetic energy, etc, can be significantly corrected by this novel Bayesian framework. The probability density distributions of QoIs show that the model-form uncertainty can be quantified as well.

  6. Solid charged-core model of ball lightning

    NASA Astrophysics Data System (ADS)

    Muldrew, D. B.

    2010-01-01

    In this study, ball lightning (BL) is assumed to have a solid, positively-charged core. According to this underlying assumption, the core is surrounded by a thin electron layer with a charge nearly equal in magnitude to that of the core. A vacuum exists between the core and the electron layer containing an intense electromagnetic (EM) field which is reflected and guided by the electron layer. The microwave EM field applies a ponderomotive force (radiation pressure) to the electrons preventing them from falling into the core. The energetic electrons ionize the air next to the electron layer forming a neutral plasma layer. The electric-field distributions and their associated frequencies in the ball are determined by applying boundary conditions to a differential equation given by Stratton (1941). It is then shown that the electron and plasma layers are sufficiently thick and dense to completely trap and guide the EM field. This model of BL is exceptional in that it can explain all or nearly all of the peculiar characteristics of BL. The ES energy associated with the core charge can be extremely large which can explain the observations that occasionally BL contains enormous energy. The mass of the core prevents the BL from rising like a helium-filled balloon - a problem with most plasma and burning-gas models. The positively charged core keeps the negatively charged electron layer from diffusing away, i.e. it holds the ball together; other models do not have a mechanism to do this. The high electrical charges on the core and in the electron layer explains why some people have been electrocuted by BL. Experiments indicate that BL radiates microwaves upon exploding and this is consistent with the model. The fact that this novel model of BL can explain these and other observations is strong evidence that the model should be taken seriously.

  7. Theoretical results on the tandem junction solar cell based on its Ebers-Moll transistor model

    NASA Technical Reports Server (NTRS)

    Goradia, C.; Vaughn, J.; Baraona, C. R.

    1980-01-01

    A one-dimensional theoretical model of the tandem junction solar cell (TJC) with base resistivity greater than about 1 ohm-cm and under low level injection has been derived. This model extends a previously published conceptual model which treats the TJC as an npn transistor. The model gives theoretical expressions for each of the Ebers-Moll type currents of the illuminated TJC and allows for the calculation of the spectral response, I(sc), V(oc), FF and eta under variation of one or more of the geometrical and material parameters and 1MeV electron fluence. Results of computer calculations based on this model are presented and discussed. These results indicate that for space applications, both a high beginning of life efficiency, greater than 15% AM0, and a high radiation tolerance can be achieved only with thin (less than 50 microns) TJC's with high base resistivity (greater than 10 ohm-cm).

  8. Core formation, evolution, and convection: A geophysical model

    NASA Technical Reports Server (NTRS)

    Ruff, L.; Anderson, D. L.

    1978-01-01

    A model is proposed for the formation and evolution of the Earth's core which provides an adequate energy source for maintaining the geodynamo. A modified inhomogeneous accretion model is proposed which leads to initial iron and refractory enrichment at the center of the planet. The probable heat source for melting of the core is the decay of Al. The refractory material is emplaced irregularly in the lowermost mantle with uranium and thorium serving as a long lived heat source. Fluid motions in the core are driven by the differential heating from above and the resulting cyclonic motions may be the source of the geodynamo.

  9. Core formation, evolution, and convection - A geophysical model

    NASA Technical Reports Server (NTRS)

    Ruff, L.; Anderson, D. L.

    1980-01-01

    A model for the formation and evolution of the earth's core, which provides an adequate energy source for maintaining the geodynamo, is proposed. A modified inhomogeneous accretion model is proposed which leads to initial iron and refractory enrichment at the center of the planet. The probable heat source for melting of the core is the decay of Al-26. The refractory material is emplaced irregularly in the lowermost mantle with uranium and thorium serving as a long-lived heat source. Fluid motions in the core are driven by the differential heating from above and the resulting cyclonic motions may be the source of the geodynamo.

  10. Experimental Testing and Modeling Analysis of Solute Mixing at Water Distribution Pipe Junctions

    EPA Science Inventory

    Flow dynamics at a pipe junction controls particle trajectories, solute mixing and concentrations in downstream pipes. Here we have categorized pipe junctions into five hydraulic types, for which flow distribution factors and analytical equations for describing the solute mixing ...

  11. Modeling the Arm II core in MicroCap IV

    SciTech Connect

    Dalton, A.C.

    1996-11-01

    This paper reports on how an electrical model for the core of the Arm II machine was created and how to use this model. We wanted to get a model for the electrical characteristics of the ARM II core, in order to simulate this machine and to assist in the design of a future machine. We wanted this model to be able to simulate saturation, variable loss, and reset. Using the Hodgdon model and the circuit analysis program MicroCap IV, this was accomplished. This paper is written in such a way as to allow someone not familiar with the project to understand it.

  12. Critical behavior of models with infinite disorder at a star junction of chains

    NASA Astrophysics Data System (ADS)

    Juhász, Róbert

    2014-08-01

    We study two models having an infinite-disorder critical point—the zero temperature random transverse-field Ising model and the random contact process—on a star-like network composed of M semi-infinite chains connected to a common central site. By the strong disorder renormalization group method, the scaling dimension xM of the local order parameter at the junction is calculated. It is found to decrease rapidly with the number M of arms, but remains positive for any finite M. This means that, in contrast with the pure transverse-field Ising model, where the transition becomes of first order for M > 2, it remains continuous in the disordered models, although, for not too small M, it is hardly distinguishable from a discontinuous one owing to a close-to-zero xM. The scaling behavior of the order parameter in the Griffiths-McCoy phase is also analyzed.

  13. Toward a mineral physics reference model for the Moon's core.

    PubMed

    Antonangeli, Daniele; Morard, Guillaume; Schmerr, Nicholas C; Komabayashi, Tetsuya; Krisch, Michael; Fiquet, Guillaume; Fei, Yingwei

    2015-03-31

    The physical properties of iron (Fe) at high pressure and high temperature are crucial for understanding the chemical composition, evolution, and dynamics of planetary interiors. Indeed, the inner structures of the telluric planets all share a similar layered nature: a central metallic core composed mostly of iron, surrounded by a silicate mantle, and a thin, chemically differentiated crust. To date, most studies of iron have focused on the hexagonal closed packed (hcp, or ε) phase, as ε-Fe is likely stable across the pressure and temperature conditions of Earth's core. However, at the more moderate pressures characteristic of the cores of smaller planetary bodies, such as the Moon, Mercury, or Mars, iron takes on a face-centered cubic (fcc, or γ) structure. Here we present compressional and shear wave sound velocity and density measurements of γ-Fe at high pressures and high temperatures, which are needed to develop accurate seismic models of planetary interiors. Our results indicate that the seismic velocities proposed for the Moon's inner core by a recent reanalysis of Apollo seismic data are well below those of γ-Fe. Our dataset thus provides strong constraints to seismic models of the lunar core and cores of small telluric planets. This allows us to propose a direct compositional and velocity model for the Moon's core. PMID:25775531

  14. Toward a mineral physics reference model for the Moon's core.

    PubMed

    Antonangeli, Daniele; Morard, Guillaume; Schmerr, Nicholas C; Komabayashi, Tetsuya; Krisch, Michael; Fiquet, Guillaume; Fei, Yingwei

    2015-03-31

    The physical properties of iron (Fe) at high pressure and high temperature are crucial for understanding the chemical composition, evolution, and dynamics of planetary interiors. Indeed, the inner structures of the telluric planets all share a similar layered nature: a central metallic core composed mostly of iron, surrounded by a silicate mantle, and a thin, chemically differentiated crust. To date, most studies of iron have focused on the hexagonal closed packed (hcp, or ε) phase, as ε-Fe is likely stable across the pressure and temperature conditions of Earth's core. However, at the more moderate pressures characteristic of the cores of smaller planetary bodies, such as the Moon, Mercury, or Mars, iron takes on a face-centered cubic (fcc, or γ) structure. Here we present compressional and shear wave sound velocity and density measurements of γ-Fe at high pressures and high temperatures, which are needed to develop accurate seismic models of planetary interiors. Our results indicate that the seismic velocities proposed for the Moon's inner core by a recent reanalysis of Apollo seismic data are well below those of γ-Fe. Our dataset thus provides strong constraints to seismic models of the lunar core and cores of small telluric planets. This allows us to propose a direct compositional and velocity model for the Moon's core.

  15. A parabolic model to control quantum interference in T-shaped molecular junctions.

    PubMed

    Nozaki, Daijiro; Sevinçli, Hâldun; Avdoshenko, Stanislav M; Gutierrez, Rafael; Cuniberti, Gianaurelio

    2013-09-01

    Quantum interference (QI) effects in molecular devices have drawn increasing attention over the past years due to their unique features observed in the conductance spectrum. For the further development of single molecular devices exploiting QI effects, it is of great theoretical and practical interest to develop simple methods controlling the emergence and the positions of QI effects like anti-resonances or Fano line shapes in conductance spectra. In this work, starting from a well-known generic molecular junction with a side group (T-shaped molecule), we propose a simple graphical method to visualize the conditions for the appearance of quantum interference, Fano resonances or anti-resonances, in the conductance spectrum. By introducing a simple graphical representation (parabolic diagram), we can easily visualize the relation between the electronic parameters and the positions of normal resonant peaks and anti-resonant peaks induced by quantum interference in the conductance spectrum. This parabolic model not only can predict the emergence and energetic position of quantum interference from a few electronic parameters but also can enable one to know the coupling between the side group and the main conduction channel from measurements in the case of orthogonal basis. The results obtained within the parabolic model are validated using density-functional based quantum transport calculations in realistic T-shaped molecular junctions.

  16. Rapid remodeling of tight junctions during paracellular diapedesis in a human model of the blood-brain barrier.

    PubMed

    Winger, Ryan C; Koblinski, Jennifer E; Kanda, Takashi; Ransohoff, Richard M; Muller, William A

    2014-09-01

    Leukocyte transendothelial migration (TEM; diapedesis) is a critical event in immune surveillance and inflammation. Most TEM occurs at endothelial cell borders (paracellular). However, there is indirect evidence to suggest that, at the tight junctions of the blood-brain barrier (BBB), leukocytes migrate directly through the endothelial cell body (transcellular). Why leukocytes migrate through the endothelial cell body rather than the cell borders is unknown. To test the hypothesis that the tightness of endothelial cell junctions influences the pathway of diapedesis, we developed an in vitro model of the BBB that possessed 10-fold higher electrical resistance than standard culture conditions and strongly expressed the BBB tight junction proteins claudin-5 and claudin-3. We found that paracellular TEM was still the predominant pathway (≥98%) and TEM was dependent on PECAM-1 and CD99. We show that endothelial tight junctions expressing claudin-5 are dynamic and undergo rapid remodeling during TEM. Membrane from the endothelial lateral border recycling compartment is mobilized to the exact site of tight junction remodeling. This preserves the endothelial barrier by sealing the intercellular gaps with membrane and engaging the migrating leukocyte with unligated adhesion molecules (PECAM-1 and CD99) as it crosses the cell border. These findings provide new insights into leukocyte-endothelial interactions at the BBB and suggest that tight junctions are more dynamic than previously appreciated. PMID:25063869

  17. Design optimization of thin-film/wafer-based tandem junction solar cells using analytical modeling

    NASA Astrophysics Data System (ADS)

    Davidson, Lauren; Toor, Fatima

    2016-03-01

    Several research groups are developing solar cells of varying designs and materials that are high efficiency as well as cost competitive with the single junction silicon (Si) solar cells commercially produced today. One of these solar cell designs is a tandem junction solar cell comprised of perovskite (CH3NH3PbI3) and silicon (Si). Loper et al.1 was able to create a 13.4% efficient tandem cell using a perovskite top cell and a Si bottom cell, and researchers are confident that the perovskite/Si tandem cell can be optimized in order to reach higher efficiencies without introducing expensive manufacturing processes. However, there are currently no commercially available software capable of modeling a tandem cell that is based on a thin-film based bottom cell and a wafer-based top cell. While PC1D2 and SCAPS3 are able to model tandem cells comprised solely of thin-film absorbers or solely of wafer-based absorbers, they result in convergence errors if a thin-film/wafer-based tandem cell, such as the perovskite/ Si cell, is modeled. The Matlab-based analytical model presented in this work is capable of modeling a thin-film/wafer-based tandem solar cell. The model allows a user to adjust the top and bottom cell parameters, such as reflectivity, material bandgaps, donor and acceptor densities, and material thicknesses, in order to optimize the short circuit current, open circuit voltage, and quantum efficiency of the tandem solar cell. Using the Matlab-based analytical model, we were able optimize a perovskite/Si tandem cell with an efficiency greater than 30%.

  18. An Intercomparison of 10 Atmospheric Model Dynamical Cores

    NASA Astrophysics Data System (ADS)

    Jablonowski, C.; Lauritzen, P. H.; Taylor, M. A.; Nair, R. D.

    2008-12-01

    The poster introduces an idealized test suite for the dynamical cores of Atmospheric General Circulation Models (GCMs) and presents results of the broadest dynamical core intercomparison project ever conducted to date. The intercomparison project was held at the National Center for Atmospheric Research (NCAR), Boulder, in June 2008. It was part of the NCAR Advanced Study Program's Summer Colloquium that not only surveyed the latest developments in numerical methods for dynamical cores but also hosted 10 modeling groups, key lecturers and 40 students for a two-week time period. The participating models represent a wide spectrum of numerical approaches and computational grids like latitude-longitude grids, Gaussian, icosahedral and cubed-sphere meshes. The comparison reveals new insights into the characteristics of the model simulations which include the diffusion and conservation properties. These were assessed via six deterministic dynamical core test cases run by the student group. The test hierarchy is now suggested as the starting point for a standard dynamical core test suite and serves as a launch pad for an even broader community driven dynamical core intercomparison experiment.

  19. SCDAP/RELAP5 lower core plate model

    SciTech Connect

    Coryell, E.W.; Griffin, F.P.

    1999-09-01

    The SCDAP/RELAP5 computer code is a best-estimate analysis tool for performing nuclear reactor severe accident simulations. This report describes the justification, theory, implementation, and testing of a new modeling capability which will refine the analysis of the movement of molten material from the core region to the vessel lower head. As molten material moves from the core region through the core support structures it may encounter conditions which will cause it to freeze in the region of the lower core plate, delaying its arrival to the vessel head. The timing of this arrival is significant to reactor safety, because during the time span for material relocation to the lower head, the core may be experiencing steam-limited oxidation. The time at which hot material arrives in a coolant-filled lower vessel head, thereby significantly increasing the steam flow rate through the core region, becomes significant to the progression and timing of a severe accident. This report is a revision of a report INEEL/EXT-00707, entitled ``Preliminary Design Report for SCDAP/RELAP5 Lower Core Plate Model''.

  20. SCDAP/RELAP5 Lower Core Plate Model

    SciTech Connect

    Coryell, Eric Wesley; Griffin, F. P.

    1999-10-01

    The SCDAP/RELAP5 computer code is a best-estimate analysis tool for performing nuclear reactor severe accident simulations. This report describes the justification, theory, implementation, and testing of a new modeling capability which will refine the analysis of the movement of molten material from the core region to the vessel lower head. As molten material moves from the core region through the core support structures it may encounter conditions which will cause it to freeze in the region of the lower core plate, delaying its arrival to the vessel head. The timing of this arrival is significant to reactor safety, because during the time span for material relocation to the lower head, the core may be experiencing steam-limited oxidation. The time at which hot material arrives in a coolant-filled lower vessel head, thereby significantly increasing the steam flow rate through the core region, becomes significant to the progression and timing of a severe accident. This report is a revision of a report INEEL/EXT-00707, entitled "Preliminary Design Report for SCDAP/RELAP5 Lower Core Plate Model".

  1. Implementation of total dose effects in the bipolar junction transistor Gummel-Poon model

    SciTech Connect

    Montagner, X.; Fouillat, P.; Briand, R.; Touboul, A.; Schrimpf, R.D.; Galloway, K.F.; Calvet, M.C.; Calvel, P.

    1997-12-01

    The effects of total dose on the SPICE model of bipolar junction transistors are investigated. The limitations of the standard Gummel-Poon model for simulating the radiation-induced excess base current are analyzed, and a new model based on an empirical approach is proposed. Four new SPICE rad-parameters are presented, and investigated for different dose rates. The relevant parameters are extracted using a new algorithmic procedure, combining a genetic approach and the standard optimization technique which minimizes the RMS error between measured and simulated excess base current. It is shown that the excess base current is accurately described by the same formula whatever the device type is. An empirical fitting of the rad-parameters as a function of total dose is proposed to use in hardening electronic circuits for space-like environments.

  2. Deriving a Core Magnetic Field Model from Swarm Satellite Data

    NASA Astrophysics Data System (ADS)

    Lesur, V.; Rother, M.; Wardinski, I.

    2014-12-01

    A model of the Earth's core magnetic field has been built using Swarm satellite mission data and observatory quasi-definitive data. The satellite data processing scheme, which was used to derive previous satellite field models (i.e. GRIMM series), has been modified to handle discrepancies between the satellite total intensity data derived from the vector fluxgate magnetometer and the absolute scalar instrument. Further, the Euler angles, i.e. the angles between the vector magnetometer and the satellite reference frame, have been recalculated on a series of 30-day windows to obtain an accurate model of the core field for 2014. Preliminary derivations of core magnetic field and SV models for 2014 present the same characteristics as during the CHAMP era. The acceleration (i.e. the field second time derivative) has shown a rapid evolution over the last few years, and is present in the current model, which confirms previous observations.

  3. Summary of multi-core hardware and programming model investigations

    SciTech Connect

    Kelly, Suzanne Marie; Pedretti, Kevin Thomas Tauke; Levenhagen, Michael J.

    2008-05-01

    This report summarizes our investigations into multi-core processors and programming models for parallel scientific applications. The motivation for this study was to better understand the landscape of multi-core hardware, future trends, and the implications on system software for capability supercomputers. The results of this study are being used as input into the design of a new open-source light-weight kernel operating system being targeted at future capability supercomputers made up of multi-core processors. A goal of this effort is to create an agile system that is able to adapt to and efficiently support whatever multi-core hardware and programming models gain acceptance by the community.

  4. Seismic tomography and deformation modeling of the junction of the San Andreas and Calaveras faults

    USGS Publications Warehouse

    Dorbath, C.; Oppenheimer, D.; Amelung, F.; King, G.

    1996-01-01

    Local earthquake P traveltime data is inverted to obtain a three-dimensional tomographic image of the region centered on the junction of the San Andreas and Calaveras faults. The resulting velocity model is then used to relocate more than 17,000 earthquakes and to produce a model of fault structure in the region. These faults serve as the basis for modeling the topography using elastic dislocation methods. The region is of interest because active faults join, it marks the transition zone from creeping to locked fault behavior on the San Andreas fault, it exhibits young topography, and it has a good spatial distribution of seismicity. The tomographic data set is extensive, consisting of 1445 events, 96 stations, and nearly 95,000 travel time readings. Tomographic images are resolvable to depths of 12 km and show significant velocity contrasts across the San Andreas and Calaveras faults, a low-velocity zone associated with the creeping section of the San Andreas fault, and shallow low-velocity sediments in the southern Santa Clara valley and northern Salinas valley. Relocated earthquakes only occur where vp>5 km/s and indicate that portions of the San Andreas and Calaveras faults are non vertical, although we cannot completely exclude the possibility that all or part of this results from ray tracing problems. The new dips are more consistent with geological observations that dipping faults intersect the surface where surface traces have been mapped. The topographic modeling predicts extensive subsidence in regions characterized by shallow low-velocity material, presumably the result of recent sedimentation. Some details of the topography at the junction of the San Andreas and Calaveras faults are not consistent with the modeling results, suggesting that the current position of this "triple junction" has changed with time. The model also predicts those parts of the fault subject to contraction or extension perpendicular to the fault strike and hence the sense of any

  5. Modelling line emission of deuterated H3+ from prestellar cores

    NASA Astrophysics Data System (ADS)

    Sipilä, O.; Hugo, E.; Harju, J.; Asvany, O.; Juvela, M.; Schlemmer, S.

    2010-01-01

    Context. The depletion of heavy elements in cold cores of interstellar molecular clouds can lead to a situation where deuterated forms of H3+ are the most useful spectroscopic probes of the physical conditions. Aims: The aim is to predict the observability of the rotational lines of H2D+ and D2H+ from prestellar cores. Methods: Recently derived rate coefficients for the H3+ + H2 isotopic system were applied to the “complete depletion” reaction scheme to calculate abundance profiles in hydrostatic core models. The ground-state lines of H2D+(o) (372 GHz) and D2H+(p) (692 GHz) arising from these cores were simulated. The excitation of the rotational levels of these molecules was approximated by using the state-to-state coefficients for collisions with H2. We also predicted line profiles from cores with a power-law density distribution advocated in some previous studies. Results: The new rate coefficients introduce some changes to the complete depletion model, but do not alter the general tendencies. One of the modifications with respect to the previous results is the increase of the D3+ abundance at the cost of other isotopologues. Furthermore, the present model predicts a lower H2D+ (o/p) ratio, and a slightly higher D2H+ (p/o) ratio in very cold, dense cores, as compared with previous modelling results. These nuclear spin ratios affect the detectability of the submm lines of H2D+(o) and D2H+(p). The previously detected H2D+ and D2H+ lines towards the core I16293E, and the H2D+ line observed towards Oph D can be reproduced using the present excitation model and the physical models suggested in the original papers.

  6. Dynamic behavior of Arabidopsis eIF4A-III, putative core protein of exon junction complex: fast relocation to nucleolus and splicing speckles under hypoxia.

    PubMed

    Koroleva, O A; Calder, G; Pendle, A F; Kim, S H; Lewandowska, D; Simpson, C G; Jones, I M; Brown, J W S; Shaw, P J

    2009-05-01

    Here, we identify the Arabidopsis thaliana ortholog of the mammalian DEAD box helicase, eIF4A-III, the putative anchor protein of exon junction complex (EJC) on mRNA. Arabidopsis eIF4A-III interacts with an ortholog of the core EJC component, ALY/Ref, and colocalizes with other EJC components, such as Mago, Y14, and RNPS1, suggesting a similar function in EJC assembly to animal eIF4A-III. A green fluorescent protein (GFP)-eIF4A-III fusion protein showed localization to several subnuclear domains: to the nucleoplasm during normal growth and to the nucleolus and splicing speckles in response to hypoxia. Treatment with the respiratory inhibitor sodium azide produced an identical response to the hypoxia stress. Treatment with the proteasome inhibitor MG132 led to accumulation of GFP-eIF4A-III mainly in the nucleolus, suggesting that transition of eIF4A-III between subnuclear domains and/or accumulation in nuclear speckles is controlled by proteolysis-labile factors. As revealed by fluorescence recovery after photobleaching analysis, the nucleoplasmic fraction was highly mobile, while the speckles were the least mobile fractions, and the nucleolar fraction had an intermediate mobility. Sequestration of eIF4A-III into nuclear pools with different mobility is likely to reflect the transcriptional and mRNA processing state of the cell. PMID:19435936

  7. Dynamic behavior of Arabidopsis eIF4A-III, putative core protein of exon junction complex: fast relocation to nucleolus and splicing speckles under hypoxia.

    PubMed

    Koroleva, O A; Calder, G; Pendle, A F; Kim, S H; Lewandowska, D; Simpson, C G; Jones, I M; Brown, J W S; Shaw, P J

    2009-05-01

    Here, we identify the Arabidopsis thaliana ortholog of the mammalian DEAD box helicase, eIF4A-III, the putative anchor protein of exon junction complex (EJC) on mRNA. Arabidopsis eIF4A-III interacts with an ortholog of the core EJC component, ALY/Ref, and colocalizes with other EJC components, such as Mago, Y14, and RNPS1, suggesting a similar function in EJC assembly to animal eIF4A-III. A green fluorescent protein (GFP)-eIF4A-III fusion protein showed localization to several subnuclear domains: to the nucleoplasm during normal growth and to the nucleolus and splicing speckles in response to hypoxia. Treatment with the respiratory inhibitor sodium azide produced an identical response to the hypoxia stress. Treatment with the proteasome inhibitor MG132 led to accumulation of GFP-eIF4A-III mainly in the nucleolus, suggesting that transition of eIF4A-III between subnuclear domains and/or accumulation in nuclear speckles is controlled by proteolysis-labile factors. As revealed by fluorescence recovery after photobleaching analysis, the nucleoplasmic fraction was highly mobile, while the speckles were the least mobile fractions, and the nucleolar fraction had an intermediate mobility. Sequestration of eIF4A-III into nuclear pools with different mobility is likely to reflect the transcriptional and mRNA processing state of the cell.

  8. Blockade of Gap Junction Hemichannel Suppresses Disease Progression in Mouse Models of Amyotrophic Lateral Sclerosis and Alzheimer's Disease

    PubMed Central

    Takeuchi, Hideyuki; Mizoguchi, Hiroyuki; Doi, Yukiko; Jin, Shijie; Noda, Mariko; Liang, Jianfeng; Li, Hua; Zhou, Yan; Mori, Rarami; Yasuoka, Satoko; Li, Endong; Parajuli, Bijay; Kawanokuchi, Jun; Sonobe, Yoshifumi; Sato, Jun; Yamanaka, Koji; Sobue, Gen; Mizuno, Tetsuya; Suzumura, Akio

    2011-01-01

    Background Glutamate released by activated microglia induces excitotoxic neuronal death, which likely contributes to non-cell autonomous neuronal death in neurodegenerative diseases, including amyotrophic lateral sclerosis and Alzheimer's disease. Although both blockade of glutamate receptors and inhibition of microglial activation are the therapeutic candidates for these neurodegenerative diseases, glutamate receptor blockers also perturbed physiological and essential glutamate signals, and inhibitors of microglial activation suppressed both neurotoxic/neuroprotective roles of microglia and hardly affected disease progression. We previously demonstrated that activated microglia release a large amount of glutamate specifically through gap junction hemichannel. Hence, blockade of gap junction hemichannel may be potentially beneficial in treatment of neurodegenerative diseases. Methods and Findings In this study, we generated a novel blood-brain barrier permeable gap junction hemichannel blocker based on glycyrrhetinic acid. We found that pharmacologic blockade of gap junction hemichannel inhibited excessive glutamate release from activated microglia in vitro and in vivo without producing notable toxicity. Blocking gap junction hemichannel significantly suppressed neuronal loss of the spinal cord and extended survival in transgenic mice carrying human superoxide dismutase 1 with G93A or G37R mutation as an amyotrophic lateral sclerosis mouse model. Moreover, blockade of gap junction hemichannel also significantly improved memory impairments without altering amyloid β deposition in double transgenic mice expressing human amyloid precursor protein with K595N and M596L mutations and presenilin 1 with A264E mutation as an Alzheimer's disease mouse model. Conclusions Our results suggest that gap junction hemichannel blockers may represent a new therapeutic strategy to target neurotoxic microglia specifically and prevent microglia-mediated neuronal death in various

  9. Micromagnetic model for studies on Magnetic Tunnel Junction switching dynamics, including local current density

    NASA Astrophysics Data System (ADS)

    Frankowski, Marek; Czapkiewicz, Maciej; Skowroński, Witold; Stobiecki, Tomasz

    2014-02-01

    We present a model introducing the Landau-Lifshitz-Gilbert equation with a Slonczewski's Spin-Transfer-Torque (STT) component in order to take into account spin polarized current influence on the magnetization dynamics, which was developed as an Object Oriented MicroMagnetic Framework extension. We implement the following computations: magnetoresistance of vertical channels is calculated from the local spin arrangement, local current density is used to calculate the in-plane and perpendicular STT components as well as the Oersted field, which is caused by the vertical current flow. The model allows for an analysis of all listed components separately, therefore, the contribution of each physical phenomenon in dynamic behavior of Magnetic Tunnel Junction (MTJ) magnetization is discussed. The simulated switching voltage is compared with the experimental data measured in MTJ nanopillars.

  10. Macro model for stochastic behavior of resistance distribution of magnetic tunnel junction

    NASA Astrophysics Data System (ADS)

    Kil, Gyuhyun; Choi, Juntae; Song, Yunheub

    2015-04-01

    In this work, we fabricated MgO-based magnetic tunnel junction (MTJ) samples to observe behavior of resistance variation, and investigated a stochastic behavior model for MTJ resistance from measured real data. We found the relationship between parallel resistance (RP), anti-parallel resistance (RAP), and TMR from the measurements. The variation of barrier thickness affects not only resistance but also TMR. This means that broad RAP distribution is caused by RP distribution. In addition, RAP distribution can be reduced by increasing temperature and bias voltage. We developed a macro model that can evaluate resistance distribution based on the stochastic behavior of MTJ resistance variation from only tox varied. The amount of resistance variation, which is considered with regard to the circuit performance, can be obtained from Δtox designed by designer. In addition, the impact for operating circumstance such as bias and temperature can be considered by using fit equations.

  11. Atomic Data For Core And Edge Modeling

    SciTech Connect

    O'Mullane, M. G.; Foster, A. R.; Whiteford, A. D.; Summers, H. P.; Loch, S. D.; Lauro-Taroni, L.

    2009-09-10

    Future magnetic fusion energy devices, will have both very high Z (tungsten) and low Z (beryllium) plasma facing components, are setting the agenda for current atomic data needs. Data for the light species are in good shape but the heavy species present some challenges. We outline an approach for systematic heavy element data production for fusion applications in addition to techniques for handling the large amount of data in modeling codes efficiently.

  12. Modeling of Core Competencies in the Registrar's Office

    ERIC Educational Resources Information Center

    Pikowsky, Reta

    2009-01-01

    The Office of the Registrar at the Georgia Institute of Technology, in cooperation with the Office of Human Resources, has been engaged since February 2008 in a pilot project to model core competencies for the leadership team and the staff. It is the hope of the office of Human resources that this pilot will result in a model that can be used…

  13. Core-oscillator model of Caulobacter crescentus

    NASA Astrophysics Data System (ADS)

    Vandecan, Yves; Biondi, Emanuele; Blossey, Ralf

    2016-06-01

    The gram-negative bacterium Caulobacter crescentus is a powerful model organism for studies of bacterial cell cycle regulation. Although the major regulators and their connections in Caulobacter have been identified, it still is a challenge to properly understand the dynamics of its circuitry which accounts for both cell cycle progression and arrest. We show that the key decision module in Caulobacter is built from a limit cycle oscillator which controls the DNA replication program. The effect of an induced cell cycle arrest is demonstrated to be a key feature to classify the underlying dynamics.

  14. Core-oscillator model of Caulobacter crescentus.

    PubMed

    Vandecan, Yves; Biondi, Emanuele; Blossey, Ralf

    2016-06-01

    The gram-negative bacterium Caulobacter crescentus is a powerful model organism for studies of bacterial cell cycle regulation. Although the major regulators and their connections in Caulobacter have been identified, it still is a challenge to properly understand the dynamics of its circuitry which accounts for both cell cycle progression and arrest. We show that the key decision module in Caulobacter is built from a limit cycle oscillator which controls the DNA replication program. The effect of an induced cell cycle arrest is demonstrated to be a key feature to classify the underlying dynamics.

  15. Core Collapse Supernova Models and Nucleosynthesis

    NASA Astrophysics Data System (ADS)

    Nomoto, Ken'ichi

    2014-01-01

    After the Big Bang, production of heavy elements in the early Universe takes place in the first stars and their supernova explosions. The nature of the first supernovae, however, has not been well understood. The signature of nucleosynthesis yields of the first supernovae can be seen in the elemental abundance patterns observed in extremely metal-poor stars. Interestingly, those abundance patterns show some peculiarities relative to the solar abundance pattern, which should provide important clues to understanding the nature of early generations of supernovae. We review the recent results of the nucleosynthesis yields of massive stars. We examine how those yields are affected by some hydrodynamical effects during the supernova explosions, namely, explosion energies from those of hypernovae to faint supernovae, mixing and fallback of processed materials, asphericity, etc. Those parameters in the supernova nucleosynthesis models are constrained from observational data of supernovae and metal-poor stars.

  16. Large magnetocapacitance effect in magnetic tunnel junctions based on Debye-Fröhlich model

    NASA Astrophysics Data System (ADS)

    Kaiju, Hideo; Takei, Masashi; Misawa, Takahiro; Nagahama, Taro; Nishii, Junji; Xiao, Gang

    2015-09-01

    The frequency dependence of tunneling magnetocapacitance (TMC) in magnetic tunnel junctions (MTJs) is investigated theoretically and experimentally. According to the calculation based on Debye-Fröhlich model combined with Julliere formula, the TMC ratio strongly depends on the frequency and it has the maximum peak at a specific frequency. The calculated frequency dependence of TMC is in good agreement with the experimental results obtained in MgO-based MTJs with a tunneling magnetoresistance (TMR) ratio of 108%, which exhibit a large TMC ratio of 155% at room temperature. This calculation also predicts that the TMC ratio can be as large as about 1000% for a spin polarization of 87%, while the TMR ratio is 623% for the same spin polarization. These theoretical and experimental findings provide a deeper understanding on AC spin-dependent transport in the MTJs and will open up wider opportunities for device applications, such as highly sensitive magnetic sensors and impedance-tunable devices.

  17. Large magnetocapacitance effect in magnetic tunnel junctions based on Debye-Fröhlich model

    SciTech Connect

    Kaiju, Hideo Takei, Masashi; Misawa, Takahiro; Nishii, Junji; Nagahama, Taro; Xiao, Gang

    2015-09-28

    The frequency dependence of tunneling magnetocapacitance (TMC) in magnetic tunnel junctions (MTJs) is investigated theoretically and experimentally. According to the calculation based on Debye-Fröhlich model combined with Julliere formula, the TMC ratio strongly depends on the frequency and it has the maximum peak at a specific frequency. The calculated frequency dependence of TMC is in good agreement with the experimental results obtained in MgO-based MTJs with a tunneling magnetoresistance (TMR) ratio of 108%, which exhibit a large TMC ratio of 155% at room temperature. This calculation also predicts that the TMC ratio can be as large as about 1000% for a spin polarization of 87%, while the TMR ratio is 623% for the same spin polarization. These theoretical and experimental findings provide a deeper understanding on AC spin-dependent transport in the MTJs and will open up wider opportunities for device applications, such as highly sensitive magnetic sensors and impedance-tunable devices.

  18. Physical model of back line-contact front-junction solar cells

    NASA Astrophysics Data System (ADS)

    Cuevas, Andres

    2013-04-01

    The analysis of advanced front-junction solar cells where the metal contact to the base region is locally formed on the back surface in the shape of lines usually requires numerical simulations. Here, we describe an approach based on a geometric formulation of carrier crowding towards the localized contact, in conjunction with a partition of the device in two distinct regions. This permits a one dimensional analysis of carrier flow, both in the region immediately adjacent to the contact and in the peripheral region surrounding it. The resulting model is simple enough to provide insight into the physics of device operation and reasonably accurate in cases of practical interest. By applying it to different cases, we identify unexpected anomalies and explain them in terms of the peculiar interplay between carrier transport and recombination that takes place in this type of solar cell.

  19. Field theoretical model of multilayered Josephson junction and dynamics of Josephson vortices

    NASA Astrophysics Data System (ADS)

    Fujimori, Toshiaki; Iida, Hideaki; Nitta, Muneto

    2016-09-01

    Multilayered Josephson junctions are modeled in the context of a field theory, and dynamics of Josephson vortices trapped inside insulators are studied. Starting from a theory consisting of complex and real scalar fields coupled to a U(1) gauge field which admit parallel N -1 domain-wall solutions, Josephson couplings are introduced weakly between the complex scalar fields. The N -1 domain walls behave as insulators separating N superconductors, where one of the complex scalar fields has a gap. We construct the effective Lagrangian on the domain walls, which reduces to a coupled sine-Gordon model for well-separated walls and contains more interactions for walls at short distance. We then construct sine-Gordon solitons emerging in an effective theory in which we identify Josephson vortices carrying singly quantized magnetic fluxes. When two neighboring superconductors tend to have the same phase, the ground state does not change with the positions of domain walls (the width of superconductors). On the other hand, when two neighboring superconductors tend to have π -phase differences, the ground state has a phase transition depending on the positions of domain walls; when the two walls are close to each other (one superconductor is thin), frustration occurs because of the coupling between the two superconductors besides the thin superconductor. Focusing on the case of three superconductors separated by two insulators, we find for the former case that the interaction between two Josephson vortices on different insulators changes its nature, i.e., attractive or repulsive, depending on the positions of the domain walls. In the latter case, there emerges fractional Josephson vortices when two degenerate ground states appear due to spontaneous charge-symmetry breaking, and the number of the Josephson vortices varies with the position of the domain walls. Our predictions should be verified in multilayered Josephson junctions.

  20. A physics-based compact model of ferroelectric tunnel junction for memory and logic design

    NASA Astrophysics Data System (ADS)

    Wang, Zhaohao; Zhao, Weisheng; Kang, Wang; Bouchenak-Khelladi, Anes; Zhang, Yue; Zhang, Youguang; Klein, Jacques-Olivier; Ravelosona, Dafiné; Chappert, Claude

    2014-01-01

    Ferroelectric tunnel junction (FTJ) is able to store non-volatile data in the spontaneous polarization direction of ferroelectric tunnel barrier. Recent progress has demonstrated its great potential to build up the next generation non-volatile memory and logic (NVM and NVL) thanks to the high OFF/ON resistance ratio, fast operation speed, low write power, non-destructive readout and so on. In this paper, we present the first physics-based compact model for Co/BTO/LSMO FTJ nanopillar, which was reported experimentally to exhibit excellent NVM performance. This model integrates related physical models of tunnel resistance, static switching voltage and dynamic switching delay. Its accuracy is shown by the good agreement between numerical model simulation and experimental measurements. This compact model has been developed in Verilog-A language and validated by single-cell simulation on Cadence Virtuoso Platform. Hybrid simulations based on 40 nm-technology node of FTJ memory arrays and non-volatile full adder were performed to demonstrate the efficiency of our compact model for the simulation and analysis of CMOS/FTJ integrated circuits.

  1. Numerical models of the Earth’s thermal history: Effects of inner-core solidification and core potassium

    NASA Astrophysics Data System (ADS)

    Butler, S. L.; Peltier, W. R.; Costin, S. O.

    2005-09-01

    Recently there has been renewed interest in the evolution of the inner core and in the possibility that radioactive potassium might be found in significant quantities in the core. The arguments for core potassium come from considerations of the age of the inner core and the energy required to sustain the geodynamo [Nimmo, F., Price, G.D., Brodholt, J., Gubbins, D., 2004. The influence of potassium on core and geodynamo evolution. Geophys. J. Int. 156, 363-376; Labrosse, S., Poirier, J.-P., Le Mouël, J.-L., 2001. The age of the inner core. Earth Planet Sci. Lett. 190, 111-123; Labrosse, S., 2003. Thermal and magnetic evolution of the Earth's core. Phys. Earth Planet Int. 140, 127-143; Buffett, B.A., 2003. The thermal state of Earth's core. Science 299, 1675-1677] and from new high pressure physics analyses [Lee, K., Jeanloz, R., 2003. High-pressure alloying of potassium and iron: radioactivity in the Earth's core? Geophys. Res. Lett. 30 (23); Murthy, V.M., van Westrenen, W., Fei, Y.W., 2003. Experimental evidence that potassium is a substantial radioactive heat source in planetary cores. Nature 423, 163-165; Gessmann, C.K., Wood, B.J., 2002. Potassium in the Earth's core? Earth Planet Sci. Lett. 200, 63-78]. The Earth's core is also located at the lower boundary of the convecting mantle and the presence of radioactive heat sources in the core will affect the flux of heat between these two regions and will, as a result, have a significant impact on the Earth's thermal history. In this paper, we present Earth thermal history simulations in which we calculate fluid flow in a spherical shell representing the mantle, coupled with a core of a given heat capacity with varying degrees of internal heating in the form of K40 and varying initial core temperatures. The mantle model includes the effects of the temperature dependence of viscosity, decaying radioactive heat sources, and mantle phase transitions. The core model includes the thermal effects of inner core

  2. Mathematical Modeling, Sense Making, and the Common Core State Standards

    ERIC Educational Resources Information Center

    Schoenfeld, Alan H.

    2013-01-01

    On October 14, 2013 the Mathematics Education Department at Teachers College hosted a full-day conference focused on the Common Core Standards Mathematical Modeling requirements to be implemented in September 2014 and in honor of Professor Henry Pollak's 25 years of service to the school. This article is adapted from my talk at this conference…

  3. Nanotube junctions

    DOEpatents

    Crespi, Vincent Henry; Cohen, Marvin Lou; Louie, Steven Gwon; Zettl, Alexander Karlwalte

    2004-12-28

    The present invention comprises a new nanoscale metal-semiconductor, semiconductor-semiconductor, or metal-metal junction, designed by introducing topological or chemical defects in the atomic structure of the nanotube. Nanotubes comprising adjacent sections having differing electrical properties are described. These nanotubes can be constructed from combinations of carbon, boron, nitrogen and other elements. The nanotube can be designed having different indices on either side of a junction point in a continuous tube so that the electrical properties on either side of the junction vary in a useful fashion. For example, the inventive nanotube may be electrically conducting on one side of a junction and semiconducting on the other side. An example of a semiconductor-metal junction is a Schottky barrier. Alternatively, the nanotube may exhibit different semiconductor properties on either side of the junction. Nanotubes containing heterojunctions, Schottky barriers, and metal-metal junctions are useful for microcircuitry.

  4. Nanotube junctions

    DOEpatents

    Crespi, Vincent Henry; Cohen, Marvin Lou; Louie, Steven Gwon Sheng; Zettl, Alexander Karlwalter

    2003-01-01

    The present invention comprises a new nanoscale metal-semiconductor, semiconductor-semiconductor, or metal-metal junction, designed by introducing topological or chemical defects in the atomic structure of the nanotube. Nanotubes comprising adjacent sections having differing electrical properties are described. These nanotubes can be constructed from combinations of carbon, boron, nitrogen and other elements. The nanotube can be designed having different indices on either side of a junction point in a continuous tube so that the electrical properties on either side of the junction vary in a useful fashion. For example, the inventive nanotube may be electrically conducting on one side of a junction and semiconducting on the other side. An example of a semiconductor-metal junction is a Schottky barrier. Alternatively, the nanotube may exhibit different semiconductor properties on either side of the junction. Nanotubes containing heterojunctions, Schottky barriers, and metal-metal junctions are useful for microcircuitry.

  5. Effective model for a short Josephson junction with a phase discontinuity

    NASA Astrophysics Data System (ADS)

    Goldobin, E.; Mironov, S.; Buzdin, A.; Mints, R. G.; Koelle, D.; Kleiner, R.

    2016-04-01

    We consider a short Josephson junction with a phase discontinuity κ created, e.g., by a pair of tiny current injectors, at some point x0 along the width of the junction. We derive the effective current-phase relation (CPR) for the system as a whole, i.e., reduce it to an effective pointlike junction. From the effective CPR we obtain the ground state of the system and predict the dependence of its critical current on κ . We show that in a large range of κ values the effective junction behaves as a φ0 Josephson junction, i.e., has a unique ground state phase φ0 within each 2 π interval. For κ ≈π and x0 near the middle of the junction one obtains a φ0±φ junction, i.e., a Josephson junction with degenerate ground state phase φ0±φ within each 2 π interval. Further, in view of possible escape experiments especially in the quantum domain, we investigate the scaling of the energy barrier and eigenfrequency close to the critical currents and predict the behavior of the escape histogram width σ (κ ) in the regime of the macroscopic quantum tunneling.

  6. Probiotics modify tight-junction proteins in an animal model of nonalcoholic fatty liver disease

    PubMed Central

    Briskey, David; Heritage, Mandy; Jaskowski, Lesley-Anne; Peake, Jonathan; Gobe, Glenda; Subramaniam, V. Nathan; Crawford, Darrell; Campbell, Catherine; Vitetta, Luis

    2016-01-01

    Background: We have investigated the effects of a multispecies probiotic preparation containing a combination of probiotic bacterial genera that included Bifidobacteria, Lactobacilli and a Streptococcus in a mouse model of high-fat diet or obesity-induced liver steatosis. Methods: Three groups of C57B1/6J mice were fed either a standard chow or a high-fat diet for 20 weeks, while a third group was fed a high-fat diet for 10 weeks and then concomitantly administered probiotics for a further 10 weeks. Serum, liver and large bowel samples were collected for analysis. Results: The expression of the tight-junction proteins ZO-1 and ZO-2 was reduced (p < 0.05) in high-fat diet-fed mice compared to chow-fed mice. Probiotic supplementation helped to maintain tight ZO-1 and ZO-2 expression compared with the high-fat diet group (p < 0.05), but did not restore ZO-1 or ZO-2 expression compared with chow-fed mice. Mice fed a high-fat diet ± probiotics had significant steatosis development compared with chow-fed mice (p < 0.05); steatosis was less severe in the probiotics group compared with the high-fat diet group. Hepatic triglyceride concentration was higher in mice fed a high-fat diet ± probiotics compared with the chow group (p < 0.05), and was lower in the probiotics group compared with the high-fat diet group (p < 0.05). Compared with chow-fed mice, serum glucose, cholesterol concentration and the activity of alanine transaminase were higher (p < 0.05), whereas serum triglyceride concentration was lower (p < 0.05) in mice fed a high-fat diet ± probiotics. Conclusions: Supplementation with a multispecies probiotic formulation helped to maintain tight-junction proteins ZO-1 and ZO-2, and reduced hepatic triglyceride concentration compared with a high-fat diet alone. PMID:27366215

  7. Two dimensional modelling of three core cable transient temperature rise

    SciTech Connect

    Lyall, J. )

    1990-01-01

    This paper describes a study of the transient temperature rise of a three core table. Results from a computer program that models the two dimensional heat flow are compared with those obtained using the normally applied one dimensional model. The modelling technique is an alternative to the finite difference and finite element methods. It develops the concept of a thermal resistance/capacitance analogue as can be done using the finite difference method but does so more directly without the need to use the partial differential equation. In addition, it provides the flexibility of the finite element method when modelling a complex geometry and material combination such as that found in a 3-core cable without the complexity of its mathematics.

  8. Model-based parameterisation of a hydrocyclone air-core

    PubMed

    Podd; Schlaberg; Hoyle

    2000-03-01

    An important metric for the accurate control of a hydrocyclone is the diameter of its air-core. Ultrasonic data from a 16-transducer, 1.5 MHz pulse-echo tomographic system are analysed to determine the variation of the air-core diameter with various operating conditions. The back-projection image reconstruction method is not accurate enough for this task. Sub-millimetre accuracy is obtained, however, by applying a combination of signal processing and model-based reconstruction, using the fact that there is a small variation in the air-core boundary position. The findings correspond well to the results obtained from X-ray and electrical resistance modalities.

  9. A simple model for induction core voltage distributions

    SciTech Connect

    Briggs, Richard J.; Fawley, William M.

    2004-07-01

    In fall 2003 T. Hughes of MRC used a full EM simulation code (LSP) to show that the electric field stress distribution near the outer radius of the longitudinal gaps between the four Metglas induction cores is very nonuniform in the original design of the DARHT-2 accelerator cells. In this note we derive a simple model of the electric field distribution in the induction core region to provide physical insights into this result. The starting point in formulating our model is to recognize that the electromagnetic fields in the induction core region of the DARHT-2 accelerator cells should be accurately represented within a quasi-static approximation because the timescale for the fields to change is much longer than the EM wave propagation time. The difficulty one faces is the fact that the electric field is a mixture of both a ''quasi-magnetostatic field'' (having a nonzero curl, with Bdot the source) and a ''quasi-electrostatic field'' (the source being electric charges on the various metal surfaces). We first discuss the EM field structure on the ''micro-scale'' of individual tape windings in Section 2. The insights from that discussion are then used to formulate a ''macroscopic'' description of the fields inside an ''equivalent homogeneous tape wound core region'' in Section 3. This formulation explicitly separates the nonlinear core magnetics from the quasi-electrostatic components of the electric field. In Section 4 a physical interpretation of the radial dependence of the electrostatic component of the electric field derived from this model is presented in terms of distributed capacitances, and the voltage distribution from gap to gap is related to various ''equivalent'' lumped capacitances. Analytic solutions of several simple multi-core cases are presented in Sections 5 and 6 to help provide physical insight into the effect of various proposed changes in the geometrical parameters of the DARHT-2 accelerator cell. Our results show that over most of the gap

  10. Experimental Model of Proximal Junctional Fracture after Multilevel Posterior Spinal Instrumentation

    PubMed Central

    Levasseur, Annie; Parent, Stefan; Petit, Yvan

    2016-01-01

    There is a high risk of proximal junctional fractures (PJF) with multilevel spinal instrumentation, especially in the osteoporotic spine. This problem is associated with significant morbidity and possibly the need for reoperation. Various techniques have been proposed in an attempt to decrease the risk of PJF but there is no experimental model described for in vitro production of PJF after multilevel instrumentation. The objective of this study is to develop an experimental model of PJF after multilevel posterior instrumentation. Initially, four porcine specimens including 4 vertebrae and instrumented at the 3 caudal vertebrae using a pedicle screw construct were subjected to different loading conditions. Loading conditions on porcine specimens involving cyclic loading along the axis of the center vertebral body line, with constrained flexion between 0° and 15° proximally, and fully constraining the specimen distally resulted in a fracture pattern most representative of a PJF seen clinically in humans, so to undergo human cadaveric testing with similar loading conditions was decided. Clinically relevant PJF were produced in all 3 human specimens. The experimental model described in this study will allow the evaluation of different parameters influencing the incidence and prevention of PJF after multilevel posterior spinal instrumentation. PMID:27610381

  11. Experimental Model of Proximal Junctional Fracture after Multilevel Posterior Spinal Instrumentation.

    PubMed

    Mac-Thiong, Jean-Marc; Levasseur, Annie; Parent, Stefan; Petit, Yvan

    2016-01-01

    There is a high risk of proximal junctional fractures (PJF) with multilevel spinal instrumentation, especially in the osteoporotic spine. This problem is associated with significant morbidity and possibly the need for reoperation. Various techniques have been proposed in an attempt to decrease the risk of PJF but there is no experimental model described for in vitro production of PJF after multilevel instrumentation. The objective of this study is to develop an experimental model of PJF after multilevel posterior instrumentation. Initially, four porcine specimens including 4 vertebrae and instrumented at the 3 caudal vertebrae using a pedicle screw construct were subjected to different loading conditions. Loading conditions on porcine specimens involving cyclic loading along the axis of the center vertebral body line, with constrained flexion between 0° and 15° proximally, and fully constraining the specimen distally resulted in a fracture pattern most representative of a PJF seen clinically in humans, so to undergo human cadaveric testing with similar loading conditions was decided. Clinically relevant PJF were produced in all 3 human specimens. The experimental model described in this study will allow the evaluation of different parameters influencing the incidence and prevention of PJF after multilevel posterior spinal instrumentation. PMID:27610381

  12. Model of radiation-induced gain degradation of NPN bipolar junction transistor at different dose rates

    NASA Astrophysics Data System (ADS)

    Qifeng, Zhao; Yiqi, Zhuang; Junlin, Bao; Wei, Hu

    2015-06-01

    Ionizing-radiation-induced current gain degradation in NPN bipolar junction transistors is due to an increase in base current as a result of recombination at the surface of the device. A model is presented which identifies the physical mechanism responsible for current gain degradation. The increase in surface recombination velocity due to interface states results in an increase in base current. Besides, changing the surface potential along the base surface induced by the oxide-trapped charges can also lead to an increased base current. By combining the production mechanisms of oxide-trapped charges and interface states, this model can explain the fact that the current gain degradation is more severe at a low dose rate than at a high dose rate. The radiations were performed in a Co60 source up to a total dose of 70 krad(Si). The low dose rate was 0.1 rad(Si)/s and the high dose rate was 10 rad(Si)/s. The model accords well with the experimental results. Project supported by the National Natural Science Foundation of China (Nos. 61076101, 61204092).

  13. Defects in neuromuscular junction remodelling in the Smn(2B/-) mouse model of spinal muscular atrophy.

    PubMed

    Murray, Lyndsay M; Beauvais, Ariane; Bhanot, Kunal; Kothary, Rashmi

    2013-01-01

    Spinal muscular atrophy (SMA) is a devastating childhood motor neuron disease caused by mutations and deletions within the survival motor neuron 1 (SMN1) gene. Although other tissues may be involved, motor neurons remain primary pathological targets, with loss of neuromuscular junctions (NMJs) representing an early and significant event in pathogenesis. Although defects in axonal outgrowth and pathfinding have been observed in cell culture and in lower organisms upon Smn depletion, developmental defects in mouse models have been less obvious. Here, we have employed the Smn(2B/-) mouse model to investigate NMJ remodelling during SMA pathology, induced reinnervation, and paralysis. We show that whilst NMJs are capable of remodelling during pathogenesis, there is a marked reduction in paralysis-induced remodelling and in the nerve-directed re-organisation of acetylcholine receptors. This reduction in remodelling potential could not be attributed to a decreased rate of axonal growth. Finally, we have identified a loss of terminal Schwann cells which could contribute to the defects in remodelling/maintenance observed. Our work demonstrates that there are specific defects in NMJ remodelling in an intermediate SMA mouse model, which could contribute to or underlie pathogenesis in SMA. The development of strategies that can promote the remodelling potential of NMJs may therefore be of significant benefit to SMA patients. PMID:22960106

  14. Experimental Model of Proximal Junctional Fracture after Multilevel Posterior Spinal Instrumentation

    PubMed Central

    Levasseur, Annie; Parent, Stefan; Petit, Yvan

    2016-01-01

    There is a high risk of proximal junctional fractures (PJF) with multilevel spinal instrumentation, especially in the osteoporotic spine. This problem is associated with significant morbidity and possibly the need for reoperation. Various techniques have been proposed in an attempt to decrease the risk of PJF but there is no experimental model described for in vitro production of PJF after multilevel instrumentation. The objective of this study is to develop an experimental model of PJF after multilevel posterior instrumentation. Initially, four porcine specimens including 4 vertebrae and instrumented at the 3 caudal vertebrae using a pedicle screw construct were subjected to different loading conditions. Loading conditions on porcine specimens involving cyclic loading along the axis of the center vertebral body line, with constrained flexion between 0° and 15° proximally, and fully constraining the specimen distally resulted in a fracture pattern most representative of a PJF seen clinically in humans, so to undergo human cadaveric testing with similar loading conditions was decided. Clinically relevant PJF were produced in all 3 human specimens. The experimental model described in this study will allow the evaluation of different parameters influencing the incidence and prevention of PJF after multilevel posterior spinal instrumentation.

  15. A New Global Core Plasma Model of the Plasmasphere

    NASA Technical Reports Server (NTRS)

    Gallagher, D. L.; Comfort, R. H.; Craven, P. D.

    2014-01-01

    The Global Core Plasma Model (GCPM) is the first empirical model for thermal inner magnetospheric plasma designed to integrate previous models and observations into a continuous in value and gradient representation of typical total densities. New information about the plasmasphere, in particular, makes possible significant improvement. The IMAGE Mission Radio Plasma Imager (RPI) has obtained the first observations of total plasma densities along magnetic field lines in the plasmasphere and polar cap. Dynamics Explorer 1 Retarding Ion Mass Spectrometer (RIMS) has provided densities in temperatures in the plasmasphere for 5 ion species. These and other works enable a new more detailed empirical model of thermal in the inner magnetosphere that will be presented.

  16. VIPRE modeling of VVER-1000 reactor core for DNB analyses

    SciTech Connect

    Sung, Y.; Nguyen, Q.; Cizek, J.

    1995-09-01

    Based on the one-pass modeling approach, the hot channels and the VVER-1000 reactor core can be modeled in 30 channels for DNB analyses using the VIPRE-01/MOD02 (VIPRE) code (VIPRE is owned by Electric Power Research Institute, Palo Alto, California). The VIPRE one-pass model does not compromise any accuracy in the hot channel local fluid conditions. Extensive qualifications include sensitivity studies of radial noding and crossflow parameters and comparisons with the results from THINC and CALOPEA subchannel codes. The qualifications confirm that the VIPRE code with the Westinghouse modeling method provides good computational performance and accuracy for VVER-1000 DNB analyses.

  17. Envelope dynamics of iron-core supernova models

    NASA Technical Reports Server (NTRS)

    Barkat, Z.; Wheeler, J. C.; Buchler, J.-R.; Rakavy, G.

    1974-01-01

    Wilson (1971) has found that the neutrino transport mechanism is unable to generate a supernova explosion in stars with collapsing iron cores. The present work uses Wilson's analysis to investigate the behavior of the overlying potentially explosive layers which Wilson omitted. The outer boundary of the core of Wilson's models moves in such a manner as to deliver a shock to the base of the envelope. We have numerically followed the progress of such shocks into the envelope of a realistic model obtained from evolutionary calculations. We find that only shocks so strong as to be inconsistent with our treatment are capable of ejecting material. For reasonable shocks the nuclear burning does not proceed rapidly at densities below 1,000 kg/cu cm, and the nuclear energy released is less than the shock energy in all models that come near to ejecting matter.

  18. Kinematic History of a Salient-recess Junction Explored through a Combined Approach of Field Data and Analog Sandbox Modeling.

    PubMed

    Ismat, Zeshan; Toeneboehn, Kevin

    2016-01-01

    Within fold-thrust belts, the junctions between salients and recesses may hold critical clues to the overall kinematic history. The deformation history within these junctions is best preserved in areas where thrust sheets extend from a salient through an adjacent recess. We examine one such junction within the Sevier fold-thrust belt (western United States) along the Leamington transverse zone, northern Utah. Deformation within this junction took place by faulting and cataclastic flow. Here, we describe a protocol that examines these fault patterns to better understand the kinematic history of the field area. Fault data is supplemented by analog sandbox experiments. This study suggests that, in detail, deformation within the overlying thrust sheet may not directly reflect the underlying basement structure. We demonstrate that this combined field-experimental approach is easy, accessible, and may provide more details to the deformation preserved in the crust than other more expensive methods, such as computer modeling. In addition, the sandbox model may help to explain why and how these details formed. This method can be applied throughout fold-thrust belts, where upper-crustal rocks are well preserved. In addition, it can be modified to study any part of the upper crust that has been deformed via elastico-frictional mechanisms. Finally, this combined approach may provide more details as to how fold-thrust belts maintain critical-taper and serve as potential targets for natural resource exploration. PMID:27585112

  19. Kinematic History of a Salient-recess Junction Explored through a Combined Approach of Field Data and Analog Sandbox Modeling.

    PubMed

    Ismat, Zeshan; Toeneboehn, Kevin

    2016-08-05

    Within fold-thrust belts, the junctions between salients and recesses may hold critical clues to the overall kinematic history. The deformation history within these junctions is best preserved in areas where thrust sheets extend from a salient through an adjacent recess. We examine one such junction within the Sevier fold-thrust belt (western United States) along the Leamington transverse zone, northern Utah. Deformation within this junction took place by faulting and cataclastic flow. Here, we describe a protocol that examines these fault patterns to better understand the kinematic history of the field area. Fault data is supplemented by analog sandbox experiments. This study suggests that, in detail, deformation within the overlying thrust sheet may not directly reflect the underlying basement structure. We demonstrate that this combined field-experimental approach is easy, accessible, and may provide more details to the deformation preserved in the crust than other more expensive methods, such as computer modeling. In addition, the sandbox model may help to explain why and how these details formed. This method can be applied throughout fold-thrust belts, where upper-crustal rocks are well preserved. In addition, it can be modified to study any part of the upper crust that has been deformed via elastico-frictional mechanisms. Finally, this combined approach may provide more details as to how fold-thrust belts maintain critical-taper and serve as potential targets for natural resource exploration.

  20. A model for core formation in the early Earth

    NASA Technical Reports Server (NTRS)

    Jones, J. H.; Drake, M. J.

    1985-01-01

    Two basic types exogenous models were proposed to account for siderophile and chalcophile element abundances in the Earth's upper mantle. The first model requires that the Earth be depleted in volatiles and that, after a core formation event which extracted the most siderophile elements into the core, additional noble siderophile elements (Pt, Ir, Au) were added as a late veneer and mixed into the mantle. The second model postulates a reduced Earth with approximately CI elemental abundances in which a primary core forming event depleted all siderophile elements in the mantle. The plausibility of models which require fine scale mixing of chondritic material into the upper mantle is analyzed. Mixing in liquids is more efficient, but large degrees of silicate partial melting will facilitate the separation of magma from residual solids. Any external events affecting the upper mantle of the Earth should also be evident in the Moon; but siderophile and chalcophile element abundance patterns inferred for the mantles of the Earth and Moon differ. There appear to be significant physical difficulties associated with chondritic veneer models.

