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Sample records for strong easy-plane anisotropy

  1. Discrete breathers in classical ferromagnetic lattices with easy-plane anisotropy

    DEFF Research Database (Denmark)

    Khalack, J. M.; Zolotaryuk, Yaroslav; Christiansen, Peter Leth

    2003-01-01

    Discrete breathers (nonlinear localized modes) have been shown to exist in various nonlinear Hamiltonian lattice systems. This paper is devoted to the investigation of a classical d-dimensional ferromagnetic lattice with easy plane anisotropy. Its dynamics is described via the Heisenberg model....... Discrete breathers exist in such a model and represent excitations with locally tilted magnetization. They possess energy thresholds and have no analogs in the continuum limit. We are going to review the previous results on such solutions and also to report new results. Among the new results we show...

  2. Union Jack and checkerboard lattices with easy plane single ion anisotropy

    Science.gov (United States)

    Pires, A. S. T.

    2017-11-01

    The zero-temperature phase diagrams of the antiferromagnetic Union Jack and checkerboard lattices, with spin one and an easy-plane single anisotropy term, are studied using the SU(3) Schwinger boson formalism (also known as flavor wave theory). We find that the Union Jack lattice has a quantum phase transition (QPT) at J2/J1 = 0.707 between a Néel and a collinear phase, while the checkerboard lattice has a QPT at J2/J1 = 0.785, from the Néel to a magnetically disordered phase. The ground state phase diagrams of the two models are different, both from each other and from that of the square lattice antiferromagnet with all the next nearest neighbors. For the checkerboard lattice, we calculate the spin gap and the ground state energy in the disordered phase. This phase is a candidate for a spin liquid state.

  3. Investigation of the spin-1 honeycomb antiferromagnet BaNi2V2O8 with easy-plane anisotropy

    Science.gov (United States)

    Klyushina, E. S.; Lake, B.; Islam, A. T. M. N.; Park, J. T.; Schneidewind, A.; Guidi, T.; Goremychkin, E. A.; Klemke, B.; Mânsson, M.

    2017-12-01

    The magnetic properties of the two-dimensional, S =1 honeycomb antiferromagnet BaNi2V2O8 have been comprehensively studied using dc susceptibility measurements and inelastic neutron scattering techniques. The magnetic excitation spectrum is found to be dispersionless within experimental resolution between the honeycomb layers, while it disperses strongly within the honeycomb plane where it consists of two gapped spin-wave modes. The magnetic excitations are compared to linear spin-wave theory allowing the Hamiltonian to be determined. The first- and second-neighbor magnetic exchange interactions are antiferromagnetic and lie within the ranges 10.90 meV ≤Jn≤13.35 meV and 0.85 meV ≤Jn n≤1.65 meV, respectively. The interplane coupling Jout is four orders of magnitude weaker than the intraplane interactions, confirming the highly two-dimensional magnetic behavior of this compound. The sizes of the energy gaps are used to extract the magnetic anisotropies and reveal substantial easy-plane anisotropy and a very weak in-plane easy-axis anisotropy. Together these results reveal that BaNi2V2O8 is a candidate compound for the investigation of vortex excitations and Berezinsky-Kosterliz-Thouless phenomenon.

  4. Large Easy-Plane Magnetic Anisotropy in a Three-Coordinate Cobalt(II) Complex [Li(THF)4][Co(NPh2)3].

    Science.gov (United States)

    Deng, Yi-Fei; Wang, Zhenxing; Ouyang, Zhong-Wen; Yin, Bing; Zheng, Zhiping; Zheng, Yan-Zhen

    2016-10-10

    Magnetic anisotropy is the key element in the construction of single-ion magnets, a kind of nanomagnets for high-density information storage. This works describes an unusual large easy-plane magnetic anisotropy (with a zero-field splitting parameter D of +40.2 cm -1 ), mainly arising from the second-order spin-orbit coupling effect in a trigonal-planar Co II complex [Li(THF) 4 ][Co(NPh 2 ) 3 ], revealed by combined studies of magnetism, high frequency/field electron paramagnetic resonance spectroscopy, and ab initio calculations. Meanwhile, the field-induced slow magnetic relaxation in this complex was mainly attributed to the Raman process. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Two Polymorphic Forms of a Six-Coordinate Mononuclear Cobalt(II) Complex with Easy-Plane Anisotropy: Structural Features, Theoretical Calculations, and Field-Induced Slow Relaxation of the Magnetization.

    Science.gov (United States)

    Roy, Subhadip; Oyarzabal, Itziar; Vallejo, Julia; Cano, Joan; Colacio, Enrique; Bauza, Antonio; Frontera, Antonio; Kirillov, Alexander M; Drew, Michael G B; Das, Subrata

    2016-09-06

    A mononuclear cobalt(II) complex [Co(3,5-dnb)2(py)2(H2O)2] {3,5-Hdnb = 3,5-dinitrobenzoic acid; py = pyridine} was isolated in two polymorphs, in space groups C2/c (1) and P21/c (2). Single-crystal X-ray diffraction analyses reveal that 1 and 2 are not isostructural in spite of having equal formulas and ligand connectivity. In both structures, the Co(II) centers adopt octahedral {CoN2O4} geometries filled by pairs of mutually trans terminal 3,5-dnb, py, and water ligands. However, the structures of 1 and 2 disclose distinct packing patterns driven by strong intermolecular O-H···O hydrogen bonds, leading to their 0D→2D (1) or 0D→1D (2) extension. The resulting two-dimensional layers and one-dimensional chains were topologically classified as the sql and 2C1 underlying nets, respectively. By means of DFT theoretical calculations, the energy variations between the polymorphs were estimated, and the binding energies associated with the noncovalent interactions observed in the crystal structures were also evaluated. The study of the direct-current magnetic properties, as well as ab initio calculations, reveal that both 1 and 2 present a strong easy-plane magnetic anisotropy (D > 0), which is larger for the latter polymorph (D is found to exhibit values between +58 and 117 cm(-1) depending on the method). Alternating current dynamic susceptibility measurements show that these polymorphs exhibit field-induced slow relaxation of the magnetization with Ueff values of 19.5 and 21.1 cm(-1) for 1 and 2, respectively. The analysis of the whole magnetic data allows the conclusion that the magnetization relaxation in these polymorphs mainly takes place through a virtual excited state (Raman process). It is worth noting that despite the notable difference between the supramolecular networks of 1 and 2, they exhibit almost identical magnetization dynamics. This fact suggests that the relaxation process is intramolecular in nature and that the virtual state involved in the

  6. Soft modes in the easy plane pyrochlore antiferromagnet

    International Nuclear Information System (INIS)

    Champion, J D M; Holdsworth, P C W

    2004-01-01

    Thermal fluctuations lift the high ground state degeneracy of the classical nearest neighbour pyrochlore antiferromagnet, with easy plane anisotropy, giving a first-order phase transition to a long range ordered state. We show, from spin wave analysis and numerical simulation, that even below this transition a continuous manifold of states, of dimension N 2/3 , exist (N is the number of degrees of freedom). As the temperature goes to zero a further 'order by disorder' selection is made from this manifold. The pyrochlore antiferromagnet Er 2 Ti 2 O 7 is believed to have an easy plane anisotropy and is reported to have the same magnetic structure. This is perhaps surprising, given that the dipole interaction lifts the degeneracy of the classical model in favour of a different structure. We interpret our results in the light of these facts

  7. Syntheses, crystal structures and magnetic properties of two mixed-valence Co(iii)Co(ii) compounds derived from Schiff base ligands: field-supported single-ion-magnet behavior with easy-plane anisotropy.

    Science.gov (United States)

    Mandal, Shuvankar; Mondal, Suraj; Rajnák, Cyril; Titiš, Ján; Boča, Roman; Mohanta, Sasankasekhar

    2017-10-14

    Two μ-phenoxo-μ 1,1 -azide dinuclear Co III Co II complexes [Co III (N 3 ) 2 L 1 (μ 1,1 -N 3 )Co II (N 3 )]·MeOH (1) and [Co III (N 3 ) 2 L 2 (μ 1,1 -N 3 )Co II (N 3 )]·MeOH (2) (HL 1 and HL 2 are two Schiff base ligands having N 2 O-N 2 O compartments) both possess one hexacoordinate Co(iii) and one pentacoordinate Co(ii) center. DC magnetic susceptibility and magnetization measurements show an appreciable amount of positive magnetic anisotropy (D/hc∼ 40 cm -1 ) that is also confirmed by ab initio CASSCF calculations. AC susceptibility measurements of 1 reveal that it exhibits a slow magnetic relaxation with two relaxation channels. The external magnetic field supports the low-frequency (LF) channel that escapes on heating more progressively than the high-frequency (HF) branch. The relaxation time is as slow as τ = 255 ms at T = 1.9 K and B DC = 0.6 T, where the LF mole fraction is 69%. The complex 2 also displays similar field-supported slow magnetic relaxation with two relaxation channels.

  8. Continuous Easy-Plane Deconfined Phase Transition on the Kagome Lattice

    Science.gov (United States)

    Zhang, Xue-Feng; He, Yin-Chen; Eggert, Sebastian; Moessner, Roderich; Pollmann, Frank

    2018-03-01

    We use large scale quantum Monte Carlo simulations to study an extended Hubbard model of hard core bosons on the kagome lattice. In the limit of strong nearest-neighbor interactions at 1 /3 filling, the interplay between frustration and quantum fluctuations leads to a valence bond solid ground state. The system undergoes a quantum phase transition to a superfluid phase as the interaction strength is decreased. It is still under debate whether the transition is weakly first order or represents an unconventional continuous phase transition. We present a theory in terms of an easy plane noncompact C P1 gauge theory describing the phase transition at 1 /3 filling. Utilizing large scale quantum Monte Carlo simulations with parallel tempering in the canonical ensemble up to 15552 spins, we provide evidence that the phase transition is continuous at exactly 1 /3 filling. A careful finite size scaling analysis reveals an unconventional scaling behavior hinting at deconfined quantum criticality.

  9. LDA+DMFT Approach to Magnetocrystalline Anisotropy of Strong Magnets

    Directory of Open Access Journals (Sweden)

    Jian-Xin Zhu

    2014-05-01

    Full Text Available The new challenges posed by the need of finding strong rare-earth-free magnets demand methods that can predict magnetization and magnetocrystalline anisotropy energy (MAE. We argue that correlated electron effects, which are normally underestimated in band-structure calculations, play a crucial role in the development of the orbital component of the magnetic moments. Because magnetic anisotropy arises from this orbital component, the ability to include correlation effects has profound consequences on our predictive power of the MAE of strong magnets. Here, we show that incorporating the local effects of electronic correlations with dynamical mean-field theory provides reliable estimates of the orbital moment, the mass enhancement, and the MAE of YCo_{5}.

  10. Strong enhancement of magnetic anisotropy energy in alloyed nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Negulyaev, Nikolay; Niebergall, Larissa; Stepanyuk, Valeri [Max-Planck-Institut fuer Mikrostrukturphysik, D-06120 Halle (Germany); Juarez Reyes, Lucila; Pastor, Gustavo [Institut fuer Theoretische Physik, Universitaet Kassel, D-34132 Kassel (Germany); Dorantes-Davila, Jesus [Instituto de Fisica, Universidad Autonoma de San Luis Potosi, 78000 San Luis Potosi (Mexico)

    2011-07-01

    One-dimensional atomic structures (monatomic wires and chains) are believed to be likely candidates for creation of nanostructures with large atomic orbital moments and hence with giant magnetic anisotropy energy (MAE) per atom. We investigate the possibility of tuning the MAE of 3d transition metal monowires alloyed with 5d elements (Ir, Pt). Our ab initio studies give clear evidence that in mixed 3d-5d atomic wires MAE is one and even two orders of magnitude more than in pure wires constructed of the corresponding 5d and 3d elements, respectively. Mechanisms responsible for the formation of such a strong MAE are revealed. The interplay between the structure of a monowire and its MAE is demonstrated. The contribution of both types of species (3d and 5d) into the MAE is discussed.

  11. Soliton–antisoliton interaction in a parametrically driven easy-plane magnetic wire

    Energy Technology Data Exchange (ETDEWEB)

    Urzagasti, D., E-mail: deterlino@yahoo.com [Instituto de Investigaciones Físicas, UMSA, P.O. Box 8635, La Paz (Bolivia, Plurinational State of); Aramayo, A. [Instituto de Investigaciones Físicas, UMSA, P.O. Box 8635, La Paz (Bolivia, Plurinational State of); Laroze, D. [Instituto de Alta Investigación, Universidad de Tarapacá, Casilla 7D, Arica (Chile); Max Planck Institute for Polymer Research, 55021 Mainz (Germany)

    2014-07-11

    In the present work we study the soliton–antisoliton interaction in an anisotropic easy-plane magnetic wire forced by a transverse uniform and oscillatory magnetic field. This system is described in the continuous framework by the Landau–Lifshitz–Gilbert equation. We find numerically that the spatio-temporal magnetization field exhibits both annihilative and repulsive soliton–antisoliton interactions. We also describe this system with the aim of the associated Parametrically Driven and Damped Nonlinear Schrödinger amplitude equation and give an approximate analytical solution that roughly describes the repulsive interaction. - Highlights: • We study the interactions of solitons with opposite polarity with the LLG equation. • We found that there exists both annihilative and repulsive interactions. • Similar results we found for the Parametrically Driven and Damped NLS equation. • We obtain an approximate analytical solution for the repulsive interaction.

  12. Soliton instabilities in the easy plane ferromagnet Heisenberg chain with out-of-plane spin deviation

    Energy Technology Data Exchange (ETDEWEB)

    Pozo, J.; Leon, A. [Instituto de Ciencias Basicas, Facultad de Ingenieria, Universidad Diego Portales, Casilla 298-V, Santiago (Chile)]. e-mail: julio.pozo@udp.cl

    2006-07-01

    In this paper we investigate the presence of out-of-plane spin deviation {rho}({xi}) in the easy-plane ferromagnetic Heisenberg chain by using the coupled-boson operators together with the Schwinger transformation for the spin operator; this method allows us to conclude that the critical behaviour of the instability is due to the velocity of the nonlinear excitations (solitons) only for an appropriate range of the magnetic field. In this case, when the velocity becomes lower, the stable soliton corresponding to {rho}({xi}) is distorted by magnons and loses stability. If we increase the velocity of {rho}({xi}), it then decays into high frequency-oscillations. Nevertheless, we find an opposite competence effect produced by the velocity and the magnetic field on {rho}({xi}). (Author)

  13. Strong near-surface seismic anisotropy of Taiwan revealed by coda interferometry

    Science.gov (United States)

    Chen, Li-Wei; Chen, Ying-Nien; Gung, Yuancheng; Lee, Jian-Cheng; Liang, Wen-Tzong

    2017-10-01

    We report the near-surface (OPA (Orogeny-Parallel Anisotropy) and SAA (Stress-Aligned Anisotropy). Both types of anisotropy fit well the local geological fabrics and/or the ambient stress, and show strong correlation with the Poisson's ratios at the borehole sites. With these new findings and reported tomographic results, we infer that the SAA are likely confined to the uppermost portion of the crust, in particular to the fluid-saturated late-Quaternary deposits. The strong near-surface anisotropy also implies that delay times contributed by the shallow crust might have been underestimated in studies of shear-wave splitting measurements using the direct arrivals of earthquake waves.

  14. Two-Dimensional Superfluidity of Exciton Polaritons Requires Strong Anisotropy

    Directory of Open Access Journals (Sweden)

    Ehud Altman

    2015-02-01

    Full Text Available Fluids of exciton polaritons, excitations of two-dimensional quantum wells in optical cavities, show collective phenomena akin to Bose condensation. However, a fundamental difference from standard condensates stems from the finite lifetime of these excitations, which necessitates continuous driving to maintain a steady state. A basic question is whether a two-dimensional condensate with long-range algebraic correlations can exist under these nonequilibrium conditions. Here, we show that such driven two-dimensional Bose systems cannot exhibit algebraic superfluid order except in low-symmetry, strongly anisotropic systems. Our result implies, in particular, that recent apparent evidence for Bose condensation of exciton polaritons must be an intermediate-scale crossover phenomenon, while the true long-distance correlations fall off exponentially. We obtain these results through a mapping of the long-wavelength condensate dynamics onto the anisotropic Kardar-Parisi-Zhang equation.

  15. Strong crustal seismic anisotropy in the Kalahari Craton based on Receiver Functions

    DEFF Research Database (Denmark)

    Thybo, Hans; Soliman, Mohammad Youssof Ahmad; Artemieva, Irina

    2015-01-01

    anisotropy in the crust of the Kalahari craton, which is 30-40% of the total anisotropy as measured by SKS splitting. Our analysis is based on calculation of receiver functions for the data from the SASE experiment which shows strong splitting between the SV and SH components. The direction of the fast axes...... is uniform within tectonic units and parallel to orogenic strike in the Limpopo and Cape fold belts. It is further parallel to the strike of major dyke swarms which indicates that a large part of the observed anisotropy is controlled by lithosphere fabrics and macroscopic effects. The directions of the fast...... axes for the crustal anisotropy are parallel to the general directions determined from SKS splitting, although the directions from our analysis of receiver functions is more homogeneous than for SKS splitting. This analysis indicates parallel fast axes in the crust and in the mantle, which suggests...

  16. Off-specular polarized neutron reflectometry study of magnetic dots with a strong shape anisotropy

    CERN Document Server

    Temst, K; Moshchalkov, V V; Bruynseraede, Y; Fritzsche, H; Jonckheere, R

    2002-01-01

    We have measured the off-specular polarized neutron reflectivity of a regular array of rectangular magnetic polycrystalline Co dots, which were prepared by a combination of electron-beam lithography, molecular beam deposition, and lift-off processes. The dots have a length-to-width ratio of 4:1 imposing a strong shape anisotropy. The intensity of the off-specular satellite reflection was monitored as a function of the magnetic field applied parallel to the rows of dots and in the plane of the sample, allowing us to analyze the magnetization-reversal process using the four spin-polarized cross sections. (orig.)

  17. Magnetotransport properties of Cr1−δTe thin films with strong perpendicular magnetic anisotropy

    Directory of Open Access Journals (Sweden)

    L. Zhou

    2017-12-01

    Full Text Available P-type ferromagnetic Cr1-δTe thin films with the Curie temperature of 170K were epitaxially grown on GaAs substrate. Low-temperature magnetotransport study reveals that the film has a strong perpendicular magnetic anisotropy (PMA and an anisotropic magnetoresistance (AMR ratio up to 8.1%. Furthermore, reduced anomalous Hall effect is observed at low temperatures in Cr1-δTe, suggesting the possible crossover of the contribution to AHE from the intrinsic mechanism to extrinsic skew scattering. Distinctive from conventional transition metal ferromagnets, the AMR ratio is also greatly suppressed at low temperatures. Our work demonstrates that epitaxial Cr1-δTe films are interesting platforms for studying the physics underlying the strong PMA and large AMR.

  18. Strong uniaxial magnetic anisotropy in Co films on highly ordered grating-like nanopatterned Ge surfaces

    Science.gov (United States)

    Alam Mollick, Safiul; Singh, Ranveer; Kumar, Mohit; Bhattacharyya, Satyaranjan; Som, Tapobrata

    2018-03-01

    We present a systematic investigation on uniaxial magnetic anisotropy (UMA) in Co thin films induced by high aspect ratio nanopatterned anisotropic substrates. Self-organized long grating-like nanostructures, with extreme regularities, are fabricated on Ge surfaces using Au-ion implantation at room temperature. Subsequently deposition of Co films are carried out on the same at two different angles. Magneto-optical Kerr effect measurements show strong UMA in Co films grown on ion-patterned Ge substrates, fabricated under different ion fluences, along and perpendicular to the direction of the patterns (long grating-like nanostructures). Magnetic force microscopy measurements under different externally applied magnetic fields reveal an easy domain wall motion when the field is applied along the grating-like nanostructures. On the other hand, high amplitude grating-like nanostructures hinder the spin rotation when the field is applied along the hard axis. The present study will be useful for magnetic recording media and ultra-small magnetic field sensors.

  19. Strong morphological and crystallographic texture and resulting yield strength anisotropy in selective laser melted tantalum

    International Nuclear Information System (INIS)

    Thijs, Lore; Montero Sistiaga, Maria Luz; Wauthle, Ruben; Xie, Qingge; Kruth, Jean-Pierre; Van Humbeeck, Jan

    2013-01-01

    Selective laser melting (SLM) makes use of a high energy density laser beam to melt successive layers of metallic powders in order to create functional parts. The energy density of the laser is high enough to melt refractory metals like Ta and produce mechanically sound parts. Furthermore, the localized heat input causes a strong directional cooling and solidification. Epitaxial growth due to partial remelting of the previous layer, competitive growth mechanism and a specific global direction of heat flow during SLM of Ta result in the formation of long columnar grains with a 〈1 1 1〉 preferential crystal orientation along the building direction. The microstructure was visualized using both optical and scanning electron microscopy equipped with electron backscattered diffraction and the global crystallographic texture was measured using X-ray diffraction. The thermal profile around the melt pool was modeled using a pragmatic model for SLM. Furthermore, rotation of the scanning direction between different layers was seen to promote the competitive growth. As a result, the texture strength increased to as large as 4.7 for rotating the scanning direction 90° every layer. By comparison of the yield strength measured by compression tests in different orientations and the averaged Taylor factor calculated using the viscoplastic self-consistent model, it was found that both the morphological and crystallographic texture observed in SLM Ta contribute to yield strength anisotropy

  20. Strong out-of-plane magnetic anisotropy in ion irradiated anatase TiO2 thin films

    Directory of Open Access Journals (Sweden)

    M. Stiller

    2016-12-01

    Full Text Available The temperature and field dependence of the magnetization of epitaxial, undoped anatase TiO2 thin films on SrTiO3 substrates was investigated. Low-energy ion irradiation was used to modify the surface of the films within a few nanometers, yet with high enough energy to produce oxygen and titanium vacancies. The as-prepared thin film shows ferromagnetism which increases after irradiation with low-energy ions. An optimal and clear magnetic anisotropy was observed after the first irradiation, opposite to the expected form anisotropy. Taking into account the experimental parameters, titanium vacancies as di-Frenkel pairs appear to be responsible for the enhanced ferromagnetism and the strong anisotropy observed in our films. The magnetic impurities concentrations was measured by particle-induced X-ray emission with ppm resolution. They are ruled out as a source of the observed ferromagnetism before and after irradiation.

  1. Anisotropy and Strong-Coupling Effects on the Collective Mode Spectrum of Chiral Superconductors: Application to Sr2RuO4

    Directory of Open Access Journals (Sweden)

    James Avery Sauls

    2015-06-01

    Full Text Available Recent theories of Sr2RuO4 based on the interplay of strong interactions, spin-orbit coupling and multi-band anisotropy predict chiral or helical ground states with strong anisotropy of the pairing states, with deep minima in the excitation gap, as well as strong phase anisotropy for the chiral ground state. We develop time-dependent mean field theory to calculate the Bosonic spectrum for the class of 2D chiral superconductors spanning 3He-A to chiral superconductors with strong anisotropy. Chiral superconductors support a pair of massive Bosonic excitations of the time-reversed pairs labeled by their parity under charge conjugation. These modes are degenerate for 2D 3He-A. Crystal field anisotropy lifts the degeneracy. Strong anisotropy also leads to low-lying Fermions, and thus to channels for the decay of the Bosonic modes. Selection rules and phase space considerations lead to large asymmetries in the lifetimes and hybridization of the Bosonic modes with the continuum of un-bound Fermion pairs. We also highlight results for the excitation of the Bosonic modes by microwave radiation that provide clear signatures of the Bosonic modes of an anisotropic chiral ground state.

  2. Strong perpendicular magnetic anisotropy at FeCoB/MgO interface with an ultrathin HfOx insertion layer

    Science.gov (United States)

    Ou, Yongxi; Ralph, Daniel; Buhrman, Robert

    The realization of robust perpendicular magnetic anisotropy (PMA) in heavy metal(HM)/FeCoB/MgO thin-film heterostructures has enabled a pathway for the implementation of high density memory elements based on perpendicularly magnetized tunnel junctions, and also provides a platform for the study and control of domain walls and of novel magnetic chiral structures such as skyrmions in nanowire structures. Here we report on the achievement of more robust PMA in Ta/FeCoB/MgO heterostructures by the insertion of an ultrathin HfOx passivation layer at the FeCoB/MgO interface. This is accomplished by depositing one to two atomic layers of Hf onto the FeCoB before the subsequent rf sputter deposition of the MgO layer, which fully oxidizes the Hf layer as confirmed by X-ray photoelectron spectroscopy measurements. The result is a strong interfacial perpendicular anisotropy energy density as large as 1.7 erg/cm-2 without any post-fabrication annealing treatment. Similar results have been achieved with the use of W and Pt HM base layers. This work broadens the class and enhances the capabilities of PMA HM/FM heterostructures for spintronics research and applications.

  3. Strong anisotropy in the low temperature Compton profiles of electron momentum distribution in α-Ga metal

    International Nuclear Information System (INIS)

    Panda, B.P.; Mohapatra, N.C.

    2002-01-01

    Compton profiles of momentum distribution of conduction electrons in the orthorhombic phase of α-Ga metal at low temperature are calculated in the band model for the three crystallographic directions (100), (010), and (001). Unlike the results at room temperature, previously reported by Lengeler, Lasser and Mair, the present results show strong anisotropy in the Compton profiles with the momentum distribution along (001) direction being substantially different from the other two directions. While experimental data on Compton profiles at low temperatures are not available for comparison with theory, the resistivity data in α-Ga at low temperature strongly support this anisotropic behaviour. Besides, the electronic heat capacity constant γ available from both experiment and present calculation suggests that conduction electron distribution at low temperature in the orthorhombic phase is markedly different from the free-electron-like-distribution at room temperature, thus lending additional support to anisotropic behaviour of Compton profiles. It would be nice to have Compton profiles data from experiment at low temperature for direct comparison with theory. It is hoped that the present work would stimulate enough interest in that direction. (author)

  4. Surface-termination-dependent magnetism and strong perpendicular magnetocrystalline anisotropy of an FeRh(001) thin film

    Czech Academy of Sciences Publication Activity Database

    Jekal, S.; Rhim, S.H.; Hong, S.C.; Son, W.-J.; Shick, Alexander

    2015-01-01

    Roč. 92, č. 6 (2015), " 064410-1"-" 064410-6" ISSN 1098-0121 R&D Projects: GA ČR GA15-07172S Institutional support: RVO:68378271 Keywords : magnetic anisotropy * magnetic recording * surface science Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.736, year: 2014

  5. Shear Wave Splitting analysis of borehole microseismic reveals weak azimuthal anisotropy hidden behind strong VTI fabric of Lower Paleozoic shales in northern Poland

    Science.gov (United States)

    Gajek, Wojciech; Verdon, James; Malinowski, Michał; Trojanowski, Jacek

    2017-04-01

    Azimuthal anisotropy plays a key-role in hydraulic fracturing experiments, since it provides information on stress orientation and pre-existing fracture system presence. The Lower Paleozoic shale plays in northern Poland are characterized by a strong (15-18%) Vertical Transverse Isotropy (VTI) fabric which dominates weak azimuthal anisotropy being of order of 1-2%. A shear wave travelling in the subsurface after entering an anisotropic medium splits into two orthogonally polarized waves travelling with different velocities. Splitting parameters which can be assessed using a microseismic array are polarization of the fast shear wave and time delay between two modes. Polarization of the fast wave characterizes the anisotropic system on the wave path while the time delay is proportional to the magnitude of anisotropy. We employ Shear Wave Splitting (SWS) technique using a borehole microseismic dataset collected during a hydraulic stimulation treatment located in northern Poland, to image fracture strike masked by a strong VTI signature. During the inversion part, the VTI background parameters were kept constant using information from 3D seismic (VTI model used for pre-stack depth migration). Obtained fracture azimuths averaged over fracturing stages are consistent with the available XRMI imager logs from the nearby vertical well, however they are different from the large-scale maximum stress direction (by 40-45 degrees). Inverted Hudson's crack density (ca. 2%) are compatible with the low shear-wave anisotropy observed in the cross-dipole sonic logs (1-2%). This work has been funded by the Polish National Centre for Research and Development within the Blue Gas project (No BG2/SHALEMECH/14). Data were provided by the PGNiG SA. Collaboration with University of Bristol was supported within TIDES COST Action ES1401.

  6. Coexistence of Low Damping and Strong Magnetoelastic Coupling in Epitaxial Spinel Ferrite Thin Films.

    Science.gov (United States)

    Emori, Satoru; Gray, Benjamin A; Jeon, Hyung-Min; Peoples, Joseph; Schmitt, Maxwell; Mahalingam, Krishnamurthy; Hill, Madelyn; McConney, Michael E; Gray, Matthew T; Alaan, Urusa S; Bornstein, Alexander C; Shafer, Padraic; N'Diaye, Alpha T; Arenholz, Elke; Haugstad, Greg; Meng, Keng-Yuan; Yang, Fengyuan; Li, Dongyao; Mahat, Sushant; Cahill, David G; Dhagat, Pallavi; Jander, Albrecht; Sun, Nian X; Suzuki, Yuri; Howe, Brandon M

    2017-09-01

    Low-loss magnetization dynamics and strong magnetoelastic coupling are generally mutually exclusive properties due to opposing dependencies on spin-orbit interactions. So far, the lack of low-damping, magnetostrictive ferrite films has hindered the development of power-efficient magnetoelectric and acoustic spintronic devices. Here, magnetically soft epitaxial spinel NiZnAl-ferrite thin films with an unusually low Gilbert damping parameter (ferrite. At the same time, the coherently strained film structure suppresses extrinsic damping, enables soft magnetic behavior, and generates large easy-plane magnetoelastic anisotropy. These findings provide a foundation for a new class of low-loss, magnetoelastic thin film materials that are promising for spin-mechanical devices. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Elastic anisotropy of crystals

    Directory of Open Access Journals (Sweden)

    Christopher M. Kube

    2016-09-01

    Full Text Available An anisotropy index seeks to quantify how directionally dependent the properties of a system are. In this article, the focus is on quantifying the elastic anisotropy of crystalline materials. Previous elastic anisotropy indices are reviewed and their shortcomings discussed. A new scalar log-Euclidean anisotropy measure AL is proposed, which overcomes these deficiencies. It is based on a distance measure in a log-Euclidean space applied to fourth-rank elastic tensors. AL is an absolute measure of anisotropy where the limiting case of perfect isotropy yields zero. It is a universal measure of anisotropy applicable to all crystalline materials. Specific examples of strong anisotropy are highlighted. A supplementary material provides an anisotropy table giving the values of AL for 2,176 crystallite compounds.

  8. Current induced multi-mode propagating spin waves in a spin transfer torque nano-contact with strong perpendicular magnetic anisotropy

    Science.gov (United States)

    Mohseni, S. Morteza; Yazdi, H. F.; Hamdi, M.; Brächer, T.; Mohseni, S. Majid

    2018-03-01

    Current induced spin wave excitations in spin transfer torque nano-contacts are known as a promising way to generate exchange-dominated spin waves at the nano-scale. It has been shown that when these systems are magnetized in the film plane, broken spatial symmetry of the field around the nano-contact induced by the Oersted field opens the possibility for spin wave mode co-existence including a non-linear self-localized spin-wave bullet and a propagating mode. By means of micromagnetic simulations, here we show that in systems with strong perpendicular magnetic anisotropy (PMA) in the free layer, two propagating spin wave modes with different frequency and spatial distribution can be excited simultaneously. Our results indicate that in-plane magnetized spin transfer nano-contacts in PMA materials do not host a solitonic self-localized spin-wave bullet, which is different from previous studies for systems with in plane magnetic anisotropy. This feature renders them interesting for nano-scale magnonic waveguides and crystals since magnon transport can be configured by tuning the applied current.

  9. Three tetracoordinate Co(II) complexes [Co(biq)X.sub.2./sub.] (X = Cl, Br, I) with easy-plane magnetic anisotropy as field-induced single-molecule magnets

    Czech Academy of Sciences Publication Activity Database

    Smolko, I.; Černák, J.; Dušek, Michal; Miklovič, C.; Titiš, J.; Boča, R.

    2015-01-01

    Roč. 44, č. 40 (2015), s. 17565-17571 ISSN 1477-9226 Institutional support: RVO:68378271 Keywords : crystal structure * cobalt * superparamagnetism * magnetic properties * biquinoline Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 4.177, year: 2015

  10. Variational cluster approximation study of Mott transition with strong spin-orbit coupling

    International Nuclear Information System (INIS)

    Shirakawa, Tomonori; Watanabe, Hiroshi; Yunoki, Seiji

    2011-01-01

    Motivated by recent experiments on Sr 2 IrO 4 , the ground state magnetic and electronic structures are studied theoretically for a two-dimensional three-band Hubbard model with strong spin-orbit coupling. To treat spin-orbit coupling, local Coulomb interactions, and band structure effects on the same footing, the variational cluster approximation based on the self-energy functional theory is employed. It is found that for a relatively large coupling region, the ground state is an anisotropic antiferromagnetic Mott insulator of an effective local angular momentum J eff = 1/2 with xy plane as an easy plane. This anisotropy is caused by the strong spin-orbit coupling along with the inter-orbital Hund's coupling. The momentum resolved one-particle excitations are also studied for the Mott insulating phase. It is found that the low-energy one-particle excitations consist mostly of the J eff = 1/2 state, a direct evidence of a novel J eff = 1/2 Mott insulator.

  11. More light on the 2ν{sub 5} Raman overtone of SF{sub 6}: Can a weak anisotropic spectrum be due to a strong transition anisotropy?

    Energy Technology Data Exchange (ETDEWEB)

    Kremer, D.; Rachet, F.; Chrysos, M., E-mail: michel.chrysos@univ-angers.fr [LUNAM Université, Université d’Angers, CNRS UMR 6200, Laboratoire MOLTECH-Anjou, 2 Bd Lavoisier, 49045 Angers (France)

    2014-01-21

    Long known as a fully polarized band with a near vanishing depolarization ratio [η{sub s} = 0.05, W. Holzer and R. Ouillon, Chem. Phys. Lett. 24, 589 (1974)], the 2ν{sub 5} Raman overtone of SF{sub 6} has so far been considered as of having a prohibitively weak anisotropic spectrum [D. P. Shelton and L. Ulivi, J. Chem. Phys. 89, 149 (1988)]. Here, we report the first anisotropic spectrum of this overtone, at room temperature and for 13 gas densities ranging between 2 and 27 amagat. This spectrum is 10 times broader and 50 times weaker than the isotropic counterpart of the overtone [D. Kremer, F. Rachet, and M. Chrysos, J. Chem. Phys. 138, 174308 (2013)] and its profile much more sensitive to pressure effects than the profile of the isotropic spectrum. From our measurements an accurate value for the anisotropy matrix-element |〈000020|Δα|000000〉| was derived and this value was found to be comparable to that of the mean-polarizability ((000020), α{sup ¯} (000000)). Among other conclusions our study offers compelling evidence that, in Raman spectroscopy, highly polarized bands or tiny depolarization ratios are not necessarily incompatible with large polarizability anisotropy transition matrix-elements. Our findings and the way to analyze them suggest that new strategies should be developed on the basis of the complementarity inherent in independent incoherent Raman experiments that run with two different incident-beam polarizations, and on concerted efforts to ab initio calculate accurate data for first and second polarizability derivatives. Values for these derivatives are still rarities in the literature of SF{sub 6}.

  12. Magnetic anisotropy of Ho-Fe-Co-Cr intermetallic compounds

    International Nuclear Information System (INIS)

    Sheloudko, N.; Sarafidis, C.; Gjoka, M.; Efthimiadis, K.G.; Kalogirou, O.

    2009-01-01

    Starting with a Ho 3 (Fe 1-x Co x ) 29-y Cr y , (x,y) = (0.6,4.5) and (0.8,5.5) nominal stoichiometry, a disordered variant of the hexagonal 2:17 phase (Th 2 Ni 17 -type, S.G. P6 3 /mmc) occurs, since both the monoclinic 3:29 and the transition-metal-rich disordered Th 2 Ni 17 -type hexagonal compounds have the same rare earth to transition metal ratio, 1:9.7. The magnetic properties and the magnetocrystalline anisotropy of these compounds have been investigated. The anisotropy constant, K's, and the anisotropy field, μ 0 H A , values have been deduced from the magnetization curves measured on powder samples magnetically aligned in a rotating magnetic field. The compound with (x,y) = (0.8,5.5) shows a compensation point at about 55 K. The magnetic anisotropy of both compounds is that of easy-plane from room temperature to low temperatures down to 5 K.

  13. Anisotropy across Superplume Boundaries

    Science.gov (United States)

    Cottaar, S.; Romanowicz, B. A.

    2011-12-01

    Sdiff data sets are presented for paths that run parallel to the African and the Pacific superplume boundaries. Objective clustering of waveforms illustrates sharp changes across these boundaries. The African plume shows a sharp offset in travel times in the SHdiff phase, while a more gradual offset towards slower arrivals is seen in the case of the Pacific superplume. Additionally, Pdiff phases display no offset around the African plume and a weak one around the Pacific plume. Here we focus mainly on another striking feature observed in both cases: outside of the superplume the Sdiff particle motion is strongly elliptical, but becomes linear within the superplume (first noticed by To et al. 2005 in the African superplume case). For the African plume we argue that these observations of delayed SV at large distances (~120 degrees) are indicative of the occurrence of azimuthal anisotropy. The SV arrivals have similar polarity as SH, opposite from what their radiation pattern predicts. Azimuthal anisotropy causes SH energy to be converted to SV (Maupin, 1994), explaining the travel time, polarity and amplitude. Forward modeling through different isotropic and anisotropic models supports this statement, although there are trade-offs between direction and magnitude of azimuthal anisotropy. The strong elliptical particle motions are also observed outside the Pacific plume, but at shorter distances (95-105 degrees). Elliptical motions can occur in the absence of anisotropy when strong velocity deviations or layering occurs close to the CMB, which, based on velocity profiles with depth in global tomographic models would be more likely within the superplume rather than on the fast side. The elliptical particle motions here can be modelled with a simple transverse isotropic model with VSH>VSV, but azimuthal anisotropy cannot be ruled out. The complexities within the Pacific superplume, including strong amplitude drop and existence of a post-cursor, are likely caused by an

  14. Laboratory seismic anisotropy in mylonites

    Science.gov (United States)

    Almqvist, B. S. G.; Herwegh, M.; Hirt, A. M.; Ebert, A.; Linckens, J.; Precigout, J.; Leiss, B.; Walter, J. M.; Burg, J.-P.

    2012-04-01

    Tectonic strain is often accommodated along narrow zones in the Earth's crust and upper mantle, and these high-strain zones represent an important mechanical and rheological component in geodynamics. In outcrop we observe the intense deformation along and across these structures. But at depth, in the mid and lower crust, and in the mantle, we are dependent on geophysical methods for analysis of structures, such as seismic reflection and refraction surveys. A natural progression has therefore been to understand the remote geophysical signal in terms of laboratory ultrasonic pulse transmission measurements on rock cores, collected in the field or from borehole drill core. Here we first present a brief review that consider key studies in the area of laboratory seismic measurements in strongly anisotropic rocks, ranging from calcite mylonites to metapelites. In the second part we focus attention on ongoing research projects targetting laboratory seismic anisotropy in mylonitized rocks, and associated challenges. Measurements of compressional (P) and shear (S) waves were made at high confining pressure (up to 5 kbar). Mineral texture analysis was performed with electron backscatter diffraction (EBSD) and neutron texture diffraction to determine crystallographic preferred orientation (CPO). So-called "rock-recipe" models are used to calculate seismic anisotropy, which consider the elastic properties of minerals that constitutes the rock, and their respective CPO. However, the outcome of such models do not always simply correspond to the measured seismic anisotropy. Differences are attributed to several factors, such as grain boundaries, mineral microstructures including shape-preferred orientation (SPO), micro-cracks and pores, and grain-scale stress-strain conditions. We highlight the combination of these factors in case studies on calcite and peridotite mylonites. In calcite mylonites, sampled in the Morcles nappe shear zone, the measured seismic anisotropy generally

  15. Anisotropy in the deep Earth

    Science.gov (United States)

    Romanowicz, Barbara; Wenk, Hans-Rudolf

    2017-08-01

    Seismic anisotropy has been found in many regions of the Earth's interior. Its presence in the Earth's crust has been known since the 19th century, and is due in part to the alignment of anisotropic crystals in rocks, and in part to patterns in the distribution of fractures and pores. In the upper mantle, seismic anisotropy was discovered 50 years ago, and can be attributed for the most part, to the alignment of intrinsically anisotropic olivine crystals during large scale deformation associated with convection. There is some indication for anisotropy in the transition zone, particularly in the vicinity of subducted slabs. Here we focus on the deep Earth - the lower mantle and core, where anisotropy is not yet mapped in detail, nor is there consensus on its origin. Most of the lower mantle appears largely isotropic, except in the last 200-300 km, in the D″ region, where evidence for seismic anisotropy has been accumulating since the late 1980s, mostly from shear wave splitting measurements. Recently, a picture has been emerging, where strong anisotropy is associated with high shear velocities at the edges of the large low shear velocity provinces (LLSVPs) in the central Pacific and under Africa. These observations are consistent with being due to the presence of highly anisotropic MgSiO3 post-perovskite crystals, aligned during the deformation of slabs impinging on the core-mantle boundary, and upwelling flow within the LLSVPs. We also discuss mineral physics aspects such as ultrahigh pressure deformation experiments, first principles calculations to obtain information about elastic properties, and derivation of dislocation activity based on bonding characteristics. Polycrystal plasticity simulations can predict anisotropy but models are still highly idealized and neglect the complex microstructure of polyphase aggregates with strong and weak components. A promising direction for future progress in understanding the origin of seismic anisotropy in the deep mantle

  16. Most spin-1/2 transition-metal ions do have single ion anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jia; Whangbo, Myung-Hwan, E-mail: hxiang@fudan.edu.cn, E-mail: mike-whangbo@ncsu.edu [Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695 (United States); Koo, Hyun-Joo [Department of Chemistry and Research Institute for Basic Sciences, Kyung Hee University, Seoul 130-701 (Korea, Republic of); Xiang, Hongjun, E-mail: hxiang@fudan.edu.cn, E-mail: mike-whangbo@ncsu.edu [Key Laboratory of Computational Physical Sciences (Ministry of Education), State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, Shanghai 200433 (China); Kremer, Reinhard K. [Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart (Germany)

    2014-09-28

    The cause for the preferred spin orientation in magnetic systems containing spin-1/2 transition-metal ions was explored by studying the origin of the easy-plane anisotropy of the spin-1/2 Cu{sup 2+} ions in CuCl{sub 2}·2H{sub 2}O, LiCuVO{sub 4}, CuCl{sub 2}, and CuBr{sub 2} on the basis of density functional theory and magnetic dipole-dipole energy calculations as well as a perturbation theory treatment of the spin-orbit coupling. We find that the spin orientation observed for these spin-1/2 ions is not caused by their anisotropic spin exchange interactions, nor by their magnetic dipole-dipole interactions, but by the spin-orbit coupling associated with their crystal-field split d-states. Our study also predicts in-plane anisotropy for the Cu{sup 2+} ions of Bi{sub 2}CuO{sub 4} and Li{sub 2}CuO{sub 2}. The results of our investigations dispel the mistaken belief that magnetic systems with spin-1/2 ions have no magnetic anisotropy induced by spin-orbit coupling.

  17. Ultrafast laser-induced changes of the magnetic anisotropy in a low-symmetry iron garnet film

    Science.gov (United States)

    Shelukhin, L. A.; Pavlov, V. V.; Usachev, P. A.; Shamray, P. Yu.; Pisarev, R. V.; Kalashnikova, A. M.

    2018-01-01

    We explore a thermal mechanism of changing the magnetic anisotropy by using femtosecond laser pulses in a low-symmetry dielectric ferrimagnetic garnet (YBiPrLu) 3(FeGa) 5O12 film grown on the (210)-type Gd3Ga5O12 substrate as a model media. Employing spectral magneto-optical pump-probe technique and phenomenological analysis, we demonstrate that the magnetization precession in this film is a result of laser-induced changes of the growth-induced magnetic anisotropy along with the ultrafast inverse Faraday effect. The change of magnetic anisotropy relies on the lattice heating induced by laser pulses of any polarization on a picosecond time scale. We show that the orientation of the external magnetic field with respect to the magnetization easy plane affects the precession noticeably. Importantly, the relative contributions from the ultrafast inverse Faraday effect and the change of different growth-induced anisotropy parameters can be controlled varying the applied magnetic field strength and direction. As a result, the amplitude and the initial phase of the excited magnetization precession can be gradually tuned.

  18. Seismic anisotropy - Introduction

    Czech Academy of Sciences Publication Activity Database

    Grechka, V.; Pšenčík, Ivan; Ravve, I.; Tsvankin, I.

    2017-01-01

    Roč. 82, č. 4 (2017), WAI-WAII ISSN 0016-8033 Institutional support: RVO:67985530 Keywords : seismic anisotropy Subject RIV: DC - Siesmology, Volcanology, Earth Structure OBOR OECD: Volcanology Impact factor: 2.391, year: 2016

  19. THz-driven demagnetization with perpendicular magnetic anisotropy: towards ultrafast ballistic switching

    Science.gov (United States)

    Polley, Debanjan; Pancaldi, Matteo; Hudl, Matthias; Vavassori, Paolo; Urazhdin, Sergei; Bonetti, Stefano

    2018-02-01

    We study THz-driven spin dynamics in thin CoPt films with perpendicular magnetic anisotropy. Femtosecond magneto-optical Kerr effect measurements show that demagnetization amplitude of about 1% can be achieved with a peak THz electric field of 300 kV cm‑1, and a corresponding peak magnetic field of 0.1 T. The effect is more than an order of magnitude larger than observed in samples with easy-plane anisotropy irradiated with the same field strength. We also utilize finite-element simulations to design a meta-material structure that can enhance the THz magnetic field by more than an order of magnitude, over an area of several tens of square micrometers. Magnetic fields exceeding 1 Tesla, generated in such meta-materials with the available laser-based THz sources, are expected to produce full magnetization reversal via ultrafast ballistic precession driven by the THz radiation. Our results demonstrate the possibility of table-top ultrafast magnetization reversal induced by THz radiation.

  20. Measuring anisotropies in the cosmic neutrino background

    Science.gov (United States)

    Lisanti, Mariangela; Safdi, Benjamin R.; Tully, Christopher G.

    2014-10-01

    Neutrino capture on tritium has emerged as a promising method for detecting the cosmic neutrino background (C ν B ). We show that relic neutrinos are captured most readily when their spin vectors are antialigned with the polarization axis of the tritium nuclei and when they approach along the direction of polarization. As a result, C ν B observatories may measure anisotropies in the cosmic neutrino velocity and spin distributions by polarizing the tritium targets. A small dipole anisotropy in the C ν B is expected due to the peculiar velocity of the lab frame with respect to the cosmic frame and due to late-time gravitational effects. The PTOLEMY experiment, a tritium observatory currently under construction, should observe a nearly isotropic background. This would serve as a strong test of the cosmological origin of a potential signal. The polarized-target measurements may also constrain nonstandard neutrino interactions that would induce larger anisotropies and help discriminate between Majorana versus Dirac neutrinos.

  1. Magnetic anisotropy engineering in square magnetic elements

    International Nuclear Information System (INIS)

    Di Bona, A.; Contri, S.F.; Gazzadi, G.C.; Valeri, S.; Vavassori, P.

    2007-01-01

    Square magnetic elements with side in the 100-500 nm range have been fabricated using the focused ion beam (FIB) milling technique from a 10 nm thick, single-crystal Fe film, epitaxially grown on MgO(0 0 1). Thanks to the good crystal quality of the film, magnetic elements with well-defined magnetocrystalline anisotropy have been prepared, while the fine control of the size and shape of the magnets allows for the effective engineering of the anisotropic behavior of the magnetostatic energy that determines the so-called configurational anisotropy. Micromagnetic calculations and experiments show that the angular dependence of the transverse susceptibility has a strong dependence on the material parameters as well as on the static applied field. This allows the effective engineering of the total anisotropy of the magnets

  2. Temperature dependence of the interfacial magnetic anisotropy in W/CoFeB/MgO

    OpenAIRE

    Kyoung-Min Lee; Jun Woo Choi; Junghyun Sok; Byoung-Chul Min

    2017-01-01

    The interfacial perpendicular magnetic anisotropy in W/CoFeB (1.2 ∼ 3 nm)/MgO thin film structures is strongly dependent on temperature, and is significantly reduced at high temperature. The interfacial magnetic anisotropy is generally proportional to the third power of magnetization, but an additional factor due to thermal expansion is required to explain the temperature dependence of the magnetic anisotropy of ultrathin CoFeB films. The reduction of the magnetic anisotropy is more prominent...

  3. Anisotropy modulated stepwise magnetization in triangular Heisenberg antiferromagnet

    International Nuclear Information System (INIS)

    Yao Xiaoyan; Liu Junming; Lo, Veng Cheong

    2011-01-01

    During the course of tuning anisotropy from Ising type to zero, the variation of magnetization (M) steps against magnetic field (h) is investigated in a triangular antiferromagnetic Heisenberg model using Monte Carlo techniques. It is revealed that the anisotropy is an essential key to induce the temperature-dependent stepwise M(h) curve observed in frustrated magnetic system, and it can be employed to modulate this steplike magnetic behavior effectively. When the anisotropy is strengthened, a ground state transition occurs from the homogeneous 120 o triangular structure to the collinear partially disordered antiferromagnetic state. No M step is detected in the system without anisotropy. But if the anisotropy is nonzero, the M 0 /3 step (where M 0 is the saturated M) will emerge on M(h) curve, which is due to an h-induced quasi-collinear ferrimagnetic state. This M 0 /3 step can be extended by increasing the anisotropy. When the M 0 /3 plateau dominates the h-range broad enough, the equidistant metastable substeps, which originates from the disorders frozen in the frustrated collinear spin structure, appear to be superposed on the M 0 /3 plateau. Thus the system with a strong anisotropy presents the whole temperature evolution of stepwise M(h) curve in quantitative agreement with the experiments of Ca 3 Co 2 O 6 . - Highlights: → Variation of M steps is investigated by tuning anisotropy from Ising type to zero. → Anisotropy is essential to induce T-dependent multistep M against magnetic field. → Simulation with strong anisotropy reproduces T-evolution of M steps in Ca 3 Co 2 O 6 . → Metastable substeps at low T can be enhanced by increasing anisotropy.

  4. Anisotropy Enhancement of Thermal Energy Transport in Supported Black Phosphorene.

    Science.gov (United States)

    Chen, Jige; Chen, Shunda; Gao, Yi

    2016-07-07

    Thermal anisotropy along the basal plane of materials possesses both theoretical importance and application value in thermal transport and thermoelectricity. Though common two-dimensional materials may exhibit in-plane thermal anisotropy when suspended, thermal anisotropy would often disappear when supported on a substrate. In this Letter, we find a strong anisotropy enhancement of thermal energy transport in supported black phosphorene. The chiral preference of energy transport in the zigzag rather than the armchair direction is greatly enhanced by coupling to the substrate, up to a factor of approximately 2-fold compared to the suspended one. The enhancement originates from its puckered lattice structure, where the nonplanar armchair energy transport relies on the out-of-plane corrugation and thus would be hindered by the flexural suppression due to the substrate, while the planar zigzag energy transport is not. As a result, thermal conductivity of supported black phosphorene shows a consistent anisotropy enhancement under different temperatures and substrate coupling strengths.

  5. Spintronic magnetic anisotropy

    OpenAIRE

    Misiorny, Maciej; Hell, Michael; Wegewijs, Maarten R.

    2014-01-01

    An attractive feature of magnetic adatoms and molecules for nanoscale applications is their superparamagnetism, the preferred alignment of their spin along an easy axis preventing undesired spin reversal. The underlying magnetic anisotropy barrier --a quadrupolar energy splitting-- is internally generated by spin-orbit interaction and can nowadays be probed by electronic transport. Here we predict that in a much broader class of quantum-dot systems with spin larger than one-half, superparamag...

  6. Supernovae anisotropy power spectrum

    Energy Technology Data Exchange (ETDEWEB)

    Ghodsi, Hoda; Baghram, Shant [Department of Physics, Sharif University of Technology, P.O. Box 11155-9161, Tehran (Iran, Islamic Republic of); Habibi, Farhang, E-mail: h.ghodsi@mehr.sharif.ir, E-mail: baghram@sharif.edu, E-mail: habibi@lal.in2p3.fr [LAL-IN2P3/CNRS, BP 34, 91898 Orsay Cedex (France)

    2017-10-01

    We contribute another anisotropy study to this field of research using Type Ia supernovae (SNe Ia). In this work, we utilise the power spectrum calculation method and apply it to both the current SNe Ia data and simulation. Using the Union2.1 data set at all redshifts, we compare the spectrum of the residuals of the observed distance moduli to that expected from an isotropic universe affected by the Union2.1 observational uncertainties at low multipoles. Through this comparison we find a dipolar anisotropy with tension of less that 2σ towards l = 171° ± 21° and b = −26° ± 28° which is mainly induced by anisotropic spatial distribution of the SNe with z > 0.2 rather than being a cosmic effect. Furthermore, we find a tension of ∼ 4σ at ℓ = 4 between the two spectra. Our simulations are constructed with the characteristics of the upcoming surveys like the Large Synoptic Survey Telescope (LSST), which shall bring us the largest SNe Ia collection to date. We make predictions for the amplitude of a possible dipolar anisotropy that would be detectable by future SNe Ia surveys.

  7. Magnetic anisotropy of ultrafine 316L stainless steel fibers

    Energy Technology Data Exchange (ETDEWEB)

    Shyr, Tien-Wei, E-mail: twshyr@fcu.edu.tw [Department of Fiber and Composite Materials, Feng Chia University, No. 100, Wenhwa Road, Seatwen, Taichung 40724, Taiwan, ROC (China); Huang, Shih-Ju [Department of Fiber and Composite Materials, Feng Chia University, No. 100, Wenhwa Road, Seatwen, Taichung 40724, Taiwan, ROC (China); Wur, Ching-Shuei [Department of Physics, National Cheng Kung University, No. 1, University Road, Tainan 70101, Taiwan, ROC (China)

    2016-12-01

    An as-received 316L stainless steel fiber with a diameter of 20 μm was drawn using a bundle drawing process at room temperature to form ultrafine stainless steel fibers with diameters of 12, 8, and 6 μm. The crystalline phases of the fibers were analyzed using the X-ray diffraction (XRD) profile fitting technique. The grain sizes of γ-austenite and α′-martensite were reduced to nanoscale sizes after the drawing process. XRD analysis and focused ion beam-scanning electron microscope observations showed that the newly formed α′-martensitic grains were closely arrayed in the drawing direction. The magnetic property was measured using a superconducting quantum interference device vibrating sample magnetometer. The magnetic anisotropy of the fibers was observed by applying a magnetic field parallel and perpendicular to the fiber axis. The results showed that the microstructure anisotropy including the shape anisotropy, magnetocrystalline anisotropy, and the orientation of the crystalline phases strongly contributed to the magnetic anisotropy. - Highlights: • The martensitic transformation of the 316L SS fiber occurred during the cold drawn. • The grain sizes of γ-austenite and α′-martensite were reduced to the nanoscale. • The newly formed martensitic grains were closely arrayed in the drawing direction. • The drawing process caused the magnetic easy axis to be aligned with the fiber axis. • The microstructure anisotropy strongly contributed to the magnetic anisotropy.

  8. Size effects of the magnetic anisotropy of fcc cobalt nanoparticles embedded in copper

    Science.gov (United States)

    Hillenkamp, Matthias; Oyarzún, Simón; Troc, Nicolas; Ramade, Julien; Tamion, Alexandre; Tournus, Florent; Dupuis, Véronique; Rodrigues, Varlei

    2017-12-01

    Cobalt nanoparticles embedded in copper matrices show strong size effects in the magnetic anisotropy with a non-monotonous dependence on the particle diameter. In this article we discuss quantitative values of the magnetic anisotropy in the frame of two models: in small clusters the surface anisotropy contribution dominates whereas larger particles ( >3 nm diameter) have an elliptic shape leading to increased shape anisotropy. The crystalline structure of the particles is shown to be face-centered cubic, justifying that the magneto-crystalline anisotropy can be neglected.

  9. Measurement of fission anisotropy for 16O + 181Ta

    Science.gov (United States)

    Behera, Bivash R.; Roy, Subinit; Basu, P.; Sharan, M. K.; Jena, S.; Satpathy, M.; Chatterjee, M. L.; Datta, S. K.

    2001-07-01

    Anisotropies in fission fragment angular distributions measured for the system 16 O + 181Ta over a range of bombarding energies from 83 MeV to 120 MeV have been analysed. It is shown that statistical transition state model (TSM) with pre-scission neutron correction described adequately the measured anisotropy data. Strong friction parameter is found to be necessary to estimate the pre-saddle to pre-scission neutron ratio.

  10. Flow stress anisotropy

    DEFF Research Database (Denmark)

    Winther, G.

    1996-01-01

    stress Variation in the rolling plane, which may be as high as 20%, are presented. The traditional Taylor model is applied to the data to account for the effect of texture. However, texture effects alone are not enough to explain all of the observed anisotropy. New models which take the combined effects...... of texture and deformation microstructure into account are presented. The models are based on the Taylor and Sachs models but modified with an anisotropic critical shear stress to account for the effect of the microstructure. The agreement between experimental data and model predictions is definitely better...

  11. Evaporation Anisotropy of Forsterite

    Science.gov (United States)

    Ozawa, K.; Nagahara, H.; Morioka, M.

    1996-03-01

    Evaporation anisotropy of a synthetic single crystal of forsterite was investigated by high temperature vacuum experiments. The (001), (010), and (001) surfaces show microstructures characteristic for each surface. Obtained overall linear evaporation rates for the (001), (010), and (001) surfaces are ~17, ~7, and ~22 mm/hour, and the intrinsic evaporation rates, obtained by the change in surface microstructures, are ~10, ~4.5, and ~35 mm/hour, respectively. The difference between the intrinsic evaporation rates and overall rates can be regarded as contribution of dislocation, which is notable for the (100) and (010) surfaces and insignificant for the (001) surface. This is consistent with observed surface microstructures.

  12. Plasma pressure and anisotropy inferred from the Tsyganenkomagnetic field model

    Directory of Open Access Journals (Sweden)

    F. Cao

    Full Text Available A numerical procedure has been developed to deduce the plasma pressure and anisotropy from the Tsyganenko magnetic field model. The Tsyganenko empirical field model, which is based on vast satellite field data, provides a realistic description of magnetic field configuration in the magnetosphere. When the force balance under the static condition is assumed, the electromagnetic <strong>J×B> force from the Tsyganenko field model can be used to infer the plasma pressure and anisotropy distributions consistent with the field model. It is found that the <strong>J×B> force obtained from the Tsyganenko field model is not curl-free. The curl-free part of the <strong>J×B> force in an empirical field model can be balanced by the gradient of the isotropic pressure, while the nonzero curl of the <strong>J×B> force can only be associated with the pressure anisotropy. The plasma pressure and anisotropy in the near-Earth plasma sheet are numerically calculated to obtain a static equilibrium consistent with the Tsyganenko field model both in the noon-midnight meridian and in the equatorial plane. The plasma pressure distribution deduced from the Tsyganenko 1989 field model is highly anisotropic and shows this feature early in the substorm growth phase. The pressure anisotropy parameter αP, defined as αP=1-PVertP, is typically ~0.3 at x ≈ -4.5RE and gradually decreases to a small negative value with an increasing tailward distance. The pressure anisotropy from the Tsyganenko 1989 model accounts for 50% of the cross-tail current at maximum and only in a highly localized region near xsim-10RE. In comparison, the plasma pressure anisotropy inferred from the Tsyganenko 1987 model is much smaller. We also find that the boundary

  13. Strong anisotropy in the low temperature Compton profiles of ...

    Indian Academy of Sciences (India)

    Compton profiles of momentum distribution of conduction electrons in the orthorhombic phase of -Ga metal at low temperature are calculated in the band model for the three crystallographic directions (100), (010), and (001). Unlike the results at room temperature, previously reported by Lengeler, Lasser and Mair, the ...

  14. How strongly are the magnetic anisotropy and coordination numbers ...

    Indian Academy of Sciences (India)

    particular interest in recent years in research area of. SMMs9 is exploration of systems ... ment in the design of novel SIMs.16–19 In SIMs coordi- .... method. So, spin-orbit free states were obtained by employing the RASSCF method whereas spin-orbit coupling has been taken into account using RASSI-SO method69 which ...

  15. Strong anisotropy in the low temperature Compton profiles of ...

    Indian Academy of Sciences (India)

    Abstract. Compton profiles of momentum distribution of conduction electrons in the orthorhom- bic phase of α-Ga metal at low temperature are calculated in the band model for the three crys- tallographic directions (100), (010), and (001). Unlike the results at room temperature, previously reported by Lengeler, Lasser and ...

  16. Strong anisotropy in the low temperature Compton profiles of ...

    Indian Academy of Sciences (India)

    B P PANDA and N C MOHAPATRA£. Department of Physics, Chikiti Mahavidyalaya, Chikiti 761 010, India. £Department of Physics, Berhampur University, Berhampur 760 007, India. MS received 12 April 2001; revised 1 September 2001. Abstract. Compton profiles of momentum distribution of conduction electrons in the ...

  17. How strongly are the magnetic anisotropy and coordination numbers ...

    Indian Academy of Sciences (India)

    Coordination number around the lanthanide ion is found to alter the magnetic behaviour of all the lanthanide complexes studied and this is contrary to the general belief that the lanthanide ions are inert and exert small ligand field interaction.High symmetric low-coordinate LnIII complexes are found to yield large Ueff values ...

  18. Current sheets and pressure anisotropy in the reconnection exhaust

    International Nuclear Information System (INIS)

    Le, A.; Karimabadi, H.; Roytershteyn, V.; Egedal, J.; Ng, J.; Scudder, J.; Daughton, W.; Liu, Y.-H.

    2014-01-01

    A particle-in-cell simulation shows that the exhaust during anti-parallel reconnection in the collisionless regime contains a current sheet extending 100 inertial lengths from the X line. The current sheet is supported by electron pressure anisotropy near the X line and ion anisotropy farther downstream. Field-aligned electron currents flowing outside the magnetic separatrices feed the exhaust current sheet and generate the out-of-plane, or Hall, magnetic field. Existing models based on different mechanisms for each particle species provide good estimates for the levels of pressure anisotropy. The ion anisotropy, which is strong enough to reach the firehose instability threshold, is also important for overall force balance. It reduces the outflow speed of the plasma

  19. Limits on the ions temperature anisotropy in turbulent intracluster medium

    Energy Technology Data Exchange (ETDEWEB)

    Santos-Lima, R. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Potsdam Univ. (Germany). Inst. fuer Physik und Astronomie; Univ. de Sao Paulo (Brazil). Inst. de Astronomia, Geofisica e Ciencias Atmosfericas; Yan, H. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Potsdam Univ. (Germany). Inst. fuer Physik und Astronomie; Gouveia Dal Pino, E.M. de [Univ. de Sao Paulo (Brazil). Inst. de Astronomia, Geofisica e Ciencias Atmosfericas; Lazarian, A. [Wisconsin Univ., Madison, WI (United States). Dept. of Astronomy

    2016-05-15

    Turbulence in the weakly collisional intracluster medium of galaxies (ICM) is able to generate strong thermal velocity anisotropies in the ions (with respect to the local magnetic field direction), if the magnetic moment of the particles is conserved in the absence of Coulomb collisions. In this scenario, the anisotropic pressure magnetohydrodynamic (AMHD) turbulence shows a very different statistical behaviour from the standard MHD one and is unable to amplify seed magnetic fields, in disagreement with previous cosmological MHD simulations which are successful to explain the observed magnetic fields in the ICM. On the other hand, temperature anisotropies can also drive plasma instabilities which can relax the anisotropy. This work aims to compare the relaxation rate with the growth rate of the anisotropies driven by the turbulence. We employ quasilinear theory to estimate the ions scattering rate due to the parallel firehose, mirror, and ion-cyclotron instabilities, for a set of plasma parameters resulting from AMHD simulations of the turbulent ICM. We show that the ICM turbulence can sustain only anisotropy levels very close to the instabilities thresholds. We argue that the AMHD model which bounds the anisotropies at the marginal stability levels can describe the Alfvenic turbulence cascade in the ICM.

  20. Angular dependence of magnetization reversal in epitaxial chromium telluride thin films with perpendicular magnetic anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Pramanik, Tanmoy, E-mail: pramanik.tanmoy@utexas.edu; Roy, Anupam, E-mail: anupam@austin.utexas.edu; Dey, Rik, E-mail: rikdey@utexas.edu; Rai, Amritesh; Guchhait, Samaresh; Movva, Hema C.P.; Hsieh, Cheng-Chih; Banerjee, Sanjay K.

    2017-09-01

    Highlights: • Perpendicular magnetic anisotropy in epitaxial Cr{sub 2}Te{sub 3} has been investigated. • Presence of a relatively strong second order anisotropy contribution is observed. • Magnetization reversal is explained quantitatively using a 1D defect model. • Relative roles of nucleation and pinning in magnetization reversal are discussed. • Domain structures and switching process are visualized by micromagnetic simulation. - Abstract: We investigate magnetic anisotropy and magnetization reversal mechanism in chromium telluride thin films grown by molecular beam epitaxy. We report existence of strong perpendicular magnetic anisotropy in these thin films, along with a relatively strong second order anisotropy contribution. The angular variation of the switching field observed from the magnetoresistance measurement is explained quantitatively using a one-dimensional defect model. The model reveals the relative roles of nucleation and pinning in the magnetization reversal, depending on the applied field orientation. Micromagnetic simulations are performed to visualize the domain structure and switching process.

  1. Flow stress anisotropy in aluminium

    DEFF Research Database (Denmark)

    Juul Jensen, D.; Hansen, N.

    1990-01-01

    tension as a function of the angle between the tensile axis and the rolling direction. Textures were determined by neutron diffraction, and Taylor M-factors were calculated. The microstructures were studied by TEM. It was found that the flow stress varies significantly with orientation both at low......The plastic anisotropy of cold-rolled high purity aluminum (99.996%) and commercially pure aluminum (99.6%) has been investigated. Sample parameters were the initial grain size and the degree of plastic strain (ϵ stresses (0.2% offset) were measured at room temperature by uniaxial...... and high strains. It is shown that for most experimental conditions, texture effects alone cannot explain the observed anisotropy, and microstructural anisotropy effects have to be taken into account. In those cases, a correlation between the microstructural anisotropy and the development of microbands...

  2. Measurement of the anisotropy ratios in MgB2 single crystals

    International Nuclear Information System (INIS)

    Kim, Heon-Jung; Kang, Byeongwon; Lee, Hyun-Sook; Lee, Sung-Ik

    2006-01-01

    We present our recent measurements on the anisotropy ratios of MgB 2 single crystals. Our measurements indicate that the anisotropy ratios of the penetration depth and of the upper critical field have different magnitudes and temperature dependences, as predicted by theoretical calculations. These results imply that the two-gap nature can strongly influence the superconducting properties of MgB 2

  3. Quantifying seismic anisotropy induced by small-scale chemical heterogeneities

    Science.gov (United States)

    Alder, C.; Bodin, T.; Ricard, Y.; Capdeville, Y.; Debayle, E.; Montagner, J. P.

    2017-12-01

    induce more than 3.9 per cent of extrinsic radial S-wave anisotropy. We thus predict that a non-negligible part of the observed anisotropy in tomographic models may be the result of unmapped small-scale heterogeneities in the mantle, mainly in the form of fine layering, and that caution should be taken when interpreting observed anisotropy in terms of LPO and mantle deformation. This effect may be particularly strong in the lithosphere where chemical heterogeneities are assumed to be the strongest.

