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Sample records for anomalous dispersion effect

  1. Anomalous x-ray scattering: Relativistic effects in x-ray dispersion analysis

    International Nuclear Information System (INIS)

    Rayleigh scattering by bound electrons is reduced from the free-electron Thomson value at x-ray wavelengths by relativistic effects. To first order this arises from the relativistic increase in mass of the core electrons. The reduction is overestimated by more than a factor of 2 by the commonly used dipole approximation. Inclusion of higher multipole and retardation terms in dispersion analysis resolves reported conflicts between values of the anomalous scattering factor as measured interferometrically and as calculated from attenuation measurements. These considerations further imply that several scattering-factor tabulations in current use for diffraction studies require revision to take relativity fully into account. This correction is particularly significant in regions of anomalous dispersion and at low energies, where the scattering factor is small relative to the atomic number

  2. Structure investigation of metal ions clustering in dehydrated gel using x-ray anomalous dispersion effect

    CERN Document Server

    Soejima, Y; Sugiyama, M; Annaka, M; Nakamura, A; Hiramatsu, N; Hara, K

    2003-01-01

    The structure of copper ion clusters in dehydrated N-isopropylacrylamide/sodium acrylate (NIPA/SA) gel has been studied by means of small angle X-ray scattering (SAXS) method. In order to distinguish the intensity scattered by Cu ions, the X-ray anomalous dispersion effect around the Cu K absorption edge has been coupled with SAXS. It is found that the dispersion effect dependent on the incident X-ray energy is remarkable only at the momentum transfer q = 0.031 A sup - sup 1 , where a SAXS peak is observed. The results indicate that copper ions form clusters in the dehydrated gel, and that the mean size of clusters is the same as that of SA clusters produced by microphase separation. It is therefore naturally presumed that copper ions are adsorbed into the SA molecules. On the basis of the presumption, a mechanism is proposed for microphase-separation and clustering of Cu ions.

  3. Relation between the structure and catalytic activity for automotive emissions. Use of x-ray anomalous dispersion effect

    CERN Document Server

    Mizuki, J; Tanaka, H

    2003-01-01

    The employment of the X-ray anomalous dispersion effect allows us to detect the change in structure of catalytic converters with the environment exposed. Here we show that palladium atoms in a perovskite crystal move into and out of the crystal by anomalous X-ray diffraction and absorption techniques. This movement of the precious metal plays an important role to keep the catalytic activity long-lived. (author)

  4. Anomalous dispersion enhanced Cerenkov phase-matching

    Energy Technology Data Exchange (ETDEWEB)

    Kowalczyk, T.C.; Singer, K.D. [Case Western Reserve Univ., Cleveland, OH (United States). Dept. of Physics; Cahill, P.A. [Sandia National Labs., Albuquerque, NM (United States)

    1993-11-01

    The authors report on a scheme for phase-matching second harmonic generation in polymer waveguides based on the use of anomalous dispersion to optimize Cerenkov phase matching. They have used the theoretical results of Hashizume et al. and Onda and Ito to design an optimum structure for phase-matched conversion. They have found that the use of anomalous dispersion in the design results in a 100-fold enhancement in the calculated conversion efficiency. This technique also overcomes the limitation of anomalous dispersion phase-matching which results from absorption at the second harmonic. Experiments are in progress to demonstrate these results.

  5. Anomalous hydrodynamical dispersion and the Coats-Smith equation: the finite size effects

    International Nuclear Information System (INIS)

    We investigate a family of probability distributions that shows anomalous hydrodynamics dispersion, by solving a particular class of coupled generalized master equations. The Fourier-Laplace solution is obtained analytically in terms of the matrix Green function method; then the Coats-Smith concentration profile is revisited in a particular case. Two models of disorder are worked out explicitly, and the mean current is asymptotically calculated. We present an approximation method to calculate the first passage time distribution for this stochastic transport process, and as an example an exact Markovian result is worked out; scaling results are also shown. We discuss the comparison with other different methods to work out complex diffusion phenomena in the presence of disordered multiple transport paths. Extensions when the models are non diffusive can also be solved in the Fourier-Laplace representation. (author)

  6. Anomalous dispersions of `hedgehog' particles

    Science.gov (United States)

    Bahng, Joong Hwan; Yeom, Bongjun; Wang, Yichun; Tung, Siu On; Hoff, J. Damon; Kotov, Nicholas

    2015-01-01

    Hydrophobic particles in water and hydrophilic particles in oil aggregate, but can form colloidal dispersions if their surfaces are chemically camouflaged with surfactants, organic tethers, adsorbed polymers or other particles that impart affinity for the solvent and increase interparticle repulsion. A different strategy for modulating the interaction between a solid and a liquid uses surface corrugation, which gives rise to unique wetting behaviour. Here we show that this topographical effect can also be used to disperse particles in a wide range of solvents without recourse to chemicals to camouflage the particles' surfaces: we produce micrometre-sized particles that are coated with stiff, nanoscale spikes and exhibit long-term colloidal stability in both hydrophilic and hydrophobic media. We find that these `hedgehog' particles do not interpenetrate each other with their spikes, which markedly decreases the contact area between the particles and, therefore, the attractive forces between them. The trapping of air in aqueous dispersions, solvent autoionization at highly developed interfaces, and long-range electrostatic repulsion in organic media also contribute to the colloidal stability of our particles. The unusual dispersion behaviour of our hedgehog particles, overturning the notion that like dissolves like, might help to mitigate adverse environmental effects of the use of surfactants and volatile organic solvents, and deepens our understanding of interparticle interactions and nanoscale colloidal chemistry.

  7. Analytical solutions for anomalous dispersion transport

    Science.gov (United States)

    O'Malley, D.; Vesselinov, V. V.

    2014-06-01

    Groundwater flow and transport often occur in a highly heterogeneous environment (potentially heterogeneous at multiple spatial scales) and is impacted by geochemical reactions, advection, diffusion, and other pore scale processes. All these factors can give rise to large-scale anomalous dispersive behavior that can make complex model representation and prediction of plume concentrations challenging due to difficulties unraveling all the complexities associated with the governing processes, flow medium, and their parameters. An alternative is to use upscaled stochastic models of anomalous dispersion, and this is the approach used here. Within a probabilistic framework, we derive a number of analytical solutions for several anomalous dispersion models. The anomalous dispersion models are allowed to be either non-Gaussian (α-stable Lévy), correlated, or nonstationary from the Lagrangian perspective. A global sensitivity analysis is performed to gain a greater understanding of the extent to which uncertainty in the parameters associated with the anomalous behavior can be narrowed by examining concentration measurements from a network of monitoring wells and to demonstrate the computational speed of the solutions. The developed analytical solutions are encoded and available for use in the open source computational framework MADS (http://mads.lanl.gov).

  8. Comparative study of anomalous dispersive transparent media

    International Nuclear Information System (INIS)

    We present a comparative theoretical analysis of five different atomic schemes with respect to their performance as negative (anomalous) dispersive transparent media. The schemes discussed are the strongly driven and the degenerate two-level system, two closely spaced gain lines, and two slightly different double-Λ schemes with incoherent pumping. The analysis shows that the degenerate two-level scheme is best suited for applications for which only modest negative dispersion but strongly reduced absorption is required, and dissipation and loss of the optical fields have to be avoided. Two closely spaced gain lines and one of the double-Λ schemes are the best choice for applications which rely on large negative dispersion, but are not too sensitive to residual absorption and dissipation

  9. Anomalous Hall effect

    Czech Academy of Sciences Publication Activity Database

    Nagaosa, N.; Sinova, Jairo; Onoda, S.; MacDonald, A. H.; Ong, N. P.

    2010-01-01

    Roč. 82, č. 2 (2010), s. 1539-1592. ISSN 0034-6861 Institutional research plan: CEZ:AV0Z10100521 Keywords : anomalous Hall effect * spintronics Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 51.695, year: 2010

  10. Nonlocal Anomalous Hall Effect

    Science.gov (United States)

    Zhang, Steven S.-L.; Vignale, Giovanni

    2016-04-01

    The anomalous Hall (AH) effect is deemed to be a unique transport property of ferromagnetic metals, caused by the concerted action of spin polarization and spin-orbit coupling. Nevertheless, recent experiments have shown that the effect also occurs in a nonmagnetic metal (Pt) in contact with a magnetic insulator [yttrium iron garnet (YIG)], even when precautions are taken to ensure that there is no induced magnetization in the metal. We propose a theory of this effect based on the combined action of spin-dependent scattering from the magnetic interface and the spin-Hall effect in the bulk of the metal. At variance with previous theories, we predict the effect to be of first order in the spin-orbit coupling, just as the conventional anomalous Hall effect—the only difference being the spatial separation of the spin-orbit interaction and the magnetization. For this reason we name this effect the nonlocal anomalous Hall effect and predict that its sign will be determined by the sign of the spin-Hall angle in the metal. The AH conductivity that we calculate from our theory is in order of magnitude agreement with the measured values in Pt /YIG structures.

  11. Normal and Anomalous Dispersion in Fluvial Sediment Transport

    Science.gov (United States)

    Bradley, D. N.; Tucker, G. E.

    2005-12-01

    Understanding the rate of motion and pattern of dispersion in fluvial sediment transport is essential for a variety of applications, including predicting the fate and transport of solid-phase contaminants and modeling the cosmogenic-nuclide inheritance of water-borne sediment. In order to create a probabilistic model of sediment particle motion, it is necessary to characterize the statistical properties of fluvial sediment dispersion. In general, two modes of behavior have been observed in advective-diffusive transport systems: normal and anomalous dispersion. Normal dispersion is characterized by a well-defined mean position and spatial variance and the time evolution of particle concentration is described by a simple advection-diffusion equation. In contrast, a transport system that exhibits anomalous dispersion will tend to have a heavy-tailed spatial distribution, a mean position that is different from the peak concentration, and a large variance. The fundamental difference lies in the probability distribution of individual particle velocities. When the distribution is sufficiently heavy-tailed, the resulting dispersion pattern will be anomalous. Anomalous dispersion has been observed in geophysical systems ranging from turbulent flow to transport in heterogeneous porous media. Several lines of evidence from the sediment transport literature suggest that fluvial sediment may undergo anomalous dispersion. Tracer experiments show a preference for right-skewed travel distance distributions, a characteristic of anomalous diffusion. Studies suggest that large inputs of sediment to rivers (such as a landslide) tend to disperse in place rather than translate downstream. In addition, the fact that sediment grains can become trapped in flood plains and bars for long periods of time and then move long distances in rare, short duration events such as floods suggests a potential for anomalous dispersion due to a broad distribution of particle residence times. We develop a

  12. The anomalous memory effect related to the relaxation of surface and core moments observed in well-dispersed CoFe2O4 nanoparticles

    Science.gov (United States)

    Huang, S.; Ma, Y. Q.; Xu, S. T.

    2015-12-01

    Well-dispersed uniform cobalt ferrite nanoparticles were synthesized by thermal decomposition of a metal-organic salt in organic solvent with a high boiling point, and characterized by XRD, TEM and detailed magnetic measurements. The moments of CoFe2O4 nanoparticles consist of the core and canted surface moments below 200 K, and the exchange-coupling between the surface and core spins enhanced the remanence (Mr) to saturation (Ms) magnetization ratio (Mr/Ms) at the temperature of 10 K. Interestingly, the anomalous memory effect was observed in a broad temperature range which can be attributed to the relaxation of surface spins below 200 K and the one from the moments of magnetically ordered entity larger than one particle above 200 K.

  13. The quantum anomalous Hall effect

    OpenAIRE

    LIU, CHAO-XING; Zhang, Shou-Cheng; Qi, Xiao-Liang

    2015-01-01

    The quantum anomalous Hall effect is defined as a quantized Hall effect realized in a system without external magnetic field. Quantum anomalous Hall effect is a novel manifestation of topological structure in many-electron systems, and may have potential applications in future electronic devices. In recent years, quantum anomalous Hall effect has been proposed theoretically and realized experimentally. In this review article, we provide a systematic overview of the theoretical and experimenta...

  14. What Matters When and Where for Anomalous Dispersion/Diffusion

    Science.gov (United States)

    O'Malley, D.; Vesselinov, V. V.

    2013-12-01

    The classical Lagrangian model of Fickian dispersion/diffusion is given by Brownian motion of fluid particles representing contaminant migration. Brownian motion is defined via three conceptual assumptions about the distribution of (spatial) displacements: 1. The displacements are independent. 2. The displacements are stationary. 3. The displacements are normally distributed. Anomalous dispersion/diffusion occurs when one or more of these assumptions fails. Two of the hallmarks of anomalous dispersion/diffusion are nonlinear mean square displacement (often modeled as a power-law) and heavy tails. While these calling cards are important indicators of anomalous behavior, its origin is in the violation of any of the three assumptions. Anomalous behavior associated with such as violation has been observed in a variety of application areas including surface and subsurface hydrology. Anomalous dispersion/diffusion can create significant problems in efforts to characterize contaminant transport and design remediation strategies that protect groundwater resources. The impact at varied spatial and temporal scales of relaxing these assumptions in concert is not well understood. In order to gain a better understanding, a global sensitivity analysis (based on Sobol's method) of predicted contaminant concentrations at a number of spatial and temporal scales is performed with respect to the relaxation of these three assumptions. That is, the sensitivity of contaminant concentration (particle density) to variations in the degree to which the displacements are correlated, nonstationary, and non-normal is computed. The analyses are performed using the code MADS (Model Analyses for Decision Support; http://mads.lanl.gov).

  15. Transfer of information in an anomalous dispersion medium

    Institute of Scientific and Technical Information of China (English)

    黄超光; 张元仲

    2003-01-01

    The transfer of information and signal velocity in an anomalous dispersion medium are studied. We propose that the discontinuous points in the envelop and its derivatives of any order are the information carried by a pulse different from others. The signal velocity will not exceed the speed of the shift of these discontinuous points. We study the propagation of pulses with a triangle envelop and with the envelop made up by three pieces of quadratic curve in dilute, anomalous dispersion gas with double gain lines. The discontinuous points of the envelop, its first derivative, and its second derivative are shown to propagate with vacuum speed of light c in the medium. A criterion has been suggested to determine theoretically whether the distortion of a pulse can be ignored.

  16. Effective actions for anomalous hydrodynamics

    International Nuclear Information System (INIS)

    We argue that an effective field theory of local fluid elements captures the constraints on hydrodynamic transport stemming from the presence of quantum anomalies in the underlying microscopic theory. Focussing on global current anomalies for an arbitrary flavour group, we derive the anomalous constitutive relations in arbitrary even dimensions. We demonstrate that our results agree with the constraints on anomaly governed transport derived hitherto using a local version of the second law of thermodynamics. The construction crucially uses the anomaly inflow mechanism and involves a novel thermofield double construction. In particular, we show that the anomalous Ward identities necessitate non-trivial interaction between the two parts of the Schwinger-Keldysh contour

  17. Hollow cathode lamp based Faraday anomalous dispersion optical filter.

    Science.gov (United States)

    Pan, Duo; Xue, Xiaobo; Shang, Haosen; Luo, Bin; Chen, Jingbiao; Guo, Hong

    2016-01-01

    The Faraday anomalous dispersion optical filter (FADOF), which has acquired wide applications, is mainly limited to some gaseous elements and low melting-point metals before, for the restriction of the attainable atomic density. In conventional FADOF systems a high atomic density is usually achieved by thermal equilibrium at the saturated vapor pressure, hence for elements with high melting-points a high temperature is required. To avoid this restriction, we propose a scheme of FADOF based on the hollow cathode lamp (HCL), instead of atomic vapor cells. Experimental results in strontium atoms verified this scheme, where a transmission peak corresponding to the (88)Sr (5s(2))(1)S0 - (5s5p)(1)P1 transition (461 nm) is obtained, with a maximum transmittance of 62.5% and a bandwith of 1.19 GHz. The dependence of transmission on magnetic field and HCL discharge current is also studied. Since the state-of-art commercial HCLs cover about 70 elements, this scheme can greatly expand the applications of FADOFs, and the abundant atomic transitions they provide bring the HCL based FADOFs potential applications for frequency stabilization. PMID:27418112

  18. Modeling the spatial variability of dispersivity to deal with anomalous mass transport in the subsurface

    Science.gov (United States)

    Capilla, J. E.; Sanchez Fuster, I.; Sanchez Barrero, L.

    2012-12-01

    The limitations of the classical Advection-Dispersion Equation (ADE) approach to model mass transport remain a subject of research. The term anomalous transport is usually applied when the ADE fails to reproduce real field or lab experiments tracer tests data. Some authors address this limitation using high-resolution heterogeneous hydraulic conductivity (K) fields. Besides, the non-Fickian behavior of transport is another issue addressed. However, the effects of the spatial variability of dispersivity, and the influence of the model support scale on this property, have been rarely studied. The lack of experimental knowledge on the dispersivity behavior leads to model this basic parameter as an averaged calibrated parameter highly dependent on the model discretization size. In order to study the local behavior of the dispersivity a porous medium tank was designed and built at the Technical University of Valencia (Spain). This paper presents new results and conclusions obtained from the experiments conducted in this lab prototype. The steady flow through the porous medium tank lab is quasi-2D, and the K field imitates the patterns of spatial variability found in a real and highly heterogeneous formation (MADE2 site). The tracer tests are run using a conservative dye tracer and the tank is monitored by a grid of pressure transducers and taking digital images that are processed to map the evolution of solute concentrations in the tank. The set of exhaustive head and concentration data is used to compute detail local information of the effective dispersivity field at different time steps, and at different support scales. The analysis of results shows that the dispersivity field displays patterns of spatial variability related with the physical nature of the local material and also with the local evolution of concentrations at every grid block. We have found that the anomalous transport behavior observed in the lab tank can be accurately modeled using the classical ADE

  19. Anomalous Hall effect in polycrystalline Ni films

    KAUST Repository

    Guo, Zaibing

    2012-02-01

    We systematically studied the anomalous Hall effect in a series of polycrystalline Ni films with thickness ranging from 4 to 200 nm. It is found that both the longitudinal and anomalous Hall resistivity increased greatly as film thickness decreased. This enhancement should be related to the surface scattering. In the ultrathin films (46 nm thick), weak localization corrections to anomalous Hall conductivity were studied. The granular model, taking into account the dominated intergranular tunneling, has been employed to explain this phenomenon, which can explain the weak dependence of anomalous Hall resistivity on longitudinal resistivity as well. © 2011 Elsevier Ltd. All rights reserved.

  20. High-energy pulse compressor using self-defocusing spectral broadening in anomalously dispersive media

    DEFF Research Database (Denmark)

    Bache, Morten; Zhou, Binbin

    A new high-energy pulse compressor uses self-defocusing spectral broadening in anomalously dispersive quadratic nonlinear crystals, followed by positive group-delay-dispersion compensation. Compression to sub-50 fs is possible from Joule-class 1.03 µm femtosecond amplifiers in large-aperture KDP....

  1. Anomalous dispersion properties of TM waves in subwavelength metallic waveguides loaded by uniaxial metamaterials

    International Nuclear Information System (INIS)

    Dispersion properties of transverse magnetic (TM) waves in a subwavelength metallic waveguide loaded by uniaxial metamaterials are investigated, based on two kinds of uniaxial metamaterials with different orientations of optical axis. The numerical results show that the existence of fundamental TM0 mode and high-order TM modes in the waveguide system is dependent on the orientation of optical axis. In addition, their anomalous dispersion properties are clarified. When the orientation of optical axis is selected properly, there are two branches of dispersion curves for each high-order mode—one is normal dispersion and another belongs to anomalous dispersion, showing a transition from a backward wave to a forward one with the increase of working frequency. Moreover, the group velocity and energy flow distribution for TM1 mode are also demonstrated. These properties may have potential applications in optical information storage, integrated optics and nanophotonic devices. - Highlights: • Two kinds of subwavelength uniaxial metamaterial waveguides are constructed. • We demonstrate anomalous dispersion properties of transverse magnetic (TM) guided modes. • There are two branches of dispersion curves for high-order TM modes, showing a transition from a backward wave to a forward one. • Group velocity can approach to zero, having potential application in optical information storage. • Negative group velocity and energy flow distribution for TM modes are shown

  2. Cs 728 nm excited state Faraday anomalous dispersion optical filter with indirect pump

    Science.gov (United States)

    Tao, Zhiming; Zhang, Xiaogang; Chen, Mo; Liu, Zhongzheng; Zhu, Chuanwen; Liu, Zhiwen; Chen, Jingbiao

    2016-06-01

    We demonstrate a Cs excited state Faraday anomalous dispersion optical filter (ESFADOF) operating at 728 nm using a novel pump method, by which the pump beam and the probe beam in the ESFADOF realized here have no a common energy level. Using this method, the ESFADOF achieves a transmission of 2.39% with a bandwidth of 22.52 MHz, which can be applied to both laser frequency stabilization and future four-level active optical clocks. Under the 455 nm laser pump, in addition to 52D5/2, other states such as 72S1/2, 72P3/2, 62P3/2, 62P1/2 and 52D3/2 have also been populated effectively. Meanwhile, multiple wavelength filters exploiting atomic transitions to these states can be realized.

  3. Poynting vector, energy density, and energy velocity in an anomalous dispersion medium

    International Nuclear Information System (INIS)

    The Poynting vector, energy density, and energy velocity of light pulses propagating in an anomalous dispersion medium with two closely spaced gain lines are calculated. The results show that a negative energy density in the medium propagates along the opposite direction of incidence with a velocity similar to the negative group velocity vg while Poynting vector is in the same direction of incidence. In other words, one might say that a positive energy density in the medium would propagate along the positive direction with a speed |vg|. We further point out that neither energy velocity nor group velocity is a good concept to describe the propagation process of light pulse inside the medium in the Wang, Kuzmich, and Dogaiu [Nature (London) 406, 277 (2000)] experiment owing to the strong accumulation and dissipation effects

  4. Multisplitting and collapse of self-focusing anisotropic beams in normal/anomalous dispersive media

    DEFF Research Database (Denmark)

    Bergé, L.; Juul Rasmussen, J.

    1996-01-01

    Three-dimensional self-focusing light pulses in normal and anomalous dispersive media are investigated by means of a waveguide instability analysis, a Lagrangian approach, and a quasi-self-similar analysis. In the case of normal dispersion for which no localized ground state exists, it is shown...... that a high-intensity elongated beam cannot self-similarly collapse. Even when the incident beam power widely exceeds the critical power for a two-dimensional self-focusing, the beam is shown to split into multiple cells that ultimately disperse when their individual mass lies below the critical power...... pulses also play an important role in an anomalous dispersive medium. In this case, unlike the former one, the beam self-contracts along its propagation axis and reconcentrates its shape back toward the center where it ultimately collapses in a finite time. (C) 1996 American Institute of Physics....

  5. Development of dispersive anomalous diffraction, application to the study of inorganic modulated structures and biological macromolecules

    International Nuclear Information System (INIS)

    X-ray diffraction has been developed since the beginning of the century for the determination of crystallographic structures. Most complex structures (proteins, incommensurate crystals...) require the use of anomalous diffraction, i.e. the measurement of diffracted intensities at several wavelengths around the absorption edge of one element of the crystal. This technique allows the determination of the phase of the structure factor, as well as the positions of the anomalous atoms. In this thesis, we present the Dispersive Anomalous Diffraction (DAD) method, which allows the simultaneous measure of diffracted intensities at a number of wavelengths for many reflections. Two collection modes can be used, either continuous (DDAFS-Dispersive Diffraction Anomalous Fine Structure) or discrete (SMAD-Simultaneous Multiwavelength Anomalous Diffraction. A specific procedure and a program (DAD) have been developed for the quantitative analysis of dispersive diffraction images. This program also allows the analysis of monochromatic diffraction images, with satellite reflections near main diffraction peaks. We present the first two quantitative experiments in dispersive diffraction for biological compounds. Our results show that the use of SMAD for structure determination is possible, although several improvements are still necessary for both data collection and analysis. An important point in this thesis is the study of quasi-1D compound (TaSe4)2I: this crystal exhibits a Peierls transition, for which no condensation of the metallic atoms was shown for the last 15 years. Our study has characterized the domain structure of this material, and anomalous diffraction has shown in a specific way the tetramerisation of tantalum atoms, which exists along the already-known acoustic modulation. (author)

  6. Anomalous Hall effect for semiclassical chiral fermions

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Pengming, E-mail: zhpm@impcas.ac.cn [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou (China); Horváthy, P.A., E-mail: horvathy@lmpt.univ-tours.fr [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou (China); Laboratoire de Mathématiques et de Physique Théorique, Université de Tours (France)

    2015-03-06

    Semiclassical chiral fermions manifest the anomalous spin-Hall effect: when put into a pure electric field they suffer a side jump, analogous to what happens to their massive counterparts in non-commutative mechanics. The transverse shift is consistent with the conservation of the angular momentum. In a pure magnetic field, instead, spiraling motion is found. Motion in Hall-type perpendicular electric and magnetic fields is also studied. - Highlights: • Chiral fermions exhibit an anomalous spin-Hall effect. • Transverse shift appears in a pure electric field. • In a pure magnetic field spiraling motion is found.

  7. Two-dimensional solitons and vortices in normal and anomalous dispersive media

    International Nuclear Information System (INIS)

    We study solitons and vortices described by the (2+1)-dimensional fourth-order generalized nonlinear Schroedinger equation with cubic-quintic nonlinearity. Necessary conditions for the existence of such structures are investigated analytically using conservation laws and asymptotic behavior of localized solutions. We derive the generalized virial relation, which describes the combined influence of linear and nonlinear effects on the evolution of the wave packet envelope. By means of refined variational analysis, we predict the main features of steady soliton solutions, which have been shown to be in good agreement with our numerical results. Soliton and vortex stability is investigated by linear analysis and direct numerical simulations. We show that stable bright solitons exist in nonlinear Kerr media both in anomalous and normal dispersive regimes, even if only the fourth-order dispersive effect is taken into account. Vortices occur robust with respect to symmetry-breaking azimuthal instability only in the presence of additional defocusing quintic nonlinearity in the strongly nonlinear regime. We apply our results to the theoretical explanation of whistler self-induced waveguide propagation in plasmas, and discuss possible applications to light beam propagation in cubic-quintic optical materials and to solitons in two-dimensional molecular systems

  8. Momentum and Energy Dependence of the Anomalous High-Energy Dispersion in the Electronic Structure of High Temperature Superconductors

    Science.gov (United States)

    Inosov, D. S.; Fink, J.; Kordyuk, A. A.; Borisenko, S. V.; Zabolotnyy, V. B.; Schuster, R.; Knupfer, M.; Büchner, B.; Follath, R.; Dürr, H. A.; Eberhardt, W.; Hinkov, V.; Keimer, B.; Berger, H.

    2007-12-01

    Using high-resolution angle-resolved photoemission spectroscopy we have studied the momentum and photon energy dependence of the anomalous high-energy dispersion, termed waterfalls, between the Fermi level and 1 eV binding energy in several high-Tc superconductors. We observe strong changes of the dispersion between different Brillouin zones and a strong dependence on the photon energy around 75 eV, which we associate with the resonant photoemission at the Cu3p→3dx2-y2 edge. We conclude that the high-energy “waterfall” dispersion results from a strong suppression of the photoemission intensity at the center of the Brillouin zone due to matrix element effects and is, therefore, not an intrinsic feature of the spectral function. This indicates that the new high-energy scale in the electronic structure of cuprates derived from the waterfall-like dispersion may be incorrect.

  9. Anomalous Hall Effect for chiral fermions

    CERN Document Server

    Zhang, P -M

    2014-01-01

    Semiclassical chiral fermions manifest the anomalous spin-Hall effect: when put into a pure electric field, they suffer a side jump, analogous to what happens to their massive counterparts in non-commutative mechanics. The transverse shift is consistent with the conservation of the angular momentum. In a pure magnetic field a cork-screw-like, spiraling motion is found.

  10. Anomalous Hall effect in disordered multiband metals

    Czech Academy of Sciences Publication Activity Database

    Kovalev, A.A.; Sinova, Jairo; Tserkovnyak, Y.

    2010-01-01

    Roč. 105, č. 3 (2010), 036601/1-036601/4. ISSN 0031-9007 Institutional research plan: CEZ:AV0Z10100521 Keywords : anomalous Hall effect * spintronics Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 7.621, year: 2010

  11. Crystal structure of thermostable catechol 2,3-dioxygenase determined by multiwavelength anomalous dispersion method

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The selenomethionyl derivative of the thermostable catechol 2,3-dioxygenase (SeMet-TC23O) is expressed,purified and crystallized. By using multiwave length anomalous dispersion (MAD) phasing techniques, the crystal structure of TC23O at 0.3 nm resolutions is determined.TC23O is a homotetramer. Each monomer is composed of N-terminal and C-terminal domains (residues 1~153 and 153~319, respectively). The two domains are proximately symmetric by a non-crystallographic axis. Each domain contains two characteristic motifs which are found in almost all of extradial dioxygenases.Kevwords: multiwavelength anomalous dispersion (MAD), X-ray diffraction, thermostable catechol 2,3-dioxygenase, crystal structure,synchrotron light source.

  12. Anomalous dispersion analysis of inhibitor flexibility: a case study of the kinase inhibitor H-89

    International Nuclear Information System (INIS)

    The anomalous dispersion signal of the bromine-containing kinase inhibitor H-89 was used to characterize discrete binding modes of the compound when complexed with the catalytic subunit of protein kinase A. With its ability to show the interactions between drug-target proteins and small-molecule ligands, X-ray crystallography is an essential tool in drug-discovery programmes. However, its usefulness can be limited by crystallization artifacts or by the data resolution, and in particular when assumptions of unimodal binding (and isotropic motion) do not apply. Discrepancies between the modelled crystal structure and the physiological range of structures generally prevent quantitative estimation of binding energies. Improved crystal structure resolution will often not aid energy estimation because the conditions which provide the highest rigidity and resolution are not likely to reflect physiological conditions. Instead, strategies must be employed to measure and model flexibility and multiple binding modes to supplement crystallographic information. One useful tool is the use of anomalous dispersion for small molecules that contain suitable atoms. Here, an analysis of the binding of the kinase inhibitor H-89 to protein kinase A (PKA) is presented. H-89 contains a bromobenzene moiety that apparently binds with multiple conformations in the kinase ATP pocket. Using anomalous dispersion methods, it was possible to resolve these conformations into two distinct binding geometries

  13. A Non-Invasive Phase Sensor for Permittivity and Moisture Estimation Based on Anomalous Dispersion

    Science.gov (United States)

    Siddiqui, Omar; Ramzan, Rashad; Amin, Muhammad; Ramahi, Omar M.

    2016-06-01

    The traditional microwave resonance sensors are based on the measurement of the frequency shift and bandwidth of a resonator’s amplitude spectrum. Here we propose a novel sensing scheme in which the material properties are estimated by determining the changes in the phase spectrum of an anomalous-phase resonator. In the proposed phase sensing, we exploit the unique double phase reversal which takes place on the edges of the anomalous dispersion region as a signature to detect the resonance. We show that with the phase sensing, a significant reduction in detection errors compared to the traditional sensing can be obtained because of the noise immunity offered by the phase detection and also due to the strong dispersive phase response that reduces the sensor’s dependence on the external environment. We also show that the bandwidth determination procedure of the resonance which is needed to characterize the sample losses is significantly simplified. The concept of phase sensing is shown by devising an experimental microstrip open stub resonator whose frequency response lies in the anomalous dispersion region. The dielectric characteristics of the samples placed on the stub are extracted from the resonant frequency and the slope of the phase response. We also demonstrate that the changes in moisture levels can also be detected by utilizing the phase sensing method.

  14. A Non-Invasive Phase Sensor for Permittivity and Moisture Estimation Based on Anomalous Dispersion

    Science.gov (United States)

    Siddiqui, Omar; Ramzan, Rashad; Amin, Muhammad; Ramahi, Omar M.

    2016-01-01

    The traditional microwave resonance sensors are based on the measurement of the frequency shift and bandwidth of a resonator’s amplitude spectrum. Here we propose a novel sensing scheme in which the material properties are estimated by determining the changes in the phase spectrum of an anomalous-phase resonator. In the proposed phase sensing, we exploit the unique double phase reversal which takes place on the edges of the anomalous dispersion region as a signature to detect the resonance. We show that with the phase sensing, a significant reduction in detection errors compared to the traditional sensing can be obtained because of the noise immunity offered by the phase detection and also due to the strong dispersive phase response that reduces the sensor’s dependence on the external environment. We also show that the bandwidth determination procedure of the resonance which is needed to characterize the sample losses is significantly simplified. The concept of phase sensing is shown by devising an experimental microstrip open stub resonator whose frequency response lies in the anomalous dispersion region. The dielectric characteristics of the samples placed on the stub are extracted from the resonant frequency and the slope of the phase response. We also demonstrate that the changes in moisture levels can also be detected by utilizing the phase sensing method. PMID:27346337

  15. Anomalous dispersion of Lagrangian particles in local regions of turbulent flows revealed by convex hull analysis

    CERN Document Server

    Pratt, J; Mueller, W -C; Chapman, S C; Watkins, N W

    2014-01-01

    Local regions of anomalous particle dispersion, and intermittent events that occur in turbulent flows can greatly influence the global statistical description of the flow. These local behaviors can be identified and analyzed by comparing the growth of neighboring convex hulls of Lagrangian tracer particles. Although in our simulations of homogeneous turbulence the convex hulls generally grow in size, after the Lagrangian particles that define the convex hulls begin to disperse, our analysis reveals short periods when the convex hulls of the Lagrangian particles shrink, evidence that particles are not dispersing simply. Shrinkage can be associated with anisotropic flows, since it occurs most frequently in the presence of a mean magnetic field or thermal convection. We compare dispersion between a wide range of statistically homogeneous and stationary turbulent flows ranging from homogeneous isotropic Navier-Stokes turbulence over different configurations of magnetohydrodynamic turbulence and Boussinesq convect...

  16. Anomalous Hall effect in Weyl superconductors

    Science.gov (United States)

    Bednik, G.; Zyuzin, A. A.; Burkov, A. A.

    2016-08-01

    We present a theory of the anomalous Hall effect in a topological Weyl superconductor with broken time reversal symmetry. Specifically, we consider a ferromagnetic Weyl metal with two Weyl nodes of opposite chirality near the Fermi energy. In the presence of inversion symmetry, such a metal experiences a weak-coupling Bardeen–Cooper–Schrieffer instability, with pairing of parity-related eigenstates. Due to the nonzero topological charge, carried by the Weyl nodes, such a superconductor is necessarily topologically nontrivial, with Majorana surface states coexisting with the Fermi arcs of the normal Weyl metal. We demonstrate that, surprisingly, the anomalous Hall conductivity of such a superconducting Weyl metal coincides with that of a nonsuperconducting one, under certain conditions, in spite of the nonconservation of charge in a superconductor. We relate this to the existence of an extra (nearly) conserved quantity in a Weyl metal, the chiral charge.

  17. Simulating Anomalous Dispersion and Multiphase Segregation in Porous Media with the Lattice Boltzmann Method

    Science.gov (United States)

    Matin, Rastin; Misztal, Marek K.; Hernandez-Garcia, Anier; Mathiesen, Joachim

    2015-11-01

    Many hydrodynamic phenomena such as flows at micron scale in porous media, large Reynolds numbers flows, non-Newtonian and multiphase flows have been simulated numerically using the lattice Boltzmann method. By solving the Lattice Boltzmann Equation on three-dimensional unstructured meshes, we efficiently model single-phase fluid flow in real rock samples. We use the flow field to estimate the permeability and further investigate the anomalous dispersion of passive tracers in porous media. By extending our single-phase model with a free-energy based method, we are able to simulate binary systems with moderate density ratios in a thermodynamically consistent way. In this presentation we will present our recent results on both anomalous transport and multiphase segregation.

  18. Excited state Faraday anomalous dispersion optical filters based on indirect laser pumping.

    Science.gov (United States)

    Yin, Longfei; Luo, Bin; Chen, Zhongjie; Zhong, Lei; Guo, Hong

    2014-02-15

    The direct pump method now used in excited state Faraday anomalous dispersion optical filters (ES-FADOFs) requires that the transition between the target and the ground state is an electric dipole allowed transition and that a laser that operates at the exact pump wavelength is available. This is not always satisfied in practice. An indirect laser pump method for ES-FADOF is proposed and experimentally realized. Compared with the commonly used direct pump method, this indirect pump method can reach the same performance using lasers at very different wavelengths. This method can greatly extend the wavelength range of FADOF and provide a novel scheme for ES-FADOF design. PMID:24562221

  19. Femtosecond laser pulse filamentation under anomalous dispersion in fused silica. Part 1. Numerical investigation

    Energy Technology Data Exchange (ETDEWEB)

    Smetanina, E O; Kompanets, V O; Chekalin, Sergei V; Kandidov, V P

    2012-10-31

    We report the results of investigation of femtosecond laser pulse filamentation in fused silica by varying the wavelength in the range from 800 to 2300 nm. It is shown that in the case of the anomalous group-velocity dispersion, a sequence of 'light bullets' with a high spatial and temporal localisation of the light field is formed along the filament. The relation of the formation and propagation of light bullets with the formation of an isolated anti-Stokes wing of the supercontinuum spectrum is established. (nonlinear optical phenomena)

  20. Theoretical analysis of the electromagnetic field inside an anomalous-dispersion microresonator under synthetical pump

    Science.gov (United States)

    Xin, Xu; Xiaohong, Hu; Ye, Feng; Yuanshan, Liu; Wei, Zhang; Zhi, Yang; Wei, Zhao; Yishan, Wang

    2016-03-01

    We study the spatiotemporal evolution of the electromagnetic field inside a microresonator showing an anomalous dispersion at the pump wavelength by using the normalized Lugiato-Lefever equation. Unlike the traditional single continuous wave (CW) pumping, an additional pump source consisting of periodical pulse train with variable repetition rate is adopted. The influences of the microresonator properties and the pump parameters on the field evolution and the electromagnetic field profile are analyzed. The simulation results indicate that, in the anomalous dispersion regime, both increases of the input pulse amplitude and the repetition frequency can result in the field profiles consisting of multiple peaks. A series of equidistant pulses can also be obtained by increasing the CW pump power. In addition, we find that a large physical detuning between the pump laser carrier and the cavity resonance frequency also causes the splitting of the inside field. Project supported by the National Major Scientific Instrumentation Development Program of China (Grant No. 2011YQ120022), CAS/SAFEA International Partnership Program for Creative Research Teams, China, and the National Natural Science Foundation of China (Grant No. 61275164).

  1. Anomalous Josephson Hall effect in magnet/triplet superconductor junctions

    OpenAIRE

    Yokoyama, Takehito

    2015-01-01

    We investigate anomalous Hall effect in a magnet coupled to a triplet superconductor under phase gradient. It is found that the anomalous Hall supercurrent arises from non-trivial structure of the magnetization. The magnetic structure manifested in the Hall supercurrent is characterized by even order terms of the exchange coupling, essentially different from that discussed in the context of anomalous Hall effect, reflecting the disspationless nature of supercurrent. We also discuss a possible...

  2. Anomalous Hall effect in YIG$|$Pt bilayers

    OpenAIRE

    Meyer, Sibylle; Schlitz, Richard; Geprägs, Stephan; Opel, Matthias; Huebl, Hans; Gross, Rudolf; Goennenwein, Sebastian T. B.

    2015-01-01

    We measure the ordinary and the anomalous Hall effect in a set of yttrium iron garnet$|$platinum (YIG$|$Pt) bilayers via magnetization orientation dependent magnetoresistance experiments. Our data show that the presence of the ferrimagnetic insulator YIG leads to an anomalous Hall like signature in Pt, sensitive to both Pt thickness and temperature. Interpretation of the experimental findings in terms of the spin Hall anomalous Hall effect indicates that the imaginary part of the spin mixing ...

  3. Anomalous Dispersion, Finite-Size Lyapunov Exponents, the Full Intermediate Scattering Function and 3D-PTV

    Science.gov (United States)

    Cushman, J. H.; Moroni, M.

    2002-12-01

    Velocity fluctuations over evolving scales of motion, on the scale of observation, often lead to anomalous dispersion of conservative tracers in fluid mechanics studies of turbulence and heterogeneous porous media. Recent theories of anomalous dispersion lead to space-time non-local constitutive models for the flux of concentration, which can adequately model this problem. We review one such model, which has its foundations in non-equilibrium statistical mechanics. The basic premise is that knowledge of the evolution of the self-part of the intermediate scattering function is all that is required to model the phenomena of interest. We derive the basic integro-partial-differential equation this function satisfies and solve the inverse problem to obtain the kernels and use these to describe the wave-vector and frequency dependent dispersion tensor. Subsequently we use this information to study the transition from anomalous to Fickian dispersion. We also make use of the finite size Lyapunov exponent in the description of the dispersive process. Three-camera, three-dimensional, particle -tracking velocimetry experiments are undertaken to study dispersion within a matched-index heterogeneous porous medium. Particle trajectories, mean square displacements, velocity covariance's, intermediate scattering functions, classical dispersion tensors, wave-vector and frequency dependent generalized dispersion tensors and the finite-size Lyapunov exponents are obtained. Comparisons are made in the small frequency and small wave vector limits to obtain the transition from preasymptotic to asymptotic dispersion.

  4. Dynamic polarization of the LiH molecule in strong light field in anomalous-dispersion domain

    CERN Document Server

    Shtoff, A V; Gusarov, S I; Dmitriev, Yu

    1995-01-01

    A new method is proposed to calculate the polarization vector of a molecule in a monochromatic external field in the anomalous-despersion domain. The method takes into account the instantaneous switching of the field. A simple modification of the method allows one to consider a more general switching procedure. As an illustration of the method Fourier components of the polarization vector of the LiH molecule in the anomalous -dispersion domain is calculated.

  5. Photoinduced Anomalous Hall Effects in Weyl Semimetals

    Science.gov (United States)

    Chan, Ching-Kit; Lee, Patrick A.; Burch, Kenneth S.; Han, Jung Hoon; Ran, Ying

    We examine theoretically the interplay between chiral photons and chiral electrons in Weyl semimetals. Owing to its monopole nature, a three-dimensional Weyl node is topologically-robust against a circularly polarized light. A driven Weyl system exhibits node shifts in the momentum space, in sharp contrast to the gap opening in a driven two-dimensional Dirac system. We show that the node shift leads to a change of the Chern vector which gives arise to a net photoinduced anomalous Hall conductivity, in the plane perpendicular to the light propagation. We shall describe the basic idea behind this generic photoinduced Hall effect, illustrate it with a concrete microscope model, and estimate its feasibility based on current optical experimental techniques.

  6. Localization corrections to the anomalous Hall effect in a ferromagnet

    OpenAIRE

    Dugaev, V. K.; Crepieux, A.; Bruno, P

    2001-01-01

    We calculate the localization corrections to the anomalous Hall conductivity related to the contribution of spin-orbit scattering into the current vertex (side-jump mechanism). We show that in contrast to the ordinary Hall effect, there exists a nonvanishing localization correction to the anomalous Hall resistivity. The correction to the anomalous Hall conductivity vanishes in the case of side-jump mechanism, but is nonzero for the skew scattering. The total correction to the nondiagonal cond...

  7. Anomalous supercurrent switching in graphene under proximity effect

    Science.gov (United States)

    Levchenko, Alex; Coskun, U. C.; Brenner, M.; Hymel, T.; Vakaryuk, V.; Bezryadin, A.

    2012-02-01

    We report a study of hysteretic current-voltage characteristics in superconductor-graphene-superconductor (SGS) junctions. The stochastic nature of the phase slips is characterized by measuring the distribution of the switching currents. We find that in SGS junctions the dispersion of the switching current scales with temperature as σIT^αG with αG 1/3. This observation is in sharp contrast with the known Josephson junction behavior where σIT^αJ with αJ=2/3. We propose an explanation using a modified version of Kurkijarvi's theory for the flux stability in rf-SQUID and attribute this anomalous effect to the temperature dependence of the critical current which persists down to low temperatures.

  8. High-power Kerr-lens mode-locked thin-disk oscillator in the anomalous and normal dispersion regimes

    Science.gov (United States)

    Pronin, Oleg; Brons, Jonathan; Seidel, Marcus; Lücking, Fabian; Grasse, Christian; Boehm, Gerhard; Amann, Marcus C.; Pervak, Vladimir; Apolonski, Alexander; Kalashnikov, Vladimir L.; Krausz, Ferenc

    2013-03-01

    A femtosecond thin-disk Yb:YAG oscillator in both the anomalous and the normal dispersion regime is demonstrated. Both regimes are realized with practically the same resonator configuration. The power scaling potential of the anomalous and normal dispersion regimes is analyzed both theoretically and experimentally. The recipe to obtain Kerr-lens mode-locking (KLM) in the thin-disk configuration is presented here and oscillator characteristics as well as start-up difficulties are described. The oscillator stability in terms of output power, beam pointing and sensitivity to back reflections is measured and corresponds to the level of commercial systems.

  9. Sub-300 femtosecond soliton tunable fiber laser with all-anomalous dispersion passively mode locked by black phosphorus.

    Science.gov (United States)

    Chen, Yu; Chen, Shuqing; Liu, Jun; Gao, Yanxia; Zhang, Wenjing

    2016-06-13

    By using evanescent field optical deposition method, we had successfully fabricated an effective optoelectronic device based on multi-layer black phosphorus (BP), which is been heavily investigating 2 dimensional (2D) semiconducting material with similar structure as graphene and thickness dependent direct band-gap. By placing this BP-based optoelectronic device inside a highly compact all-anomalous dispersion fiber laser cavity, stable passive mode-locking operation could be ensured and eventually a record 280 fs transmission limited soliton pulse with tunable central wavelength had been obtained through finely tailoring the cavity length. Other operation states, like bound soliton and noise-like state, had also been observed as well. This work demonstrates the enormous potential of BP for ultra-short pulse generation as an effective optoelectronic device. PMID:27410348

  10. Anomalous Hall Effect in non-commutative mechanics

    OpenAIRE

    Horvathy, P. A.

    2006-01-01

    The anomalous velocity term in the semiclassical model of a Bloch electron deviates the trajectory from the conventional one. When the Berry curvature (alias noncommutative parameter) is a monopole in momentum space as found recently in some ferromagnetic semiconductors while observing the anomalous Hall effect, we get a transverse shift, similar to that in the optical Hall effect.

  11. Anomalous Wien Effects in Supercooled Ionic Liquids

    Science.gov (United States)

    Patro, L. N.; Burghaus, O.; Roling, B.

    2016-05-01

    We have measured conductivity spectra of several supercooled monocationic and dicationic ionic liquids in the nonlinear regime by applying ac electric fields with large amplitudes up to about 180 kV /cm . Thereby, higher harmonic ac currents up to the 7th order were detected. Our results point to the existence of anomalous Wien effects in supercooled ionic liquids. Most ionic liquids studied here exhibit a conductivity-viscosity relation, which is close to the predictions of the Nernst-Einstein and Stokes-Einstein equations, as observed for classical strong electrolytes like KCl. These "strong" ionic liquids show a much stronger nonlinearity of the conductivity than classical strong electrolytes. On the other hand, the conductivity-viscosity relation of the ionic liquid [P6 ,6 ,6 ,14][Cl ] points to ion association effects. This "weak" ionic liquid shows a strength of the nonlinear effect, which is comparable to classical weak electrolytes. However, the nonlinearity increases quadratically with the field. We suggest that a theory for explaining these anomalies will have to go beyond the level of Coulomb lattice gas models.

  12. Anomalous Wien Effects in Supercooled Ionic Liquids.

    Science.gov (United States)

    Patro, L N; Burghaus, O; Roling, B

    2016-05-01

    We have measured conductivity spectra of several supercooled monocationic and dicationic ionic liquids in the nonlinear regime by applying ac electric fields with large amplitudes up to about 180  kV/cm. Thereby, higher harmonic ac currents up to the 7th order were detected. Our results point to the existence of anomalous Wien effects in supercooled ionic liquids. Most ionic liquids studied here exhibit a conductivity-viscosity relation, which is close to the predictions of the Nernst-Einstein and Stokes-Einstein equations, as observed for classical strong electrolytes like KCl. These "strong" ionic liquids show a much stronger nonlinearity of the conductivity than classical strong electrolytes. On the other hand, the conductivity-viscosity relation of the ionic liquid [P_{6,6,6,14}][Cl] points to ion association effects. This "weak" ionic liquid shows a strength of the nonlinear effect, which is comparable to classical weak electrolytes. However, the nonlinearity increases quadratically with the field. We suggest that a theory for explaining these anomalies will have to go beyond the level of Coulomb lattice gas models. PMID:27203333

  13. Anomalous dispersion in Lithium Niobate one-dimensional waveguide array in the near-infrared wavelength range

    CERN Document Server

    Apetrei, Alin Marian; Minot, Christophe; Moison, Jean-Marie; Belabas, Nadia; Tascu, Sorin

    2016-01-01

    Knowing the dispersion regime (normal vs anomalous) is important for both an isolated waveguide and a waveguide array. We investigate by the Finite Element Method the dispersion properties of a LiNbO3 waveguides array using two techniques. The first one assumes the Coupled Mode Theory in a 2-waveguide system. The other one uses the actual diffraction curve determined in a 7-waveguide system. In both approaches we find that by decreasing the array period, one passes from normal dispersion by achromatic point to anomalous array dispersion. We then illustrate the wavelength separation by doing Runge-Kutta light propagation simulations in waveguide array. As all the parameters values are technologically feasible, this opens new possibilities for optical data processing.

  14. Anomalous Nernst Effect with Magnetocrystalline Anisotropy (110)

    Science.gov (United States)

    Chesman, Carlos; Costa Neto, Jose; Department of Physics-UFRN Team

    2014-03-01

    When a ferromagnetic material is submitted to a temperature gradient and the magnetic field generates voltage on the edges of the samples, this is called the Anomalous Nernst Effect (ANE). The Heusler alloys that currently exhibit this effect are the most promising for spintronics and spin caloritronics. In this study we perform a theoretical investigation of voltage curves associated to the ANE, when the material displays magnetocrystalline anisotropy for experimental results in two configurations, ANE versus applied magnetic field and planar angle variations of ANE. We analyzed three types of magnetocrystalline anisotropy: cubic anisotropy (100) with C4 symmetry, uniaxial anisotropy with C2 symmetry and cubic anisotropy (110). The aim was to prove that cubic anisotropy (110) is equivalent to anisotropy (100) combined with uniaxial anisotropy. Theoretical fitting of experimental ANE data demonstrates this total equivalence and that a new interpretation with the use of cubic anisotropy (110) may be due to the atomic arrangement of the so-called full-Heusler. Comparative analyses of Co2FeAl and Co2MnGe alloys will be presented. CNPq, CAPES, FAPERN.

  15. Femtosecond laser pulse filamentation under anomalous dispersion in fused silica. Part 2. Experiment and physical interpretation

    Energy Technology Data Exchange (ETDEWEB)

    Smetanina, E O; Kompanets, V O; Chekalin, Sergei V; Kandidov, V P

    2012-10-31

    We have studied experimentally and analytically the formation of the supercontinuum (SC) spectrum during femtosecond laser pulse filamentation in fused silica under conditions of zero and anomalous group velocity dispersions. It is found that with increasing centre wavelength from 1300 to 2300 nm, the SC spectrum of the anti-Stokes wing narrows, shifting to the blue. It is shown that the anti-Stokes (blue) shift of the SC spectrum increases with the multiphoton order of the medium ionisation by the light field in the filament. It is found that a broad minimum in the SC spectrum, separating the anti-Stokes wing from the centre wavelength, is a result of the interference of radiation from a moving broadband source, stemming from self-phase modulation of the high-intensity light field. The interference factors of the SC spectra obtained for this source, which moves along the emitting region of the filament in a dispersive medium, are in agreement with experimental and numerical results. (nonlinear optical phenomena)

  16. Spurious dispersion effects at FLASH

    International Nuclear Information System (INIS)

    The performance of the Free-Electron Laser (FEL) process imposes stringent demands on the transverse trajectory and size of the electron beam. Since transverse dispersion changes off-energy particle trajectories and increases the effective beam size, dispersion must be controlled. This thesis treats the concept of dispersion in linacs, and analyses the impact of dispersion on the electron beam and on the FEL process. It presents generation mechanisms for spurious dispersion, quantifying its importance for FLASH (Free-electron Laser in Hamburg) and the XFEL (European X-ray Free-Electron Laser). A method for measuring and correcting dispersion and its implementation in FLASH is described. Experiments of dispersion e ects on the transverse beam quality and on the FEL performance are presented. (orig.)

  17. Anomalously increased effective thermal conductivities of ethylene glycol-based nanofluids containing copper nanoparticles

    International Nuclear Information System (INIS)

    It is shown that a ''nanofluid'' consisting of copper nanometer-sized particles dispersed in ethylene glycol has a much higher effective thermal conductivity than either pure ethylene glycol or ethylene glycol containing the same volume fraction of dispersed oxide nanoparticles. The effective thermal conductivity of ethylene glycol is shown to be increased by up to 40% for a nanofluid consisting of ethylene glycol containing approximately 0.3 vol% Cu nanoparticles of mean diameter <10 nm. The results are anomalous based on previous theoretical calculations that had predicted a strong effect of particle shape on effective nanofluid thermal conductivity, but no effect of either particle size or particle thermal conductivity

  18. Direct comparison of shot-to-shot noise performance of all normal dispersion and anomalous dispersion supercontinuum pumped with sub-picosecond pulse fiber-based laser

    Science.gov (United States)

    Klimczak, Mariusz; Soboń, Grzegorz; Kasztelanic, Rafał; Abramski, Krzysztof M.; Buczyński, Ryszard

    2016-01-01

    Coherence of supercontinuum sources is critical for applications involving characterization of ultrafast or rarely occurring phenomena. With the demonstrated spectral coverage of supercontinuum extending from near-infrared to over 10 μm in a single nonlinear fiber, there has been a clear push for the bandwidth rather than for attempting to optimize the dynamic properties of the generated spectrum. In this work we provide an experimental assessment of the shot-to-shot noise performance of supercontinuum generation in two types of soft glass photonic crystal fibers. Phase coherence and intensity fluctuations are compared for the cases of an anomalous dispersion-pumped fiber and an all-normal dispersion fiber. With the use of the dispersive Fourier transformation method, we demonstrate that a factor of 100 improvement in signal-to-noise ratio is achieved in the normal-dispersion over anomalous dispersion-pumped fiber for 390 fs long pump pulses. A double-clad design of the photonic lattice of the fiber is further postulated to enable a pump-related seeding mechanism of normal-dispersion supercontinuum broadening under sub-picosecond pumping, which is otherwise known for similar noise characteristics as modulation instability driven, soliton-based spectra.

  19. Direct comparison of shot-to-shot noise performance of all normal dispersion and anomalous dispersion supercontinuum pumped with sub-picosecond pulse fiber-based laser.

    Science.gov (United States)

    Klimczak, Mariusz; Soboń, Grzegorz; Kasztelanic, Rafał; Abramski, Krzysztof M; Buczyński, Ryszard

    2016-01-01

    Coherence of supercontinuum sources is critical for applications involving characterization of ultrafast or rarely occurring phenomena. With the demonstrated spectral coverage of supercontinuum extending from near-infrared to over 10 μm in a single nonlinear fiber, there has been a clear push for the bandwidth rather than for attempting to optimize the dynamic properties of the generated spectrum. In this work we provide an experimental assessment of the shot-to-shot noise performance of supercontinuum generation in two types of soft glass photonic crystal fibers. Phase coherence and intensity fluctuations are compared for the cases of an anomalous dispersion-pumped fiber and an all-normal dispersion fiber. With the use of the dispersive Fourier transformation method, we demonstrate that a factor of 100 improvement in signal-to-noise ratio is achieved in the normal-dispersion over anomalous dispersion-pumped fiber for 390 fs long pump pulses. A double-clad design of the photonic lattice of the fiber is further postulated to enable a pump-related seeding mechanism of normal-dispersion supercontinuum broadening under sub-picosecond pumping, which is otherwise known for similar noise characteristics as modulation instability driven, soliton-based spectra. PMID:26759188

  20. Understanding the anomalous dispersion of doubly-ionized carbon plasmas near 47 nm

    Energy Technology Data Exchange (ETDEWEB)

    Nilsen, J; Castor, J I; Iglesias, C A; Cheng, K T; Dunn, J; Johnson, W R; Filevich, J; Purvis, M A; Grava, J; Rocca, J J

    2008-04-15

    Over the last several years we have predicted and observed plasmas with an index of refraction greater than one in the soft X-ray regime. These plasmas are usually a few times ionized and have ranged from low-Z carbon plasmas to mid-Z tin plasmas. Our main calculational tool has been the average atom code. We have recently observed C{sup 2+} plasmas with an index of refraction greater than one at a wavelength of 46.9 nm (26.44 eV). In this paper we compare the average atom method, AVATOMKG, against two more detailed methods, OPAL and CAK, for calculating the index of refraction for the carbon plasmas and discuss the different approximations used. We present experimental measurements of carbon plasmas that display this anomalous dispersion phenomenon. It is shown that the average atom calculation is a good approximation when the strongest lines dominate the dispersion. However, when weaker lines make a significant contribution, the more detailed calculations such as OPAL and CAK are essential. During the next decade X-ray free electron lasers and other X-ray sources will be available to probe a wider variety of plasmas at higher densities and shorter wavelengths so understanding the index of refraction in plasmas will be even more essential. With the advent of tunable X-ray lasers the frequency dependent interferometer measurements of the index of refraction may enable us to determine the absorption coefficients and line-shapes and make detailed comparisons against our atomic physics codes.

  1. 780nm Rubdium Faraday Anomalous Dispersion Optical Filter with Buffer Gas Xe

    Science.gov (United States)

    Xiong, Junyu; Yin, Longfei; Luo, Bin; Guo, Hong; Cream Team

    2016-05-01

    Faraday anomalous dispersion optical filter (FADOF) is the most commonly used atomic filter, which is usually realized using alkali metal vapor cells. The filter has wide applications fields such as free-space optical communication, lidar and ghost imaging due to its high transmittance and ultra-narrow bandwidth. However, because FADOF is based on the resonant transitions of atoms, and due to the hyperfine structure of alkali elements, the transmittance spectrum of FADOF usually exhibit multi-peak form, which is not appropriate for applications requiring for single peak and will also reduce the signal to noise ratio(SNR). In this work, a 4cm long rubidium cell filled with 1torr Xenon as buffer gas has been used to realize a 780nm FADOF. Under the influence of the buffer gas Xenon, the sidebands of the transmittance spectrum has been removed, and a 780nm FADOF with single peak transmittance spectrum is achieved, which still keeps the high transmittance and ultra-narrow bandwidth. The peak transmittance of the filter is 82.7% if the power loss caused by the optical instruments (38%) is not included, and the bandwidth equals 1.2GHz. This work is supported by the National Science Fund for Distinguished Young Scholars of China (61225003), the National Natural Science Foundation of China (61401036, 61531003, 61571018), the China Postdoctoral Science Foundation (2015M580008).

  2. A classical picture of anomalous effects in a Tokamak

    Science.gov (United States)

    Hirano, K.

    1984-01-01

    Atomic collisions between plasma ions and a very small amount of neutral particles remaining in a hot plasma plays a very important role for plasma transports and may be an origin of anomalous effects observed in a Tokamak such as the diffusion coefficient independent of the field strength, a rapid plasma density increase during gas puffing and current penetration with anomalously high speed in the start-up phase. The Ohm's law derived by Cowling is used for the analysis.

  3. Large anomalous Nernst effect in a skyrmion crystal

    Science.gov (United States)

    Mizuta, Yo Pierre; Ishii, Fumiyuki

    2016-06-01

    Thermoelectric properties of a model skyrmion crystal were theoretically investigated, and it was found that its large anomalous Hall conductivity, corresponding to large Chern numbers induced by its peculiar spin structure leads to a large transverse thermoelectric voltage through the anomalous Nernst effect. This implies the possibility of finding good thermoelectric materials among skyrmion systems, and thus motivates our quests for them by means of the first-principles calculations as were employed in this study.