  1. Toxicants target cell junctions in the testis: Insights from the indazole-carboxylic acid model

    PubMed Central

    Cheng, C Yan

    2014-01-01

    There are numerous types of junctions in the seminiferous epithelium which are integrated with, and critically dependent on the Sertoli cell cytoskeleton. These include the basal tight junctions between Sertoli cells that form the main component of the blood–testis barrier, the basal ectoplasmic specializations (basal ES) and basal tubulobulbar complexes (basal TBC) between Sertoli cells; as well as apical ES and apical TBC between Sertoli cells and the developing spermatids that orchestrate spermiogenesis and spermiation. These junctions, namely TJ, ES, and TBC interact with actin microfilament-based cytoskeleton, which together with the desmosomal junctions that interact with the intermediate filament-based cytoskeleton plus the highly polarized microtubule-based cytoskeleton are working in concert to move spermatocytes and spermatids between the basal and luminal aspect of the seminiferous epithelium. In short, these various junctions are structurally complexed with the actin- and microtubule-based cytoskeleton or intermediate filaments of the Sertoli cell. Studies have shown toxicants (e.g., cadmium, bisphenol A (BPA), perfluorooctanesulfonate (PFOS), phthalates, and glycerol), and some male contraceptives under development (e.g., adjudin, gamendazole), exert their effects, at least in part, by targeting cell junctions in the testis. The disruption of Sertoli–Sertoli cell and Sertoli–germ cell junctions, results in the loss of germ cells from the seminiferous epithelium. Adjudin, a potential male contraceptive under investigation in our laboratory, produces loss of spermatids from the seminiferous tubules through disruption of the Sertoli cell spermatid junctions and disruption of the Sertoli cell cytoskeleton. The molecular and structural changes associated with adjudin administration are described, to provide an example of the profile of changes caused by disturbance of Sertoli-germ cell and also Sertoli cell-cell junctions. PMID:26413399

  2. Modeling of Intrinsic Josephson Junctions in High Temperature Superconductors under External Radiation in the Breakpoint Region

    NASA Astrophysics Data System (ADS)

    Shukrinov, Yu. M.; Rahmonov, I. R.; Plecenik, A.; Streltsova, O. I.; Zuev, M. I.; Ososkov, G. A.

    2016-02-01

    The current-voltage (IV) characteristics of the intrinsic Josephson junctions in high temperature superconductors under external electromagnetic radiation are calculated numerically in the parametric resonance region. We discuss a numerical method for calculation of the Shapiro step width on the amplitude of radiation. In order to accelerate computations we used parallelization by task parameter via Simple Linux Utility for Resource Management (SLURM) arrays and tested it in the case of a single junction. An analysis of the junction transitions between rotating and oscillating states in the branching region of IV-characteristics is presented.

  3. Development and initial evaluation of a finite element model of the pediatric craniocervical junction.

    PubMed

    Phuntsok, Rinchen; Mazur, Marcus D; Ellis, Benjamin J; Ravindra, Vijay M; Brockmeyer, Douglas L

    2016-04-01

    OBJECT There is a significant deficiency in understanding the biomechanics of the pediatric craniocervical junction (CCJ) (occiput-C2), primarily because of a lack of human pediatric cadaveric tissue and the relatively small number of treated patients. To overcome this deficiency, a finite element model (FEM) of the pediatric CCJ was created using pediatric geometry and parameterized adult material properties. The model was evaluated under the physiological range of motion (ROM) for flexion-extension, axial rotation, and lateral bending and under tensile loading. METHODS This research utilizes the FEM method, which is a numerical solution technique for discretizing and analyzing systems. The FEM method has been widely used in the field of biomechanics. A CT scan of a 13-month-old female patient was used to create the 3D geometry and surfaces of the FEM model, and an open-source FEM software suite was used to apply the material properties and boundary and loading conditions and analyze the model. The published adult ligament properties were reduced to 50%, 25%, and 10% of the original stiffness in various iterations of the model, and the resulting ROMs for flexion-extension, axial rotation, and lateral bending were compared. The flexion-extension ROMs and tensile stiffness that were predicted by the model were evaluated using previously published experimental measurements from pediatric cadaveric tissues. RESULTS The model predicted a ROM within 1 standard deviation of the published pediatric ROM data for flexion-extension at 10% of adult ligament stiffness. The model's response in terms of axial tension also coincided well with published experimental tension characterization data. The model behaved relatively stiffer in extension than in flexion. The axial rotation and lateral bending results showed symmetric ROM, but there are currently no published pediatric experimental data available for comparison. The model predicts a relatively stiffer ROM in both axial

  4. A Mouse Model of Generalized non-Herlitz Junctional Epidermolysis Bullosa

    PubMed Central

    Bubier, Jason A.; Sproule, Thomas J.; Petell, Lydia; Webb, Cameron; Fine, Jo-David; Roopenian, Derry C.; Sundberg, John P.

    2010-01-01

    Epidermolysis bullosa (EB) is a class of intractable, rare, genetic disorders characterized by fragile skin and blister formation as a result of dermal-epidermal mechanical instability. EB presents with considerable clinical and molecular heterogeneity. Viable animal models of junctional epidermolysis bullosa (JEB), that both mimic the human disease and survive beyond the neonatal period, are needed. We identified a spontaneous, autosomal recessive mutation (Lamc2 jeb) due to a Murine Leukemia Virus long terminal repeat insertion in Lamc2 that results in a hypomorphic allele with reduced levels of LAMC2 protein. These mutant mice develop a progressive blistering disease validated at the gross and microscopic levels to closely resemble generalized non-Herlitz JEB. The Lamc2 jeb mice display additional extracutaneous features such as loss of bone mineralization and abnormal teeth, as well as a respiratory phenotype that is recognized but not as well characterized in humans. This model faithfully recapitulates human JEB and provides an important preclinical tool to test novel therapeutic approaches. PMID:20336083

  5. Primary esophageal and gastro-esophageal junction cancer xenograft models: clinicopathological features and engraftment.

    PubMed

    Dodbiba, Lorin; Teichman, Jennifer; Fleet, Andrew; Thai, Henry; Sun, Bin; Panchal, Devang; Patel, Devalben; Tse, Alvina; Chen, Zhuo; Faluyi, Olusola O; Renouf, Daniel J; Girgis, Hala; Bandarchi, Bizhan; Schwock, Joerg; Xu, Wei; Bristow, Robert G; Tsao, Ming-Sound; Darling, Gail E; Ailles, Laurie E; El-Zimaity, Hala; Liu, Geoffrey

    2013-04-01

    There are very few xenograft models available for the study of esophageal (E) and gastro-esophageal junction (GEJ) cancer. Using a NOD/SCID model, we implanted 90 primary E and GEJ tumors resected from patients and six endoscopic biopsy specimens. Of 69 resected tumors with histologically confirmed viable adenocarcinoma or squamous cell carcinoma, 22 (32%) was engrafted. One of 11 tumors, considered to have had a complete pathological response to neo-adjuvant chemo-radiation, also engrafted. Of the 23 patients whose tumors were engrafted, 65% were male; 30% were early stage while 70% were late stage; 22% received neo-adjuvant chemo-radiation; 61% were GEJ cancers. Engraftment occurred in 18/54 (33%) adenocarcinomas and 5/16 (31%) squamous cell carcinomas. Small endoscopic biopsy tissue had a 50% (3/6) engraftment rate. Of the factors analyzed, pretreatment with chemo-radiation and well/moderate differentiation showed significantly lower correlation with engraftment (P<0.05). In the subset of patients who did not receive neo-adjuvant chemo-radiation, 18/41 (44%) engrafted compared with those with pretreatment where 5/29 (17%, P=0.02) engrafted. Primary xenograft lines may be continued through 4-12 passages. Xenografts maintained similar histology and morphological characteristics with only minor variations even after multiple passaging in most instances.

  6. Experimental Analysis and Modeling of the Crushing of Honeycomb Cores

    NASA Astrophysics Data System (ADS)

    Aminanda, Y.; Castanié, B.; Barrau, J.-J.; Thevenet, P.

    2005-05-01

    In the aeronautical field, sandwich structures are widely used for secondary structures like flaps or landing gear doors. The modeling of low velocity/low energy impact, which can lead to a decrease of the structure strength by 50%, remains a designer’s main problem. Since this type of impact has the same effect as quasi-static indentation, the study focuses on the behavior of honeycomb cores under compression. The crushing phenomenon has been well identified for years but its mechanism is not described explicitly and the model proposed may not satisfy industrial purposes. To understand the crushing mechanism, honeycomb test specimens made of Nomex™, aluminum alloy and paper were tested. During the crushing, a CCD camera showed that the cell walls buckled very quickly. The peak load recorded during tests corresponded to the buckling of the common edge of three honeycomb cells. Further tests on corner structures to simulate only one vertical edge of a honeycomb cell show a similar behavior. The different specimens exhibited similar load/displacement curves and the differences observed were only due to the behavior of the different materials. As a conclusion of this phenomenological study, the hypothesis that loads are mainly taken by the vertical edge can be made. So, a honeycomb core subjected to compression can be modeled by a grid of nonlinear springs. A simple analytical model was then developed and validated by tests on Nomex™ honeycomb core indented by different sized spherical indenters. A good correlation between theory and experiment was found. This result can be used to satisfactorily model using finite elements the indentation on a sandwich structure with a metallic or composite skin and honeycomb core.

  7. Geophysical Age Dating of Seamounts using Dense Core Flexure Model

    NASA Astrophysics Data System (ADS)

    Hwang, Gyuha; Kim, Seung-Sep

    2016-04-01

    Lithospheric flexure of oceanic plate is thermo-mechanical response of an elastic plate to the given volcanic construct (e.g., seamounts and ocean islands). If the shape and mass of such volcanic loads are known, the flexural response is governed by the thickness of elastic plate, Te. As the age of oceanic plate increases, the elastic thickness of oceanic lithosphere becomes thicker. Thus, we can relate Te with the age of plate at the time of loading. To estimate the amount of the driving force due to seamounts on elastic plate, one needs to approximate their density structure. The most common choice is uniform density model, which utilizes constant density value for a seamount. This approach simplifies computational processes for gravity prediction and error estimates. However, the uniform density model tends to overestimate the total mass of the seamount and hence produces more positive gravitational contributions from the load. Minimization of gravity misfits using uniform density, therefore, favors thinner Te in order to increase negative contributions from the lithospheric flexure, which can compensate for the excessive positives from the seamount. An alternative approach is dense core model, which approximate the heterogeneity nature of seamount density as three bodies of infill sediment, edifice, and dense core. In this study, we apply the dense core model to the Louisville Seamount Chain for constraining flexural deformation. We compare Te estimates with the loading time of the examined seamounts to redefine empirical geophysical age dating of seamounts.

  8. Structural and spectral studies of sunspots. [umbral core modelling

    NASA Technical Reports Server (NTRS)

    Wyller, A. A.

    1974-01-01

    Observations of umbral cores, both by multicolor photometry and by narrow band photometry in the vicinity of the sodium D lines, are described, and evidence is given which supports the validity of many umbral models, each of which describes different aspects of the observed umbral cores. Theoretical studies carried on at the observatory include the following: (1) Zeeman profiles of the sodium D sub 2 line and other lines; (2) turbulent heat conduction, sound waves, and the missing flux in sunspots; (3) chromospheric heating above spots by Alfven waves; (4) magnetic convection in the sun and solar neutrinos; (5) models of starspots on flare stars; (5) starspots on the primaries of contact binary systems; and (6) implications of starspots on red dwarfs.

  9. 98. View of IBM digital computer model 7090 magnet core ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    98. View of IBM digital computer model 7090 magnet core installation. ITT Artic Services, Inc., Official photograph BMEWS Site II, Clear, AK, by unknown photographer, 17 September 1965. BMEWS, clear as negative no. A-6606. - Clear Air Force Station, Ballistic Missile Early Warning System Site II, One mile west of mile marker 293.5 on Parks Highway, 5 miles southwest of Anderson, Anderson, Denali Borough, AK

  10. Branch structure of IV-characteristics in the capacitively coupled Josephson junctions model with the diffusion current

    NASA Astrophysics Data System (ADS)

    Shukrinov, Yu. M.; Mahfouzi, F.; Seidel, P.

    2007-09-01

    We have solved numerically a system of dynamical equations for the gauge-invariant phase differences between superconducting layers for a stack of N intrinsic junctions and obtained a total branch structure in the current-voltage characteristics (IVC) of the stack. The coupling dependence of the branch’s slopes is investigated and demonstrated that the equidistance of the branch structure in capacitively coupled Josephson junctions (CCJJ) model is broken at small values of coupling parameter. Changes in the parameters of the boundary conditions and the use of periodic boundary conditions do not affect this result. In the framework of the CCJJ model with the diffusion current we simulate an experiment and obtain the IV-characteristic with equidistant branch structure at different values of model parameters.

  11. Exchange bias phenomenology and models of core/shell nanoparticles.

    PubMed

    Iglesias, Oscar; Labarta, Amílcar; Batlle, Xavier

    2008-06-01

    Some of the main experimental observations related to the occurrence of exchange bias in magnetic systems are reviewed, focusing the attention on the peculiar phenomenology associated to nanoparticles with core/shell structure as compared to thin film bilayers. The main open questions posed by the experimental observations are presented and contrasted to existing theories and models for exchange bias formulated up to date. We also present results of simulations based on a simple model of a core/shell nanoparticle in which the values of microscopic parameters such as anisotropy and exchange constants can be tuned in the core, shell and at the interfacial regions, offering new insight on the microscopic origin of the experimental phenomenology. A detailed study of the magnetic order of the interfacial spins shows compelling evidence that most of the experimentally observed effects can be qualitatively accounted within the context of this model and allows also to quantify the magnitude of the loop shifts in striking agreement with the macroscopic observed values.

  12. Evaluating nuclear physics inputs in core-collapse supernova models

    SciTech Connect

    Lentz, Eric J; Hix, William Raphael; Baird, Mark L; Messer, Bronson; Mezzacappa, Anthony

    2010-01-01

    Core-collapse supernova models depend on the details of the nuclear and weak interaction physics inputs just as they depend on the details of the macroscopic physics (transport, hydrodynamics, etc.), numerical methods, and progenitors. We present the results of our ongoing comparison studies of nuclear and weak interaction physics inputs to core collapse supernova models using the spherically-symmetric, general relativistic, neutrino radiation hydrodynamics code Agile-Boltztran. We focus on comparisons of the effects of the nuclear EoS and the effects of improving the opacities, particularly neutrino--nucleon interactions. We present the results of our ongoing comparison studies of nuclear and weak interaction physics inputs to core collapse supernova models using the spherically-symmetric, general relativistic, neutrino radiation hydrodynamics code Agile-Boltztran. We focus on comparisons of the effects of the nuclear EoS and the effects of improving the opacities, particularly neutrino--nucleon interactions. We also investigate the feedback between different EoSs and opacities in the context of different progenitors.

  13. Comprehensive and Macrospin-Based Magnetic Tunnel Junction Spin Torque Oscillator Model- Part II: Verilog-A Model Implementation

    NASA Astrophysics Data System (ADS)

    Chen, Tingsu; Eklund, Anders; Iacocca, Ezio; Rodriguez, Saul; Malm, B. Gunnar; Akerman, Johan; Rusu, Ana

    2015-03-01

    The rapid development of the magnetic tunnel junction (MTJ) spin torque oscillator (STO) technology demands an analytical model to enable building MTJ STO-based circuits and systems so as to evaluate and utilize MTJ STOs in various applications. In Part I of this paper, an analytical model based on the macrospin approximation, has been introduced and verified by comparing it with the measurements of three different MTJ STOs. In Part II, the full Verilog-A implementation of the proposed model is presented. To achieve a reliable model, an approach to reproduce the phase noise generated by the MTJ STO has been proposed and successfully employed. The implemented model yields a time domain signal, which retains the characteristics of operating frequency, linewidth, oscillation amplitude and DC operating point, with respect to the magnetic field and applied DC current. The Verilog-A implementation is verified against the analytical model, providing equivalent device characteristics for the full range of biasing conditions. Furthermore, a system that includes an MTJ STO and CMOS RF circuits is simulated to validate the proposed model for system- and circuit-level designs. The simulation results demonstrate that the proposed model opens the possibility to explore STO technology in a wide range of applications.

  14. Variability modes in core flows inverted from geomagnetic field models

    NASA Astrophysics Data System (ADS)

    Pais, M. A.; Morozova, A. L.; Schaeffer, N.

    2014-01-01

    The flow of liquid metal inside the Earth's core produces the geomagnetic field and its time variations. Understanding the variability of those deep currents is crucial to improve the forecast of geomagnetic field variations and may provide relevant information on the core dynamics. The main goal of this study is to extract and characterize the leading variability modes of core flows over centennial periods, and to assess their statistical robustness. To this end, we use flows that we invert from two geomagnetic field models (`gufm1' and `COV-OBS'), and apply principal component analysis and singular value decomposition of coupled fields. The quasi-geostrophic (QG) flows inverted from both geomagnetic field models show similar features. However, `COV-OBS' flows have a less energetic mean and larger time variability. The statistical significance of flow components is tested from analyses performed on subareas of the whole domain. Bootstrapping methods are also used to extract significant flow features required by both `gufm1' and `COV-OBS'. Three main empirical circulation modes emerge, simultaneously constrained by both geomagnetic field models and expected to be robust against the particular a priori used to build them (large-scale QG dynamics). Mode 1 exhibits three large vortices at medium/high latitudes, with opposite circulation under the Atlantic and the Pacific hemispheres. Mode 2 interestingly accounts for most of the variations of the Earth's core angular momentum. In this mode, the regions close to the tangent cylinder and to the equator are correlated, and oscillate with a period between 80 and 90 yr. Each of these two modes is energetic enough to alter the mean flow, sometimes reinforcing the eccentric gyre, and other times breaking it up into smaller circulations. The three main circulation modes added to the mean flow account for about 70 per cent of the flows variability, 90 per cent of the rms total velocities, and 95 per cent of the secular

  15. Dynamics of sustained reentry in a loop model with discrete gap junction resistances

    NASA Astrophysics Data System (ADS)

    Chen, Wei; Potse, Mark; Vinet, Alain

    2007-08-01

    The dynamics of reentry is studied in a one-dimensional loop of model cardiac cells with discrete intercellular gap junction resistance (R) . Each cell is represented by a continuous cable with ionic current given by a modified Beeler-Reuter formulation. For R below a limiting value, propagation is found to change from period-1 to quasiperiodic (QP) at a critical loop length (Lcrit) that decreases with R . Quasiperiodic reentry exists from Lcrit to a minimum length (Lmin) , which also shortens with R . The decrease of Lcrit(R) is not a simple scaling, but the bifurcation can still be predicted from the slope of the restitution curve giving the duration of the action potential as a function of the diastolic interval. However, the shape of the restitution curve changes with R . An increase of R does not seem to increase the number of possible QP solutions since, as in the continuous cable, only two QP modes of propagation were found despite an extensive search through alternative initial conditions.

  16. Josephson junction

    DOEpatents

    Wendt, Joel R.; Plut, Thomas A.; Martens, Jon S.

    1995-01-01

    A novel method for fabricating nanometer geometry electronic devices is described. Such Josephson junctions can be accurately and reproducibly manufactured employing photolithographic and direct write electron beam lithography techniques in combination with aqueous etchants. In particular, a method is described for manufacturing planar Josephson junctions from high temperature superconducting material.

  17. Josephson junction

    DOEpatents

    Wendt, J.R.; Plut, T.A.; Martens, J.S.

    1995-05-02

    A novel method for fabricating nanometer geometry electronic devices is described. Such Josephson junctions can be accurately and reproducibly manufactured employing photolithographic and direct write electron beam lithography techniques in combination with aqueous etchants. In particular, a method is described for manufacturing planar Josephson junctions from high temperature superconducting material. 10 figs.

  18. Biaxial Nematic Phase in Model Bent-Core Systems

    NASA Astrophysics Data System (ADS)

    Grzybowski, Piotr; Longa, Lech

    2011-07-01

    We determine the bifurcation phase diagrams with isotropic (I), uniaxial (NU) and biaxial (NB) nematic phases for model bent-core mesogens using Onsager-type theory. The molecules comprise two or three Gay-Berne interacting ellipsoids of uniaxial and biaxial shape and a transverse central dipole. The Landau point is found to turn into an I-NB line for the three-center model with a large dipole moment. For the biaxial ellipsoids, a line of Landau points is observed even in the absence of the dipoles.

  19. Formation damage and filter cake buildup in laboratory core tests: Modeling and model-assisted analysis

    SciTech Connect

    Liu, X.; Civan, F.

    1996-03-01

    A mathematical model for the analysis of formation damage in laboratory core tests is presented. The model considers filter cake buildup on sand face, invasion of external particles, release of formation fines, migration and retention of external particles and formation fines, interphase transfer of particles, and alteration of porosity and permeability. The effects of wettabilities of fine particles and pore surfaces, relative permeabilities and capillary pressure on formation damage in two-phase flow conditions are also included. Simulation results from the model are in good agreement with experimental results from core tests. This model can be used for the analysis of formation damage due to particulate processes in laboratory core tests.

  20. Precessional States in a Laboratory Model of the Earth's Core

    NASA Astrophysics Data System (ADS)

    Triana, S. A.; Zimmerman, D.; Lathrop, D. P.

    2010-12-01

    A water-filled three-meter diameter spherical shell built as a model of the Earth's core shows evidence of precessionally induced flows. We identified the flow to be primarily the spin-over inertial wave mode, i.e., a uniform vorticity flow whose rotation axis is not aligned with the container's rotation axis. The mode's amplitude dependence on the Poincaré number is in qualitative agreement with Busse's laminar theory (JFM 33:739-751, 1968) while its phase differs significantly, perhaps due to topographic effects. At high rotation rates free shear layers concentrating most of the kinetic energy of the mode have been observed. Comparison with previous computational studies and implications for the Earth's core are discussed.

  1. Precessional states in a laboratory model of the Earth's core

    NASA Astrophysics Data System (ADS)

    Triana, Santiago; Zimmerman, Daniel; Lathrop, Daniel

    2010-11-01

    A water-filled three-meter diameter spherical shell built as a model of the Earth's core shows evidence of precessionally induced flows. We identified the flow to be primarily the spin-over inertial wave mode, i.e., a uniform vorticity flow whose rotation axis is not aligned with the container's rotation axis. The mode's amplitude dependence on the Poincar'e number is in qualitative agreement with Busse's laminar theory (JFM 33:739-751, 1968) while its phase differs significantly, perhaps due to topographic effects. At high rotation rates free shear layers concentrating most of the kinetic energy of the mode have been observed. Comparison with previous computational studies and implications for the Earth's core are discussed.

  2. Dynamical Models to Infer the Core Mass Fraction of Venus

    NASA Astrophysics Data System (ADS)

    Quintana, Elisa V.; Barclay, Thomas

    2016-10-01

    The uncompressed density of Venus is just a few percent lower than Earth's, however the nature of the interior core structure of Venus remains unclear. Employing state-of-the-art dynamical formation models that allow both accretion and collisional fragmentation, we perform hundreds of simulations of terrestrial planet growth around the Sun in the presence of the giant planets. For both Earth and Venus analogs, we quantify the iron-silicate ratios, water/volatile abundances and specific impact energies of all collisions that lead to their formation. Preliminary results suggest that the distributions of core mass fraction and water content are comparable among the Earth and Venus analogs, suggesting that Earth and Venus may indeed have formed with similar structures and compositions.

  3. Testing a new Free Core Nutation empirical model

    NASA Astrophysics Data System (ADS)

    Belda, Santiago; Ferrándiz, José M.; Heinkelmann, Robert; Nilsson, Tobias; Schuh, Harald

    2016-03-01

    The Free Core Nutation (FCN) is a free mode of the Earth's rotation caused by the different material characteristics of the Earth's core and mantle. This causes the rotational axes of those layers to slightly diverge from each other, resulting in a wobble of the Earth's rotation axis comparable to nutations. In this paper we focus on estimating empirical FCN models using the observed nutations derived from the VLBI sessions between 1993 and 2013. Assuming a fixed value for the oscillation period, the time-variable amplitudes and phases are estimated by means of multiple sliding window analyses. The effects of using different a priori Earth Rotation Parameters (ERP) in the derivation of models are also addressed. The optimal choice of the fundamental parameters of the model, namely the window width and step-size of its shift, is searched by performing a thorough experimental analysis using real data. The former analyses lead to the derivation of a model with a temporal resolution higher than the one used in the models currently available, with a sliding window reduced to 400 days and a day-by-day shift. It is shown that this new model increases the accuracy of the modeling of the observed Earth's rotation. Besides, empirical models determined from USNO Finals as a priori ERP present a slightly lower Weighted Root Mean Square (WRMS) of residuals than IERS 08 C04 along the whole period of VLBI observations, according to our computations. The model is also validated through comparisons with other recognized models. The level of agreement among them is satisfactory. Let us remark that our estimates give rise to the lowest residuals and seem to reproduce the FCN signal in more detail.

  4. Modelling the carbonation of cementitious matrixes by means of the unreacted-core model, UR-CORE

    SciTech Connect

    Castellote, M. Andrade, C.

    2008-12-15

    This paper presents a model for the carbonation of cementitious matrixes (UR-CORE). The model is based on the principles of the 'unreacted-core' systems, typical of chemical engineering processes, in which the reacted product remains in the solid as a layer of inert ash, adapted for the specific case of carbonation. Development of the model has been undertaken in three steps: 1) Establishment of the controlling step in the global carbonation rate, by using data of fractional conversion of different phases of the cementitious matrixes, obtained by the authors through neutron diffraction data experiments, and reported in [M. Castellote, C. Andrade, X. Turrillas, J. Campo, G. Cuello, Accelerated carbonation of cement pastes in situ monitored by neutron diffraction, Cem. Concr. Res. (2008), doi:10.1016/j.cemconres.2008.07.002]. 2) Then, the model has been adapted and applied to the cementitious materials using different concentrations of CO{sub 2}, with the introduction of the needed assumptions and factors. 3) Finally, the model has been validated with laboratory data at different concentrations (taken from literature) and for long term natural exposure of concretes. As a result, the model seems to be reliable enough to be applied to cementitious materials, being able to extrapolate the results from accelerated tests in any conditions to predict the rate of carbonation in natural exposure, being restricted, at present stage, to conditions with a constant relative humidity.

  5. Gap Junctions

    PubMed Central

    Nielsen, Morten Schak; Axelsen, Lene Nygaard; Sorgen, Paul L.; Verma, Vandana; Delmar, Mario; Holstein-Rathlou, Niels-Henrik

    2013-01-01

    Gap junctions are essential to the function of multicellular animals, which require a high degree of coordination between cells. In vertebrates, gap junctions comprise connexins and currently 21 connexins are known in humans. The functions of gap junctions are highly diverse and include exchange of metabolites and electrical signals between cells, as well as functions, which are apparently unrelated to intercellular communication. Given the diversity of gap junction physiology, regulation of gap junction activity is complex. The structure of the various connexins is known to some extent; and structural rearrangements and intramolecular interactions are important for regulation of channel function. Intercellular coupling is further regulated by the number and activity of channels present in gap junctional plaques. The number of connexins in cell-cell channels is regulated by controlling transcription, translation, trafficking, and degradation; and all of these processes are under strict control. Once in the membrane, channel activity is determined by the conductive properties of the connexin involved, which can be regulated by voltage and chemical gating, as well as a large number of posttranslational modifications. The aim of the present article is to review our current knowledge on the structure, regulation, function, and pharmacology of gap junctions. This will be supported by examples of how different connexins and their regulation act in concert to achieve appropriate physiological control, and how disturbances of connexin function can lead to disease. © 2012 American Physiological Society. Compr Physiol 2:1981-2035, 2012. PMID:23723031

  6. The Candy Wrapper Velocity Model for the Earth's Inner Core

    NASA Astrophysics Data System (ADS)

    Mattesini, M.

    2014-12-01

    Recent global expansion of seismic data motivated a number of seismological studies of the Earth's inner core that proposed the existence of increasingly complex structure and anisotropy. In the meantime, new hypotheses of dynamic mechanisms have been put forward to interpret seismological results. Here, the nature of hemispherical dichotomy and anisotropy is re-investigated by bridging the observations of PKP(bc-df) differential travel-times with the iron bcc/hcp elastic properties computed from first-principles methods.The Candy Wrapper velocity model introduced here accounts for a dynamic picture of the inner core (i.e., the eastward drift of material), where different iron crystal shapes can be stabilized at the two hemispheres. We show that seismological data are best explained by a rather complicated, mosaic-like, structure of the inner core, where well-separated patches of different iron crystals compose the anisotropic western hemispherical region, and a conglomerate of almost indistinguishable iron phases builds-up the weakly anisotropic eastern side.

  7. Astrocytic gap junctional networks suppress cellular damage in an in vitro model of ischemia

    SciTech Connect

    Shinotsuka, Takanori; Yasui, Masato; Nuriya, Mutsuo

    2014-02-07

    Highlights: • Astrocytes exhibit characteristic changes in [Ca{sup 2+}]{sub i} under OGD. • Astrocytic [Ca{sup 2+}]{sub i} increase is synchronized with a neuronal anoxic depolarization. • Gap junctional couplings protect neurons as well as astrocytes during OGD. - Abstract: Astrocytes play pivotal roles in both the physiology and the pathophysiology of the brain. They communicate with each other via extracellular messengers as well as through gap junctions, which may exacerbate or protect against pathological processes in the brain. However, their roles during the acute phase of ischemia and the underlying cellular mechanisms remain largely unknown. To address this issue, we imaged changes in the intracellular calcium concentration ([Ca{sup 2+}]{sub i}) in astrocytes in mouse cortical slices under oxygen/glucose deprivation (OGD) condition using two-photon microscopy. Under OGD, astrocytes showed [Ca{sup 2+}]{sub i} oscillations followed by larger and sustained [Ca{sup 2+}]{sub i} increases. While the pharmacological blockades of astrocytic receptors for glutamate and ATP had no effect, the inhibitions of gap junctional intercellular coupling between astrocytes significantly advanced the onset of the sustained [Ca{sup 2+}]{sub i} increase after OGD exposure. Interestingly, the simultaneous recording of the neuronal membrane potential revealed that the onset of the sustained [Ca{sup 2+}]{sub i} increase in astrocytes was synchronized with the appearance of neuronal anoxic depolarization. Furthermore, the blockade of gap junctional coupling resulted in a concurrent faster appearance of neuronal depolarizations, which remain synchronized with the sustained [Ca{sup 2+}]{sub i} increase in astrocytes. These results indicate that astrocytes delay the appearance of the pathological responses of astrocytes and neurons through their gap junction-mediated intercellular network under OGD. Thus, astrocytic gap junctional networks provide protection against tissue damage

  8. Modelling dislocation cores in MgSiO3 perovskite

    NASA Astrophysics Data System (ADS)

    Cordier, P.; Carrez, P.; Gouriet, K.; Kraych, A.

    2012-12-01

    MgSiO3 perovskite is the most abundant mineral of the Earth's lower mantle (i.e. between 700 and 2900 km depth) and accounts for half of Earth's mass. At lower mantle pressures (25-135 GPa) MgSiO3 crystallises in a distorted (orthorhombic) perovskite structure (described in the following using the Pbnm space group). In this structure, SiO6 octahedra are tilted with tilt angles increasing with increasing pressure. Since it is very difficult to perform deformation experiments under the extreme P, T conditions of the lower mantle, little is known about plastic deformation of MgSiO3 perovskite and its slip systems are still a matter of debate. To overcome this difficulty, we model dislocation core structures in this mineral taking into account the influence of pressure. In this study, we focus on dislocation core structures of dislocations with [100] and [010] Burgers vectors (which derive from <110> Burgers vectors of the underlying pseudo-cubic structure). Atomistic calculations are performed using pair-wise potentials as implemented in the LAMMPS code. The choice of potentials was initially validated by comparing generalized stacking fault (GSF) energies to similar calculations performed with the density functional theory (DFT). The core structures of screw dislocations are calculated using two independent methods. The first one is based on Peierls-Nabarro-Galerkin simulations involving GSF as an input. Direct calculations have also bee performed using cluster approach. It turns out that screw dislocations with [100] Burgers vector are characterised by a core mostly spread in the (010) plane. The core exhibits two edge-sharing octahedra in a configuration very similar to that modelled in SrTiO3 cubic perovskite. The structure of [010] screw dislocations is more complex with dissociation into two, non-collinear partial dislocations with a significant non-screw component. Both dislocations exhibit high Peierls stresses. This illustrates the effect of orthorhombic

  9. Dynamic model of pulsed laser generators based on multi-junction N-p-N-i-P heterostructures

    NASA Astrophysics Data System (ADS)

    Slipchenko, Sergey; Podoskin, Alexsandr; Soboleva, Olga; Pikhtin, Nikita; Tarasov, Il'ya; Yuferev, Valentin

    2016-03-01

    This communication presents a dynamic model of a multi-junction heterostructure that combines the functions of a fast current switch and a high-efficiency laser emitter. Approaches to designing a multi-junction heterostructure with faster switching (rise and decay times of about 1 ns) and higher peak current (>10 A) are considered. It is shown that an important role is played in the dynamics of the injection drive currents of the laser part by the modulation by excess carriers in the lightly doped base and collector regions of the N-p-N transistor part. As a result, a field domain is formed, which serves as a virtual emitter of electrons and holes via impact ionization.

  10. A compact model for magnetic tunnel junction (MTJ) switched by thermally assisted Spin transfer torque (TAS + STT).

    PubMed

    Zhao, Weisheng; Duval, Julien; Klein, Jacques-Olivier; Chappert, Claude

    2011-01-01

    Thermally assisted spin transfer torque [TAS + STT] is a new switching approach for magnetic tunnel junction [MTJ] nanopillars that represents the best trade-off between data reliability, power efficiency and density. In this paper, we present a compact model for MTJ switched by this approach, which integrates a number of physical models such as temperature evaluation and STT dynamic switching models. Many experimental parameters are included directly to improve the simulation accuracy. It is programmed in the Verilog-A language and compatible with the standard IC CAD tools, providing an easy parameter configuration interface and allowing high-speed co-simulation of hybrid MTJ/CMOS circuits.

  11. A compact model for magnetic tunnel junction (MTJ) switched by thermally assisted Spin transfer torque (TAS + STT)

    NASA Astrophysics Data System (ADS)

    Zhao, Weisheng; Duval, Julien; Klein, Jacques-Olivier; Chappert, Claude

    2011-12-01

    Thermally assisted spin transfer torque [TAS + STT] is a new switching approach for magnetic tunnel junction [MTJ] nanopillars that represents the best trade-off between data reliability, power efficiency and density. In this paper, we present a compact model for MTJ switched by this approach, which integrates a number of physical models such as temperature evaluation and STT dynamic switching models. Many experimental parameters are included directly to improve the simulation accuracy. It is programmed in the Verilog-A language and compatible with the standard IC CAD tools, providing an easy parameter configuration interface and allowing high-speed co-simulation of hybrid MTJ/CMOS circuits.

  12. A compact model for magnetic tunnel junction (MTJ) switched by thermally assisted Spin transfer torque (TAS + STT)

    PubMed Central

    2011-01-01

    Thermally assisted spin transfer torque [TAS + STT] is a new switching approach for magnetic tunnel junction [MTJ] nanopillars that represents the best trade-off between data reliability, power efficiency and density. In this paper, we present a compact model for MTJ switched by this approach, which integrates a number of physical models such as temperature evaluation and STT dynamic switching models. Many experimental parameters are included directly to improve the simulation accuracy. It is programmed in the Verilog-A language and compatible with the standard IC CAD tools, providing an easy parameter configuration interface and allowing high-speed co-simulation of hybrid MTJ/CMOS circuits. PMID:21711868

  13. Electromagnetic model for near-field microwave microscope with atomic resolution: Determination of tunnel junction impedance

    SciTech Connect

    Reznik, Alexander N.

    2014-08-25

    An electrodynamic model is proposed for the tunneling microwave microscope with subnanometer space resolution as developed by Lee et al. [Appl. Phys. Lett. 97, 183111 (2010)]. Tip-sample impedance Z{sub a} was introduced and studied in the tunneling and non-tunneling regimes. At tunneling breakdown, the microwave current between probe and sample flows along two parallel channels characterized by impedances Z{sub p} and Z{sub t} that add up to form overall impedance Z{sub a}. Quantity Z{sub p} is the capacitive impedance determined by the near field of the probe and Z{sub t} is the impedance of the tunnel junction. By taking into account the distance dependences of effective tip radius r{sub 0}(z) and tunnel resistance R{sub t}(z) = Re[Z{sub t}(z)], we were able to explain the experimentally observed dependences of resonance frequency f{sub r}(z) and quality factor Q{sub L}(z) of the microscope. The obtained microwave resistance R{sub t}(z) and direct current tunnel resistance R{sub t}{sup dc}(z) exhibit qualitatively similar behavior, although being largely different in both magnitude and the characteristic scale of height dependence. Interpretation of the microwave images of the atomic structure of test samples proved possible by taking into account the inductive component of tunnel impedance ImZ{sub t} = ωL{sub t}. Relation ωL{sub t}/R{sub t} ≈ 0.235 was obtained.

  14. Ab-Initio Shell Model with a Core

    SciTech Connect

    Lisetskiy, A F; Barrett, B R; Kruse, M; Navratil, P; Stetcu, I; Vary, J P

    2008-06-04

    We construct effective 2- and 3-body Hamiltonians for the p-shell by performing 12{h_bar}{Omega} ab initio no-core shell model (NCSM) calculations for A=6 and 7 nuclei and explicitly projecting the many-body Hamiltonians onto the 0{h_bar}{Omega} space. We then separate these effective Hamiltonians into 0-, 1- and 2-body contributions (also 3-body for A=7) and analyze the systematic behavior of these different parts as a function of the mass number A and size of the NCSM basis space. The role of effective 3- and higher-body interactions for A > 6 is investigated and discussed.

  15. Computational modeling for hexcan failure under core distruptive accidental conditions

    SciTech Connect

    Sawada, T.; Ninokata, H.; Shimizu, A.

    1995-09-01

    This paper describes the development of computational modeling for hexcan wall failures under core disruptive accident conditions of fast breeder reactors. A series of out-of-pile experiments named SIMBATH has been analyzed by using the SIMMER-II code. The SIMBATH experiments were performed at KfK in Germany. The experiments used a thermite mixture to simulate fuel. The test geometry of SIMBATH ranged from single pin to 37-pin bundles. In this study, phenomena of hexcan wall failure found in a SIMBATH test were analyzed by SIMMER-II. Although the original model of SIMMER-II did not calculate any hexcan failure, several simple modifications made it possible to reproduce the hexcan wall melt-through observed in the experiment. In this paper the modifications and their significance are discussed for further modeling improvements.

  16. Impaired Astrocytic Gap Junction Coupling and Potassium Buffering in a Mouse Model of Tuberous Sclerosis Complex

    PubMed Central

    Xu, Lin; Zeng, Ling-Hui; Wong, Michael

    2009-01-01

    Abnormalities in astrocytes occur in the brains of patients with Tuberous Sclerosis Complex (TSC) and may contribute to the pathogenesis of neurological dysfunction in this disease. Here, we report that knock-out mice with Tsc1 gene inactivation in glia (Tsc1GFAPCKO mice) exhibit decreased expression of the astrocytic connexin protein, Cx43, and an associated impairment in gap junction coupling between astrocytes. Correspondingly, hippocampal slices from Tsc1GFAPCKO mice have increased extracellular potassium concentration in response to stimulation. This impaired potassium buffering can be attributed to abnormal gap junction coupling, as a gap junction inhibitor elicits an additional increase in potassium concentration in control, but not Tsc1GFAPCKO slices. Furthermore, treatment with a mammalian target of rapamycin inhibitor reverses the deficient Cx43 expression and impaired potassium buffering. These findings suggest that Tsc1 inactivation in astrocytes causes defects in astrocytic gap junction coupling and potassium clearance, which may contribute to epilepsy in Tsc1GFAPCKO mice. PMID:19385061

  17. Beyond the Lorentzian Model in Quantum Transport: Energy-Dependent Resonance Broadening in Molecular Junctions

    NASA Astrophysics Data System (ADS)

    Liu, Zhenfei; Neaton, Jeffrey B.

    In quantum transport calculations, transmission functions of molecular junctions, as well as spectral functions of metal-organic interfaces, often feature peaks originating from molecular resonances. These resonance peaks are often assumed to be Lorentzian, with an energy-independent broadening function Γ. However, in the general case, the wide-band-limit breaks down, and the Lorentzian approximation is no longer valid. Here, we develop a new energy-dependent broadening function Γ (E) , based on diagonalization of non-Hermitian matrices within a non-equilbrium Green's function (NEGF) formalism. As defined, Γ (E) can describe resonances of non-Lorentzian nature and can be decomposed into components associated with the left and right leads, respectively; and it is particularly useful in understanding transport properties in terms of molecular orbitals in asymmetric junctions. We compute this quantity via an ab initio NEGF approach based on density functional theory and illustrate its utility with several junctions of experimental relevance, including recent work on rectification in Au-graphite junctions. This work is supported by the DOE, and computational resources are provided by NERSC.

  18. Recent Developments in No-Core Shell-Model Calculations

    SciTech Connect

    Navratil, P; Quaglioni, S; Stetcu, I; Barrett, B R

    2009-03-20

    We present an overview of recent results and developments of the no-core shell model (NCSM), an ab initio approach to the nuclear many-body problem for light nuclei. In this aproach, we start from realistic two-nucleon or two- plus three-nucleon interactions. Many-body calculations are performed using a finite harmonic-oscillator (HO) basis. To facilitate convergence for realistic inter-nucleon interactions that generate strong short-range correlations, we derive effective interactions by unitary transformations that are tailored to the HO basis truncation. For soft realistic interactions this might not be necessary. If that is the case, the NCSM calculations are variational. In either case, the ab initio NCSM preserves translational invariance of the nuclear many-body problem. In this review, we, in particular, highlight results obtained with the chiral two- plus three-nucleon interactions. We discuss efforts to extend the applicability of the NCSM to heavier nuclei and larger model spaces using importance-truncation schemes and/or use of effective interactions with a core. We outline an extension of the ab initio NCSM to the description of nuclear reactions by the resonating group method technique. A future direction of the approach, the ab initio NCSM with continuum, which will provide a complete description of nuclei as open systems with coupling of bound and continuum states is given in the concluding part of the review.

  19. A numerical strategy for modelling rotating stall in core compressors

    NASA Astrophysics Data System (ADS)

    Vahdati, M.

    2007-03-01

    The paper will focus on one specific core-compressor instability, rotating stall, because of the pressing industrial need to improve current design methods. The determination of the blade response during rotating stall is a difficult problem for which there is no reliable procedure. During rotating stall, the blades encounter the stall cells and the excitation depends on the number, size, exact shape and rotational speed of these cells. The long-term aim is to minimize the forced response due to rotating stall excitation by avoiding potential matches between the vibration modes and the rotating stall pattern characteristics. Accurate numerical simulations of core-compressor rotating stall phenomena require the modelling of a large number of bladerows using grids containing several tens of millions of points. The time-accurate unsteady-flow computations may need to be run for several engine revolutions for rotating stall to get initiated and many more before it is fully developed. The difficulty in rotating stall initiation arises from a lack of representation of the triggering disturbances which are inherently present in aeroengines. Since the numerical model represents a symmetric assembly, the only random mechanism for rotating stall initiation is provided by numerical round-off errors. In this work, rotating stall is initiated by introducing a small amount of geometric mistuning to the rotor blades. Another major obstacle in modelling flows near stall is the specification of appropriate upstream and downstream boundary conditions. Obtaining reliable boundary conditions for such flows can be very difficult. In the present study, the low-pressure compression (LPC) domain is placed upstream of the core compressor. With such an approach, only far field atmospheric boundary conditions are specified which are obtained from aircraft speed and altitude. A chocked variable-area nozzle, placed after the last compressor bladerow in the model, is used to impose boundary

  20. Systems Modeling for Crew Core Body Temperature Prediction Postlanding

    NASA Technical Reports Server (NTRS)

    Cross, Cynthia; Ochoa, Dustin

    2010-01-01

    The Orion Crew Exploration Vehicle, NASA s latest crewed spacecraft project, presents many challenges to its designers including ensuring crew survivability during nominal and off nominal landing conditions. With a nominal water landing planned off the coast of San Clemente, California, off nominal water landings could range from the far North Atlantic Ocean to the middle of the equatorial Pacific Ocean. For all of these conditions, the vehicle must provide sufficient life support resources to ensure that the crew member s core body temperatures are maintained at a safe level prior to crew rescue. This paper will examine the natural environments, environments created inside the cabin and constraints associated with post landing operations that affect the temperature of the crew member. Models of the capsule and the crew members are examined and analysis results are compared to the requirement for safe human exposure. Further, recommendations for updated modeling techniques and operational limits are included.

  1. Development of CFD model for augmented core tripropellant rocket engine

    NASA Astrophysics Data System (ADS)

    Jones, Kenneth M.

    1994-10-01

    The Space Shuttle era has made major advances in technology and vehicle design to the point that the concept of a single-stage-to-orbit (SSTO) vehicle appears more feasible. NASA presently is conducting studies into the feasibility of certain advanced concept rocket engines that could be utilized in a SSTO vehicle. One such concept is a tripropellant system which burns kerosene and hydrogen initially and at altitude switches to hydrogen. This system will attain a larger mass fraction because LOX-kerosene engines have a greater average propellant density and greater thrust-to-weight ratio. This report describes the investigation to model the tripropellant augmented core engine. The physical aspects of the engine, the CFD code employed, and results of the numerical model for a single modular thruster are discussed.

  2. Development of CFD model for augmented core tripropellant rocket engine

    NASA Technical Reports Server (NTRS)

    Jones, Kenneth M.

    1994-01-01

    The Space Shuttle era has made major advances in technology and vehicle design to the point that the concept of a single-stage-to-orbit (SSTO) vehicle appears more feasible. NASA presently is conducting studies into the feasibility of certain advanced concept rocket engines that could be utilized in a SSTO vehicle. One such concept is a tripropellant system which burns kerosene and hydrogen initially and at altitude switches to hydrogen. This system will attain a larger mass fraction because LOX-kerosene engines have a greater average propellant density and greater thrust-to-weight ratio. This report describes the investigation to model the tripropellant augmented core engine. The physical aspects of the engine, the CFD code employed, and results of the numerical model for a single modular thruster are discussed.

  3. Mean-field fluid behavior of the Gaussian core model

    NASA Astrophysics Data System (ADS)

    Louis, A. A.; Bolhuis, P. G.; Hansen, J. P.

    2000-12-01

    We show that the Gaussian core model of particles interacting via a penetrable repulsive Gaussian potential, first considered by Stillinger [J. Chem. Phys. 65, 3968 (1976)], behaves as a weakly correlated ``mean-field fluid'' over a surprisingly wide density and temperature range. In the bulk, the structure of the fluid phase is accurately described by the random phase approximation for the direct correlation function, and by the more sophisticated hypernetted chain integral equation. The resulting pressure deviates very little from a simple mean-field-like quadratic form in the density, while the low density virial expansion turns out to have an extremely small radius of convergence. Density profiles near a hard wall are also very accurately described by the corresponding mean-field free-energy functional. The binary version of the model exhibits a spinodal instability against demixing at high densities. Possible implications for semidilute polymer solutions are discussed.

  4. Baryon-Baryon Interactions ---Nijmegen Extended-Soft-Core Models---

    NASA Astrophysics Data System (ADS)

    Rijken, T. A.; Nagels, M. M.; Yamamoto, Y.

    We review the Nijmegen extended-soft-core (ESC) models for the baryon-baryon (BB) interactions of the SU(3) flavor-octet of baryons (N, Lambda, Sigma, and Xi). The interactions are basically studied from the meson-exchange point of view, in the spirit of the Yukawa-approach to the nuclear force problem [H. Yukawa, ``On the interaction of Elementary Particles I'', Proceedings of the Physico-Mathematical Society of Japan 17 (1935), 48], using generalized soft-core Yukawa-functions. These interactions are supplemented with (i) multiple-gluon-exchange, and (ii) structural effects due to the quark-core of the baryons. We present in some detail the most recent extended-soft-core model, henceforth referred to as ESC08, which is the most complete, sophisticated, and successful interaction-model. Furthermore, we discuss briefly its predecessor the ESC04-model [Th. A. Rijken and Y. Yamamoto, Phys. Rev. C 73 (2006), 044007; Th. A. Rijken and Y. Yamamoto, Ph ys. Rev. C 73 (2006), 044008; Th. A. Rijken and Y. Yamamoto, nucl-th/0608074]. For the soft-core one-boson-exchange (OBE) models we refer to the literature [Th. A. Rijken, in Proceedings of the International Conference on Few-Body Problems in Nuclear and Particle Physics, Quebec, 1974, ed. R. J. Slobodrian, B. Cuec and R. Ramavataram (Presses Universitè Laval, Quebec, 1975), p. 136; Th. A. Rijken, Ph. D. thesis, University of Nijmegen, 1975; M. M. Nagels, Th. A. Rijken and J. J. de Swart, Phys. Rev. D 17 (1978), 768; P. M. M. Maessen, Th. A. Rijken and J. J. de Swart, Phys. Rev. C 40 (1989), 2226; Th. A. Rijken, V. G. J. Stoks and Y. Yamamoto, Phys. Rev. C 59 (1999), 21; V. G. J. Stoks and Th. A. Rijken, Phys. Rev. C 59 (1999), 3009]. All ingredients of these latter models are also part of ESC08, and so a description of ESC08 comprises all models so far in principle. The extended-soft-core (ESC) interactions consist of local- and non-local-potentials due to (i) one-boson-exchanges (OBE), which are the members of nonets of

  5. Low Mach Number Modeling of Core Convection in Massive Stars

    NASA Astrophysics Data System (ADS)

    Gilet, C.; Almgren, A. S.; Bell, J. B.; Nonaka, A.; Woosley, S. E.; Zingale, M.

    2013-08-01

    This work presents three-dimensional simulations of core convection in a 15 M ⊙ star halfway through its main sequence lifetime. To perform the necessary long-time calculations, we use the low Mach number code MAESTRO, with initial conditions taken from a one-dimensional stellar model. We first identify several key factors that the one-dimensional initial model must satisfy to ensure efficient simulation of the convection process. We then use the three-dimensional simulations to examine the effects of two common modeling choices on the resulting convective flow: using a fixed composition approximation and using a reduced domain size. We find that using a fixed composition model actually increases the computational cost relative to using the full multi-species model because the fixed composition system takes longer to reach convection that is in a quasi-static state. Using a reduced (octant rather than full sphere) simulation domain yields flow with statistical properties that are within a factor of two of the full sphere simulation values. Both the octant and full sphere simulations show similar mixing across the convection zone boundary that is consistent with the turbulent entrainment model. However, the global character of the flow is distinctly different in the octant simulation, showing more rapid changes in the large-scale structure of the flow and thus a more isotropic flow on average.

  6. LOW MACH NUMBER MODELING OF CORE CONVECTION IN MASSIVE STARS

    SciTech Connect

    Gilet, C.; Almgren, A. S.; Bell, J. B.; Nonaka, A.; Woosley, S. E.; Zingale, M.

    2013-08-20

    This work presents three-dimensional simulations of core convection in a 15 M{sub Sun} star halfway through its main sequence lifetime. To perform the necessary long-time calculations, we use the low Mach number code MAESTRO, with initial conditions taken from a one-dimensional stellar model. We first identify several key factors that the one-dimensional initial model must satisfy to ensure efficient simulation of the convection process. We then use the three-dimensional simulations to examine the effects of two common modeling choices on the resulting convective flow: using a fixed composition approximation and using a reduced domain size. We find that using a fixed composition model actually increases the computational cost relative to using the full multi-species model because the fixed composition system takes longer to reach convection that is in a quasi-static state. Using a reduced (octant rather than full sphere) simulation domain yields flow with statistical properties that are within a factor of two of the full sphere simulation values. Both the octant and full sphere simulations show similar mixing across the convection zone boundary that is consistent with the turbulent entrainment model. However, the global character of the flow is distinctly different in the octant simulation, showing more rapid changes in the large-scale structure of the flow and thus a more isotropic flow on average.

  7. The Geological information and modelling Thematic Core Service of EPOS

    NASA Astrophysics Data System (ADS)

    Robida, François; Wächter, Joachim; Tulstrup, Jørgen; Lorenz, Henning; Carter, Mary; Cipolloni, Carlo

    2015-04-01

    Geological data and models are important assets for the EPOS community. The Geological information and modelling Thematic Core Service of EPOS will be designed and implemented in an efficient and sustainable access system for geological multi-scale data assets for EPOS through the integration of distributed infrastructure components (nodes) of geological surveys, research institutes and the international drilling community (ICDP) . The TCS will develop and take benefit of the synergy between the existing data infrastructures of the Geological Surveys of Europe (EuroGeoSurveys / OneGeology-Europe / EGDI) and on the large amount of information produced by the research organisations. These nodes will offer a broad range of resources including: digitised geological maps, borehole data, geophysical data (seismic data, borehole log data), archived information on physical material (samples, cores), geochemical and other analyses of rocks, soils and minerals, and Geological models (3D, 4D). The services will be implemented on international standards (such as INSPIRE, IUGS/CGI, OGC, W3C, ISO) in order to guarantee their interoperability with other EPOS TCS as well as their compliance with INSPIRE European Directive or international initiatives (such as OneGeology). This will provide future virtual research environments with means to facilitate the use of existing information for future applications. In addition, workflows will be established that allow the integration of other existing and new data and applications. Processing and the use of simulation and visualization tools will subsequently support the integrated analysis and characterization of complex subsurface structures and their inherent dynamic processes. This will in turn aid in the overall understanding of complex multi-scale geo-scientific questions. This TCS will work alongside other EPOS TCSs to create an efficient and comprehensive multidisciplinary research platform for the Earth Sciences in Europe.

  8. The Geological information and modelling Thematic Core Service of EPOS

    NASA Astrophysics Data System (ADS)

    Robida, François; Wächter, Joachim; Tulstrup, Jørgen; Lorenz, Henning; Carter, Mary; Cipolloni, Carlo; Morel, Olivier

    2016-04-01

    Geological data and models are important assets for the EPOS community. The Geological information and modelling Thematic Core Service of EPOS is being designed and will be implemented in an efficient and sustainable access system for geological multi-scale data assets for EPOS through the integration of distributed infrastructure components (nodes) of geological surveys, research institutes and the international drilling community (ICDP/IODP). The TCS will develop and take benefit of the synergy between the existing data infrastructures of the Geological Surveys of Europe (EuroGeoSurveys / OneGeology-Europe / EGDI) and of the large amount of information produced by the research organisations. These nodes will offer a broad range of resources including: geological maps, borehole data, geophysical data (seismic data, borehole log data), archived information on physical material (samples, cores), geochemical and other analyses of rocks, soils and minerals, and Geological models (3D, 4D). The services will be implemented on international standards (such as INSPIRE, IUGS/CGI, OGC, W3C, ISO) in order to guarantee their interoperability with other EPOS TCS as well as their compliance with INSPIRE European Directive or international initiatives (such as OneGeology). This will provide future virtual research environments with means to facilitate the use of existing information for future applications. In addition, workflows will be established that allow the integration of other existing and new data and applications. Processing and the use of simulation and visualization tools will subsequently support the integrated analysis and characterization of complex subsurface structures and their inherent dynamic processes. This will in turn aid in the overall understanding of complex multi-scale geo-scientific questions. This TCS will work alongside other EPOS TCSs to create an efficient and comprehensive multidisciplinary research platform for the Earth Sciences in Europe.

  9. Benchmarking spin-state chemistry in starless core models

    NASA Astrophysics Data System (ADS)

    Sipilä, O.; Caselli, P.; Harju, J.

    2015-06-01

    Aims: We aim to present simulated chemical abundance profiles for a variety of important species, giving special attention to spin-state chemistry, in order to provide reference results to which present and future models can be compared. Methods: We employ gas-phase and gas-grain models to investigate chemical abundances in physical conditions that correspond to starless cores. To this end, we have developed new chemical reaction sets for both gas-phase and grain-surface chemistry, including the deuterated forms of species with up to six atoms and the spin-state chemistry of light ions and of the species involved in the ammonia and water formation networks. The physical model is kept simple to facilitate straightforward benchmarking of other models against the results of this paper. Results: We find that the ortho/para ratios of ammonia and water are similar in both gas-phase and gas-grain models, particularly at late times, implying that the ratios are determined by gas-phase processes. Furthermore, the ratios do not exhibit any strong dependence on core density. We derive late-time ortho/para ratios of ~0.5 for ammonia and ~1.6 for water. We find that including or excluding deuterium in the calculations has little effect on the abundances of non-deuterated species and on the ortho/para ratios of ammonia and water, especially in gas-phase models where deuteration is naturally hindered by the presence of abundant heavy elements. Although we study a rather narrow temperature range (10-20 K), we find strong temperature dependence in, e.g., deuteration and nitrogen chemistry. For example, the depletion timescale of ammonia is significantly reduced when the temperature is increased from 10 to 20 K; this is because the increase in temperature translates into increased accretion rates, while the very high binding energy of ammonia prevents it from being desorbed at 20 K. Appendices are available in electronic form at http://www.aanda.org

  10. A New Global Core Plasma Model of the Plasmasphere

    NASA Technical Reports Server (NTRS)

    Gallagher, D. L.; Comfort, R. H.; Craven, P. D.

    2014-01-01

    The Global Core Plasma Model (GCPM) is the first empirical model for thermal inner magnetospheric plasma designed to integrate previous models and observations into a continuous in value and gradient representation of typical total densities. New information about the plasmasphere, in particular, make possible significant improvement. The IMAGE Mission Radio Plasma Imager (RPI) has obtained the first observations of total plasma densities along magnetic field lines in the plasmasphere and polar cap. Dynamics Explorer 1 Retarding Ion Mass Spectrometer (RIMS) has provided densities in temperatures in the plasmasphere for 5 ion species. These and other works enable a new more detailed empirical model of thermal in the inner magnetosphere that will be presented. Specifically shown here are the inner-plasmasphere RIMS measurements, radial fits to densities and temperatures for H(+), He(+), He(++), O(+), and O(+) and the error associated with these initial simple fits. Also shown are more subtle dependencies on the f10.7 P-value (see Richards et al. [1994]).

  11. Morse potential-based model for contacting composite rough surfaces: Application to self-assembled monolayer junctions

    NASA Astrophysics Data System (ADS)

    Sierra-Suarez, Jonatan A.; Majumdar, Shubhaditya; McGaughey, Alan J. H.; Malen, Jonathan A.; Higgs, C. Fred

    2016-04-01

    This work formulates a rough surface contact model that accounts for adhesion through a Morse potential and plasticity through the Kogut-Etsion finite element-based approximation. Compared to the commonly used Lennard-Jones (LJ) potential, the Morse potential provides a more accurate and generalized description for modeling covalent materials and surface interactions. An extension of this contact model to describe composite layered surfaces is presented and implemented to study a self-assembled monolayer (SAM) grown on a gold substrate placed in contact with a second gold substrate. Based on a comparison with prior experimental measurements of the thermal conductance of this SAM junction [Majumdar et al., Nano Lett. 15, 2985-2991 (2015)], the more general Morse potential-based contact model provides a better prediction of the percentage contact area than an equivalent LJ potential-based model.

  12. Integration of geometric consistency contributory factors in three-leg junctions collision prediction models of Portuguese two-lane national highways.

    PubMed

    da Costa, Jocilene Otilia; Jacques, Maria Alice Prudêncio; Soares, Francisco Emanuel Cunha; Freitas, Elisabete Fraga

    2016-01-01

    This paper aims at developing a collision prediction model for three-leg junctions located in national roads (NR) in Northern Portugal. The focus is to identify factors that contribute for collision type crashes in those locations, mainly factors related to road geometric consistency, since literature is scarce on those, and to research the impact of three modeling methods: generalized estimating equations, random-effects negative binomial models and random-parameters negative binomial models, on the factors of those models. The database used included data published between 2008 and 2010 of 177 three-leg junctions. It was split in three groups of contributing factors which were tested sequentially for each of the adopted models: at first only traffic, then, traffic and the geometric characteristics of the junctions within their area of influence; and, lastly, factors which show the difference between the geometric characteristics of the segments boarding the junctions' area of influence and the segment included in that area were added. The choice of the best modeling technique was supported by the result of a cross validation made to ascertain the best model for the three sets of researched contributing factors. The models fitted with random-parameters negative binomial models had the best performance in the process. In the best models obtained for every modeling technique, the characteristics of the road environment, including proxy measures for the geometric consistency, along with traffic volume, contribute significantly to the number of collisions. Both the variables concerning junctions and the various national highway segments in their area of influence, as well as variations from those characteristics concerning roadway segments which border the already mentioned area of influence have proven their relevance and, therefore, there is a rightful need to incorporate the effect of geometric consistency in the three-leg junctions safety studies. PMID:26513337

  13. A Single-Level Tunnel Model to Account for Electrical Transport through Single Molecule- and Self-Assembled Monolayer-based Junctions

    PubMed Central

    Garrigues, Alvar R.; Yuan, Li; Wang, Lejia; Mucciolo, Eduardo R.; Thompon, Damien; del Barco, Enrique; Nijhuis, Christian A.

    2016-01-01

    We present a theoretical analysis aimed at understanding electrical conduction in molecular tunnel junctions. We focus on discussing the validity of coherent versus incoherent theoretical formulations for single-level tunneling to explain experimental results obtained under a wide range of experimental conditions, including measurements in individual molecules connecting the leads of electromigrated single-electron transistors and junctions of self-assembled monolayers (SAM) of molecules sandwiched between two macroscopic contacts. We show that the restriction of transport through a single level in solid state junctions (no solvent) makes coherent and incoherent tunneling formalisms indistinguishable when only one level participates in transport. Similar to Marcus relaxation processes in wet electrochemistry, the thermal broadening of the Fermi distribution describing the electronic occupation energies in the electrodes accounts for the exponential dependence of the tunneling current on temperature. We demonstrate that a single-level tunnel model satisfactorily explains experimental results obtained in three different molecular junctions (both single-molecule and SAM-based) formed by ferrocene-based molecules. Among other things, we use the model to map the electrostatic potential profile in EGaIn-based SAM junctions in which the ferrocene unit is placed at different positions within the molecule, and we find that electrical screening gives rise to a strongly non-linear profile across the junction. PMID:27216489

  14. A Single-Level Tunnel Model to Account for Electrical Transport through Single Molecule- and Self-Assembled Monolayer-based Junctions

    NASA Astrophysics Data System (ADS)

    Garrigues, Alvar R.; Yuan, Li; Wang, Lejia; Mucciolo, Eduardo R.; Thompon, Damien; Del Barco, Enrique; Nijhuis, Christian A.