  4. Field-ball milling induced anisotropy in magnetic particles

    Energy Technology Data Exchange (ETDEWEB)

    Poudyal, Narayan [Department of Physics, University of Texas at Arlington, Arlington, TX 76019 (United States); Altuncevahir, Baki [Department of Physics, University of Texas at Arlington, Arlington, TX 76019 (United States); Chakka, Vamsi [Department of Physics, University of Texas at Arlington, Arlington, TX 76019 (United States); Chen Kanghua [Department of Physics, University of Texas at Arlington, Arlington, TX 76019 (United States); Black, Truman D [Department of Physics, University of Texas at Arlington, Arlington, TX 76019 (United States); Liu, J Ping [Department of Physics, University of Texas at Arlington, Arlington, TX 76019 (United States); Ding, Yong [School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332 (United States); Wang Zhonglin [School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332 (United States)

    2004-12-21

    Nd{sub 2}Fe{sub 14}B and Sm{sub 2}Co{sub 17} particles of submicrometre sizes have been prepared by ball milling in a magnetic field. Structural and magnetic characterization reveal that these submicrometre particles milled in a magnetic field, consisting of nanosize grains, exhibit strong magnetic anisotropy compared with the particles milled without a magnetic field. Based on in situ observations of the field-ball milling in a transparent container, the mechanism of field-induced anisotropy in the nanostructured hard magnetic particles is discussed. (rapid communication)

  5. Anisotropy of mechanical properties of zirconium and zirconium alloys

    International Nuclear Information System (INIS)

    Medrano, R.E.

    1975-01-01

    In studies of technological applications of zirconium to fuel elements of nuclear reactor, it was found that the use of plasticity equations for isotropic materials is not in agreement with experimental results, because of the strong anisotropy of zirconium. The present review describes recent progress on the knowledge of the influence of anisotropy on mechanical properties, after Douglass' review in 1971. The review was written to be selfconsistent, changing drastically the presentation of some of the referenced papers. It is also suggested some particular experiments to improve developments in this area

  6. Voltage Control of Magnetic Anisotropy

    Science.gov (United States)

    Hao, Guanhua; Cao, Shi; Noviasky, Nick; Ilie, Carolina; Sokolov, Andre; Yin, Yuewei; Xu, Xiaoshan; Dowben, Peter

    Pd/Co/Gd2O3/Si heterostructures were fabricated via pulsed laser deposition and e-beam evaporation. Hysteresis loops, obtained by longitudinal magneto-optical Kerr-effect (MOKE) measurements, indicates an initial in-plane magnetic anisotropy. Applying a perpendicular voltage on the sample, the differences between the polar and longitudinal MOKE and anomalous Hall effect data indicates there is a reversible change in magnetic anisotropy, from in-plane to out-of-plane, with applied voltage. Prior work by others suggests that the change in magnetic anisotropy is due to redox reactions at the Co/Gd2O3 interference. Voltage controlled magnetism can result from changing interfacial chemistry and does not always require a magneto-electric coupling tensor.

  7. Emergence of Anisotropy in Flock Simulations and Its Computational Analysis

    Science.gov (United States)

    Makiguchi, Motohiro; Inoue, Jun-Ichi

    In real flocks, it was revealed that the angular density of nearest neighbors shows a strong anisotropic structure of individuals by very recent extensive field studies [Ballerini et al, Proceedings of the National Academy of Sciences USA, 105, pp. 1232-1237 (2008)]. In this paper, we show this structure of anisotropy also emerges in an artificial flock simulation, namely, Boid simulation. To quantify the anisotropy, we evaluate a useful statistics, that is to say, the so-called γ-value which is defined as an inner product between the vector in the direction of the lowest angular density of flocks and the vector in the direction of moving of the flock. Our results concerning the emergence of the anisotropy through the γ-value might enable us to judge whether an optimal flock simulation seems to be realistic or not.

  8. Magnetic Alignment of Block Copolymer Microdomains by Intrinsic Chain Anisotropy.

    Science.gov (United States)

    Rokhlenko, Yekaterina; Gopinadhan, Manesh; Osuji, Chinedum O; Zhang, Kai; O'Hern, Corey S; Larson, Steven R; Gopalan, Padma; Majewski, Paweł W; Yager, Kevin G

    2015-12-18

    We examine the role of intrinsic chain susceptibility anisotropy in magnetic field directed self-assembly of a block copolymer using in situ x-ray scattering. Alignment of a lamellar mesophase is observed on cooling across the disorder-order transition with the resulting orientational order inversely proportional to the cooling rate. We discuss the origin of the susceptibility anisotropy, Δχ, that drives alignment and calculate its magnitude using coarse-grained molecular dynamics to sample conformations of surface-tethered chains, finding Δχ≈2×10^{-8}. From field-dependent scattering data, we estimate that grains of ≈1.2  μm are present during alignment. These results demonstrate that intrinsic anisotropy is sufficient to support strong field-induced mesophase alignment and suggest a versatile strategy for field control of orientational order in block copolymers.

  9. Tuning the Anisotropy of In-Plane Thermal Conduction in Thin Films by Modulating Thickness

    Science.gov (United States)

    Zeng, Yuqiang; Marconnet, Amy

    2018-01-01

    Anisotropy in thermal conductivity is promising for directing the heat-flow pathways in modern applications including thermal management of electronic devices. While some materials, like graphite, have strong anisotropy when comparing the in-plane thermal conductivity to cross-plane thermal conductivity, few naturally occurring materials have significant anisotropy within the in-plane directions, with an anisotropy ratio of ˜3 in few-layer black phosphorus being among the highest. In this Letter, we propose to control the thermal-conduction anisotropy by periodically modulating the thickness of thin films. Specifically, we model the thermal conduction in silicon-based thickness-modulated films using full three-dimensional simulations based on the phonon frequency-dependent Boltzmann transport equation. Our simulations demonstrate that phonon scattering with appropriately sized and shaped thickness-modulation features leads to a significant anisotropy in thermal conduction. In the diffusive regime, the same types of features lead to relatively low anisotropy (as calculated using the conventional heat diffusion equation). Thus, the enhanced thermal-conduction anisotropy with small features comes from the phonon scattering and size effects. Modulating the thickness of the thin films allows tuning the thermal-anisotropy ratio across an order of magnitude. Moreover, the proposed structures can be fabricated with currently available silicon-based nanofabrication techniques, without the need for exotic or expensive materials.

  10. Anisotropy of magnetoviscous effect in structure-forming ferrofluids

    Science.gov (United States)

    Sreekumari, Aparna; Ilg, Patrick

    2015-07-01

    The magnetoviscous effect, change in viscosity with change in magnetic field strength, and the anisotropy of the magnetoviscous effect, change in viscosity with orientation of magnetic field, have been a focus of interest for four decades. A satisfactory understanding of the microscopic origin of anisotropy of the magnetoviscous effect in magnetic fluids is still a matter of debate and a field of intense research. Here, we present an extensive simulation study to understand the relation between the anisotropy of the magnetoviscous effect and the underlying change in microstructures of ferrofluids. Our results indicate that field-induced chainlike structures respond very differently depending on their orientation relative to the direction of an externally applied shear flow, which leads to a pronounced anisotropy of viscosity. In this work, we focus on three exemplary values of dipolar interaction strengths which correspond to weak, intermediate, and strong interactions between dipolar colloidal particles. We compare our simulation results with an experimental study on cobalt-based ferrofluids as well as with an existing theoretical model called the chain model. A nonmonotonic behavior in the anisotropy of the magnetoviscous effect is observed with increasing dipolar interaction strength and is explained in terms of microstructure formation.

  11. Accuracy and sensitivity analysis on seismic anisotropy parameter estimation

    Science.gov (United States)

    Yan, Fuyong; Han, De-Hua

    2018-04-01

    There is significant uncertainty in measuring the Thomsen’s parameter δ in laboratory even though the dimensions and orientations of the rock samples are known. It is expected that more challenges will be encountered in the estimating of the seismic anisotropy parameters from field seismic data. Based on Monte Carlo simulation of vertical transversely isotropic layer cake model using the database of laboratory anisotropy measurement from the literature, we apply the commonly used quartic non-hyperbolic reflection moveout equation to estimate the seismic anisotropy parameters and test its accuracy and sensitivities to the source-receive offset, vertical interval velocity error and time picking error. The testing results show that the methodology works perfectly for noise-free synthetic data with short spread length. However, this method is extremely sensitive to the time picking error caused by mild random noises, and it requires the spread length to be greater than the depth of the reflection event. The uncertainties increase rapidly for the deeper layers and the estimated anisotropy parameters can be very unreliable for a layer with more than five overlain layers. It is possible that an isotropic formation can be misinterpreted as a strong anisotropic formation. The sensitivity analysis should provide useful guidance on how to group the reflection events and build a suitable geological model for anisotropy parameter inversion.

  12. Texture and anisotropy analysis of Qusaiba shales

    KAUST Repository

    Kanitpanyacharoen, Waruntorn

    2011-02-17

    Scanning and transmission electron microscopy, synchrotron X-ray diffraction, microtomography and ultrasonic velocity measurements were used to characterize microstructures and anisotropy of three deeply buried Qusaiba shales from the Rub\\'al-Khali basin, Saudi Arabia. Kaolinite, illite-smectite, illite-mica and chlorite show strong preferred orientation with (001) pole figure maxima perpendicular to the bedding plane ranging from 2.4-6.8 multiples of a random distribution (m.r.d.). Quartz, feldspars and pyrite crystals have a random orientation distribution. Elastic properties of the polyphase aggregate are calculated by averaging the single crystal elastic properties over the orientation distribution, assuming a nonporous material. The average calculated bulk P-wave velocities are 6.2 km/s (maximum) and 5.5 km/s (minimum), resulting in a P-wave anisotropy of 12%. The calculated velocities are compared with those determined from ultrasonic velocity measurements on a similar sample. In the ultrasonic experiment, which measures the effects of the shale matrix as well as the effects of porosity, velocities are smaller (P-wave maximum 5.3 km/s and minimum 4.1 km/s). The difference between calculated and measured velocities is attributed to the effects of anisotropic pore structure and to microfractures present in the sample, which have not been taken into account in the matrix averaging. © 2011 European Association of Geoscientists & Engineers.

  13. Magnetic alloys with vanishing anisotropies

    International Nuclear Information System (INIS)

    Couderchon, G.

    1991-01-01

    Co-based amorphous alloys and 80 Ni Permalloys have vanishingly-low anisotropies and show the highest permeabilities and lowest losses among commercial magnetic materials. In spit of their different atomic arrangements, these two types of material show close similarities in domain structure and in their temperature and frequency behavior. Information is also given concerning material technology and applications. (orig.)

  14. Azimuthal and Radial Seismic Anisotropy Beneath the Baltic Shield

    Science.gov (United States)

    Pedersen, H. A.; Bruneton, M.; Maupin, V.

    2005-12-01

    The SVEKALAPKO passive seismic array in Finland provides us with an exceptional opportunity to study seismic anisotropy in and below the lithosphere in a shield. The array was composed of almost 150 sensors - out of which 46 were broadband - in a regular 2D grid which facilitated high-quality array analysis. We analyse phase velocities of both Love and Rayleigh waves to constrain radial and azimuthal anisotropy. We invert for the anisotropic parameters ξ and Gc on the one hand, and for the percentage of aligned olivine on the other. This latter parametrization of the inverse problem makes it straightforward to quantitatively compare the radial and the azimuthal anisotropies, under the assumption that aligned olivine dominates the anisotropy. The radial anisotropy, for which we have resolution in the lithosphere only, is strong, and can be explained by 40%-60% of the rock being olivine with the a-axis in the horizontal plane, equivalent to values of ξ between 1.09 and 1.14. This radial anisotropy is stronger than observed in shield areas in global models (e.g. Beghein and Trampert, 2004). The azimuthal anisotropy is on the contrary very small in the lithosphere. This indicates that the orientation of the olivine minerals is random within the horizontal plane or that the overall effect across the area is negligible due to different orientations in different domains. Results from body-waves (Plomerová et al., 2005, Vecsey et al., in prep.) would support the latter interpretation. The azimuthal anisotropy as estimated by Rayleigh wave analysis is on the contrary significant below 200-250km depth, and corresponds to approximately 15%-20% of the rock being olivine with the a-axis aligned in direction N20. Xenolith analysis in the area shows that the rheologic lithosphere is at most 250km thick, so we suggest that this observed anisotropy is sub-lithospheric. Interestingly, the fast direction is significantly different from the absolute plate motion of the Baltic

  15. Impact of fabric, microcracks and stress field on shale anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Dewhurst, D.N.; Siggins, A.F. [CSIRO Petroleum, Australian Petrolium Co-operative Research Centre, Kensington, WA (Australia)

    2006-04-15

    Few data are available on shales in terms of seismic to ultrasonic properties and anisotropy, although all are important with regards to imaging problems often encountered in such lithologies. Additionally, mechanisms causing changes in these properties are not well documented due to the fine grain size of such materials and time required for testing under controlled pore pressure conditions. The results presented here are derived from a set of experiments run on Muderong Shale with pore pressure control in order to evaluate the effect of stress magnitude and stress anisotropy on ultrasonic response. This shale was noted to have a linear velocity-mean effective stress response and extremely high anisotropy, both likely the result of the presence of fluid-filled cracks in a low permeability porous medium. Changes in velocity and V{sub p}/V{sub s} ratios are dependent on both stress and smectite content. S-wave velocity is significantly affected by the presence of smectite in this and other shales and at low stress (<20 MPa) is less sensitive to stress change than P-wave velocity. V{sub p}/V{sub s} ratios are noted to increase in this shale up to 20 MPa effective stress, then decrease slightly due to stress-induced loss of interlayer water in smectite. Intrinsic anisotropy comes from composition, a strong compaction fabric and the presence of microfractures; changes to ultrasonic anisotropy are the result of the magnitude of the stresses, their orientation with respect to the fractures and the degree of stress anisotropy. (author)

  16. Superweak asthenosphere in light of upper mantle seismic anisotropy

    Science.gov (United States)

    Becker, Thorsten W.

    2017-05-01

    Earth's upper mantle includes a ˜200 km thick asthenosphere underneath the plates where viscosity and seismic velocities are reduced compared to the background. This zone of weakness matters for plate dynamics and may be required for the generation of plate tectonics itself. However, recent seismological and electromagnetic studies indicate strong heterogeneity in thinner layers underneath the plates which, if related to more extreme, global viscosity reductions, may require a revision of our understanding of mantle convection. Here, I use dynamically consistent mantle flow modeling and the constraints provided by azimuthal seismic anisotropy as well as plate motions to explore the effect of a range of global and local viscosity reductions. The fit between mantle flow model predictions and observations of seismic anisotropy is highly sensitive to radial and lateral viscosity variations. I show that moderate suboceanic viscosity reductions, to ˜0.01-0.1 times the upper mantle viscosity, are preferred by the fit to anisotropy and global plate motions, depending on layer thickness. Lower viscosities degrade the fit to azimuthal anisotropy. Localized patches of viscosity reduction, or layers of subducted asthenosphere, however, have only limited additional effects on anisotropy or plate velocities. This indicates that it is unlikely that regional observations of subplate anomalies are both continuous and indicative of dramatic viscosity reduction. Locally, such weak patches may exist and would be detectable by regional anisotropy analysis, for example. However, large-scale plate dynamics are most likely governed by broad continent-ocean asthenospheric viscosity contrasts rather than a thin, possibly high melt fraction layer.

  17. Temperature dependence of the interfacial magnetic anisotropy in W/CoFeB/MgO

    Directory of Open Access Journals (Sweden)

    Kyoung-Min Lee

    2017-06-01

    Full Text Available The interfacial perpendicular magnetic anisotropy in W/CoFeB (1.2 ∼ 3 nm/MgO thin film structures is strongly dependent on temperature, and is significantly reduced at high temperature. The interfacial magnetic anisotropy is generally proportional to the third power of magnetization, but an additional factor due to thermal expansion is required to explain the temperature dependence of the magnetic anisotropy of ultrathin CoFeB films. The reduction of the magnetic anisotropy is more prominent for the thinner films; as the temperature increases from 300 K to 400 K, the anisotropy is reduced ∼50% for the 1.2-nm-thick CoFeB, whereas the anisotropy is reduced ∼30% for the 1.7-nm-thick CoFeB. Such a substantial reduction of magnetic anisotropy at high temperature is problematic for data retention when incorporating W/CoFeB/MgO thin film structures into magneto-resistive random access memory devices. Alternative magnetic materials and structures are required to maintain large magnetic anisotropy at elevated temperatures.

  18. Anisotropy of domain wall resistance

    Science.gov (United States)

    Viret; Samson; Warin; Marty; Ott; Sondergard; Klein; Fermon

    2000-10-30

    The resistive effect of domain walls in FePd films with perpendicular anisotropy was studied experimentally as a function of field and temperature. The films were grown directly on MgO substrates, which induces an unusual virgin magnetic configuration composed of 60 nm wide parallel stripe domains. This allowed us to carry out the first measurements of the anisotropy of domain wall resistivity in the two configurations of current perpendicular and parallel to the walls. At 18 K, we find 8.2% and 1.3% for the domain wall magnetoresistance normalized to the wall width (8 nm) in these two respective configurations. These values are consistent with the predictions of Levy and Zhang.

  19. Artificial anisotropy and polarizing filters.

    Science.gov (United States)

    Flory, François; Escoubas, Ludovic; Lazaridès, Basile

    2002-06-01

    The calculated spectral transmittance of a multilayer laser mirror is used to determine the effective index of the single layer equivalent to the multilayer stack. We measure the artificial anisotropy of photoresist thin films whose structure is a one-dimensional, subwavelength grating obtained from interference fringes. The limitation of the theory of the first-order effective index homogenization is discussed. We designed normal-incidence, polarizing coating and a polarization rotator by embedding anisotropic films in simple multilayer structures.

  20. Magnetic anisotropy and quantized spin waves in hematite nanoparticles

    DEFF Research Database (Denmark)

    Klausen, Stine Nyborg; Lefmann, Kim; Lindgård, Per-Anker

    2004-01-01

    We report on the observation of high-frequency collective magnetic excitations, (h) over bar omegaapproximate to1.1 meV, in hematite (alpha-Fe2O3) nanoparticles. The neutron scattering experiments include measurements at temperatures in the range 6-300 K and applied fields up to 7.5 T as well...... as polarization analysis. We give an explanation for the field- and temperature dependence of the excitations, which are found to have strongly elliptical out-of-plane precession. The frequency of the excitations gives information on the magnetic anisotropy constants in the system. We have in this way determined...... the temperature dependence of the magnetic anisotropy, which is strongly related to the suppression of the Morin transition in nanoparticles of hematite. Further, the localization of the signal in both energy and momentum transfer brings evidence for finite-size quantization of spin waves in the system....

  1. Magnetocrystalline anisotropy of RCo5 intermetallics: itinerant-electron contribution

    International Nuclear Information System (INIS)

    Steinbeck, L.; Richter, M.; Eschrig, H.

    2001-01-01

    The itinerant-state magnetocrystalline anisotropy energies (MAE) of RCo 5 (R=Y, La, Pr, Nd, Sm, Gd) have been determined by relativistic density-functional calculations in local spin density approximation, with additionally taking into account orbital polarization. The calculated MAEs are found to be strongly affected by changes of the lattice geometry (c/a ratio and volume) resulting from (a) uniaxial strain in YCo 5 and (b) the lanthanide contraction along the RCo 5 series

  2. Anisotropy measurement of pyrolytic carbon layers of coated particles

    Science.gov (United States)

    Vesyolkin, Ju. A.; Ivanov, A. S.; Trushkina, T. V.

    2015-12-01

    Equipment at the National Research Center Kurchatov Institute intended for the anisotropy determination of pyrolytic carbon layers in coated particles (CPs) of the GT-MGR reactor is tested and calibrated. The dependence of the anisotropy coefficient on the size of the measurement region is investigated. The results of measuring the optical anisotropy factor (OPTAF) for an aluminum mirror, rutile crystal, and available CP samples with the known characteristics measured previously using ORNL equipment (United States) are presented. In addition, measurements of CP samples prepared at VNIINM are performed. A strong dependence of the data on the preparation quality of metallographic sections is found. Our investigations allow us to make the conclusion on the working capacity of the existing equipment for measuring the anisotropy of pyrolytic carbon CP coatings using the equipment at the Kurchatov Institute with the relative error of about 1%. It is shown that the elimination of the errors caused by the stochastic fluctuations in a measuring path by mathematical processing of the signal allows us to decrease the relative error of OPTAF measurements to ~0.3%.

  3. Anisotropy signature in reverse-time migration extended images

    KAUST Repository

    Sava, Paul C.

    2014-11-04

    Reverse-time migration can accurately image complex geologic structures in anisotropic media. Extended images at selected locations in the Earth, i.e., at common-image-point gathers, carry rich information to characterize the angle-dependent illumination and to provide measurements for migration velocity analysis. However, characterizing the anisotropy influence on such extended images is a challenge. Extended common-image-point gathers are cheap to evaluate since they sample the image at sparse locations indicated by the presence of strong reflectors. Such gathers are also sensitive to velocity error that manifests itself through moveout as a function of space and time lags. Furthermore, inaccurate anisotropy leaves a distinctive signature in common-image-point gathers, which can be used to evaluate anisotropy through techniques similar to the ones used in conventional wavefield tomography. It specifically admits a V-shaped residual moveout with the slope of the "V" flanks depending on the anisotropic parameter η regardless of the complexity of the velocity model. It reflects the fourth-order nature of the anisotropy influence on moveout as it manifests itself in this distinct signature in extended images after handling the velocity properly in the imaging process. Synthetic and real data observations support this assertion.

  4. Effect of defects, magnetocrystalline anisotropy, and shape anisotropy on magnetic structure of iron thin films by magnetic force microscopy

    Directory of Open Access Journals (Sweden)

    Ke Xu

    2017-05-01

    Full Text Available Microstructures of magnetic materials, including defects and crystallographic orientations, are known to strongly influence magnetic domain structures. Measurement techniques such as magnetic force microscopy (MFM thus allow study of correlations between microstructural and magnetic properties. The present work probes effects of anisotropy and artificial defects on the evolution of domain structure with applied field. Single crystal iron thin films on MgO substrates were milled by Focused Ion Beam (FIB to create different magnetically isolated squares and rectangles in [110] crystallographic orientations, having their easy axis 45° from the sample edge. To investigate domain wall response on encountering non-magnetic defects, a 150 nm diameter hole was created in the center of some samples. By simultaneously varying crystal orientation and shape, both magnetocrystalline anisotropy and shape anisotropy, as well as their interaction, could be studied. Shape anisotropy was found to be important primarily for the longer edge of rectangular samples, which exaggerated the FIB edge effects and provided nucleation sites for spike domains in non-easy axis oriented samples. Center holes acted as pinning sites for domain walls until large applied magnetic fields. The present studies are aimed at deepening the understanding of the propagation of different types of domain walls in the presence of defects and different crystal orientations.

  5. Seismological Evidence for General Anisotropy in the d" Layer Beneath the Caribbean

    Science.gov (United States)

    Garnero, E. J.; Maupin, V.; Lay, T.; Fouch, M. J.

    2004-12-01

    Current models of anisotropy in D" are based on time delays observed between the SH and the SV components of core-reflected or core-grazing phases, which can be explained by the simplest form for anisotropy, vertical transverse isotropy (VTI). In a detailed analysis of high-quality broadband S (or Sdiff) phases, we find that many recordings do not show such simple delays; rather, some coupling between the SH and SV components is apparent: SV components have a small initial pulse with the polarity opposite to that predicted by isotropic or VTI structures. We analyze deep South American events recorded by the Canadian National Seismic Network, sampling D" under the Caribbean Ocean and Central America. The data are corrected for upper mantle anisotropy and compared to full wave theory synthetic seismograms calculated from isotropic, transversely isotropic, and azimuthally anisotropic structures. While restrictions in azimuthal sampling of this region limit a complete characterization of D" anisotropy, the need for azimuthal anisotropy is robustly established. A simple form of azimuthal anisotropy is explored which entails tilting the symmetry axis of transverse isotropy away from the vertical (TTI). Anomalous data are reproduced by a 20 degree tilt, and discriminate between eastward and westward tilting orientations, as well as zero tilts (i.e., isotropy or VTI). However, we note this does not preclude other forms of azimuthal anisotropy. Out of the 80 highest quality records analyzed, 22 are uniquely explained by the eastward TTI structures (with 34 records compatible with such a structure); 16 are compatible with westward TTI, with 2 uniquely requiring such a tilt. This gives strong evidence for lateral heterogeneity in azimuthal anisotropy at a lateral scale of a several 100 km. Further interpretation of the results requires identification the physical mechanism behind seismic anisotropy in D". Together with the recent discovery of the possibly anisotropic post

  6. Magnetic anisotropy of Ni/Cr multilayers

    International Nuclear Information System (INIS)

    Kang, S.; Xia, H.

    1997-01-01

    The magnetic anisotropy of Ni/Cr multilayers has been investigated by using vibrating sample magnetometer (VSM) and ferromagnetic resonance techniques (FMR). The FMR spectra are obtained as a function of the orientation of the applied magnetic field from in-plane to out-of-plane. The results are fitted theoretically to determine the magnetic anisotropy. From VSM and FMR, a positive value for Ni/Cr interface anisotropy is obtained, which favours a perpendicular easy axis. The possible mechanism for the perpendicular anisotropy has been discussed and it may be attributed to the magnetostriction, caused by intrinsic stress due to lattice mismatch. (orig.). With 005 figs., 001 tabs

  7. Giant enhancement of magnetocrystalline anisotropy in ultrathin manganite films via nanoscale 1D periodic depth modulation

    Science.gov (United States)

    Rajapitamahuni, Anil; Zhang, Le; Singh, Vijay; Burton, John; Koten, Mak; Shield, Jeffrey; Tsymbal, Evgeny; Hong, Xia

    We report a unusual giant enhancement of in-plane magnetocrystalline anisotropy (MCA) in ultrathin colossal magnetoresistive oxide films due to 1D nanoscale periodic depth modulation. High quality epitaxial thin films of La0.67Sr0.33MnO3 (LSMO) of thickness 6 nm were grown on (001) SrTiO3 substrates via off-axis radio frequency magnetron sputtering. The top 2 nm of LSMO films are patterned into periodic nano-stripes using e-beam lithography and reactive ion etching. The resulting structure consists of nano-stripes of 2 nm height and 100-200 nm width on top of a 4 nm thick continuous base layer. We employed planar Hall effect measurements to study the in-plane magnetic anisotropy of the unpatterned and nanopatterned films. The unpatterned films show a biaxial anisotropy with easy axis along [110]. The extracted anisotropy energy density is ~1.1 x 105 erg/cm3, comparable to previously reported values. In the nanopatterned films, a strong uniaxial anisotropy is developed along one of the biaxial easy axes. The corresponding anisotropy energy density is ~5.6 x 106 erg/cm3 within the nano-striped volume, comparable to that of Co. We attribute the observed uniaxial MCA to MnO6 octahedral rotations/tilts and the enhancement in the anisotropy energy density to the strain gradient within the nano-stripes.

  8. Role of the pressure anisotropy in the relativistic pulsar wind

    Energy Technology Data Exchange (ETDEWEB)

    Asseo, E.; Beaufils, D. (Ecole Polytechnique, 91 - Palaiseau (France). Centre de Physique Theorique)

    1983-01-01

    We generalize the hot relativistic MHD wind analysis to include the anisotropy of the pressure created in the pulsar wind by the strong magnetic field. Even with anisotropy the relativistic MHD equations integrate. In a very intense magnetic field, the motion of relativistic particles becomes rapidly one-dimensional in the direction of the field due to the very important radiative losses. Consequently, their distribution function becomes also one-dimensional and the component of the pressure, in the direction perpendicular to the magnetic field, decrease. In the limit Psub(perpendicular to)approx.=0, Psub(parallel)not=0 we obtain a solution for the fluid flow which, starting at the neutron star surface, reaches smoothly infinity.

  9. Role of the pressure anisotropy in the relativistic pulsar wind

    Science.gov (United States)

    Asseo, E.; Beaufils, D.

    1983-01-01

    The hot relativistic MHD wind analysis is generalized to include the anisotropy of the pressure created in the pulsar wind by the strong magnetic field. Even with anisotropy the relativistic MHD equations integrate. In a very intense magnetic field, the motion of relativistic particles becomes rapidly one dimensional in the direction of the field due to the very important radiative losses. Consequently, their distribution function becomes also one-dimensional and the component of the pressure, in the direction perpendicular to the magnetic field, decrease. In the limit the transverse component of P approximately 0 the longitudinal component of P not equal 0 we obtain a solution for the fluid flow which, starting at the neutron star surface, reaches smoothly infinity.

  10. Particle physics implications of Wilkinson microwave anisotropy ...

    Indian Academy of Sciences (India)

    ... Journals; Pramana – Journal of Physics; Volume 63; Issue 6. Particle physics implications of Wilkinson microwave anisotropy project measurements. U A Yajnik. Volume 63 Issue 6 December 2004 pp 1317-1330 ... Keywords. Cosmic microwave background radiation; inflation; Wilkinson microwave anisotropy project.

  11. Geotail observations of temperature anisotropy of the two-component protons in the dusk plasma sheet

    Directory of Open Access Journals (Sweden)

    M. N. Nishino

    2007-03-01

    Full Text Available In search for clues towards the understanding of the cold plasma sheet formation under northward IMF, we study the temperature anisotropy of the two-component protons in the plasma sheet near the dusk low-latitude boundary observed by the Geotail spacecraft. The two-component protons result from mixing of the cold component from the solar wind and the hot component of the magnetospheric origin, and may be the most eloquent evidence for the transport process across the magnetopause. The cold component occasionally has a strong anisotropy in the dusk flank, and the sense of the anisotropy depends on the observed locations: the parallel temperature is enhanced in the tail flank while the perpendicular temperature is enhanced on the dayside. The hot component is nearly isotropic in the tail while the perpendicular temperature is enhanced on the dayside. We discuss possible mechanism that can lead to the observed temperature anisotropies.

  12. Slow Magnetic Relaxations in Cobalt(II) Tetranitrate Complexes. Studies of Magnetic Anisotropy by Inelastic Neutron Scattering and High-Frequency and High-Field EPR Spectroscopy.

    Science.gov (United States)

    Chen, Lei; Cui, Hui-Hui; Stavretis, Shelby E; Hunter, Seth C; Zhang, Yi-Quan; Chen, Xue-Tai; Sun, Yi-Chen; Wang, Zhenxing; Song, You; Podlesnyak, Andrey A; Ouyang, Zhong-Wen; Xue, Zi-Ling

    2016-12-19

    Three mononuclear cobalt(II) tetranitrate complexes (A) 2 [Co(NO 3 ) 4 ] with different countercations, Ph 4 P + (1), MePh 3 P + (2), and Ph 4 As + (3), have been synthesized and studied by X-ray single-crystal diffraction, magnetic measurements, inelastic neutron scattering (INS), high-frequency and high-field EPR (HF-EPR) spectroscopy, and theoretical calculations. The X-ray diffraction studies reveal that the structure of the tetranitrate cobalt anion varies with the countercation. 1 and 2 exhibit highly irregular seven-coordinate geometries, while the central Co(II) ion of 3 is in a distorted-dodecahedral configuration. The sole magnetic transition observed in the INS spectroscopy of 1-3 corresponds to the zero-field splitting (2(D 2 + 3E 2 ) 1/2 ) from 22.5(2) cm -1 in 1 to 26.6(3) cm -1 in 2 and 11.1(5) cm -1 in 3. The positive sign of the D value, and hence the easy-plane magnetic anisotropy, was demonstrated for 1 by INS studies under magnetic fields and HF-EPR spectroscopy. The combined analyses of INS and HF-EPR data yield the D values as +10.90(3), +12.74(3), and +4.50(3) cm -1 for 1-3, respectively. Frequency- and temperature-dependent alternating-current magnetic susceptibility measurements reveal the slow magnetization relaxation in 1 and 2 at an applied dc field of 600 Oe, which is a characteristic of field-induced single-molecule magnets (SMMs). The electronic structures and the origin of magnetic anisotropy of 1-3 were revealed by calculations at the CASPT2/NEVPT2 level.

  13. Distinguishing between stress-induced and structural anisotropy at Mount Ruapehu volcano, New Zealand

    Science.gov (United States)

    Johnson, Jessica H.; Savage, Martha K.; Townend, John

    2011-12-01

    We have created a benchmark of spatial variations in shear wave anisotropy around Mount Ruapehu, New Zealand, against which to measure future temporal changes. Anisotropy in the crust is often assumed to be caused by stress-aligned microcracks, and the polarization of the fast quasi-shear wave (ϕ) is thus interpreted to indicate the direction of maximum horizontal stress, but can also be due to aligned minerals or macroscopic fractures. Changes in seismic anisotropy have been observed following a major eruption in 1995/96 and were attributed to changes in stress from the depressurization of the magmatic system. Three-component broadband seismometers have been deployed to complement the permanent stations that surround Ruapehu, creating a combined network of 34 three-component seismometers. This denser observational network improves the resolution with which spatial variations in seismic anisotropy can be examined. Using an automated shear wave splitting analysis, we examine local earthquakes in 2008. We observe a strong azimuthal dependence of ϕ and so introduce a spatial averaging technique and two-dimensional tomography of recorded delay times. The anisotropy can be divided into regions in which ϕ agrees with stress estimations from focal mechanism inversions, suggesting stress-induced anisotropy, and those in which ϕ is aligned with structural features such as faults, suggesting structural anisotropy. The pattern of anisotropy that is inferred to be stress related cannot be modeled adequately using Coulomb modeling with a dike-like inflation source. We suggest that the stress-induced anisotropy is affected by loading of the volcano and a lithospheric discontinuity.

  14. Distinguishing between stress-induced and structural anisotropy at Mount Ruapehu volcano, New Zealand

    Science.gov (United States)

    Johnson, J. H.; Savage, M.K.; Townend, J.

    2011-01-01

    We have created a benchmark of spatial variations in shear wave anisotropy around Mount Ruapehu, New Zealand, against which to measure future temporal changes. Anisotropy in the crust is often assumed to be caused by stress-aligned microcracks, and the polarization of the fast quasi-shear wave (??) is thus interpreted to indicate the direction of maximum horizontal stress, but can also be due to aligned minerals or macroscopic fractures. Changes in seismic anisotropy have been observed following a major eruption in 1995/96 and were attributed to changes in stress from the depressurization of the magmatic system. Three-component broadband seismometers have been deployed to complement the permanent stations that surround Ruapehu, creating a combined network of 34 three-component seismometers. This denser observational network improves the resolution with which spatial variations in seismic anisotropy can be examined. Using an automated shear wave splitting analysis, we examine local earthquakes in 2008. We observe a strong azimuthal dependence of ?? and so introduce a spatial averaging technique and two-dimensional tomography of recorded delay times. The anisotropy can be divided into regions in which ?? agrees with stress estimations from focal mechanism inversions, suggesting stress-induced anisotropy, and those in which ?? is aligned with structural features such as faults, suggesting structural anisotropy. The pattern of anisotropy that is inferred to be stress related cannot be modeled adequately using Coulomb modeling with a dike-like inflation source. We suggest that the stress-induced anisotropy is affected by loading of the volcano and a lithospheric discontinuity. Copyright 2011 by the American Geophysical Union.

  15. A joint inversion for shear velocity and anisotropy: the Woodlark Rift, Papua New Guinea

    Science.gov (United States)

    Eilon, Zachary; Abers, Geoffrey A.; Gaherty, James B.

    2016-08-01

    Trade-offs between velocity and anisotropy heterogeneity complicate the interpretation of differential traveltime data and have the potential to bias isotropic tomographic models. By constructing a simple parametrisation to describe an elastic tensor with hexagonal symmetry, we find analytic solutions to the Christoffel equations in terms of fast and slow horizontal velocities that allow us to simultaneously invert differential traveltime data and splitting data from teleseismic S arrivals to recover 3-D velocity and anisotropy structure. This technique provides a constraint on the depth-extent of shallow anisotropy, otherwise absent from interpretations based on SKS splitting alone. This approach is well suited to the young Woodlark Rift, where previous studies have found strong velocity variation and substantial SKS splitting in a continental rift with relatively simple geometry. This study images a low-velocity rift axis with ≤4 per cent spreading-parallel anisotropy at 50-100 km depth that separates regions of pre-existing lithospheric fabric, indicating the synchronous development of extensional crystallographic preferred orientation and lithospheric thinning. A high-velocity slab fragment north of the rift axis is associated with strike-parallel anisotropic fast axes, similar to that seen in the shallow mantle of some subduction zones. In addition to the insights provided by the anisotropy structure, the improvement in fit to the differential traveltime data demonstrates the merit to a joint inversion that accounts for anisotropy.

  16. Fluctuation-driven anisotropy in effective pair interactions between nanoparticles: Thiolated gold nanoparticles in ethane

    Science.gov (United States)

    Jabes, B. Shadrack; Yadav, Hari O. S.; Kumar, Sanat K.; Chakravarty, Charusita

    2014-10-01

    Fluctuations within the ligand shell of a nanoparticle give rise to a significant degree of anisotropy in effective pair interactions for low grafting densities [B. Bozorgui, D. Meng, S. K. Kumar, C. Chakravarty, and A. Cacciuto, Nano Lett. 13, 2732 (2013)]. Here, we examine the corresponding fluctuation-driven anisotropy for gold nanocrystals densely passivated with short ligands. In particular, we consider gold nanocrystals capped by alkylthiols, both in vacuum and in ethane solvent at high density. As in the preceding study, we show that the anisotropy in the nanoparticle pair potential can be quantified by an angle-dependent correction term to the isotropic potential of mean force (PMF). We find that the anisotropy of the ligand shells is distance dependent, and strongly influenced by ligand interdigitation effects as well as expulsion of ligand chains from the interparticle region at short distances. Such fluctuation-driven anisotropy can be significant for alkylthiol-coated gold nanoparticles, specially for longer chain lengths, under good solvent conditions. The consequences of such anisotropy for self-assembly, specially as a function of grafting density, solvent quality and at interfaces, should provide some interesting insights in future work. Our results clearly show that an isotropic two-body PMF cannot adequately describe the thermodynamics and assembly behavior of nanoparticles in this dense grafting regime and inclusion of anisotropic effects, as well as possibly many-body interactions, is necessary. Extensions of this approach to other passivated nanoparticle systems and implications for self-assembly are considered.

  17. 3D analyses of cavitation instabilities accounting for plastic anisotropy

    DEFF Research Database (Denmark)

    Legarth, Brian Nyvang; Tvergaard, Viggo

    2010-01-01

    Full three dimensional cell model analyses are carried out for a solid containing a single small void, in order to determine the critical stress levels for the occurrence of cavitation instabilities. The material models applied are elastic‐viscoplastic, with a small rate‐hardening exponent...... that the quasi‐static solution is well approximated. A special procedure is used to strongly reduce the loading rate a little before the instability occurs. It is found that plastic anisotropy has a significant effect on the level of the critical stress for cavitation instabilities....

  18. Heusler compounds with perpendicular magnetic anisotropy and large tunneling magnetoresistance

    Science.gov (United States)

    Faleev, Sergey V.; Ferrante, Yari; Jeong, Jaewoo; Samant, Mahesh G.; Jones, Barbara; Parkin, Stuart S. P.

    2017-07-01

    In the present work we suggest a recipe for finding tetragonal Heusler compounds with perpendicular magnetic anisotropy (PMA) that also exhibit large tunneling magnetoresistance (TMR) when used as electrodes in magnetic tunnel junction devices with suitable tunneling barrier materials. We performed density-functional theory calculations for 286 Heusler compounds and identified 116 stable tetragonal compounds. Ten of these compounds are predicted to have strong PMA and, simultaneously, exponentially increasing TMR with increasing tunneling barrier thickness due to the so-called Brillouin zone spin filtering effect. Experimental measurements performed for 25 Heusler compounds theoretically identified as tetragonal show that ten of these compounds indeed have tetragonal structure with PMA.

  19. Preliminary results of characteristic seismic anisotropy beneath Sunda-Banda subduction-collision zone

    Energy Technology Data Exchange (ETDEWEB)

    Wiyono, Samsul H., E-mail: samsul.wiyono@bmkg.go.id [Study Program of Earth Sciences, Faculty of Earth Sciences and Technology, Institute of Technology Bandung, Bandung 40132 (Indonesia); Indonesia’s Agency for Meteorology Climatology and Geophysics, Jakarta 10610 (Indonesia); Nugraha, Andri Dian, E-mail: nugraha@gf.itb.ac.id [Indonesia’s Agency for Meteorology Climatology and Geophysics, Jakarta 10610 (Indonesia); Global Geophysics Research Group, Faculty of Mining and Petroleum Engineering, Institute of Technology Bandung, Bandung 40132, Indonesia, Phone: +62-22 2534137 (Indonesia)

    2015-04-24

    Determining of seismic anisotropy allowed us for understanding the deformation processes that occured in the past and present. In this study, we performed shear wave splitting to characterize seismic anisotropy beneath Sunda-Banda subduction-collision zone. For about 1,610 XKS waveforms from INATEWS-BMKG networks have been analyzed. From its measurements showed that fast polarization direction is consistent with trench-perpendicular orientation but several stations presented different orientation. We also compared between fast polarization direction with absolute plate motion in the no net rotation and hotspot frame. Its result showed that both absolute plate motion frame had strong correlation with fast polarization direction. Strong correlation between the fast polarization direction and the absolute plate motion can be interpreted as the possibility of dominant anisotropy is in the asthenosphere.

  20. Crustal Seismic Vs and Vs anisotropy of Northeast Japan Revealed by Ambient Noise Tomography

    Science.gov (United States)

    Chen, K. X.; Gung, Y.; Kuo, B. Y.; Huang, T. Y.

    2017-12-01

    We present 3D crustal models of Vs and Vs azimuthal anisotropy of the Tohoku region, Japan. We employ the Welch's method to derive the empirical Green's functions (EGF) of Rayleigh waves from one year of continuous records of 123 short-period stations of the dense high-sensitivity seismograph network (Hi-net). We compute EGFs for about 4000 station pairs with interstation distance less than 300 km. For each qualified EGF, we measure the dispersion in the period range from 3 to 16 seconds. We then construct the models by using a wavelet-based multi-scale inversion technique. In the resulting models, characteristics of Vs variations and Vs azimuthal anisotropy are closely related to surface geology, Quaternary volcano activities, and plate motions. For the Vs variations in the shallow crust (well correlated to the volcano belt. For the Vs anisotropy, the strength and the patterns of fast polarization directions (FPD) are depth-dependent. In the shallow crust, the anisotropy is strong, and are dominated by the typical orogeny parallel anisotropy, with FPDs parallel to the main strikes of the mountain range. While in the lower crust, the FPDs are generally parallel to the absolute plate motion. Interestingly, the distribution of PFDs is rather chaotic and strength of anisotropy is weak in the middle crust ( 8 - 20 km). We propose that the weak and random anisotropy in this layer is likely related to the presence of magma reservoirs beneath the volcano belt, as the associated active volcanism may cause the destruction of the alignment of crustal fabrics Key words: Tohoku, ambient noise, seismic anisotropy, surface wave tomography, volcano activities

  1. Solvent induced supramolecular anisotropy in molecular gels

    Energy Technology Data Exchange (ETDEWEB)

    Rogers, Michael A., E-mail: mroger09@uoguelph.ca [Department of Food Science, University of Guelph, Guelph, Ontario, N3C3X9 (Canada); Corradini, Maria G. [Department of Food Science, University of Massachusetts Amherst, Amherst, MA, 01003 (United States); Emge, Thomas [Department of Chemistry and Biochemistry, Rutgers University, New Brunswick, NJ, 08901 (United States)

    2017-06-15

    Herein is the first report of solvent induced anisotropy in 12-hydroxystearic acid self-assembled fibrillar networks. Increasing the chain length of polar solvent, such as nitriles and ketones, tailored the anisotropy of the fibrillar aggregates. 12HSA molecular gels, comprised of alkanes, exhibited an isotropic fibrillar network irrespective of the alkane chain length. In polar solvents, anisotropy, observed using 2D powder x-ray diffraction profiles, is correlated to a fibrillar supramolecular morphologies in long chain nitriles and ketones while sphereulitic crystals are correlated to x-ray diffraction patterns with an isotropic scatter intensity in short chain ketones and nitriles. These changes directly modify the final physical properties of the gels. - Highlights: • 12-HSA self-assembles into crystalline supramolecular morphologies depending on the solvent. • Alkanes, short chain nitriles and ketones led to 12-HSA displaying supramolecular isotropy. • In long chain nitriles and ketones, 12-HSA displays supramolecular anisotropy.

  2. Solvent induced supramolecular anisotropy in molecular gels

    International Nuclear Information System (INIS)

    Rogers, Michael A.; Corradini, Maria G.; Emge, Thomas

    2017-01-01

    Herein is the first report of solvent induced anisotropy in 12-hydroxystearic acid self-assembled fibrillar networks. Increasing the chain length of polar solvent, such as nitriles and ketones, tailored the anisotropy of the fibrillar aggregates. 12HSA molecular gels, comprised of alkanes, exhibited an isotropic fibrillar network irrespective of the alkane chain length. In polar solvents, anisotropy, observed using 2D powder x-ray diffraction profiles, is correlated to a fibrillar supramolecular morphologies in long chain nitriles and ketones while sphereulitic crystals are correlated to x-ray diffraction patterns with an isotropic scatter intensity in short chain ketones and nitriles. These changes directly modify the final physical properties of the gels. - Highlights: • 12-HSA self-assembles into crystalline supramolecular morphologies depending on the solvent. • Alkanes, short chain nitriles and ketones led to 12-HSA displaying supramolecular isotropy. • In long chain nitriles and ketones, 12-HSA displays supramolecular anisotropy.

  3. Higher-order anisotropies in the Buda-Lund model: Disentangling flow and density field anisotropies

    Energy Technology Data Exchange (ETDEWEB)

    Loekoes, Sandor [Eoetvoes Lorand University, Budapest (Hungary); Csanad, Mate [Eoetvoes Lorand University, Budapest (Hungary); Stony Brook University, Stony Brook, NY (United States); Tomasik, Boris [Univerzita Mateja Bela, Banska Bystrica (Slovakia); Czech Technical University in Prague, FNSPE, Prague (Czech Republic); Csoergo, Tamas [Wigner RCP, Budapest (Hungary); KRF, Gyoengyoes (Hungary)

    2016-10-15

    The Buda-Lund hydro model describes an expanding ellipsoidal fireball, and fits the observed elliptic flow and oscillating HBT radii successfully. Due to fluctuations in energy depositions, the fireball shape however fluctuates on an event-by-event basis. The transverse plane asymmetry can be translated into a series of multipole anisotropy coefficients. These anisotropies then result in measurable momentum-space anisotropies, to be measured with respect to their respective symmetry planes. In this paper we detail an extension of the Buda-Lund model to multipole anisotropies and investigate the resulting flow coefficients and oscillations of HBT radii. (orig.)

  4. Seismic anisotropy in central North Anatolian Fault Zone and its implications on crustal deformation

    Science.gov (United States)

    Licciardi, A.; Eken, T.; Taymaz, T.; Piana Agostinetti, N.; Yolsal-Çevikbilen, S.

    2018-04-01

    We investigate the crustal seismic structure and anisotropy around the central portion of the North Anatolian Fault Zone, a major plate boundary, using receiver function analysis. The characterization of crustal seismic anisotropy plays a key role in our understanding of present and past deformation processes at plate boundaries. The development of seismic anisotropy in the crust arises from the response of the rocks to complicated deformation regimes induced by plate interaction. Through the analysis of azimuthally-varying signals of teleseismic receiver functions, we map the anisotropic properties of the crust as a function of depth, by employing the harmonic decomposition technique. Although the Moho is located at a depth of about 40 km, with no major offset across the area, our results show a clear asymmetric distribution of crustal properties between the northern and southern blocks, divided by the North Anatolian Fault Zone. Heterogeneous and strongly anisotropic crust is present in the southern block, where complex intra-crustal signals are the results of strong deformation. In the north, a simpler and weakly anisotropic crust is typically observed. The strongest anisotropic signal is located in the first 15 km of the crust and is widespread in the southern block. Stations located on top of the main active faults in the area indicate the highest amplitudes, together with fault-parallel strikes of the fast plane of anisotropy. We interpret the origin of this signal as due to structure-induced anisotropy, and roughly determine its depth extent up to 15-20 km for these stations. Away from the faults, we suggest the contribution of previously documented uplifted basement blocks to explain the observed anisotropy at upper and middle crustal depths. Finally, we interpret coherent NE-SW orientations below the Moho as a result of frozen-in anisotropy in the upper mantle, as suggested by previous studies.

  5. Enhanced Locomotion Efficiency of a Bio-inspired Walking Robot using Contact Surfaces with Frictional Anisotropy

    DEFF Research Database (Denmark)

    Manoonpong, Poramate; Petersen, Dennis; Kovalev, Alexander

    2016-01-01

    stability. It shows high frictional anisotropy due to an array of sloped denticles. The orientation of the denticles to the underlying collagenous material also strongly influences their mechanical interlocking with the substrate. This study not only opens up a new way of achieving energy-efficient legged...

  6. Interaction Between Downwelling Flow and the Laterally-Varying Thickness of the North American Lithosphere Inferred from Seismic Anisotropy

    Science.gov (United States)

    Behn, M. D.; Conrad, C. P.; Silver, P. G.

    2005-12-01

    Shear flow in the asthenosphere tends to align olivine crystals in the direction of shear, producing a seismically anisotropic asthenosphere that can be detected using a number of seismic techniques (e.g., shear-wave splitting (SWS) and surface waves). In the ocean basins, where the asthenosphere has a relatively uniform thickness and lithospheric anisotropy appears to be small, observed azimuthal anisotropy is well fit by asthenospheric shear flow in global flow models driven by a combination of plate motions and mantle density heterogeneity. In contrast, beneath the continents both the lithospheric ceiling and asthenospheric thickness may vary considerably across cratonic regions and ocean-continent boundaries. To examine the influence of a continental lithosphere with variable thickness on predictions of continental seismic anisotropy, we impose lateral variations in lithospheric viscosity in global models of mantle flow driven by plate motions and mantle density heterogeneity. For the North American continent, the Farallon slab descends beneath a deep cratonic root, producing downwelling flow in the upper mantle and convergent flow beneath the cratonic lithosphere. We evaluate both the orientation of the predicted azimuthal anisotropy and the depth dependence of radial anisotropy for this downwelling flow and find that the inclusion of a strong continental root provides an improved fit to observed SWS observations beneath the North American craton. Thus, we hypothesize that at least some continental anisotropy is associated with sub-lithospheric viscous shear, although fossil anisotropy in the lithospheric layer may also contribute significantly. Although we do not observe significant variations in the direction of predicted anisotropy with depth, we do find that the inclusion of deep continental roots pushes the depth of the anisotropy layer deeper into the upper mantle. We test several different models of laterally-varying lithosphere and asthenosphere

  7. Confinining properties of QCD in strong magnetic backgrounds

    Directory of Open Access Journals (Sweden)

    Bonati Claudio

    2017-01-01

    Full Text Available Strong magnetic backgrounds are known to modify QCD properties at a nonperturbative level. We discuss recent lattice results, obtained for Nf = 2 + 1 QCD with physical quark masses, concerning in particular the modifications and the anisotropies induced at the level of the static quark-antiquark potential, both at zero and finite temperature.

  8. Theory of Spin Waves in Strongly Anisotropic Magnets

    DEFF Research Database (Denmark)

    Lindgård, Per-Anker; Cooke, J. F.

    1976-01-01

    A new infinite-order perturbation approach to the theory of spin waves in strongly anisotropic magnets is introduced. The system is transformed into one with effective two-ion anisotropy and considerably reduced ground-state corrections. A general expression for the spin-wave energy, valid to any...

  9. The expected anisotropy in solid inflation

    Energy Technology Data Exchange (ETDEWEB)

    Bartolo, Nicola; Ricciardone, Angelo [Dipartimento di Fisica e Astronomia ' ' G. Galilei' ' , Università degli Studi di Padova, via Marzolo 8, I-35131, Padova (Italy); Peloso, Marco; Unal, Caner, E-mail: nicola.bartolo@pd.infn.it, E-mail: peloso@physics.umn.edu, E-mail: angelo.ricciardone@pd.infn.it, E-mail: unal@physics.umn.edu [School of Physics and Astronomy, University of Minnesota, 116 Church Street S.E., Minneapolis 55455 (United States)

    2014-11-01

    Solid inflation is an effective field theory of inflation in which isotropy and homogeneity are accomplished via a specific combination of anisotropic sources (three scalar fields that individually break isotropy). This results in specific observational signatures that are not found in standard models of inflation: a non-trivial angular dependence for the squeezed bispectrum, and a possibly long period of anisotropic inflation (to drive inflation, the ''solid'' must be very insensitive to any deformation, and thus background anisotropies are very slowly erased). In this paper we compute the expected level of statistical anisotropy in the power spectrum of the curvature perturbations of this model. To do so, we account for the classical background values of the three scalar fields that are generated on large (superhorizon) scales during inflation via a random walk sum, as the perturbation modes leave the horizon. Such an anisotropy is unavoidably generated, even starting from perfectly isotropic classical initial conditions. The expected level of anisotropy is related to the duration of inflation and to the amplitude of the squeezed bispectrum. If this amplitude is close to its current observational limit (so that one of the most interesting predictions of the model can be observed in the near future), we find that a level of statistical anisotropy F{sup 2} gives frozen and scale invariant vector perturbations on superhorizon scales.

  10. Large Friction Anisotropy of a Polydiacetylene Monolayer

    International Nuclear Information System (INIS)

    Burns, A.R.; Carpick, R.W.; Sasaki, D.Y.

    1999-01-01

    Friction force microscopy measurements of a polydiacetylene monolayer film reveal a 300% friction anisotropy that is correlated with the film structure. The film consists of a monolayer of the red form of N-(2-ethanol)- 10,12 pentacosadiynamide, prepared on a Langmuir trough and deposited on a mica substrate. As confirmed by atomic force microscopy and fluorescence microscopy, the monolayer consists of domains of linearly oriented conjugated backbones with pendant hydrocarbon side chains above and below the backbones. Maximum friction occurs when the sliding direction is perpendicular to the backbone. We propose that the backbones impose anisotropic packing of the hydrocarbon side chains which leads to the observed friction anisotropy. Friction anisotropy is therefore a sensitive, optically-independent indicator of polymer backbone direction and monolayer structural properties

  11. Measurements of magnetic anisotropy in sickle cells

    International Nuclear Information System (INIS)

    Salvo Souza, L.H. de.

    1982-03-01

    Room temperature magnetic measurements in deoxigenated sickle cells showed the existence of magnetic anisotropy, Δchi=1,29 x 10 -3 . This effect was supposed paramagnetic and considered to be due to the iron atoms of the hemoglobin molecules which are one over the other, forming ordered chains inside the erythrocytes. Low temperature (liquid He - 4,2K) measurements of the magnetic anisotropy of sickle cells and normal red blood cells diluted in a cryoprotector was made to confirm the paramagnetic origin of the fenomena. For that purpose it was used a superconductor magnetometer coupled to a SQUID, developed in the 'Laboratorio do Estado Solido do Departamento de Fisica da PUC-RJ'. The results obtained seem to confirm the expected paramagnetic anisotropy and, furthermore, suggest the presence of magnetic interactions among the iron atoms in the sickle cells samples. (Author) [pt

  12. Radial anisotropy ambient noise tomography of volcanoes

    Science.gov (United States)

    Mordret, Aurélien; Rivet, Diane; Shapiro, Nikolai; Jaxybulatov, Kairly; Landès, Matthieu; Koulakov, Ivan; Sens-Schönfelder, Christoph

    2016-04-01

    The use of ambient seismic noise allows us to perform surface-wave tomography of targets which could hardly be imaged by other means. The frequencies involved (~ 0.5 - 20 s), somewhere in between active seismic and regular teleseismic frequency band, make possible the high resolution imaging of intermediate-size targets like volcanic edifices. Moreover, the joint inversion of Rayleigh and Love waves dispersion curves extracted from noise correlations allows us to invert for crustal radial anisotropy. We present here the two first studies of radial anisotropy on volcanoes by showing results from Lake Toba Caldera, a super-volcano in Indonesia, and from Piton de la Fournaise volcano, a hot-spot effusive volcano on the Réunion Island (Indian Ocean). We will see how radial anisotropy can be used to infer the main fabric within a magmatic system and, consequently, its dominant type of intrusion.

  13. Shaping the solar wind electron temperature anisotropy by the interplay of core and suprathermal populations

    Science.gov (United States)

    Shaaban Hamd, S. M.; Lazar, M.; Poedts, S.; Pierrard, V.; Štverák

    2017-12-01

    We present the results of an advanced parametrization of the temperature anisotropy of electrons in the slow solar wind and the electromagnetic instabilities resulting from the interplay of their thermal core and suprathermal halo populations. A large set of observational data (from the Ulysses, Helios and Cluster missions) is used to parametrize these components and establish their correlations. Comparative analysis demonstrates for the first time a particular implication of the suprathermal electrons which are less dense but hotter than thermal electrons. The instabilities are significantly stimulated by the interplay of the core and halo populations, leading to lower thresholds which shape the observed limits of the temperature anisotropy for both the core and halo populations. This double agreement strongly suggests that the selfgenerated instabilities play the major role in constraining the electron anisotropy.

  14. Magnetic Anisotropy, Damping and Interfacial Spin Transport in Pt/LSMO Bilayers

    Science.gov (United States)

    Lee, Han Kyu

    In this thesis, I describe ferromagnetic resonance measurements of magnetic anisotropy and damping in epitaxial La0.7Sr0.3MnO 3 (LSMO) and Pt capped LSMO thin films on SrTiO3 (001) substrates. The measurements reveal significant negative perpendicular magnetic anisotropy and a weaker uniaxial in-plane anisotropy that both are unaffected by the Pt cap. The Gilbert damping of the bare LSMO films is found to be low alpha = 1.9(1) x 10-3, and two-magnon scattering is determined to be significant and strongly anisotropic in the plane of the film. The Pt cap increases the damping by 50% due to spin pumping, which is also directly detected via inverse spin Hall effect in Pt. This work demonstrates efficient spin transport across the Pt/LSMO interface.

  15. Probing the Intergalactic Magnetic Field with the Anisotropy of the Extragalactic Gamma-ray Background

    Science.gov (United States)

    Venters, T. M.; Pavlidou, V.

    2013-01-01

    The intergalactic magnetic field (IGMF) may leave an imprint on the angular anisotropy of the extragalactic gamma-ray background through its effect on electromagnetic cascades triggered by interactions between very high energy photons and the extragalactic background light. A strong IGMF will deflect secondary particles produced in these cascades and will thus tend to isotropize lower energy cascade photons, thereby inducing a modulation in the anisotropy energy spectrum of the gamma-ray background. Here we present a simple, proof-of-concept calculation of the magnitude of this effect and demonstrate that current Fermi data already seem to prefer nonnegligible IGMF values. The anisotropy energy spectrum of the Fermi gamma-ray background could thus be used as a probe of the IGMF strength.

  16. Anisotropy of the Topopah Spring Member Tuff

    International Nuclear Information System (INIS)

    Martin, R.J. III; Boyd, P.J.; Haupt, R.W.; Price, R.H.

    1992-07-01

    Mechanical properties of the tuffaceous rocks within Yucca Mountain are needed for near and far-field modeling of the potential nuclear waste repository. If the mechanical properties are significantly anisotropic (i.e., direction-dependent), a more complex model is required. Relevant data from tuffs tested in earlier studies indicate that elastic and strength properties are anisotropic. This scoping study confirms the elastic anisotropy and concludes some tuffs are transversely isotropic. An approach for sampling and testing the rock to determine the magnitude of the anisotropy is proposed

  17. Anisotropy of dilepton emission from nuclear collisions

    International Nuclear Information System (INIS)

    Bratkovskaya, E.L.; Teryaev, O.V.; Toneev, V.D.; Joint Inst. for Nuclear Research, Dubna

    1994-01-01

    Attention is paid to studying the angular characteristics of e + e - pairs created in collisions with nuclear targets at intermediate and relativistic energies. Arising due to general spin and angular momentum constraints, the dilepton anisotropy seems to be quite sensitive to the contribution of different sources and may be used for disentangling these sources (or models) as well as an additional signature of a possible chiral symmetry restoration and phase transition of hadrons into the quark-gluon plasma. An anisotropy estimate for some dilepton sources is given and its relevance to the problems mentioned is discussed

  18. Anisotropy of the Topopah Spring Member Tuff

    Energy Technology Data Exchange (ETDEWEB)

    Martin, R.J. III; Boyd, P.J.; Haupt, R.W. [New England Research, Inc., White River Junction, VT (United States); Price, R.H. [Sandia National Labs., Albuquerque, NM (United States)

    1992-07-01

    Mechanical properties of the tuffaceous rocks within Yucca Mountain are needed for near and far-field modeling of the potential nuclear waste repository. If the mechanical properties are significantly anisotropic (i.e., direction-dependent), a more complex model is required. Relevant data from tuffs tested in earlier studies indicate that elastic and strength properties are anisotropic. This scoping study confirms the elastic anisotropy and concludes some tuffs are transversely isotropic. An approach for sampling and testing the rock to determine the magnitude of the anisotropy is proposed.

  19. Variation in the strain anisotropy of Zircaloy with temperature and strain

    International Nuclear Information System (INIS)

    Hindle, E.D.; Worswick, D.

    1984-01-01

    The strong crystallographic texture which is developed during the fabrication of zirconium-based alloys causes pronounced anisotropy in their mechanical properties, particularly deformation. The tendency for circular-section tension specimens with a high concentration of basal poles in one direction to become elliptical when deformed in tension has been used in this study to provide quantitative data on the effects of both strain and temperature on strain anisotropy. Tension tests were carried out over a temperature range of 293 to 1193 K on specimens machined from Zircaloy-2 plate. The strain anisotropy was found to increase markedly at temperatures over 923 K, reaching a maximum in the region of 1070 K. The strain anisotropy increased with increasing strain in this temperature region. The study was extended to Zircaloy-4 pressurized-water reactor fuel cladding by carrying out tube swelling tests and evaluating the axial deformation produced. Although scatter in the test results was higher than that exhibited in the tension tests, the general trend in the data was similar. The effects of the strain anisotropy observed are discussed in relation to the effects of temperature on the ductility of Zircaloy fuel cladding tubes during postulated largebreak loss-of-coolant accidents

  20. Anisotropy of the Vortex Magnetic Field Distribution in LuNi2B2

    Science.gov (United States)

    Eskildsen, M. R.; Debeer-Schmitt, L.; Rovira, K.; Jenkins, N.; Dewhurst, C. D.; Bud'Ko, S. L.; Canfield, P. C.

    2008-03-01

    It is well known that the vortex lattice (VL) symmetry and orientation in type-II superconductors is very sensitive to any anisotropy within the screening current plane. A classic example is the sequence of transitions from hexagonal to rhombic to square symmetry, which was first observed in the borocarbide superconductors and explained by a Fermi surface anisotropy coupled with the non-local electrodynamics responsible for vortex-vortex interactions. Recently, however, this is mounting experimental evidence for a strong gap anisotropy and possible point nodes in the basal plane of these materials. Here we report on small-angle neutron scattering studies of the VL in a carefully annealed, high quality LuNi2B2C single crystal, which permitted us to measure the VL form factor for a large number of reflections. These measurements allow a reconstruction of the real space profile of the magnetic field around the vortices, reflecting the basal plane anisotropy of the screening currents in LuNi2B2C. The results will be compared to predictions for both Fermi surface and gap anisotropies, and will serve as a valuable reference for more complicated compounds as e.g. Sr2RuO4, heavy fermions and high-Tc's.

  1. Effects of anisotropy on gravitational infall in galaxy clusters using an exact general relativistic model

    Energy Technology Data Exchange (ETDEWEB)

    Troxel, M.A.; Peel, Austin; Ishak, Mustapha, E-mail: troxel@utdallas.edu, E-mail: austin.peel@utdallas.edu, E-mail: mishak@utdallas.edu [Department of Physics, The University of Texas at Dallas, Richardson, TX, 75083 (United States)

    2013-12-01

    We study the effects and implications of anisotropies at the scale of galaxy clusters by building an exact general relativistic model of a cluster using the inhomogeneous and anisotropic Szekeres metric. The model is built from a modified Navarro-Frenk-White (NFW) density profile. We compare this to a corresponding spherically symmetric structure in the Lemaȋtre-Tolman (LT) model and quantify the impact of introducing varying levels of anisotropy. We examine two physical measures of gravitational infall — the growth rate of density and the velocity of the source dust in the model. We introduce a generalization of the LT dust velocity profile for the Szekeres metric and demonstrate its consistency with the growth rate of density. We find that the growth rate of density in one substructure increases by 0.5%, 1.5%, and 3.75% for 5%, 10%, and 15% levels of introduced anisotropy, which is measured as the fractional displaced mass relative to the spherically symmetric case. The infall velocity of the dust is found to increase by 2.5, 10, and 20 km s{sup −1} (0.5%, 2%, and 4.5%), respectively, for the same three levels of anisotropy. This response to the anisotropy in a structure is found to be strongly nonlinear with respect to the strength of anisotropy. These relative velocities correspond to an equivalent increase in the total mass of the spherically symmetric structure of 1%, 3.8%, and 8.4%, indicating that not accounting for the presence of anisotropic mass distributions in cluster models can strongly bias the determination of physical properties like the total mass.

  2. The impact of sedimentary anisotropy on solute mixing in stacked scour-pool structures

    Science.gov (United States)

    Bennett, Jeremy P.; Haslauer, Claus P.; Cirpka, Olaf A.

    2017-04-01

    The spatial variability of hydraulic conductivity is known to have a strong impact on solute spreading and mixing. In most investigations, its local anisotropy has been neglected. Recent studies have shown that spatially varying orientation in sedimentary anisotropy can lead to twisting flow enhancing transverse mixing, but most of these studies used geologically implausible geometries. We use an object-based approach to generate stacked scour-pool structures with either isotropic or anisotropic filling which are typically reported in glacial outwash deposits. We analyze how spatially variable isotropic conductivity and variation of internal anisotropy in these features impacts transverse plume deformation and both longitudinal and transverse spreading and mixing. In five test cases, either the scalar values of conductivity or the spatial orientation of its anisotropy is varied between the scour-pool structures. Based on 100 random configurations, we compare the variability of velocity components, stretching and folding metrics, advective travel-time distributions, one and two-particle statistics in advective-dispersive transport, and the flux-related dilution indices for steady state advective-dispersive transport among the five test cases. Variation in the orientation of internal anisotropy causes strong variability in the lateral velocity components, which leads to deformation in transverse directions and enhances transverse mixing, whereas it hardly affects the variability of the longitudinal velocity component and thus longitudinal spreading and mixing. The latter is controlled by the spatial variability in the scalar values of hydraulic conductivity. Our results demonstrate that sedimentary anisotropy is important for transverse mixing, whereas it may be neglected when considering longitudinal spreading and mixing.

  3. Measuring the Alfvénic nature of the interstellar medium: Velocity anisotropy revisited

    International Nuclear Information System (INIS)

    Burkhart, Blakesley; Lazarian, A.; Leão, I. C.; De Medeiros, J. R.; Esquivel, A.

    2014-01-01

    The dynamics of the interstellar medium (ISM) are strongly affected by turbulence, which shows increased anisotropy in the presence of a magnetic field. We expand upon the Esquivel and Lazarian method to estimate the Alfvén Mach number using the structure function anisotropy in velocity centroid data from Position-Position-Velocity maps. We utilize three-dimensional magnetohydrodynamic simulations of fully developed turbulence, with a large range of sonic and Alfvénic Mach numbers, to produce synthetic observations of velocity centroids with observational characteristics such as thermal broadening, cloud boundaries, noise, and radiative transfer effects of carbon monoxide. In addition, we investigate how the resulting anisotropy-Alfvén Mach number dependency found in Esquivel and Lazarian might change when taking the second moment of the Position-Position-Velocity cube or when using different expressions to calculate the velocity centroids. We find that the degree of anisotropy is related primarily to the magnetic field strength (i.e., Alfvén Mach number) and the line-of-sight orientation, with a secondary effect on sonic Mach number. If the line of sight is parallel to up to ≈45 deg off of the mean field direction, the velocity centroid anisotropy is not prominent enough to distinguish different Alfvénic regimes. The observed anisotropy is not strongly affected by including radiative transfer, although future studies should include additional tests for opacity effects. These results open up the possibility of studying the magnetic nature of the ISM using statistical methods in addition to existing observational techniques.

