WorldWideScience

Sample records for spin-polarized measurements reveal

  1. Measuring the spin polarization of alkali-metal atoms using nuclear magnetic resonance frequency shifts of noble gases

    Directory of Open Access Journals (Sweden)

    X. H. Liu

    2015-10-01

    Full Text Available We report a novel method of measuring the spin polarization of alkali-metal atoms by detecting the NMR frequency shifts of noble gases. We calculated the profile of 87Rb D1 line absorption cross sections. We then measured the absorption profile of the sample cell, from which we calculated the 87Rb number densities at different temperatures. Then we measured the frequency shifts resulted from the spin polarization of the 87Rb atoms and calculated its polarization degrees at different temperatures. The behavior of frequency shifts versus temperature in experiment was consistent with theoretical calculation, which may be used as compensative signal for the NMRG closed-loop control system.

  2. Dynamic nuclear spin polarization

    Energy Technology Data Exchange (ETDEWEB)

    Stuhrmann, H.B. [GKSS-Forschungszentrum Geesthacht GmbH (Germany)

    1996-11-01

    Polarized neutron scattering from dynamic polarized targets has been applied to various hydrogenous materials at different laboratories. In situ structures of macromolecular components have been determined by nuclear spin contrast variation with an unprecedented precision. The experiments of selective nuclear spin depolarisation not only opened a new dimension to structural studies but also revealed phenomena related to propagation of nuclear spin polarization and the interplay of nuclear polarisation with the electronic spin system. The observation of electron spin label dependent nuclear spin polarisation domains by NMR and polarized neutron scattering opens a way to generalize the method of nuclear spin contrast variation and most importantly it avoids precontrasting by specific deuteration. It also likely might tell us more about the mechanism of dynamic nuclear spin polarisation. (author) 4 figs., refs.

  3. Interface-induced chiral domain walls, spin spirals and skyrmions revealed by spin-polarized scanning tunneling microscopy.

    Science.gov (United States)

    von Bergmann, Kirsten; Kubetzka, André; Pietzsch, Oswald; Wiesendanger, Roland

    2014-10-01

    The spin textures of ultra-thin magnetic layers exhibit surprising variety. The loss of inversion symmetry at the interface of the magnetic layer and substrate gives rise to the so-called Dzyaloshinskii-Moriya interaction which favors non-collinear spin arrangements with unique rotational sense. Here we review the application of spin-polarized scanning tunneling microscopy to such systems, which has led to the discovery of interface-induced chiral domain walls and spin spirals. Recently, different interface-driven skyrmion lattices have been found, and the writing as well as the deleting of individual skyrmions based on local spin-polarized current injection has been demonstrated. These interface-induced non-collinear magnetic states offer new exciting possibilities to study fundamental magnetic interactions and to tailor material properties for spintronic applications.

  4. Measurement of transverse emittance at the source of spin-polarized electrons at the S-DALINAC

    Energy Technology Data Exchange (ETDEWEB)

    Eckardt, Christian; Barday, Roman; Bonnes, Uwe; Eichhorn, Ralf; Enders, Joachim; Hessler, Christoph; Patalakha, Oleksandr; Platz, Markus; Poltoratska, Yuliya; Rick, Wolfgang [Institut fuer Kernphysik, TU Darmstadt (Germany); Ackermann, Wolfgang; Mueller, Wolfgang F.O.; Steiner, Bastian; Weiland, Thomas [Institut fuer Theorie Elektromagnetischer Felder, TU Darmstadt (Germany)

    2008-07-01

    A new injector concept for 100 keV spin-polarized electrons (SPIN) at the S-DALINAC has been developed. The transverse emittance was measured for beam characterization. The emittance is a quantity concerning the quality of the beam, describing the phase space area. Determination of the emittance requires measurement of the beam profile and knowledge of the focal length of a beam focussing device. A wire scanner unit consisting of two 50 {mu}m diameter tungsten wires is used for the beam-profile measurement. Data analysis is performed by fitting a gaussian model distribution to estimate the 1{sigma} beam radius. Each determined beam width is correlated to the corresponding focal length of a magnetic lens, and a parabola fit is applied to calculate the parameters of the {sigma}-matrix. The square root of the determinant of the {sigma}-matrix defines the emittance. The results of the calculation are presented and the emittance is compared to theoretical estimates.

  5. Design and optimization of a modular setup for measurements of three-dimensional spin polarization with ultrafast pulsed sources

    Energy Technology Data Exchange (ETDEWEB)

    Pincelli, T., E-mail: pincelli@iom.cnr.it; Rossi, G. [Dipartimento di Fisica, Università degli studi di Milano, Via Celoria 16, 20133 Milano (Italy); Laboratorio TASC, IOM-CNR, S.S. 14 km 163.5, Basovizza, 34149 Trieste (Italy); Petrov, V. N. [Saint Petersburg State Polytechnical University, Politechnicheskaya Street 29, 195251 Saint Petersburg (Russian Federation); Brajnik, G.; Carrato, S. [Università degli Studi di Trieste, Piazzale Europa 1, 34127 Trieste (Italy); Ciprian, R.; Torelli, P.; Krizmancic, D.; Salvador, F.; De Luisa, A.; Panaccione, G. [Laboratorio TASC, IOM-CNR, S.S. 14 km 163.5, Basovizza, 34149 Trieste (Italy); Lollobrigida, V. [Dipartimento di Matematica e Fisica, Università Roma Tre, I-00146 Rome (Italy); Sergo, R.; Gubertini, A.; Cautero, G. [Sincrotrone Trieste S.C.p.A, Strada Statale 14-km 163.5 in AREA Science Park, Basovizza, 34149 Trieste (Italy)

    2016-03-15

    ULTRASPIN is an apparatus devoted to the measurement of the spin polarization (SP) of electrons ejected from solid surfaces in a UHV environment. It is designed to exploit ultrafast light sources (free electron laser or laser high harmonic generation) and to perform (photo)electron spin analysis by an arrangement of Mott scattering polarimeters that measure the full SP vector. The system consists of two interconnected UHV vessels: one for surface science sample cleaning treatments, e-beam deposition of ultrathin films, and low energy electron diffraction/AES characterization. The sample environment in the polarimeter allows for cryogenic cooling and in-operando application of electric and magnetic fields. The photoelectrons are collected by an electrostatic accelerator and transport lens that form a periaxial beam that is subsequently directed by a Y-shaped electrostatic deflector to either one of the two orthogonal Mott polarimeters. The apparatus has been designed to operate in the extreme conditions of ultraintense single-X-ray pulses as originated by free electron lasers (up to 1 kHz), but it allows also for the single electron counting mode suitable when using statistical sources such as synchrotron radiation, cw-laser, or e-gun beams (up to 150 kcps).

  6. Design and optimization of a modular setup for measurements of three-dimensional spin polarization with ultrafast pulsed sources

    Science.gov (United States)

    Pincelli, T.; Petrov, V. N.; Brajnik, G.; Ciprian, R.; Lollobrigida, V.; Torelli, P.; Krizmancic, D.; Salvador, F.; De Luisa, A.; Sergo, R.; Gubertini, A.; Cautero, G.; Carrato, S.; Rossi, G.; Panaccione, G.

    2016-03-01

    ULTRASPIN is an apparatus devoted to the measurement of the spin polarization (SP) of electrons ejected from solid surfaces in a UHV environment. It is designed to exploit ultrafast light sources (free electron laser or laser high harmonic generation) and to perform (photo)electron spin analysis by an arrangement of Mott scattering polarimeters that measure the full SP vector. The system consists of two interconnected UHV vessels: one for surface science sample cleaning treatments, e-beam deposition of ultrathin films, and low energy electron diffraction/AES characterization. The sample environment in the polarimeter allows for cryogenic cooling and in-operando application of electric and magnetic fields. The photoelectrons are collected by an electrostatic accelerator and transport lens that form a periaxial beam that is subsequently directed by a Y-shaped electrostatic deflector to either one of the two orthogonal Mott polarimeters. The apparatus has been designed to operate in the extreme conditions of ultraintense single-X-ray pulses as originated by free electron lasers (up to 1 kHz), but it allows also for the single electron counting mode suitable when using statistical sources such as synchrotron radiation, cw-laser, or e-gun beams (up to 150 kcps).

  7. Widespread spin polarization effects in photoemission from topological insulators

    Energy Technology Data Exchange (ETDEWEB)

    Jozwiak, C.; Chen, Y. L.; Fedorov, A. V.; Analytis, J. G.; Rotundu, C. R.; Schmid, A. K.; Denlinger, J. D.; Chuang, Y.-D.; Lee, D.-H.; Fisher, I. R.; Birgeneau, R. J.; Shen, Z.-X.; Hussain, Z.; Lanzara, A.

    2011-06-22

    High-resolution spin- and angle-resolved photoemission spectroscopy (spin-ARPES) was performed on the three-dimensional topological insulator Bi{sub 2}Se{sub 3} using a recently developed high-efficiency spectrometer. The topological surface state's helical spin structure is observed, in agreement with theoretical prediction. Spin textures of both chiralities, at energies above and below the Dirac point, are observed, and the spin structure is found to persist at room temperature. The measurements reveal additional unexpected spin polarization effects, which also originate from the spin-orbit interaction, but are well differentiated from topological physics by contrasting momentum and photon energy and polarization dependencies. These observations demonstrate significant deviations of photoelectron and quasiparticle spin polarizations. Our findings illustrate the inherent complexity of spin-resolved ARPES and demonstrate key considerations for interpreting experimental results.

  8. Detecting Spin-Polarized Currents in Ballistic Nanostructures

    DEFF Research Database (Denmark)

    Potok, R.; Folk, J.; M. Marcus, C.

    2002-01-01

    We demonstrate a mesoscopic spin polarizer/analyzer system that allows the spin polarization of current from a quantum point contact in an in-plane magnetic field to be measured. A transverse focusing geometry is used to couple current from an emitter point contact into a collector point contact....

  9. From epitaxial growth of ferrite thin films to spin-polarized tunnelling

    International Nuclear Information System (INIS)

    Moussy, Jean-Baptiste

    2013-01-01

    This paper presents a review of the research which is focused on ferrite thin films for spintronics. First, I will describe the potential of ferrite layers for the generation of spin-polarized currents. In the second step, the structural and chemical properties of epitaxial thin films and ferrite-based tunnel junctions will be presented. Particular attention will be given to ferrite systems grown by oxygen-assisted molecular beam epitaxy. The analysis of the structure and chemistry close to the interfaces, a key-point for understanding the spin-polarized tunnelling measurements, will be detailed. In the third part, the magnetic and magneto-transport properties of magnetite (Fe 3 O 4 ) thin films as a function of structural defects such as the antiphase boundaries will be explained. The spin-polarization measurements (spin-resolved photoemission, tunnel magnetoresistance) on this oxide predicted to be half-metallic will be discussed. Fourth, the potential of magnetic tunnel barriers, such as CoFe 2 O 4 , NiFe 2 O 4 or MnFe 2 O 4 , whose insulating behaviour and the high Curie temperatures make it exciting candidates for spin filtering at room temperature will be described. Spin-polarized tunnelling experiments, involving either Meservey–Tedrow or tunnel magnetoresistance measurements, will reveal significant spin-polarizations of the tunnelling current at low temperatures but also at room temperatures. Finally, I will mention a few perspectives with ferrite-based heterostructures. (topical review)

  10. Spin polarized electron tunneling and magnetoresistance in molecular junctions.

    Science.gov (United States)

    Szulczewski, Greg

    2012-01-01

    This chapter reviews tunneling of spin-polarized electrons through molecules positioned between ferromagnetic electrodes, which gives rise to tunneling magnetoresistance. Such measurements yield important insight into the factors governing spin-polarized electron injection into organic semiconductors, thereby offering the possibility to manipulate the quantum-mechanical spin degrees of freedom for charge carriers in optical/electrical devices. In the first section of the chapter a brief description of the Jullière model of spin-dependent electron tunneling is reviewed. Next, a brief description of device fabrication and characterization is presented. The bulk of the review highlights experimental studies on spin-polarized electron tunneling and magnetoresistance in molecular junctions. In addition, some experiments describing spin-polarized scanning tunneling microscopy/spectroscopy on single molecules are mentioned. Finally, some general conclusions and prospectus on the impact of spin-polarized tunneling in molecular junctions are offered.

  11. Spin polarized Auger electron spectroscopy of Fe and Ni

    Science.gov (United States)

    Anilturk, O. S.; Koymen, A. R.

    2001-06-01

    Surface sensitive experiments, in which the spin-polarized electrons are involved, play an important role for magnetic characterization, since the spin-polarized electrons are fingerprints for the local magnetization. Scanning electron microscope with polarization analysis (SEMPA) is one of the most powerful tools to investigate the surface magnetic domain structure of magnetic materials. On the other hand, at energies high enough to generate a two-hole final state arising from Auger transitions, it is possible to observe the spin polarization of the Auger electrons. These electrons reveal element-specific local magnetic information, particularly valuable for surface magnetic studies with composite systems. By using the uniqueness of the UTA-SEMPA tool, one can obtain the magnetic domain picture and also perform spin-polarized Auger electron spectroscopy studies by probing a single domain at the surface. In this study, precisely knowing the probed domain, spin polarization of electrons from super Coster-Kronig MMM Auger emissions on Fe and Ni samples have been investigated. The polarization enhancement above the 3p(M23) threshold is observed on both samples.

  12. Spin polarized Auger electron spectroscopy of Fe and Ni

    International Nuclear Information System (INIS)

    Anilturk, O. S.; Koymen, A. R.

    2001-01-01

    Surface sensitive experiments, in which the spin-polarized electrons are involved, play an important role for magnetic characterization, since the spin-polarized electrons are fingerprints for the local magnetization. Scanning electron microscope with polarization analysis (SEMPA) is one of the most powerful tools to investigate the surface magnetic domain structure of magnetic materials. On the other hand, at energies high enough to generate a two-hole final state arising from Auger transitions, it is possible to observe the spin polarization of the Auger electrons. These electrons reveal element-specific local magnetic information, particularly valuable for surface magnetic studies with composite systems. By using the uniqueness of the UTA-SEMPA tool, one can obtain the magnetic domain picture and also perform spin-polarized Auger electron spectroscopy studies by probing a single domain at the surface. In this study, precisely knowing the probed domain, spin polarization of electrons from super Coster - Kronig MMM Auger emissions on Fe and Ni samples have been investigated. The polarization enhancement above the 3p(M 23 ) threshold is observed on both samples. [copyright] 2001 American Institute of Physics

  13. Spin-polarized spin excitation spectroscopy

    International Nuclear Information System (INIS)

    Loth, Sebastian; Lutz, Christopher P; Heinrich, Andreas J

    2010-01-01

    We report on the spin dependence of elastic and inelastic electron tunneling through transition metal atoms. Mn, Fe and Cu atoms were deposited onto a monolayer of Cu 2 N on Cu(100) and individually addressed with the probe tip of a scanning tunneling microscope. Electrons tunneling between the tip and the substrate exchange energy and spin angular momentum with the surface-bound magnetic atoms. The conservation of energy during the tunneling process results in a distinct onset threshold voltage above which the tunneling electrons create spin excitations in the Mn and Fe atoms. Here we show that the additional conservation of spin angular momentum leads to different cross-sections for spin excitations depending on the relative alignment of the surface spin and the spin of the tunneling electron. For this purpose, we developed a technique for measuring the same local spin with a spin-polarized and a non-spin-polarized tip by exchanging the last apex atom of the probe tip between different transition metal atoms. We derive a quantitative model describing the observed excitation cross-sections on the basis of an exchange scattering process.

  14. Spin-polarized photoemission from SiGe heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Ferrari, A.; Bottegoni, F.; Isella, G.; Cecchi, S.; Chrastina, D.; Finazzi, M.; Ciccacci, F. [LNESS-Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano (Italy)

    2013-12-04

    We apply the principles of Optical Orientation to measure by Mott polarimetry the spin polarization of electrons photoemitted from different group-IV heterostructures. The maximum measured spin polarization, obtained from a Ge/Si{sub 0.31}Ge{sub 0.69} strained film, undoubtedly exceeds the maximum value of 50% attainable in bulk structures. The explanation we give for this result lies in the enhanced band orbital mixing between light hole and split-off valence bands as a consequence of the compressive strain experienced by the thin Ge layer.

  15. Spin-filter scanning tunneling microscopy : a novel technique for the analysis of spin polarization on magnetic surfaces and spintronic devices

    NARCIS (Netherlands)

    Vera Marun, I.J.

    2010-01-01

    This thesis deals with the development of a versatile technique to measure spin polarization with atomic resolution. A microscopy technique that can measure electronic spin polarization is relevant for characterization of magnetic nanostructures and spintronic devices. Scanning tunneling microscopy

  16. Nuclear spin polarization of targets

    International Nuclear Information System (INIS)

    Happer, W.

    1990-01-01

    Lasers can be used to produce milligrams to grams of noble gas nuclei with spin polarizations in excess of 50%. These quantities are sufficient to be very useful targets in nuclear physics experiments. Alkali-metal atoms are used to capture the angular momentum of circularly polarized laser photons, and the alkali-metal atoms transfer their angular momentum to noble gas atoms in binary or three-body collisions. Non-radiative collisions between the excited alkali atoms and molecular quenching gases are essential to avoid radiation trapping. The spin exchange can involve gas-phase van der Waals molecules, consisting of a noble gas atom and an alkali metal atom. Surface chemistry is also of great importance in determining the wall-induced relaxation rates of the noble gases

  17. Fusion with highly spin polarized HD and D2

    International Nuclear Information System (INIS)

    Honig, A.

    1992-01-01

    This report discusses the following topics relating to inertial confinement with spin polarized hydrogen targets: low temperature implementation of mating a target to omega; dilution-refrigerator cold-entry and retrieval system; target shell tensile strength characterization at low temperatures; and proton and deuteron spin-lattice relaxation measurements in HD in the millikelvin temperature range

  18. Thermal stability of tunneling spin polarization

    International Nuclear Information System (INIS)

    Kant, C.H.; Kohlhepp, J.T.; Paluskar, P.V.; Swagten, H.J.M.; Jonge, W.J.M. de

    2005-01-01

    We present a study of the thermal stability of tunneling spin polarization in Al/AlOx/ferromagnet junctions based on the spin-polarized tunneling technique, in which the Zeeman-split superconducting density of states in the Al electrode is used as a detector for the spin polarization. Thermal robustness of the polarization, which is of key importance for the performance of magnetic tunnel junction devices, is demonstrated for post-deposition anneal temperatures up to 500 o C with Co and Co 90 Fe 10 top electrodes, independent of the presence of an FeMn layer on top of the ferromagnet

  19. Spin polarization effects in low-energy elastic electron scattering

    International Nuclear Information System (INIS)

    Beerlage, M.J.M.

    1982-01-01

    This work describes experiments on the role of spin polarization in elastic electron scattering. Chapter I introduces the topic and in chapter II elastic scattering of 10-50 eV electrons from Ar and Kr in the angular range between 40 0 and 110 0 is studied. Noble gases have been chosen as targets in view of their relative theoretical simplicity. Below 25 eV scattered intensities measured by various authors exhibit severe disagreements. However, in the entire energy range, the spin polarization results can reasonably well be used to point out the shortcomings of the available theoretical data. The main topic of chapter III is the first attempt to determine the magnitude of a polarization phenomenon - in elastic electron scattering from the optically active camphor molecule - of which the existence has recently been predicted qualitatively from the absence of parity symmetry in such molecules. Besides these studies on gaseous targets the author has initiated a scattering experiment on crystal surfaces, using spin polarized electrons. Within the framework of this project a large new experimental arrangement has been built up. It consists of a spin polarized electron source and a LEED scattering chamber. Design, construction and test results, showing the usefulness of the set-up, are described in the last chapter. (Auth.)

  20. Tilted Foils Nuclear Spin Polarization at REX-ISOLDE

    CERN Document Server

    Törnqvist, Hans Toshihide

    2013-08-08

    This thesis will explain and summarize my work and involvement in experiments aimed at producing nuclear spin polarization of post-accelerated beams of ions with the tilted-foils technique at the REX-ISOLDE linear accelerator at CERN. Polarizing the nuclear spin of radioactive beams in particular may provide access to observables which may be difficult to obtain otherwise. Currently, the techniques commonly employed for nuclear spin polarization are restricted to specific nuclides and experimental measurement techniques. Tilted foils polarization may provide a new tool to extend the range of nuclides that can be polarized and the types of experiments that can be performed. The experiments rely not only on the production but also on the method to measure the degree of attained polarization. Two methods will be treated, based on particle scattering in Coulomb excitation that may be utilized for stable beams, and the $\\beta$-NMR that requires $\\beta$-decaying nuclei. The experimental setups and measurements will...

  1. Optical pumping production of spin polarized hydrogen

    International Nuclear Information System (INIS)

    Knize, R.J.; Happer, W.; Cecchi, J.L.

    1984-01-01

    There has been much interest recently in the production of large quantities of spin polarized hydrogen in various fields including controlled fusion, quantum fluids, high energy, and nuclear physics. One promising method for the development of large quantities of spin polarized hydrogen is the utilization of optical pumping with a laser. Optical pumping is a process where photon angular momentum is converted into electron and nuclear spin. The advent of tunable CW dye lasers (approx. 1 watt) allow the production of greater than 10 18 polarized atoms/sec. We have begun a program at Princeton to investigate the physics and technology of using optical pumping to produce large quantities of spin polarized hydrogen. Initial experiments have been done in small closed glass cells. Eventually, a flowing system, open target, or polarized ion source could be constructed

  2. Magnetoresistance through spin-polarized p states

    International Nuclear Information System (INIS)

    Papanikolaou, Nikos

    2003-01-01

    We present a theoretical study of the ballistic magnetoresistance in Ni contacts using first-principles, atomistic, electronic structure calculations. In particular we investigate the role of defects in the contact region with the aim of explaining the recently observed spectacular magnetoresistance ratio. Our results predict that the possible presence of spin-polarized oxygen in the contact region could explain conductance changes by an order of magnitude. Electronic transport essentially occurs through spin-polarized oxygen p states, and this mechanism gives a much higher magnetoresistance than that obtained assuming clean atomically sharp domain walls alone

  3. Engineering the spin polarization of one-dimensional electrons

    Science.gov (United States)

    Yan, C.; Kumar, S.; Thomas, K.; See, P.; Farrer, I.; Ritchie, D.; Griffiths, J.; Jones, G.; Pepper, M.

    2018-02-01

    We present results of magneto-focusing on the controlled monitoring of spin polarization within a one-dimensional (1D) channel, and its subsequent effect on modulating the spin–orbit interaction (SOI) in a 2D GaAs electron gas. We demonstrate that electrons within a 1D channel can be partially spin polarized as the effective length of the 1D channel is varied in agreement with the theoretical prediction. Such polarized 1D electrons when injected into a 2D region result in a split in the odd-focusing peaks, whereas the even peaks remain unaffected (single peak). On the other hand, the unpolarized electrons do not affect the focusing spectrum and the odd and even peaks remain as single peaks, respectively. The split in odd-focusing peaks is evidence of direct measurement of spin polarization within a 1D channel, where each sub-peak represents the population of a particular spin state. Confirmation of the spin splitting is determined by a selective modulation of the focusing peaks due to the Zeeman energy in the presence of an in-plane magnetic field. We suggest that the SOI in the 2D regime is enhanced by a stream of polarized 1D electrons. The spatial control of spin states of injected 1D electrons and the possibility of tuning the SOI may open up a new regime of spin-engineering with application in future quantum information schemes.

  4. Spin-polarized deuterium in magnetic traps

    International Nuclear Information System (INIS)

    Koelman, J.M.V.A.; Stoof, H.T.C.; Verhaar, B.J.; Walraven, J.T.M.

    1987-01-01

    We have calculated the spin-exchange two-body rate constants associated with the population dynamics of the hyperfine levels of atomic deuterium as a function of magnetic field in the Boltzmann zero-temperature limit. Results indicate that a gas of low-field--seeking deuterium atoms trapped in a static magnetic field minimum decays rapidly into an ultrastable gas of doubly spin-polarized deuterium. We also discuss the temperature dependence of various effects

  5. New materials research for high spin polarized current

    International Nuclear Information System (INIS)

    Tezuka, Nobuki

    2012-01-01

    The author reports here a thorough investigation of structural and magnetic properties of Co 2 FeAl 0.5 Si 0.5 Heusler alloy films, and the tunnel magnetoresistance effect for junctions with Co 2 FeAl 0.5 Si 0.5 electrodes, spin injection into GaAs semiconductor from Co 2 FeAl 0.5 Si 0.5 , and spin filtering phenomena for junctions with CoFe 2 O 4 ferrite barrier. It was observed that tunnel magnetoresistance ratio up to 832%(386%) at 9 K (room temperature), which corresponds to the tunnel spin polarization of 0.90 (0.81) for the junctions using Co 2 FeAl 0.5 Si 0.5 Heusler electrodes by optimizing the fabrication condition. It was also found that the tunnel magnetoresistance ratio are almost the same between the junctions with Co 2 FeAl 0.5 Si 0.5 Heusler electrodes on Cr buffered (1 0 0) and (1 1 0) MgO substrates, which indicates that tunnel spin polarization of Co 2 FeAl 0.5 Si 0.5 for these two direction are almost the same. The next part of this paper is a spin filtering effect using a Co ferrite. The spin filtering effect was observed through a thin Co-ferrite barrier. The inverse type tunnel magnetoresistance ratio of −124% measured at 10 K was obtained. The inverse type magnetoresistance suggests the negative spin polarization of Co-ferrite barrier. The magnetoresistance ratio of −124% corresponds to the spin polarization of −0.77 by the Co-ferrite barrier. The last part is devoted to the spin injection from Co 2 FeAl 0.5 Si 0.5 into GaAs. The spin injection signal was clearly obtained by three terminal Hanle measurement. The spin relaxation time was estimated to be 380 ps measured at 5 K.

  6. Spin-Polarized Tunneling through Chemical Vapor Deposited Multilayer Molybdenum Disulfide.

    Science.gov (United States)

    Dankert, André; Pashaei, Parham; Kamalakar, M Venkata; Gaur, Anand P S; Sahoo, Satyaprakash; Rungger, Ivan; Narayan, Awadhesh; Dolui, Kapildeb; Hoque, Md Anamul; Patel, Ram Shanker; de Jong, Michel P; Katiyar, Ram S; Sanvito, Stefano; Dash, Saroj P

    2017-06-27

    The two-dimensional (2D) semiconductor molybdenum disulfide (MoS 2 ) has attracted widespread attention for its extraordinary electrical-, optical-, spin-, and valley-related properties. Here, we report on spin-polarized tunneling through chemical vapor deposited multilayer MoS 2 (∼7 nm) at room temperature in a vertically fabricated spin-valve device. A tunnel magnetoresistance (TMR) of 0.5-2% has been observed, corresponding to spin polarization of 5-10% in the measured temperature range of 300-75 K. First-principles calculations for ideal junctions result in a TMR up to 8% and a spin polarization of 26%. The detailed measurements at different temperature, bias voltages, and density functional theory calculations provide information about spin transport mechanisms in vertical multilayer MoS 2 spin-valve devices. These findings form a platform for exploring spin functionalities in 2D semiconductors and understanding the basic phenomena that control their performance.

  7. Measurement of thermal accommodation of spin-polarized hydrogen on a saturated 4He film at 0.18--0.4 K

    International Nuclear Information System (INIS)

    Helffrich, J.; Maley, M.P.; Krusius, M.; Wheatley, J.C.

    1986-01-01

    The thermal accommodation of H-gas atoms on a saturated superfluid- 4 He-film-covered surface has been measured in the temperature range 0.18--0.4 K. A straightforward stationary-state measuring technique is employed whereby we determine the heat flux conducted by H-gas atoms from a superfluid- 4 He-film-covered bolometer, biased above ambient temperature. The results agree with recent calculations of the thermal-accommodation properties dominated by sticking-evaporation collisions mediated by ripplon creation

  8. Current-induced spin polarization in InGaAs and GaAs epilayers with varying doping densities

    Science.gov (United States)

    Luengo-Kovac, M.; Huang, S.; Del Gaudio, D.; Occena, J.; Goldman, R. S.; Raimondi, R.; Sih, V.

    2017-11-01

    The current-induced spin polarization and momentum-dependent spin-orbit field were measured in InxGa1 -xAs epilayers with varying indium concentrations and silicon doping densities. Samples with higher indium concentrations and carrier concentrations and lower mobilities were found to have larger electrical spin generation efficiencies. Furthermore, current-induced spin polarization was detected in GaAs epilayers despite the absence of measurable spin-orbit fields, indicating that the extrinsic contributions to the spin-polarization mechanism must be considered. Theoretical calculations based on a model that includes extrinsic contributions to the spin dephasing and the spin Hall effect, in addition to the intrinsic Rashba and Dresselhaus spin-orbit coupling, are found to reproduce the experimental finding that the crystal direction with the smaller net spin-orbit field has larger electrical spin generation efficiency and are used to predict how sample parameters affect the magnitude of the current-induced spin polarization.

  9. Spin polarization of electrons in a magnetic impurity doped ...

    Indian Academy of Sciences (India)

    Abstract. A theoretical model is presented in this paper for degree of spin polarization in a light emitting diode (LED) whose epitaxial region contains quantum dots doped with magnetic impurity. The model is then used to investigate the effect of electron–phonon interaction on degree of spin polarization at different ...

  10. Spin-Polarization in Quasi-Magnetic Tunnel Junctions

    Science.gov (United States)

    Xie, Zheng-Wei; Li, Ling

    2017-05-01

    Spin polarization in ferromagnetic metal/insulator/spin-filter barrier/nonmagnetic metal, referred to as quasi-magnetic tunnel junctions, is studied within the free-electron model. Our results show that large positive or negative spin-polarization can be obtained at high bias in quasi-magnetic tunnel junctions, and within large bias variation regions, the degree of spin-polarization can be linearly tuned by bias. These linear variation regions of spin-polarization with bias are influenced by the barrier thicknesses, barrier heights and molecular fields in the spin-filter (SF) layer. Among them, the variations of thickness and heights of the insulating and SF barrier layers have influence on the value of spin-polarization and the linear variation regions of spin-polarization with bias. However, the variations of molecular field in the SF layer only have influence on the values of the spin-polarization and the influences on the linear variation regions of spin-polarization with bias are slight. Supported by the Key Natural Science Fund of Sichuan Province Education Department under Grant Nos 13ZA0149 and 16ZA0047, and the Construction Plan for Scientific Research Innovation Team of Universities in Sichuan Province under Grant No 12TD008.

  11. Spin polarization at the interface and tunnel magnetoresistance

    International Nuclear Information System (INIS)

    Itoh, H.; Inoue, J.

    2001-01-01

    We propose that interfacial states of imperfectly oxidized Al ions may exist in ferromagnetic tunnel junctions with Al-O barrier and govern both the spin polarization and tunnel conductance. It is shown that the spin polarization is positive independent of materials and correlates well with the tunnel magnetoresistance

  12. Effect of spin polarization on the structural properties and bond ...

    Indian Academy of Sciences (India)

    coupled to semi-empirical hardness theory proved effective in hardness prediction for the metal borides which agree well with the experimental values. These results would help to gain insight into the spin-polarized effect on the structural and bond hardness. Keywords. Iron boride; DFT; spin polarized; critical pressure; ...

  13. Spin polarization of electrons in a magnetic impurity doped ...

    Indian Academy of Sciences (India)

    A theoretical model is presented in this paper for degree of spin polarization in alight emitting diode (LED) whose epitaxial region contains quantum dots doped with magnetic impurity. The model is then used to investigate the effect of electron–phonon interaction on degree of spin polarization at different temperatures and ...

  14. Diffusion equation and spin drag in spin-polarized transport

    DEFF Research Database (Denmark)

    Flensberg, Karsten; Jensen, Thomas Stibius; Mortensen, Asger

    2001-01-01

    We study the role of electron-electron interactions for spin-polarized transport using the Boltzmann equation, and derive a set of coupled transport equations. For spin-polarized transport the electron-electron interactions are important, because they tend to equilibrate the momentum of the two-s...

  15. Tunnel spin polarization versus energy for clean and doped Al2O3 barriers

    NARCIS (Netherlands)

    Park, B.G.; Banerjee, T.; Lodder, J.C.; Jansen, R.

    2007-01-01

    The variation of the tunnel spin-polarization (TSP) with energy is determined using a magnetic tunnel transistor, allowing quantification of the energy dependent TSP separately for both ferromagnet/insulator interfaces and direct correlation with the tunnel magnetoresistance (TMR) measured in the

  16. Tunnel Spin Polarization Versus Energy for Clean and Doped Al2O3 Barriers

    NARCIS (Netherlands)

    Park, B.G.; Banerjee, T.; Lodder, J.C.; Jansen, R.

    2007-01-01

    The variation of the tunnel spin-polarization (TSP) with energy is determined using a magnetic tunnel transistor, allowing quantification of the energy dependent TSP separately for both ferromagnet/insulator interfaces and direct correlation with the tunnel magnetoresistance (TMR) measured in the

  17. ESR and related experiments in spin-polarized atomic hydrogen

    International Nuclear Information System (INIS)

    Yperen, G.H. van.

    1984-01-01

    This thesis deals with some experiments in (gaseous) spin-polarized atomic hydrogen. One uses the expression 'stabilized' atomic hydrogen, meaning that by choosing suitable conditions one can suppress the tendency of atoms to recombine into H 2 molecules, such that the lifetime of the atomic state is extended by many orders of magnitude. Research is focused at the study of processes that determine the decay rate of polarized H samples, with the ultimate goal of preparing samples of sufficiently high density and at low enough temperature to observe experimentally the behaviour of the (degenerate) quantum gas. ESR (Electron Spin Resonance) appears to be a very suitable measurement technique to study the properties of polarized H. This work describes the introduction of ESR as detection technique, and the first results of an experiment in polarized H using this technique. (orig.)

  18. Spin-dependent scattering and the spin polarization of a diffusive current in partly disordered L10 epitaxial FePd

    International Nuclear Information System (INIS)

    Seemann, K M; Hickey, M C; Baltz, V; Hickey, B J; Marrows, C H

    2010-01-01

    We report magnetic domain wall (DW) resistance in epitaxial films of FePd. When equal numbers of Fe and Pd atoms are present, this material forms an ordered structure with alternating crystal planes of Fe and Pd. We prepared films enriched with Pd to varying degrees, gradually degrading this structure. As might be expected, this increased the electrical resistivity of the films by introducing extra defects that can scatter electrons. However, unexpectedly, the additional resistance arising from the ∼10 nm thick DWs rose as a proportion of the overall resistivity, roughly doubling when halving the degree of chemical ordering-as determined from x-ray diffraction measurements-within the films. These data can be used to infer a rise in the spin polarization of the current flowing in the layers when extra Pd atoms are introduced. On the other hand, a separate measurement of spin polarization using a superconducting point contact technique that is insensitive to electron scattering revealed no changes as extra Pd was introduced. We conclude that Pd atoms scatter electrons of one spin far more strongly than the other, suggesting a possible means of producing highly spin-polarized currents for use in spintronic devices.

  19. TOPICAL REVIEW: Highly spin-polarized materials and devices for spintronics

    Directory of Open Access Journals (Sweden)

    Koichiro Inomata et al.

    2008-01-01

    Full Text Available The performance of spintronics depends on the spin polarization of the current. In this study half-metallic Co-based full-Heusler alloys and a spin filtering device (SFD using a ferromagnetic barrier have been investigated as highly spin-polarized current sources. The multilayers were prepared by magnetron sputtering in an ultrahigh vacuum and microfabricated using photolithography and Ar ion etching. We investigated two systems of Co-based full-Heusler alloys, Co2Cr1 ? xFexAl (CCFA(x and Co2FeSi1 ? xAlx (CFSA(x and revealed the structure and magnetic and transport properties. We demonstrated giant tunnel magnetoresistance (TMR of up to 220% at room temperature and 390% at 5 K for the magnetic tunnel junctions (MTJs using Co2FeSi0.5Al0.5 (CFSA(0.5 Heusler alloy electrodes. The 390% TMR corresponds to 0.81 spin polarization for CFSA(0.5 at 5 K. We also investigated the crystalline structure and local structure around Co atoms by x-ray diffraction (XRD and nuclear magnetic resonance (NMR analyses, respectively, for CFSA films sputtered on a Cr-buffered MgO (001 substrate followed by post-annealing at various temperatures in an ultrahigh vacuum. The disordered structures in CFSA films were clarified by NMR measurements and the relationship between TMR and the disordered structure was discussed. We clarified that the TMR of the MTJs with CFSA(0.5 electrodes depends on the structure, and is significantly higher for L21 than B2 in the crystalline structure. The second part of this paper is devoted to a SFD using a ferromagnetic barrier. The Co ferrite is investigated as a ferromagnetic barrier because of its high Curie temperature and high resistivity. We demonstrate the strong spin filtering effect through an ultrathin insulating ferrimagnetic Co-ferrite barrier at a low temperature. The barrier was prepared by the surface plasma oxidization of a CoFe2 film deposited on a MgO (001 single crystal substrate, wherein the spinel structure of CoFe2O4 (CFO

  20. Designing magnetic droplet soliton nucleation employing spin polarizer

    Science.gov (United States)

    Mohseni, Morteza; Mohseni, Majid

    2018-04-01

    We show by means of micromagnetic simulations that spin polarizer in nano-contact (NC) spin torque oscillators as the representative of the fixed layer in an orthogonal pseudo-spin valve can be employed to design and to control magnetic droplet soliton nucleation and dynamics. We found that using a tilted spin polarizer layer decreases the droplet nucleation time which is more suitable for high speed applications. However, a tilted spin polarizer increases the nucleation current and decreases the frequency stability of the droplet. Additionally, by driving the magnetization inhomogenously at the NC region, it is found that a tilted spin polarizer reduces the precession angle of the droplet and through an interplay with the Oersted field of the DC current, it breaks the spatial symmetry of the droplet profile. Our findings explore fundamental insight into nano-scale magnetic droplet soliton dynamics with potential tunability parameters for future microwave electronics.

  1. A frozen spin polarized target for S134

    CERN Multimedia

    1974-01-01

    The CERN-ETH, Zurich-Helsinki-Imperial College-Southampton Collaboration used a frozen spin polarized target together with the ETH spectrometer magnet to study spin effects (S134). Beam was d31 in South Hall

  2. Neutron stars with spin polarized self-interacting dark matter

    OpenAIRE

    Rezaei, Zeinab

    2018-01-01

    Dark matter, one of the important portion of the universe, could affect the visible matter in neutron stars. An important physical feature of dark matter is due to the spin of dark matter particles. Here, applying the piecewise polytropic equation of state for the neutron star matter and the equation of state of spin polarized self-interacting dark matter, we investigate the structure of neutron stars which are influenced by the spin polarized self-interacting dark matter. The behavior of the...

  3. Spin-polarized scanning tunneling microscopy of magnetic nanostructures at the example of bcc-Co/Fe(110), Fe/Mo(110), and copper phthalocyanine/Fe(1110); Spinpolarisierte Rastertunnelmikroskopie magnetischer Nanostrukturen am Beispiel von bcc-Co/Fe(110), Fe/Mo(110) und Kupfer-Phthalocyanin/Fe(110)

    Energy Technology Data Exchange (ETDEWEB)

    Methfessel, Torsten

    2010-12-09

    This thesis provides an introduction into the technique of spin-polarized scanning tunnelling microscopy and spectroscopy as an experimental method for the investigation of magnetic nanostructures. Experimental results for the spin polarized electronic structure depending on the crystal structure of ultrathin Co layers, and depending on the direction of the magnetization for ultrathin Fe layers are presented. High-resolution measurements show the position-dependent spin polarization on a single copper-phthalocyanine molecule deposited on a ferromagnetic surface. Co was deposited by molecular beam epitaxy on the (110) surface of the bodycentered cubic metals Cr and Fe. In contrast to previous reports in the literature only two layers of Co can be stabilized in the body-centered cubic (bcc) structure. The bcc-Co films on the Fe(110) surface show no signs of epitaxial distortions. Thicker layers reconstruct into a closed-packed structure (hcp / fcc). The bcc structure increases the spin-polarization of Co to P=62 % in comparison to hcp-Co (P=45 %). The temperature-dependent spin-reorientation of ultrathin Fe/Mo(110) films was investigated by spin-polarized spectroscopy. A reorientation of the magnetic easy axis from the [110] direction along the surface normal to the in-plane [001] axis is observed at T (13.2{+-}0.5) K. This process can be identified as a discontinuous reorientation transition, revealing two simultaneous minima of the free energy in a certain temperature range. The electronic structure of mono- and double-layer Fe/Mo(110) shows a variation with the reorientation of the magnetic easy axis and with the direction of the magnetization. The investigation of the spin-polarized charge transport through a copper-phthalocyanine molecule on the Fe/Mo(110) surface provides an essential contribution to the understanding of spin-transport at the interface between metal and organic molecule. Due to the interaction with the surface of the metal the HOMO-LUMO energy

  4. Spin-polarized scanning tunneling microscopy: breakthroughs and highlights.

    Science.gov (United States)

    Bode, Matthias

    2012-01-01

    The principle of scanning tunneling microscopy, an imaging method with atomic resolution capability invented by Binnig and Rohrer in 1982, can be adapted for surface magnetism studies by using magnetic probe tips. The contrast mechanism of this so-called spin-polarized scanning tunneling microscopy, or SP-STM, relies on the tunneling magneto-resistance effect, i.e. the tip-sample distance as well as the differential conductance depend on the relative magnetic orientation of tip and sample. To illustrate the working principle and the unique capabilities of SP-STM, this compilation presents some key experiments which have been performed on various magnetic surfaces, such as the topological antiferromagnet Cr(001), a double-layer of Fe which exhibits a stripe- domain pattern with about 50 nm periodicity, and the Mn monolayer on W(110), where the combination of experiment and theory reveal an antiferromagnetic spin cycloid. Recent experimental results also demonstrate the suitability of SP-STM for studies of dynamic properties, such as the spin relaxation time of single magnetic nanostructures.

  5. Berry phase and shot noise for spin-polarized and entangled electrons

    International Nuclear Information System (INIS)

    Wang Pei; Tang Weihua; Lu Dinghui; Jiang Lixia; Zhao Xuean

    2007-01-01

    Shot noise for entangled and spin-polarized states in a four-probe geometric setup has been studied by adding two rotating magnetic fields in an incoming channel. Our results show that the noise power oscillates as the magnetic fields vary. The singlet, entangled triplet and polarized states can be distinguished by adjusting the magnetic fields. The Berry phase can be derived by measuring the shot noise power

  6. An enhancement of spin polarization by multiphoton pumping in semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Miah, M. Idrish, E-mail: m.miah@griffith.edu.au [Queensland Micro- and Nanotechnology Centre, Griffith University, Nathan, Brisbane, QLD 4111 (Australia); Department of Physics, University of Chittagong, Chittagong 4331 (Bangladesh)

    2011-08-15

    Highlights: {yields} Multiphoton pumping and spin generation in semiconductors. {yields} Optical selection rules for inter-band transitions. {yields} Calculations of spin polarization using band-energy model and the second order perturbation theory. {yields} Enhancement of the electronic spin polarization. - Abstract: A pump-probe spectroscopic study has been carried out in zinc-blende bulk semiconductors. In the semiconductor samples, a spin-polarized carrier population is produced by the absorption of a monochromatic circularly polarized light beam with two-photon energy above the direct band gap in bulk semiconductors. The production of a carrier population with a net spin is a consequence of the optical selection rules for the heavy-hole and light-hole valence-to-conduction band transitions. This production is probed by the spin-dependent transmission of the samples in the time domain. The spin polarization of the conduction-band-electrons in dependences of delay of the probe beam as well as of pumping photon energy is estimated. The spin polarization is found to depolarize rapidly for pumping energy larger than the energy gap of the split-off band to the conduction band. From the polarization decays, the spin relaxation times are also estimated. Compared to one-photon pumping, the results, however, show that an enhancement of the spin-polarization is achieved by multiphoton excitation of the samples. The experimental results are compared with those obtained in calculations using second order perturbation theory of the spin transport model. A good agreement between experiment and theory is obtained. The observed results are discussed in details.

  7. An enhancement of spin polarization by multiphoton pumping in semiconductors

    International Nuclear Information System (INIS)

    Miah, M. Idrish

    2011-01-01

    Highlights: → Multiphoton pumping and spin generation in semiconductors. → Optical selection rules for inter-band transitions. → Calculations of spin polarization using band-energy model and the second order perturbation theory. → Enhancement of the electronic spin polarization. - Abstract: A pump-probe spectroscopic study has been carried out in zinc-blende bulk semiconductors. In the semiconductor samples, a spin-polarized carrier population is produced by the absorption of a monochromatic circularly polarized light beam with two-photon energy above the direct band gap in bulk semiconductors. The production of a carrier population with a net spin is a consequence of the optical selection rules for the heavy-hole and light-hole valence-to-conduction band transitions. This production is probed by the spin-dependent transmission of the samples in the time domain. The spin polarization of the conduction-band-electrons in dependences of delay of the probe beam as well as of pumping photon energy is estimated. The spin polarization is found to depolarize rapidly for pumping energy larger than the energy gap of the split-off band to the conduction band. From the polarization decays, the spin relaxation times are also estimated. Compared to one-photon pumping, the results, however, show that an enhancement of the spin-polarization is achieved by multiphoton excitation of the samples. The experimental results are compared with those obtained in calculations using second order perturbation theory of the spin transport model. A good agreement between experiment and theory is obtained. The observed results are discussed in details.

  8. Two-photon spin-polarization spectroscopy in silicon-doped GaAs.

    Science.gov (United States)

    Miah, M Idrish

    2009-05-14

    We generate spin-polarized electrons in bulk GaAs using circularly polarized two-photon pumping with excess photon energy (DeltaE) and detect them by probing the spin-dependent transmission of the sample. The spin polarization of conduction band electrons is measured and is found to be strongly dependent on DeltaE. The initial polarization, pumped with DeltaE=100 meV, at liquid helium temperature is estimated to be approximately 49.5%, which is very close to the theoretical value (50%) permitted by the optical selection rules governing transitions from heavy-hole and light-hole states to conduction band states in a bulk sample. However, the polarization pumped with larger DeltaE decreases rapidly because of the exciting carriers from the split-off band.

  9. Spin-wave propagation and spin-polarized electron transport in single-crystal iron films

    Science.gov (United States)

    Gladii, O.; Halley, D.; Henry, Y.; Bailleul, M.

    2017-11-01

    The techniques of propagating spin-wave spectroscopy and current-induced spin-wave Doppler shift are applied to a 20-nm-thick Fe/MgO(001) film. The magnetic parameters extracted from the position of the spin-wave resonance peaks are very close to those tabulated for bulk iron. From the zero-current propagating wave forms, a group velocity of 4 km/s and an attenuation length of about 6 μ m are extracted for 1.6-μ m -wavelength spin wave at 18 GHz. From the measured current-induced spin-wave Doppler shift, we extract a surprisingly high degree of spin polarization of the current of 83 % , which constitutes the main finding of this work. This set of results makes single-crystalline iron a promising candidate for building devices utilizing high-frequency spin waves and spin-polarized currents.

  10. Neutral Silicon-Vacancy Center in Diamond: Spin Polarization and Lifetimes

    Science.gov (United States)

    Green, B. L.; Mottishaw, S.; Breeze, B. G.; Edmonds, A. M.; D'Haenens-Johansson, U. F. S.; Doherty, M. W.; Williams, S. D.; Twitchen, D. J.; Newton, M. E.

    2017-09-01

    We demonstrate optical spin polarization of the neutrally charged silicon-vacancy defect in diamond (SiV0 ), an S =1 defect which emits with a zero-phonon line at 946 nm. The spin polarization is found to be most efficient under resonant excitation, but nonzero at below-resonant energies. We measure an ensemble spin coherence time T2>100 μ s at low-temperature, and a spin relaxation limit of T1>25 s . Optical spin-state initialization around 946 nm allows independent initialization of SiV0 and NV- within the same optically addressed volume, and SiV0 emits within the telecoms down-conversion band to 1550 nm: when combined with its high Debye-Waller factor, our initial results suggest that SiV0 is a promising candidate for a long-range quantum communication technology.

  11. Spin-polarized inelastic tunneling through insulating barriers.

    Science.gov (United States)

    Lu, Y; Tran, M; Jaffrès, H; Seneor, P; Deranlot, C; Petroff, F; George, J-M; Lépine, B; Ababou, S; Jézéquel, G

    2009-05-01

    Spin-conserving hopping transport through chains of localized states has been evidenced by taking benefit of the high degree of spin-polarization of CoFeB-MgO-CoFeB magnetic tunnel junctions. In particular, our data show that relatively thick MgO barriers doped with boron favor the activation of spin-conserving inelastic channels through a chain of three localized states and leading to reduced magnetoresistance effects. We propose an extension of the Glazman-Matveev theory to the case of ferromagnetic reservoirs to account for spin-polarized inelastic tunneling through nonmagnetic localized states embedded in an insulating barrier.

  12. Observation of interface dependent spin polarized photocurrents in InAs/GaSb superlattice

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yuan, E-mail: liyuan12@semi.ac.cn; Liu, Yu; Zhu, Laipan; Qin, Xudong; Wu, Qing; Huang, Wei; Chen, Yonghai, E-mail: yhchen@semi.ac.cn [Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, 100083 Beijing (China); Niu, Zhichuan; Xiang, Wei; Hao, Hongyue [The State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, 100083 Beijing (China)

    2015-05-11

    In this letter, we investigated the spin polarized photocurrents excited by mid-infrared radiation and near-infrared radiation, respectively, in InAs/GaSb type II superlattices with different kinds of interfaces. By periodically varying the polarization state of the radiation, we analyzed Rashba-type and Dresselhaus-type spin polarized photocurrents, which present different features depending on the interface types and excitation conditions. Under mid-infrared excitation, the ratio of Rashba-type and Dresselhaus-type spin polarized photocurrents of the superlattice with InSb-like interface is obviously larger than that of the superlattice with GaAs-like interface, the ratio of the superlattice with alternate interface is in the middle. Whereas under near-infrared excitation, the ratios of the three superlattices are nearly the same. Further researches reveal the synactic effects of interface dependent strain and asymmetric interface potential on the spin splitting. Besides, the polarized Raman spectroscopies of these structures were also analyzed.

  13. Observation of interface dependent spin polarized photocurrents in InAs/GaSb superlattice

    International Nuclear Information System (INIS)

    Li, Yuan; Liu, Yu; Zhu, Laipan; Qin, Xudong; Wu, Qing; Huang, Wei; Chen, Yonghai; Niu, Zhichuan; Xiang, Wei; Hao, Hongyue

    2015-01-01

    In this letter, we investigated the spin polarized photocurrents excited by mid-infrared radiation and near-infrared radiation, respectively, in InAs/GaSb type II superlattices with different kinds of interfaces. By periodically varying the polarization state of the radiation, we analyzed Rashba-type and Dresselhaus-type spin polarized photocurrents, which present different features depending on the interface types and excitation conditions. Under mid-infrared excitation, the ratio of Rashba-type and Dresselhaus-type spin polarized photocurrents of the superlattice with InSb-like interface is obviously larger than that of the superlattice with GaAs-like interface, the ratio of the superlattice with alternate interface is in the middle. Whereas under near-infrared excitation, the ratios of the three superlattices are nearly the same. Further researches reveal the synactic effects of interface dependent strain and asymmetric interface potential on the spin splitting. Besides, the polarized Raman spectroscopies of these structures were also analyzed

  14. Recent advances in atomic-scale spin-polarized scanning tunneling microscopy.

    Science.gov (United States)

    Smith, Arthur R; Yang, Rong; Yang, Haiqiang; Dick, Alexey; Neugebauer, Joerg; Lambrecht, Walter R L

    2005-02-01

    The Mn3N2 (010) surface has been studied using spin-polarized scanning tunneling microscopy at the atomic scale. The principle objective of this work is to elucidate the properties and potential of this technique to measure atomic-scale magnetic structures. The experimental approach involves the use of a combined molecular beam epitaxy/scanning tunneling microscopy system that allows the study of atomically clean magnetic surfaces. Several key findings have been obtained. First, both magnetic and non-magnetic atomic-scale information has been obtained in a single spin-polarized image. Magnetic modulation of the height profile having an antiferromagnetic super-period of c = 12.14 A (6 atomic rows) together with a non-magnetic superstructure having a period of c/2 = 6.07 A (3 atomic rows) was observed. Methods of separation of magnetic and non-magnetic profiles are presented. Second, bias voltage-dependent spin-polarized images show a reversal of the magnetic modulation at a particular voltage. This reversal is clearly due to a change in the sign of the magnetic term in the tunnel current. Since this term depends on both the tip's as well as the sample's magnetic local density of states, the reversal can be caused by either the sample or the tip. Third, the shape of the line profile was found to vary with the bias voltage, which is related to the energy-dependent spin contribution from the 2 chemically inequivalent Mn sites on the surface. Overall, the results shown here expand the application of the method of spin-polarized scanning tunneling microscopy to measure atomic-scale magnetic structures. (c) 2005 Wiley-Liss, Inc.

  15. Current-induced spin polarization in a spin-polarized two-dimensional electron gas with spin-orbit coupling

    International Nuclear Information System (INIS)

    Wang, C.M.; Pang, M.Q.; Liu, S.Y.; Lei, X.L.

    2010-01-01

    The current-induced spin polarization (CISP) is investigated in a combined Rashba-Dresselhaus spin-orbit-coupled two-dimensional electron gas, subjected to a homogeneous out-of-plane magnetization. It is found that, in addition to the usual collision-related in-plane parts of CISP, there are two impurity-density-free contributions, arising from intrinsic and disorder-mediated mechanisms. The intrinsic parts of spin polarization are related to the Berry curvature, analogous with the anomalous and spin Hall effects. For short-range collision, the disorder-mediated spin polarizations completely cancel the intrinsic ones and the total in-plane components of CISP equal those for systems without magnetization. However, for remote disorders, this cancellation does not occur and the total in-plane components of CISP strongly depend on the spin-orbit interaction coefficients and magnetization for both pure Rashba and combined Rashba-Dresselhaus models.

  16. Electron spin injection from a regrown Fe layer in a spin-polarized vertical-cavity surface-emitting laser

    Science.gov (United States)

    Holub, M.; Bhattacharya, P.; Shin, J.; Saha, D.

    2007-04-01

    An electroluminescence circular polarization of 23% and threshold current reduction of 11% are obtained in an electrically pumped spin-polarized vertical-cavity surface-emitting laser. Electron spin injection is accomplished utilizing a regrown Fe/ n-AlGaAs Schottky tunnel barrier deposited around the base of the laser mesas. Negligible circular polarizations and threshold current reductions are measured for nonmagnetic and Fe-based control VCSELs, which provides convincing evidence of spin injection, transport, and detection in our spin-polarized laser.

  17. High-frequency dynamics of spin-polarized carriers and photons in a laser

    Science.gov (United States)

    Saha, D.; Basu, D.; Bhattacharya, P.

    2010-11-01

    The high-frequency dynamics of spin-polarized carriers and photons in a spin laser have been studied. The transient response of the device obtained from the rate equations is characterized by two sets of relaxation oscillations in the carrier and photon distributions corresponding to the two polarization modes. Consequently two distinct resonant peaks are observed in the small-signal modulation response. The calculated transient characteristics indicate that the best results are obtained from a spin laser when only the favored polarization mode, with lower threshold, is operational. Under this condition the small-signal modulation bandwidth is higher than that in a conventional laser, the threshold current is lower and the output polarization can be 100% with appropriate bias conditions, independent of the spin polarization of carriers in the active region. Measurements were made at 230 K on a InAs/GaAs quantum dot spin vertical cavity surface emitting laser. A time-averaged output polarization of 55% is measured with an active region spin polarization of 5-6% . The experimental results are in good agreement with calculated data.

  18. Spin-polarized scanning tunneling microscopy and spectroscopy study of chromium on a Cr(001) surface.

    Science.gov (United States)

    Lagoute, J; Kawahara, S L; Chacon, C; Repain, V; Girard, Y; Rousset, S

    2011-02-02

    Several tens of chromium layers were deposited at 250 °C on a Cr(001) surface and investigated by spin-polarized scanning tunneling microscopy (SP-STM), Auger electron spectroscopy (AES) and scanning tunneling spectroscopy (STS). Chromium is found to grow with a mound-like morphology resulting from the stacking of several monolayers which do not uniformly cover the whole surface of the substrate. The terminal plane consists of an irregular array of Cr islands with lateral sizes smaller than 20 × 20 nm(2). Combined AES and STS measurements reveal the presence of a significant amount of segregants prior to and after deposition. A detailed investigation of the surface shows that it consists of two types of patches. Thanks to STS measurements, the two types of area have been identified as being either chromium pure or segregant rich. SP-STM experiments have evidenced that the antiferromagnetic layer coupling remains in the chromium mounds after deposition and is not significantly affected by the presence of the segregants.

  19. Fabrication of highly spin-polarized Co2FeAl0.5Si0.5 thin-films

    Directory of Open Access Journals (Sweden)

    M. Vahidi

    2014-04-01

    Full Text Available Ferromagnetic Heusler Co2FeAl0.5Si0.5 epitaxial thin-films have been fabricated in the L21 structure with saturation magnetizations over 1200 emu/cm3. Andreev reflection measurements show that the spin polarization is as high as 80% in samples sputtered on unheated MgO (100 substrates and annealed at high temperatures. However, the spin polarization is considerably smaller in samples deposited on heated substrates.

  20. Observation of the spin-polarized surface state in a noncentrosymmetric superconductor BiPd.

    Science.gov (United States)

    Neupane, Madhab; Alidoust, Nasser; Hosen, M Mofazzel; Zhu, Jian-Xin; Dimitri, Klauss; Xu, Su-Yang; Dhakal, Nagendra; Sankar, Raman; Belopolski, Ilya; Sanchez, Daniel S; Chang, Tay-Rong; Jeng, Horng-Tay; Miyamoto, Koji; Okuda, Taichi; Lin, Hsin; Bansil, Arun; Kaczorowski, Dariusz; Chou, Fangcheng; Hasan, M Zahid; Durakiewicz, Tomasz

    2016-11-07

    Recently, noncentrosymmetric superconductor BiPd has attracted considerable research interest due to the possibility of hosting topological superconductivity. Here we report a systematic high-resolution angle-resolved photoemission spectroscopy (ARPES) and spin-resolved ARPES study of the normal state electronic and spin properties of BiPd. Our experimental results show the presence of a surface state at higher-binding energy with the location of Dirac point at around 700 meV below the Fermi level. The detailed photon energy, temperature-dependent and spin-resolved ARPES measurements complemented by our first-principles calculations demonstrate the existence of the spin-polarized surface states at high-binding energy. The absence of such spin-polarized surface states near the Fermi level negates the possibility of a topological superconducting behaviour on the surface. Our direct experimental observation of spin-polarized surface states in BiPd provides critical information that will guide the future search for topological superconductivity in noncentrosymmetric materials.

  1. Investigation of Current Induced Spin Polarization in III-V Semiconductor Epilayers

    Science.gov (United States)

    Luengo-Kovac, Marta

    In the development of a semiconductor spintronics device, a thorough understanding of spin dynamics in semiconductors is necessary. In particular, electrical control of electron spins is advantageous for its compatibility with present day electronics. In this thesis, we will discuss the electrical modification of the electron g-factor, which characterizes the strength of the interaction between a spin and a magnetic field, as well as investigate electrically generated spin polarizations as a function of various material parameters. We report on the modification of the electron g-factor by an in-plane electric field in an InGaAs epilayer. We performed external magnetic field scans of the Kerr rotation of the InGaAs film in order to measure the g-factor independently of the spin-orbit fields. The g-factor increases from -0.4473(0.0001) at 0 V/cm to -0.4419( 0.0001) at 50 V/cm applied along the [110] crystal axis. A comparison of temperature and voltage dependent photoluminescence measurements indicate that minimal channel heating occurs at these voltages. Possible explanations for this g-factor modification are discussed, including an increase in the electron temperature that is independent of the lattice temperature and the modification of the donor-bound electron wave function by the electric field. The current-induced spin polarization and momentum-dependent spin-orbit field were measured in InGaAs epilayers with varying indium concentrations and silicon doping densities. Samples with higher indium concentrations and carrier concentrations and lower mobilities were found to have larger electrical spin generation efficiencies. Furthermore, current-induced spin polarization was detected in GaAs epilayers despite the absence of measurable spin-orbit fields, indicating that the spin polarization mechanism is extrinsic. Temperature-dependent measurements of the spin dephasing rates and mobilities were used to characterize the relative strengths of the intrinsic D

  2. Spin-polarized tunneling through a ferromagnetic insulator

    NARCIS (Netherlands)

    Kok, M.; Kok, M.; Beukers, J.N.; Brinkman, Alexander

    2009-01-01

    The polarization of the tunnel conductance of spin-selective ferromagnetic insulators is modeled, providing a generalized concept of polarization including both the effects of electrode and barrier polarization. The polarization model is extended to take additional non-spin-polarizing insulating

  3. Spin-polarized current generated by magneto-electrical gating

    International Nuclear Information System (INIS)

    Ma Minjie; Jalil, Mansoor Bin Abdul; Tan, Seng Ghee

    2012-01-01

    We theoretically study spin-polarized current through a single electron tunneling transistor (SETT), in which a quantum dot (QD) is coupled to non-magnetic source and drain electrodes via tunnel junctions, and gated by a ferromagnetic (FM) electrode. The I–V characteristics of the device are investigated for both spin and charge currents, based on the non-equilibrium Green's function formalism. The FM electrode generates a magnetic field, which causes a Zeeman spin-splitting of the energy levels in the QD. By tuning the size of the Zeeman splitting and the source–drain bias, a fully spin-polarized current is generated. Additionally, by modulating the electrical gate bias, one can effect a complete switch of the polarization of the tunneling current from spin-up to spin-down current, or vice versa. - Highlights: ► The spin polarized transport through a single electron tunneling transistor is systematically studied. ► The study is based on Keldysh non-equilibrium Green's function and equation of motion method. ► A fully spin polarized current is observed. ► We propose to reverse current polarization by the means of gate voltage modulation. ► This device can be used as a bi-polarization current generator.

  4. Spin-Polarized Semiconductor Induced by Magnetic Impurities in Graphene

    OpenAIRE

    Daghofer, Maria; Zheng, Nan; Moreo, Adriana

    2010-01-01

    Magnetic impurities adsorbed on graphene are coupled magnetically via the itinerant electrons. This interaction opens a gap in the band structure of graphene. The result strongly depends on how the magnetic impurities are distributed. While random doping produces a semiconductor, if all or most impurities are located in the same sublattice, the spin degeneracy is removed and a spin-polarized semiconductor arises.

  5. Experiment on the melting pressure of spin polarized He3

    DEFF Research Database (Denmark)

    Chapellier, M.; Olsen, M.; Rasmussen, Finn Berg

    1981-01-01

    In liquid He in a Pomeranchuk cell, the melting curve has been observed to be suppressed, presumably in regions with a strong local spin polarization. In the temperature range 30-50 mK the observed suppression was 60-80 kPa. The corresponding local polarization is estimated, in a crude model, to ...

  6. Spin-polarized light-emitting diodes based on organic bipolar spin valves

    Energy Technology Data Exchange (ETDEWEB)

    Vardeny, Zeev Valentine; Nguyen, Tho Duc; Ehrenfreund, Eitan Avraham

    2017-10-25

    Spin-polarized organic light-emitting diodes are provided. Such spin-polarized organic light-emitting diodes incorporate ferromagnetic electrodes and show considerable spin-valve magneto-electroluminescence and magneto-conductivity responses, with voltage and temperature dependencies that originate from the bipolar spin-polarized space charge limited current.

  7. Universal spin-polarization fluctuations in one-dimensional wires with magnetic impurities

    DEFF Research Database (Denmark)

    Mortensen, Asger; Egues, J.C.

    2002-01-01

    -flip suppresses conductance fluctuations while enhancing spin-polarization fluctuations. More importantly, spin-polarization fluctuations attain a universal value 1/3 for large enough spin-flip strengths. This intrinsic spin-polarization fluctuation may pose a severe limiting factor to the realization of steady...

  8. Effect of spin polarization on the structural properties and bond ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 39; Issue 6. Effect of spin ... Volume 39 Issue 6 October 2016 pp 1427-1434 ... Spin-polarization calculations show that ferromagnetic state (FM) is stable for FexB structures and carry magnetic moment of 1.12, 1.83 and 2.03 μ B inFeB, Fe 2 B and Fe 3 B, respectively.

  9. Observation of nuclear spin waves in spin-polarized atomic hydrogen gas

    Energy Technology Data Exchange (ETDEWEB)

    Johson, B.R.; Denker, J.S.; Bigelow, N.; Levy, L.P.; Freed, J.H.; Lee, D.M.

    1984-04-23

    We have observed narrow, distinct resonances in the NMR spectrum of dilute spin-polarized atomic hydrogen gas (nroughly-equal10/sup 16/ atoms/cm/sup 3/). The dependence of the observed spectra on temperature, density, polarization, and magnetic field gradient is consistent with theoretical predictions for spin-wave excitations damped by diffusion. We have measured the parameter ..mu.., which is a measure of the importance of exchange effects in spin transport processes, and the diffusion coefficient D/sub 0/, both of which are in reasonable agreement with theory.

  10. Photoinduced spin polarization and microwave technology

    International Nuclear Information System (INIS)

    Antipov, Sergey; Poluektov, Oleg; Schoessow, Paul; Kanareykin, Alexei; Jing, Chunguang

    2013-01-01

    We report here on studies of optically pumped active microwave media based on various fullerene derivatives, with an emphasis on the use of these materials in microwave electronics. We have investigated a class of optically excited paramagnetic materials that demonstrate activity in the X-band as candidate materials. We found that a particular fullerene derivative, Phenyl-C 61 -butyric acid methyl ester (PCBM), produced the largest electron paramagnetic resonance (EPR) emission signal compared to other organic compounds that have been suggested for use as microwave active materials. We also studied the effects of concentration, temperature, solvent etc. on the activity of the material. In these experiments, EPR studies using a commercial spectrometer were followed up by measurements of an RF signal reflected from a resonator loaded with the PCBM-based material. The activity was directly demonstrated through the change in the quality factor and RF coupling between the resonator and waveguide feed. At the inception of these experiments the primary interest was the development of a microwave PASER. The PASER (particle acceleration by stimulated emission of radiation [1]) is a novel acceleration concept that is based on the direct energy transfer from an active medium to a charged particle beam. While the previous work on the PASER has emphasized operations at infrared or visible wavelengths, operating in the microwave regime has significant advantages in terms of the less stringent quality requirements placed on the electron beam provided an appropriate microwave active medium can be found. This paper is focused on our investigation of the possibility of a PASER operating in the microwave frequency regime [2] using active paramagnetic materials. While a high level of gain for PCBM was demonstrated compared to other candidate materials, dielectric losses and quenching effects were found to negatively impact its performance for PASER applications. We present results on

  11. Direct observation of hopping induced spin polarization current in oxygen deficient Co-doped ZnO by Andreev reflection technique

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Kung-Shang; Huang, Tzu-Yu; Dwivedi, G.D. [Department of Physics, National Sun Yat-sen University, Kaohsiung, Taiwan (China); Lin, Lu-Kuei; Lee, Shang-Fan [Taiwan Institute of Physics, Academia Sinica, Taipei, Taiwan (China); Sun, Shih-Jye [Department of Applied Physics, National Kaohsiung University, Kaohsiung, Taiwan (China); Chou, Hsiung, E-mail: hchou@mail.nsysu.edu.tw [Department of Physics, National Sun Yat-sen University, Kaohsiung, Taiwan (China)

    2017-07-01

    Highlights: • Co-doped ZnO thin-films were grown with varying V{sub O} concentartion. • PCAR measurements were done to study the SPC. • High spin polarization was observed above a certain V{sub O} concentartion. • High V{sub O} samples provide a high density of completed percolation path. • This complete percolation path gives rise to high SPC. - Abstract: Oxygen vacancy induced ferromagnetic coupling in diluted magnetic oxide (DMO) semiconductors have been reported in several studies, but technologically more crucial spin-polarized current (SPC) is still under-developed in DMOs. Few studies have claimed that VRH mechanism can originate the SPC, but, how VRH mechanism associated with percolation path, is not clearly understood. We used Point-contact Andreev reflection (PCAR) technique to probe the SPC in Co-doped ZnO (CZO) films. Since the high resistance samples cause broadening in conductance(G)-voltage(V) curves, which may result in an unreliable evaluation of spin polarization, we include two extra parameters, (i) effective temperature and (ii) spreading resistance, for the simulation to avoid the uncertainty in extracting spin polarization. The effective G-V curves and higher spin polarization can be obtained above a certain oxygen vacancy concentration. The number of completed and fragmentary percolation paths is proportional to the concentration of oxygen vacancies. For low oxygen vacancy samples, the Pb-tip has a higher probability of covering fragmentary percolation paths than the complete ones, due to its small contact size. The completed paths may remain independent of one another and get polarized in different directions, resulting in lower spin-polarization value. High oxygen vacancy samples provide a high density of completed path, most of them link to one another by crossing over, and gives rise to high spin-polarization value.

