Moenster, Mathias; Steinmeyer, Günter; Iliew, Rumen; Lederer, Falk; Petermann, Klaus
2006-11-15
For optical fibers exhibiting a radially symmetric refractive index profile, there exists an analytical relation that connects waveguide dispersion and the Petermann-II mode field radius. We extend the usefulness of this relation to the nonradially symmetric case of microstructure fibers in the anomalous dispersion regime, yielding a simple relation between dispersion and effective mode field area. Assuming a Gaussian mode distribution, we derive a fundamental upper limit for the effective mode field area that is required to obtain a certain amount of anomalous waveguide dispersion. This relation is demonstrated to show excellent agreement for fiber designs suited for supercontinuum generation and soliton lasers in the near infrared.
Dispersion relations of the acoustic modes in divalent liquid metals
Directory of Open Access Journals (Sweden)
Inui Masanori
2017-01-01
Full Text Available Collective dynamics in liquid Ca and liquid Cd was studied by inelastic x-ray scattering (IXS. Using our experimental technique to prepare proper sample cells and high performance of an IXS beamline (BL35XU at SPring-8 in Japan, the dynamic structure factor with reasonable statistics was obtained for these divalent liquid metals. For both liquids, the dynamic structure factor at low Q exhibits a central peak with a shoulder or small hump clearly visible on each side, and the inelastic excitation energy determined using the model function composed of Lorentzian and the damped harmonic oscillator function disperses with increasing Q. The dispersion curves of these liquids were compared with that of the longitudinal acoustic phonon in each crystalline phase. From these results, clear difference in the interatomic interaction be- tween liquid Ca and liquid Cd was inferred.
Acoustic modes of the phonon dispersion relation of NbD/sub x/ alloys
International Nuclear Information System (INIS)
Rowe, J.M.; Vagelatos, N.; Rush, J.J.; Flotow, H.E.
1975-01-01
The acoustic modes of the phonon dispersion relation in Nb, NbD 0 . 15 , and NbD 0 . 45 were measured at 473 0 K for phonons with wave vectors along the [100], [110], and [111] axes by coherent neutron scattering. The observed neutron groups for both alloys were well defined, with little or no apparent broadening. Results are compared to similar data for Nb--Mo alloys and with previous lattice-dynamics results for PdD 0 . 63 . This comparison shows that despite differences in detail, the general features of the dispersion relations of NbD/sub x/ and Nb--Mo are similar after allowing for the differences in lattice parameters for the two alloys. The measured dispersion curves and derived phonon frequency distributions for the Nb--D alloys are quite different from the analogous results for PdD 0 . 63 in that the average acoustic phonon frequencies increase with increasing deuterium concentration and lattice parameter
Dispersion of coupled mode-gap cavities
Lian, Jin; Sokolov, Sergei; Yuce, E.; Combrie, S.; de Rossi, A.; Mosk, Allard
2015-01-01
The dispersion of a coupled resonator optical waveguide made of photonic crystal mode-gap cavities is pronouncedly asymmetric. This asymmetry cannot be explained by the standard tight binding model. We show that the fundamental cause of the asymmetric dispersion is the inherent dispersive cavity
International Nuclear Information System (INIS)
Cavalier, J.; Lemoine, N.; Bonhomme, G.; Tsikata, S.; Honoré, C.; Grésillon, D.
2012-01-01
The effect of the collective light scattering diagnostic transfer function is considered in the context of the dispersion relation of the unstable E×B mode previously reported. This transfer function is found to have a contribution to the measured frequencies and mode amplitudes which is more or less significant depending on the measurement wavenumbers and angles. After deconvolution, the experimental data are found to be possibly compatible with the idea that the mode frequency in the jet frame (after subtraction of the Doppler effect due to the plasma motion along the thruster axis) is independent of the orientation of the wave vector in the plane orthogonal to the local magnetic field.
Directory of Open Access Journals (Sweden)
Hassan Abid Yasser
2013-01-01
Full Text Available The presence of (first and second orders polarization mode dispersion (PMD, chromatic dispersion, and initial chirp makes effects on the propagated pulses in single mode fiber. Nowadays, there is not an accurate mathematical formula that describes the pulse shape in the presence of these effects. In this work, a theoretical study is introduced to derive a generalized formula. This formula is exactly approached to mathematical relations used in their special cases. The presence of second-order PMD (SOPMD will not affect the orthogonality property between the principal states of polarization. The simulation results explain that the interaction of the SOPMD components with the conventional effects (chromatic dispersion and chirp will cause a broadening/narrowing and shape distortion. This changes depend on the specified values of SOPMD components as well as the present conventional parameters.
Energy Technology Data Exchange (ETDEWEB)
Kekesi, R., E-mail: renata.kekesi@csic.es; Meneses-Rodríguez, D.; García-Pérez, F.; González, M. U.; García-Martín, A.; Cebollada, A.; Armelles, G., E-mail: gaspar@imm.cnm.csic.es [IMM-Instituto de Microelectrónica de Madrid (CNM-CSIC), Isaac Newton 8, PTM, E-28760 Tres Cantos, Madrid (Spain)
2014-10-07
We have analysed the effect that holes have on the properties of propagative surface plasmon modes in semitransparent nanoperforated Au films. The modes have been excited in Kretschmann configuration. Contrary to continuous films, where only one mode is excited, two modes are observed in Au nanohole array. The origin of this different behavior is discussed using effective optical properties for the nanoperforated films. The presence of the holes affects the effective optical constants of the membranes in two ways: it changes the contribution of the free electrons, and it gives rise to a localized transition due to a hole induced plasmon resonance. This localized transition interacts with the propagative surface plasmon modes, originating the two detected modes.
International Nuclear Information System (INIS)
Kekesi, R.; Meneses-Rodríguez, D.; García-Pérez, F.; González, M. U.; García-Martín, A.; Cebollada, A.; Armelles, G.
2014-01-01
We have analysed the effect that holes have on the properties of propagative surface plasmon modes in semitransparent nanoperforated Au films. The modes have been excited in Kretschmann configuration. Contrary to continuous films, where only one mode is excited, two modes are observed in Au nanohole array. The origin of this different behavior is discussed using effective optical properties for the nanoperforated films. The presence of the holes affects the effective optical constants of the membranes in two ways: it changes the contribution of the free electrons, and it gives rise to a localized transition due to a hole induced plasmon resonance. This localized transition interacts with the propagative surface plasmon modes, originating the two detected modes.
Phonon dispersion relations for caesium thiocyanate
International Nuclear Information System (INIS)
Irving, M.A.; Smith, T.F.; Elcombe, M.M.
1984-01-01
Room temperature phonon dispersion relations for frequencies below 2 THz have been measured, along the three orthorhombic axes and selected diagonal directions by neutron inelastic scattering, for caesium thiocyanate. These curves, which represent 13 acoustic modes and 11 optic modes of vibration, do not agree with the dispersion behaviour calculated from the rigid-ion model developed by Ti and Ra to describe their Raman scattering observations
Geometry of physical dispersion relations
International Nuclear Information System (INIS)
Raetzel, Dennis; Rivera, Sergio; Schuller, Frederic P.
2011-01-01
To serve as a dispersion relation, a cotangent bundle function must satisfy three simple algebraic properties. These conditions are derived from the inescapable physical requirements that local matter field dynamics must be predictive and allow for an observer-independent notion of positive energy. Possible modifications of the standard relativistic dispersion relation are thereby severely restricted. For instance, the dispersion relations associated with popular deformations of Maxwell theory by Gambini-Pullin or Myers-Pospelov are not admissible. Dispersion relations passing the simple algebraic checks derived here correspond to physically admissible Finslerian refinements of Lorentzian geometry.
Dispersion and decay of collective modes in neutron star cores
Kobyakov, D. N.; Pethick, C. J.; Reddy, S.; Schwenk, A.
2017-01-01
We calculate the frequencies of collective modes of neutrons, protons and electrons in the outer core of neutron stars. The neutrons and protons are treated in a hydrodynamic approximation and the electrons are regarded as collisionless. The coupling of the nucleons to the electrons leads to Landau damping of the collective modes and to significant dispersion of the low-lying modes. We investigate the sensitivity of the mode frequencies to the strength of entrainment between neutrons and prot...
Time-Frequency Analysis of the Dispersion of Lamb Modes
Prosser, W. H.; Seale, Michael D.; Smith, Barry T.
1999-01-01
Accurate knowledge of the velocity dispersion of Lamb modes is important for ultrasonic nondestructive evaluation methods used in detecting and locating flaws in thin plates and in determining their elastic stiffness coefficients. Lamb mode dispersion is also important in the acoustic emission technique for accurately triangulating the location of emissions in thin plates. In this research, the ability to characterize Lamb mode dispersion through a time-frequency analysis (the pseudo Wigner-Ville distribution) was demonstrated. A major advantage of time-frequency methods is the ability to analyze acoustic signals containing multiple propagation modes, which overlap and superimpose in the time domain signal. By combining time-frequency analysis with a broadband acoustic excitation source, the dispersion of multiple Lamb modes over a wide frequency range can be determined from as little as a single measurement. In addition, the technique provides a direct measurement of the group velocity dispersion. The technique was first demonstrated in the analysis of a simulated waveform in an aluminum plate in which the Lamb mode dispersion was well known. Portions of the dispersion curves of the A(sub 0), A(sub 1), S(sub 0), and S(sub 2)Lamb modes were obtained from this one waveform. The technique was also applied for the analysis of experimental waveforms from a unidirectional graphite/epoxy composite plate. Measurements were made both along, and perpendicular to the fiber direction. In this case, the signals contained only the lowest order symmetric and antisymmetric modes. A least squares fit of the results from several source to detector distances was used. Theoretical dispersion curves were calculated and are shown to be in good agreement with experimental results.
Dispersion relations for 1D high-gain FELs
International Nuclear Information System (INIS)
Webb, S.D.; Litvinenko, V.N.
2010-01-01
We present analytical results for the one-dimensional dispersion relation for high-gain FELs. Using kappa-n distributions, we obtain analytical relations between the dispersion relations for various order kappa distributions. Since an exact solution exists for the kappa-1 (Lorentzian) distribution, this provides some insight into the number of modes on the way to the Gaussian distribution.
Dispersion and decay of collective modes in neutron star cores
Kobyakov, D. N.; Pethick, C. J.; Reddy, S.; Schwenk, A.
2017-08-01
We calculate the frequencies of collective modes of neutrons, protons, and electrons in the outer core of neutron stars. The neutrons and protons are treated in a hydrodynamic approximation and the electrons are regarded as collisionless. The coupling of the nucleons to the electrons leads to Landau damping of the collective modes and to significant dispersion of the low-lying modes. We investigate the sensitivity of the mode frequencies to the strength of entrainment between neutrons and protons, which is not well characterized. The contribution of collective modes to the thermal conductivity is evaluated.
Modified dispersion relations, inflation, and scale invariance
Bianco, Stefano; Friedhoff, Victor Nicolai; Wilson-Ewing, Edward
2018-02-01
For a certain type of modified dispersion relations, the vacuum quantum state for very short wavelength cosmological perturbations is scale-invariant and it has been suggested that this may be the source of the scale-invariance observed in the temperature anisotropies in the cosmic microwave background. We point out that for this scenario to be possible, it is necessary to redshift these short wavelength modes to cosmological scales in such a way that the scale-invariance is not lost. This requires nontrivial background dynamics before the onset of standard radiation-dominated cosmology; we demonstrate that one possible solution is inflation with a sufficiently large Hubble rate, for this slow roll is not necessary. In addition, we also show that if the slow-roll condition is added to inflation with a large Hubble rate, then for any power law modified dispersion relation quantum vacuum fluctuations become nearly scale-invariant when they exit the Hubble radius.
Dispersion relations in loop calculations
International Nuclear Information System (INIS)
Kniehl, B.A.
1996-01-01
These lecture notes give a pedagogical introduction to the use of dispersion relations in loop calculations. We first derive dispersion relations which allow us to recover the real part of a physical amplitude from the knowledge of its absorptive part along the branch cut. In perturbative calculations, the latter may be constructed by means of Cutkosky's rule, which is briefly discussed. For illustration, we apply this procedure at one loop to the photon vacuum-polarization function induced by leptons as well as to the γf anti-f vertex form factor generated by the exchange of a massive vector boson between the two fermion legs. We also show how the hadronic contribution to the photon vacuum polarization may be extracted from the total cross section of hadron production in e + e - annihilation measured as a function of energy. Finally, we outline the application of dispersive techniques at the two-loop level, considering as an example the bosonic decay width of a high-mass Higgs boson. (author)
Dispersion engineering of mode-locked fibre lasers
Woodward, R. I.
2018-03-01
Mode-locked fibre lasers are important sources of ultrashort pulses, where stable pulse generation is achieved through a balance of periodic amplitude and phase evolutions. A range of distinct cavity pulse dynamics have been revealed, arising from the interplay between dispersion and nonlinearity in addition to dissipative processes such as filtering. This has led to the discovery of numerous novel operating regimes, offering significantly improved laser performance. In this Topical Review, we summarise the main steady-state pulse dynamics reported to date through cavity dispersion engineering, including average solitons, dispersion-managed solitons, dissipative solitons, giant-chirped pulses and similaritons. Characteristic features and the stabilisation mechanism of each regime are described, supported by numerical modelling, in addition to the typical performance and limitations. Opportunities for further pulse energy scaling are discussed, in addition to considering other recent advances including automated self-tuning cavities and fluoride-fibre-based mid-infrared mode-locked lasers.
Dispersion relation of linearly polarized strong electromagnetic waves
Energy Technology Data Exchange (ETDEWEB)
Ferrari, A; Massaglia, S [Consiglio Nazionale delle Ricerche, Turin (Italy). Lab. di Cosmo-Geofisica; Dobrowolny, M [Comitato Nazionale per l' Energia Nucleaire, Frascati (Italy). Lab. Plasma Spazio
1975-12-15
A numerical study is presented of the dispersion relation of linearly polarized strong electromagnetic waves in a cold electron plasma. The nonlinear effects introduced by the relativistic motion of electrons are: (1) the dispersion relation depends explicitly on the field strength ..cap alpha..=eE/sub 0//mc..omega../sub 0/, and (2) the propagation of modes with frequencies below the formal electron plasma frequency is allowed.
Czech Academy of Sciences Publication Activity Database
Hartley, D. P.; Kletzing, C. A.; Kurth, W. S.; Bounds, S. R.; Averkamp, T. F.; Hospodarsky, G. B.; Wygant, J. R.; Bonnell, J. W.; Santolík, Ondřej; Watt, C. E. J.
2016-01-01
Roč. 121, č. 5 (2016), s. 4590-4606 ISSN 2169-9380 R&D Projects: GA MŠk(CZ) LH15304 Institutional support: RVO:68378289 Keywords : EFW * EMFISIS * plasmaspheric hiss * sheath impedance * Van Allen Probes * whistler mode chorus Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.733, year: 2016 http://onlinelibrary.wiley.com/doi/10.1002/2016JA022501/abstract
A linearized dispersion relation for orthorhombic pseudo-acoustic modeling
Song, Xiaolei; Alkhalifah, Tariq Ali
2012-01-01
Wavefield extrapolation in acoustic orthorhombic anisotropic media suffers from wave-mode coupling and stability limitations in the parameter range. We introduce a linearized form of the dispersion relation for acoustic orthorhombic media to model acoustic wavefields. We apply the lowrank approximation approach to handle the corresponding space-wavenumber mixed-domain operator. Numerical experiments show that the proposed wavefield extrapolator is accurate and practically free of dispersions. Further, there is no coupling of qSv and qP waves, because we use the analytical dispersion relation. No constraints on Thomsen's parameters are required for stability. The linearized expression may provide useful application for parameter estimation in orthorhombic media.
Wave dispersion relations in two-dimensional Yukawa systems
International Nuclear Information System (INIS)
Liu Yanhong; Liu Bin; Chen Yanping; Yang Size; Wang Long; Wang Xiaogang
2003-01-01
Collective modes in a two-dimensional Yukawa system are investigated by molecular dynamics simulation in a wide range of coupling parameter Γ and screening strength κ. The dispersion relations and sound speeds of the transverse and longitudinal waves obtained for hexagonal lattice are in agreement with the theoretical results. The negative dispersion of the longitudinal wave is demonstrated. Frequency gaps are found on the dispersion curves of the transverse wave due to scattering of the waves on lattice defects for proper values of Γ. The common frequency of transverse and longitudinal waves drops dramatically with the increasing screening strength κ
International Nuclear Information System (INIS)
Aksenov, V.L.; Tyutyunnikov, S.I.; Shalyapin, V.N.; Belyaev, A.D.; Artem'ev, A.N.; Kirillov, B.F.; Demkiv, A.A.; Knyazev, G.A.; Koval'chuk, M.V.; Artem'ev, N.A.
2017-01-01
The improved X-ray optical scheme, the system of registration and measurement procedure of multifunctional synchrotron radiation spectrometer in dispersive EXAFS mode are described. The results of the energy permission measurements of spectrometer are given. The advantages and disadvantages in the traditional and dispersion schematics of spectrometers EXAFS are analyzed. Examples of the EXAFS spectra measured in the dispersion mode are given.
Sakamoto, Hironori; Takeuchi, Eito; Yoshida, Kouki; Morita, Ken; Ma, Bei; Ishitani, Yoshihiro
2018-01-01
Interface phonon polaritons (IPhPs) in nano-structures excluding metal components are thoroughly investigated because they have lower loss in optical emission or absorption and higher quality factors than surface plasmon polaritons. In previous reports, it is found that strong infrared (IR) absorption is based on the interaction of p-polarized light and materials, and the resonance photon energy highly depends on the structure size and angle of incidence. We report the optical absorption by metal/semiconductor (bulk-GaAs and thin film-AlN)-stripe structures in THz to mid-IR region for the electric field of light perpendicular to the stripes, where both of s- and p-polarized light are absorbed. The absorption resonates with longitudinal optical (LO) phonon or LO phonon-plasmon coupling (LOPC) modes, and thus is independent of the angle of incidence or structure size. This absorption is attributed to the electric dipoles by the optically induced polarization charges at the metal/semiconductor, heterointerfaces, or interfaces of high electron density layers and depression ones. The electric permittivity is modified by the formation of these dipoles. It is found to be indispensable to utilize our form of altered permittivity to explain the experimental dispersion relations of metal/semiconductor-IPhP and SPhP in these samples. This analysis reveals that the IPhPs in the stripe structures of metal/AlN-film on a SiC substrate are highly confined in the AlN film, while the permittivity of the structures of metal/bulk-GaAs is partially affected by the electric-dipoles. The quality factors of the electric-dipole absorption are found to be 42-54 for undoped samples, and the value of 62 is obtained for Al/AlN-IPhP. It is thought that metal-contained structures are not obstacles to mode energy selectivity in phonon energy region of semiconductors.
Electronic predistortion for compensation of polarization-mode dispersion
Hellerbrand, Stephan; Hanik, Norbert; Weiershausen, W.
2009-01-01
One of the major impairments in high-speed optical transmission links is Polarization-Mode Dispersion (PMD). We propose the method of electronic predistortion (EPD) for the mitigation of PMD. This approach has already been successfully applied for the compensation of Chromatic Dispersion (CD) and Fiber-Nonlinearities. The advantage of this method is that impairments can efficiently be mitigated without the need for coherent reception. The proposed scheme is based on the possibility to control the optical field at the transmitter by using two complex modulators for the modulation of two orthogonally polarized optical signals. If the physical origin of PMD is exactly known then the ideal predistorted field and the corresponding electrical driving signals can be computed accurately. In practice, however, this information is not available. Therefore it is shown how to determine appropriate driving signals for a set of measured PMD parameters. Measurements will be communicated through a feedback channel in practice. We suggest a possible strategy for application of this technique in scenarios, in which the adaptation speed is intrinsically limited due to the round-trip delay. Numerical simulations reveal that the use of EPD can significantly increase the tolerance towards PMD in comparison to a system without compensation.
A terahertz study of taurine: Dispersion correction and mode couplings
Dai, Zelin; Xu, Xiangdong; Gu, Yu; Li, Xinrong; Wang, Fu; Lian, Yuxiang; Fan, Kai; Cheng, Xiaomeng; Chen, Zhegeng; Sun, Minghui; Jiang, Yadong; Yang, Chun; Xu, Jimmy
2017-03-01
The low-frequency characteristics of polycrystalline taurine were studied experimentally by terahertz (THz) absorption spectroscopy and theoretically by ab initio density-functional simulations. Full optimizations with semi-empirical dispersion correction were performed in spectral computations and vibrational mode assignments. For comparison, partial optimizations with pure density functional theory were conducted in parallel. Results indicate that adding long-range dispersion correction to the standard DFT better reproduces the measured THz spectra than the popular partial optimizations. The main origins of the observed absorption features were also identified. Moreover, a coupled-oscillators model was proposed to explain the experimental observation of the unusual spectral blue-shift with the increase of temperature. Such coupled-oscillators model not only provides insights into the temperature dynamics of non-bonded interactions but also offers an opportunity to better understand the physical mechanisms behind the unusual THz spectral behaviors in taurine. Particularly, the simulation approach and novel coupled-oscillators model presented in this work are applicable to analyze the THz spectra of other molecular systems.
Dispersion relation and relative intensity for double-plasmon satellites
International Nuclear Information System (INIS)
Srivastava, K.S.; Shiv Singh; Harsh, O.K.
1981-01-01
An expression for the dispersion relation and the relative intensity of double-plasmon oscillations and satellites has been derived by extending the dispersion relation and the extended Bohm and Pines Hamiltonian to second order. The calculated value of the relative intensity of the double-plasmon satellite for Be agrees fairly well with the value observed experimentally by other workers. (orig.)
Polarization mode dispersion in optical fiber transmission systems
Cameron, John Charles
The birefringence of optical fibers causes pulse broadening in fiber-optic communication systems. This phenomenon is known as polarization mode dispersion (PMD). PMD is one of the most important limiting factors for high capacity fiber-optic systems. A number of aspects of PMD are examined in this thesis. In Chapter 2 an expression is derived for the probability density function of the pulse broadening due to first-order PMD. This result is used to obtain an expression for the system limitation due to PMD. The birefringence of optical fibers is commonly simulated with the waveplate model. In Chapter 3 two standard versions of the waveplate model are introduced. In addition, a novel waveplate model is proposed. The characteristics of the three versions of the waveplate model are examined to confirm their suitability for use in subsequent chapters of the thesis. Simulations with the waveplate model are performed in Chapter 4 for three purposes: (1) to determine the impact of chromatic dispersion on the system limitation due to PMD, (2) to examine the effectiveness of three different PMD compensation techniques in the presence of chromatic dispersion, and (3) to examine the interaction of second-order chromatic dispersion with PMD. The simulations in Chapter 4 reveal that it is possible with one compensation technique to have output pulses that are narrower than the input pulses. In Chapter 5, this anomalous pulse narrowing is demonstrated analytically for a simple model of PMD and through experiment. It is also shown that this pulse narrowing can be explained as an interference phenomenon. Chapter 6 presents measurements of PMD and state of polarization on installed optical fibers. The PMD coefficients of 122 fibers are presented and the results are analyzed in terms of the age of the fibers and the type of cabling. Measurements of the time evolution of PMD and state of polarization are presented for fibers installed in both buried and aerial cables. The uncertainty
Guiding modes of semi-infinite nanowire and their dispersion character
International Nuclear Information System (INIS)
Sun, Yuming; Su, Yuehua; Dai, Zhenhong; Wang, Weitian
2014-01-01
Conventionally, the optical properties of finite semiconductor nanowires have been understood and explained in terms of an infinite nanowire. This work describes completely different photonic modes for a semi-finite nanowire based on a rigorous theoretical method, and the implications for the finite one. First, the special eigenvalue problem charactered by the end results in a distinctive mode spectrum for the semi-infinite dielectric nanowire. Meanwhile, the results show hybrid degenerate modes away from cutoff frequency, and transverse electric–transverse magnetic (TE–TM) degeneracy. Second, accompanying a different mode spectrum, a semi-finite nanowire also shows a distinctive dispersion relation compared to an infinite nanowire. Taking a semi-infinite, ZnO nanowire as an example, we find that the ℏω−k z space is not continuous in the interested photon energy window, implying that there is no uniform polariton dispersion relation for semi-infinite nanowire. Our method is shown correct through a field-reconstruction for a thin ZnO nanowire (55 nm in radius) and position determination of FP modes for a ZnO nanowire (200 nm in diameter). The results are of great significance to correctly understand the guiding and lasing mechanisms of semiconductor nanowires. (paper)
A linearized dispersion relation for orthorhombic pseudo-acoustic modeling
Song, Xiaolei
2012-11-04
Wavefield extrapolation in acoustic orthorhombic anisotropic media suffers from wave-mode coupling and stability limitations in the parameter range. We introduce a linearized form of the dispersion relation for acoustic orthorhombic media to model acoustic wavefields. We apply the lowrank approximation approach to handle the corresponding space-wavenumber mixed-domain operator. Numerical experiments show that the proposed wavefield extrapolator is accurate and practically free of dispersions. Further, there is no coupling of qSv and qP waves, because we use the analytical dispersion relation. No constraints on Thomsen\\'s parameters are required for stability. The linearized expression may provide useful application for parameter estimation in orthorhombic media.
Second-order polarization-mode dispersion in photonic crystal fibers
DEFF Research Database (Denmark)
Larsen, T; Bjarklev, Anders Overgaard; Peterson, A
2003-01-01
We report the first experimental measurements of second-order polarization-mode dispersion in two successive 900 meter pulls of a silica photonic crystal fiber.......We report the first experimental measurements of second-order polarization-mode dispersion in two successive 900 meter pulls of a silica photonic crystal fiber....
Energy Technology Data Exchange (ETDEWEB)
Fountaine, Katherine T., E-mail: kfountai@caltech.edu [Department of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd., Pasadena, California 91125 (United States); Joint Center for Artificial Photosynthesis, California Institute of Technology, 1200 E. California Blvd., Pasadena, California 91125 (United States); Whitney, William S. [Joint Center for Artificial Photosynthesis, California Institute of Technology, 1200 E. California Blvd., Pasadena, California 91125 (United States); Department of Physics, California Institute of Technology, 1200 E. California Blvd., Pasadena, California 91125 (United States); Atwater, Harry A. [Joint Center for Artificial Photosynthesis, California Institute of Technology, 1200 E. California Blvd., Pasadena, California 91125 (United States); Department of Applied Physics and Materials Science, California Institute of Technology, 1200 E. California Blvd., Pasadena, California 91125 (United States)
2014-10-21
We present a unified framework for resonant absorption in periodic arrays of high index semiconductor nanowires that combines a leaky waveguide theory perspective and that of photonic crystals supporting Bloch modes, as array density transitions from sparse to dense. Full dispersion relations are calculated for each mode at varying illumination angles using the eigenvalue equation for leaky waveguide modes of an infinite dielectric cylinder. The dispersion relations along with symmetry arguments explain the selectivity of mode excitation and spectral red-shifting of absorption for illumination parallel to the nanowire axis in comparison to perpendicular illumination. Analysis of photonic crystal band dispersion for varying array density illustrates that the modes responsible for resonant nanowire absorption emerge from the leaky waveguide modes.
Long wave dispersion relations for surface waves in a magnetically structured atmosphere
International Nuclear Information System (INIS)
Rae, I.C.; Roberts, B.
1983-01-01
A means of obtaining approximate dispersion relations for long wavelength magnetoacoustic surface waves propagating in a magnetically structured atmosphere is presented. A general dispersion relation applying to a wide range of magnetic profiles is obtained, and illustrated for the special cases of a single interface and a magnetic slab. In the slab geometry, for example, the dispersion relation contains both the even (sausage) and odd (kink) modes in one formalism
On normal modes and dispersive properties of plasma systems
International Nuclear Information System (INIS)
Weiland, J.
1976-01-01
The description of nonlinear wave phenomena in terms of normal modes contra that of electric fields is discussed. The possibility of defining higher order normal modes is pointed out and the field energy is expressed in terms of the normal mode and the electric field. (Auth.)
Modified dispersion relations and black hole physics
International Nuclear Information System (INIS)
Ling Yi; Li Xiang; Hu Bo
2006-01-01
A modified formulation of the energy-momentum relation is proposed in the context of doubly special relativity. We investigate its impact on black hole physics. It turns out that such a modification will give corrections to both the temperature and the entropy of black holes. In particular, this modified dispersion relation also changes the picture of Hawking radiation greatly when the size of black holes approaches the Planck scale. It can prevent black holes from total evaporation, as a result providing a plausible mechanism to treat the remnant of black holes as a candidate for dark matter
Chaotic Lagrangian models for turbulent relative dispersion.
Lacorata, Guglielmo; Vulpiani, Angelo
2017-04-01
A deterministic multiscale dynamical system is introduced and discussed as a prototype model for relative dispersion in stationary, homogeneous, and isotropic turbulence. Unlike stochastic diffusion models, here trajectory transport and mixing properties are entirely controlled by Lagrangian chaos. The anomalous "sweeping effect," a known drawback common to kinematic simulations, is removed through the use of quasi-Lagrangian coordinates. Lagrangian dispersion statistics of the model are accurately analyzed by computing the finite-scale Lyapunov exponent (FSLE), which is the optimal measure of the scaling properties of dispersion. FSLE scaling exponents provide a severe test to decide whether model simulations are in agreement with theoretical expectations and/or observation. The results of our numerical experiments cover a wide range of "Reynolds numbers" and show that chaotic deterministic flows can be very efficient, and numerically low-cost, models of turbulent trajectories in stationary, homogeneous, and isotropic conditions. The mathematics of the model is relatively simple, and, in a geophysical context, potential applications may regard small-scale parametrization issues in general circulation models, mixed layer, and/or boundary layer turbulence models as well as Lagrangian predictability studies.
Dispersion relations in three-particle systems
International Nuclear Information System (INIS)
Grach, I.L.; Harodetskij, I.M.; Shmatikov, M.Zh.
1979-01-01
Positions of all dynamical singularities of the triangular nonrelativistic diagram are calculated including the form factors. The jumps of the amplitude are written in an analitical form. The dispersion method predictions for bound states in the three-particle system are compared with the results of the Amado exactly solvable model. It is shown that the one-channel N/D method is equivalent to the pole approximation in the Amado model, and that the three-particle s channel unitarity should be taken into account calculating (in the dispersion method) the ground and excited states of the three-particle system. The relation of the three-particle unitary contribution to the Thomas theorem and Efimov effect is briefly discussed
Noureen, S.; Abbas, G.; Sarfraz, M.
2018-01-01
The study of relativistic degenerate plasmas is important in many astrophysical and laboratory environments. Using linearized relativistic Vlasov-Maxwell equations, a generalized expression for the plasma conductivity tensor is derived. Employing Fermi-Dirac distribution at zero temperature, the dispersion relation of the extraordinary mode in a relativistic degenerate electron plasma is investigated. The propagation characteristics are examined in different relativistic density ranges. The shifting of cutoff points due to relativistic effects is observed analytically and graphically. Non-relativistic and ultra-relativistic limiting cases are also presented.
Kang, Peter K.; Dentz, Marco; Le Borgne, Tanguy; Lee, Seunghak; Juanes, Ruben
2017-08-01
We investigate tracer transport on random discrete fracture networks that are characterized by the statistics of the fracture geometry and hydraulic conductivity. While it is well known that tracer transport through fractured media can be anomalous and particle injection modes can have major impact on dispersion, the incorporation of injection modes into effective transport modeling has remained an open issue. The fundamental reason behind this challenge is that-even if the Eulerian fluid velocity is steady-the Lagrangian velocity distribution experienced by tracer particles evolves with time from its initial distribution, which is dictated by the injection mode, to a stationary velocity distribution. We quantify this evolution by a Markov model for particle velocities that are equidistantly sampled along trajectories. This stochastic approach allows for the systematic incorporation of the initial velocity distribution and quantifies the interplay between velocity distribution and spatial and temporal correlation. The proposed spatial Markov model is characterized by the initial velocity distribution, which is determined by the particle injection mode, the stationary Lagrangian velocity distribution, which is derived from the Eulerian velocity distribution, and the spatial velocity correlation length, which is related to the characteristic fracture length. This effective model leads to a time-domain random walk for the evolution of particle positions and velocities, whose joint distribution follows a Boltzmann equation. Finally, we demonstrate that the proposed model can successfully predict anomalous transport through discrete fracture networks with different levels of heterogeneity and arbitrary tracer injection modes.
Dispersion of strongly confined channel plasmon polariton modes
DEFF Research Database (Denmark)
Zenin, Vladimir; Volkov, Valentyn S.; Han, Zhanghua
2011-01-01
We report on experimental (by use of scanning near-field optical microscopy) and theoretical investigations of strongly confined (∼λ/5) channel plasmon polariton (CPP) modes propagating at telecom wavelengths (1425–1630 nm) along V-grooves cut in a gold film. The main CPP characteristics (mode in...
Dispersal and noise: Various modes of synchrony in ecological oscillators
Bressloff, Paul C.
2012-10-21
We use the theory of noise-induced phase synchronization to analyze the effects of dispersal on the synchronization of a pair of predator-prey systems within a fluctuating environment (Moran effect). Assuming that each isolated local population acts as a limit cycle oscillator in the deterministic limit, we use phase reduction and averaging methods to derive a Fokker-Planck equation describing the evolution of the probability density for pairwise phase differences between the oscillators. In the case of common environmental noise, the oscillators ultimately synchronize. However the approach to synchrony depends on whether or not dispersal in the absence of noise supports any stable asynchronous states. We also show how the combination of partially correlated noise with dispersal can lead to a multistable steady-state probability density. © 2012 Springer-Verlag Berlin Heidelberg.
Dispersal and noise: Various modes of synchrony in ecological oscillators
Bressloff, Paul C.; Lai, Yi Ming
2012-01-01
We use the theory of noise-induced phase synchronization to analyze the effects of dispersal on the synchronization of a pair of predator-prey systems within a fluctuating environment (Moran effect). Assuming that each isolated local population acts as a limit cycle oscillator in the deterministic limit, we use phase reduction and averaging methods to derive a Fokker-Planck equation describing the evolution of the probability density for pairwise phase differences between the oscillators. In the case of common environmental noise, the oscillators ultimately synchronize. However the approach to synchrony depends on whether or not dispersal in the absence of noise supports any stable asynchronous states. We also show how the combination of partially correlated noise with dispersal can lead to a multistable steady-state probability density. © 2012 Springer-Verlag Berlin Heidelberg.
Photon gas with hyperbolic dispersion relations
International Nuclear Information System (INIS)
Mohseni, Morteza
2013-01-01
We investigate the density of states for a photon gas confined in a nonmagnetic metamaterial medium in which some components of the permittivity tensor are negative. We study the effect of the resulting hyperbolic dispersion relations on the black body spectral density. We show that for both of the possible wavevector space topologies, the spectral density vanishes at a certain frequency. We obtain the partition function and derive some thermodynamical quantities of the system. To leading order, the results resemble those of a one- or two-dimensional photon gas with an enhanced density of states. (paper)
All-fiber nonlinearity- and dispersion-managed dissipative soliton nanotube mode-locked laser
Energy Technology Data Exchange (ETDEWEB)
Zhang, Z. [Department of Physics, Bilkent University, 06800 Ankara (Turkey); Nanjing University of Posts and Communications, Nanjing 210003 (China); Popa, D., E-mail: dp387@cam.ac.uk; Wittwer, V. J.; Milana, S.; Hasan, T.; Jiang, Z.; Ferrari, A. C. [Cambridge Graphene Centre, University of Cambridge, Cambridge CB3 0FA (United Kingdom); Ilday, F. Ö. [Department of Physics, Bilkent University, 06800 Ankara (Turkey); Department of Electrical and Electronics Engineering, Bilkent University, 06800 Ankara (Turkey)
2015-12-14
We report dissipative soliton generation from an Yb-doped all-fiber nonlinearity- and dispersion-managed nanotube mode-locked laser. A simple all-fiber ring cavity exploits a photonic crystal fiber for both nonlinearity enhancement and dispersion compensation. The laser generates stable dissipative solitons with large linear chirp in the net normal dispersion regime. Pulses that are 8.7 ps long are externally compressed to 118 fs, outperforming current nanotube-based Yb-doped fiber laser designs.
A net normal dispersion all-fiber laser using a hybrid mode-locking mechanism
International Nuclear Information System (INIS)
Xu, Bo; Martinez, Amos; Yamashita, Shinji; Set, Sze Yun; Goh, Chee Seong
2014-01-01
We propose and demonstrate an all-fiber, dispersion-mapped, erbium-doped fiber laser with net normal dispersion generating dissipative solitons. The laser is mode-locked by a hybrid mode-locking mechanism consisting of a nonlinear amplifying loop mirror and a carbon nanotube saturable absorber. We achieve self-starting, mode-locked operation generating 2.75 nJ pulses at a fundamental repetition rate of 10.22 MHz with remarkable long term stability. (letter)
Energy Technology Data Exchange (ETDEWEB)
Omnes, Roland [Commissariat a l' energie atomique et aux energies alternatives - CEA (France)
1960-07-01
A modification of the dispersion relations demonstration for two-particle collisions in field theory is indicated. The direct study of the holomorphy domain of the reaction amplitude, without any reference to a particular coordinate system, allows to demonstrate the dispersion relations with fixed pulse transfer for any input and output particle mass. Reprint of a paper published in Comptes rendus des seances de l'Academie des Sciences, t. 250, p. 1203-1205, sitting of 15 February 1960 [French] On indique une modification de la demonstration des relations de dispersion pour les collisions a deux particules en theorie des champs. En etudiant directement le domaine d'holomorphie de l'amplitude de reaction sans se referer a un systeme de coordonnees particulier, on demontre les relations de dispersion a transfert d'impulsion fixe dans le cas ou les masses des particules entrantes et sortantes sont quelconques. Reproduction d'un article publie dans les Comptes rendus des seances de l'Academie des Sciences, t. 250, p. 1203-1205, seance du 15 fevrier 1960.
Effect of magnetic field on the wave dispersion relation in three-dimensional dusty plasma crystals
International Nuclear Information System (INIS)
Yang Xuefeng; Wang Zhengxiong
2012-01-01
Three-dimensional plasma crystals under microgravity condition are investigated by taking into account an external magnetic field. The wave dispersion relations of dust lattice modes in the body centered cubic (bcc) and the face centered cubic (fcc) plasma crystals are obtained explicitly when the magnetic field is perpendicular to the wave motion. The wave dispersion relations of dust lattice modes in the bcc and fcc plasma crystals are calculated numerically when the magnetic field is in an arbitrary direction. The numerical results show that one longitudinal mode and two transverse modes are coupled due to the Lorentz force in the magnetic field. Moreover, three wave modes, i.e., the high frequency phonon mode, the low frequency phonon mode, and the optical mode, are obtained. The optical mode and at least one phonon mode are hybrid modes. When the magnetic field is neither parallel nor perpendicular to the primitive wave motion, all the three wave modes are hybrid modes and do not have any intersection points. It is also found that with increasing the magnetic field strength, the frequency of the optical mode increases and has a cutoff at the cyclotron frequency of the dust particles in the limit of long wavelength, and the mode mixings for both the optical mode and the high frequency phonon mode increase. The acoustic velocity of the low frequency phonon mode is zero. In addition, the acoustic velocity of the high frequency phonon mode depends on the angle of the magnetic field and the wave motion but does not depend on the magnetic field strength.
International Nuclear Information System (INIS)
Hnat, B.; O’Connell, D.; Nakariakov, V. M.; Sundberg, T.
2016-01-01
We obtain dispersion relations of magnetic field fluctuations for two crossings of the terrestrial foreshock by Cluster spacecraft. These crossings cover plasma conditions that differ significantly in their plasma β and in the density of the reflected ion beam, but not in the properties of the encountered ion population, both showing shell-like distribution function. Dispersion relations are reconstructed using two-point instantaneous wave number estimations from pairs of Cluster spacecraft. The accessible range of wave vectors, limited by the available spacecraft separations, extends to ≈2 × 10 4 km. Results show multiple branches of dispersion relations, associated with different powers of magnetic field fluctuations. We find that sunward propagating fast magnetosonic waves and beam resonant modes are dominant for the high plasma β interval with a dense beam, while the dispersions of the interval with low beam density include Alfvén and fast magnetosonic modes propagating sunward and anti-sunward.
Energy Technology Data Exchange (ETDEWEB)
Hnat, B.; O’Connell, D.; Nakariakov, V. M. [Centre for Fusion, Space and Astrophysics, University of Warwick (United Kingdom); Sundberg, T., E-mail: B.Hnat@warwick.ac.uk [School of Physics and Astronomy, Queen Mary University of London (United Kingdom)
2016-08-20
We obtain dispersion relations of magnetic field fluctuations for two crossings of the terrestrial foreshock by Cluster spacecraft. These crossings cover plasma conditions that differ significantly in their plasma β and in the density of the reflected ion beam, but not in the properties of the encountered ion population, both showing shell-like distribution function. Dispersion relations are reconstructed using two-point instantaneous wave number estimations from pairs of Cluster spacecraft. The accessible range of wave vectors, limited by the available spacecraft separations, extends to ≈2 × 10{sup 4} km. Results show multiple branches of dispersion relations, associated with different powers of magnetic field fluctuations. We find that sunward propagating fast magnetosonic waves and beam resonant modes are dominant for the high plasma β interval with a dense beam, while the dispersions of the interval with low beam density include Alfvén and fast magnetosonic modes propagating sunward and anti-sunward.
Dispersive properties and attraction instability of low-frequency collective modes in dusty plasmas
International Nuclear Information System (INIS)
Tsytovich, V.N.; Rezendes, D.
1998-01-01
A dispersion relation for low-frequency collective modes in dusty plasmas is derived with allowance for attractive and repulsive forces arising between the dust grains due to dissipative fluxes of plasma particles onto the grain surfaces. It is shown that these fluxes give rise to dust attraction instabilities, which are similar to the gravitational instability. In the range of wave numbers corresponding to the stability domain, two types of dust sound waves arise, depending on whether the wavelengths of the collective modes are longer or shorter than the mean free path of the plasma particles (i.e., the distance they travel before they collide with dust grains). The dispersion relation derived is valid for any ratio between the wavelength of the perturbations and the mean free path and encompasses the entire range of intermediate wave numbers. The critical wave numbers that determine the threshold for the onset of attraction instability, which is similar to the Jeans instability, can, in particular, lie within this range. The thresholds for attraction instability and the instability growth rates are obtained numerically for a wide range of the plasma parameters (such as the ratio of the ion temperature to the electron temperature) that are of interest for present-day experiments with dust crystals, plasma etching, and space plasma studies. Computer simulation shows that, in the nonlinear stage, the attraction instability causes the dust cloud to collapse, which leads to the formation of dust plasma crystals. Our investigation makes it possible to trace the processes in the initial stage of dust crystallization. Results are obtained for hydrogen and silicon plasmas, which are most typical of laboratory experiments
Simultaneous chromatic dispersion, polarization-mode-dispersion and OSNR monitoring at 40Gbit/s.
Baker-Meflah, Lamia; Thomsen, Benn; Mitchell, John; Bayvel, Polina
2008-09-29
A novel method for independent and simultaneous monitoring of chromatic dispersion (CD), first-order PMD and OSNR in 40Gbit/s systems is proposed and demonstrated. This is performed using in-band tone monitoring of 5GHz, optically down-converted to a low intermediate-frequency (IF) of 10kHz. The measurement provides a large monitoring range with good accuracies for CD (4742+/-100ps/nm), differential group delay (DGD) (200+/-4ps) and OSNR (23+/-1dB), independently of the bit-rate. In addition, the use of electro-absorption modulators (EAM) for the simultaneous down-conversion of all channels and the use of low-speed detectors makes it cost effective for multi-channel operation.
Improvements in or relating to dispersions
International Nuclear Information System (INIS)
Woodhead, J.L.
1981-01-01
A process is described for the preparation of an aqueous dispersion of ceria which comprises forming a slurry of cerium IV hydroxide with water and an acid, the acid being capable of causing deaggregation of aggregated crystallites in the cerium IV hydroxide, heating the slurry for such a time and at such a temperature that the pH reaches a steady value, the quantity of acid in the slurry being such that the steady value of pH is below 5.4, thereby to produce a conditioned slurry, and admixing water with the conditioned slurry to produce an aqueous dispersion of ceria. (author)
Dispersion Relation for Skeletal Vibrations in Deuterated Polyethylene
Energy Technology Data Exchange (ETDEWEB)
Feldkamp, L. A.; Venkataraman, G.; King, J. S. [Department of Nuclear Engineering, University of Michigan, Ann Arbor, MI (United States)
1968-09-15
The low frequency vibrations in polyethylene have been studied previously, utilizing the incoherent scattering technique which yields an amplitude-weighted density of states. In the present work the dispersion relations have been obtained directly by observing the coherent scattering from a deuterated sample. This represents the first such measurement on a crystalline polymer. A target in which the molecular chain axes were approximately parallel was prepared by stretching polycrystalline material. The FWHM of the rocking curve for the (002) reflection was measured to be 9 Degree-Sign . Constant-Q and constant-E scans were made on the University of Michigan triple-axis spectrometer at room temperature to observe phonons propagating along the chain direction. The resulting dispersion curve for the v{sub 5} mode follows generally the calculated curve of Tasumi and Krimm with systematically lower frequencies. The maximum frequency of 1.36 x 10{sup 13} Hz agrees with the cut-off frequency determined previously from the incoherent scattering spectrum. (author)
Dispersal patterns of red foxes relative to population density
Allen, Stephen H.; Sargeant, Alan B.
1993-01-01
Factors affecting red fox (Vulpes vulpes) dispersal patterns are poorly understood but warranted investigation because of the role of dispersal in rebuilding depleted populations and transmission of diseases. We examined dispersal patterns of red foxes in North Dakota based on recoveries of 363 of 854 foxes tagged as pups and relative to fox density. Foxes were recovered up to 8.6 years after tagging; 79% were trapped or shot. Straight-line distances between tagging and recovery locations ranged from 0 to 302 km. Mean recovery distances increased with age and were greater for males than females, but longest individual recovery distances were by females. Dispersal distances were not related to population density for males (P = 0.36) or females (P = 0.96). The proportion of males recovered that dispersed was inversely related to population density (r = -0.94; n = 5; P = 0.02), but not the proportion of females (r = -0.49; n = 5; P = 0.40). Dispersal directions were not uniform for either males (P = 0.003) or females (P = 0.006); littermates tended to disperse in similar directions (P = 0.09). A 4-lane interstate highway altered dispersal directions (P = 0.001). Dispersal is a strong innate behavior of red foxes (especially males) that results in many individuals of both sexes traveling far from natal areas. Because dispersal distance was unaffected by fox density, populations can be rebuilt and diseases transmitted long distances regardless of fox abundance.
Phonon dispersion relations in monoatomic superlattices: a transfer matrix theory
International Nuclear Information System (INIS)
Albuquerque, E.L. de; Fulco, P.
1986-01-01
We present a lattice dynamical theory for monoatomic superlattices consisting of alternating layers of two different materials. Using a transfer matrix method we obtain explicit the equation for dispersion of the phonon's bulk modes, including the well known result in the long wave-length limit which can be obtained by elasticity theory. An illustation is shown and its features discussed. (Author) [pt
Dispersion relation of test waves in an electron beam plasma system
International Nuclear Information System (INIS)
Hayashi, N.; Tanaka, M.; Shinohara, S.; Kawai, Y.
1994-01-01
Test waves are propagated in an electron beam plasma system and the dispersion relation is measured. At the center of the experimental region a beam mode is excited. Near the chamber wall an electron plasma wave is excited and propagates from the chamber wall to the center of the experimental region. It is also found that observed unstable waves are standing wave which is formed by superposing the beam modes propagating in the opposite directions each other. (author). 6 refs, 6 figs
Dispersion relations and sum rules for natural optical activity
International Nuclear Information System (INIS)
Thomaz, M.T.; Nussenzveig, H.M.
1981-06-01
Dispersion relations and sum rules are derived for the complex rotatory power of an arbitrary linear (nonmagnetic) isotropic medium showing natural optical activity. Both previously known dispersion relations and sum rules as well as new ones are obtained. It is shown that the Rosenfeld-Condon dispersion formula is inconsistent with the expected asymptotic behavior at high frequencies. A new dispersion formula based on quantum eletro-dynamics removes this inconsistency; however, it still requires modification in the low-frequency limit. (Author) [pt
Femtosecond Mode-locked Fiber Laser at 1 μm Via Optical Microfiber Dispersion Management.
Wang, Lizhen; Xu, Peizhen; Li, Yuhang; Han, Jize; Guo, Xin; Cui, Yudong; Liu, Xueming; Tong, Limin
2018-03-16
Mode-locked Yb-doped fiber lasers around 1 μm are attractive for high power applications and low noise pulse train generation. Mode-locked fiber lasers working in soliton and stretched-pulse regime outperform others in terms of the laser noise characteristics, mechanical stability and easy maintenance. However, conventional optical fibers always show a normal group velocity dispersion around 1 μm, leading to the inconvenience for necessary dispersion management. Here we show that optical microfibers having a large anomalous dispersion around 1 μm can be integrated into mode-locked Yb-doped fiber lasers with ultralow insertion loss down to -0.06 dB, enabling convenient dispersion management of the laser cavity. Besides, optical microfibers could also be adopted to spectrally broaden and to dechirp the ultrashort pulses outside the laser cavity, giving rise to a pulse duration of about 110 fs. We believe that this demonstration may facilitate all-fiber format high-performance ultrashort pulse generation at 1 μm and may find applications in precision measurements, large-scale facility synchronization and evanescent-field-based optical sensing.
Dispersal from deep ocean sources: physical and related scientific processes
International Nuclear Information System (INIS)
Robinson, A.R.; Kupferman, S.L.
1985-02-01
This report presents the results of the workshop ''Dispersal from Deep Ocean Sources: Physical and Related Scientific Processes,'' together with subsequent developments and syntheses of the material discussed there. The project was undertaken to develop usable predictive descriptions of dispersal from deep oceanic sources. Relatively simple theoretical models embodying modern ocean physics were applied, and observational and experimental data bases were exploited. All known physical processes relevant to the dispersal of passive, conservative tracers were discussed, and contact points for inclusion of nonconservative processes (biological and chemical) were identified. Numerical estimates of the amplitude, space, and time scales of dispersion were made for various mechanisms that control the evolution of the dispersal as the material spreads from a bottom point source to small-, meso-, and world-ocean scales. Recommendations for additional work are given. The volume is presented as a handbook of dispersion processes. It is intended to be updated as new results become available
Dispersion relation for Bernstein waves using a new transformation for the modified Bessel function
International Nuclear Information System (INIS)
Sato, Masumi
1985-01-01
Aitken's or Shanks' transformation of the exponent-modified Bessel function produces better approximations. Dispersion relations for the hybrid and Bernstein waves using these provide better thermal and parallel wavenumber corrections. They also predict more closely the evolution and mode-conversion of these waves. (author)
Analytical Approach to Polarization Mode Dispersion in Linearly Spun Fiber with Birefringence
Directory of Open Access Journals (Sweden)
Vinod K. Mishra
2016-01-01
Full Text Available The behavior of Polarization Mode Dispersion (PMD in spun optical fiber is a topic of great interest in optical networking. Earlier work in this area has focused more on approximate or numerical solutions. In this paper we present analytical results for PMD in spun fibers with triangular spin profile function. It is found that in some parameter ranges the analytical results differ from the approximations.
Factoring the dispersion relation in the presence of Lorentz violation
International Nuclear Information System (INIS)
Colladay, Don; McDonald, Patrick; Mullins, David
2010-01-01
We produce an explicit formula for the dispersion relation for the Dirac equation in the standard model extension in the presence of Lorentz violation. Our expression is obtained using novel techniques which exploit the algebra of quaternions. The dispersion relation is found to conveniently factor in two special cases that each involve a mutually exclusive set of nonvanishing Lorentz-violating parameters. This suggests that a useful approach to studies of Lorentz-violating models is to split the parameter space into two separate pieces, each of which yields a simple, tractable dispersion relation that can be used for analysis.
Role of third-order dispersion in chirped Airy pulse propagation in single-mode fibers
Cai, Wangyang; Wang, Lei; Wen, Shuangchun
2018-04-01
The dynamic propagation of the initial chirped Airy pulse in single-mode fibers is studied numerically, special attention being paid to the role of the third-order dispersion (TOD). It is shown that for the positive TOD, the Airy pulse experiences inversion irrespective of the sign of initial chirp. The role of TOD in the dynamic propagation of the initial chirped Airy pulse depends on the combined sign of the group-velocity dispersion (GVD) and the initial chirp. If the GVD and chirp have the opposite signs, the chirped Airy pulse compresses first and passes through a breakdown area, then reconstructs a new Airy pattern with opposite acceleration, with the breakdown area becoming small and the main peak of the new Airy pattern becoming asymmetric with an oscillatory structure due to the positive TOD. If the GVD and chirp have the same signs, the finite-energy Airy pulse compresses to a focal point and then inverses its acceleration, in the case of positive TOD, the distance to the focal point becoming smaller. At zero-dispersion point, the finite-energy Airy pulse inverses to the opposite acceleration at a focal point, with the tight-focusing effect being reduced by initial chirp. Under the effect of negative TOD, the initial chirped Airy pulse disperses and the lobes split. In addition, in the anomalous dispersion region, for strong nonlinearity, the initial chirped Airy pulse splits and enters a soliton shedding regime.
Stokes-space analysis of modal dispersion in fibers with multiple mode transmission.
Antonelli, Cristian; Mecozzi, Antonio; Shtaif, Mark; Winzer, Peter J
2012-05-21
Modal dispersion (MD) in a multimode fiber may be considered as a generalized form of polarization mode dispersion (PMD) in single mode fibers. Using this analogy, we extend the formalism developed for PMD to characterize MD in fibers with multiple spatial modes. We introduce a MD vector defined in a D-dimensional extended Stokes space whose square length is the sum of the square group delays of the generalized principal states. For strong mode coupling, the MD vector undertakes a D-dimensional isotropic random walk, so that the distribution of its length is a chi distribution with D degrees of freedom. We also characterize the largest differential group delay, that is the difference between the delays of the fastest and the slowest principal states, and show that it too is very well approximated by a chi distribution, although in general with a smaller number of degrees of freedom. Finally, we study the spectral properties of MD in terms of the frequency autocorrelation functions of the MD vector, of the square modulus of the MD vector, and of the largest differential group delay. The analytical results are supported by extensive numerical simulations.
Redshift and lateshift from homogeneous and isotropic modified dispersion relations
Pfeifer, Christian
2018-05-01
Observables which would indicate a modified vacuum dispersion relations, possibly caused by quantum gravity effects, are a four momentum dependence of the cosmological redshift and the existence of a so called lateshift effect for massless or very light particles. Existence or non-existence of the latter is currently analyzed on the basis of the available observational data from gamma-ray bursts and compared to predictions of specific modified dispersion relation models. We consider the most general perturbation of the general relativistic dispersion relation of freely falling particles on homogeneous and isotropic spacetimes and derive the red- and lateshift to first order in the perturbation. Our result generalizes the existing formulae in the literature and we find that there exist modified dispersion relations causing both, one or none of the two effects to first order.
A new numerical method to solve the dispersion relation in multispecies plasma
International Nuclear Information System (INIS)
Cereceda, C.; Puerta, J.
2000-01-01
In this paper a new accurate and fast method for solving the linear dispersion relation for multispecies plasma is introduced. The method uses a four poles fractional approximation for the Z dispersion function, transforming the dispersion relation into a polynomial form. Time and space growth rates are then calculated. Calculations for a single beam - plasma are carried out being in good agreement with several authors. This method is very effective to simplify the calculation of growth rates in multi-ion plasmas. For multispecies plasmas several new modes of propagation arise. For two ion beam - plasma system, two slow modes can propagate, both which are unstable. Two maxima in the growth rates corresponding to each of these modes can be excited. The instability of one of the slow modes is fed by the energy of the light ion beam and the other one is fed by heavy beam ions. Each one of these two maxima is increased when the concentration of the corresponding species increases. But even for a small concentration of the light beam, the growth rate of the mode fed by it is the largest one, because in the single ion beam-plasma system the lighter ion yields the largest growth rate. (orig.)
Wave dispersion relation of two-dimensional plasma crystals in a magnetic field
International Nuclear Information System (INIS)
Uchida, G.; Konopka, U.; Morfill, G.
2004-01-01
The wave dispersion relation in a two-dimensional strongly coupled plasma crystal is studied by theoretical analysis and molecular dynamics simulation taking into account a constant magnetic field parallel to the crystal normal. The expression for the wave dispersion relation clearly shows that high-frequency and low-frequency branches exist as a result of the coupling of longitudinal and transverse modes due to the Lorenz force acting on the dust particles. The high-frequency and the low-frequency branches are found to belong to right-hand and left-hand polarized waves, respectively
Larson-Johnson, Kathryn
2016-01-01
As a primary determinant of spatial structure in angiosperm populations, fruit dispersal may impact large-scale ecological and evolutionary processes. Essential to understanding these mechanisms is an accurate reconstruction of dispersal mode over the entire history of an angiosperm lineage. A total-evidence phylogeny is presented for most fossil fruit and all extant genera in Fagales over its c. 95 million yr history. This phylogeny - the largest of its kind to include plant fossils - was used to reconstruct an evolutionary history directly informed by fossil morphologies and to assess relationships among dispersal mode, biogeographic range size, and diversification rate. Reconstructions indicate four transitions to wind dispersal and seven to biotic dispersal, with the phylogenetic integration of fossils crucial to understanding these patterns. Complexity further increased when more specialized behaviors were considered, with fluttering, gliding, autorotating, and scatter-hoarding evolving multiple times across the order. Preliminary biogeographic analyses suggest larger range sizes in biotically dispersed lineages, especially when pollination mode was held constant. Biotically dispersed lineages had significantly higher diversification rates than abiotically dispersed lineages, although transitions in dispersal mode alone cannot explain all detected diversification rate shifts across Fagales. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.
FM-AM Conversion Induced by Polarization Mode Dispersion in Fiber Systems
International Nuclear Information System (INIS)
Xiao-Dong, Huang; Sheng-Zhi, Zhao; Jian-Jun, Wang; Ming-Zhong, Li; Dang-Peng, Xu; Hong-Huan, Lin; Rui, Zhang; Ying, Deng; Xiao-Min, Zhang
2010-01-01
The conversion of the frequency modulated pulse induced from frequency modulation (FM) to amplitude modulation (AM) by the polarization mode dispersion (PMD) is theoretically and experimentally investigated. When there is no polarizer at the output end of a fiber system, the amplitude modulation depth is stable by 8%. Random amplitude modulation is observed when a polarizer is placed at the output end of the fiber system. The observed minimum and maximum modulation depths in our experiment are 5% and 80%, respectively. Simulation results show that the amplitude modulation is stable by 4% induced mainly by group velocity dispersion (GVD) when there is no polarizer, and the amplitude modulation depth displays the random variation character induced by the GVD and PMD. Lastly, a new fiber system scheme is proposed and little amplitude modulation is observed at the top of the output pulse
The influence of gamma radiation on polarization mode dispersion of fibers applied in communications
Directory of Open Access Journals (Sweden)
Sekulić Rade S.