  4. Tailoring perpendicular magnetic anisotropy with graphene oxide membranes

    KAUST Repository

    Ning, Keyu

    2017-11-15

    Graphene oxide (GO) membranes have been widely explored for their excellent physical and chemical properties, and abundant functional groups. In this work, we report the improvement of the perpendicular magnetic anisotropy (PMA) of CoFeB thin films by applying a coating of GO membranes. We observe that the PMA of the CoFeB/MgAl–O stacks is strongly enhanced by the coating of GO membranes and even reaches 0.6 mJ m−2 at room temperature after an annealing process. The critical thickness of the membrane-coated CoFeB for switching the magnetization from the out-of-plane to the in-plane axis exceeds 1.6 nm. First-principle calculations are performed to investigate the contribution of the GO membranes to the magnetic anisotropy energy (MAE). Due to changes in the hybridization of 3d orbitals, varying the location of the C atomic layer with Co changes the contribution of the Co–C stacks to PMA. Thus, the large PMA achieved with GO membranes can be attributed to the orbital hybridization of the C and O atoms with the Co orbitals. These results provide a comprehensive understanding of the PMA and point towards opportunities to achieve multifunctional graphene-composite spintronic devices.

  5. Complex seismic anisotropy and mantle dynamics beneath Turkey

    Science.gov (United States)

    Lemnifi, Awad A.; Elshaafi, Abdelsalam; Karaoğlu, Özgür; Salah, Mohamed K.; Aouad, Nassib; Reed, Cory A.; Yu, Youqiang

    2017-12-01

    Seismic anisotropy is an unambiguous property of the deep Earth that is often detected through shear wave splitting (SWS) and anisotropic receiver function (RF) techniques, which are then used to infer the lithospheric and asthenospheric deformational structure. The Anatolian plate and its associated Mediterranean, Eurasian, and Arabian plate boundaries represent the consequences of a variety of convergent and transform tectonic regimes; these boundaries are thus well-suited for studying seismic anisotropy related to subduction, orogenic, and strike-slip processes. We apply a joint SWS and RF analysis to identify the magnitude and orientation of deformation associated with lithosphere-asthenosphere coupling beneath the Anatolian plate system as well as intra-plate fossil fabrics resulting from ancient and ongoing collision. SWS analysis reveals the existence of complex anisotropic fabrics beneath the Anatolian region, where the upper-layer fast orientations are either parallel to strike-slip faults or orthogonal to reverse faults. Strongly oriented NE-SW lower-layer fast orientations suggest that they originate from slab-modulated flow in the mantle wedge overlying the northward-subducting African plate. The results of the RF analysis show that the fast orientations are spatially variable but are generally consistent with crustal fabrics developed mostly through intensive faulting and are possibly associated with sub-vertical lower crustal shear zones.

  6. Particle physics implications of Wilkinson microwave anisotropy ...

    Indian Academy of Sciences (India)

    1016 GeV) inflation. Keywords. Cosmic microwave background radiation; inflation; Wilkinson microwave anisotropy project. PACS Nos 98.80.-k; 98.80.Cq; 98.80.Es; 95.30.Cq; 12.10.Dm; 12.60.Jv. 1. Introduction. This review [1] is divided into ...

  7. Magnetic anisotropy in rare-earth metals

    DEFF Research Database (Denmark)

    Nielsen, Mourits; Bjerrum Møller, Hans; Lindgård, Per-Anker

    1970-01-01

    The magnetic field dependence of the energy of long- wavelength magnons in Tb-10%Ho has been studied by inelastic neutron scattering. The results agree with the `frozen-lattice' model, provided that the second-order magnetoelastic effect is taken into account. The planar anisotropy is almost...

  8. Pseudospin anisotropy classification of quantum Hall ferromagnets

    Czech Academy of Sciences Publication Activity Database

    Jungwirth, Tomáš; MacDonald, A. H.

    2000-01-01

    Roč. 63, č. 3 (2000), s. 035305-1 - 035305-9 ISSN 0163-1829 R&D Projects: GA ČR GA202/98/0085 Institutional research plan: CEZ:AV0Z1010914 Keywords : quantum Hall ferromagnets * anisotropy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.065, year: 2000

  9. Empirical evidence for inertial mass anisotropy

    International Nuclear Information System (INIS)

    Heller, M.; Siemieniec, G.

    1985-01-01

    A several attempts at measuring the possible deviations from inertial mass isotropy caused by a non-uniform distribution of matter are reviewed. A simple model of the inertial mass anisotropy and the results of the currently performed measurements concerning this effect are presented. 34 refs. (author)

  10. Acoustic axes in weak triclinic anisotropy

    Czech Academy of Sciences Publication Activity Database

    Vavryčuk, Václav

    2005-01-01

    Roč. 163, č. 2 (2005), s. 629-638 ISSN 0956-540X R&D Projects: GA AV ČR IAA3012309 Institutional research plan: CEZ:AV0Z30120515 Keywords : elastic-wave theory * perturbation methods * seismic anisotropy Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 1.826, year: 2005

  11. Effective anisotropy through traveltime and amplitude matching

    KAUST Repository

    Wang, Hui

    2014-08-05

    Introducing anisotropy to seismic wave propagation reveals more realistic physics of our Earth\\'s subsurface as compared to the isotropic assumption. However wavefield modeling, the engine of seismic inverse problems, in anisotropic media still suffers from computational burdens, in particular with complex anisotropy such as transversely isotropic (TI) and Orthorhombic anisotropy. We develop effective isotropic velocity and density models to package the effects of anisotropy such that the wave propagation behavior using these effective models approximate those of the original anisotropic model. We build these effective models through the high frequency asymptotic approximation based on the eikonal and transport equations. We match the geometrical behavior of the wave-fields, given by traveltimes, from the anisotropic and isotropic eikonal equations. This matching yields the effective isotropic velocity that approximates the kinematics of the anisotropic wavefield. Equivalently, we calculate the effective densities by equating the anisotropic and isotropic transport equations. The effective velocities and densities are then fed into the isotropic acoustic variable density wave equation to obtain cheaper anisotropic wavefields. We justify our approach by testing it on an elliptical anisotropic model. The numerical results demonstrate a good matching of both traveltime and amplitude between anisotropic and effective isotropic wavefields.

  12. Particle physics implications of Wilkinson microwave anisotropy ...

    Indian Academy of Sciences (India)

    microwave anisotropy project measurements. U A YAJNIK. Indian Institute of Technology Bombay, Mumbai 400 076, India. E-mail: yajnik@phy.iitb.ac.in. Abstract. We present an overview of the implications of the WMAP data for particle physics. The standard parameter set ϵ, η and ξ characterising the inflaton potential can.

  13. Azimuthal anisotropy of jet quenching at LHC

    Indian Academy of Sciences (India)

    Abstract. We analyze the azimuthal anisotropy of jet spectra due to energy loss of hard partons in quark–gluon plasma, created initially in nuclear overlap zone in collisions with non-zero impact parameter. The calculations are performed for semi-central Pb–Pb collisions at LHC energy.

  14. What we learn from CMB Anisotropies

    CERN Multimedia

    CERN. Geneva

    2007-01-01

    George Smoot shared the 2006 Nobel Prize with John Mathere for the discovery of the fluctuations of the cosmic microwave background. In this talk (which will not be the same as the Nobel lecture), he will discuss what we have learned about the universe in the recent past from these anisotropies.

  15. Anisotropy of Wood in the Microwave Region

    Science.gov (United States)

    Ziherl, Sasa; Bajc, Jurij; Urankar, Bernarda; Cepic, Mojca

    2010-01-01

    Wood is transparent for microwaves and due to its anisotropic structure has anisotropic dielectric properties. A laboratory experiment that allows for the qualitative demonstration and quantitative measurements of linear dichroism and birefringence in the microwave region is presented. As the proposed experiments are based on the anisotropy (of…

  16. Cosmology with cosmic microwave background anisotropy

    Indian Academy of Sciences (India)

    Measurements of CMB anisotropy and, more recently, polarization have played a very important role in allowing precise determination of various parameters of the `standard' cosmological model. The expectation of the paradigm of inflation and the generic prediction of the simplest realization of inflationary scenario in the ...

  17. On the anisotropy of the gravitational wave background from massless preheating

    Science.gov (United States)

    Bethke, Laura; Figueroa, Daniel G.; Rajantie, Arttu

    2014-06-01

    When a light scalar field is present during inflation, its value varies on superhorizon scales, modulating the preheating process at the end of inflation. Consequently, the amplitude of the gravitational wave (GW) background produced during preheating is also modulated. The observed energy density of this background appears therefore anisotropic at different angles in the sky. We provide a master formula for the angular power spectrum Cl of the anisotropies in the GW background from preheating, valid for any scenario where the anisotropies are due to the superhorizon modulation of a light degree of freedom. Using lattice field theory simulations of massless preheating with g2/λ = 2, we find a flat angular spectrum l(l+1)Cl ≈ 3 × 10-4, which represents a strong anisotropy of ~ 1% variations on large angular scales. For our choice of couplings, long wavelengths are amplified most strongly during parametric resonance, which is crucial for the development of the anisotropies. If future direct detection GW observatories are capable of detecting backgrounds of cosmological origin, they {may also} be able to detect this effect. This could eventually become a powerful tool to discriminate among inflationary and preheating scenarios.

  18. Feasibility of theoretical formulas on the anisotropy of shale based on laboratory measurement and error analysis

    Science.gov (United States)

    Xie, Jianyong; Di, Bangrang; Wei, Jianxin; Luan, Xinyuan; Ding, Pinbo

    2015-04-01

    This paper designs a total angle ultrasonic test method to measure the P-wave velocities (vp), vertically and horizontally polarized shear wave velocities (vsv and vsh) of all angles to the bedding plane on different kinds of strong anisotropic shale. Analysis has been made of the comparisons among the observations and corresponding calculated theoretical curves based on the varied vertical transversely isotropic (TI) medium theories, for which discussing the real similarity with the characterizations of the TI medium on the scope of dynamic behaviors, and further conclude a more accurate and precise theory from the varied theoretical formulas as well as its suitable range to characterize the strong anisotropy of shale. At a low phase angle (theta Berryman expressions provide a relatively much better agreement with the measured data for vp, vsv on shale. Also all of the three theories lead to more deviations in the approximation of the vsv than for the vp and vsh. Furthermore, we created synthetic comparative ideal physical models (from coarse bakelite, cambric bakelite, and paper bakelite) as supplementary models to natural shale, which are used to model shale with different anisotropy, to research the effects of the anisotropic parameters upon the applicability of the former optimal TI theories, especially for the vsv. We found the when the P-wave anisotropy, S-wave anisotropy ɛ, γ > 0.25, the Berrryman curve will be the best fit for the vp, vsv on shale.

  19. Computing magnetic anisotropy constants of single molecule magnets

    Indian Academy of Sciences (India)

    Administrator

    stringent requirements for a molecule to behave as a. SMM. Modelling magnetic anisotropy in these sys- tems becomes necessary for developing new SMMs with desired properties. Magnetic anisotropy of SMMs is computed by treating the anisotropy Hamiltonian as a perturbation over the Heisenberg exchange ...

  20. Drag force in strongly coupled, anisotropic plasma at finite chemical potential

    Energy Technology Data Exchange (ETDEWEB)

    Chakraborty, Somdeb; Haque, Najmul [Theory Division, Saha Institute of Nuclear Physics,1/AF Bidhannagar, Kolkata-700 064 (India)

    2014-12-30

    We employ methods of gauge/string duality to analyze the drag force on a heavy quark moving through a strongly coupled, anisotropic N=4,SU(N) super Yang-Mills plasma in the presence of a finite U(1) chemical potential. We present numerical results valid for any value of the anisotropy parameter and the U(1) charge density and arbitrary direction of the quark velocity with respect to the direction of anisotropy. In the small anisotropy limit we are also able to furnish analytical results.

  1. Controlling the magnetic anisotropy in epitaxial Y3F e5O12 films by manganese doping

    Science.gov (United States)

    Wang, C. T.; Liang, X. F.; Zhang, Y.; Liang, X.; Zhu, Y. P.; Qin, J.; Gao, Y.; Peng, B.; Sun, N. X.; Bi, L.

    2017-12-01

    Controlling the magnetic anisotropy in epitaxial Y3F e5O12 (YIG) thin films is critical for magnonic and photonic device applications. In this paper, we report the crystal structure, magnetic properties, and magnetic anisotropy of epitaxial Y3(F e5 -xM nx ) O12 (Mn:YIG) thin films grown on G d3G a5O12 (111) (GGG) substrates by pulsed-laser deposition. Mn doping is observed to strongly enhance the magnetoelastic coefficient of YIG thin films, which leads to large tunability of the thin film magnetic anisotropy by lattice strain. With increasing Mn concentration from x =0 to x =1.25 , a continuous increase of out-of-plane magnetic anisotropy ranging from -644.4 Oe to 1337.5 Oe is observed. In particular, a perpendicular magnetic anisotropy (PMA) is achieved in Mn:YIG thin films with a high Mn concentration of x =1.12 . Ferromagnetic resonance (FMR) measurements show low FMR linewidths of 3.4 Oe to 129 Oe at 9.5 GHz in Mn:YIG thin films. Our paper demonstrates manganese doping as an effective way to enhance the magnetoelastic anisotropy of YIG thin films by strain, which is useful for magnonic and magneto-optical device applications.

  2. Testing strong interaction theories

    International Nuclear Information System (INIS)

    Ellis, J.

    1979-01-01

    The author discusses possible tests of the current theories of the strong interaction, in particular, quantum chromodynamics. High energy e + e - interactions should provide an excellent means of studying the strong force. (W.D.L.)

  3. Large Flexoelectric Anisotropy in Paraelectric Barium Titanate.

    Science.gov (United States)

    Narvaez, Jackeline; Saremi, Sahar; Hong, Jiawang; Stengel, Massimiliano; Catalan, Gustau

    2015-07-17

    The bending-induced polarization of barium titanate single crystals has been measured with an aim to elucidate the origin of the large difference between theoretically predicted and experimentally measured flexoelectricity in this material. The results indicate that part of the difference is due to polar regions (short-range order) that exist above T(C) and up to T*≈200-225 °C. Above T*, however, the flexovoltage coefficient still shows an unexpectedly large anisotropy for a cubic material, with (001)-oriented crystals displaying 10 times more flexoelectricity than (111)-oriented crystals. Theoretical analysis shows that this anisotropy cannot be a bulk property, and we therefore interpret it as indirect evidence for the theoretically predicted but experimentally elusive contribution of surface piezoelectricity to macroscopic bending-induced polarization.

  4. Magnetic anisotropy of (Ge,Mn) nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Jain, A; Jamet, M; Barski, A; Devillers, T; Yu, I-S; Porret, C; Gambarelli, S; Maurel, V; Desfonds, G; Jacquot, J F, E-mail: abhinav.jain@cea.fr [Institut Nanosciences et Cryogenie, CEA-UJF, F-38054, Grenoble (France)

    2011-04-01

    We present a correlation between structural and magnetic properties of different (Ge,Mn) nanostructures grown on Ge(001) and Ge(111) substrates. Thin films of Ge{sub 1-x}Mn{sub x} were grown by low temperature molecular beam epitaxy to favor the out-of-equilibrium growth. Depending on the growth conditions crystalline or amorphous (Ge,Mn) nanocolumns have been observed on Ge(001) substrates. The magnetic properties were probed by superconducting quantum interference device (SQUID), vibrating sample magnetometer (VSM) and electron paramagnetic resonance (EPR). With the help of these complementary techniques (SQUID and EPR), magnetic anisotropy in these nanostructures has been investigated and different anisotropy constants were calculated.

  5. Seismic anisotropy in deforming salt bodies

    Science.gov (United States)

    Prasse, P.; Wookey, J. M.; Kendall, J. M.; Dutko, M.

    2017-12-01

    Salt is often involved in forming hydrocarbon traps. Studying salt dynamics and the deformation processes is important for the exploration industry. We have performed numerical texture simulations of single halite crystals deformed by simple shear and axial extension using the visco-plastic self consistent approach (VPSC). A methodology from subduction studies to estimate strain in a geodynamic simulation is applied to a complex high-resolution salt diapir model. The salt diapir deformation is modelled with the ELFEN software by our industrial partner Rockfield, which is based on a finite-element code. High strain areas at the bottom of the head-like strctures of the salt diapir show high amount of seismic anisotropy due to LPO development of halite crystals. The results demonstrate that a significant degree of seismic anisotropy can be generated, validating the view that this should be accounted for in the treatment of seismic data in, for example, salt diapir settings.

  6. Large Flexoelectric Anisotropy in Paraelectric Barium Titanate

    Science.gov (United States)

    Narvaez, Jackeline; Saremi, Sahar; Hong, Jiawang; Stengel, Massimiliano; Catalan, Gustau

    2015-07-01

    The bending-induced polarization of barium titanate single crystals has been measured with an aim to elucidate the origin of the large difference between theoretically predicted and experimentally measured flexoelectricity in this material. The results indicate that part of the difference is due to polar regions (short-range order) that exist above TC and up to T*≈2 00 - 2 2 5 °C . Above T* , however, the flexovoltage coefficient still shows an unexpectedly large anisotropy for a cubic material, with (001)-oriented crystals displaying 10 times more flexoelectricity than (111)-oriented crystals. Theoretical analysis shows that this anisotropy cannot be a bulk property, and we therefore interpret it as indirect evidence for the theoretically predicted but experimentally elusive contribution of surface piezoelectricity to macroscopic bending-induced polarization.

  7. Anisotropies in the cosmic microwave background: Theory

    International Nuclear Information System (INIS)

    Dodelson, S.

    1998-02-01

    Anisotropies in the Cosmic Microwave Background (CMB) contain a wealth of information about the past history of the universe and the present values of cosmological parameters. I online some of the theoretical advances of the last few years. In particular, I emphasize that for a wide class of cosmological models, theorists can accurately calculate the spectrum to better than a percent. The spectrum of anisotropies today is directly related to the pattern of inhomogeneities present at the time of recombination. This recognition leads to a powerful argument that will enable us to distinguish inflationary models from other models of structure formation. If the inflationary models turn out to be correct, the free parameters in these models will be determined to unprecedented accuracy by the upcoming satellite missions

  8. Microwave background anisotropies in quasiopen inflation

    Science.gov (United States)

    García-Bellido, Juan; Garriga, Jaume; Montes, Xavier

    1999-10-01

    Quasiopenness seems to be generic to multifield models of single-bubble open inflation. Instead of producing infinite open universes, these models actually produce an ensemble of very large but finite inflating islands. In this paper we study the possible constraints from CMB anisotropies on existing models of open inflation. The effect of supercurvature anisotropies combined with the quasiopenness of the inflating regions make some models incompatible with observations, and severely reduces the parameter space of others. Supernatural open inflation and the uncoupled two-field model seem to be ruled out due to these constraints for values of Ω0<~0.98. Others, such as the open hybrid inflation model with suitable parameters for the slow roll potential can be made compatible with observations.

  9. Ultrasonic evaluation of local human skin anisotropy

    Czech Academy of Sciences Publication Activity Database

    Tokar, Daniel; Převorovský, Zdeněk; Hradilová, Jana

    2014-01-01

    Roč. 19, č. 12 (2014) ISSN 1435-4934. [European Conference on Non-Destructive Testing (ECNDT 2014) /11./. Praha, 06.10.2014-10.10.2014] Institutional support: RVO:61388998 Keywords : anisotropy * ultrasonic testing * human skin in-vivo * fabric-fiber composite * signal processing Subject RIV: BI - Acoustics http://www.ndt.net/events/ECNDT2014/app/content/Paper/324_Tokar.pdf

  10. One-loop anisotropy for improved actions

    OpenAIRE

    Perez, Margarita Garcia; van Baal, Pierre

    1996-01-01

    We determine the one-loop correction to the anisotropy factor for the square Symanzik improved lattice action, extracted fromthe finite volume effective action for SU(N) gauge theories in the background of a zero-momentum gauge field. The result is smaller by approximately a factor 3 than the one-loop correction for the anisotropic Wilson action. We also comment on the Hamiltonian limit.

  11. Experimental investigation of ultrasonic velocity anisotropy in ...

    Indian Academy of Sciences (India)

    Permanent link: http://www.ias.ac.in/article/fulltext/pram/077/02/0345-0355. Keywords. Magnetic fluids; ultrasonic wave; sound velocity; anisotropy. Abstract. Magnetic field-induced dispersion of ultrasonic velocity in a Mn0.7Zn0.3Fe2O4 fluid (applied magnetic field is perpendicular to the ultrasonic propagation vector) is ...

  12. Assessment of velocity anisotropy in rocks

    Czech Academy of Sciences Publication Activity Database

    Lokajíček, Tomáš; Goel, R. K.; Rudajev, Vladimír; Dwivedi, R.D.

    2013-01-01

    Roč. 57, January (2013), s. 142-152 ISSN 1365-1609 R&D Projects: GA ČR(CZ) GA205/08/0676; GA AV ČR IAA300130906; GA ČR(CZ) GAP104/12/0915 Institutional research plan: CEZ:AV0Z30130516 Keywords : elastic anisotropy * acoustic emission * uniaxial loading * hydrostatic loading Subject RIV: DB - Geology ; Mineralogy Impact factor: 1.424, year: 2013

  13. Experimental investigation of ultrasonic velocity anisotropy in ...

    Indian Academy of Sciences (India)

    Permanent link: https://www.ias.ac.in/article/fulltext/pram/077/02/0345-0355. Keywords. Magnetic fluids; ultrasonic wave; sound velocity; anisotropy. Abstract. Magnetic field-induced dispersion of ultrasonic velocity in a Mn0.7Zn0.3Fe2O4 fluid (applied magnetic field is perpendicular to the ultrasonic propagation vector) is ...

  14. Measurement of the thermopower anisotropy in iron arsenide

    Energy Technology Data Exchange (ETDEWEB)

    Fujii, T., E-mail: fujii@crc.u-tokyo.ac.jp [Cryogenic Research Center, the University of Tokyo, 2-11-16 Yayoi, Bunkyo, Tokyo 113-0032 (Japan); Shirachi, T. [Department of Applied Physics, the University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan); Asamitsu, A. [Cryogenic Research Center, the University of Tokyo, 2-11-16 Yayoi, Bunkyo, Tokyo 113-0032 (Japan); Department of Applied Physics, the University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan); Ashikaga Institute of Technology, 268-1 Omae, Ashikaga, Tochigi 326-8558 (Japan)

    2016-11-15

    Highlights: • In this study, in order to investigate the origin of the in-plane anisotropy, the in-plane anisotropy of the thermopower was measured for the detwined single crystals of BFe{sub 2}As{sub 2}. And, we found no anisotropy in the thermopower above T{sub AFO}, although there is a large anisotropy in the resistivity. This result gives evidence that the anisotropy in the resistivity arise from the anisotropy of the scattering time, and the energy dependence of the scattering time can be considered negligible. In the case of iron pnictides, the proposed orbital ordering more likely results in an anisotropy of electronic structure below T{sub AFO}, whereas the spin-nematic ordering leads to an anisotropy of electron scattering above T{sub AFO}. Therefore, our results suggest that nematicity above T{sub AFO} results from anisotropic magnetic scattering. - Abstract: We investigated the in-plane anisotropy of the thermopower and electrical resistivity on detwinned single crystals of BaFe{sub 2}As{sub 2}. The in-plane anisotropy of the resistivity was clearly observed far above the magnetostructural transition temperature T{sub AFO}. While, the thermopower showed the in-plane anisotropy only below T{sub AFO}. These results are associated with the different origin of the anisotropy above and below T{sub AFO}. Since the thermopower does not depend on the scattering time, the anisotropy of the resistivity above T{sub AFO} is considered to be due to the anisotropic scattering. On the other hand, the anisotropy in the thermopower below T{sub AFO} is ascribed to the reconstructed Fermi surface.

  15. Exploring the Tectonic Evolution of the Seafloor using Roughness, Covariance, and Anisotropy in Bathymetry and Marine Gravity

    Science.gov (United States)

    Kalnins, L. M.; Simons, F.

    2017-12-01

    Between the vastness of the oceans and the technological challenges water poses, data scarcity is frequently a limiting factor in studying the tectonic and morphological evolution of the seafloor. It is therefore essential to extract maximum information from the available gravity and bathymetry data, whilst also retaining realistic estimates of uncertainties. Here, we use a frequency-domain maximum-likelihood procedure to map the roughness structure and the nature of the topographic covariance of the seafloor. Rather than requiring us to assume the covariance is Gaussian or exponential, the flexibility of the Matérn form's parameterisation (variance, range, and differentiability) lets us solve for the shape of the covariance and map out its changes without a priori assumptions.We also examine the relationship between gravity and bathymetry through their coherence and admittance, particularly the anisotropy in the relationship. We extend the robust analysis developed to map anisotropy in lithospheric strength in the continents (Kalnins et al., 2015) to the oceanic domain. This method lets us separate out measurements of anisotropy likely to be linked to anisotropy in the long-term mechanical strength of the lithosphere itself; those aligned with anisotropies in the input gravity and bathymetry data; and those that are mathematically significant, but unexplained. Ultimately, we aim to use the statistical analyses to infer geophysical parameters of interest, such as oceanic spreading rate, level of volcanic activity, and potential for energy dissipation in ocean circulation. Our first results show a general alignment of strong directions ridge-parallel and weak directions ridge-perpendicular, suggesting widespread mechanical anisotropy derived from the lithosphere's highly anisotropic formation at mid-ocean ridges. However, this pattern changes markedly near sites of significant intraplate volcanism, where little to no robust anisotropy in strength is recovered. This

  16. Dynamical anisotropy of the optical propagation paths

    Science.gov (United States)

    Arsenyan, Tatiana I.; Pisklin, Maksim V.; Suhareva, Natalia A.; Zotov, Aleksey M.

    2015-11-01

    Dynamics of laser beam intensity profile spatial modulations over a model tropospheric path with the controlled meteorological parameters was studied. Influence of the underlying surface temperature as well as the side wind load were considered. The increase of dynamic anisotropic disturbances saturation with the path length was observed. Spatio-temporal correlation characteristics of the directivity pattern in the signal beam registration plane were obtained. Proposed method of the experimental samples analysis on the base of chronogram with the following definition of the dynamic structure tensors array allows to estimate local and averaged projections of the flow velocities over the chosen spatio-temporal region and to restore their geometry in the zone of intersection with the signal beam. Additional characteristics suggested for the diagonalized local structure tensors such as local energy capacity and local structuredness are informative for the estimation of the inhomogeneities spatial dimensions, time of access through the section considered, the dynamics of energetic jets. The concepts of rotational and translational dynamic anisotropy are introduced to discriminate the types of the changes of the local ellipsoids axes orientation as well as their values. Rotational anisotropy shows itself in the changes of the local ellipsoids orientation, thus characterizing the illumination variation over the beam cross-section. Translational anisotropy describes the difference between the axes values for local ellipsoids.

  17. Anisotropy of permeability in faulted porous sandstones

    Science.gov (United States)

    Farrell, N. J. C.; Healy, D.; Taylor, C. W.

    2014-06-01

    Studies of fault rock permeabilities advance the understanding of fluid migration patterns around faults and contribute to predictions of fault stability. In this study a new model is proposed combining brittle deformation structures formed during faulting, with fluid flow through pores. It assesses the impact of faulting on the permeability anisotropy of porous sandstone, hypothesising that the formation of fault related micro-scale deformation structures will alter the host rock porosity organisation and create new permeability pathways. Core plugs and thin sections were sampled around a normal fault and oriented with respect to the fault plane. Anisotropy of permeability was determined in three orientations to the fault plane at ambient and confining pressures. Results show that permeabilities measured parallel to fault dip were up to 10 times higher than along fault strike permeability. Analysis of corresponding thin sections shows elongate pores oriented at a low angle to the maximum principal palaeo-stress (σ1) and parallel to fault dip, indicating that permeability anisotropy is produced by grain scale deformation mechanisms associated with faulting. Using a soil mechanics 'void cell model' this study shows how elongate pores could be produced in faulted porous sandstone by compaction and reorganisation of grains through shearing and cataclasis.

  18. Mapping Reflectance Anisotropy of a Potato Canopy Using Aerial Images Acquired with an Unmanned Aerial Vehicle

    Directory of Open Access Journals (Sweden)

    Peter P. J. Roosjen

    2017-04-01

    Full Text Available Viewing and illumination geometry has a strong influence on optical measurements of natural surfaces due to their anisotropic reflectance properties. Typically, cameras on-board unmanned aerial vehicles (UAVs are affected by this because of their relatively large field of view (FOV and thus large range of viewing angles. In this study, we investigated the magnitude of reflectance anisotropy effects in the 500–900 nm range, captured by a frame camera mounted on a UAV during a standard mapping flight. After orthorectification and georeferencing of the images collected by the camera, we calculated the viewing geometry of all observations of each georeferenced ground pixel, forming a dataset with multi-angular observations. We performed UAV flights on two days during the summer of 2016 over an experimental potato field where different zones in the field received different nitrogen fertilization treatments. These fertilization levels caused variation in potato plant growth and thereby differences in structural properties such as leaf area index (LAI and canopy cover. We fitted the Rahman–Pinty–Verstraete (RPV model through the multi-angular observations of each ground pixel to quantify, interpret, and visualize the anisotropy patterns in our study area. The Θ parameter of the RPV model, which controls the proportion of forward and backward scattering, showed strong correlation with canopy cover, where in general an increase in canopy cover resulted in a reduction of backward scattering intensity, indicating that reflectance anisotropy contains information on canopy structure. In this paper, we demonstrated that anisotropy data can be extracted from measurements using a frame camera, collected during a typical UAV mapping flight. Future research will focus on how to use the anisotropy signal as a source of information for estimation of physical vegetation properties.

  19. Spin-Anisotropy Commensurable Chains: Quantum Group Symmetries and N=2 SUSY

    OpenAIRE

    Berkovich, A.; Gomez, C.; Sierra, G.

    1993-01-01

    In this paper we consider a class of the 2D integrable models. These models are higher spin XXZ chains with an extra condition of the commensurability between spin and anisotropy. The mathematics underlying this commensurability is provided by the quantum groups with deformation parameter being an Nth root of unity. Our discussion covers a range of topics including new integrable deformations, thermodynamics, conformal behaviour, S-matrices and magnetization. The emerging picture strongly dep...

  20. Strong-coupling approach to nematicity in the cuprates

    Science.gov (United States)

    Orth, Peter Philipp; Jeevanesan, Bhilahari; Schmalian, Joerg; Fernandes, Rafael

    The underdoped cuprate superconductor YBa2Cu3O7-δ is known to exhibit an electronic nematic phase in proximity to antiferromagnetism. While nematicity sets in at large temperatures of T ~ 150 K, static spin density wave order only emerges at much lower temperatures. The magnetic response shows a strong in-plane anisotropy, displaying incommensurate Bragg peaks along one of the crystalline directions and a commensurate peak along the other one. Such an anisotropy persists even in the absence of long-range magnetic order at higher temperatures, marking the onset of nematic order. Here we theoretically investigate this situation using a strong-coupling method that takes into account both the localized Cu spins and the holes doped into the oxygen orbitals. We derive an effective spin Hamiltonian and show that charge fluctuations promote an enhancement of the nematic susceptibility near the antiferromagnetic transition temperature.

  1. Magnetic anisotropy of epitaxial Fe layers grown on Si(0 0 1)

    International Nuclear Information System (INIS)

    Bertoncini, P.; Wetzel, P.; Berling, D.; Mehdaoui, A.; Loegel, B.; Gewinner, G.; Poinsot, R.; Pierron-Bohnes, V.

    2001-01-01

    The magnetic properties of epitaxial iron films up to 80 monolayers (ML) thickness grown on Si(0 0 1) by using a template technique were investigated by means of superconducting quantum interference device and magneto-optic Kerr effect techniques. The thinnest films investigated (∼3 ML) exhibit a composition close to Fe 3 Si with a Curie temperature below room temperature (RT) and strong out-of-plane remanent magnetization that reflects the presence of a dominant second order surface anisotropy term. Thicker films (≥4 ML) are ferromagnetic at RT with remanent magnetization in film-plane and a composition closer to pure Fe with typically 8-10% silicon content. When deposited at normal incidence such films show simple in-plane fourfold anisotropy without uniaxial contribution. The relevant fourth-order effective anisotropy constant K 4 eff was measured versus film thickness and found to change its sign near 18 ML. The origin of this remarkable behavior is investigated by means of a Neel model and mainly traced back to fourth-order surface anisotropy and magneto-elastic effects related to the large biaxial in-plane compressive strain up to 3.5% in the thinnest (≤25 ML) films

  2. Two-photon anisotropy: Analytical description and molecular modeling for symmetrical and asymmetrical organic dyes

    International Nuclear Information System (INIS)

    Fu Jie; Przhonska, Olga V.; Padilha, Lazaro A.; Hagan, David J.; Van Stryland, Eric W.; Belfield, Kevin D.; Bondar, Mikhail V.; Slominsky, Yuriy L.; Kachkovski, Alexei D.

    2006-01-01

    One- and two-photon anisotropy spectra of a series of symmetrical and asymmetrical polymethine (PD) and fluorene molecules were measured experimentally and discussed theoretically within the framework of three-state and four-state models. For all the molecules discussed in this paper, the experimental two-photon anisotropy values, r 2PA , lie in the relatively narrow range from 0.47 to 0.57 and remain almost independent of wavelength over at least two electronic transitions. This is in contrast with their one-photon anisotropy, which shows strong wavelength dependence, typically varying from ∼0 to 0.38 over the same transitions. A detailed analysis of the two-photon absorption (2PA) processes allows us to conclude that a three-state model can explain the 2PA anisotropy spectra of most asymmetrical PDs and fluorenes. However, this model is inadequate for all the symmetrical molecules. Experimental values of r 2PA for symmetrical polymethines and fluorenes can be explained by symmetry breaking leading to the deviation of the orientation of the participating transition dipole moments from their 'classical' orientations

  3. Effect of Permeability Anisotropy on the Production of Multi-Scale Shale Gas Reservoirs

    Directory of Open Access Journals (Sweden)

    Ting Huang

    2017-10-01

    Full Text Available Shales or mudstones are fine grained and layered reservoirs, which leads to strong shale permeability anisotropy. Shale has a wide pore-size distribution, and pores with different diameters contribute differently to the apparent permeability of shales. Therefore, understanding the anisotropy of multiscale shale gas reservoirs is an important aspect to model and evaluate gas production from shales. In this paper, a novel model of permeability anisotropy for shale gas reservoirs is presented to calculate the permeability in an arbitrary direction in three dimensional space. A numerical model which is valid for the entire Knudsen’s range (continuum flow, slip flow, transition flow and free molecular flow in shale gas reservoirs was developed, and the effect of gas-water flow and the simulation of hydraulic fracturing cracks were taken into consideration as well. The simulation result of the developed model was validated with field data. Effects of critical factors such as permeability anisotropy, relative permeability curves with different nanopore radii and initial water saturation in formation on the gas production rate of multi-stage fractured horizontal well were discussed. Besides, flow regimes of gas flow in shales were classified by Knudsen number, and the effect of various flow regimes on both apparent permeability of shales and then the gas production has been analyzed thoroughly.

  4. On the Acceleration and Anisotropy of Ions Within Magnetotail Dipolarizing Flux Bundles

    Science.gov (United States)

    Zhou, Xu-Zhi; Runov, Andrei; Angelopoulos, Vassilis; Artemyev, Anton V.; Birn, Joachim

    2018-01-01

    Dipolarizing flux bundles (DFBs), earthward propagating structures with enhanced northward magnetic field Bz, are usually believed to carry a distinctly different plasma population from that in the ambient magnetotail plasma sheet. The ion distribution functions within the DFB, however, have been recently found to be largely controlled by the ion adiabaticity parameter κ in the ambient plasma sheet outside the DFB. According to these observations, the ambient κ values of 2-3 usually correspond to a strong perpendicular anisotropy of suprathermal ions within the DFB, whereas for lower κ values the DFB ions become more isotropic. Here we utilize a simple, test particle model to explore the nature of the anisotropy and its dependence on the ambient κ values. We find that the anisotropy originates from successive ion reflections and reentries to the DFB, during which the ions are consecutively accelerated in the perpendicular direction by the DFB-associated electric field. This consecutive acceleration may be interrupted, however, when magnetic field lines are highly curved in the ambient plasma sheet. In this case, the ion trajectories become stochastic outside the DFB, which makes the reflected ions less likely to return to the DFB for another cycle of acceleration; as a consequence, the perpendicular ion anisotropy does not appear. Given that the DFB ions are a free energy source for instabilities when they are injected toward Earth, our simple model (that reproduces most observational features on the anisotropic DFB ion distributions) may shed new lights on the coupling process between magnetotail and inner magnetosphere.

  5. Crust and upper-mantle seismic anisotropy variations from the coast to inland in central and Southern Mexico

    Science.gov (United States)

    Castellanos, Jorge; Pérez-Campos, Xyoli; Valenzuela, Raúl; Husker, Allen; Ferrari, Luca

    2017-07-01

    Subduction zones are among the most dynamic tectonic environments on Earth. Deformation mechanisms of various scales produce networks of oriented structures and faulting systems that result in a highly anisotropic medium for seismic wave propagation. In this study, we combine shear wave splitting inferred from receiver functions and the results from a previous SKS-wave study to quantify and constrain the vertically averaged shear wave splitting at different depths along the 100-station MesoAmerican Subduction Experiment array. This produces a transect that runs perpendicular to the trench across the flat slab portion of the subduction zone below central and southern Mexico. Strong anisotropy in the continental crust is found below the Trans-Mexican Volcanic Belt (TMVB) and above the source region of slow-slip events. We interpret this as the result of fluid/melt ascent. The upper oceanic crust and the overlying low-velocity zone exhibit highly complex anisotropy, while the oceanic lower crust is relatively homogeneous. Regions of strong oceanic crust anisotropy correlate with previously found low Vp/Vs regions, indicating that the relatively high Vs is an anisotropic effect. Upper-mantle anisotropy in the southern part of the array is in trench-perpendicular direction, consistent with the alignment of type-A olivine and with entrained subslab flow. The fast polarization direction of mantle anisotropy changes to N-S in the north, likely reflecting mantle wedge corner flow perpendicular to the TMVB.

  6. Backscatter, anisotropy, and polarization of solar hard X-rays

    International Nuclear Information System (INIS)

    Bai, T.; Ramaty, R.

    1978-01-01

    Hard X-rays incident upon the photosphere with energies > or approx. =15 keV have high probabilities of backscatter due to Compton collisions with electrons. This effect has a strong influence on the spectrum, intensity, and polarization of solar hard X-rays - especially for anisotropic models in which the primary X-rays are emitted predominantly toward the photosphere. We have carried out a detailed study of X-ray backscatter, and we have investigated the interrelated problems of anisotropy, polarization, center-to-limb variation of the X-ray spectrum, and Compton backscatter in a coherent fashion. The results of this study are compared with observational data. Because of the large contribution from backscatter, for an anisotropic primary X-ray source which is due to bremsstrahlung of accelerated electrons moving predominantly down toward the photosphere, the observed X-ray flux around 30 keV does not depend significantly on the position of flare on the Sun. For such an anisotropic source, the X-ray spectrum observed in the 15-50 keV range becomes steeper with the increasing heliocentric angle of the flare. These results are compatible with the data. The degree of polarization of the sum of the primary and reflected X-rays with energies between about 15 and 30 keV can be very large for anisotropic primary X-ray sources, but it is less than about 4% for isotropic sources. We also discuss the characteristics of the brightness distribution of the X-ray albedo patch created by the Compton backscatter. The height and anisotropy of the primary hard X-ray source might be inferred from the study of the albedo patch

  7. Altered Fractional Anisotropy in Early Huntington's Disease

    Directory of Open Access Journals (Sweden)

    Silky Singh

    2013-02-01

    Full Text Available Huntington's disease (HD is a dominantly inherited neurodegenerative disease best known for chorea. The disorder includes numerous other clinical features including mood disorder, eye movement abnormalities, cognitive disturbance, pendular knee reflexes, motor impersistence, and postural instability. We describe a mild case of HD early in the disease course with depression and subtle neurological manifestations. In addition, we review MRI and diffusion tensor imaging features in this patient. The bicaudate ratio, a measure of caudate atrophy, was increased. Fractional anisotropy values of the bilateral caudate and putamen were increased, signifying neurodegeneration of these structures in HD.

  8. Fusion barrier distributions and fission anisotropies

    International Nuclear Information System (INIS)

    Hinde, D.J.; Morton, C.R.; Dasgupta, M.; Leigh, J.R.; Lestone, J.P.; Lemmon, R.C.; Mein, J.C.; Newton, J.O.; Timmers, H.; Rowley, N.; Kruppa, A.T.

    1995-01-01

    Fusion excitation functions for 16,17 O+ 144 Sm have been measured to high precision. The extracted fusion barrier distributions show a double-peaked structure interpreted in terms of coupling to inelastic collective excitations of the target. The effect of the positive Q-value neutron stripping channel is evident in the reaction with 17 O. Fission and evaporation residue cross-sections and excitation functions have been measured for the reaction of 16 O+ 208 Pb and the fusion barrier distribution and fission anisotropies determined. It is found that the moments of the fusion l-distribution determined from the fusion and fission measurements are in good agreement. ((orig.))

  9. Anisotropy in cohesive, frictional granular media

    International Nuclear Information System (INIS)

    Luding, Stefan

    2005-01-01

    The modelling of cohesive, frictional granular materials with a discrete particle molecular dynamics is reviewed. From the structure of the quasi-static granular solid, the fabric, stress, and stiffness tensors are determined, including both normal and tangential forces. The influence of the material properties on the flow behaviour is also reported, including relations between the microscopic attractive force and the macroscopic cohesion as well as the dependence of the macroscopic friction on the microscopic contact friction coefficient. Related to the dynamics, the anisotropy of both structure and stress are exponentially approaching the maximum

  10. Magnetic anisotropy of deposited transition metal clusters

    Science.gov (United States)

    Bornemann, S.; Minár, J.; Staunton, J. B.; Honolka, J.; Enders, A.; Kern, K.; Ebert, H.

    2007-12-01

    We present results of magnetic torque calculations using the fully relativistic spin-polarized Korringa-Kohn-Rostoker approach applied to small Co and Fe clusters deposited on the Pt(111) surface. From the magnetic torque one can derive amongst others the magnetic anisotropy energy (MAE). It was found that this approach is numerically much more stable and also computationally less demanding than using the magnetic force theorem that allows to calculate the MAE directly. Although structural relaxation effects were not included our results correspond reasonably well to recent experimental data.

  11. Asymmetric beams and CMB statistical anisotropy

    International Nuclear Information System (INIS)

    Hanson, Duncan; Lewis, Antony; Challinor, Anthony

    2010-01-01

    Beam asymmetries result in statistically anisotropic cosmic microwave background (CMB) maps. Typically, they are studied for their effects on the CMB power spectrum, however they more closely mimic anisotropic effects such as gravitational lensing and primordial power asymmetry. We discuss tools for studying the effects of beam asymmetry on general quadratic estimators of anisotropy, analytically for full-sky observations as well as in the analysis of realistic data. We demonstrate this methodology in application to a recently detected 9σ quadrupolar modulation effect in the WMAP data, showing that beams provide a complete and sufficient explanation for the anomaly.

  12. Uniaxial anisotropy of two-magnon scattering in an ultrathin epitaxial Fe layer on GaAs

    Science.gov (United States)

    Kurebayashi, H.; Skinner, T. D.; Khazen, K.; Olejník, K.; Fang, D.; Ciccarelli, C.; Campion, R. P.; Gallagher, B. L.; Fleet, L.; Hirohata, A.; Ferguson, A. J.

    2013-02-01

    We report an on-chip, electrically detected ferromagnetic resonance study on microbars made from GaAs/Fe(1 nm)/GaAs layers. Our experiments, performed at several different microwave frequencies and static magnetic field directions, enable us to observe a strong in-plane uniaxial anisotropy of the linewidth. We attribute the linewidth anisotropy to the two magnon scattering process, supporting this by calculations of possible linewidth broadening mechanisms. Our findings are useful for designing future high-performance spintronic devices based on nanoscale magnetic structures.

  13. Molecular anisotropy effects in carbon K-edge scattering: depolarized diffuse scattering and optical anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Stone, Kevin H.

    2014-07-14

    Some polymer properties, such as conductivity, are very sensitive to short- and intermediate-range orientational and positional ordering of anisotropic molecular functional groups, and yet means to characterize orientational order in disordered systems are very limited. We demonstrate that resonant scattering at the carbon K-edge is uniquely sensitive to short-range orientation correlations in polymers through depolarized scattering at high momentum transfers, using atactic polystyrene as a well-characterized test system. Depolarized scattering is found to coexist with unpolarized fluorescence, and to exhibit pronounced anisotropy. We also quantify the spatially averaged optical anisotropy from low-angle reflectivity measurements, finding anisotropy consistent with prior visible, x-ray absorption, and theoretical studies. The average anisotropy is much smaller than that in the depolarized scattering and the two have different character. Both measurements exhibit clear spectral signatures from the phenyl rings and the polyethylene-like backbone. Discussion focuses on analysis considerations and prospects for using this depolarized scattering for studies of disorder in soft condensed matter.

  14. Theoretical Compton profile anisotropies in molecules and solids. VI. Compton profile anisotropies and chemical binding

    Energy Technology Data Exchange (ETDEWEB)

    Matcha, R.L.; Pettitt, B.M.

    1979-03-15

    An interesting empirical relationship between zero point Compton profile anisotropies ..delta..J (0) and nuclear charges is noted. It is shown that, for alkali halide molecules AB, to a good approximation ..delta..J (0) =N ln(Z/sub b//Z/sub a/).

  15. Lithospheric and sublithospheric anisotropy beneath the Baltic shield from surface-wave array analysis

    Science.gov (United States)

    Pedersen, Helle A.; Bruneton, Marianne; Maupin, Valérie; Svekalapko Seismic Tomography Working Group

    2006-04-01

    We report measurements of radial and azimuthal anisotropy in the upper mantle beneath southern and central Finland, which we obtained by array analysis of fundamental-mode Rayleigh and Love waves. Azimuthally averaged phase velocities were analysed in the period range 15 to 190 s for Rayleigh waves and 15 to 100 s for Love waves. The azimuthal variation of the Rayleigh wave phase velocities was obtained in the period range 20 to 100 s. The limited depth resolution of fundamental-mode surface waves necessitated strong damping constraints in the inversion for anisotropic parameters. We investigated the effects of non-unicity on the final model by experimenting with varying model geometries. The radial anisotropy beneath Finland can be explained by a lithosphere at least 200 km thick, predominantly (> 50% by volume) composed of olivine crystals having their a-axes randomly distributed in the horizontal plane. On the contrary, the measured lithospheric azimuthal anisotropy is small. This can be reconciled with body-wave observations made in the area that indicate a complex pattern of rapidly varying anisotropy. Below 200-250 km depth, that is below the petrologic lithosphere as revealed by xenolith analyses conducted in the area, the magnitude of the azimuthal anisotropy increases and would be compatible with a mantle containing 15-20% by volume of olivine crystals whose a-axes are coherently aligned in the N-NE direction. The alignment of the a-axes is off the direction of present-day absolute plate motion in either the no-net-rotation or hot-spot reference frame, currently N55-N60. We interpret this mismatch as evidence for a complex convective flow pattern of the mantle beneath the shield, which, by inference, is decoupled from the overlying lithosphere.

  16. Seismic and resistivity anisotropy analysis at the Low-Noise Underground Laboratory (LSBB) of Rustrel (France)

    Science.gov (United States)

    Zeyen, H. J.; Bereš, J.; Gaffet, S.; Sénéchal, G.; Rousset, D.; Pessel, M.

    2011-12-01

    Many geological materials exhibit anisotropic behaviour. A limestone massif, especially if cracked with fractures and faults in a predominant orientation is expected to manifest seismic and electric resistivity anisotropy. Seismic velocity within air- or water-filled cracks is smaller than in the rock matrix. Therefore, the velocity parallel to fractures, controlled mainly by the rock matrix, is expected to be faster than perpendicular to the fractures, where waves have to cross fractures and rock matrix. Seismic and resistivity measurements were conducted in three underground galleries of the Low-Noise Underground Gallery (LSBB) in southern France forming a horse-shoe setting. The galleries are located inside a karstic limestone massif. Around 22500 first arrival travel-times were picked and different types of pole-pole and dipole-dipole resistivity measurement were carried out in parallel. Resistivities and velocities vary strongly with direction of observation. The direction of fast velocities is at right angle with the one of slow velocities, a typical sign for anisotropy. Observation of a system of subparallel fractures allows to approximate the actual rock anisotropy by a horizontal transverse isotropy model. The dataset was treated by different approaches, including simple cosine fit, inversion of average anisotropy parameters using a Monte-Carlo approach, isotropic and anisotropic tomography inversion. All of the above confirm the directions of fast and slow velocities (30°N and 120°N respectively) and an anisotropy of about 10%. Common measurements of seismic and resistivity data at different periods of the year will have the potential to determine quantitatively the fracture density and the free water content in this karst massif.

  17. Mantle Flow Beneath Slow-Spreading Ridges Constrained by Seismic Anisotropy in Atlantic Lithosphere

    Science.gov (United States)

    Gaherty, J.; Dunn, R.

    2003-12-01

    Seismic anisotropy within the oceanic lithosphere provides one of the most direct means to study deformation associated with convection in the mantle. Advection beneath a mid-ocean ridge spreading center deforms the mantle rocks, and as the rocks cool to produce the oceanic lithosphere, they retain a record of this deformation in the form of lattice-preferred orientation (LPO) of olivine grains. LPO direction and strength can be estimated from directional and/or polarization dependence (anisotropy) of seismic wave speeds, and mid-ocean ridge mantle flow properties can be inferred. Mantle flow beneath the slow-spreading Mid-Atlantic Ridge (MAR) is suspected to be strongly three-dimensional due to the influence of hotspots and other thermal variations, and this thermal heterogeneity may be related to buoyancy-driven flow beneath the ridge. This notion is supported by two analyses of lithospheric anisotropy in the Atlantic, which until recently had not been well characterized. Radial anisotropy imaged near the hotspot-influenced Reykjanes Ridge implies a quasi-vertical (rather than horizontal) orientation of the lithospheric fabric. Azimuthal anisotropy within a narrow swatch of western Atlantic lithosphere that was formed via ultra-slow spreading is weaker than that found in the Pacific by a factor of two. Both can be interpreted in terms of buoyancy-driven flow beneath the MAR. Here we extend these results using regional surface-wave analyses of the Atlantic basin. Earthquakes from Atlantic source regions recorded at broad-band seismic instruments located on Atlantic islands and the surrounding margins provide excellent sensitivity to oceanic lithosphere structure, without contamination by continental heterogeneity. By characterizing such structure in both hotspot-influenced (e.g. Azores) and normal slow-spreading lithosphere, and comparing these structures to the Pacific, we evaluate the degree to which spreading rate and/or mantle source temperature control fabric

  18. Variability and origin of seismic anisotropy across eastern Canada: Evidence from shear wave splitting measurements

    Science.gov (United States)

    Darbyshire, F. A.; Bastow, I. D.; Forte, A. M.; Hobbs, T. E.; Calvel, A.; Gonzalez-Monteza, A.; Schow, B.

    2015-12-01

    Measurements of seismic anisotropy in continental regions are frequently interpreted with respect to past tectonic processes, preserved in the lithosphere as "fossil" fabrics. Models of the present-day sublithospheric flow (often using absolute plate motion as a proxy) are also used to explain the observations. Discriminating between these different sources of seismic anisotropy is particularly challenging beneath shields, whose thick (≥200 km) lithospheric roots may record a protracted history of deformation and strongly influence underlying mantle flow. Eastern Canada, where the geological record spans ˜3 Ga of Earth history, is an ideal region to address this issue. We use shear wave splitting measurements of core phases such as SKS to define upper mantle anisotropy using the orientation of the fast-polarization direction ϕ and delay time δt between fast and slow shear wave arrivals. Comparison with structural trends in surface geology and aeromagnetic data helps to determine the contribution of fossil lithospheric fabrics to the anisotropy. We also assess the influence of sublithospheric mantle flow via flow directions derived from global geodynamic models. Fast-polarization orientations are generally ENE-WSW to ESE-WNW across the region, but significant lateral variability in splitting parameters on a ≤100 km scale implies a lithospheric contribution to the results. Correlations with structural geologic and magnetic trends are not ubiquitous, however, nor are correlations with geodynamically predicted mantle flow directions. We therefore consider that the splitting parameters likely record a combination of the present-day mantle flow and older lithospheric fabrics. Consideration of both sources of anisotropy is critical in shield regions when interpreting splitting observations.

  19. Random and uniform anisotropy in soft magnetic nanocrystalline alloys (invited)

    International Nuclear Information System (INIS)

    Flohrer, Sybille; Herzer, Giselher

    2010-01-01

    In amorphous and nanocrystalline transition metal based alloys with low magnetostriction, the soft magnetic properties are mainly determined by magneto-elastic and annealing-induced anisotropies which are uniform on a scale much larger than the exchange correlation length. Though, in the nanocrystalline case, there are situations where the random magneto-crystalline anisotropy of the grains becomes relevant. The present paper surveys the interplay between the random magneto-crystalline and the uniform field-induced anisotropy in nanocrystalline FeCuNbSiB soft magnets. Typical examples where the contribution of the random anisotropy becomes particularly visible in the magnetic domain structure will be reviewed.

  20. Origin of perpendicular magnetic anisotropy in Co/Ni multilayers

    Science.gov (United States)

    Arora, M.; Hübner, R.; Suess, D.; Heinrich, B.; Girt, E.

    2017-07-01

    We studied the variation in perpendicular magnetic anisotropy of (111) textured Au /N ×[Co /Ni ]/Au films as a function of the number of bilayer repeats N . The ferromagnetic resonance and superconducting quantum interference device magnetometer measurements show that the perpendicular magnetic anisotropy of Co/Ni multilayers first increases with N for N ≤10 and then moderately decreases for N >10 . The model we propose reveals that the decrease of the anisotropy for N reduction in the magnetoelastic and magnetocrystalline anisotropies. A moderate decrease in the perpendicular magnetic anisotropy for N >10 is due to the reduction in the magnetocrystalline and the surface anisotropies. To calculate the contribution of magnetoelastic anisotropy in the Co/Ni multilayers, in-plane and out-of-plane x-ray diffraction measurements are performed to determine the spacing between Co/Ni (111) and (220) planes. The magnetocrystalline bulk anisotropy is estimated from the difference in the perpendicular and parallel g factors of Co/Ni multilayers that are measured using the in-plane and out-of-plane ferromagnetic resonance measurements. Transmission electron microscopy has been used to estimate the multilayer film roughness. These values are used to calculate the roughness-induced surface and magnetocrystalline anisotropy coefficients as a function of N .

  1. Electrical resistivity characterization of anisotropy in the Biscayne Aquifer.

    Science.gov (United States)

    Yeboah-Forson, Albert; Whitman, Dean

    2014-01-01

    Electrical anisotropy occurs when electric current flow varies with azimuth. In porous media, this may correspond to anisotropy in the hydraulic conductivity resulting from sedimentary fabric, fractures, or dissolution. In this study, a 28-electrode resistivity imaging system was used to investigate electrical anisotropy at 13 sites in the Biscayne Aquifer of SE Florida using the rotated square array method. The measured coefficient of electrical anisotropy generally ranged from 1.01 to 1.12 with values as high as 1.36 found at one site. The observed electrical anisotropy was used to estimate hydraulic anisotropy (ratio of maximum to minimum hydraulic conductivity) which ranged from 1.18 to 2.83. The largest values generally were located on the Atlantic Coastal Ridge while the lowest values were in low elevation areas on the margin of the Everglades to the west. The higher values of anisotropy found on the ridge may be due to increased dissolution rates of the oolitic facies of the Miami formation limestone compared with the bryozoan facies to the west. The predominate trend of minimum resistivity and maximum hydraulic conductivity was E-W/SE-NW beneath the ridge and E-W/SW-NE farther west. The anisotropy directions are similar to the predevelopment groundwater flow direction as indicated in published studies. This suggests that the observed anisotropy is related to the paleo-groundwater flow in the Biscayne Aquifer. © 2013, National Ground Water Association.

  2. Magnetic anisotropy of two-dimensional nanostructures: Transition-metal triangular stripes

    International Nuclear Information System (INIS)

    Dorantes-Davila, J.; Villasenor-Gonzalez, P.; Pastor, G.M.

    2005-01-01

    The magnetic anisotropy energy (MAE) of one-dimensional stripes having infinite length and triangular lateral structure are investigated in the framework of a self-consistent tight-binding method. One observes discontinuous changes in the easy magnetization direction along the crossover from one to two dimensions. The MAE oscillates as a function of stripe width and depends strongly on the considered transition metal (TM). The MAE of the two-leg ladder is strongly reduced as compared to that of the monoatomic chain and the convergence to the two-dimensional limit is rather slow

  3. Magnetic anisotropy of two-dimensional nanostructures: Transition-metal triangular stripes

    Energy Technology Data Exchange (ETDEWEB)

    Dorantes-Davila, J. [Instituto de Fisica, Universidad Autonoma de San Luis Potosi, San Luis Potosi (Mexico)]. E-mail: jdd@ifisica.uaslp.mx; Villasenor-Gonzalez, P. [Instituto de Fisica, Universidad Autonoma de San Luis Potosi, San Luis Potosi (Mexico); Pastor, G.M. [Laboratoire de Physique Quantique, Centre National de la Recherche Scientifique, Universite Paul Sabatier, Toulouse (France)

    2005-07-15

    The magnetic anisotropy energy (MAE) of one-dimensional stripes having infinite length and triangular lateral structure are investigated in the framework of a self-consistent tight-binding method. One observes discontinuous changes in the easy magnetization direction along the crossover from one to two dimensions. The MAE oscillates as a function of stripe width and depends strongly on the considered transition metal (TM). The MAE of the two-leg ladder is strongly reduced as compared to that of the monoatomic chain and the convergence to the two-dimensional limit is rather slow.

  4. Scanning anisotropy parameters in complex media

    KAUST Repository

    Alkhalifah, Tariq Ali

    2011-03-21

    Parameter estimation in an inhomogeneous anisotropic medium offers many challenges; chief among them is the trade-off between inhomogeneity and anisotropy. It is especially hard to estimate the anisotropy anellipticity parameter η in complex media. Using perturbation theory and Taylor’s series, I have expanded the solutions of the anisotropic eikonal equation for transversely isotropic (TI) media with a vertical symmetry axis (VTI) in terms of the independent parameter η from a generally inhomogeneous elliptically anisotropic medium background. This new VTI traveltime solution is based on a set of precomputed perturbations extracted from solving linear partial differential equations. The traveltimes obtained from these equations serve as the coefficients of a Taylor-type expansion of the total traveltime in terms of η. Shanks transform is used to predict the transient behavior of the expansion and improve its accuracy using fewer terms. A homogeneous medium simplification of the expansion provides classical nonhyperbolic moveout descriptions of the traveltime that are more accurate than other recently derived approximations. In addition, this formulation provides a tool to scan for anisotropic parameters in a generally inhomogeneous medium background. A Marmousi test demonstrates the accuracy of this approximation. For a tilted axis of symmetry, the equations are still applicable with a slightly more complicated framework because the vertical velocity and δ are not readily available from the data.

  5. Effects of pressure anisotropy on plasma transport

    International Nuclear Information System (INIS)

    Zawaideh, E.; Najmabadi, F.; Conn, R.W.

    1986-03-01

    In a recent paper a new set of generalized two-field equations is derived which describes plasma transport along the field lines of a space and time dependent magnetic field. These equations are valid for collisional to weakly collisional plasmas; they reduce to the conventional fluid equations of Braginskii for highly collisional plasmas. An important feature of these equations is that the anisotropy in the ion pressure is explicitly included. In this paper, these generalized transport equations are applied to a model problem of plasma flow through a magnetic mirror field. The profiles of the plasma parameters (density, flow speed, and pressures) are numerically calculated for plasma in different collisionality regimes. These profiles are explained by examining the competing terms in the transport equation. The pressure anisotropy is found to profoundly impact the plasma flow behavior. As a result, the new generalized equations predict flow behavior more accurately than the conventional transport equations. A large density and pressure drop is predicted as the flow passes through a magnetic mirror. Further, the new equations uniquely predict oscillations in the density profile, an effect missing in results from the conventional equations

  6. Crystallographic texture and mechanical anisotropy of zircaloys

    International Nuclear Information System (INIS)

    Hussien, S.A.

    1987-01-01

    Hexagonal-closed-packed metals are inherently anisotropic, and deformation during processing leads to the development of preferred orientation or texture in the finished product. Tube Reduced Extrusions (TREXs) are an intermediate product in the production of zircaloy canning tubes for nuclear reactors. The objective of this research has been to study the mechanical anisotropy which has a direct relation to the formability of Zircaloy TREXs. Anisotropy parameters (R and P) in the modified Hills equation were investigated. The use of the impression test for measuring R and P under different annealing temperatures, test temperatures and strain rates, and the grid-analysis technique for measuring R and P gradients through the TREX thickness are demonstrated. The mechanical-test results are compared with the predictions of the Bishop-Hill model using the quantitative orientation distribution function. There is a good agreement between the model prediction and the mechanical-test data. The value of R was found to be insensitive to the strain rate, test temperature, annealing temperature, and texture gradient. The value of P was found to increase with the annealing temperature within the recrystallization range and to be relatively insensitive elsewhere, to decrease with increasing test temperature and to be considerable sensitive to texture gradient

  7. Texture and Elastic Anisotropy of Mantle Olivine

    Science.gov (United States)

    Nikitin, A. N.; Ivankina, T. I.; Bourilitchev, D. E.; Klima, K.; Locajicek, T.; Pros, Z.

    Eight olivine rock samples from different European regions were collected for neu- tron texture analyses and for P-wave velocity measurements by means of ultrasonic sounding at various confining pressures. The orientation distribution functions (ODFs) of olivine were determined and pole figures of the main crystallographic planes were calculated. The spatial P-wave velocity distributions were determined at confining pressures from 0.1 to 400 MPa and modelled from the olivine textures. In dependence upon the type of rock (xenolith or dunite) different behavior of both the P-wave veloc- ity distributions and the anisotropy coefficients with various confining pressures was observed. In order to explain the interdependence of elastic anisotropy and hydrostatic pressure, a model for polycrystalline olivine rocks was suggested, which considers the influence of the crystallographic and the mechanical textures on the elastic behaviour of the polycrystal. Since the olivine texture depends upon the active slip systems and the deformation temperature, neutron texture analyses enable us to estimate depth and thermodynamical conditions during texture formation.

  8. Enhanced thermal photon and dilepton production in strongly coupled = 4 SYM plasma in strong magnetic field

    Science.gov (United States)

    Mamo, Kiminad A.

    2013-08-01

    We calculate the DC conductivity tensor of strongly coupled = 4 super-Yang-Mills (SYM) plasma in a presence of a strong external magnetic field B ≫ T 2 by using its gravity dual and employing both the RG flow approach and membrane paradigm which give the same results. We find that, since the magnetic field B induces anisotropy in the plasma, different components of the DC conductivity tensor have different magnitudes depending on whether its components are in the direction of the magnetic field B. In particular, we find that a component of the DC conductivity tensor in the direction of the magnetic field B increases linearly with B while the other components (which are not in the direction of the magnetic field B) are independent of it. These results are consistent with the lattice computations of the DC conductivity tensor of the QCD plasma in an external magnetic field B. Using the DC conductivity tensor, we calculate the soft or low-frequency thermal photon and dilepton production rates of the strongly coupled = 4 SYM plasma in the presence of the strong external magnetic field B ≫ T 2. We find that the strong magnetic field B enhances both the thermal photon and dilepton production rates of the strongly coupled = 4 SYM plasma in a qualitative agreement with the experimentally observed enhancements at the heavy-ion collision experiments.

  9. Strongly Correlated Topological Insulators

    Science.gov (United States)

    2016-02-03

    Strongly Correlated Topological Insulators In the past year, the grant was used for work in the field of topological phases, with emphasis on finding...surface of topological insulators. In the past 3 years, we have started a new direction, that of fractional topological insulators. These are materials...in which a topologically nontrivial quasi-flat band is fractionally filled and then subject to strong interactions. The views, opinions and/or

  10. Magnetic anisotropy induced by crystallographic orientation and morphological alignment in directionally-solidified eutectic Mn-Sb alloy

    International Nuclear Information System (INIS)

    Lou, Chang-Sheng; Liu, Tie; Dong, Meng; Wu, Chun; Shao, Jian-Guo; Wang, Qiang

    2017-01-01

    The influences of the crystallographic orientation and morphological alignment upon the magnetic anisotropic behavior of polycrystalline materials were investigated. Microstructures obtained in eutectic Mn-Sb alloys via directional solidification simultaneously displayed crystallographic orientation and morphological alignment. Both the crystallographic orientation and the morphological alignment were able to induce magnetic anisotropy in the alloys, wherein the influence of the crystallographic orientation and the morphological alignment upon the magnetic anisotropic behavior of the alloys strongly depended upon their directions and exhibited either mutual promotion or competition. These findings may provide useful guidance for the fabrication design of functional magnetic materials. - Highlights: • We study effects of orientation in crystal and morphology on magnetic anisotropy. • Both orientation in crystal and morphology can induce magnetic anisotropy. • Their effects depend on direction and exhibit either mutual promotion or competition.

  11. Tunable exchange bias-like effect in patterned hard-soft two-dimensional lateral composites with perpendicular magnetic anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Hierro-Rodriguez, A., E-mail: ahierro@fc.up.pt; Alvarez-Prado, L. M.; Martín, J. I.; Alameda, J. M. [Departamento de Física, Universidad de Oviedo, C/Calvo Sotelo S/N, 33007 Oviedo (Spain); Centro de Investigación en Nanomateriales y Nanotecnología—CINN (CSIC—Universidad de Oviedo—Principado de Asturias), Parque Tecnológico de Asturias, 33428 Llanera (Spain); Teixeira, J. M. [IN-IFIMUP, Departamento de Física e Astronomia, Faculdade de Ciências, Universidade do Porto, Rua Campo Alegre 687, 4169-007 Porto (Portugal); Vélez, M. [Departamento de Física, Universidad de Oviedo, C/Calvo Sotelo S/N, 33007 Oviedo (Spain)

    2014-09-08

    Patterned hard-soft 2D magnetic lateral composites have been fabricated by e-beam lithography plus dry etching techniques on sputter-deposited NdCo{sub 5} thin films with perpendicular magnetic anisotropy. Their magnetic behavior is strongly thickness dependent due to the interplay between out-of-plane anisotropy and magnetostatic energy. Thus, the spatial modulation of thicknesses leads to an exchange coupled system with hard/soft magnetic regions in which rotatable anisotropy of the thicker elements provides an extra tool to design the global magnetic behavior of the patterned lateral composite. Kerr microscopy studies (domain imaging and magneto-optical Kerr effect magnetometry) reveal that the resulting hysteresis loops exhibit a tunable exchange bias-like shift that can be switched on/off by the applied magnetic field.

  12. Influence of substitutional pairs of cobalt atoms on the magnetocrystalline anisotropy of cobalt-rich rare-earth compounds

    International Nuclear Information System (INIS)

    Deportes, J.; Givord, D.; Lemaire, R.; Nagai, H.; Yang, Y.T.

    1976-01-01

    The crystallographic structures of cobalt-rich rare-earth (R) compounds are determined by the ordering of substitutional pairs of Co atoms in the same hexagonal RCo 5 basic structure. However, RCo 5 compounds are metastable at room temperature and contain some disordered substitutions. These substitutions induce a large decrease of the anisotropy in Smsub(1-s)2Cosub(s)Co 5 and Ysub(1-s)2Cosub(s)Co 5 alloys. Consequently, with each substitution there is associated a large anisotropy with a negative value of K 1 . A comparison with the strong uniaxial anisotropy of the RCo 5 basic structure allows one to explain the changes of the direction of easy magnetization in Y 2 (Cosub(1-x)Msub(x)) alloys, and the differences in the coercivity of RCo 5 compounds. (Auth.)

  13. Strong Cosmic Censorship

    Science.gov (United States)

    Isenberg, James

    2017-01-01

    The Hawking-Penrose theorems tell us that solutions of Einstein's equations are generally singular, in the sense of the incompleteness of causal geodesics (the paths of physical observers). These singularities might be marked by the blowup of curvature and therefore crushing tidal forces, or by the breakdown of physical determinism. Penrose has conjectured (in his `Strong Cosmic Censorship Conjecture`) that it is generically unbounded curvature that causes singularities, rather than causal breakdown. The verification that ``AVTD behavior'' (marked by the domination of time derivatives over space derivatives) is generically present in a family of solutions has proven to be a useful tool for studying model versions of Strong Cosmic Censorship in that family. I discuss some of the history of Strong Cosmic Censorship, and then discuss what is known about AVTD behavior and Strong Cosmic Censorship in families of solutions defined by varying degrees of isometry, and discuss recent results which we believe will extend this knowledge and provide new support for Strong Cosmic Censorship. I also comment on some of the recent work on ``Weak Null Singularities'', and how this relates to Strong Cosmic Censorship.

