Spatial reorientation experiments for NMR of solids and partially oriented liquids.

PubMed

Martin, Rachel W; Kelly, John E; Collier, Kelsey A

2015-11-01

Motional reorientation experiments are extensions of Magic Angle Spinning (MAS) where the rotor axis is changed in order to average out, reintroduce, or scale anisotropic interactions (e.g. dipolar couplings, quadrupolar interactions or chemical shift anisotropies). This review focuses on Variable Angle Spinning (VAS), Switched Angle Spinning (SAS), and Dynamic Angle Spinning (DAS), all of which involve spinning at two or more different angles sequentially, either in successive experiments or during a multidimensional experiment. In all of these experiments, anisotropic terms in the Hamiltonian are scaled by changing the orientation of the spinning sample relative to the static magnetic field. These experiments vary in experimental complexity and instrumentation requirements. In VAS, many one-dimensional spectra are collected as a function of spinning angle. In SAS, dipolar couplings and/or chemical shift anisotropies are reintroduced by switching the sample between two different angles, often 0° or 90° and the magic angle, yielding a two-dimensional isotropic-anisotropic correlation spectrum. Dynamic Angle Spinning (DAS) is a related experiment that is used to simultaneously average out the first- and second-order quadrupolar interactions, which cannot be accomplished by spinning at any unique rotor angle in physical space. Although motional reorientation experiments generally require specialized instrumentation and data analysis schemes, some are accessible with only minor modification of standard MAS probes. In this review, the mechanics of each type of experiment are described, with representative examples. Current and historical probe and coil designs are discussed from the standpoint of how each one accomplishes the particular objectives of the experiment(s) it was designed to perform. Finally, applications to inorganic materials and liquid crystals, which present very different experimental challenges, are discussed. The review concludes with perspectives on how motional reorientation experiments can be applied to current problems in chemistry, molecular biology, and materials science, given the many advances in high-field NMR magnets, fast spinning, and sample preparation realized in recent years. Copyright © 2015 Elsevier B.V. All rights reserved.

Dynamics of 4-oxo-TEMPO-d16-15N nitroxide-propylene glycol system studied by ESR and ESE in liquid and glassy state in temperature range 10-295 K

NASA Astrophysics Data System (ADS)

Goslar, Janina; Hoffmann, Stanislaw K.; Lijewski, Stefan

2016-08-01

ESR spectra and electron spin relaxation of nitroxide radical in 4-oxo-TEMPO-d16-15N in propylene glycol were studied at X-band in the temperature range 10-295 K. The spin-lattice relaxation in the liquid viscous state determined from the resonance line shape is governed by three mechanisms occurring during isotropic molecular reorientations. In the glassy state below 200 K the spin-lattice relaxation, phase relaxation and electron spin echo envelope modulations (ESEEM) were studied by pulse spin echo technique using 2-pulse and 3-pulse induced signals. Electron spin-lattice relaxation is governed by a single non-phonon relaxation process produced by localized oscillators of energy 76 cm-1. Electron spin dephasing is dominated by a molecular motion producing a resonance-type peak in the temperature dependence of the dephasing rate around 120 K. The origin of the peak is discussed and a simple method for the peak shape analysis is proposed, which gives the activation energy of a thermally activated motion Ea = 7.8 kJ/mol and correlation time τ0 = 10-8 s. The spin echo amplitude is strongly modulated and FT spectrum contains a doublet of lines centered around the 2D nuclei Zeeman frequency. The splitting into the doublet is discussed as due to a weak hyperfine coupling of nitroxide unpaired electron with deuterium of reorienting CD3 groups.

First principles and metadynamics study of the spin-reorientation transition in Fe/Au(001) films

NASA Astrophysics Data System (ADS)

Nagyfalusi, B.; Udvardi, L.; Szunyogh, L.

2017-10-01

Based on first principles calculations, we investigate the magnetic anisotropy and spin reorientation transition (SRT) for Fe n /Au(001) (n=2,3) films. The SRT occurs at three atomic layer of Fe in agreement with experiments due to competing on-site and two-site anisotropy. We also study the temperature dependence of the magnetic anisotropy energy (MAE) by means of metadynamics Monte Carlo simulations.

Reversal magnetization, spin reorientation, and exchange bias in YCr O3 doped with praseodymium

NASA Astrophysics Data System (ADS)

Durán, A.; Escamilla, R.; Escudero, R.; Morales, F.; Verdín, E.

2018-01-01

Crystal structure, thermal properties, and magnetic properties were studied systematically in Y1 -xP rxCr O3 with 0.0 ≤x ≤0.3 compositions. Magnetic susceptibility and specific-heat measurements show an increase in the antiferromagnetic transition temperature (TN) as Pr is substituted in the Y sites and notable magnetic features are observed below TN. Strong coupling between magnetic and crystalline parameters is observed in a small range of Pr compositions. A small perturbation in the lattice parameters by a Pr ion is sufficient to induce a spin-reorientation transition followed by magnetization reversal to finally induce the exchange-bias effect. The spin-reorientation temperature (TSR) is increased from 35 to 149 K for 0.025 ≤x ≤0.1 compositions. It is found that the Cr spin sublattice rotates continuously from TSR to a new spin configuration at lower temperature. In addition, magnetization reversal is observed at T*˜35 K for x =0.05 up to T*˜63 K for x =0.20 composition. The M -H curves show a negative exchange-bias effect induced by Pr ions, which are observed below 100 K and are more intense at 5 K. At 10 K, the magnetic contribution of the specific heat as well as the ZFC magnetization show the rise of a peak with increasing Pr content. The magnetic anomaly could be associated with the freezing of the Pr magnetic moment randomly distributed at the 4 c crystallographic site. A clear correspondence between spin reorientation, magnetization reversal, and exchange-bias anisotropy with the tilting and octahedral distortion is also discussed.

Superconducting spin valves controlled by spiral re-orientation in B20-family magnets

NASA Astrophysics Data System (ADS)

Pugach, N. G.; Safonchik, M.; Champel, T.; Zhitomirsky, M. E.; Lähderanta, E.; Eschrig, M.; Lacroix, C.

2017-10-01

We propose a superconducting spin-triplet valve, which consists of a superconductor and an itinerant magnetic material, with the magnet showing an intrinsic non-collinear order characterized by a wave vector that may be aligned in a few equivalent preferred directions under the control of a weak external magnetic field. Re-orienting the spiral direction allows one to controllably modify long-range spin-triplet superconducting correlations, leading to spin-valve switching behavior. Our results indicate that the spin-valve effect may be noticeable. This bilayer may be used as a magnetic memory element for cryogenic nanoelectronics. It has the following advantages in comparison to superconducting spin valves proposed previously: (i) it contains only one magnetic layer, which may be more easily fabricated and controlled; (ii) its ground states are separated by a potential barrier, which solves the "half-select" problem of the addressed switch of memory elements.

Thickness driven spin reorientation transition of epitaxial LaCrO3 films

NASA Astrophysics Data System (ADS)

Park, Junho; Kim, Dong-Hwan; Lee, Doopyo; Ko, Kyung-Tae; Hyun Song, Jong; Kim, Jae-Young; Koo, Tae-Yeong; Lee, Seung Ran; Park, Jae-Hoon

2018-03-01

We grew fully strained epitaxial LaCrO3 (LCO) films on SrTiO3(001) under layer-by-layer control up to the film thickness of t = 130 nm using a pulsed laser deposition method. The spin axis of the antiferromagnetic LCO film was systematically examined as a function of t by using Cr L2,3-edge x-ray magnetic linear dichroism (XMLD). The XMLD results manifest a spin reorientation transition (SRT) across a transition thickness of tT ˜ 60 nm. This SRT is well explained in terms of two competing magnetic anisotropy energies of the surface/interface (KS) and the LCO film itself (KV).

INTRAMOLECULAR MOTION AND REORIENTATIONAL BARRIERS IN 9-FLUORENONE, 4-METHYL-9-FLUORENONE AND 4,5-DIMETHYL-9-FLUORENONE

EPA Science Inventory

Carbon-13 nuclear magnetic resonance spin-lattice relaxation times and nuclear Overhauser enhancements were measured as functions of temperature for the hydrogen-bearing carbons in 9-fluorenone, 4-methyl-9-fluorenone, and 4,5-dimethyl-9-fluorenone. Reorientational diffusion const...

Single crystal growth, magnetic and thermal properties of perovskite YFe0.6Mn0.4O3 single crystal

NASA Astrophysics Data System (ADS)

Xie, Tao; Shen, Hui; Zhao, Xiangyang; Man, Peiwen; Wu, Anhua; Su, Liangbi; Xu, Jiayue

2016-11-01

High quality YFe0.6Mn0.4O3 single crystal was grown by floating zone technique using a four-mirror-image-furnace under flowing air. Powder X-ray diffraction gives well evidence that the specimen has an orthorhombic structure, with space group Pbnm. Temperature dependence of the magnetizations of YFe0.6Mn0.4O3 single crystal were studied under ZFC and FC modes in the temperature range from 5 K to 400 K. A clear spin reorientation transition behavior (Γ4→Γ1) is observed in the temperature range of 322-316 K, due to the substitution of Mn at the Fe site of YFeO3. Its Néel temperature is around 385 K. Moreover, the spin reorientation is verified by the change of magnetic hysteresis loops of the sample along [001] axis in the temperature range of 50-385 K. The thermal properties of the sample were measured by the differential scanning calorimeter (DSC) from 300 K to 500 K, which also clearly appear anomaly in the spin reorientation region.

Nd-ordering-driven Mn spin reorientation and magnetization reversal in the magnetostructurally coupled compound NdMn O3

NASA Astrophysics Data System (ADS)

Kumar, A.; Yusuf, S. M.; Ritter, C.

2017-07-01

A detailed neutron diffraction study on NdMn O3 infers that the low temperature transition at 15 K is due to the ordering of Nd sublattice moment with a (0 ,-Fy,0 ) type spin arrangement. Interestingly, the ordering of the Nd sublattice drives a reorientation (by 180∘) of the net ferromagnetic moment of the Mn sublattice along the b axis. Such a Mn spin reorientation from (Ax,Fy,0 ) (with an antiferromagnetic ordering temperature of 73 K) to (Ax,-Fy,0 ) at 15 K, explains the magnetization reversal phenomenon present in this perovskite compound at 15 K. Moreover at 15 K, significant crystallographic structural distortions in terms of temperature variations of lattice parameters and bond angles are found. A sign change in the temperature variation of magnetic entropy is also found at 15 K. The present study signifies the role of rare-earth (Nd) moment ordering in tuning various physical properties, such as magnetocaloric and magnetoelastic of the larger size (>0.912 Å ) R ion based R Mn O3 compounds.

Dramatic impact of the giant local magnetic fields on spin-dependent recombination processes in gadolinium based garnets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Romanov, N. G., E-mail: nikolai.romanov@mail.ioffe.ru; Tolmachev, D. O.; Gurin, A. S.

2015-06-29

A giant magnetic field effect on spin-dependent recombination of the radiation-induced defects has been found in cerium doped gadolinium based garnet crystals and ceramics, promising materials for scintillator applications. A sharp and strong increase in the afterglow intensity stimulated by external magnetic field and an evidence of the magnetic field memory have been discovered. The effect was ascribed to huge Gd-induced internal magnetic fields, which suppress the recombination, and cross-relaxation with Gd{sup 3+} ions leading to reorientation of the spins of the electron and hole centers. Thus, the spin system of radiation-induced defects in gadolinium garnet based scintillator materials wasmore » shown to accumulate significant energy which can be released in external magnetic fields.« less

Symmetry-lowering lattice distortion at the spin reorientation in MnBi single crystals

DOE PAGES

McGuire, Michael A.; Cao, Huibo; Chakoumakos, Bryan C.; ...

2014-11-18

Here we report structural and physical properties determined by measurements on large single crystals of the anisotropic ferromagnet MnBi. The findings support the importance of magnetoelastic effects in this material. X-ray diffraction reveals a structural phase transition at the spin reorientation temperature T SR = 90 K. The distortion is driven by magneto-elastic coupling, and upon cooling transforms the structure from hexagonal to orthorhombic. Heat capacity measurements show a thermal anomaly at the crystallographic transition, which is suppressed rapidly by applied magnetic fields. Effects on the transport and anisotropic magnetic properties of the single crystals are also presented. Increasing anisotropymore » of the atomic displacement parameters for Bi with increasing temperature above T SR is revealed by neutron diffraction measurements. It is likely that this is directly related to the anisotropic thermal expansion in MnBi, which plays a key role in the spin reorientation and magnetocrystalline anisotropy. Finally, the identification of the true ground state crystal structure reported here may be important for future experimental and theoretical studies of this permanent magnet material, which have to date been performed and interpreted using only the high temperature structure.« less

Continuous reorientation of synchronous terrestrial planets due to mantle convection

NASA Astrophysics Data System (ADS)

Leconte, Jérémy

2018-03-01

Many known rocky exoplanets are thought to have been spun down by tidal interactions to a state of synchronous rotation, in which a planet's period of rotation is equal to that of its orbit around its host star. Investigations into atmospheric and surface processes occurring on such exoplanets thus commonly assume that day and night sides are fixed with respect to the surface over geological timescales. Here we use an analytical model to show that true polar wander—where a planetary body's spin axis shifts relative to its surface because of changes in mass distribution—can continuously reorient a synchronous rocky exoplanet. As occurs on Earth, we find that even weak mantle convection in a rocky exoplanet can produce density heterogeneities within the mantle sufficient to reorient the planet. Moreover, we show that this reorientation is made very efficient by the slower rotation rate of a synchronous planet when compared with Earth, which limits the stabilizing effect of rotational and tidal deformations. Furthermore, a relatively weak lithosphere limits its ability to support remnant loads and stabilize against reorientation. Although uncertainties exist regarding the mantle and lithospheric evolution of these worlds, we suggest that the axes of smallest and largest moment of inertia of synchronous exoplanets with active mantle convection change continuously over time, but remain closely aligned with the star-planet and orbital axes, respectively.

Slow molecular dynamics of water in a lyotropic complex fluid studied by deuterium conventional and spin-lattice relaxometry NMR.

PubMed

Rodríguez, C R; Pusiol, D J; Figueiredo Neto, A M; Seitter, R-O

2002-03-01

A nuclear magnetic resonance study of protons and deuterons in the mesomorphic phases of the micellar lyotropic mixture potassium laurate/1-decanol/heavy water is reported. The slow dynamical behavior of water molecules has been investigated with deuterons spin-lattice relaxation dispersion in the Larmor frequency range 10(3)

Element-resolved magnetism across the temperature- and pressure-induced spin reorientation in MnBi

DOE PAGES

Choi, Yongseong; Jiang, Xiujuan; Bi, Wenli; ...

2016-11-01

Rare-earth free permanent magnet MnBi (NiAs-type crystal structure) displays strong magnetic anisotropy above its 90 K spin reorientation transition (SRT). X-ray magnetic circular dichroism (XMCD) shows induced magnetism in Bi 5d band, which is strongly coupled to the magnetism of Mn. A clear increase in Bi orbital-to-spin moment ratio is observed above the SRT. Hydrostatic pressure mimics the e*ect of temperature on the SRT, and the pressure effect also leads to anisotropic lattice contraction, which is known to be induced by cooling. These results reveal that temperature and pressure can similarly induce the coupled structural and magnetic responses, suggesting themore » importance of the anisotropic lattice change and Mn-Bi hybridization to the magnetic anisotropy change across the SRT.« less

Origin of spin reorientation transitions in antiferromagnetic MnPt-based alloys

NASA Astrophysics Data System (ADS)

Chang, P.-H.; Zhuravlev, I. A.; Belashchenko, K. D.

2018-04-01

Antiferromagnetic MnPt exhibits a spin reorientation transition (SRT) as a function of temperature, and off-stoichiometric Mn-Pt alloys also display SRTs as a function of concentration. The magnetocrystalline anisotropy in these alloys is studied using first-principles calculations based on the coherent potential approximation and the disordered local moment method. The anisotropy is fairly small and sensitive to the variations in composition and temperature due to the cancellation of large contributions from different parts of the Brillouin zone. Concentration and temperature-driven SRTs are found in reasonable agreement with experimental data. Contributions from specific band-structure features are identified and used to explain the origin of the SRTs.

Successive field-induced transitions in BiFeO 3 around room temperature

DOE PAGES

Kawachi, Shiro; Miyake, Atsushi; Ito, Toshimitsu; ...

2017-07-21

The effects of high magnetic fields applied perpendicular to the spontaneous ferroelectric polarization on single crystals of BiFeO 3 were investigated in this paper through magnetization, magnetostriction, and neutron diffraction measurements. The magnetostriction measurements revealed lattice distortion of 2 x 10 -5 during the reorientation process of the cycloidal spin order by applied magnetic fields. Furthermore, anomalous changes in magnetostriction and electric polarization at a larger field demonstrate an intermediate phase between cycloidal and canted antiferromagnetic states, where a large magnetoelectric effect was observed. Neutron diffraction measurements clarified that incommensurate spin modulation along the [110] hex direction in the cycloidalmore » phase becomes Q = 0 commensurate along this direction in the intermediate phase. Finally, theoretical calculations based on the standard spin Hamiltonian of this material suggest an antiferromagnetic cone-type spin order in the intermediate phase.« less

Spin reorientation transition and hard magnetic properties of MnBi intermetallic compound

NASA Astrophysics Data System (ADS)

Suzuki, K.; Wu, X.; Ly, V.; Shoji, T.; Kato, A.; Manabe, A.

2012-04-01

The effects of mechanical grinding (MG) on the crystallite size, the spin reorientation transition temperature (TSR) and the hard magnetic properties in melt-spun low temperature phase (LTP) MnBi have been investigated in order to understand the origin of magnetic hardening induced by MG. The room-temperature coercive field (μ0Hcj) is enhanced dramatically from 0.08 T before MG to 1.5 T after MG for 43.2 ks while TSR is concurrently suppressed from 110 to 38 K. The coercive force exhibits positive temperature dependence approximately 50-60 K above TSR and the lowered TSR after MG could result in magnetic hardening at room temperature. The room-temperature coercive force of LTP-MnBi is highly dependent on the crystallite size (D) and is found to be described phenomenologically by the following relationship: μ0Hcj = μ0Ha(δ/D)n, where μ0Ha is ˜ 4 T, the Bloch wall width δ is 7 nm, and the exponent n is approximately 0.7. Our results suggest that the grain refinement is the primary origin of the hardening effect induced by MG with a possible minor hardening effect due to the suppression of the spin reorientation transition temperature.

Ionic Liquid Gating Control of Spin Reorientation Transition and Switching of Perpendicular Magnetic Anisotropy.

PubMed

Zhao, Shishun; Wang, Lei; Zhou, Ziyao; Li, Chunlei; Dong, Guohua; Zhang, Le; Peng, Bin; Min, Tai; Hu, Zhongqiang; Ma, Jing; Ren, Wei; Ye, Zuo-Guang; Chen, Wei; Yu, Pu; Nan, Ce-Wen; Liu, Ming

2018-05-29

Electric field (E-field) modulation of perpendicular magnetic anisotropy (PMA) switching, in an energy-efficient manner, is of great potential to realize magnetoelectric (ME) memories and other ME devices. Voltage control of the spin-reorientation transition (SRT) that allows the magnetic moment rotating between the out-of-plane and the in-plane direction is thereby crucial. In this work, a remarkable magnetic anisotropy field change up to 1572 Oe is achieved under a small operation voltage of 4 V through ionic liquid (IL) gating control of SRT in Au/[DEME] + [TFSI] - /Pt/(Co/Pt) 2 /Ta capacitor heterostructures at room temperature, corresponding to a large ME coefficient of 378 Oe V -1 . As revealed by both ferromagnetic resonance measurements and magnetic domain evolution observation, the magnetization can be switched stably and reversibly between the out-of-plane and in-plane directions via IL gating. The key mechanism, revealed by the first-principles calculation, is that the IL gating process influences the interfacial spin-orbital coupling as well as net Rashba magnetic field between the Co and Pt layers, resulting in the modulation of the SRT and in-plane/out-of-plane magnetization switching. This work demonstrates a unique IL-gated PMA with large ME tunability and paves a way toward IL gating spintronic/electronic devices such as voltage tunable PMA memories. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Magnetostructural coupling, magnetic ordering, and cobalt spin reorientation in metallic P r0.5S r0.5Co O3 cobaltite

NASA Astrophysics Data System (ADS)

García-Muñoz, José Luis; Padilla-Pantoja, Jessica; Torrelles, Xavier; Blasco, Javier; Herrero-Martín, Javier; Bozzo, Bernat; Rodríguez-Velamazán, José A.

2016-07-01

In half-doped P r0.50A0.50Co O3 metallic perovskites, the spin-lattice coupling brings about distinct magnetostructural transitions for A =Ca and A =Sr at temperatures close to ˜100 K. However, the ground magnetic properties of P r0.50S r0.50Co O3 (PSCO) strongly differ from P r0.50C a0.50Co O3 ones, where a partial P r3 + to P r4 + valence shift and Co spin transition makes the system insulating below the transition. This paper investigates and describes the relationship between the I m m a →I 4 /m c m symmetry change [Padilla-Pantoja, García-Muñoz, Bozzo, Jirák, and Herrero-Martín, Inorg. Chem. 53, 12297 (2014)] and the original magnetic behavior of PSCO versus temperature and external magnetic fields. The FM1 and FM2 ferromagnetic phases, above and below the magnetostructural transition (TS 1˜120 K ) have been investigated. The FM2 phase of PSCO is composed of [100] FM domains, with magnetic symmetry I m'm'a (mx≠0 , mz=0 ). The magnetic space group of the FM1 phase is F m'm'm (with mx=my ). Neutron data analyses in combination with magnetometry and earlier reports results agrees with a reorientation of the magnetization axis by 45∘ within the a b plane across the transition, in which the system retains its metallic character. The presence below TS 1 of conjugated magnetic domains, both of F m'm'm symmetry but having perpendicular spin orientations along the diagonals in the x y plane of the tetragonal unit cell, is at the origin of the anomalies observed in the macroscopic magnetization. A relatively small field μ0H [⊥ z ] ≳30 mT is able to reorient the magnetization within the a b plane, whereas a higher field (μ0H [∥z ] ≳1.2 T at 2 K) is necessary to align the Co moments perpendicular to the a b plane. Such a spin reorientation, in which the orbital and spin components of the Co moment rotate joined by 45∘, was not observed previously in analogous cobaltites without praseodymium.

Modeling of pulsed propellant reorientation

NASA Technical Reports Server (NTRS)

Patag, A. E.; Hochstein, J. I.; Chato, D. J.

1989-01-01

Optimization of the propellant reorientation process can provide increased payload capability and extend the service life of spacecraft. The use of pulsed propellant reorientation to optimize the reorientation process is proposed. The ECLIPSE code was validated for modeling the reorientation process and is used to study pulsed reorientation in small-scale and full-scale propellant tanks. A dimensional analysis of the process is performed and the resulting dimensionless groups are used to present and correlate the computational predictions for reorientation performance.

Electron paramagnetic resonance studies of slowly tumbling vanadyl spin probes in nematic liquid crystals

NASA Technical Reports Server (NTRS)

Bruno, G. V.; Harrington, J. K.; Eastman, M. P.

1978-01-01

An analysis of EPR line shapes by the method of Polnaszek, Bruno, and Freed is made for slowly tumbling vanadyl spin probes in viscous nematic liquid crystals. The use of typical vanadyl complexes as spin probes for nematic liquid crystals is shown to simplify the theoretical analysis and the subsequent interpretation. Rotational correlation times tau and orientational ordering parameters S sub Z where slow tumbling effects are expected to be observed in vanadyl EPR spectra are indicated in a plot. Analysis of the inertial effects on the probe reorientation, which are induced by slowly fluctuating torque components of the local solvent structure, yield quantitative values for tau and S sub Z. The weakly ordered probe VOAA is in the slow tumbling region and displays these inertial effects throughout the nematic range of BEPC and Phase V. VOAA exhibits different reorientation behavior near the isotropic-nematic transition temperature than that displayed far below this transition temperature.

High Resolution NMR Studies of Encapsulated Proteins In Liquid Ethane

PubMed Central

Peterson, Ronald W.; Lefebvre, Brian G.; Wand, A. Joshua

2005-01-01

Many of the difficulties presented by large, aggregation-prone, and membrane proteins to modern solution NMR spectroscopy can be alleviated by actively seeking to increase the effective rate of molecular reorientation. An emerging approach involves encapsulating the protein of interest within the protective shell of a reverse micelle, and dissolving the resulting particle in a low viscosity fluid, such as the short chain alkanes. Here we present the encapsulation of proteins with high structural fidelity within reverse micelles dissolved in liquid ethane. The addition of appropriate co-surfactants can significantly reduce the pressure required for successful encapsulation. At these reduced pressures, the viscosity of the ethane solution is low enough to provide sufficiently rapid molecular reorientation to significantly lengthen the spin-spin NMR relaxation times of the encapsulated protein. PMID:16028922

Dancing in the dark: galactic properties trace spin swings along the cosmic web

NASA Astrophysics Data System (ADS)

Dubois, Y.; Pichon, C.; Welker, C.; Le Borgne, D.; Devriendt, J.; Laigle, C.; Codis, S.; Pogosyan, D.; Arnouts, S.; Benabed, K.; Bertin, E.; Blaizot, J.; Bouchet, F.; Cardoso, J.-F.; Colombi, S.; de Lapparent, V.; Desjacques, V.; Gavazzi, R.; Kassin, S.; Kimm, T.; McCracken, H.; Milliard, B.; Peirani, S.; Prunet, S.; Rouberol, S.; Silk, J.; Slyz, A.; Sousbie, T.; Teyssier, R.; Tresse, L.; Treyer, M.; Vibert, D.; Volonteri, M.

2014-10-01

A large-scale hydrodynamical cosmological simulation, Horizon-AGN, is used to investigate the alignment between the spin of galaxies and the cosmic filaments above redshift 1.2. The analysis of more than 150 000 galaxies per time step in the redshift range 1.2 < z < 1.8 with morphological diversity shows that the spin of low-mass blue galaxies is preferentially aligned with their neighbouring filaments, while high-mass red galaxies tend to have a perpendicular spin. The reorientation of the spin of massive galaxies is provided by galaxy mergers, which are significant in their mass build-up. We find that the stellar mass transition from alignment to misalignment happens around 3 × 1010 M⊙. Galaxies form in the vorticity-rich neighbourhood of filaments, and migrate towards the nodes of the cosmic web as they convert their orbital angular momentum into spin. The signature of this process can be traced to the properties of galaxies, as measured relative to the cosmic web. We argue that a strong source of feedback such as active galactic nuclei is mandatory to quench in situ star formation in massive galaxies and promote various morphologies. It allows mergers to play their key role by reducing post-merger gas inflows and, therefore, keeping spins misaligned with cosmic filaments.

Anisotropic magnetic structures of the Mn R MnSbO6 high-pressure doubly ordered perovskites (R =La , Pr, and Nd)

NASA Astrophysics Data System (ADS)

Solana-Madruga, Elena; Arévalo-López, Ángel M.; Dos santos-García, Antonio J.; Ritter, Clemens; Cascales, Concepción; Sáez-Puche, Regino; Attfield, J. Paul

2018-04-01

A new type of doubly ordered perovskite (also reported as double double perovskite, DDPv) structure combining columnar and rock-salt orders of the cations at the A and B sites, respectively, was recently found at high pressure for Mn R MnSb O6 (R =La -Sm ). Here we report further magnetic structures of these compounds. M n2 + spins align into antiparallel ferromagnetic sublattices along the x axis for MnLaMnSb O6 , while the magnetic anisotropy of P r3 + magnetic moments induces their preferential order along the z direction for MnPrMnSb O6 . The magnetic structure of MnNdMnSb O6 was reported to show a spin-reorientation transition of M n2 + spins from the z axis towards the x axis driven by the ordering of N d3 + magnetic moments. The crystal-field parameters for P r3 + and N d3 + at the 4 e C2 site of their DDPv structure have been semiempirically estimated and used to derive their energy levels and associated wave functions. The results demonstrate that the spin-reorientation transition in MnNdMnSb O6 arises as a consequence of the crystal-field-induced magnetic anisotropy of N d3 + .

Giant magnetocaloric effect and temperature induced magnetization jump in GdCrO{sub 3} single crystal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yin, L. H.; Yang, J.; Kan, X. C.

2015-04-07

We report on a systematic study of the single-crystal GdCrO{sub 3}, which shows various novel magnetic features, such as temperature-induced magnetization reversal (TMR), temperature-induced magnetization jump (TMJ), spin reorientation, and giant magnetocaloric effect (MCE). In the field-cooled cooling process with modest magnetic field along the c axis, GdCrO{sub 3} first shows a TMR at T{sub comp}∼120−130 K and then an abrupt TMJ with a sign change of magnetization at T{sub jump}∼52−120 K, and finally a spin reorientation at T{sub SR}∼4−7 K. Interestingly, the remarkable TMJ behavior, which was not reported ever before, persists at higher fields up to 10 kOe even when TMRmore » disappears. In addition, giant MCE with the maximum value of magnetic entropy change reaching ∼31.6 J/kg K for a field change of 44 kOe was also observed in GdCrO{sub 3} single crystal, suggesting it could be a potential material for low-T magnetic refrigeration. A possible mechanism for these peculiar magnetic behaviors is discussed based on the various competing magnetic interactions between the 3d electrons of Cr{sup 3+} ions and 4f electrons of Gd{sup 3+} ions.« less

Investigation of technical problems related to deployment and retrieval of spinning satellites

NASA Technical Reports Server (NTRS)

Kaplan, M. H.

1973-01-01

Results of a three-year research effort on retrieval and deployment problems associated with orbiting payloads are summarized. Answers to several basic questions about rendezvous, docking, and deployment dynamics and controls were obtained. A basic retrieval mission profile was formulated in order to develop relevant technology. A remotely controlled retrieval package was conceived. Special deployment dynamics problems associated with high altitude deployment were investigated, and new knowledge of payload spin reorientation was obtained.

Elastic and inelastic scattering for the 10B+58Ni system at near-barrier energies

NASA Astrophysics Data System (ADS)

Scarduelli, V.; Crema, E.; Guimarães, V.; Abriola, D.; Arazi, A.; de Barbará, E.; Capurro, O. A.; Cardona, M. A.; Gallardo, J.; Hojman, D.; Martí, G. V.; Pacheco, A. J.; Rodrígues, D.; Yang, Y. Y.; Deshmukh, N. N.; Paes, B.; Lubian, J.; Mendes Junior, D. R.; Morcelle, V.; Monteiro, D. S.

2017-11-01

Full angular distributions of the 10B elastically and inelastically scattered by 58Ni have been measured at different energies around the Coulomb barrier. The elastic and inelastic scattering of 10B on a medium mass target has been measured for the first time. The obtained angular distributions have been analyzed in terms of large-scale coupled reaction channel calculations, where several inelastic transitions of the projectile and the target, as well as the most relevant one- and two-step transfer reactions have been included in the coupling matrix. The roles of the spin reorientation, the spin-orbit interaction, and the large ground-state deformation of the 10B, in the reaction mechanism, were also investigated. The real part of the interaction potential between projectile and target was represented by a parameter-free double-folding potential, whereas no imaginary potential at the surface was considered. In this sense, the theoretical calculations were parameter free and their results were compared to experimental data to investigate the relative importance of the different reaction channels. A striking influence of the ground-state spin reorientation of the 10B nucleus was found, while all transfer reactions investigated had a minimum contribution to the dynamics of the system. Finally, the large static deformation of the 10B and the spin-orbit coupling can also play an important role in the system studied.

Magnetic behavior of R2Fe14B hydrides (R = Gd, Tb, Dy, Ho and Er)

NASA Astrophysics Data System (ADS)

Zhang, L. Y.; Pourarian, F.; Wallace, W. E.

1988-01-01

R 2Fe 14B systems, with R = Gd, Tb, By, HoandEr were hydrogenated to the composition R 2Fe 14BH x where x ranges from 3.7 to 5.4. The pressure-composition isotherms (PCIs) of the hydrides showed only a solid solution behavior. No plateau pressure region was observed between room temperature and 300° C and at pressures down to 10 -2 atm. The absorbed hydrogen leads to an increase of 2.6 to 3.4% in unit cell volume, without a change in crystal structure. Magnetic characteristics of the present compounds were investigated over the temperature range 4.2 to 1100 K and at applied field up to 20 kOe. Saturation magnetization, Ms, and magnetic ordering temperature, Tc, were enhanced upon hydrogenation. Tc, is found to be dependent on the hydriding composition. Hydrogen induces a spin-reorientation effect (SR) in Gd- and Dy-containing compounds, while it has a marked influence in raising the spin-reorientation temperature, TSR, in the Er 2Fe 14B compound. The hydride involving Tb appears to remain uniaxial to the lowest temperature studied. In all cases the anisotropy fields, HA/' were significally reduced by hydrogen absorption. These varied magnetic behaviors can be ascribed to the effects: (1) variations in the interatomic distances, (2) strengthening the 3d-3d and weakening the 4f-3d exchange interactions and (3) the interstitial site occupations of hydrogen in the lattice. The spin-reorientation phenomena observed for Gd 2Fe 14BH x suggest that there is competition among the 6 Fe sublattices in regard to the sign and temperature coefficient of anisotropy.

Pluto followed its heart: reorientation and faulting of Pluto due to volatile loading in Sputnik Planum

NASA Astrophysics Data System (ADS)

Tuttle Keane, James; Matsuyama, Isamu; Kamata, Shunichi; Steckloff, Jordan

2016-10-01

The New Horizons flyby of Pluto revealed the dwarf planet to be a strikingly diverse, geologically active world. Perhaps the most intriguing feature on the New Horizons encounter hemisphere is Sputnik Planum—a 1000 km diameter, probable impact basin, filled with several kilometers of actively convecting volatile ices (N2, CH4, CO). One salient characteristic of Sputnik Planum is its curious alignment with the Pluto-Charon tidal axis. The alignment of large geologic features with principal axis of inertia (such as the tidal axis) is the hallmark of global reorientation, i.e. true polar wander. Here we show that the present location of Sputnik Planum is a natural consequence of loading of 1-2 km of volatile ices within the Sputnik Planum basin. Larger volatile ice thicknesses (like those inferred from studies of ice convection within Sputnik Planum) betray an underlying negative gravity anomaly associated with the basin. As Pluto reoriented in response to the loading of volatile ices within Sputnik Planum, stresses accumulated within the lithosphere (as each geographic location experiences a change in tidal/rotational potential). These reorientation stresses, coupled with loading stresses, and stresses from the freezing of a subsurface ocean resulted in the fracturing of Pluto's lithosphere in a characteristic, global pattern of extensional faults. Our predicted pattern of extensional faults due to this reorientation closely replicates the observed distribution of faults on Pluto (more so than global expansion, orbit migration, de-spinning, or loading alone). Sputnik Planum likely formed ~60° northwest of its present location, and was loaded with volatile ices over millions of years due to seasonal volatile transport cycles. This result places Pluto in a truly unique category of planetary bodies where volatiles are not only controlling surface geology and atmospheric processes, but they are also directly controlling the orientation of the entire dwarf planet. Pluto's past, present, and future orientation is controlled by complicated feedbacks between volatile transport, insolation, and interior structure.

Magnetocaloric effect in Gd1-x Ndx Zn2

NASA Astrophysics Data System (ADS)

Matsumoto, Keisuke T.; Hiraoka, Koichi

2017-09-01

The magnetization of Gd1-xNdxZn2 (0 < x ⩽ 1) was measured to study the effect of Nd substitution in GdZn2 with a Curie temperature of 85 K and a spin-reorientation transition temperature of 58 K on the magnetocaloric effect. The Nd counterpart NdZn2 shows antiferromagnetic order at 23 K. Samples of Gd1-xNdxZn2 (0 < x ⩽ 1) were prepared by the melt-growth method. In Nd-substituted systems, the anomaly due to spin-reorientation disappeared. For x ⩾ 0.6 , field-induced metamagnetic transitions were observed, indicating an antiferromagnetic ground state. This complex magnetism may originate from competition between ferromagnetic and antiferromagnetic interactions. Magnetic entropy change ΔSm was calculated based on the magnetization measurements. ΔSm was suppressed by Nd substitution for x values up to 0.6. For x = 1 (NdZn2), the maximum value of ΔSm was -9 J/K kg, which is almost the same as those of other Nd-based magnetocaloric materials.

Oxidation-induced spin reorientation in Co adatoms and CoPd dimers on Ni/Cu(100)

NASA Astrophysics Data System (ADS)

Chen, K.; Beeck, T.; Fiedler, S.; Baev, I.; Wurth, W.; Martins, M.

2016-04-01

Ultrasmall magnetic clusters and adatoms are of strong current interest because of their possible use in future technological applications. Here, we demonstrate that the magnetic coupling between the adsorbates and the substrate can be significantly changed through oxidation. The magnetic properties of Co adatoms and CoPd dimers deposited on a remanently magnetized Ni/Cu(100) substrate have been investigated by x-ray absorption and x-ray magnetic circular dichroism spectroscopy at the Co L2 ,3 edges. Using spectral differences, pure and oxidized components are distinguished, and their respective magnetic moments are determined. The Co adatoms and the CoPd dimers are coupled ferromagnetically to the substrate, while their oxides, Co-O and CoPd-O, are coupled antiferromagnetically to the substrate. Along with the spin reorientation from the pure to the oxidized state, the magnetic moment of the adatom is highly reduced from Co to Co-O. In contrast, the magnetic moment of the dimer is of similar order for CoPd and CoPd-O.

Tidal-Rotational Dynamics of Solar System Worlds, from the Moon to Pluto

NASA Astrophysics Data System (ADS)

Keane, James Tuttle

The spins of planetary bodies are not stagnant; they evolve in response to both external and internal forces. One way a planet's spin can change is through true polar wander. True polar wander is the reorientation of a planetary body with respect to its angular momentum vector, and occurs when mass is redistributed within the body, changing its principal axes of inertia. True polar wander can literally reshape a world, and has important implications for a variety of processes--from the long-term stability of polar volatiles in the permanently shadowed regions of airless worlds like the Moon and Mercury, to the global tectonic patterns of icy worlds like Pluto. In this dissertation, we investigate three specific instances of planetary true polar wander, and their associated consequences. In Chapter 2 we investigate the classic problem of the Moon's dynamical figure. By considering the effects of a fossil figure supported by an elastic lithosphere, and the contribution of impact basins to the figure, we find that the lunar figure is consistent with the Moon's lithosphere freezing in when the Moon was much closer to the Earth, on a low eccentricity synchronous orbit. The South Pole-Aitken impact basin is the single largest perturbation to the Moon's figure and resulted in tens of degrees of true polar wander after its formation. In Chapter 3 we continue our analyses of the lunar figure in light of the discovery of a lunar "volatile" paleopole, preserved in the distribution of hydrogen near the Moon's poles. We find that the formation and evolution of the Procellarum KREEP Terrain significantly altered the Moon's orientation, implying that some fraction of the Moon's polar volatiles are ancient--predating the geologic activity within the Procellarum region. In Chapter 4 we investigate how the formation of the giant, basin-filling glacier, Sputnik Planitia reoriented Pluto. This reorientation is recorded in both the present- day location of Sputnik Planitia (near the Pluto-Charon tidal axis), and the tectonic record of Pluto. This reorientation likely reflects a coupling between Pluto's volatile cycles and rotational dynamics, and may be active on other worlds with comparably large, mobile volatile reservoirs. Finally, in Chapter 5 we consider the broader context of these studies, and touch on future investigations of true polar wander on Mercury, Venus, Mars, Vesta, Ceres, and other worlds in our solar system.

Pressure-induced spin reorientation transition in layered ferromagnetic insulator Cr2Ge2Te6

NASA Astrophysics Data System (ADS)

Lin, Zhisheng; Lohmann, Mark; Ali, Zulfikhar A.; Tang, Chi; Li, Junxue; Xing, Wenyu; Zhong, Jiangnan; Jia, Shuang; Han, Wei; Coh, Sinisa; Beyermann, Ward; Shi, Jing

2018-05-01

The anisotropic magnetoresistance (AMR) of Cr2Ge2Te6 (CGT), a layered ferromagnetic insulator, is investigated under an applied hydrostatic pressure up to 2 GPa. The easy-axis direction of the magnetization is inferred from the AMR saturation feature in the presence and absence of an applied pressure. At zero applied pressure, the easy axis is along the c direction or perpendicular to the layer. Upon application of a hydrostatic pressure > 1 GPa, the uniaxial anisotropy switches to easy-plane anisotropy which drives the equilibrium magnetization from the c axis to the a b plane at zero magnetic field, which amounts to a giant magnetic anisotropy energy change (> 100%). As the temperature is increased across the Curie temperature, the characteristic AMR effect gradually decreases and disappears. Our first-principles calculations confirm the giant magnetic anisotropy energy change with moderate pressure and assign its origin to the increased off-site spin-orbit interaction of Te atoms due to a shorter Cr-Te distance. Such a pressure-induced spin reorientation transition is very rare in three-dimensional ferromagnets, but it may be common to other layered ferromagnets with similar crystal structures to CGT, and therefore offers a unique way to control magnetic anisotropy.

CALIBRATION OF EQUILIBRIUM TIDE THEORY FOR EXTRASOLAR PLANET SYSTEMS. II

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hansen, Brad M. S., E-mail: hansen@astro.ucla.edu

2012-09-20

We present a new empirical calibration of equilibrium tidal theory for extrasolar planet systems, extending a prior study by incorporating detailed physical models for the internal structure of planets and host stars. The resulting strength of the stellar tide produces a coupling that is strong enough to reorient the spins of some host stars without causing catastrophic orbital evolution, thereby potentially explaining the observed trend in alignment between stellar spin and planetary orbital angular momentum. By isolating the sample whose spins should not have been altered in this model, we also show evidence for two different processes that contribute tomore » the population of planets with short orbital periods. We apply our results to estimate the remaining lifetimes for short-period planets, examine the survival of planets around evolving stars, and determine the limits for circularization of planets with highly eccentric orbits. Our analysis suggests that the survival of circularized planets is strongly affected by the amount of heat dissipated, which is often large enough to lead to runaway orbital inflation and Roche lobe overflow.« less

Understanding spin configuration in the geometrically frustrated magnet TbB 4: A resonant soft X-ray scattering study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, H.; Jang, H.; Kang, B. Y.

The frustrated magnet has been regarded as a system that could be a promising host material for the quantum spin liquid (QSL). However, it is difficult to determine the spin configuration and the corresponding mechanism in this system, because of its geometrical frustration ( i.e., crystal structure and symmetry). Herein, we systematically investigate one of the geometrically frustrated magnets, the TbB 4 compound. Using resonant soft x-ray scattering (RSXS), we explored its spin configuration, as well as Tb's quadrupole. Comprehensive evaluations of the temperature and photon energy/polarization dependences of the RSXS signals reveal the mechanism of spin reorientation upon coolingmore » down, which is the sophisticated interplay between the Tb spin and the crystal symmetry rather than its orbit (quadrupole). Here, our results and their implications would further shed a light on the search for possible realization of QSL.« less

Understanding spin configuration in the geometrically frustrated magnet TbB 4: A resonant soft X-ray scattering study

DOE PAGES

Huang, H.; Jang, H.; Kang, B. Y.; ...

2018-05-05

The frustrated magnet has been regarded as a system that could be a promising host material for the quantum spin liquid (QSL). However, it is difficult to determine the spin configuration and the corresponding mechanism in this system, because of its geometrical frustration ( i.e., crystal structure and symmetry). Herein, we systematically investigate one of the geometrically frustrated magnets, the TbB 4 compound. Using resonant soft x-ray scattering (RSXS), we explored its spin configuration, as well as Tb's quadrupole. Comprehensive evaluations of the temperature and photon energy/polarization dependences of the RSXS signals reveal the mechanism of spin reorientation upon coolingmore » down, which is the sophisticated interplay between the Tb spin and the crystal symmetry rather than its orbit (quadrupole). Here, our results and their implications would further shed a light on the search for possible realization of QSL.« less

Modeling of impulsive propellant reorientation

NASA Technical Reports Server (NTRS)

Hochstein, John I.; Patag, Alfredo E.; Chato, David J.

1988-01-01

The impulsive propellant reorientation process is modeled using the (Energy Calculations for Liquid Propellants in a Space Environment (ECLIPSE) code. A brief description of the process and the computational model is presented. Code validation is documented via comparison to experimentally derived data for small scale tanks. Predictions of reorientation performance are presented for two tanks designed for use in flight experiments and for a proposed full scale OTV tank. A new dimensionless parameter is developed to correlate reorientation performance in geometrically similar tanks. Its success is demonstrated.

Unconventional magnetisation texture in graphene/cobalt hybrids

DOE PAGES

Vu, A. D.; Coraux, J.; Chen, G.; ...

2016-04-26

Magnetic domain structure and spin-dependent reflectivity measurements on cobalt thin films intercalated at the graphene/Ir(111) interface are investigated using spin-polarised low-energy electron microscopy. We find that graphene-covered cobalt films have surprising magnetic properties. Vectorial imaging of magnetic domains reveals an unusually gradual thickness-dependent spin reorientation transition, in which magnetisation rotates from out-of-the-film plane to the in-plane direction by less than 10° per cobalt monolayer. During this transition, cobalt films have a meandering spin texture, characterised by a complex, three-dimensional, wavy magnetisation pattern. In addition, spectroscopy measurements suggest that the electronic band structure of the unoccupied states is essentially spin-independent alreadymore » a few electron-Volts above the vacuum level. These properties strikingly differ from those of pristine cobalt films and could open new prospects in surface magnetism.« less

Dynamic solvophobic effect and its cooperativity in the hydrogen-bonding liquids studied by dielectric and nuclear magnetic resonance relaxation.

PubMed

Yamaguchi, Tsuyoshi; Furuhashi, Hiroki; Matsuoka, Tatsuro; Koda, Shinobu

2008-12-25

The reorientational relaxation of solvent molecules in the mixture of nonpolar solutes and hydrogen-bonding liquids including water, alcohols, and amides are studied by dielectric and 2H-nuclear magnetic resonance (NMR) spin-lattice relaxations. The retardation of the reorientational motion of the solvent by weak solute-solvent interaction is observed in all the solvent systems. On the other hand, no clear correlation between the strength of the solute-solvent interaction and the slowing down of the solvent motion is found in N,N-dimethylacetamide, which suggests the importance of the hydrogen bonding in the dynamic solvophobic effect. The cooperativity of the reorientational relaxation is investigated by the comparison between the collective relaxation measured by the dielectric spectroscopy and the single-molecular reorientation determined by NMR. The modification of the dielectric relaxation time caused by the dissolution of the solute is larger than that of the single-molecular reorientational relaxation time in all the solvents studied here. The effect of the static correlation between the dipole moments of different molecules is calculated from the static dielectric constant, and the effect of the dynamic correlation is estimated. The difference in the effects of the solutes on the collective and single-molecular reorientational relaxation is mainly ascribed to the dynamic cooperativity in the cases of water and alcohols, which is consistent with the picture on the dynamic solvophobicity derived by our previous theoretical analysis (Yamaguchi, T.; Matsuoka, T.; Koda, S. J. Chem. Phys. 2004, 120, 7590). On the other hand, the static correlation plays the principal role in the case of N-methylformamide.

Interplay of rare-earth and transition-metal subsystems in C u3Yb (SeO3) 2O2Cl

NASA Astrophysics Data System (ADS)

Markina, M. M.; Zakharov, K. V.; Ovchenkov, E. A.; Berdonosov, P. S.; Dolgikh, V. A.; Kuznetsova, E. S.; Olenev, A. V.; Klimin, S. A.; Kashchenko, M. A.; Budkin, I. V.; Yatsyk, I. V.; Demidov, A. A.; Zvereva, E. A.; Vasiliev, A. N.

2017-10-01

We present the synthesis and the experimental and theoretical study of the new member of the francisite family, C u3Yb (SeO3) 2O2Cl . The compound reaches an antiferromagnetic order at TN=36.7 K and experiences first-order spin-reorientation transition to weakly ferromagnetic phase at TR=8.7 K evidenced in specific heat Cp and magnetic susceptibility χ measurements. Distinctly different magnetization loops in T

Anisotropic 2H-nuclear magnetic resonance spin-lattice relaxation in cerebroside- and phospholipid-cholesterol bilayer membranes.

PubMed

Siminovitch, D J; Ruocco, M J; Olejniczak, E T; Das Gupta, S K; Griffin, R G

1988-09-01

The axially symmetric powder pattern 2H-nuclear magnetic resonance (NMR) lineshapes observed in the liquid crystalline phase of pure lipid or lipid/cholesterol bilayers are essentially invariant to temperature, or, equivalently, to variations in the correlation times characterizing C-2H bond reorientations. In either of these melted phases, where correlation times for C-2H bond motions are shorter than 10(-7) s, information on the molecular dynamics of the saturated hydrocarbon chain would be difficult to obtain using lineshape analyses alone, and one must resort to other methods, such as the measurement of 2H spin-lattice relaxation rates, in order to obtain dynamic information. In pure lipid bilayers, the full power of the spin-lattice relaxation technique has yet to be realized, since an important piece of information, namely the orientation dependence of the 2H spin-lattice relaxation rates is usually lost due to orientational averaging of T1 by rapid lateral diffusion. Under more favorable circumstances, such as those encountered in the lipid/cholesterol mixtures of this study, the effects of orientational averaging by lateral diffusion are nullified, due to either a marked reduction (by at least an order of magnitude) in the diffusion rate, or a marked increase in the radii of curvature of the liposomes. In either case, the angular dependence of 2H spin-lattice relaxation is accessible to experimental study, and can be used to test models of molecular dynamics in these systems. Simulations of the partially recovered lineshapes indicate that the observed T1 anisotropies are consistent with large amplitude molecular reorientation of the C-2H bond among a finite number of sites. Furthermore, from the observed orientation dependence of the 2H spin-lattice relaxation rates, we conclude that order director fluctuations cannot provide the dominant relaxation pathway for acyl chain deuterons.

Spin reorientation and Ce-Mn coupling in antiferromagnetic oxypnictide CeMnAsO

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Qiang; Tian, Wei; Peterson, Spencer G.

