WorldWideScience

Sample records for cell edge velocities

  1. Leading-Edge Velocities and Lifted Methane Jet Flame Stability

    Directory of Open Access Journals (Sweden)

    W. Wang

    2010-01-01

    Full Text Available Current interest exists in understanding reaction-zone dynamics and mechanisms with respect to how they counterpropagate against incoming reactants. Images of flame position and flow-field morphology are presented from flame chemiluminescence and particle image velocimetry (PIV measurements. In the present study, PIV experiments were carried out to measure the methane jet lifted-flame flow-field velocities in the vicinity of the flame leading edge. Specifically, velocity fields within the high-temperature zone were examined in detail, which complements previous studies, whose prime focus is the flow-field upstream of the high-temperature boundary. PIV data is used not only to determine the velocities, but, along with chemiluminescence images, to also indicate the approximate location of the reaction zone (further supported by/through the leading-edge flame velocity distributions. The velocity results indirectly support the concept that the flame is anchored primarily through the mechanism of partially premixed flame propagation.

  2. Quantification of ultrasound correlation-based flow velocity mapping and edge velocity gradient measurement.

    Science.gov (United States)

    Park, Dae Woo; Kruger, Grant H; Rubin, Jonathan M; Hamilton, James; Gottschalk, Paul; Dodde, Robert E; Shih, Albert J; Weitzel, William F

    2013-10-01

    This study investigated the use of ultrasound speckle decorrelation- and correlation-based lateral speckle-tracking methods for transverse and longitudinal blood velocity profile measurement, respectively. By studying the blood velocity gradient at the vessel wall, vascular wall shear stress, which is important in vascular physiology as well as the pathophysiologic mechanisms of vascular diseases, can be obtained. Decorrelation-based blood velocity profile measurement transverse to the flow direction is a novel approach, which provides advantages for vascular wall shear stress measurement over longitudinal blood velocity measurement methods. Blood flow velocity profiles are obtained from measurements of frame-to-frame decorrelation. In this research, both decorrelation and lateral speckle-tracking flow estimation methods were compared with Poiseuille theory over physiologic flows ranging from 50 to 1000 mm/s. The decorrelation flow velocity measurement method demonstrated more accurate prediction of the flow velocity gradient at the wall edge than the correlation-based lateral speckle-tracking method. The novelty of this study is that speckle decorrelation-based flow velocity measurements determine the blood velocity across a vessel. In addition, speckle decorrelation-based flow velocity measurements have higher axial spatial resolution than Doppler ultrasound measurements to enable more accurate measurement of blood velocity near a vessel wall and determine the physiologically important wall shear.

  3. Slow light with low group-velocity dispersion at the edge of photonic graphene

    International Nuclear Information System (INIS)

    We theoretically study the light propagation at the zigzag edges of a honeycomb photonic crystal (PC), or photonic graphene. It is found that the corresponding edge states have a sinusoidal dispersion similar to those found in PC coupled resonator optical waveguides [CROWs; M. Notomi et al., Nature Photon. 2, 741 (2008)]. The sinusoidal dispersion curve can be made very flat by carefully tuning edge parameters. As a result, low group velocity and small group velocity dispersion can be simultaneously obtained for light propagating at the zigzag edge of photonic graphene. Compared with PC CROWs, our slow-light system exhibits no intrinsic radiation loss and has a larger group velocity bandwidth product. Our results could find applications in on-chip optical buffers and enhanced light-matter interaction.

  4. Voltage-controlled Group Velocity of Edge Magnetoplasmon in the Quantum Hall Regime

    OpenAIRE

    KAMATA, Hiroshi; Ota, Takeshi; Muraki, Koji; Fujisawa, Toshimasa

    2010-01-01

    We investigate the group velocity of edge magnetoplasmons (EMPs) in the quantum Hall regime by means of time-of-flight measurement. The EMPs are injected from an Ohmic contact by applying a voltage pulse, and detected at a quantum point contact by applying another voltage pulse to its gate. We find that the group velocity of the EMPs traveling along the edge channel defined by a metallic gate electrode strongly depends on the voltage applied to the gate. The observed variation of the velocity...

  5. Numerical simulations of leading-edge vortex core axial velocity for flow over delta wings

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Numerical simulations have been performed to investigate the characteristics of leading-edge vortex core axial velocity over two delta wings with leading edge swept angles Λ =50°and 76°, respectively. It is obtained that Reynolds number has the most important effect on the axial velocity of the primary leading-edge vortex core. At Reynolds numbers larger than 105, the jet-like flow of the vortex core is the most common type for both the large and the moderate swept delta wings. While if Reynolds number decreases to 103―104, the core axial velocity distributions for these two delta wings present the wake-like profile for all angles of attack considered in the present investigation.

  6. Naturally Occurring Velocity Shear Layer at the Plasma Edge of HT-7 Tokamak

    Institute of Scientific and Technical Information of China (English)

    徐国盛; 万宝年; 宋梅

    2004-01-01

    A naturally occurring velocity shear layer was observed at the plasma edge of HT-7 tokamak in regular ohmic heated discharges. One fast reciprocating Langmuir probe was used to measure all quantities in the radial force balance equation for main ion, which enables us to present the first report about the radial force balance in the boundary region of the HT-7 tokamak. The sharp gradient of radial electric field and the reduced fluctuation correlation and turbulent particle flux characterized the edge velocity shear layer. It was found that the shear of turbulence poloidal velocity was dominated by the E × B flow shear and the poloidal rotation determined the structure of radial electric field profile and as a result the E × B flows.

  7. Assessment of Edge Turbulence and Convective Transport through Velocity Field Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Munsat, Tobin [Univ. of Colorado, Boulder, CO (United States). Center for Integrated Plasma Studies

    2015-03-14

    Over the course of this grant period, we have conducted three major studies, each of which has resulted in a primary publication (described below): First, we investigated the flow and shear behavior of the edge plasma and scrape-off layer (SOL) in NSTX using the GPI diagnostic. Calculation of local, time resolved velocity maps using the hybrid optical flow and pattern matching velocimetry code enabled analysis of turbulent flow and shear behavior in these plasmas. Second, we used GPI measurements made during RF heated H-mode operation, to identify intermittent periodic edge intensity fluctuations which precede ELMs and ELM-induced back transitions from H-mode to Lmode. These edge oscillations have a well-defined mode structure and are visible up to 100-200 μs preceding the ELM events. Finally, we performed an in-depth investigation between the fluctuation measurements made by the GPI and BES diagnostics on NSTX.

  8. Flat Plate Wake Velocity Statistics Obtained With Circular And Elliptic Trailing Edges

    Science.gov (United States)

    Rai, Man Mohan

    2016-01-01

    The near wake of a flat plate with circular and elliptic trailing edges is investigated with data from direct numerical simulations. The plate length and thickness are the same in both cases. The separating boundary layers are turbulent and statistically identical. Therefore the wake is symmetric in the two cases. The emphasis in this study is on a comparison of the wake-distributions of velocity components, normal intensity and fluctuating shear stress obtained in the two cases.

  9. Model of local velocity in the primary visual cortical cells.

    Science.gov (United States)

    Sherman, I; Spitzer, H

    1995-06-01

    A motion model for the early stages of motion processing in the visual cortex that focuses on velocity properties is presented. The model presents analytically the correlation between the velocity tuning curve and various cell parameters. The building block for this model is the rebound response, which makes possible the detection of spatial and temporal edges. The model suggests that adjacent subunits in the primary cortical cells display different strengths in their rebound responses, and thus a synergistic response is evoked in the preferred direction. The analysis deals separately with the two cutoff points of the velocity tuning curves. The model predicts a linear relation between the low cutoff point and the receptive-field size and an inverse correlation with the integration time. The high cutoff point is inversely correlated with the cell threshold. PMID:7769506

  10. Cavitation on a semicircular leading-edge plate and NACA0015 hydrofoil: Visualization and velocity measurement

    Science.gov (United States)

    Kravtsova, A. Yu.; Markovich, D. M.; Pervunin, K. S.; Timoshevskii, M. V.; Hanjalić, K.

    2014-12-01

    Using high-speed visualization and particle image velocimetry (PIV), cavitating flows near a plane plate with a rounded leading edge and NACA0015 hydrofoil at angles of attack from 0° to 9° are studied. In the experiments, several known types of cavitation, as well as some differences, were detected with variation of the cavitation number. In particular, at small angles of attack (up to 3°), cavitation on the plate appears in the form of a streak array; on the hydrofoil, it appears in the form of individual bubbles. For the NACA0015 hydrofoil, isolated and intermittent streaks are divided and grow in regimes with developed cavitation; then, however, they merge in bubble clouds and form an extremely regular cellular structure. With an increase in the angle of attack to 9°, the structure of the cavitation cavity on the hydrofoil is changed by the streak structure, like in the case with the plate. In this work, it is shown that PIV permits one to measure the velocity in cavitating flows, in particular, within the gas-vapor phase. It was established from the analysis of distributions of the average flow velocity and moments of velocity fluctuations that the cavitation generation is caused by the development of the carrier fluid flow near the leading edge of the hydrofoil. Down the stream, however, the flow structure strongly depends on the cavitation regime, which is seen from the comparison of the distributions with the case of a single-phase flow. The presented measurements qualitatively verify general trends and show some quantitative distinctions for the two considered flowpast bodies.

  11. Pressure-Velocity Correlations in the Cove of a Leading Edge Slat

    Science.gov (United States)

    Wilkins, Stephen; Richard, Patrick; Hall, Joseph

    2015-11-01

    One of the major sources of aircraft airframe noise is related to the deployment of high-lift devices, such as leading-edge slats, particularly when the aircraft is preparing to land. As the engines are throttled back, the noise produced by the airframe itself is of great concern, as the aircraft is low enough for the noise to impact civilian populations. In order to reduce the aeroacoustic noise sources associated with these high lift devices for the next generation of aircraft an experimental investigation of the correlation between multi-point surface-mounted fluctuating pressures measured via flush-mounted microphones and the simultaneously measured two-component velocity field measured via Particle Image Velocimetry (PIV) is studied. The development of the resulting shear-layer within the slat cove is studied for Re =80,000, based on the wing chord. For low Mach number flows in air, the major acoustic source is a dipole acoustic source tied to fluctuating surface pressures on solid boundaries, such as the underside of the slat itself. Regions of high correlations between the pressure and velocity field near the surface will likely indicate a strong acoustic dipole source. In order to study the underlying physical mechanisms and understand their role in the development of aeroacoustic noise, Proper Orthogonal Decomposition (POD) by the method of snapshots is employed on the velocity field. The correlation between low-order reconstructions and the surface-pressure measurements are also studied.

  12. Dependence of entrainment in shallow cumulus convection on vertical velocity and distance to cloud edge

    Science.gov (United States)

    Tian, Yang; Kuang, Zhiming

    2016-04-01

    The dependence of entrainment rate on environmental conditions and cloud characteristics is investigated using large eddy simulations (LES) of the response of shallow cumulus convection to a small-amplitude temperature perturbation that is horizontally uniform and localized in height. The simulated cumulus fields are analyzed in the framework of an ensemble of entraining plumes by tracking a large number of Lagrangian parcels embedded in the LES and grouping them into different plumes based on their detrainment heights. The results show that fractional entrainment rate per unit height of a plume is inversely proportional to the plume's vertical velocity and its distance to the cloud edge, while changes in environmental stratification and relative humidity, the plume's buoyancy, or the vertical gradient of its buoyancy due to the temperature perturbation have little effect on the plume's entrainment rate.

  13. Cell-Edge Multi-User Relaying with Overhearing

    DEFF Research Database (Denmark)

    Sun, Fan; Kim, Tae Min; Paulraj, Arogyaswami;

    2013-01-01

    Carefully designed protocols can turn overheard interference into useful side information to allow simultaneous transmission of multiple communication flows and increase the spectral efficiency in interference-limited regime. In this letter, we propose a novel scheme in a typical cell-edge scenario...

  14. Single velocity-component modeling of leading edge turbulence interaction noise.

    Science.gov (United States)

    Gill, J; Zhang, X; Joseph, P

    2015-06-01

    A computational aeroacoustics approach is used to predict leading edge turbulence interaction noise for real airfoils. One-component (transverse), two-component (transverse and streamwise), and three-component (transverse, streamwise, and spanwise) synthesized turbulence disturbances are modeled instead of harmonic transverse gusts, to which previous computational studies of leading edge noise have often been confined. The effects of the inclusion of streamwise and spanwise disturbances on the noise are assessed. It is shown that accurate noise predictions can be made by modeling only transverse disturbances which reduces the computational expense of simulations. The accuracy of using only transverse disturbances is assessed for symmetric and cambered airfoils, and also for airfoils at non-zero angle of attack.

  15. Focussing effects at the edge of the Large Low Shear Velocity Provinces

    Science.gov (United States)

    Rost, S.; Nowacki, A.

    2015-12-01

    Tomographic images of the Earth's lowermost mantle are dominated by two equatorial and nearly antipodal regions of large-scale reductions in seismic S-wave velocities beneath the central Pacific and Africa. These Large Low Shear Velocity Provinces (LLSVPs) are much less constrained in tomographic P-wave models. This discrepancy, together with other geophysical data, led to the interpretation of LLSVPs as thermo-chemical piles, but models of purely thermal LLSVPs might also be able to explain the geophysical data. Data from seismic arrays and high-resolution processing techniques are able to precisely determine the slowness vector of incoming seismic energy and therefore to extract velocity and directivity information from the seismic data directly. Here we use records of P and Pdiff from the medium aperture, short-period, vertical component Yellowknife array (YKA) located in northern Canada and S/Sdiff from stations of the Canadian POLARIS network. Using seismicity from the western Pacific rim allows good sampling of the lowermost mantle in the region of the Pacific LLSVP and the northern Pacific. The slowness information extracted from the array data using the high-resolution F-statistic allows detailed mapping of the LLSVP boundary and indicates a sharp boundary and velocity reductions of several percent. The data also indicate a second region of strongly reduced seismic velocities to the north of the Pacific LLSVP beneath the Sea of Okhotsk that does not seem to be connected to the main LLSVP, and which is not consistently resolved in S-wave tomography models. We observe very strong focussing and defocussing effects along the LLSVP boundary that indicate strong and small-scale heterogeneities in the vicinity of the LLSVP boundary beyond what can be explained by LLSVP material. This detection allows further insight into the structure and dynamics of the LLSVP. Using seismic wave propagation simulations we are aiming to resolve both structure and shape of these

  16. A minimal model for spontaneous cell polarization and edge activity in oscillating, rotating and migrating cells

    CERN Document Server

    Raynaud, Franck; Gabella, Chiara; Bornert, Alicia; Sbalzarini, Ivo F; Meister, Jean-Jacques; Verkhovsky, Alexander B

    2016-01-01

    How the cells break symmetry and organize their edge activity to move directionally is a fun- damental question in cell biology. Physical models of cell motility commonly rely on gradients of regulatory factors and/or feedback from the motion itself to describe polarization of edge activity. Theses approaches, however, fail to explain cell behavior prior to the onset of polarization. Our analysis using the model system of polarizing and moving fish epidermal keratocytes suggests a novel and simple principle of self-organization of cell activity in which local cell-edge dynamics depends on the distance from the cell center, but not on the orientation with respect to the front-back axis. We validate this principle with a stochastic model that faithfully reproduces a range of cell-migration behaviors. Our findings indicate that spontaneous polarization, persistent motion, and cell shape are emergent properties of the local cell-edge dynamics controlled by the distance from the cell center.

  17. Minimal model for spontaneous cell polarization and edge activity in oscillating, rotating and migrating cells

    Science.gov (United States)

    Raynaud, Franck; Ambühl, Mark E.; Gabella, Chiara; Bornert, Alicia; Sbalzarini, Ivo F.; Meister, Jean-Jacques; Verkhovsky, Alexander B.

    2016-04-01

    How cells break symmetry and organize activity at their edges to move directionally is a fundamental question in cell biology. Physical models of cell motility commonly incorporate gradients of regulatory proteins and/or feedback from the motion itself to describe the polarization of this edge activity. These approaches, however, fail to explain cell behaviour before the onset of polarization. We use polarizing and moving fish epidermal cells as a model system to bridge the gap between cell behaviours before and after polarization. Our analysis suggests a novel and simple principle of self-organizing cell activity, in which local cell-edge dynamics depends on the distance from the cell centre, but not on the orientation with respect to the front-back axis. We validate this principle with a stochastic model that faithfully reproduces a range of cell-migration behaviours. Our findings indicate that spontaneous polarization, persistent motion and cell shape are emergent properties of the local cell-edge dynamics controlled by the distance from the cell centre.

  18. Cell wall pH and auxin transport velocity

    Science.gov (United States)

    Hasenstein, K. H.; Rayle, D.

    1984-01-01

    According to the chemiosmotic polar diffusion hypothesis, auxin pulse velocity and basal secretion should increase with decreasing cell wall pH. Experiments were designed to test this prediction. Avena coleoptile sections were preincubated in either fusicoccin (FC), cycloheximide, pH 4.0, or pH 8.0 buffer and subsequently their polar transport capacities were determined. Relative to controls, FC enhanced auxin (IAA) uptake while CHI and pH 8.0 buffer reduced IAA uptake. Nevertheless, FC reduced IAA pulse velocity while cycloheximide increased velocity. Additional experiments showed that delivery of auxin to receivers is enhanced by increased receiver pH. This phenomenon was overcome by a pretreatment of the tissue with IAA. Our data suggest that while acidic wall pH values facilitate cellular IAA uptake, they do not enhance pulse velocity or basal secretion. These findings are inconsistent with the chemiosmotic hypothesis for auxin transport.

  19. ICRF-driven convective cells in the tokamak edge plasma

    International Nuclear Information System (INIS)

    Recently, the authors have shown that the release of metal impurities during ICRF heating on JET could be explained by ion acceleration into the Faraday screen (FS) surface caused by rf sheaths, which form when local magnetic field is imperfectly aligned with the FS. The theory explained many of the dependences of the impurity data, including the virtual elimination of impurities with beryllium screens and dipole antenna phasing. The good agreement between the impurity generation model and experimental data can be taken as evidence of the relevance of rf sheaths to the scrape-off-layer (SOL) plasma in tokamaks. A crucial physical point in sheath theory is that the requirement of no time-averaged current into the boundary leads to the rectification of the oscillating rf fields to produce a net time-averaged and spatially-varying potential and, hence, a DC electric field. Here, the authors investigate the possibility that the rectified sheath potential Φo can drive convective cells in the SOL which may explain the experimental observations of ICRF-enhanced edge transport on many tokamaks. Temperature (and sometimes density) profile flattening and induced DC electric fields in the SOL are often observed during ICRF heating on JET, particularly in monopole phasing. The attainment of the H-mode with ICRF heating alone is also sensitive to the phasing of the antenna. These observations suggest an rf-sheath related effect, as the magnitude of Φo is much larger in monopole phasing (∼1 kV near the FS). The authors speculate that enhanced edge cooling by rapid convection may account for the phasing sensitivity of the H-mode transition. In the present work, a modified convective cell equation for the SOL plasma is derived, which explicitly takes into account the finite length of the field lines and the appropriate sheath boundary condition for Jparallel

  20. Waves in cell monolayer without proliferation: density determines cell velocity and wave celerity

    CERN Document Server

    Tlili, S; Li, B; Cardoso, O; Ladoux, B; Delanoë-Ayari, H; Graner, F

    2016-01-01

    Collective cell migration contributes to morphogenesis, wound healing or tumor metastasis. Culturing epithelial monolayers on a substrate is an in vitro configuration suitable to quantitatively characterize such tissue migration by measuring cell velocity, density and cell-substrate interaction force. Inhibiting cell division, we limit cell density increase and favor steady cell migration, while by using long narrow strips we stabilise the migrating front shape, so that we observe migration over a day or more. In the monolayer bulk, the cell velocity is a function of the cell density, namely it increases as a linear function of the cell radius. At least ten periods of propagating velocity waves are detected with a high signal-to-noise ratio, enabling for their quantitative spatio-temporal analysis. Cell density displays waves, in phase opposition with the velocity, as predicted by mass conservation; similarly, cell-substrate force appear to display small amplitude waves, in phase quadrature with respect to ve...

  1. Edge coating apparatus with movable roller applicator for solar cell substrates

    Science.gov (United States)

    Pavani, Luca; Abas, Emmanuel

    2012-12-04

    A non-contact edge coating apparatus includes an applicator for applying a coating material on an edge of a solar cell substrate and a control system configured to drive the applicator. The control system may drive the applicator along an axis to maintain a distance with an edge of the substrate as the substrate is rotated to have the edge coated with a coating material. The applicator may include a recessed portion into which the edge of the substrate is received for edge coating. For example, the applicator may be a roller with a groove. Coating material may be introduced into the groove for application onto the edge of the substrate. A variety of coating materials may be employed with the apparatus including hot melt ink and UV curable plating resist.

  2. The Edges of Pancreatic Islet β Cells Constitute Adhesive and Signaling Microdomains

    Directory of Open Access Journals (Sweden)

    Erez Geron

    2015-01-01

    Full Text Available Pancreatic islet β cells are organized in rosette-like structures around blood vessels and exhibit an artery-to-vein orientation, but they do not display the typical epithelial polarity. It is unclear whether these cells present a functional asymmetry related to their spatial organization. Here, we identify murine β cell edges, the sites at which adjacent cell faces meet at a sharp angle, as surface microdomains of cell-cell adhesion and signaling. The edges are marked by enrichment of F-actin and E-cadherin and are aligned between neighboring cells. The edge organization is E-cadherin contact dependent and correlates with insulin secretion capacity. Edges display elevated levels of glucose transporters and SNAP25 and extend numerous F-actin-rich filopodia. A similar β cell edge organization was observed in human islets. When stimulated, β cell edges exhibit high calcium levels. In view of the functional importance of intra-islet communication, the spatial architecture of their edges may prove fundamental for coordinating physiological insulin secretion.

  3. Cell edges accumulate gamma tubulin complex components and nucleate microtubules following cytokinesis in Arabidopsis thaliana.

    Directory of Open Access Journals (Sweden)

    Chris Ambrose

    Full Text Available Microtubules emanate from distinct organizing centers in fungal and animal cells. In plant cells, by contrast, microtubules initiate from dispersed sites in the cell cortex, where they then self-organize into parallel arrays. Previous ultrastructural evidence suggested that cell edges participate in microtubule nucleation but so far there has been no direct evidence for this. Here we use live imaging to show that components of the gamma tubulin nucleation complex (GCP2 and GCP3 localize at distinct sites along the outer periclinal edge of newly formed crosswalls, and that microtubules grow predominantly away from these edges. These data confirm a role for cell edges in microtubule nucleation, and suggest that an asymmetric distribution of microtubule nucleation factors contributes to cortical microtubule organization in plants, in a manner more similar to other kingdoms than previously thought.

  4. 3D photospheric velocity field of a Supergranular cell

    CERN Document Server

    Del Moro, Dario; Berrilli, Francesco

    2007-01-01

    We investigate the plasma flow properties inside a Supergranular (SG) cell, in particular its interaction with small scale magnetic field structures. The SG cell has been identified using the magnetic network (CaII wing brightness) as proxy, applying the TST to high spatial, spectral and temporal resolution observations obtained by IBIS. The full 3D velocity vector field for the SG has been reconstructed at two different photospheric heights. In order to strengthen our findings, we also computed the mean radial flow of the SG by means of cork tracing. We also studied the behaviour of the horizontal and Line of Sight plasma flow cospatial with cluster of bright CaII structures of magnetic origin to better understand the interaction between photospheric convection and small scale magnetic features. The SG cell we investigated seems to be organized with an almost radial flow from its centre to the border. The large scale divergence structure is probably created by a compact region of costant up-flow close to the...

  5. Dkk-1 Inhibits Intestinal Epithelial Cell Migration by Attenuating Directional Polarization of Leading Edge Cells

    Science.gov (United States)

    Koch, Stefan; Capaldo, Christopher T.; Samarin, Stanislav; Nava, Porfirio; Neumaier, Irmgard; Skerra, Arne; Sacks, David B.; Parkos, Charles A.

    2009-01-01

    Wnt signaling pathways regulate proliferation, motility, and survival in a variety of human cell types. Dickkopf-1 (Dkk-1) is a secreted Wnt antagonist that has been proposed to regulate tissue homeostasis in the intestine. In this report, we show that Dkk-1 is secreted by intestinal epithelial cells after wounding and that it inhibits cell migration by attenuating the directional orientation of migrating epithelial cells. Dkk-1 exposure induced mislocalized activation of Cdc42 in migrating cells, which coincided with a displacement of the polarity protein Par6 from the leading edge. Consequently, the relocation of the microtubule organizing center and the Golgi apparatus in the direction of migration was significantly and persistently inhibited in the presence of Dkk-1. Small interfering RNA-induced down-regulation of Dkk-1 confirmed that extracellular exposure to Dkk-1 was required for this effect. Together, these data demonstrate a novel role of Dkk-1 in the regulation of directional polarization of migrating intestinal epithelial cells, which contributes to the effect of Dkk-1 on wound closure in vivo. PMID:19776352

  6. Edges of human embryonic stem cell colonies display distinct mechanical properties and differentiation potential

    OpenAIRE

    Rosowski, Kathryn A.; Mertz, Aaron F.; Samuel Norcross; Dufresne, Eric R.; Valerie Horsley

    2015-01-01

    In order to understand the mechanisms that guide cell fate decisions during early human development, we closely examined the differentiation process in adherent colonies of human embryonic stem cells (hESCs). Live imaging of the differentiation process reveals that cells on the outer edge of the undifferentiated colony begin to differentiate first and remain on the perimeter of the colony to eventually form a band of differentiation. Strikingly, this band is of constant width in all colonies,...

  7. Edge sealing for low cost stability enhancement of roll-to-roll processed flexible polymer solar cell modules

    DEFF Research Database (Denmark)

    Tanenbaum, David M.; Dam, Henrik Friis; Rösch, R.;

    2012-01-01

    Fully roll-to-roll processed polymer solar cell modules were prepared, characterized, and laminated. Cell modules were cut from the roll and matched pairs were selected, one module with exposed cut edges, the other laminated again with the same materials and adhesive sealing fully around the cut...... edges. The edge sealing rim was 10 mm wide. Cell modules were characterized by periodic measurements of IV curves over extended periods in a variety of conditions, as well as by a variety of spatial imaging techniques. Data show significant stability benefits of the edge sealing process. The results...

  8. Spectral and energy efficiency analysis of uplink heterogeneous networks with small-cells on edge

    KAUST Repository

    Shakir, Muhammad Zeeshan

    2014-12-01

    This paper presents a tractable mathematical framework to analyze the spectral and energy efficiency of an operator initiated deployment of the small-cells (e.g., femtocells) where the small-cell base stations are deliberately positioned around the edge of the macrocell. The considered deployment facilitates the cell-edge mobile users in terms of their coverage, spectral, and energy efficiency and is referred to as cell-on-edge (COE) configuration. The reduction in energy consumption is achieved by considering fast power control where the mobile users transmit with adaptive power to compensate the path loss, shadowing and fading. In particular, we develop a moment generating function (MGF) based approach to derive analytical bounds on the area spectral efficiency and exact expressions for the energy efficiency of the mobile users in the considered COE configuration over generalized-K fading channels. Besides the COE configuration, the derived bounds are also shown to be useful in evaluating the performance of random small-cell deployments, e.g., uniformly distributed small-cells. Simulation results are presented to demonstrate the improvements in spectral and energy efficiency of the COE configuration with respect to macro-only networks and other unplanned deployment strategies. © 2014 Elsevier B.V. All rights reserved.

  9. Graphene microsheets enter cells through spontaneous membrane penetration at edge asperities and corner sites.

    Science.gov (United States)

    Li, Yinfeng; Yuan, Hongyan; von dem Bussche, Annette; Creighton, Megan; Hurt, Robert H; Kane, Agnes B; Gao, Huajian

    2013-07-23

    Understanding and controlling the interaction of graphene-based materials with cell membranes is key to the development of graphene-enabled biomedical technologies and to the management of graphene health and safety issues. Very little is known about the fundamental behavior of cell membranes exposed to ultrathin 2D synthetic materials. Here we investigate the interactions of graphene and few-layer graphene (FLG) microsheets with three cell types and with model lipid bilayers by combining coarse-grained molecular dynamics (MD), all-atom MD, analytical modeling, confocal fluorescence imaging, and electron microscopic imaging. The imaging experiments show edge-first uptake and complete internalization for a range of FLG samples of 0.5- to 10-μm lateral dimension. In contrast, the simulations show large energy barriers relative to kBT for membrane penetration by model graphene or FLG microsheets of similar size. More detailed simulations resolve this paradox by showing that entry is initiated at corners or asperities that are abundant along the irregular edges of fabricated graphene materials. Local piercing by these sharp protrusions initiates membrane propagation along the extended graphene edge and thus avoids the high energy barrier calculated in simple idealized MD simulations. We propose that this mechanism allows cellular uptake of even large multilayer sheets of micrometer-scale lateral dimension, which is consistent with our multimodal bioimaging results for primary human keratinocytes, human lung epithelial cells, and murine macrophages.

  10. Cdc42-dependent leading edge coordination is essential for interstitial dendritic cell migration

    DEFF Research Database (Denmark)

    Lammermann, Tim; Renkawitz, Jorg; Wu, Xunwei;

    2009-01-01

    contraction are still initiated in response to chemotactic cues. Accordingly, the cells are able to polarize and form protrusions. However, in the absence of Cdc42 the protrusions are temporally and spatially dysregulated which leads to impaired leading edge coordination. While this defect still allows...... the cells to move on two-dimensional surfaces, their in vivo motility is completely abrogated. We show that this difference is entirely caused by the geometrical complexity of the environment as multiple competing protrusions lead to instantaneous entanglement within three-dimensional extracellular matrix...... scaffolds. This demonstrates that the decisive factor for migrating DCs is not specific interaction with the extracellular environment, but adequate coordination of cytoskeletal flow....

  11. Actin filaments at the leading edge of cancer cells are characterized by a high mobile fraction and turnover regulation by profilin I.

    Directory of Open Access Journals (Sweden)

    Gisela Lorente

    Full Text Available Cellular motility is the basis for cancer cell invasion and metastasis. In the case of breast cancer, the most common type of cancer among women, metastasis represents the most devastating stage of the disease. The central role of cellular motility in cancer development emphasizes the importance of understanding the specific mechanisms involved in this process. In this context, tumor development and metastasis would be the consequence of a loss or defect of the mechanisms that control cytoskeletal remodeling. Profilin I belongs to a family of small actin binding proteins that are thought to assist in actin filament elongation at the leading edge of migrating cells. Traditionally, Profilin I has been considered to be an essential control element for actin polymerization and cell migration. Expression of Profilin I is down-regulated in breast and various other cancer cells. In MDA-MB-231 cells, a breast cancer cell line, further inhibition of Profilin I expression promotes hypermotility and metastatic spread, a finding that contrasts with the proposed role of Profilin in enhancing polymerization. In this report, we have taken advantage of the fluorescence recovery after photobleaching (FRAP of GFP-actin to quantify and compare actin dynamics at the leading edge level in both cancer and non-cancer cell models. Our results suggest that (i a high level of actin dynamics (i.e., a large mobile fraction of actin filaments and a fast turnover is a common characteristic of some cancer cells; (ii actin polymerization shows a high degree of independence from the presence of extracellular growth factors; and (iii our results also corroborate the role of Profilin I in regulating actin polymerization, as raising the intracellular levels of Profilin I decreased the mobile fraction ratio of actin filaments and slowed their polymerization rate; furthermore, increased Profilin levels also led to reduced individual cell velocity and directionality.

  12. Direct velocity measurement of a turbulent shear flow in a planar Couette cell

    CERN Document Server

    Niebling, Michael; Toussaint, Renaud; Måløy, Knut Jørgen

    2014-01-01

    In a plane Couette cell a thin fluid layer consisting of water is sheared between a transparent band at Reynolds numbers ranging from 300 to 1400. The length of the cells flow channel is large compared to the film separation. To extract the flow velocity in the experiments a correlation image velocimetry (CIV) method is used on pictures recorded with a high speed camera. The flow is recorded at a resolution that allows to analyze flow patterns similar in size to the film separation. The fluid flow is then studied by calculating flow velocity autocorrelation functions. The turbulent pattern that arise on this scale above a critical Reynolds number of Re=360 display characteristic patterns that are proven with the calculated velocity autocorrelation functions. The patterns are metastable and reappear at different positions and times throughout the experiments. Typically these patterns are turbulent rolls which are elongated in the stream direction which is the direction the band is moving. Although the flow sta...

  13. Edge restenosis: impact of low dose irradiation on cell proliferation and ICAM-1 expression

    Directory of Open Access Journals (Sweden)

    Hannekum Andreas

    2006-07-01

    Full Text Available Abstract Background Low dose irradiation (LDI of uninjured segments is the consequence of the suggestion of many authors to extend the irradiation area in vascular brachytherapy to minimize the edge effect. Atherosclerosis is a general disease and the uninjured segment close to the intervention area is often atherosclerotic as well, consisting of neointimal smooth muscle cells (SMC and quiescent monocytes (MC. The current study imitates this complex situation in vitro and investigates the effect of LDI on proliferation of SMC and expression of intercellular adhesion molecule-1 (ICAM-1 in MC. Methods Plaque tissue from advanced primary stenosing lesions of human coronary arteries (9 patients, age: 61 ± 7 years was extracted by local or extensive thrombendarterectomy. SMC were isolated and identified by positive reaction with smooth muscle α-actin. MC were isolated from buffy coat leukocytes using the MACS cell isolation kit. For identification of MC flow-cytometry analysis of FITC-conjugated CD68 and CD14 (FACScan was applied. SMC and MC were irradiated using megavoltage photon irradiation (CLINAC2300 C/D, VARIAN, USA of 6 mV at a focus-surface distance of 100 cm and a dose rate of 6 Gy min-1 with single doses of 1 Gy, 4 Gy, and 10 Gy. The effect on proliferation of SMC was analysed at day 10, 15, and 20. Secondly, total RNA of MC was isolated 1 h, 2 h, 3 h, and 4 h after irradiation and 5 μg of RNA was used in standard Northern blot analysis with ICAM-1 cDNA-probes. Results Both inhibitory and stimulatory effects were detected after irradiation of SMC with a dose of 1 Gy. At day 10 and 15 a significant antiproliferative effect was found; at day 20 after irradiation cell proliferation was significantly stimulated. Irradiation with 4 Gy and 10 Gy caused dose dependent inhibitory effects at day 10, 15, and 20. Expression of ICAM-1 in human MC was neihter inhibited nor stimulated by LDI. Conclusion Thus, the stimulatory effect of LDI on SMC

  14. Cutting Edge: Innate Lymphoid Cells Suppress Homeostatic T Cell Expansion in Neonatal Mice.

    Science.gov (United States)

    Bank, Ute; Deiser, Katrin; Finke, Daniela; Hämmerling, Günter J; Arnold, Bernd; Schüler, Thomas

    2016-05-01

    In adult mice, lymphopenia-induced proliferation (LIP) leads to T cell activation, memory differentiation, tissue destruction, and a loss of TCR diversity. Neonatal mice are lymphopenic within the first week of life. This enables some recent thymic emigrants to undergo LIP and convert into long-lived memory T cells. Surprisingly, however, most neonatal T cells do not undergo LIP. We therefore asked whether neonate-specific mechanisms prevent lymphopenia-driven T cell activation. In this study, we show that IL-7R-dependent innate lymphoid cells (ILCs) block LIP of CD8(+) T cells in neonatal but not adult mice. Importantly, CD8(+) T cell responses against a foreign Ag are not inhibited by neonatal ILCs. This ILC-based inhibition of LIP ensures the generation of a diverse naive T cell pool in lymphopenic neonates that is mandatory for the maintenance of T cell homeostasis and immunological self-tolerance later in life.

  15. Dkk-1 Inhibits Intestinal Epithelial Cell Migration by Attenuating Directional Polarization of Leading Edge Cells

    OpenAIRE

    Koch, Stefan; Capaldo, Christopher T.; Samarin, Stanislav; Nava, Porfirio; Neumaier, Irmgard; Skerra, Arne; Sacks, David B; Parkos, Charles A.; Nusrat, Asma

    2009-01-01

    Wnt signaling pathways regulate proliferation, motility, and survival in a variety of human cell types. Dickkopf-1 (Dkk-1) is a secreted Wnt antagonist that has been proposed to regulate tissue homeostasis in the intestine. In this report, we show that Dkk-1 is secreted by intestinal epithelial cells after wounding and that it inhibits cell migration by attenuating the directional orientation of migrating epithelial cells. Dkk-1 exposure induced mislocalized activation of Cdc42 in migrating c...

  16. Two-way cooperative AF relaying in spectrum-sharing systems: Enhancing cell-edge performance

    KAUST Repository

    Xia, Minghua

    2012-09-01

    In this contribution, two-way cooperative amplify-and-forward (AF) relaying technique is integrated into spectrumsharing wireless systems to improve spectral efficiency of secondary users (SUs). In order to share the available spectrum resources originally dedicated to primary users (PUs), the transmit power of a SU is optimized with respect to the average tolerable interference power at primary receivers. By analyzing outage probability and achievable data rate at the base station and at a cell-edge SU, our results reveal that the uplink performance is dominated by the average tolerable interference power at primary receivers, while the downlink always behaves like conventional one-way AF relaying and its performance is dominated by the average signal-to-noise ratio (SNR). These important findings provide fresh perspectives for system designers to improve spectral efficiency of secondary users in next-generation broadband spectrum-sharing wireless systems. © 2012 IEEE.

  17. Stem cells, a two-edged sword: Risks and potentials of regenerative medicine

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The recent advancements in stem cell (SC) biology have led to the concept of regenerative medicine, which is based on the potential of SC for therapies aimed to facilitate the repair of degenerating or injured tissues. Nonetheless, prior to large scale clinical appli- cations, critical aspects need to be further addressed, including the long-term safety, tolerability, and efficacy of SC-based treatments. Most problematic among the risks of SC-based therapies, in addition to the pos- sible rejection or loss of function of the infused cells, is their potential neoplastic transformation. Indeed, SCs may be used to cure devastating diseases, but their specific properties of self-renewal and clonogenicity may render them prone to generate cancers. In this respect, 'Stemness' might be seen as a two-edged sword, its bright side being represented by normal SCs, its dark side by cancer SCs. A better understand- ing of SC biology will help fulfill the promise of regen- erative medicine aimed at curing human pathologies and fighting cancer from its roots.

  18. Precision near-infrared radial velocity instrumentation I: Absorption Gas Cells

    CERN Document Server

    Plavchan, Peter P; White, Russel; Gao, Peter; Davison, Cassy; Mills, Sean; Beichman, Chas; Brinkworth, Carolyn; Johnson, John Asher; Bottom, Michael; Ciardi, David; Wallace, J Kent; Mennesson, Bertrand; von Braun, Kaspar; Vasisht, Gautum; Prato, LIsa; Kane, Stephen; Tanner, Angelle; Walp, Bernie; Crawford, Sam; Lin, Sean

    2013-01-01

    We have built and commissioned gas absorption cells for precision spectroscopic radial velocity measurements in the near-infrared in the H and K bands. We describe the construction and installation of three such cells filled with 13CH4, 12CH3D, and 14NH3 for the CSHELL spectrograph at the NASA Infrared Telescope Facility (IRTF). We have obtained their high-resolution laboratory Fourier Transform spectra, which can have other practical uses. We summarize the practical details involved in the construction of the three cells, and the thermal and mechanical control. In all cases, the construction of the cells is very affordable. We are carrying out a pilot survey with the 13CH4 methane gas cell on the CSHELL spectrograph at the IRTF to detect exoplanets around low mass and young stars. We discuss the current status of our survey, with the aim of photon-noise limited radial velocity precision. For adequately bright targets, we are able to probe a noise floor of 7 m/s with the gas cell with CSHELL at cassegrain foc...

  19. Molten carbonate fuel cells: A high temperature fuel cell on the edge to commercialization

    Science.gov (United States)

    Bischoff, Manfred

    The Molten Carbonate Fuel Cell (MCFC) technology has been developed in USA, Japan, Korea and Europe for many years. What has started about 30 years ago as an interesting laboratory object has now matured to a potential alternative to conventional power generation systems. Especially the combined heat and power (CHP) generation is an area, where MCFC power plants can be applied with great advantage, due to the high efficiencies which can be achieved. It was demonstrated by several manufacturers that in the sub-MW region MCFC power plants can reach electrical efficiencies of 47%. By making use of the heat generated by the system, total efficiencies of more than 80% can be achieved. The present paper will discuss some aspects of the development work going on with a focus on the role of the molten carbonate contained in the cells. An outlook will be given for the future prospects of this young technology in a changing energy market.

  20. Calibration of the head direction network: a role for symmetric angular head velocity cells.

    Science.gov (United States)

    Stratton, Peter; Wyeth, Gordon; Wiles, Janet

    2010-06-01

    Continuous attractor networks require calibration. Computational models of the head direction (HD) system of the rat usually assume that the connections that maintain HD neuron activity are pre-wired and static. Ongoing activity in these models relies on precise continuous attractor dynamics. It is currently unknown how such connections could be so precisely wired, and how accurate calibration is maintained in the face of ongoing noise and perturbation. Our adaptive attractor model of the HD system that uses symmetric angular head velocity (AHV) cells as a training signal shows that the HD system can learn to support stable firing patterns from poorly-performing, unstable starting conditions. The proposed calibration mechanism suggests a requirement for symmetric AHV cells, the existence of which has previously been unexplained, and predicts that symmetric and asymmetric AHV cells should be distinctly different (in morphology, synaptic targets and/or methods of action on postsynaptic HD cells) due to their distinctly different functions. PMID:20354898

  1. Push-Edge and Slide-Edge: Scrolling by Pushing Against the Viewport Edge

    OpenAIRE

    Malacria, Sylvain; Aceituno, Jonathan; Quinn, Philip; Casiez, Géry; Cockburn, Andy; ROUSSEL, Nicolas

    2015-01-01

    International audience Edge-scrolling allows users to scroll a viewport while simultaneously dragging near or beyond a window’s edge. Common implementations rely on rate control, mapping the distance between the pointer and the edge of the viewport to the scrolling velocity. While ubiquitous in operating systems, edge-scrolling has received little attention, even though previous works suggest that (1) rate control may be suboptimal for isotonic pointing devices like mice and trackpads and ...

  2. Calculation of cell face velocity of non-staggered grid system

    KAUST Repository

    Li, Wang

    2012-07-28

    In this paper, the cell face velocities in the discretization of the continuity equation, the momentum equation, and the scalar equation of a non-staggered grid system are calculated and discussed. Both the momentum interpolation and the linear interpolation are adopted to evaluate the coefficients in the discretized momentum and scalar equations. Their performances are compared. When the linear interpolation is used to calculate the coefficients, the mass residual term in the coefficients must be dropped to maintain the accuracy and convergence rate of the solution. © Shanghai University and Springer-Verlag Berlin Heidelberg 2012.

  3. A Silicon-Based Nanothin Film Solid Oxide Fuel Cell Array with Edge Reinforced Support for Enhanced Thermal Mechanical Stability.

    Science.gov (United States)

    Baek, Jong Dae; Yu, Chen-Chiang; Su, Pei-Chen

    2016-04-13

    A silicon-based micro-solid oxide fuel cell (μ-SOFC) with electrolyte membrane array embedded in a thin silicon supporting membrane, featuring a unique edge reinforcement structure, was demonstrated by utilizing simple silicon micromachining processes. The square silicon supporting membrane, fabricated by combining deep reactive ion etching and through-wafer wet etching processes, has thicker edges and corners than the center portion of the membrane, which effectively improved the mechanical stability of the entire fuel cell array during cell fabrication and cell operation. The 20 μm thick single crystalline silicon membrane supports a large number of 80 nm thick free-standing yttria-stabilized zirconia (YSZ) electrolytes. The fuel cell array was stably maintained at the open circuit voltage (OCV) of 1.04 V for more than 30 h of operation at 350 °C. A high peak power density of 317 mW/cm(2) was obtained at 400 °C. During a rigorous in situ thermal cycling between 150 and 400 °C at a fast cooling and heating rate of 25 °C/min, the OCV of the μ-SOFC recovered to its high value of 1.07 V without any drop caused by membrane failure, which justifies the superior thermal stability of this novel cell architecture. PMID:26990604

  4. Understanding the dynamics of fractional edge states with composite fermions

    OpenAIRE

    Chklovskii, Dmitri B.; Halperin, Bertrand I.

    1996-01-01

    Fractional edge states can be viewed as integer edge states of composite fermions. We exploit this to discuss the conductance of the fractional quantized Hall states and the velocity of edge magnetoplasmons.

  5. Suppression Impact of Group-Velocity Dispersion on the Cell of Pulse Cleaning

    Institute of Scientific and Technical Information of China (English)

    LI Jing; DENG Ying; WANG Jian-Jun; LI Ming-Zhong; XU Dang-Peng; LIN Hong-Huan; ZHU Na; WANG Rui; JING Feng

    2011-01-01

    In order to improve the signal-to-noise ratio of an all-fiber front-end system for high-energy pete-watt (PW) laser devices, we propose a method to restrain the noise by optical Kerr effect. In terms of analytical calculation,it is found that the signal-to-noise ratio can be increased by three orders of magnitude with the cell of pulse cleaning for the pulses, with the full width at half maximum TFWHM larger than 1OOps. However, numerical calculation indicates that the group-velocity dispersion (GVD) may have a marked effect on the pulses with TFWHM smaller than 1OOps but larger than 5ps, with the help of self-phase modulation (SPM). This would debase the performance of the cell of pulse cleaning. Meanwhile, we study the methods of restraining the distortion for the pulses with different peak powers to improve the performance of an all-fiber front-end system for high-energy PW laser devices, These results are of benefit to the experiments and the improvement of signal-to-noise ratio for high-energy PW laser devices.%@@ In order to improve the signal-to-noise ratio of an all-fiber front-end system for high-energy pete-wattilW)laser devices, we propose a method to restrain the noise by optical Kerr effect.In terms of analytical calculation,it is found that the signal-to-noise ratio can be increased by three orders of magnitude with the cell of pulse cleaning for the pulses, with the full width at half maximum TFWHM larger than 100ps.However, numerical calculation indicates that the group-velocity dispersion(GVD)may have a marked effect on the pulses with TFWHM smaller than 100 ps but larger than 5ps, with the help of self-phase modulation(SPM).This would debase the performance of the cell of pulse cleaning.Meanwhile, we study the methods of restraining the distortion for the pulses with different peak powers to improve the performance of an all-fiber front-end system for high-energy PW laser devices, These results are of benefit to the experiments and the improvement

  6. Graphene nanoplatelets doped with N at its edges as metal-free cathodes for organic dye-sensitized solar cells.

    Science.gov (United States)

    Ju, Myung Jong; Jeon, In-Yup; Kim, Jae Cheon; Lim, Kimin; Choi, Hyun-Jung; Jung, Sun-Min; Choi, In Taek; Eom, Yu Kyung; Kwon, Young Jin; Ko, Jaejung; Lee, Jae-Joon; Kim, Hwan Kyu; Baek, Jong-Beom

    2014-05-21

    Challenging precious Pt-based electrocatalysts for dye-sensitized solar cells (DSSCs), graphene nanoplatelets that are N-doped at the edges (NGnPs) are prepared via simply ball-milling graphite in the presence of nitrogen gas. DSSCs based on specific nanoplatelets designated "NGnP5" display superior photovoltaic performance (power conversion efficiency, 10.27%) compared to that of conventional Pt-based devices (9.96%). More importantly, the NGnP counter electrode exhibits outstanding electrochemical stability and electrocatalytic activity with a cobalt-complex redox couple.

  7. The Azospirillum brasilense Che1 chemotaxis pathway controls swimming velocity, which affects transient cell-to-cell clumping.

    Science.gov (United States)

    Bible, Amber; Russell, Matthew H; Alexandre, Gladys

    2012-07-01

    The Che1 chemotaxis-like pathway of Azospirillum brasilense contributes to chemotaxis and aerotaxis, and it has also been found to contribute to regulating changes in cell surface adhesive properties that affect the propensity of cells to clump and to flocculate. The exact contribution of Che1 to the control of chemotaxis and flocculation in A. brasilense remains poorly understood. Here, we show that Che1 affects reversible cell-to-cell clumping, a cellular behavior in which motile cells transiently interact by adhering to one another at their nonflagellated poles before swimming apart. Clumping precedes and is required for flocculation, and both processes appear to be independently regulated. The phenotypes of a ΔaerC receptor mutant and of mutant strains lacking cheA1, cheY1, cheB1, or cheR1 (alone or in combination) or with che1 deleted show that Che1 directly mediates changes in the flagellar swimming velocity and that this behavior directly modulates the transient nature of clumping. Our results also suggest that an additional receptor(s) and signaling pathway(s) are implicated in mediating other Che1-independent changes in clumping identified in the present study. Transient clumping precedes the transition to stable clump formation, which involves the production of specific extracellular polysaccharides (EPS); however, production of these clumping-specific EPS is not directly controlled by Che1 activity. Che1-dependent clumping may antagonize motility and prevent chemotaxis, thereby maintaining cells in a metabolically favorable niche.

  8. Cutting edge: T cells respond to lipopolysaccharide innately via TLR4 signaling.

    Science.gov (United States)

    Zanin-Zhorov, Alexandra; Tal-Lapidot, Guy; Cahalon, Liora; Cohen-Sfady, Michal; Pevsner-Fischer, Meirav; Lider, Ofer; Cohen, Irun R

    2007-07-01

    LPS, a molecule produced by Gram-negative bacteria, is known to activate both innate immune cells such as macrophages and adaptive immune B cells via TLR4 signaling. Although TLR4 is also expressed on T cells, LPS was observed not to affect T cell proliferation or cytokine secretion. We now report, however, that LPS can induce human T cells to adhere to fibronectin via TLR4 signaling. This response to LPS was confirmed in mouse T cells; functional TLR4 and MyD88 were required, but T cells from TLR2 knockout mice could respond to LPS. The human T cell response to LPS depended on protein kinase C signaling and involved the phosphorylation of the proline-rich tyrosine kinase (Pyk-2) and p38. LPS also up-regulated the T cell expression of suppressor of cytokine signaling 3, which led to inhibition of T cell chemotaxis toward the chemokine stromal cell-derived factor 1alpha (CXCL12). Thus, LPS, through TLR4 signaling, can affect T cell behavior in inflammation. PMID:17579019

  9. Zero Crossing Edge Detection and Contour Tracing for Segmentation of Cervical Cell Nucleus .

    Directory of Open Access Journals (Sweden)

    B.V. Ramesh

    1993-07-01

    Full Text Available To automate the process of screening of normal and abnormal cervical cells, there is a need for automatic segmentation of the nucleus of these cells. This paper presents an algorithm using the Laplacian of Gaussian operator and contour tracer to segment the nucleus from the background. The algorithm has been tested on different kinds of images of cervical cells.

  10. Cutting Edge: Redox Signaling Hypersensitivity Distinguishes Human Germinal Center B Cells.

    Science.gov (United States)

    Polikowsky, Hannah G; Wogsland, Cara E; Diggins, Kirsten E; Huse, Kanutte; Irish, Jonathan M

    2015-08-15

    Differences in the quality of BCR signaling control key steps of B cell maturation and differentiation. Endogenously produced H2O2 is thought to fine tune the level of BCR signaling by reversibly inhibiting phosphatases. However, relatively little is known about how B cells at different stages sense and respond to such redox cues. In this study, we used phospho-specific flow cytometry and high-dimensional mass cytometry (CyTOF) to compare BCR signaling responses in mature human tonsillar B cells undergoing germinal center (GC) reactions. GC B cells, in contrast to mature naive B cells, memory B cells, and plasmablasts, were hypersensitive to a range of H2O2 concentrations and responded by phosphorylating SYK and other membrane-proximal BCR effectors in the absence of BCR engagement. These findings reveal that stage-specific redox responses distinguish human GC B cells. PMID:26157177

  11. Cutting Edge: Resident Memory CD8 T Cells Express High-Affinity TCRs.

    Science.gov (United States)

    Frost, Elizabeth L; Kersh, Anna E; Evavold, Brian D; Lukacher, Aron E

    2015-10-15

    Tissue-resident memory T (TRM) cells serve as vanguards of antimicrobial host defense in nonlymphoid tissues, particularly at barrier epithelia and in organs with nonrenewable cell types (e.g., brain). In this study, we asked whether an augmented ability to sense Ag complemented their role as early alarms of pathogen invasion. Using mouse polyomavirus, we show that brain-resident mouse polyomavirus-specific CD8 T cells, unlike memory cells in the spleen, progressively increase binding to MHC class I tetramers and CD8 coreceptor expression. Using the two-dimensional micropipette adhesion-frequency assay, we show that TRM cells in brain, as well as in kidney, express TCRs with up to 20-fold higher affinity than do splenic memory T cells, whereas effector cells express TCRs of similar high affinity in all organs. Together, these data demonstrate that TRM cells retain high TCR affinity, which endows them with the high Ag sensitivity needed for front-line defense against infectious agents. PMID:26371252

  12. Edge Matters

    DEFF Research Database (Denmark)

    Earon, Ofri

    2013-01-01

    of this container is to separate inside from outside and to protect and provide privacy, psychological as well as physical (Venturi, 1966). But, if dwelling phenomenon takes place both inside and outside the private house – why is the urban house an enclosed box? What is the differentiation between inside...... and outside the contemporary urban house? And what is the interplay between them? The research argues for re-thinking the edge zone between inside and outside the urban house. Therefore, although, residential buildings in the city are the objects of study, the focal point here is the edge zone along...... the building. The research explores and develops the architectural characteristics of correlations between the resident, the singular unit, the building and the given location at the edge zone. It approaches the edge zone of the urban house as a platform for dynamic interactions between these behaviours...

  13. At the cutting edge: applications and perspectives of laser nanosurgery in cell biology.

    Science.gov (United States)

    Ronchi, Paolo; Terjung, Stefan; Pepperkok, Rainer

    2012-04-01

    Laser-mediated nanosurgery has become popular in the last decade because of the previously unexplored possibility of ablating biological material inside living cells with sub-micrometer precision. A number of publications have shown the potential applications of this technique, ranging from the dissection of sub-cellular structures to surgical ablations of whole cells or tissues in model systems such as Drosophila melanogaster or Danio rerio . In parallel, the recent development of micropatterning techniques has given cell biologists the possibility to shape cells and reproducibly organize the intracellular space. The integration of these two techniques has only recently started yet their combination has proven to be very interesting. The aim of this review is to present recent applications of laser nanosurgery in cell biology and to discuss the possible developments of this approach, particularly in combination with micropattern-mediated endomembrane organization.

  14. Inflammation and Inflammatory Cells in Myocardial Infarction and Reperfusion Injury: A Double-Edged Sword.

    Science.gov (United States)

    Liu, Jiaqi; Wang, Haijuan; Li, Jun

    2016-01-01

    Myocardial infarction (MI) is the most common cause of cardiac injury, and subsequent reperfusion further enhances the activation of innate and adaptive immune responses and cell death programs. Therefore, inflammation and inflammatory cell infiltration are the hallmarks of MI and reperfusion injury. Ischemic cardiac injury activates the innate immune response via toll-like receptors and upregulates chemokine and cytokine expressions in the infarcted heart. The recruitment of inflammatory cells is a dynamic and superbly orchestrated process. Sequential infiltration of the injured myocardium with neutrophils, monocytes and their descendant macrophages, dendritic cells, and lymphocytes contributes to the initiation and resolution of inflammation, infarct healing, angiogenesis, and ventricular remodeling. Both detrimental effects and a beneficial role in the pathophysiology of MI and reperfusion injury may be attributed to the subset heterogeneity and functional diversity of these inflammatory cells. PMID:27279755

  15. The double-edge role of B cells in mediating antitumor T-cell immunity: Pharmacological strategies for cancer immunotherapy.

    Science.gov (United States)

    Wang, Jing-Zhang; Zhang, Yu-Hua; Guo, Xin-Hua; Zhang, Hong-Yan; Zhang, Yuan

    2016-07-01

    Emerging evidence reveals the controversial role of B cells in antitumor immunity, but the underlying mechanisms have to be explored. Three latest articles published in the issue 521 of Nature in 2015 reconfirmed the puzzling topic and put forward some explanations of how B cells regulate antitumor T-cell responses both positively and negatively. This paper attempts to demonstrate that different B-cell subpopulations have distinct immunological properties and that they are involved in either antitumor responses or immunosuppression. Recent studies supporting the positive and negative roles of B cells in tumor development were summarized comprehensively. Several specific B-cell subpopulations, such as IgG(+), IgA(+), IL-10(+), and regulatory B cells, were described in detail. The mechanisms underlying the controversial B-cell effects were mainly attributed to different B-cell subpopulations, different B-cell-derived cytokines, direct B cell-T cell interaction, different cancer categories, and different malignant stages, and the immunological interaction between B cells and T cells is mediated by dendritic cells. Promising B-cell-based antitumor strategies were proposed and novel B-cell regulators were summarized to present interesting therapeutic targets. Future investigations are needed to make sure that B-cell-based pharmacological strategies benefit cancer immunotherapy substantially.