  12. Spin-polarized quasi-one-dimensional state with finite band gap on the Bi/InSb(001) surface

    Science.gov (United States)

    Kishi, J.; Ohtsubo, Y.; Nakamura, T.; Yaji, K.; Harasawa, A.; Komori, F.; Shin, S.; Rault, J. E.; Le Fèvre, P.; Bertran, F.; Taleb-Ibrahimi, A.; Nurmamat, M.; Yamane, H.; Ideta, S.; Tanaka, K.; Kimura, S.

    2017-11-01

    One-dimensional (1D) electronic states were discovered on the 1D surface atomic structure of Bi fabricated on semiconductor InSb(001) substrates by angle-resolved photoelectron spectroscopy (ARPES). The 1D state showed steep, Dirac-cone-like dispersion along the 1D atomic structure with a finite direct band gap opening as large as 150 meV. Moreover, spin-resolved ARPES revealed the spin polarization of the 1D unoccupied states as well as that of the occupied states, the orientation of which inverted depending on the wave-vector direction parallel to the 1D array on the surface. These results reveal that a spin-polarized quasi-1D carrier was realized on the surface of 1D Bi with highly efficient backscattering suppression, showing promise for use in future spintronics and energy-saving devices.

  13. Spin-polarization of an electro-static positron beam

    International Nuclear Information System (INIS)

    Kawasuso, A.; Maekawa, M.

    2008-01-01

    We constructed an electro-static positron beam apparatus. We fabricated a simple spin-polarimeter composed of a permanent magnet with a surface magnetic field of 0.65 T and an iron pole piece. The longitudinal spin-polarization of the positron beam was determined to be 0.3 by analyzing the magnetic field dependence of the Doppler broadening of annihilation radiation from a fused silica specimen. The effect of spin rotation was examined using an iron poly-crystal and a simple E x B filter

  14. Electron-Spin Filters Would Offer Spin Polarization Greater than 1

    Science.gov (United States)

    Ting, David Z.

    2009-01-01

    A proposal has been made to develop devices that would generate spin-polarized electron currents characterized by polarization ratios having magnitudes in excess of 1. Heretofore, such devices (denoted, variously, as spin injectors, spin polarizers, and spin filters) have typically offered polarization ratios having magnitudes in the approximate range of 0.01 to 0.1. The proposed devices could be useful as efficient sources of spin-polarized electron currents for research on spintronics and development of practical spintronic devices.

  15. Joule heating and spin-transfer torque investigated on the atomic scale using a spin-polarized scanning tunneling microscope.

    Science.gov (United States)

    Krause, S; Herzog, G; Schlenhoff, A; Sonntag, A; Wiesendanger, R

    2011-10-28

    The influence of a high spin-polarized tunnel current onto the switching behavior of a superparamagnetic nanoisland on a nonmagnetic substrate is investigated by means of spin-polarized scanning tunneling microscopy. A detailed lifetime analysis allows for a quantification of the effective temperature rise of the nanoisland and the modification of the activation energy barrier for magnetization reversal, thereby using the nanoisland as a local thermometer and spin-transfer torque analyzer. Both the Joule heating and spin-transfer torque are found to scale linearly with the tunnel current. The results are compared to experiments performed on lithographically fabricated magneto-tunnel junctions, revealing a very high spin-transfer torque switching efficiency in our experiments.

  16. Effect of Orbital Hybridization on Spin-Polarized Tunneling across Co/C60 Interfaces.

    Science.gov (United States)

    Wang, Kai; Strambini, Elia; Sanderink, Johnny G M; Bolhuis, Thijs; van der Wiel, Wilfred G; de Jong, Michel P

    2016-10-26

    The interaction between ferromagnetic surfaces and organic semiconductors leads to the formation of hybrid interfacial states. As a consequence, the local magnetic moment is altered, a hybrid interfacial density of states (DOS) is formed, and spin-dependent shifts of energy levels occur. Here, we show that this hybridization affects spin transport across the interface significantly. We report spin-dependent electronic transport measurements for tunnel junctions comprising C 60 molecular thin films grown on top of face-centered-cubic (fcc) epitaxial Co electrodes, an AlO x tunnel barrier, and an Al counter electrode. Since only one ferromagnetic electrode (Co) is present, spin-polarized transport is due to tunneling anisotropic magnetoresistance (TAMR). An in-plane TAMR ratio of approximately 0.7% has been measured at 5 K under application of a magnetic field of 800 mT. The magnetic switching behavior shows some remarkable features, which are attributed to the rotation of interfacial magnetic moments. This behavior can be ascribed to the magnetic coupling between the Co thin films and the newly formed Co/C 60 hybridized interfacial states. Using the Tedrow-Meservey technique, the tunnel spin polarization of the Co/C 60 interface was found to be 43%.

  17. Construction and characterization of a spin polarized helium ion beam for surface electronic structure studies

    International Nuclear Information System (INIS)

    Harrison, A.R.

    1982-01-01

    Ion neutralization and metastable de-excitation spectroscopy, INS and MDS, allow detailed analysis of the surface electronic configuration of metals. The orthodox application of these spectroscopies may be enhanced by electronic spin polarization of the probe beams. For this reason, a spin polarized helium ion beam has been constructed. The electronic spin of helium metastables created within an rf discharge may be spacially aligned by optically pumping the atoms. Subsequent collisions between metastables produce helium ions which retain the orientation of the electronic spin. Extracted ion polarization, although not directly measurable, may be estimated from extracted electron polarization, metastable polarization, pumping radiation absorption and current modulation measurements. Ions extracted from the optically pumped discharge exhibit an estimated polarization of about ten per cent at a beam current of a few tenths of a microampere. Extraction of helium ions from the discharge requires that the ions have a high kinetic energy. However, to avoid undesirable kinetic electron ejection from the target surface, the ions must be decelerated. Examination of various deceleration configurations, in paticular exponential and linear deceleration fields, and experimental observation indicate that a linear decelerating field produces the best low energy beam to the target surface

  18. Interplay between spin polarization and color superconductivity in high density quark matter

    DEFF Research Database (Denmark)

    Tsue, Yasuhiko; da Providência, João; Providência, Constança

    2013-01-01

    Here, it is suggested that a four-point interaction of the tensor type may lead to spin polarization in quark matter at high density. It is found that the two-flavor superconducting phase and the spin polarized phase correspond to distinct local minima of a certain generalized thermodynamical...... potential. It follows that a transition from one to the other phase occurs, passing through true minima with both a spin polarization and a color superconducting gap. It is shown that the quark spin polarized phase is realized at rather high density, while the two-flavor color superconducting phase...

  19. RKKY interaction for the spin-polarized electron gas

    Science.gov (United States)

    Valizadeh, Mohammad M.; Satpathy, Sashi

    2015-11-01

    We extend the original work of Ruderman, Kittel, Kasuya and Yosida (RKKY) on the interaction between two magnetic moments embedded in an electron gas to the case where the electron gas is spin-polarized. The broken symmetry of a host material introduces the Dzyaloshinsky-Moriya (DM) vector and tensor interaction terms, in addition to the standard RKKY term, so that the net interaction energy has the form ℋ = JS1 ṡS2 + D ṡS1 ×S2 + S1 ṡΓ ↔ṡS2. We find that for the spin-polarized electron gas, a nonzero tensor interaction Γ ↔ is present in addition to the scalar RKKY interaction J, while D is zero due to the presence of inversion symmetry. Explicit expressions for these are derived for the electron gas both in 2D and 3D and we show that the net magnetic interaction can be expressed as a sum of Heisenberg and Ising like terms. The RKKY interaction exhibits a beating pattern, caused by the presence of the two Fermi momenta kF↑ and kF↓, while the R-3 distance dependence of the original RKKY result for the 3D electron gas is retained. This model serves as a simple example of the magnetic interaction in systems with broken symmetry, which goes beyond the RKKY interaction.

  20. The impact of structural relaxation on spin polarization and magnetization reversal of individual nano structures studied by spin-polarized scanning tunneling microscopy.

    Science.gov (United States)

    Sander, Dirk; Phark, Soo-Hyon; Corbetta, Marco; Fischer, Jeison A; Oka, Hirofumi; Kirschner, Jürgen

    2014-10-01

    The application of low temperature spin-polarized scanning tunneling microscopy and spectroscopy in magnetic fields for the quantitative characterization of spin polarization, magnetization reversal and magnetic anisotropy of individual nano structures is reviewed. We find that structural relaxation, spin polarization and magnetic anisotropy vary on the nm scale near the border of a bilayer Co island on Cu(1 1 1). This relaxation is lifted by perimetric decoration with Fe. We discuss the role of spatial variations of the spin-dependent electronic properties within and at the edge of a single nano structure for its magnetic properties.

  1. Fabrication of highly spin-polarized Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} thin-films

    Energy Technology Data Exchange (ETDEWEB)

    Vahidi, M.; Zhang, S. K.; Yu, L.; Huang, M.; Newman, N., E-mail: Nathan.Newman@asu.edu [School of Materials, Arizona State University, Tempe, Arizona 85287-8706 (United States); Gifford, J. A.; Chen, T. Y. [Department of Physics, Arizona State University, Tempe, Arizona 85287 (United States); Krishnamurthy, S.; Yu, Z. G. [SRI International, 301-64, Menlo Park, California 94025 (United States); Youngbull, C. [The Biodesign Institute, Arizona State University, Tempe, Arizona 85287 (United States)

    2014-04-01

    Ferromagnetic Heusler Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} epitaxial thin-films have been fabricated in the L2{sub 1} structure with saturation magnetizations over 1200 emu/cm{sup 3}. Andreev reflection measurements show that the spin polarization is as high as 80% in samples sputtered on unheated MgO (100) substrates and annealed at high temperatures. However, the spin polarization is considerably smaller in samples deposited on heated substrates.

  2. Spin-polarization dependent carrier recombination dynamics and spin relaxation mechanism in asymmetrically doped (110) n-GaAs quantum wells

    Science.gov (United States)

    Teng, Lihua; Jiang, Tianran; Wang, Xia; Lai, Tianshu

    2018-05-01

    Carrier recombination and electron spin relaxation dynamics in asymmetric n-doped (110) GaAs/AlGaAs quantum wells are investigated with time-resolved pump-probe spectroscopy. The experiment results reveal that the measured carrier recombination time depends strongly on the polarization of pump pulse. With the same pump photon flux densities, the recombination time of spin-polarized carriers is always longer than that of the spin-balanced carriers except at low pump photon flux densities, this anomaly originates from the polarization-sensitive nonlinear absorption effect. Differing from the traditional views, in the low carrier density regime, the D'yakonov-Perel' (DP) mechanism can be more important than the Bir-Aronov-Pikus (BAP) mechanism, since the DP mechanism takes effect, the spin relaxation time in (110) GaAs QWs is shortened obviously via asymmetric doping.

  3. Resonant tunneling via spin-polarized barrier states in a magnetic tunnel junction

    NARCIS (Netherlands)

    Jansen, R.; Lodder, J.C.

    2000-01-01

    Resonant tunneling through states in the barrier of a magnetic tunnel junction has been analyzed theoretically for the case of a spin-polarized density of barrier states. It is shown that for highly spin-polarized barrier states, the magnetoresistance due to resonant tunneling is enhanced compared

  4. Direct injection of spin-polarized carriers across YBa 2 Cu 3 O 7- ...

    Indian Academy of Sciences (India)

    Home; Journals; Pramana – Journal of Physics; Volume 58; Issue 5-6. Direct injection of spin-polarized ... from the CMR layer is 38 mA. This clearly shows that spin-polarized quasiparticles injected from the CMR layer into the YBCO layer suppress the critical current of the superconductor via the pair-breaking phenomena.

  5. Laser driven source of spin polarized atomic deuterium and hydrogen

    International Nuclear Information System (INIS)

    Poelker, M.; Coulter, K.P.; Holt, R.J.

    1993-01-01

    Optical pumping of potassium atoms in the presence of a high magnetic field followed by spin exchange collisions with deuterium (hydrogen) is shown to yield a high flux of spin polarized atomic deuterium (hydrogen). The performance of the laser driven source has been characterized as a function of deuterium (hydrogen) flow rate, potassium density, pump laser power, and magnetic field. Under appropriate conditions, the authors have observed deuterium atomic polarization as high as 75% at a flow rate 4.2x10 17 atoms/second. Preliminary results suggest that high nuclear polarizations are obtained in the absence of weak field rf transitions as a result of a spin temperature distribution that evolves through frequent H-H (D-D) collisions

  6. Microscopic theory of fully spin-polarized /sup 3/He

    Energy Technology Data Exchange (ETDEWEB)

    Glyde, H.R.; Hernadi, S.I.

    1983-01-01

    The ground state energy (E), Landau parameters (F) and single particle energy spectrum (epsilon(kappa) and m/sup */) in fully spin polarized liquid /sup 3/He (/sup 3/He) are calculated directly from the bare interatomic potential within the Galitskii-Feynmann T-matrix and Hartree-Fock (GFHF) approximations. The E agrees well with variational calculations, the F with model calculations and the epsilon(kappa) and m/sup */ with results expected from nuclear matter. This suggests the effective interaction in /sup 3/He is dominated by hard core repulsion and Fermi statistics and that these components of the full interaction can be well described from first principles by a GF T-matrix. 36 references, 3 figures, 1 table.

  7. Induced spin polarization effect in graphene by ferromagnetic nanocontact

    Energy Technology Data Exchange (ETDEWEB)

    Mandal, Sumit; Saha, Shyamal K., E-mail: cnssks@iacs.res.in [Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India)

    2015-03-07

    Chemically synthesized graphene contains large number of defects which act as localized spin moments at the defect sites. Cobalt nanosheets of variable thickness are grown on graphene surface to investigate spin/magnetotransport through graphene sheets containing large number of localized spins. Negative magnetoresistance (MR) is observed over the entire temperature range (5–300 K) for thin cobalt sheets, while a cross-over from negative to positive MR with increasing temperature is noticed for thicker cobalt sheets. The observed MR results are explained on the basis of recently reported spin polarization effect in graphene due to the presence of ferromagnetic atoms on the surface considering a spin valve like Co/graphene/Co nanostructures.

  8. Optically pumped electron spin polarized targets for use in the production of polarized ion beams

    International Nuclear Information System (INIS)

    Anderson, L.W.

    1979-01-01

    The production of relatively dense electron spin polarized alkali metal vapor targets by optical pumping with intense cw dye lasers is discussed. The target density and electron spin polarization depend on the dye laser intensity and bandwidth, the magnetic field at the target, and the electron spin depolarization time. For example in a magnetic field of 1.5 x 10 3 G, and using 1 W dye laser with a bandwidth of 10 10 Hz one can construct an electron spin polarized Na vapor target with a target thickness of 1.6 x 10 13 atoms/cm 2 and an average electron spin polarization of about 90% even though the Na atoms are completely depolarized at every wall collision. Possible uses of the electron spin polarized targets for the production of intense beams of polarized H - or 3 He - ions are discussed. (orig.)

  9. Electron ionization and spin polarization control of Fe atom adsorbed graphene irradiated by a femtosecond laser

    International Nuclear Information System (INIS)

    Yu, Dong; Jiang, Lan; Wang, Feng; Li, Xin; Qu, Liangti; Lu, Yongfeng

    2015-01-01

    We investigate the structural properties and ionized spin electrons of an Fe–graphene system, in which the time-dependent density functional theory (TDDFT) within the generalized gradient approximation is used. The electron dynamics, including electron ionization and ionized electron spin polarization, is described for Fe atom adsorbed graphene under femtosecond laser irradiation. The theoretical results show that the electron ionization and ionized electron spin polarization are sensitive to the laser parameters, such as the incident angle and the peak intensity. The spin polarization presents the maximum value under certain laser parameters, which may be used as a source of spin-polarized electrons. - Highlights: • The structural properties of Fe–graphene system are investigated. • The electron dynamics of Fe–graphene system under laser irradiation are described. • The Fe–graphene system may be used as a source of spin-polarized electrons

  10. Dirac cone with helical spin polarization in ultrathin α-Sn(001) films.

    Science.gov (United States)

    Ohtsubo, Yoshiyuki; Le Fèvre, Patrick; Bertran, François; Taleb-Ibrahimi, Amina

    2013-11-22

    Spin-split two-dimensional electronic states have been observed on ultrathin Sn(001) films grown on InSb(001) substrates. Angle-resolved photoelectron spectroscopy (ARPES) performed on these films revealed Dirac-cone-like linear dispersion around the Γ¯ point of the surface Brillouin zone, suggesting nearly massless electrons belonging to 2D surface states. The states disperse across a band gap between bulklike quantum well states in the films. Moreover, both circular dichroism of ARPES and spin-resolved ARPES studies show helical spin polarization of the Dirac-cone-like surface states, suggesting a topologically protected character as in a bulk topological insulator (TI). These results indicate that a quasi-3D TI phase can be realized in ultrathin films of zero-gap semiconductors.

  11. Observation of radiative spin-polarization at 60.6 GeV

    CERN Document Server

    Assmann, R W; Hildreth, M D; Matheson, J; Mugnai, G; Placidi, Massimo; Roncarolo, F; Torrence, E; Sonnemann, F; Uythoven, J; Wenninger, J; Blondel, A

    1999-01-01

    Radiative spin-polarization has been used extensively at LEP to accurately measure the beam energy around the Z resonance. As the LEP physics has moved on to the W boson the calibration based on polarization must be extended towards higher beam energies. This is difficult as the depolarizing effects of spin resonances grow rapidly with beam energy. At LEP it has been possible for the first time to measure transverse beam polarization at 60.6 GeV. To allow a build-up of polarization the tunes and the energy were chosen accurately. A low phase advance optics was used and careful orbit correction was carried out using dynamic beam based alignment data. Harmonic spin matching was applied both in a deterministic and a novel semi- empirical way. (11 refs).

  12. Coexistence of antiferromagnetism and spin polarization in double perovskite SrLaVMoO6

    International Nuclear Information System (INIS)

    Asano, H; Gotoh, H; Matsushima, H; Takeda, Y; Zhong, J; Rajanikanth, A; Hono, K

    2010-01-01

    The magnetic and transport properties of SrLaVMoO 6 bulk samples with an ordered double perovskite structure have been investigated. Magnetization measurements have indicated that the SrLaVMoO 6 compound exhibits a cusp at 125 K, which is attributable to an antiferromagnetic transition. Electrical resistivity ρ for the compound showed metallic temperature dependence from 10 to 300 K, and a spin polarization P value was measured to be 0.50 using the point-contact Andreev reflection (PCAR) technique. It has been found from X-ray photoemission spectroscopy (XPS) study that SrLaVMoO 6 closely resembles the half-metallic Sr 2 FeMoO 6 in the electronic state of the Mo.

  13. Local electron-electron interaction strength in ferromagnetic nickel determined by spin-polarized positron annihilation.

    Science.gov (United States)

    Ceeh, Hubert; Weber, Josef Andreas; Weber, Josef Andreass; Böni, Peter; Leitner, Michael; Benea, Diana; Chioncel, Liviu; Ebert, Hubert; Minár, Jan; Vollhardt, Dieter; Hugenschmidt, Christoph

    2016-02-16

    We employ a positron annihilation technique, the spin-polarized two-dimensional angular correlation of annihilation radiation (2D-ACAR), to measure the spin-difference spectra of ferromagnetic nickel. The experimental data are compared with the theoretical results obtained within a combination of the local spin density approximation (LSDA) and the many-body dynamical mean-field theory (DMFT). We find that the self-energy defining the electronic correlations in Ni leads to anisotropic contributions to the momentum distribution. By direct comparison of the theoretical and experimental results we determine the strength of the local electronic interaction U in ferromagnetic Ni as 2.0 ± 0.1 eV.

  14. Spin-polarization reversal at the interface between benzene and Fe(100)

    KAUST Repository

    Goumri-Said, Souraya

    2013-01-03

    The spin-polarization at the interface between Fe(100) and a benzene is investigated theoretically using density functional theory for two positions of the organic molecule: planar and perpendicular with respect to the substrate. The electronic and magnetic properties as well as the spin-polarization close to the Fermi level strongly depend on the benzene position on the iron surface. An inversion of the spin-polarization is induced by p-d hybridization and charge transfer from the iron to the carbon sites in both configurations.

  15. Nuclear reactivity indices in the context of spin polarized density functional theory

    International Nuclear Information System (INIS)

    Cardenas, Carlos; Lamsabhi, Al Mokhtar; Fuentealba, Patricio

    2006-01-01

    In this work, the nuclear reactivity indices of density functional theory have been generalized to the spin polarized case and their relationship to electron spin polarized indices has been established. In particular, the spin polarized version of the nuclear Fukui function has been proposed and a finite difference approximation has been used to evaluate it. Applications to a series of triatomic molecules demonstrate the ability of the new functions to predict the geometrical changes due to a change in the spin multiplicity. The main equations in the different ensembles have also been presented

  16. Spin Polarization Inversion at Benzene-Absorbed Fe4N Surface

    KAUST Repository

    Zhang, Qian

    2015-05-27

    We report a first-principle study on electronic structure and simulation of the spin-polarized scanning tunneling microscopy graphic of a benzene/Fe4N interface. Fe4N is a compound ferromagnet suitable for many spintronic applications. We found that, depending on the particular termination schemes and interface configurations, the spin polarization on the benzene surface shows a rich variety of properties ranging from cosine-type oscillation to polarization inversion. Spin-polarization inversion above benzene is resulting from the hybridizations between C pz and the out-of-plane d orbitals of Fe atom.

  17. Micromagnetic investigation of the dynamics of magnetization switching induced by a spin polarized current

    Science.gov (United States)

    Lee, Kyung-Jin; Dieny, Bernard

    2006-03-01

    Using micromagnetic modeling, we tested a prediction of single-domain spin-torque theory which switching current density depends only weakly on magnetic cell size. The switching time and current density are strongly affected by the cell size for low spin polarization. Larger samples with a small length-to-width ratio and small spin polarization can exhibit a nonmonotonous dependence of switching time on current. Excitation of incoherent spin waves caused by the circular Oersted field due to the current is responsible for this nonmonotonous dependence. However, the magnetic dynamics recovers a single-domain-like behavior when the spin polarization is high and/or the cell size is small.

  18. Orientation and thickness dependence of magnetization at the interfacesof highly spin-polarized manganite thin films

    Energy Technology Data Exchange (ETDEWEB)

    Chopdekar, Rajesh V.; Arenholz, Elke; Suzuki, Y.

    2008-08-18

    We have probed the nature of magnetism at the surface of (001), (110) and (111)-oriented La{sub 0.7}Sr{sub 0.3}MnO{sub 3} thin films. The spin polarization of La{sub 0.7}Sr{sub 0.3}MnO{sub 3} thin films is not intrinsically suppressed at all surfaces and interfaces but is highly sensitive to both the epitaxial strain state as well as the substrate orientation. Through the use of soft x-ray spectroscopy, the magnetic properties of (001), (110) and (111)-oriented La{sub 0.7}Sr{sub 0.3}MnO{sub 3}/SrTiO{sub 3} interfaces have been investigated and compared to bulk magnetometry and resistivity measurements. The magnetization of (110) and (111)-oriented La{sub 0.7}Sr{sub 0.3}MnO{sub 3}/SrTiO{sub 3} interfaces are more bulk-like as a function of thickness whereas the magnetization at the (001)-oriented La{sub 0.7}Sr{sub 0.3}MnO{sub 3}/SrTiO{sub 3} interface is suppressed significantly below a layer thickness of 20 nm. Such findings are correlated with the biaxial strain state of the La{sub 0.7}Sr{sub 0.3}MnO{sub 3} films; for a given film thickness it is the tetragonal distortion of (001) La{sub 0.7}Sr{sub 0.3}MnO{sub 3} that severely impacts the magnetization, whereas the trigonal distortion for (111)-oriented films and monoclinic distortion for (110)-oriented films have less of an impact. These observations provide evidence that surface magnetization and thus spin polarization depends strongly on the crystal surface orientation as well as epitaxial strain.

  19. Compact scanning tunneling microscope for spin polarization measurements.

    Science.gov (United States)

    Kim, Seong Heon; de Lozanne, Alex

    2012-10-01

    We present a design for a scanning tunneling microscope that operates in ultrahigh vacuum down to liquid helium temperatures in magnetic fields up to 8 T. The main design philosophy is to keep everything compact in order to minimize the consumption of cryogens for initial cool-down and for extended operation. In order to achieve this, new ideas were implemented in the design of the microscope body, dewars, vacuum chamber, manipulators, support frame, and vibration isolation. After a brief description of these designs, the results of initial tests are presented.

  20. Spin-polarized semiconductor induced by magnetic impurities in graphene

    Science.gov (United States)

    Daghofer, Maria

    2011-03-01

    Magnetic impurities adsorbed on graphene sheets are coupled antiferromangetically via the itinerant electrons in the graphene. We study this interaction and its impact on the electrons' spectral density by use of unbiased Monte-Carlo simulations. The antiferromagnetic order breaks the symmetry between the sublattices, and a gap for the itinerant electrons opens. Our simulations show that the itinerant states below and above the gap are not dispersionless states trapped by the impurities, but are instead mobile states with a large dispersion. We compare various scenarios for the impurity distribution and find that random doping produces a standard semiconductor. If, on the other hand, all or most of the impurities are localized in the same sublattice, the spin degeneracy is lifted and the conduction band becomes spin-polarized. We also discuss the properties of edge states at edges or magnetic domain boundaries. M.~Daghofer, N.~Zheng, A.~Moreo; Phys.~Rev.~B 82, 121405(R) (2010) Supported by the DFG under the Emmy-Noether Program, and the Division of Materials Sciences and Engineering, Office of Basic Energy Sciences, U.S. DOE.

  1. Spin polarization and magnetic effects in radical reactions

    International Nuclear Information System (INIS)

    Salikhov, K.M.; Molin, Yu.N.; Sagdeev, R.Z.; Buchachenko, A.L.

    1984-01-01

    Studies on the effects of chemically induced dynamic nuclear and electron polarizations (CIDNP and CIDEP), and magnetic effects in radical reactions, have given rise to a new rapidly-progressing field of chemical physics. It came into being about ten years ago and has been attracting the ever-growing attention of researchers in related areas. The present book is a fairly all-embracing review of the state of affairs in this field. The book presents the physical background (both theoretical and experimental) of CIDNP and CIDEP, of the effects of an external magnetic field and magnetic nuclear moment (magnetic isotope effects) on radical reactions in solutions. Great attention has been paid to the application of chemical spin polarization and magnetic effects to solving various problems of chemical kinetics, structural chemistry, molecular physics, magnetobiology, and radiospectroscopy. The book will be useful for physicists, chemists and biologists employing CIDNP, CIDEP and magnetic effects in their investigations, as well as for researchers in related fields of chemical physics. The book can be also recommended for postgraduates and senior undergraduate students. (Auth.)

  2. Spin-polarized magnetic tunnelling magnetoresistive effects in various junctions

    Science.gov (United States)

    Miyazaki, T.; Tezuka, N.; Kumagai, S.; Ando, Y.; Kubota, H.; Murai, J.; Watabe, T.; Yokota, M.

    1998-03-01

    Recent progress concerning spin-polarized magnetic tunnelling effects for (i) trilayer standard ferromagnet (F)/insulator (I)/ferromagnet (F) junctions, (ii) spin-valve-type junctions, (iii) trilayer or multilayer ferromagnet/granular/ferromagnet junctions and (iv) F/I/F junction with a `wedge-geometry' insulator is reviewed. Special emphasis is placed on the dependence of the tunnel magnetoresistance ratio on temperature and also the intensity of the applied voltage. It was found that the resistance for the saturation magnetization state, 0022-3727/31/6/009/img1, and the tunnelling magnetoresistance ratio, TMR, of an 0022-3727/31/6/009/img2 junction decreased rapidly with increasing temperature, whereas those of a 0022-3727/31/6/009/img3 junction were insensitive to temperature. Concerning the bias voltage dependence of 0022-3727/31/6/009/img1 and TMR, the same tendency with temperature was observed for 0022-3727/31/6/009/img2 and 0022-3727/31/6/009/img3 junctions. Spin-valve-type junction exchange biased by a FeMn layer exhibits a relatively large TMR ratio up to about 400 K.

  3. Spin-polarized scanning tunneling spectroscopy of self-organized nanoscale Co islands on Au(111) surfaces.

    Science.gov (United States)

    Schouteden, K; Muzychenko, D A; Van Haesendonck, C

    2008-07-01

    Magnetic monolayer and bilayer Co islands of only a few nanometer in size were grown by atomic deposition on atomically flat Au(111) films. The islands were studied in situ by scanning tunneling microscopy (STM) and spectroscopy at low temperatures. Spin-resolved tunneling spectroscopy, using an STM tip with a magnetic coating, revealed that the Co islands exhibit a net magnetization perpendicular to the substrate surface due to the presence of spin-polarized d-states. A random distribution of islands with either upward or downward pointing magnetization was observed, without any specific correlation of magnetization orientation with island size or island height.

  4. Spin-polarized ballistic conduction through correlated Au-NiMnSb-Au heterostructures

    KAUST Repository

    Morari, C.

    2017-11-20

    We examine the ballistic conduction through Au-NiMnSb-Au heterostructures consisting of up to four units of the half-metallic NiMnSb in the scattering region, using density functional theory (DFT) methods. For a single NiMnSb unit the transmission function displays a spin polarization of around 50% in a window of 1eV centered around the Fermi level. By increasing the number of layers, an almost complete spin polarization of the transmission is obtained in this energy range. Supplementing the DFT calculations with local electronic interactions, of Hubbard-type on the Mn sites, leads to a hybridization between the interface and many-body states. The significant reduction of the spin polarization seen in the density of states is not apparent in the spin polarization of the conduction electron transmission, which suggests that the hybridized interface and many-body induced states are localized.

  5. Biaxial-stress-driven full spin polarization in ferromagnetic hexagonal chromium telluride

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Xiang-Bo; Li, Jun [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Liu, Bang-Gui, E-mail: bgliu@iphy.ac.cn [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190 (China)

    2017-03-15

    It is important to spintronics to achieve fully-spin-polarized magnetic materials that are stable and can be easily fabricated. Here, through systematical density-functional-theory investigations, we achieve high and even full spin polarization for carriers in the ground-state phase of CrTe by applying tensile biaxial stress. The resulting strain is tensile in the xy plane and compressive in the z axis. With the in-plane tensile strain increasing, the ferromagnetic order is stable against antiferromagnetic fluctuations, and a half-metallic ferromagnetism is achieved at an in-plane strain of 4.8%. With the spin-orbit coupling taken into account, the spin polarization is equivalent to 97% at the electronic transition point, and then becomes 100.0% at the in-plane strain of 6.0%. These make us believe that the full-spin-polarized ferromagnetism in this stable and easily-realizable hexagonal phase could be realized soon, and applied in spintronics. - Highlights: • Full spin polarization in the hexagonal ground-state phase of CrTe by biaxial stress. • The stress produces in-plane tensile strain and perpendicular compressive strain. • Reliable electronic structure is calculated with improved exchange functional. • Spin polarization is calculated with spin-orbit coupling taken into account.

  6. Fusion with highly spin polarized HD and D2

    International Nuclear Information System (INIS)

    Honig, A.; Letzring, S.; Skupsky, S.

    1993-01-01

    Our experimental efforts over the past 5 years have been aimed at cazrying out ICF shots with spin-polarized 0 fuel. We successfully prepared polarized 0 in HD, and solved the problems of loading target shells with our carefully prepared isotopic -rnixt.l.l?-es, polarizing them so that the 0 polarization remains metastably frozen-in for about half a day, and carrying out the various cold transfer requirements at Syracuse, where the target is prepared, and at Rochester, where the cold target is inserted fusion chamber. Upon shooting the accurately positioned unpolarized high density cold target, no neutron yield was observed. Inspection inside the OMEGA tank after the shot indicated the absence of neutron yield was dus to mal-timing or insufficient retraction rate of OMEGA'S fast shroud mechanism, resulting in interception of at least 20 of the 24 laser beams by the faulty shroud. In spits of this, all alements of the complex experiment we originally undertook have been successfully demonstrated, and the cold retrieval concepts and methods we developed are being utilized on the ICF upgrades at Rochester and at Livermore. In addition to the solution of the interface problems, we obtained novel results on polymer shell characteristics at low temperatures, and continuation of these experiments is c = ently supported by KLUP. Extensive additional mappings were ca=ied out of nuclear spin relaxation rates of H and D in solid HD in the temperature-magnetic field rangs of 0.01 to 4.2K and 0 - 13 Tesla. New phenomena were discovered, such as association of impurity clustering with very low temperature motion, and inequality of the growth-rate and decay-rate of the magnetization

  7. Fusion with highly spin polarized HD and D2

    International Nuclear Information System (INIS)

    Honig, A.; Letzring, S.; Skupsky, S.

    1993-01-01

    The experimental efforts over the past 5 years have been aimed at carrying out ICF shots with spin-polarized D fuel. The authors successfully prepared polarized D in HD, and solved the problems of loading target shells with their carefully prepared isotopic mixtures, polarizing them so that the D polarization remains metastably frozen-in for about half a day, and carrying out the various cold transfer requirements at Syracuse, where the target is prepared, and at Rochester, where the cold target is inserted into the OMEGA fusion chamber. A principal concern during this past year was overcoming difficulties encountered in maintaining the integrity of the fragile cold target during the multitude of cold-transfers required for the experiment. These difficulties arose from insufficient rigidity of the cold transfer systems, which were constrained to be of small diameter by the narrow central access bore of the dilution refrigerator, and were exacerbated by the multitude of required target shell manipulations between different environments, each with different coupling geometry, including target shell permeation, polarization, storage, transport, retrieval and insertion into OMEGA. The authors did solve all of these problems, and were able to position a cold, high density but unpolarized target with required precision in OMEGA. Upon shooting the accurately positioned unpolarized high density cold target, no neutron yield was observed. Inspection inside the OMEGA tank after the shot indicated the absence of neutron yield was due to mal-timing or insufficient retraction rate of OMEGA's fast shroud mechanism, resulting in interception of at least 20 of the 24 laser beams by the faulty shroud. In spite of this, all elements of the complex experiment the authors originally undertook have been successfully demonstrated, and the cold retrieval concepts and methods they developed are being utilized on the ICF upgrades at Rochester and at Livermore

  8. Dimensionality effects on spin-polarized quantum beats in ferromagnetic hosts with a pair of side-coupled impurities

    Energy Technology Data Exchange (ETDEWEB)

    Guessi, L.H.; Leandro, S.C.; Seridonio, A.C.; Siqueira, E.C. [Universidade Estadual Paulista Julio de Mesquita Filho (UNESP), Ilha Solteira, SP (Brazil). Dept. de Fisico Quimica; Souza, F.M.; Vernek, E. [Universidade Federal de Uberlandia (UFU), MG (Brazil). Inst. de Fisica; Yoshida, M. [Universidade Estadual Paulista Julio de Mesquita Filho (UNESP), Rio Claro, SP (Brazil); Figueira, M.S. [Universidade Federal Fluminense (UFF), Niteroi, RJ (Brazil). Inst. de Fisica

    2012-07-01

    Full text: In this work, we report a theoretical description of the differential conductance in the low bias regime, for a normal scanning tunneling microscope (STM) probe in the presence of ferromagnetic (FM) hosts with impurities. The hosts are treated as a spin-polarized electron gas hybridized to a pair of side-coupled impurities. Two setups of different dimensionalities are considered, a quantum wire (QW) and a metallic surface (MS). In order to deal with the non-interacting and the Coulomb blockade regimes of these systems, the analysis is done in the framework of the two-impurity Anderson model (TIAM) in combination with the equation of motion (EOM) approach for the Hamiltonian Green functions (GFs). The Fano effect appears in such setups, due to the quantum interference between the transport channels composed by the spin-polarized conduction bands and the electron tunneling into (or out of) the impurities. Thus the conductance of the STM reveals as a function of the probe position, a Fano interference strong dependent on the host dimensionality. It leads to the emergence of spin-polarized quantum beats in the Friedel oscillations for the conductance signal, which are uniform in the QW system in opposite to those found in the MS case, characterized by a long-range damped behavior. We remark that, the energy levels of the impurities and the Coulomb repulsion, modulate these beats. As a result, they establish a scenario where the interplay between the Coulomb blockade and the ferromagnetism of a metallic environment, can be useful for future quantum computation devices. (author)

  9. New-type spin polarized electron source and its applications; Atarashii spin henkyoku denshi sengen to sono oyo

    Energy Technology Data Exchange (ETDEWEB)

    Saka, T.; Kato, T. [Daido Steel Co. Ltd., Nagoya (Japan); Nakanishi, T.; Okumi, S. [Nagoya University, Nagoya (Japan); Horinaka, H. [Osaka Prefectural University, Osaka (Japan). College of Engineering

    1998-08-20

    This paper reveals that using distorted thin GaAs film can realize high polarization in spin polarized electron ray, and introduces properties of the developed ray source. The paper also touches on the application thereof to property physics. Realization of the high spin polarization is based on use of the `optical polarization method`. With this method, electrons in specific spin state are excited into a conduction band by utilizing the selection law used when valency electrons of zincblende type crystal such as GaAs absorb circular polarization. These electrons are taken out into vacuum and used as polarized electron beams. In order to realize uniformly distorted GaAs film, a method was discussed, with which the thin GaAs films are grown on substrates with different lattice constants, and the films are distorted by means of lattice mismatch. GaAs(1-x)Px was used for the substrates. GaAs(1-x)Px has the lattice constant decrease as the P`s mixed crystal ratio `x` increases. If a thin GaAs film is grown on this substrate, it is possible to obtain GaAs which is subjected to compression stress in the direction parallel with the growing surface, and tensile stress in the vertical direction. 13 refs., 5 figs., 1 tab.

  10. Spin polarization tuning in the graphene quantum dot by using in-plane external electric field

    International Nuclear Information System (INIS)

    Modarresi, M.; Roknabadi, M.R.; Shahtahmasebi, N.

    2014-01-01

    Electronic, magnetic and transport properties of a nano-graphene dot have been studied by using the DFT and tight binding methods. In the tight binding calculations, the interaction between electrons is modeled using the Hubbard Hamiltonian. By comparison between the eigen-values and density of states in the tight binding and DFT models, we tabulate a set of tight-binding parameters to describe graphene quantum dots for future works. The effects of a single vacancy and an in-plane external electric field on the spin-dependent transport of graphene quantum dot have been investigated. Transport through GQD between two GNR is studied by using Green's function formalism. Our results confirm an intrinsic spin-dependent current and relatively large spin polarization through the GQD in the presence of a single vacancy and zigzag edge. It is also shown that an in-plane external electric field controls the spin-polarization in graphene quantum dot. - Graphical abstract: We study the spin polarization in the presence of an external electric field. Highlights: • A tight binding study of transport through GNR/GQD/GNR is presented. • Our results show a relatively large spin polarization in the current–voltage curve. • Spin polarization is controlled by using an in-plane external electric field

  11. Injection and detection of a spin-polarized current in a light-emitting diode

    Science.gov (United States)

    Fiederling, R.; Keim, M.; Reuscher, G.; Ossau, W.; Schmidt, G.; Waag, A.; Molenkamp, L. W.

    1999-12-01

    The field of magnetoelectronics has been growing in practical importance in recent years. For example, devices that harness electronic spin-such as giant-magnetoresistive sensors and magnetoresistive memory cells-are now appearing on the market. In contrast, magnetoelectronic devices based on spin-polarized transport in semiconductors are at a much earlier stage of development, largely because of the lack of an efficient means of injecting spin-polarized charge. Much work has focused on the use of ferromagnetic metallic contacts, but it has proved exceedingly difficult to demonstrate polarized spin injection. More recently, two groups have reported successful spin injection from an NiFe contact, but the observed effects of the spin-polarized transport were quite small (resistance changes of less than 1%). Here we describe a different approach, in which the magnetic semiconductor BexMnyZn1-x-ySe is used as a spin aligner. We achieve injection efficiencies of 90% spin-polarized current into a non-magnetic semiconductor device. The device used in this case is a GaAs/AlGaAs light-emitting diode, and spin polarization is confirmed by the circular polarization state of the emitted light.

  12. Electric field induced spin polarization oscillation in nonmagnetic benzene/Cu(100) interface: First principles calculations

    Science.gov (United States)

    Yuan, X. B.; Cai, L. L.; Tian, Y. L.; Hu, G. C.; Ren, J. F.

    2018-01-01

    First-principles calculation are presented to study the influences of external electric fields on the spin polarization properties of benzene/Cu(100) system which do not contain any magnetic atom. Our simulations show that an obvious spontaneous spin polarization oscillation occurred in the benzene molecule when the electric fields are applied. The density of states (DOS), spin density distributions, charge transfer properties are also obtained. It is found that the p-d orbital coupling between the benzene molecule and the electrode leads to spin non-degeneration of the DOS near the fermi energy, so the transferred charges from the Cu atoms to the molecule will fill these spin non-degenerate coupled orbitals, and then the benzene molecule becomes spin polarized. The strength of the p-d orbital coupling as well as the transferred charges oscillated with the external electric fields, which induce spin polarization oscillation. The results are favorable for the understanding of spin polarization properties in organic/nonmagnetic metal structures.

  13. Laser-driven source of spin-polarized atomic hydrogen and deuterium

    International Nuclear Information System (INIS)

    Poelker, M.

    1995-01-01

    A laser-driven source of spin-polarized hydrogen (H) and deuterium (D) that relies on the technique of optical pumping spin exchange has been constructed. In this source, H or D atoms and potassium atoms flow continuously through a drifilm-coated spin-exchange cell where potassium atoms are optically pumped with circularly-polarized laser light in a high magnetic field. The H or D atoms become polarized through spin-exchange collisions with polarized potassium atoms. High electron polarization (∼80%) has been measured for H and D atoms at flow rates ∼2x10 17 atoms/s. Lower polarization values are measured for flow rates exceeding 1x10 18 atoms/s. In this paper, we describe the performance of the laser-driven source as a function of H and D atomic flow rate, magnetic field strength, alkali density and pump-laser power. Polarization measurements as a function of flow rate and magnetic field suggest that, despite a high magnetic field, atoms within the optical-pumping spin-exchange apparatus evolve to spin-temperature equilibrium which results in direct polarization of the H and D nuclei. (orig.)

  14. a Spinning Polarizer and Spinning Analyzer Method for Visualizing the Isochromates in Conoscopic Interferometers

    Science.gov (United States)

    Olorunsola, Oluwatobi; Dada, Oluwaseye; Wang, Pengqian

    2013-09-01

    We have developed a spinning polarizer and spinning analyzer (SPSA) method to visualize the whole isochromatic fringes in conoscopic interferometers for the study of optically anisotropic materials. This simple method completely eliminates the broad and dark isogyre fringes appearing in a conventional conoscopic interferometer where a linear polarizer and a linear analyzer (LPLA) are used. Our method allows the direct visualization of the isochromates on the viewing screen by eyes in real time, without the need of additional optics or detectors other than those used in a conventional conoscopic interferometer, and no additional computation is required. This method works at any polarization state of the input light, and at any wavelength permitted by the polarizers. In the case of polychromatic illumination our method reveals the isochromates of all colors indiscriminatively, in comparison to the method of circular polarizer and circular analyzer (CPCA), which is considerably subject to spectrum modulation due to the dispersion in the retardation of the quarter-wave plates. The proposed method is demonstrated in a lithium niobate (LiNbO3) crystal driven by an external electric field.

  15. Spin polarization of tunneling current in barriers with spin-orbit coupling.

    Science.gov (United States)

    Fujita, T; Jalil, M B A; Tan, S G

    2008-03-19

    We present a general method for evaluating the maximum transmitted spin polarization and optimal spin axis for an arbitrary spin-orbit coupling (SOC) barrier system, in which the spins lie in the azimuthal plane and finite spin polarization is achieved by wavevector filtering of electrons. Besides momentum filtering, another prerequisite for finite spin polarization is asymmetric occupation or transmission probabilities of the eigenstates of the SOC Hamiltonian. This is achieved most efficiently by resonant tunneling through multiple SOC barriers. We apply our analysis to common SOC mechanisms in semiconductors: pure bulk Dresselhaus SOC, heterostructures with mixed Dresselhaus and Rashba SOC and strain-induced SOC. In particular, we find that the interplay between Dresselhaus and Rashba SOC effects can yield several advantageous features for spin filter and spin injector functions, such as increased robustness to wavevector spread of electrons.

  16. In situ scanning tunneling microscope tip treatment device for spin polarization imaging

    Science.gov (United States)

    Li, An-Ping [Oak Ridge, TN; Jianxing, Ma [Oak Ridge, TN; Shen, Jian [Knoxville, TN

    2008-04-22

    A tip treatment device for use in an ultrahigh vacuum in situ scanning tunneling microscope (STM). The device provides spin polarization functionality to new or existing variable temperature STM systems. The tip treatment device readily converts a conventional STM to a spin-polarized tip, and thereby converts a standard STM system into a spin-polarized STM system. The tip treatment device also has functions of tip cleaning and tip flashing a STM tip to high temperature (>2000.degree. C.) in an extremely localized fashion. Tip coating functions can also be carried out, providing the tip sharp end with monolayers of coating materials including magnetic films. The device is also fully compatible with ultrahigh vacuum sample transfer setups.

  17. Spin polarized tunnelling investigation of nanometre Co clusters by means of a Ni bulk tip

    International Nuclear Information System (INIS)

    Rastei, M V; Bucher, J P

    2006-01-01

    A massive Ni tip is used in spin polarized scanning tunnelling microscopy (SP STM) to explore the magnetization state of nanometre Co clusters, self-organized on the Au(111) surface. Constant current STM images taken at 4.6 K show a bimodal distribution of the cluster heights, accounting for the spin polarization of the STM junction. The spin polarization of the tunnel junction as a function of the bias voltage is found to depend on the local density of states of the sample examined. Changing the vacuum barrier parameters by bringing the tip closer to the surface leads to a reduction in the tunnelling magnetoresistance that may be attributed to spin flip effects. (letter to the editor)

  18. Spin polarization of tunneling current in barriers with spin-orbit coupling

    International Nuclear Information System (INIS)

    Fujita, T; Jalil, M B A; Tan, S G

    2008-01-01

    We present a general method for evaluating the maximum transmitted spin polarization and optimal spin axis for an arbitrary spin-orbit coupling (SOC) barrier system, in which the spins lie in the azimuthal plane and finite spin polarization is achieved by wavevector filtering of electrons. Besides momentum filtering, another prerequisite for finite spin polarization is asymmetric occupation or transmission probabilities of the eigenstates of the SOC Hamiltonian. This is achieved most efficiently by resonant tunneling through multiple SOC barriers. We apply our analysis to common SOC mechanisms in semiconductors: pure bulk Dresselhaus SOC, heterostructures with mixed Dresselhaus and Rashba SOC and strain-induced SOC. In particular, we find that the interplay between Dresselhaus and Rashba SOC effects can yield several advantageous features for spin filter and spin injector functions, such as increased robustness to wavevector spread of electrons

  19. Nuclear spin polarized H and D by means of spin-exchange optical pumping

    Science.gov (United States)

    Stenger, Jörn; Grosshauser, Carsten; Kilian, Wolfgang; Nagengast, Wolfgang; Ranzenberger, Bernd; Rith, Klaus; Schmidt, Frank

    1998-01-01

    Optically pumped spin-exchange sources for polarized hydrogen and deuterium atoms have been demonstrated to yield high atomic flow and high electron spin polarization. For maximum nuclear polarization the source has to be operated in spin temperature equilibrium, which has already been demonstrated for hydrogen. In spin temperature equilibrium the nuclear spin polarization PI equals the electron spin polarization PS for hydrogen and is even larger than PS for deuterium. We discuss the general properties of spin temperature equilibrium for a sample of deuterium atoms. One result are the equations PI=4PS/(3+PS2) and Pzz=PSṡPI, where Pzz is the nuclear tensor polarization. Furthermore we demonstrate that the deuterium atoms from our source are in spin temperature equilibrium within the experimental accuracy.

  20. Defect-enhanced Rashba spin-polarized currents in carbon nanotubes

    Science.gov (United States)

    Santos, Hernán; Chico, Leonor; Alvarellos, J. E.; Latgé, A.

    2017-10-01

    The production of spin-polarized currents in pristine carbon nanotubes with Rashba spin-orbit interactions has been shown to be very sensitive to the symmetry of the tubes and the geometry of the setup. Here we analyze the role of defects on the spin quantum conductances of metallic carbon nanotubes due to an external electric field. We show that localized defects, such as adsorbed hydrogen atoms or pentagon-heptagon pairs, increase the Rashba spin-polarized current. Moreover, this enhancement takes place for energies closer to the Fermi energy as compared to the response of pristine tubes. Such increments can be even larger when several equally spaced defects are introduced into the system. We explore different arrangements of defects, showing that for certain geometries there are flips of the spin-polarized current and even transport suppression. Our results indicate that spin valve devices at the nanoscale may be achieved via defect engineering in carbon nanotubes.

  1. Spin polarization versus color–flavor locking in high-density quark matter

    DEFF Research Database (Denmark)

    Tsue, Yasuhiko; da Providência, João; Providência, Constança

    2015-01-01

    It is shown that spin polarization with respect to each flavor in three-flavor quark matter occurs instead of color–flavor locking at high baryon density by using the Nambu–Jona-Lasinio model with four-point tensor-type interaction. Also, it is indicated that the order of phase transition between...... the color–flavor-locked phase and the spin-polarized phase is the first order by means of second-order perturbation theory.......It is shown that spin polarization with respect to each flavor in three-flavor quark matter occurs instead of color–flavor locking at high baryon density by using the Nambu–Jona-Lasinio model with four-point tensor-type interaction. Also, it is indicated that the order of phase transition between...

  2. Strong Linear Dichroism in Spin-Polarized Photoemission from Spin-Orbit-Coupled Surface States.

    Science.gov (United States)

    Bentmann, H; Maaß, H; Krasovskii, E E; Peixoto, T R F; Seibel, C; Leandersson, M; Balasubramanian, T; Reinert, F

    2017-09-08

    A comprehensive understanding of spin-polarized photoemission is crucial for accessing the electronic structure of spin-orbit coupled materials. Yet, the impact of the final state in the photoemission process on the photoelectron spin has been difficult to assess in these systems. We present experiments for the spin-orbit split states in a Bi-Ag surface alloy showing that the alteration of the final state with energy may cause a complete reversal of the photoelectron spin polarization. We explain the effect on the basis of ab initio one-step photoemission theory and describe how it originates from linear dichroism in the angular distribution of photoelectrons. Our analysis shows that the modulated photoelectron spin polarization reflects the intrinsic spin density of the surface state being sampled differently depending on the final state, and it indicates linear dichroism as a natural probe of spin-orbit coupling at surfaces.

  3. Switching Magnetism and Superconductivity with Spin-Polarized Current in Iron-Based Superconductor

    Science.gov (United States)

    Choi, Seokhwan; Choi, Hyoung Joon; Ok, Jong Mok; Lee, Yeonghoon; Jang, Won-Jun; Lee, Alex Taekyung; Kuk, Young; Lee, SungBin; Heinrich, Andreas J.; Cheong, Sang-Wook; Bang, Yunkyu; Johnston, Steven; Kim, Jun Sung; Lee, Jhinhwan

    2017-12-01

    We explore a new mechanism for switching magnetism and superconductivity in a magnetically frustrated iron-based superconductor using spin-polarized scanning tunneling microscopy (SPSTM). Our SPSTM study on single-crystal Sr2VO3FeAs shows that a spin-polarized tunneling current can switch the Fe-layer magnetism into a nontrivial C4 (2 ×2 ) order, which cannot be achieved by thermal excitation with an unpolarized current. Our tunneling spectroscopy study shows that the induced C4 (2 ×2 ) order has characteristics of plaquette antiferromagnetic order in the Fe layer and strongly suppresses superconductivity. Also, thermal agitation beyond the bulk Fe spin ordering temperature erases the C4 state. These results suggest a new possibility of switching local superconductivity by changing the symmetry of magnetic order with spin-polarized and unpolarized tunneling currents in iron-based superconductors.

  4. Switching Magnetism and Superconductivity with Spin-Polarized Current in Iron-Based Superconductor.

    Science.gov (United States)

    Choi, Seokhwan; Choi, Hyoung Joon; Ok, Jong Mok; Lee, Yeonghoon; Jang, Won-Jun; Lee, Alex Taekyung; Kuk, Young; Lee, SungBin; Heinrich, Andreas J; Cheong, Sang-Wook; Bang, Yunkyu; Johnston, Steven; Kim, Jun Sung; Lee, Jhinhwan

    2017-12-01

    We explore a new mechanism for switching magnetism and superconductivity in a magnetically frustrated iron-based superconductor using spin-polarized scanning tunneling microscopy (SPSTM). Our SPSTM study on single-crystal Sr_{2}VO_{3}FeAs shows that a spin-polarized tunneling current can switch the Fe-layer magnetism into a nontrivial C_{4} (2×2) order, which cannot be achieved by thermal excitation with an unpolarized current. Our tunneling spectroscopy study shows that the induced C_{4} (2×2) order has characteristics of plaquette antiferromagnetic order in the Fe layer and strongly suppresses superconductivity. Also, thermal agitation beyond the bulk Fe spin ordering temperature erases the C_{4} state. These results suggest a new possibility of switching local superconductivity by changing the symmetry of magnetic order with spin-polarized and unpolarized tunneling currents in iron-based superconductors.

  5. Spin-polarized scanning tunneling microscopy with quantitative insights into magnetic probes.

    Science.gov (United States)

    Phark, Soo-Hyon; Sander, Dirk

    2017-01-01

    Spin-polarized scanning tunneling microscopy and spectroscopy (spin-STM/S) have been successfully applied to magnetic characterizations of individual nanostructures. Spin-STM/S is often performed in magnetic fields of up to some Tesla, which may strongly influence the tip state. In spite of the pivotal role of the tip in spin-STM/S, the contribution of the tip to the differential conductance d I /d V signal in an external field has rarely been investigated in detail. In this review, an advanced analysis of spin-STM/S data measured on magnetic nanoislands, which relies on a quantitative magnetic characterization of tips, is discussed. Taking advantage of the uniaxial out-of-plane magnetic anisotropy of Co bilayer nanoisland on Cu(111), in-field spin-STM on this system has enabled a quantitative determination, and thereby, a categorization of the magnetic states of the tips. The resulting in-depth and conclusive analysis of magnetic characterization of the tip opens new venues for a clear-cut sub-nanometer scale spin ordering and spin-dependent electronic structure of the non-collinear magnetic state in bilayer high Fe nanoislands on Cu(111).

  6. Effect of the anisotropy of the electron g-factor in spin polarization

    International Nuclear Information System (INIS)

    Miah, M. Idrish; Gray, E. MacA.

    2010-01-01

    Spin polarization in the presence of an external magnetic field and electric bias in quantum confined semiconductor structures has been studied by time- and polarization-resolved spectrometry. From measurements with angular variations of the magnetic field from the Voigt configuration (VC) it was found that both the frequency (Ω) and decay rate (β) of the oscillatory component of the polarization increase with variation of the angle from the VC. Their dependences are discussed based on the electron spin dephasing related to the spread of the electron g-factor (g e ) (i.e. unequal values of the longitudinal (g e|| ) and transverse (g e -perpendicular) components of g e ) and the exchange interaction between the electron and hole spins. It is demonstrated that the increase in Ω upon deviation of the magnetic field from the VC relates to the anisotropy of g e (g e|| and g e -perpendicular) resulting from the quantum confinement effect. However, the angular dependence on β is related to the residual exchange interaction between the electron spin and rapidly relaxing hole spin.

  7. Effect of the anisotropy of the electron g-factor in spin polarization

    Energy Technology Data Exchange (ETDEWEB)

    Miah, M. Idrish, E-mail: m.miah@griffith.edu.au [Queensland Micro- and Nanotechnology Centre, Griffith University, Nathan, Brisbane, QLD 4111 (Australia); School of Biomolecular and Physical Sciences, Griffith University, Nathan, Brisbane, QLD 4111 (Australia); Department of Physics, University of Chittagong, Chittagong, Chittagong 4331 (Bangladesh); Gray, E. MacA. [Queensland Micro- and Nanotechnology Centre, Griffith University, Nathan, Brisbane, QLD 4111 (Australia); School of Biomolecular and Physical Sciences, Griffith University, Nathan, Brisbane, QLD 4111 (Australia)

    2010-02-15

    Spin polarization in the presence of an external magnetic field and electric bias in quantum confined semiconductor structures has been studied by time- and polarization-resolved spectrometry. From measurements with angular variations of the magnetic field from the Voigt configuration (VC) it was found that both the frequency ({Omega}) and decay rate ({beta}) of the oscillatory component of the polarization increase with variation of the angle from the VC. Their dependences are discussed based on the electron spin dephasing related to the spread of the electron g-factor (g{sub e}) (i.e. unequal values of the longitudinal (g{sub e||}) and transverse (g{sub e}-perpendicular) components of g{sub e}) and the exchange interaction between the electron and hole spins. It is demonstrated that the increase in {Omega} upon deviation of the magnetic field from the VC relates to the anisotropy of g{sub e} (g{sub e||} and g{sub e}-perpendicular) resulting from the quantum confinement effect. However, the angular dependence on {beta} is related to the residual exchange interaction between the electron spin and rapidly relaxing hole spin.

  8. Magnetism in grain-boundary phase of a NdFeB sintered magnet studied by spin-polarized scanning electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kohashi, Teruo, E-mail: teruo.kohashi.fc@hitachi.com; Motai, Kumi [Central Research Laboratory, Hitachi, Ltd., Hatoyama, Saitama 350-0395 (Japan); Nishiuchi, Takeshi; Hirosawa, Satoshi [Magnetic Materials Research Laboratory, Hitachi Metals Ltd., Osaka 618-0013 (Japan)

    2014-06-09

    The magnetism in the grain-boundary phase of a NdFeB sintered magnet was measured by spin-polarized scanning electron microscopy (spin SEM). A sample magnet was fractured in the ultra-high-vacuum chamber to avoid oxidation, and its magnetizations in the exposed grain-boundary phase on the fracture surface were evaluated through the spin polarization of secondary electrons. Spin-SEM images were taken as the fracture surface was milled gradually by argon ions, and the magnetization in the grain-boundary phase was quantitatively obtained separately from that of the Nd{sub 2}Fe{sub 14}B phase. The obtained magnetization shows that the grain-boundary phase of this magnet has substantial magnetization, which was confirmed to be ferromagnetic.

  9. Mechanism of ({sup 14}N, {sup 12}B) reactions at intermediate energy leading to large spin-polarization of {sup 12}B

    Energy Technology Data Exchange (ETDEWEB)

    Mitsuoka, Shin-ichi [Osaka Univ., Ibaraki (Japan). Research Center for Nuclear Physics; Shimoda, Tadashi; Miyatake, Hiroari [and others

    1996-05-01

    To study mechanisms of the ({sup 14}N, {sup 12}B) reactions at intermediate energies, double differential cross section and nuclear spin-polarization of the {sup 12}B projectile-like fragments have been measured as a function of longitudinal momentum in the angular range of 0deg - 9deg. Large spin-polarization of the reaction products {sup 12}B has been observed in the {sup 9}Be({sup 14}N, {sup 12}B) reaction at 39.3 MeV/u. The momentum distributions at forward angles exhibit characteristic features which can not be understood by the current projectile fragmentation picture. It is shown that by assuming the existence of direct two-proton transfer process in addition to the fragmentation process, both the cross section and polarization of {sup 12}B fragments are successfully explained. The target and incident energy dependence of the momentum distribution are also explained reasonably. (author)

  10. Peculiarities of spin polarization inversion at a thiophene/cobalt interface

    KAUST Repository

    Wang, Xuhui

    2013-03-20

    We perform ab initio calculations to investigate the spin polarization at the interface between a thiophene molecule and cobalt substrate. We find that the reduced symmetry in the presence of a sulfur atom (in the thiophene molecule) leads to a strong spatial dependence of the spin polarization of the molecule. The two carbon atoms far from the sulfur acquire a polarization opposite to that of the substrate, while the carbon atoms bonded directly to sulfur possess the same polarization as the substrate. We determine the origin of this peculiar spin interface property as well as its impact on the spin transport.

  11. Hardness and softness reactivity kernels within the spin-polarized density-functional theory

    International Nuclear Information System (INIS)

    Chamorro, Eduardo; De Proft, Frank; Geerlings, Paul

    2005-01-01

    Generalized hardness and softness reactivity kernels are defined within a spin-polarized density-functional theory (SP-DFT) conceptual framework. These quantities constitute the basis for the global, local (i.e., r-position dependent), and nonlocal (i.e., r and r ' -position dependents) indices devoted to the treatment of both charge-transfer and spin-polarization processes in such a reactivity framework. The exact relationships between these descriptors within a SP-DFT framework are derived and the implications for chemical reactivity in such context are outlined

  12. Photo-Induced Electron Spin Polarization in a Narrow Band Gap Semiconductor Nanostructure

    International Nuclear Information System (INIS)

    Peter, A. John; Lee, Chang Woo

    2012-01-01

    Photo-induced spin dependent electron transmission through a narrow gap InSb/InGa x Sb 1−x semiconductor symmetric well is theoretically studied using transfer matrix formulism. The transparency of electron transmission is calculated as a function of electron energy for different concentrations of gallium. Enhanced spin-polarized photon assisted resonant tunnelling in the heterostructure due to Dresselhaus and Rashba spin-orbit coupling induced splitting of the resonant level and compressed spin-polarization are observed. Our results show that Dresselhaus spin-orbit coupling is dominant for the photon effect and the computed polarization efficiency increases with the photon effect and the gallium concentration

  13. Construction of the spin-polarized slow positron beam with the RI source

    Energy Technology Data Exchange (ETDEWEB)

    Nakajyo, Terunobu; Tashiro, Mutsumi; Kanazawa, Ikuzo [Tokyo Gakugei Univ., Koganei (Japan); Komori, Fumio; Murata, Yoshimasa; Ito, Yasuo

    1997-03-01

    The electrostatic slow-positron beam is constructed by using {sup 22}Na source. We design the electrostatic lens, the system of the detector, and the Wien filter for the experiment`s system of the spin-polarized slow positron beam. The reemitted spin-polarized slow-positron spectroscopy is proposed for studying magnetic thin films and magnetic multilayers. We calculated the depolarized positron fractions in the Fe thin film Fe(10nm)/Cu(substrate) and the multilayers Cu(1nm)/Fe(10nm)/Cu(substrate). (author)

  14. Spontaneous spin-polarization and phase transition in the relativistic approach

    International Nuclear Information System (INIS)

    Maruyama, Tomoyuki; Tatsumi, Toshitaka

    2001-01-01

    We study the spin-polarization mechanism in the highly dense nuclear matter with the relativistic mean-field approach. In the relativistic Hartree-Fock framework we find that there are two kinds of spin-spin interaction channels, which are the axial-vector and tensor exchange ones. If each interaction is strong and different sign, the system loses the spherical symmetry and holds the spin-polarization in the high-density region. When the axial-vector interaction is negative enough, the system holds ferromagnetism. (author)

  15. Interplay between magnetism and conductivity derived from spin-polarized donor radicals.

    Science.gov (United States)

    Sugawara, Tadashi; Komatsu, Hideji; Suzuki, Kentaro

    2011-06-01

    Tutorial review: to achieve molecule-based spintronic devices, an organic conducting magnet that exhibits both conductivity and magnetism in a cooperative manner must be constructed. As a building block for such new materials, a spin-polarized donor radical, which serves as a molecular "spin-filter" in its singly oxidized state, was designed and synthesized. The resistivity of ion radical salts of selenium-substituted, tetrathiafulvalene-based spin-polarized donor radicals decreased substantially in the presence of a magnetic field, thus indicating cooperative conductivity and magnetism.

  16. Laser detection of spin-polarized hydrogen from HCl and HBr photodissociation: comparison of H- and halogen-atom polarizations.

    Science.gov (United States)

    Sofikitis, Dimitris; Rubio-Lago, Luis; Bougas, Lykourgos; Alexander, Andrew J; Rakitzis, T Peter

    2008-10-14

    Thermal HCl and HBr molecules were photodissociated using circularly polarized 193 nm light, and the speed-dependent spin polarization of the H-atom photofragments was measured using polarized fluorescence at 121.6 nm. Both polarization components, described by the a(0)(1)(perpendicular) and Re[a(1)(1)(parallel, perpendicular)] parameters which arise from incoherent and coherent dissociation mechanisms, are measured. The values of the a(0)(1)(perpendicular) parameter, for both HCl and HBr photodissociation, are within experimental error of the predictions of both ab initio calculations and of previous measurements of the polarization of the halide cofragments. The experimental and ab initio theoretical values of the Re[a(1)(1)(parallel, perpendicular)] parameter show some disagreement, suggesting that further theoretical investigations are required. Overall, good agreement occurs despite the fact that the current experiments photodissociate molecules at 295 K, whereas previous measurements were conducted at rotational temperatures of about 15 K.

  17. Spin-polarized electron tunneling across a Si delta-doped GaMnAs/n-GaAs interface

    DEFF Research Database (Denmark)

    Andresen, S.E.; Sørensen, B.S.; Lindelof, P.E.

    2003-01-01

    Spin-polarized electron coupling across a Si delta-doped GaMnAs/n-GaAs interface was investigated. The injection of spin-polarized electrons was detected as circular polarized emission from a GaInAs/GaAs quantum well light emitting diode. The angular momentum selection rules were simplified...

  18. Towards 100% spin-polarized charge-injection : The half-metallic NiMnSb/CdS interface

    NARCIS (Netherlands)

    de Wijs, G.A.; de Groot, R A

    2001-01-01

    Spin-electronics requires an electron source with a spin-polarization as high as possible. For this, half-metallic materials seem ideally suited as they exhibit 100% spin polarization. Because of its high Curie temperature and compatibility with existing semiconductor technology, NiMnSb is a most

  19. Spin polarized auger electron spectroscopy (SPAES): An element specific local magnetization probe of magnetic materials

    Science.gov (United States)

    Anilturk, Onder S.