2015-02-18

Structure and magnetic properties of high-quality polycrystlline CeMnAsO, a parent compound of the “1111”-type oxypnictides, have been investigated using neutron powder diffraction and magnetization measurements. We find that CeMnAsO undergoes a C-type antiferromagnetic order with Mn 2+(S = 5/2) moments pointing along the c axis below a relatively high Néel temperature of T N = 347(1) K. Below T SR = 35 K, two simultaneous transitions occur where the Mn moments reorient from the c axis to the ab plane preserving the C-type magnetic order, and Ce moments undergo long-range AFM ordering with antiparallel moments pointing in the ab plane.more » Another transition to a noncollinear magnetic structure occurs below 7 K. The ordered moments of Mn and Ce at 2 K are 3.32(4) μ B and 0.81(4)μ B, respectively. We find that CeMnAsO primarily falls into the category of a local-moment antiferromagnetic insulator in which the nearest-neighbor interaction (J 1) is dominant with J 2 < J 1/2 in the context of J 1 – J 2 – J c model. The spin reorientation transition driven by the coupling between Ce and the transition metal seems to be common to Mn, Fe, and Cr ions, but not to Co and Ni ions in the isostructural oxypnictides. As a result, a schematic illustration of magnetic structures in Mn and Ce sublattices in CeMnAsO is presented.« less

Magnetization of La2-xSrxNiO4+δ (0⩽x⩽0.5) : Spin-glass and memory effects

NASA Astrophysics Data System (ADS)

Freeman, P. G.; Boothroyd, A. T.; Prabhakaran, D.; Lorenzana, J.

2006-01-01

We have studied the magnetization of a series of spin-charge-ordered La2-xSrxNiO4+δ single crystals with 0⩽x⩽0.5 . For fields applied parallel to the ab plane there is a large irreversibility below a temperature TF1˜50K and a smaller irreversibility that persists up to near the charge-ordering temperature. We observed memory effects in the thermoremnant magnetization across the entire doping range. We found that these materials retain a memory of the temperature at which an external field was removed and that there is a pronounced increase in the thermoremnant magnetization when the system is warmed through a spin reorientation transition.

Oscillatory dynamics in the dorsal and ventral attention networks during the reorienting of attention.

PubMed

Proskovec, Amy L; Heinrichs-Graham, Elizabeth; Wiesman, Alex I; McDermott, Timothy J; Wilson, Tony W

2018-05-01

The ability to reorient attention within the visual field is central to daily functioning, and numerous fMRI studies have shown that the dorsal and ventral attention networks (DAN, VAN) are critical to such processes. However, despite the instantaneous nature of attentional shifts, the dynamics of oscillatory activity serving attentional reorientation remain poorly characterized. In this study, we utilized magnetoencephalography (MEG) and a Posner task to probe the dynamics of attentional reorienting in 29 healthy adults. MEG data were transformed into the time-frequency domain and significant oscillatory responses were imaged using a beamformer. Voxel time series were then extracted from peak voxels in the functional beamformer images. These time series were used to quantify the dynamics of attentional reorienting, and to compute dynamic functional connectivity. Our results indicated strong increases in theta and decreases in alpha and beta activity across many nodes in the DAN and VAN. Interestingly, theta responses were generally stronger during trials that required attentional reorienting relative to those that did not, while alpha and beta oscillations were more dynamic, with many regions exhibiting significantly stronger responses during non-reorienting trials initially, and the opposite pattern during later processing. Finally, stronger functional connectivity was found following target presentation (575-700 ms) between bilateral superior parietal lobules during attentional reorienting. In sum, these data show that visual attention is served by multiple cortical regions within the DAN and VAN, and that attentional reorienting processes are often associated with spectrally-specific oscillations that have largely distinct spatiotemporal dynamics. © 2018 Wiley Periodicals, Inc.

Dynamics of glass-forming di-n-butyl phthalate as studied by NMR.

PubMed

Szcześniak, E; Głowinkowski, S; Suchański, W; Jurga, S

1997-04-01

Spin-lattice relaxation times T1 and nuclear Overhauser effect (NOE) enhancement factors for the individual ring carbons in di-n-butyl phthalate (DBF) show that the reorientational correlation function corresponding to the global dynamics in supercooled liquid can be described by a Davidson-Cole distribution. Measurements of proton spin-lattice relaxation times T1 and T1p, as well as 1H NMR spectra at temperatures below the glass transition temperature, Tg, reveal that the same distribution holds also for description of local dynamics in glassy DBF. The activation parameters of the motions detected are derived.

Behavior learning in differential games and reorientation maneuvers

NASA Astrophysics Data System (ADS)

Satak, Neha

The purpose of this dissertation is to apply behavior learning concepts to incomplete- information continuous time games. Realistic game scenarios are often incomplete-information games in which the players withhold information. A player may not know its opponent's objectives and strategies prior to the start of the game. This lack of information can limit the player's ability to play optimally. If the player can observe the opponent's actions, it can better optimize its achievements by taking corrective actions. In this research, a framework to learn an opponent's behavior and take corrective actions is developed. The framework will allow a player to observe the opponent's actions and formulate behavior models. The developed behavior model can then be utilized to find the best actions for the player that optimizes the player's objective function. In addition, the framework proposes that the player plays a safe strategy at the beginning of the game. A safe strategy is defined in this research as a strategy that guarantees a minimum pay-off to the player independent of the other player's actions. During the initial part of the game, the player will play the safe strategy until it learns the opponent's behavior. Two methods to develop behavior models that differ in the formulation of the behavior model are proposed. The first method is the Cost-Strategy Recognition (CSR) method in which the player formulates an objective function and a strategy for the opponent. The opponent is presumed to be rational and therefore will play to optimize its objective function. The strategy of the opponent is dependent on the information available to the opponent about other players in the game. A strategy formulation presumes a certain level of information available to the opponent. The previous observations of the opponent's actions are used to estimate the parameters of the formulated behavior model. The estimated behavior model predicts the opponent's future actions. The second method is the Direct Approximation of Value Function (DAVF) method. In this method, unlike the CSR method, the player formulates an objective function for the opponent but does not formulates a strategy directly; rather, indirectly the player assumes that the opponent is playing optimally. Thus, a value function satisfying the HJB equation corresponding to the opponent's cost function exists. The DAVF method finds an approximate solution for the value function based on previous observations of the opponent's control. The approximate solution to the value function is then used to predict the opponent's future behavior. Game examples in which only a single player is learning its opponent's behavior are simulated. Subsequently, examples in which both players in a two-player game are learning each other's behavior are simulated. In the second part of this research, a reorientation control maneuver for a spinning spacecraft will be developed. This will aid the application of behavior learning and differential games concepts to the specific scenario involving multiple spinning spacecraft. An impulsive reorientation maneuver with coasting will be analytically designed to reorient the spin axis of the spacecraft using a single body fixed thruster. Cooperative maneuvers of multiple spacecraft optimizing fuel and relative orientation will be designed. Pareto optimality concepts will be used to arrive at mutually agreeable reorientation maneuvers for the cooperating spinning spacecraft.

Electric control of magnetization reorientation in FeRh /BaTiO3 mediated by a magnetic phase transition

NASA Astrophysics Data System (ADS)

Odkhuu, Dorj

2017-10-01

Employing first-principles calculations we predict magnetization reorientation in FeRh films epitaxially grown on BaTiO3 by reversing the electric polarization or applying the strain effect, which is associated with the recently discovered voltage-induced interfacial magnetic-phase transition by R. O. Cherifi et al. [Nat. Mater. 13, 345 (2014), 10.1038/nmat3870]. We propose that this transition from antiferromagnetic to ferromagnetic phase is the results of the mutual mechanisms of the polarization-reversal-induced volume/strain expansion in the interfacial FeRh layers and the competition between direct and indirect exchange interactions. These mechanisms are mainly driven by the ferroelectrically driven hybridization between Fe and Ti 3 d orbital states at the interface. Such a strong hybridization can further involve Rh 4 d states with large spin-orbit coupling, which, rather than the Fe 3 d orbitals, is responsible for magnetization reorientation at the magnetic-phase transition. These findings point toward the feasibility of electric field control of magnetization switching associated with the magnetic-phase transition in an antiferromagnet structure.

Slow secondary relaxation in a free-energy landscape model for relaxation in glass-forming liquids

NASA Astrophysics Data System (ADS)

Diezemann, Gregor; Mohanty, Udayan; Oppenheim, Irwin

1999-02-01

Within the framework of a free-energy landscape model for the relaxation in supercooled liquids the primary (α) relaxation is modeled by transitions among different free-energy minima. The secondary (β) relaxation then corresponds to intraminima relaxation. We consider a simple model for the reorientational motions of the molecules associated with both processes and calculate the dielectric susceptibility as well as the spin-lattice relaxation times. The parameters of the model can be chosen in a way that both quantities show a behavior similar to that observed in experimental studies on supercooled liquids. In particular we find that it is not possible to obtain a crossing of the time scales associated with α and β relaxation. In our model these processes always merge at high temperatures and the α process remains above the merging temperature. The relation to other models is discussed.

Nanoscale control of stripe-ordered magnetic domain walls by vertical spin transfer torque in La0.67Sr0.33MnO3 film

NASA Astrophysics Data System (ADS)

Wang, Jing; Wu, Shizhe; Ma, Ji; Xie, Lishan; Wang, Chuanshou; Malik, Iftikhar Ahmed; Zhang, Yuelin; Xia, Ke; Nan, Ce-Wen; Zhang, Jinxing

2018-02-01

Stripe-ordered domains with perpendicular magnetic anisotropy have been intensively investigated due to their potential applications in high-density magnetic data-storage devices. However, the conventional control methods (e.g., epitaxial strain, local heating, magnetic field, and magnetoelectric effect) of the stripe-ordered domain walls either cannot meet the demands for miniaturization and low power consumption of spintronic devices or require high strength of the electric field due to the small value of the magnetoelectric effect at room temperature. Here, a domain-wall resistive effect of 0.1% was clarified in La0.67Sr0.33MnO3 thin films between the configurations of current in the plane and perpendicular to the plane of walls. Furthermore, a reversible nanoscale control of the domain-wall re-orientation by vertical spin transfer torque across the probe/film interface was achieved, where a probe voltage of 0.1 V was applied on a manganite-based capacitor. We also demonstrated that the stripe-ordered magnetic domain-wall re-orientation strongly depends on the AC frequency of the scanning probe voltage which was applied on the capacitor.

Young Children's Use of Features to Reorient Is More than Just Associative: Further Evidence against a Modular View of Spatial Processing

ERIC Educational Resources Information Center

Newcombe, Nora S.; Ratliff, Kristin R.; Shallcross, Wendy L.; Twyman, Alexandra D.

2010-01-01

Proponents of a geometric module have argued that instances of young children's use of features as well as geometry to reorient can be explained by a two-stage process. In this model, only the first stage is a true reorientation, accomplished by using geometric information alone; features are considered in a second stage using association (Lee,…

Dynamics of asteroid family halos constrained by spin/shape models

NASA Astrophysics Data System (ADS)

Broz, Miroslav

2016-10-01

A number of asteroid families cannot be identified solely on the basis of the Hierarchical Clustering Method (HCM), because they have additional 'former' members in the surroundings which constitute a so called halo (e.g. Broz & Morbidelli 2013). They are usually mixed up with the background population which has to be taken into account too.Luckily, new photometric observations allow to derive new spin/shape models, which serve as independent constraints for dynamical models. For example, a recent census of the Eos family shows 43 core and 27 halo asteroids (including background) with known spin orientations.To this point, we present a complex spin-orbital model which includes full N-body dynamics and consequently accounts for all mean-motion, secular, or three-body gravitational resonances, the Yarkovsky drift, YORP effect, collisional reorientations and also spin-orbital interactions. These are especially important for the Koronis family. In this project, we make use of data from the DAMIT database and ProjectSoft Blue Eye 600 observatory.

The relationship between reorientational molecular motions and phase transitions in [Mg(H{sub 2}O){sub 6}](BF{sub 4}){sub 2}, studied with the use of {sup 1}H and {sup 19}F NMR and FT-MIR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mikuli, Edward, E-mail: mikuli@chemia.uj.edu.pl; Hetmańczyk, Joanna; Grad, Bartłomiej

2015-02-14

A {sup 1}H and {sup 19}F nuclear magnetic resonance study of [Mg(H{sub 2}O){sub 6}](BF{sub 4}){sub 2} has confirmed the existence of two phase transitions at T{sub c1} ≈ 257 K and T{sub c2} ≈ 142 K, detected earlier by the DSC method. These transitions were reflected by changes in the temperature dependences of both proton and fluorine of second moments M{sub 2}{sup H} and M{sub 2}{sup F} and of spin-lattice relaxation times T{sub 1}{sup H} and T{sub 1}{sup F}. The study revealed anisotropic reorientations of whole [Mg(H{sub 2}O){sub 6}]{sup 2+} cations, reorientations by 180° jumps of H{sub 2}O ligands, andmore » aniso- and isotropic reorientations of BF{sub 4}{sup −} anions. The activation parameters for these motions were obtained. It was found that the phase transition at T{sub c1} is associated with the reorientation of the cation as a whole unit around the C{sub 3} axis and that at T{sub c2} with isotropic reorientation of the BF{sub 4}{sup −} anions. The temperature dependence of the full width at half maximum value of the infrared band of ρ{sub t}(H{sub 2}O) mode (at ∼596 cm{sup −1}) indicated that in phases I and II, all H{sub 2}O ligands in [Mg(H{sub 2}O){sub 6}]{sup 2+} perform fast reorientational motions (180° jumps) with a mean value of activation energy equal to ca 10 kJ mole{sup −1}, what is fully consistent with NMR results. The phase transition at T{sub c1} is associated with a sudden change of speed of fast (τ{sub R} ≈ 10{sup −12} s) reorientational motions of H{sub 2}O ligands. Below T{sub c2} (in phase III), the reorientations of certain part of the H{sub 2}O ligands significantly slow down, while others continue their fast reorientation with an activation energy of ca 2 kJ mole{sup −1}. This fast reorientation cannot be evidenced in NMR relaxation experiments. Splitting of certain IR bands connected with H{sub 2}O ligands at the observed phase transitions suggests a reduction of the symmetry of the octahedral [Mg(H{sub 2}O){sub 6}]{sup 2+} complex cation.« less

Primary and secondary relaxation process in plastically crystalline cyanocyclohexane studied by 2H nuclear magnetic resonance. II. Quantitative analysis.

PubMed

Micko, B; Kruk, D; Rössler, E A

2013-02-21

We analyze the results of our previously reported 2H nuclear magnetic resonance (NMR) experiments in the plastically crystalline (PC) phase of cyanocyclohexane (Part I of this work) to study the fast secondary relaxation (or β-process) in detail. Both, the occurrence of an additional minimum in the spin-lattice relaxation T1 and the pronounced effects arising in the solid-echo spectrum above the glass transition temperature T(g) = 134 K, allow for a direct determination of the restricting geometry of the β-process in terms of the "wobbling-in-a-cone" model. Whereas at temperatures below T(g) the reorientation is confined to rather small solid angles (below 10°), the spatial restriction decreases strongly with temperature above T(g), i.e., the distribution of cone angles shifts continuously towards higher values. The β-process in the PC phase of cyanocyclohexane proceeds via the same mechanism as found in structural glass formers. This is substantiated by demonstrating the very similar behavior (for T < T(g)) of spin-lattice relaxation, stimulated echo decays, and spectral parameters when plotted as a function of (taken from dielectric spectroscopy). We do, however, not observe a clear-cut relation between the relaxation strength of the β-process observed by NMR (calculated within the wobbling-in-a-cone model) and dielectric spectroscopy.

Attitude Control Flight Experience: Coping with Solar Radiation and Ion Engines Leak Thrust in Hayabusa (MUSES-C)

NASA Technical Reports Server (NTRS)

Kawaguchi, Jun'ichiro; Kominato, Takashi; Shirakawa, Ken'ichi

2007-01-01

The paper presents the attitude reorientation taking the advantage of solar radiation pressure without use of any fuel aboard. The strategy had been adopted to make Hayabusa spacecraft keep pointed toward the Sun for several months, while spinning. The paper adds the above mentioned results reported in Sedona this February showing another challenge of combining ion engines propulsion tactically balanced with the solar radiation torque with no spin motion. The operation has been performed since this March for a half year successfully. The flight results are presented with the estimated solar array panel diffusion coefficient and the ion engine's swirl torque.

Molecular motions of [Beta]-carotene and a carotenoporphyrin dyad in solution. A carbon-13 NMR spin-lattice relaxation time study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, S.; Swindle, S.L.; Smith, S.K.

1995-03-09

Analysis of [sup 13]C NMR spin-lattice relaxation times (T[sub 1]) yields information concerning both overall tumbling of molecules in solution and internal rotations about single bonds. Relaxation time and nuclear Overhauser effect data have been obtained for [Beta]-carotene and two related molecules, squalane and squalene, for zinc meso-tetraphenylporphyrin, and for a dyad consisting of a porphyrin covalently linked to a carotenoid polyene through a trimethylene bridge. Squalane and squalene, which lack conjugated double bonds, behave essentially as limp string, with internal rotations at least as rapid as overall isotropic tumbling motions. In contrast, [Beta]-carotene reorients as a rigid rod, withmore » internal motions which are too slow to affect relaxation times. Modeling it as an anisotropic rotor yields a rotational diffusion coefficient for motion about the major axis which is 14 times larger than that for rotation about axes perpendicular to that axis. The porphyrin reorients more nearly isotropically and features internal librational motions about the single bonds to the phenyl groups. The relaxation time data for the carotenoporphyrin are consistent with internal motions similar to those of a medieval military flail. 31 refs., 3 figs., 5 tabs.« less

Magnetostructural transition in Fe{sub 5}SiB{sub 2} observed with neutron diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cedervall, Johan, E-mail: johan.cedervall@kemi.uu.se; Kontos, Sofia; Hansen, Thomas C.

2016-03-15

The crystal and magnetic structure of Fe{sub 5}SiB{sub 2} has been studied by a combination of X-ray and neutron diffraction. Also, the magnetocrystalline anisotropy energy constant has been estimated from magnetisation measurements. High quality samples have been prepared using high temperature synthesis and subsequent heat treatment protocols. The crystal structure is tetragonal within the space group I4/mcm and the compound behaves ferromagnetically with a Curie temperature of 760 K. At 172 K a spin reorientation occurs in the compound and the magnetic moments go from aligning along the c-axis (high T) down to the ab-plane (low T). The magnetocrystalline anisotropymore » energy constant has been estimated to 0.3 MJ/m{sup 3} at 300 K. - Highlights: • The crystal and magnetic structure of Fe{sub 5}SiB{sub 2} has been studied by diffraction. • At 172 K a spin reorientation occurs in the compound. • The magnetic moments are aligned along the c-axis at high T. • The magnetic moments are aligned in the ab-plane at low T. • The magnetocrystalline anisotropy energy constant has been estimated to 0.3 MJ/m{sup 3}.« less

Spin reorientation and magnetoelastic coupling in Tb 6Fe 1-xCo xBi 2 (x = 0, 0.125, 0.25, 0.375) alloy system

DOE PAGES

Koehler, Michael R.; Garlea, Vasile O.; McGuire, Michael A.; ...

2014-07-05

Tb 6FeBi 2 adopts a noncentrosymmetric crystal structure and orders ferromagnetically at T C1 = 250 K with an additional magnetic transition at T C2 = 60 K. The low temperature magnetoelastic response in this material is strong, and is enhanced by cobalt substitution. In this paper, the temperature dependence of the atomic and magnetic structure of Tb 6Fe 1-xCo xBi 2 (x = 0, 0.125, 0.25, and 0.375) is reported from powder X-ray diffraction (XRD) and powder neutron diffraction (PND) measurements. Below the Néel temperature a ferrimagnetic ordering between the terbium and iron moments exists in all compounds studied.more » Related to the enhanced magnetostructural response, the Co-doped compounds undergo a crystallographic phase transition below about 60 K. This transition also involves a canting of the magnetic moments away from the c-axis. The structural transition is sluggish and not fully completed in the parent Tb 6FeBi 2 compound, where a mixture of monoclinic and hexagonal phases is identified below 60 K. Lastly, the spin reorientation transition is discussed in terms of competing exchange interactions and magnetocrystalline anisotropies of the two Tb sites and Fe/Co sublattices.« less

From non-linear magnetoacoustics and spin reorientation transition to magnetoelectric micro/nano-systems

NASA Astrophysics Data System (ADS)

Tiercelin, Nicolas; Preobrazhensky, Vladimir; BouMatar, Olivier; Talbi, Abdelkrim; Giordano, Stefano; Dusch, Yannick; Klimov, Alexey; Mathurin, Théo.; Elmazria, Omar; Hehn, Michel; Pernod, Philippe

2017-09-01

The interaction of a strongly nonlinear spin system with a crystalline lattice through magnetoelastic coupling results in significant modifications of the acoustic properties of magnetic materials, especially in the vicinity of magnetic instabilities associated with the spin-reorientation transition (SRT). The magnetoelastic coupling transfers the critical properties of the magnetic subsystem to the elastic one, which leads to a strong decrease of the sound velocity in the vicinity of the SRT, and allows a large control over acoustic nonlinearities. The general principles of the non-linear magneto-acoustics (NMA) will be introduced and illustrated in `bulk' applications such as acoustic wave phase conjugation, multi-phonon coupling, explosive instability of magneto-elastic vibrations, etc. The concept of the SRT coupled to magnetoelastic interaction has been transferred into nanostructured magnetoelastic multilayers with uni-axial anisotropy. The high sensitivity and the non-linear properties have been demonstrated in cantilever type actuators, and phenomena such as magneto-mechanical RF demodulation have been observed. The combination of the magnetic layers with piezoelectric materials also led to stress-mediated magnetoelectric (ME) composites with high ME coefficients, thanks to the SRT. The magnetoacoustic effects of the SRT have also been studied for surface acoustic waves propagating in the magnetoelastic layers and found to be promising for highly sensitive magnetic field sensors working at room temperature. On the other hand, mechanical stress is a very efficient way to control the magnetic subsystem. The principle of a very energy efficient stress-mediated magnetoelectric writing and reading in a magnetic memory is described.

Synthesis and magnetic properties of LiFePO4 substitution magnesium

NASA Astrophysics Data System (ADS)

Choi, Hyunkyung; Kim, Min Ji; Hahn, Eun Joo; Kim, Sam Jin; Kim, Chul Sung

2017-06-01

LiFe0.9Mg0.1PO4 sample was prepared by using a solid-state reaction method, and the temperature-dependent magnetic properties of the sample were studied. The X-ray diffraction (XRD) pattern showed an olivine-type orthorhombic structure with space group Pnma based on Rietveld refinement method. The effect of Mg substitution in antiferromagnetic LiFe0.9Mg0.1PO4 was investigated using a vibrating sample magnetometer (VSM) and Mössbauer spectroscopy. The temperature-dependence of the magnetization curves of LiFe0.9Mg0.1PO4 shows abnormal antiferromagnetic behavior with ordering temperature. Sudden changes in both the magnetic hyperfine field (Hhf) and its slope below 15 K suggest that magnetic phase transition associated to the abrupt occurrence of spin-reorientation. The Néel temperature (TN) and spin-reorientation temperature (TS) of LiFe0.9Mg0.1PO4 are lower than those of pure LiFePO4 (TN = 51 K, TS = 23 K). This is due to the Fe-O-Fe superexchange interaction being larger than that of the Fe-O-Mg link. Also, we have confirmed a change in the electric quadrupole splitting (ΔEQ) by the spin-orbit coupling effect and the shape of Mössbauer spectrum has provided the evidence for TS and a strong crystalline field. We have found that Mg ions in LiFe0.9Mg0.1PO4 induce an asymmetric charge density due to the presence of Mg2+ ions at the FeO6 octahedral sites.

Transfer of Magnetic Order and Anisotropy through Epitaxial Integration of 3d and 4f Spin Systems.

PubMed

Bluschke, M; Frano, A; Schierle, E; Minola, M; Hepting, M; Christiani, G; Logvenov, G; Weschke, E; Benckiser, E; Keimer, B

2017-05-19

Resonant x-ray scattering at the Dy M_{5} and Ni L_{3} absorption edges was used to probe the temperature and magnetic field dependence of magnetic order in epitaxial LaNiO_{3}-DyScO_{3} superlattices. For superlattices with 2 unit cell thick LaNiO_{3} layers, a commensurate spiral state develops in the Ni spin system below 100 K. Upon cooling below T_{ind}=18  K, Dy-Ni exchange interactions across the LaNiO_{3}-DyScO_{3} interfaces induce collinear magnetic order of interfacial Dy moments as well as a reorientation of the Ni spins to a direction dictated by the strong magnetocrystalline anisotropy of Dy. This transition is reversible by an external magnetic field of 3 T. Tailored exchange interactions between rare-earth and transition-metal ions thus open up new perspectives for the manipulation of spin structures in metal-oxide heterostructures and devices.

Reorientation of the diagonal double-stripe spin structure at Fe 1+yTe bulk and thin-film surfaces

DOE PAGES

Hanke, Torben; Singh, Udai Raj; Cornils, Lasse; ...

2017-01-06

Here, establishing the relation between ubiquitous antiferromagnetism in the parent compounds of unconventional superconductors and their superconducting phase is important for understanding the complex physics in these materials. Going from bulk systems to thin films additionally affects their phase diagram. For Fe 1+yTe, the parent compound of Fe 1+ySe 1$-x$Tex superconductors, bulk-sensitive neutron diffraction revealed an in-plane oriented diagonal double-stripe antiferromagnetic spin structure. Here we show by spin-resolved scanning tunnelling microscopy that the spin direction at the surfaces of bulk Fe 1+yTe and thin films grown on the topological insulator Bi 2Te 3 is canted out of the high-symmetry directionsmore » of the surface unit cell resulting in a perpendicular spin component, keeping the diagonal double-stripe order. As the magnetism of the Fe d-orbitals is intertwined with the superconducting pairing in Fe-based materials, our results imply that the superconducting properties at the surface of the related superconducting compounds might be different from the bulk.« less

Reorientation of the diagonal double-stripe spin structure at Fe 1+yTe bulk and thin-film surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hanke, Torben; Singh, Udai Raj; Cornils, Lasse

Here, establishing the relation between ubiquitous antiferromagnetism in the parent compounds of unconventional superconductors and their superconducting phase is important for understanding the complex physics in these materials. Going from bulk systems to thin films additionally affects their phase diagram. For Fe 1+yTe, the parent compound of Fe 1+ySe 1$-x$Tex superconductors, bulk-sensitive neutron diffraction revealed an in-plane oriented diagonal double-stripe antiferromagnetic spin structure. Here we show by spin-resolved scanning tunnelling microscopy that the spin direction at the surfaces of bulk Fe 1+yTe and thin films grown on the topological insulator Bi 2Te 3 is canted out of the high-symmetry directionsmore » of the surface unit cell resulting in a perpendicular spin component, keeping the diagonal double-stripe order. As the magnetism of the Fe d-orbitals is intertwined with the superconducting pairing in Fe-based materials, our results imply that the superconducting properties at the surface of the related superconducting compounds might be different from the bulk.« less

Rotational-path decomposition based recursive planning for spacecraft attitude reorientation

NASA Astrophysics Data System (ADS)

Xu, Rui; Wang, Hui; Xu, Wenming; Cui, Pingyuan; Zhu, Shengying

2018-02-01

The spacecraft reorientation is a common task in many space missions. With multiple pointing constraints, it is greatly difficult to solve the constrained spacecraft reorientation planning problem. To deal with this problem, an efficient rotational-path decomposition based recursive planning (RDRP) method is proposed in this paper. The uniform pointing-constraint-ignored attitude rotation planning process is designed to solve all rotations without considering pointing constraints. Then the whole path is checked node by node. If any pointing constraint is violated, the nearest critical increment approach will be used to generate feasible alternative nodes in the process of rotational-path decomposition. As the planning path of each subdivision may still violate pointing constraints, multiple decomposition is needed and the reorientation planning is designed as a recursive manner. Simulation results demonstrate the effectiveness of the proposed method. The proposed method has been successfully applied in two SPARK microsatellites to solve onboard constrained attitude reorientation planning problem, which were developed by the Shanghai Engineering Center for Microsatellites and launched on 22 December 2016.

Geometry Three Ways: An fMRI Investigation of Geometric Information Processing during Reorientation

ERIC Educational Resources Information Center

Sutton, Jennifer E.; Twyman, Alexandra D.; Joanisse, Marc F.; Newcombe, Nora S.

2012-01-01

The geometry formed by the walls of a room is known to be a potent cue in reorientation, yet little is known about the use of geometric information gleaned from other contexts. We used functional magnetic resonance imaging to examine neural activity in adults while reorienting in 3 different environments: the typical rectangular walled room, a…

Progressive freezing of interacting spins in isolated finite magnetic ensembles

NASA Astrophysics Data System (ADS)

Bhattacharya, Kakoli; Dupuis, Veronique; Le-Roy, Damien; Deb, Pritam

2017-02-01

Self-organization of magnetic nanoparticles into secondary nanostructures provides an innovative way for designing functional nanomaterials with novel properties, different from the constituent primary nanoparticles as well as their bulk counterparts. Collective magnetic properties of such complex closed packing of magnetic nanoparticles makes them more appealing than the individual magnetic nanoparticles in many technological applications. This work reports the collective magnetic behaviour of magnetic ensembles comprising of single domain Fe3O4 nanoparticles. The present work reveals that the ensemble formation is based on the re-orientation and attachment of the nanoparticles in an iso-oriented fashion at the mesoscale regime. Comprehensive dc magnetic measurements show the prevalence of strong interparticle interactions in the ensembles. Due to the close range organization of primary Fe3O4 nanoparticles in the ensemble, the spins of the individual nanoparticles interact through dipolar interactions as realized from remnant magnetization measurements. Signature of super spin glass like behaviour in the ensembles is observed in the memory studies carried out in field cooled conditions. Progressive freezing of spins in the ensembles is corroborated from the Vogel-Fulcher fit of the susceptibility data. Dynamic scaling of relaxation reasserted slow spin dynamics substantiating cluster spin glass like behaviour in the ensembles.

Molecular dynamics of solid cortisol studied by NMR

NASA Astrophysics Data System (ADS)

Andrew, E. R.

Polycrystalline cortisol (hydrocortisone; 11β,17α,21-trihydroxy-4-preg- nene-3,20-dione; C21H30O5) has been investigated by continuous and pulse proton NMR methods between 78 and 400 K at Larmor frequencies of 7, 25 and 60 MHz. A reduced value of second moment was found above 90 K and is ascribed to reorientation of two methyl groups. A single asymmetric minimum was found in the temperature dependence of the spin-lattice relaxation times and this also is attributed to reorientation of two methyl groups. The asymmetry suggests an asymmetric distribution of correlation times of the motion. Using the Cole-Davidson distribution, the best computer fit yields the following parameters characterizing the motion: Ea = 11ṡ8 ± 0ṡ1 kJ mol-1, τ0 = 4ṡ6 ± 0ṡ4) x 10-13s, distribution parameter δ = 0ṡ62.

Primary and secondary relaxation process in plastically crystalline cyanocyclohexane studied by 2H nuclear magnetic resonance. I.

PubMed

Micko, B; Lusceac, S A; Zimmermann, H; Rössler, E A

2013-02-21

We study the main (α-) and secondary (β-) relaxation in the plastically crystalline (PC) phase of cyanocyclohexane by various 2H nuclear magnetic resonance (NMR) methods (line-shape, spin-lattice relaxation, stimulated echo, and two-dimensional spectra) above and below the glass transition temperature T(g) = 134 K. Our results regarding the α-process demonstrate that molecular motion is not governed by the symmetry of the lattice. Rather it is similar to the one reported for structural glass formers and can be modeled by a reorientation proceeding via a distribution of small and large angular jumps. A solid-echo line-shape analysis regarding the β-process below T(g) yields again very similar results when compared to those of the structural glass formers ethanol and toluene. Hence we cannot confirm an intramolecular origin for the β-process in cyanocyclohexane. The fast β-process in the PC phase allows for the first time a detailed 2H NMR study of the process also at T > T(g): an additional minimum in the spin-lattice relaxation time reflecting the β-process is found. Furthermore the solid-echo spectra show a distinct deviation from the rigid limit Pake pattern, which allows a direct determination of the temperature dependent spatial restriction of the process. In Part II of this work, a quantitative analysis is carried out, where we demonstrate that within the model of a "wobbling in a cone" the mean cone angle increases above T(g) and the corresponding relaxation strength is compared to dielectric results.

Low gravity reorientation in a scale-model Centaur liquid-hydrogen tank

NASA Technical Reports Server (NTRS)

Salzman, J. A.; Masica, W. J.; Lacovic, R. F.

1973-01-01

An experiment was conducted to investigate the process of liquid reorientation from one end of a scale-model Centaur liquid-hydrogen tank to the other end by means of low-level accelerations. Prior to reorientation, the liquid was stabilized at the top of the tank at a Bond number of 15. Tanks both with and without ring baffles and with tank radii of 5.5 and 7.0 centimeters were used in the study. Reorientation acceleration values were varied to obtain Bond numbers of 200 and 450. Liquid fill levels of 20 and 70 percent were used. From the data in this study, relations were developed to estimate reorientation event times in unbaffled tanks through the point of final liquid clearing from the top of the tank. The insertion of ring baffles drastically changed the reorientation flow profiles but resulted in only minor differences in the times of tank-top uncovering and liquid collection.

Microtubule array reorientation in response to hormones does not involve changes in microtubule nucleation modes at the periclinal cell surface

PubMed Central

Atkinson, Samantha; Kirik, Angela; Kirik, Viktor

2014-01-01

Aligned microtubule arrays spatially organize cell division, trafficking, and determine the direction of cell expansion in plant cells. In response to changes in environmental and developmental signals, cells reorganize their microtubule arrays into new configurations. Here, we tested the role of microtubule nucleation during hormone-induced microtubule array reorientation. We have found that in the process of microtubule array reorientation the ratios between branching, parallel, and de-novo nucleations remained constant, suggesting that the microtubule reorientation mechanism does not involve changes in nucleation modes. In the ton2/fass mutant, which has reduced microtubule branching nucleation frequency and decreased nucleation activity of the γ-tubulin complexes, microtubule arrays were able to reorient. Presented data suggest that reorientation of microtubules into transverse arrays in response to hormones does not involve changes in microtubule nucleation at the periclinal cell surface PMID:25135522

Reorientations, relaxations, metastabilities, and multidomains of skyrmion lattices

NASA Astrophysics Data System (ADS)

Bannenberg, L. J.; Qian, F.; Dalgliesh, R. M.; Martin, N.; Chaboussant, G.; Schmidt, M.; Schlagel, D. L.; Lograsso, T. A.; Wilhelm, H.; Pappas, C.

2017-11-01

Magnetic skyrmions are nanosized topologically protected spin textures with particlelike properties. They can form lattices perpendicular to the magnetic field, and the orientation of these skyrmion lattices with respect to the crystallographic lattice is governed by spin-orbit coupling. By performing small-angle neutron scattering measurements, we investigate the coupling between the crystallographic and skyrmion lattices in both Cu2OSeO3 and the archetype chiral magnet MnSi. The results reveal that the orientation of the skyrmion lattice is primarily determined by the magnetic field direction with respect to the crystallographic lattice. In addition, it is also influenced by the magnetic history of the sample, which can induce metastable lattices. Kinetic measurements show that these metastable skyrmion lattices may or may not relax to their equilibrium positions under macroscopic relaxation times. Furthermore, multidomain lattices may form when two or more equivalent crystallographic directions are favored by spin-orbit coupling and oriented perpendicular to the magnetic field.

Reversal of spontaneous magnetization and spontaneous exchange bias for Sm1-xYxCrO3: The effect of Y doping

NASA Astrophysics Data System (ADS)

Zhang, Hongguang; Wang, Jianhua; Xie, Liang; Fu, Dexiang; Guo, Yanyan; Li, Yongtao

2017-11-01

We report the crystal and electronic structures and magnetic properties of non-magnetic Y3+ ion doped SmCrO3 crystals. Structural distortion and electronic structure variation are caused by cation disorder due to Y doping. Although the spin moment of Sm3+ is diluted by nonmagnetic Y ions, spin reorientation continues to exist, and the temperature-dependent magnetization reversal effect and the spontaneous exchange bias effect under zero field cooling are simultaneously induced below Neel temperature. Significantly, the method of doping promotes the achievement of temperature dependent tunable switching of magnetization and sign of a spontaneous exchange bias from positive to negative. Our work provides more tunable ways to the sign reversal of magnetization and exchange bias, which have potential application in designing magnetic random access memory devices, thermomagnetic switches and spin-valve devices.

Effect of CorrelatedRotational Noise

NASA Astrophysics Data System (ADS)

Hancock, Benjamin; Wagner, Caleb; Baskaran, Aparna

The traditional model of a self-propelled particle (SPP) is one where the body axis along which the particle travels reorients itself through rotational diffusion. If the reorientation process was driven by colored noise, instead of the standard Gaussian white noise, the resulting statistical mechanics cannot be accessed through conventional methods. In this talk we present results comparing three methods of deriving the statistical mechanics of a SPP with a reorientation process driven by colored noise. We illustrate the differences/similarities in the resulting statistical mechanics by their ability to accurately capture the particles response to external aligning fields.

Water reorientation in the hydration shells of hydrophilic and hydrophobic solutes

NASA Astrophysics Data System (ADS)

Laage, Damien; Stirnemann, Guillaume; Hynes, James T.

2010-06-01

We discuss some key aspects of our recent theoretical work on water reorientation dynamics, which is important in a wide range of phenomena, including aqueous phase chemical reactions, protein folding, and drug binding to proteins and DNA. It is shown that, contrary to the standard conception that these dynamics are diffusional, the reorientation of a water molecule occurs by sudden, large amplitude angular jumps. The mechanism involves the exchange of one hydrogen bond for another by the reorienting water, and the process can be fruitfully viewed as a chemical reaction. The results for reorientation times, which can be well described analytically, are discussed in the context of the molecular level interpretation of recent ultrafast infrared spectroscopic results, focusing on the concepts of structure making/breaking and solvent ‘icebergs’.

Growth, and magnetic study of Sm0.4Er0.6FeO3 single crystal grown by optical floating zone technique

NASA Astrophysics Data System (ADS)

Wu, Anhua; Zhao, Xiangyang; Man, Peiwen; Su, Liangbi; Kalashnikova, A. M.; Pisarev, R. V.

2018-03-01

Sm0.4Er0.6FeO3 single crystals were successfully grown by optical floating zone method; high quality samples with various orientations were manufactured. Based on these samples, Magnetic property of Sm0.4Er0.6FeO3 single crystals were investigated systemically by means of the temperature dependence of magnetization. It indicated that compositional variations not only alter the spin reorientation temperature, but also the compensation temperature of the orthoferrites. Unlike single rare earth orthoferrites, the reversal transition temperature point of Sm0.4Er0.6FeO3 increases as magnetic field increases, which is positive for designing novel spin switching or magnetic sensor device.

Mapping the phase inhomogeneity across first order spin flop transition

NASA Astrophysics Data System (ADS)

Tripathi, Malvika; Majumder, Supriyo; Choudhary, R. J.; Phase, D. M.

2018-04-01

As a consequence of spin reorientation phase transition (SRPT, TSRPT = 34K) in SmCrO3, the two phases, high temperature uncompensated anti-ferromagnetic Γ4 configuration and low temperature collinear anti-ferromagnetic phase Γ1 coexist in the vicinity of transition. The observed unexpectedly huge coercivity (Hc ˜2T) below SRPT at 25K questions on the behavior of two co-existing phases. In the present study, we have used the FORC diagrams to monitor the distribution of clusters related to different phases and to understand the nature of interaction among the clusters of distinct phases. We observed that the nature of interaction has indeed magnetic effect and the pining across phase boundaries may cause the enhancement of coercivity at 25K.

Voltage control of magnetic monopoles in artificial spin ice

NASA Astrophysics Data System (ADS)

Chavez, Andres C.; Barra, Anthony; Carman, Gregory P.

2018-06-01

Current research on artificial spin ice (ASI) systems has revealed unique hysteretic memory effects and mobile quasi-particle monopoles controlled by externally applied magnetic fields. Here, we numerically demonstrate a strain-mediated multiferroic approach to locally control the ASI monopoles. The magnetization of individual lattice elements is controlled by applying voltage pulses to the piezoelectric layer resulting in strain-induced magnetic precession timed for 180° reorientation. The model demonstrates localized voltage control to move the magnetic monopoles across lattice sites, in CoFeB, Ni, and FeGa based ASI’s. The switching is achieved at frequencies near ferromagnetic resonance and requires energies below 620 aJ. The results demonstrate that ASI monopoles can be efficiently and locally controlled with a strain-mediated multiferroic approach.

Room-temperature observation and current control of skyrmions in Pt/Co/Os/Pt thin films

NASA Astrophysics Data System (ADS)

Tolley, R.; Montoya, S. A.; Fullerton, E. E.

2018-04-01

We report the observation of room-temperature magnetic skyrmions in Pt/Co/Os/Pt thin-film heterostructures and their response to electric currents. The magnetic properties are extremely sensitive to inserting thin Os layers between the Co-Pt interface, resulting in reduced saturation magnetization, magnetic anisotropy, and Curie temperature. The observed skyrmions exist in a narrow temperature, applied-field and layer-thickness range near the spin-reorientation transition from perpendicular to in-plane magnetic anisotropy. The skyrmions have an average diameter of 2.3 μ m and transport measurements demonstrate these features can be displaced by means of spin-orbit torques with current densities as low as J =2 ×108A / m2 and display a skyrmion Hall effect.

Transformation from an easy-plane to an easy-axis antiferromagnetic structure in the mixed rare-earth ferroborates Pr x Y1-x Fe3(BO3)4: magnetic properties and crystal field calculations.

PubMed

Pankrats, A I; Demidov, A A; Ritter, C; Velikanov, D A; Semenov, S V; Tugarinov, V I; Temerov, V L; Gudim, I A

2016-10-05

The magnetic structure of the mixed rare-earth system Pr x Y1-x Fe3(BO3)4 (x  =  0.75, 0.67, 0.55, 0.45, 0.25) was studied via magnetic and resonance measurements. These data evidence the successive spin reorientation from the easy-axis antiferromagnetic structure formed in PrFe3(BO3)4 to the easy-plane one of YFe3(BO3)4 associated with the weakening of the magnetic anisotropy of the Pr subsystem due to its diamagnetic dilution by nonmagnetic Y. This reorientation occurs through the formation of an inclined magnetic structure, as was confirmed by our previous neutron research in the range of x  =  0.67 ÷ 0.45. In the compounds with x  =  0.75 and 0.67 whose magnetic structure is close to the easy-axis one, a two-step spin reorientation takes place in the magnetic field H||c. Such a peculiarity is explained by the formation of an interjacent inclined magnetic structure with magnetic moments of Fe ions located closer to the basal plane than in the initial state, with these intermediate states remaining stable in some ranges of the magnetic field. An approach based on a crystal field model for the Pr(3+) ion and the molecular-field approximation is used to describe the magnetic characteristics of the system Pr x Y1-x Fe3(BO3)4. With the parameters of the d-d and f-d exchange interactions, of the magnetic anisotropy of the iron subsystem and of the crystal field parameters of praseodymium thus determined, it is possible to achieve a good agreement between the experimental and calculated temperature and field dependences of the magnetization curves (up to 90 kOe) and magnetic susceptibilities (2-300 K).

Magnetic behavior of R 2Co 14B hydrides (R = La, Pr, Sm, Gd, Tb and Y)

NASA Astrophysics Data System (ADS)

Zhang, L. Y.; Pourarian, F.; Wallace, W. E.

1988-08-01

The structure and magnetic properties of R 2Co 14B sysstems(R = La, Pr, Nd, Sm, Gd, Tb and Y) and their hydrides were studied by means of bulk magnetometry. All R 2Co 14B hydrides presently studied occur in the tetragonal Nd 2Fe 14B-type crystal structure. The composition-temperature isotherms measured fro selected Gd- and Nd- containing systems exhibit some indication of a platuau pressure at higher hydrogen concentrations. Hydrogenation expands the unit volume, Vc, by 1.5 to 3.0%, depending on the nature of R and the content of hydrogen. It was found that introduction of hydrogen into the lattice decreases Ms of the Co sublittice. This is attributed to the effect of electron charge transfer from Hto Co-3d sublittice. Hydrogennation significantly decreases the anistropy fields, HA, and the spin-reorientation transition temperatur, TSR, for Prand Tb-based intermetallics. The results indicates that the hydrogen makes the compounds magnetically softer, which is attributed to the influence of hydrogen on both the 3d and R sublittices. Two types of spin-reorientation transition for the Nd 2Co 14B system were observed. Hydrogenaration reduces both the low transition temperature, TSR 1, and the high transition temperature, TSR 2, which is explained using the Boltich-Wallace mechanism.

Tailoring of magnetic orderings in Fe substituted GdMnO3 bulk samples towards room temperature

NASA Astrophysics Data System (ADS)

Pal, A.; Dhana Sekhar, C.; Venimadhav, A.; Murugavel, P.

2017-10-01

The evolution of various magnetic ordering has been studied for the orthorhombic perovskite GdMn1-x Fe x O3 (0  ⩽  x  ⩽  0.7) system to obtain its comprehensive magnetic phase diagram. We observed that the substitution of Fe in GdMnO3 increases the antiferromagnetic Neel temperature (T N) from 40 K to above 400 K and importantly induces a spin-reorientation transition (T SR) for x  ⩾  0.4. These transitions are close to room temperature at x  =  0.5 and then gradually separated at a higher x value. The static orbital ordering induced by the Jahn-Teller distortion seems to play an important role in changing the T N. The variations of spin-reorientation ordering along with the competition between the magnetic orderings as a function of the composition were discussed with respect to antisymmetric exchange interactions and Mn3+ single-ion anisotropy in detail. In addition, the correlation between structural and magnetic properties suggests that the subtle structural change at composition x  =  0.4 may affect the magnetic ordering. The observed tunable T SR and T N in GdMn1-x Fe x O3 could add a practical value for these compositions in fields like spintronics and sensors.

Ab initio metadynamics simulations of oxygen/ligand interactions in organoaluminum clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alnemrat, Sufian; Hooper, Joseph P., E-mail: jphooper@nps.edu

2014-10-14

Car-Parrinello molecular dynamics combined with a metadynamics algorithm is used to study the initial interaction of O{sub 2} with the low-valence organoaluminum clusters Al{sub 4}Cp{sub 4} (Cp=C{sub 5}H{sub 5}) and Al{sub 4}Cp{sub 4}{sup *} (Cp{sup *}=C{sub 5}[CH{sub 3}]{sub 5}). Prior to reaction with the aluminum core, simulations suggest that the oxygen undergoes a hindered crossing of the steric barrier presented by the outer ligand monolayer. A combination of two collective variables based on aluminum/oxygen distance and lateral oxygen displacement was found to produce distinct reactant, product, and transition states for this process. In the methylated cluster with Cp{sup *} ligands,more » a broad transition state of 45 kJ/mol was observed due to direct steric interactions with the ligand groups and considerable oxygen reorientation. In the non-methylated cluster the ligands distort away from the oxidizer, resulting in a barrier of roughly 34 kJ/mol with minimal O{sub 2} reorientation. A study of the oxygen/cluster system fixed in a triplet multiplicity suggests that the spin state does not affect the initial steric interaction with the ligands. The metadynamics approach appears to be a promising means of analyzing the initial steps of such oxidation reactions for ligand-protected clusters.« less

Magnetoelectric coupling tuned by competing anisotropies in Mn 1 - x Ni x TiO 3

DOE PAGES

Chi, Songxue; Ye, Feng; Zhou, H. D.; ...

2014-10-24

A flop of electric polarization from Pmore » $$\\|$$c (P c) to P$$\\|$$ a (P a) is observed in MnTiO 3 as a spin flop transtion is triggered by a c-axis magnetic field, H $$\\|$$c=7 T. The critical magnetic field for P a is significantly reduced in Mn 1-xNi xTiO 3 (x=0.33). Neutron diffraction measurements revealed similar magnetic arrangements for the two compositions where the ordered spins couple antiferromagnetically with their nearest intra- and inter-planar neighbors. In the x=0.33 system, the single ion anisotropies of Mn 2+ and Ni 2+ compete and give rise to an additional spin reorientation transition at TR. A magnetic field, H c, aligns the spins along c for T RN. The rotation of the collinear spins away from the c-axis for TR alters the magnetic point symmetry and gives rise to new ME susceptibility tensor form. Such linear ME response provides satisfactory explanation for behavior of field-induced electric polarization in both compositions. As the Ni content increases to x=0.5 and 0.68, the ME effect disappears as a new magnetic phase emerges.« less

Reoriention of diprotonated DABCO (1,4-Diazabicyclo[2.2.2]octane) cation and proton transfer in organic ferroelectric adduct DABCO-2(2-Chlorobenzoic acid)

NASA Astrophysics Data System (ADS)

Asaji, Tetsuo

2018-05-01

Temperature dependences of 1H NMR as well as 35Cl NQR spin-lattice relaxation times T1 were investigated of a ferroelectric molecular adduct with Tc = 323 K, in which 1,4-diazabicyclo[2.2.2]octane (DABCO) is sandwiched between two 2-chlorobenzoic acid (2-ClBA). The NQR frequencies clearly show that proton transfer from 2-ClBA to DABCO is occurred and the molecular adduct consists of diprotonated DABCO cation and two 2-chlorobenzoate anions. The correlation time of reorientational motion of the diprotonated DABCO molecule was determined as a function of temperature. The activation energy Ea of the motion was estimated as 22 kJ mol-1 below Tc. The steep decrease of the NQR T1 with Ea = 50 kJ mol-1, observed above ca. 280 K in the ferroelectric phase, suggests a slow fluctuation of electric field gradient at chlorine nucleus.

Improvement/Maintenance and Reorientation as Central Features of Coping with Major Life Change and Loss: Contributions of Three Life-Span Theories

ERIC Educational Resources Information Center

Boerner, Kathrin; Jopp, Daniela

2007-01-01

This article focuses on the common and unique contributions of three major life-span theories in addressing improvement/maintenance and reorientation, which represent central processes of coping with major life change and loss. For this purpose, we review and compare the dual-process model of assimilative and accommodative coping, the model of…

Reorientations, relaxations, metastabilities, and multidomains of skyrmion lattices

DOE PAGES

Bannenberg, L. J.; Qian, F.; Dalgliesh, R. M.; ...

2017-11-13

Magnetic skyrmions are nanosized topologically protected spin textures with particlelike properties. They can form lattices perpendicular to the magnetic field, and the orientation of these skyrmion lattices with respect to the crystallographic lattice is governed by spin-orbit coupling. By performing small-angle neutron scattering measurements, we investigate the coupling between the crystallographic and skyrmion lattices in both Cu 2OSeO 3 and the archetype chiral magnet MnSi. The results reveal that the orientation of the skyrmion lattice is primarily determined by the magnetic field direction with respect to the crystallographic lattice. In addition, it is also influenced by the magnetic history ofmore » the sample, which can induce metastable lattices. Kinetic measurements show that these metastable skyrmion lattices may or may not relax to their equilibrium positions under macroscopic relaxation times. Moreover, multidomain lattices may form when two or more equivalent crystallographic directions are favored by spin-orbit coupling and oriented perpendicular to the magnetic field.« less

The reorientation of cell nucleus promotes the establishment of front-rear polarity in migrating fibroblasts.