  16. Cutting Edge: AhR Is a Molecular Target of Calcitriol in Human T Cells.

    Science.gov (United States)

    Takami, Mariko; Fujimaki, Kotaro; Nishimura, Michael I; Iwashima, Makio

    2015-09-15

    The immunoregulatory functions of vitamin D have been well documented in various immunological disorders, including multiple sclerosis, arthritis, and asthma. IL-10 is considered a chief effector molecule that promotes the vitamin D-induced immunosuppressive states of T cells and accessory cells. In this article, we demonstrate that the active form of vitamin D, 1,25-dihydroxyvitamin D3 (calcitriol), has a profound inhibitory effect on the development of human Th9, a CD4 T cell subset that is highly associated with asthma, in an IL-10-independent manner. Our data show that calcitriol represses the expression of BATF, a transcription factor essential for Th9, via suppressing the expression of aryl hydrocarbon receptor, without an increase in IL-10. The data show a novel link between vitamin D and two key transcription factors involved in T cell differentiation. PMID:26276877

  17. Cutting edge: membrane lymphotoxin regulates CD8(+) T cell-mediated intestinal allograft rejection.

    Science.gov (United States)

    Guo, Z; Wang, J; Meng, L; Wu, Q; Kim, O; Hart, J; He, G; Zhou, P; Thistlethwaite, J R; Alegre, M L; Fu, Y X; Newell, K A

    2001-11-01

    Blocking the CD28/B7 and/or CD154/CD40 costimulatory pathways promotes long-term allograft survival in many transplant models where CD4(+) T cells are necessary for rejection. When CD8(+) T cells are sufficient to mediate rejection, these approaches fail, resulting in costimulation blockade-resistant rejection. To address this problem we examined the role of lymphotoxin-related molecules in CD8(+) T cell-mediated rejection of murine intestinal allografts. Targeting membrane lymphotoxin by means of a fusion protein, mAb, or genetic mutation inhibited rejection of intestinal allografts by CD8(+) T cells. This effect was associated with decreased monokine induced by IFN-gamma (Mig) and secondary lymphoid chemokine (SLC) gene expression within allografts and spleens respectively. Blocking membrane lymphotoxin did not inhibit rejection mediated by CD4(+) T cells. Combining disruption of membrane lymphotoxin and treatment with CTLA4-Ig inhibited rejection in wild-type mice. These data demonstrate that membrane lymphotoxin is an important regulatory molecule for CD8(+) T cells mediating rejection and suggest a strategy to avoid costimulation blockade-resistant rejection. PMID:11673481

  18. Cutting edge: Bcl6-interacting corepressor contributes to germinal center T follicular helper cell formation and B cell helper function.

    Science.gov (United States)

    Yang, Jessica A; Tubo, Noah J; Gearhart, Micah D; Bardwell, Vivian J; Jenkins, Marc K

    2015-06-15

    CD4(+) germinal center (GC)-T follicular helper (Tfh) cells help B cells become long-lived plasma cells and memory cells. The transcriptional repressor Bcl6 plays a key role in GC-Tfh formation by inhibiting the expression of genes that promote differentiation into other lineages. We determined whether BCOR, a component of a Polycomb repressive complex that interacts with the Bcl6 BTB domain, influences GC-Tfh differentiation. T cell-targeted BCOR deficiency led to a substantial loss of peptide:MHC class II-specific GC-Tfh cells following Listeria monocytogenes infection and a 2-fold decrease following immunization with a peptide in CFA. The reduction in GC-Tfh cells was associated with diminished plasma cell and GC B cell formation. Thus, T cell-expressed BCOR is critical for optimal GC-Tfh cell differentiation and humoral immunity. PMID:25964495

  19. Cutting edge: neuronal recognition by CD8 T cells elicits central diabetes insipidus.

    Science.gov (United States)

    Scheikl, Tanja; Pignolet, Béatrice; Dalard, Cécile; Desbois, Sabine; Raison, Danièle; Yamazaki, Masanori; Saoudi, Abdelhadi; Bauer, Jan; Lassmann, Hans; Hardin-Pouzet, Hélène; Liblau, Roland S

    2012-05-15

    An increasing number of neurologic diseases is associated with autoimmunity. The immune effectors contributing to the pathogenesis of such diseases are often unclear. To explore whether self-reactive CD8 T cells could attack CNS neurons in vivo, we generated a mouse model in which the influenza virus hemagglutinin (HA) is expressed specifically in CNS neurons. Transfer of cytotoxic anti-HA CD8 T cells induced an acute but reversible encephalomyelitis in HA-expressing recipient mice. Unexpectedly, diabetes insipidus developed in surviving animals. This robust phenotype was associated with preferential accumulation of cytotoxic CD8 T cells in the hypothalamus, upregulation of MHC class I molecules, and destruction of vasopressin-expressing neurons. IFN-γ production by the pathogenic CD8 T cells was necessary for MHC class I upregulation by hypothalamic neurons and their destruction. This novel mouse model, in combination with related human data, supports the concept that autoreactive CD8 T cells can trigger central diabetes insipidus. PMID:22504649

  20. On the Quality of Velocity Interpolation Schemes for Marker-In-Cell Methods on 3-D Staggered Grids

    Science.gov (United States)

    Kaus, B.; Pusok, A. E.; Popov, A.

    2015-12-01

    The marker-in-cell method is generally considered to be a flexible and robust method to model advection of heterogenous non-diffusive properties (i.e. rock type or composition) in geodynamic problems or incompressible Stokes problems. In this method, Lagrangian points carrying compositional information are advected with the ambient velocity field on an immobile, Eulerian grid. However, velocity interpolation from grid points to marker locations is often performed without preserving the zero divergence of the velocity field at the interpolated locations (i.e. non-conservative). Such interpolation schemes can induce non-physical clustering of markers when strong velocity gradients are present (Jenny et al., 2001) and this may, eventually, result in empty grid cells, a serious numerical violation of the marker-in-cell method. Solutions to this problem include: using larger mesh resolutions and/or marker densities, or repeatedly controlling the marker distribution (i.e. inject/delete), but which does not have an established physical background. To remedy this at low computational costs, Jenny et al. (2001) and Meyer and Jenny (2004) proposed a simple, conservative velocity interpolation (CVI) scheme for 2-D staggered grid, while Wang et al. (2015) extended the formulation to 3-D finite element methods. Here, we follow up with these studies and report on the quality of velocity interpolation methods for 2-D and 3-D staggered grids. We adapt the formulations from both Jenny et al. (2001) and Wang et al. (2015) for use on 3-D staggered grids, where the velocity components have different node locations as compared to finite element, where they share the same node location. We test the different interpolation schemes (CVI and non-CVI) in combination with different advection schemes (Euler, RK2 and RK4) and with/out marker control on Stokes problems with strong velocity gradients, which are discretized using a finite difference method. We show that a conservative formulation

  1. Alignment of muscle precursor cells on the vertical edges of thick carbon nanotube films.

    Science.gov (United States)

    Holt, Ian; Gestmann, Ingo; Wright, Andrew C

    2013-10-01

    The development of scaffolds and templates is an essential aspect of tissue engineering. We show that thick (>0.5 mm) vertically aligned carbon nanotube films, made by chemical vapour deposition, can be used as biocompatible substrates for the directional alignment of mouse muscle cells where the cells grow on the exposed sides of the films. Ultra high resolution scanning electron microscopy reveals that the films themselves consist mostly of small diameter (10 nm) multi-wall carbon nanotubes of wavy morphology with some single wall carbon nanotubes. Our findings show that for this alignment to occur the nanotubes must be in pristine condition. Mechanical wiping of the films to create directional alignment is detrimental to directional bioactivity. Larger areas for study have been formed from a composite of multiply stacked narrow strips of nanotubes wipe-transferred onto elastomer supports. These composite substrates appear to show a useful degree of alignment of the cells.

  2. 青藏高原西北缘地形抬升速率与地质年代的关系%Relationships between Topographic Uplifting Velocity and Geological Times for the Northwestern Edge of Qinghai- Tibet Plateau

    Institute of Scientific and Technical Information of China (English)

    赵尚民; 周成虎; 程维明; 陈曦

    2011-01-01

    Based on digital elevation model and geological data, this paper firstly analyzed the topographic profiles and the geological times of the composite materials of the ridge line and piedmont line of the northwestern edge of the Qinghai - Tibet Plateau - West Kunlun Mountains; Accordingly, the five typical peaks were selected from northwest to southeast: Mt. Kungai, Mt. Mushitage, Mt. Tashikuzuke, Mt. Mushi and Mt. Tuokuzidaban. Taking Mt. Konggur as an experiment area, the acquiring method of typical topographic profile was studied in the peak areas. Finally, the typical topographical profiles of the five typical peaks were acquired, the geological times of the composite materials of corresponding peaks were analyzed, and the topographic uplifting velocity under different geological times was computed for every typical peak. Research results show; from northwest to southeast, the topographical uplifting velocity is small in the middle part and big in two ends, and least in Mt. Tashikuzuke and presents near "V" shape; from northwestern Mt. Kungai to southeastern Mt. Tuokuzidaban, the numbers of the geological times of composite materials are 3-4-5-4-3, which present the tendency of increasing firstly and then decreasing and "A" shape. Thus, there exists a negative correlation between the topographical uplifting velocity and geological times.%基于数字高程模型数据和地质数据,首先对青藏高原西北缘西昆仑山脉的山脊线和山麓线进行地形剖面及其地面组成物质形成的地质年代分析,据此获取了从西北到东南的5座典型山峰:昆盖山、慕士塔格山、塔什库祖克山、慕士山和托库孜达坂山的相关数据;然后以公格尔山为例,探讨了山峰区域典型地形剖面线的获取方法;最后对5座山峰进行了典型地形剖面获取及其对应山体组成物质形成的地质年代分析,计算了每座山峰在不同地质年代的组成物质下的地形抬升速率.研究结果表明:

  3. Efficient edge-guided full-waveform inversion by Canny edge detection and bilateral filtering algorithms

    Science.gov (United States)

    Xiang, Shiming; Zhang, Haijiang

    2016-11-01

    It is known full-waveform inversion (FWI) is generally ill-conditioned and various strategies including pre-conditioning and regularizing the inversion system have been proposed to obtain a reliable estimation of the velocity model. Here, we propose a new edge-guided strategy for FWI in frequency domain to efficiently and reliably estimate velocity models with structures of the size similar to the seismic wavelength. The edges of the velocity model at the current iteration are first detected by the Canny edge detection algorithm that is widely used in image processing. Then, the detected edges are used for guiding the calculation of FWI gradient as well as enforcing edge-preserving total variation (TV) regularization for next iteration of FWI. Bilateral filtering is further applied to remove noise but keep edges of the FWI gradient. The proposed edge-guided FWI in the frequency domain with edge-guided TV regularization and bilateral filtering is designed to preserve model edges that are recovered from previous iterations as well as from lower frequency waveforms when FWI is conducted from lower to higher frequencies. The new FWI method is validated using the complex Marmousi model that contains several steeply dipping fault zones and hundreds of horizons. Compared to FWI without edge guidance, our proposed edge-guided FWI recovers velocity model anomalies and edges much better. Unlike previous image-guided FWI or edge-guided TV regularization strategies, our method does not require migrating seismic data, thus is more efficient for real applications.

  4. At the edge of humanity: human stem cells, chimeras, and moral status.

    Science.gov (United States)

    Streiffer, Robert

    2005-12-01

    Experiments involving the transplantation of human stem cells and their derivatives into early fetal or embryonic nonhuman animals raise novel ethical issues due to their possible implications for enhancing the moral status of che chimeric individual. Although status-enhancing research is not necessarily objectionable from the perspective of the chimeric individual, there are grounds for objecting to it in the conditions in which it is likely to occur. Translating this ethical conclusion into a policy recommendation, however, is complicated by the fact that substantial empirical and ethical uncertainties remain about which transplants, if any, would significantly enhance the chimeric individual's moral status. Considerations of moral status justify either an early-termination policy on chimeric embryos, or, in the absence of such a policy, restrictions on the introduction of pluripotent human stem cells into early-stage developing animals, pending the resolution of those uncertainties.

  5. Cutting Edge: Developmental Regulation of IFN-γ Production by Mouse Neutrophil Precursor Cells.

    Science.gov (United States)

    Sturge, Carolyn R; Burger, Elise; Raetz, Megan; Hooper, Lora V; Yarovinsky, Felix

    2015-07-01

    Neutrophils are an emerging cellular source of IFN-γ, a key cytokine that mediates host defense to intracellular pathogens. Production of IFN-γ by neutrophils, in contrast to lymphoid cells, is TLR- and IL-12-independent and the events associated with IFN-γ production by neutrophils are not understood. In this study, we show that mouse neutrophils express IFN-γ during their lineage development in the bone marrow niche at the promyelocyte stage independently of microbes. IFN-γ accumulates in primary neutrophilic granules and is released upon induction of degranulation. The developmental mechanism of IFN-γ production in neutrophils arms the innate immune cells prior to infection and assures the potential for rapid release of IFN-γ upon neutrophil activation, the first step during responses to many microbial infections. PMID:26026057

  6. Longitudinal Dependance Of Solsticial Hadley Cell Detected At The Edge Of The Massive Martian Erg

    CERN Document Server

    Kuassivi, M

    2011-01-01

    Using public HIRISE images of MARS, I derive the wind directions at high Northern lattitudes, where many interesting eolian features are observed. BArchan dunes show prominent wind direction from the North indicating that they formed during the southern summer. But a few record consistent SE winds near the UTOPIA PLANITIA basin. The wind reversal is consistent with a local perturbation of the solsticial Hadley cell caused by geological depression.

  7. Cutting edge: Human regulatory T cells require IL-35 to mediate suppression and infectious tolerance.

    Science.gov (United States)

    Chaturvedi, Vandana; Collison, Lauren W; Guy, Clifford S; Workman, Creg J; Vignali, Dario A A

    2011-06-15

    Human regulatory T cells (T(reg)) are essential for the maintenance of immune tolerance. However, the mechanisms they use to mediate suppression remain controversial. Although IL-35 has been shown to play an important role in T(reg)-mediated suppression in mice, recent studies have questioned its relevance in human T(reg). In this study, we show that human T(reg) express and require IL-35 for maximal suppressive capacity. Substantial upregulation of EBI3 and IL12A, but not IL10 and TGFB, was observed in activated human T(reg) compared with conventional T cells (T(conv)). Contact-independent T(reg)-mediated suppression was IL-35 dependent and did not require IL-10 or TGF-β. Lastly, human T(reg)-mediated suppression led to the conversion of the suppressed T(conv) into iTr35 cells, an IL-35-induced T(reg) population, in an IL-35-dependent manner. Thus, IL-35 contributes to human T(reg)-mediated suppression, and its conversion of suppressed target T(conv) into IL-35-induced T(reg) may contribute to infectious tolerance.

  8. Cutting edge: IL-17-secreting innate lymphoid cells are essential for host defense against fungal infection.

    Science.gov (United States)

    Gladiator, André; Wangler, Nicolette; Trautwein-Weidner, Kerstin; LeibundGut-Landmann, Salomé

    2013-01-15

    IL-17-mediated immunity has emerged as a crucial host defense mechanism against fungal infections. Although Th cells are generally thought to act as the major source of IL-17 in response to Candida albicans, we show that fungal control is mediated by IL-17-secreting innate lymphoid cells (ILCs) and not by Th17 cells. By using a mouse model of oropharyngeal candidiasis we found that IL-17A and IL-17F, which are both crucial for pathogen clearance, are produced promptly upon infection in an IL-23-dependent manner, and that ILCs in the oral mucosa are the main source for these cytokines. Ab-mediated depletion of ILCs in RAG1-deficient mice or ILC deficiency in retinoic acid-related orphan receptor c(-/-) mice resulted in a complete failure to control the infection. Taken together, our data uncover the cellular basis for the IL-23/IL-17 axis, which acts right at the onset of infection when it is most needed for fungal control and host protection.

  9. Edge-nitrogenated graphene nanoplatelets as high-efficiency counter electrodes for dye-sensitized solar cells

    Science.gov (United States)

    Wang, Guiqiang; Zhang, Juan; Hou, Shuo; Zhang, Wei; Zhao, Zengdian

    2016-05-01

    Edge-nitrogenated graphene nanoplatelets (ENGNPs) are prepared by a simple and eco-friendly mechanochemical pin-grinding process using flake graphite as the precursor in the presence of nitrogen and investigated as the counter electrodes of dye-sensitized solar cells (DSCs). SEM images and nitrogen adsorption analysis indicate an effective and spontaneous delamination of the pristine graphite into small graphene nanoplatelets by a mechanochemical pin-grinding process. The mechanochemical cracking of the graphitic C-C bond generates activated carbon sites that react directly with nitrogen at the broken edges. The resultant ENGNPs are deposited on a fluorine-doped tin oxide (FTO) substrate by spray coating, and their electrocatalytic activities are investigated systemically in the I-/I3- redox electrolyte. Electrochemical measurements show that the ENGNP electrode possesses excellent electrocatalytic activity for the redox reaction of I-/I3- as evidenced by the low charge-transfer resistance at the interface of the electrode and electrolyte. Under 100 mW cm-2 illumination, the DSC with the optimized ENGNP counter electrode achieves a conversion efficiency of 7.69%, which is comparable to that of the device with Pt counter electrode.Edge-nitrogenated graphene nanoplatelets (ENGNPs) are prepared by a simple and eco-friendly mechanochemical pin-grinding process using flake graphite as the precursor in the presence of nitrogen and investigated as the counter electrodes of dye-sensitized solar cells (DSCs). SEM images and nitrogen adsorption analysis indicate an effective and spontaneous delamination of the pristine graphite into small graphene nanoplatelets by a mechanochemical pin-grinding process. The mechanochemical cracking of the graphitic C-C bond generates activated carbon sites that react directly with nitrogen at the broken edges. The resultant ENGNPs are deposited on a fluorine-doped tin oxide (FTO) substrate by spray coating, and their electrocatalytic

  10. DYRK1A: the double-edged kinase as a protagonist in cell growth and tumorigenesis.

    Science.gov (United States)

    Fernández-Martínez, P; Zahonero, C; Sánchez-Gómez, P

    2015-01-01

    DYRK1A (dual-specificity tyrosine-regulated kinase 1A) is a kinase with multiple implications for embryonic development, especially in the nervous system where it regulates the balance between proliferation and differentiation of neural progenitors. The DYRK1A gene is located in the Down syndrome critical region and may play a significant role in the developmental brain defects, early neurodegeneration, and cancer susceptibility of individuals with this syndrome. DYRK1A is also expressed in adults, where it might participate in the regulation of cell cycle, survival, and tumorigenesis, thus representing a potential therapeutic target for certain types of cancer. However, the final readout of DYRK1A overexpression or inhibition depends strongly on the cellular context, as it has both tumor suppressor and oncogenic activities. Here, we will discuss the functions and substrates of DYRK1A associated with the control of cell growth and tumorigenesis with a focus on the potential use of DYRK1A inhibitors in cancer therapy. PMID:27308401

  11. Curcumin as a double-edged sword for stem cells: dose, time and cell type-specific responses to curcumin

    OpenAIRE

    Attari, Fatemeh; Zahmatkesh, Maryam; Aligholi, Hadi; Mehr, Shahram Ejtemaei; Sharifzadeh, Mohammad; Gorji, Ali; Mokhtari, Tahmineh; Khaksarian, Mojtaba; Hassanzadeh, Gholamreza

    2015-01-01

    Background The beneficial effects of curcumin which includes its antioxidant, anti-inflammatory and cancer chemo-preventive properties have been identified. Little information is available regarding the optimal dose and treatment periods of curcumin on the proliferation rate of different sources of stem cells. Methods In this study, the effect of various concentrations of curcumin on the survival and proliferation of two types of outstanding stem cells which includes bone marrow stem cells (B...

  12. Factors influencing perceived angular velocity

    Science.gov (United States)

    Kaiser, Mary K.; Calderone, Jack B.

    1991-01-01

    Angular velocity perception is examined for rotations both in depth and in the image plane and the influence of several object properties on this motion parameter is explored. Two major object properties are considered, namely, texture density which determines the rate of edge transitions for rotations in depth, i.e., the number of texture elements that pass an object's boundary per unit of time, and object size which determines the tangential linear velocities and 2D image velocities of texture elements for a given angular velocity. Results of experiments show that edge-transition rate biased angular velocity estimates only when edges were highly salient. Element velocities had an impact on perceived angular velocity; this bias was associated with 2D image velocity rather than 3D tangential velocity. Despite these biases judgements were most strongly determined by the true angular velocity. Sensitivity to this higher order motion parameter appeared to be good for rotations both in depth (y-axis) and parallel to the line of sight (z-axis).

  13. Cutting Edge: ACVRL1 Signaling Augments CD8α+ Dendritic Cell Development.

    Science.gov (United States)

    Verma, Rohit; Jaiswal, Hemant; Chauhan, Kuldeep Singh; Kaushik, Monika; Tailor, Prafullakumar

    2016-08-15

    Dendritic cells (DCs) are a collection of different subtypes, each of which is characterized by specific surface markers, gene-expression patterns, and distinct functions. Members of the IFN regulatory factor family play critical roles in DC development and functions. Recently, Irf8 was shown to activate TGF-β signaling, which led to exacerbated neuroinflammation in the experimental autoimmune encephalomyelitis mouse model. We analyzed the effect of Irf8 on TGF-β/bone morphogenetic protein pathway-specific genes in DCs and identified Acvrl1, a type I TGF-β superfamily receptor, as a gene strongly induced by Irf8 expression. Among various DC subtypes, Acvrl1 is differentially expressed in CD8α(+) DCs. ACVRL1 signaling augmented Irf8-directed classical CD8α(+) DC development. Irf8 expression is essential for plasmacytoid DC and CD8α(+) DC development, and this study demonstrates that ACVRL1 signaling plays a pivotal role whereby it suppresses plasmacytoid DC development while enhancing that of CD8α(+) DCs, thus contributing to DC diversity development. PMID:27421479

  14. Reduction of airfoil trailing edge noise by trailing edge blowing

    Science.gov (United States)

    Gerhard, T.; Erbslöh, S.; Carolus, T.

    2014-06-01

    The paper deals with airfoil trailing edge noise and its reduction by trailing edge blowing. A Somers S834 airfoil section which originally was designed for small wind turbines is investigated. To mimic realistic Reynolds numbers the boundary layer is tripped on pressure and suction side. The chordwise position of the blowing slot is varied. The acoustic sources, i.e. the unsteady flow quantities in the turbulent boundary layer in the vicinity of the trailing edge, are quantified for the airfoil without and with trailing edge blowing by means of a large eddy simulation and complementary measurements. Eventually the far field airfoil noise is measured by a two-microphone filtering and correlation and a 40 microphone array technique. Both, LES-prediction and measurements showed that a suitable blowing jet on the airfoil suction side is able to reduce significantly the turbulence intensity and the induced surface pressure fluctuations in the trailing edge region. As a consequence, trailing edge noise associated with a spectral hump around 500 Hz could be reduced by 3 dB. For that a jet velocity of 50% of the free field velocity was sufficient. The most favourable slot position was at 90% chord length.

  15. Edge impact modeling on stiffened composite structures

    OpenAIRE

    Ostré, Benjamin; Bouvet, Christophe; Minot, Clément; Aboissière, Jacky

    2015-01-01

    Finite Element Analysis of low velocity/low energy edge impact has been carried out on carbon fiber reinforced plastic structure. Edge impact experimental results were then compared to the numerical ‘‘Discrete Ply Model’’ in order to simulate the edge impact damage. This edge impact model is inspired to out-of-plan impact model on a laminate plate with addition of new friction and crushing behaviors. From a qualitative and quantitative point of view, this edge impact model reveals a relati...

  16. Energy velocity and group velocity

    Institute of Scientific and Technical Information of China (English)

    陈宇

    1995-01-01

    A new Lagrangian method for studying the relationship between the energy velocity and the group velocity is described. It is proved that under the usual quasistatic electric field, the energy velocity is identical to the group velocity for acoustic waves in anisotropic piezoelectric (or non-piezoelectric) media.

  17. Particle-in-Cell simulation of two-dimensional electron velocity shear driven instability in relativistic domain

    CERN Document Server

    Shukla, Chandrasekhar; Patel, Kartik

    2016-01-01

    We carry out Particle-in-Cell (PIC) simulations to study the instabilities associated with a 2-D sheared electron flow configuration against a neutralizing background of ions. Both weak and strong relativistic flow velocities are considered. In the weakly relativistic case, we observe the development of electromagnetic Kelvin Helmholtz instability with similar characteristics as that predicted by the electron Magnetohydrodynamic (EMHD) model. On other hand, in strong relativistic case the compressibility effects of electron fluid dominate and introduce upper hybrid electrostatic oscillations transverse to the flow which are very distinct from EMHD fluid behaviour. In the nonlinear regime, both weak and strong relativistic cases lead to turbulence with broad power law spectrum.

  18. Angular velocity and head direction signals recorded from the dorsal tegmental nucleus of gudden in the rat: implications for path integration in the head direction cell circuit.

    Science.gov (United States)

    Sharp, P E; Tinkelman, A; Cho, J

    2001-06-01

    When a rat navigates through space, head direction (HD) cells provide an ongoing signal of the rat's directional heading. It is thought that these cells rely, in part, on angular path integration of the rat's head movements. This integration requires that the HD cell system receive information about angular head movements and that this information be combined with the current directional signal, to generate the next "predicted" direction. Recent data suggest that the dorsal tegmental nucleus (DTN) may play a critical role in helping to generate the HD cell signal. To test this, recordings were made from cells in the DTN in freely moving rats. The following cell types were found: (a) "classic" HD cells, (b) angular velocity cells, and (c) cells that fired as a function of both head direction and angular velocity. Thus, DTN cells exhibit firing characteristics that are critical to the neural circuit hypothesized for generation of the HD cell signal. PMID:11439447

  19. Escape Velocity

    OpenAIRE

    Nikola Vlacic

    2010-01-01

    In this project, we investigated if it is feasible for a single staged rocket with constant thrust to attain escape velocity. We derived an equation for the velocity and position of a single staged rocket that launches vertically. From this equation, we determined if an ideal model of a rocket is able to reach escape velocity.

  20. 31P MAS-NMR of human erythrocytes: independence of cell volume from angular velocity.

    Science.gov (United States)

    Kuchel, P W; Bubb, W A; Ramadan, S; Chapman, B E; Philp, D J; Coen, M; Gready, J E; Harvey, P J; McLean, A J; Hook, J

    2004-09-01

    31P magic angle spinning NMR (MAS-NMR) spectra were obtained from suspensions of human red blood cells (RBCs) that contained the cell-volume-sensitive probe molecule, dimethyl methylphosphonate (DMMP). A mathematical representation of the spectral-peak shape, including the separation and width-at-half-height in the 31P NMR spectra, as a function of rotor speed, enabled us to explore the extent to which a change in cell volume would be reflected in the spectra if it occurred. We concluded that a fractional volume change in excess of 3% would have been detected by our experiments. Thus, the experiments indicated that the mean cell volume did not change by this amount even at the highest spinning rate of 7 kHz. The mean cell volume and intracellular 31P line-width were independent of the packing density of the cells and of the initial cell volume. The relationship of these conclusions to other non-NMR studies of pressure effects on cells is noted. PMID:15334588

  1. Living edge

    DEFF Research Database (Denmark)

    Earon, Ofri

    2014-01-01

    was originally introduced to enhance indoor qualities including light and view. Throughout the paper, it is argued that these ecological motives have grown to architectural and urban dimensions. The paper analyzes the characteristics and potentials of these dimensions and their interconnections. The paper...... on the ground level, but there is a lack of recognition in the significance of communicative characters as well at the higher part of the edge. The city’s planning approach is “Consider urban life before urban space. Consider urban space before buildings” This urban strategy neglects the possible architectural...... contribution to the street atmosphere and its effect on urban life. Bay balcony has been a common architectural element in Copenhagen’s residential buildings, since the end of the twenties. It is a domestic border with an architectural thickness combining window, door, windowsill and balcony. The bay balcony...

  2. EMA: a developmentally regulated cell-surface glycoprotein of CNS neurons that is concentrated at the leading edge of growth cones.

    Science.gov (United States)

    Baumrind, N L; Parkinson, D; Wayne, D B; Heuser, J E; Pearlman, A L

    1992-08-01

    To identify cell-surface molecules that mediate interactions between neurons and their environment during neural development, we used monoclonal antibody techniques to define a developmentally regulated antigen in the central nervous system of the mouse. The antibody we produced (2A1) immunolabels cells throughout the central nervous system; we analyzed its distribution in the developing cerebral cortex, where it is expressed on cells very soon after they complete mitosis and leave the periventricular proliferative zone. Expression continues into adult life. The antibody also labels the epithelium of the choroid plexus and the renal proximal tubules, but does not label neurons of the peripheral nervous system in the dorsal root ganglia. In dissociated cell culture of embryonic cerebral cortex, 2A1 labels the surface of neurons but not glia. Immunolabeling of neurons in tissue culture is particularly prominent on the edge of growth cones, including filopodia and the leading edge of lamellipodia, when observed with either immunofluorescence or freeze-etch immunoelectron microscopy. Immunopurification with 2A1 of a CHAPS-extracted membrane preparation from brains of neonatal mice produces a broad (32-36 kD) electrophoretic band and a less prominent 70 kD band that are sensitive to N-glycosidase but not endoglycosidase H. Thus the 2A1 antibody recognizes a developmentally regulated, neuronal cell surface glycoprotein (or glycoproteins) with complex N-linked oligosaccharide side chains. We have termed the glycoprotein antigen EMA because of its prominence on the edge membrane of growth cones. EMA is similar to the M6 antigen (Lagenaur et al: J. Neurobiol. 23:71-88, 1992) in apparent molecular weight, distribution in tissue sections, and immunoreactivity on Western blots, suggesting that the two antigens are similar or identical. Expression of EMA is a very early manifestation of neuronal differentiation; its distribution on growth cones suggests a role in mediating the

  3. Particle-in-cell simulation of two-dimensional electron velocity shear driven instability in relativistic domain

    Science.gov (United States)

    Shukla, Chandrasekhar; Das, Amita; Patel, Kartik

    2016-08-01

    We carry out particle-in-cell simulations to study the instabilities associated with a 2-D sheared electron flow configuration against a neutralizing background of ions. Both weak and strong relativistic flow velocities are considered. In the weakly relativistic case, we observe the development of electromagnetic Kelvin-Helmholtz instability with similar characteristics as that predicted by the electron Magnetohydrodynamic (EMHD) model. On the contrary, in a strong relativistic case, the compressibility effects of electron fluid dominate and introduce upper hybrid electrostatic oscillations transverse to the flow which are very distinct from EMHD fluid behavior. In the nonlinear regime, both weak and strong relativistic cases lead to turbulence with broad power law spectrum.

  4. 1D Modeling of a Bifacial Silicon Solar Cell under Frequency Modulation Monochromatic Illumination: Determination of the Equivalent Electrical Circuit Related to the Surface Recombination Velocity

    Directory of Open Access Journals (Sweden)

    H. Ly Diallo

    2012-06-01

    Full Text Available We present in this study the determination of the equivalent electrical circuits associated to the recombination velocities for a bifacial silicon solar cell under frequency modulation and monochromatic illumination. This determination is based on Bode and Nyquist diagrams that is the variations of the phase and the module of the back surface and intrinsic junction recombination velocities. Their dependence on illumination wavelength is also shown.

  5. Secretory vesicle transport velocity in living cells depends on the myosin-V lever arm length.

    Science.gov (United States)

    Schott, Daniel H; Collins, Ruth N; Bretscher, Anthony

    2002-01-01

    Myosins are molecular motors that exert force against actin filaments. One widely conserved myosin class, the myosin-Vs, recruits organelles to polarized sites in animal and fungal cells. However, it has been unclear whether myosin-Vs actively transport organelles, and whether the recently challenged lever arm model developed for muscle myosin applies to myosin-Vs. Here we demonstrate in living, intact yeast that secretory vesicles move rapidly toward their site of exocytosis. The maximal speed varies linearly over a wide range of lever arm lengths genetically engineered into the myosin-V heavy chain encoded by the MYO2 gene. Thus, secretory vesicle polarization is achieved through active transport by a myosin-V, and the motor mechanism is consistent with the lever arm model.

  6. Cutting edge: TNFR-shedding by CD4+CD25+ regulatory T cells inhibits the induction of inflammatory mediators.

    NARCIS (Netherlands)

    Mierlo, G.J. van; Scherer, H.U.; Hameetman, M.; Morgan, M.E.; Flierman, R.; Huizinga, T.W.J.; Toes, R.E.

    2008-01-01

    CD4+CD25+ regulatory T (Treg) cells play an essential role in maintaining tolerance to self and nonself. In several models of T cell-mediated (auto) immunity, Treg cells exert protective effects by the inhibition of pathogenic T cell responses. In addition, Treg cells can modulate T cell-independent

  7. Determination of lifetime and surface recombination velocity of p-n junction solar cells and diodes by observing transients

    Science.gov (United States)

    Lindholm, Fredrik A.; Liou, Juin J.; Neugroschel, Arnost; Jung, Taewon W.

    1987-01-01

    The unified view of transient methods for the determination of recombination lifetime tau and back surface recombination velocity S presented here for silicon solar cells and diodes attempts to define limitations of existing methods and to evolve improvements. The presence of sizable junction capacitance for silicon devices under forward voltage invalidates the use of conventional open-circuit voltage decay (OCVD) and reverse recovery. This led Green (1983) to his method of compensated open-circuit voltage decay, in which the addition of an external resistor shunting the solar cell partially corrects for the presence of the junction capacitance. Setting this resistance to zero produces an electrical short-circuit current-decay method, which has the advantage of enabling determination of both tau and S. In an alternate approach, one may insert the functional dependence of the junction capacitance on forward voltage. This new method, denoted by the acronym OCVDCAP, enables the determination of tau with apparently greater accuracy than that obtained by previous methods utilizing voltage transients. But OCVDCAP has in common with the previous methods that it determines tau only and has practical utility only for determining tau of long-base devices. This means that it is useful only for thick base regions. In principle, however, it has an advantage over short-circuit current decay: it requires only pressure contacts, not ohmic contacts, and therefore may be used to determine tau after key processing steps in manufacturing.

  8. Analysis of the nitrogen K-edge x-ray absorption spectra of Zn-porphyrin/C{sub 70}-fulleren complex for solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Suchkova, S A; Soldatov, A [Southern Federal University, Sorge str. 5, 344090 Rostov-on-Don (Russian Federation); Cudia, C Castellarin, E-mail: suchkova_sv@inbox.r [Sincrotrone Trieste S.C.p.A, s.s. 14 km 163.5 in Area Science Park, 34012 Trieste (Italy)

    2009-11-15

    The atomic structure models of Zn-porphyrin/C{sub 70} multilayer for solar cells were examined. The local atomic structure of the Zn-porphyrin/C{sub 70} complex was refined with the use of previously published results [1]. Since near-edge spectral region (XANES) is sensitive to the three-dimensional atomic geometry, the theoretical analysis of the experimental XANES was performed on the basis of finite difference method (FDMnes 2008 program code). Some electronic properties of the complex were obtained from the DFT calculations performed by means of Amsterdam Density Functional program package.

  9. Analysis of the nitrogen K-edge x-ray absorption spectra of Zn-porphyrin/C70-fulleren complex for solar cells

    Science.gov (United States)

    Suchkova, S. A.; Castellarin Cudia, C.; Soldatov, A.

    2009-11-01

    The atomic structure models of Zn-porphyrin/C70 multilayer for solar cells were examined. The local atomic structure of the Zn-porphyrin/C70 complex was refined with the use of previously published results [1]. Since near-edge spectral region (XANES) is sensitive to the three-dimensional atomic geometry, the theoretical analysis of the experimental XANES was performed on the basis of finite difference method (FDMnes 2008 program code). Some electronic properties of the complex were obtained from the DFT calculations performed by means of Amsterdam Density Functional program package.

  10. Flap-Edge Blowing Experiments

    Science.gov (United States)

    Gaeta, R. J.; Englar, R. J.; Ahuja, K. K.

    2003-01-01

    This Appendix documents the salient results from an effort to mitigate the so-called flap-edge noise generated at the split between a flap edge that is deployed and the undeployed flap. Utilizing a Coanda surface installed at the flap edge, steady blowing was used in an attempt to diminish the vortex strength resulting from the uneven lift distribution. The strength of this lifting vortex was augmented by steady blowing over the deployed flap. The test article for this study was the same 2D airfoil used in the steady blowing program reported earlier (also used in pulsed blowing tests, see Appendix G), however its trailing edge geometry was modified. An exact duplicate of the airfoil shape was made out of fiberglass with no flap, and in the clean configuration. It was attached to the existing airfoil to make an airfoil that has half of its flap deployed and half un-deployed. Figure 1 shows a schematic of the planform showing the two areas where steady blowing was introduced. The flap-edge blowing or the auxiliary blowing was in the direction normal to the freestream velocity vector. Slot heights for the blowing chambers were on the order of 0.0 14 inches.

  11. Intermediate-affinity LFA-1 binds alpha-actinin-1 to control migration at the leading edge of the T cell.

    Science.gov (United States)

    Stanley, Paula; Smith, Andrew; McDowall, Alison; Nicol, Alastair; Zicha, Daniel; Hogg, Nancy

    2008-01-01

    T lymphocytes use LFA-1 to migrate into lymph nodes and inflammatory sites. To investigate the mechanisms regulating this migration, we utilize mAbs selective for conformational epitopes as probes for active LFA-1. Expression of the KIM127 epitope, but not the 24 epitope, defines the extended conformation of LFA-1, which has intermediate affinity for ligand ICAM-1. A key finding is that KIM127-positive LFA-1 forms new adhesions at the T lymphocyte leading edge. This LFA-1 links to the cytoskeleton through alpha-actinin-1 and disruption at the level of integrin or actin results in loss of cell spreading and migratory speed due to a failure of attachment at the leading edge. The KIM127 pattern contrasts with high-affinity LFA-1 that expresses both 24 and KIM127 epitopes, is restricted to the mid-cell focal zone and controls ICAM-1 attachment. Identification of distinctive roles for intermediate- and high-affinity LFA-1 in T lymphocyte migration provides a biological function for two active conformations of this integrin for the first time.

  12. Forest edge development

    OpenAIRE

    Wiström, Björn

    2015-01-01

    This thesis investigates design guidelines and management systems for the development of stationary forest edges with a graded profile in infrastructure and urban environments. The spatial restriction for the edge to move forward caused by human land use counteracts the natural dynamics and development patterns of graded forest edges. However graded forest edges with successively increasing height from the periphery to the interior of the forest edge are often seen as ideal as they supports ...

  13. 外侧膝状体细胞对边缘的响应模型%Response of Lateral Geniculate Nucleus Cells to Edges

    Institute of Scientific and Technical Information of China (English)

    任远

    2014-01-01

    Edges composing of stimuli of different intensities are common in both natural scenes and digital images.Edge detection is a basic step for machine visual systems,particularly machine biological visual systems.This paper establishes a model of lateral geniculate nucleus (LGN)cells in a primary visual pathway,describes the LGN cell response to edges,and provides feature representations for designing image processing approaches based on neural mechanism. According to physiological characteristics of retinal ganglion cells,the paper uses the classical model of difference of Gaussians to describe the LGN cell response to stimuli,and obtains a re-sponse function via reasonable simplifications.Through simple analyses,several mathematical properties of the response function are obtained,which agree with the physiological characteristics of neurons.By further simplifying the contrast of a stimulus,a normalized response function is obtained.Numeric experiments show that similarities exist between the function’s response curve and the physiological curve discovered in a previous neural science research,showing validity of the described model.%边缘检测是机器视觉系统与生物视觉系统处理视觉信息的基础阶段。为初级视觉通路中的外侧膝状体(LGN)细胞建立一个模型,描述其对边缘的响应,为构建基于神经机制的图像处理方法提供特征表征。根据神经节细胞感受野的生理特性,用经典的高斯差模型描述 LGN 细胞对刺激的响应,通过合理地简化得到相对简单的响应函数。通过简单数学分析,能够得到函数的几点数学性质,且这些性质都与神经元的生理特性相符。进一步简化刺激的对比度,得到归一化的响应函数。数值实验发现,函数的响应曲线和神经科学研究得到的生理曲线具有相似性,说明该数学模型的合理性。

  14. Effects of variations in electron thermal velocity on the whistler anisotropy instability: Particle-in-cell simulations

    Science.gov (United States)

    Hughes, R. Scott; Wang, Joseph; Decyk, Viktor K.; Gary, S. Peter

    2016-04-01

    This paper investigates how the physics of the whistler anisotropy instability (WAI) is affected by variations in the electron thermal velocity vte, referred to here in terms of the ratio v̂ t e=vt e/c , where c is the speed of light. The WAI is driven by the electron condition RT>1 , where RT=Te ⊥/Te ∥ is the temperature anisotropy ratio and ⊥/∥ signify directions perpendicular/parallel to the background magnetic field B0 . While a typical value of v̂ t e in the solar wind is ˜0.005 , electromagnetic (EM) particle-in-cell (PIC) simulations often use a value near 0.1 in order to maximize the computational time step. In this study, a two-dimensional (2D) Darwin particle-in-cell (DPIC) code, MDPIC2, is used. The time step in the DPIC model is not affected by the choice of v̂ t e , making DPIC suited for this study. A series of simulations are carried out under the condition that the electron βe is held fixed, while v̂ t e is varied over the range 0.1 ≥v̂ t e≥0.025 . The results show that, with βe held fixed, the linear dispersion properties and the nonlinear saturation amplitude and pitch angle scattering rates associated with the WAI are insensitive to the value of v̂ t e . A supplementary investigation is conducted which characterizes how the WAI model is affected at various values of v̂ t e by noise associated with the limited number of particles in a typical PIC simulation. It is found that the evolution of the WAI is more strongly influenced by electrostatic noise as v̂ t e is decreased. The electrostatic noise level is inversely proportional to the number of particles per computational cell ( Nc ); this implies that the number of particles required to remove nonphysical effects from the PIC simulation increases as v̂ t e decreases. It is concluded that PIC simulations of this instability which use an artificially large value of v̂ t e accurately reproduce the response of a cooler plasma as long as a realistic value of βe is used

  15. Cutting Edge: Distinct Glycolytic and Lipid Oxidative Metabolic Programs Are Essential for Effector and Regulatory CD4+ T Cell Subsets

    OpenAIRE

    Ryan D Michalek; Gerriets, Valerie A.; Jacobs, Sarah R.; Macintyre, Andrew N.; MacIver, Nancie J.; Mason, Emily F.; Sullivan, Sarah A.; Nichols, Amanda G.; Rathmell, Jeffrey C.

    2011-01-01

    Stimulated CD4+ T lymphocytes can differentiate into effector T cell (Teff) or inducible regulatory T cell (Treg) subsets with specific immunological roles. We show that Teff and Treg require distinct metabolic programs to support these functions. Th1, Th2, and Th17 cells expressed high surface levels of the glucose transporter Glut1 and were highly glycolytic. Treg, in contrast, expressed low levels of Glut1 and had high lipid oxidation rates. Consistent with glycolysis and lipid oxidation p...

  16. The edges of graphene

    Science.gov (United States)

    Zhang, Xiuyun; Xin, John; Ding, Feng

    2013-03-01

    The edge of two dimensional (2D) graphene, as the surface of a three dimensional (3D) crystal, plays a crucial role in the determination of its physical, electronic and chemical properties and thus has been extensively studied recently. In this review, we summarize the recent advances in the study of graphene edges, including edge formation energy, edge reconstruction, method of graphene edge synthesis and the recent progress on metal-passivated graphene edges and the role of edges in graphene CVD growth. We expect this review to provide a guideline for readers to gain a clear picture of graphene edges from several aspects, especially the catalyst-passivated graphene edges and their role in graphene CVD growth.

  17. The edges of graphene.

    Science.gov (United States)

    Zhang, Xiuyun; Xin, John; Ding, Feng

    2013-04-01

    The edge of two dimensional (2D) graphene, as the surface of a three dimensional (3D) crystal, plays a crucial role in the determination of its physical, electronic and chemical properties and thus has been extensively studied recently. In this review, we summarize the recent advances in the study of graphene edges, including edge formation energy, edge reconstruction, method of graphene edge synthesis and the recent progress on metal-passivated graphene edges and the role of edges in graphene CVD growth. We expect this review to provide a guideline for readers to gain a clear picture of graphene edges from several aspects, especially the catalyst-passivated graphene edges and their role in graphene CVD growth. PMID:23420074

  18. The edges of graphene.

    Science.gov (United States)

    Zhang, Xiuyun; Xin, John; Ding, Feng

    2013-04-01

    The edge of two dimensional (2D) graphene, as the surface of a three dimensional (3D) crystal, plays a crucial role in the determination of its physical, electronic and chemical properties and thus has been extensively studied recently. In this review, we summarize the recent advances in the study of graphene edges, including edge formation energy, edge reconstruction, method of graphene edge synthesis and the recent progress on metal-passivated graphene edges and the role of edges in graphene CVD growth. We expect this review to provide a guideline for readers to gain a clear picture of graphene edges from several aspects, especially the catalyst-passivated graphene edges and their role in graphene CVD growth.

  19. The other side of abnormal: a case series of low transcranial Doppler velocities associated with stroke in children with sickle cell disease.

    Science.gov (United States)

    Buchanan, Iris D; James-Herry, Anne; Osunkwo, Ifeyinwa

    2013-10-01

    The prevalence of cerebrovascular events in sickle cell disease (SCD) can be as low as 10% by the age of 18 for overt cerebral infarction or strokes, up to 35% for silent cerebral infarction, and as high as 43/100 patient years for acute silent cerebral ischemic events. These events typically occur during childhood with a peak incidence between the age of 4 and 7 years. The cumulative risk of central nervous system events in SCD increases with age. Transcranial Doppler (TCD) ultrasonography is an established screening tool for detecting children with SCD at highest risk for stroke by measuring the flow velocity in the large intracranial vessels. Velocities are considered abnormal with readings >200 cm/s and chronic red cell transfusions are recommended to reduce further risk or progression. Red cell transfusions have reduced the rate of cerebrovascular accidents by 90%. We describe the case of 5 children with sickle cell anemia, whose antecedent screening TCD velocities were measured to be ≤70 cm/s in the study. All patients developed some form of cerebral insults, an overt cerebral infarctions, silent stroke or transient ischemic attack, and are now receiving chronic transfusion to prevent further progression. On the basis of these cases, low TCD velocities may identify another group of children at risk for cerebrovascular disease. We suggest TCD velocities <70 cm/s in major vessels (MCA, ACA, and ICA) be considered another type of "abnormal," prompting more sensitive evaluations (such as a brain MRI and MRA) for the presence of central nervous system disease, and, if negative, decrease intervals between subsequent TCD assessments.

  20. Cutting Edge: B Cell-Intrinsic T-bet Expression Is Required To Control Chronic Viral Infection.

    Science.gov (United States)

    Barnett, Burton E; Staupe, Ryan P; Odorizzi, Pamela M; Palko, Olesya; Tomov, Vesselin T; Mahan, Alison E; Gunn, Bronwyn; Chen, Diana; Paley, Michael A; Alter, Galit; Reiner, Steven L; Lauer, Georg M; Teijaro, John R; Wherry, E John

    2016-08-15

    The role of Ab and B cells in preventing infection is established. In contrast, the role of B cell responses in containing chronic infections remains poorly understood. IgG2a (IgG1 in humans) can prevent acute infections, and T-bet promotes IgG2a isotype switching. However, whether IgG2a and B cell-expressed T-bet influence the host-pathogen balance during persisting infections is unclear. We demonstrate that B cell-specific loss of T-bet prevents control of persisting viral infection. T-bet in B cells controlled IgG2a production, as well as mucosal localization, proliferation, glycosylation, and a broad transcriptional program. T-bet controlled a broad antiviral program in addition to IgG2a because T-bet in B cells was important, even in the presence of virus-specific IgG2a. Our data support a model in which T-bet is a universal controller of antiviral immunity across multiple immune lineages. PMID:27430722

  1. High-surface-area nanomesh graphene with enriched edge sites as efficient metal-free cathodes for dye-sensitized solar cells.

    Science.gov (United States)

    Yang, Wang; Xu, Xiuwen; Gao, Yalun; Li, Zhao; Li, Cuiyu; Wang, Wenping; Chen, Yu; Ning, Guoqing; Zhang, Liqiang; Yang, Fan; Chen, Shengli; Wang, Aijun; Kong, Jing; Li, Yongfeng

    2016-07-14

    Exploiting cost-effective and highly efficient counter electrodes (CEs) has been a persistent objective for practical application of dye-sensitized solar cells (DSSCs). Here, we present an efficient CE by using pure three-dimensional (3D) nanomesh graphene frameworks (NGFs) which are synthesized via a template-directed chemical vapor deposition (CVD) approach. The high-surface-area 3D NGFs associated with the enriched surface edge defects make it very efficient towards I3(-) reduction even without any Pt catalyst. More interestingly, by virtue of the interpenetrating graphene frameworks, the NGFs exhibit excellent electron conductivity, thus leading to facile charge transfer. Consequently, the DSSCs with pure NGFs as CEs display a power conversion efficiency of 7.32%, which is comparable to that of Pt as CEs (7.28%), thereby exhibiting great potential as low-cost and highly efficient CE materials for large-scale deployment of DSSCs. PMID:27328165

  2. Composition analysis of a polymer electrolyte membrane fuel cell microporous layer using scanning transmission X-ray microscopy and near edge X-ray absorption fine structure analysis

    Science.gov (United States)

    George, Michael G.; Wang, Jian; Banerjee, Rupak; Bazylak, Aimy

    2016-03-01

    The novel application of scanning transmission X-ray microscopy (STXM) to the microporous layer (MPL) of a polymer electrolyte membrane fuel cell is investigated. A spatially resolved chemical component distribution map is obtained for the MPL of a commercially available SGL 25 BC sample. This is achieved with near edge X-ray absorption fine structure spectroscopic analysis. Prior to analysis the sample is embedded in non-reactive epoxy and ultra-microtomed to a thickness of 100 nm. Polytetrafluoroethylene (PTFE), carbon particle agglomerates, and supporting epoxy resin distributions are identified and reconstructed for a scanning area of 6 μm × 6 μm. It is observed that the spatial distribution of PTFE is strongly correlated to the carbon particle agglomerations. Additionally, agglomerate structures of PTFE are identified, possibly indicating the presence of a unique mesostructure in the MPL. STXM analysis is presented as a useful technique for the investigation of chemical species distributions in the MPL.

  3. The CRIRES Search for Planets Around the Lowest-Mass Stars. I. High-Precision Near-Infrared Radial Velocities with an Ammonia Gas Cell

    CERN Document Server

    Bean, Jacob L; Hartman, Henrik; Nilsson, Hampus; Wiedemann, Guenter; Reiners, Ansgar; Dreizler, Stefan; Henry, Todd J

    2009-01-01

    Radial velocities measured from near-infrared spectra are a potentially powerful tool to search for planets around cool stars and sub-stellar objects. However, no technique currently exists that yields near-infrared radial velocity precision comparable to that which is routinely obtained in the visible. We describe a method for measuring high-precision relative radial velocities of cool stars from K-band spectra. The method makes use of a glass cell filled with ammonia gas to calibrate the spectrograph response similar to the iodine cell technique that has been used so successfully in the visible. Stellar spectra are obtained through the ammonia cell and modeled as the product of a Doppler-shifted template spectrum of the object and a spectrum of the cell, convolved with a variable instrumental profile model. A complicating factor is that a significant number of telluric absorption lines are present in the spectral regions containing useful stellar and ammonia lines. The telluric lines are modeled simultaneou...

  4. Forebody and leading edge vortex measurements using planar Doppler velocimetry

    Science.gov (United States)

    Beutner, Thomas J.; Elliott, Gregory S.; Williams, Glenn W.; Baust, Henry D.; Crafton, Jim; Carter, Campbell D.

    2001-04-01

    The planar Doppler velocimetry (PDV) technique has been demonstrated by employing it in a large-scale wind tunnel to record velocity fields surrounding a model of a generic fighter plane. The PDV instrument employed here included the following: (i) a frequency monitoring system for measuring the laser frequency corresponding to each set of scattering images; (ii) two detector systems (each composed of two 16-bit CCD cameras), one viewing the model from the top of the wind tunnel and the second from the side; (iii) iodine vapour cells based on the starved-cell design, which eliminated the need for separate temperature control of the iodine reservoir; iv) a vibration-isolated, injection-seeded, Q-switched Nd:YAG laser and (v) custom data acquisition software for linking the four cameras, the laser and the frequency monitor. The PDV instrument was validated by comparing the PDV-derived velocity to the known value in the empty wind tunnel. An error of about 1 m s-1 out of an 18.9 m s-1 velocity component was found; the image noise component (resulting primarily from the speckle effect) was found to be about 1 m s-1. In addition, as a result of laser-sheet impingement on the model surface, velocities near the model surfaces are biased by background scattering effects. Nonetheless, it has been shown that PDV can be used effectively to map velocity fields with high spatial resolution over complex model geometries. Frame-averaged velocity images recorded at four axial stations along the model have shown the formation of forebody and leading-edge vortices and their complex interaction in the presence of the wing flow field.

  5. Stability of edge states and edge magnetism in graphene nanoribbons

    OpenAIRE

    Kunstmann, Jens; Özdoğan, Cem; Quandt, Alexander; Fehske, Holger

    2010-01-01

    We critically discuss the stability of edge states and edge magnetism in zigzag edge graphene nanoribbons (ZGNRs). We point out that magnetic edge states might not exist in real systems, and show that there are at least three very natural mechanisms - edge reconstruction, edge passivation, and edge closure - which dramatically reduce the effect of edge states in ZGNRs or even totally eliminate them. Even if systems with magnetic edge states could be made, the intrinsic magnetism would not be ...

  6. Cutting edge: Self-antigen controls the balance between effector and regulatory T cells in peripheral tissues.

    Science.gov (United States)

    Gratz, Iris K; Rosenblum, Michael D; Maurano, Megan M; Paw, Jonathan S; Truong, Hong-An; Marshak-Rothstein, Ann; Abbas, Abul K

    2014-02-15

    Immune homeostasis in peripheral tissues is achieved by maintaining a balance between pathogenic effector T cells (Teffs) and protective Foxp3(+) regulatory T cells (Tregs). Using a mouse model of an inducible tissue Ag, we demonstrate that Ag persistence is a major determinant of the relative frequencies of Teffs and Tregs. Encounter of transferred naive CD4(+) T cells with transiently expressed tissue Ag leads to generation of cytokine-producing Teffs and peripheral Tregs. Persistent expression of Ag, a mimic of self-antigen, leads to functional inactivation and loss of the Teffs with preservation of Tregs in the target tissue. The inactivation of Teffs by persistent Ag is associated with reduced ERK phosphorylation, whereas Tregs show less reduction in ERK phosphorylation and are relatively resistant to ERK inhibition. Our studies reveal a crucial role for Ag in maintaining appropriate ratios of Ag-specific Teffs to Tregs in tissues.

  7. Cutting edge: TCR stimulation by antibody and bacterial superantigen induces Stat3 activation in human T cells

    DEFF Research Database (Denmark)

    Gerwien, J; Nielsen, M; Labuda, T;

    1999-01-01

    -specific human CD4+ T cell lines. In contrast, IL-2 induces a rapid and transient tyrosine and serine phosphorylation of Stat3. Compared with IL-2, CD3 ligation induces a delayed Stat3 binding to oligonucleotide probes from the ICAM-1 and IL-2R alpha promoter. CD3-mediated activation of Stat3 is almost...

  8. Cutting Edge: Marginal Zone Macrophages Regulate Antigen Transport by B Cells to the Follicle in the Spleen via CD21.

    Science.gov (United States)

    Prokopec, Kajsa E; Georgoudaki, Anna-Maria; Sohn, Silke; Wermeling, Fredrik; Grönlund, Hans; Lindh, Emma; Carroll, Michael C; Karlsson, Mikael C I

    2016-09-15

    Marginal zone macrophages (MZM) are strategically located in the spleen, lining the marginal sinus where they sense inflammation and capture Ag from the circulation. One of the receptors expressed by MZM is scavenger receptor macrophage receptor with collagenous structure (MARCO), which has affinity for modified self-antigens. In this article, we show that engagement of MARCO on murine macrophages induces extracellular ATP and loss of CD21 and CD62L on marginal zone B cells. Engagement of MARCO also leads to reduction of Ag transport by marginal zone B cells and affects the subsequent immune response. This study highlights a novel function for MZM in regulating Ag transport and activation, and we suggest that MARCO-dependent ATP release regulates this through shedding of CD21 and CD62L. Because systemic lupus erythematosus patients were shown to acquire autoantibodies against MARCO, this highlights a mechanism that could affect a patient's ability to combat infections.

  9. Edge-selenated graphene nanoplatelets as durable metal-free catalysts for iodine reduction reaction in dye-sensitized solar cells

    Science.gov (United States)

    Ju, Myung Jong; Jeon, In-Yup; Kim, Hong Mo; Choi, Ji Il; Jung, Sun-Min; Seo, Jeong-Min; Choi, In Taek; Kang, Sung Ho; Kim, Han Seul; Noh, Min Jong; Lee, Jae-Joon; Jeong, Hu Young; Kim, Hwan Kyu; Kim, Yong-Hoon; Baek, Jong-Beom

    2016-01-01

    Metal-free carbon-based electrocatalysts for dye-sensitized solar cells (DSSCs) are sufficiently active in Co(II)/Co(III) electrolytes but are not satisfactory in the most commonly used iodide/triiodide (I−/I3−) electrolytes. Thus, developing active and stable metal-free electrocatalysts in both electrolytes is one of the most important issues in DSSC research. We report the synthesis of edge-selenated graphene nanoplatelets (SeGnPs) prepared by a simple mechanochemical reaction between graphite and selenium (Se) powders, and their application to the counter electrode (CE) for DSSCs in both I−/I3− and Co(II)/Co(III) electrolytes. The edge-selective doping and the preservation of the pristine graphene basal plane in the SeGnPs were confirmed by various analytical techniques, including atomic-resolution transmission electron microscopy. Tested as the DSSC CE in both Co(bpy)32+/3+ (bpy = 2,2′-bipyridine) and I−/I3− electrolytes, the SeGnP-CEs exhibited outstanding electrocatalytic performance with ultimately high stability. The SeGnP-CE–based DSSCs displayed a higher photovoltaic performance than did the Pt-CE–based DSSCs in both SM315 sensitizer with Co(bpy)32+/3+ and N719 sensitizer with I−/I3− electrolytes. Furthermore, the I3− reduction mechanism, which has not been fully understood in carbon-based CE materials to date, was clarified by an electrochemical kinetics study combined with density functional theory and nonequilibrium Green’s function calculations. PMID:27386557

  10. Bootstrap inversion for Pn wave velocity in North-Western Italy

    Directory of Open Access Journals (Sweden)

    C. Eva

    1997-06-01

    Full Text Available An inversion of Pn arrival times from regional distance earthquakes (180-800 km, recorded by 94 seismic stations operating in North-Western Italy and surrounding areas, was carried out to image lateral variations of P-wave velocity at the crust-mantle boundary, and to estimate the static delay time at each station. The reliability of the obtained results was assessed using both synthetic tests and the bootstrap Monte Carlo resampling technique. Numerical simulations demonstrated the existence of a trade-off between cell velocities and estimated station delay times along the edge of the model. Bootstrap inversions were carried out to determine the standard deviation of velocities and time terms. Low Pn velocity anomalies are detected beneath the outer side of the Alps (-6% and the Western Po plain (-4% in correspondence with two regions of strong crustal thickening and negative Bouguer anomaly. In contrast, high Pn velocities are imaged beneath the inner side of the Alps (+4% indicating the presence of high velocity and density lower crust-upper mantle. The Ligurian sea shows high Pn velocities close to the Ligurian coastlines (+3% and low Pn velocities (-1.5% in the middle of the basin in agreement with the upper mantle velocity structure revealed by seismic refraction profiles.