  14. Nonmonotonic anisotropy in charge conduction induced by antiferrodistortive transition in metallic SrTiO3

    Science.gov (United States)

    Tao, Qian; Loret, Bastien; Xu, Bin; Yang, Xiaojun; Rischau, Carl Willem; Lin, Xiao; Fauqué, Benoît; Verstraete, Matthieu J.; Behnia, Kamran

    2016-07-01

    Cubic SrTiO3 becomes tetragonal below 105 K. The antiferrodistortive (AFD) distortion leads to clockwise and counterclockwise rotation of adjacent TiO6 octahedra. This insulator becomes a metal upon the introduction of extremely low concentration of n -type dopants. However, signatures of the structural phase transition in charge conduction have remained elusive. Employing the Montgomery technique, we succeed in resolving the anisotropy of charge conductivity induced by the AFD transition, in the presence of different types of dopants. We find that the slight lattice distortion (liquids, the anisotropy has opposite signs for elastic and inelastic scattering. Increasing the concentration of dopants leads to a drastic shift in the temperature of the AFD transition either upward or downward. The latter result puts strong constraints on any hypothetical role played by the AFD soft mode in the formation of Cooper pairs and the emergence of superconductivity in SrTiO3.

  15. Large diffusion anisotropy and orientation sorting of phosphorene nanoflakes under a temperature gradient.

    Science.gov (United States)

    Cheng, Yuan; Zhang, Gang; Zhang, Yingyan; Chang, Tienchong; Pei, Qing-Xiang; Cai, Yongqing; Zhang, Yong-Wei

    2018-01-25

    We perform molecular dynamics simulations to investigate the motion of phosphorene nanoflakes on a large graphene substrate under a thermal gradient. It is found that the atomic interaction between the graphene substrate and the phosphorene nanoflake generates distinct rates of motion for phosphorene nanoflakes with different orientations. Remarkably, for square phosphorene nanoflakes, the motion of zigzag-oriented nanoflakes is 2-fold faster than those of armchair-oriented and randomly-oriented nanoflakes. This large diffusion anisotropy suggests that sorting of phosphorene nanoflakes into specific orientations can be realized by a temperature gradient. The findings here provide interesting insights into strong molecular diffusion anisotropy and offer a novel route for manipulating two-dimensional materials.

  16. Origin of Perpendicular Magnetic Anisotropy and Large Orbital Moment in Fe Atoms on MgO

    Science.gov (United States)

    Baumann, S.; Donati, F.; Stepanow, S.; Rusponi, S.; Paul, W.; Gangopadhyay, S.; Rau, I. G.; Pacchioni, G. E.; Gragnaniello, L.; Pivetta, M.; Dreiser, J.; Piamonteze, C.; Lutz, C. P.; Macfarlane, R. M.; Jones, B. A.; Gambardella, P.; Heinrich, A. J.; Brune, H.

    2015-12-01

    We report on the magnetic properties of individual Fe atoms deposited on MgO(100) thin films probed by x-ray magnetic circular dichroism and scanning tunneling spectroscopy. We show that the Fe atoms have strong perpendicular magnetic anisotropy with a zero-field splitting of 14.0 ±0.3 meV /atom . This is a factor of 10 larger than the interface anisotropy of epitaxial Fe layers on MgO and the largest value reported for Fe atoms adsorbed on surfaces. The interplay between the ligand field at the O adsorption sites and spin-orbit coupling is analyzed by density functional theory and multiplet calculations, providing a comprehensive model of the magnetic properties of Fe atoms in a low-symmetry bonding environment.

  17. Incorporating tissue anisotropy and heterogeneity in finite element models of trabecular bone altered predicted local stress distributions.

    Science.gov (United States)

    Hammond, Max A; Wallace, Joseph M; Allen, Matthew R; Siegmund, Thomas

    2018-04-01

    Trabecular bone is composed of organized mineralized collagen fibrils, which results in heterogeneous and anisotropic mechanical properties at the tissue level. Recently, biomechanical models computing stresses and strains in trabecular bone have indicated a significant effect of tissue heterogeneity on predicted stresses and strains. However, the effect of the tissue-level mechanical anisotropy on the trabecular bone biomechanical response is unknown. Here, a computational method was established to automatically impose physiologically relevant orientation inherent in trabecular bone tissue on a trabecular bone microscale finite element model. Spatially varying tissue-level anisotropic elastic properties were then applied according to the bone mineral density and the local tissue orientation. The model was used to test the hypothesis that anisotropy in both homogeneous and heterogeneous models alters the predicted distribution of stress invariants. Linear elastic finite element computations were performed on a 3 mm cube model isolated from a microcomputed tomography scan of human trabecular bone from the distal femur. Hydrostatic stress and von Mises equivalent stress were recorded at every element, and the distributions of these values were analyzed. Anisotropy reduced the range of hydrostatic stress in both tension and compression more strongly than the associated increase in von Mises equivalent stress. The effect of anisotropy was independent of the spatial redistribution high compressive stresses due to tissue elastic heterogeneity. Tissue anisotropy and heterogeneity are likely important mechanisms to protect bone from failure and should be included for stress analyses in trabecular bone.

  18. The role of layer-induced anisotropy in seismic exploration

    NARCIS (Netherlands)

    Hake, J.H.

    1992-01-01

    184In this thesis we focus on anisotropy caused by fine layering. We analyse the conditions that must be satisfied so that fine layering is equivalent to anisotropy. In the long-wavelength (or quasi-static) approximation an interval of thickness H, consisting of a sequence of layers, is

  19. The role of layer-induced anisotropy in seismic exploration

    NARCIS (Netherlands)

    Hake, J.H.

    1993-01-01

    In this thesis we focus on anisotropy caused by fine layering. We analyse the conditions that must be satisfied so that fine layering is equivalent to anisotropy. In the long-wavelength (or quasi-static) approximation an interval of thickness H, consisting of a sequence of layers, is effectively

  20. Stability analysis of sandy slope considering anisotropy effect in ...

    Indian Academy of Sciences (India)

    Studying the role of anisotropy in response to geotechnical structure requires the constitutive model which comprehensively accounts the effect of anisotropy on the mechanical behavior of soil. Casagrande & Carillo (1944) have presented a closed-form equation for relating between the soil cohesion in Mohr–Columb ...

  1. Magnetic anisotropy of YFe.sub.3./sub. compound

    Czech Academy of Sciences Publication Activity Database

    Bolyachkin, A.S.; Neznakhin, D.S.; Garaeva, T.V.; Andreev, Alexander V.; Bartashevich, M. I.

    2017-01-01

    Roč. 426, Mar (2017), s. 740-743 ISSN 0304-8853 R&D Projects: GA ČR GA16-03593S Institutional support: RVO:68378271 Keywords : magnetic anisotropy * magnetization anisotropy * single crystal Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 2.630, year: 2016

  2. Tuning the Magnetic Anisotropy at a Molecule-Metal Interface

    DEFF Research Database (Denmark)

    Bairagi, K.; Bellec, A.; Repain, V.

    2015-01-01

    We demonstrate that a C60 overlayer enhances the perpendicular magnetic anisotropy of a Co thin film, inducing an inverse spin reorientation transition from in plane to out of plane. The driving force is the C60/Co interfacial magnetic anisotropy that we have measured quantitatively in situ...

  3. Relationship between electron field-aligned anisotropy and dawn-dusk magnetic field: Nine years of Cluster observations in the Earth magnetotail

    Science.gov (United States)

    Yushkov, E.; Petrukovich, A.; Artemyev, A.; Nakamura, R.

    2017-09-01

    We investigate the distribution and possible origins of thermal anisotropic electrons in the Earth's magnetotail, using 9 years of Cluster observations. We mainly focus on relation between electron anisotropy and Bz and By magnetic field components (in GSM coordinates). The anisotropy of electron population is characterized by temperature ratio T∥/T⊥ and by the maximum of phase space density ratio F∥/F⊥ (∥ and ⊥ are relative to the background magnetic field). The population identified by large F∥/F⊥ is organized as short-time (dozens of seconds) bursts with enhanced F∥ and can be observed even in the plasma sheet with small T∥/T⊥. The thermal anisotropy T∥/T⊥ is larger for time intervals characterized by stronger Bz and By: the strong By corresponds to the T∥/T⊥ peak around the magnetotail neutral plane Bx=0, whereas the strong Bz corresponds to larger T∥/T⊥ with a flat profile across the magnetotail. There is a dawn-dusk asymmetry: large T∥/T⊥ corresponds mostly to strong Bz at the dusk flank and to strong By at the dawn flank. Using these differences of the electron anisotropy dependence on By and Bz, we discuss two possible mechanisms responsible for the anisotropy formation.

  4. Strong Arcwise Connectedness

    OpenAIRE

    Espinoza, Benjamin; Gartside, Paul; Kovan-Bakan, Merve; Mamatelashvili, Ana

    2012-01-01

    A space is `n-strong arc connected' (n-sac) if for any n points in the space there is an arc in the space visiting them in order. A space is omega-strong arc connected (omega-sac) if it is n-sac for all n. We study these properties in finite graphs, regular continua, and rational continua. There are no 4-sac graphs, but there are 3-sac graphs and graphs which are 2-sac but not 3-sac. For every n there is an n-sac regular continuum, but no regular continuum is omega-sac. There is an omega-sac ...

  5. Abortion: Strong's counterexamples fail

    DEFF Research Database (Denmark)

    Di Nucci, Ezio

    2009-01-01

    This paper shows that the counterexamples proposed by Strong in 2008 in the Journal of Medical Ethics to Marquis's argument against abortion fail. Strong's basic idea is that there are cases--for example, terminally ill patients--where killing an adult human being is prima facie seriously morally......'s scenarios have some valuable future or admitted that killing them is not seriously morally wrong. Finally, if "valuable future" is interpreted as referring to objective standards, one ends up with implausible and unpalatable moral claims....

  6. Non-Gaussianity and the Cosmic Microwave Background Anisotropies

    CERN Document Server

    Bartolo, N; Riotto, A

    2010-01-01

    We review in a pedagogical way the present status of the impact of non-Gaussianity (NG) on the Cosmic Microwave Background (CMB) anisotropies. We first show how to set the initial conditions at second-order for the (gauge invariant) CMB anisotropies when some primordial NG is present. However, there are many sources of NG in CMB anisotropies, beyond the primordial one, which can contaminate the primordial signal. We mainly focus on the NG generated from the post-inflationary evolution of the CMB anisotropies at second-order in perturbation theory at large and small angular scales, such as the ones generated at the recombination epoch. We show how to derive the equations to study the second-order CMB anisotropies and provide analytical computations to evaluate their contamination to primordial NG (complemented with numerical examples). We also offer a brief summary of other secondary effects. This review requires basic knowledge of the theory of cosmological perturbations at the linear level.

  7. Modeling, analysis, and visualization of anisotropy

    CERN Document Server

    Özarslan, Evren; Hotz, Ingrid

    2017-01-01

    This book focuses on the modeling, processing and visualization of anisotropy, irrespective of the context in which it emerges, using state-of-the-art mathematical tools. As such, it differs substantially from conventional reference works, which are centered on a particular application. It covers the following topics: (i) the geometric structure of tensors, (ii) statistical methods for tensor field processing, (iii) challenges in mapping neural connectivity and structural mechanics, (iv) processing of uncertainty, and (v) visualizing higher-order representations. In addition to original research contributions, it provides insightful reviews. This multidisciplinary book is the sixth in a series that aims to foster scientific exchange between communities employing tensors and other higher-order representations of directionally dependent data. A significant number of the chapters were co-authored by the participants of the workshop titled Multidisciplinary Approaches to Multivalued Data: Modeling, Visualization,...

  8. Variable Azimuthal Anisotropy in Earth's Lowermost Mantle

    Science.gov (United States)

    Garnero, Edward J.; Maupin, Valérie; Lay, Thorne; Fouch, Matthew J.

    2004-10-01

    A persistent reversal in the expected polarity of the initiation of vertically polarized shear waves that graze the D'' layer (the layer at the boundary between the outer core and the lower mantle of Earth) in some regions starts at the arrival time of horizontally polarized shear waves. Full waveform modeling of the split shear waves for paths beneath the Caribbean requires azimuthal anisotropy at the base of the mantle. Models with laterally coherent patterns of transverse isotropy with the hexagonal symmetry axis of the mineral phases tilted from the vertical by as much as 20° are consistent with the data. Small-scale convection cells within the mantle above the D'' layer may cause the observed variations by inducing laterally variable crystallographic or shape-preferred orientation in minerals in the D'' layer.

  9. Signatures of Beam - and Anisotropy Driven Oscillitons

    Science.gov (United States)

    Sauer, K.; Dubinin, E.; McKenzie, J. F.

    Oscillitons represent a new class of stationary nonlinear waves, first found in bi-ion plasmas (Sauer et al., 1991) where mode splitting of the `individual' wave modes leads to conditions for phase- and group-standing waves near the `crossing points'. The corresponding structures have signatures of the usual solitons, superimposed by spatial oscillations. Oscillitons may also occur in single-ion plasmas, e.g. in the elec- tron whistler branch. The characteristic features of different types of oscillitons under realistic conditions in space plasmas including damping, beams and anisotropies are analyzed. Relevant mechanisms of coherent waves observed in different frequency ranges (Lion Roars at Earth, ion cyclotron waves near Io and Mars) are discussed.

  10. A strong comeback

    International Nuclear Information System (INIS)

    Marier, D.

    1992-01-01

    This article presents the results of a financial rankings survey which show a strong economic activity in the independent energy industry. The topics of the article include advisor turnover, overseas banks, and the increase in public offerings. The article identifies the top project finance investors for new projects and restructurings and rankings for lenders

  11. Theoretical Compton profile anisotropies in molecules and solids. IV. Parallel--perpendicular anisotropies in alkali fluoride molecules

    Energy Technology Data Exchange (ETDEWEB)

    Matcha, R.L.; Pettitt, B.M.; Ramirez, B.I.; McIntire, W.R.

    1979-07-15

    Calculations of Compton profiles and parallel--perpendicular anisotropies in alkali fluorides are presented and analyzed in terms of molecular charge distributions and wave function character. It is found that the parallel profile associated with the valence pi orbital is the principal factor determining the relative shapes of the total profile anisotropies in the low momentum region.

  12. Daytime Thermal Anisotropy of Urban Neighbourhoods: Morphological Causation

    Directory of Open Access Journals (Sweden)

    E. Scott Krayenhoff

    2016-01-01

    Full Text Available Surface temperature is a key variable in boundary-layer meteorology and is typically acquired by remote observation of emitted thermal radiation. However, the three-dimensional structure of cities complicates matters: uneven solar heating of urban facets produces an “effective anisotropy” of surface thermal emission at the neighbourhood scale. Remotely-sensed urban surface temperature varies with sensor view angle as a consequence. The authors combine a microscale urban surface temperature model with a thermal remote sensing model to predict the effective anisotropy of simplified neighbourhood configurations. The former model provides detailed surface temperature distributions for a range of “urban” forms, and the remote sensing model computes aggregate temperatures for multiple view angles. The combined model’s ability to reproduce observed anisotropy is evaluated against measurements from a neighbourhood in Vancouver, Canada. As in previous modeling studies, anisotropy is underestimated. Addition of moderate coverages of small (sub-facet scale structure can account for much of the missing anisotropy. Subsequently, over 1900 sensitivity simulations are performed with the model combination, and the dependence of daytime effective thermal anisotropy on diurnal solar path (i.e., latitude and time of day and blunt neighbourhood form is assessed. The range of effective anisotropy, as well as the maximum difference from nadir-observed brightness temperature, peak for moderate building-height-to-spacing ratios (H/W, and scale with canyon (between-building area; dispersed high-rise urban forms generate maximum anisotropy. Maximum anisotropy increases with solar elevation and scales with shortwave irradiance. Moreover, it depends linearly on H/W for H/W < 1.25, with a slope that depends on maximum off-nadir sensor angle. Decreasing minimum brightness temperature is primarily responsible for this linear growth of maximum anisotropy. These

  13. Effects of electron pressure anisotropy on current sheet configuration

    International Nuclear Information System (INIS)

    Artemyev, A. V.; Angelopoulos, V.; Runov, A.; Vasko, I. Y.

    2016-01-01

    Recent spacecraft observations in the Earth's magnetosphere have demonstrated that the magnetotail current sheet can be supported by currents of anisotropic electron population. Strong electron currents are responsible for the formation of very thin (intense) current sheets playing the crucial role in stability of the Earth's magnetotail. We explore the properties of such thin current sheets with hot isotropic ions and cold anisotropic electrons. Decoupling of the motions of ions and electrons results in the generation of a polarization electric field. The distribution of the corresponding scalar potential is derived from the electron pressure balance and the quasi-neutrality condition. We find that electron pressure anisotropy is partially balanced by a field-aligned component of this polarization electric field. We propose a 2D model that describes a thin current sheet supported by currents of anisotropic electrons embedded in an ion-dominated current sheet. Current density profiles in our model agree well with THEMIS observations in the Earth's magnetotail.

  14. Strong Electroweak Symmetry Breaking

    CERN Document Server

    Grinstein, Benjamin

    2011-01-01

    Models of spontaneous breaking of electroweak symmetry by a strong interaction do not have fine tuning/hierarchy problem. They are conceptually elegant and use the only mechanism of spontaneous breaking of a gauge symmetry that is known to occur in nature. The simplest model, minimal technicolor with extended technicolor interactions, is appealing because one can calculate by scaling up from QCD. But it is ruled out on many counts: inappropriately low quark and lepton masses (or excessive FCNC), bad electroweak data fits, light scalar and vector states, etc. However, nature may not choose the minimal model and then we are stuck: except possibly through lattice simulations, we are unable to compute and test the models. In the LHC era it therefore makes sense to abandon specific models (of strong EW breaking) and concentrate on generic features that may indicate discovery. The Technicolor Straw Man is not a model but a parametrized search strategy inspired by a remarkable generic feature of walking technicolor,...

  15. Ambient noise tomography of Ecuador: Fore- and back-arc velocity structure and radial anisotropy

    Science.gov (United States)

    Lynner, C.; Beck, S. L.; Porritt, R.; Meltzer, A.; Alvarado, A. P.; Gabriela, P.; Ruiz, M. C.; Hoskins, M.; Stachnik, J.; Rietbrock, A.; Leon-Rios, S.; Regnier, M. M.; Agurto-Detzel, H.; Font, Y.; Charvis, P.

    2017-12-01

    In northern South America, the oceanic Nazca plate subducts beneath the South American continent, giving rise to the high mountains of the northern Andes. The Ecuador subduction zone has a history of large megathrust earthquakes, most recently the Mw=7.8 April 16, 2016, Pedernales earthquake. The volcanic arc in Ecuador is broad with active volcanoes along both the western and eastern cordilleras. Many of these volcanoes surround the city of Quito putting millions of people at risk. A recent international broadband aftershock deployment was conducted for approximately one year after the Pedernales mainshock and this data combined with a sub-set of data from from the permanent IGEPN national network provide an ideal data set to use for ambient noise tomography (ANT) to constrain absolute Vsh and Vsv across Ecuador. ANT studies use noise-generated surface wave dispersion measurements to invert for 3D shear velocity in the crust. Having a precise understanding of crustal velocity structure is necessary to advance a number of projects, including better earthquake locations of the April 16, 2016 Pedernales-earthquake aftershock sequence and identifying large-scale partial melt zones associated with the active volcanic arc. The majority of ANT studies use only Rayleigh waves to constrain Vsv structure. Initial Rayleigh wave ANT results, using periods between 8 and 40 seconds, show a fast phase velocities for the forearc and much slower phase velocities for the high elevation volcanic arc. Including Love wave dispersion measurements can improve overall crustal velocity models, as well as provide constraints on radial anisotropy. Radial anisotropy can develop in a variety of ways but most typically arises from the deformation-induced alignment of anisotropic minerals. Radial anisotropy, therefore, can inform on patterns of ductile crustal flow. Strong radial anisotropy at mid-crustal depths from ANT has already been observed south of Ecuador, in the Central Andean Plateau

  16. Magnetic Anisotropy as an aid to Identifying CRM and DRM in Red Sedimentary Rocks

    Science.gov (United States)

    Kodama, K. P.; Dekkers, M. J.

    2004-12-01

    To evaluate the usefulness of magnetic anisotropy for determining the origin of the natural remanent magnetization (NRM) in red sedimentary rocks, several new remanence anisotropy measurement techniques were investigated. The goal of the work was an accurate separation of the remanence anisotropy of magnetite and hematite in the same sedimentary rock sample. In one technique, Tertiary red and grey sedimentary rock samples from the Orera section of Spain were exposed to 13 T fields in 9 different orientations. This work was done at the High Field Magnet Laboratory of Radboud University, Nijmegen, The Netherlands. In each orientation, alternating field (af) demagnetization was used to separate the magnetite and hematite contributions to the high field isothermal remanent magnetization (IRM). Tensor subtraction was used to separate the magnetite and hematite magnetic anisotropies. Geologically interpretable fabrics did not result, probably because of the presence of goethite. In the second technique, also applied to samples from Orera, an anisotropy of anhysteretic remanence (AAR) was applied in af fields up to 240 mT to directly measure the fabric of the magnetite in the sample. IRMs applied in 2T fields followed by 240 mT af demagnetization, and thermal demagnetization at 90° C to remove the goethite contribution, were used to independently measure the hematite fabric in the same samples. This approach gave magnetic fabrics with minimum principal axes perpendicular to bedding, suggesting that the hematite and magnetite grains in the Orera samples both carry a depositional remanent magnetization (DRM). In a third experiment, IRMs applied in 13 T fields were used to measure the magnetic fabric of samples from the Dome de Barrot area in France. These samples had been demonstrated to have hematite as their only magnetic mineral. The fabrics that resulted were geologically interpretable, showing a strong NW-SE horizontal lineation consistent with AMS fabrics measured in

  17. Plasmons in strong superconductors

    International Nuclear Information System (INIS)

    Baldo, M.; Ducoin, C.

    2011-01-01

    We present a study of the possible plasmon excitations that can occur in systems where strong superconductivity is present. In these systems the plasmon energy is comparable to or smaller than the pairing gap. As a prototype of these systems we consider the proton component of Neutron Star matter just below the crust when electron screening is not taken into account. For the realistic case we consider in detail the different aspects of the elementary excitations when the proton, electron components are considered within the Random-Phase Approximation generalized to the superfluid case, while the influence of the neutron component is considered only at qualitative level. Electron screening plays a major role in modifying the proton spectrum and spectral function. At the same time the electron plasmon is strongly modified and damped by the indirect coupling with the superfluid proton component, even at moderately low values of the gap. The excitation spectrum shows the interplay of the different components and their relevance for each excitation modes. The results are relevant for neutrino physics and thermodynamical processes in neutron stars. If electron screening is neglected, the spectral properties of the proton component show some resemblance with the physical situation in high-T c superconductors, and we briefly discuss similarities and differences in this connection. In a general prospect, the results of the study emphasize the role of Coulomb interaction in strong superconductors.

  18. Precision Modeling of Solar Energetic Particle Intensity and Anisotropy Profiles

    Science.gov (United States)

    Ruffolo, D.; Sáiz, A.; Bieber, J. W.; Evenson, P.; Pyle, R.; Rujiwarodom, M.; Tooprakai, P.; Wechakama, M.; Khumlumlert, T.

    2006-12-01

    A focused transport equation for solar energetic particles is sufficiently complex that simple analytic approximations are generally inadequate, but the physics is sufficiently well established to permit precise numerical modeling of high energy particle observations at various distances from the Sun. We demonstrate how observed profiles of intensity and anisotropy vs. time can be quantitatively fit to determine an optimal injection profile at the Sun, scattering mean free path λ, and magnetic configuration. For several ground level enhancements (GLE) of solar energetic particles at energies ~ 1 GeV, the start time of injection has been determined to 1 or 2 minutes. In each case this start time coincides, within that precision, to the soft X-ray peak time, when the flare's primary energy release has ended. This is not inconsistent with acceleration at a coronal mass ejection (CME)-driven shock, though the rapid timescale is challenging to understand. For the GLE of 2005 January 20, λ decreases substantially over ~ 10 minutes, which is consistent with concepts of proton-amplified waves. The GLE of 2000 July 14 is properly fit only when a magnetic bottleneck beyond Earth is taken into account, a feature later confirmed by NEAR observations. The long-standing puzzle of the 1989 October 22 event can now be explained by simultaneous injection of relativistic solar particles along both legs of a closed interplanetary magnetic loop, while other reasonable explanations fail the test of quantitative fitting. The unusually long λ (confirming many previous reports) and a low turbulent spectral index hint at unusual properties of turbulence in the loop. While the early GLE peak on 2003 October 28 remains a mystery, the main peak's strong anisotropy is inconsistent with a suggestion of injection along the far leg of a magnetic loop; quantitative fitting fails because of reverse focusing during Sunward motion. With these modeling capabilities, one is poised to take full

  19. Electrical anisotropy in the presence of oceans - a sensitivity study

    Science.gov (United States)

    Cembrowski, Marcel; Junge, Andreas

    2018-02-01

    Electrical anisotropy in the presence of oceans is particularly relevant at continent-ocean subduction zones (e.g. Cascadian and Andean Margin), where seismic anisotropy has been found with trench-parallel or perpendicular fast direction. The identification of electrical anisotropy at such locations sheds new light on the relation between seismic and electrical anisotropy. At areas confined by two opposite oceans, e.g. the Pyrenean Area and Central America, we demonstrate that the superposed responses of both oceans generate a uniform and large phase split of the main phase tensor axes. The pattern of the tipper arrows is comparatively complicated and it is often difficult to associate their length and orientation to the coast effect. On the basis of simple forward models involving opposite oceans and anisotropic layers, we show that both structures generate similar responses. In the case of a deep anisotropic layer, the resistivity and phase split generated by the oceans alone will be increased or decreased depending on the azimuth of the conducting horizontal principal axes. The 3D isotropic inversion of the anisotropic forward responses reproduces the input data reasonably well. The anisotropy is explained by large opposed conductors outside the station grid and by tube-like elongated conductors representing a macroscopic anisotropy. If the conductive direction is perpendicular to the shorelines, the anisotropy is not recovered by 3D isotropic inversion.

  20. What can anisotropy tell us about turbulence similarity in terrain of increasing complexity?

    Science.gov (United States)

    Stiperski, I.; Calaf, M.

    2017-12-01

    One of the great remaining challenges of numerical weather prediction lies close to the surface, where unresolved boundary layer processes and surface momentum and energy exchanges require parameterizations. These parameterizations, however, still rely on the similarity theory developed over flat and horizontally homogeneous terrain even when making predictions over highly complex surfaces such as mountainous areas. This is despite the fact that experimental datasets obtained over progressively complex surfaces have shown large deviations from the curves proposed by similarity theory on horizontally homogeneous and flat terrain. Even over flat terrain, horizontal velocity variances are eluding scaling due to large scatter, and under very stable stratification lack of scaling is generally attributed to non-Kolmogorov turbulence and influence of non-turbulent submeso motions. Within this work we employ anisotropy of the Reynolds stress tensor as a means of examining the character of turbulence and its response to growing terrain complexity. The validity of similarity relationships and the cause of their failure are examined in light of turbulence topology (isotropic, two component axisymmetric and one component turbulence) from multiple experimental campaigns ranging from flat to highly complex terrain. Results illustrate that different states of anisotropy correspond to different similarity relations. Experimental data with isotropic turbulence match local scaling relationships well for all the datasets. On the other hand, strongly anisotropic turbulence significantly deviates from the traditional scaling relations. These limiting states of anisotropy can furthermore be connected with different governing parameters that help identify conditions in which different topologies occur.

  1. Detecting Population III Stars through Observations of Near-Infrared Cosmic Infrared Background Anisotropies

    Science.gov (United States)

    Kashlinsky, A.; Arendt, R.; Gardner, Jonathan P.; Mather, John C.; Moseley, S. Harvey

    2004-06-01

    Following the successful mapping of the last scattering surface by the Wilkinson Microwave Anisotropy Probe (WMAP) and balloon experiments, the epoch of the first stars, when Population III stars formed, is emerging as the next cosmological frontier. It is not clear what these stars' properties were, when they formed, or how long their era lasted before leading to the stars and galaxies we see today. We show that these questions can be answered with the current and future measurements of the near-IR cosmic infrared background (CIB). Theoretical arguments suggest that Population III stars were very massive and short-lived stars that formed at z~10-20 at rare peaks of the density field in the cold dark matter universe. Because Population III stars probably formed individually in small minihalos, they are not directly accessible to current telescopic studies. We show that these stars left a strong and measurable signature via their contribution to the CIB anisotropies for a wide range of their formation scenarios. The excess in the recently measured near-IR CIB anisotropies over that from normal galaxies can be explained by contribution from early Population III stars. These results imply that Population III were indeed very massive stars and that their epoch started at z~20 and lasted past zfuture space-based missions.

  2. Island dynamics and anisotropy during vapor phase epitaxy of m-plane GaN

    Energy Technology Data Exchange (ETDEWEB)

    Perret, Edith [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA; University of Fribourg, Department of Physics and Fribourg Center for Nanomaterials, Chemin du Musée 3, CH-1700 Fribourg, Switzerland; Xu, Dongwei [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA; Highland, M. J. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA; Stephenson, G. B. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA; Zapol, P. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA; Fuoss, P. H. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA; Munkholm, A. [Munkholm Consulting, Mountain View, California 94043, USA; Thompson, Carol [Department of Physics, Northern Illinois University, DeKalb, Illinois 60115, USA

    2017-12-04

    Using in situ grazing-incidence x-ray scattering, we have measured the diffuse scattering from islands that form during layer-by-layer growth of GaN by metal-organic vapor phase epitaxy on the (1010) m-plane surface. The diffuse scattering is extended in the (0001) in-plane direction in reciprocal space, indicating a strong anisotropy with islands elongated along [1210] and closely spaced along [0001]. This is confirmed by atomic force microscopy of a quenched sample. Islands were characterized as a function of growth rate F and temperature. The island spacing along [0001] observed during the growth of the first monolayer obeys a power-law dependence on growth rate F-n, with an exponent n = 0:25 + 0.02. The results are in agreement with recent kinetic Monte Carlo simulations, indicating that elongated islands result from the dominant anisotropy in step edge energy and not from surface diffusion anisotropy. The observed power-law exponent can be explained using a simple steady-state model, which gives n = 1/4.

  3. Reference interaction site model and optimized perturbation theories of colloidal dumbbells with increasing anisotropy.

    Science.gov (United States)

    Munaò, Gianmarco; Gámez, Francisco; Costa, Dino; Caccamo, Carlo; Sciortino, Francesco; Giacometti, Achille

    2015-06-14

    We investigate thermodynamic properties of anisotropic colloidal dumbbells in the frameworks provided by the Reference Interaction Site Model (RISM) theory and an Optimized Perturbation Theory (OPT), this latter based on a fourth-order high-temperature perturbative expansion of the free energy, recently generalized to molecular fluids. Our model is constituted by two identical tangent hard spheres surrounded by square-well attractions with same widths and progressively different depths. Gas-liquid coexistence curves are obtained by predicting pressures, free energies, and chemical potentials. In comparison with previous simulation results, RISM and OPT agree in reproducing the progressive reduction of the gas-liquid phase separation as the anisotropy of the interaction potential becomes more pronounced; in particular, the RISM theory provides reasonable predictions for all coexistence curves, bar the strong anisotropy regime, whereas OPT performs generally less well. Both theories predict a linear dependence of the critical temperature on the interaction strength, reproducing in this way the mean-field behavior observed in simulations; the critical density—that drastically drops as the anisotropy increases—turns to be less accurate. Our results appear as a robust benchmark for further theoretical studies, in support to the simulation approach, of self-assembly in model colloidal systems.

  4. Effect of anisotropy on stress-induced electrical potentials in bovine bone using ultrasound irradiation

    Science.gov (United States)

    Matsukawa, S.; Makino, T.; Mori, S.; Koyama, D.; Takayanagi, S.; Mizuno, K.; Yanagitani, T.; Matsukawa, M.

    2017-04-01

    The bone fracture healing mechanism of the low-intensity pulsed ultrasound technique is not yet clearly understood. In our previous study, the electrical potentials induced in bone were successfully measured by focusing on piezoelectricity in the MHz range. Bone is composed of collagen and hydroxyapatite and has strong anisotropy. The purpose of this study is to investigate the effects of bone anisotropy on the electrical potentials induced by ultrasound irradiation. For this study, ultrasound bone transducers were fabricated using cortical bovine bone plates as piezoelectric devices. An ultrasound of 7.4 kPapeak-peak (i.e., the peak-to-peak pressure value) was used to irradiate the side surface of each bone plate. Electrical potentials induced in the bone plate were then measured by varying the wave propagation direction in the plate. The peak-to-peak values of these ultrasonically induced electrical potentials were found to vary with changes in the ultrasound propagation direction in the bone sample. The potential was maximized at an inclination of approximately 45° to the bone axis but was minimized around the three orthogonal directions. These maxima and minima ranged from 28 to 33 μVpeak-peak and from 5 to 12 μVpeak-peak, respectively. Additionally, our ultrasound results indicated a change in polarity due to bone anisotropy in the MHz range.

  5. Seismic anisotropy: an original tool to understand the geodynamic evolution of the Italian peninsula

    Directory of Open Access Journals (Sweden)

    A. Amato

    1997-06-01

    Full Text Available Anisotropy is a common property of the Earth's crust and the upper mantle; it is related to the strain field of the medium and therefore to geodynamics. In this paper we describe the different possible origins of anisotropic behavior of the seismic waves and the seismological techniques used to define anisotropic bodies. In general it is found that the fast polarization direction is parallel to the absolute plate motion in cratonic areas, to the spreading direction near rifts or extensional zones, and to the main structural features in transpressive regimes. The delay times between fast and slow waves reflect the relative strength and penetration at depth of the deformation field. The correspondence between surface structural trends and anisotropy in the upper mantle, found in many regions of the world, strongly suggest that orogenic processes involve not only the shallow crust but the entire lithosphere. Recently in Italy both shear wave splitting analysis and Pn inversion were applied to define the trend of seismic anisotropy. Along the Northern Appeninic arc fast directions follow the strike of the arc (i.e., parallel to the strike of the Miocene-Pleistocene compressional features, whereas in the Tyrrhenian zone fast directions are about E-W SW-NE; parallel to the post-Miocene extension that is thought to have reoriented the mantle minerals fabric in the astenosphere.

  6. Suggestions for a consistent terminology for seismic anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Crampin, S. (British Geological Survey, Edinburgh (UK))

    1989-10-01

    Seismic anisotropy is an unfamiliar concept to many geophysicists and the use of misleading and ambiguous terminology has made it more difficult to understand. The author suggests here a consistent terminology in which simple expressions have specific meanings similar to their colloquial meanings. It is hoped that the use of such language will help to make the increasing number of papers reporting seismic anisotropy more readily comprehensible to the non-specialist. This is a list of terms which may make anisotropy easier to understand for those familiar with wave propagation in isotropic solids.

  7. Magneto-elastic anisotropy of ferromagnetic glass-coated microwires

    International Nuclear Information System (INIS)

    Adenot, Anne-Lise; Deprot, Sylvie; Bertin, Frederic; Bois, David; Acher, Olivier

    2004-01-01

    One of the interests of ferromagnetic glass-coated microwires is the possibility to engineer their anisotropy thanks to magneto-elastic effects. In this paper, we focus on the link between the stress models that have been established for these materials and the magneto-elastic behavior. We use the hysteresis loops under stress of microwires to determine their magneto-elastic properties. We compare the experimental magnetic anisotropy of many samples with different metallic core diameter and glass thickness with the magnetic anisotropy estimated using the magneto-striction coefficient and the total stress in the microwires: internal stress (coming from the elaboration process) and external stress (applied during the measurement)

  8. Switching the uniaxial magnetic anisotropy by ion irradiation induced compensation

    Science.gov (United States)

    Yuan, Ye; Amarouche, Teyri; Xu, Chi; Rushforth, Andrew; Böttger, Roman; Edmonds, Kevin; Campion, Richard; Gallagher, Bryan; Helm, Manfred; Jürgen von Bardeleben, Hans; Zhou, Shengqiang

    2018-04-01

    In the present work, the uniaxial magnetic anisotropy of GaMnAsP is modified by helium ion irradiation. According to the micro-magnetic parameters, e.g. resonance fields and anisotropy constants deduced from ferromagnetic resonance measurements, a rotation of the magnetic easy axis from out-of-plane [0 0 1] to in-plane [1 0 0] direction is achieved. From the application point of view, our work presents a novel avenue in modifying the uniaxial magnetic anisotropy in GaMnAsP with the possibility of lateral patterning by using lithography or focused ion beam.

  9. Remarks on anisotropy of inertia in an anisotropic cosmos

    Science.gov (United States)

    Treder, Hans-Juergen

    1992-03-01

    The astronomical and physical meaning of the anisotropy of inertia is analyzed with respect to the relativity of inertia and anisotropic distributions of gravitating matter in the universe. Attention is given to the theoretical compatibility of the anisotropy of inertial masses with Mach's principle of the relativity of inertia and the Mach-Einstein doctrine of general relativity. Mach's principle does not imply anisotropy of inertial masses in an anisotropic universe, and the isotropy of cosmological mass is supported by the Mach-Einstein theories.

  10. Magnetic transitions and phases in random-anisotropy magnets

    International Nuclear Information System (INIS)

    Sellmyer, D.J.; Nafis, S.; O'Shea, M.J.

    1988-01-01

    The generality and universality of the Ising spin-glass-like phase transitions observed in several rare-earth, random-anisotropy magnets are discussed. Some uncertainties and practical problems in determining critical exponents are considered, and a comparison is made to insulating spin glasses and crystalline spin glasses where an apparent anisotropy-induced crossover from Heisenberg to Ising-like behavior is seen. The observation of a reentrant transition in a weak anisotropy system and its correlation with the theory of Chudnovsky, Saslow, and Serota [Phys. Rev. B 33, 251 (1986)] for the correlated spin glass is discussed

  11. Magnetic transitions and phases in random-anisotropy magnets

    Science.gov (United States)

    Sellmyer, D. J.; Nafis, S.; O'Shea, M. J.

    1988-04-01

    The generality and universality of the Ising spin-glass-like phase transitions observed in several rare-earth, random-anisotropy magnets are discussed. Some uncertainties and practical problems in determining critical exponents are considered, and a comparison is made to insulating spin glasses and crystalline spin glasses where an apparent anisotropy-induced crossover from Heisenberg to Ising-like behavior is seen. The observation of a reentrant transition in a weak anisotropy system and its correlation with the theory of Chudnovsky, Saslow, and Serota [Phys. Rev. B 33, 251 (1986)] for the correlated spin glass is discussed.

  12. Helically symmetric equilibria with pressure anisotropy and incompressible plasma flow

    Science.gov (United States)

    Evangelias, A.; Kuiroukidis, A.; Throumoulopoulos, G. N.

    2018-02-01

    We derive a generalized Grad-Shafranov equation governing helically symmetric equilibria with pressure anisotropy and incompressible flow of arbitrary direction. Through the most general linearizing ansatz for the various free surface functions involved therein, we construct equilibrium solutions and study their properties. It turns out that pressure anisotropy can act either paramegnetically or diamagnetically, the parallel flow has a paramagnetic effect, while the non-parallel component of the flow associated with the electric field has a diamagnetic one. Also, pressure anisotropy and flow affect noticeably the helical current density.

  13. Geomechanical Anisotropy and Rock Fabric in Shales

    Science.gov (United States)

    Huffman, K. A.; Connolly, P.; Thornton, D. A.

    2017-12-01

    Digital rock physics (DRP) is an emerging area of qualitative and quantitative scientific analysis that has been employed on a variety of rock types at various scales to characterize petrophysical, mechanical, and hydraulic rock properties. This contribution presents a generic geomechanically focused DRP workflow involving image segmentation by geomechanical constituents, generation of finite element (FE) meshes, and application of various boundary conditions (i.e. at the edge of the domain and at boundaries of various components such as edges of individual grains). The generic workflow enables use of constituent geological objects and relationships in a computational based approach to address specific questions in a variety of rock types at various scales. Two examples are 1) modeling stress dependent permeability, where it occurs and why it occurs at the grain scale; 2) simulating the path and complexity of primary fractures and matrix damage in materials with minerals or intervals of different mechanical behavior. Geomechanical properties and fabric characterization obtained from 100 micron shale SEM images using the generic DRP workflow are presented. Image segmentation and development of FE simulation composed of relatively simple components (elastic materials, frictional contacts) and boundary conditions enable the determination of bulk static elastic properties. The procedure is repeated for co-located images at pertinent orientations to determine mechanical anisotropy. The static moduli obtained are benchmarked against lab derived measurements since material properties (esp. frictional ones) are poorly constrained at the scale of investigation. Once confidence in the input material parameters is gained, the procedure can be used to characterize more samples (i.e. images) than is possible from rock samples alone. Integration of static elastic properties with grain statistics and geologic (facies) conceptual models derived from core and geophysical logs

  14. Giant positive magneto-crystalline anisotropy in ferromagnetic Mn/W(001) overlayer

    Energy Technology Data Exchange (ETDEWEB)

    Ondracek, Martin; Shick, Alexander; Maca, Frantisek; Jungwirth, Tomas [Institute of Physics ASCR, Prague (Czech Republic)

    2008-07-01

    Proposal of the ferromagnetic (FM) ground state for Mn monatomic overlayer on W(001) is reported recently by Ferriani et al. on the basis of first-principles calculations. We study the magneto-crystalline anisotropy (MAE), spin (M{sub S}) and orbital (M{sub L}) magnetic moments, and tunneling anisotropic magneto-resistance (TAMR) of FM-Mn/W(001). The anisotropic properties of Mn/W(001) were investigated making use of the relativistic version of the FP-LAPW method, in which SO coupling is included in a self-consistent second-variational procedure. The magnetic force theorem was used to evaluate the MAE and the DOS anisotropy. For the Mn atom, out-of-plane M{sub S}=3.18 {mu}{sub B} and M{sub L}=0.09 {mu}{sub B} are calculated. There is a strong induced W-interface M{sub S}=-0.34 {mu}{sub B} and M{sub L}=-0.06 {mu}{sub B}. The spin and orbital polarizations of W are quickly decaying away from the interface, showing slow oscillations. When the magnetization is rotated in-plane, there is no anisotropy in M{sub S}, and a pronounced reduction of in-plane M{sub L}. Accordingly, the very big positive MAE of 5.6 meV per Mn-atom is calculated, which is shown to originate from the W contribution. In addition, the TAMR is estimated from the densities of states anisotropy.

  15. Application of Effective Medium Theory to the Three-Dimensional Heterogeneity of Mantle Anisotropy

    Science.gov (United States)

    Song, X.; Jordan, T. H.

    2015-12-01

    A self-consistent theory for the effective elastic parameters of stochastic media with small-scale 3D heterogeneities has been developed using a 2nd-order Born approximation to the scattered wavefield (T. H. Jordan, GJI, in press). Here we apply the theory to assess how small-scale variations in the local anisotropy of the upper mantle affect seismic wave propagation. We formulate a anisotropic model in which the local elastic properties are specified by a constant stiffness tensor with hexagonal symmetry of arbitrary orientation. This orientation is guided by a Gaussian random vector field with transversely isotropic (TI) statistics. If the outer scale of the statistical variability is small compared to a wavelength, then the effective seismic velocities are TI and depend on two parameters, a horizontal-to-vertical orientation ratio ξ and a horizontal-to-vertical aspect ratio, η. If ξ = 1, the symmetry axis is isotropically distributed; if ξ 1, it is horizontally biased (girdle distribution). If η = 1, the heterogeneity is geometrically isotropic; as η à∞, the medium becomes a horizontal stochastic laminate; as η à0, the medium becomes a vertical stochastic bundle. Using stiffness tensors constrained by laboratory measurements of mantle xenoliths, we explore the dependence of the effective P and S velocities on ξ and η. The effective velocities are strongly controlled by the orientation ratio ξ; e.g., if the hexagonal symmetry axis of the local anisotropy is the fast direction of propagation, then vPH > vPV and vSH > vSV for ξ > 1. A more surprising result is the 2nd-order insensitivity of the velocities to the heterogeneity aspect ratio η. Consequently, the geometrical anisotropy of upper-mantle heterogeneity significantly enhances seismic-wave anisotropy only through local variations in the Voigt-averaged velocities, which depend primarily on rock composition and not deformation history.

  16. Strong-coupling approximations

    International Nuclear Information System (INIS)

    Abbott, R.B.

    1984-03-01

    Standard path-integral techniques such as instanton calculations give good answers for weak-coupling problems, but become unreliable for strong-coupling. Here we consider a method of replacing the original potential by a suitably chosen harmonic oscillator potential. Physically this is motivated by the fact that potential barriers below the level of the ground-state energy of a quantum-mechanical system have little effect. Numerically, results are good, both for quantum-mechanical problems and for massive phi 4 field theory in 1 + 1 dimensions. 9 references, 6 figures

  17. Strong interaction and QFD

    International Nuclear Information System (INIS)

    Ebata, T.

    1981-01-01

    With an assumed weak multiplet structure for bosonic hadrons, which is consistent with the ΔI = 1/2 rule, it is shown that the strong interaction effective hamiltonian is compatible with the weak SU(2) x U(1) gauge transformation. Especially the rho-meson transforms as a triplet under SU(2)sub(w), and this is the origin of the rho-photon analogy. It is also shown that the existence of the non-vanishing Cabibbo angle is a necessary condition for the absence of the exotic hadrons. (orig.)

  18. Crystal growth and anisotropy of high temperature thermoelectric properties of yttrium borosilicide single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Hossain, M. Anwar [International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS), Namiki 1-1, Tsukuba 305-0044 (Japan); Center for Crystal Science and Technology, University of Yamanashi, Miyamae 7-32, Kofu, Yamanashi 400-8511 (Japan); Tanaka, Isao [Center for Crystal Science and Technology, University of Yamanashi, Miyamae 7-32, Kofu, Yamanashi 400-8511 (Japan); Tanaka, Takaho; Khan, A. Ullah [International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS), Namiki 1-1, Tsukuba 305-0044 (Japan); Mori, Takao, E-mail: MORI.Takao@nims.go.jp [International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS), Namiki 1-1, Tsukuba 305-0044 (Japan); Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba 305-8671 (Japan)

    2016-01-15

    We studied thermoelectric properties of YB{sub 41}Si{sub 1.3} single crystals grown by the floating zone method. The composition of the grown crystal was confirmed by electron probe micro-analysis. We have determined the growth direction for the first time for these borosilicides, and discovered relatively large anisotropy in electrical properties. We measured the electrical resistivity and Seebeck coefficient along [510] (the growth direction) and [052] directions and we found that this crystal exhibits strong electrical anisotropy with a maximum of more than 8 times. An interesting layered structural feature is revealed along [510] with dense boron cluster layers and yttrium layers, with conductivity enhanced along this direction. We obtained 3.6 times higher power factor along [510] compared to that along [052]. Although the ZT of the present system is low, anisotropy in the thermoelectric properties of a boride was reported for the first time, and can be a clue in developing other boride systems also. - Graphical abstract: The growth direction ([510]) was determined for the first time in YB{sub 41}Si{sub 1.3} single crystals and revealed an interesting layered feature of boron clusters and metal atoms, along which the electrical conductivity and thermoelectric power factor was strongly enhanced. - Highlights: • We have grown YB{sub 41}Si{sub 1.3} single crystals by the floating zone method. • Growth direction of [510] determined for first time in REB{sub 41}Si{sub 1.2}. • Electrical resistivity was strongly anisotropic with possible enhancement along metal layers. • The obtained power factor along [510] is 3.6 times higher than that along [052].

  19. Electron temperature anisotropy modeling and its effect on anisotropy-magnetic field coupling in an underdense laser heated plasma

    Energy Technology Data Exchange (ETDEWEB)

    Morreeuw, J.P.; Dubroca, B. [CEA Centre d' Etudes Scientifiques et Techniques d' Aquitaine, 33 - Le Barp (France); Sangam, A.; Dubroca, B.; Charrier, P.; Tikhonchuk, V.T. [Bordeaux-1 Univ., CELIA, 33 - Talence (France); Sangam, A.; Dubroca, B.; Charrier, P. [Bordeaux-1 Univ., MAB, 33 - Talence (France)

    2006-06-15

    The laser interaction with an underdense plasma leads to an anisotropic laser heating of electrons. This temperature anisotropy gradient in turn is the source of an early magnetic field, which has an important effect on the plasma evolution, due to the thermal flux reduction. We describe the temperature anisotropy by an evolution equation including the anisotropy-magnetic field coupling and observe a rather efficient magnetic field generation. However at high anisotropy levels, a small-scale instability emerges, leading to a serious problem in numerical calculations. We introduce the kinetics effects, which fix the problem by the anisotropy diffusion through the heat flux tensor. A constant-coefficient Fokker-Planck model in the 2-dimensional geometry allows us to derive an anisotropy diffusion term. The diffusion coefficient is fitted from the kinetic theory of the collisional anisotropic (Weibel) instability growth rate. Such an anisotropy diffusion term wipes out the unphysical instability without any undesirable smoothing. This diffusion along with the viscosity term leads also to a quite good restitution of the Weibel instability growth rate and to the short wavelength cutoff, even in a weakly collisional situation. This allows us to use such a model to predict the emergence of the Weibel instability as well as its saturation. (authors)

  20. Strong Coupling Holography

    CERN Document Server

    Dvali, Gia

    2009-01-01

    We show that whenever a 4-dimensional theory with N particle species emerges as a consistent low energy description of a 3-brane embedded in an asymptotically-flat (4+d)-dimensional space, the holographic scale of high-dimensional gravity sets the strong coupling scale of the 4D theory. This connection persists in the limit in which gravity can be consistently decoupled. We demonstrate this effect for orbifold planes, as well as for the solitonic branes and string theoretic D-branes. In all cases the emergence of a 4D strong coupling scale from bulk holography is a persistent phenomenon. The effect turns out to be insensitive even to such extreme deformations of the brane action that seemingly shield 4D theory from the bulk gravity effects. A well understood example of such deformation is given by large 4D Einstein term in the 3-brane action, which is known to suppress the strength of 5D gravity at short distances and change the 5D Newton's law into the four-dimensional one. Nevertheless, we observe that the ...

  1. Relationship between electrical conductivity anisotropy and fabric anisotropy in granular materials during drained triaxial compressive tests: a numerical approach

    Science.gov (United States)

    Niu, Qifei; Revil, André; Li, Zhaofeng; Wang, Yu-Hsing

    2017-07-01

    The anisotropy of granular media and its evolution during shearing are important aspects required in developing physics-based constitutive models in Earth sciences. The development of relationships between geoelectrical properties and the deformation of porous media has applications to the monitoring of faulting and landslides. However, such relationships are still poorly understood. In this study, we first investigate the definition of the electrical conductivity anisotropy tensor of granular materials in presence of surface conductivity of the grains. Fabric anisotropy is related to the components of the fabric tensor. We define an electrical anisotropy factor based on the Archie's exponent second-order symmetric tensor m of granular materials. We use numerical simulations to confirm a relationship between the evolution of electrical and fabric anisotropy factors during shearing. To realize the simulations, we build a virtual laboratory in which we can easily perform synthetic experiments. We first simulate drained compressive triaxial tests of loose and dense granular materials (porosity 0.45 and 0.38, respectively) using the discrete element method. Then, the electrical conductivity tensor of a set of deformed synthetic samples is computed using the finite-difference method. The numerical results show that shear strains are responsible for a measurable anisotropy in the bulk conductivity of granular media. The observed electrical anisotropy response, during shearing, is distinct for dense and loose synthetic samples. Electrical and fabric anisotropy factors exhibit however a unique linear correlation, regardless of the shear strain and the initial state (porosity) of the synthetic samples. The practical implication of this finding confirms the usefulness of the electrical conductivity method in studying the fabric tensor of granular media. This result opens the door in using time-lapse electrical resistivity to study non-intrusively the evolution of anisotropy

  2. Mg2+-Dependent High Mechanical Anisotropy of Three-Way-Junction pRNA as Revealed by Single-Molecule Force Spectroscopy.

    Science.gov (United States)

    Sun, Yang; Di, Weishuai; Li, Yiran; Huang, Wenmao; Wang, Xin; Qin, Meng; Wang, Wei; Cao, Yi

    2017-08-01

    Mechanical anisotropy is ubiquitous in biological tissues but is hard to reproduce in synthetic biomaterials. Developing molecular building blocks with anisotropic mechanical response is the key towards engineering anisotropic biomaterials. The three-way-junction (3WJ) pRNA, derived from ϕ29 DNA packaging motor, shows strong mechanical anisotropy upon Mg 2+ binding. In the absence of Mg 2+ , 3WJ-pRNA is mechanically weak without noticeable mechanical anisotropy. In the presence of Mg 2+ , the unfolding forces can differ by more than 4-fold along different pulling directions, ranging from about 47 pN to about 219 pN. Mechanical anisotropy of 3WJ-pRNA stems from pulling direction dependent cooperativity for the rupture of two Mg 2+ binding sites, which is a novel mechanism for the mechanical anisotropy of biomacromolecules. It is anticipated that 3WJ-pRNA can be used as a key element for the construction of biomaterials with controllable mechanical anisotropy. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Influence of fourfold anisotropy form on hysteresis loop shape in ferromagnetic nanostructures

    Directory of Open Access Journals (Sweden)

    Andrea Ehrmann

    2014-08-01

    Full Text Available The dependence of the form of different mathematical depictions of fourfold magnetic anisotropies has been examined, using a simple macro-spin model. Strong differences in longitudinal and transverse hysteresis loops occur due to deviations from the usual phenomenological model, such as using absolute value functions. The proposed possible models can help understanding measurements on sophisticated magnetic nanosystems, like exchange bias layered structures employed in magnetic hard disk heads or magnetic nano-particles, and support the development of solutions with specific magnetization reversal behavior needed in novel magneto-electronic devices.

  4. Magnetocrystalline anisotropy of RCo{sub 5} intermetallics: itinerant-electron contribution

    Energy Technology Data Exchange (ETDEWEB)

    Steinbeck, L. E-mail: l.steinbeck@ifw-dresden.de; Richter, M.; Eschrig, H

    2001-05-01

    The itinerant-state magnetocrystalline anisotropy energies (MAE) of RCo{sub 5} (R=Y, La, Pr, Nd, Sm, Gd) have been determined by relativistic density-functional calculations in local spin density approximation, with additionally taking into account orbital polarization. The calculated MAEs are found to be strongly affected by changes of the lattice geometry (c/a ratio and volume) resulting from (a) uniaxial strain in YCo{sub 5} and (b) the lanthanide contraction along the RCo{sub 5} series.

  5. Anisotropy of the magnetic susceptibility of gallium

    Science.gov (United States)

    Pankey, T.

    1960-01-01

    The bulk magnetic susceptibilities of single gallium crystals and polycrystalline gallium spheres were measured at 25??C. The following anisotropic diamagnetic susceptibilities were found: a axis (-0.119??0. 001)??10-6 emu/g, b axis (-0.416??0.002)??10 -6 emu/g, and c axis (-0.229??0.001) emu/g. The susceptibility of the polycrystalline spheres, assumed to be the average value for the bulk susceptibility of gallium, was (-0.257??0.003)??10-6 emu/g at 25??C, and (-0.299??0.003)??10-6 emu/g at -196??C. The susceptibility of liquid gallium was (0.0031??0.001) ??10-6 emu/g at 30??C and 100??C. Rotational diagrams of the susceptibilities in the three orthogonal planes of the unit cell were not sinusoidal. The anisotropy in the single crystals was presumably caused by the partial overlap of Brillouin zone boundaries by the Fermi-energy surface. The large change in susceptibility associated with the change in state was attributed to the absence of effective mass influence in the liquid state. ?? 1960 The American Institute of Physics.

  6. Patchy polymer colloids with tunable anisotropy dimensions.

    Science.gov (United States)

    Kraft, Daniela J; Hilhorst, Jan; Heinen, Maria A P; Hoogenraad, Mathijs J; Luigjes, Bob; Kegel, Willem K

    2011-06-09

    We present the synthesis of polymer colloids with continuously tunable anisotropy dimensions: patchiness, roughness, and branching. Our method makes use of controlled fusion of multiple protrusions on highly cross-linked polymer particles produced by seeded emulsion polymerization. Carefully changing the synthesis conditions, we can tune the number of protrusions, or branching, of the obtained particles from spheres with one to three patches to raspberry-like particles with multiple protrusions. In addition to that, roughness is generated on the seed particles by adsorption of secondary nucleated particles during synthesis. The size of the roughness relative to the smooth patches can be continuously tuned by the initiator, surfactant, and styrene concentrations. Seed colloids chemically different from the protrusions induce patches of different chemical nature. The underlying generality of the synthesis procedure allows for application to a variety of seed particle sizes and materials. We demonstrate the use of differently sized polyNIPAM (poly-N-isopropylacrylamide), as well as polystyrene and magnetite filled polyNIPAM seed particles, the latter giving rise to magnetically anisotropic colloids. The high yield together with the uniform, anisotropic shape make them interesting candidates for use as smart building blocks in self-assembling systems.

  7. Studies of anisotropy of iron based superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Murphy, Jason A. [Iowa State Univ., Ames, IA (United States)

    2013-01-01

    To study the electronic anisotropy in iron based superconductors, the temperature dependent London penetration depth, Δλ(T), have been measured in several compounds, along with the angular dependent upper critical field, Hc2(T). Study was undertaken on single crystals of Ba(Fe1-xCox)2As2 with x=0.108 and x=0.127, in the overdoped range of the doping phase diagram, characterized by notable modulation of the superconducting gap. Heavy ion irradiation with matching field doses of 6 T and 6.5 T respectively, were used to create columnar defects and to study their effect on the temperature Δλ(T). The variation of the low-temperature penetration depth in both pristine and irradiated samples was fitted with a power-law function Δλ(T) = ATn. Irradiation increases the magnitude of the pre-factor A and decreases the exponent n, similar to the effect on the optimally doped samples. This finding supports the universal s ± scenario for the whole doping range.

  8. Wave anisotropy of shear viscosity and elasticity

    Science.gov (United States)

    Rudenko, O. V.; Sarvazyan, A. P.

    2014-11-01

    The paper presents the theory of shear wave propagation in a "soft solid" material possessing anisotropy of elastic and dissipative properties. The theory is developed mainly for understanding the nature of the low-frequency acoustic characteristics of skeletal muscles, which carry important diagnostic information on the functional state of muscles and their pathologies. It is shown that the shear elasticity of muscles is determined by two independent moduli. The dissipative properties are determined by the fourth-rank viscosity tensor, which also has two independent components. The propagation velocity and attenuation of shear waves in muscle depend on the relative orientation of three vectors: the wave vector, the polarization vector, and the direction of muscle fiber. For one of the many experiments where attention was distinctly focused on the vector character of the wave process, it was possible to make a comparison with the theory, estimate the elasticity moduli, and obtain agreement with the angular dependence of the wave propagation velocity predicted by the theory.

  9. Bidirectional electron anisotropies in the distant tail: ISEE-3 observations of polar rain

    International Nuclear Information System (INIS)

    Baker, D.N.; Bame, S.J.; Feldman, W.C.; Gosling, J.T.; Zwickl, R.D.; Slavin, J.A.; Smith, E.J.

    1985-01-01

    A detailed observational treatment of bidirectional electrons (50 approx.500 eV) in the distant magnetotail (r greater than or equal to 100 R/sub E/) is presented. It is found that electrons in this energy range commonly exhibit strong, field-aligned anisotropies in the tail lobes. Because of large tail motions, the ISEE-3 data provide extensive sampling of both the north and south lobes in rapid succession, demonstrating directly the strong asymmetries that exist between the north and south lobes at any one time. The bidirectional fluxes are found to occur predominantly in the lobe directly connected to the sunward IMF in the open magnetosphere model (north lobe for away sectors and south lobe for toward sectors). Electron anisotropy and magnetic field data are presented which show the transition from unidirectional (sheath) electron populations to bidirectional (lobe) populations. Taken together, the present evidence suggests that the bidirectional electrons that we observe in the distant tail are closely related to the polar rain electrons observed previously at lower altitudes. Furthermore, these data provide strong evidence that the distant tail is comprised largely of open magnetic field lines in contradistinction to some recently advanced models

  10. Anisotropies of in-phase, out-of-phase,\

    Czech Academy of Sciences Publication Activity Database

    Hrouda, F.; Chadima, Martin; Ježek, J.; Kadlec, Jaroslav

    2018-01-01

    Roč. 62 (2018) ISSN 0039-3169 Institutional support: RVO:67985530 ; RVO:67985831 Keywords : anisotropy * out-of-phase susceptibility * frequency-dependent susceptibility Subject RIV: DB - Geology ; Mineralogy Impact factor: 0.764, year: 2016

  11. Dark matter electron anisotropy. A universal upper limit

    International Nuclear Information System (INIS)

    Borriello, Enrico; Maccione, Luca; Cuoco, Alessandro

    2010-12-01

    Indirect searches of particle Dark Matter (DM) with high energy Cosmic Rays (CR) are affected by large uncertainties, coming both from the DM side, and from poor understanding of the astrophysical backgrounds. We show that, on the contrary, the DM intrinsic degree of anisotropy in the arrival directions of high energy CR electrons and positrons does not suffer from these unknowns. Furthermore, if contributions from possible local sources are neglected, the intrinsic DM anisotropy sets the maximum degree of total anisotropy. As a consequence, if some anisotropy larger than the DM upper bound is detected, its origin could not be ascribed to DM, and would constitute an unambiguous evidence for the presence of astrophysical local discrete sources of high energy electrons and positrons. The Fermi-LAT will be able to probe such scenarios in the next years. (orig.)

  12. LIGO: The strong belief

    CERN Multimedia

    Antonella Del Rosso

    2016-01-01

    Twenty years of designing, building and testing a number of innovative technologies, with the strong belief that the endeavour would lead to a historic breakthrough. The Bulletin publishes an abstract of the Courier’s interview with Barry Barish, one of the founding fathers of LIGO.   The plots show the signals of gravitational waves detected by the twin LIGO observatories at Livingston, Louisiana, and Hanford, Washington. (Image: Caltech/MIT/LIGO Lab) On 11 February, the Laser Interferometer Gravitational-Wave Observatory (LIGO) and Virgo collaborations published a historic paper in which they showed a gravitational signal emitted by the merger of two black holes. These results come after 20 years of hard work by a large collaboration of scientists operating the two LIGO observatories in the US. Barry Barish, Linde Professor of Physics, Emeritus at the California Institute of Technology and former Director of the Global Design Effort for the Internat...

  13. Elastic anisotropies modeled from crystallographic preferred orientations from high- to ultrahigh-pressure rocks of the Adula Nappe (Switzerland)

    Science.gov (United States)

    Keppler, Ruth; Stipp, Michael; Froitzheim, Niko

    2017-04-01

    figure or two maxima are formed within the foliation at an angle of 45° to the lineation. Vp/Vs ratios are 1.53-1.55. Paragneisses also exhibit relatively uniform Vp anisotropies (4-5%). Two maxima lie within the foliation at an angle to the lineation. Vp/Vs ratio ranges from 1.56-1.65. Samples with weak quartz CPO and low volume percentages of quartz result in low Vp/Vs ratios. High values occur when the opposite applies. Our study shows that CPO strength and configuration as well as mineral content strongly influence elastic anisotropies of deep crustal rocks. Therefore a considerable variability of elastic anisotropy strength and pattern is to be expected in seismic investigations on subducted crust in the Alpine orogen and probably any other collisional settings.

  14. Large Magnetic Anisotropy in HfMnP

    Science.gov (United States)

    Parker, David; Lamichhane, Tej; Taufour, Valentin; Masters, Morgan; Thimmaiah, Srinivasa; Bud'Ko, Ser'gey; Canfield, Paul

    We present a theoretical and experimental study of two little-studied manganese phosphide ferromagnets, HfMnP and ZrMnP, with Curie temperatures above room temperature. We find an anisotropy field in HfMnP approaching 10 T - larger than that of the permanent magnet workhorse NdFeB magnets. From theory we determine the source of this anisotropy. Our results show the potential of 3d-element-based magnetic materials for magnetic applications.

  15. Geodynamic Constraints on the Sources of Seismic Anisotropy Beneath Madagascar

    Science.gov (United States)

    Rajaonarison, T. A.; Stamps, D. S.; Fishwick, S.

    2017-12-01

    The rheological structure of the lithosphere-asthenosphere system controls the degree in which the mantle drives surface motions. Seismic anisotropy is a proxy to infer information about previous tectonic events imprinted in lithospheric structures and/or asthenospheric flow pattern in regions absent of active volcanism, however, distinguishing between the shallow and deeper sources, respectively, remains ambiguous. Madagascar is an ideal natural laboratory to study the sources of anisotropy and the rheological implications for lithosphere-asthenosphere system because 1) active volcanism is minimal or absent, 2) there are well-exposed tectonic fabrics for comparison, and 3) numerous geological and geophysical observations provides evidence of present-day tectonic activities. Recent studies suggest new seismic anisotropy observations in southern Madagascar are sourced from both fossilized lithospheric structure and asthenospheric flow driven by rigid lithospheric plate motion. In this work we compare geodynamic simulations of the lithosphere-asthenosphere system with seismic anisotropy data set that includes all of Madagascar. We use the numerical code Advanced Solver for Problems in Earth's ConvecTion (ASPECT) to calculate instantaneous deformation in the lithosphere and edge-driven convective flow in the asthenosphere accounting for variations in buoyancy forces and temperature dependent viscosity. The initial temperature conditions are based on interpretations from high resolution regional surface wave tomography. We assume visco-plastic rheology for a uniform crust, dislocation creep for a laterally varying mantle lithospheric structure, and diffusion creep for the asthenosphere. To test for the source of anisotropy we compare our velocity solution azimuths with azimuths of anisotropy at 25 km depth intervals. Calculated asthenospheric flow aligns with measured seismic anisotropy with a 15° WRMS at 175 km depth and possibly down to 250 km suggesting the

  16. Anisotropy signature in extended images from reverse-time migration

    KAUST Repository

    Sava, Paul

    2012-11-04

    Reverse-time migration can accurately image complex geologic structures in anisotropic media. Extended images at selected locations in the earth, i.e. at common-image-point gathers (CIPs), carry enough information to characterize the angle-dependent illumination and to provide measurements for migration velocity analysis. Furthermore, inaccurate anisotropy leaves a distinctive signature in CIPs, which can be used to evaluate anisotropy through techniques similar to the ones used in conventional wavefield tomography.

  17. Anisoft 4.2. – Anisotropy data browser

    Czech Academy of Sciences Publication Activity Database

    Chadima, Martin; Jelínek, V.

    2008-01-01

    Roč. 38, special issue (2008), s. 41-41 ISSN 1335-2806. [Paleo, Rock and Environmental Magnetism. Castle Meeting /11./. 22.06.2008-28.06.2008, Bojnice] R&D Projects: GA AV ČR IAA300130612 Institutional research plan: CEZ:AV0Z30130516 Keywords : anisotropy of magnetic susceptibility * tensor statisticsntation * anisotropy of magnetic remanence Subject RIV: DE - Earth Magnetism, Geodesy, Geography http://gauss.savba.sk/GPIweb/conferences/nt2008/abstr/Chadima-2.pdf

  18. Insights into asthenospheric anisotropy and deformation in Mainland China

    Science.gov (United States)

    Zhu, Tao

    2018-03-01

    Seismic anisotropy can provide direct constraints on asthenospheric deformation which also can be induced by the inherent mantle flow within our planet. Mantle flow calculations thus have been an effective tool to probe asthenospheric anisotropy. To explore the source of seismic anisotropy, asthenospheric deformation and the effects of mantle flow on seismic anisotropy in Mainland China, mantle flow models driven by plate motion (plate-driven) and by a combination of plate motion and mantle density heterogeneity (plate-density-driven) are used to predict the fast polarization direction of shear wave splitting. Our results indicate that: (1) plate-driven or plate-density-driven mantle flow significantly affects the predicted fast polarization direction when compared with simple asthenospheric flow commonly used in interpreting the asthenospheric source of seismic anisotropy, and thus new insights are presented; (2) plate-driven flow controls the fast polarization direction while thermal mantle flow affects asthenospheric deformation rate and local deformation direction significantly; (3) asthenospheric flow is an assignable contributor to seismic anisotropy, and the asthenosphere is undergoing low, large or moderate shear deformation controlled by the strain model, the flow plane/flow direction model or both in most regions of central and eastern China; and (4) the asthenosphere is under more rapid extension deformation in eastern China than in western China.