2012-01-01
Full Text Available The fiber optics technology is constantly being developed, and is becoming an essential component of contemporary communications, medicine and industry. Fibers, their connections and system components play a major role in optical signal transmission, telecommunications, power transmission, and sensing processes using fiber technology. The two main light propagation characteristics of an optical fiber are attenuation and dispersion. The possibility of controling these parameters is of utmost importance for obtaining the requested transmission quality. This paper reports on an investigation to determine the influence of gamma radiation of 60Co on the variation of optical fiber propagation parameters, such as polarization mode dispersion. In addition, it also considers chosen topics in the field of fiber optics technology.
International Nuclear Information System (INIS)
Liu Xueming
2011-01-01
The soliton formation and evolution are numerically and experimentally investigated in passively-mode-locked lasers where pulses encounter ultralong anomalous-dispersion fibers. The pulse formation and evolution in lasers are determined by two balances, namely, nonlinearity and anomalous-dispersion balance and intracavity filtering and self-amplitude modulation balance. It is numerically found that a higher-energy soliton can be split into identical lower-energy multisolitons with exactly the same physical properties. Simulation results show that the separation of neighboring solitons is variational in the temporal domain. The temporal and spectral characteristics of solitons have large variations throughout the laser cavity, qualitatively distinct from the steady state of conventional solitons. The experimental observations confirm the theoretical predictions.
Effect of the internet commerce on dispersal modes of invasive alien species.
Lenda, Magdalena; Skórka, Piotr; Knops, Johannes M H; Moroń, Dawid; Sutherland, William J; Kuszewska, Karolina; Woyciechowski, Michał
2014-01-01
The spread of invasive alien plants has considerable environmental and economic consequences, and is one of the most challenging ecological problems. The spread of invasive alien plant species depends largely on long-distance dispersal, which is typically linked with human activity. The increasing domination of the internet will have impacts upon almost all components of our lives, including potential consequences for the spread of invasive species. To determine whether the rise of Internet commerce has any consequences for the spread of invasive alien plant species, we studied the sale of thirteen of some of the most harmful Europe invasive alien plant species sold as decorative plants from twenty-eight large, well known gardening shops in Poland that sold both via the Internet and through traditional customer sales. We also analyzed temporal changes in the number of invasive plants sold in the largest Polish internet auction portal. When sold through the Internet invasive alien plant species were transported considerably longer distances than for traditional sales. For internet sales, seeds of invasive alien plant species were transported further than were live plants saplings; this was not the case for traditional sales. Also, with e-commerce the shape of distance distribution were flattened with low skewness comparing with traditional sale where the distributions were peaked and right-skewed. Thus, e-commerce created novel modes of long-distance dispersal, while traditional sale resembled more natural dispersal modes. Moreover, analysis of sale in the biggest Polish internet auction portal showed that the number of alien specimens sold via the internet has increased markedly over recent years. Therefore internet commerce is likely to increase the rate at which ecological communities become homogenized and increase spread of invasive species by increasing the rate of long distance dispersal.
Effect of the internet commerce on dispersal modes of invasive alien species.
Directory of Open Access Journals (Sweden)
Magdalena Lenda
Full Text Available The spread of invasive alien plants has considerable environmental and economic consequences, and is one of the most challenging ecological problems. The spread of invasive alien plant species depends largely on long-distance dispersal, which is typically linked with human activity. The increasing domination of the internet will have impacts upon almost all components of our lives, including potential consequences for the spread of invasive species. To determine whether the rise of Internet commerce has any consequences for the spread of invasive alien plant species, we studied the sale of thirteen of some of the most harmful Europe invasive alien plant species sold as decorative plants from twenty-eight large, well known gardening shops in Poland that sold both via the Internet and through traditional customer sales. We also analyzed temporal changes in the number of invasive plants sold in the largest Polish internet auction portal. When sold through the Internet invasive alien plant species were transported considerably longer distances than for traditional sales. For internet sales, seeds of invasive alien plant species were transported further than were live plants saplings; this was not the case for traditional sales. Also, with e-commerce the shape of distance distribution were flattened with low skewness comparing with traditional sale where the distributions were peaked and right-skewed. Thus, e-commerce created novel modes of long-distance dispersal, while traditional sale resembled more natural dispersal modes. Moreover, analysis of sale in the biggest Polish internet auction portal showed that the number of alien specimens sold via the internet has increased markedly over recent years. Therefore internet commerce is likely to increase the rate at which ecological communities become homogenized and increase spread of invasive species by increasing the rate of long distance dispersal.
Effect of the Internet Commerce on Dispersal Modes of Invasive Alien Species
Lenda, Magdalena; Skórka, Piotr; Knops, Johannes M. H.; Moroń, Dawid; Sutherland, William J.; Kuszewska, Karolina; Woyciechowski, Michał
2014-01-01
The spread of invasive alien plants has considerable environmental and economic consequences, and is one of the most challenging ecological problems. The spread of invasive alien plant species depends largely on long-distance dispersal, which is typically linked with human activity. The increasing domination of the internet will have impacts upon almost all components of our lives, including potential consequences for the spread of invasive species. To determine whether the rise of Internet commerce has any consequences for the spread of invasive alien plant species, we studied the sale of thirteen of some of the most harmful Europe invasive alien plant species sold as decorative plants from twenty-eight large, well known gardening shops in Poland that sold both via the Internet and through traditional customer sales. We also analyzed temporal changes in the number of invasive plants sold in the largest Polish internet auction portal. When sold through the Internet invasive alien plant species were transported considerably longer distances than for traditional sales. For internet sales, seeds of invasive alien plant species were transported further than were live plants saplings; this was not the case for traditional sales. Also, with e-commerce the shape of distance distribution were flattened with low skewness comparing with traditional sale where the distributions were peaked and right-skewed. Thus, e-commerce created novel modes of long-distance dispersal, while traditional sale resembled more natural dispersal modes. Moreover, analysis of sale in the biggest Polish internet auction portal showed that the number of alien specimens sold via the internet has increased markedly over recent years. Therefore internet commerce is likely to increase the rate at which ecological communities become homogenized and increase spread of invasive species by increasing the rate of long distance dispersal. PMID:24932498
Dispersive-cavity actively mode-locked fiber laser for stable radio frequency delivery
International Nuclear Information System (INIS)
Dai, Yitang; Wang, Ruixin; Yin, Feifei; Xu, Kun; Li, Jianqiang; Lin, Jintong
2013-01-01
We report a novel technique for highly stable transfer of a radio frequency (RF) comb over long optical fiber link, which is highly dispersive and is a part of an actively mode-locked fiber laser. Phase fluctuation along the fiber link, which is mainly induced by physical vibration and temperature fluctuations, is automatically compensated by the self-adapted wavelength shifting. Without phase-locking loop or any tunable parts, stable radio frequency is transferred over a 2-km fiber link, with a time jitter suppression ratio larger than 110. (letter)
Planck-scale-modified dispersion relations in FRW spacetime
Rosati, Giacomo; Amelino-Camelia, Giovanni; Marcianò, Antonino; Matassa, Marco
2015-12-01
In recent years, Planck-scale modifications of the dispersion relation have been attracting increasing interest also from the viewpoint of possible applications in astrophysics and cosmology, where spacetime curvature cannot be neglected. Nonetheless, the interplay between Planck-scale effects and spacetime curvature is still poorly understood, particularly in cases where curvature is not constant. These challenges have been so far postponed by relying on an ansatz, first introduced by Jacob and Piran. We propose here a general strategy of analysis of the effects of modifications of the dispersion relation in Friedmann-Robertson-Walker spacetimes, applicable both to cases where the relativistic equivalence of frames is spoiled ("preferred-frame scenarios") and to the alternative possibility of "DSR-relativistic theories," theories that are fully relativistic but with relativistic laws deformed so that the modified dispersion relation is observer independent. We show that the Jacob-Piran ansatz implicitly assumes that spacetime translations are not affected by the Planck scale, while under rather general conditions, the same Planck-scale quantum-spacetime structures producing modifications of the dispersion relation also affect translations. Through the explicit analysis of one of the effects produced by modifications of the dispersion relation, an effect amounting to Planck-scale corrections to travel times, we show that our concerns are not merely conceptual but rather can have significant quantitative implications.
Dispersion relations for η '→ η π π
Isken, Tobias; Kubis, Bastian; Schneider, Sebastian P.; Stoffer, Peter
2017-07-01
We present a dispersive analysis of the decay amplitude for η '→ η π π that is based on the fundamental principles of analyticity and unitarity. In this framework, final-state interactions are fully taken into account. Our dispersive representation relies only on input for the {π π } and {π }η scattering phase shifts. Isospin symmetry allows us to describe both the charged and neutral decay channel in terms of the same function. The dispersion relation contains subtraction constants that cannot be fixed by unitarity. We determine these parameters by a fit to Dalitz-plot data from the VES and BES-III experiments. We study the prediction of a low-energy theorem and compare the dispersive fit to variants of chiral perturbation theory.
From field theory to phenomenology: the history of dispersion relations
International Nuclear Information System (INIS)
Pickering, A.
1989-01-01
The authors chart the history of quantum field theory (QFT) in the 1950s with reference to the ideas of dispersion relations. QFT failed to explain strong interaction physics and so was discarded. Connections are drawn between a central group of particle theorists working on applying Kramers-Kronig light scattering relations to high energy particle scattering and the way physics developed. The concepts of single and double dispersion relations and Regge poles, when connected with the large quantity of empirical data from the large particle accelerators of the 1950s, could not be embodied within QFT, which then fell into decline. (UK)
Source-receptor matrix calculation with a Lagrangian particle dispersion model in backward mode
Directory of Open Access Journals (Sweden)
P. Seibert
2004-01-01
Full Text Available The possibility to calculate linear-source receptor relationships for the transport of atmospheric trace substances with a Lagrangian particle dispersion model (LPDM running in backward mode is shown and presented with many tests and examples. This mode requires only minor modifications of the forward LPDM. The derivation includes the action of sources and of any first-order processes (transformation with prescribed rates, dry and wet deposition, radioactive decay, etc.. The backward mode is computationally advantageous if the number of receptors is less than the number of sources considered. The combination of an LPDM with the backward (adjoint methodology is especially attractive for the application to point measurements, which can be handled without artificial numerical diffusion. Practical hints are provided for source-receptor calculations with different settings, both in forward and backward mode. The equivalence of forward and backward calculations is shown in simple tests for release and sampling of particles, pure wet deposition, pure convective redistribution and realistic transport over a short distance. Furthermore, an application example explaining measurements of Cs-137 in Stockholm as transport from areas contaminated heavily in the Chernobyl disaster is included.
Relativistic energy-dispersion relations of 2D rectangular lattices
Ata, Engin; Demirhan, Doğan; Büyükkılıç, Fevzi
2017-04-01
An exactly solvable relativistic approach based on inseparable periodic well potentials is developed to obtain energy-dispersion relations of spin states of a single-electron in two-dimensional (2D) rectangular lattices. Commutation of axes transfer matrices is exploited to find energy dependencies of the wave vector components. From the trace of the lattice transfer matrix, energy-dispersion relations of conductance and valence states are obtained in transcendental form. Graphical solutions of relativistic and nonrelativistic transcendental energy-dispersion relations are plotted to compare how lattice parameters V0, core and interstitial size of the rectangular lattice affects to the energy-band structures in a situation core and interstitial diagonals are of equal slope.
Optical fibers with low nonlinearity and low polarization-mode dispersion for terabit communications
Baghdadi, J. A.; Safaai-Jazi, A.; Hattori, H. T.
2001-07-01
Refractive-index nonlinearities have negligible effect on the performance of short-haul fiber-optic communication links utilizing electronic repeaters. However, in long links, nonlinearities can cause severe signal degradations. To mitigate nonlinear effects, a new generation of fibers, referred to as large effective-area fibers, have been introduced in recent years. This paper reviews the latest research and development work on these fibers conducted by several research groups around the world. Attention is focused on a class of large effective-area fibers that are based on a depressed-core multiple-cladding design. Another important issue in long-haul and high capacity fiber optic systems is the polarization-mode dispersion (PMD) which has been recognized as a serious limiting factor. In this paper, an improved fiber design is proposed which, in addition to providing large effective-area and low bending loss, eliminates PMD due to elliptical deformation in the single-mode wavelength region. Furthermore, this design is allowed to provide a small chromatic dispersion about few ps/ nm km , in order to overcome four-wave mixing effects.
Geng, Y.; Li, L.; Shu, C. J.; Wang, Y. F.; Tang, D. Y.; Zhao, L. M.
2018-06-01
Broadband features of passively harmonic mode locking (HML) in dispersion-managed erbium-doped all-fiber lasers are explored. The bandwidth of HML state is generally narrower than that of fundamental mode locking before pulse breaking occurs. There exists a broadest bandwidth versus the order of HML. HML state with bandwidth up to 61.5 nm is obtained.
Uranus, H.P.; Hoekstra, Hugo; van Groesen, Embrecht W.C.
2008-01-01
Using a vectorial finite element mode solver developed earlier, we studied a hole-assisted multi-ring fiber. We report the role of the hole’s geometrical parameters in tuning the waveguide dispersion and the single/multi-modeness of the particular fiber. By correctly selecting the hole’s size and
An exact linear dispersion relation for CRM instability
International Nuclear Information System (INIS)
Choyal, Y; Minami, K
2011-01-01
An exact self-consistent linear dispersion relation of a large orbit electron beam including two principles of cyclotron emission with oscillation frequencies above and below the relativistic electron frequency is derived and analyzed numerically for the first time in the literature. The two principles are cyclotron resonance maser (CRM) instability and Cherenkov instability in the azimuthal direction. Self-consistency in the formulation and inclusion of proper boundary conditions have removed the unphysical instability existing for infinitely large k z observed in conventional dispersion relations of CRM instability.
Langmuir wave dispersion relation in non-Maxwellian plasmas
International Nuclear Information System (INIS)
Ouazene, M.; Annou, R.
2010-01-01
The Langmuir wave dispersion relation is derived in partially ionized plasmas, where free electrons are confined to move in a nearest neighbor ions' potential well. The equilibrium velocity distribution function experiences then, a departure from Maxwell distribution function. The effect of the non-Maxwellian character of the distribution function on the Langmuir phase and group velocities as well as the phase matching conditions and the nonlinear growth rate of decay instability is investigated. The proposed Langmuir wave dispersion relation is relevant to dense and cryogenic plasmas.
Energy Technology Data Exchange (ETDEWEB)
Pontikis, V., E-mail: Vassilis.Pontikis@cea.f [Commissariat a l' Energie Atomique, IRAMIS, Laboratoire des Solides Irradies, CNRS UMR 7642, Ecole Polytechnique, 91191 Gif sur Yvette Cedex (France); Gorse, D. [Commissariat a l' Energie Atomique, IRAMIS, Laboratoire des Solides Irradies, CNRS UMR 7642, Ecole Polytechnique, 91191 Gif sur Yvette Cedex (France)
2009-10-01
A statistical model is proposed to account for the influence of the dispersion of the microstructure on the ductile-to-brittle transition in body centered cubic (bcc) metals and their alloys. In this model, the dispersion of the microstructure is expressed via a normal distribution of transition temperatures whereas a simple relation exists between the values of absorbed, lower and upper shelf energies, the ductile area fraction and the distribution parameters. It is shown that via an appropriate renormalization of energies and temperatures, experimental data for different materials and ageing conditions align all together on a master curve, guaranteeing thereby the effectiveness of the proposed statistical description.
International Nuclear Information System (INIS)
Pontikis, V.; Gorse, D.
2009-01-01
A statistical model is proposed to account for the influence of the dispersion of the microstructure on the ductile-to-brittle transition in body centered cubic (bcc) metals and their alloys. In this model, the dispersion of the microstructure is expressed via a normal distribution of transition temperatures whereas a simple relation exists between the values of absorbed, lower and upper shelf energies, the ductile area fraction and the distribution parameters. It is shown that via an appropriate renormalization of energies and temperatures, experimental data for different materials and ageing conditions align all together on a master curve, guaranteeing thereby the effectiveness of the proposed statistical description.
Directory of Open Access Journals (Sweden)
Norihiko Nishizawa
2015-07-01
Full Text Available We investigated the dynamics of a dispersion-managed, passively mode-locked, ultrashort-pulse, Er-doped fiber laser using a single-wall carbon nanotube (SWNT device. A numerical model was constructed for analysis of the SWNT fiber laser. The initial process of passive mode-locking, the characteristics of the output pulse, and the dynamics inside the cavity were investigated numerically for soliton, dissipative-soliton, and stretched-pulse mode-locking conditions. The dependencies on the total dispersion and recovery time of the SWNTs were also examined. Numerical results showed similar behavior to experimental results.
Getting super-excited with modified dispersion relations
Energy Technology Data Exchange (ETDEWEB)
Ashoorioon, Amjad; Casadio, Roberto [INFN—Sezione di Bologna, viale B. Pichat 6/2, I-40127 Bologna (Italy); Geshnizjani, Ghazal; Kim, Hyung J., E-mail: amjad.ashoorioon@bo.infn.it, E-mail: roberto.casadio@bo.infn.it, E-mail: ggeshniz@uwaterloo.ca, E-mail: h268kim@uwaterloo.ca [Department of Applied Mathematics, University of Waterloo Waterloo, Ontario, N2L 3G1 (Canada)
2017-09-01
We demonstrate that in some regions of parameter space, modified dispersion relations can lead to highly populated excited states, which we dub as 'super-excited' states. In order to prepare such super-excited states, we invoke dispersion relations that have negative slope in an interim sub-horizon phase at high momenta. This behaviour of quantum fluctuations can lead to large corrections relative to the Bunch-Davies power spectrum, which mimics highly excited initial conditions. We identify the Bogolyubov coefficients that can yield these power spectra. In the course of this computation, we also point out the shortcomings of the gluing method for evaluating the power spectrum and the Bogolyubov coefficients. As we discuss, there are other regions of parameter space, where the power spectrum does not get modified. Therefore, modified dispersion relations can also lead to so-called 'calm excited states'. We conclude by commenting on the possibility of obtaining these modified dispersion relations within the Effective Field Theory of Inflation.
Xu, Yanlong
2015-08-01
The coupled mode theory with coupling of diffraction modes and waveguide modes is usually used on the calculations of transmission and reflection coefficients for electromagnetic waves traveling through periodic sub-wavelength structures. In this paper, I extend this method to derive analytical solutions of high-order dispersion relations for shear horizontal (SH) wave propagation in elastic plates with periodic stubs. In the long wavelength regime, the explicit expression is obtained by this theory and derived specially by employing an effective medium. This indicates that the periodical stubs are equivalent to an effective homogenous layer in the long wavelength. Notably, in the short wavelength regime, high-order diffraction modes in the plate and high-order waveguide modes in the stubs are considered with modes coupling to compute the band structures. Numerical results of the coupled mode theory fit pretty well with the results of the finite element method (FEM). In addition, the band structures\\' evolution with the height of the stubs and the thickness of the plate shows clearly that the method can predict well the Bragg band gaps, locally resonant band gaps and high-order symmetric and anti-symmetric thickness-twist modes for the periodically structured plates. © 2015 Elsevier B.V.
The dispersion relation of a gravitating spiral system
International Nuclear Information System (INIS)
Evangelidis, E.
1977-01-01
The dispersion relation has been found for a galaxy, without the assumption that the centrifugal force is balanced by the gravitational force. It has been shown that such a system (1) can be gravitationally unstable under appropriate conditions, and (2) that there is no resonance at ω=2Ω (Ω=angular velocity of the Galaxy). (Auth.)
Dispersion relations in real and virtual Compton scattering
International Nuclear Information System (INIS)
Drechsel, D.; Pasquini, B.; Vanderhaeghen, M.
2003-01-01
A unified presentation is given on the use of dispersion relations in the real and virtual Compton scattering processes off the nucleon. The way in which dispersion relations for Compton scattering amplitudes establish connections between low energy nucleon structure quantities, such as polarizabilities or anomalous magnetic moments, and the nucleon excitation spectrum is reviewed. We discuss various sum rules for forward real and virtual Compton scattering, such as the Gerasimov-Drell-Hearn sum rule and its generalizations, the Burkhardt-Cottingham sum rule, as well as sum rules for forward nucleon polarizabilities, and review their experimental status. Subsequently, we address the general case of real Compton scattering (RCS). Various types of dispersion relations for RCS are presented as tools for extracting nucleon polarizabilities from the RCS data. The information on nucleon polarizabilities gained in this way is reviewed and the nucleon structure information encoded in these quantities is discussed. The dispersion relation formalism is then extended to virtual Compton scattering (VCS). The information on generalized nucleon polarizabilities extracted from recent VCS experiments is described, along with its interpretation in nucleon structure models. As a summary, the physics content of the existing data is discussed and some perspectives for future theoretical and experimental activities in this field are presented
Quasi-pions with temperature dependent dispersion relation
International Nuclear Information System (INIS)
Gorenstein, M.I.
1995-01-01
We construct the procedure to calculate thermodynamical functions for a system of quasi-particles with temperature dependent dispersion relation. Two models for the hot quasi-pion system are considered to illustrate the importance of thermodynamical self consistency requirements. 8 refs., 9 figs
Mord studies in IR region by new dispersion relation
International Nuclear Information System (INIS)
Murthy, V.R.; Kumar, R. Jeevan
1994-01-01
This is the continuation of the series reporting MORD studies to typical problem in Chemistry and Polymer Science. In our earlier papers the MORDsup1.2 studied only in visible region. In this present investigation we extended the application of the New Dispersion Relation in IR region to determine the MORD and tested to some simple systems
Li, Yutian; Zhu, Jianxin
2015-05-04
In this paper we consider the problem of computing the eigen-modes for the varying refractive-index profile in an open waveguide. We first approximate the refractive-index by a piecewise polynomial of degree two, and the corresponding Sturm-Liouville problem (eigenvalue problem) of the Helmholtz operator in each layer can be solved analytically by the Kummer functions. Then, analytical approximate dispersion equations are established for both TE and TM cases. Furthermore, the approximate dispersion equations converge fast to the exact ones for the continuous refractive-index function as the maximum value of the subinterval sizes tends to zero. Suitable numerical methods, such as Müller's method or the chord secant method, may be applied to the dispersion relations to compute the eigenmodes. Numerical simulations show that our method is very practical and efficient for computing eigenmodes.
Ravenna, Matteo; Lebedev, Sergei; Celli, Nicolas
2017-04-01
We develop a Markov Chain Monte Carlo inversion of fundamental and higher mode phase-velocity curves for radially and azimuthally anisotropic structure of the crust and upper mantle. In the inversions of Rayleigh- and Love-wave dispersion curves for radially anisotropic structure, we obtain probabilistic 1D radially anisotropic shear-velocity profiles of the isotropic average Vs and anisotropy (or Vsv and Vsh) as functions of depth. In the inversions for azimuthal anisotropy, Rayleigh-wave dispersion curves at different azimuths are inverted for the vertically polarized shear-velocity structure (Vsv) and the 2-phi component of azimuthal anisotropy. The strength and originality of the method is in its fully non-linear approach. Each model realization is computed using exact forward calculations. The uncertainty of the models is a part of the output. In the inversions for azimuthal anisotropy, in particular, the computation of the forward problem is performed separately at different azimuths, with no linear approximations on the relation of the Earth's elastic parameters to surface wave phase velocities. The computations are performed in parallel in order reduce the computing time. We compare inversions of the fundamental mode phase-velocity curves alone with inversions that also include overtones. The addition of higher modes enhances the resolving power of the anisotropic structure of the deep upper mantle. We apply the inversion method to phase-velocity curves in a few regions, including the Hangai dome region in Mongolia. Our models provide constraints on the Moho depth, the Lithosphere-Asthenosphere Boundary, and the alignment of the anisotropic fabric and the direction of current and past flow, from the crust down to the deep asthenosphere.
Soliman, George; Yevick, David; Jessop, Paul
2014-09-01
This paper demonstrates that numerous calculations involving polarization transformations can be condensed by employing suitable geometric algebra formalism. For example, to describe polarization mode dispersion and polarization-dependent loss, both the material birefringence and differential loss enter as bivectors and can be combined into a single symmetric quantity. Their frequency and distance evolution, as well as that of the Stokes vector through an optical system, can then each be expressed as a single compact expression, in contrast to the corresponding Mueller matrix formulations. The intrinsic advantage of the geometric algebra framework is further demonstrated by presenting a simplified derivation of generalized Stokes parameters that include the electric field phase. This procedure simultaneously establishes the tensor transformation properties of these parameters.
International Nuclear Information System (INIS)
Umapathy, S.; Mallick, B.; Lakshmanna, A.
2010-01-01
Ultrafast Raman loss spectroscopy (URLS) enables one to obtain the vibrational structural information of molecular systems including fluorescent materials. URLS, a nonlinear process analog to stimulated Raman gain, involves a narrow bandwidth picosecond Raman pump pulse and a femtosecond broadband white light continuum. Under nonresonant condition, the Raman response appears as a negative (loss) signal, whereas, on resonance with the electronic transition the line shape changes from a negative to a positive through a dispersive form. The intensities observed and thus, the Franck-Condon activity (coordinate dependent), are sensitive to the wavelength of the white light corresponding to a particular Raman frequency with respect to the Raman pump pulse wavelength, i.e., there is a mode-dependent response in URLS.
International Nuclear Information System (INIS)
Benova, E.; Ghanashev, I.; Zhelyazkov, I.
1992-01-01
The modelling of isotropic plasma columns sustained by travelling electromagnetic waves in the dipolar mode (angular dependence exp imφ, m=±1) shows that the m=±1 modes have identical dispersion characteristics. In the presence of an external static magnetic field, however, the modes behave rather differently. This observation arose in studying the axial structures of magnetized plasma columns surrounded by vacuum and produced by travelling electromagnetic waves in the dipolar modes. We examine the propagation of electromagnetic waves along a homogeneous cold plasma column of radius R and electron number density n immersed in an axial constant magnetic field. (author) 3 refs., 3 figs
Dispersion Relations for Electroweak Observables in Composite Higgs Models
Contino, Roberto
2015-12-14
We derive dispersion relations for the electroweak oblique observables measured at LEP in the context of $SO(5)/SO(4)$ composite Higgs models. It is shown how these relations can be used and must be modified when modeling the spectral functions through a low-energy effective description of the strong dynamics. The dispersion relation for the parameter $\\epsilon_3$ is then used to estimate the contribution from spin-1 resonances at the 1-loop level. Finally, it is shown that the sign of the contribution to the $\\hat S$ parameter from the lowest-lying spin-1 states is not necessarily positive definite, but depends on the energy scale at which the asymptotic behavior of current correlators is attained.
Age--velocity-dispersion relation in the solar neighborhood
International Nuclear Information System (INIS)
Carlberg, R.G.; Dawson, P.C.; Hsu, T.; VandenBerg, D.A.
1985-01-01
The age--velocity-dispersion relation for stars in the solar neighborhood is examined as an indicator of the dominant acceleration mechanism of the stars and the formation history of the local disk. Twarog's sample of F stars, for which ages and photometric distances can be determined, is combined with astrometric data to obtain tangential velocities of a set of stars with a large age range. The resulting age--velocity-dispersion relation rises fairly steeply for stars less than 6 Gyr old, thereafter becoming nearly constant with age. These data are consistent with a simple model in which no local disk is initially present, following which stars are born at a constant rate in time and heated by transient spiral waves. The corresponding age-metallicity relation complements this dynamical measure of the formation history of the disk. The use of new stellar models and a revised metallicity calibration leads to quantitative differences from previous work
Apostolov, S. S.; Makarov, N. M.; Yampol'skii, V. A.
2018-01-01
We study theoretically the optic transmission through a slab of layered superconductor separated from two dielectric leads by spatial gaps. Based on the transfer matrix formalism along with the Josephson plasma electrodynamic approach, we derive analytic expressions for the transmittance and identify the conditions for the perfect transmission. The special interest of the study is focused on the resonant transmission, which occurs when the wave does not propagate in the spatial gaps. Far from the resonance, the transmittance is exponentially small due to the total internal reflection from the lead-gap interface. However, the excitation of electromagnetic modes localized on the layered superconductor gives rise to a remarkable resonant enhancement of the transmission. Moreover, this phenomenon is significantly modified for the layered superconductors in comparison with usual dielectrics or conductors. The dispersion curves for the modes localized on the layered superconductor are proved to be nonmonotonic, thus resulting in the specific dependence of the transmittance T on the incidence angle θ . In particular, we predict the onset of two resonant peaks in the T (θ ) dependence and their subsequent merge into the broadened single peak with increasing of the wave frequency. Our analytical results are demonstrated by numerical data.
Energy Technology Data Exchange (ETDEWEB)
Logunov, A A; Medvedev, B V; Mestvirishvili, M A; Pavlov, V P; Polivanov, M K; Sukhanov, A D [Gosudarstvennyj Komitet po Ispol' zovaniyu Atomnoj Ehnergii SSSR, Serpukhov. Inst. Fiziki Vysokikh Ehnergij
1977-11-01
Investigation of analytical structure of the three-particle forward scattering amplitude with respect to energy variable of one of particles is performed. The results obtained make it possible to draw the conclusions on crossing properties of the amplitude and to derive the generalized optical theorem relating the discontinuity of the amplitude to the distribution function of an inclusive process. For a special case when two of three particles are of zero mass, a dispersion relation is proved.
All-silica photonic bandgap fibre with zero dispersion and a large mode area at 730 nm
DEFF Research Database (Denmark)
Riishede, Jesper; Lægsgaard, Jesper; Broeng, Jes
2004-01-01
A theoretical analysis of a photonic bandgap fibre, consisting of a pure silica background with a triangular lattice of Ge-doped high-index rods, is presented. This novel fibre design guides a single, well-confined mode in a core region made from undoped silica. The fibre is found to have positive...... waveguide dispersion, which may be used to shift the zero-dispersion wavelength down to 730 nm, while maintaining an effective mode area of 17 $mu@-m$+2$/. This is an order of magnitude larger than what may be achieved in highly non-linear index-guiding microstructured fibres with comparable zero...
Improved pion pion scattering amplitude from dispersion relation formalism
International Nuclear Information System (INIS)
Cavalcante, I.P.; Coutinho, Y.A.; Borges, J. Sa
2005-01-01
Pion-pion scattering amplitude is obtained from Chiral Perturbation Theory at one- and two-loop approximations. Dispersion relation formalism provides a more economic method, which was proved to reproduce the analytical structure of that amplitude at both approximation levels. This work extends the use of the formalism in order to compute further unitarity corrections to partial waves, including the D-wave amplitude. (author)
Analytical solution of dispersion relations for the nuclear optical model
Energy Technology Data Exchange (ETDEWEB)
VanderKam, J.M. [Center for Communications Research, Thanet Road, Princeton, NJ 08540 (United States); Weisel, G.J. [Triangle Universities Nuclear Laboratory, and Duke University, Box 90308, Durham, NC 27708-0308 (United States); Penn State Altoona, 3000 Ivyside Park, Altoona, PA 16601-3760 (United States); Tornow, W. [Triangle Universities Nuclear Laboratory, and Duke University, Box 90308, Durham, NC 27708-0308 (United States)
2000-12-01
Analytical solutions of dispersion integral relations, linking the real and imaginary parts of the nuclear optical model, have been derived. These are displayed for some widely used forms of the volume- and surface-absorptive nuclear potentials. When the analytical solutions are incorporated into the optical-model search code GENOA, replacing a numerical integration, the code runs three and a half to seven times faster, greatly aiding the analysis of direct-reaction, elastic scattering data. (author)
General characteristics of relative dispersion in the ocean
Corrado, Raffaele; Lacorata, Guglielmo; Palatella, Luigi; Santoleri, Rosalia; Zambianchi, Enrico
2017-04-01
The multi-scale and nonlinear nature of the ocean dynamics dramatically affects the spreading of matter, like pollutants, marine litter, etc., of physical and chemical seawater properties, and the biological connectivity inside and among different basins. Based on the Finite-Scale Lyapunov Exponent analysis of the largest available near-surface Lagrangian data set from the Global Drifter Program, our results show that, despite the large variety of flow features, relative dispersion can ultimately be described by a few parameters common to all ocean sub-basins, at least in terms of order of magnitude. This provides valuable information to undertake Lagrangian dispersion studies by means of models and/or of observational data. Moreover, our results show that the relative dispersion rates measured at submesoscale are significantly higher than for large-scale dynamics. Auxiliary analysis of high resolution GPS-tracked drifter hourly data as well as of the drogued/undrogued status of the buoys is provided in support of our conclusions. A possible application of our study, concerning reverse drifter motion and error growth analysis, is proposed relatively to the case of the missing Malaysia Airlines MH370 aircraft.
Dispersion relations of density fluctuations observed by heavy ion beam probe in the TEXT tokamak
International Nuclear Information System (INIS)
Ross, D.W.
1990-09-01
Wave numbers as functions of frequency for density fluctuations in the core of the TEXT tokamak are measured in Heavy Ion Beam Probe experiments by analyzing the relative phases of signals originating from nearby points in the plasma. The adjacent points are typically 2 cm apart, with their relative orientation (δr, δθ) depending on position (r,θ). for angular frequencies ω ≤ 10 6 /s the signals are quite coherent, leading to reasonably well-defined ''dispersion relations.'' These do not correspond to known modes of the drift wave type, i.e., ballooning or slab-like electron drift waves or ion temperature gradient modes. The effect of finite sample volume size does not significantly alter this conclusion. 25 refs., 6 figs., 3 tabs
ICRH programmes for antennas and for plasma dispersion relation
International Nuclear Information System (INIS)
Soell, M.; Springmann, E.
1984-02-01
This report describes the computer programmes used for designing the ICRH antennas at IPP. In the first part of the report the underlying physical principles are discussed on which the programmes are based. 2-D (two-dimensional) and 3-D (three-dimensional) models are used. In the second part the input and output of the programmes is described, and in the third part some results on ICRH antennas built for existing machines at IPP and antennas for machines which are in the design and construction phase are presented. In Appendix I the formulae for the 2-D model including plasma density profiles are described and an investigation of this 2-D model on folded dipol antennae is given. In Appendix II the main formulae for a computer program for the complete hot dispersion relation is given; the application of the program for an ASDEX plasma (dispersion for the fast wave and Bernstein wave) is shown. (orig.)
Gyro-viscosity and linear dispersion relations in pair-ion magnetized plasmas
Energy Technology Data Exchange (ETDEWEB)
Kono, M. [Faculty of Policy Studies, Chuo University, Tokyo 192-0393 (Japan); Vranjes, J. [Instituto de Astrofisica de Canarias, Tenerife E38205 (Spain); Departamento de Astrofisica, Universidad de La Laguna, Tenerife E38205 (Spain)
2015-11-15
A fluid theory has been developed by taking account of gyro-viscosity to study wave propagation characteristics in a homogeneous pair-ion magnetized plasma with a cylindrical symmetry. The exact dispersion relations derived by the Hankel-Fourier transformation are shown comparable with those observed in the experiment by Oohara and co-workers. The gyro-viscosity is responsible for the change in propagation characteristics of the ion cyclotron wave from forward to backward by suppressing the effect of the thermal pressure which normally causes the forward nature of dispersion. Although the experiment has been already explained by a kinetic theory by the present authors, the kinetic derivations are so involved because of exact particle orbits in phase space, finite Lamor radius effects, and higher order ion cyclotron resonances. The present fluid theory provides a simple and transparent structure to the dispersion relations since the gyro-viscosity is renormalized into the ion cyclotron frequency which itself indicates the backward nature of dispersion. The usual disadvantage of a fluid theory, which treats only fundamental modes of eigen-waves excited in a system and is not able to describe higher harmonics that a kinetic theory does, is compensated by simple derivations and clear picture based on the renormalization of the gyro-viscosity.
Cell-compatible conducting polyaniline films prepared in colloidal dispersion mode.
Kašpárková, Věra; Humpolíček, Petr; Capáková, Zdenka; Bober, Patrycja; Stejskal, Jaroslav; Trchová, Miroslava; Rejmontová, Petra; Junkar, Ita; Lehocký, Marián; Mozetič, Miran
2017-09-01
Conducting polyaniline can be prepared and modified using several procedures, all of which can significantly influence its applicability in different fields of biomedicine or biotechnology. The modifications of surface properties are crucial with respect to the possible applications of this polymer in tissue engineering or as biosensors. Innovative technique for preparing polyaniline films via in-situ polymerization in colloidal dispersion mode using four stabilizers (poly-N-vinylpyrrolidone; sodium dodecylsulfate; Tween 20 and Pluronic F108) was developed. The surface energy, conductivity, spectroscopic features, and cell compatibility of thin polyaniline films were determined using contact-angle measurement, the van der Pauw method, Fourier-transform infrared spectroscopy, and assay conducted on mouse fibroblasts, respectively. The stabilizers significantly influenced not only the surface and electrical properties of the films but also their cell compatibility. Sodium dodecylsulfate seems preferentially to combine both the high conductivity and good cell compatibility. Moreover, the films with sodium dodecylsulfate were non-irritant for skin, which was confirmed by their in-vitro exposure to the 3D-reconstructed human tissue model. Copyright © 2017 Elsevier B.V. All rights reserved.
DEFF Research Database (Denmark)
Ramsay, Jacob Søndergaard; Dupont, Sune Vestergaard Lund; Johansen, Mikkel Willum
2013-01-01
Using femtosecond upconversion we investigate the time and wavelength structure of infrared supercontinuum generation. It is shown that radiation is scattered into higher order spatial modes (HOMs) when generating a supercontinuum using fibers that are not single-moded, such as a step-index ZBLAN...... not include scattering into HOMs, and including this provides an extra degree of freedom for tailoring supercontinuum sources....
Dispersion Management in a Harmonically Mode-Locked Fiber Soliton Laser
National Research Council Canada - National Science Library
Carruthers, Thomas F; Duling, III, Irl N; Horowitz, Moshe; Menyuk, Curtis R
1999-01-01
... because of their low-noise, dropout-free operation. We have fabricated such a laser with a strongly dispersion-managed cavity and modeled its operation, and we have found that dispersion management significantly extends the power range...
Observables and dispersion relations in κ-Minkowski spacetime
Aschieri, Paolo; Borowiec, Andrzej; Pachoł, Anna
2017-10-01
We revisit the notion of quantum Lie algebra of symmetries of a noncommutative spacetime, its elements are shown to be the generators of infinitesimal transformations and are naturally identified with physical observables. Wave equations on noncommutative spaces are derived from a quantum Hodge star operator. This general noncommutative geometry construction is then exemplified in the case of κ-Minkowski spacetime. The corresponding quantum Poincaré-Weyl Lie algebra of in-finitesimal translations, rotations and dilatations is obtained. The d'Alembert wave operator coincides with the quadratic Casimir of quantum translations and it is deformed as in Deformed Special Relativity theories. Also momenta (infinitesimal quantum translations) are deformed, and correspondingly the Einstein-Planck relation and the de Broglie one. The energy-momentum relations (dispersion relations) are consequently deduced. These results complement those of the phenomenological literature on the subject.
Radio mode feedback: Does relativity matter?
Perucho, Manel; Martí, José-María; Quilis, Vicent; Borja-Lloret, Marina
2017-10-01
Radio mode feedback, associated with the propagation of powerful outflows in active galaxies, is a crucial ingredient in galaxy evolution. Extragalactic jets are well collimated and relativistic, both in terms of thermodynamics and kinematics. They generate strong shocks in the ambient medium, associated with observed hotspots, and carve cavities that are filled with the shocked jet flow. In this Letter, we compare the pressure evolution in the hotspot and the cavity generated by relativistic and classical jets. Our results show that the classical approach underestimates the cavity pressure by a factor ≥2 for a given shocked volume during the whole active phase. The tension between both approaches can only be alleviated by unrealistic jet flow densities or gigantic jet areas in the classical case. As a consequence, the efficiency of a relativistic jet heating the ambient is typically ∼20 per cent larger compared with a classical jet, and the heated volume is 2 to 10 times larger during the time evolution. This conflict translates into two substantially disparate manners, both spatially and temporal, of heating the ambient medium. These differences are expected to have relevant implications on the star formation rates of the host galaxies and their evolution.
International Nuclear Information System (INIS)
Abd-alla, Abo-el-nour N.; Al-sheikh, Fatimah; Al-Hossain, Abdullah Y.
2009-01-01
Effect of initial stresses on dispersion relation for transverse surface waves circulating around a piezoelectric cylinder covered with perfectly conducting layers is investigated. Two overlay materials are considered: Gold and Aluminum. The piezoelectric substrate is considered to have the symmetry of a hexagonal crystal, and the layer is perfectly conducting. The dispersion equation has been given in the form of determinant involving Bessel functions. The roots of the dispersion equation give the values of the characteristic circular frequency parameters of the first three modes for various geometries. These roots are numerically calculated by 'Bisection method iterations technique' and presented graphically for various thickness of the overlayer and for different values of the initial stress. The effects of the initial stress on the natural frequencies are illustrated on the figures. It is found that both the thickness of the overlayer and the initial stress have a substantial effect on the dispersion behavior. The results obtained in this paper may not only help us get insight into the electro-mechanical coupling behavior of the piezoelectric composites cylinders, but can also offer theoretical basis and meaningful suggestions for the design of piezoelectric probes and electro-acoustic devices in the nondestructive evaluation technology. Finally, the results are compared graphically when the overlay is Gold or Aluminum with some special cases which do not have initial stresses and electric field.
DEFF Research Database (Denmark)
Ramsay, Jacob Søndergaard; Dupont, Sune Vestergaard Lund; Johansen, Mikkel Willum
2013-01-01
Using femtosecond upconversion we investigate the time and wavelength structure of infrared supercontinuum generation. It is shown that radiation is scattered into higher order spatial modes (HOMs) when generating a supercontinuum using fibers that are not single-moded, such as a step-index ZBLAN...... fiber. As a consequence of intermodal scattering and the difference in group velocity for the modes, the supercontinuum splits up spatially and temporally. Experimental results indicate that a significant part of the radiation propagates in HOMs. Conventional simulations of super-continuum generation do...
Testing ultrafast mode-locking at microhertz relative optical linewidth.
Martin, Michael J; Foreman, Seth M; Schibli, T R; Ye, Jun
2009-01-19
We report new limits on the phase coherence of the ultrafast mode-locking process in an octave-spanning Ti:sapphire comb.We find that the mode-locking mechanism correlates optical phase across a full optical octave with less than 2.5 microHZ relative linewidth. This result is at least two orders of magnitude below recent predictions for quantum-limited individual comb-mode linewidths, verifying that the mode-locking mechanism strongly correlates quantum noise across the comb spectrum.
Testing ultrafast mode-locking at microhertz relative optical linewidth
Martin, Michael J.; Foreman, Seth M.; Schibli, T. R.; Ye, Jun
2008-01-01
We report new limits on the phase coherence of the ultrafast mode-locking process in an octave-spanning Ti:sapphire comb. We find that the mode-locking mechanism correlates optical phase across a full optical octave with less than 2.5 micro Hz relative linewidth. This result is at least two orders of magnitude below recent predictions for quantum-limited individual comb-mode linewidths, verifying that the mode-locking mechanism strongly correlates quantum noise across the comb spectrum.
Dispersion relations in quantum electrodynamics on the noncommutative Minkowski space
Energy Technology Data Exchange (ETDEWEB)
Zahn, J.W.
2006-12-15
We study field theories on the noncommutative Minkowski space with noncommuting time. The focus lies on dispersion relations in quantized interacting models in the Yang-Feldman formalism. In particular, we compute the two-point correlation function of the field strength in noncommutative quantum electrodynamics to second order. At this, we take into account the covariant coordinates that allow the construction of local gauge invariant quantities (observables). It turns out that this does not remove the well-known severe infrared problem, as one might have hoped. Instead, things become worse, since nonlocal divergences appear. We also show that these cancel in a supersymmetric version of the theory if the covariant coordinates are adjusted accordingly. Furthermore, we study the {phi}{sup 3} and the Wess-Zumino model and show that the distortion of the dispersion relations is moderate for parameters typical for the Higgs field. We also discuss the formulation of gauge theories on noncommutative spaces and study classical electrodynamics on the noncommutative Minkowski space using covariant coordinates. In particular, we compute the change of the speed of light due to nonlinear effects in the presence of a background field. Finally, we examine the so-called twist approach to quantum field theory on the noncommutative Minkowski space and point out some conceptual problems of this approach. (orig.)
Dispersion relations in quantum electrodynamics on the noncommutative Minkowski space
International Nuclear Information System (INIS)
Zahn, J.W.
2006-12-01
We study field theories on the noncommutative Minkowski space with noncommuting time. The focus lies on dispersion relations in quantized interacting models in the Yang-Feldman formalism. In particular, we compute the two-point correlation function of the field strength in noncommutative quantum electrodynamics to second order. At this, we take into account the covariant coordinates that allow the construction of local gauge invariant quantities (observables). It turns out that this does not remove the well-known severe infrared problem, as one might have hoped. Instead, things become worse, since nonlocal divergences appear. We also show that these cancel in a supersymmetric version of the theory if the covariant coordinates are adjusted accordingly. Furthermore, we study the Φ 3 and the Wess-Zumino model and show that the distortion of the dispersion relations is moderate for parameters typical for the Higgs field. We also discuss the formulation of gauge theories on noncommutative spaces and study classical electrodynamics on the noncommutative Minkowski space using covariant coordinates. In particular, we compute the change of the speed of light due to nonlinear effects in the presence of a background field. Finally, we examine the so-called twist approach to quantum field theory on the noncommutative Minkowski space and point out some conceptual problems of this approach. (orig.)
From dispersion relations to spectral dimension - and back again
International Nuclear Information System (INIS)
Sotiriou, Thomas P.; Visser, Matt; Weinfurtner, Silke
2011-01-01
The so-called spectral dimension is a scale-dependent number associated with both geometries and field theories that has recently attracted much attention, driven largely, though not exclusively, by investigations of causal dynamical triangulations and Horava gravity as possible candidates for quantum gravity. We advocate the use of the spectral dimension as a probe for the kinematics of these (and other) systems in the region where spacetime curvature is small, and the manifold is flat to a good approximation. In particular, we show how to assign a spectral dimension (as a function of so-called diffusion time) to any arbitrarily specified dispersion relation. We also analyze the fundamental properties of spectral dimension using extensions of the usual Seeley-DeWitt and Feynman expansions and by using saddle point techniques. The spectral dimension turns out to be a useful, robust, and powerful probe, not only of geometry, but also of kinematics.
DEFF Research Database (Denmark)
Shibahara, K.; Mizuno, T.; Takara, H.
We demonstrate 12-core × 3-mode dense SDM transmission over 527 km graded-index multi-core few-mode fiber without mode-dispersion management. Employing low baud rate multi-carrier signal and frequency-domain equalization enables 33.2-ns DMD compensation with low computational complexity. © 2015 OSA...
Theory of pairwise coupling embedded in more general local dispersion relations
International Nuclear Information System (INIS)
Fuchs, V.; Bers, A.; Harten, L.
1985-01-01
Earlier work on the mode conversion theory by Fuchs, Ko, and Bers is detailed and expanded upon, and its relation to energy conservation is discussed. Given a local dispersion relation, D(ω; k, z) = 0, describing stable waves excited at an externally imposed frequency ω, a pairwise mode-coupling event embedded therein is extracted by expanding D(k, z) around a contour k = k/sub c/(z) given by partialD/partialk = 0. The branch points of D(k, z) = 0 are the turning points of a second-order differential-equation representation. In obtaining the fraction of mode-converted energy, the connection formula and conservation of energy must be used together. Also, proper attention must be given to distinguish cases for which the coupling disappears or persists upon confluence of the branches, a property which is shown to depend on the forward (v/sub g/v/sub ph/>0) or backward (v/sub g/v/sub ph/<0) nature of the waves. Examples occurring in ion-cyclotron and lower-hybrid heating are presented, illustrating the use of the theory
International Nuclear Information System (INIS)
Artz, B.E.; Short, M.A.
1976-01-01
A comparison was made between the direct tube excitation mode and the secondary target excitation mode using a Kevex 0810 energy dispersive x-ray fluorescence system. Relative sensitivities and detection limits were determined with two system configurations. The first configuration used a standard, high power, x-ray fluorescence tube to directly excite the specimen. Several x-ray tubes, including chromium, molybdenum, and tungsten, both filtered and not filtered, were employed. The second configuration consisted of using the x-ray tube to excite a secondary target which in turn excited the specimen. Appropriate targets were compared to the direct excitation results. Relative sensitivities and detection limits were determined for K-series lines for elements from magnesium to barium contained in a low atomic number matrix and in a high atomic number matrix
Niemann, Brand Lee
A major field program to study beta-mesoscale transport and dispersion over complex mountainous terrain was conducted during 1969 with the cooperation of three government agencies at the White Sands Missile Range in central Utah. The purpose of the program was to measure simultaneously on a large number of days the synoptic and mesoscale wind fields, the relative dispersion between pairs of particle trajectories and the rate of small scale turbulence dissipation. The field program included measurements during more than 60 days in the months of March, June, and November. The large quantity of data generated from this program has been processed and analyzed to provide case studies and statistics to evaluate and refine Lagrangian variable trajectory models. The case studies selected to illustrate the complexities of mesoscale transport and dispersion over complex terrain include those with terrain blocking, lee waves, and stagnation, as well as those with large vertical wind shears and horizontal wind field deformation. The statistics of relative particle dispersion were computed and compared to the classical theories of Richardson and Batchelor and the more recent theories of Lin and Kao among others. The relative particle dispersion was generally found to increase with travel time in the alongwind and crosswind directions, but in a more oscillatory than sustained or even accelerated manner as predicted by most theories, unless substantial wind shears or finite vertical separations between particles were present. The relative particle dispersion in the vertical was generally found to be small and bounded even when substantial vertical motions due to lee waves were present because of the limiting effect of stable temperature stratification. The data show that velocity shears have a more significant effect than turbulence on relative particle dispersion and that sufficient turbulence may not always be present above the planetary boundary layer for "wind direction shear
Approximate Dispersion Relations for Waves on Arbitrary Shear Flows
Ellingsen, S. À.; Li, Y.
2017-12-01
An approximate dispersion relation is derived and presented for linear surface waves atop a shear current whose magnitude and direction can vary arbitrarily with depth. The approximation, derived to first order of deviation from potential flow, is shown to produce good approximations at all wavelengths for a wide range of naturally occuring shear flows as well as widely used model flows. The relation reduces in many cases to a 3-D generalization of the much used approximation by Skop (1987), developed further by Kirby and Chen (1989), but is shown to be more robust, succeeding in situations where the Kirby and Chen model fails. The two approximations incur the same numerical cost and difficulty. While the Kirby and Chen approximation is excellent for a wide range of currents, the exact criteria for its applicability have not been known. We explain the apparently serendipitous success of the latter and derive proper conditions of applicability for both approximate dispersion relations. Our new model has a greater range of applicability. A second order approximation is also derived. It greatly improves accuracy, which is shown to be important in difficult cases. It has an advantage over the corresponding second-order expression proposed by Kirby and Chen that its criterion of accuracy is explicitly known, which is not currently the case for the latter to our knowledge. Our second-order term is also arguably significantly simpler to implement, and more physically transparent, than its sibling due to Kirby and Chen.Plain Language SummaryIn order to answer key questions such as how the ocean surface affects the climate, erodes the coastline and transports nutrients, we must understand how waves move. This is not so easy when depth varying currents are present, as they often are in coastal waters. We have developed a modeling tool for accurately predicting wave properties in such situations, ready for use, for example, in the complex oceanographic computer models. Our
Phonon dispersion relations in PrBa2Cu3O6+x (x≅0.2)
International Nuclear Information System (INIS)
Gardiner, C.H.; Boothroyd, A.T.; Larsen, B.H.; Reichardt, W.; Zhokhov, A.A.; Andersen, N.H.; Lister, S.J.S.; Wildes, A.R.
2004-01-01
We report measurements of the phonon dispersion relations in nonsuperconducting, oxygen-deficient PrBa 2 Cu 3 O 6+x (x≅0.2) by inelastic neutron scattering. The data are compared with a model of the lattice dynamics based on a common interatomic potential. Good agreement is achieved for all but two phonon branches, which are significantly softer than predicted. These modes are found to arise predominantly from motion of the oxygen ions in the CuO 2 planes. Analogous modes in YBa 2 Cu 3 O 6 are well described by the common interatomic potential model
Worth, J R P; Holland, B R; Beeton, N J; Schönfeld, B; Rossetto, M; Vaillancourt, R E; Jordan, G J
2017-10-17
Investigating species distributions across geographic barriers is a commonly utilized method in biogeography to help understand the functional traits that allow plants to disperse successfully. Here the biogeographic pattern analysis approach is extended by using chloroplast DNA whole-genome 'mining' to examine the functional traits that have impacted the dispersal of widespread temperate forest species across an intermittent seaway, the 200 km wide Bass Strait of south-eastern Australia. Multiple, co-distributed species of both dry and wet forests were sampled from five regions on either side of the Strait to obtain insights into past dispersal of these biomes via seed. Using a next-generation sequencing-based pool-seq method, the sharing of single nucleotide polymorphisms (SNPs) was estimated between all five regions in the chloroplast genome. A total of 3335 SNPs were detected in 20 species. SNP sharing patterns between regions provided evidence for significant seed-mediated gene flow across the study area, including across Bass Strait. A higher proportion of shared SNPs in dry forest species, especially those dispersed by birds, compared with wet forest species suggests that dry forest species have undergone greater seed-mediated gene flow across the study region during past climatic oscillations and sea level changes associated with the interglacial/glacial cycles. This finding is consistent with a greater propensity for long-distance dispersal for species of open habitats and proxy evidence that expansive areas of dry vegetation occurred during times of exposure of Bass Strait during glacials. Overall, this study provides novel genetic evidence that habitat type and its interaction with dispersal traits are major influences on dispersal of plants. © The Author 2017. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com
Energy Technology Data Exchange (ETDEWEB)
López, Rodrigo A. [Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Concepción, Concepción (Chile); Moya, Pablo S. [NASA Goddard Space Flight Center, Heliophysics Science Division, Geospace Physics Laboratory, Mail Code 673, Greenbelt, Maryland 20771 (United States); Department of Physics, Catholic University of America, Washington DC, DC 20064 (United States); Muñoz, Víctor [Departamento de Física, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago (Chile); Viñas, Adolfo F. [NASA Goddard Space Flight Center, Heliophysics Science Division, Geospace Physics Laboratory, Mail Code 673, Greenbelt, Maryland 20771 (United States); Valdivia, J. Alejandro [Departamento de Física, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago (Chile); Centro para el Desarrollo de la Nanociencia y la Nanotecnología, CEDENNA, Santiago (Chile)
2014-09-15
We use a kinetic treatment to study the linear transverse dispersion relation for a magnetized isotropic relativistic electron-positron plasma with finite relativistic temperature. The explicit linear dispersion relation for electromagnetic waves propagating along a constant background magnetic field is presented, including an analytical continuation to the whole complex frequency plane for the case of Maxwell-Jüttner velocity distribution functions. This dispersion relation is studied numerically for various temperatures. For left-handed solutions, the system presents two branches, the electromagnetic ordinary mode and the Alfvén mode. In the low frequency regime, the Alfvén branch has two dispersive zones, the normal zone (where ∂ω/∂k > 0) and an anomalous zone (where ∂ω/∂k < 0). We find that in the anomalous zone of the Alfvén branch, the electromagnetic waves are damped, and there is a maximum wave number for which the Alfvén branch is suppressed. We also study the dependence of the Alfvén velocity and effective plasma frequency with the temperature. We complemented the analytical and numerical approaches with relativistic full particle simulations, which consistently agree with the analytical results.
Drift wave dispersion relation for arbitrarily collisional plasma
International Nuclear Information System (INIS)
Angus, Justin R.; Krasheninnikov, Sergei I.
2012-01-01
The standard local linear analysis of drift waves in a plasma slab is generalized to be valid for arbitrarily collisional electrons by considering the electrons to be governed by the drift-kinetic equation with a BGK-like (Bhatnagar-Gross-Krook) collision operator. The obtained dispersion relation reduces to that found from collisionless kinetic theory when the collision frequency is zero. Electron temperature fluctuations must be retained in the standard fluid analysis in order to obtain good quantitative agreement with our general solution in the highly collisional limit. Any discrepancies between the fluid solution and our general solution in this limit are attributed to the limitations of the BGK collision operator. The maximum growth rates in both the collisional and collisionless limits are comparable and are both on the order of the fundamental drift wave frequency. The main role of the destabilizing mechanism is found to be in determining the parallel wave number at which the maximum growth rate will occur. The parallel wave number corresponding to the maximum growth rate is set by the wave-particle resonance condition in the collisionless limit and transitions to being set by the real frequency being on the order of the rate for electrons to diffuse a parallel wavelength in the collisional limit.
Drift wave dispersion relation for arbitrarily collisional plasma
Energy Technology Data Exchange (ETDEWEB)
Angus, Justin R.; Krasheninnikov, Sergei I. [Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, California 92093-0417 (United States)
2012-05-15
The standard local linear analysis of drift waves in a plasma slab is generalized to be valid for arbitrarily collisional electrons by considering the electrons to be governed by the drift-kinetic equation with a BGK-like (Bhatnagar-Gross-Krook) collision operator. The obtained dispersion relation reduces to that found from collisionless kinetic theory when the collision frequency is zero. Electron temperature fluctuations must be retained in the standard fluid analysis in order to obtain good quantitative agreement with our general solution in the highly collisional limit. Any discrepancies between the fluid solution and our general solution in this limit are attributed to the limitations of the BGK collision operator. The maximum growth rates in both the collisional and collisionless limits are comparable and are both on the order of the fundamental drift wave frequency. The main role of the destabilizing mechanism is found to be in determining the parallel wave number at which the maximum growth rate will occur. The parallel wave number corresponding to the maximum growth rate is set by the wave-particle resonance condition in the collisionless limit and transitions to being set by the real frequency being on the order of the rate for electrons to diffuse a parallel wavelength in the collisional limit.
Phonon dispersion relation of uranium nitrate above and below the Neel temperature
International Nuclear Information System (INIS)
Dolling, G.; Holden, T.M.; Evensson, E.C.; Buyers, W.J.L.; Lander, G.H.
1977-01-01
Neutron coherent inelastic scattering measurements have been made of the phonon dispersion relation of uranium nitride both above and below the Neel temperature T/sub N/ = 50 K. Within the precision of the measurements, about 1% in frequency and 10% in line width and in scattered neutron intensity, no significant changes in these phonon properties were observed as a function of temperature other than those arising from population factor changes and a small stiffening of the lattice as the temperature decreases. At 4.2 K, two acoustic and two optic branches have been determined for each of the [001], [110] and [111] directions. The optic mode measurements revealed (a) a 20% variation in frequency across the Brillouin zone and (b) an interesting disposition of the LO and TO modes, such that nu/sub LO/ > nu/sub TO/ along [001] and [110], while the reverse is true along the [111] directions. Within the experimental resolution, the LO and TO modes are degenerate near q = 0. We have been unable to obtain any satisfactory description of these results on the basis of conventional theoretical treatments (e.g. rigid-ion or shell models). Other possible interpretations of the results are discussed
Phonon dispersion relation of uranium nitride above and below the Neel temperature
International Nuclear Information System (INIS)
Dolling, G.; Holden, T.M.; Svensson, E.C.; Buyers, W.J.L.; Lander, G.H.