  4. Light bullets and supercontinuum spectrum during femtosecond pulse filamentation under conditions of anomalous group-velocity dispersion in fused silicalicati

    Energy Technology Data Exchange (ETDEWEB)

    Chekalin, Sergei V; Kompanets, V O; Smetanina, E O; Kandidov, V P

    2013-04-30

    We report the results of theoretical and experimental research on spectrum transformation and spatiotemporal distribution of the femtosecond laser radiation intensity during filamentation in fused silica. The formation of light bullets with a high power density is first observed in a femtosecond laser pulse in the anomalous group velocity dispersion regime at a wavelength of 1800 nm. The minimum duration of the light bullet is about two oscillation cycles of the light field. (extreme light fields and their applications)

  5. Anomalous magnetic field effects on graphene

    International Nuclear Information System (INIS)

    Full text: Graphene exhibits anomalous properties in externally applied magnetic field. The orbital susceptibility of graphene has a singularity expressed as a delta function in Fermi energy EF, which diverges at Dirac point (EF =0) and vanishes otherwise. The singular diamagnetism is modified by various external factors such as the disorder potential [1], and the band gap opening [2,3], the finite-size effect [4] and the multilayer stacking [5], and studying those effects give deeper insights into the origin of the diamagnetic singularity of Dirac electron. The delta-function singularity is generally weakened by the electronic coupling between different graphene layers. In usual AB-stacked multilayer graphite, the interlayer coupling changes monlayer's linear band to quadratic, and then the susceptibility peak is broadened into a less singular logarithmic curve [5]. In a turbostratic (randomly-stacked) graphene multilayer, on the other hand, the diamagnetism generally becomes much stronger than in AB-stacked graphite, because the interlayer coupling is significantly reduced in misoriented lattice structure. There the external magnetic field is significantly screened inside the sample in low temperatures, and even a perfect screening is achieved at zero temperature in an ideal sample [4]. When the stacking angle between two graphene layers becomes as small as a few degree, the electronic structure is strongly modified by the long-period lattice structure with a Moire pattern. In increasing magnetic field, the spectrum gradually evolves into a fractal band structure called Hofstadter's butterfly, where the Hall conductivity exhibits a nonmonotonic behavior as a function of Fermi energy [6]. In finite-sized graphene system such as graphene ribbon and graphene nano-islands, the finite-size effect also changes the singular diamagnetism.[4] At T=0, the susceptibility χ(EF) oscillates between diamagnetism and paramagnetism in accordance with the subband structure formed

  6. Anomalous radiation effects on oxide material surface

    International Nuclear Information System (INIS)

    Various different kind of radiation influence on surface properties, in particular, adsorptive, was revealed and at some cases the general observation regularity of the radiation adsorption is upset. So, the hydrogen photo-adsorption is not observed on silicon dioxide and on some other oxides. At the same time hydrogen adsorption takes place at the same oxides irradiation by more power nuclear particles, such as gamma-rays, protons of high energies, alpha-particles, neutrons, high-velocity electrons, and also at a X-ray irradiation. At the same time oxygen adsorption takes place on the majority of the studied oxides. So it is possible to conclude that at the irradiated adsorbents the formation of electronic centers is general regularity. The radiation adsorption of oxygen is well studied on many systems and its regularities are established on numerous experiments. On an example of such oxide systems, as silicon dioxide, oxides of rare-earth elements, beryllium oxide, aluminum oxide, the zeolites we have studied a general regularity of the oxygen and hydrogen radiation adsorption, i.e. their electron-hole properties at irradiation by protons with energy 30 MeV, alpha-particles and ions of helium-3 with energy 40 and 50 MeV, gamma-rays and ultra-violet-radiation, and also neutrons from the nuclear reactor. Parallel with adsorptive properties of oxides their paramagnetic properties and thermal desorption characteristics in a wide range of temperatures were studied. The received data have allowed to find the dependence of paramagnetic centers from adsorptive centers. It was established that the adsorptive centers do not always coincide with paramagnetic ones and vise versa. It was established that the anomalous effects in a radiation adsorption at irradiation of the oxide rare-earth elements on of scandium, lanthanum, erbium and dysprosium oxides are observed. It was found out that radiation adsorption of hydrogen is absent on oxides of a lanthanum, erbium and

  7. Phenomenological Spin Transport Theory Driven by Anomalous Nernst Effect

    Science.gov (United States)

    Taniguchi, Tomohiro

    2016-07-01

    Several experimental efforts such as material investigation and structure improvement have been made recently to find a large anomalous Nernst effect in ferromagnetic metals. Here, we develop a theory of spin transport driven by the anomalous Nernst effect in a diffusive ferromagnetic/nonmagnetic multilayer. Starting from a phenomenological formula of a spin-dependent electric current, the theoretical formulas of electric voltage and spin torque generated by the anomalous Nernst effect are derived. The magnitude of the electric voltage generated from the spin current via the inverse spin Hall effect is on the order of 0.1 µV for currently available experimental parameter values. The temperature gradient necessary to switch the magnetization is quite larger than the typical experimental value. The separation of the contributions of the Seebeck and transverse spin Seebeck effects is also discussed.

  8. Anomalous Hall effect in YIG|Pt bilayers

    International Nuclear Information System (INIS)

    We measure the ordinary and the anomalous Hall effect in a set of yttrium iron garnet|platinum (YIG|Pt) bilayers via magnetization orientation dependent magnetoresistance experiments. Our data show that the presence of the ferrimagnetic insulator YIG leads to an anomalous Hall effect like voltage in Pt, which is sensitive to both Pt thickness and temperature. Interpretation of the experimental findings in terms of the spin Hall anomalous Hall effect indicates that the imaginary part of the spin mixing conductance Gi plays a crucial role in YIG|Pt bilayers. In particular, our data suggest a sign change in Gi between 10 K and 300 K. Additionally, we report a higher order Hall effect contribution, which appears in thin Pt films on YIG at low temperatures

  9. Anomalous Hall effect in YIG|Pt bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Meyer, Sibylle, E-mail: sibylle.meyer@wmi.badw.de; Schlitz, Richard [Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching (Germany); Physik-Department, Technische Universität München, 85748 Garching (Germany); Geprägs, Stephan; Opel, Matthias [Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching (Germany); Huebl, Hans; Goennenwein, Sebastian T. B. [Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching (Germany); Nanosystems Initiative Munich, 80799 München (Germany); Gross, Rudolf [Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching (Germany); Physik-Department, Technische Universität München, 85748 Garching (Germany); Nanosystems Initiative Munich, 80799 München (Germany)

    2015-03-30

    We measure the ordinary and the anomalous Hall effect in a set of yttrium iron garnet|platinum (YIG|Pt) bilayers via magnetization orientation dependent magnetoresistance experiments. Our data show that the presence of the ferrimagnetic insulator YIG leads to an anomalous Hall effect like voltage in Pt, which is sensitive to both Pt thickness and temperature. Interpretation of the experimental findings in terms of the spin Hall anomalous Hall effect indicates that the imaginary part of the spin mixing conductance G{sub i} plays a crucial role in YIG|Pt bilayers. In particular, our data suggest a sign change in G{sub i} between 10 K and 300 K. Additionally, we report a higher order Hall effect contribution, which appears in thin Pt films on YIG at low temperatures.

  10. Anomalous dispersion and band gap reduction in UO2+x and its possible coupling to the coherent polaronic quantum state

    Science.gov (United States)

    Conradson, Steven D.; Andersson, David A.; Bagus, Paul S.; Boland, Kevin S.; Bradley, Joseph A.; Byler, Darrin D.; Clark, David L.; Conradson, Dylan R.; Espinosa-Faller, Francisco J.; Lezama Pacheco, Juan S.; Martucci, Mary B.; Nordlund, Dennis; Seidler, Gerald T.; Valdez, James A.

    2016-05-01

    Hypervalent UO2, UO2(+x) formed by both addition of excess O and photoexcitation, exhibits a number of unusual or often unique properties that point to it hosting a polaronic Bose-Einstein(-Mott) condensate. A more thorough analysis of the O X-ray absorption spectra of UO2, U4O9, and U3O7 shows that the anomalous increase in the width of the spectral features assigned to predominantly U 5f and 6d final states that points to increased dispersion of these bands occurs on the low energy side corresponding to the upper edge of the gap bordered by the conduction or upper Hubbard band. The closing of the gap by 1.5 eV is more than twice as much as predicted by calculations, consistent with the dynamical polaron found by structural measurements. In addition to fostering the excitation that is the proposed mechanism for the coherence, the likely mirroring of this effect on the occupied, valence side of the gap below the Fermi level points to increased complexity of the electronic structure that could be associated with the Fermi topology of BEC-BCS crossover and two band superconductivity.

  11. Non-Fermi-liquid scattering rates and anomalous band dispersion in ferropnictides

    Science.gov (United States)

    Fink, J.; Charnukha, A.; Rienks, E. D. L.; Liu, Z. H.; Thirupathaiah, S.; Avigo, I.; Roth, F.; Jeevan, H. S.; Gegenwart, P.; Roslova, M.; Morozov, I.; Wurmehl, S.; Bovensiepen, U.; Borisenko, S.; Vojta, M.; Büchner, B.

    2015-11-01

    Angle-resolved photoemission spectroscopy is used to study the band dispersion and the quasiparticle scattering rates in two ferropnictide systems. We find the scattering rate for any given band to depend linearly on energy but to be independent of the control parameter. We demonstrate that the linear energy dependence gives rise to a weakly dispersing band with a strong mass enhancement when the band maximum crosses the chemical potential. The resulting small effective Fermi energy favors a BCS [J. Bardeen et al., Phys. Rev. 108, 1175 (1957), 10.1103/PhysRev.108.1175] -Bose-Einstein [S. N. Bose, Z. Phys. 26, 178 (1924), 10.1007/BF01327326] crossover state in the superconducting phase.

  12. Effects of chemical dispersants on oil physical properties and dispersion

    Energy Technology Data Exchange (ETDEWEB)

    Khelifa, A.; Fingas, M.; Hollebone, B.P.; Brown, C.E. [Environment Canada, Ottawa, ON (Canada). ; Pjontek, D. [Ottawa Univ., ON (Canada). Dept. of Chemical Engineering

    2007-07-01

    Laboratory and field testing have shown that the dispersion of oil spilled in water is influenced by chemical dispersants via the modification of the interfacial properties of the oil, such as oil-brine interfacial tension (IFT). This study focused on new laboratory experiments that measured the effects on the physical properties and dispersion of oil, with particular reference to the effects of chemical dispersants on IFT and oil viscosity and the subsequent effects on oil droplet formation. Experiments were conducted at 15 degrees C using Arabian Medium, Alaska North Slope and South Louisiana crude and Corexit 9500 and Corexit 9527 chemical dispersants. The dispersants were denser than the 3 oils. The effect of IFT reduction on oil dispersion was measured and showed substantial reduction in the size and enhancement of the concentration of oil droplets in the water column. It was shown that the brine-oil IFT associated with the 3 crudes reduced to less than 3.6 mN/m with the application of the chemical dispersants, even at a low dispersant-to-oil ratio (DOR) value of 1:200. The use of chemical dispersants increased the viscosity of the dispersant-oil mixture up to 40 per cent over the neat crude oil. It was shown that for each mixing condition, an optimum value of DOR exists that provides for maximal dispersant effectiveness. The IFT reaches maximum reduction at optimum DOR. It was suggested that oil spill modelling can be improved with further study of IFT reduction with DOR and variations of critical micelle concentration with the type and solubility of chemical dispersant, oil type and oil to water ratio. 13 refs., 3 tabs., 7 figs.

  13. Quantum Anomalous Hall Effect in Magnetic Insulator Heterostructure

    OpenAIRE

    Xu, Gang; Jing WANG; FELSER, CLAUDIA; Qi, Xiao-Liang; Zhang, Shou-Cheng

    2014-01-01

    Based on ab initio calculations, we predict that a monolayer of Cr-doped (Bi,Sb)2Te3 and GdI2 heterostructure is a quantum anomalous Hall insulator with a non-trivial band gap up to 38 meV. The principle behind our prediction is that the band inversion between two topologically trivial ferromagnetic insulators can result in a non-zero Chern number, which offers a better way to realize the quantum anomalous Hall state without random magnetic doping. In addition, a simple effective model is pre...

  14. Anomalous Hall Effect in a 2D Rashba Ferromagnet.

    Science.gov (United States)

    Ado, I A; Dmitriev, I A; Ostrovsky, P M; Titov, M

    2016-07-22

    Skew scattering on rare impurity configurations is shown to dominate the anomalous Hall effect in a 2D Rashba ferromagnet. The mechanism originates in scattering on rare impurity pairs separated by distances of the order of the Fermi wavelength. The corresponding theoretical description goes beyond the conventional noncrossing approximation. The mechanism provides the only contribution to the anomalous Hall conductivity in the most relevant metallic regime and strongly modifies previously obtained results for lower energies in the leading order with respect to impurity strength. PMID:27494487

  15. Higher order mode suppression in high-Q anomalous dispersion SiN microresonators for temporal dissipative Kerr soliton formation

    CERN Document Server

    Kordts, Arne; Guo, Hairun; Brasch, Victor; Kippenberg, Tobias J

    2015-01-01

    High-Q silicon nitride (SiN) microresonators enable optical Kerr frequency comb generation on a photonic chip and have recently been shown to support fully coherent combs based on temporal dissipative Kerr soliton formation. For bright soliton formation it is necessary to operate SiN waveguides in the multimode regime so as to produce anomalous group velocity dispersion. This can lead to local disturbances of the dispersion due to avoided crossings caused by coupling between different mode families, and therefore prevent the soliton formation. Here we demonstrate that a single mode "filtering" section inside high-Q resonators enables to efficiently suppress avoided crossings, while preserving high quality factors (Q~10^6). We demonstrate the approach by single soliton formation in SiN resonators with filtering section.

  16. Higher order mode suppression in high-Q anomalous dispersion SiN microresonators for temporal dissipative Kerr soliton formation.

    Science.gov (United States)

    Kordts, A; Pfeiffer, M H P; Guo, H; Brasch, V; Kippenberg, T J

    2016-02-01

    High-Q silicon nitride (SiN) microresonators enable optical Kerr frequency comb generation on a photonic chip and have recently been shown to support fully coherent combs based on temporal dissipative Kerr soliton formation. For bright soliton formation, it is necessary to operate SiN waveguides in the multimode regime in order to produce waveguide induced anomalous group velocity dispersion. However, this regime can lead to local disturbances of the dispersion due to avoided crossings caused by coupling between different mode families and, therefore, prevent the soliton formation. Here, we demonstrate that a single-mode "filtering" section inside high-Q resonators enables efficiently suppression of avoided crossings, while preserving high quality factors (Q∼10(6)). We verify the approach by demonstrating single soliton formation in SiN resonators with a filtering section. PMID:26907395

  17. High-energy pulse compressor using self-defocusing spectral broadening in anomalously dispersive media

    DEFF Research Database (Denmark)

    2015-01-01

    A method and a pulse compressor (1) for compressing an optical pulse, wherein the pulse compressor comprising a bulk quadratic nonlinear medium (2) adapted for generating a negative nonlinear phase variation on the optical pulse and having a negative group-velocity dispersion, and a dispersive unit...... subsequently be compressed by providing normal dispersion. As KDP crystals can be glued together, large apertures of the pulse compressor are possible making this method suitable for pulse compression in Joule-class lasers....

  18. Anomalous screening in two-dimensional materials with an extremum ring in the dispersion law

    OpenAIRE

    Kolomeisky, Eugene B.; Straley, Joseph P.

    2016-01-01

    A variety of two-dimensional materials possess a band structure with an energy extremal ridge along a ring in momentum space. Examples are biased bilayer graphene, and surfaces and interfaces with a Rashba spin-orbit interaction where at low doping the carriers fill an annulus. This topological feature causes an anomalous screening behavior, which we study using the Thomas-Fermi theory. Specifically, reducing the doping is predicted to enhance the linear screening response, while at zero dopi...

  19. Anomalous Doppler effects in bulk phononic crystal

    International Nuclear Information System (INIS)

    Doppler effects in simple cubic phononic crystal are studied theoretically and numerically. In addition to observing Doppler shifts from a moving source's frequencies inside the gap, we find that Doppler shifts can be multi-order, anisotropic, and the dominant order of shift depends on the band index that the source's frequency is in.

  20. Effects of Anomalous Propagation Conditions on Weather Radar Observations

    OpenAIRE

    Bech, Joan; Magaldi, Adolfo; Codina, Bernat; Lorente, Jeroni

    2012-01-01

    In this chapter our objective is to provide an overview of the effects of anomalous propagation conditions on weather radar observations, based mostly on studies performed by the authors during the last decade, summarizing results from recent publications, presentations, or unpublished material. We believe this chapter may be useful as an introductory text for graduate students, or researchers and practitioners dealing with this topic. Throughout the text a spherical symmetric atmosphere is a...

  1. Anomalous Hall Effect in Geometrically Frustrated Magnets

    Directory of Open Access Journals (Sweden)

    D. Boldrin

    2012-01-01

    space mechanism based on spin chirality that was originally applied to the pyrochlore Nd2Mo2O7 appears unsatisfactory. Recently, an orbital description based on the Aharonov-Bohm effect has been proposed and applied to both the ferromagnetic pyrochlores Nd2Mo2O7 and Pr2Ir2O7; the first of which features long-ranged magnetic order while the latter is a chiral spin liquid. Two further examples of geometrically frustrated conducting magnets are presented in this paper—the kagome-like Fe3Sn2 and the triangular PdCrO2. These possess very different electronic structures to the 3-dimensional heavy-metal pyrochlores and provide new opportunities to explore the different origins of the AHE. This paper summarises the experimental findings in these materials in an attempt to unite the conflicting theoretical arguments.

  2. Effects of surface and interface scattering on anomalous Hall effect in Co/Pd multilayers

    KAUST Repository

    Guo, Z. B.

    2012-09-27

    In this paper, we report the results of surface and interface scattering on anomalous Hall effect in Co/Pd multilayers with perpendicular magnetic anisotropy. The surface scattering effect has been extracted from the total anomalous Hall effect. By scaling surface scattering contribution with ρAHs∼ργss, the exponent γ has been found to decrease with the increase of surface scattering resistivity, which could account for the thickness-dependent anomalous Hall effect. Interface diffusion induced by rapid thermal annealing modifies not only the magnetization and longitudinal resistivity but also the anomalous Hall effect; a large exponent γ ∼ 5.7 has been attributed to interface scattering-dominated anomalous Hall effect.

  3. Quantum anomalous Hall effect in magnetic topological insulators

    OpenAIRE

    Jing WANG; Lian, Biao; Zhang, Shou-Cheng

    2014-01-01

    The search for topologically non-trivial states of matter has become an important goal for condensed matter physics. Here, we give a theoretical introduction to the quantum anomalous Hall (QAH) effect based on magnetic topological insulators in two-dimension (2D) and three-dimension (3D). In 2D topological insulators, magnetic order breaks the symmetry between the counter-propagating helical edge states, and as a result, the quantum spin Hall effect can evolve into the QAH effect. In 3D, magn...

  4. Quantized Anomalous Hall Effect in Magnetic Topological Insulators

    Institute of Scientific and Technical Information of China (English)

    YU Rui

    2011-01-01

    The Hall effect, the anomalous Hall effect (AHE) and the spin Hall effect are thndamental transport processes in solids arising from the Lorentz force and the spin-orbit coupling respectively. The AHE, in which a voltage transverse to the electric current appears even in the absence of an external magnetic field, was first detected in ferromagnetic (FM) metals in 1881 and later found to arise from the spin-orbit coupling (SOC) between the current and magnetic moments.

  5. Filamentation of a phase-modulated pulse under conditions of normal, anomalous and zero group velocity dispersion

    Energy Technology Data Exchange (ETDEWEB)

    Chekalin, S V; Kompanets, V O [Institute of Spectroscopy, Russian Academy of Sciences, Troitsk, Moscow (Russian Federation); Smetanina, E O; Spirkov, A I; Kandidov, V P [Department of Physics, M.V. Lomonosov Moscow State University (Russian Federation)

    2014-06-30

    We have investigated experimentally and numerically the influence of the initial temporal phase modulation of a pulse on the spatiotemporal intensity distribution and the frequency-angular spectrum of femtosecond laser pulses with self-channelling in a condensed medium. We have detected a decrease in the intensity of divergent anti-Stokes frequency components during filamentation of radiation under conditions of normal group-velocity dispersion (GVD) and strong phase modulation. In the zero-GVD regime under conditions of the phase modulation of radiation, the spatiotemporal transformation of the pulse is similar to that in the normal-GVD regime, which leads to a qualitative change in the supercontinuum spectrum. In the anomalous-GVD regime, a sequence of 'light bullets' is formed in the filament for both a phase-modulated and a transform-limited pulse. (extreme light fields and their applications)

  6. Anomalous Propagation of Electromagnetic Waves in Anisotropic Media with a Unique Dispersion Relation

    Institute of Scientific and Technical Information of China (English)

    SHU Wei-Xing; LUO Hai-Lu; LI Fei; REN Zhong-Zhou

    2006-01-01

    @@ We investigate the propagation of electromagnetic waves at the interface between an isotropic material and the anisotropic medium with a unique dispersion relation. We show that the refraction behaviour of E-polarized waves is opposite to that of H-polarized waves, though the dispersion relations for E- and H-polarized waves are the same. It is found that waves exhibit different propagation properties in anisotropic media with different sign combinations of the permittivity and permeability tensors. Some interesting properties of propagation are also found in the special anisotropic media, leading to potential applications.

  7. Anomalous Hall Effect in a Feromagnetic Rare-Earth Cobalite

    Science.gov (United States)

    Samoilov, A. V.; Yeh, N. C.; Vasquez, R. P.

    1996-01-01

    Rare-Earth manganites and cobalites with the perovskite structure have been a subject of great recent interest because their electrical resistance changes significantly when a magnetic field is applied...we have studied the Hall effect in thin film La(sub 0.5)Ca(sub 0.5)CoO(sub 3) material and have obtained convincing evidence fo the so called anomalous Hall effect, typical for magnetic metals...Our results suggest that near the ferromagnetic ordering temperature, the dominant electron scattering mechanism is the spin fluctuation.

  8. Structure determination by multiple-wavelength anomalous dispersion (MAD) at the Pr LIII edge

    International Nuclear Information System (INIS)

    A successful MAD experiment has been conducted at the Pr LIII edge on HZB beamline BL14.2. The use of longer X-ray wavelengths in macromolecular crystallography has grown significantly over the past few years. The main reason for this increased use of longer wavelengths has been to utilize the anomalous signal from sulfur, providing a means for the experimental phasing of native proteins. Here, another possible application of longer X-ray wavelengths is presented: MAD at the LIII edges of various lanthanide compounds. A first experiment at the LIII edge of Pr was conducted on HZB MX beamline BL14.2 and resulted in the successful structure determination of the C-terminal domain of a spliceosomal protein. This experiment demonstrates that LIII edges of lanthanides constitute potentially attractive targets for long-wavelength MAD experiments

  9. Atomic Rayleigh scattering cross-sections and the associated anomalous dispersion in the X-ray regions

    International Nuclear Information System (INIS)

    Elastic scattering cross-sections for Pd, Ag, Cd, In, Sn, Sb, Pt, Au and Pb are measured at an angle of 90 circle in the X-ray region 5.41≤E≤8.04 keV. These energies fall between the high-energy side of the L- and M-shell absorption edges of the atoms considered. The present atomic region is significant for solid X-rays to assess the contribution of resonance and solid-state environmental effects. Also it is the anomalous scattering region for many of the atoms of the periodic table. Experimental results are compared with theoretical calculations based on form factor formalisms including the anomalous corrections and available recent S-matrix values. Based on the experimental evidence, the present results indicate the influence of solid-state environmental effects, the importance of anomalous corrections nearer to absorption edges, the correctness of revised high-energy limit values, the superiority of S-matrix predictions over form factor values on measured elastic scattering cross-sections in the X-ray regime and also show the resonance behavior around K,L and M absorption edges. (orig.)

  10. Quantized Anomalous Hall Effect in Magnetic Topological Insulators

    Institute of Scientific and Technical Information of China (English)

    YU Rui

    2011-01-01

    @@ The Hall effect, the anomalous Hall effect (AHE) and the spin Hall effect are fundamental transport processes in solids arising from the Lorentz force and the spin-orbit coupling respectively.The AHE, in which a voltage transverse to the electric current appears even in the absence of an external magnetic field, was first detected in ferromagnetic (FM) metals in 1881 and later found to arise from the spin-orbit coupling (SOC) between the current and magnetic moments.Recent progress on the mechanism of AHE has established a link between the AHE and the topological nature of the Hall current by adopting the Berry-phase concepts in close analogy to the intrinsic spin Hall effect.Given the experimental discovery of the quantum Hall and the quantum spin Hall effects, it is natural to ask whether the AHE can also be quantized.In a quantized anomalous Hall (QAH) insulator, spontaneous magnetic moments and spin-orbit coupling combine to give rise to a topologically non-trivial electronic structure, leading to the quantized Hall effect without any external magnetic field.

  11. Urbanization effects on natural radiation in anomalous areas

    International Nuclear Information System (INIS)

    The urbanization effects and their possible causes on the environmental gamma radiation levels, in an anomalous area, were studied. The field work was accomplished in Guarapari, located in the seacoast of the Brazilian state of Espirito Santo, which is rich in monazite sands, with thorium and uranium contents. The results show clearly that there was a reduction in the levels of external exposition in the streets and squares of Guarapari. It was ascertained that the reduction was due to the materials used in the urbanization. (L.C.J.A.)

  12. Quantum anomalous Hall effect in topological insulator memory

    Energy Technology Data Exchange (ETDEWEB)

    Jalil, Mansoor B. A., E-mail: elembaj@nus.edu.sg [Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, Singapore 117576 (Singapore); Data Storage Institute, Agency for Science, Technology and Research A*STAR, DSI Building, 5 Engineering Drive 1, Singapore, Singapore 117608 (Singapore); Tan, S. G. [Data Storage Institute, Agency for Science, Technology and Research A*STAR, DSI Building, 5 Engineering Drive 1, Singapore, Singapore 117608 (Singapore); Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, Singapore 117576 (Singapore); Siu, Z. B. [Data Storage Institute, Agency for Science, Technology and Research A*STAR, DSI Building, 5 Engineering Drive 1, Singapore, Singapore 117608 (Singapore); NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore (Singapore)

    2015-05-07

    We theoretically investigate the quantum anomalous Hall effect (QAHE) in a magnetically coupled three-dimensional-topological insulator (3D-TI) system. We apply the generalized spin-orbit coupling Hamiltonian to obtain the Hall conductivity σ{sup xy} of the system. The underlying topology of the QAHE phenomenon is then analyzed to show the quantization of σ{sup xy} and its relation to the Berry phase of the system. Finally, we analyze the feasibility of utilizing σ{sup xy} as a memory read-out in a 3D-TI based memory at finite temperatures, with comparison to known magnetically doped 3D-TIs.

  13. Quantum anomalous Hall effect in topological insulator memory

    International Nuclear Information System (INIS)

    We theoretically investigate the quantum anomalous Hall effect (QAHE) in a magnetically coupled three-dimensional-topological insulator (3D-TI) system. We apply the generalized spin-orbit coupling Hamiltonian to obtain the Hall conductivity σxy of the system. The underlying topology of the QAHE phenomenon is then analyzed to show the quantization of σxy and its relation to the Berry phase of the system. Finally, we analyze the feasibility of utilizing σxy as a memory read-out in a 3D-TI based memory at finite temperatures, with comparison to known magnetically doped 3D-TIs

  14. Anomalous behavior of the structural relaxation dispersion function of a carborane-containing siloxane

    Energy Technology Data Exchange (ETDEWEB)

    Pawlus, Sebastian; Paluch, Marian; Ziolo, Jerzy [Institute of Physics, University of Silesia, Uniwersytecka 4, Katowice 40-007 (Poland); Kolel-Veetil, Manoj K [Chemistry Division, Code 6127, Naval Research Laboratory, Washington, DC 20375-5342 (United States)

    2010-10-20

    Broadband dielectric spectroscopic investigations of a vinyl-terminated carboranylenesiloxane, VCS, were performed at ambient and elevated pressures. At a constant structural relaxation time, results show that the structural relaxation dispersion function of VCS narrows with both increasing pressure and temperature. This narrowing is substantial in the case of pressurization and, consequently, the breakdown of the temperature-pressure superposition rule is observed. The interpretation of this breakdown is presented.

  15. Anomalous Hall effect in Fe/Au multilayers

    KAUST Repository

    Zhang, Q.

    2016-07-22

    To understand the interfacial scattering effect on the anomalous Hall effect (AHE), we prepared multilayers of (Fe(36/n)nm/Au(12/n)nm)n using an e-beam evaporator. This structure design allowed us to investigate the effect of interfacial scattering on the AHE, while keeping the samples\\' thickness and composition unchanged. We measured the (magneto)transport properties of the samples in a wide temperature range (10–310 K) with magnetic fields up to 50 kOe. We found that the scaling between the anomalous Hall resistivity (ρAHE) and longitudinal resistivity (ρxx) can be roughly described by ρAHE∼ργxx with γ=2.65±0.10 and 1.90 ± 0.04 for samples from n=1 to n=4 and samples from n=4 to n=12, respectively. Our quantitative analysis results showed that the interfacial scattering suppresses the contribution of the intrinsic mechanism and gives rise to a side-jump contribution.

  16. Nonlinear dynamics induced anomalous Hall effect in topological insulators

    Science.gov (United States)

    Wang, Guanglei; Xu, Hongya; Lai, Ying-Cheng

    2016-01-01

    We uncover an alternative mechanism for anomalous Hall effect. In particular, we investigate the magnetisation dynamics of an insulating ferromagnet (FM) deposited on the surface of a three-dimensional topological insulator (TI), subject to an external voltage. The spin-polarised current on the TI surface induces a spin-transfer torque on the magnetisation of the top FM while its dynamics can change the transmission probability of the surface electrons through the exchange coupling and hence the current. We find a host of nonlinear dynamical behaviors including multistability, chaos, and phase synchronisation. Strikingly, a dynamics mediated Hall-like current can arise, which exhibits a nontrivial dependence on the channel conductance. We develop a physical understanding of the mechanism that leads to the anomalous Hall effect. The nonlinear dynamical origin of the effect stipulates that a rich variety of final states exist, implying that the associated Hall current can be controlled to yield desirable behaviors. The phenomenon can find applications in Dirac-material based spintronics.

  17. Correlations and anomalous transport effects related to stochastic instability

    International Nuclear Information System (INIS)

    In this paper, we analyse turbulent transport in the framework of the correlation approach to obtain the effective diffusion coefficient and characteristic increment in the scaling form. Such factors as anisotropy, seed diffusion mechanisms and reconstruction of flow topology significantly have an impact on the effective diffusivity. We consider the different aspects of stochastic instability such as the decorrelation mechanism to estimate characteristic correlation times and correlation scales in the framework of the scaling approach. The topics to be discussed include the Rechester-Rosenbluth correlation scalings, percolation transport in time dependent flows, anisotropic MHD spectra and a multi-scale approach to the analysis of anomalous transport. To treat long-range correlation effects, the percolation renormalization is analysed in time-dependent regimes. In the framework of the multiscale approach, a scaling for an increment of the stochastic instability in two-dimensional random flow is suggested

  18. Correlations and anomalous transport effects related to stochastic instability

    Energy Technology Data Exchange (ETDEWEB)

    Bakunin, O G [Department of Physics and Astronomy, University of Kansas, Malott Hall, 1251 Wescoe Hall Drive, Lawrence, KS 66044 (United States); Nuclear Fusion Institute, RRC ' Kurchatov Institute' , pl. Kurchatova 1, Moscow, 123182 (Russian Federation); FOM Instituut voor Plasmafysica ' Rijnhuizen' , Associate Euroatom-FOM, 3430 BE Nieuwegein (Netherlands)

    2005-11-15

    In this paper, we analyse turbulent transport in the framework of the correlation approach to obtain the effective diffusion coefficient and characteristic increment in the scaling form. Such factors as anisotropy, seed diffusion mechanisms and reconstruction of flow topology significantly have an impact on the effective diffusivity. We consider the different aspects of stochastic instability such as the decorrelation mechanism to estimate characteristic correlation times and correlation scales in the framework of the scaling approach. The topics to be discussed include the Rechester-Rosenbluth correlation scalings, percolation transport in time dependent flows, anisotropic MHD spectra and a multi-scale approach to the analysis of anomalous transport. To treat long-range correlation effects, the percolation renormalization is analysed in time-dependent regimes. In the framework of the multiscale approach, a scaling for an increment of the stochastic instability in two-dimensional random flow is suggested.

  19. Anomalous Skin Effect for Anisotropic Electron Velocity Distribution Function

    Energy Technology Data Exchange (ETDEWEB)

    Igor Kaganovich; Edward Startsev; Gennady Shvets

    2004-02-19

    The anomalous skin effect in a plasma with a highly anisotropic electron velocity distribution function (EVDF) is very different from skin effect in a plasma with the isotropic EVDF. An analytical solution was derived for the electric field penetrated into plasma with the EVDF described as a Maxwellian with two temperatures Tx >> Tz, where x is the direction along the plasma boundary and z is the direction perpendicular to the plasma boundary. The skin layer was found to consist of two distinctive regions of width of order nTx/w and nTz/w, where nTx,z/w = (Tx,z/m)1/2 is the thermal electron velocity and w is the incident wave frequency.

  20. Precise quantization of anomalous Hall effect near zero magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Bestwick, A. J. [Stanford Univ., Stanford, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States); Fox, E. J. [Stanford Univ., Stanford, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States); Kou, Xufeng [Univ. of California, Los Angeles, CA (United States); Pan, Lei [Univ. of California, Los Angeles, CA (United States); Wang, Kang L. [Univ. of California, Los Angeles, CA (United States); Goldhaber-Gordon, D. [Stanford Univ., Stanford, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)

    2015-05-04

    In this study, we report a nearly ideal quantum anomalous Hall effect in a three-dimensional topological insulator thin film with ferromagnetic doping. Near zero applied magnetic field we measure exact quantization in the Hall resistance to within a part per 10,000 and a longitudinal resistivity under 1 Ω per square, with chiral edge transport explicitly confirmed by nonlocal measurements. Deviations from this behavior are found to be caused by thermally activated carriers, as indicated by an Arrhenius law temperature dependence. Using the deviations as a thermometer, we demonstrate an unexpected magnetocaloric effect and use it to reach near-perfect quantization by cooling the sample below the dilution refrigerator base temperature in a process approximating adiabatic demagnetization refrigeration.

  1. Anomalous transport effects in magnetically-confined plasma columns

    International Nuclear Information System (INIS)

    The evolution of density structure in a magnetized plasma column is analyzed accounting for anomalous diffusion due to the lower hybrid drift instability. The plasma column is found to be divided into regions of classical, anomalous, and intermediate diffusivity. The bulk behavior, described in terms of radial confinement time, depends most sensitively upon the particle line density (ion/cm). For broad plasmas (large line density), the transport is characteristic of classical diffusion, and for slender plasmas (small line density) the transport is characteristic of anomalous diffusion. For intermediate line densities, the transport undertakes a rapid transition from classical to anomalous. Correlations between the theoretical results and past experiments are described

  2. Dispersant effectiveness in a simulated shallow embayment

    Energy Technology Data Exchange (ETDEWEB)

    Page, C.; Bonner, J.; Fuller, C. [Texas A and M Univ., Corpus Christi, TX (United States); Sterling, M. [Texas A and M Univ., College Station, TX (United States)

    2002-07-01

    An experiment was conducted in a wave tank at Corpus Christi, Texas to test the effectiveness of a dispersant in treating an oil spill. Dispersants can be used as a chemical countermeasure to disperse accidentally spilled oil into the water column. In the United States, however, dispersants are not pre-approved for near-shore applications. Therefore, if an oil spill occurs in shallow marine waters response teams cannot use dispersants right away and the chances for the oil to move onto shore is increased. The use of dispersants in coastal marine ecosystems is approached with caution because the first generation of dispersants were highly toxic. New formulations, however, are considered to be more effective and substantially less toxic. The tank in this study simulated a shallow embayment with wave conditions similar to those in Corpus Christi Bay. A known volume of weathered Arabian medium crude oil was intentionally spilled onto the water surface and the dispersant Corexit 9500 manufactured by Nalco/Exxon was applied in aerosol form at a dispersion to oil ratio of 1:10. A mass balance on the oil was performed to quantify the effectiveness of the dispersant. The compartments for oil accumulation were the water column, the water surface and the tank walls. Gas chromatography-mass spectrometry was used to analyze the samples. After 4 hours, more than two-thirds of the oil was found in the water column, suggesting the dispersant was effective in dispersing the crude oil under wave energy conditions. After 24 hours, much of the oil had resurfaced. A lab scale version of the same experiment showed similar results. 15 refs., 6 figs.

  3. Dispersant effectiveness in a simulated shallow embayment

    International Nuclear Information System (INIS)

    An experiment was conducted in a wave tank at Corpus Christi, Texas to test the effectiveness of a dispersant in treating an oil spill. Dispersants can be used as a chemical countermeasure to disperse accidentally spilled oil into the water column. In the United States, however, dispersants are not pre-approved for near-shore applications. Therefore, if an oil spill occurs in shallow marine waters response teams cannot use dispersants right away and the chances for the oil to move onto shore is increased. The use of dispersants in coastal marine ecosystems is approached with caution because the first generation of dispersants were highly toxic. New formulations, however, are considered to be more effective and substantially less toxic. The tank in this study simulated a shallow embayment with wave conditions similar to those in Corpus Christi Bay. A known volume of weathered Arabian medium crude oil was intentionally spilled onto the water surface and the dispersant Corexit 9500 manufactured by Nalco/Exxon was applied in aerosol form at a dispersion to oil ratio of 1:10. A mass balance on the oil was performed to quantify the effectiveness of the dispersant. The compartments for oil accumulation were the water column, the water surface and the tank walls. Gas chromatography-mass spectrometry was used to analyze the samples. After 4 hours, more than two-thirds of the oil was found in the water column, suggesting the dispersant was effective in dispersing the crude oil under wave energy conditions. After 24 hours, much of the oil had resurfaced. A lab scale version of the same experiment showed similar results. 15 refs., 6 figs

  4. Dispersant effectiveness: Studies into the causes of effectiveness variations

    International Nuclear Information System (INIS)

    Effectiveness, a key issue of using dispersants, is affected by many interrelated factors. The principal factors involved are the oil composition, dispersant formulation, sea surface turbulence and dispersant quantity. Oil composition is a very strong determinant. Current dispersant formulation effectiveness correlates strongly with the amount of saturate component in the oil. The other components of the oil, the asphaltenes, resins or polars and aromatic fractions show a negative correlation with the dispersant effectiveness. Viscosity is also a predictor of dispersant effectiveness and may have an effect because it is in turn determined by oil composition. Dispersant composition is significant and interacts with oil composition. Dispersants show high effectiveness at HLB values near 10. Sea turbulence strongly affects dispersant effectiveness.Effectiveness rises with increasing turbulence to a maximum value. Effectiveness for current commercial dispersants is gaussian around a peak salinity value. Peak effectiveness is achieved at very high dispersant quantities--at a ratio of 1:5, dispersant-to-oil volume. Dispersant effectiveness for those oils tested and under the conditions measured, is approximately logarithmic with dispersant quantity and will reach about 50% of its peak value at a dispersant to oil ratio of about 1:20 and near zero at a ratio of about 1:50

  5. Anomalous Nernst Effect of Perpendicularly Magnetic Anisotropy TbFeCo Thin Films

    Science.gov (United States)

    Ando, Ryo; Komine, Takashi; Hasegawa, Yasuhiro

    2016-07-01

    In this study, we investigated anomalous Nernst effect (ANE) of perpendicularly magnetized TbFeCo thin films with various Tb content, and especially studied the relation between ANE and anomalous Hall effect. As a result, the hysteresis of anomalous Nernst coefficient showed the same behavior as that of anomalous Hall resistivity, and the sign of anomalous Nernst coefficient was consistent with that of anomalous Hall voltage in any Tb content, whereas the Seebeck coefficient and the resistivity were almost constant even if the applied magnetic field was varied. Taking into account of thermoelectric coefficient tensor, it was revealed that the off-diagonal thermopower corresponding to the ANE in TbFeCo thin films is the product of Hall angle and Seebeck coefficient.

  6. Effectiveness of dispersants on thick oil slicks

    International Nuclear Information System (INIS)

    Experiments were conducted to determine the relationship between dispersant effectiveness and oil slick thickness, and thereby determine the optimum time for applying dispersant onto spilled oil at sea. Tests were completed at a lab-scale level by varying the three parameters of oil type, dispersant application, and oil thickness. The tests were intended to be comparative only. The primary oils used were Alberta sweet mix blend and Hibernia B-27 crude. The dispersant, Corexit 9527, was applied either premixed with the oil, dropwise in one application, or dropwise in multiple applications to simulate a multi-hit aircraft operation. The apparatus used in the experiment was an oscillating hoop tank, with oil-containing rings used to obtain and maintain uniform slick thickness. The results indicate that the effectiveness potential of a chemical dispersant does not decrease as slick thickness increases. In fact, results of the tests involving Hibernia oil suggest that oils that tend to herd easily would be treated more effectively if dispersant were applied when the oil was relatively thick (1 mm or greater) to avoid herding problems. The oil slicks premixed with dispersant did not disperse well in the thick oil tests, not because of dispersant-oil interaction problems but because of reduced mixing energy. 6 refs., 4 figs., 1 tab

  7. Quantum anomalous Hall effect in atomic crystal layers from in-plane magnetization

    Science.gov (United States)

    Ren, Yafei; Zeng, Junjie; Deng, Xinzhou; Yang, Fei; Pan, Hui; Qiao, Zhenhua

    2016-08-01

    We theoretically demonstrate that with in-plane magnetization, the quantum anomalous Hall effect (QAHE) can be realized in two-dimensional atomic crystal layers with preserved inversion symmetry but broken out-of-plane mirror reflection symmetry. By taking the honeycomb lattice system as an example, we find that the low-buckled structure satisfying the symmetry criteria is crucial to induce QAHE. The topologically nontrivial bulk gap carrying a Chern number of C =±1 opens in the vicinity of the saddle points M , where the band dispersion exhibits strong anisotropy. We further show that the QAHE with electrically tunable Chern number can be achieved in Bernal-stacked multilayer systems, and the applied interlayer potential differences can dramatically decrease the critical magnetization to make the QAHE experimentally feasible.

  8. Employment Effects of Spatial Dispersal of Refugees

    DEFF Research Database (Denmark)

    Damm, Anna Piil; Rosholm, Michael

    We argue that spatial dispersal influences labour market assimilation of refugees through two mechanisms: first, the local job offer arrival rate and, second, place utility. Our partial search model with simultaneous job and residential location search predicts that the reservation wage for local...... evaluating the employment effects of the Danish spatial dispersal policy carried out 1986-1998....

  9. Quantum anomalous Hall effect in magnetic topological insulators

    Science.gov (United States)

    Wang, Jing; Lian, Biao; Zhang, Shou-Cheng

    2015-12-01

    The search for topologically non-trivial states of matter has become an important goal for condensed matter physics. Here, we give a theoretical introduction to the quantum anomalous Hall (QAH) effect based on magnetic topological insulators in two-dimensions (2D) and three-dimensions (3D). In 2D topological insulators, magnetic order breaks the symmetry between the counter-propagating helical edge states, and as a result, the quantum spin Hall effect can evolve into the QAH effect. In 3D, magnetic order opens up a gap for the topological surface states, and chiral edge state has been predicted to exist on the magnetic domain walls. We present the phase diagram in thin films of a magnetic topological insulator and review the basic mechanism of ferromagnetic order in magnetically doped topological insulators. We also review the recent experimental observation of the QAH effect. We discuss more recent theoretical work on the coexistence of the helical and chiral edge states, multi-channel chiral edge states, the theory of the plateau transition, and the thickness dependence in the QAH effect.

  10. Origin of anomalous inverse notch effect in bulk metallic glasses

    Science.gov (United States)

    Pan, J.; Zhou, H. F.; Wang, Z. T.; Li, Y.; Gao, H. J.

    2015-11-01

    Understanding notch-related failure is crucial for the design of reliable engineering structures. However, substantial controversies exist in the literature on the notch effect in bulk metallic glasses (BMGs), and the underlying physical mechanism responsible for the apparent confusion is still poorly understood. Here we investigate the physical origin of an inverse notch effect in a Zr-based metallic glass, where the tensile strength of the material is dramatically enhanced, rather than decreased (as expected from the stress concentration point of view), by introduction of a notch. Our experiments and molecular dynamics simulations show that the seemingly anomalous inverse notch effect is in fact caused by a transition in failure mechanism from shear banding at the notch tip to cavitation and void coalescence. Based on our theoretical analysis, the transition occurs as the stress triaxiality in the notched sample exceeds a material-dependent threshold value. Our results fill the gap in the current understanding of BMG strength and failure mechanism by resolving the conflicts on notch effects and may inspire re-interpretation of previous reports on BMG fracture toughness where pre-existing notches were routinely adopted.

  11. Effect of anomalous resistivity on the dynamics of plasma switching

    International Nuclear Information System (INIS)

    Some of the conditions for electron MHD are recollected, and it is shown how this leads to anomalous resistivity which may play an important role in the dynamics of POS. It has been shown that not only the order of value of the resistance of the plasma-filled diode but rather basic scalings have to be changed in the regime of essential anomalous resistivity. (author). 11 refs

  12. Transverse Fresnel-Fizeau drag effects in strongly dispersive media

    International Nuclear Information System (INIS)

    A light beam normally incident upon an uniformly moving dielectric medium is, in general, subject to bendings due to a transverse Fresnel-Fizeau light drag effect. In most familiar dielectrics, the magnitude of this bending effect is very small and hard to detect. Yet, the effect can be dramatically enhanced in strongly dispersive media where slow group velocities in the m/s range have been recently observed taking advantage of the electromagnetically induced transparency effect. In addition to the usual downstream drag that takes place for positive group velocities, we discuss a significant anomalous upstream drag which is expected to occur for negative group velocities. Furthermore, for sufficiently fast speeds of the medium, higher-order dispersion terms are found to play an important role and to be responsible for light propagation along curved paths or the restoration of the time and space coherence of an incident noisy beam. The physics underlying this class of slow-light effects is thoroughly discussed

  13. Review of monitoring protocols for dispersant effectiveness

    International Nuclear Information System (INIS)

    Dispersant applications to an oil spill were monitored to determine their effectiveness. Current protocols consist of some visual criteria or a surface monitoring program using in-situ fluorometers to gauge the relative effectiveness of dispersant application. However, this study shows that there are many false positives and false negatives with these monitoring techniques. The problem can be addressed to some degree, by paying attention to the science and technology. The current published methods such as SMART and the SERVS protocols do not necessarily assure that effectiveness is accurately gauged. It was also argued that current protocols are very limited by basic physical and chemical problems, and therefore can only supply estimates as to the effectiveness of dispersant application. It was recommended that a screening test of the dispersant effectiveness be conducted before any test application of dispersants. The test should indicate a dispersion of approximately one-half of the oil. It was also suggested that since visual methods are the the main monitoring method, more work is needed to produce visual monitoring guidelines and visual aids. It was also suggested that monitoring of oil concentrations in the water column would provide valuable scientific information. 52 refs., 2 tabs., 5 figs

  14. Spatiotemporal instability in nonlinear dispersive media in the presence of space-time focusing effect

    Institute of Scientific and Technical Information of China (English)

    文双春; 范滇元

    2002-01-01

    Spatiotemporal instability in nonlinear dispersive media is investigated on the basis of the nonlinear envelope equation. A general expression for instability gain which includes the effects of space-time focusing, arbitrarily higher-order dispersions and self-steepening is obtained. It is found that, for both normal and anomalous group-velocity dispersions, space-time focusing may lead to the appearance of new instability regions and influence the original instability gain spectra mainly by shrinking their regions. The region of the original instability gain spectrum shrinks much more in normal dispersion case than in anomalous one. In the former case, space-time focusing completely suppresses the growing of higher frequency components. In addition, we find that all the oddth-order dispersions contribute none to instability, while all the eventh-order dispersions influence instability region and do not influence the maximum instability gain, therein the fourth-order dispersion plays the same role as space-time focusing in spatiotemporal instability. The main role played by self-steepening in spatiotemporal instability is that it reduces the instability gain and exerts much more significant influence on the new instability regions resulting from space-time focusing.

  15. Field-effect modulation of anomalous Hall effect in diluted ferromagnetic topological insulator epitaxial films

    Science.gov (United States)

    Chang, CuiZu; Liu, MinHao; Zhang, ZuoCheng; Wang, YaYu; He, Ke; Xue, QiKun

    2016-03-01

    High quality chromium (Cr) doped three-dimensional topological insulator (TI) Sb2Te3 films are grown via molecular beam epitaxy on heat-treated insulating SrTiO3 (111) substrates. We report that the Dirac surface states are insensitive to Cr doping, and a perfect robust long-range ferromagnetic order is unveiled in epitaxial Sb2- x Cr x Te3 films. The anomalous Hall effect is modulated by applying a bottom gate, contrary to the ferromagnetism in conventional diluted magnetic semiconductors (DMSs), here the coercivity field is not significantly changed with decreasing carrier density. Carrier-independent ferromagnetism heralds Sb2- x Cr x Te3 films as the base candidate TI material to realize the quantum anomalous Hall (QAH) effect. These results also indicate the potential of controlling anomalous Hall voltage in future TI-based magneto-electronics and spintronics.

  16. Generation of high energy square-wave pulses in all anomalous dispersion Er:Yb passive mode locked fiber ring laser.

    Science.gov (United States)

    Semaan, Georges; Ben Braham, Fatma; Salhi, Mohamed; Meng, Yichang; Bahloul, Faouzi; Sanchez, François

    2016-04-18

    We have experimentally demonstrated square pulses emission from a co-doped Er:Yb double-clad fiber laser operating in anomalous dispersion DSR regime using the nonlinear polarization evolution technique. Stable mode-locked pulses have a repetition rate of 373 kHz with 2.27 µJ energy per pulse under a pumping power of 30 W in cavity. With the increase of pump power, both the duration and the energy of the output square pulses broaden. The experimental results demonstrate that the passively mode-locked fiber laser operating in the anomalous regime can also realize a high-energy pulse, which is different from the conventional low-energy soliton pulse. PMID:27137277

  17. Carrier-independent ferromagnetism and giant anomalous Hall effect in magnetic topological insulator

    OpenAIRE

    Chang, Cui-Zu; Zhang, Jin-song; Liu, Min-Hao; Zhang, Zuo-Cheng; Feng, Xiao; Li, Kang; Wang, Li-Li; Chen, Xi; Dai, Xi; Fang, Zhong; Qi, Xiao-Liang; Zhang, Shou-Cheng; Wang, Yayu; He, Ke; Ma, Xu-Cun

    2011-01-01

    Breaking the time-reversal symmetry of a topological insulator (TI) by ferromagnetism can induce exotic magnetoelectric phenomena such as quantized anomalous Hall (QAH) effect. Experimental observation of QAH effect in a magnetically doped TI requires ferromagnetism not relying on the charge carriers. We have realized the ferromagnetism independent of both polarity and density of carriers in Cr-doped BixSb2-xTe3 thin films grown by molecular beam epitaxy. Meanwhile, the anomalous Hall effect ...

  18. Localization correction to the anomalous Hall effect in amorphous CoFeB thin films

    Institute of Scientific and Technical Information of China (English)

    丁进军; 吴少兵; 杨晓非; 朱涛

    2015-01-01

    An obvious weak localization correction to anomalous Hall conductance (AHC) in very thin CoFeB film is reported. We find that both the weak localization to AHC and the mechanism of anomalous Hall effect are related to the CoFeB thickness. When the film is thicker than 3 nm, the side jump mechanism dominates and the weak localization to AHC vanishes. For very thin CoFeB films, both the side jump and skew scattering mechanisms contribute to the anomalous Hall effect, and the weak localization correction to AHC is observed.

  19. Magnetic Topological Insulators and Quantum Anomalous Hall Effect

    Science.gov (United States)

    Kou, Xufeng

    The engineering of topological surface states is a key to realize applicable devices based on topological insulators (TIs). Among various proposals, introducing magnetic impurities into TIs has been proven to be an effective way to open a surface gap and integrate additional ferromagnetism with the original topological order. In this Dissertation, we study both the intrinsic electrical and magnetic properties of the magnetic TI thin films grown by molecular beam epitaxy. By doping transition element Cr into the host tetradymite-type V-VI semiconductors, we achieve robust ferromagnetic order with a strong perpendicular magnetic anisotropy. With additional top-gating capability, we realize the electric-field-controlled ferromagnetism in the magnetic TI systems, and demonstrate such magneto-electric effects can be effectively manipulated, depending on the interplays between the band topology, magnetic exchange coupling, and structural engineering. Most significantly, we report the observation of quantum anomalous Hall effect (QAHE) in the Cr-doped (BiSb)2Te3 samples where dissipationless chiral edge conduction is realized in the macroscopic millimeter-size devices without the presence of any external magnetic field, and the stability of the quantized Hall conductance of e2/h is well-maintained as the film thickness varies across the 2D hybridization limit. With additional quantum confinement, we discover the metal-to-insulator switching between two opposite QAHE states, and reveal the universal QAHE phase diagram in the thin magnetic TI samples. In addition to the uniform magnetic TIs, we further investigate the TI/Cr-doped TI bilayer structures prepared by the modulation-doped growth method. By controlling the magnetic interaction profile, we observe the Dirac hole-mediated ferromagnetism and develop an effective way to manipulate its strength. Besides, the giant spin-orbit torque in such magnetic TI-based heterostructures enables us to demonstrate the current

  20. Thickness Dependence of the Quantum Anomalous Hall Effect in Magnetic Topological Insulator Films.

    Science.gov (United States)

    Feng, Xiao; Feng, Yang; Wang, Jing; Ou, Yunbo; Hao, Zhenqi; Liu, Chang; Zhang, Zuocheng; Zhang, Liguo; Lin, Chaojing; Liao, Jian; Li, Yongqing; Wang, Li-Li; Ji, Shuai-Hua; Chen, Xi; Ma, Xucun; Zhang, Shou-Cheng; Wang, Yayu; He, Ke; Xue, Qi-Kun

    2016-08-01

    The evolution of the quantum anomalous Hall effect with the thickness of Cr-doped (Bi,Sb)2 Te3 magnetic topological insulator films is studied, revealing how the effect is caused by the interplay of the surface states, band-bending, and ferromagnetic exchange energy. Homogeneity in ferromagnetism is found to be the key to high-temperature quantum anomalous Hall material. PMID:27166762

  1. Anomalous effects due to the inertial anti-gravitational potential of the sun

    OpenAIRE

    Khokhlov, D. L.

    2007-01-01

    It is introduced inertial anti-gravitational potential into the theory of gravity to stop gravitational collapse at the nuclear density and thus prevent singularities. It is considered effective gravity which includes Newtonian potential and inertial anti-gravitational potential. It is investigated footprints of the effective gravity in the solar system. The inertial anti-gravitational potential of the sun allows to explain the anomalous acceleration of Pioneer 10 and 11, the anomalous increa...

  2. Effect of entropy on anomalous transport in electron-temperature-gradient-modes

    Energy Technology Data Exchange (ETDEWEB)

    Yaqub Khan, M., E-mail: myaqubsultani@gmail.com [Department of Basic Sciences, Riphah International University, Islamabad 44000 (Pakistan); National Centre for Physics, Quaid-i-Azam University, Islamabad 45320 (Pakistan); Iqbal, J. [Department of Mathematics, Quaid-i-Azam University, Islamabad 45320 (Pakistan); Ul Haq, A. [Faculty of Engineering and Applied Physics, Riphah International University, Islamabad 44000 (Pakistan)

    2014-05-15

    Due to the interconnection of entropy with temperature and density of plasma, it would be interesting to investigate plasma related phenomena with respect to entropy. By employing Braginskii transport equations, it is proved that entropy is proportional to a function of potential and distribution function of entropy is re-defined, ∇S–drift in obtained. New dispersion relation is derived; it is found that the anomalous transport depends on the gradient of the entropy.

  3. Anomalous Hall effect on the surface of topological Kondo insulators

    Science.gov (United States)

    König, E. J.; Ostrovsky, P. M.; Dzero, M.; Levchenko, A.

    2016-07-01

    We calculate the anomalous Hall conductivity σx y of the surface states in cubic topological Kondo insulators. We consider a generic model for the surface states with three Dirac cones on the (001) surface. The Fermi velocity, the Fermi momentum, and the Zeeman energy in different Dirac pockets may be unequal. The microscopic impurity potential mediates mixed intra- and interband extrinsic scattering processes. Our calculation of σx y is based on the Kubo-Streda diagrammatic approach. It includes diffractive skew scattering contributions originating from the rare two-impurity complexes. Remarkably, these contributions yield anomalous Hall conductivity that is independent of impurity concentration, and thus is of the same order as other known extrinsic side jump and skew scattering terms. We discuss various special cases of our results and the experimental relevance of our study in the context of the recent hysteretic magnetotransport data in SmB6 samples.

  4. Anomalous $tqZ$ coupling effects in rare B- and K-meson decays

    CERN Document Server

    Li, Xin-Qiang; Yuan, Xing-Bo

    2011-01-01

    As a top-factory, the LHC is performing a direct study of top-quark anomalous FCNC couplings, which are, however, correlated closely with the rare B- and K-meson decays. In this paper, we study the effects of anomalous $tqZ$ (with $q=u,c$) couplings in the rare decays $B_{s,d}\\to \\mu^+\\mu^-$, $B\\to X_s \

  5. Theory of the anomalous Hall effect from the Kubo formula and the Dirac equation

    OpenAIRE

    Crépieux, A.; Bruno, P

    2001-01-01

    A model to treat the anomalous Hall effect is developed. Based on the Kubo formalism and on the Dirac equation, this model allows the simultaneous calculation of the skew-scattering and side-jump contributions to the anomalous Hall conductivity. The continuity and the consistency with the weak-relativistic limit described by the Pauli Hamiltonian is shown. For both approaches, Dirac and Pauli, the Feynman diagrams, which lead to the skew-scattering and the side-jump contributions, are underli...

  6. The effect of interfacial intermixing on magnetization and anomalous Hall effect in Co/Pd multilayers

    KAUST Repository

    Guo, Zaibing

    2015-05-01

    The effect of interfacial intermixing on magnetization and anomalous Hall effect (AHE) in Co/Pd multilayers is studied by using rapid thermal annealing to enhance the interfacial diffusion. The dependence of saturation magnetization and coercivity on the temperature of rapid thermal annealing at 5 K is discussed. It is found that AHE is closely related to the relative thickness of the Co and Pd layers. Localized paramagnetism has been observed which destroys AHE, while AHE can be enhanced by annealing.

  7. Unconventional scaling of the anomalous Hall effect accompanying electron localization correction in the dirty regime

    KAUST Repository

    Lu, Y. M.

    2013-03-05

    Scaling of the anomalous Hall conductivity to longitudinal conductivity σAH∝σ2xx has been observed in the dirty regime of two-dimensional weak and strong localization regions in ultrathin, polycrystalline, chemically disordered, ferromagnetic FePt films. The relationship between electron transport and temperature reveals a quantitatively insignificant Coulomb interaction in these films, while the temperature dependent anomalous Hall conductivity experiences quantum correction from electron localization. At the onset of this correction, the low-temperature anomalous Hall resistivity begins to be saturated when the thickness of the FePt film is reduced, and the corresponding Hall conductivity scaling exponent becomes 2, which is above the recent unified theory of 1.6 (σAH∝σ1.6xx). Our results strongly suggest that the correction of the electron localization modulates the scaling exponent of the anomalous Hall effect.

  8. Large anomalous Hall effect in a non-collinear antiferromagnet at room temperature.

    Science.gov (United States)

    Nakatsuji, Satoru; Kiyohara, Naoki; Higo, Tomoya

    2015-11-12

    In ferromagnetic conductors, an electric current may induce a transverse voltage drop in zero applied magnetic field: this anomalous Hall effect is observed to be proportional to magnetization, and thus is not usually seen in antiferromagnets in zero field. Recent developments in theory and experiment have provided a framework for understanding the anomalous Hall effect using Berry-phase concepts, and this perspective has led to predictions that, under certain conditions, a large anomalous Hall effect may appear in spin liquids and antiferromagnets without net spin magnetization. Although such a spontaneous Hall effect has now been observed in a spin liquid state, a zero-field anomalous Hall effect has hitherto not been reported for antiferromagnets. Here we report empirical evidence for a large anomalous Hall effect in an antiferromagnet that has vanishingly small magnetization. In particular, we find that Mn3Sn, an antiferromagnet that has a non-collinear 120-degree spin order, exhibits a large anomalous Hall conductivity of around 20 per ohm per centimetre at room temperature and more than 100 per ohm per centimetre at low temperatures, reaching the same order of magnitude as in ferromagnetic metals. Notably, the chiral antiferromagnetic state has a very weak and soft ferromagnetic moment of about 0.002 Bohr magnetons per Mn atom (refs 10, 12), allowing us to switch the sign of the Hall effect with a small magnetic field of around a few hundred oersted. This soft response of the large anomalous Hall effect could be useful for various applications including spintronics--for example, to develop a memory device that produces almost no perturbing stray fields. PMID:26524519

  9. A laboratory dispersant effectiveness test which reflects dispersant efficiency in the field

    International Nuclear Information System (INIS)

    Oil dispersion efficiencies of surfactants, from laboratory dispersion tests and field data were compared and calibrated. Data from an oil spill, where dispersants were used as a major part of the response, was analysed. The data was accumulated through the monitoring of the dispersant operation of the Sea Empress spill incident, in which Forties Blend oil was spilled at sea. This detailed data set was used to calibrate existing laboratory dispersant tests, and to devise a new International Dispersant Effectiveness Test. The objective was to create a comprehensive guide to decision making on whether and when to start a dispersant spraying operation. The dispersion efficiencies obtained from the laboratory dispersant tests were compared with field data. Flume tests produced the highest percentage of dispersed oil for all the dispersal tests. However, it was emphasised that the total percentage of oil dispersed should not be the only measure of dispersant effectiveness, since it does not distinguish between the contribution of natural and chemically enhanced dispersion. 9 refs., 1 tab., 9 figs

  10. Anomalous Hall effect in Fe/Gd bilayers

    KAUST Repository

    Xu, W. J.

    2010-04-01

    Non-monotonic dependence of anomalous Hall resistivity on temperature and magnetization, including a sign change, was observed in Fe/Gd bilayers. To understand the intriguing observations, we fabricated the Fe/Gd bilayers and single layers of Fe and Gd simultaneously. The temperature and field dependences of longitudinal resistivity, Hall resistivity and magnetization in these films have also been carefully measured. The analysis of these data reveals that these intriguing features are due to the opposite signs of Hall resistivity/or spin polarization and different Curie temperatures of Fe and Gd single-layer films. Copyright (C) EPLA, 2010

  11. Anomalous x-ray scattering

    International Nuclear Information System (INIS)

    The availability of tunable synchrotron radiation has made it possible systematically to perform x-ray diffraction studies in regions of anomalous scattering near absorption edges, e.g. in order to derive phase information for crystal structure determination. An overview is given of recent experimental and theoretical work and discuss the properties of the anomalous atomic scattering factor, with emphasis on threshold resonances and damping effects. The results are applied to a discussion of the very strong anomalous dispersion recently observed near the L3 edge in a cesium complex. Also given is an overview of elements and levels where similar behavior can be expected. Finally, the influence of solid state and chemical effects on the absorption edge structure is discussed. 64 references

  12. Anomalous transport effects and possible environmental symmetry 'violation' in heavy-ion collisions

    Indian Academy of Sciences (India)

    Jinfeng Liao

    2015-05-01

    The heavy-ion collision provides a unique many-body environment where local domains of strongly interacting chiral medium may occur and in a sense allow environmental symmetry 'violation' phenomena. For example, certain anomalous transport processes, forbidden in usual medium, become possible in such domains. We briefly review recent progress in both the theoretical understanding and experimental search of various anomalous transport effects (such as the chiral magnetic effect, chiral separation effect, chiral electric separation effect, chiral electric/magnetic waves, etc.) in the hot QCD fluid formed by such collisions.