    2016-05-01

    We present a theoretical analysis aimed at understanding electrical conduction in molecular tunnel junctions. We focus on discussing the validity of coherent versus incoherent theoretical formulations for single-level tunneling to explain experimental results obtained under a wide range of experimental conditions, including measurements in individual molecules connecting the leads of electromigrated single-electron transistors and junctions of self-assembled monolayers (SAM) of molecules sandwiched between two macroscopic contacts. We show that the restriction of transport through a single level in solid state junctions (no solvent) makes coherent and incoherent tunneling formalisms indistinguishable when only one level participates in transport. Similar to Marcus relaxation processes in wet electrochemistry, the thermal broadening of the Fermi distribution describing the electronic occupation energies in the electrodes accounts for the exponential dependence of the tunneling current on temperature. We demonstrate that a single-level tunnel model satisfactorily explains experimental results obtained in three different molecular junctions (both single-molecule and SAM-based) formed by ferrocene-based molecules. Among other things, we use the model to map the electrostatic potential profile in EGaIn-based SAM junctions in which the ferrocene unit is placed at different positions within the molecule, and we find that electrical screening gives rise to a strongly non-linear profile across the junction.

  15. A Single-Level Tunnel Model to Account for Electrical Transport through Single Molecule- and Self-Assembled Monolayer-based Junctions.

    PubMed

    Garrigues, Alvar R; Yuan, Li; Wang, Lejia; Mucciolo, Eduardo R; Thompon, Damien; Del Barco, Enrique; Nijhuis, Christian A

    2016-01-01

    We present a theoretical analysis aimed at understanding electrical conduction in molecular tunnel junctions. We focus on discussing the validity of coherent versus incoherent theoretical formulations for single-level tunneling to explain experimental results obtained under a wide range of experimental conditions, including measurements in individual molecules connecting the leads of electromigrated single-electron transistors and junctions of self-assembled monolayers (SAM) of molecules sandwiched between two macroscopic contacts. We show that the restriction of transport through a single level in solid state junctions (no solvent) makes coherent and incoherent tunneling formalisms indistinguishable when only one level participates in transport. Similar to Marcus relaxation processes in wet electrochemistry, the thermal broadening of the Fermi distribution describing the electronic occupation energies in the electrodes accounts for the exponential dependence of the tunneling current on temperature. We demonstrate that a single-level tunnel model satisfactorily explains experimental results obtained in three different molecular junctions (both single-molecule and SAM-based) formed by ferrocene-based molecules. Among other things, we use the model to map the electrostatic potential profile in EGaIn-based SAM junctions in which the ferrocene unit is placed at different positions within the molecule, and we find that electrical screening gives rise to a strongly non-linear profile across the junction. PMID:27216489

  16. Phase diagram of the Gaussian-core model.

    PubMed

    Prestipino, Santi; Saija, Franz; Giaquinta, Paolo V

    2005-05-01

    We trace with high numerical accuracy the phase diagram of the Gaussian-core model, a classical system of point particles interacting via a Gaussian-shaped, purely repulsive potential. This model, which provides a reliable qualitative description of the thermal behavior of interpenetrable globular polymers, is known to exhibit a polymorphic fcc-bcc transition at low densities and reentrant melting at high densities. Extensive Monte Carlo simulations, carried out in conjunction with accurate calculations of the solid free energies, lead to a thermodynamic scenario that is partially modified with respect to previous knowledge. In particular, we find that: (i) the fluid-bcc-fcc triple-point temperature is about one third of the maximum freezing temperature; (ii) upon isothermal compression, the model exhibits a fluid-bcc-fcc-bcc-fluid sequence of phases in a narrow range of temperatures just above the triple point. We discuss these results in relation to the behavior of star-polymer solutions and of other softly repulsive systems. PMID:16089510

  17. Inferring ancient metabolism using ancestral core metabolic models of enterobacteria

    PubMed Central

    2013-01-01

    Background Enterobacteriaceae diversified from an ancestral lineage ~300-500 million years ago (mya) into a wide variety of free-living and host-associated lifestyles. Nutrient availability varies across niches, and evolution of metabolic networks likely played a key role in adaptation. Results Here we use a paleo systems biology approach to reconstruct and model metabolic networks of ancestral nodes of the enterobacteria phylogeny to investigate metabolism of ancient microorganisms and evolution of the networks. Specifically, we identified orthologous genes across genomes of 72 free-living enterobacteria (16 genera), and constructed core metabolic networks capturing conserved components for ancestral lineages leading to E. coli/Shigella (~10 mya), E. coli/Shigella/Salmonella (~100 mya), and all enterobacteria (~300-500 mya). Using these models we analyzed the capacity for carbon, nitrogen, phosphorous, sulfur, and iron utilization in aerobic and anaerobic conditions, identified conserved and differentiating catabolic phenotypes, and validated predictions by comparison to experimental data from extant organisms. Conclusions This is a novel approach using quantitative ancestral models to study metabolic network evolution and may be useful for identification of new targets to control infectious diseases caused by enterobacteria. PMID:23758866

  18. Analytical model and new structure of the enhancement-mode polarization-junction HEMT with vertical conduction channel

    NASA Astrophysics Data System (ADS)

    Yang, Chao; Xiong, Jiayun; Wei, Jie; Wu, Junfeng; Peng, Fu; Deng, Siyu; Zhang, Bo; Luo, Xiaorong

    2016-04-01

    A novel enhancement-mode (E-mode) polarization-junction HEMT with vertical conduction channel (PVC-HEMT) is proposed, and its analytical model for threshold voltage (Vth) is presented. It has two features: one is GaN/AlGaN/GaN double hetero-structure, the other is that source and drain locate at the same side of trench-type MOS gate (T-gate), and the source contacts with the T-gate, which forms vertical conduction channel (VC). The 2-D hole gas (2-DHG) and 2-D electron gas (2-DEG) are formed at the GaN-top/AlGaN and AlGaN/GaN-buffer interface, respectively, forming the polarization-junction. First, the E-mode operation is realized because 2-DHG under the source prevents the electrons injecting from source to 2-DEG, breaking through the conventional E-mode method by depleting 2-DEG under the gate. Second, a uniform electric field (E-field) distribution is achieved due to the assisted depletion effect by polarization-junction. Third, the source reduces the E-field peak at the T-gate side and modulates the E-field distribution. The breakdown voltage (BV) of PVC-HEMT is 705 V and specific ON-resistance (RON,sp) is 1.18 mΩ cm2. Compared with conventional HEMT (C-HEMT), PVC-HEMT has a smaller size due to the special location of the source and T-gate. An analytic threshold voltage model is presented and the analytical results agree well with the simulated results.

  19. Numerical modelling of triple-junction tectonics at Karlıova, Eastern Turkey, with implications for regional magma transport

    NASA Astrophysics Data System (ADS)

    Karaoğlu, Özgür; Browning, John; Bazargan, Mohsen; Gudmundsson, Agust

    2016-10-01

    Few places on Earth are as tectonically active as the Karlıova region of eastern Turkey. In this region, complex interactions between the Arabian, Eurasian and Anatolian plates occur at the Karlıova Triple Junction (KTJ). The relationship between tectonics and magma propagation in triple-junction tectonic settings is poorly understood. Here we present new field and numerical results on the mechanism of magma propagation at the KTJ. We explore the effects of crustal heterogeneity and anisotropy, in particular the geometry and mechanical properties of many faults and layers, on magma propagation paths under a variety of tectonic loadings. We propose that two major volcanic centres in the area, the Turnadağ volcano and the Varto caldera, are both fed by comparatively shallow magma chambers at depths of about 8 km, which, in turn, are fed by a single, much larger and deeper reservoir at about 15-18 km depth. By contrast, the nearby Özenç volcanic area is fed directly by the deeper reservoir. We present a series of two-dimensional and three-dimensional numerical models showing that the present tectonic stresses encourage magma-chamber rupture and dyke injection. The results show that inversion tectonics encourages the formation of magma paths as potential feeder dykes. Our three-dimensional models allow us to explore the local stresses induced by complex loading conditions at the Karlıova triple junction, using an approach that can in future be applied to other similar tectonic regions. The numerical results indicate a great complexity in the potential magma (dyke) paths, resulting from local stresses generated by interaction between mechanical layers, major faults, and magma chambers. In particular, the results suggest three main controls on magma path formation and eventual eruptions at KTJ: (1) the geometry and attitude of the associated faults; (2) the heterogeneity and anisotropy of the crust; and (3) mechanical (stress) interactions between deep and shallow

  20. A model of the dynamical structure of Earth's outer core

    NASA Astrophysics Data System (ADS)

    Loper, David E.

    2000-01-01

    The dynamical state of the outer core is quantified, assuming that the convective pattern consists of buoyant parcels which rise to the top, forcing a broad descending flow in the bulk of the outer core. This convective circulation is assumed sufficiently rapid that the outer core is close to a well-mixed adiabatic state. Small compositional deviations from this state, resulting from the secular evolution of composition as the solid inner core grows, make the descending portion of the outer core stably stratified. Thermal deviations result from the mismatch between effective volumetric heating and the divergence of conducted heat. Effective volumetric heating is the sum of secular cooling, compressional heating and Ohmic heating. Divergence of heat is negative and larger in magnitude than effective volumetric heating throughout the core, resulting in a stabilizing thermal gradient in the descending fluid which reinforces the compositional gradient. The compositional and thermal contributions to the stable stratification are of comparable magnitudes. The strength of stratification depends on the strength of the convective circulation, which is unquantified. This stratification, coupled with Coriolis and Lorentz forces, has the potential to inhibit turbulence in the descending portions of the outer core. The thermal and compositional perturbations arising from processes at the inner-core boundary and core-mantle boundary are quantified and the dynamic behavior of the rising parcels is discussed and quantified. Depending on the sign and magnitude of exchanges of heat and composition, convective motions may be inhibited or suppressed near the top of the outer core.

  1. Numerical Results of Earth's Core Accumulation 3-D Modelling

    NASA Astrophysics Data System (ADS)

    Khachay, Yurie; Anfilogov, Vsevolod

    2013-04-01

    For a long time as a most convenient had been the model of mega impact in which the early forming of the Earth's core and mantle had been the consequence of formed protoplanet collision with the body of Mercurial mass. But all dynamical models of the Earth's accumulation and the estimations after the Pb-Pb system, lead to the conclusion that the duration of the planet accumulation was about 1 milliard years. But isotopic results after the W-Hf system testify about a very early (5-10) million years, dividing of the geochemical reservoirs of the core and mantle. In [1,3] it is shown, that the account of energy dissipating by the decay of short living radioactive elements and first of all Al,it is sufficient for heating even small bodies with dimensions about (50-100) km up to the iron melting temperature and can be realized a principal new differentiation mechanism. The inner parts of the melted preplanets can join and they are mainly of iron content, but the cold silicate fragments return to the supply zone. Only after the increasing of the gravitational radius, the growing area of the future core can save also the silicate envelope fragments. All existing dynamical accumulation models are constructed by using a spherical-symmetrical model. Hence for understanding the further planet evolution it is significant to trace the origin and evolution of heterogeneities, which occur on the planet accumulation stage. In that paper we are modeling distributions of temperature, pressure, velocity of matter flowing in a block of 3D- spherical body with a growing radius. The boundary problem is solved by the finite-difference method for the system of equations, which include equations which describe the process of accumulation, the Safronov equation, the equation of impulse balance, equation Navier-Stocks, equation for above litho static pressure and heat conductivity in velocity-pressure variables using the Businesque approach. The numerical algorithm of the problem solution in

  2. Application of stochastic automata networks for creation of continuous time Markov chain models of voltage gating of gap junction channels.

    PubMed

    Snipas, Mindaugas; Pranevicius, Henrikas; Pranevicius, Mindaugas; Pranevicius, Osvaldas; Paulauskas, Nerijus; Bukauskas, Feliksas F

    2015-01-01

    The primary goal of this work was to study advantages of numerical methods used for the creation of continuous time Markov chain models (CTMC) of voltage gating of gap junction (GJ) channels composed of connexin protein. This task was accomplished by describing gating of GJs using the formalism of the stochastic automata networks (SANs), which allowed for very efficient building and storing of infinitesimal generator of the CTMC that allowed to produce matrices of the models containing a distinct block structure. All of that allowed us to develop efficient numerical methods for a steady-state solution of CTMC models. This allowed us to accelerate CPU time, which is necessary to solve CTMC models, ~20 times. PMID:25705700

  3. THREE-DIMENSIONAL FIELD MODELS FOR REVERSE BIASED P-N JUNCTIONS.

    SciTech Connect

    UBALDI,F.; POZZI, G.; FAZZINI, P.F.; BELEGGIA, M.

    2007-04-02

    In order to obtain reliable quantitative information on the electrostatic field associated with reverse-biased p-n junctions and on the distribution of dopants, the physics of the so-called ''dead layer'' and the influence of charged oxide layers are of paramount importance. To this purpose, experimental observations near the edge of a TEM sample can be useful. In these conditions, however, phase computations required to interpret the experimental results are very challenging as the problem is intrinsically three-dimensional. In order to cope with this problem, a mixed analytical-numerical approach is presented and discussed.

  4. Technical bases of the second generation SARIS core model (Task Number: 90-008-0)

    SciTech Connect

    Gregory, M.V.

    1991-11-01

    A methodology has been developed to rigorously derive the constants in the Savannah River Simulator (SARIS) core model from detailed, charge-design, diffusion theory solutions. This methodology is intended to replace the ill-defined, ad hoc iterative process used in the past to generate these constants. Along the development path, three shortcomings of the current core model were identified and corrected. The updated core model with revised constants is termed the second generation core model. In addition, changes in the decay heat and delayed neutron precursor models are also recommended, all in the interest of improving simulator neutronics fidelity.

  5. The composition of Earth's core from equations of state, metal-silicate partitioning, and core formation modeling

    NASA Astrophysics Data System (ADS)

    Fischer, Rebecca; Campbell, Andrew; Ciesla, Fred

    2016-04-01

    The Earth accreted in a series of increasingly large and violent collisions. Simultaneously, the metallic core segregated from the silicate mantle, acquiring its modern composition through high pressure (P), high temperature (T) partitioning reactions. Here we present a model that couples these aspects of early planetary evolution, building on recent accretion simulations and metal-silicate partitioning experiments, constrained by density measurements of Fe-rich alloys. Previously, the equations of state of FeO, Fe-9Si, Fe-16Si, and FeSi were measured to megabar pressures and several thousand K using a laser-heated diamond anvil cell. With these equations of state, we determined that the core's density can be reproduced through the addition of 11.3 +/- 0.6 wt% silicon or 8.1 +/- 1.1 wt% oxygen to an Fe-Ni alloy (Fischer et al., 2011, 2014). Metal-silicate partitioning experiments of Ni, Co, V, Cr, Si, and O have been performed in a diamond anvil cell to 100 GPa and 5700 K, allowing the effects of P, T, and composition on the partitioning behaviors of these elements to be parameterized (Fischer et al., 2015; Siebert et al., 2012). Here we apply those experimental results to model Earth's core formation, using N-body simulations to describe the delivery, masses, and original locations of planetary building blocks (Fischer and Ciesla, 2014). As planets accrete, their core and mantle compositions are modified by high P-T reactions with each collision (Rubie et al., 2011). For partial equilibration of the mantle at 55% of the evolving core-mantle boundary pressure and the liquidus temperature, we find that the core contains 5.4 wt% Si and 1.9 wt% O. This composition is consistent with the seismologically-inferred density of Earth's core, based on comparisons to our equations of state, and indicate that the core cannot contain more than ~2 wt% S or C. Earth analogues experience 1.2 +/- 0.2 log units of oxidation during accretion, due to both the effects of high P

  6. Evolution of resistive switching and its ionic models in Pt/Nb-doped SrTiO3 junctions

    NASA Astrophysics Data System (ADS)

    Yang, Mei; Ma, Xiaohua; Wang, Hong; Xi, He; Lv, Ling; Zhang, Peng; Xie, Yong; Gao, Haixia; Cao, Yanrong; Li, Shuwei; Hao, Yue

    2016-07-01

    Charge-trapping or ionic mechanisms of the resistive switching (RS) at metal/Nb-doped SrTiO3 (NSTO) interfaces are still unclear. Here, the electrical properties and RS evolution at Pt/NSTO interfaces are investigated. A volatile RS in the fresh junctions complies with Schottky theory involving an interfacial layer and electrically dependent permittivity. The RS is interpreted by a redox-reaction modulated barrier model. A nonvolatile RS emerges and evolves with increasing the forward voltage. I-V and C-V characteristics imply different conductive filament (CF) configurations in high and low resistance states. An in-barrier ionic CF model is established for the nonvolatile RS. The coherent ionic models are beneficial for understanding the interfacial role in RS and for regulating RS characteristics or realizing high quality metal/oxide diodes.

  7. Preschool Literacy and the Common Core: A Professional Development Model

    ERIC Educational Resources Information Center

    Wake, Donna G.; Benson, Tammy Rachelle

    2016-01-01

    Many states have adopted the Common Core Standards for literacy and math and have begun enacting these standards in school curriculum. In states where these standards have been adopted, professional educators working in K-12 contexts have been working to create transition plans from existing state-based standards to the Common Core standards. A…

  8. Inertial waves in a laboratory model of the Earth's core

    NASA Astrophysics Data System (ADS)

    Triana, Santiago Andres

    2011-12-01

    A water-filled three-meter diameter spherical shell built as a model of the Earth's core shows evidence of precessionally forced flows and, when spinning the inner sphere differentially, inertial modes are excited. We identified the precessionally forced flow to be primarily the spin-over inertial mode, i.e., a uniform vorticity flow whose rotation axis is not aligned with the container's rotation axis. A systematic study of the spin-over mode is carried out, showing that the amplitude dependence on the Poincare number is in qualitative agreement with Busse's laminar theory while its phase differs significantly, likely due to topographic effects. At high rotation rates free shear layers concentrating most of the kinetic energy of the spin-over mode have been observed. When spinning the inner sphere differentially, a total of 12 inertial modes have been identified, reproducing and extending previous experimental results. The inertial modes excited appear ordered according to their azimuthal drift speed as the Rossby number is varied.

  9. Spinal astrocyte gap junction and glutamate transporter expression contributes to a rat model of bortezomib-induced peripheral neuropathy

    PubMed Central

    Robinson, Caleb R.; Dougherty, Patrick M.

    2014-01-01

    There is increasing evidence implicating astrocytes in multiple forms of chronic pain, as well as in the specific context of chemotherapy-induced peripheral neuropathy (CIPN). However, it is still unclear what the exact role of astrocytes may be in the context of CIPN. Findings in oxaliplatin and paclitaxel models have displayed altered expression of astrocytic gap junctions and glutamate transporters as means by which astrocytes may contribute to observed behavioral changes. The current study investigated whether these changes were also generalizable to the bortezomib CIPN. Changes in mechanical sensitivity were verified in bortezomib-treated animals, and these changes were prevented by co-treatment with a glial activation inhibitor (minocycline), a gap junction decoupler (carbenoxolone), and by a glutamate transporter upregulator (ceftriaxone). Immunohistochemistry data at day 30 in bortezomib-treated animals showed increases in expression of GFAP and connexin 43 but decrease in GLAST expression. These changes were prevented by co-treatment with minocycline. Follow-up Western blotting data showed a shift in connexin 43 from a non-phosphorylated state to a phosphorylated state, indicating increased trafficking of expressed connexin 43 to the cell membrane. These data suggest that increases in behavioral sensitivity to cutaneous stimuli may be tied to persistent synaptic glutamate resulting from increased calcium flow between spinal astrocytes. PMID:25446343

  10. Potassium channels in the Cx43 gap junction perinexus modulate ephaptic coupling: an experimental and modeling study.

    PubMed

    Veeraraghavan, Rengasayee; Lin, Joyce; Keener, James P; Gourdie, Robert; Poelzing, Steven

    2016-10-01

    It was recently demonstrated that cardiac sodium channels (Nav1.5) localized at the perinexus, an intercalated disc (ID) nanodomain associated with gap junctions (GJ), may contribute to electrical coupling between cardiac myocytes via an ephaptic mechanism. Impairment of ephaptic coupling by acute interstitial edema (AIE)-induced swelling of the perinexus was associated with arrhythmogenic, anisotropic conduction slowing. Given that Kir2.1 has also recently been reported to localize at intercalated discs, we hypothesized that Kir2.1 channels may reside within the perinexus and that inhibiting them may mitigate arrhythmogenic conduction slowing observed during AIE. Using gated stimulated emission depletion (gSTED) and stochastic optical reconstruction microscopy (STORM) super-resolution microscopy, we indeed find that a significant proportion of Kir2.1 channels resides within the perinexus. Moreover, whereas Nav1.5 inhibition during AIE exacerbated arrhythmogenic conduction slowing, inhibiting Kir2.1 channels during AIE preferentially increased transverse conduction velocity-decreasing anisotropy and ameliorating arrhythmia risk compared to AIE alone. Comparison of our results with a nanodomain computer model identified enrichment of both Nav1.5 and Kir2.1 at intercalated discs as key factors underlying the experimental observations. We demonstrate that Kir2.1 channels are localized within the perinexus alongside Nav1.5 channels. Further, targeting Kir2.1 modulates intercellular coupling between cardiac myocytes, anisotropy of conduction, and arrhythmia propensity in a manner consistent with a role for ephaptic coupling in cardiac conduction. For over half a century, electrical excitation in the heart has been thought to occur exclusively via gap junction-mediated ionic current flow between cells. Further, excitation was thought to depend almost exclusively on sodium channels with potassium channels being involved mainly in returning the cell to rest. Here, we

  11. Little Earth Experiment: An instrument to model planetary cores.

    PubMed

    Aujogue, Kélig; Pothérat, Alban; Bates, Ian; Debray, François; Sreenivasan, Binod

    2016-08-01

    In this paper, we present a new experimental facility, Little Earth Experiment, designed to study the hydrodynamics of liquid planetary cores. The main novelty of this apparatus is that a transparent electrically conducting electrolyte is subject to extremely high magnetic fields (up to 10 T) to produce electromagnetic effects comparable to those produced by moderate magnetic fields in planetary cores. This technique makes it possible to visualise for the first time the coupling between the principal forces in a convection-driven dynamo by means of Particle Image Velocimetry (PIV) in a geometry relevant to planets. We first present the technology that enables us to generate these forces and implement PIV in a high magnetic field environment. We then show that the magnetic field drastically changes the structure of convective plumes in a configuration relevant to the tangent cylinder region of the Earth's core. PMID:27587138

  12. Little Earth Experiment: An instrument to model planetary cores

    NASA Astrophysics Data System (ADS)

    Aujogue, Kélig; Pothérat, Alban; Bates, Ian; Debray, François; Sreenivasan, Binod

    2016-08-01

    In this paper, we present a new experimental facility, Little Earth Experiment, designed to study the hydrodynamics of liquid planetary cores. The main novelty of this apparatus is that a transparent electrically conducting electrolyte is subject to extremely high magnetic fields (up to 10 T) to produce electromagnetic effects comparable to those produced by moderate magnetic fields in planetary cores. This technique makes it possible to visualise for the first time the coupling between the principal forces in a convection-driven dynamo by means of Particle Image Velocimetry (PIV) in a geometry relevant to planets. We first present the technology that enables us to generate these forces and implement PIV in a high magnetic field environment. We then show that the magnetic field drastically changes the structure of convective plumes in a configuration relevant to the tangent cylinder region of the Earth's core.

  13. An analytical model for the evolution of starless cores - I. The constant-mass case

    NASA Astrophysics Data System (ADS)

    Pattle, K.

    2016-07-01

    We propose an analytical model for the quasi-static evolution of starless cores confined by a constant external pressure, assuming that cores are isothermal and obey a spherically symmetric density distribution. We model core evolution for Plummer-like and Gaussian density distributions in the adiabatic and isothermal limits, assuming Larson-like dissipation of turbulence. We model the variation in the terms in the virial equation as a function of core characteristic radius, and determine whether cores are evolving towards virial equilibrium or gravitational collapse. We ignore accretion on to cores in the current study. We discuss the different behaviours predicted by the isothermal and adiabatic cases, and by our choice of index for the size-linewidth relation, and suggest a means of parametrizing the magnetic energy term in the virial equation. We model the evolution of the set of cores observed by Pattle et al. in the L1688 region of Ophiuchus in the `virial plane'. We find that not all virially bound and pressure-confined cores will evolve to become gravitationally bound, with many instead contracting to virial equilibrium with their surroundings, and find an absence of gravitationally dominated and virially unbound cores. We hypothesize a `starless core desert' in this quadrant of the virial plane, which may result from cores initially forming as pressure-confined objects. We conclude that a virially bound and pressure-confined core will not necessarily evolve to become gravitationally bound, and thus cannot be considered pre-stellar. A core can only be definitively considered pre-stellar (collapsing to form an individual stellar system) if it is gravitationally unstable.

  14. Continuity of Monolayer-Bilayer Junctions for Localization of Lipid Raft Microdomains in Model Membranes

    PubMed Central

    Ryu, Yong-Sang; Wittenberg, Nathan J.; Suh, Jeng-Hun; Lee, Sang-Wook; Sohn, Youngjoo; Oh, Sang-Hyun; Parikh, Atul N.; Lee, Sin-Doo

    2016-01-01

    We show that the selective localization of cholesterol-rich domains and associated ganglioside receptors prefer to occur in the monolayer across continuous monolayer-bilayer junctions (MBJs) in supported lipid membranes. For the MBJs, glass substrates were patterned with poly(dimethylsiloxane) (PDMS) oligomers by thermally-assisted contact printing, leaving behind 3 nm-thick PDMS patterns. The hydrophobicity of the transferred PDMS patterns was precisely tuned by the stamping temperature. Lipid monolayers were formed on the PDMS patterned surface while lipid bilayers were on the bare glass surface. Due to the continuity of the lipid membranes over the MBJs, essentially free diffusion of lipids was allowed between the monolayer on the PDMS surface and the upper leaflet of the bilayer on the glass substrate. The preferential localization of sphingomyelin, ganglioside GM1 and cholesterol in the monolayer region enabled to develop raft microdomains through coarsening of nanorafts. Our methodology provides a simple and effective scheme of non-disruptive manipulation of the chemical landscape associated with lipid phase separations, which leads to more sophisticated applications in biosensors and as cell culture substrates. PMID:27230411

  15. Inherited junctional epidermolysis bullosa in the German Pointer: establishment of a large animal model.

    PubMed

    Capt, Annabelle; Spirito, Flavia; Guaguere, Eric; Spadafora, Anne; Ortonne, Jean-Paul; Meneguzzi, Guerrino

    2005-03-01

    Junctional epidermolysis bullosa (JEB) is a genodermatosis suitable for gene therapy because conventional treatments are ineffective. Here, we elucidate the genetic basis of mild JEB in a breed of dogs that display all the clinical traits observed in JEB patients. The condition is associated with reduced expression of laminin 5 caused by a homozygous insertion (4818+207ins6.5 kb) of repetitive satellite DNA within intron 35 of the gene (lama3) for the laminin alpha3 chain. The intronic mutation interferes with maturation of the alpha3 pre-messenger RNA resulting in the coexpression of a transcript with a 227 nucleotide insertion and a wild-type mRNA that encodes scant amounts of the alpha3 polypeptide. Our results show that the amino acid sequence and structure of the canine and human alpha3 chain are highly conserved and that the reduced expression of laminin 5 affects the adhesion and clonogenic potential of the JEB keratinocytes. These JEB dogs provide the opportunity to perform gene delivery in a naturally occurring genodermatosis and to evaluate host tolerance to recombinant laminin 5. PMID:15737193

  16. Continuity of monolayer-bilayer junctions for localization of lipid raft microdomains in model membranes

    DOE PAGES

    Ryu, Yong -Sang; Wittenberg, Nathan J.; Suh, Jeng -Hun; Lee, Sang -Wook; Sohn, Youngjoo; Oh, Sang -Hyun; Parikh, Atul N.; Lee, Sin -Doo

    2016-05-27

    We show that the selective localization of cholesterol-rich domains and associated ganglioside receptors prefer to occur in the monolayer across continuous monolayer-bilayer junctions (MBJs) in supported lipid membranes. For the MBJs, glass substrates were patterned with poly(dimethylsiloxane) (PDMS) oligomers by thermally-assisted contact printing, leaving behind 3 nm-thick PDMS patterns. The hydrophobicity of the transferred PDMS patterns was precisely tuned by the stamping temperature. Lipid monolayers were formed on the PDMS patterned surface while lipid bilayers were on the bare glass surface. Due to the continuity of the lipid membranes over the MBJs, essentially free diffusion of lipids was allowed betweenmore » the monolayer on the PDMS surface and the upper leaflet of the bilayer on the glass substrate. The preferential localization of sphingomyelin, ganglioside GM1 and cholesterol in the monolayer region enabled to develop raft microdomains through coarsening of nanorafts. Furthermore, our methodology provides a simple and effective scheme of non-disruptive manipulation of the chemical landscape associated with lipid phase separations, which leads to more sophisticated applications in biosensors and as cell culture substrates.« less

  17. Continuity of Monolayer-Bilayer Junctions for Localization of Lipid Raft Microdomains in Model Membranes.

    PubMed

    Ryu, Yong-Sang; Wittenberg, Nathan J; Suh, Jeng-Hun; Lee, Sang-Wook; Sohn, Youngjoo; Oh, Sang-Hyun; Parikh, Atul N; Lee, Sin-Doo

    2016-01-01

    We show that the selective localization of cholesterol-rich domains and associated ganglioside receptors prefer to occur in the monolayer across continuous monolayer-bilayer junctions (MBJs) in supported lipid membranes. For the MBJs, glass substrates were patterned with poly(dimethylsiloxane) (PDMS) oligomers by thermally-assisted contact printing, leaving behind 3 nm-thick PDMS patterns. The hydrophobicity of the transferred PDMS patterns was precisely tuned by the stamping temperature. Lipid monolayers were formed on the PDMS patterned surface while lipid bilayers were on the bare glass surface. Due to the continuity of the lipid membranes over the MBJs, essentially free diffusion of lipids was allowed between the monolayer on the PDMS surface and the upper leaflet of the bilayer on the glass substrate. The preferential localization of sphingomyelin, ganglioside GM1 and cholesterol in the monolayer region enabled to develop raft microdomains through coarsening of nanorafts. Our methodology provides a simple and effective scheme of non-disruptive manipulation of the chemical landscape associated with lipid phase separations, which leads to more sophisticated applications in biosensors and as cell culture substrates. PMID:27230411

  18. A novel nanopin model based on a Y-junction carbon nanotube

    NASA Astrophysics Data System (ADS)

    Zhang, Zhong-Qiang; Zhong, Jun; Ye, Hong-Fei; Liu, Zhen; Cheng, Guang-Gui; Ding, Jian-Ning

    2016-08-01

    A prototype of nanopin based on a Y-junction carbon nanotube (CNT) is first proposed. The loading and unloading processes are investigated by using classical molecular dynamics, considering the influences of the fit dimension, positioning error, thermal effect, and the loading/unloading velocity on the performance of the proposed nanopin. The optimum size of the gap between the nanopin and the through hole in a silicon component is obtained, which is responsible for a desired fixity with the acceptable install resistance. It is found that a proper positioning error in a certain direction associated with the branched structure of the nanopin will facilitate the installation process. The performance of the proposed nanopin is not sensitive to thermal and normal axial velocity of the nanopin, while the unloading direction affects appreciably on the service performance of the nanopin attributed to the orientation of the branched CNT. Particularly, the service performance of the proposed nanopin considerably depends on several special deforming configurations in the loading and unloading processes.

  19. Continuity of Monolayer-Bilayer Junctions for Localization of Lipid Raft Microdomains in Model Membranes.

    PubMed

    Ryu, Yong-Sang; Wittenberg, Nathan J; Suh, Jeng-Hun; Lee, Sang-Wook; Sohn, Youngjoo; Oh, Sang-Hyun; Parikh, Atul N; Lee, Sin-Doo

    2016-05-27

    We show that the selective localization of cholesterol-rich domains and associated ganglioside receptors prefer to occur in the monolayer across continuous monolayer-bilayer junctions (MBJs) in supported lipid membranes. For the MBJs, glass substrates were patterned with poly(dimethylsiloxane) (PDMS) oligomers by thermally-assisted contact printing, leaving behind 3 nm-thick PDMS patterns. The hydrophobicity of the transferred PDMS patterns was precisely tuned by the stamping temperature. Lipid monolayers were formed on the PDMS patterned surface while lipid bilayers were on the bare glass surface. Due to the continuity of the lipid membranes over the MBJs, essentially free diffusion of lipids was allowed between the monolayer on the PDMS surface and the upper leaflet of the bilayer on the glass substrate. The preferential localization of sphingomyelin, ganglioside GM1 and cholesterol in the monolayer region enabled to develop raft microdomains through coarsening of nanorafts. Our methodology provides a simple and effective scheme of non-disruptive manipulation of the chemical landscape associated with lipid phase separations, which leads to more sophisticated applications in biosensors and as cell culture substrates.

  20. Effects of low-intensity pulsed ultrasound on new trabecular bone during bone-tendon junction healing in a rabbit model: a synchrotron radiation micro-CT study.

    PubMed

    Lu, Hongbin; Zheng, Cheng; Wang, Zhanwen; Chen, Can; Chen, Huabin; Hu, Jianzhong

    2015-01-01

    This study was designed to evaluate the effects of low-intensity pulsed ultrasound on bone regeneration during the bone-tendon junction healing process and to explore the application of synchrotron radiation micro computed tomography in three dimensional visualization of the bone-tendon junction to evaluate the microarchitecture of new trabecular bone. Twenty four mature New Zealand rabbits underwent partial patellectomy to establish a bone-tendon junction injury model at the patella-patellar tendon complex. Animals were then divided into low-intensity pulsed ultrasound treatment (20 min/day, 7 times/week) and placebo control groups, and were euthanized at week 8 and 16 postoperatively (n = 6 for each group and time point). The patella-patellar tendon specimens were harvested for radiographic, histological and synchrotron radiation micro computed tomography detection. The area of the newly formed bone in the ultrasound group was significantly greater than that of control group at postoperative week 8 and 16. The high resolution three dimensional visualization images of the bone-tendon junction were acquired by synchrotron radiation micro computed tomography. Low-intensity pulsed ultrasound treatment promoted dense and irregular woven bone formation at week 8 with greater bone volume fraction, number and thickness of new trabecular bone but with lower separation. At week 16, ultrasound group specimens contained mature lamellar bone with higher bone volume fraction and thicker trabeculae than that of control group; however, there was no significant difference in separation and number of the new trabecular bone. This study confirms that low-intensity pulsed ultrasound treatment is able to promote bone formation and remodeling of new trabecular bone during the bone-tendon junction healing process in a rabbit model, and the synchrotron radiation micro computed tomography could be applied for three dimensional visualization to quantitatively evaluate the

  1. Effects of low-intensity pulsed ultrasound on new trabecular bone during bone-tendon junction healing in a rabbit model: a synchrotron radiation micro-CT study.

    PubMed

    Lu, Hongbin; Zheng, Cheng; Wang, Zhanwen; Chen, Can; Chen, Huabin; Hu, Jianzhong

    2015-01-01

    This study was designed to evaluate the effects of low-intensity pulsed ultrasound on bone regeneration during the bone-tendon junction healing process and to explore the application of synchrotron radiation micro computed tomography in three dimensional visualization of the bone-tendon junction to evaluate the microarchitecture of new trabecular bone. Twenty four mature New Zealand rabbits underwent partial patellectomy to establish a bone-tendon junction injury model at the patella-patellar tendon complex. Animals were then divided into low-intensity pulsed ultrasound treatment (20 min/day, 7 times/week) and placebo control groups, and were euthanized at week 8 and 16 postoperatively (n = 6 for each group and time point). The patella-patellar tendon specimens were harvested for radiographic, histological and synchrotron radiation micro computed tomography detection. The area of the newly formed bone in the ultrasound group was significantly greater than that of control group at postoperative week 8 and 16. The high resolution three dimensional visualization images of the bone-tendon junction were acquired by synchrotron radiation micro computed tomography. Low-intensity pulsed ultrasound treatment promoted dense and irregular woven bone formation at week 8 with greater bone volume fraction, number and thickness of new trabecular bone but with lower separation. At week 16, ultrasound group specimens contained mature lamellar bone with higher bone volume fraction and thicker trabeculae than that of control group; however, there was no significant difference in separation and number of the new trabecular bone. This study confirms that low-intensity pulsed ultrasound treatment is able to promote bone formation and remodeling of new trabecular bone during the bone-tendon junction healing process in a rabbit model, and the synchrotron radiation micro computed tomography could be applied for three dimensional visualization to quantitatively evaluate the

  2. Continuously Optimized Reliable Energy (CORE) Microgrid: Models & Tools (Fact Sheet)

    SciTech Connect

    Not Available

    2013-07-01

    This brochure describes Continuously Optimized Reliable Energy (CORE), a trademarked process NREL employs to produce conceptual microgrid designs. This systems-based process enables designs to be optimized for economic value, energy surety, and sustainability. Capabilities NREL offers in support of microgrid design are explained.

  3. The Unified Core: A "Major" Learning Community Model in Action

    ERIC Educational Resources Information Center

    Powell, Gwynn M.; Johnson, Corey W.; James, J. Joy; Dunlap, Rudy

    2011-01-01

    The Unified Core is an innovative approach to higher education that blends content through linked courses within a major to create a community of learners. This article offers the theoretical background for the approach, describes the implementation, and offers suggestions to educators who would like to design their own version of this innovative…

  4. A Core Journal Decision Model Based on Weighted Page Rank

    ERIC Educational Resources Information Center

    Wang, Hei-Chia; Chou, Ya-lin; Guo, Jiunn-Liang

    2011-01-01

    Purpose: The paper's aim is to propose a core journal decision method, called the local impact factor (LIF), which can evaluate the requirements of the local user community by combining both the access rate and the weighted impact factor, and by tracking citation information on the local users' articles. Design/methodology/approach: Many…

  5. Gap junction dysfunction in the prefrontal cortex induces depressive-like behaviors in rats.

    PubMed

    Sun, Jian-Dong; Liu, Yan; Yuan, Yu-He; Li, Jing; Chen, Nai-Hong

    2012-04-01

    Growing evidence has implicated glial anomalies in the pathophysiology of major depression disorder (MDD). Gap junctional communication is a main determinant of astrocytic function. However, it is unclear whether gap junction dysfunction is involved in MDD development. This study investigates changes in the function of astrocyte gap junction occurring in the rat prefrontal cortex (PFC) after chronic unpredictable stress (CUS), a rodent model of depression. Animals exposed to CUS and showing behavioral deficits in sucrose preference test (SPT) and novelty suppressed feeding test (NSFT) exhibited significant decreases in diffusion of gap junction channel-permeable dye and expression of connexin 43 (Cx43), a major component of astrocyte gap junction, and abnormal gap junctional ultrastructure in the PFC. Furthermore, we analyzed the effects of typical antidepressants fluoxetine and duloxetine and glucocorticoid receptor (GR) antagonist mifepristone on CUS-induced gap junctional dysfunction and depressive-like behaviors. The cellular and behavioral alterations induced by CUS were reversed and/or blocked by treatment with typical antidepressants or mifepristone, indicating that the mechanism of their antidepressant action may involve the amelioration of gap junction dysfunction and the cellular changes may be related to GR activation. We then investigated the effects of pharmacological gap junction blockade in the PFC on depressive-like behaviors. The results demonstrate that carbenoxolone (CBX) infusions induced anhedonia in SPT, and anxiety in NSFT, and Cx43 mimetic peptides Gap27 and Gap26 also induced anhedonia, a core symptom of depression. Together, this study supports the hypothesis that gap junction dysfunction contributes to the pathophysiology of depression.

  6. High Flux Isotope Reactor Core Analysis-Challenges and Recent Enhancements in Modeling and Simulation

    SciTech Connect

    Ilas, Germina

    2016-01-01

    A concerted effort over the past few years has focused on enhancing the core depletion models for the High Flux Isotope Reactor (HFIR) as part of a comprehensive study for designing a HFIR core that would use low-enriched uranium (LEU) fuel. A HFIR core depletion model that is based on current state-of-the-art methods and nuclear data was needed for use as a reference for the design of an LEU fuel for HFIR and to improve the basis for analyses that support HFIR s current operation with high-enriched uranium (HEU) fuel. This paper summarizes the recent improvements in modeling and simulation for HFIR core analyses, with a focus on core depletion models.

  7. Motor neuron apoptosis and neuromuscular junction perturbation are prominent features in a Drosophila model of Fus-mediated ALS

    PubMed Central

    2012-01-01

    Backgound Amyotrophic lateral sclerosis (ALS) is progressive neurodegenerative disease characterized by the loss of motor function. Several ALS genes have been identified as their mutations can lead to familial ALS, including the recently reported RNA-binding protein fused in sarcoma (Fus). However, it is not clear how mutations of Fus lead to motor neuron degeneration in ALS. In this study, we present a Drosophila model to examine the toxicity of Fus, its Drosophila orthologue Cabeza (Caz), and the ALS-related Fus mutants. Results Our results show that the expression of wild-type Fus/Caz or FusR521G induced progressive toxicity in multiple tissues of the transgenic flies in a dose- and age-dependent manner. The expression of Fus, Caz, or FusR521G in motor neurons significantly impaired the locomotive ability of fly larvae and adults. The presynaptic structures in neuromuscular junctions were disrupted and motor neurons in the ventral nerve cord (VNC) were disorganized and underwent apoptosis. Surprisingly, the interruption of Fus nuclear localization by either deleting its nuclear localization sequence (NLS) or adding a nuclear export signal (NES) blocked Fus toxicity. Moreover, we discovered that the loss of caz in Drosophila led to severe growth defects in the eyes and VNCs, caused locomotive disability and NMJ disruption, but did not induce apoptotic cell death. Conclusions These data demonstrate that the overexpression of Fus/Caz causes in vivo toxicity by disrupting neuromuscular junctions (NMJs) and inducing apoptosis in motor neurons. In addition, the nuclear localization of Fus is essential for Fus to induce toxicity. Our findings also suggest that Fus overexpression and gene deletion can cause similar degenerative phenotypes but the underlying mechanisms are likely different. PMID:22443542

  8. Soft core fluid in a quenched matrix of soft core particles: A mobile mixture in a model gel

    NASA Astrophysics Data System (ADS)

    Archer, A. J.; Schmidt, M.; Evans, R.

    2006-01-01

    We present a density-functional study of a binary phase-separating mixture of soft core particles immersed in a random matrix of quenched soft core particles of larger size. This is a model for a binary polymer mixture immersed in a cross-linked rigid polymer network. Using the replica “trick” for quenched-annealed mixtures we derive an explicit density functional theory that treats the quenched species on the level of its one-body density distribution. The relation to a set of effective external potentials acting on the annealed components is discussed. We relate matrix-induced condensation in bulk to the behavior of the mixture around a single large particle. The interfacial properties of the binary mixture at a surface of the quenched matrix display a rich interplay between capillary condensation inside the bulk matrix and wetting phenomena at the matrix surface.

  9. Two junction effects in dc SQUID phase qubit

    NASA Astrophysics Data System (ADS)

    Cooper, B. K.; Kwon, H.; Przybysz, A. J.; Budoyo, R.; Anderson, J. R.; Lobb, C. J.; Wellstood, F. C.

    2011-03-01

    The dc SQUID phase qubit was designed to allow one isolation junction to filter bias current noise from a second junction operating as a single junction phase qubit. As junctions shrink to minimize dielectric loss, the Josephson inductances of each junction approach the coupling loop inductance and this single junction picture appears inadequate. We consider a two-junction model of the dc SQUID phase qubit, where the qubit now corresponds to one of the normal oscillatory modes of the full SQUID. We discuss applications of this model to sweet spots in various control parameters and unusual behavior in the tunneling state measurement. Funded by DOD, CNAM and JQI.

  10. Dynamics of plume-triple junction interaction: Results from a series of three-dimensional numerical models and implications for the formation of oceanic plateaus

    NASA Astrophysics Data System (ADS)

    Dordevic, Mladen; Georgen, Jennifer

    2016-03-01

    Mantle plumes rising in the vicinity of mid-ocean ridges often generate anomalies in melt production and seafloor depth. This study investigates the dynamical interactions between a mantle plume and a ridge-ridge-ridge triple junction, using a parameter space approach and a suite of steady state, three-dimensional finite element numerical models. The top domain boundary is composed of three diverging plates, with each assigned half-spreading rates with respect to a fixed triple junction point. The bottom boundary is kept at a constant temperature of 1350°C except where a two-dimensional, Gaussian-shaped thermal anomaly simulating a plume is imposed. Models vary plume diameter, plume location, the viscosity contrast between plume and ambient mantle material, and the use of dehydration rheology in calculating viscosity. Importantly, the model results quantify how plume-related anomalies in mantle temperature pattern, seafloor depth, and crustal thickness depend on the specific set of parameters. To provide an example, one way of assessing the effect of conduit position is to calculate normalized area, defined to be the spatial dispersion of a given plume at specific depth (here selected to be 50 km) divided by the area occupied by the same plume when it is located under the triple junction. For one particular case modeled where the plume is centered in an intraplate position 100 km from the triple junction, normalized area is just 55%. Overall, these models provide a framework for better understanding plateau formation at triple junctions in the natural setting and a tool for constraining subsurface geodynamical processes and plume properties.

  11. Stability of core-shell nanowires in selected model solutions

    NASA Astrophysics Data System (ADS)

    Kalska-Szostko, B.; Wykowska, U.; Basa, A.; Zambrzycka, E.

    2015-03-01

    This paper presents the studies of stability of magnetic core-shell nanowires prepared by electrochemical deposition from an acidic solution containing iron in the core and modified surface layer. The obtained nanowires were tested according to their durability in distilled water, 0.01 M citric acid, 0.9% NaCl, and commercial white wine (12% alcohol). The proposed solutions were chosen in such a way as to mimic food related environment due to a possible application of nanowires as additives to, for example, packages. After 1, 2 and 3 weeks wetting in the solutions, nanoparticles were tested by Infrared Spectroscopy, Atomic Absorption Spectroscopy, Transmission Electron Microscopy and X-ray diffraction methods.

  12. Precessional states in a laboratory model of the Earth's core

    NASA Astrophysics Data System (ADS)

    Triana, S. A.; Zimmerman, D. S.; Lathrop, D. P.

    2012-04-01

    A water-filled three-meter diameter spherical shell, geometrically similar to the Earth's core, shows precessionally forced flows. The precessional torque is supplied by the daily rotation of the laboratory by the Earth. We identify the precessionally forced flow to be primarily the spin-over inertial mode, i.e., a uniform vorticity flow whose rotation axis is not aligned with the sphere's rotation axis. A systematic study of the spin-over mode is carried out, showing that the amplitude depends on the ratio of precession to rotation rates (the Poincaré number), in marginal qualitative agreement with Busse's (1968) laminar theory. We find its phase differs significantly though, likely due to topographic effects. At high rotation rates, free shear layers are observed. Comparison with previous computational studies and implications for the Earth's core are discussed.

  13. Theoretical model of a soft particle with charged core

    NASA Astrophysics Data System (ADS)

    Tracy, Dustin; Phan, Anh

    2014-03-01

    The numerical and analytical solutions of the electrostatic potentials of soft particles with an ion-permeable charged outer layer and a non-permeable charged core with constant charge densities are found using the Poisson-Boltzmann equations. The charged core is found to significantly alter the local potential within the soft particle, yet it has little effect on the potential outside its particle's boundaries. Previous experimental research into the electrical properties of the MS2 virus agree with these findings. Our results also suggest that there is only a slight change in the potential as the temperature is increased from 290 K to 310 K. The potential profile is found to be significantly affected by the ionic strength in the 1-600 mM range.

  14. Fractional order junctions

    NASA Astrophysics Data System (ADS)

    Machado, J. Tenreiro

    2015-01-01

    Gottfried Leibniz generalized the derivation and integration, extending the operators from integer up to real, or even complex, orders. It is presently recognized that the resulting models capture long term memory effects difficult to describe by classical tools. Leon Chua generalized the set of lumped electrical elements that provide the building blocks in mathematical models. His proposal of the memristor and of higher order elements broadened the scope of variables and relationships embedded in the development of models. This paper follows the two directions and proposes a new logical step, by generalizing the concept of junction. Classical junctions interconnect system elements using simple algebraic restrictions. Nevertheless, this simplistic approach may be misleading in the presence of unexpected dynamical phenomena and requires including additional "parasitic" elements. The novel γ -junction includes, as special cases, the standard series and parallel connections and allows a new degree of freedom when building models. The proposal motivates the search for experimental and real world manifestations of the abstract conjectures.

  15. A Core-Particle Model for Periodically Focused Ion Beams with Intense Space-Charge

    SciTech Connect

    Lund, S M; Barnard, J J; Bukh, B; Chawla, S R; Chilton, S H

    2006-08-02

    A core-particle model is derived to analyze transverse orbits of test particles evolving in the presence of a core ion beam described by the KV distribution. The core beam has uniform density within an elliptical cross-section and can be applied to model both quadrupole and solenoidal focused beams in periodic or aperiodic lattices. Efficient analytical descriptions of electrostatic space-charge fields external to the beam core are derived to simplify model equations. Image charge effects are analyzed for an elliptical beam centered in a round, conducting pipe to estimate model corrections resulting from image charge nonlinearities. Transformations are employed to remove coherent utter motion associated with oscillations of the ion beam core due to rapidly varying, linear applied focusing forces. Diagnostics for particle trajectories, Poincare phase-space projections, and single-particle emittances based on these transformations better illustrate the effects of nonlinear forces acting on particles evolving outside the core. A numerical code has been written based on this model. Example applications illustrate model characteristics. The core-particle model described has recently been applied to identify physical processes leading to space-charge transport limits for an rms matched beam in a periodic quadrupole focusing channel [Lund and Chawla, Nuc. Instr. and Meth. A 561, 203 (2006)]. Further characteristics of these processes are presented here.

  16. Mesoscale modeling of functional properties in core-shell nanoparticles

    NASA Astrophysics Data System (ADS)

    Mangeri, John; Heinonen, Olle; Karpeev, Dmitry; Nakhmanson, Serge

    2015-03-01

    Core-shell nanoparticle systems of Zn-ZnO and ZnO-TiO2 are studied computationally using the highly scalable MOOSE finite-element framework, developed at Idaho National Lab. The elastic anisotropic mismatch of the core and shell create an imprinting effect within the shell that produces a wide variation of strains. Due to this diversity of strains, the sharp band gap edges of the bulk semiconductor are observed to be ``thinned-out'' much like amorphous silicon. We show that a variety of factors, such as particle size, core-to-shell volume ratio, applied hydrostatic pressure, shell microstructure, as well as the effect of surface elasticity, can influence the distribution of optical band-gap values within the particle, which may prove useful within the field of photovoltaics. Part of the work by O.H. was supported by Award 70NANB14H012 from U.S. Department of Commerce, National Institute of Standards and Technology as part of the Center for Hierarchical Material Design.

  17. Compact-device model development for the energy-delay analysis of magneto-electric magnetic tunnel junction structures

    NASA Astrophysics Data System (ADS)

    Sharma, N.; Bird, J. P.; Dowben, P. A.; Marshall, A.

    2016-06-01

    We discuss the application of a novel class of device, the magneto-electric magnetic tunnel junction (ME-MTJ) to realize a variety of computational functions, including majority logic and the XNOR/XOR gate. We also develop a compact model to describe the operation of these devices, which function by utilizing the phenomenon of ‘voltage-controlled magnetism’ to switch the operational state of MTJs. The model breaks down the switching process into three key stages of operation: electrical-to-magnetic conversion, magnetization transfer, and final-state readout. Estimates for the switching energy and delay of these devices, obtained from this compact model, reveal significant improvements in both of these parameters when compared to conventional MTJs switched by spin-transfer-torque. In fact, the capacity to use the ME-MTJ to implement complex logical operations within a single device allows its energy costs to even approach those of low-power CMOS. The added benefits of non-volatility and compact circuit footprint, combined with their potential for heterogeneous integration with CMOS, make the ME devices of considerable interest for post-CMOS technology.

  18. Impaired Tight Junctions in Atopic Dermatitis Skin and in a Skin-Equivalent Model Treated with Interleukin-17

    PubMed Central

    Yuki, Takuo; Tobiishi, Megumi; Kusaka-Kikushima, Ayumi; Ota, Yukiko; Tokura, Yoshiki

    2016-01-01

    Tight junction (TJ) dysfunction in the stratum granulosum leads to aberrant barrier function of the stratum corneum (SC) in the epidermis. However, it is unclear whether TJs are perturbed in atopic dermatitis (AD), a representative aberrant SC-related skin disease, and whether some factors related to AD pathogenesis induce TJ dysfunction. To address these issues, we investigated the alterations of TJs in AD skin and the effects of Th2 and Th17 cytokines on TJs in a skin-equivalent model. The levels of TJ proteins were determined in the epidermis of nonlesional and lesional skin sites of AD. Western blot and immunohistochemical analyses revealed that the levels of zonula occludens 1 were decreased in the nonlesional sites of AD, and the levels of zonula occludens 1 and claudin-1 were decreased in the lesional sites relative to the levels in skin from healthy subjects. Next, we examined the effects of interleukin (IL)-4, tumor necrosis factor-α, IL-17, and IL-22 on the TJ barrier in a skin-equivalent model. Only IL-17 impaired the TJ barrier. Furthermore, we observed a defect in filaggrin monomer degradation in the IL-17–treated skin model. Thus, TJs are dysfunctional in AD, at least partly, due to the effect of IL-17, which may result in an aberrant SC barrier. PMID:27588419

  19. Impaired Tight Junctions in Atopic Dermatitis Skin and in a Skin-Equivalent Model Treated with Interleukin-17.

    PubMed

    Yuki, Takuo; Tobiishi, Megumi; Kusaka-Kikushima, Ayumi; Ota, Yukiko; Tokura, Yoshiki

    2016-01-01

    Tight junction (TJ) dysfunction in the stratum granulosum leads to aberrant barrier function of the stratum corneum (SC) in the epidermis. However, it is unclear whether TJs are perturbed in atopic dermatitis (AD), a representative aberrant SC-related skin disease, and whether some factors related to AD pathogenesis induce TJ dysfunction. To address these issues, we investigated the alterations of TJs in AD skin and the effects of Th2 and Th17 cytokines on TJs in a skin-equivalent model. The levels of TJ proteins were determined in the epidermis of nonlesional and lesional skin sites of AD. Western blot and immunohistochemical analyses revealed that the levels of zonula occludens 1 were decreased in the nonlesional sites of AD, and the levels of zonula occludens 1 and claudin-1 were decreased in the lesional sites relative to the levels in skin from healthy subjects. Next, we examined the effects of interleukin (IL)-4, tumor necrosis factor-α, IL-17, and IL-22 on the TJ barrier in a skin-equivalent model. Only IL-17 impaired the TJ barrier. Furthermore, we observed a defect in filaggrin monomer degradation in the IL-17-treated skin model. Thus, TJs are dysfunctional in AD, at least partly, due to the effect of IL-17, which may result in an aberrant SC barrier. PMID:27588419

  20. Silicon fiber with p-n junction

    SciTech Connect

    Homa, D.; Cito, A.; Pickrell, G.; Hill, C.; Scott, B.

    2014-09-22

    In this study, we fabricated a p-n junction in a fiber with a phosphorous doped silicon core and fused silica cladding. The fibers were fabricated via a hybrid process of the core-suction and melt-draw techniques and maintained overall diameters ranging from 200 to 900 μm and core diameters of 20–800 μm. The p-n junction was formed by doping the fiber with boron and confirmed via the current-voltage characteristic. The demonstration of a p-n junction in a melt-drawn silicon core fiber paves the way for the seamless integration of optical and electronic devices in fibers.

  1. Simple phenomenological modeling of transition-region capacitance of forward-biased p-n junction diodes and transistor diodes

    NASA Technical Reports Server (NTRS)

    Lindholm, F. A.

    1982-01-01

    The derivation of a simple expression for the capacitance C(V) associated with the transition region of a p-n junction under a forward bias is derived by phenomenological reasoning. The treatment of C(V) is based on the conventional Shockley equations, and simpler expressions for C(V) result that are in general accord with the previous analytical and numerical results. C(V) consists of two components resulting from changes in majority carrier concentration and from free hole and electron accumulation in the space-charge region. The space-charge region is conceived as the intrinsic region of an n-i-p structure for a space-charge region markedly wider than the extrinsic Debye lengths at its edges. This region is excited in the sense that the forward bias creates hole and electron densities orders of magnitude larger than those in equilibrium. The recent Shirts-Gordon (1979) modeling of the space-charge region using a dielectric response function is contrasted with the more conventional Schottky-Shockley modeling.

  2. Sustained phenotypic reversion of junctional epidermolysis bullosa dog keratinocytes: Establishment of an immunocompetent animal model for cutaneous gene therapy

    SciTech Connect

    Spirito, Flavia; Capt, Annabelle; Rio, Marcela Del; Larcher, Fernando; Guaguere, Eric; Danos, Olivier; Meneguzzi, Guerrino . E-mail: meneguzz@unice.fr

    2006-01-20

    Gene transfer represents the unique therapeutic issue for a number of inherited skin disorders including junctional epidermolysis bullosa (JEB), an untreatable genodermatose caused by mutations in the adhesion ligand laminin 5 ({alpha}3{beta}3{gamma}2) that is secreted in the extracellular matrix by the epidermal basal keratinocytes. Because gene therapy protocols require validation in animal models, we have phenotypically reverted by oncoretroviral transfer of the curative gene the keratinocytes isolated from dogs with a spontaneous form of JEB associated with a genetic mutation in the {alpha}3 chain of laminin 5. We show that the transduced dog JEB keratinocytes: (1) display a sustained secretion of laminin 5 in the extracellular matrix; (2) recover the adhesion, proliferation, and clonogenic capacity of wild-type keratinocytes; (3) generate fully differentiated stratified epithelia that after grafting on immunocompromised mice produce phenotypically normal skin and sustain permanent expression of the transgene. We validate an animal model that appears particularly suitable to demonstrate feasibility, efficacy, and safety of genetic therapeutic strategies for cutaneous disorders before undertaking human clinical trials.

  3. Electrical signal transmission and gap junction regulation in a bone cell network: a cable model for an osteon

    NASA Technical Reports Server (NTRS)

    Zhang, D.; Cowin, S. C.; Weinbaum, S.

    1997-01-01

    A cable model is formulated to estimate the spatial distribution of intracellular electric potential and current, from the cement line to the lumen of an osteon, as the frequency of the loading and the conductance of the gap junction are altered. The model predicts that the characteristic diffusion time for the spread of current along the membrane of the osteocytic processes, 0.03 sec, is nearly the same as the predicted pore pressure relaxation time in Zeng et al. (Annals of Biomedical Engineering. 1994) for the draining of the bone fluid into the osteonal canal. This approximate equality of characteristic times causes the cable to behave as a high-pass, low-pass filter cascade with a maximum in the spectral response for the intracellular potential at approximately 30 Hz. This behavior could be related to the experiments of Rubin and McLeod (Osteoporosis, Academic Press, 1996) which show that live bone appears to be selectively responsive to mechanical loading in a specific frequency range (15-30 Hz) for several species.

  4. Silver nanoparticles induce tight junction disruption and astrocyte neurotoxicity in a rat blood–brain barrier primary triple coculture model

    PubMed Central

    Xu, Liming; Dan, Mo; Shao, Anliang; Cheng, Xiang; Zhang, Cuiping; Yokel, Robert A; Takemura, Taro; Hanagata, Nobutaka; Niwa, Masami; Watanabe, Daisuke

    2015-01-01

    Background Silver nanoparticles (Ag-NPs) can enter the brain and induce neurotoxicity. However, the toxicity of Ag-NPs on the blood–brain barrier (BBB) and the underlying mechanism(s) of action on the BBB and the brain are not well understood. Method To investigate Ag-NP suspension (Ag-NPS)-induced toxicity, a triple coculture BBB model of rat brain microvascular endothelial cells, pericytes, and astrocytes was established. The BBB permeability and tight junction protein expression in response to Ag-NPS, NP-released Ag ions, and polystyrene-NP exposure were investigated. Ultrastructural changes of the microvascular endothelial cells, pericytes, and astrocytes were observed using transmission electron microscopy (TEM). Global gene expression of astrocytes was measured using a DNA microarray. Results A triple coculture BBB model of primary rat brain microvascular endothelial cells, pericytes, and astrocytes was established, with the transendothelial electrical resistance values >200 Ω·cm2. After Ag-NPS exposure for 24 hours, the BBB permeability was significantly increased and expression of the tight junction (TJ) protein ZO-1 was decreased. Discontinuous TJs were also observed between microvascular endothelial cells. After Ag-NPS exposure, severe mitochondrial shrinkage, vacuolations, endoplasmic reticulum expansion, and Ag-NPs were observed in astrocytes by TEM. Global gene expression analysis showed that three genes were upregulated and 20 genes were downregulated in astrocytes treated with Ag-NPS. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that the 23 genes were associated with metabolic processes, biosynthetic processes, response to stimuli, cell death, the MAPK pathway, and so on. No GO term and KEGG pathways were changed in the released-ion or polystyrene-NP groups. Ag-NPS inhibited the antioxidant defense of the astrocytes by increasing thioredoxin interacting protein, which inhibits the Trx system, and

  5. Particle image velocimetry measurements in a representative gas-cooled prismatic reactor core model for the estimation of bypass flow

    NASA Astrophysics Data System (ADS)

    Conder, Thomas E.