  11. A model for the early stages of motion processing based on spatial and temporal edge detection by X-cells.

    Science.gov (United States)

    Spitzer, H; Almon, M; Sherman, I

    1994-01-01

    A model for the early stages of motion processing in the visual cortex is presented. The 'building block' for this model is the 'rebound response', which is the neuronal response evoked when a sufficient inhibitory stimulus is turned off. This response enables detection of temporal changes when the stimulus involves spatial changes. The model suggests that adjacent subunits in primary cortical cells have different weight functions for rebound responses, and thus a synergistic type of response is evoked in the preferred direction, which is predicted for both light and dark stimuli. Predictions of the model for different stimuli and receptive field structures are discussed. It appears to be more economical than previous motion models. PMID:7833301

  12. Edge physics Simulations

    Institute of Scientific and Technical Information of China (English)

    X.Q. Xu; C.S. Chang

    2007-01-01

    @@ The plasma edge includes the pedestal, scrape-off, and divertor regions. A complete edge physics should deal with the plasma, atomic, and the plasma-wall interaction phenomena. The edge provides the source of plasma through ionization of the incoming neutral particles and source of impurity through the wall sputtering. Edge plasma sets a boundary condition for the core confinement physics. Importance of the edge plasma has been elevated to the top list of the ITER physics research needs due to the necessity of the self-organized plasma pedestal and its destruction by edge localized mode activities. Extrapolation of the present tokamak data base predicts that a sufficient pedestal height is a necessary condition for the success of ITER.

  13. High-surface-area nanomesh graphene with enriched edge sites as efficient metal-free cathodes for dye-sensitized solar cells

    Science.gov (United States)

    Yang, Wang; Xu, Xiuwen; Gao, Yalun; Li, Zhao; Li, Cuiyu; Wang, Wenping; Chen, Yu; Ning, Guoqing; Zhang, Liqiang; Yang, Fan; Chen, Shengli; Wang, Aijun; Kong, Jing; Li, Yongfeng

    2016-06-01

    Exploiting cost-effective and highly efficient counter electrodes (CEs) has been a persistent objective for practical application of dye-sensitized solar cells (DSSCs). Here, we present an efficient CE by using pure three-dimensional (3D) nanomesh graphene frameworks (NGFs) which are synthesized via a template-directed chemical vapor deposition (CVD) approach. The high-surface-area 3D NGFs associated with the enriched surface edge defects make it very efficient towards I3- reduction even without any Pt catalyst. More interestingly, by virtue of the interpenetrating graphene frameworks, the NGFs exhibit excellent electron conductivity, thus leading to facile charge transfer. Consequently, the DSSCs with pure NGFs as CEs display a power conversion efficiency of 7.32%, which is comparable to that of Pt as CEs (7.28%), thereby exhibiting great potential as low-cost and highly efficient CE materials for large-scale deployment of DSSCs.Exploiting cost-effective and highly efficient counter electrodes (CEs) has been a persistent objective for practical application of dye-sensitized solar cells (DSSCs). Here, we present an efficient CE by using pure three-dimensional (3D) nanomesh graphene frameworks (NGFs) which are synthesized via a template-directed chemical vapor deposition (CVD) approach. The high-surface-area 3D NGFs associated with the enriched surface edge defects make it very efficient towards I3- reduction even without any Pt catalyst. More interestingly, by virtue of the interpenetrating graphene frameworks, the NGFs exhibit excellent electron conductivity, thus leading to facile charge transfer. Consequently, the DSSCs with pure NGFs as CEs display a power conversion efficiency of 7.32%, which is comparable to that of Pt as CEs (7.28%), thereby exhibiting great potential as low-cost and highly efficient CE materials for large-scale deployment of DSSCs. Electronic supplementary information (ESI) available: Additional SEM image, SAED image, cross-sectional SEM

  14. Tasting edge effects

    CERN Document Server

    Bocquet, L

    2006-01-01

    We show that the baking of potato wedges constitutes a crunchy example of edge effects, which are usually demonstrated in electrostatics. A simple model of the diffusive transport of water vapor around the potato wedges shows that the water vapor flux diverges at the sharp edges in analogy with its electrostatic counterpart. This increased evaporation at the edges leads to the crispy taste of these parts of the potatoes.

  15. Acoustic streaming of a sharp edge.

    Science.gov (United States)

    Ovchinnikov, Mikhail; Zhou, Jianbo; Yalamanchili, Satish

    2014-07-01

    Anomalous acoustic streaming is observed emanating from sharp edges of solid bodies that are vibrating in fluids. The streaming velocities can be orders of magnitude higher than expected from the Rayleigh streaming at similar amplitudes of vibration. Acoustic velocity of fluid relative to a solid body diverges at a sharp edge, giving rise to a localized time-independent body force acting on the fluid. This force results in a formation of a localized jet. Two-dimensional numerical simulations are performed to predict acoustic streaming for low amplitude vibration using two methods: (1) Steady-state solution utilizing perturbation theory and (2) direct transient solution of the Navier-Stokes equations. Both analyses agree with each other and correctly predict the streaming of a sharp-edged vibrating blade measured experimentally. The origin of the streaming can be attributed to the centrifugal force of the acoustic fluid flow around a sharp edge. The dependence of this acoustic streaming on frequency and velocity is examined using dimensional analysis. The dependence law is devised and confirmed by numerical simulations.

  16. Unreacted PbI2 as a Double-Edged Sword for Enhancing the Performance of Perovskite Solar Cells.

    Science.gov (United States)

    Jacobsson, T Jesper; Correa-Baena, Juan-Pablo; Halvani Anaraki, Elham; Philippe, Bertrand; Stranks, Samuel D; Bouduban, Marine E F; Tress, Wolfgang; Schenk, Kurt; Teuscher, Joël; Moser, Jacques-E; Rensmo, Håkan; Hagfeldt, Anders

    2016-08-17

    Lead halide perovskites have over the past few years attracted considerable interest as photo absorbers in PV applications with record efficiencies now reaching 22%. It has recently been found that not only the composition but also the precise stoichiometry is important for the device performance. Recent reports have, for example, demonstrated small amount of PbI2 in the perovskite films to be beneficial for the overall performance of both the standard perovskite, CH3NH3PbI3, as well as for the mixed perovskites (CH3NH3)x(CH(NH2)2)(1-x)PbBryI(3-y). In this work a broad range of characterization techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photo electron spectroscopy (PES), transient absorption spectroscopy (TAS), UV-vis, electroluminescence (EL), photoluminescence (PL), and confocal PL mapping have been used to further understand the importance of remnant PbI2 in perovskite solar cells. Our best devices were over 18% efficient, and had in line with previous results a small amount of excess PbI2. For the PbI2-deficient samples, the photocurrent dropped, which could be attributed to accumulation of organic species at the grain boundaries, low charge carrier mobility, and decreased electron injection into the TiO2. The PbI2-deficient compositions did, however, also have advantages. The record Voc was as high as 1.20 V and was found in PbI2-deficient samples. This was correlated with high crystal quality, longer charge carrier lifetimes, and high PL yields and was rationalized as a consequence of the dynamics of the perovskite formation. We further found the ion migration to be obstructed in the PbI2-deficient samples, which decreased the JV hysteresis and increased the photostability. PbI2-deficient synthesis conditions can thus be used to deposit perovskites with excellent crystal quality but with the downside of grain boundaries enriched in organic species, which act as a barrier toward

  17. Cutting Edge: Localization of linker for activation of T cells to lipid rafts is not essential in T cell activation and development.

    Science.gov (United States)

    Zhu, Minghua; Shen, Shudan; Liu, Yan; Granillo, Olivia; Zhang, Weiguo

    2005-01-01

    It has been proposed that upon T cell activation, linker for activation of T cells (LAT), a transmembrane adaptor protein localized to lipid rafts, orchestrates formation of multiprotein complexes and activates signaling cascades in lipid rafts. However, whether lipid rafts really exist or function remains controversial. To address the importance of lipid rafts in LAT function, we generated a fusion protein to target LAT to nonraft fractions using the transmembrane domain from a nonraft protein, linker for activation of X cells (LAX). Surprisingly, this fusion protein functioned well in TCR signaling. It restored MAPK activation, calcium flux, and NFAT activation in LAT-deficient cells. To further study the function of this fusion protein in vivo, we generated transgenic mice that express this protein. Analysis of these mice indicated that it was fully capable of replacing LAT in thymocyte development and T cell function. Our results demonstrate that LAT localization to lipid rafts is not essential during normal T cell activation and development.

  18. Filament velocity scaling in SOL plasmas

    International Nuclear Information System (INIS)

    In the edge region of magnetically confined plasmas one observes intermittent transport of plasma by filaments elongated along the magnetic field lines. These filaments carry excess plasma particles and heat and are referred to as blobs. Blobs are created behind the LCFS and move radially outwards through the SOL, contributing significantly to particle and heat loss as well as wall erosion. Recent experimental progress shows a broad range of blob velocities with regimes where the blobs accelerate and regimes where it presents a constant velocity in the range of the acoustic velocity. This work presents the blob velocity scaling for a electrostatic interchange model. Numerical simulations show the blob velocity scaling depending on sheath parallel currents. We identify regimes blob acceleration behaviour and a velocity scaling depending on the size of the structure.

  19. Polymer solar cell modules prepared using roll-to-roll methods: Knife-over-edge coating, slot-die coating and screen printing

    Energy Technology Data Exchange (ETDEWEB)

    Krebs, Frederik C. [Risoe National Laboratory for Sustainable Energy, Technical University of Denmark, Frederiksborgvej 399, DK-4000 Roskilde (Denmark)

    2009-04-15

    A complete polymer solar cell module prepared in the ambient atmosphere using all-solution processing with no vacuum steps and full roll-to-roll (R2R) processing is presented. The modules comprise five layers that were prepared on a 175-{mu}m flexible polyethyleneterephthalate (PET) substrate with an 80-nm layer of transparent conducting indium-tin oxide (ITO). The ITO layer was first patterned by screen printing an etch resist followed by etching. The second layer was applied by either knife-over-edge (KOE) coating or slot-die coating a solution of zinc oxide nanoparticles (ZnO-nps) followed by curing. The second layer comprised a mixture of the thermocleavable poly-(3-(2-methylhexan-2-yl)-oxy-carbonyldithiophene) (P3MHOCT) and ZnO-nps and was applied by a modified slot-die coating procedure, enabling slow coating speeds with low viscosity and low surface tension ink solutions. The third layer was patterned into stripes and juxtaposed with the ITO layer. The fourth layer comprised screen-printed or slot-die-coated PEDOT:PSS and the fifth and the final layer comprised a screen-printed or slot-die-coated silver electrode. The final module dimensions were 28 cm x 32 cm and presented four individual solar cell modules: a single-stripe cell, a two-stripe serially connected module, a three-stripe serially connected module and finally an eight-stripe serially connected module. The length of the individual stripes was 25 cm and the width was 0.9 cm. With overlaps of the individual layers this gave a width of the active layer of 0.6 cm and an active area for each stripe of 15 cm{sup 2}. The performance was increased ten fold compared to mass-produced modules employing screen printing for all five layers of the device. The processing speeds employed for the R2R processed layers were in the range of 40-50 m h{sup -1}. Finally a comparison is made with the state of the art represented by P3HT-PCBM as the active layer and full R2R solution processing using slot-die coating

  20. Adobe Edge Quickstart Guide

    CERN Document Server

    Labrecque, Joseph

    2012-01-01

    Adobe Edge Quickstart Guide is a practical guide on creating engaging content for the Web with Adobe's newest HTML5 tool. By taking a chapter-by-chapter look at each major aspect of Adobe Edge, the book lets you digest the available features in small, easily understandable chunks, allowing you to start using Adobe Edge for your web design needs immediately. If you are interested in creating engaging motion and interactive compositions using web standards with professional tooling, then this book is for you. Those with a background in Flash Professional wanting to get started quickly with Adobe

  1. Color image retrieval using edge and edge-spatial features

    Institute of Scientific and Technical Information of China (English)

    Chaobing Huang; Quan Liu

    2006-01-01

    @@ A novel methodology to integrate edge feature and edge-spatial feature of an image is proposed. The edge feature is described by edge histogram of image, the edge-spatial feature is described by spatial distribution of pixels of identical edge value in the image. Experimental results show that the method can achieve better retrieval performance, especially for color natural images with more complex spatial layout.

  2. Adobe Edge Preview 3

    CERN Document Server

    Grover, Chris

    2011-01-01

    Want to use an Adobe tool to design animated web graphics that work on iPhone and iPad? You've come to the right book. Adobe Edge Preview 3: The Missing Manual shows you how to build HTML5 graphics using simple visual tools. No programming experience? No problem. Adobe Edge writes the underlying code for you. With this eBook, you'll be designing great-looking web elements in no time. Get to know the workspace. Learn how Adobe Edge Preview 3 performs its magic.Create and import graphics. Make drawings with Edge's tools, or use art you designed in other programs.Work with text. Build menus, lab

  3. Memristive fuzzy edge detector

    CERN Document Server

    Merrikh-Bayat, Farnood

    2011-01-01

    Fuzzy inference systems always suffer from the lack of efficient structures or platforms for their hardware implementation. In this paper, we tried to overcome this problem by proposing new method for the implementation of those fuzzy inference systems which use fuzzy rule base to make inference. To achieve this goal, we have designed a multi-layer neuro-fuzzy computing system based on the memristor crossbar structure by introducing some new concepts like fuzzy minterms. Although many applications can be realized through the use of our proposed system, in this study we show how the fuzzy XOR function can be constructed and how it can be used to extract edges from grayscale images. Our memristive fuzzy edge detector (implemented in analog form) compared with other common edge detectors has this advantage that it can extract edges of any given image all at once in real-time.

  4. Edge states in honeycomb structures

    OpenAIRE

    Fefferman, Charles L.; Lee-Thorp, James P.; Weinstein, Michael I.

    2015-01-01

    An edge state is a time-harmonic solution of a conservative wave system, e.g. Schroedinger, Maxwell, which is propagating (plane-wave-like) parallel to, and localized transverse to, a line-defect or "edge". Topologically protected edge states are edge states which are stable against spatially localized (even strong) deformations of the edge. First studied in the context of the quantum Hall effect, protected edge states have attracted huge interest due to their role in the field of topological...

  5. The Edge supersonic transport

    Science.gov (United States)

    Agosta, Roxana; Bilbija, Dushan; Deutsch, Marc; Gallant, David; Rose, Don; Shreve, Gene; Smario, David; Suffredini, Brian

    1992-01-01

    As intercontinental business and tourism volumes continue their rapid expansion, the need to reduce travel times becomes increasingly acute. The Edge Supersonic Transport Aircraft is designed to meet this demand by the year 2015. With a maximum range of 5750 nm, a payload of 294 passengers and a cruising speed of M = 2.4, The Edge will cut current international flight durations in half, while maintaining competitive first class, business class, and economy class comfort levels. Moreover, this transport will render a minimal impact upon the environment, and will meet all Federal Aviation Administration Part 36, Stage III noise requirements. The cornerstone of The Edge's superior flight performance is its aerodynamically efficient, dual-configuration design incorporating variable-geometry wingtips. This arrangement combines the benefits of a high aspect ratio wing at takeoff and low cruising speeds with the high performance of an arrow-wing in supersonic cruise. And while the structural weight concerns relating to swinging wingtips are substantial, The Edge looks to ever-advancing material technologies to further increase its viability. Heeding well the lessons of the past, The Edge design holds economic feasibility as its primary focus. Therefore, in addition to its inherently superior aerodynamic performance, The Edge uses a lightweight, largely windowless configuration, relying on a synthetic vision system for outside viewing by both pilot and passengers. Additionally, a fly-by-light flight control system is incorporated to address aircraft supersonic cruise instability. The Edge will be produced at an estimated volume of 400 aircraft and will be offered to airlines in 2015 at $167 million per transport (1992 dollars).

  6. Extended Klein edges in graphene.

    Science.gov (United States)

    He, Kuang; Robertson, Alex W; Lee, Sungwoo; Yoon, Euijoon; Lee, Gun-Do; Warner, Jamie H

    2014-12-23

    Graphene has three experimentally confirmed periodic edge terminations, zigzag, reconstructed 5-7, and arm-chair. Theory predicts a fourth periodic edge of graphene called the extended Klein (EK) edge, which consists of a series of single C atoms protruding from a zigzag edge. Here, we confirm the existence of EK edges in both graphene nanoribbons and on the edge of bulk graphene using atomic resolution imaging by aberration-corrected transmission electron microscopy. The formation of the EK edge stems from sputtering and reconstruction of the zigzag edge. Density functional theory reveals minimal energy for EK edge reconstruction and bond distortion both in and out of plane, supporting our TEM observations. The EK edge can now be included as the fourth member of observed periodic edge structures in graphene.

  7. Edge detection depends on achromatic channel in Drosophila melanogaster.

    Science.gov (United States)

    Zhou, Yanqiong; Ji, Xiaoxiao; Gong, Haiyun; Gong, Zhefeng; Liu, Li

    2012-10-01

    Edges represent important information in object recognition, and thus edge detection is crucial for animal survival. Various types of edges result from visual contrast, such as luminance contrast and color contrast. So far, the molecular and neural mechanisms underlying edge detection and the relationship between different edge information-processing pathways have been largely undemonstrated. In the present study, using a color light-emitting-diode-based Buridan's paradigm, we demonstrated that a blue/green demarcation is able to generate edge-orientation behavior in the adult fly. There is a blue/green intensity ratio, the so-called point of equal luminance, at which wild-type flies did not show obvious orientation behavior towards edges. This suggests that orientation behavior towards edges is dependent on luminance contrast in Drosophila. The results of mutants ninaE(17) and sev(LY3);rh5(2);rh6(1) demonstrated that achromatic R1-R6 photoreceptor cells, but not chromatic R7/R8 photoreceptor cells, were necessary for orientation behavior towards edges. Moreover, ectopic expression of rhodopsin 4 (Rh4), Rh5 or Rh6 could efficiently restore the edge-orientation defect in the ninaE(17) mutant. Altogether, our results show that R1-R6 photoreceptor cells are both necessary and sufficient for orientation behavior towards edges in Drosophila. PMID:22735352

  8. A New Edge-directed Subpixel Edge Localization Method

    Institute of Scientific and Technical Information of China (English)

    于新瑞; 徐威; 王石刚; 李倩

    2004-01-01

    Localization of the inspected chip image is one of the key problems with machine vision aided surface mount devices (SMD) and other micro-electronic equipments. This paper presents a new edge-directed subpixel edge localization method. The image is divided into two regions, edge and non-edge, using edge detection to emphasize the edge feature. Since the edges of the chip image are straight, they have straight-line characteristics locally and globally. First,the line segments of the straight edge are located to subpixel precision, according to their local straight properties, in a 3 × 3 neighborhood of the edge region. Second, the subpixel midpoints of the line segments are computed. Finally, the straight edge is fitted using the midpoints and the least square method, according to its global straight property in the entire edge region. In this way, the edge is located to subpixel precision. While fitting the edge, the irregular points are eliminated by the angles of the line segments to improve the precision. We can also distinguish different edges and their intersections using the angles of the line segments and distances between the edge points, then give the vectorial result of the image edge with high precision.

  9. TNX GeoSiphon Cell (TGSC-1) Phase II Minimum Flushing Velocity Deployment/Demonstration Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Phifer, M.A.

    1999-10-25

    The TNX Area is a semi-works facility for the Savannah River Technology Center (SRTC), which is located one-quarter mile from the Savannah river at the Savannah River Site. As the result of TNX operation, groundwater contamination has occurred. The predominant contaminants detected in the flood plain downgradient from TNX are trichloroethylene (TCE) and nitrate.Treatability studies into the applicability of a groundwater remediation system combining GeoSiphon Cell and zero-valent iron technologies for treatment of the TCE-contaminated groundwater at TNX have been conducted. These treatability studies have been conducted by SRTC under the sponsorship of the Environmental Restoration Department.

  10. Study of plasma meniscus and beam halo in negative ion sources using three dimension in real space and three dimension in velocity space particle in cell model

    International Nuclear Information System (INIS)

    Our previous study by two dimension in real space and three dimension in velocity space-particle in cell model shows that the curvature of the plasma meniscus causes the beam halo in the negative ion sources. The negative ions extracted from the periphery of the meniscus are over-focused in the extractor due to the electrostatic lens effect, and consequently become the beam halo. The purpose of this study is to verify this mechanism with the full 3D model. It is shown that the above mechanism is essentially unchanged even in the 3D model, while the fraction of the beam halo is significantly reduced to 6%. This value reasonably agrees with the experimental result

  11. Study of plasma meniscus and beam halo in negative ion sources using three dimension in real space and three dimension in velocity space particle in cell model

    Energy Technology Data Exchange (ETDEWEB)

    Nishioka, S., E-mail: nishioka@ppl.appi.keio.ac.jp; Goto, I.; Hatayama, A. [Graduate School of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522 (Japan); Miyamoto, K. [School of Natural and Living Sciences Education, Naruto University of Education, 748 Nakashima, Takashima, Naruto-cho, Naruto-shi, Tokushima 772-8502 (Japan); Okuda, S.; Fukano, A. [Toshiba, 33 Isogo-chou, Isogo-ku, Yokohama-shi, Kanagawa 235-001 (Japan)

    2014-02-15

    Our previous study by two dimension in real space and three dimension in velocity space-particle in cell model shows that the curvature of the plasma meniscus causes the beam halo in the negative ion sources. The negative ions extracted from the periphery of the meniscus are over-focused in the extractor due to the electrostatic lens effect, and consequently become the beam halo. The purpose of this study is to verify this mechanism with the full 3D model. It is shown that the above mechanism is essentially unchanged even in the 3D model, while the fraction of the beam halo is significantly reduced to 6%. This value reasonably agrees with the experimental result.

  12. Metal supported tubular solid oxide fuel cells fabricated by suspension plasma spray and suspension high velocity oxy-fuel spray

    Science.gov (United States)

    Yoo, Yeong; Wang, Youliang; Deng, Xiaohua; Singh, Devinder; Legoux, Jean-Gabriel

    2012-10-01

    Low temperature (LT) metal supported solid oxide fuel cells (SOFCs) have many advantages in comparison to conventional electrode or electrolyte supported type SOFCs. NRC has demonstrated high performance LT metal supported planar SOFCs fabricated by either wet colloidal spray/sintering or suspension thermal spray. The combination of tubular configuration and metal supported SOFCs may produce more unique and very attractive advantages such as easy and inexpensive sealing method and materials, high specific and volumetric power density, cost-effective fabrication, enhanced robustness, rapid start up, red-ox cycle tolerance and potential use for a pressurized integrated system. In this paper, thin film solid electrolyte of Sm0.2Ce0.8O1.90 (SDC) and NiO-SDC composite anode on sintered porous tubular metal supports were deposited by suspension HVOF spray and suspension plasma spray, respectively on sintered porous tubular metal support. La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) cathode on the SDC electrolyte was formed by wet colloidal spray and subsequent sintering process as the final fabrication step. The detailed investigation of suspension and process-related parameters for suspension thermal spray was performed in order to produce thin and crack-free SDC thin film coatings. The electrochemical performance of single cells was demonstrated.

  13. On finite edge-primitive and edge-quasiprimitive graphs

    OpenAIRE

    Giudici, Michael; Li, Cai Heng

    2009-01-01

    Many famous graphs are edge-primitive, for example, the Heawood graph, the Tutte--Coxeter graph and the Higman--Sims graph. In this paper we systematically analyse edge-primitive and edge-quasiprimitive graphs via the O'Nan--Scott Theorem to determine the possible edge and vertex actions of such graphs. Many interesting examples are given and we also determine all $G$-edge-primitive graphs for $G$ an almost simple group with socle $PSL(2,q)$.

  14. Polymer solar cell modules prepared using roll-to-roll methods: Knife-over-edge coating, slot-die coating and screen printing

    DEFF Research Database (Denmark)

    Krebs, Frederik C

    2009-01-01

    -nm layer of transparent conducting indium–tin oxide (ITO). The ITO layer was first patterned by screen printing an etch resist followed by etching. The second layer was applied by either knife-over-edge (KOE) coating or slot-die coating a solution of zinc oxide nanoparticles (ZnO-nps) followed...

  15. Cell-cell interactions impacts on the rate of swarm expansion and the edge shape of a colony swarming Pseudomonas aeruginosa

    Science.gov (United States)

    Amiri, Aboutaleb; Tierra, Giordano; Xu, Zhiliang; Shrout, Joshua; Alber, Mark

    Collective motion has been observed by several bacterial species including the pathogenic bacterium P. aeruginosa. A flagellum at the pole is known to generate a self-propulsion motion. However, the role of type IV pili (TFP), distributed on the cell membrane, during swarming needs to be investigated in more details. In this work we introduce a model that combines the hydrodynamic and biophysical interactions in order to study the impact of the TFP interactions on swarming behavior of the colony. The model describes the motion and interactions of rod-shaped self propelled bacteria inside a thin liquid film. It also includes the equations describing the production and diffusion of surfactant rhamnolipids that is responsible for extraction of water from substrate, and Marangoni driven expansion of the thin liquid film by altering the surface tension. We show that TFP interactions are responsible for slower expansion rate of colonies of TFP deficient mutants compared to wild type. Experimental observations were used to calibrate the model and verify the model assumptions and predictions.

  16. Velocity anticipation in the optimal velocity model

    Institute of Scientific and Technical Information of China (English)

    DONG Li-yun; WENG Xu-dan; LI Qing-ding

    2009-01-01

    In this paper,the velocity anticipation in the optimal velocity model (OVM) is investigated.The driver adjusts the velocity of his vehicle by the desired headway,which depends on both instantaneous headway and relative velocity.The effect of relative velocity is measured by a sensitivity function.A specific form of the sensitivity function is supposed and the involved parameters are determined by the both numerical simulation and empirical data.It is shown that inclusion of velocity anticipation enhances the stability of traffic flow.Numerical simulations show a good agreement with empirical data.This model provides a better description of real traffic,including the acceleration process from standing states and the deceleration process approaching a stopped car.

  17. High Speed Edge Detection

    Science.gov (United States)

    Prokop, Norman F (Inventor)

    2016-01-01

    Analog circuits for detecting edges in pixel arrays are disclosed. A comparator may be configured to receive an all pass signal and a low pass signal for a pixel intensity in an array of pixels. A latch may be configured to receive a counter signal and a latching signal from the comparator. The comparator may be configured to send the latching signal to the latch when the all pass signal is below the low pass signal minus an offset. The latch may be configured to hold a last negative edge location when the latching signal is received from the comparator.

  18. Regulation of Localized Rac Activation in Leading Edge of Directed Migrating Cells%定向迁移细胞前沿Rac局部化激活的分子调控

    Institute of Scientific and Technical Information of China (English)

    李友军; 罗孝勇; 郭向荣

    2013-01-01

    Rac activation is strongly regulated spacially and temporally in migrating cells, leading to the formation of specific cell protrusion-lamellipodia in leading edge of the cells and generating the pushing force to put the cells forward, but the molecular mechanism of positive regulation of localized Rac activation remains unclear. We propose that the phosphorylation of the intracellular α4 integrin inhibits the interaction of α4 with paxillin, thus the signaling pathway paxillin-GITl -PIX-PAK would be formed, leading to localized Rac activation in leading edge of the migrating cells. In the paper, western blotting clearly showed that the interactions accurately exist between the cytoskeleton proteins GIT1 and paxillin or PIX respectively. Fluorescent colocalization confirmed that the interactions between GIT1 and paxillin or PIX occur in the leading edge of the cells. Rac activation assay elucidated that Rac is in activated state (GTP-bound) under the stimulation of ECM fibronectin, suggesting that the signaling pathway paxillin-GITl -PIX-PAK led to Rac activation. The results built the experimental basis for the study of regulation mechanism on localized Rac activation in leading edge of directed migrating cells.%提出构想:当α4胞内区域磷酸化而抑制其与paxillin结合时,paxillin、GIT1与PIX、PAK形成信号分子复合物.由于PIX为Rac的转换分子,PAK为Rac的效应分子,构成了paxillin-GIT1-PIX-PAK信号转导通路,从而促使Rac在细胞前沿持续地局部化激活,导致片状足的形成,产生细胞向前扩展推动力.研究结果表明,GIT1与paxillin、PIX在活细胞中均存在强烈的相互作用,且这种相互作用可发生在细胞前沿.由于Rac的转换因子PIX(PAK-interacting exchange factor)在活细胞中往往与PAK相伴而行,因而,在细胞前沿,必定存在paxillin-GIT1-PIX-PAK的信号转导通路.在纤粘蛋白(fibronectin)刺激下,整合素α4诱导Rac蛋白处于激活状态(GTP-bound).

  19. Coupled flap and edge wise blade motion due to a quadratic wind force definition

    NARCIS (Netherlands)

    Van der Male, P.; Van Dalen, K.N.

    2014-01-01

    The wind force on turbine blades, consisting of a drag and lift component, depends nonlinearly on the relative wind velocity. This relative velocity comprises mean wind speed, wind speed fluctuations and the structural response velocity. The nonlinear wind excitation couples the flap wise and edge w

  20. Quasi-chemostat behavior in the leading edge of B. subtilis biofilms

    Science.gov (United States)

    Srinivasan, Siddarth; Mahadevan, Lakshminarayanan; Rubinstein, Shmuel

    2015-11-01

    Bacillus subtilis is a gram positive bacterium that is a model system commonly used to study biofilm formation. By performing wide-field time-lapse microscopy on a fluorescently labeled B. subtilis strain, we observe a well defined steady boundary layer at the edge of a biofilm growing on an nutrient infused agar gel substrate, within which the outward radial expansion growth predominantly occurs. Using distinct fluorescent protein markers as proxies of gene expression, we quantitatively measure how the width, velocity and ratio of motile cell to matrix cell phenotypes within this boundary layer responds to changes in environmental conditions (such as substrate agar percentage & temperature). We further propose that the steady state at the leading edge can be interpreted as a quasi-chemostat which may enable well controlled response experiments on a colony scale. Finally, we show that for low agar concentration (0.5 wt%), the cells exhibit swarming behavior, whose dynamics and swimming velocities are characterized using differential dynamic microscopy. We show the swarming state is associated with an unstable front which gives rise to fingering and branching growth patterns, illustrating the varied morphological response of the biofilm to environmental conditions

  1. Canny Edge Detection using Verilog

    OpenAIRE

    D Narayana Reddy*; , Mohan A R2; , Subhramanya Bhat3

    2014-01-01

    Edge detection is one of the key stages in image processing and objects identification. The Canny Edge Detector is one of the most widely used edge detection algorithm due to its good performance. Edge detection carries preprocessing step for many image processing algorithms such as image enhancement, image segmentation, tracking and image/video coding. Canny’s edge detection algorithm that results in significantly reduced memory requirements decreased latency and increased th...

  2. Pore Velocity Estimation Uncertainties

    Science.gov (United States)

    Devary, J. L.; Doctor, P. G.

    1982-08-01

    Geostatistical data analysis techniques were used to stochastically model the spatial variability of groundwater pore velocity in a potential waste repository site. Kriging algorithms were applied to Hanford Reservation data to estimate hydraulic conductivities, hydraulic head gradients, and pore velocities. A first-order Taylor series expansion for pore velocity was used to statistically combine hydraulic conductivity, hydraulic head gradient, and effective porosity surfaces and uncertainties to characterize the pore velocity uncertainty. Use of these techniques permits the estimation of pore velocity uncertainties when pore velocity measurements do not exist. Large pore velocity estimation uncertainties were found to be located in the region where the hydraulic head gradient relative uncertainty was maximal.

  3. Analysis of the propeller wake by pressure and velocity correlation

    OpenAIRE

    Felli, Mario; Di Felice, Fabio; Guj, Giulio; Camussi, Roberto

    2004-01-01

    In the present study an experimental analysis of the velocity and pressure fields behind a marine propeller, in non cavitating regime is reported. Velocity measurements were performed in phase with the propeller angle by using 2D Particle Image Velocimetry (2D-PIV). Measurements were carried out arranging the light sheet along the mid longitudinal plane of the propeller, to investigate the evolution of the axial and the radial velocity components, from the blade trailing edge up to 2 diameter...

  4. NUMERICAL AND EXPERIMENTAL INVESTIGATION OF BEVELED TRAILING EDGE FLOW FIELDS

    Institute of Scientific and Technical Information of China (English)

    MOSALLEM M. M.

    2008-01-01

    The characteristics of flow past beveled trailing edges attached to flat plates have been investigated numerically and experimentally. The test models used in the present study were two 2D blunt-faced flat plates having asymmetric beveled trailing edges of angles 27° and 60°. The numerical simulation results display an asymmetric wake behind the 27° beveled trailing edge and von karmen street vortices behind the 60° beveled trailing edge. The flow visualization using cavitation technique showed the same observations of the numerical simulation. Therefore, it is obvious that the trailing edge geometry has a pronounced effect on the wake development and vortex shedding. Also, it is concluded that the cavitation phenomenon can be used as a visualization technique at high flow velocities.

  5. Zigzag graphene nanoribbon edge reconstruction with Stone-Wales defects

    DEFF Research Database (Denmark)

    Rodrigues, J. N. B.; Gonçalves, P. A. D; Rodrigues, N. F. G.;

    2011-01-01

    In this paper, we study zigzag graphene nanoribbons with edges reconstructed with Stone-Wales defects, by means of an empirical (first-neighbor) tight-binding method, with parameters determined by ab initio calculations of very narrow ribbons. We explore the characteristics of the electronic band...... structure with a focus on the nature of edge states. Edge reconstruction allows the appearance of a new type of edge states. They are dispersive, with nonzero amplitudes in both sublattices; furthermore, the amplitudes have two components that decrease with different decay lengths with the distance from...... the edge; at the Dirac points one of these lengths diverges, whereas the other remains finite, of the order of the lattice parameter. We trace this curious effect to the doubling of the unit cell along the edge, brought about by the edge reconstruction. In the presence of a magnetic field, the zero...

  6. Dictionary based Approach to Edge Detection

    CERN Document Server

    Chandra, Nitish

    2015-01-01

    Edge detection is a very essential part of image processing, as quality and accuracy of detection determines the success of further processing. We have developed a new self learning technique for edge detection using dictionary comprised of eigenfilters constructed using features of the input image. The dictionary based method eliminates the need of pre or post processing of the image and accounts for noise, blurriness, class of image and variation of illumination during the detection process itself. Since, this method depends on the characteristics of the image, the new technique can detect edges more accurately and capture greater detail than existing algorithms such as Sobel, Prewitt Laplacian of Gaussian, Canny method etc which use generic filters and operators. We have demonstrated its application on various classes of images such as text, face, barcodes, traffic and cell images. An application of this technique to cell counting in a microscopic image is also presented.

  7. Superpixel edges for boundary detection

    Energy Technology Data Exchange (ETDEWEB)

    Moya, Mary M.; Koch, Mark W.

    2016-07-12

    Various embodiments presented herein relate to identifying one or more edges in a synthetic aperture radar (SAR) image comprising a plurality of superpixels. Superpixels sharing an edge (or boundary) can be identified and one or more properties of the shared superpixels can be compared to determine whether the superpixels form the same or two different features. Where the superpixels form the same feature the edge is identified as an internal edge. Where the superpixels form two different features, the edge is identified as an external edge. Based upon classification of the superpixels, the external edge can be further determined to form part of a roof, wall, etc. The superpixels can be formed from a speckle-reduced SAR image product formed from a registered stack of SAR images, which is further segmented into a plurality of superpixels. The edge identification process is applied to the SAR image comprising the superpixels and edges.

  8. Knife-edge technique for laser cooling

    Institute of Scientific and Technical Information of China (English)

    WANG Zhanshan; MA Shanshan; MA Yan; ZHAO Min; LIU Hengbiao

    2007-01-01

    The transfer characteristics of an atomic beam and the effect of laser were investigated in this paper. In the application of knife-edge technique, the temperature of atoms through laser cooling was measured. Results indicate that,after atoms are emitted from an atomic oven, the longer the atoms move, the worse the distribution of the atomic beam shows, regardless the laser cooling is taken or not. Laser cooling can reduce the transverse velocity of the atomic beam to several orders of magnitude and also increase the uniformity of an atomic beam. Knife-edge technique can measure the temperature of an atomic beam through laser cooling. The measurement accuracy depends on the pixel size of the charge coupled device (CCD), which is used for the fluorescent imaging of the atomic beam. The results are very important for the future experiments of laser cooling.

  9. Graphene edges; localized edge state and electron wave interference

    Directory of Open Access Journals (Sweden)

    Enoki Toshiaki

    2012-03-01

    Full Text Available The electronic structure of massless Dirac fermion in the graphene hexagonal bipartite is seriously modified by the presence of edges depending on the edge chirality. In the zigzag edge, strongly spin polarized nonbonding edge state is created as a consequence of broken symmetry of pseudo-spin. In the scattering at armchair edges, the K-K’ intervalley transition gives rise to electron wave interference. The presence of edge state in zigzag edges is observed in ultra-high vacuum STM/STS observations. The electron wave interference phenomenon in the armchair edge is observed in the Raman G-band and the honeycomb superlattice pattern with its fine structure in STM images.

  10. Partnership for Edge Physics Simulation (EPSI)

    Energy Technology Data Exchange (ETDEWEB)

    Schroder, Peter [California Inst. of Technology, Pasadena, CA (United States)

    2015-02-11

    We propose to develop advanced simulation codes, based upon an extreme parallelism, first principles kinetic approach, to address the challenges associated with the edge region of magnetically confined plasmas. This work is relevant to both existing magnetic fusion facilities and essential for next-generation burning plasma experiments, such as ITER where success is critically dependent upon H-mode operation achieving an edge pedestal of sufficient height for good core plasma performance without producing deleterious large scale edge localized instabilities. The plasma edge presents a well-known set of multi-physics, multi-scale problems involving complex 3D magnetic geometry. Perhaps the greatest computational challenge is the lack of scale separation – temporal scales for drift waves, Alfven waves, ELM dynamics for example have strong overlap. Similar overlap occurs on the spatial scales for the ion poloidal gyro-radius, drift wave and pedestal width. The traditional approach of separating fusion problems into weakly interacting spatial or temporal domains clearly breaks down in the edge. A full kinetic model (full-f model) must be solved to understand and predict the edge physics including non-equilibrium thermodynamic issues arising from the magnetic topology (the open field lines producing a spatially sensitive velocity hole), plasma wall interactions, neutral and atomic physics. The plan here is to model these phenomena within a comprehensive first principles set of equations without the need for the insurmountable multiple-codes coupling issues by building on the XGC1 code developed under the SciDAC Proto-FSP Center for Plasma Edge Simulation (CPES). This proposal includes the critical participants in the XGC1 development. We propose enhancing the capability of XGC1 by including all the important turbulence physics contained in kinetic ion and electron electromagnetic dynamics, by extending the PIC technology to incorporate several positive features found

  11. Edge turbulence in tokamaks

    Science.gov (United States)

    Nedospasov, A. V.

    1992-12-01

    Edge turbulence is of decisive importance for the distribution of particle and energy fluxes to the walls of tokamaks. Despite the availability of extensive experimental data on the turbulence properties, its nature still remains a subject for discussion. This paper contains a review of the most recent theoretical and experimental studies in the field, including mainly the studies to which Wootton (A.J. Wooton, J. Nucl. Mater. 176 & 177 (1990) 77) referred to most in his review at PSI-9 and those published later. The available theoretical models of edge turbulence with volume dissipation due to collisions fail to fully interpret the entire combination of experimental facts. In the scrape-off layer of a tokamak the dissipation prevails due to the flow of current through potential shifts near the surface of limiters of divertor plates. The different origins of turbulence at the edge and in the core plasma due to such dissipation are discussed in this paper. Recent data on the electron temperature fluctuations enabled one to evaluate the electric probe measurements of turbulent flows of particles and heat critically. The latest data on the suppression of turbulence in the case of L-H transitions are given. In doing so, the possibility of exciting current instabilities in biasing experiments (rather than only to the suppression of existing turbulence) is given some attention. Possible objectives of further studies are also discussed.

  12. PROTOSTELLAR JETS ENCLOSED BY LOW-VELOCITY OUTFLOWS

    International Nuclear Information System (INIS)

    A protostellar jet and outflow are calculated for ∼270 yr following the protostar formation using a three-dimensional magnetohydrodynamics simulation, in which both the protostar and its parent cloud are spatially resolved. A high-velocity (∼100 km s–1) jet with good collimation is driven near the disk's inner edge, while a low-velocity (≲ 10 km s–1) outflow with a wide opening angle appears in the outer-disk region. The high-velocity jet propagates into the low-velocity outflow, forming a nested velocity structure in which a narrow high-velocity flow is enclosed by a wide low-velocity flow. The low-velocity outflow is in a nearly steady state, while the high-velocity jet appears intermittently. The time-variability of the jet is related to the episodic accretion from the disk onto the protostar, which is caused by gravitational instability and magnetic effects such as magnetic braking and magnetorotational instability. Although the high-velocity jet has a large kinetic energy, the mass and momentum of the jet are much smaller than those of the low-velocity outflow. A large fraction of the infalling gas is ejected by the low-velocity outflow. Thus, the low-velocity outflow actually has a more significant effect than the high-velocity jet in the very early phase of the star formation

  13. The conjectured S-type retrograde planet in nu Octantis: more evidence including four years of iodine-cell radial velocities

    CERN Document Server

    Ramm, D J; Endl, M; Hearnshaw, J B; Wittenmyer, R A; Gunn, F; Bergmann, C; Kilmartin, P; Brogt, E

    2016-01-01

    We report 1212 radial-velocity (RV) measurements obtained in the years 2009-2013 using an iodine cell for the spectroscopic binary nu Octantis (K1III/IV). This system (a_bin~2.6 au, P~1050 days) is conjectured to have a Jovian planet with a semi-major axis half that of the binary host. The extreme geometry only permits long-term stability if the planet is in a retrograde orbit. Whilst the reality of the planet (P~415 days) remains uncertain, other scenarios (stellar variability or apsidal motion caused by a yet unobserved third star) continue to appear substantially less credible based on CCF bisectors, line-depth ratios and many other independent details. If this evidence is validated but the planet is disproved, the claims of other planets using RVs will be seriously challenged. We also describe a significant revision to the previously published RVs and the full set of 1437 RVs now encompasses nearly 13 years. The sensitive orbital dynamics allow us to constrain the three-dimensional architecture with a bro...

  14. Cutting edge: CXCR4 is critical for CD8+ memory T cell homeostatic self-renewal but not rechallenge self-renewal.

    Science.gov (United States)

    Chaix, Julie; Nish, Simone A; Lin, Wen-Hsuan W; Rothman, Nyanza J; Ding, Lei; Wherry, E John; Reiner, Steven L

    2014-08-01

    Central memory (CM) CD8(+) T cells "remember" prior encounters because they maintain themselves through cell division in the absence of ongoing challenge (homeostatic self-renewal), as well as reproduce the CM fate while manufacturing effector cells during secondary Ag encounters (rechallenge self-renewal). We tested the consequence of conditional deletion of the bone marrow homing receptor CXCR4 on antiviral T cell responses. CXCR4-deficient CD8(+) T cells have impaired memory cell maintenance due to defective homeostatic proliferation. Upon rechallenge, however, CXCR4-deficient T cells can re-expand and renew the CM pool while producing secondary effector cells. The critical bone marrow-derived signals essential for CD8(+) T cell homeostatic self-renewal appear to be dispensable to yield self-renewing, functionally asymmetric cell fates during rechallenge.

  15. Theory of edge plasma in a spheromak

    Energy Technology Data Exchange (ETDEWEB)

    Hooper, E.B., LLNL

    1998-05-01

    Properties of the edge plasma in the SSPX spheromak during the plasma formation and sustainment phases are discussed. For the breakdown and formation phase, the main emphasis is on the analysis of possible plasma contamination by impurities from the electrodes of the plasma gun (helicity injector). The issue of an azimuthally uniform breakdown initiation is also discussed. After the plasma settles down in the main vacuum chamber, one has to sustain the current between the electrodes, in order to continuously inject helicity. We discuss properties of the plasma on the field lines intersecting the electrodes. We conclude that the thermal balance of this plasma is maintained by Joule heating competing with parallel heat losses to the electrodes. The resulting plasma temperature is in the range of 15 - 30 eV. Under the expected operational conditions, the ``current`` velocity of the electrons is only slightly below their thermal velocity. Implications of this observation are briefly discussed.

  16. Towards a novel design method for impact on leading edges

    NARCIS (Netherlands)

    Houten, van M.H.; Kaplan, H.

    2006-01-01

    Results of a parametric study concerning low velocity impact on leading edge profiles is presented. This work is the first part of a larger program on the development of an engineering design method for impact on Glare. In this first part, experimental tests and numerical simulations on two-dimensio

  17. Simulated dry deposition of nitric acid near forest edges

    NARCIS (Netherlands)

    DeJong, JJM; Klaassen, W; Jong, J.J.M. de

    1997-01-01

    Dry deposition is simulated to understand and generalize observations of enhanced deposition of air pollution near forest edges. Nitric acid is taken as an example as its deposition velocity is often assumed to be determined by turbulent transport only. The simulations are based on the micro-meteoro

  18. Estimation of vector velocity

    DEFF Research Database (Denmark)

    2000-01-01

    Using a pulsed ultrasound field, the two-dimensional velocity vector can be determined with the invention. The method uses a transversally modulated ultrasound field for probing the moving medium under investigation. A modified autocorrelation approach is used in the velocity estimation. The new...... estimator automatically compensates for the axial velocity, when determining the transverse velocity by using fourth order moments rather than second order moments. The estimation is optimized by using a lag different from one in the estimation process, and noise artifacts are reduced by using averaging...... of RF samples. Further, compensation for the axial velocity can be introduced, and the velocity estimation is done at a fixed depth in tissue to reduce spatial velocity dispersion....

  19. Efficient edge domination in regular graphs

    OpenAIRE

    Cardoso, Domingos M.; Cerdeira, J. Orestes; Delorme, Charles; Silva, Pedro C

    2008-01-01

    An induced matching of a graph G is a matching having no two edges joined by an edge. An efficient edge dominating set of G is an induced matching M such that every other edge of G is adjacent to some edge in M. We relate maximum induced matchings and efficient edge dominating sets, showing that efficient edge dominating sets are maximum induced matchings, and that maximum induced matchings on regular graphs with efficient edge dominating sets are efficient edge dominating sets. A ...

  20. Radioisotope measurement of the velocity of tracheal mucus

    International Nuclear Information System (INIS)

    A radioisotope scanning technique for measuring the velocity of tracheal mucus has been developed utilizing a canine model. A solution of stannous phytate labeled with /sup 99m/Tc is introduced percutaneously into the lower trachea and the upward movement of the leading edge of the radioactivity is followed by repeat scanning at 2-minute intervals using a modified rectilinear scanner, thus allowing calculation of the velocity of the mucus. It is believed that this technique may be of value in studying the effect of experimentally induced tracheal injuries on mucus velocity. Possible applications of the technique for the study of the velocity of mucus in the human trachea are discussed

  1. Radioisotope measurement of the velocity of tracheal mucus.

    Science.gov (United States)

    Russo, K J; Palmer, D W; Beste, D J; Carl, G A; Belson, T P; Pelc, L R; Toohill, R J

    1985-04-01

    A radioisotope scanning technique for measuring the velocity of tracheal mucus has been developed utilizing a canine model. A solution of stannous phytate labeled with 99mTc is introduced percutaneously into the lower trachea and the upward movement of the leading edge of the radioactivity is followed by repeat scanning at 2-minute intervals using a modified rectilinear scanner, thus allowing calculation of the velocity of the mucus. It is believed that this technique may be of value in studying the effect of experimentally induced tracheal injuries on mucus velocity. Possible applications of the technique for the study of the velocity of mucus in the human trachea are discussed. PMID:3921912

  2. Radioisotope measurement of the velocity of tracheal mucus

    Energy Technology Data Exchange (ETDEWEB)

    Russo, K.J.; Palmer, D.W.; Beste, D.J.; Carl, G.A.; Belson, T.P.; Pelc, L.R.; Toohill, R.J.

    1985-04-01

    A radioisotope scanning technique for measuring the velocity of tracheal mucus has been developed utilizing a canine model. A solution of stannous phytate labeled with /sup 99m/Tc is introduced percutaneously into the lower trachea and the upward movement of the leading edge of the radioactivity is followed by repeat scanning at 2-minute intervals using a modified rectilinear scanner, thus allowing calculation of the velocity of the mucus. It is believed that this technique may be of value in studying the effect of experimentally induced tracheal injuries on mucus velocity. Possible applications of the technique for the study of the velocity of mucus in the human trachea are discussed.

  3. Electrochemistry of folded graphene edges.

    Science.gov (United States)

    Ambrosi, Adriano; Bonanni, Alessandra; Pumera, Martin

    2011-05-01

    There is enormous interest in the investigation of electron transfer rates at the edges of graphene due to possible energy storage and sensing applications. While electrochemistry at the edges and the basal plane of graphene has been studied in the past, the new frontier is the electrochemistry of folded graphene edges. Here we describe the electrochemistry of folded graphene edges and compare it to that of open graphene edges. The materials were characterized in detail by high-resolution transmission electron microscopy, Raman spectroscopy, high-resolution X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy and cyclic voltammetry. We found that the heterogeneous electron transfer rate is significantly lower on folded graphene edges compared to open edge sites for ferro/ferricyanide, and that electrochemical properties of open edges offer lower potential detection of biomarkers than the folded ones. It is apparent, therefore, that for sensing and biosensing applications the folded edges are less active than open edges, which should then be preferred for such applications. As folded edges are the product of thermal treatment of multilayer graphene, such thermal procedures should be avoided when fabricating graphene for electrochemical applications.

  4. EDGE COVERING COLORING AND FRACTIONAL EDGE COVERING COLORING

    Institute of Scientific and Technical Information of China (English)

    MIAO Lianying; LIU Guizhen

    2002-01-01

    Let G be a graph with edge set E(G). S _C E(G) is called an edge cover of G if every vertex of G is an end vertex of some edges in S. The edge covering chromatic number of a graph G, denoted by X'c(G) , is the maximum size of a partition of E(G) into edge covers of G. It is known that for any graph G with minimum degree δ, δ - 1 ≤ X'c(G) ≤ δ.The fractional edge covering chromatic number of a graph G, denoted by X'cf(G), is the fractional matching number of the edge covering hypergraph H of G whose vertices are the edges of G and whose hyperedges the edge covers of G. In this paper, we study the relation between X'c(G) and δ for any graph G, and give a new simple proof of the inequalities δ - 1 ≤ X'c(G) ≤ δ by the technique of graph coloring. For any graph G, we give an exact formula of X'cf(G), that is, X'cf(G)=min{δ,λ(G)}, where λ(G)=min |C[S]|/[|S|/2]and the minimum is taken over all noempty subsets S of V(G) and C[S] is the set of edges that have at least one end in S.

  5. EDGE COVERING COLORING AND FRACTIONAL EDGE COVERING COLORING

    Institute of Scientific and Technical Information of China (English)

    MIAOLianying; LIUGuizhen

    2002-01-01

    Let G be a graph with edge set E(G).S E(G)is called an edge cover of G if every vertex of G is an end vertex of some edges in S.The edge covering chromatic number of a graph G,denoted by Xc(G),is the maximum size of a partition of E(G) into edge covers of G.It is known that for any graph G with minimum degree δ,δ-1≤Xc(G)≤δ.The fractional edge covering chromatic number of a graph G,denoted by Xcf(G),is the fractional matiching number of the edge covering hypergraph H of G whose vertices are the edges of G and whose hypereges the edge covers of G.In this paper,we study the relation between Xc(G) and δfor any graph G,and give a new simple proof of the inequalities δ-1≤Xc(G)≤δ by the technique of graph coloring.For any graph G,we give an exact formula o Xcf(G),that is,Xcf(G)=min{δ,λ(G)},where λ(G)=minCS/S/2 and the minimum is taken over all noempty subsets S of V(G) and C[S] is the set of edges that have at least one end in S.δ

  6. The conjectured S-type retrograde planet in ν Octantis: more evidence including four years of iodine-cell radial velocities

    Science.gov (United States)

    Ramm, D. J.; Nelson, B. E.; Endl, M.; Hearnshaw, J. B.; Wittenmyer, R. A.; Gunn, F.; Bergmann, C.; Kilmartin, P.; Brogt, E.

    2016-08-01

    We report 1212 radial-velocity (RV) measurements obtained in the years 2009-2013 using an iodine cell for the spectroscopic binary ν Octantis (K1 III/IV). This system (a_{bin} ˜ 2.6 au, P ˜ 1050 d) is conjectured to have a Jovian planet with a semimajor axis half that of the binary host. The extreme geometry only permits long-term stability if the planet is in a retrograde orbit. Whilst the reality of the planet (P ˜ 415 d) remains uncertain, other scenarios (stellar variability or apsidal motion caused by a yet unobserved third star) continue to appear substantially less credible based on cross-correlation function bisectors, line-depth ratios and many other independent details. If this evidence is validated but the planet is disproved, the claims of other planets using RVs will be seriously challenged. We also describe a significant revision to the previously published RVs and the full set of 1437 RVs now encompasses nearly 13 yr. The sensitive orbital dynamics allow us to constrain the 3D architecture with a broad prior probability distribution on the mutual inclination, which with posterior samples obtained from an N-body Markov chain Monte Carlo is found to be 152.5°±^{0.7}_{0.6}. None of these samples are dynamically stable beyond 106 yr. However, a grid search around the best-fitting solution finds a region that has many models stable for 107 yr, and includes one model within 1σ that is stable for at least 108 yr. The planet's exceptional nature demands robust independent verification and makes the theoretical understanding of its formation a worthy challenge.

  7. The conjectured S-type retrograde planet in ν Octantis: more evidence including four years of iodine-cell radial velocities

    Science.gov (United States)

    Ramm, D. J.; Nelson, B. E.; Endl, M.; Hearnshaw, J. B.; Wittenmyer, R. A.; Gunn, F.; Bergmann, C.; Kilmartin, P.; Brogt, E.

    2016-08-01

    We report 1212 radial-velocity (RV) measurements obtained in the years 2009-2013 using an iodine cell for the spectroscopic binary nu Octantis (K1III/IV). This system (a_bin~2.6 au, P~1050 days) is conjectured to have a Jovian planet with a semi-major axis half that of the binary host. The extreme geometry only permits long-term stability if the planet is in a retrograde orbit. Whilst the reality of the planet (P~415 days) remains uncertain, other scenarios (stellar variability or apsidal motion caused by a yet unobserved third star) continue to appear substantially less credible based on CCF bisectors, line-depth ratios and many other independent details. If this evidence is validated but the planet is disproved, the claims of other planets using RVs will be seriously challenged. We also describe a significant revision to the previously published RVs and the full set of 1437 RVs now encompasses nearly 13 years. The sensitive orbital dynamics allow us to constrain the three-dimensional architecture with a broad prior probability distribution on the mutual inclination, which with posterior samples obtained from an N-body Markov chain Monte Carlo is found to be 158.4 +/- 1.2 deg. None of these samples are dynamically stable beyond 1 Myr. However, a grid search around the best-fitting solution finds a region that has many models stable for 10 Myr, and includes one model within 1-sigma that is stable for at least 100 Myr. The planet's exceptional nature demands robust independent verification and makes the theoretical understanding of its formation a worthy challenge.

  8. The influence of sensor placement on in-situ ultrasound wave velocity measurement.

    OpenAIRE

    Arriaga Martitegui, Francisco; Fernandez Llana, Daniel; Martinez Lopez, Roberto; Esteban Herrero, Miguel; Iñiguez Gonzalez, Guillermo

    2015-01-01

    Ultrasound wave velocity was measured in 30 pieces of Spanish Scots pine (Pinus sylvestris L.), 90 x 140 mm in cross-section and 4 m long. Five different sensor placement arrangements were used: end to end (V0), face to opposite face, edge to opposite edge, face to same face and edge to same edge. The pieces were successively shortened to 3, 2 and 1 m, in order to obtain these velocities and their ratios to reference value V0 for different lengths and angles with respect to the piece axis for...

  9. Angular velocity discrimination

    Science.gov (United States)

    Kaiser, Mary K.

    1990-01-01

    Three experiments designed to investigate the ability of naive observers to discriminate rotational velocities of two simultaneously viewed objects are described. Rotations are constrained to occur about the x and y axes, resulting in linear two-dimensional image trajectories. The results indicate that observers can discriminate angular velocities with a competence near that for linear velocities. However, perceived angular rate is influenced by structural aspects of the stimuli.