1977-01-01
Neutron coherent inelastic scattering measurements have been made of the phonon dispersion relation of uranium nitride both above and below the Neel temperature T N = 50 K. Within the precision of the measurements, about 1% in frequency and 10% in line width and in scattered neutron intensity, no significant changes in these phonon properties were observed as a function of temperature other than those arising from population factor changes and a small stiffening of the lattice as the temperature decreases. At 4.2 K, two acoustic and two optic branches have been determined for each of the [001], [110] and [111] directions. The optic mode measurements revealed (a) a 20% variation in frequency across the Brillouin zone and (b) and interesting disposition of the LO and TO modes, such that ν LO > ν TO along [001] and [11-], while the reverse is true along the [111] directions. Within the experimental resolution, the LO and TO modes are degenerate near q = 0. We have been unable to obtain any satisfactory description of these results on the basis of conventional theoretical treatments (e.g. rigid-ion or shell models). Other possible interpretations of the results are discussed. (author)
DEFF Research Database (Denmark)
Verhoef, A. J.; Zhu, L.; Israelsen, Stine Møller
2015-01-01
, was investigated for different settings of the intracavity dispersion. When the cavity is operated with close to zero net dispersion, highly stable 0.5-nJ pulses externally compressed to sub-100-fs are generated. These are to our knowledge the shortest pulses generated from an all-polarization-maintaining Yb-fiber......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......, 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 coupling...
DEFF Research Database (Denmark)
Verhoef, A.J.; Zhu, L.; Israelsen, Stine Møller
2015-01-01
, was investigated for different settings of the intracavity dispersion. When the cavity is operated with close to zero net dispersion, highly stable 0.5-nJ pulses externally compressed to sub-100-fs are generated. These are to our knowledge the shortest pulses generated from an all-polarization-maintaining Yb-fiber......We present an Yb-fiber oscillator with an all-polarization-maintaining 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......, 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 coupling...
Dispersion of guided modes in two-dimensional split ring lattices
DEFF Research Database (Denmark)
Hansen, Per Lunnemann; Koenderink, A. Femius
2014-01-01
. This method takes into account all retarded electrodynamic interactions as well as radiation damping self-consistently. As illustration, we analyze the dispersion of plasmon nanorod lattices, and of 2D split ring resonator lattices. Plasmon nanorod lattices support transverse and longitudinal in...
Waterfowl endozoochory: An overlooked long-distance dispersal mode for Cuscuta (dodder).
Costea, Mihai; Stefanović, Saša; García, Miguel A; De La Cruz, Susan; Casazza, Michael L; Green, Andy J
2016-05-01
Dispersal of parasitic Cuscuta species (dodders) worldwide has been assumed to be largely anthropomorphic because their seeds do not match any previously known dispersal syndrome and no natural dispersal vectors have been reliably documented. However, the genus has a subcosmopolitan distribution and recent phylogeographic results have indicated that at least18 historical cases of long-distance dispersal (LDD) have occurred during its evolution. The objective of this study is to report the first LDD biological vector for Cuscuta seeds. Twelve northern pintails (Anas acuta) were collected from Suisun Marsh, California and the contents of their lowest part of the large intestine (rectum) were extracted and analyzed. Seed identification was done both morphologically and using a molecular approach. Extracted seeds were tested for germination and compared to seeds not subjected to gut passage to determine the extent of structural changes caused to the seed coat by passing through the digestive tract. Four hundred and twenty dodder seeds were found in the rectum of four northern pintails. From these, 411 seeds were identified as Cuscuta campestris and nine as most likely C. pacifica. The germination rate of C. campestris seeds after gut passage was 55%. Structural changes caused by the gut passage in both species were similar to those caused by an acid scarification. Endozoochory by waterbirds may explain the historical LDD cases in the evolution of Cuscuta. This also suggests that current border quarantine measures may be insufficient to stopping spreading of dodder pests along migratory flyways. © 2016 Botanical Society of America.
Cell-compatible conducting polyaniline films prepared in colloidal dispersion mode
Czech Academy of Sciences Publication Activity Database
Kašpárková, V.; Humpolíček, P.; Capáková, Z.; Bober, Patrycja; Stejskal, Jaroslav; Trchová, Miroslava; Rejmontová, P.; Junkar, I.; Lehocký, M.; Mozetič, M.
2017-01-01
Roč. 157, 1 September (2017), s. 309-316 ISSN 0927-7765 R&D Projects: GA ČR(CZ) GA17-05095S Institutional support: RVO:61389013 Keywords : polyaniline * conducting films * colloidal dispersions Subject RIV: CD - Macromolecular Chemistry OBOR OECD: Polymer science Impact factor: 3.887, year: 2016
International Nuclear Information System (INIS)
Cohen, B.I.
1987-01-01
The existence of compact dispersion relations for parametric instabilities of coherent electromagnetic waves in magnetized plasmas is addressed here. In general, comprehensive dispersion relations for parametric instabilities in unmagnetized plasmas become more complicated in the presence of an applied time-independent magnetic field. This is demonstrated with a fluid perturbation theory. A compact dispersion relation for parametric instabilities in unmagnetized plasma is heuristically extended here to the case of a magnetized plasma. This dispersion relation gives the correct results in a variety of circumstances of interest in considering electron cyclotron heating applications
Three-particle physics and dispersion relation theory
Anisovich, A V; Matveev, M A; Nikonov, V A; Nyiri, J; Sarantsev, A V
2013-01-01
The necessity of describing three-nucleon and three-quark systems have led to a constant interest in the problem of three particles. The question of including relativistic effects appeared together with the consideration of the decay amplitude in the framework of the dispersion technique. The relativistic dispersion description of amplitudes always takes into account processes connected with the investigated reaction by the unitarity condition or by virtual transitions; in the case of three-particle processes they are, as a rule, those where other many-particle states and resonances are produced. The description of these interconnected reactions and ways of handling them is the main subject of the book.
Surface Resonance Bands on (001)W: Experimental Dispersion Relations
DEFF Research Database (Denmark)
Willis, R. F.; Feuerbacher, B.; Christensen, N. Egede
1977-01-01
A band of unbound surface states (resonances), located in an energy region above the vacuum threshold corresponding to an energy band gap in the electron states of the bulk crystal, has been observed by angle-resolved secondary-electron-emission spectroscopy. The experimental dispersion behavior...... is in agreement with the two-dimensional band structure of a clean (001)W surface recently proposed by Smith and Mittheiss....
The use of dispersion relations to construct unified nucleon optical potentials
International Nuclear Information System (INIS)
Hodgson, P.E.
1991-01-01
The dispersion relations provide a simple and accurate way of parametrizing the optical potential for a particular nucleus over a range of energies. A method is proposed for obtaining a global nucleon optical potential incorporating the dispersion relations. (author). 9 refs, 3 figs
Subdiffraction-limited imaging based on longitudinal modes in a spatially dispersive slab
Yanai, Avner; Levy, Uriel
2014-08-01
It was proposed that a flat silver layer could be used to form a subdiffraction-limited image when illuminated near its surface plasmon resonance frequency [J. B. Pendry, Phys. Rev. Lett. 85, 3966 (2000), 10.1103/PhysRevLett.85.3966]. In this paper, we study the possibility of obtaining sub diffraction resolution using a different mechanism, with no surface plasmons involved. Instead, by taking into account the nonlocal response of a thin silver slab, we show that longitudinal modes contribute to the formation of a subdiffraction-limited image in a frequency regime above the plasma frequency. The differences between these two distinct mechanisms are studied and explained.
Splenic trauma management in relation to mode and grade
International Nuclear Information System (INIS)
Gangat, S.A.; Khaskhali, A.A.; Memon, I.A.
2008-01-01
To study the prevalence and management of splenic trauma in relation to its mode and grade. All cases admitted in emergency with abdominal trauma and splenic injury. The data of all the patients who had splenic trauma was entered on a proforma and analyzed. A total of 44 patients with ages between 20-40 years presented with splenic injury; 32(72.7%) were male. The commonest mode of splenic trauma was blunt abdominal injury (50%), and most (47%) patients had Grade- III injury. Splenectomy was carried out in 84% patients, while 9% underwent splenic salvage. Seven (15.9%) patients with splenectomy died in the series. Splenic injury was mostly caused by blunt abdominal trauma. Proper assessment of the grade of injury at the time of laparotomy resulted in more splenic salvage procedures with decreased risk of complications. (author)
International Nuclear Information System (INIS)
Censor, Dan
2010-01-01
Identifying invariance properties helps in simplifying calculations and consolidating concepts. Presently the Special Relativistic invariance of dispersion relations and their associated scalar wave operators is investigated for general dispersive homogeneous linear media. Invariance properties of the four-dimensional Fourier-transform integrals is demonstrated, from which the invariance of the scalar Green-function is inferred. Dispersion relations and the associated group velocities feature in Hamiltonian ray tracing theory. The derivation of group velocities for moving media from the dispersion relation for these media at rest is discussed. It is verified that the group velocity concept satisfies the relativistic velocity-addition formula. In this respect it is considered to be 'real', i.e., substantial, physically measurable, and not merely a mathematical artifact. Conversely, if we assume the group velocity to be substantial, it follows that the dispersion relation must be a relativistic invariant. (orig.)
Relation of wave energy and momentum with the plasma dispersion relation in an inhomogeneous plasma
International Nuclear Information System (INIS)
Berk, H.L.; Pfirsch, D.
1988-01-01
The expressions for wave energy and angular momentum commonly used in homogeneous and near-homogeneous media is generalized to inhomogeneous media governed by a nonlocal conductivity tensor. The expression for wave energy applies to linear excitations in an arbitrary three-dimensional equilibrium, while the expression for angular momentum applies to linear excitations of azimuthally symmetric equilibria. The wave energy E-script/sub wave/ is interpreted as the energy transferred from linear external sources to the plasma if there is no dissipation. With dissipation, such a simple interpretation is lacking as energy is also thermally absorbed. However, for azimuthally symmetric equilibria, the expression for the wave energy in a frame rotating with a frequency ω can be unambiguously separated from thermal energy. This expression is given by E-script/sub wave/ -ωL/sub wave/ l, where L/sub wave/ is the wave angular momentum defined in the text and l the azimuthal wavenumber and it is closely related to the real part of a dispersion relation for marginal stability. The imaginary part of the dispersion is closely related to the energy input into a system. Another useful quantity discussed is the impedance form, which can be used for three-dimensional equilibrium without an ignorable coordinate and the expression is closely related to the wave impedance used in antenna theory. Applications to stability theory are also discussed
International Nuclear Information System (INIS)
Wang, L R; Han, D D
2013-01-01
Pulse shape control in passively mode-locked fiber lasers with net-normal dispersion is investigated experimentally. Three kinds of pulses with different spectral and temporal shapes are observed, and their pulse-shaping mechanisms are discussed. After a polarization-resolved system external to the cavity, the maximum intensity differences of the two polarization components for the rectangular-spectrum (RS), Gaussian-spectrum (GS), and super-broadband (SB) pulses are measured as ∼20 dB, ∼15 dB, and ∼1 dB, respectively. It is suggested that the equivalent saturable absorption effect plays an increasingly important role from the RS to GS and then to SB pulses in the pulse-shaping processes, while the spectral filtering effect declines. This work could help in systematically understanding pulse formation and proposing guidelines for the realization of pulses with better performance in fiber lasers. (paper)
Surface-plasmon dispersion relation for the inhomogeneous charge-density medium
International Nuclear Information System (INIS)
Harsh, O.K.; Agarwal, B.K.
1989-01-01
The surface-plasmon dispersion relation is derived for the plane-bounded electron gas when there is an inhomogeneous charge-density distribution in the plasma. The hydrodynamical model is used. Both cphi and dcphi/dx are taken to be continuous at the surface of the slab, where cphi is the scalar potential. The dispersion relation is compared with the theoretical works of Stern and Ferrell and of Harsh and Agarwal. It is also compared with the observations of Kunz. A dispersion relation for the volume-plasmon oscillations is derived which resembles the well-known relation of Bohm and Pines
Kumar, Prashant; Fennell, Paul; Britter, Rex
2008-08-25
There have been many studies concerning dispersion of gaseous pollutants from vehicles within street canyons; fewer address the dispersion of particulate matter, particularly particle number concentrations separated into the nucleation (10-30 nm or N10-30) or accumulation (30-300 nm or N30-300) modes either separately or together (N10-300). This study aimed to determine the effect of wind direction and speed on particle dispersion in the above size ranges. Particle number distributions (PNDs) and concentrations (PNCs) were measured in the 5-2738 nm range continuously (and in real-time) for 17 days between 7th and 23rd March 2007 in a regular (aspect ratio approximately unity) street canyon in Cambridge (UK), using a newly developed fast-response differential mobility spectrometer (sampling frequency 0.5 Hz), at 1.60 m above the road level. The PNCs in each size range, during all wind directions, were better described by a proposed two regime model (traffic-dependent and wind-dependent mixing) than by simply assuming that the PNC was inversely proportional to the wind speed or by fitting the data with a best-fit single power law. The critical cut-off wind speed (Ur,crit) for each size range of particles, distinguishing the boundary between these mixing regimes was also investigated. In the traffic-dependent PNC region (UrUrwind speed and direction. In the wind speed dependent PNC region (UrUr>Ur,critUr,crit), concentrations were inversely proportional to Ur irrespective of any particle size range and wind directions. The wind speed demarcating the two regimes (Ur,critUr,crit) was 1.23+/-0.55 m s(-1) for N10-300, (1.47+/-0.72 m s(-1)) for N10-30 but smaller (0.78+/-0.29 m s(-1)) for N30-300.
Wandering stars: age-related habitat use and dispersal of Javan Hawk-eagles (Spizaetus bartelsi)
Nijman, V.; Balen, van S.
2003-01-01
Natal dispersal and philopatry have rarely been studied in tropical forest raptors. Especially with respect to endangered species with fragmented distributions more knowledge of dispersal and age-related habitat preferences is needed for proper management. We conducted an island-wide study on
The complex dispersion relation of surface plasmon polaritons at gold/para-hexaphenylene interfaces
DEFF Research Database (Denmark)
Lemke, Christoph; Leißner, Till; Klick, Alwin
2014-01-01
Two-photon photoemission electron microscopy (2P-PEEM) is used to measure the real and imaginary part of the dispersion relation of surface plasmon polaritons at different interface systems. A comparison of calculated and measured dispersion data for a gold/vacuum interface demonstrates...
Comparison of Forward Dispersion Relations with Experiments around 10 GeV
DEFF Research Database (Denmark)
Lautrup, B.; Møller-Nielsen, Peter; Olesen, P.
1965-01-01
no assumptions whatsoever about the unknown cross sections above 20 GeV. On account of the large systematic errors in the measured real parts, no definite conclusion can be drawn as to the validity of forward dispersion relations. In estimating the standard deviations in the dispersion integrals, a Monte Carlo...
Absorption Related to Hand-Held Devices in Data Mode
DEFF Research Database (Denmark)
Andersen, Jørgen Bach; Nielsen, Jesper Ødum; Pedersen, Gert F.
2016-01-01
The human body has an influence on the radiation from handheld devices like smartphones, tablets and laptops, part of the energy is absorbed and the spatial distribution of the radiated part is modified. Previous studies of whole body absorp- tion have mainly been numerical or related to talk mode....... In the present paper an experimental study involving four volunteers and three different devices is performed from 0.5 to 3 GHz. The devices are a laptop, a tablet, and a smartphone all held in the lap. The 3D distribution of radiation is measured. Comparing the integrated power in the case of a person present...
Energy Technology Data Exchange (ETDEWEB)
Mawet, D.; Ruane, G.; Xuan, W.; Echeverri, D.; Klimovich, N.; Randolph, M.; Fucik, J.; Wang, J.; Dekany, R.; Delorme, J.-R. [Department of Astronomy, California Institute of Technology, 1200 East California Boulevard, MC 249-17, Pasadena, CA 91125 (United States); Wallace, J. K.; Vasisht, G.; Mennesson, B.; Choquet, E.; Serabyn, E., E-mail: dmawet@astro.caltech.edu [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States)
2017-04-01
High-dispersion coronagraphy (HDC) optimally combines high-contrast imaging techniques such as adaptive optics/wavefront control plus coronagraphy to high spectral resolution spectroscopy. HDC is a critical pathway toward fully characterizing exoplanet atmospheres across a broad range of masses from giant gaseous planets down to Earth-like planets. In addition to determining the molecular composition of exoplanet atmospheres, HDC also enables Doppler mapping of atmosphere inhomogeneities (temperature, clouds, wind), as well as precise measurements of exoplanet rotational velocities. Here, we demonstrate an innovative concept for injecting the directly imaged planet light into a single-mode fiber, linking a high-contrast adaptively corrected coronagraph to a high-resolution spectrograph (diffraction-limited or not). Our laboratory demonstration includes three key milestones: close-to-theoretical injection efficiency, accurate pointing and tracking, and on-fiber coherent modulation and speckle nulling of spurious starlight signal coupling into the fiber. Using the extreme modal selectivity of single-mode fibers, we also demonstrated speckle suppression gains that outperform conventional image-based speckle nulling by at least two orders of magnitude.
Dispersion relation of electromagnetic waves in one-dimensional plasma photonic crystals
International Nuclear Information System (INIS)
Hojo, Hitoshi; Mase, Atsushi
2004-01-01
The dispersion relation of electromagnetic waves in one-dimensional plasma photonic crystals is studied. The plasma photonic crystal is a periodic array composed of alternating thin plasma and dielectric material. The dispersion relation is obtained by solving a Maxwell wave equation using a method analogous to Kronig-Penny's problem in quantum mechanics, and it is found that the frequency gap and cut-off appear in the dispersion relation. The frequency gap is shown to become larger with the increase of the plasma density as well as plasma width. (author)
On the relative contributions of wind vs. animals to seed dispersal of four Sierra Nevada pines.
Vander Wall, Stephen B
2008-07-01
Selective pressures that influence the form of seed dispersal syndromes are poorly understood. Morphology of plant propagules is often used to infer the means of dispersal, but morphology can be misleading. Several species of pines, for example, have winged seeds adapted for wind dispersal but owe much of their establishment to scatter-hoarding animals. Here the relative importance of wind vs. animal dispersal is assessed for four species of pines of the eastern Sierra Nevada that have winged seeds but differed in seed size: lodgepole pine (Pinus contorta murrayana, 8 mg); ponderosa pine (Pinus ponderosa ponderosa, 56 mg); Jeffrey pine (Pinus jeffreyi, 160 mg); and sugar pine (Pinus lambertiana, 231 mg). Pre-dispersal seed mortality eliminated much of the ponderosa pine seed crop (66%), but had much less effect on Jeffrey pine (32% of seeds destroyed), lodgepole pine (29%), and sugar pine (7%). When cones opened most filled seeds were dispersed by wind. Animals removed > 99% of wind-dispersed Jeffrey and sugar pine seeds from the ground within 60 days, but animals gathered only 93% of lodgepole pine seeds and 38% of ponderosa pine seeds during the same period. Animals gathered and scatter hoarded radioactively labeled ponderosa, Jeffrey, and sugar pine seeds, making a total of 2103 caches over three years of study. Only three lodgepole pine caches were found. Caches typically contained 1-4 seeds buried 5-20 mm deep, depths suitable for seedling emergence. Although Jeffrey and sugar pine seeds are initially wind dispersed, nearly all seedlings arise from animal caches. Lodgepole pine is almost exclusively wind dispersed, with animals acting as seed predators. Animals treated ponderosa pine in an intermediate fashion. Two-phased dispersal of large, winged pine seeds appears adaptive; initial wind dispersal helps to minimize pre-dispersal seed mortality whereas scatter hoarding by animals places seeds in sites with a higher probability of seedling establishment.
A Neutron Study for Phonon Dispersion Relations in HgTe
DEFF Research Database (Denmark)
Kepa, H.; Gebicki, W.; Giebultowicz, T.
1980-01-01
Dispersion relations for acoustic phonons in mercury telluride in three high symmetry directions [111], [110] and [001] are presented. The eleven-parameter rigid-ion model is fitted to the experimental data....
International Nuclear Information System (INIS)
Fuhrmann, C.; Fulfaro, R.; Vinhas, L.A.
1978-01-01
With the purpose to check the performance of IEA Triple Axis Spectrometer of which construction was recently finished, dispersion relation curves for copper at room temperature have been messured. The frequencies of phonons propagating along the three major simmetry directions [xi00] [xixi0] and [xixixi] have been determined. The measurements were carried out operating the Triple Axis Spectrometer in the 'Q constant' mode at neutron energy loss. An excellent agreement could be observed between the results obtained in the present experiment and the accurate data for copper presented in the litterature. In such way, we can conclude that the IEA Triple Axis Spectrometer is in good operational conditions and able to perform original experiments. In this report an outline of the theory of the spectrometer operation and details on the experimental procedures for the case of a Triple Axis Spectrometer operating in the 'Q constant' mode are also presented [pt
Numerical method for the dispersion relation of a hot and inhomogeneous plasma with an electron beam
International Nuclear Information System (INIS)
Devia, A.; Orrego, C.E.; Buitrago, G.
1990-01-01
A numerical method that is based in kinetic theory (Vlasov-Poison equations) was developed in order to calculate the dispersion relation for the interaction between a hot cylindrical and electron beam in any temperature and density. The plasma-beam system is located in a strong magnetic field. Many examples showing the effect of the temperatures and densities on the dispersion relation are given. (Author)
International Nuclear Information System (INIS)
Dean, N.W.
1978-01-01
New data showing that the photon-nucleon total cross section increases with energy for ν > or = 50 GeV invalidate earlier comparisons with dispersion relations. Parametrization of the data are presented and used in a new formulation of the dispersion relations, in which an assumed asymptotic behavior avoids the need for subtraction. With this form the fitted amplitude can be compared directly with the Thomson limit. The experimental uncertainties are shown to have a significant effect upon such a comparison
Fast flavor conversions of supernova neutrinos: Classifying instabilities via dispersion relations
Capozzi, Francesco; Dasgupta, Basudeb; Lisi, Eligio; Marrone, Antonio; Mirizzi, Alessandro
2017-08-01
Supernova neutrinos can exhibit a rich variety of flavor conversion mechanisms. In particular, they can experience "fast" self-induced flavor conversions almost immediately above the core. Very recently, a novel method has been proposed to investigate these phenomena, in terms of the dispersion relation for the complex frequency and wave number (ω ,k ) of disturbances in the mean field of the νeνx flavor coherence. We discuss a systematic approach to such instabilities, originally developed in the context of plasma physics, and based of the time-asymptotic behavior of the Green's function of the system. Instabilities are typically seen to emerge for complex ω and can be further characterized as convective (moving away faster than they spread) and absolute (growing locally), depending on k -dependent features. Stable cases emerge when k (but not ω ) is complex, leading to disturbances damped in space, or when both ω and k are real, corresponding to complete stability. The analytical classification of both unstable and stable modes leads not only to qualitative insights about their features but also to quantitative predictions about the growth rates of instabilities. Representative numerical solutions are discussed in a simple two-beam model of interacting neutrinos. As an application, we argue that supernova and binary neutron star mergers exhibiting a "crossing" in the electron lepton number would lead to an absolute instability in the flavor content of the neutrino gas.
Statistical analysis of dispersion relations in turbulent solar wind fluctuations using Cluster data
Perschke, C.; Narita, Y.
2012-12-01
Multi-spacecraft measurements enable us to resolve three-dimensional spatial structures without assuming Taylor's frozen-in-flow hypothesis. This is very useful to study frequency-wave vector diagram in solar wind turbulence through direct determination of three-dimensional wave vectors. The existence and evolution of dispersion relation and its role in fully-developed plasma turbulence have been drawing attention of physicists, in particular, if solar wind turbulence represents kinetic Alfvén or whistler mode as the carrier of spectral energy among different scales through wave-wave interactions. We investigate solar wind intervals of Cluster data for various flow velocities with a high-resolution wave vector analysis method, Multi-point Signal Resonator technique, at the tetrahedral separation about 100 km. Magnetic field data and ion data are used to determine the frequency- wave vector diagrams in the co-moving frame of the solar wind. We find primarily perpendicular wave vectors in solar wind turbulence which justify the earlier discussions about kinetic Alfvén or whistler wave. The frequency- wave vector diagrams confirm (a) wave vector anisotropy and (b) scattering in frequencies.
International Nuclear Information System (INIS)
Deeba, F.; Ahmad, Zahoor; Murtaza, G.
2010-01-01
A generalized dielectric constant for the electron Bernstein waves using non-Maxwellian distribution functions is derived in a collisionless, uniform magnetized plasma. Using the Neumann series expansion for the products of Bessel functions, we can derive the dispersion relations for both kappa and the generalized (r,q) distributions in a straightforward manner. The dispersion relations now become dependent upon the spectral indices κ and (r,q) for the kappa and the generalized (r,q) distribution, respectively. Our results show how the non-Maxwellian dispersion curves deviate from the Maxwellian depending upon the values of the spectral indices chosen. It may be noted that the (r,q) dispersion relation is reduced to the kappa distribution for r=0 and q=κ+1, which, in turn, is further reducible to the Maxwellian distribution for κ→∞.
International Nuclear Information System (INIS)
Huang, S S; Yan, P G; Zhang, G L; Zhao, J Q; Li, H Q; Lin, R Y; Wang, Y G
2014-01-01
We experimentally investigated soliton rains in an ytterbium-doped fiber (YDF) laser with a net normal dispersion cavity using a graphene-oxide (GO) saturable absorber (SA). The 195 m-long-cavity, the fiber birefringence filter and the inserted 2.5 nm narrow bandwidth filter play important roles in the formation of the soliton rains. The soliton rain states can be changed by the effective gain bandwidth of the laser. The experimental results can be conducive to an understanding of dissipative soliton features and mode-locking dynamics in all-normal dispersion fiber lasers with GOSAs. To the best of our knowledge, this is the first demonstration of soliton rains in a GOSA passively mode-locked YDF laser with a net normal dispersion cavity. (letter)
Dispersion relation for localized magnetic polaritons propagating at ...
Indian Academy of Sciences (India)
Abstract. Localized magnetic polaritons are investigated in the systems consisting of two magnetic superlattices, coupled by a ferromagnetic contact layer. The general dis- persion relation for localized magnetic polaritons are derived in the framework of the electromagnetic wave theory in the Voigt geometry by the 'transfer' ...
Numerical study on general dispersion relation of anisotropic and weakly relativistic plasma
International Nuclear Information System (INIS)
Ke Fujiu; Chen Yanping
1987-01-01
The key problem in heating and instability studies in plasma physics is to obtain dispersive equation and its solution. This paper presents the general dispersive equation and corresponding procedure for electromagnetic wave which nearly poloidally impinges on anisotropic, weakly relativistic Maxwellian plasma with inhomogeneous density in nonuniform magnetic field (such as plasma in TOKAMAK). The double index function F ij , significant in plasma physics, was expanded as single index function F 1 , and then the values were calculated by means of dispersive function. It was also pointed out that the severe error would be involved in the calculation of F ij from recurrence relation of F 11
Dispersion relations for the self-energy in noncommutative field theories
International Nuclear Information System (INIS)
Brandt, F.T.; Das, Ashok; Frenkel, J.
2002-01-01
We study the IR-UV connection in noncommutative φ 3 theory as well as in noncommutative QED from the point of view of the dispersion relation for self-energy. We show that, although the imaginary part of the self-energy is well behaved as the parameter of noncommutativity vanishes, the real part becomes divergent as a consequence of the high energy behavior of the dispersion integral. Some other interesting features that arise from this analysis are also briefly discussed
DEFF Research Database (Denmark)
Gibbon, Timothy Braidwood; Prince, Kamau; Pham, Tien Thang
2011-01-01
how off-center wavelength filtering of the VCSEL spectrum at an array waveguide grating can be used to mitigate the effect of chirp and the dispersion penalty. Transmission at 10Gb/s VCSEL over 23.6 km of single mode fiber is experimentally demonstrated, with a dispersion penalty of only 2.9 d......B. Simulated results are also presented which show that off-center wavelength filtering can extend the 10 Gb/s network reach from 11.7 km to 25.8 km for a 4 dB dispersion penalty. This allows for cheap and simple dispersion mitigation in next generation VCSEL based optical access networks....
'' Ideal Gas '' gluon plasma with medium dependent dispersion relation
International Nuclear Information System (INIS)
Gorenstein, M.I.
1995-01-01
An '' ideal gas '' model with temperature dependent particle mass is constructed for the gluon plasma equation of state. This simple model gives us an example of a system with temperature dependent effective Hamiltonian. To satisfy thermodynamical relations in these systems, standard statistical mechanics formulas have to be supplemented by special requirements which are considered in details. A self-consistent '' ideal gas '' formulation is used to describe Monte Carlo lattice data for the thermodynamical functions of SU(2) and SU(3) gluon plasma. 14 refs., 8 figs
On the relativistic theory of electromagnetic dispersion relations and Poynting's theorem
International Nuclear Information System (INIS)
Lerche, I.
1975-01-01
Constitutive relations, and general dispersion relations, are derived for an arbitrary, anisotropic, dispersive and dissipative medium which is moving relative to an inertial observer. The constitutive relations are expressed in terms of the ''local'' dielectric tensor, magnetic permeability, etc., where ''local'' refers to the instantaneous rest frame of the medium. We also give the generalization of Poynting's theorem for power flow including the expression for the rate at which the moving medium does work on the radiation. In view of the current interest in radiation generated in, and passing through, pulsar magnetospheres, we believe that the general results presented here are, perhaps, not without some astrophysical import
Overlap relation between free-space Laguerre Gaussian modes and step-index fiber modes
CSIR Research Space (South Africa)
Bruning, R
2015-09-01
Full Text Available to control the optical proper- ties of the emerging beam or the excited field distributions at the fiber input. The simplest connection is given by fibers with an parabolic refractive index profile, typical of graded-index fibers, whose modes can be described..., in general free space modes are not suitable to excite selective pure fiber modes and additional beam shaping techniques are required, such as the use of computer generated holograms [5]. The main disadvan- tages of such beam shaping techniques are the low...
Dispersion relation for pure dust Bernstein waves in a non-Maxwellian magnetized dusty plasma
International Nuclear Information System (INIS)
Deeba, F.; Ahmad, Zahoor; Murtaza, G.
2011-01-01
Pure dust Bernstein waves are investigated using non-Maxwellian kappa and (r,q) distribution functions in a collisionless, uniform magnetized dusty plasma. Dispersion relations for both the distributions are derived by considering waves whose frequency is of the order of dust cyclotron frequency, and dispersion curves are plotted. It is observed that the propagation band for dust Bernstein waves is rather narrow as compared with that of the electron Bernstein waves. However, the band width increases for higher harmonics, for both kappa and (r,q) distributions. Effect of dust charge on dispersion curves is also studied, and one observes that with increasing dust charge, the dispersion curves shift toward the lower frequencies. Increasing the dust to ion density ratio ((n d0 /n i0 )) causes the dispersion curve to shift toward the higher frequencies. It is also found that for large values of spectral index kappa (κ), the dispersion curves approach to the Maxwellian curves. The (r,q) distribution approaches the kappa distribution for r = 0, whereas for r > 0, the dispersion curves show deviation from the Maxwellian curves as expected. Relevance of this work can be found in astrophysical plasmas, where non-Maxwellian velocity distributions as well as dust particles are commonly observed.
Dispersion relation for pure dust Bernstein waves in a non-Maxwellian magnetized dusty plasma
Energy Technology Data Exchange (ETDEWEB)
Deeba, F. [National Tokamak Fusion Program, PAEC, P.O. Box 3329, Islamabad 44000 (Pakistan); Department of Physics, G.C. University, Lahore 54000 (Pakistan); Ahmad, Zahoor [National Tokamak Fusion Program, PAEC, P.O. Box 3329, Islamabad 44000 (Pakistan); Murtaza, G. [Salam Chair in Physics, G.C. University, Lahore 54000 (Pakistan)
2011-07-15
Pure dust Bernstein waves are investigated using non-Maxwellian kappa and (r,q) distribution functions in a collisionless, uniform magnetized dusty plasma. Dispersion relations for both the distributions are derived by considering waves whose frequency is of the order of dust cyclotron frequency, and dispersion curves are plotted. It is observed that the propagation band for dust Bernstein waves is rather narrow as compared with that of the electron Bernstein waves. However, the band width increases for higher harmonics, for both kappa and (r,q) distributions. Effect of dust charge on dispersion curves is also studied, and one observes that with increasing dust charge, the dispersion curves shift toward the lower frequencies. Increasing the dust to ion density ratio ((n{sub d0}/n{sub i0})) causes the dispersion curve to shift toward the higher frequencies. It is also found that for large values of spectral index kappa ({kappa}), the dispersion curves approach to the Maxwellian curves. The (r,q) distribution approaches the kappa distribution for r = 0, whereas for r > 0, the dispersion curves show deviation from the Maxwellian curves as expected. Relevance of this work can be found in astrophysical plasmas, where non-Maxwellian velocity distributions as well as dust particles are commonly observed.
Dispersion relations for η{sup '} → ηππ
Energy Technology Data Exchange (ETDEWEB)
Isken, Tobias; Kubis, Bastian; Schneider, Sebastian P. [Universitaet Bonn, Helmholtz-Institut fuer Strahlen- und Kernphysik and Bethe Center for Theoretical Physics, Bonn (Germany); Stoffer, Peter [Universitaet Bonn, Helmholtz-Institut fuer Strahlen- und Kernphysik and Bethe Center for Theoretical Physics, Bonn (Germany); University of California at San Diego, Department of Physics, La Jolla, CA (United States)
2017-07-15
We present a dispersive analysis of the decay amplitude for η{sup '} → ηππ that is based on the fundamental principles of analyticity and unitarity. In this framework, final-state interactions are fully taken into account. Our dispersive representation relies only on input for the ππ and πη scattering phase shifts. Isospin symmetry allows us to describe both the charged and neutral decay channel in terms of the same function. The dispersion relation contains subtraction constants that cannot be fixed by unitarity. We determine these parameters by a fit to Dalitz-plot data from the VES and BES-III experiments. We study the prediction of a low-energy theorem and compare the dispersive fit to variants of chiral perturbation theory. (orig.)
Directory of Open Access Journals (Sweden)
Malik Kemiche
2018-01-01
Full Text Available We exploit slow light (high ng modes in planar photonic crystals in order to design a compact cavity, which provides an attractive path towards the miniaturization of near-infrared integrated fast pulsed lasers. By applying dispersion engineering techniques, we can design structures with a low dispersion, as needed by mode-locking operation. Our basic InP SiO2 heterostructure is robust and well suited to integrated laser applications. We show that an optimized 30 μm long cavity design yields 9 frequency-equidistant modes with a FSR of 178 GHz within a 11.5 nm bandwidth, which could potentially sustain the generation of optical pulses shorter than 700 fs. In addition, the numerically calculated quality factors of these modes are all above 10,000, making them suitable for reaching laser operation. Thanks to the use of a high group index (28, this cavity design is almost one order of magnitude shorter than standard rib-waveguide based mode-locked lasers. The use of slow light modes in planar photonic crystal based cavities thus relaxes the usual constraints that tightly link the device size and the quality (peak power, repetition rate of the pulsed laser signal.
Kemiche, Malik; Lhuillier, Jérémy; Callard, Ségolène; Monat, Christelle
2018-01-01
We exploit slow light (high ng) modes in planar photonic crystals in order to design a compact cavity, which provides an attractive path towards the miniaturization of near-infrared integrated fast pulsed lasers. By applying dispersion engineering techniques, we can design structures with a low dispersion, as needed by mode-locking operation. Our basic InP SiO2 heterostructure is robust and well suited to integrated laser applications. We show that an optimized 30 μm long cavity design yields 9 frequency-equidistant modes with a FSR of 178 GHz within a 11.5 nm bandwidth, which could potentially sustain the generation of optical pulses shorter than 700 fs. In addition, the numerically calculated quality factors of these modes are all above 10,000, making them suitable for reaching laser operation. Thanks to the use of a high group index (28), this cavity design is almost one order of magnitude shorter than standard rib-waveguide based mode-locked lasers. The use of slow light modes in planar photonic crystal based cavities thus relaxes the usual constraints that tightly link the device size and the quality (peak power, repetition rate) of the pulsed laser signal.
International Nuclear Information System (INIS)
Frank, A.I.; Nosov, V.G.
1995-01-01
Modern theoretical concepts concerning the dispersion relation for slow neutrons in matter are considered. The generally accepted optical-potential model is apparently not quite accurate and should be supplemented with some small corrections in the energy range attainable in experiments. For ultracold neutrons, these corrections are related to the proximity of the applicability boundary of the theory; for cold neutrons, these corrections are due to correlations in the positions of scatters. The accuracy of existing experiments is insufficient for confirmation or refutation these conclusions. A precision experiment is proposed to verify the dispersion relation for long-wave neutrons. 30 refs., 3 figs
Scaling relations for soliton compression and dispersive-wave generation in tapered optical fibers
DEFF Research Database (Denmark)
Lægsgaard, Jesper
2018-01-01
In this paper, scaling relations for soliton compression in tapered optical fibers are derived and discussed. The relations allow simple and semi-accurate estimates of the compression point and output noise level, which is useful, for example, for tunable dispersive-wave generation with an agile ...
Pettengill, J B; Wendt, D E; Schug, M D; Hadfield, M G
2007-01-01
The polychaete tubeworm Hydroides elegans (Haswell) is a biofouling species with relatively limited larval dispersal. Four highly polymorphic microsatellite loci were used to make inferences about the migration and global population structure of 137 individuals from seven sub-populations located in the Atlantic, Pacific, and Indian Oceans and in the Mediterranean Sea. The results of the genetic analyses suggest minimal population sub-structure (F(st) = 0.09). Estimates of pairwise F(st) and migration rates using the coalescent-based method of MIGRATE suggest that there is little genetic differentiation between certain populations. Variation in relatedness among pairs of populations is consistent with a suite of local and global factors. The most likely explanation for close genetic relatedness among certain populations over such vast distances is the regular and consistent transport of adults and larvae on the hulls and in the ballast water of ships, respectively.
Dispersion relation and Landau damping of waves in high-energy density plasmas
International Nuclear Information System (INIS)
Zhu Jun; Ji Peiyong
2012-01-01
We present a theoretical investigation on the propagation of electromagnetic waves and electron plasma waves in high energy density plasmas using the covariant Wigner function approach. Based on the covariant Wigner function and Dirac equation, a relativistic quantum kinetic model is established to describe the physical processes in high-energy density plasmas. With the zero-temperature Fermi–Dirac distribution, the dispersion relation and Landau damping of waves containing the relativistic quantum corrected terms are derived. The relativistic quantum corrections to the dispersion relation and Landau damping are analyzed by comparing our results with those obtained in classical and non-relativistic quantum plasmas. We provide a detailed discussion on the Landau damping obtained in classical plasmas, non-relativistic Fermi plasmas and relativistic Fermi plasmas. The contributions of the Bohm potential, the Fermi statistics pressure and relativistic effects to the dispersion relation and Landau damping of waves are quantitatively calculated with real plasma parameters. (paper)
The general dispersion relation of induced streaming instabilities in quantum outflow systems
Energy Technology Data Exchange (ETDEWEB)
Mehdian, H., E-mail: mehdian@khu.ac.ir; Hajisharifi, K.; Hasanbeigi, A. [Department of Physics and Institute for Plasma Research, Kharazmi University, 49 Dr Mofatteh Avenue, Tehran 15614 (Iran, Islamic Republic of)
2015-11-15
In this manuscript the dispersion relations of streaming instabilities, by using the unique property (neutralized in charge and current by default) of plasma shells colliding, have been generalized and studied. This interesting property for interpenetrating beams enables one to find the general dispersion relations without any restrictions used in the previous works in this area. In our previous work [H. Mehdian et al., ApJ. 801, 89 (2015)], employing the plasma shell concept and boost frame method, the general dispersion relation for filamentation instability has been derived in the relativistic classical regime. But in this paper, using the above mentioned concepts, the general dispersion relations (for each of streaming instabilities, filamentation, two-stream and multi-stream) in the non-relativistic quantum regime have been derived by employing the quantum fluid equations together with Maxwell equations. The derived dispersion relations enable to describe any arbitrary system of interacting two and three beams, justified neutralization condition, by choosing the inertial reference frame embedded on the one of the beams. Furthermore, by the numerical and analytical study of these dispersion relations, many new features of streaming instabilities (E.g. their cut-off wave numbers and growth rates) in terms of all involved parameters have been illustrated. The obtained results in this paper can be used to describe many astrophysical systems and laboratory astrophysics setting, such as collision of non-parallel plasma shells over a background plasma or the collision of three neutralized plasma slabs, and justifying the many plasma phenomena such as particle accelerations and induced fields.
Dispersion and energy conservation relations of surface waves in semi-infinite plasma
International Nuclear Information System (INIS)
Atanassov, V.
1981-01-01
The hydrodynamic theory of surface wave propagation in semi-infinite homogeneous isotropic plasma is considered. Explicit linear surface wave solutions are given for the electric and magnetic fields, charge and current densities. These solutions are used to obtain the well-known dispersion relations and, together with the general energy conservation equation, to find appropriate definitions for the energy and the energy flow densities of surface waves. These densities are associated with the dispersion relation and the group velocity by formulae similar to those for bulk waves in infinite plasmas. Both cases of high-frequency (HF) and low-frequency (LF) surface waves are considered. (author)
Pion-pair formation and the pion dispersion relation in a hot pion gas
Energy Technology Data Exchange (ETDEWEB)
Chanfay, G. [Lyon-1 Univ., 69 - Villeurbanne (France). Inst. de Physique Nucleaire; Alm, T. [Rostock Univ. (Germany); Schuck, P. [Grenoble-1 Univ., 38 (France). Inst. des Sciences Nucleaires; Welke, G. [Wayne State Univ., Detroit, MI (United States). Dept. of Physics and Astronomy
1996-09-01
The possibility of pion-pair formation in a hot pion gas, based on the bosonic gap equation, is pointed out and discussed in detail. The critical temperature for condensation of pion pairs (Evans-Rashind transition) is determined as a function of the pion density. As for fermions, this phase transition is signaled by the appearance of a pole in the two-particle propagator. In Bose systems there exists a second, lower critical temperature, associated with the appearance of the single-particle condensate. Between the two critical temperatures the pion dispersion relation changes from the usual quasiparticle dispersion to a Bogoliubov-like dispersion relation at low momenta. This generalizes the non-relativistic results for an attractive Bose gas by Evans et al. Possible consequences for the inclusive pion spectra measured in heavy-ion collisions at ultra-relativistic energies are discussed. 21 refs.
TFTR L mode energy confinement related to deuterium influx
International Nuclear Information System (INIS)
Strachan, J.D.
1999-01-01
Tokamak energy confinement scaling in TFTR L mode and supershot regimes is discussed. The main result is that TFTR L mode plasmas fit the supershot scaling law for energy confinement. In both regimes, plasma transport coefficients increased with increased edge deuterium influx. The common L mode confinement scaling law on TFTR is also inversely proportional to the volume of wall material that is heated to a high temperature, possibly the temperature at which the deuterium sorbed in the material becomes detrapped and highly mobile. The deuterium influx is increased by: (a) increased beam power due to a deeper heated depth in the edge components and (b) decreased plasma current due to an increased wetted area as governed by the empirically observed dependence of the SOL width upon plasma current. (author). Letter-to-the-editor
Dispersion relation for elastic electron-hydrogen atom forward scattering amplitude
International Nuclear Information System (INIS)
Kuchiev, M.Yu.; Amusia, M.Ya.
1978-01-01
The elastic e+H forward scattering amplitude is an analytical function in the complex energy E plane and has two cuts on the real axis: 0 < E < infinity and -infinity < E < -B, B being the hydrogen ionization potential. The e+H dispersion relation contains two integrals over the right and left cuts. (Auth.)
Dispersion relation analysis of the neutral kaon regeneration amplitude in carbon
Angelopoulos, Angelos; Locher, M P; Markushin, V E; Aslanides, Elie; Backenstoss, Gerhard; Bargassa, P; Behnke, O; Benelli, A; Bertin, V; Blanc, F; Bloch, P; Carlson, P J; Carroll, M; Cawley, E; Chertok, M B; Danielsson, M; Dejardin, M; Derré, J; Ealet, A; Eleftheriadis, C; Faravel, L; Festcher, W; Fidecaro, Maria; Filipcic, A; Francis, D; Fry, J; Gabathuler, Erwin; Gamet, R; Gerber, H J; Go, A; Haselden, A; Hayman, P J; Henry-Coüannier, F; Hollander, R W; Jon-And, K; Kettle, P R; Kokkas, P; Kreuger, R; Le Gac, R; Leimgruber, F; Mandic, I; Manthos, N; Marel, Gérard; Mikuz, M; Miller, J; Montanet, François; Müller, A; Nakada, Tatsuya; Pagels, B; Papadopoulos, I M; Pavlopoulos, P; Polivka, G; Rickenbach, R; Roberts, B L; Ruf, T; Schäfer, M; Schaller, L A; Schietinger, T; Schopper, A; Tauscher, Ludwig; Thibault, C; Touchard, F; Touramanis, C; van Eijk, C W E; Vlachos, S; Weber, P; Wigger, O; Wolter, M; Zavrtanik, D; Zimmerman, D
1999-01-01
We apply a forward dispersion relation to the regeneration amplitude for kaon scattering on /sup 12/C using all available data. The CPLEAR data at low energies allow the determination of the net contribution from the subthreshold $9 region which turns out to be much smaller than earlier evaluations, solving a long standing puzzle. (29 refs).
The dispersion relation of charge and current compensated relativistic electron beam-plasma system
International Nuclear Information System (INIS)
Vrba, P.; Schroetter, J.; Jarosova, P.; Koerbel, S.
1978-01-01
The unstable regions of relativistic electron beam-plasma system were determined by analysing the general dispersion relation numerically. The external parameters were varied to ensure more effective instability excitations. The full charge- and current compensation presumptions lead to the new synchronism predictions. The slow space charge wave and slow cyclotron wave of the return current are synchronous with the plasma ion wave. (author)
Relations among the crack growth modes resulting from tensor splitting
Czech Academy of Sciences Publication Activity Database
Kafka, Vratislav
2015-01-01
Roč. 60, č. 4 (2015), s. 319-335 ISSN 0001-7043 Institutional support: RVO:68378297 Keywords : fracture mechanics * combination of crack-growth modes * non-local effect * tensor splitting Subject RIV: JL - Materials Fatigue, Friction Mechanics http://journal.it.cas.cz/60(15)4-Contents/60(15)4a.pdf
Edge Localized Modes: resent experimental findings and related issues
International Nuclear Information System (INIS)
Kamiya, K.
2007-01-01
Edge Localized Mode (ELM) measurements in the tokamaks, including JT-60U, DIII-D, ASDEX-U and JET, are reviewed. An ELMy H-mode operation having Type-I ELMs is nominated as the reference inductive operational scenario for ITER (Q DT =10), which is normally observed for the best performing H-mode in many tokamaks,. However, the ELMs produce pulsed heat and particle fluxes that can lead to a rapid erosion of the divertor plate. It is estimated that the peak heat flux to the divertor would reduce the lifetime of the divertor to several hundred shots in ITER (e.g. an acceptable divertor lifetime could be realized only by an upper limit of ELM energy loss normalized by pedestal stored energy, ΔDW ELM /W ped ∼ 5-6%). Approaches to control the Type-I ELMs, such as '' Ergodization '' on DIII-D, '' Pace making by a shallow pellet injection '' on ASDEX-U, '' Vertical motion '' on TCV, have been successfully demonstrated in many tokamaks. On the other hand, finding alternative scenarios to Type-I ELMy H-mode operation are also a key area of research for current tokamaks. Specifically, '' Quiescent H-mode (QH-mode) '' on DIII-D, ASDEX-U and JT-60U, and '' Grassy ELMs '' on JT-60U demonstrated a high confinement (being comparable to that of Type-I ELMy H-mode plasmas at similar parameters) in the absence of large, ELM induced, transient heat/particle fluxes to the divertor targets. ELM dynamics measurements in the SOL at the midplane show large, rapid variations of the SOL parameters. Recent data from a fast resolved measurements, such as scanning probe, radial interferometer chord, BES and tangentially viewing fast-gated camera at the midplane, suggest a filamentary structure of the perturbation with fast radial propagation in later phases and parallel propagation of the ELM pulse at around the sound speed of pedestal ions. The results are qualitatively consistent with nonlinear ballooning theory, although a more quantitative physics understanding, including detailed
DEFF Research Database (Denmark)
Israelsen, Stine Møller; Usuga Castaneda, Mario A.; Rottwitt, Karsten
2017-01-01
By knowing the electric field distribution of a guided mode in an optical fiber, we are able to evaluate the group velocity dispersion in a weakly guiding step-index fiber for a pure mode in the LP0X, LP1X, and LP2X mode groups independently of the fiber length. We demonstrate the method numerica...
Chiral symmetry and dispersion relations: from $\\pi \\pi$ scattering to hadronic light-by-light.
CERN. Geneva
2018-01-01
Chiral symmetry provides strong constraints on hadronic matrix elements at low energy, which are most efficiently derived with chiral perturbation theory. As an effective quantum field theory the latter also accounts for rescattering or unitarity effects, albeit only perturbatively, via the loop expansion. In cases where rescattering effects are important it becomes necessary to go beyond the perturbative expansion, e.g. by using dispersion relations. A matching between the chiral and the dispersive representation provides in several cases results of high precision. I will discuss this approach with the help of a few examples, like $\\pi \\pi$ scattering (which has been tested successfully by CERN experiments like NA48/2 and DIRAC), $\\eta \\to 3 \\pi$ and the hadronic light-by-light contribution to $(g-2)_\\mu$. For the latter quantity the implementation of the dispersive approach has opened up the way to a model-independent calculation and the concrete possibility to significantly reduce the theoretical uncertain...
International Nuclear Information System (INIS)
Mittal, R.; Chaplot, S.L.; Parthasarathy, R.; Bull, M.J.; Harris, M.J.
2000-01-01
The coherent inelastic neutron scattering technique is used for the measurements of phonon dispersion relation in a geophysically important mineral zircon using PRISMA spectrometer as ISIS, UK. Lattice dynamical calculations of the phonon dispersion relation are carried out using a shell model. The one-phonon structure factors are calculated for selecting the Bragg points for the measurements and assignment of phonons to different branches. The calculations are in good agreement with the measured phonon dispersion relation. (author)
DEFF Research Database (Denmark)
Marini, Lorenzo; Bruun, Hans Henrik; Heikkinen, Risto
2012-01-01
Aim Habitat fragmentation is a major driver of biodiversity loss but it is insufficiently known how much its effects vary among species with different life-history traits; especially in plant communities, the understanding of the role of traits related to species persistence and dispersal in dete...... rural landscapes in NW Europe, mitigating the spatial isolation of remaining grasslands should be accompanied by restoration measures aimed at improving habitat quality for low competitors, abiotically dispersed and perennial, clonal species.......Aim Habitat fragmentation is a major driver of biodiversity loss but it is insufficiently known how much its effects vary among species with different life-history traits; especially in plant communities, the understanding of the role of traits related to species persistence and dispersal...... in determining dynamics of species communities in fragmented landscapes is still limited. The primary aim of this study was to test how plant traits related to persistence and dispersal and their interactions modify plant species vulnerability to decreasing habitat area and increasing isolation. Location Five...
Ion-cyclotron modes in weakly relatavistic plasmas
International Nuclear Information System (INIS)
Venugopal, C.; Kurian, P.J.; Renuka, G.
1994-01-01
We derive a dispersion relation for the perpendicular propagation of ion-cyclotron waves around the ion gyrofrequency Ω + in a weakly relativistic, anisotropic Maxwellian plasma. Using an ordering parameter ε, we separated out two dispersion relations, one of which is independent of the relativistic terms, while the other depends sensitively on them. The solutions of the former dispersion relation yield two modes: a low-frequency (LF) mode with a frequency ω + and a high-frequency (HF) mode with ω > Ω + . The plasma is stable to the propagation of these modes. The latter dispersion relation yields a new LF mode in addition to the modes supported by the non-relativistic dispersion relation. The two LF modes can coalesce to make the plasma unstable. These results are also verified numerically using a standard root solver. (author)
Directory of Open Access Journals (Sweden)
S.-D. Zhang
2000-10-01
Full Text Available By analyzing the results of the numerical simulations of nonlinear propagation of three Gaussian gravity-wave packets in isothermal atmosphere individually, the nonlinear effects on the characteristics of gravity waves are studied quantitatively. The analyses show that during the nonlinear propagation of gravity wave packets the mean flows are accelerated and the vertical wavelengths show clear reduction due to nonlinearity. On the other hand, though nonlinear effects exist, the time variations of the frequencies of gravity wave packets are close to those derived from the dispersion relation and the amplitude and phase relations of wave-associated disturbance components are consistent with the predictions of the polarization relation of gravity waves. This indicates that the dispersion and polarization relations based on the linear gravity wave theory can be applied extensively in the nonlinear region.Key words: Meteorology and atmospheric dynamics (middle atmosphere dynamics; waves and tides
Dispersion Models to Forecast Traffic-related Emissions in Urban Areas
Directory of Open Access Journals (Sweden)
Davide Scannapieco
2011-11-01
Full Text Available Down the centuries, a direct link had been developed between increase in mobility and increase in wealth. On the other hand, air emission of greenhouse gases (GHG due to vehicles equipped with internal combustion engines can be regarded as a negative pressure over the environment. In the coming decades, road transport is likely to remain a significant contributor to air pollution in cities. Many urban trips cover distances of less than 6 km. Since the effectiveness of catalytic converters in the initial minutes of engine operation is small, the average emission per distance driven is very high in urban areas. Also, poorly maintained vehicles that lack exhaust aftertreatment systems are responsible for a major part of pollutant emissions. Therefore in urban areas, where higher concentrations of vehicles can be easily found, air pollution represents a critical issue, being it related with both environment and human health protection: in truth, research in recent decades consistently indicates the adverse effects of outdoor air pollution on human health, and the evidence points to air pollution stemming from transport as an important contributor to these effects. Several institutions (EEA, USEPA, etc. focused their interest in dispersion models because of their potential effectiveness to forecast atmospheric pollution. Furthermore, air micropollutants such as Polycyclic Aromatic Compounds (PAH and Metallic Trace Elements (MTE are traffic-related and although very low concentrations their dispersion is a serious issue. However, dispersion models are usefully implemented to better manage this estimation problem. Nonetheless, policy makers and land managers have to deal with model selection, taking into account that several dispersion models are available, each one of them focused on specific goals (e.g., wind transport of pollutants, land morphology implementation, evaluation of micropollutants transport, etc.; a further aspect to be considered is
Sociality Mental Modes Modulate the Processing of Advice-Giving: An Event-Related Potentials Study
Directory of Open Access Journals (Sweden)
Jin Li
2018-02-01
Full Text Available People have different motivations to get along with others in different sociality mental modes (i.e., communal mode and market mode, which might affect social decision-making. The present study examined how these two types of sociality mental modes affect the processing of advice-giving using the event-related potentials (ERPs. After primed with the communal mode and market mode, participants were instructed to decide whether or not give an advice (profitable or damnous to a stranger without any feedback. The behavioral results showed that participants preferred to give the profitable advice to the stranger more slowly compared with the damnous advice, but this difference was only observed in the market mode condition. The ERP results indicated that participants demonstrated more negative N1 amplitude for the damnous advice compared with the profitable advice, and larger P300 was elicited in the market mode relative to both the communal mode and the control group. More importantly, participants in the market mode demonstrated larger P300 for the profitable advice than the damnous advice, whereas this difference was not observed at the communal mode and the control group. These findings are consistent with the dual-process system during decision-making and suggest that market mode may lead to deliberate calculation for costs and benefits when giving the profitable advice to others.
International Nuclear Information System (INIS)
Bifano, Michael F P; Kaul, Pankaj B; Prakash, Vikas
2010-01-01
This paper reports dependency of specific heat and ballistic thermal conductance on cross-sectional geometry (tube versus rod) and size (i.e., diameter and wall thickness), in free-standing isotropic non-metallic crystalline nanostructures. The analysis is performed using dispersion relations found by numerically solving the Pochhammer-Chree frequency equation for a tube. Estimates for the allowable phonon dispersion relations within the crystal lattice are obtained by modifying the elastic acoustic dispersion relations so as to account for the discrete nature of the material's crystal lattice. These phonon dispersion relations are then used to evaluate the specific heat and ballistic thermal conductance in the nanostructures as a function of the nanostructure geometry and size. Two major results are revealed in the analysis: increasing the outer diameter of a nanotube while keeping the ratio of the inner to outer tube radius (γ) fixed increases the total number of available phonon modes capable of thermal population. Secondly, decreasing the wall thickness of a nanotube (i.e., increasing γ) while keeping its outer diameter fixed, results in a drastic decrease in the available phonon mode density and a reduction in the frequency of the longitudinal and flexural acoustic phonon modes in the nanostructure. The dependency of the nanostructure's specific heat on temperature indicates 1D, 2D, and 3D geometric phonon confinement regimes. Transition temperatures for each phonon confinement regime are shown to depend on both the nanostructure's wall thickness and outer radius. Compared to nanowires (γ = 0), the frequency reduction of acoustic phonon modes in thinner walled nanotubes (γ = 0.96) is shown to elevate the ballistic thermal conductance of the thin-walled nanotube between 0.2 and 150 K. At 20 K, the ballistic thermal conductance of the thin-walled nanotube (γ = 0.96) becomes 300% greater than that of a solid nanowire. For temperatures above 150 K, the trend
Scaling relations for a beam-deflecting TM110 mode in an asymmetric cavity
International Nuclear Information System (INIS)
Takeda, H.
1989-01-01
A deflecting mode in an rf cavity caused by an aperture of the coupling hole from a waveguide is studied. If the coupling hole was a finite size, the rf modes in the cavity can be distorted. We consider the distorted mode as a sum of the accelerating mode, and the deflecting mode. The finite-size coupling hole can be considered as radiating dipole sources in a closed cavity. Following the prescription given by H. Bethe, the relative strength of the deflecting mode TM 110 to the accelerating TM 010 mode is calculated by decomposing the dipole source field into cavity eigenmodes. Scaling relations are obtained as a function of the coupling hole radius. 2 refs., 6 figs
Study of Phonon Dispersion Relations in Cuprous Oxide by Inelastic Neutron Scattering
DEFF Research Database (Denmark)
Beg, M. M.; Shapiro, S. M.