    Core bypass flow is considered one of the largest contributors to uncertainty in fuel temperature within the Modular High Temperature Gas-cooled Reactor (MHTGR). It refers to the coolant that navigates through the interstitial regions between the graphite fuel blocks instead of traveling through the designated coolant channels. These flows are of concern because they reduce the desired flow rates in the coolant channels, and thereby have significant influence on the maximum fuel element and coolant exit temperatures. Thus, accurate prediction of the bypass flow is important because it directly impacts core temperature, influencing the life and efficiency of the reactor. An experiment was conducted at Idaho National Laboratory to quantify the flow in the coolant channels in relation to the interstitial gaps between fuel blocks in a representative MHTGR core. Particle Image Velocimetry (PIV) was used to measure the flow fields within a simplified model, which comprised of a stacked junction of six partial fuel blocks with nine coolant tubes, separated by a 6mm gap width. The model had three sections: The upper plenum, upper block, and lower block. Model components were fabricated from clear, fused quartz where optical access was needed for the PIV measurements. Measurements were taken in three streamwise locations: in the upper plenum and in the midsection of the large and small fuel blocks. A laser light sheet was oriented parallel to the flow, while velocity fields were measured at millimeter intervals across the width of the model, totaling 3,276 PIV measurement locations. Inlet conditions were varied to incorporate laminar, transition, and turbulent flows in the coolant channels---all which produced laminar flow in the gap and non-uniform, turbulent flow in the upper plenum. The images were analyzed to create vector maps, and the data was exported for processing and compilation. The bypass flow was estimated by calculating the flow rates through the coolant

  6. Ab Initio Study of 40Ca with an Importance Truncated No-Core Shell Model

    SciTech Connect

    Roth, R; Navratil, P

    2007-05-22

    We propose an importance truncation scheme for the no-core shell model, which enables converged calculations for nuclei well beyond the p-shell. It is based on an a priori measure for the importance of individual basis states constructed by means of many-body perturbation theory. Only the physically relevant states of the no-core model space are considered, which leads to a dramatic reduction of the basis dimension. We analyze the validity and efficiency of this truncation scheme using different realistic nucleon-nucleon interactions and compare to conventional no-core shell model calculations for {sup 4}He and {sup 16}O. Then, we present the first converged calculations for the ground state of {sup 40}Ca within no-core model spaces including up to 16{h_bar}{Omega}-excitations using realistic low-momentum interactions. The scheme is universal and can be easily applied to other quantum many-body problems.

  7. Diffused junction p(+)-n solar cells in bulk GaAs. II - Device characterization and modelling

    NASA Technical Reports Server (NTRS)

    Keeney, R.; Sundaram, L. M. G.; Rode, H.; Bhat, I.; Ghandhi, S. K.; Borrego, J. M.

    1984-01-01

    The photovoltaic characteristics of p(+)-n junction solar cells fabricated on bulk GaAs by an open tube diffusion technique are presented in detail. Quantum efficiency measurements were analyzed and compared to computer simulations of the cell structure in order to determine material parameters such as diffusion length, surface recombination velocity and junction depth. From the results obtained it is projected that proper optimization of the cell parameters can increase the efficiency of the cells to close to 20 percent.

  8. Reduction of solar cell efficiency by edge defects across the back-surface-field junction - A developed perimeter model

    NASA Technical Reports Server (NTRS)

    Sah, C. T.; Yamakawa, K. A.; Lutwack, R.

    1982-01-01

    Material imperfections, impurity clusters and fabrication defects across the back-surface-field junction can degrade the performance of high-efficiency solar cells. The degradation from defects appearing on the circumference of a solar cell is analyzed using a two-region developed perimeter device model. The width of the defective perimeter region is characterized by the range or the distance-of-influence of the defective edge and this width is about two diffusion lengths. The defective edge is characterized by a surface recombination velocity. Family of theoretical curves and numerical examples are presented to show that significant reduction of open-circuit voltage can occur in high-efficiency cells which are thin compared with the diffusion length. In one example, the degradation is decreased from 135 mV to 75 mV when the cell size is increased from 10 to 100 times the diffusion length in a thin cell whose thickness is 1% of the diffusion length.

  9. Structural and Functional Abnormalities of the Neuromuscular Junction in the Trembler-J Homozygote Mouse Model of Congenital Hypomyelinating Neuropathy.

    PubMed

    Scurry, Alexandra N; Heredia, Dante J; Feng, Cheng-Yuan; Gephart, Gregory B; Hennig, Grant W; Gould, Thomas W

    2016-04-01

    Mutations in peripheral myelin protein 22 (PMP22) result in the most common form of Charcot-Marie-Tooth (CMT) disease, CMT1A. This hereditary peripheral neuropathy is characterized by dysmyelination of peripheral nerves, reduced nerve conduction velocity, and muscle weakness. APMP22 point mutation in L16P (leucine 16 to proline) underlies a form of human CMT1A as well as the Trembler-J mouse model of CMT1A. Homozygote Trembler-J mice (Tr(J)) die early postnatally, fail to make peripheral myelin, and, therefore, are more similar to patients with congenital hypomyelinating neuropathy than those with CMT1A. Because recent studies of inherited neuropathies in humans and mice have demonstrated that dysfunction and degeneration of neuromuscular synapses or junctions (NMJs) often precede impairments in axonal conduction, we examined the structure and function of NMJs in Tr(J)mice. Although synapses appeared to be normally innervated even in end-stage Tr(J)mice, the growth and maturation of the NMJs were altered. In addition, the amplitudes of nerve-evoked muscle endplate potentials were reduced and there was transmission failure during sustained nerve stimulation. These results suggest that the severe congenital hypomyelinating neuropathy that characterizes Tr(J)mice results in structural and functional deficits of the developing NMJ.

  10. Modeling the Early Phenotype at the Neuromuscular Junction of Spinal Muscular Atrophy Using Patient-Derived iPSCs

    PubMed Central

    Yoshida, Michiko; Kitaoka, Shiho; Egawa, Naohiro; Yamane, Mayu; Ikeda, Ryunosuke; Tsukita, Kayoko; Amano, Naoki; Watanabe, Akira; Morimoto, Masafumi; Takahashi, Jun; Hosoi, Hajime; Nakahata, Tatsutoshi; Inoue, Haruhisa; Saito, Megumu K.

    2015-01-01

    Summary Spinal muscular atrophy (SMA) is a neuromuscular disorder caused by mutations of the survival of motor neuron 1 (SMN1) gene. In the pathogenesis of SMA, pathological changes of the neuromuscular junction (NMJ) precede the motor neuronal loss. Therefore, it is critical to evaluate the NMJ formed by SMA patients’ motor neurons (MNs), and to identify drugs that can restore the normal condition. We generated NMJ-like structures using MNs derived from SMA patient-specific induced pluripotent stem cells (iPSCs), and found that the clustering of the acetylcholine receptor (AChR) is significantly impaired. Valproic acid and antisense oligonucleotide treatment ameliorated the AChR clustering defects, leading to an increase in the level of full-length SMN transcripts. Thus, the current in vitro model of AChR clustering using SMA patient-derived iPSCs is useful to dissect the pathophysiological mechanisms underlying the development of SMA, and to evaluate the efficacy of new therapeutic approaches. PMID:25801509

  11. Toward a mineral physics reference model for the Moon’s core

    PubMed Central

    Antonangeli, Daniele; Morard, Guillaume; Schmerr, Nicholas C.; Komabayashi, Tetsuya; Krisch, Michael; Fiquet, Guillaume; Fei, Yingwei

    2015-01-01

    The physical properties of iron (Fe) at high pressure and high temperature are crucial for understanding the chemical composition, evolution, and dynamics of planetary interiors. Indeed, the inner structures of the telluric planets all share a similar layered nature: a central metallic core composed mostly of iron, surrounded by a silicate mantle, and a thin, chemically differentiated crust. To date, most studies of iron have focused on the hexagonal closed packed (hcp, or ε) phase, as ε-Fe is likely stable across the pressure and temperature conditions of Earth’s core. However, at the more moderate pressures characteristic of the cores of smaller planetary bodies, such as the Moon, Mercury, or Mars, iron takes on a face-centered cubic (fcc, or γ) structure. Here we present compressional and shear wave sound velocity and density measurements of γ-Fe at high pressures and high temperatures, which are needed to develop accurate seismic models of planetary interiors. Our results indicate that the seismic velocities proposed for the Moon’s inner core by a recent reanalysis of Apollo seismic data are well below those of γ-Fe. Our dataset thus provides strong constraints to seismic models of the lunar core and cores of small telluric planets. This allows us to propose a direct compositional and velocity model for the Moon’s core. PMID:25775531

  12. Consistent treatment of viscoelastic effects at junctions in one-dimensional blood flow models

    NASA Astrophysics Data System (ADS)

    Müller, Lucas O.; Leugering, Günter; Blanco, Pablo J.

    2016-06-01

    While the numerical discretization of one-dimensional blood flow models for vessels with viscoelastic wall properties is widely established, there is still no clear approach on how to couple one-dimensional segments that compose a network of viscoelastic vessels. In particular for Voigt-type viscoelastic models, assumptions with regard to boundary conditions have to be made, which normally result in neglecting the viscoelastic effect at the edge of vessels. Here we propose a coupling strategy that takes advantage of a hyperbolic reformulation of the original model and the inherent information of the resulting system. We show that applying proper coupling conditions is fundamental for preserving the physical coherence and numerical accuracy of the solution in both academic and physiologically relevant cases.

  13. Flow throughout the Earth's core inverted from geomagnetic observations and numerical dynamo models

    NASA Astrophysics Data System (ADS)

    Aubert, Julien

    2013-02-01

    This paper introduces inverse geodynamo modelling, a framework imaging flow throughout the Earth's core from observations of the geomagnetic field and its secular variation. The necessary prior information is provided by statistics from 3-D and self-consistent numerical simulations of the geodynamo. The core method is a linear estimation (or Kalman filtering) procedure, combined with standard frozen-flux core surface flow inversions in order to handle the non-linearity of the problem. The inversion scheme is successfully validated using synthetic test experiments. A set of four numerical dynamo models of increasing physical complexity and similarity to the geomagnetic field is then used to invert for flows at single epochs within the period 1970-2010, using data from the geomagnetic field models CM4 and gufm-sat-Q3. The resulting core surface flows generally provide satisfactory fits to the secular variation within the level of modelled errors, and robustly reproduce the most commonly observed patterns while additionally presenting a high degree of equatorial symmetry. The corresponding deep flows present a robust, highly columnar structure once rotational constraints are enforced to a high level in the prior models, with patterns strikingly similar to the results of quasi-geostrophic inversions. In particular, the presence of a persistent planetary scale, eccentric westward columnar gyre circling around the inner core is confirmed. The strength of the approach is to uniquely determine the trade-off between fit to the data and complexity of the solution by clearly connecting it to first principle physics; statistical deviations observed between the inverted flows and the standard model behaviour can then be used to quantitatively assess the shortcomings of the physical modelling. Such deviations include the (i) westwards and (ii) hemispherical character of the eccentric gyre. A prior model with angular momentum conservation of the core-mantle inner-core system, and

  14. An investigation of ab initio shell-model interactions derived by no-core shell model

    NASA Astrophysics Data System (ADS)

    Wang, XiaoBao; Dong, GuoXiang; Li, QingFeng; Shen, CaiWan; Yu, ShaoYing

    2016-09-01

    The microscopic shell-model effective interactions are mainly based on the many-body perturbation theory (MBPT), the first work of which can be traced to Brown and Kuo's first attempt in 1966, derived from the Hamada-Johnston nucleon-nucleon potential. However, the convergence of the MBPT is still unclear. On the other hand, ab initio theories, such as Green's function Monte Carlo (GFMC), no-core shell model (NCSM), and coupled-cluster theory with single and double excitations (CCSD), have made many progress in recent years. However, due to the increasing demanding of computing resources, these ab initio applications are usually limited to nuclei with mass up to A = 16. Recently, people have realized the ab initio construction of valence-space effective interactions, which is obtained through a second-time renormalization, or to be more exactly, projecting the full-manybody Hamiltonian into core, one-body, and two-body cluster parts. In this paper, we present the investigation of such ab initio shell-model interactions, by the recent derived sd-shell effective interactions based on effective J-matrix Inverse Scattering Potential (JISP) and chiral effective-field theory (EFT) through NCSM. In this work, we have seen the similarity between the ab initio shellmodel interactions and the interactions obtained by MBPT or by empirical fitting. Without the inclusion of three-body (3-bd) force, the ab initio shell-model interactions still share similar defects with the microscopic interactions by MBPT, i.e., T = 1 channel is more attractive while T = 0 channel is more repulsive than empirical interactions. The progress to include more many-body correlations and 3-bd force is still badly needed, to see whether such efforts of ab initio shell-model interactions can reach similar precision as the interactions fitted to experimental data.

  15. Confocal Annular Josephson Tunnel Junctions

    NASA Astrophysics Data System (ADS)

    Monaco, Roberto

    2016-09-01

    The physics of Josephson tunnel junctions drastically depends on their geometrical configurations and here we show that also tiny geometrical details play a determinant role. More specifically, we develop the theory of short and long annular Josephson tunnel junctions delimited by two confocal ellipses. The behavior of a circular annular Josephson tunnel junction is then seen to be simply a special case of the above result. For junctions having a normalized perimeter less than one, the threshold curves in the presence of an in-plane magnetic field of arbitrary orientations are derived and computed even in the case with trapped Josephson vortices. For longer junctions, a numerical analysis is carried out after the derivation of the appropriate motion equation for the Josephson phase. We found that the system is modeled by a modified and perturbed sine-Gordon equation with a space-dependent effective Josephson penetration length inversely proportional to the local junction width. Both the fluxon statics and dynamics are deeply affected by the non-uniform annulus width. Static zero-field multiple-fluxon solutions exist even in the presence of a large bias current. The tangential velocity of a traveling fluxon is not determined by the balance between the driving and drag forces due to the dissipative losses. Furthermore, the fluxon motion is characterized by a strong radial inward acceleration which causes electromagnetic radiation concentrated at the ellipse equatorial points.

  16. Positive field-cooled dc susceptibility in granular superconductors interpreted through numerical simulations on a simple Josephson-junction-array model

    SciTech Connect

    Auletta, C.; Raiconi, G.; De Luca, R.; Pace, S.

    1995-05-01

    We have performed numerical simulations of a field-cooled dc susceptibility experiment carried out for granular superconductors by modeling these systems with a simple Josephson-junction array proposed by the authors. By this analysis the temperature dependence of the positive field-cooled susceptibility at very low values of the applied magnetic field, observed by Braunisch {ital et} {ital al}. [Phys. Rev. Lett. 68, 1908 (1992)] for some ceramic superonductors, has been reproduced and interpreted.

  17. String junction as a baryonic constituent

    NASA Astrophysics Data System (ADS)

    Kalashnikova, Yu. S.; Nefediev, A. V.

    1996-02-01

    We extend the model for QCD string with quarks to consider the Mercedes Benz string configuration describing the three-quark baryon. Under the assumption of adiabatic separation of quark and string junction motion we formulate and solve the classical equation of motion for the junction. We dare to quantize the motion of the junction, and discuss the impact of these modes on the baryon spectra.

  18. Structure and thermodynamics of core-softened models for alcohols

    SciTech Connect

    Munaò, Gianmarco; Urbic, Tomaz

    2015-06-07

    The phase behavior and the fluid structure of coarse-grain models for alcohols are studied by means of reference interaction site model (RISM) theory and Monte Carlo simulations. Specifically, we model ethanol and 1-propanol as linear rigid chains constituted by three (trimers) and four (tetramers) partially fused spheres, respectively. Thermodynamic properties of these models are examined in the RISM context, by employing closed formulæ for the calculation of free energy and pressure. Gas-liquid coexistence curves for trimers and tetramers are reported and compared with already existing data for a dimer model of methanol. Critical temperatures slightly increase with the number of CH{sub 2} groups in the chain, while critical pressures and densities decrease. Such a behavior qualitatively reproduces the trend observed in experiments on methanol, ethanol, and 1-propanol and suggests that our coarse-grain models, despite their simplicity, can reproduce the essential features of the phase behavior of such alcohols. The fluid structure of these models is investigated by computing radial distribution function g{sub ij}(r) and static structure factor S{sub ij}(k); the latter shows the presence of a low−k peak at intermediate-high packing fractions and low temperatures, suggesting the presence of aggregates for both trimers and tetramers.

  19. CoNTub v2.0--algorithms for constructing C3-symmetric models of three-nanotube junctions.

    PubMed

    Melchor, Santiago; Martin-Martinez, Francisco J; Dobado, José A

    2011-06-27

    Here, a method is described for easily building three-carbon nanotube junctions. It allows the geometry to be found and bond connectivity of C(3) symmetric nanotube junctions to be established. Such junctions may present a variable degree of pyramidalization and are composed of three identical carbon nanotubes with arbitrary chirality. From the indices of the target nanotube, applying the formulas of strip algebra, the possible positions of the six defects (heptagonal rings) needed can be found. Given the multiple possibilities that arise for a specific pair of indices, the relation between the macroscopic geometry (interbranch angles, junction size, and pyramidalization) and each specific solution is found. To automate the construction of these structures, we implemented this algorithm with CoNTub software, version 2.0, which is available at ( http://www.ugr.es/local/gmdm/contub2 ). In addition, a classification of three-nanotube junctions, 3TJ, in seven types based on the location of defects has been proposed, i.e. 3TJ(0:0:6), 3TJ(0:1:5), 3TJ(0:2:4), 3TJ(0:3:3), 3TJ(1:1:4), 3TJ(1:2:3), and 3TJ(2:2:2) types.

  20. Chaos induced by coupling between Josephson junctions

    NASA Astrophysics Data System (ADS)

    Shukrinov, Yu. M.; Azemtsa-Donfack, H.; Botha, A. E.

    2015-02-01

    It is found that, in a stack of intrinsic Josephson junctions in layered high temperature superconductors under external electromagnetic radiation, the chaotic features are triggered by interjunction coupling, i.e., the coupling between different junctions in the stack. While the radiation is well known to produce chaotic effects in the single junction, the effect of interjunction coupling is fundamentally different and it can lead to the onset of chaos via a different route to that of the single junction. A precise numerical study of the phase dynamics of intrinsic Josephson junctions, as described by the CCJJ+DC model, is performed. We demonstrate the charging of superconducting layers, in a bias current interval corresponding to a Shapiro step subharmonic, due to the creation of a longitudinal plasma wave along the stack of junctions. With increase in radiation amplitude chaotic behavior sets in. The chaotic features of the coupled Josephson junctions are analyzed by calculations of the Lyapunov exponents. We compare results for a stack of junctions to the case of a single junction and prove that the observed chaos is induced by the coupling between the junctions. The use of Shapiro step subharmonics may allow longitudinal plasma waves to be excited at low radiation power.

  1. Competency Model 101. The Process of Developing Core Competencies.

    ERIC Educational Resources Information Center

    Eichelberger, Lisa Wright; Hewlett, Peggy O'Neill

    1999-01-01

    The Mississippi Competency Model defines nurses' roles as provider (caregiver, teacher, counselor, advocate), professional (scholar, collaborator, ethicist, researcher), and manager (leader, facilitator, intrapreneur, decision maker, technology user) for four levels of nursing: licensed practical nurse, associate degree, bachelor's degree, and…

  2. Core-shell particle model for optical transparency in glass ceramics

    NASA Astrophysics Data System (ADS)

    Edgar, Andrew

    2006-07-01

    The light scattering from particles in a glass ceramic is calculated for a particle model comprising a crystalline core and a surrounding shell, created by nucleation and diffusive processes from the original homogeneous glass, with diffusing atoms limited to the core-shell volume. The scatterings from core and shell are found to cancel in first order for small particles within the approximations of the Rayleigh-Debye theory. The residual scattering varies as the inverse eighth power of wavelength and is most pronounced in the backscatter geometry.

  3. State space modeling of reactor core in a pressurized water reactor

    SciTech Connect

    Ashaari, A.; Ahmad, T.; M, Wan Munirah W.; Shamsuddin, Mustaffa; Abdullah, M. Adib

    2014-07-10

    The power control system of a nuclear reactor is the key system that ensures a safe operation for a nuclear power plant. However, a mathematical model of a nuclear power plant is in the form of nonlinear process and time dependent that give very hard to be described. One of the important components of a Pressurized Water Reactor is the Reactor core. The aim of this study is to analyze the performance of power produced from a reactor core using temperature of the moderator as an input. Mathematical representation of the state space model of the reactor core control system is presented and analyzed in this paper. The data and parameters are taken from a real time VVER-type Pressurized Water Reactor and will be verified using Matlab and Simulink. Based on the simulation conducted, the results show that the temperature of the moderator plays an important role in determining the power of reactor core.

  4. State space modeling of reactor core in a pressurized water reactor

    NASA Astrophysics Data System (ADS)

    Ashaari, A.; Ahmad, T.; Shamsuddin, Mustaffa; M, Wan Munirah W.; Abdullah, M. Adib

    2014-07-01

    The power control system of a nuclear reactor is the key system that ensures a safe operation for a nuclear power plant. However, a mathematical model of a nuclear power plant is in the form of nonlinear process and time dependent that give very hard to be described. One of the important components of a Pressurized Water Reactor is the Reactor core. The aim of this study is to analyze the performance of power produced from a reactor core using temperature of the moderator as an input. Mathematical representation of the state space model of the reactor core control system is presented and analyzed in this paper. The data and parameters are taken from a real time VVER-type Pressurized Water Reactor and will be verified using Matlab and Simulink. Based on the simulation conducted, the results show that the temperature of the moderator plays an important role in determining the power of reactor core.

  5. Neuronal gap junctions play a role in the secondary neuronal death following controlled cortical impact.

    PubMed

    Belousov, Andrei B; Wang, Yongfu; Song, Ji-Hoon; Denisova, Janna V; Berman, Nancy E; Fontes, Joseph D

    2012-08-22

    In the mammalian CNS, excessive release of glutamate and overactivation of glutamate receptors are responsible for the secondary (delayed) neuronal death following neuronal injury, including ischemia, traumatic brain injury (TBI) and epilepsy. Recent studies in mice showed a critical role for neuronal gap junctions in NMDA receptor-mediated excitotoxicity and ischemia-mediated neuronal death. Here, using controlled cortical impact (CCI) in adult mice, as a model of TBI, and Fluoro-Jade B staining for analysis of neuronal death, we set to determine whether neuronal gap junctions play a role in the CCI-mediated secondary neuronal death. We report that 24h post-CCI, substantial neuronal death is detected in a number of brain regions outside the injury core, including the striatum. The striatal neuronal death is reduced both in wild-type mice by systemic administration of mefloquine (a relatively selective blocker of neuronal gap junctions) and in knockout mice lacking connexin 36 (neuronal gap junction protein). It is also reduced by inactivation of group II metabotropic glutamate receptors (with LY341495) which, as reported previously, control the rapid increase in neuronal gap junction coupling following different types of neuronal injury. The results suggest that neuronal gap junctions play a critical role in the CCI-induced secondary neuronal death. PMID:22781494

  6. Entropy-Driven Folding of an RNA Helical Junction: An Isothermal Titration Calorimetric Analysis of the Hammerhead Ribozyme†

    PubMed Central

    Mikulecky, Peter J.; Takach, Jennifer C.; Feig, Andrew L.

    2008-01-01

    Helical junctions are extremely common motifs in naturally occurring RNAs, but little is known about the thermodynamics that drive their folding. Studies of junction folding face several challenges: non-two-state folding behavior, superposition of secondary and tertiary structural energetics, and drastically opposing enthalpic and entropic contributions to folding. Here we describe a thermodynamic dissection of the folding of the hammerhead ribozyme, a three-way RNA helical junction, by using isothermal titration calorimetry of bimolecular RNA constructs. By using this method, we show that tertiary folding of the hammerhead core occurs with a highly unfavorable enthalpy change, and is therefore entropically driven. Furthermore, the enthalpies and heat capacities of core folding are the same whether supported by monovalent or divalent ions. These properties appear to be general to the core sequence of bimolecular hammerhead constructs. We present a model for the ion-induced folding of the hammerhead core that is similar to those advanced for the folding of much larger RNAs, involving ion-induced collapse to a structured, non-native state accompanied by rearrangement of core residues to produce the native fold. In agreement with previous enzymological and structural studies, our thermodynamic data suggest that the hammerhead structure is stabilized in vitro predominantly by diffusely bound ions. Our approach addresses several significant challenges that accompany the study of junction folding, and should prove useful in defining the thermodynamic determinants of stability in these important RNA motifs. PMID:15134461

  7. Towards 12% stabilised efficiency in single junction polymorphous silicon solar cells: experimental developments and model predictions

    NASA Astrophysics Data System (ADS)

    Abolmasov, Sergey; Cabarrocas, Pere Roca i.; Chatterjee, Parsathi

    2016-01-01

    We have combined recent experimental developments in our laboratory with modelling to devise ways of maximising the stabilised efficiency of hydrogenated amorphous silicon (a-Si:H) PIN solar cells. The cells were fabricated using the conventional plasma enhanced chemical vapour deposition (PECVD) technique at various temperatures, pressures and gas flow ratios. A detailed electrical-optical simulator was used to examine the effect of using wide band gap P-and N-doped μc-SiOx:H layers, as well as a MgF2 anti-reflection coating (ARC) on cell performance. We find that with the best quality a-Si:H so far produced in our laboratory and optimised deposition parameters for the corresponding solar cell, we could not attain a 10% stabilised efficiency due to the high stabilised defect density of a-Si:H, although this landmark has been achieved in some laboratories. On the other hand, a close cousin of a-Si:H, hydrogenated polymorphous silicon (pm-Si:H), a nano-structured silicon thin film produced by PECVD under conditions close to powder formation, has been developed in our laboratory. This material has been shown to have a lower initial and stabilised defect density as well as higher hole mobility than a-Si:H. Modelling indicates that it is possible to attain stabilised efficiencies of 12% when pm-Si:H is incorporated in a solar cell, deposited in a NIP configuration to reduce the P/I interface defects and combined with P- and N-doped μc-SiOx:H layers and a MgF2 ARC.

  8. CAM-SE: A scalable spectral element dynamical core for the Community Atmosphere Model.

    SciTech Connect

    Dennis, John; Edwards, Jim; Evans, Kate J; Guba, O; Lauritzen, Peter; Mirin, Art; St.-Cyr, Amik; Taylor, Mark; Worley, Patrick H

    2012-01-01

    The Community Atmosphere Model (CAM) version 5 includes a spectral element dynamical core option from NCAR's High-Order Method Modeling Environment. It is a continuous Galerkin spectral finite element method designed for fully unstructured quadrilateral meshes. The current configurations in CAM are based on the cubed-sphere grid. The main motivation for including a spectral element dynamical core is to improve the scalability of CAM by allowing quasi-uniform grids for the sphere that do not require polar filters. In addition, the approach provides other state-of-the-art capabilities such as improved conservation properties. Spectral elements are used for the horizontal discretization, while most other aspects of the dynamical core are a hybrid of well tested techniques from CAM's finite volume and global spectral dynamical core options. Here we first give a overview of the spectral element dynamical core as used in CAM. We then give scalability and performance results from CAM running with three different dynamical core options within the Community Earth System Model, using a pre-industrial time-slice configuration. We focus on high resolution simulations of 1/4 degree, 1/8 degree, and T340 spectral truncation.

  9. Developing a theory of the strategic core of teams: a role composition model of team performance.

    PubMed

    Humphrey, Stephen E; Morgeson, Frederick P; Mannor, Michael J

    2009-01-01

    Although numerous models of team performance have been articulated over the past 20 years, these models have primarily focused on the individual attribute approach to team composition. The authors utilized a role composition approach, which investigates how the characteristics of a set of role holders impact team effectiveness, to develop a theory of the strategic core of teams. Their theory suggests that certain team roles are most important for team performance and that the characteristics of the role holders in the "core" of the team are more important for overall team performance. This theory was tested in 778 teams drawn from 29 years of major league baseball (1974'-2002). Results demonstrate that although high levels of experience and job-related skill are important predictors of team performance, the relationships between these constructs and team performance are significantly stronger when the characteristics are possessed by core role holders (as opposed to non-core role holders). Further, teams that invest more of their financial resources in these core roles are able to leverage such investments into significantly improved performance. These results have implications for team composition models, as they suggest a new method for considering individual contributions to a team's success that shifts the focus onto core roles. (PsycINFO Database Record (c) 2009 APA, all rights reserved).

  10. Developing a theory of the strategic core of teams: a role composition model of team performance.

    PubMed

    Humphrey, Stephen E; Morgeson, Frederick P; Mannor, Michael J

    2009-01-01

    Although numerous models of team performance have been articulated over the past 20 years, these models have primarily focused on the individual attribute approach to team composition. The authors utilized a role composition approach, which investigates how the characteristics of a set of role holders impact team effectiveness, to develop a theory of the strategic core of teams. Their theory suggests that certain team roles are most important for team performance and that the characteristics of the role holders in the "core" of the team are more important for overall team performance. This theory was tested in 778 teams drawn from 29 years of major league baseball (1974'-2002). Results demonstrate that although high levels of experience and job-related skill are important predictors of team performance, the relationships between these constructs and team performance are significantly stronger when the characteristics are possessed by core role holders (as opposed to non-core role holders). Further, teams that invest more of their financial resources in these core roles are able to leverage such investments into significantly improved performance. These results have implications for team composition models, as they suggest a new method for considering individual contributions to a team's success that shifts the focus onto core roles. (PsycINFO Database Record (c) 2009 APA, all rights reserved). PMID:19186895

  11. Common features of a vortex structure in long exponentially shaped Josephson junctions and Josephson junctions with inhomogeneities

    NASA Astrophysics Data System (ADS)

    Boyadjiev, T. L.; Semerdjieva, E. G.; Shukrinov, Yu. M.

    2007-09-01

    We study the vortex structure in three different models of the long Josephson junction: the exponentially shaped Josephson junction and the Josephson junctions with the resistor and the shunt inhomogeneities in the barrier layer. For these three models the critical curves “critical current-magnetic field” are numerically constructed. We develop the idea of the equivalence of the exponentially shaped Josephson junction and the rectangular junction with the distributed inhomogeneity and demonstrate that at some parameters of the shunt and the resistor inhomogeneities in the ends of the junction the corresponding critical curves are very close to the exponentially shaped one.

  12. Interfacing Cultured Neurons to Microtransducers Arrays: A Review of the Neuro-Electronic Junction Models.

    PubMed

    Massobrio, Paolo; Massobrio, Giuseppe; Martinoia, Sergio

    2016-01-01

    Microtransducer arrays, both metal microelectrodes and silicon-based devices, are widely used as neural interfaces to measure, extracellularly, the electrophysiological activity of excitable cells. Starting from the pioneering works at the beginning of the 70's, improvements in manufacture methods, materials, and geometrical shape have been made. Nowadays, these devices are routinely used in different experimental conditions (both in vivo and in vitro), and for several applications ranging from basic research in neuroscience to more biomedical oriented applications. However, the use of these micro-devices deeply depends on the nature of the interface (coupling) between the cell membrane and the sensitive active surface of the microtransducer. Thus, many efforts have been oriented to improve coupling conditions. Particularly, in the latest years, two innovations related to the use of carbon nanotubes as interface material and to the development of micro-structures which can be engulfed by the cell membrane have been proposed. In this work, we review what can be simulated by using simple circuital models and what happens at the interface between the sensitive active surface of the microtransducer and the neuronal membrane of in vitro neurons. We finally focus our attention on these two novel technological solutions capable to improve the coupling between neuron and micro-nano transducer. PMID:27445657

  13. Interfacing Cultured Neurons to Microtransducers Arrays: A Review of the Neuro-Electronic Junction Models

    PubMed Central

    Massobrio, Paolo; Massobrio, Giuseppe; Martinoia, Sergio

    2016-01-01

    Microtransducer arrays, both metal microelectrodes and silicon-based devices, are widely used as neural interfaces to measure, extracellularly, the electrophysiological activity of excitable cells. Starting from the pioneering works at the beginning of the 70's, improvements in manufacture methods, materials, and geometrical shape have been made. Nowadays, these devices are routinely used in different experimental conditions (both in vivo and in vitro), and for several applications ranging from basic research in neuroscience to more biomedical oriented applications. However, the use of these micro-devices deeply depends on the nature of the interface (coupling) between the cell membrane and the sensitive active surface of the microtransducer. Thus, many efforts have been oriented to improve coupling conditions. Particularly, in the latest years, two innovations related to the use of carbon nanotubes as interface material and to the development of micro-structures which can be engulfed by the cell membrane have been proposed. In this work, we review what can be simulated by using simple circuital models and what happens at the interface between the sensitive active surface of the microtransducer and the neuronal membrane of in vitro neurons. We finally focus our attention on these two novel technological solutions capable to improve the coupling between neuron and micro-nano transducer. PMID:27445657

  14. Symplectic Symmetry and the Ab Initio No-Core Shell Model

    SciTech Connect

    Draayer, Jerry P.; Dytrych, Tomas; Sviratcheva, Kristina D.; Bahri, Chairul; Vary, James P.; /Iowa State U. /LLNL, Livermore /SLAC

    2007-03-14

    The symplectic symmetry of eigenstates for the 0{sub gs}{sup +} in {sup 16}O and the 0{sub gs}{sup +} and lowest 2{sup +} and 4{sup +} configurations of {sup 12}C that are well-converged within the framework of the no-core shell model with the JISP16 realistic interaction is examined. These states are found to project at the 85-90% level onto very few symplectic representations including the most deformed configuration, which confirms the importance of a symplectic no-core shell model and reaffirms the relevance of the Elliott SU(3) model upon which the symplectic scheme is built.

  15. Mesenchymal Stem Cell Therapy Regenerates the Native Bone-Tendon Junction after Surgical Repair in a Degenerative Rat Model

    PubMed Central

    Nourissat, Geoffroy; Diop, Amadou; Maurel, Nathalie; Salvat, Colette; Dumont, Sylvie; Pigenet, Audrey; Gosset, Marjolaine; Houard, Xavier; Berenbaum, Francis

    2010-01-01

    Background The enthesis, which attaches the tendon to the bone, naturally disappears with aging, thus limiting joint mobility. Surgery is frequently needed but the clinical outcome is often poor due to the decreased natural healing capacity of the elderly. This study explored the benefits of a treatment based on injecting chondrocyte and mesenchymal stem cells (MSC) in a new rat model of degenerative enthesis repair. Methodology The Achilles' tendon was cut and the enthesis destroyed. The damage was repaired by classical surgery without cell injection (group G1, n = 52) and with chondrocyte (group G2, n = 51) or MSC injection (group G3, n = 39). The healing rate was determined macroscopically 15, 30 and 45 days later. The production and organization of a new enthesis was assessed by histological scoring of collagen II immunostaining, glycoaminoglycan production and the presence of columnar chondrocytes. The biomechanical load required to rupture the bone-tendon junction was determined. Principal Findings The spontaneous healing rate in the G1 control group was 40%, close to those observed in humans. Cell injection significantly improved healing (69%, p = 0.0028 for G2 and p = 0.006 for G3) and the load-to-failure after 45 days (p<0.05) over controls. A new enthesis was clearly produced in cell-injected G2 and G3 rats, but not in the controls. Only the MSC-injected G3 rats had an organized enthesis with columnar chondrocytes as in a native enthesis 45 days after surgery. Conclusions Cell therapy is an efficient procedure for reconstructing degenerative entheses. MSC treatment produced better organ regeneration than chondrocyte treatment. The morphological and biomechanical properties were similar to those of a native enthesis. PMID:20805884

  16. Singular PP waves, Junction Conditions and BPS States

    SciTech Connect

    Canfora, Fabrizio; Vilasi, Gaetano

    2005-03-16

    A simple model to study the collision of PP waves via the Israel junction conditions is proposed. The junction conditions are interpreted as topological conservation laws, and the relation with BPS states is shortly described.

  17. Non-hollow-core Cybister trabeculae and compressive properties of two biomimetic models of beetle forewings.

    PubMed

    Tuo, Wanyong; Xie, Juan; Chen, Jinxiang; Guo, Xiaojun

    2016-12-01

    In 2006, the forewing trabeculae of Cybister tripunctatus Olivier (i.e., Cybister) beetles were reported to be hollow, and a biomimetic structural model (i.e., Song's model) was reported to exhibit better compressive mechanical properties than a solid-core trabecula-honeycomb model (i.e., Chen's model). To test these assertions, the current study first observed the trabecular microstructure of the Cybister beetle and confirmed that the trabeculae are solid. Second, the finite element method (FEM) was used to perform a contrast analysis of the compressive mechanical properties of Song's and Chen's biomimetic models. The results indicated that Chen's model exhibited better compressive mechanical properties. These findings, which are completely opposite of Song's findings, were obtained because the comparison models designed for use in Song's study were not comparable to that of Chen's model in terms of the core volumes. This study will benefit the development of beetle forewing biomimetic research. PMID:27612788

  18. Benchmark calculation of no-core Monte Carlo shell model in light nuclei

    SciTech Connect

    Abe, T.; Shimizu, N.; Maris, P.; Vary, J. P.; Otsuka, T.; Utsuno, Y.

    2011-05-06

    The Monte Carlo shell model is firstly applied to the calculation of the no-core shell model in light nuclei. The results are compared with those of the full configuration interaction. The agreements between them are within a few % at most.

  19. The modeling of core melting and in-vessel corium relocation in the APRIL code

    SciTech Connect

    Kim. S.W.; Podowski, M.Z.; Lahey, R.T.

    1995-09-01

    This paper is concerned with the modeling of severe accident phenomena in boiling water reactors (BWR). New models of core melting and in-vessel corium debris relocation are presented, developed for implementation in the APRIL computer code. The results of model testing and validations are given, including comparisons against available experimental data and parametric/sensitivity studies. Also, the application of these models, as parts of the APRIL code, is presented to simulate accident progression in a typical BWR reactor.

  20. Muscle spindles exhibit core lesions and extensive degeneration of intrafusal fibers in the Ryr1{sup I4895T/wt} mouse model of core myopathy

    SciTech Connect

    Zvaritch, Elena; MacLennan, David H.

    2015-04-24

    Muscle spindles from the hind limb muscles of adult Ryr1{sup I4895T/wt} (IT/+) mice exhibit severe structural abnormalities. Up to 85% of the spindles are separated from skeletal muscle fascicles by a thick layer of connective tissue. Many intrafusal fibers exhibit degeneration, with Z-line streaming, compaction and collapse of myofibrillar bundles, mitochondrial clumping, nuclear shrinkage and pyknosis. The lesions resemble cores observed in the extrafusal myofibers of this animal model and of core myopathy patients. Spindle abnormalities precede those in extrafusal fibers, indicating that they are a primary pathological feature in this murine Ryr1-related core myopathy. Muscle spindle involvement, if confirmed for human core myopathy patients, would provide an explanation for an array of devastating clinical features characteristic of these diseases and provide novel insights into the pathology of RYR1-related myopathies. - Highlights: • Muscle spindles exhibit structural abnormalities in a mouse model of core myopathy. • Myofibrillar collapse and mitochondrial clumping is observed in intrafusal fibers. • Myofibrillar degeneration follows a pattern similar to core formation in extrafusal myofibers. • Muscle spindle abnormalities are a part of the pathological phenotype in the mouse model of core myopathy. • Direct involvement of muscle spindles in the pathology of human RYR1-related myopathies is proposed.

  1. Probability modeling of the number of positive cores in a prostate cancer biopsy session, with applications.

    PubMed

    Serfling, Robert; Ogola, Gerald

    2016-02-10

    Among men, prostate cancer (CaP) is the most common newly diagnosed cancer and the second leading cause of death from cancer. A major issue of very large scale is avoiding both over-treatment and under-treatment of CaP cases. The central challenge is deciding clinical significance or insignificance when the CaP biopsy results are positive but only marginally so. A related concern is deciding how to increase the number of biopsy cores for larger prostates. As a foundation for improved choice of number of cores and improved interpretation of biopsy results, we develop a probability model for the number of positive cores found in a biopsy, given the total number of cores, the volumes of the tumor nodules, and - very importantly - the prostate volume. Also, three applications are carried out: guidelines for the number of cores as a function of prostate volume, decision rules for insignificant versus significant CaP using number of positive cores, and, using prior distributions on total tumor size, Bayesian posterior probabilities for insignificant CaP and posterior median CaP. The model-based results have generality of application, take prostate volume into account, and provide attractive tradeoffs of specificity versus sensitivity. Copyright © 2015 John Wiley & Sons, Ltd.

  2. Josephson junctions in SPICE3

    SciTech Connect

    Whiteley, S.R.

    1991-03-01

    This paper reports on SPICE3 which is the most recent version of the venerable circuit simulator SPICE from the University of California, Berkeley. Unlike its predecessors, SPICE3 is written in the C programming language, and is designed for interactive use under a modern multitasking operating system. SPICE3, being an interactive program, offers the user great control and flexibility in performing simulations, and provides a powerful graphics capability for viewing simulation results. A C-shell like control syntax is supported, as well as such features as plotting while simulating, parameter alteration during simulation, and simulation data controlled breakpoints. Unfortunately, the Berkeley distribution of SPICE3 lacks support for Josephson junctions. As a consequence, the author has developed a customize version of SPICE3b.1 which incorporates a Josephson junction model. The model supports control current modulation, as well as a fifth order polynomial description of the quasiparticle current suitable for NbN junctions.

  3. Synaptic Deficits at Neuromuscular Junctions in Two Mouse Models of Charcot–Marie–Tooth Type 2d

    PubMed Central

    Spaulding, Emily L.; Sleigh, James N.; Morelli, Kathryn H.; Pinter, Martin J.; Burgess, Robert W.

    2016-01-01

    Patients with Charcot–Marie–Tooth Type 2D (CMT2D), caused by dominant mutations in Glycl tRNA synthetase (GARS), present with progressive weakness, consistently in the hands, but often in the feet also. Electromyography shows denervation, and patients often report that early symptoms include cramps brought on by cold or exertion. Based on reported clinical observations, and studies of mouse models of CMT2D, we sought to determine whether weakened synaptic transmission at the neuromuscular junction (NMJ) is an aspect of CMT2D. Quantal analysis of NMJs in two different mouse models of CMT2D (GarsP278KY, GarsC201R), found synaptic deficits that correlated with disease severity and progressed with age. Results of voltage-clamp studies revealed presynaptic defects characterized by: (1) decreased frequency of spontaneous release without any change in quantal amplitude (miniature endplate current), (2) reduced amplitude of evoked release (endplate current) and quantal content, (3) age-dependent changes in the extent of depression in response to repetitive stimulation, and (4) release failures at some NMJs with high-frequency, long-duration stimulation. Drugs that modify synaptic efficacy were tested to see whether neuromuscular performance improved. The presynaptic action of 3,4 diaminopyridine was not beneficial, whereas postsynaptic-acting physostigmine did improve performance. Smaller mutant NMJs with correspondingly fewer vesicles and partial denervation that eliminates some release sites also contribute to the reduction of release at a proportion of mutant NMJs. Together, these voltage-clamp data suggest that a number of release processes, while essentially intact, likely operate suboptimally at most NMJs of CMT2D mice. SIGNIFICANCE STATEMENT We have uncovered a previously unrecognized aspect of axonal Charcot–Marie–Tooth disease in mouse models of CMT2D. Synaptic dysfunction contributes to impaired neuromuscular performance and disease progression. This

  4. Degradation modeling of InGaP/GaAs/Ge triple-junction solar cells irradiated by protons

    NASA Astrophysics Data System (ADS)

    Maximenko, S. I.; Lumb, M. P.; Messenger, S. R.; Hoheisel, R.; Affouda, C.; Scheiman, D.; Gonzalez, M.; Lorentzen, J.; Jenkins, P. P.; Walters, R. J.

    2014-03-01

    Experimental results on triple-junction solar cells irradiated by 3 MeV proton irradiation to very high damage levels are presented. The minority carrier transport properties were obtained through quantum efficiency and EBIC measurements and an analytical drift-diffusion solver was used in understanding the results for different degradation levels where multiple damage mechanisms are evident.

  5. Ex-Vessel Core Melt Modeling Comparison between MELTSPREAD-CORQUENCH and MELCOR 2.1

    SciTech Connect

    Robb, Kevin R.; Farmer, Mitchell; Francis, Matthew W.

    2014-03-01

    System-level code analyses by both United States and international researchers predict major core melting, bottom head failure, and corium-concrete interaction for Fukushima Daiichi Unit 1 (1F1). Although system codes such as MELCOR and MAAP are capable of capturing a wide range of accident phenomena, they currently do not contain detailed models for evaluating some ex-vessel core melt behavior. However, specialized codes containing more detailed modeling are available for melt spreading such as MELTSPREAD as well as long-term molten corium-concrete interaction (MCCI) and debris coolability such as CORQUENCH. In a preceding study, Enhanced Ex-Vessel Analysis for Fukushima Daiichi Unit 1: Melt Spreading and Core-Concrete Interaction Analyses with MELTSPREAD and CORQUENCH, the MELTSPREAD-CORQUENCH codes predicted the 1F1 core melt readily cooled in contrast to predictions by MELCOR. The user community has taken notice and is in the process of updating their systems codes; specifically MAAP and MELCOR, to improve and reduce conservatism in their ex-vessel core melt models. This report investigates why the MELCOR v2.1 code, compared to the MELTSPREAD and CORQUENCH 3.03 codes, yield differing predictions of ex-vessel melt progression. To accomplish this, the differences in the treatment of the ex-vessel melt with respect to melt spreading and long-term coolability are examined. The differences in modeling approaches are summarized, and a comparison of example code predictions is provided.

  6. Prestellar core modeling in the presence of a filament. The dense heart of L1689B

    NASA Astrophysics Data System (ADS)

    Steinacker, J.; Bacmann, A.; Henning, Th.; Heigl, S.

    2016-08-01

    Context. Lacking a paradigm for the onset of star formation, it is important to derive basic physical properties of prestellar cores and filaments like density and temperature structures. Aims: We aim to disentangle the spatial variation in density and temperature across the prestellar core L1689B, which is embedded in a filament. We want to determine the range of possible central densities and temperatures that are consistent with the continuum radiation data. Methods: We apply a new synergetic radiative transfer method: the derived 1D density profiles are both consistent with a cut through the Herschel PACS/SPIRE and JCMT SCUBA-2 continuum maps of L1689B and with a derived local interstellar radiation field. Choosing an appropriate cut along the filament major axis, we minimize the impact of the filament emission on the modeling. Results: For the bulk of the core (5000-20 000 au) an isothermal sphere model with a temperature of around 10 K provides the best fits. We show that the power law index of the density profile, as well as the constant temperature can be derived directly from the radial surface brightness profiles. For the inner region (<5000 au), we find a range of densities and temperatures that are consistent with the surface brightness profiles and the local interstellar radiation field. Based on our core models, we find that pixel-by-pixel single temperature spectral energy distribution fits are incapable of determining dense core properties. Conclusions: We conclude that, to derive physical core properties, it is important to avoid azimuthally-averaging core and filament. Correspondingly, derived core masses are too high since they include some mass of the filament, and might introduce errors when determining core mass functions. The forward radiative transfer methods also avoids the loss of information owing to smearing of all maps to the coarsest spatial resolution. We find the central core region to be colder and denser than estimated in recent

  7. Core-scale solute transport model selection using Monte Carlo analysis

    NASA Astrophysics Data System (ADS)

    Malama, Bwalya; Kuhlman, Kristopher L.; James, Scott C.

    2013-06-01

    Model applicability to core-scale solute transport is evaluated using breakthrough data from column experiments conducted with conservative tracers tritium (3H) and sodium-22 (22Na ), and the retarding solute uranium-232 (232U). The three models considered are single-porosity, double-porosity with single-rate mobile-immobile mass-exchange, and the multirate model, which is a deterministic model that admits the statistics of a random mobile-immobile mass-exchange rate coefficient. The experiments were conducted on intact Culebra Dolomite core samples. Previously, data were analyzed using single-porosity and double-porosity models although the Culebra Dolomite is known to possess multiple types and scales of porosity, and to exhibit multirate mobile-immobile-domain mass transfer characteristics at field scale. The data are reanalyzed here and null-space Monte Carlo analysis is used to facilitate objective model selection. Prediction (or residual) bias is adopted as a measure of the model structural error. The analysis clearly shows single-porosity and double-porosity models are structurally deficient, yielding late-time residual bias that grows with time. On the other hand, the multirate model yields unbiased predictions consistent with the late-time -5/2 slope diagnostic of multirate mass transfer. The analysis indicates the multirate model is better suited to describing core-scale solute breakthrough in the Culebra Dolomite than the other two models.

  8. Combined application of low-intensity pulsed ultrasound and functional electrical stimulation accelerates bone-tendon junction healing in a rabbit model.

    PubMed

    Hu, Jianzhong; Qu, Jin; Xu, Daqi; Zhang, Tao; Qin, Ling; Lu, Hongbin

    2014-02-01

    The objective of this study was to elucidate the combined use of low-intensity pulsed ultrasound (LIPUS) and functional electrical stimulation (FES) on patella-patellar tendon (PPT) junction healing using a partial patellectomy model in rabbits. LIPUS was delivered continuously starting day 3 postoperative until week 6. FES was applied on quadriceps muscles to induce tensile force to the repaired PPT junction 5 days per week for 6 weeks since week 7 postoperatively. Forty rabbits with partial patellectomy were randomly divided into four groups: control, LIPUS alone, FES alone, and LIPUS + FES groups. At week 12, the PPT complexes were harvested for histology, radiographs, peripheral quantitative computed tomography, and biomechanical testing. There was better remodeling of newly formed bone and fibrocartilage zone in the three treatment groups compared with the control group. LIPUS and/or FES treatments significantly increased the area and bone mineral content of new bone. The failure load and ultimate strength of PPT complex were also highly improved in the three treatment groups. More new bone formed and higher tensile properties were showed in the LIPUS + FES group compared with the LIPUS or FES alone groups. Early LIPUS treatment and later FES treatment showed the additive effects of accelerating PPT junction healing.

  9. Endophenotype Network Models: Common Core of Complex Diseases.

    PubMed

    Ghiassian, Susan Dina; Menche, Jörg; Chasman, Daniel I; Giulianini, Franco; Wang, Ruisheng; Ricchiuto, Piero; Aikawa, Masanori; Iwata, Hiroshi; Müller, Christian; Zeller, Tania; Sharma, Amitabh; Wild, Philipp; Lackner, Karl; Singh, Sasha; Ridker, Paul M; Blankenberg, Stefan; Barabási, Albert-László; Loscalzo, Joseph

    2016-01-01

    Historically, human diseases have been differentiated and categorized based on the organ system in which they primarily manifest. Recently, an alternative view is emerging that emphasizes that different diseases often have common underlying mechanisms and shared intermediate pathophenotypes, or endo(pheno)types. Within this framework, a specific disease's expression is a consequence of the interplay between the relevant endophenotypes and their local, organ-based environment. Important examples of such endophenotypes are inflammation, fibrosis, and thrombosis and their essential roles in many developing diseases. In this study, we construct endophenotype network models and explore their relation to different diseases in general and to cardiovascular diseases in particular. We identify the local neighborhoods (module) within the interconnected map of molecular components, i.e., the subnetworks of the human interactome that represent the inflammasome, thrombosome, and fibrosome. We find that these neighborhoods are highly overlapping and significantly enriched with disease-associated genes. In particular they are also enriched with differentially expressed genes linked to cardiovascular disease (risk). Finally, using proteomic data, we explore how macrophage activation contributes to our understanding of inflammatory processes and responses. The results of our analysis show that inflammatory responses initiate from within the cross-talk of the three identified endophenotypic modules. PMID:27278246

  10. Endophenotype Network Models: Common Core of Complex Diseases.

    PubMed

    Ghiassian, Susan Dina; Menche, Jörg; Chasman, Daniel I; Giulianini, Franco; Wang, Ruisheng; Ricchiuto, Piero; Aikawa, Masanori; Iwata, Hiroshi; Müller, Christian; Zeller, Tania; Sharma, Amitabh; Wild, Philipp; Lackner, Karl; Singh, Sasha; Ridker, Paul M; Blankenberg, Stefan; Barabási, Albert-László; Loscalzo, Joseph

    2016-06-09

    Historically, human diseases have been differentiated and categorized based on the organ system in which they primarily manifest. Recently, an alternative view is emerging that emphasizes that different diseases often have common underlying mechanisms and shared intermediate pathophenotypes, or endo(pheno)types. Within this framework, a specific disease's expression is a consequence of the interplay between the relevant endophenotypes and their local, organ-based environment. Important examples of such endophenotypes are inflammation, fibrosis, and thrombosis and their essential roles in many developing diseases. In this study, we construct endophenotype network models and explore their relation to different diseases in general and to cardiovascular diseases in particular. We identify the local neighborhoods (module) within the interconnected map of molecular components, i.e., the subnetworks of the human interactome that represent the inflammasome, thrombosome, and fibrosome. We find that these neighborhoods are highly overlapping and significantly enriched with disease-associated genes. In particular they are also enriched with differentially expressed genes linked to cardiovascular disease (risk). Finally, using proteomic data, we explore how macrophage activation contributes to our understanding of inflammatory processes and responses. The results of our analysis show that inflammatory responses initiate from within the cross-talk of the three identified endophenotypic modules.

  11. Endophenotype Network Models: Common Core of Complex Diseases

    PubMed Central

    Ghiassian, Susan Dina; Menche, Jörg; Chasman, Daniel I.; Giulianini, Franco; Wang, Ruisheng; Ricchiuto, Piero; Aikawa, Masanori; Iwata, Hiroshi; Müller, Christian; Zeller, Tania; Sharma, Amitabh; Wild, Philipp; Lackner, Karl; Singh, Sasha; Ridker, Paul M.; Blankenberg, Stefan; Barabási, Albert-László; Loscalzo, Joseph

    2016-01-01

    Historically, human diseases have been differentiated and categorized based on the organ system in which they primarily manifest. Recently, an alternative view is emerging that emphasizes that different diseases often have common underlying mechanisms and shared intermediate pathophenotypes, or endo(pheno)types. Within this framework, a specific disease’s expression is a consequence of the interplay between the relevant endophenotypes and their local, organ-based environment. Important examples of such endophenotypes are inflammation, fibrosis, and thrombosis and their essential roles in many developing diseases. In this study, we construct endophenotype network models and explore their relation to different diseases in general and to cardiovascular diseases in particular. We identify the local neighborhoods (module) within the interconnected map of molecular components, i.e., the subnetworks of the human interactome that represent the inflammasome, thrombosome, and fibrosome. We find that these neighborhoods are highly overlapping and significantly enriched with disease-associated genes. In particular they are also enriched with differentially expressed genes linked to cardiovascular disease (risk). Finally, using proteomic data, we explore how macrophage activation contributes to our understanding of inflammatory processes and responses. The results of our analysis show that inflammatory responses initiate from within the cross-talk of the three identified endophenotypic modules. PMID:27278246

  12. Steady flows at the top of the core from geomagnetic field models - The steady motions theorem

    NASA Technical Reports Server (NTRS)

    Voorhies, C. V.; Backus, G. E.

    1985-01-01

    It is demonstrated that the steady tangential velocity at the closed surface of a perfect-fluid conductor bounded by a rigid impenetrable exterior can be uniquely determined from knowledge of the normal component of the time-varying magnetic-flux density on the surface. In the context of a simple earth model consisting of an electrically insulating mantle surrounding a perfectly conducting core, the assumption of steady flow provides enough extra information to eliminate the toroidal ambiguity and to allow derivation of a unique global flow at the top of the core from a model of the geomagnetic field.

  13. On the joint inversion of geophysical data for models of the coupled core-mantle system

    NASA Technical Reports Server (NTRS)

    Voorhies, Coerte V.

    1991-01-01

    Joint inversion of magnetic, earth rotation, geoid, and seismic data for a unified model of the coupled core-mantle system is proposed and shown to be possible. A sample objective function is offered and simplified by targeting results from independent inversions and summary travel time residuals instead of original observations. These data are parameterized in terms of a very simple, closed model of the topographically coupled core-mantle system. Minimization of the simplified objective function leads to a nonlinear inverse problem; an iterative method for solution is presented. Parameterization and method are emphasized; numerical results are not presented.

  14. VERA-CS Modeling and Simulation of PWR Main Steam Line Break Core Response to DNB

    SciTech Connect

    Salko, Robert K; Sung, Yixing; Kucukboyaci, Vefa; Xu, Yiban; Cao, Liping

    2016-01-01

    The Virtual Environment for Reactor Applications core simulator (VERA-CS) being developed by the Consortium for the Advanced Simulation of Light Water Reactors (CASL) includes coupled neutronics, thermal-hydraulics, and fuel temperature components with an isotopic depletion capability. The neutronics capability employed is based on MPACT, a three-dimensional (3-D) whole core transport code. The thermal-hydraulics and fuel temperature models are provided by the COBRA-TF (CTF) subchannel code. As part of the CASL development program, the VERA-CS (MPACT/CTF) code system was applied to model and simulate reactor core response with respect to departure from nucleate boiling ratio (DNBR) at the limiting time step of a postulated pressurized water reactor (PWR) main steamline break (MSLB) event initiated at the hot zero power (HZP), either with offsite power available and the reactor coolant pumps in operation (high-flow case) or without offsite power where the reactor core is cooled through natural circulation (low-flow case). The VERA-CS simulation was based on core boundary conditions from the RETRAN-02 system transient calculations and STAR-CCM+ computational fluid dynamics (CFD) core inlet distribution calculations. The evaluation indicated that the VERA-CS code system is capable of modeling and simulating quasi-steady state reactor core response under the steamline break (SLB) accident condition, the results are insensitive to uncertainties in the inlet flow distributions from the CFD simulations, and the high-flow case is more DNB limiting than the low-flow case.

  15. Triple junction distributions in polycrystals

    SciTech Connect

    King, W.E.; Kumar, M.; Schwartz, A.J.

    1999-07-01

    Recently, it has been demonstrated that some material properties can be enhanced by grain boundary engineering, i.e., the systematic modifications in the topology of the microstructure through thermomechanical processing. Experimental observations have shown that the microstructural parameter likely responsible for improved properties is the grain boundary character distribution (GBCD). It has been suggested that improvements in the fractions of special boundaries as defined by the coincident site lattice model (1) are necessary, but not fully sufficient to cause property improvements. For example, it has been observed that cracks propagating along interconnected networks of random grain boundaries can be arrested (2) when intersecting a triple junction where the remaining two pathways are special boundaries. Therefore, it is of interest to characterize microstructures in terms of the distributions of triple junction types. A simple method to describe a triple junction is by the types of grain boundaries intersecting at that junction [special vs. random, as described by the coincident site lattice (CSL) model]. The distribution of 0-CSL, 1-CSL, 2-CSL and 3-CSL triple junctions in the microstructure can then be plotted as a function of the fraction of special boundaries. Such data has been collected using orientation-imaging microscopy (OIM) (3--5) for oxygen-free-electronic (ofe)-Cu and Inconel 600 over a range of special fraction of grain boundaries. These results have been compared with theoretical models considering isolated triple junctions and invoking the {Sigma}-product rule (6) where {Sigma} is the inverse density of coincident lattice sites (7).

  16. Microanatomy of the cervical and anorectal squamocolumnar junctions: a proposed model for anatomical differences in HPV-related cancer risk

    PubMed Central

    Yang, Eric J.; Quick, Matthew C.; Hanamornroongruang, Suchanan; Lai, Keith; Doyle, Leona; McKeon, Frank D.; Xian, Wa; Crum, Christopher P.; Herfs, Michael

    2015-01-01

    Human papilloma virus (HPV) infection causes cancers and their precursors (high grade squamous intraepithelial lesions) near cervical and anal squamocolumnar junctions. Recently described cervical squamocolumnar junctions cells are putative residual embryonic cells near the cervical transformation zone. These cells appear multipotential and share an identical immunophenotype (strongly CK7-positive) with over 90% of high grade squamous intraepithelial lesions and cervical carcinomas. However, because the number of new cervical cancers discovered yearly world-wide is 17-fold that of anal cancer, we posed the hypothesis that this difference in cancer risk reflects differences in the transition zones at the two sites. The microanatomy of the normal anal transformation zone (n = 37) and topography and immunophenotype of anal squamous neoplasms (n = 97) were studied. A discrete anal transition zone was composed of multi-layered CK7-positive/p63-negative superficial columnar cells and an uninterrupted layer of CK7-negative/p63-positive basal cells. The CK7-negative/p63-positive basal cells were continuous with – and identical in appearance to - the basal cells of the mature squamous epithelium. This was in contrast to the cervical squamocolumnar junction, that harbored a single-layered CK7-positive/p63-negative squamocolumnar junction cell population. Of the 97 Anal intraepithelial neoplasia/squamous cell carcinomas evaluated, only 27% (26/97) appeared to originate near the anal transition zone and only 23% (22/97) were CK7-positive. This study thus reveals two fundamental differences between the anus and cervix: 1) the anal transition zone does not harbor a single monolayer of residual un-differentiated embryonic cells and 2) the dominant tumor immuno-phenotype is in keeping with an origin in metaplastic (CK7-negative) squamous rather than squamocolumnar junction (CK7-positive) epithelium. The implication is that at birth, the embryonic cells in the anal transition

  17. Microanatomy of the cervical and anorectal squamocolumnar junctions: a proposed model for anatomical differences in HPV-related cancer risk.