  19. Magnetic anisotropies of (Ga,Mn)As films and nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Hoffmann, Frank

    2011-02-02

    In this work the magnetic anisotropies of the diluted magnetic semiconductor (Ga,Mn)As were investigated experimentally. (Ga,Mn)As films show a superposition of various magnetic anisotropies which depend sensitively on various parameters such as temperature, carrier concentration or lattice strain. However, the anisotropies of lithographically prepared (Ga,Mn)As elements differ significantly from an unpatterned (Ga,Mn)As film. In stripe-shaped structures this behaviour is caused by anisotropic relaxation of the compressive lattice strain. In order to determine the magnetic anisotropies of individual (Ga,Mn)As nanostructures a combination of ferromagnetic resonance and time-resolved scanning Kerr microscopy was employed in this thesis. In addition, local changes of the magnetic anisotropy in circular and rectangular structures were visualized by making use of spatially resolved measurements. Finally, also the influence of the laterally inhomogeneous magnetic anisotropies on the static magnetic properties, such as coercive fields, was investigated employing spatially resolved static MOKE measurements on individual (Ga,Mn)As elements. (orig.)

  20. Changes in reflectance anisotropy of wheat crop during different phenophases

    Science.gov (United States)

    Lunagaria, Manoj M.; Patel, Haridas R.

    2017-04-01

    The canopy structure of wheat changes significantly with growth stages and leads to changes in reflectance anisotropy. Bidirectional reflectance distribution function characterises the reflectance anisotropy of the targets, which can be approximated. Spectrodirectional reflectance measurements on wheat crop were acquired using a field goniometer system. The bidirectional reflectance spectra were acquired at 54 view angles to cover the hemispheric span up to 60° view zenith. The observations were made during early growth stages till maturity of the crop. The anisotropy was not constant for all wavelengths and anisotropic factors clearly revealed spectral dependence, which was more pronounced in near principal plane. In near infrared, wheat canopy expressed less reflectance anisotropy because of higher multiple scattering. The broad hotspot signature was noticeable in reflectance of canopy whenever view and solar angles were close. Distinct changes in bidirectional reflectance distribution function were observed during booting to flowering stages as the canopy achieves more uniformity, height and head emergence. The function clearly reveals bowl shape during heading to early milking growth stages of the crop. Late growth stages show less prominent gap and shadow effects. Anisotropy index revealed that wheat exhibits changes in reflectance anisotropy with phenological development and with spectral bands.

  1. Classical Spin Liquid Instability Driven By Off-Diagonal Exchange in Strong Spin-Orbit Magnets

    Science.gov (United States)

    Rousochatzakis, Ioannis; Perkins, Natalia B.

    2017-04-01

    We show that the off-diagonal exchange anisotropy drives Mott insulators with strong spin-orbit coupling to a classical spin liquid regime, characterized by an infinite number of ground states and Ising variables living on closed or open strings. Depending on the sign of the anisotropy, quantum fluctuations either fail to lift the degeneracy down to very low temperatures, or select noncoplanar magnetic states with unconventional spin correlations. The results apply to all 2D and 3D tricoordinated materials with bond-directional anisotropy and provide a consistent interpretation of the suppression of the x-ray magnetic circular dichroism signal reported recently for β -Li2IrO3 under pressure.

  2. Seismic anisotropy and its relation with crust structure and stress field in the Reggio Emilia Region (Northern Italy)

    Science.gov (United States)

    Margheriti, L.; Ferulano, M. F.; Di Bona, M.

    2006-11-01

    Shear wave splitting is measured at 14 seismic stations in the Reggio Emilia region above local background seismicity and two sequences of seismic events. The good quality of the waveforms together with the favourable distribution of earthquake foci allows us to place strong constraints on the geometry and the depth of the anisotropic volume. It is about 60 km2 wide and located between 6 and 11 km depth, inside Mesozoic age carbonate rocks. The splitting results suggest also the presence of a shallower anisotropic layer about 1 km thick and few km wide in the Pliocene-Quaternary alluvium above the Mesozoic layer. The fast polarization directions (N30°E) are approximately parallel to the maximum horizontal stress (σ1 is SSW-NNE) in the region and also parallel to the strike of the main structural features in the Reggio Emilia area. The size of the delay times suggests about 4.5 per cent shear wave velocity anisotropy. These parameters agree with an interpretation of seismic anisotropy in terms of the extensive-dilatancy anisotropy model which considers the rock volume to be pervaded by fluid-saturated microcracks aligned by the active stress field. We cannot completely rule out the contribution of aligned macroscopic fractures as the cause of the shear wave anisotropy even if the parallel shear wave polarizations we found are diagnostic of transverse isotropy with a horizontal axis of symmetry. This symmetry is commonly explained by parallel stress-aligned microcracks.

  3. Perpendicular magnetic anisotropy of ultrathin FeCo alloy films on Pd(0 0 1) surface: First principles study

    International Nuclear Information System (INIS)

    Kim, Dongyoo; Hong, Jisang

    2009-01-01

    Using the full potential linearized augmented plane wave (FLAPW) method, thickness dependent magnetic anisotropy of ultrathin FeCo alloy films in the range of 1 monolayer (ML) to 5 ML coverage on Pd(0 0 1) surface has been explored. We have found that the FeCo alloy films have close to half metallic state and well-known surface enhancement in thin film magnetism is observed in Fe atom, whereas the Co has rather stable magnetic moment. However, the largest magnetic moment in Fe and Co is found at 1 ML thickness. Interestingly, it has been observed that the interface magnetic moments of Fe and Co are almost the same as those of surface elements. The similar trend exists in orbital magnetic moment. This indicates that the strong hybridization between interface FeCo alloy and Pd gives rise to the large magnetic moment. Theoretically calculated magnetic anisotropy shows that the 1 ML FeCo alloy has in-plane magnetization, but the spin reorientation transition (SRT) from in-plane to perpendicular magnetization is observed above 2 ML thickness with huge magnetic anisotropy energy. The maximum magnetic anisotropy energy for perpendicular magnetization is as large as 0.3 meV/atom at 3 ML film thickness with saturation magnetization of 2.36μ B . Besides, the calculated X-ray magnetic circular dichroism (XMCD) has been presented.

  4. John Strong (1941 - 2006)

    CERN Multimedia

    Wickens, F

    Our friend and colleague John Strong was cruelly taken from us by a brain tumour on Monday 31st July, a few days before his 65th birthday John started his career working with a group from Westfield College, under the leadership of Ted Bellamy. He obtained his PhD and spent the early part of his career on experiments at Rutherford Appleton Laboratory (RAL), but after the early 1970s his research was focussed on experiments in CERN. Over the years he made a number of notable contributions to experiments in CERN: The Omega spectrometer adopted a system John had originally developed for experiments at RAL using vidicon cameras to record the sparks in the spark chambers; He contributed to the success of NA1 and NA7, where he became heavily involved in the electronic trigger systems; He was responsible for the second level trigger system for the ALEPH detector and spent five years leading a team that designed and built the system, which ran for twelve years with only minor interventions. Following ALEPH he tur...

  5. Stirring Strongly Coupled Plasma

    CERN Document Server

    Fadafan, Kazem Bitaghsir; Rajagopal, Krishna; Wiedemann, Urs Achim

    2009-01-01

    We determine the energy it takes to move a test quark along a circle of radius L with angular frequency w through the strongly coupled plasma of N=4 supersymmetric Yang-Mills (SYM) theory. We find that for most values of L and w the energy deposited by stirring the plasma in this way is governed either by the drag force acting on a test quark moving through the plasma in a straight line with speed v=Lw or by the energy radiated by a quark in circular motion in the absence of any plasma, whichever is larger. There is a continuous crossover from the drag-dominated regime to the radiation-dominated regime. In the crossover regime we find evidence for significant destructive interference between energy loss due to drag and that due to radiation as if in vacuum. The rotating quark thus serves as a model system in which the relative strength of, and interplay between, two different mechanisms of parton energy loss is accessible via a controlled classical gravity calculation. We close by speculating on the implicati...

  6. Strong-interaction nonuniversality

    International Nuclear Information System (INIS)

    Volkas, R.R.; Foot, R.; He, X.; Joshi, G.C.

    1989-01-01

    The universal QCD color theory is extended to an SU(3) 1 direct product SU(3) 2 direct product SU(3) 3 gauge theory, where quarks of the ith generation transform as triplets under SU(3)/sub i/ and singlets under the other two factors. The usual color group is then identified with the diagonal subgroup, which remains exact after symmetry breaking. The gauge bosons associated with the 16 broken generators then form two massive octets under ordinary color. The interactions between quarks and these heavy gluonlike particles are explicitly nonuniversal and thus an exploration of their physical implications allows us to shed light on the fundamental issue of strong-interaction universality. Nonuniversality and weak flavor mixing are shown to generate heavy-gluon-induced flavor-changing neutral currents. The phenomenology of these processes is studied, as they provide the major experimental constraint on the extended theory. Three symmetry-breaking scenarios are presented. The first has color breaking occurring at the weak scale, while the second and third divorce the two scales. The third model has the interesting feature of radiatively induced off-diagonal Kobayashi-Maskawa matrix elements

  7. Pre Stack Depth Migration (Psdm) Anisotropi Vti (Vertical Tilted Isotropy) Untuk Pencitraan Struktur Bawah Permukaan

    OpenAIRE

    Priambodo, Panji Aziz; Maryanto, Sukir; Nurudin, Hasan

    2013-01-01

    Medium isotropi jarang ditemukan di lapisan bumi sehingga perlu dilakukan pendekatan secara anisotropi untuk menghasilkan pemodelan yang baik. Medium anisotropi dapat menyebabkan efek pada data seismik contohnya efek hockey sticks sehingga perlu ditangani secara anisotropi. Jenis anisotropi yang digunakan adalah VTI (Vertical Transverse Isotropy). Secara teori parameter medium anisotropi disebut dengan parameter Thomsen yang terdiri dari delta (δ) dan epsilon (ε). Dengan melakukan PSDM anisot...

  8. Optical anisotropy of quasi-1D rare-earth silicide nanostructures on Si(001)

    Energy Technology Data Exchange (ETDEWEB)

    Chandola, S., E-mail: sandhya.chandola@isas.de [Leibniz-Institut für Analytische Wissenschaften – ISAS – e.V., Schwarzschildstraße 8, 12489 Berlin (Germany); Speiser, E.; Esser, N. [Leibniz-Institut für Analytische Wissenschaften – ISAS – e.V., Schwarzschildstraße 8, 12489 Berlin (Germany); Appelfeller, S.; Franz, M.; Dähne, M. [Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstraße 36, 10623 Berlin (Germany)

    2017-03-31

    Highlights: • Reflectance anisotropy spectroscopy (RAS) is capable of distinguishing optically between the semiconducting wetting layer and the metallic nanowires of rare earth (Tb and Dy) silicide nanostructures grown on vicinal Si(001). • The spectra of the wetting layer show a distinctive line shape with a large peak appearing at 3.8 eV, which is assigned to the formation of 2 × 3 and 2 × 4-like subunits of the 2 × 7 reconstruction. The spectra of the metallic nanowires show peaks at the E{sub 1} and E{sub 2} transitions of bulk Si which is assigned to strong substrate strain induced by the nanowires. • The optical anisotropy of the Tb nanowires is larger than for the Dy nanowires, which is related to the preferential formation of more strained bundles as well as larger areas of clean Si surfaces in the case of Tb. • RAS is shown to be a powerful addition to surface science techniques for studying the formation of rare-earth silicide nanostructures. Its surface sensitivity and rapidity of response make it an ideal complement to the slower but higher resolution of scanning probes of STM and AFM. - Abstract: Rare earth metals are known to interact strongly with Si(001) surfaces to form different types of silicide nanostructures. Using STM to structurally characterize Dy and Tb silicide nanostructures on vicinal Si(001), it will be shown that reflectance anisotropy spectroscopy (RAS) can be used as an optical fingerprint technique to clearly distinguish between the formation of a semiconducting two-dimensional wetting layer and the metallic one-dimensional nanowires. Moreover, the distinctive spectral features can be related to structural units of the nanostructures. RAS spectra of Tb and Dy nanostructures are found to show similar features.

  9. An Indication of Anisotropy in Arrival Directions of Ultra-high-energy Cosmic Rays through Comparison to the Flux Pattern of Extragalactic Gamma-Ray Sources

    NARCIS (Netherlands)

    Aab, A.; Abreu, P.; Aglietta, M.; Albuquerque, I. F. M.; Allekotte, I.; Almela, A.; Alvarez Castillo, J.; Alvarez-Muniz, J.; Anastasi, G. A.; Anchordoqui, L.; Andrada, B.; Aramo, C.; Arsene, N.; Asorey, H.; Assis, P.; Avila, G.; Badescu, A. M.; Balaceanu, A.; Barbato, F.; Barreira Luz, R. J.; Beatty, J. J.; Bellido, J. A.; Berat, C.; Bertaina, M. E.; Bertou, X.; Biermann, P. L.; Biteau, J.; Blaess, S. G.; Blanco, A.; Blazek, J.; Bleve, C.; Bohacova, M.; Bonifazi, C.; Borodai, N.; Botti, A. M.; Brack, J.; Brancus, I.; Bretz, T.; Bridgeman, A.; Briechle, F. L.; Bueno, A.; Buitink, S.; Buscemi, M.; Caballero-Mora, K. S.; Caccianiga, L.; Cancio, A.; Canfora, F.; Caruso, R.; Castellina, A.; Catalani, F.; Cataldi, G.; Cazon, L.; Chavez, A. G.; Chinellato, J. A.; Chudoba, J.; Clay, R. W.; Cobos Cerutti, A. C.; Colalillo, R.; Collica, L.; Coluccia, M. R.; Conceicao, R.; Consolati, G.; Contreras, F.; Cooper, M. J.; Coutu, S.; Covault, C. E.; Cronin, J.; D'Amico, S.; Daniel, B.; Dasso, S.; Daumiller, K.; Dawson, B. R.; De Mauro, G.; de Mello Neto, J. R. T.; De Mitri, I.; de Oliveira, J.; de Souza, V.; Debatin, J.; Deligny, O.; Diaz Castro, M. L.; Diogo, F.; Dobrigkeit, C.; D'Olivo, J. C.; Dorosti, Q.; dos Anjos, R. C.; Dova, M. T.; Dundovic, A.; Ebr, J.; Engel, R.; Erfani, M.; Escobar, C. O.; Espadanal, J.; Etchegoyen, A.; Falcke, H.; Farmer, J.; Farrar, G.; Fauth, A. C.; Fazzini, N.; Fenu, F.; Fick, B.; Figueira, J. M.; Filipcic, A.; Freire, M. M.; Fujii, T.; Fuster, A.; Gaior, R.; Garcia, B.; Gate, F.; Gemmeke, H.; Gherghel-Lascu, A.; Ghia, P. L.; Giaccari, U.; Giammarchi, M.; Giller, M.; Glas, D.; Glaser, C.; Golup, G.; Gomez Berisso, M.; Gomez Vitale, P. F.; Gonzalez, N.; Gorgi, A.; Grillo, A. F.; Grubb, T. D.; Guarino, F.; Guedes, G. P.; Halliday, R.; Hampel, M. R.; Hansen, P.; Harari, D.; Harrison, T. A.; Haungs, A.; Hebbeker, T.; Heck, D.; Heimann, P.; Herve, A. E.; Hill, G. C.; Hojvat, C.; Holt, E.; Homola, P.; Horandel, J. R.; Horvath, P.; Hrabovsky, M.; Huege, T.; Hulsman, J.; Insolia, A.; Isar, P. G.; Jandt, I.; Johnsen, J. A.; Josebachuili, M.; Jurysek, J.; Kaeaepae, A.; Kambeitz, O.; Kampert, K. H.; Keilhauer, B.; Kemmerich, N.; Kemp, E.; Kieckhafer, R. M.; Klages, H. O.; Kleifges, M.; Kleinfeller, J.; Krohm, N.; Kuempel, D.; Mezek, G. Kukec; Kunka, N.; Awad, A. Kuotb; Lago, B. L.; LaHurd, D.; Lang, R. G.; Lauscher, M.; Legumina, R.; Leigui de Oliveira, M. A.; Letessier-Selvon, A.; Lhenry-Yvon, I.; Link, K.; Lo Presti, D.; Lopes, L.; Lopez, R.; Lopez Casado, A.; Lorek, R.; Luce, Q.; Lucero, A.; Malacari, M.; Mallamaci, M.; Mandat, D.; Mantsch, P.; Mariazzi, A. G.; Marsella, G.; Martello, D.; Martinez, H.; Martinez Bravo, O.; Masias Meza, J. J.; Mathes, H. J.; Mathys, S.; Matthews, J.; Matthiae, G.; Mayotte, E.; Mazur, P. O.; Medina, C.; Medina-Tanco, G.; Melo, D.; Menshikov, A.; Merenda, K. -D.; Michal, S.; Micheletti, M. I.; Middendorf, L.; Miramonti, L.; Mitrica, B.; Mockler, D.; Mollerach, S.; Montanet, F.; Morello, C.; Morlino, G.; Mostafa, M.; Mueller, G.; Mueller, S.; Mussa, R.; Naranjo, I.; Nellen, L.; Niculescu-Oglinzanu, M.; Niechciol, M.; Niemietz, L.; Niggemann, T.; Nitz, D.; Nosek, D.; Novotny, V.; Nozka, L.; Nunez, L. A.; Oikonomou, F.; Olinto, A.; Palatka, M.; Pallotta, J.; Papenbreer, P.; Parente, G.; Parra, A.; Paul, T.; Pech, M.; Pedreira, F.; Pekala, J.; Pelayo, R.; Pena-Rodriguez, J.; Pereira, L. A. S.; Perlin, M.; Perrone, L.; Petrera, S.; Phuntsok, J.; Pierog, T.; Pimenta, M.; Pirronello, V.; Platino, M.; Plum, M.; Poh, J.; Porowski, C.; Prado, R. R.; Privitera, P.; Prouza, M.; Quel, E. J.; Querchfeld, S.; Quinn, S.; Ramos-Pollan, R.; Rautenberg, J.; Ravignani, D.; Ridky, J.; Riehn, F.; Risse, M.; Ristori, P.; Rizi, V.; Rodrigues de Carvalho, W.; Fernandez, G. Rodriguez; Rodriguez Rojo, J.; Roncoroni, M. J.; Roth, M.; Roulet, E.; Rovero, A. C.; Ruehl, P.; Saffi, S. J.; Saftoiu, A.; Salamida, F.; Salazar, H.; Salina, G.; Sanchez, F.; Sanchez-Lucas, P.; Santos, E. M.; Santos, E.; Sarazin, F.; Sarmento, R.; Sarmiento-Cano, C.; Sato, R.; Schauer, M.; Scherini, V.; Schieler, H.; Schimp, M.; Schmidt, D.; Scholten, O.; Schovanek, P.; Schroeder, F. G.; Schroeder, S.; Schumacher, J.; Sciutto, S. J.; Segreto, A.; Shadkam, A.; Shellard, R. C.; Sigl, G.; Silli, G.; Smida, R.; Snow, G. R.; Sommers, P.; Sonntag, S.; Soriano, J. F.; Squartini, R.; Stanca, D.; Stanic, S.; Stasielak, J.; Stassi, P.; Stolpovskiy, M.; Strafella, F.; Streich, A.; Suarez, F.; Suarez Duran, M.; Sudholz, T.; Suomijarvi, T.; Supanitsky, A. D.; Supik, J.; Swain, J.; Szadkowski, Z.; Taboada, A.; Taborda, O. A.; Theodoro, V. M.; Todero Peixoto, C. J.; Tomankova, L.; Tome, B.; Torralba Elipe, G.; Travnicek, P.; Trini, M.; Ulrich, R.; Unger, M.; Urban, M.; Valdes Galicia, J. F.; Valino, I.; Valore, L.; van Aar, G.; van Bodegom, P.; van den Berg, A. M.; Varela, E.; Vargas Cardenas, B.; Vazquez, R. A.; Veberic, D.; Ventura, C.; Vergara Quispe, I. D.; Verzi, V.; Vicha, J.; Villasenor, L.; Vorobiov, S.; Wahlberg, H.; Wainberg, O.; Walz, D.; Weber, M.; Weindl, A.; Wiedenski, M.; Wiencke, L.; Wilczynski, H.; Wirtz, M.; Wittkowski, D.; Wundheiler, B.; Yushkov, A.; Zas, E.; Zavrtanik, D.; Zavrtanik, M.; Zepeda, A.; Zimmermann, B.; Ziolkowski, M.; Zong, Z.; Zuccarello, F.; Collaboration, Pierre Auger

    2018-01-01

    A new analysis of the data set from the Pierre Auger Observatory provides evidence for anisotropy in the arrival directions of ultra-high-energy cosmic rays on an intermediate angular scale, which is indicative of excess arrivals from strong, nearby sources. The data consist of 5514 events above 20

  10. Seismic Anisotropy of Soft Sands, Offshore Western AUstralia

    Science.gov (United States)

    Urosevic, M.; Gurevich, B.

    2007-05-01

    Seismic anisotropy is commonly measured in sand shale environment. Intrinsic polar anisotropy of the shale and its effect on seismic data processing and analysis is well established and reasonably well understood. In sandstone, azimuthal anisotropy is often detected and is typically connected to an in situ stress regime and the brittleness of the rock. This type of anisotropy, commonly referred to as fractured induced anisotropy, has been widely and extensively studied as it directly affects both permeability and the strength of the rock. Hence fracture induced anisotropy is not only important for hydrocarbon exploration but also for geotechnical studies, underground mining, etc. Interestingly, in the last few years azimuthal anisotropy has also been detected in soft, poorly consolidated clean sands, mainly by cross-dipole sonic log measurements. This is somewhat surprising as in such soft, typically highly porous and permeable rocks stress induced fractures are unlikely to be abundant. In this study we analyse the anisotropy in such sand class using well-log measurements, three-component VSP data, as well as 2D and 3D surface seismic (reflection) data. High-quality cross-dipole sonic log measurements showed significant shear wave splitting over unconsolidated, highly porous and permeable sand interval. The shear wave anisotropy was computed to be around 10-15%. This is commonly seen as an indication that the rock is fractured and that the fractures are likely to be open. However, image log data over the same sand section suggested dilute most likely non-conductive fractures. Analysis of the shear wave splitting in VSP data also suggested low fracture density. The frequency content of the direct fast and slow shear waves on the VSP data was very similar, not supporting the presence of open fluid saturated fractures. Unfortunately, the evidence from the VSP data is not very compelling because the reservoir is thin compared to the wavelength and sampling interval of

  11. Magnetic-ordering transitions of the effective XY-spin-1/2 compound Cs{sub 2}CoCl{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Breunig, Oliver; Niesen, Sandra; Mueller, Ralf; Lorenz, Thomas [II. Physikalisches Institut, Universitaet zu Koeln (Germany); Sela, Eran; Rosch, Achim; Buldmann, Benjamin [Institut fuer Theoretische Physik, Universitaet zu Koeln (Germany); Becker, Petra; Bohaty, Ladislav [Institut fuer Kristallographie, Universitaet zu Koeln (Germany)

    2013-07-01

    Cs{sub 2}CoCl{sub 4} is a model system for studying the magnetism of one-dimensional spin chains with an XY-like anisotropy. It contains CoCl{sub 4} tetrahedra which form chains along the crystallographic b axis. Due to a strong crystal field, an easy-plane anisotropy of magnetization is established. For symmetry reasons, easy planes in Cs{sub 2}CoCl{sub 4} appear in two orientations. At temperatures between 0.3 and 4 K, the compound is well described by the one-dimensional XXZ model. At lower temperatures magnetic order arises due to finite inter-chain coupling. Our measurements of thermal expansion and specific heat down to 50 mK and in magnetic fields up to 3 T reveal a field-dependent ordering temperature T{sub C}(H). Depending on the orientation of the magnetic field with respect to the easy planes' orientation various ordered phases arise. We present phase diagrams for different field directions and discuss possible ordering mechanisms.

  12. Evidence of unfrozen liquids and seismic anisotropy at the base of the polar ice sheets

    Science.gov (United States)

    Wittlinger, Gérard; Farra, Véronique

    2015-03-01

    We analyze seismic data from broadband stations located on the Antarctic and Greenland ice sheets to determine polar ice seismic velocities. P-to-S converted waves at the ice/rock interface and inside the ice sheets and their multiples (the P-receiver functions) are used to estimate in-situ P-wave velocity (Vp) and P-to-S velocity ratio (Vp/Vs) of polar ice. We find that the polar ice sheets have a two-layer structure; an upper layer of variable thickness (about 2/3 of the total thickness) with seismic velocities close to the standard ice values, and a lower layer of approximately constant thickness with standard Vp but ∼25% smaller Vs. The lower layer ceiling corresponds approximately to the -30 °C isotherm. Synthetic modeling of P-receiver functions shows that strong seismic anisotropy and low vertical S velocity are needed in the lower layer. The seismic anisotropy results from the preferred orientation of ice crystal c-axes toward the vertical. The low vertical S velocity may be due to the presence of unfrozen liquids resulting from premelting at grain joints and/or melting of chemical solutions buried in the ice. The strongly preferred ice crystal orientation fabric and the unfrozen fluids may facilitate polar ice sheet basal flow.

  13. Anisotropy of the Faraday effect in the weak ferromagnetic YFeO3

    International Nuclear Information System (INIS)

    Zenkov, A.V.; Krichevtsov, B.B.; Moskvin, A.S.; Mukimov, K.M.; Pisarev, R.V.; Ruvinshtejn, M.M.

    1989-01-01

    The field strength dependence of the Faraday effect in the weak ferromagnetic YFeO 3 at the wavelength λ=0.63 μm are investigated experimentally for various directions of propagation of the light k-vector and magnetic field H-vector. It is shown that the variation of the Faraday effect for k-vector parallel c-vector and H-vector parallel a-vector is not proportional to the change of the magnetic moment component m z . The ferro-, antiferro- and diamagnetic contributions to the Faraday effect are separated on the basis of a phenomenological description of the Faraday effect in YFeO 3 . It is found that the antiferromagnetic contribution which determines the Faraday effect is strongly anisotropic. The microscopic mechanisms of the Faraday effect in YFeO 3 are considered theoretically for the case of the dipole-allowed 6 A 1g → 6 T 1u transition. It is shown that the mechanisms proposed earlier cannot explain the strong anisotropy of the antiferromagnetic contribution. In order to explain the anisotropy the spin-foreign orbit exchange-relativistic interaction should be taken into account

  14. Determination of elastic anisotropy of rocks from P- and S-wave velocities: numerical modelling and lab measurements

    Science.gov (United States)

    Svitek, Tomáš; Vavryčuk, Václav; Lokajíček, Tomáš; Petružálek, Matěj

    2014-12-01

    The most common type of waves used for probing anisotropy of rocks in laboratory is the direct P wave. Information potential of the measured P-wave velocity, however, is limited. In rocks displaying weak triclinic anisotropy, the P-wave velocity depends just on 15 linear combinations of 21 elastic parameters, called the weak-anisotropy parameters. In strong triclinic anisotropy, the P-wave velocity depends on the whole set of 21 elastic parameters, but inversion for six of them is ill-conditioned and these parameters are retrieved with a low accuracy. Therefore, in order to retrieve the complete elastic tensor accurately, velocities of S waves must also be measured and inverted. For this purpose, we developed a lab facility which allows the P- and S-wave ultrasonic sounding of spherical rock samples in 132 directions distributed regularly over the sphere. The velocities are measured using a pair of P-wave sensors with the transmitter and receiver polarized along the radial direction and using two pairs of S-wave sensors with the transmitter and receiver polarized tangentially to the spherical sample in mutually perpendicular directions. We present inversion methods of phase and ray velocities for elastic parameters describing general triclinic anisotropy. We demonstrate on synthetic tests that the inversion becomes more robust and stable if the S-wave velocities are included. This applies even to the case when the velocity of the S waves is measured in a limited number of directions and with a significantly lower accuracy than that of the P wave. Finally, we analyse velocities measured on a rock sample from the Outokumpu deep drill hole, Finland. We present complete sets of elastic parameters of the sample including the error analysis for several levels of confining pressure ranging from 0.1 to 70 MPa.

  15. Procedure for measurement of anisotropy factor for neutron sources

    International Nuclear Information System (INIS)

    Creazolla, Prycylla Gomes

    2017-01-01

    Radioisotope neutron sources allow the production of reference fields for calibration of neutron detectors for radiation protection and analysis purposes. When the emission rate of these sources is isotropic, no correction is necessary. However, variations in source encapsulation and in the radioactive material concentration produce differences in its neutron emission rate, relative to the source axis, this effect is called anisotropy. In this study, is describe a procedure for measuring the anisotropy factor of neutron sources performed in the Laboratório de Metrologia de Neutrons (LN) using a Precision Long Counter (PLC) detector. A measurement procedure that takes into account the anisotropy factor of neutron sources contributes to solve some issues, particularly with respect to the high uncertainties associated with neutron dosimetry. Thus, a bibliographical review was carried out based on international standards and technical regulations specific to the area of neutron fields, and were later reproduced in practice by means of the procedure for measuring the anisotropy factor in neutron sources of the LN. The anisotropy factor is determined as a function of the angle of 90° in relation to the cylindrical axis of the source. This angle is more important due to its high use in measurements and also of its higher neutron emission rate if compared with other angles. (author)

  16. Azimuthal anisotropy in the D″ layer beneath the Caribbean

    Science.gov (United States)

    Maupin, ValéRie; Garnero, Edward J.; Lay, Thorne; Fouch, Matthew J.

    2005-08-01

    The lowermost mantle beneath Central America has anisotropic seismic velocity structure manifested in shear wave splitting of signals from South American earthquakes recorded at North American broadband recording stations. Prior studies of deep mantle anisotropy in this region have characterized the structure as having vertical transverse isotropy (VTI), which is sufficient to explain a general trend of early tangential (SH) component arrivals. However, VTI models cannot quantitatively match systematic waveform complexities in the onset of many of the shear waves that graze this region. After accounting for splitting effects of upper mantle anisotropy beneath the recording stations, we model the corrected waveform data using full wave theory for mantle velocity models with an anisotropic D″ layer. This is the first attempt to quantitatively model a large data set including azimuthal anisotropy in D″. The models include transverse isotropy with either a vertical or tilted symmetry axis, the latter resulting in azimuthal anisotropy. For some initial shear wave polarizations, tilted transverse isotropy (TTI) produces small, reversed polarity arrivals on the SV components at the arrival time of SH, consistent with the data. Geographical variations in the azimuth of the TTI symmetry axis are indicated by the data. The lack of azimuthal coverage prevents unique resolution of the TTI orientation and also precludes distinguishing between TTI and other azimuthal anisotropy structures such as that predicted for lattice preferred orientation of minerals. Nonetheless, our modeling demonstrates the need for laterally varying anisotropic structure of more complex form than VTI for this region.

  17. Scaling of coercivity in a 3d random anisotropy model

    Energy Technology Data Exchange (ETDEWEB)

    Proctor, T.C., E-mail: proctortc@gmail.com; Chudnovsky, E.M., E-mail: EUGENE.CHUDNOVSKY@lehman.cuny.edu; Garanin, D.A.

    2015-06-15

    The random-anisotropy Heisenberg model is numerically studied on lattices containing over ten million spins. The study is focused on hysteresis and metastability due to topological defects, and is relevant to magnetic properties of amorphous and sintered magnets. We are interested in the limit when ferromagnetic correlations extend beyond the size of the grain inside which the magnetic anisotropy axes are correlated. In that limit the coercive field computed numerically roughly scales as the fourth power of the random anisotropy strength and as the sixth power of the grain size. Theoretical arguments are presented that provide an explanation of numerical results. Our findings should be helpful for designing amorphous and nanosintered materials with desired magnetic properties. - Highlights: • We study the random-anisotropy model on lattices containing up to ten million spins. • Irreversible behavior due to topological defects (hedgehogs) is elucidated. • Hysteresis loop area scales as the fourth power of the random anisotropy strength. • In nanosintered magnets the coercivity scales as the six power of the grain size.

  18. Role of the magnetic anisotropy in organic spin valves

    Directory of Open Access Journals (Sweden)

    V. Kalappattil

    2017-09-01

    Full Text Available Magnetic anisotropy plays an important role in determining the magnetic functionality of thin film based electronic devices. We present here, the first systematic study of the correlation between magnetoresistance (MR response in organic spin valves (OSVs and magnetic anisotropy of the bottom ferromagnetic electrode over a wide temperature range (10 K–350 K. The magnetic anisotropy of a La0.67Sr0.33MnO3 (LSMO film epitaxially grown on a SrTiO3 (STO substrate was manipulated by reducing film thickness from 200 nm to 20 nm. Substrate-induced compressive strain was shown to drastically increase the bulk in-plane magnetic anisotropy when the LSMO became thinner. In contrast, the MR response of LSMO/OSC/Co OSVs for many organic semiconductors (OSCs does not depend on either the in-plane magnetic anisotropy of the LSMO electrodes or their bulk magnetization. All the studied OSV devices show a similar temperature dependence of MR, indicating a similar temperature-dependent spinterface effect irrespective of LSMO thickness, resulting from the orbital hybridization of carriers at the OSC/LSMO interface.

  19. Optical anisotropy in vertically coupled quantum dots

    DEFF Research Database (Denmark)

    Yu, Ping; Langbein, Wolfgang Werner; Leosson, Kristjan

    1999-01-01

    We have studied the polarization of surface and edge-emitted photoluminescence (PL) from structures with vertically coupled In0.5Ga0.5As/GaAs quantum dots (QD's) grown by molecular beam epitaxy. The PL polarization is found to be strongly dependent on the number of stacked layers. While single...... number due to increasing dot size....

  20. Correlation between tetragonal zinc-blende structure and magnetocrystalline anisotropy of MnGa epilayers on GaAs(111)

    Energy Technology Data Exchange (ETDEWEB)

    Arins, A.W.; Jurca, H.F. [Laboratório de Superfícies e Interfaces, Universidade Federal do Paraná, Caixa Postal 19044, 81531-990 Curitiba, Paraná (Brazil); Zarpellon, J. [Laboratório de Superfícies e Interfaces, Universidade Federal do Paraná, Caixa Postal 19044, 81531-990 Curitiba, Paraná (Brazil); Universidade Estadual do Centro-Oeste-Campus Irati, PR 153km 7, CEP 84500-000, Irati, Paraná (Brazil); Fabrim, Z.E.; Fichtner, P.F.P. [Departamento de Metalurgia e Laboratório de Implantação Iônica-Universidade Federal do Rio Grande do Sul, Caixa Postal 15051, 91501-970 Porto Alegre, RS (Brazil); Varalda, J; Schreiner, W.H.; Mosca, D.H [Laboratório de Superfícies e Interfaces, Universidade Federal do Paraná, Caixa Postal 19044, 81531-990 Curitiba, Paraná (Brazil)

    2015-05-01

    MnGa films of few nanometer thickness with tetragonal zinc-blende (TZB) structure were grown by molecular beam epitaxy on GaAs(111) substrates. These ultrathin films have high magnetization at room temperature with magnetic moment as high as 3.2 μ{sub B} per formula unit. A strong magnetocrystalline anisotropy energy (MAE) comparable to that reported to δ-MnGa films with body-centered tetragonal (BCT) structure with similar c/a=1.1 is observed. Electronic structure calculations using density functional theory (DFT) reveal a robust ferrimagnetic ground state at room temperature and confirm that zinc-blende structure with tetragonal distortion has a metastable character. The strong MAE is associated with anisotropy of orbital magnetic moment which is described by the symmetry of the spin-polarized charge density along the crystallographic axes. - Highlights: • MnGa epilayers with tetragonal zinc-blende structure were grown. • Density functional theory calculations reveal a robust ferrimagnetic ground state at room temperature. • Substantial magnetocrystalline anisotropy is associated with the symmetry of the spin-polarized charge density of Mn 4d sites. • MnGa alloy films are promising for spintronics applications.

  1. Irradiation creep induced anisotropy in a/2 dislocation populations

    International Nuclear Information System (INIS)

    Gelles, D.S.

    1984-05-01

    The contribution of anisotropy in Burgers vector distribution to irradiation creep behavior has been largely ignored in irradiation creep models. However, findings on Frank loops suggest that it may be very important. Procedures are defined to identify the orientations of a/2 Burgers vectors for dislocations in face-centered cubic crystals. By means of these procedures the anisotropy in Burgers vector populations was determined for three Nimonic PE16 pressurized tube specimens irradiated under stress. Considerable anisotropy in Burgers vector population develops during irradiation creep. It is inferred that dislocation motion during irradiation creep is restricted primarily to a climb of a/2 dislocations on 100 planes. Effect of these results on irradiation creep modeling and deformation induced irradiation growth is considered

  2. The quantification of crystallographic preferred orientation using magnetic anisotropy

    Science.gov (United States)

    Richter, Carl; van Der Pluijm, Ben A.; Housen, Bernard A.

    1993-01-01

    Magnetic anisotropy analysis presents an alternative and fast method for obtaining and quantifying crystallographic preferred orientations in rocks, using relatively simple equipment. Two natural examples and numerical modeling demonstrate that magnetic anisotropy increases with increasing degree of crystallographic preferred orientation. The normalized magnetic parameters M i = ln( {k i}/{(k max} ∗ k int ∗ k min) {1}/{3}) (k max ≥ k int ≥ k min are the principal magnetic susceptibilities) correlate directly with March 'strains' obtained from X-ray texture goniometry. The additional advantage of our method is that the preferred fabrics are determined from large sample volumes (typically about 11 cm 3) rather than the essentially two-dimensional slice used in optical and X-ray methods. Thus, magnetic anisotropy provides a reliable measure of bulk crystallographic preferred orientation in rocks.

  3. Scaling of coercivity in a 3d random anisotropy model

    Science.gov (United States)

    Proctor, T. C.; Chudnovsky, E. M.; Garanin, D. A.

    2015-06-01

    The random-anisotropy Heisenberg model is numerically studied on lattices containing over ten million spins. The study is focused on hysteresis and metastability due to topological defects, and is relevant to magnetic properties of amorphous and sintered magnets. We are interested in the limit when ferromagnetic correlations extend beyond the size of the grain inside which the magnetic anisotropy axes are correlated. In that limit the coercive field computed numerically roughly scales as the fourth power of the random anisotropy strength and as the sixth power of the grain size. Theoretical arguments are presented that provide an explanation of numerical results. Our findings should be helpful for designing amorphous and nanosintered materials with desired magnetic properties.

  4. Understanding the magnetic anisotropy in Fe-Si amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Diaz, J.; Hamdan, N.M.; Jalil, P.; Hussain, Z.; Valvidares, S.M.; Alameda, J.M.

    2002-08-01

    The origin of the magnetic anisotropy in a very disordered Fe-Si alloy has been investigated. The alloy containing 40 percent at. Si was prepared in the form of a thin film in a DC magnetron sputtering chamber. Structural disorder was obtained from Extended X-ray Absorption Fine Structure spectroscopy. The uniformity and lack of inhomogeneities at a microscopic level was checked by measuring their transverse magnetic susceptibility and hysteresis loops. The orbital component of the magnetic moment was measured by X-ray Magnetic Circular Dichroism spectroscopy. The orbital moment was extraordinary high, 0.4mB. Such a high value contrasted with the relatively small uniaxial anisotropy energy of the thin film (2kJ/m3). This suggests that the cause of the magnetic anisotropy in this alloy was a small degree of correlation in the orientation of the local orbital moments along a preferential direction.

  5. Understanding the magnetic anisotropy in Fe-Si amorphous alloys

    International Nuclear Information System (INIS)

    Diaz, J.; Hamdan, N.M.; Jalil, P.; Hussain, Z.; Valvidares, S.M.; Alameda, J.M.

    2002-01-01

    The origin of the magnetic anisotropy in a very disordered Fe-Si alloy has been investigated. The alloy containing 40 percent at. Si was prepared in the form of a thin film in a DC magnetron sputtering chamber. Structural disorder was obtained from Extended X-ray Absorption Fine Structure spectroscopy. The uniformity and lack of inhomogeneities at a microscopic level was checked by measuring their transverse magnetic susceptibility and hysteresis loops. The orbital component of the magnetic moment was measured by X-ray Magnetic Circular Dichroism spectroscopy. The orbital moment was extraordinary high, 0.4mB. Such a high value contrasted with the relatively small uniaxial anisotropy energy of the thin film (2kJ/m3). This suggests that the cause of the magnetic anisotropy in this alloy was a small degree of correlation in the orientation of the local orbital moments along a preferential direction

  6. Linking strain anisotropy and plasticity in copper metallization

    Energy Technology Data Exchange (ETDEWEB)

    Murray, Conal E., E-mail: conal@us.ibm.com; Jordan-Sweet, Jean [IBM T.J. Watson Research Center, Yorktown Heights, New York 10598 (United States); Priyadarshini, Deepika; Nguyen, Son [IBM Semiconductor Research, Albany, New York 12203 (United States)

    2015-05-04

    The elastic anisotropy of copper leads to significant variation in the x-ray elastic constants (XEC), which link diffraction-based strain measurements to stress. An accurate depiction of the mechanical response in copper thin films requires a determination of an appropriate grain interaction model that lies between Voigt and Reuss limits. It is shown that the associated XEC weighting fraction, x*, between these limits provides a metric by which strain anisotropy can be quantified. Experimental values of x*, as determined by a linear regression scheme of diffraction data collected from multiple reflections, reveal the degree of strain anisotropy and its dependence on plastic deformation induced during in-situ and ex-situ thermal treatments.

  7. Linking strain anisotropy and plasticity in copper metallization

    International Nuclear Information System (INIS)

    Murray, Conal E.; Jordan-Sweet, Jean; Priyadarshini, Deepika; Nguyen, Son

    2015-01-01

    The elastic anisotropy of copper leads to significant variation in the x-ray elastic constants (XEC), which link diffraction-based strain measurements to stress. An accurate depiction of the mechanical response in copper thin films requires a determination of an appropriate grain interaction model that lies between Voigt and Reuss limits. It is shown that the associated XEC weighting fraction, x*, between these limits provides a metric by which strain anisotropy can be quantified. Experimental values of x*, as determined by a linear regression scheme of diffraction data collected from multiple reflections, reveal the degree of strain anisotropy and its dependence on plastic deformation induced during in-situ and ex-situ thermal treatments

  8. Ion temperature anisotropy limitation in high beta plasmas

    International Nuclear Information System (INIS)

    Scime, Earl E.; Keiter, Paul A.; Balkey, Matthew M.; Boivin, Robert F.; Kline, John L.; Blackburn, Melanie; Gary, S. Peter

    2000-01-01

    Measurements of parallel and perpendicular ion temperatures in the Large Experiment on Instabilities and Anisotropies (LEIA) space simulation chamber display an inverse correlation between the upper bound on the ion temperature anisotropy and the parallel ion beta (β=8πnkT/B 2 ). Fluctuation measurements indicate the presence of low frequency, transverse, electromagnetic waves with wave numbers and frequencies that are consistent with predictions for Alfven Ion Cyclotron instabilities. These observations are also consistent with in situ spacecraft measurements in the Earth's magnetosheath and with a theoretical/computational model that predicts that such an upper bound on the ion temperature anisotropy is imposed by scattering from enhanced fluctuations due to growth of the Alfven ion cyclotron instability. (c) 2000 American Institute of Physics

  9. Simulation of inhomogeneous magnetoelastic anisotropy in ferroelectric/ferromagnetic nanocomposites

    Science.gov (United States)

    Aimon, Nicolas M.; Liao, Jiexi; Ross, C. A.

    2012-12-01

    The magnetic response of CoFe2O4/BiFeO3 (CFO/BFO) nanocomposite thin films, in which ferromagnetic CFO nanopillars are embedded in a ferroelectric BFO matrix, has been modeled by including the position-dependent magnetoelastic anisotropy of the CFO. A finite element simulation of the strain state of an arrangement of CFO pillars was performed in which the BFO matrix surrounding one or all of the pillars was subject to a piezoelectric strain. The strain transferred to the CFO pillars was calculated and transformed into a spatially varying magnetoelastic anisotropy in the CFO, and a micromagnetic model was then used to calculate the hysteresis of the pillar, which differed significantly from a macrospin model. The position-dependent anisotropy led to a complex reversal process and to a reorientation of the easy axis to the in-plane direction at sufficient applied electric fields.

  10. Studies of anisotropy of iron based superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Murphy, Jason [Iowa State Univ., Ames, IA (United States)

    2013-01-01

    To study the electronic anisotropy in iron based superconductors, the temperature dependent London penetration depth, Δλ (T), have been measured in several compounds, along with the angular dependent upper critical field, Hc2(T). Study was undertaken on single crystals of Ba(Fe1-xCox)2As2 with x=0.108 and x=0.127, in the overdoped range of the doping phase diagram, characterized by notable modulation of the superconducting gap. Heavy ion irradiation with matching field doses of 6 T and 6.5 T respectively, were used to create columnar defects and to study their effect on the temperature Δλ (T). The variation of the low-temperature penetration depth in both pristine and irradiated samples was fitted with a power-law function Δλ (T) = ATn. Irradiation increases the magnitude of the pre-factor A and decreases the exponent n, similar to the effect on the optimally doped samples. This finding supports the universal s± scenario for the whole doping range. Knowing that the s± gap symmetry exists across the superconducting dome for the electron doped systems, we next looked at λ (T), in optimally - doped, SrFe2(As1-xPx)2, x =0.35. Both, as-grown (Tc ~ 25 K) and annealed (Tc ~ 35 K) single crystals of SrFe2(As1-xPx)2 were measured. Annealing decreases the absolute value of the London penetration depth from λ(0) = 300 ± 10 nm in as-grown samples to λ (0) = 275±10 nm. At low temperatures, λ (T) ~ T indicates a superconducting gap with line nodes. Analysis of the full-temperature range superfluid density is consistent with the line nodes, but differs from the simple single-gap d-wave. The observed behavior is very similar to that of BaFe2(As1-xPx)2, showing that isovalently substituted pnictides are inherently different from

  11. Study of Ion Temperature Anisotropy Boundaries in the Magnetosheath

    Science.gov (United States)

    Lin, N.; Travnicek, P. M.; McFadden, J. P.; Parks, G. K.; Yoon, P. H.; Johnson, J.; Chaston, C. C.

    2012-12-01

    The magnetosheath plasma often exhibits proton temperature anisotropy which may develop several instabilities. For anisotropy Tperp>Tpara, where Tperp and Tpara are the perpendicular and parallel (to the ambient magnetic field) proton temperatures, respectively, electromagnetic ion cyclotron (EMIC) and mirror mode instabilities can be excited, while for TperpHellinger et al., 2006] with linear theory, by assuming bi-Maxwellian protons, in the form of Tperp/Tpara = 1+ a /(beta_para-beta_0)^b, where a, b, and beta_0 are fitting parameters for the threshold condition of maximum growth rate γmax =10^-3 ωcp, and ωcp is the proton cyclotron frequency. We have used plasma and magnetic field observations from several magnetosheath passes of THEMIS and Cluster spacecraft to examine the anisotropy boundary and compare the observations with the theoretical stability boundary. Three wave parameters |δB||/B0|, |δBperp/B0|, and the magnetic compressibility, δB||^2/( δB||^2+ δBperp^2), are calculated and distributions of their intensities on the Tperp/Tpara vs beta_para plane are examined. The data are shown to cluster around the thresholds of the mirror mode and the EMIC mode. For compressional waves there exist enhancements above the mirror mode threshold, which may indicate evolving process of the magnetosheath unstable plasma. The transverse variations are better constrained by the theoretical EMIC marginal curve. The distributions are notably different compared to previous observations of the solar wind fluctuations, which are enhanced along the temperature anisotropy thresholds of the four instabilities, indicating that the proton temperature anisotropy in the solar wind is constrained by the threshold defined in the above equation. We will discuss the interpretation of the results which may provide observational support or constraints on the theoretical and modeling developments of the marginal condition for the proton temperature anisotropy instabilities in the

  12. Simultaneous determination of glycols based on fluorescence anisotropy

    International Nuclear Information System (INIS)

    Garcia Sanchez, F.; Navas Diaz, A.; Lopez Guerrero, M.M.

    2007-01-01

    Simultaneous determination of non-fluorescent glycols in mixtures without separation or chemical transformation steps is described. Two methods based in the measure of fluorescence anisotropy of a probe such as fluorescein dissolved in the analyte or analyte mixtures are described. In the first method, the anisotropy spectra of pure and mixtures of analytes are used to quantitative determination (if the fluorophor concentration is in a range where fluorescence intensity is proportional to concentration). In the second method, a calibration curve anisotropy-concentration based on the application of the Perrin equation is established. The methods presented here are capable of directly resolving binary mixtures of non-fluorescent glycols on the basis of differences on the fluorescence anisotropy of a fluorescence tracer. Best analytical performances were obtained by application of the method based on Perrin equation. This method is simple, rapid and allows the determination of mixtures of glycols with reasonable accuracy and precision. Detection limits are limited by the quantum yield and anisotropy values of the tracer in the solvents. Recovery values are related to the differences in anisotropy values of the tracer in the pure solvents. Mixtures of glycerine/ethylene glycol (GL/EG), ethylene glycol/1,2-propane diol (EG/1,2-PPD) and polyethylene glycol 400/1,2-propane diol (PEG 400/1,2-PPD) were analysed and recovery values are within 95-120% in the Perrin method. Relative standard deviation are in the range 1.3-2.9% and detection limits in the range 3.9-8.9%

  13. FIRE HOSE INSTABILITY DRIVEN BY ALPHA PARTICLE TEMPERATURE ANISOTROPY

    Energy Technology Data Exchange (ETDEWEB)

    Matteini, L.; Schwartz, S. J. [Department of Physics, Imperial College London, London SW7 2AZ (United Kingdom); Hellinger, P. [Astronomical Institute, CAS, Prague (Czech Republic); Landi, S. [Dipartimento di Fisica e Astronomia, Università di Firenze, Firenze (Italy)

    2015-10-10

    We investigate properties of a solar wind-like plasma, including a secondary alpha particle population exhibiting a parallel temperature anisotropy with respect to the background magnetic field, using linear and quasi-linear predictions and by means of one-dimensional hybrid simulations. We show that anisotropic alpha particles can drive a parallel fire hose instability analogous to that generated by protons, but that, remarkably, can also be triggered when the parallel plasma beta of alpha particles is below unity. The wave activity generated by the alpha anisotropy affects the evolution of the more abundant protons, leading to their anisotropic heating. When both ion species have sufficient parallel anisotropies, both of them can drive the instability, and we observe the generation of two distinct peaks in the spectra of the fluctuations, with longer wavelengths associated to alphas and shorter ones to protons. If a non-zero relative drift is present, the unstable modes propagate preferentially in the direction of the drift associated with the unstable species. The generated waves scatter particles and reduce their temperature anisotropy to a marginally stable state, and, moreover, they significantly reduce the relative drift between the two ion populations. The coexistence of modes excited by both species leads to saturation of the plasma in distinct regions of the beta/anisotropy parameter space for protons and alpha particles, in good agreement with in situ solar wind observations. Our results confirm that fire hose instabilities are likely at work in the solar wind and limit the anisotropy of different ion species in the plasma.

  14. Characteristics of trapped proton anisotropy at Space Station Freedom altitudes

    Science.gov (United States)

    Armstrong, T. W.; Colborn, B. L.; Watts, J. W.

    1990-01-01

    The ionizing radiation dose for spacecraft in low-Earth orbit (LEO) is produced mainly by protons trapped in the Earth's magnetic field. Current data bases describing this trapped radiation environment assume the protons to have an isotropic angular distribution, although the fluxes are actually highly anisotropic in LEO. The general nature of this directionality is understood theoretically and has been observed by several satellites. The anisotropy of the trapped proton exposure has not been an important practical consideration for most previous LEO missions because the random spacecraft orientation during passage through the radiation belt 'averages out' the anisotropy. Thus, in spite of the actual exposure anisotropy, cumulative radiation effects over many orbits can be predicted as if the environment were isotropic when the spacecraft orientation is variable during exposure. However, Space Station Freedom will be gravity gradient stabilized to reduce drag, and, due to this fixed orientation, the cumulative incident proton flux will remain anisotropic. The anisotropy could potentially influence several aspects of Space Station design and operation, such as the appropriate location for radiation sensitive components and experiments, location of workstations and sleeping quarters, and the design and placement of radiation monitors. Also, on-board mass could possible be utilized to counteract the anisotropy effects and reduce the dose exposure. Until recently only omnidirectional data bases for the trapped proton environment were available. However, a method to predict orbit-average, angular dependent ('vector') trapped proton flux spectra has been developed from the standard omnidirectional trapped proton data bases. This method was used to characterize the trapped proton anisotropy for the Space Station orbit (28.5 degree inclination, circular) in terms of its dependence on altitude, solar cycle modulation (solar minimum vs. solar maximum), shielding thickness

  15. Anisotropy and relaxation processes of uniaxially oriented CoFe{sub 2}O{sub 4} nanoparticles dispersed in PDMS

    Energy Technology Data Exchange (ETDEWEB)

    Antonel, P.S.; Negri, R.M. [Instituto de Quimica Fisica de Materiales, Ambiente y Energia (INQUIMAE), Departamento de Quimica Inorganica, Analitica y Quimica Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellon II, Av. Cantilo s/n (1428), Buenos Aires (Argentina); Leyva, A.G. [Grupo de Materia Condensada, Gerencia de Investigacion y Aplicaciones, Centro Atomico Constituyentes, Comision Nacional de Energia Atomica, Avda. Gral. Paz 1499 (1650) San Martin, Pcia. de Buenos Aires, Argentina - Escuela de Ciencia y Tecnologia, UNSAM (Argentina); Jorge, G.A., E-mail: gjorge@df.uba.ar [Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellon I, Av. Cantilo s/n (1428), Buenos Aires (Argentina)

    2012-08-15

    When a uniaxial magnetic field is applied to a non-magnetic dispersive medium filled with magnetic nanoparticles, they auto-assemble into thin needles parallel to the field direction, due to the strong dipolar interaction among them. We have prepared in this way magnetically oriented nanocomposites of nanometer-size CoFe{sub 2}O{sub 4} particles in a polydimethylsiloxane polymer matrix, with 10% w/w of magnetic particles. We present the characteristic magnetic relaxation curves measured after the application of a magnetic field forming an angle {alpha} with respect to the needle direction. We show that the magnetic viscosity (calculated from the logarithmic relaxation curves) as a function of {alpha} presents a minimum at {alpha}=0, indicating slower relaxation processes associated with this configuration of fields. The results seems to point out that the local magnetic anisotropy of the nanoparticles is oriented along the needles, resulting in the macroscopic magnetic anisotropy observed in our measurements.

  16. Enhancement of the point defect pinning effect in Mo-doped Bi2212 single crystals of reduced anisotropy

    CERN Document Server

    Han, S H; Dai, Y; Zhang, Y; Zhang, H; Zhao, Y

    2002-01-01

    High quality Bi sub 2 Sr sub 2 CaCu sub 2 sub - sub x Mo sub x O sub y (x = 0, 0.01 and 0.02) single crystals have been grown by a self-flux method in a horizontal temperature gradient and their flux pinning and irreversibility behaviour have been investigated. The irreversibility lines of the undoped and Mo-doped Bi2212 crystals have been greatly improved by reducing the anisotropy parameter gamma. However, this improvement is much more pronounced for Mo-doped crystals than for the undoped ones. The peak effect of magnetization loops also changes with both Mo-doping and gamma. The results provide strong evidence that the point defect pinning served by Mo is greatly enhanced when the anisotropy of the system is reduced.

  17. Anisotropy and relaxation processes of uniaxially oriented CoFe2O4 nanoparticles dispersed in PDMS

    International Nuclear Information System (INIS)

    Antonel, P.S.; Negri, R.M.; Leyva, A.G.; Jorge, G.A.

    2012-01-01

    When a uniaxial magnetic field is applied to a non-magnetic dispersive medium filled with magnetic nanoparticles, they auto-assemble into thin needles parallel to the field direction, due to the strong dipolar interaction among them. We have prepared in this way magnetically oriented nanocomposites of nanometer-size CoFe 2 O 4 particles in a polydimethylsiloxane polymer matrix, with 10% w/w of magnetic particles. We present the characteristic magnetic relaxation curves measured after the application of a magnetic field forming an angle α with respect to the needle direction. We show that the magnetic viscosity (calculated from the logarithmic relaxation curves) as a function of α presents a minimum at α=0, indicating slower relaxation processes associated with this configuration of fields. The results seems to point out that the local magnetic anisotropy of the nanoparticles is oriented along the needles, resulting in the macroscopic magnetic anisotropy observed in our measurements.

  18. Anisotropy and compression/tension asymmetry of PP containing soft and hard particles and short glass fibers

    Directory of Open Access Journals (Sweden)

    A. M. Hartl

    2015-07-01

    Full Text Available Polypropylene (PP composites are used in a wide range of structural applications. Except for fiber reinforced PP, most PP particle composites are commonly considered to be isotropic or at least quasi-isotropic. In this paper, however, the anisotropy of several PP composites containing soft (rubber and hard (talc particles and glass fibers is characterized in detail in terms of the material microstructure as well as the resulting mechanical properties in monotonic tensile and compressive experiments. The microstructural investigations showed that all composites displayed a certain surface-core layer structure of distinctly different orientation patterns and with a higher degree of orientation in the surface layer. Also in mechanical testing an anisotropic behavior was observed with the degree of anisotropy being more pronounced in tension than compression. Moreover, the compression/tension asymmetry also strongly depends on filler type and orientation.

  19. Energy-based ferromagnetic material model with magnetic anisotropy

    International Nuclear Information System (INIS)

    Steentjes, Simon; Henrotte, François; Hameyer, Kay

    2017-01-01

    Non-oriented soft magnetic materials are commonly assumed to be magnetically isotropic. However, due to the rolling process a preferred direction exists along the rolling direction. This uniaxial magnetic anisotropy, and the related magnetostriction effect, are critical to the accurate calculation of iron losses and magnetic forces in rotating electrical machines. This paper proposes an extension of an isotropic energy-based vector hysteresis model to account for these two effects. - Highlights: • Energy-based vector hysteresis model with magnetic anisotropy. • Two-scale model to account for pinning field distribution. • Pinning force and reluctivity are extended to anisotropic case.

  20. Procedures for measurement of anisotropy factor of neutron sources

    International Nuclear Information System (INIS)

    Creazolla, P.G.; Camargo, A.; Astuto, A.; Silva, F.; Pereira, W.W.

    2017-01-01

    Radioisotope sources of neutrons allow the production of reference fields for calibration of neutron measurement devices for radioprotection and analysis purposes. When the emission rate of these sources is isotropic, no correction is necessary. However, variations in the source capsule material and variations in the concentration of the emitting material may produce differences in its neutron emission rate relative to the source axis, this effect is called anisotropy. A proposed procedure for measuring the anisotropy factor of the sources belonging to the IRD/LNMRI/LN Neutron Metrology Laboratory using a Precision Long Counter (PLC) detector will be presented

  1. Friction anisotropy-driven domain imaging on exfoliated monolayer graphene.

    Science.gov (United States)

    Choi, Jin Sik; Kim, Jin-Soo; Byun, Ik-Su; Lee, Duk Hyun; Lee, Mi Jung; Park, Bae Ho; Lee, Changgu; Yoon, Duhee; Cheong, Hyeonsik; Lee, Ki Ho; Son, Young-Woo; Park, Jeong Young; Salmeron, Miquel

    2011-07-29

    Graphene produced by exfoliation has not been able to provide an ideal graphene with performance comparable to that predicted by theory, and structural and/or electronic defects have been proposed as one cause of reduced performance. We report the observation of domains on exfoliated monolayer graphene that differ by their friction characteristics, as measured by friction force microscopy. Angle-dependent scanning revealed friction anisotropy with a periodicity of 180° on each friction domain. The friction anisotropy decreased as the applied load increased. We propose that the domains arise from ripple distortions that give rise to anisotropic friction in each domain as a result of the anisotropic puckering of the graphene.

  2. Effects of scattering anisotropy approximation in multigroup radiation shielding calculations

    International Nuclear Information System (INIS)

    Altiparmakov, D.

    1983-01-01

    Expansion of the scattering cross sections into Legendre series is the usual way of solving neutron transport problems. Because of the large space gradients of the neutron flux, the effects of that approximation become especially remarkable in the radiation shielding calculations. In this paper, a method taking into account the scattering anisotropy is presented. From the point od view of the accuracy and computing rate, the optimal approximation of the scattering anisotropy is established for the basic protective materials on the basis of simple problem calculations. (author)

  3. Measuring the cosmological lepton asymmetry through the CMB anisotropy

    CERN Document Server

    Kinney, W H; Kinney, William H.; Riotto, Antonio

    1999-01-01

    A large lepton asymmetry in the Universe is still a viable possibility and leads to many interesting phenomena such as gauge symmetry nonrestoration at high temperature. We show that a large lepton asymmetry changes the predicted cosmic microwave background (CMB) anisotropy and that any degeneracy in the relic neutrino sea will be measured to a precision of 1% or better when the CMB anisotropy is measured at the accuracy expected to result from the planned satellite missions MAP and Planck. In fact, the current measurements already put an upper limit on the lepton asymmetry of the Universe which is stronger than the one coming from considerations of primordial nucleosynthesis and structure formation.

  4. Magnetic anisotropy of nonmodulated Ni-Mn-Ga martensite revisited

    Czech Academy of Sciences Publication Activity Database

    Heczko, Oleg; Straka, L.; Novák, Václav; Fähler, S.

    2010-01-01

    Roč. 107, č. 9 (2010), 09A914/1-09A914/3 ISSN 0021-8979 Grant - others:AV ČR(CZ) M100100913 Institutional research plan: CEZ:AV0Z10100520 Keywords : magnetic anisotropy of non-modulated martensite * temperature dependence of anisotropy * Ni-Mn-Ga * adaptive martensite Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.064, year: 2010 http://jap.aip.org/resource/1/japiau/v107/i9/p09A914_s1

  5. Topographical Anisotropy and Wetting of Ground Stainless Steel Surfaces

    Directory of Open Access Journals (Sweden)

    Cornelia Bellmann

    2012-12-01

    Full Text Available Microscopic and physico-chemical methods were used for a comprehensive surface characterization of different mechanically modified stainless steel surfaces. The surfaces were analyzed using high-resolution confocal microscopy, resulting in detailed information about the topographic properties. In addition, static water contact angle measurements were carried out to characterize the surface heterogeneity of the samples. The effect of morphological anisotropy on water contact angle anisotropy was investigated. The correlation between topography and wetting was studied by means of a model of wetting proposed in the present work, that allows quantifying the air volume of the interface water drop-stainless steel surface.

  6. Banana regime pressure anisotropy in a bumpy cylinder magnetic field

    International Nuclear Information System (INIS)

    Garcia-Perciante, A.L.; Callen, J.D.; Shaing, K.C.; Hegna, C.C.

    2006-01-01

    The pressure anisotropy is calculated for a plasma in a bumpy cylindrical magnetic field in the low collisionality (banana) regime for small magnetic-field modulations (ε≡ΔB/2B parallel is then calculated and is shown to exceed the flux-surface-averaged parallel viscous force parallel > by a factor of O(1/ε). A high-frequency limit (ω>>ν) for the pressure anisotropy is also determined and the calculation is then extended to include the full frequency dependence by using an expansion in Cordey eigenfunctions

  7. Electromagnetic Weible Instability in Intense Charged Particle Beams with Large Energy Anisotropy

    International Nuclear Information System (INIS)

    Startsev, Edward A.; Davidson, Ronald C.

    2003-01-01

    In plasmas with strongly anisotropic distribution functions, collective instabilities may develop if there is sufficient coupling between the transverse and longitudinal degrees of freedom. Our previous numerical and theoretical studies of intense charged particle beams with large temperature anisotropy [E. A. Startsev, R. C. Davidson and H. Qin, PRSTAB, 6, 084401 (2003); Phys. Plasmas 9, 3138 (2002)] demonstrated that a fast, electrostatic, Harris-like instability develops, and saturates nonlinearly, for sufficiently large temperature anisotropy (T perpendi c ular b /T parallelb >> 1). The total distribution function after saturation, however, is still far from equipartitioned. In this paper the linearized Vlasov-Maxwell equations are used to investigate detailed properties of the transverse electromagnetic Weibel-type instability for a long charge bunch propagating through a cylindrical pipe of radius r w . The kinetic stability analysis is carried out for azimuthally symmetric perturbations about a two-temperature thermal equilibrium distribution in the smooth-focusing approximation. The most unstable modes are identified, and their eigenfrequencies, radial mode structure and instability thresholds are determined. The stability analysis shows that, although there is free energy available to drive the electromagnetic Weibel instability, the finite transverse geometry of the charged particle beam introduces a large threshold value for the temperature anisotropy ((T perpendi c ularb /T parallelb ) Weibel >> (T perpendi c ularb /T parallelb ) Harris ) below which the instability is absent. Hence, unlike the case of an electrically neutral plasma, the Weibel instability is not expected to play as significant a role in the process of energy isotropization of intense unneutralized charged particle beams as the electrostatic Harris-type instability

  8. Understanding particle size and distance driven competition of interparticle interactions and effective single-particle anisotropy.

    Science.gov (United States)

    Pacakova, B; Mantlikova, A; Niznansky, D; Kubickova, S; Vejpravova, J

    2016-05-25

    Magnetic response of single-domain nanoparticles (NPs) in concentrated systems is strongly affected by mutual interparticle interactions. However, particle proximity significantly influences single-particle effective anisotropy. To solve which of these two phenomena plays a dominant role in the magnetic response of real NP systems, systematic study on samples with well-defined parameters is required. In our work, we prepared a series of nanocomposites constituted of highly-crystalline and well-isolated CoFe2O4 NPs embedded in an amorphous SiO2 matrix using a single-molecule precursor method. This preparation method enabled us to reach a wide interval of particle size and concentration. We observed that the characteristic parameters of the single-domain state (coercivity, blocking temperature) and dipole-dipole interaction energy ([Formula: see text]) scaled with each other and increased with increasing [Formula: see text], where d XRD was the NP diameter and r was the interparticle distance. Our results are in excellent agreement with Monte-Carlo simulations of the particle growth. Moreover, we demonstrated that the contribution of [Formula: see text] acting as an additional energetic barrier to the superspin reversal or as an average static field did not sufficiently explain how the concentrated NP systems responded to an external magnetic field. Alternations in the blocking temperature and coercivity of our NP systems accounted for reformed relaxations of the NP superspins and modified effective anisotropy energy of the interacting NPs. Therefore, the concept of modified NP effective anisotropy explains the magnetic response of our concentrated NP systems better than the concept of the energy barrier influenced by interparticle interactions.

  9. Magnetic anisotropy in GaMnAs; Magnetische Anisotropie in GaMnAs

    Energy Technology Data Exchange (ETDEWEB)

    Daeubler, Joachim

    2009-07-02

    The goal of the present work was the detailed investigation of the impact of parameters like vertical strain, hole concentration, substrate orientation and patterning on the MA in GaMnAs. At first a method is introduced enabling us to determine the MA from angle-dependent magnetotransport measurements. This method was used to analyze the impact of vertical strain {epsilon}{sub zz} on the MA in a series of GaMnAs layers with a Mn content of 5% grown on relaxed InGaAs-templates. While hole concentration and Curie temperature were found to be unaffected by vertical strain, a significant dependence of the MA on {epsilon}{sub zz} was found. The most pronounced dependence was observed for the anisotropy parameter B{sub 2} {sub perpendicular} {sub to}, representing the intrinsic contribution to the MA perpendicular to the layer plane. For this parameter a linear dependence on {epsilon}{sub zz} was found, resulting in a strain-induced transition of the magnetic easy axis with increasing strain from in-plane to out-of-plane at {epsilon}{sub zz} {approx} -0.13%. Post-growth annealing of the samples leads to an outdiffusion and/or regrouping of the highly mobile Mn interstitial donor defects, resulting in an increase in both p and T{sub C}. For the annealed samples, the transition from in-plane to out-of-plane easy axis takes place at {epsilon}{sub zz} {approx} -0.07%. From a comparison of as-grown and annealed samples, B{sub 2} {sub perpendicular} {sub to} was found to be proportional to both p and {epsilon}{sub zz}, B{sub 2} {sub perpendicular} {sub to} {proportional_to} p .{epsilon}{sub zz}. To study the influence of substrate orientation on the magnetic properties of GaMnAs, a series of GaMnAs layers with Mn contents up to 5% was grown on (001)- and (113)A-oriented GaAs substrates. The hole densities and Curie temperatures, determined from magnetotransport measurements, are drastically reduced in the (113)A layers. The differences in the magnetic properties of (113)A- and

  10. NoMelt Experiment: High-resolution constraints on Pacific upper mantle fabric inferred from radial and azimuthal anisotropy

    Science.gov (United States)

    Russell, J. B.; Gaherty, J. B.; Lin, P. P.; Lizarralde, D.; Collins, J. A.; Hirth, G.; Evans, R. L.