PubMed

Maninová, Miloslava; Klímová, Zuzana; Parsons, J Thomas; Weber, Michael J; Iwanicki, Marcin P; Vomastek, Tomáš

2013-06-12

The establishment of cell polarity is an essential step in the process of cell migration. This process requires precise spatiotemporal coordination of signaling pathways that in most cells create the typical asymmetrical profile of a polarized cell with nucleus located at the cell rear and the microtubule organizing center (MTOC) positioned between the nucleus and the leading edge. During cell polarization, nucleus rearward positioning promotes correct microtubule organizing center localization and thus the establishment of front-rear polarity and directional migration. We found that cell polarization and directional migration require also the reorientation of the nucleus. Nuclear reorientation is manifested as temporally restricted nuclear rotation that aligns the nuclear axis with the axis of cell migration. We also found that nuclear reorientation requires physical connection between the nucleus and cytoskeleton mediated by the LINC (linker of nucleoskeleton and cytoskeleton) complex. Nuclear reorientation is controlled by coordinated activity of lysophosphatidic acid (LPA)-mediated activation of GTPase Rho and the activation of integrin, FAK (focal adhesion kinase), Src, and p190RhoGAP signaling pathway. Integrin signaling is spatially induced at the leading edge as FAK and p190RhoGAP are predominantly activated or localized at this location. We suggest that integrin activation within lamellipodia defines cell front, and subsequent FAK, Src, and p190RhoGAP signaling represents the polarity signal that induces reorientation of the nucleus and thus promotes the establishment of front-rear polarity. Copyright © 2013 Elsevier Ltd. All rights reserved.

Modulation of Jahn-Teller effect on magnetization and spontaneous electric polarization of CuFeO2

NASA Astrophysics Data System (ADS)

Xiao, Guiling; Xia, Zhengcai; Wei, Meng; Huang, Sha; Shi, Liran; Zhang, Xiaoxing; Wu, Huan; Yang, Feng; Song, Yujie; Ouyang, Zhongwen

2018-03-01

CuFe0.99Mn0.01O2 and CuFe0.99Co0.01O2 single crystal samples are grown by a floating zone technique and their magnetization and spontaneous electric polarization have been investigated. Similarly with pure CuFeO2, an obviously anisotropic magnetization and spontaneous electric polarization were observed in the both doped samples, and their phase transition critical fields and temperatures are directly doping ion dependent. Considering the different d-shell configuration and ionic size between Mn3+, Co3+ and Fe3+ ions, in which the Mn3+ ion with Jahn-Teller (J-T) effect has different distortion on the geometry frustration from both of Fe3+ and Co3+ ion. Since for Mn3+ ion, the orbital splitting results from the low-symmetry J-T distortion in a crystal-field environment leads to a distorted MnO6 octahedron, which different from undistorted FeO6 and CoO6 octahedrons. The strain between distorted and undistorted octahedrons produces different effects on the spin reorientation transition and spontaneous electric polarization. Although the pure CuFeO2 has a very strong and robust frustration, the presence of the strain due to the random distribution of distorted MnO6 octahedron and undistorted CoO6 (FeO6) octahedrons leads to its spin reorientation transitions and spontaneous electric polarization different from CuFeO2.

Magnetic domains in Tb-Fe-Co thin films under anisotropy tilt

NASA Astrophysics Data System (ADS)

Talapatra, A.; Umadevi, K.; Arout Chelvane, J.; Mohanty, J.; Jayalakshmi, V.

2018-04-01

Tailoring of magnetic domains of Tb-Fe-Co thin films with rapid thermal processing has been reported in this paper. While the as-deposited films show elongated, inter-connected domains with high out-of-plane magnetic phase contrast, the rapid thermal processed films at 550 °C with different time intervals display deterioration of magnetic contrast. A longitudinal extension of domains has been observed with the processing time of 5 min. With subsequent increase in processing time, the domain patterns exhibit considerable decrease in magnetic phase difference combined with strong intermixing between two oppositely magnetized areas. The out-of-plane magnetic contrast is seen to be very weak for the Tb-Fe-Co film processed for 30 min. The domain morphology and the contrast variation have been modeled with micromagnetic simulations, considering the in-plane (along xz plane) tilt of anisotropy axis. The ground state energy profile and the variation in magnetic properties indicate the threshold tilt angle to be around 30 ° wherein the in-plane and out-of-plane squareness ratio and coercivities are comparable and hence the system shows a spin re-orientation behavior at higher tilt angles.

The overlap between false belief and spatial reorientation in the temporo-parietal junction: The role of input modality and task.

PubMed

Özdem, Ceylan; Brass, Marcel; Van der Cruyssen, Laurens; Van Overwalle, Frank

2017-04-01

Neuroimaging research has demonstrated that the temporo-parietal junction (TPJ) is activated when unexpected stimuli appear in spatial reorientation tasks as well as during thinking about the beliefs of other people triggered by verbal scenarios. While the role of potential common component processes subserved by the TPJ has been extensively studied to explain this common activation, the potential confounding role of input modality (spatial vs. verbal) has been largely ignored. To investigate the role of input modality apart from task processes, we developed a novel spatial false belief task based on moving shapes. We explored the overlap in TPJ activation across this novel task and traditional tasks of spatial reorientation (Posner) and verbal belief (False Belief vs. Photo stories). The results show substantial overlap across the same spatial input modality (both reorientation and false belief) as well as across the common task process (verbal and spatial belief), but no triple overlap. This suggests the potential for an overarching function of the TPJ, with some degree of specialization in different subregions due to modality, function and connectivity. The results are discussed with respect to recent theoretical models of the TPJ.

Re-evaluating the role of TPJ in attentional control: Contextual updating?☆

PubMed Central

Geng, Joy J.; Vossel, Simone

2013-01-01

The right temporo-parietal junction (TPJ) is widely considered as part of a network that reorients attention to task-relevant, but currently unattended stimuli (Corbetta and Shulman, 2002). Despite the prevalence of this theory in cognitive neuroscience, there is little direct evidence for the principal hypothesis that TPJ sends an early reorientation signal that “circuit breaks” attentional processing in regions of the dorsal attentional network (e.g., the frontal eye fields) or is completely right lateralized during attentional processing. In this review, we examine both functional neuroimaging work on TPJ in the attentional literature as well as anatomical findings. We first critically evaluate the idea that TPJ reorients attention and is right lateralized; we then suggest that TPJ signals might rather reflect post-perceptual processes involved in contextual updating and adjustments of top-down expectations; and then finally discuss how these ideas relate to the electrophysiological (P300) literature, and to TPJ findings in other cognitive and social domains. We conclude that while much work is needed to define the computational functions of regions encapsulated as TPJ, there is now substantial evidence that it is not specialized for stimulus-driven attentional reorienting. PMID:23999082

NMR relaxation studies in doped poly-3-methylthiophene

NASA Astrophysics Data System (ADS)

Singh, K. Jugeshwar; Clark, W. G.; Gaidos, G.; Reyes, A. P.; Kuhns, P.; Thompson, J. D.; Menon, R.; Ramesh, K. P.

2015-05-01

NMR relaxation rates (1 /T1 ), magnetic susceptibility, and electrical conductivity studies in doped poly-3-methylthiophene are reported in this paper. The magnetic susceptibility data show the contributions from both Pauli and Curie spins, with the size of the Pauli term depending strongly on the doping level. Proton and fluorine NMR relaxation rates have been studied as a function of temperature (3-300 K) and field (for protons at 0.9, 9.0, 16.4, and 23.4 T, and for fluorine at 9.0 T). The temperature dependence of T1 is classified into three regimes: (a) For T <(g μBB /2 kB ) , the relaxation mechanism follows a modified Korringa relation due to electron-electron interactions and disorder. 1H - T1 is due to the electron-nuclear dipolar interaction in addition to the contact term. (b) For the intermediate temperature range (g μBB /2 kB )

Cooling field and ion-beam bombardment effects on exchange bias behavior in NiFe/(Ni,Fe)O bilayers.

PubMed

Lin, K W; Wei, M R; Guo, J Y

2009-03-01

The dependence of the cooling field and the ion-beam bombardment on the exchange bias effects in NiFe/(Ni,Fe)O bilayers were investigated. The positive exchange bias was found in the zero-field-cooled (ZFC) process whereas a negative exchange bias occurred in the FC process. The increased exchange field, H(ex) with increasing (Ni,Fe)O thicknesses indicates the thicker the AF (Ni,Fe)O, the stronger the exchange coupling between the NiFe layer and the (Ni,Fe)O layer. In addition, the dependence of the H(ex) (ZFC vs. FC) on the (Ni,Fe)O thicknesses reflects the competition between the applied magnetic field and the (Ni,Fe)O surface layer exchange coupled to the NiFe layer. Further, an unusual oscillating exchange bias was observed in NiFe/(Ni,Fe)O bilayers that results from the surface of the (Ni,Fe)O layer being bombarded with different Ar-ion energies using End-Hall deposition voltages (V(EH)) from 0 to 150 V. The behavior of the H(ex) and the H(c) with the V(EH) is attributed to the surface spin reorientation that is due to moderate ion-beam bombardment effects on the surface of the (Ni,Fe)O layer. Whether the (Ni,Fe)O antiferromagnetic spins are coupled to the NiFe moments antiferromagnetically or ferromagnetically changes the sign of the exchange bias.

Initial Satellite Formation Flight Results from the Magnetospheric Multiscale Mission

NASA Technical Reports Server (NTRS)

Williams, Trevor; Ottenstein, Neil; Palmer, Eric; Farahmand, Mitra

2016-01-01

This paper will describe the results that have been obtained to date concerning MMS formation flying. The MMS spacecraft spin at a rate of 3.1 RPM, with spin axis roughly aligned with Ecliptic North. Several booms are used to deploy instruments: two 5 m magnetometer booms in the spin plane, two rigid booms of length 12.5 m along the positive and negative spin axes, and four flexible wire booms of length 60 m in the spin plane. Minimizing flexible motion of the wire booms requires that reorientation of the spacecraft spin axis be kept to a minimum: this is limited to attitude maneuvers to counteract the effects of gravity-gradient and apparent solar motion. Orbital maneuvers must therefore be carried out in essentially the nominal science attitude. These burns make use of a set of monopropellant hydrazine thrusters: two (of thrust 4.5 N) along the spin axis in each direction, and eight (of thrust 18 N) in the spin plane; the latter are pulsed at the spin rate to produce a net delta-v. An on-board accelerometer-based controller is used to accurately generate a commanded delta-v. Navigation makes use of a weak-signal GPS-based system: this allows signals to be received even when MMS is flying above the GPS orbits, producing a highly accurate determination of the four MMS orbits. This data is downlinked to the MMS Mission Operations Center (MOC) and used by the MOC Flight Dynamics Operations Area (FDOA) for maneuver design. These commands are then uplinked to the spacecraft and executed autonomously using the controller, with the ground monitoring the burns in real time.

Education for Sustainability in University Studies: A Model for Reorienting the Curriculum

ERIC Educational Resources Information Center

Junyent, Merce; de Ciurana, Anna M. Geli

2008-01-01

A decisive factor for achieving a culture of sustainability is university training for future professionals. The aim of this article is to bring new elements to the process of reorienting university studies towards sustainability. Presented here is the ACES model (Curriculum Greening of Higher Education, acronym in Spanish), which is the result of…

Spin reorientation and magnetoelastic properties of ferromagnetic T b1 -xN dxC o2 systems with a morphotropic phase boundary

NASA Astrophysics Data System (ADS)

Murtaza, Adil; Yang, Sen; Chang, Tieyan; Ghani, Awais; Khan, Muhammad Tahir; Zhang, Rui; Zhou, Chao; Song, Xiaoping; Suchomel, Matthew; Ren, Yang

2018-03-01

The spin reorientation (SR) and magnetoelastic properties of pseudobinary ferromagnetic T b1 -xN dxC o2 (0 ≤x ≤1.0 ) systems involving a morphotropic phase boundary (MPB) were studied by high-resolution synchrotron x-ray diffraction (XRD), magnetization, and magnetostriction measurements. The easy magnetization direction of the Laves phase lies along the 〈111 〉 axis with x <0.65 , whereas it lies along the 〈100 〉 axis for x >0.65 below Curie temperature (TC). The temperature-dependent magnetization curves showed SR; this can be explained by a two-sublattice model. Based on the synchrotron (XRD) and magnetization measurements, the SR phase diagram for a MPB composition of T b0.35N d0.65C o2 was obtained. Contrary to previously reported ferromagnetic systems involving MPB, the MPB composition of T b0.35N d0.65C o2 exhibits a low saturation magnetization (MS), indicating a compensation of the Tb and Nd magnetic moments at MPB. The anisotropic magnetostriction (λS) first decreased until x =0.8 and then continuously increased in the negative direction with further increase of Nd concentration. The decrease in magnetostriction can be attributed to the decrease of spontaneous magnetostriction λ111 and increase of λ100 with opposite sign to λ111. This paper indicates an anomalous type of MPB in the ferromagnetic T b1 -xN dxC o2 system and provides an active way to design novel functional materials with exotic properties.

Young children's use of features to reorient is more than just associative: further evidence against a modular view of spatial processing.

PubMed

Newcombe, Nora S; Ratliff, Kristin R; Shallcross, Wendy L; Twyman, Alexandra D

2010-01-01

Proponents of a geometric module have argued that instances of young children's use of features as well as geometry to reorient can be explained by a two-stage process. In this model, only the first stage is a true reorientation, accomplished by using geometric information alone; features are considered in a second stage using association (Lee, Shusterman & Spelke, 2006). This account is contradicted by the data from two experiments. Experiment 1a sets the stage for Experiment 1b by showing that young children use geometric information to reorient in a complex geometric figure without a single principal axis of symmetry (an octagon). In such a figure, there are two sets of geometrically congruent corners, with four corners in each set. The addition of a colored wall leads to the existence of three geometrically congruent but, crucially, all unmarked corners; using the colored wall to distinguish among them could not be done associatively. In Experiment 1b, both 3- and 5-year-old children showed true non-associative reorientation using features by performing at above-chance levels on all-white trials. Experiment 2 used a paradigm without distinctive geometry, modeled on Lee et al. (2006), involving an equilateral triangle of hiding places located within a circular enclosure, but with a large stable feature rather than a small moveable one. Four-year-olds (the age group studied by Lee et al.) used features at above-chance levels. Thus, features can be used to reorient, in a way not dependent on association, in contradiction to the two-stage version of the modular view.

Biotechnology

NASA Image and Video Library

2003-01-12

The short-arm centrifuge subjects an astronaut to conflicting sensory input and study the astronaut's perception of motion. It is one of several instruments used in the Spatial Reorientation Following Space Flight investigation to be conducted after astronauts return to Earth. During space flight, the vestibular organs no longer respond in a familiar way. Instead, inputs from the irner ear do not match those coming from the eyes. While on Earth, you can open your eyes to see if you truly are spinning, but astronauts do not have this luxury. Astronauts can see the floor, but have no sense of down; when they bend their heads forward, the otoliths are not stimulated properly. This state, called sensory conflict, must be resolved by the brain to maintain orientation. When they first return to Earth, astronauts are again disoriented because of sensory conflict. They undergo a period of spatial reorientation, as their brains reconcile what their eyes see and what their vestibular system senses. Recovery can take anywhere from hours to days depending on the length of the mission. Principal Investigator: Dr. William Paloski, Johnson Space Center, Houston, TX.

Microgravity

NASA Image and Video Library

2003-01-12

The short-arm centrifuge subjects an astronaut to conflicting sensory input and study the astronaut's perception of motion. It is one of several instruments used in the Spatial Reorientation Following Space Flight investigation to be conducted on crewmembers. During space flight, the vestibular organs no longer respond in a familiar way. Instead, inputs from the irner ear do not match those coming from the eyes. While on Earth, you can open your eyes to see if you truly are spinning, but astronauts do not have this luxury. Astronauts can see the floor, but have no sense of down; when they bend their heads forward, the otoliths are not stimulated properly. This state, called sensory conflict, must be resolved by the brain to maintain orientation. When they first return to Earth, astronauts are again disoriented because of sensory conflict. They undergo a period of spatial reorientation, as their brains reconcile what their eyes see and what their vestibular system senses. Recovery can take anywhere from hours to days depending on the length of the mission. Principal Investigator: Dr. William Paloski, Johnson Space Center, Houston, TX.

The mechanisms of the effects of magnetic fields on cells

NASA Astrophysics Data System (ADS)

Kondrachuk, A.

The evolution of organisms in conditions of the Earth magnetism results in close dependence of their functioning on the properties of the Earth magnetic field. The magnetic conditions in space flight differ from those on the Earth (e.g. much smaller values of magnetic filed) that effect various processes in living organisms. Meanwhile the mechanisms of interaction of magnetic fields with cell structures are poorly understood and systemized. The goal of the present work is to analyze and estimate the main established mechanisms of "magnetic fields - cell" interaction. Due to variety and complexity of the effects the analysis is mainly restricted to biological effects of the static magnetic field at a cellular level. 1) Magnetic induction. Static magnetic fields exert forces on moving ions in solution (e.g., electrolytes), giving rise to induced electric fields and currents. This effect may be especially important when the currents changed due to the magnetic field application are participating in some receptor functions of cells (e.g. plant cells). 2) Magneto-mechanical effect of reorientation. Uniform static magnetic fields produce torques on certain molecules with anisotropic magnetic properties, which results in their reorientation and spatial ordering. Since the structures of biological cells are magnetically and mechanically inhomogeneous, the application of a homogeneous magnetic field may cause redistribution of stresses within cells, deformation of intracellular structures, change of membrane permeability, etc. 3) Ponderomotive effects. Spatially non-uniform magnetic field exerts ponderomotive force on magnetically non-uniform cell structures. This force is proportional to the gradient of the square of magnetic field and the difference of magnetic susceptibilities of the component of the cell and its environment. 4) Biomagnetic effects. Magnetic fields can exert torques and translational forces on ferromagnetic structures, such as magnetite and ferritins presented in the cells. 5) Electronic interactions. Static magnetic fields can alter energy levels and spin orientation of electrons. Similar interactions can also occur with nuclear spins, but these are very weak compared to electron interactions. 6) Free radicals. Magnetic fields alter the spin states of the radicals, which, in turn, changes the relative probabilities of recombination and other interactions, possibly with biological consequences. 7) Non-linear effects. A number of non-linear mechanisms of magnetic effects on cells were recently proposed to explain how the cell could extract a weak magnetic signal from noise (e.g. stochastic non-linear resonance, self-tuned Hopf bifurcations). These new models need further experimental testing.

Solution-processed BiI 3 thin films for photovoltaic applications: Improved carrier collection via solvent annealing

DOE PAGES

Hamdeh, Umar H.; Nelson, Rainie D.; Ryan, Bradley J.; ...

2016-08-26

Here, we report all-inorganic solar cells based on solution-processed BiI 3. Two-electron donor solvents such as tetrahydrofuran and dimethylformamide were found to form adducts with BiI 3, which make them highly soluble in these solvents. BiI 3 thin films were deposited by spin-coating. Solvent annealing BiI 3 thin films at relatively low temperatures (≤100 °C) resulted in increased grain size and crystallographic reorientation of grains within the films. The BiI3 films were stable against oxidation for several months and could withstand several hours of annealing in air at temperatures below 150 °C without degradation. Surface oxidation was found to improvemore » photovoltaic device performance due to the formation of a BiOI layer at the BiI 3 surface which facilitated hole extraction. Nonoptimized BiI 3 solar cells achieved the highest power conversion efficiencies of 1.0%, demonstrating the potential of BiI 3 as a nontoxic, air-stable metal-halide absorber material for photovoltaic applications.« less

Gravitropism of cut shoots is mediated by oxidative processes: A physiological and molecular study

NASA Astrophysics Data System (ADS)

Philosoph-Hadas, Sonia; Friedman, Haya; Meir, Shimon

2012-07-01

The signal transduction events occurring during shoot gravitropism are mediated through amyloplasts sedimentation, reorientation of actin filaments in the endodermis, and differential changes in level and action of auxin, associated with differential growth leading to shoot curvature. Since increase in reactive oxygen species (ROS) was shown to be associated with growth, we examined the possible use of antioxidants in controlling the gravitropic response, via their interaction with events preceding shoot bending. Reoriented snapdragon (Antirrhinum majus L.) spikes and tomato (Solanum lycopersicum cv. MicroTom) shoots showed a visual upward bending after a lag period of 3 or 5 h, respectively, which was inhibited by the antioxidants N-acetyl-cysteine (NAC) and reduced glutathione (GSH). This suggests the involvement of oxidative reactions in the process. The two antioxidants prevented the sedimentation of amyloplasts to the bottom of the endodermis cells following 0.5-5 h of snapdragon shoot reorientation, suggesting that oxidative reactions are involved already at a very early signal perception stage prior to the visual bending. In addition, a differential distribution in favor of the lower shoot side of various oxidative elements, including H2O2 concentrations and activity of the NADPH-oxidase enzyme, was observed during reorientation of snapdragon spikes. Application of the two antioxidants reduced the levels of these elements and abolished their differential distribution across the shoot. On the other hand, the activity of the antioxidative enzyme, superoxide dismutase (SOD), which was not differentially distributed across the shoot, increased significantly following application of the two antioxidants. The auxin redistribution in reoriented shoots was analyzed using transgenic tomato plants expressing the GUS reporter gene under the Aux/IAA4 promoter (a generous gift of M. Bouzayen, France). GUS response, detected in control shoots 4 h after their reorientation in favor of the lower shoot side was completely eliminated in the NAC-treated shoots, in which the bending response was inhibited. These results suggest that the gravitropic-induced asymmetric auxin redistribution precedes shoot bending, and NAC inhibits this response by abolishing the auxin gradient across the shoot. Our microarray analysis of tomato shoots, using the Affymetrix Tomato GeneChip, revealed differential changes in expression of 266 genes, occurring during the initial 0.5-5 h of shoot reorientation prior to bending. The differential changes in expression of auxin-related genes in favor of the lower shoot side occurred already following 0.5 h of reorientation, while those of cell wall-related genes, associated with shoot bending, occurred only 3 h following shoot reorientation. Among the identified genes, 11 genes were related to auxin, and 36 genes were associated with oxidative processes, demonstrating the involvement of ROS in early events of shoot gravitropism. Taken together, our results suggest that ROS mediate the early gravity-induced amyloplast sedimentation required for signal perception, as well as the lateral auxin movement across the shoot, which is necessary for the auxin asymmetric distribution leading to shoot upward bending.

Electrophysiological correlates of stimulus-driven reorienting deficits after interference with right parietal cortex during a spatial attention task: a TMS-EEG study

PubMed Central

Capotosto, Paolo; Corbetta, Maurizio; Romani, Gian Luca; Babiloni, Claudio

2013-01-01

Transcranial magnetic stimulation (TMS) interference over right intraparietal sulcus (IPS) causally disrupts behaviorally and electroencephalographic (EEG) rhythmic correlates of endogenous spatial orienting prior to visual target presentation (Capotosto et al. 2009; 2011). Here we combine data from our previous studies to examine whether right parietal TMS during spatial orienting also impairs stimulus-driven re-orienting or the ability to efficiently process unattended stimuli, i.e. stimuli outside the current focus of attention. Healthy subjects (N=24) performed a Posner spatial cueing task while their EEG activity was being monitored. Repetitive TMS (rTMS) was applied for 150 milliseconds (ms) simultaneously to the presentation of a central arrow directing spatial attention to the location of an upcoming visual target. Right IPS-rTMS impaired target detection, especially for stimuli presented at unattended locations; it also caused a modulation of the amplitude of parieto-occipital positive ERPs peaking at about 480 ms (P3) post-target. The P3 significantly decreased for unattended targets, and significantly increased for attended targets after right IPS-rTMS as compared to Sham stimulation. Similar effects were obtained for left IPS stimulation albeit in a smaller group of subjects. We conclude that disruption of anticipatory processes in right IPS has prolonged effects that persist during target processing. The P3 decrement may reflect interference with post-decision processes that are part of stimulus-driven re-orienting. Right IPS is a node of functional interaction between endogenous spatial orienting and stimulus-driven re-orienting processes in human vision. PMID:22905824

Pseudonematic order fluctuations of the director in the smectic phase of thermotropic liquid crystals.

PubMed

Acosta, R H; Pusiol, D J

1999-08-01

The NMR spin-lattice proton relaxation dispersion in the smectic mesophase of two liquid crystals, 4cyano-4'-8-alkylbiphenyl and 4,4'-bis-heptyloxyazoxybenzene, are studied over several decades of Larmor frequencies. The results show that the order fluctuation of the local smectic director contribution to T1(nu(L)) undergoes a transition between two power regimes: from T1(nu(L)) proportional, variantnu(1)(L) to nu(1/2)(L) on going from low to high Larmor frequencies. We explain this behavior by assuming, in the smectic mesophases, short coherence length nematiclike cooperative molecular reorientations.

Analytic Theory and Control of the Motion of Spinning Rigid Bodies

NASA Technical Reports Server (NTRS)

Tsiotras, Panagiotis

1993-01-01

Numerical simulations are often resorted to, in order to understand the attitude response and control characteristics of a rigid body. However, this approach in performing sensitivity and/or error analyses may be prohibitively expensive and time consuming, especially when a large number of problem parameters are involved. Thus, there is an important role for analytical models in obtaining an understanding of the complex dynamical behavior. In this dissertation, new analytic solutions are derived for the complete attitude motion of spinning rigid bodies, under minimal assumptions. Hence, we obtain the most general solutions reported in the literature so far. Specifically, large external torques and large asymmetries are included in the problem statement. Moreover, problems involving large angular excursions are treated in detail. A new tractable formulation of the kinematics is introduced which proves to be extremely helpful in the search for analytic solutions of the attitude history of such kinds of problems. The main utility of the new formulation becomes apparent however, when searching for feedback control laws for stabilization and/or reorientation of spinning spacecraft. This is an inherently nonlinear problem, where standard linear control techniques fail. We derive a class of control laws for spin axis stabilization of symmetric spacecraft using only two pairs of gas jet actuators. Practically, this could correspond to a spacecraft operating in failure mode, for example. Theoretically, it is also an important control problem which, because of its difficulty, has received little, if any, attention in the literature. The proposed control laws are especially simple and elegant. A feedback control law that achieves arbitrary reorientation of the spacecraft is also derived, using ideas from invariant manifold theory. The significance of this research is twofold. First, it provides a deeper understanding of the fundamental behavior of rigid bodies subject to body-fixed torques. Assessment of the analytic solutions reveals that they are very accurate; for symmetric bodies the solutions of Euler's equations of motion are, in fact, exact. Second, the results of this research have a fundamental impact on practical scientific and mechanical applications in terms of the analysis and control of all finite-sized rigid bodies ranging from nanomachines to very large bodies, both man made and natural. After all, Euler's equations of motion apply to all physical bodies, barring only the extreme limits of quantum mechanics and relativity.

Magnetic Phase Transition in Ion-Irradiated Ultrathin CoN Films via Magneto-Optic Faraday Effect.

PubMed

Su, Chiung-Wu; Chang, Yen-Chu; Chang, Sheng-Chi

2013-11-15

The magnetic properties of 1 nm thick in-plane anisotropic Co ultrathin film on ZnO(0001) were investigated through successive 500 eV nitrogen-ion sputtering. Magneto-optical Faraday effects were used to observe the evolution of the ion-irradiated sample in longitudinal and perpendicular magnetic fields. The ferromagnetic phase of the initial in-plane anisotropic fcc β-Co phase transformation to β-Co(N) phase was terminated at paramagnetic CoN x phase. In-plane anisotropy with weak out-of-plane anisotropy of the Co/ZnO sample was initially observed in the as-grown condition. In the sputtering process, the N⁺ ions induced simultaneous sputtering and doping. An abrupt spin reorientation behavior from in-plane to out-of-plane was found under prolonged sputtering condition. The existence of perpendicular anisotropy measured from the out-of-plane Faraday effect may be attributed to the co-existence of residual β-Co and Co₄N exchange bonding force by the gradual depletion of Co-N thickness.

Evolution from 4f-electron antiferromagnetic to ferromagnetic order in the CeCu(Ge1-xSnx ) alloy series (0 ≤x ≤1 )

NASA Astrophysics Data System (ADS)

Altayeb, A.; Sondezi, B. M.; Tchoula Tchokonté, M. B.; Strydom, A. M.; Doyle, T. B.; Kaczorowski, D.

2017-05-01

We report the evolution from ferromagnetic (FM) to antiferromagnetic (AFM) state in CeCu(Ge1-xSnx ) investigated by means of magnetic and heat capacity measurements. X-ray diffraction studies for all compositions indicate the ZrBeSi - type hexagonal crystal structure with space group P63/mmc (No. 194). The magnetic susceptibility, χ (T ) at high temperature follows the Curie - Weiss relation with an effective magnetic moment close to the value of 2.54 μB expected for free Ce3+ - ion. At low temperatures, χ (T ) data indicate AFM transition for alloys in the concentration range 0.7 ≤x ≤1 and FM for x ≤0.6 . The magnetization, M (μ0H ) of samples exhibiting AFM behaviour shows metamagnetic transition at low magnetic fields with some irreversibility in the process of increasing and decreasing magnetic field. In turn, M (μ0H ) of samples exhibiting FM behaviour shows saturation in high magnetic fields. Heat capacity, Cp(T) data confirm the AFM and FM transitions observed in magnetic measurements. An additional anomaly below TC and TN is observed in Cp(T)/T, which likely arises from spin reorientation or rearrangement in FM or AFM structure. Below in FM region, Cp(T) can be well described assuming spin-waves excitations with an energy gap ΔC.

Hydrostatic pressure effect on the spin reorientation transition of ferromagnetic Sm0.7-xLaxSr0.3MnO3 (x = 0, 0.1) polycrystals

NASA Astrophysics Data System (ADS)

Thiyagarajan, R.; Arumugam, S.; Sivaprakash, P.; Kannan, M.; Saravanan, C.; Yang, Wenge

2017-06-01

The hydrostatic pressure effect on the resistivity and magnetization of the narrow band gap manganite Sm0.7-xLaxSr0.3MnO3 (x = 0, 0.1) systems has been investigated. At ambient pressure measurements, the parent compound Sm0.7Sr0.3MnO3 showed a ferromagnetic-insulating nature, whereas the 10% La-doped compound Sm0.6La0.1Sr0.3MnO3 showed a ferromagnetic-metallic nature. Furthermore, both samples showed a spin-reorientation transition (TSR) below Curie temperature, which originated from the Mn sublattice and was supported by an antiferromagnetic Sm(4f)-Mn(3d) interaction. Both samples exhibited a normal and inverse magnetocaloric effect as a result of these two different magnetic transitions. Magnetization measurements on Sm0.7Sr0.3MnO3 under pressure did not show an appreciable change in the Curie temperature, but enhanced TSR, whereas an insulator-metallic transition was observed during resistivity measurements under pressure. On the other hand, for Sm0.6La0.1Sr0.3MnO3, TC increased and TSR reduced upon the application of pressure. The metallic nature which is observed at ambient pressure resistivity measurement was further enhanced with 97% of piezoresistance. The pressure did not change the normal magnetocaloric effect of Sm0.7Sr0.3MnO3, but increased it in Sm0.6La0.1Sr0.3MnO3. However, there was not much change in the inverse magnetocaloric effect of both compounds. These studies were analyzed based on the pressure effect on the activation energy and scattering interaction factors.

Europium III binding and the reorientation of magnetically aligned bicelles: insights from deuterium NMR spectroscopy.

PubMed Central

Crowell, K J; Macdonald, P M

2001-01-01

Solid-state deuterium ((2)H) NMR spectroscopy was used to study the reorientation of magnetically ordered bicelles in the presence of the paramagnetic lanthanide Eu(3+). Bicelles were composed of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) plus 1,2-dihexanoyl-sn-glycero-3-phosphocholine plus either the anionic lipid 1,2-dimyristoyl-sn-3-phosphoglycerol, or the cationic lipid 1,2-dimyristoyl-3-trimethyl ammonium propane. Alignment of the bicelles in the magnetic field produced (2)H NMR spectra consisting of a pair of quadrupole doublets, one from the alpha-deuterons and one from the beta-deuterons of DMPC-alpha,beta-d(4). Eu(3+) addition induced the appearance of a second set of quadrupole doublets, having approximately twice the quadrupolar splittings of the originals, and growing progressively in intensity with increasing Eu(3+), at the expense of the intensity of the originals. The new resonances were attributed to bicelles having a parallel alignment with respect to the magnetic field, as opposed to the perpendicular alignment preferred in the absence of Eu(3+). Therefore, the equilibrium degree and kinetics of reorientation could be evaluated from the (2)H NMR spectra. For more cationic initial surface charges, higher amounts of added Eu(3+) were required to induce a given degree of reorientation. However, the equilibrium degree of bicellar reorientation was found to depend solely on the amount of bound Eu(3+), regardless of the bicelle composition. The kinetics of reorientation were a function of lipid concentration. At high lipid concentration, a single fast rate of reorientation (minutes) described the approach to the equilibrium degree of orientation. At lower lipid concentrations, two rates processes were discernible: one fast (minutes) and one slow (hours). The data indicate, therefore, that bicelle reorientation is a phase transition made critical by bicelle-bicelle interactions. PMID:11423411

Coercivity enhancement mechanism in Dy-substituted Nd-Fe-B nanoparticles synthesized by sol-gel base method followed by a reduction-diffusion process

NASA Astrophysics Data System (ADS)

Rahimi, Hamed; Ghasemi, Ali; Mozaffarinia, Reza; Tavoosi, Majid

2017-05-01

In current work, Nd15-xDyxFe77.5B7.5 (at%) nanoparticles with different Dy-content (x=0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0) were synthesized by sol-gel method followed by a reduction-diffusion process. The effects of Dy on the magnetic properties and the relations between the microstructure and the coercivity of Dy-substituted Nd-Fe-B nanoparticles have been studied. The coercivity of Nd-Fe-B nanoparticles with the addition of Dy first increase, reaches a maximum, and then starts to decrease. The coercivity of Dy-substituted Nd-Fe-B nanoparticle synthesized by sol-gel method increased from 938.9 to 1663.9 kA/m while the remanence decreased slightly from 1.16 to 1.06 T. The results show that with an increase in Dy content the variation of maximum energy product ((BH)max), lowest-order uniaxial magnetocrystalline anisotropy constant (Ku1), and Curie temperature (Tc) had a trend as same as the coercivity. The Henkel plot showed that the existence of exchange coupling interaction between grains, and the exchange coupling interactions increased with increasing x from 0.0 to 2.0 and then decrease with further increasing x≥2.5. The optimum magnetic properties of Nd-Fe-B nanoparticles with (BH)max =40.38 MGOe, Hc=1663.9 kA/m, Br=1.08 T were obtained by substituted 2.0 at% Dy. The effects of increasing temperature on magnetic properties of Dy-substituted Nd-Fe-B nanoparticle magnets with 2.0 at% Dy was investigated. The reduced spin-reorientation temperature was obtained for Dy-substituted Nd-Fe-B nanoparticles with 2.0 at% Dy. Below 100 K a spin-reorientation transition was takes place. The temperature coefficient of coercivity (β) was -0.36, -0.46, -0.41, -0.34, -0.29, -0.24, -0.25%/°C at different temperature 50, 100, 150, 200, 250, 300, 350 °C, respectively. Mössbauer spectroscopy was applied to study the composition and properties of Dy-substituted Nd-Fe-B magnet. Microstructure analysis showed a homogeneous distribution of Dy in produced samples. The possible reason for observed magnetic behavior is improving the intrinsic material parameter and optimizing the microstructure by a uniform enhancement of magnetocrystalline anisotropy by formation the nanocrystalline compound (Nd,Dy)2Fe14B.

Growth and microtubule orientation of Zea mays roots subjected to osmotic stress

NASA Technical Reports Server (NTRS)

Blancaflor, E. B.; Hasenstein, K. H.

1995-01-01

Previous work has shown that microtubule (MT) reorientation follows the onset of growth inhibition on the lower side of graviresponding roots, indicating that growth reduction can occur independently of MT reorientation. To test this observation further, we examined whether the reduction in growth in response to osmotic stress is correlated with MT reorientation. The distribution and rate of growth in maize roots exposed to 350 mOsm sorbitol and KCl or 5 mM Mes/Tris buffer were measured with a digitizer. After various times roots were processed for indirect immunofluorescence microscopy. Application of sorbitol or KCl had no effect on the organization of MTs in the apical 2 mm of the root but resulted in striking and different effects in the basal region of the root. Sorbitol treatment caused rapid appearance of oval to circular holes in the microtubular array that persisted for at least 9 h. Between 30 min and 4 h of submersion in KCl, MTs in cortical cells 4 mm and farther from the quiescent center began to reorient oblique to the longitudinal axis. After 9 h, the alignment of MTs had shifted to parallel to the root axis but MTs of the epidermal cells remained transverse. In KCl-treated roots MT reorientation appeared to follow a pattern of development similar to that in controls but without elongation. Our data provide additional evidence that MT reorientation is not the cause but a consequence of growth inhibition.

Structural and Magnetic Properties of Mn1.5X0.5Sn (X = Cr, Mn, Fe, Co) Melt-spun Ribbons

NASA Astrophysics Data System (ADS)

Fuglsby, R.; Kharel, P.; Zhang, W.; Valloppilly, S.; Huh, Y.; Sellmyer, D. J.

2015-03-01

Mn1.5X0.5Sn (X = Cr, Mn, Fe, Co) nanomaterials in a hexagonal Ni2In-type crystal structure have been prepared using arc-melting and melt spinning. All the samples show moderate saturation magnetization at 100 K with a highest value of 458 emu/cm3 for Mn1.5Fe0.5Sn, but their Curie temperatures (Tc) are less than 300 K. The highest Tc is 206 K for the Fe containing sample. All samples except the Cr containing one show irreversibility between the zero-field-cooled and field-cooled measurements at the low temperature, showing a spin reorientation or spin-glass-like behavior. The magnetic anisotropy constants calculated at 100 K are on the order of 1 Merg/cm3. The magnetic properties of these materials have substantially improved due to vacuum annealing, where the Tc for Mn2Sn annealed at 450 °C has increased by about 75 K from 190 K to 265 K. Research is supported by Department of Physics, SDSU. Research at UNL is supported by NSF-MRSEC Grant DMR-0820521 and DOE-BES-DMSE Grant DE-FG 02-04ER46152.

Basis set study of classical rotor lattice dynamics.

PubMed

Witkoskie, James B; Wu, Jianlan; Cao, Jianshu

2004-03-22

The reorientational relaxation of molecular systems is important in many phenomenon and applications. In this paper, we explore the reorientational relaxation of a model Brownian rotor lattice system with short range interactions in both the high and low temperature regimes. In this study, we use a basis set expansion to capture collective motions of the system. The single particle basis set is used in the high temperature regime, while the spin wave basis is used in the low temperature regime. The equations of motion derived in this approach are analogous to the generalized Langevin equation, but the equations render flexibility by allowing nonequilibrium initial conditions. This calculation shows that the choice of projection operators in the generalized Langevin equation (GLE) approach corresponds to defining a specific inner-product space, and this inner-product space should be chosen to reveal the important physics of the problem. The basis set approach corresponds to an inner-product and projection operator that maintain the orthogonality of the spherical harmonics and provide a convenient platform for analyzing GLE expansions. The results compare favorably with numerical simulations, and the formalism is easily extended to more complex systems. (c) 2004 American Institute of Physics

Ultrafast inter- and intramolecular vibrational energy transfer between molecules at interfaces studied by time- and polarization-resolved SFG spectroscopy.

PubMed

Yamamoto, Susumu; Ghosh, Avishek; Nienhuys, Han-Kwang; Bonn, Mischa

2010-10-28

We present experimental results on femtosecond time-resolved surface vibrational spectroscopy aimed at elucidating the sub-picosecond reorientational dynamics of surface molecules. The approach, which relies on polarization- and time-resolved surface sum frequency generation (SFG), provides a general means to monitor interfacial reorientational dynamics through vibrations inherent in surface molecules in their electronic ground state. The technique requires an anisotropic vibrational excitation of surface molecules using orthogonally polarized infrared excitation light. The decay of the resulting anisotropy is followed in real-time. We employ the technique to reveal the reorientational dynamics of vibrational transition dipoles of long-chain primary alcohols on the water surface, and of water molecules at the water-air interface. The results demonstrate that, in addition to reorientational motion of specific molecules or molecular groups at the interface, inter- and intramolecular energy transfer processes can serve to scramble the initial anisotropy very efficiently. In the two exemplary cases demonstrated here, energy transfer occurs much faster than reorientational motion of interfacial molecules. This has important implications for the interpretation of static SFG spectra. Finally, we suggest experimental schemes and strategies to decouple effects resulting from energy transfer from those associated with surface molecular motion.

Mechanistic analysis of the search behaviour of Caenorhabditis elegans

PubMed Central

Salvador, Liliana C. M.; Bartumeus, Frederic; Levin, Simon A.; Ryu, William S.

2014-01-01

A central question in movement research is how animals use information and movement to promote encounter success. Current random search theory identifies reorientation patterns as key to the compromise between optimizing encounters for both nearby and faraway targets, but how the balance between intrinsic motor programmes and previous environmental experience determines the occurrence of these reorientation behaviours remains unknown. We used high-resolution tracking and imaging data to describe the complete motor behaviour of Caenorhabditis elegans when placed in a novel environment (one in which food is absent). Movement in C. elegans is structured around different reorientation behaviours, and we measured how these contributed to changing search strategies as worms became familiar with their new environment. This behavioural transition shows that different reorientation behaviours are governed by two processes: (i) an environmentally informed ‘extrinsic’ strategy that is influenced by recent experience and that controls for area-restricted search behaviour, and (ii) a time-independent, ‘intrinsic’ strategy that reduces spatial oversampling and improves random encounter success. Our results show how movement strategies arise from a balance between intrinsic and extrinsic mechanisms, that search behaviour in C. elegans is initially determined by expectations developed from previous environmental experiences, and which reorientation behaviours are modified as information is acquired from new environments. PMID:24430127

Tunnelling anisotropic magnetoresistance at La{sub 0.67}Sr{sub 0.33}MnO{sub 3}-graphene interfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Phillips, L. C., E-mail: lee.phillips@cantab.net; Yan, W.; Kar-Narayan, S.

2016-03-14

Using ferromagnetic La{sub 0.67}Sr{sub 0.33}MnO{sub 3} electrodes bridged by single-layer graphene, we observe magnetoresistive changes of ∼32–35 MΩ at 5 K. Magneto-optical Kerr effect microscopy at the same temperature reveals that the magnetoresistance arises from in-plane reorientations of electrode magnetization, evidencing tunnelling anisotropic magnetoresistance at the La{sub 0.67}Sr{sub 0.33}MnO{sub 3}-graphene interfaces. Large resistance switching without spin transport through the non-magnetic channel could be attractive for graphene-based magnetic-sensing applications.

Identification of the low-energy excitations in a quantum critical system

NASA Astrophysics Data System (ADS)

Heitmann, Tom; Lamsal, Jagat; Watson, Shannon; Erwin, Ross; Chen, Wangchun; Zhao, Yang; Montfrooij, Wouter

2017-05-01

We have identified low-energy magnetic excitations in a doped quantum critical system by means of polarized neutron scattering experiments. The presence of these excitations could explain why Ce(Fe0.76Ru0.24)2Ge2 displays dynamical scaling in the absence of local critical behavior or long-range spin-density wave criticality. The low-energy excitations are associated with the reorientations of the superspins of fully ordered, isolated magnetic clusters that form spontaneously upon lowering the temperature. The system houses both frozen clusters and dynamic clusters, as predicted by Hoyos and Vojta [Phys. Rev. B 74, 140401(R) (2006)].

Magnetic structure of Ho0.5Y0.5Mn6Sn6 compound studied by powder neutron diffraction

NASA Astrophysics Data System (ADS)

Li, X.-Y.; Peng, L.-C.; He, L.-H.; Zhang, S.-Y.; Yao, J.-L.; Zhang, Y.; Wang, F.-W.

2018-05-01

The crystallographic and magnetic structures of the HfFe6Ge6-type compound Ho0.5Y0.5Mn6Sn6 have been studied by powder neutron diffraction and in-situ Lorentz transmission electron microscopy. Besides the nonlinear thermal expansion of lattice parameters, an incommensurate conical spiral magnetic structure was determined in the temperature interval of 2-340 K. A spin reorientation transition has been observed from 50 to 300 K, where the alignment of the c-axis component of magnetic moments of the Ho sublattice and the Mn sublattice transfers from ferrimagnetic to ferromagnetic.

Magnetostructural phase transformations in Tb 1-x Mn 2

DOE PAGES

Zou, Junding; Paudyal, Durga; Liu, Jing; ...

2015-01-16

Magnetism and phase transformations in non-stoichiometric Tb 1-xMn 2 (x = 0.056, 0.039) have been studied as functions of temperature and magnetic field using magnetization, heat capacity, and X-ray powder diffraction measurements. Lowering the temperature, the compounds sequentially order ferrimagnetically and antiferromagnetically, and finally, exhibit spin reorientation transitions. Moreover, these structural distortions from room temperature cubic to low temperature rhombohedral structures occur at T N, and are accompanied by large volume changes reaching ~-1.27% and -1.42%, respectively. First principles electronic structure calculations confirm the phase transformation from the ferrimagnetic cubic structure to the antiferromagnetic rhombohedral structure in TbMn 2.

Intragranular twinning, detwinning, and twinning-like lattice reorientation in magnesium alloys

DOE PAGES

Wu, Wei; Gao, Yanfei; Oak Ridge National Lab.; ...

2016-09-11

We present that deformation twinning plays a critical role on improving metals or alloys ductility, especially for hexagonal close-packed materials with low symmetry crystal structure. A rolled Mg alloy was selected as a model system to investigate the extension twinning behaviors and characteristics of parent-twin interactions by nondestructive in situ 3D synchrotron X-ray microbeam diffraction. Besides twinning- detwinning process, the twinning-like lattice reorientation process was captured within an individual grain inside a bulk material during the strain reversal. The distributions of parent, twin, and reorientated grains and sub-micron level strain variation across the twin boundary are revealed. A theoretical calculationmore » of the lattice strain confirms that the internal strain distribution in parent and twinned grains correlates with the experimental setup, grain orientation of parent, twin, and surrounding grains, as well as the strain path changes. In conclusion, the study suggests a novel deformation mechanism within the hexagonal close-packed structure that cannot be determined from surface-based characterization methods.« less

Atomic-scale control of magnetic anisotropy via novel spin–orbit coupling effect in La 2/3Sr 1/3MnO 3/SrIrO 3 superlattices

DOE PAGES

Yi, Di; Liu, Jian; Hsu, Shang-Lin; ...

2016-05-19

Magnetic anisotropy (MA) is one of the most important material properties for modern spintronic devices. Conventional manipulation of the intrinsic MA, i.e., magnetocrystalline anisotropy (MCA), typically depends upon crystal symmetry. Extrinsic control over the MA is usually achieved by introducing shape anisotropy or exchange bias from another magnetically ordered material. Here we demonstrate a pathway to manipulate MA of 3d transition-metal oxides (TMOs) by digitally inserting nonmagnetic 5d TMOs with pronounced spin-orbit coupling (SOC). High-quality superlattices comprising ferromagnetic La 2/3Sr 1/3MnO 3 (LSMO) and paramagnetic SrIrO 3 (SIO) are synthesized with the precise control of thickness at the atomic scale.more » Magnetic easy-axis reorientation is observed by controlling the dimensionality of SIO, mediated through the emergence of a novel spin-orbit state within the nominally paramagnetic SIO.« less

A Review of the NASA MLAS Flight Demonstration

NASA Technical Reports Server (NTRS)

Taylor, Anthony P.; Kelley, Christopher; Manger, Eldred; Peterson, David; Hahn, Jeffrey; Yuchnovicz, Daniel

2011-01-01

The NASA Engineering and Safety Center (NESC) has tested the Max Launch Abort System (MLAS) as a risk-mitigation design should problems arise with the baseline Orion spacecraft launch abort design. The Max in MLAS is not Maximum, but rather dedicated to Max Faget, the renowned NASA Spacecraft designer. In July 2009, the mission was flown, with great success, from the NASA Wallops Flight Facility. The MLAS flight test vehicle prototype consists of a boost skirt, coast skirt, and the MLAS fairing itself, which houses an Orion Command Module (CM) boilerplate. The objective of the MLAS flight test is to reorient the fairing with the CM, weighing approximately 29,000 lbs and traveling 290 fps, 180 degrees to an orientation suitable for the release of the CM during a pad abort or low altitude abort. The boost and coast skirts provide the necessary thrust and stability to establish the flight test conditions and are released prior to the reorientation of the fairing. A secondary test objective after successful release of the CM from the fairing is to demonstrate the removal of the CM forward bay cover (FBC) with the CM drogue parachutes, and subsequent deployment of the CM main parachutes attached to the FBC. Although multiple parachute deployments are used in the MLAS flight test vehicle to complete its objective, there are only two parachute types employed in the flight test. Five of the nine parachutes used for MLAS are 27.6 ft DO ribbon parachutes already proven as a spin/stall parachute for military aircraft, and the remaining four are G-12 cargo parachutes modified for increased strength and reefing. This paper presents an overview of the 27.6 ft DO ribbon parachute system employed on the MLAS flight test vehicle for coast skirt separation, fairing reorientation, and as CM drogue parachutes. Discussion will include: the process used to select this design; descriptions of all components of the parachute system; the minor modifications necessary to adapt the parachute to the MLAS program; the techniques used to analyze the parachute for the multiple roles it performs including discussions of how the evolution of the program affected parachute usage and analysis; a summary of the results of the highly successful flight test, including video of the flight test; and an overview of the subsequent post-test analysis.

Fluorescence quenching studies of potential-dependent DNA reorientation dynamics at glassy carbon electrode surfaces.