1976-01-01
Phonon dispersion relations in Cu2O have been studied at 20°C using inelastic neutron scattering. Seven acoustic branches and twelve optical branches have been studied in detail in the three symmetry directions [00ζ], [ζζ0], and [ζζζ] of the cubic lattice. Four of the six zone-center phonons have...... been observed and the assignments and energies are confirmed as Γ25=87±2 cm-1, Γ12′=105±3 cm-1, Γ15=146±1 cm-1, and Γ2′≈347 cm-1. The dispersion relations agree only qualitatively with the rigid-ion-model calculations. It is suggested that more detailed calculations may be performed in the light...
Spin-wave dispersion relations in disordered Fe-V alloys
International Nuclear Information System (INIS)
Nakai, Y.; Schibuya, N.; Kunitomi, N.; Wakabayashi, N.; Cooke, J.F.
1982-01-01
The spin-wave dispersion relations of the ferromagnetic disordered alloys Fe/sub 1-x/V/sub x/(x = 0.076, 0.135, 0.160, and 0.187) were studied by means of the inelastic scattering of neutrons. The observed dispersion relations are adequately represented by the power law, E = Dq 2 (1-βq 2 ), in a wide energy range up to 80 meV. The concentration dependence of the exchange stiffness constant D shows good agreement with previous results obtained by means of the small-angle scattering of neutrons and by the analysis of the temperature dependence of the bulk magnetization. The observed results can be explained by the Heisenberg model and, to some extent, by the itinerant-electron model
On the Sensitivity of Neutrino Telescopes to a Modified Dispersion Relation
International Nuclear Information System (INIS)
Bustamante, M.; Gago, A. M.; Bazo, J. L.; Miranda, O. G.
2008-01-01
We consider a modified dispersion relation and its effect on the flavour ratios of high-energy neutrinos originated at distant astrophysical sources such as active galactic nuclei. This dispersion relation arise naturally in different new physics (NP) effects such as violation of CPT invariance, of the equivalence principle and of Lorentz invariance. It is a common notion in the literature that by using the flux of high-energy neutrinos expected from distant astrophysical sources, the sensitivity to possible NP effects may be improved beyond the current bounds. However, performing a realistic analysis that takes into account the expected number of events in future neutrino telescopes, we find that the average detected flavour ratios with and without the inclusion of new physics have essentially the same value, making difficult to obtain an improved bound for this type of new physics
Rainbows without unicorns: metric structures in theories with modified dispersion relations
International Nuclear Information System (INIS)
Lobo, Iarley P.; Loret, Niccolo; Nettel, Francisco
2017-01-01
Rainbow metrics are a widely used approach to the metric formalism for theories with modified dispersion relations. They have had a huge success in the quantum gravity phenomenology literature, since they allow one to introduce momentum-dependent space-time metrics into the description of systems with a modified dispersion relation. In this paper, we introduce the reader to some realizations of this general idea: the original rainbow metrics proposal, the momentum-space-inspired metric and a Finsler geometry approach. As the main result of this work we also present an alternative definition of a four-velocity dependent metric which allows one to handle the massless limit. This paper aims to highlight some of their properties and how to properly describe their relativistic realizations. (orig.)
Rainbows without unicorns: metric structures in theories with modified dispersion relations
Lobo, Iarley P.; Loret, Niccoló; Nettel, Francisco
2017-07-01
Rainbow metrics are a widely used approach to the metric formalism for theories with modified dispersion relations. They have had a huge success in the quantum gravity phenomenology literature, since they allow one to introduce momentum-dependent space-time metrics into the description of systems with a modified dispersion relation. In this paper, we introduce the reader to some realizations of this general idea: the original rainbow metrics proposal, the momentum-space-inspired metric and a Finsler geometry approach. As the main result of this work we also present an alternative definition of a four-velocity dependent metric which allows one to handle the massless limit. This paper aims to highlight some of their properties and how to properly describe their relativistic realizations.
Rainbows without unicorns: metric structures in theories with modified dispersion relations
Energy Technology Data Exchange (ETDEWEB)
Lobo, Iarley P. [Universita ' ' La Sapienza' ' , Dipartimento di Fisica, Rome (Italy); ICRANet, Pescara (Italy); CAPES Foundation, Ministry of Education of Brazil, Brasilia (Brazil); Universidade Federal da Paraiba, Departamento de Fisica, Joao Pessoa, PB (Brazil); INFN Sezione Roma 1 (Italy); Loret, Niccolo [Ruder Boskovic Institute, Division of Theoretical Physics, Zagreb (Croatia); Nettel, Francisco [Universita ' ' La Sapienza' ' , Dipartimento di Fisica, Rome (Italy); Universidad Nacional Autonoma de Mexico, Instituto de Ciencias Nucleares, Mexico (Mexico); INFN Sezione Roma 1 (Italy)
2017-07-15
Rainbow metrics are a widely used approach to the metric formalism for theories with modified dispersion relations. They have had a huge success in the quantum gravity phenomenology literature, since they allow one to introduce momentum-dependent space-time metrics into the description of systems with a modified dispersion relation. In this paper, we introduce the reader to some realizations of this general idea: the original rainbow metrics proposal, the momentum-space-inspired metric and a Finsler geometry approach. As the main result of this work we also present an alternative definition of a four-velocity dependent metric which allows one to handle the massless limit. This paper aims to highlight some of their properties and how to properly describe their relativistic realizations. (orig.)
Correction of Cardy–Verlinde formula for Fermions and Bosons with modified dispersion relation
Energy Technology Data Exchange (ETDEWEB)
Sadatian, S. Davood, E-mail: sd-sadatian@um.ac.ir; Dareyni, H.
2017-05-15
Cardy–Verlinde formula links the entropy of conformal symmetry field to the total energy and its Casimir energy in a D-dimensional space. To correct black hole thermodynamics, modified dispersion relation can be used which is proposed as a general feature of quantum gravity approaches. In this paper, the thermodynamics of Schwarzschild four-dimensional black hole is corrected using the modified dispersion relation for Fermions and Bosons. Finally, using modified thermodynamics of Schwarzschild four-dimensional black hole, generalization for Cardy–Verlinde formula is obtained. - Highlights: • The modified Cardy–Verlinde formula obtained using MDR for Fermions and Bosons. • The modified entropy of the black hole used to correct the Cardy–Verlinde formula. • The modified entropy of the CFT has been obtained.
$K^{\\pm}n$ forward dispersion relations and the KN$\\Sigma$ coupling constant
Baillon, Paul; Ferro-Luzzi, M; Jenni, Peter; Perreau, J M; Tripp, R D; Ypsilantis, Thomas; Déclais, Y; Séguinot, Jacques
1976-01-01
Recent measurements of the K/sup -/n forward scattering amplitude at 1.2, 1.4, 2.6 GeV/c are used in a once-subtracted dispersion relation to determine the value of the KN Sigma coupling constant. The result is g/sub Sigma //sup 2/=1.9+or-3.2, in agreement with the prediction of the SU(3) theory.
Dispersion relation of Raman FEL with helical Wiggler and ion channel
International Nuclear Information System (INIS)
Hosseinalinezhad, M.; Bahmani, M.; Hasanbeigi, A.; Salehkoutahi, M.
2012-01-01
In this paper the theory of free electron laser with helical wiggler and ion channel guiding has been presented. The equations of motion for an electron have been analyzed. A formula for the dispersion relation is then derived in the low-gain-per-pass limit. The results of a numerical study of the growth rate enhancement due to the ion channel are presented and discussed.
Dispersion relation approach to sub-barrier heavy ion fusion reactions
International Nuclear Information System (INIS)
Franzin, V.L.M.; Hussein, M.S.
1986-07-01
With the aid of an inverse dispersion relation, which gives the imaginary part of the fusion inclusive polarization potential (IPP) in terms of the principal part integral involving the real part of the IPP, the sub-barrier fusion of heavy ions is discussed. The system 16 O+ A Sm is taken as an example. The reactive content of the extracted IPP is analysed within the coupled channels theory. (Author) [pt
The dispersion relation for the forward elastic electron-atom scattering amplitude
International Nuclear Information System (INIS)
Amusia, M.Y.
1978-01-01
The analytical properties of forward elastic electron-atom scattering amplitude are discussed. It is noted that the occurrence of exchange between the incoming and atomic electrons leads to the appearance of a number of singularities on the negative real axis in the complex energy plane. The conclusion is drawn that the dispersion relation for the forward electron-atom scattering amplitude should also include an integration over the negative energy from - I to - infinity, where I is the ionization potential. (author)
Energy Technology Data Exchange (ETDEWEB)
Wang Ru [Quantitative Light Imaging Laboratory, Department of Mechanical Science and Engineering, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States); Wang Zhuo; Leigh, Joe; Popescu, Gabriel [Quantitative Light Imaging Laboratory, Department of Electrical and Computer Engineering, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States); Sobh, Nahil [Beckman Institute for Advanced Science and Technology, Department of Civil and Environmental Engineering, and Department of Mechanical Engineering and Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States); Millet, Larry; Gillette, Martha U [Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States); Levine, Alex J, E-mail: alevine@chem.ucla.edu, E-mail: gpopescu@illinois.edu [Department of Chemistry and Biochemistry and Department of Physics and Astronomy, University of California at Los Angeles, Los Angeles, CA 90095 (United States)
2011-09-21
We studied the active transport of intracellular components along neuron processes using a new method developed in our laboratory: dispersion-relation phase spectroscopy. This method is able to quantitatively map spatially the heterogeneous dynamics of the concentration field of the cargos at submicron resolution without the need for tracking individual components. The results in terms of density correlation function reveal that the decay rate is linear in wavenumber, which is consistent with a narrow Lorentzian distribution of cargo velocity. (paper)
Calculation of the Green functions by the coupling constant dispersion relations
International Nuclear Information System (INIS)
Bogomalny, E.B.
1977-01-01
The discontinuities of the Green functions on the cut in the complex plane of the coupling constant are calculated by the steepest descent method. The saddle points are given by the solutions of the classical field equations at those values of the coupling constant for which the classical theory has no ground state. The Green functions at the physical values of the coupling constant are determined by dispersion relations. (Auth.)
International Nuclear Information System (INIS)
Chen, C.
1994-01-01
A Pierce-type dispersion relation is derived for the interaction of an intense relativistic electron beam with a cylindrical slow-wave structure of arbitrary corrugation depth. It is shown that near a resonance, the Pierce parameter can be expressed in terms of the vacuum dispersion function and the beam current. The dispersion relation is valid in both the low-current (Compton) regime and the high-current (Raman) regime. The dispersion characteristics of the interaction, such as the linear instability growth rate and bandwidth, are analyzed for both regimes
Subtracted Dispersion Relations for In-medium Meson Correlators in QCD Sum Rules
Energy Technology Data Exchange (ETDEWEB)
Florkowski, W; Broniowski, W [The H. Niewodniczanski Institute of Nuclear Physics, Cracow (Poland)
1999-01-01
We analyze subtracted dispersion relations for meson correlators at finite baryon density and temperature. Such relations are needed for QCD sum rules. We point out that importance of scattering terms, as well as finite, well-defined subtraction constants. Both are necessary for consistency, in particular for the equality of the longitudinal and transverse correlators in the limit of the vanishing three-momentum of mesons relative to the medium. We present detailed calculations in various mesonic channels of the Fermi gas of nucleons. (author)
Black hole radiation with modified dispersion relation in tunneling paradigm: Static frame
Directory of Open Access Journals (Sweden)
Jun Tao
2017-09-01
Full Text Available To study possible deviations from the Hawking's prediction, we assume that the dispersion relations of matter fields are modified at high energies and use the Hamilton–Jacobi method to investigate the corresponding effects on the Hawking radiation in this paper. The preferred frame is the static frame of the black hole. The dispersion relation adopted agrees with the relativistic one at low energies but is modified near the Planck mass mp. We calculate the corrections to the Hawking temperature for massive and charged particles to O(mp−2 and massless and neutral particles to all orders. Our results suggest that the thermal spectrum of radiations near horizon is robust, e.g. corrections to the Hawking temperature are suppressed by mp. After the spectrum of radiations near the horizon is obtained, we use the brick wall model to compute the thermal entropy of a massless scalar field near the horizon of a 4D spherically symmetric black hole. We find that the subleading logarithmic term of the entropy does not depend on how the dispersion relations of matter fields are modified. Finally, the luminosities of black holes are computed by using the geometric optics approximation.
International Nuclear Information System (INIS)
Bhattacharya, Sayak; Shah, Kushal
2015-01-01
The analytical dispersion relation of spoof surface plasmon (SSP) is known only in the low-frequency limit and thus cannot be used to describe various practically important characteristics of SSP in the high-frequency limit (such as multimodal nature, anisotropic propagation, self-collimation). In this article, we consider a square lattice of holes made on a perfect electric conductor and derive a closed form expression of the SSP dispersion relation in the high-frequency limit using a tight binding model. Instead of using prior knowledge of the band diagram along the entire first Brillouin zone (BZ) edge, we analytically determine the hopping parameters by using the eigenfrequencies only at the three high-symmetry points of the square lattice. Using this dispersion relation, we derive an expression for the self-collimation frequency of SSP. We show that this analytical formulation is also applicable to dielectric photonic crystals and can be used to predict the frequencies corresponding to centimetre-scale supercollimation and second band self-collimation in these structures. Finally, we show that our analytical results are in agreement with the simulation results for both SSP and photonic crystals. (paper)
Accurate mode characterization of two-mode optical fibers by in-fiber acousto-optics.
Alcusa-Sáez, E; Díez, A; Andrés, M V
2016-03-07
Acousto-optic interaction in optical fibers is exploited for the accurate and broadband characterization of two-mode optical fibers. Coupling between LP 01 and LP 1m modes is produced in a broadband wavelength range. Difference in effective indices, group indices, and chromatic dispersions between the guided modes, are obtained from experimental measurements. Additionally, we show that the technique is suitable to investigate the fine modes structure of LP modes, and some other intriguing features related with modes' cut-off.
de Waal, C; Rodger, J G; Anderson, B; Ellis, A G
2014-05-01
Dispersal and breeding system traits are thought to affect colonization success. As species have attained their present distribution ranges through colonization, these traits may vary geographically. Although several theories predict associations between dispersal ability, selfing ability and the relative position of a population within its geographic range, there is little theoretical or empirical consensus on exactly how these three variables are related. We investigated relationships between dispersal ability, selfing ability and range position across 28 populations of 13 annual, wind-dispersed Asteraceae species from the Namaqualand region of South Africa. Controlling for phylogeny, relative dispersal ability--assessed from vertical fall time of fruits--was positively related to an index of autofertility--determined from hand-pollination experiments. These findings support the existence of two discrete syndromes: high selfing ability associated with good dispersal and obligate outcrossing associated with lower dispersal ability. This is consistent with the hypothesis that selection for colonization success drives the evolution of an association between these traits. However, no general effect of range position on dispersal or breeding system traits was evident. This suggests selection on both breeding system and dispersal traits acts consistently across distribution ranges. © 2014 The Authors. Journal of Evolutionary Biology © 2014 European Society For Evolutionary Biology.
1982-11-01
time of application. Such designs were probably influenced by the ready availabilit " 51 of fire-fighting hoses on ships and tugs; the water stream not...8217 I I1 ---- i . . .. . IIII . . . I I PREFACE The use of chemicals for the dispersal of oil spilled on water has been the subject of discussion (and of...20 Oil Type, Weathering and Emulsification.. 20 Slick Thickness .......................... 28 Water Temperature
Directory of Open Access Journals (Sweden)
Shunsuke Kono
2015-09-01
Full Text Available We investigated the spectral and temporal characteristics of blue-violetfemtosecond optical pulses generated by a passively mode-locked GaInN laser diode ina dispersion-compensated external cavity. The output optical pulses at 400 nm wereanalyzed in detail by intensity auto- and cross-correlation measurements using secondharmonic generation on the surface of a β-BaB2O4 crystal. The obtained results clarifiedwavelength-dependent chirp characteristics of the optical pulses. The analysis suggestedthat a large frequency shift due to saturation in the saturable absorber and gain sectionsplayed an important role in the generation of femtosecond optical pulses.
Measurement of average density and relative volumes in a dispersed two-phase fluid
Sreepada, Sastry R.; Rippel, Robert R.
1992-01-01
An apparatus and a method are disclosed for measuring the average density and relative volumes in an essentially transparent, dispersed two-phase fluid. A laser beam with a diameter no greater than 1% of the diameter of the bubbles, droplets, or particles of the dispersed phase is directed onto a diffraction grating. A single-order component of the diffracted beam is directed through the two-phase fluid and its refraction is measured. Preferably, the refracted beam exiting the fluid is incident upon a optical filter with linearly varing optical density and the intensity of the filtered beam is measured. The invention can be combined with other laser-based measurement systems, e.g., laser doppler anemometry.
EXPERIMENTAL DETERMINATION OF WHISTLER WAVE DISPERSION RELATION IN THE SOLAR WIND
Energy Technology Data Exchange (ETDEWEB)
Stansby, D.; Horbury, T. S.; Chen, C. H. K.; Matteini, L., E-mail: david.stansby14@imperial.ac.uk [Department of Physics, Imperial College London, London SW7 2AZ (United Kingdom)
2016-09-20
The origins and properties of large-amplitude whistler wavepackets in the solar wind are still unclear. In this Letter, we utilize single spacecraft electric and magnetic field waveform measurements from the ARTEMIS mission to calculate the plasma frame frequency and wavevector of individual wavepackets over multiple intervals. This allows direct comparison of experimental measurements with theoretical dispersion relations to identify the observed waves as whistler waves. The whistlers are right-hand circularly polarized, travel anti-sunward, and are aligned with the background magnetic field. Their dispersion is strongly affected by the local electron parallel beta in agreement with linear theory. The properties measured are consistent with the electron heat flux instability acting in the solar wind to generate these waves.
Relation between the behaviors of P-wave and QT dispersions in elderly patients with heart failure
Directory of Open Access Journals (Sweden)
Szlejf Cláudia
2002-01-01
Full Text Available OBJECTIVE: To assess the relation between P-wave and QT dispersions in elderly patients with heart failure. METHODS: Forty-seven elderly patients (75.6±6 years with stable heart failure in NYHA functional classes II or III and with ejection fractions of 37±6% underwent body surface mapping to analyze P-wave and QT dispersions. The degree of correlation between P-wave and QT dispersions was assessed, and P-wave dispersion values in patients with QT dispersion greater than and smaller than 100 ms were compared. RESULTS: The mean values of P-wave and QT dispersions were 54±14 ms and 68±27 ms, respectively. The correlation between the 2 variables was R=0.41 (p=0.04. In patients with QT dispersion values > 100 ms, P-wave dispersion was significantly greater than in those with QT dispersion values < 100 ms (58±16 vs 53±12 ms, p=0.04 . CONCLUSION: Our results suggest that, in elderly patients with heart failure, a correlation between the values of P-wave and QT dispersions exists. These findings may have etiopathogenic, pathophysiologic, prognostic, and therapeutic implications, which should be investigated in other studies.
Diffusion related isotopic fractionation effects with one-dimensional advective–dispersive transport
Energy Technology Data Exchange (ETDEWEB)
Xu, Bruce S. [Civil Engineering Department, University of Toronto, 35 St George Street, Toronto, ON M5S 1A4 (Canada); Lollar, Barbara Sherwood [Earth Sciences Department, University of Toronto, 22 Russell Street, Toronto, ON M5S 3B1 (Canada); Passeport, Elodie [Civil Engineering Department, University of Toronto, 35 St George Street, Toronto, ON M5S 1A4 (Canada); Chemical Engineering and Applied Chemistry Department, University of Toronto, 200 College Street, Toronto, ON M5S 3E5 (Canada); Sleep, Brent E., E-mail: sleep@ecf.utoronto.ca [Civil Engineering Department, University of Toronto, 35 St George Street, Toronto, ON M5S 1A4 (Canada)
2016-04-15
Aqueous phase diffusion-related isotope fractionation (DRIF) for carbon isotopes was investigated for common groundwater contaminants in systems in which transport could be considered to be one-dimensional. This paper focuses not only on theoretically observable DRIF effects in these systems but introduces the important concept of constraining “observable” DRIF based on constraints imposed by the scale of measurements in the field, and on standard limits of detection and analytical uncertainty. Specifically, constraints for the detection of DRIF were determined in terms of the diffusive fractionation factor, the initial concentration of contaminants (C{sub 0}), the method detection limit (MDL) for isotopic analysis, the transport time, and the ratio of the longitudinal mechanical dispersion coefficient to effective molecular diffusion coefficient (D{sub mech}/D{sub eff}). The results allow a determination of field conditions under which DRIF may be an important factor in the use of stable carbon isotope measurements for evaluation of contaminant transport and transformation for one-dimensional advective–dispersive transport. This study demonstrates that for diffusion-dominated transport of BTEX, MTBE, and chlorinated ethenes, DRIF effects are only detectable for the smaller molar mass compounds such as vinyl chloride for C{sub 0}/MDL ratios of 50 or higher. Much larger C{sub 0}/MDL ratios, corresponding to higher source concentrations or lower detection limits, are necessary for DRIF to be detectable for the higher molar mass compounds. The distance over which DRIF is observable for VC is small (less than 1 m) for a relatively young diffusive plume (< 100 years), and DRIF will not easily be detected by using the conventional sampling approach with “typical” well spacing (at least several meters). With contaminant transport by advection, mechanical dispersion, and molecular diffusion this study suggests that in field sites where D{sub mech}/D{sub eff} is
Diffusion related isotopic fractionation effects with one-dimensional advective–dispersive transport
International Nuclear Information System (INIS)
Xu, Bruce S.; Lollar, Barbara Sherwood; Passeport, Elodie; Sleep, Brent E.
2016-01-01
Aqueous phase diffusion-related isotope fractionation (DRIF) for carbon isotopes was investigated for common groundwater contaminants in systems in which transport could be considered to be one-dimensional. This paper focuses not only on theoretically observable DRIF effects in these systems but introduces the important concept of constraining “observable” DRIF based on constraints imposed by the scale of measurements in the field, and on standard limits of detection and analytical uncertainty. Specifically, constraints for the detection of DRIF were determined in terms of the diffusive fractionation factor, the initial concentration of contaminants (C_0), the method detection limit (MDL) for isotopic analysis, the transport time, and the ratio of the longitudinal mechanical dispersion coefficient to effective molecular diffusion coefficient (D_m_e_c_h/D_e_f_f). The results allow a determination of field conditions under which DRIF may be an important factor in the use of stable carbon isotope measurements for evaluation of contaminant transport and transformation for one-dimensional advective–dispersive transport. This study demonstrates that for diffusion-dominated transport of BTEX, MTBE, and chlorinated ethenes, DRIF effects are only detectable for the smaller molar mass compounds such as vinyl chloride for C_0/MDL ratios of 50 or higher. Much larger C_0/MDL ratios, corresponding to higher source concentrations or lower detection limits, are necessary for DRIF to be detectable for the higher molar mass compounds. The distance over which DRIF is observable for VC is small (less than 1 m) for a relatively young diffusive plume (< 100 years), and DRIF will not easily be detected by using the conventional sampling approach with “typical” well spacing (at least several meters). With contaminant transport by advection, mechanical dispersion, and molecular diffusion this study suggests that in field sites where D_m_e_c_h/D_e_f_f is larger than 10, DRIF
Morakinyo, Tobi Eniolu; Lam, Yun Fat
2016-11-01
Numerical experiments involving street canyons of varying aspect ratio with traffic-induced pollutants (PM 2.5 ) and implanted trees of varying aspect ratio, leaf area index, leaf area density distribution, trunk height, tree-covered area, and tree planting pattern under different wind conditions were conducted using a computational fluid dynamics (CFD) model, ENVI-met. Various aspects of dispersion and deposition were investigated, which include the influence of various tree configurations and wind condition on dispersion within the street canyon, pollutant mass at the free stream layer and street canyon, and comparison between mass removal by surface (leaf) deposition and mass enhancement due to the presence of trees. Results revealed that concentration level was enhanced especially within pedestrian level in street canyons with trees relative to their tree-free counterparts. Additionally, we found a dependence of the magnitude of concentration increase (within pedestrian level) and decrease (above pedestrian level) due to tree configuration and wind condition. Furthermore, we realized that only ∼0.1-3 % of PM 2.5 was dispersed to the free stream layer while a larger percentage (∼97 %) remained in the canyon, regardless of its aspect ratio, prevailing wind condition, and either tree-free or with tree (of various configuration). Lastly, results indicate that pollutant removal due to deposition on leaf surfaces is potentially sufficient to counterbalance the enhancement of PM 2.5 by such trees under some tree planting scenarios and wind conditions.
Black hole radiation with modified dispersion relation in tunneling paradigm: free-fall frame
Energy Technology Data Exchange (ETDEWEB)
Wang, Peng; Yang, Haitang; Ying, Shuxuan [Sichuan University, Center for Theoretical Physics, College of Physical Science and Technology, Chengdu (China)
2016-01-15
Due to the exponential high gravitational red shift near the event horizon of a black hole, it might appear that the Hawking radiation would be highly sensitive to some unknown high energy physics. To study the effects of any unknown physics at the Planck scale on the Hawking radiation, the dispersive field theory models have been proposed, which are variations of Unruh's sonic black hole analogy. In this paper, we use the Hamilton-Jacobi method to investigate the dispersive field theory models. The preferred frame is the free-fall frame of the black hole. The dispersion relation adopted agrees with the relativistic one at low energy but is modified near the Planck mass m{sub p}. The corrections to the Hawking temperature are calculated for massive and charged particles to O(m{sub p}{sup -2}) and neutral and massless particles with λ = 0 to all orders. The Hawking temperature of radiation agrees with the standard one at the leading order. After the spectrum of radiation near the horizon is obtained, we use the brick wall model to compute the thermal entropy of a massless scalar field near the horizon of a 4D spherically symmetric black hole and a 2D one. Finally, the luminosity of a Schwarzschild black hole is calculated by using the geometric optics approximation. (orig.)
Reciprocity relations and the mode conversion-absorption equation with an inhomogeneous source term
International Nuclear Information System (INIS)
Cho, S.; Swanson, D.G.
1990-01-01
The fourth-order mode conversion equation is solved completely via the Green's function to include an inhomogeneous source term. This Green's function itself contains all the plasma responsive effects such as mode conversion and absorption, and can be used to describe the spontaneous emission. In the course of the analysis, the reciprocity relations between coupling parameters are proved
Directory of Open Access Journals (Sweden)
M S Islam
2010-03-01
Full Text Available Cross-phase modulation (XPM changes the state-of-polarization (SOP of the channels through nonlinear polarization rotation and induces nonlinear time dependent phase shift for polarization components that leads to amplitude modulation of the propagating waves in a wavelength division multiplexing (WDM system. Due to the presence of birefringence, the angle between the SOP changes randomly and as a result polarization mode dispersion (PMD causes XPM modulation amplitude fluctuation random in the perturbed channel. In this paper we analytically determine the probability density function of the random angle between the SOP of pump and probe, and evaluate the impact of polarization mode dispersion on XPM in terms of bit error rate, channel spacing etc for a two channel intensity modulation-direct detection WDM system at 10 Gb/s. It is found that the XPM induced crosstalk is polarization independent for channel spacing greater than 3 nm or PMD coefficient larger than 2 ps/√km. We also investigate the dependence of SOP variance on PMD coefficient and channel spacing.
Gao, Li; Wei, Yinmao
2016-08-01
A novel mixed-mode adsorbent was prepared by functionalizing silica with tris(2-aminoethyl)amine and 3-phenoxybenzaldehyde as the main mixed-mode scaffold due to the presence of the plentiful amino groups and benzene rings in their molecules. The adsorption mechanism was probed with acidic, natural and basic compounds, and the mixed hydrophobic and ion-exchange interactions were found to be responsible for the adsorption of analytes. The suitability of dispersive solid-phase extraction was demonstrated in the determination of chlorophenols in environmental water. Several parameters, including sample pH, desorption solvent, ionic strength, adsorbent dose, and extraction time were optimized. Under the optimal extraction conditions, the proposed dispersive solid-phase extraction coupled with high-performance liquid chromatography showed good linearity range and acceptable limits of detection (0.22∽0.54 ng/mL) for five chlorophenols. Notably, the higher extraction recoveries (88.7∽109.7%) for five chlorophenols were obtained with smaller adsorbent dose (10 mg) and shorter extraction time (15 min) compared with the reported methods. The proposed method might be potentially applied in the determination of trace chlorophenols in real water samples. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Relative dispersion of clustered drifters in a small micro-tidal estuary
Suara, Kabir; Chanson, Hubert; Borgas, Michael; Brown, Richard J.
2017-07-01
Small tide-dominated estuaries are affected by large scale flow structures which combine with the underlying bed generated smaller scale turbulence to significantly increase the magnitude of horizontal diffusivity. Field estimates of horizontal diffusivity and its associated scales are however rare due to limitations in instrumentation. Data from multiple deployments of low and high resolution clusters of GPS-drifters are used to examine the dynamics of a surface flow in a small micro-tidal estuary through relative dispersion analyses. During the field study, cluster diffusivity, which combines both large- and small-scale processes ranged between, 0.01 and 3.01 m2/s for spreading clusters and, -0.06 and -4.2 m2/s for contracting clusters. Pair-particle dispersion, Dp2, was scale dependent and grew as Dp2 ∼ t1.83 in streamwise and Dp2 ∼ t0.8 in cross-stream directions. At small separation scale, pair-particle (d law and became weaker as separation scale increases. Pair-particle diffusivity was described as Kp ∼ d1.01 and Kp ∼ d0.85 in the streamwise and cross-stream directions, respectively for separation scales ranging from 0.1 to 10 m. Two methods were used to identify the mechanism responsible for dispersion within the channel. The results clearly revealed the importance of strain fields (stretching and shearing) in the spreading of particles within a small micro-tidal channel. The work provided input for modelling dispersion of passive particle in shallow micro-tidal estuaries where these were not previously experimentally studied.
Digital Image Stabilization Method Based on Variational Mode Decomposition and Relative Entropy
Directory of Open Access Journals (Sweden)
Duo Hao
2017-11-01
Full Text Available Cameras mounted on vehicles frequently suffer from image shake due to the vehicles’ motions. To remove jitter motions and preserve intentional motions, a hybrid digital image stabilization method is proposed that uses variational mode decomposition (VMD and relative entropy (RE. In this paper, the global motion vector (GMV is initially decomposed into several narrow-banded modes by VMD. REs, which exhibit the difference of probability distribution between two modes, are then calculated to identify the intentional and jitter motion modes. Finally, the summation of the jitter motion modes constitutes jitter motions, whereas the subtraction of the resulting sum from the GMV represents the intentional motions. The proposed stabilization method is compared with several known methods, namely, medium filter (MF, Kalman filter (KF, wavelet decomposition (MD method, empirical mode decomposition (EMD-based method, and enhanced EMD-based method, to evaluate stabilization performance. Experimental results show that the proposed method outperforms the other stabilization methods.
International Nuclear Information System (INIS)
Shirakata, Hikari; Kawaguchi, Toshihiro; Okamoto, Takashi; Ishiyama, Tomoaki
2017-01-01
We present the galactic stellar age—velocity dispersion relation obtained from a semi-analytic model of galaxy formation. We divide galaxies into two populations: galaxies which have over-massive/under-massive black holes (BHs) against the best-fitting BH mass—velocity dispersion relation. We find that galaxies with larger velocity dispersion have older stellar ages. We also find that galaxies with over-massive BHs have older stellar ages. These results are consistent with observational results obtained from Martín-Navarro et al. (2016). We tested the model with weak AGN feedback and find that galaxies with larger velocity dispersion have a younger stellar age.
Energy Technology Data Exchange (ETDEWEB)
Shirakata, Hikari [Department of Cosmosciences, Graduate School of Science, Hokkaido University, Sapporo (Japan); Kawaguchi, Toshihiro [Department of Economics, Management and Information Science, Onomichi City University, Onomichi, Hiroshima (Japan); Okamoto, Takashi [Department of Cosmosciences, Graduate School of Science, Hokkaido University, Sapporo (Japan); Ishiyama, Tomoaki, E-mail: shirakata@astro1.sci.hokudai.ac.jp [Institute of Management and Information Technologies, Chiba University, Chiba (Japan)
2017-09-12
We present the galactic stellar age—velocity dispersion relation obtained from a semi-analytic model of galaxy formation. We divide galaxies into two populations: galaxies which have over-massive/under-massive black holes (BHs) against the best-fitting BH mass—velocity dispersion relation. We find that galaxies with larger velocity dispersion have older stellar ages. We also find that galaxies with over-massive BHs have older stellar ages. These results are consistent with observational results obtained from Martín-Navarro et al. (2016). We tested the model with weak AGN feedback and find that galaxies with larger velocity dispersion have a younger stellar age.
An Analysis of the New LHC Data through the Dispersion Relations
Selyugin, O.V.
2017-01-01
We analyse the tension between the (indirect) measurements of the total cross section, and show the impact of various assumptions on the extraction of the parameters from the elastic scattering amplitude, with a special attention to the total cross section. In particular, the determination of the phase of the elastic scattering amplitude will play an important role, and we shall study it via dispersion relations. We shall also examine the origin of the dependence on momentum transfer of the slopes of the different parts of the scattering amplitude in different models. We shall also give the results of another similar analysis based on a Regge-trajectory approach for the hadron scattering amplitude.
Bounds on Cubic Lorentz-Violating Terms in the Fermionic Dispersion Relation
Bertolami, O.; Rosa, J. G.
2004-01-01
We study the recently proposed Lorentz-violating dispersion relation for fermions and show that it leads to two distinct cubic operators in the momentum. We compute the leading order terms that modify the non-relativistic equations of motion and use experimental results for the hyperfine transition in the ground state of the ${}^9\\textrm Be^+$ ion to bound the values of the Lorentz-violating parameters $\\eta_1$ and $\\eta_2$ for neutrons. The resulting bounds depend on the value of the Lorenz-...
Further study of a new dispersion relation for electron-atom scattering
International Nuclear Information System (INIS)
Bhatia, A.K.; Temkin, A.
1988-01-01
A new recently proposed dispersion relation (DR) [Temkin, Bhatia, and Kim, J. Phys. B 19, L707 (1986)] is tested for e-He scattering; the results show that the new DR is not satisfied. Therefore we start to investigate the analytic structure of the difference amplitude, previously assumed to be nonsingular, on the negative scattering energy axis. Even under severe approximations we find that the difference amplitude contains both poles and branch points. This suggests, however, a useful approximation of these contributions to the DR which gives very satisfactory agreement in both e-H and e-He scattering. We conclude with some brief general remarks on this problem
RELATION OF DEAF PERSONS TOWARDS BILINGUALISM AS COMMUNICATION MODE
Directory of Open Access Journals (Sweden)
Naim Salkić
2013-02-01
Full Text Available Bilingualism of a deaf child implies concurrent cognition and usage of sign language, as community language and oral-voice language as language of greater community in which deaf persons live. Today, most authors consider that deaf persons should know both of these languages and that deaf persons need to be educated in both languages, because of their general communication and complete psycho-social development. Through research on sample of 80 deaf examinees, we affirmed the kind of relation that deaf persons have towards bilingualism, bilingual way of education and communication. The research results have shown that bilingualism and bilingual way of education and communication is acceptable to deaf persons and that there is no statistically significant difference between the sub-samples of examinees.
Transport-related lifestyle and environmentally-friendly travel mode choices
DEFF Research Database (Denmark)
Thøgersen, John
2018-01-01
. Finally, a multivariate GLM analysis reveals that three behavioral tendencies of importance for transport-related environmental impacts vary significantly and substantially between lifestyle segments: vehicle ownership, everyday travel-mode choice and environmentally-friendly transport innovativeness...
Three-dimensional analysis of relationship between relative orientation and motion modes
Directory of Open Access Journals (Sweden)
Fan Shijie
2014-12-01
Full Text Available Target motion modes have a close relationship with the relative orientation of missile-to-target in three-dimensional highly maneuvering target interception. From the perspective of relationship between the sensor coordinate system and the target body coordinate system, a basic model of sensor is stated and the definition of relative angular velocity between the two coordinate systems is introduced firstly. Then, the three-dimensional analytic expressions of relative angular velocity for different motion modes are derived and simplified by analyzing the influences of target centroid motion, rotation around centroid and relative motion. Finally, the relationships of the relative angular velocity directions and values with motion modes are discussed. Simulation results validate the rationality of the theoretical analysis. It is demonstrated that there are significant differences of the relative orientation in different motion modes which include luxuriant information about motion modes. The conclusions are significant for the research of motion mode identification, maneuver detection, maneuvering target tracking and interception using target signatures.
Keefe, Laurence
2016-11-01
Parabolized acoustic propagation in transversely inhomogeneous media is described by the operator update equation U (x , y , z + Δz) =eik0 (- 1 +√{ 1 + Z }) U (x , y , z) for evolution of the envelope of a wavetrain solution to the original Helmholtz equation. Here the operator, Z =∇T2 + (n2 - 1) , involves the transverse Laplacian and the refractive index distribution. Standard expansion techniques (on the assumption Z << 1)) produce pdes that approximate, to greater or lesser extent, the full dispersion relation of the original Helmholtz equation, except that none of them describe evanescent/damped waves without special modifications to the expansion coefficients. Alternatively, a discretization of both the envelope and the operator converts the operator update equation into a matrix multiply, and existing theorems on matrix functions demonstrate that the complete (discrete) Helmholtz dispersion relation, including evanescent/damped waves, is preserved by this discretization. Propagation-constant/damping-rates contour comparisons for the operator equation and various approximations demonstrate this point, and how poorly the lowest-order, textbook, parabolized equation describes propagation in lined ducts.
International Nuclear Information System (INIS)
Bacri, C.O.; Roussel, P.
1990-01-01
An original method based on the use of a double magnetic spectrometer in a telescopic mode is proposed for the studies of heavy ions collisions both at very forward angles and for magnetic rigidities close to that of the beam. It consists in the direct measurement of angular distributions on doubly - Bρ and angle - sorted events. The method has been tested on the LISE spectrometer at GANIL with a 44 MeV/A 40 Ar beam impinging on C, Al, Ni and Au targets. Milliradian angular accuracy have been obtained at magnetic rigidities as close as 0.9977 of that of the beam
Dispersion relations in the noncommutative φ3 and Wess-Zumino model in the Yang-Feldman formalism
International Nuclear Information System (INIS)
Doescher, C.; Zahn, J.
2006-05-01
We study dispersion relations in the noncommutative φ 3 and Wess-Zumino model in the Yang-Feldman formalism at one-loop order. Non-planar graphs lead to a distortion of the dispersion relation. We find that this effect is small if the scale of noncommutativity is identified with the Planck scale and parameters typical for a Higgs field are employed. (Orig.)
Huang, N. E.; Tung, C.-C.
1977-01-01
The influence of the directional distribution of wave energy on the dispersion relation is calculated numerically using various directional wave spectrum models. The results indicate that the dispersion relation varies both as a function of the directional energy distribution and the direction of propagation of the wave component under consideration. Furthermore, both the mean deviation and the random scatter from the linear approximation increase as the energy spreading decreases. Limited observational data are compared with the theoretical results. The agreement is favorable.
The age-velocity dispersion relation of the Galactic discs from LAMOST-Gaia data
Yu, Jincheng; Liu, Chao
2018-03-01
We present the age-velocity dispersion relation (AVR) in three dimensions in the solar neighbourhood using 3564 commonly observed sub-giant/red giant branch stars selected from The Large Sky Area Multi-Object Fiber Spectroscopic Telescope, which gives the age and radial velocity, and Gaia, which measures the distance and proper motion. The stars are separated into metal-poor ([Fe/H] -0.2 dex) groups, so that the metal-rich stars are mostly α-poor, while the metal-poor group are mostly contributed by α-enhanced stars. Thus, the old and metal-poor stars likely belong to the chemically defined thick disc population, while the metal-rich sample is dominated by the thin disc. The AVR for the metal-poor sample shows an abrupt increase at ≳7 Gyr, which is contributed by the thick disc component. On the other hand, most of the thin disc stars with [Fe/H] > -0.2 dex display a power-law-like AVR with indices of about 0.3-0.4 and 0.5 for the in-plane and vertical dispersions, respectively. This is consistent with the scenario that the disc is gradually heated by the spiral arms and/or the giant molecular clouds. Moreover, the older thin disc stars (>7 Gyr) have a rounder velocity ellipsoid, i.e. σϕ/σz is close to 1.0, probably due to the more efficient heating in vertical direction. Particularly for the old metal-poor sample located with |z| > 270 pc, the vertical dispersion is even larger than its azimuthal counterpart. Finally, the vertex deviations and the tilt angles are plausibly around zero with large uncertainties.
The standardization of data relational mode in the materials database for nuclear power engineering
International Nuclear Information System (INIS)
Wang Xinxuan
1996-01-01
A relational database needs standard data relation ships. The data relation ships include hierarchical structures and repeat set records. Code database is created and the relational database is created between spare parts and materials and properties of the materials. The data relation ships which are not standard are eliminated and all the relation modes are made to meet the demands of the 3NF (Third Norm Form)
Directory of Open Access Journals (Sweden)
Sophie S. Shamailov, Joachim Brand
2018-03-01
Full Text Available Superconducting Josephson vortices have direct analogues in ultracold-atom physics as solitary-wave excitations of two-component superfluid Bose gases with linear coupling. Here we numerically extend the zero-velocity Josephson vortex solutions of the coupled Gross-Pitaevskii equations to non-zero velocities, thus obtaining the full dispersion relation. The inertial mass of the Josephson vortex obtained from the dispersion relation depends on the strength of linear coupling and has a simple pole divergence at a critical value where it changes sign while assuming large absolute values. Additional low-velocity quasiparticles with negative inertial mass emerge at finite momentum that are reminiscent of a dark soliton in one component with counter-flow in the other. In the limit of small linear coupling we compare the Josephson vortex solutions to sine-Gordon solitons and show that the correspondence between them is asymptotic, but significant differences appear at finite values of the coupling constant. Finally, for unequal and non-zero self- and cross-component nonlinearities, we find a new solitary-wave excitation branch. In its presence, both dark solitons and Josephson vortices are dynamically stable while the new excitations are unstable.
Evaluation of the real parts of fermion and boson propagators using dispersion relations
International Nuclear Information System (INIS)
Davies, K.T.R.; Davies, R.W.
1991-01-01
General methods are developed for efficiently evaluating principal-value integrals containing fermion and boson causal propagators. These methods are particularly applicable to integrals containing step functions which appear in the zero temperature limit of infinite nuclear matter. Examples are given for the Green functions that occur in the solution of Dyson's equations, with the inclusion of nucleon-delta-mesonic interactions. It is shown how to discretize in order to evaluate numerically the real parts of the propagators. If the real and purely imaginary self-energies of a propagator obey a dispersion relation, then the propagator itself satisfies such a relation. Finally, we discuss the two types of resonances occurring in the pion Green function. (orig.)
Quantum-optical input-output relations for dispersive and lossy multilayer dielectric plates
International Nuclear Information System (INIS)
Gruner, T.; Welsch, D.
1996-01-01
Using the Green-function approach to the problem of quantization of the phenomenological Maxwell theory, the propagation of quantized radiation through dispersive and absorptive multilayer dielectric plates is studied. Input-output relations are derived, with special emphasis on the determination of the quantum noise generators associated with the absorption of radiation inside the dielectric matter. The input-output relations are used to express arbitrary correlation functions of the outgoing field in terms of correlation functions of the incoming field and those of the noise generators. To illustrate the theory, photons at dielectric tunneling barriers are considered. It is shown that inclusion in the calculations of losses in the photonic band gaps may substantially change the barrier traversal times. copyright 1996 The American Physical Society
Magnon dispersion relation and exchange interactions in MnF2
DEFF Research Database (Denmark)
Nikotin, O.; Lindgård, Per-Anker; Dietrich, O. W.
1969-01-01
The magnon dispersion relation for MnF2 at 4·2 °K has been measured by means of the triple-axis neutron scattering technique along the symmetry lines in the (010) plane of the Brillouin zone. Using an exact dipole model, the three nearest-neighbour exchange constants were found to be J1 = 0·028 ± 0......·001 mev, J2 = -0·152 ± 0·001 mev and J3 = -0·004 ± 0·001 mev. The second moment was also calculated with this model. The density of magnon states was evaluated by applying a six-parameter simulation of the dispersion surface. The critical points in the density of states agree well with those obtained...... by optical double-magnon experiments, whereas the detailed shape of the density of states differs significantly, indicating that the effect of magnon-magnon interactions rather than that of distant-neighbour exchange is of primary importance in the optical measurements....
Guo, Xiao; Wei, Peijun
2016-03-01
The dispersion relations of elastic waves in a one-dimensional phononic crystal formed by periodically repeating of a pre-stressed piezoelectric slab and a pre-stressed piezomagnetic slab are studied in this paper. The influences of initial stress on the dispersive relation are considered based on the incremental stress theory. First, the incremental stress theory of elastic solid is extended to the magneto-electro-elasto solid. The governing equations, constitutive equations, and boundary conditions of the incremental stresses in a magneto-electro-elasto solid are derived with consideration of the existence of initial stresses. Then, the transfer matrices of a pre-stressed piezoelectric slab and a pre-stressed piezomagnetic slab are formulated, respectively. The total transfer matrix of a single cell in the phononic crystal is obtained by the multiplication of two transfer matrixes related with two adjacent slabs. Furthermore, the Bloch theorem is used to obtain the dispersive equations of in-plane and anti-plane Bloch waves. The dispersive equations are solved numerically and the numerical results are shown graphically. The oblique propagation and the normal propagation situations are both considered. In the case of normal propagation of elastic waves, the analytical expressions of the dispersion equation are derived and compared with other literatures. The influences of initial stresses, including the normal initial stresses and shear initial stresses, on the dispersive relations are both discussed based on the numerical results. Copyright © 2015 Elsevier B.V. All rights reserved.
Effects of weak nonlinearity on dispersion relations and frequency band-gaps of periodic structures
DEFF Research Database (Denmark)
Sorokin, Vladislav; Thomsen, Jon Juel
2015-01-01
of these for nonlinear problems is impossible or cumbersome, since Floquet theory is applicable for linear systems only. Thus the nonlinear effects for periodic structures are not yet fully uncovered, while at the same time applica-tions may demand effects of nonlinearity on structural response to be accounted for....... The present work deals with analytically predicting dynamic responses for nonlinear continuous elastic periodic structures. Specifically, the effects of weak nonlinearity on the dispersion re-lation and frequency band-gaps of a periodic Bernoulli-Euler beam performing bending os-cillations are analyzed......The analysis of the behaviour of linear periodic structures can be traced back over 300 years, to Sir Isaac Newton, and still attracts much attention. An essential feature of periodic struc-tures is the presence of frequency band-gaps, i.e. frequency ranges in which waves cannot propagate...
Guo, Xiaohao; Lu, Chunsong; Zhao, Tianliang; Liu, Yangang; Zhang, Guang Jun; Luo, Shi
2018-01-01
This study investigates the influence of entrainment rate (λ) on relative dispersion (ε) of cloud droplet size distributions (CDSD) in the 99 growing precipitating deep convective clouds during TOGA-COARE. The results show that entrainment suppresses ε, which is opposite to the traditional understanding that entrainment-mixing broadens CDSD. To examine how the relationship between ε and λ is affected by droplets with different sizes, CDSDs are divided into three portions with droplet radius processes is developed to illustrate the possible scenarios entailing different relationships between ε and λ. The number concentration of small droplets and the degree of evaporation of small droplets are found to be key factors that shift the sign (i.e., positive or negative) of the ε-λ relationship.
Modified Dispersion Relations: from Black-Hole Entropy to the Cosmological Constant
Garattini, Remo
2012-07-01
Quantum Field Theory is plagued by divergences in the attempt to calculate physical quantities. Standard techniques of regularization and renormalization are used to keep under control such a problem. In this paper we would like to use a different scheme based on Modified Dispersion Relations (MDR) to remove infinities appearing in one loop approximation in contrast to what happens in conventional approaches. In particular, we apply the MDR regularization to the computation of the entropy of a Schwarzschild black hole from one side and the Zero Point Energy (ZPE) of the graviton from the other side. The graviton ZPE is connected to the cosmological constant by means of of the Wheeler-DeWitt equation.
Heavy-ion optical potential for sub-barrier fusion deduced from a dispersion relation
International Nuclear Information System (INIS)
Kim, B.T.; Kim, H.C.; Park, K.E.
1988-01-01
The heavy-ion energy-dependent optical potentials for the 16 O+ 208 Pb system are deduced from a dispersion relation. These potentials are used to analyze the elastic scattering, fusion, and spin distributions of compound nuclei for the system in a unified way based on the direct reaction theory. It turns out that the energy dependence of the optical potential is essential in explaining the data at near- and sub-barrier energies. The real part of the energy-dependent optical potential deduced was also used in calculating the elastic and fusion cross sections by the conventional barrier penetration model using an incoming wave boundary condition. The predictions of the elastic scattering, fusion cross sections, and the spin distributions of compound nuclei are not satisfactory compared with those from the direct reaction approach. It seems to originate from the fact that this model neglects absorption around the Coulomb barrier region
Zirak, H.; Jafari, S.
2015-06-01
In this study, a theory of free-electron laser (FEL) with a Langmuir wave wiggler in the presence of an axial magnetic field has been presented. The small wavelength of the plasma wave (in the sub-mm range) allows obtaining higher frequency than conventional wiggler FELs. Electron trajectories have been obtained by solving the equations of motion for a single electron. In addition, a fourth-order Runge-Kutta method has been used to simulate the electron trajectories. Employing a perturbation analysis, the dispersion relation for an electromagnetic and space-charge waves has been derived by solving the momentum transfer, continuity, and wave equations. Numerical calculations show that the growth rate increases with increasing the e-beam energy and e-beam density, while it decreases with increasing the strength of the axial guide magnetic field.
Dispersion relation and growth rate in a Cherenkov free electron laser: Finite axial magnetic field
International Nuclear Information System (INIS)
Kheiri, Golshad; Esmaeilzadeh, Mahdi
2013-01-01
A theoretical analysis is presented for dispersion relation and growth rate in a Cherenkov free electron laser with finite axial magnetic field. It is shown that the growth rate and the resonance frequency of Cherenkov free electron laser increase with increasing axial magnetic field for low axial magnetic fields, while for high axial magnetic fields, they go to a saturation value. The growth rate and resonance frequency saturation values are exactly the same as those for infinite axial magnetic field approximation. The effects of electron beam self-fields on growth rate are investigated, and it is shown that the growth rate decreases in the presence of self-fields. It is found that there is an optimum value for electron beam density and Lorentz relativistic factor at which the maximum growth rate can take place. Also, the effects of velocity spread of electron beam are studied and it is found that the growth rate decreases due to the electron velocity spread
Measurements of the power spectrum and dispersion relation of self-excited dust acoustic waves
Nosenko, V.; Zhdanov, S. K.; Kim, S.-H.; Heinrich, J.; Merlino, R. L.; Morfill, G. E.
2009-12-01
The spectrum of spontaneously excited dust acoustic waves was measured. The waves were observed with high temporal resolution using a fast video camera operating at 1000 frames per second. The experimental system was a suspension of micron-size kaolin particles in the anode region of a dc discharge in argon. Wave activity was found at frequencies as high as 450 Hz. At high wave numbers, the wave dispersion relation was acoustic-like (frequency proportional to wave number). At low wave numbers, the wave frequency did not tend to zero, but reached a cutoff frequency instead. The cutoff value declined with distance from the anode. We ascribe the observed cutoff to the particle confinement in this region.
Dispersion relation for hadronic light-by-light scattering: two-pion contributions
Energy Technology Data Exchange (ETDEWEB)
Colangelo, Gilberto [Albert Einstein Center for Fundamental Physics, Institute for Theoretical Physics, University of Bern, Sidlerstrasse 5, 3012 Bern (Switzerland); Hoferichter, Martin [Institute for Nuclear Theory, University of Washington, Seattle, WA 98195-1550 (United States); Kavli Institute for Theoretical Physics, University of California,Santa Barbara, CA 93106 (United States); Procura, Massimiliano [Theoretical Physics Department, CERN, Geneva (Switzerland); Stoffer, Peter [Helmholtz-Institut für Strahlen- und Kernphysik (Theory)and Bethe Center for Theoretical Physics, University of Bonn, 53115 Bonn (Germany); Department of Physics, University of California at San Diego, La Jolla, CA 92093 (United States)
2017-04-27
In this third paper of a series dedicated to a dispersive treatment of the hadronic light-by-light (HLbL) tensor, we derive a partial-wave formulation for two-pion intermediate states in the HLbL contribution to the anomalous magnetic moment of the muon (g−2){sub μ}, including a detailed discussion of the unitarity relation for arbitrary partial waves. We show that obtaining a final expression free from unphysical helicity partial waves is a subtle issue, which we thoroughly clarify. As a by-product, we obtain a set of sum rules that could be used to constrain future calculations of γ{sup ∗}γ{sup ∗}→ππ. We validate the formalism extensively using the pion-box contribution, defined by two-pion intermediate states with a pion-pole left-hand cut, and demonstrate how the full known result is reproduced when resumming the partial waves. Using dispersive fits to high-statistics data for the pion vector form factor, we provide an evaluation of the full pion box, a{sub μ}{sup π-box}=−15.9(2)×10{sup −11}. As an application of the partial-wave formalism, we present a first calculation of ππ-rescattering effects in HLbL scattering, with γ{sup ∗}γ{sup ∗}→ππ helicity partial waves constructed dispersively using ππ phase shifts derived from the inverse-amplitude method. In this way, the isospin-0 part of our calculation can be interpreted as the contribution of the f{sub 0}(500) to HLbL scattering in (g−2){sub μ}. We argue that the contribution due to charged-pion rescattering implements corrections related to the corresponding pion polarizability and show that these are moderate. Our final result for the sum of pion-box contribution and its S-wave rescattering corrections reads a{sub μ}{sup π-box}+a{sub μ,J=0}{sup ππ,π-pole} {sup LHC}=−24(1)×10{sup −11}.
Directory of Open Access Journals (Sweden)
Robert SZABO
2011-12-01
Full Text Available The dispersion relations, appearing in the analysis of the stability of a gas flow in a straight acoustically-lined duct with respect to perturbations produced by a time harmonic source, beside the wave number and complex frequency contain the solution of a boundary value problem of the Pridmore-Brown equation depending on the wave number and frequency. For this reason, in practice the dispersion relations are rarely simple enough for carried out the zeros. The determination of zeros of these dispersion relations is crucial for the prediction of the perturbation attenuation or amplification. In this paper an approximation of the dispersion relations is given. Our approach preserves the general character of the mean flow, the general Pridmore-Brown equation and it’s only in the shear flow that we replace the exact solution of the boundary value problem with its Taylor polynomial approximate. In this way new approximate dispersion relations are obtained which zero’s can be found by computer.
Influence of local parameters on the dispersion of traffic-related pollutants within street canyons
Karra, Styliani; Malki-Epshtein, Liora; Martin Hyde Collaboration
2011-11-01
Ventilation within urban cities and street canyons and the associated air quality is a problem of increasing interest in the last decades. It is important for to minimise exposure of the population to traffic-related pollutants at street level. The residence time of pollutants within the street canyons depends on the meteorological conditions such as wind speed and direction, geometry layout and local parameters (position of traffic lane within the street). An experimental study was carried out to investigate the influence of traffic lane position on the dispersion of traffic-related pollutants within different street canyons geometries: symmetrical (equal building heights on both sides of the street), non-symmetrical (uniform building heights but lower on one side of the street) and heterogeneous (non-uniform building heights on both sides of the street) under constant meteorological conditions. Laboratory experiments were carried out within a water channel and simultaneous measurements of velocity field and concentration scalar levels within and above the street canyons using PIV and PLIF techniques. Traffic -related emissions were simulated using a line emission source. Two positions were examined for all street geometries: line emission source was placed in the centre of the street canyon; line emission source was placed off the centre of the street. TSI Incorporated.
Vanel, Florence O.; Baysal, Oktay
1995-01-01
Important characteristics of the aeroacoustic wave propagation are mostly encoded in their dispersion relations. Hence, a computational aeroacoustic (CAA) algorithm, which reasonably preserves these relations, was investigated. It was derived using an optimization procedure to ensure, that the numerical derivatives preserved the wave number and angular frequency of the differential terms in the linearized, 2-D Euler equations. Then, simulations were performed to validate the scheme and a compatible set of discretized boundary conditions. The computational results were found to agree favorably with the exact solutions. The boundary conditions were transparent to the outgoing waves, except when the disturbance source was close to a boundary. The time-domain data generated by such CAA solutions were often intractable until their spectra was analyzed. Therefore, the relative merits of three different methods were included in the study. For simple, periodic waves, the periodogram method produced better estimates of the steep-sloped spectra than the Blackman-Tukey method. Also, for this problem, the Hanning window was more effective when used with the weighted-overlapped-segment-averaging and Blackman-Tukey methods gave better results than the periodogram method. Finally, it was demonstrated that the representation of time domain-data was significantly dependent on the particular spectral analysis method employed.
Dinh, Khuong Van; Janssens, Lizanne; Therry, Lieven; Bervoets, Lieven; Bonte, Dries; Stoks, Robby
2016-11-01
How exposure to contaminants may interfere with the widespread poleward range expansions under global warming is largely unknown. Pesticide exposure may negatively affect traits shaping the speed of range expansion, including traits related to population growth rate and dispersal-related traits. Moreover, rapid evolution of growth rates during poleward range expansions may come at a cost of a reduced investment in detoxification and repair thereby increasing the vulnerability to contaminants at expanding range fronts. We tested effects of a sublethal concentration of the widespread pesticide chlorpyrifos on traits related to range expansion in replicated edge and core populations of the poleward moving damselfly Coenagrion scitulum reared at low and high food levels in a common garden experiment. Food limitation in the larval stage had strong negative effects both in the larval stage and across metamorphosis in the adult stage. Exposure to chlorpyrifos during the larval stage did not affect larval traits but caused delayed effects across metamorphosis by increasing the incidence of wing malformations during metamorphosis and by reducing a key component of the adult immune response. There was some support for an evolutionary trade-off scenario as the faster growing edge larvae suffered a higher mortality during metamorphosis. Instead, there was no clear support for the faster growing edge larvae being more vulnerable to chlorpyrifos. Our data indicate that sublethal delayed effects of pesticide exposure, partly in association with the rapid evolution of faster growth rates, may slow down range expansions. Copyright © 2016 Elsevier Ltd. All rights reserved.