    2017-12-01

    Observations of seismic anisotropy in the ocean basins are important for constraining deformation and melting processes in the upper mantle. The NoMelt OBS array was deployed on relatively pristine, 70 Ma seafloor in the central Pacific with the aim of constraining upper mantle circulation and the evolution of the lithosphere-asthenosphere system. Surface-waves traversing the array provide a unique opportunity to estimate a comprehensive set of anisotropic parameters. Azimuthal variations in Rayleigh-wave velocity over a period band of 15-180 s suggest strong anisotropic fabric both in the lithosphere and deep in the asthenosphere. High-frequency ambient noise (4-10 s) provides constraints on average VSV and VSH as well as azimuthal variations in both VS and VP in the upper ˜10 km of the mantle. Our best fitting models require radial anisotropy in the uppermost mantle with VSH > VSV by 3 - 7% and as much as 2% radial anisotropy in the crust. Additionally, we find a strong azimuthal dependence for Rayleigh- and Love-wave velocities, with Rayleigh 2θ fast direction parallel to the fossil spreading direction (FSD) and Love 2θ and 4θ fast directions shifted 90º and 45º from the FSD, respectively. These are some of the first direct observations of the Love 2θ and 4θ azimuthal signal, which allows us to directly invert for anisotropic terms G, B, and E in the uppermost Pacific lithosphere, for the first time. Together, these observations of radial and azimuthal anisotropy provide a comprehensive picture of oceanic mantle fabric and are consistent with horizontal alignment of olivine with the a-axis parallel to fossil spreading and having an orthorhombic or hexagonal symmetry.

  11. Thermoelectric response of a periodic composite medium in the presence of a magnetic field: Angular anisotropy

    Science.gov (United States)

    Strelniker, Yakov M.; Bergman, David J.

    2017-12-01

    A calculational method based on Fourier expansion is developed and applied to the study of the strong-field galvanomagnetic thermoelectric properties of a free-electron metal, inside of which is embedded a simple cubic array of identical spheres or cylinders, which have different thermoelectric and conductivity tensors. When the magnetic field is strong enough, the effective galvanomagnetic thermoelectric properties of such composites exhibit very strong variations with the direction of the applied magnetic field with respect to the symmetry axes of the composite microstructure. This is qualitatively similar to the predicted magnetoinduced angular magnetoresistance anisotropy [D. J. Bergman and Y. M. Strelniker, Phys. Rev. B 49, 16256 (1994), 10.1103/PhysRevB.49.16256] which was verified experimentally [M. Tornow et al., Phys. Rev. Lett. 77, 147 (1996), 10.1103/PhysRevLett.77.147]. This is a purely classical effect, even though it is qualitatively similar to what is observed in some metallic crystals which have a noncompact Fermi surface. The current results can be useful for studying the possibility of increasing the thermoelectric figure of merit in periodic composites by application of a strong magnetic field. As follows from our very preliminary results, the figure of merit can be increased by application of a strong magnetic field to the composite.

  12. The effect of stress and magnetostriction on the anisotropy of CoNi/Pt multilayers

    NARCIS (Netherlands)

    van Drent, W.P.; van Drent, W.P.; Bijker, M.D.; Lodder, J.C.

    1996-01-01

    An attempt is made to correlate the effective magnetic anisotropy of sputtered CoNi/Pt multilayers to the average stress in the thin film. It was found that compressive film stress decreases the perpendicular magnetic anisotropy.

  13. Enhancement of perpendicular magnetic anisotropy and anomalous hall effect in Co/Ni multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yiwei; Zhang, Jingyan, E-mail: jyzhang@ustb.edu.cn; Jiang, Shaolong; Liu, Qianqian; Li, Xujing; Yu, Guanghua, E-mail: ghyu@mater.ustb.edu.cn

    2016-12-15

    The perpendicular magnetic anisotropy (PMA) and the anomalous Hall effect (AHE) in Co/Ni multilayer were optimized by manipulating its interface structure (inducing HfO{sub 2} capping layer and Pt insertion) and post-annealing treatment. A strong PMA can be obtained in Co/Ni multilayers with HfO{sub 2} capping layer even after annealing at 400 °C. The heavy metal Hf may improve the interfacial spin-orbit coupling, which responsible for the enhanced PMA and high annealing stability. Moreover, the multilayer containing HfO{sub 2} capping layer also exhibited high saturation anomalous Hall resistivity through post-annealing, which is 0.85 μΩ cm after annealing at 375 °C, 211% larger than in the sample at deposited state which is only 0.27 μΩ cm. The enhancement of AHE is mainly attributed to the interface scattering through post-annealing treatment. - Highlights: • The perpendicular magnetic anisotropy and anomalous Hall effect of Co/Ni multilayer films were studied. • The PMA thermal stability of the Co/Ni ML can be enhanced by HfO{sub 2} capping layer and Pt insertion. • The anomalous Hall resistivity of Co/Ni ML covered by HfO{sub 2} was enhanced by post-annealing treatment.

  14. Lithospheric anisotropy on the Kerguelen hotspot track inferred from Rayleigh wave polarisation anomalies

    Science.gov (United States)

    Pettersen, Øyvind; Maupin, Valérie

    2002-04-01

    Rayleigh waves recorded at the Geoscope station PAF on the Kerguelen Isles in the Indian Ocean, show strong polarisation anomalies in the period range 20-50 s, as demonstrated by dispersion analysis of 3-component recordings. The largest and most consistent anomalies are observed for events located in the southern part of the Java Trench. At 25 s the Rayleigh waves present transverse components with an amplitude of up to 55 per cent of the amplitude of the longitudinal components. The particle motion in the horizontal plane is largely elliptical. By comparison, very few and mostly small polarisation anomalies are detected at the nearby Geoscope stations AIS and CRZF on the Amsterdam and Crozet Isles, respectively. Wave path deviations from the epicentre-receiver great circle, as calculated in tomographic models of the Indian Ocean, cannot explain the polarisation anomalies. Using a multiple-scattering scheme for modelling surface waves in 3-D heterogeneous and anisotropic structures, we show that wavefield distortion due to the geometrical structure of the Kerguelen Plateau in the vicinity of the station cannot explain the anomalies either, but that anisotropy can. We infer the presence of an anisotropic structure in the lithosphere to the north of the Kerguelen Isles, containing 40 per cent oriented pyrolite, with fast axis tilting downwards in a north-north-east direction. The anisotropy may be caused by deformation of the lithosphere related to the Kerguelen hotspot.

  15. Atomic-scale engineering of magnetic anisotropy of nanostructures through interfaces and interlines.

    Science.gov (United States)

    Ouazi, S; Vlaic, S; Rusponi, S; Moulas, G; Buluschek, P; Halleux, K; Bornemann, S; Mankovsky, S; Minár, J; Staunton, J B; Ebert, H; Brune, H

    2012-01-01

    The central goals of nanoscale magnetic materials science are the self-assembly of the smallest structure exhibiting ferromagnetic hysteresis at room temperature, and the assembly of these structures into the highest density patterns. The focus has been on chemically ordered alloys combining magnetic 3d elements with polarizable 5d elements having high spin-orbit coupling and thus yielding the desired large magneto-crystalline anisotropy. The chemical synthesis of nanoparticles of these alloys yields disordered phases requiring annealing to transform them to the high-anisotropy L1(0) structure. Despite considerable efforts, so far only part of the nanoparticles can be transformed without coalescence. Here we present an alternative approach to homogeneous alloys, namely the creation of nanostructures with atomically sharp bimetallic interfaces and interlines. They exhibit unexpectedly high magnetization reversal energy with values and directions of the easy magnetization axes strongly depending on chemistry and texture. We find significant deviations from the expected behaviour for commonly used element combinations. Ab-initio calculations reproduce these results and unravel their origin.

  16. First-principles calculations of the magnetic anisotropy energy of Fe-V multilayers

    International Nuclear Information System (INIS)

    Le Bacq, O.; Eriksson, O.; Johansson, B.; James, P.; Delin, A.

    2002-06-01

    The magnetic anisotropy energy (MAE) of Fe 2 V-6, Fe 3 , and Fe 4 V 4 multilayers are investigated using first-principles spin-polarized and relativistic band-structure calculations based upon the full-potential linearized muffin-tin-orbital method. A strong difference in the MAE and the easy axis of magnetization (calculated for the experimental lattice parameters) is observed between the three studied multilayer systems, with easy axes of (001), (110), and (100) for Fe 2 V 6 , Fe 3 V 5 , and Fe-4V 4 , respectively. The MAE of the Fe 2 V6 and Fe 4 V 4 multilayers agrees well with the experimental data. The origin of this difference of behavior is analyzed, via a study of the influence of the atomic volume as well as a relaxation study of the multilayers with respect to the tetragonal deformation. The important role played by the c/a axial ratio, imposed by the alloying effects, is outlined. The magnetic anisotropy coefficients entering the expression of the MAE, as a function of the directional cosines, are extracted from a series of calculations for four independent spin directions. Finally, the band-filling effects on the MAE are analyzed as well as the different contributions in reciprocal space. (author)

  17. Temperature-dependent elastic anisotropy and mesoscale deformation in a nanostructured ferritic alloy

    Science.gov (United States)

    Stoica, G. M.; Stoica, A. D.; Miller, M. K.; Ma, D.

    2014-10-01

    Nanostructured ferritic alloys are a new class of ultrafine-grained oxide dispersion-strengthened steels that have promising properties for service in extreme environments in future nuclear reactors. This is due to the remarkable stability of their complex microstructures containing numerous Y-Ti-O nanoclusters within grains and along grain boundaries. Although nanoclusters account primarily for the exceptional resistance to irradiation damage and high-temperature creep, little is known about the mechanical roles of the polycrystalline grains that constitute the ferritic matrix. Here we report an in situ mesoscale characterization of anisotropic responses of ultrafine ferrite grains to stresses using state-of-the-art neutron diffraction. We show the experimental determination of single-crystal elastic constants for a 14YWT alloy, and reveal a strong temperature-dependent elastic anisotropy that leads to elastic softening and instability of the ferrite. We also demonstrate, from anisotropy-induced intergranular strains, that a deformation crossover exists from low-temperature lattice hardening to high-temperature lattice softening in response to extensive plastic deformation.

  18. Review- Magnetic orientation and magnetic anisotropy in paramagnetic layered oxides containing rare-earth ions

    Directory of Open Access Journals (Sweden)

    Shigeru Horii, Atsushi Ishihara, Takayuki Fukushima, Tetsuo Uchikoshi, Hiraku Ogino, Tohru S Suzuki, Yoshio Sakka, Jun-ichi Shimoyama and Kohji Kishio

    2009-01-01

    Full Text Available The magnetic anisotropies and easy axes of magnetization at room temperature were determined, and the effects of rare-earth (RE ions were clarified for RE-based cuprates, RE-doped bismuth-based cuprates and RE-doped Bi-based cobaltite regarding the grain orientation by magnetic field. The easy axis, determined from the powder orientation in a static field of 10 T, depended qualitatively on the type of RE ion for all three systems. On the other hand, the magnetization measurement of the c-axis oriented powders, aligned in static or rotating fields, revealed that the type of RE ion strongly affected not only the directions of the easy axis but also the absolute value of magnetic anisotropy, and an appropriate choice of RE ion is required to minimize the magnetic field used for grain orientation. We also studied the possibility of triaxial grain orientation in high-critical-temperature superconductors by a modulated oval magnetic field. In particular, triaxial orientation was attempted in a high-oxygen-pressure phase of orthorhombic RE-based cuprates Y2Ba4Cu7Oy. Although the experiment was performed in epoxy resin, which is not practical, in-plane alignment within 3° was achieved.

  19. Origin of interfacial perpendicular magnetic anisotropy in MgO/CoFe/metallic capping layer structures

    Science.gov (United States)

    Peng, Shouzhong; Wang, Mengxing; Yang, Hongxin; Zeng, Lang; Nan, Jiang; Zhou, Jiaqi; Zhang, Youguang; Hallal, Ali; Chshiev, Mairbek; Wang, Kang L.; Zhang, Qianfan; Zhao, Weisheng

    2015-12-01

    Spin-transfer-torque magnetic random access memory (STT-MRAM) attracts extensive attentions due to its non-volatility, high density and low power consumption. The core device in STT-MRAM is CoFeB/MgO-based magnetic tunnel junction (MTJ), which possesses a high tunnel magnetoresistance ratio as well as a large value of perpendicular magnetic anisotropy (PMA). It has been experimentally proven that a capping layer coating on CoFeB layer is essential to obtain a strong PMA. However, the physical mechanism of such effect remains unclear. In this paper, we investigate the origin of the PMA in MgO/CoFe/metallic capping layer structures by using a first-principles computation scheme. The trend of PMA variation with different capping materials agrees well with experimental results. We find that interfacial PMA in the three-layer structures comes from both the MgO/CoFe and CoFe/capping layer interfaces, which can be analyzed separately. Furthermore, the PMAs in the CoFe/capping layer interfaces are analyzed through resolving the magnetic anisotropy energy by layer and orbital. The variation of PMA with different capping materials is attributed to the different hybridizations of both d and p orbitals via spin-orbit coupling. This work can significantly benefit the research and development of nanoscale STT-MRAM.

  20. Computational study of flow anisotropy in sheared fractures with self-affine surfaces

    Science.gov (United States)

    Selzer, Michael; Schoenball, Martin; Ankit, Kumar; Nestler, Britta; Kohl, Thomas; Kühnle, Natalie; Schmittbuhl, Jean

    2013-04-01

    Characterization of the hydraulic conductivities of rock masses is imperative for the development and engineering of various underground installations like geothermal power plants, waste repositories or tunnelling. The intrinsic permeability of intact rock is extremely low; however the rock mass usually contains a dense network of fractures with a relatively high hydraulic conductivity, which determines the hydraulic properties of the rock mass. Conventionally, in order to estimate the hydraulic conductivities of fractures, the cubic law for laminar fluid flow in a parallel plate model with constant aperture is applied. However, the surface of natural fractures is rough, which strongly affects the hydraulic properties of fractures and causes deviation from the analytical result. To enhance fluid flow in a fractured rock mass, well bores in an intact rock mass are pressurized with fluid to reduce effective normal stresses on pre-existing fractures to enable shearing. The shearing motion of rock enhances hydraulic anisotropy, since the rocks become more conductive parallel to the shearing direction and less conduction perpendicular to the shearing direction. In the current work, we present a numerical study of hydraulic anisotropy introduced as a result of shearing of algorithmically generated fractures. A rough surface can be mathematically described as self-affine structure with a correlation between heights of asperities and their spatial distribution. Fractures are generated by displacing two identical fractal rough surfaces incorporating dilation to obtain an aperture distribution. To investigate the geometrical and hydraulic properties of generated fractures, we use a finite element method to solve the Reynolds equations in a simplified 2D model. We identify a regime, where a simplified hydraulic fracture model is permitted. Using the 2D model, we make a statistical study of the hydraulic anisotropy for a representative set of 1000 algorithmically generated

  1. Textural and microstructural development of the Barro Alto Complex: implications for seismic anisotropy

    Science.gov (United States)

    Silveira, Camila; Lagoeiro, Leonardo; Barbosa, Paola; Cavalcante, Geane Carolina; Ferreira, Filippe; Suita, Marcos; Conte, Thailli

    2017-04-01

    Crustal rheology is associated with the behavior of its constituents in response to stress and strain, while the seismic anisotropy is a property that can correlate these parameters. Seismic properties are strongly related to the microstructures and crystallographic preferred orientation (CPO) of the rocks. In this work, we study CPO-derived seismic anisotropy of metamorphosed gabbro-norites from the Barro Alto (Brazil central) layered complex. The EBSD technique was employed to analyze the crystallographic orientation of the main mineral assembly, diopside and feldspar. The Barro Alto complex belongs to the Tocantins Structural Province, developed between the Amazon and São Francisco cratons, during the Neoproterozoic Brasiliano orogenic cycle. This complex was formed by a mafic-ultramafic layered intrusion mylonitized and metamorphosed under granulite facies conditions. The mylonitic foliation shows compositional segregation into felsic and mafic bands. The samples are composed of porphyroclasts of plagioclase and diopside in a fine matrix of plagioclase, clinopyroxene, orthopyroxene and, less commonly, amphibole and biotite. The plagioclase porphyroclasts exhibit undulose extinction and core-mantle structure. In fine matrix samples the poles to a(100), b(010) and c(001) are randomly distributed in both phases. However, for increasing matrix grain size plagioclase grains shows maxima of a(100) poles sub-parallel to the foliation and b(010) normal to the foliation. The low value of the J index (2.4 for plagioclase and 1.8 for diopside) indicates poorly developed fabric. Misorientation profiles showing high frequency of small angle boundaries are typical of recrystallization by subgrain rotation mechanisms. The microstructural and CPO analyses suggest deformation controlled by diffusive processes. The CPO models were compared to models described in the literature, based on the anorthite + diopside assembly, since these are the major phases, and thus control the

  2. Deformation and seismic anisotropy of silicate post-perovskite in the Earth's lowermost mantle

    Science.gov (United States)

    wu, X.; Lin, J.; Mao, Z.; Liu, J.; Kaercher, P. M.; Wenk, H.; Prakapenka, V.; Zhuravlev, K. K.

    2013-12-01

    The D' layer in the Earth's lowermost mantle with an average thickness of 250 km right above the core-mantle boundary plays a significant role in the geophysics, geochemistry, and geodynamics of the planet's interior. Seismic observations of the region have shown a number of enigmatic features including shear wave discontinuity and seismic wave anisotropy. The seismic anisotropy, in which the horizontally-polarized shear wave (VSH) travels faster than the vertically-polarized shear wave (VSV) by 1%~3% in areas below the circum Pacific, has been proposed to be a result of the lattice-preferred orientation of silicate post-perovskite (PPv) that is to be the most abundant phase in the D' layer [1]. Therefore, understanding the elasticity and deformation of the PPv phase is critical under relevant P-T conditions of the region. However, experimental results on the textures and the elastic anisotropy of PPv remain largely limited and controversial. Specifically, a number of slip systems of PPv, such as (010), (100), (110) and (001), have been proposed based on experimental and theoretical results [2-4]. Here we have studied the textures and deformation mechanism of iron-bearing PPv ((Mg0.75,Fe0.25)SiO3) at relevant P-T conditions of the lowermost mantle using synchrotron radiation radial x-ray diffraction in a membrane-driven laser-heated diamond anvil cell. The diffraction patterns were recorded from the laser-heated PPv sample during further compression between 130 GPa and 150 GPa. Analyses of the diffraction patterns and simulation results from viscoplastic self-consistent polycrystal plasticity code (VPSC) show that the development of active slip systems can be strongly influenced by experimental pressure-temperature-time conditions. At relevant P-T conditions of the lowermost mantle, our results demonstrate that the dominant slip systems of PPv should be (001)[100] and (001)[010]. Combined these results with the elasticity of PPv, we provide more constrains on the

  3. Anisotropy of magnetic susceptibility (AMS) studies of Campanian ...

    Indian Academy of Sciences (India)

    Oriented samples of sediments from Ariyalur Group, Cauvery Basin, south India, were studied for low field anisotropy of magnetic susceptibility (AMS) measurements to unravel the magnetic fabrics and pale- ocurrent directions. The results of AMS parameters of the sediments indicate primary depositional fabrics.

  4. Computing magnetic anisotropy constants of single molecule magnets

    Indian Academy of Sciences (India)

    Administrator

    Abstract. We present here a theoretical approach to compute the molecular magnetic anisotropy parameters, DM and EM for single molecule magnets in any given spin eigenstate of exchange spin Hami- ltonian. We first describe a hybrid constant MS-valence bond (VB) technique of solving spin Hamilto- nians employing ...

  5. Computing magnetic anisotropy constants of single molecule magnets

    Indian Academy of Sciences (India)

    We present here a theoretical approach to compute the molecular magnetic anisotropy parameters, and for single molecule magnets in any given spin eigenstate of exchange spin Hamiltonian. We first describe a hybrid constant -valence bond (VB) technique of solving spin Hamiltonians employing full spatial ...

  6. Fluorescence anisotropy of acridinedione dyes in glycerol: Prolate ...

    Indian Academy of Sciences (India)

    TECS

    of rotational reorientation of molecules in liquid so- lution using ... sition metal ions has been studied. 29. In the present work, ..... of-plane rotation. ADR dyes show single exponen- tial fluorescence anisotropy decay at 250 nm due to slower in-plane rotation. The absorption and emission dipoles are nearly collinear at 394 ...

  7. Stability analysis of sandy slope considering anisotropy effect in ...

    Indian Academy of Sciences (India)

    This paper aims to investigate the effect of anisotropy of shear strength parameter on the stability of a sandy slope by performing the limit equilibrium analysis. Because of scarcity of mathematical equation for anisotropic friction angle of sand, at first, all results of principal stress rotation tests are processed by artificial neural ...

  8. Illustrative view on the magnetocrystalline anisotropy of adatoms and monolayers

    Czech Academy of Sciences Publication Activity Database

    Šipr, Ondřej; Mankovsky, S.; Polesya, S.; Bornemann, S.; Minár, J.; Ebert, H.

    2016-01-01

    Roč. 93, č. 17 (2016), s. 1-13, č. článku 174409. ISSN 2469-9950 R&D Projects: GA ČR(CZ) GAP108/11/0853 Institutional support: RVO:68378271 Keywords : magnetic anisotropy * adatom * monolayer * spin-orbit coupling Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.836, year: 2016

  9. Magnetocrystalline anisotropy of FePt: a detailed view

    Czech Academy of Sciences Publication Activity Database

    Khan, S.A.; Blaha, P.; Ebert, H.; Minár, J.; Šipr, Ondřej

    2016-01-01

    Roč. 94, č. 14 (2016), 1-10, č. článku 144436. ISSN 2469-9950 Institutional support: RVO:68378271 Keywords : magnetocrystalline anisotropy * FePt * LDA Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.836, year: 2016

  10. Employing the fluorescence anisotropy and quenching kinetics of ...

    Indian Academy of Sciences (India)

    TECS

    Five proteins, namely ribonuclease T1, bovine serum albumin, melittin, barstar and hen egg white lysozyme appear likely to possess tryptophan(s) in hydrophobic clusters based on their reduced bimole- cular quenching rates and higher steady-state anisotropy in proportion to their chain length. We also show that the ...

  11. Angular anisotropy of the cosmic microwave background radiation

    International Nuclear Information System (INIS)

    Silk, J.

    1982-01-01

    The theory of fluctuations in the cosmic microwave background radiation is reviewed. Anisotropy on large-scale (dipole and quadrupole) and on small scales is discussed. The smoothing effects of secondary ionization (fractional ionization x) are found to be unimportant over an angular scale greater than approx.= 5(OMEGAx)sup(1/3) degrees. (author)

  12. Anisotropy of NEWS damage parameters in CFRP composite

    Czech Academy of Sciences Publication Activity Database

    Převorovský, Zdeněk; Kober, Jan; Tokar, Daniel; Krofta, Josef

    s. 9-9 [World Conference on Non-Destructive Testing /19./. 13.06.2016-17.06.2016, Mnichov] Institutional support: RVO:61388998 Keywords : carbon fiber composites * anisotropy * damage detection * nonlinear elastic wave spectroscopy Subject RIV: BI - Acoustics https://www.wcndt2016.com/Programme/show/Mo-1-B-3

  13. Diffusion tensor MR microscopy of tissues with low diffusional anisotropy.

    Science.gov (United States)

    Bajd, Franci; Mattea, Carlos; Stapf, Siegfried; Sersa, Igor

    2016-06-01

    Diffusion tensor imaging exploits preferential diffusional motion of water molecules residing within tissue compartments for assessment of tissue structural anisotropy. However, instrumentation and post-processing errors play an important role in determination of diffusion tensor elements. In the study, several experimental factors affecting accuracy of diffusion tensor determination were analyzed. Effects of signal-to-noise ratio and configuration of the applied diffusion-sensitizing gradients on fractional anisotropy bias were analyzed by means of numerical simulations. In addition, diffusion tensor magnetic resonance microscopy experiments were performed on a tap water phantom and bovine articular cartilage-on-bone samples to verify the simulation results. In both, the simulations and the experiments, the multivariate linear regression of the diffusion-tensor analysis yielded overestimated fractional anisotropy with low SNRs and with low numbers of applied diffusion-sensitizing gradients. An increase of the apparent fractional anisotropy due to unfavorable experimental conditions can be overcome by applying a larger number of diffusion sensitizing gradients with small values of the condition number of the transformation matrix. This is in particular relevant in magnetic resonance microscopy, where imaging gradients are high and the signal-to-noise ratio is low.

  14. Anisotropy of the mobility of pentacene from frustration

    NARCIS (Netherlands)

    de Wijs, GA; Mattheus, CC; de Groot, RA; Palstra, TTM; Wijs, Gilles A. de

    2003-01-01

    The bandstructure of pentacene is calculated using first-principles density functional theory. A large anisotropy of the hole and electron effective masses within the molecular planes is found. The band dispersion of the HOMO and the LUMO is analyzed with the help of a tight-binding (TB) fit. The

  15. Fission anisotropy of Tl produced in fusion reactions in the ...

    Indian Academy of Sciences (India)

    Abstract. The anisotropy of fission fragment angular distribution, evaporation residue cross- section and the fission cross-section were calculated for 197Tl formed in 16O+181Ta reactions in the framework of the modified statistical model and the results were compared with the experimental data. The effects of temperature ...

  16. Employing the fluorescence anisotropy and quenching kinetics of ...

    Indian Academy of Sciences (India)

    TECS

    phobic clusters in 8 M urea. Melittin which is almost similar in size to peptide glucagon, shows a significantly higher steady state anisotropy and lower kq in contrast to glucagon. This strengthens the possibility that Trp in melittin is part of a residual structure. Figure 2. Corrected fluorescence emission spectra of.

  17. The large scale microwave background anisotropy in decaying particle cosmology

    International Nuclear Information System (INIS)

    Panek, M.

    1987-06-01

    We investigate the large-scale anisotropy of the microwave background radiation in cosmological models with decaying particles. The observed value of the quadrupole moment combined with other constraints gives an upper limit on the redshift of the decay z/sub d/ < 3-5. 12 refs., 2 figs

  18. Magnetic anisotropy of plastically deformed low-carbon steel

    Czech Academy of Sciences Publication Activity Database

    Stupakov, Oleksandr; Uchimoto, T.; Takagi, T.

    2010-01-01

    Roč. 73, č. 19 (2010), 195003/1-195003/7 ISSN 0022-3727 R&D Projects: GA ČR GP102/09/P108 Institutional research plan: CEZ:AV0Z10100520 Keywords : magnetic anisotropy * plastic deformation * magnetic hysteresis * Barkhausen noise Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.105, year: 2010

  19. Seismic anisotropy of serpentinite from Val Malenco, Italy

    Czech Academy of Sciences Publication Activity Database

    Kern, H.; Lokajíček, Tomáš; Svitek, Tomáš; Wenk, H.-R.

    2015-01-01

    Roč. 120, č. 6 (2015), s. 4113-4129 ISSN 2169-9313 R&D Projects: GA MŠk LH13102 Institutional support: RVO:67985831 Keywords : serpentinite * anisotropy Subject RIV: DE - Earth Magnetism, Geodesy, Geography Impact factor: 3.318, year: 2015

  20. Anisotropy in Dynamical Models of Elliptical Galaxy Dark Halos

    Science.gov (United States)

    Forestell, Amy; Gebhardt, K.

    2013-07-01

    Abstract (2,250 Maximum Characters): We discuss the orbital anisotropy results of axisymmetric orbit-superposition dynamical models of elliptical galaxies NGC 821 and NGC 4697. For NGC 821 stellar kinematics are used to determine the best-fitted dark halo (Forestell 2010), then we determine the orbital properties required for planetary nebulae to match the observed kinematic data (Romanowsky et al. 2003) in that assumed dark halo. For NGC 4697 we use both stellar and planetary nebula kinematics (Pinkney et al. 2003, Mendez et al. 2009) to model the galaxy dark halo. In both galaxies we find that the planetary nebulae, which are located at large radii, show radial anisotropy. This is consistent with the results of Dekel et al. (2005), who use disk galaxy merger simulations to show that large anisotropies can be created in the resulting elliptical galaxies and that this anisotropy in combination with the different density profile of a young population could explain how the low dispersions from planetary nebulae measurements are also consistent with typical dark matter halos.

  1. Anisotropy in elastic properties of lithium sodium sulphate ...

    Indian Academy of Sciences (India)

    Anisotropy in elastic properties of lithium sodium sulphate hexahydrate single crystal—An ultrasonic study. GEORGE VARUGHESE. ,∗. , A S KUMAR†, J PHILIP†† and GODFREY LOUIS#. Department of Physics, Catholicate College, Pathanamthitta 689 648, India. †SPAP, M.G. University, Kottayam 686 560, India. ††STIC ...

  2. Magnetic anisotropies of quantum dots doped with magnetic ions

    Czech Academy of Sciences Publication Activity Database

    Výborný, Karel; Han, J.E.; Oszwałdowski, R.; Žutić, I.; Petukhov, A.G.

    2012-01-01

    Roč. 85, č. 15 (2012), "155312-1"-"155312-8" ISSN 1098-0121 Institutional research plan: CEZ:AV0Z10100521 Keywords : magnetocrystalline anisotropy * quantum dot s * dilute magnetic semiconductors Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.767, year: 2012

  3. Fission anisotropy of Tl produced in fusion reactions in the ...

    Indian Academy of Sciences (India)

    Fission anisotropy of. 197. Tl produced in fusion reactions in the framework of the modified statistical model. HADI ESLAMIZADEH. Department of Physics, Persian Gulf University, 75169 Bushehr, Iran. E-mail: m_eslamizadeh@yahoo.com. MS received 4 July 2014; revised 22 September 2014; accepted 27 September 2014.

  4. Anisotropy of magnetic susceptibility (AMS) studies of Campanian ...

    Indian Academy of Sciences (India)

    Oriented samples of sediments from Ariyalur Group, Cauvery Basin, south India, were studied for low field anisotropy of magnetic susceptibility (AMS) measurements to unravel the magnetic fabrics and paleocurrent directions. The results of AMS parameters of the sediments indicate primary depositional fabrics for Sillakkudi ...

  5. Fluorescence anisotropy of acridinedione dyes in glycerol: Prolate ...

    Indian Academy of Sciences (India)

    Time-dependent reorientations of resorcinol-based acridinidione (ADR) dyes in glycerol were studied using steady-state and time-resolved fluorescence studies. The difference between fluorescence anisotropy decays recorded at 460 nm when exciting at 250 nm and those obtained when exciting at 394 nm are reported.

  6. New Results in Microwave Background Anisotropy from WMAP

    Indian Academy of Sciences (India)

    2003-02-11

    NASA released on February 11, 2003 new data for the anisotropy of the microwave background radiation of the Universe, which will be used by cosmologists over the next few years to uncover the parameters impor- tant for the evolution and dynamics of the. Universe. Preliminary results support the standard Big bang ...

  7. Solar energetic particle anisotropies and insights into particle transport

    Energy Technology Data Exchange (ETDEWEB)

    Leske, R. A., E-mail: ral@srl.caltech.edu; Cummings, A. C.; Cohen, C. M. S.; Mewaldt, R. A.; Labrador, A. W.; Stone, E. C. [California Institute of Technology, Pasadena, CA 91125 (United States); Wiedenbeck, M. E. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Christian, E. R.; Rosenvinge, T. T. von [NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

    2016-03-25

    As solar energetic particles (SEPs) travel through interplanetary space, their pitch-angle distributions are shaped by the competing effects of magnetic focusing and scattering. Measurements of SEP anisotropies can therefore reveal information about interplanetary conditions such as magnetic field strength, topology, and turbulence levels at remote locations from the observer. Onboard each of the two STEREO spacecraft, the Low Energy Telescope (LET) measures pitch-angle distributions for protons and heavier ions up to iron at energies of about 2-12 MeV/nucleon. Anisotropies observed using LET include bidirectional flows within interplanetary coronal mass ejections, sunward-flowing particles when STEREO was magnetically connected to the back side of a shock, and loss-cone distributions in which particles with large pitch angles underwent magnetic mirroring at an interplanetary field enhancement that was too weak to reflect particles with the smallest pitch angles. Unusual oscillations in the width of a beamed distribution at the onset of the 23 July 2012 SEP event were also observed and remain puzzling. We report LET anisotropy observations at both STEREO spacecraft and discuss their implications for SEP transport, focusing exclusively on the extreme event of 23 July 2012 in which a large variety of anisotropies were present at various times during the event.

  8. Inversion for weak triclinic anisotropy from acoustic axes

    Czech Academy of Sciences Publication Activity Database

    Vavryčuk, Václav

    2013-01-01

    Roč. 50, č. 8 (2013), s. 1271-1282 ISSN 0165-2125 R&D Projects: GA AV ČR IAA300120801 Institutional support: RVO:67985530 Keywords : acoustic axis * weak anisotropy * elastic waves * wave polarization Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 1.303, year: 2013

  9. The anisotropy of multi-TeV cosmic rays

    Science.gov (United States)

    Dingus, Brenda

    2013-02-01

    The arrival directions of cosmic rays will be isotropized by the deflection of these charged particles in the Galactic magnetic fields. For example, a 10 TeV proton in a typical Galactic field of 2 micro Gauss has a gyroradius of only 0.005 parsec (=1000 AU) which is much smaller than the distance to any postulated sources. However, observations of TeV cosmic rays by Milagro, Tibet III, ARGO, and IceCube, show anisotropies on both large and small angular scales. These observations require the detection of large numbers of cosmic rays because the anisotropies are less than a few parts in 1000. The large angular scale anisotropies, such as a dipole, could point to diffusion from a nearby source, but the smaller scale anisotropies of extent ~10 degrees are much more difficult to explain. Possibilities that have been explored in the literature include magnetic funneling of cosmic rays from nearby sources and acceleration by magnetic reconnection in the heliosphere's magnetotail. No matter what the mechanism, these observations provide new information about cosmic ray production, nearby magnetic fields, and how the cosmic rays observed at Earth are affected by their propagation.

  10. Effect of permeability anisotropy on forced convection thermal ...

    African Journals Online (AJOL)

    Forced convective flow through anisotropic porous saturated circular tube was analysed to determine the entrance length to the hydrodynamic flow. The porous medium saturated with an incompressible viscous fluid was characterized by anisotropy permeability ratio, inclination angle of the principal axes and Prandtl ...

  11. Influence of magnetic anisotropy on the superferromagnetic ordering in nanocomposites

    DEFF Research Database (Denmark)

    Mørup, Steen; Christiansen, Gunnar Dan

    1993-01-01

    Magnetic interaction between ultrafine particles may result in superferromagnetism, i.e., ordering of the magnetic moments of particles which would be superparamagnetic if they were noninteracting. In this article we discuss the influence of the magnetic anisotropy on the temperature dependence o...

  12. Anisotropy of the magnetocaloric effect in DyNiAl

    Czech Academy of Sciences Publication Activity Database

    Kaštil, J.; Javorský, P.; Andreev, Alexander V.

    2009-01-01

    Roč. 321, č. 15 (2009), s. 2318-2321 ISSN 0304-8853 Institutional research plan: CEZ:AV0Z10100520 Keywords : magnetocaloric effec * DyNiAl * magnetism * anisotropy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.204, year: 2009

  13. Deep Crustal Anisotropy and its Distortion Through the Seismological Lens

    Science.gov (United States)

    Schulte-Pelkum, V.; Mahan, K. H.

    2011-12-01

    Seismic interpretations of crustal anisotropy often appear to be at odds with expectations based on structural geology. We provide a solution to the apparent discrepancy based on petrological data and synthetic seismograms and present results across the continental US. Seismic investigations of crustal anisotropy offer one of the best chances to observe lower crustal flow in situ, and receiver function (converted wave) studies have good horizontal and depth resolution and are less expensive than active source studies, and suffer from less tradeoff than tomographic studies. A puzzling observation in receiver function studies of the continental crust has been a prevalence of observed plunging axis anisotropy in subhorizontal layers interpreted to have accommodated a significant component of simple shear. In contrast, geological field observations and deformation experiments suggest that shear zones develop a significant boundary-parallel foliation (C-planes in S-C mylonite) after only modest amounts of strain accumulation (~gamma A2), while plunging P anisotropy shows a much higher amplitude single peak and trough (termed A1). Published crustal sample P versus S anisotropies range within a factor of 2 of each other, with the majority of samples showing comparable P and S anisotropy. While the A2 signal theoretically provides a robust detector for anisotropy, we suggest that a search for the larger A1 signal is more likely to be successful. We present seismic forward modeling results for petrological crustal deformation fabrics with aligned mica, amphibole, and quartz for different geometries. We also show results from the EarthScope Transportable Array across areas with presumed past or present lower crustal flow. When observed receiver function signal amplitudes are decomposed into A0 (isotropic, 1-D), A1, and A2 components, the A1 component dominates A2 by a factor of ~3 averaged across the entire network. The A1 component also contains information on isotropic

  14. Complex seismic anisotropy beneath the IPOC stations of northern Chile

    Science.gov (United States)

    Reiss, Miriam Christina; Wölbern, Ingo; Rümpker, Georg

    2017-04-01

    The subduction of the Nazca plate beneath Central South America has been subject to numerous seismological studies. Here, we focus on seismic anisotropy which provides a direct link to the dynamic processes acting within the upper mantle and crust. The main mechanisms responsible for the development of large scale anisotropy are: i) crystallographic preferred orientation of upper mantle minerals and ii) shape-preferred orientation caused by cracks, melt-filled lenses or alternating layers within the crust. In this context, subduction zones represent a complex anisotropic puzzle as seismic anisotropy can be located in regions beneath, within, and above the subducting slab. We use the analysis of teleseismic shear-wave splitting to measure seismic anisotropy in response to subduction-related deformation processes. Previous studies on shear-wave splitting from South America have reported partly contradicting results and interpretations in terms of mantle flow and crustal deformation. Russo and Silver (1994) mostly found trench-parallel fast polarizations which they attributed to trench-parallel mantle flow beneath the slab and confined zones of oblique polarization directions. Wölbern et al. (2014) reported significant short-scale variations of fast polarization directions. They proposed that anisotropy results from fossil anisotropy in the subducting slab, whereas deviating fast polarizations in trench-parallel orientation were attributed to crustal anisotropy related to deep-reaching local shear zones. Long et al. (2016) found complex splitting measurements which they interpreted as the result of different anisotropic source regions. Overall, the complexity of splitting measurements yield a departure from a conventional 2D corner flow model. To investigate the upper mantle and crust in this subduction setting further, we use data from the Integrated Plate boundary Observatory Chile (IPOC) located in northern Chile, which consists of 21 stations with up to ten years

  15. Composite Fermions with Tunable Fermi Contour Anisotropy

    Science.gov (United States)

    Kamburov, D.; Liu, Yang; Shayegan, M.; Pfeiffer, L. N.; West, K. W.; Baldwin, K. W.

    2013-05-01

    The composite fermion formalism elegantly describes some of the most fascinating behaviors of interacting two-dimensional carriers at low temperatures and in strong perpendicular magnetic fields. In this framework, carriers minimize their energy by attaching two flux quanta and forming new quasiparticles, the so-called composite fermions. Thanks to the flux attachment, when a Landau level is half-filled, the composite fermions feel a vanishing effective magnetic field and possess a Fermi surface with a well-defined Fermi contour. Our measurements in a high-quality two-dimensional hole system confined to a GaAs quantum well demonstrate that a parallel magnetic field can significantly distort the hole-flux composite fermion Fermi contour.

  16. Slab detachment under the Eastern Alps seen by seismic anisotropy.

    Science.gov (United States)

    Qorbani, Ehsan; Bianchi, Irene; Bokelmann, Götz

    2015-01-01

    We analyze seismic anisotropy for the Eastern Alpine region by inspecting shear-wave splitting from SKS and SKKS phases. The Eastern Alpine region is characterized by a breakdown of the clear mountain-chain-parallel fast orientation pattern that has been previously documented for the Western Alps and for the western part of the Eastern Alps. The main interest of this paper is a more detailed analysis of the anisotropic character of the Eastern Alps, and the transition to the Carpathian-Pannonian region. SK(K)S splitting measurements reveal a rather remarkable lateral change in the anisotropy pattern from the west to the east of the Eastern Alps with a transition area at about 12°E. We also model the backazimuthal variation of the measurements by a vertical change of anisotropy. We find that the eastern part of the study area is characterized by the presence of two layers of anisotropy, where the deeper layer has characteristics similar to those of the Central Alps, in particular SW-NE fast orientations of anisotropic axes. We attribute the deeper layer to a detached slab from the European plate. Comparison with tomographic studies of the area indicates that the detached slab might possibly connect with the lithosphere that is still in place to the west of our study area, and may also connect with the slab graveyard to the East, at the depth of the upper mantle transition zone. On the other hand, the upper layer has NW-SE fast orientations coinciding with a low-velocity layer which is found above a more-or-less eastward dipping high-velocity body. The anisotropy of the upper layer shows large-scale NW-SE fast orientation, which is consistent with the presence of asthenospheric flow above the detached slab foundering into the deeper mantle.

  17. RADIOACTIVE UHECR ASTRONOMY: CORRELATING GAMMA ANISOTROPY AND NEUTRINO PEV EVENTS

    Directory of Open Access Journals (Sweden)

    Daniele Fargion

    2013-12-01

    Full Text Available UHECR (Ultra High Energy Cosmic Rays were expected to be protons, to fly straight and to suffer of a GZK (opacity on CMB radiation cut off. AUGER did suggest on 2007 that such early UHECR anisotropy was compatible with the foreseen Super-Galactic plane while both HIRES and AUGER confirmed such apparent GZK cut-off in the spectra. However the same AUGER composition since 2007 was favoring nuclei (and not nucleon. The recent absence of narrow angle clustering in UHECR maps, as it should be expected by protons, the missing of events along nearest Cluster Virgo, the wide spread (16° angle of UHECR along CenA are in disagreement with first proton–UHECR AUGER understanding. We claimed since 2008 a light nuclei role for CenA crowded area. On the other side the ICECUBE absence of TeVs neutrino clustering or anisotropy, its spectra steepening is favoring mostly a ruling atmospheric neutrino noise up to tens TeV. However recent two PeV neutrino event cannot easily coexist or being extrapolate with such atmospheric ruling scenario, nor with GZK (either nucleon or nuclei secondaries expected spectra. Finally tens TeV gamma anisotropy in ARGO–MILAGRO–ICECUBE maps may hardly be associated with known hadronic sources. Weimagine such anisotropy ruled by diffused gamma secondaries, being shine along UHECR bending and flight: radioactive light and heavy UHECR nuclei, while decaying in flight, may paint in the sky (by gamma, electrons and neutrinos their trajectories and bending, connecting UHECR spread events with TeV anisotropy, as well offering a very realistic source of first, otherwise puzzling, observed PeV neutrinos.

  18. Three-dimensional visualization of magnetic domain structure with strong uniaxial anisotropy via scanning hard X-ray microtomography

    Science.gov (United States)

    Suzuki, Motohiro; Kim, Kab-Jin; Kim, Sanghoon; Yoshikawa, Hiroki; Tono, Takayuki; Yamada, Kihiro T.; Taniguchi, Takuya; Mizuno, Hayato; Oda, Kent; Ishibashi, Mio; Hirata, Yuushou; Li, Tian; Tsukamoto, Arata; Chiba, Daichi; Ono, Teruo

    2018-03-01

    An X-ray tomographic technique was developed to investigate the internal magnetic domain structure in a micrometer-sized ferromagnetic sample. The technique is based on a scanning hard X-ray nanoprobe using X-ray magnetic circular dichroism (XMCD). From transmission XMCD images at the Gd L3 edge as a function of the sample rotation angle, the three-dimensional (3D) distribution of a single component of the magnetic vector in a GdFeCo microdisc was reconstructed with a spatial resolution of 360 nm, using a modified algebraic reconstruction algorithm. The method is applicable to practical magnetic materials and can be extended to 3D visualization of the magnetic domain formation process under external magnetic fields.

  19. A reliable, non-invasive measurement tool for anisotropy in normal skin and scar tissue

    NARCIS (Netherlands)

    Verhaegen, Pauline D. H. M.; Res, Evelien M.; van Engelen, Arna; Middelkoop, Esther; van Zuijlen, Paul P. M.

    2010-01-01

    Anisotropy of the skin varies depending on different locations and pathological conditions. Currently, no reliable non-invasive measurement tool is available for tissue anisotropy. The Reviscometer is an anisotropy measurement tool that measures the resonance running time (RRT) of a shock wave. This

  20. The effect of optical anisotropies on building glass façades and its measurement methods

    Directory of Open Access Journals (Sweden)

    M. Illguth

    2015-06-01

    Furthermore a method for the quantitative measurement of anisotropies is proposed and prescribed in detail. This method can assist in the quality assurance process. Measurements are showing that probably the best tempered glass offers slight anisotropies and that under unfavorable conditions these anisotropies can become evident.

  1. Perpendicular magnetic anisotropy and the magnetization process in CoFeB/Pd multilayer films

    DEFF Research Database (Denmark)

    Ngo, Duc-The; Quach, Duy-Truong; Hung, Tran Quang

    2014-01-01

    with an effective uniaxial anisotropy up to 7.7 × 106 Jm−3 and a saturation magnetization as low as 200 emu cm−3 are achieved. The surface/interfacial anisotropy of the CoFeB/Pd interfaces—the main contribution to the PMA—is separated from the effective uniaxial anisotropy of the films and appears to increase...

  2. Weak-anisotropy moveout approximations for P-waves in homogeneous layers of monoclinic or higher anisotropy symmetries

    Czech Academy of Sciences Publication Activity Database

    Farra, V.; Pšenčík, Ivan; Jílek, P.

    2016-01-01

    Roč. 81, č. 2 (2016), C39-C59 ISSN 0016-8033 R&D Projects: GA ČR(CZ) GAP210/11/0117 Institutional support: RVO:67985530 Keywords : anisotropy * P-wave * traveltime * moveout Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 2.391, year: 2016

  3. Weak-anisotropy approximations of P-wave phase and ray velocities for anisotropy of arbitrary symmetry

    Czech Academy of Sciences Publication Activity Database

    Farra, V.; Pšenčík, Ivan

    2016-01-01

    Roč. 60, č. 3 (2016), s. 403-418 ISSN 0039-3169 Institutional support: RVO:67985530 Keywords : weak anisotropy * P-wave * phase velocity * ray velocity Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 0.764, year: 2016

  4. Quantum electrodynamics of strong fields

    International Nuclear Information System (INIS)

    Greiner, W.

    1983-01-01

    Quantum Electrodynamics of Strong Fields provides a broad survey of the theoretical and experimental work accomplished, presenting papers by a group of international researchers who have made significant contributions to this developing area. Exploring the quantum theory of strong fields, the volume focuses on the phase transition to a charged vacuum in strong electric fields. The contributors also discuss such related topics as QED at short distances, precision tests of QED, nonperturbative QCD and confinement, pion condensation, and strong gravitational fields In addition, the volume features a historical paper on the roots of quantum field theory in the history of quantum physics by noted researcher Friedrich Hund

  5. Subsurface structure of the Nojima fault from dipole shear velocity/anisotropy and borehole Stoneley wave

    Energy Technology Data Exchange (ETDEWEB)

    Ito, H. [Geological Survey of Japan, Tsukuba (Japan); Yamamoto, H.; Brie, A.

    1996-10-01

    Fracture and permeability in the fault zone of the active fault drilling at the Nojima fault were evaluated from acoustic waveforms. There were several permeable intervals in the fault zone. There was strong Stoneley wave attenuation, very large S-Se below the fault and in the interval above the fault. In the fault zone, there were also several short intervals where S-Se was very large; 667 m-674 m and 706 m-710 m. In these intervals, the Stoneley attenuation was large, but there was no Stoneley reflection from within the interval. Reflections were observed at the upper and lower boundaries, going away from the bed up above, and down below. In this well, the shear wave was very strongly attenuated at and below the fault zone. The fast shear azimuth changed at the fault. The slowness anisotropy was fairly strong above the fault from 602 m to 612 m, but smaller below the fault. The changes in fast shear azimuth were much more pronounced near the fault, which suggested a strong influence of the fault. 6 refs., 5 figs.

  6. Anisotropy of the cosmic blackbody radiation.

    Science.gov (United States)

    Wilkinson, D T

    1986-06-20

    The universe is filled with thermal radiation having a current temperature of 2.75 K. Originating in the very early universe, this radiation furnishes strong evidence that the Big Bang cosmology best describes our expanding universe from an incredibly hot, compacted early stage until now. The model can be used to extrapolate our physics backward in time to predict events whose effects might be observable in the 2.75 K radiation today. The spectrum and isotropy are being studied with sophisticated microwave radiometers on the ground, in balloons, and in satellites. The results are as predicted by the simple theory: the spectrum is that of a blackbody (to a few percent) and the radiation is isotropic (to 0.01 percent) except for a local effect due to our motion through the radiation. However, a problem is emerging. Primordial fluctuations in the mass density, which later became the great clusters of galaxies that we see today, should have left an imprint on the 2.75 K radiation-bumpiness on the sky at angular scales of about 10 arc minutes. They have not yet been seen.

  7. Anisotropy in the ternary cold fission

    CERN Document Server

    Delion, D S; Greiner, W

    2003-01-01

    We describe the spontaneous ternary cold fission of sup 2 sup 5 sup 2 Cf, accompanied by sup 4 He, sup 1 sup 0 Be and sup 1 sup 4 C within a stationary scattering formalism. We show that the light cluster should be born in the neck region. It decays from the first resonant eigenstate in the Coulomb plus harmonic oscillator potential, centred in this region and eccentric with respect to the symmetry axis. This description gives a simple answer to the question why the averaged values in the energy spectra of emitted clusters are close to each other, in spite of different Coulomb barriers. We have shown that the angular distribution of the emitted light particle is strongly connected with its deformation and the equatorial distance. Experimental angular distributions can be explained by the spherical shapes of emitted clusters, except for a deformed sup 1 sup 0 Be. We also predicted some dependences of half-lives for such tri-nuclear systems upon potential parameters.

  8. Structural and magnetic anisotropy in the epitaxial FeV2O4 (110 spinel thin films

    Directory of Open Access Journals (Sweden)

    Xiaolan Shi

    2015-11-01

    Full Text Available The epitaxial 200-nm-thick FeV2O4(110 films on (110-oriented SrTiO3, LaAlO3 and MgAl2O4 substrates were fabricated for the first time by pulsed laser deposition, and the structural, magnetic, and magnetoresistance anisotropy were investigated systematically. All the films are monoclinic, whereas its bulk is cubic. Compared to FeV2O4 single crystals, films on SrTiO3 and MgAl2O4 are strongly compressively strained in [001] direction, while slightly tensily strained along normal [110] and in-plane [ 1 1 ¯ 0 ] directions. In contrast, films on LaAlO3 are only slightly distorted from cubic. The magnetic hard axis is in direction, while the easier axis is along normal [110] direction for films on SrTiO3 and MgAl2O4, and in-plane [ 1 1 ¯ 0 ] direction for films on LaAlO3. Magnetoresistance anisotropy follows the magnetization. The magnetic anisotropy is dominated by the magnetocrystalline energy, and tuned by the magneto-elastic coupling.

  9. Electric field dependence of the spin relaxation anisotropy in (111) GaAs/AlGaAs quantum wells

    International Nuclear Information System (INIS)

    Balocchi, A; Amand, T; Renucci, P; Duong, Q H; Marie, X; Wang, G; Liu, B L

    2013-01-01

    Time-resolved optical spectroscopy experiments in (111)-oriented GaAs/AlGaAs quantum wells (QWs) show a strong electric field dependence of the conduction electron spin relaxation anisotropy. This results from the interplay between the Dresselhaus and Rashba spin splitting in this system with C 3v symmetry. By varying the electric field applied perpendicular to the QW plane from 20 to 50 kV cm −1 the anisotropy of the spin relaxation time parallel (τ s ∥ ) and perpendicular (τ s ⊥ ) to the growth axis can be first canceled and eventually inversed with respect to the one usually observed in III–V zinc-blende QW (τ s ⊥ = 2τ s ∥ ). This dependence stems from the nonlinear contributions of the k-dependent conduction band spin splitting terms which begin to play the dominant spin relaxing role while the linear Dresselhaus terms are compensated by the Rashba ones through the applied bias. A spin density matrix model for the conduction band spin splitting including both linear and cubic terms of the Dresselhaus Hamiltonian is used which allows a quantitative description of the measured electric field dependence of the spin relaxation anisotropy. The existence of an isotropic point where the spin relaxation tensor reduces to a scalar is predicted and confirmed experimentally. The spin splitting compensation electric field and collision processes type in the QW can be likewise directly extracted from the model without complementary measurements. (paper)

  10. Unusually large magnetic anisotropy in a CuO-based semiconductor Cu5V2O10.

    Science.gov (United States)

    He, Zhangzhen; Lin, Chensheng; Cheng, Wendan; Okazawa, Atsushi; Kojima, Norimichi; Yamaura, Jun-ichi; Ueda, Yutaka

    2011-02-09

    A CuO-based material Cu(5)V(2)O(10) was successfully grown in a closed crucible using Sr(OH)(2)·8H(2)O as flux. The structure of Cu(5)V(2)O(10) can be viewed as being composed of two types of zigzag Cu-O chains running along the b- and c-axes, which shows a two-dimensional crosslike framework with 12-column square tunnels along the a-axis. Magnetic measurements show that Cu(5)V(2)O(10) exhibits unexpected large magnetic anisotropy, which is the first time magnetic anisotropy energy of ∼10(7) erg/cm(3) in the CuO-based materials has been observed. The origins of large anisotropy are suggested to arise from strong anisotropic exchanges due to the particular bonding geometry and the Jahn-Teller distortion of Cu(2+) ions. Further, the band structure investigated by the GGA+U method suggests that Cu(5)V(2)O(10) is a semiconductor.

  11. Structural and magnetic anisotropy in the epitaxial FeV2O4 (110) spinel thin films

    Science.gov (United States)

    Shi, Xiaolan; Wang, Yuhang; Zhao, Kehan; Liu, Na; Sun, Gaofeng; Zhang, Liuwan

    2015-11-01

    The epitaxial 200-nm-thick FeV2O4(110) films on (110)-oriented SrTiO3, LaAlO3 and MgAl2O4 substrates were fabricated for the first time by pulsed laser deposition, and the structural, magnetic, and magnetoresistance anisotropy were investigated systematically. All the films are monoclinic, whereas its bulk is cubic. Compared to FeV2O4 single crystals, films on SrTiO3 and MgAl2O4 are strongly compressively strained in [001] direction, while slightly tensily strained along normal [110] and in-plane [ 1 1 ¯ 0 ] directions. In contrast, films on LaAlO3 are only slightly distorted from cubic. The magnetic hard axis is in direction, while the easier axis is along normal [110] direction for films on SrTiO3 and MgAl2O4, and in-plane [ 1 1 ¯ 0 ] direction for films on LaAlO3. Magnetoresistance anisotropy follows the magnetization. The magnetic anisotropy is dominated by the magnetocrystalline energy, and tuned by the magneto-elastic coupling.

  12. Effects of anisotropy in spin molecular-orbital coupling on effective spin models of trinuclear organometallic complexes

    Science.gov (United States)

    Merino, J.; Jacko, A. C.; Khosla, A. L.; Powell, B. J.

    2017-11-01

    We consider layered decorated honeycomb lattices at two-thirds filling, as realized in some trinuclear organometallic complexes. Localized S =1 moments with a single-spin anisotropy emerge from the interplay of Coulomb repulsion and spin molecular-orbit coupling (SMOC). Magnetic anisotropies with bond-dependent exchange couplings occur in the honeycomb layers when the direct intracluster exchange and the spin molecular-orbital coupling are both present. We find that the effective spin exchange model within the layers is an XXZ + 120∘ honeycomb quantum compass model. The intrinsic nonspherical symmetry of the multinuclear complexes leads to very different transverse and longitudinal spin molecular-orbital couplings, which greatly enhances the single-spin and exchange coupling anisotropies. The interlayer coupling is described by an XXZ model with anisotropic biquadratic terms. As the correlation strength increases the system becomes increasingly one-dimensional. Thus, if the ratio of SMOC to the interlayer hopping is small this stabilizes the Haldane phase. However, as the ratio increases there is a quantum phase transition to the topologically trivial "D phase." We also predict a quantum phase transition from a Haldane phase to a magnetically ordered phase at sufficiently strong external magnetic fields.

  13. Synchronization in primate cerebellar granule cell layer local field potentials: Basic anisotropy and dynamic changes during active expectancy

    Directory of Open Access Journals (Sweden)

    Richard Courtemanche

    2009-07-01

    Full Text Available The cerebellar cortex is remarkable for its organizational regularity, out of which task-related neural networks should emerge. So, in Purkinje cells, both complex and simple spike network patterns are evident in sensorimotor behavior. However, task-related patterns of activity in the granule cell layer (GCL have been less studied. We recorded local field potential (LFP activity simultaneously in pairs of GCL sites in monkeys performing an active expectancy (lever-press task, in passive expectancy, and at rest. LFP sites were selected when they showed strong 10-25 Hz oscillations; pair orientation was in stereotaxic sagittal and coronal (mainly, and diagonal. As shown previously, LFP oscillations at each site were modulated during the lever-press task. Synchronization across LFP pairs showed an evident basic anisotropy at rest: sagittal pairs of LFPs were better synchronized (more than double the cross-correlation coefficients than coronal pairs, and more than diagonal pairs. On the other hand, this basic anisotropy was modifiable: during the active expectancy condition, where sagittal and coronal orientations were tested, synchronization of LFP pairs would increase just preceding movement, most notably for the coronal pairs. This lateral extension of synchronization was not observed in passive expectancy. The basic pattern of synchronization at rest, favoring sagittal synchrony, thus seemed to adapt in a dynamic fashion, potentially extending laterally to include more cerebellar cortex elements. This dynamic anisotropy in LFP synchronization could underlie GCL network organization in the context of sensorimotor tasks.

  14. Lithospheric deformation inferred from electrical anisotropy of magnetotelluric data

    Science.gov (United States)

    Yin, Y.; Wei, W.; Jin, S.; Ye, G.; Unsworth, M. J.; Zhang, L.

    2013-12-01

    In our research, a comprehensive procedure of analyzing and modeling electrical anisotropy for MT data is suggested, based on the field examples of the Great Slave Lake shear zone (GSLsz) in western Canada, the North China Craton (NCC) and the Altyn Tagh fault in northern Tibet. Diverse dimensionality tools are used to distinguish heterogeneity and anisotropy from MT data. In addition to the phase splits and phase tensor polarizations, a combination of the phase tensor and induction arrows is applied to judge anisotropy. The skin depths of specific period band are considered to determine whether these features result from anisotropy or heterogeneity. Specific resistivity structures in the 2-D isotropic inversion models can indicate electrical anisotropy as well, like the dike-like media or a series of conductive ';blobs' can be observed in the 2-D isotropic inversion models of the GSLsz and NCC data. Anisotropic inversions can be undertaken using an improved inversion code based on isotropic code but incorporating a trade-off parameter for electrical anisotropy named anisotropic tau. A series of anisotropic tau have been applied to test its effect and to get a best trade-off between anisotropy and heterogeneity. Then, 2-D and 3-D forward modeling works are undertaken to test the robustness of the major anisotropic features. The anisotropic structures inferred from the inversion models are replaced by various alternating isotropic or anisotropic structures to see if they are required. The fitting of the response curves compared with the field data and corresponding r.m.s misfits can help us choose the best model that can generally illustrate the underground structure. Finally, the analysis and modeling result of the MT data from North China Craton is taken as an example to demonstrate how the electrical anisotropy can be linked with the lithospheric deformation. According to the reliable models we got, there may be an anisotropic layer at the mid-lower crustal to

  15. Anisotropy of exciton spectrum and spin-orbit interactions in quantum wells in tilted magnetic field

    International Nuclear Information System (INIS)

    Olendski, Oleg; Shahbazyan, Tigran V

    2006-01-01

    We study theoretically excitonic energy spectrum and optical absorption in narrowgap semiconductor quantum wells in strong magnetic field. We show that, in the presence of an in-plane field component, the absorption coefficient exhibit a double-peak structure due to hybridization of bright and dark excitons. If both Rashba and Dresselhaus spin-orbit terms are present, the spectrum is anisotropic in in-plane field orientation with respect to [100] axis. In particular, the magnitude of the splitting can be tuned in a wide interval by varying the azimuthal angle of the in-plane field. The absorption spectrrum anisotropy would allow simultaneous measurement Dresselhaus and Rashba spin-orbit coefficients

  16. Magnetic ground and remanent states of synthetic metamagnets with perpendicular anisotropy

    International Nuclear Information System (INIS)

    Kiselev, N S; Roessler, U K; Bogdanov, A N; Hellwig, O

    2011-01-01

    In this work, we summarize our theoretical results within a phenomenological micromagnetic approach for magnetic ground state and nonequilibrium states as topological magnetic defects in multilayers with strong perpendicular anisotropy and antiferromagnetic (AF) interlayer exchange coupling (IEC), e.g. [Co/Pt(Pd)]/Ru(Ir, NiO). We give detailed analysis of our model together with the most representative results which elucidate common features of such systems. We discuss phase diagrams of the magnetic ground state, and compare solutions of our model with experimental data. A model to assess the stability of so-called tiger tail patterns is presented. It is found that these modulated topological defect cannot be stabilized by an interplay between magnetostatic and IEC energies only. It is argued that tiger tail patterns arise as nuclei of ferro-stripe structure in AF domain walls and that they are stabilized by domain wall pinning.

  17. Phase-field study of crystal growth in three-dimensional capillaries: Effects of crystalline anisotropy

    Science.gov (United States)

    Debierre, Jean-Marc; Guérin, Rahma; Kassner, Klaus

    2016-07-01

    Phase-field simulations are performed to explore the thermal solidification of a pure melt in three-dimensional capillaries. Motivated by our previous work for isotropic or slightly anisotropic materials, we focus here on the more general case of anisotropic materials. Different channel cross sections are compared (square, hexagonal, circular) to reveal the influence of geometry and the effects of a competition between the crystal and the channel symmetries. In particular, a compass effect toward growth directions favored by the surface energy is identified. At given undercooling and anisotropy, the simulations generally show the coexistence of several growth modes. The relative stability of these growth modes is tested by submitting them to a strong spatiotemporal noise for a short time, which reveals a subtle hierarchy between them. Similarities and differences with experimental growth modes in confined geometry are discussed qualitatively.

  18. Synthesis, Characterization and Photoinduction of Optical Anisotropy in Liquid Crystalline Diblock Azo-Copolymers

    DEFF Research Database (Denmark)

    Forcén, P; Oriol, L; Sánchez, C

    2007-01-01

    Diblock copolymers with polymethyl methacrylate and side chain liquid crystalline WC) azopolymethacrylate blocks were synthesized by atom transfer radical polymerization (ATRP). The azobeazene content in these copolymers ranges from 52 to 7 wt %. For an azo conteat dowri to 20% they exhibit a LC...... anisotropy induced in these films by illumination with linearly polarized 488 nm light was studied and the resuits compared with those of the azo homopolymer and of a random copolymer with a similar composition. The formation of azo aggregates inside the azo blocks is strongly reduced in going from...... the homopolymer to the copolymers. Photoinduced azo orientation perpendicular to the 488 nm light polarization was found in aH the polymers. The orientational order parameter is very similar in the homopolymer and in the block copolymers with an azo content down to 20 wt %, while it is much lower in the random...

  19. A Low-Symmetry Dysprosium Metallocene Single-Molecule Magnet with a High Anisotropy Barrier.

    Science.gov (United States)

    Pugh, Thomas; Chilton, Nicholas F; Layfield, Richard A

    2016-09-05

    The single-molecule magnet (SMM) properties of the isocarbonyl-ligated dysprosium metallocene [Cp*2 Dy{μ-(OC)2 FeCp}]2 (1Dy ), which contains a rhombus-shaped Dy2 Fe2 core, are described. Combining a strong axial [Cp*](-) ligand field with a weak equatorial field consisting of the isocarbonyl ligands leads to an anisotropy barrier of 662 cm(-1) in zero applied field. The dominant thermal relaxation pathways in 1Dy involves at least the fourth-excited Kramers doublet, thus demonstrating that prominent SMM behavior can be observed for dysprosium in low-symmetry environments. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Relaxation dynamics of magnetization transitions in synthetic antiferromagnet with perpendicular anisotropy

    Science.gov (United States)

    Talantsev, A.; Lu, Y.; Fache, T.; Lavanant, M.; Hamadeh, A.; Aristov, A.; Koplak, O.; Morgunov, R.; Mangin, S.

    2018-04-01

    Two synthetic antiferromagnet bilayer systems with strong perpendicular anisotropy CoFeB/Ta/CoFeB and Pt/Co/Ir/Co/Pt have been grown using sputtering techniques. For both systems two types of magnetization transitions have been studied. The first one concerns transitions from a state where magnetizations of the two magnetic layers are parallel (P state) to a state where magnetizations of the two layers are aligned antiparallel (AP state). The second one concerns transitions between the two possible antiparallel alignments (AP+  to AP-). For both systems and both transitions after-effect measurements can be understood in the frame of nucleation—propagation model. Time derivative analysis of magnetic relaxation curves and mapping of the first order reversal curves at different temperature allowed us to demonstrate the presence of different pinning centers, which number can be controlled by magnetic field and temperature.

  1. Strong WW Interaction at LHC

    Energy Technology Data Exchange (ETDEWEB)

    Pelaez, Jose R

    1998-12-14

    We present a brief pedagogical introduction to the Effective Electroweak Chiral Lagrangians, which provide a model independent description of the WW interactions in the strong regime. When it is complemented with some unitarization or a dispersive approach, this formalism allows the study of the general strong scenario expected at the LHC, including resonances.

  2. Diffusion creep in the mantle may create and maintain anisotropy

    Science.gov (United States)

    Wheeler, John

    2014-05-01

    Diffusion creep is thought to play an important role in lower mantle deformation and hence must be understood in detail if Earth behaviour is to be explained. It is commonly claimed that diffusion creep gives rise to equant grain shapes and destroys any crystallographic preferred orientation (CPO), so all physical properties would be isotropic. Some experiments on olivine support the first assertion but other minerals, and polyphase rocks, commonly show inequant grain shapes in nature and experiment even when diffusion creep is thought to be a major contribution to strain. Numerical models allow rigorous exploration of the effects of deformation under conditions not easily reached in experiments. A numerical model named 'DiffForm' (Wheeler & Ford 2007) gives insight into how grain shapes and microstructures evolve during diffusion creep. Modelling shows that whilst grains may initially rotate in apparently chaotic fashion during diffusion creep, such rotations slow down as grains become inequant. Consequently, an initial CPO (formed, for example, by dislocation creep at higher strain rates) will be decreased in intensity but not destroyed. Seismic anisotropy will decrease but not disappear (Wheeler 2009). Diffusion creep is also predicted to have intense mechanical anisotropy. In simple models diffusion creep is controlled entirely by diffusion and sliding along grain boundaries; there is no crystallographic influence. An aggregate of equant grains must then be mechanically isotropic, but a model microstructure with inequant grains has marked mechanical anisotropy (Wheeler 2010) - an effect related to the fact that grain boundary sliding is an intrinsic part of diffusion creep. That work was based on a very simple microstructure with a single inequant grain shape but I present here new results showing that for more complicated microstructures, mechanical anisotropy is intense even for quite modest grain elongations. There will be feedback between strain and

  3. Membrane-mediated interaction between strongly anisotropic protein scaffolds.

    Directory of Open Access Journals (Sweden)

    Yonatan Schweitzer

    2015-02-01

    Full Text Available Specialized proteins serve as scaffolds sculpting strongly curved membranes of intracellular organelles. Effective membrane shaping requires segregation of these proteins into domains and is, therefore, critically dependent on the protein-protein interaction. Interactions mediated by membrane elastic deformations have been extensively analyzed within approximations of large inter-protein distances, small extents of the protein-mediated membrane bending and small deviations of the protein shapes from isotropic spherical segments. At the same time, important classes of the realistic membrane-shaping proteins have strongly elongated shapes with large and highly anisotropic curvature. Here we investigated, computationally, the membrane mediated interaction between proteins or protein oligomers representing membrane scaffolds with strongly anisotropic curvature, and addressed, quantitatively, a specific case of the scaffold geometrical parameters characterizing BAR domains, which are crucial for membrane shaping in endocytosis. In addition to the previously analyzed contributions to the interaction, we considered a repulsive force stemming from the entropy of the scaffold orientation. We computed this interaction to be of the same order of magnitude as the well-known attractive force related to the entropy of membrane undulations. We demonstrated the scaffold shape anisotropy to cause a mutual aligning of the scaffolds and to generate a strong attractive interaction bringing the scaffolds close to each other to equilibrium distances much smaller than the scaffold size. We computed the energy of interaction between scaffolds of a realistic geometry to constitute tens of kBT, which guarantees a robust segregation of the scaffolds into domains.