  10. Mechanisms of cell propulsion by active stresses

    Energy Technology Data Exchange (ETDEWEB)

    Carlsson, A E, E-mail: aec@wustl.edu [Department of Physics, Washington University, Campus Box 1105, One Brookings Drive, St. Louis, MO 63130 (United States)

    2011-07-15

    The mechanisms by which cytoskeletal flows and cell-substrate interactions interact to generate cell motion are explored by using a simplified model of the cytoskeleton as a viscous gel containing active stresses. This model yields explicit general results relating cell speed and traction forces to the distributions of active stress and cell-substrate friction. It is found that (i) the cell velocity is given by a function that quantifies the asymmetry of the active-stress distribution, (ii) gradients in cell-substrate friction can induce motion even when the active stresses are symmetrically distributed, (iii) the traction-force dipole is enhanced by protrusive stresses near the cell edges or contractile stresses near the center of the cell and (iv) the cell velocity depends biphasically on the cell-substrate adhesion strength if active stress is enhanced by adhesion. Specific experimental tests of the calculated dependences are proposed.

  11. Edge remap for solids

    Energy Technology Data Exchange (ETDEWEB)

    Kamm, James R.; Love, Edward; Robinson, Allen C; Young, Joseph G.; Ridzal, Denis

    2013-12-01

    We review the edge element formulation for describing the kinematics of hyperelastic solids. This approach is used to frame the problem of remapping the inverse deformation gradient for Arbitrary Lagrangian-Eulerian (ALE) simulations of solid dynamics. For hyperelastic materials, the stress state is completely determined by the deformation gradient, so remapping this quantity effectively updates the stress state of the material. A method, inspired by the constrained transport remap in electromagnetics, is reviewed, according to which the zero-curl constraint on the inverse deformation gradient is implicitly satisfied. Open issues related to the accuracy of this approach are identified. An optimization-based approach is implemented to enforce positivity of the determinant of the deformation gradient. The efficacy of this approach is illustrated with numerical examples.

  12. Edge-on!

    Science.gov (United States)

    2007-08-01

    Peering at Uranus's Rings as they Swing Edge-on to Earth for the First Time Since their Discovery in 1977 As Uranus coasts through a brief window of time when its rings are edge-on to Earth - a view of the planet we get only once every 42 years - astronomers peering at the rings with ESO's Very Large Telescope and other space or ground-based telescopes are getting an unprecedented view of the fine dust in the system, free from the glare of the bright rocky rings. They may even find a new moon or two. ESO PR Photo 37/07 ESO PR Photo 37/07 The Uranus System "ESO's VLT took data at the precise moment when the rings were edge-on to Earth," said Imke de Pater, of University of California, Berkeley who coordinated the worldwide campaign. She worked with two team members observing in Chile: Daphne Stam of the Technical University Delft in the Netherlands and Markus Hartung of ESO. The observations were done with NACO, one of the adaptive optics instruments installed at the VLT. With adaptive optics, it is possible to obtain images almost free from the blurring effect of the atmosphere. It is as if the 8.2-m telescope were observing from space. Observations were also done with the Keck telescope in Hawaii, the Hubble Space Telescope, and at the Palomar Observatory. "Using different telescopes around the world allows us to observe as much of the changes during the ring-plane crossing as possible: when Uranus sets as seen from the VLT, it can still be observed by the Keck," emphasised Stam. Uranus orbits the Sun in 84 years. Twice during a Uranian year, the rings appear edge-on to Earth for a brief period. The rings were discovered in 1977, so this is the first time for a Uranus ring-crossing to be observed from Earth. The advantage of observations at a ring-plane crossing is that it becomes possible to look at the rings from the shadowed or dark side. From that vantage point, the normally bright outer rings grow fainter because their centimetre- to metre-sized rocks obscure

  13. Unsteady behavior of leading-edge vortex and diffuser stall in a centrifugal compressor with vaned diffuser

    Science.gov (United States)

    Fujisawa, Nobumichi; Hara, Shotaro; Ohta, Yutaka

    2016-02-01

    The characteristics of a rotating stall of an impeller and diffuser and the evolution of a vortex generated at the diffuser leading-edge (i.e., the leading-edge vortex (LEV)) in a centrifugal compressor were investigated by experiments and numerical analysis. The results of the experiments revealed that both the impeller and diffuser rotating stalls occurred at 55 and 25 Hz during off-design flow operation. For both, stall cells existed only on the shroud side of the flow passages, which is very close to the source location of the LEV. According to the CFD results, the LEV is made up of multiple vortices. The LEV is a combination of a separated vortex near the leading- edge and a longitudinal vortex generated by the extended tip-leakage flow from the impeller. Therefore, the LEV is generated by the accumulation of vorticity caused by the velocity gradient of the impeller discharge flow. In partial-flow operation, the spanwise extent and the position of the LEV origin are temporarily transmuted. The LEV develops with a drop in the velocity in the diffuser passage and forms a significant blockage within the diffuser passage. Therefore, the LEV may be regarded as being one of the causes of a diffuser stall in a centrifugal compressor.

  14. About measuring velocity dispersions

    Science.gov (United States)

    Fellhauer, M.

    A lot of our knowledge about the dynamics and total masses of pressure dominated stellar systems relies on measuring the internal velocity disper- sion of the system. We assume virial equilibrium and that we are able to measure only the bound stars of the system without any contamination. This article shows how likely it is to measure the correct velocity dispersion in reality. It will show that as long as we have small samples of velocity mea- surements the distribution of possible outcomes can be very large and as soon as we have a source of error the velocity dispersion can wrong by several standard deviations especially in large samples.

  15. Edge colouring by total labellings

    DEFF Research Database (Denmark)

    Brandt, Stephan; Rautenbach, D.; Stiebitz, M.;

    2010-01-01

    We introduce the concept of an edge-colouring total k-labelling. This is a labelling of the vertices and the edges of a graph G with labels 1, 2, ..., k such that the weights of the edges define a proper edge colouring of G. Here the weight of an edge is the sum of its label and the labels of its...... two endvertices. We define χ (G) to be the smallest integer k for which G has an edge-colouring total k-labelling. This parameter has natural upper and lower bounds in terms of the maximum degree Δ of G : ⌈ (Δ + 1) / 2 ⌉ ≤ χ (G) ≤ Δ + 1. We improve the upper bound by 1 for every graph and prove χ (G...

  16. Edge phonons in black phosphorus.

    Science.gov (United States)

    Ribeiro, H B; Villegas, C E P; Bahamon, D A; Muraca, D; Castro Neto, A H; de Souza, E A T; Rocha, A R; Pimenta, M A; de Matos, C J S

    2016-01-01

    Black phosphorus has recently emerged as a new layered crystal that, due to its peculiar and anisotropic crystalline and electronic band structures, may have important applications in electronics, optoelectronics and photonics. Despite the fact that the edges of layered crystals host a range of singular properties whose characterization and exploitation are of utmost importance for device development, the edges of black phosphorus remain poorly characterized. In this work, the atomic structure and behaviour of phonons near different black phosphorus edges are experimentally and theoretically studied using Raman spectroscopy and density functional theory calculations. Polarized Raman results show the appearance of new modes at the edges of the sample, and their spectra depend on the atomic structure of the edges (zigzag or armchair). Theoretical simulations confirm that the new modes are due to edge phonon states that are forbidden in the bulk, and originated from the lattice termination rearrangements. PMID:27412813

  17. Trailing edges projected to move faster than leading edges for large pelagic fish habitats under climate change

    Science.gov (United States)

    Robinson, L. M.; Hobday, A. J.; Possingham, H. P.; Richardson, A. J.

    2015-03-01

    There is mounting evidence to suggest that many species are shifting their ranges in concordance with the climate velocity of their preferred environmental conditions/habitat. While accelerated rates in species' range shifts have been noted in areas of intense warming, due to climate change, few studies have considered the influence that both spatial temperature gradients and rates of warming (i.e., the two components of climate velocity) could have on rates of movement in species habitats. We compared projected shifts in the core habitat of nine large pelagic fish species (five tuna, two billfish and two shark species) off the east coast of Australia at different spatial points (centre, leading and trailing edges of the core habitat), during different seasons (summer and winter), in the near-(2030) and long-term (2070), using independent species distribution models and habitat suitability models. Model projections incorporated depth integrated temperature data from 11 climate models with a focus on the IPCC SRES A2 general emission scenario. Projections showed a number of consistent patterns: southern (poleward) shifts in all species' core habitats; trailing edges shifted faster than leading edges; shifts were faster by 2070 than 2030; and there was little difference in shifts among species and between seasons. Averaging across all species and climate models, rates of habitat shifts for 2030 were 45-60 km decade-1 at the trailing edge, 40-45 km decade-1 at the centre, and 20-30 km decade-1 at the leading edge. Habitat shifts for 2070 were 60-70 km decade-1 at the trailing edge, 50-55 km decade-1 at the centre, and 30-40 km decade-1 at the leading edge. It is often assumed that the leading edge of a species range will shift faster than the trailing edge, but there are few projections or observations in large pelagic fish to validate this assumption. We found that projected shifts at the trailing edge were greater than at the centre and leading of core habitats in

  18. Lipid membranes with an edge

    OpenAIRE

    Capovilla, R.; Guven, J.; Santiago, J. A.

    2002-01-01

    Consider a lipid membrane with a free exposed edge. The energy describing this membrane is quadratic in the extrinsic curvature of its geometry; that describing the edge is proportional to its length. In this note we determine the boundary conditions satisfied by the equilibria of the membrane on this edge, exploiting variational principles. The derivation is free of any assumptions on the symmetry of the membrane geometry. With respect to earlier work for axially symmetric configurations, we...

  19. High-Velocity Clouds

    NARCIS (Netherlands)

    Wakker, Bart P.; Woerden, Hugo van; Oswalt, Terry D.; Gilmore, Gerard

    2013-01-01

    The high-velocity clouds (HVCs) are gaseous objects that do not partake in differential galactic rotation, but instead have anomalous velocities. They trace energetic processes on the interface between the interstellar material in the Galactic disk and intergalactic space. Three different processes

  20. Transverse Spectral Velocity Estimation

    DEFF Research Database (Denmark)

    Jensen, Jørgen Arendt

    2014-01-01

    A transverse oscillation (TO)-based method for calculating the velocity spectrum for fully transverse flow is described. Current methods yield the mean velocity at one position, whereas the new method reveals the transverse velocity spectrum as a function of time at one spatial location. A convex...... array probe is used along with two different estimators based on the correlation of the received signal. They can estimate the velocity spectrum as a function of time as for ordinary spectrograms, but they also work at a beam-to-flow angle of 90°. The approach is validated using simulations of pulsatile...... flow using the Womersly–Evans flow model. The relative bias of the mean estimated frequency is 13.6% and the mean relative standard deviation is 14.3% at 90°, where a traditional estimator yields zero velocity. Measurements have been conducted with an experimental scanner and a convex array transducer...

  1. Experimental Study of Wake / Flap Interaction Noise and the Reduction of Flap Side Edge Noise

    Science.gov (United States)

    Hutcheson, Florence V.; Stead, Daniel J.; Plassman, Gerald E.

    2016-01-01

    The effects of the interaction of a wake with a half-span flap on radiated noise are examined. The incident wake is generated by bars of various widths and lengths or by a simplified landing gear model. Single microphone and phased array measurements are used to isolate the effects of the wake interaction on the noise radiating from the flap side edge and flap cove regions. The effects on noise of the wake generator's geometry and relative placement with respect to the flap are assessed. Placement of the wake generators upstream of the flap side edge is shown to lead to the reduction of flap side edge noise by introducing a velocity deficit and likely altering the instabilities in the flap side edge vortex system. Significant reduction in flap side edge noise is achieved with a bar positioned directly upstream of the flap side edge. The noise reduction benefit is seen to improve with increased bar width, length and proximity to the flap edge. Positioning of the landing gear model upstream of the flap side edge also leads to decreased flap side edge noise. In addition, flap cove noise levels are significantly lower than when the landing gear is positioned upstream of the flap mid-span. The impact of the local flow velocity on the noise radiating directly from the landing gear is discussed. The effects of the landing gear side-braces on flap side edge, flap cove and landing gear noise are shown.

  2. Toroidal drift waves with an equilibrium velocity field

    International Nuclear Information System (INIS)

    The author investigated the effect of a radially sheared poloidal velocity field on the toroidal drift wave which is well known to escape magnetic shear damping through toroidal coupling between different poloidal harmonics centered on individual rational surfaces. He endeavored to model the velocity profile according to that observed at the plasma edge during H-mode shots. The resultant wave formed by the interference of different poloidal harmonics now sees an antiwell created by the H-mode type velocity profile in the radial direction (in contrast to a well formed by the diamagnetic frequency in the absence of velocity fields). The wave, therefore, convects energy outward and hence undergoes damping. Outgoing wave boundary condition then introduces a negative imaginary contribution to the global eigenvalue -- once again confirming the stabilizing role of H-mode type velocity profiles. On the other hand, L-mode type velocity profiles have destabilizing action on toroidal drift waves

  3. Giant edge state splitting at atomically precise graphene zigzag edges

    Science.gov (United States)

    Wang, Shiyong; Talirz, Leopold; Pignedoli, Carlo A.; Feng, Xinliang; Müllen, Klaus; Fasel, Roman; Ruffieux, Pascal

    2016-05-01

    Zigzag edges of graphene nanostructures host localized electronic states that are predicted to be spin-polarized. However, these edge states are highly susceptible to edge roughness and interaction with a supporting substrate, complicating the study of their intrinsic electronic and magnetic structure. Here, we focus on atomically precise graphene nanoribbons whose two short zigzag edges host exactly one localized electron each. Using the tip of a scanning tunnelling microscope, the graphene nanoribbons are transferred from the metallic growth substrate onto insulating islands of NaCl in order to decouple their electronic structure from the metal. The absence of charge transfer and hybridization with the substrate is confirmed by scanning tunnelling spectroscopy, which reveals a pair of occupied/unoccupied edge states. Their large energy splitting of 1.9 eV is in accordance with ab initio many-body perturbation theory calculations and reflects the dominant role of electron-electron interactions in these localized states.

  4. Giant edge state splitting at atomically precise graphene zigzag edges.

    Science.gov (United States)

    Wang, Shiyong; Talirz, Leopold; Pignedoli, Carlo A; Feng, Xinliang; Müllen, Klaus; Fasel, Roman; Ruffieux, Pascal

    2016-05-16

    Zigzag edges of graphene nanostructures host localized electronic states that are predicted to be spin-polarized. However, these edge states are highly susceptible to edge roughness and interaction with a supporting substrate, complicating the study of their intrinsic electronic and magnetic structure. Here, we focus on atomically precise graphene nanoribbons whose two short zigzag edges host exactly one localized electron each. Using the tip of a scanning tunnelling microscope, the graphene nanoribbons are transferred from the metallic growth substrate onto insulating islands of NaCl in order to decouple their electronic structure from the metal. The absence of charge transfer and hybridization with the substrate is confirmed by scanning tunnelling spectroscopy, which reveals a pair of occupied/unoccupied edge states. Their large energy splitting of 1.9 eV is in accordance with ab initio many-body perturbation theory calculations and reflects the dominant role of electron-electron interactions in these localized states.

  5. Status and Verification of Edge Plasma Turbulence Code BOUT

    Energy Technology Data Exchange (ETDEWEB)

    Umansky, M V; Xu, X Q; Dudson, B; LoDestro, L L; Myra, J R

    2009-01-08

    The BOUT code is a detailed numerical model of tokamak edge turbulence based on collisional plasma uid equations. BOUT solves for time evolution of plasma uid variables: plasma density N{sub i}, parallel ion velocity V{sub {parallel}i}, electron temperature T{sub e}, ion temperature T{sub i}, electric potential {phi}, parallel current j{sub {parallel}}, and parallel vector potential A{sub {parallel}}, in realistic 3D divertor tokamak geometry. The current status of the code, physics model, algorithms, and implementation is described. Results of verification testing are presented along with illustrative applications to tokamak edge turbulence.

  6. Cutting Edge: IL-4, IL-21, and IFN-γ Interact To Govern T-bet and CD11c Expression in TLR-Activated B Cells.

    Science.gov (United States)

    Naradikian, Martin S; Myles, Arpita; Beiting, Daniel P; Roberts, Kenneth J; Dawson, Lucas; Herati, Ramin Sedaghat; Bengsch, Bertram; Linderman, Susanne L; Stelekati, Erietta; Spolski, Rosanne; Wherry, E John; Hunter, Christopher; Hensley, Scott E; Leonard, Warren J; Cancro, Michael P

    2016-08-15

    T-bet and CD11c expression in B cells is linked with IgG2c isotype switching, virus-specific immune responses, and humoral autoimmunity. However, the activation requisites and regulatory cues governing T-bet and CD11c expression in B cells remain poorly defined. In this article, we reveal a relationship among TLR engagement, IL-4, IL-21, and IFN-γ that regulates T-bet expression in B cells. We find that IL-21 or IFN-γ directly promote T-bet expression in the context of TLR engagement. Further, IL-4 antagonizes T-bet induction. Finally, IL-21, but not IFN-γ, promotes CD11c expression independent of T-bet. Using influenza virus and Heligmosomoides polygyrus infections, we show that these interactions function in vivo to determine whether T-bet(+) and CD11c(+) B cells are formed. These findings suggest that T-bet(+) B cells seen in health and disease share the common initiating features of TLR-driven activation within this circumscribed cytokine milieu. PMID:27430719

  7. Narrow-band, near-uv, high-repetition-rate laser-induced fluorescence system for use as an edge diagnostic in fusion machines

    International Nuclear Information System (INIS)

    A laser system for impurity diagnostics in the edge region of fusion devices is described, representing a substantial advance in repetition rate and capacity for velocity distribution measurements. A single mode cw dye laser with scan capability of 30 GHz in 100 msec is amplified by 3 fast flow dye cells, pumped by a high repetition rate excimer laser (60 mJ/pulse at 130 Hz at 308 rm). Average power during the 8 ns pulses of about 0.8 MW for amplified narrowband output at 604 rm, and 80 kW after frequency doubling in KD*P was achieved, with spectral bandwidth in the tenths of GHz regime. The usefulness of such high resolution is demonstrated by a model calculation for Fe velocity spectra involving the presence of thermal and sputtered flux, and spatial averaging. Laboratory velocity spectra are presented for Fe atoms, sputtered in the a5D4 ground state

  8. 2.5D Simulation of basin-edge effects on the ground motion characteristics

    Indian Academy of Sciences (India)

    J P Narayan

    2003-09-01

    The effects of basin-edge and soil velocity on the ground motion characteristics have been simulated using 2.5D modeling. One of the most significant advantages of the 2.5D simulation is that 3D radiation pattern can be generated in a 2D numerical grid using double-couple shear dislocation source. Further, 2.5D numerical modeling avoids the extensive computational cost of 3D modeling. The responses of basin-edge model using different soil velocities revealed that surface waves were generated near the edge of the basin and propagated normal to the edge, towards the basin. Further, the results depict increase of amplification, duration and surface wave generation with the decrease in soil velocity.

  9. Rock Segmentation through Edge Regrouping

    Science.gov (United States)

    Burl, Michael

    2008-01-01

    Rockster is an algorithm that automatically identifies the locations and boundaries of rocks imaged by the rover hazard cameras (hazcams), navigation cameras (navcams), or panoramic cameras (pancams). The software uses edge detection and edge regrouping to identify closed contours that separate the rocks from the background.

  10. FAME Radial Velocity Survey

    Science.gov (United States)

    Salim, S.; Gould, A.

    2000-12-01

    Full-Sky Astrometric Mapping Explorer (FAME) belongs to a new generation of astrometry satellites and will probe the surrounding space some 20 times deeper than its predecessor Hipparcos. As a result we will acquire precise knowledge of 5 out of 6 components of phase-space for millions of stars. The remaining coordinate, radial velocity, will remain unknown. In this study, we look at how the knowledge of radial velocity affects the determination of the structure of the Galaxy, and its gravitational potential. We therefore propose a radial velocity survey of FAME stars, and discuss its feasibility and technical requirements.

  11. The Robotic Edge Finishing Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Loucks, C.S.; Selleck, C.B.

    1990-08-01

    The Robotic Edge Finishing Laboratory at Sandia National Laboratories is developing four areas of technology required for automated deburring, chamfering, and blending of machined edges: (1) the automatic programming of robot trajectories and deburring processes using information derived from a CAD database, (2) the use of machine vision for locating the workpiece coupled with force control to ensure proper tool contact, (3) robotic deburring, blending, and machining of precision chamfered edges, and (4) in-process automated inspection of the formed edge. The Laboratory, its components, integration, and results from edge finishing experiments to date are described here. Also included is a discussion of the issues regarding implementation of the technology in a production environment. 24 refs., 17 figs.

  12. On the velocity space discretization for the Vlasov-Poisson system: comparison between implicit Hermite spectral and Particle-in-Cell methods

    NARCIS (Netherlands)

    Camporeale, E.; Delzanno, G.L.; Bergen, B.K.; Moulton, J.D.

    2016-01-01

    We describe a spectral method for the numerical solution of the Vlasov–Poisson system where the velocity space is decomposed by means of an Hermite basis, and the configuration space is discretized via a Fourier decomposition. The novelty of our approach is an implicit time discretization that allow

  13. Naegleria fowleri: contact-dependent secretion of electrondense granules (EDG).

    Science.gov (United States)

    Chávez-Munguía, Bibiana; Villatoro, Lizbeth Salazar; Omaña-Molina, Maritza; Rodríguez-Monroy, Marco Aurelio; Segovia-Gamboa, Norma; Martínez-Palomo, Adolfo

    2014-07-01

    The free living amoeba Naegleria fowleri is pathogenic to humans but also to other mammalians. These amoebae may invade the nasal mucosa and migrate into the brain causing cerebral hemorrhagic necrosis, a rapidly fatal infection. Knowledge of the cytolytic mechanism involved in the destruction of brain tissues by Naegleria trophozoites is limited. In other amoebic species, such as Entamoeba histolytica, we have previously reported the possible lytic role of small cytoplasmic components endowed with proteolytic activities, known as electrondense granules (EDG). Using transmission electron microscopy we now report that EDG, seldom found in long term cultured N. fowleri, are present in abundance in trophozoites recovered from experimental mice brain lesions. Numerous EDG were also observed in amoebae incubated with collagen substrates or cultured epithelial cells. SDS-PAGE assays of concentrated supernatants of these trophozoites, containing EDG, revealed proteolytic activities. These results suggest that EDG may have a clear role in the cytopathic mechanisms of this pathogenic amoeba.

  14. Superluminal Recession Velocities

    CERN Document Server

    Davis, T M; Davis, Tamara M.; Lineweaver, Charles H.

    2000-01-01

    Hubble's Law, v=HD (recession velocity is proportional to distance), is a theoretical result derived from the Friedmann-Robertson-Walker metric. v=HD applies at least as far as the particle horizon and in principle for all distances. Thus, galaxies with distances greater than D=c/H are receding from us with velocities greater than the speed of light and superluminal recession is a fundamental part of the general relativistic description of the expanding universe. This apparent contradiction of special relativity (SR) is often mistakenly remedied by converting redshift to velocity using SR. Here we show that galaxies with recession velocities faster than the speed of light are observable and that in all viable cosmological models, galaxies above a redshift of three are receding superluminally.

  15. High Velocity Gas Gun

    Science.gov (United States)

    1988-01-01

    A video tape related to orbital debris research is presented. The video tape covers the process of loading a High Velocity Gas Gun and firing it into a mounted metal plate. The process is then repeated in slow motion.

  16. The critical ionization velocity

    International Nuclear Information System (INIS)

    The critical ionization velocity effect was first proposed in the context of space plasmas. This effect occurs for a neutral gas moving through a magnetized plasma and leads to rapid ionization and braking of the relative motion when a marginal velocity, 'the critical velocity', is exceeded. Laboratory experiments have clearly established the significance of the critical velocity and have provided evidence for an underlying mechanism which relies on the combined action of electron impact ionization and a collective plasma interaction heating electrons. There is experimental support for such a mechanism based on the heating of electrons by the modified two-stream instability as part of a feedback process. Several applications to space plasmas have been proposed and the possibility of space experiments has been discussed. (author)

  17. Investigation of Slipstream Velocity

    Science.gov (United States)

    Crowley, J W , Jr

    1925-01-01

    These experiments were made at the request of the Bureau of Aeronautics, Navy Department, to investigate the velocity of the air in the slipstream in horizontal and climbing flight to determine the form of expression giving the slipstream velocity in terms of the airspeed of the airplane. The method used consisted in flying the airplane both on a level course and in climb at full throttle and measuring the slipstream velocity at seven points in the slipstream for the whole speed range of the airplane in both conditions. In general the results show that for both condition, horizontal and climbing flights, the slipstream velocity v subscript 3 and airspeed v can be represented by straight lines and consequently the equations are of the form: v subscript s = mv+b where m and b are constant. (author)

  18. Average Angular Velocity

    OpenAIRE

    Van Essen, H.

    2004-01-01

    This paper addresses the problem of the separation of rotational and internal motion. It introduces the concept of average angular velocity as the moment of inertia weighted average of particle angular velocities. It extends and elucidates the concept of Jellinek and Li (1989) of separation of the energy of overall rotation in an arbitrary (non-linear) $N$-particle system. It generalizes the so called Koenig's theorem on the two parts of the kinetic energy (center of mass plus internal) to th...

  19. Impurity and trace tritium transport in tokamak edge turbulence

    DEFF Research Database (Denmark)

    Naulin, V.

    2005-01-01

    The turbulent transport of impurity or minority species, as for example tritium, is investigated in drift-Alfven edge turbulence. The full effects of perpendicular and parallel convection are kept for the impurity species. The impurity density develops a granular structure with steep gradients...... and locally exceeds its initial values due to the compressibility of the flow. An approximate decomposition of the impurity flux into a diffusive part and an effective convective part (characterized by a pinch velocity) is performed and a net inward pinch effect is recovered. The pinch velocity is explained...

  20. Hydrogen-free graphene edges

    Science.gov (United States)

    He, Kuang; Lee, Gun-Do; Robertson, Alex W.; Yoon, Euijoon; Warner, Jamie H.

    2014-01-01

    Graphene edges and their functionalization influence the electronic and magnetic properties of graphene nanoribbons. Theoretical calculations predict saturating graphene edges with hydrogen lower its energy and form a more stable structure. Despite the importance, experimental investigations of whether graphene edges are always hydrogen-terminated are limited. Here we study graphene edges produced by sputtering in vacuum and direct measurements of the C-C bond lengths at the edge show ~86% contraction relative to the bulk. Density functional theory reveals the contraction is attributed to the formation of a triple bond and the absence of hydrogen functionalization. Time-dependent images reveal temporary attachment of a single atom to the arm-chair C-C bond in a triangular configuration, causing expansion of the bond length, which then returns back to the contracted value once the extra atom moves on and the arm-chair edge is returned. Our results provide confirmation that non-functionalized graphene edges can exist in vacuum.

  1. Hydrogen-free graphene edges.

    Science.gov (United States)

    He, Kuang; Lee, Gun-Do; Robertson, Alex W; Yoon, Euijoon; Warner, Jamie H

    2014-01-01

    Graphene edges and their functionalization influence the electronic and magnetic properties of graphene nanoribbons. Theoretical calculations predict saturating graphene edges with hydrogen lower its energy and form a more stable structure. Despite the importance, experimental investigations of whether graphene edges are always hydrogen-terminated are limited. Here we study graphene edges produced by sputtering in vacuum and direct measurements of the C-C bond lengths at the edge show ~86% contraction relative to the bulk. Density functional theory reveals the contraction is attributed to the formation of a triple bond and the absence of hydrogen functionalization. Time-dependent images reveal temporary attachment of a single atom to the arm-chair C-C bond in a triangular configuration, causing expansion of the bond length, which then returns back to the contracted value once the extra atom moves on and the arm-chair edge is returned. Our results provide confirmation that non-functionalized graphene edges can exist in vacuum.

  2. Edge magnetization in Bernal-stacked trilayer zigzag graphene nanoribbons

    Science.gov (United States)

    Pérez, Juan Antonio Casao

    2016-06-01

    We have used a tight-binding Hamiltonian of an ABA-stacked trilayer zigzag graphene nanoribbon with β-alignment edges to study the edge magnetizations. Our model includes the effect of the intralayer next-nearest-neighbor hopping, the interlayer hopping responsible for the trigonal warping and the interaction between electrons, which is considered by a single band Hubbard model in the mean field approximation. Firstly, in the neutral system we analyzed the two magnetic states in which both edge magnetizations reach their maximum value; the first one is characterized by an intralayer ferromagnetic coupling between the magnetizations at opposite edges, whereas in the second state that coupling is antiferromagnetic. The band structure, the location of the edge-state bands and the local density of states resolved in spin are calculated in order to understand the origins of the edge magnetizations. We have also introduced an electron doping so that the number of electrons in the ribbon unit cell is higher than in neutral case. As a consequence, we have obtained magnetization steps and charge accumulation at the edges of the sample, which are caused by the edge-state flat bands.

  3. USING INTERNAL QUANTUM EFFICIENCY TO DETERMINE FRONT SURFACE RECOMBINATION VELOCITY OF CRYSTALLINE SILICON SOLAR CELLS%利用内光谱响应测量晶体硅太阳电池前表面复合速度

    Institute of Scientific and Technical Information of China (English)

    马逊; 刘祖明; 廖华; 李景天

    2011-01-01

    根据发射区电流密度的连续性方程,推导出了发射区杂质服从高斯函数和余误差函数分布情况下短波内光谱响应与前表面复合速度的模型,该模型短波波长的选择与扩散结深有关.并利用该模型对不同扩散条件下的晶体硅太阳电池前表面复合速度进行计算,结果与PC1D模拟结果符合较好.%Front surface recombination velocity of solar cells can be obtained by internal quantum efficiency (IQE) in short-wavelength. However, the existing models are almost dealing with emitter region where the profile is uniformity. Doping concentration in emitter region is obeyed Gaussian or Complementary Error distribution for commercial crystalline silicon solar cells. This paper, based on current density continuity function, deduced the models of measuring front surface recombination velocity. The models adapt to the emitter region profile with Gauss or Complementary Error distribution. The range of short-wavelength is selected by diffusion junction length. At last, the paper using the models calculated front surface recombination velocity of different diffusion emitter and found them matched with PC1D.

  4. Effect of Leading Edge Tubercles on Marine Tidal Turbine Blades

    Science.gov (United States)

    Murray, Mark; Gruber, Timothy; Fredriksson, David

    2010-11-01

    This project investigated the impact that the addition of leading edge protuberances (tubercles) have on the effectiveness of marine tidal turbine blades, especially at lower flow speeds. The addition of leading edge tubercles to lifting foils has been shown, in previous research, to delay the onset of stall without significant hydrodynamic costs. The experimental results obtained utilizing three different blade designs (baseline and two tubercle modified) are compared. All blades were designed in SolidWorks and manufactured utilizing rapid prototype techniques. All tests were conducted in the 120 ft tow tank at the U.S. Naval Academy using a specifically designed experimental apparatus. Results for power coefficients are presented for a range of tip speed ratios. Cut-in velocity is also compared between the blade designs. For all test criteria, the tubercle modified blades significantly outperformed the smooth leading edge baseline design blades.

  5. Non-linear Heat Transport Modelling with Edge Localized Modes and Plasma Edge Control in Tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Becoulet, M.; Huysmans, G.; Thomas, P.; Ghendrih, P.; Grosman, A.; Monier-Garbet, P.; Garbet, X.; Zwingman, W.; Nardon, E. [Euratom-CEA, Centre d' Etudes de Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. de Recherches sur la Fusion Controlee; Moyer, R. [California Univ., San Diego, La Jolla CA (United States); Evans, T.; Leonard, A. [General Atomics, San Diego, CA (United States)

    2004-07-01

    The paper presents a new approach for the modelling of the pedestal energy transport in the presence of Type I ELMs (edge localized mode) based on the linear ideal MHD code MISHKA coupled with the non-linear energy transport code TELM in a realistic tokamak geometry. The main mechanism of increased transport through the External Transport Barrier (ETB) in this model of ELMs is the increased convective flux due to the MHD velocity perturbation and an additional conductive flux due the radial perturbation of the magnetic field leading to a flattening of the pressure profile in the unstable zone. The typical Type I ELM time-cycle including the destabilization of the ballooning modes leading to the fast (200 {mu}s) collapse of the pedestal pressure followed by the edge pressure profile re-building on a diffusive time scale was reproduced numerically. The possible mechanism of Type I ELMs control using a stochastic plasma boundary created by external coils is modelled in the paper. In the stochastic layer the transverse transport is effectively increased by the magnetic field line diffusion. The modelling results for DIII-D experiment on Type I ELM suppression using the external perturbation from the I-coils demonstrated the possibility to decrease the edge pressure gradient just under the ideal ballooning limit, leading to the high confinement regime without Type I ELMs. (authors)

  6. Effect of heat treatment on the activity and stability of PtCo/C catalyst and application of in-situ X-ray absorption near edge structure for proton exchange membrane fuel cell

    Science.gov (United States)

    Lin, Rui; Zhao, Tiantian; Shang, Mingfeng; Wang, Jianqiang; Tang, Wenchao; Guterman, Vladimir E.; Ma, Jianxin

    2015-10-01

    For the purpose of reducing the cost and improving the performance of the proton exchange membrane fuel cell (PEMFC), some low-Pt or non-Pt catalysts have been studied in recent years. PtCo/C electrocatalysts are synthesized by a two-step reduction approach followed by the heat treatment. PtCo metal particles are uniformly dispersed on the surface of XC-72 carbon support, with a uniform particle size distribution. The PtCo/C catalyst after 400 °C heat treatment has the best electrochemical performance among the as-prepared catalysts, even superior to the commercial Pt/C catalyst. In the durability test, PtCo/C-400 also shows excellent stability with only 6.9% decline of electrochemical surface area (ECSA) after 1000 cyclic voltammetry (CV) cycles. In-situ X-ray absorption near edge structure (XANES) technique is conducted to explore the nanostructure change of Pt during the PEMFC operation. For PtCo/C catalyst, with the fuel cell operation potential decreasing from open circuit voltage (OCV) to 0.3 V, the Pt L3 white line intensity decreases continuously, indicating the decline of Pt 5d-vacancy due to the adsorption of oxygenated species.

  7. On the wake flow of asymmetrically beveled trailing edges

    Science.gov (United States)

    Guan, Yaoyi; Pröbsting, Stefan; Stephens, David; Gupta, Abhineet; Morris, Scott C.

    2016-05-01

    Trailing edge and wake flows are of interest for a wide range of applications. Small changes in the design of asymmetrically beveled or semi-rounded trailing edges can result in significant difference in flow features which are relevant for the aerodynamic performance, flow-induced structural vibration and aerodynamically generated sound. The present study describes in detail the flow field characteristics around a family of asymmetrically beveled trailing edges with an enclosed trailing-edge angle of 25° and variable radius of curvature R. The flow fields over the beveled trailing edges are described using data obtained by particle image velocimetry (PIV) experiments. The flow topology for different trailing edges was found to be strongly dependent on the radius of curvature R, with flow separation occurring further downstream as R increases. This variation in the location of flow separation influences the aerodynamic force coefficients, which were evaluated from the PIV data using a control volume approach. Two-point correlations of the in-plane velocity components are considered to assess the structure in the flow field. The analysis shows large-scale coherent motions in the far wake, which are associated with vortex shedding. The wake thickness parameter yf is confirmed as an appropriate length scale to characterize this large-scale roll-up motion in the wake. The development in the very near wake was found to be critically dependent on R. In addition, high-speed PIV measurements provide insight into the spectral characteristics of the turbulent fluctuations. Based on the time-resolved flow field data, the frequency range associated with the shedding of coherent vortex pairs in the wake is identified. By means of time-correlation of the velocity components, turbulent structures are found to convect from the attached or separated shear layers without distinct separation point into the wake.

  8. Velocities in Solar Pores

    Science.gov (United States)

    Balasubramaniam, K. S.; Keil, S. L.; Smaldone, L. A.

    1996-05-01

    We investigate the three dimensional structure of solar pores and their surroundings using high spatial and spectral resolution data. We present evidence that surface velocities decrease around pores with a corresponding increase in the line-of-sight (LOS) velocities. LOS velocities in pores increase with the strength of the magnetic field. Surface velocities show convergence toward a weak downflow which appear to trace boundaries resembling meso-granular and super granular flows. The observed magnetic fields in the pores appear near these boundaries. We analyze the vertical velocity structure in pores and show that they generally have downflows decreasing exponentially with height, with a scale height of about 90 km. Evidence is also presented for the expanding nature of flux tubes. Finally we describe a phenomenological model for pores. This work was supported by AFOSR Task 2311G3. LAS was partially supported by the Progetto Nazionale Astrofisica e Fisica Cosmica of MURST and Scambi Internazionali of the Universita degli Studi di Napoli Frederico II. National Solar Observatory, NOAO, is operated for the National Science Foundation by AURA, Inc.

  9. Fast tracking using edge histograms

    Science.gov (United States)

    Rokita, Przemyslaw

    1997-04-01

    This paper proposes a new algorithm for tracking objects and objects boundaries. This algorithm was developed and applied in a system used for compositing computer generated images and real world video sequences, but can be applied in general in all tracking systems where accuracy and high processing speed are required. The algorithm is based on analysis of histograms obtained by summing along chosen axles pixels of edge segmented images. Edge segmentation is done by spatial convolution using gradient operator. The advantage of such an approach is that it can be performed in real-time using available on the market hardware convolution filters. After edge extraction and histograms computation, respective positions of maximums in edge intensity histograms, in current and previous frame, are compared and matched. Obtained this way information about displacement of histograms maximums, can be directly converted into information about changes of target boundaries positions along chosen axles.

  10. Flatband Engineering of Mobility Edges

    OpenAIRE

    Danieli, Carlo; Bodyfelt, Joshua D.; Flach, Sergej

    2015-01-01

    Properly modulated flatband lattices have a divergent density of states at the flatband energy. Quasiperiodic modulations are known to host a metal insulator transition already in one space dimension. Their embedding into flatband geometries consequently allows for a precise engineering and fine tuning of mobility edges. We obtain analytic expressions for singular mobility edges for two flatband lattice examples. In particular, we engineer cases with arbitrarily small energy separations of mo...

  11. Quantitative velocity modulation spectroscopy

    Science.gov (United States)

    Hodges, James N.; McCall, Benjamin J.

    2016-05-01

    Velocity Modulation Spectroscopy (VMS) is arguably the most important development in the 20th century for spectroscopic study of molecular ions. For decades, interpretation of VMS lineshapes has presented challenges due to the intrinsic covariance of fit parameters including velocity modulation amplitude, linewidth, and intensity. This limitation has stifled the growth of this technique into the quantitative realm. In this work, we show that subtle changes in the lineshape can be used to help address this complexity. This allows for determination of the linewidth, intensity relative to other transitions, velocity modulation amplitude, and electric field strength in the positive column of a glow discharge. Additionally, we explain the large homogeneous component of the linewidth that has been previously described. Using this component, the ion mobility can be determined.

  12. Fluidic angular velocity sensor

    Science.gov (United States)

    Berdahl, C. M. (Inventor)

    1986-01-01

    A fluidic sensor providing a differential pressure signal proportional to the angular velocity of a rotary input is described. In one embodiment the sensor includes a fluid pump having an impeller coupled to a rotary input. A housing forming a constricting fluid flow chamber is connected to the fluid input of the pump. The housing is provided with a fluid flow restrictive input to the flow chamber and a port communicating with the interior of the flow chamber. The differential pressure signal measured across the flow restrictive input is relatively noise free and proportional to the square of the angular velocity of the impeller. In an alternative embodiment, the flow chamber has a generally cylindrical configuration and plates having flow restrictive apertures are disposed within the chamber downstream from the housing port. In this embodiment, the differential pressure signal is found to be approximately linear with the angular velocity of the impeller.

  13. Edge instabilities of topological superconductors

    Science.gov (United States)

    Hofmann, Johannes S.; Assaad, Fakher F.; Schnyder, Andreas P.

    2016-05-01

    Nodal topological superconductors display zero-energy Majorana flat bands at generic edges. The flatness of these edge bands, which is protected by time-reversal and translation symmetry, gives rise to an extensive ground-state degeneracy. Therefore, even arbitrarily weak interactions lead to an instability of the flat-band edge states towards time-reversal and translation-symmetry-broken phases, which lift the ground-state degeneracy. We examine the instabilities of the flat-band edge states of dx y-wave superconductors by performing a mean-field analysis in the Majorana basis of the edge states. The leading instabilities are Majorana mass terms, which correspond to coherent superpositions of particle-particle and particle-hole channels in the fermionic language. We find that attractive interactions induce three different mass terms. One is a coherent superposition of imaginary s -wave pairing and current order, and another combines a charge-density-wave and finite-momentum singlet pairing. Repulsive interactions, on the other hand, lead to ferromagnetism together with spin-triplet pairing at the edge. Our quantum Monte Carlo simulations confirm these findings and demonstrate that these instabilities occur even in the presence of strong quantum fluctuations. We discuss the implications of our results for experiments on cuprate high-temperature superconductors.

  14. 双向差速法制备高纯度雪旺细胞的实验研究%Novel method of Schwann cell purification by differential velocity of cell attachment and detachment

    Institute of Scientific and Technical Information of China (English)

    刘炎; 彭江; 卢世壁; 张莉; 宫旭; 陈继凤; 王玉; 赵斌; 任志午; 詹胜峰; 许文静

    2011-01-01

    [Objective]To establish a novel efficient method of Schwann cell purification by the characteristic that there has been a different velocity of attachment and detachment between Schwann cells and fibroblast. [ Method] Postnatal SD rat's(3 day old) sciatic nerve segments were harvested and epinuims were striped off aseptically under a dissecting microscope. The nerve segments were digested by Collagenase NB4 at a concentratin of 0.2% with a rotator for 15 min. After enzymatic and mechanical dissociation,the cell digest was allowed to settle on polylysine-coated flasks for 30 min with intermittent shaking,and then the suspended cells were transferred to new flasks. After 48h primary culture,culture media was replaced with the 0. 05% collagenase. After incubation at 37 t for 30 min, the flasks were shaked horizontally to release rounded up or detaching cells after another 48h culture. The final purified cells were identified with immunocytochemistry and flow cytometric analysis. [ Result] After two rounds of attach and detach purification the number of Schwann cells reached about (117. 2 ± 3.4) x 104 per 25 cm2 and purity was a-chieved 97.9%. [ Conclusion] A large number of purified Schwann cells can be obtained by our simple,fast and safe method within only 72h,and might be valuable for studies related to basic science of peripheral nerve injury and regeneration.%[目的]利用乳鼠的雪旺细胞与成纤维细胞贴壁及复合酶消化分离速度不同的特点,建立简单而快速提取和纯化雪旺细胞的方法.[方法]取3 dSD大鼠双侧坐骨神经,在解剖镜下剥离去除神经外膜,剪碎后用0.2%复合胶原酶( Collagenase NB4)消化,细胞悬液接种于预先用多聚赖氨酸包被的培养瓶差速贴壁30 rain,然后将细胞悬液移入一新的培养瓶培养48 h;用0.05%复合胶原酶37℃消化30 min,振荡分离雪旺细胞与成纤维细胞,培养48 h后在相差显微镜下观察细胞形态;计数、纯度测定;免

  15. MSE velocity survey

    Science.gov (United States)

    Schimd, C.; Courtois, H.; Koda, J.

    2015-12-01

    A huge velocity survey based on the Maunakea Spectroscopic Explorer facility (MSE) is proposed, aiming at investigating the structure and dynamics of the cosmic web over 3π steradians up to ˜1 Gpc and at unprecedented spatial resolution, its relationship with the galaxy formation process, and the bias between galaxies and dark matter during the last three billions years. The cross-correlation of velocity and density fields will further allow the probe any deviation from General Relativity by measuring the the linear-growth rate of cosmic structures at precision competitive with high-redshift spectroscopic redshift surveys.

  16. The Prescribed Velocity Method

    DEFF Research Database (Denmark)

    Nielsen, Peter Vilhelm

    The- velocity level in a room ventilated by jet ventilation is strongly influenced by the supply conditions. The momentum flow in the supply jets controls the air movement in the room and, therefore, it is very important that the inlet conditions and the numerical method can generate a satisfactory...... description of this momentum flow. The Prescribed Velocity Method is a practical method for the description of an Air Terminal Device which will save grid points close to the opening and ensure the right level of the momentum flow....

  17. Cirrus Crystal Terminal Velocities.

    Science.gov (United States)

    Heymsfield, Andrew J.; Iaquinta, Jean

    2000-04-01

    Cirrus crystal terminal velocities are of primary importance in determining the rate of transport of condensate from upper- to middle-tropospheric levels and profoundly influence the earth's radiation balance through their effect on the rate of buildup or decay of cirrus clouds. In this study, laboratory and field-based cirrus crystal drag coefficient data, as well as analytical descriptions of cirrus crystal shapes, are used to derive more physically based expressions for the velocities of cirrus crystals than have been available in the past.Polycrystals-often bullet rosettes-are shown to be the dominant crystal types in synoptically generated cirrus, with columns present in varying but relatively large percentages, depending on the cloud. The two critical parameters needed to calculate terminal velocity are the drag coefficient and the ratio of mass to cross-sectional area normal to their fall direction. Using measurements and calculations, it is shown that drag coefficients from theory and laboratory studies are applicable to crystals of the types found in cirrus. The ratio of the mass to area, which is shown to be relatively independent of the number of bullets in the rosette, is derived from an analytic model that represents bullet rosettes containing one to eight bullets in 19 primary geometric configurations. The ratio is also derived for columns. Using this information, a general set of equations is developed to calculate the terminal velocities and masses in terms of the aspect ratio (width divided by length), ice density, and rosette maximum dimension. Simple expressions for terminal velocity and mass as a function of bullet rosette maximum dimension are developed by incorporating new information on bullet aspect ratios.The general terminal velocity and mass relations are then applied to a case from the First International Satellite Cloud Climatology Project (ISCCP) Research Experiment (FIRE) 2, when size spectra from a balloon-borne ice crystal

  18. DVL Angular Velocity Recorder

    Science.gov (United States)

    Liebe, Wolfgang

    1944-01-01

    In many studies, especially of nonstationary flight motion, it is necessary to determine the angular velocities at which the airplane rotates about its various axes. The three-component recorder is designed to serve this purpose. If the angular velocity for one flight attitude is known, other important quantities can be derived from its time rate of change, such as the angular acceleration by differentiations, or - by integration - the angles of position of the airplane - that is, the angles formed by the airplane axes with the axis direction presented at the instant of the beginning of the motion that is to be investigated.

  19. Average Angular Velocity

    CERN Document Server

    Essén, H

    2003-01-01

    This paper addresses the problem of the separation of rotational and internal motion. It introduces the concept of average angular velocity as the moment of inertia weighted average of particle angular velocities. It extends and elucidates the concept of Jellinek and Li (1989) of separation of the energy of overall rotation in an arbitrary (non-linear) $N$-particle system. It generalizes the so called Koenig's theorem on the two parts of the kinetic energy (center of mass plus internal) to three parts: center of mass, rotational, plus the remaining internal energy relative to an optimally translating and rotating frame.

  20. Improved performance of dye sensitized solar cells using Cu-doped TiO2 as photoanode materials: Band edge movement study by spectroelectrochemistry

    Science.gov (United States)

    Zhou, Li; Wei, Liguo; Yang, Yulin; Xia, Xue; Wang, Ping; Yu, Jia; Luan, Tianzhu

    2016-08-01

    Cu-doped TiO2 nanoparticles are prepared and used as semiconductor materials of photoanode to improve the performance of dye sensitized solar cells (DSSCs). UV-Vis spectroscopy and variable temperature spectroelectrochemistry study are used to characterize the influence of copper dopant with different concentrations on the band gap energies of TiO2 nanoparticles. The prepared Cu-doped TiO2 semiconductor has avoided the formation of CuO during hydrothermal process and lowered the conduction band position of TiO2, which contribute to increase the short circuit current density of DSSCs. At the optimum Cu concentration of 1.0 at.%, the short circuit current density increased from 12.54 to 14.98 mA cm-2, full sun solar power conversion efficiencies increased from 5.58% up to 6.71% as compared to the blank DSSC. This showed that the presence of copper in DSSCs leads to improvements of up to 20% in the conversion efficiency of DSSCs.

  1. Arsenate reduction and methylation in the cells of Trichoderma asperellum SM-12F1, Penicillium janthinellum SM-12F4, and Fusarium oxysporum CZ-8F1 investigated with X-ray absorption near edge structure

    Energy Technology Data Exchange (ETDEWEB)

    Su, S.M., E-mail: shimingsu@163.com [Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences/Key Laboratory of Agro-Environment, Ministry of Agriculture, Beijing (China); Zeng, X.B., E-mail: zengxb@ieda.org.cn [Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences/Key Laboratory of Agro-Environment, Ministry of Agriculture, Beijing (China); Li, L.F.; Duan, R.; Bai, L.Y. [Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences/Key Laboratory of Agro-Environment, Ministry of Agriculture, Beijing (China); Li, A.G.; Wang, J.; Jiang, S. [Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai (China)

    2012-12-15

    Highlights: Black-Right-Pointing-Pointer Three fungal strains are capable of As(V) reduction and methylation. Black-Right-Pointing-Pointer As(V) reduction might be more easily processed than the methylation in fungal cells. Black-Right-Pointing-Pointer As sequestration and speciation transformation might be the detoxification processes. - Abstract: Synchrotron radiation-based X-ray absorption near edge structure (XANES) was introduced to directly analysis chemical species of arsenic (As) in the cells of Trichoderma asperellum SM-12F1, Penicillium janthinellum SM-12F4, and Fusarium oxysporum CZ-8F1 capable of As accumulation and volatilisation. After exposure to As(V) of 500 mg L{sup -1} for 15 days, a total of 60.5% and 65.3% of the accumulated As in the cells of T. asperellum SM-12F1 and P. janthinellum SM-12F4, respectively, was As(III), followed by 31.3% and 32.4% DMA (dimethylarsinic acid), 8.3% and 2.3% MMA (monomethylarsonic acid), respectively. However, for F. oxysporum CZ-8F1, 54.5% of the accumulated As was As(III), followed by 37.8% MMA and 7.7% As(V). The reduction and methylation of As(V) formed As(III), MMA, and DMA as the primacy products, and the reduction of As(V) might be more easily processed than the methylation. These results will help to understanding the mechanisms of As detoxification and its future application in bioremediation.

  2. Computation of Edge-Edge-Edge Events Based on Conicoid Theory for 3-D Object Recognition

    Institute of Scientific and Technical Information of China (English)

    WU Chenye; MA Huimin

    2009-01-01

    The availability of a good viewpoint space partition is crucial in three dimensional (3-D) object rec-ognition on the approach of aspect graph. There are two important events depicted by the aspect graph ap-proach, edge-edge-edge (EEE) events and edge-vertex (EV) events. This paper presents an algorithm to compute EEE events by characteristic analysis based on conicoid theory, in contrast to current algorithms that focus too much on EV events and often overlook the importance of EEE events. Also, the paper provides a standard flowchart for the viewpoint space partitioning based on aspect graph theory that makes it suitable for perspective models. The partitioning result best demonstrates the algorithm's efficiency with more valu-able viewpoints found with the help of EEE events, which can definitely help to achieve high recognition rate for 3-D object recognition.

  3. Orientation Relationships between Ferrite and Cementite by Edge-to-edge Matching Principle

    Institute of Scientific and Technical Information of China (English)

    Ning Zhong; Xiaodong Wang; Zhenghong Guo; Yonghua Rong

    2011-01-01

    The crystallographic features of pearlite were investigated by experiments and edge-to-edge matching principle. Two new orientation relationships between ferrite and cementite were determinated by selected area electron diffraction and then explained by our modified edge-to-edge matching method. The consistence of the experimental results with theoretical prediction confirms the practicability of the modified edge-to-edge matching model.

  4. Improved bound on facial parity edge coloring

    OpenAIRE

    Lužar, Borut; Škrekovski, Riste

    2013-01-01

    A facial parity edge coloring of a 2-edge connected plane graph is an edge coloring where no two consecutive edges of a facial walk of any face receive the same color. Additionally, for every face f and every color c either no edge or an odd number of edges incident to f are colored by c. Czap, Jendrol', Kardo\\v{s} and Sotak showed that every 2-edge connected plane graph admits a facial parity edge coloring with at most 20 colors. We improve this bound to 16 colors.

  5. Decay patterns of edge states at reconstructed armchair graphene edges

    Science.gov (United States)

    Park, Changwon; Ihm, Jisoon; Kim, Gunn

    Density functional theory calculations are used to investigate the electronic structures of localized states at reconstructed armchair graphene edges. We consider graphene nanoribbons with two different edge types and obtain the energy band structures and charge densities of the edge states. By examining the imaginary part of the wave vector in the forbidden energy region, we reveal the decay behavior of the wave functions in graphene. The complex band structures of graphene in the armchair and zigzag directions are presented in the first-principles framework. G.K. acknowledges the support of the Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Education (Grant No. 2013R1A1A2009131) and the Priority Research Center Program (Grant No. 2010-0020207).

  6. On the edge: haptic discrimination of edge sharpness.

    Directory of Open Access Journals (Sweden)

    Andy L Skinner

    Full Text Available The increasing ubiquity of haptic displays (e.g., smart phones and tablets necessitates a better understanding of the perceptual capabilities of the human haptic system. Haptic displays will soon be capable of locally deforming to create simple 3D shapes. This study investigated the sensitivity of our haptic system to a fundamental component of shapes: edges. A novel set of eight high quality shape stimuli with test edges that varied in sharpness were fabricated in a 3D printer. In a two alternative, forced choice task, blindfolded participants were presented with two of these shapes side by side (one the reference, the other selected randomly from the remaining set of seven and after actively exploring the test edge of each shape with the tip of their index finger, reported which shape had the sharper edge. We used a model selection approach to fit optimal psychometric functions to performance data, and from these obtained just noticeable differences and Weber fractions. In Experiment 1, participants performed the task with four different references. With sharpness defined as the angle at which one surface meets the horizontal plane, the four JNDs closely followed Weber's Law, giving a Weber fraction of 0.11. Comparisons to previously reported Weber fractions from other haptic manipulations (e.g. amplitude of vibration suggests we are sufficiently sensitive to changes in edge sharpness for this to be of potential utility in the design of future haptic displays. In Experiment 2, two groups of participants performed the task with a single reference but different exploration strategies; one was limited to a single touch, the other unconstrained and free to explore as they wished. As predicted, the JND in the free exploration condition was lower than that in the single touch condition, indicating exploration strategy affects sensitivity to edge sharpness.

  7. Three Dimensional velocity Structure in the New Madrid and Other SCR Seismic Zones

    Science.gov (United States)

    Powell, C. A.

    2002-12-01

    Recent tomographic inversions of travel time data accumulated for active SCR seismic zones have revealed strong velocity contrasts that appear to control the distribution of seismicity. Velocity images have been obtained for the New Madrid seismic zone (NMSZ), the eastern Tennessee seismic zone (ETSZ), and the Charlevoix seismic zone (CSZ). We have also obtained a preliminary velocity model for the aftershock region associated with the Mw=7.7 January 26th Bhuj, India earthquake. Both P and S waves were inverted for velocity structure in the NMSZ. High velocity bodies were imaged and are interpreted to be intrusions associated with the axis and edge of the Reelfoot graben. Low velocities were imaged near the intersection of the long NE arm of seismicity and the NW trending arm; the low velocities are attributed to highly fractured, fluid saturated crust and are associated with shallow earthquake swarms. In general, earthquakes tend to avoid regions with higher than average velocities and concentrate in areas of low velocity or along the edges of high velocity zones. Similar results were obtained for both the ETSZ and the CSZ. A prominent low-velocity zone was detected in the ETSZ; most earthquakes occur in rocks that surround the lowest-velocity regions. An elongated, high velocity region is present at mid-crustal depths in the CSZ; earthquakes avoid the high velocity body and separate into two bands, one on either side of the feature. Larger earthquakes (exceeding magnitude 4) have occurred along the northern edge of the high velocity region. Our results suggest that earthquakes in SCR seismic zones tend to occur in rocks where strain energy is concentrating. This observation is consistent with results from high resolution tomographic images of fault zones in California.

  8. Edge-injective and edge-surjective vertex labellings

    DEFF Research Database (Denmark)

    Brandt, Stephan; Rautenbach, D.; Regen, F.;

    2010-01-01

    For a graph G = (V, E) we consider vertex-k-labellings f : V → {1,2, ,k} for which the induced edge weighting w : E → {2, 3,., 2k} with w(uv) = f(u) + f(v) is injective or surjective or both. We study the relation between these labellings and the number theoretic notions of an additive basis...... a recent conjecture of Ivančo and Jendroł concerning edge-irregular total labellings for graphs that are sparse enough. © 2010 Societ y for Industrial and Applied Mathematics....

  9. Mantle structure beneath the western edge of the Colorado Plateau

    Science.gov (United States)

    Sine, C.R.; Wilson, D.; Gao, W.; Grand, S.P.; Aster, R.; Ni, J.; Baldridge, W.S.

    2008-01-01

    Teleseismic traveltime data are inverted for mantle Vp and Vs variations beneath a 1400 km long line of broadband seismometers extending from eastern New Mexico to western Utah. The model spans 600 km beneath the moho with resolution of ???50 km. Inversions show a sharp, large-magnitude velocity contrast across the Colorado Plateau-Great Basin transition extending ???200 km below the crust. Also imaged is a fast anomaly 300 to 600 km beneath the NW portion of the array. Very slow velocities beneath the Great Basin imply partial melting and/or anomalously wet mantle. We propose that the sharp contrast in mantle velocities across the western edge of the Plateau corresponds to differential lithospheric modification, during and following Farallon subduction, across a boundary defining the western extent of unmodified Proterozoic mantle lithosphere. The deep fast anomaly corresponds to thickened Farallon plate or detached continental lithosphere at transition zone depths. Copyright 2008 by the American Geophysical Union.