Carvalho Coutinho, Ludmilla; Alves de Oliveira, João
2017-10-01
Sigmodontinae rodents constitute the second-largest subfamily among mammals. Alongside the taxonomic diversity, they are also ecologically diverse, exhibiting a wide array of locomotion modes, with semifossorial, terrestrial, semiaquatic, scansorial, arboreal, and saltatorial forms. To understand the ecomorphologic aspects that allow these rodents to display such locomotion diversity, we analyzed 35 qualitative characters of the appendicular skeleton (humerus, ulna, radius, scapula, femur, tibia, ilium, ischium and pubis) in 795 specimens belonging to 64 species, 34 genera and 10 tribes, representing all locomotion modes assigned to this subfamily. We performed a statistical analysis based upon the coefficient of trait differentiation to test the congruence of character states and the different locomotion modes. We also mapped characters states in a molecular phylogeny in order to reconstruct ancestral states and to evaluate how appendicular characters evolved within main lineages of Sigmodontinae radiation under a phylogenetic framework. The statistical analyses revealed six characters related to specific locomotion modes, except terrestrial. The mapping and parsimony ancestral states reconstruction identified two characters with phylogenetical signal and eight characters that are exclusively or more frequently recorded in certain modes of locomotion, four of them also detected by the statistical analysis. Notwithstanding the documented morphological variation, few changes characterize the transition to each of the locomotion modes, at least regarding the appendicular skeleton. This finding corroborates previous results that showed that sigmodontines exhibit an all-purpose appendicular morphology that allows them to use and explore a great variety of habitats. © 2017 Anatomical Society.
Neutron optical potential of 28Si derived from the dispersion relation
International Nuclear Information System (INIS)
Kitazawa, H.; Igarasi, S.; Katsuragi, D.; Harima, Y.
1992-01-01
Based upon the dispersion theory, an optical potential of 28 Si was determined at the neutron energies from the Fermi energy to 20 MeV. In particular, discussion was given on a characteristic behavior of the optical potential for low-energy neutrons. Moreover, the validity of the dispersion theory was investigated for neutron single-particle bound states in 29 Si. (orig.)
Assessing the relative importance of dispersal in plant communities using an ecoinformatics approach
Ozinga, W.A.; Hennekens, S.M.; Schaminée, J.H.J.; Bekker, R.M.; Prinzing, A.; Bonn, S.; Poschlod, P.; Tackenberg, O.; Thompson, K.; Bakker, J.P.; Groenendael, van J.M.
2005-01-01
Increased insight into the factors that determine the importance of dispersal limitation on species richness and species composition is of paramount importance for conservation and restoration ecology. One way to explore the importance of dispersal limitation is to use seed-sowing experiments, but
On the rule of thumb for flipping the dispersion relation in BAW devices
Jose, Sumy; Hueting, Raymond Josephus Engelbart; Jansman, Andreas
2011-01-01
High-performance solidly mounted bulk acoustic wave resonators (SMRs) can be obtained by employing frame region, if these exhibit type I dispersion. The commonly used piezoelectric material Aluminum Nitride is a type II material, for which type I dispersion can be enforced by increasing the top
Relative toxicity of oil dispersants to Mytilus viridis and Macrobrachium idella
Digital Repository Service at National Institute of Oceanography (India)
DeSilva, C.; Row, A.
) was almost identical for both the species tested, although there was a significant shift in the range of LC sub(50) values, indicating that one species is less sensitive than the other. Oil dispersant mixtures were less toxic than the dispersants alone...
Health-Related Factors Associated with Mode of Travel to Work
Directory of Open Access Journals (Sweden)
Melissa Bopp
2013-01-01
Full Text Available Active commuting (AC to the workplace is a potential strategy for incorporating physical activity into daily life and is associated with health benefits. This study examined the association between health-related factors and mode of travel to the workplace. Methods. A volunteer convenience sample of employed adults completed an online survey regarding demographics, health-related factors, and the number of times/week walking, biking, driving, and using public transit to work (dichotomized as no walk/bike/drive/PT and walk/bike/drive/PT 1 + x/week. Logistic regression was used to predict the likelihood of each mode of transport and meeting PA recommendations from AC according to demographics and health-related factors. Results. The sample was aged 43.5 11.4 years and was primarily White (92.7% and female (67.9%. Respondents reported walking (7.3%, biking (14.4%, taking public transit (20.3%, and driving (78.3% to work at least one time/week. Among those reporting AC, 9.6% met PA recommendations from AC alone. Mode of travel to work was associated with several demographic and health-related factors, including age, number of chronic diseases, weight status, and AC beliefs. Discussion. Mode of transportation to the workplace and health-related factors such as disease or weight status should be considered in future interventions targeting AC.
Health-related factors associated with mode of travel to work.
Bopp, Melissa; Kaczynski, Andrew T; Campbell, Matthew E
2013-01-01
Active commuting (AC) to the workplace is a potential strategy for incorporating physical activity into daily life and is associated with health benefits. This study examined the association between health-related factors and mode of travel to the workplace. Methods. A volunteer convenience sample of employed adults completed an online survey regarding demographics, health-related factors, and the number of times/week walking, biking, driving, and using public transit to work (dichotomized as no walk/bike/drive/PT and walk/bike/drive/PT 1 + x/week). Logistic regression was used to predict the likelihood of each mode of transport and meeting PA recommendations from AC according to demographics and health-related factors. Results. The sample (n = 1175) was aged 43.5 ± 11.4 years and was primarily White (92.7%) and female (67.9%). Respondents reported walking (7.3%), biking (14.4%), taking public transit (20.3%), and driving (78.3%) to work at least one time/week. Among those reporting AC, 9.6% met PA recommendations from AC alone. Mode of travel to work was associated with several demographic and health-related factors, including age, number of chronic diseases, weight status, and AC beliefs. Discussion. Mode of transportation to the workplace and health-related factors such as disease or weight status should be considered in future interventions targeting AC.
Causality and dispersion relations and the role of the S-matrix in the ongoing research
International Nuclear Information System (INIS)
Schroer, Bert; Freie Univ. , Berlin
2011-01-01
The adaptation of the Kramers-Kronig dispersion relations to the causal localization structure of QFT led to an important project in particle physics, the only one with a successful closure. The same cannot be said about the subsequent attempts to formulate particle physics as a pure S-matrix project. The feasibility of a pure S-matrix approach are critically analyzed and their seri- ous shortcomings are highlighted. Whereas the conceptual/mathematical demands of renormalized perturbation theory are modest and misunderstandings could easily be corrected, the correct understanding about the origin of the crossing property demands the use of the mathematical theory of modular localization and its relation to the thermal KMS condition. These concepts which combine localization, vacuum polarization and thermal properties under the roof of modular theory will be explained and their use in a new constructive (nonperturbative) approach to QFT will be indicated. The S-matrix still plays a predominant role, but different from Heisenberg's and Mandelstam's proposals the new project is not a pure S-matrix approach. (author)
Causality and dispersion relations and the role of the S-matrix in the ongoing research
Energy Technology Data Exchange (ETDEWEB)
Schroer, Bert, E-mail: schroer@cbpf.b [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil); Freie Univ. , Berlin (Germany). Inst. fur Theoretische Physik
2011-07-01
The adaptation of the Kramers-Kronig dispersion relations to the causal localization structure of QFT led to an important project in particle physics, the only one with a successful closure. The same cannot be said about the subsequent attempts to formulate particle physics as a pure S-matrix project. The feasibility of a pure S-matrix approach are critically analyzed and their seri- ous shortcomings are highlighted. Whereas the conceptual/mathematical demands of renormalized perturbation theory are modest and misunderstandings could easily be corrected, the correct understanding about the origin of the crossing property demands the use of the mathematical theory of modular localization and its relation to the thermal KMS condition. These concepts which combine localization, vacuum polarization and thermal properties under the roof of modular theory will be explained and their use in a new constructive (nonperturbative) approach to QFT will be indicated. The S-matrix still plays a predominant role, but different from Heisenberg's and Mandelstam's proposals the new project is not a pure S-matrix approach. (author)
Zhou, Lulu; Forman, Henry Jay; Ge, Yi; Lunec, Joseph
2017-08-01
Chemical functionalization broadens carbon nanotube (CNT) applications, conferring new functions, but at the same time potentially altering toxicity. Although considerable experimental data related to CNT toxicity, at the molecular and cellular levels, have been reported, there is very limited information available for the corresponding mechanism involved (e.g. cell apoptosis and genotoxicity). The threshold dose for safe medical application in relation to both pristine and functionalized carbon nanotubes remains ambiguous. In this study, we evaluated the in vitro cytotoxicity of pristine and functionalized (OH, COOH) multi-walled carbon nanotubes (MWCNTs) for cell viability, oxidant detection, apoptosis and DNA mutations, to determine the non-toxic dose and influence of functional group in a human lung-cancer cell line exposed to 1-1000μg/ml MWCNTs for 24, 48 and 72h. The findings suggest that pristine MWCNTs induced more cell death than functionalized MWCNTs while functionalized MWCNTs are more genotoxic compared to their pristine form. The level of both dose and dispersion in the matrix used should be taken into consideration before applying further clinical applications of MWCNTs. Copyright © 2017 Elsevier Ltd. All rights reserved.
Operational evaluation of the RLINE dispersion model for studies of traffic-related air pollutants
Milando, Chad W.; Batterman, Stuart A.
2018-06-01
Exposure to traffic-related air pollutants (TRAP) remains a key public health issue, and improved exposure measures are needed to support health impact and epidemiologic studies and inform regulatory responses. The recently developed Research LINE source model (RLINE), a Gaussian line source dispersion model, has been used in several epidemiologic studies of TRAP exposure, but evaluations of RLINE's performance in such applications have been limited. This study provides an operational evaluation of RLINE in which predictions of NOx, CO and PM2.5 are compared to observations at air quality monitoring stations located near high traffic roads in Detroit, MI. For CO and NOx, model performance was best at sites close to major roads, during downwind conditions, during weekdays, and during certain seasons. For PM2.5, the ability to discern local and particularly the traffic-related portion was limited, a result of high background levels, the sparseness of the monitoring network, and large uncertainties for certain processes (e.g., formation of secondary aerosols) and non-mobile sources (e.g., area, fugitive). Overall, RLINE's performance in near-road environments suggests its usefulness for estimating spatially- and temporally-resolved exposures. The study highlights considerations relevant to health impact and epidemiologic applications, including the importance of selecting appropriate pollutants, using appropriate monitoring approaches, considering prevailing wind directions during study design, and accounting for uncertainty.
Possibility of estimation of bare coupling of grand unification via theory of dispersion relations
International Nuclear Information System (INIS)
Perel'manl, C.
2004-01-01
Full Text:All processes of point particle elastic scatterings on the fixed point-like force center of any nature of coupling can be kinematically subdivided onto two classes: (proper) processes, at which complete energy throughout is not lesser kinetical one: E > If, and (improper) processes, at some interval of which potential energy become bigger complete energy (tunneling, backward scattering, etc.). The projector of proper processes, expressed via the Heaviside unit operator, P = θ(E - f), extracts from the general response functions (scattering amplitudes F) parts that describe all these processes: f (E, p, ...) = 9(E - E)F(E, p, ...). Its Fourier transformation leads to the dispersion relations in (t,r)-representation, which can be infinitely iterated and is represented in form of the Neumann series for the integral Fredholm equation. At this calculation the unique numerical constant α 0 = 2(2π) -5/2 ∼1/50 for (3+1) metrics is appeared, which does not depend from nature of coupling and therefore can be considered as the constant of decomposition of complete amplitude over number of interactions. Precisely this value, independent from dynamics, can be considered as the universal bare coupling. Via the Gell-Mann - Low relations it results in the GUT energy A-f = 10 18 GeV with consistent magnitudes of all running couplings and reasonable values of electron and nucleon masses as dynamical fields objects. Moreover it allows the consideration of some problems of black holes also
International Nuclear Information System (INIS)
Goel, P.
2001-01-01
This paper reports inelastic neutron scattering (INS) measurements of the phonon dispersion relations of the aluminum silicate minerals andalusite and sillimanite, Al 2 SiO 5 . The single crystal INS measurements were undertaken using the Triple-axis-spectrometer at the Dhruva reactor, Trombay for andalusite and at the Oak Ridge National Laboratory, USA for sillimanite. The phonon dispersion relations (upto 50 mev) along various high symmetry directions have been measured and have been analyzed on the basis of lattice dynamics shell model calculations. The calculated structure factors based on the model calculations were used as guides for planning these single crystal measurements and were used to identify regions in reciprocal space with large cross-sections. The calculated structure factors have been very useful in the planning, execution and analysis of the experimental data. The calculated phonon dispersion relations are found to be in good agreement with the measured data
Directory of Open Access Journals (Sweden)
Hikari Shirakata
2017-09-01
Full Text Available We present the galactic stellar age—velocity dispersion relation obtained from a semi-analytic model of galaxy formation. We divide galaxies into two populations: galaxies which have over-massive/under-massive black holes (BHs against the best-fitting BH mass—velocity dispersion relation. We find that galaxies with larger velocity dispersion have older stellar ages. We also find that galaxies with over-massive BHs have older stellar ages. These results are consistent with observational results obtained from Martín-Navarro et al. (2016. We tested the model with weak AGN feedback and find that galaxies with larger velocity dispersion have a younger stellar age.
Roe, Mark A; Collings, Rachel; Hoogewerff, Jurian; Fairweather-Tait, Susan J
2009-03-01
Food iron fortification is a sustainable and relatively simple strategy to reduce/prevent iron deficiency but is a challenge for the food industry because of possible adverse organoleptic changes caused by the added iron. A micronized dispersible ferric pyrophosphate, trademarked as SunActive Fe, has recently been developed. SunActive Fe has a small particle size, is water soluble and may be suitable for fortifying liquid products. To determine the relative bioavailability of SunActive Fe and its suitability for addition to pure apple juice. Iron absorption from SunActive Fe added to pure apple juice (Minute Maid) was compared with absorption from ferrous sulphate, a highly bioavailable form of iron, in 15 women with relatively low iron stores. Both forms of iron were enriched with an iron stable isotope and iron absorption from the apple juice drinks was calculated from the isotopic enrichment of red blood cells 14 days after the last test meal. Although mean absorption of iron from SunActive Fe was significantly lower than from ferrous sulphate (5.5% compared with 9.1%), the mean bioavailability of SunActive Fe iron relative to ferrous sulphate was 0.6, indicating that it is a good source of bioavailable iron. Iron Absorption from SunActive Fe was positively correlated (r = 0.97, P = 0.01) with absorption from ferrous sulphate, and negatively correlated with serum ferritin concentration (ferrous sulphate r = -0.81, P apple juice and is a potentially useful fortificant for liquid food products.
Period--luminosity--color relations and pulsation modes of pulsating variable stars
International Nuclear Information System (INIS)
Breger, M.; Bregman, J.N.
1975-01-01
The periods of delta Scuti, RR Lyrae, dwarf Cepheid, and W Virginis variables have been investigated for their dependence on luminosity, color, mass, and pulsation modes. A maximum-likelihood method, which includes consideration of the observational errors in each coordinate, has been applied to obtain observational period-luminosity-color (P-L-C) relations
Average and dispersion of the luminosity-redshift relation in the concordance model
Energy Technology Data Exchange (ETDEWEB)
Ben-Dayan, I. [DESY Hamburg (Germany). Theory Group; Gasperini, M. [Bari Univ. (Italy). Dipt. di Fisica; Istituto Nazionale di Fisica Nucleare, Bari (Italy); Marozzi, G. [College de France, 75 - Paris (France); Geneve Univ. (Switzerland). Dept. de Physique Theorique and CAP; Nugier, F. [Ecole Normale Superieure CNRS, Paris (France). Laboratoire de Physique Theorique; Veneziano, G. [College de France, 75 - Paris (France); CERN, Geneva (Switzerland). Physics Dept.; New York Univ., NY (United States). Dept. of Physics
2013-03-15
Starting from the luminosity-redshift relation recently given up to second order in the Poisson gauge, we calculate the effects of the realistic stochastic background of perturbations of the so-called concordance model on the combined light-cone and ensemble average of various functions of the luminosity distance, and on their variance, as functions of redshift. We apply a gauge-invariant light-cone averaging prescription which is free from infrared and ultraviolet divergences, making our results robust with respect to changes of the corresponding cutoffs. Our main conclusions, in part already anticipated in a recent letter for the case of a perturbation spectrum computed in the linear regime, are that such inhomogeneities not only cannot avoid the need for dark energy, but also cannot prevent, in principle, the determination of its parameters down to an accuracy of order 10{sup -3} - 10{sup -5}, depending on the averaged observable and on the regime considered for the power spectrum. However, taking into account the appropriate corrections arising in the non-linear regime, we predict an irreducible scatter of the data approaching the 10% level which, for limited statistics, will necessarily limit the attainable precision. The predicted dispersion appears to be in good agreement with current observational estimates of the distance-modulus variance due to Doppler and lensing effects (at low and high redshifts, respectively), and represents a challenge for future precision measurements.
The Riemann Surface of Static Limit Dispersion Relation and Projective Spaces
Majewski, M; Meshcheryakov, D V; Tran Quang Tuyet
2004-01-01
The rigorous Bogoliubov's prove of the dispersion relations (DR) for pion-nucleon scattering is a good foundation for the static models. DR contain the small parameter (ratio of the pion-nucleon masses). The static models arise when this parameter goes to zero. The S-matrix in the static models has a block structure. Each block of the S-matrix has a finite order N\\times N and is a matrix of meromorphic functions of the light particle energy \\omega in the complex plane with cuts (-\\inf,-1], [+1, +\\inf). In the elastic case, it reduces to N functions S_{i}(\\omega) connected by N\\times N the crossing-symmetry matrix A. The unitarity and the crossing symmetry are the base for the system of nonlinear boundary value problems. It defines the analytical continuation of S_{i}(\\omega) from the physical sheet to the unphysical ones and can be treated as a system of nonlinear difference equations. The problem is solvable for any 2\\times 2 crossing-symmetry matrix A that permits one to calculate the Regge trajectories for...
Plakhotnik, Taras; Reichardt, Jens
2018-03-01
A theoretical framework is presented that permits investigations of the relation between inelastic backscattering from microparticles and bulk samples of Raman-active materials. It is based on the Lorentz reciprocity theorem and no fundamental restrictions concerning the microparticle shape apply. The approach provides a simple and intuitive explanation for the enhancement of the differential backscattering cross-section in particles in comparison to bulk. The enhancement factor for scattering of water droplets in the diameter range from 0 to 60 μm (vitally important for the a priori measurement of liquid water content of warm clouds with spectroscopic Raman lidars) is about a factor of 1.2-1.6 larger (depending on the size of the sphere) than an earlier study has shown. The numerical calculations are extended to 1000 μm and demonstrate that dispersion of the refractive index of water becomes an important factor for spheres larger than 100 μm. The physics of the oscillatory phenomena predicted by the simulations is explained.
The Riemann surface of static limit dispersion relation and projective spaces
International Nuclear Information System (INIS)
Majewski, M.; Meshcheryakov, V.A.; Meshcheryakov, D.V.; Tran Quang Tuyet
2004-01-01
The rigorous Bogolyubov's proof of the dispersion relations (DR) for pion-nucleon scattering is a good foundation for the static models. DR contain a small parameter (ratio of the pion-nucleon masses). The static models arise when this parameter goes to zero. The S-matrix in the static models has a block structure. Each block of the S-matrix has a finite order NxN and is a matrix of meromorphic functions of the light particle energy ω in the complex plane with cuts (-∞, -1], [+1,+∞). In the elastic case, it reduces to N functions S i (ω) connected by the NxN crossing-symmetry matrix A. The unitarity and the crossing symmetry are the base for the system of nonlinear boundary value problems. It defines the analytical continuation of S i (ω) from the physical sheet to the unphysical ones and can be treated as a system of nonlinear difference equations. The problem is solvable for any 2x2 crossing-symmetry matrix A that permits one to calculate the Regge trajectories for the SU(2) static model. It is shown that global analyses of this system can be carried out effectively in projective spaces P N-1 and P N . The connection between the spaces P N-1 and P N is discussed. Some particular solutions of the system are found
Determining the near-surface current profile from measurements of the wave dispersion relation
Smeltzer, Benjamin; Maxwell, Peter; Aesøy, Eirik; Ellingsen, Simen
2017-11-01
The current-induced Doppler shifts of waves can yield information about the background mean flow, providing an attractive method of inferring the current profile in the upper layer of the ocean. We present measurements of waves propagating on shear currents in a laboratory water channel, as well as theoretical investigations of inversion techniques for determining the vertical current structure. Spatial and temporal measurements of the free surface profile obtained using a synthetic Schlieren method are analyzed to determine the wave dispersion relation and Doppler shifts as a function of wavelength. The vertical current profile can then be inferred from the Doppler shifts using an inversion algorithm. Most existing algorithms rely on a priori assumptions of the shape of the current profile, and developing a method that uses less stringent assumptions is a focus of this study, allowing for measurement of more general current profiles. The accuracy of current inversion algorithms are evaluated by comparison to measurements of the mean flow profile from particle image velocimetry (PIV), and a discussion of the sensitivity to errors in the Doppler shifts is presented.
Health-Related Factors Associated with Mode of Travel to Work
Bopp, Melissa; Kaczynski, Andrew T.; Campbell, Matthew E.
2013-01-01
Active commuting (AC) to the workplace is a potential strategy for incorporating physical activity into daily life and is associated with health benefits. This study examined the association between health-related factors and mode of travel to the workplace. Methods. A volunteer convenience sample of employed adults completed an online survey regarding demographics, health-related factors, and the number of times/week walking, biking, driving, and using public transit to work (dichotomized as...
Relation between Protein Intrinsic Normal Mode Weights and Pre-Existing Conformer Populations.
Ozgur, Beytullah; Ozdemir, E Sila; Gursoy, Attila; Keskin, Ozlem
2017-04-20
Intrinsic fluctuations of a protein enable it to sample a large repertoire of conformers including the open and closed forms. These distinct forms of the protein called conformational substates pre-exist together in equilibrium as an ensemble independent from its ligands. The role of ligand might be simply to alter the equilibrium toward the most appropriate form for binding. Normal mode analysis is proved to be useful in identifying the directions of conformational changes between substates. In this study, we demonstrate that the ratios of normalized weights of a few normal modes driving the protein between its substates can give insights about the ratios of kinetic conversion rates of the substates, although a direct relation between the eigenvalues and kinetic conversion rates or populations of each substate could not be observed. The correlation between the normalized mode weight ratios and the kinetic rate ratios is around 83% on a set of 11 non-enzyme proteins and around 59% on a set of 17 enzymes. The results are suggestive that mode motions carry intrinsic relations with thermodynamics and kinetics of the proteins.
Phonon dispersion relations in PrBa2Cu3O6+x (x approximate to 0.2)
DEFF Research Database (Denmark)
Gardiner, C.H.; Boothroyd, A.T.; Larsen, B.H.
2004-01-01
We report measurements of the phonon dispersion relations in nonsuperconducting, oxygen-deficient PrBa2Cu3O6+x (xapproximate to0.2) by inelastic neutron scattering. The data are compared with a model of the lattice dynamics based on a common interatomic potential. Good agreement is achieved for all...
Gromke, C.B.; Blocken, B.J.E.
2013-01-01
The relative importance of vegetation terms was analysed for flow and dispersion in an urban street canyon with avenue-trees. To this end, simulations with three k-e turbulence models and different approaches to model vegetation were performed. The different approaches resulted in rather slight
International Nuclear Information System (INIS)
Amusia, M.Ya.; Kuchiev, M.Yu.
1979-01-01
The jump in the electron - atomic-hydrogen forward scattering amplitude at the cut extending to the left from E = -0.5 au is calculated as a function of the incident electron energy, E, by using the second Born approximation. The contribution from this singularity to the dispersion relation is determined. (Auth.)
Kanoun, Mohammed; Cavallo, Luigi
2014-01-01
an energy barrier close to 20 kcal/mol on Ag38, which decreases to slightly more than 10 kcal/mol on Au38. This behavior is analyzed to quantify the impact of relativity and of dispersion interactions through a comparison of nonrelativistic, scalar
Breast density and mode of detection in relation to breast cancer specific survival: a cohort study
International Nuclear Information System (INIS)
Olsson, Åsa; Sartor, Hanna; Borgquist, Signe; Zackrisson, Sophia; Manjer, Jonas
2014-01-01
The aim of this study was to examine breast density in relation to breast cancer specific survival and to assess if this potential association was modified by mode of detection. An additional aim was to study whether the established association between mode of detection and survival is modified by breast density. The study included 619 cases from a prospective cohort, The Malmö Diet and Cancer Study. Breast density estimated qualitatively, was analyzed in relation to breast cancer death, in non-symptomatic and symptomatic women, using Cox regression calculating hazard ratios (HR) with 95% confidence intervals. Adjustments were made in several steps for; diagnostic age, tumour size, axillary lymph node involvement, grade, hormone receptor status, body mass index (baseline), diagnostic period, use of hormone replacement therapy at diagnosis and mode of detection. Detection mode in relation to survival was analyzed stratified for breast density. Differences in HR following different adjustments were analyzed by Freedmans%. After adjustment for age and other prognostic factors, women with dense, as compared to fatty breasts, had an increased risk of breast cancer death, HR 2.56:1.07-6.11, with a statistically significant trend over density categories, p = 0.04. In the stratified analysis, the effect was less pronounced in non-symptomatic women, HR 2.04:0.49-8.49 as compared to symptomatic, HR 3.40:1.06-10.90. In the unadjusted model, symptomatic women had a higher risk of breast cancer death, regardless of breast density. Analyzed by Freedmans%, age, tumour size, lymph nodes, grade, diagnostic period, ER and PgR explained 55.5% of the observed differences in mortality between non-symptomatic and symptomatic cases. Additional adjustment for breast density caused only a minor change. High breast density at diagnosis may be associated with decreased breast cancer survival. This association appears to be stronger in women with symptomatic cancers but breast density could
Energy Technology Data Exchange (ETDEWEB)
Pippig, G
1975-01-01
Taking the Compton scattering of pions and deuterons as an example it is shown that low-energy theorems which are valid for the order e/sup 2/ are also valid for the next higher order of electromagnetic interactions. The imaginary component of the scattering amplitude was exactly calculated for the energy of incident photons in the order e/sup 4/ up to the desired one, whereas the real component was obtained from dispersion relations. It is proved that the results derived from the dispersion theory of strong interactions are equivalent to those obtained from quantum electrodynamics for spin 0 and spin 1, respectively.
Hydrodynamic modes, Green-Kubo relations, and velocity correlations in dilute granular gases
International Nuclear Information System (INIS)
Brey, J Javier; Ruiz-Montero, M J; Maynar, P; Garcia de Soria, M I
2005-01-01
It is shown that the hydrodynamic modes of a dilute granular gas of inelastic hard spheres can be identified, and calculated in the long wavelength limit. Assuming they dominate at long times, formal expressions for the Navier-Stokes transport coefficients are derived. They can be expressed in a form that generalizes the Green-Kubo relations for molecular systems, and it is shown that they can also be evaluated by means of N-particle simulation methods. The form of the hydrodynamic modes to zeroth order in the gradients is used to detect the presence of inherent velocity correlations in the homogeneous cooling state, even in the low density limit. They manifest themselves in the fluctuations of the total energy of the system. The theoretical predictions are shown to be in agreement with molecular dynamics simulations. Relevant related questions deserving further attention are pointed out
Hydrological dispersion of radioactive material in relation to nuclear power plant siting
International Nuclear Information System (INIS)
1985-01-01
This Guide discusses the dispersion of normal and accidental releases of radioactive materials from nuclear power plants into surface water, including the washout of airborne radionuclides, and gives recommendations on information to be collected during the various stages of the siting procedure, a minimum measurement programme and the selection and validation of appropriate mathematical models for predicting dispersion. Guidelines are also provided for the optimal use of models for a specific site situation and for defining the necessary input parameters. Results of existing validation studies are given
Feeding habit and mode of living of benthic organisms, in relation to the radioecology
International Nuclear Information System (INIS)
Horikoshi, Masuoki
1975-01-01
The type of feeding habit, size spectrum (megalo-, macro-, meio-, and micro-benthos), life form (epi-, and endo-biose) and other modes of living of benthic organisms on and within the bottom sediments are briefly mentioned. Knowledge hitherto obtained concerning radio-ecology is also briefly reviewed in relation to those items mentioned above. Special attention is given to the relationship between the stratification and the mixing of bottom deposits, and the reworking and feeding activities of benthic animals. (auth.)
Buhmann, Stefan Yoshi
2012-01-01
In this book, a modern unified theory of dispersion forces on atoms and bodies is presented which covers a broad range of advanced aspects and scenarios. Macroscopic quantum electrodynamics is shown to provide a powerful framework for dispersion forces which allows for discussing general properties like their non-additivity and the relation between microscopic and macroscopic interactions. It is demonstrated how the general results can be used to obtain dispersion forces on atoms in the presence of bodies of various shapes and materials. Starting with a brief recapitulation of volume I, this volume II deals especially with bodies of irregular shapes, universal scaling laws, dynamical forces on excited atoms, enhanced forces in cavity quantum electrodynamics, non-equilibrium forces in thermal environments and quantum friction. The book gives both the specialist and those new to the field a thorough overview over recent results in the field. It provides a toolbox for studying dispersion forces in various contex...
International Nuclear Information System (INIS)
Andreani, M.; Yadigaroglu, G.
1989-12-01
Dispersed flow film boiling is the heat transfer regime that occurs at high void fractions in a heated channel. The way this transfer mode is modelled in the NRC computer codes (RELAP5 and TRAC) and the validity of the assumption and empirical correlations used is discussed. An extensive review of the theoretical and experimental work related with heat transfer to highly dispersed mixtures reveals the basic deficiencies of these models: the investigation refers mostly to the typical conditions of low rate bottom reflooding, since the simulation of this physical situation by the computer codes has often showed poor results. The alternative models that are available in the literature are reviewed, and their merits and limits are highlighted. The modification that could improve the physics of the models implemented in the codes are identified. (author) 13 figs., 123 refs
International Nuclear Information System (INIS)
Hasan, M. Khayrul; Ali, M. Hossain
2009-01-01
We formulate the general relativistic magnetohydrodynamic equations for isothermal plasma in spatially flat Reissner–Nordström–de Sitter metric by using 3+1 split of spacetime. Respective perturbed equations are linearized for rotating magnetized surroundings. These are then Fourier analyzed and the corresponding dispersion relations are obtained. These relations are discussed both analytically and numerically in order to investigate the nature of waves with positive angular frequency around the horizon
The Mean and Scatter of the Velocity Dispersion-Optical Richness Relation for MaxBCG Galaxy Clusters
Energy Technology Data Exchange (ETDEWEB)
Becker, M.R.; McKay, T.A.; /Michigan U.; Koester, B.; /Chicago U., Astron. Astrophys. Ctr.; Wechsler, R.H.; /KIPAC, Menlo Park /SLAC /Stanford U., Phys. Dept.; Rozo, E.; /Ohio State U.; Evrard, A.; /Michigan U. /Michigan U., MCTP; Johnston, D.; /Caltech, JPL; Sheldon, E.; /New York U.; Annis, J.; /Fermilab; Lau, E.; /Chicago U., Astron. Astrophys. Ctr.; Nichol, R.; /Portsmouth U., ICG; Miller, C.; /Michigan U.
2007-06-05
The distribution of galaxies in position and velocity around the centers of galaxy clusters encodes important information about cluster mass and structure. Using the maxBCG galaxy cluster catalog identified from imaging data obtained in the Sloan Digital Sky Survey, we study the BCG--galaxy velocity correlation function. By modeling its non-Gaussianity, we measure the mean and scatter in velocity dispersion at fixed richness. The mean velocity dispersion increases from 202 {+-} 10 km s{sup -1} for small groups to more than 854 {+-} 102 km s{sup -1} for large clusters. We show the scatter to be at most 40.5{+-}3.5%, declining to 14.9{+-}9.4% in the richest bins. We test our methods in the C4 cluster catalog, a spectroscopic cluster catalog produced from the Sloan Digital Sky Survey DR2 spectroscopic sample, and in mock galaxy catalogs constructed from N-body simulations. Our methods are robust, measuring the scatter to well within one-sigma of the true value, and the mean to within 10%, in the mock catalogs. By convolving the scatter in velocity dispersion at fixed richness with the observed richness space density function, we measure the velocity dispersion function of the maxBCG galaxy clusters. Although velocity dispersion and richness do not form a true mass--observable relation, the relationship between velocity dispersion and mass is theoretically well characterized and has low scatter. Thus our results provide a key link between theory and observations up to the velocity bias between dark matter and galaxies.
Reilly, Christopher M; Morris, Rebecca; Dubielzig, Richard R
2005-01-01
To investigate the role of pigment dispersion and inflammation in the pathogenesis of goniodysgenesis-related glaucoma (GDRG). Cases of GDRG were selected when the duration of the disease was specified and there was not any confounding pathology. Cases were grouped into 7-day (chronic) durations, based on the time required to effect end-stage retinal damage. Acute cases were further divided into pigment dispersion: segmental loss of posterior iris pigment epithelium, clumping of posterior iris pigment epithelium, pigmented cells in the trabecular meshwork or anterior chamber and preferential settling of pigmented cells in the ventral aspect of the iridocorneal angle. Slides were also evaluated for the presence of neutrophils and/or lymphoplasmacytic cells in the trabecular meshwork (TM). Differences between groups were analyzed statistically. Of 100 cases evaluated, 34 were 7-days (chronic) in duration. Of all globes examined, 96% had at least one sign of pigment dispersion, with no significant difference between groups. Two or more signs of pigment dispersion were present in 76% of all globes. The 4-7-day group was significantly more likely than the 7-day groups. Neutrophils were present in the TM of 86% of 7-day cases to have neutrophils in the TM, with 65% and 17% [corrected] positive cases, respectively. Lymphoplasmacytic inflammation was present in 53% of all cases, with no significant difference between groups. Cases in the 7-day cases to have both types of inflammation. Our results indicate that both acute inflammation and pigment dispersion may be key factors in the pathogenesis of GDRG. Pigment dispersion is prevalent at all time points and increases during the first 7 days. The finding of iris pigment epithelial loss supports the theory that pupillary block associated with iris-lens touching may be important in the pathogenesis of GDRG.
Failure modes of safety-related components at fires on nuclear power plants
International Nuclear Information System (INIS)
Aaslund, A.
2000-03-01
Probabilistic assessment methods can be used to identify specific plant vulnerabilities. Application of such methods can also facilitate selection among system design alternatives available for safety enhancements. The quality of assessment results is however strongly dependent on realistic and accurate input data for modelling of system component behaviour and failure modes during conditions to be assessed. Use of conservative input data may not lead to results providing guidance on safety upgrades. Adequate input data for probabilistic assessments seems to be lacking for at least failure modes of some electrical components when exposed to a fire. This report presents an attempt to improve the situation with respect to such input data. In order to take advantage of information in existing documentation of fire incident occurrences some of the lessons learned from the fire at Browns Ferry Nuclear Power Plant on March 22, 1975 are discussed in this report. Also a summary of results from different fire tests of electrical cables presented in a fire risk analysis report is a part of the references. The failure modes used to describe fire-induced damage are 'open circuit' and 'hot short' which seems to be commonly accepted terms within the branch. Definitions of the terms are included in the report. Effects of the failure modes when occurring in some of the channels of the reactor protection system are discussed with respect to the existing design of the reactor protection system at Ringhals 2 nuclear power unit. Experiences from the Browns Ferry fire and results from fire tests of electrical cables indicate that the dominating failure mode for electrical cables is 'open circuit'. An 'open circuit' failure leads to circuit disjunction and loss of continuity. The circuit can no longer transmit its signal or power. When affecting channels of the reactor protection system an 'open circuit' failure can cause extensive inadvertent actions of safety related equipment
Estimation of the intrinsic stresses in α-alumina in relation with its elaboration mode
International Nuclear Information System (INIS)
Boumaza, A.; Djelloul, A.
2010-01-01
The specific signatures of α-Al 2 O 3 by Fourier transform infrared (FTIR) spectroscopy were investigated to estimate the intrinsic stress in this compound according to its elaboration mode. Thus, α-alumina was prepared either by calcination of boehmite or gibbsite and also generated by oxidation of a metallic FeCrAl alloy. FTIR results were mainly supported by X-ray diffraction (XRD) patterns that allowed to determine the crystallite size and the strain in the various alpha aluminas. Moreover, the infrared peak at 378.7 cm -1 was used as a reference for stress free α-alumina and the shift of this peak allowed to estimate intrinsic stresses, which were related to the morphology and to the specific surface area of aluminas according to their elaboration mode. These interpretations were confirmed by results obtained by cathodoluminescence experiments. - Graphical abstract: The infrared peak at 378.7 cm -1 was used as a reference for stress free α-alumina and the shift of this peak allowed to estimate intrinsic stresses, which were related to the morphology and to the specific surface area of aluminas according to their elaboration mode.
Reporter Concerns in 300 Mode-Related Incident Reports from NASA's Aviation Safety Reporting System
McGreevy, Michael W.
1996-01-01
A model has been developed which represents prominent reporter concerns expressed in the narratives of 300 mode-related incident reports from NASA's Aviation Safety Reporting System (ASRS). The model objectively quantifies the structure of concerns which persist across situations and reporters. These concerns are described and illustrated using verbatim sentences from the original narratives. Report accession numbers are included with each sentence so that concerns can be traced back to the original reports. The results also include an inventory of mode names mentioned in the narratives, and a comparison of individual and joint concerns. The method is based on a proximity-weighted co-occurrence metric and object-oriented complexity reduction.
PERIOD-LUMINOSITY RELATIONS DERIVED FROM THE OGLE-III FUNDAMENTAL MODE CEPHEIDS
International Nuclear Information System (INIS)
Ngeow, Chow-Choong; Kanbur, Shashi M.; Neilson, Hilding R.; Nanthakumar, A.; Buonaccorsi, John
2009-01-01
In this paper, we have derived Cepheid period-luminosity (P-L) relations for the Large Magellanic Cloud (LMC) fundamental mode Cepheids, based on the data released from OGLE-III. We have applied an extinction map to correct for the extinction of these Cepheids. In addition to the VIW-band P-L relations, we also include JHK and four Spitzer IRAC-band P-L relations, derived by matching the OGLE-III Cepheids to the Two Micron All Sky Survey and SAGE data sets, respectively. We also test the nonlinearity of the Cepheid P-L relations based on extinction-corrected data. Our results (again) show that the LMC P-L relations are nonlinear in VIJH bands and linear in KW and the four IRAC bands, respectively.
A simple theory of linear mode conversion
International Nuclear Information System (INIS)
Cairns, R.A.; Lashmore-Davies, C.N.; Woods, A.M.
1984-01-01
A summary is given of the basic theory of linear mode conversion involving the construction of differential equations for the mode amplitudes based on the properties of the dispersion relation in the neighbourhood of the mode conversion point. As an example the transmission coefficient for tunneling from the upper hybrid resonance through the evanescent region to the adjacent cut-off is treated. 7 refs, 3 figs
International Nuclear Information System (INIS)
Barry, J.P.
1994-08-01
Analyses of ocean currents in the vicinity of McMurdo Station, Antarctica, are relevant to the transport and dispersal of wastewater from the McMurdo Station sewage outfall pipe. Observations of ocean currents during the initial phases of this study have been presented by Howington and McFeters. These studies, using coliform bacterial counts as an indicator of dispersion of the wastewater plume and current meters to measure flow patterns, indicated that dispersal of the plume by local currents does not effectively remove the plume from the vicinity of McMurdo Sound, under the present outfall pipe location. Moreover, these studies suggest that, although the flow pattern is generally consistent with transport of the plume away from McMurdo Station, episodes of current reversal are sufficient to transport the wastewater plume along the shore toward the southeast, eventually overlapping the seawater intake area near the McMurdo jetty. Several concerns included (a) impacts of wastewater inputs to nearshore benthic and pelagic habitats adjacent to McMurdo Station, (b) effects of wastewater input to the McMurdo Station fresh water intake source, and (c) reduction in human impacts on the McMurdo Sound ecosystem. These concerns motivated studies to characterize nearshore currents more extensively in relation to dispersal of the wastewater plume. This report discusses analysis results of current observations from November 1992 to November 1993
International Nuclear Information System (INIS)
Fuhrmann, C.
1979-01-01
The Triple-Axis Crystal Neutron Spectrometer is the best instrument for the study of lattice dynamics, when the neutron inelastic scattering technique is used. Design, construction and operation of a triple-axis crystal neutron spectrometer, whose construction was recently finished at IEA are described. The design principles employed are directed to mechanical simplicity, facility of construction and flexibility in operation, with no adapted components to industrial applications were used in the construction. The operational characteristics of the spectrometer, such as the neutron wavelenght of the incoming beam and the resolution have been determined. With the purpose to check the performance of IEA Triple-Axis Crystal Neutron Spectrometer, dispersion relation curves for copper, at room temperature, have been measured. The frequency of phonons propagating along three major symmetry directions have been determined. The measurements were carried out operating the Triple-Axis Spectrometer in the 'sup(→)Q-constant' mode. An excelent agreement could be observed between the results obtained in the present experiment and the data for copper presented in the literature. This comparison indicates that the IEA Triple-Axis Crystal Neutron Spectrometer is in good operational conditions and is able to perform original experiments. Details on the experimental procedures for the case of a Triple-Axis Spectrometer operating in 'sup(→)Q-constant' mode are also presented. (Author) [pt
DEFF Research Database (Denmark)
Lindgård, Per-Anker; Kowalska, A.; Laut, Peter
1967-01-01
curves are suggested. The magnon cross section for unpolarized neutrons is calculated and shown to be dependent on the anisotropy in the spin interaction. Thus in principle it allows the detection of anisotropy in the exchange interaction. Some remarks are made concerning antiferromagnetic and plane...... for the exchange interaction seem to be necessary for agreement with experimental dispersion curves be obtained. The effect of the anisotropy in the cross section is estimated and shown to be important for small magnon energies....
Directory of Open Access Journals (Sweden)
Liu Yongjun
2015-01-01
Full Text Available In this thesis, the influence of complete Coriolis force (the model includes both the vertical and horizontal components of Coriolis force on the dispersion relation of ocean internal-wave under background currents field are studied, it is important to the study of ocean internal waves in density-stratified ocean. We start from the control equation of sea water movement in the background of the non-traditional approximation, and the vertical velocity solution is derived where buoyancy frequency N(z gradually varies with the ocean depth z. The results show that the influence of complete Coriolis force on the dispersion relation of ocean internal-wave under background currents field is obvious, and these results provide strong evidence for the understanding of dynamic process of density stratified ocean internal waves.
Phonon dispersion of metallic glass CuZr{sub 2}
Energy Technology Data Exchange (ETDEWEB)
Nakashima, S [Department of Condensed Matter Chemistry and Physics, Graduate School of Sciences, Kyushu University, 4-2-1 Ropponmatsu, Chuo-ku, Fukuoka 810-8560 (Japan); Kawakita, Y [Department of Physics, Faculty of Sciences, Kyushu University, 4-2-1 Ropponmatsu, Chuo-ku, Fukuoka 810-8560 (Japan); Otomo, T [Japan Proton Accelerator Research Complex, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba 305-0801, Japan (Japan); Suenaga, R [Department of Condensed Matter Chemistry and Physics, Graduate School of Sciences, Kyushu University, 4-2-1 Ropponmatsu, Chuo-ku, Fukuoka 810-8560 (Japan); Baron, A Q R [Materials Dynamics Laboratory, Harima RIKEN, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); Tsutsui, S [Japan Synchrotron Radiation Research Institute (JASRI, SPring-8), 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198, Japan (Japan); Kohara, S [Japan Synchrotron Radiation Research Institute (JASRI, SPring-8), 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198, Japan (Japan); Takeda, S [Department of Physics, Faculty of Sciences, Kyushu University, 4-2-1 Ropponmatsu, Chuo-ku, Fukuoka 810-8560 (Japan); Itoh, K [Research Reactor Institute, Kyoto University, Kumatori-cho, Sennnan-gun, Osaka 590-0494 (Japan); Kato, H [Institute for Material Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Fukunaga, T [Research Reactor Institute, Kyoto University, Kumatori-cho, Sennnan-gun, Osaka 590-0494 (Japan); Hasegawa, M [Department of Materials, Physics and Energy Engineering, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8603 (Japan)
2007-12-15
Collective dynamics of metallic glass CuZr{sub 2} has been studied in the first pseudo Brillouin zone using high-resolution inelastic X-ray scattering. Acoustic-like longitudinal propagating excitations were observed and the dispersion relation was determined. In addition of longitudinal mode, transverse mode with half excitation energy contributes to medium energy-transfer region.
International Nuclear Information System (INIS)
Pelaez, J.R.; Garcia Martin, R.; Kaminski, R.; Yndurain, F.J.
2009-01-01
This talk is dedicated to the memory of Paco Yndurain, the original speaker in the conference. After a short account of his scientific career, we briefly review our ongoing collaboration to determine precisely the ππ scattering amplitude including the most recent data by means of Forward Dispersion Relations and Roy Equations. A remarkable improvement in precision over the intermediate energy region is obtained by using once-subtracted Roy Equations in addition to the standard twice-subtracted ones
International Nuclear Information System (INIS)
Ding Huafeng; Lu, Jun Q; Wooden, William A; Kragel, Peter J; Hu Xinhua
2006-01-01
The refractive index of human skin tissues is an important parameter in characterizing the optical response of the skin. We extended a previously developed method of coherent reflectance curve measurement to determine the in vitro values of the complex refractive indices of epidermal and dermal tissues from fresh human skin samples at eight wavelengths between 325 and 1557 nm. Based on these results, dispersion relations of the real refractive index have been obtained and compared in the same spectral region
Koumans, R.G.M.P.; Roijen, van R.
1996-01-01
We present a theory for passive mode-locking in semiconductor laser structures using a semiconductor laser amplifier and absorber. The mode-locking system is described in terms of the different elements in the semiconductor laser structure. We derive mode-locking conditions and show how other
Liao, Li; Hua, Hua; Zhao, Jun-Ning; Luo, Heng; Yang, An-Dong
2014-03-01
To establish a fast sensitive, reproducible LC-MS/MS method to study pharmacokinetic properties of THC, and compare relative bioavailability of THC and its solid dispersion in mice. 200 mice were divided randomly into two groups, and administered orally with THC and THC-solid dispersion after fasting (calculate on THC:400 mg x kg(-1)), used HPLC-MS/MS method to determine the THC concentration of each period at the following times: baseline ( predose ), 15, 30, 45 min, 1, 1.5, 2, 3, 4, 6, 24 h after dosing. Calculating the pharmacokinetic parameters according to the C-t curv, and then use the Phoenix WinNonlin software for data analysis. The calibration curves were linear over the range 9.06-972 microg x L(-1) for THC (R2 = 0.999). The limit of detection (LOD) was 0.7 microg x L(-1), respectively. The average extraction recoveries for THC was above 75%, The methodology recoveries were between 79% and 108%. The intra-day and inter-day RSD were less than 13%, the stability test showed that the plasma samples was stable under different conditions (RSD THC and THC-solid dispersion orally to mice shows as fllows: T(max), were 60 and 15 min, AUC(0-t) were 44 500.43 and 57 497.81 mg x L(-1) x min, AUC(0-infinity) were 51 226.00 and 68 031.48 mg x L(-1) x min, MRT(0-infinity) were 596.915 6, 661.747 7 min, CL(z)/F were 0.007 809 and 0.005 88 L x min(-1) x kg(-1). Compared with THC, the MRT and t1/2 of the THC-solid dispersion were all slightly extended, the t(max) was significantly reduced, AUC(0-24 h), AUC(0-infinity) and C(max) were all significantly higher, the relative bioavailability of THC-solid dispersion is 1.34 times of THC. The results of the experiment shows that the precision, accuracy, recovery and applicability were found to be adequate for the pharmacokinetic studies. After oral administration to mice, the relative bioavailability of THC-solid dispersion show significant improvement compared to THC.
Xu, Yanlong
2015-01-01
structures' evolution with the height of the stubs and the thickness of the plate shows clearly that the method can predict well the Bragg band gaps, locally resonant band gaps and high-order symmetric and anti-symmetric thickness-twist modes
International Nuclear Information System (INIS)
Gebbie, Tim; Ellis, G.F.R.
2000-01-01
This is the first of a series of papers systematically extending a 1+3 covariant and gauge-invariant treatment of kinetic theory in curved space-times to a treatment of cosmic microwave background temperature anisotropies arising from inhomogeneities in the early universe. The present paper deals with algebraic issues, both generically and in the context of models linearised about Robertson-Walker geometries. The approach represents radiation anisotropies by projected symmetric and trace-free tensors. The angular correlation functions for the mode coefficients are found in terms of these quantities, following the Wilson-Silk approach, but derived and dealt with in 1+3 covariant and gauge-invariant form. The covariant multipole and mode-expanded angular correlation functions are related to the usual treatments in the literature. The 1+3 covariant and gauge-invariant mode expansion is related to the coordinate approach by linking the Legendre functions to the projected symmetric trace-free representation, using a covariant addition theorem for the tensors to generate the Legendre polynomial recursion relation. This paper lays the foundation for further papers in the series, which use this formalism in a covariant and gauge-invariant approach to developing solutions of the Boltzmann and Liouville equations for the cosmic microwave background before and after decoupling, thus providing a unified covariant and gauge-invariant derivation of the variety of approaches to cosmic microwave background anisotropies in the current literature, as well as a basis for extension of the theory to include nonlinearities
International Nuclear Information System (INIS)
Mine, M.; Okumura, M.; Yamanaka, Y.
2005-01-01
The two approaches of consistent quantum field theory for systems of the trapped Bose-Einstein condensates are known, one is the Bogoliubov-de Gennes approach and the other is the generalized Bogoliubov approach. In this paper, we investigate the relation between the two approaches and show that they are formally equivalent to each other. To do this one must carefully treat the Nambu-Goldstone mode which plays a crucial role in the condensation. It is emphasized that the choice of vacuum is physically relevant
Cohesive traction-separation relations for plate tearing under mixed mode loading
DEFF Research Database (Denmark)
Andersen, R. G.; Woelke, P. B.; Nielsen, K. L.
2018-01-01
The present study investigates a sequence of failure events related to steady-state tearing of large-scale ductile plates by employing the micro-mechanics based Gurson-Tvergaard-Needleman (GTN) model. The fracture process in front of an advancing crack is approximated by a series of 2D plane strain...... finite element models to facilitate a comprehensive study of mixed mode fracture behavior as well as a parameter study of the cohesive energy and tractions involved in the process. The results from the conducted GTN model simulations are used to define cohesive zone models suitable for plate tearing...
International Nuclear Information System (INIS)
Doak, R.B.
1981-01-01
A crystal surface terminates abruptly one dimension of lattice periodicity, constituting a lattice defect with concomitant localized modes of vibration, termed surface phonons. Such surface phonons have previously been investigated in the long wavelength, non-dispersive regime. The present work reports the first observation of surface phonons in the short wavelength, dispersive range. The data allow for the first time a surface phonon dispersion curve to be plotted completely from origin to edge of the surface Brillouin zone. Measurements were made of phonons along the (anti GAMMA anti M) and (anti GAMMA anti X) azimuths of the LiF(001) surface and along the azimuth of NaF(001) and KC1(001) surfaces. The results are in substantial agreement with theoretical predictions, although for LiF the measured Rayleigh dispersion curve at M lies appreciably below the theoretical value, possibly reflecting the effects of surface relaxation. (orig.)
Abdoli-Arani, A.; Montazeri, M. M.
2018-04-01
Two special types of metallic waveguide having dielectric cladding and plasma core including the combined circular and elliptical structure are studied. Longitudinal and transverse field components in the different regions are obtained. Applying the boundary conditions, dispersion relations of the electromagnetic waves in the structures are obtained and then plotted. The acceleration of an injected external relativistic electron in the considered waveguides is studied. The obtained differential equations related to electron motion are solved by the fourth-order Runge-Kutta method. Numerical computations are made, and the results are graphically presented.
Modes of relating to contingency: An exploration of experiences in advanced cancer patients.
Kruizinga, Renske; Hartog, Iris D; Scherer-Rath, Michael; Schilderman, Hans; Van Laarhoven, Hanneke
2017-08-01
Throughout their lives, people are confronted with unexpected life events, which can be difficult to incorporate into their life narratives. Such a confrontation can result in an experience of contingency. Different ways of relating to contingency have been described by Wuchterl: denying, acknowledging, and "encounter with the Other." In the present article, we aim to trace these theoretical distinctions in real-life experiences of patients. We analyzed 45 interviews using the constant comparative method with a directed content analysis approach in the Atlas.ti coding program. The interviews originated from a randomized controlled trial evaluating an assisted reflection on life events and ultimate life goals. Seven spiritual counselors from six hospitals in the Netherlands conducted the interviews from July of 2014 to March of 2016. All 45 patients had advanced cancer. We found four different modes into which relating to contingency can be classified: denying, acknowledging, accepting, and receiving. With denying, patients did not mention any impact of the life event on their lives. In acknowledging, the impact was recognized and a start was made to incorporate the event into their life. In accepting, patients went through a process of reinterpretation of the event. In receiving, patients talked about receiving insights from their illness and living a more conscious life. Our study is the first to investigate the different ways of relating to contingency in clinical practice. The defined modes will improve our understanding of the various ways in which cancer patients relate to their disease, allowing caregivers to better target and shape individual care.
Verbeek, Lianne; Zhao, Depeng P; Te Pas, Arjan B; Middeldorp, Johanna M; Hooper, Stuart B; Oepkes, Dick; Lopriore, Enrico
2016-06-01
To determine the differences in hemoglobin (Hb) levels in the first 2 days after birth in uncomplicated monochorionic twins in relation to birth order and mode of delivery. All consecutive uncomplicated monochorionic pregnancies with two live-born twins delivered at our center were included in this retrospective study. We recorded Hb levels at birth and on day 2, and analyzed Hb levels in association with birth order, mode of delivery, and time interval between delivery of twin 1 and 2. A total of 290 monochorionic twin pairs were analyzed, including 171 (59%) twins delivered vaginally and 119 (41%) twins born by cesarean section (CS). In twins delivered vaginally, mean Hb levels at birth and on day 2 were significantly higher in second-born twins compared to first-born twins: 17.8 versus 16.1 g/dL and 18.0 versus 14.8 g/dL, respectively (p < .01). Polycythemia was detected more often in second-born twins (12%, 20/166) compared to first-born twins (1%, 2/166; p < .01). Hb differences within twin pairs delivered by CS were not statistically or clinically significant. We found no association between inter-twin delivery time intervals and Hb differences. Second-born twins after vaginal delivery have higher Hb levels and more often polycythemia than their co-twin, but not when born by CS.
Sommet, Nicolas; Darnon, Céline; Mugny, Gabriel; Quiamzade, Alain; Pulfrey, Caroline; Dompnier, Benoît; Butera, Fabrizio
2014-03-01
Socio-cognitive conflict has been defined as a situation of confrontation with a disagreeing other. Previous research suggests that individuals can regulate conflict in a relational way, namely by focusing on social comparison between relative levels of competences. Relational conflict regulation has been described as yielding particularly negative effects on social interactions and learning, but has been understudied. The present research addresses the question of the origin of relational conflict regulation by introducing a fundamental distinction between two types of regulation, one based on the affirmation of one's own point of view and the invalidation of the other's (i.e., 'competitive' regulation), the other corresponding to the protection of self-competence via compliance (i.e., 'protective' regulation). Three studies show that these modes of relational conflict regulation result from the endorsement of distinct performance goals, respectively, performance-approach goals (trying to outperform others) and performance-avoidance goals (avoiding performing more poorly than others). Theoretical implications for the literature on both conflict regulation and achievement goals are discussed. © 2012 The British Psychological Society.
Belz, Regina G
2016-01-01
Parthenin is a metabolite of Parthenium hysterophorus and is believed to contribute to the weed's invasiveness via allelopathy. Despite the potential of parthenin to suppress competitors, low doses stimulate plant growth. This biphasic action was hypothesized to be auxin-like and, therefore, an auxin-related mode of parthenin action was investigated using two approaches: joint action experiments with Lactuca sativa, and dose-response experiments with auxin/antiauxin-resistant Arabidopsis thaliana genotypes. The joint action approach comprised binary mixtures of subinhibitory doses of the auxin 3-indoleacetic acid (IAA) mixed with parthenin or one of three reference compounds [indole-3-butyric acid (IBA), 2,3,5-triiodobenzoic acid (TIBA), 2-(p-chlorophenoxy)-2-methylpropionic acid (PCIB)]. The reference compounds significantly interacted with IAA at all doses, but parthenin interacted only at low doses indicating that parthenin hormesis may be auxin-related, in contrast to its inhibitory action. The genetic approach investigated the response of four auxin/antiauxin-resistant mutants and a wildtype to parthenin or two reference compounds (IAA, PCIB). The responses of mutant plants to the reference compounds confirmed previous reports, but differed from the responses observed for parthenin. Parthenin stimulated and inhibited all mutants independent of resistance. This provided no indication for an auxin-related action of parthenin. Therefore, the hypothesis of an auxin-related inhibitory action of parthenin was rejected in two independent experimental approaches, while the hypothesis of an auxin-related stimulatory effect could not be rejected.
Energy Technology Data Exchange (ETDEWEB)
Klanderud, K.; Totland, Oe. [Norwegian Univ. of Life Science, Dept. of Ecology and Natural Resource Management, Aas (Norway)
2007-08-15
Most studies on factors determining diversity are conducted in temperate or warm regions, whereas studies in climatically harsh and low productivity areas, such as alpine regions, are rare. We examined the relative roles of seed availability and different biotic and abiotic factors for the diversity of an alpine plant community in southern Norway. Furthermore, because climate warming is predicted to be an important driver of alpine species diversity, we assessed how the relative impacts of dispersal and local interactions on diversity might change under experimental warming (open top chambers, OTCs). Addition of seeds from 27 regional species increased community diversity. The establishment of the species was negatively related both to the diversity of the existing system and the cover of the abundant dwarf shrub Dryas octopetala. These results show that both species dispersal limitation and local biotic interactions are important factors for alpine plant community diversity. Despite relatively harsh environmental conditions and low productivity, competition from the resident vegetation appeared to have a greater role for species establishment and diversity than facilitation and experimental warming. Higher temperature appeared to increase the negative relationship between resident species diversity and species establishment. This may suggest that climate warming can increase the role of interspecific competition for alpine plant community structure, and thus alter the long-term effects of biotic interactions on diversity. (au)
Robert J. Warren; Jason P. Love; Mark A. Bradford
2017-01-01
Many plant seeds travel on the wind and through animal ingestion or adhesion; however, an overlooked dispersal mode may lurk within those dispersal modes. Viable seeds may remain attached or embedded within materials birds gather for nest building. Our objective was to determine if birds inadvertently transport seeds when they forage for plant materials to...