    Spin Polarized Auger Electron Spectroscopy (SPAES) is found to have application for investigating fundamental properties as well as element specific local magnetization information on magnetic materials. By using the uniqueness of the UTA-SEMPA tool, one can obtain the surface magnetic domain microstructure and also perform SPAES studies by probing a single domain at the surface. In the current study, knowing the probed domain, spin polarization of electrons from super Coster-Kronig MVV Auger emissions on 3%Si-Fe sheets have been investigated. It is observed that on both sides of 180° domains, separated by a domain wall with an out-of-plane component of magnetization, the spin polarized Auger spectra exhibit similar distributions with high polarization structures, which are consistent with the published data. The element specificity of the system is applied to Gd-Co composite system. Details of 4d core hole initiated Auger transitions showed that the 5d states have enhanced spin polarization, confirming the coupling of moments in the composite system via 5d states of Gd. It is also unambiguously observed that Co magnetic moments are indeed aligned antiparallel to the Gd ones via 4f-5d positive exchange and 3d-5d hybridization.

  20. Probing spin-polarized tunneling at high bias and temperature with a magnetic tunnel transistor

    NARCIS (Netherlands)

    Park, B.G.; Banerjee, T.; Min, B.C.; Sanderink, Johannes G.M.; Lodder, J.C.; Jansen, R.

    2005-01-01

    The magnetic tunnel transistor (MTT) is a three terminal hybrid device that consists of a tunnel emitter, a ferromagnetic (FM) base, and a semiconductor collector. In the MTT with a FM emitter and a single FM base, spin-polarized hot electrons are injected into the base by tunneling. After

  1. Tunneling Spectroscopy Study of Spin-Polarized Quasiparticle Injection Effects in Cuparate/Manganite Heterostructures

    Science.gov (United States)

    Wei, J. Y. T.; Yeh, N. C.; Vasquez, R. P.

    1998-01-01

    Scanning tunneling spectroscopy was performed at 4.2K on epitaxial thin-film heterostructures comprising YBa2Cu3O7 and La0.7Ca0.3MnO3, to study the microscopic effects of spin-polarized quasiparticle injection from the half-metallic ferromagnetic manganite on the high-Tc cuprate superconductor.

  2. Spin polarization in top pair production in association with two photons at NLO+PS

    CERN Document Server

    Luisoni, Gionata

    2017-01-01

    This talk focuses on the impact of top-quark spin polarization effects in Higgs boson production in association with a top-quark pair, where the Higgs boson decays to two photons. Predictions for the signal are compared with direct top-quark pair production in association with two photons at NLO+PS.

  3. Spin-polarized versus chiral condensate in quark matter at finite temperature and density

    DEFF Research Database (Denmark)

    Matsuoka, Hiroaki; Tsue, Yasuhiko; da Providencia, Joao

    2016-01-01

    It is shown that the spin-polarized condensate appears in quark matter at high baryon density and low temperature due to the tensor-type four-point interaction in the Nambu-Jona-Lasiniotype model as a low-energy effective theory of quantum chromodynamics. It is indicated within this low...

  4. Spin-polarized transport in a δ-doped magnetic-barrier nanostructure

    Energy Technology Data Exchange (ETDEWEB)

    Li, Shuai; Lu, Mao-Wang, E-mail: maowanglu@126.com; Jiang, Ya-Qing; Chen, Sai-Yan

    2014-09-05

    We theoretically investigate the electron spin transport properties through a δ-doped magnetic-barrier nanostructure, which can be realized experimentally by depositing two identical ferromagnetic stripes with the opposite in-plane magnetization on the top of a semiconductor heterostructure in parallel configuration and by using atomic layer doping technique. The δ-doping dependent transmission, conductance and spin polarization are calculated exactly by analytically solving Schrödinger equation of the spin electron. It is found that the electronic spin-polarized behavior in this device can be manipulated by changing the weight and/or the position of the δ-doping. Therefore, such a device can be used as a controllable spin filter, which may be helpful for spintronics applications. - Highlights: • Spin-polarized transport in a δ-doped magnetic-barrier nanostructure is explored. • Both magnitude and sign of spin polarization depend on the δ-doping. • A controllable spin filter can be achieved for spintronics applications.

  5. Spin-polarized transport in a two-dimensional electron gas with interdigital-ferromagnetic contacts

    DEFF Research Database (Denmark)

    Hu, C.-M.; Nitta, Junsaku; Jensen, Ane

    2001-01-01

    Ferromagnetic contacts on a high-mobility, two-dimensional electron gas (2DEG) in a narrow gap semiconductor with strong spin-orbit interaction are used to investigate spin-polarized electron transport. We demonstrate the use of magnetized contacts to preferentially inject and detect specific spi...

  6. Transient charging and discharging of spin-polarized electrons in a quantum dot

    DEFF Research Database (Denmark)

    De Souza, Fabricio; Leao, S.A.; Gester, R. M.

    2007-01-01

    We study spin-polarized transient transport in a quantum dot coupled to two ferromagnetic leads subjected to a rectangular bias voltage pulse. Time-dependent spin-resolved currents, occupations, spin accumulation, and tunneling magnetoresistance TMR are calculated using both nonequilibrium Green...

  7. High-resolution vector magnetometry: Piezo-spin-polarization effect and in-plane strain-induced dominating uniaxial magnetic anisotropy in a 200-nm-thick Ni thin film

    Science.gov (United States)

    Benito, L.

    2018-04-01

    Owing to its high-sensitivity, reliability, fast, versatile and cost-effective operation, vibrating sample magnetometers (VSM) are massively popular characterization instruments at Magnetism laboratories worldwide. Nevertheless, the inherent appearance of synchronous noise represents a major drawback, which critically limits the fine probing of nanometer-sized media. I here report on an innovative approach to eliminate synchronous noise in VSM. This consists of fitting engineered mechanical devices that absorbs vibration energy, dissipating that into heat. Complementarily, a novel transversal pick-up coil system is also presented and analyzed; this detection system has been engineered to enhance the noise-to-signal ratio and optimized for measuring small size thin film samples. The implementation of a combined mechanical and electromagnetic approach enables to notably enhance the VSM performance, achieving a sensitivity better than 1 ×10-6 emu and a resolution below 5 ×10-8 emu, so that the magnetization vector in nanostructured media can be accurately mapped out down to cryogenic temperatures. I lastly show precision magnetometry measurements carried out in an epitaxial (0 0 1)-oriented 200 nm-thick Ni thin film. The analysis reveals the arising of an in-plane dominating strain-induced uniaxial magnetic anisotropy, K2ef = - 6.455kJ m - 3 , and a stunning piezo-spin-polarization effect resulting in a remarkable 10% modulation of the magnetization vector, ∼ 27 emu/cm3, with respect to the cubic lattice axes. Both effects are attributed to the likely existence of an orthorhombic lattice distortion, i.e.εxx -εyy ≈ - 2 ×10-3 . This categorical link enables to assign the observed anisotropic spin-polarization in the Ni overlayer to a two-ion magnetoelastic coupling effect.

  8. Production of highly spin-polarized atomic hydrogen and deuterium by spin-exchange

    International Nuclear Information System (INIS)

    Redsun, S.G.

    1990-01-01

    The first part of this work is a study of the production of highly spin-polarized atomic hydrogen and deuterium by spin-exchange optical pumping. A tunable ring dye laser is used to polarize rubidium atoms by optical pumping. The cell containing the rubidium vapor is coated with paraffin in order to reduce spin relaxation due to wall collisions. Hydrogen gas is dissociated in an inductive discharge and flows continuously through the cell, in which the hydrogen atoms are polarized by spin-exchange collisions with the polarized rubidium atoms. The hydrogen polarization is determined by a combination of fluorescence monitoring and magnetic resonance spectroscopy. Atomic hydrogen polarization as high as 2 z > H = 0.72(6) has been observed, which is the highest degree of polarization yet produced by this method. However, the polarization may be limited to this value due to the depolarization of the rubidium by radiation trapping. The spin-relaxation rate of atomic hydrogen on a paraffin-coated cell is also measured for the first time, and corresponds to about 3,800 wall bounces before electron-spin randomization. The second part of this work is a theoretical analysis of the problem of radiation trapping in a dense optically pumped alkali vapor. A Monte Carlo routine is used to simulate the trajectories of multiply scattered photons. The average spin angular momentum transfer from the photons to the vapor is used to determine the equilibrium polarization of the vapor as a function of the alkali density and the frequency of the pumping light

  9. Quantum properties of spin polarized helium 3 optically oriented by a LNA laser

    International Nuclear Information System (INIS)

    Leduc, M.; Laloe, F.; Nacher, P.J.; Tastevin, G.; Daniels, J.M.; Betts, D.

    1986-01-01

    Spin polarized helium 3 (/sup 3/He increasing) and also atomic hydrogen (H decreasing) are systems exhibiting a number of unusual and interesting properties at low temperature. This is true even for dilute polarized gases in spite of the weakness of the nuclear magnetic interaction between atoms. The changes in the macroscopic properties of the gas with the nuclear polarization P are pure consequences of the indistinguishability of the particles and of the symmetrization principle in quantum mechanics. The transport properties of the gas, such as viscosity and thermal conductivity, have been calculated and found to be strongly dependent on P below a few kelvins. Spin transport in /sup 3/He increasing gives rise at low temperature to collective oscillatory modes: the transverse spin waves. Large changes are also expected with P in the case of more dense /sup 3/He fluids, such as an increase with P in the saturated vapor pressure. Optical pumping is a convenient technique for efficient polarization of the nuclear spins in /sup 3/He gas/sup 2/ making use of the 2/sup 3/S-2/sup 3/P atomic line at 1.08 μm. The arrival of cw tunable lasers in the near IR in the early 1980s gave a strong impulse to the buildup of experiments with a view to measuring quantum properties of /sup 3/He increasing at low temperature. Color center lasers (F/sup +//sub 2/ in NaF) provide P values up to 70%. They are now being replaced by more easy to handle LNA lasers which have given so far P in excess of 50% at room temperature. At low temperature, direct optical pumping of a /sup 3/He cell leads to poor P values; for that reason a different technique is used

  10. EDITORIAL: New materials with high spin polarization: half-metallic Heusler compounds

    Science.gov (United States)

    Felser, Claudia; Hillebrands, Burkard

    2007-03-01

    , with emphasis on new rational design of Heusler compounds and advanced characterization tools. This volume of Journal of Physics D: Applied Physics summarizes the latest research results obtained in the Research Unit and presents it to the scientific public as a cluster of refereed papers. Half-metallic ferromagnets are an impressive example for the rational design of new materials based on computational physics. The paper of Kandpal et al demonstrates how a detailed understanding of the electronic structure, especially from the viewpoint of the properties of the minority band gap and the peculiar magnetic behaviour, enables us to predict new half-metallic compounds. A high interface quality and a well ordered compound are the preconditions to realize the predicted half-metallic properties. Wurmehl et al have carefully studied the surface and bulk structure of the classical Heusler compound CCFA using a combination of characterization methods. A deposition process of epitaxial thin films of CCFA was described by Conca et al. Kallmayer et al have correlated the structural properties of thin magnetron sputtered films determined by x-ray diffraction with details of the x-ray magnetic circular dichroism (XMCD) spectra. From the value of the magnetic moment located at the Cr atom and features of the Co absorption spectra, they conclude that the buffer layers lead to an improvement of local atomic order. A highlight of this Cluster Issue is the spin resolved photoemission result of Cinchetti and co-workers. A careful in situ preparation of the sample surface of CCFA leads to values for the room temperature spin polarization up to 45% at the Fermi level, the highest value measured so far at the surface region of a full Heusler compound at room temperature. Co2FeSi (CFS) is the half-metal Heusler compound with the highest Curie temperature reported so far [4]. Schneider et al report the deposition of well ordered thin Co2FeSi films by RF magnetron sputtering. The thickness

  11. Pellet fusion gain calculations modified by electrostatic double layers and by spin polarized nuclei

    International Nuclear Information System (INIS)

    Hora, H.; Cicchitelli, L.; Elijah, J.S.; Ghatak, A.K.; Goldsworthy, M.T.; Lalousis, P.; Eliezer, S.

    1984-01-01

    All preceding hydrodynamic computations of plasmas are wrong if the thermal conductivity is essential because electronic thermal conductivity is decreased in plasma inhomogeneities due to electrostatic double layers. In the worst case, ionic conductivity remains. We compare this with a possible electronic conductivity by the fast tail of the energy distribution. Using the volume ignition for fusion gain computations, we study the increase of gain by spin-polarization of nuclei for the DT reaction especially in non-linear ranges. Gain can increase by a factor 3.1. Contents are the following: electrostatic fields and double layers in inhomogeneous plasma, change of thermal conduction by double layers, consequences for pellet fusion, gain calculation with spin polarized nuclei. (Mori, K.)

  12. Spin-polarized spin-orbit-split quantum-well states in a metal film

    Energy Technology Data Exchange (ETDEWEB)

    Varykhalov, Andrei; Sanchez-Barriga, Jaime; Gudat, Wolfgang; Eberhardt, Wolfgang; Rader, Oliver [BESSY Berlin (Germany); Shikin, Alexander M. [St. Petersburg State University (Russian Federation)

    2008-07-01

    Elements with high atomic number Z lead to a large spin-orbit coupling. Such materials can be used to create spin-polarized electronic states without the presence of a ferromagnet or an external magnetic field if the solid exhibits an inversion asymmetry. We create large spin-orbit splittings using a tungsten crystal as substrate and break the structural inversion symmetry through deposition of a gold quantum film. Using spin- and angle-resolved photoelectron spectroscopy, it is demonstrated that quantum-well states forming in the gold film are spin-orbit split and spin polarized up to a thickness of at least 10 atomic layers. This is a considerable progress as compared to the current literature which reports spin-orbit split states at metal surfaces which are either pure or covered by at most a monoatomic layer of adsorbates.

  13. Spin-polarized free electron beam interaction with radiation and superradiant spin-flip radiative emission

    Directory of Open Access Journals (Sweden)

    A. Gover

    2006-06-01

    Full Text Available The problems of spin-polarized free-electron beam interaction with electromagnetic wave at electron-spin resonance conditions in a magnetic field and of superradiant spin-flip radiative emission are analyzed in the framework of a comprehensive classical model. The spontaneous emission of spin-flip radiation from electron beams is very weak. We show that the detectivity of electron spin resonant spin-flip and combined spin-flip/cyclotron-resonance-emission radiation can be substantially enhanced by operating with ultrashort spin-polarized electron beam bunches under conditions of superradiant (coherent emission. The proposed radiative spin-state modulation and the spin-flip radiative emission schemes can be used for control and noninvasive diagnostics of polarized electron/positron beams. Such schemes are of relevance in important scattering experiments off nucleons in nuclear physics and off magnetic targets in condensed matter physics.

  14. Transport Properties of Spin-Polarized Atomic Hydrogen Using Generalized Scattering Theory

    Science.gov (United States)

    Joudeh, B. R.; Sandouqa, A. S.

    2018-02-01

    Our results for the scattering and thermophysical properties of spin-polarized atomic hydrogen (H{\\downarrow }) have been presented in the temperature range 0.01-10 K using the Galitskii-Migdal-Feynman formalism. These results include the quantum second virial coefficient, the average total and viscosity cross sections, the viscosity, the diffusion coefficient, and the thermal conductivity. The calculations have been undertaken using three triplet-state potentials: Morse-type, Silvera and Born-Oppenheimer potentials. The Morse potential is less attractive and very simple, but less accurate to describe spin-polarized atomic hydrogen. That explains the differences between it and the other two potentials, which are clearly better. From the results of the average total cross sections, it is concluded the H{\\downarrow } remains a gas even at low temperature. The viscosity, the thermal conductivity, and the diffusion coefficients of H{\\downarrow } increase in all cases with increasing temperature.

  15. Control of the spin polarization of photoelectrons/photoions using short laser pulses

    International Nuclear Information System (INIS)

    Nakajima, Takashi

    2004-01-01

    We present a generic pump-probe scheme to control spin polarization of photoelectrons/photoions by short laser pulses. By coherently exciting fine structure manifolds of a multi-valence-electron system by the pump laser, a superposition of fine structure states is created. Since each fine structure state can be further decomposed into a superposition of various spin states of valence electrons, each spin component evolves differently in time. This means that varying the time delay between the pump and probe lasers leads to the control of spin states. Specific theoretical results are presented for two-valence-electron atoms, in particular for Mg, which demonstrate that not only the degree of spin polarization but also its sign can be manipulated through time delay. Since the underline physics is rather general and transparent, the presented idea may be potentially applied to nanostructures such as quantum wells and quantum dots

  16. Intense source of spin-polarized electrons using laser-induced optical pumping

    International Nuclear Information System (INIS)

    Gray, L.G.; Giberson, K.W.; Cheng, C.; Keiffer, R.S.; Dunning, F.B.; Walters, G.K.

    1983-01-01

    A source of spin-polarized electrons based on a laser-pumped flowing helium afterglow is described. He(2 3 S) atoms contained in the afterglow are optically pumped using circularly polarized 1.08-μm (2 3 S→2 3 P) radiation provided by a NaF (F 2+ )( color-center laser. Spin angular momentum conservation in subsequent chemi-ionization reactions with CO 2 produces polarized electrons that are extracted from the afterglow. At low currents, < or approx. =1 μA, polarizations of approx.70%--80% are achieved. At higher currents the polarization decreases, falling to approx.40% at 50 μA. The spin polarization can be simply reversed (P→-P) and the source is suitable for use in the majority of low-energy spin-dependent scattering experiments proposed to date

  17. Coupled spin and charge collective excitations in a spin polarized electron gas

    International Nuclear Information System (INIS)

    Marinescu, D.C.; Quinn, J.J.; Yi, K.S.

    1997-01-01

    The charge and longitudinal spin responses induced in a spin polarized quantum well by a weak electromagnetic field are investigated within the framework of the linear response theory. The authors evaluate the excitation frequencies for the intra- and inter-subband transitions of the collective charge and longitudinal spin density oscillations including many-body corrections beyond the random phase approximation through the spin dependent local field factors, G σ ± (q,ω). An equation-of-motion method was used to obtain these corrections in the limit of long wavelengths, and the results are given in terms of the equilibrium pair correlation function. The finite degree of spin polarization is shown to introduce coupling between the charge and spin density modes, in contrast with the result for an unpolarized system

  18. Illuminating "spin-polarized" Bloch wave-function projection from degenerate bands in decomposable centrosymmetric lattices

    Science.gov (United States)

    Li, Pengke; Appelbaum, Ian

    2018-03-01

    The combination of space inversion and time-reversal symmetries results in doubly degenerate Bloch states with opposite spin. Many lattices with these symmetries can be constructed by combining a noncentrosymmetric potential (lacking this degeneracy) with its inverted copy. Using simple models, we unravel the evolution of local spin splitting during this process of inversion symmetry restoration, in the presence of spin-orbit interaction and sublattice coupling. Importantly, through an analysis of quantum mechanical commutativity, we examine the difficulty of identifying states that are simultaneously spatially segregated and spin polarized. We also explain how surface-sensitive experimental probes (such as angle-resolved photoemission spectroscopy, or ARPES) of "hidden spin polarization" in layered materials are susceptible to unrelated spin splitting intrinsically induced by broken inversion symmetry at the surface.

  19. High spin-polarization in ultrathin Co{sub 2}MnSi/CoPd multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Galanakis, I., E-mail: galanakis@upatras.gr

    2015-03-01

    Half-metallic Co{sub 2}MnSi finds a broad spectrum of applications in spintronic devices either in the form of thin films or as spacer in multilayers. Using state-of-the-art ab-initio electronic structure calculations we exploit the electronic and magnetic properties of ultrathin Co{sub 2}MnSi/CoPd multilayers. We show that these heterostructures combine high values of spin-polarization at the Co{sub 2}MnSi spacer with the perpendicular magnetic anisotropy of binary compounds such as CoPd. Thus they could find application in spintronic/magnetoelectronic devices. - Highlights: • Ab-initio study of ultrathin Co{sub 2}MnSi/CoPd multilayers. • Large values of spin-polarization at the Fermi are retained. • Route for novel spintronic/magnetoelectronic devices.

  20. Micromagnetism in (001) magnetite by spin-polarized low-energy electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Figuera, Juan de la, E-mail: juan.delafiguera@iqfr.csic.es [Instituto de Química-Física “Rocasolano”, CSIC, Madrid 28006 (Spain); Vergara, Lucía [Instituto de Química-Física “Rocasolano”, CSIC, Madrid 28006 (Spain); N' Diaye, Alpha T. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Quesada, Adrian [Instituto de Cerámica y Vidrio, CSIC, Calle Kelsen 5, 28049, Madrid (Spain); Schmid, Andreas K. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)

    2013-07-15

    Spin-polarized low-energy electron microscopy was used to image a magnetite crystal with (001) surface orientation. Sets of spin-dependent images of magnetic domain patterns observed in this surface were used to map the direction of the magnetization vector with high spatial and angular resolution. We find that domains are magnetized along the surface <110> directions, and domain wall structures include 90° and 180° walls. A type of unusually curved domain walls are interpreted as Néel-capped surface terminations of 180° Bloch walls. - Highlights: ► The (001) surface of magnetite is imaged by spin-polarized low-energy electron microscopy. ► The magnetic domain microstructure is resolved. ► Magnetic easy axes in this surface are found to be along <110> directions. ► Magnetic domain wall structures include wide Néel-caps.

  1. Magnetic Switching of a Single Molecular Magnet due to Spin-Polarized Current

    OpenAIRE

    Misiorny, Maciej; Barnas, Józef

    2006-01-01

    Magnetic switching of a single molecular magnet (SMM) due to spin-polarized current flowing between ferromagnetic metallic electrodes is investigated theoretically. Magnetic moments of the electrodes are assumed to be collinear and parallel to the magnetic easy axis of the molecule. Electrons tunneling through a barrier between magnetic leads are coupled to the SMM via exchange interaction. The current flowing through the system as well as the spin relaxation times of the SMM are calculated f...

  2. Application of the Ursell-Mayer method in the theory of spin-polarized atomic hydrogen

    International Nuclear Information System (INIS)

    Kilic, S.; Radelja, T.

    1981-01-01

    Employing the Ursell-Mayer method and Ljolje semi-free gas model analytic relations describing ground state properties (energy, pressure, compressibility, sound velocity, radial distribution function and one-particle density matrix) of spin-polarized atomic hydrogen were derived. The expressions are valid up to density 2 10 26 atoms/m 3 . It was found out that at density of 2 10 26 atoms/m 3 the condensation of particle in momentum space is 88% (at absolute zero). (orig.)

  3. Spin polarization in quantum dots by radiation field with circular polarization

    CERN Document Server

    Bulgakov, E N

    2001-01-01

    For circular quantum dot (QD) with account of the Razhba spin-orbit interaction (SOI) an exact energy spectrum is obtained. For the small SOI constant the Eigen functions of the QD are found. It is shown that application of radiation field with circular polarization lifts the Kramers degeneracy of the Eigen states of the QD. Effective spin polarization of transmitted electrons through the QD by radiation field with circular polarization is demonstrated

  4. Sensing Noncollinear Magnetism at the Atomic Scale Combining Magnetic Exchange and Spin-Polarized Imaging.

    Science.gov (United States)

    Hauptmann, Nadine; Gerritsen, Jan W; Wegner, Daniel; Khajetoorians, Alexander A

    2017-09-13

    Storing and accessing information in atomic-scale magnets requires magnetic imaging techniques with single-atom resolution. Here, we show simultaneous detection of the spin-polarization and exchange force with or without the flow of current with a new method, which combines scanning tunneling microscopy and noncontact atomic force microscopy. To demonstrate the application of this new method, we characterize the prototypical nanoskyrmion lattice formed on a monolayer of Fe/Ir(111). We resolve the square magnetic lattice by employing magnetic exchange force microscopy, demonstrating its applicability to noncollinear magnetic structures for the first time. Utilizing distance-dependent force and current spectroscopy, we quantify the exchange forces in comparison to the spin-polarization. For strongly spin-polarized tips, we distinguish different signs of the exchange force that we suggest arises from a change in exchange mechanisms between the probe and a skyrmion. This new approach may enable both nonperturbative readout combined with writing by current-driven reversal of atomic-scale magnets.

  5. Effect of spin polarization on the structural properties and bond ...

    Indian Academy of Sciences (India)

    The population of Fe–B bond increases from 0.175 (FM) to 0.2 (NM) in FeB. On the other hand, the calculated bond overlap populations in Fe2B kept unchanged and the value is 0.15 electrons in the two cases. 3.3 Bond hardness. Hardness is a measure of the resistance of materials against permanent deformations.

  6. Electron-spin polarization of photoions produced through photoionization from the laser-excited triplet state of Sr

    International Nuclear Information System (INIS)

    Yonekura, Nobuaki; Nakajima, Takashi; Matsuo, Yukari; Kobayashi, Tohru; Fukuyama, Yoshimitsu

    2004-01-01

    We report the detailed experimental study on the production of electron-spin-polarized Sr + ions through one-photon resonant two-photon ionization via laser-excited 5s5p 3 P 1 (M J =+1) of Sr atoms produced by laser-ablation. We have experimentally confirmed that the use of laser-ablation for the production of Sr atoms prior to photoionization does not affect the electron-spin polarization. We have found that the degree of electron-spin polarization is 64±9%, which is in good agreement with our recent theoretical prediction. As we discuss in detail, we infer, from a simple analysis, that photoelectrons, being the counterpart of electron-spin-polarized Sr + ions, have approximately the same degree of electron-spin polarization. Our experimental results demonstrate that the combined use of laser-ablation technique and pulsed lasers for photoionization would be a compact and effective way to realize a pulsed source for spin-polarized ions and electrons for the studies of various spin-dependent dynamics in chemical physics

  7. A cryostat to hold frozen-spin polarized HD targets in CLAS: HDice-II

    International Nuclear Information System (INIS)

    The design, fabrication, operation, and performance of a 3/4 He dilution refrigerator and superconducting magnet system for holding a frozen-spin polarized hydrogen deuteride target in the Jefferson Laboratory CLAS detector during photon beam running is reported. The device operates both vertically (for target loading) and horizontally (for target bombardment). The device proves capable of maintaining a base temperature of 50 mK and a holding field of 1 T for extended periods. These characteristics enabled multi-month polarization lifetimes for frozen spin HD targets having proton polarization of up to 50% and deuteron up to 27%.

  8. A cryostat to hold frozen-spin polarized HD targets in CLAS: HDice-II

    Energy Technology Data Exchange (ETDEWEB)

    Lowry, M.M., E-mail: mlowry@jlab.org [Thomas Jefferson National Accelerator Facility, 12000 Jefferson Avenue, Newport News, VA 23606 (United States); Bass, C.D. [Thomas Jefferson National Accelerator Facility, 12000 Jefferson Avenue, Newport News, VA 23606 (United States); D' Angelo, A. [Thomas Jefferson National Accelerator Facility, 12000 Jefferson Avenue, Newport News, VA 23606 (United States); Universita' di Roma ‘Tor Vergata’, and INFN Sezione di Roma ‘Tor Vergata’, Via della Ricerca Scientifica, 1, I-00133 Roma (Italy); Deur, A.; Dezern, G. [Thomas Jefferson National Accelerator Facility, 12000 Jefferson Avenue, Newport News, VA 23606 (United States); Hanretty, C. [University of Virginia, 1400 University Avenue, Charlottesville, VA 22903 (United States); Ho, D. [Carnegie-Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213 (United States); Kageya, T.; Kashy, D. [Thomas Jefferson National Accelerator Facility, 12000 Jefferson Avenue, Newport News, VA 23606 (United States); Khandaker, M. [Norfolk State University, 700 Park Avenue, Norfolk, VA 23504 (United States); Laine, V. [Thomas Jefferson National Accelerator Facility, 12000 Jefferson Avenue, Newport News, VA 23606 (United States); Université Blaise Pascal, 34 Avenue Carnot, 63000 Clermont-Ferrand (France); O' Connell, T. [University of Connecticut, 115 N Eagleville Road, Storrs-Mansfield, CT 06269 (United States); Pastor, O. [Thomas Jefferson National Accelerator Facility, 12000 Jefferson Avenue, Newport News, VA 23606 (United States); Peng, P. [University of Virginia, 1400 University Avenue, Charlottesville, VA 22903 (United States); Sandorfi, A.M. [Thomas Jefferson National Accelerator Facility, 12000 Jefferson Avenue, Newport News, VA 23606 (United States); Sokhan, D. [Institut de Physique Nucleaire, Bat 100 – M053, Orsay 91406 (France); and others

    2016-04-11

    The design, fabrication, operation, and performance of a {sup 3/4}He dilution refrigerator and superconducting magnet system for holding a frozen-spin polarized hydrogen deuteride target in the Jefferson Laboratory CLAS detector during photon beam running is reported. The device operates both vertically (for target loading) and horizontally (for target bombardment). The device proves capable of maintaining a base temperature of 50 mK and a holding field of 1 T for extended periods. These characteristics enabled multi-month polarization lifetimes for frozen spin HD targets having proton polarization of up to 50% and deuteron up to 27%.

  9. Low energy spin polarized radioactive beams as a probe of thin films and interfaces

    CERN Document Server

    Kiefl, R F; Amaudruz, P A; Arseneau, D; Baartman, R; Beals, T R; Behr, J; Brewer, J; Daviel, S; Hatakeyama, A; Hitti, B; Kreitzman, S R; Levy, C D P; Miller, R; Olivo, M; Poutissou, R; Morris, G D; Dunsiger, S R; Heffner, R; Chow, K H; Hirayama, Y; Izumi, H; Bommas, C; Dumont, E; Greene, L H

    2003-01-01

    A spectrometer for beta-detected nuclear magnetic resonance (beta-NMR) has been commissioned at the ISAC facility at TRIUMF. A beam of low energy highly spin polarized sup 8 Li sup + can be decelerated and implanted into ultra-thin structures 6-400 nm thick. beta-NMR provides local information on the electronic and magnetic properties of materials which is similar to conventional NMR but can be used as a sensitive probe of ultra-thin films, interfaces and other nanostructures. We report here on the status of the spectrometer and preliminary results on a simple metal film.

  10. Light-free magnetic resonance force microscopy for studies of electron spin polarized systems

    International Nuclear Information System (INIS)

    Pelekhov, Denis V.; Selcu, Camelia; Banerjee, Palash; Chung Fong, Kin; Chris Hammel, P.; Bhaskaran, Harish; Schwab, Keith

    2005-01-01

    Magnetic resonance force microscopy is a scanned probe technique capable of three-dimensional magnetic resonance imaging. Its excellent sensitivity opens the possibility for magnetic resonance studies of spin accumulation resulting from the injection of spin polarized currents into a para-magnetic collector. The method is based on mechanical detection of magnetic resonance which requires low noise detection of cantilever displacement; so far, this has been accomplished using optical interferometry. This is undesirable for experiments on doped silicon, where the presence of light is known to enhance spin relaxation rates. We report a non-optical displacement detection scheme based on sensitive microwave capacitive readout

  11. Spin-polarized transport in manganite-based magnetic nano structures

    International Nuclear Information System (INIS)

    Granada, Mara

    2007-01-01

    Giant magnetoresistance (G M R) and tunnel magnetoresistance are spin polarized transport phenomena which are observed in magnetic multilayers.They consist in a large variation of the electrical resistivity of the system depending on whether the magnetizations of the magnetic layers are aligned parallel or anti-parallel to each other. In order to be able to align the magnetic layers by means of an external magnetic field, they must not be strongly ferromagnetically coupled.The extrinsic magnetoresistance effects in magnetic multilayers, either G M R in the case of a metallic spacer, or T M R in the case of an insulating spacer, are observed at low magnetic fields, which makes these phenomena interesting for technological applications.We studied the possibility of using the ferromagnetic manganite La 0 ,75Sr 0 ,25MnO 3 (L S M O) in magneto resistive devices, with different materials as a spacer layer.As the main result of this work, we report G M R and T M R measurements in L S M O/LaNiO 3 /L S M O and L S M O/CaMnO 3 /L S M O tri layers, respectively, observed for the first time in these systems.This work included the deposition of films and multilayers by sputtering, the structural characterization of the samples and the study of their magnetic and electric transport properties.Our main interest was the study of G M R in L S M O/LaNiO 3 /L S M O tri layers.It was necessary to firstly characterize the magnetic coupling of L S M O layers through the L N O spacer. After that, we performed electric transport measurements with the current in the plane of the samples.We measured a G M R contribution of ∼ 0,55 % at T = 83 K.We designed a procedure for patterning the samples by e-beam lithography for electric transport measurements with the current perpendicular to the plane. We also performed the study of L S M O/CaMnO 3 /L S M O tri layers with an insulating spacer.We studied the magnetic coupling, as in the previous case.Then we fabricated a tunnel junction for

  12. Very efficient spin polarization analysis (VESPA): new exchange scattering-based setup for spin-resolved ARPES at APE-NFFA beamline at Elettra.

    Science.gov (United States)

    Bigi, Chiara; Das, Pranab K; Benedetti, Davide; Salvador, Federico; Krizmancic, Damjan; Sergo, Rudi; Martin, Andrea; Panaccione, Giancarlo; Rossi, Giorgio; Fujii, Jun; Vobornik, Ivana

    2017-07-01

    Complete photoemission experiments, enabling measurement of the full quantum set of the photoelectron final state, are in high demand for studying materials and nanostructures whose properties are determined by strong electron and spin correlations. Here the implementation of the new spin polarimeter VESPA (Very Efficient Spin Polarization Analysis) at the APE-NFFA beamline at Elettra is reported, which is based on the exchange coupling between the photoelectron spin and a ferromagnetic surface in a reflectometry setup. The system was designed to be integrated with a dedicated Scienta-Omicron DA30 electron energy analyzer allowing for two simultaneous reflectometry measurements, along perpendicular axes, that, after magnetization switching of the two targets, allow the three-dimensional vectorial reconstruction of the spin polarization to be performed while operating the DA30 in high-resolution mode. VESPA represents the very first installation for spin-resolved ARPES (SPARPES) at the Elettra synchrotron in Trieste, and is being heavily exploited by SPARPES users since autumn 2015.

  13. Regular and irregular dynamics of spin-polarized wavepackets in a mesoscopic quantum dot at the edge of topological insulator

    Energy Technology Data Exchange (ETDEWEB)

    Khomitsky, D. V., E-mail: khomitsky@phys.unn.ru; Chubanov, A. A.; Konakov, A. A. [Lobachevsky National Research State University of Nizhny Novgorod, Department of Physics (Russian Federation)

    2016-12-15

    The dynamics of Dirac–Weyl spin-polarized wavepackets driven by a periodic electric field is considered for the electrons in a mesoscopic quantum dot formed at the edge of the two-dimensional HgTe/CdTe topological insulator with Dirac–Weyl massless energy spectra, where the motion of carriers is less sensitive to disorder and impurity potentials. It is observed that the interplay of strongly coupled spin and charge degrees of freedom creates the regimes of irregular dynamics in both coordinate and spin channels. The border between the regular and irregular regimes determined by the strength and frequency of the driving field is found analytically within the quasiclassical approach by means of the Ince–Strutt diagram for the Mathieu equation, and is supported by full quantum-mechanical simulations of the driven dynamics. The investigation of quasienergy spectrum by Floquet approach reveals the presence of non-Poissonian level statistics, which indicates the possibility of chaotic quantum dynamics and corresponds to the areas of parameters for irregular regimes within the quasiclassical approach. We find that the influence of weak disorder leads to partial suppression of the dynamical chaos. Our findings are of interest both for progress in the fundamental field of quantum chaotic dynamics and for further experimental and technological applications of spindependent phenomena in nanostructures based on topological insulators.

  14. Photoemission of Bi_{2}Se_{3} with Circularly Polarized Light: Probe of Spin Polarization or Means for Spin Manipulation?

    Directory of Open Access Journals (Sweden)

    J. Sánchez-Barriga

    2014-03-01

    Full Text Available Topological insulators are characterized by Dirac-cone surface states with electron spins locked perpendicular to their linear momenta. Recent theoretical and experimental work implied that this specific spin texture should enable control of photoelectron spins by circularly polarized light. However, these reports questioned the so far accepted interpretation of spin-resolved photoelectron spectroscopy. We solve this puzzle and show that vacuum ultraviolet photons (50–70 eV with linear or circular polarization indeed probe the initial-state spin texture of Bi_{2}Se_{3} while circularly polarized 6-eV low-energy photons flip the electron spins out of plane and reverse their spin polarization, with its sign determined by the light helicity. Our photoemission calculations, taking into account the interplay between the varying probing depth, dipole-selection rules, and spin-dependent scattering effects involving initial and final states, explain these findings and reveal proper conditions for light-induced spin manipulation. Our results pave the way for future applications of topological insulators in optospintronic devices.

  15. Simultaneous production of spin-polarized ions/electrons based on two-photon ionization of laser-ablated metallic atoms

    International Nuclear Information System (INIS)

    Nakajima, Takashi; Yonekura, Nobuaki; Matsuo, Yukari; Kobayashi, Tohru; Fukuyama, Yoshimitsu

    2003-01-01

    We demonstrate the simultaneous production of spin-polarized ions/electrons using two-color, two-photon ionization of laser-ablated metallic atoms. Specifically, we have applied the developed technique to laser-ablated Sr atoms, and found that the electron-spin polarization of Sr + ions, and accordingly, the spin polarization of photoelectrons is 64%±9%, which is in good agreement with the theoretical prediction we have recently reported [T. Nakajima and N. Yonekura, J. Chem. Phys. 117, 2112 (2002)]. Our experimental results open up a simple way toward the construction of a spin-polarized dual ion/electron source

  16. Electron-spin polarization in tunnel junctions with ferromagnetic EuS barriers

    International Nuclear Information System (INIS)

    Hao, X.; Moodera, J.S.; Meservey, R.

    1989-01-01

    The authors report here spin-polarized tunneling experiments using non-ferromagnetic electrodes and ferromagnetic EuS barriers. Because of the conduction band in EuS splits into spin-up and spin-down subbands when the temperature is below 16.7 K, the Curie temperature of EuS, the tunnel barrier for electrons with different spin directions is different, therefore giving rise to tunnel current polarization. The spin-filter effect, as it may be called, was observed earlier, directly or indirectly, by several groups: Esaki et al. made a tunneling study on junctions having EuS and EuSe barriers; Thompson et al. studied Schottky barrier tunneling between In and doped EuS; Muller et al. and Kisker et al. performed electron field emission experiments on EuS-coated tungsten tips. The field emission experiments gave a maximum polarization of (89 + 7)% for the emitted electrons. Although the previous tunneling studies did not directly show electron polarization, their results were explained by the same spin- filter effect. This work uses the spin-polarized tunneling technique to show directly that tunnel current is indeed polarized and polarization can be as high as 85%

  17. Antiferromagnetic Spin Coupling between Rare Earth Adatoms and Iron Islands Probed by Spin-Polarized Tunneling.

    Science.gov (United States)

    Coffey, David; Diez-Ferrer, José Luis; Serrate, David; Ciria, Miguel; de la Fuente, César; Arnaudas, José Ignacio

    2015-09-03

    High-density magnetic storage or quantum computing could be achieved using small magnets with large magnetic anisotropy, a requirement that rare-earth iron alloys fulfill in bulk. This compelling property demands a thorough investigation of the magnetism in low dimensional rare-earth iron structures. Here, we report on the magnetic coupling between 4f single atoms and a 3d magnetic nanoisland. Thulium and lutetium adatoms deposited on iron monolayer islands pseudomorphically grown on W(110) have been investigated at low temperature with scanning tunneling microscopy and spectroscopy. The spin-polarized current indicates that both kind of adatoms have in-plane magnetic moments, which couple antiferromagnetically with their underlying iron islands. Our first-principles calculations explain the observed behavior, predicting an antiparallel coupling of the induced 5d electrons magnetic moment of the lanthanides with the 3d magnetic moment of iron, as well as their in-plane orientation, and pointing to a non-contribution of 4f electrons to the spin-polarized tunneling processes in rare earths.

  18. Multispin-assisted optical pumping of bulk 13C nuclear spin polarization in diamond

    Science.gov (United States)

    Pagliero, Daniela; Rao, K. R. Koteswara; Zangara, Pablo R.; Dhomkar, Siddharth; Wong, Henry H.; Abril, Andrea; Aslam, Nabeel; Parker, Anna; King, Jonathan; Avalos, Claudia E.; Ajoy, Ashok; Wrachtrup, Joerg; Pines, Alexander; Meriles, Carlos A.

    2018-01-01

    One of the most remarkable properties of the nitrogen-vacancy (NV) center in diamond is that optical illumination initializes its electronic spin almost completely, a feature that can be exploited to polarize other spin species in their proximity. Here we use field-cycled nuclear magnetic resonance to investigate the mechanisms of spin-polarization transfer from NVs to 13C spins in diamond at room temperature. We focus on the dynamics near 51 mT, where a fortuitous combination of energy-matching conditions between electron and nuclear spin levels gives rise to alternative polarization transfer channels. By monitoring the 13C spin polarization as a function of the applied magnetic field, we show 13C spin pumping takes place via a multispin cross-relaxation process involving the N V- spin and the electronic and nuclear spins of neighboring P1 centers. Further, we find that this mechanism is insensitive to the crystal orientation relative to the magnetic field, although the absolute level of 13C polarization—reaching up to ˜3 % under optimal conditions—can vary substantially depending on the interplay between optical pumping efficiency, photogenerated carriers, and laser-induced heating.

  19. Spin-polarized radioactive isotope beam produced by tilted-foil technique

    International Nuclear Information System (INIS)

    Hirayama, Yoshikazu; Mihara, Mototsugu; Watanabe, Yutaka; Jeong, Sun-Chan; Miyatake, Hiroari; Momota, Sadao; Hashimoto, Takashi; Imai, Nobuaki; Matsuta, Kensaku; Ishiyama, Hironobu; Ichikawa, Shin-ichi; Ishii, Tetsuro; Izumikawa, Takuji; Katayama, Ichiro; Kawakami, Hirokane; Kawamura, Hirokazu; Nishinaka, Ichiro; Nishio, Katsuhisa; Makii, Hiroyuki; Mitsuoka, Shin-ichi

    2013-01-01

    Highlights: • Detail study for tilted foil technique. • New equation for estimating nuclear polarization dependence on the beam energy. • Production of nuclear polarization for heaviest nucleus 123 In in ground state. -- Abstract: The tilted-foil method for producing spin-polarized radioactive isotope beams has been studied using the re-accelerated radioactive 8 Li and 123 In beams produced at Tokai Radioactive Ion Accelerator Complex (TRIAC) facility. We successfully produced polarization in a 8 Li beam of 7.3(5)% using thin polystyrene foils (4.2 μg/cm 2 ). The systematic study of the nuclear polarization as a function of the number of foils and beam energy has been performed, confirming the features of the tilted-foil technique experimentally. After the study, a spin-polarized radioactive 123 In beam, which is the heaviest ever polarized in its ground state by this method, has been successfully generated by the tilted-foil method, for the nuclear spectroscopy around the doubly magic nucleus 132 Sn

  20. Generalized nuclear Fukui functions in the framework of spin-polarized density-functional theory

    International Nuclear Information System (INIS)

    Chamorro, E.; Proft, F. de; Geerlings, P.

    2005-01-01

    An extension of Cohen's nuclear Fukui function is presented in the spin-polarized framework of density-functional theory (SP-DFT). The resulting new nuclear Fukui function indices Φ Nα and Φ Sα are intended to be the natural descriptors for the responses of the nuclei to changes involving charge transfer at constant multiplicity and also the spin polarization at constant number of electrons. These generalized quantities allow us to gain new insights within a perturbative scheme based on DFT. Calculations of the electronic and nuclear SP-DFT quantities are presented within a Kohn-Sham framework of chemical reactivity for a sample of molecules, including H 2 O, H 2 CO, and some simple nitrenes (NX) and phosphinidenes (PX), with X=H, Li, F, Cl, OH, SH, NH 2 , and PH 2 . Results have been interpreted in terms of chemical bonding in the context of Berlin's theorem, which provides a separation of the molecular space into binding and antibinding regions

  1. Enhancing current-induced torques by abutting additional spin polarizer layer to nonmagnetic metal layer

    Science.gov (United States)

    Go, Gyungchoon; Lee, Kyung-Jin; Kim, Young Keun

    2017-04-01

    Recently, the switching of a perpendicularly magnetized ferromagnet (FM) by injecting an in-plane current into an attached non-magnet (NM) has become of emerging technological interest. This magnetization switching is attributed to the spin-orbit torque (SOT) originating from the strong spin-orbit coupling of the NM layer. However, the switching efficiency of the NM/FM structure itself may be insufficient for practical use, as for example, in spin transfer torque (STT)-based magnetic random access memory (MRAM) devices. Here we investigate spin torque in an NM/FM structure with an additional spin polarizer (SP) layer abutted to the NM layer. In addition to the SOT contribution, a spin-polarized current from the SP layer creates an extra spin chemical potential difference at the NM/FM interface and gives rise to a STT on the FM layer. We show that, using typical parameters including device width, thickness, spin diffusion length, and the spin Hall angle, the spin torque from the SP layer can be much larger than that from the spin Hall effect (SHE) of the NM.

  2. Tunable spin-polarized edge transport in inverted quantum-well junctions

    Science.gov (United States)

    Nanclares, Dimy; Lima, Leandro R. F.; Lewenkopf, Caio H.; da Silva, Luis G. G. V. Dias

    2017-10-01

    Inverted HgTe/CdTe quantum wells have been used as a platform for the realization of two-dimensional topological insulators, bulk insulator materials with spin-helical metallic edge states protected by time-reversal symmetry. This paper investigates the spectrum and the charge transport in HgTe/CdTe quantum well junctions both in the topological regime and in the absence of time-reversal symmetry. We model the system using the Bernevig-Hughes-Zhang effective Hamiltonian and compute the transport properties using recursive Green's functions with a finite differences' method. Specifically, we have studied the material's spatially resolved conductance in a setup with a gated central region, forming monopolar (n -n'-n ) and heteropolar (n -p -n , n -TI-n ) double junctions, which have been recently realized in experiments. We find regimes in which the edge states carry spin-polarized currents in the central region even in the presence of a small magnetic field, which breaks time-reversal symmetry. More interestingly, the conductance displays spin-dependent, Fabry-Perót-like oscillations as a function of the central gate voltage producing tunable, fully spin-polarized currents through the device.

  3. Magnetic adatoms in two and four terminal graphene nanoribbons: A comparison between their spin polarized transport

    Science.gov (United States)

    Ganguly, Sudin; Basu, Saurabh

    2018-04-01

    We study the charge and spin transport in two and four terminal graphene nanoribbons (GNR) decorated with random distribution of magnetic adatoms. The inclusion of the magnetic adatoms generates only the z-component of the spin polarized conductance via an exchange bias in the absence of Rashba spin-orbit interaction (SOI), while in presence of Rashba SOI, one is able to create all the three (x, y and z) components. This has important consequences for possible spintronic applications. The charge conductance shows interesting behaviour near the zero of the Fermi energy. Where in presence of magnetic adatoms the familiar plateau at 2e2 / h vanishes, thereby transforming a quantum spin Hall insulating phase to an ordinary insulator. The local charge current and the local spin current provide an intuitive idea on the conductance features of the system. We found that, the local charge current is independent of Rashba SOI, while the three components of the local spin currents are sensitive to Rashba SOI. Moreover the fluctuations of the spin polarized conductance are found to be useful quantities as they show specific trends, that is, they enhance with increasing adatom densities. A two terminal GNR device seems to be better suited for possible spintronic applications.

  4. Stability of superfluid phases in the 2D spin-polarized attractive Hubbard model

    Science.gov (United States)

    Kujawa-Cichy, A.; Micnas, R.

    2011-08-01

    We study the evolution from the weak coupling (BCS-like limit) to the strong coupling limit of tightly bound local pairs (LPs) with increasing attraction, in the presence of the Zeeman magnetic field (h) for d=2, within the spin-polarized attractive Hubbard model. The broken symmetry Hartree approximation as well as the strong coupling expansion are used. We also apply the Kosterlitz-Thouless (KT) scenario to determine the phase coherence temperatures. For spin-independent hopping integrals (t↑=t↓), we find no stable homogeneous polarized superfluid (SCM) state in the ground state for the strong attraction and obtain that for a two-component Fermi system on a 2D lattice with population imbalance, phase separation (PS) is favoured for a fixed particle concentration, even on the LP (BEC) side. We also examine the influence of spin-dependent hopping integrals (mass imbalance) on the stability of the SCM phase. We find a topological quantum phase transition (Lifshitz type) from the unpolarized superfluid phase (SC0) to SCM and tricritical points in the h-|U| and t↑/t↓-|U| ground-state phase diagrams. We also construct the finite temperature phase diagrams for both t↑=t↓ and t↑≠t↓ and analyze the possibility of occurrence of a spin-polarized KT superfluid.

  5. Improved Electron Yield and Spin-Polarization from III-V Photocathodes Via Bias Enhanced Carrier Drift

    CERN Document Server

    Mulhollan, Gregory A; Brachmann, Axel; Clendenin, James E; Garwin, Edward; Kirby, Robert; Luh Dah An; Maruyama, Takashi; Prepost, Richard

    2005-01-01

    Spin-polarized electrons are commonly used in high energy physics. Future work will benefit from greater polarization. Polarizations approaching 90% have been achieved at the expense of yield. The primary paths to higher polarization are material design and electron transport. Our work addresses the latter. Photoexcited electrons may be preferentially emitted or suppressed by an electric field applied across the active region. We are tuning this forward bias for maximum polarization and yield, together with other parameters, e.g., doping profile Preliminary measurements have been carried out on bulk GaAs. As expected, the yield change far from the bandgap is quite large. The bias is applied to the bottom (non-activated) side of the cathode so that the accelerating potential as measured with respect to the ground potential chamber walls is unchanged for different front-to-back cathode bias values. For a bias which enhances emission, the yield nearly doubles. For a bias which diminishes emission, the yield is a...

  6. Improved Electron Yield and Spin-Polarization from III-V Photocathodes via Bias Enhanced Carrier Drift: Final Report

    International Nuclear Information System (INIS)

    Mulhollan, Gregory A.

    2006-01-01

    In this DOE STTR program, Saxet Surface Science, with the Stanford Linear Accelerator Center as partner, designed, built and tested photocathode structures such that optimal drift-enhanced spin-polarization from GaAs based photoemitters was achieved with minimal bias supply requirements. The forward bias surface grid composition was optimized for maximum polarization and yield, together with other construction parameters including doping profile. This program has culminated in a cathode bias structure affording increased electron spin polarization when applied to III-V based photocathodes. The optimized bias structure has been incorporated into a cathode mounting and biasing design for use in a polarized electron gun.

  7. Spin-polarized x-ray emission of 3d transition-metal ions : A comparison via K alpha and K beta detection

    NARCIS (Netherlands)

    Wang, Xin; deGroot, F.M.F.; Cramer, SP

    1997-01-01

    This paper demonstrates that spin-polarized x-ray-excitation spectra can be obtained using K alpha emission as well as K beta lines. A spin-polarized analysis of K alpha x-ray emission and the excitation spectra by K alpha detection on a Ni compound is reported. A systematic analysis of the

  8. Dark states in spin-polarized transport through triple quantum dot molecules

    Science.gov (United States)

    Wrześniewski, K.; Weymann, I.

    2018-02-01

    We study the spin-polarized transport through a triple-quantum-dot molecule weakly coupled to ferromagnetic leads. The analysis is performed by means of the real-time diagrammatic technique, including up to the second order of perturbation expansion with respect to the tunnel coupling. The emphasis is put on the impact of dark states on spin-resolved transport characteristics. It is shown that the interplay of coherent population trapping and cotunneling processes results in a highly nontrivial behavior of the tunnel magnetoresistance, which can take negative values. Moreover, a super-Poissonian shot noise is found in transport regimes where the current is blocked by the formation of dark states, which can be additionally enhanced by spin dependence of tunneling processes, depending on the magnetic configuration of the device. The mechanisms leading to those effects are thoroughly discussed.

  9. Spin-polarized scanning-tunneling probe for helical Luttinger liquids.

    Science.gov (United States)

    Das, Sourin; Rao, Sumathi

    2011-06-10

    We propose a three-terminal spin-polarized STM setup for probing the helical nature of the Luttinger liquid edge state that appears in the quantum spin Hall system. We show that the three-terminal tunneling conductance depends on the angle (θ) between the magnetization direction of the tip and the local orientation of the electron spin on the edge while the two terminal conductance is independent of this angle. We demonstrate that chiral injection of an electron into the helical Luttinger liquid (when θ is zero or π) is associated with fractionalization of the spin of the injected electron in addition to the fractionalization of its charge. We also point out a spin current amplification effect induced by the spin fractionalization.

  10. Theoretical consideration of spin-polarized resonant tunneling in magnetic tunnel junctions

    International Nuclear Information System (INIS)

    Mu Haifeng; Zhu Zhengang; Zheng Qingrong; Jin Biao; Wang Zhengchuan; Su Gang

    2004-01-01

    A recent elegant experimental realization [S. Yuasa et al., Science 297 (2002) 234] of the spin-polarized resonant tunneling in magnetic tunnel junctions is interpreted in terms of a two-band model. It is shown that the tunnel magnetoresistance (TMR) decays oscillatorily with the thickness of the normal metal (NM) layer, being fairly in agreement with the experimental observation. The tunnel conductance is found to decay with slight oscillations with the increase of the NM layer thickness, which is also well consistent with the experiment. In addition, when the magnetizations of both ferromagnet electrodes are not collinearly aligned, TMR is found to exhibit sharp resonant peaks at some particular thickness of the NM layer. The peaked TMR obeys nicely a Gaussian distribution against the relative orientation of the magnetizations

  11. Magnetic switching of a single molecular magnet due to spin-polarized current

    Science.gov (United States)

    Misiorny, Maciej; Barnaś, Józef

    2007-04-01

    Magnetic switching of a single molecular magnet (SMM) due to spin-polarized current flowing between ferromagnetic metallic leads (electrodes) is investigated theoretically. Magnetic moments of the leads are assumed to be collinear and parallel to the magnetic easy axis of the molecule. Electrons tunneling through the barrier between magnetic leads are coupled to the SMM via exchange interaction. The current flowing through the system, as well as the spin relaxation times of the SMM, are calculated from the Fermi golden rule. It is shown that spin of the SMM can be reversed by applying a certain voltage between the two magnetic electrodes. Moreover, the switching may be visible in the corresponding current-voltage characteristics.

  12. Reconstruction of mono-vacancies in carbon nanotubes: Atomic relaxation vs. spin polarization

    International Nuclear Information System (INIS)

    Berber, S.; Oshiyama, A.

    2006-01-01

    We have investigated the reconstruction of mono-vacancies in carbon nanotubes using density functional theory (DFT) geometry optimization and electronic structure calculations, employing a numerical basis set. We considered mono-vacancies in achiral nanotubes with diameter range ∼4-9A. Contrary to previous tight-binding calculations, our results indicate that mono-vacancies could have several metastable geometries, confirming the previous plane-wave DFT results. Formation energy of mono-vacancies is 4.5-5.5eV, increasing with increasing tube diameter. Net magnetic moment decreases from ideal mono-vacancy value after reconstruction, reflecting the reduction of the number of dangling bonds. In spite of the existence of a dangling bond, ground state of mono-vacancies in semiconducting tubes have no spin polarization. Metallic carbon nanotubes show net magnetic moment for most stable structure of mono-vacancy, except for very small diameter tubes

  13. Spin polarized solid target as a prospective tool for radioactive ion beam physics

    Science.gov (United States)

    Urrego-Blanco, J. P.; van den Brandt, B.; Bunyatova, E. I.; Galindo-Uribarri, A.; Hautle, P.; Konter, J. A.

    2005-12-01

    Spin polarized probes are used in a wide range of experiments in nuclear physics including the determination of spin structure functions and tests of fundamental symmetries. At low energies, light stable polarized beams have been used for spectroscopic purposes. We propose to extend these types of experiments to nuclei far from stability by using radioactive ion beams (RIBs) and polarized targets. Towards this goal we intend to develop a solid polarized proton and/or deuterium target in the thickness range between 20 μm and 100 μm based on a scintillating (active) polymeric foil. Such a target would be a useful tool in the determination of excitation functions in resonant reactions, in studies of one-nucleon transfer reactions using RIBs as well as in probing the matter density of atomic nuclei. If scintillating, it could also help remove the background associated with the scattering of the radioactive beam.

  14. Spin polarized solid target as a prospective tool for radioactive ion beam physics

    Energy Technology Data Exchange (ETDEWEB)

    Urrego-Blanco, J.P. [Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996 (United States); Physics Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6371 (United States); Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland); Brandt, B. van den [Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland); Bunyatova, E.I. [Joint Institute for Nuclear Research, Dubna, Head P.O. Box 79, 101000 Moscow (Russian Federation); Galindo-Uribarri, A. [Physics Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6371 (United States)]. E-mail: uribarri@mail.phy.ornl.gov; Hautle, P. [Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland); Konter, J.A. [Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland)

    2005-12-15

    Spin polarized probes are used in a wide range of experiments in nuclear physics including the determination of spin structure functions and tests of fundamental symmetries. At low energies, light stable polarized beams have been used for spectroscopic purposes. We propose to extend these types of experiments to nuclei far from stability by using radioactive ion beams (RIBs) and polarized targets. Towards this goal we intend to develop a solid polarized proton and/or deuterium target in the thickness range between 20 {mu}m and 100 {mu}m based on a scintillating (active) polymeric foil. Such a target would be a useful tool in the determination of excitation functions in resonant reactions, in studies of one-nucleon transfer reactions using RIBs as well as in probing the matter density of atomic nuclei. If scintillating, it could also help remove the background associated with the scattering of the radioactive beam.

  15. Confinement effect on spin-polarized edge states in graphene nanostructures

    Science.gov (United States)

    Ramos-Castillo, Carlos; de Coss, Romeo

    2014-03-01

    One of the most intriguing phenomena in condensed matter physics is the existence of edge states on the boundary of a 2D system. In graphene, the edge states have distinct properties from the bulk states and play important roles in the physicochemical properties of the material. In this work, we show ab-initio results of spin-polarized electronic edge states in graphene quantum dots of different sizes and shape. We found a critical size at which the singlet nonmagnetic ground state becomes singlet open-shell with antiferromagnetic order. We found that the critical size is strongly influenced by the shape of the quantum dot. We discuss this behavior based on energetics and electronic structure of the system under study. The calculations are base on the Density functional Theory (DFT). The Linear Combination of Atomic Orbital (LCAO) method for bases functions it was used. For exchange-correlation functional has been used the Generalized Gradient Approximation (GGA).

  16. Spin polarization and magnetic dichroism in core-level photoemission from ferromagnets

    Energy Technology Data Exchange (ETDEWEB)

    Menchero, Jose Gabriel [Univ. of California, Berkeley, CA (United States). Dept. of Physics

    1997-05-01

    In this thesis we present a theoretical investigation of angle- and spin-resolved core-level photoemission from ferromagnetic Fe and Ni. We also consider magneto-dichroic effects due to reversal of the photon helicity or reversal of the sample magnetization direction. In chapter 1, we provide a brief outline of the history of photoemission, and show how it has played an important role in the development of modern physics. We then review the basic elements of the theory of core-level photoemission, and discuss the validity of the some of the commonly-used approximations. In chapter 2, we present a one-electron theory to calculate spin- and angle-resolved photoemission spectra for an arbitrary photon polarization. The Hamiltonian includes both spin-orbit and exchange interactions. As test cases for the theory, we calculate the spin polarization and magnetic dichroism for the Fe 2p core level, and find that agreement with experiment is very good.

  17. Nuclear spin polarized alkali beams (Na, Li): Optical pumping with electro-optically modulated laser beam

    International Nuclear Information System (INIS)

    Reich, H.; Jaensch, H.J.

    1990-01-01

    An improvement of the Heidelberg source for polarized heavy ions (PSI) is described. To produce a nuclear spin polarized atomic Na beam an electro-optically modulated laser beam has been used for optical pumping. An electro-optic modulator (EOM) was constructed with a bandwidth of 1.8 GHz. Without a spin separating Stern-Gerlach magnet it is now possible to prepare a Na atomic beam in one single hyperfine magnetic substate. Thus the beam figure of merit (polarization 2 x intensity of the beam) has been improved by a factor of 4 as compared to the previous setup. Experiences with the new system collected from several beam times are discussed. (orig.)

  18. Lateral-electric-field-induced spin polarization in a suspended GaAs quantum point contact

    Science.gov (United States)

    Pokhabov, D. A.; Pogosov, A. G.; Zhdanov, E. Yu.; Shevyrin, A. A.; Bakarov, A. K.; Shklyaev, A. A.

    2018-02-01

    The conductance of a GaAs-based suspended quantum point contact (QPC) equipped with lateral side gates has been experimentally studied in the absence of the external magnetic field. The half-integer conductance plateau ( 0.5 ×2 e2/h ) has been observed when an asymmetric voltage between the side gates is applied. The appearance of this plateau has been attributed to the spin degeneracy lifting caused by the spin-orbit coupling associated with the lateral electric field in the asymmetrically biased QPC. We have experimentally demonstrated that, despite the relatively small g-factor in GaAs, the observation of the spin polarization in the GaAs-based QPC became possible after the suspension due to the enhancement of the electron-electron interaction and the effect of the electric field guiding. These features are caused by a partial confinement of the electric field lines within a suspended semiconductor layer with a high dielectric constant.

  19. Theory of current-induced spin polarization in an electron gas

    Science.gov (United States)

    Gorini, Cosimo; Maleki Sheikhabadi, Amin; Shen, Ka; Tokatly, Ilya V.; Vignale, Giovanni; Raimondi, Roberto

    2017-05-01

    We derive the Bloch equations for the spin dynamics of a two-dimensional electron gas in the presence of spin-orbit coupling. For the latter we consider both the intrinsic mechanisms of structure inversion asymmetry (Rashba) and bulk inversion asymmetry (Dresselhaus), and the extrinsic ones arising from the scattering from impurities. The derivation is based on the SU(2) gauge-field formulation of the Rashba-Dresselhaus spin-orbit coupling. Our main result is the identification of a spin-generation torque arising from Elliot-Yafet scattering, which opposes a similar term arising from Dyakonov-Perel relaxation. Such a torque, which to the best of our knowledge has gone unnoticed so far, is of basic nature, i.e., should be effective whenever Elliott-Yafet processes are present in a system with intrinsic spin-orbit coupling, irrespective of further specific details. The spin-generation torque contributes to the current-induced spin polarization (CISP), also known as inverse spin-galvanic or Edelstein effect. As a result, the behavior of the CISP turns out to be more complex than one would surmise from consideration of the internal Rashba-Dresselhaus fields alone. In particular, the symmetry of the current-induced spin polarization does not necessarily coincide with that of the internal Rashba-Dresselhaus field, and an out-of-plane component of the CISP is generally predicted, as observed in recent experiments. We also discuss the extension to the three-dimensional electron gas, which may be relevant for the interpretation of experiments in thin films.

  20. Fermi wave vector for the partially spin-polarized composite-fermion Fermi sea

    Science.gov (United States)

    Balram, Ajit C.; Jain, J. K.

    2017-12-01

    The fully spin-polarized composite-fermion (CF) Fermi sea at the half-filled lowest Landau level has a Fermi wave vector kF*=√{4 π ρe } , where ρe is the density of electrons or composite fermions, supporting the notion that the interaction between composite fermions can be treated perturbatively. Away from ν =1 /2 , the area is seen to be consistent with kF*=√{4 π ρe } for ν 1 /2 , where ρh is the density of holes in the lowest Landau level. This result is consistent with particle-hole symmetry in the lowest Landau level. We investigate in this article the Fermi wave vector of the spin-singlet CF Fermi sea (CFFS) at ν =1 /2 , for which particle-hole symmetry is not a consideration. Using the microscopic CF theory, we find that for the spin-singlet CFFS the Fermi wave vectors for up- and down-spin CFFSs at ν =1 /2 are consistent with kF*↑,↓=√{4 π ρe↑,↓ } , where ρe↑=ρe↓=ρe/2 , which implies that the residual interactions between composite fermions do not cause a nonperturbative correction for spin-singlet CFFS either. Our results suggest the natural conjecture that for arbitrary spin polarization the CF Fermi wave vectors are given by kF*↑=√{4 π ρe↑ } and kF*↓=√{4 π ρe↓ } .

  1. New directions in the theory of spin-polarized atomic hydrogen and deuterium

    International Nuclear Information System (INIS)

    Koelman, J.M.V.A.

    1988-01-01

    The three chapters of this thesis dealing with collisions between hydrogen (or deuterium) atoms in their ground state, each treat a different development in the theory of atomic hydrogen or deuterium gas. The decay due to interatomic collisions hindered till now all attempts to reach the low temperature, high-density regime where effects due to degeneracy are expected to show up. In ch. 2 a simple way out is presented for the case of Fermi gases: In spin-polarized Fermi systems at very low temperatures collisions are much effective than in Bose systems. For the Fermi gas, consisting of magnetically confined deuterium atoms, it appears that fast spin-exchange collisions automatically lead to a completely spin-polarized gas for which the spin-relaxation limited lifetime increases dramatically with decreasing temperature. As also the ratio of internal thermalization rate over decay rate increases with decreasing temperature, this gas can be cooled by forced evaporation down to very low temperatures. In ch. 3 it iis shown that the nuclear spin dynamics due to the hyperfine interaction during collisions, strongly limits the improvement in frequency stability attainable by H masers operating at low temperatures. In ch. 4 the phenomenon of spin waves is studied. It is shown that, despite the fact that interactions between two atoms are nuclear-spin independent, the outcome of a scattering event does not depend on the nuclear spins involved due to the particle indistinguishability effects at low collision energies. This effect gives rise to quantum phenomena on a macroscopic scale via the occurrence of spin waves. (author). 185 refs.; 34 figs

  2. Modeling optically pumped NMR and spin polarization in GaAs/AlGaAs quantum wells

    Science.gov (United States)

    Saha, D.; Wood, R.; Tokarski, J. T.; McCarthy, L. A.; Bowers, C. R.; Sesti, E. L.; Hayes, S. E.; Kuhns, P. L.; McGill, S. A.; Reyes, A. R.; Sanders, G. D.; Stanton, C. J.

    2014-08-01

    Optically-pumped nuclear magnetic resonance (OPNMR) spectroscopy is an emerging technique to probe electronic and nuclear spin properties in bulk and quantum well semiconductors. In OPNMR, one uses optical pumping with light to create spin-polarized electrons in a semiconductor. The electron spin can be transferred to the nuclear spin bath through the Fermi contact hyperfine interaction which can then be detected by conventional NMR. The resulting NMR signal can be enhanced four to five orders of magnitude or more over the thermal equilibrium signal. In previous work, we studied OPNMR in bulk GaAs where we investigated the strength of the OPNMR signal as a function of the pump laser frequency. This allowed us to study the spin-split valence band. Here we report on OPNMR studies in GaAs/AlGaAs quantum wells. We focus on theoretical calculations for the average electron spin polarization at different photon energies for different values of external magnetic field in both unstrained and strained quantum wells. Our calculations allow us to identify the Landau level transitions which are responsible for the peaks in the photon energy dependence of the OPNMR signal intensity. The calculations are based on the 8- band Pidgeon-Brown model generalized to include the effects of the quantum confinement potential as well as pseudomorphic strain at the interfaces. Optical properties are calculated within the golden rule approximation. Detailed comparison to experiment allows one to accurately determine valence band spin splitting in the quantum wells including the effects of strain.