  10. Oscillations of a Turbulent Jet Incident Upon an Edge

    Energy Technology Data Exchange (ETDEWEB)

    J.C. Lin; D. Rockwell

    2000-09-19

    For the case of a jet originating from a fully turbulent channel flow and impinging upon a sharp edge, the possible onset and nature of coherent oscillations has remained unexplored. In this investigation, high-image-density particle image velocimetry and surface pressure measurements are employed to determine the instantaneous, whole-field characteristics of the turbulent jet-edge interaction in relation to the loading of the edge. It is demonstrated that even in absence of acoustic resonant or fluid-elastic effects, highly coherent, self-sustained oscillations rapidly emerge above the turbulent background. Two clearly identifiable modes of instability are evident. These modes involve large-scale vortices that are phase-locked to the gross undulations of the jet and its interaction with the edge, and small-scale vortices, which are not phase-locked. Time-resolved imaging of instantaneous vorticity and velocity reveals the form, orientation, and strength of the large-scale concentrations of vorticity approaching the edge in relation to rapid agglomeration of small-scale vorticity concentrations. Such vorticity field-edge interactions exhibit rich complexity, relative to the simplified pattern of vortex-edge interaction traditionally employed for the quasi-laminar edgetone. Furthermore, these interactions yield highly nonlinear surface pressure signatures. The origin of this nonlinearity, involving coexistence of multiple frequency components, is interpreted in terms of large- and small-scale vortices embedded in distributed vorticity layers at the edge. Eruption of the surface boundary layer on the edge due to passage of the large-scale vortex does not occur; rather apparent secondary vorticity concentrations are simply due to distension of the oppositely-signed vorticity layer at the tip of the edge. The ensemble-averaged turbulent statistics of the jet quickly take on an identity that is distinct from the statistics of the turbulent boundary layer in the channel

  11. Wave propagation and group velocity

    CERN Document Server

    Brillouin, Léon

    1960-01-01

    Wave Propagation and Group Velocity contains papers on group velocity which were published during the First World War and are missing in many libraries. It introduces three different definitions of velocities: the group velocity of Lord Rayleigh, the signal velocity of Sommerfeld, and the velocity of energy transfer, which yields the rate of energy flow through a continuous wave and is strongly related to the characteristic impedance. These three velocities are identical for nonabsorbing media, but they differ considerably in an absorption band. Some examples are discussed in the last chapter

  12. Correction of edge-flame propagation speed in a counterflow, annular slot burner

    KAUST Repository

    Tran, Vu Manh

    2015-10-22

    To characterize the propagation modes of flames, flame propagation speed must be accurately calculated. The impact of propagating edge-flames on the flow fields of unburned gases is limited experimentally. Thus, few studies have evaluated true propagation speeds by subtracting the flow velocities of unburned gases from flame displacement speeds. Here, we present a counterflow, annular slot burner that provides an ideal one-dimensional strain rate and lengthwise zero flow velocity that allowed us to study the fundamental behaviors of edge-flames. In addition, our burner has easy optical access for detailed laser diagnostics. Flame displacement speeds were measured using a high-speed camera and related flow fields of unburned gases were visualized by particle image velocimetry. These techniques allowed us to identify significant modifications to the flow fields of unburned gases caused by thermal expansion of the propagating edges, which enabled us to calculate true flame propagation speeds that took into account the flow velocities of unburned gases.

  13. Edges and Corners With Shearlets.

    Science.gov (United States)

    Duval-Poo, Miguel A; Odone, Francesca; De Vito, Ernesto

    2015-11-01

    Shearlets are a relatively new and very effective multi-scale framework for signal analysis. Contrary to the traditional wavelets, shearlets are capable to efficiently capture the anisotropic information in multivariate problem classes. Therefore, shearlets can be seen as the valid choice for multi-scale analysis and detection of directional sensitive visual features like edges and corners. In this paper, we start by reviewing the main properties of shearlets that are important for edge and corner detection. Then, we study algorithms for multi-scale edge and corner detection based on the shearlet representation. We provide an extensive experimental assessment on benchmark data sets which empirically confirms the potential of shearlets feature detection. PMID:26353351

  14. Continued Growth on Graphene Edges

    Science.gov (United States)

    Luo, Zhengtang

    Previously, we have shown that the large-size single crystal graphene can be obtained by suppressing the nucleation density during Chemical Vapor Deposition (CVD) growth. Here we demonstrate that the graphene single crystal can be amplified by a continued growth method. In this process, we used a mild oxidation step after the first-growth, which lead to the observed fromation of oxides at the vicinity of graphene edges, which allows the graphene growth at seed edges due to reduced activation energy. Consequently, we successful grown a secondary single-crystal graphene structures with the same lattice structure, orientation on the graphene edges. This amplification method would enable the production of graphene electronics with controlled properties.

  15. All-graphene edge contacts

    DEFF Research Database (Denmark)

    Jacobsen, Kåre Wedel; Falkenberg, Jesper Toft; Papior, Nick Rübner;

    2016-01-01

    Using ab-initio methods we investigate the possibility of three-terminalgraphene "T-junction" devices and show that these all-graphene edge contactsare energetically feasible when the 1D interface itself is free from foreignatoms. We examine the energetics of various junction structures...... to be in therange of 1-10 kΩμm which is comparable to the best contact resistance reportedfor edge-contacted graphene-metal contacts. We conclude that conductingall-carbon T-junctions should be feasible....

  16. Edge shape and comfort of rigid lenses.

    Science.gov (United States)

    La Hood, D

    1988-08-01

    One of the main factors determining the comfort of a rigid contact lens is the shape of the edge. The comfort of four different contact lens edge shapes was assessed with four unadapted subjects in a randomized masked trial. Lenses with well rounded anterior edge profiles were found to be significantly more comfortable than lenses with square anterior edges. There was no significant difference in subjective comfort between a rounded and square posterior edge profile. The results suggest that the interaction of the edge with the eyelid is more important in determining comfort than edge effects on the cornea, when lenses are fitted according to a corneal alignment philosophy. PMID:3177585

  17. Edge detection based on morphological amoebas

    CERN Document Server

    Lee, Won Yeol; Kim, Se Yun; Lim, Jae Young; Lim, Dong Hoon

    2011-01-01

    Detecting the edges of objects within images is critical for quality image processing. We present an edge-detecting technique that uses morphological amoebas that adjust their shape based on variation in image contours. We evaluate the method both quantitatively and qualitatively for edge detection of images, and compare it to classic morphological methods. Our amoeba-based edge-detection system performed better than the classic edge detectors.

  18. Design and Simulation of Canny Edge Detection

    OpenAIRE

    D Narayana Reddy*; Vaijanath V.Yerigeri; Harish Sanu

    2014-01-01

    Edge is one of the prominent features in the image processing applications. The edge detection algorithm is carried out by using different methods. Canny edge algorithm is one of the well known edge detection algorithm. In proposed design, the canny edge detection algorithm is designed in verilog and simulated using the MATLAB and Modelsim. The input image is converted to text/pixel values using MATLAB and is stored in a new text file. Verilog with test bench program is used to as...

  19. A Signature of Self-Organized Criticality in the HT-6M Edge Plasma Turbulence

    Institute of Scientific and Technical Information of China (English)

    WANG Wen-Hao; YU Chang-Xuan; WEN Yi-Zhi; XU Yu-Hong; LING Bi-Li; GONG Xian-Zu; LIU Bao-Hua; WAN Bao-Nian

    2001-01-01

    ower spectra of electron density and floating potential fluctuations in the velocity shear layer of the HT-6M edge region have been measured and analysed. All the spectra have three distinct frequency regions with the spectral decay indices typical of self-organized criticality systems (0, -1 and -4) when Doppler shift effects induced by the plasma E × B flow velocity have been taken into account. These results are consistent with the predictions of the self-organized criticality models, which may be an indication of edge plasma turbulence in the HT-6M tokamak evolving into a critical state independent of local plasma parameters.

  20. At the edge of intonation

    DEFF Research Database (Denmark)

    Niebuhr, Oliver

    2012-01-01

    The paper is concerned with the 'edge of intonation' in a twofold sense. It focuses on utterance-final F0 movements and crosses the traditional segment-prosody divide by investigating the interplay of F0 and voiceless fricatives in speech production. An experiment was performed for German with four...

  1. Edge classification for color constancy

    NARCIS (Netherlands)

    A. Gijsenij; T. Gevers; J. van de Weijer

    2008-01-01

    The goal of color constancy is to measure image colors despite differences in the color of the light source. Traditionally, the computational method of obtaining this ability is by using pixel values only. Recently, methods using edges instead of pixel values have been proposed. However, different e

  2. The Problem of the Edge.

    Science.gov (United States)

    Faatz, Judith A.

    1998-01-01

    Describes a field study in a local ecosystem which allows high school students to investigate the edge effect, where a meadow and a forest meet. Students measure soil moisture content, soil temperature, air temperature, relative humidity, wind intensity, and illumination level. Teachers can help students apply their findings to understand problems…

  3. Introduction to vector velocity imaging

    DEFF Research Database (Denmark)

    Jensen, Jørgen Arendt; Udesen, Jesper; Hansen, Kristoffer Lindskov;

    Current ultrasound scanners can only estimate the velocity along the ultrasound beam and this gives rise to the cos() factor on all velocity estimates. This is a major limitation as most vessels are close to perpendicular to the beam. Also the angle varies as a function of space and time making...... it virtually impossible to compensate for the factor and obtain correct velocity estimates for either CFM or spectral velocity estimation. This talk will describe methods for finding the correct velocity by estimating both the axial and lateral component of the velocity vector. The transverse oscillation...... method introduces an ultrasound field that oscillation not only along the ultrasound beam both also transverse to it to estimate both the lateral and axial velocity for the full velocity vector. The correct velocity magnitude can be found from this as well as the instantaneous angle. This can be obtained...

  4. Poloidal rotation induced by injecting lower hybrid waves in tokamak plasma edge

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The poloidal rotation of the magnetized edge plasma in tokamak driven by theponderomotive force which is generated by injecting lower hybrid wave(LHW) electric field hasbeen studied. The LHW is launched from a waveguide in the plasma edge, and by Brambilla’sgrill theory, analytic expressions for the wave electric field in the slab model of an inhomogeneouscold plasma have been derived. It is shown that a strong wave electric field will be generated inthe plasma edge by injecting LH wave of the power in MW magnitude, and this electric field willinduce a poloidal rotation with a sheared poloidal velocity.PACS: 52.55.Fa

  5. Transverse velocity shifts in protostellar jets: rotation or velocity asymmetries?

    CERN Document Server

    De Colle, Fabio; Riera, Angels

    2016-01-01

    Observations of several protostellar jets show systematic differences in radial velocity transverse to the jet propagation direction, which have been interpreted as evidence of rotation in the jets. In this paper we discuss the origin of these velocity shifts, and show that they could be originated by rotation in the flow, or by side to side asymmetries in the shock velocity, which could be due to asymmetries in the jet ejection velocity/density or in the ambient medium. For typical poloidal jet velocities (~ 100-200 km/s), an asymmetry >~ 10% can produce velocity shifts comparable to those observed. We also present three dimensional numerical simulations of rotating, precessing and asymmetric jets, and show that, even though for a given jet there is a clear degeneracy between these effects, a statistical analysis of jets with different inclination angles can help to distinguish between the alternative origins of transverse velocity shifts. Our analysis indicate that side to side velocities asymmetries could ...

  6. Vertices of degree k in edge-minimal, k-edge-connected graphs

    OpenAIRE

    Kingsford, Carl; Marçais, Guillaume

    2009-01-01

    Halin showed that every edge minimal, k-vertex connected graph has a vertex of degree k. In this note, we prove the analogue to Halin's theorem for edge-minimal, k-edge-connected graphs. We show there are two vertices of degree k in every edge-minimal, k-edge-connected graph.

  7. Particle rebound characteristics of turbomachinery cascade leading edge geometry

    Science.gov (United States)

    Siravuri, Sastri

    The objective of this research work is to investigate and understand the complex phenomena associated with the mechanism of particle impacts on turbomachinery cascade leading edge geometry. At present, there is a need for experimental work in basic and applied research to find out the parameters that are relevant to particle rebound characteristics on turbomachinery blades. In the present work, experiments were conducted with air velocity at 15 m/s (˜50 ft/sec) and at 30 m/s (˜100 ft/sec) using high-speed photography and Laser Doppler Velocimetry (LDV). Silica sand particles of 1000--1500 micron size were used for this study. In the present investigation, particle rebound data was obtained for cylindrical targets with radius of curvature representative of leading edge geometry (cylinder diameter = 4.5mm & 6.5 mm) using LDV. The numerical simulations, which are based on non-linear dynamic analysis, were also performed using the finite element code DYNA3-D. Several different material models viz elastic-elastic, elastic-plastic, elastic-plastic with friction & isotropic-elastic-plastic with dynamic friction and particle rotation were used in the DYNA3-D numerical analysis. The computational results include a time history of the displacement, stress and strain profiles through the particle collision. Numerical results are presented for the rebound conditions of spherical silica sand particle for different pre-collision velocities. The computed particle restitution coefficients, after they reach steady rebound conditions, are compared with experimental results obtained from LDV. A probabilistic model was developed to incorporate the uncertainties in the impact velocity in the numerical model. Histograms and Cumulative Distribution Functions (CDFs) for impact velocity were obtained from experimental LDV data. Ten randomly selected probabilities for each impact angle were used to calculate the impact velocity from cumulative distribution function. This randomly selected

  8. ELECTROSTATIC MODE ASSOCIATED WITH PINCH VELOCITY IN RFPS

    Energy Technology Data Exchange (ETDEWEB)

    DELZANNO, GIAN LUCA [Los Alamos National Laboratory; FINN, JOHN M. [Los Alamos National Laboratory; CHACON, LUIS [Los Alamos National Laboratory

    2007-02-08

    The existence of a new electrostatic instability is shown for RFP (reversed field pinch) equilibria. This mode arises due to the non-zero equilibrium radial flow (pinch flow). In RFP simulations with no-stress boundary conditions on the tangential velocity at the radial wall, this electrostatic mode is unstable and dominates the nonlinear dynamics, even in the presence of the MHD modes typically responsible for the reversal of the axial magnetic field at edge. Nonlinearly, this mode leads to two beams moving azimuthally towards each other, which eventually collide. The electrostatic mode can be controlled by using Dirichlet (no-slip) boundary conditions on the azimuthal velocity at the radial wall.

  9. Dark Matter Velocity Spectroscopy

    CERN Document Server

    Speckhard, Eric G; Beacom, John F; Laha, Ranjan

    2016-01-01

    Dark matter decays or annihilations that produce line-like spectra may be smoking-gun signals. However, even such distinctive signatures can be mimicked by astrophysical or instrumental causes. We show that velocity spectroscopy-the measurement of energy shifts induced by relative motion of source and observer-can separate these three causes with minimal theoretical uncertainties. The principal obstacle has been energy resolution, but upcoming and proposed experiments will make significant improvements. As an example, we show that the imminent Astro-H mission can use Milky Way observations to separate possible causes of the 3.5-keV line. We discuss other applications.

  10. Dark Matter Velocity Spectroscopy.

    Science.gov (United States)

    Speckhard, Eric G; Ng, Kenny C Y; Beacom, John F; Laha, Ranjan

    2016-01-22

    Dark matter decays or annihilations that produce linelike spectra may be smoking-gun signals. However, even such distinctive signatures can be mimicked by astrophysical or instrumental causes. We show that velocity spectroscopy-the measurement of energy shifts induced by relative motion of source and observer-can separate these three causes with minimal theoretical uncertainties. The principal obstacle has been energy resolution, but upcoming experiments will have the precision needed. As an example, we show that the imminent Astro-H mission can use Milky Way observations to separate possible causes of the 3.5-keV line. We discuss other applications.

  11. Determination of the velocity

    OpenAIRE

    Kopp, Robert William

    1989-01-01

    Hypervelocity flows for velocities is excess of 1.4 km/sec (Mach 5) require very high stagnation temperature to avoid liquefaction. The arc heater wind tunnel has been designed to provide such flows. The electric-are driven wind tunnel can develop stagnation temperatures up to 13,000 K which will produce hypervelocity flows up to 7 km/sec (earth orbital speed). The nature of the flow, however, is such that the high temperature source flow may cause severe gradients at the nozzle exit. In orde...

  12. Mechanism of Water Droplet Breakup Near the Leading Edge of an Airfoil

    Science.gov (United States)

    Vargas, Mario; Sor, Suthyvann; Magarino, Adelaida, Garcia

    2012-01-01

    This work presents results of an experimental study on droplet deformation and breakup near the leading edge of an airfoil. The experiment was conducted in the rotating rig test cell at the Instituto Nacional de Tecnica Aeroespacial (INTA) in Madrid, Spain. The airfoil model was placed at the end of the rotating arm and a monosize droplet generator produced droplets that fell from above, perpendicular to the path of the airfoil. The interaction between the droplets and the airfoil was captured with high speed imaging and allowed observation of droplet deformation and breakup as the droplet approached the airfoil near the stagnation line. Image processing software was used to measure the position of the droplet centroid, equivalent diameter, perimeter, area, and the major and minor axes of an ellipse superimposed over the deforming droplet. The horizontal and vertical displacement of each droplet against time was also measured, and the velocity, acceleration, Weber number, Bond number, Reynolds number, and the drag coefficients were calculated along the path of the droplet to the beginning of breakup. Droplet deformation is defined and studied against main parameters. The high speed imaging allowed observation of the actual mechanism of breakup and identification of the sequence of configurations from the initiation of the breakup to the disintegration of the droplet. Results and comparisons are presented for droplets of diameters in the range of 500 to 1800 microns, and airfoil velocities of 70 and 90 m/sec.

  13. Drag Coefficient of Water Droplets Approaching the Leading Edge of an Airfoil

    Science.gov (United States)

    Vargas, Mario; Sor, Suthyvann; Magarino, Adelaida Garcia

    2013-01-01

    This work presents results of an experimental study on droplet deformation and breakup near the leading edge of an airfoil. The experiment was conducted in the rotating rig test cell at the Instituto Nacional de Tecnica Aeroespacial (INTA) in Madrid, Spain. An airfoil model was placed at the end of the rotating arm and a monosize droplet generator produced droplets that fell from above, perpendicular to the path of the airfoil. The interaction between the droplets and the airfoil was captured with high speed imaging and allowed observation of droplet deformation and breakup as the droplet approached the airfoil near the stagnation line. Image processing software was used to measure the position of the droplet centroid, equivalent diameter, perimeter, area, and the major and minor axes of an ellipse superimposed over the deforming droplet. The horizontal and vertical displacement of each droplet against time was also measured, and the velocity, acceleration, Weber number, Bond number, Reynolds number, and the drag coefficients were calculated along the path of the droplet to the beginning of breakup. Results are presented and discussed for drag coefficients of droplets with diameters in the range of 300 to 1800 micrometers, and airfoil velocities of 50, 70 and 90 meters/second. The effect of droplet oscillation on the drag coefficient is discussed.

  14. Edge detection based on directional space

    Institute of Scientific and Technical Information of China (English)

    YUAN Wei-qi; LI De-sheng

    2006-01-01

    A new method for edge detection based on directional space is proposed.The principle is that:firstly,the directional differential space is set up in which the ridge edge pixels and valley edge pixels are abstracted with the help of the method of logical judgments along the direction of differential function,forming a directional roof edge map;secondly,step edge pixels are abstracted between the neighboring directional ridge edge and directional valley edge along the direction of differential function;finally,the ridge edge map,valley edge map and step edge map gained along different directions are combined into corresponding ridge edge map,valley edge map and step edge map.This method is different from classical algorithms in which the gray differential values of the mutual vertical direction are combined into one gradient value.The experiment of edge detection is made for the images of nature scenery,human body and accumulative raw material,whose result is compared with the one of classical algorithms and showing the robustness of the proposed method.

  15. Reynolds Stress and Sheared Poloidal Flow in the Edge Plasma Region of the HT-6M Tokamak

    Institute of Scientific and Technical Information of China (English)

    WANG Wen-Hao; YU Chang-Xuan; XU Yu-Hong; LING Bi-Li; GONG Xian-Zu; LIU Bao-Hua; WAN Bao-Nian

    2001-01-01

    High spatial resolution measurements of the electrostatic Reynolds stress, radial electric field and poloidal phase velocity of fluctuations in the edge region of the HT-6M tokamak are carried out. The Reynolds stress shows a radial gradient in proximity to the poloidal velocity shear. A comparison of the profiles between the Reynolds stress gradient and the poloidal velocity damping reveals some similarity in their magnitude and radial structure. These facts suggest that the turbulence-induced Reynolds stress may play a significant role in generating the poloidal flow in the plasma edge region.

  16. Numerical Investigation on Dynamic Crushing Behavior of Auxetic Honeycombs with Various Cell-Wall Angles

    Directory of Open Access Journals (Sweden)

    Xin-chun Zhang

    2015-02-01

    Full Text Available Auxetic honeycombs have proven to be an attractive advantage in actual engineering applications owing to their unique mechanical characteristic and better energy absorption ability. The in-plane dynamic crushing behaviors of the honeycombs with various cell-wall angles are studied by means of explicit dynamic finite element simulation. The influences of the cell-wall angle, the impact velocity, and the edge thickness on the macro/microdeformation behaviors, the plateau stresses, and the specific energy absorption of auxetic honeycombs are discussed in detail. Numerical results show, that except for the impact velocity and the edge thickness, the in-plane dynamic performances of auxetic honeycombs also rely on the cell-wall angle. The “> <”-mode local deformation bands form under low- or moderate-velocity impacting, which results in lateral compression shrinkage and shows negative Poisson's ratio during the crushing. For the given impact velocity, the plateau stress at the proximal end and the energy-absorbed ability can be improved by increasing the negative cell angle, the relative density, the impact velocity, and the matrix material strength. When the microcell parameters are the constant, the plateau stresses are proportional to the square of impact velocity.

  17. CFAR Edge Detector for Polarimetric SAR Images

    DEFF Research Database (Denmark)

    Schou, Jesper; Skriver, Henning; Nielsen, Allan Aasbjerg;

    2003-01-01

    Finding the edges between different regions in an image is one of the fundamental steps of image analysis, and several edge detectors suitable for the special statistics of synthetic aperture radar (SAR) intensity images have previously been developed. In this paper, a new edge detector for polar......Finding the edges between different regions in an image is one of the fundamental steps of image analysis, and several edge detectors suitable for the special statistics of synthetic aperture radar (SAR) intensity images have previously been developed. In this paper, a new edge detector...

  18. Edge-on thick discs

    Science.gov (United States)

    Kasparova, A.; Katkov, I.; Chilingarian, I.; Silchenko, O.; Moiseev, A.; Borisov, S.

    2016-06-01

    Although thick stellar discs are detected in nearly all edge-on disc galaxies, their formation scenarios still remain a matter of debate. Due to observational difficulties, there is a lack of information about their stellar populations. Using the Russian 6-m telescope BTA we collected deep spectra of thick discs in three edge-on early-type disc galaxies located in different environments: NGC4111 in a dense group, NGC4710 in the Virgo cluster, and NGC5422 in a sparse group. We see intermediate age (4 ‑ 5 Gyr) metal rich ([Fe/H] ~ ‑0.2 ‑ 0.0 dex) stellar populations in NGC4111 and NGC4710. On the other hand, NGC5422 does not harbour young stars, its only disc is thick and old (10 Gyr) and its α-element abundance suggests a long formation epoch implying its formation at high redshift. Our results prove the diversity of thick disc formation scenarios.

  19. Precise Near-Infrared Radial Velocities

    CERN Document Server

    Plavchan, Peter; Gagne, Jonathan; Furlan, Elise; Brinkworth, Carolyn; Bottom, Michael; Tanner, Angelle; Anglada-Escude, Guillem; White, Russel; Davison, Cassy; Mills, Sean; Beichman, Chas; Johnson, John Asher; Ciardi, David; Wallace, Kent; Mennesson, Bertrand; Vasisht, Gautam; Prato, Lisa; Kane, Stephen; Crawford, Sam; Crawford, Tim; Sung, Keeyoon; Drouin, Brian; Lin, Sean; Leifer, Stephanie; Catanzarite, Joe; Henry, Todd; von Braun, Kaspar; Walp, Bernie; Geneser, Claire; Ogden, Nick; Stufflebeam, Andrew; Pohl, Garrett; Regan, Joe

    2016-01-01

    We present the results of two 2.3 micron near-infrared radial velocity surveys to detect exoplanets around 36 nearby and young M dwarfs. We use the CSHELL spectrograph (R ~46,000) at the NASA InfraRed Telescope Facility, combined with an isotopic methane absorption gas cell for common optical path relative wavelength calibration. We have developed a sophisticated RV forward modeling code that accounts for fringing and other instrumental artifacts present in the spectra. With a spectral grasp of only 5 nm, we are able to reach long-term radial velocity dispersions of ~20-30 m/s on our survey targets.

  20. Direct Ejecta Velocity Measurements of Tycho's Supernova Remnant

    CERN Document Server

    Sato, Toshiki

    2016-01-01

    We present the first direct ejecta velocity measurements of Tycho's supernova remnant (SNR). Chandra's high angular resolution images reveal a patchy structure of radial velocities in the ejecta that can be separated into distinct redshifted, blueshifted, and low velocity ejecta clumps or blobs. The typical velocities of the redshifted and blueshifted blobs are <~ 7,800 km/s and <~ 5,000 km/s, respectively. The highest velocity blobs are located near the center, while the low velocity ones appear near the edge as expected for a generally spherical expansion. Systematic uncertainty on the velocity measurements from gain calibration was assessed by carrying out joint fits of individual blobs with both the ACIS-I and ACIS-S detectors. We identified an annular region (~3.3'-3.5'), where the surface brightness in the Si, S, and Fe K lines reaches a peak while the line width reaches a minimum value. These minimum line widths correspond to ion temperatures of ~1 MeV for each of the three species, in excellent ...

  1. EDGE-ORIENTED HEXAGONAL ELEMENTS

    Institute of Scientific and Technical Information of China (English)

    Chao Yang; Jiachang Sun

    2007-01-01

    In this paper, two new nonconforming hexagonal elements are presented, which are based on the trilinear function space Q(3)1 and are edge-oriented, analogical to the case of the rotated Q1 quadrilateral element. A priori error estimates are given to show that the new elements achieve first-order accuracy in the energy norm and second-order accuracy in the L2 norm. This theoretical result is confirmed by the numerical tests.

  2. Edge-driven microplate kinematics

    Science.gov (United States)

    Schouten, Hans; Klitgord, Kim D.; Gallo, David G.

    1993-01-01

    It is known from plate tectonic reconstructions that oceanic microplates undergo rapid rotation about a vertical axis and that the instantaneous rotation axes describing the microplate's motion relative to the bounding major plates are frequently located close to its margins with those plates, close to the tips of propagating rifts. We propose a class of edge-driven block models to illustrate how slip across the microplate margins, block rotation, and propagation of rifting may be related to the relative motion of the plates on either side. An important feature of these edge-driven models is that the instantaneous rotation axes are always located on the margins between block and two bounding plates. According to those models the pseudofaults or traces of disrupted seafloor resulting from the propagation of rifting between microplate and major plates may be used independently to approximately trace the continuous kinematic evolution of the microplate back in time. Pseudofault geometries and matching rotations of the Easter microplate show that for most of its 5 m.y. history, block rotation could be driven by the drag of the Nazca and Pacific plates on the microplate's edges rather than by a shear flow of mantle underneath.

  3. Leading Edge Device Aerodynamic Optimization

    Directory of Open Access Journals (Sweden)

    Marius Gabriel COJOCARU

    2015-12-01

    Full Text Available Leading edge devices are conventionally used as aerodynamic devices that enhance performances during landing and in some cases during takeoff. The need to increase the efficiency of the aircrafts has brought the idea of maintaining as much as possible a laminar flow over the wings. This is possible only when the leading edge of the wings is free from contamination, therefore using the leading edge devices with the additional role of shielding during takeoff. Such a device based on the Krueger flap design is aerodynamically analyzed and optimized. The optimization comprises three steps: first, the positioning of the flap such that the shielding criterion is kept, second, the analysis of the flap size and third, the optimization of the flap shape. The first step is subject of a gradient based optimization process of the position described by two parameters, the position along the line and the deflection angle. For the third step the Adjoint method is used to gain insight on the shape of the Krueger flap that will extend the most the stall limit. All these steps have been numerically performed using Ansys Fluent and the results are presented for the optimized shape in comparison with the baseline configuration.

  4. Continuum Edge Gyrokinetic Theory and Simulations

    Energy Technology Data Exchange (ETDEWEB)

    Xu, X Q; Xiong, Z; Dorr, M R; Hittinger, J A; Bodi, K; Candy, J; Cohen, B I; Cohen, R H; Colella, P; Kerbel, G D; Krasheninnikov, S; Nevins, W M; Qin, H; Rognlien, T D; Snyder, P B; Umansky, M V

    2007-01-09

    The following results are presented from the development and application of TEMPEST, a fully nonlinear (full-f) five dimensional (3d2v) gyrokinetic continuum edge-plasma code. (1) As a test of the interaction of collisions and parallel streaming, TEMPEST is compared with published analytic and numerical results for endloss of particles confined by combined electrostatic and magnetic wells. Good agreement is found over a wide range of collisionality, confining potential, and mirror ratio; and the required velocity space resolution is modest. (2) In a large-aspect-ratio circular geometry, excellent agreement is found for a neoclassical equilibrium with parallel ion flow in the banana regime with zero temperature gradient and radial electric field. (3) The four-dimensional (2d2v) version of the code produces the first self-consistent simulation results of collisionless damping of geodesic acoustic modes and zonal flow (Rosenbluth-Hinton residual) with Boltzmann electrons using a full-f code. The electric field is also found to agree with the standard neoclassical expression for steep density and ion temperature gradients in the banana regime. In divertor geometry, it is found that the endloss of particles and energy induces parallel flow stronger than the core neoclassical predictions in the SOL. (5) Our 5D gyrokinetic formulation yields a set of nonlinear electrostatic gyrokinetic equations that are for both neoclassical and turbulence simulations.

  5. Nonreference Medical Image Edge Map Measure

    Directory of Open Access Journals (Sweden)

    Karen Panetta

    2014-01-01

    Full Text Available Edge detection is a key step in medical image processing. It is widely used to extract features, perform segmentation, and further assist in diagnosis. A poor quality edge map can result in false alarms and misses in cancer detection algorithms. Therefore, it is necessary to have a reliable edge measure to assist in selecting the optimal edge map. Existing reference based edge measures require a ground truth edge map to evaluate the similarity between the generated edge map and the ground truth. However, the ground truth images are not available for medical images. Therefore, a nonreference edge measure is ideal for medical image processing applications. In this paper, a nonreference reconstruction based edge map evaluation (NREM is proposed. The theoretical basis is that a good edge map keeps the structure and details of the original image thus would yield a good reconstructed image. The NREM is based on comparing the similarity between the reconstructed image with the original image using this concept. The edge measure is used for selecting the optimal edge detection algorithm and optimal parameters for the algorithm. Experimental results show that the quantitative evaluations given by the edge measure have good correlations with human visual analysis.

  6. Minimal information in velocity space

    CERN Document Server

    Evrard, Guillaume

    1995-01-01

    Jaynes' transformation group principle is used to derive the objective prior for the velocity of a non-zero rest-mass particle. In the case of classical mechanics, invariance under the classical law of addition of velocities, leads to an improper constant prior over the unbounded velocity space of classical mechanics. The application of the relativistic law of addition of velocities leads to a less simple prior. It can however be rewritten as a uniform volumetric distribution if the relativistic velocity space is given a non-trivial metric.

  7. Pulsed supersonic helium beams for plasma edge diagnosis

    Science.gov (United States)

    Diez-Rojo, T.; Herrero, V. J.; Tanarro, I.; Tabarés, F. L.; Tafalla, D.

    1997-03-01

    An experimental setup for the production of pulsed supersonic He beams to be used for plasma edge diagnosis in fusion devices is described. A compromise between compact design, low cost, and good quality of the probe beams has been met. The main characteristics of the generated beams, such as pulse shape, absolute flux intensity, and velocity distribution, differ in general from those expected for ideal beam performance and have been determined and optimized experimentally. A first test of this He beam source at the TJ-I UP Torsatron in Madrid is also reported.

  8. Pulsed supersonic helium beams for plasma edge diagnosis

    Energy Technology Data Exchange (ETDEWEB)

    Diez-Rojo, T.; Herrero, V.J.; Tanarro, I. [Instituto de Estructura de la Materia (CSIC), Serrano 123, 28006 Madrid (Spain); Tabares, F.L.; Tafalla, D. [Asociacion EURATOM-CIEMAT para Fusion, Avenue Complutense 22, 28040 Madrid (Spain)

    1997-03-01

    An experimental setup for the production of pulsed supersonic He beams to be used for plasma edge diagnosis in fusion devices is described. A compromise between compact design, low cost, and good quality of the probe beams has been met. The main characteristics of the generated beams, such as pulse shape, absolute flux intensity, and velocity distribution, differ in general from those expected for ideal beam performance and have been determined and optimized experimentally. A first test of this He beam source at the TJ-I UP Torsatron in Madrid is also reported. {copyright} {ital 1997 American Institute of Physics.}

  9. Edge effect on weevils and spiders

    Directory of Open Access Journals (Sweden)

    R. Horváth

    2002-05-01

    Full Text Available The edge effect on weevils and spiders was tested along oak forest – meadow transects using sweep-net samples at the Síkfökút Project in Hungary. For spiders the species richness was significantly higher in the forest edge than either in the meadow or the forest interior. For weevils the species richness of the forest edge was higher than that of the meadow, but the difference was not statistically significant whereas the species richness of the forest interior was significantly lower than that of the forest edge and the meadow. The composition of the spider assemblage of the edge was more similar to the forest, while the composition of weevils in the edge was more similar to the meadow. Our results based on two invertebrate groups operating on different trophic levels suggest that there is a significant edge effect for the studied taxa resulting in higher species richness in the edge.

  10. Environmental Dataset Gateway (EDG) Search Widget

    Data.gov (United States)

    U.S. Environmental Protection Agency — Use the Environmental Dataset Gateway (EDG) to find and access EPA's environmental resources. Many options are available for easily reusing EDG content in other...

  11. Environmental Dataset Gateway (EDG) REST Interface

    Data.gov (United States)

    U.S. Environmental Protection Agency — Use the Environmental Dataset Gateway (EDG) to find and access EPA's environmental resources. Many options are available for easily reusing EDG content in other...

  12. Chemistry at the Edge of Graphene.

    Science.gov (United States)

    Bellunato, Amedeo; Arjmandi Tash, Hadi; Cesa, Yanina; Schneider, Grégory F

    2016-03-16

    The selective functionalization of graphene edges is driven by the chemical reactivity of its carbon atoms. The chemical reactivity of an edge, as an interruption of the honeycomb lattice of graphene, differs from the relative inertness of the basal plane. In fact, the unsaturation of the pz orbitals and the break of the π conjugation on an edge increase the energy of the electrons at the edge sites, leading to specific chemical reactivity and electronic properties. Given the relevance of the chemistry at the edges in many aspects of graphene, the present Review investigates the processes and mechanisms that drive the chemical functionalization of graphene at the edges. Emphasis is given to the selective chemical functionalization of graphene edges from theoretical and experimental perspectives, with a particular focus on the characterization tools available to investigate the chemistry of graphene at the edge.

  13. Tunable skewed edges in puckered structures

    OpenAIRE

    Grujić, Marko M.; Ezawa, Motohiko; Tadić, Milan Ž.; Peeters, Françios M.

    2015-01-01

    We propose a new type of edges, arising due to the anisotropy inherent in the puckered structure of a honeycomb system such as in phosphorene. Skewed-zigzag and skewed-armchair nanoribbons are semiconducting and metallic, respectively, in contrast to their normal edge counterparts. Their band structures are tunable, and a metal-insulator transition is induced by an electric field. We predict a field-effect transistor based on the edge states in skewed-armchair nanoribbons, where the edge stat...

  14. Impurity and Trace Tritium Transport in Tokamak Edge Turbulence

    CERN Document Server

    Naulin, V

    2004-01-01

    The turbulent transport of impurity or minority species, as for example Tritium, is investigated in drift-Alfv\\'en edge turbulence. The full effects of perpendicular and parallel convection are kept for the impurity species. The impurity density develops a granular structure with steep gradients and locally exceeds its initial values due to the compressibility of the flow. An approximate decomposition of the impurity flux into a diffusive part and an effective convective part (characterized by a pinch velocity) is performed and a net inward pinch effect is recovered. The pinch velocity is explained in terms of Turbulent Equipartition and is found to vary poloidally. The results show that impurity transport modeling needs to be two-dimensional, considering besides the radial direction also the strong poloidal variation in the transport coefficients.

  15. Predicting the Performance of Edge Seal Materials for PV (Presentation)

    Energy Technology Data Exchange (ETDEWEB)

    Kempe, M.; Panchagade, D.; Dameron, A.; Reese, M.

    2012-03-01

    Edge seal materials were evaluated using a 100-nm film of Ca deposited on glass and laminated to another glass substrate. As moisture penetrates the package it converts the Ca metal to transparent CaOH2 giving a clear indication of the depth to which moisture has entered. Using this method, we have exposed test samples to a variety of temperature and humidity conditions ranging from 45C and 10% RH up to 85C and 85% RH, to ultraviolet radiation and to mechanical stress. We are able to show that edge seal materials are capable of keeping moisture away from sensitive cell materials for the life of a module.

  16. Evaluation of edge detectors using avarage risk

    NARCIS (Netherlands)

    Spreeuwers, L.J.; Heijden, van der F.

    1992-01-01

    A new method for evaluation of edge detectors, based on the average risk of a decision, is discussed. The average risk is a performance measure well-known in Bayesian decision theory. Since edge detection can be regarded as a compound decision making process, the performance of an edge detector is

  17. Coronal upflows from edges of an active region observed with EUV Imaging Spectrometer onboard Hinode

    CERN Document Server

    Kitagawa, Naomasa

    2014-01-01

    In order to better understand the plasma supply and leakage at active regions, we investigated physical properties of the upflows from edges of active region NOAA AR10978 observed with the EUV Imaging Spectrometer (EIS) onboard Hinode. Our observational aim is to measure two quantities of the outflows: Doppler velocity and electron density.

  18. On the use of Particle Image Velocimetry to predict trailing edge noise

    NARCIS (Netherlands)

    Tuinstra, M.; Probsting, S.; Scarano, F.

    2013-01-01

    The feasibility of aeroacoustic noise predictions based on Particle Image Velocimetry (PIV) measurements is studied. For this purpose, experiments are conducted on a sharp trailing edge (TE) flow developed along a flat plate at free stream velocity of 15m/s. The acoustic emissions were characterized

  19. Structure and kinematics of edge-on galaxy discs - V. The dynamics of stellar discs

    NARCIS (Netherlands)

    Kregel, M; van der Kruit, PC; Freeman, KC

    2005-01-01

    In earlier papers in this series we determined the intrinsic stellar disc kinematics of 15 intermediate- to late-type edge-on spiral galaxies using a dynamical modelling technique. The sample covers a substantial range in maximum rotation velocity and deprojected face-on surface brightness, and cont

  20. Effect of shear stress on the expression of growth factors in endothelial cells around stent edge%切应力对支架边缘内皮细胞生长因子表达的影响

    Institute of Scientific and Technical Information of China (English)

    王安才; 李利芳; 张步春; 白玲

    2007-01-01

    增生的原因之一.%BACKGROUND:Alterations in secondary hemodynamics around the stent edge can be caused by stent planted. Is there different effect of shear stress on platelet growth factors-A, B (PDGF-A, B) and basic fibroblast growth factor (bFGF) of endothelial cells around stent edge after stent planted?OBJECTIVE: To explore the effect of shear stress on growth factors of endothelial cells around stent edge.DESIGN: Observational comparative study.SETTING: Department of Cardiology, Yijishan Hospital, Wannan Medical College; Laboratory of Biomechanics (National Laboratory), Medical College of Shanghai Jiao Tong University.MATERIALS: The experiment was carried out in the Laboratory of Biomechanics, Medical College of Shanghai Jiaotong University from April to October 2006. The main reagents were detailed as follows: trypsin (Hyclon Company); M-199 medium (Gibco BRL Company); fetal bovine serum (Hangzhou Sijiqing Bioengineering Material Institute); aFGF, Heparin and Hepes (Sigma Company); thymide, Ⅷ factor monoclonal antibody (Rabbit anti-human),biotinylated horse anti-rabbit IgG and propidium lodide (Sigma Company); neonate belly band (Delivery Room of Shanghai the Fifth People's Hospital); trizol (Invitrogene Company); reverse transcription polymerase chain reaction (RT-PCR) kit (Fermentas Company); penicillin/streptomycin (AB/M), objective gene primer (Shanghai Bioengineering Company).METHODS: Traditional parallel-plate streaming cavity was modified into rectangular and gradient shear stress models;while static group was established at the same time. Two shear stress groups were subjected to 11.37 dyne/cm2 and 5.66-14.38 dyne/cm2 shear stress, respectively for 3 hours, 6 hours and 12 hours.MAIN OUTCOME MEASURES: The expressions of PDGF-A, B and bFGF mRNA of human umbilical endothelial cells (HUVECs) were measured by RT-PCR at different time points.RESULTS: Compared with static group, the maximal expression of PDGF-A, B and bFGF mRNA was reached peak at 3 hours in gradient shear stress group and this

  1. Velocity dependant splash behaviour

    Science.gov (United States)

    Hamlett, C. A. E.; Shirtcliffe, N. J.; McHale, G.; Ahn, S.; Doerr, S. H.; Bryant, R.; Newton, M. I.

    2012-04-01

    Extreme soil water repellency can occur in nature via condensation of volatile organic compounds released during wildfires and can lead to increased erosion rate. Such extreme water repellent soil can be classified as superhydrophobic and shares similar chemical and topographical features to specifically designed superhydrophobic surfaces. Previous studies using high speed videography to investigate single droplet impact behaviour on artificial superhydrophobic have revealed three distinct modes of splash behaviour (rebound, pinned and fragmentation) which are dependent on the impact velocity of the droplet. In our studies, using high-speed videography, we show that such splash behaviour can be replicated on fixed 'model' water repellent soils (hydrophobic glass beads/particles). We show that the type of splash behaviour is dependent on both the size and chemical nature of the fixed particles. The particle shape also influences the splash behaviour as shown by drop impact experiments on fixed sand samples. We have also studied soil samples, as collected from the field, which shows that the type of droplet splash behaviour can lead to enhanced soil particle transport.

  2. Particle Velocity Measuring System

    Science.gov (United States)

    Arndt, G. Dickey (Inventor); Carl, James R. (Inventor)

    1998-01-01

    Method and apparatus are provided for determining the velocity of individual food particles within a liquid/solid food mixture that is cooked by an aseptic cooking method whereby the food mixture is heated as it flows through a flowline. At least one upstream and at least one downstream microwave transducer are provided to determine the minimum possible travel time of the fastest food particle through the flowline. In one embodiment, the upstream detector is not required. In another embodiment, a plurality of small dipole antenna markers are secured to a plurality of food particles to provide a plurality of signals as the markers pass the upstream and downstream transducers. The dipole antenna markers may also include a non-linear element to reradiate a harmonic frequency of a transmitter frequency. Upstream and downstream transducers include dipole antennas that are matched to the impedance of the food slurry and a signal transmission cable by various impedance matching means including unbalanced feed to the antennas.

  3. Instant Adobe Edge Inspect starter

    CERN Document Server

    Khan, Joseph

    2013-01-01

    Get to grips with a new technology, understand what it is and what it can do for you, and then get to work with the most important features and tasks. This easy-to-understand Starter guide will get you up to speed with Adobe Edge Inspect quickly and with little effort.This book is for frontend web developers and designers who are developing and testing web applications targeted for mobile browsers. It's assumed that you have a basic understanding of creating web applications using HTML, CSS, and JavaScript, as well as being familiar with running web pages from local HTTP servers. Readers are a

  4. Planar velocity analysis of diesel spray shadow images

    CERN Document Server

    Sedarsky, David; Blaisot, J-B; Rozé, C

    2012-01-01

    The focus of this work is to demonstrate how spatially resolved image information from diesel fuel injection events can be obtained using a forward-scatter imaging geometry, and used to calculate the velocities of liquid structures on the periphery of the spray. In order to obtain accurate velocities directly from individual diesel spray structures, those features need to be spatially resolved in the measurement. The distributed structures measured in a direct shadowgraphy arrangement cannot be reliably analyzed for this kind of velocity information. However, by utilizing an intense collimated light source and adding imaging optics which modify the signal collection, spatially resolved optical information can be retrieved from spray edge regions within a chosen object plane. This work discusses a set of measurements where a diesel spray is illuminated in rapid succession by two ultrafast laser pulses generated by a mode-locked Ti-Sapphire oscillator seeding a matched pair of regenerative amplifiers. Light fro...

  5. Measurement of Poloidal Velocity on the National Spherical Torus Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Ronald E. Bell and Russell Feder

    2010-06-04

    A diagnostic suite has been developed to measure impurity poloidal flow using charge exchange recombination spectroscopy on the National Spherical Torus Experiment. Toroidal and poloidal viewing systems measure all quantities required to determine the radial electric field. Two sets of up/down symmetric poloidal views are used to measure both active emission in the plane of the neutral heating beams and background emission in a radial plane away from the neutral beams. Differential velocity measurements isolate the line-integrated poloidal velocity from apparent flows due to the energy-dependent chargeexchange cross section. Six f/1.8 spectrometers measure 276 spectra to obtain 75 active and 63 background channels every 10 ms. Local measurements from a similar midplane toroidal viewing system are mapped into two dimensions to allow the inversion of poloidal line-integrated measurements to obtain local poloidal velocity profiles. Radial resolution after inversion is 0.6-1.8 cm from the plasma edge to the center.

  6. Tunable skewed edges in puckered structures

    Science.gov (United States)

    Grujić, Marko M.; Ezawa, Motohiko; Tadić, Milan Ž.; Peeters, François M.

    2016-06-01

    We propose a type of edges arising due to the anisotropy inherent in the puckered structure of a honeycomb system such as in phosphorene. Skewed-zigzag and skewed-armchair nanoribbons are semiconducting and metallic, respectively, in contrast to their normal edge counterparts. Their band structures are tunable, and a metal-insulator transition is induced by an electric field. We predict a field-effect transistor based on the edge states in skewed-armchair nanoribbons, where the edge state is gapped by applying arbitrary small electric field Ez. A topological argument is presented, revealing the condition for the emergence of such edge states.

  7. Topological edge states of bound photon pairs

    CERN Document Server

    Gorlach, Maxim A

    2016-01-01

    We predict the existence of interaction-driven edge states of bound two-photon quasiparticles in a dimer periodic array of nonlinear optical cavities. Energy spectrum of photon pairs is dramatically richer than in the noninteracting case or in a simple lattice, featuring collapse and revival of multiple edge and bulk modes as well as edge states in continuum. Despite the unexpected breakdown of the Zak phase technique and the edge mixing of internal and center-of-mass motion we link the edge state existence to the two-photon quantum walk graph connectivity, thus uncovering the topological nature of the many-body problem in complex lattices.

  8. Image edge detection based on beamlet transform

    Institute of Scientific and Technical Information of China (English)

    Li Jing; Huang Peikang; Wang Xiaohu; Pan Xudong

    2009-01-01

    Combining beamlet transform with steerable filters, a new edge detection method based on line gra-dient is proposed. Compared with operators based on point local properties, the edge-detection results with this method achieve higher SNR and position accuracy, and are quite helpful for image registration, object identification, etc. Some edge-detection experiments on optical and SAR images that demonstrate the significant improvement over classical edge operators are also presented. Moreover, the template matching result based on edge information of optical reference image and SAR image also proves the validity of this method.

  9. The anisotropy1 D604N Mutation in the Arabidopsis Cellulose Synthase1 Catalytic Domain Reduces Cell Wall Crystallinity and the Velocity of Cellulose Synthase Complexes1[W][OA

    Science.gov (United States)

    Fujita, Miki; Himmelspach, Regina; Ward, Juliet; Whittington, Angela; Hasenbein, Nortrud; Liu, Christine; Truong, Thy T.; Galway, Moira E.; Mansfield, Shawn D.; Hocart, Charles H.; Wasteneys, Geoffrey O.

    2013-01-01

    Multiple cellulose synthase (CesA) subunits assemble into plasma membrane complexes responsible for cellulose production. In the Arabidopsis (Arabidopsis thaliana) model system, we identified a novel D604N missense mutation, designated anisotropy1 (any1), in the essential primary cell wall CesA1. Most previously identified CesA1 mutants show severe constitutive or conditional phenotypes such as embryo lethality or arrest of cellulose production but any1 plants are viable and produce seeds, thus permitting the study of CesA1 function. The dwarf mutants have reduced anisotropic growth of roots, aerial organs, and trichomes. Interestingly, cellulose microfibrils were disordered only in the epidermal cells of the any1 inflorescence stem, whereas they were transverse to the growth axis in other tissues of the stem and in all elongated cell types of roots and dark-grown hypocotyls. Overall cellulose content was not altered but both cell wall crystallinity and the velocity of cellulose synthase complexes were reduced in any1. We crossed any1 with the temperature-sensitive radial swelling1-1 (rsw1-1) CesA1 mutant and observed partial complementation of the any1 phenotype in the transheterozygotes at rsw1-1’s permissive temperature (21°C) and full complementation by any1 of the conditional rsw1-1 root swelling phenotype at the restrictive temperature (29°C). In rsw1-1 homozygotes at restrictive temperature, a striking dissociation of cellulose synthase complexes from the plasma membrane was accompanied by greatly diminished motility of intracellular cellulose synthase-containing compartments. Neither phenomenon was observed in the any1 rsw1-1 transheterozygotes, suggesting that the proteins encoded by the any1 allele replace those encoded by rsw1-1 at restrictive temperature. PMID:23532584

  10. Influence of elasticity parameters and direction of material axes on velocity of R-waves in thin composite panel

    Directory of Open Access Journals (Sweden)

    Kroupa T.

    2008-11-01

    Full Text Available The paper is aimed at the determination of Rayleigh wave velocity at the edge of a thin unidirectional carbon-epoxy composite panel. Velocities are calculated for various fiber angles and elasticity parameters. Numerical simulation is performed using finite element analysis. Results from the numerical analysis are compared with experimental results and analytical solution.

  11. Haptic Edge Detection Through Shear

    Science.gov (United States)

    Platkiewicz, Jonathan; Lipson, Hod; Hayward, Vincent

    2016-01-01

    Most tactile sensors are based on the assumption that touch depends on measuring pressure. However, the pressure distribution at the surface of a tactile sensor cannot be acquired directly and must be inferred from the deformation field induced by the touched object in the sensor medium. Currently, there is no consensus as to which components of strain are most informative for tactile sensing. Here, we propose that shape-related tactile information is more suitably recovered from shear strain than normal strain. Based on a contact mechanics analysis, we demonstrate that the elastic behavior of a haptic probe provides a robust edge detection mechanism when shear strain is sensed. We used a jamming-based robot gripper as a tactile sensor to empirically validate that shear strain processing gives accurate edge information that is invariant to changes in pressure, as predicted by the contact mechanics study. This result has implications for the design of effective tactile sensors as well as for the understanding of the early somatosensory processing in mammals. PMID:27009331

  12. Examples of Vector Velocity Imaging

    DEFF Research Database (Denmark)

    Hansen, Peter M.; Pedersen, Mads M.; Hansen, Kristoffer L.;

    2011-01-01

    To measure blood flow velocity in vessels with conventional ultrasound, the velocity is estimated along the direction of the emitted ultrasound wave. It is therefore impossible to obtain accurate information on blood flow velocity and direction, when the angle between blood flow and ultrasound wave...... approaches 90°. The majority of the vessels in the human body is parallel to the surface and therefore positioned in a way that prevents proper placement and angulation of the transducer, when the velocity and direction of blood flow is to be estimated. Different techniques to circumvent this problem have...

  13. Hydroxyl induced edge magnetism and metallicity in armchair MoS2 nanoribbons

    Science.gov (United States)

    Cheng, Xue-Mei; Wang, Xue-Feng; Liu, Yu-Sheng; Dong, Yao-Jun; Xu, Long

    2016-03-01

    Based on ab initio density functional theory, we demonstrate systematically how nonmagnetic semiconductor armchair MoS2 nanoribbons (AMoS2NRs) become magnetic or/and metallic when being edge-passivated by OH groups. Both the Mo and S edge atoms of an AMoS2NR can adsorb OH groups but an S atom can catch one OH group only when each of its neighbor Mo atoms has already been passivated by two. The AMoS2NR becomes edge magnetic in low passivation density and edge conductive in high density. In the case of uniform edge passivation, one or both of the edges usually become metallic and nonmagnetic if the number i of OH groups per primitive cell satisfies 1≤slant inanoribbon becomes magnetic semiconductor. For i=8 the nanoribbon become nonmagnetic semiconductor again.

  14. Tokamak edge plasma rotation in the presence of the biased electrode

    Energy Technology Data Exchange (ETDEWEB)

    Ghoranneviss, M.; Mohammadi, S. [Plasma Physics Research Center, Science and Research Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of); Elahi, A. Salar, E-mail: Salari_phy@yahoo.com [Plasma Physics Research Center, Science and Research Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of); Arvin, R. [Plasma Physics Research Center, Science and Research Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of)

    2013-02-15

    Electrode biasing system was designed, constructed, and installed on the IR-T1 tokamak, and then biasing experiments were carried out. Also, using a Mach probes the effects of radial electric field (produced by biased electrode) on the poloidal and toroidal components of the edge plasma velocity were investigated. The results showed an increase in both toroidal and poloidal components of the edge plasma velocity during biasing regime. Results compared and discussed. During positive biasing, increased E{sub r} tends to slow the poloidal rotation in the electron diamagnetic drift direction, i.e., to speed up rotation in the ion diamagnetic drift direction. An increased toroidal rotation velocity has the opposite effect on the poloidal rotation.

  15. Influence of edge conditions on material ejection from periodic grooves in laser shock-loaded tin

    Science.gov (United States)

    de Rességuier, T.; Roland, C.; Prudhomme, G.; Lescoute, E.; Loison, D.; Mercier, P.

    2016-05-01

    In a material subjected to high dynamic compression, the breakout of a shock wave at a rough free surface can lead to the ejection of high velocity debris. Anticipating the ballistic properties of such debris is a key safety issue in many applications involving shock loading, including pyrotechnics and inertial confinement fusion experiments. In this paper, we use laser driven shocks to investigate particle ejection from calibrated grooves of micrometric dimensions and approximately sinusoidal profile in tin samples, with various boundary conditions at the groove edges, including single groove and periodic patterns. Fast transverse shadowgraphy provides ejection velocities after shock breakout. They are found to depend not only on the groove depth and wavelength, as predicted theoretically and already observed in the past, but also, unexpectedly, on the edge conditions, with a jet tip velocity significantly lower in the case of a single groove than behind a periodic pattern.

  16. Velocity and velocity-difference distributions in Burgers turbulence

    OpenAIRE

    Boldyrev, S.; Linde, T.; Polyakov, A.

    2003-01-01

    We consider the one-dimensional Burgers equation randomly stirred at large scales by a Gaussian short-time correlated force. Using the method of dissipative anomalies, we obtain velocity and velocity-difference probability density functions and confirm the results with high-resolution numerical simulations.

  17. Unconventional quantized edge transport in the presence of interedge coupling in intercalated graphene

    Science.gov (United States)

    Li, Yuanchang

    2016-07-01

    It is generally believed that the interedge coupling destroys the quantum spin Hall (QSH) effect along with the gap opening at the Dirac points. Using first-principles calculations, we find that the quantized edge transport persists in the presence of interedge coupling in Ta intercalated epitaxial graphene on SiC(0001), being a QSH insulator with the nontrivial gap of 81 meV. In this case, the band is characterized by two perfect Dirac cones with different Fermi velocities, yet only one maintains the edge state feature. We attribute such an anomalous behavior to the orbital-dependent decay of edge states into the bulk, which allows the interedge coupling between just one pair of edge states rather than two.

  18. Edge states as mediators of bypass transition in boundary-layer flows

    CERN Document Server

    Khapko, Taras; Schlatter, Philipp; Duguet, Yohann; Eckhardt, Bruno; Henningson, Dan S

    2016-01-01

    The concept of edge state is investigated in the asymptotic suction boundary layer in relation with the receptivity process to noisy perturbations and the nucleation of turbulent spots. Edge tracking is first performed numerically, without imposing any discrete symmetry, in a large computational domain allowing for full spatial localisation of the perturbation velocity. The edge state is a three-dimensional localised structure recurrently characterised by a single low-speed streak that experiences erratic bursts and planar shifts. This recurrent streaky structure is then compared with predecessors of individual spot nucleation events, triggered by non-localised initial noise. The present results suggest a nonlinear picture, rooted in dynamical systems theory, of the nucleation process of turbulent spots in boundary-layer flows, in which the localised edge state play the role of state-space mediator.

  19. Edge states as mediators of bypass transition in boundary-layer flows

    Science.gov (United States)

    Khapko, T.; Kreilos, T.; Schlatter, P.; Duguet, Y.; Eckhardt, B.; Henningson, D. S.

    2016-08-01

    The concept of edge state is investigated in the asymptotic suction boundary layer in relation with the receptivity process to noisy perturbations and the nucleation of turbulent spots. Edge tracking is first performed numerically, without imposing any discrete symmetry, in a large computational domain allowing for full spatial localisation of the perturbation velocity. The edge state is a three-dimensional localised structure recurrently characterised by a single low-speed streak that experiences erratic bursts and planar shifts. This recurrent streaky structure is then compared with predecessors of individual spot nucleation events, triggered by non-localised initial noise. The present results suggest a nonlinear picture, rooted in dynamical systems theory, of the nucleation process of turbulent spots in boundary-layer flows, in which the localised edge state play the role of state-space mediator.

  20. Ca L2,3-edge XANES and Sr K-edge EXAFS study of hydroxyapatite and fossil bone apatite

    Science.gov (United States)

    Zougrou, I. M.; Katsikini, M.; Brzhezinskaya, M.; Pinakidou, F.; Papadopoulou, L.; Tsoukala, E.; Paloura, E. C.