    PubMed

    Yang, Eric J; Quick, Matthew C; Hanamornroongruang, Suchanan; Lai, Keith; Doyle, Leona A; McKeon, Frank D; Xian, Wa; Crum, Christopher P; Herfs, Michael

    2015-07-01

    Human papilloma virus (HPV) infection causes cancers and their precursors (high-grade squamous intraepithelial lesions) near cervical and anal squamocolumnar junctions. Recently described cervical squamocolumnar junction cells are putative residual embryonic cells near the cervical transformation zone. These cells appear multipotential and share an identical immunophenotype (strongly CK7-positive) with over 90% of high-grade squamous intraepithelial lesions and cervical carcinomas. However, because the number of new cervical cancers discovered yearly world wide is 17-fold that of anal cancer, we posed the hypothesis that this difference in cancer risk reflects differences in the transition zones at the two sites. The microanatomy of the normal anal transformation zone (n=37) and topography and immunophenotype of anal squamous neoplasms (n=97) were studied. A discrete anal transition zone was composed of multilayered CK7-positive/p63-negative superficial columnar cells and an uninterrupted layer of CK7-negative/p63-positive basal cells. The CK7-negative/p63-positive basal cells were continuous with-and identical in appearance to-the basal cells of the mature squamous epithelium. This was in contrast to the cervical squamocolumnar junction, which harbored a single-layered CK7-positive/p63-negative squamocolumnar junction cell population. Of the 97 anal intraepithelial neoplasia/squamous cell carcinomas evaluated, only 27% (26/97) appeared to originate near the anal transition zone and only 23% (22/97) were CK7-positive. This study thus reveals two fundamental differences between the anus and the cervix: (1) the anal transition zone does not harbor a single monolayer of residual undifferentiated embryonic cells and (2) the dominant tumor immunophenotype is in keeping with an origin in metaplastic (CK7-negative) squamous rather than squamocolumnar junction (CK7-positive) epithelium. The implication is that, at birth, the embryonic cells in the anal transition zone have

  18. Comparison of retrograde endo-pyelotomy and endo-balloon rupture of the ureteropelvic junction in a porcine model.

    PubMed

    Pearle, M S; Moon, Y T; Endicott, R C; Gardner, S M; Humphrey, P; Clayman, R V

    1994-12-01

    Excellent results and durable success have been achieved with antegrade and retrograde endo-pyelotomy for treating primary and secondary ureteropelvic junction obstruction. Recently, a 30F dilating balloon was used to rupture the ureteropelvic junction (ENDOBRST) with encouraging results. While balloon distention of the ureteropelvic junction is a technically simpler procedure than endo-pyelotomy, clinical and laboratory data comparing the 2 methods are lacking. In an acute and chronic animal study we compared endo-pyelotomy via a ureteral cutting balloon incision to balloon rupture (that is 30F) of the normal ureteropelvic junction in each of 20 female farm pigs. Eight pigs were harvested acutely after treatment, and a macroscopic and histological examination of the treated ureteropelvic junction was completed. In 11 chronic pigs after endo-pyelotomy a 7F double pigtail ureteral stent was placed bilaterally and then removed after 6 weeks. Evaluation in the chronic group consisted of a furosemide washout renogram and retrograde pyelogram immediately preoperatively and 6 weeks after stent removal. The animals were likewise harvested 6 weeks after stent removal. One control pig underwent passage of the balloon cutting catheter and balloon dilating catheters without activation or dilation, respectively. Ureteral stents were placed bilaterally for 6 weeks and the pig was otherwise treated similarly to the other chronic study animals. In the acute group all ureters after endo-pyelotomy demonstrated retroperitoneal extravasation of contrast material. At harvest the ureters had been cleanly incised along a length of 3 to 4 cm. through the adventitial layer. In contrast, the balloon treated ureters showed free retroperitoneal extravasation in only half of the animals. Among the balloon treated ureters 7 of 8 had a linear tear of varying length (1 to 5 cm.) involving all but a thin adventitial layer of tissue. Histologically, the endo-pyelotomy ureters demonstrated a clean

  19. Robust normal mode constraints on inner-core anisotropy from model space search.

    PubMed

    Beghein, Caroline; Trampert, Jeannot

    2003-01-24

    A technique for searching full model space that was applied to measurements of anomalously split normal modes showed a robust pattern of P-wave and S-wave anisotropy in the inner core. The parameter describing P-wave anisotropy changes sign around a radius of 400 kilometers, whereas S-wave anisotropy is small in the upper two-thirds of the inner core and becomes negative at greater depths. Our results agree with observed travel-time anomalies of rays traveling at epicentral distances varying from 150 degrees to 180 degrees. The models may be explained by progressively tilted hexagonal close-packed iron in the upper half of the inner core and could suggest a different iron phase in the center.

  20. A low resolution model for the chromatin core particle by neutron scattering

    PubMed Central

    Suau, Pedro; Kneale, G.Geoff; Braddock, Gordon W.; Baldwin, John P.; Bradbury, E.Morton

    1977-01-01

    Neutron scattering studies have been applied to chromatin core particles in solution, using the contrast variation technique. On the basis of the contrast dependance of the radius of gyration and the radial distribution function it is shown that the core particle consists of a core containing most of the histone around which is wound the DNA helix,following a path with a mean radius of 4.5 nm,in association with a small proportion of the histones. Separation of the shape from the internal structure, followed by model calculations shows that the overall shape of the particle is that of a flat cylinder with dimensions ca. 11×11×6 nm. Further details of the precise folding of the DNA cannot be deduced from the data, but detailed model calculations support concurrent results from crystallographic studies25. Images PMID:593885

  1. Detailed OEDGE modeling of core-pedestal fueling in DIII-D

    SciTech Connect

    Elder, J. D.; Leonard, A. W.; Stangeby, P. C.; Boedo, J.A.; Bray, B. D.; Brooks, N. H.; Fenstermacher, M. E.; Reiter, D.; Unterberg, Ezekial A; Watkins, J. G.; Lisgo, S.

    2013-01-01

    The OEDGE code is used to model core fueling for attached L-mode plasmas and between edge localized modes (ELMs) for attached H-mode plasmas in DIII-D. Empirical plasma reconstruction has been used to determine the plasma conditions in these discharges. EIRENE is used to model the hydrogen recycling. Divertor recycling accounts for 65 100% of the core fueling. The fraction of the total divertor target flux ionized inside the separatrix ranges from 5% to 20%. The fraction of total wall flux ionized inside the separatrix ranges from 20% to 50%. Neutrals originating from wall regions closer to the separatrix are more likely to ionize in the confined plasma. Ionization in the confined plasma is concentrated below the midplane with peaks in the poloidal profiles just above the X-point. Radial core ionization in high density H-mode is peaked strongly near the separatrix.

  2. A Model for Enhancing Internet Medical Document Retrieval with “Medical Core Metadata”

    PubMed Central

    Malet, Gary; Munoz, Felix; Appleyard, Richard; Hersh, William

    1999-01-01

    Objective: Finding documents on the World Wide Web relevant to a specific medical information need can be difficult. The goal of this work is to define a set of document content description tags, or metadata encodings, that can be used to promote disciplined search access to Internet medical documents. Design: The authors based their approach on a proposed metadata standard, the Dublin Core Metadata Element Set, which has recently been submitted to the Internet Engineering Task Force. Their model also incorporates the National Library of Medicine's Medical Subject Headings (MeSH) vocabulary and Medline-type content descriptions. Results: The model defines a medical core metadata set that can be used to describe the metadata for a wide variety of Internet documents. Conclusions: The authors propose that their medical core metadata set be used to assign metadata to medical documents to facilitate document retrieval by Internet search engines. PMID:10094069

  3. Final Report, NERI Project: ''An Innovative Reactor Analysis Methodology Based on a Quasidiffusion Nodal Core Model''

    SciTech Connect

    Dmitriy Y. Anistratov; Marvin L. Adams; Todd S. Palmer; Kord S. Smith; Kevin Clarno; Hikaru Hiruta; Razvan Nes

    2003-08-04

    OAK (B204) Final Report, NERI Project: ''An Innovative Reactor Analysis Methodology Based on a Quasidiffusion Nodal Core Model'' The present generation of reactor analysis methods uses few-group nodal diffusion approximations to calculate full-core eigenvalues and power distributions. The cross sections, diffusion coefficients, and discontinuity factors (collectively called ''group constants'') in the nodal diffusion equations are parameterized as functions of many variables, ranging from the obvious (temperature, boron concentration, etc.) to the more obscure (spectral index, moderator temperature history, etc.). These group constants, and their variations as functions of the many variables, are calculated by assembly-level transport codes. The current methodology has two main weaknesses that this project addressed. The first weakness is the diffusion approximation in the full-core calculation; this can be significantly inaccurate at interfaces between different assemblies. This project used the nodal diffusion framework to implement nodal quasidiffusion equations, which can capture transport effects to an arbitrary degree of accuracy. The second weakness is in the parameterization of the group constants; current models do not always perform well, especially at interfaces between unlike assemblies. The project developed a theoretical foundation for parameterization and homogenization models and used that theory to devise improved models. The new models were extended to tabulate information that the nodal quasidiffusion equations can use to capture transport effects in full-core calculations.

  4. A dissolution model that accounts for coverage of mineral surfaces by precipitation in core floods

    NASA Astrophysics Data System (ADS)

    Pedersen, Janne; Jettestuen, Espen; Madland, Merete V.; Hildebrand-Habel, Tania; Korsnes, Reidar I.; Vinningland, Jan Ludvig; Hiorth, Aksel

    2016-01-01

    In this paper, we propose a model for evolution of reactive surface area of minerals due to surface coverage by precipitating minerals. The model is used to interpret results from an experiment where a chalk core was flooded with MgCl2 for 1072 days, giving rise to calcite dissolution and magnesite precipitation. The model successfully describes both the long-term behavior of the measured effluent concentrations and the more or less homogeneous distribution of magnesite found in the core after 1072 days. The model also predicts that precipitating magnesite minerals form as larger crystals or aggregates of smaller size crystals, and not as thin flakes or as a monomolecular layer. Using rate constants obtained from literature gave numerical effluent concentrations that diverged from observed values only after a few days of flooding. To match the simulations to the experimental data after approximately 1 year of flooding, a rate constant that is four orders of magnitude lower than reported by powder experiments had to be used. We argue that a static rate constant is not sufficient to describe a chalk core flooding experiment lasting for nearly 3 years. The model is a necessary extension of standard rate equations in order to describe long term core flooding experiments where there is a large degree of textural alteration.

  5. RADIATION TRANSFER OF MODELS OF MASSIVE STAR FORMATION. I. DEPENDENCE ON BASIC CORE PROPERTIES

    SciTech Connect

    Zhang Yichen; Tan, Jonathan C. E-mail: jt@astro.ufl.edu

    2011-05-20

    Radiative transfer calculations of massive star formation are presented. These are based on the Turbulent Core Model of McKee and Tan and self-consistently included a hydrostatic core, an inside-out expansion wave, a zone of free-falling rotating collapse, wide-angle dust-free outflow cavities, an active accretion disk, and a massive protostar. For the first time for such models, an optically thick inner gas disk extends inside the dust destruction front. This is important to conserve the accretion energy naturally and for its shielding effect on the outer region of the disk and envelope. The simulation of radiation transfer is performed with the Monte Carlo code of Whitney, yielding spectral energy distributions (SEDs) for the model series, from the simplest spherical model to the fiducial one, with the above components each added step by step. Images are also presented in different wavebands of various telescope cameras, including Spitzer IRAC and MIPS, SOFIA FORCAST, and Herschel PACS and SPIRE. The existence of the optically thick inner disk produces higher optical wavelength fluxes but reduces near- and mid-IR emission. The presence of outflow cavities, the inclination angle to the line of sight, and the thickness of the disk all affect the SEDs and images significantly. For the high-mass surface density cores considered here, the mid-IR emission can be dominated by the outflow cavity walls, as has been suggested by De Buizer. The effect of varying the pressure of the environment bounding the surface of the massive core is also studied. With lower surface pressures, the core is larger, has lower extinction and accretion rates, and the observed mid-IR flux from the disk can then be relatively high even though the accretion luminosity is lower. In this case the silicate absorption feature becomes prominent, in contrast to higher density cores forming under higher pressures.

  6. Models of molecular cloud cores. II. Multitransition study of CS-34

    SciTech Connect

    Mundy, L.G.; Evans, N.J.,II; Snell, R.L.; Goldsmith, P.F.; Bally, J.

    1986-07-01

    The dense cores embedded in the M17, S140 and NGC 2024 molecular clouds are mapped in the J = 5-4, J = 3-2, and J = 2-1 transitions of CS-34, and these lines are found to be a factor of 3-4 weaker, and 25 percent narrower, than the CS lines mapped in these cores by Snell et al. (1984). The data are well fitted by spherical LGV models for the excitation, and the excellent correlation between the CS-34 and CS column densities corroborates the absence of a systematic increase in the gas density with decreasing core radius found by Snell et al. Though the CS/CS-34 column density ratio is 9-17, rather than the terrestrial value of 22.5, the column density relationship is linear. The data support of a clump model in which the column density distribution in the core is determined by the volume filling factor of clumps with high, fairly uniform gas density, and it is suggested that the dense gas in the data represents the dominant component of the core gas. 22 references.

  7. Effect of superconducting solenoid model cores on spanwise iron magnet roll control

    NASA Technical Reports Server (NTRS)

    Britcher, C. P.

    1985-01-01

    Compared with conventional ferromagnetic fuselage cores, superconducting solenoid cores appear to offer significant reductions in the projected cost of a large wind tunnel magnetic suspension and balance system. The provision of sufficient magnetic roll torque capability has been a long-standing problem with all magnetic suspension and balance systems; and the spanwise iron magnet scheme appears to be the most powerful system available. This scheme utilizes iron cores which are installed in the wings of the model. It was anticipated that the magnetization of these cores, and hence the roll torque generated, would be affected by the powerful external magnetic field of the superconducting solenoid. A preliminary study has been made of the effect of the superconducting solenoid fuselage model core concept on the spanwise iron magnet roll torque generation schemes. Computed data for one representative configuration indicate that reductions in available roll torque occur over a range of applied magnetic field levels. These results indicate that a 30-percent increase in roll electromagnet capacity over that previously determined will be required for a representative 8-foot wind tunnel magnetic suspension and balance system design.

  8. Electroelastic fields in artificially created vortex cores in epitaxial BiFeO3 thin films

    DOE PAGES

    Winchester, Ben; Wisinger, Nina Balke; Cheng, X. X.; Morozovska, A. N.; Kalinin, Sergei; Chen, L. Q.

    2015-08-03

    Here we employ phase-field modeling to explore the elastic properties of artificially created 1-D domain walls in (001)p-oriented BiFeO3 thin films, composed of a junction of the four polarization variants, all with the same out-of-plane polarization. It was found that these junctions exhibit peculiarly high electroelastic fields induced by the neighboring ferroelastic/ferroelectric domains. The vortex core exhibits a volume expansion, while the anti-vortex core is more compressive. We also discuss possible ways to control the electroelastic field, such as varying material constant and applying transverse electric field.

  9. Reflector modelling of small high leakage cores making use of multi-group nodal equivalence theory

    SciTech Connect

    Theron, S. A.; Reitsma, F.

    2012-07-01

    This research focuses on modelling reflectors in typical material testing reactors (MTRs). Equivalence theory is used to homogenise and collapse detailed transport solutions to generate equivalent nodal parameters and albedo boundary conditions for reflectors, for subsequent use in full core nodal diffusion codes. This approach to reflector modelling has been shown to be accurate for two-group large commercial light water reactor (LWR) analysis, but has not been investigated for MTRs. MTRs are smaller, with much larger leakage, environment sensitivity and multi-group spectrum dependencies than LWRs. This study aims to determine if this approach to reflector modelling is an accurate and plausible homogenisation technique for the modelling of small MTR cores. The successful implementation will result in simplified core models, better accuracy and improved efficiency of computer simulations. Codes used in this study include SCALE 6.1, OSCAR-4 and EQUIVA (the last two codes are developed and used at Necsa). The results show a five times reduction in calculational time for the proposed reduced reactor model compared to the traditional explicit model. The calculated equivalent parameters however show some sensitivity to the environment used to generate them. Differences in the results compared to the current explicit model, require more careful investigation including comparisons with a reference result, before its implementation can be recommended. (authors)

  10. Broad bounds on Earth's accretion and core formation constrained by geochemical models

    NASA Astrophysics Data System (ADS)

    Rudge, John F.; Kleine, Thorsten; Bourdon, Bernard

    2010-06-01

    The Earth formed through the accretion of numerous planetary embryos that were already differentiated into a metallic core and silicate mantle. Prevailing models of Earth's formation, constrained by the observed abundances of metal-loving siderophile elements in Earth's mantle, assume full metal-silicate equilibrium, whereby all memory of the planetary embryos' earlier differentiation is lost. Using the hafnium-tungsten (Hf-W) and uranium-lead (U-Pb) isotopic dating systems, these models suggest rapid accretion of Earth's main mass within about 10 million years (Myr) of the formation of the Solar System. Accretion terminated about 30 or 100 Myr after formation of the Solar System, owing to a giant impact that formed the Moon. Here we present geochemical models of Earth's accretion that preserve some memory of the embryos' original differentiation. These disequilibrium models allow some fraction of the embryos' metallic cores to directly enter the Earth's core, without equilibrating with Earth's mantle. We show that disequilibrium models are as compatible with the geochemical observations as equilibrium models, yet still provide bounds on Earth's accretion and core formation. We find that the Hf-W data mainly constrain the degree of equilibration rather than the timing, whereas the U-Pb data confirm that the end of accretion is consistent with recent estimates of the age of the Moon. Our results indicate that only 36% of the Earth's core must have formed in equilibrium with Earth's mantle. This low degree of equilibration is consistent with the siderophile element abundances in Earth's mantle.

  11. Development of high frequency spice models for ferrite core inductors and transformers

    SciTech Connect

    Muyshondt, G.P.; Portnoy, W.M. . Dept. of Electrical Engineering)

    1989-01-01

    In this work high frequency SPICE models were developed to simulate the hysteresis and saturation effects of toroidal shaped ferrite core inductors and transformers. The models include the nonlinear, multi-valued B-H characteristic of the core material, leakage flux, stray capacitances, and core losses. The saturation effects were modeled using two diode clamping arrangements in conjunction with nonlinear dependent sources. Two possible controlling schemes were developed for the saturation switch. One of the arrangements used the current flowing through a series RC branch to control the switch, while the other used a NAND gate. The NAND gate implementation of the switch proved to be simpler and the parameters associated with it were easier to determine from the measurements and the B-H characteristics of the material. Lumped parameters were used to simulate the parasitic effects. Techniques for measuring these parasitic are described. The models were verified using manganese-zinc ferrite-type toroidal cores and they have general applicability to all circuit analysis codes equivalent function blocks such as multipliers, adders, and logic components. 7 refs., 22 figs.

  12. Using an Agricultural Model to Establish Core Occupational Competencies for Secondary Vocational Programs.

    ERIC Educational Resources Information Center

    Waidelich, William D.; Hillison, John

    A model was developed for determining critical secondary vocational occupational competencies as rated by industry representatives. The method used to generate the information was an item analysis of competencies that industry experts identified as core competencies in the Ohio Competency Analysis Profile (OCAP) process. The study identified the…

  13. A Search for Core Values: Towards a Model Code of Ethics for Information Professionals.

    ERIC Educational Resources Information Center

    Koehler, Wallace C.; Pemberton, J. Michael

    2000-01-01

    Examines ethical codes and standards of professional practice promulgated by diverse associations of information professionals from varied national outlooks to identify a core set of ethical principles. Offers a model code based on a textual consensus of those ethical codes and standards examined. Three appendices provide information on…

  14. Development of high frequency spice models for ferrite core inductors and transformers

    NASA Astrophysics Data System (ADS)

    Muyshondt, G. Patrick; Portnoy, William M.

    In this work high frequency SPICE models were developed to simulate the hysteresis and saturation effects of toroidal shaped ferrite core inductors and transformers. The models include the nonlinear, multi-valued B-H characteristic of the core material, leakage flux, stray capacitances, and core losses. The saturation effects were modeled using two diode clamping arrangements in conjunction with nonlinear dependent sources. Two possible controlling schemes were developed for the saturation switch. One of the arrangements used the current flowing through a series RC branch to control the switch, while the other used a NAND gate. The NAND gate implementation of the switch proved to be simpler and the parameters associated with it were easier to determine from the measurements and the B-H characteristics of the material. Lumped parameters were used to simulate the parasitic effects. Techniques for measuring these effects are described. The models were verified using manganese-zinc ferrite-type toroidal cores and they have general applicability to all circuit analysis codes equivalent function blocks such as multipliers, adders, and logic components.

  15. Model Core Teaching Standards: A Resource for State Dialogue. (Draft for Public Comment)

    ERIC Educational Resources Information Center

    Council of Chief State School Officers, 2010

    2010-01-01

    With this document, the Council of Chief State School Officers (CCSSO) offers for public dialogue and comment a set of model core teaching standards that outline what teachers should know and be able to do to help all students reach the goal of being college- and career-ready in today's world. These standards are an update of the 1992 Interstate…

  16. Can Cognitive Writing Models Inform the Design of the Common Core State Standards?

    ERIC Educational Resources Information Center

    Hayes, John R.; Olinghouse, Natalie G.

    2015-01-01

    In this article, we compare the Common Core State Standards in Writing to the Hayes cognitive model of writing, adapted to describe the performance of young and developing writers. Based on the comparison, we propose the inclusion of standards for motivation, goal setting, writing strategies, and attention by writers to the text they have just…

  17. Resolution and Dynamical Core Dependence of Atmospheric River Frequency in Global Model Simulations

    SciTech Connect

    Hagos, Samson M.; Leung, Lai-Yung R.; Yang, Qing; Zhao, Chun; Lu, Jian

    2015-04-01

    This study examines the sensitivity of atmospheric river (AR) frequency simulated by a global model with different grid resolutions and dynamical cores. Analysis is performed on aquaplanet simulations using version 4 of Community Atmosphere Model (CAM4) at 240, 120, 60 and 30 km model resolutions each with the Model for Prediction Across Scales (MPAS) and High-Order Methods Modeling Environment (HOMME) dynamical cores. The frequency of AR events decreases with model resolution and the HOMME dynamical core produces more AR events than MPAS. Comparing the frequencies determined using absolute and percentile thresholds of large-scale conditions used to define an AR, model sensitivity is found to be related to the overall sensitivity of sub-tropical westerlies, atmospheric precipitable water content and profile and to a lesser extent on extra-tropical Rossby wave activity to model resolution and dynamical core. Real world simulations using MPAS at 120 km and 30 km grid resolutions also exhibit a decrease of AR frequency with increasing resolution over southern East Pacific, but there difference is smaller over northern East Pacific. This inter-hemispheric difference is related to the enhancement of convection in over the tropics with increased resolution. This anomalous convection sets off Rossby wave patterns that weaken the subtropical westerlies over southern East Pacific but have relatively little effect on those over northern East Pacific. In comparison to NCEP2 reanalysis, MPAS real world simulations are found to underestimate AR frequencies at both resolutions likely because of their climatologically drier sub-tropics and poleward shifted jets. This study highlights the important links between model climatology of large-scale conditions and extremes.

  18. Immunoglobulins from Animal Models of Motor Neuron Disease and from Human Amyotrophic Lateral Sclerosis Patients Passively Transfer Physiological Abnormalities to the Neuromuscular Junction

    NASA Astrophysics Data System (ADS)

    Apel, Stanley H.; Engelhardt, Jozsef I.; Garcia, Jesus; Stefani, Enrico

    1991-01-01

    Amyotrophic lateral sclerosis (ALS) is a devastating human disease of upper and lower motoneurons of unknown etiology. In support of the potential role of autoimmunity in ALS, two immune-mediated animal models of motoneuron disease have been developed that resemble ALS with respect to the loss of motoneurons, the presence of IgG within motoneurons and at the neuromuscular junction, and with respect to altered physiology of the motor nerve terminal. To provide direct evidence for the primary role of humoral immunity, passive transfer with immunoglobulins from the two animal models and human ALS was carried out. Mice injected with serum or immunoglobulins from the animal disease models and human ALS but not controls demonstrated IgG in motoneurons and at the neuromuscular junction. The mice also demonstrated an increase in miniature end-plate potential (mepp) frequency, with normal amplitude and time course and normal resting membrane potential, indicating an increased resting quantal release of acetylcholine from the nerve terminal. The ability to transfer motoneuron dysfunction with serum immunoglobulins provides evidence for autoimmune mechanisms in the pathogenesis of both the animal models and human ALS.

  19. Synthesis of Cu(core) Pt(shell) nanoparticles as model structures for core-shell electrocatalysts by direct platinum electrodeposition on copper.

    PubMed

    Kulp, Christian; Gillmeister, Konrad; Widdra, Wolf; Bron, Michael

    2013-04-15

    The synthesis of Cu(core)Pt(shell) model catalysts by the direct electrochemical deposition of Pt on Cu particles is presented. Cu particles with an average diameter of 200 nm have been deposited on glassy-carbon electrodes by double pulse electrodeposition from a copper sulfate solution. Subsequent deposition from a platinum nitrate solution under potential control allows for a high selectivity of the Pt deposition towards Cu. Using a combination of cyclic voltammetry, XPS and sputtering, the structure of the generated particles has been analyzed and their core-shell configuration proven. It is shown that the electrocatalytic activity for the oxygen reduction is similar to that of other PtCu catalyst systems. The synthesized structures could allow for the analysis of structure-activity relations of core-shell catalysts on the way to the simple and controlled synthesis of supported Cu(core)Pt(shell) nanoparticles as oxygen reduction catalysts.

  20. Does the Core Contain Potassium?: An Assessment of the Uncertainties in Thermal and Dynamo Evolution Models

    NASA Astrophysics Data System (ADS)

    Nimmo, F.

    2006-12-01

    The long-term thermal evolution of the core, and the history of the geodynamo, are determined by the rate at which heat is extracted from the core, and the presence of any heat sources within the core [1,2]. Radioactive potassium may provide one such heat source: mineral physics results [3,4] are permissive but not definitive; cosmochemical constraints are weak [5]; and geoneutrino detection [6] does not yet have the required resolution. Theoretical models [1-2,7-9] can help to address whether or not potassium is present in the core. Since the evolution of the CMB heat flux is hard to calculate, a better approach is to assume that the entropy available to power the geodynamo has remained constant over time, and to infer the resulting heat flux [2]. Unfortunately, several important parameters, notably core thermal conductivity and the entropy production rate required to sustain the geodynamo, are uncertain. I have carried out a suite of models using a wide range of parameter values based on published results. In the absence of potassium, an ancient inner core [10] and a continuously active geodynamo are only possible if 1) the dissipation generated by the dynamo is small, <0.25 TW 2) the CMB heat flux has stayed constant at ~ 4 TW for the whole of Earth history. The latter condition is in conflict with recent estimates of the present-day CMB heat flux of 10± 4 TW [11,12]. An ancient inner core, if correct, appears to require the presence of 100 ppm potassium in the core. [1] Buffett, GRL 29, 1566, 2002. [2] Labrosse, PEPI 140, 127-143, 2003. [3] Lee et al., GRL 31, L11603, 2004. [4] Gessmann and Wood, EPSL 200, 63-78, 2002. [5] Lassiter G3, Q11012, 2004. [6] Araki et al., Nature 436, 499-503, 2005. [7] Lister PEPI 140, 145-158, 2003. [8] Roberts et al., in Earth's Core and Lower Mantle, ed. Jones et al. [9] Nimmo et al. GJI 156, 363-376, 2004. [10] Brandon et al., EPSL 206, 411-426, 2003. [11] Hernlund et al., Nature 434, 882-886, 2005. [12] Zhong, JGR 111, B04409

  1. Ab Initio Modeling of the Herpesvirus VP26 Core Domain Assessed by CryoEM Density

    PubMed Central

    Baker, Matthew L; Jiang, Wen; Wedemeyer, William J; Rixon, Frazer J; Baker, David; Chiu, Wah

    2006-01-01

    Efforts in structural biology have targeted the systematic determination of all protein structures through experimental determination or modeling. In recent years, 3-D electron cryomicroscopy (cryoEM) has assumed an increasingly important role in determining the structures of these large macromolecular assemblies to intermediate resolutions (6–10 Å). While these structures provide a snapshot of the assembly and its components in well-defined functional states, the resolution limits the ability to build accurate structural models. In contrast, sequence-based modeling techniques are capable of producing relatively robust structural models for isolated proteins or domains. In this work, we developed and applied a hybrid modeling approach, utilizing cryoEM density and ab initio modeling to produce a structural model for the core domain of a herpesvirus structural protein, VP26. Specifically, this method, first tested on simulated data, utilizes the cryoEM density map as a geometrical constraint in identifying the most native-like models from a gallery of models generated by ab initio modeling. The resulting model for the core domain of VP26, based on the 8.5-Å resolution herpes simplex virus type 1 (HSV-1) capsid cryoEM structure and mutational data, exhibited a novel fold. Additionally, the core domain of VP26 appeared to have a complementary interface to the known upper-domain structure of VP5, its cognate binding partner. While this new model provides for a better understanding of the assembly and interactions of VP26 in HSV-1, the approach itself may have broader applications in modeling the components of large macromolecular assemblies. PMID:17069457

  2. NUMERICAL MODELING OF MULTI-WAVELENGTH SPECTRA OF M87 CORE EMISSION

    SciTech Connect

    Hilburn, G.; Liang, E. P.

    2012-02-10

    Spectral fits to M87 core data from radio to hard X-ray are generated via a specially selected software suite, comprised of the High-Accuracy Relativistic Magnetohydrodynamics GRMHD accretion disk model and a two-dimensional Monte Carlo radiation transport code. By determining appropriate parameter changes necessary to fit X-ray-quiescent and flaring behavior of M87's core, we assess the reasonableness of various flaring mechanisms. This shows that an accretion disk model of M87's core out to 28 GM/c{sup 2} can describe the inner emissions. High spin rates show GRMHD-driven polar outflow generation, without citing an external jet model. Our results favor accretion rate changes as the dominant mechanism of X-ray flux and index changes, with variations in density of approximately 20% necessary to scale between the average X-ray spectrum and flaring or quiescent spectra. The best-fit parameters are black hole spin a/M > 0.8 and maximum accretion flow density n {<=} 3 Multiplication-Sign 10{sup 7} cm{sup -3}, equivalent to horizon accretion rates between m-dot = M-dot / M-dot{sub Edd}{approx}2 Multiplication-Sign 10{sup -6} and 1 Multiplication-Sign 10{sup -5} (with M-dot{sub Edd} defined assuming a radiative efficiency {eta} = 0.1). These results demonstrate that the immediate surroundings of M87's core are appropriate to explain observed X-ray variability.

  3. Transport model based on three-dimensional cross-section generation for TRIGA core analysis

    NASA Astrophysics Data System (ADS)

    Kriangchaiporn, Nateekool

    This dissertation addresses the development of a reactor core physics model based on 3-D transport methodology utilizing 3-D multigroup fuel lattice cross-section generation and core calculation for PSBR. The proposed 3-D transport calculation scheme for reactor core simulations is based on the TORT code. The methodology includes development of algorithms for 2-D and 3-D cross-section generation. The fine- and broad-group structures for the TRIGA cross-section generation problems were developed based on the CPXSD (Contributon and Point-wise Cross-Section Driven) methodology that selects effective group structure. Along with the study of cross section generation, the parametric studies for SN calculations were performed to evaluate the impact of the spatial meshing, angular, and scattering order variables and to obtain the suitable values for cross-section collapsing of the TRIGA cell problem. The TRIGA core loading 2 is used to verify and validate the selected effective group structures. Finally, the 13 group structure was selected to use for core calculations. The results agree with continuous energy for eigenvalues and normalized pin power distribution. The Monte Carlo solutions are used as the references.

  4. Models for the binary complex of bacteriophage T4 gp59 helicase loading protein: gp32 single-stranded DNA-BINDING protein and ternary complex with pseudo-Y junction DNA.

    PubMed

    Hinerman, Jennifer M; Dignam, J David; Mueser, Timothy C

    2012-05-25

    Bacteriophage T4 gp59 helicase assembly protein (gp59) is required for loading of gp41 replicative helicase onto DNA protected by gp32 single-stranded DNA-binding protein. The gp59 protein recognizes branched DNA structures found at replication and recombination sites. Binding of gp32 protein (full-length and deletion constructs) to gp59 protein measured by isothermal titration calorimetry demonstrates that the gp32 protein C-terminal A-domain is essential for protein-protein interaction in the absence of DNA. Sedimentation velocity experiments with gp59 protein and gp32ΔB protein (an N-terminal B-domain deletion) show that these proteins are monomers but form a 1:1 complex with a dissociation constant comparable with that determined by isothermal titration calorimetry. Small angle x-ray scattering (SAXS) studies indicate that the gp59 protein is a prolate monomer, consistent with the crystal structure and hydrodynamic properties determined from sedimentation velocity experiments. SAXS experiments also demonstrate that gp32ΔB protein is a prolate monomer with an elongated A-domain protruding from the core. Fitting structures of gp59 protein and the gp32 core into the SAXS-derived molecular envelope supports a model for the gp59 protein-gp32ΔB protein complex. Our earlier work demonstrated that gp59 protein attracts full-length gp32 protein to pseudo-Y junctions. A model of the gp59 protein-DNA complex, modified to accommodate new SAXS data for the binary complex together with mutational analysis of gp59 protein, is presented in the accompanying article (Dolezal, D., Jones, C. E., Lai, X., Brister, J. R., Mueser, T. C., Nossal, N. G., and Hinton, D. M. (2012) J. Biol. Chem. 287, 18596-18607).

  5. Models for the Binary Complex of Bacteriophage T4 Gp59 Helicase Loading Protein. GP32 Single-Stranded DNA-Binding Protein and Ternary Complex with Pseudo-Y Junction DNA

    SciTech Connect

    Hinerman, Jennifer M.; Dignam, J. David; Mueser, Timothy C.

    2012-04-05

    The bacteriophage T4 gp59 helicase assembly protein (gp59) is required for loading of gp41 replicative helicase onto DNA protected by gp32 single-stranded DNA-binding protein. The gp59 protein recognizes branched DNA structures found at replication and recombination sites. Binding of gp32 protein (full-length and deletion constructs) to gp59 protein measured by isothermal titration calorimetry demonstrates that the gp32 protein C-terminal A-domain is essential for protein-protein interaction in the absence of DNA. Sedimentation velocity experiments with gp59 protein and gp32ΔB protein (an N-terminal B-domain deletion) show that these proteins are monomers but form a 1:1 complex with a dissociation constant comparable with that determined by isothermal titration calorimetry. Small angle x-ray scattering (SAXS) studies indicate that the gp59 protein is a prolate monomer, consistent with the crystal structure and hydrodynamic properties determined from sedimentation velocity experiments. SAXS experiments also demonstrate that gp32ΔB protein is a prolate monomer with an elongated A-domain protruding from the core. Moreover, fitting structures of gp59 protein and the gp32 core into the SAXS-derived molecular envelope supports a model for the gp59 protein-gp32ΔB protein complex. Our earlier work demonstrated that gp59 protein attracts full-length gp32 protein to pseudo-Y junctions. A model of the gp59 protein-DNA complex, modified to accommodate new SAXS data for the binary complex together with mutational analysis of gp59 protein, is presented in the accompanying article (Dolezal, D., Jones, C. E., Lai, X., Brister, J. R., Mueser, T. C., Nossal, N. G., and Hinton, D. M. (2012) J. Biol. Chem. 287, 18596–18607).

  6. Studies of mixed HEU-LEU-MTR cores using 3D models

    SciTech Connect

    Haenggi, P.; Lehmann, E.; Hammer, J.; Christen, R.

    1997-08-01

    Several different core loadings were assembled at the SAPHIR research reactor in Switzerland combining the available types of MTR-type fuel elements, consisting mainly of both HEU and LEU fuel. Bearing in mind the well known problems which can occur in such configurations (especially power peaking), investigations have been carried out for each new loading with a 2D neutron transport code (BOXER). The axial effects were approximated by a global buckling value and therefore the radial effects could be studied in considerably detail. Some of the results were reported at earlier RERTR meetings and were compared to those obtained by other methods and with experimental values. For the explicit study of the third dimension of the core, another code (SILWER), which has been developed in PSI for LWR power plant cores, has been selected. With the help of an adapted model for the MTR-core of SAPHIR, several important questions have been addressed. Among other aspects, the estimation of the axial contribution to the hot channel factors, the influence of the control rod position and of the Xe-poisoning on the power distribution were studied. Special attention was given to a core position where a new element was assumed placed near a empty, water filled position. The comparison of elements of low and high enrichments at this position was made in terms of the induced power peaks, with explicit consideration of axial effects. The program SILWER has proven to be applicable to MTR-cores for the investigation of axial effects. For routine use as for the support of reactor operation, this 3D code is a good supplement to the standard 2D model.

  7. Solute drag in polycrystalline materials: Derivation and numerical analysis of a variational model for the effect of solute on the motion of boundaries and junctions during coarsening

    NASA Astrophysics Data System (ADS)

    Wilson, Seth Robert

    A mathematical model that results in an expression for the local acceleration of a network of sharp interfaces interacting with an ambient solute field is proposed. This expression comprises a first-order differential equation for the local velocity that, given the appropriate initial conditions, may be used to predict the subsequent time evolution of the system, including non-steady state absorption and desorption of solute. Evolution equations for both interfaces and the junction of interfaces are derived by maximizing a functional approximating the rate at which the local Gibbs free energy density decreases, as a function of the local solute content and the instantaneous velocity. The model has been formulated in three dimensions, and non-equilibrium effects such as grain boundary diffusion, solute gradients, and time-dependant segregation are taken into account. As a consequence of this model, it is shown that both interfaces and the junctions between interfaces obey evolution equations that closely resemble Newton's second law. In particular, the concept of "thrust" in variable-mass systems is shown to have a direct analog in solute-interface interaction. Numerical analysis of the equations that result reveals that a double cusp catastrophe governs the behavior of the solute-interface system, for which trajectories that include hysteresis, slip-stick motion, and jerky motion are all conceivable. The geometry of the cusp catastrophe is quantified, and a number of relations between physical parameters and system behavior are consequently predicted.

  8. The treatment of mixing in core helium burning models - II. Constraints from cluster star counts

    NASA Astrophysics Data System (ADS)

    Constantino, Thomas; Campbell, Simon W.; Lattanzio, John C.; van Duijneveldt, Adam

    2016-03-01

    The treatment of convective boundaries during core helium burning is a fundamental problem in stellar evolution calculations. In the first paper of this series, we showed that new asteroseismic observations of these stars imply they have either very large convective cores or semiconvection/partially mixed zones that trap g modes. We probe this mixing by inferring the relative lifetimes of asymptotic giant branch (AGB) and horizontal branch (HB) from R2, the observed ratio of these stars in recent HST photometry of 48 Galactic globular clusters. Our new determinations of R2 are more self-consistent than those of previous studies and our overall calculation of R2 = 0.117 ± 0.005 is the most statistically robust now available. We also establish that the luminosity difference between the HB and the AGB clump is Δ log {L}_HB^AGB = 0.455 ± 0.012. Our results accord with earlier findings that standard models predict a lower R2 than is observed. We demonstrate that the dominant sources of uncertainty in models are the prescription for mixing and the stochastic effects that can result from its numerical treatment. The luminosity probability density functions that we derive from observations feature a sharp peak near the AGB clump. This constitutes a strong new argument against core breathing pulses, which broaden the predicted width of the peak. We conclude that the two mixing schemes that can match the asteroseismology are capable of matching globular cluster observations, but only if (i) core breathing pulses are avoided in models with a semiconvection/partially mixed zone, or (ii) that models with large convective cores have a particular depth of mixing beneath the Schwarzschild boundary during subsequent early-AGB `gravonuclear' convection.

  9. Sequential processing of hepatitis C virus core protein by host cell signal peptidase and signal peptide peptidase: a reassessment.

    PubMed

    Pène, V; Hernandez, C; Vauloup-Fellous, C; Garaud-Aunis, J; Rosenberg, A R

    2009-10-01

    Hepatitis C virus (HCV) core protein is believed to play critical roles in the virus morphogenesis and pathogenesis. In HCV polyprotein, core protein terminates with a signal peptide followed by E1 envelope protein. It has remained unclear whether cleavage by host cell signal peptidase (SP) at the core-E1 junction to generate the complete form of core protein, which is anchored in the endoplasmic reticulum membrane, is absolutely required for cleavage within the signal peptide by host cell signal peptide peptidase (SPP) to liberate the mature form of core protein, which is then free for trafficking to lipid droplets. In this study, the possible sources of disagreement in published reports have been examined, and we conclude that a product generated upon inhibition of SP-catalysed cleavage at the core-E1 junction in heterologous expression systems was incorrectly identified as mature core protein. Moreover, inhibition of this cleavage in the most relevant model of human hepatoma cells replicating a full-length HCV genome was shown to abolish interaction of core protein with lipid droplets and production of infectious progeny virus. These results firmly establish that SPP-catalysed liberation of mature core protein is absolutely dependent on prior cleavage by SP at the correct core-E1 site to generate the complete form of core protein, consistent with this obligatory order of processing playing a role in HCV infectious cycle. PMID:19281487

  10. Core and Crustal Geomagnetic Field Modeling Using Oersted and Magsat Data

    NASA Technical Reports Server (NTRS)

    Constable, Catherine; Parker, Robert L.

    1999-01-01

    This grant supplied funding to use Magsat and Oersted magnetic field data to model the magnetic field due to Earth's core and crust. Since the launch of Oersted was significantly delayed and no data were yet available by 5/31/99, the end of the funding period, it is perhaps fortunate that our primary goals were to develop and exploit innovative schemes for modeling the geomagnetic field, including new techniques for minimizing the influence of crustal magnetic fields in core field modelling. We were able to proceed with these efforts independently despite the lack of new observations. The work carried out under this grant has resulted in four peer-reviewed publications, with ongoing work contributing to a fifth in press paper. The research also provided significant contributions to education in PhD theses. Details of the results from this work can be found in the attached copies of the published work.

  11. Modeling Shallow Core-Level Transitions in the Reflectance Spectra of Gallium-Containing Semiconductors

    NASA Astrophysics Data System (ADS)

    Stoute, Nicholas; Aspnes, David

    2012-02-01

    The electronic structure of covalent materials is typically approached by band theory. However, shallow core level transitions may be better modeled by an atomic-scale approach. We investigate shallow d-core level reflectance spectra in terms of a local atomic-multiplet theory, a novel application of a theory typically used for higher-energy transitions on more ionic type material systems. We examine specifically structure in reflectance spectra of GaP, GaAs, GaSb, GaSe, and GaAs1-xPx due to transitions that originate from Ga3d core levels and occur in the 20 to 25 eV range. We model these spectra as a Ga^+3 closed-shell ion whose transitions are influenced by perturbations on 3d hole-4p electron final states. These are specifically spin-orbit effects on the hole and electron, and a crystal-field effect on the hole, attributed to surrounding bond charges and positive ligand anions. Empirical radial-strength parameters were obtained by least-squares fitting. General trends with respect to anion electronegativity are consistent with expectations. In addition to the spin-orbit interaction, crystal-field effects play a significant role in breaking the degeneracy of the d levels, and consequently are necessary to understand shallow 3d core level spectra.

  12. Local Frame Junction Trees in SLAM

    NASA Astrophysics Data System (ADS)

    Kuehnel, Frank O.

    2005-11-01

    Junction trees (JT) is a general purpose tool for exact inference on graphical models. Many of the existing algorithms for building junction trees require a fixed static graphical model. The construction process is not unique, finding the one with the best computational structure (smallest clique size) is also a hard problem. For large scale inference problems, such as Geo-referencing using triangular geodetic networks or equivalent, the simultaneous localization and mapping (SLAM) problem in robotics pose some challenges to junction tree applications. Incremental junction tree techniques for dynamic graphical models prescribe heuristic methods for growing the tree structure, and are applicable to large scale graphical models. Of concern are the proliferative widening of the tree, which makes message passing expensive. In the context of SLAM we present a new apporach that exploits the local frame dependence of novel observation variables.

  13. Reprogramming of cell junction modules during stepwise epithelial to mesenchymal transition and accumulation of malignant features in vitro in a prostate cell model

    SciTech Connect

    Ke, Xi-song; Li, Wen-cheng; Hovland, Randi; Qu, Yi; Liu, Run-hui; McCormack, Emmet; Thorsen, Frits; Olsen, Jan Roger; Molven, Anders; Kogan-Sakin, Ira; Rotter, Varda; Akslen, Lars A.; Oyan, Anne Margrete; Kalland, Karl-Henning

    2011-01-15

    Epithelial to mesenchymal transition (EMT) is pivotal in tumor metastasis. Our previous work reported an EMT model based on primary prostate epithelial cells (EP156T) which gave rise to cells with mesenchymal phenotype (EPT1) without malignant transformation. To promote prostate cell transformation, cells were maintained in saturation density cultures to select for cells overriding quiescence. Foci formed repeatedly following around 8 weeks in confluent EPT1 monolayers. Only later passage EPT1, but not EP156T cells of any passage, could form foci. Cells isolated from the foci were named EPT2 and formed robust colonies in soft agar, a malignant feature present neither in EP156T nor in EPT1 cells. EPT2 cells showed additional malignant traits in vitro, including higher ability to proliferate following confluence, higher resistance to apoptosis and lower dependence on exogenous growth factors than EP156T and EPT1 cells. Microarray profiling identified gene sets, many of which belong to cell junction modules, that changed expression from EP156T to EPT1 cells and continued to change from EPT1 to EPT2 cells. Our findings provide a novel stepwise cell culture model in which EMT emerges independently of transformation and is associated with subsequent accumulation of malignant features in prostate cells. Reprogramming of cell junction modules is involved in both steps.

  14. A statistical model of the human core-temperature circadian rhythm

    NASA Technical Reports Server (NTRS)

    Brown, E. N.; Choe, Y.; Luithardt, H.; Czeisler, C. A.

    2000-01-01

    We formulate a statistical model of the human core-temperature circadian rhythm in which the circadian signal is modeled as a van der Pol oscillator, the thermoregulatory response is represented as a first-order autoregressive process, and the evoked effect of activity is modeled with a function specific for each circadian protocol. The new model directly links differential equation-based simulation models and harmonic regression analysis methods and permits statistical analysis of both static and dynamical properties of the circadian pacemaker from experimental data. We estimate the model parameters by using numerically efficient maximum likelihood algorithms and analyze human core-temperature data from forced desynchrony, free-run, and constant-routine protocols. By representing explicitly the dynamical effects of ambient light input to the human circadian pacemaker, the new model can estimate with high precision the correct intrinsic period of this oscillator ( approximately 24 h) from both free-run and forced desynchrony studies. Although the van der Pol model approximates well the dynamical features of the circadian pacemaker, the optimal dynamical model of the human biological clock may have a harmonic structure different from that of the van der Pol oscillator.

  15. Ion bipolar junction transistors

    PubMed Central

    Tybrandt, Klas; Larsson, Karin C.; Richter-Dahlfors, Agneta; Berggren, Magnus

    2010-01-01

    Dynamic control of chemical microenvironments is essential for continued development in numerous fields of life sciences. Such control could be achieved with active chemical circuits for delivery of ions and biomolecules. As the basis for such circuitry, we report a solid-state ion bipolar junction transistor (IBJT) based on conducting polymers and thin films of anion- and cation-selective membranes. The IBJT is the ionic analogue to the conventional semiconductor BJT and is manufactured using standard microfabrication techniques. Transistor characteristics along with a model describing the principle of operation, in which an anionic base current amplifies a cationic collector current, are presented. By employing the IBJT as a bioelectronic circuit element for delivery of the neurotransmitter acetylcholine, its efficacy in modulating neuronal cell signaling is demonstrated. PMID:20479274

  16. Simulating High Flux Isotope Reactor Core Thermal-Hydraulics via Interdimensional Model Coupling

    SciTech Connect

    Travis, Adam R

    2014-05-01

    A coupled interdimensional model is presented for the simulation of the thermal-hydraulic characteristics of the High Flux Isotope Reactor core at Oak Ridge National Laboratory. The model consists of two domains a solid involute fuel plate and the surrounding liquid coolant channel. The fuel plate is modeled explicitly in three-dimensions. The coolant channel is approximated as a twodimensional slice oriented perpendicular to the fuel plate s surface. The two dimensionally-inconsistent domains are linked to one another via interdimensional model coupling mechanisms. The coupled model is presented as a simplified alternative to a fully explicit, fully three-dimensional model. Involute geometries were constructed in SolidWorks. Derivations of the involute construction equations are presented. Geometries were then imported into COMSOL Multiphysics for simulation and modeling. Both models are described in detail so as to highlight their respective attributes in the 3D model, the pursuit of an accurate, reliable, and complete solution; in the coupled model, the intent to simplify the modeling domain as much as possible without affecting significant alterations to the solution. The coupled model was created with the goal of permitting larger portions of the reactor core to be modeled at once without a significant sacrifice to solution integrity. As such, particular care is given to validating incorporated model simplifications. To the greatest extent possible, the decrease in solution time as well as computational cost are quantified versus the effects such gains have on the solution quality. A variant of the coupled model which sufficiently balances these three solution characteristics is presented alongside the more comprehensive 3D model for comparison and validation.

  17. Small-scale disturbances in the stratigraphy of ice cores: observations and numerical model simulations

    NASA Astrophysics Data System (ADS)

    Jansen, Daniela; LLorens, Maria-Gema; Westhoff, Julien; Steinbach, Florian; Kipfstuhl, Sepp; Bons, Paul D.; Griera, Albert; Eichler, Jan; Weikusat, Ilka

    2016-04-01

    Visual stratigraphy of ice cores from Greenland as well as Antarctica revealed folding on a cm scale, with fold amplitudes varying from less than 1 cm to a few decimetres. Stratigraphy bands are visualized by an indirect light source scattering on surfaces inside the ice, mainly particles and air bubbles / hydrates. Due to their potential influence on the integrity of the climatic record, folds have been subject to modelling studies, however, the initial formation of the disturbances is not fully understood. In this study we present a detailed analysis of the visible folds from the NEEM ice core from Greenland and the EDML ice core from Antarctica, discuss their characteristics and frequency and present examples of typical fold structures. We also analyse the structures with regard to the deformation boundary conditions under which they formed. In case of the NEEM core the structures evolve from gentle waves at about 1500 m to overturned z-folds with increasing depth. Occasionally, the folding causes significant thickening of layers. Their similar-fold shape indicates that they are passive features and are probably not initiated by rheology differences between alternating layers. Layering is heavily disturbed and tracing of single layers is no longer possible below a depth of 2160 m. C-axes orientation distributions for the corresponding core sections were analysed where available in addition to visual stratigraphy. The data show axial-plane parallel strings of grains with c-axis orientations that deviate from that of the matrix, which shows a single-maximum fabric at the depth where the folding occurs. In case of the EDML ice cores the folding starts at a depth of about 1700 m and show very similar characteristics as found in the NEEM core. Numerical modelling of crystal viscoplasticity deformation and dynamic recrystallisation was used to improve the understanding of the formation of the observed structures during deformation. The modelling reproduces the

  18. Preliminary design report for SCDAP/RELAP5 lower core plate model

    SciTech Connect

    Coryell, E.W.; Griffin, F.P.

    1998-07-01

    The SCDAP/RELAP5 computer code is a best-estimate analysis tool for performing nuclear reactor severe accident simulations. Under primary sponsorship of the US Nuclear Regulatory Commission (NRC), Idaho National Engineering and Environmental Laboratory (INEEL) is responsible for overall maintenance of this code and for improvements for pressurized water reactor (PWR) applications. Since 1991, Oak Ridge National Laboratory (ORNL) has been improving SCDAP/RELAP5 for boiling water reactor (BWR) applications. The RELAP5 portion of the code performs the thermal-hydraulic calculations for both normal and severe accident conditions. The structures within the reactor vessel and coolant system can be represented with either RELAP5 heat structures or SCDAP/RELAP5 severe accident structures. The RELAP5 heat structures are limited to normal operating conditions (i.e., no structural oxidation, melting, or relocation), while the SCDAP portion of the code is capable of representing structural degradation and core damage progression that can occur under severe accident conditions. DCDAP/RELAP5 currently assumes that molten material which leaves the core region falls into the lower vessel head without interaction with structural materials. The objective of this design report is to describe the modifications required for SCDAP/RELAP5 to treat the thermal response of the structures in the core plate region as molten material relocates downward from the core, through the core plate region, and into the lower plenum. This has been a joint task between INEEL and ORNL, with INEEL focusing on PWR-specific design, and ORNL focusing upon the BWR-specific aspects. Chapter 2 describes the structures in the core plate region that must be represented by the proposed model. Chapter 3 presents the available information about the damage progression that is anticipated to occur in the core plate region during a severe accident, including typical SCDAP/RELAP5 simulation results. Chapter 4 provides a

  19. The Cusp/Core problem: supernovae feedback versus the baryonic clumps and dynamical friction model

    NASA Astrophysics Data System (ADS)

    Del Popolo, A.; Pace, F.

    2016-05-01

    In the present paper, we compare the predictions of two well known mechanisms considered able to solve the cusp/core problem (a. supernova feedback; b. baryonic clumps-DM interaction) by comparing their theoretical predictions to recent observations of the inner slopes of galaxies with masses ranging from dSphs to normal spirals. We compare the α-V_{rot} and the α-M_{ast} relationships, predicted by the two models with high resolution data coming from Adams et al. (Astrophys. J. 789, 63, 2014), Simon et al. (Astrophys. J. 621, 757, 2005), LITTLE THINGS (Oh et al. in Astron. J. 149, 180, 2015), THINGS dwarves (Oh et al. in Astron. J. 141, 193, 2011a; Oh et al. in Astron. J. 142, 224, 2011b), THINGS spirals (Oh et al. in Astron. J. 149, 180, 2015), Sculptor, Fornax and the Milky Way. The comparison of the theoretical predictions with the complete set of data shows that the two models perform similarly, while when we restrict the analysis to a smaller subsample of higher quality, we show that the method presented in this paper (baryonic clumps-DM interaction) performs better than the one based on supernova feedback. We also show that, contrarily to the first model prediction, dSphs of small mass could have cored profiles. This means that observations of cored inner profiles in dSphs having a stellar mass <106 M_{⊙} not necessarily imply problems for the ΛCDM model.

  20. Monte Carlo Error Analysis Applied to Core Formation: The Single-stage Model Revived

    NASA Astrophysics Data System (ADS)

    Cottrell, E.; Walter, M. J.

    2009-12-01

    The last decade has witnessed an explosion of studies that scrutinize whether or not the siderophile element budget of the modern mantle can plausibly be explained by metal-silicate equilibration in a deep magma ocean during core formation. The single-stage equilibrium scenario is seductive because experiments that equilibrate metal and silicate can then serve as a proxy for the early earth, and the physical and chemical conditions of core formation can be identified. Recently, models have become more complex as they try to accommodate the proliferation of element partitioning data sets, each of which sets its own limits on the pressure, temperature, and chemistry of equilibration. The ability of single stage models to explain mantle chemistry has subsequently been challenged, resulting in the development of complex multi-stage core formation models. Here we show that the extent to which extant partitioning data are consistent with single-stage core formation depends heavily upon (1) the assumptions made when regressing experimental partitioning data (2) the certainty with which regression coefficients are known and (3) the certainty with which the core/mantle concentration ratios of the siderophile elements are known. We introduce a Monte Carlo algorithm coded in MATLAB that samples parameter space in pressure and oxygen fugacity for a given mantle composition (nbo/t) and liquidus, and returns the number of equilibrium single-stage liquidus “solutions” that are permissible, taking into account the uncertainty in regression parameters and range of acceptable core/mantle ratios. Here we explore the consequences of regression parameter uncertainty and the impact of regression construction on model outcomes. We find that the form of the partition coefficient (Kd with enforced valence state, or D) and the handling of the temperature effect (based on 1-atm free energy data or high P-T experimental observations) critically affects model outcomes. We consider the most

  1. Zipper and freeway shear zone junctions

    NASA Astrophysics Data System (ADS)

    Passchier, Cees; Platt, John

    2016-04-01

    Ductile shear zones are usually presented as isolated planar high-strain domains in a less deformed wall rock, characterised by shear sense indicators such as characteristic deflected foliation traces. Many shear zones, however, form branched systems and if movement on such branches is contemporaneous, the resulting geometry can be complicated and lead to unusual fabric geometries in the wall rock. For Y-shaped shear zone junctions with three simultaneously operating branches, and with slip directions at a high angle to the branch line, eight basic types of shear zone triple junctions are possible, divided into three groups. The simplest type, called freeway junctions, have similar shear sense on all three branches. If shear sense is different on the three branches, this can lead to space problems. Some of these junctions have shear zone branches that join to form a single branch, named zipper junctions, or a single shear zone which splits to form two, known as wedge junctions. Closing zipper junctions are most unusual, since they form a non-active high-strain zone with opposite deflection of foliations. Shear zipper and shear wedge junctions have two shear zones with similar shear sense, and one with the opposite sense. All categories of shear zone junctions show characteristic flow patterns in the shear zone and its wall rock. Shear zone junctions with slip directions normal to the branch line can easily be studied, since ideal sections of shear sense indicators lie in the plane normal to the shear zone branches and the branch line. Expanding the model to allow slip oblique and parallel to the branch line in a full 3D setting gives rise to a large number of geometries in three main groups. Slip directions can be parallel on all branches but oblique to the branch line: two slip directions can be parallel and a third oblique, or all three branches can have slip in different directions. Such more complex shear zone junctions cannot be studied to advantage in a

  2. A Common Core for Active Conceptual Modeling for Learning from Surprises

    NASA Astrophysics Data System (ADS)

    Liddle, Stephen W.; Embley, David W.

    The new field of active conceptual modeling for learning from surprises (ACM-L) may be helpful in preserving life, protecting property, and improving quality of life. The conceptual modeling community has developed sound theory and practices for conceptual modeling that, if properly applied, could help analysts model and predict more accurately. In particular, we need to associate more semantics with links, and we need fully reified high-level objects and relationships that have a clear, formal underlying semantics that follows a natural, ontological approach. We also need to capture more dynamic aspects in our conceptual models to more accurately model complex, dynamic systems. These concepts already exist, and the theory is well developed; what remains is to link them with the ideas needed to predict system evolution, thus enabling risk assessment and response planning. No single researcher or research group will be able to achieve this ambitious vision alone. As a starting point, we recommend that the nascent ACM-L community agree on a common core model that supports all aspects—static and dynamic—needed for active conceptual modeling in support of learning from surprises. A common core will more likely gain the traction needed to sustain the extended ACM-L research effort that will yield the advertised benefits of learning from surprises.

  3. Coherent network analysis of gravitational waves from three-dimensional core-collapse supernova models

    NASA Astrophysics Data System (ADS)

    Hayama, Kazuhiro; Kuroda, Takami; Kotake, Kei; Takiwaki, Tomoya

    2015-12-01

    Using predictions from three-dimensional (3D) hydrodynamics simulations of core-collapse supernovae (CCSNe), we present a coherent network analysis for the detection, reconstruction, and source localization of the gravitational-wave (GW) signals. We use the RIDGE pipeline for the analysis, in which the network of LIGO Hanford, LIGO Livingston, VIRGO, and KAGRA is considered. By combining with a GW spectrogram analysis, we show that several important hydrodynamics features in the original waveforms persist in the waveforms of the reconstructed signals. The characteristic excess in the spectrograms originates not only from the rotating core collapse, bounce, and subsequent ringdown of the proto-neutron star (PNS) as previously identified, but also from the formation of magnetohydrodynamics jets and nonaxisymmetric instabilities in the vicinity of the PNS. Regarding the GW signals emitted near the rotating core bounce, the horizon distance extends up to ˜18 kpc for the most rapidly rotating 3D model in this work. Following the rotating core bounce, the dominant source of the GW emission shifts to the nonaxisymmetric instabilities. The horizon distances extend maximally up to ˜40 kpc seen from the spin axis. With an increasing number of 3D models trending towards explosion recently, our results suggest that in addition to the best-studied GW signals due to rotating core collapse and bounce, the time is ripe to consider how we can do science from GWs of CCSNe much more seriously than before. In particular, the quasiperiodic signals due to the nonaxisymmetric instabilities and the detectability deserves further investigation to elucidate the inner workings of the rapidly rotating CCSNe.

  4. Beyond the No Core Shell Model: Extending the NCSM to Heavier Nuclei

    SciTech Connect

    Barrett, Bruce R.

    2011-05-06

    The No Core Shell Model (NCSM) is an ab initio method for calculating the properties of light nuclei, up to about A = 20, in which all A nucleons are treated as being active. It is difficult to go to larger A values due to the rapid grow of the basis spaces required in order to obtain converged results. In this presentation we briefly discuss three new techniques for extending the NCSM to heavier mass nuclei.

  5. Modeling heterogeneous polymer-grafted nanoparticle networks having biomimetic core-shell structure

    NASA Astrophysics Data System (ADS)

    Mbanga, Badel L.; Yashin, Victor V.; Holten-Andersen, Niels; Balazs, Anna C.