  13. Anomalous transport effects and possible environmental symmetry violation in heavy-ion collisions

    International Nuclear Information System (INIS)

    The heavy-ion collision provides a unique many-body environment where local domains of strongly interacting chiral medium may occur and in a sense allow environmental symmetry 'violation' phenomena. For example, certain anomalous transport processes, forbidden in usual medium, become possible in such domains. We briefly review recent progress in both the theoretical understanding and experimental search of various anomalous transport effects (such as the chiral magnetic effect, chiral separation effect, chiral electric separation effect, chiral electric/magnetic waves, etc.) in the hot QCD fluid formed by such collisions. (author)

  14. Absence of anomalous Nernst effect in spin Seebeck effect of Pt/YIG

    International Nuclear Information System (INIS)

    The Pt/YIG structure has been widely used to study spin Seebeck effect (SSE), inverse spin Hall effect, and other pure spin current phenomena. However, the magnetic proximity effect in Pt when in contact with YIG, and the potential anomalous Nernst effect (ANE) may compromise the spin current phenomena in Pt/YIG. By inserting a Cu layer of various thicknesses between Pt and YIG, we have separated the signals from the SSE and that of the ANE. It is demonstrated that the thermal voltage in Pt/YIG mainly comes from spin current due to the longitudinal SSE with negligible contribution from the ANE

  15. Absence of anomalous Nernst effect in spin Seebeck effect of Pt/YIG

    Energy Technology Data Exchange (ETDEWEB)

    Miao, B. F., E-mail: bfmiao@nju.edu.cn [National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093 (China); Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); Huang, S. Y. [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); Department of Physics, National Taiwan University, Taipei 10617, Taiwan (China); Qu, D.; Chien, C. L., E-mail: clchien@jhu.edu [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States)

    2016-01-15

    The Pt/YIG structure has been widely used to study spin Seebeck effect (SSE), inverse spin Hall effect, and other pure spin current phenomena. However, the magnetic proximity effect in Pt when in contact with YIG, and the potential anomalous Nernst effect (ANE) may compromise the spin current phenomena in Pt/YIG. By inserting a Cu layer of various thicknesses between Pt and YIG, we have separated the signals from the SSE and that of the ANE. It is demonstrated that the thermal voltage in Pt/YIG mainly comes from spin current due to the longitudinal SSE with negligible contribution from the ANE.

  16. Absence of anomalous Nernst effect in spin Seebeck effect of Pt/YIG

    Science.gov (United States)

    Miao, B. F.; Huang, S. Y.; Qu, D.; Chien, C. L.

    2016-01-01

    The Pt/YIG structure has been widely used to study spin Seebeck effect (SSE), inverse spin Hall effect, and other pure spin current phenomena. However, the magnetic proximity effect in Pt when in contact with YIG, and the potential anomalous Nernst effect (ANE) may compromise the spin current phenomena in Pt/YIG. By inserting a Cu layer of various thicknesses between Pt and YIG, we have separated the signals from the SSE and that of the ANE. It is demonstrated that the thermal voltage in Pt/YIG mainly comes from spin current due to the longitudinal SSE with negligible contribution from the ANE.

  17. Absence of anomalous Nernst effect in spin Seebeck effect of Pt/YIG

    Directory of Open Access Journals (Sweden)

    B. F. Miao

    2016-01-01

    Full Text Available The Pt/YIG structure has been widely used to study spin Seebeck effect (SSE, inverse spin Hall effect, and other pure spin current phenomena. However, the magnetic proximity effect in Pt when in contact with YIG, and the potential anomalous Nernst effect (ANE may compromise the spin current phenomena in Pt/YIG. By inserting a Cu layer of various thicknesses between Pt and YIG, we have separated the signals from the SSE and that of the ANE. It is demonstrated that the thermal voltage in Pt/YIG mainly comes from spin current due to the longitudinal SSE with negligible contribution from the ANE.

  18. Anomalous Hall effect from vortex motion in high-Tc superconductors

    International Nuclear Information System (INIS)

    In this work, the unusual Seebeck effect is taken into consideration in explaining the possible origin of the anomalous Hall effect for high-Tc superconductors. Combining Maki's theory of transport entropy and Tinkham's theory of resistive transition, we explain why the anomalous Hall effect can be observed in high-Tc superconductors, but is absent in most conventional superconductors. The behavior of ρxy(H,T) in our theory is qualitatively consistent with experiments. In addition, our theory not only predicts that ρxy will become positive from ρxyxy|∝ρxx2 in the region of ρxyxy will diminish with increasing defect concentration

  19. Anomalous effects of moderation in transportation and storage arrays - revisited

    International Nuclear Information System (INIS)

    A number of anomalies have been observed for fissile material arrays. This paper will review anomalous behavior associated with interstitial array moderation and correct one previously-mis-identified anomaly. Most arrays show a maximum keff with low-density water moderation. An earlier study, however, did not show this maximum for unreflected 5x5x5 and 10x10x10 arrays of 15-kg 235U spheres. Our present calculations with MCNP and KENO V.a, however, show low-density maximums for both unreflected and reflected arrays of these units. We conclude that the earlier calculations for unreflected arrays were in error -- perhaps due to problem setup or code errors. The reactivity enhancement due to fissile material density reductions, however, still exits and is now seen to occur for both unreflected and water-reflected arrays

  20. Inverse Spin Hall Effect and Anomalous Hall Effect in a Two-Dimensional Electron Gas

    OpenAIRE

    Schwab, Peter; Raimondi, Roberto; Gorini, Cosimo

    2010-01-01

    We study the coupled dynamics of spin and charge currents in a two-dimensional electron gas in the transport diffusive regime. For systems with inversion symmetry there are established relations between the spin Hall effect, the anomalous Hall effect and the inverse spin Hall effect. However, in two-dimensional electron gases of semiconductors like GaAs, inversion symmetry is broken so that the standard arguments do not apply. We demonstrate that in the presence of a Rashba type of spin-orbit...

  1. Effects of surface charge on the anomalous light extinction from metallic nanoparticles

    Science.gov (United States)

    Sijercic, Edin; Leung, P. T.

    2016-07-01

    The effects of extraneous surface charges on the anomalous extinction from metallic nanoparticles are studied via an application of the extended Mie theory by Bohren and Hunt. Due to the sensitivity of the higher multipolar resonance on the surface charges, it is found that quenching of the anomalous resonance can be observed with presence of only a modest amount of charges on these particles. The observed effects thus provide a rather sensitive mechanism for the monitoring of the neutrality of these nanoparticles using far field scattering approaches.

  2. Spontaneous magnetization and anomalous Hall effect in an emergent Dice lattice

    Science.gov (United States)

    Dutta, Omjyoti; Przysiężna, Anna; Zakrzewski, Jakub

    2015-06-01

    Ultracold atoms in optical lattices serve as a tool to model different physical phenomena appearing originally in condensed matter. To study magnetic phenomena one needs to engineer synthetic fields as atoms are neutral. Appropriately shaped optical potentials force atoms to mimic charged particles moving in a given field. We present the realization of artificial gauge fields for the observation of anomalous Hall effect. Two species of attractively interacting ultracold fermions are considered to be trapped in a shaken two dimensional triangular lattice. A combination of interaction induced tunneling and shaking can result in an emergent Dice lattice. In such a lattice the staggered synthetic magnetic flux appears and it can be controlled with external parameters. The obtained synthetic fields are non-Abelian. Depending on the tuning of the staggered flux we can obtain either anomalous Hall effect or its quantized version. Our results are reminiscent of Anomalous Hall conductivity in spin-orbit coupled ferromagnets.

  3. Noise-like femtosecond pulse in passively mode-locked Tm-doped NALM-based oscillator with small net anomalous dispersion

    Science.gov (United States)

    Liu, Shuo; Yan, Feng-Ping; Zhang, Lu-Na; Han, Wen-Guo; Bai, Zhuo-Ya; Zhou, Hong

    2016-01-01

    A passively mode-locked thulium-doped fiber laser (TDFL) based on a nonlinear amplifying loop mirror (NALM) is presented. By adjusting the polarization controllers, stable noise-like (NL) mode-locked femtosecond pulse operation is obtained at the 2 μm band. In the experimental period of 200 min, the output power fluctuation is less than 0.06 dB and the 3 dB spectral bandwidth variation is less than 0.02 nm, indicating that the pulsed TDFL possesses good long-term stability. To the best of our knowledge, this is the first 2 μm band NALM-based TDFL with small net anomalous dispersion for a NL femtosecond pulse. At the maximum pump power of 3.52 W, the emitting laser has a NL pulse width of 460 fs, the repetition rate of 9.1 MHz, and the NL pulse energy of 32.72 nJ.

  4. Correlated motion of electrons on the Au(111) surface: anomalous acoustic surface-plasmon dispersion and single-particle excitations.

    Science.gov (United States)

    Vattuone, L; Smerieri, M; Langer, T; Tegenkamp, C; Pfnür, H; Silkin, V M; Chulkov, E V; Echenique, P M; Rocca, M

    2013-03-22

    The linear dispersion of the low-dimensional acoustic surface plasmon (ASP) opens perspectives in energy conversion, transport, and confinement far below optical frequencies. Although the ASP exists in a wide class of materials, ranging from metal surfaces and ultrathin films to graphene and topological insulators, its properties are still largely unexplored. Taking Au(111) as a model system, our combined experimental and theoretical study revealed an intriguing interplay between collective and single particle excitations, causing the ASP associated with the Shockley surface state to be embedded within the intraband transitions without losing its sharp character and linear dispersion. PMID:25166849

  5. Effects of chemical dispersants on oil physical properties and dispersion. Volume 1

    Energy Technology Data Exchange (ETDEWEB)

    Khelifa, A.; Fingas, M.; Hollebone, B.P.; Brown, C.E. [Environment Canada, Ottawa, ON (Canada). ; Pjontek, D. [Ottawa Univ., ON (Canada). Dept. of Chemical Engineering

    2007-07-01

    Laboratory and field testing have shown that the dispersion of oil spilled in water is influenced by chemical dispersants via the modification of the interfacial properties of the oil, such as oil-brine interfacial tension (IFT). This study focused on new laboratory experiments that measured the effects on the physical properties and dispersion of oil, with particular reference to the effects of chemical dispersants on IFT and oil viscosity and the subsequent effects on oil droplet formation. Experiments were conducted at 15 degrees C using Arabian Medium, Alaska North Slope and South Louisiana crude and Corexit 9500 and Corexit 9527 chemical dispersants. The dispersants were denser than the 3 oils. The effect of IFT reduction on oil dispersion was measured and showed substantial reduction in the size and enhancement of the concentration of oil droplets in the water column. It was shown that the brine-oil IFT associated with the 3 crudes reduced to less than 3.6 mN/m with the application of the chemical dispersants, even at a low dispersant-to-oil ratio (DOR) value of 1:200. The use of chemical dispersants increased the viscosity of the dispersant-oil mixture up to 40 per cent over the neat crude oil. It was shown that for each mixing condition, an optimum value of DOR exists that provides for maximal dispersant effectiveness. The IFT reaches maximum reduction at optimum DOR. It was suggested that oil spill modelling can be improved with further study of IFT reduction with DOR and variations of critical micelle concentration with the type and solubility of chemical dispersant, oil type and oil to water ratio. 13 refs., 3 tabs., 7 figs.

  6. Scaling of anomalous hall effect in amorphous CoFeB Films with accompanying quantum correction

    KAUST Repository

    Zhang, Yan

    2015-05-08

    Scaling of anomalous Hall effect in amorphous CoFeB films with thickness ranging from 2 to 160 nm have been investigated. We have found that the scaling relationship between longitudinal (ρxx) and anomalous Hall (ρAH) resistivity is distinctly different in the Bloch and localization regions. For ultrathin CoFeB films, the sheet resistance (Rxx) and anomalous Hall conductance (GAH) received quantum correction from electron localization showing two different scaling relationships at different temperature regions. In contrast, the thicker films show a metallic conductance, which have only one scaling relationship in the entire temperature range. Furthermore, in the dirty regime of localization regions, an unconventional scaling relationship View the MathML sourceσAH∝σxxα with α=1.99 is found, rather than α=1.60 predicted by the unified theory.

  7. Intensity noise in normal-pumped picosecond supercontinuum generation, where higher-order Raman lines cross into anomalous dispersion regime

    DEFF Research Database (Denmark)

    Møller, Uffe Visbech; Bang, Ole

    2013-01-01

    The relative intensity noise (RIN) properties at different wavelengths and power levels for picosecond supercontinuum (SC) generated by pumping a PCF in its normal dispersion regime is investigated. For low power levels the all-normal SC is generated while the generated SC extends beyond the zero...

  8. Compact graphene mode-locked wavelength-tunable erbium-doped fiber lasers: from all anomalous dispersion towards all normal dispersion

    CERN Document Server

    Zhang, Han; Zhao, Luming; Bao, Qiaoliang; Loh, Kian Ping; Lin, Bo; Tjin, Swee Chuan

    2010-01-01

    Soliton operation and soliton wavelength tuning of erbium-doped fiber lasers mode locked with atomic layer graphene was experimentally investigated under various cavity dispersion conditions. It was shown that not only wide range soliton wavelength tuning but also soltion pulse width variation could be obtained in the fiber lasers. Our results show that the graphene mode locked erbium-doped fiber lasers provide a compact, user friendly and low cost wavelength tunable ultrahsort pulse source.

  9. Switching field distribution of arrays of Co-Pt Nanodots determined by anomalous hall effect measurements

    NARCIS (Netherlands)

    Delalande, M.; Engelen, J.B.C.; Febre, le A.J.; Abelmann, L.; Lodder, J.C.

    2008-01-01

    Anomalous Hall Effect (AHE) measurements have previously been used to measure the magnetization of L10-FePt [1] and Co/Pt multilayer nanodots [2]. The high sensitivity allows us to measure the magnetization reversal behaviour of sub-100-nm dots. In this work, we investigate the magnetization reversa

  10. Anomalous Hall effects in pseudo-single-crystal γ'-Fe4N thin films

    Science.gov (United States)

    Kabara, Kazuki; Tsunoda, Masakiyo; Kokado, Satoshi

    2016-05-01

    The anomalous Hall effects (AHE) were investigated at various temperatures for the pseudo-single-crystal Fe4N films, deposited on MgO substrates with changing the degree of order (S) of the nitrogen site. Both the anomalous Hall resistivity and the longitudinal resistivity simply decrease with lowering temperature for all the specimens. The AHE of the Fe4N films is presumed to arise from an intrinsic mechanism because of the relationship between the anomalous Hall resistivity and longitudinal resistivity. The anomalous Hall conductivity, σAH, exhibits a specific behavior at low temperature. In the case of the film with S = 0.93, the σAH drastically drops below 50 K, while it simply increases with lowering temperature in the range of 50-300 K. This low-temperature anomaly decays with decreasing S of the film and nearly vanishes in the films with low S. The threshold temperature and the dependence on S of the low-temperature anomaly of the σAH well correspond to those of the anisotropic magnetoresistance effects in the Fe4N films, reported in the literatures. From these results, it is suggested that the low-temperature anomaly of the σAH originates from the crystal field effect which reflects the structural transformation from a cubic to a tetragonal symmetry below 50 K and provides a modulation of the orbital angular momentum of the 3d orbitals at the Fermi level.

  11. Quantized topological magnetoelectric effect of the zero-plateau quantum anomalous Hall state

    OpenAIRE

    Jing WANG; Lian, Biao; Qi, Xiao-Liang; Zhang, Shou-Cheng

    2015-01-01

    Topological magnetoelectric effect in a three-dimensional topological insulator is a novel phenomenon, where an electric field induces a magnetic field in the same direction, with a universal coefficient of proportionality quantized in units of $e^2/2h$. Here we propose that the topological magnetoelectric effect can be realized in the zero-plateau quantum anomalous Hall state of magnetic topological insulators or ferromagnet-topological insulator heterostructure. The finite-size effect is al...

  12. Prospect of quantum anomalous Hall and quantum spin Hall effect in doped kagome lattice Mott insulators

    OpenAIRE

    Daniel Guterding; Jeschke, Harald O.; Roser Valentí

    2015-01-01

    Electronic states with non-trivial topology host a number of novel phenomena with potential for revolutionizing information technology. The quantum anomalous Hall effect provides spin-polarized dissipation-free transport of electrons, while the quantum spin Hall effect in combination with superconductivity has been proposed as the basis for realizing decoherence-free quantum computing. We introduce a new strategy for realizing these effects, namely by hole and electron doping kagome lattice M...

  13. Artificial ferroelectricity due to anomalous Hall effect in magnetic tunnel junctions

    OpenAIRE

    Vedyayev, A.; Ryzhanova, N.; Strelkov, N.; Dieny, B

    2012-01-01

    We theoretically investigated Anomalous Hall Effect (AHE) and Spin Hall Effect (SHE) transversally to the insulating spacer O, in magnetic tunnel junctions of the form F/O/F where F are ferromagnetic layers and O represents a tunnel barrier. We considered the case of purely ballistic (quantum mechanical) transport, taking into account the assymetric scattering due to spin-orbit interaction in the tunnel barrier. AHE and SHE in the considered case have a surface nature due to proximity effect....

  14. The neutron diffraction anomalous dispersion technique and its application to vitreous Sm2O3.4P2O5

    International Nuclear Information System (INIS)

    The first successful complete neutron diffraction anomalous dispersion experiment has been performed to investigate the role of the Sm3+ ions in the structure of vitreous Sm2O3.4P2O5. The ideal form of this technique, which employs the wavelength dependence of the real and imaginary parts of the neutron scattering length close to an absorption resonance, is used and involves measurements at two pairs of wavelengths: the real part of the scattering length is varied, keeping the imaginary part constant, and then the imaginary part is varied, keeping the real part constant. If A denotes the element with the isotope (149Sm) having the absorption resonance and X any other element present in the sample, the first measurement can be used to extract the A-A+A-X or A-A+X-X contribution to the real space correlation function, T(r), and the second yields the A-A component correlation function. For the present glass, the Sm-Sm+Sm-X contribution (X=P or O) reveals that the Sm3+ ions have an average co-ordination number, n Sm(O), of 7, with a mean Sm-O bond length of 2.375±0.005 A, while the anomalous difference correlation function indicates that the Sm3+ ions are ∼4.6 A apart. The paper concludes with a discussion of the relative merits of the various neutron diffraction techniques for isolating individual or subsets of real-space component correlation functions

  15. 佛克脱反常色散原子滤光器工作机理研究%Mechanism of Voigt Anomalous Dispersion Optical Filter

    Institute of Scientific and Technical Information of China (English)

    王江波; 汤俊雄; 段明浩; 李吉红

    2001-01-01

    对佛克脱(Voigt)型反常色散原子滤光器的工作机理和各种性能进行讨论,该种滤光器的实验研究表明理论与实验结果符合得很好。滤光器在外加磁场为0.02T、汽室温度为110℃的单峰带宽为0.8GHz,比相同条件下的法拉第型反常色散原子滤光器小0.5GHz,并且工程化实现比法拉第型反常色散原子滤光器容易。佛克脱型反常色散原子滤光器在卫星光通信领域有潜在的极大应用前景。%The mechanism and performances of Voigt anomalous dispersionatomic optical filter (VADOF) are studied. The experimental results agree well with the theoretical calculation. When the magnetic field is 0.02 T and the cell temperature is 110 ℃, this kind of filter exhibited a FWHM of 0.8 GHz which is 0.5 GHz smaller than that of Faraday anomalous dispersion optical filter (FADOF), and the VADOF is easy to be integrated than FADOF. VADOF has a potential application in the field of optical communication inter-satellite.

  16. An anomalous extinction law in the Cep OB3b young cluster: Evidence for dust processing during gas dispersal

    Energy Technology Data Exchange (ETDEWEB)

    Allen, Thomas S.; Prchlik, Jakub J.; Megeath, S. Thomas [University of Toledo, Ritter Astrophysical Observatory, Department of Physics and Astronomy, Toledo, OH 43606 (United States); Gutermuth, Robert A. [Five College Astronomy Department, Smith College, Northampton, MA 01063 (United States); Pipher, Judith L. [Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627 (United States); Naylor, Tim [School of Physics, University of Exeter, Exeter, UK EX4 4QL (United Kingdom); Jeffries, R. D. [Astrophysics Group, School of Physical and Geographical Sciences, Keele University, Keele, Staffordshire, UK ST5 5BG (United Kingdom)

    2014-05-10

    We determine the extinction law through Cep OB3b, a young cluster of 3000 stars undergoing gas dispersal. The extinction is measured toward 76 background K giants identified with MMT/Hectospec spectra. Color excess ratios were determined toward each of the giants using V and R photometry from the literature, g, r, i, and z photometry from the Sloan Digital Sky Survey and J, H, and K{sub s} photometry from the Two Micron All Sky Survey. These color excess ratios were then used to construct the extinction law through the dusty material associated with Cep OB3b. The extinction law through Cep OB3b is intermediate between the R{sub V} = 3.1 and R{sub V} = 5 laws commonly used for the diffuse atomic interstellar medium and dense molecular clouds, respectively. The dependence of the extinction law on line-of-sight A{sub V} is investigated and we find the extinction law becomes shallower for regions with A{sub V} > 2.5 mag. We speculate that the intermediate dust law results from dust processing during the dispersal of the molecular cloud by the cluster.

  17. Effect of anomalous plasma transport on radial electric field in torsatron/heliotron

    International Nuclear Information System (INIS)

    Anomalous cross field plasma fluxes induced by the electric field fluctuations has been evaluated in a rotating plasma with shear flow in a helical system. The plasma rotation frequency due to the radial electric field makes the Doppler frequency shift which does not explicitly affect the cross field flux. The anomalous ion flux is evaluated by the ion curvature drift resonance continuum in the test particle model. The curvature drift resonance induces a new force term '/ which did not make large influence in the ion flux. The shear flow term in the anomalous flux combined with the electric field in neoclassical flux reduces to a first order differential equation which governs the radial profile of the electric field. A general exact analytical solution for the differential equation is derived and a simple approximate solution for the radial electric field is also given. Numerical results indicate that the shear flow effect is important for the anomalous cross field flux and for determination of the radial electric field particularly in the peripheral region. (author)

  18. Prospect of quantum anomalous Hall and quantum spin Hall effect in doped kagome lattice Mott insulators.

    Science.gov (United States)

    Guterding, Daniel; Jeschke, Harald O; Valentí, Roser

    2016-01-01

    Electronic states with non-trivial topology host a number of novel phenomena with potential for revolutionizing information technology. The quantum anomalous Hall effect provides spin-polarized dissipation-free transport of electrons, while the quantum spin Hall effect in combination with superconductivity has been proposed as the basis for realizing decoherence-free quantum computing. We introduce a new strategy for realizing these effects, namely by hole and electron doping kagome lattice Mott insulators through, for instance, chemical substitution. As an example, we apply this new approach to the natural mineral herbertsmithite. We prove the feasibility of the proposed modifications by performing ab-initio density functional theory calculations and demonstrate the occurrence of the predicted effects using realistic models. Our results herald a new family of quantum anomalous Hall and quantum spin Hall insulators at affordable energy/temperature scales based on kagome lattices of transition metal ions. PMID:27185665

  19. Weak localization and Anomalous Hall Effect in Chemically Disordered L10-Mn1.5Ga

    OpenAIRE

    Zhu, L. J.; Pan, D.; J. H. Zhao

    2013-01-01

    The anomalous Hall effect (AHE) in perpendicularly magnetized L10-Mn1.5Ga single-crystalline films is investigated as a function of degree of long-range chemical ordering and temperature. Our results provide firm evidence that weak localization, phonons and magnons have negligibly smaller effect on skew scattering contributions to AHE resistivity than defects, the overlook of which in conventional scaling laws results in significant discrepancies and exponent n beyond 2 when fitting the data....

  20. Study of the anomalous presence of iron in olive trees leaves by energy dispersion X-ray fluorescence

    International Nuclear Information System (INIS)

    In this work, we made use of the technique of X-ray fluorescence for dispersion in energy, to study a phytopathology denominated 'sooty mould' on leaves of Olive trees of Mediterranean area. The Olive trees are quite common and of great economical value in that area,especially in the island of Sardegna in Italy, where this work was developed, for treating one of the income main sources of the local economy. We observed a correlation between the elements Fe and Ca among infected leaves of Olive trees and not infected that is: leaves infected by the sooty mould present a large concentration of Fe and a low concentration of Ca when compared to the leaves not infected by the sooty mould. The oxidation state of Fe was determined by Moessbauer spectroscopy that revealed that this was Fe3+. (author)

  1. Dispersant effectiveness testing : laboratory studies of fresh and weathered oils

    Energy Technology Data Exchange (ETDEWEB)

    Fingas, M.F.; Fieldhouse, B.; Sigouin, L.; Wang, Z. [Environment Canada, Ottawa, ON (Canada). Emergencies Science Div

    2001-07-01

    A dispersant called Corexit 9500 was tested to determine its effectiveness on various oils including several new and weathered oils. Dispersant effectiveness is defined as the amount of oil that the dispersant puts into the water column versus that which remains on the surface. Many factors influence dispersant effectiveness, including sea energy, oil composition, state of oil weathering, rate of dispersant application, dispersant type, temperature, and salinity of the water. In this study, a series of 6 oil-in-solvent standards were prepared for evaluating the efficiency of the dispersant for each dispersant/oil combination. The effectiveness of these oils was measured using the swirling flask test. Tests of crude oil as well as weathered crude oil were presented. The effectiveness for the weathered crude oils was found to drop off significantly. The weathering effect was analyzed using mathematical regressions. It was concluded that the dispersabilities of crude oils vary and the effectiveness of dispersion decreases as the oils are weathered or evaporated. The typical trend that emerged is oil specific and does not correlate with simple oil properties such as density, viscosity or maximum weathering percentage. 4 refs., 2 tabs., 4 figs.

  2. Charge transport in manganites: Hopping conduction, the anomalous Hall effect, and universal scaling

    International Nuclear Information System (INIS)

    The low-temperature Hall resistivity ρxy of La2/3A1/3MnO3 single crystals (where A stands for Ca, Pb, and Ca, or Sr) can be separated into ordinary and anomalous contributions, giving rise to ordinary and anomalous Hall effects, respectively. However, no such decomposition is possible near the Curie temperature which, in these systems, is close to metal-to-insulator transition. Rather, for all of these compounds and to a good approximation, the ρxy data at various temperatures and magnetic fields collapse (up to an overall scale), on to a single function of the reduced magnetization m(equivalent to)M/Msat, the extremum of this function lying at m∼0.4. A mechanism for the anomalous Hall effect in the inelastic hopping regime, which reproduces these scaling curves, is identified. This mechanism, which is an extension of Holstein's model for the ordinary Hall effect in the hopping regime, arises from the combined effects of the double-exchange-induced quantal phase in triads of Mn ions and spin-orbit interactions. We identify processes that lead to the anomalous Hall effect for localized carriers and, along the way, analyze issues of quantum interference in the presence of phonon-assisted hopping. Our results suggest that, near the ferromagnet-to-paramagnet transition, it is appropriate to describe transport in manganites in terms of carrier hopping between states that are localized due to the combined effect of magnetic and nonmagnetic disorder. We attribute the qualitative variations in resistivity characteristics across manganite compounds to the differing strengths of their carrier self-trapping, and conclude that both disorder-induced localization and self-trapping effects are important for transport

  3. Temperature correction to the Casimir force in cryogenic range and anomalous skin effect

    International Nuclear Information System (INIS)

    The temperature correction to the Casimir force is considered for real metals at low temperatures. With the temperature decrease, the mean free path for electrons becomes larger than the field penetration depth. In this condition, description of metals with the impedance of anomalous skin effect is shown to be more appropriate than with the permittivity. The effect is crucial for the temperature correction. It is demonstrated that in the zero-frequency limit, the reflection coefficients should coincide with those of ideal metal if we demand the entropy to be zero at T=0. All the other prescriptions discussed in the literature for the n=0 term in the Lifshitz formula give negative entropy. It is shown that the temperature correction in the region of anomalous skin effect is not suppressed as it happens in the plasma model. This correction will be important in the future cryogenic measurements of the Casimir force

  4. Numerical study of effective optical nonlinear properties in composites with anomalous distribution

    International Nuclear Information System (INIS)

    We investigate the nonlinear optical response of random composites consisting of nonlinear conductors and linear conductors with an anomalous distribution. Random resistor-capacitor networks are used to simulate our model, in which the nonlinear component with the fraction p is taken as i=g1ν+χ1 vertical ν vertical bar2v and the linear component with the fraction 1-p obeys an anomalous distribution h(g2)∼g2-α, where 02<1. We find that the distribution exponent α plays an important role in the effective linear and nonlinear optical response. As α decreases, the enhancement of optical nonlinear χe can be achieved. Moreover, the effective nonlinear optical response exhibits a sharp peak at a moderate volume fraction, dependent on α. The effective medium approximation is found to be in good agreement with linear response of numerical simulation, and describes nonlinear response of our numerical results qualitatively

  5. Finite-volume effects in the muon anomalous magnetic moment on the lattice

    Science.gov (United States)

    Aubin, Christopher; Blum, Thomas; Chau, Peter; Golterman, Maarten; Peris, Santiago; Tu, Cheng

    2016-03-01

    We investigate finite-volume effects in the hadronic vacuum polarization, with an eye toward the corresponding systematic error in the muon anomalous magnetic moment. We consider both recent lattice data as well as lowest-order, finite-volume chiral perturbation theory, in order to get a quantitative understanding. Even though leading-order chiral perturbation theory does not provide a good description of the hadronic vacuum polarization, it turns out that it gives a good representation of finite-volume effects. We find that finite-volume effects cannot be ignored when the aim is a few percent level accuracy for the leading-order hadronic contribution to the muon anomalous magnetic moment, even when using ensembles with mπL ≳4 and mπ˜200 MeV .

  6. Finite-volume effects in the muon anomalous magnetic moment on the lattice

    CERN Document Server

    Aubin, Christopher; Chau, Peter; Golterman, Maarten; Peris, Santiago; Tu, Cheng

    2015-01-01

    We investigate finite-volume effects in the hadronic vacuum polarization, with an eye toward the corresponding systematic error in the muon anomalous magnetic moment. We consider both recent lattice data as well as lowest-order, finite-volume chiral perturbation theory, in order to get a quantitative understanding. Even though leading-order chiral perturbation theory does not provide a good description of the hadronic vacuum polarization, it turns out that it gives a reasonably good representation of finite-volume effects. We find that finite-volume effects cannot be ignored when the aim is a few percent level accuracy for the leading-order hadronic contribution to the muon anomalous magnetic moment, even when using ensembles with $m_\\pi L> 4$ and $m_\\pi \\sim 200$ MeV.

  7. Employment Effects of Dispersal Policies on Refugee Immigrants

    DEFF Research Database (Denmark)

    Damm, Anna Piil; Rosholm, Michael

    Do spatial dispersal policies on refugees promote their labour market outcomes? To investigate this we estimate the effects of location characteristics and the average effect of geographical mobility on the hazard rate into first job of refugees subjected to the Danish spatial dispersal policy 1986...... findings support dispersal policies. Second, on average geographical mobility had large, positive effects on the hazard rate into first job, suggesting that restrictions on placed refugees' subsequent out-migration would hamper labour market integration of refugees....

  8. Monolayer dispersion thresholds and threshold effect displayed by supported catalysts

    Institute of Scientific and Technical Information of China (English)

    Cun DENG

    2008-01-01

    The principle of spontaneous monolayer dis-persion holds that active components of many supported catalysts will disperse spontaneously onto the surface of the carrier. The monolayer dispersion threshold of the active component on the surface of the carrier can be measured by X-ray diffraction phase-quantitative extra-polation method, etc. By measuring the monolayer disper-sion threshold, beneficial information on the surface structure and dispersion of supported catalysts can be obtained, and the optimal preparative processing condi-tions of the catalysts can be chosen. The proportion of the active component of many supported catalysts can be optimized while its monolayer dispersion threshold is observed. Mutation values of many physicochemical properties of supported catalysts are related to monolayer dispersion thresholds; the threshold effect on catalysts is apparent, and the proposal regarding the threshold effect provides instruction for the research on catalysts.

  9. Anomalous effective charges and far-IR optical absorption of Al2Ru from first principles

    International Nuclear Information System (INIS)

    For the orthorhombic intermetallic semiconductor Al2Ru, the band structure, valence charge density, zone-center optical-phonon frequencies, and Born effective-charge and electronic dielectric tensors are calculated using variational density-functional perturbation theory with ab initio pseudopotentials and a plane-wave basis set. Good agreement is obtained with recent measurements on polycrystalline samples, which showed anomalously strong far-IR absorption by optical phonons, while analysis of the valence charge density shows that the static ionic charges of Al and Ru are negligible. Hybridization is proposed as the single origin both of the semiconducting gap and the anomalous Born effective charges. Analogous behavior is expected in related compounds such as NiSnZr, PbTe, skutterudites, and Al-transition-metal quasicrystals. copyright 1996 The American Physical Society

  10. Surface impedance in the anomalous skin effect regime

    Science.gov (United States)

    Chrzanowski, Janusz; Kirkiewicz, Józef

    2008-12-01

    An analytical solution of the surface impedance is obtained using the kinetic equation with the collision integral that takes into account the Fermi liquid effects. It is assumed that the reflection of electrons is purely diffusive. Particular attention is paid to the influence of external magnetic field and polarization of the incident wave on the real and imagine part of the surface impedance.

  11. Crystal structure determination of solar cell materials: Cu2ZnSnS4 thin films using X-ray anomalous dispersion

    International Nuclear Information System (INIS)

    Highlights: ► Cu2ZnSnS4 thin films as a solar cell material were synthesized. ► The wavelength dependences of the diffraction intensity were measured. ► The crystal structures were clearly identified as kesterite structure for all samples. ► Crystal structure analysis revealed that the atomic compositions were Cu/(Zn + Sn) = 0.97 and Zn/Sn = 1.42 for the sample synthesized using stoichiometric amount of starting materials. - Abstract: The crystal structure of Cu2ZnSnS4 (CZTS) thin films fabricated by vapor-phase sulfurization was determined using X-ray anomalous dispersion. High statistic synchrotron radiation X-ray diffraction data were collected from very small amounts of powder. By analyzing the wavelength dependencies of the diffraction peak intensities, the crystal structure was clearly identified as kesterite. Rietveld analysis revealed that the atomic composition deviated from stoichiometric composition, and the compositions were Cu/(Zn + Sn) = 0.97, and Zn/Sn = 1.42.

  12. Critical Review of Theoretical Models for Anomalous Effects (Cold Fusion) in Deuterated Metals

    OpenAIRE

    Chechin, V. A.; Tsarev, V. A.; Rabinowitz, M; Kim, Y. E.

    2003-01-01

    We briefly summarize the reported anomalous effects in deuterated metals at ambient temperature, commonly known as "Cold Fusion" (CF), with an emphasis on important experiments as well as the theoretical basis for the opposition to interpreting them as cold fusion. Then we critically examine more than 25 theoretical models for CF, including unusual nuclear and exotic chemical hypotheses. We conclude that they do not explain the data.

  13. Critical Review of Theoretical Models for Anomalous Effects (Cold Fusion) in Deuterated Metals

    CERN Document Server

    Chechin, V A; Rabinowitz, M; Kim, Y E

    1994-01-01

    We briefly summarize the reported anomalous effects in deuterated metals at ambient temperature, commonly known as "Cold Fusion" (CF), with an emphasis on important experiments as well as the theoretical basis for the opposition to interpreting them as cold fusion. Then we critically examine more than 25 theoretical models for CF, including unusual nuclear and exotic chemical hypotheses. We conclude that they do not explain the data.

  14. Semiclassical origin of anomalous shell effect for tetrahedral deformation in radial power-law potential model

    CERN Document Server

    Arita, Ken-ichiro

    2014-01-01

    Shell structures in single-particle energy spectra are investigated against regular tetrahedral type deformation using radial power-law potential model. Employing a natural way of shape parametrization which interpolate sphere and regular tetrahedron, we find prominent shell effects at rather large tetrahedral deformations, which bring about shell energies much larger than the cases of spherical and quadrupole type shapes. We discuss the semiclassical origin of these anomalous shell structures using periodic orbit theory.

  15. 3d Transition Metal Adsorption Induced Vally-polarized Anomalous Hall Effect in Germanene

    OpenAIRE

    Zhou, P; Sun, L. Z.

    2015-01-01

    Based on DFT+U and Berry curvature calculations, we study the electronic structures and topological properties of 3d transition metal (TM) atom (from Ti to Co) adsorbed germanene (TM-germanene). We find that valley-polarized anomalous hall effect (VAHE) can be realized in germanene by adsorbing Cr, Mn, or Co atom on its surface. A finite valley hall voltage can be easily detected in its nanoribbon, which is important for valleytronics devices. Moreover, different valley-polarized current and ...

  16. Nonadiabatic Effects in Ultracold Molecules via Anomalous Linear and Quadratic Zeeman Shifts

    OpenAIRE

    McGuyer, B. H.; Osborn, C. B.; McDonald, M.; Reinaudi, G.; Skomorowski, W.; Moszynski, R.; Zelevinsky, T.

    2013-01-01

    Anomalously large linear and quadratic Zeeman shifts are measured for weakly bound ultracold $^{88}$Sr$_2$ molecules near the intercombination-line asymptote. Nonadiabatic Coriolis coupling and the nature of long-range molecular potentials explain how this effect arises and scales roughly cubically with the size of the molecule. The linear shifts yield nonadiabatic mixing angles of the molecular states. The quadratic shifts are sensitive to nearby opposite $f$-parity states and exhibit fourth...

  17. Anomalous effective action, Noether current, Virasoro algebra and Horizon entropy

    International Nuclear Information System (INIS)

    Several investigations show that in a very small length scale there exist corrections to the entropy of black hole horizon. Due to fluctuations of the background metric and the external fields the action incorporates corrections. In the low energy regime, the one-loop effective action in four dimensions leads to trace anomaly. We start from the Noether current corresponding to the Einstein-Hilbert plus the one-loop effective action to calculate the charge for the diffeomorphisms which preserve the Killing horizon structure. Then a bracket for the charges is calculated. We show that the Fourier modes of the bracket are exactly similar to the Virasoro algebra. Then using the Cardy formula the entropy is evaluated. Finally, the explicit terms of the entropy expression is calculated for a classical background. It turns out that the usual expression for the entropy; i.e. the Bekenstein-Hawking form, is not modified. (orig.)

  18. Evidence for Anomalous Effects on the Current Evolution in Tokamak Operating Scenarios

    Energy Technology Data Exchange (ETDEWEB)

    Casper, T; Jayakumar, R; Allen, S; Holcomb, C; Makowski, M; Pearlstein, L; Berk, H; Greenfield, C; Luce, T; Petty, C; Politzer, P; Wade, M; Murakami, M; Kessel, C

    2006-10-03

    Alternatives to the usual picture of advanced tokamak (AT) discharges are those that form when anomalous effects alter the plasma current and pressure profiles and those that achieve stationary characteristics through mechanisms so that a measure of desired AT features is maintained without external current-profile control. Regimes exhibiting these characteristics are those where the safety factor (q) evolves to a stationary profile with the on-axis and minimum q {approx} 1 and those with a deeply hollow current channel and high values of q. Operating scenarios with high fusion performance at low current and where the inductively driven current density achieves a stationary configuration with either small or non-existing sawteeth may enhance the neutron fluence per pulse on ITER and future burning plasmas. Hollow current profile discharges exhibit high confinement and a strong ''box-like'' internal transport barrier (ITB). We present results providing evidence for current profile formation and evolution exhibiting features consistent with anomalous effects or with self-organizing mechanisms. Determination of the underlying physical processes leading to these anomalous effects is important for scaling of current experiments for application in future burning plasmas.

  19. Giant Anomalous Hall Effect in the Chiral Antiferromagnet Mn3Ge

    Science.gov (United States)

    Kiyohara, Naoki; Tomita, Takahiro; Nakatsuji, Satoru

    2016-06-01

    The external field control of antiferromagnetism is a significant subject both for basic science and technological applications. As a useful macroscopic response to detect magnetic states, the anomalous Hall effect (AHE) is known for ferromagnets, but it has never been observed in antiferromagnets until the recent discovery in Mn3Sn . Here we report another example of the AHE in a related antiferromagnet, namely, in the hexagonal chiral antiferromagnet Mn3Ge . Our single-crystal study reveals that Mn3Ge exhibits a giant anomalous Hall conductivity |σx z|˜60 Ω-1 cm-1 at room temperature and approximately 380 Ω-1 cm-1 at 5 K in zero field, reaching nearly half of the value expected for the quantum Hall effect per atomic layer with Chern number of unity. Our detailed analyses on the anisotropic Hall conductivity indicate that in comparison with the in-plane-field components |σx z| and |σz y|, which are very large and nearly comparable in size, we find |σy x| obtained in the field along the c axis to be much smaller. The anomalous Hall effect shows a sign reversal with the rotation of a small magnetic field less than 0.1 T. The soft response of the AHE to magnetic field should be useful for applications, for example, to develop switching and memory devices based on antiferromagnets.

  20. Anomalous piezoelectric effects, found in the laboratory and reconstructed by numerical simulation

    Directory of Open Access Journals (Sweden)

    K. P. Teisseyre

    2002-06-01

    Full Text Available Various rocks and minerals, which are not piezoelectric in the common sense, exhibit transient electric polarization in response to sudden changes in stress load. This anomalous piezoelectric effect differs from the regular, static piezoelectric response, in which electric charges appear as a result of crystal lattice deformation. The anomalous piezoelectricity is dynamic decaying in a few seconds or a few tens of seconds. However, in some materials different polarization properties are discovered. To explain certain aspects of the polarization signal increase and decay, some complicated mechanisms of electric charge generation and relaxation need to be assumed in their number ? concurrence of two or three relaxation processes. The hypothetical mechanisms are only mentioned, as the purpose of this work is to construct numerical models, behaving like the rocks investigated. Examples of experimental plots are shown together with the results of the numerical simulation of these experiments.

  1. Predicting molecular scale skin-effect in electrochemical impedance due to anomalous subdiffusion mediated adsorption phenomenon

    Science.gov (United States)

    Kushagra, Arindam

    2016-02-01

    Anomalous subdiffusion governs the processes which are not energetically driven, on a molecular scale. This paper proposes a model to predict the response of electrochemical impedance due to such diffusion process. Previous works considered the use of fractional calculus to predict the impedance behaviour in response to the anomalous diffusion. Here, we have developed an expression which predicts the skin-effect, marked by an increase in the impedance with increasing frequency, in this regime. Negative inductances have also been predicted as a consequence of the inertial response of adsorbed species upon application of frequency-mediated perturbations. It might help the researchers in the fields of impedimetric sensors to choose the working frequency and those working in the field of batteries to choose the parameters, likewise. This work would shed some light into the molecular mechanisms governing the impedance when exposed to frequency-based perturbations like electromagnetic waves (microwaves to ionizing radiations) and in charge storage devices like batteries etc.

  2. Origin of enhanced anomalous Hall effect in ultrathin Pt/permalloy bilayers

    Directory of Open Access Journals (Sweden)

    Y. Q. Zhang

    2016-02-01

    Full Text Available There are two mechanisms which could enhance spin-dependent scattering in a low dimensional Pt/Ferromagnetic metal structure. One is magnetic proximity effect. The other is spin orbit coupling proximity effect which was suggested recently. This work demonstrates that, through a series of experiments on anomalous Hall effect, the spin orbit coupling proximity effect dominates the enhancement in very thin Pt/Permalloy bilayers. It may help to find a way to optimize magnetic transport property of spintronics devices in which the spin orbit coupling is deeply involved.

  3. Quantum Anomalous Hall Effect in Hg_1-yMn_yTe Quantum Wells

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Chao-Xing; /Tsinghua U., Beijing /Stanford U., Phys. Dept.; Qi, Xiao-Liang; /Stanford U., Phys. Dept.; Dai, Xi; Fang, Zhong; /Beijing, Inst. Phys.; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.

    2010-03-19

    The quantum Hall effect is usually observed when the two-dimensional electron gas is subjected to an external magnetic field, so that their quantum states form Landau levels. In this work we predict that a new phenomenon, the quantum anomalous Hall effect, can be realized in Hg{sub 1-y}Mn{sub y}Te quantum wells, without the external magnetic field and the associated Landau levels. This effect arises purely from the spin polarization of the Mn atoms, and the quantized Hall conductance is predicted for a range of quantum well thickness and the concentration of the Mn atoms. This effect enables dissipationless charge current in spintronics devices.

  4. Anomalous diffraction in hyperbolic materials

    CERN Document Server

    Alberucci, Alessandro; Boardman, Allan D; Assanto, Gaetano

    2016-01-01

    We demonstrate that light is subject to anomalous (i.e., negative) diffraction when propagating in the presence of hyperbolic dispersion. We show that light propagation in hyperbolic media resembles the dynamics of a quantum particle of negative mass moving in a two-dimensional potential. The negative effective mass implies time reversal if the medium is homogeneous. Such property paves the way to diffraction compensation, spatial analogue of dispersion compensating fibers in the temporal domain. At variance with materials exhibiting standard elliptic dispersion, in inhomogeneous hyperbolic materials light waves are pulled towards regions with a lower refractive index. In the presence of a Kerr-like optical response, bright (dark) solitons are supported by a negative (positive) nonlinearity.

  5. Large anomalous Hall effect driven by a nonvanishing Berry curvature in the noncolinear antiferromagnet Mn3Ge.

    Science.gov (United States)

    Nayak, Ajaya K; Fischer, Julia Erika; Sun, Yan; Yan, Binghai; Karel, Julie; Komarek, Alexander C; Shekhar, Chandra; Kumar, Nitesh; Schnelle, Walter; Kübler, Jürgen; Felser, Claudia; Parkin, Stuart S P

    2016-04-01

    It is well established that the anomalous Hall effect displayed by a ferromagnet scales with its magnetization. Therefore, an antiferromagnet that has no net magnetization should exhibit no anomalous Hall effect. We show that the noncolinear triangular antiferromagnet Mn3Ge exhibits a large anomalous Hall effect comparable to that of ferromagnetic metals; the magnitude of the anomalous conductivity is ~500 (ohm·cm)(-1) at 2 K and ~50 (ohm·cm)(-1) at room temperature. The angular dependence of the anomalous Hall effect measurements confirms that the small residual in-plane magnetic moment has no role in the observed effect except to control the chirality of the spin triangular structure. Our theoretical calculations demonstrate that the large anomalous Hall effect in Mn3Ge originates from a nonvanishing Berry curvature that arises from the chiral spin structure, and that also results in a large spin Hall effect of 1100 (ħ/e) (ohm·cm)(-1), comparable to that of platinum. The present results pave the way toward the realization of room temperature antiferromagnetic spintronics and spin Hall effect-based data storage devices. PMID:27152355

  6. Added mass and effective density of dispersed media

    International Nuclear Information System (INIS)

    The review of dependences of added mass (AM) coefficients of liquid on concentration of inclusions in dispersion medium available in literature are given. It is shown that in the processes taking place under the action of surface forces effecting dispersion medium (pressure wave propagation, equipment vibrations), AM of liquid grows with the increase of concentration of inclusions. When dispersion medium moves under the action of body forces AM of liquid decreases with the increase of concentration of inclusions. The examples of calculations of effective density of dispersion media with the use of considered concentration dependences of AM coefficient are given. The comparison with experimental results is conducted

  7. Dispersion engineering for integrated nanophotonics

    CERN Document Server

    Vanbésien, Olivier

    2014-01-01

    This book shows how dispersion engineering in two dimensional dielectric photonic crystals can provide new effects for the precise control of light propagation for integrated nanophotonics.Dispersion engineering in regular and graded photonic crystals to promote anomalous refraction effects is studied from the concepts to experimental demonstration via nanofabrication considerations. Self collimation, ultra and negative refraction, second harmonic generation, mirage and invisibility effects which lead to an unprecedented control of light propagation at the (sub-)wavelength scale for the

  8. Employment Effects of Spatial Dispersal of Refugees

    DEFF Research Database (Denmark)

    Damm, Anna Piil; Rosholm, Michael

    Spatial dispersal policies may influence labour market integration of refugees through two mechanisms. First, it may affect the local job offer arrival rate, and second, it may affect place utility. We investigate the second mechanism theoretically by formulating a partial search model in which an...... individual searches simultaneously for a job and for a new residential location. The model predicts that the reservation wage for local jobs is decreasing in place utility. We argue that spatial dispersal policies decrease average place utility of refugees which decrease the transition rate into first job...

  9. Intrinsic quantum spin Hall and anomalous Hall effects in h-Sb/Bi epitaxial growth on a ferromagnetic MnO2 thin film

    Science.gov (United States)

    Zhou, Jian; Sun, Qiang; Wang, Qian; Kawazoe, Yoshiyuki; Jena, Puru

    2016-05-01

    Exploring a two-dimensional intrinsic quantum spin Hall state with a large band gap as well as an anomalous Hall state in realizable materials is one of the most fundamental and important goals for future applications in spintronics, valleytronics, and quantum computing. Here, by combining first-principles calculations with a tight-binding model, we predict that Sb or Bi can epitaxially grow on a stable and ferromagnetic MnO2 thin film substrate, forming a flat honeycomb sheet. The flatness of Sb or Bi provides an opportunity for the existence of Dirac points in the Brillouin zone, with its position effectively tuned by surface hydrogenation. The Dirac points in spin up and spin down channels split due to the proximity effects induced by MnO2. In the presence of both intrinsic and Rashba spin-orbit coupling, we find two band gaps exhibiting a large band gap quantum spin Hall state and a nearly quantized anomalous Hall state which can be tuned by adjusting the Fermi level. Our findings provide an efficient way to realize both quantized intrinsic spin Hall conductivity and anomalous Hall conductivity in a single material.Exploring a two-dimensional intrinsic quantum spin Hall state with a large band gap as well as an anomalous Hall state in realizable materials is one of the most fundamental and important goals for future applications in spintronics, valleytronics, and quantum computing. Here, by combining first-principles calculations with a tight-binding model, we predict that Sb or Bi can epitaxially grow on a stable and ferromagnetic MnO2 thin film substrate, forming a flat honeycomb sheet. The flatness of Sb or Bi provides an opportunity for the existence of Dirac points in the Brillouin zone, with its position effectively tuned by surface hydrogenation. The Dirac points in spin up and spin down channels split due to the proximity effects induced by MnO2. In the presence of both intrinsic and Rashba spin-orbit coupling, we find two band gaps exhibiting a large

  10. Anomalous lattice expansion in yttria stabilized zirconia under simultaneous applied electric and thermal fields: A time-resolved in situ energy dispersive x-ray diffractometry study with an ultrahigh energy synchrotron probe

    Energy Technology Data Exchange (ETDEWEB)

    Akdogan, E. K.; Savkl Latin-Small-Letter-Dotless-I y Latin-Small-Letter-Dotless-I ld Latin-Small-Letter-Dotless-I z, I.; Bicer, H.; Paxton, W.; Toksoy, F.; Tsakalakos, T. [Department of Materials Science and Engineering, Rutgers University, Piscataway, New Jersey 08854-8065 (United States); Zhong, Z. [National Synchrotron Light Source, Brookhaven National Laboratory, Upton, New York 11973 (United States)

    2013-06-21

    Nonisothermal densification in 8% yttria doped zirconia (8YSZ) particulate matter of 250 nm median particle size was studied under 215 V/cm dc electric field and 9 Degree-Sign C/min heating rate, using time-resolved in-situ high temperature energy dispersive x-ray diffractometry with a polychromatic 200 keV synchrotron probe. Densification occurred in the 876-905 Degree-Sign C range, which resulted in 97% of the theoretical density. No local melting at particle-particle contacts was observed in scanning electron micrographs, implying densification was due to solid state mass transport processes. The maximum current draw at 905 Degree-Sign C was 3 A, corresponding to instantaneous absorbed power density of 570 W/cm{sup 3}. Densification of 8YSZ was accompanied by anomalous elastic volume expansions of the unit cell by 0.45% and 2.80% at 847 Degree-Sign C and 905 Degree-Sign C, respectively. The anomalous expansion at 905 Degree-Sign C at which maximum densification was observed is characterized by three stages: (I) linear stage, (II) anomalous stage, and (III) anelastic recovery stage. The densification in stage I (184 s) and II (15 s) was completed in 199 s, while anelastic relaxation in stage III lasted 130 s. The residual strains ({epsilon}) at room temperature, as computed from tetragonal (112) and (211) reflections, are {epsilon}{sub (112)} = 0.05% and {epsilon}{sub (211)} = 0.13%, respectively. Time dependence of (211) and (112) peak widths ({beta}) show a decrease with both exhibiting a singularity at 905 Degree-Sign C. An anisotropy in (112) and (211) peak widths of {l_brace} {beta}{sub (112)}/{beta}{sub (211)}{r_brace} = (3:1) magnitude was observed. No phase transformation occurred at 905 Degree-Sign C as verified from diffraction spectra on both sides of the singularity, i.e., the unit cell symmetry remains tetragonal. We attribute the reduction in densification temperature and time to ultrafast ambipolar diffusion of species arising from the

  11. Quantum Anomalous Hall Effect in Hg$_{1-y}$Mn$_{y}$Te Quantum Wells

    OpenAIRE

    Liu, Chao-Xing; Qi, Xiao-Liang; Dai, Xi; Fang, Zhong; Zhang, Shou-Cheng

    2008-01-01

    The quantum Hall effect is usually observed when the two-dimensional electron gas is subjected to an external magnetic field, so that their quantum states form Landau levels. In this work we predict that a new phenomenon, the quantum anomalous Hall effect, can be realized in Hg$_{1-y}$Mn$_{y}$Te quantum wells, without the external magnetic field and the associated Landau levels. This effect arises purely from the spin polarization of the $Mn$ atoms, and the quantized Hall conductance is predi...

  12. When effective theories predict: the inevitability of Mercury's anomalous perihelion precession

    CERN Document Server

    Wells, James D

    2012-01-01

    If the concepts underlying Effective Theory were appreciated from the earliest days of Newtonian gravity, Le Verrier's announcement in 1845 of the anomalous perihelion precession of Mercury would have been no surprise. Furthermore, the size of the effect could have been anticipated through "naturalness" arguments well before the definitive computation in General Relativity. Thus, we have an illustration of how Effective Theory concepts can guide us in extending our knowledge to "new physics", and not just in how to reduce larger theories to restricted (e.g., lower energy) domains.

  13. Anomalous coupling, top-mass and parton-shower effects in W + W - production

    Science.gov (United States)

    Bellm, J.; Gieseke, S.; Greiner, N.; Heinrich, G.; Plätzer, S.; Reuschle, C.; von Soden-Fraunhofen, J. F.

    2016-05-01

    We calculate the process ppto {W}+{W}-to {e}+{ν}_e{μ}-{overline{ν}}_{μ } at NLO QCD, including also effective field theory (EFT) operators mediating the ggW + W - interaction, which first occur at dimension eight. We further combine the NLO and EFT matrix elements produced by G oS am with the H erwig7/M atchbox framework, which offers the possibility to study the impact of a parton shower. We assess the effects of the anomalous couplings by comparing them to top-mass effects as well as uncertainties related to variations of the renormalisation, factorisation and hard shower scales.

  14. Polarization of free electrons by means of resonance microwave pumping using normal and anomalous doppler effect

    International Nuclear Information System (INIS)

    The method of electron polarization by pumping the electron spin resonance (ESR), using a running wave with a phase velocity close to the electron beam velocity,is proposed. Repeatedly alternating pumping by the following wave and by the counter wave, it is possible to realize nearly full electron polarization. Similar,and even more effective, this method can make electron polarization using alternation of a normal Doppler effect on the following wave (thus the wave phase velocity exceeds the velocity of the beam) and an anomalous Doppler effect on the following wave too (when, on the contrary, the velocity of the beam exceeds the phase velocity of the wave)

  15. Sex-biased dispersal promotes adaptive parental effects

    OpenAIRE

    Franc Alain; Revardel Emmanuelle; Petit Rémy J

    2010-01-01

    Abstract Background In heterogeneous environments, sex-biased dispersal could lead to environmental adaptive parental effects, with offspring selected to perform in the same way as the parent dispersing least, because this parent is more likely to be locally adapted. We investigate this hypothesis by simulating varying levels of sex-biased dispersal in a patchy environment. The relative advantage of a strategy involving pure maternal (or paternal) inheritance is then compared with a strategy ...

  16. The effect of dispersion mechanisms on aroma delivery

    OpenAIRE

    Pearson, Kris S.K.

    2005-01-01

    Dispersion of aroma compounds in food matrices is a common process in the production of many food products. However, the degrees of dispersion on the distribution and subsequent release of these compounds during consumption may have considerable consequences for perception of these flavours. This thesis investigates the effects of a range of dispersion techniques on the delivery and release of aroma compounds from several solid and semi-solid matrices which commonly contain added flavouri...

  17. Spectrum of anomalous magnetohydrodynamics

    Science.gov (United States)

    Giovannini, Massimo

    2016-05-01

    The equations of anomalous magnetohydrodynamics describe an Abelian plasma where conduction and chiral currents are simultaneously present and constrained by the second law of thermodynamics. At high frequencies the magnetic currents play the leading role, and the spectrum is dominated by two-fluid effects. The system behaves instead as a single fluid in the low-frequency regime where the vortical currents induce potentially large hypermagnetic fields. After deriving the physical solutions of the generalized Appleton-Hartree equation, the corresponding dispersion relations are scrutinized and compared with the results valid for cold plasmas. Hypermagnetic knots and fluid vortices can be concurrently present at very low frequencies and suggest a qualitatively different dynamics of the hydromagnetic nonlinearities.

  18. Employment effects of spatial dispersal of refugees

    DEFF Research Database (Denmark)

    Damm, Anna Piil; Rosholm, Michael

    2010-01-01

    Refugees subjected to a spatial dispersal tend to be assigned to a location outside the immigrant-dense cities. We argue that such locations are associated with low place utility. Our partial equilibrium search model with simultaneous job and residential location search predicts that the reservat...

  19. Ice Ih anomalies: Thermal contraction, anomalous volume isotope effect, and pressure-induced amorphization

    Science.gov (United States)

    Salim, Michael A.; Willow, Soohaeng Yoo; Hirata, So

    2016-05-01

    Ice Ih displays several anomalous thermodynamic properties such as thermal contraction at low temperatures, an anomalous volume isotope effect (VIE) rendering the volume of D2O ice greater than that of H2O ice, and a pressure-induced transition to the high-density amorphous (HDA) phase. Furthermore, the anomalous VIE increases with temperature, despite its quantum-mechanical origin. Here, embedded-fragment ab initio second-order many-body perturbation (MP2) theory in the quasiharmonic approximation (QHA) is applied to the Gibbs energy of an infinite, proton-disordered crystal of ice Ih at wide ranges of temperatures and pressures. The quantum effect of nuclei moving in anharmonic potentials is taken into account from first principles without any empirical or nonsystematic approximation to either the electronic or vibrational Hamiltonian. MP2 predicts quantitatively correctly the thermal contraction at low temperatures, which is confirmed to originate from the volume-contracting hydrogen-bond bending modes (acoustic phonons). It qualitatively reproduces (but underestimates) the thermal expansion at higher temperatures, caused by the volume-expanding hydrogen-bond stretching (and to a lesser extent librational) modes. The anomalous VIE is found to be the result of subtle cancellations among closely competing isotope effects on volume from all modes. Consequently, even ab initio MP2 with the aug-cc-pVDZ and aug-cc-pVTZ basis sets has difficulty reproducing this anomaly, yielding qualitatively varied predictions of the sign of the VIE depending on such computational details as the choice of the embedding field. However, the temperature growth of the anomalous VIE is reproduced robustly and is ascribed to the librational modes. These solid-state MP2 calculations, as well as MP2 Born-Oppenheimer molecular dynamics, find a volume collapse and a loss of symmetry and long-range order in ice Ih upon pressure loading of 2.35 GPa or higher. Concomitantly, rapid softening of

  20. Spin Seebeck Effect vs. Anomalous Nernst Effect in Ta/CoFeB /Ta Structures

    Science.gov (United States)

    Yang, Bowen; Xu, Yadong; Schneider, Mike; Shi, Jing; Univ of California-Riverside Team; Everspin Technologies Inc. Team

    2014-03-01

    We have studied the spin Seebeck effect (SSE) and anomalous Nernst effect (ANE) in a vertical trilayer structure under a vertical temperature gradient. The structure consists of a 3nm CoFeB layer sandwiched by β-phase tantalum (Ta) layers. The samples are deposited by magnetron sputtering. The existence of Ta β-phase is verified by the resistivity and its negative temperature coefficient of resistance(TCR). Under a fixed vertical temperature gradient, the measured transverse thermoelectric voltage is linearly proportional to the total sample resistance when the Ta thickness exceeds 2 nm, which can be explained by a shunting resistor model. When the Ta thickness is below 2 nm, the voltage deviates from the linear resistance dependence and merges to the ANE voltage of the CoFeB single layer, due to a weakened inverse spin Hall effect (ISHE) in Ta thinner than the spin diffusion length. In the linear regime, the slope contains both a varying SSE and a fixed ANE responses, thus the SSE contribution could be quantitatively separated out from the ANE of CoFeB. Our results indicate a large SSE from the β-phase Ta due to its large Spin Hall Angle. This work was supported by CNN/DMEA and DOE.