Kazemi, Elahe; Dadfarnia, Shayessteh; Haji Shabani, Ali Mohammad; Abbasi, Amir; Rashidian Vaziri, Mohammad Reza; Behjat, Abbas
2016-01-15
A simple and rapid dispersive micro-solid phase extraction (DMSPE) combined with mode-mismatched thermal lens spectrometry as well as fiber optic linear array spectrophotometry was developed for the separation, extraction and determination of sulfadiazine. Graphene oxide was synthesized using the modified Hummers method and functionalized with iron oxide nanoparticles by means of a simple one step chemical coprecipitation method. The synthesized iron oxide functionalized graphene oxide was utilized as an efficient sorbent in DMSPE of sulfadiazine. The retained analyte was eluted by using 180µL of a 6:4 mixture of methanol/acetic acid solution and was spectrophotometrically determined based on the formation of an azo dye through coupling with thenoyltrifluoroacetone. Under the optimized conditions, with the application of spectrophotometry technique and with a sample volume of 100mL, the method exhibited a linear dynamic range of 3-80µg L(-1) with a detection limit of 0.82µg L(-1), an enrichment factor of 200 as well as the relative standard deviations of 2.6% and 4.3% (n=6) at 150µg L(-1) level of sulfadiazine for intra- and inter-day analyses, respectively. Whereas, through the application of the thermal lens spectrometry and a sample volume of 10mL, the method exhibited a linear dynamic range of 1-800µg L(-1) with a detection limit of 0.34µg L(-1) and the relative standard deviations of 3.1% and 5.4% (n=6) at 150µg L(-1) level of sulfadiazine for intra- and inter-day analyses, respectively. The method was successfully applied to the determination of sulfadiazine in milk, honey and water samples. Copyright © 2015 Elsevier B.V. All rights reserved.
International Nuclear Information System (INIS)
Nagata, M.
1983-01-01
A derived addition to the BGK collision term,is improved and expressed in simple form. The collision frequency for scattering depends anisotropically on the velocity vector. The improved macroscopic equation of momentum flow is applied to the Hall effect, the cold plasma dispersion relation and the cyclotron resonance. The Hall coefficient which is constant in the case of the BGK collision term now depends on the magnetic field. It is also shown that, compared with the almost symmetric classical curves of cyclotron resonance, the new curves are considerably asymmetric and their half-widths are about 3/2 times the classical ones. (autho)
International Nuclear Information System (INIS)
Mehdian, Hassan; Abbasi, Negar
2008-01-01
A linear theory of two-stream free electron laser (FEL) with helical wiggler and ion channel guiding is presented. The dispersion relation is obtained with the help of fluid theory and the growth rate is analyzed through the numerical solutions. The considerable enhancement of the growth rate is demonstrated due to the two-stream instability and continuous tuning of peak growth rate ratio, two-stream FEL compared to single-stream FEL, in terms of varying the ion channel frequency is illustrated
Talla Mbé, Jimmi H.; Milián, Carles; Chembo, Yanne K.
2017-07-01
We use the generalized Lugiato-Lefever model to investigate the phenomenon of Kerr optical frequency comb generation when group-velocity dispersion is null. In that case, the first dispersion term that plays a leading role is third-order dispersion. We show that this term is sufficient to allow for the existence of both bright and dark solitons. We identify the areas in the parameter space where both kind of solitons can be excited inside the resonator. We also unveil a phenomenon of hysteretic switching between these two types of solitons when the power of the pump laser is cyclically varied. Contribution to the Topical Issue "Theory and Applications of the Lugiato-Lefever Equation", edited by Yanne K. Chembo, Damia Gomila, Mustapha Tlidi, Curtis R. Menyuk.
Linear theory of drift-tearing and interchange modes in a screw pinch
International Nuclear Information System (INIS)
Copenhaver, C.
1978-04-01
A drift dispersion relation, as applied to a resistive incompressible plasma in a screw pinch, is derived. This dispersion relation incorporates both drift-tearing and drift-interchange modes and is valid throughout the collisional regime by including kinetic theory factors. The dispersion relation reduces to the drift-tearing dispersion relation in the zero pressure gradient limit, and to the classical resistive dispersion relation in the zero drift limit. The electron temperature gradient instability is still present. Now, however, the introduction of the interchange-drift instability increases the growth rate further above the tearing-drift case. (orig.) [de
Directory of Open Access Journals (Sweden)
Eduardo Luís Hettwer Giehl
2007-03-01
Full Text Available A dispersão de diásporos é um evento de elevada importância para as espécies vegetais, que dispõem de diversas estratégias para este fim. O presente estudo teve por objetivos conhecer e caracterizar o espectro das diferentes estratégias de dispersão do componente arbóreo em uma floresta estacional de Santa Maria, Rio Grande do Sul, Brasil (próximo às coordenadas 53º54'W e 29º38'S e, a partir desses dados, investigar sua relação com os estratos verticais da floresta. Foram amostrados todos os indivíduos com perímetro à altura do peito > 15 cm, em 100 unidades amostrais de 10×10 m. A caracterização das estratégias de dispersão foi realizada por meio de observações a campo de frutos e potenciais dispersores, e consulta à bibliografia especializada. Foram amostradas 58 espécies pertencentes a 26 famílias botânicas. Dessas espécies, 74% apresentaram estratégia de dispersão zoocórica; 24%, estratégia de dispersão anemocórica e apenas Gymnanthes concolor Spreng. apresentou a estratégia autocórica. Analisando-se a proporção das estratégias de dispersão por meio da densidade relativa, verificou-se que 80% dos indivíduos são zoocóricos, 12% anemocóricos e 8% autocóricos. Para a floresta analisada foram encontradas diferenças significativas nos padrões de distribuição vertical das espécies agrupadas de acordo com a estratégia de dispersão. A zoocoria ocorreu em espécies de todos os estratos, enquanto a autocoria ficou limitada ao sub-bosque. Já a anemocoria foi mais importante entre as espécies com indivíduos emergentes.Diaspore dispersal is presumed to have great fitness for plants, which could be enhanced by different dispersal modes. Our aim was to generate a dispersal spectrum and to seek for analyze relative ecological importance of tree-species dispersal modes in a seasonal forest in Santa Maria, Rio Grande do Sul, Brazil (approximately 53º54'W and 29º38'S and, with these data, to
DEFF Research Database (Denmark)
Pedersen, Martin Erland Vestergaard; Cheng, Ji; Xu, Chris
2013-01-01
An improved version of the generalized nonlinear Schrödinger equation is derived, which takes into account the correct dispersion of the transverse field distribution. The new improved version of the generalized nonlinear Schrödinger equation is verified to give the same results as the standard...
DEFF Research Database (Denmark)
Mahmud, Russel Reza; Razzak, S. M Abdur; Hasan, Md Imran
2016-01-01
Analysis of numerical design and properties of a new silica based photonic crystal fiber (PCF) are proposed in this manuscript. The design performs ultra-flattened negative chromatic dispersion (UNCD) in the optical windows 2nd and 3rd involving O to U bands in the infrared (IF) portion. The guid...
International Nuclear Information System (INIS)
Waxman, A.M.
1980-01-01
This paper concerns the geometry and physical properties of waves which arise from a shear-flow (i.e. inflection point) instability of the galactic boundary layer circulation. This circulation was shown to exist in the meridional plane of a model galaxy containing a gaseous disk embedded in a rotating gaseous halo. Previously derived equations describe the local effects of Boussinesq perturbations, in the form of spiral waves with aribitrary pitch angle, on the model disk-halo system. The equations are solved asymptotically for large values of the local Reynolds number. In passing to the limit of inviscid waves, it is possible to derive a locally valid dispersion relation. A perturbation technique is developed whereby the inviscid wave eigenvalues can be corrected for the effects of small but finite viscosity. In this way the roles of the buoyancy force, Coriolis acceleration, viscous stresses, and their interactions can be studied. It is found that, locally, the most unstable inviscid waves are leading and open with large azimuthal wavenumbers. However, these waves display little or no coherence over the face of the disk and so would not emerge as modes in a global analysis.The geometry of the dominant inviscid waves is found to be leading, tightly wound spirals. Viscous corrections shift the dominant wave form to trailing, tightly wound spirals with small azimuthal wavenumbers. These waves grow on a time scale of about 10 7 years. It is suggested that these waves can initiate spiral structure in galaxies during disk formation and that a subsequent transition to a self-gravitating acoustical mode with the same spiral geometry may occur. This transition becomes possible once the contrast in gas densities between the disk and surrounding halo becomes sufficiently large
Kanoun, Mohammed
2014-06-26
We compared the mechanism of O2 dissociation catalyzed by Cu38, Ag38, and Au38 nanoparticles. Overall, our results indicate that O2 dissociation is extremely easy on Cu38, with an almost negligible barrier for the O-O breaking step. It presents an energy barrier close to 20 kcal/mol on Ag38, which decreases to slightly more than 10 kcal/mol on Au38. This behavior is analyzed to quantify the impact of relativity and of dispersion interactions through a comparison of nonrelativistic, scalar-relativistic, and dispersioncorrected DFT methods. Nonrelativistic calculations show a clear trend down the triad, with larger in size nanoparticle (NP), weaker O2 adsorption energy, and higher O2 dissociation barrier, which is so high for Au38 to be in sharp contrast with the mild conditions used experimentally. Inclusion of relativity has no impact on the O2 adsorption energy, but it reduces the energy barrier for O2 dissociation on Au38 from 30.1 to 11.4 kcal/mol, making it even lower than that on Ag38 and consistent with the mild conditions used experimentally. Dispersion interactions have a remarkable role in improving the adsorption ability of O2 on the heavier Ag38 and especially Au38 NPs, contributing roughly 50% of the total adsorption energy, while they have much less impact on O2 adsorption on Cu38.
Brakstad, Odd G; Throne-Holst, Mimmi; Netzer, Roman; Stoeckel, Donald M; Atlas, Ronald M
2015-01-01
The Deepwater Horizon (DWH) accident in 2010 created a deepwater plume of small oil droplets from a deepwater well in the Mississippi Canyon lease block 252 (‘Macondo oil’). A novel laboratory system was used in the current study to investigate biodegradation of Macondo oil dispersions (10 μm or 30 μm median droplet sizes) at low oil concentrations (2 mg l−1) in coastal Norwegian seawater at a temperature of 4–5°C. Whole metagenome analyses showed that oil biodegradation was associated with the successive increased abundances of Gammaproteobacteria, while Alphaproteobacteria (Pelagibacter) became dominant at the end of the experiment. Colwellia and Oceanospirillales were related to n-alkane biodegradation, while particularly Cycloclasticus and Marinobacter were associated with degradation of aromatic hydrocarbons (HCs). The larger oil droplet dispersions resulted in delayed sequential changes of Oceanospirillales and Cycloclasticus, related with slower degradation of alkanes and aromatic HCs. The bacterial successions associated with oil biodegradation showed both similarities and differences when compared with the results from DWH field samples and laboratory studies performed with deepwater from the Gulf of Mexico. PMID:26485443
Unified theory of ballooning instabilities and temperature gradient driven trapped ion modes
International Nuclear Information System (INIS)
Xu, X.Q.
1990-08-01
A unified theory of temperature gradient driven trapped ion modes and ballooning instabilities is developed using kinetic theory in banana regimes. All known results, such as electrostatic and purely magnetic trapped particle modes and ideal MHD ballooning modes (or shear Alfven waves) are readily derived from our single general dispersion relation. Several new results from ion-ion collision and trapped particle modification of ballooning modes are derived and discussed and the interrelationship between those modes is established. 24 refs
Task-Related Modulations of BOLD Low-Frequency Fluctuations within the Default Mode Network
Directory of Open Access Journals (Sweden)
Silvia Tommasin
2017-07-01
Full Text Available Spontaneous low-frequency Blood-Oxygenation Level-Dependent (BOLD signals acquired during resting state are characterized by spatial patterns of synchronous fluctuations, ultimately leading to the identification of robust brain networks. The resting-state brain networks, including the Default Mode Network (DMN, are demonstrated to persist during sustained task execution, but the exact features of task-related changes of network properties are still not well characterized. In this work we sought to examine in a group of 20 healthy volunteers (age 33 ± 6 years, 8 F/12 M the relationship between changes of spectral and spatiotemporal features of one prominent resting-state network, namely the DMN, during the continuous execution of a working memory n-back task. We found that task execution impacted on both functional connectivity and amplitude of BOLD fluctuations within large parts of the DMN, but these changes correlated between each other only in a small area of the posterior cingulate. We conclude that combined analysis of multiple parameters related to connectivity, and their changes during the transition from resting state to continuous task execution, can contribute to a better understanding of how brain networks rearrange themselves in response to a task.
Chen, Mo; Liu, Chao; Xian, Hao
2015-10-10
High-speed free-space optical communication systems using fiber-optic components can greatly improve the stability of the system and simplify the structure. However, propagation through atmospheric turbulence degrades the spatial coherence of the signal beam and limits the single-mode fiber (SMF) coupling efficiency. In this paper, we analyze the influence of the atmospheric turbulence on the SMF coupling efficiency over various turbulences. The results show that the SMF coupling efficiency drops from 81% without phase distortion to 10% when phase root mean square value equals 0.3λ. The simulations of SMF coupling with adaptive optics (AO) indicate that it is inevitable to compensate the high-order aberrations for SMF coupling over relatively strong turbulence. The SMF coupling efficiency experiments, using an AO system with a 137-element deformable mirror and a Hartmann-Shack wavefront sensor, obtain average coupling efficiency increasing from 1.3% in open loop to 46.1% in closed loop under a relatively strong turbulence, D/r0=15.1.
Task-Related Modulations of BOLD Low-Frequency Fluctuations within the Default Mode Network
Tommasin, Silvia; Mascali, Daniele; Gili, Tommaso; Assan, Ibrahim Eid; Moraschi, Marta; Fratini, Michela; Wise, Richard G.; Macaluso, Emiliano; Mangia, Silvia; Giove, Federico
2017-01-01
Spontaneous low-frequency Blood-Oxygenation Level-Dependent (BOLD) signals acquired during resting state are characterized by spatial patterns of synchronous fluctuations, ultimately leading to the identification of robust brain networks. The resting-state brain networks, including the Default Mode Network (DMN), are demonstrated to persist during sustained task execution, but the exact features of task-related changes of network properties are still not well characterized. In this work we sought to examine in a group of 20 healthy volunteers (age 33 ± 6 years, 8 F/12 M) the relationship between changes of spectral and spatiotemporal features of one prominent resting-state network, namely the DMN, during the continuous execution of a working memory n-back task. We found that task execution impacted on both functional connectivity and amplitude of BOLD fluctuations within large parts of the DMN, but these changes correlated between each other only in a small area of the posterior cingulate. We conclude that combined analysis of multiple parameters related to connectivity, and their changes during the transition from resting state to continuous task execution, can contribute to a better understanding of how brain networks rearrange themselves in response to a task. PMID:28845420
Task-related modulations of BOLD low-frequency fluctuations within the default mode network
Tommasin, Silvia; Mascali, Daniele; Gili, Tommaso; Eid Assan, Ibrahim; Moraschi, Marta; Fratini, Michela; Wise, Richard G.; Macaluso, Emiliano; Mangia, Silvia; Giove, Federico
2017-07-01
Spontaneous low-frequency Blood-Oxygenation Level-Dependent (BOLD) signals acquired during resting state are characterized by spatial patterns of synchronous fluctuations, ultimately leading to the identification of robust brain networks. The resting-state brain networks, including the Default Mode Network (DMN), are demonstrated to persist during sustained task execution, but the exact features of task-related changes of network properties are still not well characterized. In this work we sought to examine in a group of 20 healthy volunteers (age 33±6 years, 8F/12M) the relationship between changes of spectral and spatiotemporal features of one prominent resting-state network, namely the DMN, during the steady-state execution of a sustained working memory n-back task. We found that the steady state execution of such a task impacted on both functional connectivity and amplitude of BOLD fluctuations within large parts of the DMN, but these changes correlated between each other only in a small area of the posterior cingulate. We conclude that combined analysis of multiple parameters related to connectivity, and their changes during the transition from resting state to steady-state task execution, can contribute to a better understanding of how brain networks rearrange themselves in response of a task.
Directory of Open Access Journals (Sweden)
Valentina Boccia
2015-01-01
Full Text Available Long gravity waves or swell dominating the sea surface is known to be very useful to estimate seabed morphology in coastal areas. The paper reviews the main phenomena related to swell waves propagation that allow seabed morphology to be sensed. The linear dispersion is analysed and an error budget model is developed to assess the achievable depth accuracy when Synthetic Aperture Radar (SAR data are used. The relevant issues and potentials of swell-based bathymetry by SAR are identified and discussed. This technique is of particular interest for characteristic regions of the Mediterranean Sea, such as in gulfs and relatively close areas, where traditional SAR-based bathymetric techniques, relying on strong tidal currents, are of limited practical utility.
International Nuclear Information System (INIS)
Czachor, A.; Al-Wahsh, H.
1999-01-01
Complete text of publication follows. To determine the neutron inelastic coherent scattering (MS) cross section for disordered magnets a system of equations of motion for the Green functions (GF) related to the localized-spin correlation-functions, has been exploited. The higher-order Green functions are decoupled using a symmetric 'equal access' (EA) form of the RPA decoupling scheme. The quasi-crystal approximation (QCA) was applied to construct the space-time Fourier transformed GF Q (ω)> related to neutron scattering. On assuming isotropy of the magnetic structure and a short range coupling between the spins (on the sphere approximation, OSA) we have found an explicit analytic form of this function. Poles of the Q (ω)> determine the dispersion relation ω = ω Q for elementary excitations, such as they are seen in the MS experiment - the positions of the MS profile maxima in the ω-Q space. Single formula for the dispersion relations derived here covers a variety of isotropic spin structures: in particular disordered 'longitudinal' ferrornagnets (ω ∼Q z , Q→ 0), disordered 'transverse' spin structures (ω ∼Q, Q→0), and some intermediate cases. For the system of spins coupled identically - the magnetization and the magnetic susceptibility calculated within the present EA-RPA approach do agree with the results of exact calculations. It provides an interesting insight into the nature of the RPA approach do agree with the results of exact calculations. It provides an interesting insight into the nature of the RPA - treatment of the localized spin dynamics. (author)
Strength of Default Mode Resting-State Connectivity Relates to White Matter Integrity in Children
Gordon, Evan M.; Lee, Philip S.; Maisog, Jose M.; Foss-Feig, Jennifer; Billington, Michael E.; VanMeter, John; Vaidya, Chandan J.
2011-01-01
A default mode network of brain regions is known to demonstrate coordinated activity during the resting state. While the default mode network is well characterized in adults, few investigations have focused upon its development. We scanned 9-13-year-old children with diffusion tensor imaging and resting-state functional magnetic resonance imaging.…
Dispersion engineering in metamaterials and metasurfaces
Li, Xiong; Pu, Mingbo; Ma, Xiaoliang; Guo, Yinghui; Gao, Ping; Luo, Xiangang
2018-02-01
Dispersion engineering is essential for spectral utilization in electromagnetic systems. However, it is difficult to manage the dispersions in both natural materials and traditional electromagnetic waveguides since they are tightly related to fine structures of atoms, molecules and causality. The emergence of metamaterials and metasurfaces, which are made of subwavelength inclusions offers tremendous freedom to manipulate the electromagnetic parameters of materials and modes. Here, we review the basic principles, practical applications and recent advancements of the dispersion engineering in metadevices. The contributions of dispersion management in metadevice-based super-resolution imaging/nanolithography systems, planar functional devices, as well as the broadband perfect absorbers/polarization converters are discussed in depth. The challenges faced by this field as well as future developing trends are also presented in the conclusions.
Subramaniam, Shankar; Sun, Bo
2015-11-01
The presence of solid particles in a steady laminar flow generates velocity fluctuations with respect to the mean fluid velocity that are termed pseudo-turbulence. The level of these pseudo-turbulent velocity fluctuations has been characterized in statistically homogeneous fixed particle assemblies and freely evolving suspensions using particle-resolved direct numerical simulation (PR-DNS) by Mehrabadi et al. (JFM, 2015), and it is found to be a significant contribution to the total kinetic energy associated with the flow. The correlation of these velocity fluctuations with temperature (or a passive scalar) generates a flux term that appears in the transport equation for the average fluid temperature (or average scalar concentration). The magnitude of this transport of temperature-velocity covariance is quantified using PR-DNS of thermally fully developed flow past a statistically homogeneous fixed assembly of particles, and the budget of the average fluid temperature equation is presented. The relation of this transport term to the axial dispersion coefficient (Brenner, Phil. Trans. Roy. Soc. A, 1980) is established. The simulation results are then interpreted in the context of our understanding of axial dispersion in gas-solid flow. NSF CBET 1336941.
DEFF Research Database (Denmark)
Pugliese, Lorenzo; Poulsen, Tjalfe; Straface, Salvatore
2013-01-01
Measurements of solute dispersion in porous media is generally much more time consuming than gas dispersion measurements performed under equivalent conditions. Significant time savings may therefore, be achieved if solute dispersion coefficients can be estimated based on measured gas dispersion...... data. This paper evaluates the possibility for estimating solute dispersion based on gas dispersion measurements. Breakthrough measurements were carried out at different fluid velocities (covering the same range in Reynolds number), using O2 and NaCl as gas and solute tracers, respectively. Three...... different, granular porous materials were used: (1) crushed granite (very angular particles), (2) gravel (particles of intermediate roundness) and (3) Leca® (almost spherical particles). For each material, 21 different particle size fractions were used. Gas and solute dispersion coefficients were determined...
Default mode network as a potential biomarker of chemotherapy-related brain injury
Kesler, Shelli R.
2014-01-01
Chronic medical conditions and/or their treatments may interact with aging to alter or even accelerate brain senescence. Adult onset cancer, for example, is a disease associated with advanced aging and emerging evidence suggests a profile of subtle but diffuse brain injury following cancer chemotherapy. Breast cancer is currently the primary model for studying these “chemobrain” effects. Given the widespread changes to brain structure and function as well as the common impairment of integrated cognitive skills observed following breast cancer chemotherapy, it is likely that large-scale brain networks are involved. Default mode network (DMN) is a strong candidate considering its preferential vulnerability to aging and sensitivity to toxicity and disease states. Additionally, chemotherapy is associated with several physiologic effects including increased inflammation and oxidative stress that are believed to elevate toxicity in the DMN. Biomarkers of DMN connectivity could aid in the development of treatments for chemotherapy-related cognitive decline. For example, certain nutritional interventions could potentially reduce the metabolic changes (e.g. amyloid beta toxicity) associated with DMN disruption. PMID:24913897
International Nuclear Information System (INIS)
Briscese, F.
2012-01-01
We show that harmonically trapped Bose-Einstein condensates can be used to constrain Planck-scale physics. In particular we prove that a Planck-scale induced deformation of the Minkowski energy-momentum dispersion relation δE≃ξ 1 mcp/2M p produces a shift in the condensation temperature T c of about ΔT c /T c 0 ≃10 -6 ξ 1 for typical laboratory conditions. Such a shift allows to bound the deformation parameter up to |ξ 1 |≤10 4 . Moreover we show that it is possible to enlarge ΔT c /T c 0 and improve the bound on ξ 1 lowering the frequency of the harmonic trap. Finally we compare the Planck-scale induced shift in T c with similar effects due to interboson interactions and finite size effects.
DEFF Research Database (Denmark)
Shibahara, Kohki; Lee, Doohwan; Kobayashi, Takayuki
2016-01-01
We propose long-haul space-division-multiplexing (SDM) transmission systems employing parallel multiple-input multiple-output (MIMO) frequency-domain equalization (FDE) and transmission fiber with low differential mode delay (DMD). We first discuss the advantages of parallel MIMO FDE technique in...
International Nuclear Information System (INIS)
Johnson, C.H.; Horen, D.J.; Mahaux, C.
1987-01-01
The real part of the central neutron-/sup 208/Pb mean field is the sum of a Hartree-Fock component plus a dispersive component. In keeping with theoretical expectations, the Hartree-Fock field is assumed to have a Woods-Saxon shape whose depth decreases exponentially with increasing energy and whose radius and diffuseness are independent of energy. The dispersive component is determined from the imaginary part of the optical-model potential by making use of the dispersion relation which connects these two quantities. The imaginary part is written as the sum of a volume and a surface-peaked contribution. The dispersion relation then implies that the real dispersive contribution is also the sum of volume and surface-peaked components. The parameters of the complex mean field are determined by fitting the available differential and polarization cross sections in the energy domain [4, 40 MeV] and the total cross sections in the domain [1,120 MeV]; these data are contained in previous published or unpublished reports, but new measurements of the total cross sections are presented from 1 to 25 MeV. Good fits to these cross sections, and also to unpublished total cross sections for energies up to 165 MeV, are obtained despite the fact that the number of adjusted parameters is quite small because of our use of the constraint implied by the dispersion relation
International Nuclear Information System (INIS)
Hota, P.K.; Vijayan, V.; Singh, L.P.
2001-01-01
Food is the principal media for intake of elements from environment to human body. Thus, it is felt important to determine the daily dietary intake of such elements in the field of toxicity and nutrition, the deficiency or sufficiency of which may lead to various diseases, disorders and allergies in human health. In this study, the elements present in commonly used cereals, pulses, noodles, some condiments/spices, tobacco products, some common leaves used in herbal medicine and tea leaves have been analyzed using EDXRF spectrometry technique. Elemental concentrations of K, Ca, Fe, Sr, Mn, Zn, Cu, Pb, As and Se are detected and quantified in all the samples using this method. The results are discussed in relation to cancer. (author)
Anomalous magnetoresistance effect in sputtered TbFeCo relating to dispersed magnetic moment
International Nuclear Information System (INIS)
Yumoto, S.; Toki, K.; Okada, O.; Gokan, H.
1988-01-01
The electric resistance is sputtered TbFeCo has been measured at room temperature as a function of magnetic field perpendicular to the film plane. Two kinds of anomalous magnetoresistance have been observed. One is a magnetoresistance peak in the magnetization reversal region. The other is reversible change proportional to the applied magnetic field, appearing in the other region. The magnetoresistance peak agrees well with a curve calculated from experimental Hall loop, using a phenomenological relation between anomalous magnetoresistance and anomalous Hall voltage. The magnetoresistance peak is found to originate from magnetic domain walls. The linear magnetoresistance change for TM dominant samples appears in a direction opposite to that for RE dominant samples. The linear change can't be derived from Hall loop
Arshad, Muhammad; Seadawy, Aly R.; Lu, Dianchen
2018-01-01
In mono-mode optical fibers, the higher order non-linear Schrödinger equation (NLSE) describes the propagation of enormously short light pulses. We constructed optical solitons and, solitary wave solutions of higher order NLSE mono-mode optical fibers via employing modified extended mapping method which has important applications in Mathematics and physics. Furthermore, the formation conditions are also given on parameters in which optical bright and dark solitons can exist for this media. The moment of the obtained solutions are also given graphically, that helps to realize the physical phenomena's of this model. The modulation instability analysis is utilized to discuss the model stability, which verifies that all obtained solutions are exact and stable. Many other such types of models arising in applied sciences can also be solved by this reliable, powerful and effective method. The method can also be functional to other sorts of higher order nonlinear problems in contemporary areas of research.
International Nuclear Information System (INIS)
Lee, Yoon Hee; Cho, Bum Hee; Cho, Nam Zin
2016-01-01
As a type of accident-tolerant fuel, fully ceramic microencapsulated (FCM) fuel was proposed after the Fukushima accident in Japan. The FCM fuel consists of tristructural isotropic particles randomly dispersed in a silicon carbide (SiC) matrix. For a fuel element with such high heterogeneity, we have proposed a two-temperature homogenized model using the particle transport Monte Carlo method for the heat conduction problem. This model distinguishes between fuel-kernel and SiC matrix temperatures. Moreover, the obtained temperature profiles are more realistic than those of other models. In Part I of the paper, homogenized parameters for the FCM fuel in which tristructural isotropic particles are randomly dispersed in the fine lattice stochastic structure are obtained by (1) matching steady-state analytic solutions of the model with the results of particle transport Monte Carlo method for heat conduction problems, and (2) preserving total enthalpies in fuel kernels and SiC matrix. The homogenized parameters have two desirable properties: (1) they are insensitive to boundary conditions such as coolant bulk temperatures and thickness of cladding, and (2) they are independent of operating power density. By performing the Monte Carlo calculations with the temperature-dependent thermal properties of the constituent materials of the FCM fuel, temperature-dependent homogenized parameters are obtained
International Nuclear Information System (INIS)
Schweitzer-Stenner, R.; Stichternath, A.; Dreybrodt, W.; Jentzen, W.; Song, X.; Shelnutt, J.A.; Nielsen, O.F.; Medforth, C.J.; Smith, K.M.
1997-01-01
We have measured the polarized Raman cross sections and depolarization ratios of 16 fundamental modes of nickel octaethyltetraphenylporphyrin in a CS 2 solution for 16 fundamental modes, i.e., the A 1g -type vibrations ν 1 , ν 2 , ν 3 , ν 4 , ν 5 , and φ 8 , the B 1g vibrations ν 11 and ν 14 , the B 2g vibrations ν 28 , ν 29 , and ν 30 and the antisymmetric A 2g modes ν 19 , ν 20 , ν 22 , and ν 23 as function of the excitation wavelength. The data cover the entire resonant regions of the Q- and B-bands. They were analyzed by use of a theory which describes intra- and intermolecular coupling in terms of a time-independent nonadiabatic perturbation theory [E. Unger, U. Bobinger, W. Dreybrodt, and R. Schweitzer-Stenner, J. Phys. Chem. 97, 9956 (1993)]. This approach explicitly accounts in a self-consistent way for multimode mixing with all Raman modes investigated. The vibronic coupling parameters obtained from this procedure were then used to successfully fit the vibronic side bands of the absorption spectrum and to calculate the resonance excitation profiles in absolute units. Our results show that the porphyrin macrocycle is subject to B 2u -(saddling) and B 1u -(ruffling) distortions which lower its symmetry to S 4 . Thus, evidence is provided that the porphyrin molecule maintains the nonplanar structure of its crystal phase in an organic solvent. The vibronic coupling parameters indicate a breakdown of the four-orbital model. This notion is corroborated by (ZINDO/S) calculations which reveal that significant configurational interaction occurs between the electronic transitions into |Q right-angle- and |1B right-angle-states and various porphyrin→porphyrin, metal→porphyrin, and porphyrin→metal transitions. (Abstract Truncated)
From dressed particle to dressed mode in plasmas
Energy Technology Data Exchange (ETDEWEB)
Itoh, Sanae-I. [Kyushu Univ., Research Inst. for Applied Mechanics, Kasuga, Fukuoka (Japan); Itoh, Kimitaka [National Inst. for Fusion Science, Toki, Gifu (Japan)
2002-05-01
A theoretical method to analyze the strong turbulence in far-nonequilibrium plasma is discussed. In this approach, a test mode is treated being dressed with interactions with other modes. Nonlinear dispersion relation of the dressed mode and statistical treatment of turbulence is briefly explained. Analogue to the method of dressed particle, which has given Balescu-Lenard collision operator for inter-particle collisions, is mentioned. (author)
International Nuclear Information System (INIS)
Efrosinin, V.P.; Zaikin, D.A.
1983-01-01
We study the possible reasons for the disagreement between the estimates of the pion-nucleon sigma term obtained by the method of dispersion relations with extrapolation to the Cheng-Dashen point and by other methods which do not involve this extrapolation. One reason for the disagreement may be the nonanalyticity of the πN amplitude in the variable t for ν = 0. We propose a method for estimating the sigma term using the threshold data for the πN amplitude, in which the effect of this nonanalyticity is minimized. We discuss the relation between scale invariance violation and chiral symmetry breaking and give the corresponding estimate of the sigma term. The two estimates are similar (42 and 34 MeV) and are in agreement when the uncertainties of the two methods are taken into consideration
Directory of Open Access Journals (Sweden)
Günther Zeck
Full Text Available BACKGROUND: Visual stimuli elicit action potentials in tens of different retinal ganglion cells. Each ganglion cell type responds with a different latency to a given stimulus, thus transforming the high-dimensional input into a temporal neural code. The timing of the first spikes between different retinal projection neurons cells may further change along axonal transmission. The purpose of this study is to investigate if intraretinal conduction velocity leads to a synchronization or dispersion of the population signal leaving the eye. METHODOLOGY/PRINCIPAL FINDINGS: We 'imaged' the initiation and transmission of light-evoked action potentials along individual axons in the rabbit retina at micron-scale resolution using a high-density multi-transistor array. We measured unimodal conduction velocity distributions (1.3±0.3 m/sec, mean ± SD for axonal populations at all retinal eccentricities with the exception of the central part that contains myelinated axons. The velocity variance within each piece of retina is caused by ganglion cell types that show narrower and slightly different average velocity tuning. Ganglion cells of the same type respond with similar latency to spatially homogenous stimuli and conduct with similar velocity. For ganglion cells of different type intraretinal conduction velocity and response latency to flashed stimuli are negatively correlated, indicating that differences in first spike timing increase (up to 10 msec. Similarly, the analysis of pair-wise correlated activity in response to white-noise stimuli reveals that conduction velocity and response latency are negatively correlated. CONCLUSION/SIGNIFICANCE: Intraretinal conduction does not change the relative spike timing between ganglion cells of the same type but increases spike timing differences among ganglion cells of different type. The fastest retinal ganglion cells therefore act as indicators of new stimuli for postsynaptic neurons. The intraretinal dispersion
Entanglement generation between two atoms via surface modes
International Nuclear Information System (INIS)
Xu Jingping; Yang Yaping; Al-Amri, M.; Zhu Shiyao; Zubairy, M. Suhail
2011-01-01
We discuss the coupling of two identical atoms, separated by a metal or metamaterial slab, through surface modes. We show that the coupling through the surface modes can induce entanglement. We discuss how to control the coupling for the metal or metamaterial slab by adjusting the symmetrical and antisymmetrical property of the surface modes. We analyze the dispersion relation of the surface modes and study the parameter ranges that support the surface modes with the same properties. Our results have potential applications in quantum communication and quantum computation.
Dalton, Alice M; Jones, Andrew P; Panter, Jenna R; Ogilvie, David
2013-01-01
Commuting provides opportunities for regular physical activity which can reduce the risk of chronic disease. Commuters' mode of travel may be shaped by their environment, but understanding of which specific environmental characteristics are most important and might form targets for intervention is limited. This study investigated associations between mode choice and a range of objectively assessed environmental characteristics. Participants in the Commuting and Health in Cambridge study reported where they lived and worked, their usual mode of travel to work and a variety of socio-demographic characteristics. Using geographic information system (GIS) software, 30 exposure variables were produced capturing characteristics of areas around participants' homes and workplaces and their shortest modelled routes to work. Associations between usual mode of travel to work and personal and environmental characteristics were investigated using multinomial logistic regression. Of the 1124 respondents, 50% reported cycling or walking as their usual mode of travel to work. In adjusted analyses, home-work distance was strongly associated with mode choice, particularly for walking. Lower odds of walking or cycling rather than driving were associated with a less frequent bus service (highest versus lowest tertile: walking OR 0.61 [95% CI 0.20-1.85]; cycling OR 0.43 [95% CI 0.23-0.83]), low street connectivity (OR 0.22, [0.07-0.67]; OR 0.48 [0.26-0.90]) and free car parking at work (OR 0.24 [0.10-0.59]; OR 0.55 [0.32-0.95]). Participants were less likely to cycle if they had access to fewer destinations (leisure facilities, shops and schools) close to work (OR 0.36 [0.21-0.62]) and a railway station further from home (OR 0.53 [0.30-0.93]). Covariates strongly predicted travel mode (pseudo r-squared 0.74). Potentially modifiable environmental characteristics, including workplace car parking, street connectivity and access to public transport, are associated with travel mode choice
Directory of Open Access Journals (Sweden)
Alice M Dalton
Full Text Available Commuting provides opportunities for regular physical activity which can reduce the risk of chronic disease. Commuters' mode of travel may be shaped by their environment, but understanding of which specific environmental characteristics are most important and might form targets for intervention is limited. This study investigated associations between mode choice and a range of objectively assessed environmental characteristics.Participants in the Commuting and Health in Cambridge study reported where they lived and worked, their usual mode of travel to work and a variety of socio-demographic characteristics. Using geographic information system (GIS software, 30 exposure variables were produced capturing characteristics of areas around participants' homes and workplaces and their shortest modelled routes to work. Associations between usual mode of travel to work and personal and environmental characteristics were investigated using multinomial logistic regression.Of the 1124 respondents, 50% reported cycling or walking as their usual mode of travel to work. In adjusted analyses, home-work distance was strongly associated with mode choice, particularly for walking. Lower odds of walking or cycling rather than driving were associated with a less frequent bus service (highest versus lowest tertile: walking OR 0.61 [95% CI 0.20-1.85]; cycling OR 0.43 [95% CI 0.23-0.83], low street connectivity (OR 0.22, [0.07-0.67]; OR 0.48 [0.26-0.90] and free car parking at work (OR 0.24 [0.10-0.59]; OR 0.55 [0.32-0.95]. Participants were less likely to cycle if they had access to fewer destinations (leisure facilities, shops and schools close to work (OR 0.36 [0.21-0.62] and a railway station further from home (OR 0.53 [0.30-0.93]. Covariates strongly predicted travel mode (pseudo r-squared 0.74.Potentially modifiable environmental characteristics, including workplace car parking, street connectivity and access to public transport, are associated with travel mode
Directory of Open Access Journals (Sweden)
Filipe Pereira
Full Text Available The pinewood nematode, Bursaphelenchus xylophilus, is one of the greatest threats to coniferous forests worldwide, causing severe ecological damage and economic loss. The biology of B. xylophilus is similar to that of its closest relative, B. mucronatus, as both species share food resources and insect vectors, and have very similar morphological characteristics, although little pathogenicity to conifers has been associated with B. mucronatus. Using both nuclear and mitochondrial DNA markers, we show that B. xylophilus and B. mucronatus form distinct phylogenetic groups with contrasting phylogeographic patterns. B. xylophilus presents lower levels of intraspecific diversity than B. mucronatus, as expected for a species that evolved relatively recently through geographical or reproductive isolation. Genetic diversity was particularly low in recently colonised areas, such as in southwestern Europe. By contrast, B. mucronatus displays high levels of genetic diversity and two well-differentiated clades in both mitochondrial and nuclear DNA phylogenies. The lack of correlation between genetic and geographic distances in B. mucronatus suggests intense gene flow among distant regions, a phenomenon that may have remained unnoticed due to the reduced pathogenicity of the species. Overall, our findings suggest that B. xylophilus and B. mucronatus have different demographic histories despite their morphological resemblance and ecological overlap. These results suggest that Bursaphelenchus species are a valuable model for understanding the dispersion of invasive species and the risks posed to native biodiversity and ecosystems.
The Higgs boson and the quark top in the formalism of dispersion relations and the standard model
International Nuclear Information System (INIS)
Bouayed, N.
2008-11-01
The mechanism of spontaneous symmetry breaking responsible for the generation of masses for both the bosons and the fermions of the Standard Model remains a mystery, especially that the Higgs has still not been discovered. In this thesis I concentrate on the study of the scalar sector of the Standard Model where the Higgs with the other Goldstone Bosons reside. This sector can best be probed through the massive vector bosons and the top quark. The former, for their privileged coupling to the Higgs and because their longitudinal mode represents the Goldstone Bosons, and the top, because of its very strong Yukawa coupling, are very sensitive to the mechanism of symmetry breaking. I first focus on a situation where the Higgs is light and study the processes W - W + → tt-bar and ZZ → tt-bar. In order to unambiguously reveal a sign of New Physics, the Standard Model needs to be predicted precisely. In a first step I therefore study the electroweak and QCD one loop corrections for these processes. This requires a renormalisation of the electroweak gauge and top sectors and mastering some one-loop techniques. I then concentrate on extracting the purely electroweak contributions to the above processes after setting up an analytical formula for the universal photonic contribution. The New Physics affecting the top and W system is parameterized with the help of effective operators describing symmetry breaking. The effect of these operators is carefully compared to the effect of the one-loop radiative corrections before setting a limit on the parameters of these New Physics operators. To give more realistic results the WW and ZZ cross sections are turned into e + e - and pp cross sections by using a structure function approach. This allows an application to the phenomenology at future colliders (LHC:Large Hadron Collider and ILC: International Linear Collider). A second aspect of the work presented here concerns the situation where the Higgs is heavy. For a heavy Higgs
Yilmaz, Yucel
2012-01-01
This study investigated the effects of negative feedback type (i.e., explicit correction vs. recasts), communication mode (i.e., face-to-face communication vs. synchronous computer-mediated communication), and target structure salience (i.e., salient vs. nonsalient) on the acquisition of two Turkish morphemes. Forty-eight native speakers of…
Giant magnon solution and dispersion relation in string theory in AdS3×S3×T4 with mixed flux
International Nuclear Information System (INIS)
Hoare, B.; Stepanchuk, A.; Tseytlin, A.A.
2014-01-01
We address the question of the exact form of the dispersion relation for light-cone string excitations in string theory in AdS 3 ×S 3 ×T 4 with mixed R–R and NS–NS 3-form fluxes. The analogy with string theory in AdS 5 ×S 5 suggests that in addition to the data provided by the perturbative near-BMN expansion and symmetry algebra considerations there is another source of information for the dispersion relation – the semiclassical giant magnon solution. In earlier work in (arXiv:1303.1037) and (arXiv:1304.4099) we found that the symmetry algebra constraints, which are consistent with a perturbative expansion, do not completely determine the form of the dispersion relation. The aim of the present paper is to fix the dispersion relation by constructing a generalisation of the known dyonic giant magnon soliton on S 3 to the presence of a non-zero NS–NS flux described by a WZ term in the string action (with coefficient q). We find that the angular momentum of this soliton gets shifted by a term linear in world-sheet momentum p. We also discuss the symmetry algebra of the string light-cone S-matrix and show that the exact dispersion relation, which should have the correct perturbative BMN and semiclassical giant magnon limits, should also contain such a linear momentum term. The simplicity of the resulting bound-state picture provides a strong argument in favour of this dispersion relation
DEFF Research Database (Denmark)
Jørgensen, Anna Cecilia; Torstenson, Anette Seo
2008-01-01
The purpose of this study is to investigate the effect of cooling mode and storage conditions on the dissolution rate of a solid dispersion prepared by melt agglomeration. The aim has been to relate this effect to the solid state properties of the agglomerates. The cooling mode had an effect on t...
International Nuclear Information System (INIS)
Kazemi, Elahe; Haji Shabani, Ali Mohammad; Dadfarnia, Shayessteh; Abbasi, Amir; Rashidian Vaziri, Mohammad Reza; Behjat, Abbas
2016-01-01
This study aims at developing a novel, sensitive, fast, simple and convenient method for separation and preconcentration of trace amounts of fluoxetine before its spectrophotometric determination. The method is based on combination of magnetic mixed hemimicelles solid phase extraction and dispersive micro solid phase extraction using 1-hexadecyl-3-methylimidazolium bromide coated magnetic graphene as a sorbent. The magnetic graphene was synthesized by a simple coprecipitation method and characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM). The retained analyte was eluted using a 100 μL mixture of methanol/acetic acid (9:1) and converted into fluoxetine-β-cyclodextrin inclusion complex. The analyte was then quantified by fiber optic linear array spectrophotometry as well as mode-mismatched thermal lens spectroscopy (TLS). The factors affecting the separation, preconcentration and determination of fluoxetine were investigated and optimized. With a 50 mL sample and under optimized conditions using the spectrophotometry technique, the method exhibited a linear dynamic range of 0.4–60.0 μg L"−"1, a detection limit of 0.21 μg L"−"1, an enrichment factor of 167, and a relative standard deviation of 2.1% and 3.8% (n = 6) at 60 μg L"−"1 level of fluoxetine for intra- and inter-day analyses, respectively. However, with thermal lens spectrometry and a sample volume of 10 mL, the method exhibited a linear dynamic range of 0.05–300 μg L"−"1, a detection limit of 0.016 μg L"−"1 and a relative standard deviation of 3.8% and 5.6% (n = 6) at 60 μg L"−"1 level of fluoxetine for intra- and inter-day analyses, respectively. The method was successfully applied to determine fluoxetine in pharmaceutical formulation, human urine and environmental water samples. - Graphical abstract: A novel, sensitive, fast, simple and convenient mixed hemimicelles dispersive micro solid
Energy Technology Data Exchange (ETDEWEB)
Kazemi, Elahe; Haji Shabani, Ali Mohammad [Department of Chemistry, Yazd University, Safaieh, 89195-741, Yazd (Iran, Islamic Republic of); Dadfarnia, Shayessteh, E-mail: sdadfarnia@yazd.ac.ir [Department of Chemistry, Yazd University, Safaieh, 89195-741, Yazd (Iran, Islamic Republic of); Abbasi, Amir [Department of Physics, Yazd University, Safaieh, 89195-741, Yazd (Iran, Islamic Republic of); Rashidian Vaziri, Mohammad Reza [Laser and Optics Research School, 14155-1339, Tehran (Iran, Islamic Republic of); Behjat, Abbas [Department of Physics, Yazd University, Safaieh, 89195-741, Yazd (Iran, Islamic Republic of)
2016-01-28
This study aims at developing a novel, sensitive, fast, simple and convenient method for separation and preconcentration of trace amounts of fluoxetine before its spectrophotometric determination. The method is based on combination of magnetic mixed hemimicelles solid phase extraction and dispersive micro solid phase extraction using 1-hexadecyl-3-methylimidazolium bromide coated magnetic graphene as a sorbent. The magnetic graphene was synthesized by a simple coprecipitation method and characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM). The retained analyte was eluted using a 100 μL mixture of methanol/acetic acid (9:1) and converted into fluoxetine-β-cyclodextrin inclusion complex. The analyte was then quantified by fiber optic linear array spectrophotometry as well as mode-mismatched thermal lens spectroscopy (TLS). The factors affecting the separation, preconcentration and determination of fluoxetine were investigated and optimized. With a 50 mL sample and under optimized conditions using the spectrophotometry technique, the method exhibited a linear dynamic range of 0.4–60.0 μg L{sup −1}, a detection limit of 0.21 μg L{sup −1}, an enrichment factor of 167, and a relative standard deviation of 2.1% and 3.8% (n = 6) at 60 μg L{sup −1} level of fluoxetine for intra- and inter-day analyses, respectively. However, with thermal lens spectrometry and a sample volume of 10 mL, the method exhibited a linear dynamic range of 0.05–300 μg L{sup −1}, a detection limit of 0.016 μg L{sup −1} and a relative standard deviation of 3.8% and 5.6% (n = 6) at 60 μg L{sup −1} level of fluoxetine for intra- and inter-day analyses, respectively. The method was successfully applied to determine fluoxetine in pharmaceutical formulation, human urine and environmental water samples. - Graphical abstract: A novel, sensitive, fast, simple and convenient mixed hemimicelles
Convective instability of RCP modes for a magnetized chiral plasma
International Nuclear Information System (INIS)
Torres-Silva, Hector; Sakanaka, P.H.; Reggiani, N.
1998-01-01
Using the Maxwell's equations and the proposed constitutive relations for a chiral plasma medium, the dispersion relations for right circularly polarized waves, (RCP), depending on the characteristics of the distribution, a new mode conversion and instabilities are found due to the chiral effect. From the dispersion relations and considering that the chirowave magnetic field may be important when the condition of velocity isotropy is dropped, we find that growing modes (instabilities) can occur at resonance and for frequencies below the electron gyrofrequency. We study, in this paper, the convective instability of RCP waves in a two-component bi-Lorentzian chiroplasma which can model the solar wind particle distributions. (author)
Van Belleghem, Steven M; Hendrickx, Frederik
2014-02-01
Local adaptation likely involves selection on multiple, genetically unlinked traits to increase fitness in divergent habitats. Conversely, recombination is expected to counteract local adaptation under gene flow by breaking down adaptive gene combinations. Western European populations of the salt marsh beetle Pogonus chalceus are characterized by large interpopulation variation at various geographical ranges in two traits related to dispersal ability, i.e. wing size and different allozymes of the mitochondrial NADP(+)-dependent isocitrate dehydrogenase (mtIdh) gene. In this study, we tested whether variation in wing length was as strongly genetically determined in locally adapted populations in a sympatric mosaic compared to allopatric populations, and if variation in mtIDH and wing size was genetically unlinked. We demonstrate that the genetic determination of wing size is very high (h (2) = 0.90) in sympatry and of comparable magnitude as geographically separated populations. Second, we show that, although frequencies of mtIDH allozymes are tightly associated with mean population wing size across Western European populations, the correlation is strongly reduced within some of the populations. These findings demonstrate that the divergence involves at least two traits under independent genetic control and that the genetically distinct ecotypes are retained at geographical distances with ample opportunity for gene flow.
Cramer, J. M.; Pal, S.; Marshall, W. M.; Santoro, R. J.
2003-01-01
Contents include the folloving: 1. Motivation. Support NASA's 3d generation launch vehicle technology program. RBCC is promising candidate for 3d generation propulsion system. 2. Approach. Focus on ejector mode p3erformance (Mach 0-3). Perform testing on established flowpath geometry. Use conventional propulsion measurement techniques. Use advanced optical diagnostic techniques to measure local combustion gas properties. 3. Objectives. Gain physical understanding of detailing mixing and combustion phenomena. Establish an experimental data set for CFD code development and validation.
International Nuclear Information System (INIS)
Van de Sande, Jesse; Franx, Marijn; Labbe, Ivo; Kriek, Mariska; Van Dokkum, Pieter G.; Bezanson, Rachel; Whitaker, Katherine E.; Brammer, Gabriel; Groot, Paul J.; Kaper, Lex
2011-01-01
Recent photometric studies have shown that early-type galaxies at fixed stellar mass were smaller and denser at earlier times. In this Letter, we assess that finding by deriving the dynamical mass of such a compact quiescent galaxy at z = 1.8. We have obtained a high-quality spectrum with full UV-NIR wavelength coverage of galaxy NMBS-C7447 using X-Shooter on the Very Large Telescope. We determined a velocity dispersion of 294 ± 51 km s -1 . Given this velocity dispersion and the effective radius of 1.64 ± 0.15 kpc (as determined from Hubble Space Telescope Wide Field Camera 3 F160W observations) we derive a dynamical mass of (1.7 ± 0.5) x 10 11 M sun . Comparison of the full spectrum with stellar population synthesis models indicates that NMBS-C774 has a relatively young stellar population (0.40 Gyr) with little or no star formation and a stellar mass of M * ∼ 1.5 x 10 11 M sun . The dynamical and photometric stellar masses are in good agreement. Thus, our study supports the conclusion that the mass densities of quiescent galaxies were indeed higher at earlier times, and this earlier result is not caused by systematic measurement errors. By combining available spectroscopic measurements at different redshifts, we find that the velocity dispersion at fixed dynamical mass was a factor of ∼1.8 higher at z = 1.8 compared with z = 0. Finally, we show that the apparent discrepancies between the few available velocity dispersion measurements at z > 1.5 are consistent with the intrinsic scatter of the mass-size relation.
Damping Measurements of Plasma Modes
Anderegg, F.; Affolter, M.; Driscoll, C. F.
2010-11-01
For azimuthally symmetric plasma modes in a magnesium ion plasma, confined in a 3 Tesla Penning-Malmberg trap with a density of n ˜10^7cm-3, we measure a damping rate of 2s-1plasma column, alters the frequency of the mode from 16 KHz to 192 KHz. The oscillatory fluid displacement is small compared to the wavelength of the mode; in contrast, the fluid velocity, δvf, can be large compared to v. The real part of the frequency satisfies a linear dispersion relation. In long thin plasmas (α> 10) these modes are Trivelpiece-Gould (TG) modes, and for smaller values of α they are Dubin spheroidal modes. However the damping appears to be non-linear; initially large waves have weaker exponential damping, which is not yet understood. Recent theoryootnotetextM.W. Anderson and T.M. O'Neil, Phys. Plasmas 14, 112110 (2007). calculates the damping of TG modes expected from viscosity due to ion-ion collisions; but the measured damping, while having a similar temperature and density dependence, is about 40 times larger than calculated. This discrepancy might be due to an external damping mechanism.
Highly dispersive transparency in coupled metamaterials
International Nuclear Information System (INIS)
Thuy, V T T; Park, J W; Lee, Y P; Tung, N T; Lam, V D; Rhee, J Y
2010-01-01
We investigate the coupling between bright and quasi-dark eigenmodes in a planar metamaterial supporting highly dispersive transparency. The specific design of such a metamaterial consists of a cut wire (CW) and a single-gap split-ring resonator (SRR). Through the numerical simulation and the equivalent-circuit analysis, we demonstrate that the response of the SRR, which is weakly excited by external electric field, plays the role of a quasi-dark eigenmode in the presence of a strongly radiative CW. Furthermore, by extending and relating our study to the trapped mode resonances and the coupling between dark and bright modes, a more comprehensive perspective for the metamaterial realization of highly dispersive transmission and slow-light applications is provided
van Turnhout, J.
2016-01-01
The dielectric spectra of colloidal systems often contain a typical low frequency dispersion, which usually remains unnoticed, because of the presence of strong conduction losses. The KK relations offer a means for converting ε′ into ε″ data. This allows us to calculate conduction free ε″ spectra in
Zong, Baoyu; Ho, Pin; Zhang, Zhiguo; Ng, Gingmeng; Yao, Kui; Guo, Zaibing
2014-01-01
in open air from relatively stable liquid dark-color polypyrrole-based dispersions, which were synthesized using appropriate surfactants during the in situ polymerization of pyrrole with FeCl3 or both H2O2 and FeCl3 as the oxidizers. The performance
International Nuclear Information System (INIS)
Kaidatzis, A; García-Martín, J M
2013-01-01
We present experimental work that reveals the benefits of performing magnetic force microscopy measurements employing the torsional resonance mode of cantilever oscillation. This approach provides two clear advantages: the ability of performing magnetic imaging without topography-related interference and the significant lateral resolution improvement (approximately 15%). We believe that this work demonstrates a significant improvement to a versatile magnetic imaging technique widely used in academia and in industry. (paper)
Badmos, Abdulyezir A.; Sun, Qizhen; Sun, Zhongyuan; Zhang, Junxi; Yan, Zhijun; Lutsyk, Petro; Rozhin, Alex; Zhang, Lin
2017-02-01
Enzyme-functionalized dual-peak long-period fiber grating (LPFG) inscribed in 80-μm-cladding B/Ge codoped single-mode fiber is presented for sugar-level and specific glucose detection. Before enzyme functionalization, the dual-peak LPFG was employed for refractive index sensing and sugar-level detection and high sensitivities of ˜4298.20 nm/RIU and 4.6696 nm/% were obtained, respectively. Glucose detection probe was attained by surface functionalization of the dual-peak LPFG via covalent binding with aminopropyl triethoxysilane used as a binding site. Optical micrographs confirmed the presence of enzyme. The surface-functionalized dual-peak LPFG was tested with D-(+)-glucose solution of different concentrations. While the peak 2 at the longer wavelength was suitable only to measure lower glucose concentration (0.1 to 1.6 mg/ml) recording a high sensitivity of 12.21±0.19 nm/(mg/ml), the peak 1 at the shorter wavelength was able to measure a wider range of glucose concentrations (0.1 to 3.2 mg/ml) exhibiting a maximum resonance wavelength shift of 7.12±0.12 nm/mg/ml. The enzyme-functionalized dual-peak LPFG has the advantage of direct inscription of highly sensitive grating structures in thin-cladding fibre without etching, and most significantly, its sensitivity improvement of approximately one order of magnitude higher than previously reported LPFG and excessively tilted fibre grating (Ex-TFG) for glucose detection.
Directory of Open Access Journals (Sweden)
Justin M J Travis
Full Text Available The eco-evolutionary dynamics of dispersal are recognised as key in determining the responses of populations to environmental changes. Here, by developing a novel modelling approach, we show that predators are likely to have evolved to emigrate more often and become more selective over their destination patch when their prey species exhibit spatio-temporally complex dynamics. We additionally demonstrate that the cost of dispersal can vary substantially across space and time. Perhaps as a consequence of current environmental change, many key prey species are currently exhibiting major shifts in their spatio-temporal dynamics. By exploring similar shifts in silico, we predict that predator populations will be most vulnerable when prey dynamics shift from stable to complex. The more sophisticated dispersal rules, and greater variance therein, that evolve under complex dynamics will enable persistence across a broader range of prey dynamics than the rules which evolve under relatively stable prey conditions.
Mode of Action of Lactoperoxidase as Related to Its Antimicrobial Activity: A Review
Directory of Open Access Journals (Sweden)
F. Bafort
2014-01-01
Full Text Available Lactoperoxidase is a member of the family of the mammalian heme peroxidases which have a broad spectrum of activity. Their best known effect is their antimicrobial activity that arouses much interest in in vivo and in vitro applications. In this context, the proper use of lactoperoxidase needs a good understanding of its mode of action, of the factors that favor or limit its activity, and of the features and properties of the active molecules. The first part of this review describes briefly the classification of mammalian peroxidases and their role in the human immune system and in host cell damage. The second part summarizes present knowledge on the mode of action of lactoperoxidase, with special focus on the characteristics to be taken into account for in vitro or in vivo antimicrobial use. The last part looks upon the characteristics of the active molecule produced by lactoperoxidase in the presence of thiocyanate and/or iodide with implication(s on its antimicrobial activity.
Dispersion modeling by kinematic simulation: Cloud dispersion model
International Nuclear Information System (INIS)
Fung, J C H; Perkins, R J
2008-01-01
A new technique has been developed to compute mean and fluctuating concentrations in complex turbulent flows (tidal current near a coast and deep ocean). An initial distribution of material is discretized into any small clouds which are advected by a combination of the mean flow and large scale turbulence. The turbulence can be simulated either by kinematic simulation (KS) or direct numerical simulation. The clouds also diffuse relative to their centroids; the statistics for this are obtained from a separate calculation of the growth of individual clouds in small scale turbulence, generated by KS. The ensemble of discrete clouds is periodically re-discretized, to limit the size of the small clouds and prevent overlapping. The model is illustrated with simulations of dispersion in uniform flow, and the results are compared with analytic, steady state solutions. The aim of this study is to understand how pollutants disperses in a turbulent flow through a numerical simulation of fluid particle motion in a random flow field generated by Fourier modes. Although this homogeneous turbulent is rather a 'simple' flow, it represents a building block toward understanding pollutant dispersion in more complex flow. The results presented here are preliminary in nature, but we expect that similar qualitative results should be observed in a genuine turbulent flow.