  3. Conductance and spin polarization for a quantum wire with the competition of Rashba and Dresselhaus spin-orbit coupling

    International Nuclear Information System (INIS)

    Fu Xi; Chen Zeshun; Zhong Feng; Zhou Guanghui

    2010-01-01

    We investigate theoretically the spin transport of a quantum wire (QW) with weak Rashba and Dresselhaus spin-orbit coupling (SOC) nonadiabatically connected to two normal leads. Using scattering matrix method and Landauer-Buettiker formula within effective free-electron approximation, we have calculated spin-dependent conductances G ↑ and G ↓ , total conductance G and spin polarization P z for a hard-wall potential confined QW. It is demonstrated that, the SOCs induce the splitting of G ↑ and G ↓ and form spin polarization P z . Moreover, the conductances present quantized plateaus, the plateaus and P z show oscillation structures near the subband edges. Furthermore, with the increase of QW width a strong spin polarization (P z ∼1) gradually becomes weak, which can be used to realize a spin filter. When the two SOCs coexist, the total conductance presents an isotropy transport due to the Rashba and Dresselhaus Hamiltonians being fixed, and the alteration of two SOCs strength ratio changes the sign of spin polarization. This may provide a way of realizing the expression of unit information by tuning gate voltage.

  4. Direct injection of spin-polarized carriers across YBa2Cu3O7−δ ...

    Indian Academy of Sciences (India)

    In summary, we have shown that the direct injection of spin-polarized carriers from LCMO into YBCO suppresses the critical current of the YBCO layer due to the breaking of the time reversal symmetry of the Cooper pairs. Further, our experiments show that when the ferromagnetic LCMO layer is in direct contact with YBCO, ...

  5. Real-space observation of a right-rotating inhomogeneous cycloidal spin spiral by spin-polarized scanning tunneling microscopy in a triple axes vector magnet.

    Science.gov (United States)

    Meckler, S; Mikuszeit, N; Pressler, A; Vedmedenko, E Y; Pietzsch, O; Wiesendanger, R

    2009-10-09

    Using spin-polarized scanning tunneling microscopy performed in a triple axes vector magnet, we show that the magnetic structure of the Fe double layer on W(110) is an inhomogeneous right-rotating cycloidal spin spiral. The magnitude of the Dzyaloshinskii-Moriya vector is extracted from the experimental data using micromagnetic calculations. The result is confirmed by comparison of the measured saturation field along the easy axis to the respective value as obtained from Monte Carlo simulations. We find that the Dzyaloshinskii-Moriya interaction is too weak to destabilize the single domain state. However, it can define the sense of rotation and the cycloidal spiral type once the single domain state is destabilized by dipolar interaction.

  6. Spin-polarized supercurrents for spintronics: a review of current progress.

    Science.gov (United States)

    Eschrig, Matthias

    2015-10-01

    During the past 15 years a new field has emerged, which combines superconductivity and spintronics, with the goal to pave a way for new types of devices for applications combining the virtues of both by offering the possibility of long-range spin-polarized supercurrents. Such supercurrents constitute a fruitful basis for the study of fundamental physics as they combine macroscopic quantum coherence with microscopic exchange interactions, spin selectivity, and spin transport. This report follows recent developments in the controlled creation of long-range equal-spin triplet supercurrents in ferromagnets and its contribution to spintronics. The mutual proximity-induced modification of order in superconductor-ferromagnet hybrid structures introduces in a natural way such evasive phenomena as triplet superconductivity, odd-frequency pairing, Fulde-Ferrell-Larkin-Ovchinnikov pairing, long-range equal-spin supercurrents, [Formula: see text]-Josephson junctions, as well as long-range magnetic proximity effects. All these effects were rather exotic before 2000, when improvements in nanofabrication and materials control allowed for a new quality of hybrid structures. Guided by pioneering theoretical studies, experimental progress evolved rapidly, and since 2010 triplet supercurrents are routinely produced and observed. We have entered a new stage of studying new phases of matter previously out of our reach, and of merging the hitherto disparate fields of superconductivity and spintronics to a new research direction: super-spintronics.

  7. Perfect switching of the spin polarization in a ferromagnetic gapless graphene/superconducting gapped graphene junction

    International Nuclear Information System (INIS)

    Soodchomshom, Bumned; Tang, I-Ming; Hoonsawat, Rassmidara

    2010-01-01

    With the fabrication of gapped graphene, interest in the tunneling spectroscopy in graphene-based FG/SG junctions in which one side consists of a gapless ferro-magnetic graphene (FG) and the other side, of a gapped superconducting graphene (SG) has arisen. The carriers in the gapless (gapped) graphene are 2D relativistic particles having an energy spectrum given by E=√(h 2 v F 2 k 2 +(mv F 2 ) 2 ) (where mv F 2 is the gap and v F is the Fermi velocity). The spin currents in this FG/SG junction are obtained within the framework of the extended Blonder-Tinkham-Klapwijk (BTK) formalism. The effects of the superconducting energy gap in SG, of the gap mv F 2 which opened in the superconducting graphene, of the exchange field in FG, of the spin-dependent specular Andreev reflection, of the effective Fermi energy (E FF ) of FG and of the bias voltage across the junction (V) are simulated. It is seen that by adjusting E FF or V, the spin polarization (defined as SP(%) = 100% x (G ↑ - G ↓ )/(G ↑ + G ↓ )) can be switched from a pure spin up (SP = +100%) state to pure spin down (SP = -100%) state.

  8. Electrically tunable dynamic nuclear spin polarization in GaAs quantum dots at zero magnetic field

    Science.gov (United States)

    Manca, M.; Wang, G.; Kuroda, T.; Shree, S.; Balocchi, A.; Renucci, P.; Marie, X.; Durnev, M. V.; Glazov, M. M.; Sakoda, K.; Mano, T.; Amand, T.; Urbaszek, B.

    2018-04-01

    In III-V semiconductor nano-structures, the electron and nuclear spin dynamics are strongly coupled. Both spin systems can be controlled optically. The nuclear spin dynamics are widely studied, but little is known about the initialization mechanisms. Here, we investigate optical pumping of carrier and nuclear spins in charge tunable GaAs dots grown on 111A substrates. We demonstrate dynamic nuclear polarization (DNP) at zero magnetic field in a single quantum dot for the positively charged exciton X+ state transition. We tune the DNP in both amplitude and sign by variation of an applied bias voltage Vg. Variation of ΔVg on the order of 100 mV changes the Overhauser splitting (nuclear spin polarization) from -30 μeV (-22%) to +10 μeV (+7%) although the X+ photoluminescence polarization does not change sign over this voltage range. This indicates that absorption in the structure and energy relaxation towards the X+ ground state might provide favourable scenarios for efficient electron-nuclear spin flip-flops, generating DNP during the first tens of ps of the X+ lifetime which is on the order of hundreds of ps. Voltage control of DNP is further confirmed in Hanle experiments.

  9. Spin-polarized transport through single-molecule magnet Mn6 complexes

    KAUST Repository

    Cremades, Eduard

    2013-01-01

    The coherent transport properties of a device, constructed by sandwiching a Mn6 single-molecule magnet between two gold surfaces, are studied theoretically by using the non-equilibrium Green\\'s function approach combined with density functional theory. Two spin states of such Mn6 complexes are explored, namely the ferromagnetically coupled configuration of the six MnIII cations, leading to the S = 12 ground state, and the low S = 4 spin state. For voltages up to 1 volt the S = 12 ground state shows a current one order of magnitude larger than that of the S = 4 state. Furthermore this is almost completely spin-polarized, since the Mn6 frontier molecular orbitals for S = 12 belong to the same spin manifold. As such the high-anisotropy Mn6 molecule appears as a promising candidate for implementing, at the single molecular level, both spin-switches and low-temperature spin-valves. © 2013 The Royal Society of Chemistry.

  10. Domain Wall Dynamics Driven by a Localized Injection of a Spin-Polarized Current

    Science.gov (United States)

    Finocchio, Giovanni; Maugeri, Natale; Torres, Luis; Azzerboni, Bruno

    2010-06-01

    This paper introduces an oscillator scheme based on the oscillations of magnetic domain walls due to spin-polarized currents, where the current is injected perpendicular to the sample plane in a localized part of a nanowire. Depending on the geometrical and physical characteristic of the system, we identify two different dynamical regimes (auto-oscillations) when an out-of-plane external field is applied. The first regime is characterized by nucleation of domain walls (DWs) below the current injection site and the propagation of those up to the end of the nanowire, we also found an oscillation frequency larger than 5GHz with a linear dependence on the applied current density. This simple system can be used as a tuneable steady-state domain wall oscillator. In the second dynamical regime, we observe the nucleation of two DWs which propagate back and forth in the nanowire with a sub-GHz oscillation frequency. The micromagnetic spectral mapping technique shows the spatial distribution of the output power is localized symmetrically in the nanowire. We suggest that this configuration can be used as micromagnetic transformer to decouple electrically two different circuits.

  11. Dresselhaus spin-orbit coupling induced spin-polarization and resonance-split in n-well semiconductor superlattices

    International Nuclear Information System (INIS)

    Ye Chengzhi; Xue Rui; Nie, Y.-H.; Liang, J.-Q.

    2009-01-01

    Using the transfer matrix method, we investigate the electron transmission over multiple-well semiconductor superlattices with Dresselhaus spin-orbit coupling in the potential-well regions. The superlattice structure enhances the effect of spin polarization in the transmission spectrum. The minibands of multiple-well superlattices for electrons with different spin can be completely separated at the low incident energy, leading to the 100% spin polarization in a broad energy windows, which may be an effective scheme for realizing spin filtering. Moreover, for the transmission over n-quantum-well, it is observed that the resonance peaks in the minibands split into n-folds or (n-1)-folds depending on the well-width and barrier-thickness, which is different from the case of tunneling through n-barrier structure

  12. Thermally induced pure and spin polarized currents in a zigzag silicene nanoribbon based FM/normal/AFM junction

    Science.gov (United States)

    Ghanbari, Atousa; Esmaeilzadeh, Mahdi; Pournaghavi, Nezhat

    2018-01-01

    We study thermally induced spin resolved current in a zigzag silicene nanoribbon when the left and right leads are respectively affected by ferromagnetic (FM) and anti-ferromagnetic (AFM) exchange fields (FM/normal/AFM junction). We show that pure spin current is generated due to the leads temperature difference and the junction can work as a spin Seebeck diode. The pure spin current can be easily controlled by a perpendicular electric field and the junction, in this case, can work as a spin current switch. In addition, we study the effect of a single vacancy and show that the vacancy can slightly destroy the pure spin current property which leads to induce a weak spin polarized current. In the presence of both vacancy and electric field, current with high and tunable spin polarization can be achieved.

  13. Spin polarization driven by a charge-density wave in monolayer 1T−TaS2

    KAUST Repository

    Zhang, Qingyun

    2014-08-06

    Using first-principles calculations, we investigate the electronic and vibrational properties of monolayer T-phase TaS2. We demonstrate that a charge-density wave is energetically favorable at low temperature, similar to bulk 1T-TaS2. Electron-phonon coupling is found to be essential for the lattice reconstruction. The charge-density wave results in a strong localization of the electronic states near the Fermi level and consequently in spin polarization, transforming the material into a magnetic semiconductor with enhanced electronic correlations. The combination of inherent spin polarization with a semiconducting nature distinguishes the monolayer fundamentally from the bulk compound as well as from other two-dimensional transition metal dichalcogenides. Monolayer T-phase TaS2 therefore has the potential to enable two-dimensional spintronics. © 2014 American Physical Society.

  14. Period-doubling bifurcation cascade observed in a ferromagnetic nanoparticle under the action of a spin-polarized current

    Energy Technology Data Exchange (ETDEWEB)

    Horley, Paul P., E-mail: paul.horley@cimav.edu.mx [Centro de Investigación en Materiales Avanzados, S.C. (CIMAV), Chihuahua/Monterrey, 120 Avenida Miguel de Cervantes, 31109 Chihuahua (Mexico); Kushnir, Mykola Ya. [Yuri Fedkovych Chernivtsi National University, 2 Kotsyubynsky str., 58012 Chernivtsi (Ukraine); Morales-Meza, Mishel [Centro de Investigación en Materiales Avanzados, S.C. (CIMAV), Chihuahua/Monterrey, 120 Avenida Miguel de Cervantes, 31109 Chihuahua (Mexico); Sukhov, Alexander [Institut für Physik, Martin-Luther Universität Halle-Wittenberg, 06120 Halle (Saale) (Germany); Rusyn, Volodymyr [Yuri Fedkovych Chernivtsi National University, 2 Kotsyubynsky str., 58012 Chernivtsi (Ukraine)

    2016-04-01

    We report on complex magnetization dynamics in a forced spin valve oscillator subjected to a varying magnetic field and a constant spin-polarized current. The transition from periodic to chaotic magnetic motion was illustrated with bifurcation diagrams and Hausdorff dimension – the methods developed for dissipative self-organizing systems. It was shown that bifurcation cascades can be obtained either by tuning the injected spin-polarized current or by changing the magnitude of applied magnetic field. The order–chaos transition in magnetization dynamics can be also directly observed from the hysteresis curves. The resulting complex oscillations are useful for development of spin-valve devices operating in harmonic and chaotic modes.

  15. Non-dipole effects in spin polarization of photoelectrons from 3d electrons of Xe, Cs and Ba

    Energy Technology Data Exchange (ETDEWEB)

    Amusia, M Ya [Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel); Cherepkov, N A [State University of Aerospace Instrumentation, St. Petersburg 190000 (Russian Federation); Chernysheva, L V [A F Ioffe Physical-Technical Institute, St. Petersburg 194021 (Russian Federation); Felfli, Z [Department of Physics and Center for Theoretical Studies of Physical Systems, Clark Atlanta University, Atlanta GA 30314 (United States); Msezane, A Z [Department of Physics and Center for Theoretical Studies of Physical Systems, Clark Atlanta University, Atlanta GA 30314 (United States)

    2005-04-28

    The non-dipole contribution to spin polarization of photoelectrons from Xe, Cs and Ba 3d{sub 5/2} and 3d{sub 3/2} levels is calculated. The calculation is carried out within the framework of a modified version of the spin-polarized random phase approximation with exchange. The effects of relaxation of excited electrons due to the 3d-vacancy creation are also accounted for. It is demonstrated that the parameters that characterize the photoelectron angular distribution as functions of the incoming photon energy, although being predictably small, acquire additional peculiarities when the interaction between electrons that belong to the 3d{sub 5/2} and 3d{sub 3/2} components of the spin-orbit doublet is taken into account.

  16. Influence of intrinsic spin-flip processes on spin-polarized transport through quantum dots in the cotunneling regime

    International Nuclear Information System (INIS)

    Weymann, I.; Barnas, J.

    2006-01-01

    The influence of intrinsic spin relaxation on spin-polarized cotunneling through quantum dots coupled to ferromagnetic leads is analyzed theoretically. It is shown that the zero bias anomaly, which occurs due to the interplay of single-barrier and double-barrier cotunneling processes, becomes suppressed by spin relaxation processes on the dot. Diode-like features of the transport characteristics in the cotunneling regime have been found in asymmetrical systems. These features are also suppressed by the spin relaxation processes

  17. Monte Carlo studies of thermalization of electron-hole pairs in spin-polarized degenerate electron gas in monolayer graphene

    Science.gov (United States)

    Borowik, Piotr; Thobel, Jean-Luc; Adamowicz, Leszek

    2018-02-01

    Monte Carlo method is applied to the study of relaxation of excited electron-hole (e-h) pairs in graphene. The presence of background of spin-polarized electrons, with high density imposing degeneracy conditions, is assumed. To such system, a number of e-h pairs with spin polarization parallel or antiparallel to the background is injected. Two stages of relaxation: thermalization and cooling are clearly distinguished when average particles energy and its standard deviation σ _E are examined. At the very beginning of thermalization phase, holes loose energy to electrons, and after this process is substantially completed, particle distributions reorganize to take a Fermi-Dirac shape. To describe the evolution of and σ _E during thermalization, we define characteristic times τ _ {th} and values at the end of thermalization E_ {th} and σ _ {th}. The dependence of these parameters on various conditions, such as temperature and background density, is presented. It is shown that among the considered parameters, only the standard deviation of electrons energy allows to distinguish between different cases of relative spin polarizations of background and excited electrons.

  18. Insight into electronic, mechanical and transport properties of quaternary CoVTiAl: Spin-polarized DFT + U approach

    Energy Technology Data Exchange (ETDEWEB)

    Yousuf, Saleem, E-mail: nengroosaleem17@gmail.com; Gupta, D.C., E-mail: sosfizix@gmail.com

    2017-07-15

    Highlights: • 100% spin-polarized material important for the application in spintronics. • It is ferromagnetic and ductile in nature. • Shows semiconducting behavior with a band gap of 1.06 eV. • Possibly efficient high temperature thermoelectric material. - Abstract: We present a preliminary investigation of band structure and thermoelectric properties of new quaternary CoVTiAl Heusler alloy. Structural, magnetic property and 100% spin polarization of equiatomic CoVTiAl predicts ferromagnetic stable ground state. Band profile outlines the indirect semiconducting behavior in spin down channel with band gap of 1.06 eV, and the magnetic moment of 3 µ{sub B} in accordance with Slater-Pauling rule. To evaluate the accuracy of different approximations in predicting thermoelectric properties, the comparison with available experimental data is made which shows fair agreement for the transport coefficients. The high temperature (800 K) positive Seebeck coefficient of 73.71 µV/K describes the p-type character of the material with high efficiency due to highly influential semiconducting behavior around the Fermi level. Considering the combination of 100% spin-polarization, high Seebeck coefficient and large figure of merit, ferromagnetic semiconducting CoVTiAl may prove as a potential candidate for high temperature thermoelectrics and an ideal spin source material for spintronic applications.

  19. NMR investigations of surfaces and interfaces using spin-polarized xenon

    Energy Technology Data Exchange (ETDEWEB)

    Gaede, Holly Caroline [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry

    1995-07-01

    129Xe NMR is potentially useful for the investigation of material surfaces, but has been limited to high surface area samples in which sufficient xenon can be loaded to achieve acceptable signal to noise ratios. In Chapter 2 conventional 129Xe NMR is used to study a high surface area polymer, a catalyst, and a confined liquid crystal to determine the topology of these systems. Further information about the spatial proximity of different sites of the catalyst and liquid crystal systems is determined through two dimensional exchange NMR in Chapter 3. Lower surface area systems may be investigated with spin-polarized xenon, which may be achieved through optical pumping and spin exchange. Optically polarized xenon can be up to 105times more sensitive than thermally polarized xenon. In Chapter 4 highly polarized xenon is used to examine the surface of poly(acrylonitrile) and the formation of xenon clathrate hydrates. An attractive use of polarized xenon is as a magnetization source in cross polarization experiments. Cross polarization from adsorbed polarized xenon may allow detection of surface nuclei with drastic enhancements. A non-selective low field thermal mixing technique is used to enhance the 13C signal of CO2 of xenon occluded in solid CO2 by a factor of 200. High-field cross polarization from xenon to proton on the surface of high surface area polymers has enabled signal enhancements of ~1,000. These studies, together with investigations of the efficiency of the cross polarization process from polarized xenon, are discussed in Chapter 5. Another use of polarized xenon is as an imaging contrast agent in systems that are not compatible with traditional contrast agents. The resolution attainable with this method is determined through images of structured phantoms in Chapter 6.

  20. Large positive spin polarization and giant inverse tunneling magnetoresistance in Fe/PbTiO3/Fe multiferroic tunnel junction

    International Nuclear Information System (INIS)

    Dai, Jian-Qing; Zhang, Hu; Song, Yu-Min

    2014-01-01

    We perform first-principles electronic structure and spin-dependent transport calculations of a multiferroic tunnel junction (MFTJ) with an epitaxial Fe/PbTiO 3 /Fe heterostructure. We predict a large positive spin-polarization (SP) and an intriguing giant inverse tunneling magnetoresistance (TMR) ratio in this tunnel junction. We demonstrate that the tunneling properties are determined by ferroelectric (FE) polarization screening and electronic reconstruction at the interface with lower electrostatic potential. The intricate complex band structure of PbTiO 3 , in particular the lowest decay rates concerning Pb 6p z and Ti 3d z2 states near the Γ ¯ point, gives rise to the large positive SP of the tunneling current in the parallel magnetic configuration. However, the giant inverse TMR ratio is attributed to the minority-spin electrons of the interfacial Ti 3d xz +3d yz orbitals which have considerably weight in the extended area around the Γ ¯ point at the Fermi energy and causes remarkable contributions to the conductance in the antiparallel magnetic configuration. - Highlights: • We study spin-dependent tunneling in Fe/PbTiO 3 /Fe multiferroic tunnel junction. • We find a large positive spin polarization in the parallel magnetic configuration. • An intriguing giant inverse TMR ratio (about −2000%) is predicted. • Complex band structure of PbTiO 3 causes the large positive spin polarization. • Negative TMR is due to minority-spin electrons of interfacial Ti d xz +d yz orbitals

  1. Development, construction and characterization of a variable repetitive spin-polarized electron gun with an inverted-geometry insulator

    International Nuclear Information System (INIS)

    Espig, Martin

    2016-02-01

    Within the scope of this thesis a pulsed source of spin polarized electrons Photo-CATCH was designed, constructed, characterized and has been put into operation. This source is based on the photoemission of spin-polarized electrons from GaAs-photocathodes. Both the design of the electron gun, consisting of an ultra-high vacuum chamber and an electrode with Pierce geometry, as well as the properties of the electron beam have been simulated with CST Studio. Results were a maximum electric field of (0.064±0.001) MV/m/kV on the electrode surface and a beam emittance as a function of the radius of the laser spot on the photocathode of element of n,x =(1.7478(4).10 -4 .(r)/(μm)+2.8(18).10 -5 ) mm mrad at a beam current of 100 μA. Currently Photo-CATCH provides electron beams with an energy of 60 keV, which can be expanded up to 100 keV by upgrading the high-voltage power supply. The electron gun has an inverted-geometry insulator to ensure a compact design of the ultra-high vacuum chamber and a maximum person- and machine-safety from sparkovers. Since the properties of the laser light directly affect the properties of the generated electron beam a pulsed semiconductor laser system has been specially developed and built for Photo-CATCH. This is characterized by a high variability of its operating parameters, in particular its wavelength and repetition rate, in order to fulfill the broad variety of requirements of various nuclear physics experiments. By selecting the wavelength of the used laser diode highly polarized or high-current electron beams can be generated from GaAs-photocathodes. The time profile of the laser has direct influence to the longitudinal profile of the electron bunch. Through the radiofrequency modulation of the pumping current of the impedance-matched semiconductor laser system, consisting of a DC power source and an electrical pulse generator with 881 ps broad pump pulses, Lorentz shaped laser pulses with a minimum FWHM of (43.8±1.2) ps at a

  2. Experimental verification of the rotational type of chiral spin spiral structures by spin-polarized scanning tunneling microscopy.

    Science.gov (United States)

    Haze, Masahiro; Yoshida, Yasuo; Hasegawa, Yukio

    2017-10-16

    We report on experimental verification of the rotational type of chiral spin spirals in Mn thin films on a W(110) substrate using spin-polarized scanning tunneling microscopy (SP-STM) with a double-axis superconducting vector magnet. From SP-STM images using Fe-coated W tips magnetized to the out-of-plane and [001] directions, we found that both Mn mono- and double-layers exhibit cycloidal rotation whose spins rotate in the planes normal to the propagating directions. Our results agree with the theoretical prediction based on the symmetry of the system, supporting that the magnetic structures are driven by the interfacial Dzyaloshinskii-Moriya interaction.

  3. Spin-polarized relativistic linear-muffin-tin-orbital method: Volume-dependent electronic structure and magnetic moment of plutonium

    International Nuclear Information System (INIS)

    Solovyev, I.V.; Liechtenstein, A.I.; Gubanov, V.A.; Antropov, V.P.; Andersen, O.K.

    1991-01-01

    The linear-muffin-tin-orbital method is generalized to the case of relativistic and spin-polarized self-consistent band calculations. Our formalism is analogous to the standard orthogonal--linear-muffin-tin-orbital formalism, except that the potential functions and the potential parameters are now matrices. The method is used to perform density-functional calculations for fcc plutonium with different atomic volumes. The formation of spin and orbital magnetic moments, as well as the changes in the energy bands for volume changes corresponding to the α-δ transition, are investigated. The calculated magnetic moments agree quite well with the experimental ones

  4. Observation of layered antiferromagnetism in self-assembled parallel NiSi nanowire arrays on Si(110) by spin-polarized scanning tunneling spectromicroscopy

    Science.gov (United States)

    Hong, Ie-Hong; Hsu, Hsin-Zan

    2018-03-01

    The layered antiferromagnetism of parallel nanowire (NW) arrays self-assembled on Si(110) have been observed at room temperature by direct imaging of both the topographies and magnetic domains using spin-polarized scanning tunneling microscopy/spectroscopy (SP-STM/STS). The topographic STM images reveal that the self-assembled unidirectional and parallel NiSi NWs grow into the Si(110) substrate along the [\\bar{1}10] direction (i.e. the endotaxial growth) and exhibit multiple-layer growth. The spatially-resolved SP-STS maps show that these parallel NiSi NWs of different heights produce two opposite magnetic domains, depending on the heights of either even or odd layers in the layer stack of the NiSi NWs. This layer-wise antiferromagnetic structure can be attributed to an antiferromagnetic interlayer exchange coupling between the adjacent layers in the multiple-layer NiSi NW with a B2 (CsCl-type) crystal structure. Such an endotaxial heterostructure of parallel magnetic NiSi NW arrays with a layered antiferromagnetic ordering in Si(110) provides a new and important perspective for the development of novel Si-based spintronic nanodevices.

  5. Facility for low-temperature spin-polarized-scanning tunneling microscopy studies of magnetic/spintronic materials prepared in situ by nitride molecular beam epitaxy.

    Science.gov (United States)

    Lin, Wenzhi; Foley, Andrew; Alam, Khan; Wang, Kangkang; Liu, Yinghao; Chen, Tianjiao; Pak, Jeongihm; Smith, Arthur R

    2014-04-01

    Based on the interest in, as well as exciting outlook for, nitride semiconductor based structures with regard to electronic, optoelectronic, and spintronic applications, it is compelling to investigate these systems using the powerful technique of spin-polarized scanning tunneling microscopy (STM), a technique capable of achieving magnetic resolution down to the atomic scale. However, the delicate surfaces of these materials are easily corrupted by in-air transfers, making it unfeasible to study them in stand-alone ultra-high vacuum STM facilities. Therefore, we have carried out the development of a hybrid system including a nitrogen plasma assisted molecular beam epitaxy/pulsed laser epitaxy facility for sample growth combined with a low-temperature, spin-polarized scanning tunneling microscope system. The custom-designed molecular beam epitaxy growth system supports up to eight sources, including up to seven effusion cells plus a radio frequency nitrogen plasma source, for epitaxially growing a variety of materials, such as nitride semiconductors, magnetic materials, and their hetero-structures, and also incorporating in situ reflection high energy electron diffraction. The growth system also enables integration of pulsed laser epitaxy. The STM unit has a modular design, consisting of an upper body and a lower body. The upper body contains the coarse approach mechanism and the scanner unit, while the lower body accepts molecular beam epitaxy grown samples using compression springs and sample skis. The design of the system employs two stages of vibration isolation as well as a layer of acoustic noise isolation in order to reduce noise during STM measurements. This isolation allows the system to effectively acquire STM data in a typical lab space, which during its construction had no special and highly costly elements included, (such as isolated slabs) which would lower the environmental noise. The design further enables tip exchange and tip coating without

  6. Facility for low-temperature spin-polarized-scanning tunneling microscopy studies of magnetic/spintronic materials prepared in situ by nitride molecular beam epitaxy

    International Nuclear Information System (INIS)

    Lin, Wenzhi; Foley, Andrew; Alam, Khan; Wang, Kangkang; Liu, Yinghao; Chen, Tianjiao; Pak, Jeongihm; Smith, Arthur R.

    2014-01-01

    Based on the interest in, as well as exciting outlook for, nitride semiconductor based structures with regard to electronic, optoelectronic, and spintronic applications, it is compelling to investigate these systems using the powerful technique of spin-polarized scanning tunneling microscopy (STM), a technique capable of achieving magnetic resolution down to the atomic scale. However, the delicate surfaces of these materials are easily corrupted by in-air transfers, making it unfeasible to study them in stand-alone ultra-high vacuum STM facilities. Therefore, we have carried out the development of a hybrid system including a nitrogen plasma assisted molecular beam epitaxy/pulsed laser epitaxy facility for sample growth combined with a low-temperature, spin-polarized scanning tunneling microscope system. The custom-designed molecular beam epitaxy growth system supports up to eight sources, including up to seven effusion cells plus a radio frequency nitrogen plasma source, for epitaxially growing a variety of materials, such as nitride semiconductors, magnetic materials, and their hetero-structures, and also incorporating in situ reflection high energy electron diffraction. The growth system also enables integration of pulsed laser epitaxy. The STM unit has a modular design, consisting of an upper body and a lower body. The upper body contains the coarse approach mechanism and the scanner unit, while the lower body accepts molecular beam epitaxy grown samples using compression springs and sample skis. The design of the system employs two stages of vibration isolation as well as a layer of acoustic noise isolation in order to reduce noise during STM measurements. This isolation allows the system to effectively acquire STM data in a typical lab space, which during its construction had no special and highly costly elements included, (such as isolated slabs) which would lower the environmental noise. The design further enables tip exchange and tip coating without

  7. Simple and efficient method of spin-polarizing a metastable helium beam by diode laser optical pumping

    International Nuclear Information System (INIS)

    Granitza, B.; Salvietti, M.; Torello, E.; Mattera, L.; Sasso, A.

    1995-01-01

    Diode laser optical pumping to produce a highly spin-polarized metastable He beam to be used in a spin-polarized metastable atom deexcitation spectroscopy experiment on magnetized surfaces is described. Efficient pumping of the beam is performed by means of an SDL-6702 distributed Bragg reflector diode laser which yields 50 mW of output power in a single longitudinal mode at 1083 nm, the resonance wavelength for the 2 3 S→2 3 P 0,1,2 (D 0 , D 1 , and D 2 ) transitions of He*. The light is circularly polarized by a quarter-wave plate, allowing easy change of the sense of atomic polarization. The laser frequency can be locked to the atomic transition for several hours by phase-sensitive detection of the saturated absorption signal in a He discharge cell. Any of the three transitions of the triplet system can be pumped with the laser but the maximum level of atomic polarization of 98.5% is found pumping the D 2 line. copyright 1995 American Institute of Physics

  8. Oliver E. Buckley Prize Talk: Spin polarized tunneling and tunnel magnetoresistance -- Learning from the past and moving forward

    Science.gov (United States)

    Moodera, Jagadeesh

    2009-03-01

    Electron tunneling phenomenon has contributed enormously to our understanding of various branches of physics over the years. The technique of spin polarized tunneling (SPT), sensing the spin polarization of tunneling electrons using a superconducting spin detector, discovered by Meservey and Tedrow in the early seventies has been successfully utilized over the years to understand many aspects of magnetism and superconductivity. Electrical spin injection/detection in a semiconductor is strongly believed to succeed through such an approach. The successful observation of a large change in tunnel current in magnetic tunnel junctions (MTJ) in the mid nineties has brought extreme activity in this field -- both from fundamental study as well as extensive application in mind (as sensors, nonvolatile memory devices, logic elements etc). From the early history of this field that led to the discovery of room temperature TMR effect to the observation of many novel phenomena to the exciting recent work on spin filtering, spin transport in semiconductors to toggling of the superconducting state with spin current will be highlighted and reviewed. Work done in collaboration with Drs. Meservey and Tedrow, PhD students, postdoctorals, as well as high school students and undergraduates. NSF, ONR, DARPA and KIST-MIT project funds supported the research over the years.

  9. Spin polarization, orbital occupation and band gap opening in vanadium dioxide: The effect of screened Hartree-Fock exchange

    KAUST Repository

    Wang, Hao

    2014-07-01

    The metal-insulator transition of VO2 so far has evaded an accurate description by density functional theory. The screened hybrid functional of Heyd, Scuseria and Ernzerhof leads to reasonable solutions for both the low-temperature monoclinic and high-temperature rutile phases only if spin polarization is excluded from the calculations. We explore whether a satisfactory agreement with experiment can be achieved by tuning the fraction of Hartree Fock exchange (α) in the density functional. It is found that two branches of locally stable solutions exist for the rutile phase for 12.5%≤α≤20%. One is metallic and has the correct stability as compared to the monoclinic phase, the other is insulating with lower energy than the metallic branch. We discuss these observations based on the V 3d orbital occupations and conclude that α=10% is the best possible choice for spin-polarized VO2 calculations. © 2014 Elsevier B.V. All rights reserved.

  10. Effect of Rashba and Dresselhaus Spin-Orbit Couplings on Electron Spin Polarization in a Hybrid Magnetic-Electric Barrier Nanostructure

    Science.gov (United States)

    Yang, Shi-Peng; Lu, Mao-Wang; Huang, Xin-Hong; Tang, Qiang; Zhou, Yong-Long

    2017-04-01

    A theoretical study has been carried out on the spin-dependent electron transport in a hybrid magnetic-electric barrier nanostructure with both Rashba and Dresselhaus spin-orbit couplings, which can be experimentally realized by depositing a ferromagnetic strip and a Schottky metal strip on top of a semiconductor heterostructure. The spin-orbit coupling-dependent transmission coefficient, conductance, and spin polarization are calculated by solving the Schrödinger equation exactly with the help of the transfer-matrix method. We find that both the magnitude and sign of the electron spin polarization vary strongly with the spin-orbit coupling strength. Thus, the degree of electron spin polarization can be manipulated by properly adjusting the spin-orbit coupling strength, and such a nanosystem can be employed as a controllable spin filter for spintronics applications.

  11. The effects of Rashba spin-orbit coupling on spin-polarized transport in hexagonal graphene nano-rings and flakes

    Science.gov (United States)

    Laghaei, M.; Heidari Semiromi, E.

    2018-03-01

    Quantum transport properties and spin polarization in hexagonal graphene nanostructures with zigzag edges and different sizes were investigated in the presence of Rashba spin-orbit interaction (RSOI). The nanostructure was considered as a channel to which two semi-infinite armchair graphene nanoribbons were coupled as input and output leads. Spin transmission and spin polarization in x, y, and z directions were calculated through applying Landauer-Buttiker formalism with tight binding model and the Green's function to the system. In these quantum structures it is shown that changing the size of system, induce and control the spin polarized currents. In short, these graphene systems are typical candidates for electrical spintronic devices as spin filtering.

  12. Anisotropic magnetoresistance and spin polarization of La0.7Sr0.3MnO3/SrTiO3 superlattices

    International Nuclear Information System (INIS)

    Wang, L.M.; Guo, C.-C.

    2005-01-01

    The crystalline structure, anisotropic magnetoresistance (AMR), and magnetization of La 0.7 Sr 0.3 MnO 3 /SrTiO 3 (LSMO/STO) superlattices grown by a rf sputtering system are systematically analyzed to study the spin polarization of manganite at interfaces. The presence of positive low-temperature AMR in LSMO/STO superlattices implies that two bands of majority and minority character contribute to the transport properties, leading to a reduced spin polarization. Furthermore, the magnetization of superlattices follows the T 3/2 law and decays more quickly as the thickness ratio d STO /d LSMO increases, corresponding to a reduced exchange coupling. The results clearly show that the spin polarization is strongly correlated with the influence of interface-induced strain on the structure

  13. Development of a LabVIEW-based surface with innovative controls for the control system of the spin-polarized electron test source Photo-CATCH

    Energy Technology Data Exchange (ETDEWEB)

    Roesch, Heidi Ayse; Enders, Joachim; Espig, Martin; Fritzsche, Yuliya; Wagner, Markus [TU Darmstadt, Institut fuer Kernphysik (Germany)

    2016-07-01

    Operations of the spin-polarized electron source of the S-DALINAC will be supported by a photo-cathode activation, test and cleaning system, Photo-CATCH. Besides cathode-performance studies, this teststand produces spin-polarized electron bunches from a GaAs photo-cathode that are then transported, manipulated, and characterized by devices in a low-energy beam line. To set and monitor the various components of the beamline, a control system was developed, based on the EPICS framework. As interfaces, LabVIEW was used in combination with a gamepad as a controlling device.

  14. Electronic Structures of Magnetic Iron and Cobalt Thin Films on TUNGSTEN(001): a Spin-Polarized Inverse Photoemission Study

    Science.gov (United States)

    Cai, Qing

    Electronic structure is a central question in metallic magnetism as well as in magnetic materials research. The electronic properties in a two-dimensional system such as thin films of a few atomic layers is an important issue in surface science. The epitaxial thin film preparation and morphology are of special technological interests. In this thesis, these questions are addressed. Spin-polarized inverse photoemission spectroscopy is used to study the unoccupied electron band states in magnetic thin film magnets of Fe and Co epitaxially grown on W(001) surface. The clean W(001) surface was studied by angle -resolved inverse photoemission spectroscopy and the bulk band dispersion was determined. Ultrathin Fe overlayers on W(001) show a square lateral crystal structure similar to the bcc-Fe(001) surface. The electronic structure develops into a structure that is close to that of bulk Fe at about four atomic layers. In the normal-incidence spin polarized inverse photoemission spectra, direct transitions to the majority and minority final states near the H^'_ {25} point are identified in good agreement with the theoretical calculations. One Fe monolayer, or multilayers less than four, showed behavior corresponding to a gradually reduced Curie temperature. When the film thickness is reduced, the spin-resolved spectral behavior show that the majority spin signal peak moves from near the Fermi energy to about 1.3 eV while the minority peak stays at about the same position near 1.3 eV. The results are used to examine the spatial correlation of the spin fluctuations in the system in comparison with a theoretical spectral calculation, and favors the disordered-local-moment picture in the contemporary theory of itinerant magnetism. The Co overlayer shows an overlayer structure that consists of equivalent, mutually rotated domains of distorted hexagonal lateral structure. For one atomic layer of Co in that structure, which has a nominal lateral atomic density twice that of the

  15. The tunneling magnetoresistance and spin-polarized optoelectronic properties of graphyne-based molecular magnetic tunnel junctions

    International Nuclear Information System (INIS)

    Yang, Zhi; Ouyang, Bin; Lan, Guoqing; Xu, Li-Chun; Liu, Ruiping; Liu, Xuguang

    2017-01-01

    Using density functional theory and the non-equilibrium Green’s function method, we investigate the spin-dependent transport and optoelectronic properties of the graphyne-based molecular magnetic tunnel junctions (MMTJs). We find that these MMTJs exhibit an outstanding tunneling magnetoresistance (TMR) effect. The TMR value is as high as 10 6 %. When the magnetization directions of two electrodes are antiparallel under positive or negative bias voltages, two kinds of pure spin currents can be obtained in the systems. Furthermore, under the irradiation of infrared, visible or ultraviolet light, spin-polarized photocurrents can be generated in the MMTJs, but the corresponding microscopic mechanisms are different. More importantly, if the magnetization directions of two electrodes are antiparallel, the photocurrents with different spins are spatially separated, appearing at different electrodes. This phenomenon provides a new way to simultaneously generate two spin currents. (paper)

  16. Spin-polarized charge transport in HgTe/CdTe quantum well topological insulator under a ferromagnetic metal strip

    Science.gov (United States)

    Wu, Zhenhua; Luo, Kun; Yu, Jiahan; Wu, Xiaobo; Lin, Liangzhong

    2018-02-01

    Electron tunneling through a single magnetic barrier in a HgTe topological insulator has been theoretically investigated. We find that the perpendicular magnetic field would not lead to spin-flip of the edge states due to the conservation of the angular moment. By tuning the magnetic field and the Fermi energy, the edge channels can be transited from switch-on states to switch-off states and the current from unpolarized states can be filtered to fully spin polarized states. These features offer us an efficient way to control charge/spin transport in a HgTe/CdTe quantum well, and pave a way to construct the nanoelectronic devices utilizing the topological edge states.

  17. Effects of Be acceptors on the spin polarization of carriers in p-i-n resonant tunneling diodes

    Energy Technology Data Exchange (ETDEWEB)

    Awan, I. T.; Galvão Gobato, Y. [Departamento de Física, Universidade Federal de São Carlos (UFSCAR) 13560-905, São Carlos, SP (Brazil); Galeti, H. V. A. [Departamento de Engenharia Elétrica, Universidade Federal de São Carlos 13560-905, São Carlos, SP (Brazil); Brasil, M. J. S. P. [Institute of Physics Gleb Wataghin, UNICAMP, Campinas (Brazil); Taylor, D.; Henini, M. [School of Physics and Astronomy, Nottingham Nanotechnology and Nanoscience Centre, University of Nottingham, Nottingham NG7 2RD (United Kingdom)

    2014-08-07

    In this paper, we have investigated the effect of Be acceptors on the electroluminescence and the spin polarization in GaAs/AlAs p-i-n resonant tunneling diodes. The quantum well emission comprise two main lines separated by ∼20 meV attributed to excitonic and Be-related transitions, which intensities show remarkably abrupt variations at critical voltages, particularly at the electron resonant peak where it shows a high-frequency bistability. The circular-polarization degree of the quantum-well electroluminescence also shows strong and abrupt variations at the critical bias voltages and it attains relatively large values (of ∼−75% at 15 T). These effects may be explored to design novel devices for spintronic applications such as a high-frequency spin-oscillators.

  18. Tailoring electronic structure of α-AlH3 to enhance spin polarization: Insights from density functional calculations

    Science.gov (United States)

    Lu, Yi-Lin; Dong, Shengjie; Zhou, Baozeng; Sun, Lili; Zhao, Hui; Wu, Ping

    2017-09-01

    The effects of 3d transition metals doping on the structural, electronic, and magnetic properties of aluminum hydride were investigated based on spin-polarized first-principles calculations. The studies indicated that V, Cr, Mn, and Fe doping could produce polarization of high-spin state, while Co and Ni doping would induce polarization of low-spin state. It was found that the magnetic ground state depended on the distance between two substitutions and the long-range ferromagnetic coupling was achieved upon doping V, Mn, and Fe. The present work indicated that the introduced 3d-block dopants could tailor aluminum hydride into either a potential half-metallic or n-type magnetic semiconductor by tuning the valence electrons of the impurities. The main findings of this work pointed out the possibilities of the applications of hydrides in future hydride electronics and spintronics.

  19. Self-energy-part resummed quark and gluon propagators in a spin-polarized quark matter and generalized Boltzmann equations

    International Nuclear Information System (INIS)

    Niegawa, A.

    2003-01-01

    We construct perturbative frameworks for studying nonequilibrium spin-polarized quark matter. We employ the closed-time-path formalism and use the gradient approximation in derivative expansion. After constructing self-energy-part resummed quark and gluon propagators, we formulate two kinds of mutually equivalent perturbative frameworks: The first one is formulated on the basis of the initial-particle distribution function, and the second one is formulated on the basis of a 'physical' particle distribution function. In the course of the construction of the second framework, the generalized Boltzmann equations and their relatives directly come out, which describe the evolution of the system. The frameworks are relevant to the study of a magnetic character of quark matter, e.g., possible quark stars

  20. Signatures of field induced spin polarization of neutron star matter in seismic vibrations of paramagnetic neutron star

    International Nuclear Information System (INIS)

    Bastrukov, S I; Yang, J; Podgainy, D V; Weber, F

    2003-01-01

    A macroscopic model of the dissipative magneto-elastic dynamics of viscous spin polarized nuclear matter is discussed in the context of seismic activity of a paramagnetic neutron star. The source of the magnetic field of such a star is attributed to Pauli paramagnetism of baryon matter promoted by a seed magnetic field frozen into the star in the process of gravitational collapse of a massive progenitor. Particular attention is given to the effect of shear viscosity of incompressible stellar material on the timing of non-radial torsional magneto-elastic pulsations of the star triggered by starquakes. By accentuating the fact that this kind of vibration is unique to the seismology of a paramagnetic neutron star we show that the high-frequency modes decay faster than the low-frequency modes. The obtained analytic expressions for the period and relaxation time of this mode, in which the magnetic susceptibility and viscosity enter as input parameters, are then quantified by numerical estimates for these parameters taken from early and current works on transport coefficients of dense matter. It is found that the effect of viscosity is crucial for the lifetime of magneto-torsion vibrations but it does not appreciably affect the periods of this seismic mode which fall in the realm of periods of pulsed emission of soft gamma-ray repeaters and anomalous x-ray pulsars - young super-magnetized neutron stars, radiating, according to the magnetar model, at the expense of the magnetic energy release. Finally, we present arguments that the long periodic pulsed emission of these stars in a quiescent regime of radiation can be interpreted as a manifestation of weakly damped seismic magneto-torsion vibrations exhibiting the field induced spin polarization of baryon matter

  1. Spin-polarized high-energy scattering of charged leptons on nucleons

    Energy Technology Data Exchange (ETDEWEB)

    Burkardt, Matthias; Nowak, Wolf-Dieter; MILLER, A.

    2009-01-01

    The proton is a composite object with spin one-half, understood to contain highly relativistic spin one-half quarks exchanging spin-one gluons, each possibly with significant orbital angular momenta. While their fundamental interactions are well described by Quantum ChromoDynamics (QCD), our standard theory of the strong interaction, nonperturbative calculations of the internal structure of the proton based directly on QCD are beginning to provide reliable results. Most of our present knowledge of the structure of the proton is based on experimental measurements interpreted within the rich framework of QCD. An area presently attracting intense interest, both experimental and theoretical, is the relationship between the spin of the proton and the spins and orbital angular momenta of its constituents. While remarkable progress has been made, especially in the last decade, the discovery and investigation of new concepts have revealed that much more remains to be learned. This progress i

  2. Theory for Spin Selective Andreev Re ection in Vortex Core of Topological Superconductor: Majorana Zero Modes on Spherical Surface and Application to Spin Polarized Scanning Tunneling Microscope Probe

    Science.gov (United States)

    Zhang, Fu-Chun; Hu, Lun-Hui; Li, Chuang; Xu, Dong-Hui; Zhou, Yi

    Majorana zero modes (MZMs) have been predicted to exist in the topological insulator (TI)/superconductor (SC) heterostructure. Recent spin polarized scanning tunneling microscope(STM) experiment has observed spin-polarization dependence of the zero bias differential tunneling conductance at the center of vortex core. Here we consider a helical electron system described by a Rashba spin orbit coupling Hamiltonian on a spherical surface with a s-wave superconducting pairing due to proximity effect. We examine in-gap excitations of a pair of vortices with one at the north pole and the other at the south pole. While the MZM is not a spin eigenstate, the spin wavefunction of the MZM at the center of the vortex core, r = 0, is parallel to the magnetic field, and the local Andreev reflection of the MZM is spin selective, namely occurs only when the STM tip has the spin polarization parallel to the magnetic field, similar to the case in 1-dimensional nanowire. The total local differential tunneling conductance consists of the normal term proportional to the local density of states and an additional term arising from the Andreev reflection. We apply our theory to examine the recently reported spin-polarized STM experiments and show good agreement with the experiments

  3. Spin-polarized current and shot noise in the presence of spin flip in a quantum dot via nonequilibrium Green's functions

    DEFF Research Database (Denmark)

    De Souza, Fabricio; Jauho, Antti-Pekka; Egues, J.C.

    2008-01-01

    Using nonequilibrium Green's functions we calculate the spin-polarized current and shot noise in a ferromagnet-quantum-dot-ferromagnet system. Both parallel (P) and antiparallel (AP) magnetic configurations are considered. Coulomb interaction and coherent spin flip (similar to a transverse magnet...

  4. Spin-polarized high-energy scattering of charged leptons on nucleons

    Energy Technology Data Exchange (ETDEWEB)

    Burkardt, M. [New Mexico State Univ., Las Cruces, NM (United States). Dept. of Physics; Miller, C.A. [TRIUMF, Vancouver, BC (Canada); Nowak, W.D. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany)

    2009-08-15

    The proton is a composite object with spin one-half, understood to contain highly relativistic spin one-half quarks exchanging spin-one gluons, each possibly with significant orbital angular momenta. While their fundamental interactions are well described by Quantum ChromoDynamics (QCD), our standard theory of the strong interaction, nonperturbative calculations of the internal structure of the proton based directly on QCD are beginning to provide reliable results. Most of our present knowledge of the structure of the proton is based on experimental measurements interpreted within the rich framework of QCD. An area presently attracting intense interest, both experimental and theoretical, is the relationship between the spin of the proton and the spins and orbital angular momenta of its constituents. While remarkable progress has been made, especially in the last decade, the discovery and investigation of new concepts have revealed that much more remains to be learned. This progress is reviewed and an outlook for the future is offered. (orig.)

  5. Spin-polarized scanning tunneling microscopy experiments on the rough surface of a polycrystalline NiFe film with a fine magnetic tip sensitive to a well-defined magnetization component

    Directory of Open Access Journals (Sweden)

    H. Matsuyama

    2016-03-01

    Full Text Available We developed a micrometer-sized magnetic tip integrated onto the write head of a hard disk drive for spin-polarized scanning tunneling microscopy (SP-STM in the modulated tip magnetization mode. Using SP-STM, we measured a well-defined in-plane spin-component of the tunneling current of the rough surface of a polycrystalline NiFe film. The spin asymmetry of the NiFe film was about 1.3% within the bias voltage range of -3 to 1 V. We obtained the local spin component image of the sample surface, switching the magnetic field of the sample to reverse the sample magnetization during scanning. We also obtained a spin image of the rough surface of a polycrystalline NiFe film evaporated on the recording medium of a hard disk drive.

  6. Co on Pt(111) studied by spin-polarized scanning tunneling microscopy and spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Meier, F.K.

    2006-07-01

    In this thesis the electronic properties of the bare Pt(111) surface, the structural, electronic, and magnetic properties of monolayer and double-layer high Co nanostructures as well as the spin-averaged electronic structure of single Co atoms on Pt(111) were studied by low-temperature scanning tunneling microscopy (STM) and spectroscopy (STS). The experiments on the bare Pt(111) surface and on single Co atoms have been performed in an STM facility operating at temperatures of down to 0.3 K and at magnetic fields of up to 14 T under ultra-high vacuum conditions. The facility has been taken into operation within the time period of this thesis and its specifications were tested by STS measurements. These characterization measurements show a very high stability of the tunneling junction and an energy resolution of about 100 {mu}eV, which is close to the thermal limit. The investigation of the electronic structure of the bare Pt(111) surface reveals the existence of an unoccupied surface state. By a comparison of the measured dispersion to first-principles electronic structure calculations the state is assigned to an sp-derived surface band at the lower boundary of the projected bulk band gap. The surface state exhibits a strong spin-orbit coupling induced spin splitting. The close vicinity to the bulk bands leads to a strong linear contribution to the dispersion and thus to a deviant appearance in the density of states in comparison to the surface states of the (111) surfaces of noble metals. A detailed study of Co monolayer and double-layer nanostructures on the Pt(111) surface shows that both kinds of nanostructures exhibit a highly inhomogeneous electronic structure which changes at the scale of only a few Aa due to a strong stacking dependence with respect to the Pt(111) substrate. With the help of first principles calculations the different spectroscopic appearance for Co atoms within the Co monolayer is assigned to a stacking dependent hybridization of Co states

  7. Signatures of field induced spin polarization of neutron star matter in seismic vibrations of paramagnetic neutron star

    CERN Document Server

    Bastrukov, S I; Podgainy, D V; Weber, F

    2003-01-01

    A macroscopic model of the dissipative magneto-elastic dynamics of viscous spin polarized nuclear matter is discussed in the context of seismic activity of a paramagnetic neutron star. The source of the magnetic field of such a star is attributed to Pauli paramagnetism of baryon matter promoted by a seed magnetic field frozen into the star in the process of gravitational collapse of a massive progenitor. Particular attention is given to the effect of shear viscosity of incompressible stellar material on the timing of non-radial torsional magneto-elastic pulsations of the star triggered by starquakes. By accentuating the fact that this kind of vibration is unique to the seismology of a paramagnetic neutron star we show that the high-frequency modes decay faster than the low-frequency modes. The obtained analytic expressions for the period and relaxation time of this mode, in which the magnetic susceptibility and viscosity enter as input parameters, are then quantified by numerical estimates for these parameter...

  8. Magnetization switching of a metallic nanomagnet via current-induced surface spin-polarization of an underlying topological insulator

    International Nuclear Information System (INIS)

    Roy, Urmimala; Dey, Rik; Pramanik, Tanmoy; Ghosh, Bahniman; Register, Leonard F.; Banerjee, Sanjay K.

    2015-01-01

    We consider a thermally stable, metallic nanoscale ferromagnet (FM) subject to spin-polarized current injection and exchange coupling from the spin-helically locked surface states of a topological insulator (TI) to evaluate possible non-volatile memory applications. We consider parallel transport in the TI and the metallic FM, and focus on the efficiency of magnetization switching as a function of transport between the TI and the FM. Transport is modeled as diffusive in the TI beneath the FM, consistent with the mobility in the TI at room temperature, and in the FM, which essentially serves as a constant potential region albeit spin-dependent except in the low conductivity, diffusive limit. Thus, it can be captured by drift-diffusion simulation, which allows for ready interpretation of the results. We calculate switching time and energy consumed per write operation using self-consistent transport, spin-transfer-torque (STT), and magnetization dynamics calculations. Calculated switching energies and times compare favorably to conventional spin-torque memory schemes for substantial interlayer conductivity. Nevertheless, we find that shunting of current from the TI to a metallic nanomagnet can substantially limit efficiency. Exacerbating the problem, STT from the TI effectively increases the TI resistivity. We show that for optimum performance, the sheet resistivity of the FM layer should be comparable to or larger than that of the TI surface layer. Thus, the effective conductivity of the FM layer becomes a critical design consideration for TI-based non-volatile memory

  9. Spin-polarized electron gas in Co2MSi/SrTiO3(M= Ti, V, Cr, Mn, and Fe) heterostructures

    KAUST Repository

    Nazir, S.

    2016-06-08

    Spin-polarized density functional theory is used to study the TiO2 terminated interfaces between the magnetic Heusler alloys Co2Si (M = Ti, V, Cr, Mn, and Fe) and the non-polar band insulator SrTiO3. The structural relaxation at the interface turns out to depend systematically on the lattice mis- match. Charge transfer from the Heusler alloys (mainly the M 3d orbitals) to the Ti dxy orbitals of the TiO2 interface layer is found to gradually grow from M = Ti to Fe, resulting in an electron gas with increasing density of spin-polarized charge carriers. (© 2016 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  10. Single-Spin Polarization Effects and the Determination of Timelike Proton Form Factors

    Energy Technology Data Exchange (ETDEWEB)

    Brodsky, S

    2003-10-24

    We show that measurements of the proton's polarization in e{sup +}e{sup -} {yields} p{bar p} strongly discriminate between analytic forms of models which fit the proton form factors in the spacelike region. In particular, the single-spin asymmetry normal to the scattering plane measures the relative phase difference between the timelike G{sub E} and G{sub M} form factors. The expected proton polarization in the timelike region is large, of order of several tens of percent.

  11. Shot noise as a probe of spin-polarized transport through single atoms

    DEFF Research Database (Denmark)

    Burtzlaff, Andreas; Weismann, Alexander; Brandbyge, Mads

    2015-01-01

    Single atoms on Au(111) surfaces have been contacted with the Au tip of a low temperature scanning tunneling microscope. The shot noise of the current through these contacts has been measured up to frequencies of 120 kHz and Fano factors have been determined to characterize the transport channels...

  12. Voltage switching technique for detecting nuclear spin polarization in a quantum dot

    International Nuclear Information System (INIS)

    Takahashi, Ryo; Kono, Kimitoshi; Tarucha, Seigo; Ono, Keiji

    2010-01-01

    We have introduced a source-drain voltage switching technique for studying nuclear spins in a vertical double quantum dot. Switching the source-drain voltage between the spin-blockade state and the zero-bias Coulomb blockade state can tune the energy difference between the spin singlet and triplet, and effectively turn on/off the hyperfine interaction. Since the change in the nuclear spin state affects the source-drain current, nuclear spin properties can only be detected by transport measurement. Using this technique, we have succeeded in measuring the timescale of nuclear spin depolarization. Furthermore, combining this technique and an RF ac magnetic field, we successfully detected continuous-wave NMR signals of 75 As, 69 Ga, and 71 Ga, which are contained in a quantum dot. (author)

  13. Calculations of static properties of spin-polarized 3He--4He mixtures

    International Nuclear Information System (INIS)

    Owers-Bradley, J.R.; Bowley, R.M.; Main, P.C.

    1985-01-01

    The theory of dilute mixtures of 3 He in 4 He that have been polarized by a strong magnetic field is developed. The interaction between the quasiparticles is taken to be constant, an approximation valid at low temperatures. The polarization of the mixture depends on the strength of the interaction. The internal energy, the specific heat, the osmotic pressure, and the velocity of second sound are also calculated. The specific heat is relatively insensitive to the interaction, but it does change significantly with magnetic field. The osmotic pressure is more sensitive to the effects of the interaction for some 3 He concentrations and temperatures. The velocity of second sound behaves qualitatively like the osmotic pressure. The measurement of these quantities as a function of temperature and magnetic field is discussed with a view to obtaining the strength of the interaction between quasiparticles

  14. Bounds on the maximum attainable equilibrium spin polarization of protons at high energy in HERA

    International Nuclear Information System (INIS)

    Vogt, M.

    2000-12-01

    For some years HERA has been supplying longitudinally spin polarised electron and positron (e ± ) beams to the HERMES experiment and in the future longitudinal polarisation will be supplied to the II1 and ZEUS experiments. As a result there has been a development of interest in complementing the polarised e ± beams with polarised protons. In contrast to the case of e ± where spin flip due to synchrotron radiation in the main bending dipoles leads to self polarisation owing to an up-down asymmetry in the spin flip rates (Sokolov-Ternov effect), there is no convincing self polarisation mechanism for protons at high energy. Therefore protons must be polarised almost at rest in a source and then accelerated to the working energy. At HERA, if no special measures are adopted, this means that the spins must cross several thousand ''spin-orbit resonances''. Resonance crossing can lead to loss of polarisation and at high energy such effects are potentially strong since spin precession is very pronounced in the very large magnetic fields needed to contain the proton beam in HERA-p. Moreover simple models which have been successfully used to describe spin motion at low and medium energies are no longer adequate. Instead, careful numerical spin-orbit tracking simulations are needed and a new, mathematically rigorous look at the theoretical concepts is required. This thesis describes the underlying theoretical concepts, the computational tools (SPRINT) and the results of such a study. In particular strong emphasis is put on the concept of the invariant spin field and its non-perturbative construction. The invariant spin field is then used to define the amplitude dependent spin tune and to obtain numerical non-perturbative estimates of the latter. By means of these two key concepts the nature of higher order resonances in the presence of snakes is clarified and their impact on the beam polarisation is analysed. We then go on to discuss the special aspects of the HERA-p ring

  15. Tuning Fermi level of Cr{sub 2}CoZ (Z=Al and Si) inverse Heusler alloys via Fe-doping for maximum spin polarization

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Mukhtiyar [Department of Physics, Kurukshetra University, Kurukshetra-136119, Haryana (India); Saini, Hardev S. [Department of Physics, Panjab University, Chandigarh-160014 (India); Thakur, Jyoti [Department of Physics, Kurukshetra University, Kurukshetra-136119, Haryana (India); Reshak, Ali H. [New Technologies—Research Center, University of West Bohemia, Univerzitni 8, 306 14 Pilsen (Czech Republic); Center of Excellence Geopolymer and Green Technology, School of Material Engineering, University Malaysia Perlis, 01007 Kangar, Perlis (Malaysia); Kashyap, Manish K., E-mail: manishdft@gmail.com [Department of Physics, Kurukshetra University, Kurukshetra-136119, Haryana (India)

    2014-12-15

    We report full potential treatment of electronic and magnetic properties of Cr{sub 2−x}Fe{sub x}CoZ (Z=Al, Si) Heusler alloys where x=0.0, 0.25, 0.5, 0.75 and 1.0, based on density functional theory (DFT). Both parent alloys (Cr{sub 2}CoAl and Cr{sub 2}CoSi) are not half-metallic frromagnets. The gradual replacement of one Cr sublattice with Fe induces the half-metallicity in these systems, resulting maximum spin polarization. The half-metallicity starts to appear in Cr{sub 2−x}Fe{sub x}CoAl and Cr{sub 2−x}Fe{sub x}CoSi with x=0.50 and x=0.25, respectively, and the values of minority-spin gap and half-metallic gap or spin-flip gap increase with further increase of x. These gaps are found to be maximum for x=1.0 for both cases. An excellent agreement between the structural properties of CoFeCrAl with available experimental study is obtained. The Fermi level tuning by Fe-doping makes these alloys highly spin polarized and thus these can be used as promising candidates for spin valves and magnetic tunnelling junction applications. - Highlights: • Tuning of E{sub F} in Cr{sub 2}CoZ (Z=Al, Si) has been demonstrated via Fe doping. • Effect of Fe doping on half-metallicity and magnetism have been discussed. • The new alloys have a potential of being used as spin polarized electrodes.

  16. Anomalous Hall effect and current spin polarization in Co2Fe X Heusler compounds (X =Al , Ga , In , Si , Ge , and Sn ): A systematic ab initio study

    Science.gov (United States)

    Huang, Hung-Lung; Tung, Jen-Chuan; Guo, Guang-Yu

    2015-04-01

    Co-based Heusler compounds are ferromagnetic with a high Curie temperature and a large magnetization density, and thus are promising for spintronic applications. In this paper, we perform a systematic ab initio study of two principal spin-related phenomena, namely, anomalous Hall effect and current spin polarization, in Co2-based Heusler compounds Co2Fe X (X =Al , Ga , In , Si , Ge , Sn ) in the cubic L2 1 structure within the density functional theory with the generalized gradient approximation (GGA). The accurate all-electron full-potential linearized augmented plane-wave method is used. First, we find that the spin polarization of the longitudinal current (PL) in Co2Fe X (X =Al , Ga , In , Al0.5Si0.5 , and Sn ) is ˜100 % even though that of the electronic states at the Fermi level (PD) is not. Further, the other compounds also have a high current spin polarization with PL>85 %. This indicates that all the Co2Fe X compounds considered are promising for spin-transport devices. Interestingly, PD is negative in Co2Fe X (X =Si , Ge , and Sn ), differing in sign from the PL as well as that from the transport experiments. Second, the calculated anomalous Hall conductivities (AHCs) are moderate, being within 200 S/cm, and agree well with the available experiments on a highly L2 1 ordered Co2FeSi specimen although they differ significantly from the reported experiments on other compounds where the B2 antisite disorders were present. Surprisingly, the AHC in Co2FeSi decreases and then changes sign when Si is replaced by Ge and finally by Sn. Third, the calculated total magnetic moments agree well with the corresponding experimental ones in all the studied compounds except Co2FeSi where a difference of 0.3 μB/f .u . exists. We also perform the GGA plus on-site Coulomb interaction U calculations in the GGA + U scheme. We find that including the U affects the calculated total magnetic moment, spin polarization and AHC significantly, and in most cases, unfortunately

  17. Excitation of Self-Localized Spin-Wave Bullets by Spin-Polarized Current in In-Plane Magnetized Magnetic Nano-Contacts: A Micromagnetic Study

    Science.gov (United States)

    2007-10-08

    excitation of microwave spin waves.3,10,11 The analytical theory of spin-wave excitation in magnetic nanocontacts by spin-polarized current performed...linear theory ,3 the propagating spin- wave mode excited at the threshold is a cylindrical spin- wave with the wave vector kL=1.2/Rc and frequency L... Oersted magnetic field, and/or by any other small interaction, neglected in the micromagnetic model. To make the excitation of subcritical modes12,15

  18. Spin polarization of (Ga,Mn)As measured by Andreev spectroscopy: the role of spin-active scattering

    Czech Academy of Sciences Publication Activity Database

    Piano, S.; Grein, R.; Mellor, C.J.; Výborný, Karel; Campion, R.; Wang, M.; Eschrig, M.; Gallagher, B. L.

    2011-01-01

    Roč. 83, č. 8 (2011), 081305/1-081305/4 ISSN 1098-0121 R&D Projects: GA AV ČR KJB100100802; GA MŠk(CZ) 7E08087 EU Projects: European Commission(XE) 214499 - NAMASTE; European Commission(XE) 237375 - SemiSpinNano Grant - others:AV ČR(CZ) AP0801 Program:Akademická prémie - Praemium Academiae Institutional research plan: CEZ:AV0Z10100521 Keywords : Andreev spectroscopy * magnetic semiconductors Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.691, year: 2011

  19. Measuring absolute spin polarization in dissolution-DNP by Spin PolarimetrY Magnetic Resonance (SPY-MR).

    Science.gov (United States)

    Vuichoud, Basile; Milani, Jonas; Chappuis, Quentin; Bornet, Aurélien; Bodenhausen, Geoffrey; Jannin, Sami

    2015-11-01

    Dynamic nuclear polarization at 1.2 K and 6.7 T allows one to achieve spin temperatures on the order of a few millikelvin, so that the high-temperature approximation (ΔEPolarimetrY Magnetic Resonance (SPY-MR), is illustrated for various pairs of (13)C spins (I, S) in acetate and pyruvate. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

  20. Electron spin polarization effects in low-energy electron diffraction, ion neutralization, and metastable-atom deexcitation at solid surfaces. Progress report No. 3, January 1-December 31, 1983

    International Nuclear Information System (INIS)

    Walters, G.K.; Dunning, F.B.

    1983-01-01

    The importance of electron spin polarization (ESP) effects in the various spectroscopies used to study solid surfaces has become increasingly apparent in recent years. Recent low energy electron diffraction (LEED) investigations in this laboratory and elsewhere have shown that a great deal of new information contributing to the understanding of the geometrical arrangements of atoms at a surface can be obtained if the polarization of the various LEED beams is measured, or if the incident electron beam is polarized. Polarized LEED studies have shown large polarization features that are very sensitive to the presence of adsorbed layers, surface reconstruction, etc. In addition, theory suggests that polarization measurements can provide a more sensitive test of many of the parameters used in a surface model than can conventional LEED intensity measurements alone. Polarized LEED has also been applied to the study of surface magnetism. In the present contract year, polarized LEED has been used, together with Auger analysis and LEED intensity measurements, as a diagnostic to characterize Ni(001) surfaces produced by laser annealing

  1. Direct evidence of hidden local spin polarization in a centrosymmetric superconductor LaO0.55F0.45BiS2.

    Science.gov (United States)

    Wu, Shi-Long; Sumida, Kazuki; Miyamoto, Koji; Taguchi, Kazuaki; Yoshikawa, Tomoki; Kimura, Akio; Ueda, Yoshifumi; Arita, Masashi; Nagao, Masanori; Watauchi, Satoshi; Tanaka, Isao; Okuda, Taichi

    2017-12-04

    Conventional Rashba spin polarization is caused by the combination of strong spin-orbit interaction and spatial inversion asymmetry. However, Rashba-Dresselhaus-type spin-split states are predicted in the centrosymmetric LaOBiS 2 system by recent theory, which stem from the local inversion asymmetry of active BiS 2 layer. By performing high-resolution spin- and angle-resolved photoemission spectroscopy, we have investigated the electronic band structure and spin texture of superconductor LaO 0.55 F 0.45 BiS 2 . Here we present direct spectroscopic evidence for the local spin polarization of both the valence band and the conduction band. In particular, the coexistence of Rashba-like and Dresselhaus-like spin textures has been observed in the conduction band. The finding is of key importance for fabrication of proposed dual-gated spin-field effect transistor. Moreover, the spin-split band leads to a spin-momentum locking Fermi surface from which superconductivity emerges. Our demonstration not only expands the scope of spintronic materials but also enhances the understanding of spin-orbit interaction-related superconductivity.