  1. Effect of third-order dispersion on dark solitons

    Science.gov (United States)

    Afanasjev, Vsevolod V.; Kivshar, Yuri S.; Menyuk, Curtis R.

    1996-12-01

    Third-order dispersion has a detrimental effect on dark solitons, leading to resonant generation of growing soliton tails and soliton decay. This effect is shown to be much stronger than that for bright solitons.

  2. Effect of Center High Explosive in Dispersion of Fuel

    Institute of Scientific and Technical Information of China (English)

    张奇; 林大超; 白春华; 郭彦懿

    2004-01-01

    The dispersion of the fuel due to the center high explosive, including several different physical stages, is analyzed by means of experimental results observed with a high speed motion analysis system, and the effect of center high explosive charge is suggested. The process of the fuel dispersion process can be divided into three main stages, acceleration, deceleration and turbulence. Within a certain scope, the radius of the final fuel cloud dispersed is independent of the center explosive charge mass in an FAE (fuel air explosive) device, while only dependent both on the duration of acceleration stage and on that of the deceleration. In these two stages, the dispersion of the fuel dust mainly occurs along the radial direction. There is a close relation between the fuel dispersion process and the center explosive charge mass. To describe the motion of fuel for different stages of dispersion, different mechanical models should be applied.

  3. Measurement of the intrinsic anomalous Hall effect in a 2D hole system with Rashba spin-orbit coupling

    International Nuclear Information System (INIS)

    The anomalous Hall effect of two-dimensional holes in a GaAs/AlGaAs heterostructure was measured under a slightly tilted-from-parallel magnetic field (B). In addition to the dominant ordinary Hall resistivity, which is linear in B, there is a small anomalous Hall resistivity correlated with the perpendicular spin magnetization of the holes due to the subband depopulation. When the anomalous Hall conductivity (σAxy) is extracted from the experimental data, it exhibits a nonmonotonic dependence on B, a behavior expected for the intrinsic anomalous Hall effect in the 2D Rashba model. If σAxy is plotted as a function of the longitudinal conductivity (σxx), an intrinsic region in which σAxy is almost constant and is several tenths of e2/h for σxx of several tens of e2/h is identified.

  4. Anomalous Josephson Effect in Junctions with Rashba Spin-Orbit Coupling

    Science.gov (United States)

    Nesterov, Konstantin; Houzet, Manuel; Meyer, Julia

    2015-03-01

    We study two-dimensional double-barrier SINIS Josephson junctions in which the inversion symmetry in the normal part is broken by Rashba spin-orbit coupling. In the presence of a suitably oriented Zeeman field in the normal part, the system displays the anomalous Josephson effect: the current is nonzero even at zero phase difference between two superconductors. We investigate this effect by means of the Ginzburg-Landau formalism and microscopic Green's functions approach in the clean limit. This work was supported in part by the Grants No. ANR-12-BS04-0016-03 and an EU-FP7 Marie Curie IRG.

  5. Anomalous acoustic effect during martensitic transformations in titanium nickelide base alloys

    International Nuclear Information System (INIS)

    One carried out experiments to determine effect of external static stress on martensitic transformations and acoustic emission, Martensitic transformations in titanium nickelide base alloys under mechanical stress were determined to change nature of acoustic emission to anomalous one - cycling of transformations under gradual increase of mechanical stress during direct martensitic transformation was followed by increase of acoustic emission energy instead of reduction. The mentioned nature of acoustic emission is indicative of essential effect of external stress on martensitic transformations and energy dissipation during transformations

  6. Inverted effective SUSY with combined Z' and gravity mediation, and muon anomalous magnetic moment

    OpenAIRE

    Kim, Jihn E.

    2012-01-01

    Effective supersymmetry(SUSY) where stop is the lightest squark may run into a two-loop tachyonic problem in some Z' mediation models. In addition, a large A term or/and a large stop mass are needed to have about a 126 GeV Higgs boson with three families of quarks and leptons. Thus, we suggest an inverted effective SUSY(IeffSUSY) where stop mass is larger compared to those of the first two families. In this case, it is possible to have a significant correction to the anomalous magnetic moment...

  7. Stacking order dependence of inverse spin Hall effect and anomalous Hall effect in spin pumping experiments

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sang-Il; Seo, Min-Su; Park, Seung-Young, E-mail: parksy@kbsi.re.kr [Division of Materials Science, Korea Basic Science Institute, Daejeon 305-806 (Korea, Republic of); Kim, Dong-Jun; Park, Byong-Guk [Department of Materials Science and Engineering, KAIST, Daejeon 305-701 (Korea, Republic of)

    2015-05-07

    The dependence of the measured DC voltage on the non-magnetic material (NM) in NM/CoFeB and CoFeB/NM bilayers is studied under ferromagnetic resonance conditions in a TE{sub 011} resonant cavity. The directional change of the inverse spin Hall effect (ISHE) voltage V{sub ISHE} for the stacking order of the bilayer can separate the pure V{sub ISHE} and the anomalous Hall effect (AHE) voltage V{sub AHE} utilizing the method of addition and subtraction. The Ta and Ti NMs show a broad deviation of the spin Hall angle θ{sub ISH}, which originates from the AHE in accordance with the high resistivity of NMs. However, the Pt and Pd NMs show that the kinds of NMs with low resistivity are consistent with the previously reported θ{sub ISH} values. Therefore, the characteristics that NM should simultaneously satisfy to obtain a reasonable V{sub ISHE} value in bilayer systems are large θ{sub ISH} and low resistivity.

  8. The structure of the rare-earth phosphate glass (Sm2O3)0.205(P2O5)0.795 studied by anomalous dispersion neutron diffraction

    International Nuclear Information System (INIS)

    The role of the Sm3+ ions in the structure of vitreous Sm2O3·4P2O5 has been investigated using the neutron diffraction anomalous dispersion technique, which employs the wavelength dependence of the real and imaginary parts of the neutron scattering length close to an absorption resonance. The data described here represent the first successful complete neutron anomalous dispersion study on an amorphous material. This experimental methodology permits one to determine exclusively the closest Sm-Sm separation. Knowledge of the R - R (R = rare-earth) pairwise correlation is key to understanding the optical and magnetic properties of rare-earth phosphate glasses. The anomalous difference correlation function, ΔT''(r), shows a dominant feature pertaining to a Sm - Sm separation, centred at 4.8 A. The substantial width and marked asymmetry of this peak indicates that the minimum approach of Sm3+ ions could be as close as 4 A. Information on other pairwise correlations is also revealed via analysis of T(r) and ΔT(r) correlation functions: Sm3+ ions display an average co-ordination number, nSm(O), of 7, with a mean Sm-O bond length of 2.375(5) A whilst the PO4 tetrahedra have a mean P-O bond length of 1.538(2) A. Second- and third-neighbour correlations are also identified. These results corroborate previous findings. Such consistency lends support to the application of the anomalous dispersion technique to determine Sm - Sm separations

  9. Effect of anomalous vertex on decay-lepton distributions in + -→ t\\overline{t}$ and CP-violating asymmetries

    Indian Academy of Sciences (India)

    Saurabh D Rindani

    2000-06-01

    We obtain analytic expressions for the energy and polar-angle double differential distributions of a secondary lepton +(-) arising from the decay of ($\\overline{t}$) in + - → $t\\overline{t}$ with an anomalous decay vertex. We also obtain analytic expressions for the various differential cross-sections with the lepton energy integrat ed over. In this case, we find that the angular distributions of the secondary lepton do not depend on the anomalous coupling in the decay, regardless of possible anomalous couplings occurring in the production amplitude for + - → $t\\overline{t}$. Our study includes the effect of longitudinal - and + beam polarization. We also study the lepton energy and beam polarization dependence of certain CP-violating lepton angular asymmetries arising from an anomalous decay vertex and compare them with the asymmetries arising due to CP-violation in the production process due to the top electric or weak dipole moment.

  10. Evaluation of three oil spill laboratory dispersant effectiveness tests

    Energy Technology Data Exchange (ETDEWEB)

    Sullivan, D.; Farlow, J.; Sahatjian, K.A.

    1993-01-01

    EPA evaluated three laboratory methods: the Revised Standard Dispersant Effectiveness Test currently used (and currently required by regulation) in the United States, the Swirling Flask Test (developed by Environment Canada), and the IFP-Dilution Test (used in France and other European countries). Six test oils and three dispersants were evaluated; dispersants were applied to the oil at an average 1:10 ratio (dispersant to oil) for each of the three laboratory methods. A screening criterion was established that required a combination that gave at least 20 percent effectiveness results. The selected combination turned out to be Prudhoe Bay crude oil (an EPA-American Petroleum Institute Standard Reference Oil) and the dispersant Corexit 9527. EPA's evaluation concluded that the three tests give similar precision results, but that the Swirling Flask Test was fastest, cheapest, simplest, and required least operator skill.

  11. From magnetically doped topological insulator to the quantum anomalous Hall effect

    Institute of Scientific and Technical Information of China (English)

    He Ke; Ma Xu-Cun; Chen Xi; Lü Li; Wang Ya-Yu; Xue Qi-Kun

    2013-01-01

    Quantum Hall effect (QHE),as a class of quantum phenomena that occur in macroscopic scale,is one of the most important topics in condensed matter physics.It has long been expected that QHE may occur without Landau levels so that neither extemal magnetic field nor high sample mobility is required for its study and application.Such a QHE free of Landau levels,can appear in topological insulators (TIs) with ferromagnetism as the quantized version of the anomalous Hall effect,i.e.,quantum anomalous Hall (QAH) effect.Here we review our recent work on experimental realization of the QAH effect in magnetically doped TIs.With molecular beam epitaxy,we prepare thin films of Cr-doped (Bi,Sb)2Te3 TIs with wellcontrolled chemical potential and long-range ferromagnetic order that can survive the insulating phase.In such thin films,we eventually observed the quantization of the Hall resistance at h/e2 at zero field,accompanied by a considerable drop in the longitudinal resistance.Under a strong magnetic field,the longitudinal resistance vanishes,whereas the Hall resistance remains at the quantized value.The realization of the QAH effect provides a foundation for many other novel quantum phenomena predicted in TIs,and opens a route to practical applications of quantum Hall physics in low-power-consumption electronics.

  12. Effectiveness of chemical dispersants under breaking wave conditions

    Energy Technology Data Exchange (ETDEWEB)

    Mackay, D. [Univ. of Toronto, Ontario (Canada). Chemical Engineering Dept.

    1995-06-01

    A study is described in which the effectiveness of Corexit 9527 on Alaskan North Slope crude oil was assessed by conducting laboratory and wave basin tests. Three laboratory dispersant test systems were used: the MNS, Labofina and EXDET procedures. It was concluded that for the present purposes the EXDET system was most suitable, and it was used for subsequent tests. The dependence of effectiveness on dispersant to oil ratio, extent of weathering, temperature, water salinity, energy level and the presence of emulsified water (mousse) were determined. The results were used to guide a subsequent program of tests at the Esso Resources Canada Ltd. Wave Basin in Calgary in which the effectiveness was determined under breaking wave conditions. From the results a correlating equation was developed to express effectiveness as a function of dispersant to oil ratio and delay time between dispersant application and the onset of breaking waves. Significant quantities of oil were dispersed under breaking wave conditions, even at what are conventionally regarded as low dispersant to oil ratios. The implications of the results for assessing the actual and potential extent of chemical dispersion following the Exxon Valdez spill in March 1989 are discussed. Assuming that the dispersion efficiencies from the wave basin could have been achieved at the incident, it is believed that because of the onset of the storm with breaking wave conditions some 60 hours after the grounding, approximately 38% of the spilled oil could have been dispersed had available dispersants been applied to the spilled oil in the days following the grounding.

  13. Experimental research of electron beam instability on the Doppler anomalous effect

    International Nuclear Information System (INIS)

    Beam instability caused by the Doppler anomalous effect (DAE) at electron beam interaction with the decelerating electrodynamic system (a resonator with a single-thread spiral and a resonator with a space-periodic structure) placed in the external homogeneous field are studied experimentally to investigate main mechanisms of instability of charged particle beams. Such general properties of DAE as resonance conditions for instability excitation, increase of the internal energy of oscillators (Larmor and Langmuir) during radiation, energy ratios for slow cyclotron and plasma waves of an electron beam are studied. Good agreement between experimental and theoretical results is obtained

  14. 3d Transition Metal Adsorption Induced the valley-polarized Anomalous Hall Effect in Germanene

    Science.gov (United States)

    Zhou, P.; Sun, L. Z.

    2016-06-01

    Based on DFT + U and Berry curvature calculations, we study the electronic structures and topological properties of 3d transition metal (TM) atom (from Ti to Co) adsorbed germanene (TM-germanene). We find that valley-polarized anomalous Hall effect (VAHE) can be realized in germanene by adsorbing Cr, Mn, or Co atoms on its surface. A finite valley Hall voltage can be easily detected in their nanoribbon, which is important for valleytronics devices. Moreover, different valley-polarized current and even reversible valley Hall voltage can be archived by shifting the Fermi energy of the systems. Such versatile features of the systems show potential in next generation electronics devices.

  15. Evidence of local effects in anomalous refraction and focusing properties of dodecagonal photonic quasicrystals

    CERN Document Server

    Di Gennaro, Emiliano; Savo, Salvatore; Andreone, Antonello; Morello, Davide; Galdi, Vincenzo; Castaldi, Giuseppe; Pierro, Vincenzo

    2008-01-01

    We present the key results from a comprehensive study of the refraction and focusing properties of a two-dimensional dodecagonal photonic ``quasicrystal'' (PQC), carried out via both full-wave numerical simulations and microwave measurements on a slab made of alumina rods inserted in a parallel-plate waveguide. We observe anomalous refraction and focusing in several frequency regions, confirming some recently published results. However, our interpretation, based on numerical and experimental evidence, differs substantially from the one in terms of ``effective negative refractive-index'' that was originally proposed. Instead, our study highlights the critical role played by short-range interactions associated with local order and symmetry.

  16. Hysteretic magnetoresistance and unconventional anomalous Hall effect in the frustrated magnet TmB4

    Science.gov (United States)

    Sunku, Sai Swaroop; Kong, Tai; Ito, Toshimitsu; Canfield, Paul C.; Shastry, B. Sriram; Sengupta, Pinaki; Panagopoulos, Christos

    2016-05-01

    We study TmB4, a frustrated magnet on the Archimedean Shastry-Sutherland lattice, through magnetization and transport experiments. The lack of anisotropy in resistivity shows that TmB4 is an electronically three-dimensional system. The magnetoresistance (MR) is hysteretic at low temperature even though a corresponding hysteresis in magnetization is absent. The Hall resistivity shows unconventional anomalous Hall effect (AHE) and is linear above saturation despite a large MR. We propose that complex structures at magnetic domain walls may be responsible for the hysteretic MR and may also lead to the AHE.

  17. Global Constraints on Anomalous Triple Gauge Couplings in the Effective Field Theory Approach

    Science.gov (United States)

    Falkowski, Adam; González-Alonso, Martín; Greljo, Admir; Marzocca, David

    2016-01-01

    We present a combined analysis of LHC Higgs data (signal strengths) together with LEP-2 W W production measurements. To characterize possible deviations from the standard model (SM) predictions, we employ the framework of an effective field theory (EFT) where the SM is extended by higher-dimensional operators suppressed by the mass scale of new physics Λ . The analysis is performed consistently at the order Λ-2 in the EFT expansion keeping all the relevant operators. While the two data sets suffer from flat directions, together they impose stringent model-independent constraints on the anomalous triple gauge couplings.

  18. Anomalous transport model study of chiral magnetic effects in heavy ion collisions

    CERN Document Server

    Sun, Yifeng; Li, Feng

    2016-01-01

    Using an anomalous transport model for massless quarks, we study the effect of magnetic field on the elliptic flows of quarks and antiquarks in relativistic heavy ion collisions. With initial conditions from a blast wave model and assuming that the strong magnetic field produced in non-central heavy ion collisions can last for a sufficiently long time, we obtain an appreciable electric quadrupole moment in the transverse plane of a heavy ion collision, which subsequently leads to a splitting between the elliptic flows of quarks and antiquarks as expected from the chiral magnetic wave formed in the produced QGP and observed in experiments at the Relativistic Heavy Ion Collider (RHIC).

  19. Anomalous Hall effect of heavy holes in Ⅲ-Ⅴ semiconductor quantum wells

    Institute of Scientific and Technical Information of China (English)

    Wang Zhi-Gang; Zhang Ping

    2007-01-01

    The anomalous Hall effect of heavy holes in semiconductor quantum wells is studied in the intrinsic transport regime, where the Berry curvature governs the Hall current properties. Based on the first-order perturbation of wave function the expression of the Hall conductivity the same as that from the semiclassical equation of motion of the Bloch particles is derived. The dependence of Hall conductivity on the system parameters is shown. The amplitude of Hall conductivity is found to be balanced by a competition between the Zeeman splitting and the spin-orbit splitting.

  20. Nonadiabatic effects in ultracold molecules via anomalous linear and quadratic Zeeman shifts.

    Science.gov (United States)

    McGuyer, B H; Osborn, C B; McDonald, M; Reinaudi, G; Skomorowski, W; Moszynski, R; Zelevinsky, T

    2013-12-13

    Anomalously large linear and quadratic Zeeman shifts are measured for weakly bound ultracold 88Sr2 molecules near the intercombination-line asymptote. Nonadiabatic Coriolis coupling and the nature of long-range molecular potentials explain how this effect arises and scales roughly cubically with the size of the molecule. The linear shifts yield nonadiabatic mixing angles of the molecular states. The quadratic shifts are sensitive to nearby opposite f-parity states and exhibit fourth-order corrections, providing a stringent test of a state-of-the-art ab initio model. PMID:24483652

  1. Measurement of Nonadiabatic Effects in Ultracold Molecules via Anomalous Linear and Quadratic Zeeman Shifts

    CERN Document Server

    McGuyer, B H; McDonald, M; Reinaudi, G; Skomorowski, W; Moszynski, R; Zelevinsky, T

    2013-01-01

    Anomalously large linear and quadratic Zeeman shifts are measured for weakly bound ultracold $^{88}$Sr$_2$ molecules near the intercombination line asymptote. Nonadiabatic Coriolis coupling and the nature of long-range molecular potentials explain how this effect arises and scales roughly cubically with the size of the molecule. The linear shifts yield nonadiabatic mixing angles of the molecular states. The quadratic shifts are sensitive to fourth-order contributions and to nearby opposite $f$-parity states, and provide a stringent test of a state-of-the-art ab initio model.

  2. Evaluating Chemical Dispersant Efficacy In An Experimental Wave Tank: 1, Dispersant Effectiveness As A Function Of Energy Dissipation Rate

    Science.gov (United States)

    Numerous laboratory test systems have been developed for the comparison of efficacy between various chemical oil dispersant formulations. However, for the assessment of chemical dispersant effectiveness under realistic sea state, test protocols are required to produce hydrodynam...

  3. Dispersant effectiveness testing in cold water and brash ice

    Energy Technology Data Exchange (ETDEWEB)

    Owens, C.K. [ExxonMobil Upstream Research Co., Houston, TX (United States); Belore, R.S. [S.L. Ross Environmental Research Ltd., Ottawa, ON (Canada)

    2004-07-01

    This paper presents the results of a wave tank test conducted at OHMSETT to determine the effectiveness of chemical dispersants on oil spilled in brash ice. In particular, Alaska North Slope, Hibernia and Chayvo crude oils were tested and the factors affecting the dispersion process were examined. The dispersant, Corexit 9527 was tested on both fresh and weathered oils under cold water and icy conditions. Dispersion was observed for waves with 17 cm average height and a 5.5 second period, as well as with waves of 33 cm average height and 4 second period. The energy level in the tank was much lower than typically found in open waters. The presence of ice enhanced the dispersion processes compared to what would occur in similar open water conditions. Higher wave energy levels were needed to disperse oil in rings containing a 4/10 ice cover than in rings containing a 8/10 ice cover. This result is likely due to the the higher surface activity observed in the 8/10 covered rings. More than 90 per cent dispersion was achieved in all tests with fresh crude oil in ice. For weathered crudes, the dispersion was less effective but still significant. 11 refs., 4 tabs., 12 figs.

  4. The effectiveness of dispersants under various temperature and salinity regimes

    Energy Technology Data Exchange (ETDEWEB)

    Fingas, M.; Fieldhouse, B.; Wang, Z. [Environment Canada, Ottawa, ON (Canada). Emergencies Science and Technology Div; Environment Canada, Ottawa, ON (Canada). Environmental Technology Centre

    2005-07-01

    A series of tests were conducted to determine the effectiveness of dispersants in Arctic waters where salinity and temperature interactions play a critical role. In particular, Corexit 9500 was tested on Alaska North Slope oil at different temperatures and salinity using the ASTM standard test and variations of this test. Results were compared to the only historically reported test in which both temperature and salinity were changed over a range of values. This series of tests demonstrated that there is an interaction between salinity, temperature and dispersant effectiveness. It was shown that conventional and currently available dispersants are nearly ineffective at 0 salinity. Dispersant effectiveness peaks at 20 to 40 units of salinity, depending on the type of dispersant. Corexit is less sensitive to salinity, while Corexit 9527 is more sensitive to salinity. There is a smooth gradient of effectiveness with salinity both as the salinity rises to a peak point of effectiveness and as it exceeds this value. Results from the 2 field trials in fresh water suggest that laboratory tests correctly conclude that the effectiveness of dispersants is very low in freshwater. The study also examined several analytical factors such as the total petroleum hydrocarbon (TPH) versus relative petroleum hydrocarbon (RPH) methods, specific versus general calibration curves, and automatic versus manual baseline placement. The analytical variations of effectiveness by RPH or TPH methods do not affect the fundamental relationship between salinity and temperature. 6 refs., 6 tabs., 8 figs.

  5. Identification of Dispersion Effects in 2k Factorial Design

    OpenAIRE

    Viviane Leite Mattos; Pedro Alberto Barbetta; Dalton Francisco de Andrade

    2010-01-01

    The identification of dispersion effects is a very important stage in developing robust products and processes. Several methods to identify dispersion effects are present in statistical and quality engineering literature, especially methods which use 2K or 2K-p
    unreplicated factorial designs, such as Box-Meyer, Harvey, Brenemann-Nair and Bergman- Hynén methods. In this paper we considered generalizations of these methods for replicated
    experiments, and compare...

  6. Shade Effects on the Dispersal of Airborne Hemileia vastatrix Uredospores.

    Science.gov (United States)

    Boudrot, Audrey; Pico, Jimmy; Merle, Isabelle; Granados, Eduardo; Vílchez, Sergio; Tixier, Philippe; Filho, Elías de Melo Virginio; Casanoves, Fernando; Tapia, Ana; Allinne, Clémentine; Rice, Robert A; Avelino, Jacques

    2016-06-01

    Hemileia vastatrix caused a severe epidemic in Central America in 2012-13. The gradual development of that epidemic on nearly a continental scale suggests that dispersal at different scales played a significant role. Shade has been proposed as a way of reducing uredospore dispersal. The effect of shade (two strata: Erythrina poeppigiana below and Chloroleucon eurycyclum above) and full sun on H. vastatrix dispersal was studied with Burkard traps in relation to meteorological records. Annual and daily patterns of dispersal were observed, with peaks of uredospore capture obtained during wet seasons and in the early afternoon. A maximum of 464 uredospores in 1 day (in 14.4 m(3) of air) was recorded in October 2014. Interactions between shade/full sun and meteorological conditions were found. Rainfall, possibly intercepted by tree cover and redistributed by raindrops of higher kinetic energy, was the main driver of uredospore dispersal under shade. Wind gusts reversed this effect, probably by inhibiting water accumulation on leaves. Wind gusts also promoted dispersal under dry conditions in full sun, whereas they had no effect under shaded conditions, probably because the canopy blocked the wind. Our results indicate the importance of managing shade cover differentially in rainy versus dry periods to control the dispersal of airborne H. vastatrix uredospores. PMID:26828230

  7. Dispersive force between dissimilar materials: Geometrical effects

    International Nuclear Information System (INIS)

    We calculate the Casimir force or dispersive van der Waals force between a spherical nanoparticle and a planar substrate, both with arbitrary dielectric properties. We show that the force between the sphere and half-space can be calculated through the interacting surface plasmons of the bodies. Using a Spectral Representation formalism, we show that the force of a sphere made of a material A and a half-space made of a material B differs from the case when the sphere is made of B, and the half-space is made of A. We find that the difference depends on the plasma frequency of the materials, the geometry, and the distance of separation between the sphere and half-space. The differences show the importance of the geometry, and make evident the necessity of realistic descriptions of the system beyond the Derjaguin Approximation or Proximity Theorem Approximation

  8. Large anomalous Hall effect in Pt interfaced with perpendicular anisotropy ferrimagnetic insulator

    Science.gov (United States)

    Tang, Chi; Sellappan, Pathikumar; Liu, Yawen; Garay, Javier; Shi, Jing; Shines Team

    We demonstrate the strain induced perpendicular magnetic anisotropy (PMA) in a ferrimagnetic insulator (FMI), Tm3Fe5O12 (TIG) and the first observation of large anomalous Hall effect (AHE) in TIG/Pt bilayers. Atomically flat TIG films were deposited by a laser molecular beam epitaxy system on (111)-orientated substituted gadolinium gallium garnet substrates. The strength of PMA could be effectively tuned by controlling the oxygen pressure during deposition. Sharp squared anomalous Hall hysteresis loops were observed in bilayers of TIG/Pt over a range of thicknesses of Pt, with the maximum AHE conductivity reaching 1 S/cm at room temperature. The AHE vanishes when a 5 nm Cu layer was inserted between Pt and TIG, strongly indicating the proximity-induced ferromagnetism in Pt. The large AHE in the bilayer structures demonstrates a potential use of PMA-FMI related heterostructures in spintronics. This work was supported as part of the SHINES, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award # SC0012670.

  9. Effect of Solvation Film on the Viscosity of Colloidal Dispersions

    Institute of Scientific and Technical Information of China (English)

    PENG Chang-Sheng; GU Qing-Bao; SONG Shao-Xian

    2005-01-01

    Viscosity is one of the most important properties of colloids in mixing, transportation, stabilization, energy consumption, and so on. According to Einstein's viscosity equation, the viscosity of a colloidal dispersion increases with the increase of particle concentration. And the equation can be applicable to all micro-particle dispersions, because the effect of solvation films coated on particles can be neglectable in that case. But with the decrease of particle size to nano-scale, the formation of solvation films on nano-particles can greatly affect the viscosity of a dispersion, and Einstein's equation may not be applicable to this case. In this work, one kind of micro-size silica particle and two kinds of nano-size silica particles were used to investigate the effect of solvation films on dispersion viscosity, dispersed in water and ethyl alcohol solvents, respectively. The results of theoretical calculation and experimental investigation show that the increase of viscosity is contributed from solvation films by more than 95 percent for nano-particle dispersions, while less than 10 percent for micro-particle dispersions.

  10. EFFECTS OF CHEMICAL DISPERSANTS AND MINERAL FINES ON CRUDE OIL DISPERSION IN A WAVE TANK UNDER BREAKING WAVES

    Science.gov (United States)

    The interaction of chemical dispersants and suspended sediments with crude oil influences the fate and transport of oil spills in coastal waters. A wave tank study was conducted to investigate the effects of chemical dispersants and mineral fines on the dispersion of oil and the ...

  11. Anomalous Hall effect in the prospective spintronic material Eu1‑x Gd x O integrated with Si

    Science.gov (United States)

    Parfenov, Oleg E.; Averyanov, Dmitry V.; Tokmachev, Andrey M.; Taldenkov, Alexander N.; Storchak, Vyacheslav G.

    2016-06-01

    Remarkable properties of EuO make it a versatile spintronic material. Despite numerous experimental and theoretical studies of EuO, little is known about the anomalous Hall effect in this ferromagnet. So far, the effect has not been observed in bulk EuO, though has been detected in EuO films with uncontrolled distribution of defects. In the present work doping is taken under control: epitaxial films of Gd-doped EuO are synthesized integrated with Si using molecular beam epitaxy and characterized with x-ray diffraction and magnetization measurements. Nanoscale transport studies reveal the anomalous Hall effect in the ferromagnetic region for samples with different Gd concentration. The saturated anomalous Hall effect conductivity value of 5.0 S·cm‑1 in Gd-doped EuO is more than an order of magnitude larger than those reported so far for Eu chalcogenides doped with anion vacancies.

  12. Anomalous Hall effect in the prospective spintronic material Eu1-x Gd x O integrated with Si.

    Science.gov (United States)

    Parfenov, Oleg E; Averyanov, Dmitry V; Tokmachev, Andrey M; Taldenkov, Alexander N; Storchak, Vyacheslav G

    2016-06-01

    Remarkable properties of EuO make it a versatile spintronic material. Despite numerous experimental and theoretical studies of EuO, little is known about the anomalous Hall effect in this ferromagnet. So far, the effect has not been observed in bulk EuO, though has been detected in EuO films with uncontrolled distribution of defects. In the present work doping is taken under control: epitaxial films of Gd-doped EuO are synthesized integrated with Si using molecular beam epitaxy and characterized with x-ray diffraction and magnetization measurements. Nanoscale transport studies reveal the anomalous Hall effect in the ferromagnetic region for samples with different Gd concentration. The saturated anomalous Hall effect conductivity value of 5.0 S·cm(-1) in Gd-doped EuO is more than an order of magnitude larger than those reported so far for Eu chalcogenides doped with anion vacancies. PMID:27165844

  13. Anomalous skin effects in relativistic parallel propagating weakly magnetized electron plasma waves

    International Nuclear Information System (INIS)

    Fully relativistic analysis of anomalous skin effects for parallel propagating waves in a weakly magnetized electron plasma is presented and general expressions for longitudinal and transverse permittivites are derived. It is found that the penetration depth for R- and L-waves increases as we move from non-relativistic to highly relativistic regime. The ambient magnetic field reduces/enhances the skin effects for R-wave/L-wave as the strength of the field is increased. In general, the weak magnetic field effects are pronounced for the weakly relativistic regime as compared with other relativistic cases. The results are also graphically illustrated. On switching off the magnetic field, previous results for field free case are retrieved [A. F. Alexandrov, A. S. Bogdankevich, and A. A. Rukhadze, Priniples of Plasma Electrodynamics (Springer-Verlag, Berlin, Heidelberg, 1984), Vol. 9, p. 106].

  14. Nanoparticles modulate autophagic effect in a dispersity-dependent manner

    Science.gov (United States)

    Huang, Dengtong; Zhou, Hualu; Gao, Jinhao

    2015-09-01

    Autophagy plays a key role in human health and disease, especially in cancer and neurodegeneration. Many autophagy regulators are developed for therapy. Diverse nanomaterials have been reported to induce autophagy. However, the underlying mechanisms and universal rules remain unclear. Here, for the first time, we show a reliable and general mechanism by which nanoparticles induce autophagy and then successfully modulate autophagy via tuning their dispersity. Various well-designed univariate experiments demonstrate that nanomaterials induce autophagy in a dispersity-dependent manner. Aggregated nanoparticles induce significant autophagic effect in comparison with well-dispersed nanoparticles. As the highly stable nanoparticles may block autophagic degradation in autolysosomes, endocytosis and intracellular accumulation of nanoparticles can be responsible for this interesting phenomenon. Our results suggest dispersity-dependent autophagic effect as a common cellular response to nanoparticles, reveal the relationship between properties of nanoparticles and autophagy, and offer a new alternative way to modulate autophagy.

  15. Anomalous scaling in magnetohydrodynamic turbulence: Effects of anisotropy and compressibility in the kinematic approximation

    Science.gov (United States)

    Antonov, N. V.; Kostenko, M. M.

    2015-11-01

    The field-theoretic renormalization group and the operator product expansion are applied to the model of passive vector (magnetic) field advected by a random turbulent velocity field. The latter is governed by the Navier-Stokes equation for compressible fluid, subject to external random force with the covariance ∝δ (t -t') k4 -d -y , where d is the dimension of space and y is an arbitrary exponent. From physics viewpoints, the model describes magnetohydrodynamic turbulence in the so-called kinematic approximation, where the effects of the magnetic field on the dynamics of the fluid are neglected. The original stochastic problem is reformulated as a multiplicatively renormalizable field-theoretic model; the corresponding renormalization group equations possess an infrared attractive fixed point. It is shown that various correlation functions of the magnetic field and its powers demonstrate anomalous scaling behavior in the inertial-convective range already for small values of y . The corresponding anomalous exponents, identified with scaling (critical) dimensions of certain composite fields ("operators" in the quantum-field terminology), can be systematically calculated as series in y . The practical calculation is performed in the leading one-loop approximation, including exponents in anisotropic contributions. It should be emphasized that, in contrast to Gaussian ensembles with finite correlation time, the model and the perturbation theory presented here are manifestly Galilean covariant.

  16. Anomalous scaling in magnetohydrodynamic turbulence: Effects of anisotropy and compressibility in the kinematic approximation.

    Science.gov (United States)

    Antonov, N V; Kostenko, M M

    2015-11-01

    The field-theoretic renormalization group and the operator product expansion are applied to the model of passive vector (magnetic) field advected by a random turbulent velocity field. The latter is governed by the Navier-Stokes equation for compressible fluid, subject to external random force with the covariance ∝ δ(t-t')k(4-d-y), where d is the dimension of space and y is an arbitrary exponent. From physics viewpoints, the model describes magnetohydrodynamic turbulence in the so-called kinematic approximation, where the effects of the magnetic field on the dynamics of the fluid are neglected. The original stochastic problem is reformulated as a multiplicatively renormalizable field-theoretic model; the corresponding renormalization group equations possess an infrared attractive fixed point. It is shown that various correlation functions of the magnetic field and its powers demonstrate anomalous scaling behavior in the inertial-convective range already for small values of y. The corresponding anomalous exponents, identified with scaling (critical) dimensions of certain composite fields ("operators" in the quantum-field terminology), can be systematically calculated as series in y. The practical calculation is performed in the leading one-loop approximation, including exponents in anisotropic contributions. It should be emphasized that, in contrast to Gaussian ensembles with finite correlation time, the model and the perturbation theory presented here are manifestly Galilean covariant. PMID:26651785

  17. Anomalous memory effect in the breakdown of low-pressure argon in a long discharge tube

    International Nuclear Information System (INIS)

    The characteristics of breakdown of argon in a long tube (with a gap length of 75 cm and diameter of 2.8 cm) at pressures of 1 and 5 Torr and stationary discharge currents of 5–40 mA were studied experimentally. The breakdown was initiated by paired positive voltage pulses with a rise rate of ∼108–109 V/s and duration of ∼1–10 ms. The time interval between pairs was varied in the range of Τ ∼ 0.1–1 s, and that between pulses in a pair was varied from τ = 0.4 ms to ≈Τ/2. The aim of this work was to detect and study the so-called “anomalous memory effect” earlier observed in breakdown in nitrogen. The effect consists in the dynamic breakdown voltage in the second pulse in a pair being higher than in the first pulse (in contrast to the “normal” memory effect, in which the relation between the breakdown voltages is opposite). It is found that this effect is observed when the time interval between pairs of pulses is such that the first pulse in a pair is in the range of the normal memory effect of the preceding pair (under the given conditions, Τ ≈ 0.1–0.4 s). In this case, at τ ∼ 10 ms, the breakdown voltage of the second pulse is higher than the reduced breakdown voltage of the first pulse. Optical observations of the ionization wave preceding breakdown in a long tube show that, in the range of the anomalous memory effect and at smaller values of τ, no ionization wave is detected before breakdown in the second pulse. A qualitative interpretation of the experimental results is given

  18. Partitioning of fresh crude oil between floating, dispersed and sediment phases: Effect of exposure order to dispersant and granular materials.

    Science.gov (United States)

    Boglaienko, Daria; Tansel, Berrin

    2016-06-15

    When three or more high and low energy substrates are mixed, wetting order can significantly affect the behavior of the mixture. We analyzed the phase distribution of fresh floating Louisiana crude oil into dispersed, settled and floating phases depending on the exposure sequence to Corexit 9500A (dispersant) and granular materials. In the experiments artificial sea water at salinity 34‰ was used. Limestone (2.00-0.300 mm) and quartz sand (0.300-0.075 mm) were used as the natural granular materials. Dispersant Corexit 9500A increased the amount of dispersed oil up to 33.76 ± 7.04%. Addition of granular materials after the dispersant increased dispersion of oil to 47.96 ± 1.96%. When solid particles were applied on the floating oil before the dispersant, oil was captured as oil-particle aggregates and removed from the floating layer. However, dispersant addition led to partial release of the captured oil, removing it from the aggregated form to the dispersed and floating phases. There was no visible oil aggregation with the granular materials when quartz or limestone was at the bottom of the flask before the addition of oil and dispersant. The results show that granular materials can be effective when applied from the surface for aggregating or dispersing oil. However, the granular materials in the sediments are not effective neither for aggregating nor dispersing floating oil. PMID:27019358

  19. Resonant cavity mode dependence of anomalous and inverse spin Hall effect

    International Nuclear Information System (INIS)

    The direct current electric voltage induced by the Inverse Spin Hall Effect (ISHE) and Anomalous Hall Effect (AHE) was investigated in the TE011 and TE102 cavities. The ISHE and AHE components were distinguishable through the fitting of the voltage spectrum. The unwanted AHE was minimized by placing the DUT (Device Under Test) at the center of both the TE011 and TE102 cavities. The voltage of ISHE in the TE011 cavity was larger than that in the TE102 cavity due to the higher quality factor of the former. Despite optimized centering, AHE voltage from TE011 cavity was also higher. The reason was attributed to the E-field distribution inside the cavity. In the case of the TE011 cavity, the DUT was easily exposed to the E-field in all directions. Therefore, the parasitic AHE voltage in the TE102 cavity was less sensitive than that in the TE011 cavity to decentering problem

  20. Anomalous finite-size effects for the mean-squared gyration radius of Gaussian random knots

    International Nuclear Information System (INIS)

    Anomalously strong finite-size effects have been observed for the mean square radius of gyration R2K of Gaussian random polygons with a fixed knot K as a function of the number N of polygonal nodes. Through computer simulations with N2K can be approximated by a power law, R2K∼N2νKeff, for several knots, where the effective exponents νKeff are larger than 0.5 and less than 0.6. Furthermore, a crossover occurs for the gyration radius of the trivial knot, when N is roughly equal to the characteristic length Nc of random knotting. Assuming an asymptotic fitting formula, we also discuss possible asymptotic behaviours for RK2 of Gaussian random polygons. (author). Letter-to-the-editor

  1. Scaling of Anomalous Hall Effects in Facing-Target Reactively Sputtered Fe4N Films

    KAUST Repository

    Zhang, Yan

    2015-05-13

    Anomalous Hall effect (AHE) in the reactively sputtered epitaxial and polycrystalline γ′-Fe4N films is investigated systematically. The Hall resistivity is positive in the entire temperature range. The magnetization, carrier density and grain boundaries scattering have a major impact on the AHE scaling law. The scaling exponent γ in the conventional scaling of is larger than 2 in both the epitaxial and polycrystalline γ′-Fe4N films. Although γ>2 has been found in heterogeneous systems due to the effects of the surface and interface scattering on AHE, γ>2 is not expected in homogenous epitaxial systems. We demonstrated that γ>2 results from residual resistivity (ρxx0) in γ′-Fe4N films. Furthermore, the side-jump and intrinsic mechanisms are dominant in both epitaxial and polycrystalline samples according to the proper scaling relation.

  2. Effect of polysaccharides on the gelatinization properties of cornstarch dispersions.

    Science.gov (United States)

    Xu, Zhiting; Zhong, Fang; Li, Yue; Shoemaker, Charles F; Yokoyama, Wallace H; Xia, Wenshui

    2012-01-18

    Konjac glucomannan (KG, neutral), carboxymethylcellulose (CMC, negatively charged), and chitosan (positively charged) were added to cornstarch dispersions to study the effect of polysaccharide-starch interactions on starch gelatinization properties. Pasting and retrogradation properties were measured with a rheometer and DSC. Swelling properties of the starch granules were determined by solubility index, swelling power, and particle size distribution. Depending on the nature of the different polysaccharides, viscosities of cornstarch dispersions were affected differently. The particle size distributions were not influenced by the addition of any of the polysaccharides. Swelling results showed that the KG and CMC molecules interacted with the released or partly released amylose in the cornstarch dispersions. This was correlated with the short-term retrogradation of the starch pastes being retarded by the additions of KG and CMC. However, the chitosan molecules appeared not to associate with the amylose, so the retrogradation of the chitosan-cornstarch dispersions was not retarded. PMID:22224479

  3. Toxic effects of oil and dispersant on marine microalgae.

    Science.gov (United States)

    Garr, Amber L; Laramore, Susan; Krebs, William

    2014-12-01

    To better understand the potential impacts of the deepwater horizon oil spill on lower trophic level food sources, a series of toxicological laboratory experiments were conducted with two microalgae species. The acute toxicity of oil (tar mat and MC252 crude oil), dispersant (Corexit 9500A), and dispersed oil on growth inhibition (IC50) and motility of Isochrysis galbana and Chaetoceros sp. were determined. There was no impact on cell division (growth) for microalgae exposed to both oil types and mean motility of I. galbana never dropped below 79 %. However, the addition of dispersant inhibited cell division and motility within 24 h, with Chaetoceros sp. being more susceptible to sublethal effects than I. galbana. These results highlight microalgae sensitivity to the use of dispersants in bioremediation processes, which may be a concern for long-term impacts on fisheries recruitment. PMID:25283369

  4. Reducing losses and dispersion effects in multilayer metamaterial tunnelling devices

    International Nuclear Information System (INIS)

    This paper focuses on reduction of losses and dispersion effects on tunnelling through waveguides filled with metamaterial. It will be shown that these unwanted effects could be reduced by dividing the metamaterial into several regions separated by air slabs. In the first part, these effects will be studied for isotropic left-handed media (LHM). Later this will be substituted by an anisotropic magnetic medium which will lead to a practical realization with broadside coupled split ring resonators (BC-SRRs). Finally, it is shown that quasi-perfect tunnelling is possible, even in the presence of unavoidable losses and dispersion in the metamaterial

  5. Sub-100 fs pulses from an all-polarization maintaining Yb-fiber oscillator with an anomalous dispersion higher-order-mode fiber

    DEFF Research Database (Denmark)

    Verhoef, A. J.; Zhu, L.; Israelsen, Stine Møller; Grüner-Nielsen, Lars Erik; Unterhuber, A.; Kautek, W.; Rottwitt, Karsten; Baltuška, A.; Fernandez, Alicia Jimenez

    2015-01-01

    We present an Yb-fiber oscillator with an all-polarizationmaintaining cavity with a higher-order-mode fiber for dispersion compensation. The polarization maintaining higher order mode fiber introduces not only negative second order dispersion but also negative third order dispersion in the cavity...

  6. Anomalous Hall effect and magnetoresistance behavior in Co/Pd1−xAgx multilayers

    KAUST Repository

    Guo, Z. B.

    2013-02-13

    In this paper, we report anomalous Hall effect (AHE) correlated with the magnetoresistance behavior in [Co/Pd1-xAg x]n multilayers. For the multilayers with n = 6, the increase in Ag content from x = 0 to 0.52 induces the change in AHE sign from negative surface scattering-dominated AHE to positive interface scattering-dominated AHE, which is accompanied with the transition from anisotropy magnetoresistance (AMR) dominated transport to giant magnetoresistance (GMR) dominated transport. For n = 80, scaling analysis with Rs ∝ρ xx γ yields γ ∼ 3.44 for x = 0.52 which presents GMR-type transport, in contrast to γ ∼ 5.7 for x = 0 which presents AMR-type transport. © 2013 American Institute of Physics.

  7. Theory for the anomalous electron transport in Hall effect thrusters. II. Kinetic model

    Science.gov (United States)

    Lafleur, T.; Baalrud, S. D.; Chabert, P.

    2016-05-01

    In Paper I [T. Lafleur et al., Phys. Plasmas 23, 053502 (2016)], we demonstrated (using particle-in-cell simulations) the definite correlation between an anomalously high cross-field electron transport in Hall effect thrusters (HETs), and the presence of azimuthal electrostatic instabilities leading to enhanced electron scattering. Here, we present a kinetic theory that predicts the enhanced scattering rate and provides an electron cross-field mobility that is in good agreement with experiment. The large azimuthal electron drift velocity in HETs drives a strong instability that quickly saturates due to a combination of ion-wave trapping and wave-convection, leading to an enhanced mobility many orders of magnitude larger than that expected from classical diffusion theory. In addition to the magnetic field strength, B0, this enhanced mobility is a strong function of the plasma properties (such as the plasma density) and therefore does not, in general, follow simple 1 /B02 or 1 /B0 scaling laws.

  8. Global constraints on anomalous triple gauge couplings in effective field theory approach

    CERN Document Server

    Falkowski, Adam; Greljo, Admir; Marzocca, David

    2016-01-01

    We present a combined analysis of LHC Higgs data (signal strengths) together with LEP-2 WW production measurements. To characterize possible deviations from the Standard Model (SM) predictions, we employ the framework of an Effective Field Theory (EFT) where the SM is extended by higher-dimensional operators suppressed by the mass scale of new physics $\\Lambda$. The analysis is performed consistently at the order $\\Lambda^{-2}$ in the EFT expansion keeping all the relevant operators. While the two data sets suffer from flat directions, together they impose stringent model-independent constraints on the anomalous triple gauge couplings. As a side product, we provide the results of the combined fit in different EFT bases.

  9. Theory of Multifarious Quantum Phases and Large Anomalous Hall Effect in Pyrochlore Iridate Thin Films

    Science.gov (United States)

    Hwang, Kyusung; Kim, Yong Baek

    2016-01-01

    We theoretically investigate emergent quantum phases in the thin film geometries of the pyrochore iridates, where a number of exotic quantum ground states are proposed to occur in bulk materials as a result of the interplay between electron correlation and strong spin-orbit coupling. The fate of these bulk phases as well as novel quantum states that may arise only in the thin film platforms, are studied via a theoretical model that allows layer-dependent magnetic structures. It is found that the magnetic order develop in inhomogeneous fashions in the thin film geometries. This leads to a variety of magnetic metal phases with modulated magnetic ordering patterns across different layers. Both the bulk and boundary electronic states in these phases conspire to promote unusual electronic properties. In particular, such phases are akin to the Weyl semimetal phase in the bulk system and they would exhibit an unusually large anomalous Hall effect. PMID:27418293

  10. Theory of Multifarious Quantum Phases and Large Anomalous Hall Effect in Pyrochlore Iridate Thin Films.

    Science.gov (United States)

    Hwang, Kyusung; Kim, Yong Baek

    2016-01-01

    We theoretically investigate emergent quantum phases in the thin film geometries of the pyrochore iridates, where a number of exotic quantum ground states are proposed to occur in bulk materials as a result of the interplay between electron correlation and strong spin-orbit coupling. The fate of these bulk phases as well as novel quantum states that may arise only in the thin film platforms, are studied via a theoretical model that allows layer-dependent magnetic structures. It is found that the magnetic order develop in inhomogeneous fashions in the thin film geometries. This leads to a variety of magnetic metal phases with modulated magnetic ordering patterns across different layers. Both the bulk and boundary electronic states in these phases conspire to promote unusual electronic properties. In particular, such phases are akin to the Weyl semimetal phase in the bulk system and they would exhibit an unusually large anomalous Hall effect. PMID:27418293

  11. Evidence of local effects in anomalous refraction and focusing properties of dodecagonal photonic quasicrystals

    Science.gov (United States)

    di Gennaro, Emiliano; Miletto, Carlo; Savo, Salvatore; Andreone, Antonello; Morello, Davide; Galdi, Vincenzo; Castaldi, Giuseppe; Pierro, Vincenzo

    2008-05-01

    We present the key results from a comprehensive study of the refraction and focusing properties of a two-dimensional dodecagonal photonic “quasicrystal” (PQC), which was carried out via both full-wave numerical simulations and microwave measurements on a slab made of alumina rods inserted in a parallel-plate waveguide. We observe an anomalous refraction and focusing in several frequency regions, which confirm some recently published results. However, our interpretation, which is based on numerical and experimental evidence, substantially differs from the one in terms of “effective negative refractive index” that was originally proposed. Instead, our study highlights the critical role played by short-range interactions associated with local order and symmetry.

  12. Anomalous Brownian motion of colloidal particle in a nematic environment: effect of the director fluctuations

    Directory of Open Access Journals (Sweden)

    T. Turiv

    2015-06-01

    Full Text Available As recently reported [Turiv T. et al., Science, 2013, Vol. 342, 1351], fluctuations in the orientation of the liquid crystal (LC director can transfer momentum from the LC to a colloid, such that the diffusion of the colloid becomes anomalous on a short time scale. Using video microscopy and single particle tracking, we investigate random thermal motion of colloidal particles in a nematic liquid crystal for the time scales shorter than the expected time of director fluctuations. At long times, compared to the characteristic time of the nematic director relaxation we observe typical anisotropic Brownian motion with the mean square displacement (MSD linear in time τ and inversly proportional to the effective viscosity of the nematic medium. At shorter times, however, the dynamics is markedly nonlinear with MSD growing more slowly (subdiffusion or faster (superdiffusion than τ. These results are discussed in the context of coupling of colloidal particle's dynamics to the director fluctuation dynamics.

  13. 3d Transition Metal Adsorption Induced the valley-polarized Anomalous Hall Effect in Germanene.

    Science.gov (United States)

    Zhou, P; Sun, L Z

    2016-01-01

    Based on DFT + U and Berry curvature calculations, we study the electronic structures and topological properties of 3d transition metal (TM) atom (from Ti to Co) adsorbed germanene (TM-germanene). We find that valley-polarized anomalous Hall effect (VAHE) can be realized in germanene by adsorbing Cr, Mn, or Co atoms on its surface. A finite valley Hall voltage can be easily detected in their nanoribbon, which is important for valleytronics devices. Moreover, different valley-polarized current and even reversible valley Hall voltage can be archived by shifting the Fermi energy of the systems. Such versatile features of the systems show potential in next generation electronics devices. PMID:27312176

  14. Extrinsic anomalous Hall effect in epitaxial Mn{sub 4}N films

    Energy Technology Data Exchange (ETDEWEB)

    Meng, M.; Wu, S. X., E-mail: wushx3@mail.sysu.edu.cn; Ren, L. Z.; Zhou, W. Q.; Wang, Y. J.; Wang, G. L.; Li, S. W., E-mail: stslsw@mail.sysu.edu.cn [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China)

    2015-01-19

    Anomalous Hall effect (AHE) in ferrimagnetic Mn{sub 4}N epitaxial films grown by molecular-beam epitaxy is investigated. The longitudinal conductivity σ{sub xx} is within the superclean regime, indicating Mn{sub 4}N is a highly conducting material. We further demonstrate that the AHE signal in 40-nm-thick films is mainly due to the extrinsic contributions based on the analysis fitted by ρ{sub AH}=a′ρ{sub xx0}+bρ{sub xx}{sup 2} and σ{sub AH}∝σ{sub xx}. Our study not only provide a strategy for further theoretical work on antiperovskite manganese nitrides but also shed promising light on utilizing their extrinsic AHE to fabricate spintronic devices.

  15. Anomalous finite-size effects in the Battle of the Sexes

    CERN Document Server

    Cremer, Jonas; Frey, Erwin

    2007-01-01

    The Battle of the Sexes describes asymmetric conflicts in mating behavior of males and females. Males can be philanderer or faithful, while females are either fast or coy, leading to a cyclic dynamics. The adjusted replicator equation predicts stable coexistence of all four strategies. In this situation, we consider the effects of fluctuations stemming from a finite population size. We show that they unavoidably lead to extinction of two strategies in the population. However, the typical time until extinction occurs strongly prolongs with increasing system size. In the meantime, a quasi-stationary probability distribution forms that is anomalously flat in the vicinity of the coexistence state. This behavior originates in a vanishing linear deterministic drift near the fixed point. We provide numerical data as well as an analytical approach to the mean extinction time and the quasi-stationary probability distribution.

  16. The temperature dependent anomalous Hall effect in La-Ca-Mn-O films

    International Nuclear Information System (INIS)

    The colossal magnetoresistance of La1-xCaxMnO3 has been reported in many experiments. The authors present their study of the anomalous Hall effect in epitaxial La0.67Ca0.33MnO3 thin films. They have measured the temperature dependence of resistivity, magnetization and AHE coefficients between 300K and 5K for the samples grown on different substrates. From these studies, the relation between the resistivity and AHE coefficient as well as the temperature dependence of AHE coefficient are explored. The results show that the direction of AHE is reversed below approximately 100K. This sign reversal is discussed in term of the change of band structure and the co-existence of hole-like and electron-like conduction

  17. Employment Effects of Dispersal Policies. Part II: Empirical evidence

    DEFF Research Database (Denmark)

    Damm, Anna Piil; Rosholm, Michael

    2003-01-01

    the concentration of fellow countrymen and decreasing in the regional unemployment rate, the size of the local population and the percentage of immigrants in the local population. The two latter findings support dispersal policies. The two former findings emphasize that refugees should be dispersed in......How do dispersal policies affect labour market integration of refugee immigrants subjected to such policy? To investigate this, we estimate the effects of location characteristics and the average effect of geographical mobility on the hazard rate into first job of refugee immigrants subjected to...... big clusters of refugees of the same ethnic origin across regions with low unemployment. Second, on average, geographical mobility had large, positive effects on the job finding rate, suggesting that either relocations were carried out to improve employment prospects, or they were carried out to...

  18. Effect of Initial Frequency Chirp on Supercontinuum Generation in Dispersion-flattened Fibers

    Institute of Scientific and Technical Information of China (English)

    CHEN Yong-zhu; LI Yong-yao; YU Zhi-qiang Yu; FENG Ming-neng

    2009-01-01

    . Supercontinuum generation in dispersion-flattened fibers is studied theoretically. It is found that the flat spectral width of the supercontinuum generation in normal dispersion-flattened fiber can be increased from 66 nm to over 100 nm when the absolute value of the initial frequency chirps is increased from zero to 10. It is further found that initial frequency chirps are adverse to flat and wideband supercontinuum generation in anomalous dispersion-flattened fiber, and when the absolute value of the frequency chirps is increased to a certain degree, supercontinuum spectrum even can not be achieved.

  19. Employment Effects of Dispersal Policies on Refugee Immigrants

    DEFF Research Database (Denmark)

    Damm, Anna Piil; Rosholm, Michael

    transition rate into employment outside the local labour market, but decreases the transition rate into local employment. Thus, a decrease in current place utility decreases the overall job-finding rate if the local reservation wage effect dominates. We argue that spatial dispersal policies on refugees are...... characterised by low average values of current place utility. Hence, the model predicts that dispersal policies increase the geographical mobility rates of refugees and, for a sufficiently large local reservation wage effect, decrease their job-finding rates....

  20. In-situ fluorometry for dispersant effectiveness monitoring

    International Nuclear Information System (INIS)

    The use of chemical dispersant for oil spills on water is often a preferred response option because it reduces the overall environmental impact by reducing the likelihood of shoreline impact. Dispersants consist of a solvent carrier and a surfactant to enhance the natural dispersion processes of spilled oil. They generate large amounts of tiny oil droplets, producing a coffee-coloured plume under the water surface. When dispersant is applied, its effectiveness must be verified continually so that the response can be terminated as soon as the dispersant is no longer effective. This is normally done by visual observation, but this may be impaired due to poor weather or light conditions, high sediment content in waters and when dispersing pale-coloured oils. This paper demonstrated that advancement in detection and communication technology has made it possible to monitor dispersed oil in water column in a more scientific manner using instrumentation that provides real-time feedback to the incident command centre to help in the decision making process. Oil Spill Response Limited has acquired the capability to conduct in-situ fluorometry monitoring. The system consists of a solid state fluorometer, a laptop with built in global positioning system (GPS), a georeferencing software and satellite communication. The system provides a qualitative indication of a relative increase of oil in the water column, the location of monitoring points and high quality images that can be delivered to clients via Internet. This paper reported on results of a recent deployment of the system in an offshore oil response operation in Australia. The lessons learned were discussed along with the limitation and operational challenges of the system. Fluorometry was shown to be a sensitive but not necessarily accurate means of oil determination. 25 refs., 5 figs.

  1. Anomalous Magnetohydrodynamics

    OpenAIRE

    Giovannini, Massimo

    2013-01-01

    Anomalous symmetries induce currents which can be parallel rather than orthogonal to the hypermagnetic field. Building on the analogy with charged liquids at high magnetic Reynolds numbers, the persistence of anomalous currents is scrutinized for parametrically large conductivities when the plasma approximation is accurate. Different examples in globally neutral systems suggest that the magnetic configurations minimizing the energy density with the constraint that the helicity be conserved co...

  2. Testing dependence of anomalous Hall effect on resistivity in SrRuO3 by its increase with electron irradiation

    NARCIS (Netherlands)

    Haham, N.; Konczykowski, M.; Kuiper, B.; Koster, G.; Klein, L.

    2013-01-01

    We measure the anomalous Hall effect (AHE) in several patterns of the itinerant ferromagnet SrRuO 3 before and after the patterns are irradiated with electrons. The irradiation increases the resistivity of the patterns due to the introduction of point defects and we find that the AHE coefficient R

  3. Vacuum effects in magnetic field with with account for fermion anomalous magnetic moment and axial-vector interaction

    Science.gov (United States)

    Bubnov, Andrey; Gubina, Nadezda; Zhukovsky, Vladimir

    2016-05-01

    We study vacuum polarization effects in the model of Dirac fermions with additional interaction of an anomalous magnetic moment with an external magnetic field and fermion interaction with an axial-vector condensate. The proper time method is used to calculate the one-loop vacuum corrections with consideration for different configurations of the characteristic parameters of these interactions.

  4. Anomalous Chiral Superfluidity

    OpenAIRE

    Lublinsky, Michael(Physics Department, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel); Zahed, Ismail

    2009-01-01

    We discuss both the anomalous Cartan currents and the energy-momentum tensor in a left chiral theory with flavour anomalies as an effective theory for flavored chiral phonons in a chiral superfluid with the gauged Wess-Zumino-Witten term. In the mean-field (leading tadpole) approximation the anomalous Cartan currents and the energy momentum tensor take the form of constitutive currents in the chiral superfluid state. The pertinence of higher order corrections and the Adler-Bardeen theorem is ...

  5. Acoustomagnetoelectric effect in nondegenerate semiconductor with nonparabolic energy dispersion law

    International Nuclear Information System (INIS)

    We have studied acoustomagnetoelectric effect in nondegenerate semiconductor with nonparabolic energy dispersion Law. Attention was focused on the surface acoustomagnetoelectric effect (SAME). This is to reduce Joule's energy dissipated in the sample. It was observed that in a weak magnetic field the SAME is proportional to H2 whiles in strong magnetic field it is independent of H. The effect is also dependent on the the scattering mechanism and finally SAME changes sign when the magnetic field is turned through 90 deg. (author)

  6. Site-specific Incorporation of 3-Iodo-L-tyrosine into Proteins and Single-wavelength Anomalous Dispersion Phasing with Soft X-ray in Protein Crystallography

    Science.gov (United States)

    Murayama, Kazutaka; Sakamoto, Kensaku

    Iodine is a good anomalous scatter for radiations from in-house X-ray generators (Cu/CrKα). Non-natural amino acid, 3-iodo-L-tyrosine, is able to be site-specifically incorporated into proteins with amber suppresser tRNA and mutated TyrRS from M. jannaschii in the E. coli expression system. To determine the crystal structure of acetyl transferase from T. thermophilus, iodotyrosine-containing proteins were prepared and crystallized. Structure determination was successfully conducted with the protein variant with iodotyrosine at position 111. Anomalous signals from iodotyrosine with Cu/CrKα radiations were both sufficient to calculate clear electron density map. In the crystal structure, iodotyrosine did not significantly disturb the native structure.

  7. Effects of dispersive wave modes on charged particles transport

    CERN Document Server

    Schreiner, Cedric

    2015-01-01

    The transport of charged particles in the heliosphere and the interstellar medium is governed by the interaction of particles and magnetic irregularities. For the transport of protons a rather simple model using a linear Alfv\\'en wave spectrum which follows the Kolmogorov distribution usually yields good results. Even magnetostatic spectra may be used. For the case of electron transport, particles will resonate with the high-k end of the spectrum. Here the magnetic fluctuations do not follow the linear dispersion relation, but the kinetic regime kicks in. We will discuss the interaction of fluctuations of dispersive waves in the kinetic regime using a particle-in-cell code. Especially the scattering of particles following the idea of Lange et al. (2013) and its application to PiC codes will be discussed. The effect of the dispersive regime on the electron transport will be discussed in detail.