    Inspired by the remarkable mechanical properties of such biological structures as mussel adhesive fibers, we use 3D computational modeling to study the behavior of heterogeneous polymer-grafted nanoparticle (PGN) networks under tensile deformation. The building block of a PGN network is a nanoparticle with grafted polymer chains whose free ends' reactive groups can form both permanent and labile bonds with the end chains on the nearby particles. The tunable behavior of cross-linked PGN networks makes them excellent candidates for designing novel materials with enhanced mechanical properties. Here, we consider the PGN networks having the core-shell structures, in which the type and strength of the inter-particle bonds in the outer shell differ from those in the core. Using the computer simulations, we obtain and compare the ultimate tensile properties (strength, toughness, ductility) and the strain recovery properties for the uniform samples and various core-shell structures. We demonstrate that the core-shell structures could be designed to obtain highly resilient self-healing materials

  6. GALFIT-CORSAIR: Implementing the Core-Sérsic Model Into GALFIT

    NASA Astrophysics Data System (ADS)

    Bonfini, Paolo

    2014-10-01

    We introduce GALFIT-CORSAIR: a publicly available, fully retro-compatible modification of the two-dimensional (2D) fitting software GALFIT (ver. 3), which adds an implementation of the core-Sérsic model. We demonstrate the software by fitting the images of NGC 5557 and NGC 5813, which have been previously identified as core-Sérsic galaxies by their one-dimensional radial light profiles. These two examples are representative of different dust obscuration conditions, and of bulge/disk decomposition. To perform the analysis, we obtained deep Hubble Legacy Archive (HLA) mosaics in the F555W filter (~V band). We successfully reproduce the results of the previous one-dimensional analysis, modulo the intrinsic differences between the one-dimensional and the 2D fitting procedures. The code and the analysis procedure described here have been developed for the first coherent 2D analysis of a sample of core-Sérsic galaxies, which will be presented in a forthcoming paper. As the 2D analysis provides better constraining on multicomponent fitting, and is fully seeing-corrected, it will yield complementary constraints on the missing mass in depleted galaxy cores.

  7. A two-dimensional approach to modelling the short timescale zonal flow in Earth's core

    NASA Astrophysics Data System (ADS)

    More, C.; Dumberry, M.

    2015-12-01

    Reconstructions of flow in Earth's outer core based on surface magnetic data predict mean zonal accelerations on several timescales. Since accelerations in the core couple to the angular momentum of the mantle, their existence has been confirmed by length-of-day observations. Recent studies suggest that free modes of torsional oscillations are responsible for relatively weak signals with a 5-6 year period. The mechanisms responsible for stronger decadal signals are less well understood.To address the problem, we construct a quasi-geostrophic model of magnetoconvection, with thermally-driven flows perturbing a steady, imposed background magnetic field. This approach is justified by the Taylor-Proudman theorem, in which velocities in a rapidly rotating system vary little parallel to the rotational axis. Using only two dimensions allows a much more rapid exploration of parameter space than traditional three-dimensional approaches.Our model is capable of producing mean zonal accelerations similar to those predicted by the geomagnetic reconstructions of Earth. In particular, we see a clear separation in period between the free modes (short) and forced modes (long) of torsional oscillations. We then systematically run the model with a variety of parameters, attempting to extrapolate our results to the conditions found in Earth's core.

  8. Failure Predictions for VHTR Core Components using a Probabilistic Contiuum Damage Mechanics Model

    SciTech Connect

    Fok, Alex

    2013-10-30

    The proposed work addresses the key research need for the development of constitutive models and overall failure models for graphite and high temperature structural materials, with the long-term goal being to maximize the design life of the Next Generation Nuclear Plant (NGNP). To this end, the capability of a Continuum Damage Mechanics (CDM) model, which has been used successfully for modeling fracture of virgin graphite, will be extended as a predictive and design tool for the core components of the very high- temperature reactor (VHTR). Specifically, irradiation and environmental effects pertinent to the VHTR will be incorporated into the model to allow fracture of graphite and ceramic components under in-reactor conditions to be modeled explicitly using the finite element method. The model uses a combined stress-based and fracture mechanics-based failure criterion, so it can simulate both the initiation and propagation of cracks. Modern imaging techniques, such as x-ray computed tomography and digital image correlation, will be used during material testing to help define the baseline material damage parameters. Monte Carlo analysis will be performed to address inherent variations in material properties, the aim being to reduce the arbitrariness and uncertainties associated with the current statistical approach. The results can potentially contribute to the current development of American Society of Mechanical Engineers (ASME) codes for the design and construction of VHTR core components.

  9. Core-envelope and regular models in Einstein-Maxwell fields

    NASA Astrophysics Data System (ADS)

    Hansraj, Sudan; Maharaj, Sunil Dutt; Mlaba, Sphakamiso

    2016-01-01

    New classes of exact solutions which could serve as sources for the Reissner-Nordstrom metric representing the exterior gravitational field of an isolated charged sphere are derived. Firstly, we sacrifice the requirement that the stellar centre is free of a singularity and then obtain a core-envelope model. The charged fluid envelope is matched suitably to the neutral core and the vacuum exterior solution. Next we investigate models of charged stars that are regular at the stellar centre. The Einstein-Maxwell system of partial differential equations is reduced to the study of a single first-order differential equation in which two of the matter or geometrical variables must be specified at the outset. In each case mentioned above, new exact models are found by choosing functional forms for the electric field intensity and one of the gravitational potentials. A Riccati equation is then solved to obtain the remaining potential. The charged spherical shell model as well as the non-singular models are shown to display necessary qualitative features that are demanded for physical acceptability. It is shown that the regular model has a vanishing pressure-free hypersurface. The density and pressure profiles are positive and monotonically decreasing outwards from the centre of the sphere for a chosen set of parameters. The weak strong and dominant energy conditions are also satisfied. A drawback of the model is that the causality criterion is not satisfied within the fluid boundary.

  10. The soundproof dynamical core for COSMO model: representation of convective flows.

    NASA Astrophysics Data System (ADS)

    Wójcik, Damian; Piotrowski, Zbigniew; Rosa, Bogdan; Ziemiański, Michał

    2014-05-01

    Research conducted at Polish Institute of Meteorology and Water Management, National Research Institute, in collaboration with Consortium for Small Scale Modeling (COSMO) are aimed at developing new conservative dynamical core for next generation operational weather prediction model. As the result, a new prototype model was developed with dynamical core based on anelastic set of equation and numerics adopted from the EULAG model. An employment of EULAG allowed to profit from its desirable conservative properties and numerical robustness confirmed in number of benchmark tests and widely documented in scientific literature. The hybrid model consists of EULAG dynamical core implemented into the software environment of the operational COSMO model and basic COSMO physical parameterizations involving turbulence, friction, radiation, moist processes and surface fluxes (COSMO-EULAG). The tool is capable to compute weather forecast in mountainous area for the horizontal resolution of 0.28 km and with slopes reaching 60 degrees of inclination. The presentation is focused on two current research topics. First, the model and especially its dynamics-physics coupling is examined within idealized framework for representation of convective flows. The study is based on two complementary convection benchmarks of Weisman and Klemp (Mon. Wea. Rev. 110:504, 1982) and Grabowski et al. (Q. J. R. Meteorol. Soc. 132:317, 2006). While the first experiment can be used to examine a life cycle of a single convective storm structure in COSMO-EULAG model, the second experiment allows to evaluate the model representation of statistical properties of daytime convective development over land, involving convection initiation as well as is transition into a deep phase. The study involves also the comparison of COSMO-EULAG results with results of standard compressible COSMO-Runge-Kutta model to test the suitability of the anelastic dynamical core for operational mesoscale high-resolution NWP. Next

  11. Decreasing Cx36 Gap Junction Coupling Compensates for Overactive KATP Channels to Restore Insulin Secretion and Prevent Hyperglycemia in a Mouse Model of Neonatal Diabetes

    PubMed Central

    Nguyen, Linda M.; Pozzoli, Marina; Hraha, Thomas H.; Benninger, Richard K.P.

    2014-01-01

    Mutations to the ATP-sensitive K+ channel (KATP channel) that reduce the sensitivity of ATP inhibition cause neonatal diabetes mellitus via suppression of β-cell glucose-stimulated free calcium activity ([Ca2+]i) and insulin secretion. Connexin-36 (Cx36) gap junctions also regulate islet electrical activity; upon knockout of Cx36, β-cells show [Ca2+]i elevations at basal glucose. We hypothesized that in the presence of overactive ATP-insensitive KATP channels, a reduction in Cx36 would allow elevations in glucose-stimulated [Ca2+]i and insulin secretion to improve glucose homeostasis. To test this, we introduced a genetic knockout of Cx36 into mice that express ATP-insensitive KATP channels and measured glucose homeostasis and islet metabolic, electrical, and insulin secretion responses. In the normal presence of Cx36, after expression of ATP-insensitive KATP channels, blood glucose levels rapidly rose to >500 mg/dL. Islets from these mice showed reduced glucose-stimulated [Ca2+]i and no insulin secretion. In mice lacking Cx36 after expression of ATP-insensitive KATP channels, normal glucose levels were maintained. Islets from these mice had near-normal glucose-stimulated [Ca2+]i and insulin secretion. We therefore demonstrate a novel mechanism by which islet function can be recovered in a monogenic model of diabetes. A reduction of gap junction coupling allows sufficient glucose-stimulated [Ca2+]i and insulin secretion to prevent the emergence of diabetes. PMID:24458355

  12. Plasticity of single-atom Pb junctions

    NASA Astrophysics Data System (ADS)

    Müller, M.; Salgado, C.; Néel, N.; Palacios, J. J.; Kröger, J.

    2016-06-01

    A low-temperature scanning tunneling microscope was used to fabricate atomic contacts on Pb(111). Conductance characteristics of the junctions were simultaneously recorded with forming and subsequent breaking of the contacts. A pronounced hysteresis effect in conductance traces was observed from junctions comprising the clean Pb(111) surface. The hysteretic behavior was less profound in contacts to single Pb atoms adsorbed to Pb(111). Density-functional calculations reproduced the experimental results by performing a full ab initio modeling of plastic junction deformations. A comprehensive description of the experimental findings was achieved by considering different atomic tip apex geometries.

  13. Competitive repetition suppression (CoRe) clustering: a biologically inspired learning model with application to robust clustering.

    PubMed

    Bacciu, Davide; Starita, Antonina

    2008-11-01

    Determining a compact neural coding for a set of input stimuli is an issue that encompasses several biological memory mechanisms as well as various artificial neural network models. In particular, establishing the optimal network structure is still an open problem when dealing with unsupervised learning models. In this paper, we introduce a novel learning algorithm, named competitive repetition-suppression (CoRe) learning, inspired by a cortical memory mechanism called repetition suppression (RS). We show how such a mechanism is used, at various levels of the cerebral cortex, to generate compact neural representations of the visual stimuli. From the general CoRe learning model, we derive a clustering algorithm, named CoRe clustering, that can automatically estimate the unknown cluster number from the data without using a priori information concerning the input distribution. We illustrate how CoRe clustering, besides its biological plausibility, posses strong theoretical properties in terms of robustness to noise and outliers, and we provide an error function describing CoRe learning dynamics. Such a description is used to analyze CoRe relationships with the state-of-the art clustering models and to highlight CoRe similitude with rival penalized competitive learning (RPCL), showing how CoRe extends such a model by strengthening the rival penalization estimation by means of loss functions from robust statistics.

  14. A spectral transform dynamical core option within the Community Atmosphere Model (CAM4)

    SciTech Connect

    Evans, Katherine J; Mahajan, Salil; Branstetter, Marcia L; McClean, Julie L.; Caron, Julie M.; Maltrud, Matthew E.; Hack, James J; Bader, David C; Neale, Rich

    2014-01-01

    A spectral transform dynamical core with an 85 spectral truncation resolution (T85) within the Community Atmosphere Model (CAM), version 4, is evaluated within the recently released Community Earth System Model, version 1.0 (CESM) global climate model. The spectral dynamical core option provides a well-known base within the climate model community from which to assess climate behavior and statistics, and its relative computational efficiency for smaller computing platforms allows it to be extended to perform climate length simulations using high-resolution configurations in the near term. To establish the characteristics of the CAM4 T85, an ensemble of simulations covering the present day observational period using forced sea surface temperatures and prescribed sea-ice extent are evaluated. Overall, the T85 ensemble attributes and biases are similar to a companion ensemble of simulations using the one degree finite volume (FV1) dynamical core, relative to observed and model derived datasets. Notable improvements with T85 compared to FV1 include the representation of wintertime Arctic sea level pressure and summer precipitation over the Western Indian subcontinent. The mean and spatial patterns of the land surface temperature trends over the AMIP period are generally well simulated with the T85 ensemble relative to observations, however the model is not able to capture the extent nor magnitude of changes in temperature extremes over the boreal summer, where the changes are most dramatic. Biases in the wintertime Arctic surface temperature and annual mean surface stress fields persist with T85 as with the CAM3 version of T85.

  15. Three-junction solar cell

    DOEpatents

    Ludowise, Michael J.

    1986-01-01

    A photovoltaic solar cell is formed in a monolithic semiconductor. The cell contains three junctions. In sequence from the light-entering face, the junctions have a high, a medium, and a low energy gap. The lower junctions are connected in series by one or more metallic members connecting the top of the lower junction through apertures to the bottom of the middle junction. The upper junction is connected in voltage opposition to the lower and middle junctions by second metallic electrodes deposited in holes 60 through the upper junction. The second electrodes are connected to an external terminal.

  16. Electroelastic fields in artificially created vortex cores in epitaxial BiFeO3 thin films

    SciTech Connect

    Winchester, Ben; Wisinger, Nina Balke; Cheng, X. X.; Morozovska, A. N.; Kalinin, Sergei; Chen, L. Q.

    2015-08-03

    Here we employ phase-field modeling to explore the elastic properties of artificially created 1-D domain walls in (001)p-oriented BiFeO3 thin films, composed of a junction of the four polarization variants, all with the same out-of-plane polarization. It was found that these junctions exhibit peculiarly high electroelastic fields induced by the neighboring ferroelastic/ferroelectric domains. The vortex core exhibits a volume expansion, while the anti-vortex core is more compressive. We also discuss possible ways to control the electroelastic field, such as varying material constant and applying transverse electric field.

  17. Mean-spherical model for soft potentials - The hard core revealed as a perturbation

    NASA Technical Reports Server (NTRS)

    Rosenfeld, Y.; Ashcroft, N. W.

    1979-01-01

    The mean-spherical approximation for fluids is extended to treat the case of dense systems interacting via soft potentials. The extension takes the form of a generalized statement concerning the behavior of the direct-correlation function c(r) and the radial-distribution function g(r). From a detailed analysis that views the hard-core portion of a potential as a perturbation on the whole, a specific model is proposed which possesses analytic solutions for both Coulomb and Yukawa potentials, in addition to certain other remarkable properties. A variational principle for the model leads to a relatively simple method for obtaining numerical solutions.

  18. A mean spherical model for soft potentials: The hard core revealed as a perturbation

    NASA Technical Reports Server (NTRS)

    Rosenfeld, Y.; Ashcroft, N. W.

    1978-01-01

    The mean spherical approximation for fluids is extended to treat the case of dense systems interacting via soft-potentials. The extension takes the form of a generalized statement concerning the behavior of the direct correlation function c(r) and radial distribution g(r). From a detailed analysis that views the hard core portion of a potential as a perturbation on the whole, a specific model is proposed which possesses analytic solutions for both Coulomb and Yukawa potentials, in addition to certain other remarkable properties. A variational principle for the model leads to a relatively simple method for obtaining numerical solutions.

  19. Converging sequences in the ab initio no-core shell model

    SciTech Connect

    Forssen, C.; Vary, J. P.; Caurier, E.; Navratil, P.

    2008-02-15

    We demonstrate the existence of multiple converging sequences in the ab initio no-core shell model. By examining the underlying theory of effective operators, we expose the physical foundations for the alternative pathways to convergence. This leads us to propose a revised strategy for evaluating effective interactions for A-body calculations in restricted model spaces. We suggest that this strategy is particularly useful for applications to nuclear processes in which states of both parities are used simultaneously, such as for transition rates. We demonstrate the utility of our strategy with large-scale calculations in light nuclei.

  20. N Reactor core heatup sensitivity study for the 32-inch unit cell model

    SciTech Connect

    Martin, F.; Zimmerman, B.; Heard, F.

    1988-02-01

    A number of N Reactor core heatup studies have been performed using the TRUMP-BD computer code. These studies were performed to address questions concerning the dependency of results on potential variations in the material properties and/or modeling assumptions. This report described and documents a series of 31 TRUMP-BD runs that were performed to determine the sensitivity of calculated inner-fuel temperatures to a variety of TRUMP input parameters and also to a change in the node density in a high-temperature-gradient region. The results of this study are based on the 32-in. model. 18 refs., 17 figs., 2 tab.

  1. Fuel performance models for high-temperature gas-cooled reactor core design

    SciTech Connect

    Stansfield, O.M.; Simon, W.A.; Baxter, A.M.

    1983-09-01

    Mechanistic fuel performance models are used in high-temperature gas-cooled reactor core design and licensing to predict failure and fission product release. Fuel particles manufactured with defective or missing SiC, IPyC, or fuel dispersion in the buffer fail at a level of less than 5 x 10/sup -4/ fraction. These failed particles primarily release metallic fission products because the OPyC remains intact on 90% of the particles and retains gaseous isotopes. The predicted failure of particles using performance models appears to be conservative relative to operating reactor experience.

  2. NUMERICAL VERIFICATION OF THE RELAP-7 CORE CHANNEL SINGLE-PHASE MODEL

    SciTech Connect

    Haihua Zhao; Ling Zou; Hongbin Zhang; Richard Martineau

    2014-06-01

    The RELAP-7 code is the next generation of nuclear reactor system safety analysis code being developed at the Idaho National Laboratory (INL). All the physics in RELAP-7 are fully coupled and the errors resulted from the traditional operator-splitting approach are eliminated. By using 2nd order methods in both time and space and eliminating operator-splitting errors, the numerical error of RELAP-7 can be minimized. Numerical verification is the process to verify the orders of numerical methods. It is an important part of modern verification and validation process. The core channel component in RELAP-7 is designed to simulate coolant flow as well as the conjugated heat transfer between coolant flow and the fuel rod. A special treatment at fuel centerline to avoid numerical singularity for the cylindrical heat conduction in the continuous finite element mesh is discussed. One steady state test case and one fast power up transient test case are utilized for the verification of the core channel model with single-phase flow. Analytical solution for the fuel pin temperature and figures of merit such as peak clad temperature and peak fuel temperature are used to define numerical errors. These cases prove that the mass and energy are well conserved and 2nd order convergence rates for both time and space are achieved in the core channel model.

  3. Long-term reactive transport modelling of Berea and chalk core flood experiment

    NASA Astrophysics Data System (ADS)

    Souza, A. V.; Godoy, J.; Tonietto, G.

    2013-12-01

    Carbon sequestration in geological structures establishes a long-term chemical system between the dissolved gas, fluids and rocks from the injection site. Thus, the time scale used to assess the progress of chemical reactions is normally between tens and hundreds of years. Geochemical modeling is used in a variety of fields, including environmental protection and remediation, the petroleum industry, and economic geology and it is one of the best alternatives to evaluate the reactions with geochemical data possible injection sites. In this work we used data presented in a recent article (SPE165500) in different scenarios injection with three scales 50, 100, 250 and 1000 years. The experimental data used were from core flood experiment Berea and chalk in a condition similar to those found in the reservoirs of the North Sea. (340 bar and 130 C). The approach used to the lack of appropriate kinetic parameter in reservoir conditions, was the use of experimental data collected in two different conditions (340 bar and 130 C) and (2 Bar at room temperature) after the rocky core. The numerical simulations carried out using the same conditions with two different geochemical softwares PHREEQC and TOUGHREACTS. The results provide a detailed understanding of the system resulting rock-fluid-CO2 in the medium and long term. However, the accuracy of the models is strongly dependent on the mineral primary and secondary cores found in rocks.

  4. Advanced Test Reactor Core Modeling Update Project Annual Report for Fiscal Year 2010

    SciTech Connect

    Rahmat Aryaeinejad; Douglas S. Crawford; Mark D. DeHart; George W. Griffith; D. Scott Lucas; Joseph W. Nielsen; David W. Nigg; James R. Parry; Jorge Navarro

    2010-09-01

    Legacy computational reactor physics software tools and protocols currently used for support of Advanced Test Reactor (ATR) core fuel management and safety assurance and, to some extent, experiment management are obsolete, inconsistent with the state of modern nuclear engineering practice, and are becoming increasingly difficult to properly verify and validate (V&V). Furthermore, the legacy staff knowledge required for application of these tools and protocols from the 1960s and 1970s is rapidly being lost due to staff turnover and retirements. In 2009 the Idaho National Laboratory (INL) initiated a focused effort to address this situation through the introduction of modern high-fidelity computational software and protocols, with appropriate V&V, within the next 3-4 years via the ATR Core Modeling and Simulation and V&V Update (or “Core Modeling Update”) Project. This aggressive computational and experimental campaign will have a broad strategic impact on the operation of the ATR, both in terms of improved computational efficiency and accuracy for support of ongoing DOE programs as well as in terms of national and international recognition of the ATR National Scientific User Facility (NSUF).

  5. A Journey in Standard Development: The Core Manufacturing Simulation Data (CMSD) Information Model

    PubMed Central

    Lee, Yung-Tsun Tina

    2015-01-01

    This report documents a journey “from research to an approved standard” of a NIST-led standard development activity. That standard, Core Manufacturing Simulation Data (CMSD) information model, provides neutral structures for the efficient exchange of manufacturing data in a simulation environment. The model was standardized under the auspices of the international Simulation Interoperability Standards Organization (SISO). NIST started the research in 2001 and initiated the standardization effort in 2004. The CMSD standard was published in two SISO Products. In the first Product, the information model was defined in the Unified Modeling Language (UML) and published in 2010 as SISO-STD-008-2010. In the second Product, the information model was defined in Extensible Markup Language (XML) and published in 2013 as SISO-STD-008-01-2012. Both SISO-STD-008-2010 and SISO-STD-008-01-2012 are intended to be used together. PMID:26958450

  6. Maximizing Multi-core Performance of the Weather Research and Forecast Model over the Hawaiian Islands

    NASA Astrophysics Data System (ADS)

    Roe, K.; Stevens, D.

    2010-09-01

    The Hawaiian Islands consist of dramatic terrain changes over short distances, resulting in a variety of microclimates in close proximity. To handle these challenging conditions, weather models must be run at very fine vertical and horizontal resolutions to produce accurate forecasts. Computational demands require WRF to be executed in parallel on the Maui High Performance Computing Center’s Mana system, a PowerEdge M610 Linux cluster. This machine has 1,152 compute nodes, each with two 2.8 GHz quad-core Intel® Nehalem processors and 24 GB RAM. Realizing maximum performance on Mana relied on the determination of an optimal number of cores to use per socket, the efficiency of an MPI only implementation, an optimal set of parameters for adaptive time stepping, a way to meet the strict stability requirements necessary for Hawaii, effective choices for processor and memory affinity, and parallel automation techniques for producing forecast imagery.

  7. Characterizing the nucleation flux of linked-flux model for core-shell composite nucleus

    NASA Astrophysics Data System (ADS)

    Iwamatsu, Masao

    2013-05-01

    The kinetics of nucleation of a core-shell composite nucleus that consists of a core of stable final phase surrounded by a wetting layer of an intermediate metastable phase is studied using the linked-flux model where the nucleation flux is considered in the two-dimensional space of stable and metastable components. The steady-state solution of the Fokker-Planck equation is considered not only in the size and composition space but also in the component space. It is shown that the kinetics of critical nucleus at the saddle point is more appropriately characterized in the size and composition space, while the kinetics of the post-critical nucleus is more appropriately described in the component space. Although both the free-energy landscape and the reaction rates play decisive role to determine the kinetics of nucleation at the saddle point, the details of the free energy landscape are irrelevant to the kinetics of the post critical nucleus.

  8. Accounting for crustal magnetization in models of the core magnetic field

    NASA Technical Reports Server (NTRS)

    Jackson, Andrew

    1990-01-01

    The problem of determining the magnetic field originating in the earth's core in the presence of remanent and induced magnetization is considered. The effect of remanent magnetization in the crust on satellite measurements of the core magnetic field is investigated. The crust as a zero-mean stationary Gaussian random process is modelled using an idea proposed by Parker (1988). It is shown that the matrix of second-order statistics is proportional to the Gram matrix, which depends only on the inner-products of the appropriate Green's functions, and that at a typical satellite altitude of 400 km the data are correlated out to an angular separation of approximately 15 deg. Accurate and efficient means of calculating the matrix elements are given. It is shown that the variance of measurements of the radial component of a magnetic field due to the crust is expected to be approximately twice that in horizontal components.

  9. Wind Tunnel Magnetic Suspension and Balance Systems With Transversely Magnetized Model Cores

    NASA Technical Reports Server (NTRS)

    Britcher, Colin P.

    1998-01-01

    This paper discusses the possibility of using vertically magnetized model cores for wind tunnel Magnetic Suspension and Balance Systems (MSBS) in an effort to resolve the traditional "roll control" problem. A theoretical framework is laid out, based on previous work related to generic technology development efforts at NASA Langley Research Center. The impact of the new roll control scheme on traditional wind tunnel MSBS configurations is addressed, and the possibility of demonstrating the new scheme with an existing electromagnet assembly is explored. The specific system considered is the ex- Massachusetts Institute of Technology (MIT), ex-NASA, 6-inch MSBS currently in the process of recommissioning at Old Dominion University. This system has a sufficiently versatile electromagnet configuration such that straightforward "conversion" to vertically magnetized cores appears possible.

  10. TRACE/PARCS Core Modeling of a BWR/5 for Accident Analysis of ATWS Events

    SciTech Connect

    Cuadra A.; Baek J.; Cheng, L.; Aronson, A.; Diamond, D.; Yarsky, P.

    2013-11-10

    The TRACE/PARCS computational package [1, 2] isdesigned to be applicable to the analysis of light water reactor operational transients and accidents where the coupling between the neutron kinetics (PARCS) and the thermal-hydraulics and thermal-mechanics (TRACE) is important. TRACE/PARCS has been assessed for itsapplicability to anticipated transients without scram(ATWS) [3]. The challenge, addressed in this study, is to develop a sufficiently rigorous input model that would be acceptable for use in ATWS analysis. Two types of ATWS events were of interest, a turbine trip and a closure of main steam isolation valves (MSIVs). In the first type, initiated by turbine trip, the concern is that the core will become unstable and large power oscillations will occur. In the second type,initiated by MSIV closure,, the concern is the amount of energy being placed into containment and the resulting emergency depressurization. Two separate TRACE/PARCS models of a BWR/5 were developed to analyze these ATWS events at MELLLA+ (maximum extended load line limit plus)operating conditions. One model [4] was used for analysis of ATWS events leading to instability (ATWS-I);the other [5] for ATWS events leading to emergency depressurization (ATWS-ED). Both models included a large portion of the nuclear steam supply system and controls, and a detailed core model, presented henceforth.

  11. A Numerical Model for Magnetohydrodynamic Waves in a Stably-Stratified Layer in Earth's Core

    NASA Astrophysics Data System (ADS)

    Knezek, N. R.; Buffett, B. A.

    2015-12-01

    A numerical model for magnetohydrodynamic waves in a thin shell is developed and applied to study the effect of a stably-stratified layer in Earth's core on geomagnetic secular variation. The model employs a spherical coordinate system with finite differences in r and θ and Fourier decomposition in Φ. The model is linearized assuming a background azimuthal velocity field UΦ(r,θ) and an arbitrary background magnetic field Br,θ,Φ(r,θ). The Boussinesq approximation is employed and the buoyancy forces are prescribed in terms of a spatially variable Brunt-Vaisala frequency N(r,θ). The equations are cast into a sparse generalized eigenvalue problem by assuming solutions of the form uj,bj,p=CjeimΦ+λt and eigenmodes are found. Good agreement is obtained with previous approximate analytical solutions for zonal (m=0) magnetic-Archimedes-Coriolis (MAC) waves (e.g. Braginsky, 1993), global magnetic-Rossby (m>0) waves (e.g. Braginsky, 1998), and equatorially-trapped magnetic-Rossby waves (e.g. Bergman, 1993). This model is employed to study the origins of the fast equatorial waves observed by Chulliat et al. (2015) in recent high-resolution magnetic field models to constrain plausible properties of the stably-stratified layer and core-surface magnetic field.

  12. Washington State Core Competencies Model Curriculum: English as a Second Language, Level 3. Version 1.0

    ERIC Educational Resources Information Center

    Hagen, Stacey, Ed.; And Others

    The Washington State Core Competencies Project is designed to implement competency-based adult education in the state's 38 adult basic education programs. A model curriculum was developed and field-tested over several years. The resulting curriculum outline of core competencies for English as a Second Language, level 3, is presented here. The…

  13. Washington State Core Competencies Model Curriculum: English as a Second Language, Level 2. Version 1.0.

    ERIC Educational Resources Information Center

    Hagen, Stacey, Ed.; And Others

    The Washington State Core Competencies Project is designed to implement competency-based adult education in the state's 38 adult basic education programs. A model curriculum was developed and field-tested over several years. The resulting curriculum outline of core competencies for English as a Second Language, level 2, is presented here. The…

  14. Wisconsin Model Early Learning Standards Alignment with Wisconsin Common Core State Standards for English Language Arts and Mathematics

    ERIC Educational Resources Information Center

    Wisconsin Department of Public Instruction, 2011

    2011-01-01

    Wisconsin's adoption of the Common Core State Standards provides an excellent opportunity for Wisconsin school districts and communities to define expectations from birth through preparation for college and work. By aligning the existing Wisconsin Model Early Learning Standards with the Wisconsin Common Core State Standards, expectations can be…

  15. MODELING THE FORMATION OF GIANT PLANET CORES. I. EVALUATING KEY PROCESSES

    SciTech Connect

    Levison, Harold F.; Thommes, Edward; Duncan, Martin J.

    2010-04-15

    One of the most challenging problems we face in our understanding of planet formation is how Jupiter and Saturn could have formed before the solar nebula dispersed. The most popular model of giant planet formation is the so-called core accretion model. In this model a large planetary embryo formed first, mainly by two-body accretion. This is then followed by a period of inflow of nebular gas directly onto the growing planet. The core accretion model has an Achilles heel, namely the very first step. We have undertaken the most comprehensive study of this process to date. In this study, we numerically integrate the orbits of a number of planetary embryos embedded in a swarm of planetesimals. In these experiments, we have included a large number of physical processes that might enhance accretion. In particular, we have included (1) aerodynamic gas drag, (2) collisional damping between planetesimals, (3) enhanced embryo cross sections due to their atmospheres, (4) planetesimal fragmentation, and (5) planetesimal-driven migration. We find that the gravitational interaction between the embryos and the planetesimals leads to the wholesale redistribution of material-regions are cleared of material and gaps open near the embryos. Indeed, in 90% of our simulations without fragmentation, the region near those embryos is cleared of planetesimals before much growth can occur. Thus, the widely used assumption that the surface density distribution of planetesimals is smooth can lead to misleading results. In the remaining 10% of our simulations, the embryos undergo a burst of outward migration that significantly increases growth. On timescales of {approx}10{sup 5} years, the outer embryo can migrate {approx}6 AU and grow to roughly 30 M {sub +}. This represents a largely unexplored mode of core formation. We also find that the inclusion of planetesimal fragmentation tends to inhibit growth except for a narrow range of fragment migration rates.

  16. A THREE-PHASE CHEMICAL MODEL OF HOT CORES: THE FORMATION OF GLYCINE

    SciTech Connect

    Garrod, Robin T.

    2013-03-01

    A new chemical model is presented that simulates fully coupled gas-phase, grain-surface, and bulk-ice chemistry in hot cores. Glycine (NH{sub 2}CH{sub 2}COOH), the simplest amino acid, and related molecules such as glycinal, propionic acid, and propanal, are included in the chemical network. Glycine is found to form in moderate abundance within and upon dust-grain ices via three radical-addition mechanisms, with no single mechanism strongly dominant. Glycine production in the ice occurs over temperatures {approx}40-120 K. Peak gas-phase glycine fractional abundances lie in the range 8 Multiplication-Sign 10{sup -11}-8 Multiplication-Sign 10{sup -9}, occurring at {approx}200 K, the evaporation temperature of glycine. A gas-phase mechanism for glycine production is tested and found insignificant, even under optimal conditions. A new spectroscopic radiative-transfer model is used, allowing the translation and comparison of the chemical-model results with observations of specific sources. Comparison with the nearby hot-core source NGC 6334 IRS1 shows excellent agreement with integrated line intensities of observed species, including methyl formate. The results for glycine are consistent with the current lack of a detection of this molecule toward other sources; the high evaporation temperature of glycine renders the emission region extremely compact. Glycine detection with ALMA is predicted to be highly plausible, for bright, nearby sources with narrow emission lines. Photodissociation of water and subsequent hydrogen abstraction from organic molecules by OH, and NH{sub 2}, are crucial to the buildup of complex organic species in the ice. The inclusion of alternative branches within the network of radical-addition reactions appears important to the abundances of hot-core molecules; less favorable branching ratios may remedy the anomalously high abundance of glycolaldehyde predicted by this and previous models.

  17. Modeling of BWR core meltdown accidents - for application in the MELRPI. MOD2 computer code

    SciTech Connect

    Koh, B R; Kim, S H; Taleyarkhan, R P; Podowski, M Z; Lahey, Jr, R T

    1985-04-01

    This report summarizes improvements and modifications made in the MELRPI computer code. A major difference between this new, updated version of the code, called MELRPI.MOD2, and the one reported previously, concerns the inclusion of a model for the BWR emergency core cooling systems (ECCS). This model and its computer implementation, the ECCRPI subroutine, account for various emergency injection modes, for both intact and rubblized geometries. Other changes to MELRPI deal with an improved model for canister wall oxidation, rubble bed modeling, and numerical integration of system equations. A complete documentation of the entire MELRPI.MOD2 code is also given, including an input guide, list of subroutines, sample input/output and program listing.

  18. Constraints on geomagnetic secular variation modeling from electromagnetism and fluid dynamics of the Earth's core

    NASA Technical Reports Server (NTRS)

    Benton, E. R.

    1986-01-01

    A spherical harmonic representation of the geomagnetic field and its secular variation for epoch 1980, designated GSFC(9/84), is derived and evaluated. At three epochs (1977.5, 1980.0, 1982.5) this model incorporates conservation of magnetic flux through five selected patches of area on the core/mantle boundary bounded by the zero contours of vertical magnetic field. These fifteen nonlinear constraints are included like data in an iterative least squares parameter estimation procedure that starts with the recently derived unconstrained field model GSFC (12/83). Convergence is approached within three iterations. The constrained model is evaluated by comparing its predictive capability outside the time span of its data, in terms of residuals at magnetic observatories, with that for the unconstrained model.

  19. Molecular series-tunneling junctions.

    PubMed

    Liao, Kung-Ching; Hsu, Liang-Yan; Bowers, Carleen M; Rabitz, Herschel; Whitesides, George M

    2015-05-13

    Charge transport through junctions consisting of insulating molecular units is a quantum phenomenon that cannot be described adequately by classical circuit laws. This paper explores tunneling current densities in self-assembled monolayer (SAM)-based junctions with the structure Ag(TS)/O2C-R1-R2-H//Ga2O3/EGaIn, where Ag(TS) is template-stripped silver and EGaIn is the eutectic alloy of gallium and indium; R1 and R2 refer to two classes of insulating molecular units-(CH2)n and (C6H4)m-that are connected in series and have different tunneling decay constants in the Simmons equation. These junctions can be analyzed as a form of series-tunneling junctions based on the observation that permuting the order of R1 and R2 in the junction does not alter the overall rate of charge transport. By using the Ag/O2C interface, this system decouples the highest occupied molecular orbital (HOMO, which is localized on the carboxylate group) from strong interactions with the R1 and R2 units. The differences in rates of tunneling are thus determined by the electronic structure of the groups R1 and R2; these differences are not influenced by the order of R1 and R2 in the SAM. In an electrical potential model that rationalizes this observation, R1 and R2 contribute independently to the height of the barrier. This model explicitly assumes that contributions to rates of tunneling from the Ag(TS)/O2C and H//Ga2O3 interfaces are constant across the series examined. The current density of these series-tunneling junctions can be described by J(V) = J0(V) exp(-β1d1 - β2d2), where J(V) is the current density (A/cm(2)) at applied voltage V and βi and di are the parameters describing the attenuation of the tunneling current through a rectangular tunneling barrier, with width d and a height related to the attenuation factor β. PMID:25871745

  20. The Dependence of ITCZ Structure on Model Resolution and Dynamical Core in Aquaplanet Simulations

    SciTech Connect

    Landu, Kiranmayi; Leung, Lai-Yung R.; Hagos, Samson M.; Vinoj, V.; Rauscher, Sara; Ringler, Todd; Taylor, Mark

    2014-03-15

    Aqua-planet simulations using the Community Atmosphere Model version 4 (CAM4) with the Model for Prediction Across Scales Atmosphere (MPAS-A) and Higher Order Method Modeling Environment (HOMME) dynamical cores and zonally symmetric sea surface temperature (SST) structure are studied to understand the dependence of the inter-tropical convergence zone (ITCZ) structure on resolution and dynamical core. While all resolutions in HOMME and the low-resolution MPAS-A simulations give a single equatorial peak in zonal mean precipitation, the high-resolution MPAS-A simulations give a double ITCZ with precipitation peaking around 2° to 3° on either side of the equator. This study reveals that the structure of ITCZ is dependent on the feedbacks among convection and large-scale circulation and surface heat fluxes. We show that, by increasing convective available potential energy (CAPE) off the equator, the simulations with higher wind induced surface heat fluxes result in double ITCZ structure. This in turn leads to stronger convection and positive feedback with the large-scale circulation. We further show that the dominance of anti-symmetric waves in a model is not enough to cause double ITCZ, and the lateral extent of equatorial waves does not play an important role in determining the width of the ITCZ but rather the latter may influence the former.

  1. Advanced Test Reactor Core Modeling Update Project Annual Report for Fiscal Year 2011

    SciTech Connect

    David W. Nigg; Devin A. Steuhm

    2011-09-01

    Legacy computational reactor physics software tools and protocols currently used for support of Advanced Test Reactor (ATR) core fuel management and safety assurance and, to some extent, experiment management are obsolete, inconsistent with the state of modern nuclear engineering practice, and are becoming increasingly difficult to properly verify and validate (V&V). Furthermore, the legacy staff knowledge required for application of these tools and protocols from the 1960s and 1970s is rapidly being lost due to staff turnover and retirements. In 2009 the Idaho National Laboratory (INL) initiated a focused effort to address this situation through the introduction of modern high-fidelity computational software and protocols, with appropriate V&V, within the next 3-4 years via the ATR Core Modeling and Simulation and V&V Update (or 'Core Modeling Update') Project. This aggressive computational and experimental campaign will have a broad strategic impact on the operation of the ATR, both in terms of improved computational efficiency and accuracy for support of ongoing DOE programs as well as in terms of national and international recognition of the ATR National Scientific User Facility (NSUF). The ATR Core Modeling Update Project, targeted for full implementation in phase with the anticipated ATR Core Internals Changeout (CIC) in the 2014 time frame, began during the last quarter of Fiscal Year 2009, and has just completed its first full year. Key accomplishments so far have encompassed both computational as well as experimental work. A new suite of stochastic and deterministic transport theory based reactor physics codes and their supporting nuclear data libraries (SCALE, KENO-6, HELIOS, NEWT, and ATTILA) have been installed at the INL under various permanent sitewide license agreements and corresponding baseline models of the ATR and ATRC are now operational, demonstrating the basic feasibility of these code packages for their intended purpose. Furthermore, a

  2. Junctional Adhesion Molecule A Promotes Epithelial Tight Junction Assembly to Augment Lung Barrier Function

    PubMed Central

    Mitchell, Leslie A.; Ward, Christina; Kwon, Mike; Mitchell, Patrick O.; Quintero, David A.; Nusrat, Asma; Parkos, Charles A.; Koval, Michael

    2016-01-01

    Epithelial barrier function is maintained by tight junction proteins that control paracellular fluid flux. Among these proteins is junctional adhesion molecule A (JAM-A), an Ig fold transmembrane protein. To assess JAM-A function in the lung, we depleted JAM-A in primary alveolar epithelial cells using shRNA. In cultured cells, loss of JAM-A caused an approximately 30% decrease in transepithelial resistance, decreased expression of the tight junction scaffold protein zonula occludens 1, and disrupted junctional localization of the structural transmembrane protein claudin-18. Consistent with findings in other organs, loss of JAM-A decreased β1 integrin expression and impaired filamentous actin formation. Using a model of mild systemic endoxotemia induced by i.p. injection of lipopolysaccharide, we report that JAM-A−/− mice showed increased susceptibility to pulmonary edema. On injury, the enhanced susceptibility of JAM-A−/− mice to edema correlated with increased, transient disruption of claudin-18, zonula occludens 1, and zonula occludens 2 localization to lung tight junctions in situ along with a delay in up-regulation of claudin-4. In contrast, wild-type mice showed no change in lung tight junction morphologic features in response to mild systemic endotoxemia. These findings support a key role of JAM-A in promoting tight junction homeostasis and lung barrier function by coordinating interactions among claudins, the tight junction scaffold, and the cytoskeleton. PMID:25438062

  3. Selective vulnerability of motor neurons and dissociation of pre- and post-synaptic pathology at the neuromuscular junction in mouse models of spinal muscular atrophy.

    PubMed

    Murray, Lyndsay M; Comley, Laura H; Thomson, Derek; Parkinson, Nick; Talbot, Kevin; Gillingwater, Thomas H

    2008-04-01

    Proximal spinal muscular atrophy (SMA) is a common autosomal recessive childhood form of motor neuron disease. Previous studies have highlighted nerve- and muscle-specific events in SMA, including atrophy of muscle fibres and post-synaptic motor endplates, loss of lower motor neuron cell bodies and denervation of neuromuscular junctions caused by loss of pre-synaptic inputs. Here we have undertaken a detailed morphological investigation of neuromuscular synaptic pathology in the Smn-/-;SMN2 and Smn-/-;SMN2;Delta7 mouse models of SMA. We show that neuromuscular junctions in the transversus abdominis (TVA), levator auris longus (LAL) and lumbrical muscles were disrupted in both mouse models. Pre-synaptic inputs were lost and abnormal accumulations of neurofilament were present, even in early/mid-symptomatic animals in the most severely affected muscle groups. Neuromuscular pathology was more extensive in the postural TVA muscle compared with the fast-twitch LAL and lumbrical muscles. Pre-synaptic pathology in Smn-/-;SMN2;Delta7 mice was reduced compared with Smn-/-;SMN2 mice at late-symptomatic time-points, although post-synaptic pathology was equally severe. We demonstrate that shrinkage of motor endplates does not correlate with loss of motor nerve terminals, signifying that one can occur in the absence of the other. We also demonstrate selective vulnerability of a subpopulation of motor neurons in the caudal muscle band of the LAL. Paralysis with botulinum toxin resulted in less terminal sprouting and ectopic synapse formation in the caudal band compared with the rostral band, suggesting that motor units conforming to a Fast Synapsing (FaSyn) phenotype are likely to be more vulnerable than those with a Delayed Synapsing (DeSyn) phenotype. PMID:18065780

  4. An approach to model reactor core nodalization for deterministic safety analysis

    NASA Astrophysics Data System (ADS)

    Salim, Mohd Faiz; Samsudin, Mohd Rafie; Mamat @ Ibrahim, Mohd Rizal; Roslan, Ridha; Sadri, Abd Aziz; Farid, Mohd Fairus Abd

    2016-01-01

    Adopting good nodalization strategy is essential to produce an accurate and high quality input model for Deterministic Safety Analysis (DSA) using System Thermal-Hydraulic (SYS-TH) computer code. The purpose of such analysis is to demonstrate the compliance against regulatory requirements and to verify the behavior of the reactor during normal and accident conditions as it was originally designed. Numerous studies in the past have been devoted to the development of the nodalization strategy for small research reactor (e.g. 250kW) up to the bigger research reactor (e.g. 30MW). As such, this paper aims to discuss the state-of-arts thermal hydraulics channel to be employed in the nodalization for RTP-TRIGA Research Reactor specifically for the reactor core. At present, the required thermal-hydraulic parameters for reactor core, such as core geometrical data (length, coolant flow area, hydraulic diameters, and axial power profile) and material properties (including the UZrH1.6, stainless steel clad, graphite reflector) have been collected, analyzed and consolidated in the Reference Database of RTP using standardized methodology, mainly derived from the available technical documentations. Based on the available information in the database, assumptions made on the nodalization approach and calculations performed will be discussed and presented. The development and identification of the thermal hydraulics channel for the reactor core will be implemented during the SYS-TH calculation using RELAP5-3D® computer code. This activity presented in this paper is part of the development of overall nodalization description for RTP-TRIGA Research Reactor under the IAEA Norwegian Extra-Budgetary Programme (NOKEBP) mentoring project on Expertise Development through the Analysis of Reactor Thermal-Hydraulics for Malaysia, denoted as EARTH-M.

  5. Modelling of Equilibrium Between Mantle and Core: Refractory, Volatile, and Highly Siderophile Elements

    NASA Technical Reports Server (NTRS)

    Righter, K.; Danielson, L.; Pando, K.; Shofner, G.; Lee, C. -T.

    2013-01-01

    Siderophile elements have been used to constrain conditions of core formation and differentiation for the Earth, Mars and other differentiated bodies [1]. Recent models for the Earth have concluded that the mantle and core did not fully equilibrate and the siderophile element contents of the mantle can only be explained under conditions where the oxygen fugacity changes from low to high during accretion and the mantle and core do not fully equilibrate [2,3]. However these conclusions go against several physical and chemical constraints. First, calculations suggest that even with the composition of accreting material changing from reduced to oxidized over time, the fO2 defined by metal-silicate equilibrium does not change substantially, only by approximately 1 logfO2 unit [4]. An increase of more than 2 logfO2 units in mantle oxidation are required in models of [2,3]. Secondly, calculations also show that metallic impacting material will become deformed and sheared during accretion to a large body, such that it becomes emulsified to a fine scale that allows equilibrium at nearly all conditions except for possibly the length scale for giant impacts [5] (contrary to conclusions of [6]). Using new data for D(Mo) metal/silicate at high pressures, together with updated partitioning expressions for many other elements, we will show that metal-silicate equilibrium across a long span of Earth s accretion history may explain the concentrations of many siderophile elements in Earth's mantle. The modeling includes refractory elements Ni, Co, Mo, and W, as well as highly siderophile elements Au, Pd and Pt, and volatile elements Cd, In, Bi, Sb, Ge and As.

  6. A moist aquaplanet variant of the Held–Suarez test for atmospheric model dynamical cores

    DOE PAGES

    Thatcher, Diana R.; Jablonowski, Christiane

    2016-04-04

    A moist idealized test case (MITC) for atmospheric model dynamical cores is presented. The MITC is based on the Held–Suarez (HS) test that was developed for dry simulations on “a flat Earth” and replaces the full physical parameterization package with a Newtonian temperature relaxation and Rayleigh damping of the low-level winds. This new variant of the HS test includes moisture and thereby sheds light on the nonlinear dynamics–physics moisture feedbacks without the complexity of full-physics parameterization packages. In particular, it adds simplified moist processes to the HS forcing to model large-scale condensation, boundary-layer mixing, and the exchange of latent and sensible heat betweenmore » the atmospheric surface and an ocean-covered planet. Using a variety of dynamical cores of the National Center for Atmospheric Research (NCAR)'s Community Atmosphere Model (CAM), this paper demonstrates that the inclusion of the moist idealized physics package leads to climatic states that closely resemble aquaplanet simulations with complex physical parameterizations. This establishes that the MITC approach generates reasonable atmospheric circulations and can be used for a broad range of scientific investigations. This paper provides examples of two application areas. First, the test case reveals the characteristics of the physics–dynamics coupling technique and reproduces coupling issues seen in full-physics simulations. In particular, it is shown that sudden adjustments of the prognostic fields due to moist physics tendencies can trigger undesirable large-scale gravity waves, which can be remedied by a more gradual application of the physical forcing. Second, the moist idealized test case can be used to intercompare dynamical cores. These examples demonstrate the versatility of the MITC approach and suggestions are made for further application areas. The new moist variant of the HS test can be considered a test case of intermediate complexity.« less

  7. A moist aquaplanet variant of the Held-Suarez test for atmospheric model dynamical cores

    NASA Astrophysics Data System (ADS)

    Thatcher, Diana R.; Jablonowski, Christiane

    2016-04-01

    A moist idealized test case (MITC) for atmospheric model dynamical cores is presented. The MITC is based on the Held-Suarez (HS) test that was developed for dry simulations on "a flat Earth" and replaces the full physical parameterization package with a Newtonian temperature relaxation and Rayleigh damping of the low-level winds. This new variant of the HS test includes moisture and thereby sheds light on the nonlinear dynamics-physics moisture feedbacks without the complexity of full-physics parameterization packages. In particular, it adds simplified moist processes to the HS forcing to model large-scale condensation, boundary-layer mixing, and the exchange of latent and sensible heat between the atmospheric surface and an ocean-covered planet. Using a variety of dynamical cores of the National Center for Atmospheric Research (NCAR)'s Community Atmosphere Model (CAM), this paper demonstrates that the inclusion of the moist idealized physics package leads to climatic states that closely resemble aquaplanet simulations with complex physical parameterizations. This establishes that the MITC approach generates reasonable atmospheric circulations and can be used for a broad range of scientific investigations. This paper provides examples of two application areas. First, the test case reveals the characteristics of the physics-dynamics coupling technique and reproduces coupling issues seen in full-physics simulations. In particular, it is shown that sudden adjustments of the prognostic fields due to moist physics tendencies can trigger undesirable large-scale gravity waves, which can be remedied by a more gradual application of the physical forcing. Second, the moist idealized test case can be used to intercompare dynamical cores. These examples demonstrate the versatility of the MITC approach and suggestions are made for further application areas. The new moist variant of the HS test can be considered a test case of intermediate complexity.

  8. Paired octamer rings of retinoschisin suggest a junctional model for cell–cell adhesion in the retina

    PubMed Central

    Tolun, Gökhan; Vijayasarathy, Camasamudram; Huang, Rick; Zeng, Yong; Li, Yan; Steven, Alasdair C.; Sieving, Paul A.

    2016-01-01

    Retinoschisin (RS1) is involved in cell–cell junctions in the retina, but is unique among known cell-adhesion proteins in that it is a soluble secreted protein. Loss-of-function mutations in RS1 lead to early vision impairment in young males, called X-linked retinoschisis. The disease is characterized by separation of inner retinal layers and disruption of synaptic signaling. Using cryo-electron microscopy, we report the structure at 4.1 Å, revealing double octamer rings not observed before. Each subunit is composed of a discoidin domain and a small N-terminal (RS1) domain. The RS1 domains occupy the centers of the rings, but are not required for ring formation and are less clearly defined, suggesting mobility. We determined the structure of the discoidin rings, consistent with known intramolecular and intermolecular disulfides. The interfaces internal to and between rings feature residues implicated in X-linked retinoschisis, indicating the importance of correct assembly. Based on this structure, we propose that RS1 couples neighboring membranes together through octamer–octamer contacts, perhaps modulated by interactions with other membrane components. PMID:27114531

  9. Exploring the Membrane Potential of Simple Dual-Membrane Systems as Models for Gap-Junction Channels.

    PubMed

    Escalona, Yerko; Garate, Jose A; Araya-Secchi, Raul; Huynh, Tien; Zhou, Ruhong; Perez-Acle, Tomas

    2016-06-21

    The conductance of ion channels can be modulated by a transmembrane potential difference, due to alterations on ion-mobility and also by changes in the pore structure. Despite the vast knowledge regarding the influence of voltage on transport properties of ion channels, little attention has been paid to describe, with atomic detail, the modulation of ionic transport in gap-junction channels (GJCs). Hence, molecular dynamics simulations were performed to explore the conductance of simple dual-membrane systems that account for the very basic features of GJCs. In doing so, we studied the influence of different charge distributions in the channel surface on these idealized systems under external electric fields, paying attention to the behavior of the electrostatic potential, ion density, ion currents, and equilibrium properties. Our results demonstrate that the incorporation of a charge distribution akin GJCs decreased anionic currents, favoring the transport of cationic species. Moreover, a thermodynamic characterization of ionic transport in these systems demonstrate the existence of a kinetic barrier that hinders anionic currents, reinforcing the role played by the internal arrangement of charges in GJCs. Overall, our results provide insights at the atomic scale on the effects of charge distributions over ionic transport, constituting a step forward into a better understanding of GJCs. PMID:27332126

  10. Paired octamer rings of retinoschisin suggest a junctional model for cell-cell adhesion in the retina.

    PubMed

    Tolun, Gökhan; Vijayasarathy, Camasamudram; Huang, Rick; Zeng, Yong; Li, Yan; Steven, Alasdair C; Sieving, Paul A; Heymann, J Bernard

    2016-05-10

    Retinoschisin (RS1) is involved in cell-cell junctions in the retina, but is unique among known cell-adhesion proteins in that it is a soluble secreted protein. Loss-of-function mutations in RS1 lead to early vision impairment in young males, called X-linked retinoschisis. The disease is characterized by separation of inner retinal layers and disruption of synaptic signaling. Using cryo-electron microscopy, we report the structure at 4.1 Å, revealing double octamer rings not observed before. Each subunit is composed of a discoidin domain and a small N-terminal (RS1) domain. The RS1 domains occupy the centers of the rings, but are not required for ring formation and are less clearly defined, suggesting mobility. We determined the structure of the discoidin rings, consistent with known intramolecular and intermolecular disulfides. The interfaces internal to and between rings feature residues implicated in X-linked retinoschisis, indicating the importance of correct assembly. Based on this structure, we propose that RS1 couples neighboring membranes together through octamer-octamer contacts, perhaps modulated by interactions with other membrane components. PMID:27114531

  11. Modeling light-induced charge transfer dynamics across a metal-molecule-metal junction: bridging classical electrodynamics and quantum dynamics.

    PubMed

    Hu, Zixuan; Ratner, Mark A; Seideman, Tamar

    2014-12-14

    We develop a numerical approach for simulating light-induced charge transport dynamics across a metal-molecule-metal conductance junction. The finite-difference time-domain method is used to simulate the plasmonic response of the metal structures. The Huygens subgridding technique, as adapted to Lorentz media, is used to bridge the vastly disparate length scales of the plasmonic metal electrodes and the molecular system, maintaining accuracy. The charge and current densities calculated with classical electrodynamics are transformed to an electronic wavefunction, which is then propagated through the molecular linker via the Heisenberg equations of motion. We focus mainly on development of the theory and exemplify our approach by a numerical illustration of a simple system consisting of two silver cylinders bridged by a three-site molecular linker. The electronic subsystem exhibits fascinating light driven dynamics, wherein the charge density oscillates at the driving optical frequency, exhibiting also the natural system timescales, and a resonance phenomenon leads to strong conductance enhancement.

  12. Modeling light-induced charge transfer dynamics across a metal-molecule-metal junction: Bridging classical electrodynamics and quantum dynamics

    SciTech Connect

    Hu, Zixuan; Ratner, Mark A.; Seideman, Tamar

    2014-12-14

    We develop a numerical approach for simulating light-induced charge transport dynamics across a metal-molecule-metal conductance junction. The finite-difference time-domain method is used to simulate the plasmonic response of the metal structures. The Huygens subgridding technique, as adapted to Lorentz media, is used to bridge the vastly disparate length scales of the plasmonic metal electrodes and the molecular system, maintaining accuracy. The charge and current densities calculated with classical electrodynamics are transformed to an electronic wavefunction, which is then propagated through the molecular linker via the Heisenberg equations of motion. We focus mainly on development of the theory and exemplify our approach by a numerical illustration of a simple system consisting of two silver cylinders bridged by a three-site molecular linker. The electronic subsystem exhibits fascinating light driven dynamics, wherein the charge density oscillates at the driving optical frequency, exhibiting also the natural system timescales, and a resonance phenomenon leads to strong conductance enhancement.

  13. Excimer laser activation of ultra-shallow junctions in doped Si: Modeling, experiments and real time process monitoring

    NASA Astrophysics Data System (ADS)

    Semmar, Nadjib; Darif, Mohamed; Millon, Eric; Petit, Agnès; Etienne, Hasnaa; Delaporte, Philippe

    2012-07-01

    This work concerns the ALDIP (Laser Activation of Doping agents Implanted by Plasma immersion) project that was a successful collaboration with Ion Beam Services (IBS) corporation, the "Lasers, Plasmas and Photonic Processes" (LP3) laboratory and the GREMI laboratory. The aim of this work is to control the melted thickness (i.e. junction thickness in the range 10-100 nm) by the Real Time Reflectivity (TRR) monitoring during the Laser Thermal Processing (LTP). The LTP is achieved by using a KrF laser beam (248 nm, 27 ns) with a homogeneous 'Top-Hat' space distribution to induce a selective melting and the resolidification of the doped Si:B samples on few nanometers. This recrystallization is conducted here after the pre-amorphisation process resulting from the ionic implantation of Si (PIII IBS implanter). Thus, all the studied samples are partially amorphized and boron doped. TRR method allows the accurate evaluation of the melting threshold, the duration of the melting phase, and the maximum melted thickness. Obtained results versus laser fluence are shown in the new case of under vacuum treatment. In order to calibrate the TRR method (to determine the intensity and the profile of the TRR signal versus the melting depth), we have used the secondary ion mass spectrometry (TOF-SIMS) analysis. This technique gives the doping agents profile versus the depth before and after LTP and confirms also the melting kinetics from TRR results.

  14. Chirality effect in disordered graphene ribbon junctions

    NASA Astrophysics Data System (ADS)

    Long, Wen

    2012-05-01

    We investigate the influence of edge chirality on the electronic transport in clean or disordered graphene ribbon junctions. By using the tight-binding model and the Landauer-Büttiker formalism, the junction conductance is obtained. In the clean sample, the zero-magnetic-field junction conductance is strongly chirality-dependent in both unipolar and bipolar ribbons, whereas the high-magnetic-field conductance is either chirality-independent in the unipolar or chirality-dependent in the bipolar ribbon. Furthermore, we study the disordered sample in the presence of magnetic field and find that the junction conductance is always chirality-insensitive for both unipolar and bipolar ribbons with adequate disorders. In addition, the disorder-induced conductance plateaus can exist in all chiral bipolar ribbons provided the disorder strength is moderate. These results suggest that we can neglect the effect of edge chirality in fabricating electronic devices based on the magnetotransport in a disordered graphene ribbon.

  15. No-Core Shell Model Calculations in Light Nuclei with Three-Nucleon Forces

    SciTech Connect

    Barrett, B R; Vary, J P; Nogga, A; Navratil, P; Ormand, W E

    2004-01-08

    The ab initio No-Core Shell Model (NCSM) has recently been expanded to include nucleon-nucleon (NN) and three-nucleon (3N) interactions at the three-body cluster level. Here it is used to predict binding energies and spectra of p-shell nuclei based on realistic NN and 3N interactions. It is shown that 3N force (3NF) properties can be studied in these nuclear systems. First results show that interactions based on chiral perturbation theory lead to a realistic description of {sup 6}Li.

  16. Improved models of stellar core collapse and still no explosions: what is missing?

    PubMed

    Buras, R; Rampp, M; Janka, H-Th; Kifonidis, K

    2003-06-20

    Two-dimensional hydrodynamic simulations of stellar core collapse are presented which for the first time were performed by solving the Boltzmann equation for the neutrino transport including a state-of-the-art description of neutrino interactions. Stellar rotation is also taken into account. Although convection develops below the neutrinosphere and in the neutrino-heated region behind the supernova shock, the models do not explode. This suggests missing physics, possibly with respect to the nuclear equation of state and weak interactions in the subnuclear regime. However, it might also indicate a fundamental problem with the neutrino-driven explosion mechanism.

  17. Fractional charge separation in the hard-core Bose Hubbard Model on the Kagome Lattice

    NASA Astrophysics Data System (ADS)

    Zhang, Xue Feng; Eggert, Sebastian

    2013-03-01

    We consider the hard core Bose Hubbard Model on a Kagome lattice with fixed (open) boundary conditions on two edges. We find that the fixed boundary conditions lift the degeneracy and freeze the system at 1/3 and 2/3 filling at small hopping. At larger hopping strengths, fractional charges spontaneously separate and are free to move to the edges of the system, which leads to a novel compressible phase with solid order. The compressibility is due to excitations on the edge which display a chrial symmetry breaking that is reminiscent of the quantum Hall effect. Large scale Monte Carlo simulations confirm the analytical calculations.

  18. Jacobi no-core shell model for p-shell nuclei

    NASA Astrophysics Data System (ADS)

    Liebig, S.; Meißner, U.-G.; Nogga, A.

    2016-04-01

    We introduce an algorithm to obtain coefficients of fractional parentage for light p-shell nuclei. The coefficients enable one to use Jacobi coordinates in no-core shell model calculations separating off the center-of-mass motion. Fully antisymmetrized basis states are given together with recoupling coefficients that allow one to apply two- and three-nucleon operators. As an example, we study the dependence on the harmonic oscillator frequency of 3H, 4He, 6He, 6Li and 7Li and extract their binding and excitation energies. The coefficients will be made openly accessible as HDF5 data files.

  19. Equivalent Josephson junctions

    NASA Astrophysics Data System (ADS)

    Boyadjiev, T. L.; Semerdjieva, E. G.; Shukrinov, Yu. M.