    2016-08-01

    Upon burial, the organic and inorganic components of hard tissues such as bone, teeth, and tusks are subjected to various alterations as a result of interactions with the chemical milieu of soil, groundwater, and presence of microorganisms. In this study, simulation of the Ca L 2,3-edge X-ray absorption near edge structure (XANES) spectrum of hydroxyapatite, using the CTM4XAS code, reveals that the different symmetry of the two nonequivalent Ca(1) and Ca(2) sites in the unit cell gives rise to specific spectral features. Moreover, Ca L 2,3-edge XANES spectroscopy is applied in order to assess variations in fossil bone apatite crystallinity due to heavy bacterial alteration and catastrophic mineral dissolution, compared to well-preserved fossil apatite, fresh bone, and geologic apatite reference samples. Fossilization-induced chemical alterations are investigated by means of Ca L 2,3-edge XANES and scanning electron microscopy (SEM) and are related to histological evaluation using optical microscopy images. Finally, the variations in the bonding environment of Sr and its preference for substitution in the Ca(1) or Ca(2) sites upon increasing the Sr/Ca ratio is assessed by Sr K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy.

  1. Velocity ratio and its application to predicting velocities

    Science.gov (United States)

    Lee, Myung W.

    2003-01-01

    The velocity ratio of water-saturated sediment derived from the Biot-Gassmann theory depends mainly on the Biot coefficient?a property of dry rock?for consolidated sediments with porosity less than the critical porosity. With this theory, the shear moduli of dry sediments are the same as the shear moduli of water-saturated sediments. Because the velocity ratio depends on the Biot coefficient explicitly, Biot-Gassmann theory accurately predicts velocity ratios with respect to differential pressure for a given porosity. However, because the velocity ratio is weakly related to porosity, it is not appropriate to investigate the velocity ratio with respect to porosity (f). A new formulation based on the assumption that the velocity ratio is a function of (1?f)n yields a velocity ratio that depends on porosity, but not on the Biot coefficient explicitly. Unlike the Biot-Gassmann theory, the shear moduli of water-saturated sediments depend not only on the Biot coefficient but also on the pore fluid. This nonclassical behavior of the shear modulus of water-saturated sediment is speculated to be an effect of interaction between fluid and the solid matrix, resulting in softening or hardening of the rock frame and an effect of velocity dispersion owing to local fluid flow. The exponent n controls the degree of softening/hardening of the formation. Based on laboratory data measured near 1 MHz, this theory is extended to include the effect of differential pressure on the velocity ratio by making n a function of differential pressure and consolidation. However, the velocity dispersion and anisotropy are not included in the formulation.

  2. Sodium Velocity Maps on Mercury

    Science.gov (United States)

    Potter, A. E.; Killen, R. M.

    2011-01-01

    The objective of the current work was to measure two-dimensional maps of sodium velocities on the Mercury surface and examine the maps for evidence of sources or sinks of sodium on the surface. The McMath-Pierce Solar Telescope and the Stellar Spectrograph were used to measure Mercury spectra that were sampled at 7 milliAngstrom intervals. Observations were made each day during the period October 5-9, 2010. The dawn terminator was in view during that time. The velocity shift of the centroid of the Mercury emission line was measured relative to the solar sodium Fraunhofer line corrected for radial velocity of the Earth. The difference between the observed and calculated velocity shift was taken to be the velocity vector of the sodium relative to Earth. For each position of the spectrograph slit, a line of velocities across the planet was measured. Then, the spectrograph slit was stepped over the surface of Mercury at 1 arc second intervals. The position of Mercury was stabilized by an adaptive optics system. The collection of lines were assembled into an images of surface reflection, sodium emission intensities, and Earthward velocities over the surface of Mercury. The velocity map shows patches of higher velocity in the southern hemisphere, suggesting the existence of sodium sources there. The peak earthward velocity occurs in the equatorial region, and extends to the terminator. Since this was a dawn terminator, this might be an indication of dawn evaporation of sodium. Leblanc et al. (2008) have published a velocity map that is similar.

  3. Ionized gas at the edge of the Central Molecular Zone

    CERN Document Server

    Langer, W D; Pineda, J L; Velusamy, T; Requena-Torres, M A; Wiesemeyer, H

    2015-01-01

    To determine the properties of the ionized gas at the edge of the CMZ near Sgr E we observed a small portion of the edge of the CMZ near Sgr E with spectrally resolved [C II] 158 micron and [N II] 205 micron fine structure lines at six positions with the GREAT instrument on SOFIA and in [C II] using Herschel HIFI on-the-fly strip maps. We use the [N II] spectra along with a radiative transfer model to calculate the electron density of the gas and the [C II] maps to illuminate the morphology of the ionized gas and model the column density of CO-dark H2. We detect two [C II] and [N II] velocity components, one along the line of sight to a CO molecular cloud at -207 km/s associated with Sgr E and the other at -174 km/s outside the edge of another CO cloud. From the [N II] emission we find that the average electron density is in the range of about 5 to 25 cm{-3} for these features. This electron density is much higher than that of the warm ionized medium in the disk. The column density of the CO-dark H$_2$ layer ...

  4. Si K Edge Structure and Variability in Galactic X-Ray Binaries

    Science.gov (United States)

    Schulz, Norbert S.; Corrales, Lia; Canizares, Claude R.

    2016-08-01

    We survey the Si K edge structure in various absorbed Galactic low-mass X-ray binaries (LMXBs) to study states of silicon in the inter- and circum-stellar medium. The bulk of these LMXBs lie toward the Galactic bulge region and all have column densities above 1022 cm‑2. The observations were performed using the Chandra High Energy Transmission Grating Spectrometer. The Si K edge in all sources appears at an energy value of 1844 ± 0.001 eV. The edge exhibits significant substructure that can be described by a near edge absorption feature at 1849 ± 0.002 eV and a far edge absorption feature at 1865 ± 0.002 eV. Both of these absorption features appear variable with equivalent widths up to several mÅ. We can describe the edge structure using several components: multiple edge functions, near edge absorption excesses from silicates in dust form, signatures from X-ray scattering optical depths, and a variable warm absorber from ionized atomic silicon. The measured optical depths of the edges indicate much higher values than expected from atomic silicon cross sections and interstellar medium abundances, and they appear consistent with predictions from silicate X-ray absorption and scattering. A comparison with models also indicates a preference for larger dust grain sizes. In many cases, we identify Si xiii resonance absorption and determine ionization parameters between log ξ = 1.8 and 2.8 and turbulent velocities between 300 and 1000 km s‑1. This places the warm absorber in close vicinity of the X-ray binaries. In some data, we observe a weak edge at 1.840 keV, potentially from a lesser contribution of neutral atomic silicon.

  5. Jet formation at the sea ice edge

    Science.gov (United States)

    Feltham, D. L.; Heorton, H. D.

    2014-12-01

    The sea ice edge presents a region of many feedback processes between the atmosphere, ocean and sea ice, which are inadequately represented in current climate models. Here we focus on on-ice atmospheric and oceanic flows at the sea ice edge. Mesoscale jet formation due to the Coriolis effect is well understood over sharp changes in surface roughness such as coastlines. This sharp change in surface roughness is experienced by the atmosphere flowing over, and ocean flowing under, a compacted sea ice edge. We have studied a dynamic sea ice edge responding to atmospheric and oceanic jet formation. The shape and strength of atmospheric and oceanic jets during on-ice flows is calculated from existing studies of the sea ice edge and prescribed to idealised models of the sea ice edge. An idealised analytical model of sea ice drift is developed and compared to a sea ice climate model (the CICE model) run on an idealised domain. The response of the CICE model to jet formation is tested at various resolutions. We find that the formation of atmospheric jets during on-ice winds at the sea ice edge increases the wind speed parallel to the sea ice edge and results in the formation of a sea ice edge jet. The modelled sea ice edge jet is in agreement with an observed jet although more observations are needed for validation. The increase in ice drift speed is dependent upon the angle between the ice edge and wind and can result in a 40% increase in ice transport along the sea ice edge. The possibility of oceanic jet formation during on-ice currents and the resultant effect upon the sea ice edge is less conclusive. Observations and climate model data of the polar oceans has been analysed to show areas of likely atmospheric jet formation, with the Fram Strait being of particular interest.

  6. Seismic refraction study of the continental edge off the eastern united states

    Science.gov (United States)

    Sheridan, R.E.; Grow, J.A.; Behrendt, John C.; Bayer, K.C.

    1979-01-01

    Three long, strike-parallel, seismic-refraction profiles were made on the continental shelf edge, slope and upper rise off New Jersey during 1975. The shelf edge line lies along the axis of the East Coast Magnetic Anomaly (ECMA), while the continental rise line lies 80 km seaward of the shelf edge. Below the unconsolidated sediments (1.7-3.6 km/sec), high-velocity sedimentary rocks (4.2-6.2 km/sec) were found at depths of 2.6-8.2 km and are inferred to be cemented carbonates. Although multichannel seismic-reflection profiles and magnetic depth-to-source data predicted the top of oceanic basement at 6-8 km beneath the shelf edge and 10-11 km beneath the rise, no refracted events occurred as first arrivals from either oceanic basement (layer 2, approximately 5.5 km/ sec) or the upper oceanic crust (layer 3A, approximately 6.8 km/sec). Second arrivals from 10.5 km depth beneath the shelf edge are interpreted as events from a 5.9 km/sec refractor within igneous basement. Other refracted events from either layers 2 or 3A could not be resolved within the complex second arrivals. A well-defined crustal layer with a compressional velocity of 7.1-7.2 km/sec, which can be interpreted as oceanic layer 3B, occurred at 15.8 km depth beneath the shelf and 12.9 km beneath the upper rise. A well-reversed mantle velocity of 8.3 km/sec was measured at 18-22 km depth beneath the upper continental rise. Comparison with other deep-crustal profiles along the continental edge of the Atlantic margin off the United States, specifically in the inner magnetically quiet zone, indicates that the compressional wave velocities and layer depths determined on the U.S.G.S. profiles are very similar to those of nearby profiles. This suggests that the layers are continuous and that the interpretation of the oceanic layer 3B under the shelf edge east of New Jersey implies progradation of the shelf outward over the oceanic crust in that area. This agrees with magnetic anomaly evidence which shows the

  7. Measuring Oscillatory Velocity Fields Due to Swimming Algae

    CERN Document Server

    Guasto, Jeffrey S; Gollub, J P

    2010-01-01

    In this fluid dynamics video, we present the first time-resolved measurements of the oscillatory velocity field induced by swimming unicellular microorganisms. Confinement of the green alga C. reinhardtii in stabilized thin liquid films allows simultaneous tracking of cells and tracer particles. The measured velocity field reveals complex time-dependent flow structures, and scales inversely with distance. The instantaneous mechanical power generated by the cells is measured from the velocity fields and peaks at 15 fW. The dissipation per cycle is more than four times what steady swimming would require.

  8. Kriging Interpolating Cosmic Velocity Field

    CERN Document Server

    Yu, Yu; Jing, Yipeng; Zhang, Pengjie

    2015-01-01

    [abridge] Volume-weighted statistics of large scale peculiar velocity is preferred by peculiar velocity cosmology, since it is free of uncertainties of galaxy density bias entangled in mass-weighted statistics. However, measuring the volume-weighted velocity statistics from galaxy (halo/simulation particle) velocity data is challenging. For the first time, we apply the Kriging interpolation to obtain the volume-weighted velocity field. Kriging is a minimum variance estimator. It predicts the most likely velocity for each place based on the velocity at other places. We test the performance of Kriging quantified by the E-mode velocity power spectrum from simulations. Dependences on the variogram prior used in Kriging, the number $n_k$ of the nearby particles to interpolate and the density $n_P$ of the observed sample are investigated. (1) We find that Kriging induces $1\\%$ and $3\\%$ systematics at $k\\sim 0.1h{\\rm Mpc}^{-1}$ when $n_P\\sim 6\\times 10^{-2} ({\\rm Mpc}/h)^{-3}$ and $n_P\\sim 6\\times 10^{-3} ({\\rm Mpc...

  9. Composite superconducting transition edge bolometer

    International Nuclear Information System (INIS)

    A composite far-infrared bolometer has been constructed that uses an aluminum film at the superconducting transition temperature of 1.3 K as the temperature-sensitive element. The film is evaporated on one edge of a 4 x 4-mm sapphire substrate, which is coated on the reverse side with an absorbing film of bismuth. The best bolometer has an electrical NEP of (1.7 +- 0.1) x 10-15 W Hz-1/2 at 2 Hz, and a specific detectivity D* of (1.1 +- 0.1) x 1014 cm W-1 Hz1/2. This measured electrical NEP is within a factor 2 of the fundamental thermal noise limit

  10. Compact K-edge densitometer

    International Nuclear Information System (INIS)

    Los Alamos National Laboratory has designed, built, and is currently testing a compact K-edge densitometer for use by International Atomic Energy Agency (IAEA) inspectors. The unit, which can easily be moved from one location to another within a facility, is positioned outside a glovebox with the body of the instrument inserted into the glove. A fixture inside the glovebox fits around the body and positions a sample holder. A hand-held high-purity germanium detector powered by a battery pack and a Davidson portable multichannel analyzer (MCA) is used to measure the transmission through plutonium nitrate solutions at E/sub Y/ = 121.1 and 122.2 keV. The Davidson MCA is programmed to lead the user through the measurement procedure and perform all the data analyses. The instrument is currently installed at the Safeguards Analytical Laboratory, where IAEA personnel are evaluating its accuracy, ease of operation, and safety. 5 references, 5 figures, 5 tables

  11. On the Edge of Existence

    DEFF Research Database (Denmark)

    Richter, Line

    2016-01-01

    Based on ethnographic fieldwork among Malian migrants and migration brokers in Mali, Algeria, Morocco, and France, this article investigates life in exile on the edge of Europe. Zooming in on the experiences of interlocutors in Morocco and Algeria, the article will explore the experiential......-nating what this specific type of permanent liminality entails. I posit that a more suitable term to call this is ‘limbo’. This, I argue, consists of three main features. First, the motivation for leaving Mali is for most migrants embedded in the lack of opportunities for social mobility: the Malian youth who...... end up leaving, are in Honwana’s words, stuck in ‘waithood’ at home, in what many argue is a liminal social position. Second, social and political structures are not absent in the Ma-ghreb, rather they are quite discernable and can be seen as continuations and mim-icking of existing structures. Third...

  12. Imaging edges of nanostructured graphene

    DEFF Research Database (Denmark)

    Kling, Jens; Cagliani, Alberto; Booth, T. J.;

    Graphene, as the forefather of 2D-materials, attracts much attention due to its extraordinary properties like transparency, flexibility and outstanding high conductivity, together with a thickness of only one atom. However, graphene also possesses no band gap, which makes it unsuitable for many...... electronic applications like transistors. It has been shown theoretically that by nanostructuring pristine graphene, e.g. with regular holes, the electronic properties can be tuned and a band gap introduced. The size, distance and edge termination of these “defects” influence the adaptability....... Such nanostructuring can be done experimentally, but especially characterization at atomic level is a huge challenge. High-resolution TEM (HRTEM) is used to characterize the atomic structure of graphene. We optimized the imaging conditions used for the FEI Titan ETEM. To reduce the knock-on damage of the carbon atoms...

  13. Analysis of the propeller wake evolution by pressure and velocity phase measurements

    OpenAIRE

    Felli, Mario; Di Felice, Fabio; Guj, Giulio; Camussi, Roberto

    2006-01-01

    In the present study an experimental analysis of the velocity and pressure fields behind a marine propeller, in non-cavitating regime is reported. Particle image velocimetry measurements were performed in phase with the propeller angle, to investigate the evolution of the axial and the radial velocity components, from the blade trailing edge up to two diameters downstream. In phase pressure measurements were performed at four radial and eight longitudinal positions downstream the propeller mo...

  14. Structure of complex networks: Quantifying edge-to-edge relations by failure-induced flow redistribution

    CERN Document Server

    Schaub, Michael T; Yaliraki, Sophia N; Barahona, Mauricio

    2013-01-01

    The analysis of complex networks has so far revolved mainly around the role of nodes and communities of nodes. However, the dynamics of interconnected systems is commonly focalised on edge processes, and a dual edge-centric perspective can often prove more natural. Here we present graph-theoretical measures to quantify edge-to-edge relations inspired by the notion of flow redistribution induced by edge failures. Our measures, which are related to the pseudo-inverse of the Laplacian of the network, are global and reveal the dynamical interplay between the edges of a network, including potentially non-local interactions. Our framework also allows us to define the embeddedness of an edge, a measure of how strongly an edge features in the weighted cuts of the network. We showcase the general applicability of our edge-centric framework through analyses of the Iberian Power grid, traffic flow in road networks, and the C. elegans neuronal network.

  15. Diffraction imaging and velocity analysis using oriented velocity continuation

    KAUST Repository

    Decker, Luke

    2014-08-05

    We perform seismic diffraction imaging and velocity analysis by separating diffractions from specular reflections and decomposing them into slope components. We image slope components using extrapolation in migration velocity in time-space-slope coordinates. The extrapolation is described by a convection-type partial differential equation and implemented efficiently in the Fourier domain. Synthetic and field data experiments show that the proposed algorithm is able to detect accurate time-migration velocities by automatically measuring the flatness of events in dip-angle gathers.

  16. Bound on m-restricted Edge Connectivity

    Institute of Scientific and Technical Information of China (English)

    Jian-ping Ou; Fu-ji Zhang

    2003-01-01

    An m-restricted edge cut is an edge cut that separates a connected graph into a disconnected one with no components having order less than m. m-restricted edge connectivity λm is the cardinality of a minimum m-restricted edge cut. Let G be a connected k-regular graph of order at least 2m that contains m-restricted edge cuts and X be a subgraph of G. Let( )(X) denote the number of edges with one end in X and the other not in X and ξm = min{( )(X): X is a connected vertex-induced subgraph of order m}. It is proved in this paper that if G has girth at least m/2 + 2, then λm ≤ξm. The upper bound of λm is sharp.

  17. Edge Magnon Excitation in Spin Dimer Systems

    Science.gov (United States)

    Sakaguchi, Ryo; Matsumoto, Masashige

    2016-10-01

    Magnetic excitation in a spin dimer system on a bilayer honeycomb lattice is investigated in the presence of a zigzag edge, where disordered and ordered phases can be controlled by a quantum phase transition. In analogy with the case of graphene with a zigzag edge, a flat edge magnon mode appears in the disordered phase. In an ordered phase, a finite magnetic moment generates a mean-field potential to the magnon. Since the potential is nonuniform on the edge and bulk sites, it affects the excitation, and the dispersion of the edge mode deviates from the flat shape. We investigate how the edge magnon mode evolves when the phase changes through the quantum phase transition and discuss the similarities to ordered spin systems on a monolayer honeycomb lattice.

  18. Experimental evidence of edge intrinsic momentum source driven by kinetic ion loss and edge radial electric fields in tokamaks

    Science.gov (United States)

    Boedo, J. A.; deGrassie, J. S.; Grierson, B.; Stoltzfus-Dueck, T.; Battaglia, D. J.; Rudakov, D. L.; Belli, E. A.; Groebner, R. J.; Hollmann, E.; Lasnier, C.; Solomon, W. M.; Unterberg, E. A.; Watkins, J.

    2016-09-01

    Bulk ion toroidal velocity profiles, V| | D + , peaking at 40-60 km/s are observed with Mach probes in a narrow edge region of DIII-D discharges without external momentum input. This intrinsic rotation can be well reproduced by a first principle, collisionless kinetic loss model of thermal ion loss that predicts the existence of a loss-cone distribution in velocity space resulting in a co-Ip directed velocity. We consider two kinetic models, one of which includes turbulence-enhanced momentum transport, as well as the Pfirsch-Schluter (P-S) fluid mechanism. We measure a fine structure of the boundary radial electric field, Er, insofar ignored, featuring large (10-20 kV/m) positive peaks in the scrape off layer (SOL) at, or slightly inside, the last closed flux surface of these low power L- and H-mode discharges in DIII-D. The Er structure significantly affects the ion-loss model, extended to account for a non-uniform electric field. We also find that V| | D + is reduced when the magnetic topology is changed from lower single null to upper single null. The kinetic ion loss model containing turbulence-enhanced momentum transport can explain the reduction, as we find that the potential fluctuations decay with radius, while we need to invoke a topology-enhanced collisionality on the simpler kinetic model. The P-S mechanism fails to reproduce the damping. We show a clear correlation between the near core V| | C 6 + velocity and the peak edge V| | D + in discharges with no external torque, further supporting the hypothesis that ion loss is the source for intrinsic torque in the present tokamaks. However, we also show that when external torque is injected in the core, it can complete with, and eventually overwhelm, the edge source, thus determining the near SOL flows. Finally, we show some additional evidence that the ion/electron distribution in the SOL is non-Maxwellian.

  19. Edge effect on weevils and spiders

    OpenAIRE

    Horváth, R; Magura, T.; G. Péter; B. Tóthmérész

    2002-01-01

    The edge effect on weevils and spiders was tested along oak forest – meadow transects using sweep-net samples at the Síkfökút Project in Hungary. For spiders the species richness was significantly higher in the forest edge than either in the meadow or the forest interior. For weevils the species richness of the forest edge was higher than that of the meadow, but the difference was not statistically significant whereas the species richness of the forest...

  20. Edge Detection for Pattern Recognition: A Survey

    OpenAIRE

    James, Alex Pappachen

    2016-01-01

    This review provides an overview of the literature on the edge detection methods for pattern recognition that inspire from the understanding of human vision. We note that edge detection is one of the most fundamental process within the low level vision and provides the basis for the higher level visual intelligence in primates. The recognition of the patterns within the images relate closely to the spatiotemporal processes of edge formations, and its implementation needs a crossdisciplanry ap...

  1. Selective Electroless Silver Deposition on Graphene Edges

    DEFF Research Database (Denmark)

    Durhuus, D.; Larsen, M. V.; Andryieuski, Andrei;

    2015-01-01

    We demonstrate a method of electroless selective silver deposition on graphene edges or between graphene islands without covering the surface of graphene. Modifications of the deposition recipe allow for decoration of graphene edges with silver nanoparticles or filling holes in damaged graphene...... on silica substrate and thus potentially restoring electric connectivity with minimal influence on the overall graphene electrical and optical properties. The presented technique could find applications in graphene based transparent conductors as well as selective edge functionalization and can be extended...

  2. Low-Speed Fan Noise Reduction With Trailing Edge Blowing

    Science.gov (United States)

    Sutliff, Daniel L.; Tweedt, Daniel L.; Fite, E. Brian; Envia, Edmane

    2002-01-01

    An experimental proof-of-concept test was conducted to demonstrate reduction of rotor-stator interaction noise through rotor-trailing edge blowing. The velocity deficit from the viscous wake of the rotor blades was reduced by injecting air into the wake from a trailing edge slot. Composite hollow rotor blades with internal flow passages were designed based on analytical codes modeling the internal flow. The hollow blade with interior guide vanes creates flow channels through which externally supplied air flows from the root of the blade to the trailing edge. The impact of the rotor wake-stator interaction on the acoustics was also predicted analytically. The Active Noise Control Fan, located at the NASA Glenn Research Center, was used as the proof- of-concept test bed. In-duct mode and farfield directivity acoustic data were acquired at blowing rates (defined as mass supplied to trailing edge blowing system divided by fan mass flow) ranging from 0.5 to 2.0 percent. The first three blade passing frequency harmonics at fan rotational speeds of 1700 to 1900 rpm were analyzed. The acoustic tone power levels (PWL) in the inlet and exhaust were reduced 11.5 and -0.1, 7.2 and 11.4, 11.8 and 19.4 PWL dB, respectively. The farfield tone power levels at the first three harmonics were reduced 5.4, 10.6, and 12.4 dB PWL. At selected conditions, two-component hotwire and stator vane unsteady surface pressures were acquired. These measurements illustrate the physics behind the noise reduction.

  3. TWO-DIMENSIONAL KINEMATICS OF THE EDGE-ON SPIRAL GALAXY ESO 379-006

    Energy Technology Data Exchange (ETDEWEB)

    Rosado, M.; Gabbasov, R. F.; Repetto, P.; Martos, M. [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-264, CP 04510 Mexico, D. F. (Mexico); Fuentes-Carrera, I. [Escuela Superior de Fisica y Matematicas, Instituto Politecnico Nacional, U. P. Adolfo Lopez Mateos, Zacatenco, 07730 Mexico, D. F. (Mexico); Amram, P.; Hernandez, O. [Laboratoire d' Astrophysique de Marseille, Aix-Marseille University (France); CNRS, 38 rue Frederic Joliot-Curie, 13338 Marseille Cedex 13 (France)

    2013-05-15

    We present a kinematical study of the nearly edge-on galaxy ESO 379-006 that shows the existence of extraplanar ionized gas. With Fabry-Perot spectroscopy at H{alpha}, we study the kinematics of ESO 379-006 using velocity maps and position-velocity diagrams parallel to the major and to the minor axis of the galaxy. We build the rotation curve of the disk and discuss the role of projection effects due to the fact of viewing this galaxy nearly edge-on. The twisting of the isovelocities in the radial velocity field of the disk of ESO 379-006 as well as the kinematical asymmetries found in some position-velocity diagrams parallel to the minor axis of the galaxy suggest the existence of deviations to circular motions in the disk that can be modeled and explained with the inclusion of a radial inflow probably generated by a bar or by spiral arms. We succeeded in detecting extraplanar diffuse ionized gas in this galaxy. At the same time, from the analysis of position-velocity diagrams, we found some evidence that the extraplanar gas could lag in rotation velocity with respect to the midplane rotation.

  4. Edge and line detection of complicated and blurred objects

    OpenAIRE

    Haugsdal, Kari

    2010-01-01

    This report deals with edge and line detection in pictures with complicated and/or blurred objects. It explores the alternatives available, in edge detection, edge linking and object recognition. Choice of methods are the Canny edge detection and Local edge search processing combined with regional edge search processing in the form of polygon approximation.

  5. A Gravitational Edge Detection for Multispectral Images

    Directory of Open Access Journals (Sweden)

    Genyun Sun

    2013-07-01

    Full Text Available Gravitational edge detection is one of the new edge detection algorithms that is based on the law of gravity. This algorithm assumes that each image pixel is a celestial body with a mass represented by its grayscale intensity and their interactions are based on the Newtonian laws of gravity. In this article, a multispectral version of the algorithm is introduced. The method uses gravitational techniques in combination with metric tensor to detect edges of multispectral images including color images. To evaluate the performances of the proposed algorithm, several experiments are performed. The experimental results confirm the efficiency of the multispectral gravitational edge detection.  

  6. An edge index for topological insulators

    Science.gov (United States)

    Prodan, Emil

    2009-03-01

    Topological insulators display dissipationless currents flowing at the edges of the samples. These currents are associated to chiral edge modes, whose existence is intrinsically linked to the topology of the electronic states of the bulk. The edge modes can be easily investigated when the edges are smooth and have a periodicity, but as soon as the periodicity is absent, the problem becomes un-traceable by purely theoretical means. In my talk I will exemplify the use of non-commutative calculus to explore the properties, especially the stability of the edge modes. For example, using such techniques one can give a fairly elementary proof that the edge modes in Chern insulators survive even for a rough (random) edge. Similarly, for the Spin-Hall effect, one can define an observable and its associated current whose conductance remains quantized during various deformations of the Hamiltonian system. It turns out that in all cases, the edge conductance is given by the index of a Fredholm operator, which provides a new topological invariant linked directly to the edge rather than the bulk.

  7. Moveable Leading Edge Device for a Wing

    Science.gov (United States)

    Pitt, Dale M. (Inventor); Eckstein, Nicholas Stephen (Inventor)

    2013-01-01

    A method and apparatus for managing a flight control surface system. A leading edge section on a wing of an aircraft is extended into a deployed position. A deformable section connects the leading edge section to a trailing section. The deformable section changes from a deformed shape to an original shape when the leading edge section is moved into the deployed position. The leading edge section on the wing is moved from the deployed position to an undeployed position. The deformable section changes to the deformed shape inside of the wing.

  8. A new fuzzy edge detection algorithm

    Institute of Scientific and Technical Information of China (English)

    SunWei; XiaLiangzheng

    2003-01-01

    Based upon the maximum entropy theorem of information theory, a novel fuzzy approach for edge detection is presented. Firsdy, a definition of fuzzy partition entropy is proposed after introducing the concepts of fuzzy probability and fuzzy partition. The relation of the probability partition and the fuzzy c-partition of the image gradient are used in the algorithm. Secondly, based on the conditional probabilities and the fuzzy partition, the optimal thresholding is searched adaptively through the maximum fuzzy entropy principle, and then the edge image is obtained. Lastly, an edge-enhancing procedure is executed on the edge image. The experimental results show that the proposed approach performs well.

  9. IMAGE ANALYSIS BASED ON EDGE DETECTION TECHNIQUES

    Institute of Scientific and Technical Information of China (English)

    纳瑟; 刘重庆

    2002-01-01

    A method that incorporates edge detection technique, Markov Random field (MRF), watershed segmentation and merging techniques was presented for performing image segmentation and edge detection tasks. It first applies edge detection technique to obtain a Difference In Strength (DIS) map. An initial segmented result is obtained based on K-means clustering technique and the minimum distance. Then the region process is modeled by MRF to obtain an image that contains different intensity regions. The gradient values are calculated and then the watershed technique is used. DIS calculation is used for each pixel to define all the edges (weak or strong) in the image. The DIS map is obtained. This help as priority knowledge to know the possibility of the region segmentation by the next step (MRF), which gives an image that has all the edges and regions information. In MRF model,gray level l, at pixel location i, in an image X, depends on the gray levels of neighboring pixels. The segmentation results are improved by using watershed algorithm. After all pixels of the segmented regions are processed, a map of primitive region with edges is generated. The edge map is obtained using a merge process based on averaged intensity mean values. A common edge detectors that work on (MRF) segmented image are used and the results are compared. The segmentation and edge detection result is one closed boundary per actual region in the image.

  10. Edge Segment-Based Automatic Video Surveillance

    Directory of Open Access Journals (Sweden)

    Oksam Chae

    2007-12-01

    Full Text Available This paper presents a moving-object segmentation algorithm using edge information as segment. The proposed method is developed to address challenges due to variations in ambient lighting and background contents. We investigated the suitability of the proposed algorithm in comparison with the traditional-intensity-based as well as edge-pixel-based detection methods. In our method, edges are extracted from video frames and are represented as segments using an efficiently designed edge class. This representation helps to obtain the geometric information of edge in the case of edge matching and moving-object segmentation; and facilitates incorporating knowledge into edge segment during background modeling and motion tracking. An efficient approach for background initialization and robust method of edge matching is presented, to effectively reduce the risk of false alarm due to illumination change and camera motion while maintaining the high sensitivity to the presence of moving object. Detected moving edges are utilized along with watershed algorithm for extracting video object plane (VOP with more accurate boundary. Experiment results with real image sequence reflect that the proposed method is suitable for automated video surveillance applications in various monitoring systems.

  11. Stabilization of MHD turbulence by applied steady and oscillating velocity shear

    Science.gov (United States)

    Hung, Ching Pui

    Some aspects of velocity shear stabilization of magnetized plasma instabilities are considered. In the first part, steady externally forced flow shears are considered. In the second part, resonantly excited oscillating flow shears are considered. The stabilizing effect of steady forced velocity shear on the ideal interchange instability is studied in linear and nonlinear regimes, with a 2D dissipative magnetohydrodynamic (MHD) code. With increasing flow shear V', the linearly unstable band in wavenumber-space shrinks so that the peak growth results for modes that correspond to intermediate wavenumbers. In the nonlinear turbulent state, the convection cells are roughly circular on the scale of the density gradient. Unstable modes are almost completely stabilized, with the density profile reverting to laminar, when V' is a few times the classic interchange growth rate. The simulations are compared with measurements of magnetic fluctuations from the Maryland Centrifugal Experiment. The spectral data, taken in the plasma edge, are in general agreement with data obtained in higher viscosity simulations. Finally, concomitant Kelvin-Helmholtz instabilities in the system are also examined. Geodesic acoustic modes (GAMs) are axisymmetric electrostatic poloidal oscillations of plasma in tokamaks. It has been proposed to drive GAMs resonantly by external drivers, thus setting up velocity shears to suppress turbulence. Here, we study enhanced damping of GAMs from (1) phase mixing of oscillations and (2) nonlinear detuning of the resonance. It is well-known that phase mixing of Alfven waves propagating in inhomogeneous media results in enhanced damping. The enhancement goes as the 1/3 power of the dissipation. We study this phenomenon for GAMs in tokamaks with temperature profiles. Our analysis is verified by numerical simulation. In addition, the system of nonlinear GAM equations is shown to resemble the Duffing oscillator. Resonant amplification is shown to be suppressed

  12. Improved Trailing Edge Noise Model

    DEFF Research Database (Denmark)

    Bertagnolio, Franck

    2012-01-01

    The modeling of the surface pressure spectrum under a turbulent boundary layer is investigated in the presence of an adverse pressure gradient along the flow direction. It is shown that discrepancies between measurements and results from a well-known model increase as the pressure gradient...... increases. This model is modified by introducing anisotropy in the definition of the vertical velocity component spectrum across the boundary layer. The degree of anisotropy is directly related to the strength of the pressure gradient. It is shown that by appropriately normalizing the pressure gradient...... and by tuning the anisotropy factor, experimental results can be closely reproduced by the modified model. In this section, the original TNO-Blake model is modified in order to account for the effects of a pressure gradient through turbulence anisotropy. The model results are compared with measurements...

  13. Settling velocities in batch sedimentation

    International Nuclear Information System (INIS)

    The sedimentation of mixtures containing one and two sizes of spherical particles (44 and 62 μm in diameter) was studied. Radioactive tracing with 57Co was used to measure the settling velocities. The ratio of the settling velocity U of uniformly sized particles to the velocity predicted to Stokes' law U0 was correlated to an expression of the form U/U0 = epsilon/sup α/, where epsilon is the liquid volume fraction and α is an empirical constant, determined experimentally to be 4.85. No effect of viscosity on the ratio U/U0 was observed as the viscosity of the liquid medium was varied from 1x10-3 to 5x10-3 Pa.s. The settling velocities of particles in a bimodal mixture were fit by the same correlation; the ratio U/U0 was independent of the concentrations of different-sized particles

  14. Kriging interpolating cosmic velocity field

    Science.gov (United States)

    Yu, Yu; Zhang, Jun; Jing, Yipeng; Zhang, Pengjie

    2015-10-01

    Volume-weighted statistics of large-scale peculiar velocity is preferred by peculiar velocity cosmology, since it is free of the uncertainties of galaxy density bias entangled in observed number density-weighted statistics. However, measuring the volume-weighted velocity statistics from galaxy (halo/simulation particle) velocity data is challenging. Therefore, the exploration of velocity assignment methods with well-controlled sampling artifacts is of great importance. For the first time, we apply the Kriging interpolation to obtain the volume-weighted velocity field. Kriging is a minimum variance estimator. It predicts the most likely velocity for each place based on the velocity at other places. We test the performance of Kriging quantified by the E-mode velocity power spectrum from simulations. Dependences on the variogram prior used in Kriging, the number nk of the nearby particles to interpolate, and the density nP of the observed sample are investigated. First, we find that Kriging induces 1% and 3% systematics at k ˜0.1 h Mpc-1 when nP˜6 ×1 0-2(h-1 Mpc )-3 and nP˜6 ×1 0-3(h-1 Mpc )-3 , respectively. The deviation increases for decreasing nP and increasing k . When nP≲6 ×1 0-4(h-1 Mpc )-3 , a smoothing effect dominates small scales, causing significant underestimation of the velocity power spectrum. Second, increasing nk helps to recover small-scale power. However, for nP≲6 ×1 0-4(h-1 Mpc )-3 cases, the recovery is limited. Finally, Kriging is more sensitive to the variogram prior for a lower sample density. The most straightforward application of Kriging on the cosmic velocity field does not show obvious advantages over the nearest-particle method [Y. Zheng, P. Zhang, Y. Jing, W. Lin, and J. Pan, Phys. Rev. D 88, 103510 (2013)] and could not be directly applied to cosmology so far. However, whether potential improvements may be achieved by more delicate versions of Kriging is worth further investigation.

  15. Reduction in Edge-Ringing in Aberrated Images of Coherent Edge Objects by Multishaded Aperture

    OpenAIRE

    Venkanna Mekala; Karuna Sagar Dasari

    2014-01-01

    The images of a straight edge in coherent illumination produced by an optical system with circular aperture and apodized with multiple filters have been studied. The most common problem encountered in the coherent-imaging techniques is the edge-ringing. To minimize the edge-ringing, multishaded aperture method has been proposed. Image intensity distribution curves are drawn and edge-ringing values are evaluated. The results are compared to that of the airy case with the use of single, double ...

  16. Edge Detection with Sub-pixel Accuracy Based on Approximation of Edge with Erf Function

    OpenAIRE

    M. Hagara; P. Kulla

    2011-01-01

    Edge detection is an often used procedure in digital image processing. For some practical applications is desirable to detect edges with sub-pixel accuracy. In this paper we present edge detection method for 1-D images based on approximation of real image function with Erf function. This method is verified by simulations and experiments for various numbers of samples of simulated and real images. Results of simulations and experiments are also used to compare proposed edge detection scheme wi...

  17. Absence of edge states in covalently bonded zigzag edges of graphene on Ir(111).

    Science.gov (United States)

    Li, Yan; Subramaniam, Dinesh; Atodiresei, Nicolae; Lazić, Predrag; Caciuc, Vasile; Pauly, Christian; Georgi, Alexander; Busse, Carsten; Liebmann, Marcus; Blügel, Stefan; Pratzer, Marco; Morgenstern, Markus; Mazzarello, Riccardo

    2013-04-11

    The zigzag edges of graphene on Ir(111) are studied by ab initio simulations and low-temperature scanning tunneling spectroscopy, providing information about their structural, electronic, and magnetic properties. No edge state is found to exist, which is explained in terms of the interplay between a strong geometrical relaxation at the edge and a hybridization of the d orbitals of Ir atoms with the graphene orbitals at the edge.

  18. The integration of angular velocity

    OpenAIRE

    Boyle, Michael

    2016-01-01

    A common problem in physics and engineering is determination of the orientation of an object given its angular velocity. When the direction of the angular velocity changes in time, this is a nontrivial problem involving coupled differential equations. Several possible approaches are examined, along with various improvements over previous efforts. These are then evaluated numerically by comparison to a complicated but analytically known rotation that is motivated by the important astrophysical...

  19. Annotated Bibliography of EDGE2D Use

    International Nuclear Information System (INIS)

    This annotated bibliography is intended to help EDGE2D users, and particularly new users, find existing published literature that has used EDGE2D. Our idea is that a person can find existing studies which may relate to his intended use, as well as gain ideas about other possible applications by scanning the attached tables

  20. Annotated Bibliography of EDGE2D Use

    Energy Technology Data Exchange (ETDEWEB)

    J.D. Strachan and G. Corrigan

    2005-06-24

    This annotated bibliography is intended to help EDGE2D users, and particularly new users, find existing published literature that has used EDGE2D. Our idea is that a person can find existing studies which may relate to his intended use, as well as gain ideas about other possible applications by scanning the attached tables.

  1. Product of normal edge transitive Cayley graphs

    Directory of Open Access Journals (Sweden)

    Amir Assari

    2014-09-01

    Full Text Available For two normal edge transitive Cayley graphs on two groups H and K whichhave no common direct factor and gcd(|H|/|H'|, |Z(K| = 1 = gcd(|K=K′|,|Z(H|,we consider four standard product of them and proved that only tensor product ofthem can be normal edge transitive.

  2. Coupled flow and anisotropy in the UltraLow Velocity Zones

    Science.gov (United States)

    Hier-Majumder, Saswata; Drombosky, Tyler W.

    2016-09-01

    Seismic observations reveal a patchwork of thin and dense structures, named UltraLow Velocity Zones (ULVZs) atop the Earth's core mantle boundary. The high width to height ratio of the ULVZs, their spatial correlation with the edges of Large Low Shear Velocity Provinces (LLSVPs), and their preservation as distinct structures in the convecting mantle remain an enigmatic problem. In this article, we carry out a series of numerical simulations using Fast Multipole Boundary Elements Method (FMBEM) to address these questions and study the internal deformation within the ULVZs. Our results demonstrate that coupled flow between dense, low viscosity ULVZ patches and the LLSVP accumulates the ULVZ into stable piles along LLSVP corners, while coalescence and gravitational drainage leads to thin and wide ULVZs away from the corners. Deformation of the matrix is localized within the weaker ULVZ and the LLSVP edges, while the strain in the interior of the LLSVP remains uniform and low, explaining the observed localized anisotropy near LLSVP edges.

  3. On edge graceful labelings of disjoint unions of $2r$-regular edge graceful graphs

    OpenAIRE

    Riskin, Adrian; Weidman, Georgia

    2006-01-01

    We prove that if $G$ is a $2r$-regular edge graceful $(p,q)$ graph with $(r,kp)=1$ then $kG$ is edge graceful for odd $k$. We also prove that for certain specific classes of $2r$-regular edge graceful graphs it is possible to drop the requirement that $(r,kp)=1$

  4. Localized Edge Vibrations and Edge Reconstruction by Joule Heating in Graphene Nanostructures

    DEFF Research Database (Denmark)

    Engelund, Mads; Fürst, Joachim Alexander; Jauho, Antti-Pekka;

    2010-01-01

    for current-induced edge reconstruction using density functional theory. Our calculations provide evidence for localized vibrations at edge interfaces involving unpassivated armchair edges. We demonstrate that these vibrations couple to the current, estimate their excitation by Joule heating, and argue...

  5. Three dimensional simulations of the parallel velocity shear instability

    International Nuclear Information System (INIS)

    The authors have performed fully nonlinear three-dimensional fluid simulations of the electrostatic parallel velocity shear instability as applied to a tokamak edge plasma. In the present study a source terms in the parallel momentum equation drives the sheared parallel flow. Studied are the effects of magnetic shear on the turbulence of the mode and the associated fluctuation levels. The inclusion of the nonlinear polarization drift in the perpendicular dynamics is found to significantly affect the final nonlinear state. Dependence of the anomalous momentum transport on the magnetic shear and the gyroradius parameter, associated with the polarization drift, are presented

  6. Edge exchangeable models for network data

    CERN Document Server

    Crane, Harry

    2016-01-01

    Exchangeable models for vertex labeled graphs cannot replicate the large sample behaviors of sparsity and power law degree distributions observed in many network datasets. Out of this mathematical impossibility emerges the question of how network data can be modeled in a way that reflects known empirical behaviors and respects basic statistical principles. We address this question by observing that edges, not vertices, act as the statistical units in most network datasets, making a theory of edge labeled networks more natural for most applications. Within this context we introduce the new invariance principle of {\\em edge exchangeability}, which unlike its vertex exchangeable counterpart can produce networks with sparse and/or power law structure. We characterize the class of all edge exchangeable network models and identify a particular two parameter family of models with suitable theoretical properties for statistical inference. We discuss issues of estimation from edge exchangeable models and compare our a...

  7. Cascading Edge Failures: A Dynamic Network Process

    CERN Document Server

    Zhang, June

    2016-01-01

    This paper considers the dynamics of edges in a network. The Dynamic Bond Percolation (DBP) process models, through stochastic local rules, the dependence of an edge $(a,b)$ in a network on the states of its neighboring edges. Unlike previous models, DBP does not assume statistical independence between different edges. In applications, this means for example that failures of transmission lines in a power grid are not statistically independent, or alternatively, relationships between individuals (dyads) can lead to changes in other dyads in a social network. We consider the time evolution of the probability distribution of the network state, the collective states of all the edges (bonds), and show that it converges to a stationary distribution. We use this distribution to study the emergence of global behaviors like consensus (i.e., catastrophic failure or full recovery of the entire grid) or coexistence (i.e., some failed and some operating substructures in the grid). In particular, we show that, depending on...

  8. A synthesis for exactly 3-edge-connected graphs

    OpenAIRE

    Kingsford, Carl; Marçais, Guillaume

    2009-01-01

    A multigraph is exactly k-edge-connected if there are exactly k edge-disjoint paths between any pair of vertices. We characterize the class of exactly 3-edge-connected graphs, giving a synthesis involving two operations by which every exactly 3-edge-connected multigraph can be generated. Slightly modified syntheses give the planar exactly 3-edge-connected graphs and the exactly 3-edge-connected graphs with the fewest possible edges.

  9. Gait phase varies over velocities.

    Science.gov (United States)

    Liu, Yancheng; Lu, Kun; Yan, Songhua; Sun, Ming; Lester, D Kevin; Zhang, Kuan

    2014-02-01

    We sought to characterize the percent (PT) of the phases of a gait cycle (GC) as velocity changes to establish norms for pathological gait characteristics with higher resolution technology. Ninety five healthy subjects (49 males and 46 females with age 34.9 ± 11.8 yrs, body weight 64.0 ± 11.7 kg and BMI 23.5 ± 3.6) were enrolled and walked comfortably on a 10-m walkway at self-selected slower, normal, and faster velocities. Walking was recorded with a high speed camera (250 frames per second) and the eight phases of a GC were determined by examination of individual frames for each subject. The correlation coefficients between the mean PT of the phases of the three velocities gaits and PT defined by previous publications were all greater than 0.99. The correlation coefficient between velocity and PT of gait phases is -0.83 for loading response (LR), -0.75 for mid stance (MSt), and -0.84 for pre-swing (PSw). While the PT of the phases of three velocities from this study are highly correlated with PT described by Dr. Jacquenlin Perry decades ago, actual PT of each phase varied amongst these individuals with the largest coefficient variation of 24.31% for IC with slower velocity. From slower to faster walk, the mean PT of MSt diminished from 35.30% to 25.33%. High resolution recording revealed ambiguity of some gait phase definitions, and these data may benefit GC characterization of normal and pathological gait in clinical practice. The study results indicate that one should consider individual variations and walking velocity when evaluating gaits of subjects using standard gait phase classification.

  10. Edge Detection with Sub-pixel Accuracy Based on Approximation of Edge with Erf Function

    Directory of Open Access Journals (Sweden)

    M. Hagara

    2011-06-01

    Full Text Available Edge detection is an often used procedure in digital image processing. For some practical applications is desirable to detect edges with sub-pixel accuracy. In this paper we present edge detection method for 1-D images based on approximation of real image function with Erf function. This method is verified by simulations and experiments for various numbers of samples of simulated and real images. Results of simulations and experiments are also used to compare proposed edge detection scheme with two often used moment-based edge detectors with sub-pixel precision.

  11. Modeling the ICRF-edge interaction in H-modes

    International Nuclear Information System (INIS)

    The understanding of the ICRF-edge plasma interaction has increased greatly in recent years. One important result has been the virtual elimination of ICRF-specific impurities during ICRF heating on JET. It has been shown that impurity release from ICRF antennas is an effect of rf sheaths. An rf-sheath model gives good agreement with JET impurity influx data and suggests a practical prescription for reducing impurities to negligible levels. Another important development, made possible by the reduction in impurities, was the achievement of H-modes induced by ICRF heating alone under conditions in which rf sheaths were expected to be robust (monopole phasing) and to be negligible (dipole phasing). It was found that the quality, duration and termination mechanism of the H-mode was different in the two cases. In this paper, the authors describe simulation results and experimental data which provide a possible explanation for the unique properties of the monopole ICRF H-mode. The simulation shows that the rf sheaths near the antenna drive large convective cells, which penetrate the SOL and cause enhanced edge transport. The edge convection is a good candidate to explain the reduction in quality of the highly-sheared, poloidally uniform H-mode transport barrier, and the resulting flattening of the SOL density and temperature profiles may explain the longer duration and the absence of a radiative collapse for the monopole H-mode. An analysis of JET data shows the existence of phasing-dependent ICRF-enhanced edge transport in agreement with the theoretical model. The 2D simulation results are discussed and compared with the available experimental data. This work suggest that ICRF antennas in monopole or FWCD phasing provide another practical means of biasing the edge plasma to control the global confinement, central density and impurity accumulation in H-mode operation

  12. The Hidden K-edge Signal in K-edge Imaging

    CERN Document Server

    Bateman, Christopher J; de Ruiter, Niels J A; Butler, Anthony P; Butler, Philip H; Renaud, Peter F

    2015-01-01

    K-edge imaging is commonly used for viewing contrast pharmaceuticals in a variety of multi-energy x-ray imaging techniques, ranging from dual-energy and spectral computed tomography to fluoroscopy. When looking for the K-edge signal of a specific contrast, by taking measurements either side of the K-edge, it is found that the K-edge is not always observable for low concentrations. We have also observed that the ability to see the K-edge is unit dependent - a K-edge that is not observable in computed tomography (CT) reconstructed linear attenuation units can often be made visible by converting to Hounsfield units. This paper presents an investigation of this K-edge hiding phenomenon. We conclude that if a multi-energy x-ray measurement of any K-edge material contains a signal of any other material, then there will be a positive concentration of that K-edge material below which its K-edge cannot be observed without extracting the K-edge signal through means of basis decomposition. Mathematical descriptions of t...

  13. Velocity Requirements for Causality Violation

    Science.gov (United States)

    Modanese, Giovanni

    We re-examine the "Regge-Tolman paradox" with reference to some recent experimental results. It is straightforward to find a formula for the velocity v of the moving system required to produce causality violation. This formula typically yields a velocity very close to the speed of light (for instance, v/c > 0.97 for X-shaped microwaves), which raises some doubts about the real physical observability of the violations. We then compute the velocity requirement introducing a delay between the reception of the primary signal and the emission of the secondary. It turns out that in principle for any delay it is possible to find moving observers able to produce active causal violation. This is mathematically due to the singularity of the Lorentz transformations for β →1. For a realistic delay due to the propagation of a luminal precursor, we find that causality violations in the reported experiments are still more unlikely (v/c > 0.989), and even in the hypothesis that the superluminal propagation velocity goes to infinity, the velocity requirement is bounded by v/c > 0.62. We also prove that if two oscopic bodies exchange energy and momentum through superluminal signals, then the swap of signal source and target is incompatible with the Lorentz transformations; therefore it is not possible to distinguish between source and target, even with reference to a definite reference frame.

  14. Magnetic signature of current carrying edge localized modes filaments on the Joint European Torus tokamak

    DEFF Research Database (Denmark)

    Migliucci, P.; Naulin, Volker

    2010-01-01

    Fast magnetic pickup coils are used in forward modeling to match parameters in a simple edge localized mode (ELM) filament model. This novel method allows us to determine key parameters for the evolution of the ELM filaments, as effective mode number, radial and toroidal velocities, and average...... tokamaks, obtained by a range of different diagnostics. It is found that the forward modeling produces key parameters such as the number of filaments and their toroidal velocity in agreement with other observations and in addition allows an estimate of the filament current....

  15. AliEn - EDG Interoperability in ALICE

    CERN Document Server

    Bagnasco, S; Buncic, P; Carminati, F; Cerello, P G; Saiz, P

    2003-01-01

    AliEn (ALICE Environment) is a GRID-like system for large scale job submission and distributed data management developed and used in the context of ALICE, the CERN LHC heavy-ion experiment. With the aim of exploiting upcoming Grid resources to run AliEn-managed jobs and store the produced data, the problem of AliEn-EDG interoperability was addressed and an in-terface was designed. One or more EDG (European Data Grid) User Interface machines run the AliEn software suite (Cluster Monitor, Storage Element and Computing Element), and act as interface nodes between the systems. An EDG Resource Broker is seen by the AliEn server as a single Computing Element, while the EDG storage is seen by AliEn as a single, large Storage Element; files produced in EDG sites are registered in both the EDG Replica Catalogue and in the AliEn Data Catalogue, thus ensuring accessibility from both worlds. In fact, both registrations are required: the AliEn one is used for the data management, the EDG one to guarantee the integrity and...

  16. Background Modelling Using Edge-Segment Distributions

    Directory of Open Access Journals (Sweden)

    Jaemyun Kim

    2013-02-01

    Full Text Available We propose an edge‐segment‐based statistical background modelling algorithm to detect the moving edges for the detection of moving objects using a static camera. Traditional pixel intensity‐based background modelling algorithms face difficulties in dynamic environments since they cannot handle sudden changes in illumination. They also bring out ghosts when a sudden change occurs in the scene. To cope with this issue, intensity and noise robust edge‐based features have emerged. However, existing edge‐pixel‐based methods suffer from scattered moving edge pixels since they cannot utilize the shape. Moreover, traditional segment‐ based methods cannot handle edge shape variations and miss moving edges when they come close to the background edges. Unlike traditional approaches, our proposed method builds the background model from ordinary training frames that may contain moving objects. Furthermore, it does not leave any ghosts behind. Moreover, our method uses an automatic threshold for every background edge distribution for matching. This makes our approach robust to illumination change, camera movement and background motion. Experiments show that our method outperforms others and can detect moving edges efficiently despite the above mentioned difficulties.

  17. Auditing to the cutting edge

    Energy Technology Data Exchange (ETDEWEB)

    Good, L.; Wirdzek, P.

    1999-07-01

    Equipment? System? Building? Campus? Neighborhood? Community? Region? What is to be audited and what needs to be corrected? Can the energy management professional decide, or should the customer? Over the last few decades, energy professionals have been evaluating energy use in order to balance clients' expenditures with acceptable levels of service. Traditionally, professional expertise and creativity have been limited more by budget than any other single element. Today, energy and the environment are tightly intertwined. In the future, effective energy management may not be possible without considering the relationships between them. Conversely, environmental protection cannot be achieved without considering energy production, distribution, and use. To this end, two powerful federal organizations, the US Environmental Protection Agency (EPA) and the US Department of Energy (DOE), have been engaged in defining the interrelationships of these areas and fashioning national energy policies aimed at awakening Americans to these facts. Environmental demands are becoming a factor in efficiency equations. Energy management professionals should prepare a response. They will face demands for cutting-edge audits that reach further than giving utility power just a trim in the energy barber shop. Survival in the business of energy management will require a broader perspective. One need only look to current advertisements by national and international corporations which praise the environmental benefits of their products and even their places of business as cleaner than their competitors'. For the energy management professional then, energy diversity and source versus site considerations are opportunities to be identified in the audit process, in addition to replacement of inefficient equipment. The country is rich with technology choices, with documented experience, and with the knowledge to create systems that can mine deep savings. True, some have niche

  18. Numerical simulation of airfoil trailing edge serration noise

    DEFF Research Database (Denmark)

    Zhu, Wei Jun; Shen, Wen Zhong

    In the present work, numerical simulations are carried out for a low noise airfoil with and without serrated Trailing Edge. The Ffowcs Williams-Hawkings acoustic analogy is implemented into the in-house incompressible flow solver EllipSys3D. The instantaneous hydrodynamic pressure and velocity...... field are obtained using Large Eddy Simulation. To obtain the time history data of sound pressure, the flow quantities are integrated around the airfoil surface through the FW-H approach. The extended length of the serration is about 16.7% of the airfoil chord and the geometric angle of the serration...... is 28 degrees. The chord based Reynolds number is around 1.5x106. Simulations are compared with existing wind tunnel experiments at various angles of attack. Even though the airfoil under investigation is already optimized for low noise emission, numerical simulations and wind tunnel experiments show...

  19. Flow tilt angles near forest edges - Part 1: Sonic anemometry

    DEFF Research Database (Denmark)

    Dellwik, Ebba; Mann, Jakob; Larsen, Klaus Steenberg

    2010-01-01

    An analysis of flow tilt angles from a fetch-limited beech forest site with clearings is presented in the context of vertical advection of carbon dioxide. Flow angles and vertical velocities from two sonic anemometers by different manufacturers were analyzed. Instead of using rotations, where zero......-flow angles were assumed for neutral flow, the data was interpreted in relation to upstream and downstream forest edges. Uncertainties caused by flow distortion, vertical misalignment and limited sampling time (statistical uncertainty) were evaluated and found to be highly significant. Since the attack angle...... distribution of the wind on the sonic anemometer is a function of atmospheric stratification, an instrumental error caused by imperfect flow distortion correction is also a function of the atmospheric stratification. In addition, it is discussed that the sonic anemometers have temperature dependent off...

  20. Spiral-induced velocity and metallicity patterns in a cosmological zoom simulation of a Milky Way-sized galaxy

    CERN Document Server

    Grand, Robert J J; Kawata, Daisuke; Minchev, Ivan; Sánchez-Blázquez, Patricia; Gómez, Facundo A; Marinacci, Federico; Pakmor, Rüdiger; Campbell, David J R

    2016-01-01

    We use a high resolution cosmological zoom simulation of a Milky Way-sized halo to study the observable features in velocity and metallicity space associated with the dynamical influence of spiral arms. For the first time, we demonstrate that spiral arms, that form in a disc in a fully cosmological environment with realistic galaxy formation physics, drive large-scale systematic streaming motions. In particular, on the trailing edge of the spiral arms the peculiar galacto-centric radial and tangential velocity field is directed radially outward and tangentially backward, whereas it is radially inward and tangentially forward on the leading edge. Owing to the negative radial metallicity gradient, this systematic motion drives, at a given radius, an azimuthal variation in the residual metallicity that is characterised by a metal rich trailing edge and a metal poor leading edge. We show that these signatures are theoretically observable in external galaxies with Integral Field Unit instruments such as VLT/MUSE, ...

  1. Shallow velocity structure and hidden faults of Kunming city region

    Science.gov (United States)

    Yu, Geng-Xin; Lou, Hai; Wang, Chun-Yong; Fu, Li-Yun; Zhang, Jian-Guo; Qin, Jia-Zheng; Yang, Run-Hai; Li, Hai-Ou

    2008-09-01

    In order to image the 3-D velocity structure of its shallow crust in Kunming region, China, finite-difference seismic tomography is used to invert the seismic data selected carefully from six-shot data. The result lays a foundation for the discussion of the relationship between the obtained velocity structure and the hidden faults, and for the illumination of the depth extents of main active faults surrounding Kunming city. Puduhe-Xishan fault lies on the western margin of the Kunming basin and is just situated on the west edge of the low velocity anomaly zone found at all depth levels. This indicates that this fault is a borderline fault of the Kunming basin. It can be concluded that the fault dips eastwards with a steep angle and its depth extent is large. Puji-Hanjiacun fault and Heilongtan-Guandu fault play a role in controlling the low velocity anomaly zone in middle basin. The depth extents of the two faults are comparatively small, without traversing the interface of basin floor.