  2. Energy spectrum, the spin polarization, and the optical selection rules of the Kronig-Penney superlattice model with spin-orbit coupling

    Science.gov (United States)

    Li, Rui

    2018-02-01

    The Kronig-Penney model, an exactly solvable one-dimensional model of crystal in solid physics, shows how the allowed and forbidden bands are formed in solids. In this paper, we study this model in the presence of both strong spin-orbit coupling and the Zeeman field. We analytically obtain four transcendental equations that represent an implicit relation between the energy and the Bloch wave vector. Solving these four transcendental equations, we obtain the spin-orbital bands exactly. In addition to the usual band gap opened at the boundary of the Brillouin zone, a much larger spin-orbital band gap is also opened at some special sites inside the Brillouin zone. The x component of the spin-polarization vector is an even function of the Bloch wave vector, while the z component of the spin-polarization vector is an odd function of the Bloch wave vector. At the band edges, the optical transition rates between adjacent bands are nonzero.

  3. Spin-polarized semiconductors: tuning the electronic structure of graphene by introducing a regular pattern of sp3 carbons on the graphene plane.

    Science.gov (United States)

    Jing, Long; Huang, Ping; Zhu, Huarui; Gao, Xueyun

    2013-01-28

    First-principles calculations (generalized gradient approximation, density functional therory (DFT) with dispersion corrections, and DFT plus local atomic potential) are carried out on the stability and electronic structures of superlattice configurations of nitrophenyl diazonium functionalized graphene with different coverage. In the calculations, the stabilities of these structures are strengthened significantly since van der Waals interactions between nitrophenyl groups are taken into account. Furthermore, spin-polarized and wider-bandgap electronic structures are obtained when the nitrophenyl groups break the sublattice symmetry of the graphene. The unpaired quasi-localized p electrons are responsible for this itinerant magnetism. The results provide a novel approach to tune graphene's electronic structures as well as to form ferromagnetic semiconductive graphene. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Strain effects on the spin polarized electron gas in ABO3/SrTiO3 (A = Pr, Nd and B = Al, Ga) heterostructures

    KAUST Repository

    Nazir, Safdar

    2013-04-11

    The spin polarized two dimensional electron gas in the correlated ABO3/SrTiO3 (A = Pr, Nd and B = Al, Ga) heterostructures is investigated by ab-initio calculations using density functional theory. Structural relaxation shows a strong buckling at and near the TiO2 terminated n-type interface (IFs) due to significant TiO6 octahedral distortions. We find in all cases, metallic states in a very narrow region of the SrTiO3, in agreement with experimental results. We demonstrate that the interface magnetism strongly reacts to the magnitude of the lattice strain. The orbital occupations and, hence, the charge carrier density change systematically as a function of the lattice mismatch between the component materials.

  5. Spin-polarized 3He nuclear targets and metastable 4He atoms by optical pumping with a tunable, Nd:YAP laser

    International Nuclear Information System (INIS)

    Bohler, C.L.; Schearer, L.D.; Leduc, M.; Nacher, P.J.; Zachorowski, L.; Milner, R.G.; McKeown, R.D.; Woodward, C.E.

    1988-01-01

    Several Nd:YAP lasers were constructed which could be broadly tuned in the 1083-nm region which includes the helium 2 3 S-2 3 P transition, using a Lyot filter and thin, uncoated etalons within the laser cavity. 1 W of power could be extracted at 1083 nm through a 1% transmitting output coupler. This laser beam was used to optically pump metastable 4 He and 3 He 2 3 S helium atoms in a weak discharge cell, spin polarizing the metastable ensemble. In a 3 He cell the polarization is transferred to the nuclear spin system. A 3 He target cell at 0.3 Torr was polarized to 52% in a few minutes. We describe the application of this system to the design of polarized targets for experiments in nuclear physics

  6. Relativistic spin-polarized KKR theory for superconducting heterostructures: Oscillating order parameter in the Au layer of Nb/Au/Fe trilayers

    Science.gov (United States)

    Csire, Gábor; Deák, András; Nyári, Bendegúz; Ebert, Hubert; Annett, James F.; Újfalussy, Balázs

    2018-01-01

    The fully relativistic spin-polarized multiple-scattering theory is developed for inhomogeneous superconductors, including superconducting/normal-metal/ferromagnet heterostructures. The method allows the solution of the first-principles Dirac-Bogoliubov-de Gennes equations combined with a semiphenomenological parametrization of the exchange-correlation functional. Simple conditions are derived for the case when the right-hand-side and left-hand-side solutions must be treated separately when setting up the corresponding Green's function. As an application of the theory, we calculate the order parameters of Nb/Fe and Nb/Au/Fe systems. We find Fulde-Ferrell-Larkin-Ovchinnikov-like oscillations in the iron layers, but more interestingly an oscillatory behavior is observed in the gold layers as well. The band-structure calculations suggest that this is the consequence of an interplay between the quantum-well states and ferromagnetism.

  7. Thomas-Fermi-von Weizsäcker theory for a harmonically trapped, two-dimensional, spin-polarized dipolar Fermi gas

    Science.gov (United States)

    van Zyl, B. P.; Zaremba, E.; Pisarski, P.

    2013-04-01

    We systematically develop a density functional description for the equilibrium properties of a two-dimensional, harmonically trapped, spin-polarized dipolar Fermi gas based on the Thomas-Fermi-von Weizsäcker approximation. We pay particular attention to the construction of the two-dimensional kinetic energy functional, where corrections beyond the local density approximation must be motivated with care. We also present an intuitive derivation of the interaction energy functional associated with the dipolar interactions and provide physical insight into why it can be represented as a local functional. Finally, a simple and highly efficient self-consistent numerical procedure is developed to determine the equilibrium density of the system for a range of dipole interaction strengths.

  8. Shape coexistence in the N=19 neutron-rich nucleus 31Mg explored by β–γ spectroscopy of spin-polarized 31Na

    Directory of Open Access Journals (Sweden)

    H. Nishibata

    2017-04-01

    Full Text Available The structure of excited states in the neutron-rich nucleus 31Mg, which is in the region of the “island of inversion” associated with the neutron magic number N=20, is studied by β–γ spectroscopy of spin-polarized 31Na. Among the 31Mg levels below the one neutron separation energy of 2.3 MeV, the spin values of all five positive-parity levels are unambiguously determined by observing the anisotropic β decay. Two rotational bands with Kπ=1/2+ and 1/2− are proposed based on the spins and energies of the levels. Comparison on a level-by-level basis is performed between the experimental results and theoretical calculations by the antisymmetrized molecular dynamics (AMD plus generator coordinate method (GCM. It is found that various nuclear structures coexist in the low excitation energy region in 31Mg.

  9. Reduced interface spin polarization by antiferromagnetically coupled Mn segregated to the C o2MnSi /GaAs (001) interface

    Science.gov (United States)

    Rath, Ashutosh; Sivakumar, Chockalingam; Sun, C.; Patel, Sahil J.; Jeong, Jong Seok; Feng, J.; Stecklein, G.; Crowell, Paul A.; Palmstrøm, Chris J.; Butler, William H.; Voyles, Paul M.

    2018-01-01

    We have investigated the interfacial structure and its correlation with the calculated spin polarization in C o2MnSi /GaAs(001) lateral spin valves. C o2MnSi (CMS) films were grown on As-terminated c(4 ×4 ) GaAs(100) by molecular beam epitaxy using different first atomic layers: MnSi, Co, and Mn. Atomically resolved Z -contrast scanning transmission electron microscopy (STEM) imaging and electron energy loss spectroscopy (EELS) were used to develop atomic structural models of the CMS/GaAs interfaces that were used as inputs for first-principles calculations to understand the magnetic and electronic properties of the interface. First-principles structures were relaxed and then validated by comparing experimental and simulated high-resolution STEM images. STEM-EELS results show that all three films have similar six atomic layer thick, Mn- and As-rich multilayer interfaces. However, the Co-initiated interface contains a M n2As -like layer, which is antiferromagnetic, and which is not present in the other two interfaces. Density functional theory calculations show a higher degree of interface spin polarization in the Mn- and MnSi-initiated cases, compared to the Co-initiated case, although none of the interfaces are half-metallic. The loss of half-metallicity is attributed, at least in part, to the segregation of Mn at the interface, which leads to the formation of interface states. The implications for the performance of lateral spin valves based on these interfaces are discussed briefly.

  10. Spin-polarized structural, elastic, electronic and magnetic properties of half-metallic ferromagnetism in V-doped ZnSe

    Energy Technology Data Exchange (ETDEWEB)

    Monir, M. El Amine.; Baltache, H. [Laboratoire de Physique Quantique de la Matière et de la Modélisation Mathématique (LPQ3M), Faculté des Sciences, Université de Mascara, Mascara 29000 (Algeria); Murtaza, G., E-mail: murtaza@icp.edu.pk [Materials Modeling Lab, Department of Physics, Islamia College University, Peshawar (Pakistan); Khenata, R., E-mail: khenata_rabah@yahoo.fr [Laboratoire de Physique Quantique de la Matière et de la Modélisation Mathématique (LPQ3M), Faculté des Sciences, Université de Mascara, Mascara 29000 (Algeria); Ahmed, Waleed K. [ERU, Faculty of Engineering, United Arab Emirates University, Al Ain (United Arab Emirates); Bouhemadou, A. [Laboratory for Developing New Materials and their Characterization, Department of Physics, Faculty of Science, University of Setif, 19000 Setif (Algeria); Omran, S. Bin [Department of Physics and Astronomy, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451 (Saudi Arabia); Seddik, T. [Laboratoire de Physique Quantique de la Matière et de la Modélisation Mathématique (LPQ3M), Faculté des Sciences, Université de Mascara, Mascara 29000 (Algeria)

    2015-01-15

    Based on first principles spin-polarized density functional theory, the structural, elastic electronic and magnetic properties of Zn{sub 1−x}V{sub x}Se (for x=0.25, 0.50, 0.75) in zinc blende structure have been studied. The investigation was done using the full-potential augmented plane wave method as implemented in WIEN2k code. The exchange-correlation potential was treated with the generalized gradient approximation PBE-GGA for the structural and elastic properties. Moreover, the PBE-GGA+U approximation (where U is the Hubbard correlation terms) is employed to treat the “d” electrons properly. A comparative study between the band structures, electronic structures, total and partial densities of states and local moments calculated within both GGA and GGA+U schemes is presented. The analysis of spin-polarized band structure and density of states shows the half-metallic ferromagnetic character and are also used to determine s(p)-d exchange constants N{sub 0}α (conduction band ) and N{sub 0}β (valence band) due to Se(4p)–V(3d) hybridization. It has been clearly evidence that the magnetic moment of V is reduced from its free space change value of 3 µ{sub B} and the minor atomic magnetic moment on Zn and Se are generated. - Highlights: • Half metallicity origins by doping V in ZnSe. • PBE-GGA+U approximation is employed to treat the “d” electrons properly. • s(p)-d Exchange constants N{sub 0}α (conduction band ) and N{sub 0}β (valence band) are due to Se(4p)-V(3d) hybridization.

  11. K-edge x-ray dichroism investigation of Fe1-xCoxSi: Experimental evidence for spin polarization crossover

    Science.gov (United States)

    Hearne, G. R.; Diguet, G.; Baudelet, F.; Itié, J.-P.; Manyala, N.

    2015-04-01

    Both Fe and Co K-edge x-ray magnetic circular dichroism (XMCD) have been employed as element-specific probes of the magnetic moments in the composition series of the disordered ferromagnet Fe1-xCoxSi (for x=0.2, 0.3, 0.4, 0.5). A definitive single peaked XMCD profile occurs for all compositions at both Fe and Co K-edges. The Fe 4p orbital moment, deduced from the integral of the XMCD signal, has a steep dependence on x at low doping levels and evolves to a different (weaker) dependence at x≥0.3, similar to the behavior of the magnetization in the Co composition range studied here. It is systematically higher, by at least a factor of two, than the corresponding Co orbital moment for most of the composition series. Fine structure beyond the K-edge absorption (limited range EXAFS) suggests that the local order (atomic environment) is very similar across the series, from the perspective of both the Fe and Co absorbing atom. The variation in the XMCD integral across the Co composition range has two regimes, that which occurs below x=0.3 and then evolves to different behavior at higher doping levels. This is more conspicuously present in the Fe contribution. This is rationalized as the evolution from a half-metallic ferromagnet at low Co doping to that of a strong ferromagnet at x>0.3 and as such, spin polarization crossover occurs. The Fermi level is tuned from the majority spin band for x<0.3 where a strongly polarized majority spin electron gas prevails, to a regime where minority spin carriers dominate at higher doping. The evolution of the Fe-derived spin polarized (3d) bands, indirectly probed here via the 4p states, is the primary determinant of the doping dependence of the magnetism in this alloy series.

  12. A modular designed ultra-high-vacuum spin-polarized scanning tunneling microscope with controllable magnetic fields for investigating epitaxial thin films.

    Science.gov (United States)

    Wang, Kangkang; Lin, Wenzhi; Chinchore, Abhijit V; Liu, Yinghao; Smith, Arthur R

    2011-05-01

    A room-temperature ultra-high-vacuum scanning tunneling microscope for in situ scanning freshly grown epitaxial films has been developed. The core unit of the microscope, which consists of critical components including scanner and approach motors, is modular designed. This enables easy adaptation of the same microscope units to new growth systems with different sample-transfer geometries. Furthermore the core unit is designed to be fully compatible with cryogenic temperatures and high magnetic field operations. A double-stage spring suspension system with eddy current damping has been implemented to achieve ≤5 pm z stability in a noisy environment and in the presence of an interconnected growth chamber. Both tips and samples can be quickly exchanged in situ; also a tunable external magnetic field can be introduced using a transferable permanent magnet shuttle. This allows spin-polarized tunneling with magnetically coated tips. The performance of this microscope is demonstrated by atomic-resolution imaging of surface reconstructions on wide band-gap GaN surfaces and spin-resolved experiments on antiferromagnetic Mn(3)N(2)(010) surfaces.

  13. First-principles study of spin-polarized electronic band structures in ferromagnetic Zn1-xTMxS (TM = Fe, Co and Ni)

    KAUST Repository

    Saeed, Yasir

    2010-10-01

    We report a first-principles study of structural, electronic and magnetic properties of crystalline alloys Zn1-xTMxS (TM = Fe, Co and Ni) at x = 0.25. Structural properties are computed from the total ground state energy convergence and it is found that the cohesive energies of Zn 1-xTMxS are greater than that of zincblende ZnS. We also study the spin-polarized electronic band structures, total and partial density of states and the effect of TM 3d states. Our results exhibit that Zn 0.75Fe0.25S, Zn0.75Co0.25S and Zn0.75Ni0.25S are half-metallic ferromagnetic with a magnetic moment of 4μB, 3μB and 2μB, respectively. Furthermore, we calculate the TM 3d spin-exchange-splitting energies Δx (d), Δx (x-d), exchange constants N0α and N0β, crystal field splitting (ΔEcrystEt2g-Eeg), and find that p-d hybridization reduces the local magnetic moment of TM from its free space charge value. Moreover, robustness of Zn1-xTMxS with respect to the variation of lattice constants is also discussed. © 2010 Elsevier B.V. All rights reserved.

  14. Band structure of topological insulators from noise measurements in tunnel junctions

    Energy Technology Data Exchange (ETDEWEB)

    Cascales, Juan Pedro, E-mail: juanpedro.cascales@uam.es; Martínez, Isidoro; Aliev, Farkhad G., E-mail: farkhad.aliev@uam.es [Dpto. Fisica Materia Condensada C3, Instituto Nicolas Cabrera (INC), Condensed Matter Physics Institute (IFIMAC), Universidad Autonoma de Madrid, Madrid 28049 (Spain); Katmis, Ferhat; Moodera, Jagadeesh S. [Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Chang, Cui-Zu [Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Guerrero, Rubén [Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia), Cantoblanco, 28049 Madrid (Spain)

    2015-12-21

    The unique properties of spin-polarized surface or edge states in topological insulators (TIs) make these quantum coherent systems interesting from the point of view of both fundamental physics and their implementation in low power spintronic devices. Here we present such a study in TIs, through tunneling and noise spectroscopy utilizing TI/Al{sub 2}O{sub 3}/Co tunnel junctions with bottom TI electrodes of either Bi{sub 2}Te{sub 3} or Bi{sub 2}Se{sub 3}. We demonstrate that features related to the band structure of the TI materials show up in the tunneling conductance and even more clearly through low frequency noise measurements. The bias dependence of 1/f noise reveals peaks at specific energies corresponding to band structure features of the TI. TI tunnel junctions could thus simplify the study of the properties of such quantum coherent systems that can further lead to the manipulation of their spin-polarized properties for technological purposes.

  15. Spin-polarized electron tunneling in bcc FeCo/MgO/FeCo(001) magnetic tunnel junctions.

    Science.gov (United States)

    Bonell, F; Hauet, T; Andrieu, S; Bertran, F; Le Fèvre, P; Calmels, L; Tejeda, A; Montaigne, F; Warot-Fonrose, B; Belhadji, B; Nicolaou, A; Taleb-Ibrahimi, A

    2012-04-27

    In combining spin- and symmetry-resolved photoemission, magnetotransport measurements and ab initio calculations we detangled the electronic states involved in the electronic transport in Fe(1-x)Co(x)(001)/MgO/Fe(1-x)Co(x)(001) magnetic tunnel junctions. Contrary to previous theoretical predictions, we observe a large reduction in TMR (from 530 to 200% at 20 K) for Co content above 25 atomic% as well as anomalies in the conductance curves. We demonstrate that these unexpected behaviors originate from a minority spin state with Δ(1) symmetry that exists below the Fermi level for high Co concentration. Using angle-resolved photoemission, this state is shown to be a two-dimensional state that occurs at both Fe(1-x)Co(x)(001) free surface, and more importantly at the interface with MgO. The combination of this interface state with the peculiar density of empty states due to chemical disorder allows us to describe in details the complex conduction behavior in this system.

  16. Lyin' eyes: ocular-motor measures of reading reveal deception.

    Science.gov (United States)

    Cook, Anne E; Hacker, Douglas J; Webb, Andrea K; Osher, Dahvyn; Kristjansson, Sean D; Woltz, Dan J; Kircher, John C

    2012-09-01

    Our goal was to evaluate an alternative to current methods for detecting deception in security screening contexts. We evaluated a new cognitive-based test of deception that measured participants' ocular-motor responses (pupil responses and reading behaviors) while they read and responded to statements on a computerized questionnaire. In Experiment 1, participants from a university community were randomly assigned to either a "guilty" group that committed one of two mock crimes or an "innocent" group that only learned about the crime. Participants then reported for testing, where they completed the computer-administered questionnaire that addressed their possible involvement in the crimes. Experiment 2 also manipulated participants' incentive to pass the test and difficulty of statements on the test. In both experiments, guilty participants had increased pupil responses to statements answered deceptively; however, they spent less time fixating on, reading, and rereading those statements than statements answered truthfully. These ocular-motor measures were optimally weighted in a discrimination function that correctly classified 85% of participants as either guilty or innocent. Findings from Experiment 2 indicated that group discrimination was improved with greater incentives to pass the test and the use of statements with simple syntax. The present findings suggest that two cognitive processes are involved in deception-vigilance and strategy-and that these processes are reflected in different ocular-motor measures. The ocular-motor test reported here represents a new approach to detecting deception that may fill an important need in security screening contexts.

  17. Lyin’ Eyes: Ocular-motor Measures of Reading Reveal Deception

    Science.gov (United States)

    Cook, Anne E.; Hacker, Douglas J.; Webb, Andrea K.; Osher, Dahvyn; Kristjansson, Sean; Woltz, Dan J.; Kircher, John C.

    2013-01-01

    Our goal was to evaluate an alternative to current methods for detecting deception in security screening contexts. We evaluated a new cognitive-based test of deception that measured participants’ ocular-motor responses (pupil responses and reading behaviors) while they read and responded to statements on a computerized questionnaire. In Experiment 1, participants from a university community were randomly assigned to either a “guilty” group that committed one of two mock crimes or an “innocent” group that only learned about the crime. Participants then reported for testing, where they completed the computer-administered questionnaire that addressed their possible involvement in the crimes. Experiment 2 also manipulated participants’ incentive to pass the test and difficulty of statements on the test. In both experiments, guilty participants had increased pupil responses to statements answered deceptively; however, they spent less time fixating on, reading, and re-reading those statements than statements answered truthfully. These ocular-motor measures were optimally weighted in a discrimination function that correctly classified 85% of participants as either guilty or innocent. Findings from Experiment 2 indicated that group discrimination was improved with greater incentives to pass the test and the use of statements with simple syntax. The present findings suggest that two cognitive processes are involved in deception -- vigilance and strategy -- and that these processes are reflected in different ocular-motor measures. The ocular-motor test reported here represents a new approach to detecting deception that may fill an important need in security screening contexts. PMID:22545928

  18. Development, construction and characterization of a variable repetitive spin-polarized electron gun with an inverted-geometry insulator; Entwicklung, Aufbau und Charakterisierung einer variabel repetierenden, spinpolarisierten Elektronenkanone mit invertierter Isolatorgeometrie

    Energy Technology Data Exchange (ETDEWEB)

    Espig, Martin

    2016-02-15

    Within the scope of this thesis a pulsed source of spin polarized electrons Photo-CATCH was designed, constructed, characterized and has been put into operation. This source is based on the photoemission of spin-polarized electrons from GaAs-photocathodes. Both the design of the electron gun, consisting of an ultra-high vacuum chamber and an electrode with Pierce geometry, as well as the properties of the electron beam have been simulated with CST Studio. Results were a maximum electric field of (0.064±0.001) MV/m/kV on the electrode surface and a beam emittance as a function of the radius of the laser spot on the photocathode of element of {sub n,x}=(1.7478(4).10{sup -4}.(r)/(μm)+2.8(18).10{sup -5}) mm mrad at a beam current of 100 μA. Currently Photo-CATCH provides electron beams with an energy of 60 keV, which can be expanded up to 100 keV by upgrading the high-voltage power supply. The electron gun has an inverted-geometry insulator to ensure a compact design of the ultra-high vacuum chamber and a maximum person- and machine-safety from sparkovers. Since the properties of the laser light directly affect the properties of the generated electron beam a pulsed semiconductor laser system has been specially developed and built for Photo-CATCH. This is characterized by a high variability of its operating parameters, in particular its wavelength and repetition rate, in order to fulfill the broad variety of requirements of various nuclear physics experiments. By selecting the wavelength of the used laser diode highly polarized or high-current electron beams can be generated from GaAs-photocathodes. The time profile of the laser has direct influence to the longitudinal profile of the electron bunch. Through the radiofrequency modulation of the pumping current of the impedance-matched semiconductor laser system, consisting of a DC power source and an electrical pulse generator with 881 ps broad pump pulses, Lorentz shaped laser pulses with a minimum FWHM of (43.8±1

  19. Calculations of spin-polarized Goos-Hänchen displacement in magnetically confined GaAs/Al x Ga1-x As nanostructure modulated by spin-orbit couplings

    Science.gov (United States)

    Lu, Mao-Wang; Chen, Sai-Yan; Zhang, Gui-Lian; Huang, Xin-Hong

    2018-04-01

    We theoretically investigate Goos-Hänchen (GH) displacement by modelling the spin transport in an archetypal device structure—a magnetically confined GaAs/Al x Ga1-x As nanostructure modulated by spin-orbit coupling (SOC). Both Rashba and Dresselhaus SOCs are taken into account. The degree of spin-polarized GH displacement can be tuned by Rashba or Dresselhaus SOC, i.e. interfacial confining electric field or strain engineering. Based on such a semiconductor nanostructure, a controllable spatial spin splitter can be proposed for spintronics applications.

  20. Revealing the correlation between real-space structure and chiral magnetic order at the atomic scale

    Science.gov (United States)

    Hauptmann, Nadine; Dupé, Melanie; Hung, Tzu-Chao; Lemmens, Alexander K.; Wegner, Daniel; Dupé, Bertrand; Khajetoorians, Alexander A.

    2018-03-01

    We image simultaneously the geometric, the electronic, and the magnetic structures of a buckled iron bilayer film that exhibits chiral magnetic order. We achieve this by combining spin-polarized scanning tunneling microscopy and magnetic exchange force microscopy (SPEX) to independently characterize the geometric as well as the electronic and magnetic structures of nonflat surfaces. This new SPEX imaging technique reveals the geometric height corrugation of the reconstruction lines resulting from strong strain relaxation in the bilayer, enabling the decomposition of the real-space from the electronic structure at the atomic level and the correlation with the resultant spin-spiral ground state. By additionally utilizing adatom manipulation, we reveal the chiral magnetic ground state of portions of the unit cell that were not previously imaged with spin-polarized scanning tunneling microscopy alone. Using density functional theory, we investigate the structural and electronic properties of the reconstructed bilayer and identify the favorable stoichiometry regime in agreement with our experimental result.

  1. 2D Electron Gas with 100% Spin-Polarization in the (LaMnO3)2/(SrTiO3)2 Superlattice under Uniaxial Strain

    KAUST Repository

    Cossu, Fabrizio

    2014-07-28

    By first-principles calculations we investigate the structural, electronic, and magnetic properties of the (LaMnO3)2/(SrTiO3)2 superlattice. We find that a monoclinic C2h symmetry is energetically favorable and that the spins order ferromagnetically. Under both compressive and tensile uniaxial strain the electronic structure of the superlattice shows a half-metallic character. In particular, a fully spin-polarized two-dimensional electron gas, which traces back to the Ti 3dxy orbitals, is achieved under compressive uniaxial strain. The (LaMnO3)2/(SrTiO3)2 superlattice is analysed with respect to its structure, magnetism, and electronic properties. Our results demonstrate that uniaxial strain in an experimentally accessible range, both tensile and compressive, can be used to induce half-metallicity. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. What can we learn about the dynamics of transported spins by measuring shot noise in spin–orbit-coupled nanostructures?

    International Nuclear Information System (INIS)

    Nikolić, Branislav K; Dragomirova, Ralitsa L

    2009-01-01

    We review recent studies of the shot noise of spin-polarized charge currents and pure spin currents in multiterminal semiconductor nanostructures, while focusing on the effects brought by the intrinsic Rashba spin–orbit (SO) coupling and/or extrinsic SO scattering off impurities in two-dimensional electron gas (2DEG) based devices. By generalizing the scattering theory of quantum shot noise to include the full spin-density matrix of electrons injected from a spin-filtering electrode, we show how decoherence and dephasing in the course of spin precession can lead to the substantial enhancement of the Fano factor (noise-to-current ratio) of spin-polarized charge currents. These processes are suppressed by decreasing the width of the diffusive Rashba wire, so that purely electrical measurement of the shot noise in a ferromagnet|SO-coupled-diffusive-wire|paramagnet setup can quantify the degree of quantum coherence of transported spin through a remarkable one-to-one correspondence between the purity of the spin state and the Fano factor. In four-terminal SO-coupled nanostructures, injection of unpolarized charge current through the longitudinal leads is responsible not only for the pure spin Hall current in the transverse leads, but also for nonequilibrium random time-dependent current fluctuations. The analysis of the shot noise of transverse pure spin Hall current and zero charge current, or transverse spin current and non-zero charge Hall current, driven by unpolarized or spin-polarized injected longitudinal charge current, respectively, reveals a unique experimental tool to differentiate between the intrinsic Rashba and extrinsic SO mechanisms underlying the spin Hall effect in 2DEG devices. When the intrinsic mechanisms responsible for spin precession start to dominate the spin Hall effect, they also enhance the shot noise of transverse spin and charge transport in multiterminal geometries. Finally, we discuss the shot noise of transverse spin and zero charge

  3. Study of the nuclear structure far from stability: Coulomb excitation of neutron-rich Rb isotopes around N=60; Production of nuclear spin polarized beams using the tilted foils technique

    International Nuclear Information System (INIS)

    Sotty, C.

    2013-01-01

    The underlying structure in the region A ∼ 100, N ∼ 60 has been under intensive and extensive investigation, mainly by β-decay and γ-ray spectroscopy from fission processes. Around N ∼ 60, by adding just few neutrons, protons a rapid shape change occurs from spherical-like to well deformed g.s. shape. Shape coexistence has been observed in the Sr and Zr nuclei, and is expected to take place in the whole region. The mechanisms involved in the appearance of the deformation is not well understood. The interplay between down-sloping and up-sloping neutron Nilsson orbital is evoked as one of the main reasons for the sudden shape change. However, a clear identification of the active proton and neutron orbitals was still on-going. For that purpose, the neutron rich 93;95;97;99 Rb isotopes have been studied by Coulomb excitation at CERN (ISOLDE) using the REX-ISOLDE post-accelerator and the MINIBALL setup. The completely unknown structures of 97;99 Rb have been populated and observed. Prompt γ-ray coincidences of low-lying states have been observed and time-correlated in order to build level schemes. The associated transition strengths have been extracted with the GOSIA code. The observed matrix elements of the electromagnetic operator constituted new inputs of further theoretical calculations giving new insight on the involved orbitals. The sensitivity of such experiment can be increased using nuclear spin polarized radioactive ion beam. For that purpose the Tilted Foils Technique (TFT) of polarization has been investigated at CERN. This technique consists to spin polarize the ion beam, passing through thin foils tilted at an oblique angle with respect to the beam direction. The initially obtained atomic polarization is transferred to the nucleus by hyperfine interaction. This technique does not depend on the chemical nature of the element. Short lived nuclei can be polarized in-flight without any need to be stopped in a catcher. It opens up the possibility to

  4. Partial spin polarization of a conductance in a bi-layer In0.52 Al0.48 As / In0.53 Ga0.47 As heterostructure based nanowire for the rectangular and the smooth lateral confinement potentials

    Science.gov (United States)

    Chwiej, T.

    2016-03-01

    We simulate the electron transport in a vertical bi-layer nanowire in order to study an influence of the lateral confinement's shape on a spin polarization of wire's conductance. The active part of considered quantum wire constitutes a double inverted heterojunction In0.52 Al0.48 As /In0.53 Ga0.47 As which nanostructure can be fabricated in molecular beam epitaxy process while the lateral confinement potential can be finally formed by means of cleaved overgrowth or surface oxidization methods giving the desired rectangular and smooth lateral confinement. In calculations we take into account interaction between charge carriers using DFT within local spin density approximation. We show that if the magnetic field is perpendicular to the wire axis, the pseudogaps are opened in energy dispersion relation E (k) what in conjunction with spin Zeeman shift of spin-up and spin-down subbands may enhance the spin polarization of conductance with reference to a single layer wire. For nanowire with rectangular lateral confinement potential we found that the electron density has two maximums localized at wire edges in each layers. This modificates strongly all magnetosubbands giving up to four energy minimums in lowest subband and considerably diminishes widths of pseudogaps what translates into low maximal spin polarization of conductance, not exceeding 40%. This drawback is absent in wire with smooth lateral confinement. However, in order to gain a large spin polarization simultaneous tuning of magnetic field as well as the Fermi energies in both layers of nanowire are required.

  5. Electron spin polarization effects in low energy electron diffraction, ion neutralization and metastable atom deexcitation at solid surfaces. Progress report No. 4, 1 January-31 December 1984

    International Nuclear Information System (INIS)

    1984-01-01

    In the present contract year, a GaAs polarized electron source has been used to undertake a polarized LEED study of order-disorder transformations at Cu 3 Au (100) and (111) surfaces. A polarized LEED study of Cu (100) has also been initiated. A polarized MDS study of Ni(110) surface magnetism has been completed. Spin dependences in the Auger electron yield were observed that provide a measure of the surface magnetism and were used to probe the dependence of surface magnetism on temperature and adsorbate coverage. A similar study using a ferromagnetic glass is now underway. A Mott polarization analyzer, constructed to measure the ESP of the ejected electrons, is also being installed on the apparatus. Such measurements provide direct information concerning the dynamics of secondary electron ejection and the details of adsorbate-substrate bonding

  6. Design and performance of an ultra-high vacuum spin-polarized scanning tunneling microscope operating at 30 mK and in a vector magnetic field

    Science.gov (United States)

    von Allwörden, Henning; Eich, Andreas; Knol, Elze J.; Hermenau, Jan; Sonntag, Andreas; Gerritsen, Jan W.; Wegner, Daniel; Khajetoorians, Alexander A.

    2018-03-01

    We describe the design and performance of a scanning tunneling microscope (STM) that operates at a base temperature of 30 mK in a vector magnetic field. The cryogenics is based on an ultra-high vacuum (UHV) top-loading wet dilution refrigerator that contains a vector magnet allowing for fields up to 9 T perpendicular and 4 T parallel to the sample. The STM is placed in a multi-chamber UHV system, which allows in situ preparation and exchange of samples and tips. The entire system rests on a 150-ton concrete block suspended by pneumatic isolators, which is housed in an acoustically isolated and electromagnetically shielded laboratory optimized for extremely low noise scanning probe measurements. We demonstrate the overall performance by illustrating atomic resolution and quasiparticle interference imaging and detail the vibrational noise of both the laboratory and microscope. We also determine the electron temperature via measurement of the superconducting gap of Re(0001) and illustrate magnetic field-dependent measurements of the spin excitations of individual Fe atoms on Pt(111). Finally, we demonstrate spin resolution by imaging the magnetic structure of the Fe double layer on W(110).

  7. Nanoscale Measurements of Magnetism & Spin Coherence in Semiconductors

    Science.gov (United States)

    2015-12-17

    Office P.O. Box 12211 Research Triangle Park, NC 27709-2211 spin polarized measurements, single spins, single spin manipulation REPORT DOCUMENTATION...Received Paper 6.00 Ali Yazdani. Visualizing Majorana fermions in a chain of magnetic atoms on a superconductor, Nobel Symposium 156, New forms of...level and also for the first time probe spin orbit coupling. This system led to first direct visualization of a Majorana fermion in a condensed

  8. Fibrinogen adsorption mechanisms at the gold substrate revealed by QCM-D measurements and RSA modeling.

    Science.gov (United States)

    Kubiak, Katarzyna; Adamczyk, Zbigniew; Cieśla, Michał

    2016-03-01

    Adsorption kinetics of fibrinogen at a gold substrate at various pHs was thoroughly studied using the QCM-D method. The experimental were interpreted in terms of theoretical calculations performed according to the random sequential adsorption model (RSA). In this way, the hydration functions and water factors of fibrinogen monolayers were quantitatively evaluated at various pHs. It was revealed that for the lower range of fibrinogen coverage the hydration function were considerably lower than previously obtained for the silica sensor [33]. The lower hydration of fibrinogen monolayers on the gold sensor was attributed to its higher roughness. However, for higher fibrinogen coverage the hydration functions for both sensors became identical exhibiting an universal behavior. By using the hydration functions, the fibrinogen adsorption/desorption runs derived from QCM-D measurements were converted to the Γd vs. the time relationships. This allowed to precisely determine the maximum coverage that varied between 1.6mgm(-2) at pH 3.5 and 4.5mgm(-2) at pH 7.4 (for ionic strength of 0.15M). These results agree with theoretical eRSA modeling and previous experimental data derived by using ellipsometry, OWLS and TIRF. Various fibrinogen adsorption mechanisms were revealed by exploiting the maximum coverage data. These results allow one to develop a method for preparing fibrinogen monolayers of well-controlled coverage and molecule orientation. Copyright © 2015 Elsevier B.V. All rights reserved.

  9. Hydrophobic attraction as revealed by AFM force measurements and molecular dynamics simulation.

    Science.gov (United States)

    Fa, Keqing; Nguyen, Anh V; Miller, Jan D

    2005-07-14

    Spherical calcium dioleate particles ( approximately 10 mum in diameter) were used as AFM (atomic force microscope) probes to measure interaction forces of the collector colloid with calcite and fluorite surfaces. The attractive AFM force between the calcium dioleate sphere and the fluorite surface is strong and has a longer range than the DLVO (Derjaguin-Landau-Verwey-Overbeek) prediction. The AFM force between the calcium dioleate sphere and the mineral surfaces does not agree with the DLVO prediction. Consideration of non-DLVO forces, including the attractive hydrophobic force and the repulsive hydration force, was necessary to explain the experimental results. The non-DLVO interactions considered were justified by the different interfacial water structures at calcite- and fluorite-water interfaces as revealed by the numerical computation experiments with molecular dynamics simulation.

  10. Physical processes in spin polarized plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Kulsrud, R.M.; Valeo, E.J.; Cowley, S.

    1984-05-01

    If the plasma in a nuclear fusion reactor is polarized, the nuclear reactions are modified in such a way as to enhance the reactor performance. We calculate in detail the modification of these nuclear reactions by different modes of polarization of the nuclear fuel. We also consider in detail the various physical processes that can lead to depolarization and show that they are by and large slow enough that a high degree of polarization can be maintained.

  11. Spin-polarized current in noncollinear antiferromagnets

    Czech Academy of Sciences Publication Activity Database

    Železný, Jakub; Zhang, Y.; Felser, C.; Yan, B.

    2017-01-01

    Roč. 119, č. 18 (2017), s. 1-7, č. článku 187204. ISSN 0031-9007 Institutional support: RVO:68378271 Keywords : anisotropic magnetoresistance * wannier functions * room-temperature * torques * spintronics Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 8.462, year: 2016

  12. Collective effects in spin polarized plasmas

    International Nuclear Information System (INIS)

    Coppi, B.; Cowley, S.; Detragiache, P.; Kulsrud, R.; Pegoraro, F.

    1984-10-01

    A fusing plasma with coherently polarized spin nuclei can be subject to instabilities due to the anisotropy of the reaction product distributions in velocity space, which is a result of their polarization. The characteristics of these instabilities depend strongly on the plasma spatial inhomogeneities and a significant rate of spin depolarization can be produced by them if adequate fluctuation amplitudes are reached. The results of the relevant analysis are, in addition, of interest for plasma heating processes with frequencies in the range of the cyclotron frequencies of the considered nuclei

  13. Spin polarization in high density quark matter

    DEFF Research Database (Denmark)

    Bohr, Henrik; Panda, Prafulla K.; Providênci, Constanca

    2013-01-01

    We investigate the occurrence of a ferromagnetic phase transition in high density hadronic matter (e.g., in the interior of a neutron star). This could be induced by a four-fermion interaction analogous to the one which is responsible for chiral symmetry breaking in the Nambu-Jona-Lasinio model...... the so-called 2 flavor super-conducting phase to the ferromagnetic phase arises. The color-flavor-locked phase may be completely hidden by the FP....

  14. New Aspects of Photocurrent Generation at Graphene pn Junctions Revealed by Ultrafast Optical Measurements

    Science.gov (United States)

    Aivazian, Grant; Sun, Dong; Jones, Aaron; Ross, Jason; Yao, Wang; Cobden, David; Xu, Xiaodong

    2012-02-01

    The remarkable electrical and optical properties of graphene make it a promising material for new optoelectronic applications. However, one important, but so far unexplored, property is the role of hot carriers in charge and energy transport at graphene interfaces. Here we investigate the photocurrent (PC) dynamics at a tunable graphene pn junction using ultrafast scanning PC microscopy. Pump-probe measurements show a temperature dependent relaxation time of photogenerated carriers that increases from 1.5ps at 290K to 4ps at 20K; while the amplitude of the PC is independent of the lattice temperature. These observations imply that it is hot carriers, not phonons, which dominate ultrafast energy transport. Gate dependent measurements show many interesting features such as pump induced saturation, enhancement, and sign reversal of probe generated PC. These observations reveal that the underlying PC mechanism is a combination of the thermoelectric and built-in electric field effects. Our results enhance the understanding of non-equilibrium electron dynamics, electron-electron interactions, and electron-phonon interactions in graphene. They also determine fundamental limits on ultrafast device operation speeds (˜500 GHz) for graphene-based photodetectors.

  15. Revealing time-unlocked brain activity from MEG measurements by common waveform estimation.

    Directory of Open Access Journals (Sweden)

    Yusuke Takeda

    Full Text Available Brain activities related to cognitive functions, such as attention, occur with unknown and variable delays after stimulus onsets. Recently, we proposed a method (Common Waveform Estimation, CWE that could extract such brain activities from magnetoencephalography (MEG or electroencephalography (EEG measurements. CWE estimates spatiotemporal MEG/EEG patterns occurring with unknown and variable delays, referred to here as unlocked waveforms, without hypotheses about their shapes. The purpose of this study is to demonstrate the usefulness of CWE for cognitive neuroscience. For this purpose, we show procedures to estimate unlocked waveforms using CWE and to examine their role. We applied CWE to the MEG epochs during Go trials of a visual Go/NoGo task. This revealed unlocked waveforms with interesting properties, specifically large alpha oscillations around the temporal areas. To examine the role of the unlocked waveform, we attempted to estimate the strength of the brain activity of the unlocked waveform in various conditions. We made a spatial filter to extract the component reflecting the brain activity of the unlocked waveform, applied this spatial filter to MEG data under different conditions (a passive viewing, a simple reaction time, and Go/NoGo tasks, and calculated the powers of the extracted components. Comparing the powers across these conditions suggests that the unlocked waveforms may reflect the inhibition of the task-irrelevant activities in the temporal regions while the subject attends to the visual stimulus. Our results demonstrate that CWE is a potential tool for revealing new findings of cognitive brain functions without any hypothesis in advance.

  16. High-resolution Bio-Argo and Argo Measurements to Reveal Specific Oceanic Processes.

    Science.gov (United States)

    Poteau, A.; Claustre, H.; Briggs, N.; D'Ortenzio, F.; Schmechtig, C.; Prieur, L. M.; Boss, E.

    2016-02-01

    Together with temperature and salinity measurements, Bio-Argo profiling floats now measure a significant range of biogeochemical (e.g. O2, NO3) and bio-optical variables (Chla, backscattering coefficient and radiometry). To transmit the very large amount of data acquired by this new generation of floats, it was required to substitute the Argos telemetry (Argo program) with iridium telemetry. The obvious consequence is not only a much greater flexibly on data transmission but also on data acquisition thanks to the two-way communication allowed by iridium. Our group has now deployed and managed over 100 Bio-Argo floats of this type. In particular we have set up high-resolution mode of acquisition for certain periods of time or for dedicated portions of the water column. Here we illustrate with three examples the potential of conducting high-resolution measurement to identify and explore certain oceanic processes. (1) High resolution measurements of pressure, temperature and salinity (every 2 s) when the float is finishing its ascent (without any pump action) in the upper 10 m layer are analyzed with respect to sea state. We particularly focus on the study of the speed anomaly as compared to a nominal speed expected for a calm sea state. By comparison between speed anomaly of a float in the Mediterranean Sea and concurrent sea state measurements by a weather buoy in the same area, we suggest that float behaviour can be an indicator of sea state. (2) Each year, in response to springtime phytoplankton blooms, the resolution of bio-optical variables (backscattering and Chla) in the top 1000 m was increased to at least 1 m (every 10 s) for all floats in the North Atlantic and Southern Ocean. This resolution allowed accurate estimation of the concentration of large phytoplankton aggregates and revealed systematic differences in bulk aggregate sinking rate between ocean basins. (3) Finally we continuously record all the variables at a 10 min resolution during the float

  17. Micrometeorological Measurements Reveal Large Nitrous Oxide Losses during Spring Thaw in Alberta

    Directory of Open Access Journals (Sweden)

    Thomas K. Flesch

    2018-03-01

    Full Text Available Agricultural soils in Canada have been observed to emit a large pulse of nitrous oxide (N2O gas during the spring thaw, representing a large percentage of the annual emissions. We report on three years of spring thaw N2O flux measurements taken at three Alberta agricultural sites: a crop production site (Crop, cattle winter-feeding site (WF, and a cattle winter-grazing site (WG. Soil fluxes were calculated with a micrometeorological technique based on the vertical gradient in N2O concentration above each site measured with an open-path (line-averaging FTIR gas detector. The Crop and WG sites showed a clear N2O emission pulse lasting 10 to 25 days after thawing began. During this pulse there was a strong diurnal cycle in emissions that paralleled the cycle in near-surface soil temperature. The emission pulse was less pronounced at the WF site. The average spring thaw losses (over 25 to 31 days were 5.3 (Crop, 7.0 (WF, and 8.0 (WG kg N2O-N ha−1, representing 1 to 3.5% of the annual nitrogen input to the sites. These large losses are higher than found in most previous western Canadian studies, and generally higher than the annual losses estimated from the Intergovernmental Panel on Climate Change and Canadian National Inventory Report calculations. The high N2O losses may be explained by high soil nitrate levels which promoted rapid denitrification during thawing. The application of a high resolution (temporal micrometeorological technique was critical to revealing these losses.

  18. Long term kinetic measurements revealing precision and general performance of surface plasmon resonance biosensors.

    Science.gov (United States)

    Steinicke, Franziska; Oltmann-Norden, Imke; Wätzig, Hermann

    2017-08-01

    This work presents an extensive parameter list that facilitates a survey of biosensor performance using Biacore instruments for kinetic binding studies. Six long term measurements were performed using a strongly interacting antigen-antibody (β2 microglobulin) system. Both Single Cycle Kinetic (SCK) and Multi Cycle Kinetic (MCK) were executed each with five different analyte concentrations. The overall comparison of the long term monitored parameters, like the dissociation constant (K D with approximately 3-6% relative percental standard deviation), the association and dissociation rate constants (k a , k d ), the analyte binding capacity (R max ), chi 2 and the sum of the absolute values of the residuals, revealed the delicate factors that make the system performance vulnerable. The main influential factors on kinetic performance were the regeneration conditions, the quality of the sensor surface, the usage time and alteration of the sensor surface, the dilution series and the number of run cycles (about 250-600 per chip). Moreover the direct comparison of MCK and SCK uncovered distinct differences in the accuracy of the K D values. The study of sensor chips from two manufacturers showed distinct differences in the precision of the data. Using control charts for the surveillance of these parameters contributes to an overall better system performance. Copyright © 2017 Elsevier Inc. All rights reserved.

  19. Automated gray level index measurements reveal only minor cytoarchitectonic changes of Brodmann area 9 in schizophrenia.

    Science.gov (United States)

    Tepest, Ralf; Vogeley, Kai; Viebahn, Bettina; Schneider-Axmann, Thomas; Honer, William G; Falkai, Peter

    2008-07-15

    Using an automatized gray level index (GLI) method, we recently found cytoarchitectonic abnormalities in schizophrenia in Brodmann area 10 (BA10) [Vogeley, K., Tepest, R., Schneider-Axmann, T., Hutte, H., Zilles, K., Honer, W.G., Falkai, P., 2003. Automated image analysis of disturbed cytoarchitecture in Brodmann area 10 in schizophrenia, Schizophrenia Research 62, 133-140]. As another potential key region involved in the pathophysiology of schizophrenia, we have now investigated BA9 in the same sample consisting of 20 schizophrenic cases and 20 controls. The GLI value represents the area-percentage covered by perikarya in measuring fields of microscopic images. BA9 was analyzed with respect to the factors diagnosis and gender for six different compartments approximately corresponding to the neocortical layers. The main result in BA9 was a significant interaction of diagnosis and gender for GLI in layers IV and V on the left side. Subsequent analyses separately performed concerning gender revealed a significant GLI increase in layer V on the left side in male patients compared with controls. However, after an adjustment of error probabilities for multiple testing, differences did not reach significance. No GLI difference was observed in the sample between diagnostic groups for females and between the diagnostic groups in general. Comparisons with our BA10 results suggest that cytoarchitectural changes relevant to schizophrenia appear different in various Brodmann areas. Since increases in GLI were found only in selected layers (V and VI) of BA9, these findings do not support a generalized neuropil reduction across all cortical layers.

  20. Redox-controlled backbone dynamics of human cytochrome c revealed by 15N NMR relaxation measurements

    International Nuclear Information System (INIS)

    Sakamoto, Koichi; Kamiya, Masakatsu; Uchida, Takeshi; Kawano, Keiichi; Ishimori, Koichiro

    2010-01-01

    Research highlights: → The dynamic parameters for the backbone dynamics in Cyt c were determined. → The backbone mobility of Cyt c is highly restricted due to the covalently bound heme. → The backbone mobility of Cyt c is more restricted upon the oxidation of the heme. → The redox-dependent dynamics are shown in the backbone of Cyt c. → The backbone dynamics of Cyt c would regulate the electron transfer from Cyt c. -- Abstract: Redox-controlled backbone dynamics in cytochrome c (Cyt c) were revealed by 2D 15 N NMR relaxation experiments. 15 N T 1 and T 2 values and 1 H- 15 N NOEs of uniformly 15 N-labeled reduced and oxidized Cyt c were measured, and the generalized order parameters (S 2 ), the effective correlation time for internal motion (τ e ), the 15 N exchange broadening contributions (R ex ) for each residue, and the overall correlation time (τ m ) were estimated by model-free dynamics formalism. These dynamic parameters clearly showed that the backbone dynamics of Cyt c are highly restricted due to the covalently bound heme that functions as the stable hydrophobic core. Upon oxidation of the heme iron in Cyt c, the average S 2 value was increased from 0.88 ± 0.01 to 0.92 ± 0.01, demonstrating that the mobility of the backbone is further restricted in the oxidized form. Such increases in the S 2 values were more prominent in the loop regions, including amino acid residues near the thioether bonds to the heme moiety and positively charged region around Lys87. Both of the regions are supposed to form the interaction site for cytochrome c oxidase (CcO) and the electron pathway from Cyt c to CcO. The redox-dependent mobility of the backbone in the interaction site for the electron transfer to CcO suggests an electron transfer mechanism regulated by the backbone dynamics in the Cyt c-CcO system.

  1. Present status of the {sup 129}Xe comagnetometer development for neutron EDM measurement

    Energy Technology Data Exchange (ETDEWEB)

    Mihara, M., E-mail: mihara@vg.phys.sci.osaka-u.ac.jp [Osaka University, Department of Physics (Japan); Masuda, Y. [Institute of Particle and Nuclear Studies (IPNS), High Energy Accelerator Research Organization (KEK) (Japan); Matsuta, K. [Osaka University, Department of Physics (Japan); Kawasaki, S.; Watanabe, Y. [Institute of Particle and Nuclear Studies (IPNS), High Energy Accelerator Research Organization (KEK) (Japan); Hatanaka, K.; Matsumiya, R. [Osaka University, Research Center for Nuclear Physics (RCNP) (Japan)

    2016-12-15

    A {sup 129}Xe comagnetometer designed for the measurement of neutron electric dipole moment (nEDM) as precisely as 1 × 10{sup −27}e cm is presented. Highly nuclear spin polarized {sup 129}Xe are introduced into an EDM cell where the {sup 129}Xe spin precession is detected by means of the two-photon transition. The geometric phase effect (GPE) which generates the false nEDM was quantitatively discussed and the systematic error of nEDM from the GPE was estimated considering the buffer-gas suppression due to Xe atomic collisions. Research and development are in progress to construct the {sup 129}Xe comagnetometer with a field sensitivity of 0.3 fT. At present, about 70 % nuclear spin polarized {sup 129}Xe atoms have been obtained in a spin exchange opitial pumping cell, that are in the process of being transferred into the EDM cell via a cold trap.

  2. In situ measurements reveal extremely low pH in soil

    DEFF Research Database (Denmark)

    Nielsen, Knud Erik; Loibide, Amaia Irixar; Nielsen, Lars Peter

    2017-01-01

    We measured pH in situ in the top organic soil horizons in heathland and pine forest and found values between 2.6 and 3.2. This was 0.5e0.8 units lower than concurrent laboratory pH measurements of the same soil, which raises questions about the interpretation of pH measurements. We propose...... that the higher pH recorded by standard laboratory methods may be due to buffering ions from soil biota released from drying, grinding and rewetting of soil samples, whereas the in situ pH reflects the correct level of acidification....

  3. Revealing the connectivity of groundwater and surface water using electromagnetic induction measurements

    Science.gov (United States)

    Binley, A. M.; McLachlan, P.; Chambers, J. E.; Uhlemann, S.

    2016-12-01

    It is now widely recognised that hydrological and biogeochemical processes that occur at the interface of groundwater (GW) and surface water (SW) can have a significant impact on catchment water quality and ecosystem health. Significant heterogeneity in the fabric of the subsurface at the GW-SW interface can lead to complex fluid flow pathways, both of which can exert a strong control on biogeochemical cycling. Revealing such heterogeneity remains a challenge because of the limitations of traditional field experimental processes. Such traditional techniques are often invasive, which often prevents their use in ecologically sensitive environments. Furthermore, they are often limited to localised characterisation. Studies to date have thus focussed on relatively small (easily accessible) stream environments, at short reach, or plot, scales. There is a clear demand for techniques that can capture the heterogeneity of sediments and pore fluids over larger scales. Geophysical methods may offer valuable information at such scales, particularly when used in combination with traditional sampling approaches. The value of electrical methods for revealing detailed information about the heterogeneity of sediments at the GW-SW interface has been demonstrated, and in a few studies such methods have assisted tracer tests in mapping the solute pathways. However, most investigations have been confined to relatively small scale (tens of metres). There is growing (and renewed) interest in the use of frequency domain electromagnetic induction (EMI) techniques in hydrogeophysics. At the GW-SW interface these methods allow rapid, non-invasive exploration of the top few metres. Relatively recent technological developments have provided multi-coil instrumentation, permitting rapid assessment of electrical conductivity at multiple depths of investigation. Here, we demonstrate the effectiveness of EMI for revealing the heterogeneity of sediments and flow pathways at the GW-SW interface. We

  4. Revealed Comparative Advantage and the Alternatives as Measures of International Specialization

    DEFF Research Database (Denmark)

    Laursen, Keld

    2015-01-01

    discussion focuses on the properties of RSCA and empirical evidence, based on the Jarque-Bera test for normality of the regression error terms, using both the RCA and RSCA indices. We compare RSCA to other measures of international trade specialization including the Michaely index, the Contribution to Trade...

  5. Measurement of refractive index by nanoparticle tracking analysis reveals heterogeneity in extracellular vesicles

    Directory of Open Access Journals (Sweden)

    Chris Gardiner

    2014-11-01

    Full Text Available Introduction: Optical techniques are routinely used to size and count extracellular vesicles (EV. For comparison of data from different methods and laboratories, suitable calibrators are essential. A suitable calibrator must have a refractive index (RI as close to that of EV as possible but the RI of EV is currently unknown. To measure EV, RI requires accurate knowledge of size and light scattering. These are difficult to measure as most EVs cannot be resolved by light microscopy and their diameter is smaller than the wavelength of visible light. However, nanoparticle tracking analysis (NTA provides both size and relative light scattering intensity (rLSI values. We therefore sought to determine whether it was possible to use NTA to measure the RI of individual EVs. Methods: NTA was used to measure the rLSI and size of polystyrene and silica microspheres of known size and RI (1.470 and 1.633, respectively and of EV isolated from a wide range of cells. We developed software, based on Mie scattering code, to calculate particle RI from the rLSI data. This modelled theoretical scattering intensities for polystyrene and silica microspheres of known size (100 and 200 nm and RI. The model was verified using data from the polystyrene and silica microspheres. Size and rLSI data for each vesicle were processed by the software to generate RI values. Results: The following modal RI measurements were obtained: fresh urinary EV 1.374, lyophilised urinary EV 1.367, neuroblastoma EV 1.393, blood EV 1.398, EV from activated platelets 1.390, small placental EV 1.364–1.375 and 1.398–1.414 for large placental EV (>200 nm. Large placental EV had a significantly higher RI than small placental EV (p1.40 were observed for some large (>200 nm microvesicles. Conclusion: This method for measuring EV RI will be useful for developing appropriate calibrators for EV measurement.

  6. Calculations of Non-equilibrium Effects in Nano-conductors

    DEFF Research Database (Denmark)

    Christensen, Rasmus Bjerregaard

    : An adatom on a Ag(111)surface and a C60 molecule on a Cu(111) surface. The calculated photon yield is found to agree with experiments for photons with energies below the applied bias (hω tunneling spectroscopy (IETS) serves as a powerful tool for non-destructive characterization...... and armchair chirality, and related the IETS signal to the phononic band structure. For the spin-polarized zigzag GNRs the role of the spin-polarization is investigated, revealing IETSas an indirect measurement of spin-polarization. Further, the role of impurities is explored, revealing the possibility...

  7. Direct measurements reveal non-Markovian fluctuations of DNA threading through a solid-state nanopore

    OpenAIRE

    Bell, Nicholas A. W.; Keyser, Ulrich F.

    2016-01-01

    The threading of a polymer chain through a small pore is a classic problem in polymer dynamics and underlies nanopore sensing technology. However important experimental aspects of the polymer motion in a solid-state nanopore, such as an accurate measurement of the velocity variation during translocation, have remained elusive. In this work we analysed the translocation through conical quartz nanopores of a 7 kbp DNA double-strand labelled with six markers equally spaced along its contour. The...

  8. Soil gases and SAR measurements reveal hidden faults on the sliding flank of Mt. Etna (Italy)

    Science.gov (United States)

    Bonforte, Alessandro; Federico, Cinzia; Giammanco, Salvatore; Guglielmino, Francesco; Liuzzo, Marco; Neri, Marco

    2013-02-01

    From October 2008 to November 2009, soil CO2, radon and structural field surveys were performed on Mt. Etna, in order to acquire insights into active tectonic structures in a densely populated sector of the south-eastern flank of the volcano, which is involved in the flank dynamics, as highlighted by satellite data (InSAR). The studied area extends about 150 km2, in a sector of the volcano where InSAR results detected several lineaments that were not well-defined from previous geological surveys. In order to validate and better constrain these features with ground data evidences, soil CO2 and soil radon measurements were performed along transects roughly orthogonal to the newly detected faults, with measurement points spaced about 100 m. In each transect, the highest CO2 values were found very close to the lineaments evidenced by InSAR observations. Anomalous soil CO2 and radon values were also measured at old eruptive fractures. In some portions of the investigated area soil gas anomalies were rather broad over transects, probably suggesting a complex structural framework consisting of several parallel volcano-tectonic structures, instead of a single one. Soil gas measurements proved particularly useful in areas at higher altitude on Mt. Etna (i.e. above 900 m asl), where InSAR results are not very informative/are fairly limited, and allowed recognizing the prolongation of some tectonic lineaments towards the summit of the volcano. At a lower altitude on the volcanic edifice, soil gas anomalies define the active structures indicated by InSAR results prominently, down to almost the coastline and through the northern periphery of the city of Catania. Coupling InSAR with soil gas prospecting methods has thus proved to be a powerful tool in detecting hidden active structures that do not show significant field evidences.

  9. Multigap Superconductivity in the Ferromagnetic Superconductor UCoGe Revealed by Thermal Conductivity Measurements

    Directory of Open Access Journals (Sweden)

    Ludovic Howald

    2014-01-01

    Full Text Available We performed thermal conductivity measurements on a single crystal of the ferromagnetic superconductor UCoGe under magnetic field. Two different temperature dependencies of the thermal conductivity are observed, for H→∥b→: linear at low magnetic field and quadratic for magnetic field larger than 1 Tesla. At the same field value, a plateau appears in the field dependency of the residual term of thermal conductivity. Such observations suggest a multigap superconductivity with a line of nodes in the superconducting gap.

  10. One-neutron removal measurement reveals 24O as a new doubly magic nucleus.

    Science.gov (United States)

    Kanungo, R; Nociforo, C; Prochazka, A; Aumann, T; Boutin, D; Cortina-Gil, D; Davids, B; Diakaki, M; Farinon, F; Geissel, H; Gernhäuser, R; Gerl, J; Janik, R; Jonson, B; Kindler, B; Knöbel, R; Krücken, R; Lantz, M; Lenske, H; Litvinov, Y; Lommel, B; Mahata, K; Maierbeck, P; Musumarra, A; Nilsson, T; Otsuka, T; Perro, C; Scheidenberger, C; Sitar, B; Strmen, P; Sun, B; Szarka, I; Tanihata, I; Utsuno, Y; Weick, H; Winkler, M

    2009-04-17

    The first measurement of the momentum distribution for one-neutron removal from (24)O at 920A MeV performed at GSI, Darmstadt is reported. The observed distribution has a width (FWHM) of 99 +/- 4 MeV/c in the projectile rest frame and a one-neutron removal cross section of 63 +/- 7 mb. The results are well explained with a nearly pure 2s_{1/2} neutron spectroscopic factor of 1.74 +/- 0.19 within the eikonal model. This large s-wave probability shows a spherical shell closure thereby confirming earlier suggestions that (24)O is a new doubly magic nucleus.

  11. Revealing strong bias in common measures of galaxy properties using new inclination-independent structures

    Science.gov (United States)

    Devour, Brian M.; Bell, Eric F.

    2017-06-01

    Accurate measurement of galaxy structures is a prerequisite for quantitative investigation of galaxy properties or evolution. Yet, the impact of galaxy inclination and dust on commonly used metrics of galaxy structure is poorly quantified. We use infrared data sets to select inclination-independent samples of disc and flattened elliptical galaxies. These samples show strong variation in Sérsic index, concentration and half-light radii with inclination. We develop novel inclination-independent galaxy structures by collapsing the light distribution in the near-infrared on to the major axis, yielding inclination-independent 'linear' measures of size and concentration. With these new metrics we select a sample of Milky Way analogue galaxies with similar stellar masses, star formation rates, sizes and concentrations. Optical luminosities, light distributions and spectral properties are all found to vary strongly with inclination: When inclining to edge-on, r-band luminosities dim by >1 magnitude, sizes decrease by a factor of 2, 'dust-corrected' estimates of star formation rate drop threefold, metallicities decrease by 0.1 dex and edge-on galaxies are half as likely to be classified as star forming. These systematic effects should be accounted for in analyses of galaxy properties.

  12. Long-Term Measurements of Human Inflammatory Cytokines Reveal Complex Baseline Variations between Individuals.

    Science.gov (United States)

    Wu, Danlu; Dinh, Trinh L; Bausk, Bruce P; Walt, David R

    2017-12-01

    Comprehensive characterization of the healthy human proteome baseline is essential for personalized medicine. Baseline data are necessary to understand the variation between individuals, as well as longitudinal variation within individuals. Many important protein biomarkers, such as cytokines, exist at extremely low or undetectable levels in the healthy state. This paper describes results from a 14-week study of healthy human subjects using ultrasensitive single-molecule array (Simoa) assays to measure both intra and intersubject variation of 15 cytokines. The results show a wide variation in the ranges of some cytokines between individuals and demonstrate that individual baseline values will be essential for predicting disease presence and progression. Although all of the studied cytokines demonstrated high temporal stability (or low intrasubject variation) over the entire study period, there were two distinct groups of cytokines that demonstrated either high (IL-8, IFN-γ, IL-2, IL-6, and IL-1β) or low (IL-15, TNF-α, IL-12 p70, IL-17A, GM-CSF, IL-12 p40, IL-10, IL-7, IL-1α, and IL-5) subject-to-subject variation. This work demonstrates that ultrasensitive assays are essential for characterizing human cytokines in healthy subjects. The results show that some cytokines vary by more than two orders of magnitude between individuals, making it an imperative to obtain individual baseline measurements if they are to play a role in health and disease diagnosis. Copyright © 2017 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.

  13. Equilibrium moisture content of radiata pine at elevated temperature and pressure reveals measurement challenges

    DEFF Research Database (Denmark)

    Pearson, Hamish; Gabbitas, Brian; Ormarsson, Sigurdur

    2012-01-01

    moisture contents were attributed to condensation of liquid water on the specimen with subsequent evaporation at a rate that was too slow for the moisture content to reach equilibrium before it was measured. Reliable EMC data at elevated temperatures require (1) tight process control of experimental......Relatively few studies have been performed on the equilibrium moisture content (EMC) of wood under conditions of elevated temperature and pressure. Eight studies indicated that EMC near saturation decreased between 100 and 150 °C, whilst five studies indicated that EMC increased. The aim...... of this study was to identify the likely source of the disagreement using radiata pine (Pinus radiata D. Don) sapwood which was conditioned to a moisture content of around 3 % and then exposed for 1 h at 150 °C and relative humidities of either 50, 70 or 90 %. Mean values of EMC, obtained through in situ...

  14. Planetary science. Low-altitude magnetic field measurements by MESSENGER reveal Mercury's ancient crustal field.

    Science.gov (United States)

    Johnson, Catherine L; Phillips, Roger J; Purucker, Michael E; Anderson, Brian J; Byrne, Paul K; Denevi, Brett W; Feinberg, Joshua M; Hauck, Steven A; Head, James W; Korth, Haje; James, Peter B; Mazarico, Erwan; Neumann, Gregory A; Philpott, Lydia C; Siegler, Matthew A; Tsyganenko, Nikolai A; Solomon, Sean C

    2015-05-22

    Magnetized rocks can record the history of the magnetic field of a planet, a key constraint for understanding its evolution. From orbital vector magnetic field measurements of Mercury taken by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft at altitudes below 150 kilometers, we have detected remanent magnetization in Mercury's crust. We infer a lower bound on the average age of magnetization of 3.7 to 3.9 billion years. Our findings indicate that a global magnetic field driven by dynamo processes in the fluid outer core operated early in Mercury's history. Ancient field strengths that range from those similar to Mercury's present dipole field to Earth-like values are consistent with the magnetic field observations and with the low iron content of Mercury's crust inferred from MESSENGER elemental composition data. Copyright © 2015, American Association for the Advancement of Science.

  15. Field measurement of beef pen manure methane and nitrous oxide reveals a surprise for inventory calculations.

    Science.gov (United States)

    Redding, M R; Devereux, J; Phillips, F; Lewis, R; Naylor, T; Kearton, T; Hill, C J; Weidemann, S

    2015-05-01

    Few data exist on direct greenhouse gas emissions from pen manure at beef feedlots. However, emission inventories attempt to account for these emissions. This study used a large chamber to isolate NO and CH emissions from pen manure at two Australian commercial beef feedlots (stocking densities, 13-27 m head) and related these emissions to a range of potential emission control factors, including masses and concentrations of volatile solids, NO, total N, NH, and organic C (OC), and additional factors such as total manure mass, cattle numbers, manure pack depth and density, temperature, and moisture content. Mean measured pen NO emissions were 0.428 kg ha d (95% confidence interval [CI], 0.252-0.691) and 0.00405 kg ha d (95% CI, 0.00114-0.0110) for the northern and southern feedlots, respectively. Mean measured CH emission was 0.236 kg ha d (95% CI, 0.163-0.332) for the northern feedlot and 3.93 kg ha d (95% CI, 2.58-5.81) for the southern feedlot. Nitrous oxide emission increased with density, pH, temperature, and manure mass, whereas negative relationships were evident with moisture and OC. Strong relationships were not evident between NO emission and masses or concentrations of NO or total N in the manure. This is significant because many standard inventory calculation protocols predict NO emissions using the mass of N excreted by the animal. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

  16. Simple pain measures reveal psycho-social pathology in patients with Crohn's disease.

    Science.gov (United States)

    Odes, Shmuel; Friger, Michael; Sergienko, Ruslan; Schwartz, Doron; Sarid, Orly; Slonim-Nevo, Vered; Singer, Terri; Chernin, Elena; Vardi, Hillel; Greenberg, Dan; Israel Ibd Research Nucleus

    2017-02-14

    To determine whether pain has psycho-social associations in adult Crohn's disease (CD) patients. Patients completed demographics, disease status, Patient Harvey-Bradshaw Index (P-HBI), Short Form Health Survey (SF-36), Short Inflammatory Bowel Disease Questionnaire (SIBDQ), and five socio-psychological questionnaires: Brief Symptom Inventory, Brief COPE Inventory, Family Assessment Device, Satisfaction with Life Scale, and Work Productivity and Activity Impairment Questionnaire. Pain sub-scales in P-HBI, SF-36 and SIBDQ measures were recoded into 4 identical scores for univariate and multinomial logistic regression analysis of associations with psycho-social variables. The cohort comprised 594 patients, mean age 38.6 ± 14.8 years, women 52.5%, P-HBI 5.76 ± 5.15. P-HBI, SF-36 and SIBDQ broadly agreed in their assessment of pain intensity. More severe pain was significantly associated with female gender, low socio-economic status, unemployment, Israeli birth and smoking. Higher pain scores correlated positively with psychological stress, dysfunctional coping strategies, poor family relationships, absenteeism, presenteeism, productivity loss and activity impairment and all WPAI sub-scores. Patients exhibiting greater satisfaction with life had less pain. The regression showed increasing odds ratios for psychological stress (lowest 2.26, highest 12.17) and female gender (highest 3.19) with increasing pain. Internet-recruited patients were sicker and differed from hardcopy questionnaire patients in their associations with pain. Pain measures in P-HBI, SF-36 and SIBDQ correlate with psycho-social pathology in CD. Physicians should be aware also of these relationships in approaching CD patients with pain.