PubMed

Li, Qin; Cui, Chenchen; Higgins, Daniel A; Li, Jun

2012-09-05

The potential-dependent reorientation dynamics of double-stranded DNA (ds-DNA) attached to planar glassy carbon electrode (GCE) surfaces were investigated. The orientation state of surface-bound ds-DNA was followed by monitoring the fluorescence from a 6-carboxyfluorescein (FAM6) fluorophore covalently linked to the distal end of the DNA. Positive potentials (i.e., +0.2 V vs open circuit potential, OCP) caused the ds-DNA to align parallel to the electrode surface, resulting in strong dipole-electrode quenching of FAM6 fluorescence. Switching of the GCE potential to negative values (i.e., -0.2 V vs OCP) caused the ds-DNA to reorient perpendicular to the electrode surface, with a concomitant increase in FAM6 fluorescence. In addition to the very fast (submilliseconds) dynamics of the initial reorientation process, slow (0.1-0.9 s) relaxation of FAM6 fluorescence to intermediate levels was also observed after potential switching. These dynamics have not been previously described in the literature. They are too slow to be explained by double layer charging, and chronoamperometry data showed no evidence of such effects. Both the amplitude and rate of the dynamics were found to depend upon buffer concentration, and ds-DNA length, demonstrating a dependence on the double layer field. The dynamics are concluded to arise from previously undetected complexities in the mechanism of potential-dependent ds-DNA reorientation. The possible origins of these dynamics are discussed. A better understanding of these dynamics will lead to improved models for potential-dependent ds-DNA reorientation at electrode surfaces and will facilitate the development of advanced electrochemical devices for detection of target DNAs.

Intragranular twinning, detwinning, and twinning-like lattice reorientation in magnesium alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Wei; Gao, Yanfei; Li, Nan

2016-12-01

Deformation twinning plays a critical role on improving metals or alloys ductility, especially for hexagonal close-packed materials with low symmetry crystal structure. A rolled Mg alloy was selected as a model system to investigate the extension twinning behaviors and characteristics of parent-twin interactions by nondestructive in situ 3D synchrotron X-ray microbeam diffraction. Besides twinning-detwinning process, the "twinning-like" lattice reorientation process was captured within an individual grain inside a bulk material during the strain reversal. The distributions of parent, twin, and reorientated grains and sub-micron level strain variation across the twin boundary are revealed. A theoretical calculation of the lattice strainmore » confirms that the internal strain distribution in parent and twinned grains correlates with the experimental setup, grain orientation of parent, twin, and surrounding grains, as well as the strain path changes. The study suggests a novel deformation mechanism within the hexagonal close-packed structure that cannot be determined from surface-based characterization methods. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.« less

Low-temperature magnetoelectric effect in multiferroic h-Yb1-xHoxMnO3

NASA Astrophysics Data System (ADS)

Zhang, Jincang; Gang, Qiang; Fang, Yifei

In this work, we study the low-temperature ferroelectricity, magnetic property and ME effect in Yb1-xHoxMnO3. In YbMnO3, ferroelectric polarization (P) is closely related with the structure change derived from spin-reorientation process. The initial symmetric relationship of P between the upper and lower half of magnetic sublattice will be broken, which gives rise to the detectable polarization. Additionally, the asymmetry of the P - T curves revealed the pinning effect of the defects in the material. In Ho-doped samples 2D antiferromagnetic perturbation as well as the second AFM ordering have been observed. Substitution of Yb by Ho atoms shows great influences on electric properties and the lowdoping concentration tend to be more favorable for the enhancement of P. The maximum polarization has been promoted hugely in Yb0.8Ho0.2MnO3. We suggested the variation of P is closely related with the stronger exchange interaction in Mn-O-Ho as well as the establishment of new Ho layers with the increase of Ho.

Fluorescence lifetime, dipole orientation and bilayer polymer films

NASA Astrophysics Data System (ADS)

Ho, Xuan Long; Chen, Po-Jui; Woon, Wei-Yen; White, Jonathon David

2017-10-01

Bilayer films consisting of the optically transparent polymers, polystyrene (PS) and poly(methyl methacrylate) (PMMA) were spin-cast on glass substrates. The upper 13.5 nm layer (PS) was lightly doped with Rhodamine-6 G (RH6G) or MEH-PPV. While the fluorescence of MEH-PPV was independent of PMMA thickness, the lifetime of RH6G increased 3-fold as the underlying PMMA thickness increased from 0 to 500 nm while the collected flux decreased suggesting a reorientation of the smaller molecule's dipole with respect to the air-polymer interface with PMMA thickness. This suggests lifetime may find application for nondestructive thickness measurements of transparent films with sub-micron lateral resolution and large range.

Spin ordering and electronic texture in the bilayer iridate Sr3Ir2O7

NASA Astrophysics Data System (ADS)

Dhital, Chetan; Khadka, Sovit; Yamani, Z.; de la Cruz, Clarina; Hogan, T. C.; Disseler, S. M.; Pokharel, Mani; Lukas, K. C.; Tian, Wei; Opeil, C. P.; Wang, Ziqiang; Wilson, Stephen D.

2012-09-01

Through a neutron scattering, charge transport, and magnetization study, the correlated ground state in the bilayer iridium oxide Sr3Ir2O7 is explored. Our combined results resolve scattering consistent with a high temperature magnetic phase that persists above 600 K, reorients at the previously defined TAF=280 K, and coexists with an electronic ground state whose phase behavior suggests the formation of a fluctuating charge or orbital phase that freezes below T*≈70 K. Our study provides a window into the emergence of multiple electronic order parameters near the boundary of the metal to insulator phase transition of the 5d Jeff=1/2 Mott phase.

Anisotropic bulk and planar Heisenberg ferromagnets in uniform, arbitrarily oriented magnetic fields

NASA Astrophysics Data System (ADS)

Vanherck, Joren; Sorée, Bart; Magnus, Wim

2018-07-01

Today, further downscaling of mobile electronic devices poses serious problems, such as energy consumption and local heat dissipation. In this context, spin wave majority gates made of very thin ferromagnetic films may offer a viable alternative. However, similar downscaling of magnetic thin films eventually enforces the latter to operate as quasi-2D magnets, the magnetic properties of which are not yet fully understood, especially those related to anisotropies and external magnetic fields in arbitrary directions. To this end, we have investigated the behaviour of an easy-plane and easy-axis anisotropic ferromagnet—both in two and three dimensions—subjected to a uniform magnetic field, applied along an arbitrary direction. In this paper, a spin- Heisenberg Hamiltonian with anisotropic exchange interactions is solved using double-time temperature-dependent Green’s functions and the Tyablikov decoupling approximation. We determine various magnetic properties such as the Curie temperature and the magnetization as a function of temperature and the applied magnetic field, discussing the impact of the system’s dimensionality and the type of anisotropy. The magnetic reorientation transition taking place in anisotropic Heisenberg ferromagnets is studied in detail. Importantly, spontaneous magnetization is found to be absent for easy-plane 2D spin systems with short range interactions.

A rapid decrease in the rotation rate of comet 41P/Tuttle–Giacobini–Kresák

NASA Astrophysics Data System (ADS)

Bodewits, Dennis; Farnham, Tony L.; Kelley, Michael S. P.; Knight, Matthew M.

2018-01-01

Cometary outgassing can produce torques that change the spin state of the cometary nucleus, which in turn influences the evolution and lifetime of the comet. If these torques increase the rate of rotation to the extent that centripetal forces exceed the material strength of the nucleus, the comet can fragment. Torques that slow down the rotation can cause the spin state to become unstable, but if the torques persist the nucleus can eventually reorient itself and the rotation rate can increase again. Simulations predict that most comets go through a short phase of rapid changes in spin state, after which changes occur gradually over longer times. Here we report observations of comet 41P/Tuttle–Giacobini–Kresák during its close approach to Earth (0.142 astronomical units, approximately 21 million kilometres, on 1 April 2017) that reveal a rapid decrease in rotation rate. Between March and May 2017, the apparent rotation period of the nucleus increased from 20 hours to more than 46 hours—a rate of change of more than an order of magnitude larger than has hitherto been measured. This phenomenon must have been caused by the gas emission from the comet aligning in such a way that it produced an anomalously strong torque that slowed the spin rate of the nucleus. The behaviour of comet 41P/Tuttle–Giacobini–Kresák suggests that it is in a distinct evolutionary state and that its rotation may be approaching the point of instability.

Fragmented Perception: Slower Space-Based but Faster Object-Based Attention in Recent-Onset Psychosis with and without Schizophrenia

PubMed Central

Smid, Henderikus G. O. M.; Bruggeman, Richard; Martens, Sander

2013-01-01

Background Schizophrenia is associated with impairments of the perception of objects, but how this affects higher cognitive functions, whether this impairment is already present after recent onset of psychosis, and whether it is specific for schizophrenia related psychosis, is not clear. We therefore tested the hypothesis that because schizophrenia is associated with impaired object perception, schizophrenia patients should differ in shifting attention between objects compared to healthy controls. To test this hypothesis, a task was used that allowed us to separately observe space-based and object-based covert orienting of attention. To examine whether impairment of object-based visual attention is related to higher order cognitive functions, standard neuropsychological tests were also administered. Method Patients with recent onset psychosis and normal controls performed the attention task, in which space- and object-based attention shifts were induced by cue-target sequences that required reorienting of attention within an object, or reorienting attention between objects. Results Patients with and without schizophrenia showed slower than normal spatial attention shifts, but the object-based component of attention shifts in patients was smaller than normal. Schizophrenia was specifically associated with slowed right-to-left attention shifts. Reorienting speed was significantly correlated with verbal memory scores in controls, and with visual attention scores in patients, but not with speed-of-processing scores in either group. Conclusions deficits of object-perception and spatial attention shifting are not only associated with schizophrenia, but are common to all psychosis patients. Schizophrenia patients only differed by having abnormally slow right-to-left visual field reorienting. Deficits of object-perception and spatial attention shifting are already present after recent onset of psychosis. Studies investigating visual spatial attention should take into account the separable effects of space-based and object-based shifting of attention. Impaired reorienting in patients was related to impaired visual attention, but not to deficits of processing speed and verbal memory. PMID:23536901

Fragmented perception: slower space-based but faster object-based attention in recent-onset psychosis with and without Schizophrenia.

PubMed

Smid, Henderikus G O M; Bruggeman, Richard; Martens, Sander

2013-01-01

Schizophrenia is associated with impairments of the perception of objects, but how this affects higher cognitive functions, whether this impairment is already present after recent onset of psychosis, and whether it is specific for schizophrenia related psychosis, is not clear. We therefore tested the hypothesis that because schizophrenia is associated with impaired object perception, schizophrenia patients should differ in shifting attention between objects compared to healthy controls. To test this hypothesis, a task was used that allowed us to separately observe space-based and object-based covert orienting of attention. To examine whether impairment of object-based visual attention is related to higher order cognitive functions, standard neuropsychological tests were also administered. Patients with recent onset psychosis and normal controls performed the attention task, in which space- and object-based attention shifts were induced by cue-target sequences that required reorienting of attention within an object, or reorienting attention between objects. Patients with and without schizophrenia showed slower than normal spatial attention shifts, but the object-based component of attention shifts in patients was smaller than normal. Schizophrenia was specifically associated with slowed right-to-left attention shifts. Reorienting speed was significantly correlated with verbal memory scores in controls, and with visual attention scores in patients, but not with speed-of-processing scores in either group. deficits of object-perception and spatial attention shifting are not only associated with schizophrenia, but are common to all psychosis patients. Schizophrenia patients only differed by having abnormally slow right-to-left visual field reorienting. Deficits of object-perception and spatial attention shifting are already present after recent onset of psychosis. Studies investigating visual spatial attention should take into account the separable effects of space-based and object-based shifting of attention. Impaired reorienting in patients was related to impaired visual attention, but not to deficits of processing speed and verbal memory.

Optimal switching between geocentric and egocentric strategies in navigation

PubMed Central

Mahadevan, L.

2016-01-01

Animals use a combination of egocentric navigation driven by the internal integration of environmental cues, interspersed with geocentric course correction and reorientation. These processes are accompanied by uncertainty in sensory acquisition of information, planning and execution. Inspired by observations of dung beetle navigational strategies that show switching between geocentric and egocentric strategies, we consider the question of optimal reorientation rates for the navigation of an agent moving along a preferred direction in the presence of multiple sources of noise. We address this using a model that takes the form of a correlated random walk at short time scales that is punctuated by reorientation events leading to a biased random walks at long time scales. This allows us to identify optimal alternation schemes and characterize their robustness in the context of noisy sensory acquisition as well as performance errors linked with variations in environmental conditions and agent–environment interactions. PMID:27493769

Reorientation from Altered States: Please, More Carefully.

ERIC Educational Resources Information Center

Heikkinen, Charles A.

1989-01-01

Claims counselors too often appear to forget to reorient clients from altered states of consciousness used in counseling and that failure to reorient can result in unnecessary discomfort for clients. Provides suggestions for when and how to reorient to avoid unwanted, lingering aftereffects. (Author/ABL)

Flexibility at a glycosidic linkage revealed by molecular dynamics, stochastic modeling, and (13)C NMR spin relaxation: conformational preferences of α-L-Rhap-α-(1 → 2)-α-L-Rhap-OMe in water and dimethyl sulfoxide solutions.

PubMed

Pendrill, Robert; Engström, Olof; Volpato, Andrea; Zerbetto, Mirco; Polimeno, Antonino; Widmalm, Göran

2016-01-28

The monosaccharide L-rhamnose is common in bacterial polysaccharides and the disaccharide α-L-Rhap-α-(1 → 2)-α-L-Rhap-OMe represents a structural model for a part of Shigella flexneri O-antigen polysaccharides. Utilization of [1'-(13)C]-site-specific labeling in the anomeric position at the glycosidic linkage between the two sugar residues facilitated the determination of transglycosidic NMR (3)JCH and (3)JCC coupling constants. Based on these spin-spin couplings the major state and the conformational distribution could be determined with respect to the ψ torsion angle, which changed between water and dimethyl sulfoxide (DMSO) as solvents, a finding mirrored by molecular dynamics (MD) simulations with explicit solvent molecules. The (13)C NMR spin relaxation parameters T1, T2, and heteronuclear NOE of the probe were measured for the disaccharide in DMSO-d6 at two magnetic field strengths, with standard deviations ≤1%. The combination of MD simulation and a stochastic description based on the diffusive chain model resulted in excellent agreement between calculated and experimentally observed (13)C relaxation parameters, with an average error of <2%. The coupling between the global reorientation of the molecule and the local motion of the spin probe is deemed essential if reproduction of NMR relaxation parameters should succeed, since decoupling of the two modes of motion results in significantly worse agreement. Calculation of (13)C relaxation parameters based on the correlation functions obtained directly from the MD simulation of the solute molecule in DMSO as solvent showed satisfactory agreement with errors on the order of 10% or less.

Hexamethylbenzene as a sensitive nuclear magnetic resonance probe for studying organic crystals and glasses

NASA Astrophysics Data System (ADS)

Jansen-Glaw, B.; Rössler, E.; Taupitz, M.; Vieth, H. M.

1989-06-01

Deuterated hexamethylbenzene (HMB) is used as a probe molecule for 2H NMR studies of the crystalline state of hexachlorobenzene and of several organic glasses. By measuring the spin-lattice relaxation and the line shape in the temperature range of 4-300 K the dynamical parameters of the molecular reorientation are investigated. For the system HMB/hexachlorobenzene, we find exponential relaxation and for the corresponding T1 an increase of its activation energy by a factor of 2 in comparison to the neat HMB. A homogeneous mixing of the guest and host molecules is found at least for guest concentrations up to 7%. In contrast, nonexponential spin-lattice relaxation is characteristic for all glass matrices, indicating motional heterogeneities. A log-Gauss distribution for the corresponding motional correlation times gives a good fit of the data. Its width parameter decreases linearly with temperature, while the mean correlation times are described by an Arrhenius law. The mean activation energy is reduced by a factor of about 3.5 as compared to neat HMB, demonstrating a loose packing of the molecules in the glass matrices.

Magnetic properties of Fe doped SmCrO{sub 3} perovskite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bakshi, Venugopal Rao; Devarasetty, Suresh Babu, E-mail: s-devarasetty1956@yahoo.co.uk; Prasad, Bandi Vittal

2014-04-24

The compound SmCr{sub 1−x} Fe{sub x}O{sub 3} perovskites were prepared by citric acid route. the samples were characterized by XRD and SEM. The temperature and field dependent magnetization measurements were carried out in the temperature range of 5K −400 K at 0.01T field and −5T to 5T field at 2K. SmCrO3 compound has shown two magnetic transition temperatures at 197 K and 38 K. The observed behavior at 197 K is the characteristic of anti-ferromagnetic ordering of Cr{sup 3+} moments with weak ferromagnetism. The drop in magnetization below 38 K is due to the spin reorientation of Sm{sup 3+} inmore » anti ferromagnetic arrangement and Cr{sup 3+}spins. the doping of Fe in SmCrO{sub 3} compound has shown a decrease in T{sub N1} and also the two magnetization reversals at 177K and 57K. The magnetic behavior at low temperatures is (T« less

Magnetic phase transitions and magnetization reversal in MnRuP

NASA Astrophysics Data System (ADS)

Lampen-Kelley, P.; Mandrus, D.

The ternary phosphide MnRuP is an incommensurate antiferromagnetic metal crystallizing in the non-centrosymmetric Fe2P-type crystal structure. Below the Neel transition at 250 K, MnRuP exhibits hysteretic anomalies in resistivity and magnetic susceptibility curves as the propagation vectors of the spiral spin structure change discontinuously across T1 = 180 K and T2 = 100 K. Temperature-dependent X-ray diffraction data indicate that the first-order spin reorientation occurs in the absence of a structural transition. A strong magnetization reversal (MR) effect is observed upon cooling the system through TN in moderate dc magnetic fields. Positive magnetization is recovered on further cooling through T1 and maintained in subsequent warming curves. The field dependence and training of the MR effect in MnRuP will be discussed in terms of the underlying magnetic structures and compared to anomalous MR observed in vanadate systems. This work is supported by the Gordon and Betty Moore Foundation GBMF4416 and U.S. DOE, Office of Science, BES, Materials Science and Engineering Division.

Electron Paramagnetic Resonance of a Single NV Nanodiamond Attached to an Individual Biomolecule

NASA Astrophysics Data System (ADS)

Teeling-Smith, Richelle M.; Jung, Young Woo; Scozzaro, Nicolas; Cardellino, Jeremy; Rampersaud, Isaac; North, Justin A.; Šimon, Marek; Bhallamudi, Vidya P.; Rampersaud, Arfaan; Johnston-Halperin, Ezekiel; Poirier, Michael G.; Hammel, P. Chris

2016-05-01

A key limitation of electron paramagnetic resonance (EPR), an established and powerful tool for studying atomic-scale biomolecular structure and dynamics is its poor sensitivity, samples containing in excess of 10^12 labeled biomolecules are required in typical experiments. In contrast, single molecule measurements provide improved insights into heterogeneous behaviors that can be masked by ensemble measurements and are often essential for illuminating the molecular mechanisms behind the function of a biomolecule. We report EPR measurements of a single labeled biomolecule that merge these two powerful techniques. We selectively label an individual double-stranded DNA molecule with a single nanodiamond containing nitrogen-vacancy (NV) centers, and optically detect the paramagnetic resonance of NV spins in the nanodiamond probe. Analysis of the spectrum reveals that the nanodiamond probe has complete rotational freedom and that the characteristic time scale for reorientation of the nanodiamond probe is slow compared to the transverse spin relaxation time. This demonstration of EPR spectroscopy of a single nanodiamond labeled DNA provides the foundation for the development of single molecule magnetic resonance studies of complex biomolecular systems.

A Framework for the Development of Automatic DFA Method to Minimize the Number of Components and Assembly Reorientations

NASA Astrophysics Data System (ADS)

Alfadhlani; Samadhi, T. M. A. Ari; Ma’ruf, Anas; Setiasyah Toha, Isa

2018-03-01

Assembly is a part of manufacturing processes that must be considered at the product design stage. Design for Assembly (DFA) is a method to evaluate product design in order to make it simpler, easier and quicker to assemble, so that assembly cost is reduced. This article discusses a framework for developing a computer-based DFA method. The method is expected to aid product designer to extract data, evaluate assembly process, and provide recommendation for the product design improvement. These three things are desirable to be performed without interactive process or user intervention, so product design evaluation process could be done automatically. Input for the proposed framework is a 3D solid engineering drawing. Product design evaluation is performed by: minimizing the number of components; generating assembly sequence alternatives; selecting the best assembly sequence based on the minimum number of assembly reorientations; and providing suggestion for design improvement.

Recovery and recrystalization kinetics of cold-worked Zircaloy-4 plate and tubing (LWBR Development Program)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Katz, O.M.

1968-02-01

Empirical kinetic equations were derived to describe the recovery region between 550 and 1020/sup 0/F for times to 4000 hours for 15 to 78% cold-worked Zircaloy-4 plate and tubing. The properties studied were electrical resistivity and X-ray line sharpening. Recrystallization kinetics were described with sigmoidal curves derived from X-ray intensity and microhardness data. Light, replica, and transmission electron microscopy and selected-area electron diffraction were used to postulate recovery and recrystallization mechanisms. From a structural aspect, the annealing process in cold-worked Zircaloy-4 is visualized as a dislocation climb and annihilation process to the limit allowed by the size of the deformationmore » subcells, a reorientation of the subgrain material into a recrystallization texture, a growth of reoriented cells located in the most highly worked bands, and a consumption of less favorably strained and/or oriented cells by the high-angle boundaries of the reoriented cells. Comparison of 15 and 73% cold-worked tubing showed the activation energy to be less (21 versus 60 kcal/mol) and the subcell size greater (8000A versus 1000A) for the 15% cold-worked material. (NSA 22: 21698)« less

Electric field control of magnon-induced magnetization dynamics in multiferroics.

PubMed

Risinggård, Vetle; Kulagina, Iryna; Linder, Jacob

2016-08-24

We consider theoretically the effect of an inhomogeneous magnetoelectric coupling on the magnon-induced dynamics of a ferromagnet. The magnon-mediated magnetoelectric torque affects both the homogeneous magnetization and magnon-driven domain wall motion. In the domains, we predict a reorientation of the magnetization, controllable by the applied electric field, which is almost an order of magnitude larger than that observed in other physical systems via the same mechanism. The applied electric field can also be used to tune the domain wall speed and direction of motion in a linear fashion, producing domain wall velocities several times the zero field velocity. These results show that multiferroic systems offer a promising arena to achieve low-dissipation magnetization rotation and domain wall motion by exciting spin-waves.

Competing magnetostructural phases in a semiclassical system

NASA Astrophysics Data System (ADS)

O'Neal, Kenneth R.; Lee, Jun Hee; Kim, Maeng-Suk; Manson, Jamie L.; Liu, Zhenxian; Fishman, Randy S.; Musfeldt, Janice L.

2017-11-01

The interplay between charge, structure, and magnetism gives rise to rich phase diagrams in complex materials with exotic properties emerging when phases compete. Molecule-based materials are particularly advantageous in this regard due to their low energy scales, flexible lattices, and chemical tunability. Here, we bring together high pressure Raman scattering, modeling, and first principles calculations to reveal the pressure-temperature-magnetic field phase diagram of Mn[N(CN)2]2. We uncover how hidden soft modes involving octahedral rotations drive two pressure-induced transitions triggering the low → high magnetic anisotropy crossover and a unique reorientation of exchange planes. These magnetostructural transitions and their mechanisms highlight the importance of spin-lattice interactions in establishing phases with novel magnetic properties in Mn(II)-containing systems.

Hydrogen absorption and its effect on magnetic properties of Nd2Fe14B

NASA Astrophysics Data System (ADS)

Bezdushnyi, R.; Damianova, R.; Tereshina, I. S.; Pankratov, N. Yu.; Nikitin, S. A.

2018-05-01

Magnetic properties of hydrides of the intermetallic compound Nd2Fe14BHx are investigated in the temperature range covering the Curie temperatures (TC) of the compounds (up to 670 K). The temperature dependencies of magnetization are measured under continuous control of hydrogen content in the investigated samples. The dependencies of Curie and spin-reorientation transition (TSR) temperatures on the hydrogen concentration are studied in detail. The dependence of hydrogen concentration on pressure at a constant temperature (near TC) and on the temperature at various pressures are obtained. We attempted to estimate the contributions of the unit cell volume increase upon hydrogenation and the electronic structure change in the variation of TC of the hydrogenated Nd2Fe14 B .

Ultrafast all-optical control of the magnetization in magnetic dielectrics

NASA Astrophysics Data System (ADS)

Kirilyuk, Andrei; Kimel, Alexey; Hansteen, Fredrik; Rasing, Theo; Pisarev, Roman V.

2006-08-01

The purpose of this review is to summarize the recent progress on laser-induced magnetization dynamics in magnetic dielectrics. Due to the slow phonon-magnon interaction in these materials, direct thermal effects of the laser excitation can only be seen on the time scale of almost a nanosecond and thus are clearly distinguished from the ultrafast nonthermal effects. However, laser pulses are shown to indirectly modify the magnetic anisotropy in rare-earth orthoferrites via the crystal field, and to bring about spin reorientation within a few picoseconds. More interesting, however, are the direct nonthermal effects of light on spin systems. We demonstrate coherent optical control of the magnetization in ferrimagnetic garnet films on a femtosecond time scale through a combination of two different ultrafast and nonthermal photomagnetic effects and by employing multiple pump pulses. Linearly polarized laser pulses are shown to create a long-lived modification of the magnetocrystalline anisotropy via optically induced electron transfer between nonequivalent ion sites. In addition, circularly polarized pulses are shown to act as strong transient magnetic field pulses originating from the nonabsorptive inverse Faraday effect. An all-optical scheme of excitation and detection of different antiferromagnetic resonance modes with frequencies of up to 500GHz will be discussed as well. The reported effects open new and exciting possibilities for ultrafast manipulation of spins by light and provide new insight into the physics of magnetism on ultrafast time scales.

Features of Relaxation of a Stress Tensor in the Microscopic Volume of Nematic Phase under the Action of a Strong Electric Field

NASA Astrophysics Data System (ADS)

Zakharov, A. V.

2018-02-01

A numerical study of new regimes of reorientation of director field n̂, velocity v, and components of stress tensor σ ij ( ij = x, y, z) of nematic liquid crystal (LC) encapsulated in a rectangular channel under the action of a strong electric field E directed at angle α ( {˜{π }/{2}} ) to the horizontal surfaces bounding the LC channel is proposed. The numerical calculations performed in the framework of nonlinear generalization of the classical Eriksen-Leslie theory have shown that at certain relations between the torques and momenta affecting the unit LC volume and E ≫ E th, transition periodic structures can emerge during reorientation of n̂, if the corresponding distortion mode has the fastest response, and, thus, suppress all other modes. Rotating domains originating within this process decrease the energy dissipation rate and create more favorable regimes of the director field reorientation, as compared with the uniform rotational displacement.

The effect of ageing on the mechanical properties of the silk of the bridge spider Larinioides cornutus (Clerck, 1757)

NASA Astrophysics Data System (ADS)

Lepore, Emiliano; Isaia, Marco; Mammola, Stefano; Pugno, Nicola

2016-05-01

Spider silk is regarded as one of the best natural polymer fibers especially in terms of low density, high tensile strength and high elongation until breaking. Since only a few bio-engineering studies have been focused on spider silk ageing, we conducted nano-tensile tests on the vertical naturally spun silk fibers of the bridge spider Larinioides cornutus (Clerck, 1757) (Arachnida, Araneae) to evaluate changes in the mechanical properties of the silk (ultimate stress and strain, Young’s modulus, toughness) over time. We studied the natural process of silk ageing at different time intervals from spinning (20 seconds up to one month), comparing silk fibers spun from adult spiders collected in the field. Data were analyzed using Linear Mixed Models. We detected a positive trend versus time for the Young’s modulus, indicating that aged silks are stiffer and possibly less effective in catching prey. Moreover, we observed a negative trend for the ultimate strain versus time, attesting a general decrement of the resistance force. These trends are interpreted as being due to the drying of the silk protein chains and the reorientation among the fibers.

Giant magnetic impedance of wires with a thin magnetic coating

NASA Astrophysics Data System (ADS)

Kurlyandskaya, G. V.; Bebenin, N. G.; Vas'kovsky, V. O.

2011-02-01

In this review, we analyzed and generalized the results of experimental investigations of physical processes that occur in composite wires with a thin magnetic coating under the conditions of the appearance in them of a giant magnetoimpedance (GMI) effect. Principles of the measurements of high-frequency impedance are described in short; basic definitions are given, and the differences in the linear and nonlinear GMI regimes are described. Data are systemized on the giant magnetic impedance of wires with a thin magnetic coating (composite materials) under the conditions of a strong nonlinearity of the GMI effect, which is accompanied by the appearance of higher harmonics in the output signal. The extremely high susceptibility of the harmonic parameters to external actions can be used in the technical applications for creating ultrasensitive detectors of low magnetic fields. Special attention is paid to model calculations, which confirm the fact that the experimentally observed features of a nonlinear GMI effect are connected with the high sensitivity of the magnetic system to a circular magnetic field near the spin-reorientation phase transitions. Fine features of the effective magnetic anisotropy can play the key role and therefore cannot be ignored in the general case.

Magnetic phase transitions and ferromagnetic short-range correlations in single-crystal Tb5Si2.2Ge1.8

NASA Astrophysics Data System (ADS)

Zou, M.; Pecharsky, V. K.; Gschneidner, K. A., Jr.; Schlagel, D. L.; Lograsso, T. A.

2008-07-01

Magnetic phase transitions in a Tb5Si2.2Ge1.8 single crystal have been studied as a function of temperature and magnetic field. Magnetic-field dependencies of the critical temperatures are highly anisotropic for both the main magnetic ordering process occurring around 120 K and a spin reorientation transition at ˜70K . Magnetic-field-induced phase transitions occur with the magnetic field applied isothermally along the a and b axes (but not along the c axis) between 1.8 and 70 K in fields below 70 kOe. Strong anisotropic thermal irreversibility is observed in the Griffiths phase regime between 120 and 200 K with applied fields ranging from 10 to 1000 Oe. Our data (1) show that the magnetic and structural phase transitions around 120 K are narrowly decoupled; (2) uncover the anisotropy of ferromagnetic short-range order in the Griffiths phase; and (3) reveal some unusual magnetic domain effects in the long-range ordered state of the Tb5Si2.2Ge1.8 compound. The temperature-magnetic field phase diagrams with field applied along the three major crystallographic directions have been constructed.

Time course and auxin sensitivity of cortical microtubule reorientation in maize roots

NASA Technical Reports Server (NTRS)

Blancaflor, E. B.; Hasenstein, K. H.

1995-01-01

The kinetics of MT [microtubule] reorientation in primary roots of Zea mays cv. Merit, were examined 15, 30, 45, and 60 min after horizontal positioning. Confocal microscopy of longitudinal tissue sections showed no change in MT orientation 15 and 30 min after horizontal placement. However, after 45 and 60 min, MTs of the outer 4-5 cortical cell layers along the lower side were reoriented. In order to test whether MT reorientation during graviresponse is caused by an auxin gradient, we examined the organization of MTs in roots that were incubated for 1 h in solutions containing 10(-9) to 10(-6) M IAA. IAA treatment at 10(-8) M or less showed no major or consistent changes but 10(-7) M IAA resulted in MT reorientation in the cortex. The auxin effect does not appear to be acid-induced since benzoic acid (10(-5) M) did not cause MT reorientation. The region closest to the maturation zone was most sensitive to IAA. The data indicate that early stages of gravity induced curvature occur in the absence of MT reorientation but sustained curvature leads to reoriented MTs in the outer cortex. Growth inhibition along the lower side of graviresponding roots appears to result from asymmetric distribution of auxin following gravistimulation.

Modelling and analysis of bacterial tracks suggest an active reorientation mechanism in Rhodobacter sphaeroides

PubMed Central

Rosser, Gabriel; Baker, Ruth E.; Armitage, Judith P.; Fletcher, Alexander G.

2014-01-01

Most free-swimming bacteria move in approximately straight lines, interspersed with random reorientation phases. A key open question concerns varying mechanisms by which reorientation occurs. We combine mathematical modelling with analysis of a large tracking dataset to study the poorly understood reorientation mechanism in the monoflagellate species Rhodobacter sphaeroides. The flagellum on this species rotates counterclockwise to propel the bacterium, periodically ceasing rotation to enable reorientation. When rotation restarts the cell body usually points in a new direction. It has been assumed that the new direction is simply the result of Brownian rotation. We consider three variants of a self-propelled particle model of bacterial motility. The first considers rotational diffusion only, corresponding to a non-chemotactic mutant strain. Two further models incorporate stochastic reorientations, describing ‘run-and-tumble’ motility. We derive expressions for key summary statistics and simulate each model using a stochastic computational algorithm. We also discuss the effect of cell geometry on rotational diffusion. Working with a previously published tracking dataset, we compare predictions of the models with data on individual stopping events in R. sphaeroides. This provides strong evidence that this species undergoes some form of active reorientation rather than simple reorientation by Brownian rotation. PMID:24872500

Reorienting programme budgeting and marginal analysis (PBMA) towards disinvestment.

PubMed

Mortimer, Duncan

2010-10-14

Remarkable progress has been made over the past 40 years in developing rational, evidence-based mechanisms for the allocation of health resources. Much of this progress has centred on mechanisms for commissioning new medical devices and pharmaceuticals. The attention of fund-managers and policy-makers is only now turning towards development of mechanisms for decommissioning, disinvesting or redeploying resources from currently funded interventions. While Programme Budgeting and Marginal Analysis would seem well-suited to this purpose, past applications include both successes and failures in achieving disinvestment and resource release. Drawing on recent successes/failures in achieving disinvestment and resource release via PBMA, this paper identifies four barriers/enablers to disinvestment via PBMA: (i) specification of the budget constraint, (ii) scope of the programme budget, (iii) composition and role of the advisory group, and (iv) incentives for/against contributing to a 'shift list' of options for disinvestment and resource release. A number of modifications to the PBMA process are then proposed with the aim of reorienting PBMA towards disinvestment. The reoriented model is differentiated by four features: (i) hard budget constraint with budgetary pressure; (ii) programme budgets with broad scope but specific investment proposals linked to disinvestment proposals with similar input requirements; (iii) advisory/working groups that include equal representation of sectional interests plus additional members with responsibility for advocating in favour of disinvestment, (iv) 'shift lists' populated and developed prior to 'wish lists' and investment proposals linked to disinvestment proposals within a relatively narrow budget area. While the argument and evidence presented here suggest that the reoriented model will facilitate disinvestment and resource release, this remains an empirical question. Likewise, further research will be required to determine whether or not the re-oriented model sacrifices feasibility and acceptability to obtain its hypothesised greater emphasis on disinvestment.

Reorienting programme budgeting and marginal analysis (PBMA) towards disinvestment

PubMed Central

2010-01-01

Background Remarkable progress has been made over the past 40 years in developing rational, evidence-based mechanisms for the allocation of health resources. Much of this progress has centred on mechanisms for commissioning new medical devices and pharmaceuticals. The attention of fund-managers and policy-makers is only now turning towards development of mechanisms for decommissioning, disinvesting or redeploying resources from currently funded interventions. While Programme Budgeting and Marginal Analysis would seem well-suited to this purpose, past applications include both successes and failures in achieving disinvestment and resource release. Discussion Drawing on recent successes/failures in achieving disinvestment and resource release via PBMA, this paper identifies four barriers/enablers to disinvestment via PBMA: (i) specification of the budget constraint, (ii) scope of the programme budget, (iii) composition and role of the advisory group, and (iv) incentives for/against contributing to a 'shift list' of options for disinvestment and resource release. A number of modifications to the PBMA process are then proposed with the aim of reorienting PBMA towards disinvestment. Summary The reoriented model is differentiated by four features: (i) hard budget constraint with budgetary pressure; (ii) programme budgets with broad scope but specific investment proposals linked to disinvestment proposals with similar input requirements; (iii) advisory/working groups that include equal representation of sectional interests plus additional members with responsibility for advocating in favour of disinvestment, (iv) 'shift lists' populated and developed prior to 'wish lists' and investment proposals linked to disinvestment proposals within a relatively narrow budget area. While the argument and evidence presented here suggest that the reoriented model will facilitate disinvestment and resource release, this remains an empirical question. Likewise, further research will be required to determine whether or not the re-oriented model sacrifices feasibility and acceptability to obtain its hypothesised greater emphasis on disinvestment. PMID:20942972

Multiferroic Applications of Nanoarchitectured, Solution-Processed Materials

NASA Astrophysics Data System (ADS)

Buditama, Abraham Nataniel

This dissertation compiles work on sol-gel syntheses of multiferroic materials and applications thereof. Multiferroics, or materials that simultaneously exhibit multiple order parameters such as ferromagnetism, ferroelectricity, or ferroelasticity, may be fabricated by solution processing techniques. Specifically, these techniques may be used to control both the atomic and the nanoscale structures of piezoelectric lead zirconate titanate (PbZrxTi 1-xO3 or PZT) and magnetostrictive cobalt ferrite (CoFe 2O4 or CFO). The first part of this work focuses on strain-coupling PZT and CFO into a magnetoelectric composite. A mesoporous CFO framework was synthesized using block copolymer templating, which was subsequently conformally filled by PZT by atomic layer deposition (ALD). The final porosity of the film is controlled by the ALD PZT layer, and we show that this porosity influences the magnetoelectric coupling of the composite. An ex situ external electric field is applied to the composite, and samples with the greatest porosity, and thus greatest mechanical flexibility, were able to accommodate strain transfer to the CFO, resulting in a greater reduction of the sample saturation magnetization. The second part of this work focuses on using solution processing to control domain-level contributions to the material's ferroic properties. An iterative spin coating process can be used to create PZT films of arbitrary thickness. Electric domains are generally pinned in nanoscale PZT thin films, but models of PZT films on the mesoscale must consider domain reorientation. As for CFO, solution processing may be used to control the CFO grain size, which in turn limits the size of its magnetic domains, and subsequently its static magnetic properties.

The Hidden Other Within: An Alternative to Psycho-Biological Interpretations of Intrapersonal Communication.

ERIC Educational Resources Information Center

Crouse, Janice Shaw; Crouse, Gilbert L.

Communication scholars have only recently begun to consider internal processes of thought as essential components of interpersonal communication. In 1964 a reorientation of thinking to include intrapersonal processes as integral to the communication process was first urged. The "hidden other" refers to the wellspring of the mind and its…

Self-Reorientation Following Colorectal Cancer Treatment - A Grounded Theory Study.

PubMed

Johansson, Ann-Caroline B; Axelsson, Malin; Berndtsson, Ina; Brink, Eva

2015-01-01

After colorectal cancer (CRC) treatment, people reorganize life in ways that are consistent with their understanding of the illness and their expectations for recovery. Incapacities and abilities that have been lost can initiate a need to reorient the self. To the best of our knowledge, no studies have explicitly focused on the concept of self-reorientation after CRC treatment. The aim of the present study was therefore to explore self-reorientation in the early recovery phase after CRC surgery. Grounded theory analysis was undertaken, using the method presented by Charmaz. The present results explained self-reorientation as the individual attempting to achieve congruence in self-perception. A congruent self-perception meant bringing together the perceived self and the self that was mirrored in the near environs. The results showed that societal beliefs and personal explanations are essential elements of self-reorientation, and that it is therefore important to make them visible.

Simultaneous occurrence of multiferroism and short-range magnetic order in DyFeO 3

DOE PAGES

Wang, Jinchen; Liu, Juanjuan; Sheng, Jieming; ...

2016-04-06

In this paper, we present a combined neutron scattering and magnetization study on the multiferroic DyFeO 3, which shows a very strong magnetoelectric effect. Applying magnetic field along the c axis, the weak ferromagnetic order of the Fe ions is quickly recovered from a spin reorientation transition, and the long-range antiferromagnetic order of Dy becomes a short-range one. We found that the short-range order concurs with the multiferroic phase and is responsible for its sizable hysteresis. In conclusion, our H-T phase diagram suggests that the strong magnetoelectric effect in DyFeO 3 has to be understood with not only the weakmore » ferromagnetism of Fe but also the short-range antiferromagnetic order of Dy.« less

Strain-driven electric control of magnetization reversal at multiferroic interfaces

NASA Astrophysics Data System (ADS)

Odkhuu, Dorj; Kioussis, Nicholas

2018-03-01

We predict that biaxial strain of several percent has a colossal effect on the magnetic anisotropy of ultrathin Fe /X TiO3 (X =Sr ,Ba ) bilayers grown epitaxially on appropriate substrates. We demonstrate that under large compressive biaxial strain the Fe film undergoes an in-plane to out-of-plane spin reorientation via ferroelectric polarization switching, where the critical strain depends on the Fe film thickness. The underlying mechanism is the interplay between the strain-enhanced magnetoelectric coupling associated with the enhanced polarization in the ferroelectric substrate and the strain-reduced magnetic anisotropy energy of the Fe overlayer. These findings open interesting prospects for exploiting stain engineering to harvest higher electric field efficiency of magnetic anisotropy for the next generation of magnetoelectric random access memory devices.

Electric field control of magnon-induced magnetization dynamics in multiferroics

PubMed Central

Risinggård, Vetle; Kulagina, Iryna; Linder, Jacob

2016-01-01

We consider theoretically the effect of an inhomogeneous magnetoelectric coupling on the magnon-induced dynamics of a ferromagnet. The magnon-mediated magnetoelectric torque affects both the homogeneous magnetization and magnon-driven domain wall motion. In the domains, we predict a reorientation of the magnetization, controllable by the applied electric field, which is almost an order of magnitude larger than that observed in other physical systems via the same mechanism. The applied electric field can also be used to tune the domain wall speed and direction of motion in a linear fashion, producing domain wall velocities several times the zero field velocity. These results show that multiferroic systems offer a promising arena to achieve low-dissipation magnetization rotation and domain wall motion by exciting spin-waves. PMID:27554064

ESR and PALS detection of the dynamic crossover in the supercooled liquid states of short and medium-sized n-alkanes

NASA Astrophysics Data System (ADS)

Bartoš, J.; Zgardzinska, B.; Švajdlenková, H.; Lukešová, M.; Zaleski, R.

2018-05-01

A joint study of the spin probe TEMPO dynamics by ESR and the annihilation rate of ortho-positronium by PALS in four short-and medium-sized n-alkanes is presented. In addition to the usually observed changes in both the reorientation dynamics and size of free volumes at the temperature of melting, Tm, and solid-solid phase transition, Tss, an additional coincidence between the characteristic ESR and PALS temperatures TX1fast ≅ Tb1sol < Tm, Tss was found. The phenomenological analysis of the viscosity data of n-alkanes using the power law equation indicates a presence of locally disordered regions in which the dynamic change occurs at the crossover temperature TX ≅ TX1fast ≅ Tb1sol.

Managerial strategies to reorient hospitals towards health promotion: lessons from organisational theory.

PubMed

Röthlin, Florian

2013-01-01

Reorienting health services towards health promotion is one of the major health promotion strategies stipulated by the Ottawa Charter). Important contradictions, tensions and barriers to health promotion implementation associated with organisational structures have, thus far, been underexposed in the hospital health promotion discourse. This paper aims at identifying risks and the chances for hospital management to strategically and sustainably reorient their hospitals towards health promotion. The paper combines theories and findings from organisational science and management studies as well as from capacity development in the form of a narrative literature review. The aim is to focus on the conditions hospitals, as organisational systems with a highly professionalised workforce, provide for a strategically managed reorientation towards health promotion. Models and principles helping managers to navigate the difficulties and complexities of health promotion reorientation will be suggested. Hospital managers have to deal with genuine obstacles in the complexity and structural formation of hospital organisations. Against this background, continuous management support, a transformative leadership style, participative strategic management and expert governance can be considered important organisational capacities for the reorientation towards a new concept such as health promotion. This paper discusses managerial strategies, effective structural transformations and important organisational capacities that can contribute to a sustainable reorientation of hospitals towards health promotion. It supports hospital managers in exploring their chances of facilitating and effectively supporting a sustainable health promotion reorientation of their hospitals. The paper provides an innovative approach where the focus is on enhanced possibilities for hospital managers to strategically manage the reorientation towards health promotion.

Spin re-orientation in heavy fermion system α - YbAl1 - x FexB4

NASA Astrophysics Data System (ADS)

Wu, Shan; Broholm, C.; Kuga, K.; Suzuki, Shintaro; Nakatsuji, S.; Mourigal, M.; Stone, M.; Tian, Wei; Qiu, Y.; Rodriguez-Rivera, Jose

Non centro-symmetric α - YbAlB4 has a heavy Fermi liquid ground state and shares many characteristics with centro-symmetric β - YbAlB4 . Both isomorphs display intermediate valence, associated with a fluctuation scale of T0 = 200 K and a Kondo lattice scale of T* = 8 K. Unlike β - YbAlB4 , α - YbAlB4 is at the boundary of a transition from a Fermi liquid metallic state to an antiferromagnetic (AFM) insulating state, driven by Fe substitution of Al. Magnetization and specific heat measurements reveal two different antiferromagnetic phases with TN = 9 K and TN = 2 K for Fe concentration above and below x =0.07. We report single crystal neutron scattering experiments on Fe doped YbAlB4 with x =0.035 and x =0.125. While the ordering wave vector is identical, k -> = (1 , 0 , 0) , the spin orientation switches from c to a with increasing Fe concentration. This suggests different anisotropic hybridization between 4f and conduction electrons that we confirmed by determining the crystal field levels. Supported by DOE, BES through DE-FG02-08ER46544.

Breakdown of antiferromagnet order in polycrystalline NiFe/NiO bilayers probed with acoustic emission

NASA Astrophysics Data System (ADS)

Lebyodkin, M. A.; Lebedkina, T. A.; Shashkov, I. V.; Gornakov, V. S.

2017-07-01

Magnetization reversal of polycrystalline NiFe/NiO bilayers was investigated using magneto-optical indicator film imaging and acoustic emission techniques. Sporadic acoustic signals were detected in a constant magnetic field after the magnetization reversal. It is suggested that they are related to elastic waves excited by sharp shocks in the NiO layer with strong magnetostriction. Their probability depends on the history and number of repetitions of the field cycling, thus testifying the thermal-activation nature of the long-time relaxation of an antiferromagnetic order. These results provide evidence of spontaneous thermally activated switching of the antiferromagnetic order in NiO grains during magnetization reversal in ferromagnet/antiferromagnet (FM/AFM) heterostructures. The respective deformation modes are discussed in terms of the thermal fluctuation aftereffect in the Fulcomer and Charap model which predicts that irreversible breakdown of the original spin orientation can take place in some antiferromagnetic grains with disordered anisotropy axes during magnetization reversal of exchange-coupled FM/AFM structures. The spin reorientation in the saturated state may induce abrupt distortion of isolated metastable grains because of the NiO magnetostriction, leading to excitation of shock waves and formation of plate (or Lamb) waves.

Magnetic and morphological characterization of Nd2Fe14B magnets with different quality grades at low temperature 5-300 K

NASA Astrophysics Data System (ADS)

Diez-Jimenez, E.; Perez-Diaz, J. L.; Ferdeghini, C.; Canepa, F.; Bernini, C.; Cristache, C.; Sanchez-Garcia-Casarrubios, J.; Valiente-Blanco, I.; Ruiz-Navas, E. M.; Martínez-Rojas, J. A.

2018-04-01

An increasing number of cryogenic devices may benefit from the use of Nd2Fe14B permanent magnets. However, it is necessary to precisely know their behavior because magnetization varies significantly due to Spin Reorientation Transition. In this work, magnetic and morphological characterization of Nd2Fe14B commercial polycrystalline magnets with different quality grades from 5 to 300 K is provided. A set of magnets ranging from N35 to N52 quality have been analyzed. Mean grain dimension as well as material composition elements are provided. Higher quality magnets show smaller mean grain dimensions. Regarding cryogenic temperatures, the well know spin transition effect appears in all the magnets as expected, however, the transition temperature occurs at different temperatures in a range from 112 to 120 K which is lower than those obtained for single crystal samples. Moreover, the relative variation of the remanence from 300 to 5 K is lower than 4% while the maximum expected variation is in average 11%. As extra information, the same analyzes are provided for additional quality grades N40M, N40S, N40SH and N40UH.

Visually-induced reorientation illusions as a function of age.

PubMed

Howard, I P; Jenkin, H L; Hu, G

2000-09-01

We reported previously that supine subjects inside a furnished room who are tilted 90 degrees may experience themselves and the room as upright to gravity. We call this the levitation illusion because it creates sensations similar to those experienced in weightlessness. It is an example of a larger class of novel static reorientation illusions that we have explored. Stationary subjects inside a furnished room rotating about a horizontal axis experience complete self rotation about the roll or pitch axis. We call this a dynamic reorientation illusion. We have determined the incidence of static and dynamic reorientation illusions in subjects ranging in age from 9 to 78 yr. Some 90% of subjects of all ages experienced the dynamic reorientation illusion but the percentage of subjects experiencing static reorientation illusions increased with age. We propose that the dynamic illusion depends on a primitive mechanism of visual-vestibular interaction but that static reorientation illusions depend on learned visual cues to the vertical arising from the perceived tops and bottoms of familiar objects and spatial relationships between objects. Older people become more dependent on visual polarity to compensate for loss in vestibular sensitivity. Of 9 astronauts, 4 experienced the levitation illusion. The relationship between susceptibility to reorientation illusions on Earth and in space has still to be determined. We propose that the Space Station will be less disorienting if pictures of familiar objects line the walls.

Magnetostructural Phase Diagram of Multiferroic (ND 4) 2FeCl 5.H 2O

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clune, A.; Hughey, K.; Musfeldt, J. L.

2017-02-13

Spin and polarization flop transitions are fascinating, especially when controlled by external stimuli like magnetic and electric field and accompanied by large material responses involving multiple degrees of freedom. Multiferroics like MnWO 4, TbMnO 3, and Ni 3TeO 6 are flagship examples and owe their remarkable properties, for instance field control of polarization and polarization flops combined with spin helix reorientation, to the anisotropy and heavy centers that bring in spin-orbit coupling. The family of A 2FeX 5.H 2O erythrosiderites (A = K, Rb, NH 4; B = Fe, Mn, Co; X = Cl, Br, H 2O) drew our attentionmore » due to the rich chemical tuning possibilities, complex phase diagrams, and topological similarities to oxide multiferroics.1 (NH 4) 2FeCl 5.H 2O is the flagship example (Fig. 1(a)). It displays a high temperature order-disorder transition involving long-range hydrogen bonding of the NH 4 + group and two successive low temperature magnetic transitions below which non-collinear magnetic order and ferroelectricity are established.1 In addition to the magnetically-induced electric polarization that arises below 6.9 K (P = 3 μC/m 2 along a and a smaller component along b), applied field reveals a peculiar hysteretic spin flop transition near 4.5 T above which polarization flops from the a- to the c-axis. There are elastic components as well. Taken together, these findings raise questions about the interactions that induce this behavior and whether additional non-equilibrium phases might be accessed under even higher magnetic fields.« less

Accurate determination of chemical shift tensor orientations of single-crystals by solid-state magic angle spinning NMR

NASA Astrophysics Data System (ADS)

Avadhut, Yamini S.; Weber, Johannes; Schmedt auf der Günne, Jörn

2017-09-01

An improved implementation of single-crystal magic-angle-spinning (MAS) NMR is presented which gives access to chemical shift tensors both in orientation (relative to the crystal axis system) and principal axis values. For mounting arbitrary crystals inside ordinary MAS rotors, a mounting tool is described which allows to relate the crystal orientation determined by diffraction techniques to the rotor coordinate system. The crystal is finally mounted into a MAS rotor equipped with a special insert which allows a defined reorientation of the single-crystal by 90°. The approach is based on the idea that the dispersive spectra, which are obtained when applying read-pulses at specific rotor-phases, not only yield the size of the eigenvalues but also encode the orientation of the different chemical shift (rank-2) tensors. For this purpose two 2D-data sets with orthogonal crystal orientation are fitted simultaneously. The presented analysis for chemical shift tensors is supported by an analytical formula which allows fast calculation of phase and amplitude of individual spinning side-bands and by a protocol which solves the problem of finding the correct reference phase of the spectrum. Different rotor-synchronized pulse-sequences are introduced for the same reason. Experiments are performed on L-alanine and O-phosphorylethanolamine and the observed errors are analyzed in detail. The experimental data are opposed to DFT-computed chemical shift tensors which have been obtained by the extended embedded ion method.