  2. Geostatistical Modeling of Pore Velocity

    Energy Technology Data Exchange (ETDEWEB)

    Devary, J.L.; Doctor, P.G.

    1981-06-01

    A significant part of evaluating a geologic formation as a nuclear waste repository involves the modeling of contaminant transport in the surrounding media in the event the repository is breached. The commonly used contaminant transport models are deterministic. However, the spatial variability of hydrologic field parameters introduces uncertainties into contaminant transport predictions. This paper discusses the application of geostatistical techniques to the modeling of spatially varying hydrologic field parameters required as input to contaminant transport analyses. Kriging estimation techniques were applied to Hanford Reservation field data to calculate hydraulic conductivity and the ground-water potential gradients. These quantities were statistically combined to estimate the groundwater pore velocity and to characterize the pore velocity estimation error. Combining geostatistical modeling techniques with product error propagation techniques results in an effective stochastic characterization of groundwater pore velocity, a hydrologic parameter required for contaminant transport analyses.

  3. Velocity requirements for causality violation

    CERN Document Server

    Modanese, Giovanni

    2013-01-01

    It is known that the hypothetical existence of superluminal signals would imply the logical possibility of active causal violation: an observer in relative motion with respect to a primary source could in principle emit secondary superluminal signals (triggered by the primary ones) which go back in time and deactivate the primary source before the initial emission. This is a direct consequence of the structure of the Lorentz transformations, sometimes called "Regge-Tolman paradox". It is straightforward to find a formula for the velocity of the moving observer required to produce the causality violation. When applied to some recent claims of slight superluminal propagation, this formula yields a required velocity very close to the speed of light; this raises some doubts about the real physical observability of such violations. We re-compute this velocity requirement introducing a realistic delay between the reception of the primary signal and the emission of the secondary. It turns out that for -any- delay it...

  4. Differential Search Algorithm Based Edge Detection

    Science.gov (United States)

    Gunen, M. A.; Civicioglu, P.; Beşdok, E.

    2016-06-01

    In this paper, a new method has been presented for the extraction of edge information by using Differential Search Optimization Algorithm. The proposed method is based on using a new heuristic image thresholding method for edge detection. The success of the proposed method has been examined on fusion of two remote sensed images. The applicability of the proposed method on edge detection and image fusion problems have been analysed in detail and the empirical results exposed that the proposed method is useful for solving the mentioned problems.

  5. Image Edge Extraction via Fuzzy Reasoning

    Science.gov (United States)

    Dominquez, Jesus A. (Inventor); Klinko, Steve (Inventor)

    2008-01-01

    A computer-based technique for detecting edges in gray level digital images employs fuzzy reasoning to analyze whether each pixel in an image is likely on an edge. The image is analyzed on a pixel-by-pixel basis by analyzing gradient levels of pixels in a square window surrounding the pixel being analyzed. An edge path passing through the pixel having the greatest intensity gradient is used as input to a fuzzy membership function, which employs fuzzy singletons and inference rules to assigns a new gray level value to the pixel that is related to the pixel's edginess degree.

  6. Adobe Edge Animate CC for dummies

    CERN Document Server

    Rohde, Michael

    2013-01-01

    The easy way to build HTML5 mobile and web apps using Adobe's new Edge Animate CC Edge Animate CC is an approachable WYSIWYG alternative for leveraging the power of languages like HTML5, CSS3, and JavaScript to design and develop for the web and mobile devices, even if you have no programming experience. Written by Michael Rohde, the book calls on this seasoned web developer's wealth of experience using Edge Animate CC, and a companion website includes all code from the book to help you apply what you learn as you go. Features an easy-to-use interface, with a propert

  7. Edge-Disjoint Fibonacci Trees in Hypercube

    Directory of Open Access Journals (Sweden)

    Indhumathi Raman

    2014-01-01

    Full Text Available The Fibonacci tree is a rooted binary tree whose number of vertices admit a recursive definition similar to the Fibonacci numbers. In this paper, we prove that a hypercube of dimension h admits two edge-disjoint Fibonacci trees of height h, two edge-disjoint Fibonacci trees of height h-2, two edge-disjoint Fibonacci trees of height h-4 and so on, as subgraphs. The result shows that an algorithm with Fibonacci trees as underlying data structure can be implemented concurrently on a hypercube network with no communication latency.

  8. Flat-band engineering of mobility edges

    Science.gov (United States)

    Danieli, Carlo; Bodyfelt, Joshua D.; Flach, Sergej

    2015-06-01

    Properly modulated flat-band lattices have a divergent density of states at the flat-band energy. Quasiperiodic modulations are known to host a metal-insulator transition already in one space dimension. Their embedding into flat-band geometries consequently allows for a precise engineering and fine tuning of mobility edges. We obtain analytic expressions for singular mobility edges for two flat-band lattice examples. In particular, we engineer cases with arbitrarily small energy separations of mobility edge, zeroes, and divergencies.

  9. Cavitation on hydrofoils with sinusoidal leading edge

    Science.gov (United States)

    Johari, H.

    2015-12-01

    Cavitation characteristics of hydrofoils with sinusoidal leading edge were examined experimentally at a Reynolds number of 7.2 × 105. The hydrofoils had an underlying NACA 634-021 profile and an aspect ratio of 4.3. The sinusoidal leading edge geometries included three amplitudes of 2.5%, 5%, and 12% and two wavelengths of 25% and 50% of the mean chord length. Results revealed that cavitation on the leading edge-modified hydrofoils existed in pockets behind the troughs whereas the baseline hydrofoil produced cavitation along its entire span. Moreover, cavitation on the modified hydrofoils appeared at consistently lower angles of attack than on the baseline hydrofoil.

  10. The Effect of Break Edge Configuration on the Aerodynamics of Anti-Ice Jet Flow

    Directory of Open Access Journals (Sweden)

    Tatar V.

    2015-01-01

    Full Text Available One of the components of a turboprop gas turbine engine is the Front Bearing Structure (FBS which leads air into the compressor. FBS directly encounters with ambient air, as a consequence ice accretion may occur on its static vanes. There are several aerodynamic parameters which should be considered in the design of anti-icing system of FBS, such as diameter, position, exit angle of discharge holes, etc. This research focuses on the effects of break edge configuration over anti-ice jet flow. Break edge operation is a process which is applied to the hole in order to avoid sharp edges which cause high stress concentration. Numerical analyses and flow visualization test have been conducted. Four different break edge configurations were used for this investigation; without break edge, 0.35xD, 74xD, 0.87xD. Three mainstream flow conditions at the inlet of the channel are defined; 10m/s, 20 m/s and 40 m/s. Shear stresses are extracted from numerical analyses near the trailing edge of pressure surface where ice may occur under icing conditions. A specific flow visualization method was used for the experimental study. Vane surface near the trailing edge was dyed and thinner was injected into anti-ice jet flow in order to remove dye from the vane surface. Hence, film effect on the surface could be computed for each testing condition. Thickness of the dye removal area of each case was examined. The results show noticeable effects of break edge operation on jet flow, and the air film effectiveness decreases when mainstream inlet velocity decreases.

  11. The Effect of Break Edge Configuration on the Aerodynamics of Anti-Ice Jet Flow

    Science.gov (United States)

    Tatar, V.; Yildizay, H.; Aras, H.

    2015-05-01

    One of the components of a turboprop gas turbine engine is the Front Bearing Structure (FBS) which leads air into the compressor. FBS directly encounters with ambient air, as a consequence ice accretion may occur on its static vanes. There are several aerodynamic parameters which should be considered in the design of anti-icing system of FBS, such as diameter, position, exit angle of discharge holes, etc. This research focuses on the effects of break edge configuration over anti-ice jet flow. Break edge operation is a process which is applied to the hole in order to avoid sharp edges which cause high stress concentration. Numerical analyses and flow visualization test have been conducted. Four different break edge configurations were used for this investigation; without break edge, 0.35xD, 74xD, 0.87xD. Three mainstream flow conditions at the inlet of the channel are defined; 10m/s, 20 m/s and 40 m/s. Shear stresses are extracted from numerical analyses near the trailing edge of pressure surface where ice may occur under icing conditions. A specific flow visualization method was used for the experimental study. Vane surface near the trailing edge was dyed and thinner was injected into anti-ice jet flow in order to remove dye from the vane surface. Hence, film effect on the surface could be computed for each testing condition. Thickness of the dye removal area of each case was examined. The results show noticeable effects of break edge operation on jet flow, and the air film effectiveness decreases when mainstream inlet velocity decreases.

  12. ANALYSIS OF SLAB EDGING BY A 3-D RIGID VISCO-PLASTIC FINITE ELEMENT METHOD

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    3-D rigid visco-plastic finite element method (FEM) is used in the analysis of metal forming processes, including strip and plate rolling, shape rolling, slab edging, special strip rolling. The shifted incomplete Cholesky decomposition of the stiffness matrix with the solution of the equations for velocity increment by the conjugate gradient method is combined. This technique, termed the shifted ICCG method, is then employed to solve the slab edging problem. The performance of this algorithm in terms of the number of iterations, friction variation, shifted parameter ( and the results of simulation for processing parameters are analysed. Numerical tests and application of this technique verify the efficiency and stability of the shifted ICCG method in the analysis of slab edging.

  13. Observation of a Helical Luttinger Liquid in InAs/GaSb Quantum Spin Hall Edges.

    Science.gov (United States)

    Li, Tingxin; Wang, Pengjie; Fu, Hailong; Du, Lingjie; Schreiber, Kate A; Mu, Xiaoyang; Liu, Xiaoxue; Sullivan, Gerard; Csáthy, Gábor A; Lin, Xi; Du, Rui-Rui

    2015-09-25

    We report on the observation of a helical Luttinger liquid in the edge of an InAs/GaSb quantum spin Hall insulator, which shows characteristic suppression of conductance at low temperature and low bias voltage. Moreover, the conductance shows power-law behavior as a function of temperature and bias voltage. The results underscore the strong electron-electron interaction effect in transport of InAs/GaSb edge states. Because of the fact that the Fermi velocity of the edge modes is controlled by gates, the Luttinger parameter can be fine tuned. Realization of a tunable Luttinger liquid offers a one-dimensional model system for future studies of predicted correlation effects. PMID:26451576

  14. Synthetic plasma edge diagnostics for EMC3-EIRENE, highlighted for Wendelstein 7-X

    Science.gov (United States)

    Frerichs, H.; Effenberg, F.; Schmitz, O.; Biedermann, C.; Feng, Y.; Jakubowski, M.; König, R.; Krychowiak, M.; Lore, J.; Niemann, H.; Pedersen, T. S.; Stephey, L.; Wurden, G. A.

    2016-11-01

    Interpretation of spectroscopic measurements in the edge region of high-temperature plasmas can be a challenge since line of sight integration effects make direct interpretation in terms of quantitative, local emission strengths often impossible. The EMC3-EIRENE code—a 3D fluid edge plasma and kinetic neutral gas transport code—is a suitable tool for full 3D reconstruction of such signals. A versatile synthetic diagnostic module has been developed recently which allows the realistic 3D setup of various plasma edge diagnostics to be captured. We highlight these capabilities with two examples for Wendelstein 7-X (W7-X): a visible camera for the analysis of recycling, and a coherent-imaging system for velocity measurements.

  15. Edge- and Node-Disjoint Paths in P Systems

    Directory of Open Access Journals (Sweden)

    Michael J. Dinneen

    2010-10-01

    Full Text Available In this paper, we continue our development of algorithms used for topological network discovery. We present native P system versions of two fundamental problems in graph theory: finding the maximum number of edge- and node-disjoint paths between a source node and target node. We start from the standard depth-first-search maximum flow algorithms, but our approach is totally distributed, when initially no structural information is available and each P system cell has to even learn its immediate neighbors. For the node-disjoint version, our P system rules are designed to enforce node weight capacities (of one, in addition to edge capacities (of one, which are not readily available in the standard network flow algorithms.

  16. Incoherent synchrotron emission of laser-driven plasma edge

    Energy Technology Data Exchange (ETDEWEB)

    Serebryakov, D. A., E-mail: dmserebr@gmail.com; Nerush, E. N.; Kostyukov, I. Yu. [Institute of Applied Physics of the Russian Academy of Sciences, 46 Ulyanov St., Nizhny Novgorod 603950 (Russian Federation); Nizhny Novgorod State University, 23 Gagarin Avenue, Nizhny Novgorod 603950 (Russian Federation)

    2015-12-15

    When a relativistically intense linearly polarized laser pulse is incident on an overdense plasma, a dense electron layer is formed on the plasma edge which relativistic motion results in high harmonic generation, ion acceleration, and incoherent synchrotron emission of gamma-photons. Here we present a self-consistent analytical model that describes the edge motion and apply it to the problem of incoherent synchrotron emission by ultrarelativistic plasma electrons. The model takes into account both coherent radiation reaction from high harmonics and incoherent radiation reaction in the Landau–Lifshitz form. The analytical results are in agreement with 3D particle-in-cell simulations in a certain parameter region that corresponds to the relativistic electronic spring interaction regime.

  17. Angle independent velocity spectrum determination

    DEFF Research Database (Denmark)

    2014-01-01

    An ultrasound imaging system (100) includes a transducer array (102) that emits an ultrasound beam and produces at least one transverse pulse-echo field that oscillates in a direction transverse to the emitted ultrasound beam and that receive echoes produced in response thereto and a spectral vel...... velocity estimator (110) that determines a velocity spectrum for flowing structure, which flows at an angle of 90 degrees and flows at angles less than 90 degrees with respect to the emitted ultrasound beam, based on the received echoes....

  18. Velocity fluctuations of fission fragments

    CERN Document Server

    Llanes-Estrada, Felipe J; Martinez, Jose L Muñoz

    2015-01-01

    We propose event by event velocity fluctuations of nuclear fission fragments as an additional interesting observable that gives access to the nuclear temperature in an independent way from spectral measurements and relates the diffusion and friction coefficients for the relative fragment coordinate in Kramer-like models (in which some aspects of fission can be understood as the diffusion of a collective variable through a potential barrier). We point out that neutron emission by the heavy fragments can be treated in effective theory if corrections to the velocity distribution are needed.

  19. Experimental Measurements of Two-dimensional Planar Propagating Edge Flames

    Science.gov (United States)

    Villa-Gonzalez, Marcos; Marchese, Anthony J.; Easton, John W.; Miller, Fletcher J.

    2007-01-01

    The study of edge flames has received increased attention in recent years. This work reports the results of a recent study into two-dimensional, planar, propagating edge flames that are remote from solid surfaces (called here, free-layer flames, as opposed to layered flames along floors or ceilings). They represent an ideal case of a flame propagating down a flammable plume, or through a flammable layer in microgravity. The results were generated using a new apparatus in which a thin stream of gaseous fuel is injected into a low-speed laminar wind tunnel thereby forming a flammable layer along the centerline. An airfoil-shaped fuel dispenser downstream of the duct inlet issues ethane from a slot in the trailing edge. The air and ethane mix due to mass diffusion while flowing up towards the duct exit, forming a flammable layer with a steep lateral fuel concentration gradient and smaller axial fuel concentration gradient. We characterized the flow and fuel concentration fields in the duct using hot wire anemometer scans, flow visualization using smoke traces, and non-reacting, numerical modeling using COSMOSFloWorks. In the experiment, a hot wire near the exit ignites the ethane air layer, with the flame propagating downwards towards the fuel source. Reported here are tests with the air inlet velocity of 25 cm/s and ethane flows of 967-1299 sccm, which gave conditions ranging from lean to rich along the centerline. In these conditions the flame spreads at a constant rate faster than the laminar burning rate for a premixed ethane air mixture. The flame spread rate increases with increasing transverse fuel gradient (obtained by increasing the fuel flow rate), but appears to reach a maximum. The flow field shows little effect due to the flame approach near the igniter, but shows significant effect, including flow reversal, well ahead of the flame as it approaches the airfoil fuel source.

  20. On the use of Particle Image Velocimetry to predict trailing edge noise

    OpenAIRE

    Tuinstra, M.; Probsting, S.; Scarano, F.

    2013-01-01

    The feasibility of aeroacoustic noise predictions based on Particle Image Velocimetry (PIV) measurements is studied. For this purpose, experiments are conducted on a sharp trailing edge (TE) flow developed along a flat plate at free stream velocity of 15m/s. The acoustic emissions were characterized in the NLR Small Anechoic Wind Tunnel (KAT) by means of microphone measurements. The result is used for benchmarking the PIV based noise predictions. PIV measurements were carried in a low-speed w...

  1. XMCD under pressure at the Fe K edge on the energy dispersive beamline of the ESRF

    OpenAIRE

    Mathon, Olivier; Baudelet, Francois; Itié, Jean-Paul; Pasternak, Sébastien; Polian, Alain; Pascarelli, Sakura

    2004-01-01

    The present paper demonstrates the feasibility of X-ray Absorption Spectroscopy (XAS) and X-ray Magnetic Circular Dichroism (XMCD) at high pressure at the Fe-K edge on the ID24 energy dispersive beamline of the ESRF. In 3d transition metals, performing experiments at the hard X-ray K-edge rather than at the magnetically interesting soft X-ray L-edges represents, the only way to access the high pressure regime obtainable with Diamond Anvil Cells. The simultaneous availability of a local struct...

  2. Experimental observation of bulk and edge transport in photonic Lieb lattices

    CERN Document Server

    Guzman-Silva, D; Bandres, M A; Rechtsman, M C; Weimann, S; Nolte, S; Segev, M; Szameit, A; Vicencio, R A

    2014-01-01

    We analyze the transport of light in the bulk and at the edge of photonic Lieb lattices, whose unique feature is the existence of a flat band representing stationary states in the middle of the band structure that can form localized bulk states. We find that transport in bulk Lieb lattices is significantly affected by the particular excitation site within the unit cell, due to overlap with the flat band states. Additionally, we demonstrate the existence of new edge states in anisotropic Lieb lattices. These states arise due to a virtual defect at the lattice edges and are not described by the standard tight-binding model.

  3. The edge-based face element method for 3D-stream function and flux calculations in porous media flow

    NARCIS (Netherlands)

    Zijl, W.; Nawalany, M.

    2004-01-01

    We present a velocity-oriented discrete analog of the partial differential equations governing porous media flow: the edge-based face element method. Conventional finite element techniques calculate pressures in the nodes of the grid. However, such methods do not satisfy the requirement of flux cont

  4. Effect of guide wall on jet impingement cooling in blade leading edge channel

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Qing-Yang; Chung, Heeyoon; Choi, Seok Min; Cho, Hyung Hee [Yonsei University, Seoul (Korea, Republic of)

    2016-02-15

    The characteristics of fluid flow and heat transfer, which are affected by the guide wall in a jet impinged leading edge channel, have been investigated numerically using three-dimensional Reynolds-averaged Navier-Stokes analysis via the shear stress transport turbulence model and gamma theta transitional turbulence model. A constant wall heat flux condition has been applied to the leading edge surface. The jet-to-surface distance is constant, which is three times that of the jet diameter. The arrangement of the guide wall near the jet hole is set as a variable. Results presented in this study include the Nusselt number contour, velocity vector, streamline with velocity, and local Nusselt number distribution along the central line on the leading edge surface. The average Nusselt number and average pressure loss between jet nozzle and channel exit are calculated to assess the thermal performance. The application of the guide wall is aimed at improving heat transfer uniformity on the leading edge surface. Results indicated that the streamwise guide wall ensures the vertical jet impingement flow intensity and prevents the flow after impingement to reflux into jet flow. Thus, a combined rectangular guide wall benefits the average heat transfer, thermal performance and heat transfer distribution uniformity.

  5. A mimetic finite difference method for the Stokes problem with elected edge bubbles

    Energy Technology Data Exchange (ETDEWEB)

    Lipnikov, K [Los Alamos National Laboratory; Berirao, L [DIPARTMENTO DI MATERMATICA

    2009-01-01

    A new mimetic finite difference method for the Stokes problem is proposed and analyzed. The unstable P{sub 1}-P{sub 0} discretization is stabilized by adding a small number of bubble functions to selected mesh edges. A simple strategy for selecting such edges is proposed and verified with numerical experiments. The discretizations schemes for Stokes and Navier-Stokes equations must satisfy the celebrated inf-sup (or the LBB) stability condition. The stability condition implies a balance between discrete spaces for velocity and pressure. In finite elements, this balance is frequently achieved by adding bubble functions to the velocity space. The goal of this article is to show that the stabilizing edge bubble functions can be added only to a small set of mesh edges. This results in a smaller algebraic system and potentially in a faster calculations. We employ the mimetic finite difference (MFD) discretization technique that works for general polyhedral meshes and can accomodate non-uniform distribution of stabilizing bubbles.

  6. Strain imaging by Bragg edge neutron transmission

    CERN Document Server

    Santisteban, J R; Fitzpatrick, M E; Steuwer, A; Withers, P J; Daymond, M R; Johnson, M W; Rhodes, N; Schooneveld, E M

    2002-01-01

    The Bragg edges appearing in the transmitted time-of-flight spectra of polycrystalline materials have been recorded using a two-dimensional array of detectors. Subsequent analysis has enabled maps of the elastic strain to be produced.

  7. Flow distortion at a dense forest edge

    DEFF Research Database (Denmark)

    Dellwik, Ebba; Bingöl, Ferhat; Mann, Jakob

    2014-01-01

    The flow near tall forest edges is complex, yet poorly described. A field experiment using two meteorological masts equipped with sonic anemometers and a horizontally staring lidar was performed upwind and downwind of the interface between an open flat farmland and a tall (hc = 24 m) beech forest......, relative to the measurements upwind of the edge. The lidar data taken at several positions between the masts at 1.25hc show that the minimum wind speed occurred just upwind of the edge. At the 1.25hc level, at the forest mast, the momentum flux (\\documentclass...... qualitatively be explained with the concept of eddy‐blocking by the canopy top, which could also explain the observed increase in lateral variance and the decrease in the vertical variance. Despite the short distance to the edge of approximately 1.5hc, the beginning of a new internal boundary layer was visible...

  8. Ergodic divertor impact on Tore Supra edge

    International Nuclear Information System (INIS)

    The present ergodic divertor experiments in Tore Supra have been devoted to benchmarking the operational regimes of the apparatus. Two major effects are reported: on the one hand, strong changes occur in the ergodized boundary layer (up to 20% of the minor radius), and on the other hand, the central plasma and especially the confinement is not directly affected, i.e. the observed modifications are induced by edge effects. The basic trends, which are recorded are a decrease of both the edge electronic temperature and the edge density gradient while the radiated power is increased at the very edge of the ergodic region. The latter feature is in agreement with the impurity line emission characterized by an increase of the peripheral lines with a strong decrease of the central lines. (orig.)

  9. Imaging The Leading Edge Of A Weld

    Science.gov (United States)

    Mcgee, William F.; Rybicki, Daniel J.

    1994-01-01

    Proposed optical system integrated into plasma arc welding torch provides image of leading edge of weld pool and welding-arc-initiation point. Welding torch aligned better with joint. System includes coherent bundle of optical fibers and transparent cup.

  10. Mechanotunable monatomic metal structures at graphene edges.

    Science.gov (United States)

    Wei, Ning; Chang, Cheng; Zhu, Hongwei; Xu, Zhiping

    2014-06-14

    Monatomic metal (e.g. silver) structures could form preferably at graphene edges. We explore their structural and electronic properties by performing density functional theory based first-principles calculations. The results show that cohesion between metal atoms, as well as electronic coupling between metal atoms and graphene edges offer remarkable structural stability of the hybrid. We find that the outstanding mechanical properties of graphene allow tunable properties of the metal monatomic structures by straining the structure. The concept is extended to metal rings and helices that form at open ends of carbon nanotubes and edges of twisted graphene ribbons. These findings demonstrate the role of graphene edges as an efficient one-dimensional template for low-dimensional metal structures that are mechanotunable.

  11. Magnetic quantum dots and magnetic edge states

    International Nuclear Information System (INIS)

    Starting with defining the magnetic edge state in a magnetic quantum dot, which becomes quite popular nowadays conjunction with a possible candidate for a high density memory device or spintronic materials, various magnetic nano-quantum structures are reviewed in detail. We study the magnetic edge states of the two dimensional electron gas in strong perpendicular magnetic fields. We find that magnetic edge states are formed along the boundary of the magnetic dot, which is formed by a nonuniform distribution of magnetic fields. These magnetic edge states circulate either clockwise or counterclockwise, depending on the number of missing flux quanta, and exhibit quite different properties, as compared to the conventional ones which are induced by electrostatic confinements in the quantum Hall system. We also find that a close relation between the quantum mechanical eigenstates and the classical trajectories in the magnetic dot. When a magnetic dot is located inside a quantum wire, the edge-channel scattering mechanism by the magnetic quantum dot is very different from that by electrostatic dots. Here, the magnetic dot is formed by two different magnetic fields inside and outside the dot. We study the ballistic edge-channel transport and magnetic edge states in this situation. When the inner field is parallel to the outer one, the two-terminal conductance is quantized and shows the features of a transmission barrier and a resonator. On the other hand, when the inner field is reversed, the conductance is not quantized and all channels can be completely reflected in some energy ranges. The difference between the above two cases results from the distinct magnetic confinements. We also describe successfully the edge states of magnetic quantum rings and others in detail

  12. Edge states of periodically kicked quantum rotors

    CERN Document Server

    Floß, Johannes

    2015-01-01

    We present a quantum localization phenomenon that exists in periodically kicked 3D rotors, but is absent in the commonly studied 2D ones: edge localization. We show that under the condition of a fractional quantum resonance there are states of the kicked rotor that are strongly localized near the edge of the angular momentum space at $J=0$. These states are analogs of surface states in crystalline solids, and they significantly affect resonant excitation of molecular rotation by laser pulse trains.

  13. Refining Nodes and Edges of State Machines

    OpenAIRE

    Hallerstede, Stefan; Snook, Colin

    2011-01-01

    State machines are hierarchical automata that are widely used to structure complex behavioural specifications. We develop two notions of refinement of state machines, node refinement and edge refinement. We compare the two notions by means of examples and argue that, by adopting simple conventions, they can be combined into one method of refinement. In the combined method, node refinement can be used to develop architectural aspects of a model and edge refinement to develop algorithmic aspect...

  14. Image Edge Detection Based on Oscillation

    Institute of Scientific and Technical Information of China (English)

    FAN Hong; WANG Zhi-jie

    2005-01-01

    A new method for image edge detection based on a pulse neural network is proposed in this paper. The network is locally connected. The external input of each neuron of the network is gray value of the corresponding pixel. The synchrony of the neuron and its neighbors is detected by detection neurons. The edge of the image can be read off at minima of the total activity of the detection neurons.

  15. Development of K-edge Densitometer

    Institute of Scientific and Technical Information of China (English)

    HE; Li-xia; BAI; Lei; XU; Xiao-ming; ZHU; Li-qun

    2013-01-01

    K-edge densitometer is designed to quantify heavy elements concentration in homogeneous solution of nuclear fuel reprocessing.It is based on principle of hybrid K-edge densitometer(KED)measurement and X-ray fluorescence(XRF)analysis of induced X rays.It has proven to give approximately the same precision as destructive analysis methods,yet is much simpler and faster to use.The system consists of a

  16. The perceptual contrast of impossible shadow edges

    OpenAIRE

    Soranzo, Alessandro; Galmonte, Alessandra; Agostini, Tiziano

    2009-01-01

    Luminance ratios along shadow edges remain the same even when they cross reflectance borders. According to Gilchrist (1988, Perception & Psychophysics 43 415 ^ 424) this so-called ratio-invariance property is a crucial factor in the perception of shadows. However, Soranzo and Agostini (2004, Perception 33 1359 ^ 1368) suggested that in some conditions (named `impossible shadows'), a luminance pattern might still be perceived as a shadow even if the ratio-invariance property along its edge ...

  17. Face analysis using curve edge maps

    OpenAIRE

    Deboeverie, Francis; Veelaert, Peter; Philips, Wilfried

    2011-01-01

    This paper proposes an automatic and real-time system for face analysis, usable in visual communication applications. In this approach, faces are represented with Curve Edge Maps, which are collections of polynomial segments with a convex region. The segments are extracted from edge pixels using an adaptive incremental linear-time fitting algorithm, which is based on constructive polynomial fitting. The face analysis system considers face tracking, face recognition and facial feature detectio...

  18. FACIAL EXPRESSION RECOGNITION BASED ON EDGE DETECTION

    OpenAIRE

    Chen, Xiaoming; Cheng, Wushan

    2015-01-01

    Relational Over the last two decades, the advances in computer vision and pattern recognition power have opened the door to new opportunity of automatic facial expression recognition system[1]. This paper use Canny edge detection method for facial expression recognition. Image color space transformation in the first place and then to identify and locate human face .Next pick up the edge of eyes and mouth's features extraction. Last we judge the facial expressions after compared wi...

  19. Pulsar Velocities without Neutrino Mass

    CERN Document Server

    Grasso, D; Valle, José W F

    1998-01-01

    We show that pulsar velocities may arise from anisotropic neutrino emission induced by resonant conversions of massless neutrinos in the presence of a strong magnetic field. The main ingredient is a small violation of weak universality and neither neutrino masses nor magnetic moments are required.

  20. Turbodrill rod angular velocity indicator

    Energy Technology Data Exchange (ETDEWEB)

    Rogachev, O.K.; Belozerova, L.P.; Konenkov, A.K.

    1984-01-01

    This paper outlines shortcomings of existing types of telemetry systems which resulted in production of the IChT-1 unit. Unit is intended for control of angular velocity of serially produced turbodrill rods, during drilling of wells up to 5000 m deep, and bottomhole temperatures to 100C. The paper provides a detailed description and diagrams for installing this unit.

  1. Edge states in polariton honeycomb lattices

    Science.gov (United States)

    Milićević, M.; Ozawa, T.; Andreakou, P.; Carusotto, I.; Jacqmin, T.; Galopin, E.; Lemaître, A.; Le Gratiet, L.; Sagnes, I.; Bloch, J.; Amo, A.

    2015-09-01

    The experimental study of edge states in atomically thin layered materials remains a challenge due to the difficult control of the geometry of the sample terminations, the stability of dangling bonds, and the need to measure local properties. In the case of graphene, localized edge modes have been predicted in zigzag and bearded edges, characterized by flat dispersions connecting the Dirac points. Polaritons in semiconductor microcavities have recently emerged as an extraordinary photonic platform to emulate 1D and 2D Hamiltonians, allowing the direct visualization of the wavefunctions in both real- and momentum-space as well as of the energy dispersion of eigenstates via photoluminescence experiments. Here we report on the observation of edge states in a honeycomb lattice of coupled micropillars. The lowest two bands of this structure arise from the coupling of the lowest energy modes of the micropillars, and emulate the π and π* bands of graphene. We show the momentum-space dispersion of the edge states associated with the zigzag and bearded edges, holding unidimensional quasi-flat bands. Additionally, we evaluate polarization effects characteristic of polaritons on the properties of these states.

  2. Cutting edge: The adapters EAT-2A and -2B are positive regulators of CD244- and CD84-dependent NK cell functions in the C57BL/6 mouse.

    Science.gov (United States)

    Wang, Ninghai; Calpe, Silvia; Westcott, Jill; Castro, Wilson; Ma, Chunyan; Engel, Pablo; Schatzle, John D; Terhorst, Cox

    2010-11-15

    EWS/FLI1-activated transcript 2 (EAT-2)A and EAT-2B are single SH2-domain proteins, which bind to phosphorylated tyrosines of signaling lymphocyte activation molecule family receptors in murine NK cells. While EAT-2 is a positive regulator in human cells, a negative regulatory role was attributed to the adapter in NK cells derived from EAT-2A-deficient 129Sv mice. To evaluate whether the genetic background or the presence of a selection marker in the mutant mice could influence the regulatory mode of these adapters, we generated EAT-2A-, EAT-2B-, and EAT-2A/B-deficient mice using C57BL/6 embryonic stem cells. We found that NK cells from EAT-2A- and EAT-2A/B-deficient mice were unable to kill tumor cells in a CD244- or CD84-dependent manner. Furthermore, EAT-2A/B positively regulate phosphorylation of Vav-1, which is known to be implicated in NK cell killing. Thus, as in humans, the EAT-2 adapters act as positive regulators of signaling lymphocyte activation molecule family receptor-specific NK cell functions in C57BL/6 mice.

  3. Edge-Fault-Tolerant Edge-Bipancyclicity of Bubble-Sort Graphs

    Institute of Scientific and Technical Information of China (English)

    Xin Ping XU; Min XU; Jin JING

    2012-01-01

    The bubble-sort graph Bn is a bipartite graph.Kikuchi and Araki [Edge-bipancyclicity and edge-fault-tolerant bipancyclicity of bubble-sort graphs.Information Processing Letters,100,52-59 (2006)] have proved that Bn is edge-bipancyclic for n ≥ 5 and Bn - F is bipancyclic when n ≥ 4and |F| ≤ n - 3.In this paper,we improve this result by showing that for any edge set F of Bn with |F| ≤ n - 3,every edge of Bn - F lies on a cycle of every even length from 6 to n! for n ≥ 5 and every edge of Bn - F lies on a cycle of every even length from 8 to n! for n =4.

  4. Influence of Edge Rolling Reduction on Plate-Edge Stress Distribution During Finish Rolling

    Institute of Scientific and Technical Information of China (English)

    YU Hai-liang; LIU Xiang-hua; CHEN Li-qing; LI Chang-sheng; ZHI Ying; LI Xin-wen

    2009-01-01

    Dimensions of one kind of stainless steel plate before finish rolling were obtained through analysis of the rough rolling processes by finite element method and updated geometrical method.The FE models of finish rolling process with a front edge roll were built,and influences of the edge rolling reduction on-the stress change in the plate edge during finish roiling were analyzed.The results show that when the edge rolling reduction is increased from 0 mm to 2 ram,the compressive stress in plate corner clearly increases in edge rolling process,and the zone of tensile stress during whole rolling decreases;when the edge rolling reduction is increased from 2 mm to 5 mm,the compressive stress in the plate corner seldom changes,and the compressive stress decreases after the horizontal rolling.

  5. Edge subdivision and edge multisubdivision versus some domination related parameters in generalized corona graphs

    Directory of Open Access Journals (Sweden)

    Magda Dettlaff

    2016-01-01

    Full Text Available Given a graph \\(G=(V,E\\, the subdivision of an edge \\(e=uv\\in E(G\\ means the substitution of the edge \\(e\\ by a vertex \\(x\\ and the new edges \\(ux\\ and \\(xv\\. The domination subdivision number of a graph \\(G\\ is the minimum number of edges of \\(G\\ which must be subdivided (where each edge can be subdivided at most once in order to increase the domination number. Also, the domination multisubdivision number of \\(G\\ is the minimum number of subdivisions which must be done in one edge such that the domination number increases. Moreover, the concepts of paired domination and independent domination subdivision (respectively multisubdivision numbers are defined similarly. In this paper we study the domination, paired domination and independent domination (subdivision and multisubdivision numbers of the generalized corona graphs.

  6. Spatiotemporal velocity-velocity correlation function in fully developed turbulence

    CERN Document Server

    Canet, Léonie; Wschebor, Nicolás; Balarac, Guillaume

    2016-01-01

    Turbulence is an ubiquitous phenomenon in natural and industrial flows. Since the celebrated work of Kolmogorov in 1941, understanding the statistical properties of fully developed turbulence has remained a major quest. In particular, deriving the properties of turbulent flows from a mesoscopic description, that is from Navier-Stokes equation, has eluded most theoretical attempts. Here, we provide a theoretical prediction for the {\\it space and time} dependent velocity-velocity correlation function of homogeneous and isotropic turbulence from the field theory associated to Navier-Stokes equation with stochastic forcing. This prediction is the analytical fixed-point solution of Non-Perturbative Renormalisation Group flow equations, which are exact in a certain large wave-number limit. This solution is compared to two-point two-times correlation functions computed in direct numerical simulations. We obtain a remarkable agreement both in the inertial and in the dissipative ranges.

  7. A Shearlets-based Edge Identification Algorithem for Infrared Image

    OpenAIRE

    Rui-bin ZOU; Cai-cheng SHI

    2013-01-01

    A shearlets-based edge identification algorithem for infrared image is proposed. The algorithem demonstrates the performance of edge detection based on shearlets, combines with the edge hysteresis thresholding, designs steps of edge detection, which is proper to use in infrared images.Simultaneously, with the advantage of edge geometric features provided by the shearlets, infrared image were extracted the direction information of edge of Infrared image, and classified. In computer simulations...

  8. Influence of Immersion Lithography on Wafer Edge Defectivity

    OpenAIRE

    Jami, K.; Pollentier, I.; Vedula, S; Blumenstock, G

    2010-01-01

    In this paper, we investigated the impact of immersion lithography on wafer edge defectivity. In the past, such work has been limited to inspection of the flat top part of the wafer edge due to the inspection challenges at the curved wafer edge and lack of a comprehensive defect inspection solution. Our study used a new automated edge inspection system that provides full wafer edge imaging and automatic defect classification. The work revealed several key challenges to controlling wafer edge-...

  9. Image edge detection based on adaptive weighted morphology

    Institute of Scientific and Technical Information of China (English)

    Lihui Jiang; Yanying Guo

    2007-01-01

    A novel morphological edge detector based on adaptive weighted morphological operators is presented. It judges image edge and direction by adaptive weighted morphological structuring elements (SEs). If the edge direction exists, a big weight factor in SE is put; if it does not exist, a small weight factor in SE is put. Thus we can achieve an intensified edge detector. Experimental results prove that the new operator's performance dominates those of classical operators for images in edge detection, and obtains superbly detail edges.

  10. Losing your edge: climate change and the conservation value of range‐edge populations

    OpenAIRE

    Evan M. Rehm; Olivas, Paulo; Stroud, James; Feeley, Kenneth J.

    2015-01-01

    Abstract Populations occurring at species' range edges can be locally adapted to unique environmental conditions. From a species' perspective, range‐edge environments generally have higher severity and frequency of extreme climatic events relative to the range core. Under future climates, extreme climatic events are predicted to become increasingly important in defining species' distributions. Therefore, range‐edge genotypes that are better adapted to extreme climates relative to core populat...

  11. EFFECT OF VELOCITY ON DUCTILITY UNDER HIGH VELOCITY FORMING

    Institute of Scientific and Technical Information of China (English)

    LI Zhong; LI Chunfeng

    2007-01-01

    The ring expansion procedures over various forming velocities are calculated with ANSYS software in order to show the effect of forming velocity on ductility of rate insensitive materials. Ring expansion procedures are simplified to one-dimensional tension by constraining the radial deformation, with element birth and death method, fracture problem of circular ring are considered. The calculated results show that for insensitive materials of 1060 aluminum and 3A21 aluminum alloy, fracture strain increases corresponding to the increase of forming velocity. This trend agrees well with experimental results, and indicates inertia is the key factor to affect ductility; With element birth and death methods, fracture problems can be solved effectively. Experimental studies on formability of tubular workpieces are also conducted, experimental results show that the formability of 1060 aluminum and 3A21 aluminum alloy under electromagnetic forming is higher than that under quasistatic forming, according to the characteristics of electromagnetic forming, the forming limit diagrams of the two materials tube are also built respectively, this is very important to promote the development of electromagnetic forming and guide the engineering practices.

  12. Hopfield neural network and its applications on image edge detection

    Institute of Scientific and Technical Information of China (English)

    Yonghong Zhang(张永宏); Dejin Hu(胡德金); Kai Zhang(张凯); Junjie Xu(徐俊杰)

    2004-01-01

    A method of image edge detection using the Hopfield neural network (HNN) is proposed in this paper.The image edge parameters are introduced in detail, and the energy function of HNN is given based on the edge parameters. Tests on the image edge detection show that images detected by the proposed method have good edge closeness and true edge, at the same time it has good anti-noise performance. The image edge detection using HNN is better than that obtained by some other edge detection operators.

  13. Losing your edge: climate change and the conservation value of range-edge populations.

    Science.gov (United States)

    Rehm, Evan M; Olivas, Paulo; Stroud, James; Feeley, Kenneth J

    2015-10-01

    Populations occurring at species' range edges can be locally adapted to unique environmental conditions. From a species' perspective, range-edge environments generally have higher severity and frequency of extreme climatic events relative to the range core. Under future climates, extreme climatic events are predicted to become increasingly important in defining species' distributions. Therefore, range-edge genotypes that are better adapted to extreme climates relative to core populations may be essential to species' persistence during periods of rapid climate change. We use relatively simple conceptual models to highlight the importance of locally adapted range-edge populations (leading and trailing edges) for determining the ability of species to persist under future climates. Using trees as an example, we show how locally adapted populations at species' range edges may expand under future climate change and become more common relative to range-core populations. We also highlight how large-scale habitat destruction occurring in some geographic areas where many species range edge converge, such as biome boundaries and ecotones (e.g., the arc of deforestation along the rainforest-cerrado ecotone in the southern Amazonia), can have major implications for global biodiversity. As climate changes, range-edge populations will play key roles in helping species to maintain or expand their geographic distributions. The loss of these locally adapted range-edge populations through anthropogenic disturbance is therefore hypothesized to reduce the ability of species to persist in the face of rapid future climate change. PMID:26664681

  14. Sound velocities of hot dense iron: Birch's law revisited.

    Science.gov (United States)

    Lin, Jung-Fu; Sturhahn, Wolfgang; Zhao, Jiyong; Shen, Guoyin; Mao, Ho-Kwang; Hemley, Russell J

    2005-06-24

    Sound velocities of hexagonal close-packed iron (hcp-Fe) were measured at pressures up to 73 gigapascals and at temperatures up to 1700 kelvin with nuclear inelastic x-ray scattering in a laser-heated diamond anvil cell. The compressional-wave velocities (VP) and shear-wave velocities (VS) of hcp-Fe decreased significantly with increasing temperature under moderately high pressures. VP and VS under high pressures and temperatures thus cannot be fitted to a linear relation, Birch's law, which has been used to extrapolate measured sound velocities to densities of iron in Earth's interior. This result means that there are more light elements in Earth's core than have been inferred from linear extrapolation at room temperature. PMID:15976298

  15. Tuning Multiple Motor Travel Via Single Motor Velocity

    Science.gov (United States)

    Xu, Jing; Shu, Zhanyong; King, Stephen J.; Gross, Steven P.

    2012-01-01

    Microtubule-based molecular motors often work in small groups to transport cargos in cells. A key question in understanding transport (and its regulation in vivo) is to identify the sensitivity of multiple-motor-based motion to various single molecule properties. Whereas both single-motor travel distance and microtubule binding rate have been demonstrated to contribute to cargo travel, the role of single-motor velocity is yet to be explored. Here, we recast a previous theoretical study, and make explicit a potential contribution of velocity to cargo travel. We test this possibility experimentally, and demonstrate a strong negative correlation between single-motor velocity and cargo travel for transport driven by two motors. Our study thus discovers a previously unappreciated role of single-motor velocity in regulating multiple-motor transport. PMID:22672518

  16. Ionized gas at the edge of the central molecular zone

    Science.gov (United States)

    Langer, W. D.; Goldsmith, P. F.; Pineda, J. L.; Velusamy, T.; Requena-Torres, M. A.; Wiesemeyer, H.

    2015-04-01

    Context. The edge of the central molecular zone (CMZ) is the location where massive dense molecular clouds with large internal velocity dispersions transition to the surrounding more quiescent and lower CO emissivity region of the Galaxy. Little is known about the ionized gas surrounding the molecular clouds and in the transition region. Aims: We determine the properties of the ionized gas at the edge of the CMZ near Sgr E using observations of N+ and C+. Methods: We observed a small portion of the edge of the CMZ near Sgr E with spectrally resolved [C ii] 158 μm and [N ii] 205 μm fine structure lines at six positions with the GREAT instrument on SOFIA and in [C ii] using Herschel HIFI on-the-fly strip maps. We use the [N ii] spectra along with a radiative transfer model to calculate the electron density of the gas and the [C ii] maps to illuminate the morphology of the ionized gas and model the column density of CO-dark H2. Results: We detect two [C ii] and [N ii] velocity components, one along the line of sight to a CO molecular cloud at - 207 km s-1 associated with Sgr E and the other at -174 km s-1 outside the edge of another CO cloud. From the [N ii] emission we find that the average electron density is in the range of ~5 to 21 cm-3 for these features. This electron density is much higher than that of the disk's warm ionized medium, but is consistent with densities determined for bright diffuse H ii nebula. The column density of the CO-dark H2 layer in the -207 km s-1 cloud is ~1-2 × 1021 cm-2 in agreement with theoretical models. The CMZ extends further out in Galactic radius by ~7 to 14 pc in ionized gas than it does in molecular gas traced by CO. Conclusions: The edge of the CMZ likely contains dense hot ionized gas surrounding the neutral molecular material. The high fractional abundance of N+ and high electron density require an intense EUV field with a photon flux of order 106 to 107 photons cm-2 s-1, and/or efficient proton charge exchange with

  17. Bearing Abilities and Progressive Damage Analysis of Three Dimensional Four-Directional Braided Composites with Cut-Edge

    Science.gov (United States)

    Lei, Bing; Liu, Zhenguo; Ya, Jixuan; Wang, Yibo; Li, Xiaokang

    2016-08-01

    Cut-edge is a kind of damage for the three-dimensional four-directional (3D4d) braided composites which is inevitable because of machining to meet requisite shape and working in the abominable environment. The longitudinal tensile experiment of the 3D4d braided composites with different braiding angles between cut-edge and the ones without cut-edge was conducted. Then representative volume cell (RVC) with interface zones was established to analyze the tensile properties through the fracture and damage mechanics. The periodic boundary conditions under the cut-edge and uncut-edge conditions were imposed to simulate the failure mechanism. Stress-strain distribution and the damage evolution nephogram in cut-edge condition were conducted. Numerical results were coincident with the experimental results. Finally the variation of cut-edge effect with the specimen thickness was simulated by superimposing inner cells. The consequence showed that thickness increase can effectively reduce cut-edge influence on longitudinal strength for 3D4d braided composites. Cut-edge simulation of braided composites has guiding significance on the actual engineering application.

  18. Statistical theory of relaxation of high-energy electrons in quantum Hall edge states

    Science.gov (United States)

    Lunde, Anders Mathias; Nigg, Simon E.

    2016-07-01

    We investigate theoretically the energy exchange between the electrons of two copropagating, out-of-equilibrium edge states with opposite spin polarization in the integer quantum Hall regime. A quantum dot tunnel coupled to one of the edge states locally injects electrons at high energy. Thereby a narrow peak in the energy distribution is created at high energy above the Fermi level. A second downstream quantum dot performs an energy-resolved measurement of the electronic distribution function. By varying the distance between the two dots, we are able to follow every step of the energy exchange and relaxation between the edge states, even analytically under certain conditions. In the absence of translational invariance along the edge, e.g., due to the presence of disorder, energy can be exchanged by non-momentum-conserving two-particle collisions. For weakly broken translational invariance, we show that the relaxation is described by coupled Fokker-Planck equations. From these we find that relaxation of the injected electrons can be understood statistically as a generalized drift-diffusion process in energy space for which we determine the drift velocity and the dynamical diffusion parameter. Finally, we provide a physically appealing picture in terms of individual edge-state heating as a result of the relaxation of the injected electrons.

  19. Optimization of the poro-serrated trailing edges for airfoil broadband noise reduction.

    Science.gov (United States)

    Chong, Tze Pei; Dubois, Elisa

    2016-08-01

    This paper reports an aeroacoustic investigation of a NACA0012 airfoil with a number of poro-serrated trailing edge devices that contain porous materials of various air flow resistances at the gaps between adjacent members of the serrated-sawtooth trailing edge. The main objective of this work is to determine whether multiple-mechanisms on the broadband noise reduction can co-exist on a poro-serrated trailing edge. When the sawtooth gaps are filled with porous material of low-flow resistivity, the vortex shedding tone at low-frequency could not be completely suppressed at high-velocity, but a reasonably good broadband noise reduction can be achieved at high-frequency. When the sawtooth gaps are filled with porous material of very high-flow resistivity, no vortex shedding tone is present, but the serration effect on the broadband noise reduction becomes less effective. An optimal choice of the flow resistivity for a poro-serrated configuration has been identified, where it can surpass the conventional serrated trailing edge of the same geometry by achieving a further 1.5 dB reduction in the broadband noise while completely suppressing the vortex shedding tone. A weakened turbulent boundary layer noise scattering at the poro-serrated trailing edge is reflected by the lower-turbulence intensity at the near wake centreline across the whole spanwise wavelength of the sawtooth.

  20. Dense velocity reconstruction from tomographic PTV with material derivatives

    Science.gov (United States)

    Schneiders, Jan F. G.; Scarano, Fulvio

    2016-09-01

    A method is proposed to reconstruct the instantaneous velocity field from time-resolved volumetric particle tracking velocimetry (PTV, e.g., 3D-PTV, tomographic PTV and Shake-the-Box), employing both the instantaneous velocity and the velocity material derivative of the sparse tracer particles. The constraint to the measured temporal derivative of the PTV particle tracks improves the consistency of the reconstructed velocity field. The method is christened as pouring time into space, as it leverages temporal information to increase the spatial resolution of volumetric PTV measurements. This approach becomes relevant in cases where the spatial resolution is limited by the seeding concentration. The method solves an optimization problem to find the vorticity and velocity fields that minimize a cost function, which includes next to instantaneous velocity, also the velocity material derivative. The velocity and its material derivative are related through the vorticity transport equation, and the cost function is minimized using the limited-memory Broyden-Fletcher-Goldfarb-Shanno (L-BFGS) algorithm. The procedure is assessed numerically with a simulated PTV experiment in a turbulent boundary layer from a direct numerical simulation (DNS). The experimental validation considers a tomographic particle image velocimetry (PIV) experiment in a similar turbulent boundary layer and the additional case of a jet flow. The proposed technique (`vortex-in-cell plus', VIC+) is compared to tomographic PIV analysis (3D iterative cross-correlation), PTV interpolation methods (linear and adaptive Gaussian windowing) and to vortex-in-cell (VIC) interpolation without the material derivative. A visible increase in resolved details in the turbulent structures is obtained with the VIC+ approach, both in numerical simulations and experiments. This results in a more accurate determination of the turbulent stresses distribution in turbulent boundary layer investigations. Data from a jet

  1. The integration of angular velocity

    CERN Document Server

    Boyle, Michael

    2016-01-01

    A common problem in physics and engineering is determination of the orientation of an object given its angular velocity. When the direction of the angular velocity changes in time, this is a nontrivial problem involving coupled differential equations. Several possible approaches are examined, along with various improvements over previous efforts. These are then evaluated numerically by comparison to a complicated but analytically known rotation that is motivated by the important astrophysical problem of precessing black-hole binaries. It is shown that a straightforward solution directly using quaternions is most efficient and accurate, and that the norm of the quaternion is irrelevant. Integration of the generator of the rotation can also be made roughly as efficient as integration of the rotation. Both methods will typically be twice as efficient naive vector- or matrix-based methods. Implementation by means of standard general-purpose numerical integrators is stable and efficient, so that such problems can ...

  2. Preflare magnetic and velocity fields

    Science.gov (United States)

    Hagyard, M. J.; Gaizauskas, V.; Chapman, G. A.; Deloach, A. C.; Gary, G. A.; Jones, H. P.; Karpen, J. T.; Martres, M.-J.; Porter, J. G.; Schmeider, B.

    1986-01-01

    A characterization is given of the preflare magnetic field, using theoretical models of force free fields together with observed field structure to determine the general morphology. Direct observational evidence for sheared magnetic fields is presented. The role of this magnetic shear in the flare process is considered within the context of a MHD model that describes the buildup of magnetic energy, and the concept of a critical value of shear is explored. The related subject of electric currents in the preflare state is discussed next, with emphasis on new insights provided by direct calculations of the vertical electric current density from vector magnetograph data and on the role of these currents in producing preflare brightenings. Results from investigations concerning velocity fields in flaring active regions, describing observations and analyses of preflare ejecta, sheared velocities, and vortical motions near flaring sites are given. This is followed by a critical review of prevalent concepts concerning the association of flux emergence with flares

  3. Velocity fluctuations of fission fragment.

    OpenAIRE

    Llanes Estrada, Felipe José; Martínez Carmona, Belén; Muñoz Martínez, José L.

    2016-01-01

    We propose event by event velocity fluctuations of nuclear fission fragments as an additional interesting observable that gives access to the nuclear temperature in an independent way from spectral measurements and relates the diffusion and friction coefficients for the relative fragment coordinate in Kramers-like models (in which some aspects of fission can be understood as the diffusion of a collective variable through a potential barrier). We point out that neutron emission by the heavy fr...

  4. Integrating rotation from angular velocity

    OpenAIRE

    Zupan, Eva; Saje, Miran

    2011-01-01

    Abstract The integration of the rotation from a given angular velocity is often required in practice. The present paper explores how the choice of the parametrization of rotation, when employed in conjuction with different numerical time-integration schemes, effects the accuracy and the computational efficiency. Three rotation parametrizations – the rotational vector, the Argyris tangential vector and the rotational quaternion – are combined with three different numerical time-integration ...

  5. Power spectrum weighted edge analysis for straight edge detection in images

    Science.gov (United States)

    Karvir, Hrishikesh V.; Skipper, Julie A.

    2007-04-01

    Most man-made objects provide characteristic straight line edges and, therefore, edge extraction is a commonly used target detection tool. However, noisy images often yield broken edges that lead to missed detections, and extraneous edges that may contribute to false target detections. We present a sliding-block approach for target detection using weighted power spectral analysis. In general, straight line edges appearing at a given frequency are represented as a peak in the Fourier domain at a radius corresponding to that frequency, and a direction corresponding to the orientation of the edges in the spatial domain. Knowing the edge width and spacing between the edges, a band-pass filter is designed to extract the Fourier peaks corresponding to the target edges and suppress image noise. These peaks are then detected by amplitude thresholding. The frequency band width and the subsequent spatial filter mask size are variable parameters to facilitate detection of target objects of different sizes under known imaging geometries. Many military objects, such as trucks, tanks and missile launchers, produce definite signatures with parallel lines and the algorithm proves to be ideal for detecting such objects. Moreover, shadow-casting objects generally provide sharp edges and are readily detected. The block operation procedure offers advantages of significant reduction in noise influence, improved edge detection, faster processing speed and versatility to detect diverse objects of different sizes in the image. With Scud missile launcher replicas as target objects, the method has been successfully tested on terrain board test images under different backgrounds, illumination and imaging geometries with cameras of differing spatial resolution and bit-depth.

  6. Examining the lateral displacement of HL60 cells rolling on asymmetric P-selectin patterns.

    Science.gov (United States)

    Lee, Chia-Hua; Bose, Suman; Van Vliet, Krystyn J; Karp, Jeffrey M; Karnik, Rohit

    2011-01-01

    The lateral displacement of cells orthogonal to a flow stream by rolling on asymmetrical receptor patterns presents a new opportunity for the label-free separation and analysis of cells. Understanding the nature of cell rolling trajectories on such substrates is necessary to the engineering of substrates and the design of devices for cell separation and analysis. Here, we investigate the statistical nature of cell rolling and the effect of pattern geometry and flow shear stress on cell rolling trajectories using micrometer-scale patterns of biomolecular receptors with well-defined edges. Leukemic myeloid HL60 cells expressing the PSGL-1 ligand were allowed to flow across a field of patterned lines fabricated using microcontact printing and functionalized with the P-selectin receptor, leveraging both the specific adhesion of this ligand-receptor pair and the asymmetry of the receptor pattern inclination angle with respect to the fluid shear flow direction (α = 5, 10, 15, and 20°). The effects of the fluid shear stress magnitude (τ = 0.5, 1, 1.5, and 2.0 dyn/cm(2)), α, and P-selectin incubation concentration were quantified in terms of the rolling velocity and edge tracking length. Rolling cells tracked along the inclined edges of the patterned lines before detaching and reattaching on another line. The detachment of rolling cells after tracking along the edge was consistent with a Poisson process of history-independent interactions. Increasing the edge inclination angle decreased the edge tracking length in an exponential manner, contrary to the shear stress magnitude and P-selectin incubation concentration, which did not have a significant effect. On the basis of these experimental data, we constructed an empirical model that predicted the occurrence of the maximum lateral displacement at an edge angle of 7.5°. We also used these findings to construct a Monte Carlo simulation for the prediction of rolling trajectories of HL60 cells on P

  7. Trailing edge modifications for flatback airfoils.

    Energy Technology Data Exchange (ETDEWEB)

    Kahn, Daniel L. (University of California, Davis, CA); van Dam, C.P. (University of California, Davis, CA); Berg, Dale E.

    2008-03-01

    The adoption of blunt trailing edge airfoils (also called flatback airfoils) for the inboard region of large wind turbine blades has been proposed. Blunt trailing edge airfoils would not only provide a number of structural benefits, such as increased structural volume and ease of fabrication and handling, but they have also been found to improve the lift characteristics of thick airfoils. Therefore, the incorporation of blunt trailing edge airfoils would allow blade designers to more freely address the structural demands without having to sacrifice aerodynamic performance. These airfoils do have the disadvantage of generating high levels of drag as a result of the low-pressure steady or periodic flow in the near-wake of the blunt trailing edge. Although for rotors, the drag penalty appears secondary to the lift enhancement produced by the blunt trailing edge, high drag levels are of concern in terms of the negative effect on the torque and power generated by the rotor. Hence, devices are sought that mitigate the drag of these airfoils. This report summarizes the literature on bluff body vortex shedding and bluff body drag reduction devices and proposes four devices for further study in the wind tunnel.