    2008-01-01

    The magnetic field dependences of critical current are numerically constructed for a long Josephson junction with a shunt-or resistor-type microscopic inhomogeneities and compared to the critical curve of a junction with exponentially varying width. The numerical results show that it is adequate to replace the distributed inhomogeneity of a long Josephson junction by an inhomogeneity localized at one of its ends, which has certain technological advantages. It is also shown that the critical curves of junctions with exponentially varying width and inhomogeneities localized at the ends are unaffected by the mixed fluxon-antifluxon distributions of the magnetic flow. This fact may explain the improvement of the spectra of microwave radiation noted in the literature.

  20. Multi-core CPU or GPU-accelerated Multiscale Modeling for Biomolecular Complexes.

    PubMed

    Liao, Tao; Zhang, Yongjie; Kekenes-Huskey, Peter M; Cheng, Yuhui; Michailova, Anushka; McCulloch, Andrew D; Holst, Michael; McCammon, J Andrew

    2013-07-01

    Multi-scale modeling plays an important role in understanding the structure and biological functionalities of large biomolecular complexes. In this paper, we present an efficient computational framework to construct multi-scale models from atomic resolution data in the Protein Data Bank (PDB), which is accelerated by multi-core CPU and programmable Graphics Processing Units (GPU). A multi-level summation of Gaus-sian kernel functions is employed to generate implicit models for biomolecules. The coefficients in the summation are designed as functions of the structure indices, which specify the structures at a certain level and enable a local resolution control on the biomolecular surface. A method called neighboring search is adopted to locate the grid points close to the expected biomolecular surface, and reduce the number of grids to be analyzed. For a specific grid point, a KD-tree or bounding volume hierarchy is applied to search for the atoms contributing to its density computation, and faraway atoms are ignored due to the decay of Gaussian kernel functions. In addition to density map construction, three modes are also employed and compared during mesh generation and quality improvement to generate high quality tetrahedral meshes: CPU sequential, multi-core CPU parallel and GPU parallel. We have applied our algorithm to several large proteins and obtained good results.

  1. Modeling Stress Strain Relationships and Predicting Failure Probabilities For Graphite Core Components

    SciTech Connect

    Duffy, Stephen

    2013-09-09

    This project will implement inelastic constitutive models that will yield the requisite stress-strain information necessary for graphite component design. Accurate knowledge of stress states (both elastic and inelastic) is required to assess how close a nuclear core component is to failure. Strain states are needed to assess deformations in order to ascertain serviceability issues relating to failure, e.g., whether too much shrinkage has taken place for the core to function properly. Failure probabilities, as opposed to safety factors, are required in order to capture the bariability in failure strength in tensile regimes. The current stress state is used to predict the probability of failure. Stochastic failure models will be developed that can accommodate possible material anisotropy. This work will also model material damage (i.e., degradation of mechanical properties) due to radiation exposure. The team will design tools for components fabricated from nuclear graphite. These tools must readily interact with finite element software--in particular, COMSOL, the software algorithm currently being utilized by the Idaho National Laboratory. For the eleastic response of graphite, the team will adopt anisotropic stress-strain relationships available in COMSO. Data from the literature will be utilized to characterize the appropriate elastic material constants.

  2. No-Core Shell Model for 48-Ca, 48-Sc and 48-Ti

    SciTech Connect

    Popescu, S; Stoica, S; Vary, J P; Navratil, P

    2004-10-26

    The authors report the first no-core shell model results for {sup 48}Ca, {sup 48}Sc and {sup 48}Ti with derived and modified two-body Hamiltonians. We use an oscillator basis with a limited {bar h}{Omega} range around 40/A{sup 1/3} = 11 MeV and a limited model space up to 1 {bar h}{Omega}. No single-particle energies are used. They find that the charge dependence of the bulk binding energy of eight A = 48 nuclei is reasonably described with an effective Hamiltonian derived from the CD-Bonn interaction while there is an overall underbinding by about 0.4 MeV/nucleon. However, resulting spectra exhibit deficiencies that are anticipated due to: (1) basis space limitations and/or the absence of effective many-body interactions; and, (2) the absence of genuine three-nucleon interactions. They introduce phenomenological modifications to obtain fits to total binding and low-lying spectra. The resulting no-core shell model opens a path for applications to experiments such as the double-beta ({beta}{beta}) decay process.

  3. Inference of ICF implosion core mix using experimental data and theoretical mix modeling

    SciTech Connect

    Sherrill, Leslie Welser; Haynes, Donald A; Cooley, James H; Sherrill, Manolo E; Mancini, Roberto C; Tommasini, Riccardo; Golovkin, Igor E; Haan, Steven W

    2009-01-01

    The mixing between fuel and shell materials in Inertial Confinement Fusion (lCF) implosion cores is a current topic of interest. The goal of this work was to design direct-drive ICF experiments which have varying levels of mix, and subsequently to extract information on mixing directly from the experimental data using spectroscopic techniques. The experimental design was accomplished using hydrodynamic simulations in conjunction with Haan's saturation model, which was used to predict the mix levels of candidate experimental configurations. These theoretical predictions were then compared to the mixing information which was extracted from the experimental data, and it was found that Haan's mix model predicted trends in the width of the mix layer as a function of initial shell thickness. These results contribute to an assessment of the range of validity and predictive capability of the Haan saturation model, as well as increasing confidence in the methods used to extract mixing information from experimental data.

  4. The high density phase of the k-NN hard core lattice gas model

    NASA Astrophysics Data System (ADS)

    Nath, Trisha; Rajesh, R.

    2016-07-01

    The k-NN hard core lattice gas model on a square lattice, in which the first k next nearest neighbor sites of a particle are excluded from being occupied by another particle, is the lattice version of the hard disc model in two dimensional continuum. It has been conjectured that the lattice model, like its continuum counterpart, will show multiple entropy-driven transitions with increasing density if the high density phase has columnar or striped order. Here, we determine the nature of the phase at full packing for k up to 820 302 . We show that there are only eighteen values of k, all less than k  =  4134, that show columnar order, while the others show solid-like sublattice order.

  5. A simple model for solute-solvent separation through nanopores based on core-softened potentials

    NASA Astrophysics Data System (ADS)

    de Vasconcelos, Cláudia K. B.; Batista, Ronaldo J. C.; da Rocha Régis, McGlennon; Manhabosco, Taíse M.; de Oliveira, Alan B.

    2016-07-01

    We propose an effective model for solute separation from fluids through reverse osmosis based on core-softened potentials. Such potentials have been used to investigate anomalous fluids in several situations under a great variety of approaches. Due to their simplicity, computational simulations become faster and mathematical treatments are possible. Our model aims to mimic water desalination through nano-membranes through reverse osmosis, for which we have found reasonable qualitative results when confronted against all-atoms simulations found in the literature. The purpose of this work is not to replace any fully atomistic simulation at this stage, but instead to pave the first steps towards coarse-grained models for water desalination processes. This may help to approach problems in larger scales, in size and time, and perhaps make analytical theories more viable.

  6. Numerical modelling of impedance spectra of ionic conductor-insulator core-shell composites

    NASA Astrophysics Data System (ADS)

    Laugier, J.-M.; Raymond, L.; Albinet, G.; Knauth, P.

    2011-09-01

    Impedance spectra of ionic conductor-insulator core-shell composites are simulated in Cole-Cole and Bode representation using a 3D lattice of parallel resistance-capacitance elements. The composite model is based on a random ternary network, considering three impedance elements: good conductor (representing interface regions), conductor and insulator. The favourable interactions between the two phases lead to a significant non-random situation versus usual percolation models. Two percolation transitions are well observed: the first corresponds to ionic conduction enhancement by space charge layers. After the second transition, the conduction pathways are blocked by the insulator and the conductivity drops dramatically. Experimental impedance spectra of model copper- and lithium-ion conducting composites and nanocomposites are in good agreement with the simulation. The dc conductivity maximum can be described by a master equation: σmax ~ N-0.79 where N is proportional to the ionic conductor grain size.

  7. Advanced Test Reactor Core Modeling Update Project Annual Report for Fiscal Year 2012

    SciTech Connect

    David W. Nigg, Principal Investigator; Kevin A. Steuhm, Project Manager

    2012-09-01

    Legacy computational reactor physics software tools and protocols currently used for support of Advanced Test Reactor (ATR) core fuel management and safety assurance, and to some extent, experiment management, are inconsistent with the state of modern nuclear engineering practice, and are difficult, if not impossible, to properly verify and validate (V&V) according to modern standards. Furthermore, the legacy staff knowledge required for application of these tools and protocols from the 1960s and 1970s is rapidly being lost due to staff turnover and retirements. In late 2009, the Idaho National Laboratory (INL) initiated a focused effort, the ATR Core Modeling Update Project, to address this situation through the introduction of modern high-fidelity computational software and protocols. This aggressive computational and experimental campaign will have a broad strategic impact on the operation of the ATR, both in terms of improved computational efficiency and accuracy for support of ongoing DOE programs as well as in terms of national and international recognition of the ATR National Scientific User Facility (NSUF). The ATR Core Modeling Update Project, targeted for full implementation in phase with the next anticipated ATR Core Internals Changeout (CIC) in the 2014-2015 time frame, began during the last quarter of Fiscal Year 2009, and has just completed its third full year. Key accomplishments so far have encompassed both computational as well as experimental work. A new suite of stochastic and deterministic transport theory based reactor physics codes and their supporting nuclear data libraries (HELIOS, KENO6/SCALE, NEWT/SCALE, ATTILA, and an extended implementation of MCNP5) has been installed at the INL under various licensing arrangements. Corresponding models of the ATR and ATRC are now operational with all five codes, demonstrating the basic feasibility of the new code packages for their intended purpose. Of particular importance, a set of as-run core

  8. Towards self-consistent modelling of the Martian dichotomy: Coupled models of simultaneous core and crust formation

    NASA Astrophysics Data System (ADS)

    Keller, T.; Golabek, G. J.; Gerya, T.; Connolly, J.

    2009-12-01

    One of the most striking surface features on Mars is the crustal dichotomy. It is the oldest geological features on Mars and was formed more than 4.1 Ga ago by either exogenic or endogenic processes (e.g. Keller and Tackley, 2009). In order to find an internal origin of the crustal dichotomy, located within a maximum of 400 Ma of planetary differentiation, the thermal state of the planet resulting from core formation needs to be considered. It was suggested that a primordial crust with up to 45 km thickness can be formed already during the Martian core formation (Norman, 1999). Therefore we suggest that the sinking of iron diapirs delivered by pre-differentiated impactors induced impact- and shear heating-related temperature anomalies in the mantle that fostered the formation of early Martian crust. In this study, we examine parameter sets that will likely cause an onset of hemispherical low-degree mantle convection directly after, and coupled to, an already hemispherical core formation. To test this hypothesis we use a numerical model to simulate the formation of the Martian iron core, while peridotite melting is enabled to track melting caused by shear and radioactive heating. We perform 2D simulations using the spherical-Cartesian code I2ELVIS (Gerya and Yuen, 2007). It combines finite differences on a fully staggered rectangular Eulerian grid with Lagrangian marker-in-cell technique. In our model setup, the planet is surrounded by a low viscosity, massless fluid (“sticky air”) to simulate a free surface. We apply a temperature- and stress-dependent viscoplastic rheology inside a Mars-sized planet. Radioactive and shear-heating as well as consumption of latent heat by silicate melting are taken into account. The depth of neutral buoyancy of silicate melt with respect to solid silicates is determined by the difference in compressibility of the liquid and solid phase. To self-consistently simulate the silicate phase changes expected inside a Mars-sized body

  9. NON-EQUILIBRIUM CHEMISTRY OF DYNAMICALLY EVOLVING PRESTELLAR CORES. I. BASIC MAGNETIC AND NON-MAGNETIC MODELS AND PARAMETER STUDIES

    SciTech Connect

    Tassis, Konstantinos; Willacy, Karen; Yorke, Harold W.; Turner, Neal J.

    2012-07-01

    We combine dynamical and non-equilibrium chemical modeling of evolving prestellar molecular cloud cores and investigate the evolution of molecular abundances in the contracting core. We model both magnetic cores, with varying degrees of initial magnetic support, and non-magnetic cores, with varying collapse delay times. We explore, through a parameter study, the competing effects of various model parameters in the evolving molecular abundances, including the elemental C/O ratio, the temperature, and the cosmic-ray ionization rate. We find that different models show their largest quantitative differences at the center of the core, whereas the outer layers, which evolve slower, have abundances which are severely degenerate among different dynamical models. There is a large range of possible abundance values for different models at a fixed evolutionary stage (central density), which demonstrates the large potential of chemical differentiation in prestellar cores. However, degeneracies among different models, compounded with uncertainties induced by other model parameters, make it difficult to discriminate among dynamical models. To address these difficulties, we identify abundance ratios between particular molecules, the measurement of which would have maximal potential for discrimination among the different models examined here. In particular, we find that the ratios between NH{sub 3} and CO, NH{sub 2} and CO, and NH{sub 3} and HCO{sup +} are sensitive to the evolutionary timescale, and that the ratio between HCN and OH is sensitive to the C/O ratio. Finally, we demonstrate that measurements of the central deviation (central depletion or enhancement) of abundances of certain molecules are good indicators of the dynamics of the core.

  10. Cell culture model predicts human disease: Altered expression of junction proteins and matrix metalloproteinases in cervical dysplasia

    PubMed Central

    2012-01-01

    Background Cervical cancer is necessarily caused by human papillomaviruses, which encode three oncogenes manifesting their functions by interfering with a number of cellular proteins and pathways: the E5, E6, and E7 proteins. We have earlier found in our microarray studies that the E5 oncogene crucially affects the expression of cellular genes involved in adhesion and motility of epithelial cells. Methods In order to biologically validate our previous experimental findings we performed immunohistochemical staining of a representative set of tissue samples from different grades of high-risk human papillomavirus associated cervical disease as well as normal squamous and columnar cervical epithelium. Three-dimensional collagen raft cultures established from E5-expressing and control epithelial cells were also examined. The expression of p16, matrix metalloproteinase (MMP) -7, MMP-16, cytokeratin (CK) 8/18, laminin, E-cadherin and beta-catenin was studied. Results In agreement with our previous microarray studies, we found intense staining for E-cadherin and beta-catenin in adherens junctions even in high-grade cervical lesions. Staining for MMP-16 was increased in severe disease as well. No significant change in staining for MMP-7 and cytokeratin 8/18 along with the grade of cervical squamous epithelial disease was observed. Conclusions Here we have confirmed, using tissue material from human papillomavirus associated lesions, some of the cellular gene expression modifications that we earlier reported in an experimental system studying specifically the E5 oncogene of papillomaviruses. These findings were partially surprising in the context of cervical carcinogenesis and emphasize that the complexity of carcinogenesis is not yet fully understood. Microarray approaches provide a wide overwiev of gene expression in experimental settings, which may yield biologically valid biomarkers for disease diagnostics, prognosis, and follow-up. PMID:22863036

  11. A core stochastic population projection model for Florida manatees (Trichechus manatus latirostris)

    USGS Publications Warehouse

    Runge, Michael C.; Sanders-Reed, Carol A.; Fonnesbeck, Christopher J.

    2007-01-01

    probability of extinction is low, the model predicts that current and emerging threats are likely to result in a long-term decline in the statewide population and a change in the regional distribution of manatees. Analyses of sensitivity and variance contribution highlight the importance of reducing uncertainty in some life-history parameters, particularly adult survival, temporal variance of adult survival, and long-term warm-water capacity. This core biological model is expected to evolve over time, as better information becomes available about manatees and their habitat, and as new assessment needs arise. We anticipate that this core model will be customized for other state and federal assessments in the near future.

  12. A core stochastic population projection model for Florida manatees (Trichechus manatus latirostris)

    USGS Publications Warehouse

    Runge, M.C.; Sanders-Reed, C.A.; Fonnesbeck, C.J.

    2007-01-01

    probability of extinction is low, the model predicts that current and emerging threats are likely to result in a long-term decline in the statewide population and a change in the regional distribution of manatees. Analyses of sensitivity and variance contribution highlight the importance of reducing uncertainty in some life-history parameters, particularly adult survival, temporal variance of adult survival, and long-term warm-water capacity. This core biological model is expected to evolve over time, as better information becomes available about manatees and their habitat, and as new assessment needs arise. We anticipate that this core model will be customized for other state and federal assessments in the near future.

  13. Proposed Core Competencies and Empirical Validation Procedure in Competency Modeling: Confirmation and Classification.

    PubMed

    Baczyńska, Anna K; Rowiński, Tomasz; Cybis, Natalia

    2016-01-01

    Competency models provide insight into key skills which are common to many positions in an organization. Moreover, there is a range of competencies that is used by many companies. Researchers have developed core competency terminology to underline their cross-organizational value. The article presents a theoretical model of core competencies consisting of two main higher-order competencies called performance and entrepreneurship. Each of them consists of three elements: the performance competency includes cooperation, organization of work and goal orientation, while entrepreneurship includes innovativeness, calculated risk-taking and pro-activeness. However, there is lack of empirical validation of competency concepts in organizations and this would seem crucial for obtaining reliable results from organizational research. We propose a two-step empirical validation procedure: (1) confirmation factor analysis, and (2) classification of employees. The sample consisted of 636 respondents (M = 44.5; SD = 15.1). Participants were administered a questionnaire developed for the study purpose. The reliability, measured by Cronbach's alpha, ranged from 0.60 to 0.83 for six scales. Next, we tested the model using a confirmatory factor analysis. The two separate, single models of performance and entrepreneurial orientations fit quite well to the data, while a complex model based on the two single concepts needs further research. In the classification of employees based on the two higher order competencies we obtained four main groups of employees. Their profiles relate to those found in the literature, including so-called niche finders and top performers. Some proposal for organizations is discussed. PMID:27014111

  14. Two-dimensional Core-collapse Supernova Models with Multi-dimensional Transport

    NASA Astrophysics Data System (ADS)

    Dolence, Joshua C.; Burrows, Adam; Zhang, Weiqun

    2015-02-01

    We present new two-dimensional (2D) axisymmetric neutrino radiation/hydrodynamic models of core-collapse supernova (CCSN) cores. We use the CASTRO code, which incorporates truly multi-dimensional, multi-group, flux-limited diffusion (MGFLD) neutrino transport, including all relevant {O}(v/c) terms. Our main motivation for carrying out this study is to compare with recent 2D models produced by other groups who have obtained explosions for some progenitor stars and with recent 2D VULCAN results that did not incorporate {O}(v/c) terms. We follow the evolution of 12, 15, 20, and 25 solar-mass progenitors to approximately 600 ms after bounce and do not obtain an explosion in any of these models. Though the reason for the qualitative disagreement among the groups engaged in CCSN modeling remains unclear, we speculate that the simplifying "ray-by-ray" approach employed by all other groups may be compromising their results. We show that "ray-by-ray" calculations greatly exaggerate the angular and temporal variations of the neutrino fluxes, which we argue are better captured by our multi-dimensional MGFLD approach. On the other hand, our 2D models also make approximations, making it difficult to draw definitive conclusions concerning the root of the differences between groups. We discuss some of the diagnostics often employed in the analyses of CCSN simulations and highlight the intimate relationship between the various explosion conditions that have been proposed. Finally, we explore the ingredients that may be missing in current calculations that may be important in reproducing the properties of the average CCSNe, should the delayed neutrino-heating mechanism be the correct mechanism of explosion.

  15. TWO-DIMENSIONAL CORE-COLLAPSE SUPERNOVA MODELS WITH MULTI-DIMENSIONAL TRANSPORT

    SciTech Connect

    Dolence, Joshua C.; Burrows, Adam; Zhang, Weiqun E-mail: burrows@astro.princeton.edu

    2015-02-10

    We present new two-dimensional (2D) axisymmetric neutrino radiation/hydrodynamic models of core-collapse supernova (CCSN) cores. We use the CASTRO code, which incorporates truly multi-dimensional, multi-group, flux-limited diffusion (MGFLD) neutrino transport, including all relevant O(v/c) terms. Our main motivation for carrying out this study is to compare with recent 2D models produced by other groups who have obtained explosions for some progenitor stars and with recent 2D VULCAN results that did not incorporate O(v/c) terms. We follow the evolution of 12, 15, 20, and 25 solar-mass progenitors to approximately 600 ms after bounce and do not obtain an explosion in any of these models. Though the reason for the qualitative disagreement among the groups engaged in CCSN modeling remains unclear, we speculate that the simplifying ''ray-by-ray'' approach employed by all other groups may be compromising their results. We show that ''ray-by-ray'' calculations greatly exaggerate the angular and temporal variations of the neutrino fluxes, which we argue are better captured by our multi-dimensional MGFLD approach. On the other hand, our 2D models also make approximations, making it difficult to draw definitive conclusions concerning the root of the differences between groups. We discuss some of the diagnostics often employed in the analyses of CCSN simulations and highlight the intimate relationship between the various explosion conditions that have been proposed. Finally, we explore the ingredients that may be missing in current calculations that may be important in reproducing the properties of the average CCSNe, should the delayed neutrino-heating mechanism be the correct mechanism of explosion.

  16. Proposed Core Competencies and Empirical Validation Procedure in Competency Modeling: Confirmation and Classification

    PubMed Central

    Baczyńska, Anna K.; Rowiński, Tomasz; Cybis, Natalia

    2016-01-01

    Competency models provide insight into key skills which are common to many positions in an organization. Moreover, there is a range of competencies that is used by many companies. Researchers have developed core competency terminology to underline their cross-organizational value. The article presents a theoretical model of core competencies consisting of two main higher-order competencies called performance and entrepreneurship. Each of them consists of three elements: the performance competency includes cooperation, organization of work and goal orientation, while entrepreneurship includes innovativeness, calculated risk-taking and pro-activeness. However, there is lack of empirical validation of competency concepts in organizations and this would seem crucial for obtaining reliable results from organizational research. We propose a two-step empirical validation procedure: (1) confirmation factor analysis, and (2) classification of employees. The sample consisted of 636 respondents (M = 44.5; SD = 15.1). Participants were administered a questionnaire developed for the study purpose. The reliability, measured by Cronbach’s alpha, ranged from 0.60 to 0.83 for six scales. Next, we tested the model using a confirmatory factor analysis. The two separate, single models of performance and entrepreneurial orientations fit quite well to the data, while a complex model based on the two single concepts needs further research. In the classification of employees based on the two higher order competencies we obtained four main groups of employees. Their profiles relate to those found in the literature, including so-called niche finders and top performers. Some proposal for organizations is discussed. PMID:27014111

  17. Proposed Core Competencies and Empirical Validation Procedure in Competency Modeling: Confirmation and Classification.

    PubMed

    Baczyńska, Anna K; Rowiński, Tomasz; Cybis, Natalia

    2016-01-01

    Competency models provide insight into key skills which are common to many positions in an organization. Moreover, there is a range of competencies that is used by many companies. Researchers have developed core competency terminology to underline their cross-organizational value. The article presents a theoretical model of core competencies consisting of two main higher-order competencies called performance and entrepreneurship. Each of them consists of three elements: the performance competency includes cooperation, organization of work and goal orientation, while entrepreneurship includes innovativeness, calculated risk-taking and pro-activeness. However, there is lack of empirical validation of competency concepts in organizations and this would seem crucial for obtaining reliable results from organizational research. We propose a two-step empirical validation procedure: (1) confirmation factor analysis, and (2) classification of employees. The sample consisted of 636 respondents (M = 44.5; SD = 15.1). Participants were administered a questionnaire developed for the study purpose. The reliability, measured by Cronbach's alpha, ranged from 0.60 to 0.83 for six scales. Next, we tested the model using a confirmatory factor analysis. The two separate, single models of performance and entrepreneurial orientations fit quite well to the data, while a complex model based on the two single concepts needs further research. In the classification of employees based on the two higher order competencies we obtained four main groups of employees. Their profiles relate to those found in the literature, including so-called niche finders and top performers. Some proposal for organizations is discussed.

  18. Evaluating the Efficiency of a Multi-core Aware Multi-objective Optimization Tool for Calibrating the SWAT Model

    SciTech Connect

    Zhang, X.; Izaurralde, R. C.; Zong, Z.; Zhao, K.; Thomson, A. M.

    2012-08-20

    The efficiency of calibrating physically-based complex hydrologic models is a major concern in the application of those models to understand and manage natural and human activities that affect watershed systems. In this study, we developed a multi-core aware multi-objective evolutionary optimization algorithm (MAMEOA) to improve the efficiency of calibrating a worldwide used watershed model (Soil and Water Assessment Tool (SWAT)). The test results show that MAMEOA can save about 1-9%, 26-51%, and 39-56% time consumed by calibrating SWAT as compared with sequential method by using dual-core, quad-core, and eight-core machines, respectively. Potential and limitations of MAMEOA for calibrating SWAT are discussed. MAMEOA is open source software.

  19. Different Paths to Core Pathology: The Equifinal Model of the Schizophrenia Syndrome.

    PubMed

    Green, Isobel W; Glausier, Jill R

    2016-05-01

    Schizophrenia is a clinically heterogeneous disorder that is perhaps more accurately characterized as "the schizophrenia syndrome." This clinical heterogeneity is reflected in the heterogeneous neurobiological presentations associated with the illness. Moreover, even highly specific neural aberrations that are associated with distinct symptoms of schizophrenia are linked to a wide range of risk factors. As such, any individual with schizophrenia likely has a particular set of risk factors that interact and converge to cross the disease threshold, forming a particular etiology that ultimately generates a core pathophysiology. This core pathophysiology may then produce 1 or more symptoms of schizophrenia, leading to common symptoms across individuals in spite of disparate etiologies. As such, the schizophrenia syndrome can be considered as anequifinalentity: a state of dysfunction that can arise from different upstream etiologies. Moreover, schizophrenia etiologies are multifactorial and can involve the interactive effects of a broad range of genetic, environmental, and developmental risk factors. Through a consideration of how disparate etiologies, caused by different sets of risk factors, converge on the same net dysfunction, this paper aims to model the equifinal nature of schizophrenia symptoms. To demonstrate the equifinal model, we discuss how maternal infection and adolescent cannabis use, 2 recognized schizophrenia risk factors, may interact with other genetic, environmental, and/or developmental risk factors to cause the conserved clinical presentation of impaired working memory. PMID:26392629

  20. Zonal Flow Velocimetry using Acoustic Modes in Experimental Models of a Planetary Core

    NASA Astrophysics Data System (ADS)

    Adams, M. M.; Mautino, A. R.; Stone, D.; Triana, S. A.; Lekic, V.; Lathrop, D. P.

    2015-12-01

    Rotating hydromagnetic experiments can serve as models of planetary cores, matching some of the dimensionless parameters relevant to planets. One challenge with such experiments is determining the flows present. The opacity of the fluids used in these experiments (e.g. liquid sodium) prevents direct flow visualization techniques from being employed. One method allowing determination of zonal flows in such experiments is acoustic mode velocimetry. In this technique, the rotational splittings of acoustic mode spectra are used to infer the azimuthal velocity profile of the flow. Here we present the use of this technique to study flows in experimental models of the Earth's core. Most of these results were obtained in a 60 cm diameter spherical Couette device, with a 20 cm diameter inner sphere, and using nitrogen gas as the working fluid. Turbulent flow is driven in the system via differential rotation of the outer shell and inner sphere. Acoustic modes are excited in the fluid volume using a speaker, and microphones are used to measure the frequencies and rotational splittings of the modes. We compare the observed splittings with those predicted by theory as a way of validating the method, and infer mean flows from these observations. We also present some preliminary results of acoustic studies in the 3 m diameter liquid sodium spherical Couette experiment. Finally, we discuss future prospects for this experimental technique.

  1. Using archaeomagnetic field models to constrain the physics of the core: robustness and preferred locations of reversed flux patches

    NASA Astrophysics Data System (ADS)

    Terra-Nova, Filipe; Amit, Hagay; Hartmann, Gelvam A.; Trindade, Ricardo I. F.

    2016-09-01

    Archaeomagnetic field models cover longer timescales than historical models and may therefore resolve the motion of geomagnetic features on the core-mantle boundary (CMB) in a more meaningful statistical sense. Here we perform a detailed appraisal of archaeomagnetic field models to infer some aspects of the physics of the outer core. We characterize and compare the identification and tracking of reversed flux patches (RFPs) in order to assess the RFPs robustness. We find similar behaviour within a family of models but differences among different families, suggesting that modelling strategy is more influential than data set. Similarities involve recurrent positions of RFPs, but no preferred direction of motion is found. The tracking of normal flux patches shows similar qualitative behaviour confirming that RFPs identification and tracking is not strongly biased by their relative weakness. We also compare the tracking of RFPs with that of the historical field model gufm1 and with seismic anomalies of the lowermost mantle to explore the possibility that RFPs have preferred locations prescribed by lower mantle lateral heterogeneity. The archaeomagnetic field model that most resembles the historical field is interpreted in terms of core dynamics and core-mantle thermal interactions. This model exhibits correlation between RFPs and low seismic shear velocity in co-latitude and a shift in longitude. These results shed light on core processes, in particular we infer toroidal field lines with azimuthal orientation below the CMB and large fluid upwelling structures with a width of about 80° (Africa) and 110° (Pacific) at the top of the core. Finally, similar preferred locations of RFPs in the past 9 and 3 kyr of the same archaeomagnetic field model suggest that a 3 kyr period is sufficiently long to reliably detect mantle control on core dynamics. This allows estimating an upper bound of 220-310 km for the magnetic boundary layer thickness below the CMB.

  2. Using archaeomagnetic field models to constrain the physics of the core: robustness and preferred locations of reversed flux patches

    NASA Astrophysics Data System (ADS)

    Terra-Nova, Filipe; Amit, Hagay; Hartmann, Gelvam A.; Trindade, Ricardo I. F.

    2016-06-01

    Archaeomagnetic field models cover longer timescales than historical models and may therefore resolve the motion of geomagnetic features on the core-mantle boundary (CMB) in a more meaningful statistical sense. Here we perform a detailed appraisal of archaeomagnetic field models to infer some aspects of the physics of the outer core. We characterize and compare the identification and tracking of reversed flux patches (RFPs) in order to assess the RFPs robustness. We find similar behaviour within a family of models but differences among different families, suggesting that modelling strategy is more influential than data set. Similarities involve recurrent positions of RFPs, but no preferred direction of motion is found. The tracking of normal flux patches (NFPs) shows similar qualitative behaviour confirming that RFPs identification and tracking is not strongly biased by their relative weakness. We also compare the tracking of RFPs with that of the historical field model gufm1 and with seismic anomalies of the lowermost mantle to explore the possibility that RFPs have preferred locations prescribed by lower mantle lateral heterogeneity. The archaeomagnetic field model that most resembles the historical field is interpreted in terms of core dynamics and core-mantle thermal interactions. This model exhibits correlation between RFPs and low seismic shear velocity in co-latitude and a shift in longitude. These results shed light on core processes, in particular we infer toroidal field lines with azimuthal orientation below the CMB and large fluid upwelling structures with a width of about 80° (Africa) and 110° (Pacific) at the top of the core. Finally, similar preferred locations of RFPs in the past 9 kyr and 3 kyr of the same archaeomagnetic field model suggests that a 3 kyr period is sufficiently long to reliably detect mantle control on core dynamics. This allows estimating an upper bound of 220 - 310 km for the magnetic boundary layer thickness below the CMB.

  3. Modelling the effects of internal heating in the core and lowermost mantle on the earth’s magnetic history

    NASA Astrophysics Data System (ADS)

    Costin, S. O.; Butler, S. L.

    2006-08-01

    Recently, an incompatible-element enriched reservoir, bearing a high degree of radioactive heating, has been proposed to exist at the base of the mantle. This scenario has been discussed based on parameterized thermal and magnetic models of the core [Buffett, B.A., 2002. Estimates of heat flow in the deep mantle based on the power requirements for the geodynamo. Geophys. Res. Lett. 29(12), 7], as well as on geochemical grounds [Tolstikhin, I., Hofmann, A.W., 2005. Early crust on top of the Earth's core. Phys. Earth Plan. Int., 148, 109-130; Boyet M., Carlson, R.W., 2005. Nd142 Evidence for early ( >4.53 Ga) global differentiation of the sillicate earth. Science 309, 576-581]. A high degree of radioactivity at the base of the mantle [ Buffett, B.A., 2003. The thermal state of Earth's core. Science 299, 1675-1677], or alternatively the presence of radioactivity in the core [e.g., Labrosse, S., 2003. Thermal and magnetic evolution of the Earth's core. Phys. Earth Plan. Int. 140, 127-143; Nimmo F., Price, G.D., Brodholt, J., Gubbins, D., 2004. The influence of potassium on core and geodynamo evolution. Geophys. J. Int. 156, 363-376], have been proposed as means to allow sufficient buoyancy to power the geodynamo and maintain a magnetic field throughout most of the Earth's history as palaeomagnetic records indicate [ McElhinny, M.W., Senanayake, W.E., 1980. Paleomagnetic evidence for the existence of the geomagnetic field 3.5 Ga ago. J. Geophys. Res. 85, 3523-3528; Hale, C.J., D.J. Dunlop, 1984. Evidence for an early Archean geomagnetic field: a paleomagnetic study of the Komati Formation, Barberton Greenstone Belt, South Africa. Geophys. Res. Lett. 11, 97-100], while maintaining a sufficiently high temperature in the core. The present paper analyzes the consequences of internal heating in the core and the lowermost mantle on the core's magnetic history using numerical simulations of convection in the mantle coupled to an energy balance model for the core. This method

  4. A professional development model for medical laboratory scientists working in the Core Laboratory.

    PubMed

    Ali, Faheem A; Pulido, Lila A; Garza, Melinda N; Amerson, Megan H; Greenhill, Brandy; Brown, Krystyna N; Lim, Shari K; Manyam, Venkatesara R; Nguyen, Hannah N; Prudhomme, Carrie C; Regan, Laura E; Sims, Willie R; Umeh, Afamefuna U; Williams, Rosemary; Tillman, Patricia K; Hu, Peter C

    2012-01-01

    The Division of Pathology and Laboratory Medicine at The University of Texas MD Anderson Cancer Center has implemented a professional development model designed to further the education, expertise, and experiences of medical laboratory scientists in the core laboratory. The professional development model (PDM) has four competency levels: Discovery, Application, Maturation and Expert. All levels require the medical laboratory scientist to learn new skill sets, complete task and projects, and meet continuing education and certification requirements. Each level encourages personal development, recognizes increased competencies, and sets high standards for all services provided. Upon completion of a level within a given timeframe, the medical laboratory scientist receives a salary adjustment based on the competency level completed.

  5. Gas Core Reactor Numerical Simulation Using a Coupled MHD-MCNP Model

    NASA Technical Reports Server (NTRS)

    Kazeminezhad, F.; Anghaie, S.

    2008-01-01

    Analysis is provided in this report of using two head-on magnetohydrodynamic (MHD) shocks to achieve supercritical nuclear fission in an axially elongated cylinder filled with UF4 gas as an energy source for deep space missions. The motivation for each aspect of the design is explained and supported by theory and numerical simulations. A subsequent report will provide detail on relevant experimental work to validate the concept. Here the focus is on the theory of and simulations for the proposed gas core reactor conceptual design from the onset of shock generations to the supercritical state achieved when the shocks collide. The MHD model is coupled to a standard nuclear code (MCNP) to observe the neutron flux and fission power attributed to the supercritical state brought about by the shock collisions. Throughout the modeling, realistic parameters are used for the initial ambient gaseous state and currents to ensure a resulting supercritical state upon shock collisions.

  6. Mean-field dynamic criticality and geometric transition in the Gaussian core model

    NASA Astrophysics Data System (ADS)

    Coslovich, Daniele; Ikeda, Atsushi; Miyazaki, Kunimasa

    2016-04-01

    We use molecular dynamics simulations to investigate dynamic heterogeneities and the potential energy landscape of the Gaussian core model (GCM). Despite the nearly Gaussian statistics of particles' displacements, the GCM exhibits giant dynamic heterogeneities close to the dynamic transition temperature. The divergence of the four-point susceptibility is quantitatively well described by the inhomogeneous version of the mode-coupling theory. Furthermore, the potential energy landscape of the GCM is characterized by large energy barriers, as expected from the lack of activated, hopping dynamics, and display features compatible with a geometric transition. These observations demonstrate that all major features of mean-field dynamic criticality can be observed in a physically sound, three-dimensional model.

  7. Mean-field dynamic criticality and geometric transition in the Gaussian core model.

    PubMed

    Coslovich, Daniele; Ikeda, Atsushi; Miyazaki, Kunimasa

    2016-04-01

    We use molecular dynamics simulations to investigate dynamic heterogeneities and the potential energy landscape of the Gaussian core model (GCM). Despite the nearly Gaussian statistics of particles' displacements, the GCM exhibits giant dynamic heterogeneities close to the dynamic transition temperature. The divergence of the four-point susceptibility is quantitatively well described by the inhomogeneous version of the mode-coupling theory. Furthermore, the potential energy landscape of the GCM is characterized by large energy barriers, as expected from the lack of activated, hopping dynamics, and display features compatible with a geometric transition. These observations demonstrate that all major features of mean-field dynamic criticality can be observed in a physically sound, three-dimensional model. PMID:27176347

  8. Triple junction motion and grain microstructure evolution

    SciTech Connect

    Gottstein, G. . E-mail: gottstein@imm.rwth-aachen.de; Ma, Y.; Shvindlerman, L.S.

    2005-03-01

    The classical concepts of grain growth in polycrystals are based on the dominant role of grain boundaries. This is reflected by the well known von Neumann-Mullins relation. According to this approach triple junctions do not affect grain boundary motion, and their role in grain growth is reduced to maintaining the thermodynamically prescribed equilibrium angles at the lines where boundaries meet. In the current study the experimental data of triple junction mobility are considered with respect to the process of grain growth in 2D systems, in particular with regard to the controlling kinetics. When boundary kinetics prevails grain growth in a polycrystal complies with the von Neumann-Mullins relation. When grain growth is governed by the mobility of triple junctions the kinetics change, and the von Neumann-Mullins relation does not hold anymore. This is the more pronounced the smaller the triple junction mobility. We present a generalized theory of 2D grain growth including a limited triple junction mobility. In this concept the criterion {lambda} plays a central role. It reflects the ratio of boundary to triple junction mobility but is proportional to the grain size as well. The generalized von Neumann-Mullins relation can be expressed in terms of {lambda}. For small values of {lambda}, conspicuous changes of microstructure evolution during grain growth and of microstructural stability are predicted. The theoretical predictions are compared to results of computer simulations by a virtual vertex model.

  9. Preservice Secondary Teachers' Conceptions from a Mathematical Modeling Activity and Connections to the Common Core State Standards

    ERIC Educational Resources Information Center

    Stohlmann, Micah; Maiorca, Cathrine; Olson, Travis A.

    2015-01-01

    Mathematical modeling is an essential integrated piece of the Common Core State Standards. However, researchers have shown that mathematical modeling activities can be difficult for teachers to implement. Teachers are more likely to implement mathematical modeling activities if they have their own successful experiences with such activities. This…

  10. Classical phase diffusion in small hysteretic Josephson junctions

    SciTech Connect

    Martinis, J.M.; Kautz, R.L. )

    1989-10-02

    The existence of classical phase diffusion in hysteretic junctions is demonstrated by quantitative agreement between experimental and simulated {ital I}-{ital V} curves. The simulations are based on a circuit that accurately models both the junction and its external shunting impedance at microwave frequencies. We show that the bias current at which the junction switches from the phase diffusion state to the voltage state is sensitive to dissipation at microwave frequencies.

  11. Noise characteristics and instabilities of long Josephson junctions

    SciTech Connect

    Han, B.S.; Lee, B.; Symko, O.G.; Yeh, W.J.; Zheng, D.J.

    1989-03-01

    In a magnetic field, current biased long Josephson junctions exhibit the dynamics of fluxon motion which are affected by fluctuations. These consist of telegraph noise at voltage steps and instabilities due to chaotic behavior. Results on long junctions with McCumber number ..beta../sub c/ ranging from 10 to 100 show such behavior. The telegraph noise is driven by thermal fluctuations. Modeling of our junctions using a perturbed sine-Gordon equation shows the chaotic regions and the periodic ones.

  12. Thermodynamic properties of Fe-S alloys from molecular dynamics modeling: Implications for the lunar fluid core

    NASA Astrophysics Data System (ADS)

    Kuskov, Oleg L.; Belashchenko, David K.

    2016-09-01

    Density and sound velocity of Fe-S liquids for the P-T parameters of the lunar core have not been constrained well. From the analysis of seismic wave travel time, Weber et al. (2011) proposed that the lunar core is composed of iron alloyed with ⩽6 wt% of light elements, such as S. A controversial issue in models of planetary core composition concerns whether Fe-S liquids under high pressure - temperature conditions provide sound velocity and density data, which match the seismic model. Here we report the results of molecular dynamics (MD) simulations of iron-sulfur alloys based on Embedded Atom Model (EAM). The results of calculations include caloric, thermal and elastic properties of Fe-S alloys at concentrations of sulfur 0-18 at.%, temperatures up to 2500 K and pressures up to 14 GPa. The effect of sulfur on the elastic properties of Fe-rich melts is most evident in the notably decreased density with added S content. In the MD simulation, the density and bulk modulus KT of liquid Fe-S decrease with increasing sulfur content, while the bulk modulus KS decreases as a whole but has some fluctuations with increasing sulfur content. The sound velocity increases with increasing pressure, but depends weakly on temperature and the concentration of sulfur. For a fluid Fe-S core of the Moon (∼5 GPa/2000 K) with 6-16 at.% S (3.5-10 wt%), the sound velocity and density may be estimated at the level of 4000 m s-1 and 6.25-7.0 g cm-3. Comparison of thermodynamic calculations with the results of interpretation of seismic observations shows good agreement of P-wave velocities in the liquid outer core, while the core density does not match the seismic models. At such concentrations of sulfur and a density by 20-35% higher than the model seismic density, a radius for the fluid outer core should be less than about 330 km found by Weber et al. because at the specified mass and moment of inertia values of the Moon an increase of the core density leads to a decrease of the core

  13. An Iron-Rain Model for Core Formation on Asteroid 4 Vesta

    NASA Technical Reports Server (NTRS)

    Kiefer, Walter S.; Mittlefehldt, David W.

    2016-01-01

    Asteroid 4 Vesta is differentiated into a crust, mantle, and core, as demonstrated by studies of the eucrite and diogenite meteorites and by data from NASA's Dawn spacecraft. Most models for the differentiation and thermal evolution of Vesta assume that the metal phase completely melts within 20 degrees of the eutectic temperature, well before the onset of silicate melting. In such a model, core formation initially happens by Darcy flow, but this is an inefficient process for liquid metal and solid silicate. However, the likely chemical composition of Vesta, similar to H chondrites with perhaps some CM or CV chondrite, has 13-16 weight percent S. For such compositions, metal-sulfide melting will not be complete until a temperature of at least 1350 degrees Centigrade. The silicate solidus for Vesta's composition is between 1100 and 1150 degrees Centigrade, and thus metal and silicate melting must have substantially overlapped in time on Vesta. In this chemically and physically more likely view of Vesta's evolution, metal sulfide drops will sink by Stokes flow through the partially molten silicate magma ocean in a process that can be envisioned as "iron rain". Measurements of eucrites show that moderately siderophile elements such as Ni, Mo, and W reached chemical equilibrium between the metal and silicate phases, which is an important test for any Vesta differentiation model. The equilibration time is a function of the initial metal grain size, which we take to be 25-45 microns based on recent measurements of H6 chondrites. For these sizes and reasonable silicate magma viscosities, equilibration occurs after a fall distance of just a few meters through the magma ocean. Although metal drops may grow in size by merger with other drops, which increases their settling velocities and decreases the total core formation time, the short equilibration distance ensures that the moderately siderophile elements will reach chemical equilibrium between metal and silicate before

  14. Geoacoustic model at the DH-1 long-core site in the Korean continental margin of the East Sea

    NASA Astrophysics Data System (ADS)

    Ryang, Woo Hun; Kim, Seong Pil

    2014-05-01

    A long core of 23.6 m was acquired at the DH-1 site (37°36.651'N and 129°19.709'E) in the Korean continental margin of the western East Sea. The core site is located near the Donghae City and the water depth is 357.8 m deep. The long-core sediment was recovered using the Portable Remotely Operated Drill (PROD), a fully contained drilling system, remotely operated at the seafloor. The recovered core sediments were analyzed for physical, sedimentological, and geoacoustic properties mostly at 10~30 cm intervals. Based on the long-core data with subbottom and air-gun profiles at the DH-1 core site, a geoacoustic model was firstly reconstructed including water mass. The geoacoustic model comprises 7 geoacoustic units of the core sediments, based on the measurements of 125 P-wave velocities and 121 attenuations. The P-wave speed was compensated to in situ depth below the sea floor using the Hamilton method. The geoacoustic model DH-1 probably contributes for reconstruction of geoacoustic models reflecting vertical and lateral variability of acoustic properties in the Korean continental margin of the western East Sea. Keywords: long core, geoacoustic model, East Sea, continental margin, P-wave speed Acknowledgements: This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2010-0025733) and by the Ministry of Knowledge Economy through the grant of Marine Geology and Geophysical Mapping Project (GP2010-013).

  15. Core layering

    NASA Astrophysics Data System (ADS)

    Jacobson, S. A.; Rubie, D. C.; Hernlund, J. W.; Morbidelli, A.

    2015-12-01

    We have created a planetary accretion and differentiation model that self-consistently builds and evolves Earth's core. From this model, we show that the core grows stably stratified as the result of rising metal-silicate equilibration temperatures and pressures, which increases the concentrations of light element impurities into each newer core addition. This stable stratification would naturally resist convection and frustrate the onset of a geodynamo, however, late giant impacts could mechanically mix the distinct accreted core layers creating large homogenous regions. Within these regions, a geodynamo may operate. From this model, we interpret the difference between the planetary magnetic fields of Earth and Venus as a difference in giant impact histories. Our planetary accretion model is a numerical N-body integration of the Grand Tack scenario [1]—the most successful terrestrial planet formation model to date [2,3]. Then, we take the accretion histories of Earth-like and Venus-like planets from this model and post-process the growth of each terrestrial planet according to a well-tested planetary differentiation model [4,5]. This model fits Earth's mantle by modifying the oxygen content of the pre-cursor planetesimals and embryos as well as the conditions of metal-silicate equilibration. Other non-volatile major, minor and trace elements included in the model are assumed to be in CI chondrite proportions. The results from this model across many simulated terrestrial planet growth histories are robust. If the kinetic energy delivered by larger impacts is neglected, the core of each planet grows with a strong stable stratification that would significantly impede convection. However, if giant impact mixing is very efficient or if the impact history delivers large impacts late, than the stable stratification can be removed. [1] Walsh et al. Nature 475 (2011) [2] O'Brien et al. Icarus 223 (2014) [3] Jacobson & Morbidelli PTRSA 372 (2014) [4] Rubie et al. EPSL 301

  16. MUTILS - a set of efficient modeling tools for multi-core CPUs implemented in MEX

    NASA Astrophysics Data System (ADS)

    Krotkiewski, Marcin; Dabrowski, Marcin

    2013-04-01

    The need for computational performance is common in scientific applications, and in particular in numerical simulations, where high resolution models require efficient processing of large amounts of data. Especially in the context of geological problems the need to increase the model resolution to resolve physical and geometrical complexities seems to have no limits. Alas, the performance of new generations of CPUs does not improve any longer by simply increasing clock speeds. Current industrial trends are to increase the number of computational cores. As a result, parallel implementations are required in order to fully utilize the potential of new processors, and to study more complex models. We target simulations on small to medium scale shared memory computers: laptops and desktop PCs with ~8 CPU cores and up to tens of GB of memory to high-end servers with ~50 CPU cores and hundereds of GB of memory. In this setting MATLAB is often the environment of choice for scientists that want to implement their own models with little effort. It is a useful general purpose mathematical software package, but due to its versatility some of its functionality is not as efficient as it could be. In particular, the challanges of modern multi-core architectures are not fully addressed. We have developed MILAMIN 2 - an efficient FEM modeling environment written in native MATLAB. Amongst others, MILAMIN provides functions to define model geometry, generate and convert structured and unstructured meshes (also through interfaces to external mesh generators), compute element and system matrices, apply boundary conditions, solve the system of linear equations, address non-linear and transient problems, and perform post-processing. MILAMIN strives to combine the ease of code development and the computational efficiency. Where possible, the code is optimized and/or parallelized within the MATLAB framework. Native MATLAB is augmented with the MUTILS library - a set of MEX functions that

  17. An Intercomparison of the Dynamical Cores of Global Atmospheric Circulation Models for Mars

    NASA Technical Reports Server (NTRS)

    Hollingsworth, Jeffery L.; Bridger, Alison F. C.; Haberle, Robert M.

    1998-01-01

    This is a Final Report for a Joint Research Interchange (JRI) between NASA Ames Research Cen- ter and San Jose State University, Department of Meteorology. The focus of this JRI has been to evaluate the dynamical "cores" of two global atmospheric circulation models for Mars that are in operation at the NASA Ames Research Center. ne two global circulation models in use are fundamentally different: one uses spherical harmonics in its horizontal representation of field variables; the other uses finite differences on a uniform longitude-latitude grid. Several simulations have been conducted to assess how the dynamical processors of each of these circulation models perform using identical "simple physics" parameterizations. A variety of climate statistics (e.g., time-mean flows and eddy fields) have been compared for realistic solstitial mean basic states. Results of this research have demonstrated that the two Mars circulation models with completely different spatial representations and discretizations produce rather similar circulation statistics for first-order meteorological fields, suggestive of a tendency for convergence of numerical solutions. Second and higher-order fields can, however, vary significantly between the two models.

  18. An Intercomparison of the Dynamical Cores of Global Atmospheric Circulation Models for Mars

    NASA Technical Reports Server (NTRS)

    Hollingsworth, Jeffery L.; Bridger, Alison F. C.; Haberle, Robert M.

    1998-01-01

    This is a Final Report for a Joint Research Interchange (JRI) between NASA Ames Research Center and San Jose State University, Department of Meteorology. The focus of this JRI has been to evaluate the dynamical "cores" of two global atmospheric circulation models for Mars that are in operation at the NASA Ames Research Center. The two global circulation models in use are fundamentally different: one uses spherical harmonics in its horizontal representation of field variables; the other uses finite differences on a uniform longitude-latitude grid. Several simulations have been conducted to assess how the dynamical processors of each of these circulation models perform using identical "simple physics" parameterizations. A variety of climate statistics (e.g., time-mean flows and eddy fields) have been compared for realistic solstitial mean basic states. Results of this research have demonstrated that the two Mars circulation models with completely different spatial representations and discretizations produce rather similar circulation statistics for first-order meteorological fields, suggestive of a tendency for convergence of numerical solutions. Second and higher-order fields can, however, vary significantly between the two models.

  19. An Intercomparison of the Dynamical Cores of Global Atmospheric Circulation Models for Mars

    NASA Technical Reports Server (NTRS)

    Hollingsworth, Jeffery L.; Bridger, Alison F. C.; Haberle, Robert M.

    1998-01-01

    This is a Final Report for a Joint Research Interchange (JRI) between NASA Ames Research Center and San Jose State University, Department of Meteorology. The focus of this JRI has been to evaluate the dynamical 'cores' of two global atmospheric circulation models for Mars that are in operation at the NASA Ames Research Center. The two global circulation models in use are fundamentally different: one uses spherical harmonics in its horizontal representation of field variables; the other uses finite differences on a uniform longitude-latitude grid. Several simulations have been conducted to assess how the dynamical processors of each of these circulation models perform using identical 'simple physics' parameterizations. A variety of climate statistics (e.g., time-mean flows and eddy fields) have been compared for realistic solstitial mean basic states. Results of this research have demonstrated that the two Mars circulation models with completely different spatial representations and discretizations produce rather similar circulation statistics for first-order meteorological fields, suggestive of a tendency for convergence of numerical solutions. Second and higher-order fields can, however, vary significantly between the two models.

  20. Multiple phase transitions in extended hard-core lattice gas models in two dimensions.

    PubMed

    Nath, Trisha; Rajesh, R

    2014-07-01

    We study the k-NN hard-core lattice gas model in which the first k next-nearest-neighbor sites of a particle are excluded from occupation by other particles on a two-dimensional square lattice. This model is the lattice version of the hard-disk system with increasing k corresponding to decreasing lattice spacing. While the hard-disk system is known to undergo a two-step freezing process with increasing density, the lattice model has been known to show only one transition. Here, based on Monte Carlo simulations and high-density expansions of the free energy and density, we argue that for k = 4,10,11,14,⋯, the lattice model undergoes multiple transitions with increasing density. Using Monte Carlo simulations, we confirm the same for k = 4,...,11. This, in turn, resolves an existing puzzle as to why the 4-NN model has a continuous transition against the expectation of a first-order transition.

  1. Multiple phase transitions in extended hard-core lattice gas models in two dimensions.

    PubMed

    Nath, Trisha; Rajesh, R

    2014-07-01

    We study the k-NN hard-core lattice gas model in which the first k next-nearest-neighbor sites of a particle are excluded from occupation by other particles on a two-dimensional square lattice. This model is the lattice version of the hard-disk system with increasing k corresponding to decreasing lattice spacing. While the hard-disk system is known to undergo a two-step freezing process with increasing density, the lattice model has been known to show only one transition. Here, based on Monte Carlo simulations and high-density expansions of the free energy and density, we argue that for k = 4,10,11,14,⋯, the lattice model undergoes multiple transitions with increasing density. Using Monte Carlo simulations, we confirm the same for k = 4,...,11. This, in turn, resolves an existing puzzle as to why the 4-NN model has a continuous transition against the expectation of a first-order transition. PMID:25122264

  2. Modeling active galactic nucleus feedback in cool-core clusters: The balance between heating and cooling

    SciTech Connect

    Li, Yuan; Bryan, Greg L.

    2014-07-01

    We study the long-term evolution of an idealized cool-core galaxy cluster under the influence of momentum-driven active galactic nucleus (AGN) feedback using three-dimensional high-resolution (60 pc) adaptive mesh refinement simulations. The feedback is modeled with a pair of precessing jets whose power is calculated based on the accretion rate of the cold gas surrounding the supermassive black hole (SMBH). The intracluster medium first cools into clumps along the propagation direction of the jets. As the jet power increases, gas condensation occurs isotropically, forming spatially extended structures that resemble the observed Hα filaments in Perseus and many other cool-core clusters. Jet heating elevates the gas entropy, halting clump formation. The cold gas that is not accreted onto the SMBH settles into a rotating disk of ∼10{sup 11} M {sub ☉}. The hot gas cools directly onto the disk while the SMBH accretes from its innermost region, powering the AGN that maintains a thermally balanced state for a few Gyr. The mass cooling rate averaged over 7 Gyr is ∼30 M {sub ☉} yr{sup –1}, an order of magnitude lower than the classic cooling flow value. Medium resolution simulations produce similar results, while in low resolution runs, the cluster experiences cycles of gas condensation and AGN outbursts. Owing to its self-regulating mechanism, AGN feedback can successfully balance cooling with a wide range of model parameters. Our model also produces cold structures in early stages that are in good agreement with the observations. However, the long-lived massive cold disk is unrealistic, suggesting that additional physical processes are still needed.

  3. Advanced Test Reactor Core Modeling Update Project Annual Report for Fiscal Year 2013

    SciTech Connect

    David W. Nigg

    2013-09-01

    Legacy computational reactor physics software tools and protocols currently used for support of Advanced Test Reactor (ATR) core fuel management and safety assurance, and to some extent, experiment management, are inconsistent with the state of modern nuclear engineering practice, and are difficult, if not impossible, to verify and validate (V&V) according to modern standards. Furthermore, the legacy staff knowledge required for effective application of these tools and protocols from the 1960s and 1970s is rapidly being lost due to staff turnover and retirements. In late 2009, the Idaho National Laboratory (INL) initiated a focused effort, the ATR Core Modeling Update Project, to address this situation through the introduction of modern high-fidelity computational software and protocols. This aggressive computational and experimental campaign will have a broad strategic impact on the operation of the ATR, both in terms of improved computational efficiency and accuracy for support of ongoing DOE programs as well as in terms of national and international recognition of the ATR National Scientific User Facility (NSUF).

  4. A transmission line model for propagation in elliptical core optical fibers

    SciTech Connect

    Georgantzos, E.; Boucouvalas, A. C.; Papageorgiou, C.

    2015-12-31

    The calculation of mode propagation constants of elliptical core fibers has been the purpose of extended research leading to many notable methods, with the classic step index solution based on Mathieu functions. This paper seeks to derive a new innovative method for the determination of mode propagation constants in single mode fibers with elliptic core by modeling the elliptical fiber as a series of connected coupled transmission line elements. We develop a matrix formulation of the transmission line and the resonance of the circuits is used to calculate the mode propagation constants. The technique, used with success in the case of cylindrical fibers, is now being extended for the case of fibers with elliptical cross section. The advantage of this approach is that it is very well suited to be able to calculate the mode dispersion of arbitrary refractive index profile elliptical waveguides. The analysis begins with the deployment Maxwell’s equations adjusted for elliptical coordinates. Further algebraic analysis leads to a set of equations where we are faced with the appearance of harmonics. Taking into consideration predefined fixed number of harmonics simplifies the problem and enables the use of the resonant circuits approach. According to each case, programs have been created in Matlab, providing with a series of results (mode propagation constants) that are further compared with corresponding results from the ready known Mathieu functions method.

  5. A numerical model for elliptical instability of the Earth's fluid outer core

    NASA Astrophysics Data System (ADS)

    Seyed-Mahmoud, Behnam; Henderson, Gary; Aldridge, Keith

    2000-01-01

    A dynamical model is proposed for the elliptical instability that has been reported by Aldridge et al. [Aldridge, K.D., Seyed-Mahmoud, B., Henderson, G.A., van Wijngaarden, W., 1997. Elliptical instability of the Earth's fluid core. Phys. Earth Planet. Inter., 103, 365-374] in connection with recent experiments on an ellipsoidal shell of rotating fluid. The frequencies and growth rates of the instability are obtained numerically by means of a Galerkin method that is based upon the normal modes of the contained fluid. A finite-element method has been employed to approximately solve the ill-posed Poincaré problem for the normal modes. The numerical results for a special case are compared with their analytical counterparts, and the agreement is to within 0.1% for shells of small ellipticity. Results are presented for other cases, including some where the boundary perturbation is allowed to rotate slowly with respect to the inertial frame. The conclusion is that such investigations are of geophysical interest, since tidal forcing might be sufficient to excite an elliptical instability of the fluid outer core of the Earth and thus contribute to the geomagnetic field.

  6. [Kampo Medicine in the New Model Core Curriculum of Pharmaceutical Education].

    PubMed

    Kobayashi, Yoshinori

    2016-01-01

    What should we educate for Kampo medicine in the model core curriculum of pharmaceutical education? The curricular core should be discussed considering the points mentioned below. (1) Positioning of Kampo medicine in the Japanese medical care system. Kampo medicine is an authorized medical care category in the National Health Insurance (NHI) program in Japan. The NHI drug price list carries 148 Kampo formulations. According to the report of the Japan Kampo Medicines Manufacturers Association in 2011, approximately 90% of Japanese physicians prescribe Kampo medicines. (2) Differences between Kampo medicine and western medicine: In Kampo medicine, the most suitable formula among various Kampo formulas to normalize the psychophysical state of individual patients is selected. In other words, if there is a complaint, there are always some treatments. (3) A strong point of Kampo medicine: Kampo medicine enables physicians to deal with difficult-to-treat conditions by western medicine alone. Also, by using the scale of Kampo medicine, each patient can grasp his or her own systemic state and improve their lifestyle. To extend healthy life expectancy, a basic knowledge of Kampo medicine may play a significant role in integrated health care. "The guide book of the approval standards for OTC Kampo products", "the pharmaceutical advanced educational guideline", and "the manual of the exam questions preparation for registered sales clerks" should also be consulted before selecting the area and contents that should be covered. PMID:26935081

  7. Strain-rate dependent shear viscosity of the Gaussian core model fluid.

    PubMed

    Ahmed, Alauddin; Mausbach, Peter; Sadus, Richard J

    2009-12-14

    Nonequilibrium molecular dynamics simulations are reported for the shear viscosity of the Gaussian core model (GCM) fluid over a wide range of densities, temperatures and strain rates. A transition from Newtonian and non-Newtonian behavior is observed in all cases for sufficiently high strain rates. On the high-density side of the solid region where re-entrant melting occurs, the shear viscosity decreases significantly when the density is increased at constant temperature and Newtonian behavior persists until very high strain rates. This behavior, which is attributed to particle overlap, is in contrast to the monotonic increase in shear viscosity with density observed for the Lennard-Jones potential. Contrary to the behavior of normal fluids, the viscosity is observed to increase with increasing temperatures at high densities. This reflects a peculiarity of the GCM, namely the approach to the "infinite-density ideal-gas limit." The behavior is also consistent with viscosity measurements of cationic surfactant solutions. In contrast to other potentials, the shear viscosities for the Gaussian core potential at low to moderate strain rates are obtained with modest statistical uncertainties. Zero shear viscosities extrapolated from the nonequilibrium simulations are in good agreement with equilibrium Green-Kubo calculations.

  8. A Refined Prediction Model for Core and Lower Extremity Sprains and Strains Among Collegiate Football Players

    PubMed Central

    Wilkerson, Gary B.; Colston, Marisa A.