  8. Study of an anomalous pinch effect in the T-11M tokamak

    International Nuclear Information System (INIS)

    The peaked density profiles ne(r) are typical for tokamaks with ohmic heating. This contradicts to the fact that the sources of plasma - gas puffing and hydrogen recycling are localized in plasma periphery. Usually one try to resolve this contradiction by assumption of impurity accumulation or development of neoclassical Ware pinch or by supposition of its version - turbulence-driven particle pinch. In the T-11M experiments with Li-limiter, where impurity effects were excluded and plasma collisionality was rather high (ν*∼0.5), the peaked density profiles ne(r) have been observed also and this seems to be an evidence of plasma density accumulation (anomalous pinch effect). The measurements of ne(r) were carried out with help of five-channel jump-free Cotton-Mouton interferometer (polarimeter) using the conventional Abel-procedure. The ne(r) profiles can be approximated by set of parabolas: ne(r) = ne (0)·(1-r2/a2)α. The alpha parameter was an indicator of profile peaking and varied in range from 0.3 to ∼1.5. The analysis of experimental results showed that the formation of bell-shaped profile ne(r) with α∼1.5 in condition of internal gas puffing can take place only under strong plasma influx from the periphery to the plasma center (along the gradient of ne(r)) with velocity about of 3-4 m/s, which is 3-5 times more than assumed velocity of neoclassical Ware pinch. This effect does not depend on plasma purity and it is observed both with lithium and graphite limiters. Visible anomalous pinch effect increased following the growth of ne. Any assumptions about influence of direct flux of neutral atoms on creation of ne(r) profile are eliminated thereby. The development of convective transport processes from the periphery to the plasma core seems to be the most probable reason of peaked profiles ne(r) generated in conditions of a peripheral source. (author)

  9. Application of focused-beam flat-sample method to synchrotron powder X-ray diffraction with anomalous scattering effect

    Science.gov (United States)

    Tanaka, M.; Katsuya, Y.; Matsushita, Y.

    2013-03-01

    The focused-beam flat-sample method (FFM), which is a method for high-resolution and rapid synchrotron X-ray powder diffraction measurements by combination of beam focusing optics, a flat shape sample and an area detector, was applied for diffraction experiments with anomalous scattering effect. The advantages of FFM for anomalous diffraction were absorption correction without approximation, rapid data collection by an area detector and good signal-to-noise ratio data by focusing optics. In the X-ray diffraction experiments of CoFe2O4 and Fe3O4 (By FFM) using X-rays near the Fe K absorption edge, the anomalous scattering effect between Fe/Co or Fe2+/Fe3+ can be clearly detected, due to the change of diffraction intensity. The change of observed diffraction intensity as the incident X-ray energy was consistent with the calculation. The FFM is expected to be a method for anomalous powder diffraction.

  10. Quantum anomalous Hall effect in time-reversal-symmetry breaking topological insulators

    Science.gov (United States)

    Chang, Cui-Zu; Li, Mingda

    2016-03-01

    The quantum anomalous Hall effect (QAHE), the last member of Hall family, was predicted to exhibit quantized Hall conductivity {σyx}=\\frac{{{e}2}}{h} without any external magnetic field. The QAHE shares a similar physical phenomenon with the integer quantum Hall effect (QHE), whereas its physical origin relies on the intrinsic topological inverted band structure and ferromagnetism. Since the QAHE does not require external energy input in the form of magnetic field, it is believed that this effect has unique potential for applications in future electronic devices with low-power consumption. More recently, the QAHE has been experimentally observed in thin films of the time-reversal symmetry breaking ferromagnetic (FM) topological insulators (TI), Cr- and V- doped (Bi,Sb)2Te3. In this topical review, we review the history of TI based QAHE, the route to the experimental observation of the QAHE in the above two systems, the current status of the research of the QAHE, and finally the prospects for future studies.

  11. Quantum anomalous Hall effect in time-reversal-symmetry breaking topological insulators.

    Science.gov (United States)

    Chang, Cui-Zu; Li, Mingda

    2016-03-31

    The quantum anomalous Hall effect (QAHE), the last member of Hall family, was predicted to exhibit quantized Hall conductivity σ(yx) = e2/h without any external magnetic field. The QAHE shares a similar physical phenomenon with the integer quantum Hall effect (QHE), whereas its physical origin relies on the intrinsic topological inverted band structure and ferromagnetism. Since the QAHE does not require external energy input in the form of magnetic field, it is believed that this effect has unique potential for applications in future electronic devices with low-power consumption. More recently, the QAHE has been experimentally observed in thin films of the time-reversal symmetry breaking ferromagnetic (FM) topological insulators (TI), Cr- and V- doped (Bi,Sb)2Te3. In this topical review, we review the history of TI based QAHE, the route to the experimental observation of the QAHE in the above two systems, the current status of the research of the QAHE, and finally the prospects for future studies. PMID:26934535

  12. Sub-100 fs pulses from an all-polarization maintaining Yb-fiber oscillator with an anomalous dispersion higher-order-mode fiber

    DEFF Research Database (Denmark)

    Verhoef, A. J.; Zhu, L.; Israelsen, Stine Møller;

    2015-01-01

    , in contrast to dispersion compensation schemes used in previous demonstrations of all-polarization maintaining Yb-fiber oscillators. The performance of the saturable absorber mirror modelocked oscillator, that employs a free space scheme for coupling onto the saturable absorber mirror and output......We present an Yb-fiber oscillator with an all-polarizationmaintaining cavity with a higher-order-mode fiber for dispersion compensation. The polarization maintaining higher order mode fiber introduces not only negative second order dispersion but also negative third order dispersion in the cavity......-polarization-maintaining Yb-fiber oscillator. The spectral phase of the output pulses is well behaved and can be compensated such that wing-free Fourier transform limited pulses can be obtained. Further reduction of the net intracavity third order dispersion will allow generating broader output spectra and consequently...

  13. High-order dispersion effects in two-photon interference

    CERN Document Server

    Mazzotta, Z; Cipriani, D; Olivares, S; Paris, M G A

    2016-01-01

    Two-photon interference and Hong-Ou-Mandel (HOM) effect are relevant tools for quantum metrology and quantum information processing. In optical coherence tomography, HOM effect is exploited to achieve high-resolution measurements with the width of the HOM dip being the main parameter. On the other hand, applications like dense coding require high-visibility performances. Here we address high-order dispersion effects in two-photon interference and study, theoretically and experimentally, the dependence of the visibility and the width of the HOM dip on both the pump spectrum and the downconverted photon spectrum. In particular, a spatial light modulator is exploited to experimentally introduce and manipulate a custom phase function to simulate the high-order dispersion effects.

  14. Effects of vertical shear in modelling horizontal oceanic dispersion

    Science.gov (United States)

    Lanotte, A. S.; Corrado, R.; Palatella, L.; Pizzigalli, C.; Schipa, I.; Santoleri, R.

    2016-02-01

    The effect of vertical shear on the horizontal dispersion properties of passive tracer particles on the continental shelf of the South Mediterranean is investigated by means of observation and model data. In situ current measurements reveal that vertical gradients of horizontal velocities in the upper mixing layer decorrelate quite fast ( ˜ 1 day), whereas an eddy-permitting ocean model, such as the Mediterranean Forecasting System, tends to overestimate such decorrelation time because of finite resolution effects. Horizontal dispersion, simulated by the Mediterranean sea Forecasting System, is mostly affected by: (1) unresolved scale motions, and mesoscale motions that are largely smoothed out at scales close to the grid spacing; (2) poorly resolved time variability in the profiles of the horizontal velocities in the upper layer. For the case study we have analysed, we show that a suitable use of deterministic kinematic parametrizations is helpful to implement realistic statistical features of tracer dispersion in two and three dimensions. The approach here suggested provides a functional tool to control the horizontal spreading of small organisms or substance concentrations, and is thus relevant for marine biology, pollutant dispersion as well as oil spill applications.

  15. Anomalous refractive effects in honeycomb lattice photonic crystals formed by holographic lithography.

    Science.gov (United States)

    Dong, G Y; Yang, X L; Cai, L Z

    2010-08-01

    We have investigated for the first time the anomalous refractive effects of a photonic crystal (PhC) formed by holographic lithography (HL) with triangular rods arranged in a honeycomb lattice in air. Possibilities of left-handed negative refraction and superlens are discussed for the case of TM2 band with the index contrast n = 3.4:1. In contrast to the conventional honeycomb PhC made of regular rods in air, the HL PhCs show left-handed negative refraction over a wider and higher frequency range with high transmissivity (>90%), and the effective indices quite close to -1 for a wide range of incident angles with a larger all-angle left-handed negative refraction (AALNR) frequency range (Deltaomega/omega approximately 14.8%). Calculations and FDTD simulations demonstrate the high-performance negative refraction properties can happen in the holographic structures for a wide filling ratio and can be modulated by changing the filling ratio easily. PMID:20721016

  16. Strong and Anomalous Thermal Expansion Precedes the Thermosalient Effect in Dynamic Molecular Crystals.

    Science.gov (United States)

    Panda, Manas K; Centore, Roberto; Causà, Mauro; Tuzi, Angela; Borbone, Fabio; Naumov, Panče

    2016-01-01

    The ability of thermosalient solids, organic analogues of inorganic martensites, to move by rapid mechanical reconfiguration or ballistic event remains visually appealing and potentially useful, yet mechanistically elusive phenomenon. Here, with a material that undergoes both thermosalient and non-thermosalient phase transitions, we demonstrate that the thermosalient effect is preceded by anomalous thermal expansion of the unit cell. The crystal explosion occurs as sudden release of the latent strain accumulated during the anisotropic, exceedingly strong expansion of the unit cell with αa = 225.9 × 10(-6) K(-1), αb = 238.8 × 10(-6) K(-1) and αc = -290.0 × 10(-6) K(-1), the latter being the largest negative thermal expansivity observed for an organic compound thus far. The results point out to the occurence of the thermosalient effect in phase transitions as means to identify new molecular materials with strong positive and/or negative thermal expansion which prior to this work could only be discovered serendipitously. PMID:27403616

  17. Clustering effects for explaining an anomalous JLab result on the Be-9 structure function

    CERN Document Server

    Hirai, M; Saito, K; Watanabe, T

    2011-01-01

    An anomalous nuclear modification was reported by JLab measurements on the beryllium-9 structure function F_2. It is unexpected in the sense that a nuclear modification slope is too large to be expected from its average nuclear density. We investigated whether it is explained by a nuclear clustering configuration in Be-9 with two \\alpha nuclei and surrounding neutron clouds. Such clustering aspects are studied by using antisymmetrized molecular dynamics (AMD) and also by a simple shell model for comparison. We consider that nuclear structure functions F_2^A consist of a mean conventional part and a remaining one depending on the maximum local density. The first mean part does not show a significant cluster effect on F_2. However, we propose that the remaining one could explain the anonymous JLab slope, and it is associated with high densities created by the cluster formation in Be-9. The JLab measurement is possibly the first signature of clustering effects in high-energy nuclear reactions. A responsible phys...

  18. Strong and Anomalous Thermal Expansion Precedes the Thermosalient Effect in Dynamic Molecular Crystals

    Science.gov (United States)

    Panda, Manas K.; Centore, Roberto; Causà, Mauro; Tuzi, Angela; Borbone, Fabio; Naumov, Panče

    2016-01-01

    The ability of thermosalient solids, organic analogues of inorganic martensites, to move by rapid mechanical reconfiguration or ballistic event remains visually appealing and potentially useful, yet mechanistically elusive phenomenon. Here, with a material that undergoes both thermosalient and non-thermosalient phase transitions, we demonstrate that the thermosalient effect is preceded by anomalous thermal expansion of the unit cell. The crystal explosion occurs as sudden release of the latent strain accumulated during the anisotropic, exceedingly strong expansion of the unit cell with αa = 225.9 × 10−6 K−1, αb = 238.8 × 10−6 K−1 and αc = −290.0 × 10−6 K−1, the latter being the largest negative thermal expansivity observed for an organic compound thus far. The results point out to the occurence of the thermosalient effect in phase transitions as means to identify new molecular materials with strong positive and/or negative thermal expansion which prior to this work could only be discovered serendipitously. PMID:27403616

  19. Shell effects and α particle anomalous yield in reactions With nucleons

    International Nuclear Information System (INIS)

    The results of the spectra and cross section calculations for nucleons, alpha-particle and gamma-emission are discussed. The calculations were performed in the framework of the statistical theory of nuclear reactions for the nucleons interacting with 208Pb nuclei at energies up to 50 MeV. It is shown that the use for the level density of Fermi gas model and of systematics based on the neutron resonance density data results in an anomalously big alpha-yield at the first evaporation step if the incident nucleon energy exceeds 30 MeV. The shell effect damping leads to the decrease in difference between level density in competing channels. Alpha-particle yield strongly diminishes as compared to neutron one. Therefore the relative value of neutron and alpha-particle emission cross sections could indicate to the conservation of the shell structure at high excitation energies. The comparison with experiment confirms the conclusions concerning the shell effects damping at high excitation energies

  20. Correction to the Casimir force due to the anomalous skin effect

    International Nuclear Information System (INIS)

    The surface impedance approach is discussed in connection with the precise calculation of the Casimir force between metallic plates. It allows us to take into account the nonlocal connection between the current density and electric field inside of metals. In general, a material has to be described by two impedances Zs(ω,q) and Zp(ω,q) corresponding to two different polarization states. In contrast with the approximate Leontovich impedance they depend not only on frequency ω but also on the wave vector along the plate q. In this paper only the nonlocal effects happening at frequencies ωp (plasma frequency) are analyzed. We refer to all of them as the anomalous skin effect. The impedances are calculated for the propagating and evanescent fields in the Boltzmann approximation. It is found that Zp significantly deviates from the local impedance as a result of the Thomas-Fermi screening. The nonlocal correction to the Casimir force is calculated at zero temperature. This correction is small but observable at small separations between bodies. The same theory can be used to find more significant nonlocal contribution at ω∼ωp due to the plasmon excitation

  1. Magnetoresistance and anomalous Hall effect of reactive sputtered polycrystalline Ti1 - XCrxN films

    KAUST Repository

    Duan, Xiaofei

    2013-09-01

    The reactive-sputtered polycrystalline Ti1 - xCrxN films with 0.17 ≤ x ≤ 0.51 are ferromagnetic and at x = 0.47 the Curie temperature TC shows a maximum of ~ 120 K. The films are metallic at 0 ≤ x ≤ 0.47, while the films with x = 0.51 and 0.78 are semiconducting-like. The upturn of resistivity below 70 K observed in the films with 0.10 ≤ x ≤ 0.47 is from the effects of the electron-electron interaction and weak localization. The negative magnetoresistance (MR) of the films with 0.10 ≤ x ≤ 0.51 is dominated by the double-exchange interaction, while at x = 0.78, MR is related to the localized magnetic moment scattering at the grain boundaries. The scaling ρxyA/n ∝ ρxx2.19 suggests that the anomalous Hall effect in the polycrystalline Ti1 - xCrxN films is scattering-independent. © 2013 Elsevier B.V. All rights reserved.

  2. Anomalous Higgs couplings

    CERN Document Server

    González-Garciá, M Concepción

    1999-01-01

    We review the effects of new effective interactions on Higgs-boson phenomenology. New physics in the electroweak bosonic sector is expected to induce additional interactions between the Higgs doublet field and the electroweak gauge bosons, leading to anomalous Higgs couplings as well as anomalous gauge-boson self-interactions. Using a linearly realized SU(2)/sub L/*U(1)/sub Y/ invariant effective Lagrangian to describe the bosonic sector of the Standard Model, we review the effects of the new effective interactions on the Higgs- boson production rates and decay modes. We summarize the results from searches for the new Higgs signatures induced by the anomalous interactions in order to constrain the scale of new physics, in particular at CERN LEP and Fermilab Tevatron colliders. (43 refs).

  3. Review of specific effects in atmospheric dispersion calculations

    International Nuclear Information System (INIS)

    This report consists of a series of 7 individual review chapters -written between 1980 and 1983- together with a summary document linking and overviewing the work. The topics covered are as follows: ''atmospheric dispersion in urban environments''; ''topographical effects in nuclear safety studies''; coastal effects and transport over water''; ''time-varying meteorology in consequence assessment''; ''building effects in nuclear safety studies''; effect of variations in mixing height on atmospheric dispersion''; ''the effect of turning of the wind with height on lateral dispersion''. Although the reviews are, on the whole, general in approach, emphasis has been given where appropriate to the impact of various phenomena on the assessment of reactor accident consequences. In general the work focuses on the 0-100 km range of distance downwind of the source. The reviews fulfil several functions: they serve as introductions to the subject areas; they outline theoretical and experimental developments; they act as reference documents providing a copious source of references for more detailed investigation of particular points; they raise unresolved technical issues and attempt to indicate principal uncertainties; they point to areas requiring further development

  4. Effects of Surface Modification on the Dispersion Property of VGCF

    Institute of Scientific and Technical Information of China (English)

    FU Yaqin; HAN Chunshao; NI Qingqing

    2009-01-01

    In view of the easy agglomeration issue of vapor grown carbon fiber (VGCF) and the poor interfacial adhesion between VGCF and matrix resin, two-step surface modification with hydrogen peroxide and concentrated nitric acid was performed on VGCF. The surface structure and dispersion of VGCF before and after modification were tested and analyzed by XRD, TGA, FTIR, UV-visible spectrum and SEM. Moreover, VGCF/SMPU composites were prepared via a solution mixing method taking shape memory polyurethane (SMPU) as matrix, and the mechanical properties of the composites were also tested. The graphite crystal structure of VGCF showed very little change af-ter modification, the concentration of oxygen-containing functional groups on the surface of VGCF was visibly in-creased, and the dispersion and dispersion stability of VGCF in organic solvent were also clearly improved. In the cross section of the VGCF/SMPU composites, the dispersion of VGCF in matrix and the VGCF-matrix interfacial adhesion observed through SEM were both enhanced to a certain extent after surface modification. The two-step surface modified VGCF had more obvious mechanical reinforcement effects on the composites than that of the pris-tine VGCF.

  5. Optical properties of metals: Infrared emissivity in the anomalous skin effect spectral region

    Energy Technology Data Exchange (ETDEWEB)

    Echániz, T. [Departamento de Física de la Materia Condensada, Facultad de Ciencia y Tecnología, UPV/EHU, Sarriena s/n, Leioa 48940 (Spain); Pérez-Sáez, R. B., E-mail: raul.perez@ehu.es; Tello, M. J. [Departamento de Física de la Materia Condensada, Facultad de Ciencia y Tecnología, UPV/EHU, Sarriena s/n, Leioa 48940 (Spain); Instituto de Síntesis y Estudio de Materiales, Universidad del País Vasco, Apdo. 644, Bilbao 48080 (Spain)

    2014-09-07

    When the penetration depth of an electromagnetic wave in a metal is similar to the mean free path of the conduction electrons, the Drude classical theory is no longer satisfied and the skin effect becomes anomalous. Physical parameters of this theory for twelve metals were calculated and analyzed. The theory predicts an emissivity peak ε{sub peak} at room temperature in the mid-infrared for smooth surface metals that moves towards larger wavelengths as temperature decreases. Furthermore, the theory states that ε{sub peak} increases with the emission angle but its position, λ{sub peak}, is constant. Copper directional emissivity measurements as well as emissivity obtained using optical constants data confirm the predictions of the theory. Considering the relationship between the specularity parameter p and the sample roughness, it is concluded that p is not the simple parameter it is usually assumed to be. Quantitative comparison between experimental data and theoretical predictions shows that the specularity parameter can be equal to one for roughness values larger than those predicted. An exhaustive analysis of the experimental optical parameters shows signs of a reflectance broad peak in Cu, Al, Au, and Mo around the wavelength predicted by the theory for p = 1.

  6. Optical properties of metals: Infrared emissivity in the anomalous skin effect spectral region

    International Nuclear Information System (INIS)

    When the penetration depth of an electromagnetic wave in a metal is similar to the mean free path of the conduction electrons, the Drude classical theory is no longer satisfied and the skin effect becomes anomalous. Physical parameters of this theory for twelve metals were calculated and analyzed. The theory predicts an emissivity peak εpeak at room temperature in the mid-infrared for smooth surface metals that moves towards larger wavelengths as temperature decreases. Furthermore, the theory states that εpeak increases with the emission angle but its position, λpeak, is constant. Copper directional emissivity measurements as well as emissivity obtained using optical constants data confirm the predictions of the theory. Considering the relationship between the specularity parameter p and the sample roughness, it is concluded that p is not the simple parameter it is usually assumed to be. Quantitative comparison between experimental data and theoretical predictions shows that the specularity parameter can be equal to one for roughness values larger than those predicted. An exhaustive analysis of the experimental optical parameters shows signs of a reflectance broad peak in Cu, Al, Au, and Mo around the wavelength predicted by the theory for p = 1

  7. Magnetic modulation doping in topological insulators toward higher-temperature quantum anomalous Hall effect

    Energy Technology Data Exchange (ETDEWEB)

    Mogi, M., E-mail: mogi@cmr.t.u-tokyo.ac.jp; Yoshimi, R.; Yasuda, K.; Kozuka, Y. [Department of Applied Physics and Quantum Phase Electronics Center (QPEC), University of Tokyo, Tokyo 113-8656 (Japan); Tsukazaki, A. [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); PRESTO, Japan Science and Technology Agency (JST), Chiyoda-ku, Tokyo 102-0075 (Japan); Takahashi, K. S. [RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198 (Japan); Kawasaki, M.; Tokura, Y. [Department of Applied Physics and Quantum Phase Electronics Center (QPEC), University of Tokyo, Tokyo 113-8656 (Japan); RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198 (Japan)

    2015-11-02

    Quantum anomalous Hall effect (QAHE), which generates dissipation-less edge current without external magnetic field, is observed in magnetic-ion doped topological insulators (TIs) such as Cr- and V-doped (Bi,Sb){sub 2}Te{sub 3}. The QAHE emerges when the Fermi level is inside the magnetically induced gap around the original Dirac point of the TI surface state. Although the size of gap is reported to be about 50 meV, the observable temperature of QAHE has been limited below 300 mK. We attempt magnetic-Cr modulation doping into topological insulator (Bi,Sb){sub 2}Te{sub 3} films to increase the observable temperature of QAHE. By introducing the rich-Cr-doped thin (1 nm) layers at the vicinity of both the surfaces based on non-Cr-doped (Bi,Sb){sub 2}Te{sub 3} films, we have succeeded in observing the QAHE up to 2 K. The improvement in the observable temperature achieved by this modulation-doping appears to be originating from the suppression of the disorder in the surface state interacting with the rich magnetic moments. Such a superlattice designing of the stabilized QAHE may pave a way to dissipation-less electronics based on the higher-temperature and zero magnetic-field quantum conduction.

  8. Neutral cloud theory of the Jovian nebula: Anomalous ionization effect of superthermal electrons

    Science.gov (United States)

    Barbosa, D. D.

    1994-01-01

    The standard model of the Jovian nebula postulates that its particle source is the extended cloud of neutral sulfur and oxygen atoms that escape from the satellite Io and become ionized through electron impact from the corotating plasma. Its energy source is the gyroenergy acquired by newly formed pickup ions as they are swept up to corotation velocity by the planetary magnetic field. Elastic collisions between plasma ions and electrons cool the ions and heat the electrons, while inelastic collisions cool the electrons and excite the ions to radiate intense line emission, which is the primary energy-loss mechanism for the plasma. This neutral cloud theory of the Io plasma torus, as it has come to be known, has been the subject of recent critcism which asserts that the theory cannot account for the observed charge state of the plasma which features O(+) and S(2+) as the dominant ions. It is shown in this work that the inclusion of a small population of super-thermal electrons is required to achieve the correct ion partitioning among various charge states. It is also argued that the anomalous ionization effect of the superthermal electrons is responsible for the overall spatial bifurcation of the nebula into a hot multiply charged plasma region outside of 5.7 Jovian radii and a cool singly ionized plasma inside this distance.

  9. Magnetic modulation doping in topological insulators toward higher-temperature quantum anomalous Hall effect

    International Nuclear Information System (INIS)

    Quantum anomalous Hall effect (QAHE), which generates dissipation-less edge current without external magnetic field, is observed in magnetic-ion doped topological insulators (TIs) such as Cr- and V-doped (Bi,Sb)2Te3. The QAHE emerges when the Fermi level is inside the magnetically induced gap around the original Dirac point of the TI surface state. Although the size of gap is reported to be about 50 meV, the observable temperature of QAHE has been limited below 300 mK. We attempt magnetic-Cr modulation doping into topological insulator (Bi,Sb)2Te3 films to increase the observable temperature of QAHE. By introducing the rich-Cr-doped thin (1 nm) layers at the vicinity of both the surfaces based on non-Cr-doped (Bi,Sb)2Te3 films, we have succeeded in observing the QAHE up to 2 K. The improvement in the observable temperature achieved by this modulation-doping appears to be originating from the suppression of the disorder in the surface state interacting with the rich magnetic moments. Such a superlattice designing of the stabilized QAHE may pave a way to dissipation-less electronics based on the higher-temperature and zero magnetic-field quantum conduction

  10. Seed disperser effectiveness: the quantity component and patterns of seed rain for Prunus mahaleb

    OpenAIRE

    Jordano, Pedro; Schupp, Eugene W.

    2000-01-01

    In this paper we analyze the seed dispersal stage of the Prunus mahaleb–frugivorous bird inter- action from fruit removal through seed deliver y within the context of disperser effectiveness. The effectiveness of a frugivorous species as a seed disperser is the contribution it makes to plant fitness. Effectiveness depends on the quantity of seed dispersed (‘‘quantity component’’) and the quality of dispersal provided each seed (‘‘quality component’’). For the main frug...

  11. Dispersion effects in elastic electron scattering from 12C

    International Nuclear Information System (INIS)

    The results of an experiment, especially designed to investigate to what extent dispersion effects contribute to the reaction mechanism of elastic electron scattering from 12C, are presented and discussed. Particular attention is given to the discussion of corrections to parameters used in the calculation of the cross section. Tables of the resulting cross sections are given for the ground state and for the 2+ and 0+ states at, respectively, 4.439 and 7.655 MeV. The one-photon exchange approximation for elastic electron scattering from 12C is investigated by testing the energy dependence of the form factor in the region of the first diffraction minimum. The energy dependence observed is interpreted in terms of dispersion effects. 109 refs.; 33 figs.; 14 tabs

  12. Effects of dispersed sulfides in bronze under line contact conditions

    Directory of Open Access Journals (Sweden)

    Tomohiro Sato

    2016-03-01

    Full Text Available A sintered bronze system is applied to plane bearings with some lubricants. A bronze-based, sulfide-dispersed Cu alloy was developed via sintering. Sulfides had some functions, reduction of friction resistance, preventing scoring and seizure. Effects of the developed sulfide-containing bronze were investigated using a journal-type testing apparatus in wet conditions; results indicate that the developed bronze may have some anti-scoring properties.

  13. The spectrum of anomalous magnetohydrodynamics

    CERN Document Server

    Giovannini, Massimo

    2016-01-01

    The equations of anomalous magnetohydrodynamics describe an Abelian plasma where conduction and chiral currents are simultaneously present and constrained by the second law of thermodynamics. At high frequencies the magnetic currents play the leading role and the spectrum is dominated by two-fluid effects. The system behaves instead as a single fluid in the low-frequency regime where the vortical currents induce potentially large hypermagnetic fields. After deriving the physical solutions of the generalized Appleton-Hartree equation, the corresponding dispersion relations are scrutinized and compared with the results valid for cold plasmas. Hypermagnetic knots and fluid vortices can be concurrently present at very low frequencies and suggest a qualitatively different dynamics of the hydromagnetic nonlinearities.

  14. Note on anomalous Higgs-boson couplings in effective field theory

    Directory of Open Access Journals (Sweden)

    G. Buchalla

    2015-11-01

    Full Text Available We propose a parametrization of anomalous Higgs-boson couplings that is both systematic and practical. It is based on the electroweak chiral Lagrangian, including a light Higgs boson, as the effective field theory (EFT at the electroweak scale v. This is the appropriate framework for the case of sizeable deviations in the Higgs couplings of order 10% from the Standard Model, considered to be parametrically larger than new-physics effects in the sector of electroweak gauge interactions. The role of power counting in identifying the relevant parameters is emphasized. The three relevant scales, v, the scale of new Higgs dynamics f, and the cut-off Λ=4πf, admit expansions in ξ=v2/f2 and f2/Λ2. The former corresponds to an organization of operators by their canonical dimension, the latter by their loop order or chiral dimension. In full generality the EFT is thus organized as a double expansion. However, as long as ξ≫1/16π2 the EFT systematics is closer to the chiral counting. The leading effects in the consistent approximation provided by the EFT, relevant for the presently most important processes of Higgs production and decay, are given by a few (typically six couplings. These parameters allow us to describe the properties of the Higgs boson in a general and systematic way, and with a precision adequate for the measurements to be performed at the LHC. The framework can be systematically extended to include loop corrections and higher-order terms in the EFT.

  15. Note on anomalous Higgs-boson couplings in effective field theory

    Science.gov (United States)

    Buchalla, G.; Catà, O.; Celis, A.; Krause, C.

    2015-11-01

    We propose a parametrization of anomalous Higgs-boson couplings that is both systematic and practical. It is based on the electroweak chiral Lagrangian, including a light Higgs boson, as the effective field theory (EFT) at the electroweak scale v. This is the appropriate framework for the case of sizeable deviations in the Higgs couplings of order 10% from the Standard Model, considered to be parametrically larger than new-physics effects in the sector of electroweak gauge interactions. The role of power counting in identifying the relevant parameters is emphasized. The three relevant scales, v, the scale of new Higgs dynamics f, and the cut-off Λ = 4 πf, admit expansions in ξ =v2 /f2 and f2 /Λ2. The former corresponds to an organization of operators by their canonical dimension, the latter by their loop order or chiral dimension. In full generality the EFT is thus organized as a double expansion. However, as long as ξ ≫ 1 / 16π2 the EFT systematics is closer to the chiral counting. The leading effects in the consistent approximation provided by the EFT, relevant for the presently most important processes of Higgs production and decay, are given by a few (typically six) couplings. These parameters allow us to describe the properties of the Higgs boson in a general and systematic way, and with a precision adequate for the measurements to be performed at the LHC. The framework can be systematically extended to include loop corrections and higher-order terms in the EFT.

  16. Effect of band filling on anomalous Hall conductivity and magneto-crystalline anisotropy in NiFe epitaxial thin films

    International Nuclear Information System (INIS)

    The anomalous Hall effect (AHE) and magneto-crystalline anisotropy (MCA) are investigated in epitaxial NixFe1−x thin films grown on MgO (001) substrates. The scattering independent term b of anomalous Hall conductivity shows obvious correlation with cubic magneto-crystalline anisotropy K1. When nickel content x decreasing, both b and K1 vary continuously from negative to positive, changing sign at about x = 0.85. Ab initio calculations indicate NixFe1−x has more abundant band structures than pure Ni due to the tuning of valence electrons (band fillings), resulting in the increased b and K1. This remarkable correlation between b and K1 can be attributed to the effect of band filling near the Fermi surface

  17. Room-temperature anomalous Hall effect and magnetroresistance in (Ga, Co)-codoped ZnO diluted magnetic semiconductor films

    Institute of Scientific and Technical Information of China (English)

    Liu Xue-Chao; Chen Zhi-Zhan; Shi Er-Wei; Liao Da-Qian; Zhou Ke-Jin

    2011-01-01

    This paper reports that the (Ga, Co)-codoped ZnO thin films have been grown by inductively coupled plasma enhanced physical vapour deposition. Room-temperature ferromagnetism is observed for the as-grown thin films. The x-ray absorption fine structure characterization reveals that Co2+ and Ga3+ ions substitute for Zn2+ ions in the ZnO lattice and exclude the possibility of extrinsic ferromagnetism origin. The ferromagnetic (Ga, Co)-codoped ZnO thin films exhibit carrier concentration dependent anomalous Hall effect and positive magnetoresistance at room temperature. The mechanism of anomalous Hall effect and magneto-transport in ferromagnetic ZnO-based diluted magnetic semiconductors is discussed.

  18. Effect of band filling on anomalous Hall conductivity and magneto-crystalline anisotropy in NiFe epitaxial thin films

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Zhong; Jiang, Hang-Yu; Zhou, Shi-Ming, E-mail: shiming@tongji.edu.cn [Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology & Pohl Institute of Solid State Physics, School of Physics Science and Engineering, Tongji University, Shanghai 200092 (China); Hou, Yan-Liang; Ye, Quan-Lin [Department of Physics, Hangzhou Normal University, Hangzhou 310036 (China); Su Si, Ming [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China)

    2016-01-15

    The anomalous Hall effect (AHE) and magneto-crystalline anisotropy (MCA) are investigated in epitaxial Ni{sub x}Fe{sub 1−x} thin films grown on MgO (001) substrates. The scattering independent term b of anomalous Hall conductivity shows obvious correlation with cubic magneto-crystalline anisotropy K{sub 1}. When nickel content x decreasing, both b and K{sub 1} vary continuously from negative to positive, changing sign at about x = 0.85. Ab initio calculations indicate Ni{sub x}Fe{sub 1−x} has more abundant band structures than pure Ni due to the tuning of valence electrons (band fillings), resulting in the increased b and K{sub 1}. This remarkable correlation between b and K{sub 1} can be attributed to the effect of band filling near the Fermi surface.

  19. Effect of band filling on anomalous Hall conductivity and magneto-crystalline anisotropy in NiFe epitaxial thin films

    Directory of Open Access Journals (Sweden)

    Zhong Shi

    2016-01-01

    Full Text Available The anomalous Hall effect (AHE and magneto-crystalline anisotropy (MCA are investigated in epitaxial NixFe1−x thin films grown on MgO (001 substrates. The scattering independent term b of anomalous Hall conductivity shows obvious correlation with cubic magneto-crystalline anisotropy K1. When nickel content x decreasing, both b and K1 vary continuously from negative to positive, changing sign at about x = 0.85. Ab initio calculations indicate NixFe1−x has more abundant band structures than pure Ni due to the tuning of valence electrons (band fillings, resulting in the increased b and K1. This remarkable correlation between b and K1 can be attributed to the effect of band filling near the Fermi surface.

  20. Effects of Three Types of Oil Dispersants on Biodegradation of Dispersed Crude Oil in Water Surrounding Two Persian Gulf Provinces

    OpenAIRE

    Azadeh Zolfaghari-Baghbaderani; Mozhgan Emtyazjoo; Parinaz Poursafa; Sedigheh Mehrabian; Samira Bijani; Daryoush Farkhani; Parisa Mirmoghtadaee

    2012-01-01

    Objective. To determine the most effective and biodegradable dispersant of spilled oil in water surrounding two Persian Gulf provinces. Methods. This study compared the effects of three dispersants, Pars 1, Pars 2, and Gamlen OD4000 on removal of oil in two Persian Gulf provinces' water. Overall, 16 stations were selected. Using the Well method, the growth rate of isolated bacteria and fungi was identified. To specify the growth rate of microorganisms and their usage of oil in the presence of...

  1. Anomalous Hall Effect in SnMnEuTe and SnMnErTe mixed crystals

    OpenAIRE

    Racka, K.; Kuryliszyn, I.; Arciszewska, M.; Dobrowolski, W.; Broto, J. -M.; Goiran, M.; Portugall, O.; Rakoto, H.; Raquet, B.; Dugaev, V.; Slynko, E. I.; Slynko, V. E.

    2002-01-01

    The Anomalous Hall Effect was investigated in IV-VI ferromagnetic semimagnetic semiconductors of Sn1-xMnxTe codoped with either Eu or Er. The analysis of experimental data: Hall resisitivity and magnetization showed that AHE coefficient RS depends on temperature, its value decreases with the temperature increase. We observe that above ferromagnet-paramagnet transition temperature RS changes sign. We discuss the possible physical mechanisms responsible for observed temperature dependence of RS...

  2. The correlation of chemical characteristics of an oil to dispersant effectiveness

    Energy Technology Data Exchange (ETDEWEB)

    Fingas, M.F.; Wang, Z.D.; Fieldhouse, B.G.; Smith, P. [Environment Canada, Ottawa, ON (Canada). River Road Environmental Technology Centre

    2003-07-01

    The effectiveness of a dispersant is defined as the amount of oil that the dispersant puts into the water column compared to what is dispersed. The effectiveness of the dispersant depends mostly on the composition of the oil, followed by sea energy and the amount of dispersant applied. Other significant factors include the state of oil weathering, type of dispersant, temperature, and salinity of the water. Oil properties and dispersant effectiveness can be correlated to determine the amount of oil dispersion. The correlation can be used to determine which oil properties would inhibit or facilitate oil dispersion. This paper presents thirteen newly developed models that predict chemical dispersibility. They were created from data on 295 oils and 29 of their chemical and physical properties. The key parameter was dispersibility of Corexit 9500 in the swirling flask apparatus. Each model varies significantly in terms of input parameters and in statistical quality, but all can be used to predict the chemical dispersibility of oils given the required input parameters. Many essentials of chemical dispersions were discovered during the development of these models. For example, small n-alkanes were found to be prone to dispersion. It was shown that some parameters, such as chemical composition indicators, are very good predictors of chemical dispersibility, while physical properties were found to be poor predictors of chemical dispersibility. Wax content, interfacial tension, and flash point were among the properties that did not help in predicting dispersibility. 10 refs., 8 tabs., 26 figs.

  3. Local orbitals approach to the anomalous Hall and Nernst effects in itinerant ferromagnets

    Directory of Open Access Journals (Sweden)

    Středa Pavel

    2014-07-01

    Full Text Available Linear response of the orbital momentum to the gradient of the chemical potential is used to obtain anomalous Hall conductivity. Transition from the ideal Bloch system for which the conductivity is determined by the Berry phase curvatures to the case of strong disorder for which the conductivity becomes dependent on the relaxation time is analysed. Presented tight-binding model reproduces experimentally observed qualitative features of the anomalous Hall conductivity and the transverse Peltier coefficient in the so called bad-metal and scattering-independent regimes.

  4. Density Effects on the Pion Dispersion Relation at Finite Temperature

    International Nuclear Information System (INIS)

    We study the behavior of the pion dispersion relation in a pion medium at finite density and temperature, introducing a chemical potential to describe the finite pion number density. Such description is particularly important during the hadronic phase of a relativistic heavy-ion collision, between chemical and thermal freeze-out, where the pion number changing processes, driven by the strong interaction, can be considered to be frozen. We make use of an effective Lagrangian that explicitly respects chiral symmetry through the enforcement of the chiral Ward identities. The pion dispersion relation is computed through the computation of the pion self-energy in a non-perturbative fashion by giving an approximate solution to the Schwinger-Dyson equation for this self-energy. The dispersion relation is described in terms of a density and temperature dependent mass and an index of refraction which is also temperature, density as well as momentum dependent. The index of refraction is larger than unity for all values of the momentum for finite μ and T. Given the strong coupling between ρ vectors and pions, we argue that the modification of the pion mass due to finite pion density effects has to be taken into account self-consistently for the description of the in-medium modifications of ρ's

  5. CFD Modeling of LNG Spill: Humidity Effect on Vapor Dispersion

    Science.gov (United States)

    Giannissi, S. G.; Venetsanos, A. G.; Markatos, N.

    2015-09-01

    The risks entailed by an accidental spill of Liquefied Natural Gas (LNG) should be indentified and evaluated, in order to design measures for prevention and mitigation in LNG terminals. For this purpose, simulations are considered a useful tool to study LNG spills and to understand the mechanisms that influence the vapor dispersion. In the present study, the ADREA-HF CFD code is employed to simulate the TEEX1 experiment. The experiment was carried out at the Brayton Fire Training Field, which is affiliated with the Texas A&M University system and involves LNG release and dispersion over water surface in open- obstructed environment. In the simulation the source was modeled as a two-phase jet enabling the prediction of both the vapor dispersion and the liquid pool spreading. The conservation equations for the mixture are solved along with the mass fraction for natural gas. Due to the low prevailing temperatures during the spill ambient humidity condenses and this might affect the vapor dispersion. This effect was examined in this work by solving an additional conservation equation for the water mass fraction. Two different models were tested: the hydrodynamic equilibrium model which assumes kinetic equilibrium between the phases and the non hydrodynamic equilibrium model, in order to assess the effect of slip velocity on the prediction. The slip velocity is defined as the difference between the liquid phase and the vapor phase and is calculated using the algebraic slip model. Constant droplet diameter of three different sizes and a lognormal distribution of the droplet diameter were applied and the results are discussed and compared with the measurements.

  6. Effects of the solar wind termination shock and heliosheath on theheliospheric modulation of galactic and anomalous Helium

    Directory of Open Access Journals (Sweden)

    U. W. Langner

    2004-09-01

    Full Text Available The interest in the role of the solar wind termination shock and heliosheath in cosmic ray modulation studies has increased significantly as the Voyager 1 and 2 spacecraft approach the estimated position of the solar wind termination shock. The effect of the solar wind termination shock on charge-sign dependent modulation, as is experienced by galactic cosmic ray Helium (He++ and anomalous Helium (He+, is the main topic of this work, and is complementary to the previous work on protons, anti-protons, electrons, and positrons. The modulation of galactic and anomalous Helium is studied with a numerical model including a more fundamental and comprehensive set of diffusion coefficients, a solar wind termination shock with diffusive shock acceleration, a heliosheath and particle drifts. The model allows a comparison of modulation with and without a solar wind termination shock and is applicable to a number of cosmic ray species during both magnetic polarity cycles of the Sun. The modulation of Helium, including an anomalous component, is also done to establish charge-sign dependence at low energies. We found that the heliosheath is important for cosmic ray modulation and that its effect on modulation is very similar for protons and Helium. The local Helium interstellar spectrum may not be known at energies <~1GeV until a spacecraft actually approaches the heliopause because of the strong modulation that occurs in the heliosheath, the effect of the solar wind termination shock and the presence of anomalous Helium.

  7. Motional dispersions and ratchet effect in inertial systems

    Indian Academy of Sciences (India)

    W L Reenbohn; S Saikia; R Roy; Mangal C Mahato

    2008-08-01

    We obtain ratchet effect in inertial structureless systems in symmetric periodic potentials where the asymmetry comes from the non-uniform friction offered by the medium and driven by symmetric periodic forces. In the adiabatic limit the calculations are done by extending the matrix continued fraction method and also by numerically solving the appropriate Langevin equation. For finite frequency field drive the ratchet effect is obtained only numerically. In the transient time scales the system shows dispersionless behaviour as reported earlier when a constant force is applied. In the periodic drive case the dispersion behaviour is more complex. In this brief communication we report some of the results of our work.

  8. Anomalous polymer dynamics is non-Markovian: memory effects and the generalized Langevin equation formulation

    International Nuclear Information System (INIS)

    Any first course on polymer physics teaches that the dynamics of a tagged monomer of a polymer is anomalously subdiffusive, i.e., the mean-square displacement of a tagged monomer increases as tα for some α < 1 until the terminal relaxation time τ of the polymer. Beyond time τ the motion of the tagged monomer becomes diffusive. Classical examples of anomalous dynamics in polymer physics are single polymeric systems, such as phantom Rouse, self-avoiding Rouse, self-avoiding Zimm, reptation, translocation through a narrow pore in a membrane, and many-polymeric systems such as polymer melts. In this pedagogical paper I report that all these instances of anomalous dynamics in polymeric systems are robustly characterized by power-law memory kernels within a unified generalized Langevin equation (GLE) scheme, and therefore are non-Markovian. The exponents of the power-law memory kernels are related to the relaxation response of the polymers to local strains, and are derived from the equilibrium statistical physics of polymers. The anomalous dynamics of a tagged monomer of a polymer in these systems is then reproduced from the power-law memory kernels of the GLE via the fluctuation-dissipation theorem (FDT). Using this GLE formulation I further show that the characteristics of the drifts caused by a (weak) applied field on these polymeric systems are also obtained from the corresponding memory kernels

  9. Magnetoresistance and Anomalous Hall Effect of InSb Doped with Mn

    Directory of Open Access Journals (Sweden)

    A.V. Kochura

    2013-12-01

    Full Text Available Transport properties of polycrystalline (In, MnSb samples are investigated. Behavior of the temperature and magnetic field dependencies of the resistivity, anomalous Hall coefficient and magnetoresistivity at low temperatures points out the influence of Mn complexes, Mn ions and nano- and microsizes MnSb precipitates on charge transport.

  10. Anomalous polymer dynamics is non-Markovian: memory effects and the generalized Langevin equation formulation

    NARCIS (Netherlands)

    D. Panja

    2010-01-01

    Any first course on polymer physics teaches that the dynamics of a tagged monomer of a polymer is anomalously subdiffusive, i.e., the mean-square displacement of a tagged monomer increases as tα for some α < 1 until the terminal relaxation time τ of the polymer. Beyond time τ the motion of the tagge

  11. Effects of anomalous magnetic moment in the quantum motion of neutral particle in magnetic and conical spacetime electric fields produced by a linear source in a conical spacetime

    International Nuclear Information System (INIS)

    In this paper we analyse the effect of the anomalous magnetic moment on the non-relativistic quantum motion of a neutral particle in magnetic and electric fields produced by linear sources of constant current and charge density, respectively. (author)

  12. Quantitative analysis of the effects of the exotic Argentine ant on seed-dispersal mutualisms

    OpenAIRE

    Rodriguez-Cabal, Mariano A.; Stuble, Katharine L.; Nuñez, Martin A.; Sanders, Nathan J.

    2009-01-01

    Although it is increasingly clear that exotic invasive species affect seed-dispersal mutualisms, a synthetic examination of the effect of exotic invasive species on seed-dispersal mutualisms is lacking. Here, we review the impacts of the invasive Argentine ant (Linepithema humile) on seed dispersal. We found that sites with L. humile had 92 per cent fewer native ant seed dispersers than did sites where L. humile was absent. In addition, L. humile did not replace native seed dispersers, as rat...

  13. Influence of defects and disorder on anomalous Hall effect and spin Seebeck effect on permalloy and Heusler compounds

    Energy Technology Data Exchange (ETDEWEB)

    Vilanova Vidal, Enrique

    2012-09-19

    In this work Heusler thin films have been prepared and their transport properties have been studied. Of particularly interest is the anomalous Hall effect (AHE). The effect is a long known but still not fully understood transport effect. Most theory papers focus on the influence of one particular contribution to the AHE. Actual measured experimental data, however, often are not in accordance with idealized assumptions. This thesis discusses the data analysis for materials with low residual resistivity ratios. As prototypical materials, half metallic Heusler compounds are studied. Here, the influence of defects and disorder is apparent in a material with a complex topology of the Fermi surface. Using films with different degrees of disorder, the different scattering mechanisms can be separated. For Co{sub 2}FeSi{sub 0.6}Al{sub 0.4} and Co{sub 2}FeGa{sub 0.5}Ge{sub 0.5}, the AHE induced by B2-type disorder and temperature-dependent scattering is positive, while DO{sub 3}-type disorder and possible intrinsic contributions possess a negative sign. For these compounds, magneto-optical Kerr effects (MOKE) are investigated. First order contributions as a function of intrinsic and extrinsic parameters are qualitatively analyzed. The relation between the crystalline ordering and the second order contributions to the MOKE signal is studied. In addition, sets of the Heusler compound Co{sub 2}MnAl thin films were grown on MgO(100) and Si(100) substrates by radio frequency magnetron sputtering. Composition, magnetic and transport properties were studied systematically for samples deposited at different conditions. In particular, the anomalous Hall effect resistivity presents an extraordinarily temperature independent behavior in a moderate magnetic field range from 0 to 0.6 T. The off-diagonal transport at temperatures up to 300 C was analyzed. The data show the suitability of the material for Hall sensors working well above room temperature. Recently, the spin Seebeck effect

  14. Effects of Three Types of Oil Dispersants on Biodegradation of Dispersed Crude Oil in Water Surrounding Two Persian Gulf Provinces

    Directory of Open Access Journals (Sweden)

    Azadeh Zolfaghari-Baghbaderani

    2012-01-01

    Full Text Available Objective. To determine the most effective and biodegradable dispersant of spilled oil in water surrounding two Persian Gulf provinces. Methods. This study compared the effects of three dispersants, Pars 1, Pars 2, and Gamlen OD4000 on removal of oil in two Persian Gulf provinces' water. Overall, 16 stations were selected. Using the Well method, the growth rate of isolated bacteria and fungi was identified. To specify the growth rate of microorganisms and their usage of oil in the presence of the above-mentioned dispersants, as exclusive sources of carbon, the bacteria were grown in culture medium for 28 days at 120 rpm, 30∘C, and their optical density was measured by spectrophotometry. Then, we tested biological oxygen demand (BOD and chemical oxygen demand (COD in microorganisms. Results. The highest growth rate was documented for the growth of microorganisms on either Pars 1 or Pars 2 dispersants or their mixtures with oil. However, the culture having microorganisms grown on Pars 1 had higher BOD and COD than the other two dispersants (9200 and 16800 versus 500 and 960, P<0.05. Mixture of oil and Pars 2 as well as oil and Pars 1 dispersants showed the highest BODs and CODs, respectively. In the Bahregan province, microorganisms grown on Pars 2 had maximum amount of BOD and COD in comparison with Pars 1 and Gamlen dispersants (7100 and 15200 versus 6000 and 10560, P<0.05. Conclusion. Pars 1 and Pars 2 were the most effective dispersants with highest degradability comparing Gamlen. In each region, the most suitable compound for removing oil spill from offshores with least secondary contamination should be investigated.

  15. Effects of Three Types of Oil Dispersants on Biodegradation of Dispersed Crude Oil in Water Surrounding Two Persian Gulf Provinces

    International Nuclear Information System (INIS)

    Objective. To determine the most effective and biodegradable dispersant of spilled oil in water surrounding two Persian Gulf provinces. Methods. This study compared the effects of three dispersants, Pars 1, Pars 2, and Gamlen OD4000 on removal of oil in two Persian Gulf provinces' water. Overall, 16 stations were selected. Using the Well method, the growth rate of isolated bacteria and fungi was identified. To specify the growth rate of microorganisms and their usage of oil in the presence of the above-mentioned dispersants, as exclusive sources of carbon, the bacteria were grown in culture medium for 28 days at 120 rpm, 30 C, and their optical density was measured by spectrophotometry. Then, we tested biological oxygen demand (BOD) and chemical oxygen demand (COD) in microorganisms. Results. The highest growth rate was documented for the growth of microorganisms on either Pars 1 or Pars 2 dispersants or their mixtures with oil. However, the culture having microorganisms grown on Pars 1 had higher BOD and COD than the other two dispersants (9200 and 16800 versus 500 and 960, P<0.05). Mixture of oil and Pars 2 as well as oil and Pars 1 dispersants showed the highest BODs and CODs, respectively. In the Bahregan province, microorganisms grown on Pars 2 had maximum amount of BOD and COD in comparison with Pars 1 and Gamlen dispersants (7100 and 15200 versus 6000 and 10560, P<0.05). Conclusion. Pars 1 and Pars 2 were the most effective dispersants with highest degradability comparing Gamlen. In each region, the most suitable compound for removing oil spill from off shores with least secondary contamination should be investigated.

  16. Effects of dispersion forces in the instability of polymer films

    Institute of Scientific and Technical Information of China (English)

    Zhao He-Ping; Ophelia K.C.Tsui; Liu Zheng-You

    2006-01-01

    Spontaneous rupture of some polymer films upon heating is commonplace. The very criterion for this instability is the system free energy possessing a negative curvature. Within the framework of full frequency-dependent theory of dispersion forces, we have derived the excess free energy of a typical system-polystyrene film deposited on the silicon substrate. The excess free energy, wavelengths and growth rates are calculate and a comparison is made between the accurate results and the approximate results. It is found that the stability of the film can be tuned by the variation of the thickness of the coating and the retardation effects can be significant sometimes.

  17. Estimates of dispersive effects in a bent NLC Main Linac

    Energy Technology Data Exchange (ETDEWEB)

    Michael Syphers and Leo Michelotti

    2000-10-31

    An alternative being considered for the Next Linear Collider (NLC) is not to tunnel in a straight line but to bend the Main Linac into an arc so as to follow a gravitational equipotential. The authors begin here an examination of the effects that this would have on vertical dispersion, with its attendant consequences on synchrotron radiation and emittance growth by looking at two scenarios: a gentle continuous bending of the beam to follow an equipotential surface, and an introduction of sharp bends at a few sites in the linac so as to reduce the maximum sagitta produced.

  18. Anomalous polymer dynamics is non-Markovian: memory effects and the generalized Langevin equation formulation

    Science.gov (United States)

    Panja, Debabrata

    2010-06-01

    Any first course on polymer physics teaches that the dynamics of a tagged monomer of a polymer is anomalously subdiffusive, i.e., the mean-square displacement of a tagged monomer increases as tα for some α kernels within a unified generalized Langevin equation (GLE) scheme, and therefore are non-Markovian. The exponents of the power-law memory kernels are related to the relaxation response of the polymers to local strains, and are derived from the equilibrium statistical physics of polymers. The anomalous dynamics of a tagged monomer of a polymer in these systems is then reproduced from the power-law memory kernels of the GLE via the fluctuation-dissipation theorem (FDT). Using this GLE formulation I further show that the characteristics of the drifts caused by a (weak) applied field on these polymeric systems are also obtained from the corresponding memory kernels.

  19. Anomalous Nernst-effect and spin fluctuations in LaFeAsO1-xFx

    International Nuclear Information System (INIS)

    We present Nernst-effect investigations on LaFeAsO1-xFx. In the parent compound the formation of a SDW state leads to a huge enhancement of the Nernst coefficient at TN. Despite the absence of SDW order at underdoped superconducting doping levels, a similar anomalous behavior is also observed (with smaller magnitude), which is suggestive of a spin-fluctuation enhanced Nernst-effect. Interestingly, at optimal doping level the Nernst coefficient is only weakly temperature dependent and appears more conventional.

  20. Anomalous Doppler effect at interaction of electromagnetic waves with electron beams: experimental researches and opportunities for application

    International Nuclear Information System (INIS)

    The anomalous Doppler effect (ADE) in systems consisting of an electron beam and slow wave structure in longitudinal magnetic field is considered. Resonance condition for amplifiers and generators based on ADE enables resonance maintaining in case of wave phase velocity or beam velocity changing (acceleration of ions at ADE, reception of high efficiency at microwave generation). Essential advantages can be reached at combination of ADE and normal Doppler effect. The review of experimental studies of ADE is presented: amplification and generation of microwaves, energetic relations, excitation of accelerating IH-structures, development of ion acceleration

  1. On estimating the effect of control element relative vibrations during anomalous motions of the reactor barrel

    International Nuclear Information System (INIS)

    Following the motivation by a theoretical paper, the fraction δ arising additionally in ex-core neutron flux fluctuations synchronously to the barrel motion due to the control element motion relative to the core is estimated from experimental data on anomalous core barrel motions at the WWER-440 type reactor. The experimental result of δ ∼ 0.25 confirms the numerical values obtained by theoretical estimation. (author)

  2. Effects of high-order dispersions on dark-bright vector soliton propagation and interaction

    Institute of Scientific and Technical Information of China (English)

    Hong Li; Dongning Wang

    2011-01-01

    The dynamics of dark-bright vector solitons is investigated in a birefringent fiber with the high-order dispersions, and their effects on vector soliton propagation and interaction are analyzed using the numerical method. The combined role of the high-order dispersions, such as the third-order dispersion (TOD) and the fourth-order dispersion (FOD), may cause various deformation of the vector soliton and enhance interaction. These effects depend strictly on the sign of the high-order dispersions. Results indicate that the disadvantageous effects can be reduced effectively via proper mapping of the high-order dispersions.%@@ The dynamics of dark-bright vector solitons is investigated in a birefringent fiber with the high-order dispersions, and their effects on vector soliton propagation and interaction are analyzed using the numerical method.The combined role of the high-order dispersions, such as the third-order dispersion (TOD) and the fourth-order dispersion (FOD), may cause various deformation of the vector soliton and enhance interaction.These effects depend strictly on the sign of the high-order dispersions.Results indicate that the disadvantageous effects can be reduced effectively via proper mapping of the high-order dispersions.

  3. Magnetic Instability in Accretion Disks with Anomalous Viscosity

    Institute of Scientific and Technical Information of China (English)

    ZHOU Ai-Ping; LI Xiao-Qing

    2004-01-01

    @@ Using the new model of anomalous viscosity, we investigate the magnetic instability in the accretion disks and give the dispersion formula. On the basis of the dispersion relation obtained, it is numerically shown that the instability condition of viscous accretion disk is well consistent with that of the ideal accretion disk, namely there would be magneto-rotational instability in the presence of a vertical weak magnetic field. For a given distance R from the centre of the disk, the growth rate in the anomalous case deviates from the ideal case more greatly when the vertical magnetic field is smaller. The large viscosity limits to the instability. In the two cases, the distributions of growth rate with wave number k approach each other when the magnetic field increases. It greatly represses the effect of viscosity.

  4. Attenuation, dispersion and nonlinearity effects in graphene-based waveguides

    Directory of Open Access Journals (Sweden)

    Almir Wirth Lima Jr.

    2015-05-01

    Full Text Available We simulated and analyzed in detail the behavior of ultrashort optical pulses, which are typically used in telecommunications, propagating through graphene-based nanoribbon waveguides. In this work, we showed the changes that occur in the Gaussian and hyperbolic secant input pulses due to the attenuation, high-order dispersive effects and nonlinear effects. We concluded that it is possible to control the shape of the output pulses with the value of the input signal power and the chemical potential of the graphene nanoribbon. We believe that the obtained results will be highly relevant since they can be applied to other nanophotonic devices, for example, filters, modulators, antennas, switches and other devices.

  5. Dispersant use as a response to oil spills: toxicological effects on fish cardiac performance

    OpenAIRE

    Milinkovitch, Thomas; Thomas-Guyon, Hélène; Lefrançois, Christel; Imbert, Nathalie

    2013-01-01

    Dispersant use is a controversial technique used to respond to oil spills in nearshore areas. In order to assess the toxicity of this technique, this study evaluated the cardiac toxicological effects on juvenile golden grey mullets Liza aurata exposed for 48 h to either dispersant alone, chemically dispersed oil, mechanically dispersed oil, the water soluble fraction of oil or to a control condition. Following exposure, the positive inotropic effects of adrenaline were assessed in order to ev...

  6. Effect of combined treatments on viscosity of whey dispersions

    International Nuclear Information System (INIS)

    Whey proteins, enriched protein fractions from milk, are of great interest as ingredients due to nutritional value associated with its functional properties. These proteins could have their structural properties improved when some treatments are applied, such as thermal and gamma irradiation or when some compounds are added. The current work aimed to study the viscometer behavior of whey dispersions submitted to two different combined treatments: (1) thermal plus irradiation and (2) thermal plus vacuum and N2 plus irradiation. Dispersions of whey protein in water (5% and 8% protein (w/v) base) and containing proteins and glycerol at ratios 1:1 and 2:1 (protein:glycerol) were submitted to both combined treatments. The irradiation doses were 0, 5, 15 and 25 kGy. The viscosity of the two combined treatments and for four levels of absorbed doses is presented and the combined effects are discussed. The thermal treatment combined with gamma irradiation contributed to increase the viscosity as irradiation doses increases for both (5% and 8%) concentrations of proteins (p<0.05). For protein and glycerol solutions, the irradiation dose seemed to result in a slightly increase. The vacuum applied before the irradiation showed a small contribution

  7. Effect of combined treatments on viscosity of whey dispersions

    Science.gov (United States)

    Camillo, A.; Sabato, S. F.

    2004-09-01

    Whey proteins, enriched protein fractions from milk, are of great interest as ingredients due to nutritional value associated with its functional properties. These proteins could have their structural properties improved when some treatments are applied, such as thermal and gamma irradiation or when some compounds are added. The current work aimed to study the viscometer behavior of whey dispersions submitted to two different combined treatments: (1) thermal plus irradiation and (2) thermal plus vacuum and N 2 plus irradiation. Dispersions of whey protein in water (5% and 8% protein (w/v) base) and containing proteins and glycerol at ratios 1:1 and 2:1 (protein:glycerol) were submitted to both combined treatments. The irradiation doses were 0, 5, 15 and 25 kGy. The viscosity of the two combined treatments and for four levels of absorbed doses is presented and the combined effects are discussed. The thermal treatment combined with gamma irradiation contributed to increase the viscosity as irradiation doses increases for both (5% and 8%) concentrations of proteins ( p<0.05). For protein and glycerol solutions, the irradiation dose seemed to result in a slightly increase. The vacuum applied before the irradiation showed a small contribution.

  8. Anomalous temperature effect on the hydrogen bond strength and phase transition in 2,4,6-trimethylpyridinium pentachlorophenolate.

    Science.gov (United States)

    Majerz, Irena; Jakubas, Ryszard

    2004-06-01

    The phase transition in 2,4,6-trimethylpyridinium pentachlorophenolate has been studied by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and dielectric method as well as theoretical calculations. The crystal undergoes a first order phase transition of order-disorder type at 376 K. The transition to the high temperature phase causes anomalous hydrogen-bond shortening. Experimental and theoretical results show that the change in the mutual orientation of the phenol and pyridine rings is connected with the change of the hydrogen bond. Such an effect, which appears in the present simple hydrogen-bond complex, may be common also for the other hydrogen-bond complexes.