  17. Comparison of Dolphins' Body and Brain Measurements with Four Other Groups of Cetaceans Reveals Great Diversity.

    Science.gov (United States)

    Ridgway, Sam H; Carlin, Kevin P; Van Alstyne, Kaitlin R; Hanson, Alicia C; Tarpley, Raymond J

    2016-01-01

    We compared mature dolphins with 4 other groupings of mature cetaceans. With a large data set, we found great brain diversity among 5 different taxonomic groupings. The dolphins in our data set ranged in body mass from about 40 to 6,750 kg and in brain mass from 0.4 to 9.3 kg. Dolphin body length ranged from 1.3 to 7.6 m. In our combined data set from the 4 other groups of cetaceans, body mass ranged from about 20 to 120,000 kg and brain mass from about 0.2 to 9.2 kg, while body length varied from 1.21 to 26.8 m. Not all cetaceans have large brains relative to their body size. A few dolphins near human body size have human-sized brains. On the other hand, the absolute brain mass of some other cetaceans is only one-sixth as large. We found that brain volume relative to body mass decreases from Delphinidae to a group of Phocoenidae and Monodontidae, to a group of other odontocetes, to Balaenopteroidea, and finally to Balaenidae. We also found the same general trend when we compared brain volume relative to body length, except that the Delphinidae and Phocoenidae-Monodontidae groups do not differ significantly. The Balaenidae have the smallest relative brain mass and the lowest cerebral cortex surface area. Brain parts also vary. Relative to body mass and to body length, dolphins also have the largest cerebellums. Cortex surface area is isometric with brain size when we exclude the Balaenidae. Our data show that the brains of Balaenidae are less convoluted than those of the other cetaceans measured. Large vascular networks inside the cranial vault may help to maintain brain temperature, and these nonbrain tissues increase in volume with body mass and with body length ranging from 8 to 65% of the endocranial volume. Because endocranial vascular networks and other adnexa, such as the tentorium cerebelli, vary so much in different species, brain size measures from endocasts of some extinct cetaceans may be overestimates. Our regression of body length on endocranial

  18. Urban eddy covariance measurements reveal significant missing NOx emissions in Central Europe.

    Science.gov (United States)

    Karl, T; Graus, M; Striednig, M; Lamprecht, C; Hammerle, A; Wohlfahrt, G; Held, A; von der Heyden, L; Deventer, M J; Krismer, A; Haun, C; Feichter, R; Lee, J

    2017-05-30

    Nitrogen oxide (NO x ) pollution is emerging as a primary environmental concern across Europe. While some large European metropolitan areas are already in breach of EU safety limits for NO 2 , this phenomenon does not seem to be only restricted to large industrialized areas anymore. Many smaller scale populated agglomerations including their surrounding rural areas are seeing frequent NO 2 concentration violations. The question of a quantitative understanding of different NO x emission sources is therefore of immanent relevance for climate and air chemistry models as well as air pollution management and health. Here we report simultaneous eddy covariance flux measurements of NO x , CO 2 , CO and non methane volatile organic compound tracers in a city that might be considered representative for Central Europe and the greater Alpine region. Our data show that NO x fluxes are largely at variance with modelled emission projections, suggesting an appreciable underestimation of the traffic related atmospheric NO x input in Europe, comparable to the weekend-weekday effect, which locally changes ozone production rates by 40%.

  19. In God we trust? Neural measures reveal lower social conformity among non-religious individuals.

    Science.gov (United States)

    Thiruchselvam, Ravi; Gopi, Yashoda; Kilekwang, Leonard; Harper, Jessica; Gross, James J

    2017-06-01

    Even in predominantly religious societies, there are substantial individual differences in religious commitment. Why is this? One possibility is that differences in social conformity (i.e. the tendency to think and behave as others do) underlie inclination towards religiosity. However, the link between religiosity and conformity has not yet been directly examined. In this study, we tested the notion that non-religious individuals show dampened social conformity, using both self-reported and neural (EEG-based ERPs) measures of sensitivity to others' influence. Non-religious vs religious undergraduate subjects completed an experimental task that assessed levels of conformity in a domain unrelated to religion (i.e. in judgments of facial attractiveness). Findings showed that, although both groups yielded to conformity pressures at the self-report level, non-religious individuals did not yield to such pressures in their neural responses. These findings highlight a novel link between religiosity and social conformity, and hold implications for prominent theories about the psychological functions of religion. © The Author (2017). Published by Oxford University Press.

  20. Revealing the link between licensed outlets and violence: counting venues versus measuring alcohol availability.

    Science.gov (United States)

    Liang, Wenbin; Chikritzhs, Tanya

    2011-09-01

    Associations between alcohol-related harms and numbers of outlets at the neighbourhood level have been demonstrated; however, the degree to which alcohol consumption or sales plays a part in levels of violence is not clear. This has contributed to uncertainty regarding the actual mechanisms by which outlet density may influence levels of violence. This ecological cross-sectional study investigated the effect of outlet numbers and alcohol sales on the risk of assault in Western Australia. For 2000/2001, information on type, number and wholesale alcohol purchases of all licensed outlets in operation, police-reported assault offences, socioeconomic/demographic data were obtained from official sources. Multivariate negative binomial regression was applied to at local government area level in order to assess associations between outlet density, alcohol sales and violence occurring in both licensed and domestic settings. Average alcohol sales volume per off-site outlet was significantly associated with all measures of assault. Numbers of on-site outlets significantly predicted violence with the exception of assaults occurring at residential premises. Alcohol sales from off-site outlets predicted violence occurring at on-site outlets. The link between on-site outlets and violence may be primarily underpinned by negative amenity effects while off-site outlet effects occur via increased availability. Alcohol sales volumes from off-site outlets influence levels of violence, which occur at both licensed and residential settings. The substantial and wide-ranging effects of liquor stores on alcohol-related harms may have been underestimated in the literature and by policy makers. © 2011 Australasian Professional Society on Alcohol and other Drugs.

  1. Multiple measures reveal antiretroviral adherence successes and challenges in HIV-infected Ugandan children.

    Directory of Open Access Journals (Sweden)

    Jessica E Haberer

    Full Text Available Adherence to HIV antiretroviral therapy (ART among children in developing settings is poorly understood.To understand the level, distribution, and correlates of ART adherence behavior, we prospectively determined monthly ART adherence through multiple measures and six-monthly HIV RNA levels among 121 Ugandan children aged 2-10 years for one year. Median adherence levels were 100% by three-day recall, 97.4% by 30-day visual analog scale, 97.3% by unannounced pill count/liquid formulation weights, and 96.3% by medication event monitors (MEMS. Interruptions in MEMS adherence of ≥ 48 hours were seen in 57.0% of children; 36.3% had detectable HIV RNA at one year. Only MEMS correlated significantly with HIV RNA levels (r = -0.25, p = 0.04. Multivariable regression found the following to be associated with <90% MEMS adherence: hospitalization of child (adjusted odds ratio [AOR] 3.0, 95% confidence interval [CI] 1.6-5.5; p = 0.001, liquid formulation use (AOR 1.4, 95%CI 1.0-2.0; p = 0.04, and caregiver's alcohol use (AOR 3.1, 95%CI 1.8-5.2; p<0.0001. Child's use of co-trimoxazole (AOR 0.5, 95%CI 0.4-0.9; p = 0.009, caregiver's use of ART (AOR 0.6, 95%CI 0.4-0.9; p = 0.03, possible caregiver depression (AOR 0.6, 95%CI 0.4-0.8; p = 0.001, and caregiver feeling ashamed of child's HIV status (AOR 0.5, 95%CI 0.3-0.6; p<0.0001 were protective against <90% MEMS adherence. Change in drug manufacturer (AOR 4.1, 95%CI 1.5-11.5; p = 0.009 and caregiver's alcohol use (AOR 5.5, 95%CI 2.8-10.7; p<0.0001 were associated with ≥ 48-hour interruptions by MEMS, while second-line ART (AOR 0.3, 95%CI 0.1-0.99; p = 0.049 and increasing assets (AOR 0.7, 95%CI 0.6-0.9; p = 0.0007 were protective against these interruptions.Adherence success depends on a well-established medication taking routine, including caregiver support and adequate education on medication changes. Caregiver-reported depression and shame may reflect fear of poor outcomes, functioning as motivation for

  2. Vocanic Deformations During Repose Interval Revealed by GPS Measurements, Batur Volcano, Indonesia

    Science.gov (United States)

    Nishimae, K.; Fujii, N.; Kimata, F.; Murase, M.; Suganda, O. K.; Abidin, H. Z.

    2005-12-01

    Batur volcano is located north west of Bali Island in Indonesia.This volcano has two calderas with more than 10 km in diameter. Recent eruptions with lava flow occurred in 1963 and 1974. No effusion of lava has been observed since 1990, although steam explosions occurred August 1994, November 1997 and June 1998.This suggests that magmatic activity of this volcano would keep its high level since 1994.GPS observation network of this volcano has been kept by Institute Technology of Bandung (ITB) and Volcano Survey of Indonesia (VSI).The network was consisted of 10 observation points at the beginning in 1999, and now it becomes 23 observation points. We have made GPS campaign observations about five times from 2003 to 2005. Each campaign observation consisted of a couple of days of measurements for each observation point. In order to keep the quality of data as high as possible, observations have been made at least 12 hours of continuous data for each point. In this report, results of two campaign observations (December 2004 and July 2005) are used for the analysis. The data thus obtained are fitted to the Mogi source (i.e. a point source model) to locate the depth and amount of volume changes for 7 months. Location of the Mogi source was obtained about 4km southeast of the summit of central cone, and 3km depth with deflation volume change of 1.3_~106 m3 for about 7months. For the period from 1999 to 2004, estimated volume change suggests a continuous deflation throughout this period, although the reliability of data was not so high. Continuous deflations might be likely after the last effusive eruption in 1974, would suggest that shallow part of magma beneath the central cone would probably be drained down to further deep, or shrinkage of magma associated with the cooling or solidification. Further data are obviously needed to discriminate the mechanisms of the deformation process during the repose period in this volcano.

  3. Ex vivo measures of muscle mitochondrial capacity reveal quantitative limits of oxygen delivery by the circulation during exercise

    DEFF Research Database (Denmark)

    Boushel, Robert; Saltin, Bengt

    2013-01-01

    Muscle mitochondrial respiratory capacity measured ex vivo provides a physiological reference to assess cellular oxidative capacity as a component in the oxygen cascade in vivo. In this article, the magnitude of muscle blood flow and oxygen uptake during exercise involving a small-to-large fracti...... capacity measured ex vivo underestimates the maximal in vivo oxygen uptake of muscle by up to ∼2-fold. This article is part of a Directed Issue entitled: Bioenergetic dysfunction, adaptation and therapy.......Muscle mitochondrial respiratory capacity measured ex vivo provides a physiological reference to assess cellular oxidative capacity as a component in the oxygen cascade in vivo. In this article, the magnitude of muscle blood flow and oxygen uptake during exercise involving a small-to-large fraction...... of the body mass will be discussed in relation to mitochondrial capacity measured ex vivo. These analyses reveal that as the mass of muscle engaged in exercise increases from one-leg knee extension, to 2-arm cranking, to 2-leg cycling and x-country skiing, the magnitude of blood flow and oxygen delivery...

  4. Towards Polarization Measurements of Laser-accelerated Helium-3 Ions

    OpenAIRE

    Engin, Ilhan

    2016-01-01

    In the framework of this thesis, preparatory investigations for the spin-polarization measurement of 3He ions from laser-induced plasmas have been performed.Therefore, experiments aiming at an efficient laser-induced ion acceleration out of a 4He gas target were carried out at two high-intensity laser facilities: the Arcturus laser at Heinrich-Heine-Universität Düsseldorf as well as PHELIX at GSI Darmstadt. The scientific goal of both experiments was to investigate the ion-acceleration proces...

  5. In-Plane Electronic Anisotropy of Underdoped ___122___ Fe-Arsenide Superconductors Revealed by Measurements of Detwinned Single Crystals

    Energy Technology Data Exchange (ETDEWEB)

    Fisher, Ian Randal

    2012-05-08

    The parent phases of the Fe-arsenide superconductors harbor an antiferromagnetic ground state. Significantly, the Neel transition is either preceded or accompanied by a structural transition that breaks the four fold symmetry of the high-temperature lattice. Borrowing language from the field of soft condensed matter physics, this broken discrete rotational symmetry is widely referred to as an Ising nematic phase transition. Understanding the origin of this effect is a key component of a complete theoretical description of the occurrence of superconductivity in this family of compounds, motivating both theoretical and experimental investigation of the nematic transition and the associated in-plane anisotropy. Here we review recent experimental progress in determining the intrinsic in-plane electronic anisotropy as revealed by resistivity, reflectivity and ARPES measurements of detwinned single crystals of underdoped Fe arsenide superconductors in the '122' family of compounds.

  6. Revealing the hidden faults in the SE flank of Mt. Etna using radon in-soil gas measurement.

    Science.gov (United States)

    Johnová, K; Thinová, L; Giammanco, S

    2014-07-01

    Although there are many methods for investigating tectonic structures, many faults remain hidden, and they can endanger the life and property of people living along them. The slopes of volcanoes are covered with such hidden faults, near which strong earthquakes and gas releases can appear. Revealing hidden faults can therefore contribute significantly to the protection of people living in volcanic areas. In the study, seven different techniques were used for making measurements of in-soil radon concentrations in order to search for hidden faults on the SE flank of the Mt. Etna volcano. These reported methods had previously been proved to be useful tools for investigating fault structures. The main aim of the experiment presented here was to evaluate the usability of these methods in the geological conditions of the Mt. Etna region, and to find the best place for continual radon monitoring using a permanent station in the near future. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  7. Mathematics revealed

    CERN Document Server

    Berman, Elizabeth

    1979-01-01

    Mathematics Revealed focuses on the principles, processes, operations, and exercises in mathematics.The book first offers information on whole numbers, fractions, and decimals and percents. Discussions focus on measuring length, percent, decimals, numbers as products, addition and subtraction of fractions, mixed numbers and ratios, division of fractions, addition, subtraction, multiplication, and division. The text then examines positive and negative numbers and powers and computation. Topics include division and averages, multiplication, ratios, and measurements, scientific notation and estim

  8. Negative muon spin precession measurement of the hyperfine states of muonic sodium

    International Nuclear Information System (INIS)

    Brewer, J.H.; Ghandi, K.; Froese, A.M.; Fryer, B.A.

    2005-01-01

    Both hyperfine states of muonic 23 Na and the rate R of conversion between them have been observed directly in a high field negative muon spin precession experiment using a backward muon beam with transverse spin polarization. The result in metallic sodium, R=13.7±2.2 μs -1 , is consistent with Winston's prediction in 1963 based on Auger emission of core electrons, and with the measurements of Gorringe et al. in Na metal, but not with their smaller result in NaF. In NaOH we find R=23.5±8 μs -1 , leaving medium-dependent effects ambiguous

  9. REVEALED COMPARATIVE ADVANTAGE AND THE MEASUREMENT OF INTERNATIONAL COMPETITIVENESS FOR AGRICULTURAL COMMODITIES: AN EMPIRICAL ANALYSIS OF WOOL EXPORTERS

    OpenAIRE

    Leishman, David; Menkhaus, Dale J.; Whipple, Glen D.

    1999-01-01

    Trade liberalization and laissez-faire economics are altering the structure of agricultural production and trade. The principle of comparative advantage, a classic tenet of economics, is a useful tool for understanding the future of world agriculture. This study employs a "Revealed Comparative Advantage" approach to investigate patterns of comparative advantage among six major wool exporting countries.

  10. Spin-polarized deuterium : stabilization in magnetic traps

    NARCIS (Netherlands)

    Koelman, J.M.V.A.; Stoof, H.T.C.; Verhaar, B.J.; Walraven, J.T.M.

    1987-01-01

    We report on a calculation of the spin-exchange two-body rate constants associated with the population dynamics of the hyperfine levels of atomic deuterium as a function of magnetic field in the Boltzmann zero temperature limit. We find that a gas of low field seeking deuterium atoms trapped in a

  11. Light-induced spin polarizations in quantum rings

    NARCIS (Netherlands)

    Joibari, F.K.; Blanter, Y.M.; Bauer, G.E.W.

    2014-01-01

    Nonresonant circularly polarized electromagnetic radiation can exert torques on magnetizations by the inverse Faraday effect (IFE). Here, we discuss the enhancement of IFE by spin-orbit interactions. We illustrate the principle by studying a simple generic model system, i.e., the

  12. Role of spin polarized tunneling in magnetoresistance and low ...

    Indian Academy of Sciences (India)

    Lowering of ρ0 value (table 2) on application of magnetic field suggests that such imperfections are .... Soma Das and T K Dey. 636. Table 3. Best-fit parameters obtained from intergranular tun- neling model. H ρ0 ρ1 × 105. JS/KB. (Tesla). (Ω cm). (Ω cm K–3/2) ε. (K) x = 0⋅05. 0. 0⋅0731. 6⋅00. 0⋅4175. 95⋅61. 0⋅8.

  13. Improved Superlattices for Spin-Polarized Electron Sources

    Energy Technology Data Exchange (ETDEWEB)

    Mamaev, Yu.A.; Gerchikov, L.G.; Yashin, Yu.P.; Kuz-michev, V.; Vasiliev, D.; /St. Petersburg Polytechnic Inst.; Maruymama, T.; Clendenin, J.E.; /SLAC; Ustinov, V.M.; Zhukov, A.E.; /Ioffe Phys. Tech. Inst.

    2006-12-08

    Photoemission of polarized electrons from heterostructures based on InAlGaAs/GaAs superlattices with minimum conduction-band offsets is investigated. The comparison of the excitation energy dependence of the photoemission polarization degree with the calculated spectra makes it possible to determine the polarization losses at different stages of the photoemission. A maximum polarization of P = 91% and a quantum efficiency of QE = 0.5% are close to the best results obtained for photocathodes that are based on strained semiconductor superlattices.

  14. In1-xMnxSb: spin polarization, conductivity

    Science.gov (United States)

    Matsukura, F.

    This document is part of Subvolume D 'New Data and Updates for IV-IV; III-V; II-VI and I-VII Compounds; their Mixed Crystals and Diluted Magnetic Semiconductors' of Volume 44 'Semiconductors' of Landolt-Börnstein - Group III 'Condensed Matter'.

  15. Role of spin polarized tunneling in magnetoresistance and low ...

    Indian Academy of Sciences (India)

    KMnO3 has been investigated between 10 K and 300 K with and without the magnetic field ( = 0.8 T). All the samples show metal–insulator transitions with Curie temperature (C) ranging between 260 K and 309 K. At temperature below 60 ...

  16. Spin polarization of electrons in a magnetic impurity doped ...

    Indian Academy of Sciences (India)

    The spin of electrons in semiconductors strongly couple with electric and magnetic fields due to ... where ckμ and d−kμ are annihilation operators for electron with momentum k and spin μ and hole with momentum −k ... kμ and ekμ are annihilation and creation operators for impurity electrons. Qkμ and Qkμ are the coefficient ...

  17. Spin-polarized quantum transport properties through flexible phosphorene

    Science.gov (United States)

    Chen, Mingyan; Yu, Zhizhou; Xie, Yiqun; Wang, Yin

    2016-10-01

    We report a first-principles study on the tunnel magnetoresistance (TMR) and spin-injection efficiency (SIE) through phosphorene with nickel electrodes under the mechanical tension and bending on the phosphorene region. Both the TMR and SIE are largely improved under these mechanical deformations. For the uniaxial tension (ɛy) varying from 0% to 15% applied along the armchair transport (y-)direction of the phosphorene, the TMR ratio is enhanced with a maximum of 107% at ɛy = 10%, while the SIE increases monotonously from 8% up to 43% with the increasing of the strain. Under the out-of-plane bending, the TMR overall increases from 7% to 50% within the bending ratio of 0%-3.9%, and meanwhile the SIE is largely improved to around 70%, as compared to that (30%) of the flat phosphorene. Such behaviors of the TMR and SIE are mainly affected by the transmission of spin-up electrons in the parallel configuration, which is highly dependent on the applied mechanical tension and bending. Our results indicate that the phosphorene based tunnel junctions have promising applications in flexible electronics.

  18. Electronic anisotropies revealed by detwinned angle-resolved photo-emission spectroscopy measurements of FeSe

    Science.gov (United States)

    Watson, Matthew D.; Haghighirad, Amir A.; Rhodes, Luke C.; Hoesch, Moritz; Kim, Timur K.

    2017-10-01

    We report high resolution angle-resolved photo-emission spectroscopy (ARPES) measurements of detwinned FeSe single crystals. The application of a mechanical strain is used to promote the volume fraction of one of the orthorhombic domains in the sample, which we estimate to be 80 % detwinned. While the full structure of the electron pockets consisting of two crossed ellipses may be observed in the tetragonal phase at temperatures above 90 K, we find that remarkably, only one peanut-shaped electron pocket oriented along the longer a axis contributes to the ARPES measurement at low temperatures in the nematic phase, with the expected pocket along b being not observed. Thus the low temperature Fermi surface of FeSe as experimentally determined by ARPES consists of one elliptical hole pocket and one orthogonally-oriented peanut-shaped electron pocket. Our measurements clarify the long-standing controversies over the interpretation of ARPES measurements of FeSe.

  19. Whole-brain analytic measures of network communication reveal increased structure-function correlation in right temporal lobe epilepsy

    Directory of Open Access Journals (Sweden)

    Jonathan Wirsich

    2016-01-01

    In rTLE patients, we found a widespread hypercorrelated functional network. Network communication analysis revealed greater unspecific branching of the shortest path (search information in the structural connectome and a higher global correlation between the structural and functional connectivity for the patient group. We also found evidence for a preserved structural rich-club in the patient group. In sum, global augmentation of structure-function correlation might be linked to a smaller functional repertoire in rTLE patients, while sparing the central core of the brain which may represent a pathway that facilitates the spread of seizures.

  20. The mind-set of teens towards food communications revealed by conjoint measurement and multi-food databases.

    Science.gov (United States)

    Foley, Michele; Beckley, Jacqueline; Ashman, Hollis; Moskowitz, Howard R

    2009-06-01

    We introduce a new type of study that combines self-profile of behaviors and attitudes regarding food together with responses to structured, systematically varied concepts about the food. We deal here with the responses of teens, for 28 different foods and beverages. The study creates a database that reveals how a person responds to different types of messaging about the food. We show how to develop the database for many different foods, from which one can compare foods to each other, or compare the performance of messages within a specific food.

  1. Detailed characteristics of radiation belt electrons revealed by CSSWE/REPTile measurements: Geomagnetic activity response and precipitation observation

    Science.gov (United States)

    Zhang, K.; Li, X.; Schiller, Q.; Gerhardt, D.; Zhao, H.; Millan, R.

    2017-08-01

    Earth's outer radiation belt electrons are highly dynamic. We study the detailed characteristics of relativistic electrons in the outer belt using measurements from the Colorado Student Space Weather Experiment (CSSWE) mission, a low Earth orbit (LEO) CubeSat, which traverses the radiation belt four times in one orbit ( 1.5 h) and has the advantage of measuring the dynamic activities of the electrons including their rapid precipitation. We focus on the measured electron response to geomagnetic activity for different energies to show that there are abundant sub-MeV electrons in the inner belt and slot region. These electrons are further enhanced during active times, while there is a lack of >1.63 MeV electrons in these regions. We also show that the variation of measured electron flux at LEO is strongly dependent on the local magnetic field strength, which is far from a dipole approximation. Moreover, a specific precipitation band, which happened on 19 January 2013, is investigated based on the conjunctive measurement of CSSWE, the Balloon Array for Radiation belt Relativistic Electron Losses, and one of the Polar Operational Environmental Satellites. In this precipitation band event, the net loss of the 0.58-1.63 MeV electrons (L = 3.5-6) is estimated to account for 6.8% of the total electron content.

  2. Single molecule activity measurements of cytochrome P450 oxidoreductase reveal the existence of two discrete functional states

    DEFF Research Database (Denmark)

    Laursen, Tomas; Singha, Aparajita; Rantzau, Nicolai

    2014-01-01

    450 enzymes. Measurements and statistical analy-sis of individual catalytic turnover cycles shows POR to sample at least two major functional states. This phenotype may underlie regulatory interactions with different cytochromes P450 but to date remained masked in bulk kinetics. To ensure that we...

  3. Objective measurement of function following lumbar spinal stenosis decompression reveals improved functional capacity with stagnant real-life physical activity.

    Science.gov (United States)

    Smuck, Matthew; Muaremi, Amir; Zheng, Patricia; Norden, Justin; Sinha, Aman; Hu, Richard; Tomkins-Lane, Christy

    2018-01-01

    Lumbar spinal stenosis (LSS) is a prevalent and costly condition associated with significant dysfunction. Alleviation of pain and improvement of function are the primary goals of surgical intervention. Although prior studies have measured subjective improvements in function after surgery, few have examined objective markers of functional improvement. We aimed to objectively measure and quantify changes in physical capacity and physical performance following surgical decompression of LSS. Prospective cohort study. Thirty-eight patients with LSS determined by the treating surgeon's clinical and imaging evaluation, and who were scheduled for surgical treatment, were consecutively recruited at two academic medical facilities, with 28 providing valid data for analysis at baseline and 6 months after surgery. Before surgery and at 6 months after surgery, participants provided 7 days of real-life physical activity (performance) using ActiGraph accelerometers; completed two objective functional capacity measures, the Short Physical Performance Battery and Self-Paced Walking Test; and completed three subjective functional outcome questionnaires, Oswestry Disability Index, Spinal Stenosis Symptom Questionnaire, and Short-Form 36. Physical activity, as measured by continuous activity monitoring, was analyzed as previously described according to the 2008 American Physical Activity Guidelines. Paired t tests were performed to assess for postsurgical changes in all questionnaire outcomes and all objective functional capacity measures. Chi-square analysis was used to categorically assess whether patients were more likely to meet these physical activity recommendations after surgery. Participants were 70.1 years old (±8.9) with 17 females (60.7%) and an average body mass index of 28.4 (±6.2). All subjective measures (Oswestry Disability Index, Spinal Stenosis Symptom Questionnaire, and Short-Form 36) improved significantly at 6 months after surgery, as did objective functional

  4. Back-Arc Opening in the Western End of the Okinawa Trough Revealed From GNSS/Acoustic Measurements

    Science.gov (United States)

    Chen, Horng-Yue; Ikuta, Ryoya; Lin, Cheng-Horng; Hsu, Ya-Ju; Kohmi, Takeru; Wang, Chau-Chang; Yu, Shui-Beih; Tu, Yoko; Tsujii, Toshiaki; Ando, Masataka

    2018-01-01

    We measured seafloor movement using a Global Navigation Satellite Systems (GNSS)/Acoustic technique at the south of the rifting valley in the western end of the Okinawa Trough back-arc basin, 60 km east of northeastern corner of Taiwan. The horizontal position of the seafloor benchmark, measured eight times between July 2012 and May 2016, showed a southeastward movement suggesting a back-arc opening of the Okinawa Trough. The average velocity of the seafloor benchmark shows a block motion together with Yonaguni Island. The westernmost part of the Ryukyu Arc rotates clockwise and is pulled apart from the Taiwan Island, which should cause the expansion of the Yilan Plain, Taiwan. Comparing the motion of the seafloor benchmark with adjacent seismicity, we suggest a gentle episodic opening of the rifting valley accompanying a moderate seismic activation, which differs from the case in the segment north off-Yonaguni Island where a rapid dyke intrusion occurs with a significant seismic activity.

  5. Edge detection applied to Cassini images reveals no measurable displacement of Ontario Lacus' margin between 2005 and 2010

    Science.gov (United States)

    Cornet, Thomas; Bourgeois, Olivier; Le Mouélic, Stéphane; Rodriguez, Sébastien; Sotin, Christophe; Barnes, Jason W.; Brown, Robert H.; Baines, Kevin H.; Buratti, Bonnie J.; Clark, Roger N.; Nicholson, Phillip D.

    2012-07-01

    Ontario Lacus is thus far the largest flat-floored topographic depression of Titan's southern hemisphere interpreted as a permanent or ephemeral lake. From 2005 to 2010, it was imaged several times and at various wavelengths by ISS, VIMS and RADAR instruments onboard Cassini's spacecraft. We analyze the position and uncertainty of Ontario Lacus' margin in all these images using an edge detection method based on image derivation. We find that, given the range of uncertainties in contour locations derived from images, no measurable displacement of Ontario Lacus' margin can be detected between 2005 and 2010 at the actual image spatial resolutions. The discrepancy between this result and previous ones is attributable to differences in (1) the basics behind the methods used, (2) the actual spatial resolutions and contrasts of the available images due to differential atmospheric scattering effects at different wavelengths, and (3) the geomorphological interpretation of contours derived from images acquired at different wavelengths. This lack of measurable displacement in the images suggests that the imaged contour corresponds either (1) to the border of a surface liquid body, provided that potential changes in its extent over five terrestrial years were not sufficiently large to be measured, or (2) to the stationary topographic border between Ontario Lacus' depression and the surrounding alluvial plain. Potential displacements of Ontario Lacus' margin between 2005 and 2010 are thus below the actual resolution of currently available images or have to be sought for within the extent of the topographic depression rather than along its borders.

  6. Satellite chlorophyll fluorescence measurements reveal large-scale decoupling of photosynthesis and greenness dynamics in boreal evergreen forests.

    Science.gov (United States)

    Walther, Sophia; Voigt, Maximilian; Thum, Tea; Gonsamo, Alemu; Zhang, Yongguang; Köhler, Philipp; Jung, Martin; Varlagin, Andrej; Guanter, Luis

    2016-09-01

    Mid-to-high latitude forests play an important role in the terrestrial carbon cycle, but the representation of photosynthesis in boreal forests by current modelling and observational methods is still challenging. In particular, the applicability of existing satellite-based proxies of greenness to indicate photosynthetic activity is hindered by small annual changes in green biomass of the often evergreen tree population and by the confounding effects of background materials such as snow. As an alternative, satellite measurements of sun-induced chlorophyll fluorescence (SIF) can be used as a direct proxy of photosynthetic activity. In this study, the start and end of the photosynthetically active season of the main boreal forests are analysed using spaceborne SIF measurements retrieved from the GOME-2 instrument and compared to that of green biomass, proxied by vegetation indices including the Enhanced Vegetation Index (EVI) derived from MODIS data. We find that photosynthesis and greenness show a similar seasonality in deciduous forests. In high-latitude evergreen needleleaf forests, however, the length of the photosynthetically active period indicated by SIF is up to 6 weeks longer than the green biomass changing period proxied by EVI, with SIF showing a start-of-season of approximately 1 month earlier than EVI. On average, the photosynthetic spring recovery as signalled by SIF occurs as soon as air temperatures exceed the freezing point (2-3 °C) and when the snow on the ground has not yet completely melted. These findings are supported by model data of gross primary production and a number of other studies which evaluated in situ observations of CO2 fluxes, meteorology and the physiological state of the needles. Our results demonstrate the sensitivity of space-based SIF measurements to light-use efficiency of boreal forests and their potential for an unbiased detection of photosynthetic activity even under the challenging conditions interposed by evergreen

  7. Whole-brain analytic measures of network communication reveal increased structure-function correlation in right temporal lobe epilepsy.

    Science.gov (United States)

    Wirsich, Jonathan; Perry, Alistair; Ridley, Ben; Proix, Timothée; Golos, Mathieu; Bénar, Christian; Ranjeva, Jean-Philippe; Bartolomei, Fabrice; Breakspear, Michael; Jirsa, Viktor; Guye, Maxime

    2016-01-01

    The in vivo structure-function relationship is key to understanding brain network reorganization due to pathologies. This relationship is likely to be particularly complex in brain network diseases such as temporal lobe epilepsy, in which disturbed large-scale systems are involved in both transient electrical events and long-lasting functional and structural impairments. Herein, we estimated this relationship by analyzing the correlation between structural connectivity and functional connectivity in terms of analytical network communication parameters. As such, we targeted the gradual topological structure-function reorganization caused by the pathology not only at the whole brain scale but also both in core and peripheral regions of the brain. We acquired diffusion (dMRI) and resting-state fMRI (rsfMRI) data in seven right-lateralized TLE (rTLE) patients and fourteen healthy controls and analyzed the structure-function relationship by using analytical network communication metrics derived from the structural connectome. In rTLE patients, we found a widespread hypercorrelated functional network. Network communication analysis revealed greater unspecific branching of the shortest path (search information) in the structural connectome and a higher global correlation between the structural and functional connectivity for the patient group. We also found evidence for a preserved structural rich-club in the patient group. In sum, global augmentation of structure-function correlation might be linked to a smaller functional repertoire in rTLE patients, while sparing the central core of the brain which may represent a pathway that facilitates the spread of seizures.

  8. Satellite-based measurements of surface deformation reveal fluid flow associated with the geological storage of carbon dioxide

    Energy Technology Data Exchange (ETDEWEB)

    Vasco, D.W.; Rucci, A.; Ferretti, A.; Novali, F.; Bissell, R.; Ringrose, P.; Mathieson, A.; Wright, I.

    2009-10-15

    Interferometric Synthetic Aperture Radar (InSAR), gathered over the In Salah CO{sub 2} storage project in Algeria, provides an early indication that satellite-based geodetic methods can be effective in monitoring the geological storage of carbon dioxide. An injected volume of 3 million tons of carbon dioxide, from one of the first large-scale carbon sequestration efforts, produces a measurable surface displacement of approximately 5 mm/year. Using geophysical inverse techniques we are able to infer flow within the reservoir layer and within a seismically detected fracture/ fault zone intersecting the reservoir. We find that, if we use the best available elastic Earth model, the fluid flow need only occur in the vicinity of the reservoir layer. However, flow associated with the injection of the carbon dioxide does appear to extend several kilometers laterally within the reservoir, following the fracture/fault zone.

  9. Thermoelastic properties of liquid Fe-C revealed by sound velocity and density measurements at high pressure

    Science.gov (United States)

    Shimoyama, Yuta; Terasaki, Hidenori; Urakawa, Satoru; Takubo, Yusaku; Kuwabara, Soma; Kishimoto, Shunpachi; Watanuki, Tetsu; Machida, Akihiko; Katayama, Yoshinori; Kondo, Tadashi

    2016-11-01

    Carbon is one of the possible light elements in the cores of the terrestrial planets. The P wave velocity (VP) and density (ρ) are important factors for estimating the chemical composition and physical properties of the core. We simultaneously measured the VP and ρ of Fe-3.5 wt % C up to 3.4 GPa and 1850 K by using ultrasonic pulse-echo method and X-ray absorption methods. The VP of liquid Fe-3.5 wt % C decreased linearly with increasing temperature at constant pressure. The addition of carbon decreased the VP of liquid Fe by about 2% at 3 GPa and 1700 K and decreased the Fe density by about 2% at 2 GPa and 1700 K. The bulk modulus of liquid Fe-C and its pressure (P) and temperature (T) effects were precisely determined from directly measured ρ and VP data to be K0,1700 K = 83.9 GPa, dKT/dP = 5.9(2), and dKT/dT = -0.063 GPa/K. The addition of carbon did not affect the isothermal bulk modulus (KT) of liquid Fe, but it decreased the dK/dT of liquid Fe. In the ρ-VP relationship, VP increases linearly with ρ and can be approximated as VP (m/s) = -6786(506) + 1537(71) × ρ (g/cm3), suggesting that Birch's law is valid for liquid Fe-C at the present P-T conditions. Our results imply that at the conditions of the lunar core, the elastic properties of an Fe-C core are more affected by temperature than those of Fe-S core.

  10. High resolution LiDAR measurements reveal fine internal structure and variability of sediment-carrying coastal plume

    Science.gov (United States)

    Zavialov, P. O.; Pelevin, V. V.; Belyaev, N. A.; Izhitskiy, A. S.; Konovalov, B. V.; Krementskiy, V. V.; Goncharenko, I. V.; Osadchiev, A. A.; Soloviev, D. M.; Garcia, C. A. E.; Pereira, E. S.; Sartorato, L.; Moller, O. O.

    2018-05-01

    We report results of a field survey conducted in the buoyant, sediment-carrying coastal plume generated by the discharge from the Patos Lagoon, the World's largest choked lagoon. The concentration of total suspended matter (TSM) and organic matter (as represented by total organic carbon, TOC) were mapped using an ultraviolet fluorescent LiDAR, which allowed for extensive data coverage (total of 79,387 simultaneous determinations of TSM and TOC) during 3 consecutive days. These observations were accompanied by hydrographic measurements from the ship and at a mooring station. We first describe synoptic variability of the plume, which responded energetically to wind forcing. We then analyze the TSM, TOC and hydrographic data jointly and develop a simple approach to estimate the rates of suspended matter removal from the upper layer due to gravitational settling and turbulent mixing based on relative changes in TSM and TOC concentrations. Four distinct regions within the plume exhibiting different dynamics of suspended and dissolved constituents were identified on this basis.

  11. Simple measurements reveal the feeding history, the onset of reproduction, and energy conversion efficiencies in captive bluefin tuna

    Science.gov (United States)

    Jusup, Marko; Klanjšček, Tin; Matsuda, Hiroyuki

    2014-11-01

    We present a numerical approach that, in conjunction with a fully set up Dynamic Energy Budget (DEB) model, aims at consistently approximating the feeding history of cultivated fish from the commonly measured aquaculture data (body length, body mass, or the condition factor). We demonstrate the usefulness of the approach by performing validation of a DEB-based model for Pacific bluefin tuna (Thunnus orientalis) on an independent dataset and exploring the implied bioenergetics of this species in captivity. In the context of validation, the results indicate that the model successfully accounts for more than 75% of the variance in actual fish feed. At the 5% significance level, predictions do not underestimate nor overestimate observations and there is no bias. The overall model accuracy of 87.6% is satisfactory. In the context of tuna bioenergetics, we offer an explanation as to why the first reproduction in the examined case occurred only after the fish reached seven years of age, whereas it takes five years in the wild and sometimes as little as three years in captivity. Finally, we calculate energy conversion efficiencies and the supply stress throughout the entire lifetime to theoretically underpin the relatively low contribution of growth to aerobic metabolism implied by respirometry and high feed conversion ratio observed in bluefin tuna aquaculture.

  12. Tidal and flood signatures of settling particles in the Gaoping submarine canyon (SW Taiwan) revealed from radionuclide and flow measurements

    Science.gov (United States)

    Huh, C.-A.; Liu, J.T.; Lin, H.-L.; Xu, J. P.

    2009-01-01

    Sediment transport and sedimentation processes in the Gaoping submarine canyon were studied using sediment trap and current meter moorings deployed at a location during the winter (January-March) and the summer (July-September) months in 2008. At the end of each deployment, sediment cores were also collected from the canyon floor at the mooring site. Samples from sediment traps and sediment cores were analyzed for 210Pb and 234Th by gamma spectrometry. In conjunction with particle size and flow measurements, the datasets suggest that sediment transport in the canyon is tidally-modulated in the drier winter season and flood (river)-dominated in the wetter summer season. From the magnitude and temporal variation of sediment flux in the canyon with respect to the burial flux and sediment budget on the open shelf and slope region, we reaffirm that, on annual or longer timescales, the Gaoping submarine canyon is an effective conduit transporting sediments from the Gaoping River's drainage basin (the source) to the deep South China Sea (the ultimate sink). ?? 2009 Elsevier B.V.

  13. Redefining "Learning" in Statistical Learning: What Does an Online Measure Reveal About the Assimilation of Visual Regularities?

    Science.gov (United States)

    Siegelman, Noam; Bogaerts, Louisa; Kronenfeld, Ofer; Frost, Ram

    2017-10-07

    From a theoretical perspective, most discussions of statistical learning (SL) have focused on the possible "statistical" properties that are the object of learning. Much less attention has been given to defining what "learning" is in the context of "statistical learning." One major difficulty is that SL research has been monitoring participants' performance in laboratory settings with a strikingly narrow set of tasks, where learning is typically assessed offline, through a set of two-alternative-forced-choice questions, which follow a brief visual or auditory familiarization stream. Is that all there is to characterizing SL abilities? Here we adopt a novel perspective for investigating the processing of regularities in the visual modality. By tracking online performance in a self-paced SL paradigm, we focus on the trajectory of learning. In a set of three experiments we show that this paradigm provides a reliable and valid signature of SL performance, and it offers important insights for understanding how statistical regularities are perceived and assimilated in the visual modality. This demonstrates the promise of integrating different operational measures to our theory of SL. © 2017 Cognitive Science Society, Inc.

  14. Continuous gravity measurements reveal a low-density lava lake at Kīlauea Volcano, Hawai‘i

    Science.gov (United States)

    Carbone, Daniele; Poland, Michael P.; Patrick, Matthew R.; Orr, Tim R.

    2013-01-01

    On 5 March 2011, the lava lake within the summit eruptive vent at Kīlauea Volcano, Hawai‘i, began to drain as magma withdrew to feed a dike intrusion and fissure eruption on the volcanoʼs east rift zone. The draining was monitored by a variety of continuous geological and geophysical measurements, including deformation, thermal and visual imagery, and gravity. Over the first ∼14 hours of the draining, the ground near the eruptive vent subsided by about 0.15 m, gravity dropped by more than 100 μGal, and the lava lake retreated by over 120 m. We used GPS data to correct the gravity signal for the effects of subsurface mass loss and vertical deformation in order to isolate the change in gravity due to draining of the lava lake alone. Using a model of the eruptive vent geometry based on visual observations and the lava level over time determined from thermal camera data, we calculated the best-fit lava density to the observed gravity decrease — to our knowledge, the first geophysical determination of the density of a lava lake anywhere in the world. Our result, 950 +/- 300 kg m-3, suggests a lava density less than that of water and indicates that Kīlaueaʼs lava lake is gas-rich, which can explain why rockfalls that impact the lake trigger small explosions. Knowledge of such a fundamental material property as density is also critical to investigations of lava-lake convection and degassing and can inform calculations of pressure change in the subsurface magma plumbing system.

  15. Functional diversity measures revealed impacts of non-native species and habitat degradation on species-poor freshwater fish assemblages.

    Science.gov (United States)

    Colin, Nicole; Villéger, Sébastien; Wilkes, Martin; de Sostoa, Adolfo; Maceda-Veiga, Alberto

    2018-06-01

    Trait-based ecology has been developed for decades to infer ecosystem responses to stressors based on the functional structure of communities, yet its value in species-poor systems is largely unknown. Here, we used an extensive dataset in a Spanish region highly prone to non-native fish invasions (15 catchments, N=389 sites) to assess for the first time how species-poor communities respond to large-scale environmental gradients using a taxonomic and functional trait-based approach in riverine fish. We examined total species richness and three functional trait-based indices available when many sites have ≤3 species (specialization, FSpe; originality, FOri and entropy, FEnt). We assessed the responses of these taxonomic and functional indices along gradients of altitude, water pollution, physical habitat degradation and non-native fish biomass. Whilst species richness was relatively sensitive to spatial effects, functional diversity indices were responsive across natural and anthropogenic gradients. All four diversity measures declined with altitude but this decline was modulated by physical habitat degradation (richness, FSpe and FEnt) and the non-native:total fish biomass ratio (FSpe and FOri) in ways that varied between indices. Furthermore, FSpe and FOri were significantly correlated with Total Nitrogen. Non-native fish were a major component of the taxonomic and functional structure of fish communities, raising concerns about potential misdiagnosis between invaded and environmentally-degraded river reaches. Such misdiagnosis was evident in a regional fish index widely used in official monitoring programs. We recommend the application of FSpe and FOri to extensive datasets from monitoring programs in order to generate valuable cross-system information about the impacts of non-native species and habitat degradation, even in species-poor systems. Scoring non-native species apart from habitat degradation in the indices used to determine ecosystem health is

  16. Distinct degassing processes during lava fountains revealed by OP-FTIR measurements: Mt. Etna's 2001 lava fountain sequence

    Science.gov (United States)

    La Spina, Alessandro; Burton, Mike; Allard, Patrick; Alparone, Salvatore; Murè, Filippo

    2010-05-01

    During the two months preceding the 2001 July-August flank eruption of Mt. Etna, 17 discrete lava fountaining events were observed at the southeast crater (SEC, 3250 m a.s.l.). Each episode was preceded by lava effusion and mild strombolian activity from a fracture on the NE flank of the SEC. We used an open-path Fourier transform infrared spectrometer (OP-FTIR) to measure every about 5 seconds an IR absorption spectrum of the gas powering the lava fountains, lava being the source of radiation. Spectral-fitting procedures allowed retrieval of the relative amounts of H2O, CO2, SO2, HCl and HF present in the volcanic gas phase, allowing us to track variations in the gas composition both during each fountain event and over the entire sequence. We present the chemical composition of gases emitted from the SEC during 9 of the 17 lava fountaining events. Three distinct phases in each fountain were observed in terms of seismic tremor, volcanic activity and gas composition. We observed the following: (i) The highest CO2/SO2 ratio observed during each paroxysm coincided with the peak in fountaining intensity and seismic tremor amplitude; (ii) The longer the pause between lava fountains the higher the observed peak CO2/SO2 ratio and tremor amplitude; and (iii) the SO2/HCl ratio noticeably decreased during phases of enhanced fine ash emission. We interpret the variations in gas composition and volcanic activity as due to the combined effects of two distinct processes: periodic emptying of a bubble foam layer accumulating at ~2 km depth and syn-eruptive degassing during magma fragmentation. The clear correlation between the repose time between lava fountains and their intensity and CO2/SO2 peak ratio evidences a main control of the fountain series by bubble foam accumulation and emptying. The surprising decrease in SO2/HCl during the peaks in eruptive activity is attributed to enhanced HCl outgassing during more extensive magma fragmentation and entrainment of atmospheric air

  17. Triplex DNA-binding proteins are associated with clinical outcomes revealed by proteomic measurements in patients with colorectal cancer

    Directory of Open Access Journals (Sweden)

    Nelson Laura D

    2012-06-01

    Full Text Available Abstract Background Tri- and tetra-nucleotide repeats in mammalian genomes can induce formation of alternative non-B DNA structures such as triplexes and guanine (G-quadruplexes. These structures can induce mutagenesis, chromosomal translocations and genomic instability. We wanted to determine if proteins that bind triplex DNA structures are quantitatively or qualitatively different between colorectal tumor and adjacent normal tissue and if this binding activity correlates with patient clinical characteristics. Methods Extracts from 63 human colorectal tumor and adjacent normal tissues were examined by gel shifts (EMSA for triplex DNA-binding proteins, which were correlated with clinicopathological tumor characteristics using the Mann-Whitney U, Spearman’s rho, Kaplan-Meier and Mantel-Cox log-rank tests. Biotinylated triplex DNA and streptavidin agarose affinity binding were used to purify triplex-binding proteins in RKO cells. Western blotting and reverse-phase protein array were used to measure protein expression in tissue extracts. Results Increased triplex DNA-binding activity in tumor extracts correlated significantly with lymphatic disease, metastasis, and reduced overall survival. We identified three multifunctional splicing factors with biotinylated triplex DNA affinity: U2AF65 in cytoplasmic extracts, and PSF and p54nrb in nuclear extracts. Super-shift EMSA with anti-U2AF65 antibodies produced a shifted band of the major EMSA H3 complex, identifying U2AF65 as the protein present in the major EMSA band. U2AF65 expression correlated significantly with EMSA H3 values in all extracts and was higher in extracts from Stage III/IV vs. Stage I/II colon tumors (p = 0.024. EMSA H3 values and U2AF65 expression also correlated significantly with GSK3 beta, beta-catenin, and NF- B p65 expression, whereas p54nrb and PSF expression correlated with c-Myc, cyclin D1, and CDK4. EMSA values and expression of all three splicing factors correlated

  18. Chemical modulation of electronic structure at the excited state

    Science.gov (United States)

    Li, F.; Song, C.; Gu, Y. D.; Saleem, M. S.; Pan, F.

    2017-12-01

    Spin-polarized electronic structures are the cornerstone of spintronics, and have thus attracted a significant amount of interest; in particular, researchers are looking into how to modulate the electronic structure to enable multifunctional spintronics applications, especially in half-metallic systems. However, the control of the spin polarization has only been predicted in limited two-dimensional systems with spin-polarized Dirac structures and is difficult to achieve experimentally. Here, we report the modulation of the electronic structure in the light-induced excited state in a typical half-metal, L a1 /2S r1 /2Mn O3 -δ . According to the spin-transport measurements, there appears a light-induced increase in magnetoresistance due to the enhanced spin scattering, which is closely associated with the excited spin polarization. Strikingly, the light-induced variation can be enhanced via alcohol processing and reduced by oxygen annealing. X-ray photoelectron spectroscopy measurements show that in the chemical process, a redox reaction occurs with a change in the valence of Mn. Furthermore, first-principles calculations reveal that the change in the valence of Mn alters the electronic structure and consequently modulates the spin polarization in the excited state. Our findings thus report a chemically tunable electronic structure, demonstrating interesting physics and the potential for multifunctional applications and ultrafast spintronics.

  19. Time-measured phylogenies of gag, pol and env sequence data reveal the direction and time interval of HIV-1 transmission.

    Science.gov (United States)

    Rachinger, Andrea; Groeneveld, Paul H P; van Assen, Sander; Lemey, Philippe; Schuitemaker, Hanneke

    2011-05-15

    To investigate whether time-measured phylogenetic analysis of longitudinal viral sequences can establish the direction and timing of HIV-1 transmission in an epidemiologically linked transmission cluster of three homosexual men. An HIV-1-infected homosexual man (patient 1) and his long-term HIV-negative partner (patient 2) engaged in a triangular relationship with an additional partner (patient 3). On the basis of phylogenetic analysis of gag sequences, patient 3 was previously identified as the source for superinfection of patient 1 but the source of HIV-1 infection of patient 2, who seroconverted during the triangular relationship, remained unclear. Here, we set out to analyze newly obtained gag, pol and env sequences from all three patients to fully elucidate the transmission history in this epidemiologically linked cluster. Bayesian Markov Chain Monte Carlo (MCMC) phylogenetic analyses incorporating a relaxed clock model and a flexible Bayesian skyride tree prior were applied to the longitudinally obtained gag, pol and env sequences from all three patients. Our time-measured evolutionary reconstructions convincingly supported transmission of HIV-1 from the new partner patient 3 to both patients 1 and 2. In addition, estimates of viral divergence times assisted in narrowing down the transmission intervals delineated by seroconversion estimates. Our analysis implies that Bayesian MCMC phylogenetic reconstruction incorporating temporal information can indeed reveal the direction of multiple HIV-1 transmission events in an epidemiologically linked cluster and provide more detail on the timing of transmission.

  20. Image processing techniques revealing the relationship between the field-measured ambient gamma dose equivalent rate and geological conditions at a granitic area, Velence Mountains, Hungary

    Science.gov (United States)

    Beltran Torres, Silvana; Petrik, Attila; Zsuzsanna Szabó, Katalin; Jordan, Gyozo; Szabó, Csaba

    2017-04-01

    In order to estimate the annual dose that the public receive from natural radioactivity, the identification of the potential risk areas is required which, in turn, necessitates understanding the relationship between the spatial distribution of natural radioactivity and the geogenic risk factors (e.g., rock types, dykes, faults, soil conditions, etc.). A detailed spatial analysis of ambient gamma dose equivalent rate was performed in the western side of Velence Mountains, the largest outcropped granitic area in Hungary. In order to assess the role of local geology in the spatial distribution of ambient gamma dose rates, field measurements were carried out at ground level at 300 sites along a 250 m x 250 m regular grid in a total surface of 14.7 km2. Digital image processing methods were applied to identify anomalies, heterogeneities and spatial patterns in the measured gamma dose rates, including local maxima and minima determination, digital cross sections, gradient magnitude and gradient direction, second derivative profile curvature, local variability, lineament density, 2D autocorrelation and directional variogram analyses. Statistical inference showed that different gamma dose rate levels are associated with the rock types (i.e., Carboniferous granite, Pleistocene colluvial, proluvial, deluvial sediments and talus, and Pannonian sand and pebble), with the highest level on the Carboniferous granite including outlying values. Moreover, digital image processing revealed that linear gamma dose rate spatial features are parallel to the SW-NE dyke system and possibly to the NW-SE main fractures. The results of this study underline the importance of understanding the role of geogenic risk factors influencing the ambient gamma dose rate received by public. The study also demonstrates the power of the image processing techniques for the identification of spatial pattern in field-measured geogenic radiation.

  1. The Boulder measurement of parity violation and an anapole moment in cesium

    International Nuclear Information System (INIS)

    Cho, D.; Wood, C.S.; Bennett, S.C.; Roberts, J.L.; Masterson, B.P.; Tanner, C.E.; Wieman, C.E.

    1999-01-01

    The amplitude of the parity-nonconserving transition between the 6S and 7S states of cesium was precisely measured with the use of a spin-polarized atomic beam. This measurement gives Im(E1 pnc )/β = - 1.5935(56) milli-volts per centimeter and provides an improved test of the standard model at low energy, including a value for the S parameter of -1.3(3) exp (11) theory . The nuclear spin-dependent contributions was 0.077(11) milli-volts per centimeter, this contribution is a manifestation of parity violation in atomic nuclei and is a measurement of the long-sought anapole moment. (authors)

  2. In vivo measurements of cerebral metabolic abnormalities by proton spectroscopy after a transient ischemic attack revealing an internal carotid stenosis > 70%

    International Nuclear Information System (INIS)

    Giroud, M.; Becker, F.; Lemesle, M.; Walker, P.; Guy, F.; Martin, D.; Baudouin, N.; Brunotte, F.; Dumas, R.

    1996-01-01

    Aims: The aim of this work is to look for cerebral metabolic abnormalities within the first 3 days after a transient ischemic attack revealing an internal carotid stenosis > 70 %. Methods: Five patients with a transient ischemic attack lasting between 30 and 180 minutes, affecting sensory and motor brachio-facial territory, with or without aphasia. Were studied. A CT-scan, an EEG, a cervical Doppler ultrasound, a standard arteriography, a magnetic resonance imaging and a proton spectroscopy were performed within the cerebral area affected by the transient ischemic attack. We measured 2 markers: N-acetyl-aspartate, the marker of the neuronal mass, and lactate, the marker of anaerobe metabolism. In each case, a contralateral internal stenosis was diagnosed by cervical Doppler ultrasound and standard arteriography. No cerebral infarction was observed. Results: With the affected cerebral area defined according to clinical and EEG features, proton spectroscopy showed a significant rise of lactate, without any change in N-acetyl-aspartate levels. Conclusions: Within the first 3 days after a transient ischemic attack, there is a significant risk of lactate inside the affected cerebral area. This change may reflect a localized and transient hypoperfusion, but long enough to induce a rise of lactate but not sufficient to produce a cerebral infarct. This area is probably at risk to induce cerebral infarct. This data lead us to study the metabolic change induced by the asymptomatic internal carotid stenosis. (authors). 18 refs

  3. Regular in situ measurements of HDO/H216O in the northern and southern hemispherical upper troposphere reveal tropospheric transport processes.

    Science.gov (United States)

    Christner, Emanuel; Dyroff, Christoph; Sanati, Shahrokh; Brenninkmeijer, Carl; Zahn, Andreas

    2013-04-01

    Atmospheric water in form of water vapor and clouds is an enormously crucial trace species. It is responsible for ~70 % of the natural greenhouse effect (Schmidt et al., JGR, 2010), carries huge amounts of latent heat, and is the major source of OH in the troposphere. The isotopic composition of water vapor is an elegant tracer for a better understanding and quantification of the extremely complex and variable hydrological cycle in Earth's atmosphere (evaporation, cloud condensation, rainout, re-evaporation, snow), which in turn is a prerequisite to improve climate modeling and predictions. In this context, water-isotopologues (here the isotope ratio HDO/H216O) can be used to study the atmospheric transport of water and in-cloud processes. As H216O and HDO differ in vapor pressure and molecular diffusion, fractionation occurs during condensation and rainout events. For that reason the ratio HDO/H216O preserves information about the transport and condensation history of an air mass. The tunable diode-laser absorption spectrometer ISOWAT was developed for airborne measurements of the water-isotopologue concentrations of H216O and HDO, probing fundamental rovibrational water-absorption lines at around 2.66 μm. Since April 2010 the spectrometer is regularly operated aboard the CARIBIC passenger aircraft (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container - Lufthansa, Airbus 340-600), which measures ~100 trace gases and aerosol components in the UTLS (9-12 km altitude) on four long-distance flights per month. During several flights across the equator (Africa) or close to the equator (Venezuela and Malaysia) an increase of HDO/H216O from the subtropics towards the tropics was measured (by more than 100 permil) at an altitude of ~12 km. This isotopic gradient can partly be attributed to differences in humidity. In addition there is a humidity independent latitudinal gradient (by more than 50 permil), revealing the strong

  4. Spin Tunneling in Junctions with Disordered Ferromagnets

    NARCIS (Netherlands)

    Paluskar, P.V.; Attema, J.J.; de Wijs, G.A.; Fiddy, S.; Snoeck, E.; Kohlhepp, J.T.; Swagten, H.J.M.; de Groot, R. A.; Koopmans, H.

    2008-01-01

    We provide compelling evidence to establish that, contrary to one’s elementary guess, the tunneling spin polarization (TSP) of amorphous CoFeB is larger than that of fcc CoFeB. First-principles atomic and electronic structure calculations reveal striking agreement between the measured TSP and the

  5. Measurements of salivary alpha amylase and salivary cortisol in hominoid primates reveal within-species consistency and between-species differences.

    Directory of Open Access Journals (Sweden)

    Verena Behringer

    Full Text Available Salivary alpha amylase (sAA is the most abundant enzyme in saliva. Studies in humans found variation in enzymatic activity of sAA across populations that could be linked to the copy number of loci for salivary amylase (AMY1, which was seen as an adaptive response to the intake of dietary starch. In addition to diet dependent variation, differences in sAA activity have been related to social stress. In a previous study, we found evidence for stress-induced variation in sAA activity in the bonobos, a hominoid primate that is closely related to humans. In this study, we explored patterns of variation in sAA activity in bonobos and three other hominoid primates, chimpanzee, gorilla, and orangutan to (a examine if within-species differences in sAA activity found in bonobos are characteristic for hominoids and (b assess the extent of variation in sAA activity between different species. The results revealed species-differences in sAA activity with gorillas and orangutans having higher basal sAA activity when compared to Pan. To assess the impact of stress, sAA values were related to cortisol levels measured in the same saliva samples. Gorillas and orangutans had low salivary cortisol concentrations and the highest cortisol concentration was found in samples from male bonobos, the group that also showed the highest sAA activity. Considering published information, the differences in sAA activity correspond with differences in AMY1 copy numbers and match with general features of natural diet. Studies on sAA activity have the potential to complement molecular studies and may contribute to research on feeding ecology and nutrition.

  6. Characterizing an Integrated Annual Global Measure of the Earth's Maximum Land Surface Temperatures from 2003 to 2012 Reveals Strong Biogeographic Influences

    Science.gov (United States)

    Mildrexler, D. J.; Zhao, M.; Running, S. W.

    2014-12-01

    Land Surface Temperature (LST) is a good indicator of the surface energy balance because it is determined by interactions and energy fluxes between the atmosphere and the ground. The variability of land surface properties and vegetation densities across the Earth's surface changes these interactions and gives LST a unique biogeographic influence. Natural and human-induced disturbances modify the surface characteristics and alter the expression of LST. This results in a heterogeneous and dynamic thermal environment. Measurements that merge these factors into a single global metric, while maintaining the important biophysical and biogeographical factors of the land surface's thermal environment are needed to better understand integrated temperature changes in the Earth system. Using satellite-based LST we have developed a new global metric that focuses on one critical component of LST that occurs when the relationship between vegetation density and surface temperature is strongly coupled: annual maximum LST (LSTmax). A 10 year evaluation of LSTmax histograms that include every 1-km pixel across the Earth's surface reveals that this integrative measurement is strongly influenced by the biogeographic patterns of the Earth's ecosystems, providing a unique comparative view of the planet every year that can be likened to the Earth's thermal maximum fingerprint. The biogeographical component is controlled by the frequency and distribution of vegetation types across the Earth's land surface and displays a trimodal distribution. The three modes are driven by ice covered polar regions, forests, and hot desert/shrubland environments. In ice covered areas the histograms show that the heat of fusion results in a convergence of surface temperatures around the melting point. The histograms also show low interannual variability reflecting two important global land surface dynamics; 1) only a small fraction of the Earth's surface is disturbed in any given year, and 2) when

  7. Observation of spin Hall effect in photon tunneling via weak measurements.

    Science.gov (United States)

    Zhou, Xinxing; Ling, Xiaohui; Zhang, Zhiyou; Luo, Hailu; Wen, Shuangchun

    2014-12-09

    Photonic spin Hall effect (SHE) manifesting itself as spin-dependent splitting escapes detection in previous photon tunneling experiments due to the fact that the induced beam centroid shift is restricted to a fraction of wavelength. In this work, we report on the first observation of this tiny effect in photon tunneling via weak measurements based on preselection and postselection technique on the spin states. We find that the spin-dependent splitting is even larger than the potential barrier thickness when spin-polarized photons tunneling through a potential barrier. This photonic SHE is attributed to spin-redirection Berry phase which can be described as a consequence of the spin-orbit coupling. These findings provide new insight into photon tunneling effect and thereby offer the possibility of developing spin-based nanophotonic applications.

  8. Measuring Pancharatnam's relative phase for SO(3) evolutions using spin polarimetry

    International Nuclear Information System (INIS)

    Larsson, Peter; Sjoeqvist, Erik

    2003-01-01

    In polarimetry, a superposition of internal quantal states is exposed to a single Hamiltonian and information about the evolution of the quantal states is inferred from projection measurements on the final superposition. In this framework, we here extend the polarimetric test of Pancharatnam's relative phase for spin-(1/2) proposed by Wagh and Rakhecha [Phys. Lett. A 197, 112 (1995)] to spin j≥1 undergoing noncyclic SO(3) evolution. We demonstrate that the output intensity for higher spin values is a polynomial function of the corresponding spin-(1/2) intensity. We further propose a general method to extract the noncyclic SO(3) phase and visibility by rigid translation of two π/2 spin flippers. Polarimetry on higher spin states may in practice be done with spin polarized atomic beams

  9. Transport measurements on superconducting iron pnictides and Heusler compounds; Transportmessungen an Supraleitenden Eisenpniktiden und Heusler-Verbindungen

    Energy Technology Data Exchange (ETDEWEB)

    Bombor, Dirk

    2014-09-05

    In this work, results of electronic transport measurements are discussed for superconducting iron pnictides as well as for ferromagnetic Heusler compounds. The iron pnictides are a recently discovered class of high temperature superconductors where magnetism might play a crucial role. While the 122-pnictides show antiferromagnetism and migrate to the superconducting state upon doping, ferromagnetism has been observed in doped LiFeAs. On the other hand, in the undoped state this material shows interesting superconducting properties. Among other properties, Heusler compounds are well known due to their ferromagnetism. Co{sub 2}FeSi, which was investigated in this work, is one of the strongest ferromagnets. Beside this, one predicts this compound to be a half-metallic ferromagnet with completely spin polarized electronic transport where all conducting electrons have the same spin. The here addressed properties can well be investigated with the method of electronic transport measurements, whose results on single crystals are discussed in this work.

  10. Repeated measurements of cerebral blood flow in the left superior temporal gyrus reveal tonic hyperactivity in patients with auditory verbal hallucinations: A possible trait marker

    Directory of Open Access Journals (Sweden)

    Philipp eHoman

    2013-06-01

    Full Text Available Background: The left superior temporal gyrus (STG has been suggested to play a key role in auditory verbal hallucinations in patients with schizophrenia. Methods: Eleven medicated subjects with schizophrenia and medication-resistant auditory verbal hallucinations and 19 healthy controls underwent perfusion magnetic resonance imaging with arterial spin labeling. Three additional repeated measurements were conducted in the patients. Patients underwent a treatment with transcranial magnetic stimulation (TMS between the first 2 measurements. The main outcome measure was the pooled cerebral blood flow (CBF, which consisted of the regional CBF measurement in the left superior temporal gyrus (STG and the global CBF measurement in the whole brain.Results: Regional CBF in the left STG in patients was significantly higher compared to controls (p < 0.0001 and to the global CBF in patients (p < 0.004 at baseline. Regional CBF in the left STG remained significantly increased compared to the global CBF in patients across time (p < 0.0007, and it remained increased in patients after TMS compared to the baseline CBF in controls (p < 0.0001. After TMS, PANSS (p = 0.003 and PSYRATS (p = 0.01 scores decreased significantly in patients.Conclusions: This study demonstrated tonically increased regional CBF in the left STG in patients with schizophrenia and auditory hallucinations despite a decrease in symptoms after TMS. These findings were consistent with what has previously been termed a trait marker of auditory verbal hallucinations in schizophrenia.

  11. The inverted chevron plot measured by NMR relaxation reveals a native-like unfolding intermediate in acyl-CoA binding protein

    DEFF Research Database (Denmark)

    Teilum, Kaare; Poulsen, F. M.; Akke, M.

    2006-01-01

    under conditions favoring folding, for which the folding rate constant (k f) dominates the relaxation in stopped-flow kinetic measurements. Conversely, k f was determined under conditions favoring unfolding, for which k u dominates stopped-flow data. The rates determined by NMR therefore complement...

  12. Atmospheric measurements of Δ17O in CO2 in Göttingen, Germany reveal a seasonal cycle driven by biospheric uptake

    NARCIS (Netherlands)

    Hofmann, M. E. G.; Horvath, B.; Schneider, L.; Peters, W.; Schützenmeister, K.; Pack, A.