Low temperature magneto-dielectric measurements on BiFeO{sub 3} lightly substituted by cobalt

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ray, J.; Biswal, A. K.; Vishwakarma, P. N., E-mail: prakashn@nitrkl.ac.in, E-mail: pnviisc@gmail.com

2015-04-07

Dielectric and magnetodielectric measurements are done on BiFe{sub 1−x}Co{sub x}O{sub 3}: x = 0, 0.01, and 0.02 in the temperature range 70–300 K and up to magnetic field 1.3 T. The dielectric data are well described by Haverliak–Negami expression plus an additional term for the Maxwell Wagner (MW) type relaxations, whose contribution is dominant near room temperature. The parameters obtained from the fitting of data using the above mentioned expression, suggest slowing down of relaxation and approach towards ideal Debye type relaxations, as the temperature is lowered. The dielectric relaxations obey polaronic variable range hopping model with distinct activation energies (E{sub a}) in themore » extrinsic (6.67T{sup 3/4 }meV) and intrinsic (2.88T{sup 3/4 }meV) regions for the parent sample (x = 0), and thus a distinct transition from extrinsic to intrinsic behavior is seen at 215 K while lowering the temperature. This distinct transition is missing for Co substituted samples probably due to the extrinsic region values of E{sub a} (3.42T{sup 3/4 }meV and 2.42T{sup 3/4 }meV for x = 0.01 and 0.02, respectively) comparable to that of the intrinsic region (see x = 0). The magnetodielectric measurement shows positive magnetodielectricity (MD) in the intrinsic region (T < 215 K for x = 0) and negative MD in the extrinsic region (T > 215 K for x = 0). The extrinsic region is found to be dominated by MW and magnetoresistance effects, whereas MD in intrinsic regions is due to the spin reorientation transitions. The Co substitution is found to increase the extrinsic and non-Debye contributions to dielectricity, which becomes so large that no spin reorientation transitions are seen in x = 0.02 sample. The pyroelectric active region in x = 0 is found to be dominated by the diffusive behavior having contribution of the form ω{sup −0.5}.« less

Microtubule bundling plays a role in ethylene-mediated cortical microtubule reorientation in etiolated Arabidopsis hypocotyls.

PubMed

Ma, Qianqian; Sun, Jingbo; Mao, Tonglin

2016-05-15

The gaseous hormone ethylene is known to regulate plant growth under etiolated conditions (the 'triple response'). Although organization of cortical microtubules is essential for cell elongation, the underlying mechanisms that regulate microtubule organization by hormone signaling, including ethylene, are ambiguous. In the present study, we demonstrate that ethylene signaling participates in regulation of cortical microtubule reorientation. In particular, regulation of microtubule bundling is important for this process in etiolated hypocotyls. Time-lapse analysis indicated that selective stabilization of microtubule-bundling structures formed in various arrays is related to ethylene-mediated microtubule orientation. Bundling events and bundle growth lifetimes were significantly increased in oblique and longitudinal arrays, but decreased in transverse arrays in wild-type cells in response to ethylene. However, the effects of ethylene on microtubule bundling were partially suppressed in a microtubule-bundling protein WDL5 knockout mutant (wdl5-1). This study suggests that modulation of microtubule bundles that have formed in certain orientations plays a role in reorienting microtubule arrays in response to ethylene-mediated etiolated hypocotyl cell elongation. © 2016. Published by The Company of Biologists Ltd.

Fundamental experiments on hydride reorientation in zircaloy

NASA Astrophysics Data System (ADS)

Colas, Kimberly B.

In the current study, an in-situ X-ray diffraction technique using synchrotron radiation was used to follow directly the kinetics of hydride dissolution and precipitation during thermomechanical cycles. This technique was combined with conventional microscopy (optical, SEM and TEM) to gain an overall understanding of the process of hydride reorientation. Thus this part of the study emphasized the time-dependent nature of the process, studying large volume of hydrides in the material. In addition, a micro-diffraction technique was also used to study the spatial distribution of hydrides near stress concentrations. This part of the study emphasized the spatial variation of hydride characteristics such as strain and morphology. Hydrided samples in the shape of tensile dog-bones were used in the time-dependent part of the study. Compact tension specimens were used during the spatial dependence part of the study. The hydride elastic strains from peak shift and size and strain broadening were studied as a function of time for precipitating hydrides. The hydrides precipitate in a very compressed state of stress, as measured by the shift in lattice spacing. As precipitation proceeds the average shift decreases, indicating average stress is reduced, likely due to plastic deformation and morphology changes. When nucleation ends the hydrides follow the zirconium matrix thermal contraction. When stress is applied below the threshold stress for reorientation, hydrides first nucleate in a very compressed state similar to that of unstressed hydrides. After reducing the average strain similarly to unstressed hydrides, the average hydride strain reaches a constant value during cool-down to room temperature. This could be due to a greater ease of deforming the matrix due to the applied far-field strain which would compensate for the strains due to thermal contraction. Finally when hydrides reorient, the average hydride strains become tensile during the first precipitation regime and remain constant in the tensile direction during the second precipitation regime. This could be due to the fact that the face of reoriented hydride platelet is in compression once these platelets have grown to a sufficient size. The second goal of this study was to perform a spatially resolved study of the effect of a stress concentration such as a notch or a crack on hydride reorientation. Using SEM and image analysis, it was found that a sharp crack induces a different hydride microstructure than a blunt notch. In the case of sharp crack, hydrides are more localized and align more with the defect than for blunt notches. The hydride connectivity also increases close to a stress concentration which will assist in crack propagation during DHC. Using TEM, the microstructure of hydrides grown near crack tips were observed to be similar to that of circumferential hydrides grown in the bulk. The orientation relationship studied with SEM and micro-X-ray diffraction was found to be in most cases δ(111)// α(0002) for hydrides grown both near and far from stress concentrations. Using the same micro-X-ray diffraction technique local hydride and matrix elastic strains were measured and observed to vary significantly from grain to grain. It was however observed that hydrides grown close to the stress concentration are in tension in the face of the platelet, similar to reoriented hydrides, while those grown far from the stress concentration are in tension, similar to circumferential hydrides. The orders of magnitude of the measured strains in the hydrides and the zirconium matrix compared well to those predicted by finite element models. This study shows that it is possible to study hydride dissolution and precipitation in-situ using time-dependent techniques. It was found that the precipitation temperature is lowered by hydride reorientation. The evolution of hydride strains during precipitation was found to be different for unstressed, stressed and reoriented hydrides. The reoriented hydride fraction and connectivity increase with number of cycles which could lead to more dangerous microstructure for storage of spent fuel. Pre-existing cracks were also found to affect hydride connectivity and morphology which directly impacts DHC and fuel integrity. (Abstract shortened by UMI.).

Observation of magnetic anomalies in one-step solvothermally synthesized nickel-cobalt ferrite nanoparticles.

PubMed

Datt, Gopal; Sen Bishwas, Mousumi; Manivel Raja, M; Abhyankar, A C

2016-03-07

Magnetic anomalies corresponding to the Verwey transition and reorientation of anisotropic vacancies are observed at 151 K and 306 K, respectively, in NiCoFe2O4 nanoparticles (NPs) synthesized by a modified-solvothermal method followed by annealing. Cationic disorder and spherical shape induced non-stoichiometry suppress the Verwey transition in the as-synthesized NPs. On the other hand, reorientation of anisotropic vacancies is quite robust. XRD and electron microscopy investigations confirm a single phase spinel structure and the surface morphology of the as-synthesized NPs changes from spherical to octahedral upon annealing. Rietveld analysis reveals that the Ni(2+) ions migrate from tetrahedral (A) to octahedral (B) sites upon annealing. The Mössbauer results show canted spins in both the NPs and the strength of superexchange is stronger in Co-O-Fe than Ni-O-Fe. Magnetic force images show that the as-synthesised NPs are single-domain whereas the annealed NPs are multi-domain octahedral particles. The FMR study reveals that both the NPs have a broad FMR line-width; and resonance properties are consistent with the random anisotropy model. The broad inhomogeneous FMR line-width, observation of the Verwey transition, tuning of the magnetic domain structure as well as the magnetic properties suggest that the NiCoFe2O4 ferrite NPs may be promising for future generation spintronics, magneto-electronics, and ultra-high-density recording media as well as for radar absorbing applications.

Role of space charges on light-induced effects in nematic liquid crystals doped by methyl red.

PubMed

Lucchetti, L; Simoni, F

2014-03-01

We show that both the extraordinarily large nonlinear response and the light-induced permanent reorientation in liquid crystals doped by the azo dye methyl red originates from the same phenomenon of modification of the charge density on the irradiated surface. The demonstration is done by applying ac voltage to the samples, showing that in this case no permanent anchoring is possible. The measurements confirm the role of photoisomerization that gives a transient contribution to the actual reorientation process only in the high dose regime. This result allows us to draw a picture for light-induced effects that might be applied to a large class of compounds.

In situ neutron diffraction study of twin reorientation and pseudoplastic strain in Ni-Mn-Ga single crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stoica, Alexandru Dan

2011-01-01

Twin variant reorientation in single-crystal Ni-Mn-Ga during quasi-static mechanical compression was studied using in situ neutron diffraction. The volume fraction of reoriented twin variants for different stress amplitudes were obtained from the changes in integrated intensities of high-order neutron diffraction peaks. It is shown that, during compressive loading, {approx}85% of the twins were reoriented parallel to the loading direction resulting in a maximum pseudoplasticstrain of {approx}5.5%, which is in agreement with measured macroscopic strain.

Twin-variant reorientation strain in Ni-Mn-Ga single crystal during quasi-static mechanical compression

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pramanick, Abhijit; An, Ke; Stoica, Alexandru Dan

2011-01-01

Twin variant reorientation in single crystal Ni-Mn-Ga during quasi-static mechanical compression was studied using in-situ neutron diffraction. The volume fraction of reoriented twin variants for different stress amplitudes were obtained from the changes in integrated intensities of high-order neutron diffraction peaks. It is shown that during compressive loading, ~85% of the twins were reoriented parallel to the loading direction resulting in a maximum macroscopic strain of ~5.5%, which is in agreement with measured macroscopic strain.

Topographical Organization of Attentional, Social, and Memory Processes in the Human Temporoparietal Cortex123

PubMed Central

Webb, Taylor W.; Kelly, Yin T.; Graziano, Michael S. A.

2016-01-01

Abstract The temporoparietal junction (TPJ) is activated in association with a large range of functions, including social cognition, episodic memory retrieval, and attentional reorienting. An ongoing debate is whether the TPJ performs an overarching, domain-general computation, or whether functions reside in domain-specific subdivisions. We scanned subjects with fMRI during five tasks known to activate the TPJ, probing social, attentional, and memory functions, and used data-driven parcellation (independent component analysis) to isolate task-related functional processes in the bilateral TPJ. We found that one dorsal component in the right TPJ, which was connected with the frontoparietal control network, was activated in all of the tasks. Other TPJ subregions were specific for attentional reorienting, oddball target detection, or social attribution of belief. The TPJ components that participated in attentional reorienting and oddball target detection appeared spatially separated, but both were connected with the ventral attention network. The TPJ component that participated in the theory-of-mind task was part of the default-mode network. Further, we found that the BOLD response in the domain-general dorsal component had a longer latency than responses in the domain-specific components, suggesting an involvement in distinct, perhaps postperceptual, computations. These findings suggest that the TPJ performs both domain-general and domain-specific computations that reside within spatially distinct functional components. PMID:27280153

Control of Rotational Energy and Angular Momentum Orientation with an Optical Centrifuge

NASA Astrophysics Data System (ADS)

Ogden, Hannah M.; Murray, Matthew J.; Mullin, Amy S.

2017-04-01

We use an optical centrifuge to trap and spin molecules to an angular frequency of 30 THz with oriented angular momenta and extremely high rotational energy and then investigate their subsequent collision dynamics with transient high resolution IR spectroscopy. The optical centrifuge is formed by combining oppositely-chirped pulses of 800 nm light, and overlapping them spatially and temporally. Polarization-sensitive Doppler-broadened line profiles characterize the anisotropic kinetic energy release of the super rotor molecules, showing that they behave like molecular gyroscopes. Studies are reported for collisions of CO2 super rotors with CO2, He and Ar. These studies reveal how mass, velocity and rotational adiabaticity impact the angular momentum relaxation and reorientation. Quantum scattering calculations provide insight into the J-specific collision cross sections that control the relaxation. NSF-CHE 105 8721.

Perpendicular magnetic anisotropy and spin reorientation transition in L1{sub 0} FePt films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ahn, Jae Young; Lee, Nyun Jong; Kim, Tae Hee

2011-04-01

We investigated the thickness and composition dependence of perpendicular magnetic anisotropy (PMA) in L1{sub 0} Fe{sub 1-x}Pt{sub x} (x = 0.4, 0.5, and 0.55) films. The FePt films with different thicknesses of 35 and 70 A were grown at the substrate temperature T{sub s} = 300 deg. C by molecular beam epitaxy coevaporation technique. A (001)-oriented epitaxial L1{sub 0} FePt film was grown on the thin (001)-oriented fcc Pt layer, while a poorly crystallized FePt film was formed on the (111)-textured Pt layer. Our results showed that, at a fixed thickness of 70 A, the PMA of FePt alloy filmsmore » is enhanced as Pt content increases from 40% to 55%.« less

Rethinking the role of the rTPJ in attention and social cognition in light of the opposing domains hypothesis: findings from an ALE-based meta-analysis and resting-state functional connectivity

PubMed Central

Kubit, Benjamin; Jack, Anthony I.

2013-01-01

The right temporo-parietal junction (rTPJ) has been associated with two apparently disparate functional roles: in attention and in social cognition. According to one account, the rTPJ initiates a “circuit-breaking” signal that interrupts ongoing attentional processes, effectively reorienting attention. It is argued this primary function of the rTPJ has been extended beyond attention, through a process of evolutionarily cooption, to play a role in social cognition. We propose an alternative account, according to which the capacity for social cognition depends on a network which is both distinct from and in tension with brain areas involved in focused attention and target detection: the default mode network (DMN). Theory characterizing the rTPJ based on the area's purported role in reorienting may be falsely guided by the co-occurrence of two distinct effects in contiguous regions: activation of the supramarginal gyrus (SMG), associated with its functional role in target detection; and the transient release, during spatial reorienting, of suppression of the angular gyrus (AG) associated with focused attention. Findings based on meta-analysis and resting functional connectivity are presented which support this alternative account. We find distinct regions, possessing anti-correlated patterns of resting connectivity, associated with social reasoning (AG) and target detection (SMG) at the rTPJ. The locus for reorienting was spatially intermediate between the AG and SMG and showed a pattern of connectivity with similarities to social reasoning and target detection seeds. These findings highlight a general methodological concern for brain imaging. Given evidence that certain tasks not only activate some areas but also suppress activity in other areas, it is suggested that researchers need to distinguish two distinct putative mechanisms, either of which may produce an increase in activity in a brain area: functional engagement in the task vs. release of suppression. PMID:23847497

Is Language Necessary for Human Spatial Reorientation? Reconsidering Evidence from Dual Task Paradigms

ERIC Educational Resources Information Center

Ratliff, Kristin R.; Newcombe, Nora S.

2008-01-01

Being able to reorient to the spatial environment after disorientation is a basic adaptive challenge. There is clear evidence that reorientation uses geometric information about the shape of the surrounding space. However, there has been controversy concerning whether use of geometry is a modular function, and whether use of features is dependent…

The finite element simulation analysis research of 38CrSi cylindrical power spinning

NASA Astrophysics Data System (ADS)

Liang, Wei; Lv, Qiongying; Zhao, Yujuan; Lv, Yunxia

2018-01-01

In order to grope for the influence of the main cylindrical spinning process parameters on the spinning process, this paper combines with real tube power spinning process and uses ABAQUS finite element analysis software to simulate the tube power spinning process of 38CrSi steel materials, through the analysis of the stress, strain of the part forming process, analyzes the influence of the thickness reduction and the feed rate to the forming process, and analyzes the variation of the spinning force, finally determines the reasonable main spinning process parameters combination.

Reorienting with terrain slope and landmarks.

PubMed

Nardi, Daniele; Newcombe, Nora S; Shipley, Thomas F

2013-02-01

Orientation (or reorientation) is the first step in navigation, because establishing a spatial frame of reference is essential for a sense of location and heading direction. Recent research on nonhuman animals has revealed that the vertical component of an environment provides an important source of spatial information, in both terrestrial and aquatic settings. Nonetheless, humans show large individual and sex differences in the ability to use terrain slope for reorientation. To understand why some participants--mainly women--exhibit a difficulty with slope, we tested reorientation in a richer environment than had been used previously, including both a tilted floor and a set of distinct objects that could be used as landmarks. This environment allowed for the use of two different strategies for solving the task, one based on directional cues (slope gradient) and one based on positional cues (landmarks). Overall, rather than using both cues, participants tended to focus on just one. Although men and women did not differ significantly in their encoding of or reliance on the two strategies, men showed greater confidence in solving the reorientation task. These facts suggest that one possible cause of the female difficulty with slope might be a generally lower spatial confidence during reorientation.

Molecular dynamics of 17α- and 21-hydroxy progesterone studied by NMR. Relation between molecule conformation and height of the barrier for methyl group reorientations in steroid compounds

NASA Astrophysics Data System (ADS)

Szyczewski, A.; Hołderna-Natkaniec, K.

2005-01-01

For the two steroid compounds 17αOH-progesterone and 21OH-progesterone, the activation energies of reorientations of the methyl groups have been determined. Their values together with results of the quantum chemical calculations permitted establishment of the sequence of the onset of the methyl group reorientations about the three-fold symmetry axis of the C-C bond. On the basis of the asymmetry parameters, the conformations of the hitherto studied pregnane derivatives and testosterone have been determined. It has been found that the conformation of ring A has dominant effect on the activation energies of the reorientation of C(19)H 3. The reorientation of the methyl group C(18)H 3 significantly depends on the conformation of the side chain 17β (torsional angle C(13)-C(17)-C(20)-O(20)) and the distance between C18 and O20. The study has proved that the 1H NMR method in combination with the quantum chemistry calculations and inelastic incoherent neutron scattering (IINS) are effective for prediction of the sequence of the methyl group reorientations about the three-fold symmetry axis.

Test of a flexible spacecraft dynamics simulator

NASA Technical Reports Server (NTRS)

Dichmann, Donald; Sedlak, Joseph

1998-01-01

There are a number of approaches one can take to modeling the dynamics of a flexible body. While one can attempt to capture the full dynamical behavior subject to disturbances from actuators and environmental torques, such a detailed description often is unnecessary. Simplification is possible either by limiting the amplitude of motion to permit linearization of the dynamics equations or by restricting the types of allowed motion. In this work, we study the nonlinear dynamics of bending deformations of wire booms on spinning spacecraft. The theory allows for large amplitude excursions from equilibrium while enforcing constraints on the dynamics to prohibit those modes that are physically less relevant or are expected to damp out fast. These constraints explicitly remove the acoustic modes (i.e., longitudinal sound waves and shear waves) while allowing for arbitrary bending and twisting, motions which typically are of lower frequency. As a test case, a spin axis reorientation maneuver by the Polar Plasma Laboratory (POLAR) spacecraft has been simulated. POLAR was chosen as a representative spacecraft because it has flexible wire antennas that extend to a length of 65 meters. Bending deformations in these antennas could be quite large and have a significant effect on the attitude dynamics of the spacecraft body. Summary results from the simulation are presented along, with a comparison with POLAR flight data.

The NASA MLAS Flight Demonstration - A Review of a Highly Successful Test

NASA Technical Reports Server (NTRS)

Taylor, Anthony P.; Kelley, Christopher; Magner, Eldred; Peterson, David; Hahn, Jeffrey; Yuchnovicz, Daniel

2010-01-01

NASA has tested the Max Launch Abort System (MLAS) as a risk-mitigation design should problems arise with the baseline Orion spacecraft launch abort design. The Max in MLAS is not Maximum, but rather dedicated to Max Faget, The renowned NASA Spacecraft designer. In the fall of 2009, the mission was flown, with great success, from the NASA Wallops Flight Facility. The MLAS flight test vehicle prototype consists of a boost ring, coast ring, and the MLAS fairing itself, which houses an Orion Command Module (CM) boilerplate. The objective of the MLAS flight test is to reorient the fairing with the CM, weighing approximately 29,000 lbs and traveling 290 fps, 180 degrees to an orientation suitable for the release of the CM during a pad abort and low altitude abort. Although multiple parachute deployments are used in the MLAS flight test vehicle to complete its objective, there are only two parachute types employed in the flight test. Five of the nine parachutes used for MLAS are 27.6 ft DO ribbon parachutes, and the remaining four are standard G-12 cargo parachutes. This paper presents an overview of the 27.6 ft DO ribbon parachute system employed on the MLAS flight test vehicle for coast ring separation, fairing reorientation, and as drogue parachutes for the CM after separation from the fairing. Discussion will include: the process used to select this design, previously proven as a spin/stall recovery parachute; descriptions of all components of the parachute system; the minor modifications necessary to adapt the parachute to the MLAS program; the techniques used to analyze the parachute for the multiple roles it performs; a discussion of the rigging techniques used to interface the parachute system to the vehicle; a brief description of how the evolution of the program affected parachute usage and analysis; and a summary of the results of the flight test, including video of the flight test and subsequent summary analysis. . A discussion of the flight test which was highly successful as well as the flight test observations will be a significant portion of the review.

Thermocapillary reorientation of Janus drops

NASA Astrophysics Data System (ADS)

Rosales, Rodolfo; Saenz, Pedro

2017-11-01

Janus drops, named after the Ancient Roman two-faced god, are liquid drops formed from two immiscible fluids. Experimental observations indicate that a Janus drop may re-orientate in response to an applied external thermal gradient due to the Marangoni effect. Depending on the angle between the interior interface and the direction of the temperature gradient, disparities in the physical properties of the constituent liquids may lead to asymmetries in the thermocapillary flow. As a result, the drop will move along a curved path until a torque-free configuration is achieved, point after which it will continue on a straight trajectory. Here, we present the results of a theoretical investigation of this realignment phenomenon in the Stokes regime and in the limit of non-deformable interfaces. A 3D semi-analytical method in terms of polar spherical harmonics is developed to characterize and rationalize the hydrodynamic response (forces and torques), flow (velocity and temperature distribution) and trajectory of a Janus drop moving during the temperature-driven reorientation process. Furthermore, we discuss how this phenomenon may be exploited to develop dynamically reconfigurable micro-lenses. This work was partially supported by the US National Science Foundation through Grants DMS-1614043 and DMS-1719637.

Reorientation Timescales and Pattern Dynamics for Titan's Dunes: Does the Tail Wag the Dog or the Dragon?

NASA Astrophysics Data System (ADS)

Ewing, R. C.; Hayes, A. G.; McCormick, C.; Ballard, C.; Troy, S. A.

2012-04-01

Fields of bedform patterns persist across many orders of magnitude, from cm-scale sub-aqueous current ripples to km-scale aeolian dunes, and form with surprisingly little difference in expression despite a range of formative environments. Because of the remarkable similarity among bedform patterns, extracting information about climate and environment from these patterns is a challenge. For example, crestline orientation is not diagnostic of a particular flow regime; similar patterns form under many different flow configurations. On Titan, these challenges have played out with many attempts to reconcile dune crestline orientation with modeled and expected wind regimes. We propose that thinking about the time-scale of the change in dune orientation, rather than the orientation itself, can provide new insights on the long-term stability of the dune-field patterns and the formative wind regime. In this work, we apply the crestline re-orientation model developed by Werner and Kocurek [Geology, 1997] to the equatorial dune fields of Titan. We use Cassini Synthetic Aperture Radar images processed through a de-noising algorithm recently developed by Lucas et al. [LPSC, 2012] to measure variations in pattern parameters (crest spacing, crest length and defect density, which is the number of defect pairs per total crest length) both within and between Titan's dune fields to describe pattern maturity and identify areas where changes in dune orientation are likely to occur (or may already be occurring). Measured defect densities are similar to Earth's largest linear dune fields, such as the Namib Sand Sea and the Simpson Desert. We use measured defect densities in the Werner and Kocurek model to estimate crestline reorientation rates. We find reorientation timescales varying from ten to a hundred thousand times the average migration timescale (time to migrate a bedform one meter, ~1 Titan year according to Tokano (Aeolian Research, 2010)). Well-organized patterns have the longest reorientation time scales (~105 migration timescales), while the topographically or spatially isolated patches of dunes show the shortest reorientation times (~103 migration timescales). In addition, comparisons between spacing and defect density reveal that the well-organized patterns plot along an expected trend with Earth and Mars' largest, well-organized fields. Patterns on Earth and Mars that have been degraded and broken by environmental change fall off this trend and similarly, so do the isolated dune patterns on Titan fall suggesting changing environmental conditions such as wind regime and/or sediment availability have influenced the dunes on Titan. Crestline orientations in these areas suggest star and crescentic (barchans) morphologies in addition to linear dunes. Our results suggest that Titan's dunes may react to gross bedform transport averaged over orbital timescales, relaxing the requirement that a single modern wind regime is necessary to produce the observed well-organized dune patterns. We find signals of environmental change within the smallest patterns suggesting that the dunes may be recently reoriented or are reorienting to one component of a longer timescale wind regime with a duty cycle that persists over many seasonal cycles.

Magneto-crystalline anisotropy of NdFe0.9Mn0.1O3 single crystal

NASA Astrophysics Data System (ADS)

Mihalik, Marián; Mihalik, Matúš; Zentková, Mária; Uhlířová, Klára; Kratochvílová, Marie; Roupcová, Pavla

2018-05-01

Our present study on oriented single crystal revealed huge magneto-crystalline anisotropy with respect to principal crystallographic axes, even several magnetic transitions were observed below TN = 748 K (c-axis) at 700 K (a-axis) as well 657 K (b-axis). The spin reorientation of magnetic moment takes place in very narrow temperature range between 135 K and 125 K and is attributed to vanishing of ferromagnetic component aligned along b-axis. Measurements of magnetic isotherms trace the development of ferromagnetic component and revealed the intermediate temperature range between 120 K and 20 K which is characterised by zero ferromagnetic components in any principal crystal direction. The ferromagnetic component develops consecutive at low temperature below 20 K along a-axis. Our study indicates completely different magnetic structure of NdFe0.9Mn0.1O3 below 135 K in comparison with NdFeO3.

Magnetic properties of Mn{sub 1.9}Cu{sub 0.1}Sb under high pressure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matsumoto, Yoshihiro; Hiroi, Masahiko; Mitsui, Yoshifuru

2016-08-26

Magnetization measurements were carried out for polycrystalline Mn{sub 1.9}Cu{sub 0.1}Sb in magnetic fields up to 5 T in the 10-300 K temperature range under high pressures up to 1 GPa in order to investigate the magnetic properties and the thermal transformation arrest (TTA) phenomenon under high pressures. The spin-reorientation temperature increased from 202 K for 0.1 MPa to 244 K for 1 GPa, whereas the transition temperature from the ferrimagnetic (FRI) to antiferromagnetic (AFM) state did not drastically change at ∼116 K. The magnetic relaxation behavior from the FRI to AFM state was observed in 10 < T ≤ 70more » K, which was analyzed using the Kohlrausch-Williams-Watts model. Obtained results indicated that the TTA phenomenon of Mn{sub 1.9}Cu{sub 0.1}Sb was suppressed by the application of high pressures.« less

Structural basis of lipid-driven conformational transitions in the KvAP voltage-sensing domain.

PubMed

Li, Qufei; Wanderling, Sherry; Sompornpisut, Pornthep; Perozo, Eduardo

2014-02-01

Voltage-gated ion channels respond to transmembrane electric fields through reorientations of the positively charged S4 helix within the voltage-sensing domain (VSD). Despite a wealth of structural and functional data, the details of this conformational change remain controversial. Recent electrophysiological evidence showed that equilibrium between the resting ('down') and activated ('up') conformations of the KvAP VSD from Aeropyrum pernix can be biased through reconstitution in lipids with or without phosphate groups. We investigated the structural transition between these functional states, using site-directed spin-labeling and EPR spectroscopic methods. Solvent accessibility and interhelical distance determinations suggest that KvAP gates through S4 movements involving an ∼3-Å upward tilt and simultaneous ∼2-Å axial shift. This motion leads to large accessibly changes in the intracellular water-filled crevice and supports a new model of gating that combines structural rearrangements and electric-field remodeling.

Navigation as a Source of Geometric Knowledge: Young Children's Use of Length, Angle, Distance, and Direction in a Reorientation Task

ERIC Educational Resources Information Center

Lee, Sang Ah; Sovrano, Valeria A.; Spelke, Elizabeth S.

2012-01-01

Geometry is one of the highest achievements of our species, but its foundations are obscure. Consistent with longstanding suggestions that geometrical knowledge is rooted in processes guiding navigation, the present study examines potential sources of geometrical knowledge in the navigation processes by which young children establish their sense…

Gravitropism in cut flower stalks of snapdragon

NASA Astrophysics Data System (ADS)

Philosoph-Hadas, S.; Friedman, H.; Meir, S.; Berkovitz-SimanTov, R.; Rosenberger, I.; Halevy, A. H.; Kaufman, P. B.; Balk, P.; Woltering, E. J.

The negative gravitropic response of cut flower stalks is a complex multistep process that requires the participation of various cellular components acting in succession or in parallel. The process was particularly characterized in snapdragon (Antirrhinum majus L.) spikes with regard to (1) gravity stimulus perception associated with amyloplast reorientation; (2) stimulus transduction mediated through differential changes in the level, action and related genes of auxin and ethylene and their possible interaction; (3) stimulus response associated with differential growth leading to stalk curvature; (4) involvement of cytosolic calcium and actin cytoskeleton. Results show that the gravity-induced amyloplast reorientation, differential over-expression of two early auxin responsive genes and asymmetrical distribution of free IAA are early events in the bending process. These precede the asymmetrical ethylene production and differential stem growth, which was derived from initial shrinkage of the upper stem side and a subsequent elongation of the lower stem side. Results obtained with various calcium- and cytoskeleton-related agents indicate that cytosolic calcium and actin filaments may play essential roles in gravitropism-related processes of cut flower stalks. Therefore, modulators of these two physiological mediators may serve as means for controlling any undesired gravitropic bending.

Children's use of geometry for reorientation.

PubMed

Lee, Sang Ah; Spelke, Elizabeth S

2008-09-01

Research on navigation has shown that humans and laboratory animals recover their sense of orientation primarily by detecting geometric properties of large-scale surface layouts (e.g. room shape), but the reasons for the primacy of layout geometry have not been clarified. In four experiments, we tested whether 4-year-old children reorient by the geometry of extended wall-like surfaces because such surfaces are large and perceived as stable, because they serve as barriers to vision or to locomotion, or because they form a single, connected geometric figure. Disoriented children successfully reoriented by the shape of an arena formed by surfaces that were short enough to see and step over. In contrast, children failed to reorient by the shape of an arena defined by large and stable columns or by connected lines on the floor. We conclude that preschool children's reorientation is not guided by the functional relevance of the immediate environmental properties, but rather by a specific sensitivity to the geometric properties of the extended three-dimensional surface layout.

On the role of the notochord in somite formation and the possible evolutionary significance of the concomitant cell re-orientation.

PubMed

Burgess, A M

1983-06-01

Homoplastic grafts of re-orientated unsegmented paraxial mesoderm transplanted from stage 20 Xenopus embryos into host embryos of the same age resulted in segmentation and the formation of somites in the same axis as if they had been left in situ. Because grafts transplanted with various orientations came under the stretching effect of the notochord in different directions but never the less maintained their original pattern and direction of segmentation, it would appear that the notochord has no effect on somite formation which thus emerges as an autonomous process independent of the elongation of the embryo. The re-alignment of cells which occurs as the somites are formed and which, in normal unimpeded development, results in the long axis of the cells lying parallel to that of the notochord, is considered in the light of the evolution of sinusoid locomotion and it is suggested that it may be the primary process with the formation of somite blocks as one of its consequences.

Growing swimming algae for bioenergy

NASA Astrophysics Data System (ADS)

Croze, Ottavio

Biofuel production from photosynthetic microalgae is not commercially viable due to high processing costs. New engineering and biological solutions are being sought to reduce these costs by increasing processing efficiency (productivity per energy input). Important physics, however, is ignored. For example, the fluid dynamics of algal suspensions in photobioreactors (ponds or tube arrays) is non-trivial, particularly if the algae swim. Cell reorientation by passive viscous and gravitational torques (gyrotaxis) or active reorientation by light (phototaxis) cause swimming algae in suspension to structure in flows, even turbulent ones. This impacts the distribution and dispersion of swimmers, with significant consequences for photobioreactor operation and design. In this talk, I will describe a theory that predicts swimmer dispersion in laminar pipe flows. I will then then present experimental tests of the theory, as well as new results on the circadian suspension dynamics of the algaChlamydomonas reinhardtii in lab-scale photobioreactors. Finally, I will briefly consider the implications of our work, and related active matter research, for improving algal bioprocessing efficiency. Winton Programme for the Physics of Sustainability.

From environment to sustainable development: China's strategies for ESD in basic education

NASA Astrophysics Data System (ADS)

Zhang, Tiedao

2010-06-01

This paper intends to provide an overview of the reorientation of education in China in the period 1998-2009 with regard to development issues. During this time, the focus has shifted gradually from the environment and health to education for sustainable development. The article centres on highlighting the main interventions and strategies adopted by China's schools to make this reorientation possible, including: the introduction of new visions of sustainable development and project planning; the establishment of organisational mechanisms and capacity-building measures for their implementation in the field; the integration of ESD into teaching and learning processes; the maintenance of an action-research mechanism for innovations; and the sharing of lessons with both the national and the international community in order to make the implementation of ESD more effective.

Metallic behavior induced by potassium doping of the trigonal antiferromagnetic insulator EuMn 2 As 2

DOE PAGES

Anand, V. K.; Johnston, D. C.

2016-07-22

Here, we report magnetic susceptibility χ, isothermal magnetization M, heat capacity C p, and electrical resistivity ρ measurements on undoped EuMn 2As 2 and K-doped Eu 0.96K 0.04Mn 2As 2 and Eu 0.93K 0.07Mn 2As 2 single crystals with the trigonal CaAl 2Si 2-type structure as a function of temperature T and magnetic field H. EuMn 2As 2 has an insulating ground state with an activation energy of 52 meV and exhibits antiferromagnetic (AFM) ordering of the Eu +2 spins S=7/2 at T N1=15 K from C p(T) and χ(T) data with a likely spin-reorientation transition at T N2=5.0 K.more » The Mn +2 3d 5 spins-5/2 exhibit AFM ordering at T N=142 K from all three types of measurements. The M(H) isotherm and χ(T) data indicate that the Eu AFM structure is both noncollinear and noncoplanar. The AFM structure of the Mn spins is also unclear. A 4% substitution of K for Eu in Eu 0.96K 0.04Mn 2As 2 is sufficient to induce a metallic ground state. We found evidence for a difference in the AFM structure of the Eu moments in the metallic crystals from that of undoped EuMn 2As 2 versus both T and H. For metallic Eu 0.96K 0.04Mn 2As 2 and Eu 0.93K 0.07Mn 2As 2, an anomalous S-shape T dependence of ρ related to the Mn magnetism is found. Upon cooling from 200 K, ρ exhibits a strong negative curvature, reaches maximum positive slope at the Mn T N≈150 K, and then continues to decrease but more slowly below T N. Finally, this suggests that dynamic short-range AFM order of the Mn spins above the Mn T N strongly suppresses the resistivity, contrary to the conventional decrease of ρ that is only observed upon cooling below T N of an antiferromagnet.« less

EPR and ESE of CuS4 complex in Cu(dmit)2: g-Factor and hyperfine splitting correlation in tetrahedral Cu-sulfur complexes

NASA Astrophysics Data System (ADS)

Hoffmann, Stanisław K.; Goslar, Janina; Lijewski, Stefan; Zalewska, Alina

2013-11-01

Pseudotetrahedral CuS4 complexes of Cu(dmit)2 compound in DMF solution were studied by EPR, UV-Vis and electron spin echo methods. After rapid freezing at 77 K a good glassy state is formed and the CuS4 complex has a D2d symmetry of a compressed tetrahedron with xy ground state and spin-Hamiltonian parameters g|| = 2.089, g⊥ = 2.026, A|| = 146 × 10-4 cm-1 and A⊥ = 30 × 10-4 cm-1. The complex is not deformed in the glassy state and is very rigid as indicated by the echo detected spectrum and by electron spin relaxation which is governed by reorientations of methyl groups of surrounding DMF molecules as shown by electron spin echo envelope modulation (ESEEM) spectrum. The g|| and A|| of Cu(dmit)2 and other CuS4 complexes collected in Peisach-Blumberg correlation diagram were analyzed using extended Molecular Orbital theory. We explain why the correlation line for copper-sulfur complexes has larger slope compared to the CuO4 and CuN4 tetrahedra. Along the correlation line the delocalization of unpaired electron density onto ligand is constant and varies from β = 0.78-0.83 for g|| in the range 2.06-2.10 of correlation diagram. The slope of the line is determined by the product of MO-coefficients αc1, where α is a parameter characterizing delocalization of unpaired electron in x2-y2 and c1 < 1 is a mixing parameter decreasing when 4p contribution grows. We found, unexpectedly, that αc1≈0.7 for all CuS4 complexes suggesting a correlation between degree of tetrahedral deformation and MO-parameters. MO-coefficients for Cu(dmit)2 are α = 0.753, β = 0.752 and c1 = 0.930 confirming a strong delocalization of unpaired electron in xy and x2-y2 orbitals.

Planar reorientation maneuvers of space multibody systems using internal controls

NASA Technical Reports Server (NTRS)

Reyhanoglu, Mahmut; Mcclamroch, N. H.

1992-01-01

In this paper a reorientation maneuvering strategy for an interconnection of planar rigid bodies in space is developed. It is assumed that there are no exogeneous torques, and torques generated by joint motors are used as means of control so that the total angular momentum of the multibody system is a constant, assumed to be zero in this paper. The maneuver strategy uses the nonintegrability of the expression for the angular momentum. We demonstrate that large-angle maneuvers can be designed to achieve an arbitrary reorientation of the multibody system with respect to an inertial frame. The theoretical background for carrying out the required maneuvers is briefly summarized. Specifications and computer simulations of a specific reorientation maneuver, and the corresponding control strategies, are described.

Model-free estimation of the effective correlation time for C–H bond reorientation in amphiphilic bilayers: {sup 1}H–{sup 13}C solid-state NMR and MD simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ferreira, Tiago Mendes, E-mail: tiago.ferreira@fkem1.lu.se; Physical Chemistry, Lund University, P.O. Box 124, SE-221 00 Lund; Ollila, O. H. Samuli

2015-01-28

Molecular dynamics (MD) simulations give atomically detailed information on structure and dynamics in amphiphilic bilayer systems on timescales up to about 1 μs. The reorientational dynamics of the C–H bonds is conventionally verified by measurements of {sup 13}C or {sup 2}H nuclear magnetic resonance (NMR) longitudinal relaxation rates R{sub 1}, which are more sensitive to motional processes with correlation times close to the inverse Larmor frequency, typically around 1-10 ns on standard NMR instrumentation, and are thus less sensitive to the 10-1000 ns timescale motion that can be observed in the MD simulations. We propose an experimental procedure for atomicallymore » resolved model-free estimation of the C–H bond effective reorientational correlation time τ{sub e}, which includes contributions from the entire range of all-atom MD timescales and that can be calculated directly from the MD trajectories. The approach is based on measurements of {sup 13}C R{sub 1} and R{sub 1ρ} relaxation rates, as well as {sup 1}H−{sup 13}C dipolar couplings, and is applicable to anisotropic liquid crystalline lipid or surfactant systems using a conventional solid-state NMR spectrometer and samples with natural isotopic composition. The procedure is demonstrated on a fully hydrated lamellar phase of 1-palmitoyl-2-oleoyl-phosphatidylcholine, yielding values of τ{sub e} from 0.1 ns for the methyl groups in the choline moiety and at the end of the acyl chains to 3 ns for the g{sub 1} methylene group of the glycerol backbone. MD simulations performed with a widely used united-atom force-field reproduce the τ{sub e}-profile of the major part of the acyl chains but underestimate the dynamics of the glycerol backbone and adjacent molecular segments. The measurement of experimental τ{sub e}-profiles can be used to study subtle effects on C–H bond reorientational motions in anisotropic liquid crystals, as well as to validate the C–H bond reorientation dynamics predicted in MD simulations of amphiphilic bilayers such as lipid membranes.« less

Recombinant spider silk from aqueous solutions via a bio-inspired microfluidic chip

NASA Astrophysics Data System (ADS)

Peng, Qingfa; Zhang, Yaopeng; Lu, Li; Shao, Huili; Qin, Kankan; Hu, Xuechao; Xia, Xiaoxia

2016-11-01

Spiders achieve superior silk fibres by controlling the molecular assembly of silk proteins and the hierarchical structure of fibres. However, current wet-spinning process for recombinant spidroins oversimplifies the natural spinning process. Here, water-soluble recombinant spider dragline silk protein (with a low molecular weight of 47 kDa) was adopted to prepare aqueous spinning dope. Artificial spider silks were spun via microfluidic wet-spinning, using a continuous post-spin drawing process (WS-PSD). By mimicking the natural spinning apparatus, shearing and elongational sections were integrated in the microfluidic spinning chip to induce assembly, orientation of spidroins, and fibril structure formation. The additional post-spin drawing process following the wet-spinning section partially mimics the spinning process of natural spider silk and substantially contributes to the compact aggregation of microfibrils. Subsequent post-stretching further improves the hierarchical structure of the fibres, including the crystalline structure, orientation, and fibril melting. The tensile strength and elongation of post-treated fibres reached up to 510 MPa and 15%, respectively.

Low speed maneuvering flight of the rose-breasted cockatoo (Eolophus roseicapillus). II. Inertial and aerodynamic reorientation.

PubMed

Hedrick, T L; Usherwood, J R; Biewener, A A

2007-06-01

The reconfigurable, flapping wings of birds allow for both inertial and aerodynamic modes of reorientation. We found evidence that both these modes play important roles in the low speed turning flight of the rose-breasted cockatoo Eolophus roseicapillus. Using three-dimensional kinematics recorded from six cockatoos making a 90 degrees turn in a flight corridor, we developed predictions of inertial and aerodynamic reorientation from estimates of wing moments of inertia and flapping arcs, and a blade-element aerodynamic model. The blade-element model successfully predicted weight support (predicted was 88+/-17% of observed, N=6) and centripetal force (predicted was 79+/-29% of observed, N=6) for the maneuvering cockatoos and provided a reasonable estimate of mechanical power. The estimated torque from the model was a significant predictor of roll acceleration (r(2)=0.55, P<0.00001), but greatly overestimated roll magnitude when applied with no roll damping. Non-dimensional roll damping coefficients of approximately -1.5, 2-6 times greater than those typical of airplane flight dynamics (approximately -0.45), were required to bring our estimates of reorientation due to aerodynamic torque back into conjunction with the measured changes in orientation. Our estimates of inertial reorientation were statistically significant predictors of the measured reorientation within wingbeats (r(2) from 0.2 to 0.37, P<0.0005). Components of both our inertial reorientation and aerodynamic torque estimates correlated, significantly, with asymmetries in the activation profile of four flight muscles: the pectoralis, supracoracoideus, biceps brachii and extensor metacarpi radialis (r(2) from 0.27 to 0.45, P<0.005). Thus, avian flight maneuvers rely on production of asymmetries throughout the flight apparatus rather than in a specific set of control or turning muscles.

Planned Axial Reorientation Investigation on Sloshsat

NASA Technical Reports Server (NTRS)

Chato, David J.

2000-01-01

This paper details the design and logic of an experimental investigation to study axial reorientation in low gravity. The Sloshsat free-flyer is described. The planned axial reorientation experiments and test matrixes are presented. Existing analytical tools are discussed. Estimates for settling range from 64 to 1127 seconds. The planned experiments are modelled using computational fluid dynamics. These models show promise in reducing settling estimates and demonstrate the ability of pulsed high thrust settling to emulate lower thrust continuous firing.

Using Neutron Diffraction to Investigate Texture Evolution During Consolidation of Deuterated Triaminotrinitrobenzene (d-TATB) Explosive Powder

DOE PAGES

Luscher, Darby J.; Yeager, John D.; Clausen, Bjørn; ...

2017-05-14

Triaminotrinitrobenzene (TATB) is a highly anisotropic molecular crystal used in several plastic-bonded explosive (PBX) formulations. A complete understanding of the orientation distribution of TATB particles throughout a PBX charge is required to understand spatially variable, anisotropic macroscale properties of the charge. Although texture of these materials can be measured after they have been subjected to mechanical or thermal loads, measuring texture evolution in situ is important in order to identify mechanisms of crystal deformation and reorientation used to better inform thermomechanical models. Neutron diffraction measurements were used to estimate crystallographic reorientation while deuterated TATB (d-TATB) powder was consolidated into amore » cylindrical pellet via a uniaxial die-pressing operation at room temperature. Both the final texture of the pressed pellet and the in situ evolution of texture during pressing were measured, showing that the d-TATB grains reorient such that (001) poles become preferentially aligned with the pressing direction. A compaction model is used to predict the evolution of texture in the pellet during the pressing process, finding that the original model overpredicted the texture strength compared to these measurements. The theory was extended to account for initial particle shape and pore space, bringing the results into good agreement with the data.« less

Using Neutron Diffraction to Investigate Texture Evolution During Consolidation of Deuterated Triaminotrinitrobenzene (d-TATB) Explosive Powder

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luscher, Darby J.; Yeager, John D.; Clausen, Bjørn

Triaminotrinitrobenzene (TATB) is a highly anisotropic molecular crystal used in several plastic-bonded explosive (PBX) formulations. A complete understanding of the orientation distribution of TATB particles throughout a PBX charge is required to understand spatially variable, anisotropic macroscale properties of the charge. Although texture of these materials can be measured after they have been subjected to mechanical or thermal loads, measuring texture evolution in situ is important in order to identify mechanisms of crystal deformation and reorientation used to better inform thermomechanical models. Neutron diffraction measurements were used to estimate crystallographic reorientation while deuterated TATB (d-TATB) powder was consolidated into amore » cylindrical pellet via a uniaxial die-pressing operation at room temperature. Both the final texture of the pressed pellet and the in situ evolution of texture during pressing were measured, showing that the d-TATB grains reorient such that (001) poles become preferentially aligned with the pressing direction. A compaction model is used to predict the evolution of texture in the pellet during the pressing process, finding that the original model overpredicted the texture strength compared to these measurements. The theory was extended to account for initial particle shape and pore space, bringing the results into good agreement with the data.« less

Towards Ultra-High Resolution Fibre Tract Mapping of the Human Brain – Registration of Polarised Light Images and Reorientation of Fibre Vectors

PubMed Central

Palm, Christoph; Axer, Markus; Gräßel, David; Dammers, Jürgen; Lindemeyer, Johannes; Zilles, Karl; Pietrzyk, Uwe; Amunts, Katrin

2009-01-01

Polarised light imaging (PLI) utilises the birefringence of the myelin sheaths in order to visualise the orientation of nerve fibres in microtome sections of adult human post-mortem brains at ultra-high spatial resolution. The preparation of post-mortem brains for PLI involves fixation, freezing and cutting into 100-μm-thick sections. Hence, geometrical distortions of histological sections are inevitable and have to be removed for 3D reconstruction and subsequent fibre tracking. We here present a processing pipeline for 3D reconstruction of these sections using PLI derived multimodal images of post-mortem brains. Blockface images of the brains were obtained during cutting; they serve as reference data for alignment and elimination of distortion artefacts. In addition to the spatial image transformation, fibre orientation vectors were reoriented using the transformation fields, which consider both affine and subsequent non-linear registration. The application of this registration and reorientation approach results in a smooth fibre vector field, which reflects brain morphology. PLI combined with 3D reconstruction and fibre tracking is a powerful tool for human brain mapping. It can also serve as an independent method for evaluating in vivo fibre tractography. PMID:20461231

Structure and dynamics of water in nonionic reverse micelles: a combined time-resolved infrared and small angle x-ray scattering study.

PubMed

van der Loop, Tibert H; Panman, Matthijs R; Lotze, Stephan; Zhang, Jing; Vad, Thomas; Bakker, Huib J; Sager, Wiebke F C; Woutersen, Sander

2012-07-28

We study the structure and reorientation dynamics of nanometer-sized water droplets inside nonionic reverse micelles (water/Igepal-CO-520/cyclohexane) with time-resolved mid-infrared pump-probe spectroscopy and small angle x-ray scattering. In the time-resolved experiments, we probe the vibrational and orientational dynamics of the O-D bonds of dilute HDO:H(2)O mixtures in Igepal reverse micelles as a function of temperature and micelle size. We find that even small micelles contain a large fraction of water that reorients at the same rate as water in the bulk, which indicates that the polyethylene oxide chains of the surfactant do not penetrate into the water volume. We also observe that the confinement affects the reorientation dynamics of only the first hydration layer. From the temperature dependent surface-water dynamics, we estimate an activation enthalpy for reorientation of 45 ± 9 kJ mol(-1) (11 ± 2 kcal mol(-1)), which is close to the activation energy of the reorientation of water molecules in ice.

Water dynamics in large and small reverse micelles: From two ensembles to collective behavior

PubMed Central

Moilanen, David E.; Fenn, Emily E.; Wong, Daryl; Fayer, Michael D.