    2015-01-01

    Context Researchers have identified high exposure to game conditions, low back dysfunction, and poor endurance of the core musculature as strong predictors for the occurrence of sprains and strains among collegiate football players. Objective To refine a previously developed injury-prediction model through analysis of 3 consecutive seasons of data. Design Cohort study. Setting National Collegiate Athletic Association Division I Football Championship Subdivision football program. Patients or Other Participants For 3 consecutive years, all 152 team members (age = 19.7 ± 1.5 years, height = 1.84 ± 0.08 m, mass = 101.08 ± 19.28 kg) presented for a mandatory physical examination on the day before initiation of preseason practice sessions. Main Outcome Measure(s) Associations between preseason measurements and the subsequent occurrence of a core or lower extremity sprain or strain were established for 256 player-seasons of data. We used receiver operating characteristic analysis to identify optimal cut points for dichotomous categorizations of cases as high risk or low risk. Both logistic regression and Cox regression analyses were used to identify a multivariable injury-prediction model with optimal discriminatory power. Results Exceptionally good discrimination between injured and uninjured cases was found for a 3-factor prediction model that included equal to or greater than 1 game as a starter, Oswestry Disability Index score equal to or greater than 4, and poor wall-sit–hold performance. The existence of at least 2 of the 3 risk factors demonstrated 56% sensitivity, 80% specificity, an odds ratio of 5.28 (90% confidence interval = 3.31, 8.44), and a hazard ratio of 2.97 (90% confidence interval = 2.14, 4.12). Conclusions High exposure to game conditions was the dominant injury risk factor for collegiate football players, but a surprisingly mild degree of low back dysfunction and poor core-muscle endurance appeared to be important modifiable risk factors that

  9. A core observational data model for enhancing the interoperability of ontologically annotated environmental data

    NASA Astrophysics Data System (ADS)

    Schildhauer, M.; Bermudez, L. E.; Bowers, S.; Dibner, P. C.; Gries, C.; Jones, M. B.; McGuinness, D. L.; Cao, H.; Cox, S. J.; Kelling, S.; Lagoze, C.; Lapp, H.; Madin, J.

    2010-12-01

    Research in the environmental sciences often requires accessing diverse data, collected by numerous data providers over varying spatiotemporal scales, incorporating specialized measurements from a range of instruments. These measurements are typically documented using idiosyncratic, disciplinary specific terms, and stored in management systems ranging from desktop spreadsheets to the Cloud, where the information is often further decomposed or stylized in unpredictable ways. This situation creates major informatics challenges for broadly discovering, interpreting, and merging the data necessary for integrative earth science research. A number of scientific disciplines have recognized these issues, and been developing semantically enhanced data storage frameworks, typically based on ontologies, to enable communities to better circumscribe and clarify the content of data objects within their domain of practice. There is concern, however, that cross-domain compatibility of these semantic solutions could become problematic. We describe here our efforts to address this issue by developing a core, unified Observational Data Model, that should greatly facilitate interoperability among the semantic solutions growing organically within diverse scientific domains. Observational Data Models have emerged independently from several distinct scientific communities, including the biodiversity sciences, ecology, evolution, geospatial sciences, and hydrology, to name a few. Informatics projects striving for data integration within each of these domains had converged on identifying "observations" and "measurements" as fundamental abstractions that provide useful "templates" through which scientific data can be linked— at the structural, composited, or even cell value levels— to domain terms stored in ontologies or other forms of controlled vocabularies. The Scientific Observations Network, SONet (http://sonet.ecoinformatics.org) brings together a number of these observational

  10. Four-junction superconducting circuit

    PubMed Central

    Qiu, Yueyin; Xiong, Wei; He, Xiao-Ling; Li, Tie-Fu; You, J. Q.

    2016-01-01

    We develop a theory for the quantum circuit consisting of a superconducting loop interrupted by four Josephson junctions and pierced by a magnetic flux (either static or time-dependent). In addition to the similarity with the typical three-junction flux qubit in the double-well regime, we demonstrate the difference of the four-junction circuit from its three-junction analogue, including its advantages over the latter. Moreover, the four-junction circuit in the single-well regime is also investigated. Our theory provides a tool to explore the physical properties of this four-junction superconducting circuit. PMID:27356619

  11. Four-junction superconducting circuit.

    PubMed

    Qiu, Yueyin; Xiong, Wei; He, Xiao-Ling; Li, Tie-Fu; You, J Q

    2016-01-01

    We develop a theory for the quantum circuit consisting of a superconducting loop interrupted by four Josephson junctions and pierced by a magnetic flux (either static or time-dependent). In addition to the similarity with the typical three-junction flux qubit in the double-well regime, we demonstrate the difference of the four-junction circuit from its three-junction analogue, including its advantages over the latter. Moreover, the four-junction circuit in the single-well regime is also investigated. Our theory provides a tool to explore the physical properties of this four-junction superconducting circuit. PMID:27356619

  12. Four-junction superconducting circuit.

    PubMed

    Qiu, Yueyin; Xiong, Wei; He, Xiao-Ling; Li, Tie-Fu; You, J Q

    2016-06-30

    We develop a theory for the quantum circuit consisting of a superconducting loop interrupted by four Josephson junctions and pierced by a magnetic flux (either static or time-dependent). In addition to the similarity with the typical three-junction flux qubit in the double-well regime, we demonstrate the difference of the four-junction circuit from its three-junction analogue, including its advantages over the latter. Moreover, the four-junction circuit in the single-well regime is also investigated. Our theory provides a tool to explore the physical properties of this four-junction superconducting circuit.

  13. Performance measurements of a pilot superconducting solenoid model core for a wind tunnel magnetic suspension and balance system

    NASA Technical Reports Server (NTRS)

    Goodyer, M. J.; Britcher, C. P.

    1983-01-01

    The results of experimental demonstrations of a superconducting solenoid model core in the Southampton University Magnetic Suspension and Balance System are detailed. Technology and techniques relevant to large-scale wind tunnel MSBSs comprise the long term goals. The magnetic moment of solenoids, difficulties peculiar to superconducting solenoid cores, lift force and pitching moment, dynamic lift calibration, and helium boil-off measurements are discussed.

  14. Aberrant expression and function of gap junctions during carcinogenesis.

    PubMed Central

    Yamasaki, H

    1991-01-01

    Gap junctional intercellular communication plays a key role in the maintenance of homeostasis in multicellular organisms. Reflecting deranged homeostasis in cancer cells, most transformed or cancerous cells show aberrant gap junctional intercellular communication; they have decreased junctional communication between each other and/or with surrounding normal cells. Studies with in vitro cell transformation and animal carcinogenesis models suggest an involvement of blocked intercellular communication in later stages of carcinogenesis. Analysis of expression of gap junction proteins (connexins) and corresponding mRNA indicates that a number of regulation sites are involved in aberrant function of gap junctions during carcinogenesis. Suppression of transformed phenotypes is often seen when transformed cells are physically in contact with their normal counterparts. Some studies suggest that gap junctional intercellular communication is involved in such tumor suppression. PMID:1663449

  15. Spiral waves in two-dimensional models of ventricular muscle: formation of a stationary core.

    PubMed Central

    Beaumont, J; Davidenko, N; Davidenko, J M; Jalife, J

    1998-01-01

    Previous experimental studies have clearly demonstrated the existence of drifting and stationary electrical spiral waves in cardiac muscle and their involvement in cardiac arrhythmias. Here we present results of a study of reentrant excitation in computer simulations based on a membrane model of the ventricular cell. We have explored in detail the parameter space of the model, using tools derived from previous numerical studies in excitation-dynamics models. We have found appropriate parametric conditions for sustained stable spiral wave dynamics (1 s of activity or approximately 10 rotations) in simulations of an anisotropic (ratio in velocity 4:1) cardiac sheet of 2 cm x 2 cm. Initially, we used a model that reproduced well the characteristics of planar electrical waves exhibited by thin sheets of sheep ventricular epicardial muscle during rapid pacing at a cycle length of 300 ms. Under these conditions, the refractory period was 147 ms; the action potential duration (APD) was 120 ms; the propagation velocity along fibers was 33 cm/s; and the wavelength along fibers was 4.85 cm. Using cross-field stimulation in this model, we obtained a stable self-sustaining spiral wave rotating around an unexcited core of 1.75 mm x 7 mm at a period of 115 ms, which reproduced well the experimental results. Thus the data demonstrate that stable spiral wave activity can occur in small cardiac sheets whose wavelength during planar wave excitation in the longitudinal direction is larger than the size of the sheet. Analysis of the mechanism of this observation demonstrates that, during rotating activity, the core exerts a strong electrotonic influence that effectively abbreviates APD (and thus wavelength) in its immediate surroundings and is responsible for the stabilization and perpetuation of the activity. We conclude that appropriate adjustments in the kinetics of the activation front (i.e., threshold for activation and upstroke velocity of the initiating beat) of currently

  16. A Kinetic Vlasov Model for Plasma Simulation Using Discontinuous Galerkin Method on Many-Core Architectures

    NASA Astrophysics Data System (ADS)

    Reddell, Noah

    Advances are reported in the three pillars of computational science achieving a new capability for understanding dynamic plasma phenomena outside of local thermodynamic equilibrium. A continuum kinetic model for plasma based on the Vlasov-Maxwell system for multiple particle species is developed. Consideration is added for boundary conditions in a truncated velocity domain and supporting wall interactions. A scheme to scale the velocity domain for multiple particle species with different temperatures and particle mass while sharing one computational mesh is described. A method for assessing the degree to which the kinetic solution differs from a Maxwell-Boltzmann distribution is introduced and tested on a thoroughly studied test case. The discontinuous Galerkin numerical method is extended for efficient solution of hyperbolic conservation laws in five or more particle phase-space dimensions using tensor-product hypercube elements with arbitrary polynomial order. A scheme for velocity moment integration is integrated as required for coupling between the plasma species and electromagnetic waves. A new high performance simulation code WARPM is developed to efficiently implement the model and numerical method on emerging many-core supercomputing architectures. WARPM uses the OpenCL programming model for computational kernels and task parallelism to overlap computation with communication. WARPM single-node performance and parallel scaling efficiency are analyzed with bottlenecks identified guiding future directions for the implementation. The plasma modeling capability is validated against physical problems with analytic solutions and well established benchmark problems.

  17. Infrared length scale and extrapolations for the no-core shell model

    NASA Astrophysics Data System (ADS)

    Wendt, K. A.; Forssén, C.; Papenbrock, T.; Sääf, D.

    2015-06-01

    We precisely determine the infrared (IR) length scale of the no-core shell model (NCSM). In the NCSM, the A -body Hilbert space is truncated by the total energy, and the IR length can be determined by equating the intrinsic kinetic energy of A nucleons in the NCSM space to that of A nucleons in a 3 (A -1 ) -dimensional hyper-radial well with a Dirichlet boundary condition for the hyper radius. We demonstrate that this procedure indeed yields a very precise IR length by performing large-scale NCSM calculations for 6Li. We apply our result and perform accurate IR extrapolations for bound states of 4He,6He,6Li , and 7Li . We also attempt to extrapolate NCSM results for 10B and 16O with bare interactions from chiral effective field theory over tens of MeV.

  18. Infrared length scale and extrapolations for the no-core shell model

    DOE PAGES

    Wendt, K. A.; Forssén, C.; Papenbrock, T.; Sääf, D.

    2015-06-03

    In this paper, we precisely determine the infrared (IR) length scale of the no-core shell model (NCSM). In the NCSM, the A-body Hilbert space is truncated by the total energy, and the IR length can be determined by equating the intrinsic kinetic energy of A nucleons in the NCSM space to that of A nucleons in a 3(A-1)-dimensional hyper-radial well with a Dirichlet boundary condition for the hyper radius. We demonstrate that this procedure indeed yields a very precise IR length by performing large-scale NCSM calculations for 6Li. We apply our result and perform accurate IR extrapolations for bound statesmore » of 4He, 6He, 6Li, and 7Li. Finally, we also attempt to extrapolate NCSM results for 10B and 16O with bare interactions from chiral effective field theory over tens of MeV.« less

  19. On the Requirements for Realistic Modeling of Neutrino Transport in Simulations of Core-collapse Supernovae

    SciTech Connect

    Lentz, Eric J; Mezzacappa, Anthony; Messer, Bronson; Liebendoerfer, Matthias; Hix, William Raphael; Bruenn, S. W.

    2012-01-01

    We have conducted a series of numerical experiments with the spherically-symmetric, general-relativistic neutrino radiation hydrodynamics code Agile-BOLTZTRAN to examine the effects of several approximations used in multidimensional core-collapse supernova simulations. Our code permits us to examine the effects of these approximations quantitatively by removing, or substituting for, the pieces of supernova physics of interest. These approximations include: (1) using Newtonian versus general-relativistic gravity, hydrodynamics, and transport; (2) using older weak interactions, including the omission of non-isoenergetic neutrino scattering, versus up-to-date weak interactions; and (3) omitting the velocity-dependent terms, or observer corrections, from the neutrino Boltzmann kinetic equation. We demonstrate that each of these changes has non-negligible effects on the outcomes of our simulations. Finally, we discuss the impact these results have for current, and future, multidimensional models.

  20. A scalable implementation of a finite-volume dynamical core in the Community Atmosphere Model

    SciTech Connect

    Mirin, A A; Sawyer, W B

    2004-09-24

    A distributed memory message-passing parallel implementation of a finite-volume discretization of the primitive equations in the Community Atmosphere Model is presented. Due to the data dependencies resulting from the polar singularity of the latitude-longitude coordinate system, we employ two separate domain decompositions within the dynamical core--one in latitude/level space, and the other in longitude/latitude space. This requires that the data be periodically redistributed between these two decompositions. In addition, the domains contain halo regions that cover the nearest neighbor data dependencies. A combination of several techniques, such as one-sided communication and multithreading, are presented to optimize data movements. The resulting algorithm is shown to scale to very large machine configurations, even for relatively coarse resolutions.

  1. A Scalable Implementation of a Finite-Volume Dynamical Core in the Community Atmosphere Model

    SciTech Connect

    Sawyer, W; Mirin, A

    2004-06-25

    A distributed memory message-passing parallel implementation of a finite-volume discretization of the primitive equations in the Community Atmosphere Model is presented. Due to the data dependencies resulting from the polar singularity of the latitude-longitude coordinate system, it is necessary to employ two separate domain decompositions within the dynamical core. Data must be periodically redistributed between these two decompositions. In addition, the domains contain halo regions that cover the nearest neighbor data dependencies. A combination of several techniques, such as one-sided communication and multithreading, are presented to optimize data movements. The resulting algorithm is shown to scale to very large machine configurations, even for relatively coarse resolutions.

  2. Ab Initio No-Core Shell Model Calculations Using Realistic Two- and Three-Body Interactions

    SciTech Connect

    Navratil, P; Ormand, W E; Forssen, C; Caurier, E

    2004-11-30

    There has been significant progress in the ab initio approaches to the structure of light nuclei. One such method is the ab initio no-core shell model (NCSM). Starting from realistic two- and three-nucleon interactions this method can predict low-lying levels in p-shell nuclei. In this contribution, we present a brief overview of the NCSM with examples of recent applications. We highlight our study of the parity inversion in {sup 11}Be, for which calculations were performed in basis spaces up to 9{Dirac_h}{Omega} (dimensions reaching 7 x 10{sup 8}). We also present our latest results for the p-shell nuclei using the Tucson-Melbourne TM three-nucleon interaction with several proposed parameter sets.

  3. Magnetic Tunnel Junctions

    NASA Astrophysics Data System (ADS)

    Reiss, Günter; Schmalhorst, Jan; Thomas, Andre; Hütten, Andreas; Yuasa, Shinji

    In magnetoelectronic devices large opportunities are opened by the spin dependent tunneling resistance, where a strong dependence of the tunneling current on the relative orientation of the magnetization of the electrodes is found. Within a short time, the amplitude of the resistance change of the junctions increased dramatically. We will cover Al-O and MgO based junctions and present highly spin-polarized electrode materials such as Heusler alloys. Furthermore, we will give a short overview on applications such as read heads in hard disk drives, storage cells in MRAMs, field programmable logic circuits and biochips. Finally, we will discuss the currently growing field of current induced magnetization switching.

  4. Percentage of Positive Biopsy Cores: A Better Risk Stratification Model for Prostate Cancer?

    SciTech Connect

    Huang Jiayi; Vicini, Frank A.; Williams, Scott G.; Ye Hong; McGrath, Samuel; Ghilezan, Mihai; Krauss, Daniel; Martinez, Alvaro A.; Kestin, Larry L.

    2012-07-15

    Purpose: To assess the prognostic value of the percentage of positive biopsy cores (PPC) and perineural invasion in predicting the clinical outcomes after radiotherapy (RT) for prostate cancer and to explore the possibilities to improve on existing risk-stratification models. Methods and Materials: Between 1993 and 2004, 1,056 patients with clinical Stage T1c-T3N0M0 prostate cancer, who had four or more biopsy cores sampled and complete biopsy core data available, were treated with external beam RT, with or without a high-dose-rate brachytherapy boost at William Beaumont Hospital. The median follow-up was 7.6 years. Multivariate Cox regression analysis was performed with PPC, Gleason score, pretreatment prostate-specific antigen, T stage, PNI, radiation dose, androgen deprivation, age, prostate-specific antigen frequency, and follow-up duration. A new risk stratification (PPC classification) was empirically devised to incorporate PPC and replace the T stage. Results: On multivariate Cox regression analysis, the PPC was an independent predictor of distant metastasis, cause-specific survival, and overall survival (all p < .05). A PPC >50% was associated with significantly greater distant metastasis (hazard ratio, 4.01; 95% confidence interval, 1.86-8.61), and its independent predictive value remained significant with or without androgen deprivation therapy (all p < .05). In contrast, PNI and T stage were only predictive for locoregional recurrence. Combining the PPC ({<=}50% vs. >50%) with National Comprehensive Cancer Network risk stratification demonstrated added prognostic value of distant metastasis for the intermediate-risk (hazard ratio, 5.44; 95% confidence interval, 1.78-16.6) and high-risk (hazard ratio, 4.39; 95% confidence interval, 1.70-11.3) groups, regardless of the use of androgen deprivation and high-dose RT (all p < .05). The proposed PPC classification appears to provide improved stratification of the clinical outcomes relative to the National

  5. Josephson junction in a thin film

    SciTech Connect

    Kogan, V. G.; Dobrovitski, V. V.; Clem, J. R.; Mawatari, Yasunori; Mints, R. G.

    2001-04-01

    The phase difference {phi}(y) for a vortex at a line Josephson junction in a thin film attenuates at large distances as a power law, unlike the case of a bulk junction where it approaches exponentially the constant values at infinities. The field of a Josephson vortex is a superposition of fields of standard Pearl vortices distributed along the junction with the line density {phi}'(y)/2{pi}. We study the integral equation for {phi}(y) and show that the phase is sensitive to the ratio l/{Lambda}, where l={lambda}{sub J}{sup 2}/{lambda}{sub L}, {Lambda}=2{lambda}{sub L}{sup 2}/d, {lambda}{sub L}, and {lambda}{sub J} are the London and Josephson penetration depths, and d is the film thickness. For l<<{Lambda}, the vortex ''core'' of the size l is nearly temperature independent, while the phase ''tail'' scales as l{Lambda}/y{sup 2}={lambda}{sub J}2{lambda}{sub L}/d/y{sup 2}; i.e., it diverges as T{yields}T{sub c}. For l>>{Lambda}, both the core and the tail have nearly the same characteristic length l{Lambda}.

  6. New geochemical models of core formation in the Moon from metal-silicate partitioning of 15 siderophile elements

    NASA Astrophysics Data System (ADS)

    Steenstra, E. S.; Rai, N.; Knibbe, J. S.; Lin, Y. H.; van Westrenen, W.

    2016-05-01

    We re-examine the conditions at which core formation in the Moon may have occurred by linking the observed lunar mantle depletions of 15 siderophile elements, including volatile siderophile elements (VSE) to predictive equations derived from a database compilation of metal-silicate partition coefficients obtained at lunar-relevant pressure-temperature-oxygen fugacity (P- T- fO2) conditions. Our results suggest that at mantle temperatures between the solidus and liquidus the depletions for all elements considered can be satisfied, but only if the Moon was essentially fully molten at the time of core formation while assuming a S-rich (>8 wt%) core comprising 2.5 wt% of the mass of the Moon. However, we observe that at temperatures exceeding the mantle liquidus, with increasing temperature the core S content required to satisfy the element depletions is reduced. As a S-poor core is likely from recent lunar mantle estimates of S abundance, this suggests much higher temperatures during lunar core formation than previously proposed. We conclude that the VSE depletions in the lunar mantle can be solely explained by core formation depletion, suggesting that no significant devolatilization has occurred in later periods of lunar evolution. This is in agreement with the discovery of significant amounts of other volatiles in the lunar interior, but hard to reconcile with current lunar formation models.

  7. Parameter Sensitivity Study of the Unreacted-Core Shrinking Model: A Computer Activity for Chemical Reaction Engineering Courses

    ERIC Educational Resources Information Center

    Tudela, Ignacio; Bonete, Pedro; Fullana, Andres; Conesa, Juan Antonio

    2011-01-01

    The unreacted-core shrinking (UCS) model is employed to characterize fluid-particle reactions that are important in industry and research. An approach to understand the UCS model by numerical methods is presented, which helps the visualization of the influence of the variables that control the overall heterogeneous process. Use of this approach in…

  8. Vortex structures in exponentially shaped Josephson junctions

    NASA Astrophysics Data System (ADS)

    Shukrinov, Yu. M.; Semerdjieva, E. G.; Boyadjiev, T. L.

    2005-04-01

    We report the numerical calculations of the static vortex structure and critical curves in exponentially shaped long Josephson junctions for in-line and overlap geometries. Stability of the static solutions is investigated by checking the sign of the smallest eigenvalue of the associated Sturm-Liouville problem. The change in the junction width leads to the renormalization of the magnetic flux in comparison with the case of a linear one-dimensional model. We study the influence of the model's parameters, and particularly, the shape parameter on the stability of the states of the magnetic flux. We compare the vortex structure and critical curves for the in-line and overlap geometries. Our numerically constructed critical curve of the Josephson junction matches well with the experimental one.

  9. No-core configuration-interaction model for the isospin- and angular-momentum-projected states

    NASA Astrophysics Data System (ADS)

    Satuła, W.; Båczyk, P.; Dobaczewski, J.; Konieczka, M.

    2016-08-01

    Background: Single-reference density functional theory is very successful in reproducing bulk nuclear properties like binding energies, radii, or quadrupole moments throughout the entire periodic table. Its extension to the multireference level allows for restoring symmetries and, in turn, for calculating transition rates. Purpose: We propose a new variant of the no-core-configuration-interaction (NCCI) model treating properly isospin and rotational symmetries. The model is applicable to any nucleus irrespective of its mass and neutron- and proton-number parity. It properly includes polarization effects caused by an interplay between the long- and short-range forces acting in the atomic nucleus. Methods: The method is based on solving the Hill-Wheeler-Griffin equation within a model space built of linearly dependent states having good angular momentum and properly treated isobaric spin. The states are generated by means of the isospin and angular-momentum projection applied to a set of low-lying (multi)particle-(multi)hole deformed Slater determinants calculated using the self-consistent Skyrme-Hartree-Fock approach. Results: The theory is applied to calculate energy spectra in N ≈Z nuclei that are relevant from the point of view of a study of superallowed Fermi β decays. In particular, a new set of the isospin-symmetry-breaking corrections to these decays is given. Conclusions: It is demonstrated that the NCCI model is capable of capturing main features of low-lying energy spectra in light and medium-mass nuclei using relatively small model space and without any local readjustment of its low-energy coupling constants. Its flexibility and a range of applicability makes it an interesting alternative to the conventional nuclear shell model.

  10. High accuracy modeling for advanced nuclear reactor core designs using Monte Carlo based coupled calculations

    NASA Astrophysics Data System (ADS)

    Espel, Federico Puente

    The main objective of this PhD research is to develop a high accuracy modeling tool using a Monte Carlo based coupled system. The presented research comprises the development of models to include the thermal-hydraulic feedback to the Monte Carlo method and speed-up mechanisms to accelerate the Monte Carlo criticality calculation. Presently, deterministic codes based on the diffusion approximation of the Boltzmann transport equation, coupled with channel-based (or sub-channel based) thermal-hydraulic codes, carry out the three-dimensional (3-D) reactor core calculations of the Light Water Reactors (LWRs). These deterministic codes utilize nuclear homogenized data (normally over large spatial zones, consisting of fuel assembly or parts of fuel assembly, and in the best case, over small spatial zones, consisting of pin cell), which is functionalized in terms of thermal-hydraulic feedback parameters (in the form of off-line pre-generated cross-section libraries). High accuracy modeling is required for advanced nuclear reactor core designs that present increased geometry complexity and material heterogeneity. Such high-fidelity methods take advantage of the recent progress in computation technology and coupled neutron transport solutions with thermal-hydraulic feedback models on pin or even on sub-pin level (in terms of spatial scale). The continuous energy Monte Carlo method is well suited for solving such core environments with the detailed representation of the complicated 3-D problem. The major advantages of the Monte Carlo method over the deterministic methods are the continuous energy treatment and the exact 3-D geometry modeling. However, the Monte Carlo method involves vast computational time. The interest in Monte Carlo methods has increased thanks to the improvements of the capabilities of high performance computers. Coupled Monte-Carlo calculations can serve as reference solutions for verifying high-fidelity coupled deterministic neutron transport methods

  11. Towards self-consistent modelling of the Martian dichotomy: Coupled models of simultaneous core and crust formation

    NASA Astrophysics Data System (ADS)

    Keller, T.; Golabek, G.; Gerya, T. V.; Connolly, J.

    2009-04-01

    One of the most striking surface features on Mars is the crustal dichotomy. The crustal dichotomy, a large difference in elevation and crustal thickness between the southern highlands and the northern lowlands, is the oldest geological feature on Mars. It was formed more than 4.1 Ga ago [Solomon et al., 2005; Nimmo and Tanaka, 2005; Frey, 2006] owing to either exogenic [e.g. Nimmo et al., 2008; Andrews-Hanna et al., 2008] or endogenic processes [e.g. Zhong and Zuber, 2001; Roberts and Zhong, 2006; Keller and Tackley, 2009]. Based on the geochemical analysis of SNC meteorites it was suggested that a primordial crust with up to 45 km thickness can be formed already during the Martian core formation [Norman, 1999]. The final accretion stage of terrestrial planets is based on stochastically distributed impacts [e.g. Chambers, 2004; Rubie et al., 2007]. Therefore we suggest that the sinking of iron diapirs, delivered by late pre-differentiated impactors, might have induced shear heating-related temperature anomalies in the mantle, which fostered the formation of early Martian crust. In this study, we examine parameter sets that will likely cause an onset of hemispherical low-degree mantle convection directly after, and coupled to, an already asymmetrical core formation. To test this hypothesis we use a numerical model, where we self-consistently couple the formation of the Martian iron core to the onset of mantle convection and crust formation. We perform 2D spherical simulations using the code I2ELVIS applying the newly developed "spherical-Cartesian" methodology [Gerya and Yuen, 2007]. It combines finite differences on a fully staggered rectangular Eulerian grid and Lagrangian marker-in-cell technique for solving momentum, continuity and temperature equations as well as Poisson equation for gravity potential in a self-gravitating planetary body. In this model, the planet is surrounded by a low viscosity, massless fluid ("sticky air") to simulate a free surface

  12. Phase diagram of the uniaxial and biaxial soft-core Gay-Berne model

    NASA Astrophysics Data System (ADS)

    Berardi, Roberto; Lintuvuori, Juho S.; Wilson, Mark R.; Zannoni, Claudio

    2011-10-01

    Classical molecular dynamics simulations have been used to explore the phase diagrams for a family of attractive-repulsive soft-core Gay-Berne models [R. Berardi, C. Zannoni, J. S. Lintuvuori, and M. R. Wilson, J. Chem. Phys. 131, 174107 (2009)] and determine the effect of particle softness, i.e., of a moderately repulsive short-range interaction, on the order parameters and phase behaviour of model systems of uniaxial and biaxial ellipsoidal particles. We have found that isotropic, uniaxial, and biaxial nematic and smectic phases are obtained for the model. Extensive calculations of the nematic region of the phase diagram show that endowing mesogenic particles with such soft repulsive interactions affect the stability range of the nematic phases, and in the case of phase biaxiality it also shifts it to lower temperatures. For colloidal particles, stabilised by surface functionalisation, (e.g., with polymer chains), we suggest that it should be possible to tune liquid crystal behaviour to increase the range of stability of uniaxial and biaxial phases (by varying solvent quality). We calculate second virial coefficients and show that they are a useful means of characterising the change in effective softness for such systems. For thermotropic liquid crystals, the introduction of softness in the interactions between mesogens with overall biaxial shape (e.g., through appropriate conformational flexibility) could provide a pathway for the actual chemical synthesis of stable room-temperature biaxial nematics.

  13. Equivalent source modeling of the core magnetic field using magsat data

    NASA Technical Reports Server (NTRS)

    Mayhew, M. A.; Estes, R. H.

    1983-01-01

    Experiments are carried out on fitting the main field using different numbers of equivalent sources arranged in equal area at fixed radii at and inside the core-mantle boundary. In fixing the radius for a given series of runs, the convergence problems that result from the extreme nonlinearity of the problem when dipole positions are allowed to vary are avoided. Results are presented from a comparison between this approach and the standard spherical harmonic approach for modeling the main field in terms of accuracy and computational efficiency. The modeling of the main field with an equivalent dipole representation is found to be comparable to the standard spherical harmonic approach in accuracy. The 32 deg dipole density (42 dipoles) corresponds approximately to an eleventh degree/order spherical harmonic expansion (143 parameters), whereas the 21 dipole density (92 dipoles) corresponds to approximately a seventeenth degree and order expansion (323 parameters). It is pointed out that fixing the dipole positions results in rapid convergence of the dipole solutions for single-epoch models.

  14. The Status of Multi-Dimensional Core-Collapse Supernova Models

    NASA Astrophysics Data System (ADS)

    Müller, B.

    2016-09-01

    Models of neutrino-driven core-collapse supernova explosions have matured considerably in recent years. Explosions of low-mass progenitors can routinely be simulated in 1D, 2D, and 3D. Nucleosynthesis calculations indicate that these supernovae could be contributors of some lighter neutron-rich elements beyond iron. The explosion mechanism of more massive stars remains under investigation, although first 3D models of neutrino-driven explosions employing multi-group neutrino transport have become available. Together with earlier 2D models and more simplified 3D simulations, these have elucidated the interplay between neutrino heating and hydrodynamic instabilities in the post-shock region that is essential for shock revival. However, some physical ingredients may still need to be added/improved before simulations can robustly explain supernova explosions over a wide range of progenitors. Solutions recently suggested in the literature include uncertainties in the neutrino rates, rotation, and seed perturbations from convective shell burning. We review the implications of 3D simulations of shell burning in supernova progenitors for the `perturbations-aided neutrino-driven mechanism,' whose efficacy is illustrated by the first successful multi-group neutrino hydrodynamics simulation of an 18 solar mass progenitor with 3D initial conditions. We conclude with speculations about the impact of 3D effects on the structure of massive stars through convective boundary mixing.

  15. Victory Junction Gang Camp

    ERIC Educational Resources Information Center

    Shell, Ryan

    2007-01-01

    This article describes the Victory Junction Gang Camp, a not-for-profit, NASCAR-themed camp for children with chronic medical conditions that serves 24 different disease groups. The mission of the camp is to give children life-changing camping experiences that are exciting, fun, and empowering in a safe and medically sound environment. While doing…

  16. Shapiro and parametric resonances in coupled Josephson junctions

    NASA Astrophysics Data System (ADS)

    Gaafar, Ma A.; Shukrinov, Yu M.; Foda, A.

    2012-11-01

    The effect of microwave irradiation on the phase dynamics of intrinsic Josephson junctions in high temperature superconductors is investigated. We compare the current-voltage characteristics for a stack of coupled Josephson junctions under external irradiation calculated in the framework of CCJJ and CCJJ+DC models.

  17. Self consistent model of core formation and the effective metal-silicate partitioning

    NASA Astrophysics Data System (ADS)

    Ichikawa, H.; Labrosse, S.; Kameyama, M.

    2010-12-01

    It has been long known that the formation of the core transforms gravitational energy into heat and is able to heat up the whole Earth by about 2000 K. However, the distribution of this energy within the Earth is still debated and depends on the core formation process considered. Iron rain in the surface magma ocean is supposed to be the first mechanism of separation for large planets, iron then coalesces to form a pond at the base of the magma ocean [Stevenson 1990]. The time scale of the separation can be estimated from falling velocity of the iron phase, which is estimated by numerical simulation [Ichikawa et al., 2010] as ˜ 10cm/s with iron droplet of centimeter-scale. A simple estimate of the metal-silicate partition from the P-T condition of the base of the magma ocean, which must coincide with between peridotite liquidus and solidus by a single-stage model, is inconsistent with Earth's core-mantle partition. P-T conditions where silicate equilibrated with metal are far beyond the liquidus or solidus temperature for about ˜ 700K. For example, estimated P-T conditions are: 40GPa at 3750K for Wade and Wood, 2005, T ≧ 3600K for Chabot and Agee, 2003 and 35GPa at T ≧ 3300K for Gessmann and Rubie, 2000. Meanwhile, Rubie et al., 2003 shown that metal couldn't equilibrate with silicate on the base of the magma ocean before crystallization of silicate. On the other hand, metal-silicate equilibration is achieved only ˜ 5 s in the state of iron rain. Therefore metal and silicate simultaneously separate and equilibrate each other at the P-T condition during the course to the iron pond. Taking into account the release of gravitational energy, temperature of the middle of the magma ocean would be higher than the liquidus. Estimation of the thermal structure during the iron-silicate separation requires the development of a planetary-sized calculation model. However, because of the huge disparity of scales between the cm-sized drops and the magma ocean, a direct

  18. Brain barriers: Crosstalk between complex tight junctions and adherens junctions

    PubMed Central

    Tietz, Silvia

    2015-01-01

    Unique intercellular junctional complexes between the central nervous system (CNS) microvascular endothelial cells and the choroid plexus epithelial cells form the endothelial blood–brain barrier (BBB) and the epithelial blood–cerebrospinal fluid barrier (BCSFB), respectively. These barriers inhibit paracellular diffusion, thereby protecting the CNS from fluctuations in the blood. Studies of brain barrier integrity during development, normal physiology, and disease have focused on BBB and BCSFB tight junctions but not the corresponding endothelial and epithelial adherens junctions. The crosstalk between adherens junctions and tight junctions in maintaining barrier integrity is an understudied area that may represent a promising target for influencing brain barrier function. PMID:26008742

  19. Can core flows inferred from geomagnetic field models explain the Earth's dynamo?

    NASA Astrophysics Data System (ADS)

    Schaeffer, N.; Silva, E. Lora; Pais, M. A.

    2016-02-01

    We test the ability of large-scale velocity fields inferred from geomagnetic secular variation data to produce the global magnetic field of the Earth. Our kinematic dynamo calculations use quasi-geostrophic (QG) flows inverted from geomagnetic field models which, as such, incorporate flow structures that are Earth-like and may be important for the geodynamo. Furthermore, the QG hypothesis allows straightforward prolongation of the flow from the core surface to the bulk. As expected from previous studies, we check that a simple QG flow is not able to sustain the magnetic field against ohmic decay. Additional complexity is then introduced in the flow, inspired by the action of the Lorentz force. Indeed, on centennial timescales, the Lorentz force can balance the Coriolis force and strict quasi-geostrophy may not be the best ansatz. When our columnar flow is modified to account for the action of the Lorentz force, magnetic field is generated for Elsasser numbers larger than 0.25 and magnetic Reynolds numbers larger than 100. This suggests that our large-scale flow captures the relevant features for the generation of the Earth's magnetic field and that the invisible small-scale flow may not be directly involved in this process. Near the threshold, the resulting magnetic field is dominated by an axial dipole, with some reversed flux patches. Time dependence is also considered, derived from principal component analysis applied to the inverted flows. We find that time periods from 120 to 50 yr do not affect the mean growth rate of the kinematic dynamos. Finally, we note that the footprint of the inner core in the magnetic field generated deep in the bulk of the shell, although we did not include one in our computations.

  20. Experiments and theoretical modelling for a core catcher concept for future light water reactors

    SciTech Connect

    Tromm, W.; Alsmeyer, H.; Buerger, M.; Widmann, W.; Buck, M.

    1996-12-31

    The COMET concept of corium cooling is proposed to be integrated into future reactors. The concept is based on spreading of the ex-vessel core-melt on a sacrificial concrete layer and, after erosion of this layer, flooding the melt by totally passive water ingression from below through a multitude of melt plugs. The resulting evaporation and interaction processes should lead to a fragmented and porously solidified melt, rapidly coolable through open flow channels. The important processes of melt fragmentation and heat transfer from the melt at direct water contact are investigated with thermite melts in medium scale experiments, and with decay heat simulation in large scale experiments in the modified BETA facility. The experiments show fast cool-down of the melt and solidification of the metallic and oxidic fraction of the melt as a porous structure which, due to its high permeability for the steam-water flow, ensures short-term and long-term coolability. As the experiments are 1-dimensional representations of the central section of the core catcher in the characteristic scale, they should be directly applicable to reactor conditions. Specific tests on the possibility of steam explosions at the initial melt water contact showed very low mechanical loads. The conceptual and experimental work at FZK is accompanied by theoretical investigations at IKE, Stuttgart. Main aims are to optimize the cooling behavior and to evaluate the possible threat by strong steam explosions. Penetration of water jets into an overlying melt layer and resulting phenomena of fragmentation, coolant channel and porous medium formation constitute the key physical processes. Basic models have been developed and applied to the experiments.

  1. Hexavalent chromium at low concentration alters Sertoli cell barrier and connexin 43 gap junction but not claudin-11 and N-cadherin in the rat seminiferous tubule culture model

    SciTech Connect

    Carette, Diane; Perrard, Marie-Hélène; Prisant, Nadia; Gilleron, Jérome; Pointis, Georges; Segretain, Dominique; Durand, Philippe

    2013-04-01

    Exposure to toxic metals, specifically those belonging to the nonessential group leads to human health defects and among them reprotoxic effects. The mechanisms by which these metals produce their negative effects on spermatogenesis have not been fully elucidated. By using the Durand's validated seminiferous tubule culture model, which mimics the in vivo situation, we recently reported that concentrations of hexavalent chromium, reported in the literature to be closed to that found in the blood circulation of men, increase the number of germ cell cytogenetic abnormalities. Since this metal is also known to affect cellular junctions, we investigated, in the present study, its potential influence on the Sertoli cell barrier and on junctional proteins present at this level such as connexin 43, claudin-11 and N-cadherin. Cultured seminiferous tubules in bicameral chambers expressed the three junctional proteins and ZO-1 for at least 12 days. Exposure to low concentrations of chromium (10 μg/l) increased the trans-epithelial resistance without major changes of claudin-11 and N-cadherin expressions but strongly delocalized the gap junction protein connexin 43 from the membrane to the cytoplasm of Sertoli cells. The possibility that the hexavalent chromium-induced alteration of connexin 43 indirectly mediates the effect of the toxic metal on the blood–testis barrier dynamic is postulated. - Highlights: ► Influence of Cr(VI) on the Sertoli cell barrier and on junctional proteins ► Use of cultured seminiferous tubules in bicameral chambers ► Low concentrations of Cr(VI) (10 μg/l) altered the trans-epithelial resistance. ► Cr(VI) did not alter claudin-11 and N-cadherin. ► Cr(VI) delocalized connexin 43 from the membrane to the cytoplasm of Sertoli cells.

  2. CORCON-MOD3: An integrated computer model for analysis of molten core-concrete interactions. User`s manual

    SciTech Connect

    Bradley, D.R.; Gardner, D.R.; Brockmann, J.E.; Griffith, R.O.

    1993-10-01

    The CORCON-Mod3 computer code was developed to mechanistically model the important core-concrete interaction phenomena, including those phenomena relevant to the assessment of containment failure and radionuclide release. The code can be applied to a wide range of severe accident scenarios and reactor plants. The code represents the current state of the art for simulating core debris interactions with concrete. This document comprises the user`s manual and gives a brief description of the models and the assumptions and limitations in the code. Also discussed are the input parameters and the code output. Two sample problems are also given.

  3. Multiphase model of metal segregation and core formation in growing planetesimals and planetary embryos

    NASA Astrophysics Data System (ADS)

    Dubuffet, F.; Sramek, O.; Ricard, Y. R.

    2009-12-01

    The differentiation of terrestrial planets with segregation of metal from silicates took place contemporaneously with the last stage of planetary accretion and was likely completed in few tens of Myrs. The separation of metal occurs when at least the metallic phase is liquid and proceeds via a combination of transport by diapiric instabilities, a more diffuse percolation flow and liquid separation in a magma ocean. The complex nature of the problem (i.e., the presence of multiple phases, density anomalies comparable in magnitude to the density itself) has posed challenges to numerical modeling attempts. We present a formalism derived from a two-phase model by Bercovici et al. (2001). Our model can handle two components simultaneously, silicates and metal. Depending on local temperature, the metal is present either in solid or liquid state. Below the melting point of the metal, the two components are locked together and their mixture is treated as a single phase fluid where density is a function of composition (iron/silicate proportions). When the metal is liquid, it can separate from the silicates and the two phases interact through shear stress (e.g., Darcy flow) and normal stress. Energy conservation takes into account the different mechanisms by which the gravitational energy is dissipated as heat. We show 1-D spherical calculations of the thermal evolution of growing planetesimals. These accreting bodies are initially heated from within by the decay of short-lived radionuclides and in later stages by impacts in a near-surface layer. We further present 2-D Cartesian numerical simulations of core-mantle differentiation set off by an impact event on a planetary embryo. We show that the first impact that melts the iron phase near the surface is potentially able to trigger the whole core-mantle segregation in a runaway phenomenon, and possibly results in the formation of a magma ocean at the surface of the growing planet. The segregation of the metal in regions

  4. Numerical modeling of coupled nitrification-denitrification in sediment perfusion cores from the hyporheic zone of the Shingobee River, MN

    USGS Publications Warehouse

    Sheibley, R.W.; Jackman, A.P.; Duff, J.H.; Triska, F.J.

    2003-01-01

    Nitrification and denitrification kinetics in sediment perfusion cores were numerically modeled and compared to experiments on cores from the Shingobee River MN, USA. The experimental design incorporated mixing groundwater discharge with stream water penetration into the cores, which provided a well-defined, one-dimensional simulation of in situ hydrologic conditions. Ammonium (NH+4) and nitrate (NO-3) concentration gradients suggested the upper region of the cores supported coupled nitrification-denitrification, where groundwater-derived NH+4 was first oxidized to NO-3 then subsequently reduced via denitrification to N2. Nitrification and denitrification were modeled using a Crank-Nicolson finite difference approximation to a one-dimensional advection-dispersion equation. Both processes were modeled using first-order reaction kinetics because substrate concentrations (NH+4 and NO-3) were much smaller than published Michaelis constants. Rate coefficients for nitrification and denitrification ranged from 0.2 to 15.8 h-1 and 0.02 to 8.0 h-1, respectively. The rate constants followed an Arrhenius relationship between 7.5 and 22 ??C. Activation energies for nitrification and denitrification were 162 and 97.3 kJ/mol, respectively. Seasonal NH+4 concentration patterns in the Shingobee River were accurately simulated from the relationship between perfusion core temperature and NH+4 flux to the overlying water. The simulations suggest that NH+4 in groundwater discharge is controlled by sediment nitrification that, consistent with its activation energy, is strongly temperature dependent. ?? 2003 Elsevier Ltd. All rights reserved.

  5. Analytic model for the complex effective index dispersion of metamaterial-cladding large-area hollow core fibers.

    PubMed

    Zeisberger, Matthias; Tuniz, Alessandro; Schmidt, Markus A

    2016-09-01

    We present a mathematical model that allows interpreting the dispersion and attenuation of modes in hollow-core fibers (HCFs) on the basis of single interface reflection, giving rise to analytic and semi-analytic expressions for the complex effective indices in the case where the core diameter is large and the guiding is based on the reflection by a thin layer. Our model includes two core-size independent reflection parameters and shows the universal inverse-cubed core diameter dependence of the modal attenuation of HCFs. It substantially reduces simulation complexity and enables large scale parameter sweeps, which we demonstrate on the example of a HCF with a highly anisotropic metallic nanowire cladding, resembling an indefinite metamaterial at high metal filling fractions. We reveal design rules that allow engineering modal discrimination and show that metamaterial HCFs can principally have low losses at mid-IR wavelengths (< 1 dB/m at 10.6 µm). Our model can be applied to a great variety of HCFs with large core diameters and can be used for advanced HCF design and performance optimization, in particular with regard to dispersion engineering and modal discrimination. PMID:27607656

  6. A computational model for an open-cycle gas core nuclear rocket

    SciTech Connect

    Poston, D.I.; Kammash, T.

    1996-01-01

    A computational model of an open-cycle gas core nuclear rocket (GCR) is developed. The solution is divided into two distinct areas--thermal hydraulics and neutronics. To obtain the thermal-hydraulic solution, a computer code is written that solves the Navier-Stokes, energy, and species diffusion equations. The two-dimensional transport code TWODANT is used to obtain the neutronics solution. The thermal-hydraulic and neutronic models are coupled, and the solution proceeds in an iterative manner until a consistent power density profile is obtained. Various open-cycle GCR designs are evaluated. First, it is assumed that the fuel and propellant do not mix. In this ideal case, it is found that the limiting factor in determining thrust and specific impulse is the maximum allowable wall heat flux. Following this simplified study, the results from a complete thermal-hydraulic/neutronic solution are presented, and the use of alternate fuels and propellants is considered. Next, a parametric design study is conducted that examine the rocket performance of the open-cycle GCR as a function of various design and operational parameters. It is found that fuel containment is very adversely affected by high reactor power or rocket acceleration. Finally, some concepts are discussed that could help improve fuel containment.

  7. Hydrogel core flexible matrix composite (H-FMC) actuators: theory and preliminary modelling

    NASA Astrophysics Data System (ADS)

    Dicker, M. P. M.; Weaver, P. M.; Rossiter, J. M.; Bond, I. P.

    2014-09-01

    The underlying theory of a new actuator concept based on hydrogel core flexible matrix composites (H-FMC) is presented. The key principle that underlines the H-FMC actuator operation is that the three-dimensional swelling of a hydrogel is partially constrained in order to improve the amount of useful work done. The partial constraint is applied to the hydrogel by a flexible matrix composite (FMC) that minimizes the hydrogel's volume expansion while swelling. This constraint serves to maximize the fixed charge density and resulting osmotic pressure, the driving force behind actuation. In addition, for certain FMC fibre orientations the Poisson's ratio of the anisotropic FMC laminate converts previously unused hydrogel swelling in the radial and circumferential directions into useful axial strains. The potential benefit of the H-FMC concept to hydrogel actuator performance is shown through comparison of force-stroke curves and evaluation of improvements in useful actuation work. The model used to achieve this couples chemical and electrical components, represented with the Nernst-Plank and Poisson equations, as well as a linear elastic mechanical material model, encompassing limited geometric nonlinearities. It is found that improvements in useful actuation work in the order of 1500% over bare hydrogel performance are achieved by the H-FMC concept. A parametric study is also undertaken to determine the effect of various FMC design parameters on actuator free strain and blocking stress. A comparison to other actuator concepts is also included.

  8. STOCHASTICITY AND EFFICIENCY IN SIMPLIFIED MODELS OF CORE-COLLAPSE SUPERNOVA EXPLOSIONS

    SciTech Connect

    Cardall, Christian Y.; Budiardja, Reuben D. E-mail: reubendb@utk.edu

    2015-11-01

    We present an initial report on 160 simulations of a highly simplified model of the post-bounce core-collapse supernova environment in three spatial dimensions (3D). We set different values of a parameter characterizing the impact of nuclear dissociation at the stalled shock in order to regulate the post-shock fluid velocity, thereby determining the relative importance of convection and the stationary accretion shock instability (SASI). While our convection-dominated runs comport with the paradigmatic notion of a “critical neutrino luminosity” for explosion at a given mass accretion rate (albeit with a nontrivial spread in explosion times just above threshold), the outcomes of our SASI-dominated runs are much more stochastic: a sharp threshold critical luminosity is “smeared out” into a rising probability of explosion over a ∼20% range of luminosity. We also find that the SASI-dominated models are able to explode with 3–4 times less efficient neutrino heating, indicating that progenitor properties, and fluid and neutrino microphysics, conducive to the SASI would make the neutrino-driven explosion mechanism more robust.

  9. Modeling of the Reactor Core Isolation Cooling Response to Beyond Design Basis Operations - Interim Report

    SciTech Connect

    Ross, Kyle; Cardoni, Jeffrey N.; Wilson, Chisom Shawn; Morrow, Charles; Osborn, Douglas; Gauntt, Randall O.

    2015-12-01

    Efforts are being pursued to develop and qualify a system-level model of a reactor core isolation (RCIC) steam-turbine-driven pump. The model is being developed with the intent of employing it to inform the design of experimental configurations for full-scale RCIC testing. The model is expected to be especially valuable in sizing equipment needed in the testing. An additional intent is to use the model in understanding more fully how RCIC apparently managed to operate far removed from its design envelope in the Fukushima Daiichi Unit 2 accident. RCIC modeling is proceeding along two avenues that are expected to complement each other well. The first avenue is the continued development of the system-level RCIC model that will serve in simulating a full reactor system or full experimental configuration of which a RCIC system is part. The model reasonably represents a RCIC system today, especially given design operating conditions, but lacks specifics that are likely important in representing the off-design conditions a RCIC system might experience in an emergency situation such as a loss of all electrical power. A known specific lacking in the system model, for example, is the efficiency at which a flashing slug of water (as opposed to a concentrated jet of steam) could propel the rotating drive wheel of a RCIC turbine. To address this specific, the second avenue is being pursued wherein computational fluid dynamics (CFD) analyses of such a jet are being carried out. The results of the CFD analyses will thus complement and inform the system modeling. The system modeling will, in turn, complement the CFD analysis by providing the system information needed to impose appropriate boundary conditions on the CFD simulations. The system model will be used to inform the selection of configurations and equipment best suitable of supporting planned RCIC experimental testing. Preliminary investigations with the RCIC model indicate that liquid water ingestion by the turbine

  10. Plasmaspheric Density Troughs: Global IMAGE EUV Observations and Analysis via Global Core Plasma Modeling

    NASA Technical Reports Server (NTRS)

    Adrian, M. L.; Gallagher, D. L.; Green, J. L.; Sandel, B. R.; Six, N. Frank (Technical Monitor)

    2002-01-01

    To date, the IMAGE EUV camera has observed several plasmaspheric density trough features inside the plasmapause under a wide range of geomagnetic activity. From the perspective of EUV, a density trough feature appears as a channel of diminished pixel counts which spans a width of L-shell (DELTA L) and magnetic local time (MLT) inside the plasmapause. Plasmaspheric density troughs are found to be morphologically complex possessing considerable spatial and temporal variability. We present an analysis of the evolution of trough DELTA L and MLT extent as functions of associated D (sub ST) and K (sub p) history. Trough features range in size from 0.16 less than or equal to DELTA L less than or equal to 1.2 with azimuthal extent from 1500 less than or equal to MLT less than or equal to 1200. All cases of plasmaspheric density troughs studied to date appear to have evolved as a result of the inner edge of the afternoon/evening plasma drainage plume being wrapped around through the nightside plasmasphere. The structure of plasmaspheric density trough features is further probed by analyzing simulated EUV images produced by forward modeling artificially introduced regions of depleted density into both static and dynamic global core plasmaspheric models. Forward modeling suggests that (1) L-shell refilling of density troughs during storm recovery can be modeled as filling from the ionosphere toward the equator (i.e., bottom-up refilling), and (2) that an erosion process is operating within flux tubes beyond the outer L-shell wall of the observed density troughs.

  11. Josephson junctions with alternating critical current density

    SciTech Connect

    Mints, R.G.; Kogan, V.G.

    1997-04-01

    The magnetic-field dependence of the critical current I{sub c}(H) is considered for a short Josephson junction with the critical current density j{sub c} alternating along the tunnel contact. Two model cases, periodic and randomly alternating j{sub c}, are treated in detail. Recent experimental data on I{sub c}(H) for grain-boundary Josephson junctions in YBa{sub 2}Cu{sub 3}O{sub x} are discussed. {copyright} {ital 1997} {ital The American Physical Society}

  12. Thermionic refrigeration at CNT-CNT junctions

    NASA Astrophysics Data System (ADS)

    Li, C.; Pipe, K. P.

    2016-10-01

    Monte Carlo (MC) simulation is used to study carrier energy relaxation following thermionic emission at the junction of two van der Waals bonded single-walled carbon nanotubes (SWCNTs). An energy-dependent transmission probability gives rise to energy filtering at the junction, which is predicted to increase the average electron transport energy by as much as 0.115 eV, leading to an effective Seebeck coefficient of 386 μV/K. MC results predict a long energy relaxation length (˜8 μm) for hot electrons crossing the junction into the barrier SWCNT. For SWCNTs of optimal length, an analytical transport model is used to show that thermionic cooling can outweigh parasitic heat conduction due to high SWCNT thermal conductivity, leading to a significant cooling capacity (2.4 × 106 W/cm2).

  13. Pore - to - Core Modeling of Soil Organic Matter Decomposition in 3D Soil Structures

    NASA Astrophysics Data System (ADS)

    Falconer, R. E.; Battaia, G.; Baveye, P.; Otten, W.

    2013-12-01

    There is a growing body of literature supporting the need for microbial contributions to be considered explicitly in carbon-climate models. There is also overwhelming evidence that physical protection within aggregates can play a significant role in organic matter dynamics. Yet current models of soil organic matter dynamics divide soil organic matter into conceptual pools with distinct turnover times, assuming that a combination of biochemical and physical properties control decay without explicit description. Albeit robust in their application, such models are not capable to account for changes in soil structure or microbial populations, or accurately predict the effect of wetness or priming. A spatially explicit model is presented that accounts for microbial dynamics and physical processes, permitting consideration of the heterogeneity of the physical and chemical microenvironments at scales relevant for microbes. Exemplified for fungi, we investigate how micro-scale processes manifest at the core scale with particular emphasis on evolution of CO2 and biomass distribution. The microbial model is based upon previous (Falconer et al, 2012) and includes the following processes: uptake, translocation, recycling, enzyme production, growth, spread and respiration. The model is parameterised through a combination of literature data and parameter estimation (Cazelles et al., 2012).The Carbon model comprises two pools, particulate organic matter which through enzymatic activity is converted into dissolved organic matter. The microbial and carbon dynamics occur within a 3D soil structure obtained by X-ray CT. We show that CO2 is affected not only by the amount of Carbon in the soil but also by microbial dynamics, soil structure and the spatial distribution of OM. The same amount of OM can result in substantially different respiration rates, with surprisingly more CO2 with increased clustering of OM. We can explain this from the colony dynamics, production of enzymes and

  14. Appropriateness of Using Patient-Derived Xenograft Models for Pharmacologic Evaluation of Novel Therapies for Esophageal/Gastro-Esophageal Junction Cancers

    PubMed Central

    Dodbiba, Lorin; Teichman, Jennifer; Fleet, Andrew; Thai, Henry; Starmans, Maud H. W.; Navab, Roya; Chen, Zhuo; Girgis, Hala; Eng, Lawson; Espin-Garcia, Osvaldo; Shen, Xiaowei; Bandarchi, Bizhan; Schwock, Joerg; Tsao, Ming-Sound; El-Zimaity, Hala; Der, Sandy D.; Xu, Wei; Bristow, Robert G.; Darling, Gail E.; Boutros, Paul C.

    2015-01-01

    The high morbidity and mortality of patients with esophageal (E) and gastro-esophageal junction (GEJ) cancers, warrants new pre-clinical models for drug testing. The utility of primary tumor xenografts (PTXGs) as pre-clinical models was assessed. Clinicopathological, immunohistochemical markers (p53, p16, Ki-67, Her-2/neu and EGFR), and global mRNA abundance profiles were evaluated to determine selection biases of samples implanted or engrafted, compared with the underlying population. Nine primary E/GEJ adenocarcinoma xenograft lines were further characterized for the spectrum and stability of gene/protein expression over passages. Seven primary esophageal adenocarcinoma xenograft lines were treated with individual or combination chemotherapy. Tumors that were implanted (n=55) in NOD/SCID mice had features suggestive of more aggressive biology than tumors that were never implanted (n=32). Of those implanted, 21/55 engrafted; engraftment was associated with poorly differentiated tumors (p=0.04) and older patients (p=0.01). Expression of immunohistochemical markers were similar between patient sample and corresponding xenograft. mRNA differences observed between patient tumors and first passage xenografts were largely due to loss of human stroma in xenografts. mRNA patterns of early vs late passage xenografts and of small vs large tumors of the same passage were similar. Complete resistance was present in 2/7 xenografts while the remaining tumors showed varying degrees of sensitivity, that remained constant across passages. Because of their ability to recapitulate primary tumor characteristics during engraftment and across serial passaging, PTXGs can be useful clinical systems for assessment of drug sensitivity of human E/GEJ cancers. PMID:25826681

  15. Experiences modeling ocean circulation problems on a 30 node commodity cluster with 3840 GPU processor cores.

    NASA Astrophysics Data System (ADS)

    Hill, C.

    2008-12-01

    Low cost graphic cards today use many, relatively simple, compute cores to deliver support for memory bandwidth of more than 100GB/s and theoretical floating point performance of more than 500 GFlop/s. Right now this performance is, however, only accessible to highly parallel algorithm implementations that, (i) can use a hundred or more, 32-bit floating point, concurrently executing cores, (ii) can work with graphics memory that resides on the graphics card side of the graphics bus and (iii) can be partially expressed in a language that can be compiled by a graphics programming tool. In this talk we describe our experiences implementing a complete, but relatively simple, time dependent shallow-water equations simulation targeting a cluster of 30 computers each hosting one graphics card. The implementation takes into account the considerations (i), (ii) and (iii) listed previously. We code our algorithm as a series of numerical kernels. Each kernel is designed to be executed by multiple threads of a single process. Kernels are passed memory blocks to compute over which can be persistent blocks of memory on a graphics card. Each kernel is individually implemented using the NVidia CUDA language but driven from a higher level supervisory code that is almost identical to a standard model driver. The supervisory code controls the overall simulation timestepping, but is written to minimize data transfer between main memory and graphics memory (a massive performance bottle-neck on current systems). Using the recipe outlined we can boost the performance of our cluster by nearly an order of magnitude, relative to the same algorithm executing only on the cluster CPU's. Achieving this performance boost requires that many threads are available to each graphics processor for execution within each numerical kernel and that the simulations working set of data can fit into the graphics card memory. As we describe, this puts interesting upper and lower bounds on the problem sizes

  16. Subgap conductivity in SIN-junctions of high barrier transparency

    NASA Astrophysics Data System (ADS)

    Lotkhov, S. V.; Balashov, D. V.; Khabipov, M. I.; Buchholz, F.-I.; Zorin, A. B.

    2006-11-01

    We investigate the current-voltage characteristics of high-transparency superconductor-insulator-normal metal (SIN) junctions with the specific tunnel resistance ρ ≲ 30 Ω μm2. The junctions were fabricated from different superconducting and normal conducting materials, including Nb, Al, AuPd and Cu. The subgap leakage currents were found to be appreciably larger than those given by the standard tunnelling model. We explain our results using the model of two-electron tunnelling in the coherent diffusive transport regime. We demonstrate that even in the high-transparency SIN-junctions, a noticeable reduction of the subgap current can be achieved by splitting a junction into several submicron sub-junctions. These structures can be used as nonlinear low-noise shunts in rapid-single-flux-quantum (RSFQ) circuitry for controlling Josephson qubits.

  17. Combustion and Energy Transfer Experiments: A Laboratory Model for Linking Core Concepts across the Science Curriculum

    ERIC Educational Resources Information Center

    Barreto, Jose C.; Dubetz, Terry A.; Schmidt, Diane L.; Isern, Sharon; Beatty, Thomas; Brown, David W.; Gillman, Edward; Alberte, Randall S.; Egiebor, Nosa O.

    2007-01-01

    Core concepts can be integrated throughout lower-division science and engineering courses by using a series of related, cross-referenced laboratory experiments. Starting with butane combustion in chemistry, the authors expanded the underlying core concepts of energy transfer into laboratories designed for biology, physics, and engineering. This…

  18. Using the Information Orientation Maturity Model to Increase the Effectiveness of the Core MBA IS Course

    ERIC Educational Resources Information Center

    Aytes, Kregg; Beachboard, John

    2007-01-01

    Although information systems are an integral part of every modern organization, IS faculty often struggle to show MBA students the value of the core IS course in the MBA curriculum. This is also evidenced by the fact that some business schools do not have an IS course in the core MBA curriculum. MBA courses often use case analyses to provide…

  19. Electric Field Effect in Intrinsic Josephson Junctions

    NASA Astrophysics Data System (ADS)

    Koyama, T.

    The electric field effect in intrinsic Josephson junction stacks (IJJ's) is investigated on the basis of the capacitively-coupled IJJ model. We clarify the current-voltage characteristics of the IJJ's in the presence of an external electric field. It is predicted that the IJJ's show a dynamical transition to the voltage state as the external electric field is increased.

  20. Local trap spectroscopy in superconducting tunnel junctions

    SciTech Connect

    Kozorezov, A. G.; Wigmore, J. K.; Peacock, A.; Poelaert, A.; Verhoeve, P.; den Hartog, R.; Brammertz, G.

    2001-06-04

    We show that thermal activation of quasiparticles from local traps is responsible for the temperature variation of responsivity observed for some superconducting tunneling junction photon detectors. With this model, the depth of the local traps in two different proximized Ta structures was found to be the same, 0.20{+-}0.02 meV. {copyright} 2001 American Institute of Physics.