  4. Structural origins of magnetic anisotropy in sputtered amorphous Tb-Fe films

    Science.gov (United States)

    Harris, V. G.; Aylesworth, K. D.; Das, B. N.; Elam, W. T.; Koon, N. C.

    1992-09-01

    Using x-ray-absorption fine-structure measurements we have obtained clear evidence for structural anisotropy in amorphous sputter-deposited TbFe films exhibiting perpendicular magnetic anisotropy. Modeling of the data shows that perpendicular anisotropy in these films is associated with Fe-Fe and Tb-Tb pair correlations which are greater in plane and Tb-Fe correlations which are greater perpendicular to the film plane. Upon annealing at 300 °C the measured structural anisotropy disappears and the magnetic anisotropy decreases to a level consistent with magnetoelastic interactions between the film and substrate.

  5. Strong-back safety latch

    International Nuclear Information System (INIS)

    DeSantis, G.N.

    1995-01-01

    The calculation decides the integrity of the safety latch that will hold the strong-back to the pump during lifting. The safety latch will be welded to the strong-back and will latch to a 1.5-in. dia cantilever rod welded to the pump baseplate. The static and dynamic analysis shows that the safety latch will hold the strong-back to the pump if the friction clamps fail and the pump become free from the strong-back. Thus, the safety latch will meet the requirements of the Lifting and Rigging Manual for under the hook lifting for static loading; it can withstand shock loads from the strong-back falling 0.25 inch

  6. Strong-back safety latch

    Energy Technology Data Exchange (ETDEWEB)

    DeSantis, G.N.

    1995-03-06

    The calculation decides the integrity of the safety latch that will hold the strong-back to the pump during lifting. The safety latch will be welded to the strong-back and will latch to a 1.5-in. dia cantilever rod welded to the pump baseplate. The static and dynamic analysis shows that the safety latch will hold the strong-back to the pump if the friction clamps fail and the pump become free from the strong-back. Thus, the safety latch will meet the requirements of the Lifting and Rigging Manual for under the hook lifting for static loading; it can withstand shock loads from the strong-back falling 0.25 inch.

  7. Characterization and scaling of anisotropy of fabrics and fractures at laboratory scales: insights from volumetric analysis using computed tomography

    Science.gov (United States)

    Ketcham, Richard A.

    2017-04-01

    Anisotropy in three-dimensional quantities such as geometric shape and orientation is commonly quantified using principal components analysis, in which a second order tensor determines the orientations of orthogonal components and their relative magnitudes. This approach has many advantages, such as simplicity and ability to accommodate many forms of data, and resilience to data sparsity. However, when data are sufficiently plentiful and precise, they sometimes show that aspects of the principal components approach are oversimplifications that may affect how the data are interpreted or extrapolated for mathematical or physical modeling. High-resolution X-ray computed tomography (CT) can effectively extract thousands of measurements from a single sample, providing a data density sufficient to examine the ways in which anisotropy on the hand-sample scale and smaller can be quantified, and the extent to which the ways the data are simplified are faithful to the underlying distributions. Features within CT data can be considered as discrete objects or continuum fabrics; the latter can be characterized using a variety of metrics, such as the most commonly used mean intercept length, and also the more specialized star length and star volume distributions. Each method posits a different scaling among components that affects the measured degree of anisotropy. The star volume distribution is the most sensitive to anisotropy, and commonly distinguishes strong fabric components that are not orthogonal. Although these data are well-presented using a stereoplot, 3D rose diagrams are another visualization option that can often help identify these components. This talk presents examples from a number of cases, starting with trabecular bone and extending to geological features such as fractures and brittle and ductile fabrics, in which non-orthogonal principal components identified using CT provide some insight into the origin of the underlying structures, and how they should be

  8. A search for anisotropy in the arrival directions of ultra high energy cosmic rays recorded at the Pierre Auger Observatory

    Energy Technology Data Exchange (ETDEWEB)

    Abreu, P.

    2012-01-01

    Observations of cosmic ray arrival directions made with the Pierre Auger Observatory have previously provided evidence of anisotropy at the 99% CL using the correlation of ultra high energy cosmic rays (UHECRs) with objects drawn from the Veron-Cetty Veron catalog. In this paper we report on the use of three catalog independent methods to search for anisotropy. The 2pt-L, 2pt+ and 3pt methods, each giving a different measure of self-clustering in arrival directions, were tested on mock cosmic ray data sets to study the impacts of sample size and magnetic smearing on their results, accounting for both angular and energy resolutions. If the sources of UHECRs follow the same large scale structure as ordinary galaxies in the local Universe and if UHECRs are deflected no more than a few degrees, a study of mock maps suggests that these three methods can efficiently respond to the resulting anisotropy with a P-value = 1.0% or smaller with data sets as few as 100 events. Using data taken from January 1, 2004 to July 31, 2010 we examined the 20, 30, ..., 110 highest energy events with a corresponding minimum energy threshold of about 51 EeV. The minimum P-values found were 13.5% using the 2pt-L method, 1.0% using the 2pt+ method and 1.1% using the 3pt method for the highest 100 energy events. In view of the multiple (correlated) scans performed on the data set, these catalog-independent methods do not yield strong evidence of anisotropy in the highest energy cosmic rays.

  9. Perpendicular magnetic anisotropy and magnetization dynamics in oxidized CoFeAl films

    Science.gov (United States)

    Wu, Di; Zhang, Zhe; Li, Le; Zhang, Zongzhi; Zhao, H. B.; Wang, J.; Ma, B.; Jin, Q. Y.

    2015-07-01

    Half-metallic Co-based full-Heusler alloys with perpendicular magnetic anisotropy (PMA), such as Co2FeAl in contact with MgO, are receiving increased attention recently due to its full spin polarization for high density memory applications. However, the PMA induced by MgO interface can only be realized for very thin magnetic layers (usually below 1.3 nm), which would have strong adverse effects on the material properties of spin polarization, Gilbert damping parameter, and magnetic stability. In order to solve this issue, we fabricated oxidized Co50Fe25Al25 (CFAO) films with proper thicknesses without employing the MgO layer. The samples show controllable PMA by tuning the oxygen pressure (PO2) and CFAO thickness (tCFAO), large perpendicular anisotropy field of ~8.0 kOe can be achieved at PO2 = 12% for the sample of tCFAO = 2.1 nm or at PO2 = 7% for tCFAO = 2.8 nm. The loss of PMA at thick tCFAO or high PO2 results mainly from the formation of large amount of CoFe oxides, which are superparamagnetic at room temperature but become hard magnetic at low temperatures. The magnetic CFAO films, with strong PMA in a relatively wide thickness range and small intrinsic damping parameter below 0.028, would find great applications in developing advanced spintronic devices.

  10. A Bayesian approach to infer the radial distribution of temperature and anisotropy in the transition zone from seismic data

    Science.gov (United States)

    Drilleau, M.; Beucler, E.; Mocquet, A.; Verhoeven, O.; Moebs, G.; Burgos, G.; Montagner, J.

    2013-12-01

    Mineralogical transformations and matter transfers within the Earth's mantle make the 350-1000 km depth range (considered here as the mantle transition zone) highly heterogeneous and anisotropic. Most of the 3-D global tomographic models are anchored on small perturbations from 1-D models such as PREM, and are secondly interpreted in terms of temperature and composition distributions. However, the degree of heterogeneity in the transition zone can be strong enough so that the concept of a 1-D reference seismic model may be addressed. To avoid the use of any seismic reference model, we developed a Markov chain Monte Carlo algorithm to directly interpret surface wave dispersion curves in terms of temperature and radial anisotropy distributions, considering a given composition of the mantle. These interpretations are based on laboratory measurements of elastic moduli and Birch-Murnaghan equation of state. An originality of the algorithm is its ability to explore both smoothly varying models and first-order discontinuities, using C1-Bézier curves, which interpolate the randomly chosen values for depth, temperature and radial anisotropy. This parameterization is able to generate a self-adapting parameter space exploration while reducing the computing time. Using a Bayesian exploration, the probability distributions on temperature and anisotropy are governed by uncertainties on the data set. The method was successfully applied to both synthetic data and real dispersion curves. Surface wave measurements along the Vanuatu- California path suggest a strong anisotropy above 400 km depth which decreases below, and a monotonous temperature distribution between 350 and 1000 km depth. On the contrary, a negative shear wave anisotropy of about 2 % is found at the top of the transition zone below Eurasia. Considering compositions ranging from piclogite to pyrolite, the overall temperature profile and temperature gradient are higher for the continental path than for the oceanic

  11. Random-anisotropy model: Monotonic dependence of the coercive field on D/J

    Science.gov (United States)

    Saslow, W. M.; Koon, N. C.

    1994-02-01

    We present the results of a numerical study of the zero-temperature remanence and coercivity for the random anisotropy model (RAM), showing that, contrary to early calculations for this model, the coercive field increases monotonically with increases in the strength D of the random anisotropy relative to the strength J at the exchange field. Local-field adjustments with and without spin flips are considered. Convergence is difficult to obtain for small values of the anisotropy, suggesting that this is the likely source of the nonmonotonic behavior found in earlier studies. For both large and small anisotropy, each spin undergoes about one flip per hysteresis cycle, and about half of the spin flips occur in the vicinity of the coercive field. When only non-spin-flip adjustments are considered, at large anisotropy the coercivity is proportional to the anisotropy. At small anisotropy, the rate of convergence is comparable to that when spin flips are included.

  12. Scattering of light from small nematic spheres with radial dielectric anisotropy

    International Nuclear Information System (INIS)

    Karacali, H.; Risser, S.M.; Ferris, K.F.

    1997-01-01

    We have calculated the scattering cross sections of small anisotropic nematic droplets embedded in a polymer matrix as a function of the dielectric constants of the nematic and the polymer. We have derived the general form for the Helmholtz wave equation for a droplet which has spatially varying radial anisotropy, and have explicitly solved this equation for three distinct models of the dielectric anisotropy, including one model where the anisotropy increases linearly with droplet radius. Numerical calculations of the scattering amplitudes for droplets much smaller than the wavelength of the incident radiation show that droplets with continual variation in the dielectric anisotropy have much larger scattering amplitude than droplets with fixed anisotropy. The scattering from droplets with linearly varying anisotropy exhibits a scattering minimum for much smaller polymer dielectric constants than the other models. These results show that the scattering from small anisotropic droplets is sensitive to details of the internal structure and anisotropy of the droplet. copyright 1997 The American Physical Society

  13. Anisotropy of neutrons sources of the Neutron Metrology Laboratory

    International Nuclear Information System (INIS)

    Silva, A.C.F.; Silva, F.S.; Creazolla, P.G.; Patrão, K.C.S.; Fonseca, E.S. da; Pereira, W.W.

    2017-01-01

    The anisotropy measurements have as main objective to define the emission of the radiation by different angles of an encapsulated neutron source. Measurements were performed using a Precision Long Counter (PLC) detector in the Laboratório de Baixo Espalhamento of the LNMRI / IRD. In this study were used an 241 AmBe (α,n) 5.92 GBq and a 238 PuBe (α,n) 1.85 TBq. The anisotropy factor was 8.65% to 241 AmBe and 4.36% to 238 PuBe, due to variations in the source encapsulation. The results in this work will focus mainly on the area of radiation protection and studies that will improve the process of routine measurements in laboratories and instrument calibrations. (author)

  14. Optical and mechanical anisotropy of oxide glass fibers

    DEFF Research Database (Denmark)

    Deubener, J.; Yue, Yuanzheng

    2012-01-01

    products [1], whereas stretching (frozen-in strain) results in optical and mechanical anisotropy of glass fibers, which is quantified inter alia by the specific birefringence [2]. The paper will stress the later effects by combining previous results on the structural origins of birefringence......Upon fiber drawing, glass forming oxide melts are thermally quenched and mechanically stretched. High cooling rates (up to 106 K/min) of quenched glass fibres lead to higher enthalpy state of liquids, thereby, to higher fictive temperature than regular quenching (e.g. 20 K/min) of bulk glass...... and anisotropic shrinkage in silica and phosphate fibers with recent studies on relaxation of optical anisotropy in E-glass fibers [3,4]....

  15. Effects of plastic anisotropy on crack-tip behaviour

    DEFF Research Database (Denmark)

    Legarth, Brian Nyvang; Tvergaard, Viggo; Kuroda, Mitsutoshi

    2002-01-01

    For a crack in a homogeneous material the effect of plastic anisotropy on crack-tip blunting and on the near-tip stress and strain fields is analyzed numerically. The full finite strain analyses are carried out for plane strain under small scale yielding conditions, with purely symmetric mode I...... loading remote from the crack-tip. In cases where the principal axes of the anisotropy are inclined to the plane of the crack it is found that the plastic zones as well as the stress and strain fields just around the blunted tip of the crack become non-symmetric. In these cases the peak strain...... on the blunted tip occurs off the center line of the crack, thus indicating that the crack may want to grow in a different direction. When the anisotropic axes are parallel to the crack symmetry is retained, but the plastic zones and the near-tip fields still differ from those predicted by standard isotropic...

  16. CMB statistical anisotropies of classical and quantum origins

    International Nuclear Information System (INIS)

    Chen, Xingang; Emami, Razieh; Firouzjahi, Hassan; Wang, Yi

    2015-01-01

    We examine the impact of different anisotropic relics on inflation, in particular the predictions on the density perturbations. These relics can be the source of the large scale anomalies in the cosmic microwave background. There are two different types of background relics, one from the matter sector and the other purely from the metric. Although the angular-dependence of the statistical anisotropy in both cases are degenerate, the scale-dependence are observationally distinctive. In addition, we demonstrate that non-Bunch-Davies vacuum states can extend the statistical anisotropy to much shorter scales, and leave a scale-dependence that is insensitive to the different backgrounds but sensitive to the initial quantum state

  17. Temperature dependence of magnetic anisotropies in ultra-thin films

    CERN Document Server

    Hucht, A

    1999-01-01

    shown that in contrast to other works the temperature driven spin reorientation transition in the monolayer is discontinuous also in the simulations, whereas in general it is continuous for the bilayer. Consequently the molecular field theory and the Monte Carlo simulations agree qualitatively. Exemplary for thicker films the influence of an external magnetic field is investigated in the bilayer, furthermore the effective anisotropies K sub n (T) of the phenomenological Landau theory are calculated numerically for the microscopic model. Analytic expressions for the dependence of the anisotropies K sub n (T) on the parameters of the model are obtained by the means of perturbation theory, which lead to a deeper understanding of the spin reorientation transition. Accordingly to this the origin for the spin reorientation transition lies in the differing temperature dependence of the dipolar and spin-orbit parts of the K sub n (T). Additionally the magnetization in the surface of the film decreases more rapidly wi...

  18. Late time CMB anisotropies constrain mini-charged particles

    Energy Technology Data Exchange (ETDEWEB)

    Burrage, C.; Redondo, J.; Ringwald, A. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Jaeckel, J. [Univ. of Durham, Inst. for Particle Physics Phenomenology (United Kingdom)

    2009-09-15

    Observations of the temperature anisotropies induced as light from the CMB passes through large scale structures in the late universe are a sensitive probe of the interactions of photons in such environments. In extensions of the Standard Model which give rise to mini-charged particles, photons propagating through transverse magnetic fields can be lost to pair production of such particles. Such a decrement in the photon flux would occur as photons from the CMB traverse the magnetic fields of galaxy clusters. Therefore late time CMB anisotropies can be used to constrain the properties of mini- charged particles. We outline how this test is constructed, and present new constraints on mini-charged particles from observations of the Sunyaev-Zel'dovich effect in the Coma cluster. (orig.)

  19. Polarimetric study of the optical anisotropy of polymers

    Science.gov (United States)

    Sinyavsky, N.; Korneva, I.

    2017-07-01

    This paper presents the results of an optical anisotropy study of a polymer film and the effect of temperature on birefringence. A method using a polariscope for the quantitative determination of the optical path difference is offered. The research findings are useful to students of physical and engineering specialities studying electromagnetic theory and optics. The described experiments and theoretical approaches are based on prominent aspects of modern optics. This work can be used to teach students the methods of polarimetry, the method of measuring optical anisotropy, and the basics of colorimetry. Students will learn a color description system to demonstrate the interference of polarized light, as well as being able to make a comparison between the numerical simulation and experiment of the interference pattern.

  20. Exhaustive Study of Cosmic Microwave Background Anisotropies in Quintessential Scenarios

    CERN Document Server

    Brax, P; Riazuelo, A; Brax, Philippe; Martin, Jerome; Riazuelo, Alain

    2000-01-01

    Recent high precision measurements of the CMB anisotropies performed by the BOOMERanG and MAXIMA-1 experiments provide an unmatched set of data allowing to probe different cosmological models. Among these scenarios, motivated by the recent measurements of the luminosity distance versus redshift relation for type Ia supernovae, is the quintessence hypothesis. It consists in assuming that the acceleration of the Universe is due to a scalar field whose final evolution is insensitive to the initial conditions. Within this framework we investigate the cosmological perturbations for two well-motivated potentials: the Ratra-Peebles and the SUGRA tracking potentials. We show that the solutions of the perturbed equations possess an attractor and that, as a consequence, the insensitivity to the initial conditions is preserved at the perturbed level. Then, we study the predictions of these two models for structure formation and CMB anisotropies and investigate the general features of the multipole moments in the presenc...

  1. Uniaxial anisotropy in magnetite thin film-Magnetization studies

    International Nuclear Information System (INIS)

    Wiechec, A.; Korecki, J.; Handke, B.; Kakol, Z.; Owoc, D.; Antolak, D.A.; Kozlowski, A.

    2006-01-01

    Magnetization and electrical resistivity measurements have been performed on a stoichiometric single crystalline magnetite Fe 3 O 4 thin film (thickness of ca. 500 nm) MBE deposited on MgO (1 0 0) substrate. The aim of these studies was to check the influence of preparation method and sample form (bulk vs. thin film) on magnetic anisotropy properties in magnetite. The film magnetization along versus applied magnetic field has been determined both in the direction parallel and perpendicular to the film surface, and at temperatures above and below the Verwey transition. We have found, in agreement with published results, that the in-plane field of 10 kOe was not sufficient to saturate the sample. This can be understood if some additional factor, on top of the bulk magnetocrystalline anisotropy, is taken into account

  2. Applications of Sunphotometry to Aerosol Extinction and Surface Anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Tsay, S.

    2002-09-30

    Support cost-sharing of a newly developed sunphotometer in field deployment for aerosol studies. This is a cost-sharing research to deploy a newly developed sun-sky-surface photometer for studying aerosol extinction and surface anisotropy at the ARM SGP, TWP, and NSA-AAO CART sites and in many field campaigns. Atmospheric aerosols affect the radiative energy balance of the Earth, both directly by perturbing the incoming/outgoing radiation fields and indirectly by influencing the properties/processes of clouds and reactive greenhouse gases. The surface bidirectional reflectance distribution function (BRDF) also plays a crucial role in the radiative energy balance, since the BRDF is required to determine (i) the spectral and spectrally-averaged surface albedo, and (ii) the top-of-the-atmosphere (TOA) angular distribution of radiance field. Therefore, the CART sites provide an excellent, albeit unique, opportunity to collect long-term climatic data in characterizing aerosol properties and various types of surface anisotropy.

  3. CMB statistical anisotropies of classical and quantum origins

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xingang [Department of Physics, The University of Texas at Dallas, Richardson, TX 75083 (United States); Emami, Razieh [School of Physics, Institute for Research in Fundamental Sciences (IPM), P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of); Firouzjahi, Hassan [School of Astronomy, Institute for Research in Fundamental Sciences (IPM), P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of); Wang, Yi, E-mail: Xingang.Chen@utdallas.edu, E-mail: emami@ipm.ir, E-mail: firouz@ipm.ir, E-mail: yw366@cam.ac.uk [Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong (China)

    2015-04-01

    We examine the impact of different anisotropic relics on inflation, in particular the predictions on the density perturbations. These relics can be the source of the large scale anomalies in the cosmic microwave background. There are two different types of background relics, one from the matter sector and the other purely from the metric. Although the angular-dependence of the statistical anisotropy in both cases are degenerate, the scale-dependence are observationally distinctive. In addition, we demonstrate that non-Bunch-Davies vacuum states can extend the statistical anisotropy to much shorter scales, and leave a scale-dependence that is insensitive to the different backgrounds but sensitive to the initial quantum state.

  4. Accordion-like honeycombs for tissue engineering of cardiac anisotropy

    Science.gov (United States)

    Engelmayr, George C.; Cheng, Mingyu; Bettinger, Christopher J.; Borenstein, Jeffrey T.; Langer, Robert; Freed, Lisa E.

    2008-12-01

    Tissue-engineered grafts may be useful in myocardial repair; however, previous scaffolds have been structurally incompatible with recapitulating cardiac anisotropy. Here, we use microfabrication techniques to create an accordion-like honeycomb microstructure in poly(glycerol sebacate), which yields porous, elastomeric three-dimensional (3D) scaffolds with controllable stiffness and anisotropy. Accordion-like honeycomb scaffolds with cultured neonatal rat heart cells demonstrated utility through: (1) closely matched mechanical properties compared to native adult rat right ventricular myocardium, with stiffnesses controlled by polymer curing time; (2) heart cell contractility inducible by electric field stimulation with directionally dependent electrical excitation thresholds (pthe formation of grafts with aligned heart cells and mechanical properties more closely resembling native myocardium.

  5. Azimuthal anisotropy of strange hadrons in U+U collisions at √SNN = 193 GeV at RHIC

    Science.gov (United States)

    Bairathi, Vipul

    2018-02-01

    We present the measurement of the azimuthal anisotropy of strange hadrons (K0s, ϕ and Λ) at mid-rapidity (|y| n = 2, 3, 4. A strong centrality dependence of υ2 is observed for the particles K0s, ϕ and Λ in U+U collisions at = 193 GeV similar to Au+Au collisions at = 200 GeV. We studied the number of constituent quark scaling (NCQ) of the flow coefficients. The NCQ scaling of the flow coefficients holds within uncertainties for the particles studied in the U+U collisions. We also present the comparison of the results to the AMPT transport model.

  6. Impacts of fossil anisotropy on the electric and permeability anisotropy of highly fossiliferous limestone: a case study

    Science.gov (United States)

    Nabawy, Bassem S.

    2017-11-01

    The Middle Eocene Lutetian Samalut formation is among the best examples of anisotropic fossiliferous rocks in Egypt, where the effect of the anisotropic Nummulite Gizehensis fossils on the petrophysical behavior can be traced. The Samalut formation has been sampled and studied at Wadi Feiran in SW Sinai. Petrographically, it is composed of two microfacies; Nummulitic packstone and Fusulinid mudstone. Tight cementation by micro to pseudosparite, aggrading neomorphism and compaction with increasing load pressure are the most important porosity-reducing factors. The anisotropy of the fossil content (λF), due to shape and orientation, and its effect on the petrophysical properties were assigned by measuring the lengths of the longest and shortest axes. Petrophysically, both microfacies are characterized by low porosity values (1.47 ≤ ptyset _{{He}} ≤ 5.29%). The formation resistivity factor (F) and permeability (k) were measured in the horizontal and vertical directions (parallel and perpendicular to the bedding plane, respectively). The studied samples are characterized by high to very high formation resistivity factor (190 ≤ F ≤ 8938) and relatively very low permeability (0.012 ≤ k ≤ 0.110 md). The studied samples are characterized by fair to medium electric anisotropy `λE', which is attributed to a relatively medium to fair degree of electric foliation. It has been shown that, the fossil shape anisotropy and orientation `λF' (1.5 ≤ λF ≤ 3.5) is the main contributor for the electric and permeability anisotropy that corrected for the same porosity value (1.61 ≤ λEC ≤ 2.25 and 1.03 ≤ λkC ≤ 2.04; respectively). Foliation of the studied microfacies has been contributed to the orientation of the fossil remains parallel to the bedding plane. The anisotropy degree is relatively greater for the Nummulitic packstone microfacies than that of the Fusulinid mudstone. The present study refers to the possible anisotropic effect of fossil content (due

  7. Titanium: light, strong, and white

    Science.gov (United States)

    Woodruff, Laurel; Bedinger, George

    2013-01-01

    Titanium (Ti) is a strong silver-gray metal that is highly resistant to corrosion and is chemically inert. It is as strong as steel but 45 percent lighter, and it is twice as strong as aluminum but only 60 percent heavier. Titanium dioxide (TiO2) has a very high refractive index, which means that it has high light-scattering ability. As a result, TiO2 imparts whiteness, opacity, and brightness to many products. ...Because of the unique physical properties of titanium metal and the whiteness provided by TiO2, titanium is now used widely in modern industrial societies.

  8. Extracting the polarizability anisotropy from the transient alignment of HBr.

    Science.gov (United States)

    Pinkham, D; Vogt, T; Jones, R R

    2008-08-14

    We use 40 fs, 780 nm laser pulses to transiently align HBr molecules. We study the temporal dynamics of the resultant rotational wavepacket to gain insight into the electronic properties of the molecule. We show that the HBr polarization anisotropy can be extracted by comparing the time dependence of the HBr alignment with both the analogous alignment behavior of N(2) and the predictions of a rigid-rotor model.

  9. Electron temperature anisotropy constraints in the solar wind

    Czech Academy of Sciences Publication Activity Database

    Štverák, Štěpán; Trávníček, Pavel M.; Maksimovic, M.; Marsch, E.; Fazakerley, A.; Scime, E. E.

    2008-01-01

    Roč. 113, A3 /2008/ (2008), A03103/1-A03103/10 ISSN 0148-0227 R&D Projects: GA AV ČR IAA300420602 Grant - others:EU(XE) ESA-PECS project No. 98024 Institutional research plan: CEZ:AV0Z10030501; CEZ:AV0Z30420517 Keywords : solar wind electrons * temperature anisotropy * radial Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 3.147, year: 2008

  10. On the threshold anisotropy for unstable spherical stellar systems

    Energy Technology Data Exchange (ETDEWEB)

    Polyachenko, V. L.; Polyachenko, E. V., E-mail: epolyach@inasan.ru [Russian Academy of Sciences, Institute of Astronomy (Russian Federation); Shukhman, I. G., E-mail: shukhman@iszf.irk.ru [Russian Academy of Sciences, Institute of Solar-Terrestrial Physics, Siberian Branch (Russian Federation)

    2012-04-15

    The radial orbit instability generally arises in anisotropic collisionless stellar systems with the dominance of radial motions over transverse ones. Using the simplest anisotropic generalization of polytrope models for spherical clusters as an example, we show that the instability growth rates become exponentially small as the isotropic limit is approached. Given the finite lifetime of real astronomical objects, these systems should be assumed to become stable at some finite radial anisotropy.

  11. The BEAN experiment - An EISCAT study of ion temperature anisotropies

    Directory of Open Access Journals (Sweden)

    I. W. McCrea

    Full Text Available Results are presented from a novel EISCAT special programme, SP-UK-BEAN, intended for the direct measurement of the ion temperature anisotropy during ion frictional heating events in the high-latitude F-region. The experiment employs a geometry which provides three simultaneous estimates of the ion temperature in a single F-region observing volume at a range of aspect angles from 0° to 36°. In contrast to most previous EISCAT experiments to study ion temperature anisotropies, field-aligned observations are made using the Sodankylä radar, while the Kiruna radar measures at an aspect angle of the order of 30°. Anisotropic effects can thus be studied within a small common volume whose size and altitude range is limited by the radar beamwidth, rather than in volumes which overlap but cover different altitudes. The derivation of line-of-sight ion temperature is made more complex by the presence of an unknown percentage of atomic and molecular ions at the observing altitude and the possibility of non-Maxwellian distortion of the ion thermal velocity distribution. The first problem has been partly accounted for by insisting that a constant value of electron temperature be maintained. This enables an estimate of the ion composition to be made, and facilitates the derivation of more realistic line-of-sight ion temperatures and temperature anisotropies. The latter problem has been addressed by assuming that the thermal velocity distribution remains bi-Maxwellian. The limitations of these approaches are discussed. The ion temperature anisotropies and temperature partition coefficients during two ion heating events give values intermediate between those expected for atomic and for molecular species. This result is consistent with an analysis which indicates that significant proportions of molecular ions (up to 50% were present at the times of greatest heating.

  12. Flux and anisotropy of galactic cosmic rays: beyond homogeneous models

    International Nuclear Information System (INIS)

    Bernard, Guilhem

    2013-01-01

    In this thesis I study the consequence of non homogeneously distributed cosmic ray sources in the Milky way. The document starts with theoretical and experimental synthesis. Firstly, I will describe the interstellar medium to understand the mechanism of propagation and acceleration of cosmic rays. Then, the detailed study of cosmic rays diffusion on the galactic magnetic field allows to write a commonly used propagation equation. I will recall the Steady-state solutions of this equation, then I will focus on the time dependant solutions with point-like sources. A statistical study is performed in order to estimate the standard deviation of the flux around its mean value. The computation of this standard deviation leads to mathematical divergences. Thus, I will develop statistical tools to bypass this issue. So i will discuss the effect of the granularity of cosmic ray sources. Its impact on cosmic ray spectrum can explain some recent features observed by the experiments CREAM and PAMELA.Besides, this thesis is focused on the study of the anisotropy of cosmic rays. I will recap experimental methods of measurements, and I will show how to connect theoretical calculation from propagation theories to experimental measurements. Then, the influence of the local environment on the anisotropy measurements will be discussed, particularly the effect of a local diffusion coefficient. Then, I will compute anisotropy and its variance in a framework of point-like local sources with the tools developed in the first part. Finally, the possible influence of local sources on the anisotropy is discussed in the light of the last experimental results. (author) [fr

  13. A method to detect positron anisotropies with Pamela data

    Energy Technology Data Exchange (ETDEWEB)

    Panico, B. [INFN, Sezione di Naples, I-80126 Naples (Italy); Adriani, O. [University of Florence, Department of Physics and Astronomy, I-50019 Sesto Fiorentino, Florence (Italy); INFN, Sezione di Florence, I-50019 Sesto Fiorentino, Florence (Italy); Barbarino, G.C. [INFN, Sezione di Naples, I-80126 Naples (Italy); University of Naples Federico II”, Department of Physics, I-80126 Naples (Italy); Bazilevskaya, G.A. [Lebedev Physical Institute, RU-119991, Moscow (Russian Federation); Bellotti, R. [University of Bari, Department of Physics, I-70126 Bari (Italy); INFN, Sezione di Bari, I-70126 Bari (Italy); Boezio, M. [INFN, Sezione di Trieste, I-34149 Trieste (Italy); Bogomolov, E.A. [Ioffe Physical Technical Institute, RU-194021 St. Petersburg (Russian Federation); Bongi, M. [University of Florence, Department of Physics and Astronomy, I-50019 Sesto Fiorentino, Florence (Italy); INFN, Sezione di Florence, I-50019 Sesto Fiorentino, Florence (Italy); Bonvicini, V. [INFN, Sezione di Trieste, I-34149 Trieste (Italy); Bottai, S. [University of Naples Federico II”, Department of Physics, I-80126 Naples (Italy); Bruno, A. [University of Bari, Department of Physics, I-70126 Bari (Italy); INFN, Sezione di Bari, I-70126 Bari (Italy); Cafagna, F. [INFN, Sezione di Bari, I-70126 Bari (Italy); Campana, D. [INFN, Sezione di Naples, I-80126 Naples (Italy); Carbone, R. [INFN, Sezione di Trieste, I-34149 Trieste (Italy); Carlson, P. [KTH, Department of Physics, and the Oskar Klein Centre for Cosmoparticle Physics, AlbaNova University Centre, SE-10691 Stockholm (Sweden); Casolino, M. [INFN, Sezione di Rome Tor Vergata, I-00133 Rome (Italy); RIKEN, Advanced Science Institute, Wako-shi, Saitama (Japan); Castellini, G. [IFAC, I-50019 Sesto Fiorentino, Florence (Italy); De Donato, C. [INFN, Sezione di Rome Tor Vergata, I-00133 Rome (Italy); and others

    2014-11-15

    The PAMELA experiment is collecting data since 2006; its results indicate the presence of a large flux of positron with respect to electrons in the CR spectrum above 10 GeV. This excess might also be originated in objects such as pulsars and microquasars or through dark matter annihilation. Here the electrons and positrons events collected by PAMELA have been analized searching for anisotropies. The analysis is performed at different angular scales and results will be presented at the conference.

  14. Modification of magnetic anisotropy in metallic glasses using high ...

    Indian Academy of Sciences (India)

    metallic glass ribbons. 90 MeV 127I beam was used for the irradiations. Irradiation doses were. 5×1013 and 7.5×1013 ions/cm2. The relative intensity ratios D23 of the second and third lines of the. Mössbauer spectra were measured to determine the magnetic anisotropy. The virgin samples of both the materials display ...

  15. Stress-Induced Seismic Anisotropy Revisited Nouveau regard sur l'anisotropie sismique induite par les contraintes

    Directory of Open Access Journals (Sweden)

    Rasolofosaon P.

    2006-12-01

    Full Text Available This summary contains formulas (*** which can not be displayed on the screenA general principle outlined by P. Curie (1894 regarding the influence of symmetry in physical phenomena states, in modern language, that the symmetry group of the causes is a sub-group of the symmetry group of the effects. For instance, regarding stress-induced seismic anisotropy, the most complex symmetry exhibited by an initially isotropic medium when tri-axially stressed is orthorhombic, or orthotropic, symmetry characterized by three symmetry planes mutually perpendicular (Nur, 1971. In other respects, Schwartz et al. (1994 demonstrated that two very different rock models, namely a cracked model and a weakly consolidated granular model, always lead to elliptical anisotropy when uniaxially stressed. The addressed questions are : Is this result true for any rock model? and more generally : Do initially isotropic rock form a well-defined sub-set of orthorhombic media when triaxially stressed?Under the hypothesis of 3rd order nonlinear isotropic hyperelasticity (i. e. , no hysteresis and existence of an elastic energy function developed to the 3rd order in the strain components it is demonstrated that the qP-wave stress-induced anisotropy is always ellipsoidal, for any strength of anisotropy. For instance point sources generate ellipsoidal qP-wave fronts. This result is general and absolutely independent of the rock model, that is to say independent of the causes of nonlinearity, as far as the initial assumptions are verified. This constitutes the main result of this paper. Thurston (1965 pointed out that an initially isotropic elastic medium, when non-isotropically pre-stressed, is never strictly equivalent to an unstressed anisotropic crystal. For instance the components of the stressed elastic tensor lack the familiar symmetry with respect to indices permutation. This would prohibit Voigt's notation of contracted indices. However if the magnitude of the components of

  16. Anisotropy of x-ray reflectivity: chemical and structural effects on K-shell excitations in hexagonal BN crystal

    CERN Document Server

    Filatova, E O

    2002-01-01

    The experimental investigation of the B and N K-reflection spectra using both s-polarized synchrotron radiation and unpolarized radiation for different crystal orientations with respect to the electric field vector E was carried out. The absorption spectra calculated from the reflection spectra using Kramers-Kronig analysis are presented. A strong orientation dependence of both reflection and absorption spectra is exhibited. Analysis of the orientation dependences of the x-ray reflection and absorption spectra near both edges strongly supports a possibility of tracing the role of each excitation canal in the formation of fine structure. The high sensitivity of the reflection spectra fine structure to the vibronic interaction connected with Jahn-Teller distortions as well to the core-hole relaxation is discussed. A very strong dependence of the absolute values of the reflectivity on planar crystal anisotropy was discovered.

  17. Kinetic instabilities in the solar wind driven by temperature anisotropies

    Science.gov (United States)

    Yoon, Peter H.

    2017-12-01

    The present paper comprises a review of kinetic instabilities that may be operative in the solar wind, and how they influence the dynamics thereof. The review is limited to collective plasma instabilities driven by the temperature anisotropies. To limit the scope even further, the discussion is restricted to the temperature anisotropy-driven instabilities within the model of bi-Maxwellian plasma velocity distribution function. The effects of multiple particle species or the influence of field-aligned drift will not be included. The field-aligned drift or beam is particularly prominent for the solar wind electrons, and thus ignoring its effect leaves out a vast portion of important physics. Nevertheless, for the sake of limiting the scope, this effect will not be discussed. The exposition is within the context of linear and quasilinear Vlasov kinetic theories. The discussion does not cover either computer simulations or data analyses of observations, in any systematic manner, although references will be made to published works pertaining to these methods. The scientific rationale for the present analysis is that the anisotropic temperatures associated with charged particles are pervasively detected in the solar wind, and it is one of the key contemporary scientific research topics to correctly characterize how such anisotropies are generated, maintained, and regulated in the solar wind. The present article aims to provide an up-to-date theoretical development on this research topic, largely based on the author's own work.

  18. Magnetic anisotropies in ultrathin bismuth iron garnet films

    International Nuclear Information System (INIS)

    Popova, Elena; Franco Galeano, Andres Felipe; Deb, Marwan; Warot-Fonrose, Bénédicte; Kachkachi, Hamid; Gendron, François; Ott, Frédéric

    2013-01-01

    Ultrathin bismuth iron garnet Bi 3 Fe 5 O 12 films were grown epitaxially on (001)-oriented gadolinium gallium garnet substrates. Film thickness varied from two to three dozens of unit cells. Bi 3 Fe 5 O 12 films grow pseudomorphically on substrates up to a thickness of 20 nm, and then a lattice relaxation occurs. Magnetic properties of the films were studied as a function of bismuth iron garnet thickness. The magnetization and cubic anisotropy decrease with decreasing film thickness. The uniaxial magnetocrystalline anisotropy is constant for all film thicknesses. For two unit cell thick films, the easy magnetization axis changes from in-plane to perpendicular to the plane direction. Such a reorientation takes place as a result of the competition of constant uniaxial perpendicular anisotropy with weakening film magnetization. - Highlights: ► Ultrathin Bi 3 Fe 5 O 12 films were grown epitaxially on structure-matching substrates. ► Magnetic properties of Bi 3 Fe 5 O 12 were studied down to the thickness of 2.5 nm. ► Reorientation of easy magnetization axis as a function of film thickness was observed

  19. Magnetic anisotropies in ultrathin bismuth iron garnet films

    Energy Technology Data Exchange (ETDEWEB)

    Popova, Elena, E-mail: popova@physique.uvsq.fr [Groupe d' Etude de la Matière Condensée (GEMaC), CNRS/Université de Versailles-Saint-Quentin, 45 Avenue des Etats-Unis, 78035 Versailles (France); Franco Galeano, Andres Felipe [Laboratoire PROcédés, Matériaux et Energie Solaire (PROMES), CNRS/Université de Perpignan Via Domitia, 52 Avenue Paul Alduy, 66860 Perpignan (France); Deb, Marwan [Groupe d' Etude de la Matière Condensée (GEMaC), CNRS/Université de Versailles-Saint-Quentin, 45 Avenue des Etats-Unis, 78035 Versailles (France); Warot-Fonrose, Bénédicte [Centre d' Elaboration de Matériaux et d' Etudes Structurales (CEMES), CNRS, 29 rue Jeanne Marvig, 31055 Toulouse (France); Transpyrenean Associated Laboratory for Electron Microscopy (TALEM), CEMES-INA, CNRS–Universidad de Zaragoza (Spain); Kachkachi, Hamid [Laboratoire PROcédés, Matériaux et Energie Solaire (PROMES), CNRS/Université de Perpignan Via Domitia, 52 Avenue Paul Alduy, 66860 Perpignan (France); Gendron, François [Institut des NanoSciences de Paris (INSP), CNRS/Université Pierre et Marie Curie-Paris 6, 4 place Jussieu, Boîte courrier 840, 75252 Paris Cedex 05 (France); Ott, Frédéric [Laboratoire Léon Brillouin (LLB), CNRS/CEA, Bâtiment 563, CEA Saclay, 91191 Gif sur Yvette Cedex (France); and others

    2013-06-15

    Ultrathin bismuth iron garnet Bi{sub 3}Fe{sub 5}O{sub 12} films were grown epitaxially on (001)-oriented gadolinium gallium garnet substrates. Film thickness varied from two to three dozens of unit cells. Bi{sub 3}Fe{sub 5}O{sub 12} films grow pseudomorphically on substrates up to a thickness of 20 nm, and then a lattice relaxation occurs. Magnetic properties of the films were studied as a function of bismuth iron garnet thickness. The magnetization and cubic anisotropy decrease with decreasing film thickness. The uniaxial magnetocrystalline anisotropy is constant for all film thicknesses. For two unit cell thick films, the easy magnetization axis changes from in-plane to perpendicular to the plane direction. Such a reorientation takes place as a result of the competition of constant uniaxial perpendicular anisotropy with weakening film magnetization. - Highlights: ► Ultrathin Bi{sub 3}Fe{sub 5}O{sub 12} films were grown epitaxially on structure-matching substrates. ► Magnetic properties of Bi{sub 3}Fe{sub 5}O{sub 12} were studied down to the thickness of 2.5 nm. ► Reorientation of easy magnetization axis as a function of film thickness was observed.

  20. Stochastic Modelling of the Hydraulic Anisotropy of Ash Impoundment Sediment

    Science.gov (United States)

    Slávik, Ivan

    2017-12-01

    In the case reported here the impoundments of a 400 MW coal heated power plant with an annual production of about 1.5 million tons of fuel ash are of the cross-valley type, operated by the simple and cheap „upstream method”. The aim of the research was to determine overall and local values of the permeability in horizontal as well as in vertical direction and the anisotropy of the thin-layered sedimented ash. The coal ashes are hydraulically transported through pipelines in form of a slurry and periodically floated on the beach of the impoundment. The ashes are deposited in the form of a thin-layered sediment, with random alternation of layers with a coarser or finer granularity. The ash impoundment sediment is anthropogenic sediment with horizontally laminated texture. Therefore, the sediment is anisotropic from the viewpoint of water seepage. The knowledge of the permeability and the seepage anisotropy of the sediment is a basic requirement for the design of an appropriate dewatering system. The seepage anisotropy of the ash sediment has been checked by means of stochastic modelling, based on the correlation between the effective grain diameter and the coefficient of permeability of the ash: the effective grain diameter and the thickness of individual layers have been proposed to be random events.

  1. Cosmic ray anisotropy: 1012 - 1020eV

    International Nuclear Information System (INIS)

    Watson, A.A.

    1981-01-01

    The results of experiments designed to study the arrival direction distribution of cosmic rays of energy 10 12 - 10 20 eV are reviewed. It is shown that at all energies there is evidence for anisotropy, the amplitude of which ranges from 0.75% at the lowest energies to 90+-20% above 4.10 19 eV. The increase of anisotropy with energy is not smooth, showing features which occur at energies similar to those at which features are observed in the cosmic ray energy spectrum. At least up to 2.10 17 eV it seems probable that the acceleration sites lie within our Galaxy, and it is hard to escape the conclusion that particles of energy >10 19 eV are extragalactic. Sources of the highest energy particles (approximately 10 20 eV) must lie within 200Mpc, and considerably closer if, as seems likely, the intergalactic medium is such as to prevent rectilinear propagation. Between 2.10 17 and 10 19 eV the location of the sources is less certain. The aim of future arrival direction experiments should be to study anisotropy as a function of primary mass composition

  2. Temperature dependence of magnetic anisotropy: An ab initio approach

    Science.gov (United States)

    Staunton, J. B.; Szunyogh, L.; Buruzs, A.; Gyorffy, B. L.; Ostanin, S.; Udvardi, L.

    2006-10-01

    We present a first-principles theory of the variation of magnetic anisotropy, K , with temperature, T , in metallic ferromagnets. It is based on relativistic electronic structure theory and calculation of magnetic torque. Thermally induced local moment magnetic fluctuations are described within the relativistic generalization of the disordered local moment theory from which the T dependence of the magnetization, m , is found. We apply the theory to a uniaxial magnetic material with tetragonal crystal symmetry, L10 -ordered FePd, and find its uniaxial K consistent with a magnetic easy axis perpendicular to the Fe/Pd layers for all m and proportional to m2 for a broad range of values of m . This is the same trend that we have previously found in L10 -ordered FePt and which agrees with experiment. We also study a magnetically soft cubic magnet, the Fe50Pt50 solid solution, and find that its small magnetic anisotropy constant K1 rapidly diminishes from 8μeV to zero. K1 evolves from being proportional to m7 at low T to m4 near the Curie temperature. The accounts of both the tetragonal and cubic itinerant electron magnets differ from those extracted from single ion anisotropy models and instead receive clear interpretations in terms of two ion anisotropic exchange.

  3. On the Resolution of Inversion for Orthorhombic Anisotropy

    KAUST Repository

    Kazei, Vladimir

    2017-05-26

    We investigate the resolution of elastic anisotropic inversion for orthorhombic media with P-waves by remapping classic radiation patterns into the wavenumber domain. We show analytically that dynamic linearized inversion (linearized reverse-time migration and full-waveform inversion) for orthorhombic anisotropy based on longitudinal waves is fundamentally sensitive to emph{six} parameters only and density, in which the perturbing effects can be represented by particular anisotropy configuration. Singular value decomposition of spectral sensitivities allows us to provide estimates of the number of parameters one could invert in specific acquisition settings, and with certain parametrization. In most acquisition scenarios, a hierarchical parameterization based on the $P$, and $S$-wave velocities, along with dimensionless parameters that describe the anisotropy as velocity ratio in the radial and azimuthal directions, minimizes the tradeoff and increases the sensitivity of the data to velocity compared to the standard (stiffness, density) parametrization. These features yield more robust velocity estimation, by focusing the inversion on a subset of invertible parameters.

  4. Anisotropy of Single-Crystal Silicon in Nanometric Cutting.

    Science.gov (United States)

    Wang, Zhiguo; Chen, Jiaxuan; Wang, Guilian; Bai, Qingshun; Liang, Yingchun

    2017-12-01

    The anisotropy exhibited by single-crystal silicon in nanometric cutting is very significant. In order to profoundly understand the effect of crystal anisotropy on cutting behaviors, a large-scale molecular dynamics model was conducted to simulate the nanometric cutting of single-crystal silicon in the (100)[0-10], (100)[0-1-1], (110)[-110], (110)[00-1], (111)[-101], and (111)[-12-1] crystal directions in this study. The simulation results show the variations of different degrees in chip, subsurface damage, cutting force, and friction coefficient with changes in crystal plane and crystal direction. Shear deformation is the formation mechanism of subsurface damage, and the direction and complexity it forms are the primary causes that result in the anisotropy of subsurface damage. Structurally, chips could be classified into completely amorphous ones and incompletely amorphous ones containing a few crystallites. The formation mechanism of the former is high-pressure phase transformation, while the latter is obtained under the combined action of high-pressure phase transformation and cleavage. Based on an analysis of the material removal mode, it can be found that compared with the other crystal direction on the same crystal plane, the (100)[0-10], (110)[-110], and (111)[-101] directions are more suitable for ductile cutting.

  5. Biased Brownian motion in narrow channels with asymmetry and anisotropy

    Science.gov (United States)

    To, Kiwing; Peng, Zheng

    2016-11-01

    We study Brownian motion of a single millimeter size bead confined in a quasi-two-dimensional horizontal channel with built-in anisotropy and asymmetry. Channel asymmetry is implemented by ratchet walls while anisotropy is introduced using a channel base that is grooved along the channel axis so that a bead can acquire a horizontal impulse perpendicular to the longitudinal direction when it collides with the base. When energy is injected to the channel by vertical vibration, the combination of asymmetric walls and anisotropic base induces an effective force which drives the bead into biased diffusive motion along the channel axis with diffusivity and drift velocity increase with vibration strength. The magnitude of this driving force, which can be measured in experiments of tilted channel, is found to be consistent to those obtained from dynamic mobility and position probability distribution measurements. These results are explained by a simple collision model that suggests the random kinetic energies transfer between different translational degrees of freedom may be turned into useful work in the presence of asymmetry and anisotropy.

  6. Perpendicular magnetic anisotropy at transition metal/oxide interfaces and applications

    Science.gov (United States)

    Dieny, B.; Chshiev, M.

    2017-04-01

    Spin electronics is a rapidly expanding field stimulated by a strong synergy between breakthrough basic research discoveries and industrial applications in the fields of magnetic recording, magnetic field sensors, nonvolatile memories [magnetic random access memories (MRAM) and especially spin-transfer-torque MRAM (STT-MRAM)]. In addition to the discovery of several physical phenomena (giant magnetoresistance, tunnel magnetoresistance, spin-transfer torque, spin-orbit torque, spin Hall effect, spin Seebeck effect, etc.), outstanding progress has been made on the growth and nanopatterning of magnetic multilayered films and nanostructures in which these phenomena are observed. Magnetic anisotropy is usually observed in materials that have large spin-orbit interactions. However, in 2002 perpendicular magnetic anisotropy (PMA) was discovered to exist at magnetic metal/oxide interfaces [for instance Co (Fe )/alumina ]. Surprisingly, this PMA is observed in systems where spin-orbit interactions are quite weak, but its amplitude is remarkably large—comparable to that measured at Co /Pt interfaces, a reference for large interfacial anisotropy (anisotropy˜1.4 erg /cm2=1.4 mJ /m2 ). Actually, this PMA was found to be very common at magnetic metal/oxide interfaces since it has been observed with a large variety of amorphous or crystalline oxides, including AlOx, MgO, TaOx, HfOx, etc. This PMA is thought to be the result of electronic hybridization between the oxygen and the magnetic transition metal orbit across the interface, a hypothesis supported by ab initio calculations. Interest in this phenomenon was sparked in 2010 when it was demonstrated that the PMA at magnetic transition metal/oxide interfaces could be used to build out-of-plane magnetized magnetic tunnel junctions for STT-MRAM cells. In these systems, the PMA at the CoFeB /MgO interface can be used to simultaneously obtain good memory retention, thanks to the large PMA amplitude, and a low write current

  7. Negative tunneling magneto-resistance in quantum wires with strong spin-orbit coupling.

    Science.gov (United States)

    Han, Seungju; Serra, Llorenç; Choi, Mahn-Soo

    2015-07-01

    We consider a two-dimensional magnetic tunnel junction of the FM/I/QW(FM+SO)/I/N structure, where FM, I and QW(FM+SO) stand for a ferromagnet, an insulator and a quantum wire with both magnetic ordering and Rashba spin-orbit (SOC), respectively. The tunneling magneto-resistance (TMR) exhibits strong anisotropy and switches sign as the polarization direction varies relative to the quantum-wire axis, due to interplay among the one-dimensionality, the magnetic ordering, and the strong SOC of the quantum wire.

  8. Detection of zero anisotropy at 5.2 AU during the November 1998 solar particle event: Ulysses Anisotropy Telescopes observations

    Directory of Open Access Journals (Sweden)

    S. Dalla

    Full Text Available For the first time during the mission, the Anisotropy Telescopes instrument on board the Ulysses spacecraft measured constant zero anisotropy of protons in the 1.3-2.2 MeV energy range, for a period lasting more than three days. This measurement was made during the energetic particle event taking place at Ulysses between 25 November and 15 December 1998, an event characterised by constant high proton fluxes within a region delimited by two interplanetary forward shocks, at a distance of 5.2 AU from the Sun and heliographic latitude of 17°S. We present the ATs results for this event and discuss their possible interpretation and their relevance to the issue of intercalibration of the two telescopes.

    Key words: Interplanetary physics (energetic particles - Solar physics, astrophysics and astronomy (energetic particles - Space plasma physics (instruments and techniques

  9. Complex, multilayered azimuthal anisotropy beneath Tibet: evidence for co-existing channel flow and pure-shear crustal thickening

    Science.gov (United States)

    Agius, Matthew R.; Lebedev, Sergei

    2017-09-01

    Of the two debated, end-member models for the late-Cenozoic thickening of Tibetan crust, one invokes 'channel flow' (rapid viscous flow of the mid-lower crust, driven by topography-induced pressure gradients and transporting crustal rocks eastward) and the other 'pure shear' (faulting and folding in the upper crust, with viscous shortening in the mid-lower crust). Deep-crustal deformation implied by each model is different and would produce different anisotropic rock fabric. Observations of seismic anisotropy can thus offer a discriminant. We use broad-band phase-velocity curves-each a robust average of tens to hundreds of measurements-to determine azimuthal anisotropy in the entire lithosphere-asthenosphere depth range and constrain its amplitude. Inversions of the differential dispersion from path pairs, region-average inversions and phase-velocity tomography yield mutually consistent results, defining two highly anisotropic layers with different fast-propagation directions within each: the middle crust and the asthenosphere. In the asthenosphere beneath central and eastern Tibet, anisotropy is 2-4 per cent and has an NNE-SSW fast-propagation azimuth, indicating flow probably driven by the NNE-ward, shallow-angle subduction of India. The distribution and complexity of published shear wave splitting measurements can be accounted for by the different anisotropy in the mid-lower crust and asthenosphere. The estimated splitting times that would be accumulated in the crust alone are 0.25-0.8 s; in the upper mantle-0.5-1.2 s, depending on location. In the middle crust (20-45 km depth) beneath southern and central Tibet, azimuthal anisotropy is 3-5 and 4-6 per cent, respectively, and its E-W fast-propagation directions are parallel to the current extension at the surface. The rate of the extension is relatively low, however, whereas the large radial anisotropy observed in the middle crust requires strong alignment of mica crystals, implying large finite strain and

  10. Quantifying angular dependence of spin-orbit torques in Ta/CoFeB/MgO trilayers with perpendicular magnetic anisotropy

    Science.gov (United States)

    Chen, Yunpeng; Celik, Halise; Wang, Tao; Kannan, Harsha; Krivorotov, Ilya N.; Xiao, John Q.

    2017-04-01

    The spin-orbit interactions in heavy-metal/ferromagnet heterostructures have attracted considerable attention because they provide an efficient way to manipulate the magnetization with strong current-driven spin-orbit torques (SOTs) via the spin Hall effect in the heavy metal or Rashba effect due to the symmetry breaking at the interface. Theoretical calculations predict no dependence of the SOTs on the out-of-plane angle of magnetization due to spin Hall effect, but Rashba effect induces a nontrivial angular dependence of SOTs. Quantitative measurements with adiabatic harmonic Hall technique have observed the angular dependence in Ta/CoFeB/MgO or Pt /Co /Al Ox with perpendicular magnetic anisotropy. However, this method is complicated because the signal consists of both anomalous and planar Hall contributions. In addition, the fitting of the measurement data is sensitive to the fitting parameters, particularly to the perpendicular anisotropy, in a certain angle region (40-70°). To avoid this uncertainty, we have developed a scheme to quantify the angular dependence of SOTs based on the magneto-optic Kerr effect with field calibration. Without fitting procedures, we precisely determine the SOTs and their angle dependence on the magnetization orientation. We observe a strong angular dependence that is different from the previous experimental observations. Based on this strong dependence, we conclude that a Rashba effect at the same interface, that is responsible for the perpendicular magnetic anisotropy, is the dominant mechanism for the current-driven SOTs in this system.

  11. The effects of structure anisotropy on lensing observables in an exact general relativistic setting for precision cosmology

    Energy Technology Data Exchange (ETDEWEB)

    Troxel, M. A.; Ishak, Mustapha; Peel, Austin, E-mail: troxel@utdallas.edu, E-mail: mishak@utdallas.edu, E-mail: austin.peel@utdallas.edu [Department of Physics, The University of Texas at Dallas, Richardson, TX 75080 (United States)

    2014-03-01

    The study of relativistic, higher order, and nonlinear effects has become necessary in recent years in the pursuit of precision cosmology. We develop and apply here a framework to study gravitational lensing in exact models in general relativity that are not restricted to homogeneity and isotropy, and where full nonlinearity and relativistic effects are thus naturally included. We apply the framework to a specific, anisotropic galaxy cluster model which is based on a modified NFW halo density profile and described by the Szekeres metric. We examine the effects of increasing levels of anisotropy in the galaxy cluster on lensing observables like the convergence and shear for various lensing geometries, finding a strong nonlinear response in both the convergence and shear for rays passing through anisotropic regions of the cluster. Deviation from the expected values in a spherically symmetric structure are asymmetric with respect to path direction and thus will persist as a statistical effect when averaged over some ensemble of such clusters. The resulting relative difference in various geometries can be as large as approximately 2%, 8%, and 24% in the measure of convergence (1−κ) for levels of anisotropy of 5%, 10%, and 15%, respectively, as a fraction of total cluster mass. For the total magnitude of shear, the relative difference can grow near the center of the structure to be as large as 15%, 32%, and 44% for the same levels of anisotropy, averaged over the two extreme geometries. The convergence is impacted most strongly for rays which pass in directions along the axis of maximum dipole anisotropy in the structure, while the shear is most strongly impacted for rays which pass in directions orthogonal to this axis, as expected. The rich features found in the lensing signal due to anisotropic substructure are nearly entirely lost when one treats the cluster in the traditional FLRW lensing framework. These effects due to anisotropic structures are thus likely to

  12. Magnetic anisotropy of [Mo(CN)7]4- anions and fragments of cyano-bridged magnetic networks.

    Science.gov (United States)

    Chibotaru, Liviu F; Hendrickx, Marc F A; Clima, Sergiu; Larionova, Joulia; Ceulemans, Arnout

    2005-08-18

    Quantum chemistry calculations of CASSCF/CASPT2 level together with ligand field analysis are used for the investigation of magnetic anisotropy of [Mo(CN)7]4- complexes. We have considered three types of heptacyano environments: two ideal geometries, a pentagonal bipyramid and a capped trigonal prism, and the heptacyanomolybdate fragment of the cyano-bridged magnetic network K2[Mn(H2O)2]3[Mo(CN)7]2.6H2O. At all geometries the first excited Kramers doublet is found remarkably close to the ground one due to a small orbital energy gap in the ligand field spectrum, which ranges between a maximal value in the capped trigonal prism (800 cm(-1)) and zero in the pentagonal bipyramid. The small value of this gap explains (i) the axial form of the g tensor and (ii) the strong magnetic anisotropy even in strongly distorted complexes. Comparison with available experimental data for the g tensor of the mononuclear precursors reveals good agreement with the present calculations for the capped trigonal prismatic complex and a significant discrepancy for the pentagonal bipyramidal one. The calculations for the heptacyanomolybdate fragment of K2[Mn(H2O)2]3[Mo(CN)7]2.6H2O give g(perpendicular)/g(parallel) approximately 0.5 and the orientation of the local anisotropy axis close to the symmetry axis of an idealized pentagonal bipyramid. These findings are expected to be important for the understanding of the magnetism of anisotropic Mo(III)-Mn(II) cyano-bridged networks based on the [Mo(CN)7]4- building block.

  13. A Bayesian Method to Quantify Azimuthal Anisotropy Model Uncertainties: Application to Global Azimuthal Anisotropy in the Upper Mantle and Transition Zone

    Science.gov (United States)

    Yuan, K.; Beghein, C.

    2018-01-01

    Seismic anisotropy is a powerful tool to constrain mantle deformation, but its existence in the deep upper mantle and topmost lower mantle is still uncertain. Recent results from higher mode Rayleigh waves have, however, revealed the presence of 1 % azimuthal anisotropy between 300 km and 800 km depth, and changes in azimuthal anisotropy across the mantle transition zone boundaries. This has important consequences for our understanding of mantle convection patterns and deformation of deep mantle material. Here, we propose a Bayesian method to model depth variations in azimuthal anisotropy and to obtain quantitative uncertainties on the fast seismic direction and anisotropy amplitude from phase velocity dispersion maps. We applied this new method to existing global fundamental and higher mode Rayleigh wave phase velocity maps to assess the likelihood of azimuthal anisotropy in the deep upper mantle and to determine whether previously detected changes in anisotropy at the transition zone boundaries are robustly constrained by those data. Our results confirm that deep upper mantle azimuthal anisotropy is favored and well-constrained by the higher mode data employed. The fast seismic directions are in agreement with our previously published model. The data favor a model characterized, on average, by changes in azimuthal anisotropy at the top and bottom of the transition zone. However, this change in fast axes is not a global feature as there are regions of the model where the azimuthal anisotropy direction is unlikely to change across depths in the deep upper mantle. We were, however, unable to detect any clear pattern or connection with surface tectonics. Future studies will be needed to further improve the lateral resolution of this type of model at transition zone depths.

  14. The SNAP Strong Lens Survey

    Energy Technology Data Exchange (ETDEWEB)

    Marshall, P.

    2005-01-03

    Basic considerations of lens detection and identification indicate that a wide field survey of the types planned for weak lensing and Type Ia SNe with SNAP are close to optimal for the optical detection of strong lenses. Such a ''piggy-back'' survey might be expected even pessimistically to provide a catalogue of a few thousand new strong lenses, with the numbers dominated by systems of faint blue galaxies lensed by foreground ellipticals. After sketching out our strategy for detecting and measuring these galaxy lenses using the SNAP images, we discuss some of the scientific applications of such a large sample of gravitational lenses: in particular we comment on the partition of information between lens structure, the source population properties and cosmology. Understanding this partitioning is key to assessing strong lens cosmography's value as a cosmological probe.

  15. Strong coupling phase in QED

    International Nuclear Information System (INIS)

    Aoki, Ken-ichi

    1988-01-01

    Existence of a strong coupling phase in QED has been suggested in solutions of the Schwinger-Dyson equation and in Monte Carlo simulation of lattice QED. In this article we recapitulate the previous arguments, and formulate the problem in the modern framework of the renormalization theory, Wilsonian renormalization. This scheme of renormalization gives the best understanding of the basic structure of a field theory especially when it has a multi-phase structure. We resolve some misleading arguments in the previous literature. Then we set up a strategy to attack the strong phase, if any. We describe a trial; a coupled Schwinger-Dyson equation. Possible picture of the strong coupling phase QED is presented. (author)

  16. Towards Detection of Magnetofossils in Sediments: Magnetostatic Interaction and Magnetic Anisotropy Effects

    Science.gov (United States)

    Pan, Y.; Li, J.

    2012-12-01

    state of magnetofossils. Results show that intact MTB and well-dispersed magnetosome chains are characterized by strong magnetic anisotropy and weak magnetostatic interactions, but progressive chain breakup and particle clumping significantly increases the degree of the magnetostatic interaction and a change of magnetic signature towards the typical properties of interacting, single-domain particles. Specifically, the progressive chain breakup and particle clumping systematically decrease of the ratio of anhysteretic remanent magnetization to the saturation isothermal remanent magnetization (ARM/SIRM or χARM/SIRM), the crossing point of the Wohlfarth-Cisowski test, and the delta ratio (δFC/δZFC) between losses of field and zero-field cooled remanent magnetization across the Verwey transition. We hence propose a delta-plot (δFC/δZFC vs. δZFC) as a new approach to diagnose magnetosome chains of magnetosomes, and detect magnetofossils in sediments and rocks.

  17. Polarisation-sensitive switch: An integrated intensity-independent solution for 1.3 μm based on the polarisation anisotropy of ordered InGaAsP

    International Nuclear Information System (INIS)

    Kraemer, S.; Malzer, S.; Doehler, G.H.; Neumann, S.; Prost, W.; Tegude, F.J.

    2005-01-01

    Ordered materials provide new possibilities for optical device applications. Through a strong polarisation anisotropy of absorption a high functional polarisation-sensitive switch can be fabricated which in addition is nearly independent on the optical power. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. Airborne spectral measurements of surface-atmosphere anisotropy for several surfaces and ecosystems over southern Africa

    Science.gov (United States)

    Gatebe, Charles K.; King, Michael D.; Platnick, Steve; Arnold, G. Thomas; Vermote, Eric F.; Schmid, Beat

    2003-07-01

    The Cloud Absorption Radiometer (CAR) was flown aboard the University of Washington Convair CV-580 research aircraft during the Southern Africa Regional Science Initiative 2000 (SAFARI 2000) dry season campaign and obtained measurements of bidirectional reflectance distribution function (BRDF) for a variety of natural surfaces and ecosystems in southern Africa. To measure the BRDF of the surface-atmosphere system, the University of Washington CV-580 banked at a roll angle of ˜20° and flew circles about 3 km in diameter above the surface, taking approximately 2 min. Multiple circular orbits were acquired over selected surfaces so that average BRDFs could be acquired, smoothing out small-scale surface and atmospheric inhomogeneities. In this paper, we present results of BRDFs taken over two Earth Observing System (EOS) validation sites: Skukuza tower, South Africa (25.0°S, 31.5°E) and Mongu tower, Zambia (15.4°S, 23.3°E). Additional sites are discussed and include the Maun tower, Botswana (20.0°S, 23.6°E), Sua Pan, Botswana (20.6°S, 25.9°E), Etosha Pan, Namibia (19.0°S, 16.0°E), and marine stratocumulus clouds off the west coast of Namibia (20.5°S, 13.1°E). Results clearly show anisotropy in reflected solar radiation over the various surfaces types: savanna, salt pans, and cloud. The greatest anisotropy is observed over marine stratus clouds, which exhibit strong forward scattering as well as important water cloud scattering features such as the rainbow and glory. The BRDF over savanna is characterized by a distinct backscattering peak in the principal plane and shows directional and spectral variations. Over the pans, the BRDF is more enhanced in the backscattering plane than forward scattering plane and shows little directional variation.

  19. Mapping of coma anisotropies to plasma structures of weak comets: a 3-D hybrid simulation study

    Directory of Open Access Journals (Sweden)

    N. Gortsas

    2009-04-01

    Full Text Available The effects of coma anisotropies on the plasma environment of comets have been studied by means of a 3-D hybrid model which treats electrons as a massless, charge-neutralizing fluid, whereas ion dynamics are covered by a kinetic approach. From Earth-based observations as well as from in-situ spacecraft measurements the shape of the coma of many comets is ascertained to be anisotropic. However, most plasma simulation studies deploy a spherically symmetric activity pattern. In this paper anisotropy is studied by considering three different coma shape models. The first model is derived from the Haser model and is characterised by spherically symmetry. This reference model is then compared with two different neutral gas shape models: the dayside restricted model with no nightside activity and a cone shaped model with opening angle of π/2. In all models the integrated surface activity is kept constant. The simulations have been done for the Rosetta target comet 67P/Churyumov-Gerasimenko for two heliocentric distances, 1.30 AU and 3.25 AU. It is found that shock formation processes are modified as a result of increasing spatial confinement. Characteristic plasma structures of comets such as the bow shock, magnetic barrier region and the ion composition boundary exhibit a shift towards the sun. In addition, the cone shaped model leads to a strong increase of the mass-loaded region which in turn leads to a smooth deceleration of the solar wind flow and an increasing degree of mixture between the solar wind and cometary ion species. This creates an additional transport channel of the magnetic field from the magnetic barrier region away which in turn leads to a broadening of this region. In addition, it leads to an ion composition boundary which is only gradually developed.

  20. Halo assembly bias and the tidal anisotropy of the local halo environment

    Science.gov (United States)

    Paranjape, Aseem; Hahn, Oliver; Sheth, Ravi K.

    2018-02-01

    We study the role of the local tidal environment in determining the assembly bias of dark matter haloes. Previous results suggest that the anisotropy of a halo's environment (i.e, whether it lies in a filament or in a more isotropic region) can play a significant role in determining the eventual mass and age of the halo. We statistically isolate this effect using correlations between the large-scale and small-scale environments of simulated haloes at z = 0 with masses between 1011.6 ≲ (m/h-1M⊙) ≲ 1014.9. We probe the large-scale environment using a novel halo-by-halo estimator of linear bias. For the small-scale environment, we identify a variable αR that captures the tidal anisotropy in a region of radius R = 4R200b around the halo and correlates strongly with halo bias at fixed mass. Segregating haloes by αR reveals two distinct populations. Haloes in highly isotropic local environments (αR ≲ 0.2) behave as expected from the simplest, spherically averaged analytical models of structure formation, showing a negative correlation between their concentration and large-scale bias at all masses. In contrast, haloes in anisotropic, filament-like environments (αR ≳ 0.5) tend to show a positive correlation between bias and concentration at any mass. Our multi-scale analysis cleanly demonstrates how the overall assembly bias trend across halo mass emerges as an average over these different halo populations, and provides valuable insights towards building analytical models that correctly incorporate assembly bias. We also discuss potential implications for the nature and detectability of galaxy assembly bias.