2009-01-01

The dynamics of water in Aerosol-OT reverse micelles are investigated with ultrafast infrared spectroscopy of the hydroxyl stretch. In large reverse micelles, the dynamics of water are separable into two ensembles: slow interfacial water and bulklike core water. As the reverse micelle size decreases, the slowing effect of the interface and the collective nature of water reorientation begin to slow the dynamics of the core water molecules. In the smallest reverse micelles, these effects dominate and all water molecules have the same long time reorientational dynamics. To understand and characterize the transition in the water dynamics from two ensembles to collective reorientation, polarization and frequency selective infrared pump-probe experiments are conducted on the complete range of reverse micelle sizes from a diameter of 1.6–20 nm. The crossover between two ensemble and collective reorientation occurs near a reverse micelle diameter of 4 nm. Below this size, the small number of confined water molecules and structural changes in the reverse micelle interface leads to homogeneous long time reorientation. PMID:19586114

Are we ready for sexual reorientation therapy in the U.S. military? A response to David W. Lutz.

PubMed

Hierholzer, Robert

2004-01-01

In his paper "The Catholic Church, the American Military, and Homosexual Reorientation Therapy," David W. Lutz ultimately concludes that it is "appropriate, and highly ethical" for the American military to offer reorientation therapy to help homosexuals overcome "the vice of sodomy." The major thrust of his paper, however, is to call for abandonment of the "Don't Ask/Don't Tell" policy currently in place in the military. Lutz's paper covers much ground, and this review begins by examining whether such a wide view is necessary for the ultimate conclusions. It goes on to ask whether Lutz has omitted to mention important considerations bearing on this issue, and whether Lutz's call for the introduction of reorientation therapy is a serious call or a symbolic response to homosexual activities. Lutz fails to address essential issues such as the actual experiences of other nations having homosexuals in the military, and issues regarding what constitutes "reorientation therapy," the latter leading to questions about how such a therapy would actually be implemented.

Optical spectroscopic study of multiferroic BiFeO3 and LuFe2O4

NASA Astrophysics Data System (ADS)

Xu, Xiaoshan

2010-03-01

Iron-based multiferroics such as BiFeO3 and LuFe2O4 exhibit the highest magnetic and ferroelectric ordering temperatures among known multiferroics. LuFe2O4 is a frustrated system with several phase transitions that result in electronically driven multiferroicity. To understand how this peculiar multiferroic mechanism correlates with magnetism, we studied electronic excitations by optical spectroscopy and other complementary techniques. We show that the charge order, which determines the dielectric properties, is due to the ``order by fluctuation'' mechanism, evidenced by the onset of charge fluctuation well below the charge ordering transition. We also find a low temperature monoclinic distortion driven by both temperature and magnetic field, indicating strong coupling between structure, magnetism and charge order. BiFeO3 is the only known single phase multiferroics with room temperature magnetism and ferroelectricity. To investigate the spin-charge coupling, we measured the optical properties of BiFeO3. We find that the absorption onset occurs due to on-site Fe^3+ excitations at 1.41 and 1.90 eV. Temperature and magnetic-field-induced spectral changes reveal complex interactions between on-site crystal-field and magnetic excitations in the form of magnon sidebands. The sensitivity of the magnon sidebands allows us to map out the magnetic-field temperature phase diagram which demonstrates optical evidence for spin spiral quenching above 20 T and suggests a spin domain reorientation near 10 T. Work done in collaboration with T.V. Brinzari, R.C. Rai, M. Angst, R.P. Hermann, A.D. Christianson, J.-W. Kim, Z. Islam, B.C. Sales, D. Mandrus, S. Lee, Y.H. Chu, L. W. Martin, A. Kumar, R. Ramesh, S.W. Cheong, S. McGill, and J.L. Musfeldt.

Distributions of spin/shape parameters of asteroid families and targeted photometry by ProjectSoft robotic observatory

NASA Astrophysics Data System (ADS)

Broz, Miroslav; Durech, Josef; Hanus, Josef; Lehky, Martin

2014-11-01

In our recent work (Hanus et al. 2013) we studied dynamics of asteroid families constrained by the distribution of pole latitudes vs semimajor axis. The model contained the following ingredients: (i) the Yarkovsky semimajor-axis drift, (ii) secular spin evolution due to the YORP effect, (iii) collisional reorientations, (iv) a simple treatment of spin-orbit resonances and (v) of mass shedding.We suggest to use a different complementary approach, based on distribution functions of shape parameters. Based on ~1000 old and new convex-hull shape models, we construct the distributions of suitable quantities (ellipticity, normalized facet areas, etc.) and we discuss differences among asteroid populations. We also check for outlier points which may then serve as a possible identification of (large) interlopers among "real" family members.This has also implications for SPH models of asteroid disruptions which can be possibly further constrained by the shape models of resulting fragments. Up to now, the observed size-frequency distribution and velocity field were used as constraints, sometimes allowing for a removal of interlopers (Michel et al. 2011).We also describe ongoing observations by the ProjectSoft robotic observatory called "Blue Eye 600", which supports our efforts to complete the sample of shapes for a substantial fraction of (large) family members. Dense photometry is targeted in such a way to maximize a possibility to derive a new pole/shape model.Other possible applications of the observatory include: (i) fast resolved observations of fireballs (thanks to a fast-motion capability, up to 90 degrees/second), or (ii) an automatic survey of a particular population of objects (MBAs, NEAs, variable stars, novae etc.)Acknowledgements: This work was supported by the Technology Agency of the Czech Republic (grant no. TA03011171) and Czech Science Foundation (grant no. 13-01308S).

Asteroid families spin and shape models to be supported by the ProjectSoft robotic observatory

NASA Astrophysics Data System (ADS)

Brož, M.; Ďurech, J.; Hanuš, J.; Lehký, M.

2014-07-01

In our recent work (Hanuš et al. 2013), we studied dynamics of asteroid families constrained by the distribution of pole latitudes vs semimajor axis. The model contained the following ingredients: (i) the Yarkovsky semimajor-axis drift; (ii) secular spin evolution due to the YORP effect; (iii) collisional re-orientations; (iv) a simple treatment of spin-orbit resonances; and (v) of mass shedding. We suggest to use a different complementary approach, based on distribution functions of shape parameters. Based on ˜1000 old and new convex-hull shape models, we construct the distributions of suitable quantities (ellipticity, normalized facet areas, etc.) and we discuss a significance of differences among asteroid populations. We check for outlier points which may then serve as a possible identification of (large) interlopers among ''real'' family members. This has also implications for SPH models of asteroid disruptions which can be possibly further constrained by the shape models of resulting fragments. Up to now, the observed size-frequency distribution and velocity field were used as constraints, sometimes allowing for a removal of interlopers (Michel et al. 2011). We also outline an ongoing construction of the ProjectSoft robotic observatory called ''Blue Eye 600'', which will support our efforts to complete the sample of shapes for a substantial fraction of (large) family members. Dense photometry will be targeted in such a way to maximize a possibility to derive a new pole/shape model. Other possible applications of the observatory include: (i) fast resolved observations of fireballs (thanks to a fast-motion capability, tens of degrees per second); or, (ii) an automatic survey of a particular population of objects (main-belt and near-Earth asteroids, variable stars, novae etc.)

Picosecond Dynamics of Excitonic Magnetic Polarons in Colloidal Diffusion-Doped Cd(1-x)Mn(x)Se Quantum Dots.

PubMed

Nelson, Heidi D; Bradshaw, Liam R; Barrows, Charles J; Vlaskin, Vladimir A; Gamelin, Daniel R

2015-11-24

Spontaneous magnetization is observed at zero magnetic field in photoexcited colloidal Cd(1-x)Mn(x)Se (x = 0.13) quantum dots (QDs) prepared by diffusion doping, reflecting strong Mn(2+)-exciton exchange coupling. The picosecond dynamics of this phenomenon, known as an excitonic magnetic polaron (EMP), are examined using a combination of time-resolved photoluminescence, magneto-photoluminescence, and Faraday rotation (TRFR) spectroscopies, in conjunction with continuous-wave absorption, magnetic circular dichroism (MCD), and magnetic circularly polarized photoluminescence (MCPL) spectroscopies. The data indicate that EMPs form with random magnetization orientations at zero external field, but their formation can be directed by an external magnetic field. After formation, however, external magnetic fields are unable to reorient the EMPs within the luminescence lifetime, implicating anisotropy in the EMP potential-energy surfaces. TRFR measurements in a transverse magnetic field reveal rapid (<5 ps) spin transfer from excitons to Mn(2+) followed by coherent EMP precession at the Mn(2+) Larmor frequency for over a nanosecond. A dynamical TRFR phase inversion is observed during EMP formation attributed to the large shifts in excitonic absorption energies during spontaneous magnetization. Partial optical orientation of the EMPs by resonant circularly polarized photoexcitation is also demonstrated. Collectively, these results highlight the extraordinary physical properties of colloidal diffusion-doped Cd(1-x)Mn(x)Se QDs that result from their unique combination of strong quantum confinement, large Mn(2+) concentrations, and relatively narrow size distributions. The insights gained from these measurements advance our understanding of spin dynamics and magnetic exchange in colloidal doped semiconductor nanostructures, with potential ramifications for future spin-based information technologies.

Spin relaxation 1/f noise in graphene

NASA Astrophysics Data System (ADS)

Omar, S.; Guimarães, M. H. D.; Kaverzin, A.; van Wees, B. J.; Vera-Marun, I. J.

2017-02-01

We report the first measurement of 1/f type noise associated with electronic spin transport, using single layer graphene as a prototypical material with a large and tunable Hooge parameter. We identify the presence of two contributions to the measured spin-dependent noise: contact polarization noise from the ferromagnetic electrodes, which can be filtered out using the cross-correlation method, and the noise originated from the spin relaxation processes. The noise magnitude for spin and charge transport differs by three orders of magnitude, implying different scattering mechanisms for the 1/f fluctuations in the charge and spin transport processes. A modulation of the spin-dependent noise magnitude by changing the spin relaxation length and time indicates that the spin-flip processes dominate the spin-dependent noise.

DOE Office of Scientific and Technical Information (OSTI.GOV)

de Miguel, E.; Rull, L.F.; Gubbins, K.E.

Using molecular-dynamics computer simulation, we study the dynamical behavior of the isotropic and nematic phases of highly anisotropic molecular fluids. The interactions are modeled by means of the Gay-Berne potential with anisotropy parameters {kappa}=3 and {kappa}{prime}=5. The linear-velocity autocorrelation function shows no evidence of a negative region in the isotropic phase, even at the higher densities considered. The self-diffusion coefficient parallel to the molecular axis shows an anomalous increase with density as the system enters the nematic region. This enhancement in parallel diffusion is also observed in the isotropic side of the transition as a precursor effect. The molecular reorientationmore » is discussed in the light of different theoretical models. The Debye diffusion model appears to explain the reorientational mechanism in the nematic phase. None of the models gives a satisfactory account of the reorientation process in the isotropic phase.« less

Global-scale tectonic patterns on Pluto

NASA Astrophysics Data System (ADS)

Matsuyama, I.; Keane, J. T.; Kamata, S.

2016-12-01

The New Horizons spacecraft revealed a global-scale tectonic pattern on the surface of Pluto which is presumably related to its formation and early evolution. Changes in the rotational and tidal potentials, expansion, and loading can generate stresses capable of producing global-scale tectonic patterns. The current alignment of Sputnik Planum with the tidal axis suggests a reorientation of Pluto relative to the rotation and tidal axes, or true polar wander. This reorientation can be driven by mass loading associated with Sputnik Planum. We developed a general theoretical formalism for the calculation of tectonic patterns due to a variety of process including true polar wander, loading, and expansion. The formalism is general enough to be applicable to non-axisymmetric loads. We illustrate that the observed global-scale tectonic pattern can be explained by stresses generated by true polar wander, Sputnik Planum loading, and expansion.

Computational prediction of propellant reorientation

NASA Technical Reports Server (NTRS)

Hochstein, John I.

1987-01-01

Viewgraphs from a presentation on computational prediction of propellant reorientation are given. Information is given on code verification, test conditions, predictions for a one-quarter scale cryogenic tank, pulsed settling, and preliminary results.

Time-dependent solution for reorientation of rotating tidally deformed visco-elastic bodies

NASA Astrophysics Data System (ADS)

Hu, Haiyang; van der Wal, Wouter; Vermeersen, Bert

2017-04-01

Many icy satellites or planets contain features which suggest a (past) reorientation of the body, such as the tiger stripes on Enceladus and the heart-shaped Sputnik Planum on Pluto. Most of these icy bodies are tidally locked and this creates a large tidal bulge which is about three times of its centrifugal (equatorial) bulge. To study the reorientation of such rotating tidally deformed body is complicated and most previous studies apply the so-called fluid limit method. The fluid limit approach ignores the viscous response of the body and assumes that it immediately reaches its fluid limit when simulating the reorientation due to a changing load. As a result, this method can only simulate cases when the change in the load is much slower than the dominant viscous modes of the body. For other kinds of load, for instance, a Heaviside load due to an impact which creates an instant relocation of mass, it does not give us a prediction of how the reorientation is accomplished (e.g. How fast? Along which path?). We establish a new method which can give an accurate time-dependent solution for reorientation of rotating tidally deformed bodies. Our method can be applied both semi-analytically or numerically (with finite element method) to include features such as lateral heterogeneity or non-linear material. We also present an extension of our method to simulate the effect of a fossil bulge. With our method, we show that reorientation of a tidally deformed body driven by a positive mass anomaly near the poles has a preference for rotating around the tidal axis instead of towards it, contrary to predictions in previous studies. References Hu, H., W. van der Wal and L.L.A. Vermeersen (2017). A numerical method for reorientation of rotating tidally deformed visco-elastic bodies. Journal of Geophysical Research: Planets, doi:10.1002/2016JE005114, 2016JE005114. Matsuyama, I. and Nimmo, F. (2007). Rotational stability of tidally deformed planetary bodies. Journal of Geophysical Research: Planets, 112(E11).

Negative magnetization and the sign reversal of exchange bias field in Co(Cr1-xMnx)2O4 (0≤x≤0.6)

NASA Astrophysics Data System (ADS)

Li, Canglong; Yan, Tengyun; Chakrabarti, Chiranjib; Zhang, Run; Chen, Xinghan; Fu, Qingshan; Yuan, Songliu; Barasa, Godfrey Okumu

2018-03-01

A series of Co(Cr1-xMnx)2O4 (0 ≤ x ≤ 0.6) ceramic samples have been synthesized by using the sol-gel method. The magnetic properties of the ceramics are experimentally studied through different protocols of dc magnetization measurements. It is found that Mn-doping continuously decreases the total magnetization for x in the range of 0 ≤ x ≤ 0.2 and the net magnetization becomes negative in the range of 0.3 ≤ x ≤ 0.5. The net magnetization reverses and becomes positive upon further increasing x to 0.6. This unusual magnetic phenomenon in the system for x = 0.3-0.5 can be called as negative magnetization. It is regarded as arising from the competition of the two magnetic sublattices at different crystallographic sites. For the sample x = 0.3, the magnetic switching effect near the compensation temperature Tcomp has been studied, and it shows potential applications in the spintronic devices. The magnetic configuration of the sample could be changed under a high magnetic field, and the spin is reoriented at TSR. Both positive and negative exchange bias effects are observed, which are ascribed to the pinning force of uncompensated spins on ferromagnetic moments and the magneto-structural transition, respectively.

Giant Controllable Magnetization Changes Induced by Structural Phase Transitions in a Metamagnetic Artificial Multiferroic

PubMed Central

Bennett, S. P.; Wong, A. T.; Glavic, A.; Herklotz, A.; Urban, C.; Valmianski, I.; Biegalski, M. D.; Christen, H. M.; Ward, T. Z.; Lauter, V.

2016-01-01

The realization of a controllable metamagnetic transition from AFM to FM ordering would open the door to a plethora of new spintronics based devices that, rather than reorienting spins in a ferromagnet, harness direct control of a materials intrinsic magnetic ordering. In this study FeRh films with drastically reduced transition temperatures and a large magneto-thermal hysteresis were produced for magnetocaloric and spintronics applications. Remarkably, giant controllable magnetization changes (measured to be as high has ~25%) are realized by manipulating the strain transfer from the external lattice when subjected to two structural phase transitions of BaTiO3 (001) single crystal substrate. These magnetization changes are the largest seen to date to be controllably induced in the FeRh system. Using polarized neutron reflectometry we reveal how just a slight in plane surface strain change at ~290C results in a massive magnetic transformation in the bottom half of the film clearly demonstrating a strong lattice-spin coupling in FeRh. By means of these substrate induced strain changes we show a way to reproducibly explore the effects of temperature and strain on the relative stabilities of the FM and AFM phases in multi-domain metamagnetic systems. This study also demonstrates for the first time the depth dependent nature of a controllable magnetic order using strain in an artificial multiferroic heterostructure. PMID:26940159

Giant Controllable Magnetization Changes Induced by Structural Phase Transitions in a Metamagnetic Artificial Multiferroic

DOE PAGES

Bennett, S. P.; Wong, A. T.; Glavic, A.; ...

2016-03-04

We realize that a controllable metamagnetic transition from AFM to FM ordering would open the door to a plethora of new spintronics based devices that, rather than reorienting spins in a ferromagnet, harness direct control of a materials intrinsic magnetic ordering. In this study FeRh films with drastically reduced transition temperatures and a large magneto-thermal hysteresis were produced for magnetocaloric and spintronics applications. Remarkably, giant controllable magnetization changes (measured to be as high has ~25%) are realized and by manipulating the strain transfer from the external lattice when subjected to two structural phase transitions of BaTiO3 (001) single crystal substrate.more » These magnetization changes are the largest seen to date to be controllably induced in the FeRh system. Using polarized neutron reflectometry we reveal how just a slight in plane surface strain change at ~290C results in a massive magnetic transformation in the bottom half of the film clearly demonstrating a strong lattice-spin coupling in FeRh. By means of these substrate induced strain changes we show a way to reproducibly explore the effects of temperature and strain on the relative stabilities of the FM and AFM phases in multi-domain metamagnetic systems. In our study also demonstrates for the first time the depth dependent nature of a controllable magnetic order using strain in an artificial multiferroic heterostructure.« less

Origin of Magnetic Lineations on Mars

NASA Technical Reports Server (NTRS)

Grimm, Robert E.

2002-01-01

The magnetic lineations discovered by MGS (Mars Global Surveyor) have been considered to be evidence of early plate tectonics on Mars. However, the lineations approximately follow lines of latitude, i.e., small circles. This presents significant geometrical problems for plate-like spreading, particularly at high latitudes. However, the sublatitudinal orientation of the lineations is consistent with meridianal extension and perhaps limited crustal spreading due to a stress event centered near the geographic pole. We hypothesize that this event was the early formation of the crustal dichotomy through mantle-convective processes. This could have taken the form of a southern megaplume that formed the thick highlands crust or as subduction or downwelling in the north. Both would result in tensional stresses in the south that would form extensional fractures perpendicular to the CM-CF (center-of-mass/center-of-gravity) offset. The observed magnitude and distribution of magnetization indicates that crustal intrusion associated with this major mantle-convective event resulted in approximately 1000 km of extension in the Southern highlands. Subsequent spin-axis reorientation due to loss of crust in the north or gain of crust in the south brought the CM-CF offset into its present N-S alignment. A portion of the ancient valley networks observed in the southern highlands are spatially associated with crustal magnetism and are quantitatively shown to be consistent with hydrothermal discharge over crustal intrusions.

ATP-dependent Conformational Changes Trigger Substrate Capture and Release by an ECF-type Biotin Transporter.

PubMed

Finkenwirth, Friedrich; Sippach, Michael; Landmesser, Heidi; Kirsch, Franziska; Ogienko, Anastasia; Grunzel, Miriam; Kiesler, Cornelia; Steinhoff, Heinz-Jürgen; Schneider, Erwin; Eitinger, Thomas

2015-07-03

Energy-coupling factor (ECF) transporters for vitamins and metal ions in prokaryotes consist of two ATP-binding cassette-type ATPases, a substrate-specific transmembrane protein (S component) and a transmembrane protein (T component) that physically interacts with the ATPases and the S component. The mechanism of ECF transporters was analyzed upon reconstitution of a bacterial biotin transporter into phospholipid bilayer nanodiscs. ATPase activity was not stimulated by biotin and was only moderately reduced by vanadate. A non-hydrolyzable ATP analog was a competitive inhibitor. As evidenced by cross-linking of monocysteine variants and by site-specific spin labeling of the Q-helix followed by EPR-based interspin distance analyses, closure and reopening of the ATPase dimer (BioM2) was a consequence of ATP binding and hydrolysis, respectively. A previously suggested role of a stretch of small hydrophobic amino acid residues within the first transmembrane segment of the S units for S unit/T unit interactions was structurally and functionally confirmed for the biotin transporter. Cross-linking of this segment in BioY (S) using homobifunctional thiol-reactive reagents to a coupling helix of BioN (T) indicated a reorientation rather than a disruption of the BioY/BioN interface during catalysis. Fluorescence emission of BioY labeled with an environmentally sensitive fluorophore was compatible with an ATP-induced reorientation and consistent with a hypothesized toppling mechanism. As demonstrated by [(3)H]biotin capture assays, ATP binding stimulated substrate capture by the transporter, and subsequent ATP hydrolysis led to substrate release. Our study represents the first experimental insight into the individual steps during the catalytic cycle of an ECF transporter in a lipid environment. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

ATP-dependent Conformational Changes Trigger Substrate Capture and Release by an ECF-type Biotin Transporter*

PubMed Central

Finkenwirth, Friedrich; Sippach, Michael; Landmesser, Heidi; Kirsch, Franziska; Ogienko, Anastasia; Grunzel, Miriam; Kiesler, Cornelia; Steinhoff, Heinz-Jürgen; Schneider, Erwin; Eitinger, Thomas

2015-01-01

Energy-coupling factor (ECF) transporters for vitamins and metal ions in prokaryotes consist of two ATP-binding cassette-type ATPases, a substrate-specific transmembrane protein (S component) and a transmembrane protein (T component) that physically interacts with the ATPases and the S component. The mechanism of ECF transporters was analyzed upon reconstitution of a bacterial biotin transporter into phospholipid bilayer nanodiscs. ATPase activity was not stimulated by biotin and was only moderately reduced by vanadate. A non-hydrolyzable ATP analog was a competitive inhibitor. As evidenced by cross-linking of monocysteine variants and by site-specific spin labeling of the Q-helix followed by EPR-based interspin distance analyses, closure and reopening of the ATPase dimer (BioM2) was a consequence of ATP binding and hydrolysis, respectively. A previously suggested role of a stretch of small hydrophobic amino acid residues within the first transmembrane segment of the S units for S unit/T unit interactions was structurally and functionally confirmed for the biotin transporter. Cross-linking of this segment in BioY (S) using homobifunctional thiol-reactive reagents to a coupling helix of BioN (T) indicated a reorientation rather than a disruption of the BioY/BioN interface during catalysis. Fluorescence emission of BioY labeled with an environmentally sensitive fluorophore was compatible with an ATP-induced reorientation and consistent with a hypothesized toppling mechanism. As demonstrated by [3H]biotin capture assays, ATP binding stimulated substrate capture by the transporter, and subsequent ATP hydrolysis led to substrate release. Our study represents the first experimental insight into the individual steps during the catalytic cycle of an ECF transporter in a lipid environment. PMID:25991724

Shifting attention in viewer- and object-based reference frames after unilateral brain injury.

PubMed

List, Alexandra; Landau, Ayelet N; Brooks, Joseph L; Flevaris, Anastasia V; Fortenbaugh, Francesca C; Esterman, Michael; Van Vleet, Thomas M; Albrecht, Alice R; Alvarez, Bryan D; Robertson, Lynn C; Schendel, Krista

2011-06-01

The aims of the present study were to investigate the respective roles that object- and viewer-based reference frames play in reorienting visual attention, and to assess their influence after unilateral brain injury. To do so, we studied 16 right hemisphere injured (RHI) and 13 left hemisphere injured (LHI) patients. We used a cueing design that manipulates the location of cues and targets relative to a display comprised of two rectangles (i.e., objects). Unlike previous studies with patients, we presented all cues at midline rather than in the left or right visual fields. Thus, in the critical conditions in which targets were presented laterally, reorienting of attention was always from a midline cue. Performance was measured for lateralized target detection as a function of viewer-based (contra- and ipsilesional sides) and object-based (requiring reorienting within or between objects) reference frames. As expected, contralesional detection was slower than ipsilesional detection for the patients. More importantly, objects influenced target detection differently in the contralesional and ipsilesional fields. Contralesionally, reorienting to a target within the cued object took longer than reorienting to a target in the same location but in the uncued object. This finding is consistent with object-based neglect. Ipsilesionally, the means were in the opposite direction. Furthermore, no significant difference was found in object-based influences between the patient groups (RHI vs. LHI). These findings are discussed in the context of reference frames used in reorienting attention for target detection. Published by Elsevier Ltd.

Reorientation and Swimming Stability in Sea Urchin Larvae

NASA Astrophysics Data System (ADS)

Wheeler, J.; Chan, K. Y. K.; Anderson, E.; Helfrich, K. R.; Mullineaux, L. S.; Sengupta, A.; Stocker, R.

2016-02-01

Many benthic marine invertebrates have two-phase life histories, relying on planktonic larval stages for dispersal and exchange of individuals between adult populations. The dispersal of planktonic larvae is determined by two factors: passive advection by the ambient flow and active motility. By modifying dispersal and ultimately settlement, larval motility influences where and when individuals recruit into benthic communities. Despite its ecological relevance, our understanding of larval motility and behavior in the plankton remains limited, especially regarding the interactions of larval motility and ambient turbulence. As most larvae are smaller than the Kolmogorov scale, they experience ocean turbulence in part as a time-changing viscous torque produced by local fluid shear. This torque causes larval reorientation, impacting swimming direction and potentially dispersal at the macroscale. It is therefore paramount to understand the mechanisms of larval reorientation and the stability of larvae against reorientation. Here we report on the larval reorientation behavior of the sea urchins Arbacia punctulata and Heliocidaris crassispina. Both species have life histories characterized by ontogenetic changes to internal density structure and morphology, which we hypothesized to impact stability. To test this hypothesis, we performed "flip chamber" experiments, in which larvae swim freely in a small chamber that is intermittently inverted, mimicking the overturning experienced by larvae in turbulence. We investigated the role of larval age, body size, species, morphology (number of arms), and motility (live versus dead) on the reorientation dynamics. Our work contributes to a more mechanistic understanding of the role of hydrodynamics in the motility and transport of planktonic larvae.

Change to Open Education. Two Schools in the Process.

ERIC Educational Resources Information Center

Orton, Peter; Dickison, Wayne

Case studies describe attempts to develop educational forms that are personally, intellectually, and socially valid in two Massachusetts elementary schools--the Charles River School, a small private school in Dover; and the Parmenter School, a public school. Both schools have tried to reorient the first six or seven years of formal education along…

Sports and Physical Education in American High Schools: Some Historical Reflections.

ERIC Educational Resources Information Center

O'Hanlon, Timothy P.

Public schooling was restructured and reoriented in fundamental ways during the decades immediately preceding the First World War. Schools were engaged in the process of preparing people for specialized work roles, but reformers were also concerned that the schools inculcate common social values. A wide range of extracurricular activities was…

Intercultural and Media Literacy: Global Tendencies in Metacontent of Teacher Education in Latvia

ERIC Educational Resources Information Center

Belousa, Inga; Stakle, Alnis

2010-01-01

Under the influence of processes of globalisation, higher education in the countries of Europe, including Latvia, has been reshaped, restructured, re-evaluated and reoriented towards the establishment of a European higher education area. New issues have emerged at both the content and metacontent level, the most significant of which are…

Design Criteria for Visual Cues Used in Disruptive Learning Interventions within Sustainability Education

ERIC Educational Resources Information Center

Tillmanns, Tanja; Holland, Charlotte; Filho, Alfredo Salomão

2017-01-01

This paper presents the design criteria for Visual Cues--visual stimuli that are used in combination with other pedagogical processes and tools in Disruptive Learning interventions in sustainability education--to disrupt learners' existing frames of mind and help re-orient learners' mind-sets towards sustainability. The theory of Disruptive…

Higher Romanian Education Post-Bologna: Required Changes, Instruments and Ethical Issues

ERIC Educational Resources Information Center

Petrisor, Alexandru-Ionut

2011-01-01

In 1999 Romania became part of the Bologna process, focused on the European Credit Transfer and Accumulation System, design to increase the compatibility of European universities, ensuring the mobility of students and professors in the context of re-orienting education to the formation of competences continuously adapted to market requirements.…

Organization of cortical microtubules in graviresponding maize roots

NASA Technical Reports Server (NTRS)

Blancaflor, E. B.; Hasenstein, K. H.

1993-01-01

Immunofluorescence labeling of cortical microtubules (MTs) was used to investigate the relationship between MT arrangement and changes in growth rate of the upper and lower sides of horizontally placed roots of maize (Zea mays L. cv. Merit). Cap cells and cells of the elongation zone of roots grown vertically in light or darkness showed MT arrangements that were transverse (perpendicular) to the growth direction. Microtubules of cells basal to the elongation zone typically showed oblique orientation. Two hours after horizontal reorientation, cap cells of gravicompetent, light-grown and curving roots contained MTs parallel to the gravity vector. The MT arrangement on the upper side of the elongation zone remained transverse but the MTs of the outer four to five layers of cortical cells along the lower side of the elongation zone showed reorientation parallel to the axis of the root. The MTs of the lower epidermis retained their transverse orientation. Dark-grown roots did not curve and did not show reorientation of MTs in cells of the root cap or elongation zone. The data indicate that MT depolymerization and reorientation is correlated with reduction in growth rate, and that MT reorientation is one of the steps of growth control of graviresponding roots.

Free energy barrier for melittin reorientation from a membrane-bound state to a transmembrane state.

PubMed

Irudayam, Sheeba J; Pobandt, Tobias; Berkowitz, Max L

2013-10-31

An important step in a phospholipid membrane pore formation by melittin antimicrobial peptide is a reorientation of the peptide from a surface into a transmembrane conformation. Experiments measure the fraction of peptides in the surface state and the transmembrane state, but no computational study exists that quantifies the free energy curve for the reorientation. In this work we perform umbrella sampling simulations to calculate the potential of mean force (PMF) for the reorientation of melittin from a surface-bound state to a transmembrane state and provide a molecular level insight in understanding the peptide-lipid properties that influence the existence of the free energy barrier. The PMFs were calculated for a peptide to lipid (P/L) ratio of 1/128 and 4/128. We observe that the free energy barrier is reduced when the P/L ratio increases. In addition, we study the cooperative effect; specifically we investigate if the reorientation barrier is smaller for a second melittin, given that another neighboring melittin was already in the transmembrane orientation. We observe that indeed the barrier of the PMF curve is reduced in this case, thus confirming the presence of a cooperative effect.

One and two-phonon processes of the spin-flip relaxation in quantum dots: Spin-phonon coupling mechanism

NASA Astrophysics Data System (ADS)

Wang, Zi-Wu; Li, Shu-Shen

2012-07-01

We investigate the spin-flip relaxation in quantum dots using a non-radiation transition approach based on the descriptions for the electron-phonon deformation potential and Fröhlich interaction in the Pavlov-Firsov spin-phonon Hamiltonian. We give the comparisons of the electron relaxations with and without spin-flip assisted by one and two-phonon processes. Calculations are performed for the dependence of the relaxation time on the external magnetic field, the temperature and the energy separation between the Zeeman sublevels of the ground and first-excited state. We find that the electron relaxation time of the spin-flip process is more longer by three orders of magnitudes than that of no spin-flip process.

Inferior parietal and right frontal contributions to trial-by-trial adaptations of attention to memory.

PubMed

Kizilirmak, Jasmin M; Rösler, Frank; Bien, Siegfried; Khader, Patrick H

2015-07-21

The attention to memory theory (AtoM) proposes that the same brain regions might be involved in selective processing of perceived stimuli (selective attention) and memory representations (selective retrieval). Although this idea is compelling, given consistently found neural overlap between perceiving and remembering stimuli, recent comparisons brought evidence for overlap as well as considerable differences. Here, we present a paradigm that enables the investigation of the AtoM hypothesis from a novel perspective to gain further insight into the neural resources involved in AtoM. Selective attention in perception is often investigated as a control process that shows lingering effects on immediately following trials. Here, we employed a paradigm capable of modulating selective retrieval in a similarly dynamic manner as in such selective-attention paradigms by inducing trial-to-trial shifts between relevant and irrelevant memory representations as well as changes of the width of the internal focus on memory. We found evidence for an involvement of bilateral inferior parietal lobe and right inferior frontal gyrus in reorienting the attentional focus on previously accessed memory representations. Moreover, we could dissociate the right inferior from the parietal activation in separate contrasts, suggesting that the right inferior frontal gyrus plays a role in facilitating attentional reorienting to memory representations when competing representations have been activated in the preceding trial, potentially by resolving this competition. Our results support the AtoM theory, i.e. that ventral frontal and parietal regions are involved in automatic attentional reorienting in memory, and highlight the importance of further investigations of the overlap and differences between regions involved in internal (memory) and external (perceptual) attentional selection. Copyright © 2015 Elsevier B.V. All rights reserved.

Building health promotion capacity in a primary health care workforce in the Northern Territory: some lessons from practice.

PubMed

Judd, Jenni; Keleher, Helen

2013-12-01

Reorientation of the workforce in primary health care is a complex process and requires specific strategies and interventions. Primary health care providers are a key health care workforce that is expected to deliver tangible outcomes from disease prevention and health promotion strategies. This paper describes a training intervention that occurred as part of a broader participatory action research process for building health promotion capacity in the primary health care workforce. Participatory action research (PAR) was conducted over six action and reflection cycles in a two-year period (2001-02) in an urban community health setting in the Northern Territory. One of the PAR cycles was a training intervention that was identified as a need from a survey in the first action and reflection cycle. This training was facilitated by a health promotion specialist, face-to-face and comprised five 3.5-h sessions over a 5-month period. A pre-post questionnaire was used to measure the knowledge and skills components of the training intervention. The results reinforced the importance of using a participatory approach that involved the primary health care providers themselves. Multiple strategies such as workforce development within capacity building frameworks assisted in shifting work practice more upstream. Additionally, these strategies encouraged more reflective practice and built social capital within the primary health care workforce. Lessons from practice reinforce that workforce development influenced work practice change and is an important element in building the health promotion capacity of primary health care centres. SO WHAT?: Workforce development is critical for reorienting health services. Health promotion specialists play an important role in reorienting practice, which is only effective when combined with other strategies, and driven and led by the primary health care workforce.

Liquid hydrogen slosh waves excited by constant reverse gravity acceleration of geyser initiation

NASA Technical Reports Server (NTRS)

Hung, R. J.; Shyu, K. L.; Lee, C. C.

1992-01-01

The requirement to settle or to position liquid fuel over the outlet end of the spacecraft propellant tank before main engine restart poses a microgravity fluid behavior problem. Resettlement or reorientation of liquid propellant can be accomplished by providing the optimal acceleration to the spacecraft such that the propellant is reoriented over the tank outlet. In this study slosh wave excitation induced by the resettling flowfield during the course of liquid reorientation with the initiation of geyser for liquid-filled levels of 30, 50, 65, 70, and 80 percent have been studied. Characteristics of slosh waves with various frequencies excited are discussed. Slosh wave excitations will affect the fluid stress distribution exerted on the container wall and shift the fluid mass distribution inside the container, which imposes the time-dependent variations in the moment of inertia of the container. This information is important for the spacecraft control during the course of liquid reorientation.

Ultrafast spin exchange-coupling torque via photo-excited charge-transfer processes

NASA Astrophysics Data System (ADS)

Ma, X.; Fang, F.; Li, Q.; Zhu, J.; Yang, Y.; Wu, Y. Z.; Zhao, H. B.; Lüpke, G.

2015-10-01

Optical control of spin is of central importance in the research of ultrafast spintronic devices utilizing spin dynamics at short time scales. Recently developed optical approaches such as ultrafast demagnetization, spin-transfer and spin-orbit torques open new pathways to manipulate spin through its interaction with photon, orbit, charge or phonon. However, these processes are limited by either the long thermal recovery time or the low-temperature requirement. Here we experimentally demonstrate ultrafast coherent spin precession via optical charge-transfer processes in the exchange-coupled Fe/CoO system at room temperature. The efficiency of spin precession excitation is significantly higher and the recovery time of the exchange-coupling torque is much shorter than for the demagnetization procedure, which is desirable for fast switching. The exchange coupling is a key issue in spin valves and tunnelling junctions, and hence our findings will help promote the development of exchange-coupled device concepts for ultrafast coherent spin manipulation.

The effect of memory in the stochastic master equation analyzed using the stochastic Liouville equation of motion. Electronic energy migration transfer between reorienting donor-donor, donor-acceptor chromophores

NASA Astrophysics Data System (ADS)

Håkansson, Pär; Westlund, Per-Olof

2005-01-01

This paper discusses the process of energy migration transfer within reorientating chromophores using the stochastic master equation (SME) and the stochastic Liouville equation (SLE) of motion. We have found that the SME over-estimates the rate of the energy migration compared to the SLE solution for a case of weakly interacting chromophores. This discrepancy between SME and SLE is caused by a memory effect occurring when fluctuations in the dipole-dipole Hamiltonian ( H( t)) are on the same timescale as the intrinsic fast transverse relaxation rate characterized by (1/ T2). Thus the timescale critical for energy-transfer experiments is T2≈10 -13 s. An extended SME is constructed, accounting for the memory effect of the dipole-dipole Hamiltonian dynamics. The influence of memory on the interpretation of experiments is discussed.

Large spin current injection in nano-pillar-based lateral spin valve

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nomura, Tatsuya; Ohnishi, Kohei; Kimura, Takashi, E-mail: t-kimu@phys.kyushu-u.ac.jp

We have investigated the influence of the injection of a large pure spin current on a magnetization process of a non-locally located ferromagnetic dot in nano-pillar-based lateral spin valves. Here, we prepared two kinds of the nano-pillar-type lateral spin valve based on Py nanodots and CoFeAl nanodots fabricated on a Cu film. In the Py/Cu lateral spin valve, although any significant change of the magnetization process of the Py nanodot has not been observed at room temperature. The magnetization reversal process is found to be modified by injecting a large pure spin current at 77 K. Switching the magnetization bymore » the nonlocal spin injection has also been demonstrated at 77 K. In the CoFeAl/Cu lateral spin valve, a room temperature spin valve signal was strongly enhanced from the Py/Cu lateral spin valve because of the highly spin-polarized CoFeAl electrodes. The room temperature nonlocal switching has been demonstrated in the CoFeAl/Cu lateral spin valve.« less

Spin Current Noise of the Spin Seebeck Effect and Spin Pumping

NASA Astrophysics Data System (ADS)

Matsuo, M.; Ohnuma, Y.; Kato, T.; Maekawa, S.

2018-01-01

We theoretically investigate the fluctuation of a pure spin current induced by the spin Seebeck effect and spin pumping in a normal-metal-(NM-)ferromagnet(FM) bilayer system. Starting with a simple ferromagnet-insulator-(FI-)NM interface model with both spin-conserving and non-spin-conserving processes, we derive general expressions of the spin current and the spin-current noise at the interface within second-order perturbation of the FI-NM coupling strength, and estimate them for a yttrium-iron-garnet-platinum interface. We show that the spin-current noise can be used to determine the effective spin carried by a magnon modified by the non-spin-conserving process at the interface. In addition, we show that it provides information on the effective spin of a magnon, heating at the interface under spin pumping, and spin Hall angle of the NM.

Rotational reorientation dynamics of Aerosol-OT reverse micelles formed in near-critical propane

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heitz, M.P.; Bright, F.V.

1996-06-01

The rotational reorientation kinetics of two fluorescent solutes (rhodamine 6G, R6G, and rhodamine 101, R101) have been determined in sodium bis(2-ethylhexyl) sulfosuccinate (Aerosol-OT, AOT) reverse micelles formed in liquid and near-critical propane. We show that the amount of water loading ([water]/[AOT], R), continuous phase density, and temperature all influence the solute rotational dynamics. In all cases, the decay of anisotropy data (i.e., frequency-dependent differential polarized phase angle and polarized modulation ratio) are well described by a bi-exponential decay law. We find that the faster rotational correlation times are similar to but slightly less than the values predicted for an individualmore » AOT reverse micelle rotating in propane. The recovered rotational correlation times range from 200 to 500 ps depending on experimental conditions. This faster rotational process is explained in terms of lateral diffusion of the fluorophore along the water/headgroup interfacial region within the reverse micelle. The recovered values for the slower rotational correlation times range from 7 to 18 ns. These larger rotational reorientation times are assigned to varying micelle-micelle (i.e., tail-tail) interactions in the low-density, highly compressible fluid region. We also quantify the contribution of the reverse micellar {open_quotes}aggregate{close_quotes} to the total decay of anisotropy. {copyright} {ital 1996} {ital Society for Applied Spectroscopy}« less

Evolution of topological skyrmions across the spin reorientation transition in Pt/Co/Ta multilayers

NASA Astrophysics Data System (ADS)

He, Min; Li, Gang; Zhu, Zhaozhao; Zhang, Ying; Peng, Licong; Li, Rui; Li, Jianqi; Wei, Hongxiang; Zhao, Tongyun; Zhang, X.-G.; Wang, Shouguo; Lin, Shi-Zeng; Gu, Lin; Yu, Guoqiang; Cai, J. W.; Shen, Bao-gen

2018-05-01

Magnetic skyrmions in multilayers are particularly appealing as next generation memory devices due to their topological compact size, the robustness against external perturbations, the capability of electrical driving and detection, and the compatibility with the existing spintronic technologies. To date, Néel-type skyrmions at room temperature (RT) have been studied mostly in multilayers with easy-axis magnetic anisotropy. Here, we systematically broadened the evolution of magnetic skyrmions with sub-50-nm size in a series of Pt/Co/Ta multilayers where the magnetic anisotropy is tuned continuously from easy axis to easy plane by increasing the ferromagnetic Co layer thickness. The existence of nontrivial skyrmions is identified via the combination of in situ Lorentz transmission electron microscopy (L-TEM) and Hall transport measurements. A high density of magnetic skyrmions over a wide temperature range is observed in the multilayers with easy-plane anisotropy, which will stimulate further exploration for new materials and accelerate the development of skyrmion-based spintronic devices.

Anisotropy induced anomalies in Dy 1$-$xTb xAl 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khan, M.; Miami Univ., Oxford, OH; Pathak, A. K.

2017-01-02

The Dy 1$-$xTb xAl 2 alloys have been investigated by X-ray powder diffraction, heat capacity, and magnetic measurements. All samples exhibit cubic Laves phase crystal structure at room temperature but at T C, DyAl2 and TbAl 2 show tetragonal and rhombohedral distortions, respectively. First order phase transitions are observed below T C (at the spin-reorientation transition, T SR) in the alloys with 0.15 ≤ x ≤ 0.35. These transitions are signified by sharp heat capacity peaks and corresponding anomalies in the magnetization and ac magnetic susceptibility data. The observations are interpreted by taking into consideration the differences in easy magnetizationmore » directions of DyAl 2 and TbAl 2. Due to the competing magnetic structures, the anisotropy-related instability and magnetic frustrations are prominent in the Dy 1$-$xTb xAl 2 alloys at certain concentrations resulting in the first order transitions.« less

Cryogenic Field Measurement of Pr2Fe14B Undulator and Performance Enhancement Options at the NSLS-II

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tanabe, T.; Chubar, O.; Harder, David A.

2009-09-27

Short period (14.5mm) hybrid undulator arrays composed of Praseodymium Iron Boron (Pr{sub 2}Fe{sub 14}B) magnets (CR53, NEOMAX, Inc.) and vanadium permendur poles have been fabricated at Brookhaven National Laboratory. Unlike Neodymium Iron Boron (Nd{sub 2}Fe{sub 14}B) magnets which exhibit spin reorientation at temperatures below 150K, PrFeB arrays monotonically increase performance with lower operating temperature. It opens up the posibility for use in operating a cryo-permanent magnet undulator (CPMU) in the range of 40K to 60K where very efficient cryocoolers are available. Magnetic flux density profiles were measured at various temperature ranges from room temperature down to liquid helium (LHe) usingmore » the Vertical Testing Facility (VTF) at the National Snchrotron Light Source-II (NSLS-II). Temperature variations of phase error have been characterized. In addition, we examined the use of textured Dysprosium (Dy) poles to replace permendur poles to obtain further improvement in performance.« less

Neutron diffraction study of Tb0.5Ho0.5Mn2Si2

NASA Astrophysics Data System (ADS)

Pandey, Swati; Siruguri, Vasudeva; Rawat, Rajeev

2018-02-01

The magnetic properties of tetragonal polycrystalline intermetallic compound Tb0.5Ho0.5Mn2Si2 have been investigated using temperature dependent dc magnetic susceptibility and neutron powder diffraction studies. Results of high temperature susceptibility data shows anomaly at TN = 510 K while low temperature susceptibility data indicate two successive anomalies at T1 = 11 K and T2 = 25 K. Metamagnetic transition is observed in magnetization versus field curves. Our neutron diffraction results indicate three different magnetic regions with different magnetic structures. Neutron diffraction data shows that below T2, the intensities of some of the nuclear peaks get enhanced indicating ferromagnetic ordering, while additional magnetic reflections are observed below T1, indicating antiferromagnetic order. Ordering of rare earth sublattice at low temperature rearranges the ordering of Mn sublattice and results in reorientation of Mn spins at T1. At 2 K Tb/Ho moments are aligned along c-axis while Mn moments are aligned perpendicular to c-axis.

Complex magnetic order in the kagome ferromagnet Pr3Ru4Al12

NASA Astrophysics Data System (ADS)

Henriques, M. S.; Gorbunov, D. I.; Andreev, A. V.; Fabrèges, X.; Gukasov, A.; Uhlarz, M.; Petříček, V.; Ouladdiaf, B.; Wosnitza, J.

2018-01-01

In the hexagonal crystal structure of Pr3Ru4Al12 , the Pr atoms form a distorted kagome lattice, and their magnetic moments, are subject to competing exchange and anisotropy interactions. We performed magnetization, magnetic-susceptibility, specific-heat, electrical-resistivity, and neutron-scattering measurements. Pr3Ru4Al12 is a uniaxial ferromagnet with TC=39 K that displays a collinear magnetic structure (in the high-temperature range of the magnetically ordered state) for which the only crystallographic position of Pr is split into two sites carrying different magnetic moments. A spin-reorientation phase transition is found at 7 K. Below this temperature, part of the Pr moments rotate towards the basal plane, resulting in a noncollinear magnetic state with a lower magnetic symmetry. We argue that unequal RKKY exchange interactions competing with the crystal electric field lead to a moment instability and qualitatively explain the observed magnetic phases in Pr3Ru4Al12 .

Negative Oxygen Isotope Effect in Manganites with an Ordered Cation Arrangement in a High Magnetic Field

NASA Astrophysics Data System (ADS)

Taldenkov, A. N.; Snegirev, V. V.; Babushkina, N. A.; Kalitka, V. S.; Kaul', A. R.

2018-03-01

The oxygen isotope effect in PrBaMn2 16-18 O5.97 manganite with an ordered cation arrangement is studied. The field dependences of magnetic susceptibility and magnetization are measured in the temperature range 100-270 K and magnetic fields up to 32 T. A significant increase in the temperature of the spin-reorientation antiferromagnet-ferromagnet phase transition is detected in samples enriched in heavy oxygen 18O (negative isotope effect). The transition temperature and the isotope effect depend strongly on the magnetic field. An H-T phase diagram is plotted for samples with various isotope compositions. An analysis of the experimental results demonstrates that the detected negative isotope effect and the giant positive isotope effect revealed earlier in doped manganites have the same nature. The mechanisms of appearance of isotope effects are discussed in terms of the double exchange model under a polaron narrowing of the free carrier band.

Balancing structural distortions via competing 4f and itinerant interactions: A case of polymorphism in magnetocaloric HoCo 2

DOE PAGES

Mudryk, Y.; Paudyal, D.; Pathak, A. K.; ...

2016-04-13

The nature of multiple magnetostructural transformations in HoCo 2 has been studied by employing magnetic and specific heat measurements, temperature and magnetic field dependent X-ray powder diffraction, and first-principles calculations. Unexpected increase of magnetization observed below the spin-reorientation temperature (T SR) suggests that the low-temperature transition involves a reduction of Co moment. First principles calculations confirm that the paramagnetic cubic to ferrimagnetic tetragonal transformation at T C is assisted by itinerant electron metamagnetism, and that the reduction of Co moment in HoCo 2 occurs in parallel with the ferrimagnetic tetragonal to the nearly ferromagnetic orthorhombic transformation at T SRvia themore » rearrangement of both 3d states of Co and 5d states of Ho. The ac magnetic susceptibility measurements show significant magnetic frustration below T C. Furthermore, in contrast to earlier reports neither ac nor dc magnetic susceptibilities show anomalies in the paramagnetic region obeying the Curie–Weiss law.« less

Electrical manipulation of perpendicular magnetic anisotropy in a Pt/Co/Pt trilayer grown on PMN-PT(0 1 1) substrate

NASA Astrophysics Data System (ADS)

Xiao, X.; Sun, L.; Luo, Y. M.; Zhang, D.; Liang, J. H.; Wu, Y. Z.

2018-03-01

Strain-induced modulation of perpendicular magnetic anisotropy (PMA) is demonstrated in a wedge-shaped Pt/Co/Pt sandwich grown on PMN-PT(0 1 1) substrate using magnetic torque measurements. An anisotropic in-plane strain is generated by applying an electric field across the PMN-PT substrate and transferred to the ferromagnetic Pt/Co/Pt sandwich. The critical thickness of spin reorientation transition is tuned to the thicker region of the Pt/Co/Pt wedge. The strain-induced change of PMA is quantitatively extracted. Only the first order anisotropy term is tuned by the electric field, while the second order anisotropy term has negligible electric field-dependence. Both of the volume and interface contributions of the first order anisotropy term show tunable electric field modulation. These results may benefit the understanding of strain-mediated magnetoelectric coupling effect in artificial multiferroic structures containing a ferromagnetic layer with PMA.

Nanoscale magnetic ratchets based on shape anisotropy

NASA Astrophysics Data System (ADS)

Cui, Jizhai; Keller, Scott M.; Liang, Cheng-Yen; Carman, Gregory P.; Lynch, Christopher S.