Energy Technology Data Exchange (ETDEWEB)
Shaltout, Abdallah A., E-mail: shaltout_a@hotmail.com [Spectroscopy Department, Physics Division, National Research Center, El Behooth Str., 12622 Dokki, Cairo (Egypt); Faculty of science, Taif University, 21974 Taif, P.O. Box 888 (Saudi Arabia); Moharram, Mohammed A. [Spectroscopy Department, Physics Division, National Research Center, El Behooth Str., 12622 Dokki, Cairo (Egypt); Mostafa, Nasser Y. [Faculty of science, Taif University, 21974 Taif, P.O. Box 888 (Saudi Arabia); Chemistry Department, Faculty of Science, Suez Canal University, Ismailia (Egypt)
2012-01-15
This work is the first attempt to quantify trace elements in the Catha edulis plant (Khat) with a fundamental parameter approach. C. edulis is a famous drug plant in east Africa and Arabian Peninsula. We have previously confirmed that hydroxyapatite represents one of the main inorganic compounds in the leaves and stalks of C. edulis. Comparable plant leaves from basil, mint and green tea were included in the present investigation as well as trifolium leaves were included as a non-related plant. The elemental analyses of the plants were done by Wavelength Dispersive X-Ray Fluorescence (WDXRF) spectroscopy. Standard-less quantitative WDXRF analysis was carried out based on the fundamental parameter approaches. According to the standard-less analysis algorithms, there is an essential need for an accurate determination of the amount of organic material in the sample. A new approach, based on the differential thermal analysis, was successfully used for the organic material determination. The obtained results based on this approach were in a good agreement with the commonly used methods. Depending on the developed method, quantitative analysis results of eighteen elements including; Al, Br, Ca, Cl, Cu, Fe, K, Na, Ni, Mg, Mn, P, Rb, S, Si, Sr, Ti and Zn were obtained for each plant. The results of the certified reference materials of green tea (NCSZC73014, China National Analysis Center for Iron and Steel, Beijing, China) confirmed the validity of the proposed method. - Highlights: Black-Right-Pointing-Pointer Quantitative analysis of Catha edulis was carried out using standardless WDXRF. Black-Right-Pointing-Pointer Differential thermal analysis was used for determination of the loss of ignition. Black-Right-Pointing-Pointer The existence of hydroxyapatite in Catha edulis plant has been confirmed. Black-Right-Pointing-Pointer The CRM results confirmed the validity of the developed method.
International Nuclear Information System (INIS)
Shaltout, Abdallah A.; Moharram, Mohammed A.; Mostafa, Nasser Y.
2012-01-01
This work is the first attempt to quantify trace elements in the Catha edulis plant (Khat) with a fundamental parameter approach. C. edulis is a famous drug plant in east Africa and Arabian Peninsula. We have previously confirmed that hydroxyapatite represents one of the main inorganic compounds in the leaves and stalks of C. edulis. Comparable plant leaves from basil, mint and green tea were included in the present investigation as well as trifolium leaves were included as a non-related plant. The elemental analyses of the plants were done by Wavelength Dispersive X-Ray Fluorescence (WDXRF) spectroscopy. Standard-less quantitative WDXRF analysis was carried out based on the fundamental parameter approaches. According to the standard-less analysis algorithms, there is an essential need for an accurate determination of the amount of organic material in the sample. A new approach, based on the differential thermal analysis, was successfully used for the organic material determination. The obtained results based on this approach were in a good agreement with the commonly used methods. Depending on the developed method, quantitative analysis results of eighteen elements including; Al, Br, Ca, Cl, Cu, Fe, K, Na, Ni, Mg, Mn, P, Rb, S, Si, Sr, Ti and Zn were obtained for each plant. The results of the certified reference materials of green tea (NCSZC73014, China National Analysis Center for Iron and Steel, Beijing, China) confirmed the validity of the proposed method. - Highlights: ► Quantitative analysis of Catha edulis was carried out using standardless WDXRF. ► Differential thermal analysis was used for determination of the loss of ignition. ► The existence of hydroxyapatite in Catha edulis plant has been confirmed. ► The CRM results confirmed the validity of the developed method.
Kalimeris, Anastasios; Ranieri, Ezio; Founda, Dimitra; Norrant, Caroline
2017-12-01
This study analyses a century-long set of precipitation time series in the Central Mediterranean (encompassing the Greek Ionian and the Italian Puglia regions) and investigates the statistically significant modes of the interannual precipitation variability using efficient methods of spectral decomposition. The statistical relations and the possible physical couplings between the detected modes and the global or hemispheric patterns of climatic variability (the El Niño Southern Oscillation or ENSO, the North Atlantic Oscillation or NAO, the East Atlantic or EA, the Scandinavian or SCAND, and others) were examined in the time-frequency domain and low-order synchronization events were sought. Significant modes of precipitation variability were detected in the Taranto Gulf and the southern part of the Greek Ionian region at the sub-decadal scales (mostly driven by the SCAND pattern) and particularly at the decadal and quasi-decadal scales, where strong relations found with the ENSO activity (under complex implications of EA and NAO) prior to the 1930s or after the early-1970s. The precipitation variations in the Adriatic stations of Puglia are dominated by significant bi-decadal modes which found to be coherent with the ENSO activity and also weakly related with the Atlantic Ocean sea surface temperature intrinsic variability. Additionally, important discontinuities characterize the evolution of precipitation in certain stations of the Taranto Gulf and the Greek Ionian region during the early-1960s and particularly during the early-1970s, followed by significant reductions in the mean annual precipitation. These discontinuities seem to be associated with regional effects of NAO and SCAND, probably combined with the impact of the 1970s climatic shift in the Pacific and the ENSO variability.
Das, Shyamal; Larson, Ian; Young, Paul; Stewart, Peter
2009-06-28
This study investigated changes in agglomeration and the mechanism of dispersibility decrease of salmeterol xinafoate (SX) from SX-lactose mixtures for inhalation after storage at 75% RH for 3 months. The dispersibility, PSD and in situ PSD of aerosol plumes of SX alone and SX-coarse lactose (CL) mixtures containing 0, 5, 10 and 20% micronized lactose (ML) before and after storage were determined by a Next Generation Impactor (NGI), a Mastersizer 2000 and a Spraytec, respectively. The PSD of ML increased after storage at 75% RH, but dispersibility of SX using the stored ML increased. After storage, the %SX of the mixture containing 20% ML (M20F) significantly increased (Pagglomerates, probably occurring through enhanced capillary interaction and/or solid bridging of ML, entrapping and preventing the release of SX particles.
DEFF Research Database (Denmark)
Poulsen, P L; Ebbehøj, E; Arildsen, H
2001-01-01
. The association between QTc dispersion and diastolic night BP persisted after controlling for potential confounders such as sex, age, duration of diabetes, urinary albumin excretion, and HbA1c. Power spectral analysis suggested an altered sympathovagal balance in patients with QTc dispersion above the median...... (ratio of low-frequency/high-frequency power: 1.0 vs. 0.85, P fall in BP and an altered sympathovagal balance. This coexistence may be operative in the ability of these parameters......A reduced nocturnal fall in blood pressure (BP) and increased QT dispersion both predict an increased risk of cardiovascular events in diabetic as well as nondiabetic subjects. The relationship between these two parameters remains unclear. The role of diabetic autonomic neuropathy in both QT...
International Nuclear Information System (INIS)
Tovio, D. O.; Gonzalez, A.C.; Mugica, G. W.; Cuyas, J. C.
2003-01-01
In the present work the effect of iron (0.15, 0.42 and 0.86%) content in feeding mechanisms for 380 aluminium alloy has been studied. The feeding capacity has been evaluated by a device that produces a barrier removable to allowing the movement of the inter dendritic liquid. The results show the flow of different quantity of liquid, it depends of the temperature of operating the device and of the iron content. For minimum and maximum iron content, the inter dendritic and bursts feeding mechanisms are fundamentally involved, for 0.42% of iron the feeding mechanisms was the inter dendritic. The authors establish this behavior by the solidification mode of alloy, which promotes the presence of particles of Si or plates of b-Al 3 FeDi phase, in the inter dendritic channels and produce the different feeding mechanisms. (Author) 15 refs
Low frequency electrostatic modes in a magnetized dusty plasma
International Nuclear Information System (INIS)
Salimullah, M.; Hassan, M.H.A.
1991-09-01
The dispersion properties of low frequency electrostatic modes in a dusty plasma in the presence of a static homogeneous magnetic field are examined. It is found that the presence of the dust particles and the static magnetic field have significant effects on the dispersion relations. For the parallel propagation the electrostatic mode is slightly modified by the magnetic field for the ion acoustic branch. A new longitudinal mode arises at the extreme low frequency limit, which is unaffected by the magnetic field for the parallel propagation. For the transverse propagation the ion acoustic mode is not affected by the magnetic field. However, the undamped extreme low frequency mode is significantly modified by the presence of the magnetic field for the propagation transverse to the direction of the magnetic field. (author). 23 refs
Mode conversion and its utilization of degenerating surface wave modes on a plasma column
International Nuclear Information System (INIS)
Nonaka, S.; Akao, Y.
1983-01-01
Both mode conversion at degenerating points of dispersion relations for surface wave modes on a discharge plasma column and the methods for their detection and utilization are presented. Mode conversions at three degenerating points become observable by using a surface wave resonator when an azimuthal inhomogeneity of plasma is produced by a static magnetic field of about 1 G applied perpendicular to the column axis. Two of the three detected degenerating points can be utilized for an easy and exact determination of the electron density and its distribution in the discharge tube
Energy Technology Data Exchange (ETDEWEB)
Bulatov, A.I.; Chernov, V.S.; Prokopov, L.I.; Proselkov, Yu.M.; Tikhonov, Yu.P.
1980-01-15
A hydrodynamic disperser is suggested which contains a housing, slit nozzles installed on a circular base arranged opposite from each other, resonators secured opposite the nozzle and outlet sleeve. In order to improve the effectiveness of dispersion by throttling the flow, each resonator is made in the form of a crimped plate with crimpings that decrease in height in a direction towards the nozzle.
Kevin T. Smith; Jean Christophe Balouet; Walter C. Shortle; Michel Chalot; François Beaujard; Hakan Grudd; Don A. Vroblesky; Joel G. Burken
2014-01-01
Energy dispersive X-ray fluorescence (EDXRF) provides highly sensitive and precise spatial resolution of cation content in individual annual growth rings in trees. The sensitivity and precision have prompted successful applications to forensic dendrochemistry and the timing of environmental releases of contaminants. These applications have highlighted the need to...
Fallah-Shorshani, Masoud; Shekarrizfard, Maryam; Hatzopoulou, Marianne
2017-10-01
Dispersion of road transport emissions in urban metropolitan areas is typically simulated using Gaussian models that ignore the turbulence and drag induced by buildings, which are especially relevant for areas with dense downtown cores. To consider the effect of buildings, street canyon models are used but often at the level of single urban corridors and small road networks. In this paper, we compare and validate two dispersion models with widely varying algorithms, across a modelling domain consisting of the City of Montreal, Canada accounting for emissions of more 40,000 roads. The first dispersion model is based on flow decomposition into the urban canopy sub-flow as well as overlying airflow. It takes into account the specific height and geometry of buildings along each road. The second model is a Gaussian puff dispersion model, which handles complex terrain and incorporates three-dimensional meteorology, but accounts for buildings only through variations in the initial vertical mixing coefficient. Validation against surface observations indicated that both models under-predicted measured concentrations. Average weekly exposure surfaces derived from both models were found to be reasonably correlated (r = 0.8) although the Gaussian dispersion model tended to underestimate concentrations around the roadways compared to the street canyon model. In addition, both models were used to estimate exposures of a representative sample of the Montreal population composed of 1319 individuals. Large differences were noted whereby exposures derived from the Gaussian puff model were significantly lower than exposures derived from the street canyon model, an expected result considering the concentration of population around roadways. These differences have large implications for the analyses of health effects associated with NO2 exposure.
International Nuclear Information System (INIS)
Pryce, M.H.L.
1985-01-01
A dominant mechanism contributing to hydrodynamic dispersion in fluid flow through rocks is variation of travel speeds within the channels carrying the fluid, whether these be interstices between grains, in granular rocks, or cracks in fractured crystalline rocks. The complex interconnections of the channels ensure a mixing of those parts of the fluid which travel more slowly and those which travel faster. On a macroscopic scale this can be treated statistically in terms of the distribution of times taken by a particle of fluid to move from one surface of constant hydraulic potential to another, lower, potential. The distributions in the individual channels are such that very long travel times make a very important contribution. Indeed, while the mean travel time is related to distance by a well-defined transport speed, the mean square is effectively infinite. This results in an asymmetrical plume which differs markedly from a gaussian shape. The distribution of microscopic travel times is related to the distribution of apertures in the interstices, or in the microcracks, which in turn are affected in a complex way by the stresses acting on the rock matrix
Middleton, B.; Van Diggelen, R.; Jensen, K.
2006-01-01
Question: How does seed dispersal reduce fen isolation and contribute to biodiversity? Location: European and North American fens. Methods: This paper reviews the literature on seed dispersal to fens. Results: Landscape fragmentation may reduce dispersal opportunities thereby isolating fens and reducing genetic exchange. Species in fragmented wetlands may have lower reproductive success, which can lead to biodiversity loss. While fens may have always been relatively isolated from each other, they have become increasingly fragmented in modern times within agricultural and urban landscapes in both Europe and North America. Dispersal by water, animals and wind has been hampered by changes related to development in landscapes surrounding fens. Because the seeds of certain species are long-lived in the seed bank, frequent episodes of dispersal are not always necessary to maintain the biodiversity of fens. However, of particular concern to restoration is that some dominant species, such as the tussock sedge Carex stricta, may not disperse readily between fens. Conclusions: Knowledge of seed dispersal can be used to maintain and restore the biodiversity of fens in fragmented landscapes. Given that development has fragmented landscapes and that this situation is not likely to change, the dispersal of seeds might be enhanced by moving hay or cattle from fens to damaged sites, or by reestablishing lost hydrological connections. ?? IAVS; Opulus Press.
Chusai, Chatinai; Manomaiphiboon, Kasemsan; Saiyasitpanich, Phirun; Thepanondh, Sarawut
2012-08-01
Map Ta Phut industrial area (MA) is the largest industrial complex in Thailand. There has been concern about many air pollutants over this area. Air quality management for the area is known to be difficult, due to lack of understanding of how emissions from different sources or sectors (e.g., industrial, power plant, transportation, and residential) contribute to air quality degradation in the area. In this study, a dispersion study of NO2 and SO2 was conducted using the AERMOD model. The area-specific emission inventories of NOx and SO2 were prepared, including both stack and nonstack sources, and divided into 11 emission groups. Annual simulations were performed for the year 2006. Modeled concentrations were evaluated with observations. Underestimation of both pollutants was Jbund, and stack emission estimates were scaled to improve the modeled results before quantifying relative roles of individual emission groups to ambient concentration overfour selected impacted areas (two are residential and the others are highly industrialized). Two concentration measures (i.e., annual average area-wide concentration or AC, and area-wide robust highest concentration or AR) were used to aggregately represent mean and high-end concentrations Jbfor each individual area, respectively. For AC-NO2, on-road mobile emissions were found to be the largest contributor in the two residential areas (36-38% of total AC-NO2), while petrochemical-industry emissions play the most important role in the two industrialized areas (34-51%). For AR-NO2, biomass burning has the most influence in all impacted areas (>90%) exceptJor one residential area where on-road mobile is the largest (75%). For AC-SO2, the petrochemical industry contributes most in all impacted areas (38-56%). For AR-SO2, the results vary. Since the petrochemical industry was often identified as the major contributor despite not being the largest emitter, air quality workers should pay special attention to this emission group
Svob, Connie; Wang, Zhishun; Weissman, Myrna M; Wickramaratne, Priya; Posner, Jonathan
2016-11-10
Individuals at high risk for depression have increased default mode network (DMN) connectivity, as well as reduced inverse connectivity between the DMN and the central executive network (CEN) [8]. Other studies have indicated that the belief in the importance of religion/spirituality (R/S) is protective against depression in high risk individuals [5]. Given these findings, we hypothesized that R/S importance would moderate DMN connectivity, potentially reducing DMN connectivity or increasing DMN-CEN inverse connectivity in individuals at high risk for depression. Using resting-state functional connectivity MRI (rs-fcMRI) in a sample of 104 individuals (aged 11-60) at high and low risk for familial depression, we previously reported increased DMN connectivity and reduced DMN-CEN inverse connectivity in high risk individuals. Here, we found that this effect was moderated by self-report measures of R/S importance. Greater R/S importance in the high risk group was associated with decreased DMN connectivity. These results may represent a protective neural adaptation in the DMN of individuals at high risk for depression, and may have implications for other meditation-based therapies for depression. Published by Elsevier Ireland Ltd.
International Nuclear Information System (INIS)
Bruynooghe, Christiane; Noel, Marc
2009-01-01
This work is part of the European Clearinghouse on Nuclear Power Plant Operational Experience Feedback (NPP-OEF) activity carried out at the Joint Research Centre/Institute for Energy (JRC/IE) with the participation of nine EU Regulatory Authorities. It investigates the 1999 Shika-1 criticality event together with other shortcomings in reactivity management reported to the IAE4 Incident Reporting System in the period 1981-2008. The aim of the work was to identify reactivity control failure modes, reactor status and corrective actions. Initiating factors and associated root causes were also analysed. Five of the 7 factors identified for all events were present in the 1999 Shika-1 event where criticality has been unexpectedly reached and maintained during 15 minutes. Most of the events resulted in changes in procedures, material or staff and management training. The analysis carried out put in evidence that in several instances appropriate communication based on operational experience feedback would have prevented incident to occur. This paper also summarises the action taken at power plants and by the regulatory bodies in different countries to avoid repetition of similar events. It identifies insights that might be useful to reduce the likelihood of operational events caused by shortcomings in reactivity management. (orig.)
Resonant MHD modes with toroidal coupling
International Nuclear Information System (INIS)
Connor, J.W.; Hastie, R.J.; Taylor, J.B.
1990-07-01
This is part 2 of a study of resonant perturbations, such as resistive tearing and ballooning modes, in a torus. These are described by marginal ideal mhd equations in the regions between resonant surfaces; matching across these surfaces provides the dispersion relation. In part 1 we described how all the necessary information from the ideal mhd calculations could be represented by a so-called E-matrix. We also described the calculation of this E-matrix for tearing modes (even parity in perturbed magnetic field) in a large aspect ratio torus. There the toroidal modes comprise coupled cylinder tearing modes and the E-matrix is a generalization of the familiar Δ' quantity in a cylinder. In the present paper we discuss resistive ballooning, or twisting-modes, which have odd-parity in perturbed magnetic field. We show that, unlike the tearing modes, these odd-parity modes are instrinsically toroidal and are not directly related to the odd-parity modes in a cylinder. This is evident from the analysis of the high-n limit in ballooning-space, where a transition from a stable Δ' to an unstable Δ' occurs for the twisting mode when the ballooning effect exceeds the interchange effect, which can occur even at large aspect ratio (as in a tokamak). Analysis of the high-n limit in coordinate space, rather than ballooning space, clarifies this singular behaviour and indicates how one may define twisting-mode Δ'. It also yields a prescription for treating low-n twisting modes and a method for calculating an E-matrix for resistive ballooning modes in a large aspect ratio tokamak. The elements of this matrix are given in terms of cylindrical tearing mode solutions
Li, Xixi; He, Mei; Wang, Haiyan
2017-12-01
In this study, failure mode and effect analysis (FMEA), a proactive tool, was applied to reduce errors associated with the process which begins with assessment of patient and ends with treatment of complications. The aim of this study is to assess whether FMEA implementation will significantly reduce the incidence of catheter-related bloodstream infections (CRBSIs) in intensive care unit.The FMEA team was constructed. A team of 15 medical staff from different departments were recruited and trained. Their main responsibility was to analyze and score all possible processes of central venous catheterization failures. Failure modes with risk priority number (RPN) ≥100 (top 10 RPN scores) were deemed as high-priority-risks, meaning that they needed immediate corrective action. After modifications were put, the resulting RPN was compared with the previous one. A centralized nursing care system was designed.A total of 25 failure modes were identified. High-priority risks were "Unqualified medical device sterilization" (RPN, 337), "leukopenia, very low immunity" (RPN, 222), and "Poor hand hygiene Basic diseases" (RPN, 160). The corrective measures that we took allowed a decrease in the RPNs, especially for the high-priority risks. The maximum reduction was approximately 80%, as observed for the failure mode "Not creating the maximal barrier for patient." The averaged incidence of CRBSIs was reduced from 5.19% to 1.45%, with 3 months of 0 infection rate.The FMEA can effectively reduce incidence of CRBSIs, improve the security of central venous catheterization technology, decrease overall medical expenses, and improve nursing quality. Copyright © 2017 The Authors. Published by Wolters Kluwer Health, Inc. All rights reserved.
Fu, Xiangwen; Liu, Junfeng; Ban-Weiss, George A.; Zhang, Jiachen; Huang, Xin; Ouyang, Bin; Popoola, Olalekan; Tao, Shu
2017-09-01
Street canyons are ubiquitous in urban areas. Traffic-related air pollutants in street canyons can adversely affect human health. In this study, an urban-scale traffic pollution dispersion model is developed considering street distribution, canyon geometry, background meteorology, traffic assignment, traffic emissions and air pollutant dispersion. In the model, vehicle exhausts generated from traffic flows first disperse inside street canyons along the micro-scale wind field generated by computational fluid dynamics (CFD) model. Then, pollutants leave the street canyon and further disperse over the urban area. On the basis of this model, the effects of canyon geometry on the distribution of NOx and CO from traffic emissions were studied over the center of Beijing. We found that an increase in building height leads to heavier pollution inside canyons and lower pollution outside canyons at pedestrian level, resulting in higher domain-averaged concentrations over the area. In addition, canyons with highly even or highly uneven building heights on each side of the street tend to lower the urban-scale air pollution concentrations at pedestrian level. Further, increasing street widths tends to lead to lower pollutant concentrations by reducing emissions and enhancing ventilation simultaneously. Our results indicate that canyon geometry strongly influences human exposure to traffic pollutants in the populated urban area. Carefully planning street layout and canyon geometry while considering traffic demand as well as local weather patterns may significantly reduce inhalation of unhealthy air by urban residents.
Directory of Open Access Journals (Sweden)
Denize Cristina Kaminski Ferreira
2011-12-01
Full Text Available The present article has as objective to analyze the relation between education and work throughout the history of the humanity, for in such a way, the starting point is the conceptualization of the related categories, as well as the exposition of its variations and relation in the different ways of material production of the existence human being (primitive community, slavery society, feudal system and capitalism, aiming at to apprehend the multiple influences that both exert between itself, in order to make possible a bigger understanding of the historical and social evolution of the man
Ahmed, Chaara El Mouez
Nous avons etudie les relations de dispersion et la diffusion des glueballs et des mesons dans le modele U(1)_{2+1} compact. Ce modele a ete souvent utilise comme un simple modele de la chromodynamique quantique (QCD), parce qu'il possede le confinement ainsi que les etats de glueballs. Par contre, sa structure mathematique est beaucoup plus simple que la QCD. Notre methode consiste a diagonaliser l'Hamiltonien de ce modele dans une base appropriee de graphes et sur reseau impulsion, afin de generer les relations de dispersion des glueballs et des mesons. Pour la diffusion, nous avons utilise la methode dependante du temps pour calculer la matrice S et la section efficace de diffusion des glueballs et des mesons. Les divers resultats obtenus semblent etre en accord avec les travaux anterieurs de Hakim, Alessandrini et al., Irving et al., qui eux, utilisent plutot la theorie des perturbations en couplage fort, et travaillent sur un reseau espace-temps.
Orton, E S; Brasier, C M; Bilham, L J; Bansal, A; Webber, J F; Brown, J K M
2018-02-01
The ash dieback fungus, Hymenoscyphus fraxineus , a destructive, alien pathogen of common ash ( Fraxinus excelsior ), has spread across Europe over the past 25 years and was first observed in the UK in 2012. To investigate the relationship of the pathogen's population structure to its mode of arrival, isolates were obtained from locations in England and Wales, either where established natural populations of ash had been infected by wind-dispersed ascospores or where the fungus had been introduced on imported planting stock. Population structure was determined by tests for vegetative compatibility (VC), mating type and single-nucleotide polymorphisms (SNPs). VC heterogeneity was high at all locations, with 96% of isolate pairings being incompatible. Frequencies of the MAT1-1-1 and MAT1-2-1 idiomorphs were approximately equal, consistent with H. fraxineus being an obligate outbreeder. Most SNP variation occurred within study location and there was little genetic differentiation between the two types of location in the UK, or between pathogen populations in the UK and continental Europe. There was modest differentiation between UK subpopulations, consistent with genetic variation between source populations in continental Europe. However, there was no evidence of strong founder effects, indicating that numerous individuals of H. fraxineus initiated infection at each location, regardless of the route of pathogen transmission. The ssRNA virus HfMV1 was present at moderate to high frequencies in all UK subpopulations. The results imply that management of an introduced plant pathogen requires action against its spread at the continental level involving coordinated efforts by European countries.
Theory of a beam-induced electromagnetic mode in a magnetized plasma
International Nuclear Information System (INIS)
Baumgaertel, K.; Sauer, K.
1985-01-01
The theory of a recently discovered plasma wave mode is presented. In a non-Maxwellian high-beta plasma a new electromagnetic mode was detected containing a group of energetic field-aligned electrons. The theory uses the standard method for derivation of the dispersion relation, allowing non-Maxwellian electron distributions and right-hand polarization. The theoretical dispersion relation is compared with the empirical data. This comparison confirmes the existence of a right-hand circularly polarized mode propagating parallel to the external magnetic field. (D.Gy.)
International Nuclear Information System (INIS)
Van Dorpe, F.; Jourdain, F.
2006-01-01
Full text: The numerical code M.I.R.A.G.E. (Module of Radiological impact calculations on the Environment due to accidental or chronic nuclear releases through Aqueous and Gas media) has been developed to simulate the radionuclides transfer in the biosphere and food chains, as well as the dosimetric impact on man, after accidental or chronic releases in the environment by nuclear installations. The originality of M.I.R.A.G.E. is to propose a single tool chained downstream with various atmospheric and liquid dispersion codes. The code M.I.R.A.G.E. is a series of modules which makes it possible to carry out evaluations on the transfers in food chains and human dose impact. Currently, M.I.R.A.G.E. is chained with a Gaussian atmospheric dispersion code H.A.R.M.A.T.T.A.N. (Cea), a 3 D atmospheric dispersion code with Lagrangian model named M.I.N.E.R.V.E.-S.P.R.A.Y. (Aria Technology) and a 3 D groundwater transfer code named M.A.R.T.H.E. (B.R.G.M.). M.I.R.A.G.E. uses concentration or activity result files as initial data input for its calculations. The application initially calculates the concentrations in the various compartments of the environment (soils, plants, animals). The results are given in the shape of concentration and dose maps and also on a particular place called a reference group for dosimetric impact (like a village or a specific population group located around a nuclear installation). The input and output data of M.I.R.A.G.E. can have geographic coordinates and thus readable by a G.I.S. M.I.R.A.G. E.is an opened system with which it is easy to chain other codes of dispersion that those currently used. The calculations uncoupled with dispersion calculations are also possible by manual seizure of the dispersion data (contamination of a tablecloth, particular value in a point, etc.). M.I.R.A.G.E. takes into account soil deposits and resuspension phenomenon, transfers in plants and animals (choice of agricultural parameters, types of plants and animals, etc
A robust approach for analysing dispersion of elastic waves in an orthotropic cylindrical shell
Kaplunov, J.; Nobili, A.
2017-08-01
Dispersion of elastic waves in a thin orthotropic cylindrical shell is considered, within the framework of classical 2D Kirchhoff-Love theory. In contrast to direct multi-parametric analysis of the lowest propagating modes, an alternative robust approach is proposed that simply requires evaluation of the evanescent modes (quasi-static edge effect), which, at leading order, do not depend on vibration frequency. A shortened dispersion relation for the propagating modes is then derived by polynomial division and its accuracy is numerically tested against the full Kirchhoff-Love dispersion relation. It is shown that the same shortened relation may be also obtained from a refined dynamic version of the semi-membrane theory for cylindrical shells. The presented results may be relevant for modelling various types of nanotubes which, according to the latest experimental findings, possess strong material anisotropy.
The effect of work-related factors on the bicycle commute mode choice in the Netherlands
Heinen, E.; Maat, K.; Van Wee, G.P.
2012-01-01
Increasing the number of people cycling to work brings a number of benefits: it can lead to reductions in air pollution and traffic jams, and increases people’s physical activity levels. We investigated the extent to which work-related factors influence (1) whether an individual decides to cycle to
Characterization of Non-Linearized Spacecraft Relative Motion using Nonlinear Normal Modes
2016-04-20
the HCW equation (Eq. (2) expressed in terms of relative orbit elements (ROEs) [17], x(t) = −ae 2 cos(β) + xd y(t) = ae sin(β) + yd z(t) = zm cos(ψ...30) where ae, xd , zm are constant and yd(t) = yd0− 32nxdt, β(t) = β0 +nt and ψ(t) = ψ0 +nt are time dependent. It is clear that (ae, zm, xd , yd0, β0...quantities correspond to the ambiguous orbit. It is noted that if the non- drifting condition xd = 0 is satisfied, Eqs. (37-40) will vanish. In the
Baldassarri, Marta; Zhang, Yu; Thompson, Van P.; Rekow, Elizabeth D.; Stappert, Christian F. J.
2011-01-01
Summary Objectives To compare fatigue failure modes and reliability of hand-veneered and over-pressed implant-supported three-unit zirconium-oxide fixed-dental-prostheses(FDPs). Methods Sixty-four custom-made zirconium-oxide abutments (n=32/group) and thirty-two zirconium-oxide FDP-frameworks were CAD/CAM manufactured. Frameworks were veneered with hand-built up or over-pressed porcelain (n=16/group). Step-stress-accelerated-life-testing (SSALT) was performed in water applying a distributed contact load at the buccal cusp-pontic-area. Post failure examinations were carried out using optical (polarized-reflected-light) and scanning electron microscopy (SEM) to visualize crack propagation and failure modes. Reliability was compared using cumulative-damage step-stress analysis (Alta-7-Pro, Reliasoft). Results Crack propagation was observed in the veneering porcelain during fatigue. The majority of zirconium-oxide FDPs demonstrated porcelain chipping as the dominant failure mode. Nevertheless, fracture of the zirconium-oxide frameworks was also observed. Over-pressed FDPs failed earlier at a mean failure load of 696 ± 149 N relative to hand-veneered at 882 ± 61 N (profile I). Weibull-stress-number of cycles-unreliability-curves were generated. The reliability (2-sided at 90% confidence bounds) for a 400N load at 100K cycles indicated values of 0.84 (0.98-0.24) for the hand-veneered FDPs and 0.50 (0.82-0.09) for their over-pressed counterparts. Conclusions Both zirconium-oxide FDP systems were resistant under accelerated-life-time-testing. Over-pressed specimens were more susceptible to fatigue loading with earlier veneer chipping. PMID:21557985
Almeida, Carlos Humberto; Duarte, Ricardo; Volossovitch, Anna; Ferreira, António Paulo
2016-07-01
This study aimed to examine the scoring mode (line goal, double goal or central goal) and age-related effects on the defensive performance of youth soccer players during 4v4 small-sided games (SSGs). Altogether, 16 male players from 2 age groups (U13, n = 8, mean age: 12.61 ± 0.65 years; U15, n = 8, 14.86 ± 0.47 years) were selected as participants. In six independent sessions, participants performed the three SSGs each during 10-min periods. Teams' defensive performance was analysed at every instant ball possession was regained through the variables: ball-recovery type, ball-recovery sector, configuration of play and defence state. Multinomial logistic regression analysis used in this study revealed the following significant main effects of scoring mode and age: (1) line goal (vs. central goal) increased the odds of regaining possession through tackle and in the defensive midfield sector, and decreased the odds of successful interceptions; (2) double goal (vs. central goal) decreased the odds of regaining possession through turnover won and with elongated playing shapes; (3) the probability of regaining possession through interception significantly decreased with age. Moreover, as youth players move forward in age groups, teams tend to structurally evolve from elongated playing shapes to flattened shapes and, at a behavioural level, from defending in depth to more risky flattened configurations. Overall, by manipulating the scoring mode in SSGs, coaches can promote functional and coadaptive behaviours between teams not only in terms of configurations of play, but also on the pitch locations that teams explore to regain possession.
Yasuda, C; Yasuda, S; Yamashita, H; Okada, J; Hisada, T; Sugiura, S
2015-08-01
The majority of drug induced arrhythmias are related to the prolongation of action potential duration following inhibition of rapidly activating delayed rectifier potassium current (I(Kr)) mediated by the hERG channel. However, for arrhythmias to develop and be sustained, not only the prolongation of action potential duration but also its transmural dispersion are required. Herein, we evaluated the effect of hERG inhibition on transmural dispersion of action potential duration using the action potential clamp technique that combined an in silico myocyte model with the actual I(Kr) measurement. Whole cell I(Kr) current was measured in Chinese hamster ovary cells stably expressing the hERG channel. The measured current was coupled with models of ventricular endocardial, M-, and epicardial cells to calculate the action potentials. Action potentials were evaluated under control condition and in the presence of 1, 10, or 100 μM disopyramide, an hERG inhibitor. Disopyramide dose-dependently increased the action potential durations of the three cell types. However, action potential duration of M-cells increased disproportionately at higher doses, and was significantly different from that of epicardial and endocardial cells (dispersion of repolarization). By contrast, the effects of disopyramide on peak I(Kr) and instantaneous current-voltage relation were similar in all cell types. Simulation study suggested that the reduced repolarization reserve of M-cell with smaller amount of slowly activating delayed rectifier potassium current levels off at longer action potential duration to make such differences. The action potential clamp technique is useful for studying the mechanism of arrhythmogenesis by hERG inhibition through the transmural dispersion of repolarization.
Prinzing, A.; Dauber, J.; Hammer, E.; Hammouti, N.; Bohning-Gaese, K.
2008-01-01
Many plant species use ants as seed dispersers. This dispersal mode is considered to be susceptible to disturbances, but the effect of natural, small-scale disturbances is still unknown. We investigated how small-scale disturbances due to inundation affect seed dispersal in Viola reichenbachiana, a
Theory of electrostatic fluid modes in a cold spheroidal non-neutral plasma
International Nuclear Information System (INIS)
Dubin, D.H.E.
1991-01-01
The normal modes of a magnetized spheroidally shaped pure ion plasma have recently been measured. Here the theory of these modes is presented. Although one might expect that a numerical solution is required (because the plasma dielectric is anisotropic and the plasma is inhomogeneous), the problem is actually separable in an unusual coordinate system. The result is a simple electrostatic fluid dispersion relation for modes in a cloud of any spheroidal shape
IAEA mode-related research in the safe transport of radioactive material
Energy Technology Data Exchange (ETDEWEB)
Blalock, L.G.; Rawl, R.R. [International Atomic Energy Agency, IAEA, Vienna (Austria)
1998-07-01
The International Atomic Energy Agency sponsors Co-ordinated Research Programmes (CRP) in the safe transport of radioactive material. The CRPs are intended to encourage research by Member States in identified areas and to facilitate co-ordination of exchange of information and resources to reach a common understanding of the problem and alternative solutions. Two of these programmes are: Accident Severity at Sea During the Transport of Radioactive Material and Accident Severity During the Air Transport of Radioactive Material. This paper will discuss these two programmes and their relationship to the continuing regulatory revision process and interfaces with the International Maritime Organization (IMO) and the International Civil Aviation Organization (ICAO). Some Member States and non-governmental organizations in IMO meetings expressed concerns that accidents on board ships may be more severe than the IAEA regulatory tests account for, and that package failure with subsequent release of radioactive material may occur. The CRP on accident severity at sea was established to develop further quantitative information on potential accident severities during the transport of radioactive material by ships. The primary objective of this programme is to collect and evaluate statistical data of marine accidents, perform analyses of potential accident conditions and evaluate the risks resulting from such shipments. The CRP on air transport was established to make a major international effort to collect relevant frequency and severity data and to analyze it so the accident forces to which a packages of radioactive material might be subjected to in a severe air accident can be more confidently quantified. Several countries have ongoing data collection activities related to aircraft accidents and severity and other sources of statistics for in-flight aircraft accidents will be explored. The International Civil Aviation Organization informed the IAEA of their plans to improve
IAEA mode-related research in the safe transport of radioactive material
International Nuclear Information System (INIS)
Blalock, L.G.; Rawl, R.R.
1998-01-01
The International Atomic Energy Agency sponsors Co-ordinated Research Programmes (CRP) in the safe transport of radioactive material. The CRPs are intended to encourage research by Member States in identified areas and to facilitate co-ordination of exchange of information and resources to reach a common understanding of the problem and alternative solutions. Two of these programmes are: Accident Severity at Sea During the Transport of Radioactive Material and Accident Severity During the Air Transport of Radioactive Material. This paper will discuss these two programmes and their relationship to the continuing regulatory revision process and interfaces with the International Maritime Organization (IMO) and the International Civil Aviation Organization (ICAO). Some Member States and non-governmental organizations in IMO meetings expressed concerns that accidents on board ships may be more severe than the IAEA regulatory tests account for, and that package failure with subsequent release of radioactive material may occur. The CRP on accident severity at sea was established to develop further quantitative information on potential accident severities during the transport of radioactive material by ships. The primary objective of this programme is to collect and evaluate statistical data of marine accidents, perform analyses of potential accident conditions and evaluate the risks resulting from such shipments. The CRP on air transport was established to make a major international effort to collect relevant frequency and severity data and to analyze it so the accident forces to which a packages of radioactive material might be subjected to in a severe air accident can be more confidently quantified. Several countries have ongoing data collection activities related to aircraft accidents and severity and other sources of statistics for in-flight aircraft accidents will be explored. The International Civil Aviation Organization informed the IAEA of their plans to improve
Yin, Kedong; Zhang, Ya; Li, Xuemei
2017-01-01
Owing to the difference of the sequences’ orders and the surface structure in the current panel grey relational models, research results will not be unique. In addition, individual measurement of indicators and objects and the subjectivity of combined weight would significantly weaken the effective information of panel data and reduce the reliability and accuracy of research results. Therefore, we propose the concept and calculation method of dispersion of panel data, establish the grey relational model based on dispersion of panel data (DPGRA), and prove that DPGRA exhibits the effective properties of uniqueness, symmetry, and normality. To demonstrate its applicability, the proposed DPGRA model is used to research on storm-tide disaster losses in China’s coastal areas. Comparing research results of three models, which are DPGRA, Euclidean distance grey relational model, and grey grid relational model, it was shown that DPGRA is more effective, feasible, and stable. It is indicated that DPGRA can entirely utilize the effective information of panel data; what’s more, it can not only handle the non-uniqueness of the grey relational model’s results but also improve the reliability and accuracy of research results. The research results are of great significance for coastal areas to focus on monitoring storm–tide disasters hazards, strengthen the protection measures of natural disasters, and improve the ability of disaster prevention and reduction. PMID:29104262
Yin, Kedong; Zhang, Ya; Li, Xuemei
2017-11-01
Owing to the difference of the sequences' orders and the surface structure in the current panel grey relational models, research results will not be unique. In addition, individual measurement of indicators and objects and the subjectivity of combined weight would significantly weaken the effective information of panel data and reduce the reliability and accuracy of research results. Therefore, we propose the concept and calculation method of dispersion of panel data, establish the grey relational model based on dispersion of panel data (DPGRA), and prove that DPGRA exhibits the effective properties of uniqueness, symmetry, and normality. To demonstrate its applicability, the proposed DPGRA model is used to research on storm-tide disaster losses in China's coastal areas. Comparing research results of three models, which are DPGRA, Euclidean distance grey relational model, and grey grid relational model, it was shown that DPGRA is more effective, feasible, and stable. It is indicated that DPGRA can entirely utilize the effective information of panel data; what's more, it can not only handle the non-uniqueness of the grey relational model's results but also improve the reliability and accuracy of research results. The research results are of great significance for coastal areas to focus on monitoring storm-tide disasters hazards, strengthen the protection measures of natural disasters, and improve the ability of disaster prevention and reduction.
Directory of Open Access Journals (Sweden)
Ludmyla Kandratavicius
2013-01-01
Full Text Available Background. Despite strong association between epilepsy and psychiatric comorbidities, biological substrates are unknown. We have previously reported decreased mossy fiber sprouting in mesial temporal lobe epilepsy (MTLE patients with psychosis and increased in those with major depression. Microtubule associated proteins (MAPs are essentially involved in dendritic and synaptic sprouting. Methods. MTLE hippocampi of subjects without psychiatric history, MTLE + major depression, and MTLE + interictal psychosis derived from epilepsy surgery and control necropsies were investigated for neuronal density, granular layer dispersion, and MAP2 and tau immunohistochemistry. Results. Altered MAP2 and tau expression in MTLE and decreased tau expression in MTLE with psychosis were found. Granular layer dispersion correlated inversely with verbal memory scores, and with MAP2 and tau expression in the entorhinal cortex. Patients taking fluoxetine showed increased neuronal density in the granular layer and those taking haloperidol decreased neuronal density in CA3 and subiculum. Conclusions. Our results indicate relations between MAPs, granular layer dispersion, and memory that have not been previously investigated. Differential MAPs expression in human MTLE hippocampi with and without psychiatric comorbidities suggests that psychopathological states in MTLE rely on differential morphological and possibly neurochemical backgrounds. This clinical study was approved by our institution’s Research Ethics Board (HC-FMRP no. 1270/2008 and is registered under the Brazilian National System of Information on Ethics in Human Research (SISNEP no. 0423.0.004.000-07.
Smith, Kevin T.; Balouet, Jean Christophe; Shortle, Walter C.; Chalot, Michel; Beaujard, François; Grudd, Håkan; Vroblesky, Don A.; Burkem, Joel G.
2014-01-01
Energy dispersive X-ray fluorescence (EDXRF) provides highly sensitive and precise spatial resolution of cation content in individual annual growth rings in trees. The sensitivity and precision have prompted successful applications to forensic dendrochemistry and the timing of environmental releases of contaminants. These applications have highlighted the need to distinguish dendrochemical effects of internal processes from environmental contamination. Calcium, potassium, and zinc are three marker cations that illustrate the influence of these processes. We found changes in cation chemistry in tree rings potentially due to biomineralization, development of cracks or checks, heartwood/sapwood differentiation, intra-annual processes, and compartmentalization of infection. Distinguishing internal from external processes that affect dendrochemistry will enhance the value of EDXRF for both physiological and forensic investigations.
International Nuclear Information System (INIS)
Lazar, M.; Schlickeiser, R.
2006-01-01
The properties of transverse waves parallel propagating in magnetized plasmas with arbitrary composition and thermally anisotropic, are investigated on the basis of relativistic Vlasov-Maxwell equations. The transverse dispersion relations for plasmas with arbitrary distribution functions are derived. These dispersion relations describe the linear response of the system to the initial perturbations and thus define all existing linear (transverse) plasma modes in the system. By analytic continuation the dispersion relations in the whole complex frequency plane are constructed. Further analysis is restricted to the important case of anisotropic bi-Maxwellian equilibrium plasma distribution functions. Explicit forms of the relativistically correct transverse dispersion relations are derived that hold for any values of the plasma temperatures and the temperature anisotropy. In the limit of nonrelativistic plasma temperatures the dispersion relations are expressed in terms of plasma dispersion function, however, the dependence on frequency and wave numbers is markedly different from the standard noncovariant nonrelativistic analysis. Only in the strictly unphysical formal limit of an infinitely large speed of light, c→∞, does the nonrelativistic dispersion relations reduce to the standard noncovariant dispersion relations
International Nuclear Information System (INIS)
Aydemir, A.Y.
1990-01-01
We derive the dispersion relations for both small and large-Δ' modes (m ≥ 2, and m = 1 modes, respectively) driven by anomalous electron viscosity. Under the assumption that the anomalous kinematic electron viscosity is comparable to the anomalous electron thermal diffusivity, we find that the viscous mode typically has a higher growth rate than the corresponding resistive mode. We compare computational results in cylindrical and toroidal geometries with theory and present some nonlinear results for viscous m = 1 modes in both circular and D-shaped boundaries and discuss their possible rile in fast sawtooth crashes. 30 ref., 5 figs., 1 tab
Paired modes of heterostructure cavities in photonic crystal waveguides with split band edges
DEFF Research Database (Denmark)
Mahmoodian, Sahand; Sukhorukov, Andrey A.; Ha, Sangwoo
2010-01-01
We investigate the modes of double heterostructure cavities where the underlying photonic crystal waveguide has been dispersion engineered to have two band-edges inside the Brillouin zone. By deriving and using a perturbative method, we show that these structures possess two modes. For unapodized...... cavities, the relative detuning of the two modes can be controlled by changing the cavity length, and for particular lengths, a resonant-like effect makes the modes degenerate. For apodized cavities no such resonances exist and the modes are always non-degenerate....
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
Tearing modes with pressure gradient effect in pair plasmas
International Nuclear Information System (INIS)
Cai Huishan; Li Ding; Zheng Jian
2009-01-01
The general dispersion relation of tearing mode with pressure gradient effect in pair plasmas is derived analytically. If the pressure gradients of positron and electron are not identical in pair plasmas, the pressure gradient has significant influence at tearing mode in both collisionless and collisional regimes. In collisionless regime, the effects of pressure gradient depend on its magnitude. For small pressure gradient, the growth rate of tearing mode is enhanced by pressure gradient. For large pressure gradient, the growth rate is reduced by pressure gradient. The tearing mode can even be stabilized if pressure gradient is large enough. In collisional regime, the growth rate of tearing mode is reduced by the pressure gradient. While the positron and electron have equal pressure gradient, tearing mode is not affected by pressure gradient in pair plasmas.
Jockwitz, Christiane; Caspers, Svenja; Lux, Silke; Jütten, Kerstin; Schleicher, Axel; Eickhoff, Simon B; Amunts, Katrin; Zilles, Karl
2017-01-01
Healthy aging is accompanied by changes in the functional architecture of the default mode network (DMN), e.g. a posterior to anterior shift (PASA) of activations. The putative structural correlate for this functional reorganization, however, is largely unknown. Changes in gyrification, i.e. decreases of cortical folding were found to be a marker of atrophy of the brain in later decades of life. Therefore, the present study assessed local gyrification indices of the DMN in relation to age and cognitive performance in 749 older adults aged 55-85 years. Age-related decreases in local gyrification indices were found in the anterior part of the DMN [particularly; medial prefrontal cortex (mPFC)] of the right hemisphere, and the medial posterior parts of the DMN [particularly; posterior cingulate cortex (PCC)/precuneus] of both hemispheres. Positive correlations between cognitive performance and local gyrification indices were found for (1) selective attention and left PCC/precuneus, (2) visual/visual-spatial working memory and bilateral PCC/precuneus and right angular gyrus (AG), and (3) semantic verbal fluency and right AG and right mPFC. The more pronounced age-related decrease in local gyrification indices of the posterior parts of the DMN supports the functionally motivated PASA theory by correlated structural changes. Surprisingly, the prominent age-related decrease in local gyrification indices in right hemispheric ROIs provides evidence for a structural underpinning of the right hemi-aging hypothesis. Noticeably, the performance-related changes in local gyrification largely involved the same parts of the DMN that were subject to age-related local gyrification decreases. Thus, the present study lends support for a combined structural and functional theory of aging, in that the functional changes in the DMN during aging are accompanied by comparably localized structural alterations.
Directory of Open Access Journals (Sweden)
Marielle Salvador-Perignon
2011-09-01
Full Text Available Cette recherche se propose d’aborder le mode de production du produit alimentaire sous l’angle des représentations mentales en France. Dans le langage commun on entend souvent les termes « industriel » ou « artisanal » pour caractériser les produits alimentaires, sans que l’on sache vraiment ce que ces termes désignent. Le contexte actuel d’incertitude et de méconnaissance des systèmes de production chez les consommateurs nous permet d’émettre l’hypothèse de l’existence d’une représentation mentale du mode de production. Nous tentons de vérifier cette hypothèse par une étude qualitative à l’issue de laquelle les premières caractéristiques du produit alimentaire industriel ou artisanal sont précisées.This research approaches the food product through the mental representations concerning manufacturing processes. In the common language we often find such terms as “industrial” or “traditional” to qualify production methods and characterize food products, but do we know what these terms really mean? Uncertainties and misunderstandings regarding food production enable us to highlight the existence of consumers’ mental representations regarding manufacturing processes. Such representations have been studied by means of a qualitative study which enabled us to define the primary characteristics of industrial or traditional food products.
Directory of Open Access Journals (Sweden)
Athanasia M. Mowinckel
2017-01-01
Full Text Available Insufficient suppression and connectivity of the default mode network (DMN is a potential mediator of cognitive dysfunctions across various disorders, including attention deficit/hyperactivity disorder (ADHD. However, it remains unclear if alterations in sustained DMN suppression, variability and connectivity during prolonged cognitive engagement are implicated in adult ADHD pathophysiology, and to which degree methylphenidate (MPH remediates any DMN abnormalities. This randomized, double-blinded, placebo-controlled, cross-over clinical trial of MPH (clinicaltrials.gov/ct2/show/NCT01831622 explored large-scale brain network dynamics in 20 adults with ADHD on and off MPH, compared to 27 healthy controls, while performing a reward based decision-making task. DMN task-related activation, variability, and connectivity were estimated and compared between groups and conditions using independent component analysis, dual regression, and Bayesian linear mixed models. The results show that the DMN exhibited more variable activation patterns in unmedicated patients compared to healthy controls. Group differences in functional connectivity both between and within functional networks were evident. Further, functional connectivity between and within attention and DMN networks was sensitive both to task performance and case-control status. MPH altered within-network connectivity of the DMN and visual networks, but not between-network connectivity or temporal variability. This study thus provides novel fMRI evidence of reduced sustained DMN suppression in adults with ADHD during value-based decision-making, a pattern that was not alleviated by MPH. We infer from multiple analytical approaches further support to the default mode interference hypothesis, in that higher DMN activation variability is evident in adult ADHD and associated with lower task performance.
Zong, Baoyu
2014-01-01
Organic hybrid solar cells with a large open-circuit voltage, up to above that of 1.5 V standard battery voltage, were demonstrated using blends of polypyrrole: Fe2O3·ZnO nanoparticles as active-layers. The cell active-layers were readily coated in open air from relatively stable liquid dark-color polypyrrole-based dispersions, which were synthesized using appropriate surfactants during the in situ polymerization of pyrrole with FeCl3 or both H2O2 and FeCl3 as the oxidizers. The performance of the cells depends largely on the synthesized blend phase, which is determined by the surfactants, oxidizers, as well as the reactant ratio. Only the solar cells fabricated from the stable dispersions can produce both a high open-circuit voltage (>1.0 V) and short-circuit current (up to 7.5 mA cm-2) due to the relatively uniform porous network nanomorphology and higher shunt to series resistance ratio of the active-layers. The cells also display a relatively high power-conversion efficiency of up to ∼3.8%. This journal is
A graphical method for estimating the tunneling factor for mode conversion processes
International Nuclear Information System (INIS)
Swanson, D.G.
1994-01-01
The fundamental parameter characterizing the strength of any mode conversion process is the tunneling parameter, which is typically determined from a model dispersion relation which is transformed into a differential equation. Here a graphical method is described which gives the tunneling parameter from quantities directly measured from a simple graph of the dispersion relation. The accuracy of the estimate depends only on the accuracy of the measurements
Amplification of magnetic modes in laser-created plasmas
International Nuclear Information System (INIS)
Matte, J.P.; Bendib, A.; Luciani, J.F.
1987-01-01
The amplification of magnetic (Weibel) modes in laser-plasma interaction is investigated by use of unperturbed distribution functions given by Fokker-Planck simulations and a dispersion relation valid for all collisionality regimes. In the five cases studied, a strongly growing mode is found in the underdense plasma, where v-bar/sub x/ 2 2 , and the usual slowly growing one in the overdense plasma. The first mode grows convectively outwards by more than 10 4 . The convection velocities are found to be very different from Nernst values
Optical phonon modes of wurtzite InP
Gadret, E. G.; de Lima, M. M.; Madureira, J. R.; Chiaramonte, T.; Cotta, M. A.; Iikawa, F.; Cantarero, A.
2013-03-01
Optical vibration modes of InP nanowires in the wurtzite phase were investigated by Raman scattering spectroscopy. The wires were grown along the [0001] axis by the vapor-liquid-solid method. The A1(TO), E2h, and E1(TO) phonon modes of the wurtzite symmetry were identified by using light linearly polarized along different directions in backscattering configuration. Additionally, forbidden longitudinal optical modes have also been observed. Furthermore, by applying an extended 11-parameter rigid-ion model, the complete dispersion relations of InP in the wurtzite phase have been calculated, showing a good agreement with the Raman experimental data.
Fickian dispersion is anomalous
Cushman, John H.; O'Malley, Dan
2015-12-01
The thesis put forward here is that the occurrence of Fickian dispersion in geophysical settings is a rare event and consequently should be labeled as anomalous. What people classically call anomalous is really the norm. In a Lagrangian setting, a process with mean square displacement which is proportional to time is generally labeled as Fickian dispersion. With a number of counter examples we show why this definition is fraught with difficulty. In a related discussion, we show an infinite second moment does not necessarily imply the process is super dispersive. By employing a rigorous mathematical definition of Fickian dispersion we illustrate why it is so hard to find a Fickian process. We go on to employ a number of renormalization group approaches to classify non-Fickian dispersive behavior. Scaling laws for the probability density function for a dispersive process, the distribution for the first passage times, the mean first passage time, and the finite-size Lyapunov exponent are presented for fixed points of both deterministic and stochastic renormalization group operators. The fixed points of the renormalization group operators are p-self-similar processes. A generalized renormalization group operator is introduced whose fixed points form a set of generalized self-similar processes. Power-law clocks are introduced to examine multi-scaling behavior. Several examples of these ideas are presented and discussed.
Wilcox, Claire E; Claus, Eric D; Calhoun, Vince D; Rachakonda, Srinivas; Littlewood, Rae A; Mickey, Jessica; Arenella, Pamela B; Goodreau, Natalie; Hutchison, Kent E
2018-01-01
Identifying predictors of treatment outcome for nicotine use disorders (NUDs) may help improve efficacy of established treatments, like varenicline. Brain reactivity to drug stimuli predicts relapse risk in nicotine and other substance use disorders in some studies. Activity in the default mode network (DMN) is affected by drug cues and other palatable cues, but its clinical significance is unclear. In this study, 143 individuals with NUD (male n = 91, ages 18-55 years) received a functional magnetic resonance imaging scan during a visual cue task during which they were presented with a series of smoking-related or food-related video clips prior to randomization to treatment with varenicline (n = 80) or placebo. Group independent components analysis was utilized to isolate the DMN, and temporal sorting was used to calculate the difference between the DMN blood-oxygen-level dependent signal during smoke cues and that during food cues for each individual. Food cues were associated with greater deactivation compared with smoke cues in the DMN. In correcting for baseline smoking and other clinical variables, which have been shown to be related to treatment outcome in previous work, a less positive Smoke - Food difference score predicted greater smoking at 6 and 12 weeks when both treatment groups were combined (P = 0.005, β = -0.766). An exploratory analysis of executive control and salience networks demonstrated that a more positive Smoke - Food difference score for executive control network predicted a more robust response to varenicline relative to placebo. These findings provide further support to theories that brain reactivity to palatable cues, and in particular in DMN, may have a direct clinical relevance in NUD. © 2017 Society for the Study of Addiction.
Kalosakas, G.; Aubry, S.; Tsironis, G. P.
1998-10-01
We use a stationary and normal mode analysis of the semiclassical Holstein model in order to connect the low-frequency linear polaron modes to low-lying far-infrared lines of the acetanilide spectrum and through parameter fitting we comment on the validity of the polaron results in this system.
Ofer, Isabell; Jacobs, Julia; Jaiser, Nathalie; Akin, Burak; Hennig, Jürgen; Schulze-Bonhage, Andreas; LeVan, Pierre
2018-01-01
Rolandic epilepsy (RE) is characterized by typical interictal-electroencephalogram (EEG) patterns mainly localized in centrotemporal and parietooccipital areas. An aberrant intrinsic organization of the default mode network (DMN) due to repeated disturbances from spike-generating areas may be able to account for specific cognitive deficits and behavioral problems in RE. The aim of the present study was to investigate cognitive development (CD) and socioemotional development (SED) in patients with RE during active disease in relation to DMN connectivity and network topology. In 10 children with RE and active EEG, CD was assessed using the Wechsler Intelligence Scale for Children-IV (WISC-IV); SED was assessed using the Fünf-Faktoren-Fragebogen für Kinder (FFFK), a Big-Five inventory for the assessment of personality traits in children. Functional connectivity (FC) in the DMN was determined from a 15-minute resting state functional magnetic resonance imaging (fMRI), and network properties were calculated using standard graph-theoretical measures. More severe deficits of verbal abilities tended to be associated with an earlier age at epilepsy onset, but were not directly related to the number of seizures and disease duration. Nonetheless, at the network level, disease duration was associated with alterations of the efficiency and centrality of parietal network nodes and midline structures. Particularly, centrality of the left inferior parietal lobe (IPL) was found to be linked with CD. Reduced centrality of the left IPL and alterations supporting a rather segregated processing within DMN's subsystems was associated with a more favorable CD. A more complicated SED was associated with high seizure frequency and long disease duration, and revealed links with a less favorable CD. An impaired CD and - because of their interrelation - SED might be mediated by a common pathomechanism reflected in an aberrant organization, and thus, a potential functional deficit of the DMN
Le Higgs et le quark top dans le formalisme des relations de dispersion et le modèle standard
Bouayed, Noureddine
The mechanism of spontaneous symmetry breaking responsible for the generation of masses for both the bosons and the fermions of the Standard Model remains a mystery, especially that the Higgs has still not been discovered. In this thesis I concentrate on the study of the scalar sector of the Standard Model where the Higgs with the other Goldstone Boson reside. This sector can best be probed through the massive vector bosons and the top quark. The former, for their privileged coupling to the Higgs and because their longitudinal mode represents the Goldstone Bosons, and the top, because of its very strong Yukawa coupling, are very sensitive to the mechanism of symmetry breaking. I first focus on a situation where the Higgs is light and study the processes ${W^-W^+ \\to t\\bar{t}}$ and ${ZZ \\to t\\bar{t}}$. In order to unambiguously reveal a sign of New Physics, the Standard Model needs to be predicted precisely. In a first step I therefore study the electroweak and QCD one-loop corrections for these processes. Thi...
Dispersion bias, dispersion effect, and the aerosol-cloud conundrum
International Nuclear Information System (INIS)
Liu Yangang; Daum, Peter H; Guo Huan; Peng Yiran
2008-01-01
This work examines the influences of relative dispersion (the ratio of the standard deviation to the mean radius of the cloud droplet size distribution) on cloud albedo and cloud radiative forcing, derives an analytical formulation that accounts explicitly for the contribution from droplet concentration and relative dispersion, and presents a new approach to parameterize relative dispersion in climate models. It is shown that inadequate representation of relative dispersion in climate models leads to an overestimation of cloud albedo, resulting in a negative bias of global mean shortwave cloud radiative forcing that can be comparable to the warming caused by doubling CO 2 in magnitude, and that this dispersion bias is likely near its maximum for ambient clouds. Relative dispersion is empirically expressed as a function of the quotient between cloud liquid water content and droplet concentration (i.e., water per droplet), yielding an analytical formulation for the first aerosol indirect effect. Further analysis of the new expression reveals that the dispersion effect not only offsets the cooling from the Twomey effect, but is also proportional to the Twomey effect in magnitude. These results suggest that unrealistic representation of relative dispersion in cloud parameterization in general, and evaluation of aerosol indirect effects in particular, is at least in part responsible for several outstanding puzzles of the aerosol-cloud conundrum: for example, overestimation of cloud radiative cooling by climate models compared to satellite observations; large uncertainty and discrepancy in estimates of the aerosol indirect effect; and the lack of interhemispheric difference in cloud albedo.