  9. Suppression of particle dispersion by sweeping effects in synthetic turbulence

    Science.gov (United States)

    Eyink, Gregory L.; Benveniste, Damien

    2013-02-01

    Synthetic models of Eulerian turbulence like so-called kinematic simulations (KS) are often used as computational shortcuts for studying Lagrangian properties of turbulence. These models have been criticized by Thomson and Devenish (2005), who argued on physical grounds that sweeping decorrelation effects suppress pair dispersion in such models. We derive analytical results for Eulerian turbulence modeled by Gaussian random fields, in particular for the case with zero mean velocity. Our starting point is an exact integrodifferential equation for the particle pair separation distribution obtained from the Gaussian integration-by-parts identity. When memory times of particle locations are short, a Markovian approximation leads to a Richardson-type diffusion model. We obtain a time-dependent pair diffusivity tensor of the form Kij(r,t)=Sij(r)τ(r,t), where Sij(r) is the structure-function tensor and τ(r,t) is an effective correlation time of velocity increments. Crucially, this is found to be the minimum value of three times: the intrinsic turnover time τeddy(r) at separation r, the overall evolution time t, and the sweeping time r/v0 with v0 the rms velocity. We study the diffusion model numerically by a Monte Carlo method. With inertial ranges like the largest achieved in most current KS (about 6 decades long), our model is found to reproduce the t9/2 power law for pair dispersion predicted by Thomson and Devenish and observed in the KS. However, for much longer ranges, our model exhibits three distinct pair-dispersion laws in the inertial range: a Batchelor t2 regime, followed by a Kraichnan-model-like t1 diffusive regime, and then a t6 regime. Finally, outside the inertial range, there is another t1 regime with particles undergoing independent Taylor diffusion. These scalings are exactly the same as those predicted by Thomson and Devenish for KS with large mean velocities, which we argue hold also for KS with zero mean velocity. Our results support the basic

  10. Effectiveness of primate seed dispersers for an "oversized" fruit, Garcinia benthamii.

    Science.gov (United States)

    McConkey, Kim R; Brockelman, Warren Y; Saralamba, Chanpen; Nathalang, Anuttara

    2015-10-01

    The largest fruits found in tropical forests may depend on complementary seed dispersal strategies. These fruits are dispersed most effectively by megafauna, but populations can persist where megafauna are absent or erratic visitors. Smaller animals often consume these large fruits, but their capacity to disperse these seeds effectively has rarely been assessed. We evaluated the contributions of gibbons (Hylobates lar) and other frugivores in the seed dispersal of the megafaunal fruit Garcinia benthamii, using the SDE (seed dispersal effectiveness) landscape. Gibbons preferentially consumed G. benthamii fruits and were the main seed disperser that we observed. However, gibbons became satiated when availability was high, with 57% of fruits falling to the ground unhandled. Recruitment of seedlings from gibbon-dispersed seeds was also very low. Elephants consumed G. benthamii fruit, but occurred at low density and were rare visitors to the trees. We suggest that gibbons might complement the seed dispersal role of elephants for G. benthamii, allowing limited recruitment in areas (such as the study site) where elephants occur at low density. Fruit availability varied between years; when availability was low, gibbons reliably consumed most of the crop and dispersed some seeds that established seedlings, albeit at low numbers (2.5 seedlings per crop). When fruit availability was high, the fruit supply overwhelmed the gibbons and other arboreal frugivores, ensuring a large abundance of fruit available to terrestrial seed dispersers. Although gibbons effectively dispersed more seeds at these times (20.7 seedlings per crop), there was the potential for elephants to move many more seeds. Complementary seed dispersal strategies may be important for megafaunal fruit, because they ensure that very large fruits are able to benefit from megafaunal dispersal but also persist where this dispersal becomes erratic. However, our data suggest that smaller seed dispersers might not be

  11. Anomalous-Magnetic-Moment Effects in a Strongly Magnetized and Dense Medium

    CERN Document Server

    Ferrer, E J; Paret, D Manreza; Martínez, A Pérez

    2013-01-01

    We investigate the quantum corrections of the anomalous magnetic moment (AMM) for fermions in the presence of a strong magnetic field using the Ritus's approach. At strong fields the particles get different AMM's depending on the LL's. This result is different from what is obtained with the Schwinger's approximation at weak field where the AMM is independent of the LL. We analyze the significance of the AMM contribution to the Equation of State (EoS) of the magnetized system, in the weak and strong field approximations.

  12. Dispersion and nonlinear effects in OFDM-RoF system

    Science.gov (United States)

    Alhasson, Bader H.; Bloul, Albe M.; Matin, M.

    2010-08-01

    The radio-over-fiber (RoF) network has been a proven technology to be the best candidate for the wireless-access technology, and the orthogonal frequency division multiplexing (OFDM) technique has been established as the core technology in the physical layer of next generation wireless communication system, as a result OFDM-RoF has drawn attentions worldwide and raised many new research topics recently. At the present time, the trend of information industry is towards mobile, wireless, digital and broadband. The next generation network (NGN) has motivated researchers to study higher-speed wider-band multimedia communication to transmit (voice, data, and all sorts of media such as video) at a higher speed. The NGN would offer services that would necessitate broadband networks with bandwidth higher than 2Mbit/s per radio channel. Many new services emerged, such as Internet Protocol TV (IPTV), High Definition TV (HDTV), mobile multimedia and video stream media. Both speed and capacity have been the key objectives in transmission. In the meantime, the demand for transmission bandwidth increased at a very quick pace. The coming of 4G and 5G era will provide faster data transmission and higher bit rate and bandwidth. Taking advantages of both optical communication and wireless communication, OFDM Radio over Fiber (OFDM-RoF) system is characterized by its high speed, large capacity and high spectral efficiency. However, up to the present there are some problems to be solved, such as dispersion and nonlinearity effects. In this paper we will study the dispersion and nonlinearity effects and their elimination in OFDM-radio-over-fiber system.

  13. 40 CFR Appendix C to Part 300 - Swirling Flask Dispersant Effectiveness Test, Revised Standard Dispersant Toxicity Test, and...

    Science.gov (United States)

    2010-07-01

    ... Chemicals) in 40 CFR part 300 (National Oil and Hazardous Substances Pollution Contingency Plan). They are... agents are provided in 40 CFR 300.5. 2.0Swirling Flask Dispersant Effectiveness Test 2.1Summary of Method... reintegration of the spectral data is required. 4.6.5QA/QC procedures. The reliability of this method...

  14. Two-patch population models with adaptive dispersal: the effects of varying dispersal speeds

    Czech Academy of Sciences Publication Activity Database

    Cressman, R.; Křivan, Vlastimil

    2013-01-01

    Roč. 67, č. 2 (2013), s. 329-358. ISSN 0303-6812 Grant ostatní: The University of Tennessee(US) EF-0832858; National Science Foundation(US) DMS 0931642 Institutional support: RVO:60077344 Keywords : competition * dispersal * evolution Subject RIV: EH - Ecology, Behaviour Impact factor: 2.388, year: 2013 http://link.springer.com/content/pdf/10.1007%2Fs00285-012-0548-3.pdf

  15. Giant gap quantum spin Hall effect and valley-polarized quantum anomalous Hall effect in cyanided bismuth bilayers

    Science.gov (United States)

    Ji, Wei-xiao; Zhang, Chang-wen; Ding, Meng; Zhang, Bao-min; Li, Ping; Li, Feng; Ren, Miao-juan; Wang, Pei-ji; Zhang, Run-wu; Hu, Shu-jun; Yan, Shi-shen

    2016-08-01

    Bismuth (Bi) has attracted a great deal of attention for its strongest spin–orbit coupling (SOC) strength among main group elements. Although quantum anomalous Hall (QAH) state is predicted in half-hydrogenated Bi honeycomb monolayers Bi2H, the experimental results are still missing. Halogen atoms (X = F, Cl and Br) were also frequently used as modifications, but Bi2X films show a frustrating metallic character that masks the QAH effects. Here, first-principle calculations are performed to predict the full-cyanided bismuthene (Bi2(CN)2) as 2D topological insulator supporting quantum spin Hall state with a record large gap up to 1.10 eV, and more importantly, half-cyanogen saturated bismuthene (Bi2(CN)) as a Chern insulator supporting a valley-polarized QAH state, with a Curie temperature to be 164 K, as well as a large gap reaching 0.348 eV which could be further tuned by bi-axial strain and SOC strength. Our findings provide an appropriate and flexible material family candidate for spintronic and valleytronic devices.

  16. Polarization modulational instability in a birefringent optical fiber with fourth order dispersion

    Indian Academy of Sciences (India)

    R Ganapathy; V C Kuriakose

    2001-10-01

    We obtain conditions for the occurrence of polarization modulational instability in the anomalous and normal dispersion regimes for the coupled nonlinear Schrödinger equation modelling fourth order dispersion effects when the linearly polarized pump is oriented at arbitrary angles with respect to the slow and fast axes of the birefringent fiber.

  17. Effect of microstructure on anomalous strain-rate-dependent behaviour of bacterial cellulose hydrogel.

    Science.gov (United States)

    Gao, Xing; Shi, Zhijun; Lau, Andrew; Liu, Changqin; Yang, Guang; Silberschmidt, Vadim V

    2016-05-01

    This study is focused on anomalous strain-rate-dependent behaviour of bacterial cellulose (BC) hydrogel that can be strain-rate insensitive, hardening, softening, or strain-rate insensitive in various ranges of strain rate. BC hydrogel consists of randomly distributed nanofibres and a large content of free water; thanks to its ideal biocompatibility, it is suitable for biomedical applications. Motivated by its potential applications in complex loading conditions of body environment, its time-dependent behaviour was studied by means of in-aqua uniaxial tension tests at constant temperature of 37 °C at various strain rates ranging from 0.000 1s(-1) to 0.3s(-1). Experimental results reflect anomalous strain-rate-dependent behaviour that was not documented before. Micro-morphological observations allowed identification of deformation mechanisms at low and high strain rates in relation to microstructural changes. Unlike strain-rate softening behaviours in other materials, reorientation of nanofibres and kinematics of free-water flow dominate the softening behaviour of BC hydrogel at high strain rates. PMID:26952406

  18. Potential lethal and non-lethal effects of predators on dispersal of spider mites.

    OpenAIRE

    Otsuki, Hatsune; Yano, Shuichi

    2014-01-01

    Predators can affect prey dispersal lethally by direct consumption or non-lethally by making prey hesitate to disperse. These lethal and non-lethal effects are detectable only in systems where prey can disperse between multiple patches. However, most studies have drawn their conclusions concerning the ability of predatory mites to suppress spider mites based on observations of their interactions on a single patch or on heavily infested host plants where spider mites could hardly disperse towa...

  19. Ion thermal and dispersion effects in Farley-Buneman instabilities

    International Nuclear Information System (INIS)

    Farley-Buneman modes are an example of the collisional instability, which is thought to be the dominant mechanism for the irregularities in low ionosphere region. Despite high collisionality due to electron-neutral and ion-neutral collisions, the kinetic effects associated with finite temperature are important for determination of the mode frequencies and growth rate. This is especially important for ion component that is largely unmagnetized due to low ion cyclotron frequency. The ion thermal effects are strongly pronounced for shorter wavelengths and are crucial for the growth rate cut-off at high wavenumbers. We develop an extended fluid model for ion dynamics to incorporate the effects of ion thermal motion. The model is based on the extended MHD model that includes the evolution equations for higher order moments such as ion viscosity and ion heat flux. We also develop the generalized Chapman-Enskog closure model that provides exact linear closures based on the linearized kinetic equation. The results of these models are compared and tested against the linear kinetic model. The dispersion of Farley-Buneman modes and growth rate behavior are investigated in the short wavelength region

  20. Ion thermal and dispersion effects in Farley-Buneman instabilities

    Energy Technology Data Exchange (ETDEWEB)

    Litt, S. K., E-mail: sandeep.litt@usask.ca; Smolyakov, A. I., E-mail: andrei.smolyakov@usask.ca [Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2 (Canada); Hassan, E., E-mail: ehab@utexas.edu [Department of Physics, University of Texas at Austin, Austin, Texas 78712 (United States); Department of Physics, Ain Shams University, Cairo (Egypt); Horton, W., E-mail: wendell.horton@gmail.com [Department of Physics, University of Texas at Austin, Austin, Texas 78712 (United States); Applied Research Laboratory, University of Texas at Austin, Austin, Texas 78758 (United States)

    2015-08-15

    Farley-Buneman modes are an example of the collisional instability, which is thought to be the dominant mechanism for the irregularities in low ionosphere region. Despite high collisionality due to electron-neutral and ion-neutral collisions, the kinetic effects associated with finite temperature are important for determination of the mode frequencies and growth rate. This is especially important for ion component that is largely unmagnetized due to low ion cyclotron frequency. The ion thermal effects are strongly pronounced for shorter wavelengths and are crucial for the growth rate cut-off at high wavenumbers. We develop an extended fluid model for ion dynamics to incorporate the effects of ion thermal motion. The model is based on the extended MHD model that includes the evolution equations for higher order moments such as ion viscosity and ion heat flux. We also develop the generalized Chapman-Enskog closure model that provides exact linear closures based on the linearized kinetic equation. The results of these models are compared and tested against the linear kinetic model. The dispersion of Farley-Buneman modes and growth rate behavior are investigated in the short wavelength region.

  1. An exact solution for the Hawking effect in a dispersive fluid

    CERN Document Server

    Philbin, T G

    2016-01-01

    We consider the wave equation for sound in a moving fluid with a fourth-order anomalous dispersion relation. The velocity of the fluid is a linear function of position, giving two points in the flow where the fluid velocity matches the group velocity of low-frequency waves. We find the exact scattering coefficients for wave propagation in the flow. The scattering shows amplification of classical waves, leading to spontaneous emission when the waves are quantized. In the dispersionless limit the system corresponds to a 1+1-dimensional black-hole or white-hole binary and there is a thermal spectrum of Hawking radiation from each horizon. Dispersion changes the scattering coefficients so that the quantum emission is no longer thermal.

  2. Hall effects on anomalous heat, particle and helicity transports through tearing-mode turbulence

    International Nuclear Information System (INIS)

    The helicity transport in a current-carrying plasma results in heat and particle transports in the direction opposite to the helicity flux. Tearing-mode turbulence produces helicity flux that is proportional to the gradient of equilibrium parallel current. The helicity flux is a consequence of a fluctuating electric field with a circularly polarized component, which also causes a nonlinear parallel current (primarily an electron flux) and a nonlinear polarization current (primarily an ion flux). Such anomalous heat and particle fluxes are driven by the free-energy associated with the perturbed magnetic field in the tearing-mode turbulence, and are typically directed inward to the plasma. Both fluxes becomes large when the gradient of the equilibrium current is large. 12 refs

  3. Do Sweeping Effects Suppress Particle Dispersion in Synthetic Turbulence?

    CERN Document Server

    Eyink, Gregory L

    2012-01-01

    Synthetic models of Eulerian turbulence like so called "Kinematic Simulations" (KS) have been criticized by Thomson & Devenish (TD) (2005), who argued that sweeping decorrelation effects suppress pair dispersion in such models. We derive analytical results for Eulerian turbulence modeled by Gaussian random fields for the case with zero mean velocity. Our starting point is an exact integrodifferential equation for the particle pair separation distribution. When memory times of particle locations are short, a Markovian approximation leads to a Richardson-type diffusion model. We obtain a diffusivity tensor of the form $K_{ij}(r,t)=S_{ij}(r)\\tau(r,t)$ where $S_{ij}(r)$ is the structure-function tensor and $\\tau(r,t)$ is an effective correlation time of velocity increments. This is found to be the minimum value of three times: the intrinsic turnover time $\\tau_{eddy}(r)$ at separation $r$, the overall evolution time $t,$ and the sweeping time $r/v_0$ with $v_0$ the rms velocity. We study the diffusion model n...

  4. In-resonator variation of waveguide cross-sections for dispersion control of aluminum nitride micro-rings

    CERN Document Server

    Jung, Hojoong; Tang, Hong X

    2015-01-01

    We propose and demonstrate a dispersion control technique by combination of different waveguide cross sections in an aluminum nitride micro-ring resonator. Narrow and wide waveguides with normal and anomalous dispersion, respectively, are linked with tapering waveguides and enclosed in a ring resonator to produce a total dispersion near zero. The mode-coupling in multimoded waveguides is also effectively suppressed. This technique provides new degrees of freedom and enhanced flexibility in engineering the dispersion of microcomb resonators.

  5. Excitation wavelength dependence of the anomalous circular photogalvanic effect in undoped InGaAs/AlGaAs quantum wells

    International Nuclear Information System (INIS)

    The excitation wavelength dependence of the anomalous circular photogalvanic effect (ACPGE) current arising from the reciprocal spin Hall effect (RSHE) in undoped InGaAs/AlGaAs quantum wells is measured under normal incidence of circularly polarized light at room temperature. We found that the spot location with the maximum ACPGE current is wavelength independent. And the normalized ACPGE current decreases at smaller wavelengths, which can be attributed to the sharp decrease of the spin relaxation time (τs) and the hot electron relaxation time (τ1) at smaller wavelengths. The study of the excitation wavelength dependence of ACPGE current is a good supplement to the in-depth investigation of RSHE

  6. The effect of plasma shear flow on drift Alfven instabilities of a finite beta plasma and on anomalous heating of ions by ion cyclotron turbulence

    Science.gov (United States)

    Jo, Young Hyun; Lee, Hae June; Mikhailenko, Vladimir V.; Mikhailenko, Vladimir S.

    2016-01-01

    It was derived that the drift-Alfven instabilities with the shear flow parallel to the magnetic field have significant difference from the drift-Alfven instabilities of a shearless plasma when the ion temperature is comparable with electron temperature for a finite plasma beta. The velocity shear not only modifies the frequency and the growth rate of the known drift-Alfven instability, which develops due to the inverse electron Landau damping, but also triggers a combined effect of the velocity shear and the inverse ion Landau damping, which manifests the development of the ion kinetic shear-flow-driven drift-Alfven instability. The excited unstable waves have the phase velocities along the magnetic field comparable with the ion thermal velocity, and the growth rate is comparable with the frequency. The development of this instability may be the efficient mechanism of the ion energization in shear flows. The levels of the drift--Alfven turbulence, resulted from the development of both instabilities, are determined from the renormalized nonlinear dispersion equation, which accounts for the nonlinear effect of the scattering of ions by the electromagnetic turbulence. The renormalized quasilinear equation for the ion distribution function, which accounts for the same effect of the scattering of ions by electromagnetic turbulence, is derived and employed for the analysis of the ion viscosity and ions heating, resulted from the interactions of ions with drift-Alfven turbulence. In the same way, the phenomena of the ion cyclotron turbulence and anomalous anisotropic heating of ions by ion cyclotron plasma turbulence has numerous practical applications in physics of the near-Earth space plasmas. Using the methodology of the shearing modes, the kinetic theory of the ion cyclotron turbulence of the plasma with transverse current with strong velocity shear has been developed.

  7. Anomalous effect in Schumann resonance phenomena observed in Japan, possibly associated with the Chi-chi earthquake in Taiwan

    Directory of Open Access Journals (Sweden)

    M. Hayakawa

    2005-06-01

    Full Text Available The Schumann resonance phenomenon has been monitored at Nakatsugawa (near Nagoya in Japan since the beginning of 1999, and due to the occurance of a severe earthquake (so-called Chi-chi earthquake on 21 September 1999 in Taiwan we have examined our Schumann resonance data at Nakatsugawa during the entire year of 1999. We have found a very anomalous effect in the Schumann resonance, possibly associated with two large land earthquakes (one is the Chi-chi earthquake and another one on 2 November 1999 (Chia-yi earthquake with a magnitude again greater than 6.0. Conspicuous effects are observed for the larger Chi-chi earthquake, so that we summarize the characteristics for this event. The anomaly is characterized mainly by the unusual increase in amplitude of the fourth Schumann resonance mode and a significant frequency shift of its peak frequency (~1.0Hz from the conventional value on the By magnetic field component which is sensitive to the waves propagating in the NS meridian plane. Anomalous Schumann resonance signals appeared from about one week to a few days before the main shock. Secondly, the goniometric estimation of the arrival angle of the anomalous signal is found to coincide with the Taiwan azimuth (the unresolved dual direction indicates toward South America. Also, the pulsed signals, such as the Q-bursts, were simultaneously observed with the "carrier" frequency around the peak frequency of the fourth Schumann resonance mode. The anomaly for the second event for the Chia-yi earthquake on 2 November had much in common. But, most likely due to a small magnitude, the anomaly appears one day before and lasts until one day after the main shock, with the enhancement at the fourth Schumann resonance mode being smaller in amplitude than the case of the Chi-chi earthquake. Yet, the other characteristics, including the goniometric direction finding result, frequency shift, etc., are nearly the same. Although the emphasis of

  8. Anomalous transport phenomena in px+i py superconductors

    Science.gov (United States)

    Li, Songci; Andreev, A. V.; Spivak, B. Z.

    2015-09-01

    Spontaneous breaking of time-reversal symmetry in superconductors with the px+i py symmetry of the order parameter allows for a class of effects which are analogous to the anomalous Hall effect in ferromagnets. These effects exist below the critical temperature, T effects. In particular, we consider anomalous Hall thermal conductivity, the polar Kerr effect, the anomalous Hall effect, and the anomalous photo- and acousto-galvanic effects.

  9. Micro-instabilities and anomalous transport effects in collisionless guide field reconnection

    Science.gov (United States)

    Munoz Sepulveda, Patricio Alejandro; Büchner, Jörg; Kilian, Patrick

    2016-07-01

    It is often the case that magnetic reconnection takes place in collisionless plasmas with a current aligned guide magnetic field, such as in the Solar corona. The general characteristics of this process have been exhaustively analyzed with theory and numerical simulations, under different approximations, since some time ago. However, some consequences and properties of the secondary instabilities arising spontaneously -other than tearing instability-, and their dependence on the guide field strength, have not been completely understood yet. For this sake, we use the results of fully kinetic 2D PIC numerical simulations of guide field reconnection. By using a mean field approach for the Generalized Ohm's law that explains the balance of the reconnected electric field, we find that some of the cross-streaming and gradient driven instabilities -in the guide field case- produce an additional anomalous transport term. The latter can be interpreted as a result of the enhanced correlated electromagnetic fluctuations, leading to a slow down of the current carriers and kinetic scale turbulence. We characterize these processes on dependence on the guide field strength, and explore the causal relation with the source of free energy driving the mentioned instabilities. Finally, we show the main consequences that a fully 3D approach have on all those phenomena in contrast to the reduced 2D description.

  10. Ferromagnetism, variable range hopping, and the anomalous Hall effect in epitaxial Co:ZnO thin film

    Institute of Scientific and Technical Information of China (English)

    Bai Hong-Liang; Chen Yan-Xue; Mei Liang-Mo; He Shu-Min; Xu Tong-Shuai; Liu Guo-Lei; Yan Shi-Shen; Zhu Da-Peng; Dai Zheng-Kun; Yang Feng-Fan; Dai You-Yong

    2012-01-01

    A series of high quality single crystalline epitaxial Zn0.95Co0.05O thin films is prepared by molecular beam epitaxy.Superparamagnetism and ferromagnetism are observed when the donor density is manipulated in a range of 1018 cm-3- 1020 cm-3 by changing the oxygen partial pressure during film growth.The conduction shows variable range hopping at low temperature and thermal activation conduction at high temperature.The ferromagnetism can be maintained up to room temperature.However,the anomalous Hall effect is observed only at low temperature and disappears above 160 K.This phenomenon can be attributed to the local ferromagnetism and the decreased optimal hopping distance at high temperatures.

  11. Anomalous decay and scattering processes of the eta meson

    CERN Document Server

    Kubis, Bastian

    2015-01-01

    We amend a recent dispersive analysis of the anomalous $\\eta$ decay process $\\eta\\to\\pi^+\\pi^-\\gamma$ by the effects of the $a_2$ tensor meson, the lowest-lying resonance that can contribute in the $\\pi\\eta$ system. While the net effects on the measured decay spectrum are small, they may be more pronounced for the analogous $\\eta'$ decay. There are nonnegligible consequences for the $\\eta$ transition form factor, which is an important quantity for the hadronic light-by-light scattering contribution to the muon's anomalous magnetic moment. We predict total and differential cross sections, as well as a marked forward-backward asymmetry, for the crossed process $\\gamma\\pi^-\\to\\pi^-\\eta$ that could be measured in Primakoff reactions in the future.

  12. Anomalous decay and scattering processes of the η meson

    International Nuclear Information System (INIS)

    We amend a recent dispersive analysis of the anomalous η decay process η → π+π-γ by the effects of the a2 tensor meson, the lowest-lying resonance that can contribute in the πη system. While the net effects on the measured decay spectrum are small, they may be more pronounced for the analogous η' decay. There are nonnegligible consequences for the η transition form factor, which is an important quantity for the hadronic light-by-light scattering contribution to the muon's anomalous magnetic moment. We predict total and differential cross sections, as well as a marked forward.backward asymmetry, for the crossed process γπ- → π-η, which could be measured in Primakoff reactions in the future. (orig.)

  13. Anomalous decay and scattering processes of the η meson

    Energy Technology Data Exchange (ETDEWEB)

    Kubis, Bastian [Universitaet Bonn, Helmholtz-Institut fuer Strahlen- und Kernphysik, Bonn (Germany); Universitaet Bonn, Bethe Center for Theoretical Physics, Bonn (Germany); Plenter, Judith [Universitaet Bonn, Helmholtz-Institut fuer Strahlen- und Kernphysik, Bonn (Germany)

    2015-06-15

    We amend a recent dispersive analysis of the anomalous η decay process η → π{sup +}π{sup -}γ by the effects of the a2 tensor meson, the lowest-lying resonance that can contribute in the πη system. While the net effects on the measured decay spectrum are small, they may be more pronounced for the analogous η' decay. There are nonnegligible consequences for the η transition form factor, which is an important quantity for the hadronic light-by-light scattering contribution to the muon's anomalous magnetic moment. We predict total and differential cross sections, as well as a marked forward.backward asymmetry, for the crossed process γπ{sup -} → π{sup -}η, which could be measured in Primakoff reactions in the future. (orig.)

  14. Anomalous Hall effect in the Co-based Heusler compounds Co2FeSi and Co2FeAI

    Science.gov (United States)

    Imort, I.-M.; Thomas, P.; Reiss, G.; Thomas, A.

    2012-04-01

    The anomalous Hall effect (AHE) in the Heusler compounds Co2FeSi and Co2FeAl is studied in dependence of the annealing temperature to achieve a general comprehension of its origin. We have demonstrated that the crystal quality affected by annealing processes is a significant control parameter to tune the electrical resistivity ρxx as well as the anomalous Hall resistivity ρahe. Analyzing the scaling behavior of ρahe in terms of ρxx points to a temperature-dependent skew scattering as the dominant mechanism in both Heusler compounds.

  15. Quantum cascade laser combs: effects of modulation and dispersion.

    Science.gov (United States)

    Villares, Gustavo; Faist, Jérôme

    2015-01-26

    Frequency comb formation in quantum cascade lasers is studied theoretically using a Maxwell-Bloch formalism based on a modal decomposition, where dispersion is considered. In the mid-infrared, comb formation persists in the presence of weak cavity dispersion (500 fs2 mm-1) but disappears when much larger values are used (30'000 fs2 mm-1). Active modulation at the round-trip frequency is found to induce mode-locking in THz devices, where the upper state lifetime is in the tens of picoseconds. Our results show that mode-locking based on four-wave mixing in broadband gain, low dispersion cavities is the most promising way of achieving broadband quantum cascade laser frequency combs. PMID:25835922

  16. The Effect of Height, Wing Length, and Wing Symmetry on Tabebuia rosea Seed Dispersal

    Directory of Open Access Journals (Sweden)

    Yasmeen Moussa

    2014-12-01

    Full Text Available The relationship between the vertical drop height and the horizontal distance traveled (dispersal ratio was investigated for a sample of fifty Tabebuia rosea seeds by dropping the seeds from five heights ranging from 1.00 to 2.00 meters. The dispersal ratio was found to be a constant 0.16 m/m for these heights. The effects of total seed length and asymmetry of seed wings on dispersal ratio were also measured using separate samples of fifty Tabebuia rosea seeds. It was found that neither seed length nor asymmetry had a significant effect on the dispersal ratio.

  17. Effects of periodic kicking on dispersion and wave packet dynamics in graphene

    Science.gov (United States)

    Agarwala, Adhip; Bhattacharya, Utso; Dutta, Amit; Sen, Diptiman

    2016-05-01

    We study the effects of δ -function periodic kicks on the Floquet energy-momentum dispersion in graphene. We find that a rich variety of dispersions can appear depending on the parameters of the kicking: at certain points in the Brillouin zone, the dispersion can become linear but anisotropic, linear in one direction and quadratic in the perpendicular direction, gapped with a quadratic dispersion, or completely flat (called dynamical localization). We show all these results analytically and demonstrate them numerically through the dynamics of wave packets propagating in graphene. We propose experimental methods for producing these effects.

  18. Effect of oil dispersants on microbially-mediated processes in freshwater systems

    International Nuclear Information System (INIS)

    The effect of 15 oil dispersants on the microbial degradation of Norman Wells oil has been investigated using capillary gas chromatography (CGC) and C14-radiometric techniques. Other ecologically important microbial biochemical processes, such as phosphatase, aerobic and anaerobic nitrogen fixation and methane production in natural waters and sediments were studied with selected dispersants. Several dispersants, when used at manufacturer's recommended rates, were found by CGC to have slightly stimulatory or no inhibitory effects on oil degradation under laboratory conditions. Other dispersants were toxic or inhibited degradation. The CGC results were confirmed by C14-labelled CO2 evolution from labelled substrates in laboratory cultures and natural waters. phosphatase activity was stimulated by 2 of 4 dispersants tested in the presence of oil. In the absence of oil, all 4 dispersants stimulated phosphatase activity. Aerobic N2 fixation was stimulated by three dispersants, while anaerobic N2-fixation was stimulated only at high concentrations of dispersants. One dispersant stimulated methane production in anaerobic sediments in proportion to the dispersant concentration. 16 refs., 8 figs., 3 tabs

  19. Effects of nonlocal dispersive interactions on self-trapping excitations

    DEFF Research Database (Denmark)

    Gaididei, Yu.B.; Mingaleev, S.F.; Christiansen, Peter Leth;

    1997-01-01

    A one-dimensional discrete nonlinear Schrodinger (NLS) model with the power dependence r(-s) on the distance r of the dispersive interactions is proposed. The stationary states psi(n) of the system are studied both analytically and numerically. Two types of stationary states are investigated: on...... excitation number N = Sigma(n)\\psi(n)\\(2). For cubic nonlinearity the bistability of on-site solitons may occur for dipole-dipole dispersive interaction (s = 3), while s(cr) for intersite solitons is close to 2.1. For increasing degree of nonlinearity sigma, s(cr) increases. The long-distance behavior of the...

  20. Analysis of anomalous electrical conductivity and magnetic permeability effects using a frequency domain controlled-source electromagnetic method

    Science.gov (United States)

    Noh, Kyubo; Oh, Seokmin; Seol, Soon Jee; Lee, Ki Ha; Byun, Joongmoo

    2016-03-01

    We present a series of processes for understanding and analysing controlled-source electromagnetic (CSEM) responses for a conductive and permeable earth. To realize the CSEM response, a new 3-D CSEM forward modelling algorithm based on an edge finite element method for both electrically conductive and magnetically permeable heterogeneities is developed. The algorithm shows highly accurate results in validation tests against a semi-analytic solution for stratified earth and an integral form of the scattered field. We describe the vector behaviour of an anomalous magnetic field originating from a conductive and permeable anomaly when the loop sources are deployed over a conductive half-space. The CSEM response of the conductive and permeable anomaly is classified into three effects originating from: conductivity perturbations, permeability perturbations and the coupling of these two effects. The separated individual results and the corresponding integral equation form of the anomalous field help to better understand the physical behaviour. We confirm the characteristic features of the CSEM response from the conductive and permeable anomaly, for example, (1) the general dominance of the induction effect in the out-of-phase response accompanied by a non-negligible magnetization effect from the magnetic anomaly in a conductive half-space and (2) the dominance of near frequency-independent magnetization effects in the in-phase response at relatively low frequencies and change in ruling part of the in-phase response into the induction effect as the frequency increases. We also demonstrate the effect of coupling mode and show that its maximum contribution is limited to a few per cent level of other two modes, induction and magnetization mode, even when the heterogeneity of our model is strong. In our synthetic survey, using examples of land-based profiling surveys of low induction number and intermediate regime, we find that the effect of magnetization can be used as an

  1. The comparative effects of oil dispersants and oil/dispersant conjugates on germination of the marine macroalga Phyllospora comosa (Fucales: Phaeophyta)

    International Nuclear Information System (INIS)

    Germination inhibition of the marine macrophyte Phyllospora comosa was utilized as a sub-lethal end-point to assess and compare the effects of four oil dispersants and dispersed diesel fuel and crude oil combinations. Inhibition of germination by the water-soluble fraction of diesel fuel increased following the addition of each of the dispersants; the nominal 48-h EC50 concentration of diesel fuel declined from 6800 to approximately 400 μl 1-1 nominal for each dispersed combination. This contrasted with crude oil, where the addition of two dispersants resulted in an enhanced germination rate and an increase in nominal EC50 concentrations from 130 μl 1-1 for the undispersed crude to 4000 and 2500 μl 1-1. The results indicate that, while germination inhibition of P. comosa may be enhanced by the chemical dispersal of oil response varies with type of both oil and oil dispersant. (author)

  2. Effects of Dispersal and Initial Diversity on the Composition and Functional Performance of Bacterial Communities

    OpenAIRE

    Yinghua Zha; Mercè Berga; Jérôme Comte; Silke Langenheder

    2016-01-01

    Natural communities are open systems and consequently dispersal can play an important role for the diversity, composition and functioning of communities at the local scale. It is, however, still unclear how effects of dispersal differ depending on the initial diversity of local communities. Here we implemented an experiment where we manipulated the initial diversity of natural freshwater bacterioplankton communities using a dilution-to-extinction approach as well as dispersal from a regional ...

  3. Characterization of gliclazide-polyethylene glycol solid dispersion and its effect on dissolution

    OpenAIRE

    Moreshwar Pandharinath Patil; Naresh Janardan Gaikwad

    2011-01-01

    The present study was initiated with the objective of studying the in vitro dissolution behavior of gliclazide from its solid dispersion with polyethylene glycol 6000. In this work, a solid dispersion of gliclazide with polyethylene glycol was prepared by the fusion method. In vitro dissolution study of gliclazide, its physical mixture and solid dispersion were carried out to demonstrate the effect of PEG 6000. Analytical techniques of FT-IR spectroscopy, differential scanning calorimetry and...

  4. Residential mobility and the spatial dispersion of personal networks: effects on social support

    OpenAIRE

    Viry, Gil

    2011-01-01

    Using a representative national sample of personal networks, this article explores how the spatial dispersion of networks, residential mobility and social support are linked. Three issues will be addressed here. Firstly, how is the spatial dispersion of personal networks related to individuals’ social characteristics, network composition and residential mobility? Secondly, how do the spatial dispersion of networks, residential mobility and their combined effect influence the number and (third...

  5. Residential Mobility and the Spatial Dispersion of Personal Networks:Effects on Social Support

    OpenAIRE

    Viry, Gil

    2012-01-01

    Using a representative national sample of personal networks, this article explores how the spatial dispersion of networks, residential mobility and social support are linked. Three issues will be addressed here. Firstly, how is the spatial dispersion of personal networks related to individuals’ social characteristics, network composition and residential mobility? Secondly, how do the spatial dispersion of networks, residential mobility and their combined effect influence the number and (third...

  6. Effects of oil dispersant on solubilization, sorption and desorption of polycyclic aromatic hydrocarbons in sediment–seawater systems

    International Nuclear Information System (INIS)

    Highlights: • Oil dispersant enhances solubilization of PAHs more effectively than surfactants. • Dispersant and dispersed oil enhance sediment sorption of PAHs and induce hysteresis. • Partitioning to sediment-sorbed dispersant is the mechanism for enhanced PAH uptake. • Dual-mode models well simulate dispersant-facilitated sorption of PAHs on sediment. • Deepwater conditions reduce solubilization of PAHs and lessen dispersant effects. - Abstract: This work investigated effects of a prototype oil dispersant on solubilization, sorption and desorption of three model PAHs in sediment–seawater systems. Increasing dispersant dosage linearly enhanced solubility for all PAHs. Conversely, the dispersant enhanced the sediment uptake of the PAHs, and induced significant desorption hysteresis. Such contrasting effects (adsolubilization vs. solubilization) of dispersant were found dependent of the dispersant concentration and PAH hydrophobicity. The dual-mode models adequately simulated the sorption kinetics and isotherms, and quantified dispersant-enhanced PAH uptake. Sorption of naphthalene and 1-methylnaphthalene by sediment positively correlated with uptake of the dispersant, while sorption of pyrene dropped sharply when the dispersant exceeded its critical micelle concentration (CMC). The deepwater conditions diminished the dispersant effects on solubilization, but enhanced uptake of the PAHs, albeit sorption of the dispersant was lowered. The information may aid in understanding roles of dispersants on distribution, fate and transport of petroleum PAHs in marine systems

  7. Effect of mean network coordination number on dispersivity characteristics

    NARCIS (Netherlands)

    Vasilyev, L.; Raoof, A.; Nordbotten, J.M.

    2012-01-01

    In this study, we investigate the role of topology on the macroscopic (centimeter scale) dispersion characteristics derived from pore-network models.We consider 3D random porous networks extracted from a regular cubic lattice with coordination number distributed in accordance with real porous struct

  8. The signatures of Anthropocene defaunation: cascading effects of the seed dispersal collapse.

    Science.gov (United States)

    Pérez-Méndez, Néstor; Jordano, Pedro; García, Cristina; Valido, Alfredo

    2016-01-01

    Anthropogenic activity is driving population declines and extinctions of large-bodied, fruit-eating animals worldwide. Loss of these frugivores is expected to trigger negative cascading effects on plant populations if remnant species fail to replace the seed dispersal services provided by the extinct frugivores. A collapse of seed dispersal may not only affect plant demography (i.e., lack of recruitment), but should also supress gene flow via seed dispersal. Yet little empirical data still exist demonstrating the genetic consequences of defaunation for animal-dispersed plant species. Here, we first document a significant reduction of seed dispersal distances along a gradient of human-driven defaunation, with increasing loss of large- and medium-bodied frugivores. We then show that local plant neighbourhoods have higher genetic similarity, and smaller effective population sizes when large seed dispersers become extinct (i.e., only small frugivores remain) or are even partially downgraded (i.e., medium-sized frugivores providing less efficient seed dispersal). Our results demonstrate that preservation of large frugivores is crucial to maintain functional seed dispersal services and their associated genetic imprints, a central conservation target. Early signals of reduced dispersal distances that accompany the Anthropogenic defaunation forecast multiple, cascading effects on plant populations. PMID:27091677

  9. Dirac spin gapless semiconductors: Ideal platforms for massless and dissipationless spintronics and new (quantum) anomalous spin Hall effects

    OpenAIRE

    Wang, Xiao-lin

    2016-01-01

    It is proposed that the new generation of spintronics should be ideally massless and dissipationless for the realization of ultra-fast and ultra-low-power spintronic devices. We demonstrate that the spin-gapless materials with linear energy dispersion are unique materials that can realize these massless and dissipationless states. Furthermore, we propose four new types of spin Hall effects which consist of spin accumulation of equal numbers of electrons and holes having the same or opposite s...

  10. Evaluation of the aquatic effects of crude oil, dispersants, and their mixtures

    International Nuclear Information System (INIS)

    Toxicity tests were conducted on several dispersants using advanced toxicity test apparatus and techniques under closed, flow-through conditions. The objective of the study was to understand the effects of dispersants on natural oil toxicity, and the consequences of their use. To do so, it was necessary to conduct tests on the toxicity of the surfactants and oil, alone and in combination. Results of a preliminary investigation of the toxicity of both dispersed and undispersed Prudhoe Bay crude oil using juvenile crustaceans were cited. Toxicity results were intended to be used as a guidance as to when dispersants may or may not be appropriate. 30 refs., 2 tabs., 6 figs

  11. The Effect of Shipping Stresses on Vaccine Re-dispersion Time.

    Science.gov (United States)

    Guo, Jianxin; Lewis, Lavinia M; Billones, Hilbert; Torres, Ekaterina; Kolhe, Parag

    2016-06-01

    A case study is presented for a vaccine drug product (DP) that showed variable re-dispersion times between syringes within a given DP lot and between different DP lots when shipped from the manufacturing site to the receiving site. A simulated shipping study was designed to understand the effect of individual shipping stresses on re-dispersion time and product quality. Shipping stresses simulating shock/drop, aircraft, and truck vibrations were applied separately to 3 syringe orientations, namely tip up, tip down, and tip horizontal (TH). Results from the simulated shipping study showed that shock/drop reduced re-dispersion time while truck and aircraft vibrations increased re-dispersion time in the tip down orientation. The dissimilar effects of different shipping stresses on re-dispersion resulted in the observed intra and inter DP lot variability in re-dispersion time. Shipping stresses did not impact re-dispersion in the TH or tip up orientation. No vaccine product quality attributes or physical properties were affected by shipping stresses. Actual shipping results correlated well with simulated shipping data. Because re-dispersion time was influenced mainly by shipping stress and syringe orientation, the mitigation measure to reduce end-user re-dispersion time was to implement the TH orientation for DP syringes during shipment and storage. PMID:27155766

  12. Effects of Dispersal and Initial Diversity on the Composition and Functional Performance of Bacterial Communities

    Science.gov (United States)

    Zha, Yinghua; Berga, Mercè; Comte, Jérôme; Langenheder, Silke

    2016-01-01

    Natural communities are open systems and consequently dispersal can play an important role for the diversity, composition and functioning of communities at the local scale. It is, however, still unclear how effects of dispersal differ depending on the initial diversity of local communities. Here we implemented an experiment where we manipulated the initial diversity of natural freshwater bacterioplankton communities using a dilution-to-extinction approach as well as dispersal from a regional species pool. The aim was further to test whether dispersal effects on bacterial abundance and functional parameters (average community growth rates, respiration rates, substrate utilisation ability) differ in dependence of the initial diversity of the communities. First of all, we found that both initial diversity and dispersal rates had an effect on the recruitment of taxa from a regional source, which was higher in communities with low initial diversity and at higher rates of dispersal. Higher initial diversity and dispersal also promoted higher levels of richness and evenness in local communities and affected, both, separately or interactively, the functional performance of communities. Our study therefore suggests that dispersal can influence the diversity, composition and functioning of bacterial communities and that this effect may be enhanced if the initial diversity of communities is depleted. PMID:27182596

  13. Measuring the Equilibrium Effects of Unemployment Benefits Dispersion

    OpenAIRE

    Vuuren, van, A.; Berg, van den, V.A.C.; Ridder, Geert

    1999-01-01

    This discussion paper resulted in a publication in the Journal of Applied Econometrics (2000). Volume 15, issue 6, pages 547-574. We analyze the impact of unemployment benefits and minimum wagesusing an equilibrium search model which allows for dispersion ofbenefits and productivity levels, job-to-job transitions, andstructural and frictional unemployment. The estimation method usesreadily available aggregate data on marginal distributions ofunemployment durations as well as wages and benefit...

  14. Effect of ultrasonic irradiation on dispersed polymer droplets in water

    OpenAIRE

    HATATE, Yasuo; IKARI, Atsushi; Kondo, Kazuo; NAKASHIO, Fumiyuki; ハタテ, ヤスオ; イカリ, アツシ; コンドウ, カズオ; ナカシオ, フミユキ; 幡手, 泰雄; 碇, 醇; 近藤, 和生; 中塩, 文行

    1984-01-01

    A condition of 30 to 50% monomer conversion in styrene suspension polymerization was approximated by dispersing toluene containing 30 to 50wt% polystyrene in water. The size distribution of those polymer droplets, in which no polymerization occurs, was measured under conditions of ultrasonic irradiation and of no irradiation to obtain more detailed information about viscous droplets in a stirred tank reactor under ultrasonic irradiation. The ultrasonics caused a comparatively strong cohesive ...

  15. Suppressing the neoclassical tearing modes in tokamaks during anomalous transverse transport owing to predomination of the magnetic well effect over the bootstrap drive

    International Nuclear Information System (INIS)

    Suppression of neoclassical tearing modes in tokamaks under anomalous transverse transport conditions when the magnetic well effect predominates over the bootstrap drive is studied. Reduced equations of transfer are used in the description. Geodetic effects are considered during the magnetic well calculation. A criterion for the stabilization of neoclassical tearing modes by the compound effect at an arbitrary level of the transverse heat transport by electrons and ions is derived

  16. Quantum anomalous Hall effect and a nontrivial spin-texture in ultra-thin films of magnetic topological insulators

    Energy Technology Data Exchange (ETDEWEB)

    Duong, Le Quy; Das, Tanmoy; Feng, Y. P.; Lin, Hsin, E-mail: nilnish@gmail.com [Graphene Research Centre and Department of Physics, National University of Singapore, Singapore 117546 (Singapore)

    2015-05-07

    We study the evolution of quantum anomalous Hall (QAH) effect for a Z{sub 2} topological insulator (TI) thin films in a proximity induced magnetic phase by a realistic layered k·p model with interlayer coupling. We examine three different magnetic configurations in which ferromagnetic (FM) layer(s) is added either from one side (FM-TI), from both sides (FM-TI-FM), or homogeneously distributed (magnetically doped) in a TI slab. We map out the thickness-dependent topological phase diagram under various experimental conditions. The critical magnetic exchange energy for the emergence of QAH effect in the latter two cases decreases monotonically with increasing number of quintuple layers (QLs), while it becomes surprisingly independent of the film thickness in the former case. The gap size of the emergent QAH insulator depends on the non-magnetic “parent” gap of the TI thin film and is tuned by the FM exchange energy, opening a versatile possibility to achieve room-temperature QAH insulator in various topological nanomaterials. Finally, we find that the emergent spin-texture in the QAH effect is very unconventional, non-“hedgehog” type; and it exhibits a chiral out-of-plane spin-flip texture within the same valence band which is reminiscent of dynamical “skyrmion” pattern, except our results are in the momentum space.

  17. Potential lethal and non-lethal effects of predators on dispersal of spider mites.

    Science.gov (United States)

    Otsuki, Hatsune; Yano, Shuichi

    2014-11-01

    Predators can affect prey dispersal lethally by direct consumption or non-lethally by making prey hesitate to disperse. These lethal and non-lethal effects are detectable only in systems where prey can disperse between multiple patches. However, most studies have drawn their conclusions concerning the ability of predatory mites to suppress spider mites based on observations of their interactions on a single patch or on heavily infested host plants where spider mites could hardly disperse toward intact patches. In these systems, specialist predatory mites that penetrate protective webs produced by spider mites quickly suppress the spider mites, whereas generalist predators that cannot penetrate the webs were ineffective. By using a connected patch system, we revealed that a generalist ant, Pristomyrmex punctatus Mayr (Hymenoptera: Formicidae), effectively prevented dispersal of spider mites, Tetranychus kanzawai Kishida (Acari: Tetranychidae), by directly consuming dispersing individuals. We also revealed that a generalist predatory mite, Euseius sojaensis Ehara (Acari: Phytoseiidae), prevented between-patch dispersal of T. kanzawai by making them hesitate to disperse. In contrast, a specialist phytoseiid predatory mite, Neoseiulus womersleyi Schicha, allowed spider mites to escape an initial patch, increasing the number of colonized patches within the system. Our results suggest that ants and generalist predatory mites can effectively suppress Tetranychus species under some conditions, and should receive more attention as agents for conservation biological control in agroecosystems. PMID:24867061

  18. THE EFFECT OF CLAY DISPERSION ON THE CRYSTALLIZATION AND MORPHOLOGY OF POLYPROPYLENE/CLAY COMPOSITES

    Institute of Scientific and Technical Information of China (English)

    Qin Zhang; Xiao-lin Gao; Ke Wang; Qiang Fu

    2004-01-01

    PP/clay composites with different dispersions, namely, exfoliated dispersion, intercalated dispersion and agglomerates and panicle-like dispersion, were prepared by direct melt intercalation or compounding. The effect of clay dispersion on the crystallization and morphology of PP was investigated via PLM, SAXS and DSC. Experimental results show that exfoliated clay layers are much more efficient than intercalated clay and agglomerates of clay in serving as nucleation agent due to the nano-scale dispersion of clay, resulting in a dramatic decrease in crystal size (lamellar thickness and spherulites) and an increase of crystallization temperature and crystallization rate. On the other hand, a decrease of melting temperature and crystallinity was also observed in PP/clay composites with exfoliated dispersion, due to the strong interaction between PP and clay. Compared with exfoliated clay layers, the intercalated clay layers have a less important effect on the crystallization and crystal morphology. No effect is seen for samples with agglomerates and panicle-like dispersion, in regard to melting temperature, crystallization temperature, crystal thickness and crystallinity.

  19. Effects of mixing energy and flow dynamics on chemical dispersion of crude oil. Volume 1

    International Nuclear Information System (INIS)

    Oil spills at sea can be treated with chemical dispersants to reduce the oil-water interfacial tension and facilitate entrainment of the oil into the water column as small droplets. Removing the floating oil protects surface-swelling organisms and sensitive shorelines. The environmental impacts can be further minimized if the dispersed oil droplets can be diluted into a sufficiently large volume of water by turbulent diffusion. Therefore, this study investigated the effects of mixing energy and mixing systems on dispersion effectiveness of Mars crude oil using 2 bench-scale experimental systems. Two dispersant HLB (hydrophile-lipofile balance) of 10 and 12 were tested for size distribution and dispersed oil droplets. Dispersion effectiveness was defined as the volume of mass fraction of floating oil that becomes entrained in the water column after mixing energy is introduced. The size distribution of the dispersed oil droplets provides another measure of dispersion effectiveness since smaller oil droplets have a stronger tendency to remain suspended in the water column. In this study, dispersion effectiveness was measured at 4 different energy dissipation rates in 2 different mixing systems, namely a baffled flask system and a paddle jar system. It was shown that even when the average energy dissipation rate was the same, the fluid flow dynamics were quite different in the two systems. The droplet-size distributions were multimodal, with 2 major modes occurring in dispersions produced in the baffled-flask system. The diameters of mean volume of the major modes were not found to be sensitive to changes in the energy dissipation rates. However, in the baffled-flask system, the distribution of oil among the modes was influenced by the energy dissipation rate. 25 refs., 5 figs

  20. Effects of mixing energy and flow dynamics on chemical dispersion of crude oil. Volume 1

    Energy Technology Data Exchange (ETDEWEB)

    Mukherjee, B.; Wrenn, B.A. [Washington Univ., St. Louis, MO (United States). Dept. of Energy, Environment and Chemical Engineering

    2007-07-01

    Oil spills at sea can be treated with chemical dispersants to reduce the oil-water interfacial tension and facilitate entrainment of the oil into the water column as small droplets. Removing the floating oil protects surface-swelling organisms and sensitive shorelines. The environmental impacts can be further minimized if the dispersed oil droplets can be diluted into a sufficiently large volume of water by turbulent diffusion. Therefore, this study investigated the effects of mixing energy and mixing systems on dispersion effectiveness of Mars crude oil using 2 bench-scale experimental systems. Two dispersant HLB (hydrophile-lipofile balance) of 10 and 12 were tested for size distribution and dispersed oil droplets. Dispersion effectiveness was defined as the volume of mass fraction of floating oil that becomes entrained in the water column after mixing energy is introduced. The size distribution of the dispersed oil droplets provides another measure of dispersion effectiveness since smaller oil droplets have a stronger tendency to remain suspended in the water column. In this study, dispersion effectiveness was measured at 4 different energy dissipation rates in 2 different mixing systems, namely a baffled flask system and a paddle jar system. It was shown that even when the average energy dissipation rate was the same, the fluid flow dynamics were quite different in the two systems. The droplet-size distributions were multimodal, with 2 major modes occurring in dispersions produced in the baffled-flask system. The diameters of mean volume of the major modes were not found to be sensitive to changes in the energy dissipation rates. However, in the baffled-flask system, the distribution of oil among the modes was influenced by the energy dissipation rate. 25 refs., 5 figs.

  1. Effects of mixing energy and flow dynamics on chemical dispersion of crude oil

    Energy Technology Data Exchange (ETDEWEB)

    Mukherjee, B.; Wrenn, B.A. [Washington Univ., St. Louis, MO (United States). Dept. of Energy, Environment and Chemical Engineering

    2007-07-01

    Oil spills at sea can be treated with chemical dispersants to reduce the oil-water interfacial tension and facilitate entrainment of the oil into the water column as small droplets. Removing the floating oil protects surface-swelling organisms and sensitive shorelines. The environmental impacts can be further minimized if the dispersed oil droplets can be diluted into a sufficiently large volume of water by turbulent diffusion. Therefore, this study investigated the effects of mixing energy and mixing systems on dispersion effectiveness of Mars crude oil using 2 bench-scale experimental systems. Two dispersant HLB (hydrophile-lipofile balance) of 10 and 12 were tested for size distribution and dispersed oil droplets. Dispersion effectiveness was defined as the volume of mass fraction of floating oil that becomes entrained in the water column after mixing energy is introduced. The size distribution of the dispersed oil droplets provides another measure of dispersion effectiveness since smaller oil droplets have a stronger tendency to remain suspended in the water column. In this study, dispersion effectiveness was measured at 4 different energy dissipation rates in 2 different mixing systems, namely a baffled flask system and a paddle jar system. It was shown that even when the average energy dissipation rate was the same, the fluid flow dynamics were quite different in the two systems. The droplet-size distributions were multimodal, with 2 major modes occurring in dispersions produced in the baffled-flask system. The diameters of mean volume of the major modes were not found to be sensitive to changes in the energy dissipation rates. However, in the baffled-flask system, the distribution of oil among the modes was influenced by the energy dissipation rate. 25 refs., 5 figs.

  2. Environmental effects of the Deepwater Horizon oil spill: focus on effects on fish and effects of dispersants

    Energy Technology Data Exchange (ETDEWEB)

    Trannum, H.; Bakke, T.

    2012-07-01

    NIVA has conducted a literature study on environmental effects of the Deepwater Horizon accident for the Norwegian Oil Industry Association, and the present report summarizes this work with particular focus on fish and dispersants. The report also briefly discusses relevance for Norwegian waters. In the literature, negative effects on the population level of fish have not been reported, although there is evidence of effects on the cellular level of fish. Several exploited species were even characterized by notably higher catch rates during 2010. Despite this, the economic losses for the fishing industry were huge due to an extensive closure of fisheries and effects in the marked. Following the oil spill, large amounts of dispersants were used, mainly Corexit, and for the first time, the dispersants were added under the sea surface. It is not clear whether the dispersants were successful in reducing the overall impacts of the oil. Furthermore, there are indications that the dispersants had the potential to inhibit the natural degradation of oil. Although the use of Corexit was criticized, laboratory studies have shown that Corexit generally tends to be less toxic than several other dispersants. (Author)

  3. Magnetoresistance and anomalous Hall effect of reactive sputtered polycrystalline Ti1−xCrxN films

    International Nuclear Information System (INIS)

    The reactive-sputtered polycrystalline Ti1−xCrxN films with 0.17 ≤ x ≤ 0.51 are ferromagnetic and at x = 0.47 the Curie temperature TC shows a maximum of ∼ 120 K. The films are metallic at 0 ≤ x ≤ 0.47, while the films with x = 0.51 and 0.78 are semiconducting-like. The upturn of resistivity below 70 K observed in the films with 0.10 ≤ x ≤ 0.47 is from the effects of the electron–electron interaction and weak localization. The negative magnetoresistance (MR) of the films with 0.10 ≤ x ≤ 0.51 is dominated by the double-exchange interaction, while at x = 0.78, MR is related to the localized magnetic moment scattering at the grain boundaries. The scaling ρxyA/n ∝ ρxx2.19 suggests that the anomalous Hall effect in the polycrystalline Ti1−xCrxN films is scattering-independent. - Highlights: • The reactive-sputtered polycrystalline Ti1−xCrxN films are ferromagnetic. • The highest Curie temperature TC of ∼ 120 K appears at x = 0.47. • The negative magnetoresistance is dominated by the double-exchange interaction. • The scaling ρxyA/n ∝ ρxx2.19 was observed

  4. Pictures of blockscale transport: Effective versus ensemble dispersion and its uncertainty

    Science.gov (United States)

    de Barros, Felipe P. J.; Dentz, Marco

    2016-05-01

    Solute transport models tend to use coarse numerical grid blocks to alleviate computational costs. Aside from computational issues, the subsurface environment is usually characterized over a coarse measurement network where only large scale fluctuations of the flow field are captured. Neglecting the subscale velocity fluctuations in transport simulators can lead to erroneous predictions with consequences in risk analysis and remediation. For such reasons, upscaled dispersion coefficients in spatially heterogeneous flow fields must (1) account for the subscale variability that is filtered out by homogenization and (2) be modeled as a random function to incorporate the uncertainty associated with non-ergodic solute bodies. In this work, we examine the low order statistical properties of the blockscale dispersion tensor. The blockscale is defined as the scale upon which the spatially variable flow field is homogenized (e.g. the numerical grid block). Using a Lagrangian framework, we discuss different conceptualizations of the blockscale dispersion tensor. We distinguish effective and ensemble blockscale dispersion, which measure the impact of subscale velocity fluctuations on solute dispersion. Ensemble dispersion quantifies subscale velocity fluctuations between realizations, which overestimates the actual velocity variability. Effective dispersion on the other hand quantifies the actual blockscale velocity variability and thus reflects the impact of subscale velocity fluctuations on mixing and spreading. Based on these concepts, we quantify the impact of subscale velocity fluctuations on solute particle spreading and determine the governing equations for the coarse-grained concentration distributions. We develop analytical and semi-analytical expressions for the average and variance of the blockscale dispersion tensor in 3D flow fields as a function of the structural parameters characterizing the subsurface. Our results illustrate the relevance of the blockscale

  5. On the effect of damping on dispersion curves in plates

    DEFF Research Database (Denmark)

    Manconia, Elisabetta; Sorokin, Sergey

    2013-01-01

    This paper presents a study on quantitative prediction and understanding of time-harmonic wave characteristics in damped plates. Material dissipation is modelled by using complex-valued velocities of free dilatation and shear waves in an unbounded volume. As a numerical example, solution of the...... classical Rayleigh–Lamb problem for a viscoelastic plate is presented to illustrate and discuss the role of dissipation in the cut-off phenomenon and in the phenomenon of veering for dispersion curves. These phenomena are explained in more detail considering a simple model, which allows accurate asymptotic...

  6. Effects of Schwarzschild Geometry on Isothermal Plasma Wave Dispersion

    CERN Document Server

    Sharif, M

    2007-01-01

    The behavior of isothermal plasma waves has been analyzed near the Schwarzschild horizon. We consider a non-rotating background with non-magnetized and magnetized plasmas. The general relativistic magnetohydrodynamical equations for the Schwarzschild planar analogue spacetime with an isothermal state of the plasma are formulated. The perturbed form of these equations is linearized and Fourier analyzed by introducing simple harmonic waves. The determinant of these equations in each case leads to a complex dispersion relation, which gives complex values of the wave number. This has been used to discuss the nature of the waves and their characteristics near the horizon.

  7. Anomalous Hall effect suppression in anatase Co:TiO2 by the insertion of an interfacial TiO2 buffer layer

    NARCIS (Netherlands)

    Lee, Y.J.; Jong, de M.P.; Wiel, van der W.G.; Kim, Y.; Brock, J.D.

    2010-01-01

    We present the effect of introducing a TiO2 buffer layer at the SrTiO3/Co:TiO2 interface on the magnetic and structural properties of anatase Co:TiO2 (1.4 at. % Co). Inserting the buffer layer leads to suppression of the room-temperature anomalous Hall effect, accompanied by a reduced density of Co

  8. A correction technique for the dispersive effects of mass lumping for transport problems

    KAUST Repository

    Guermond, Jean-Luc

    2013-01-01

    This paper addresses the well-known dispersion effect that mass lumping induces when solving transport-like equations. A simple anti-dispersion technique based on the lumped mass matrix is proposed. The method does not require any non-trivial matrix inversion and has the same anti-dispersive effects as the consistent mass matrix. A novel quasi-lumping technique for P2 finite elements is introduced. Higher-order extensions of the method are also discussed. © 2012 Elsevier B.V.

  9. Variable effects of dispersal on productivity of bacterial communities due to changes in functional trait composition.

    Directory of Open Access Journals (Sweden)

    Ina Severin

    Full Text Available Previous studies have shown variable relationships between dispersal rate and ecosystem functioning, but the reasons for and mechanisms behind variable dispersal rate-functioning patterns are currently unknown. In this study we used six bacterial lake water communities in a laboratory experiment in order to investigate how dispersal among communities influences community productivity by evaluating three different mechanisms: 1 changes in taxonomic diversity, 2 changes in phylogenetic diversity or 3 changes in the composition of functional traits. The experiment was conducted in two phases; (A a dialysis bag experiment where the dispersal rate among six communities was manipulated and the subsequent change in bacterial diversity and growth rate was recorded, and (B a regrowth experiment where we manipulated available resources to study how well a taxon grows on certain organic carbon resources, i.e. their functional traits. From experiment (B we could thus estimate changes in functional traits in communities in experiment (A. Bacterial production was affected by dispersal, but not consistently among lakes. Neither change in taxonomic or phylogenetic diversity with dispersal could explain the observed dispersal-productivity relationships. Instead, changes in trait composition with dispersal, especially the communities' ability to use p-coumaric acid, an aromatic compound, could explain the observed dispersal-productivity relationships. Changes in this trait caused by dispersal seemed especially important for bacterial productivity in waters with a high aromaticity of the organic matter pool. We conclude that the effect of dispersal on bacterial communities can affect ecosystem functioning in different ways, through changes in functional key-traits which are important for the local environment.

  10. Theory of the Dirac half metal and quantum anomalous Hall effect in Mn-intercalated epitaxial graphene

    Science.gov (United States)

    Li, Yuanchang; West, Damien; Huang, Huaqing; Li, Jia; Zhang, S. B.; Duan, Wenhui

    2015-11-01

    The prospect of a Dirac half metal, a material which is characterized by a band structure with a gap in one spin channel but a Dirac cone in the other, is of both fundamental interest and a natural candidate for use in spin-polarized current applications. However, while the possibility of such a material has been reported based on model calculations [H. Ishizuka and Y. Motome, Phys. Rev. Lett. 109, 237207 (2012), 10.1103/PhysRevLett.109.237207], it remains unclear what material system might realize such an exotic state. Using first-principles calculations, we show that the experimentally accessible Mn-intercalated epitaxial graphene on SiC(0001) transits to a Dirac half metal when the coverage is >1 /3 monolayer. This transition results from an orbital-selective breaking of quasi-two-dimensional inversion symmetry, leading to symmetry breaking in a single spin channel which is robust against randomness in the distribution of Mn intercalates. Furthermore, the inclusion of spin-orbit interaction naturally drives the system into the quantum anomalous Hall (QAH) state. Our results thus not only demonstrate the practicality of realizing the Dirac half metal beyond a toy model, but also open up an avenue to the realization of the QAH effect.