  8. Edge states of zigzag bilayer graphite nanoribbons

    Science.gov (United States)

    Rhim, Jun-Won; Moon, Kyungsun

    2008-09-01

    The electronic structures of zigzag bilayer graphite nanoribbons (Z-BGNRs) with various ribbon widths N are studied within the tight binding approximation. Neglecting the inter-layer hopping amplitude γ4, which is an order of magnitude smaller than the other inter-layer hopping parameters, there exist two fixed Fermi points ± k* independent of the ribbon width with a peculiar energy dispersion near k* as ɛ(k)~ ± (k-k*)N. By investigating the edge states of Z-BGNRs, we notice that the trigonal warping of the bilayer graphene sheets is reflected in the edge state structure. With the inclusion of γ4, the above two Fermi points are not fixed but drift toward the vicinity of the Dirac point with increasing width N, as shown by the finite scaling method, and the peculiar dispersions change to parabolic ones. The edge magnetism of Z-BGNRs is also examined by solving the half-filled Hubbard Hamiltonian for the ribbon using the Hartree-Fock approximation. We have shown that within the same side of the edges, the edge spins are aligned ferromagnetically for the experimentally relevant set of parameters.

  9. Edge states of zigzag bilayer graphite nanoribbons

    Energy Technology Data Exchange (ETDEWEB)

    Rhim, Jun-Won; Moon, Kyungsun [Department of Physics and Institute of Physics and Applied Physics, Yonsei University, Seoul 120-749 (Korea, Republic of)], E-mail: kmoon@yonsei.ac.kr

    2008-09-10

    The electronic structures of zigzag bilayer graphite nanoribbons (Z-BGNRs) with various ribbon widths N are studied within the tight binding approximation. Neglecting the inter-layer hopping amplitude {gamma}{sub 4}, which is an order of magnitude smaller than the other inter-layer hopping parameters, there exist two fixed Fermi points {+-} k{sup *} independent of the ribbon width with a peculiar energy dispersion near k{sup *} as {epsilon}(k){approx} {+-} (k-k{sup *}){sup N}. By investigating the edge states of Z-BGNRs, we notice that the trigonal warping of the bilayer graphene sheets is reflected in the edge state structure. With the inclusion of {gamma}{sub 4}, the above two Fermi points are not fixed but drift toward the vicinity of the Dirac point with increasing width N, as shown by the finite scaling method, and the peculiar dispersions change to parabolic ones. The edge magnetism of Z-BGNRs is also examined by solving the half-filled Hubbard Hamiltonian for the ribbon using the Hartree-Fock approximation. We have shown that within the same side of the edges, the edge spins are aligned ferromagnetically for the experimentally relevant set of parameters.

  10. Three-dimensional turbulence simulation of edge transport and impact of plasma rotation

    International Nuclear Information System (INIS)

    Global simulations of edge plasma turbulence are studied. The gradient-flux relation is fitted to a model with two parameters: stiffness and intercept. The slope of the grad-p vs flux curve is clearly lower in the case of spontaneous rotation than in the case of artificially suppressed rotation. The causes of this difference are studied by imposing a specified velocity shear. The slopes are similar between cases of controlled rotation with different amplitudes. That is, the stiffness does not change significantly, while the intercept changes. Therefore, the change in the slope observed in the case of spontaneous rotation has to be attributed to the fact that the velocity shear amplitude itself is increasing with the pressure source. The increase in the velocity shear is conjectured to cause a change in the intercept in the case of spontaneous rotation, but not a change in the stiffness. (author)

  11. Partial core hole screening in the Cu $L_{3}$ edge

    CERN Document Server

    Luitz, J; Hetbert, C; Schattschneider, P; Blaha, P; Schwarz, K; Jouffrey, B

    2001-01-01

    The fine structure of the copper L/sub 3/ edge in fcc Cu was simulated using a full potential linearised augmented plane wave method (WIEN97). The computations were based on a single cell-model by introducing a partial core hole and on a 2*2*1 super-cell-model with one full core hole. No difference between the single cell with a full core hole and the 16 atoms supercell with one core hole could be observed. Comparison with experimental spectra of two Cu specimens prepared by different methods showed that after removing the Cu/sub 2 /O contribution to the spectrum the best fit was obtained for half a core hole. This shows that the core hole in Cu metal is only partially screened by the valence electrons. (22 refs).

  12. Velocities measured in small scale solar magnetic elements

    CERN Document Server

    Langangen, O; van der Voort, L R; Stein, R F; Carlsson, Mats; Voort, Luc Rouppe van der

    2006-01-01

    We have obtained high resolution spectrograms of small scale magnetic structures with the Swedish 1-m Solar Telescope. We present Doppler measurements at $0\\farcs{2}$ spatial resolution of bright points, ribbons and flowers and their immediate surroundings, in the C {\\small{I}} 5380.3 {\\AA} line (formed in the deep photosphere) and the two Fe {\\small{I}} lines at 5379.6 {\\AA} and 5386.3 {\\AA}. The velocity inside the flowers and ribbons are measured to be almost zero, while we observe downflows at the edges. These downflows are increasing with decreasing height. We also analyze realistic magneto-convective simulations to obtain a better understanding of the interpretation of the observed signal. We calculate how the Doppler signal depends on the velocity field in various structures. Both the smearing effect of the non-negligible width of this velocity response function along the line of sight and of the smearing from the telescope and atmospheric point spread function are discussed. These studies lead us to t...

  13. Reduction of wafer-edge overlay errors using advanced correction models, optimized for minimal metrology requirements

    Science.gov (United States)

    Kim, Min-Suk; Won, Hwa-Yeon; Jeong, Jong-Mun; Böcker, Paul; Vergaij-Huizer, Lydia; Kupers, Michiel; Jovanović, Milenko; Sochal, Inez; Ryan, Kevin; Sun, Kyu-Tae; Lim, Young-Wan; Byun, Jin-Moo; Kim, Gwang-Gon; Suh, Jung-Joon

    2016-03-01

    In order to optimize yield in DRAM semiconductor manufacturing for 2x nodes and beyond, the (processing induced) overlay fingerprint towards the edge of the wafer needs to be reduced. Traditionally, this is achieved by acquiring denser overlay metrology at the edge of the wafer, to feed field-by-field corrections. Although field-by-field corrections can be effective in reducing localized overlay errors, the requirement for dense metrology to determine the corrections can become a limiting factor due to a significant increase of metrology time and cost. In this study, a more cost-effective solution has been found in extending the regular correction model with an edge-specific component. This new overlay correction model can be driven by an optimized, sparser sampling especially at the wafer edge area, and also allows for a reduction of noise propagation. Lithography correction potential has been maximized, with significantly less metrology needs. Evaluations have been performed, demonstrating the benefit of edge models in terms of on-product overlay performance, as well as cell based overlay performance based on metrology-to-cell matching improvements. Performance can be increased compared to POR modeling and sampling, which can contribute to (overlay based) yield improvement. Based on advanced modeling including edge components, metrology requirements have been optimized, enabling integrated metrology which drives down overall metrology fab footprint and lithography cycle time.

  14. Edge-Matching Problems with Rotations

    DEFF Research Database (Denmark)

    Ebbesen, Martin; Fischer, Paul; Witt, Carsten

    2011-01-01

    Edge-matching problems, also called puzzles, are abstractions of placement problems with neighborhood conditions. Pieces with colored edges have to be placed on a board such that adjacent edges have the same color. The problem has gained interest recently with the (now terminated) Eternity II...... puzzle, and new complexity results. In this paper we consider a number of settings which differ in size of the puzzles and the manipulations allowed on the pieces. We investigate the effect of allowing rotations of the pieces on the complexity of the problem, an aspect that is only marginally treated so...... far. We show that some problems have polynomial time algorithms while others are NP-complete. Especially we show that allowing rotations in one-row puzzles makes the problem NP-hard. We moreover show that many commonly considered puzzles can be emulated by simple puzzles with quadratic pieces, so...

  15. Study of airfoil trailing edge bluntness noise

    DEFF Research Database (Denmark)

    Zhu, Wei Jun; Shen, Wen Zhong; Sørensen, Jens Nørkær

    2010-01-01

    -Stokes equations. It provides us possibilities to study details about noise generation mechanism. The formulation of the semi-empirical model is based on acoustic analogy and then curve-fitted with experimental data. Due to its high efficiency, such empirical relation is used for purpose of low noise airfoil......This paper deals with airfoil trailing edge noise with special focus on airfoils with blunt trailing edges. Two methods are employed to calculate airfoil noise: The flow/acoustic splitting method and the semi-empirical method. The flow/acoustic splitting method is derived from compressible Navier...... design or optimization. Calculations from both methods are compared with exist experiments. The airfoil blunt noise is found as a function of trailing edge bluntness, Reynolds number, angle of attack, etc....

  16. AUTOMATED EDGE DETECTION USING CONVOLUTIONAL NEURAL NETWORK

    Directory of Open Access Journals (Sweden)

    Mohamed A. El-Sayed

    2013-11-01

    Full Text Available The edge detection on the images is so important for image processing. It is used in a various fields of applications ranging from real-time video surveillance and traffic management to medical imaging applications. Currently, there is not a single edge detector that has both efficiency and reliability. Traditional differential filter-based algorithms have the advantage of theoretical strictness, but require excessive post-processing. Proposed CNN technique is used to realize edge detection task it takes the advantage of momentum features extraction, it can process any input image of any size with no more training required, the results are very promising when compared to both classical methods and other ANN based methods

  17. Exploring topological edge states in photonic quasicrystals

    CERN Document Server

    Baboux, F; Lemaître, A; Gomez, C; Galopin, E; Gratiet, L Le; Sagnes, I; Amo, A; Bloch, J; Akkermans, E

    2016-01-01

    We experimentally investigate the topological properties of quasiperiodic chains using cavity polaritons confined in a potential following the Fibonacci sequence. Edge states forming in the gaps of a fractal energy spectrum are imaged both in real and momentum space. These edge states periodically traverse the gaps when varying a structural degree of freedom $\\phi$ of the Fibonacci sequence. The period and direction of the traverses are directly related to the Chern numbers assigned to each gap by the gap-labeling theorem. Additionally, we show that the Chern numbers determine the spatial symmetry properties of the edge states. These results highlight the potential of cavity polaritons to emulate nontrivial topological properties in a controlled environment.

  18. Edge Detection By Differences Of Gaussians

    Science.gov (United States)

    Marthon, Ph.; Thiesse, B.; Bruel, A.

    1986-06-01

    The Differences of Gaussians (DOGs) are of fundamental importance in edge detection. They belong to the human vision system as shown by Enroth-Cugell and Robson [ENR66]. The zero-crossings of their outputs mark the loci of the intensity changes. The set of descriptions from different operator sizes forms the input for later visual processes, such as stereopsis and motion analysis. We show that DOGs uniformly converge to the Laplacian of a Gaussian (ΔG2,σ) when both the inhibitory and excitatory variables converge to σ. Spatial and spectral properties of DOGs and ΔGs are compared: width and height of their central positive regions, bandiwidths... Finally, DOGs' responses to some features such as ideal edge, right angle corner, general corner..., are presented and magnitudes of error on edge position are given.

  19. Predictability of the Arctic sea ice edge

    Science.gov (United States)

    Goessling, H. F.; Tietsche, S.; Day, J. J.; Hawkins, E.; Jung, T.

    2016-02-01

    Skillful sea ice forecasts from days to years ahead are becoming increasingly important for the operation and planning of human activities in the Arctic. Here we analyze the potential predictability of the Arctic sea ice edge in six climate models. We introduce the integrated ice-edge error (IIEE), a user-relevant verification metric defined as the area where the forecast and the "truth" disagree on the ice concentration being above or below 15%. The IIEE lends itself to decomposition into an absolute extent error, corresponding to the common sea ice extent error, and a misplacement error. We find that the often-neglected misplacement error makes up more than half of the climatological IIEE. In idealized forecast ensembles initialized on 1 July, the IIEE grows faster than the absolute extent error. This means that the Arctic sea ice edge is less predictable than sea ice extent, particularly in September, with implications for the potential skill of end-user relevant forecasts.

  20. Improved Edge Awareness in Discontinuity Preserving Smoothing

    CERN Document Server

    Heinrich, Stuart B

    2011-01-01

    Discontinuity preserving smoothing is a fundamentally important procedure that is useful in a wide variety of image processing contexts. It is directly useful for noise reduction, and frequently used as an intermediate step in higher level algorithms. For example, it can be particularly useful in edge detection and segmentation. Three well known algorithms for discontinuity preserving smoothing are nonlinear anisotropic diffusion, bilateral filtering, and mean shift filtering. Although slight differences make them each better suited to different tasks, all are designed to preserve discontinuities while smoothing. However, none of them satisfy this goal perfectly: they each have exception cases in which smoothing may occur across hard edges. The principal contribution of this paper is the identification of a property we call edge awareness that should be satisfied by any discontinuity preserving smoothing algorithm. This constraint can be incorporated into existing algorithms to improve quality, and usually ha...

  1. Edge excitations in fractional Chern insulators

    Science.gov (United States)

    Luo, Wei-Wei; Chen, Wen-Chao; Wang, Yi-Fei; Gong, Chang-De

    2013-10-01

    Recent theoretical papers have demonstrated the realization of fractional quantum anomalous Hall states (also called fractional Chern insulators) in topological flat band lattice models without an external magnetic field. Such newly proposed lattice systems play a vital role in obtaining a large class of fractional topological phases. Here we report the exact numerical studies of edge excitations for such systems in a disk geometry loaded with hard-core bosons, which will serve as a more viable experimental probe for such topologically ordered states. We find convincing numerical evidence of a series of edge excitations characterized by the chiral Luttinger liquid theory for the bosonic fractional Chern insulators in both the honeycomb disk Haldane model and the kagome-lattice disk model. We further verify these current-carrying chiral edge states by inserting a central flux to test their compressibility.

  2. Topological edge modes in multilayer graphene systems

    KAUST Repository

    Ge, Lixin

    2015-08-10

    Plasmons can be supported on graphene sheets as the Dirac electrons oscillate collectively. A tight-binding model for graphene plasmons is a good description as the field confinement in the normal direction is strong. With this model, the topological properties of plasmonic bands in multilayer graphene systems are investigated. The Zak phases of periodic graphene sheet arrays are obtained for different configurations. Analogous to Su-Schrieffer-Heeger (SSH) model in electronic systems, topological edge plasmon modes emerge when two periodic graphene sheet arrays with different Zak phases are connected. Interestingly, the dispersion of these topological edge modes is the same as that in the monolayer graphene and is invariant as the geometric parameters of the structure such as the separation and period change. These plasmonic edge states in multilayer graphene systems can be further tuned by electrical gating or chemical doping. © 2015 Optical Society of America.

  3. Diagnosing Topological Edge States via Entanglement Monogamy.

    Science.gov (United States)

    Meichanetzidis, K; Eisert, J; Cirio, M; Lahtinen, V; Pachos, J K

    2016-04-01

    Topological phases of matter possess intricate correlation patterns typically probed by entanglement entropies or entanglement spectra. In this Letter, we propose an alternative approach to assessing topologically induced edge states in free and interacting fermionic systems. We do so by focussing on the fermionic covariance matrix. This matrix is often tractable either analytically or numerically, and it precisely captures the relevant correlations of the system. By invoking the concept of monogamy of entanglement, we show that highly entangled states supported across a system bipartition are largely disentangled from the rest of the system, thus, usually appearing as gapless edge states. We then define an entanglement qualifier that identifies the presence of topological edge states based purely on correlations present in the ground states. We demonstrate the versatility of this qualifier by applying it to various free and interacting fermionic topological systems.

  4. Intraoperative evaluation of transmitral pressure gradients after edge-to-edge mitral valve repair.

    Directory of Open Access Journals (Sweden)

    Jan N Hilberath

    Full Text Available OBJECTIVE: Edge-to-edge repair of the mitral valve (MV has been described as a viable option used for the surgical management of mitral regurgitation (MR. Based on the significant changes in MV geometry associated with this technique, we hypothesized that edge-to-edge MV repairs are associated with higher intraoperative transmitral pressure gradients (TMPG compared to conventional methods. METHODS: Patient records and intraoperative transesophageal echocardiography (TEE examinations of 552 consecutive patients undergoing MV repair at a single institution over a three year period were assessed. After separation from cardiopulmonary bypass (CPB, peak and mean TMPG were recorded for each patient and subsequently analyzed. RESULTS: 84 patients (15% underwent edge-to-edge MV repair. Peak and mean TMPG were significantly higher compared to gradients in patients undergoing conventional repairs: 10.7 ± 0.5 mmHg vs 7.1 ± 0.2 mmHg; P<0.0001 and 4.3 ± 0.2 mmHg vs 2.8 ± 0.1 mmHg; P<0.0001. Only patients with mean TMPG ≥ 7 mmHg (n = 9 required prompt reoperation for iatrogenic mitral stenosis (MS. No differences in peak and mean TMPG were observed among edge-to-edge repairs performed in isolation, compared to those performed in combination with annuloplasty: 11.0 ± 0.7 mmHg vs 10.3 ± 0.6 mmHg and 4.4 ± 0.3 mmHg vs 4.3 ± 0.3 mmHg. There were no differences in TMPG between various types of annuloplasty techniques used in combination with the edge-to-edge repairs. CONCLUSIONS: Edge-to-edge MV repairs are associated with higher intraoperative peak and mean TMPG after separation from CPB compared to conventional repair techniques. Unless gradients are severely elevated, these findings are not necessarily suggestive of iatrogenic MS. Thus, in the immediate postoperative period mildly elevated TMPG can be expected and tolerated after edge-to-edge mitral repairs.

  5. Velocity Correction and Measurement Uncertainty Analysis of Light Screen Velocity Measuring Method

    Institute of Scientific and Technical Information of China (English)

    ZHENG Bin; ZUO Zhao-lu; HOU Wen

    2012-01-01

    Light screen velocity measuring method with unique advantages has been widely used in the velocity measurement of various moving bodies.For large air resistance and friction force which the big moving bodies are subjected to during the light screen velocity measuring,the principle of velocity correction was proposed and a velocity correction equation was derived.A light screen velocity measuring method was used to measure the velocity of big moving bodies which have complex velocity attenuation,and the better results were gained in practical tests.The measuring uncertainty after the velocity correction was calculated.

  6. Electro-oxidation of Formic Acid on Carbon Supported Edge-Truncated Cubic Platinum Nanoparticles Catalysts

    Institute of Scientific and Technical Information of China (English)

    LI She-Qiang; FU Xing-Qiu; HU Bing; DENG Jia-Jun; CHEN Lei

    2009-01-01

    The oxidation of formic acid on edge-truncated cubic platinum nanoparticles/C catalysts is investigated. X-ray photoelectron spectroscopy analysis indicates that the surface of edge-truncated cubic platinum nanoparticles is composed of two types of coordination sites. The oxidation behavior of formic acid on edge-truncated cubic platinum nanoparticles/C is investigated using cyclic voltammetry. The apparent activation energies are found to be 54.2, 55.0, 61.8, 69.5, 71.9, 69.26, 65.28kJ/mol at 0.15, 0.3, 0.4, 0.5, 0.6, 0.65, 0.7 V, respectively. A specific surface area activity of 1.76mA·cm~(-2) at 0.4 V indicates that the edge-truncated cubic Platinum nanoparticles are a promising anode catalyst for direct formic acid fuel cells.

  7. Edge detection in landing budgerigars (Melopsittacus undulatus.

    Directory of Open Access Journals (Sweden)

    Partha Bhagavatula

    Full Text Available BACKGROUND: While considerable scientific effort has been devoted to studying how birds navigate over long distances, relatively little is known about how targets are detected, obstacles are avoided and smooth landings are orchestrated. Here we examine how visual features in the environment, such as contrasting edges, determine where a bird will land. METHODOLOGY/PRINCIPAL FINDINGS: Landing in budgerigars (Melopsittacus undulatus was investigated by training them to fly from a perch to a feeder, and video-filming their landings. The feeder was placed on a grey disc that produced a contrasting edge against a uniformly blue background. We found that the birds tended to land primarily at the edge of the disc and walk to the feeder, even though the feeder was in the middle of the disc. This suggests that the birds were using the visual contrast at the boundary of the disc to target their landings. When the grey level of the disc was varied systematically, whilst keeping the blue background constant, there was one intermediate grey level at which the budgerigar's preference for the disc boundary disappeared. The budgerigars then landed randomly all over the test surface. Even though this disc is (for humans clearly distinguishable from the blue background, it offers very little contrast against the background, in the red and green regions of the spectrum. CONCLUSIONS: We conclude that budgerigars use visual edges to target and guide landings. Calculations of photoreceptor excitation reveal that edge detection in landing budgerigars is performed by a color-blind luminance channel that sums the signals from the red and green photoreceptors, or, alternatively, receives input from the red double-cones. This finding has close parallels to vision in honeybees and primates, where edge detection and motion perception are also largely color-blind.

  8. A Double-edged sword — the impact of autophagy on diabetes and pancreatic beta cells%一把双刃剑——自噬对糖尿病和胰岛β细胞的影响

    Institute of Scientific and Technical Information of China (English)

    朱丽波; 李艳波

    2013-01-01

    Autophagy is an intracellular catabolic system, which enables cells to capture cytoplasmic components for degradation within lysosomes. Autophagy is involved in development, differentiation and tissue remodeling in various organisms, and is also implicated in certain diseases. Recent studies demonstrate that autophagy is necessary to maintain architecture and function of pancreatic beta cells. Inhibited autophagy is also involved in pancreatic beta cell death. Whether autophagy plays a protective or harmful role in diabetes is still not clear. This article summarizes the current knowledge about the role of autophagy in pancreatic beta cells and diabetes.%自噬是一种细胞内的代谢降解过程,能够在溶酶体内降解损伤的细胞质或细胞器.自噬参与多种生物体的生长、分化和组织重构,同时也与某些疾病有关.有研究表明,自噬在维持胰岛β细胞结构和功能中起重要作用.抑制自噬可增加胰岛β细胞死亡.然而自噬在糖尿病中的作用还不清楚.

  9. An experimental study of airfoil instability tonal noise with trailing edge serrations

    Science.gov (United States)

    Chong, Tze Pei; Joseph, Phillip F.

    2013-11-01

    This paper presents an experimental study of the effect of trailing edge serrations on airfoil instability noise. Detailed aeroacoustic measurements are presented of the noise radiated by an NACA-0012 airfoil with trailing edge serrations in a low to moderate speed flow under acoustical free field conditions. The existence of a separated boundary layer near the trailing edge of the airfoil at an angle of attack of 4.2 degree has been experimentally identified by a surface mounted hot-film arrays technique. Hot-wire results have shown that the saw-tooth surface can trigger a bypass transition and prevent the boundary layer from becoming separated. Without the separated boundary layer to act as an amplifier for the incoming Tollmien-Schlichting waves, the intensity and spectral characteristic of the radiated tonal noise can be affected depending upon the serration geometry. Particle Imaging Velocimetry (PIV) measurements of the airfoil wakes for a straight and serrated trailing edge are also reported in this paper. These measurements show that localized normal-component velocity fluctuations that are present in a small region of the wake from the laminar airfoil become weakened once serrations are introduced. Owing to the above unique characteristics of the serrated trailing edges, we are able to further investigate the mechanisms of airfoil instability tonal noise with special emphasis on the assessment of the wake and non-wake based aeroacoustic feedback models. It has been shown that the instability tonal noise generated at an angle of attack below approximately one degree could involve several complex mechanisms. On the other hand, the non-wake based aeroacoustic feedback mechanism alone is sufficient to predict all discrete tone frequencies accurately when the airfoil is at a moderate angle of attack. Larger Δf, which is defined as (fn+1-fn). In other words, a larger margin of velocity increase is required in order to "shift" the fn and fn+1 across fs

  10. Edge states of periodically kicked quantum rotors.

    Science.gov (United States)

    Floss, Johannes; Averbukh, Ilya Sh

    2015-05-01

    We present a quantum localization phenomenon that exists in periodically kicked three-dimensional rotors, but is absent in the commonly studied two-dimensional ones: edge localization. We show that under the condition of a fractional quantum resonance there are states of the kicked rotor that are strongly localized near the edge of the angular momentum space at J=0. These states are analogs of surface states in crystalline solids, and they significantly affect resonant excitation of molecular rotation by laser pulse trains.

  11. AliEn - EDG Interoperability in ALICE

    OpenAIRE

    Bagnasco, S.; Barbera, R.; Buncic, P.; Carminati, F.; P. Cerello; Saiz, P.

    2003-01-01

    AliEn (ALICE Environment) is a GRID-like system for large scale job submission and distributed data management developed and used in the context of ALICE, the CERN LHC heavy-ion experiment. With the aim of exploiting upcoming Grid resources to run AliEn-managed jobs and store the produced data, the problem of AliEn-EDG interoperability was addressed and an in-terface was designed. One or more EDG (European Data Grid) User Interface machines run the AliEn software suite (Cluster Monitor, Stora...

  12. Active-edge planar radiation sensors

    OpenAIRE

    Kenney, C. J.; Segal, J.D.; Westbrook, E.; Parker, Sherwood; Hasi, J.; Da Via, C.; Watts, S.; Morse, J

    2006-01-01

    Many systems in medicine, biology, high-energy physics, and astrophysics require large area radiation sensors. In most of these applications, minimizing the amount of dead area or dead material is crucial. We have developed a new type of silicon radiation sensor in which the device is active to within a few microns of the mechanical edge. Their perimeter is made by a plasma etcher rather than a diamond saw. Their edges can be defined and also passivated by growing, in an intermediate step, a ...

  13. Wing Leading Edge Concepts for Noise Reduction

    Science.gov (United States)

    Shmilovich, Arvin; Yadlin, Yoram; Pitera, David M.

    2010-01-01

    This study focuses on the development of wing leading edge concepts for noise reduction during high-lift operations, without compromising landing stall speeds, stall characteristics or cruise performance. High-lift geometries, which can be obtained by conventional mechanical systems or morphing structures have been considered. A systematic aerodynamic analysis procedure was used to arrive at several promising configurations. The aerodynamic design of new wing leading edge shapes is obtained from a robust Computational Fluid Dynamics procedure. Acoustic benefits are qualitatively established through the evaluation of the computed flow fields.

  14. Edge detection techniques for iris recognition system

    International Nuclear Information System (INIS)

    Nowadays security and authentication are the major parts of our daily life. Iris is one of the most reliable organ or part of human body which can be used for identification and authentication purpose. To develop an iris authentication algorithm for personal identification, this paper examines two edge detection techniques for iris recognition system. Between the Sobel and the Canny edge detection techniques, the experimental result shows that the Canny's technique has better ability to detect points in a digital image where image gray level changes even at slow rate

  15. Edge detection techniques for iris recognition system

    Science.gov (United States)

    Tania, U. T.; Motakabber, S. M. A.; Ibrahimy, M. I.

    2013-12-01

    Nowadays security and authentication are the major parts of our daily life. Iris is one of the most reliable organ or part of human body which can be used for identification and authentication purpose. To develop an iris authentication algorithm for personal identification, this paper examines two edge detection techniques for iris recognition system. Between the Sobel and the Canny edge detection techniques, the experimental result shows that the Canny's technique has better ability to detect points in a digital image where image gray level changes even at slow rate.

  16. Genus Polynomials of Cycles with Double Edges

    Institute of Scientific and Technical Information of China (English)

    Eunyoung BAEK; Jongyook PARK

    2011-01-01

    Two cellular embeddings i : G → S and j : G → S of a connected graph G into a closed orientable surface S are equivalent if there is an orientation-preserving surface homeomorphism h: S → S such that hi = j. The genus polynomial of a graph G is defined by g[G](x)=∑∞g=0agxg,where ag is the number of equivalence classes of embeddings of G into the orientable surface Sg with g genera.In this paper, we compute the genus polynomial of a graph obtained from a cycle by replacing each edge by two multiple edges.

  17. Particle Size Estimation Based on Edge Density

    Institute of Scientific and Technical Information of China (English)

    WANG Wei-xing

    2005-01-01

    Given image sequences of closely packed particles, the underlying aim is to estimate diameters without explicit segmentation. In a way, this is similar to the task of counting objects without directly counting them. Such calculations may, for example, be useful fast estimation of particle size in different application areas. The topic is that of estimating average size (=average diameter) of packed particles, from formulas involving edge density, and the edges from moment-based thresholding are used. An average shape factor is involved in the calculations, obtained for some frames from crude partial segmentation. Measurement results from about 80 frames have been analyzed.

  18. Active-edge planar radiation sensors

    International Nuclear Information System (INIS)

    Many systems in medicine, biology, high-energy physics, and astrophysics require large area radiation sensors. In most of these applications, minimizing the amount of dead area or dead material is crucial. We have developed a new type of silicon radiation sensor in which the device is active to within a few microns of the mechanical edge. Their perimeter is made by a plasma etcher rather than a diamond saw. Their edges can be defined and also passivated by growing, in an intermediate step, a field oxide on the side surfaces. In this paper, the basic architecture and results from a synchrotron beam test are presented

  19. A Nobel Hybrid Approach for Edge Detection

    Directory of Open Access Journals (Sweden)

    Palvi Rani

    2013-05-01

    Full Text Available The objective of this paper is to present the hybrid approach for edge detection. Under this technique, edgedetection isperformed in two phase. In first phase,Canny Algorithm is applied for image smoothing and insecond phase neural network is to detecting actual edges. Neural network is a wonderful tool for edgedetection. As it is a non-linear network with built-in thresholding capability. Neural Network can be trainedwith back propagation technique using few training patterns but the most important and difficult part is toidentify the correct and proper training set.

  20. Group edge choosability of planar graphs without adjacent short cycles

    OpenAIRE

    Xin ZHANG; Liu, Guizhen

    2011-01-01

    In this paper, we aim to introduce the group version of edge coloring and list edge coloring, and prove that all 2-degenerate graphs along with some planar graphs without adjacent short cycles is group $(\\Delta(G)+1)$-edge-choosable while some planar graphs with large girth and maximum degree is group $\\Delta(G)$-edge-choosable.

  1. Optimization of K-edge imaging with spectral CT

    OpenAIRE

    He, Peng; Wei, Biao; Cong, Wenxiang; Wang, Ge

    2012-01-01

    Purpose: Spectral/multienergy CT has the potential to distinguish different materials by K-edge characteristics. K-edge imaging involves the two energy bins on both sides of a K-edge. The authors propose a K-edge imaging optimization model to determine these two energy bins.

  2. Natural domains for edge-degenerate differential operators

    OpenAIRE

    Seiler, Jörg

    2010-01-01

    We study cone differential operators on the half-axis and edge-degenerate differential operators on a half-space. We construct subspaces of edge Sobolev spaces that can be considered as natural domains for edge-degenerate operators and indicate how they can be used in the study of boundary problems for edge-degenerate operators.

  3. Tilings of the Sphere by Edge Congruent Pentagons

    OpenAIRE

    Cheuk, Ka Yue; Cheung, Ho Man; Yan, Min

    2013-01-01

    We study edge-to-edge tilings of the sphere by edge congruent pentagons, under the assumption that there are tiles with all vertices having degree 3. We develop the technique of neighborhood tilings and apply the technique to completely classify edge congruent earth map tilings.

  4. Physics-based edge evaluation for improved color constancy

    NARCIS (Netherlands)

    A. Gijsenij; T. Gevers; J. van de Weijer

    2009-01-01

    Edge-based color constancy makes use of image derivatives to estimate the illuminant. However, different edge types exist in real-world images such as shadow, geometry, material and highlight edges. These different edge types may have a distinctive influence on the performance of the illuminant esti

  5. Coupling Between Velocities in a Radial Supercharger

    Science.gov (United States)

    Pavlechko, V. N.; Petrov, O. A.

    2014-03-01

    We have analyzed the velocities of the medium and impeller in a radial supercharger with consideration of the Coriolis acceleration. We have derived an expression for determining the angular velocity of the medium that differs from the angular velocity of the impeller. Dependences have been obtained to determine the velocity of the medium at the exit from the impeller on the inclination angle of the supercharger blades and their coupling with the circumferential velocity of the impeller in the absence of energy losses. Graphical dependences of velocities on the inclination angle of the blades at different ratios of inside radius to outside radius have been constructed.

  6. Restricted Edge Connectivity of BinaryUndirected Kautz Graphs

    Institute of Scientific and Technical Information of China (English)

    OUJian-ping

    2004-01-01

    A restricted edge cut is an edge cut of a connected graph whose removal resultsin a disconnected graph without isolated vertices. The size of a minimum restricted edge cutof a graph G is called its restricted edge connectivity, and is denoted by λ′(G). Let ξ(G) bethe minimum edge degree of graph G. It is known that λ′(G) ≤ξ(G) if G contains restrictededge cuts. Graph G is called maximal restricted edge connected if the equality holds in thethe preceding inequality. In this paper, undirected Kautz graph UK(2, n) is proved to bemaximal restricted edge connected if n ≥ 2.

  7. Edge Cut Domination, Irredundance, and Independence in Graphs

    OpenAIRE

    Fenstermacher, Todd; Hedetniemi, Stephen; Laskar, Renu

    2016-01-01

    An edge dominating set $F$ of a graph $G=(V,E)$ is an \\textit{edge cut dominating set} if the subgraph $\\langle V,G-F \\rangle$ is disconnected. The \\textit{edge cut domination number} $\\gamma_{ct}(G)$ of $G$ is the minimum cardinality of an edge cut dominating set of $G.$ In this paper we study the edge cut domination number and investigate its relationships with other parameters of graphs. We also introduce the properties edge cut irredundance and edge cut independence.

  8. Outlier Edge Detection Using Random Graph Generation Models and Applications

    CERN Document Server

    Zhang, Honglei; Gabbouj, Moncef

    2016-01-01

    Outliers are samples that are generated by different mechanisms from other normal data samples. Graphs, in particular social network graphs, may contain nodes and edges that are made by scammers, malicious programs or mistakenly by normal users. Detecting outlier nodes and edges is important for data mining and graph analytics. However, previous research in the field has merely focused on detecting outlier nodes. In this article, we study the properties of edges and propose outlier edge detection algorithms using two random graph generation models. We found that the edge-ego-network, which can be defined as the induced graph that contains two end nodes of an edge, their neighboring nodes and the edges that link these nodes, contains critical information to detect outlier edges. We evaluated the proposed algorithms by injecting outlier edges into some real-world graph data. Experiment results show that the proposed algorithms can effectively detect outlier edges. In particular, the algorithm based on the Prefe...

  9. Maximum heat flux propagation velocity during quenching by water jet impingement

    Energy Technology Data Exchange (ETDEWEB)

    Mozumder, Aloke Kumar; Woodfield, Peter Lloyd; Ashraful Islam, Md.; Monde, Masanori [Department of Mechanical Engineering, Saga University, 1 Honjo-machi, Saga 840-8502 (Japan)

    2007-04-15

    Maximum heat flux propagation characteristics during quenching of hot cylindrical blocks with initial temperature 250-600 C have been investigated experimentally using a subcooled water jet. When the wetted area starts moving towards the circumferential region, the heat flux reaches its maximum value and the position of maximum heat flux follows the visible leading edge of the wetting front. If wetting starts immediately after the jet strikes the surface, the velocity of this maximum heat flux point increases with the increase of jet velocity and subcooling and decreases with the increase of block initial temperature. These trends are opposite if there is a long delay before movement of the front. (author)

  10. Velocity condensation for magnetotactic bacteria

    CERN Document Server

    Rupprecht, Jean-Francois; Bocquet, Lydéric

    2015-01-01

    Magnetotactic swimmers tend to align along magnetic field lines against stochastic reorientations. We show that the swimming strategy, e.g. active Brownian motion versus run-and-tumble dynamics, strongly affects the orientation statistics. The latter can exhibit a velocity condensation whereby the alignment probability density diverges. As a consequence, we find that the swimming strategy affects the nature of the phase transition to collective motion, indicating that L\\'evy run-and-tumble walks can outperform active Brownian processes as strategies to trigger collective behavior.

  11. Velocity peaks and caustic rings

    International Nuclear Information System (INIS)

    The late infall of cold dark matter onto an isolated galaxy produces flows with definite velocity vectors at any physical point in the galactic halo. It also produces caustic rings, which are places in space where the dark matter density is very large. The self-similar model of galactic halo formation predicts that the caustic ring radii an follow the approximate law an ≅ 1/n. Bumps in the rotation curves of NGC 3198 and of our own galaxy are interpreted as due to caustic rings of dark matter

  12. PRECISION RADIAL VELOCITIES WITH CSHELL

    International Nuclear Information System (INIS)

    Radial velocity (RV) identification of extrasolar planets has historically been dominated by optical surveys. Interest in expanding exoplanet searches to M dwarfs and young stars, however, has motivated a push to improve the precision of near-infrared RV techniques. We present our methodology for achieving 58 m s-1 precision in the K band on the M0 dwarf GJ 281 using the CSHELL spectrograph at the 3 m NASA Infrared Telescope Facility. We also demonstrate our ability to recover the known 4 MJUP exoplanet Gl 86 b and discuss the implications for success in detecting planets around 1-3 Myr old T Tauri stars.

  13. Velocity Condensation for Magnetotactic Bacteria.

    Science.gov (United States)

    Rupprecht, Jean-François; Waisbord, Nicolas; Ybert, Christophe; Cottin-Bizonne, Cécile; Bocquet, Lydéric

    2016-04-22

    Magnetotactic swimmers tend to align along magnetic field lines against stochastic reorientations. We show that the swimming strategy, e.g., active Brownian motion versus run-and-tumble dynamics, strongly affects the orientation statistics. The latter can exhibit a velocity condensation whereby the alignment probability density diverges. As a consequence, we find that the swimming strategy affects the nature of the phase transition to collective motion, indicating that Lévy run-and-tumble walks can outperform active Brownian processes as strategies to trigger collective behavior. PMID:27152825

  14. Peculiar velocities in dynamic spacetimes

    CERN Document Server

    Bini, Donato

    2014-01-01

    We investigate the asymptotic behavior of peculiar velocities in certain physically significant time-dependent gravitational fields. Previous studies of the motion of free test particles have focused on the \\emph{collapse scenario}, according to which a double-jet pattern with Lorentz factor $\\gamma \\to \\infty$ develops asymptotically along the direction of complete gravitational collapse. In the present work, we identify a second \\emph{wave scenario}, in which a single-jet pattern with Lorentz factor $\\gamma \\to \\infty$ develops asymptotically along the direction of wave propagation. The possibility of a connection between the two scenarios for the formation of cosmic jets is critically examined.

  15. The Role of T Helper (TH)17 Cells as a Double-Edged Sword in the Interplay of Infection and Autoimmunity with a Focus on Xenobiotic-Induced Immunomodulation

    OpenAIRE

    Hemdan, Nasr Y.A.; Abu El-Saad, Ahmed M.; Ulrich Sack

    2013-01-01

    Extensive research in recent years suggests that exposure to xenobiotic stimuli plays a critical role in autoimmunity induction and severity and that the resulting response would be exacerbated in individuals with an infection-aroused immune system. In this context, heavy metals constitute a prominent category of xenobiotic substances, known to alter divergent immune cell responses in accidentally and occupationally exposed individuals, thereby increasing the susceptibility to autoimmunity an...

  16. Branching influences force-velocity curves and length fluctuations in actin networks

    Science.gov (United States)

    Hansda, Deepak Kumar; Sen, Shamik; Padinhateeri, Ranjith

    2014-12-01

    We investigate collective dynamics of branched actin networks growing against a rigid movable wall constrained by a resistive force. Computing the force velocity relations, we show that the stall force of such networks depends not only on the average number of filaments touching the wall, but also on the amount of fluctuation of the leading edge of the network. These differences arise due to differences in the network architecture, namely, distance between two adjacent branching points and the initial distance of the starting filament from the wall, with their relative magnitudes influencing the nature of the force velocity curves (convex versus concave). We also show that the introduction of branching results in nonmonotonic diffusion constant, a quantity that measures the growth in length fluctuation of the leading edge of the network, as a function of externally applied force. Together our results demonstrate how the collective dynamics of a branched network differs from that of a parallel filament network.

  17. Branching influences force-velocity curves and length fluctuations in actin networks.

    Science.gov (United States)

    Hansda, Deepak Kumar; Sen, Shamik; Padinhateeri, Ranjith

    2014-12-01

    We investigate collective dynamics of branched actin networks growing against a rigid movable wall constrained by a resistive force. Computing the force velocity relations, we show that the stall force of such networks depends not only on the average number of filaments touching the wall, but also on the amount of fluctuation of the leading edge of the network. These differences arise due to differences in the network architecture, namely, distance between two adjacent branching points and the initial distance of the starting filament from the wall, with their relative magnitudes influencing the nature of the force velocity curves (convex versus concave). We also show that the introduction of branching results in nonmonotonic diffusion constant, a quantity that measures the growth in length fluctuation of the leading edge of the network, as a function of externally applied force. Together our results demonstrate how the collective dynamics of a branched network differs from that of a parallel filament network.

  18. Feature fusion method for edge detection of color images

    Institute of Scientific and Technical Information of China (English)

    Ma Yu; Gu Xiaodong; Wang Yuanyuan

    2009-01-01

    A novel feature fusion method is proposed for the edge detection of color images. Except for the typical features used in edge detection, the color contrast similarity and the orientation consistency are also selected as the features. The four features are combined together as a parameter to detect the edges of color images. Experimental results show that the method can inhibit noisy edges and facilitate the detection for weak edges. It has a better performance than conventional methods in noisy environments.

  19. Tiling Problem: Convex Pentagons for Edge-to-Edge Monohedral Tiling and Convex Polygons for Aperiodic Tiling

    OpenAIRE

    Sugimoto, Teruhisa

    2015-01-01

    We show that convex pentagons that can generate edge-to-edge monohedral tilings of the plane can be classified into exactly eight types. Using these results, it is also proved that no single convex polygon can be an aperiodic prototile without matching conditions other than "edge-to-edge."

  20. Edge maps: Representing flow with bounded error

    KAUST Repository

    Bhatia, Harsh

    2011-03-01

    Robust analysis of vector fields has been established as an important tool for deriving insights from the complex systems these fields model. Many analysis techniques rely on computing streamlines, a task often hampered by numerical instabilities. Approaches that ignore the resulting errors can lead to inconsistencies that may produce unreliable visualizations and ultimately prevent in-depth analysis. We propose a new representation for vector fields on surfaces that replaces numerical integration through triangles with linear maps defined on its boundary. This representation, called edge maps, is equivalent to computing all possible streamlines at a user defined error threshold. In spite of this error, all the streamlines computed using edge maps will be pairwise disjoint. Furthermore, our representation stores the error explicitly, and thus can be used to produce more informative visualizations. Given a piecewise-linear interpolated vector field, a recent result [15] shows that there are only 23 possible map classes for a triangle, permitting a concise description of flow behaviors. This work describes the details of computing edge maps, provides techniques to quantify and refine edge map error, and gives qualitative and visual comparisons to more traditional techniques. © 2011 IEEE.

  1. Partial Degree Bounded Edge Packing Problem

    CERN Document Server

    Zhang, Peng

    2012-01-01

    In [1], whether a target binary string s can be represented from a boolean formula with operands chosen from a set of binary strings W was studied. In this paper, we first examine selecting a maximum subset X from W, so that for any string t in X, t is not representable by X\\{t}. We rephrase this problem as graph, and surprisingly find it give rise to a broad model of edge packing problem, which itself falls into the model of forbidden subgraph problem. Specifically, given a graph G(V;E) and a constant c, the problem asks to choose as many as edges to form a subgraph G'. So that in G', for each edge, at least one of its endpoints has degree no more than c. We call such G' partial c degree bounded. When c = 1, it turns out to be the complement of dominating set. We present several results about hardness, approximation for the general graph and efficient exact algorithm on trees. This edge packing problem model also has a direct interpretation in resource allocation. There are n types of resources and m jobs. E...

  2. Superconducting Metallic Glass Transition-Edge-Sensors

    Science.gov (United States)

    Hays, Charles C. (Inventor)

    2013-01-01

    A superconducting metallic glass transition-edge sensor (MGTES) and a method for fabricating the MGTES are provided. A single-layer superconducting amorphous metal alloy is deposited on a substrate. The single-layer superconducting amorphous metal alloy is an absorber for the MGTES and is electrically connected to a circuit configured for readout and biasing to sense electromagnetic radiation.

  3. Nonlocal edge state transport in topological insulators

    Science.gov (United States)

    Protogenov, Alexander P.; Verbus, Valery A.; Chulkov, Evgueni V.

    2013-11-01

    We use the N-terminal scheme for studying the edge-state transport in two-dimensional topological insulators. We find the universal nonlocal response in the ballistic transport approach. This macroscopic exhibition of the topological order offers different areas for applications.

  4. Diffraction Anomalous Near-Edge Structure

    Science.gov (United States)

    Moltaji, Habib O., Jr.

    1995-11-01

    To determine the atomic structure about atom of an element in a sample of a condensed multicomponent single crystal, contrast radiation is proposed with the use of Diffraction Anomalous Near-Edge Structure (DANES), which combines the long-range order sensitivity of the x-ray diffraction and short-range order of the x-ray absorption near-edge techniques. This is achieved by modulating the photon energy of the x-ray beam incident on the sample over a range of energies near an absorption edge of the selected element. Due to anomalous dispersion, x-ray diffraction, and x-ray absorption, the DANES intensity with respect to the selected element is obtained in a single experiment. I demonstrate that synchrotron DANES measurements for the single crystal of thin film and the powder samples and provide the same local atomic structural information as the x-ray absorption near-edge with diffraction condition and can be used to provide enhanced site selectivity. I demonstrate calculations of DAFS intensity and measurements of polarized DANES and XANES intensity.

  5. Impurity transport in plasma edge turbulence

    CERN Document Server

    Naulin, V; Rasmussen, J J; Naulin, Volker; Wood, Martin Priego; Rasmussen, Jens Juul

    2004-01-01

    The turbulent transport of minority species/impurities is investigated in 2D drift-wave turbulence as well as in 3D toroidal drift-Alfven edge turbulence. The full effects of perpendicular and -- in 3D -- parallel advection are kept for the impurity species. Anomalous pinch effects are recovered and explained in terms of Turbulent EquiPartition (TEP)

  6. Edge-disjoint Hamiltonian cycles in hypertournaments

    DEFF Research Database (Denmark)

    Thomassen, Carsten

    2006-01-01

    We introduce a method for reducing k-tournament problems, for k >= 3, to ordinary tournaments, that is, 2-tournaments. It is applied to show that a k-tournament on n >= k + 1 + 24d vertices (when k >= 4) or on n >= 30d + 2 vertices (when k = 3) has d edge-disjoint Hamiltonian cycles if and only i...

  7. Reading Edge. What Works Clearinghouse Intervention Report

    Science.gov (United States)

    What Works Clearinghouse, 2012

    2012-01-01

    "Reading Edge" is a middle school literacy program that emphasizes cooperative learning, goal setting, feedback, classroom management techniques, and the use of metacognitive strategy, whereby students assess their own skills and learn to apply new ones. The program is a component of the "Success for All"[superscript 2] ("SFA")[R] whole-school…

  8. Students at the Edge of Space

    Science.gov (United States)

    Kennon, Tillman; Roberts, Ed; Fuller, Teresa

    2008-01-01

    Space travel, even low Earth orbit, is probably several years away for most of us; however, students and teachers can research the edge of space by participating in the BalloonSat program. BalloonSat is an offshoot of the Space Grant Consortium's very successful RocketSat program. The Arkansas BalloonSat program consists of teacher-initiated…

  9. Edge-on T Tauri stars

    CERN Document Server

    Appenzeller, I; Stahl, O; Appenzeller, Immo; Bertout, Claude; Stahl, Otmar

    2005-01-01

    Using the UVES echelle spectrograph at the ESO VLT we obtained two-dimensional high-resolution (R = 50 000) spectra of the edge-on disk objects HH30*, HK Tau B, and HV Tau C. For comparison purposes we also observed with the same equipment both the classical T Tauri star HL Tau and the active late-type star LDN 1551-9. The spectra of all three observed edge-on disks consist of a T Tauri emission and absorption line spectrum with superimposed jet emission lines. Analysis of the spectra confirmed that the disks are completely opaque at visible wavelengths and that light from the central objects reaches us only via scattering layers above and below the disk planes. The central objects of our targets were found to be normal T Tauri stars showing moderate but different amounts of veiling of their photospheric spectra, indicating different accretion rates or evolutionary stages. We suggest that all classical T Tauri stars (CTTSs) show this observed morphology when viewed edge-on. Part of the jet emission from edge-...

  10. Leading-Edge Vortex lifts swifts

    NARCIS (Netherlands)

    Videler, JJ; Stamhuis, EJ; Povel, GDE

    2004-01-01

    The current understanding of how birds fly must be revised, because birds use their hand-wings in an unconventional way to generate lift and drag. Physical models of a common swift wing in gliding posture with a 60degrees sweep of the sharp hand-wing leading edge were tested in a water tunnel. Inter

  11. Social Justice as a Pedagogy of Edge

    Science.gov (United States)

    Sonu, Debbie J.

    2010-01-01

    In this article, the author discusses social justice as a "pedagogy of edge." She argues that educators hold the privilege to begin reframing the dialogue on social justice as a relation of all subjects and to dredge from within the meanings drawn and practices made in honor of justice. This may require a shift away from social justice as a…

  12. Time-resonant tokamak plasma edge instabilities?

    NARCIS (Netherlands)

    Webster, A. J.; Dendy, R. O.; Calderon, F. A.; Chapman, S. C.; Delabie, E.; Dodt, D.; Felton, R.; Todd, T. N.; Maviglia, F.; Morris, J.; Riccardo, V.; Alper, B.; Brezinsek, S.; Coad, P.; Likonen, J.; Rubel, M.; JET-EFDA Contributors,

    2014-01-01

    For a two week period during the Joint European Torus 2012 experimental campaign, the same high confinement plasma was repeated 151 times. The dataset was analysed to produce a probability density function (pdf) for the waiting times between edge-localized plasma instabilities (ELMs). The result was

  13. Anomalous transport in the tokamak edge

    International Nuclear Information System (INIS)

    The tokamak edge has been studied with arrays of Langmuir and magnetic probes on the DITE and COMPASS-C devices. Measurements of plasma parameters such as density, temperature and radial magnetic field were taken in order to elucidate the character, effect on transport and origin of edge fluctuations. The tokamak edge is a strongly-turbulent environment, with large electrostatic fluctuation levels and broad spectra. The observations, including direct correlation measurements, are consistent with a picture in which the observed magnetic field fluctuations are driven by the perturbations in electrostatic parameters. The propagation characteristics of the turbulence, investigated using digital spectral techniques, appear to be dominated by the variation of the radial electric field, both in limiter and divertor plasmas. A shear layer is formed, associated in each case with the last closed flux surface. In the shear layer, the electrostatic wavenumber spectra are significantly broader. The predictions of a drift wave model (DDGDT) and of a family of models evolving from the rippling mode (RGDT group), are compared with experimental results. RGDT, augmented by impurity radiation effects, is shown to be the most reasonable candidate to explain the nature of the edge turbulence, only failing in its estimate of the wavenumber range. (Author)

  14. Universality in edge-source diffusion dynamics

    DEFF Research Database (Denmark)

    Mortensen, Asger; Okkels, Fridolin; Bruus, Henrik

    2006-01-01

    We show that in edge-source diffusion dynamics the integrated concentration N(t) has a universal dependence with a characteristic time scale tau=(A/P)(2)pi/(4D), where D is the diffusion constant while A and P are the cross-sectional area and perimeter of the domain, respectively. For the short...

  15. On the phase velocity of plasma waves in a self-modulated laser wake-field accelerator

    NARCIS (Netherlands)

    Andreev, N. E.; Kirsanov, V. I.; Sakharov, A. S.; van Amersfoort, P. W.; Goloviznin, V. V.

    1996-01-01

    The properties of the wake field excited by a flattop laser pulse with a sharp leading edge and a power below the critical one for relativistic self-focusing are studied analytically and numerically with emphasis on the phase velocity of the plasma wave. The paraxial model describing modulation of t

  16. Tangential 2-D Edge Imaging for GPI and Edge/Impurity Modeling

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Ricardo Maqueda; Dr. Fred M. Levinton

    2011-12-23

    Nova Photonics, Inc. has a collaborative effort at the National Spherical Torus Experiment (NSTX). This collaboration, based on fast imaging of visible phenomena, has provided key insights on edge turbulence, intermittency, and edge phenomena such as edge localized modes (ELMs) and multi-faceted axisymmetric radiation from the edge (MARFE). Studies have been performed in all these areas. The edge turbulence/intermittency studies make use of the Gas Puff Imaging diagnostic developed by the Principal Investigator (Ricardo Maqueda) together with colleagues from PPPL. This effort is part of the International Tokamak Physics Activity (ITPA) edge, scrape-off layer and divertor group joint activity (DSOL-15: Inter-machine comparison of blob characteristics). The edge turbulence/blob study has been extended from the current location near the midplane of the device to the lower divertor region of NSTX. The goal of this effort was to study turbulence born blobs in the vicinity of the X-point region and their circuit closure on divertor sheaths or high density regions in the divertor. In the area of ELMs and MARFEs we have studied and characterized the mode structure and evolution of the ELM types observed in NSTX, as well as the study of the observed interaction between MARFEs and ELMs. This interaction could have substantial implications for future devices where radiative divertor regions are required to maintain detachment from the divertor plasma facing components.

  17. Numerical study on the vortex evolution from a sharp-edged, wall-mounted obstacle

    International Nuclear Information System (INIS)

    Direct numerical simulation was carried out to study the vortical structures of the flow around a wall-mounted cube in a channel at Re=1,000 and Re=3,500 based on cubic height and bulk mean velocity. The cubic obstacle is situated in the entrance region of the channel flow where the boundary layers are developing. Upstream of the obstacle, steady and unsteady laminar horseshoe vortex systems are observed at Re=1,000 and Re=3,500, respectively; the near-wake flow is turbulent in both cases. The flow separates at each leading sharp edge of the cube, and subsequent vortex roll-up is noticed in the corresponding free-shear layer. The vortex shedding from the upper leading edge (upper vortices) and that from the two lateral leading edges (lateral vortices) are both quasi-periodic and their frequencies are computed. The upper and lateral vortices further develop into hairpin and Λ vortices, respectively. A series of instantaneous contours of the second invariant of velocity gradient tensor helps us identify spatial and temporal behaviors of the vortices in detail. The results indicate that the length and time scales of the vortical structures at Re=3,500 are much shorter than those at Re=1,000. Correlations between the upper and lateral vortices are also reported

  18. Velocity of sound in hadron matter

    Energy Technology Data Exchange (ETDEWEB)

    Epele, L.N.; Fanchiotti, H.; Garcia Canal, C.A.; Roulet, E.

    1987-09-01

    The velocity of sound in hadron matter, in both the confined and deconfined phases, is studied. This velocity of sound appears to be an important tool to distinguish among different bag-model-based thermodynamical descriptions of hadronic matter.

  19. Calculating the Velocity in the Moss

    Science.gov (United States)

    Womebarger, Amy R.; Tripathi, Durgesh; Mason, Helen

    2011-01-01

    The velocity of the warm (1 MK) plasma in the footpoint of the hot coronal loops (commonly called moss) could help discriminate between different heating frequencies in the active region core. Strong velocities would indicated low-frequency heating, while velocities close to zero would indicate high-frequency heating. Previous results have found disparaging observations, with both strong velocities and velocities close to zero reported. Previous results are based on observations from Hinode/EIS. The wavelength arrays for EIS spectra are typically calculated by assuming quiet Sun velocities are zero. In this poster, we determine the velocity in the moss using observations with SoHO/SUMER. We rely on neutral or singly ionized spectral lines to determine accurately the wavelength array associated with the spectra. SUMER scanned the active region twice, so we also report the stability of the velocity.

  20. Atomic-scale investigation of point defects and hydrogen-solute atmospheres on the edge dislocation mobility in alpha iron

    Energy Technology Data Exchange (ETDEWEB)

    Bhatia, M. A.; Solanki, K. N., E-mail: kiran.solanki@asu.edu [School for Engineering of Matter, Transport, and Energy, Arizona State University, Tempe, Arizona 85287 (United States); Groh, S. [Institute of Mechanics and Fluid Dynamics, TU Bergakademie Freiberg, Freiberg 09556 (Germany)

    2014-08-14

    In this study, we present atomistic mechanisms of 1/2 [111](11{sup ¯}0) edge dislocation interactions with point defects (hydrogen and vacancies) and hydrogen solute atmospheres in body centered cubic (bcc) iron. In metals such as iron, increases in hydrogen concentration can increase dislocation mobility and/or cleavage-type decohesion. Here, we first investigate the dislocation mobility in the presence of various point defects, i.e., change in the frictional stress as the edge dislocation interacts with (a) vacancy, (b) substitutional hydrogen, (c) one substitutional and one interstitial hydrogen, (d) interstitial hydrogen, (e) vacancy and interstitial hydrogen, and (f) two interstitial hydrogen. Second, we examine the role of a hydrogen-solute atmosphere on the rate of local dislocation velocity. The edge dislocation simulation with a vacancy in the compression side of the dislocation and an interstitial hydrogen atom at the tension side exhibit the strongest mechanical response, suggesting a higher potential barrier and hence, the higher frictional stress (i.e., ∼83% higher than the pure iron Peierls stress). In the case of a dislocation interacting with a vacancy on the compressive side, the vacancy binds with the edge dislocation, resulting in an increase in the friction stress of about 28% when compared with the Peierls stress of an edge dislocation in pure iron. Furthermore, as the applied strain increases, the vacancy migrates through a dislocation transportation mechanism by attaining a velocity of the same order as the dislocation velocity. For the case of the edge dislocation interacting with interstitial hydrogen on the tension side, the hydrogen atom jumps through one layer perpendicular to the glide plane during the pinning-unpinning process. Finally, our simulation of dislocation interactions with hydrogen show first an increase in the local dislocation velocity followed by a pinning of the dislocation core in the atmosphere, resulting in