    2017-01-01

    The triple oxygen isotope composition of tropospheric CO2 might be a promising new tracer for terrestrial gross carbon fluxes. This notion is based on global box modeling of its abundance, and on highly challenging and therefore very sparse measurements of 16O, 17O and 18O in CO2 in the lower

  13. Time-measured phylogenies of gag, pol and env sequence data reveal the direction and time interval of HIV-1 transmission

    NARCIS (Netherlands)

    Rachinger, Andrea; Groeneveld, Paul H. P.; van Assen, Sander; Lemey, Philippe; Schuitemaker, Hanneke

    2011-01-01

    Objective: To investigate whether time-measured phylogenetic analysis of longitudinal viral sequences can establish the direction and timing of HIV-1 transmission in an epidemiologically linked transmission cluster of three homosexual men. Design: An HIV-1-infected homosexual man (patient 1) and his

  14. Patient burden of Sjögren’s: a comprehensive literature review revealing the range and heterogeneity of measures used in assessments of severity

    Science.gov (United States)

    Hammitt, Katherine M; Naegeli, April N; van den Broek, Remon W M; Birt, Julie A

    2017-01-01

    Context The severity of Sjögren’s syndrome has been evaluated using a wide variety of clinical measures and patient-reported outcomes (PROs). This may contribute to the lack of clarity concerning the burden of Sjögren’s from the patient perspective. Objective To perform a comprehensive peer-reviewed literature analysis of the patient aspects of Sjögren’s, focusing on PROs, to investigate the complexity underlying the evaluation of the syndrome and to elucidate the discordance between the different measures. Methods We searched Embase for articles published between January 2005 and September 2015. Research articles, clinical and diagnostic reviews, and validation studies with a focus on patient aspects of Sjögren’s were selected as the primary information source. Results 157 articles met the eligibility criteria. A wide variety of assessment measures used to evaluate glandular, extraglandular and functional domains were observed. Many different, non-validated Visual Analogue Scales, with a wide range of anchor words, were used in the quantification of Sjögren’s disease burden, impeding comparisons between studies. Relatively few clinical trials of drug therapies used validated scales: European League Against Rheumatism Sjögren’s Syndrome Patient Reported Index was used most often for symptom assessment and 36 Item Short Form Survey for quality of life (QoL). Conclusion A wide range and diversity of measures are used to evaluate the patient burden of Sjögren’s; most are not validated for use in this disease. PRO endpoints, validated specifically in Sjögren’s, that demonstrate improvement are needed. These measures should focus on QoL aspects important to patients and will most likely involve gauging change in function rather than patient-reported symptoms. PMID:28955493

  15. Multiple acquisitions via sequential transfer of orphan spin polarization (MAeSTOSO): How far can we push residual spin polarization in solid-state NMR?

    Science.gov (United States)

    Gopinath, T; Veglia, Gianluigi

    2016-06-01

    Conventional multidimensional magic angle spinning (MAS) solid-state NMR (ssNMR) experiments detect the signal arising from the decay of a single coherence transfer pathway (FID), resulting in one spectrum per acquisition time. Recently, we introduced two new strategies, namely DUMAS (DUal acquisition Magic Angle Spinning) and MEIOSIS (Multiple ExperIments via Orphan SpIn operatorS), that enable the simultaneous acquisitions of multidimensional ssNMR experiments using multiple coherence transfer pathways. Here, we combined the main elements of DUMAS and MEIOSIS to harness both orphan spin operators and residual polarization and increase the number of simultaneous acquisitions. We show that it is possible to acquire up to eight two-dimensional experiments using four acquisition periods per each scan. This new suite of pulse sequences, called MAeSTOSO for Multiple Acquisitions via Sequential Transfer of Orphan Spin pOlarization, relies on residual polarization of both (13)C and (15)N pathways and combines low- and high-sensitivity experiments into a single pulse sequence using one receiver and commercial ssNMR probes. The acquisition of multiple experiments does not affect the sensitivity of the main experiment; rather it recovers the lost coherences that are discarded, resulting in a significant gain in experimental time. Both merits and limitations of this approach are discussed. Copyright © 2016 Elsevier Inc. All rights reserved.

  16. Measuring $\

    Energy Technology Data Exchange (ETDEWEB)

    Mitchell, Jessica Sarah [Univ. of Cambridge (United Kingdom)

    2011-01-01

    The MINOS Experiment consists of two steel-scintillator calorimeters, sampling the long baseline NuMI muon neutrino beam. It was designed to make a precise measurement of the ‘atmospheric’ neutrino mixing parameters, Δm2 atm. and sin2 (2 atm.). The Near Detector measures the initial spectrum of the neutrino beam 1km from the production target, and the Far Detector, at a distance of 735 km, measures the impact of oscillations in the neutrino energy spectrum. Work performed to validate the quality of the data collected by the Near Detector is presented as part of this thesis. This thesis primarily details the results of a vμ disappearance analysis, and presents a new sophisticated fitting software framework, which employs a maximum likelihood method to extract the best fit oscillation parameters. The software is entirely decoupled from the extrapolation procedure between the detectors, and is capable of fitting multiple event samples (defined by the selections applied) in parallel, and any combination of energy dependent and independent sources of systematic error. Two techniques to improve the sensitivity of the oscillation measurement were also developed. The inclusion of information on the energy resolution of the neutrino events results in a significant improvement in the allowed region for the oscillation parameters. The degree to which sin2 (2θ )= 1.0 could be disfavoured with the exposure of the current dataset if the true mixing angle was non-maximal, was also investigated, with an improved neutrino energy reconstruction for very low energy events. The best fit oscillation parameters, obtained by the fitting software and incorporating resolution information were: | Δm2| = 2.32+0.12 -0.08×10-3 eV2 and sin2 (2θ ) > 0.90(90% C.L.). The analysis provides the current world best measurement of the atmospheric neutrino mass

  17. Ratiometric measurements of adiponectin by mass spectrometry in bottlenose dolphins (Tursiops truncatus with iron overload reveal an association with insulin resistance and glucagon

    Directory of Open Access Journals (Sweden)

    Benjamin A Neely

    2013-09-01

    Full Text Available High molecular weight (HMW adiponectin levels are reduced in humans with type 2 diabetes and insulin resistance. Similar to humans with insulin resistance, managed bottlenose dolphins (Tursiops truncatus diagnosed with hemochromatosis (iron overload have higher levels of 2 h post-prandial plasma insulin than healthy controls. A parallel reaction monitoring assay for dolphin serum adiponectin was developed based on tryptic peptides identified by mass spectrometry. Using identified post-translational modifications, a differential measurement was constructed. Total and unmodified adiponectin levels were measured in sera from dolphins with (n=4 and without (n=5 iron overload. This measurement yielded total adiponectin levels as well as site specific percent unmodified adiponectin that may inversely correlate with HMW adiponectin. Differences in insulin levels between iron overload cases and controls were observed 2 h post-prandial, but not during the fasting state. Thus, post-prandial as well as fasting serum adiponectin levels were measured to determine whether adiponectin and insulin would follow similar patterns. There was no difference in total adiponectin or percent unmodified adiponectin from case or control fasting animals. There was no difference in post-prandial total adiponectin levels between case and control dolphins (mean ± S.D. at 763 ± 298 and 727 ± 291 pmol/ml, respectively (p = 0.91; however, percent unmodified adiponectin was significantly higher in post-prandial cases compared controls (30.0 ± 6.3 versus 17.0 ± 6.6%, respectively; p = 0.016. Interestingly, both total and percent unmodified adiponectin were correlated with glucagon levels in controls (r = 0.999, p < 0.001, but not in cases, which is possibly a reflection of insulin resistance. Although total adiponectin levels were not significantly different, the elevated percent unmodified adiponectin follows a trend similar to HMW adiponectin reported for humans with

  18. In vivo intracellular pH measurements in tobacco and Arabidopsis reveal an unexpected pH gradient in the endomembrane system.

    Science.gov (United States)

    Martinière, Alexandre; Bassil, Elias; Jublanc, Elodie; Alcon, Carine; Reguera, Maria; Sentenac, Hervé; Blumwald, Eduardo; Paris, Nadine

    2013-10-01

    The pH homeostasis of endomembranes is essential for cellular functions. In order to provide direct pH measurements in the endomembrane system lumen, we targeted genetically encoded ratiometric pH sensors to the cytosol, the endoplasmic reticulum, and the trans-Golgi, or the compartments labeled by the vacuolar sorting receptor (VSR), which includes the trans-Golgi network and prevacuoles. Using noninvasive live-cell imaging to measure pH, we show that a gradual acidification from the endoplasmic reticulum to the lytic vacuole exists, in both tobacco (Nicotiana tabacum) epidermal (ΔpH -1.5) and Arabidopsis thaliana root cells (ΔpH -2.1). The average pH in VSR compartments was intermediate between that of the trans-Golgi and the vacuole. Combining pH measurements with in vivo colocalization experiments, we found that the trans-Golgi network had an acidic pH of 6.1, while the prevacuole and late prevacuole were both more alkaline, with pH of 6.6 and 7.1, respectively. We also showed that endosomal pH, and subsequently vacuolar trafficking of soluble proteins, requires both vacuolar-type H(+) ATPase-dependent acidification as well as proton efflux mediated at least by the activity of endosomal sodium/proton NHX-type antiporters.

  19. Comparison of multiple non-invasive methods of measuring cardiac output during pregnancy reveals marked heterogeneity in the magnitude of cardiac output change between women.

    Science.gov (United States)

    Petersen, John W; Liu, Jing; Chi, Yueh-Yun; Lingis, Melissa; Williams, R Stan; Rhoton-Vlasak, Alice; Segal, Mark S; Conrad, Kirk P

    2017-04-01

    Various non-invasive methods are available to measure cardiac output (CO) during pregnancy. We compared serial measures of CO using various methods to determine which provided the least variability. Ten patients with spontaneous pregnancy had estimation of CO at baseline prior to becoming pregnant and at the end of the first and third trimesters. Echocardiographic data were used to estimate CO using the Teichholz method, Simpson's biplane method, and the Doppler determined velocity time integral (VTI) method. In addition, a Bioz Dx device was used to estimate CO by impedance cardiography. CO estimated with the VTI method had the lowest beat-to-beat variability. CO estimated with the VTI method was higher than CO estimated with the 2D-Teichholz method and Simpson's method. The percent change in CO during pregnancy was similar for all echo methods (VTI, Teichholz, and Simpson's biplane). Baseline CO determined with impedance cardiography was higher than CO determined with the VTI method. However, change in CO during pregnancy was significantly lower when measured with impedance cardiography. There was marked heterogeneity in the degree of rise in CO during the first trimester (-3 to 55%). The wide variation in the gestational rise in CO was unexpected, and at least in part secondary to variable increase in heart rate. We recommend the use of the Doppler determined VTI method for the estimation of CO in pregnancy. © 2017 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.

  20. Electrical transport characteristics of Sn/p-Si schottky contacts revealed from I-V-T and C-V-T measurements

    Energy Technology Data Exchange (ETDEWEB)

    Karatas, S. [Department of Physics, Faculty of Sciences and Arts, University of Kahramanmaras Suetcue Imam, 46100 Kahramanmaras (Turkey)]. E-mail: skaratas@ksu.edu.tr; Altindal, S. [Department of Physics, Faculty of Arts and Sciences, Gazi University, 06500 Ankara (Turkey); Tueruet, A. [Department of Physics, Faculty of Sciences and Arts, Atatuerk University, 25240 Erzurum (Turkey); Cakar, M. [Department of Chemistry, Faculty of Sciences and Arts, University of Kahramanmaras Suetcue Imam, 46100 Kahramanmaras (Turkey)

    2007-04-15

    The current-voltage (I-V) and capacitance-voltage (C-V) characteristics of metal-semiconductor (Sn/p-Si) Schottky contacts were measured in the temperature range 150-400 K. The effect of the temperature on the series resistances R {sub S}, ideality factors n, the barrier height {phi} {sub b} and interface state density N {sub SS} obtained from the I-V and C-V characteristics were investigated. The n, {phi} {sub b}, R {sub S}, and N {sub SS} values were seen to be strongly temperature dependent. The ideality factors, series resistances and interface state densities decreased with increasing temperature for all diodes and the values of n, R {sub S}, and N {sub SS} obtained from I-V and C-V measurements were found in the ranges of 2.024-1.108, 2.083-1.121; 79.508-33.397 {omega}; and 2.14x10{sup 13}-0.216x10{sup 13} cm{sup 2} eV{sup -1}, 2.277x10{sup 13}-0.254x10{sup 13} cm{sup 2} eV{sup -1}, respectively. The temperature dependence of energy distribution of interface state density (N {sub SS}) profiles has been determined from I-V measurements by taking into account the bias dependence of the effective barrier height and ideality factor.

  1. The variation of dust content with intrinsic galaxy properties: revealing strong dust biases in many commonly-used galaxy property measurements

    Science.gov (United States)

    Devour, Brian; Bell, Eric F.

    2018-01-01

    Dust strongly affects many observations of galaxy properties, and quantifying galaxy dust content and correcting for its effects is a delicate and often uncertain task. In particular, both the impact of dust on commonly-used metrics of galaxy structure and the variation of dust content with intrinsic galaxy properties are poorly quantified. The inclination dependence of dust attenuation is a powerful tool to quantify dust amounts and the effects of dust on galaxy property measurements; this requires the construction of dust and inclination-independent selection techniques to isolate samples of intrinsically similar galaxies for study. To this end we construct dust and inclination-independent measurements of galaxy mass and star formation rate using dust-penetrated infrared datasets, and we develop novel dust and inclination-independent galaxy ‘linear’ size and concentration measurements by collapsing the light distribution in the near-infrared onto the major axis. With these new metrics we select a sample of Milky Way analog galaxies with similar stellar masses, star formation rates, and linear sizes and concentrations. These galaxies - identical save for their orientation - show strong systematic dust and inclination dependence in their Sérsic index, concentration, half-light radius, luminosity, (dust-corrected!) star formation rate and metallicitity, and spectral classification. We use these new metrics to study the variation in relative face-on to edge-on attenuation as a function of intrinsic stellar mass, star formation rate, and linear size and concentration. We find that, if one accounts for geometric and radiative transfer effects, the complex patterns of variation in relative attenuation can be reproduced by simple scaling relation-based dust density models in which dust optical depth is set primarily by gas density and metallicity.

  2. In-vivo nonlinear optical microscopy (NLOM of epithelial-connective tissue interface (ECTI reveals quantitative measures of neoplasia in hamster oral mucosa.

    Directory of Open Access Journals (Sweden)

    Rahul Pal

    Full Text Available The epithelial-connective tissue interface (ECTI plays an integral role in epithelial neoplasia, including oral squamous cell carcinoma (OSCC. This interface undergoes significant alterations due to hyperproliferating epithelium that supports the transformation of normal epithelium to precancers and cancer. We present a method based on nonlinear optical microscopy to directly assess the ECTI and quantify dysplastic alterations using a hamster model for oral carcinogenesis. Neoplastic and non-neoplastic normal mucosa were imaged in-vivo by both multiphoton autofluorescence microscopy (MPAM and second harmonic generation microscopy (SHGM to obtain cross-sectional reconstructions of the oral epithelium and lamina propria. Imaged sites were biopsied and processed for histopathological grading and measurement of ECTI parameters. An ECTI shape parameter was calculated based on deviation from the linear geometry (ΔLinearity seen in normal mucosa was measured using MPAM-SHGM and histology. The ECTI was readily visible in MPAM-SHGM and quantitative shape analysis showed ECTI deformation in dysplasia but not in normal mucosa. ΔLinearity was significantly (p < 0.01 higher in dysplasia (0.41±0.24 than normal (0.11±0.04 as measured in MPAM-SHGM and results were confirmed in histology which showed similar trends in ΔLinearity. Increase in ΔLinearity was also statistically significant for different grades of dysplasia. In-vivo ΔLinearity measurement alone from microscopy discriminated dysplasia from normal tissue with 87.9% sensitivity and 97.6% specificity, while calculations from histology provided 96.4% sensitivity and 85.7% specificity. Among other quantifiable architectural changes, a progressive statistically significant increase in epithelial thickness was seen with increasing grade of dysplasia. MPAM-SHGM provides new noninvasive ways for direct characterization of ECTI which may be used in preclinical studies to investigate the role of this

  3. Patient burden of Sjögren’s: a comprehensive literature review revealing the range and heterogeneity of measures used in assessments of severity

    OpenAIRE

    Hammitt, Katherine M; Naegeli, April N; van den Broek, Remon W M; Birt, Julie A

    2017-01-01

    Context The severity of Sjögren’s syndrome has been evaluated using a wide variety of clinical measures and patient-reported outcomes (PROs). This may contribute to the lack of clarity concerning the burden of Sjögren’s from the patient perspective. Objective To perform a comprehensive peer-reviewed literature analysis of the patient aspects of Sjögren’s, focusing on PROs, to investigate the complexity underlying the evaluation of the syndrome and to elucidate the discordance between the diff...

  4. Weak Interaction Measurements with Optically Trapped Radioactive Atoms

    International Nuclear Information System (INIS)

    Vieira, D.J.; Crane, S.G.; Guckert, R.; Zhao, X.; Brice, S.J.; Goldschmidt, A.; Hime, A.; Tupa, D.

    1999-01-01

    This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The goal of this project is to apply the latest in magneto-optical and pure magnetic trapping technology to concentrate, cool, confine, and polarize radioactive atoms for precise electroweak interaction measurements. In particular, the authors have concentrated their efforts on the trapping of 82 Rb for a parity-violating, beta-asymmetry measurement. Progress has been made in successfully trapping of up to 6 million 82 Rb(t 1/2 =75s) atoms in a magneto-optical trap coupled to a mass separator. This represents a two order of magnitude improvement in the number trapped radioactive atoms over all previous work. They have also measured the atomic hyperfine structure of 82 Rb and demonstrated the MOT-to-MOT transfer and accumulation of atoms in a second trap. Finally, they have constructed and tested a time-orbiting-potential magnetic trap that will serve as a rotating beacon of spin-polarized nuclei and a beta-telescope detection system. Prototype experiments are now underway with the initial goal of making a 1% measurements of the beta-asymmetry parameter A which would match the world's best measurements

  5. Comparison of the Calibration Standards of Three Commercially Available Multiplex Kits for Human Cytokine Measurement to WHO Standards Reveals Striking Differences

    Directory of Open Access Journals (Sweden)

    Ivan M. Roitt

    2008-01-01

    Full Text Available Serum parameters as indicators for the efficacy of therapeutic drugs are currently in the focus of intensive research. The induction of certain cytokines (or cytokine patterns is known to be related to the status of the immune response e.g. in regulating the TH1/TH2 balance. Regarding their potential value as surrogate parameters in clinical trials and subsequently for the assignment of treatment effi cacy, the accurate and reliable determination of cytokines in patient serum is mandatory. Because serum samples are precious and limited, test methods—like the xMAP multiplex technology—that allow for the simultaneous determination of a variety of cytokines from only a small sample aliquot, can offer great advantages.We here have compared multiplex kits from three different manufactures and found striking differences upon standardizing using WHO standards for selected cytokines. We therefore extended our xMAP multiplex measurements investigations to an ex-vivo situation by testing serum samples and found that the cytokine amounts measured was critically influenced by the actual kit used. The presented data indicate that statements regarding the quantitive determination of cytokines—and therefore their use as biomarkers—in serum samples have to be interpreted with caution.

  6. In-vivo nonlinear optical microscopy (NLOM) of epithelial-connective tissue interface (ECTI) reveals quantitative measures of neoplasia in hamster oral mucosa.

    Science.gov (United States)

    Pal, Rahul; Yang, Jinping; Ortiz, Daniel; Qiu, Suimin; Resto, Vicente; McCammon, Susan; Vargas, Gracie

    2015-01-01

    The epithelial-connective tissue interface (ECTI) plays an integral role in epithelial neoplasia, including oral squamous cell carcinoma (OSCC). This interface undergoes significant alterations due to hyperproliferating epithelium that supports the transformation of normal epithelium to precancers and cancer. We present a method based on nonlinear optical microscopy to directly assess the ECTI and quantify dysplastic alterations using a hamster model for oral carcinogenesis. Neoplastic and non-neoplastic normal mucosa were imaged in-vivo by both multiphoton autofluorescence microscopy (MPAM) and second harmonic generation microscopy (SHGM) to obtain cross-sectional reconstructions of the oral epithelium and lamina propria. Imaged sites were biopsied and processed for histopathological grading and measurement of ECTI parameters. An ECTI shape parameter was calculated based on deviation from the linear geometry (ΔLinearity) seen in normal mucosa was measured using MPAM-SHGM and histology. The ECTI was readily visible in MPAM-SHGM and quantitative shape analysis showed ECTI deformation in dysplasia but not in normal mucosa. ΔLinearity was significantly (p epithelial thickness was seen with increasing grade of dysplasia. MPAM-SHGM provides new noninvasive ways for direct characterization of ECTI which may be used in preclinical studies to investigate the role of this interface in early transformation. Further development of the method may also lead to new diagnostic approaches to differentiate non-neoplastic tissue from precancers and neoplasia, possibly with other cellular and layer based indicators of abnormality.

  7. Using Continuous In-situ Measurement of Fluorescence to Reveal Hot Spots and Hot Moments of Dissolved Organic Matter Dynamics in a Forested Watershed

    Science.gov (United States)

    Ryan, K. A.; Hosen, J. D.; Raymond, P. A.; Stubbins, A.; Shanley, J. B.

    2017-12-01

    River systems serve as net carbon exporters from land to the ocean, fueling downstream aquatic ecosystem food webs. Fluorescence signatures of aquatic organic matter can be used as a proxy for dissolved organic carbon (DOC) concentration and can characterize DOC composition, reactivity, and source to improve our understanding of ecological processes. In-situ measurement of fluorescence using fifteen-minute interval data logging allows greater temporal resolution than laboratory studies. However, in-situ data must be corrected for interferences from temperature, absorbance and turbidity changes occurring in the field. We installed multiparameter water quality sondes (Eureka Mantas) and in-situ fluorometers (Turner Designs Cyclops) at sites nested within streams and riparian zones in the Sleepers River Research Watershed in Vermont in 2017. We coupled these measurements with simultaneous intensive field sampling campaigns and laboratory analysis of DOC and fluorescence Excitation-Emission Matrices. The data loggers from the nested sites recorded fluorescence peaks responding to discharge events and tracked changes in fluorescence occurring from upstream to downstream sites. Laboratory results confirm a nonlinear, hysteretic relationship between discharge and DOC where peak DOC lags peak discharge. This hysteresis is predicted to be controlled by multiple flow paths and DOC sources (i.e. groundwater, overland flow). We conclude that continuous in-situ records of river water fluorescence can be used to inform ecological processes and test new hypotheses concerning dissolved organic matter dynamics in watersheds.

  8. Different emissive states in the bulk and at the surface of methylammonium lead bromide perovskite revealed by two-photon micro-spectroscopy and lifetime measurements

    Directory of Open Access Journals (Sweden)

    Khadga Jung Karki

    2016-07-01

    Full Text Available Two photon photoluminescence (2PPL from single crystals of methyl ammonium lead bromide (CH3NH3PbBr3, MAPbBr3 is studied. We observe two components in the 2PPL spectra, which we assign to the photoluminescence (PL from the carrier recombination at the band edge and the recombination due to self-trapping of excitons. The PL Stokes shift of self-trapped excitons is about 100 meV from the band-gap energy. Our measurements show that about 15% of the total PL from regions about 40 μm deep inside the crystal is due to the emission from self-trapped exciton. This contribution increases to about 20% in the PL from the regions close to the surface. Time resolved measurements of 2PPL show that the PL due to band-edge recombination has a life time of about 8 ns while the PL lifetime of self-trapped excitons is in the order of 100 ns. Quantification of self-trapped excitons in the materials used in photovoltaics is important as such excitons hinder charge separation. As our results also show that an appreciable fraction of photo-generated carriers get trapped, the results are important in rational design of photovoltaics. On the other hand, our results also show that the self-trapped excitons broaden the emission spectrum, which may be useful in designing broadband light emitting devices.

  9. Complexities of bloom dynamics in the toxic dinoflagellate Alexandrium fundyense revealed through DNA measurements by imaging flow cytometry coupled with species-specific rRNA probes

    Science.gov (United States)

    Brosnahan, Michael L.; Farzan, Shahla; Keafer, Bruce A.; Sosik, Heidi M.; Olson, Robert J.; Anderson, Donald M.

    2014-05-01

    Measurements of the DNA content of different protist populations can shed light on a variety of processes, including cell division, sex, prey ingestion, and parasite invasion. Here, we modified an Imaging FlowCytobot (IFCB), a custom-built flow cytometer that records images of microplankton, to measure the DNA content of large dinoflagellates and other high-DNA content species. The IFCB was also configured to measure fluorescence from Cy3-labeled rRNA probes, aiding the identification of Alexandrium fundyense (syn. A. tamarense Group I), a photosynthetic dinoflagellate that causes paralytic shellfish poisoning (PSP). The modified IFCB was used to analyze samples from the development, peak and termination phases of an inshore A. fundyense bloom (Salt Pond, Eastham, MA, USA), and from a rare A. fundyense ‘red tide’ that occurred in the western Gulf of Maine, offshore of Portsmouth, NH (USA). Diploid or G2 phase (‘2C’) A. fundyense cells were frequently enriched at the near-surface, suggesting an important role for aggregation at the air-sea interface during sexual events. Also, our analysis showed that large proportions of A. fundyense cells in both the Salt Pond and red tide blooms were planozygotes during bloom decline, highlighting the importance of sexual fusion to bloom termination. At Salt Pond, bloom decline also coincided with a dramatic rise in infections by the parasite genus Amoebophrya. The samples that were most heavily infected contained many large cells with higher DNA-associated fluorescence than 2C vegetative cells, but these cells' nuclei were also frequently consumed by Amoebophrya trophonts. Neither large cell size nor increased DNA-associated fluorescence could be replicated by infecting an A. fundyense culture of vegetative cells. Therefore, we attribute these characteristics of the large Salt Pond cells to planozygote maturation rather than Amoebophrya infection, though an interaction between infection and planozygote maturation may

  10. Anisotropic phase diagram and spin fluctuations of the hyperkagome magnet Gd3Ga5O12 as revealed by sound velocity measurements

    Science.gov (United States)

    Rousseau, Alexandre; Parent, Jean-Michel; Quilliam, Jeffrey A.

    2017-08-01

    Sound velocity and attenuation measurements on the frustrated garnet material Gd3Ga5O12 (GGG) are presented as a function of field and temperature, with two different magnetic field orientations: [100 ] and [110 ] . We demonstrate that the phase diagram is highly anisotropic, with two distinct field-induced ordered phases for H ||[110 ] and only one for H ||[100 ] . Extensive lattice softening is found to occur at low fields, which can be associated with spin fluctuations. However, deep within the spin liquid phase a low-temperature stiffening of the lattice and reduced attenuation provide evidence for a spin gap which may be related to short-range antiferromagnetic correlations over minimal ten-spin loops.

  11. An optimized method for measuring hypocretin-1 peptide in the mouse brain reveals differential circadian regulation of hypocretin-1 levels rostral and caudal to the hypothalamus

    DEFF Research Database (Denmark)

    Justinussen, Jessica; Holm, A; Kornum, B R

    2015-01-01

    The hypocretin/orexin system regulates, among other things, sleep and energy homeostasis. The system is likely regulated by both homeostatic and circadian mechanisms. Little is known about local differences in the regulation of hypocretin activity. The aim of this study was to establish...... an optimized peptide quantification method for hypocretin-1 extracted from different mouse brain areas and use this method for investigating circadian fluctuations of hypocretin-1 levels in these areas. The results show that hypocretin-1 peptide can be extracted from small pieces of intact tissue......, with sufficient yield for measurements in a standard radioimmunoassay. Utilizing the optimized method, it was found that prepro-hypocretin mRNA and peptide show circadian fluctuations in the mouse brain. This study further demonstrates that the hypocretin-1 peptide level in the frontal brain peaks during dark...

  12. Compaction and gas loss in welded pyroclastic deposits as revealed by porosity, permeability, and electrical conductivity measurements of the Shevlin Park Tuff

    Science.gov (United States)

    Wright, Heather M.; Cashman, Katharine V.

    2014-01-01

    Pyroclastic flows produced by large volcanic eruptions commonly densify after emplacement. Processes of gas escape, compaction, and welding in pyroclastic-flow deposits are controlled by the physical and thermal properties of constituent material. Through measurements of matrix porosity, permeability, and electrical conductivity, we provide a framework for understanding the evolution of pore structure during these processes. Using data from the Shevlin Park Tuff in central Oregon, United States, and from the literature, we find that over a porosity range of 0%–70%, matrix permeability varies by almost 10 orders of magnitude (from 10–20 to 10–11 m2), with over three orders of magnitude variation at any given porosity. Part of the variation at a given porosity is due to permeability anisotropy, where oriented core samples indicate higher permeabilities parallel to foliation (horizontally) than perpendicular to foliation (vertically). This suggests that pore space is flattened during compaction, creating anisotropic crack-like networks, a geometry that is supported by electrical conductivity measurements. We find that the power law equation: k1 = 1.3 × 10–21 × ϕ5.2 provides the best approximation of dominant horizontal gas loss, where k1 = permeability, and ϕ = porosity. Application of Kozeny-Carman fluid-flow approximations suggests that permeability in the Shevlin Park Tuff is controlled by crack- or disk-like pore apertures with minimum widths of 0.3 and 7.5 μm. We find that matrix permeability limits compaction over short times, but deformation is then controlled by competition among cooling, compaction, water resorption, and permeable gas escape. These competing processes control the potential for development of overpressure (and secondary explosions) and the degree of welding in the deposit, processes that are applicable to viscous densification of volcanic deposits in general. Further, the general relationships among porosity, permeability, and

  13. Air-sea interaction regimes in the sub-Antarctic Southern Ocean and Antarctic marginal ice zone revealed by icebreaker measurements

    Science.gov (United States)

    Yu, Lisan; Jin, Xiangze; Schulz, Eric W.; Josey, Simon A.

    2017-08-01

    This study analyzed shipboard air-sea measurements acquired by the icebreaker Aurora Australis during its off-winter operation in December 2010 to May 2012. Mean conditions over 7 months (October-April) were compiled from a total of 22 ship tracks. The icebreaker traversed the water between Hobart, Tasmania, and the Antarctic continent, providing valuable in situ insight into two dynamically important, yet poorly sampled, regimes: the sub-Antarctic Southern Ocean and the Antarctic marginal ice zone (MIZ) in the Indian Ocean sector. The transition from the open water to the ice-covered surface creates sharp changes in albedo, surface roughness, and air temperature, leading to consequential effects on air-sea variables and fluxes. Major effort was made to estimate the air-sea fluxes in the MIZ using the bulk flux algorithms that are tuned specifically for the sea-ice effects, while computing the fluxes over the sub-Antarctic section using the COARE3.0 algorithm. The study evidenced strong sea-ice modulations on winds, with the southerly airflow showing deceleration (convergence) in the MIZ and acceleration (divergence) when moving away from the MIZ. Marked seasonal variations in heat exchanges between the atmosphere and the ice margin were noted. The monotonic increase in turbulent latent and sensible heat fluxes after summer turned the MIZ quickly into a heat loss regime, while at the same time the sub-Antarctic surface water continued to receive heat from the atmosphere. The drastic increase in turbulent heat loss in the MIZ contrasted sharply to the nonsignificant and seasonally invariant turbulent heat loss over the sub-Antarctic open water.Plain Language SummaryThe icebreaker Aurora Australis is a research and supply vessel that is regularly chartered by the Australian Antarctic Division during the southern summer to operate in waters between Hobart, Tasmania, and Antarctica. The vessel serves as the main lifeline to three permanent research stations on the

  14. THE BURSTY STAR FORMATION HISTORIES OF LOW-MASS GALAXIES AT 0.4 < z < 1 REVEALED BY STAR FORMATION RATES MEASURED FROM H β AND FUV

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Yicheng; Faber, S. M.; Koo, David C.; Krumholz, Mark R.; Barro, Guillermo; Yesuf, Hassen [UCO/Lick Observatory, Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA (United States); Rafelski, Marc; Gardner, Jonathan P.; Pacifici, Camilla [Goddard Space Flight Center, Code 665, Greenbelt, MD (United States); Trump, Jonathan R. [Department of Astronomy and Astrophysics and Institute for Gravitation and the Cosmos, Pennsylvania State University, University Park, PA (United States); Willner, S. P. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States); Amorín, Ricardo [INAF-Osservatorio Astronomico di Roma, Monte Porzio Catone (Italy); Bell, Eric F. [Department of Astronomy, University of Michigan, Ann Arbor, MI (United States); Gawiser, Eric [Department of Physics and Astronomy, Rutgers University, New Brunswick, NJ (United States); Hathi, Nimish P. [Aix Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, Marseille (France); Koekemoer, Anton M.; Ravindranath, Swara [Space Telescope Science Institute, Baltimore, MD (United States); Pérez-González, Pablo G. [Departamento de Astrofísica, Facultad de CC. Físicas, Universidad Complutense de Madrid, E-28040 Madrid (Spain); Reddy, Naveen [Department of Physics and Astronomy, University of California, Riverside, CA (United States); Teplitz, Harry I., E-mail: ycguo@ucolick.org [Infrared Processing and Analysis Center, Caltech, Pasadena, CA 91125 (United States)

    2016-12-10

    We investigate the burstiness of star formation histories (SFHs) of galaxies at 0.4 <  z  < 1 by using the ratio of star formation rates (SFRs) measured from H β and FUV (1500 Å) (H β -to-FUV ratio). Our sample contains 164 galaxies down to stellar mass ( M {sub *}) of 10{sup 8.5} M {sub ⊙} in the CANDELS GOODS-N region, where Team Keck Redshift Survey Keck/DEIMOS spectroscopy and Hubble Space Telescope /WFC3 F275W images from CANDELS and Hubble Deep UV Legacy Survey are available. When the ratio of H β - and FUV-derived SFRs is measured, dust extinction correction is negligible (except for very dusty galaxies) with the Calzetti attenuation curve. The H β -to-FUV ratio of our sample increases with M {sub *} and SFR. The median ratio is ∼0.7 at M {sub *} ∼ 10{sup 8.5} M {sub ⊙} (or SFR ∼ 0.5 M {sub ⊙} yr{sup −1}) and increases to ∼1 at M {sub *} ∼ 10{sup 10} M {sub ⊙} (or SFR ∼ 10 M {sub ⊙} yr{sup −1}). At M {sub *} < 10{sup 9.5} M {sub ⊙}, our median H β -to-FUV ratio is lower than that of local galaxies at the same M {sub *}, implying a redshift evolution. Bursty SFH on a timescale of a few tens of megayears on galactic scales provides a plausible explanation for our results, and the importance of the burstiness increases as M {sub *} decreases. Due to sample selection effects, our H β -to-FUV ratio may be an upper limit of the true value of a complete sample, which strengthens our conclusions. Other models, e.g., non-universal initial mass function or stochastic star formation on star cluster scales, are unable to plausibly explain our results.

  15. Effect of aging on phosphate metabolites of rat brain as revealed by the in vivo and in vitro 31P NMR measurements

    International Nuclear Information System (INIS)

    Liu, Hsiuchih; Chi, Chinwen; Liu, Tsungyun; Liu, Lianghui; Luh, Wenming; Hsieh, Changhuain; Wu, Wenguey

    1991-01-01

    Changes of phosphate metabolism in brains of neonate, weaning and adult rats were compared using both in vivo and in vitro nuclear magnetic resonance spectra. Ratios of phosphocreatine/nucleoside triphosphate (PCr/NTP) were the same in neonatal brain in both in vivo and in vitro studies, but not in weaning and adult brains. This discrepancy may have resulted from extended cerebral hypoxia due to slowed freezing of the brain by the increased skull thickness and brain mass in the weaning and adult rats. Variations of in vitro extraction condition for this age-related study may lead to systematic errors in the adult rats. Nevertheless, the phosphomonoester/nucleoside triphosphate (PME/NTP) ratios in extracts of brain from neonatal rats were higher than those obtained in vivo. In addition, the glycerophosphorylethanolamine plus glycerophosphorylcholine/nucleoside triphosphate (GPE+GPC/NTP) ratios, which were not measurable in vivo, showed age-dependent increase in extracts of rat brain. Some of the phosphomonoester and phosphodiester molecules in rat brain may be undetectable in in vivo NMR analysis because of their interaction with cellular components. The total in vitro GPE and GPC concentration in brain from neonatal rat was estimated to be 0.34 mmole/g wet tissue

  16. An optimized method for measuring hypocretin-1 peptide in the mouse brain reveals differential circadian regulation of hypocretin-1 levels rostral and caudal to the hypothalamus.

    Science.gov (United States)

    Justinussen, J L; Holm, A; Kornum, B R

    2015-12-03

    The hypocretin/orexin system regulates, among other things, sleep and energy homeostasis. The system is likely regulated by both homeostatic and circadian mechanisms. Little is known about local differences in the regulation of hypocretin activity. The aim of this study was to establish an optimized peptide quantification method for hypocretin-1 extracted from different mouse brain areas and use this method for investigating circadian fluctuations of hypocretin-1 levels in these areas. The results show that hypocretin-1 peptide can be extracted from small pieces of intact tissue, with sufficient yield for measurements in a standard radioimmunoassay. Utilizing the optimized method, it was found that prepro-hypocretin mRNA and peptide show circadian fluctuations in the mouse brain. This study further demonstrates that the hypocretin-1 peptide level in the frontal brain peaks during dark as does prepro-hypocretin mRNA in the hypothalamus. However, in midbrain and brainstem tissue caudal to the hypothalamus, there was less circadian fluctuation and a tendency for higher levels during the light phase. These data suggest that regulation of the hypocretin system differs between brain areas. Copyright © 2015 IBRO. Published by Elsevier Ltd. All rights reserved.

  17. Atmospheric boundary layer structures associated with the Ora del Garda wind in the Alps as revealed from airborne and surface measurements

    Science.gov (United States)

    Laiti, Lavinia; Zardi, Dino; de Franceschi, Massimiliano; Rampanelli, Gabriele

    2013-10-01

    The paper investigates a coupled lake-breeze and valley-wind system, known as Ora del Garda. The latter typically originates on clear-sky days over the northern shore of Lake Garda in the Alps. After channelling into the nearby Sarca Valley and Lakes Valley, this airflow finally breaks out, through an elevated saddle, into the adjacent Adige Valley, where it strongly interacts with the local valley wind. Two flights of an instrumented motorglider explored, under different synoptic conditions, the thermal structure of the atmospheric boundary layer (ABL) associated with this wind at selected vertical sections-namely over the lake shore, at mid-valley, and at the junction with the Adige Valley. Data from airborne measurements, as well as from weather stations disseminated along the valley floor, provided the basis for mapping 3D fields of potential temperature over high-resolution grids by means of a Residual Kriging (RK) technique. This representation allowed the identification of site-specific ABL features associated with the Ora del Garda. In particular, a typical daytime coastal-breeze structure is detected in the lake shore region, where the advection of colder air tends to stabilize the atmosphere throughout the ABL depth. Mid-valley vertical profiles from both flights display shallow convective mixed layers, surmounted by deeper weakly stable layers. On the other hand, RK-gridded temperature maps show cross-valley thermal asymmetries, amenable to the complex topography and to the inhomogeneous surface coverage, as well as to a curvature of the valley axis. Finally, in the area where the upper Lakes Valley joins the Adige Valley, specific features associated with the complex interaction between the Ora del Garda and the local up-valley wind are found.

  18. Long-term behavior of the Kelvin waves revealed by CHAMP/GPS RO measurements and their effects on the tropopause structure

    Directory of Open Access Journals (Sweden)

    M. Venkat Ratnam

    2006-07-01

    Full Text Available The vertical and temporal variations of Kelvin waves and the associated effects on the tropical tropopause were studied using long-term (from May 2001 to October 2005 CHAMP/GPS (CHAllenging Mini satellite Payload/Global Positioning System radio occultation (RO measurements. The periods of these waves were found to be varying in between 10 and 15 days, with vertical wavelengths 5–8 km. These variations clearly show eastward phase propagation in the time-longitude section and eastward phase tilts with height in altitude-longitude, displaying the characteristics of Kelvin waves. The peak variance in the temperature is found over the Indian Ocean and into the western Pacific within the broad region of the equator. Kelvin wave amplitudes were found significantly enhanced in the eastward shear of the quasi-biennial oscillation (QBO and are confined in and around the tropopause during westward phase of QBO, where it extends between 17 and 25 km during the eastward phase of QBO and is damped away above, consistent with earlier reported results. The amplitudes are increasing during the months of Northern Hemisphere winter and sometimes they are highly sporadic in nature. Seasonal and inter-annual variations in the Kelvin wave amplitudes near the tropical tropopause coincide exactly with the tropopause height and temperature, with a sharp tropopause during maximum Kelvin wave activity. A clear annual oscillation, along with a month-to-month coincidence is evident most of the time in both the tropopause height and Kelvin wave activity, with maximum and minimum Kelvin wave amplitudes during the Northern Hemisphere winter and summer, respectively. In addition, a signature of quasi-biennial oscillation (QBO in the tropopause structure is also seen in long-term tropopause variations, although the amplitudes are less when compared to the annual oscillation. In the westward phase of QBO (during strong Kelvin wave activity at 20km (in 2001–2002 winter and

  19. Nuclear spin polarized alkali beams (Li and Na): Production and acceleration

    International Nuclear Information System (INIS)

    Jaensch, H.; Becker, K.; Blatt, K.; Leucker, H.; Fick, D.

    1987-01-01

    Recent improvements of the Heidelberg source for polarized heavy ions (PSI) are described. By means of optical pumping in combination with the existing multipole separation magnet the beam figure of merit (polarization 2 x intensity) was doubled. 7 Li and 23 Na atomic beams can now be produced in pure hyperfine magnetic substates. Fast switching of the polarization is achieved by an adiabatic medium field transition. The hyperfine magnetic substate population is determined by laser-induced fluorescence spectroscopy. In routine operation atomic beams with nuclear polarization p α ≥0.85 (α=z, zz) are obtained. The acceleration of polarized 23 Na - ions by a 12 MV tandem accelerator introduces a new problem: the energy at the terminal stripper foil is not sufficient to produce a usable yield of naked ions. For partially stripped ions hyperfine interaction of the remaining electrons with the nuclear spin reduces the nuclear polarization. Using in addition the Heidelberg postaccelerator 23 Na 9+ beams of energies between 49 and 184 MeV were obtained with an alignment on target of P zz ≅0.45. 7 Li beams have also been accelerated up to 45 MeV with an alignment of P zz =0.69. (orig.)

  20. Effect of orbital hybridization on spin-polarized tunneling across Co/C60 interfaces

    NARCIS (Netherlands)

    Wang, Kai; Strambini, Elia; Sanderink, Johannes G.M.; Bolhuis, Thijs; van der Wiel, Wilfred Gerard; de Jong, Machiel Pieter

    2016-01-01

    The interaction between ferromagnetic surfaces and organic semiconductors leads to the formation of hybrid interfacial states. As a consequence, the local magnetic moment is altered, a hybrid interfacial density of states (DOS) is formed, and spin-dependent shifts of energy levels occur. Here, we

  1. Spin-polarized transport properties of a pyridinium-based molecular spintronics device

    Science.gov (United States)

    Zhang, J.; Xu, B.; Qin, Z.

    2018-05-01

    By applying a first-principles approach based on non-equilibrium Green's functions combined with density functional theory, the transport properties of a pyridinium-based "radical-π-radical" molecular spintronics device are investigated. The obvious negative differential resistance (NDR) and spin current polarization (SCP) effect, and abnormal magnetoresistance (MR) are obtained. Orbital reconstruction is responsible for novel transport properties such as that the MR increases with bias and then decreases and that the NDR being present for both parallel and antiparallel magnetization configurations, which may have future applications in the field of molecular spintronics.

  2. Beamline for Photoemission Spectromicroscopy and Spin Polarized Microscopy with Slow Electrons at CESLAB

    Czech Academy of Sciences Publication Activity Database

    Frank, Luděk

    2008-01-01

    Roč. 15, č. 1 (2008), s. 111-112 ISSN 1210-8529 Institutional research plan: CEZ:AV0Z20650511 Keywords : CESLAB * beamline * LEEM/PEEM Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering

  3. Study of mechanical compression of spin-polarized 3He gas

    International Nuclear Information System (INIS)

    Becker, J.; Heil, W.; Krug, B.; Leduc, M.; Meyerhoff, M.; Nacher, P.J.; Otten, E.W.; Prokscha, T.; Schearer, L.D.; Surkau, R.

    1994-01-01

    We have piloted mechanical compression of spinpolarized 3He by a titanium piston compressor. Questions of materials and design are discussed, followed by a thorough investigation of relaxation sources in the course of compression. The latter are traced mainly to regions with large surface to volume ratio, through which fast passage is demanded, therefore. We conclude from this feasibility study that polarized 3He may be compressed this way up to many bars without serious polarization losses. ((orig.))

  4. Manipulating NiFe/AlOx interfacial chemistry for the spin-polarized electrons transport

    International Nuclear Information System (INIS)

    Zhao, Chong-Jun; Sun, Li; Ding, Lei; Li, Jian-Wei; Zhang, Jing-Yan; Cao, Yi; Yu, Guang-Hua

    2013-01-01

    Through vacuum annealing, interfacial chemical composition of sputter-deposited AlO x /NiFe/AlO x can be controlled for electron transport manipulation. Chemical status change at the NiFe/AlO x interface was quantified by X-ray photoelectron spectroscopy and correlated to the structure and electron transport properties of the heterostructure. It is found that elemental Al existed in the insulting AlO x after annealing at intermediate temperature can improve the AlO x /NiFe interface and thus favor the electronic transport. Annealing at higher temperature will result in native AlO x formation and degrade transport properties due to the NiFe/AlO x interfaces deterioration caused by significant difference in thermal expansion coefficients of the two materials.

  5. Spin polarization in high density quark matter under a strong external magnetic field

    DEFF Research Database (Denmark)

    Tsue, Yasuhiko; Da Providência, João; Providência, Constança

    2016-01-01

    In high density quark matter under a strong external magnetic field, possible phases are investigated by using the two-flavor Nambu-Jona-Lasinio (NJL) model with tensor-type four-point interaction between quarks, as well as the axial-vector-type four-point interaction. In the tensor-type interact......In high density quark matter under a strong external magnetic field, possible phases are investigated by using the two-flavor Nambu-Jona-Lasinio (NJL) model with tensor-type four-point interaction between quarks, as well as the axial-vector-type four-point interaction. In the tensor...... phase appears in the wide range of the quark chemical potential. In both the interactions, the quark mass in zero and small chemical potential regions increases which indicates that the chiral symmetry breaking is enhanced, namely the magnetic catalysis occurs....

  6. Influence of doping admixture and anisotropic tension on behaviour of muon spin polarization in insulators

    International Nuclear Information System (INIS)

    Gorelkin, V.N.; Rubtsov, D.V.

    1997-01-01

    We investigate the model describing a muon tunneling between two equivalent positions in (magnetic) insulators. Crystals are assumed to have concentrations such that the muon tunneling states in a double well potential can be considered as real during the muon lifetime τ μ . In the simplest model there are only two such states: the ground state and the first excited state. Our aim is to calculate lifetimes τ 1 (T) and τ 0 (T) of these muon tunneling states resulting from interaction between the muon and phonons of the sample. In the case of a distorted double well potential, all matrix elements of H-circumflex (ph) int are finite. This leads to rescaling of the first and second orders of the perturbation theory compared with the results for the muon in 'pure' samples. We explain the vanishing of some part of the oscillation frequencies of the muon polarization vector in the framework of a muon-phonon interaction model: for example, it is necessary to take into account that τ 1 (T) decreases more rapidly than τ 0 (T) when the temperature increases. If the muon tunnels through a set of equivalent interstitial positions in a unit cell, the experimental picture of the polarization vector behaviour can change drastically under the action of various strain fields

  7. A laser driven source of spin polarized atomic hydrogen and deuterium

    International Nuclear Information System (INIS)

    Poelker, M.; Coulter, K.P.; Holt, R.J.; Jones, C.E.; Kowalczyk, R.S.; Young, L.; Toporkov, D.

    1993-01-01

    Recent results from a laser-driven source of polarized hydrogen (H) and deuterium (D) are presented. The performance of the source is described as a function of atomic flow rate and magnetic field. The data suggest that because atomic densities in the source are high, the system can approach spin-temperature equilibrium although applied magnetic fields are much larger than the critical field of the atoms. The authors also observe that potassium contamination in the source emittance can be reduced to a negligible amount using a teflon-lined transport tube

  8. Spin-filtering junctions with double ferroelectric barriers

    International Nuclear Information System (INIS)

    Yan, Ju; Ding-Yu, Xing

    2009-01-01

    An FS/FE/NS/FE/FS double tunnel junction is suggested to have the ability to inject, modulate and detect the spin-polarized current electrically in a single device, where FS is the ferromagnetic semiconductor electrode, NS is the nonmagnetic semiconductor, and FE the ferroelectric barrier. The spin polarization of the current injected into the NS region can be switched between a highly spin-polarized state and a spin unpolarized state. The high spin polarization may be detected by measuring the tunneling magnetoresistance ratio of the double tunnel junction

  9. Interplays of μSR, susceptibility, and neutron studies on dilute-alloy spin glasses

    International Nuclear Information System (INIS)

    Uemura, Y.J.

    1983-04-01

    Static spin polarization of Fe moments in a spin glass AuFe, determined by zero-field μSR, is compared to an ac-susceptibility measurement below the cusp temperature T/sub g/, and a rather uniform amplitude of the static polarization is pointed out for frozen spins. Completely random orientation of frozen spins is revealed by neutron scattering in a dilute 1% CuMn, and an importance of comparing results of these different methods is demonstrated

  10. Measurement of single-top cross section and test of anomalous $Wtb$ coupling

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Ji-Eun [Seoul National Univ. (Korea, Republic of)

    2010-01-01

    The top quark is most often produced in tt pairs via the strong interaction, however electroweak production of a singly-produced top quark is also possible. Electroweak single-top production is more difficult to observe than tt production. Studying single-top production is important for the following reasons. It provides direct measurement of the CKM matrix element and also single-top events are a background to several searches for SM or non-SM signals, such as Higgs boson searches. The information of spin polarization of top-quark can be used to t est anomalous W-t-b coupling. This thesis describes the result of a measurement of single-top cross-section and a test of anomalous W-t-b coupling using 4.8 f b-1 of data collected by the CDF Run II experiment at the Fermilab Tevatron. The measured cross-section is 1.83$+0.7\\atop{-0.6}$ pb and measured limit of |Vtb| is 0.41 at 95% CL. The fraction of V+A coupling is 0 ± 28 (%).

  11. Size effects in van der Waals clusters studied by spin and angle-resolved electron spectroscopy and multi-coincidence ion imaging

    International Nuclear Information System (INIS)

    Rolles, D; Pesic, Z D; Zhang, H; Bilodeau, R C; Bozek, J D; Berrah, N

    2007-01-01

    We have studied the valence and inner-shell photoionization of free rare-gas clusters by means of angle and spin resolved photoelectron spectroscopy and momentum resolving electron-multi-ion coincidence spectroscopy. The electron measurements probe the evolution of the photoelectron angular distribution and spin polarization parameters as a function of photon energy and cluster size, and reveal a strong cluster size dependence of the photoelectron angular distributions in certain photon energy regions. In contrast, the spin polarization parameter of the cluster photoelectrons is found to be very close to the atomic value for all covered photon energies and cluster sizes. The ion imaging measurements, which probe the fragmentation dynamics of multiply charged van der Waals clusters, also exhibit a pronounced cluster size dependence

  12. Structure, magnetic ordering, and spin filtering efficiency of NiFe{sub 2}O{sub 4}(111) ultrathin films

    Energy Technology Data Exchange (ETDEWEB)

    Matzen, S.; Moussy, J.-B., E-mail: jean-baptiste.moussy@cea.fr [CEA, IRAMIS, SPCSI, F-91191 Gif-sur-Yvette (France); Wei, P. [Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Gatel, C. [CEMES-CNRS, F-31055 Toulouse (France); Cezar, J. C. [ESRF, F-38043 Grenoble (France); Arrio, M. A.; Sainctavit, Ph. [IMPMC, F-75015 Paris (France); Moodera, J. S. [Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Physics Department, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2014-05-05

    NiFe{sub 2}O{sub 4}(111) ultrathin films (3–5 nm) have been grown by oxygen-assisted molecular beam epitaxy and integrated as effective spin-filter barriers. Structural and magnetic characterizations have been performed in order to investigate the presence of defects that could limit the spin filtering efficiency. These analyses have revealed the full strain relaxation of the layers with a cationic order in agreement with the inverse spinel structure but also the presence of antiphase boundaries. A spin-polarization up to +25% has been directly measured by the Meservey-Tedrow technique in Pt(111)/NiFe{sub 2}O{sub 4}(111)/γ-Al{sub 2}O{sub 3}(111)/Al tunnel junctions. The unexpected positive sign and relatively small value of the spin-polarization are discussed, in comparison with predictions and previous indirect tunnelling magnetoresistance measurements.

  13. A Two-Dimensional Manganese Gallium Nitride Surface Structure Showing Ferromagnetism at Room Temperature.

    Science.gov (United States)

    Ma, Yingqiao; Chinchore, Abhijit V; Smith, Arthur R; Barral, María Andrea; Ferrari, Valeria

    2018-01-10

    Practical applications of semiconductor spintronic devices necessitate ferromagnetic behavior at or above room temperature. In this paper, we demonstrate a two-dimensional manganese gallium nitride surface structure (MnGaN-2D) which is atomically thin and shows ferromagnetic domain structure at room temperature as measured by spin-resolved scanning tunneling microscopy and spectroscopy. Application of small magnetic fields proves that the observed magnetic domains follow a hysteretic behavior. Two initially oppositely oriented MnGaN-2D domains are rotated into alignment with only 120 mT and remain mostly in alignment at remanence. The measurements are further supported by first-principles theoretical calculations which reveal highly spin-polarized and spin-split surface states with spin polarization of up to 95% for manganese local density of states.

  14. Graphene mediated domain formation in exchange coupled graphene/Co3O4(111)/Co(0001) trilayers.

    Science.gov (United States)

    Wang, Yi; Kong, Lingmei; Pasquale, Frank L; Cao, Yuan; Dong, Bin; Tanabe, Iori; Binek, Christian; Dowben, Peter A; Kelber, Jeffry A

    2013-11-27

    Graphene grown directly on Co3O4(111)/Co(0001) by molecular beam epitaxy exhibits extrinsic p-type doping, as demonstrated by photoemission and conductivity measurements. Trilayer heterostructures of graphene/Co3O4(111)/Co(0001) reveal an unconventional magneto-optical Kerr hysteresis with vanishing remanence for temperatures up to 400 K. Magnetic force microscopy measurements demonstrate that the vanishing remanence is due to a complex domain state, indicating substrate-induced graphene spin polarization. The domain formation of the Co magnetization is in strong contrast to the magnetic behavior of Co in Co/Co3O4 bilayers. This suggests that the Co3O4 interlayer mediates the variable Co magnetization and induced graphene spin polarization, with possible retroaction of graphene on the Co film.

  15. Optics measurement and correction during beam acceleration in the Relativistic Heavy Ion Collider

    Energy Technology Data Exchange (ETDEWEB)

    Liu, C. [Brookhaven National Lab. (BNL), Upton, NY (United States). Collider-Accelerator Dept.; Marusic, A. [Brookhaven National Lab. (BNL), Upton, NY (United States). Collider-Accelerator Dept.; Minty, M. [Brookhaven National Lab. (BNL), Upton, NY (United States). Collider-Accelerator Dept.

    2014-09-09

    To minimize operational complexities, setup of collisions in high energy circular colliders typically involves acceleration with near constant β-functions followed by application of strong focusing quadrupoles at the interaction points (IPs) for the final beta-squeeze. At the Relativistic Heavy Ion Collider (RHIC) beam acceleration and optics squeeze are performed simultaneously. In the past, beam optics correction at RHIC has taken place at injection and at final energy with some interpolation of corrections into the acceleration cycle. Recent measurements of the beam optics during acceleration and squeeze have evidenced significant beta-beats which if corrected could minimize undesirable emittance dilutions and maximize the spin polarization of polarized proton beams by avoidance of higher-order multipole fields sampled by particles within the bunch. In this report the methodology now operational at RHIC for beam optics corrections during acceleration with simultaneous beta-squeeze will be presented together with measurements which conclusively demonstrate the superior beam control. As a valuable by-product, the corrections have minimized the beta-beat at the profile monitors so reducing the dominant error in and providing more precise measurements of the evolution of the beam emittances during acceleration.

  16. Multichannel spin polarimeter for energy- and angle-dispersive photoemission measurements; Vielkanal-Spinpolarimeter fuer energie- und winkeldispersive Photoemissionsmessungen

    Energy Technology Data Exchange (ETDEWEB)

    Kolbe, Michaela

    2011-09-09

    Spin polarization measurements of free electrons remain challenging since their first realization by Mott. The relevant quantity of a spin polarimeter is its figure of merit, FoM=S{sup 2}I/I{sub 0}, with the asymmetry function S and the ratio between scattered and primary intensity I/I{sub 0}. State-of-the-art devices are based on single-channel scattering (spin-orbit or exchange interaction) which is characterized by FoM {approx_equal}10{sup -4}. On the other hand, modern hemispherical analyzers feature an efficient multichannel detection of spin-integral intensity with more than 10{sup 4} data points simultaneously. In comparison between spin-resolved and spin-integral electron spectroscopy we are thus faced with a difference in counting efficiency by 8 orders of magnitude. The present work concentrates on the development and investigation of a novel technique for increasing the efficiency in spin-resolved electron spectroscopy by multichannel detection. The spin detector was integrated in a {mu}-metal shielded UHV-chamber and mounted behind a conventional hemispherical analyzer. The electrostatic lens system's geometry was determined by electron-optical simulations. The basic concept is the k {sub parallel} -conserving elastic scattering of the (0,0)-beam on a W(100) scattering crystal under 45 impact angle. It could be demonstrated that app. 960 data points (15 energy and 64 angular points) could be displayed simultaneously on a delayline detector in an energy interval of {approx_equal}3 eV. This leads to a two-dimensional figure of merit of FoM{sub 2D}=1.7. Compared to conventional spin detectors, the new type is thus characterized by a gain in efficiency of 4 orders of magnitude. The operational reliability of the new spin polarimeter could be proven by measurements with a Fe/MgO(100) and O p(1 x 1)/Fe(100)-sample, where results from the literature were reproduced with strongly decreased measuring time. Due to the high intensity it becomes possible, to

  17. Optically polarized 3He

    Science.gov (United States)

    Gentile, T. R.; Nacher, P. J.; Saam, B.; Walker, T. G.

    2018-01-01

    This article reviews the physics and technology of producing large quantities of highly spin-polarized 3He nuclei using spin-exchange (SEOP) and metastability-exchange (MEOP) optical pumping. Both technical developments and deeper understanding of the physical processes involved have led to substantial improvements in the capabilities of both methods. For SEOP, the use of spectrally narrowed lasers and K-Rb mixtures has substantially increased the achievable polarization and polarizing rate. For MEOP nearly lossless compression allows for rapid production of polarized 3He and operation in high magnetic fields has likewise significantly increased the pressure at which this method can be performed, and revealed new phenomena. Both methods have benefitted from development of storage methods that allow for spin-relaxation times of hundreds of hours, and specialized precision methods for polarimetry. SEOP and MEOP are now widely applied for spin-polarized targets, neutron spin filters, magnetic resonance imaging, and precision measurements. PMID:29503479

  18. Optically polarized 3He

    Science.gov (United States)

    Gentile, T. R.; Nacher, P. J.; Saam, B.; Walker, T. G.

    2017-10-01

    This article reviews the physics and technology of producing large quantities of highly spin-polarized 3He nuclei using spin-exchange (SEOP) and metastability-exchange (MEOP) optical pumping. Both technical developments and deeper understanding of the physical processes involved have led to substantial improvements in the capabilities of both methods. For SEOP, the use of spectrally narrowed lasers and K-Rb mixtures has substantially increased the achievable polarization and polarizing rate. For MEOP nearly lossless compression allows for rapid production of polarized 3He and operation in high magnetic fields has likewise significantly increased the pressure at which this method can be performed, and revealed new phenomena. Both methods have benefitted from development of storage methods that allow for spin-relaxation times of hundreds of hours, and specialized precision methods for polarimetry. SEOP and MEOP are now widely applied for spin-polarized targets, neutron spin filters, magnetic resonance imaging, and precision measurements.

  19. Majorana spin in magnetic atomic chain systems

    Science.gov (United States)

    Li, Jian; Jeon, Sangjun; Xie, Yonglong; Yazdani, Ali; Bernevig, B. Andrei

    2018-03-01

    In this paper, we establish that Majorana zero modes emerging from a topological band structure of a chain of magnetic atoms embedded in a superconductor can be distinguished from trivial localized zero energy states that may accidentally form in this system using spin-resolved measurements. To demonstrate this key Majorana diagnostics, we study the spin composition of magnetic impurity induced in-gap Shiba states in a superconductor using a hybrid model. By examining the spin and spectral densities in the context of the Bogoliubov-de Gennes (BdG) particle-hole symmetry, we derive a sum rule that relates the spin densities of localized Shiba states with those in the normal state without superconductivity. Extending our investigations to a ferromagnetic chain of magnetic impurities, we identify key features of the spin properties of the extended Shiba state bands, as well as those associated with a localized Majorana end mode when the effect of spin-orbit interaction is included. We then formulate a phenomenological theory for the measurement of the local spin densities with spin-polarized scanning tunneling microscopy (STM) techniques. By combining the calculated spin densities and the measurement theory, we show that spin-polarized STM measurements can reveal a sharp contrast in spin polarization between an accidental-zero-energy trivial Shiba state and a Majorana zero mode in a topological superconducting phase in atomic chains. We further confirm our results with numerical simulations that address generic parameter settings.

  20. Measuring exchange interactions between atomic spins using electron spin resonance STM

    Science.gov (United States)

    Yang, Kai; Paul, William; Natterer, Fabian; Choi, Taeyoung; Heinrich, Andreas; Lutz, Christopher

    Exchange interactions between neighboring atoms give rise to magnetic order in magnetic materials. As the size of the electronic device is miniaturized toward the limit of single atoms, magnetic nanostructures such as coupled atomic dimers and clusters are explored more as prototypes for possible data storage, spintronics as well as quantum computing applications. Characterizing inter-atom exchange interactions calls for increasing spatial resolution and higher energy sensitivity to better understand this fundamental interaction. Here, using spin-polarized scanning tunneling microscopy (STM), we studied a magnetically coupled atomic dimer consisting of two 3d transition metal atoms, with one adsorbed on an insulating layer (MgO) and the other attached to the STM tip. We demonstrate the ability to measure the short-range exchange interaction between the two atomic spins with orders-of-magnitude variation ranging from milli-eV all the way to micro-eV. This is realized by the successful combination of inelastic electron tunneling spectroscopy (IETS) and electron spin resonance (ESR) techniques in STM implemented at different energy scales. We unambiguously confirm the exponential decay behavior of the direct exchange interaction.

  1. Polarization measurement of atomic hydrogen beam spin-exchanged with optically oriented sodium atoms

    International Nuclear Information System (INIS)

    Ueno, Akira; Ogura, Kouichi; Wakuta, Yoshihisa; Kumabe, Isao

    1988-01-01

    The spin-exchange reaction between hydrogen atoms and optically oriented sodium atoms was used to produce a polarized atomic hydrogen beam. The electron-spin polarization of the atomic hydrogen beam, which underwent the spin-exchange reaction with the optically oriented sodium atoms, was measured. A beam polarization of -(8.0±0.6)% was obtained when the thickness and polarization of the sodium target were (5.78±0.23)x10 13 atoms/cm 2 and -(39.6±1.6)%, respectively. The value of the spin-exchange cross section in the forward scattering direction, whose scattering angle in the laboratory system was less than 1.0 0 , was obtained from the experimental results as Δσ ex =(3.39±0.34)x10 -15 cm 2 . This value is almost seven times larger than the theoretical value calculated from the Na-H potential. The potential was computed quantum mechanically in the space of the appropriate wave functions of the hydrogen and the sodium atoms. (orig./HSI)

  2. Econometric models of road use, accidents, and road investment decisions. Volume 1 : introductory overview, the barely revealed preference behind road investment priorities (essay 1), measuring the contribution of randomness, exposure, weather, and daylig

    Science.gov (United States)

    1999-11-01

    This volume contains the forst part of the author's PhD dissertation, and includes an introductory overview as well as two essays. The first essay entitled "The barely revealed preference behind road investment priorities," co-authored by Rune Elvik,...

  3. Towards polarization measurements of laser-accelerated helium-3 ions

    Energy Technology Data Exchange (ETDEWEB)

    Engin, Ilhan

    2015-08-28

    In the framework of this thesis, preparatory investigations for the spin-polarization measurement of {sup 3}He ions from laser-induced plasmas have been performed. Therefore, experiments aiming at an efficient laser-induced ion acceleration out of a {sup 4}He gas target were carried out at two high-intensity laser facilities: the Arcturus laser at Heinrich-Heine-Universitaet Duesseldorf as well as PHELIX at GSI Darmstadt. The scientific goal of both experiments was to investigate the ion-acceleration process in underdense plasmas by measuring the ion energy spectra and the angular distribution of the ion signal around the gas-jet target. Laser-accelerated MeV-He-ions could successfully be detected. The main acceleration direction at large angles with regard to the laser propagation direction was determined. In a second step, unpolarized {sup 3}He gas was attached in order to cross-check the experimental results with those of {sup 4}He. With the help of the achieved ion yield data, the expected rates of the fusion reaction D({sup 3}He,p){sup 4}He in the polarized case have been estimated: the information regarding the fusion proton yield from this nuclear reaction allows an experimentally based estimation for future experiments with pre-polarized {sup 3}He gas as plasma target. The experimental data is in line with supporting Particle-in-Cell (PIC) simulations performed on the Juelich supercomputers. For this purpose, the simulated target was defined as a neutral gas. The use of pre-polarized {sup 3}He gas demands a special preparation of a polarized {sup 3}He target for laser-acceleration experiments. This layout includes an (external) homogeneous magnetic holding field (field strength of ∝1.4 mT) for storing the pre-polarized gas for long time durations inside the PHELIX target chamber. For this purpose, a precise Halbach array consisting of horizontally arranged rings with built-in permanent magnets had to be designed, optimized, and constructed to deliver high

  4. TypeScript revealed

    CERN Document Server

    Maharry, Dan

    2013-01-01

    TypeScript Revealed is a quick 100-page guide to Anders Hejlsberg's new take on JavaScript. With this brief, fast-paced introduction to TypeScript, .NET, Web and Windows 8 application developers who are already familiar with JavaScript will easily get up to speed with TypeScript and decide whether or not to start incorporating it into their own development. TypeScript is 'JavaScript for Application-scale development'; a superset of JavaScript that brings to it an additional object-oriented-like syntax familiar to .NET programmers that compiles down into simple, clean JavaScript that any browse

  5. Revealing the programming process

    DEFF Research Database (Denmark)

    Bennedsen, Jens; Caspersen, Michael Edelgaard

    2005-01-01

    One of the most important goals of an introductory programming course is that the students learn a systematic approach to the development of computer programs. Revealing the programming process is an important part of this; however, textbooks do not address the issue -- probably because...... the textbook medium is static and therefore ill-suited to expose the process of programming. We have found that process recordings in the form of captured narrated programming sessions are a simple, cheap, and efficient way of providing the revelation.We identify seven different elements of the programming...

  6. Android Emotions Revealed

    DEFF Research Database (Denmark)

    Vlachos, Evgenios; Schärfe, Henrik

    2012-01-01

    This work presents a method for designing facial interfaces for sociable android robots with respect to the fundamental rules of human affect expression. Extending the work of Paul Ekman towards a robotic direction, we follow the judgment-based approach for evaluating facial expressions to test...... in which case an android robot like the Geminoid|DK –a duplicate of an Original person- reveals emotions convincingly; when following an empirical perspective, or when following a theoretical one. The methodology includes the processes of acquiring the empirical data, and gathering feedback on them. Our...... findings are based on the results derived from a number of judgments, and suggest that before programming the facial expressions of a Geminoid, the Original should pass through the proposed procedure. According to our recommendations, the facial expressions of an android should be tested by judges, even...