  1. Strong Decomposition of Random Variables

    DEFF Research Database (Denmark)

    Hoffmann-Jørgensen, Jørgen; Kagan, Abram M.; Pitt, Loren D.

    2007-01-01

    A random variable X is stongly decomposable if X=Y+Z where Y=Φ(X) and Z=X-Φ(X) are independent non-degenerated random variables (called the components). It is shown that at least one of the components is singular, and we derive a necessary and sufficient condition for strong decomposability...

  2. Strong interaction at finite temperature

    Indian Academy of Sciences (India)

    Abstract. We review two methods discussed in the literature to determine the effective parameters of strongly interacting particles as they move through a heat bath. The first one is the general method of chiral perturbation theory, which may be readily applied to this problem. The other is the method of thermal QCD sum rules ...

  3. Strong-strong beam-beam simulation on parallel computer

    Energy Technology Data Exchange (ETDEWEB)

    Qiang, Ji

    2004-08-02

    The beam-beam interaction puts a strong limit on the luminosity of the high energy storage ring colliders. At the interaction points, the electromagnetic fields generated by one beam focus or defocus the opposite beam. This can cause beam blowup and a reduction of luminosity. An accurate simulation of the beam-beam interaction is needed to help optimize the luminosity in high energy colliders.

  4. Strong-strong beam-beam simulation on parallel computer

    International Nuclear Information System (INIS)

    Qiang, Ji

    2004-01-01

    The beam-beam interaction puts a strong limit on the luminosity of the high energy storage ring colliders. At the interaction points, the electromagnetic fields generated by one beam focus or defocus the opposite beam. This can cause beam blowup and a reduction of luminosity. An accurate simulation of the beam-beam interaction is needed to help optimize the luminosity in high energy colliders

  5. Model of coordination melting of crystals and anisotropy of physical and chemical properties of the surface

    Science.gov (United States)

    Bokarev, Valery P.; Krasnikov, Gennady Ya

    2018-02-01

    Based on the evaluation of the properties of crystals, such as surface energy and its anisotropy, the surface melting temperature, the anisotropy of the work function of the electron, and the anisotropy of adsorption, were shown the advantages of the model of coordination melting (MCM) in calculating the surface properties of crystals. The model of coordination melting makes it possible to calculate with an acceptable accuracy the specific surface energy of the crystals, the anisotropy of the surface energy, the habit of the natural crystals, the temperature of surface melting of the crystal, the anisotropy of the electron work function and the anisotropy of the adhesive properties of single-crystal surfaces. The advantage of our model is the simplicity of evaluating the surface properties of the crystal based on the data given in the reference literature. In this case, there is no need for a complex mathematical tool, which is used in calculations using quantum chemistry or modeling by molecular dynamics.

  6. Anisotropy of the structure factor of magnetic fluids under a field probed by small-angle neutron scattering

    International Nuclear Information System (INIS)

    Gazeau, F.; Bacri, J.-C.; Perzynski, R.; Dubois, E.; Boue, F.; Cebers, A.

    2002-01-01

    Small-angle neutron scattering is used to measure the two-dimensional diffraction pattern of a monophasic magnetic colloid, under an applied magnetic field. This dipolar system presents in zero field a fluidlike structure. It is well characterized by an interaction parameter K T 0 proportional to the second virial coefficient, which is here positive, expressing a repulsion of characteristic length κ 0 -1 . Under the field a strong anisotropy is observed at the lowest q vectors. The length κ 0 -1 remains isotropic, but the interaction parameter K T becomes anisotropic due to the long-range dipolar interaction. However, the system remains stable, the interaction being repulsive in all directions. Thus No.No.we do not observe any chaining of the nanoparticles under magnetic field. On the contrary, the revealed structure of our anisotropic colloid is a lowering of the concentration fluctuations along the field while the fluidlike structure, observed without field, is roughly preserved perpendicularly to the field. It expresses a strong anisotropy of the Brownian motion of the nanoparticles in the solution under applied field

  7. Anisotropy of the structure factor of magnetic fluids under a field probed by small-angle neutron scattering.

    Science.gov (United States)

    Gazeau, F; Dubois, E; Bacri, J C; Boué, F; Cebers, A; Perzynski, R

    2002-03-01

    Small-angle neutron scattering is used to measure the two-dimensional diffraction pattern of a monophasic magnetic colloid, under an applied magnetic field. This dipolar system presents in zero field a fluidlike structure. It is well characterized by an interaction parameter K(0)(T) proportional to the second virial coefficient, which is here positive, expressing a repulsion of characteristic length kappa-10. Under the field a strong anisotropy is observed at the lowest q vectors. The length kappa-10 remains isotropic, but the interaction parameter K(T) becomes anisotropic due to the long-range dipolar interaction. However, the system remains stable, the interaction being repulsive in all directions. Thus we do not observe any chaining of the nanoparticles under magnetic field. On the contrary, the revealed structure of our anisotropic colloid is a lowering of the concentration fluctuations along the field while the fluidlike structure, observed without field, is roughly preserved perpendicularly to the field. It expresses a strong anisotropy of the Brownian motion of the nanoparticles in the solution under applied field.

  8. Magnetization and anisotropy of cobalt ferrite thin films

    Science.gov (United States)

    Eskandari, F.; Porter, S. B.; Venkatesan, M.; Kameli, P.; Rode, K.; Coey, J. M. D.

    2017-12-01

    The magnetization of thin films of cobalt ferrite frequently falls far below the bulk value of 455 kA m-1 , which corresponds to an inverse cation distribution in the spinel structure with a significant orbital moment of about 0.6 μB that is associated with the octahedrally coordinated Co2+ ions. The orbital moment is responsible for the magnetostriction and magnetocrystalline anisotropy and its sensitivity to imposed strain. We have systematically investigated the structure and magnetism of films produced by pulsed-laser deposition on different substrates (Ti O2 , MgO, MgA l2O4 , SrTi O3 , LSAT, LaAl O3 ) and as a function of temperature (500 -700 °C) and oxygen pressure (10-4-10 Pa ) . Magnetization at room-temperature ranges from 60 to 440 kA m-1 , and uniaxial substrate-induced anisotropy ranges from +220 kJ m-3 for films on deposited on MgO (100) to -2100 kJ m-3 for films deposited on MgA l2O4 (100), where the room-temperature anisotropy field reaches 14 T. No rearrangement of high-spin Fe3+ and Co2+ cations on tetrahedral and octahedral sites can reduce the magnetization below the bulk value, but a switch from Fe3+ and Co2+ to Fe2+ and low-spin Co3+ on octahedral sites will reduce the low-temperature magnetization to 120 kA m-1 , and a consequent reduction of Curie temperature can bring the room-temperature value to near zero. Possible reasons for the appearance of low-spin cobalt in the thin films are discussed.

  9. Effective wavefield extrapolation in anisotropic media: Accounting for resolvable anisotropy

    KAUST Repository

    Alkhalifah, Tariq Ali

    2014-04-30

    Spectral methods provide artefact-free and generally dispersion-free wavefield extrapolation in anisotropic media. Their apparent weakness is in accessing the medium-inhomogeneity information in an efficient manner. This is usually handled through a velocity-weighted summation (interpolation) of representative constant-velocity extrapolated wavefields, with the number of these extrapolations controlled by the effective rank of the original mixed-domain operator or, more specifically, by the complexity of the velocity model. Conversely, with pseudo-spectral methods, because only the space derivatives are handled in the wavenumber domain, we obtain relatively efficient access to the inhomogeneity in isotropic media, but we often resort to weak approximations to handle the anisotropy efficiently. Utilizing perturbation theory, I isolate the contribution of anisotropy to the wavefield extrapolation process. This allows us to factorize as much of the inhomogeneity in the anisotropic parameters as possible out of the spectral implementation, yielding effectively a pseudo-spectral formulation. This is particularly true if the inhomogeneity of the dimensionless anisotropic parameters are mild compared with the velocity (i.e., factorized anisotropic media). I improve on the accuracy by using the Shanks transformation to incorporate a denominator in the expansion that predicts the higher-order omitted terms; thus, we deal with fewer terms for a high level of accuracy. In fact, when we use this new separation-based implementation, the anisotropy correction to the extrapolation can be applied separately as a residual operation, which provides a tool for anisotropic parameter sensitivity analysis. The accuracy of the approximation is high, as demonstrated in a complex tilted transversely isotropic model. © 2014 European Association of Geoscientists & Engineers.

  10. A "2-omega" technique for measuring anisotropy of thermal conductivity.

    Science.gov (United States)

    Ramu, Ashok T; Bowers, John E

    2012-12-01

    A popular method of measuring the thermal conductivity of thin films and substrates, the "3-omega" method, is modified to yield a new technique for measuring the anisotropy in thermal transport in bulk materials. The validity of the proposed technique is established by measuring the thermal conductivity of strontium titanate, which is expected to be isotropic because of its cubic unit cell. The technique is then applied to rutile TiO(2). The analysis of experimental results on (100) and (001) TiO(2) reveals that the anisotropy is a function of the crystalline quality, as quantified by the effective thermal conductivity obtained through conventional "3-omega" measurements. The advantages of the proposed technique are similar to those of the standard "3-omega" method, namely the simplicity of sample preparation and measurement, and negligible errors due to radiation because of the small volume of material being heated. For anisotropy determination, the proposed technique has the additional advantage that a single sample is sufficient to determine both components of the thermal conductivity, namely the values in and perpendicular to the plane of cleavage. This is significant for materials in which there is a large variation in the crystalline quality from sample to sample. For such materials, it is unreliable to use two different samples, one for measuring the thermal conductivity in each direction. Experimental data are analyzed using a 3D Fourier-series based method developed in this work. The proposed method determines each component of the thermal conductivity with an estimated accuracy of about 10%.

  11. PREFACE: Strongly correlated electron systems Strongly correlated electron systems

    Science.gov (United States)

    Saxena, Siddharth S.; Littlewood, P. B.

    2012-07-01

    This special section is dedicated to the Strongly Correlated Electron Systems Conference (SCES) 2011, which was held from 29 August-3 September 2011, in Cambridge, UK. SCES'2011 is dedicated to 100 years of superconductivity and covers a range of topics in the area of strongly correlated systems. The correlated electronic and magnetic materials featured include f-electron based heavy fermion intermetallics and d-electron based transition metal compounds. The selected papers derived from invited presentations seek to deepen our understanding of the rich physical phenomena that arise from correlation effects. The focus is on quantum phase transitions, non-Fermi liquid phenomena, quantum magnetism, unconventional superconductivity and metal-insulator transitions. Both experimental and theoretical work is presented. Based on fundamental advances in the understanding of electronic materials, much of 20th century materials physics was driven by miniaturisation and integration in the electronics industry to the current generation of nanometre scale devices. The achievements of this industry have brought unprecedented advances to society and well-being, and no doubt there is much further to go—note that this progress is founded on investments and studies in the fundamentals of condensed matter physics from more than 50 years ago. Nevertheless, the defining challenges for the 21st century will lie in the discovery in science, and deployment through engineering, of technologies that can deliver the scale needed to have an impact on the sustainability agenda. Thus the big developments in nanotechnology may lie not in the pursuit of yet smaller transistors, but in the design of new structures that can revolutionise the performance of solar cells, batteries, fuel cells, light-weight structural materials, refrigeration, water purification, etc. The science presented in the papers of this special section also highlights the underlying interest in energy-dense materials, which

  12. Spin-Orbit Torque-Assisted Switching in Magnetic Insulator Thin Films with Perpendicular Magnetic Anisotropy

    Science.gov (United States)

    Wu, Mingzhong

    As an in-plane charge current flows in a heavy metal film with spin-orbit coupling, it produces a torque that can induce magnetization switching in a neighboring ferromagnetic metal film. Such spin-orbit torque (SOT)-induced switching has been studied extensively in recent years and has shown higher efficiency than switching using conventional spin-transfer torque. This presentation reports the SOT-assisted switching in heavy metal/magnetic insulator systems.1 The experiments made use of Pt/BaFe12O19 bi-layered structures. Thanks to its strong spin-orbit coupling, Pt has been widely used to produce pure spin currents in previous studies. BaFe12O19 is an M-type barium hexagonal ferrite and is often referred as BaM. It is one of the few magnetic insulators with strong magneto-crystalline anisotropy and shows an effective uniaxial anisotropy field of about 17 kOe. It's found that the switching response in the BaM film strongly depends on the charge current applied to the Pt film. When a constant magnetic field is applied in the film plane, the charge current in the Pt film can switch the normal component of the magnetization (M⊥) in the BaM film between the up and down states. The current also dictates the up and down states of the remnant magnetization when the in-plane field is reduced to zero. When M⊥ is measured by sweeping an in-plane field, the response manifests itself as a hysteresis loop, which evolves in a completely opposite manner if the sign of the charge current is flipped. When the coercivity is measured by sweeping an out-of-plane field, its value can be reduced or increased by as much as about 500 Oe if an appropriate charge current is applied. 1. P. Li, T. Liu, H. Chang, A. Kalitsov, W. Zhang, G. Csaba, W. Li, D. Richardson, A. Demann, G. Rimal, H. Dey, J. S. Jiang, W. Porod, S. Field, J. Tang, M. C. Marconi, A. Hoffmann, O. Mryasov, and M. Wu, Nature Commun. 7:12688 doi: 10.1038/ncomms12688 (2016).

  13. Positive temperature coefficient of magnetic anisotropy in polyvinylidene fluoride (PVDF)-based magnetic composites

    OpenAIRE

    Liu, Yiwei; Wang, Baomin; Zhan, Qingfeng; Tang, Zhenhua; Yang, Huali; Liu, Gang; Zuo, Zhenghu; Zhang, Xiaoshan; Xie, Yali; Zhu, Xiaojian; Chen, Bin; Wang, Junling; Li, Run-Wei

    2014-01-01

    The magnetic anisotropy is decreased with increasing temperature in normal magnetic materials, which is harmful to the thermal stability of magnetic devices. Here, we report the realization of positive temperature coefficient of magnetic anisotropy in a novel composite combining β-phase polyvinylidene fluoride (PVDF) with magnetostrictive materials (magnetostrictive film/PVDF bilayer structure). We ascribe the enhanced magnetic anisotropy of the magnetic film at elevated temperature to the st...

  14. Estimation of anisotropy parameters in organic-rich shale: Rock physics forward modeling approach

    Energy Technology Data Exchange (ETDEWEB)

    Herawati, Ida, E-mail: ida.herawati@students.itb.ac.id; Winardhi, Sonny; Priyono, Awali [Mining and Petroleum Engineering Faculty, Institut Teknologi Bandung, Bandung, 40132 (Indonesia)

    2015-09-30

    Anisotropy analysis becomes an important step in processing and interpretation of seismic data. One of the most important things in anisotropy analysis is anisotropy parameter estimation which can be estimated using well data, core data or seismic data. In seismic data, anisotropy parameter calculation is generally based on velocity moveout analysis. However, the accuracy depends on data quality, available offset, and velocity moveout picking. Anisotropy estimation using seismic data is needed to obtain wide coverage of particular layer anisotropy. In anisotropic reservoir, analysis of anisotropy parameters also helps us to better understand the reservoir characteristics. Anisotropy parameters, especially ε, are related to rock property and lithology determination. Current research aims to estimate anisotropy parameter from seismic data and integrate well data with case study in potential shale gas reservoir. Due to complexity in organic-rich shale reservoir, extensive study from different disciplines is needed to understand the reservoir. Shale itself has intrinsic anisotropy caused by lamination of their formed minerals. In order to link rock physic with seismic response, it is necessary to build forward modeling in organic-rich shale. This paper focuses on studying relationship between reservoir properties such as clay content, porosity and total organic content with anisotropy. Organic content which defines prospectivity of shale gas can be considered as solid background or solid inclusion or both. From the forward modeling result, it is shown that organic matter presence increases anisotropy in shale. The relationships between total organic content and other seismic properties such as acoustic impedance and Vp/Vs are also presented.

  15. Estimation of anisotropy parameters in organic-rich shale: Rock physics forward modeling approach

    International Nuclear Information System (INIS)

    Herawati, Ida; Winardhi, Sonny; Priyono, Awali

    2015-01-01

    Anisotropy analysis becomes an important step in processing and interpretation of seismic data. One of the most important things in anisotropy analysis is anisotropy parameter estimation which can be estimated using well data, core data or seismic data. In seismic data, anisotropy parameter calculation is generally based on velocity moveout analysis. However, the accuracy depends on data quality, available offset, and velocity moveout picking. Anisotropy estimation using seismic data is needed to obtain wide coverage of particular layer anisotropy. In anisotropic reservoir, analysis of anisotropy parameters also helps us to better understand the reservoir characteristics. Anisotropy parameters, especially ε, are related to rock property and lithology determination. Current research aims to estimate anisotropy parameter from seismic data and integrate well data with case study in potential shale gas reservoir. Due to complexity in organic-rich shale reservoir, extensive study from different disciplines is needed to understand the reservoir. Shale itself has intrinsic anisotropy caused by lamination of their formed minerals. In order to link rock physic with seismic response, it is necessary to build forward modeling in organic-rich shale. This paper focuses on studying relationship between reservoir properties such as clay content, porosity and total organic content with anisotropy. Organic content which defines prospectivity of shale gas can be considered as solid background or solid inclusion or both. From the forward modeling result, it is shown that organic matter presence increases anisotropy in shale. The relationships between total organic content and other seismic properties such as acoustic impedance and Vp/Vs are also presented

  16. No Giant Two-Ion Anisotropy in the Heavy-Rare-Earth Metals

    DEFF Research Database (Denmark)

    Lindgård, Per-Anker

    1976-01-01

    A new Bose-operator expansion of tensor operators is applied to the heavy-rare-earth metals. The Er data for the cone phase have been analyzed successfully with single-ion anisotropy and isotropic exchange interaction. The Tb data can be understood on the same basis. The previously found large two......-ion anisotropy was due to an inadequate treatment of the large single-ion anisotropy leading to an incorrect expression for the spin-wave energy....

  17. Mosaic anisotropy model for magnetic interactions in mesostructured crystals

    Directory of Open Access Journals (Sweden)

    Abby R. Goldman

    2017-10-01

    Full Text Available We propose a new model for interpreting the magnetic interactions in crystals with mosaic texture called the mosaic anisotropy (MA model. We test the MA model using hematite as a model system, comparing mosaic crystals to polycrystals, single crystal nanoparticles, and bulk single crystals. Vibrating sample magnetometry confirms the hypothesis of the MA model that mosaic crystals have larger remanence (Mr/Ms and coercivity (Hc compared to polycrystalline or bulk single crystals. By exploring the magnetic properties of mesostructured crystalline materials, we may be able to develop new routes to engineering harder magnets.

  18. Elastic anisotropy in multifilament Nb$_3$Sn superconducting wires

    CERN Document Server

    Scheuerlein, C; Alknes, P; Arnau, G; Bjoerstad, R; Bordini, B

    2015-01-01

    The elastic anisotropy caused by the texture in the Nb3Sn filaments of PIT and RRP wires has been calculated by averaging the estimates of Voigt and Reuss, using published Nb3Sn single crystal elastic constants and the Nb3Sn grain orientation distribution determined in both wire types by Electron Backscatter Diffraction. At ambient temperature the calculated Nb3Sn E-moduli in axial direction in the PIT and the RRP wire are 130 GPa and 140 GPa, respectively. The calculated E-moduli are compared with tensile test results obtained for the corresponding wires and extracted filament bundles.

  19. Mathematical modelling of anisotropy of illite-rich shale

    Science.gov (United States)

    Chesnokov, E.M.; Tiwary, D.K.; Bayuk, I.O.; Sparkman, M.A.; Brown, R.L.

    2009-01-01

    The estimation of illite-rich shale anisotropy to account for the alignment of clays and gas- or brine-filled cracks is presented via mathematical modelling. Such estimation requires analysis to interpret the dominance of one effect over another. This knowledge can help to evaluate the permeability in the unconventional reservoir, stress orientation, and the seal capacity for the conventional reservoir. Effective media modelling is used to predict the elastic properties of the illite-rich shale and to identify the dominant contributions to the shale anisotropy. We consider two principal reasons of the shale anisotropy: orientation of clay platelets and orientation of fluid-filled cracks. In reality, both of these two factors affect the shale anisotropy. The goal of this study is, first, to separately analyse the effect of these two factors to reveal the specific features in P- and S-wave velocity behaviour typical of each of the factors, and, then, consider a combined effect of the factors when the cracks are horizontally or vertically aligned. To do this, we construct four models of shale. The behaviour of P- and S-wave velocities is analysed when gas- and water-filled cracks embedded in a host matrix are randomly oriented, or horizontally or vertically aligned. The host matrix can be either isotropic or anisotropic (of VTI symmetry). In such a modelling, we use published data on mineralogy and clay platelet alignment along with other micromechanical measurements. In the model, where the host matrix is isotropic, the presence of a singularity point (when the difference VS1 - VS2 changes its sign) in shear wave velocities is an indicator of brine-filled aligned cracks. In the model with the VTI host matrix and horizontally aligned cracks filled with gas, an increase in their volume concentration leads to that the azimuth at which the singularity is observed moves toward the symmetry axis. In this case, if the clay content is small (around 20 per cent), the

  20. Neutronographic investigations into homogeneity and crystalline anisotropy of graphite materials

    International Nuclear Information System (INIS)

    Kajzar, F.; Oles, A.; Pawpowski, K.; Szudek, M.

    1976-01-01

    A numerical methods is proposed for evaluating the share of components having various graphitization degree in the graphite material. This method consists in adjusting the diffraction lines of separated components characterized by a different graphitization degree to the profile of an experimental diffraction line. Results are also given which were obtained by this method for some selected graphite materials manufactured at the Coal Electrodes Factory in Nowy Sacz. Using the technique of neutron diffraction, investigation were carried out in like manner into crystalline anisotropy in the semi-conducting graphite and in the connecting material. (author)

  1. Anisotropy in "isotropic diffusion" measurements due to nongaussian diffusion

    DEFF Research Database (Denmark)

    Jespersen, Sune Nørhøj; Olesen, Jonas Lynge; Ianuş, Andrada

    2017-01-01

    Designing novel diffusion-weighted NMR and MRI pulse sequences aiming to probe tissue microstructure with techniques extending beyond the conventional Stejskal-Tanner family is currently of broad interest. One such technique, multidimensional diffusion MRI, has been recently proposed to afford...... model-free decomposition of diffusion signal kurtosis into terms originating from either ensemble variance of isotropic diffusivity or microscopic diffusion anisotropy. This ability rests on the assumption that diffusion can be described as a sum of multiple Gaussian compartments, but this is often...

  2. Neutron diffraction study of artificial graphites crystalline anisotropy

    International Nuclear Information System (INIS)

    Lecomte, Marcel

    1961-01-01

    The Saclay spectrometer at E.L.2 has been used to investigate the structural properties of artificial graphite. Information as to the local texture at different points of a small block of graphite has been obtained. The method is more rapid and yields results which are statistically more accurate than those found by X-Ray diffraction. In particular, the method allows the determination of the degree of anisotropy in directions normal to the axis along which the block was compressed during its manufacture. (author) [fr

  3. Southern Hemisphere Measurement of the Anisotropy in the CosmicMicrowave Background Radiation

    Energy Technology Data Exchange (ETDEWEB)

    Smoot, George F.; Lubin, Phil M.

    1979-06-01

    A recent measurement of the anisotropy in the Cosmic Background Radiation from the southern hemisphere (Lima, Peru) is essentially in agreement with previous measurements from the northern hemisphere. The net anisotropy can be described as a first order spherical harmonic (Doppler) anisotropy of amplitude 3.1 {+-} 0.4 m{sup o}K with a quadrupole anisotropy of less than 1 m{sup o}K. In addition, measurements of the linear polarization yield an upper limit of 1 m{sup o}K, or one part in 3000, at 95% C.L. for the amplitudes of any spherical harmonic through third order.

  4. Observations of the anisotropy of cosmic rays at TeV-PeV

    Science.gov (United States)

    BenZvi, S.

    2014-07-01

    During the past decade, multiple observatories have reported significant observations of the anisotropy of cosmic rays in the TeV energy band. The anisotropy has been observed at large scales and small scales in both the Northern and Southern Hemispheres. The source of the anisotropy is not well-understood, though both a galactic and a heliospheric origin have been suggested. We discuss recent observations of the shape and energy dependence of the anisotropy, with particular attention to measurements by the IceCube Neutrino Observatory in the Southern Hemisphere and the Milagro and High-Altitude Water Cherenkov (HAWC) observatories in the Northern Hemisphere.

  5. UV-Induced Anisotropy In CdBr2-CdBr2: Cu Nanostructures

    Directory of Open Access Journals (Sweden)

    El-Naggar A. M.

    2015-09-01

    Full Text Available We have found an occurrence of anisotropy in the nanostructure CdBr2-CdBr2: Cu nanocrystalline films. The film thickness was varied from 4 nm up to 80 nm. The films were prepared by successive deposition of the novel layers onto the basic nanocrystals. The detection of anisotropy was performed by occurrence of anisotropy in the polarized light at 633 nm He-Ne laser wavelength. The occurrence of anisotropy was substantially dependent on the film thickness and the photoinduced power density. Possible mechanisms of the observed phenomena are discussed.

  6. The magnetic anisotropy of rocks: principles, techniques and geodynamic applications in the Italian peninsula

    Directory of Open Access Journals (Sweden)

    F. Speranza

    1997-06-01

    Full Text Available Magnetic anisotropy studies have recently come to the forefront as accurate, fast and inexpensive methods in the investigation of the rock fabric. In this paper we summarize the physical principles and the experimental techniques commonly used to resolve the Anisotropy of Magnetic Susceptibility (AMS and the Anisotropy of Anhysteretic Remanence (AAR tensors, and we give a description of the parameters which usually describe the magnetic anisotropy properties of a rock. A synthetic review of the magnetic fabric studies carried out on sedimentary rocks of the Italian peninsula is also given, discussing the potentiality of this technique in geodynamic studies.

  7. Covalent magnetism, exchange interactions and anisotropy of the high temperature layered antiferromagnet MnB₂.

    Science.gov (United States)

    Khmelevskyi, S; Mohn, P

    2012-01-11

    The investigation of the electronic structure and magnetism for the compound MnB(2) with crystal structure type AlB(2) has been revisited to resolve contradictions between various experimental and theoretical results present in the literature. We find that MnB(2) exhibits an interesting example of a Kübler's covalent magnetism (Williams et al 1981 J. Appl. Phys. 52 2069). The covalent magnetism also appears to be the source of some disagreement between the calculated values of the magnetic moments and those given by neutron diffraction experiments. We show that this shortcoming is due to the atomic sphere approximation applied in earlier calculations. The application of the disordered local moment approach and the calculation of the inter-atomic exchange interactions within the Liechtenstein formalism reveal strong local moment antiferromagnetism with a high Néel temperature predicted from Monte Carlo simulations. A fully relativistic band structure calculation and then the application of the torque method yields a strong in-plane anisotropy of the Mn magnetic moments. The agreement of these results with neutron diffraction studies rules out any possible weak itinerant electron magnetism scenarios as proposed earlier for MnB(2).

  8. Neutron scattering investigation of the magnetic excitations in CoBr2

    International Nuclear Information System (INIS)

    Yoshizawa, Hideki; Ubukoshi, Koji; Hirakawa, Kinshiro

    1980-01-01

    In order to investigate the two-dimensionality and the easy plane anisotropy, the spin waves propagating along the [h, 0, 0], [h, h, 0], [h, 0.5h, 0] and [0, 0, l] directions in CoBr 2 were observed using inelastic neutron scattering technique. The spin dynamics of CoBr 2 can be described by the anisotropic exchange Hamiltonian for S = 1/2 with interaplanar exchange constants J 1 = 2.01 meV, J 2 = 0.019 meV and J 3 = -0.338 meV, interplanar exchange J' = -0.97 meV, and planar anisotropies D 1 = 1.14 meV and D' = -0.06 meV. As shown by these numerical values, CoBr 2 has fairly strong XY characters, but the two-dimensionality is definitely poor. We point out, however, that in a planar antiferromagnet, the easy plane type anisotropy should remove the degeneracy of the excitation spectrum for the 'in-plane' and the 'out-of-plane' correlations, and in fact, these excitations are observed separately in this experiment. (author)

  9. Strongly correlated systems experimental techniques

    CERN Document Server

    Mancini, Ferdinando

    2015-01-01

    The continuous evolution and development of experimental techniques is at the basis of any fundamental achievement in modern physics. Strongly correlated systems (SCS), more than any other, need to be investigated through the greatest variety of experimental techniques in order to unveil and crosscheck the numerous and puzzling anomalous behaviors characterizing them. The study of SCS fostered the improvement of many old experimental techniques, but also the advent of many new ones just invented in order to analyze the complex behaviors of these systems. Many novel materials, with functional properties emerging from macroscopic quantum behaviors at the frontier of modern research in physics, chemistry and materials science, belong to this class of systems. The volume presents a representative collection of the modern experimental techniques specifically tailored for the analysis of strongly correlated systems. Any technique is presented in great detail by its own inventor or by one of the world-wide recognize...

  10. Strongly Correlated Systems Theoretical Methods

    CERN Document Server

    Avella, Adolfo

    2012-01-01

    The volume presents, for the very first time, an exhaustive collection of those modern theoretical methods specifically tailored for the analysis of Strongly Correlated Systems. Many novel materials, with functional properties emerging from macroscopic quantum behaviors at the frontier of modern research in physics, chemistry and materials science, belong to this class of systems. Any technique is presented in great detail by its own inventor or by one of the world-wide recognized main contributors. The exposition has a clear pedagogical cut and fully reports on the most relevant case study where the specific technique showed to be very successful in describing and enlightening the puzzling physics of a particular strongly correlated system. The book is intended for advanced graduate students and post-docs in the field as textbook and/or main reference, but also for other researchers in the field who appreciates consulting a single, but comprehensive, source or wishes to get acquainted, in a as painless as po...

  11. Strongly correlated systems numerical methods

    CERN Document Server

    Mancini, Ferdinando

    2013-01-01

    This volume presents, for the very first time, an exhaustive collection of those modern numerical methods specifically tailored for the analysis of Strongly Correlated Systems. Many novel materials, with functional properties emerging from macroscopic quantum behaviors at the frontier of modern research in physics, chemistry and material science, belong to this class of systems. Any technique is presented in great detail by its own inventor or by one of the world-wide recognized main contributors. The exposition has a clear pedagogical cut and fully reports on the most relevant case study where the specific technique showed to be very successful in describing and enlightening the puzzling physics of a particular strongly correlated system. The book is intended for advanced graduate students and post-docs in the field as textbook and/or main reference, but also for other researchers in the field who appreciate consulting a single, but comprehensive, source or wishes to get acquainted, in a as painless as possi...

  12. Strongly nonlinear oscillators analytical solutions

    CERN Document Server

    Cveticanin, Livija

    2014-01-01

    This book provides the presentation of the motion of pure nonlinear oscillatory systems and various solution procedures which give the approximate solutions of the strong nonlinear oscillator equations. The book presents the original author’s method for the analytical solution procedure of the pure nonlinear oscillator system. After an introduction, the physical explanation of the pure nonlinearity and of the pure nonlinear oscillator is given. The analytical solution for free and forced vibrations of the one-degree-of-freedom strong nonlinear system with constant and time variable parameter is considered. Special attention is given to the one and two mass oscillatory systems with two-degrees-of-freedom. The criteria for the deterministic chaos in ideal and non-ideal pure nonlinear oscillators are derived analytically. The method for suppressing chaos is developed. Important problems are discussed in didactic exercises. The book is self-consistent and suitable as a textbook for students and also for profess...

  13. Flavour Democracy in Strong Unification

    CERN Document Server

    Abel, S A; Abel, Steven; King, Steven

    1998-01-01

    We show that the fermion mass spectrum may naturally be understood in terms of flavour democratic fixed points in supersymmetric theories which have a large domain of attraction in the presence of "strong unification". Our approach provides an alternative to the approximate Yukawa texture zeroes of the Froggatt-Nielsen mechanism. We discuss a particular model based on a broken gauged $SU(3)_L\\times SU(3)_R$ family symmetry which illustrates our approach.

  14. Fabric and elastic properties of antigorite, mica and amphibole-rich rocks and implications for the tectonic interpretation of seismic anisotropy

    Science.gov (United States)

    Shao, Tongbin

    C. Comparisons of laboratory velocities measured at high pressure with CPO data measured using EBSD techniques demonstrate that seismic anisotropy in high temperature serpentinites, which is essentially controlled by the antigorite c-axis fabric, is independent on the operating slip system but strongly dependent on the regime and magnitude of finite strain experienced by the rock. Extrapolation of experimental data with both pressure and temperature suggests that Vp anisotropy decreases but shear-wave splitting (DeltaVs) and V p/Vs increase with increasing pressure in either cold or hot subduction zones. For a cold, steeply subducting slab, antigorite is most likely deformed by nearly coaxial flattening or trench-parallel movement, forming trench-parallel seismic anisotropy. For a hot, shallowly subducting slab, however, antigorite is most likely deformed by simple shear or transpression. Trench-normal seismic anisotropy can be observed when the subducting dip angle is smaller than 30°. The geophysical characteristics of the Tibetan Plateau, such as strong heterogeneity in V p, Vs and attenuation, shear-wave splitting and electric conductivity, may be explained by the presence of strongly deformed serpentinites in lithospheric shear zones reactivated along former suture zones between amalgamated blocks, hydrated zones of subducting lithospheric mantle, and the crust-mantle boundary if the temperature is below 700 °C in the region of interest. Chapter 3 provides a detailed calibration on the magnitude and symmetry of seismic anisotropy for 132 schists to constrain their departures from transverse isotropy (TI) that is usually assumed in the interpretation of seismic data. The average bulk Vp anisotropy at 600 MPa for chlorite schists, mica schists, phyllites, sillimanite-mica schists, and amphibole schists examined is 12.0%, 12.8%, 12.8%, 17.0%, and 12.9%, respectively. Most of the schists show Vp anisotropy in the foliation plane which averages 2.4% for phyllites, 3.3% for

  15. Influence of domain structure induced coupling on magnetization reversal of Co/Pt/Co film with perpendicular anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Matczak, Michał [Institute of Molecular Physics, Polish Academy of Sciences, M. Smoluchowskiego 17, 60-179 Poznań (Poland); NanoBioMedical Centre, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland); Schäfer, Rudolf [Leibniz Institute for Solid State and Materials Research (IFW) Dresden, Institute for Metallic Materials, PO 270116, D-01171 Dresden (Germany); Dresden University of Technology, Institute for Materials Science, D-01062 Dresden (Germany); Urbaniak, Maciej; Kuświk, Piotr; Szymański, Bogdan; Schmidt, Marek; Aleksiejew, Jacek [Institute of Molecular Physics, Polish Academy of Sciences, M. Smoluchowskiego 17, 60-179 Poznań (Poland); Stobiecki, Feliks, E-mail: Feliks.Stobiecki@ifmpan.poznan.pl [Institute of Molecular Physics, Polish Academy of Sciences, M. Smoluchowskiego 17, 60-179 Poznań (Poland); NanoBioMedical Centre, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland)

    2017-01-15

    A magnetic multilayer of substrate/Pt-15 nm/Co-0.8 nm/Pt-wedge 0–7 nm/Co-0.6 nm/Pt-2 nm structure is characterized by a perpendicular anisotropy of the Co layers and by graded interlayer coupling between them. Using magnetooptical Kerr microscopy we observed a distinct influence of magnetic domains in one Co layer on the nucleation field and positions of nucleation sites of reversed domains in the second Co layer. For sufficiently strong interlayer coupling a replication of magnetic domains from the magnetically harder layer to the magnetically softer layer is observed. - Highlights: • Co/Pt-wedge/Co layered film is characterized by a gradient of interlayer coupling. • Magnetic field controls propagation of straight domain wall. • Replication of magnetic domains in multilayers with strong ferromagnetic coupling. • Coupling induced by domains influences magnetization reversal of spin valves.

  16. Anisotropic shear viscosity of a strongly coupled non-Abelian plasma from magnetic branes

    Science.gov (United States)

    Critelli, R.; Finazzo, S. I.; Zaniboni, M.; Noronha, J.

    2014-09-01

    Recent estimates for the electromagnetic fields produced in the early stages of noncentral ultrarelativistic heavy ion collisions indicate the presence of magnetic fields B ˜O(0.1-15mπ2), where mπ is the pion mass. It is then of special interest to study the effects of strong (Abelian) magnetic fields on the transport coefficients of strongly coupled non-Abelian plasmas, such as the quark-gluon plasma formed in heavy ion collisions. In this paper we study the anisotropy in the shear viscosity induced by an external magnetic field in a strongly coupled N =4 super Yang-Mills (SYM) plasma. Due to the spatial anisotropy created by the magnetic field, the most general viscosity tensor of a magnetized plasma has five shear viscosity coefficients and two bulk viscosities. We use the holographic correspondence to evaluate two of the shear viscosities, η⊥≡ηxyxy (perpendicular to the magnetic field) and η∥≡ηxzxz=ηyzyz (parallel to the field). When B ≠0 the shear viscosity perpendicular to the field saturates the viscosity bound η⊥/s=1/(4π), while in the direction parallel to the field the bound is violated since η∥/s<1/(4π). However, the violation of the bound in the case of strongly coupled SYM is minimal even for the largest value of B that can be reached in heavy ion collisions.

  17. Role of Ta-spacer layer on tuning the tilt angle magnetic anisotropy of L1{sub 1}-CoPt/Ta/NiFe exchange springs

    Energy Technology Data Exchange (ETDEWEB)

    Saravanan, P., E-mail: psdrdo@gmail.com [Defence Metallurgical Research Laboratory, Hyderabad 500058 (India); Talapatra, A.; Mohanty, J. [Department of Physics, Indian Institute of Technology Hyderabad, Hyderabad 502285 (India); Hsu, Jen-Hwa, E-mail: jhhsu@phys.ntu.edu.tw [Department of Physics, National Taiwan University, Taipei 106, Taiwan (China); Kamat, S.V. [Defence Metallurgical Research Laboratory, Hyderabad 500058 (India)

    2017-06-15

    Highlights: • Role of Ta-spacer layer in L1{sub 1}-CoPt(10 nm)/Ta//NiFe(4 nm) trilayers was investigated. • Domain size increased at the expense of magnetic phase contrast with increasing t{sub Ta}. • Tilt angle magnetization increased from 43° to 77° upon increasing t{sub Ta} (0–2.5 nm). • Micromagnetic studies confirmed the existence of tilted magnetic anisotropy. • Ta-spacer is effective in preserving competing anisotropies of CoPt and NiFe-layers. - Abstract: L1{sub 1}-CoPt/Ta/NiFe trilayers are chosen as model films for probing the role of spacer layer on tuning the tilt angle magnetization (θ{sub M}) in such exchange springs. For this purpose, a non-magnetic layer (Ta) with varying thickness (t{sub Ta}) from 0 to 2.5 nm was inserted between 10-nm thick CoPt film exhibiting strong perpendicular magnetic anisotropy (PMA) and 4-nm thick NiFe film having in-plane magnetic anisotropy (IMA). With the insertion of Ta-spacer, the magnetic hysteresis loops become more and more tilted as t{sub Ta} increases. Upon increasing the t{sub Ta} from 0 to 2.5 nm, the estimated SQR{sub ⊥} (=M{sub r⊥}/M{sub s⊥}) from the M–H loops is found to decrease moderately; while the θ{sub M} increases significantly from 43° to 77°. MFM images revealed maze-like domain patterns and the domain size tends to increase at the expense of magnetic phase contrast with increasing t{sub Ta}. Micro-magnetic simulation of tilt in the anisotropy axis with respect to the bare CoPt-layer showed a trend similar to that of those observed with the M–H loops obtained by VSM measurements. The results of present study suggest that the insertion of Ta-spacer is not only beneficial in terms of preserving the competing anisotropies such as PMA and IMA of CoPt and NiFe-layers respectively through weakened exchange coupling; but also, act as an appropriate means for realizing tunable tilted magnetic anisotropy in the L1{sub 1}-CoPt/NiFe exchange springs.

  18. Nonlinear δf particle simulations of collective excitations and energy-anisotropy instabilities in high-intensity bunched beams

    Directory of Open Access Journals (Sweden)

    Hong Qin

    2007-06-01

    Full Text Available Collective effects with strong coupling between the longitudinal and transverse dynamics are of fundamental importance for applications of high-intensity bunched beams. The self-consistent Vlasov-Maxwell equations are applied to high-intensity finite-length charge bunches, and a generalized δf particle simulation algorithm is developed for bunched beams with or without energy anisotropy. The nonlinear δf method exhibits minimal noise and accuracy problems in comparison with standard particle-in-cell simulations. Systematic studies are carried out under conditions corresponding to strong 3D nonlinear space-charge forces in the beam frame. For charge bunches with isotropic energy, finite bunch-length effects are clearly evident by the fact that the spectra for an infinitely long coasting beam and a nearly spherical charge bunch have strong similarities, whereas the spectra have distinctly different features when the bunch length is varied between these two limiting cases. For bunched beams with anisotropic energy, there exists no exact kinetic equilibrium because the particle dynamics do not conserve transverse energy and longitudinal energy separately. A reference state in approximate dynamic equilibrium has been constructed theoretically, and a quasi-steady state has been established in the simulations for the anisotropic case. Collective excitations relative to the reference state have been simulated using the generalized δf algorithm. In particular, the electrostatic Harris instability driven by strong energy anisotropy is investigated for a finite-length charge bunch. The observed growth rates are larger than those obtained for infinitely long coasting beams. However, the growth rate decreases for increasing bunch length to a value similar to the case of a long coasting beam. For long bunches, the instability is axially localized symmetrically relative to the beam center, and the characteristic wavelength in the longitudinal direction is

  19. 2D seismic reflection tomography in strongly anisotropic media

    Science.gov (United States)

    Huang, Guangnan; Zhou, Bing; Li, Hongxi; Zhang, Hua; Li, Zelin

    2014-12-01

    Seismic traveltime tomography is an effective method to reconstruct underground anisotropic parameters. Currently, most anisotropic tomographic methods were developed under the assumption of weak anisotropy. The tomographic method proposed here can be implemented for imaging subsurface targets in strongly anisotropic media with a known tilted symmetry axis, since the adopted ray tracing method is suitable for anisotropic media with arbitrary degree. There are three kinds of reflection waves (qP, qSV and qSH waves) that were separately used to invert the blocky abnormal body model. The reflection traveltime tomographiy is developed here because a surface observation system is the most economical and practical way compared with crosswell and VSP. The numerical examples show that the traveltimes of qP reflection wave have inverted parameters {{c}11},{{c}13},{{c}33} \\text{and} {{c}44} successfully. Traveltimes of qSV reflection wave have inverted parameters {{c}11},{{c}33} \\text{and} {{c}44} successfully, with the exception of the {{c}13}, since it is less sensitive than other parameters. Traveltimes of qSH reflection wave also have inverted parameters {{c}44} \\text{and} {{c}66} successfully. In addition, we find that the velocity sensitivity functions (derivatives of phase velocity with respect to elastic moduli parameters) and raypath illuminating angles have a great influence on the qualities of tomograms according to the inversion of theoretical models. Finally, the numerical examples confirm that the reflection traveltime tomography can be applied to invert strongly anisotropic models.

  20. Increased anisotropy in neonatal meningitis: an indicator of meningeal inflammation

    Energy Technology Data Exchange (ETDEWEB)

    Trivedi, Richa; Gupta, Rakesh K.; Nath, Kavindra [Sanjay Gandhi Post Graduate Institute of Medical Sciences, Department of Radiodiagnosis, Lucknow, UP (India); Malik, Gyanendra K.; Gupta, Amit [King George' s Medical University, Department of Pediatrics, Lucknow (India); Prasad, Kashi N. [Sanjay Gandhi Postgraduate Institute of Medical Sciences, Department of Microbiology, Lucknow (India); Purwar, Ankur; Rathore, Divya; Rathore, Ram K.S. [Indian Institute of Technology, Department of Mathematics, Kanpur (India); Narayana, Ponnada A. [University of Texas Medical School at Houston, Department of Diagnostic and Interventional Imaging, Houston, TX (United States)

    2007-09-15

    Increased anisotropy in brain abscesses has been shown to be due to adhesion of inflammatory cells and is suggestive of an active inflammatory process. The objective of this study was to determine if similar changes occur in the pia-arachnoid on the surface of the cerebral cortex in patients with pyogenic meningitis, and if these changes regress following antibiotic therapy. Diffusion tensor imaging (DTI) was performed on 14 term neonates (mean age 13 days) with bacterial meningitis and 10 healthy age- and sex-matched controls. Regions of interest (ROIs) were placed on areas including the leptomeninges, the cerebral cortex and adjoining subcortical white matter for quantitation of mean fractional anisotropy (FA) and diffusivity (MD) values. Follow-up MRI was performed in five of the neonates in the patient group after 2 weeks of antibiotic treatment. FA and MD values were compared in patients before and after antibiotic treatment as well as with those in the healthy controls. Significantly higher FA values but no difference in MD values were observed in the patient group as compared to the healthy controls at both time points (before and after antibiotic treatment). Significantly decreased FA values in the frontal, occipital and temporal cortical regions were observed in patients following antibiotic treatment. DTI-derived FA may be of value in the noninvasive assessment of meningeal inflammatory activity and treatment response in neonates. (orig.)

  1. Mapping the CMB with the Wilkinson Microwave Anisotropy Probe

    Science.gov (United States)

    Hinshaw, Gary F.

    2007-01-01

    The data from the Wilkinson Microwave Anisotropy Probe (WMAP) satellite provide detailed full-sky maps of the cosmic microwave background temperature anisotropy and new full-sky maps of the polarization. Together, the data provide a wealth of cosmological information, including the age of the universe, the epoch when the first stars formed, and the overall composition of baryonic matter, dark matter, and dark energy. The results also provide constraints on the period of inflationary expansion in the very first moments of time. These and other aspects of the mission results will be discussed and commented on. WMAP, part of NASA's Explorers program, was launched on June 30,200 1. The WMAP satellite was produced in a partnership between the Goddard Space Flight Center and Princeton University. The WMAP team also includes researchers at the Johns Hopkins University; the Canadian Institute of Theoretical Astrophysics; University of Texas; University of Chicago; Brown University; University of British Columbia; and University of California, Los Angeles.

  2. Anisotropy of neutron sources of Neutron Metrology Laboratory, IRD, Brazil

    International Nuclear Information System (INIS)

    Silva, A.C.F.; Silva, F.S.; Leite, S.P.; Creazolla, P.G; Patrão, K.C.S.; Fonseca, E.S. da; Fernandes, S.S.; Pereira, W.W.

    2017-01-01

    The anisotropy measurements have as main objective to define the emission of the radiation by different angles of an encapsulated neutron source. The measurements were performed using a Long Accuracy Counter (PLC) Detector in the Low Dispersion Room of the LNMRI / IRD with different neutron sources. Each measurement was made using a support for the source, emulated through an arduino system to rotate it. The carrier is marked with a variation of 5 °, ranging from 0 ° to 360 °, for the work in question only half, 0 ° to 180 ° is used for a total of nineteen steps. In this paper three sources of 241 AmBe (α, n) 5.92 GBq (16 Ci) were used, neutron sources having the following dimensions: 105 mm in height and 31 mm in diameter. The PLC was positioned at a distance of 2 meters from the neutron source and has a radius of 15 cm for the detection area. The anisotropy factor of the 241 AmBe source was 17%. The results in this work will focus mainly on the area of radioprotection and studies that will improve the process of routine measurements in laboratories and instrument calibrations. (author)

  3. Magnetic anisotropy in rapidly quenched amorphous glass-coated nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Óvári, T.-A.; Rotărescu, C.; Atițoaie, A.; Corodeanu, S.; Lupu, N., E-mail: nicole@phys-iasi.ro; Chiriac, H.

    2016-07-15

    Results on the roles played by the magnetoelastic and magnetostatic anisotropy terms in the magnetic behavior of glass-coated magnetostrictive amorphous nanowires prepared by means of rapid solidification are reported. Their contributions have been analyzed both experimentally, through hysteresis loop measurements, and theoretically, using micromagnetic simulations. All the investigated samples exhibit a magnetically bistable behavior, characterized by a single-step magnetization reversal when the applied field reaches a critical threshold value, called switching field. The combined interpretation of the experimental and theoretical data allows one to understand the effect of the magnetoelastic term on the value of the switching field, on one hand, and the effect of the magnetostatic term on the nucleation mechanism on the other, both with an essential impact on the characteristics of the nanowires’ magnetic bistability. The results are crucial for understanding the basic magnetic properties of these novel rapidly solidified ultrathin magnetic wires, as well as for tailoring their properties according to the specific requirements of various sensing applications. - Highlights: • Glass-coated nanowires have been very recently prepared by rapid solidification. • Amorphous wires change their properties as their diameter reaches the nano range. • Here we report on their main anisotropy terms: magnetoelastic and shape. • The results are essential for tailoring their properties for future applications.

  4. Write operation in MRAM with voltage controlled magnetic anisotropy

    Science.gov (United States)

    Munira, Kamaram; Pandey, Sumeet; Sandhu, Gurtej

    In non-volatile Magnetic RAM, information is saved in the bistable configuration of the free layer in a magnetic tunnel junction (MTJ). New information can be written to the free layer through magnetic induction (Toggle MRAM) or manipulation of magnetization using electric currents (Spin Transfer Torque MRAM or STT-MRAM). Both of the writing methods suffer from a shortcoming in terms of energy efficiency. This limitation on energy performance is brought about by the need for driving relatively large electrical charge currents through the devices for switching. In STT-MRAM, the nonzero voltage drop across the resistive MTJ leads to significant power dissipation. An energy efficient way to write may be with the assistance of voltage controlled magnetic anisotropy (VCMA), where voltage applied across the MTJ creates an electric field that modulates the interfacial anisotropy between the insulator and free layer. However, VCMA cannot switch the free layer completely by 180 degree rotation of magnetization. It can lower the barrier between the two stable configurations or at best, cancel the barrier, allowing 90 degree rotation. A second mechanism, spin torque or magnetic field, is needed to direct the final switching destination.

  5. Tunnel Junction with Perpendicular Magnetic Anisotropy: Status and Challenges

    Directory of Open Access Journals (Sweden)

    Mengxing Wang

    2015-08-01

    Full Text Available Magnetic tunnel junction (MTJ, which arises from emerging spintronics, has the potential to become the basic component of novel memory, logic circuits, and other applications. Particularly since the first demonstration of current induced magnetization switching in MTJ, spin transfer torque magnetic random access memory (STT-MRAM has sparked a huge interest thanks to its non-volatility, fast access speed, and infinite endurance. However, along with the advanced nodes scaling, MTJ with in-plane magnetic anisotropy suffers from modest thermal stability, high power consumption, and manufactural challenges. To address these concerns, focus of research has converted to the preferable perpendicular magnetic anisotropy (PMA based MTJ, whereas a number of conditions still have to be met before its practical application. This paper overviews the principles of PMA and STT, where relevant issues are preliminarily discussed. Centering on the interfacial PMA in CoFeB/MgO system, we present the fundamentals and latest progress in the engineering, material, and structural points of view. The last part illustrates potential investigations and applications with regard to MTJ with interfacial PMA.

  6. Magnetic anisotropy and anisotropic ballistic conductance of thin magnetic wires

    International Nuclear Information System (INIS)

    Sabirianov, R.

    2006-01-01

    The magnetocrystalline anisotropy of thin magnetic wires of iron and cobalt is quite different from the bulk phases. The spin moment of monatomic Fe wire may be as high as 3.4 μ B , while the orbital moment as high as 0.5 μ B . The magnetocrystalline anisotropy energy (MAE) was calculated for wires up to 0.6 nm in diameter starting from monatomic wire and adding consecutive shells for thicker wires. I observe that Fe wires exhibit the change sign with the stress applied along the wire. It means that easy axis may change from the direction along the wire to perpendicular to the wire. We find that ballistic conductance of the wire depends on the direction of the applied magnetic field, i.e. shows anisotropic ballistic magnetoresistance. This effect occurs due to the symmetry dependence of the splitting of degenerate bands in the applied field which changes the number of bands crossing the Fermi level. We find that the ballistic conductance changes with applied stress. Even for thicker wires the ballistic conductance changes by factor 2 on moderate tensile stain in our 5x4 model wire. Thus, the ballistic conductance of magnetic wires changes in the applied field due to the magnetostriction. This effect can be observed as large anisotropic BMR in the experiment

  7. Investigation of span-chordwise bending anisotropy of honeybee forewings

    Directory of Open Access Journals (Sweden)

    JianGuo Ning

    2017-05-01

    Full Text Available In this study, the spanwise and chordwise bending stiffness EI of honeybee forewings were measured by a cantilevered bending test. The test results indicate that the spanwise EI of the forewing is two orders of magnitude larger than the chordwise EI. Three structural aspects result in this span-chordwise bending anisotropy: the distribution of resilin patches, the corrugation along the span and the leading edge vein of the venation. It was found that flexion lines formed by resilin patches revealed through fluorescence microscopy promoted the chordwise bending of the forewing during flapping flight. Furthermore, the corrugation of the wing and leading edge veins of the venation, revealed by micro-computed tomography, determines the relatively greater spanwise EI of the forewing. The span-chordwise anisotropy exerts positive structural and aerodynamic influences on the wing. In summary, this study potentially assists researchers in understanding the bending characteristics of insect wings and might be an important reference for the design and manufacture of bio-inspired wings for flapping micro aerial vehicles.

  8. Fragment Angular Anisotropies for Magic and Non-Magic Nuclei

    Science.gov (United States)

    Behkami, A. N.; Maroofi, S.; Esmailipour, A.; Rasooli, S.

    2007-10-01

    Fission fragment angular distributions have been studied for ^239 Pu (n, f) reaction at several neutron energies. Theoretical calculations have been utilized to determine the variance K0^2 at each bombarding energy from the observed angular anisotropies. The values of K0^2 show sharp rise from a value of 5-6 to about 13 for higher neutron energies. From the position of one of the breaks in the K0^2 value, the magnitude of the pairing gap 2δ in the highly deformed transition nucleus ^240 Pu is estimated to be 2.4 MeV. Fission fragment angular anisotropies from changed particle fission of ^208 Pb, ^209 Bi, ^235U and ^238U at laboratory energy of 43.0 MeV have also been analyzed using the traditional transition state model. In all these calculations, optical model transmission coefficients with spin-orbit interaction have been used. In the case of magic nuclei, ^208Pb and ^209 Bi it is found that the deduced values of K0^2 are very small as compared to their corresponding values for ^235U and ^238U nuclei. This interpreted as due to shell structure, since significant shell and pairing effects appear for the magic nuclei ^208 Pb and ^209 Bi.

  9. To the problem of the secondary CMB anisotropy separation

    Directory of Open Access Journals (Sweden)

    Verkhodanov Oleg

    2016-01-01

    Full Text Available We study contribution to the secondary anisotropy maps of cosmic microwave background (CMB radiation which difficult to account for faint sources. Two effects are investigated. They are the Sunyaev–Zeldovich effect connected with the inverse Compton scattering of CMB photons on hot electrons of cluster of galaxies, and contamination of the background by weak extragalctic sources. First, we study fields of the Planck CMB maps around radio sources of the RATAN-600 catalog. We see weak microwave sources which make an additional contribution to the secondary anisotropy on angular small scales (< 7′. An algorithm for selecting candidate objects with the Sunyaev–Zeldovich effect was proposed, based on the use of data on the radio spectral indices and the signal in cosmic-microwave background maps. Second, applying the stacking method, we examine the areas of the CMB maps, constructed according to the Planck Space Observatory data in the neighborhood of different populations of radio sources and giant elliptical galaxies. The samples of objects include giant radio galaxies (GRG, radio sources, selected by the radio spectral index and redshift, as well as the gammaray bursts, used as a secondary comparative sample. The signal from this objects exists on CMB maps and its difference in the neighborhood of GRGs from the other types of objects was discovered.

  10. Seismic anisotropy and mantle flow below subducting slabs

    Science.gov (United States)

    Walpole, Jack; Wookey, James; Kendall, J.-Michael; Masters, T.-Guy

    2017-05-01

    Subduction is integral to mantle convection and plate tectonics, yet the role of the subslab mantle in this process is poorly understood. Some propose that decoupling from the slab permits widespread trench parallel flow in the subslab mantle, although the geodynamical feasibility of this has been questioned. Here, we use the source-side shear wave splitting technique to probe anisotropy beneath subducting slabs, enabling us to test petrofabric models and constrain the geometry of mantle fow. Our global dataset contains 6369 high quality measurements - spanning ∼ 40 , 000 km of subduction zone trenches - over the complete range of available source depths (4 to 687 km) - and a large range of angles in the slab reference frame. We find that anisotropy in the subslab mantle is well characterised by tilted transverse isotropy with a slow-symmetry-axis pointing normal to the plane of the slab. This appears incompatible with purely trench-parallel flow models. On the other hand it is compatible with the idea that the asthenosphere is tilted and entrained during subduction. Trench parallel measurements are most commonly associated with shallow events (source depth slab. This may correspond to the shape preferred orientation of cracks, fractures, and faults opened by slab bending. Meanwhile the deepest events probe the upper lower mantle where splitting is found to be consistent with deformed bridgmanite.

  11. Role of material property gradient and anisotropy in thermoelectric materials

    International Nuclear Information System (INIS)

    Wang, X; Pan, E; Albrecht, J D

    2008-01-01

    It was recently discovered that inclusions, fatigue damage and other types of material imperfections and defects in metals can be nondestructively detected by noncontacting magnetic measurements that sense the thermoelectric currents produced by directional heating and cooling. Since detection of small defects in thermoelectric materials is ultimately limited by intrinsic thermoelectric anisotropy and inhomogeneity of the material to be inspected, a thorough study is required on their impact on the nondestructive capability. Therefore, in this investigation the induced electric current densities and thermal fluxes are first derived for a steady line heat source in an inhomogeneous and anisotropic thermoelectric material. The exact closed-form solutions are obtained by converting the original problem into two inhomogeneous Helmholtz equations via eigenvalue/eigenvector separation. The material properties are assumed to vary exponentially in the same manner in an arbitrary direction. For the corresponding homogeneous but anisotropic material case, we also present an elegant formulation based on the complex variable method. It is shown that the induced magnetic fields can be expressed in a concise and exact closed form for a line heat source in an infinite homogeneous anisotropic material and in one of the two bonded anisotropic half-planes. Our numerical results demonstrate clearly that both property anisotropy and gradient in thermoelectric materials can significantly influence the induced thermoelectric currents and magnetic fields

  12. Noninvasive measurement of conductivity anisotropy at larmor frequency using MRI.

    Science.gov (United States)

    Lee, Joonsung; Song, Yizhuang; Choi, Narae; Cho, Sungmin; Seo, Jin Keun; Kim, Dong-Hyun

    2013-01-01

    Anisotropic electrical properties can be found in biological tissues such as muscles and nerves. Conductivity tensor is a simplified model to express the effective electrical anisotropic information and depends on the imaging resolution. The determination of the conductivity tensor should be based on Ohm's law. In other words, the measurement of partial information of current density and the electric fields should be made. Since the direct measurements of the electric field and the current density are difficult, we use MRI to measure their partial information such as B1 map; it measures circulating current density and circulating electric field. In this work, the ratio of the two circulating fields, termed circulating admittivity, is proposed as measures of the conductivity anisotropy at Larmor frequency. Given eigenvectors of the conductivity tensor, quantitative measurement of the eigenvalues can be achieved from circulating admittivity for special tissue models. Without eigenvectors, qualitative information of anisotropy still can be acquired from circulating admittivity. The limitation of the circulating admittivity is that at least two components of the magnetic fields should be measured to capture anisotropic information.

  13. Parton self-energies for general momentum-space anisotropy

    Science.gov (United States)

    Kasmaei, Babak S.; Strickland, Michael

    2018-03-01

    We introduce an efficient general method for calculating the self-energies, collective modes, and dispersion relations of quarks and gluons in a momentum-anisotropic high-temperature quark-gluon plasma. The method introduced is applicable to the most general classes of deformed anisotropic momentum distributions and the resulting self-energies are expressed in terms of a series of hypergeometric basis functions which are valid in the entire complex phase-velocity plane. Comparing to direct numerical integration of the self-energies, the proposed method is orders of magnitude faster and provides results with similar or better accuracy. To extend previous studies and demonstrate the application of the proposed method, we present numerical results for the parton self-energies and dispersion relations of partonic collective excitations for the case of an ellipsoidal momentum-space anisotropy. Finally, we also present, for the first time, the gluon unstable mode growth rate for the case of an ellipsoidal momentum-space anisotropy.

  14. Increased anisotropy in neonatal meningitis: an indicator of meningeal inflammation

    International Nuclear Information System (INIS)

    Trivedi, Richa; Gupta, Rakesh K.; Nath, Kavindra; Malik, Gyanendra K.; Gupta, Amit; Prasad, Kashi N.; Purwar, Ankur; Rathore, Divya; Rathore, Ram K.S.; Narayana, Ponnada A.

    2007-01-01

    Increased anisotropy in brain abscesses has been shown to be due to adhesion of inflammatory cells and is suggestive of an active inflammatory process. The objective of this study was to determine if similar changes occur in the pia-arachnoid on the surface of the cerebral cortex in patients with pyogenic meningitis, and if these changes regress following antibiotic therapy. Diffusion tensor imaging (DTI) was performed on 14 term neonates (mean age 13 days) with bacterial meningitis and 10 healthy age- and sex-matched controls. Regions of interest (ROIs) were placed on areas including the leptomeninges, the cerebral cortex and adjoining subcortical white matter for quantitation of mean fractional anisotropy (FA) and diffusivity (MD) values. Follow-up MRI was performed in five of the neonates in the patient group after 2 weeks of antibiotic treatment. FA and MD values were compared in patients before and after antibiotic treatment as well as with those in the healthy controls. Significantly higher FA values but no difference in MD values were observed in the patient group as compared to the healthy controls at both time points (before and after antibiotic treatment). Significantly decreased FA values in the frontal, occipital and temporal cortical regions were observed in patients following antibiotic treatment. DTI-derived FA may be of value in the noninvasive assessment of meningeal inflammatory activity and treatment response in neonates. (orig.)

  15. Three-dimensional phonon population anisotropy in silicon nanomembranes

    Energy Technology Data Exchange (ETDEWEB)

    McElhinny, Kyle M.; Gopalakrishnan, Gokul; Holt, Martin V.; Czaplewski, David A.; Evans, Paul G.

    2017-07-01

    Nanoscale single crystals possess modified phonon dispersions due to the truncation of the crystal. The introduction of surfaces alters the population of phonons relative to the bulk and introduces anisotropy arising from the breaking of translational symmetry. Such modifications exist throughout the Brillouin zone, even in structures with dimensions of several nanometers, posing a challenge to the characterization of vibrational properties and leading to uncertainty in predicting the thermal, optical, and electronic properties of nanomaterials. Synchrotron x-ray thermal diffuse scattering studies find that freestanding Si nanomembranes with thicknesses as large as 21 nm exhibit a higher scattering intensity per unit thickness than bulk silicon. In addition, the anisotropy arising from the finite thickness of these membranes produces particularly intense scattering along reciprocal-space directions normal to the membrane surface compared to corresponding in-plane directions. These results reveal the dimensions at which calculations of materials properties and device characteristics based on bulk phonon dispersions require consideration of the nanoscale size of the crystal.

  16. A laboratory goniometer system for measuring reflectance and emittance anisotropy.

    Science.gov (United States)

    Roosjen, Peter P J; Clevers, Jan G P W; Bartholomeus, Harm M; Schaepman, Michael E; Schaepman-Strub, Gabriela; Jalink, Henk; van der Schoor, Rob; de Jong, Arjan

    2012-12-13

    In this paper, a laboratory goniometer system for performing multi-angular measurements under controlled illumination conditions is described. A commercially available robotic arm enables the acquisition of a large number of measurements over the full hemisphere within a short time span making it much faster than other goniometers. In addition, the presented set-up enables assessment of anisotropic reflectance and emittance behaviour of soils, leaves and small canopies. Mounting a spectrometer enables acquisition of either hemispherical measurements or measurements in the horizontal plane. Mounting a thermal camera allows directional observations of the thermal emittance. This paper also presents three showcases of these different measurement set-ups in order to illustrate its possibilities. Finally, suggestions for applying this instrument and for future research directions are given, including linking the measured reflectance anisotropy with physically-based anisotropy models on the one hand and combining them with field goniometry measurements for joint analysis with remote sensing data on the other hand. The speed and flexibility of the system offer a large added value to the existing pool of laboratory goniometers.

  17. Atoms in strong laser fields

    International Nuclear Information System (INIS)

    L'Huillier, A.

    2002-01-01

    When a high-power laser focuses into a gas of atoms, the electromagnetic field becomes of the same magnitude as the Coulomb field which binds a 1s electron in a hydrogen atom. 3 highly non-linear phenomena can happen: 1) ATI (above threshold ionization): electrons initially in the ground state absorb a large number of photons, many more than the minimum number required for ionization; 2) multiple ionization: many electrons can be emitted one at a time, in a sequential process, or simultaneously in a mechanism called direct or non-sequential; and 3) high order harmonic generation (HHG): efficient photon emission in the extreme ultraviolet range, in the form of high-order harmonics of the fundamental laser field can occur. The theoretical problem consists in solving the time dependent Schroedinger equation (TDSE) that describes the interaction of a many-electron atom with a laser field. A number of methods have been proposed to solve this problem in the case of a hydrogen atom or a single-active electron atom in a strong laser field. A large effort is presently being devoted to go beyond the single-active approximation. The understanding of the physics of the interaction between atoms and strong laser fields has been provided by a very simple model called ''simple man's theory''. A unified view of HHG, ATI, and non-sequential ionization, originating from the simple man's model and the strong field approximation, expressed in terms of electrons trajectories or quantum paths is slowly emerging. (A.C.)

  18. Strongly Interacting Light Dark Matter

    Directory of Open Access Journals (Sweden)

    Sebastian Bruggisser, Francesco Riva, Alfredo Urbano

    2017-09-01

    Full Text Available In the presence of approximate global symmetries that forbid relevant interactions, strongly coupled light Dark Matter (DM can appear weakly coupled at small energy and generate a sizable relic abundance. Fundamental principles like unitarity restrict these symmetries to a small class, where the leading interactions are captured by effective operators up to dimension-8. Chiral symmetry, spontaneously broken global symmetries and non-linearly realized supersymmetry are examples of this. Their DM candidates (composite fermions, pseudo Nambu-Goldstone Bosons and Goldstini are interesting targets for LHC missing-energy searches.

  19. Strongly interacting light dark matter

    International Nuclear Information System (INIS)

    Bruggisser, Sebastian; Riva, Francesco; Urbano, Alfredo

    2016-07-01

    In the presence of approximate global symmetries that forbid relevant interactions, strongly coupled light Dark Matter (DM) can appear weakly coupled at small-energy and generate a sizable relic abundance. Fundamental principles like unitarity restrict these symmetries to a small class, where the leading interactions are captured by effective operators up to dimension-8. Chiral symmetry, spontaneously broken global symmetries and non-linearly realized supersymmetry are examples of this. Their DM candidates (composite fermions, pseudo-Nambu-Goldstone Bosons and Goldstini) are interesting targets for LHC missing-energy searches.

  20. Rydberg atoms in strong fields

    International Nuclear Information System (INIS)

    Kleppner, D.; Tsimmerman, M.

    1985-01-01

    Experimental and theoretical achievements in studying Rydberg atoms in external fields are considered. Only static (or quasistatic) fields and ''one-electron'' atoms, i.e. atoms that are well described by one-electron states, are discussed. Mainly behaviour of alkali metal atoms in electric field is considered. The state of theoretical investigations for hydrogen atom in magnetic field is described, but experimental data for atoms of alkali metals are presented as an illustration. Results of the latest experimental and theoretical investigations into the structure of Rydberg atoms in strong fields are presented