He, Yongrui; Zhao, Xian-En; Wang, Renjun; Wei, Na; Sun, Jing; Dang, Jun; Chen, Guang; Liu, Zhiqiang; Zhu, Shuyun; You, Jinmao
2016-11-02
A simple, rapid, sensitive, selective, and environmentally friendly method, based on in situ derivatization ultrasound-assisted dispersive liquid-liquid microextraction (in situ DUADLLME) coupled with ultra-high-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) using multiple reaction monitoring (MRM) mode has been developed for the simultaneous determination of food-related biogenic amines and amino acids. A new mass-spectrometry-sensitive derivatization reagent 4'-carbonyl chloride rosamine (CCR) was designed, synthesized, and first reported. Parameters and conditions of in situ DUADLLME and UHPLC-MS/MS were optimized in detail. Under the optimized conditions, the in situ DUADLLME was completed speedily (within 1 min) with high derivatization efficiencies (≥98.5%). With the cleanup and concentration of microextraction step, good analytical performance was obtained for the analytes. The results showed that this method was accurate and practical for quantification of biogenic amines and amino acids in common food samples (red wine, beer, wine, cheese, sausage, and fish).
A synthesis of empirical plant dispersal kernels
Czech Academy of Sciences Publication Activity Database
Bullock, J. M.; González, L. M.; Tamme, R.; Götzenberger, Lars; White, S. M.; Pärtel, M.; Hooftman, D. A. P.
2017-01-01
Roč. 105, č. 1 (2017), s. 6-19 ISSN 0022-0477 Institutional support: RVO:67985939 Keywords : dispersal kernel * dispersal mode * probability density function Subject RIV: EH - Ecology, Behaviour OBOR OECD: Ecology Impact factor: 5.813, year: 2016
Interaction between molecular complexes in dispersive media
International Nuclear Information System (INIS)
Banagas, E.A.; Manykin, E.A.
1987-01-01
The interaction between molecular complexes in different dispersive media with local and nonlocal screening is investigated theoretically. On the basis of results of numerical analysis on a computer, the dependence of the coupled-system spectrum and the interaction energy of the polarized modes on the characteristic parameters of the dispersive media is considered
International Nuclear Information System (INIS)
Efrosinin, V.P.; Zaikin, D.A.
1983-01-01
Possible reasons of disagreement between estimates of the pion-nucleon σ term obtained by the method of dispersion relations with extrapolation to the Chang-Dashen point and by alternative methods, making no use of such extrapolation are investigated. One of the reasons may be, that the πN amplitude is not analytic in the variable t at ν=0. A method, which is not so strongly influenced by the nonanalyticity, is suggested to estimate the σ term making use of the threshold data for the πN amplitude. Relation between the scale and chiral invariance breakings is discussed and the resulting estimate of the σ term is presented. Both estimates give close results (42 and 34 MeV) which do not contradict one another within the uncertainties of the methods
Cáceda, Ricardo; James, G Andrew; Ely, Timothy D; Snarey, John; Kilts, Clinton D
2011-02-25
Moral sensitivity refers to the interpretive awareness of moral conflict and can be justice or care oriented. Justice ethics is associated primarily with human rights and the application of moral rules, whereas care ethics is related to human needs and a situational approach involving social emotions. Among the core brain regions involved in moral issue processing are: medial prefrontal cortex, anterior (ACC) and posterior (PCC) cingulate cortex, posterior superior temporal sulcus (pSTS), insula and amygdala. This study sought to inform the long standing debate of whether care and justice moral ethics represent one or two different forms of cognition. Model-free and model-based connectivity analysis were used to identify functional neural networks underlying care and justice ethics for a moral sensitivity task. In addition to modest differences in patterns of associated neural activity, distinct modes of functional and effective connectivity were observed for moral sensitivity for care and justice issues that were modulated by individual variation in moral ability. These results support a neurobiological differentiation between care and justice ethics and suggest that human moral behavior reflects the outcome of integrating opposing rule-based, self-other perspectives, and emotional responses.
Cáceda, Ricardo; James, G. Andrew; Ely, Timothy D.; Snarey, John; Kilts, Clinton D.
2011-01-01
Background Moral sensitivity refers to the interpretive awareness of moral conflict and can be justice or care oriented. Justice ethics is associated primarily with human rights and the application of moral rules, whereas care ethics is related to human needs and a situational approach involving social emotions. Among the core brain regions involved in moral issue processing are: medial prefrontal cortex, anterior (ACC) and posterior (PCC) cingulate cortex, posterior superior temporal sulcus (pSTS), insula and amygdala. This study sought to inform the long standing debate of whether care and justice moral ethics represent one or two different forms of cognition. Methodology/Principal Findings Model-free and model-based connectivity analysis were used to identify functional neural networks underlying care and justice ethics for a moral sensitivity task. In addition to modest differences in patterns of associated neural activity, distinct modes of functional and effective connectivity were observed for moral sensitivity for care and justice issues that were modulated by individual variation in moral ability. Conclusions/Significance These results support a neurobiological differentiation between care and justice ethics and suggest that human moral behavior reflects the outcome of integrating opposing rule-based, self-other perspectives, and emotional responses. PMID:21364916
Directory of Open Access Journals (Sweden)
Ricardo Cáceda
Full Text Available BACKGROUND: Moral sensitivity refers to the interpretive awareness of moral conflict and can be justice or care oriented. Justice ethics is associated primarily with human rights and the application of moral rules, whereas care ethics is related to human needs and a situational approach involving social emotions. Among the core brain regions involved in moral issue processing are: medial prefrontal cortex, anterior (ACC and posterior (PCC cingulate cortex, posterior superior temporal sulcus (pSTS, insula and amygdala. This study sought to inform the long standing debate of whether care and justice moral ethics represent one or two different forms of cognition. METHODOLOGY/PRINCIPAL FINDINGS: Model-free and model-based connectivity analysis were used to identify functional neural networks underlying care and justice ethics for a moral sensitivity task. In addition to modest differences in patterns of associated neural activity, distinct modes of functional and effective connectivity were observed for moral sensitivity for care and justice issues that were modulated by individual variation in moral ability. CONCLUSIONS/SIGNIFICANCE: These results support a neurobiological differentiation between care and justice ethics and suggest that human moral behavior reflects the outcome of integrating opposing rule-based, self-other perspectives, and emotional responses.
Directory of Open Access Journals (Sweden)
H. A. M. Leymann
2017-06-01
Full Text Available We investigate the switching of the coherent emission mode of a bimodal microcavity device, occurring when the pump power is varied. We compare experimental data to theoretical results and identify the underlying mechanism based on the competition between the effective gain, on the one hand, and the intermode kinetics, on the other. When the pumping is ramped up, above a threshold, the mode with the largest effective gain starts to emit coherent light, corresponding to lasing. In contrast, in the limit of strong pumping, it is the intermode kinetics that determines which mode acquires a large occupation and shows coherent emission. We point out that this latter mechanism is akin to the equilibrium Bose-Einstein condensation of massive bosons. Thus, the mode switching in our microcavity device can be viewed as a minimal instance of Bose-Einstein condensation of photons. Moreover, we show that the switching from one cavity mode to the other always occurs via an intermediate phase where both modes are emitting coherent light and that it is associated with both superthermal intensity fluctuations and strong anticorrelations between both modes.
International Nuclear Information System (INIS)
Thuburn, J.; Woollings, T.J.
2005-01-01
Accurate representation of different kinds of wave motion is essential for numerical models of the atmosphere, but is sensitive to details of the discretization. In this paper, numerical dispersion relations are computed for different vertical discretizations of the compressible Euler equations and compared with the analytical dispersion relation. A height coordinate, an isentropic coordinate, and a terrain-following mass-based coordinate are considered, and, for each of these, different choices of prognostic variables and grid staggerings are considered. The discretizations are categorized according to whether their dispersion relations are optimal, are near optimal, have a single zero-frequency computational mode, or are problematic in other ways. Some general understanding of the factors that affect the numerical dispersion properties is obtained: heuristic arguments concerning the normal mode structures, and the amount of averaging and coarse differencing in the finite difference scheme, are shown to be useful guides to which configurations will be optimal; the number of degrees of freedom in the discretization is shown to be an accurate guide to the existence of computational modes; there is only minor sensitivity to whether the equations for thermodynamic variables are discretized in advective form or flux form; and an accurate representation of acoustic modes is found to be a prerequisite for accurate representation of inertia-gravity modes, which, in turn, is found to be a prerequisite for accurate representation of Rossby modes
Destabilization of low-n peeling modes by trapped energetic particles
Energy Technology Data Exchange (ETDEWEB)
Hao, G. Z.; Wang, A. K.; Mou, Z. Z.; Qiu, X. M. [Southwestern Institute of Physics, PO Box 432, Chengdu 610041 (China); Liu, Y. Q. [Euratom/CCFE Fusion Association, Culham Science Centre, Abingdon, OX14 3DB (United Kingdom); Matsunaga, G. [Japan Atomic Energy Agency, 801-1, Mukouyama, Naka, Ibaraki 311-0193 (Japan); Okabayashi, M. [Princeton Plasma Physics Laboratory, PO Box 451, Princeton, New Jersey 08543-0451 (United States)
2013-06-15
The kinetic effect of trapped energetic particles (EPs), arising from perpendicular neutral beam injection, on the stable low-n peeling modes in tokamak plasmas is investigated, through numerical solution of the mode's dispersion relation derived from an energy principle. A resistive-wall peeling mode with m/n=6/1, with m and n being the poloidal and toroidal mode numbers, respectively, is destabilized by trapped EPs as the EPs' pressure exceeds a critical value β{sub c}{sup *}, which is sensitive to the pitch angle of trapped EPs. The dependence of β{sub c}{sup *} on the particle pitch angle is eventually determined by the bounce average of the mode eigenfunction. Peeling modes with higher m and n numbers can also be destabilized by trapped EPs. Depending on the wall distance, either a resistive-wall peeling mode or an ideal-kink peeling mode can be destabilized by EPs.
Counihan, Timothy D.; Chapman, Colin G.
2018-01-01
The goals were to (i) determine if river discharge and water temperature during various early life history stages were predictors of age‐0 White Sturgeon, Acipenser transmontanus, recruitment, and (ii) provide an example of how over‐dispersed catch data, including data with many zero observations, can be used to better understand the effects of regulated rivers on the productivity of depressed sturgeon populations. An information theoretic approach was used to develop and select negative binomial and zero‐inflated negative binomial models that model the relation of age‐0 White Sturgeon survey data from three contiguous Columbia River reservoirs to river discharge and water temperature during spawning, egg incubation, larval, and post‐larval phases. Age‐0 White Sturgeon were collected with small mesh gill nets in The Dalles and John Day reservoirs from 1997 to 2014 and a bottom trawl in Bonneville Reservoir from 1989 to 2006. Results suggest that seasonal river discharge was positively correlated with age‐0 recruitment; notably that discharge, 16 June–31 July was positively correlated to age‐0 recruitment in all three reservoirs. The best approximating models for two of the three reservoirs also suggest that seasonal water temperature may be a determinant of age‐0 recruitment. Our research demonstrates how over‐dispersed catch data can be used to better understand the effects of environmental conditions on sturgeon populations caused by the construction and operation of dams.
Comments on the dispersion equation of a turbulent plasma - an inhomogeneous, magnetoactive case
International Nuclear Information System (INIS)
Ag, A.
1978-03-01
A weakly turbulent, magnetoactive plasma is considered in an inhomogeneous case with anisotropic temperature distribution. The dispersion relation is established following a method developed by Tsytovich and Nekrasov. The correction coefficients are calculated in the three principal scaling modes: (1) the turbulent frequencies predominate, (2) the cyclotronic velocities of the macroinstabilities predominate, (3) the turbulent frequencies are lower. (D.P.)
Interface, a dispersed architecture
Vissers, C.A.
1976-01-01
Past and current specification techniques use timing diagrams and written text to describe the phenomenology of an interface. This paper treats an interface as the architecture of a number of processes, which are dispersed over the related system parts and the message path. This approach yields a
International Nuclear Information System (INIS)
Mikhailovskii, A.B.; Smolyakov, A.I.; Kovalishen, E.A.; Shirokov, M.S.; Tsypin, V.S.; Galvao, R.M.O.
2006-01-01
Generation of zonal flows by primary waves that are more complex than those considered in the standard drift-wave model is studied. The effects of parallel ion velocity and ion perturbed temperature and the part of the nonlinear mode interaction proportional to the ion pressure are taken into account. This generalization of the standard model allows the analysis of generation of zonal flows by a rather wide variety of primary modes, including ion temperature gradients, ion sound, electron drift, and drift-sound modes. All the listed effects, which are present in the slab geometry model, are complemented by effects of neoclassical viscosity inherent to toroidal geometry. We show that the electrostatic potential of secondary small-scale modes is expressed in terms of a nonlinear shift of the mode frequency and interpret this shift in terms of the perpendicular and parallel Doppler, nonlinear Kelvin-Helmholtz (KH), and nonlinear ion-pressure-gradient effects. A basic assumption of our model is that the primary modes form a nondispersive monochromatic wave packet. The analysis of zonal-flow generation is performed following an approach similar to that of convective-cell theory. Neoclassical zonal-flow instabilities are separated into fast and slow ones, and these are divided into two varieties. The first of them is independent of the nonlinear KH effect, while the second one is sensitive to it
Optimized nonlinear inversion of surface-wave dispersion data
International Nuclear Information System (INIS)
Raykova, Reneta B.
2014-01-01
A new code for inversion of surface wave dispersion data is developed to obtain Earth’s crustal and upper mantle velocity structure. The author developed Optimized Non–Linear Inversion ( ONLI ) software, based on Monte-Carlo search. The values of S–wave velocity VS and thickness h for a number of horizontal homogeneous layers are parameterized. Velocity of P–wave VP and density ρ of relevant layers are calculated by empirical or theoretical relations. ONLI explores parameters space in two modes, selective and full search, and the main innovation of software is evaluation of tested models. Theoretical dispersion curves are calculated if tested model satisfied specific conditions only, reducing considerably the computation time. A number of tests explored impact of parameterization and proved the ability of ONLI approach to deal successfully with non–uniqueness of inversion problem. Key words: Earth’s structure, surface–wave dispersion, non–linear inversion, software
Resistive effect on ion fishbone mode in tokamak plasma
International Nuclear Information System (INIS)
Shi Bingren; Vandam, J.W.; Carrera, R.; Zhang, Y.Z.
1992-07-01
A consistent theoretical description of the resistive internal mode is presented to discuss the effect of resistivity on fishbone mode for different parameter regime of bulk and hot components. It is found that the ideal fishbone mode theory ceases to be correct for the low frequency fishbone branch, the so-called ion fishbone mode, which has a real frequency very close to ω *i (the diamagnetic frequency) in marginal state. The stability domain analysis in β h , γ mhd ) space based on the resistive dispersion relation shows that the transition between the stable and unstable region is more complicated than predicted by the ideal limit theory. Another salient feature of the resistive fishbone mode is the existence of a weakly unstable regime. For high frequency fishbone with ω ∼ ω dm (the toroidal precession frequency of the hot ions) resistivity has negligible effect and the ideal theory is correct
Directory of Open Access Journals (Sweden)
Jixiong Xiao
2017-01-01
Full Text Available A linear theory for the electromagnetic properties and interactions of an annular beam-ion channel system in plasma waveguide is presented. The dispersion relations for two families of propagating modes, including the electrostatic and transverse magnetic modes, are derived. The dependencies of the dispersion behavior and interaction for different wave modes on the thickness of the annular beam and betatron oscillation frequency are studied in detail by numerical calculations. The results show that the inner and outer radii of the beam have different influences on propagation properties of the electrostatic and electromagnetic modes with different betatron oscillation parameters. In the weak ion channel situation, the two types of electrostatic waves, that is, space charge and betatron modes, have no interaction with the transverse magnetic modes. However, in the strong ion channel situation, the transverse magnetic modes will have two branches and a low frequency mode emerged as the new branch. In this case, compared with the solid beam case, the betatron modes not only can interact with the high frequency branch at small wavenumber but also can interact with the low frequency branch at large wavenumber.
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Pedro Castro
2017-06-01
Full Text Available This work analyzes some key aspects of the behavior of sensors based on piezoelectric Thickness Shear Mode (TSM resonators to study and monitor microbial biofilms. The operation of these sensors is based on the analysis of their resonance properties (both resonance frequency and dissipation factor that vary in contact with the analyzed sample. This work shows that different variations during the microorganism growth can be detected by the sensors and highlights which of these changes are indicative of biofilm formation. TSM sensors have been used to monitor in real time the development of Staphylococcus epidermidis and Escherichia coli biofilms, formed on the gold electrode of the quartz crystal resonators, without any coating. Strains with different ability to produce biofilm have been tested. It was shown that, once a first homogeneous adhesion of bacteria was produced on the substrate, the biofilm can be considered as a semi-infinite layer and the quartz sensor reflects only the viscoelastic properties of the region immediately adjacent to the resonator, not being sensitive to upper layers of the biofilm. The experiments allow the microrheological evaluation of the complex shear modulus (G* = G′ + jG″ of the biofilm at 5 MHz and at 15 MHz, showing that the characteristic parameter that indicates the adhesion of a biofilm for the case of S. epidermidis and E. coli, is an increase in the resonance frequency shift of the quartz crystal sensor, which is connected with an increase of the real shear modulus, related to the elasticity or stiffness of the layer. In addition both the real and the imaginary shear modulus are frequency dependent at these high frequencies in biofilms.
International Nuclear Information System (INIS)
Scattergood, R.O.; Das, E.S.P.
1976-01-01
Using digital computer-based methods, models for dispersion strengthening can now be developed which take into account many of the important effects that have been neglected in the past. In particular, the self interaction of a dislocation can be treated, and a computer simulation method was developed to determine the flow stress of a random distribution of circular, impenetrable obstacles, taking into account all such interactions. The flow stress values depended on the obstacle sizes and spacings, over and above the usual 1/L dependence where L is the average obstacle spacing. From an analysis of the results, it was found that the main effects of the self interactions can be captured in a line tension analogue in which the obstacles appear to be penetrable
Stability of longitudinal modes in a bunched beam with mode coupling
International Nuclear Information System (INIS)
Satoh, K.
1981-06-01
In this paper we study a longitudinal coherent bunch instability in which the growth time is comparable to or less than the period of synchrotron oscillations. Both longitudinal and transverse bunch instabilities have been studied. In most treatments, however, the coherent force is assumed to be small and is treated as a perturbation compared with the synchrotron force. This makes the problem simpler because an individual synchrotron mode is decoupled. As bunch current increases, the coherent force is no longer small and the mode frequency shift becomes significant compared with the synchrotron frequency. Therefore in this case it is necessary to include coupling of the synchrotron modes. Recently a fast blow-up instability which comes from mode coupling was studied. Their method is to derive a dispersion relation for a bunched beam using the Vlasov equation and to analyze it as in a coasting beam. They showed that if mode coupling is included the Vlasov equation predicts a fast microwave instability with a stability condition similar to that for a coasting beam. In this paper we will partly follow their method and present a formalism which includes coupling between higher-order radial modes as well as coupling between synchrotron modes. The formalism is considered to be generalization of the Sacherer formalism without mode coupling. This theory predicts that instability is induced not only by coupling between different synchrotron modes, but also by coupling between positive and negative modes, since negative synchrotron modes are included in the theory in a natural manner. This formalism is to be used for a Gaussian bunch and a parabolic bunch, and is also useful for transverse problems
DEFF Research Database (Denmark)
Israelsen, Stine Møller
This PhD thesis considers higher order modes (HOMs) in optical fibers. That includes their excitation and characteristics. Within the last decades, HOMs have been applied both for space multiplexing in optical communications, group velocity dispersion management and sensing among others......-radial polarization as opposed to the linear polarization of the LP0X modes. The effect is investigated numerically in a double cladding fiber with an outer aircladding using a full vectorial modesolver. Experimentally, the bowtie modes are excited using a long period grating and their free space characteristics...... and polarization state are investigated. For this fiber, the onset of the bowtie effect is shown numerically to be LP011. The characteristics usually associated with Bessel-likes modes such as long diffraction free length and selfhealing are shown to be conserved despite the lack of azimuthal symmetry...
Normal modes of vibration in nickel
Energy Technology Data Exchange (ETDEWEB)
Birgeneau, R J [Yale Univ., New Haven, Connecticut (United States); Cordes, J [Cambridge Univ., Cambridge (United Kingdom); Dolling, G; Woods, A D B
1964-07-01
The frequency-wave-vector dispersion relation, {nu}(q), for the normal vibrations of a nickel single crystal at 296{sup o}K has been measured for the [{zeta}00], [{zeta}00], [{zeta}{zeta}{zeta}], and [0{zeta}1] symmetric directions using inelastic neutron scattering. The results can be described in terms of the Born-von Karman theory of lattice dynamics with interactions out to fourth-nearest neighbors. The shapes of the dispersion curves are very similar to those of copper, the normal mode frequencies in nickel being about 1.24 times the corresponding frequencies in copper. The fourth-neighbor model was used to calculate the frequency distribution function g({nu}) and related thermodynamic properties. (author)
Parametric study of guided waves dispersion curves for composite plates
Predoi, Mihai Valentin; Petre, Cristian Cǎtǎlin; Kettani, Mounsif Ech Cherif El; Leduc, Damien
2018-02-01
Nondestructive testing of composite panels benefit from the relatively long range propagation of guided waves in sandwich structures. The guided waves are sensitive to delamination, air bubbles inclusions and cracks and can thus bring information about hidden defects in the composite panel. The preliminary data in all such inspections is represented by the dispersion curves, representing the dependency of the phase/group velocity on the frequency for the propagating modes. In fact, all modes are more or less attenuated, so it is even more important to compute the dispersion curves, which provide also the modal attenuation as function of frequency. Another important aspect is the sensitivity of the dispersion curves on each of the elastic constant of the composite, which are orthotropic in most cases. All these aspects are investigated in the present work, based on our specially developed finite element numerical model implemented in Comsol, which has several advantages over existing methods. The dispersion curves and modal displacements are computed for an example of composite plate. Comparison with literature data validates the accuracy of our results.
Directory of Open Access Journals (Sweden)
Jan van Turnhout
2016-05-01
Full Text Available The dielectric spectra of colloidal systems often contain a typical low frequency dispersion, which usually remains unnoticed, because of the presence of strong conduction losses. The KK relations offer a means for converting into data. This allows us to calculate conduction free spectra in which the l.f. dispersion will show up undisturbed. This interconversion can be done on line with a moving frame of logarithmically spaced data. The coefficients of the conversion frames were obtained by kernel matching and by using symbolic differential operators. Logarithmic derivatives and differences of and provide another option for conduction free data analysis. These difference-based functions actually derived from approximations to the distribution function, have the additional advantage of improving the resolution power of dielectric studies. A high resolution is important because of the rich relaxation structure of colloidal suspensions. The development of all-in-1 modelling facilitates the conduction free and high resolution data analysis. This mathematical tool allows the apart-together fitting of multiple data and multiple model functions. It proved also useful to go around the KK conversion altogether. This was achieved by the combined approximating and data with a complex rational fractional power function. The all-in-1 minimization turned out to be also highly useful for the dielectric modelling of a suspension with the complex dipolar coefficient. It guarantees a secure correction for the electrode polarization, so that the modelling with the help of the differences and can zoom in on the genuine colloidal relaxations.
Nislow, K.H.; Hudy, M.; Letcher, B.H.; Smith, E.P.
2011-01-01
1.Barriers to immigration, all else being equal, should in principle depress local abundance and reduce local species richness. These issues are particularly relevant to stream-dwelling species when improperly designed road crossings act as barriers to migration with potential impacts on the viability of upstream populations. However, because abundance and richness are highly spatially and temporally heterogeneous and the relative importance of immigration on demography is uncertain, population- and community-level effects can be difficult to detect. 2.In this study, we tested the effects of potential barriers to upstream movements on the local abundance and species richness of a diverse assemblage of resident stream fishes in the Monongahela National Forest, West Virginia, U.S.A. Fishes were sampled using simple standard techniques above- and below road crossings that were either likely or unlikely to be barriers to upstream fish movements (based on physical dimensions of the crossing). We predicted that abundance of resident fishes would be lower in the upstream sections of streams with predicted impassable barriers, that the strength of the effect would vary among species and that variable effects on abundance would translate into lower species richness. 3.Supporting these predictions, the statistical model that best accounted for variation in abundance and species richness included a significant interaction between location (upstream or downstream of crossing) and type (passable or impassable crossing). Stream sections located above predicated impassable culverts had fewer than half the number of species and less than half the total fish abundance, while stream sections above and below passable culverts had essentially equivalent richness and abundance. 4.Our results are consistent with the importance of immigration and population connectivity to local abundance and species richness of stream fishes. In turn, these results suggest that when measured at
Directory of Open Access Journals (Sweden)
Chhabi Mohan
2010-06-01
Full Text Available .Research Question: What is the level of awareness about different modes of transmission and related misconception about HIV/AIDS among secondary school going females of public and Govt. Schools of Kanpur city. Study Area: Public and Govt. Schools of Kanpur city. Participatns: 120 Govt. and 120 Public secondary School females students. Results: 100% Public school female students knew about heterosexual mode of transmission of HI V/AIDS as compared to 80% of Govt. School students. Among Public School students knowledge about transmission of HIV/AIDS by contaminated needle and syringe intravenous drug abuse, blood transfusion and mother to child was known to almost 80% student. Among Govt. School students except for knowledge about transmission by contaminated needle and syringe (60% and mother to child transmission (55% the other modes were poorly known (<50%.
Hoenders, B.J.
1986-01-01
We consider an infinitely long conducting cylinder whose dielectric and magnetic permittivity and conductivity are functions of the distance from a point inside the cylinder to its axis. It is shown that the r-dependent part of the set of electromagnetic modes associated with such a cylinder is
Energy Technology Data Exchange (ETDEWEB)
Stirling, A [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires
1966-07-01
The {pi}{sup +} P and {pi}{sup -} P total cross sections have been measured between 500 and 1700 MeV to eliminate discrepancies in the experimental data. These new values have permitted a more precise calculation of the forward dispersion relation. These relations are well satisfied by the experimental data up to 18 GeV for charge exchange scattering. The dispersion relation for the spin-flip amplitude gives an efficient test for the phase-shift analysis solutions. (author) [French] Les sections efficaces totales {pi}{sup +} P et {pi}{sup -} P ont ete mesurees entre 500 et 1700 MeV pour eliminer les divergences qui existaient entre les resultats experimentaux anterieurs. Ces nouvelles valeurs ont permis de preciser le calcul des relations de dispersion vers l'avant. Dans le cas de la diffusion avec echange de charge ces relations sont en bon accord avec les resultats experimentaux entre 0 et 18 GeV. L'application des relations de dispersion vers l'avant a l'amplitude de spin-flip fournit une methode tres sensible pour comparer differentes series de dephasages en fonction de l'energie. (auteur)
International Nuclear Information System (INIS)
Li, D.
2001-01-01
The neoclassical and double tearing modes have been analyzed with related new phenomena in the reversed magnetic shear tokamak plasmas. The instability threshold, and the linear and nonlinear evolution are derived for the neoclassical tearing modes. It is found that the perturbed bootstrap current in the resistive layer has a stabilizing effect while the equilibrium bootstrap current in the outer region can destabilize the modes. The dispersion relation is derived for the double tearing mode. It is found that the onset of ''annular crash'' is due to the fast reconnection of the hot and cold islands, triggered by the interaction of both branches. The onset of ''core crash'' is mainly due to the coalescence between the hot islands, triggered by the explosive growth of the inner branch. (author)
International Nuclear Information System (INIS)
Li Ding
1999-01-01
The neoclassical and double tearing modes have been analyzed with related new phenomena in the reversed magnetic shear tokamak plasmas. The instability threshold, and the linear and nonlinear evolution are derived for the neoclassical tearing modes. It is found that the perturbed bootstrap current in the resistive layer has a stabilizing effect while the equilibrium bootstrap current in the outer region can destabilize the modes. The dispersion relation is derived for the double tearing mode. It is found that the onset of 'annular crash' is due to the fast reconnection of the hot and cold islands, triggered by the interaction of both branches. The onset of 'core crash' is mainly due to the coalescence between the hot islands, triggered by the explosive growth of the inner branch. (author)
International Nuclear Information System (INIS)
Shukla, P.K.; Bharuthram, R.; Schlickeiser, R.
2004-01-01
It is shown that the dispersive Shukla mode [P.K. Shukla, Phys. Lett. A 316, 238 (2003)] can become unstable in the presence of equilibrium density and magnetic field inhomogeneities in a dusty plasma. A new dispersion relation for our nonuniform dusty magnetoplasma is derived and analyzed to show the modification of the Shukla mode frequency and its amplification due to combined action of the plasma density and magnetic field gradients. The present instability may account for the origin of low-frequency electromagnetic turbulence in molecular clouds and in cometary plasmas
Stability of coupled tearing and twisting modes in tokamaks
International Nuclear Information System (INIS)
Fitzpatrick, R.
1994-03-01
A dispersion relation is derived for resistive modes of arbitrary parity in a tokamak plasma. At low mode amplitude, tearing and twisting modes which have nonideal MHD behavior at only one rational surface at a time in the plasma are decoupled via sheared rotation and diamagnetic flows. At higher amplitude, more unstable open-quote compound close-quote modes develop which have nonideal behavior simultaneously at many surfaces. Such modes possess tearing parity layers at some of the nonideal surfaces, and twisting parity layers at others, but mixed parity layers are generally disallowed. At low mode number, open-quote compound close-quote modes are likely to have tearing parity layers at all of the nonideal surfaces in a very low-β plasma, but twisting parity layers become more probable as the plasma β is increased. At high mode number, unstable twisting modes which exceed a critical amplitude drive conventional magnetic island chains on alternate rational surfaces, to form an interlocking structure in which the O-points and X-points of neighboring chains line up
Hindle, Tony; Hindle, Giles; Spollen, Martin
2009-02-01
The aim of this research has been to make a contribution to deliberations concerning the relative costs of provision of domiciliary services for the elderly in local authorities in England and the implications for funding. The main services considered have been day-centre services and home-care services, and the particular cost areas investigated have been travel-related costs as associated with distances travelled by day-centre vehicles and care workers and with worker travelling hours. These costs are influenced by the population settlement and dispersion characteristics of the areas served and funding mechanisms are needed (and are in place) to compensate service providers. However, current mechanisms have been widely criticized and the research reported here reaches conclusions about whether such criticisms are justified and how improvements might be brought about. The methods used have involved detailed operational modelling of the selected services in a sample of local authority areas and the generalization of the findings to England as a whole.
Guided modes of elliptical metamaterial waveguides
International Nuclear Information System (INIS)
Halterman, Klaus; Feng, Simin; Overfelt, P. L.
2007-01-01
The propagation of guided electromagnetic waves in open elliptical metamaterial waveguide structures is investigated. The waveguide contains a negative-index media core, where the permittivity ε and permeability μ are negative over a given bandwidth. The allowed mode spectrum for these structures is numerically calculated by solving a dispersion relation that is expressed in terms of Mathieu functions. By probing certain regions of parameter space, we find the possibility exists to have extremely localized waves that transmit along the surface of the waveguide
Databases of surface wave dispersion
Directory of Open Access Journals (Sweden)
L. Boschi
2005-06-01
Full Text Available Observations of seismic surface waves provide the most important constraint on the elastic properties of the Earths lithosphere and upper mantle. Two databases of fundamental mode surface wave dispersion were recently compiled and published by groups at Harvard (Ekström et al., 1997 and Utrecht/Oxford (Trampert and Woodhouse, 1995, 2001, and later employed in 3-d global tomographic studies. Although based on similar sets of seismic records, the two databases show some significant discrepancies. We derive phase velocity maps from both, and compare them to quantify the discrepancies and assess the relative quality of the data; in this endeavour, we take careful account of the effects of regularization and parametrization. At short periods, where Love waves are mostly sensitive to crustal structure and thickness, we refer our comparison to a map of the Earths crust derived from independent data. On the assumption that second-order effects like seismic anisotropy and scattering can be neglected, we find the measurements of Ekström et al. (1997 of better quality; those of Trampert and Woodhouse (2001 result in phase velocity maps of much higher spatial frequency and, accordingly, more difficult to explain and justify geophysically. The discrepancy is partly explained by the more conservative a priori selection of data implemented by Ekström et al. (1997. Nevertheless, it becomes more significant with decreasing period, which indicates that it could also be traced to the different measurement techniques employed by the authors.
Propagative modes along a superfluid helium-4 meniscus
International Nuclear Information System (INIS)
Poujade, M.; Guthmann, C.; Rolley, E.
2002-01-01
We have studied the dynamics of a superfluid helium-4 meniscus on a solid substrate. In a pseudo-non-wetting situation, there is no hysteresis of the contact angle. We show that distortions of a liquid meniscus do propagate along the contact line. We have analyzed the propagation of pulses. We find a good agreement with theoretical predictions by Brochard for the dispersion relation of oscillation modes of the contact line. (authors)
Middleton, Beth; van Diggelen, Rudy; Jensen, Kai
Question: How does seed dispersal reduce fen isolation and contribute to biodiversity? Location: European and North American fens. Methods: This paper reviews the literature on seed dispersal to fens. Results: Landscape fragmentation may reduce dispersal opportunities thereby isolating fens and
Cavity enhanced interference of orthogonal modes in a birefringent medium
Kolluru, Kiran; Saha, Sudipta; Gupta, S. Dutta
2018-03-01
Interference of orthogonal modes in a birefringent crystal mediated by a rotator is known to lead to interesting physical effects (Solli et al., 2003). In this paper we show that additional feedback offered by a Fabry-Perot cavity (containing the birefringent crystal and the rotator) can lead to a novel strong interaction regime. Usual signatures of the strong interaction regime like the normal mode splitting and avoided crossings, sensitive to the rotator orientation, are reported. A high finesse cavity is shown to offer an optical setup for measuring small angles. The results are based on direct calculations of the cavity transmissions along with an analysis of its dispersion relation.
Danilo Garcia; Alexander Jimmefors; Fariba Mousavi; Lillemor Adrianson; Patricia Rosenberg; Trevor Archer
2015-01-01
Background. Self-regulation is the procedure implemented by an individual striving to reach a goal and consists of two inter-related strategies: assessment and locomotion. Moreover, both subjective and psychological well-being along exercise behaviour might also play a role on adolescents academic achievement. Method. Participants were 160 Swedish high school pupils (111 boys and 49 girls) with an age mean of 17.74 (sd = 1.29). We used the Regulatory Mode Questionnaire to measure self-regulat...
On the ordinary mode instability for low beta plasmas
Energy Technology Data Exchange (ETDEWEB)
Hadi, F.; Qamar, A. [Institute of Physics and Electronics, University of Peshawar, Peshawar (Pakistan); Bashir, M. F. [Department of Physics, G. C. University, Lahore (Pakistan); Salam Chair in Physics, G. C. University, Lahore (Pakistan); Yoon, P. H. [Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742-2431 (United States); School of Space Research, Kyung Hee University, Yongin (Korea, Republic of); Schlickeiser, R. [Institut für Theoretische Physik, Lehrstuhl IV: Weltraum- and Astrophysik, Ruhr-Universität, Bochum (Germany)
2014-05-15
The purely growing ordinary (O) mode instability, first discussed by Davidson and Wu [Phys. Fluids 13, 1407 (1970)], has recently received renewed attention owing to its potential applicability to the solar wind plasma. In a series of papers, Ibscher, Schlickeiser, and their colleagues [Phys. Plasmas 19, 072116 (2012); ibid. 20, 012103 (2013); ibid. 20, 042121 (2013); ibid. 21, 022110 (2014)] revisited the O mode instability and extended it to the low-beta plasma regime by considering a counter-streaming bi-Maxwellian model. However, the O-mode instability is, thus, far discussed only on the basis of the marginal stability condition rather than actual numerical solutions of the dispersion relation. The present paper revisits the O-mode instability by considering the actual complex roots. The marginal stability condition as a function of the (electron) temperature anisotropy and beta naturally emerges in such a scheme.
Kink and tearing mode instabilities in a tokamak
International Nuclear Information System (INIS)
Pogutse, O.P.
The continuous transition from a free-boundary-kink mode to a tearing mode in a current carrying plasma column is investigated. It is shown that in the real experimental situation, even for high temperatures in the plasma periphery, the kink mode exists due to electron inertia, the growth rate of the instability being at least a few times smaller than the growth rate with a free boundary. We find the dispersion relation allowing us to calculate the growth rate for plasma parameters of physical interest. It is shown that as the size of the current channel increases the growth rate falls, but the range of values of the safety factor where the mode is unstable broadens
Energy Technology Data Exchange (ETDEWEB)
Soni, Dilip [Government P G Madhav Science College, Ujjain (M P) (India); Sharma, Giriraj, E-mail: grsharma@gmail.com [SRJ Government Girls’ College, Neemuch (M P) (India); Saxena, Ajay [Government College, Garoth, Dist. Mandsaur (M P) (India); Jadhav, Akhilesh [Government J Yoganandam Chhattisgarh College, Raipur (C G) (India)
2015-07-31
An analytical study on propagation characteristics of longitudinal electro-kinetic (LEK) waves is presented. Based on multi-fluid model of plasma, we have derived a dispersion relation for LEK waves in colloid laden GaN semiconductor plasmas. It is assumed that ions are implanted to form colloids in the GaN sample. The colloids are continuously bombarded by the plasma particles and stick on them, but they acquire a net negative charge due to relatively higher mobility of electrons. It is found from the dispersion relation that the presence of charged colloids not only modifies the existing modes but also supports new novel modes of LEKWs. It is hoped that the study would enhance understanding on dispersion and absorption of LEKWs and help in singling out the appropriate configurations in which GaN crystal would be better suited for fabrication of microwave devices.
Spatial stability of jets - the nonaxisymmetric fundamental and reflection modes
International Nuclear Information System (INIS)
Hardee, P.E.
1987-01-01
A spatial stability analysis of the relativistic dispersion relation governing the growth and propagation of harmonic components comprising a perturbation to the surface of a cylindrical jet is performed. The spatial growth of harmonic components associated with the nonaxisymmetric fundamental solution and reflection solutions of several Fourier modes are analyzed. Approximate analytical expressions describing resonant frequencies and wavelengths, and maximum growth rates at resonance applicable to relativistic jets are found from the dispersion relation, and the nature of the resonances is explored. On transonic jets there is only a fundamental solution for each Fourier mode with no resonance or maximum growth rate. On supersonic jets there is a fundamental solution and reflection solutions for each Fourier mode, and each solution contains a resonance at which the growth rate is a maximum. A numerical analysis of the fundamental and first three reflection solutions of the axisymmetric and first three nonaxisymmetric Fourier modes is performed. The numerical analysis is restricted to nonrelativistic flows but otherwise covers a broad range of Mach numbers and jet densities. The numerical results are used along with the analytical results to obtain accurate expressions for resonant frequencies, wavelengths, and growth rates as a function of Mach numnber and jet density. In all cases the fastest spatial growth rate at a given frequency is of harmonic components associated with the fundamental solution of one of the nonaxisymmetric Fourier modes. The application of these results to jet structure and implication of these results for jet structure in extragalactic radio sources are considered. 23 references
Viscoelasticity and diffusional properties of colloidal model dispersions
Naegele, G
2003-01-01
We examine linear viscoelastic, and translational and rotational diffusion properties of colloidal model dispersions. Theoretical results are discussed, in comparison with experiments, for monodisperse suspensions of charged and neutral colloidal spheres, and for binary dispersions of differently sized tracer and host particles. The theoretical methods employed comprise a mode-coupling scheme for Brownian particles, and a rooted cluster expansion scheme of tracer diffusion with two- and three-body hydrodynamic interactions included. We analyse in particular the validity of various empirical generalized Stokes-Einstein-Debye (SED) relations between the (dynamic) shear viscosity and translational/rotational diffusion coefficients. Some of these generalized SED relations are basic to microrheological measurements aimed at characterizing the viscoelasticity of complex fluids on the basis of the diffusional properties of immersed tracer particles.
Viscoelasticity and diffusional properties of colloidal model dispersions
International Nuclear Information System (INIS)
Naegele, Gerhard
2003-01-01
We examine linear viscoelastic, and translational and rotational diffusion properties of colloidal model dispersions. Theoretical results are discussed, in comparison with experiments, for monodisperse suspensions of charged and neutral colloidal spheres, and for binary dispersions of differently sized tracer and host particles. The theoretical methods employed comprise a mode-coupling scheme for Brownian particles, and a rooted cluster expansion scheme of tracer diffusion with two- and three-body hydrodynamic interactions included. We analyse in particular the validity of various empirical generalized Stokes-Einstein-Debye (SED) relations between the (dynamic) shear viscosity and translational/rotational diffusion coefficients. Some of these generalized SED relations are basic to microrheological measurements aimed at characterizing the viscoelasticity of complex fluids on the basis of the diffusional properties of immersed tracer particles
Mode damping in a commensurate monolayer solid
DEFF Research Database (Denmark)
Bruch, Ludwig Walter; Hansen, Flemming Yssing
1997-01-01
with an elastic-continuum theory of the response of modes of either parallel or perpendicular polarization for a spherical adsorbate on a hexagonal substrate. The results are applied to the discussion of computer simulations and inelastic atomic-scattering experiments for adsorbates on graphite. The extreme...... of substrate modes with strong anomalous dispersion, and enables a semiquantitative account of observed avoided crossings of the adlayer perpendicular vibration mode and the substrate Rayleigh mode....
Dispersion Engineering of Bose-Einstein Condensates
Khamehchi, Mohammad Amin
The subject of this dissertation is engineering the dispersion relation for dilute Bose-Einstein condensates (BECs). When a BEC is immersed into suitably tailored laser fields its dispersion can be strongly modified. Prominent examples for such laser fields include optical lattice geometries and Raman dressing fields. The ability to engineer the dispersion of a BEC allows for the investigation of a range of phenomena related to quantum hydrodynamics and condensed matter. In the first context, this dissertation studies the excitation spectrum of a spin-orbit coupled (SOC) BEC. The spin-orbit coupling is generated by " dressing" the atoms with two Raman laser fields. The excitation spectrum has a Roton-like feature that can be altered by tuning the Raman laser parameters. It is demonstrated that the Roton mode can be softened, but it does not reach the ground state energy for the experimental conditions we had. Furthermore, the expansion of SOC BECs in 1D is studied by relaxing the trap allowing the BEC to expand in the SOC direction. Contrary to the findings for optical lattices, it is observed that the condensate partially occupies quasimomentum states with negative effective mass, and therefore an abrupt deceleration is observed although the mean field force is along the direction of expansion. In condensed-matter systems, a periodic lattice structure often plays an important role. In this context, an alternative to the Raman dressing scheme can be realized by coupling the s- and p- bands of a static optical lattice via a weak moving lattice. The bands can be treated as pseudo-spin states. It is shown that similar to the dispersion relation of a Raman dressed SOC, the quasimomentum of the ground state is different from zero. Coherent coupling of the SOC dispersion minima can lead to the realization of the stripe phase even though it is not the thermodynamic ground state of the system. Along the lines of studying the hydrodynamics of BECs, three novel
Sakkal, Leon A; Rajkowski, Kyle Z; Armen, Roger S
2017-06-05
Following insights from recent crystal structures of the muscarinic acetylcholine receptor, binding modes of Positive Allosteric Modulators (PAMs) were predicted under the assumption that PAMs should bind to the extracellular surface of the active state. A series of well-characterized PAMs for adenosine (A 1 R, A 2A R, A 3 R) and muscarinic acetylcholine (M 1 R, M 5 R) receptors were modeled using both rigid and flexible receptor CHARMM-based molecular docking. Studies of adenosine receptors investigated the molecular basis of the probe-dependence of PAM activity by modeling in complex with specific agonist radioligands. Consensus binding modes map common pharmacophore features of several chemical series to specific binding interactions. These models provide a rationalization of how PAM binding slows agonist radioligand dissociation kinetics. M 1 R PAMs were predicted to bind in the analogous M 2 R PAM LY2119620 binding site. The M 5 R NAM (ML-375) was predicted to bind in the PAM (ML-380) binding site with a unique induced-fit receptor conformation. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.
Velocity Dispersions Across Bulge Types
International Nuclear Information System (INIS)
Fabricius, Maximilian; Bender, Ralf; Hopp, Ulrich; Saglia, Roberto; Drory, Niv; Fisher, David
2010-01-01
We present first results from a long-slit spectroscopic survey of bulge kinematics in local spiral galaxies. Our optical spectra were obtained at the Hobby-Eberly Telescope with the LRS spectrograph and have a velocity resolution of 45 km/s (σ*), which allows us to resolve the velocity dispersions in the bulge regions of most objects in our sample. We find that the velocity dispersion profiles in morphological classical bulge galaxies are always centrally peaked while the velocity dispersion of morphologically disk-like bulges stays relatively flat towards the center--once strongly barred galaxies are discarded.
Wave power balance in resonant dissipative media with spatial and temporal dispersion
International Nuclear Information System (INIS)
Tokman, M.D.; Gavrilova, M.A.; Westerhof, E. . www.rijnh.nl
2003-01-01
A power balance for waves in resonant dissipative media is formulated, which generalizes well-known expressions for dielectric wave energy density, wave energy flux, and dissipated power density. The identification of the different terms with wave energy density and flux remains only phenomenological. The result is better viewed as an equation for the evolution of wave intensity. In that form, its consequences are discussed in particular in relation to anomalous dispersion. A discrimination is made between boundary and initial value problems. For boundary value problems, anomalous dispersion is shown not to lead to unphysical results. In contrast, for initial value problems the solution for the evolution of wave intensity is shown to be at fault in the case of anomalous dispersion. Further illustration is provided by consideration of wave dispersion in a medium of charged harmonic oscillators and of ordinary-mode dispersion in plasma. Both are characterized by anomalous dispersion and show marked differences in the solutions of the dispersion relation solved either for complex wave vector at real frequency, k(ω) (applicable to boundary value problems), or for complex frequency at real wave vector ω(k) (applicable to initial value problems). (author)
Petrou, Stavros; Kim, Sung Wook; McParland, Penny; Boyle, Elaine M
2017-06-01
Relatively little is known about the effects of mode of delivery on long-term health-related quality-of-life outcomes. Furthermore, no previous study has expressed these outcomes in preference-based (utility) metrics. The study population comprised 2,161 mothers recruited from a prospective population-based study in the East Midlands of England encompassing live births and stillbirths between 32 +0 and 36 +6 weeks' gestation and a sample of term-born controls. Perinatal data were extracted from the mothers' maternity records. Health-related quality-of-life outcomes were assessed at 12 months postpartum, using the EuroQol Five Dimensions (EQ-5D) measure with responses to the EQ-5D descriptive system converted into health utility scores. Descriptive statistics and multivariable analyses were used to estimate the relationship between the mode of delivery and health-related quality-of-life outcomes. The overall health-related quality-of-life profile of the women in the study cohort mirrored that of the English adult population as revealed by national health surveys. A significantly higher proportion of women delivering by cesarean delivery reported some, moderate, severe, or extreme pain or discomfort at 12 months postpartum than women undergoing spontaneous vaginal delivery. Multivariable analyses, using the Ordinary Least Squares estimator revealed that, after controlling for maternal sociodemographic characteristics, cesarean delivery without maternal or fetal compromise was associated with a significant EQ-5D utility decrement in comparison to spontaneous vaginal delivery among all women (-0.026; p = 0.038) and among mothers of term-born infants (-0.062; p quality of life in comparison to spontaneous vaginal delivery. Further longitudinal studies are needed to understand the magnitude, trajectory, and underpinning mechanisms of health-related quality-of-life outcomes following different modes of delivery. © 2016 Wiley Periodicals, Inc.
On Kinetic Slow Modes, Fluid Slow Modes, and Pressure-balanced Structures in the Solar Wind
Energy Technology Data Exchange (ETDEWEB)
Verscharen, Daniel [Space Science Center and Department of Physics, University of New Hampshire, Durham, NH 03824 (United States); Chen, Christopher H. K. [Department of Physics, Imperial College London, London SW7 2AZ (United Kingdom); Wicks, Robert T., E-mail: daniel.verscharen@unh.edu, E-mail: christopher.chen@imperial.ac.uk, E-mail: r.wicks@ucl.ac.uk [Mullard Space Science Laboratory, University College London, London WC1E 6BT (United Kingdom)
2017-05-10
Observations in the solar wind suggest that the compressive component of inertial-range solar-wind turbulence is dominated by slow modes. The low collisionality of the solar wind allows for nonthermal features to survive, which suggests the requirement of a kinetic plasma description. The least-damped kinetic slow mode is associated with the ion-acoustic (IA) wave and a nonpropagating (NP) mode. We derive analytical expressions for the IA-wave dispersion relation in an anisotropic plasma in the framework of gyrokinetics and then compare them to fully kinetic numerical calculations, results from two-fluid theory, and magnetohydrodynamics (MHD). This comparison shows major discrepancies in the predicted wave phase speeds from MHD and kinetic theory at moderate to high β . MHD and kinetic theory also dictate that all plasma normal modes exhibit a unique signature in terms of their polarization. We quantify the relative amplitude of fluctuations in the three lowest particle velocity moments associated with IA and NP modes in the gyrokinetic limit and compare these predictions with MHD results and in situ observations of the solar-wind turbulence. The agreement between the observations of the wave polarization and our MHD predictions is better than the kinetic predictions, which suggests that the plasma behaves more like a fluid in the solar wind than expected.
On Kinetic Slow Modes, Fluid Slow Modes, and Pressure-balanced Structures in the Solar Wind
International Nuclear Information System (INIS)
Verscharen, Daniel; Chen, Christopher H. K.; Wicks, Robert T.
2017-01-01
Observations in the solar wind suggest that the compressive component of inertial-range solar-wind turbulence is dominated by slow modes. The low collisionality of the solar wind allows for nonthermal features to survive, which suggests the requirement of a kinetic plasma description. The least-damped kinetic slow mode is associated with the ion-acoustic (IA) wave and a nonpropagating (NP) mode. We derive analytical expressions for the IA-wave dispersion relation in an anisotropic plasma in the framework of gyrokinetics and then compare them to fully kinetic numerical calculations, results from two-fluid theory, and magnetohydrodynamics (MHD). This comparison shows major discrepancies in the predicted wave phase speeds from MHD and kinetic theory at moderate to high β . MHD and kinetic theory also dictate that all plasma normal modes exhibit a unique signature in terms of their polarization. We quantify the relative amplitude of fluctuations in the three lowest particle velocity moments associated with IA and NP modes in the gyrokinetic limit and compare these predictions with MHD results and in situ observations of the solar-wind turbulence. The agreement between the observations of the wave polarization and our MHD predictions is better than the kinetic predictions, which suggests that the plasma behaves more like a fluid in the solar wind than expected.
Two chiroptical modes of silver nanospirals
International Nuclear Information System (INIS)
Bai, Fan; Deng, Junhong; Fu, Junxue; Ng, Jack; Huang, Zhifeng; Yang, Mengsu
2016-01-01
As an emerging three-dimensional chiral metamaterial, plasmonic nanospirals (NSs) possess inherent chiroptical activity that has attracted increasing attention for developing potential photonic applications. However, the study of chiroptical activity of plasmonic NSs is still in its infancy, especially for NSs made of silver, which is a typical plasmonic material with high plasmonic quality. Herein, we present a systematic study of circular dichroism (CD) of silver NSs (AgNSs) that are fabricated and engineered in helical lengths by glancing-angle deposition (GLAD) and dispersed in ethanol. The CD spectrum is composed of a bisignated mode of two peaks, one in the UV regime and the other in the visible. The UV mode has a resonance wavelength saturating at ∼375 nm and a linewidth decoupled from the helical elongation, while the visible mode tends to have a redshift and its linewidth broadens linearly with the elongation of AgNS. Helical elongation generally amplifies the chiroptical activity of both modes. Finite-element simulation shows good agreement with the experimental CD results, and accounts for the wavelength-related chiroptical distinction in terms of the resonance wavelength. This work contributes to understanding the bisignated chiroptical responses of plasmonic nanospirals, and introduces a simple method to tailor the visible chiroptical activity that is strongly desired to explore a wide range of chirality-related bio-applications. (paper)
Energy Technology Data Exchange (ETDEWEB)
Fang, Hung-Chung [Univ. of California, Berkeley, CA (United States)
2011-01-01
Using 1.3 fb^{-1} of data from p$\\bar{p}$ collisions at √s = 1.96 TeV collected with the CDF II detector at the Fermilab Tevatron, we have measured the relative branching ratio $BR(B^- \\to D^0 K^-) / BR(B^- \\to D^0 \\pi^-)$ in Three $D^0$ and its charge conjugate in the D^{0} flavor decay mode D$0\\atop{f}$ → K^{-}π^{+} and the CP-even decay modes D^{0} → K^{-}K^{+} and D^{0} → π^{-}π^{+}
Energy Technology Data Exchange (ETDEWEB)
Kalaee, Mohammad Javad, E-mail: mjkalaee@ut.ac.ir [Space Physics Group, Institute of Geophysics, University of Tehran (Iran, Islamic Republic of); Katoh, Yuto, E-mail: yuto@stpp.gp.tohoku.ac.jp [Department of Geophysics, Graduate School of Science, Tohoku University (Japan)
2016-07-15
One of the mechanisms for generating electromagnetic plasma waves (Z-mode and LO-mode) is mode conversion from electrostatic waves into electromagnetic waves in inhomogeneous plasma. Herein, we study a condition required for mode conversion of electrostatic waves propagating purely perpendicular to the ambient magnetic field, by numerically solving the full dispersion relation. An approximate model is derived describing the coupling between electrostatic waves (hot plasma Bernstein mode) and Z-mode waves at the upper hybrid frequency. The model is used to study conditions required for mode conversion from electrostatic waves (electrostatic electron cyclotron harmonic waves, including Bernstein mode) into electromagnetic plasma waves (LO-mode). It is shown that for mode conversion to occur in inhomogeneous plasma, the angle between the boundary surface and the magnetic field vector should be within a specific range. The range of the angle depends on the norm of the k vector of waves at the site of mode conversion in the inhomogeneous region. The present study reveals that inhomogeneity alone is not a sufficient condition for mode conversion from electrostatic waves to electromagnetic plasma waves and that the angle between the magnetic field and the density gradient plays an important role in the conversion process.
Theory of energetic trapped particle-induced resistive interchange-ballooning modes
International Nuclear Information System (INIS)
Biglari, H.; Chen, L.
1986-02-01
A theory describing the influence of energetic trapped particles on resistive interchange-ballooning modes in tokamaks is presented. It is shown that a population of hot particles trapped in the region of adverse curvature can resonantly interact with and destabilize the resistive interchange mode, which is stable in their absence because of favorable average curvature. The mode is different from the usual resistive interchange mode not only in its destabilization mechanism, but also in that it has a real component to its frequency comparable to the precessional drift frequency of the rapidly circulating energetic species. Corresponding growth rate and threshold conditions for this trapped-particle-driven instability are derived and finite banana width effects are shown to have a stabilizing effect on the mode. Finally, the ballooning/tearing dispersion relation is generalized to include hot particles, so that both the ideal and the resistive modes are derivable in the appropriate limits. 23 refs., 7 figs
Quantum dash based single section mode locked lasers for photonic integrated circuits.
Joshi, Siddharth; Calò, Cosimo; Chimot, Nicolas; Radziunas, Mindaugas; Arkhipov, Rostislav; Barbet, Sophie; Accard, Alain; Ramdane, Abderrahim; Lelarge, Francois
2014-05-05
We present the first demonstration of an InAs/InP Quantum Dash based single-section frequency comb generator designed for use in photonic integrated circuits (PICs). The laser cavity is closed using a specifically designed Bragg reflector without compromising the mode-locking performance of the self pulsating laser. This enables the integration of single-section mode-locked laser in photonic integrated circuits as on-chip frequency comb generators. We also investigate the relations between cavity modes in such a device and demonstrate how the dispersion of the complex mode frequencies induced by the Bragg grating implies a violation of the equi-distance between the adjacent mode frequencies and, therefore, forbids the locking of the modes in a classical Bragg Device. Finally we integrate such a Bragg Mirror based laser with Semiconductor Optical Amplifier (SOA) to demonstrate the monolithic integration of QDash based low phase noise sources in PICs.
Green, Josephine M; Baston, Helen A
2007-03-01
Concern has increased about rising rates of cesarean section and other obstetric interventions, and it has been suggested that a change in women's attitudes may be partly responsible. Our objectives were, first, to examine changes in women's antenatal willingness to accept obstetric interventions between 1987 and 2000 and, second, to look at the relationship between willingness to accept obstetric interventions and mode of birth. Data on willingness to accept obstetric interventions were collected at 35-36 weeks of pregnancy using postal questionnaires, and follow-up of women was conducted 6 weeks postnatally. Data are presented for 977 women drawn from 8 maternity units in England who were due to give birth in April to May 2000. To address the first objective, data were compared with the parent study carried out in 1987. The sample had significantly more positive antenatal attitudes toward obstetric interventions than the comparable sample in 1987 (F= 42.25, df= 1, p < 0.001). Willingness to accept obstetric interventions was related to mode of birth. Binary logistic regression controlling for age, education, and parity showed that women with high "willingness to accept intervention" scores had a nearly twofold increase in the odds of an operative or instrumental birth (OR 1.94, 95% CI 1.28-2.95) compared with women who had low scores. These attitudes also predicted epidural analgesia use, and differences in mode of birth were no longer significant when epidural use was included in the regression model. A shift toward greater willingness to accept obstetric interventions appears to have occurred since 1987, and this shift does appear to relate to mode of birth in the 2000 cohort but not in 1987. The findings suggest that epidural analgesia use mediates the link.
DEFF Research Database (Denmark)
Pærregaard, Karsten
This book presents a comparative study of Peruvian transnational migration to the United States, Spain, Japan and Argentina. It applies a multi-sited ethnographic fieldwork approach to study is the multicultural life-world of Peruvians and the economic, social, political and ritual relations...... that link them together in a diasporic network across national boundaries and tie them to their country of origin. The book has three aims: 1) to examine how Peruvians create networks and design strategies to cope with the mechanisms of inclusion and exclusion that mediate their incorporation......). Analytically, the study operates on two levels. On the one hand, it draws on ethnographic data gathered in particular localities in the United States, Spain, Japan and Argentina to analyze a variety of issues such as livelihoods, family networks, religious institutions, migrant organizations, identity...
Dispersion - does it degrade a pulse envelope
International Nuclear Information System (INIS)
Deighton, M.O.
1985-01-01
In hostile environments, transmitting information as ultrasonic Lamb wave pulses has advantages, since the stainless steel strip serving as a waveguide is very durable. Besides attenuation, velocity dispersion (inherent in Lamb waves) can be important even in fairly short guides. Theory shows that unlimited propagation of a pulsed r.f. envelope is possible, even with dispersion present. The constant group velocity needed would favour asub(o)-mode pulses over other modes, provided ordinary attenuation is small. An approximate formula indicates the useful range of a pulse, when group velocity does vary. (author)