  11. Theory for the anomalous electron transport in Hall effect thrusters. I. Insights from particle-in-cell simulations

    Science.gov (United States)

    Lafleur, T.; Baalrud, S. D.; Chabert, P.

    2016-05-01

    Using a 1D particle-in-cell simulation with perpendicular electric, E0, and magnetic, B0, fields, and modelling the azimuthal direction (i.e., the E0 × B0 direction), we study the cross-field electron transport in Hall effect thrusters (HETs). For low plasma densities, the electron transport is found to be well described by classical electron-neutral collision theory, but at sufficiently high densities (representative of typical HETs), a strong instability is observed to significantly enhance the electron mobility, even in the absence of electron-neutral collisions. This instability is associated with correlated high-frequency (of the order of MHz) and short-wavelength (of the order of mm) fluctuations in both the electric field and the plasma density, which are shown to be the cause of the anomalous transport. Saturation of the instability is observed to occur due to a combination of ion-wave trapping in the E0 × B0 direction, and convection in the E0 direction.

  12. Anomalous enhancement and suppression of ionization induced by an effective few-cycle pulse in the frequency domain

    Science.gov (United States)

    Foote, David; Lin, Yingda; Hill, Wendell T., III

    2015-05-01

    In a recent set of coherent control experiments, an anomalous sinusoidal variation of the ionization yield was observed in Xe when ionized by a pairs of phase-locked, many-cycle 800 nm pulses. Compared with the signal of a single transform limited pulse, both enhancement and suppression was possible, which depended on the temporal separation and relative phase of the pulses. In the time domain, the control can be viewed as a temporal Young's double slit experiment - two coherent electron wavepackets interfering. In the frequency domain, the photoelectron spectrum is given by the modulus squared of the Fourier transform of the field, which is a few-cycle squared sinusodial function. In analogy to a few-cycle pulse where the carrier phase dictates the ejection direction of rescattered electrons, enhancement (suppression) occurs when the effective carrier waveform is cos[w-w0]2 (sin[w-w0]2). The contrast decreased with increasing pulse separation and decreasing multiphoton order. Detailed results and a model simulation will be presented.

  13. Effect of polydimethylsiloxane viscosity on the electrorheological activity of dispersions based on it

    Science.gov (United States)

    Davydova, O. I.; Kraev, A. S.; Redozubov, A. A.; Trusova, T. A.; Agafonov, A. V.

    2016-06-01

    The effect the viscosity of a dispersion medium of a polymethylsiloxane fluid (PMS) with a kinematic viscosity over a wide range of values from 5 to 300 cSt has on the electrorheological properties of suspensions based on nanosized titanium dioxide obtained via the sol-gel method is investigated. The investigations are conducted in a wide range of concentrations of suspensions: from 30 to 60 wt % (from 15 to 38 vol %) of the dispersed phase. The role the dispersion medium in two-phase disperse systems plays in the formation of structures of dispersed phase in the presence of an electric field is determined from the dependence of yield points of TiO2 in PMS with different viscosities on the applied electric field strength.

  14. Anomalous Earth flybys of spacecraft

    Science.gov (United States)

    Wilhelm, Klaus; Dwivedi, Bhola N.

    2015-07-01

    A small deviation from the potential is expected for the gravitational interaction of extended bodies. It is explained as a consequence of a recently proposed gravitational impact model (Wilhelm et al. in Astrophys. Space Sci. 343:135-144, 2013) and has been applied to anomalous perihelion advances by Wilhelm and Dwivedi (New Astron. 31:51-55, 2014). The effect—an offset of the effective gravitational centre from the geometric centre of a spherical symmetric body—might also be responsible for the observed anomalous orbital energy gains and speed increases during Earth flybys of several spacecraft. However, close flybys would require detailed considerations of the orbit geometry. In this study, an attempt is made to explain the anomalous Earth flybys of the Galileo, NEAR Shoemaker and Rosetta spacecraft.

  15. Biodegradation of oil-contaminated sediments : effect of a dispersant and natural organic matter

    Energy Technology Data Exchange (ETDEWEB)

    LaRiviere, D.; Autenrieth, R.L. [Texas A and M Univ., College Station, TX (United States). Dept. of Civil Engineering; Bonner, J.S. [Texas A and M Univ., Corpus Christi, TX (United States). Conrad Blucher Inst. for Surveying and Science

    2003-07-01

    Dispersants are mixtures of surfactants and solvents that help dissolve oil in water through the formation of small mixed oil-surfactant micelles. They were initially developed to prevent oil slicks at sea from reaching shorelines. Dispersants, however, shift the impact of contamination to the water column and its underlying sediment. A study was conducted to examine the microbial response of sediment slurries to oil and dispersed oil. It also examined the consumption of oxygen by dispersants, the mineralization of organic carbon, and the degradation of alkane and aromatic fractions. In particular, the study found that Corexit 9500 is a dispersant which raises the respirometric activity in aerobic incubations of wetland sediment slurries contaminated with Arabian medium crude. The remaining total target saturates were found to be much higher in the dispersant treated reactors, but a significant effect was not noted. Aromatics were found to be the same in the dispersant treated slurries, suggesting that oil degradation is not enhanced, but that the dispersant acted as a competitive substrate. Sediments with higher organic matter showed higher respirometric activity in oil degradation. It was concluded that the natural organic matter found in sediments must support indigenous microbial populations that promote oil degradation. 22 refs., 1 tab., 7 figs.

  16. Effects of oil dispersants on photodegradation of pyrene in marine water

    International Nuclear Information System (INIS)

    Highlights: • Oil dispersant enhances pyrene photodegradation in seawater. • Oil dispersant increases formation of superoxide radicals. • Pyrene photodegradation shows a two-stage kinetics and follows first-order rate law. • Pyrene is degraded mainly through electron transfer from excited pyrene to oxygen. • Higher ionic strength and temperature and lower HA favor pyrene photodegradation. - Abstract: This work investigated effects of a popular oil dispersant (Corexit EC9500A) on UV- or sunlight-mediated photodegradation of pyrene (a model polycyclic aromatic hydrocarbon) in seawater. The presence of 18 and 180 mg/L of the dispersant increased the first-order photodegradation rate by 5.5% and 16.7%, respectively, and reduced or ceased pyrene volatilization. By combining individual first-order rate laws for volatilization and photodegradation, we proposed an integrated kinetic model that can adequately predict the overall dissipation of pyrene from seawater. Mechanistic studies indicated that superoxide radicals played a predominant role in pyrene photodegradation, and the dispersant enhanced formation of superoxide radicals. 1-Hydroxypyrene was the main intermediate regardless of the dispersant, suggesting that electrons were transferred from excited pyrene to oxygen. In the presence of 18 mg/L of the dispersant, the photodegradation rate increased with increasing ionic strength and temperature, but decreased with increasing HA concentration, and remained independent of solution pH. The results are important in understanding roles of oil dispersants on environmental fate of persistent oil components in natural and engineered systems

  17. Effects of oil dispersants on photodegradation of pyrene in marine water

    Energy Technology Data Exchange (ETDEWEB)

    Gong, Yanyan [Environmental Engineering Program, Department of Civil Engineering, Auburn University, Auburn, AL 36849 (United States); College of Environmental Science and Engineering, Nankai University, Tianjin 300071 (China); Fu, Jie [Environmental Engineering Program, Department of Civil Engineering, Auburn University, Auburn, AL 36849 (United States); O’Reilly, S.E. [U.S. Department of the Interior, Gulf of Mexico OCS, Office of Environment, New Orleans, LA 70123 (United States); Zhao, Dongye, E-mail: zhaodon@auburn.edu [Environmental Engineering Program, Department of Civil Engineering, Auburn University, Auburn, AL 36849 (United States)

    2015-04-28

    Highlights: • Oil dispersant enhances pyrene photodegradation in seawater. • Oil dispersant increases formation of superoxide radicals. • Pyrene photodegradation shows a two-stage kinetics and follows first-order rate law. • Pyrene is degraded mainly through electron transfer from excited pyrene to oxygen. • Higher ionic strength and temperature and lower HA favor pyrene photodegradation. - Abstract: This work investigated effects of a popular oil dispersant (Corexit EC9500A) on UV- or sunlight-mediated photodegradation of pyrene (a model polycyclic aromatic hydrocarbon) in seawater. The presence of 18 and 180 mg/L of the dispersant increased the first-order photodegradation rate by 5.5% and 16.7%, respectively, and reduced or ceased pyrene volatilization. By combining individual first-order rate laws for volatilization and photodegradation, we proposed an integrated kinetic model that can adequately predict the overall dissipation of pyrene from seawater. Mechanistic studies indicated that superoxide radicals played a predominant role in pyrene photodegradation, and the dispersant enhanced formation of superoxide radicals. 1-Hydroxypyrene was the main intermediate regardless of the dispersant, suggesting that electrons were transferred from excited pyrene to oxygen. In the presence of 18 mg/L of the dispersant, the photodegradation rate increased with increasing ionic strength and temperature, but decreased with increasing HA concentration, and remained independent of solution pH. The results are important in understanding roles of oil dispersants on environmental fate of persistent oil components in natural and engineered systems.

  18. Limited Dispersal Drives Clustering and Reduces Coexistence by the Storage Effect.

    Science.gov (United States)

    Usinowicz, Jacob

    2015-11-01

    Temporal variation can facilitate the coexistence of competitors through the temporal storage effect. However, this theoretical result was derived with the assumption that species have high dispersal rates. Here, I show that limited dispersal diminishes the storage effect in the classical lottery model. Populations become highly clustered during invasion, and population growth rates and extinction probabilities are functions of cluster size. I adopt the term "nucleation" from the physics literature to describe these characteristics. I developed approximations that incorporated nucleation to capture the spatiotemporal dynamics of the simulated model. Using analytical results from these approximations, I show that limited dispersal dampens asynchronous fluctuations in reproduction between species. This makes species appear to be more similar in their growth rate responses to the environment, thus reducing the potential for the storage effect. Theoretical results lead to simple rules relating average dispersal distances to relative reductions in potential coexistence. To demonstrate their use, I perform a preliminary analysis of two plant communities: tropical trees and desert annuals. In both communities, small-seeded species that disperse short distances on average have the strongest reductions in potential coexistence; species with wind- or animal-driven dispersal disperse farther distances, on average, and experience moderate or small reductions. PMID:26655776

  19. Strength effects in micropillars of a dispersion strengthened superalloy

    International Nuclear Information System (INIS)

    The present paper investigates the uniaxial compression behavior of highly alloyed, focused ion beam (FIB) manufactured micropillars, ranging from 200 up to 4000 nm in diameter. The material used was the Ni-based oxide-dispersion strengthened (ODS) alloy Inconel MA6000. Stress-strain curves show a change in slip behavior comparable to those observed in pure fcc metals. Contrary to pure Ni pillar experiments, high critical resolved shear stress (CRSS) values were found independent of pillar diameter. This suggests that the deformation behavior is primarily controlled by the internal obstacle spacing, overwhelming any pillar-size-dependent mechanisms such as dislocation source action or starvation. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  20. Uncoupling the effects of seed predation and seed dispersal by granivorous ants on plant population dynamics.

    Directory of Open Access Journals (Sweden)

    Xavier Arnan

    Full Text Available Secondary seed dispersal is an important plant-animal interaction, which is central to understanding plant population and community dynamics. Very little information is still available on the effects of dispersal on plant demography and, particularly, for ant-seed dispersal interactions. As many other interactions, seed dispersal by animals involves costs (seed predation and benefits (seed dispersal, the balance of which determines the outcome of the interaction. Separate quantification of each of them is essential in order to understand the effects of this interaction. To address this issue, we have successfully separated and analyzed the costs and benefits of seed dispersal by seed-harvesting ants on the plant population dynamics of three shrub species with different traits. To that aim a stochastic, spatially-explicit individually-based simulation model has been implemented based on actual data sets. The results from our simulation model agree with theoretical models of plant response dependent on seed dispersal, for one plant species, and ant-mediated seed predation, for another one. In these cases, model predictions were close to the observed values at field. Nonetheless, these ecological processes did not affect in anyway a third species, for which the model predictions were far from the observed values. This indicates that the balance between costs and benefits associated to secondary seed dispersal is clearly related to specific traits. This study is one of the first works that analyze tradeoffs of secondary seed dispersal on plant population dynamics, by disentangling the effects of related costs and benefits. We suggest analyzing the effects of interactions on population dynamics as opposed to merely analyzing the partners and their interaction strength.

  1. Anomalous near-field heat transfer between a cylinder and a perforated surface

    OpenAIRE

    Rodriguez, Alejandro W.; Reid, M. T. Homer; Varela, Jaime; Joannopoulos, John D.; Capasso, Federico; Johnson, Steven G.

    2012-01-01

    We predict that the radiative heat-transfer rate between a cylinder and a perforated surface depends non-monotonically on their separation. This anomalous behavior, which arises due to near-field effects, is explained using a heuristic model based on the interaction of a dipole with a plate. We show that nonmonotonicity depends not only on geometry and temperature but also on material dispersion - for micron and submicron objects, nonmonotonicity is present in polar dielectrics but absent in ...

  2. Bird and ant synergy increases the seed dispersal effectiveness of an ornithochoric shrub.

    Science.gov (United States)

    Camargo, Paulo H S A; Martins, Milene M; Feitosa, Rodrigo M; Christianini, Alexander V

    2016-06-01

    Seed dispersal may involve different vectors of dispersal in two or more sequential phases (i.e., diplochory). However, contributions of each phase to the overall seed dispersal effectiveness (SDE) are poorly understood and hard to evaluate due to post-dispersal processes that affect seed and seedling survival. We investigated the simultaneous bird (phase 1, in plant canopy) and ant (phase 2, on the floor) contributions to SDE with the ornithochoric shrub Erythroxylum ambiguum in a Brazilian Atlantic forest. Twelve species of birds fed on fruit and dispersed approximately 26 % of the seed crop. The remaining seed crop, 90 % of which contained viable seeds, fell to the ground beneath the parental plant. Ants either cleaned seeds in fruits or carried fallen fruit and seeds from bird feces to their nests. Although E. ambiguum has no adaptation for ant dispersal, ants were as quantitatively important as birds. Birds and ants equally increased germination rates compared to controls. However, birds deposited seeds farther from the parent, where seedling survival was higher (78 %) than it was beneath the parent (44 %), whereas ants carried seeds to their nests, where seedling survival was higher (83 %) than in controls away from their nests (63 %). Diplochory allowed a 42 % increase in SDE compared to dispersal in phase 1 alone. High lipid content in the fruit pulp of E. ambiguum may facilitate the inclusion of ants in a second step of dispersal after diaspores reach the floor. Ants can also buffer the dispersal of diplochorous plants against decreases in phase 1 dispersers. PMID:26899481

  3. On the theory of the anomalous photoelectric effect stemming from a substructure of matter waves

    CERN Document Server

    Krasnoholovets, V

    1999-01-01

    The two opposite concepts - multiphoton and effective photon - readily describing the photoelectric effect under strong irradiation in the case that the energy of the incident light is essentially smaller than the ionisation potential of gas atoms and the work function of the metal are treated. Based on the submicroscopic construction of quantum mechanics developed in the previous papers by the author [Phys. Essays vol. 6, 554 (1993); vol. 10, 407 (1997)] the analysis of the reasons of the two concepts discrepancies is led. Taking into account the main hypothesis of those works, i.e. that the electron is an extended object that is not point-like, the study of the interaction between the electron and a photon flux is carried out in detail. A comparison with numerous experiments is performed.

  4. Anomalous Hall effect in anatase Co:TiO2 ferromagnetic semiconductor

    NARCIS (Netherlands)

    Ramaneti, R.; Lodder, J.C.; Jansen, R.

    2007-01-01

    We have investigated the effects of modification of the SrTiO3 /Co interface as well as the SrTiO3 barrier on the tunnel magnetoresistance TMR of La0.67Sr0.33MnO3 /SrTiO3 /Co junctions. Modification was realized by the introduction of one atomic layer of either TiO2 or SrO at the SrTiO3 /Co interfac

  5. Barrier widths, barrier heights, and the origins of anomalous kinetic H/D isotope effects

    International Nuclear Information System (INIS)

    Proton transfer between MeO- and HOMe has been studied using ab initio molecular orbital theory. At the highest level employed (MP2/6-31+G(d)//6-31G(d)+ZPE), -ΔH298 and -ΔG298 for the formation of the ion-molecule complex MeO-hor-ellipsis HOMe from the separated reactants are 26.3 and 15.2 kcal/mol, respectively. At the 6-31G(d)//6-31G(d) level of theory, the (MeO-H-OMe)- transition structure is 2.19 kcal/mol higher in energy than the ion-molecule complex (ΔEdouble-dagger = 2.19), but this barrier disappears when zero-point energies are taken into account. The performance of AM1 on this system is quantitatively different (-ΔH298 = 13.3; -ΔG298 = 6.9; ΔEdouble-dagger = 4.91; kH/kD = 5.13, increasing to 5.79 when quantum mechanical tunneling is invoked) but appears to be acceptable for the research envisaged in the title. The effect of an enforced separation of the heavy atoms upon proton transfer barriers and isotope effects (which simulates steric effects) has been studied briefly at the 6-31G(d) level and in some detail using AM1

  6. Efimov effect and anomalous transport properties of a quantum Lorentz gas

    International Nuclear Information System (INIS)

    The Lorentz gas is one of the simplest many-body systems which admits a detailed theoretical analysis still having a meaningful physical interpretation. The author studies a complication for the description of the equilibrium state of a gas due to the so called Efimov effect, being an anomaly of the quantum mechanical three-body system. In statistical mechanical studies concerning the thermodynamic properties of gases it is usually assumed that the constituents interact via short-range potentials, which excludes for instance the Coulomb gas. The author investigates the consequences of the effective long-range behaviour due to the Efimov effect in the three-body sub-systems for a binary gas mixture. In particular problems arise in the cluster expansion of the quantum mechanical partition function where it can readily be shown that the bound-state part of the three-particle contribution diverges logarithmically at the Efimov point. The question is whether this implies the divergence of the complete three particle contribution or not. Some aspects of the non-equilibrium behaviour of the quantum Lorentz gas are studied. (Auth.)

  7. Combined effect of magnetic field and thermal dispersion on a non-darcy mixed convection

    KAUST Repository

    El-Amin, Mohamed

    2011-05-21

    This paper is devoted to investigate the influences of thermal dispersion and magnetic field on a hot semi-infinite vertical porous plate embedded in a saturated Darcy-Forchheimer-Brinkman porous medium. The coefficient of thermal diffusivity has been assumed to be the sum of the molecular diffusivity and the dynamic diffusivity due to mechanical dispersion. The effects of transverse magnetic field parameter (Hartmann number Ha), Reynolds number Re (different velocities), Prandtl number Pr (different types of fluids) and dispersion parameter on the wall shear stress and the heat transfer rate are discussed. © 2011 Science Press, Institute of Engineering Thermophysics, CAS and Springer-Verlag Berlin Heidelberg.

  8. Transport theory for disordered multiple-band systems: Anomalous Hall effect and anisotropic magnetoresistance

    Czech Academy of Sciences Publication Activity Database

    Kovalev, A.A.; Tserkovnyak, Y.; Výborný, Karel; Sinova, J.

    2009-01-01

    Roč. 79, č. 19 (2009), 19529/1-19529/19. ISSN 1098-0121 R&D Projects: GA MŠk LC510; GA AV ČR KJB100100802 Institutional research plan: CEZ:AV0Z10100521 Keywords : ferromagnetic materials * Hall effect * magnetoresistance * quasiparticles * spin-orbit interactions * two-dimensional electron gas Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.475, year: 2009 http://link.aps.org/doi/10.1103/PhysRevB.79.195129

  9. Chiral magnetic effect and anomalous transport from real-time lattice simulations

    CERN Document Server

    Mueller, Niklas; Sharma, Sayantan

    2016-01-01

    We present a first-principle study of anomaly induced transport phenomena by performing real-time lattice simulations with dynamical fermions coupled simultaneously to non-Abelian $SU(N_c)$ and Abelian $U(1)$ gauge fields. Investigating the behavior of vector and axial currents during a sphaleron transition in the presence of an external magnetic field, we demonstrate how the interplay of the Chiral magnetic (CME) and Chiral separation effect (CSE) lead to the formation of a propagating wave. We further analyze the dependence of the magnitude of the induced vector current and the propagation of the wave on the amount of explicit chiral symmetry breaking due to finite quark mass.

  10. Nonlocal homogenization theory in metamaterials: effective electromagnetic spatial dispersion and artificial chirality

    CERN Document Server

    Ciattoni, Alessandro

    2015-01-01

    We develop, from first principles, a general and compact formalism for predicting the electromagnetic response of a metamaterial with non-magnetic inclusions in the long wavelength limit, including spatial dispersion up to the second order. Specifically, by resorting to a suitable multiscale technique, we show that medium effective permittivity tensor and the first and second order tensors describing spatial dispersion can be evaluated by averaging suitable spatially rapidly-varying fields each satysifing electrostatic-like equations within the metamaterial unit cell. For metamaterials with negligible second-order spatial dispersion, we exploit the equivalence of first-order spatial dispersion and reciprocal bianisotropic electromagnetic response to deduce a simple expression for the metamaterial chirality tensor. Such an expression allows us to systematically analyze the effect of the composite spatial symmetry properties on electromagnetic chirality. We find that even if a metamaterial is geometrically achi...

  11. Effects of Spatial Dispersion on Reflection from Mushroom-type Artificial Impedance Surfaces

    CERN Document Server

    Luukkonen, Olli; Yakovlev, Alexander B; Simovski, Constantin R; Nefedov, Igor S; Tretyakov, Sergei A

    2008-01-01

    Several recent works have emphasized the role of spatial dispersion in wire media, and demonstrated that arrays of parallel metallic wires may behave very differently from a uniaxial local material with negative permittivity. Here, we investigate using local and non-local homogenization methods the effect of spatial dispersion on reflection from the mushroom structure introduced by Sievenpiper. The objective of the paper is to clarify the role of spatial dispersion in the mushroom structure and demonstrate that under some conditions it is suppressed. The metamaterial substrate, or metasurface, is modeled as a wire medium covered with an impedance surface. Surprisingly, it is found that in such configuration the effects of spatial dispersion may be nearly suppressed when the slab is electrically thin, and that the wire medium can be modeled very accurately using a local model. This result paves the way for the design of artificial surfaces that exploit the plasmonic-type response of the wire medium slab.

  12. Anomalous quantum and isotope effects in water clusters: Physical phenomenon, model artifact, or bad approximation?

    CERN Document Server

    Brown, Sandra E

    2014-01-01

    Free energy differences $\\Delta F:=F-F_{\\text{prism}}$ are computed for several isomers of water hexamer relative to the "prism" isomer using the self-consistent phonons method. %$\\Delta F:=F-F({prism})$ We consider the isotope effect defined by the quantity $\\delta F_{D_2O}:=\\Delta F_{\\rm D_2O}-\\Delta F_{\\rm H_2O}$, and the quantum effect, $\\delta F_{\\hbar=0}:=\\Delta F_{\\hbar=0}-\\Delta F_{\\rm H_2O}$, and evaluate them using different flexible water models. While both $\\delta F_{D_2O}$ and $\\delta F_{\\hbar=0}$ are found to be rather small for all of the potentials, they are especially small for two of the empirical models, q-TIP4P/F and TTM3-F, compared to q-SPC/Fw and the two {\\it abinitio}-based models, WHBB and HBB2-pol. This qualitative difference in the properties of different water models cannot be explained by one being "more accurate" than the other. We speculate as to whether the observed anomalies are caused by the special properties of water systems, or are an artifact of either the potential energ...

  13. Possible anomalous doppler shift effect in superconductor Sr sub 2 RuO sub 4

    CERN Document Server

    Tanaka, Y; Tanuma, Y; Kashiwaya, S

    2003-01-01

    The effect of Doppler shift is studied in a model for the alpha-beta bands of Sr sub 2 RuO sub 4 consisting of two hybridized one-dimensional (1D) bands. Assuming a superconducting gap with nodes in a diagonal direction, we examine the oscillation of surface density of states and thermal conductivity under a rotating magnetic field. Upon varying the strength of hybridization, the oscillation of these quantities is found to exhibit 2D to 1D crossover. In the crossover regime, which corresponds to the actual Sr sub 2 RuO sub 4 , the thermal conductivity exhibits a two-fold-symmetry oscillation, while a four-fold-symmetry component in the oscillation is barely detectable.

  14. Possible anomalous doppler shift effect in superconductor Sr2RuO4

    International Nuclear Information System (INIS)

    The effect of Doppler shift is studied in a model for the α-β bands of Sr2RuO4 consisting of two hybridized one-dimensional (1D) bands. Assuming a superconducting gap with nodes in a diagonal direction, we examine the oscillation of surface density of states and thermal conductivity under a rotating magnetic field. Upon varying the strength of hybridization, the oscillation of these quantities is found to exhibit 2D to 1D crossover. In the crossover regime, which corresponds to the actual Sr2RuO4, the thermal conductivity exhibits a two-fold-symmetry oscillation, while a four-fold-symmetry component in the oscillation is barely detectable. (author)

  15. Ultrahighly Dispersed Titanium Oxide on Silica : Effect of Precursors on the Structure and Photocatalysis

    OpenAIRE

    Yoshida, S.; Takenaka, S.; Tanaka, T.; Funabiki, T.

    1997-01-01

    The effect of precursor on the dispersion and catalytic performance of titanium oxide supported on silica has ben investigated. The catalysts were prepared by a simple impregnation method with three kinds of titanium complexes of different ligands (bis(isopropyato)-bis(pivaroylmethanato) : DPM, acetylacetonato : ACAC, tetrakis(isopropylato) : IPRO) with the aim of preparing ultrahighly dispersed titanium oxide on silica. The XAFS study revealed that titanium species in the catalyst prepared f...

  16. Effects of forest fragmentation on seed dispersal and seedling establishment in ornithochorous trees.

    Science.gov (United States)

    Herrera, José Manuel; García, Daniel

    2010-08-01

    Habitat fragmentation increases seed dispersal limitation across the landscape and may also affect subsequent demographic stages such as seedling establishment. Thus, the development of adequate plans for forest restoration requires an understanding of mechanisms by which fragmentation hampers seed delivery to deforested areas and knowledge of how fragmentation affects the relationship between seed-deposition patterns and seedling establishment. We evaluated the dispersal and recruitment of two bird-dispersed, fleshy-fruited tree species (Crataegus monogyna and Ilex aquifolium) in fragmented secondary forests of northern Spain. Forest fragmentation reduced the probability of seed deposition for both trees because of decreased availability of woody perches and fruit-rich neighborhoods for seed dispersers, rather than because of reductions in tree cover by itself. The effects of fragmentation went beyond effects on the dispersal stage in Crataegus because seedling establishment was proportional to the quantities of bird-dispersed seeds arriving at microsites. In contrast, postdispersal mortality in Ilex was so high that it obscured the seed-to-seedling transition. These results suggest that the effects of fragmentation are not necessarily consistent across stages of recruitment across species. Habitat management seeking to overcome barriers to forest recovery must include the preservation, and even the planting, of fleshy-fruited trees in the unforested matrix as a measure to encourage frugivorous birds to enter into open and degraded areas. An integrative management strategy should also explicitly consider seed-survival expectancies at microhabitats to preserve plant-population dynamics and community structure in fragmented landscapes. PMID:20184646

  17. Observation of anomalous linear photogalvanic effect and its dependence on wavelength in undoped InGaAs/AlGaAs multiple quantum well.

    Science.gov (United States)

    Zhu, Laipan; Liu, Yu; Gao, Hansong; Qin, Xudong; Li, Yuan; Wu, Qing; Chen, Yonghai

    2014-01-01

    We observed an anomalous linear photogalvanic effect (ALPGE) in undoped InGaAs/AlGaAs multiple quantum well and studied its wavelength dependence in details. This effect is believed to originate from the optical momentum alignment effect and the inhomogeneity of light intensity. We find that the spot location with the maximum ALPGE current is wavelength independent. And the normalized ALPGE current decreasing at smaller wavelengths is attributed to the sharp decrease of the momentum and energy relaxation time. The electrical measurement of the spectra dependence of ALPGE is highly sensitive proving to be an effective method for detecting the momentum anisotropy of photoinduced carriers and band coupling. PMID:25258612

  18. Characteristics of anomalous skin effect and evolution of power absorption regions in a cylindrical radio frequency inductively coupled plasma

    International Nuclear Information System (INIS)

    In a low-pressure radio-frequency (13.56 MHz), inductively coupled argon plasma generated by a normal cylindrical rf coil, electric field, current density, and absorbed power density is calculated from magnetic field measured with a phase-resolved magnetic probe. The anomalous skin effect (ASE) for the cylindrical rf coil is compared to those previously reported for the planar and re-entrant cylindrical rf coils. Physical reasons for our observed characteristics of ASE are presented. With the increasing discharge power, the size and the number of negative and positive power absorption regions evolve into several distinct patterns. For the low discharge power (at 156.9 W), there is one area of positive and one area of negative power absorption in the radial direction. For the medium discharge power (279 W–683.5 W), there are two areas of negative and two areas of positive power absorption. For the even higher discharge power (above 803.5 W), the number of areas is the same as that of the medium discharge power, but the size of the inner positive and negative power absorption areas is approximately doubled and halved, respectively, while the outer positive and negative power absorption areas slightly shrinks. The evolution of positive and negative power absorption regions is explained as a result of electron thermal diffusion and the energy conversion between rf current and electric field. The spatial decays of electric field and current density are also elucidated by linking them with the positive and negative power absorption pattern

  19. Characteristics of anomalous skin effect and evolution of power absorption regions in a cylindrical radio frequency inductively coupled plasma

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Z. F., E-mail: zfding@dlut.edu.cn [Key Laboratory of Materials Modification by Laser, Ion, and Electron Beams, Ministry of Education, School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116023 (China); Sun, B. [Key Laboratory of Materials Modification by Laser, Ion, and Electron Beams, Ministry of Education, School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116023 (China); Xi' an Aerospace Propulsion Institute, China Aerospace Science and Technology Corporation, Xi' an 710100 (China); Huo, W. G. [Key Laboratory of Materials Modification by Laser, Ion, and Electron Beams, Ministry of Education, School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116023 (China); School of Physics and Electronic Technology, Liaoning Normal University, Dalian 116029 (China)

    2015-06-15

    In a low-pressure radio-frequency (13.56 MHz), inductively coupled argon plasma generated by a normal cylindrical rf coil, electric field, current density, and absorbed power density is calculated from magnetic field measured with a phase-resolved magnetic probe. The anomalous skin effect (ASE) for the cylindrical rf coil is compared to those previously reported for the planar and re-entrant cylindrical rf coils. Physical reasons for our observed characteristics of ASE are presented. With the increasing discharge power, the size and the number of negative and positive power absorption regions evolve into several distinct patterns. For the low discharge power (at 156.9 W), there is one area of positive and one area of negative power absorption in the radial direction. For the medium discharge power (279 W–683.5 W), there are two areas of negative and two areas of positive power absorption. For the even higher discharge power (above 803.5 W), the number of areas is the same as that of the medium discharge power, but the size of the inner positive and negative power absorption areas is approximately doubled and halved, respectively, while the outer positive and negative power absorption areas slightly shrinks. The evolution of positive and negative power absorption regions is explained as a result of electron thermal diffusion and the energy conversion between rf current and electric field. The spatial decays of electric field and current density are also elucidated by linking them with the positive and negative power absorption pattern.

  20. Effects of oil dispersant and oil on sorption and desorption of phenanthrene with Gulf Coast marine sediments

    International Nuclear Information System (INIS)

    Effects of a model oil dispersant (Corexit EC9500A) on sorption/desorption of phenanthrene were investigated with two marine sediments. Kinetic data revealed that the presence of the dispersant at 18 mg/L enhanced phenanthrene uptake by up to 7%, whereas the same dispersant during desorption reduced phenanthrene desorption by up to 5%. Sorption isotherms confirmed that at dispersant concentrations of 18 and 180 mg/L, phenanthrene uptake progressively increased for both sediments. Furthermore, the presence of the dispersant during desorption induced remarkable sorption hysteresis. The effects were attributed to added phenanthrene affinity and capacity due to sorption of the dispersant on the sediments. Dual-mode models adequately simulated sorption isotherms and kinetic data in the presence of the dispersant. Water accommodated oil (WAO) and dispersant-enhanced WAO increased phenanthrene sorption by up to 22%. This information is important for understanding roles of oil dispersants on the distribution and transport of petroleum PAHs in seawater-sediments. Highlights: • Presence of oil dispersant enhances phenanthrene sorption in Gulf Coast sediments. • Oil dispersant present during desorption induces phenanthrene sorption hysteresis. • Dual-mode models adequately represent phenanthrene sorption isotherms and kinetics. • Dispersed oil substantially increases sediment sorption of phenanthrene. -- Oil dispersant and dispersed oil in seawater increase phenanthrene sorption capacity by marine sediments and induce remarkable sorption hysteresis

  1. Effects of corexit oil dispersants and the WAF of dispersed oil on DNA damage and repair in cultured human bronchial airway cells, BEAS-2B

    Science.gov (United States)

    Major, Danielle; Derbes, Rebecca S.; Wang, He; Roy-Engel, Astrid M.

    2016-01-01

    Large quantities of dispersants were used as a method to disperse the roughly 210 million gallons of spilled crude oil that consumed the Gulf of Mexico. Little is known if the oil-dispersant and oil-dispersant mixtures on human airway BEAS-2B epithelial cells. Here we present the cytotoxic and genotoxic in vitro effects on the human lung cells BEAS-2B following exposure to and oil-dispersant mixtures on human airway BEAS-2B epithelial cells. Here we present the cytotoxic and genotoxic in vitro effects on the human lung cells BEAS-2B following exposure to Corexit dispersants EC9500 and EC9527, Water Accommodated Fraction (WAF) -crude, WAF-9500 + Oil, and WAF-9527 + Oil. Cellular cytotoxicity to WAF-dispersed oil samples was observed at concentrations greater than 1000 ppm with over 70% of observed cellular death. At low concentration exposures (100 and 300 ppm) DNA damage was evidenced by the detection of single strand breaks (SSBs) and double strand breaks (DSBs) as measured by alkaline and neutral comet assay analyses. Immunoblot analyses of the phosphorylated histone H2A.X (ɣ-H2A.X) and tumor suppressor p53 protein confirmed activation of the DNA damage response due to the exposure-induced DNA breaks. Although, many xenobiotics interfere with DNA repair pathways, in vitro evaluation of the nucleotide excision repair (NER) and DSB repair pathways appear to be unaffected by the oil-dispersant mixtures tested. Overall, this study supports that oil-dispersant mixtures induce genotoxic effects in culture.

  2. Hot electron production, anomalous absorption, and effect of intense electromagnetic fields on inverse bremsstrahlung absorption near the electron plasma frequency

    International Nuclear Information System (INIS)

    Anomalous heating was studied on a well-controlled low-density plasma subjected to short microwave pulses. Absorption measurements along with parametric instabilities are described. The influence of intense ac electric fields on the electron-ion collision rate in the plasma is also discussed

  3. The effect of energy, settling time and shaking time on the swirling flask dispersant apparatus

    International Nuclear Information System (INIS)

    The effects of basic operational variables associated with the swirling flask test are reported. Changing energy levels, changes in settling times and changes in the amount of shaking time were measured and the effects observed. Increasing the energy level causes the dispersion to begin rapidly. Increase in settling time of 10 minutes from five to 80 minutes decreases effectiveness after 10 minutes, indicating that mostly large, unstable droplets resurface during the initial period of time. Increase in the shaking time ranging from 10 to 160 minutes produced only a small increase in effectiveness, confirming that dispersion is primarily a threshold phenomenon rather than a continuous process. 7 refs., 3 tabs., 3 figs

  4. Spill-of-opportunity testing of dispersant effectiveness at the Mega Borg oil spill

    International Nuclear Information System (INIS)

    The release of 3.9 million gallons of Angola Planca crude oil from the stricken tanker Mega Borg 57 miles offshore of Galveston, Texas in June 1990 provided a valuable opportunity to document dispersant effectiveness under field conditions. Aerial application of Corexit 9527 (968 gallons total in four adjacent passes) onto an identified test portion of the slick was evaluated by concurrent observations from a command-and-control aircraft and surface vessels (with videotape and 35-mm photographic documentation) and ground truth measurements, including continuous 4-meter-depth ultraviolet/fluorescence and a discrete water sampling program. Using the study plan outlined by Payne and colleagues, target and control areas were designated before dispersant application by deployment of smoke bombs and coded three-meter drogues. Postdispersant surface vessel placement and 30 liter water sampling activities from the Texas A ampersand M research vessel HOS Citation were aided by the smoke bombs, the free-drifting drogues, and directions from the command-and-control aircraft. Subsequent FID GC and GC/MS analyses of water sample extracts allowed quantitation of the dispersed oil concentrations under both treated and control areas. Although the spilled oil was extremely light (API gravity 39.0) and subject to significant natural dispersion, the field observations, filmed documentation, and water column data clearly demonstrated an increase in dispersed oil concentrations beneath the treated slick. The distribution of dispersed oil droplets was very heterogeneous and reflected the patchy distribution of oil on the water surface before dispersant application. Maximum concentrations of dispersed hydrocarbons in the center of the treated zone were 22,000 μg/L (22 ppm) for total aliphatic and 5.6 μg/L (5.6 ppb) for total aromatics 60 to 90 minutes after dispersant application. Elevated levels were generally limited to the upper 1 to 3 meters of the water column

  5. Optically Anomalous Crystals

    CERN Document Server

    Shtukenberg, Alexander; Kahr, Bart

    2007-01-01

    Optical anomalies in crystals are puzzles that collectively constituted the greatest unsolved problems in crystallography in the 19th Century. The most common anomaly is a discrepancy between a crystal’s symmetry as determined by its shape or by X-ray analysis, and that determined by monitoring the polarization state of traversing light. These discrepancies were perceived as a great impediment to the development of the sciences of crystals on the basis of Curie’s Symmetry Principle, the grand organizing idea in the physical sciences to emerge in the latter half of the 19th Century. Optically Anomalous Crystals begins with an historical introduction covering the contributions of Brewster, Biot, Mallard, Brauns, Tamman, and many other distinguished crystallographers. From this follows a tutorial in crystal optics. Further chapters discuss the two main mechanisms of optical dissymmetry: 1. the piezo-optic effect, and 2. the kinetic ordering of atoms. The text then tackles complex, inhomogeneous crystals, and...

  6. Boundary effects and gapped dispersion in rotating fermionic matter

    CERN Document Server

    Ebihara, Shu; Mameda, Kazuya

    2016-01-01

    We discuss the importance of boundary effects on fermionic matter in a rotating frame. By explicit calculations at zero temperature we show that the scalar condensate of fermion and anti-fermion cannot be modified by the rotation once the boundary condition is properly implemented. The situation is qualitatively changed at finite temperature and/or in the presence of a sufficiently strong magnetic field that supersedes the boundary effects. Therefore, to establish an interpretation of the rotation as an effective chemical potential, it is crucial to consider further environmental effects such as the finite temperature and magnetic field.

  7. The effect of unresolved binaries on globular cluster proper-motion dispersion profiles

    CERN Document Server

    Bianchini, P; van de Ven, G; Schinnerer, E; Bellini, A; van der Marel, R P; Watkins, L L; Anderson, J

    2016-01-01

    High-precision kinematic studies of globular clusters require an accurate knowledge of all possible sources of contamination. Amongst other sources, binary stars can introduce systematic biases in the kinematics. Using a set of Monte Carlo cluster simulations with different concentrations and binary fractions, we investigate the effect of unresolved binaries on proper-motion dispersion profiles, treating the simulations like HST proper-motion samples. Since globular clusters evolve towards a state of partial energy equipartition, more massive stars lose energy and decrease their velocity dispersion. As a consequence, on average, binaries have a lower velocity dispersion, since they are more massive kinematic tracers. We show that, in the case of clusters with high binary fraction (initial binary fraction of 50%) and high concentration (i.e., closer to energy equipartition), unresolved binaries introduce a color-dependent bias in the velocity dispersion of main-sequence stars of the order of 0.1-0.3 km s$^{-1}...

  8. Effectiveness of selected dispersants on magnetite deposition at simulated PWR heat-transfer surfaces

    International Nuclear Information System (INIS)

    The effectiveness of 3 different dispersants-a polyphosphonic acid (PIPPA), a polymethacrylic acid (PMA), and a hydroxyethylidene methacrylic acid (HEME)-at controlling magnetite deposition was examined under steam generator operating conditions. Tests in a cycling research model boiler showed that the dispersants resulted in corrosion products of a smaller average size and a bimodal size distribution. At a concentration in the boiler of 10 mg/kg, density weight deposit on heated probes was reduced 4-, 3-, and 2-fold for PMA, PIPPA, and HEME, respectively. PIPPA was the most effective at increasing iron transport out of the boiler. In deposition loop tests using an 59Fe radiotracer, only PIPPA and HEME were effective at reducing the particle deposition rate under flow-boiling conditions. None of the dispersants had any effect on deposition under single-phase forced-convective flow. (author)

  9. Dark matter velocity dispersion effects on CMB and matter power spectra

    CERN Document Server

    Piattella, O F; Fabris, J C; Pacheco, J A de Freitas

    2015-01-01

    Effects of velocity dispersion of dark matter particles on the CMB TT power spectrum and on the matter linear power spectrum are investigated using a modified CAMB code. Cold dark matter originated from thermal equilibrium processes does not produce appreciable effects but this is not the case if particles have a non-thermal origin. A cut-off in the matter power spectrum at small scales, similar to that produced by warm dark matter or that produced in the late forming dark matter scenario, appears as a consequence of velocity dispersion effects, which acts as a pressure perturbation.

  10. Ion thermal and dispersion effects in Farley-Buneman instabilities

    Science.gov (United States)

    Litt, Sandeep; Smolyakov, Andrei; Hassan, Ehab; Horton, Wendell; University of Saskatchewan Team; University of Texas Team

    2015-11-01

    Farley Buneman instability is most commonly observed in the collisional part of ionospheric E-layer and solar chromosphere. Despite high collisionality, the kinetic effects associated with finite temperature are important for determination of the mode frequencies and growth rate, especially for largely unmagnetized ion component. The kinetic theory offers a comprehensive tool for studies of thermal effects but remains to be a challenge even for modern computers. Alternatively, we develop an extended ion fluid model that incorporates ion thermal and kinetic effects via the linear closures for higher order moments. The ion thermal effects on dynamics of FB type modes are investigated in the short wavelength region using the first and second order closure and the full kinetic response. It is shown that the ion thermal effects are primarily reasons for mode cutoff at shorter wavelength and FB instability is limited by the finite range of wavevectors. The proposed fluid like equations with closures could be useful alternative for the analysis of weakly driven situations, in contrast to the PIC simulations which can handle strongly driven cases but are noisy near the marginal stability boundary. Our results also indicate that the mode growth rate is a nonmonotonic function of the wave vector and also depends on the collisionality. The critical phase velocity (or threshold) for the unstable modes is shown to be modified due to the ion thermal effects. NSERC.

  11. Suppression of the Neoclassical Tearing Modes in Tokamaks under Anomalous Transverse Transport Conditions when the Magnetic Well Effect Predominates over the Bootstrap Drive

    International Nuclear Information System (INIS)

    A study is made of the suppression of neoclassical tearing modes in tokamaks under anomalous transverse transport conditions when the magnetic well effect predominates over the bootstrap drive. It is stressed that the corresponding effect, which is called the compound suppression effect, depends strongly on the profiles of the electron and ion temperature perturbations. Account is taken of the fact that the temperature profile can be established as a result of the competition between anomalous transverse heat transport, on the one hand, and longitudinal collisional heat transport, longitudinal heat convection, longitudinal inertial transport, and transport due to the rotation of magnetic islands, on the other hand. The role of geodesic effects is discussed. The cases of competition just mentioned are described by the model sets of reduced transport equations, which are called, respectively, collisional, convective, inertial, and rotational plasmophysical models. The magnetic well is calculated with allowance for geodesic effects. It is shown that, for strong anomalous heat transport conditions, the contribution of the magnetic well to the generalized Rutherford equation for the island width W is independent of W not only in the collisional model (which has been investigated earlier) but also in the convective and inertial models and depends very weakly (logarithmically) on W in the rotational model. It is this weak dependence that gives rise to the compound effect, which is the subject of the present study. A criterion for the stabilization of neoclassical tearing modes by the compound effect at an arbitrary level of the transverse heat transport by electrons and ions is derived and is analyzed for two cases: when the electron heat transport and ion heat transport are both strong, and when the electron heat transport is strong and the ion heat transport is weak

  12. Laboratory study to compare the effectiveness of chemical dispersants when applied dilute versus neat

    Energy Technology Data Exchange (ETDEWEB)

    Belore, R.; Ross, S. [S.L. Ross Environmental Research Ltd., Ottawa, ON (Canada)

    2000-07-01

    This study was aimed at comparing the effectiveness of chemical dispersants in neat and dilute form. Two dispersants were selected for this study: Corexit 9500 and Corexit 9527 on Alaska North Slope crude oil. Tests were conducted in the laboratory where the dispersants were applied neat and diluted with salt water. When diluted with salt water in a ratio 1:10, Corexit 9527 did not show a reduction in its effectiveness when used on Alaska North Slope (ANS) crude oil. Corexit 9500, on the other hand, saw its effectiveness on ANS crude oil drastically reduced when diluted with salt water at a ratio 1:10 and 3:10. Since these results are preliminary, the use of diluted Corexit 9500 with salt water in high capacity fire-monitor systems must be carefully considered. Reduced effectiveness of Corexit 9500 could be avoided by using a single-nozzle application in neat form. Further testing was recommended to determine the cause of the reduced efficiency. Some factors to be considered could be the type of oil, method of mixing or delivery of the dispersant, or the contact time between the dispersant and the water carrier. 12 refs., 8 tabs., 5 figs., 1 append.

  13. The relative effect of behaviour in larval dispersal in a low energy embayment

    Science.gov (United States)

    Daigle, Rémi M.; Chassé, Joël; Metaxas, Anna

    2016-05-01

    This study examined the relative importance of tidal phase, larval behaviour, release site, depth layer, and vertical swimming velocity on mean in-sea dispersal distance, retention, distance from shore, and population connectivity. Using a biophysical model, we simulated larval dispersal of marine benthic invertebrates for 6 taxonomic groups representing different combinations of swimming speed, and depth preference in St. George's Bay, NS, Canada, a shallow bay with low energy (e.g. lack of estuarine circulation). The biophysical model was run over a period of 3 months, from Jul to Sep, representing the period when larvae of the targeted species were present, and at each of 3 years. Overall, release site had the strongest effect of all factors on the dispersal metrics. Although less important than release site in our system, vertical distribution and swim speed had a significant effect which would likely be more pronounced in high (i.e. with features such as estuarine circulation or internal waves) than low energy environments. Retention and distance from shore were more responsive to our manipulations than dispersal distance, both in terms of the number of ecologically significant effects and the magnitudes of their effect size. These findings allow for the prioritization of biophysical model parameters and improved simulations of larval dispersal.

  14. A dispersive approach to Sudakov resummation

    International Nuclear Information System (INIS)

    We present a general all-order formulation of Sudakov resummation in QCD in terms of dispersion integrals. We show that the Sudakov exponent can be written as a dispersion integral over spectral density functions, weighted by characteristic functions that encode information on power corrections. The characteristic functions are defined and computed analytically in the large-β0 limit. The spectral density functions encapsulate the non-Abelian nature of the interaction. They are defined by the time-like discontinuity of specific effective charges (couplings) that are directly related to the familiar Sudakov anomalous dimensions and can be computed order-by-order in perturbation theory. The dispersive approach provides a realization of dressed gluon exponentiation, where Sudakov resummation is enhanced by an internal resummation of running-coupling corrections. We establish all-order relations between the scheme-invariant Borel formulation and the dispersive one, and address the difference in the treatment of power corrections. We find that in the context of Sudakov resummation the infrared-finite-coupling hypothesis is of special interest because the relevant coupling can be uniquely identified to any order, and may have an infrared fixed point already at the perturbative level. We prove that this infrared limit is universal: it is determined by the cusp anomalous dimension. To illustrate the formalism we discuss a few examples including B-meson decay spectra, deep inelastic structure functions and Drell-Yan or Higgs production

  15. Anomalous extracellular diffusion in rat cerebellum.

    Science.gov (United States)

    Xiao, Fanrong; Hrabe, Jan; Hrabetova, Sabina

    2015-05-01

    Extracellular space (ECS) is a major channel transporting biologically active molecules and drugs in the brain. Diffusion-mediated transport of these substances is hindered by the ECS structure but the microscopic basis of this hindrance is not fully understood. One hypothesis proposes that the hindrance originates in large part from the presence of dead-space (DS) microdomains that can transiently retain diffusing molecules. Because previous theoretical and modeling work reported an initial period of anomalous diffusion in similar environments, we expected that brain regions densely populated by DS microdomains would exhibit anomalous extracellular diffusion. Specifically, we targeted granular layers (GL) of rat and turtle cerebella that are populated with large and geometrically complex glomeruli. The integrative optical imaging (IOI) method was employed to evaluate diffusion of fluorophore-labeled dextran (MW 3000) in GL, and the IOI data analysis was adapted to quantify the anomalous diffusion exponent dw from the IOI records. Diffusion was significantly anomalous in rat GL, where dw reached 4.8. In the geometrically simpler turtle GL, dw was elevated but not robustly anomalous (dw = 2.6). The experimental work was complemented by numerical Monte Carlo simulations of anomalous ECS diffusion in several three-dimensional tissue models containing glomeruli-like structures. It demonstrated that both the duration of transiently anomalous diffusion and the anomalous exponent depend on the size of model glomeruli and the degree of their wrapping. In conclusion, we have found anomalous extracellular diffusion in the GL of rat cerebellum. This finding lends support to the DS microdomain hypothesis. Transiently anomalous diffusion also has a profound effect on the spatiotemporal distribution of molecules released into the ECS, especially at diffusion distances on the order of a few cell diameters, speeding up short-range diffusion-mediated signals in less permeable

  16. A literature review of the variation of dispersant effectiveness and salinity

    Energy Technology Data Exchange (ETDEWEB)

    Fingas, M. [Environment Canada, Ottawa, ON (Canada). Emergencies Science Div; Ka' aihue, L. [Prince William Regional Citizen' s Advisory Council, Anchorage, AK (United States)

    2005-07-01

    Surfactants have varying solubilities in water and varying actions toward oil and water. This paper presents a summary of the effects of water salinity on chemical dispersion. Literature reveals that effectiveness testing with salinity variations shows a consistent decrease in effectiveness at lower salinities and a decrease after a maximum salinity is reached between 20 to 40 units of salinity. In waters with 0 salinity, conventional and currently available dispersants have a very low effectiveness or are sometimes even completely ineffective, a fact which is consistent in surfactant literature. Dispersant effectiveness peaks in waters with a salinity ranging from 20 to 40. Corexit 9500 appears to be less sensitive to salinity, but still peaks at about 35. There is a relatively smooth gradient of effectiveness with salinity both as the salinity rises to a peak point of effectiveness and after it exceeds this value. The curves for this salinity effect appear to be Gaussian. While there is some evidence for a temperature-salinity interaction as noted in the data, there is not enough data to make solid conclusions. Recent data is almost exclusively measured using Corexit 9527 and Corexit 9500. Since these have the same surfactant packages, there is a concern that the results may be more relevant to these formulations than to all possible formulations. Observations on 2 field trials in freshwater appear to indicate that the laboratory tests were correct in concluding very low dispersant effectiveness in freshwater. There were few studies on the biological effects of varying salinity and given oil exposure. It was concluded that the findings in the dispersant literature reviewed here are in agreement with those in the theoretical and basic surfactant literature. The effect of ionic strength and salinity on both hydrophilic-lipophilic balance and stability is the reason for the decreased effectiveness noted at low salinities and the same decrease at high salinities

  17. The effect of berberine hydrochloride on Enterococcus faecalis biofilm formation and dispersion in vitro.

    Science.gov (United States)

    Chen, Lihua; Bu, Qianqian; Xu, Huan; Liu, Yuan; She, Pengfei; Tan, Ruichen; Wu, Yong

    2016-01-01

    Enterococcus faecalis (E. faecalis) is one of the major causes of biofilm infections. Berberine hydrochloride (BBH) has diverse pharmacological effects; however, the effects and mechanisms of BBH on E. faecalis biofilm formation and dispersion have not been reported. In this study, 99 clinical isolates from the urine samples of patients with urinary tract infections (UTIs) were collected and identified. Ten strains of E. faecalis with biofilm formation ability were studied. BBH inhibited E. faecalis biofilm formation and promoted the biofilm dispersion of E. faecalis. In addition, sortase A and esp expression levels were elevated during early E. faecalis biofilm development, whereas BBH significantly reduced their expression levels. The results of this study indicated that BBH effectively prevents biofilm formation and promotes biofilm dispersion in E. faecalis, most likely by inhibiting the expressions of sortase A and esp. PMID:27242142

  18. Effectiveness of selected dispersants on magnetite deposition at simulated PWR heat transfer surfaces

    International Nuclear Information System (INIS)

    The effectiveness of three different dispersants - a polyphosphonic acid (PIPPA); a polymethacrylic acid (PMA); and a hydroxyethylidene methacrylic acid (HEME) - at controlling magnetite deposition has been examined under steam generator operating conditions. Tests in a cycling research model boiler showed that the dispersants resulted in corrosion products with a smaller average size and a bimodal size distribution. At a concentration in the boiler of 10 mg/kg, density weight deposit on heated probes was reduced 4-, 3-, and 2-fold for PMA, PIPPA, and HEME, respectively. PIPPA was the most effective at increasing iron transport out of the boiler. In deposition loop tests using a 59-Fe radiotracer, only PIPPA and HEME were effective at reducing the particle deposition rate under flow-boiling conditions. None of the dispersants had any impact on deposition under single-phase forced-convective flow. (author)

  19. Effects of oil and dispersant on formation of marine oil snow and transport of oil hydrocarbons.

    Science.gov (United States)

    Fu, Jie; Gong, Yanyan; Zhao, Xiao; O'Reilly, S E; Zhao, Dongye

    2014-12-16

    This work explored the formation mechanism of marine oil snow (MOS) and the associated transport of oil hydrocarbons in the presence of a stereotype oil dispersant, Corexit EC9500A. Roller table experiments were carried out to simulate natural marine processes that lead to formation of marine snow. We found that both oil and the dispersant greatly promoted the formation of MOS, and MOS flocs as large as 1.6-2.1 mm (mean diameter) were developed within 3-6 days. Natural suspended solids and indigenous microorganisms play critical roles in the MOS formation. The addition of oil and the dispersant greatly enhanced the bacterial growth and extracellular polymeric substance (EPS) content, resulting in increased flocculation and formation of MOS. The dispersant not only enhanced dissolution of n-alkanes (C9-C40) from oil slicks into the aqueous phase, but facilitated sorption of more oil components onto MOS. The incorporation of oil droplets in MOS resulted in a two-way (rising and sinking) transport of the MOS particles. More lower-molecular-weight (LMW) n-alkanes (C9-C18) were partitioned in MOS than in the aqueous phase in the presence of the dispersant. The information can aid in our understanding of dispersant effects on MOS formation and oil transport following an oil spill event. PMID:25420231

  20. Pauli isotonic oscillatorwith an anomalous magnetic moment in the presence of the Aharonov-Bohm effect: Laplace transform approach

    Science.gov (United States)

    Roshanzamir-Nikou, M.; Goudarzi, H.

    2016-02-01

    A strong magnetic field significantly affects the intrinsic magnetic moment of fermions. In quantum electrodynamics, it was shown that the anomalous magnetic moment of an electron arises kinematically, while it results from a dynamical interaction with an external magnetic field for hadrons (proton). Taking the anomalous magnetic moment of a fermion into account, we find an exact expression for the boundstate energy and the corresponding eigenfunctions of a two-dimensional nonrelativistic spin-1/2 harmonic oscillator with a centripetal barrier (known as the isotonic oscillator) including an Aharonov-Bohm term in the presence of a strong magnetic field. We use the Laplace transform method in the calculations. We find that the singular solution contributes to the phase of the wave function at the origin and the phase depends on the spin and magnetic flux.

  1. Experimental observation of strong coupling effects on the dispersion of dust acoustic waves in a plasma

    CERN Document Server

    Bandyopadhyay, P; Sen, A; Kaw, P K

    2016-01-01

    The dispersion properties of low frequency dust acoustic waves in the strong coupling regime are investigated experimentally in an argon plasma embedded with a mixture of kaolin and $MnO_2$ dust particles. The neutral pressure is varied over a wide range to change the collisional properties of the dusty plasma. In the low collisional regime the turnover of the dispersion curve at higher wave numbers and the resultant region of $\\partial\\omega/\\partial k < 0$ are identified as signatures of dust-dust correlations. In the high collisional regime dust neutral collisions produce a similar effect and prevent an unambiguous identification of strong coupling effects.

  2. Effect of spatial dispersion and medium boundaries on resonant radiation transport

    International Nuclear Information System (INIS)

    The integral equation for the excited atoms spectral density is obtained by the example of the optically dense limited dispersive media. It is established that accounting for the atoms thermal motion and effects, conditioned by the boundary existence, leads to the nonlocal relationship between the excited particles concentration and electromagnetic field intensity in the medium. It is shown that in neglect of the dielectric permittivity spatial dispersion and boundary effects the obtained result transforms into the known Biberman-Holstein equation. The problem on the spectral intensity of the heated half-space radiation is also studied

  3. Different dispersions of group II catalysts over SBA 15 and MCM-41: Effects on transesterification reactivity

    OpenAIRE

    Sullivan, James A; Sherry, Linda

    2015-01-01

    Activities of CaO catalysts on SBA-15 and MCM-41 have been compared in transesterification and SBA-15 supported samples invariably more active than those on MCM-41. Increased activity is not due to diffusional effects (as measured using substrates of differing size) but rather to increased dispersion of CaO on SBA-15 (as measured using NOx TPD). The effect, i.e. increased reactivity of SBA-15 supported catalysts being related to increased dispersion, is also noted in supported BaO catalysts w...

  4. Memory effect of polymer dispersed liquid crystal by hybridization with nanoclay

    Directory of Open Access Journals (Sweden)

    2010-01-01

    Full Text Available The electro-optical performances of polymer dispersed liquid crystal (PDLC were investigated in the presence of organically modified clays. With the addition and increasing amount of modified clay, driving voltage and memory effect, viz. transparent state of the film after the electricity is off simultaneously increased due most likely to the increased viscosity. Among the two types of modifier, 4-(4-aminophenyl benzonitrile having greater chemical affinity with LC than hexylamine, gave finer dispersion of clay in liquid crystal, greater viscosity, larger driving voltage and response time, and greater memory effect.

  5. Experimental observation of strong coupling effects on the dispersion of dust acoustic waves in a plasma

    Energy Technology Data Exchange (ETDEWEB)

    Bandyopadhyay, P. [Institute for Plasma Research, Bhat, Gandhinagar 382428 (India)], E-mail: pintu@ipr.res.in; Prasad, G.; Sen, A.; Kaw, P.K. [Institute for Plasma Research, Bhat, Gandhinagar 382428 (India)

    2007-09-03

    The dispersion properties of low frequency dust acoustic waves in the strong coupling regime are investigated experimentally in an argon plasma embedded with a mixture of kaolin and MnO{sub 2} dust particles. The neutral pressure is varied over a wide range to change the collisional properties of the dusty plasma. In the low collisional regime the turnover of the dispersion curve at higher wave numbers and the resultant region of {partial_derivative}{omega}/{partial_derivative}k<0 are identified as signatures of dust-dust correlations. In the high collisional regime dust neutral collisions produce a similar effect and prevent an unambiguous identification of strong coupling effects.

  6. Experimental observation of strong coupling effects on the dispersion of dust acoustic waves in a plasma

    International Nuclear Information System (INIS)

    The dispersion properties of low frequency dust acoustic waves in the strong coupling regime are investigated experimentally in an argon plasma embedded with a mixture of kaolin and MnO2 dust particles. The neutral pressure is varied over a wide range to change the collisional properties of the dusty plasma. In the low collisional regime the turnover of the dispersion curve at higher wave numbers and the resultant region of ∂ω/∂k<0 are identified as signatures of dust-dust correlations. In the high collisional regime dust neutral collisions produce a similar effect and prevent an unambiguous identification of strong coupling effects

  7. Dispersion effect in optical microscopy systems with a supersphere solid immersion lens

    Institute of Scientific and Technical Information of China (English)

    Zhang Yao-Ju; Zhuang You-Yi

    2009-01-01

    This paper studies the dispersion effect of the supersphere solid immersion lens (SIL) on a near field optical microscopy system by using the vector diffraction theory. Results show that when a real non-monochromatic beam illuminates a supersphere SIL microscopy, the dispersion effect of the SIL has an important influence on the image quality. As the wavelength bandwidth of the non-monochromatic beam increases, the size of the focused spot increases and its intensity decreases in near-field microscopy systems with a supersphere SIL.