2017-02-01

Controlling magnetization using piezoelectric strain through the magnetoelectric effect offers several orders of magnitude reduction in energy consumption for spintronic applications. However strain is a uniaxial effect and, unlike directional magnetic field or spin-polarized current, cannot induce a full 180° reorientation of the magnetization vector when acting alone. We have engineered novel ‘peanut’ and ‘cat-eye’ shaped nanomagnets on piezoelectric substrates that undergo repeated deterministic 180° magnetization rotations in response to individual electric-field-induced strain pulses by breaking the uniaxial symmetry using shape anisotropy. This behavior can be likened to a magnetic ratchet, advancing magnetization clockwise with each piezostrain trigger. The results were validated using micromagnetics implemented in a multiphysics finite elements code to simulate the engineered spatial and temporal magnetic behavior. The engineering principles start from a target device function and proceed to the identification of shapes that produce the desired function. This approach opens a broad design space for next generation magnetoelectric spintronic devices.

Additives influence on spinning solution and nano web properties

NASA Astrophysics Data System (ADS)

Kukle, S.; Jegina, S.; Sutka, A.; Makovska, R.

2017-10-01

Needleless electrospinning operated as a one-stage process producing nanofibres webs from spinning solutions with the corresponding to the final use properties seems has a good future prospects. Complicated spinning solution designing started with the selection of composition and components proportion, pre-processing sequence and parameters establishing for every component and for their mixing. Spinning solution viscosity and electro conductivity together with the spinning distance and intensity of electromagnetic field are main parameters determined spin ability and properties of obtained nanofibers. Influence of some pre-processing parameters of components, combinations of organic and non-organic components and their concentration influence on spinning solution viscosity and conductivity, as well on fibres diameters are under discussion.

Using escaped prescribed fire reviews to improve organizational learning

Treesearch

Anne E. Black; James Saveland; Dave Thomas; Jennifer Ziegler

2012-01-01

The US wildland fire community has been interested in cultivating organizational learning to improve safety and overall performance for a number of years. A key focus has been on understanding the difference between culpability (to be guilty) and accountability (to explain) and on re-orienting review processes towards building a collective account of (as opposed to...

The Incongruence of the Breton Linguistic Landscape for Young Speakers of Breton

ERIC Educational Resources Information Center

Hornsby, Michael

2008-01-01

Globalisation processes, often accused of imposing uniformity the world over, also open up opportunities for minorities (including linguistic ones) to exploit a variety of spaces for self-definition and self-expression. The expansion in the use of minority languages in public signage is one consequence of this present phase of reorientation in…

Removing the barrier to the calculation of activation energies: Diffusion coefficients and reorientation times in liquid water.

PubMed

Piskulich, Zeke A; Mesele, Oluwaseun O; Thompson, Ward H

2017-10-07

General approaches for directly calculating the temperature dependence of dynamical quantities from simulations at a single temperature are presented. The method is demonstrated for self-diffusion and OH reorientation in liquid water. For quantities which possess an activation energy, e.g., the diffusion coefficient and the reorientation time, the results from the direct calculation are in excellent agreement with those obtained from an Arrhenius plot. However, additional information is obtained, including the decomposition of the contributions to the activation energy. These results are discussed along with prospects for additional applications of the direct approach.

Sexual reorientation therapy: an orthodox perspective.

PubMed

Carlton, Clark

2004-01-01

This article evaluates the phenomenon of sexual reorientation therapy from the standpoint of Orthodox Christian theology. It is argued that homosexual desire is the product of the fall of mankind and cannot be considered "normal." At the same time, however, reorientation therapies, whether secular or Christian, are inherently reductionistic and fail to address the underlying spiritual pathologies involved in homosexual desire (or any other deep-seated passion). The purpose of therapeia in the Orthodox Church is the psycho-somatic transfiguration of the whole person into the image of Christ, not merely the cessation of homosexual activity or the "reidentification" of one's "lifestyle."

(Not) Keeping the stem straight: a proteomic analysis of maritime pine seedlings undergoing phototropism and gravitropism.

PubMed

Herrera, Raul; Krier, Catherine; Lalanne, Celine; Ba, El Hadji Maodo; Stokes, Alexia; Salin, Franck; Fourcaud, Thierry; Claverol, Stéphane; Plomion, Christophe

2010-10-06

Plants are subjected to continuous stimuli from the environment and have evolved an ability to respond through various growth and development processes. Phototropism and gravitropism responses enable the plant to reorient with regard to light and gravity. We quantified the speed of maritime pine seedlings to reorient with regard to light and gravity over 22 days. Seedlings were inclined at 15, 30 and 45 degrees with vertical plants as controls. A lateral light source illuminated the plants and stem movement over time was recorded. Depending on the initial angle of stem lean, the apical response to the lateral light source differed. In control and 15° inclined plants, the apex turned directly towards the light source after only 2 h. In plants inclined at 30° and 45°, the apex first reoriented in the vertical plane after 2 h, then turned towards the light source after 24 h. Two-dimensional gel electrophoresis coupled with mass spectrometry was then used to describe the molecular response of stem bending involved in photo- and gravi-tropism after 22 hr and 8 days of treatment. A total of 486 spots were quantitatively analyzed using image analysis software. Significant changes were determined in the protein accumulation of 68 protein spots. Early response gravitropic associated proteins were identified, which are known to function in energy related and primary metabolism. A group of thirty eight proteins were found to be involved in primary metabolism and energy related metabolic pathways. Degradation of Rubisco was implicated in some protein shifts. Our study demonstrates a rapid gravitropic response in apices of maritime pine seedlings inclined >30°. Little or no response was observed at the stem bases of the same plants. The primary gravitropic response is concomitant with a modification of the proteome, consisting of an over accumulation of energy and metabolism associated proteins, which may allow the stem to reorient rapidly after bending.

(Not) Keeping the stem straight: a proteomic analysis of maritime pine seedlings undergoing phototropism and gravitropism

PubMed Central

2010-01-01

Background Plants are subjected to continuous stimuli from the environment and have evolved an ability to respond through various growth and development processes. Phototropism and gravitropism responses enable the plant to reorient with regard to light and gravity. Results We quantified the speed of maritime pine seedlings to reorient with regard to light and gravity over 22 days. Seedlings were inclined at 15, 30 and 45 degrees with vertical plants as controls. A lateral light source illuminated the plants and stem movement over time was recorded. Depending on the initial angle of stem lean, the apical response to the lateral light source differed. In control and 15° inclined plants, the apex turned directly towards the light source after only 2 h. In plants inclined at 30° and 45°, the apex first reoriented in the vertical plane after 2 h, then turned towards the light source after 24 h. Two-dimensional gel electrophoresis coupled with mass spectrometry was then used to describe the molecular response of stem bending involved in photo- and gravi-tropism after 22 hr and 8 days of treatment. A total of 486 spots were quantitatively analyzed using image analysis software. Significant changes were determined in the protein accumulation of 68 protein spots. Early response gravitropic associated proteins were identified, which are known to function in energy related and primary metabolism. A group of thirty eight proteins were found to be involved in primary metabolism and energy related metabolic pathways. Degradation of Rubisco was implicated in some protein shifts. Conclusions Our study demonstrates a rapid gravitropic response in apices of maritime pine seedlings inclined >30°. Little or no response was observed at the stem bases of the same plants. The primary gravitropic response is concomitant with a modification of the proteome, consisting of an over accumulation of energy and metabolism associated proteins, which may allow the stem to reorient rapidly after bending. PMID:20925929

Electrical control of cell polarization in the fission yeast Schizosaccharomyces pombe.

PubMed

Minc, Nicolas; Chang, Fred

2010-04-27

Electric signals surround tissues and cells and have been proposed to participate in directing cell polarity in processes such as development, wound healing, and host invasion [1, 2]. The application of exogenous electric fields (EFs) can direct cell polarization in cell types ranging from bacteria and fungi to neurons and neutrophils [3-7]. The mechanisms by which EFs modulate cell polarity, however, remain poorly understood. Here we introduce the fission yeast Schizosaccharomyces pombe as a model organism to elucidate the mechanisms underlying this process. In these rod-shaped cells, an exogenous EF reorients cell growth in a direction orthogonal to the field, producing cells with a bent morphology. A candidate genetic screen identifies conserved factors involved in this process: an integral membrane proton ATPase pma1p that regulates intracellular pH, the small GTPase cdc42p, and the formin for3p that assembles actin cables. Interestingly, mutants in these genes still respond to the EF but orient in a different direction, toward the anode. In addition, EFs also cause electrophoretic movement of cell wall synthase complex proteins toward the anode. These data suggest molecular models for how the EF reorients cell polarization by modulating intracellular pH and steering cell polarity factors in multiple directions. Copyright © 2010 Elsevier Ltd. All rights reserved.

Ultrafast spin exchange-coupling torque via photo-excited charge-transfer processes

DOE PAGES

Ma, X.; Fang, F.; Li, Q.; ...

2015-10-28

In this study, optical control of spin is of central importance in the research of ultrafast spintronic devices utilizing spin dynamics at short time scales. Recently developed optical approaches such as ultrafast demagnetization, spin-transfer and spin-orbit torques open new pathways to manipulate spin through its interaction with photon, orbit, charge or phonon. However, these processes are limited by either the long thermal recovery time or the low-temperature requirement. Here we experimentally demonstrate ultrafast coherent spin precession via optical charge-transfer processes in the exchange-coupled Fe/CoO system at room temperature. The efficiency of spin precession excitation is significantly higher and the recoverymore » time of the exchange-coupling torque is much shorter than for the demagnetization procedure, which is desirable for fast switching. The exchange coupling is a key issue in spin valves and tunnelling junctions, and hence our findings will help promote the development of exchange-coupled device concepts for ultrafast coherent spin manipulation.« less

Use of geometric properties of landmark arrays for reorientation relative to remote cities and local objects.

PubMed

Mou, Weimin; Nankoo, Jean-François; Zhou, Ruojing; Spetch, Marcia L

2014-03-01

Five experiments investigated how human adults use landmark arrays in the immediate environment to reorient relative to the local environment and relative to remote cities. Participants learned targets' directions with the presence of a proximal 4 poles forming a rectangular shape and an array of more distal poles forming a rectangular shape. Then participants were disoriented and pointed to targets with the presence of the proximal poles or the distal poles. Participants' orientation was estimated by the mean of their pointing error across targets. The targets could be 7 objects in the immediate local environment in which the poles were located or 7 cities around Edmonton (Alberta, Canada) where the experiments occurred. The directions of the 7 cities could be learned from reading a map first and then from pointing to the cities when the poles were presented. The directions of the 7 cities could also be learned from viewing labels of cities moving back and forth in the specific direction in the immediate local environment in which the poles were located. The shape of the array of the distal poles varied in salience by changing the number of poles on each edge of the rectangle (2 vs. 34). The results showed that participants regained their orientation relative to local objects using the distal poles with 2 poles on each edge; participants could not reorient relative to cities using the distal pole array with 2 poles on each edge but could reorient relative to cities using the distal pole array with 34 poles on each edge. These results indicate that use of cues in reorientation depends not only on the cue salience but also on which environment people need to reorient to.

Physical strain-mediated microtubule reorientation in the epidermis of gravitropically or phototropically stimulated maize coleoptiles.

PubMed

Fischer, K; Schopfer, P

1998-07-01

During gravitropic and phototropic curvature of the maize coleoptile, the cortical microtubules (MTs) adjacent to the outer epidermal cell wall assume opposite orientations at the two sides of the organ. Starting from a uniformly random pattern during straight growth in darkness, the MTs reorientate perpendicularly to the organ axis at the outer (faster growing) side and parallel to the organ axis at the inner (slower growing) side. As similar reorientations can be induced during straight growth by increasing or decreasing the effective auxin concentration, it has been proposed that these reorientations may be used as a diagnostic test for assessing the auxin status of the epidermal cells during tropic curvature. This idea was tested by determining the MT orientations in the coleoptile of intact maize seedlings in which the gravitropic or phototropic curvature was prevented or inversed by an appropriate mechanical counterforce. Forces that just prevented the coleoptile from curving in a gravity or light field prevented reorientations of the MTs. Forces strong enough to overcompensate the tropic stimuli by enforcing curvature in the opposite direction induced reorientations of the MTs opposite to those produced by tropic stimulation. These results show that the MTs at the outer surface of the coleoptile respond to changes in mechanical tissue strain rather than to gravitropic or phototropic stimuli and associated changes at the level of auxin or any other element in the signal transduction chain between perception of tropic stimuli and asymmetric growth response. It is proposed that cortical MTs can act as strain gauges in a positive feed-back regulatory circle utilized for amplification and stabilization of environmentally induced changes in the direction of elongation growth.

Is language necessary for human spatial reorientation? Reconsidering evidence from dual task paradigms.

PubMed

Ratliff, Kristin R; Newcombe, Nora S

2008-03-01

Being able to reorient to the spatial environment after disorientation is a basic adaptive challenge. There is clear evidence that reorientation uses geometric information about the shape of the surrounding space. However, there has been controversy concerning whether use of geometry is a modular function, and whether use of features is dependent on human language. A key argument for the role of language comes from shadowing findings where adults engaged in a linguistic task during reorientation ignored a colored wall feature and only used geometric information to reorient [Hermer-Vazquez, L., Spelke, E., & Katsnelson, A. (1999). Sources of flexibility in human cognition: Dual task studies of space and language. Cognitive Psychology, 39, 3-36]. We report three studies showing: (a) that the results of Hermer-Vazques et al. [Hermer-Vazquez, L., Spelke, E., & Katsnelson, A. (1999). Sources of flexibility in human cognition: Dual task studies of space and language. Cognitive Psychology, 39, 3-36] are obtained in incidental learning but not with explicit instructions, (b) that a spatial task impedes use of features at least as much as a verbal shadowing task, and (c) that neither secondary task impedes use of features in a room larger than that used by Hermer-Vazquez et al. These results suggest that language is not necessary for successful use of features in reorientation. In fact, whether or not there is an encapsulated geometric module is currently unsettled. The current findings support an alternative to modularity; the adaptive combination view hypothesizes that geometric and featural information are utilized in varying degrees, dependent upon the certainty and variance with which the two kinds of information are encoded, along with their salience and perceived usefulness.

EPR Studies of Spin-Spin Exchange Processes: A Physical Chemistry Experiment.

ERIC Educational Resources Information Center

Eastman, Michael P.

1982-01-01

Theoretical background, experimental procedures, and analysis of experimental results are provided for an undergraduate physical chemistry experiment on electron paramagnetic resonance (EPR) linewidths. Source of line broadening observed in a spin-spin exchange process between radicals formed in aqueous solutions of potassium peroxylamine…

Fluidization, resolidification, and reorientation of the endothelial cell in response to slow tidal stretches

PubMed Central

Krishnan, Ramaswamy; Canović, Elizabeth Peruski; Iordan, Andreea L.; Rajendran, Kavitha; Manomohan, Greeshma; Pirentis, Athanassios P.; Smith, Michael L.; Butler, James P.; Fredberg, Jeffrey J.

2012-01-01

Mechanical stretch plays an important role in regulating shape and orientation of the vascular endothelial cell. This morphological response to stretch is basic to angiogenesis, neovascularization, and vascular homeostasis, but mechanism remains unclear. To elucidate mechanisms, we used cell mapping rheometry to measure traction forces in primary human umbilical vein endothelial cells subjected to periodic uniaxial stretches. Onset of periodic stretch of 10% strain amplitude caused a fluidization response typified by attenuation of traction forces almost to zero. As periodic stretch continued, the prompt fluidization response was followed by a slow resolidification response typified by recovery of the traction forces, but now aligned along the axis perpendicular to the imposed stretch. Reorientation of the cell body lagged reorientation of the traction forces, however. Together, these observations demonstrate that cellular reorientation in response to periodic stretch is preceded by traction attenuation by means of cytoskeletal fluidization and subsequent traction recovery transverse to the stretch direction by means of cytoskeletal resolidification. PMID:22700796

Optimal reorientation of asymmetric underactuated spacecraft using differential flatness and receding horizon control

NASA Astrophysics Data System (ADS)

Cai, Wei-wei; Yang, Le-ping; Zhu, Yan-wei

2015-01-01

This paper presents a novel method integrating nominal trajectory optimization and tracking for the reorientation control of an underactuated spacecraft with only two available control torque inputs. By employing a pseudo input along the uncontrolled axis, the flatness property of a general underactuated spacecraft is extended explicitly, by which the reorientation trajectory optimization problem is formulated into the flat output space with all the differential constraints eliminated. Ultimately, the flat output optimization problem is transformed into a nonlinear programming problem via the Chebyshev pseudospectral method, which is improved by the conformal map and barycentric rational interpolation techniques to overcome the side effects of the differential matrix's ill-conditions on numerical accuracy. Treating the trajectory tracking control as a state regulation problem, we develop a robust closed-loop tracking control law using the receding-horizon control method, and compute the feedback control at each control cycle rapidly via the differential transformation method. Numerical simulation results show that the proposed control scheme is feasible and effective for the reorientation maneuver.

Microgravity liquid propellant management

NASA Technical Reports Server (NTRS)

Hung, R. J.

1990-01-01

The requirement to settle or to position liquid fluid over the outlet end of a spacecraft propellant tank prior to main engine restart, poses a microgravity fluid behavior problem. Resettlement or reorientation of liquid propellant can be accomplished by providing optimal acceleration to the spacecraft such that the propellant is reoriented over the tank outlet without any vapor entrainment, any excessive geysering, or any other undersirable fluid motion for the space fluid management under microgravity environment. The most efficient technique is studied for propellant resettling through the minimization of propellant usage and weight penalties. Both full scale and subscale liquid propellant tank of Space Transfer Vehicle were used to simulate flow profiles for liquid hydrogen reorientation over the tank outlet. In subscale simulation, both constant and impulsive resettling acceleration were used to simulate the liquid flow reorientation. Comparisons between the constant reverse gravity acceleration and impulsive reverse gravity acceleration to be used for activation of propellant resettlement shows that impulsive reverse gravity thrust is superior to constant reverse gravity thrust.

Evolution of magnetic phases in SmCrO3: A neutron diffraction and magnetometric study

NASA Astrophysics Data System (ADS)

Tripathi, Malvika; Choudhary, R. J.; Phase, D. M.; Chatterji, T.; Fischer, H. E.

2017-11-01

The classical belief about the mechanism of spin reorientation phase transition (SRPT) and ground-state magnetic structure in SmCrO3 has become intriguing because of inconsistent bulk magnetization observations. The presence of highly neutron-absorbing Sm atom has so far evaded the determination of microscopic magnetic structure. In the present report, we have utilized very high-energy "hot neutrons" to overcome the Sm absorption and to determine the thermal evolution of magnetic configurations. Unambiguously, three distinct phases are observed: the uncompensated canted antiferromagnetic structure Γ4(Gx,Ay,Fz;FzR) occurring below the Néel temperature (TN=191 K), the collinear antiferromagnetic structure Γ1(Ax,Gy,Cz;CzR) occurring below 10 K, and a nonequilibrium configuration with cooccurring Γ1 and Γ4 phases in the neighborhood of the SRPT (10 K ≤T ≤ 40 K). In differing to the earlier predictions, we divulge the SRPT to be a discontinuous transition where chromium spins switch from the a -b crystallographic plane to the b -c crystallographic plane in a discrete manner with no allowed intermediate configuration. The canting angle of chromium ions in the a -b plane is unusually not a thermal constant, rather it is empirically discerned to follow exponential behavior. The competition between magnetocrystalline anisotropy and free energy derived by isotropic and antisymmetric exchange interactions between different pairs of magnetic ions is observed to govern the mechanism of SRPT.

The Response of the Left Ventral Attentional System to Invalid Targets and its Implication for the Spatial Neglect Syndrome: a Multivariate fMRI Investigation.

PubMed

Silvetti, Massimo; Lasaponara, Stefano; Lecce, Francesca; Dragone, Alessio; Macaluso, Emiliano; Doricchi, Fabrizio

2016-12-01

In humans, invalid visual targets that mismatch spatial expectations induced by attentional cues are considered to selectively engage a right hemispheric "reorienting" network that includes the temporal parietal junction (TPJ), the inferior frontal gyrus (IFG), and the medial frontal gyrus (MFG). However, recent findings suggest that this hemispheric dominance is not absolute and that it is rather observed because the TPJ and IFG areas in the left hemisphere are engaged both by invalid and valid cued targets. Because of this, the BOLD response of the left hemisphere to invalid targets is usually cancelled out by the standard "invalid versus valid" contrast used in functional magnetic resonance imaging investigations of spatial attention. Here, we used multivariate pattern recognition analysis (MVPA) to gain finer insight into the role played by the left TPJ and IFG in reorienting to invalid targets. We found that in left TPJ and IFG blood oxygen level-dependent (BOLD) responses to invalid and valid targets were associated to different patterns of neural activity, possibly reflecting the presence of functionally distinct neuronal populations. Pattern segregation was significant at group level, it was present in almost all of the participants to the study and was observed both for targets in the left and right side of space. A control whole-brain MVPA ("Searchlight" analysis) confirmed the results obtained in predefined regions of interest and highlighted that also other areas, that is, superior parietal and frontal-polar cortex, show different patterns of BOLD response to valid and invalid targets. These results confirm and expand previous evidence highlighting the involvement of the left hemisphere in reorienting of visual attention (Doricchi et al. 2010; Dragone et al. 2015). These findings suggest that asymmetrical reorienting deficits suffered by right brain damaged patients with left spatial neglect, who have severe impairments in contralesional reorienting and less severe impairments in ipsilesional reorienting, are due to preserved reorienting abilities in the intact left hemisphere. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Raman study of the molecular motions of pivalic acid: the liquid—plastic phase transition

NASA Astrophysics Data System (ADS)

Balevičius, V.; Orel, B.; Hadži, D.

Raman spectra of pivalic acid in the plastic and liquid phase have been measured. The reorientational correlation times have been evaluated from the ν asCH, νCO and νCC bands as a function of temperature. The reorientational correlation time corresponding to ν as CH and νCC bands is τ < 10 -11 s whilst for the νCO band τ = 4ps ( T = 20°C). The calculated activation energy is 26 KJ mol -1. The reorientation of the carboxylic groups which may be assisted by the proton transfer along the hydrogen bonds in dimers is discussed.

Tectonic tests of proposed polar wander paths for Mars and the moon

NASA Technical Reports Server (NTRS)

Grimm, R. E.; Solomon, S. C.

1986-01-01

A comparison of the lithospheric stress field predicted for rapid global reorientations against observed tectonic features is used to test the polar wander paths proposed for Mars by Schultz and Lutz-Garihan (1981). A calculation of the reorientation stresses leads to the suggestion that the formation of normal faults or graben in broad regions around the former rotation poles should be the minimum tectonic signature of a reorientation that generates lithospheric stresses in excess of the extensional strength of near-surface material. It is concluded that polar wander of the magnitude and timing envisioned by Schultz and Lutz-Garihan did not occur.

Epitaxial Ni-Mn-Ga films deposited on SrTiO{sub 3} and evidence of magnetically induced reorientation of martensitic variants at room temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heczko, O.; Thomas, M.; Buschbeck, J.

2008-02-18

Epitaxial Ni-Mn-Ga films were grown on SrTiO{sub 3} by sputter deposition. The films deposited at 673 K are ferromagnetic and martensitic at room temperature. Pole figure measurements indicate that the twinned orthorhombic martensite microstructure of the film has a lower symmetry compared to bulk. Magnetically induced reorientation or magnetic shape memory effect is indicated by magnetization curve measurements. Though the overall extension of the film is constrained by a rigid substrate, the reorientation is possible due to the additional degree of freedom in the orthorhombic phase.

Reconfigurable nanoscale spin-wave directional coupler

PubMed Central

Wang, Qi; Pirro, Philipp; Verba, Roman; Slavin, Andrei; Hillebrands, Burkard; Chumak, Andrii V.

2018-01-01

Spin waves, and their quanta magnons, are prospective data carriers in future signal processing systems because Gilbert damping associated with the spin-wave propagation can be made substantially lower than the Joule heat losses in electronic devices. Although individual spin-wave signal processing devices have been successfully developed, the challenging contemporary problem is the formation of two-dimensional planar integrated spin-wave circuits. Using both micromagnetic modeling and analytical theory, we present an effective solution of this problem based on the dipolar interaction between two laterally adjacent nanoscale spin-wave waveguides. The developed device based on this principle can work as a multifunctional and dynamically reconfigurable signal directional coupler performing the functions of a waveguide crossing element, tunable power splitter, frequency separator, or multiplexer. The proposed design of a spin-wave directional coupler can be used both in digital logic circuits intended for spin-wave computing and in analog microwave signal processing devices. PMID:29376117

Reconfigurable nanoscale spin-wave directional coupler.

PubMed

Wang, Qi; Pirro, Philipp; Verba, Roman; Slavin, Andrei; Hillebrands, Burkard; Chumak, Andrii V

2018-01-01

Spin waves, and their quanta magnons, are prospective data carriers in future signal processing systems because Gilbert damping associated with the spin-wave propagation can be made substantially lower than the Joule heat losses in electronic devices. Although individual spin-wave signal processing devices have been successfully developed, the challenging contemporary problem is the formation of two-dimensional planar integrated spin-wave circuits. Using both micromagnetic modeling and analytical theory, we present an effective solution of this problem based on the dipolar interaction between two laterally adjacent nanoscale spin-wave waveguides. The developed device based on this principle can work as a multifunctional and dynamically reconfigurable signal directional coupler performing the functions of a waveguide crossing element, tunable power splitter, frequency separator, or multiplexer. The proposed design of a spin-wave directional coupler can be used both in digital logic circuits intended for spin-wave computing and in analog microwave signal processing devices.

NMR (Nuclear Magnetic Resonance) of solid biopolymers

NASA Technical Reports Server (NTRS)

Andrew, E. R.

1983-01-01

It has been possible through the study of proton relaxation in solid proteins and related molecules to identify and characterize the following molecular motions which contribute to relaxation: (1) methyl group reorientation; (2) segmental motion; (3) side chain motion; (4) proline ring puckering; and (5) water molecule reorientation.

Educating Academic Staff to Reorient Curricula in ESD

ERIC Educational Resources Information Center

Biasutti, Michele; Makrakis, Vassilios; Concina, Eleonora; Frate, Sara

2018-01-01

Purpose: The purpose of this paper is to present a professional development experience for higher education academic staff within the framework of an international Tempus project focused on reorienting university curricula to address sustainability. The project included revising curricula to phase sustainable development principles into university…

Inductive detection of fieldlike and dampinglike ac inverse spin-orbit torques in ferromagnet/normal-metal bilayers

NASA Astrophysics Data System (ADS)

Berger, Andrew J.; Edwards, Eric R. J.; Nembach, Hans T.; Karenowska, Alexy D.; Weiler, Mathias; Silva, Thomas J.

2018-03-01

Functional spintronic devices rely on spin-charge interconversion effects, such as the reciprocal processes of electric field-driven spin torque and magnetization dynamics-driven spin and charge flow. Both dampinglike and fieldlike spin-orbit torques have been observed in the forward process of current-driven spin torque and dampinglike inverse spin-orbit torque has been well studied via spin pumping into heavy metal layers. Here, we demonstrate that established microwave transmission spectroscopy of ferromagnet/normal metal bilayers under ferromagnetic resonance can be used to inductively detect the ac charge currents driven by the inverse spin-charge conversion processes. This technique relies on vector network analyzer ferromagnetic resonance (VNA-FMR) measurements. We show that in addition to the commonly extracted spectroscopic information, VNA-FMR measurements can be used to quantify the magnitude and phase of all ac charge currents in the sample, including those due to spin pumping and spin-charge conversion. Our findings reveal that Ni80Fe20/Pt bilayers exhibit both dampinglike and fieldlike inverse spin-orbit torques. While the magnitudes of both the dampinglike and fieldlike inverse spin-orbit torque are of comparable scale to prior reported values for similar material systems, we observed a significant dependence of the dampinglike magnitude on the order of deposition. This suggests interface quality plays an important role in the overall strength of the dampinglike spin-to-charge conversion.

Theoretical model of dynamic spin polarization of nuclei coupled to paramagnetic point defects in diamond and silicon carbide

NASA Astrophysics Data System (ADS)

Ivády, Viktor; Szász, Krisztián; Falk, Abram L.; Klimov, Paul V.; Christle, David J.; Janzén, Erik; Abrikosov, Igor A.; Awschalom, David D.; Gali, Adam

2015-09-01

Dynamic nuclear spin polarization (DNP) mediated by paramagnetic point defects in semiconductors is a key resource for both initializing nuclear quantum memories and producing nuclear hyperpolarization. DNP is therefore an important process in the field of quantum-information processing, sensitivity-enhanced nuclear magnetic resonance, and nuclear-spin-based spintronics. DNP based on optical pumping of point defects has been demonstrated by using the electron spin of nitrogen-vacancy (NV) center in diamond, and more recently, by using divacancy and related defect spins in hexagonal silicon carbide (SiC). Here, we describe a general model for these optical DNP processes that allows the effects of many microscopic processes to be integrated. Applying this theory, we gain a deeper insight into dynamic nuclear spin polarization and the physics of diamond and SiC defects. Our results are in good agreement with experimental observations and provide a detailed and unified understanding. In particular, our findings show that the defect electron spin coherence times and excited state lifetimes are crucial factors in the entire DNP process.

Engineering fibrin-based tissue constructs from myofibroblasts and application of constraints and strain to induce cell and collagen reorganization.

PubMed

de Jonge, Nicky; Baaijens, Frank P T; Bouten, Carlijn V C

2013-10-28

Collagen content and organization in developing collagenous tissues can be influenced by local tissue strains and tissue constraint. Tissue engineers aim to use these principles to create tissues with predefined collagen architectures. A full understanding of the exact underlying processes of collagen remodeling to control the final tissue architecture, however, is lacking. In particular, little is known about the (re)orientation of collagen fibers in response to changes in tissue mechanical loading conditions. We developed an in vitro model system, consisting of biaxially-constrained myofibroblast-seeded fibrin constructs, to further elucidate collagen (re)orientation in response to i) reverting biaxial to uniaxial static loading conditions and ii) cyclic uniaxial loading of the biaxially-constrained constructs before and after a change in loading direction, with use of the Flexcell FX4000T loading device. Time-lapse confocal imaging is used to visualize collagen (re)orientation in a nondestructive manner. Cell and collagen organization in the constructs can be visualized in real-time, and an internal reference system allows us to relocate cells and collagen structures for time-lapse analysis. Various aspects of the model system can be adjusted, like cell source or use of healthy and diseased cells. Additives can be used to further elucidate mechanisms underlying collagen remodeling, by for example adding MMPs or blocking integrins. Shape and size of the construct can be easily adapted to specific needs, resulting in a highly tunable model system to study cell and collagen (re)organization.

Dual descriptors within the framework of spin-polarized density functional theory.

PubMed

Chamorro, E; Pérez, P; Duque, M; De Proft, F; Geerlings, P

2008-08-14

Spin-polarized density functional theory (SP-DFT) allows both the analysis of charge-transfer (e.g., electrophilic and nucleophilic reactivity) and of spin-polarization processes (e.g., photophysical changes arising from electron transitions). In analogy with the dual descriptor introduced by Morell et al. [J. Phys. Chem. A 109, 205 (2005)], we introduce new dual descriptors intended to simultaneously give information of the molecular regions where the spin-polarization process linking states of different multiplicity will drive electron density and spin density changes. The electronic charge and spin rearrangement in the spin forbidden radiative transitions S(0)-->T(n,pi(*)) and S(0)-->T(pi,pi(*)) in formaldehyde and ethylene, respectively, have been used as benchmark examples illustrating the usefulness of the new spin-polarization dual descriptors. These quantities indicate those regions where spin-orbit coupling effects are at work in such processes. Additionally, the qualitative relationship between the topology of the spin-polarization dual descriptors and the vertical singlet triplet energy gap in simple substituted carbene series has been also discussed. It is shown that the electron density and spin density rearrangements arise in agreement with spectroscopic experimental evidence and other theoretical results on the selected target systems.

Discrimination between spin-dependent charge transport and spin-dependent recombination in π-conjugated polymers by correlated current and electroluminescence-detected magnetic resonance

NASA Astrophysics Data System (ADS)

Kavand, Marzieh; Baird, Douglas; van Schooten, Kipp; Malissa, Hans; Lupton, John M.; Boehme, Christoph

2016-08-01

Spin-dependent processes play a crucial role in organic electronic devices. Spin coherence can give rise to spin mixing due to a number of processes such as hyperfine coupling, and leads to a range of magnetic field effects. However, it is not straightforward to differentiate between pure single-carrier spin-dependent transport processes which control the current and therefore the electroluminescence, and spin-dependent electron-hole recombination which determines the electroluminescence yield and in turn modulates the current. We therefore investigate the correlation between the dynamics of spin-dependent electric current and spin-dependent electroluminescence in two derivatives of the conjugated polymer poly(phenylene-vinylene) using simultaneously measured pulsed electrically detected (pEDMR) and optically detected (pODMR) magnetic resonance spectroscopy. This experimental approach requires careful analysis of the transient response functions under optical and electrical detection. At room temperature and under bipolar charge-carrier injection conditions, a correlation of the pEDMR and the pODMR signals is observed, consistent with the hypothesis that the recombination currents involve spin-dependent electronic transitions. This observation is inconsistent with the hypothesis that these signals are caused by spin-dependent charge-carrier transport. These results therefore provide no evidence that supports earlier claims that spin-dependent transport plays a role for room-temperature magnetoresistance effects. At low temperatures, however, the correlation between pEDMR and pODMR is weakened, demonstrating that more than one spin-dependent process influences the optoelectronic materials' properties. This conclusion is consistent with prior studies of half-field resonances that were attributed to spin-dependent triplet exciton recombination, which becomes significant at low temperatures when the triplet lifetime increases.

Power-induced evolution and increased dimensionality of nonlinear modes in reorientational soft matter.

PubMed

Laudyn, Urszula A; Jung, Paweł S; Zegadło, Krzysztof B; Karpierz, Miroslaw A; Assanto, Gaetano

2014-11-15

We demonstrate the evolution of higher order one-dimensional guided modes into two-dimensional solitary waves in a reorientational medium. The observations, carried out at two different wavelengths in chiral nematic liquid crystals, are in good agreement with a simple nonlocal nonlinear model.

Quenching of dynamic nuclear polarization by spin-orbit coupling in GaAs quantum dots.

PubMed

Nichol, John M; Harvey, Shannon P; Shulman, Michael D; Pal, Arijeet; Umansky, Vladimir; Rashba, Emmanuel I; Halperin, Bertrand I; Yacoby, Amir

2015-07-17

The central-spin problem is a widely studied model of quantum decoherence. Dynamic nuclear polarization occurs in central-spin systems when electronic angular momentum is transferred to nuclear spins and is exploited in quantum information processing for coherent spin manipulation. However, the mechanisms limiting this process remain only partially understood. Here we show that spin-orbit coupling can quench dynamic nuclear polarization in a GaAs quantum dot, because spin conservation is violated in the electron-nuclear system, despite weak spin-orbit coupling in GaAs. Using Landau-Zener sweeps to measure static and dynamic properties of the electron spin-flip probability, we observe that the size of the spin-orbit and hyperfine interactions depends on the magnitude and direction of applied magnetic field. We find that dynamic nuclear polarization is quenched when the spin-orbit contribution exceeds the hyperfine, in agreement with a theoretical model. Our results shed light on the surprisingly strong effect of spin-orbit coupling in central-spin systems.

Collisional spin-oriented Sherman function in electron-hole semiconductor plasmas: Landau damping effect

NASA Astrophysics Data System (ADS)

Lee, Myoung-Jae; Jung, Young-Dae

2018-04-01

The influence of Landau damping on the spin-oriented collisional asymmetry is investigated in electron-hole semiconductor plasmas. The analytical expressions of the spin-singlet and the spin-triplet scattering amplitudes as well as the spin-oriented asymmetry Sherman function are obtained as functions of the scattering angle, the Landau parameter, the effective Debye length, and the collision energy. It is found that the Landau damping effect enhances the spin-singlet and spin-triplet scattering amplitudes in the forward and back scattering domains, respectively. It is also found that the Sherman function increases with an increase in the Landau parameter. In addition, the spin-singlet scattering process is found to be dominant rather than the spin-triplet scattering process in the high collision energy domain.

Direct Measurement of the Flip-Flop Rate of Electron Spins in the Solid State

NASA Astrophysics Data System (ADS)

Dikarov, Ekaterina; Zgadzai, Oleg; Artzi, Yaron; Blank, Aharon

2016-10-01

Electron spins in solids have a central role in many current and future spin-based devices, ranging from sensitive sensors to quantum computers. Many of these apparatuses rely on the formation of well-defined spin structures (e.g., a 2D array) with controlled and well-characterized spin-spin interactions. While being essential for device operation, these interactions can also result in undesirable effects, such as decoherence. Arguably, the most important pure quantum interaction that causes decoherence is known as the "flip-flop" process, where two interacting spins interchange their quantum state. Currently, for electron spins, the rate of this process can only be estimated theoretically, or measured indirectly, under limiting assumptions and approximations, via spin-relaxation data. This work experimentally demonstrates how the flip-flop rate can be directly and accurately measured by examining spin-diffusion processes in the solid state for physically fixed spins. Under such terms, diffusion can occur only through this flip-flop-mediated quantum-state exchange and not via actual spatial motion. Our approach is implemented on two types of samples, phosphorus-doped 28Si and nitrogen vacancies in diamond, both of which are significantly relevant to quantum sensors and information processing. However, while the results for the former sample are conclusive and reveal a flip-flop rate of approximately 12.3 Hz, for the latter sample only an upper limit of approximately 0.2 Hz for this rate can be estimated.

Photoreceptor-mediated bending towards UV-B in Arabidopsis.

PubMed

Vandenbussche, Filip; Tilbrook, Kimberley; Fierro, Ana Carolina; Marchal, Kathleen; Poelman, Dirk; Van Der Straeten, Dominique; Ulm, Roman

2014-06-01

Plants reorient their growth towards light to optimize photosynthetic light capture--a process known as phototropism. Phototropins are the photoreceptors essential for phototropic growth towards blue and ultraviolet-A (UV-A) light. Here we detail a phototropic response towards UV-B in etiolated Arabidopsis seedlings. We report that early differential growth is mediated by phototropins but clear phototropic bending to UV-B is maintained in phot1 phot2 double mutants. We further show that this phototropin-independent phototropic response to UV-B requires the UV-B photoreceptor UVR8. Broad UV-B-mediated repression of auxin-responsive genes suggests that UVR8 regulates directional bending by affecting auxin signaling. Kinetic analysis shows that UVR8-dependent directional bending occurs later than the phototropin response. We conclude that plants may use the full short-wavelength spectrum of sunlight to efficiently reorient photosynthetic tissue with incoming light. © The Author 2014. Published by the Molecular Plant Shanghai Editorial Office in association with Oxford University Press on behalf of CSPB and IPPE, SIBS, CAS.

Meeting patient expectations: healthcare professionals and service re-engineering.

PubMed

Laing, Angus

2002-08-01

A central theme underpinning the reform of healthcare systems in western economies since the 1980s has been the emphasis on reorienting service provision around the patient. Healthcare organizations have been forced to re-appraise the design of the service delivery process, specifically the service encounter, to take account of these changing patient expectations. This reorientation of healthcare services around the patient has fundamental implications for healthcare professionals, specifically challenging the dominance of service professionals in the design and delivery of health services. Utilizing a qualitative methodological framework, this paper explores the responses of healthcare professionals to service redesign initiatives implemented in acute NHS hospitals in Scotland and considers the implications of such professional responses for the development of patient-focused service delivery. Within this, it specifically examines evolving professional perspectives on the place of a service user focus in a publicly funded healthcare system, professional attitudes towards private sector managerial practices, and the dynamics of changing professional behaviour.

Curvature induced L-defects in water conduction in carbon nanotubes.

PubMed

Zimmerli, Urs; Gonnet, Pedro G; Walther, Jens H; Koumoutsakos, Petros

2005-06-01

We conduct molecular dynamics simulations to study the effect of the curvature induced static dipole moment of small open-ended single-walled carbon nanotubes (CNTs) immersed in water. This dipole moment generates a nonuniform electric field, changing the energy landscape in the CNT and altering the water conduction process. The CNT remains practically filled with water at all times, whereas intermittent filling is observed when the dipole term is not included. In addition, the dipole moment induces a preferential orientation of the water molecules near the end regions of the nanotube, which in turn causes a reorientation of the water chain in the middle of the nanotube. The most prominent feature of this reorientation is an L-defect in the chain of water molecules inside the CNT. The analysis of the water energetics and structural characteristics inside and in the vicinity of the CNT helps to identify the role of the dipole moment and to suggest possible mechanisms for controlled water and proton transport at the nanoscale.

Solution-processed organic spin-charge converter.

PubMed

Ando, Kazuya; Watanabe, Shun; Mooser, Sebastian; Saitoh, Eiji; Sirringhaus, Henning

2013-07-01

Conjugated polymers and small organic molecules are enabling new, flexible, large-area, low-cost optoelectronic devices, such as organic light-emitting diodes, transistors and solar cells. Owing to their exceptionally long spin lifetimes, these carbon-based materials could also have an important impact on spintronics, where carrier spins play a key role in transmitting, processing and storing information. However, to exploit this potential, a method for direct conversion of spin information into an electric signal is indispensable. Here we show that a pure spin current can be produced in a solution-processed conducting polymer by pumping spins through a ferromagnetic resonance in an adjacent magnetic insulator, and that this generates an electric voltage across the polymer film. We demonstrate that the experimental characteristics of the generated voltage are consistent with it being generated through an inverse spin Hall effect in the conducting polymer. In contrast with inorganic materials, the conducting polymer exhibits coexistence of high spin-current to charge-current conversion efficiency and long spin lifetimes. Our discovery opens a route for a new generation of molecular-structure-engineered spintronic devices, which could lead to important advances in plastic spintronics.

Use of Geometry for Spatial Reorientation in Children Applies Only to Symmetric Spaces

ERIC Educational Resources Information Center

Lew, Adina R.; Gibbons, Bryony; Murphy, Caroline; Bremner, J. Gavin

2010-01-01

Proponents of the geometric module hypothesis argue that following disorientation, many species reorient by use of macro-environment geometry. It is suggested that attention to the surface layout geometry of natural terrain features may have been selected for over evolutionary time due to the enduring and unambiguous location information it…

Leadership and Organization in Education: Time for a Re-Orientation?

ERIC Educational Resources Information Center

Glatter, Ron

2006-01-01

The article raises issues about the current direction of the field of educational leadership and management. It argues that we should consider a re-orientation of the field in order to renew its concern with ideas connected with organization, which include viewing organizations as complex adaptive systems and taking an institutional perspective.…

Why Size Counts: Children's Spatial Reorientation in Large and Small Enclosures

ERIC Educational Resources Information Center

Learmonth, Amy E.; Newcombe, Nora S.; Sheridan, Natalie; Jones, Meredith

2008-01-01

When mobile organisms are spatially disoriented, for instance by rapid repetitive movement, they must re-establish orientation. Past research has shown that the geometry of enclosing spaces is consistently used for reorientation by a wide variety of species, but that non-geometric features are not always used. Based on these findings, some…

Reorientation in a Rhombic Environment: No Evidence for an Encapsulated Geometric Module

ERIC Educational Resources Information Center

Hupbach, A.; Nadel, L.

2005-01-01

Reorientation behavior of young children has been described as dependent upon a geometric module that is incapable of interacting with landmark information. Whereas previous studies typically used rectangular spaces that provided geometric information about distance, we used a rhombic space that allowed us to explore the way children use geometric…

Growing cells push back under pressure.

PubMed

Gibson, W T; Gibson, M C

2012-04-13

In both plants and animals, the interplay between mechanical force generation and mechanical sensing plays a stabilizing role in many developmental processes. Uyttewaal et al. now demonstrate that cells in the Arabidopsis shoot apical meristem respond to local mechanical stresses by reorienting their growth, thereby guiding morphogenesis. Notably, the mechanism underlying such guidance is amplification--not suppression--of growth-rate heterogeneity. Copyright © 2012 Elsevier Inc. All rights reserved.

Spin-Dependent Processes Measured without a Permanent Magnet.

PubMed

Fontanesi, Claudio; Capua, Eyal; Paltiel, Yossi; Waldeck, David H; Naaman, Ron

2018-05-07

A novel Hall circuit design that can be incorporated into a working electrode, which is used to probe spin-selective charge transfer and charge displacement processes, is reviewed herein. The general design of a Hall circuit based on a semiconductor heterostructure, which forms a shallow 2D electron gas and is used as an electrode, is described. Three different types of spin-selective processes have been studied with this device in the past: i) photoinduced charge exchange between quantum dots and the working electrode through chiral molecules is associated with spin polarization that creates a local magnetization and generates a Hall voltage; ii) charge polarization of chiral molecules by an applied voltage is accompanied by a spin polarization that generates a Hall voltage; and iii) cyclic voltammetry (current-voltage) measurements of electrochemical redox reactions that can be spin-analyzed by the Hall circuit to provide a third dimension (spin) in addition to the well-known current and voltage dimensions. The three studies reviewed open new doors into understanding both the spin current and the charge current in electronic materials and electrochemical processes. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A morphometric analysis of the redistribution of organelles in columella cells of horizontally-oriented roots of Zea mays

NASA Technical Reports Server (NTRS)

Moore, R.

1986-01-01

In order to determine what structural changes in graviperceptive cells are associated with onset of root gravicurvature, the redistribution of organelles in columella cells of horizontally-oriented, graviresponding roots of Zea mays has been quantified. Root gravicurvature began by 15 min after reorientation, and did not involve significant changes in the (i) volume of individual columella cells or amyloplasts, (ii) relative volume of any cellular organelle, (iii) number of amyloplasts per columella cell, or (iv) surface area of cellular location of endoplasmic reticulum. Sedimentation of amyloplasts began within 1 to 2 min after reorientation, and was characterized by an intensely staining area of cytoplasm adjacent to the sedimenting amyloplasts. By 5 min after reorientation, amyloplasts were located in the lower distal corner of columella cells, and, by 15 min after reorientation, overlaid the entire length of the lower cell wall. No consistent contact between amyloplasts and any cellular structure was detected at any stage of gravicurvature. Centrally-located nuclei initially migrated upward in columella cells of horizontally-oriented roots, after which they moved to the proximal ends of the cells by 15 min after reorientation. No significant pattern of redistribution of vacuoles, mitochondria, dictyosomes, or hyaloplasm was detected that correlated with the onset of gravicurvature. These results indicate that amyloplasts and nuclei are the only organelles whose movements correlate positively with the onset of gravicurvature by primary roots of this cultivar of Zea mays.

Nonurgent patients in the emergency department? A French formula to prevent misuse

PubMed Central

2010-01-01

Background Overcrowding in emergency department (EDs) is partly due to the use of EDs by nonurgent patients. In France, the authorities responded to the problem by creating primary care units (PCUs): alternative structures located near hospitals. The aims of the study were to assess the willingness of nonurgent patients to be reoriented to a PCU and to collect the reasons that prompted them to accept or refuse. Methods We carried out a cross sectional survey on patients' use of EDs. The study was conducted in a French hospital ED. Patients were interviewed about their use of health services, ED visits, referrals, activities of daily living, and insurance coverage status. Patients' medical data were also collected. Results 85 patients considered nonurgent by a triage nurse were asked to respond to a questionnaire. Sex ratio was 1.4; mean age was 36.3 +/- 11.7 years. Most patients went to the ED autonomously (76%); one third (31.8%) had consulted a physician. The main reasons for using the ED were difficulty to get an appointment with a general practitioner (22.3%), feelings of pain (68.5%), and the availability of medical services in the ED, like imaging, laboratory tests, and drug prescriptions (37.6%). Traumatisms and wounds were the main medical reasons for going to the ED (43.5%). More than two-thirds of responders (68%) were willing to be reoriented towards PCUs. In the multivariate analysis, only employment and the level of urgency perceived by the patient were associated with the willingness to accept reorientation. Employed persons were 4.5 times more likely to accept reorientation (OR = 4.5 CI (1.6-12.9)). Inversely, persons who perceived a high level of urgency were the least likely to accept reorientation (OR = 0.9 CI (0.8-0.9). Conclusions Our study provides information on the willingness of ED patients to accept reorientation and shows the limits of its feasibility. Alternative structures such as PCUs near the ED seem to respond appropriately to the growing demands of nonurgent patients. Reorientation, however, will be successful only if the new structures adapt their opening hours to the needs of nonurgent patients and if their physicians can perform specific technical skills. PMID:20230602

Vibrations and reorientations of H2O molecules in [Sr(H2O)6]Cl2 studied by Raman light scattering, incoherent inelastic neutron scattering and proton magnetic resonance.

PubMed

Hetmańczyk, Joanna; Hetmańczyk, Lukasz; Migdał-Mikuli, Anna; Mikuli, Edward; Florek-Wojciechowska, Małgorzata; Harańczyk, Hubert

2014-04-24

Vibrational-reorientational dynamics of H2O ligands in the high- and low-temperature phases of [Sr(H2O)6]Cl2 was investigated by Raman Spectroscopy (RS), proton magnetic resonance ((1)H NMR), quasielastic and inelastic incoherent Neutron Scattering (QENS and IINS) methods. Neutron powder diffraction (NPD) measurements, performed simultaneously with QENS, did not indicated a change of the crystal structure at the phase transition (detected earlier by differential scanning calorimetry (DSC) at TC(h)=252.9 K (on heating) and at TC(c)=226.5K (on cooling)). Temperature dependence of the full-width at half-maximum (FWHM) of νs(OH) band at ca. 3248 cm(-1) in the RS spectra indicated small discontinuity in the vicinity of phase transition temperature, what suggests that the observed phase transition may be associated with a change of the H2O reorientational dynamics. However, an activation energy value (Ea) for the reorientational motions of H2O ligands in both phases is nearly the same and equals to ca. 8 kJ mol(-1). The QENS peaks, registered for low temperature phase do not show any broadening. However, in the high temperature phase a small QENS broadening is clearly visible, what implies that the reorientational dynamics of H2O ligands undergoes a change at the phase transition. (1)H NMR line is a superposition of two powder Pake doublets, differentiated by a dipolar broadening, suggesting that there are two types of the water molecules in the crystal lattice of [Sr(H2O)6]Cl2 which are structurally not equivalent average distances between the interacting protons are: 1.39 and 1.18 Å. However, their reorientational dynamics is very similar (τc=3.3⋅10(-10) s). Activation energies for the reorientational motion of these both kinds of H2O ligands have nearly the same values in an experimental error limit: and equal to ca. 40 kJ mole(-1). The phase transition is not seen in the (1)H NMR spectra temperature dependencies. Infrared (IR), Raman (RS) and inelastic incoherent neutron scattering (IINS) spectra were calculated by the DFT method and quite a good agreement with the experimental data was obtained. Copyright © 2014 Elsevier B.V. All rights reserved.