  7. Chemistry of plutonium revealed

    International Nuclear Information System (INIS)

    Connick, R.E.

    1992-01-01

    In 1941 one goal of the Manhattan Project was to unravel the chemistry of the synthetic element plutonium as rapidly as possible. In this paper the work carried out at Berkeley from the spring of 1942 to the summer of 1945 is described briefly. The aqueous chemistry of plutonium is quite remarkable. Important insights were obtained from tracer experiments, but the full complexity was not revealed until macroscopic amounts (milligrams) became available. Because processes for separation from fission products were based on aqueous solutions, such solution chemistry was emphasized, particularly precipitation and oxidation-reduction behavior. The latter turned out to be unusually intricate when it was discovered that two more oxidation states existed in aqueous solution than had previously been suspected. Further, an equilibrium was rapidly established among the four aqueous oxidation states, while at the same time any three were not in equilibrium. These and other observations made while doing a crash study of a previously unknown element are reported

  8. In vivo measurement of cytosolic and mitochondrial pH using a pH-sensitive GFP derivative in Saccharomyces cerevisiae reveals a relation between intracellular pH and growth

    NARCIS (Netherlands)

    Orij, R.; Postmus, J.; ter Beek, A.; Brul, S.; Smits, G.J.

    2009-01-01

    The specific pH values of cellular compartments affect virtually all biochemical processes, including enzyme activity, protein folding and redox state. Accurate, sensitive and compartment-specific measurements of intracellular pH (pHi) dynamics in living cells are therefore crucial to the

  9. Selling Myths Revealed

    OpenAIRE

    Hopkins, Tom

    2017-01-01

    The true measure of the success of any business is the bottom line—sales minus cost of sales. That’s about as bare-bones as you can get when looking at it. Managing the cost of sales is an analytical process. It’s pretty much black and white. Managing sales, however, is a different matter.

  10. Direct measurement of Bisphenol A (BPA), BPA glucuronide and BPA sulfate in a diverse and low-income population of pregnant women reveals high exposure, with potential implications for previous exposure estimates: a cross-sectional study

    OpenAIRE

    Gerona, Roy R.; Pan, Janet; Zota, Ami R.; Schwartz, Jackie M.; Friesen, Matthew; Taylor, Julia A.; Hunt, Patricia A.; Woodruff, Tracey J.

    2016-01-01

    Background Bisphenol A (BPA) is a ubiquitous, endocrine-disrupting environmental contaminant that increases risk of some adverse developmental effects. Thus, it is important to characterize BPA levels, metabolic fate and sources of exposure in pregnant women. Methods We used an improved liquid chromatography-tandem mass spectrometry (LC-MS/MS) analytic method to directly and simultaneously measure unconjugated BPA (uBPA), BPA glucuronide and BPA sulfate in the urine of a population of ethnica...

  11. REVEAL: Software Documentation and Platform Migration

    Science.gov (United States)

    Wilson, Michael A.; Veibell, Victoir T.; Freudinger, Lawrence C.

    2008-01-01

    The Research Environment for Vehicle Embedded Analysis on Linux (REVEAL) is reconfigurable data acquisition software designed for network-distributed test and measurement applications. In development since 2001, it has been successfully demonstrated in support of a number of actual missions within NASA s Suborbital Science Program. Improvements to software configuration control were needed to properly support both an ongoing transition to operational status and continued evolution of REVEAL capabilities. For this reason the project described in this report targets REVEAL software source documentation and deployment of the software on a small set of hardware platforms different from what is currently used in the baseline system implementation. This report specifically describes the actions taken over a ten week period by two undergraduate student interns and serves as a final report for that internship. The topics discussed include: the documentation of REVEAL source code; the migration of REVEAL to other platforms; and an end-to-end field test that successfully validates the efforts.

  12. Real-space distribution of the Hall current densities and their spin polarization in nonmagnetic zine-blende semiconductors

    Czech Academy of Sciences Publication Activity Database

    Středa, Pavel; Drchal, Václav

    2012-01-01

    Roč. 86, č. 19 (2012), "195204-1"-"195204-8" ISSN 1098-0121 R&D Projects: GA ČR(CZ) GAP204/11/1228 Institutional research plan: CEZ:AV0Z10100521; CEZ:AV0Z10100520 Keywords : nonmagnetic semiconductors * spin Hall currents Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.767, year: 2012

  13. Development status of a test stand for semiconductor photocathodes with 60 keV spin-polarized beamline

    Energy Technology Data Exchange (ETDEWEB)

    Kurichijanil, Neeraj; Enders, Joachim; Espig, Martin; Fritzsche, Yuliya; Heichelt, Dominic; Kaiser, Andreas; Roesch, Heidi; Wagner, Markus [Institut fuer Kernphysik, TU Darmstadt (Germany)

    2016-07-01

    A test facility for Photo-Cathode Activation, Test and Cleaning using atomic-Hydrogen (Photo-CATCH) is being constructed at TU Darmstadt's Institute for Nuclear Physics (IKP) which houses the Superconducting Darmstadt Linear Accelerator (S-DALINAC). In order to improve the performance of the SDALINAC's photoelectron source based on GaAs, systematic studies in terms of quantum efficiency (QE), cathode rejuvenation, lifetimes and polarization (P) have to be conducted on different photocathode types. These factors strongly depend on handling of the cathode, the vacuum condition in the chambers, cathode surface cleaning as well as preservation of stoichiometry, negative electron affinity (NEA) activation of the cathode and the type and structure of the semiconductor material. With Photo-CATCH, experiments such as atomic-hydrogen cleaning, multi-alkali and oxidant NEA activation of the cathode and tests of QE, P and lifetimes can be performed in an improved vacuum. Additionally, experiments with polarized-electron beams of up to 60 keV are foreseen.

  14. Hyperfine fields in a Ag/Fe magnetic multilayer probed with low energy spin polarized {sup 8}Li

    Energy Technology Data Exchange (ETDEWEB)

    Keeler, T.A. [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, V6T 1Z1 (Canada); Salman, Z. [TRIUMF, 4004 Wesbrook Mall, Vancouver, V6T 2A3 (Canada); Chow, K.H. [Department of Physics, University of Alberta, Edmonton, AB, T6G 2J1 (Canada); Heinrich, B. [Department of Physics, Simon Fraser University, Vancouver, BC (Canada); Hossain, M.D. [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, V6T 1Z1 (Canada); Kardasz, B. [Department of Physics, Simon Fraser University, Vancouver, BC (Canada); Kiefl, R.F. [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, V6T 1Z1 (Canada)]. E-mail: kiefl@triumf.ca; Kreitzman, S.R. [TRIUMF, 4004 Wesbrook Mall, Vancouver, V6T 2A3 (Canada); MacFarlane, W.A. [Department of Chemistry, University of British Columbia, Vancouver, V6T 1Z1 (Canada); Mosendz, O. [Department of Physics, Simon Fraser University, Vancouver, BC (Canada); Parolin, T.J. [Department of Chemistry, University of British Columbia, Vancouver, V6T 1Z1 (Canada); Wang, D. [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, V6T 1Z1 (Canada)

    2006-03-31

    A beam of low energy Li8 has been used to probe the hyperfine field distribution in a magnetic multilayer composed of Au(4nm)/Ag(80nm)/Fe(2nm) grown on a GaAs substrate. The {beta}-NMR frequency spectrum is shown to be a strong function of the implantation energy reflecting the depth dependence of the local hyperfine fields. Correlating the spectra with TRIM.SP implantation profiles allows us to identify signals from the GaAs, Ag and Au layers. The frequency spectrum in Ag is a strong function of energy. A very narrow line, and corresponding distribution of hyperfine fields, is observed when the beam in centered well away from the Fe whereas a much broader distribution is observed when the Li stops close to the Fe. These results demonstrate that low energy {beta}-NMR can act as a sensitive probe of the induced magnetism in the otherwise non-magnetic Ag spacer layers.

  15. Unravelling the magnetism, high spin polarization and thermoelectric efficiency of ZrFeSi half-Heusler

    Science.gov (United States)

    Yousuf, Saleem; Gupta, D. C.

    2018-04-01

    We report the systematic investigation of structural properties, occupancy of density of states, nature of bonding and thermoelectric efficiency of half-Heusler ZrFeSi. The band structure analysis predicts the hybridization of Zr-d and Fe-d metal atoms resulting in occupation of density of states above the Fermi level (EF) while Fe-p and Si-p occupy the lower energy states below the EF. Thermoelectric transport coefficients are predicted using the Boltzmann transport theory under constant relaxation approximation, where Seebeck coefficient (S), total thermal conductivity and figure of merit are calculated. The negative value of total S as -14.02 μV/K predicts the material as n-type with thermoelectric figure of merit (zT) of 0.5 at 800 K. The lattice thermal conductivity decreases with increasing temperature with room temperature value of 4.18 W/mK and shows a significant reduction towards higher temperatures. In view of above elements, structural stability, high zT, ZrFeSi alloy have the capabilities to stimulate experimental verification as a promising materials for high temperature power generation and spintronic device fabrications.

  16. Cu–Ni core–shell nanoparticles: structure, stability, electronic, and magnetic properties: a spin-polarized density functional study

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Qiang, E-mail: wangqiang@njtech.edu.cn; Wang, Xinyan; Liu, Jianlan; Yang, Yanhui [Nanjing Tech University, School of Chemistry and Molecular Engineering, Institute of Advanced Synthesis (IAS) (China)

    2017-02-15

    Bimetallic core–shell nanoparticles (CSNPs) have attracted great interest not only because of their superior stability, selectivity, and catalytic activity but also due to their tunable properties achieved by changing the morphology, sequence, and sizes of both core and shell. In this study, the structure, stability, charge transfer, electronic, and magnetic properties of 13-atom and 55-atom Cu and Cu–Ni CSNPs were investigated using the density functional theory (DFT) calculations. The results show that Ni@Cu CSNPs with a Cu surface shell are more energetically favorable than Cu@Ni CSNPs with a Ni surface shell. Interestingly, three-shell Ni@Cu{sub 12}@Ni{sub 42} is more stable than two-shell Cu{sub 13}@Ni{sub 42}, while two-shell Ni{sub 13}@Cu{sub 42} is more stable than three-shell Cu@Ni{sub 12}@Cu{sub 42}. Analysis of Bader charge illustrates that the charge transfer increases from Cu core to Ni shell in Cu@Ni NPs, while it decreases from Ni core to Cu shell in Ni@Cu NPs. Furthermore, the charge transfer results that d-band states have larger shift toward the Fermi level for the Ni@Cu CSNPs with Cu surface shell, while the Cu@Ni CSNPs with Ni surface shell have similar d-band state curves and d-band centers with the monometallic Ni NPs. In addition, the Cu–Ni CSNPs possess higher magnetic moment when the Ni atoms aggregated at core region of CSNPs, while having lower magnetic moment when the Ni atoms segregate on surface region. The change of the Cu atom location in CSNPs has a weak effect on the total magnetic moment. Our findings provide useful insights for the design of bimetallic core–shell catalysts.

  17. P-state-to-P-state transitions in optically prepared atomic collisions: I. Theory of measurement in terms of Stokes parameters

    Energy Technology Data Exchange (ETDEWEB)

    Sidky, E.Y. [Niels Bohr Institute, Oersted Laboratory, Copenhagen (Denmark); JR Mcdonald Laboratory, Department of Physics, Kansas State University, Manhattan, KS (United States); Grego, S.; Andersen, N. [Niels Bohr Institute, Oersted Laboratory, Copenhagen (Denmark); Dowek, D. [Laboratoire des Collisions Atomiques et Moleculaires, Batiment 351, Universite Paris-Sud, Orsay (France)

    2002-05-14

    We present a parametrization in terms of Stokes parameters for the scattering from a P state to a P state for atomic collisions in a beam experiment. The classic approach to a 'complete scattering experiment', well known for S-state-to-P-state transitions, is generalized by a systematic combination of optical preparation of specific initial P states with Stokes parameter analysis of the radiation pattern from the final P state. The anisotropy of the initial and final state provides the possibility of extraction of a complete set of nine parameters describing the reaction at the level of five independent scattering amplitudes. We discuss the minimum number of experiments required to obtain a complete set of parameters in the cases of scattering angle-integrated and scattering angle-differential measurements. Relations to collision parameters for the reverse process are derived. Finally, effects due to fine and hyperfine depolarization, as well as inclusion of electron spin polarization, are treated. (author)

  18. Performance assessment of a new laser system for efficient spin exchange optical pumping in a spin maser measurement of 129Xe EDM

    International Nuclear Information System (INIS)

    Funayama, C.; Furukawa, T.; Sato, T.; Ichikawa, Y.; Ohtomo, Y.; Sakamoto, Y.; Kojima, S.; Suzuki, T.; Hirao, C.; Chikamori, M.; Hikota, E.; Tsuchiya, M.; Yoshimi, A.; Bidinosti, C. P.; Ino, T.; Ueno, H.; Matsuo, Y.; Fukuyama, T.; Asahi, K.

    2015-01-01

    We demonstrate spin-exchange optical pumping of 129 Xe atoms with our newly made laser system. The new laser system was prepared to provide higher laser power required for the stable operation of spin maser oscillations in the 129 Xe EDM experiment. We studied the optimum cell temperature and pumping laser power to improve the degree of 129 Xe spin polarization. The best performance was achieved at the cell temperature of 100 ∘ C with the presently available laser power of 1 W. The results show that a more intense laser is required for further improvement of the spin polarization at higher cell temperatures in our experiment

  19. Hydrologic Cycle Response to the Paleocene-Eocene Thermal Maximum at Austral, High-Latitude Site 690 as Revealed by In Situ Measurements of Foraminiferal Oxygen Isotope and Mg/Ca Ratios

    Science.gov (United States)

    Kozdon, R.; Kelly, D.; Fournelle, J.; Valley, J. W.

    2012-12-01

    published whole-shell δ18O records for this site; however, the mean baseline of the SIMS δ18O record is consistently ~1-2‰ lower than that of the published records. We attribute this δ18O offset to post-depositional diagenesis, which added 18O-enriched secondary calcite to planktic shells biasing conventional measurements. In the SIMS δ18O record, a minimum value of -4.4‰ is attained ~43 ka after the CIE onset. This δ18O minimum coincides with both the minimum δ13C value of the CIE and an abundance peak in warm-water immigrant taxa (morozovellids) of planktic foraminifera. Congruence of these two datasets reflects warming of sea-surface temperatures (SSTs), but the magnitude of the SST anomaly captured by complementary Mg/Ca data (~5°C) cannot account for the full magnitude of the δ18O decrease. This discrepancy is reconciled by lowering seawater δ18O to a value (-2‰) well below that computed for an ice-free world (-1.2‰). We therefore conclude that, much like in the Arctic, increased poleward moisture transport enhanced Antarctic continental runoff and reduced SSSs in the Weddell Sea region during the PETM.

  20. Temperature dependent electron Lande g-factor and interband matrix element in GaAs

    Energy Technology Data Exchange (ETDEWEB)

    Huebner, Jens; Doehrmann, Stefanie; Haegele, Daniel; Oestreich, Michael [Institute for Solid State Physics, Gottfried Wilhelm Leibniz University Hannover (Germany)

    2007-07-01

    High precision measurements of the electron Lande g-factor in GaAs are presented using spin quantum beat spectroscopy at low excitation densities and temperatures ranging from 2.6 to 300 K. Influences of nuclear spin polarization at low temperatures have been fully compensated. Comparing these measurements with available data for the temperature dependent effective mass reveals an unexpected strong temperature dependence of the interband matrix element and resolves a long lasting discrepancy between experiment and kp - theory. The strong decrease of the interband matrix element with increasing temperature is explained by phonon induced fluctuations of the interatomic spacing and adiabatic following of the electrons.

  1. Continuous phosphorus measurements reveal catchment-scale transport processes

    NARCIS (Netherlands)

    Velde, Y. van der; Rozemeijer, J.C.

    2012-01-01

    A small fraction of the nutrients used for agriculture is transported by rivers and artificial drainage networks to downstream waters. In lakes and coastal seas such as the Baltic Sea and the Gulf of Mexico these nutrients cause large-scale algal blooms and hypoxia and thus are a major

  2. Partial radiogenic heat model for Earth revealed by geoneutrino measurements

    NARCIS (Netherlands)

    Abe, S.; et al., [Unknown; Decowski, M.P.

    2011-01-01

    The Earth has cooled since its formation, yet the decay of radiogenic isotopes, and in particular uranium, thorium and potassium, in the planet’s interior provides a continuing heat source. The current total heat flux from the Earth to space is 44.2±1.0 TW, but the relative contributions from

  3. REVEAL: Software Documentation and Platform Migration

    Science.gov (United States)

    Wilson, Michael A.; Veibell, Victoir T.

    2011-01-01

    The Research Environment for Vehicle Embedded Analysis on Linux (REVEAL) is reconfigurable data acquisition software designed for network-distributed test and measurement applications. In development since 2001, it has been successfully demonstrated in support of a number of actual missions within NASA's Suborbital Science Program. Improvements to software configuration control were needed to properly support both an ongoing transition to operational status and continued evolution of REVEAL capabilities. For this reason the project described in this report targets REVEAL software source documentation and deployment of the software on a small set of hardware platforms different from what is currently used in the baseline system implementation. This presentation specifically describes the actions taken over a ten week period by two undergraduate student interns and serves as an overview of the content of the final report for that internship.

  4. Anomalous Hall effect in Fe/Gd bilayers

    KAUST Repository

    Xu, W. J.

    2010-04-01

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

  5. Revealing the Economic Consequences of Group Cohesion

    OpenAIRE

    Gächter, Simon; Starmer, Chris; Tufano, Fabio

    2017-01-01

    We introduce the concept of "group cohesion" to capture the economic consequences of ubiquitous social relationships in group production. We measure group cohesion, adapting the "oneness scale" from psychology. A comprehensive program of new experiments reveals the considerable economic impact of cohesion: higher cohesion groups are significantly more likely to achieve Pareto-superior outcomes in classic weak-link coordination games. We show that effects of cohesion are economically large, ro...

  6. Spin dependence in superelastic electron scattering from Na(3P)

    International Nuclear Information System (INIS)

    McClelland, J.J.; Kelley, M.H.; Celotta, R.J.

    1985-01-01

    Measurements are presented of spin asymmetries for superelastic scattering of 10-eV spin polarized electrons from the excited Na(3P/sub 3/2/) state created by linearly polarized laser optical pumping. Asymmetries as large as 16% are observed in scattering from a state which is not spin-polarized. Results are shown both as a function of scattering angle with fixed laser polarization direction, and as a function of the laser polarization direction at a fixed scattering angle

  7. Amplification of spin-current polarization

    Science.gov (United States)

    Saha, D.; Holub, M.; Bhattacharya, P.

    2007-08-01

    A ferromagnet/semiconductor based electrically controlled spin-current amplifier using a dual-drain nonlocal lateral spin valve is demonstrated. The spin polarization injected by the source into the channel is amplified at the second drain contact. An amplified current spin polarization of 100% is measured. The controlled variation of amplifier gain with bias is also demonstrated. The observations are explained in the framework of the spin drift-diffusion model.

  8. Decision Making and Revealed Preference

    DEFF Research Database (Denmark)

    de la Rosa, Leonidas Enrique

    If our decision-making processes are to some extent shaped by evolutionary pressures and our environment is different from that to which we adapted, some of our choices will not be in our best interest. But revealed preference is the only tool that we have so far to conduct a normative analysis...

  9. Revealing and Concealing in Antiquity

    DEFF Research Database (Denmark)

    Secrecy and the act of concealing and revealing knowledge effectually segregate the initiated and the uninitiated. The act of sharing or hiding knowledge plays a central role in all human relations private or public, political or religious. This volume explores the concept of secrecy and its...

  10. Revealed preference with limited consideration

    NARCIS (Netherlands)

    Demuynck, T.; Seel, C.

    2014-01-01

    We derive revealed preference tests for models where individuals use consideration sets to simplify their consumption problem. Our basic test provides necessary and sufficient conditions for consistency of observed choices with the existence of consideration set restrictions. The same conditions can

  11. SQUIDs as detectors in a new experiment to measure the neutron electric dipole moment

    International Nuclear Information System (INIS)

    Espy, M.A.; Cooper, M.; Lamoreaux, S.; Kraus, R.H. Jr.; Matlachov, A.; Ruminer, P.

    1998-01-01

    A new experiment has been proposed at Los Alamos National Laboratory to measure the neutron electric dipole moment (EDM) to 4x10 -28 ecm, a factor of 250 times better than the current experimental limit. Such a measure of the neutron EDM would challenge the theories of supersymmetry and time reversal violation as the origin of the observed cosmological asymmetry in the ratio of baryons to antibaryons. One possible design for this new experiment includes the use of LTC SQUIDs coupled to large (∼100 cm 2 ) pick-up coils to measure the precision frequency of the spin-polarized 3 He atoms that act as polarizer, spin analyzer, detector, and magnetometer for the ultra-cold neutrons used in the experiment. The method of directly measuring the 3 He precession signal eliminates the need for very uniform magnetic fields (a major source of systematic error in these types of experiments). It is estimated that a flux of ∼2x10 -16 Tm 2 (0.1 Φ 0 ) will be coupled into the pick-up coils. To achieve the required signal-to-noise ratio one must have a flux resolution of dΦ SQ = 2x10 -6 Φ 0 /√Hz at 10 Hz. While this is close to the sensitivity available in commercial devices, the effects of coupling to such a large pick-up coil and flux noise from other sources in the experiment still need to be understood. To determine the feasibility of using SQUIDs in such an application the authors designed and built a superconducting test cell, which simulates major features of the proposed EDM experiment, and they developed a two-SQUID readout system that will reduce SQUID noise in the experiment. They present an overview of the EDM experiment with SQUIDs, estimations of required SQUID parameters and experimental considerations. The authors also present the measured performance of a single magnetometer in the test cell as well as the performance of the two SQUID readout technique

  12. Hyposplenism revealed by Plasmodium malariae infection.

    Science.gov (United States)

    Hommel, Benjamin; Galloula, Alexandre; Simon, Anne; Buffet, Pierre

    2013-08-02

    Hyposplenism, due to splenectomy, inherited red blood cell disorders or acquired conditions such as celiac disease, has an important impact on the severity of malaria, especially in non-immune patients. Conversely, that malaria may reveal functional hyposplenism has not been described previously. A 31-year old gardener was diagnosed with an uncomplicated attack of Plasmodium malariae 11 years after leaving the endemic area. In addition to trophozoites and schizonts, thick and thin smears also showed Howell-Jolly bodies, pointing to functional hyposplenism. This was later confirmed by the presence of a calcified spleen in the context of S/β + sickle-cell syndrome in a patient previously unaware of this condition. Malaria may reveal hyposplenism. Although Howell-Jolly bodies are morphologically similar to nuclei of young Plasmodium trophozoite, distinction on smears is based on the absence of cytoplasm and irregular size of Howell-Jolly bodies. In the patient reported here, hyposplenism was revealed by the occurrence of P. malariae infection relatively late in life. Timely diagnosis of hyposplenism resulted in the implementation of appropriate measures to prevent overwhelming infection with capsulated bacteria. This observation highlights the importance of diagnosing hyposplenism in patients with malaria despite the morphological similarities between ring nuclei and Howell-Jolly bodies on thick smears.

  13. Transparency masters for mathematics revealed

    CERN Document Server

    Berman, Elizabeth

    1980-01-01

    Transparency Masters for Mathematics Revealed focuses on master diagrams that can be used for transparencies for an overhead projector or duplicator masters for worksheets. The book offers information on a compilation of master diagrams prepared by John R. Stafford, Jr., audiovisual supervisor at the University of Missouri at Kansas City. Some of the transparencies are designed to be shown horizontally. The initial three masters are number lines and grids that can be used in a mathematics course, while the others are adaptations of text figures which are slightly altered in some instances. The

  14. To Reveal Thy Heart Perchance to Reveal the World

    Directory of Open Access Journals (Sweden)

    Robert B. Faux

    2005-05-01

    Full Text Available Ronald PELIAS, a professor of speech communications, employs a variety of writing methods as examples of alternative ways to do research and to share with the reader a seldom seen and seldom considered aspect of academic life: Heart. In the early chapters of the book, PELIAS sets out to establish a way to place his Heart in the foreground; baring his emotional vulnerability, his humanness, his being in the world. Later chapters of the book encompass an autoethnographic study of academic life in which the previously revealed Heart is placed in context. In this review essay I discuss PELIAS' book in relation to the larger literature on autoethnography and subjectivist research; I follow this by discussing the need for and usefulness of such alternative methods using PELIAS' autoethnography of academic life as a context. URN: urn:nbn:de:0114-fqs050279

  15. In vivo measurements of cerebral metabolic abnormalities by proton spectroscopy after a transient ischemic attack revealing an internal carotid stenosis > 70%; Anomalies metaboliques cerebrales mesurees in vivo par la spectroscopie du proton dans les accidents ischemiques transitoires revelant une stenose de la carotide interne superieure a 70%

    Energy Technology Data Exchange (ETDEWEB)

    Giroud, M.; Becker, F.; Lemesle, M.; Walker, P.; Guy, F.; Martin, D.; Baudouin, N.; Brunotte, F.; Dumas, R. [Centre Hospitalier Universitaire, 21 -Dijon (France)

    1996-06-01

    Aims: The aim of this work is to look for cerebral metabolic abnormalities within the first 3 days after a transient ischemic attack revealing an internal carotid stenosis > 70 %. Methods: Five patients with a transient ischemic attack lasting between 30 and 180 minutes, affecting sensory and motor brachio-facial territory, with or without aphasia. Were studied. A CT-scan, an EEG, a cervical Doppler ultrasound, a standard arteriography, a magnetic resonance imaging and a proton spectroscopy were performed within the cerebral area affected by the transient ischemic attack. We measured 2 markers: N-acetyl-aspartate, the marker of the neuronal mass, and lactate, the marker of anaerobe metabolism. In each case, a contralateral internal stenosis was diagnosed by cervical Doppler ultrasound and standard arteriography. No cerebral infarction was observed. Results: With the affected cerebral area defined according to clinical and EEG features, proton spectroscopy showed a significant rise of lactate, without any change in N-acetyl-aspartate levels. Conclusions: Within the first 3 days after a transient ischemic attack, there is a significant risk of lactate inside the affected cerebral area. This change may reflect a localized and transient hypoperfusion, but long enough to induce a rise of lactate but not sufficient to produce a cerebral infarct. This area is probably at risk to induce cerebral infarct. This data lead us to study the metabolic change induced by the asymptomatic internal carotid stenosis. (authors). 18 refs.

  16. Plan competitions reveal entrepreneurial talent

    Energy Technology Data Exchange (ETDEWEB)

    Madison, Alison L.

    2011-05-15

    Monthly economic diversity column for Tri-City Herald business section. Excerpt below: There’s something to be said for gaining valuable real-world experience in a structured, nurturing environment. Take for instance learning to scuba dive in the comfort of my resort pool rather than immediately hanging out with sharks while I figure out little things like oxygen tanks and avoiding underwater panic attacks. Likewise, graduate students are getting some excellent, supportive real-world training through university business plan competitions. These competitions are places where smart minds, new technologies, months of preparation and coaching, and some healthy pre-presentation jitters collide to reveal not only solid new business ideas, but also some promising entrepreneurial talent. In fact, professionals from around our region descend upon college campuses every spring to judge these events, which help to bridge the gap between academics and the real technology and business-driven economy.

  17. Communication Games Reveal Preparation Contextuality

    Science.gov (United States)

    Hameedi, Alley; Tavakoli, Armin; Marques, Breno; Bourennane, Mohamed

    2017-12-01

    A communication game consists of distributed parties attempting to jointly complete a task with restricted communication. Such games are useful tools for studying limitations of physical theories. A theory exhibits preparation contextuality whenever its predictions cannot be explained by a preparation noncontextual model. Here, we show that communication games performed in operational theories reveal the preparation contextuality of that theory. For statistics obtained in a particular family of communication games, we show a direct correspondence with correlations in spacelike separated events obeying the no-signaling principle. Using this, we prove that all mixed quantum states of any finite dimension are preparation contextual. We report on an experimental realization of a communication game involving three-level quantum systems from which we observe a strong violation of the constraints of preparation noncontextuality.

  18. Communication Games Reveal Preparation Contextuality.

    Science.gov (United States)

    Hameedi, Alley; Tavakoli, Armin; Marques, Breno; Bourennane, Mohamed

    2017-12-01

    A communication game consists of distributed parties attempting to jointly complete a task with restricted communication. Such games are useful tools for studying limitations of physical theories. A theory exhibits preparation contextuality whenever its predictions cannot be explained by a preparation noncontextual model. Here, we show that communication games performed in operational theories reveal the preparation contextuality of that theory. For statistics obtained in a particular family of communication games, we show a direct correspondence with correlations in spacelike separated events obeying the no-signaling principle. Using this, we prove that all mixed quantum states of any finite dimension are preparation contextual. We report on an experimental realization of a communication game involving three-level quantum systems from which we observe a strong violation of the constraints of preparation noncontextuality.

  19. The chemistry of plutonium revealed

    International Nuclear Information System (INIS)

    Connick, R.E.

    1990-01-01

    In 1941 one goal of the Manhattan Project was to unravel the chemistry of the synthetic element plutonium as rapidly as possible. Important insights were obtained from tracer experiments, but the full complexity of plutonium chemistry was not revealed until macroscopic amounts (milligrams) became available. Because processes for separation from fission products were aqueous solution based, such solution chemistry was emphasized, particularly precipitation and oxidation-reduction behavior. The latter turned out to be unusually intricate when it was discovered that two more oxidation states existed in aqueous solution than had previously been suspected. Further, it was found that an equilibrium was rapidly established among the four aqueous oxidation states while at the same time any three were not in equilibrium. These and other observations made while doing a crash study of a previously unknown element will be reported

  20. Revealing ontological commitments by magic.

    Science.gov (United States)

    Griffiths, Thomas L

    2015-03-01

    Considering the appeal of different magical transformations exposes some systematic asymmetries. For example, it is more interesting to transform a vase into a rose than a rose into a vase. An experiment in which people judged how interesting they found different magic tricks showed that these asymmetries reflect the direction a transformation moves in an ontological hierarchy: transformations in the direction of animacy and intelligence are favored over the opposite. A second and third experiment demonstrated that judgments of the plausibility of machines that perform the same transformations do not show the same asymmetries, but judgments of the interestingness of such machines do. A formal argument relates this sense of interestingness to evidence for an alternative to our current physical theory, with magic tricks being a particularly pure source of such evidence. These results suggest that people's intuitions about magic tricks can reveal the ontological commitments that underlie human cognition. Copyright © 2014 Elsevier B.V. All rights reserved.

  1. Measures for Measures

    DEFF Research Database (Denmark)

    Jørgensen, Sune Lehman; A.D., Jackson; Lautrup, B.E.

    2006-01-01

    Are some ways of measuring scientific quality better than others? Sune Lehmann, Andrew D. Jackson and Benny E. Lautrup analyse the reliability of commonly used methods for comparing citation records.......Are some ways of measuring scientific quality better than others? Sune Lehmann, Andrew D. Jackson and Benny E. Lautrup analyse the reliability of commonly used methods for comparing citation records....

  2. Hubble Images Reveal Jupiter's Auroras

    Science.gov (United States)

    1996-01-01

    These images, taken by the Hubble Space Telescope, reveal changes in Jupiter's auroral emissions and how small auroral spots just outside the emission rings are linked to the planet's volcanic moon, Io. The images represent the most sensitive and sharply-detailed views ever taken of Jovian auroras.The top panel pinpoints the effects of emissions from Io, which is about the size of Earth's moon. The black-and-white image on the left, taken in visible light, shows how Io and Jupiter are linked by an invisible electrical current of charged particles called a 'flux tube.' The particles - ejected from Io (the bright spot on Jupiter's right) by volcanic eruptions - flow along Jupiter's magnetic field lines, which thread through Io, to the planet's north and south magnetic poles. This image also shows the belts of clouds surrounding Jupiter as well as the Great Red Spot.The black-and-white image on the right, taken in ultraviolet light about 15 minutes later, shows Jupiter's auroral emissions at the north and south poles. Just outside these emissions are the auroral spots. Called 'footprints,' the spots are created when the particles in Io's 'flux tube' reach Jupiter's upper atmosphere and interact with hydrogen gas, making it fluoresce. In this image, Io is not observable because it is faint in the ultraviolet.The two ultraviolet images at the bottom of the picture show how the auroral emissions change in brightness and structure as Jupiter rotates. These false-color images also reveal how the magnetic field is offset from Jupiter's spin axis by 10 to 15 degrees. In the right image, the north auroral emission is rising over the left limb; the south auroral oval is beginning to set. The image on the left, obtained on a different date, shows a full view of the north aurora, with a strong emission inside the main auroral oval.The images were taken by the telescope's Wide Field and Planetary Camera 2 between May 1994 and September 1995.This image and other images and data

  3. Spin injection and detection in lanthanum- and niobium-doped SrTiO3 using the Hanle technique

    KAUST Repository

    Han, Wei

    2013-07-08

    There has been much interest in the injection and detection of spin-polarized carriers in semiconductors for the purposes of developing novel spintronic devices. Here we report the electrical injection and detection of spin-polarized carriers into Nb-doped strontium titanate single crystals and La-doped strontium titanate epitaxial thin films using MgO tunnel barriers and the three-terminal Hanle technique. Spin lifetimes of up to ∼100 ps are measured at room temperature and vary little as the temperature is decreased to low temperatures. However, the mobility of the strontium titanate has a strong temperature dependence. This behaviour and the carrier doping dependence of the spin lifetime suggest that the spin lifetime is limited by spin-dependent scattering at the MgO/strontium titanate interfaces, perhaps related to the formation of doping induced Ti 3+. Our results reveal a severe limitation of the three-terminal Hanle technique for measuring spin lifetimes within the interior of the subject material. © 2013 Macmillan Publishers Limited. All rights reserved.

  4. Saturn Probe: Revealing Solar System Origins

    Science.gov (United States)

    Spilker, T. R.

    2015-12-01

    Comparative studies of the gas giant and ice giant planets are needed to reliably discriminate among competing theories of the origin and evolution of giant planets and the solar system, but we lack critical measurements. A Saturn atmospheric entry probe mission would fill a vital part of that gap, allowing comparative studies of Jupiter and Saturn, providing the basis for later comparisons with the ice giants Uranus and Neptune, and informing studies of extrasolar planetary systems now being characterized. The Galileo Probe mission provided the first in situ studies of Jupiter's atmosphere. Similar measurements at Saturn, Uranus and Neptune would provide an important comparative planetology context for the Galileo results. Cassini's "Proximal Orbits" in 2017 will reveal Saturn's internal structure to complement the Juno mission's similar measurements at Jupiter. A Saturn entry probe, complementing the Galileo Probe investigations at Jupiter, would complete a solid basis for improved understanding of both Jupiter and Saturn, an important stepping stone to understanding Uranus and Neptune and solar system formation and evolution. The 2012 Decadal Survey ("DS") added Saturn Probe science objectives to NASA's New Frontiers Program: highest-priority Tier 1 objectives any New Frontiers implementation must achieve, and Tier 2, high priority but lower than Tier 1. A DS mission concept study using extremely conservative assumptions concluded that a Saturn Probe project could fit within New Frontiers resource constraints, giving a PI confidence that they could pursue some Tier 2 objectives, customizing for the proper balance of science return, science team composition, procured or contributed instruments, etc. Contributed instruments could significantly enhance the payload and the science team for greater science return. They also provide international collaboration opportunities, with science benefits well demonstrated by missions such as Cassini-Huygens and Rosetta.

  5. Measurement Engineering

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Jun Hui; Kim, Hyeong Cheol

    2001-08-15

    This book deals with conception of measurement such as measuring and test, instrument for measurement, and types and methods of measuring, general things for precision measurement like indicator, gauge standard and Abbe's principle, measuring instrument such as vernier calipers, micrometer calipers, each gage, an optical instrument, and 3D instrument, choice and using of measuring instrument on length measurement, angle measurement, and side measurement, application and calculation for measuring using trigonometrical function, sin law, and the Pythagorean Theorem.

  6. Puerto Rico Revealed Preference Survey Data 2004

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Revealed preference models provide insights into recreational angler behavior and the economic value of recreational fishing trips. Revealed preference data is...

  7. Hidden acoustic information revealed by intentional nonlinearity

    Science.gov (United States)

    Dowling, David R.

    2017-11-01

    Acoustic waves are omnipresent in modern life and are well described by the linearized equations of fluid dynamics. Once generated, acoustic waves carry and collect information about their source and the environment through which they propagate, respectively, and this information may be retrieved by analyzing recordings of these waves. Because of this, acoustics is the primary means for observation, surveillance, reconnaissance, and remote sensing in otherwise opaque environments, such as the Earth's oceans and crust, and the interior of the human body. For such information-retrieval tasks, acoustic fields are nearly always interrogated within their recorded frequency range or bandwidth. However, this frequency-range restriction is not general; acoustic fields may also carry (hidden) information at frequencies outside their bandwidth. Although such a claim may seem counter intuitive, hidden acoustic-field information can be revealed by re-introducing a marquee trait of fluid dynamics: nonlinearity. In particular, an intentional quadratic nonlinearity - a form of intra-signal heterodyning - can be used to obtain acoustic field information at frequencies outside a recorded acoustic field's bandwidth. This quadratic nonlinearity enables a variety of acoustic remote sensing applications that were long thought to be impossible. In particular, it allows the detrimental effects of sparse recordings and random scattering to be suppressed when the original acoustic field has sufficient bandwidth. In this presentation, the topic is developed heuristically, with a just brief exposition of the relevant mathematics. Hidden acoustic field information is then revealed from simulated and measured acoustic fields in simple and complicated acoustic environments involving frequencies from a few Hertz to more than 100 kHz, and propagation distances from tens of centimeters to hundreds of kilometers. Sponsored by ONR, NAVSEA, and NSF.

  8. Search for positron localization near transition-metal solutes of negative effective charge in Ni and Cu

    International Nuclear Information System (INIS)

    Hunter, D.M.; Grynszpan, R.I.; Arrott, A.S.

    1993-01-01

    Results of an early (1973) angular correlation (ACAR) study of dilute (0.5 at.%) Cu based alloys by a Japanese group were interpreted in terms of an attraction of e + by transition metal solutes of effective negative charge. Doppler Broadening (DB) measurements reveal no such an effect for Cu(Mn) and Cu(Ni) solid solutions as well as for Ni alloys with 3d, 4d and 5d transition metal solutes (0.1 to 1.5 at.%) i.e. no evidence of e + localization near these impurities is seen. Our results strongly suggest that the ACAR results are due to the metallurgical state of the samples. In contrast, significant DB lineshape parameter variations, observed for our Ni(Zr) alloys, are attributed to positron trapping in and near Ni 5 Zr precipitates. Our DB results for a series of Ni(Au) alloys are understood in terms of a combination of the effect of an overall lattice expansion and a positron preference for clusters of Au atoms. The above comparison between DB and ACAR results is supported by our 'spin polarized' DB results for a (001) Ni single crystal which resemble those obtained by other groups using a 'spin polarized' 2D-ACAR technique. (orig.)

  9. Measure for measure

    Science.gov (United States)

    Weinberger, Peter

    2012-06-01

    The present system of measures for length, weight and capacity (volume) originates from scientific ideas expressed during the French Revolution in 1789. The history of a compatible unit of length, however, turns out to be less of a scientific but rather of a political character. Here reports to the Philosophical Magazine made in the first quarter of the nineteenth century are used to trace the cultural split between meters and inches, and between kilograms and pounds, that can be experienced in many parts of the world.

  10. Revealing household characteristics from smart meter data

    International Nuclear Information System (INIS)

    Beckel, Christian; Sadamori, Leyna; Staake, Thorsten; Santini, Silvia

    2014-01-01

    Utilities are currently deploying smart electricity meters in millions of households worldwide to collect fine-grained electricity consumption data. We present an approach to automatically analyzing this data to enable personalized and scalable energy efficiency programs for private households. In particular, we develop and evaluate a system that uses supervised machine learning techniques to automatically estimate specific “characteristics” of a household from its electricity consumption. The characteristics are related to a household's socio-economic status, its dwelling, or its appliance stock. We evaluate our approach by analyzing smart meter data collected from 4232 households in Ireland at a 30-min granularity over a period of 1.5 years. Our analysis shows that revealing characteristics from smart meter data is feasible, as our method achieves an accuracy of more than 70% over all households for many of the characteristics and even exceeds 80% for some of the characteristics. The findings are applicable to all smart metering systems without making changes to the measurement infrastructure. The inferred knowledge paves the way for targeted energy efficiency programs and other services that benefit from improved customer insights. On the basis of these promising results, the paper discusses the potential for utilities as well as policy and privacy implications. - Highlights: • Many household characteristics can be automatically inferred from smart meter data. • We develop a system to infer employment status and number of occupants, for instance. • We evaluate our system analyzing data collected from 4232 households in Ireland. • The insights enable personalized and scalable efficiency campaigns for utilities. • Energy efficiency measures must be complemented by privacy protection

  11. Mn concentration and quantum size effects on spin-polarized transport through CdMnTe based magnetic resonant tunneling diode.

    Science.gov (United States)

    Mnasri, S; Abdi-Ben Nasrallahl, S; Sfina, N; Lazzari, J L; Saïd, M

    2012-11-01

    Theoretical studies on spin-dependent transport in magnetic tunneling diodes with giant Zeeman splitting of the valence band are carried out. The studied structure consists of two nonmagnetic layers CdMgTe separated by a diluted magnetic semiconductor barrier CdMnTe, the hole is surrounded by two p-doped CdTe layers. Based on the parabolic valence band effective mass approximation and the transfer matrix method, the magnetization and the current densities for holes with spin-up and spin-down are studied in terms of the Mn concentration, the well and barrier thicknesses as well as the voltage. It is found that, the current densities depend strongly on these parameters and by choosing suitable values; this structure can be a good spin filter. Such behaviors are originated from the enhancement and suppression in the spin-dependent resonant states.

  12. First-principles study of high spin-polarization and thermoelectric efficiency of ferromagnetic CoFeCrAs quaternary Heusler alloy

    Science.gov (United States)

    Bhat, Tahir Mohiuddin; Gupta, Dinesh C.

    2018-03-01

    The ground state properties along with thermodynamic and thermoelectric properties of quaternary CoFeCrAs alloy within the ordered LiMgPdSn-type structure have been investigated by employing first-principles calculations. The alloy offers half-metallic ferromagnet character with an indirect band gap of 1.12 eV in the minority spin state with total spin magnetic moment of 4μB and follows Slater-Pauling relation. Effects on various properties of the material has been studied by the variation of the pressure and temperature. CoFeCrAs tenders large value of the Grüneisen parameter and small value for the thermal expansion coefficient. The materials present high Seebeck coefficient and huge power factor with the room temperature value of ∼-40 μV/K and 18 (1014 μWcm-1 K-2 s-1) respectively, which make CoFeCrAs promising candidate for efficient thermoelectric material.

  13. Comparison of Electron Transmittance and Tunneling Current through a Trapezoidal Potential Barrier with Spin Polarization Consideration by using Analytical and Numerical Approaches

    Science.gov (United States)

    Nabila, Ezra; Noor, Fatimah A.; Khairurrijal

    2017-07-01

    In this study, we report an analytical calculation of electron transmittance and polarized tunneling current in a single barrier heterostructure of a metal-GaSb-metal by considering the Dresselhaus spin orbit effect. Exponential function, WKB method and Airy function were used in calculating the electron transmittance and tunneling current. A Transfer Matrix Method, as a numerical method, was utilized as the benchmark to evaluate the analytical calculation. It was found that the transmittances calculated under exponential function and Airy function is the same as that calculated under TMM method at low electron energy. However, at high electron energy only the transmittance calculated under Airy function approach is the same as that calculated under TMM method. It was also shown that the transmittances both of spin-up and spin-down conditions increase as the electron energy increases for low energies. Furthermore, the tunneling current decreases with increasing the barrier width.

  14. Spin polarization induced by optical and microwave resonance radiation in a Si Vacancy in SiC: a promising subject for the spectroscopy of single defects

    NARCIS (Netherlands)

    Baranov, P.G.; Bundakova, A.P.; Borovykh, I.V.; Orlinskii, S.B.; Zondervan, R.; Schmidt, J.

    2007-01-01

    Depending on the temperature, crystal polytype, and crystal position, two opposite schemes have been observed for the optical alignment of the populations of spin sublevels in the ground state of a Si vacancy in SiC upon irradiation with unpolarized light at frequencies of zero-phonon lines. A giant

  15. Thermoelectric properties of TbFe{sub 2} and TbCo{sub 2} in C15- laves phase: Spin-polarized DFT+U approach

    Energy Technology Data Exchange (ETDEWEB)

    Reshak, A.H., E-mail: maalidph@yahoo.co.uk [New Technologies - Research Centre, University of West Bohemia, Univerzitni 8, Pilsen 306 14 (Czech Republic); School of Material Engineering, University Malaysia Perlis, Kangar, Perlis 01007 (Malaysia)

    2017-01-15

    Thermoelectric properties of materials are intimately related to their electronic band structure. Combining first- and second-principles calculations, we have obtained the transport properties for the spin-up and spin-down electrons of the laves phase TbFe{sub 2} and TbCo{sub 2} compounds. The unique band structure feature and the density of states at Fermi level (E{sub F}) promote the E{sub F} to a point where carriers are in energetic proximity to these features. The non-zero density of states at E{sub F} for the spin-up (↑) and spin-down (↓) electrons leads to unusual transport properties because both the (↑) and (↓) densities contributes to the states at E{sub F}. The parabolic bands in the vicinity of E{sub F} enhance the carriers mobility and hence the transport properties of TbFe{sub 2} and TbCo{sub 2}. Calculations show that the spin-up/down transport coefficients are temperature-dependent. It has been found that TbCo{sub 2} possess larger Seebeck coefficient than that of TbFe{sub 2} and hence the power factor. The calculated Seebeck coefficient of TbCo{sub 2} agree well with the available experimental data. - Highlights: • The transport properties of TbFe{sub 2} and TbCo{sub 2} are obtained. • The non-zero density of states at E{sub F} leads to unusual transport properties. • Spin-up/down transport coefficients are temperature-dependent. • The calculated Seebeck coefficient of TbCo{sub 2} agree with the experimental data. • TbCo{sub 2} possesses larger Seebeck coefficient than that of TbFe{sub 2}.

  16. Rich eight-branch spectrum of the oblique propagating longitudinal waves in partially spin-polarized electron-positron-ion plasmas

    Science.gov (United States)

    Andreev, Pavel A.; Iqbal, Z.

    2016-03-01

    We consider the separate spin evolution of electrons and positrons in electron-positron and electron-positron-ion plasmas. We consider the oblique propagating longitudinal waves in these systems. Working in a regime of high-density n0˜1027cm-3 and high-magnetic-field B0=1010 G, we report the presence of the spin-electron acoustic waves and their dispersion dependencies. In electron-positron plasmas, similarly to the electron-ion plasmas, we find one spin-electron acoustic wave (SEAW) at the propagation parallel or perpendicular to the external field and two spin-electron acoustic waves at the oblique propagation. At the parallel or perpendicular propagation of the longitudinal waves in electron-positron-ion plasmas, we find four branches: the Langmuir wave, the positron-acoustic wave, and a pair of waves having spin nature, they are the SEAW and the wave discovered in this paper, called the spin-electron-positron acoustic wave (SEPAW). At the oblique propagation we find eight longitudinal waves: the Langmuir wave, the Trivelpiece--Gould wave, a pair of positron-acoustic waves, a pair of SEAWs, and a pair of SEPAWs. Thus, for the first time, we report the existence of the second positron-acoustic wave existing at the oblique propagation and the existence of SEPAWs.

  17. Revealing the interface in polymer nanocomposites.

    Science.gov (United States)

    Zammarano, Mauro; Maupin, Paul H; Sung, Li-Piin; Gilman, Jeffrey W; McCarthy, Edward D; Kim, Yeon S; Fox, Douglas M

    2011-04-26

    The morphological characterization of polymer nanocomposites over multiple length scales is a fundamental challenge. Here, we report a technique for high-throughput monitoring of interface and dispersion in polymer nanocomposites based on Förster resonance energy transfer (FRET). Nanofibrillated cellulose (NFC), fluorescently labeled with 5-(4,6-dichlorotriazinyl)-aminofluorescein (FL) and dispersed into polyethylene (PE) doped with Coumarin 30 (C30), is used as a model system to assess the ability of FRET to evaluate the effect of processing on NFC dispersion in PE. The level of energy transfer and its standard deviation, measured by fluorescence spectroscopy and laser scanning confocal microscopy (LSCM), are exploited to monitor the extent of interface formation and composite homogeneity, respectively. FRET algorithms are used to generate color-coded images for a real-space observation of energy transfer efficiency. These images reveal interface formation at a nanoscale while probing a macroscale area that is large enough to be representative of the entire sample. The unique ability of this technique to simultaneously provide orientation/spatial information at a macroscale and nanoscale features, encoded in the FRET signal, provides a new powerful tool for structure-property-processing investigation in polymer nanocomposites.

  18. The 'revealed preferences' theory: Assumptions and conjectures

    International Nuclear Information System (INIS)

    Green, C.H.

    1983-01-01

    Being kind of intuitive psychology the 'Revealed-Preferences'- theory based approaches towards determining the acceptable risks are a useful method for the generation of hypotheses. In view of the fact that reliability engineering develops faster than methods for the determination of reliability aims the Revealed-Preferences approach is a necessary preliminary help. Some of the assumptions on which the 'Revealed-Preferences' theory is based will be identified and analysed and afterwards compared with experimentally obtained results. (orig./DG) [de

  19. Tunneling conductance of a two-dimensional electron gas with Dresselhaus spin-orbit coupling

    International Nuclear Information System (INIS)

    Srisongmuang, B.; Ka-oey, A.

    2012-01-01

    We theoretically studied the spin-dependent charge transport in a two-dimensional electron gas with Dresselhaus spin-orbit coupling (DSOC) and metal junctions. It is shown that the DSOC energy can be directly measured from the tunneling conductance spectrum. We found that spin polarization of the conductance in the propagation direction can be obtained by injecting from the DSOC system. We also considered the effect of the interfacial scattering barrier (both spin-flip and non-spin-flip scattering) on the overall conductance and the spin polarization of the conductance. It is found that the increase of spin-flip scattering can enhance the conductance under certain conditions. Moreover, both types of scattering can increase the spin polarization below the branches crossing of the energy band. - Highlights: → DSOC energy can be directly measured from tunneling conductance spectrum. → Spin polarization of conductance in the propagation direction can be obtained by injecting from DSOC system. → Both types of scattering can increase spin polarization.

  20. Measuring the chargino parameters

    Indian Academy of Sciences (India)

    After the supersymmetric particles have been discovered, the priority will be to determine independently the fundamental parameters to reveal the structure of the underlying supersymmetric theory. In my talk I discuss how the chargino sector can be reconstructed completely by measuring the cross-sections with polarized ...

  1. Revealing Conceptual Understanding of International Business

    Science.gov (United States)

    Ashley, Sue; Schaap, Harmen; de Bruijn, Elly

    2017-01-01

    This study aims to identify an adequate approach for revealing conceptual understanding in higher professional education. Revealing students' conceptual understanding is an important step towards developing effective curricula, assessment and aligned teaching strategies to enhance conceptual understanding in higher education. Essays and concept…

  2. The critical role of the barrier thickness in spin filter tunneling

    International Nuclear Information System (INIS)

    Miller, Casey W.

    2009-01-01

    Spin filter tunneling is considered in the low bias limit as functions of the temperature dependent barrier parameters. We demonstrate the generation of spin polarized tunneling currents in relation to the magnetic order parameter, and discuss how an interfacially suppressed order parameter leads to a temperature dependent tunneling current asymmetry. Analyzing the full parameter space reveals that the often overlooked barrier thickness plays a critical role in spin filter tunneling. With all else fixed, thicker barriers yield higher spin polarization, and allow a given polarization to be achieved at higher temperatures. This insight may open the door for new materials to serve as spin filter barriers.

  3. Abrasive supply for ancient Egypt revealed

    International Nuclear Information System (INIS)

    Peltz, C.; Bichler, M.

    2008-01-01

    In the framework of the major research scheme 'Synchronization of Civilizations in the Eastern Mediterranean Region in the 2nd Millennium B.C' instrumental neutron activation analysis (INAA) was used to determine 30 elements in pumice from archaeological excavations to reveal their specific volcanic origin. In ancient time, the widespread pumiceous products of several eruptions in the Aegean region have been used as abrasive tools and were therefore popular trade objects. The correlation of such archaeological findings to a specific eruption of known age would therefore allow to certify a maximum age of the respective stratum ('dating by first appearance'). Pumices from the Aegean region can easily be distinguished by their trace element distribution patterns. This has been shown by previous studies of the group. The elements Al, Ba, Ca, Ce, Co, Cr, Cs, Dy, Eu, Fe, Hf, K, La, Lu, Mn, Na, Nd, Rb, Sb, Sc, Sm, Ta, Tb, Th, Ti, U, V, Yb, Zr and Zn were determined in 16 samples of pumice lumps from excavations in Tell-el-Dab'a and Tell-el-Herr (Egypt). Two irradiation cycles and five measurement runs were applied. To show the accuracy of the results obtained, typical samples of the most important pumice sources in the Aegean region, particularly from Milos, Nisyros, Kos and Thera were analyzed together with the Egyptian samples of unknown origin. A reliable identification of the samples is achieved by comparing these results to the database compiled in previous studies. The geographical positions of these islands are shown. Within the error range, most of the elements determined in typical representatives of Milos, Nisyros, Kos and Santorini were in perfect agreement with values from the literature. On the basis of the Cluster graphics presented, it is possible to relate unknown pumice to its primary source, just by comparing the relation of a few elements, like Ta-Eu and Th-Hf. One concludes that all samples except one can be related to the Minoan eruption of Thera

  4. Study of 3He Rabi nutations by optically-pumped cesium magnetometers

    Science.gov (United States)

    Koch, Hans-Christian; Bison, Georg; Grujić, Zoran Dragan; Heil, Werner; Kasprzak, Malgorzata; Knowles, Paul; Kraft, Andreas; Pazgalev, Anatoly; Schnabel, Allard; Voigt, Jens; Weis, Antoine

    2017-10-01

    We describe a method for recording the Rabi nutation of nuclear spin polarized 3He by optically pumped cesium magnetometers. The measurement is performed by detecting the time-dependent magnetic field produced by the 3He magnetization. The observed signals are compared to theoretical models and the results are used to precisely trace the evolution of the magnetization. This procedure represents a convenient way to control and measure the Rabi flip angle and the degree of spin polarization in experiments using 3He magnetometers. The method requires only very coarse knowledge of the applied magnetic field's magnitude.

  5. Spin-resolved photoemission of surface states of W(110)-(1x1)H

    International Nuclear Information System (INIS)

    Hochstrasser, M.; Tobin, J.G.; Rotenberg, Eli; Kevan, S.D.

    2002-01-01

    The surface electronic states of W(110)-(1x1)H have been measured using spin- and angle-resolved photoemission. We directly demonstrate that the surface bands are both split and spin-polarized by the spin-orbit interaction in association with the loss of inversion symmetry near a surface. We observe 100 percent spin polarization of the surface states, with the spins aligned in the plane of the surface and oriented in a circular fashion relative to the S-bar symmetry point. In contrast, no measurable polarization of nearby bulk states is observed

  6. Photo-galvanic effect in Bi2Se3 thin films with ionic liquid gating

    Science.gov (United States)

    Pan, Yu; Richardella, Anthony; Lee, Joon Sue; Flanagan, Thomas; Samarth, Nitin

    2013-03-01

    A key challenge in three dimensional (3D) topological insulators (TIs) is to reveal the helical spin-polarized surface states via electrical transport measurements. A recent study [Nature Nanotech. 7, 96 (2012)] showed that circularly polarized light can be used to generate and control photocurrents in the 3D TI Bi2Se3, even at photon energies that are well above the bulk band gap. Symmetry considerations suggest that this ``photo-galvanic effect'' arises purely from photo-currents induced in the surface Dirac states. To gain insights into this phenomenon, we have carried out systematic measurements of the photo-galvanic effect in electrically gated MBE-grown Bi2Se3 thin films of varying thickness. By using an ionic liquid as an optically transparent gate, we map out the behavior of the photo-galvanic effect as a function of Fermi energy over a temperature range 5 K <= T <= 300 K. Supported by ONR and NSF.

  7. Measuring worker productivity: frameworks and measures.

    Science.gov (United States)

    Beaton, Dorcas; Bombardier, Claire; Escorpizo, Reuben; Zhang, Wei; Lacaille, Diane; Boonen, Annelies; Osborne, Richard H; Anis, Aslam H; Strand, C Vibeke; Tugwell, Peter S

    2009-09-01

    Worker productivity is a combination of time off work (absenteeism) due to an illness and time at work but with reduced levels of productivity while at work (also known as presenteeism). Both can be gathered with a focus on application as a cost indicator and/or as an outcome state for intervention studies. We review the OMERACT worker productivity groups' progress in evaluating measures of worker productivity for use in arthritis using the OMERACT filter. Attendees at OMERACT 9 strongly endorsed the importance of work as an outcome in arthritis. Consensus was reached (94% endorsement) for fielding a broader array of indicators of absenteeism. Twenty-one measures of at-work productivity loss, ranging from single item indicators to multidimensional scales, were reviewed for measurement properties. No set of at-work productivity measures was endorsed because of variability in the concepts captured, and the need for a better framework for the measurement of worker productivity that also incorporates contextual issues such as job demands and other paid and unpaid life responsibilities. Progress has been made in this area, revealing an ambivalent set of results that directed us back to the need to further define and then contextualize the measurement of worker productivity.

  8. Electrical Initialization of Electron and Nuclear Spins in a Single Quantum Dot at Zero Magnetic Field.

    Science.gov (United States)

    Cadiz, Fabian; Djeffal, Abdelhak; Lagarde, Delphine; Balocchi, Andrea; Tao, Bingshan; Xu, Bo; Liang, Shiheng; Stoffel, Mathieu; Devaux, Xavier; Jaffres, Henri; George, Jean-Marie; Hehn, Michel; Mangin, Stephane; Carrere, Helene; Marie, Xavier; Amand, Thierry; Han, Xiufeng; Wang, Zhanguo; Urbaszek, Bernhard; Lu, Yuan; Renucci, Pierre

    2018-04-11

    The emission of circularly polarized light from a single quantum dot relies on the injection of carriers with well-defined spin polarization. Here we demonstrate single dot electroluminescence (EL) with a circular polarization degree up to 35% at zero applied magnetic field. The injection of spin-polarized electrons is achieved by combining ultrathin CoFeB electrodes on top of a spin-LED device with p-type InGaAs quantum dots in the active region. We measure an Overhauser shift of several microelectronvolts at zero magnetic field for the positively charged exciton (trion X + ) EL emission, which changes sign as we reverse the injected electron spin orientation. This is a signature of dynamic polarization of the nuclear spins in the quantum dot induced by the hyperfine interaction with the electrically injected electron spin. This study paves the way for electrical control of nuclear spin polarization in a single quantum dot without any external magnetic field.

  9. Spin separation in a T ballistic nanojunction due to lateral-confinement-induced spin-orbit coupling

    International Nuclear Information System (INIS)

    Bellucci, S; Carillo, F; Onorato, P

    2007-01-01

    We propose a new scheme of spin filtering employing ballistic nanostructures in two-dimensional electron gases (2DEGs). The proposal is essentially based on the spin-orbit (SO) interaction arising from the lateral confining electric field. This sets the basic difference from other works employing ballistic crosses and T junctions with the conventional SO term arising from 2DEG confinement. We discuss the consequences of this different approach for the magnetotransport properties of the device, showing that the filter can in principle be used not only to generate a spin polarized current but also to perform an electric measurement of the spin polarization of a charge current. We focus on single-channel transport and investigate numerically the spin polarization of the current

  10. $\\beta$-NMR of copper isotopes in ionic liquids

    CERN Multimedia

    We propose to test the feasibility of spin-polarization and $\\beta$-NMR studies on several short-lived copper isotopes, $^{58}$ Cu, $^{74}$Cu and $^{75}$Cu in crystals and liquids. The motivation is given by biological studies of Cu with $\\beta$-NMR in liquid samples, since Cu is present in a large number of enzymes involved in electron transfer and activation of oxygen. The technique is based on spin-polarization via optical pumping in the new VITO beamline. We will use the existing lasers, NMR magnet and NMR chambers and we will prepare a new optical pumping system. The studies will be devoted to tests of achieved $\\beta$-asymmetry in solid hosts, the behaviour of asymmetry when increasing vacuum, and finally NMR scans in ionic liquids. The achieved spin polarization will be also relevant for the plans to measure with high precision the magnetic moments of neutron-rich Cu isotopes.

  11. Spin and Angular Momentum in Strong-Field Ionization

    Science.gov (United States)

    Trabert, D.; Hartung, A.; Eckart, S.; Trinter, F.; Kalinin, A.; Schöffler, M.; Schmidt, L. Ph. H.; Jahnke, T.; Kunitski, M.; Dörner, R.

    2018-01-01

    The spin polarization of electrons from multiphoton ionization of Xe by 395 nm circularly polarized laser pulses at 6 ×1013 W /cm2 has been measured. At this photon energy of 3.14 eV the above-threshold ionization peaks connected to Xe+ ions in the ground state (J =3 /2 , ionization potential Ip=12.1 eV ) and the first excited state (J =1 /2 , Ip=13.4 eV ) are clearly separated in the electron energy distribution. These two combs of above-threshold ionization peaks show opposite spin polarizations. The magnitude of the spin polarization is a factor of 2 higher for the J =1 /2 than for the J =3 /2 final ionic state. In turn, the data show that the ionization probability is strongly dependent on the sign of the magnetic quantum number.

  12. Temperature measurement

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/003400.htm Temperature measurement To use the sharing features on this page, please enable JavaScript. The measurement of body temperature can help detect illness. It can also monitor ...

  13. Importance measures

    International Nuclear Information System (INIS)

    Gomez Cobo, A.

    1997-01-01

    The presentation discusses the following: general concepts of importance measures; example fault tree, used to illustrate importance measures; Birnbaum's structural importance; criticality importance; Fussel-Vesely importance; upgrading function; risk achievement worth; risk reduction worth

  14. Adaptation to High Ethanol Reveals Complex Evolutionary Pathways.

    Directory of Open Access Journals (Sweden)

    Karin Voordeckers

    2015-11-01

    Full Text Available Tolerance to high levels of ethanol is an ecologically and industrially relevant phenotype of microbes, but the molecular mechanisms underlying this complex trait remain largely unknown. Here, we use long-term experimental evolution of isogenic yeast populations of different initial ploidy to study adaptation to increasing levels of ethanol. Whole-genome sequencing of more than 30 evolved populations and over 100 adapted clones isolated throughout this two-year evolution experiment revealed how a complex interplay of de novo single nucleotide mutations, copy number variation, ploidy changes, mutator phenotypes, and clonal interference led to a significant increase in ethanol tolerance. Although the specific mutations differ between different evolved lineages, application of a novel computational pipeline, PheNetic, revealed that many mutations target functional modules involved in stress response, cell cycle regulation, DNA repair and respiration. Measuring the fitness effects of selected mutations introduced in non-evolved ethanol-sensitive cells revealed several adaptive mutations that had previously not been implicated in ethanol tolerance, including mutations in PRT1, VPS70 and MEX67. Interestingly, variation in VPS70 was recently identified as a QTL for ethanol tolerance in an industrial bio-ethanol strain. Taken together, our results show how, in contrast to adaptation to some other stresses, adaptation to a continuous complex and severe stress involves interplay of different evolutionary mechanisms. In addition, our study reveals functional modules involved in ethanol resistance and identifies several mutations that could help to improve the ethanol tolerance of industrial yeasts.

  15. Omics strategies for revealing Yersinia pestis virulence

    Science.gov (United States)

    Yang, Ruifu; Du, Zongmin; Han, Yanping; Zhou, Lei; Song, Yajun; Zhou, Dongsheng; Cui, Yujun

    2012-01-01

    Omics has remarkably changed the way we investigate and understand life. Omics differs from traditional hypothesis-driven research because it is a discovery-driven approach. Mass datasets produced from omics-based studies require experts from different fields to reveal the salient features behind these data. In this review, we summarize omics-driven studies to reveal the virulence features of Yersinia pestis through genomics, trascriptomics, proteomics, interactomics, etc. These studies serve as foundations for further hypothesis-driven research and help us gain insight into Y. pestis pathogenesis. PMID:23248778

  16. Measurement evaluation

    CERN Document Server

    Boros, A

    1990-01-01

    The information obtained about a measured object is called ``crude'' measurement information and must be related to the conditions under which the measurement took place. Using ``crude'' measurement information as a starting point, evaluation produces physically correctly interpreted data with their estimated (or corrected) error. Although a number of works deal with the evaluation of measurements, they either appeared a long time ago or serve essentially different aims. This book gives a comprehensive and current overview on the basic principles, aids, devices, and methods in the eval

  17. Comparing SessionStateReveal and EphemeralKeyReveal for Diffie-Hellman Protocols

    Science.gov (United States)

    Ustaoglu, Berkant

    Both the "eCK" model, by LaMacchia, Lauter and Mityagin, and the "CK01" model, by Canetti and Krawczyk, address the effect of leaking session specific ephemeral data on the security of key establishment schemes. The CK01-adversary is given a SessionStateReveal query to learn session-specific private data defined by the protocol specification, whereas the eCK-adversary is equipped with an EphemeralKeyReveal query to access all ephemeral private input required to carry session computations. SessionStateReveal cannot be issued against the test session; by contrast EphemeralKeyReveal can be used against the test session under certain conditions. On the other hand, it is not obvious how EphemeralKeyReveal compares to SessionStateReveal. Thus it is natural to ask which model is more useful and practically relevant.

  18. Monosomic analysis reveals duplicated chromosomal segments in ...

    Indian Academy of Sciences (India)

    Monosomic analysis reveals duplicated chromosomal segments in maize genome. MAHESH C. YADAV1,2∗, J. K. S. ... cated chromosomal segments in maize genome. Materials and methods. Development and .... each in chromosomes 2 and 7, while 10 other pairs of du- plicate loci had one copy in chromosome 3 and the ...

  19. [Scaphoid enchondroma revealed by a fracture].

    Science.gov (United States)

    El Mrini, A; Daoudi, A; Loudyi, D; Boutayeb, F; Agoumi, O; El Yaacoubi, M

    2006-06-01

    Enchondroma is a common bone tumor of hand. It is rarely localized in scaphoid. We report a new case of this tumor revealed by fracture. The diagnosis was suggested by standard radiography and confirmed then by anatomic pathology examination. Enucleation and bone graft with osteosynthesis yielded good result.

  20. Genetic relationship among Musa genotypes revealed by ...

    African Journals Online (AJOL)

    Genetic relationship among Musa genotypes revealed by microsatellite markers. NAP Abdullah, GB Saleh, ETS Putra, ZB Wahab. Abstract. A banana germplasm was established containing 44 Musa genotypes collected from various locations in Malaysia. To detect their genetic variation and to rule out duplicates among ...