  8. Effects of Sonication Conditions on Ultrasonic Dispersion of Inorganic Particles in Acrylic Resin

    Science.gov (United States)

    Tuziuti, Toru; Yasui, Kyuichi; Towata, Atsuya; Kato, Kazumi

    2011-07-01

    The effects of sonication conditions on the ultrasonic dispersion of titanium dioxide particles in acrylic resin are investigated. Pulsing operation at appropriate on-off duty cycles enables us to attain a particle size smaller than that at a continuous wave (CW) at the same net time of sonication between operations. It is useful that frequency-sweep operation attains almost the same particle size as that at CW, which can provide a constant dispersion of particles even if the resonant frequency used to effectively drive an ultrasonic transducer changes with liquid conditions, such as the temperature and acoustic impedance of a liquid.

  9. Size-class effect contributes to tree species assembly through influencing dispersal in tropical forests.

    Directory of Open Access Journals (Sweden)

    Yue-Hua Hu

    Full Text Available We have investigated the processes of community assembly using size classes of trees. Specifically our work examined (1 whether point process models incorporating an effect of size-class produce more realistic summary outcomes than do models without this effect; (2 which of three selected models incorporating, respectively environmental effects, dispersal and the joint-effect of both of these, is most useful in explaining species-area relationships (SARs and point dispersion patterns. For this evaluation we used tree species data from the 50-ha forest dynamics plot in Barro Colorado Island, Panama and the comparable 20 ha plot at Bubeng, Southwest China. Our results demonstrated that incorporating an size-class effect dramatically improved the SAR estimation at both the plots when the dispersal only model was used. The joint effect model produced similar improvement but only for the 50-ha plot in Panama. The point patterns results were not improved by incorporation of size-class effects using any of the three models. Our results indicate that dispersal is likely to be a key process determining both SARs and point patterns. The environment-only model and joint-effects model were effective at the species level and the community level, respectively. We conclude that it is critical to use multiple summary characteristics when modelling spatial patterns at the species and community levels if a comprehensive understanding of the ecological processes that shape species' distributions is sought; without this results may have inherent biases. By influencing dispersal, the effect of size-class contributes to species assembly and enhances our understanding of species coexistence.

  10. Lagrangian stochastic modeling of anomalous diffusion in two-dimensional turbulence

    Science.gov (United States)

    Reynolds, A. M.

    2002-04-01

    It is shown that at intermediate times, the Langevin equation corresponding to the nonlinear Fokker-Planck equation with exponents μ=1 and ν>1 produces trajectories with multifractal scaling and anomalous power-law dispersion, in common with observations of drifters in the ocean and numerical simulations of tracer particles in two-dimensional turbulence. The extent of this regime and the occurrence of anomalously large normal diffusion at much later times are shown to be in close agreement with dispersion data from numerical simulations of two-dimensional turbulence. In analogy with the dynamics of point vortices in two-dimensional turbulence, the modeled dynamics are nonergodic and effectively comprise of a background Ornstein-Uhlenbeck process punctuated by occasional fast long flights. It is shown that these dynamics optimize the nonextensive (Tsallis) entropy. It is tentatively suggested that the anomalous dispersion in two-dimensional turbulence is a consequence of smaller than average Lagrangian accelerations in regions of the flow with faster than average velocities.

  11. Silica nanoparticles and biological dispersants: genotoxic effects on A549 lung epithelial cells

    Energy Technology Data Exchange (ETDEWEB)

    Brown, David M., E-mail: d.brown@hw.ac.uk [Heriot-Watt University, Nanosafety Research Group, School of Life Sciences (United Kingdom); Varet, Julia, E-mail: julia.varet@IOM-world.org [Institute of Occupational Medicine (United Kingdom); Johnston, Helinor, E-mail: h.johnston@hw.ac.uk; Chrystie, Alison; Stone, Vicki, E-mail: v.stone@hw.ac.uk [Heriot-Watt University, Nanosafety Research Group, School of Life Sciences (United Kingdom)

    2015-10-15

    Silica nanoparticle exposure could be intentional (e.g. medical application or food) or accidental (e.g. occupational inhalation). On entering the body, particles become coated with specific proteins depending on the route of entry. The ability of silica particles of different size and charge (non-functionalized 50 and 200 nm and aminated 50 and 200 nm) to cause genotoxic effects in A549 lung epithelial cells was investigated. Using the modified comet assay and the micronucleus assay, we examined the effect of suspending the particles in different dispersion media [RPMI or Hanks’ balanced salt solution (HBSS), supplemented with bovine serum albumin (BSA), lung lining fluid (LLF) or serum] to determine if this influenced the particle’s activity. Particle characterisation suggested that the particles were reasonably well dispersed in the different media, with the exception of aminated 50 nm particles which showed evidence of agglomeration. Plain 50, 200 nm and aminated 50 nm particles caused significant genotoxic effects in the presence of formamidopyrimidine-DNA glycosylase when dispersed in HBSS or LLF. These effects were reduced when the particles were dispersed in BSA and serum. There was no significant micronucleus formation produced by any of the particles when suspended in any of the dispersants. The data suggest that silica particles can produce a significant genotoxic effect according to the comet assay in A549 cells, possibly driven by an oxidative stress-dependent mechanism which may be modified depending on the choice of dispersant employed.

  12. Silica nanoparticles and biological dispersants: genotoxic effects on A549 lung epithelial cells

    International Nuclear Information System (INIS)

    Silica nanoparticle exposure could be intentional (e.g. medical application or food) or accidental (e.g. occupational inhalation). On entering the body, particles become coated with specific proteins depending on the route of entry. The ability of silica particles of different size and charge (non-functionalized 50 and 200 nm and aminated 50 and 200 nm) to cause genotoxic effects in A549 lung epithelial cells was investigated. Using the modified comet assay and the micronucleus assay, we examined the effect of suspending the particles in different dispersion media [RPMI or Hanks’ balanced salt solution (HBSS), supplemented with bovine serum albumin (BSA), lung lining fluid (LLF) or serum] to determine if this influenced the particle’s activity. Particle characterisation suggested that the particles were reasonably well dispersed in the different media, with the exception of aminated 50 nm particles which showed evidence of agglomeration. Plain 50, 200 nm and aminated 50 nm particles caused significant genotoxic effects in the presence of formamidopyrimidine-DNA glycosylase when dispersed in HBSS or LLF. These effects were reduced when the particles were dispersed in BSA and serum. There was no significant micronucleus formation produced by any of the particles when suspended in any of the dispersants. The data suggest that silica particles can produce a significant genotoxic effect according to the comet assay in A549 cells, possibly driven by an oxidative stress-dependent mechanism which may be modified depending on the choice of dispersant employed

  13. Effects of acclimation on poststocking dispersal and physiological condition of age-1 pallid sturgeon

    Science.gov (United States)

    Oldenburg, E.W.; Guy, C.S.; Cureton, E.S.; Webb, M.A.H.; Gardner, W.M.

    2011-01-01

    The objective of this study was to evaluate the effects of acclimation to flow and site-specific physicochemical water conditions on poststocking dispersal and physiological condition of age-1 hatchery-reared pallid sturgeon. Fish from three acclimation treatments were radio-tagged, released at two locations (Missouri River and Marias River), and monitored using passive telemetry stations. Marias treatment was acclimated to flow and site-specific physicochemical conditions, Bozeman treatment was acclimated to flow only, and controls had no acclimation (reared under traditional conservation propagation protocol). During both years, fish released in the Missouri River dispersed less than fish released in the Marias River. In 2005, Marias treatment dispersed less and nearly twice as many fish remained in the Missouri River reach as compared to control fish. In 2006, pallid sturgeon dispersed similarly among treatments and the number of fish remaining in the Missouri River reach was similar among all treatments. Differences in poststocking dispersal between years were related to fin curl which was present in all fish in 2005 and only 26% in 2006. Pallid sturgeon from all treatments in both years had a greater affinity for the lower reaches of the Missouri River than the upper reaches. Thus, release site influenced poststocking dispersal more than acclimation treatment. No difference was observed in relative growth rate among treatments. However, acclimation to flow (i.e., exercise conditioning) prevented fat accumulation from rupturing hepatocytes. Acclimation conditions used in this study did not benefit pallid sturgeon unless physiological maladies were present. Overriding all treatment effects was stocking location; thus, natural resource agencies need to consider stocking location carefully to reduce poststocking dispersal. ?? 2011 Blackwell Verlag, Berlin.

  14. Effect of Additional Structure on Effective Stack Height of Gas Dispersion in Atmosphere

    Directory of Open Access Journals (Sweden)

    Takenobu Michioka

    2016-03-01

    Full Text Available Wind-tunnel experiments were conducted to evaluate the effect of additional structure (building, sea wall and banking on the effective stack height, which is usually used in safety analyses of nuclear power facilities in Japan. The effective stack heights were estimated with and without the additional structure in addition to the reactor building while varying several conditions such as the source height, the height of additional structure and the distance between the source position and the additional structure. When the source height is equivalent to the reactor building height, the additional structure enhances both the vertical and horizontal gas dispersion widths and decreases the ground gas concentration, and it means that the additional structure does not decrease the effective stack height. When the source height is larger than the reactor height, the additional structures might affect the effective stack height. As the distance between the source and the additional structure decreases, or as the height of the additional structure increases, the structure has a larger effect on the effective stack height.

  15. Effect of sodium dodecyl sulfate on flow and electrokinetic properties of Na-activated bentonite dispersions

    Indian Academy of Sciences (India)

    E Günıster; S İşçı; A Alemdar; N Güngör

    2004-06-01

    The present study reports the effect of anionic surfactant sodium dodecyl sulfate (SDS, C12H25 OSO3Na) upon the electrokinetic (electrophoretic mobility, zeta potential) and rheological (viscosity, yield value) properties of the Ca-bentonitic clay found in Turkey and its Na-activated form. The SDS dispersant was added in different concentrations in the range of 1 × 10-5-5 × 10-2 mol/l. The results show that the viscosity and zeta potential values of bentonite dispersion are affected by the addition of anionic surfactant. The obtained data are analysed by considering the kind of exchangeable cations. Thixotropic property effect was observed in bentonite dispersions.

  16. Solitonization of a dispersive wave.

    Science.gov (United States)

    Braud, F; Conforti, M; Cassez, A; Mussot, A; Kudlinski, A

    2016-04-01

    We report the observation of a nonlinear propagation scenario in which a dispersive wave is transformed into a fundamental soliton in an axially varying optical fiber. The dispersive wave is initially emitted in the normal dispersion region and the fiber properties change longitudinally so that the dispersion becomes anomalous at the dispersive wave wavelength, which allows it to be transformed into a soliton. The solitonic nature of the field is demonstrated by solving the direct Zakharov-Shabat scattering problem. Experimental characterization performed in spectral and temporal domains show evidence of the solitonization process in an axially varying photonic crystal fiber. PMID:27192249

  17. Inclusion of Dispersion Effects in Density Functional Theory

    DEFF Research Database (Denmark)

    Møgelhøj, Andreas

    In this thesis, applications and development will be presented within the field of van der Waals interactions in density functional theory. The thesis is based on the three projects: i) van der Waals interactions effect on the structure of liquid water at ambient conditions, ii) development and...... fitting to high-level ab initio and experimental results. The fitting scheme, based on Baysian theory, focuses on the three aspects: a) model space, b) datasets, and c) model selection. The model space consists of a flexible expansion of the exchange enhancement factor in the generalized gradient...... parameters to close to 7. The ideal weights for the combined solution are found by minimizing the product of relative cost functions. Error estimation is naturally obtained from a distribution of functionals around the optimum solution. The produced exchange-correlation functional is benchmarked against...

  18. Fermi surface versus Fermi sea contributions to intrinsic anomalous and spin Hall effects of multiorbital metals in the presence of Coulomb interaction and spin-Coulomb drag

    Science.gov (United States)

    Arakawa, Naoya

    2016-06-01

    Anomalous Hall effect (AHE) and spin Hall effect (SHE) are fundamental phenomena, and their potential for application is great. However, we understand the interaction effects unsatisfactorily, and should have clarified issues about the roles of the Fermi sea term and Fermi surface term of the conductivity of the intrinsic AHE or SHE of an interacting multiorbital metal and about the effects of spin-Coulomb drag on the intrinsic SHE. Here, we resolve the first issue and provide the first step about the second issue by developing a general formalism in the linear response theory with appropriate approximations and using analytic arguments. The most striking result is that even without impurities, the Fermi surface term, a non-Berry-curvature term, plays dominant roles at high or slightly low temperatures. In particular, this Fermi surface term causes the temperature dependence of the dc anomalous Hall or spin Hall conductivity due to the interaction-induced quasiparticle damping and the correction of the dc spin Hall conductivity due to the spin-Coulomb drag. Those results revise our understanding of the intrinsic AHE and SHE. We also find that the differences between the dc anomalous Hall and longitudinal conductivities arise from the difference in the dominant multiband excitations. This not only explains why the Fermi sea term such as the Berry-curvature term becomes important in clean and low-temperature case only for interband transports, but also provides the useful principles on treating the electron-electron interaction in an interacting multiorbital metal for general formalism of transport coefficients. Several correspondences between our results and experiments are finally discussed.

  19. Effect of gelatin on the water dispersion and centrifugal purification of single-walled carbon nanotubes

    Science.gov (United States)

    Hanium Maria, Kazi; Mieno, Tetsu

    2016-01-01

    We report a convenient and effective procedure for the water dispersion and purification of single-walled carbon nanotubes (SWNTs). The purification procedure involves a combination of dispersion and centrifugation, in which gelatin; an environmentally friendly material is used as a dispersing agent. It has been found that an aqueous solution of gelatin effectively disperses SWNTs for more than a month. Another advantage of using gelatin as a dispersing agent is that it can be easily removed by washing with water and filtration. The centrifugation procedure employs a centrifugal force of about 2500 times the gravitational force to separate the particles. Although carbonaceous and metallic impurities usually have higher density than SWNTs in arc-produced carbon soot, the centrifugation can easily remove impurities leaving undamaged SWNTs in solution when appropriate centrifugal force and a centrifugation time are used. Centrifugation is carried out for three times to sufficiently remove impurities. Finally, the SWNTs are separated from the gelatin by heating in water and filtering.

  20. The effectiveness of dispersants on Alaska North Slope crude oil under various temperature and salinity regimes

    Energy Technology Data Exchange (ETDEWEB)

    Fingas, M.; Fieldhouse, B.; Wang, Z. [Environment Canada, Ottawa, ON (Canada). Emergencies Science and Technology Division, Environmental Technology Centre, Science and Technology Branch

    2006-07-01

    The results of a study investigating the influence of salinity and temperature interactions on dispersants were presented. Experiments were conducted on Alaska North Slope oil at lower temperatures and lower salinity in order to determine optimal dispersant application measurements. Dispersant was pre-mixed with oil and placed on water in a test vessel. The test vessel was agitated on a moving table shaker. At the end of the shaking period, a settling period was allowed and a sample of water was taken. The oil in the water column was extracted from the water using a pentane/dichloromethane mixture and analyzed using gas chromatography. A set of calibration samples was run concurrently with the test samples to establish a calibration curve. ASMB standard oil premixed with Corexit 9500 was tested for effectiveness at 3 temperatures and 8 salinities, including fresh water. Results indicated that the maximum effectiveness was obtained at a temperature of 10 degrees C and at a salinity of 25 per mil. It was noted that temperature and salinity effects are interrelated, with the salinity effect peaking at a select value depending on specific surfactant content. It was suggested that the match between ionic strength and its relation to the surfactant polarity may be the factor that causes the reversal of results. It was concluded that there is an interrelationship between temperature, salinity and the effectiveness of dispersants, indicating that a 3-way correlation may yield a predictive model with good reliability. 6 refs., 1 tab., 2 figs.

  1. Dispersion of dilatation wave propagation in single-wall carbon nanotubes using nonlocal scale effects

    International Nuclear Information System (INIS)

    Nonlocal continuum mechanics allows one to account for the small length scale effect that becomes significant when dealing with micro- or nano-structures. This paper investigates a model of wave propagation in single-wall carbon nanotubes (SWCNTs) with small scale effects are studied. The equation of motion of the dilatation wave is obtained using the nonlocal elastic theory. We show that a dispersive wave equation is obtained from a nonlocal elastic constitutive law, based on a mixture of a local and a nonlocal strain. The SWCNTs structures are treated within the multilayer thin shell approximation with the elastic properties taken to be those of the graphene sheet. The SWCNT was the (40,0) zigzag tube with an effective diameter of 3.13 nm. Nonlinear frequency equations of wave propagation in SWCNTs are described through the effect of small scale. The phase velocity and the group velocity are derived, respectively. The nonlinear dispersion relation is analyzed with different wave numbers versus scale coefficient. It can be observed from the results that the dispersion properties of the dilatation wave are induced by the small scale effects, which will disappear in local continuous models. The dispersion degree can be strengthened by increasing the scale coefficient and the wave number. Furthermore, the characteristics for the group velocity of the dilatation wave in carbon nanotubes can also be tuned by these factors.

  2. Anomalous damping effects of magneto-quantum oscillations in the extremely 2D electronic system κ-(BEDT-TTF)2I3

    International Nuclear Information System (INIS)

    The electronic system of the organic superconductor κ-(BEDT-TTF)2I3 (BEDT-TTF=bis(ethylenedithiolo)tetrathi afulvalene) is identified as extremely two-dimensional (2D). The topology of the Fermi surface (FS) was investigated by means of Shubnikov-de Haas (SdH) as well as de Haas-van Alphen (dHvA) experiments focusing on the verification of the 2D character of the system. This two-dimensionality specially takes effect as soon as the magnetic field is oriented exactly perpendicular to the conducting planes (i.e. Θ=0 ). Under such conditions strong anomalous damping effects in the field and temperature dependence of quantum oscillation amplitudes are observed. These anomalous damping effects are discussed in terms of the occurrence of quasi-particle excitations with fractional statistics (QPFS) which may only occur in extremely 2D systems at high magnetic fields and low temperatures (i.e., only when ℎωC>>kBT). Taking up these requirements, the aim of this work is to quantify the extreme two-dimensionality of the electronic system of κ-(BEDT-TTF)2I3 and to show that the observed damping effects in fact are determined by the ratio ℎωC/kBT. These facts may support the interpretation of the observed damping effects of quantum oscillation amplitudes at high magnetic fields, low temperatures and Θ=0 as generated by the possible occurrence of such QPFS. (orig.)

  3. The charmonium dissociation in an "anomalous wind"

    CERN Document Server

    Sadofyev, Andrey V

    2016-01-01

    We study the charmonium dissociation in a strongly coupled chiral plasma in the presence of magnetic field and axial charge imbalance. This type of plasma carries ``anomalous flow" induced by the chiral anomaly and exhibits novel transport phenomena such as chiral magnetic effect. We found that the ``anomalous flow" would modify the charmonium color screening length by using the gauge/gravity correspondence. We derive an analytical expression quantifying the ``anomalous flow" experienced by a charmonium for a large class of chiral plasma with a gravity dual. We elaborate on the similarity and {\\it qualitative} difference between anomalous effects on the charmonium color screening length which are {\\it model-dependent} and those on the heavy quark drag force which are fixed by the second law of thermodynamics. We speculate on the possible charmonium dissociation induced by chiral anomaly in heavy ion collisions.

  4. The charmonium dissociation in an "anomalous wind"

    Science.gov (United States)

    Sadofyev, Andrey V.; Yin, Yi

    2016-01-01

    We study the charmonium dissociation in a strongly coupled chiral plasma in the presence of magnetic field and axial charge imbalance. This type of plasma carries "anomalous flow" induced by the chiral anomaly and exhibits novel transport phenomena such as chiral magnetic effect. We found that the "anomalous flow" would modify the charmonium color screening length by using the gauge/gravity correspondence. We derive an analytical expression quantifying the "anomalous flow" experienced by a charmonium for a large class of chiral plasma with a gravity dual. We elaborate on the similarity and qualitative difference between anomalous effects on the charmonium color screening length which are model-dependent and those on the heavy quark drag force which are fixed by the second law of thermodynamics. We speculate on the possible charmonium dissociation induced by the chiral anomaly in heavy ion collisions.

  5. Quantification of surface amorphous content using dispersive surface energy: the concept of effective amorphous surface area.

    Science.gov (United States)

    Brum, Jeffrey; Burnett, Daniel

    2011-09-01

    We investigate the use of dispersive surface energy in quantifying surface amorphous content, and the concept of effective amorphous surface area is introduced. An equation is introduced employing the linear combination of surface area normalized square root dispersive surface energy terms. This equation is effective in generating calibration curves when crystalline and amorphous references are used. Inverse gas chromatography is used to generate dispersive surface energy values. Two systems are investigated, and in both cases surface energy data collected for physical mixture samples comprised of amorphous and crystalline references fits the predicted response with good accuracy. Surface amorphous content of processed lactose samples is quantified using the calibration curve, and interpreted within the context of effective amorphous surface area. Data for bulk amorphous content is also utilized to generate a thorough picture of how disorder is distributed throughout the particle. An approach to quantifying surface amorphous content using dispersive surface energy is presented. Quantification is achieved by equating results to an effective amorphous surface area based on reference crystalline, and amorphous materials. PMID:21725707

  6. Flow Dynamics In Eccentrically Rotating Flasks Used For Dispersant Effectiveness Testing

    Science.gov (United States)

    The evaluation of dispersant effectiveness used for oil spills is commonly done using tests conducted in laboratory flasks. We used a Hot Wire Anemometer (HWA) to characterize mixing dynamics in the Swirling Flask (SF) and the Baffled Flask (BF), the latter is being considered b...

  7. Dispersion of Co/CNTs via strong electrostatic adsorption method: Thermal treatment effect

    International Nuclear Information System (INIS)

    The effect of different thermal treatment temperature on the structure of multi-walled carbon nanotubes (MWCNTs) and Co particle dispersion on CNTs support is studied using Strong electrostatic adsorption (SEA) method. The samples tested by N2-adsorption, field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). N2-adsorption results showed BET surface area increased using thermal treatment and TEM images showed that increasing the thermal treatment temperature lead to flaky CNTs and defects introduced on the outer surface and Co particle dispersion increased

  8. Large power factor and anomalous Hall effect and their correlation with observed linear magneto resistance in Co-doped Bi2Se3 3D topological insulator.

    Science.gov (United States)

    Singh, Rahul; Shukla, K K; Kumar, A; Okram, G S; Singh, D; Ganeshan, V; Lakhani, Archana; Ghosh, A K; Chatterjee, Sandip

    2016-09-21

    Magnetoresistance (MR), thermo power, magnetization and Hall effect measurements have been performed on Co-doped Bi2Se3 topological insulators. The undoped sample shows that the maximum MR as a destructive interference due to a π-Berry phase leads to a decrease of MR. As the Co is doped, the linearity in MR is increased. The observed MR of Bi2Se3 can be explained with the classical model. The low temperature MR behavior of Co doped samples cannot be explained with the same model, but can be explained with the quantum linear MR model. Magnetization behavior indicates the establishment of ferromagnetic ordering with Co doping. Hall effect data also supports the establishment of ferromagnetic ordering in Co-doped Bi2Se3 samples by showing the anomalous Hall effect. Furthermore, when spectral weight suppression is insignificant, Bi2Se3 behaves as a dilute magnetic semiconductor. Moreover, the maximum power factor is observed when time reversal symmetry (TRS) is maintained. As the TRS is broken the power factor value is decreased, which indicates that with the rise of Dirac cone above the Fermi level the anomalous Hall effect and linearity in MR increase and the power factor decreases. PMID:27419361

  9. Large power factor and anomalous Hall effect and their correlation with observed linear magneto resistance in Co-doped Bi2Se3 3D topological insulator

    Science.gov (United States)

    Singh, Rahul; Shukla, K. K.; Kumar, A.; Okram, G. S.; Singh, D.; Ganeshan, V.; Lakhani, Archana; Ghosh, A. K.; Chatterjee, Sandip

    2016-09-01

    Magnetoresistance (MR), thermo power, magnetization and Hall effect measurements have been performed on Co-doped Bi2Se3 topological insulators. The undoped sample shows that the maximum MR as a destructive interference due to a π-Berry phase leads to a decrease of MR. As the Co is doped, the linearity in MR is increased. The observed MR of Bi2Se3 can be explained with the classical model. The low temperature MR behavior of Co doped samples cannot be explained with the same model, but can be explained with the quantum linear MR model. Magnetization behavior indicates the establishment of ferromagnetic ordering with Co doping. Hall effect data also supports the establishment of ferromagnetic ordering in Co-doped Bi2Se3 samples by showing the anomalous Hall effect. Furthermore, when spectral weight suppression is insignificant, Bi2Se3 behaves as a dilute magnetic semiconductor. Moreover, the maximum power factor is observed when time reversal symmetry (TRS) is maintained. As the TRS is broken the power factor value is decreased, which indicates that with the rise of Dirac cone above the Fermi level the anomalous Hall effect and linearity in MR increase and the power factor decreases.

  10. Nutrient effects on the biodegradation rates of chemically-dispersed crude oil

    Energy Technology Data Exchange (ETDEWEB)

    Harris, B.C. [Environmental Resources Management, Houston, TX (United States); Bonner, J.S.; McDonald, T.J.; Fuller, C.B.; Page, C.A.; Dimitriou-Christidis, P.; Sterling, M.C.; Autenrieth, R.L. [Texas A and M Univ., College Station, TX (United States)

    2002-07-01

    In addition to causing environmental, health, and economic problems, oil spills onto bodies of water present the problem of spill containment because they spread on the water surface. Booms and skimmers can be used to contain and capture the oil, but chemical dispersants are another way to reduce the adverse affects associated with oil spills. They increase the dispersion of the oil in the water column and stimulate the biodegradation of oil compounds. This study examined whether nitrogen and phosphorus addition would stimulate biodegradation. Crude oil was chemically dispersed with dispersant Corexit 9500 in Corpus Christi Bay water in a swirling flask. Nitrogen and phosphorus were then added to observe the nutrient effects. Analysis was done using gas chromatography-mass spectrometry. It was determined that the addition of nitrogen stimulated the biodegradation of alkane and polycyclic aromatic hydrocarbons (PAH). The addition of phosphorus increased the biodegradation rates of alkanes only, not PAH. The saturation attenuation factor constants for nitrogen concentrations related to biodegradation rates of alkanes and PAHs were 2.32 and 1.69 mg N per litre respectively. The attenuation factor constant for phosphorus addition was 1.42 mg P per litre. It was suggested that oil recovery can be further improved with more research into attenuation factors and methods to increase nutrient levels in oil plumes that have been chemically dispersed. 15 refs., 1 tab., 6 figs.

  11. The effect of dispersed Petrobaltic oil droplet size on photosynthetically active radiation in marine environment.

    Science.gov (United States)

    Haule, Kamila; Freda, Włodzimierz

    2016-04-01

    Oil pollution in seawater, primarily visible on sea surface, becomes dispersed as an effect of wave mixing as well as chemical dispersant treatment, and forms spherical oil droplets. In this study, we examined the influence of oil droplet size of highly dispersed Petrobaltic crude on the underwater visible light flux and the inherent optical properties (IOPs) of seawater, including absorption, scattering, backscattering and attenuation coefficients. On the basis of measured data and Mie theory, we calculated the IOPs of dispersed Petrobaltic crude oil in constant concentration, but different log-normal size distributions. We also performed a radiative transfer analysis, in order to evaluate the influence on the downwelling irradiance E d , remote sensing reflectance R rs and diffuse reflectance R, using in situ data from the Baltic Sea. We found that during dispersion, there occurs a boundary size distribution characterized by a peak diameter d 0  = 0.3 μm causing a maximum E d increase of 40 % within 0.5-m depth, and the maximum E d decrease of 100 % at depths below 5 m. Moreover, we showed that the impact of size distribution on the "blue to green" ratios of R rs and R varies from 24 % increase to 27 % decrease at the same crude oil concentration. PMID:26635218

  12. Effects of periodicity on flow and dispersion through closely packed fixed beds of spheres

    Science.gov (United States)

    Reynolds, A. M.

    2002-02-01

    A lattice-Boltzmann formulation is used to investigate the effects of ``periodicity'' (geometry) on fluid flow and tracer-particle dispersion through fixed beds of spheres comprising of closely packed layers. In the ``period-1'' arrangement, spheres in the adjacent layers contact at their poles while the ``period-2'' and ``period-3'' arrangements correspond to hexagonal and faced-centered cubic close packing. For all three packing arrangements, there is a transition with increasing Reynolds number from a power law to a log-normal distribution of kinetic energies and, velocity and vorticity become more closely aligned giving rise to helical tracer-particle trajectories. It is suggested that these flow characteristics, unlike the stability of flow and the distribution of helicity, are largely insensitive to geometry, even when the geometry creates direct channels through the pack bed orientated along the gradient in applied pressure. For steady flows and strongly turbulent flows, such channels are predicted to provide direct routes for dispersion through a packed bed, while for weakly turbulent flows they influence dispersion primarily by destabilizing the flow and thereby promoting dispersion throughout a bed. The dispersion of tracer-particles released from a source located on or close to a ``stagnation streamline'' is predicted to be faster than ballistic in the near field and the transition to long-time Fickian diffusion is predicted to be distinguished by a regime of subdiffusion.

  13. Effects of Fiber Dispersion on the Performance of Optical CDMA Systems

    Science.gov (United States)

    Kharazi, Seyed Mohammad Saleh Seyedzadeh; Mahdiraji, Ghafour Amouzad; Sahbudin, Ratna Kalos Zakiah; Abas, Ahmad Fauzi; Anas, Siti Barirah Ahmad

    2012-12-01

    In recent years, Optical Code Division Multiple Access (OCDMA) system had received great attentions due to its potential to support applications with various data rates and Quality of Service requirements in physical layer. Since the main part of any fiber-based transmission system is the optical fiber itself, OCDMA also suffers from fiber impairments especially dispersion. In this paper, a review of fiber dispersion effects on system performance of different coding techniques is presented, focusing on single mode fiber. The different coding techniques include direct-sequence, spectral amplitude encoding and wavelength hopping/time spreading. In addition, the basic dispersion compensation approaches, which have been proposed in the literature, for these particular coding schemes are also discussed.

  14. Superparamagnetism, magnetoresistance and anomalous Hall effect in amorphous Mn{sub x}Si{sub 1−x} semiconductor films

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Ai-chun; Zhang, Kun; Yan, Shi-shen; Kang, Shi-shou [School of Physics, National Key Laboratory of Crystal Materials, Shandong University, Jinan, Shandong 250100 (China); Qin, Yu-feng [Department of Applied Physics, School of Information Science and Engineering, Shandong Agricultural University, Taian, Shandong 271018 (China); Pei, Juan; He, Li-min; Li, Huan-huan; Dai, You-yong; Xiao, Shu-qin; Tian, Yu-feng [School of Physics, National Key Laboratory of Crystal Materials, Shandong University, Jinan, Shandong 250100 (China)

    2015-02-25

    Graphical abstract: (a) The Hall resistivity ρ{sub xy}(H) measured at different temperatures and the M(H) hysteresis loops at 5 K for the Mn{sub 0.48}Si{sub 0.52} film with a thickness of 20 nm. (b) The relationship between ρ{sub xy} and M obtained by using the data in Figs. 4(a) and 2(a). (c) The relationship between the anomalous Hall coefficient R{sub s} and the longitudinal resistivity ρ{sub xx.} - Highlights: • Magnetic and transport properties of Mn{sub x}Si{sub 1−x} films are systematically studied. • Superparamagnetism is observed in Mn{sub 0.48}Si{sub 0.52} above 17 K. • Small negative magnetoresistance indicates that spin-dependent scattering is weak. • Remarkable anomalous Hall effect is observed in the whole temperature range. • Electron–electron and electron–phonon interactions dominate the conductivity. - Abstract: A systematic study focusing on the magnetic and transport properties of Mn{sub 0.48}Si{sub 0.52} semiconductor films is performed. The Mn{sub 0.48}Si{sub 0.52} films show superparamagnetism above 17 K. The temperature dependence of the electrical transport reveals that electron–electron and electron–phonon interactions dominate the conductivity of weakly localized carriers. Very small negative magnetoresistance suggests that spin-dependent scattering between conductive carriers and local magnetic moments of Mn atoms is rather weak. On the contrary, the anomalous Hall effect due to the skew scattering is observed in the whole temperature range, indicating the spin–orbit coupling of the conducting carriers is significantly strong.

  15. Anomalous transport due to scale anomaly

    CERN Document Server

    Chernodub, M N

    2016-01-01

    We show that the scale anomaly in field theories leads to new anomalous transport effects that emerge in external electromagnetic field in inhomogeneous gravitational background. In inflating geometry the QED scale anomaly generates electric current which flows in opposite direction with respect to background electric field. In static spatially inhomogeneous gravitational background the dissipationless electric current flows transversely both to the magnetic field axis and to the gradient of the inhomogeneity. The anomalous currents are proportional to the beta function of the theory.

  16. Resolving anomalous strain effects on two-dimensional phonon flows: The cases of graphene, boron nitride, and planar superlattices

    Science.gov (United States)

    Zhu, Taishan; Ertekin, Elif

    2015-05-01

    The physics of thermal transport on strained, two-dimensional (2D) materials graphene, boron nitride, and their superlattices is analyzed by molecular dynamics, lattice dynamics, and numerical solutions to Boltzmann transport equation. The thermal conductivity of these materials is found to be highly sensitive to tensile strain, and the strain dependence itself is also highly dependent on the sample total length. Both finite-sized systems (varying from ˜100 to 300 nm long) as well as infinitely long systems are considered. In contrast to the typical reduction of thermal conductivity with strain exhibited by bulk 3D materials, the thermal conductivity initially increases to a peak value, after which it then decreases with further strain. Modal decomposition of the phonon spectrum shows that the nonmonotonic behavior arises from a competition between in-plane softening and flexural stiffening of phonons. The length sensitivity arises from the nature of the linear/quadratic dispersion of the in-plane/flexural modes and their distinct scattering selection rules: longer systems favor out-of-plane flexural phonon stiffening while smaller systems favor in-plane phonon softening. Additionally, we show that this competition occurs in concert with a strain-induced transition in the nature of the phonon flow from ballistic dominant to diffusive dominant. Overall these effects give rise to a complex dependence of thermal conductivity on strain and sample size.

  17. Dispersion effect and auto-reconditioning performance of nanometer WS2 particles in green lubricant

    Indian Academy of Sciences (India)

    Shi Chen; Mao Daheng; Zhou Ming

    2010-10-01

    This paper reported on dispersion effect and dispersing techniques of nanometer WS2 particles in the green lubricant concocted by us. And it also researched on auto-reconditioning performance of nanometer WS2 particles to the abrasive surfaces of steel ball from four-ball tribology test and piston ring from engine lubrication test. The treated and untreated nanometer WS2 particles were analysed by infrared spectrum. And the elementary component and interior elementary distribution of abrasive surface repaired by nanometer WS2 particles were analysed by multifunction electron spectrometer. The results showed that the combinative method of ultrasonic dispersion, mechanical agitation and surface modification could improve the dispersion uniformity and stability of nanometer WS2 particles in the green lubricant effectively. And the optimal ratio of the mass between surface modifier and nanometer WS2 particles was 1 : 2.5, the optimal treating time was 5 h. And IR analysis indicated that surface modifier could react with hydroxide radicals on surfaces of WS2 particles and modify the surfaces, and the long lipophilic groups on surfaces of nanometer WS2 particles could stretch in oil adequately and form steric hindrance layers between particles which prevented particles from conglomerating and depositing. In addition, tribological tests and surface analysis indicated that there were WS2 adsorption film and reaction film on abrasive surfaces during the tribological tests, which could fill and level up the furrows on abrasive surfaces. As a result, the abrasive surfaces were repaired effectively by nanometer WS2 particles.

  18. Effects of BURP Maneuver on the Hemodynamics and QT and P Dispersions in ECG in Cardiac Surgery Patients

    OpenAIRE

    DEMİRHAN, A.; BİLGİ, M.; TEKELİOĞLU, Ü. Y.; Akkaya, A; ERDEM, K.; Öztürk, S.; KURT, A. D.; Koçoğlu, H.

    2014-01-01

    Effects of BURP Maneuver on the Hemodynamics and QT and P Dispersions in ECG in Cardiac Surgery PatientsObjective: In this study, we aimed to investigate the possible effects of “backward-upward right-sided pressure” (BURP) maneuver applied during tracheal intubation (TI) in patients who will undergo coronary artery baypas surgery on hemodynamic response and QT dispersion (QTd) and P wave dispersion (Pd).Material and Methods: 40 patients undergoing elective coronary artery bypas graft surgery...

  19. Study of long term effects of oil and oil-dispersant mixtures on freshwater microbial populations in man made ponds

    Energy Technology Data Exchange (ETDEWEB)

    Dutka, B.J.; Kwan, K.K.

    1984-04-19

    In this paper, the results of a 19 month investigation of microbial communities subjected to the effects of oil and oil plus dispersant additions in man made ponds are reported. Microbial biomass estimations by ATP (adenosine triphosphate) and microscopic procedures using epifluorescence indicated that oil and oil plus dispersants had little or no effect on these parameters, and any effect noted was stimulatory. However, detailed examination of specific populations indicated that oil and oil plus dispersant additions were stimulatory for short periods of time to the populations studied. Seven days after the oil and dispersant additions to the ponds, no mutagenic or toxic activities to bacteria were noted.

  20. Effect of Autonomic Nervous System on the Transmurai Dispersion of Ventricular Repolarization in Intact Canine

    Institute of Scientific and Technical Information of China (English)

    张存泰; 徐大文; 李泱; 刘念; 王琳; 陆再英

    2004-01-01

    Summary: The effect of the autonomic nerves on the transmural dispersion of ventricular repolarization in intact canine was investigated. By using the monophasic action potential (MAP) recording technique, monophasic action potentials (MAPs) of the epicardium (Epi), midmyocardium (Mid)and endocardium (Endo) were recorded simultaneously by specially designed plunge-needle electrodes at the left ventricular free wall in 12 open-chest dogs. MAPD90 and transmural dispersion of repolarization among three myocardial layers as well as the incidence of the EAD before autonomic nervous stimulation and during autonomic nervous stimulation were compared. The results showed that the MAPD90 of Epi, Mid and Endo before autonomic nervous stimulation were 278±11 ms,316± 16 ms and 270± 12 ms respectively, the MAPD90of Mid was significantly longer than that of Epi or Endo (P<0.01). MAPD90 of Epi, Mid and Endo were shortened by 19±4 ms, 45±6 ms,18± 3 ms respectively during sympathetic stimulation. Compared with that of the control, the transmural dispersion of repolarization during sympathetic stimulation was shortened from 44 ± 4 ms to 15±3 ms (P<0. 01), but early afterdepolarizations were elicited in the Mid of 5 dogs (41 0%)during sympathetic stimulation. Parasympathetic stimulation did not significantly affect the MAPD90 in the three layers. It is concluded that there is the transmural dispersion of ventricular repolarization in intact canine. Sympathetic stimulation can reduce transmural dispersion of repolarization, but it can produce early afterdepolarizations in the Mid. Parasympathetic stimulation does not significantly affect the transmural dispersion of ventricular repolarization.

  1. Effect of spatial dispersion on transient acoustic wave propagation in 3D.

    Science.gov (United States)

    Every, A G

    2006-12-22

    Spatial dispersion is the variation of wave speed with wavelength. It sets in when the acoustic wavelength approaches the natural scale of length of the medium, which could, for example, be the lattice constant of a crystal, the repeat distance in a superlattice, or the grain size in a granular material. In centrosymmetric media, the first onset of dispersion is accommodated by the introduction of fourth order spatial derivatives into the wave equation. These lead to a correction to the phase velocity which is quadratic in the spatial frequency. This paper treats the effect of spatial dispersion on the point force elastodynamic Green's functions of solids. The effects of dispersion are shown to be most pronounced in the vicinity of wave arrivals. These lose their singular form, and are transformed into wave trains known as quasi-arrivals. The step and ramp function wave arrivals are treated, and it is shown that their unfolded quasi-arrival forms can be expressed in terms of integrals involving the Airy function. PMID:16828830

  2. Nonlocal homogenization theory in metamaterials: Effective electromagnetic spatial dispersion and artificial chirality

    Science.gov (United States)

    Ciattoni, Alessandro; Rizza, Carlo

    2015-05-01

    We develop, from first principles, a general and compact formalism for predicting the electromagnetic response of a metamaterial with nonmagnetic inclusions in the long-wavelength limit, including spatial dispersion up to the second order. Specifically, by resorting to a suitable multiscale technique, we show that the effective medium permittivity tensor and the first- and second-order tensors describing spatial dispersion can be evaluated by averaging suitable spatially rapidly varying fields, each satisfying electrostatic-like equations within the metamaterial unit cell. For metamaterials with negligible second-order spatial dispersion, we exploit the equivalence of first-order spatial dispersion and reciprocal bianisotropic electromagnetic response to deduce a simple expression for the metamaterial chirality tensor. Such an expression allows us to systematically analyze the effect of the composite spatial symmetry properties on electromagnetic chirality. We find that even if a metamaterial is geometrically achiral, i.e., it is indistinguishable from its mirror image, it shows pseudo-chiral-omega electromagnetic chirality if the rotation needed to restore the dielectric profile after the reflection is either a 0∘ or 90∘ rotation around an axis orthogonal to the reflection plane. These two symmetric situations encompass two-dimensional and one-dimensional metamaterials with chiral response. As an example admitting full analytical description, we discuss one-dimensional metamaterials whose single chirality parameter is shown to be directly related to the metamaterial dielectric profile by quadratures.

  3. Pre-dispersal predation effect on seed packaging strategies and seed viability.

    Science.gov (United States)

    DeSoto, Lucía; Tutor, David; Torices, Rubén; Rodríguez-Echeverría, Susana; Nabais, Cristina

    2016-01-01

    An increased understanding of intraspecific seed packaging (i.e. seed size/number strategy) variation across different environments may improve current knowledge of the ecological forces that drive seed evolution in plants. In particular, pre-dispersal seed predation may influence seed packaging strategies, triggering a reduction of the resources allocated to undamaged seeds within the preyed fruits. Assessing plant reactions to pre-dispersal seed predation is crucial to a better understanding of predation effects, but the response of plants to arthropod attacks remains unexplored. We have assessed the effect of cone predation on the size and viability of undamaged seeds in populations of Juniperus thurifera with contrasting seed packaging strategies, namely, North African populations with single-large-seeded cones and South European populations with multi-small-seeded cones. Our results show that the incidence of predation was lower on the single-large-seeded African cones than on the multi-small-seeded European ones. Seeds from non-preyed cones were also larger and had a higher germination success than uneaten seeds from preyed cones, but only in populations with multi-seeded cones and in cones attacked by Trisetacus sp., suggesting a differential plastic response to predation. It is possible that pre-dispersal seed predation has been a strong selective pressure in European populations with high cone predation rates, being a process which maintains multi-small-seeded cones and empty seeds as a strategy to save some seeds from predation. Conversely, pre-dispersal predation might not have a strong effect in the African populations with single-large-seeded cones characterized by seed germination and filling rates higher than those in the European populations. Our results indicate that differences in pre-dispersal seed predators and predation levels may affect both selection on and intraspecific variation in seed packaging. PMID:26400794

  4. Three octave spanning supercontinuum by red-shifted dispersive wave in photonic crystal fibers

    CERN Document Server

    Sharma, Mohit

    2015-01-01

    This paper presents a three layer index guided lead silicate (SF57) photonic crystal fiber which simultaneously promises to yield large effective optical nonlinear coefficient and low anomalous dispersion that makes it suitable for supercontinuum generation. At an operating wavelength 1550 nm, the typical optimized value of anomalous dispersion and effective nonlinear coefficient turns out to be ~4 ps/km/nm and ~1078 W^(-1) km^(-1), respectively. Through numerical simulation it is realized that the designed fiber promises to exhibit three octave spanning supercontinuum from 900 to 7200 nm by using 50 fs sech optical pulses of 5 kW peak power. Due to the cross-phase modulation and four-wave mixing processes, a long range of red-shifted dispersive wave generated, which assist to achieve such large broadening. In addition, we have investigated the compatibility of supercontinuum generation with input pulse peak power increment and briefly discussed the impact of nonlinear processes on supercontinuum generation.

  5. Methods for estimating cleaning effectiveness, dispersion, and toxicity of shoreline cleaning agents at oil spills

    International Nuclear Information System (INIS)

    Chemical shoreline cleaning agents (SCAs) are designed to enhance removal of stranded oil from shoreline surfaces. However, difficulties associated with estimating cleaning effectiveness and toxicity of SCAs for site-specific conditions make it desirable to perform measurements in the field with onsite oil, substrates, and resident or otherwise appropriate test organisms. Information for onsite testing should address the following questions: (1) does use of an SCA promote removal of oil from substate surfaces; (2) does use of an SCA increase the amount of dispersed oil in the water column; (3) does toxicity for resident organisms indicate a likelihood for adverse effects; (4) does toxicity with a portable test organism indicate a likelihood for adverse effects? Methodologies are described for use in a portable kit to estimate quantitative and qualitative information for cleaning effectiveness, dispersion of oil, and toxicity of SCAs in the field. Toxicity methodologies for resident organisms include echinoderm fertilization, byssal thread attachment for mussels, and righting/water-escaping ability for periwinkle snails. Microtox trademark is used for toxicity measurements as a portable test organism/assay. Use of portable methodologies for assessing cleaning effectiveness, dispersion of oil, and toxicity of SCAs in the field can assist onsite evaluations for cleaning performance and relative risk to biological resources, which are important for supporting use-no use decisions for SCAs

  6. The effect of hydrodynamic dispersion parameters on process optimization of S-109 partial waste retrieval

    International Nuclear Information System (INIS)

    The removal of cesium by draining the supernate and interstitial salt solution from the salt-cake while fresh water is continuously being added at the top of the tank requires modeling of the transport in variably saturated porous media, and possibly includes a diffusion component. The uncertainties in this method are based on the highly inhomogeneous properties of the salt-cake and limited knowledge of the drainage and transport parameters, more specifically, its hydraulic constraints and hydrodynamic dispersion properties. The hydraulic parameters of the salt-cake (hydraulic conductivity and van Genuchten parameters) have significance with respect to tank drainage and re-saturation and determine the kinetics of the flow through the salt waste. The unsaturated properties are needed in order to assess not only the time frame of tank drainage but also the equilibrium conditions. One of the most important parameters for determining the transport properties of the porous media is the hydrodynamic dispersion tensor. The hydrodynamic dispersion can be applied to describe the spreading of cesium mass spatially and temporally. It combines effects from local variations in pore fluid velocity dispersion and molecular diffusion. In this study, the hydrodynamic dispersion parameters, the Peclet number for molecular diffusion, and the resulting uncertainties have been estimated from pilot scale column experiments using S-109 salt-cake simulant. A 2-D axisymmetric finite element model has been developed to couple the flow in variably saturated regime with transport of non-reacting cesium. The model used unsaturated hydraulic properties as determined from previous experimental work. The study performed sensitivity analysis of the hydrodynamic dispersion factor and provided information about its significance with respect to cesium temporal and spatial distribution. The model was used to compare relevant operating parameters during the replacement of cesium rich supernatant with

  7. Partial oxidation of Step-Bound Water Leads to Anomalous pH Effects on Metal Electrode Step-Edges

    CERN Document Server

    Schwarz, Kathleen; Yan, Yushan; Sundararaman, Ravishankar

    2016-01-01

    The design of better heterogeneous catalysts for applications such as fuel cells and electrolyzers requires a mechanistic understanding of electrocatalytic reactions and the dependence of their activity on operating conditions such as pH. A satisfactory explanation for the unexpected pH dependence of electrochemical properties of platinum surfaces has so far remained elusive, with previous explanations resorting to complex co-adsorption of multiple species and resulting in limited predictive power. This knowledge gap suggests that the fundamental properties of these catalysts are not yet understood, limiting systematic improvement. Here, we analyze the change in charge and free energies upon adsorption using density-functional theory (DFT) to establish that water adsorbs on platinum step edges across a wide voltage range, including the double-layer region, with a loss of approximately 0.2 electrons upon adsorption. We show how the change in net surface charge due to this water explains the anomalous pH variat...

  8. Post-release dispersal in animal translocations: social attraction and the "vacuum effect".

    Science.gov (United States)

    Mihoub, Jean-Baptiste; Robert, Alexandre; Le Gouar, Pascaline; Sarrazin, François

    2011-01-01

    Animal translocations are human-induced colonizations that can represent opportunities to contribute to the knowledge on the behavioral and demographic processes involved in the establishment of animal populations. Habitat selection behaviors, such as social cueing, have strong implications on dispersal and affect the establishment success of translocations. Using modeling simulations with a two-population network model (a translocated population and a remnant population), we investigated the consequences of four habitat selection strategies on post-translocation establishment probabilities in short- and long-lived species. Two dispersal strategies using social cues (conspecific attraction and habitat copying) were compared to random and quality-based strategies. We measured the sensitivity of local extinctions to dispersal strategies, life cycles, release frequencies, remnant population and release group sizes, the proportion of breeders and the connectivity between populations. Our results indicate that social behaviors can compromise establishment as a result of post-release dispersal, particularly in long-lived species. This behavioral mechanism, the "vacuum effect", arises from increased emigration in populations that are small relative to neighboring populations, reducing their rate of population growth. The vacuum effect can drive small remnant populations to extinction when a translocated group is large. In addition, the magnitude of the vacuum effect varies non-linearly with connectivity. The vacuum effect represents a novel form of the behaviorally mediated Allee effect that can cause unexpected establishment failures or population extinctions in response to social cueing. Accounting for establishment probabilities as a conditional step to the persistence of populations would improve the accuracy of predicting the fates of translocated or natural (meta)populations. PMID:22194784

  9. Post-release dispersal in animal translocations: social attraction and the "vacuum effect".

    Directory of Open Access Journals (Sweden)

    Jean-Baptiste Mihoub

    Full Text Available Animal translocations are human-induced colonizations that can represent opportunities to contribute to the knowledge on the behavioral and demographic processes involved in the establishment of animal populations. Habitat selection behaviors, such as social cueing, have strong implications on dispersal and affect the establishment success of translocations. Using modeling simulations with a two-population network model (a translocated population and a remnant population, we investigated the consequences of four habitat selection strategies on post-translocation establishment probabilities in short- and long-lived species. Two dispersal strategies using social cues (conspecific attraction and habitat copying were compared to random and quality-based strategies. We measured the sensitivity of local extinctions to dispersal strategies, life cycles, release frequencies, remnant population and release group sizes, the proportion of breeders and the connectivity between populations. Our results indicate that social behaviors can compromise establishment as a result of post-release dispersal, particularly in long-lived species. This behavioral mechanism, the "vacuum effect", arises from increased emigration in populations that are small relative to neighboring populations, reducing their rate of population growth. The vacuum effect can drive small remnant populations to extinction when a translocated group is large. In addition, the magnitude of the vacuum effect varies non-linearly with connectivity. The vacuum effect represents a novel form of the behaviorally mediated Allee effect that can cause unexpected establishment failures or population extinctions in response to social cueing. Accounting for establishment probabilities as a conditional step to the persistence of populations would improve the accuracy of predicting the fates of translocated or natural (metapopulations.

  10. Many-body dispersion effects in the binding of adsorbates on metal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Maurer, Reinhard J. [Department of Chemistry, Yale University, New Haven, Connecticut 06520 (United States); Ruiz, Victor G.; Tkatchenko, Alexandre [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin (Germany)

    2015-09-14

    A correct description of electronic exchange and correlation effects for molecules in contact with extended (metal) surfaces is a challenging task for first-principles modeling. In this work, we demonstrate the importance of collective van der Waals dispersion effects beyond the pairwise approximation for organic–inorganic systems on the example of atoms, molecules, and nanostructures adsorbed on metals. We use the recently developed many-body dispersion (MBD) approach in the context of density-functional theory [Tkatchenko et al., Phys. Rev. Lett. 108, 236402 (2012) and Ambrosetti et al., J. Chem. Phys. 140, 18A508 (2014)] and assess its ability to correctly describe the binding of adsorbates on metal surfaces. We briefly review the MBD method and highlight its similarities to quantum-chemical approaches to electron correlation in a quasiparticle picture. In particular, we study the binding properties of xenon, 3,4,9,10-perylene-tetracarboxylic acid, and a graphene sheet adsorbed on the Ag(111) surface. Accounting for MBD effects, we are able to describe changes in the anisotropic polarizability tensor, improve the description of adsorbate vibrations, and correctly capture the adsorbate–surface interaction screening. Comparison to other methods and experiment reveals that inclusion of MBD effects improves adsorption energies and geometries, by reducing the overbinding typically found in pairwise additive dispersion-correction approaches.

  11. Many-body dispersion effects in the binding of adsorbates on metal surfaces

    Science.gov (United States)

    Maurer, Reinhard J.; Ruiz, Victor G.; Tkatchenko, Alexandre

    2015-09-01

    A correct description of electronic exchange and correlation effects for molecules in contact with extended (metal) surfaces is a challenging task for first-principles modeling. In this work, we demonstrate the importance of collective van der Waals dispersion effects beyond the pairwise approximation for organic-inorganic systems on the example of atoms, molecules, and nanostructures adsorbed on metals. We use the recently developed many-body dispersion (MBD) approach in the context of density-functional theory [Tkatchenko et al., Phys. Rev. Lett. 108, 236402 (2012) and Ambrosetti et al., J. Chem. Phys. 140, 18A508 (2014)] and assess its ability to correctly describe the binding of adsorbates on metal surfaces. We briefly review the MBD method and highlight its similarities to quantum-chemical approaches to electron correlation in a quasiparticle picture. In particular, we study the binding properties of xenon, 3,4,9,10-perylene-tetracarboxylic acid, and a graphene sheet adsorbed on the Ag(111) surface. Accounting for MBD effects, we are able to describe changes in the anisotropic polarizability tensor, improve the description of adsorbate vibrations, and correctly capture the adsorbate-surface interaction screening. Comparison to other methods and experiment reveals that inclusion of MBD effects improves adsorption energies and geometries, by reducing the overbinding typically found in pairwise additive dispersion-correction approaches.

  12. Many-body dispersion effects in the binding of adsorbates on metal surfaces.

    Science.gov (United States)

    Maurer, Reinhard J; Ruiz, Victor G; Tkatchenko, Alexandre

    2015-09-14

    A correct description of electronic exchange and correlation effects for molecules in contact with extended (metal) surfaces is a challenging task for first-principles modeling. In this work, we demonstrate the importance of collective van der Waals dispersion effects beyond the pairwise approximation for organic-inorganic systems on the example of atoms, molecules, and nanostructures adsorbed on metals. We use the recently developed many-body dispersion (MBD) approach in the context of density-functional theory [Tkatchenko et al., Phys. Rev. Lett. 108, 236402 (2012) and Ambrosetti et al., J. Chem. Phys. 140, 18A508 (2014)] and assess its ability to correctly describe the binding of adsorbates on metal surfaces. We briefly review the MBD method and highlight its similarities to quantum-chemical approaches to electron correlation in a quasiparticle picture. In particular, we study the binding properties of xenon, 3,4,9,10-perylene-tetracarboxylic acid, and a graphene sheet adsorbed on the Ag(111) surface. Accounting for MBD effects, we are able to describe changes in the anisotropic polarizability tensor, improve the description of adsorbate vibrations, and correctly capture the adsorbate-surface interaction screening. Comparison to other methods and experiment reveals that inclusion of MBD effects improves adsorption energies and geometries, by reducing the overbinding typically found in pairwise additive dispersion-correction approaches. PMID:26374001

  13. Chemical dispersants

    NARCIS (Netherlands)

    Rahsepar, Shokouhalsadat; Smit, Martijn P.J.; Murk, Albertinka J.; Rijnaarts, Huub H.M.; Langenhoff, Alette A.M.

    2016-01-01

    Chemical dispersants were used in response to the Deepwater Horizon oil spill in the Gulf of Mexico, both at the sea surface and the wellhead. Their effect on oil biodegradation is unclear, as studies showed both inhibition and enhancement. This study addresses the effect of Corexit on oil biodeg

  14. Self-organized anomalous aggregation of particles performing nonlinear and non-Markovian random walks

    Science.gov (United States)

    Fedotov, Sergei; Korabel, Nickolay

    2015-12-01

    We present a nonlinear and non-Markovian random walks model for stochastic movement and the spatial aggregation of living organisms that have the ability to sense population density. We take into account social crowding effects for which the dispersal rate is a decreasing function of the population density and residence time. We perform stochastic simulations of random walks and discover the phenomenon of self-organized anomaly (SOA), which leads to a collapse of stationary aggregation pattern. This anomalous regime is self-organized and arises without the need for a heavy tailed waiting time distribution from the inception. Conditions have been found under which the nonlinear random walk evolves into anomalous state when all particles aggregate inside a tiny domain (anomalous aggregation). We obtain power-law stationary density-dependent survival function and define the critical condition for SOA as the divergence of mean residence time. The role of the initial conditions in different SOA scenarios is discussed. We observe phenomenon of transient anomalous bimodal aggregation.

  15. Hyperbolic Mild Slope Equations with Inclusion of Amplitude Dispersion Effect: Random Waves

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    New hyperbolic mild slope equations for random waves are developed with the inclusion of amplitude dispersion. The frequency perturbation around the peak frequency of random waves is adopted to extend the equations for regular waves to random waves. The nonlinear effect of amplitude dispersion is incorporated approximately into the model by only considering the nonlinear effect on the carrier waves of random waves, which is done by introducing a representative wave amplitude for the carrier waves. The computation time is greatly saved by the introduction of the representative wave amplitude. The extension of the present model to breaking waves is also considered in order to apply the new equations to surf zone. The model is validated for random waves propagate over a shoal and in surf zone against measurements.

  16. Observation of Autler–Townes effect in a dispersively dressed Jaynes–Cummings system

    International Nuclear Information System (INIS)

    We report on the spectrum of a superconducting transmon device coupled to a planar superconducting resonator in the strong dispersive limit where discrete peaks, each corresponding to a different number of photons, are resolved. A thermal population of 5.474 GHz photons at an effective resonator temperature of T = 120 mK results in a weak n = 1 photon peak along with the n = 0 photon peak in the qubit spectrum in the absence of a coherent drive on the resonator. Two-tone spectroscopy using independent coupler and probe tones reveals an Autler–Townes splitting in the thermal n = 1 photon peak. The observed effect is explained accurately using the four lowest levels of the dispersively dressed qubit–resonator system and compared to results from numerical simulations of the steady-state master equation for the coupled system. (paper)

  17. Anomalous law of cooling

    Energy Technology Data Exchange (ETDEWEB)

    Lapas, Luciano C., E-mail: luciano.lapas@unila.edu.br [Universidade Federal da Integração Latino-Americana, Caixa Postal 2067, 85867-970 Foz do Iguaçu, Paraná (Brazil); Ferreira, Rogelma M. S., E-mail: rogelma.maria@gmail.com [Centro de Ciências Exatas e Tecnológicas, Universidade Federal do Recôncavo da Bahia, 44380-000 Cruz das Almas, Bahia (Brazil); Rubí, J. Miguel, E-mail: mrubi@ub.edu [Departament de Física Fonamental, Facultat de Física, Universitat de Barcelona, Av. Diagonal 647, 08028 Barcelona (Spain); Oliveira, Fernando A., E-mail: fernando.oliveira@pq.cnpq.br [Instituto de Física and Centro Internacional de Física da Matéria Condensada, Universidade de Brasília, Caixa Postal 04513, 70919-970 Brasília, Distrito Federal (Brazil)

    2015-03-14

    We analyze the temperature relaxation phenomena of systems in contact with a thermal reservoir that undergoes a non-Markovian diffusion process. From a generalized Langevin equation, we show that the temperature is governed by a law of cooling of the Newton’s law type in which the relaxation time depends on the velocity autocorrelation and is then characterized by the memory function. The analysis of the temperature decay reveals the existence of an anomalous cooling in which the temperature may oscillate. Despite this anomalous behavior, we show that the variation of entropy remains always positive in accordance with the second law of thermodynamics.

  18. Anomalous gauge boson interactions

    International Nuclear Information System (INIS)

    We discuss the direct measurement of the trilinear vector boson couplings in present and future collider experiments. The major goals of such experiments will be the confirmation of the Standard Model (SM) predictions and the search for signals of new physics. We review our current theoretical understanding of anomalous trilinear gauge-boson self interactions. If the energy scale of the new physics is ∼ 1 TeV, these low energy anomalous couplings are expected to be no larger than Ο(10-2). Constraints from high precision measurements at LEP and low energy charged and neutral current processes are critically reviewed

  19. Anomalous law of cooling

    International Nuclear Information System (INIS)

    We analyze the temperature relaxation phenomena of systems in contact with a thermal reservoir that undergoes a non-Markovian diffusion process. From a generalized Langevin equation, we show that the temperature is governed by a law of cooling of the Newton’s law type in which the relaxation time depends on the velocity autocorrelation and is then characterized by the memory function. The analysis of the temperature decay reveals the existence of an anomalous cooling in which the temperature may oscillate. Despite this anomalous behavior, we show that the variation of entropy remains always positive in accordance with the second law of thermodynamics

  20. Anomalous law of cooling

    Science.gov (United States)

    Lapas, Luciano C.; Ferreira, Rogelma M. S.; Rubí, J. Miguel; Oliveira, Fernando A.

    2015-03-01

    We analyze the temperature relaxation phenomena of systems in contact with a thermal reservoir that undergoes a non-Markovian diffusion process. From a generalized Langevin equation, we show that the temperature is governed by a law of cooling of the Newton's law type in which the relaxation time depends on the velocity autocorrelation and is then characterized by the memory function. The analysis of the temperature decay reveals the existence of an anomalous cooling in which the temperature may oscillate. Despite this anomalous behavior, we show that the variation of entropy remains always positive in accordance with the second law of thermodynamics.