Angles No Longer Weigh In: The Effect of Geometric Cue Directness on Reorientation

ERIC Educational Resources Information Center

Huang, Zhenzhen; Hu, Qingfen; Shao, Yi

2017-01-01

Previous research in spatial reorientation, which only presented the target location in the corner, has found that adults weighed angles more than wall lengths. We proposed that in previous research, angular cues were available for direct use whereas length cues had to be associated with the left/right sense. We thus investigated whether the…

The World Is Not Flat: Can People Reorient Using Slope?

ERIC Educational Resources Information Center

Nardi, Daniele; Newcombe, Nora S.; Shipley, Thomas F.

2011-01-01

Studies of spatial representation generally focus on flat environments and visual input. However, the world is not flat, and slopes are part of most natural environments. In a series of 4 experiments, we examined whether humans can use a slope as a source of allocentric, directional information for reorientation. A target was hidden in a corner of…

Medium-frequency impulsive-thrust-activated liquid hydrogen reorientation with Geyser

NASA Technical Reports Server (NTRS)

Hung, R. J.; Shyu, K. L.

1992-01-01

Efficient technique are studied for accomplishing propellant resettling through the minimization of propellant usage through impulsive thrust. A comparison between the use of constant-thrust and impulsive-thrust accelerations for the activation of propellant resettlement shows that impulsive thrust is superior to constant thrust for liquid reorientation in a reduced-gravity environment. This study shows that when impulsive thrust with 0.1-1.0-, and 10-Hz frequencies for liquid-fill levels in the range between 30-80 percent is considered, the selection of 1.0-Hz-frequency impulsive thrust over the other frequency ranges of impulsive thrust is the optimum. Characteristics of the slosh waves excited during the course of 1.0-Hz-frequency impulsive-thrust liquid reorientation were also analyzed.

A Solid-State Intrinsically Stretchable Polymer Solar Cell.

PubMed

Li, Lu; Liang, Jiajie; Gao, Huier; Li, Ying; Niu, Xiaofan; Zhu, Xiaodan; Xiong, Yan; Pei, Qibing

2017-11-22

An organic solar cell based on a bulk heterojunction of a conjugated polymer and a methanofullerene PC 61 BM or PC 71 BM exhibits a complex morphology that controls both its photovoltaic and mechanical compliance (flexibility and stretchability). Here, the donor-acceptor blend of poly(thieno[3,4-b]-thiophene/benzodithiophene) (PTB7) and PC 71 BM containing a small amount of diiodooctane (DIO) in the spin-casting solution is reported to exhibit elastic deformability. The blend comprises nanometer-size, nanocrystalline grains that are relatively uniformly distributed. Large external deformation is accommodated by relative sliding between the grains. Reorientation of the nanocrystallites and the global reorientation of the PTB7 polymer chain were observed along the stretching direction up to 100% strain, which was reversible as the blend was allowed to relax to 0% strain. The polymer solar cell based on PTB7:PC 71 BM:DIO with such reversible morphological changes exhibited a rubbery elasticity at room temperature. The device could be stretched up to 100% strain, and the power-conversion efficiency shows a slight increase up to 30% strain and a global increase of power generation as the photoactive area increases with strain. Solar cells were fabricated employing a layer of the PTB7:PC 71 BM:DIO blend sandwiched between a pair of stretchable transparent electrodes, each comprising a stack of a silver nanowire percolation network and a single-wall carbon nanotube network embedded in the surface of a poly(urethane acylate) elastomer film. The solar cells were semitransparent and could be stretched like a rubbery film by as much as 100% strain. The measured power-conversion efficiency was 3.48%, which was increased to 3.67% after one cycle of stretching to 50% strain and lowered to 2.99% after 100 stretching cycles. The total power generation from the cells was significantly increased, thanks to the expanded active area as the cells were stretched.

Mechanisms of optical orientation of an individual Mn2+ ion spin in a II-VI quantum dot

NASA Astrophysics Data System (ADS)

Smoleński, T.; Cywiński, Ł.; Kossacki, P.

2018-02-01

We provide a theoretical description of the optical orientation of a single Mn2+ ion spin under quasi-resonant excitation demonstrated experimentally by Goryca et al (2009 Phys. Rev. Lett. 103 087401). We build and analyze a hierarchy of models by starting with the simplest assumptions (transfer of perfectly spin-polarized excitons from Mn-free dot to the other dot containing a single Mn2+ spin, followed by radiative recombination) and subsequently adding more features, such as spin relaxation of electrons and holes. Particular attention is paid to the role of the influx of the dark excitons and the process of biexciton formation, which are shown to contribute significantly to the orientation process in the quasi-resonant excitation case. Analyzed scenarios show how multiple features of the excitonic complexes in magnetically-doped quantum dots, such as the values of exchange integrals, spin relaxation times, etc, lead to a plethora of optical orientation processes, characterized by distinct dependencies on light polarization and laser intensity, and occurring on distinct timescales. Comparison with experimental data shows that the correct description of the optical orientation mechanism requires taking into account Mn2+ spin-flip processes occurring not only when the exciton is already in the orbital ground state of the light-emitting dot, but also those that happen during the exciton transfer from high-energy states to the ground state. Inspired by the experimental results on energy relaxation of electrons and holes in nonmagnetic dots, we focus on the process of biexciton creation allowed by mutual spin-flip of an electron and the Mn2+ spin, and we show that by including it in the model, we obtain good qualitative and quantitative agreement with the experimental data on quasi-resonantly driven Mn2+ spin orientation.

Bulk electron spin polarization generated by the spin Hall current

NASA Astrophysics Data System (ADS)

Korenev, V. L.

2006-07-01

It is shown that the spin Hall current generates a nonequilibrium spin polarization in the interior of crystals with reduced symmetry in a way that is drastically different from the previously well-known “equilibrium” polarization during the spin relaxation process. The steady state spin polarization value does not depend on the strength of spin-orbit interaction offering possibility to generate relatively high spin polarization even in the case of weak spin-orbit coupling.

Patterns of cell elongation in the determination of the final shape in galls of Baccharopelma dracunculifoliae (Psyllidae) on Baccharis dracunculifolia DC (Asteraceae).

PubMed

Magalhães, Thiago Alves; de Oliveira, Denis Coelho; Suzuki, Aline Yasko Marinho; Isaias, Rosy Mary dos Santos

2014-07-01

Cell redifferentiation, division, and elongation are recurrent processes, which occur during gall development, and are dependent on the cellulose microfibrils reorientation. We hypothesized that changes in the microfibrils orientation from non-galled tissues to galled ones occur and determine the final gall shape. This determination is caused by a new tissue zonation, its hyperplasia, and relative cell hypertrophy. The impact of the insect's activity on these patterns of cell development was herein tested in Baccharopelma dracunculifoliae-Baccharis dracunculifolia system. In this system, the microfibrils are oriented perpendicularly to the longest cell axis in elongated cells and randomly in isodiametric ones, either in non-galled or in galled tissues. The isodiametric cells of the abaxial epidermis in non-galled tissues divided and elongated periclinally, forming the outer gall epidermis. The anticlinally elongated cells of the abaxial palisade layer and the isodiametric cells of the spongy parenchyma originated the gall outer cortex with hypertrophied and periclinally elongated cells. The anticlinally elongated cells of the adaxial palisade layer originated the inner cortex with hypertrophied and periclinally elongated cells in young and mature galls and isodiametric cells in senescent galls. The isodiametric cells of the adaxial epidermis elongated periclinally in the inner gall epidermis. The current investigation demonstrates the role of cellulose microfibril reorientation for gall development. Once many factors other than this reorientation act on gall development, it should be interesting to check the possible relationship of the new cell elongation patterns with the pectic composition of the cell walls.

Is there a geometric module for spatial orientation? Insights from a rodent navigation model.

PubMed

Sheynikhovich, Denis; Chavarriaga, Ricardo; Strösslin, Thomas; Arleo, Angelo; Gerstner, Wulfram

2009-07-01

Modern psychological theories of spatial cognition postulate the existence of a geometric module for reorientation. This concept is derived from experimental data showing that in rectangular arenas with distinct landmarks in the corners, disoriented rats often make diagonal errors, suggesting their preference for the geometric (arena shape) over the nongeometric (landmarks) cues. Moreover, sensitivity of hippocampal cell firing to changes in the environment layout was taken in support of the geometric module hypothesis. Using a computational model of rat navigation, the authors proposed and tested the alternative hypothesis that the influence of spatial geometry on both behavioral and neuronal levels can be explained by the properties of visual features that constitute local views of the environment. Their modeling results suggest that the pattern of diagonal errors observed in reorientation tasks can be understood by the analysis of sensory information processing that underlies the navigation strategy employed to solve the task. In particular, 2 navigation strategies were considered: (a) a place-based locale strategy that relies on a model of grid and place cells and (b) a stimulus-response taxon strategy that involves direct association of local views with action choices. The authors showed that the application of the 2 strategies in the reorientation tasks results in different patterns of diagonal errors, consistent with behavioral data. These results argue against the geometric module hypothesis by providing a simpler and biologically more plausible explanation for the related experimental data. Moreover, the same model also describes behavioral results in different types of water-maze tasks. Copyright (c) 2009 APA, all rights reserved.

Tidal reorientation and the fracturing of Jupiter's moon Europa

USGS Publications Warehouse

McEwen, A.S.

1986-01-01

The most striking characteristic of Europa is the network of long linear albedo markings over the surface, suggestive of global-scale tectonic processes. Various explanations for the fractures have been proposed: Freezing and expansion of an early liquid water ocean1, planetary expansion due to dehydration of hydrated silicates2, localization by weak points in the crust generated by impacts3, and a combination of stresses due to planetary volume change and tidal distortions from orbital recession and orbital eccentricity4,5. Calculations by Yoder6 and Greenberg and Weidenschilling7 have shown that Europa may rotate slightly more rapidly than the synchronous rate, with a rotation period (reorientation through 360??) ranging from 20 to >103 yr if a liquid mantle is present, or up to 1010 yr if the satellite is essentially solid7. Helfen-stein and Parmentier8 modelled the stresses due to nonsynchronous rotation, and concluded that this could explain the long fractures in part of the anti-jovian hemisphere. In this note, I present a global map of lineaments with long arc lengths (>20?? or 550 km), and compare the lineament orientations to the tensile stress trajectories due to tidal distortions (changes in the lengths of three principal semiaxes) and to nonsynchronous rotation (longitudinal reorientation of two of the principal semiaxes). An excellent orthogonal fit to the lineaments is achieved by the stresses due to nonsynchronous rotation with the axis radial to Jupiter located 25?? east of its present position. This fit suggests that nonsynchronous rotation occurred at some time in Europa's history. ?? 1986 Nature Publishing Group.

[Archaic stereotypies and modern approaches for understanding of ageing].

PubMed

Grigoryeva, I A; Kelasev, V N

2017-01-01

In the article we discussed the processes of awareness of the place of elderly people in modern society, elaboration of adequate relation to global aging and elderly themselves are still going in social sciences. These processes are expressed in a clash of archaic stereotypes and new approaches which changed social and age structure requires. Not only elderly people are providers of archaic stereotypes, but scientific institutions and practices as well. Reorientation of science, media and social policy towards study and realization of «postponed aging» opportunities is needed.

Charge density wave behavior and order-disorder in the antiferromagnetic metallic series Eu (Ga1 -xAlx)4

NASA Astrophysics Data System (ADS)

Stavinoha, Macy; Cooley, Joya A.; Minasian, Stefan G.; McQueen, Tyrel M.; Kauzlarich, Susan M.; Huang, C.-L.; Morosan, E.

2018-05-01

The solid solution Eu (Ga1-xAlx) 4 was grown in single crystal form to reveal a rich variety of crystallographic, magnetic, and electronic properties that differ from the isostructural end compounds EuGa4 and EuAl4, despite the similar covalent radii and electronic configurations of Ga and Al. Here we report the onset of magnetic spin reorientation and metamagnetic transitions for x =0 -1 evidenced by magnetization and temperature-dependent specific heat measurements. TN changes nonmonotonously with x , and it reaches a maximum around 20 K for x =0.50 , where the a lattice parameter also shows an extreme (minimum) value. Anomalies in the temperature-dependent resistivity consistent with charge density wave behavior exist only for x =0.50 and 1. Density functional theory calculations show increased polarization between the Ga-Al covalent bonds in the x =0.50 structure compared to the end compounds, such that crystallographic order and chemical pressure are proposed as the causes of the charge density wave behavior.

THE ABUNDANCE OF X-SHAPED RADIO SOURCES: IMPLICATIONS FOR THE GRAVITATIONAL WAVE BACKGROUND

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roberts, David H.; Saripalli, Lakshmi; Subrahmanyan, Ravi, E-mail: roberts@brandeis.edu

Coalescence of supermassive black holes (SMBHs) in galaxy mergers is potentially the dominant contributor to the low frequency gravitational wave background (GWB). It was proposed by Merritt and Ekers that X-shaped radio galaxies are signposts of such coalescences and that their abundance might be used to predict the magnitude of the GWB. In Roberts et al. we presented radio images of all 52 X-shaped radio source candidates out of the sample of 100 selected by Cheung for which archival VLA data were available. These images indicate that at most 21% of the candidates might be genuine X-shaped radio sources thatmore » were formed by a restarting of beams in a new direction following a major merger. This suggests that fewer than 1.3% of extended radio sources appear to be candidates for genuine axis reorientations (“spin flips”), much smaller than the 7% suggested by Leahy and Parma. Thus, the associated GWB may be substantially smaller than previous estimates. These results can be used to normalize detailed calculations of the SMBH coalescence rate and the GWB.« less

Cryogenic Field Measurement of Pr{sub 2}Fe{sub 14}B Undulator and Performance Enhancement Options at the NSLS-II

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tanabe, Toshiya; Chubar, Oleg; Harder, David A.

2010-06-23

Short period (14.5mm) hybrid undulator arrays composed of Praseodymium Iron Boron (Pr{sub 2}Fe{sub 14}B) magnets (CR53, NEOMAX, Inc.) and vanadium permendur poles have been fabricated at Brookhaven National Laboratory. Unlike Neodymium Iron Boron (Nd{sub 2}Fe{sub 14}B) magnets which exhibit spin reorientation at a temperatures below 150 K, PrFeB arrays monotonically increase performance with lower operating temperature. It opens up the possibility for use in operating a cryo-permanent magnet undulator (CPMU) in the range of 40 K to 60 K where very efficient cryocoolers are available. Magnetic flux density profiles were measured at various temperature ranges from room temperature down tomore » liquid helium (LHe) using the Vertical Testing Facility (VTF) at the National Synchrotron Light Source-II (NSLS-II). Temperature variations of phase error have been characterized. In addition, we examined the use of textured Dysprosium (Dy) poles to replace permendur poles to obtain further improvement in performance.« less

The effect of the MgO buffer layer thickness on magnetic anisotropy in MgO/Fe/Cr/MgO buffer/MgO(001)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kozioł-Rachwał, Anna, E-mail: a.koziolrachwal@aist.go.jp; AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, al. Mickiewicza 30, 30-059 Kraków; Nozaki, Takayuki

2016-08-28

The relationship between the magnetic properties and MgO buffer layer thickness d was studied in epitaxial MgO/Fe(t)/Cr/MgO(d) layers grown on MgO(001) substrate in which the Fe thickness t ranged from 0.4 nm to 1.1 nm. For 0.4 nm ≤ t ≤ 0.7 nm, a non-monotonic coercivity dependence on the MgO buffer thickness was shown by perpendicular magneto-optic Kerr effect magnetometry. For thicker Fe films, an increase in the buffer layer thickness resulted in a spin reorientation transition from perpendicular to the in-plane magnetization direction. Possible origins of these unusual behaviors were discussed in terms of the suppression of carbon contamination at the Fe surface and changes inmore » the magnetoelastic anisotropy in the system. These results illustrate a method to control magnetic anisotropy in MgO/Fe/Cr/MgO(d) via an appropriate choice of MgO buffer layer thickness d.« less

High-Field Magnetization Study of R_{2} {Fe}_{17} {N}_{2} R 2 Fe 17 N 2 ( R = {Ho} R = Ho and Er) Nitrides

NASA Astrophysics Data System (ADS)

Tereshina, I. S.; Tereshina-Chitrova, E. A.; Pelevin, I. A.; Doerr, M.; Law, J. M.; Verbetski, V. N.; Salamova, A. A.

2018-03-01

The structure and magnetic properties of the nitrided compounds R2Fe_{17}N2 (R = Ho and Er) are studied. The type of crystal structure Th2Ni_{17} is preserved upon nitrogenation, and the relative unit cell volume Δ V{/}V increase exceeds 6%. Magnetic studies are performed in fields up to 60 T at 4.2 K on aligned powder samples. Field-induced spin-reorientation (SR) transitions are observed in the M( H) curves of R2Fe_{17}N2. Unlike the parent R2Fe_{17} compounds, where the magnetization increases in steps as the field grows stronger, R2Fe_{17}N2 demonstrate a gradual increase in magnetization. It is indicative of the change of the SR transition from first to the second type. Extrapolation of magnetization curves to the theoretical value of magnetization in the forced ferromagnetic state yields the coefficient of the inter-sublattice R-Fe exchange interaction. The inter-sublattice exchange is found to decrease upon nitrogenation.

Magnetic properties of bulk, and rapidly solidified nanostructured (Nd 1-xCe x) 2Fe 14-yCo yB ribbons

DOE PAGES

Pathak, Arjun K.; Khan, M.; Gschneidner, Jr., K. A.; ...

2015-11-06

Magnetic properties of Ce and Co co-doped (Nd 1-xCe x) 2Fe 14-yCo yB compounds have been investigated both in bulk polycrystalline and rapidly solidified nanostructured ribbon forms. For certain Ce concentrations the materials exhibit spin re-orientation transitions below 140 K. The Curie temperatures, saturation magnetizations, and other magnetic properties relevant for applications as permanent magnets are controlled by Ce and Co substitutions for Nd and Fe, respectively. Most importantly, the results show that Ce, Co co-doped compounds are excellent replacements for several Dy-based high performance permanent magnets (dysprosium is one of the critical elements and is, therefore, in short supply).more » As a result, the high temperature (>375 K) magnetic properties for Nd–Ce–Fe–Co–B based alloys show promise not only as a replacement for Dy-doped Nd 2Fe 14B permanent magnets, but the new alloys also require significantly lower amounts of Nd, which too is the critical element that can be replaced by a more abundant Ce.« less

Large magnetocaloric effect of NdGa compound due to successive magnetic transitions

NASA Astrophysics Data System (ADS)

Zheng, X. Q.; Xu, J. W.; Shao, S. H.; Zhang, H.; Zhang, J. Y.; Wang, S. G.; Xu, Z. Y.; Wang, L. C.; Chen, J.; Shen, B. G.

2018-05-01

The magnetic behavior and MCE property of NdGa compound were studied in detail. According to the temperature dependence of magnetization (M-T) curve at 0.01 T, two sharp changes were observed at 20 K (TSR) and 42 K (TC), respectively, corresponding to spin reorientation and FM-PM transition. Isothermal magnetization curves up to 5 T at different temperatures were measured and magnetic entropy change (ΔSM) was calculated based on M-H data. Temperature dependences of -ΔSM for a field change of 0-2 T and 0-5 T show that there are two peaks on the curves corresponding to TSR and TC, respectively. The value of the two peaks is 6.4 J/kg K and 15.5 J/kg K for the field change of 0-5 T. Since the two peaks are close, the value of -ΔSM in the temperature range between TSR and TC keeps a large value. The excellent MCE performance of NdGa compound benefits from the existence of two successive magnetic transitions.

Observation of magnetization reversal behavior in Sm0.9Gd0.1Cr0.85Mn0.15O3 orthochromites

NASA Astrophysics Data System (ADS)

Panwar, Neeraj; Joby, Jostin P.; Kumar, Surendra; Coondoo, Indrani; Vasundhara, M.; Kumar, Nitu; Palai, Ratnakar; Singhal, Rahul; Katiyar, Ram S.

2018-05-01

Impact of co-doping (Gd and Mn) on the magnetic properties has been systematically investigated in SmCrO3 compound. For the synthesized compound Sm0.9Gd0.1Cr0.85Mn0.15O3 (SGCMO), below the Neel transition temperature and under low applied magnetic field, temperature induced magnetization reversal at 105 K (crossover temperature) was noticed in the field cooled magnetization curve. Magnetization reversal attained maximum value of -1.03 emu/g at 17 K where spin reorientation occurred. The magnetization reversal disappeared under higher applied field. From the M-H plots an enhancement in the magnetization was observed due to Gd doping. Magnetocaloric effect at low temperatures measured through the magnetic entropy change was found sixteen times higher for this compound as compared to pristine SmCrO3 and twice to that of SmCr0.85Mn0.15O3 compound. The study reveals the importance of co-doping in tailoring the magnetic properties of rare-earth chromites.

Reversible electric-field manipulation of the adsorption morphology and magnetic anisotropy of small Fe and Co clusters on graphene

NASA Astrophysics Data System (ADS)

Tanveer, M.; Dorantes-Dávila, J.; Pastor, G. M.

2017-12-01

First-principles electronic calculations show how the adsorption morphology, orbital magnetism, and magnetic anisotropy energy (MAE) of small CoN and FeN clusters (N ≤3 ) on graphene (G) can be reversibly controlled under the action of an external electric field (EF). A variety of cluster-specific and EF-induced effects are revealed, including (i) perpendicular or canted adsorption configurations of the dimers and trimers, (ii) significant morphology-dependent permanent dipole moments and electric susceptibilities, (iii) EF-induced reversible transitions among the different metastable adsorption morphologies of Fe3 and Co3 on graphene, (iv) qualitative changes in the MAE landscape driven by structural changes, (v) colossal values of the magnetic anisotropy Δ E ≃45 meV per atom in Co2/G , (vi) EF-induced spin-reorientation transitions in Co3/G , and (vii) reversibly tunable coercive field and blocking temperatures, which in some cases allow a barrierless magnetization reversal of the cluster. These remarkable electric and magnetic fingerprints open new possibilities of characterizing and exploiting the size- and structural-dependent properties of magnetic nanostructures at surfaces.

Structural and magnetic phase diagram of CrAs and its relationship with pressure-induced superconductivity

DOE PAGES

Shen, Yao; Wang, Qisi; Hao, Yiqing; ...

2016-02-01

In this paper, we use neutron diffraction to study the structure and magnetic phase diagram of the newly discovered pressure-induced superconductor CrAs. Unlike most magnetic unconventional superconductors where the magnetic moment direction barely changes upon doping, here we show that CrAs exhibits a spin reorientation from the ab plane to the ac plane, along with an abrupt drop of the magnetic propagation vector at a critical pressure (P c ≈ 0.6 GPa). This magnetic phase transition, accompanied by a lattice anomaly, coincides with the emergence of bulk superconductivity. With further increasing pressure, the magnetic order completely disappears near the optimalmore » T c regime (P ≈ 0.94 GPa). Moreover, the Cr magnetic moments tend to be aligned antiparallel between nearest neighbors with increasing pressure toward the optimal superconductivity regime. Finally, our findings suggest that the noncollinear helimagnetic order is strongly coupled to structural and electronic degrees of freedom, and that the antiferromagnetic correlations between nearest neighbors might be essential for superconductivity.« less

Symmetry mismatch-driven perpendicular magnetic anisotropy for perovskite/brownmillerite heterostructures.

PubMed

Zhang, Jing; Zhong, Zhicheng; Guan, Xiangxiang; Shen, Xi; Zhang, Jine; Han, Furong; Zhang, Hui; Zhang, Hongrui; Yan, Xi; Zhang, Qinghua; Gu, Lin; Hu, Fengxia; Yu, Richeng; Shen, Baogen; Sun, Jirong

2018-05-15

Grouping different transition metal oxides together by interface engineering is an important route toward emergent phenomenon. While most of the previous works focused on the interface effects in perovskite/perovskite heterostructures, here we reported on a symmetry mismatch-driven spin reorientation toward perpendicular magnetic anisotropy in perovskite/brownmillerite heterostructures, which is scarcely seen in tensile perovskite/perovskite heterostructures. We show that alternately stacking perovskite La 2/3 Sr 1/3 MnO 3 and brownmillerite LaCoO 2.5 causes a strong interface reconstruction due to symmetry discontinuity at interface: neighboring MnO 6 octahedra and CoO 4 tetrahedra at the perovskite/brownmillerite interface cooperatively relax in a manner that is unavailable for perovskite/perovskite interface, leading to distinct orbital reconstructions and thus the perpendicular magnetic anisotropy. Moreover, the perpendicular magnetic anisotropy is robust, with an anisotropy constant two orders of magnitude greater than the in-plane anisotropy of the perovskite/perovskite interface. The present work demonstrates the great potential of symmetry engineering in designing artificial materials on demand.

Reason, emotion and decision-making: risk and reward computation with feeling.

PubMed

Quartz, Steven R

2009-05-01

Many models of judgment and decision-making posit distinct cognitive and emotional contributions to decision-making under uncertainty. Cognitive processes typically involve exact computations according to a cost-benefit calculus, whereas emotional processes typically involve approximate, heuristic processes that deliver rapid evaluations without mental effort. However, it remains largely unknown what specific parameters of uncertain decision the brain encodes, the extent to which these parameters correspond to various decision-making frameworks, and their correspondence to emotional and rational processes. Here, I review research suggesting that emotional processes encode in a precise quantitative manner the basic parameters of financial decision theory, indicating a reorientation of emotional and cognitive contributions to risky choice.

Accumulation of actin in subsets of pioneer growth cone filopodia in response to neural and epithelial guidance cues in situ

PubMed Central

1993-01-01

Directed outgrowth of neural processes must involve transmission of signals from the tips of filopodia to the central region of the growth cone. Here, we report on the distribution and dynamics of one possible element in this process, actin, in live growth cones which are reorienting in response to in situ guidance cues. In grasshopper embryonic limbs, pioneer growth cones respond to at least three types of guidance cues: a limb axis cue, intermediate target cells, and a circumferential band of epithelial cells. With time-lapse imaging of intracellularly injected rhodamine-phalloidin and rhodamine-actin, we monitored the distribution of actin during growth cone responses to these cues. In distal limb regions, accumulation of actin in filopodia and growth cone branches accompanies continued growth, while reduction of actin accompanies withdrawal. Where growth cones are reorienting to intermediate target cells, or along the circumferential epithelial band, actin selectively accumulates in the proximal regions of those filopodia that have contacted target cells or are extending along the band. Actin accumulations can be retrogradely transported along filopodia, and can extend into the central region of the growth cone. These results suggest that regulation and translocation of actin may be a significant element in growth cone steering. PMID:8227150

Magnetic Ordering in Gold Nanoclusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agrachev, Mikhail; Antonello, Sabrina; Dainese, Tiziano

Here, several research groups have observed magnetism in monolayer-protected gold-cluster samples, but the results were often contradictory and thus a clear understanding of this phenomenon is still missing. We used Au 25(SCH 2CH 2Ph) 18 0, which is a paramagnetic cluster that can be prepared with atomic precision and whose structure is known precisely. Previous magnetometry studies only detected paramagnetism. We used samples representing a range of crystallographic orders and studied their magnetic behaviors by electron paramagnetic resonance (EPR). As a film, Au 25(SCH 2CH 2Ph) 18 0 displays paramagnetic behavior but, at low temperature, ferromagnetic interactions are detectable. Onemore » or few single crystals undergo physical reorientation with the applied field and display ferromagnetism, as detected through hysteresis experiments. A large collection of microcrystals is magnetic even at room temperature and shows distinct paramagnetic, superparamagnetic, and ferromagnetic behaviors. Simulation of the EPR spectra shows that both spin-orbit coupling and crystal distortion are important to determine the observed magnetic behaviors. DFT calculations carried out on single cluster and periodic models predict values of spin6orbit coupling and crystal6splitting effects in agreement with the EPR derived quantities. Magnetism in gold nanoclusters is thus demonstrated to be the outcome of a very delicate balance of factors. To obtain reproducible results, the samples must be (i) controlled for composition and thus be monodispersed with atomic precision, (ii) of known charge state, and (iii) well defined also in terms of crystallinity and experimental conditions. This study highlights the efficacy of EPR spectroscopy to provide a molecular understanding of these phenomena« less

Magnetic Ordering in Gold Nanoclusters

DOE PAGES

Agrachev, Mikhail; Antonello, Sabrina; Dainese, Tiziano; ...

2017-06-12

Here, several research groups have observed magnetism in monolayer-protected gold-cluster samples, but the results were often contradictory and thus a clear understanding of this phenomenon is still missing. We used Au 25(SCH 2CH 2Ph) 18 0, which is a paramagnetic cluster that can be prepared with atomic precision and whose structure is known precisely. Previous magnetometry studies only detected paramagnetism. We used samples representing a range of crystallographic orders and studied their magnetic behaviors by electron paramagnetic resonance (EPR). As a film, Au 25(SCH 2CH 2Ph) 18 0 displays paramagnetic behavior but, at low temperature, ferromagnetic interactions are detectable. Onemore » or few single crystals undergo physical reorientation with the applied field and display ferromagnetism, as detected through hysteresis experiments. A large collection of microcrystals is magnetic even at room temperature and shows distinct paramagnetic, superparamagnetic, and ferromagnetic behaviors. Simulation of the EPR spectra shows that both spin-orbit coupling and crystal distortion are important to determine the observed magnetic behaviors. DFT calculations carried out on single cluster and periodic models predict values of spin6orbit coupling and crystal6splitting effects in agreement with the EPR derived quantities. Magnetism in gold nanoclusters is thus demonstrated to be the outcome of a very delicate balance of factors. To obtain reproducible results, the samples must be (i) controlled for composition and thus be monodispersed with atomic precision, (ii) of known charge state, and (iii) well defined also in terms of crystallinity and experimental conditions. This study highlights the efficacy of EPR spectroscopy to provide a molecular understanding of these phenomena« less

The Influence of Cue Reliability and Cue Representation on Spatial Reorientation in Young Children

ERIC Educational Resources Information Center

Lyons, Ian M.; Huttenlocher, Janellen; Ratliff, Kristin R.

2014-01-01

Previous studies of children's reorientation have focused on cue representation (e.g., whether cues are geometric) as a predictor of performance but have not addressed cue reliability (the regularity of the relation between a given cue and an outcome) as a predictor of performance. Here we address both factors within the same series of…

Use of Geometric Properties of Landmark Arrays for Reorientation Relative to Remote Cities and Local Objects

ERIC Educational Resources Information Center

Mou, Weimin; Nankoo, Jean-François; Zhou, Ruojing; Spetch, Marcia L.

2014-01-01

Five experiments investigated how human adults use landmark arrays in the immediate environment to reorient relative to the local environment and relative to remote cities. Participants learned targets' directions with the presence of a proximal 4 poles forming a rectangular shape and an array of more distal poles forming a rectangular shape. Then…

Children Reorient Using the Left/Right Sense of Coloured Landmarks at 18-24 Months

ERIC Educational Resources Information Center

Nardini, Marko; Atkinson, Janette; Burgess, Neil

2008-01-01

In previous studies, children disoriented in small enclosures used room shape, but not wall colors, to find hidden objects. Their reorientation was said to depend solely on a "geometric module" informationally encapsulated with respect to color. We argue that previous studies did not fully evaluate children's use of color owing to a bias in the…

Diapir-induced reorientation of Saturn's moon Enceladus.

PubMed

Nimmo, Francis; Pappalardo, Robert T

2006-06-01

Enceladus is a small icy satellite of Saturn. Its south polar region consists of young, tectonically deformed terrain and has an anomalously high heat flux. This heat flux is probably due to localized tidal dissipation within either the ice shell or the underlying silicate core. The surface deformation is plausibly due to upwelling of low-density material (diapirism) as a result of this tidal heating. Here we show that the current polar location of the hotspot can be explained by reorientation of the satellite's rotation axis because of the presence of a low-density diapir. If the diapir is in the ice shell, then the shell must be relatively thick and maintain significant rigidity (elastic thickness greater than approximately 0.5 km); if the diapir is in the silicate core, then Enceladus cannot possess a global subsurface ocean, because the core must be coupled to the overlying ice for reorientation to occur. The reorientation generates large (approximately 10 MPa) tectonic stress patterns that are compatible with the observed deformation of the south polar region. We predict that the distribution of impact craters on the surface will not show the usual leading hemisphere-trailing hemisphere asymmetry. A low-density diapir also yields a potentially observable negative gravity anomaly.

The persistence of the gravity signal in flax roots

NASA Astrophysics Data System (ADS)

Hasenstein, Karl H.

Although the presentation time of gravitropism has been studied, no data exist as to how long a reorientation stimulus affects the gravitropic response of a root. We tested the duration of gravitropic curvature in roots of Linum usitatissimum after reversing a one hour, 90 degree gravistimulus by increasing time intervals in vertical orientation before clinorotating the roots and acquiring infrared digital images. Clinorotation was performed either parallel or perpendicular to the gravity vector. Under either condition the gravistimulus affected curvature during clinorotation only between two to three minutes. Maximal curvature after one minute of vertical reorientation was 15 degrees within one hour. After three minutes in vertical orientation the observed curvature was not statistically different from vertically growing roots. In both orientations, maximum curvature occurred after 1hr. Perpendicular (horizontal) clinorotation showed decreasing curvature with increasing reorientation time. Parallel (vertical) clinorotation resulted in greater variability to the reorientation time. These data indicate that the gravity stimulus operates essentially memory free and that clinorotation affects the gravity response. Therefore all aspects of clinorotation need to be studied before an assessment of clinostats for the simulation of microgravity is possible and a time limit for memory effects of mechanostimulation can be determined.

Dynamic nuclear polarization assisted spin diffusion for the solid effect case.

PubMed

Hovav, Yonatan; Feintuch, Akiva; Vega, Shimon

2011-02-21

The dynamic nuclear polarization (DNP) process in solids depends on the magnitudes of hyperfine interactions between unpaired electrons and their neighboring (core) nuclei, and on the dipole-dipole interactions between all nuclei in the sample. The polarization enhancement of the bulk nuclei has been typically described in terms of a hyperfine-assisted polarization of a core nucleus by microwave irradiation followed by a dipolar-assisted spin diffusion process in the core-bulk nuclear system. This work presents a theoretical approach for the study of this combined process using a density matrix formalism. In particular, solid effect DNP on a single electron coupled to a nuclear spin system is considered, taking into account the interactions between the spins as well as the main relaxation mechanisms introduced via the electron, nuclear, and cross-relaxation rates. The basic principles of the DNP-assisted spin diffusion mechanism, polarizing the bulk nuclei, are presented, and it is shown that the polarization of the core nuclei and the spin diffusion process should not be treated separately. To emphasize this observation the coherent mechanism driving the pure spin diffusion process is also discussed. In order to demonstrate the effects of the interactions and relaxation mechanisms on the enhancement of the nuclear polarization, model systems of up to ten spins are considered and polarization buildup curves are simulated. A linear chain of spins consisting of a single electron coupled to a core nucleus, which in turn is dipolar coupled to a chain of bulk nuclei, is considered. The interaction and relaxation parameters of this model system were chosen in a way to enable a critical analysis of the polarization enhancement of all nuclei, and are not far from the values of (13)C nuclei in frozen (glassy) organic solutions containing radicals, typically used in DNP at high fields. Results from the simulations are shown, demonstrating the complex dependences of the DNP-assisted spin diffusion process on variations of the relevant parameters. In particular, the effect of the spin lattice relaxation times on the polarization buildup times and the resulting end polarization are discussed, and the quenching of the polarizations by the hyperfine interaction is demonstrated.

Friction spinning - Twist phenomena and the capability of influencing them

NASA Astrophysics Data System (ADS)

Lossen, Benjamin; Homberg, Werner

2016-10-01

The friction spinning process can be allocated to the incremental forming techniques. The process consists of process elements from both metal spinning and friction welding. The selective combination of process elements from these two processes results in the integration of friction sub-processes in a spinning process. This implies self-induced heat generation with the possibility of manufacturing functionally graded parts from tube and sheets. Compared with conventional spinning processes, this in-process heat treatment permits the extension of existing forming limits and also the production of more complex geometries. Furthermore, the defined adjustment of part properties like strength, grain size/orientation and surface conditions can be achieved through the appropriate process parameter settings and consequently by setting a specific temperature profile in combination with the degree of deformation. The results presented from tube forming start with an investigation into the resulting twist phenomena in flange processing. In this way, the influence of the main parameters, such as rotation speed, feed rate, forming paths and tool friction surface, and their effects on temperature, forces and finally the twist behavior are analyzed. Following this, the significant correlations with the parameters and a new process strategy are set out in order to visualize the possibility of achieving a defined grain texture orientation.

Distance measurements across randomly distributed nitroxide probes from the temperature dependence of the electron spin phase memory time at 240 GHz

NASA Astrophysics Data System (ADS)

Edwards, Devin T.; Takahashi, Susumu; Sherwin, Mark S.; Han, Songi

2012-10-01

At 8.5 T, the polarization of an ensemble of electron spins is essentially 100% at 2 K, and decreases to 30% at 20 K. The strong temperature dependence of the electron spin polarization between 2 and 20 K leads to the phenomenon of spin bath quenching: temporal fluctuations of the dipolar magnetic fields associated with the energy-conserving spin "flip-flop" process are quenched as the temperature of the spin bath is lowered to the point of nearly complete spin polarization. This work uses pulsed electron paramagnetic resonance (EPR) at 240 GHz to investigate the effects of spin bath quenching on the phase memory times (TM) of randomly-distributed ensembles of nitroxide molecules below 20 K at 8.5 T. For a given electron spin concentration, a characteristic, dipolar flip-flop rate (W) is extracted by fitting the temperature dependence of TM to a simple model of decoherence driven by the spin flip-flop process. In frozen solutions of 4-Amino-TEMPO, a stable nitroxide radical in a deuterated water-glass, a calibration is used to quantify average spin-spin distances as large as r¯=6.6 nm from the dipolar flip-flop rate. For longer distances, nuclear spin fluctuations, which are not frozen out, begin to dominate over the electron spin flip-flop processes, placing an effective ceiling on this method for nitroxide molecules. For a bulk solution with a three-dimensional distribution of nitroxide molecules at concentration n, we find W∝n∝1/r, which is consistent with magnetic dipolar spin interactions. Alternatively, we observe W∝n for nitroxides tethered to a quasi two-dimensional surface of large (Ø ˜ 200 nm), unilamellar, lipid vesicles, demonstrating that the quantification of spin bath quenching can also be used to discern the geometry of molecular assembly or organization.

Hot Electron Injection into Uniaxially Strained Silicon

NASA Astrophysics Data System (ADS)

Kim, Hyun Soo

In semiconductor spintronics, silicon attracts great attention due to the long electron spin lifetime. Silicon is also one of the most commonly used semiconductor in microelectronics industry. The spin relaxation process of diamond crystal structure such as silicon is dominant by Elliot-Yafet mechanism. Yafet shows that intravalley scattering process is dominant. The conduction electron spin lifetime measured by electron spin resonance measurement and electronic measurement using ballistic hot electron method well agrees with Yafet's theory. However, the recent theory predicts a strong contribution of intervalley scattering process such as f-process in silicon. The conduction band minimum is close the Brillouin zone edge, X point which causes strong spin mixing at the conduction band. A recent experiment of electric field-induced hot electron spin relaxation also shows the strong effect of f-process in silicon. In uniaxially strained silicon along crystal axis [100], the suppression of f-process is predicted which leads to enhance electron spin lifetime. By inducing a change in crystal structure due to uniaxial strain, the six fold degeneracy becomes two fold degeneracy, which is valley splitting. As the valley splitting increases, intervalley scattering is reduced. A recent theory predicts 4 times longer electron spin lifetime in 0.5% uniaxially strained silicon. In this thesis, we demonstrate ballistic hot electron injection into silicon under various uniaxial strain. Spin polarized hot electron injection under strain is experimentally one of the most challenging part to measure conduction electron spin lifetime in silicon. Hot electron injection adopts tunnel junction which is a thin oxide layer between two conducting materials. Tunnel barrier, which is an oxide layer, is only 4 ˜ 5 nm thick. Also, two conducting materials are only tens of nanometer. Therefore, under high pressure to apply 0.5% strain on silicon, thin films on silicon substrate can be easily destroyed. In order to confirm the performance of tunnel junction, we use tunnel magnetoresistance(TMR). TMR consists of two kinds of ferromagnetic materials and an oxide layer as tunnel barrier in order to measure spin valve effect. Using silicon as a collector with Schottky barrier interface between metal and silicon, ballistic hot spin polarized electron injection into silicon is demonstrated. We also observed change of coercive field and magnetoresistance due to modification of local states in ferromagnetic materials and surface states at the interface between metal and silicon due to strain.

Quantum Information Processing with Large Nuclear Spins in GaAs Semiconductors

NASA Astrophysics Data System (ADS)

Leuenberger, Michael N.; Loss, Daniel; Poggio, M.; Awschalom, D. D.

2002-10-01

We propose an implementation for quantum information processing based on coherent manipulations of nuclear spins I=3/2 in GaAs semiconductors. We describe theoretically an NMR method which involves multiphoton transitions and which exploits the nonequidistance of nuclear spin levels due to quadrupolar splittings. Starting from known spin anisotropies we derive effective Hamiltonians in a generalized rotating frame, valid for arbitrary I, which allow us to describe the nonperturbative time evolution of spin states generated by magnetic rf fields. We identify an experimentally observable regime for multiphoton Rabi oscillations. In the nonlinear regime, we find Berry phase interference.

Collisional Penrose process with spinning particles

NASA Astrophysics Data System (ADS)

Mukherjee, Sajal

2018-03-01

In this article, we have investigated collisional Penrose process (CPP) using spinning particles in a Kerr spacetime. Recent studies have shown that the collision between two spinning particles can produce a significantly high energy in the center of mass frame. Here, we explicitly compute the energy extraction and efficiency as measured by an observer at infinity. We consider the colliding particles as well as the escaping particles may contain spins. It has been shown that the energy extraction is larger than the non-spinning case and also their possibility to escape to infinity is wider than the geodesics.

Magneto-transport and microstructure of Co{sub 2}Fe(Ga{sub 0.5}Ge{sub 0.5})/Cu lateral spin valves prepared by top-down microfabrication process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ikhtiar,; Mitani, S.; Hono, K., E-mail: kazuhiro.hono@nims.go.jp

Heusler alloy-based lateral spin valves with ohmic contacts are prepared for the Co{sub 2}Fe(Ga{sub 0.5}Ge{sub 0.5})/Cu system by means of the top-down microfabrication process. The magneto-transport and microstructure are characterized to investigate the influence of the microfabrication route on the spin dependent transport of lateral spin valves systematically. A large non-local spin signal (△R{sub S}) of 17.3 mΩ is observed at room temperature, which is attributed to the highly spin-polarized Co{sub 2}Fe(Ga{sub 0.5}Ge{sub 0.5}) ferromagnet and the clean Co{sub 2}Fe(Ga{sub 0.5}Ge{sub 0.5})/Cu interfaces confirmed by transmission electron microscopy. Based on the general expression of one-dimensional spin diffusion model, we discuss themore » importance of interfacial spin polarization in Heusler alloy-based lateral spin valves.« less

Density matrix-based time-dependent configuration interaction approach to ultrafast spin-flip dynamics

NASA Astrophysics Data System (ADS)

Wang, Huihui; Bokarev, Sergey I.; Aziz, Saadullah G.; Kühn, Oliver

2017-08-01

Recent developments in attosecond spectroscopy yield access to the correlated motion of electrons on their intrinsic timescales. Spin-flip dynamics is usually considered in the context of valence electronic states, where spin-orbit coupling is weak and processes related to the electron spin are usually driven by nuclear motion. However, for core-excited states, where the core-hole has a nonzero angular momentum, spin-orbit coupling is strong enough to drive spin-flips on a much shorter timescale. Using density matrix-based time-dependent restricted active space configuration interaction including spin-orbit coupling, we address an unprecedentedly short spin-crossover for the example of L-edge (2p→3d) excited states of a prototypical Fe(II) complex. This process occurs on a timescale, which is faster than that of Auger decay (∼4 fs) treated here explicitly. Modest variations of carrier frequency and pulse duration can lead to substantial changes in the spin-state yield, suggesting its control by soft X-ray light.

Demonstration of a robust magnonic spin wave interferometer.

PubMed

Kanazawa, Naoki; Goto, Taichi; Sekiguchi, Koji; Granovsky, Alexander B; Ross, Caroline A; Takagi, Hiroyuki; Nakamura, Yuichi; Inoue, Mitsuteru

2016-07-22

Magnonics is an emerging field dealing with ultralow power consumption logic circuits, in which the flow of spin waves, rather than electric charges, transmits and processes information. Waves, including spin waves, excel at encoding information via their phase using interference. This enables a number of inputs to be processed in one device, which offers the promise of multi-input multi-output logic gates. To realize such an integrated device, it is essential to demonstrate spin wave interferometers using spatially isotropic spin waves with high operational stability. However, spin wave reflection at the waveguide edge has previously limited the stability of interfering waves, precluding the use of isotropic spin waves, i.e., forward volume waves. Here, a spin wave absorber is demonstrated comprising a yttrium iron garnet waveguide partially covered by gold. This device is shown experimentally to be a robust spin wave interferometer using the forward volume mode, with a large ON/OFF isolation value of 13.7 dB even in magnetic fields over 30 Oe.

Demonstration of a robust magnonic spin wave interferometer

PubMed Central

Kanazawa, Naoki; Goto, Taichi; Sekiguchi, Koji; Granovsky, Alexander B.; Ross, Caroline A.; Takagi, Hiroyuki; Nakamura, Yuichi; Inoue, Mitsuteru

2016-01-01

Magnonics is an emerging field dealing with ultralow power consumption logic circuits, in which the flow of spin waves, rather than electric charges, transmits and processes information. Waves, including spin waves, excel at encoding information via their phase using interference. This enables a number of inputs to be processed in one device, which offers the promise of multi-input multi-output logic gates. To realize such an integrated device, it is essential to demonstrate spin wave interferometers using spatially isotropic spin waves with high operational stability. However, spin wave reflection at the waveguide edge has previously limited the stability of interfering waves, precluding the use of isotropic spin waves, i.e., forward volume waves. Here, a spin wave absorber is demonstrated comprising a yttrium iron garnet waveguide partially covered by gold. This device is shown experimentally to be a robust spin wave interferometer using the forward volume mode, with a large ON/OFF isolation value of 13.7 dB even in magnetic fields over 30 Oe. PMID:27443989

Spin-dependent delay time in ferromagnet/insulator/ferromagnet heterostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, ZhengWei; Zheng Shi, De; Lv, HouXiang

2014-07-07

We study theoretically spin-dependent group delay and dwell time in ferromagnet/insulator/ferromagnet (FM/I/FM) heterostructure. The results indicate that, when the electrons with different spin orientations tunnel through the FM/I/FM junction, the spin-up process and the spin-down process are separated on the time scales. As the self-interference delay has the spin-dependent features, the variations of spin-dependent dwell-time and spin-dependent group-delay time with the structure parameters appear different features, especially, in low incident energy range. These different features show up as that the group delay times for the spin-up electrons are always longer than those for spin-down electrons when the barrier height ormore » incident energy increase. In contrast, the dwell times for the spin-up electrons are longer (shorter) than those for spin-down electrons when the barrier heights (the incident energy) are under a certain value. When the barrier heights (the incident energy) exceed a certain value, the dwell times for the spin-up electrons turn out to be shorter (longer) than those for spin-down electrons. In addition, the group delay time and the dwell time for spin-up and down electrons also relies on the comparative direction of magnetization in two FM layers and tends to saturation with the thickness of the barrier.« less

Study of flowability effect on self-planarization performance at SOC materials

NASA Astrophysics Data System (ADS)

Yun, Huichan; Kim, Jinhyung; Park, Youjung; Kim, Yoona; Jeong, Seulgi; Baek, Jaeyeol; Yoon, Byeri; Lim, Sanghak

2017-03-01

For multilayer process, importance of carbon-based spin-on hardmask material that replaces amorphous carbon layer (ACL) is ever increasing. Carbon-based spin-on hardmask is an organic polymer with high carbon content formulated in organic solvents for spin-coating application that is cured through baking. In comparison to CVD process for ACL, carbon-based spin-on hardmask material can offer several benefits: lower cost of ownership (CoO) and improved process time, as well as better gap-fill and planarization performances. Thus carbon-based spin-on hardmask material of high etch resistance, good gap-fill properties and global planarization performances over various pattern topographies are desired to achieve the fine patterning and high aspect ratio (A/R). In particular, good level of global planarization of spin coated layer over the underlying pattern topographies is important for self-aligned double patterning (SADP) process as it dictates the photolithographic margin. Herein, we report a copolymer carbon-based spin-on hardmask resin formulation that exhibits favorable film shrinkage profile and good etch resistance properties. By combining the favorable characteristics of each resin - one resin with good shrinkage property and the other with excellent etch resistance into the copolymer, it was possible to achieve a carbonbased spin-on hardmask formulation with desirable level of etch resistance and the planarization performances across various underlying substrate pattern topographies.

Spin-resolved electron waiting times in a quantum-dot spin valve

NASA Astrophysics Data System (ADS)

Tang, Gaomin; Xu, Fuming; Mi, Shuo; Wang, Jian

2018-04-01

We study the electronic waiting-time distributions (WTDs) in a noninteracting quantum-dot spin valve by varying spin polarization and the noncollinear angle between the magnetizations of the leads using the scattering matrix approach. Since the quantum-dot spin valve involves two channels (spin up and down) in both the incoming and outgoing channels, we study three different kinds of WTDs, which are two-channel WTD, spin-resolved single-channel WTD, and cross-channel WTD. We analyze the behaviors of WTDs in short times, correlated with the current behaviors for different spin polarizations and noncollinear angles. Cross-channel WTD reflects the correlation between two spin channels and can be used to characterize the spin-transfer torque process. We study the influence of the earlier detection on the subsequent detection from the perspective of cross-channel WTD, and define the influence degree quantity as the cumulative absolute difference between cross-channel WTDs and first-passage time distributions to quantitatively characterize the spin-flip process. We observe that influence degree versus spin-transfer torque for different noncollinear angles as well as different polarizations collapse into a single curve showing universal behaviors. This demonstrates that cross-channel WTDs can be a pathway to characterize spin correlation in spintronics system.

Phase stability, single crystal growth, and anisotropic magnetic properties of Ca-La magnetoplumbite-type ferrite

NASA Astrophysics Data System (ADS)

Uji, K.; Waki, T.; Tabata, Y.; Nakamura, H.

2017-01-01

The cation compositions in the Ca-La magnetoplumbite-type (M-type) ferrite, CaxLayFezO19, prepared from various initial fractions of reagents, were analyzed by wavelength-dispersive X-ray (WDX) spectroscopy. The reliability of the WDX composition analysis was confirmed by a crosscheck using inductively coupled plasma atomic emission spectrometry (ICP-AES). For particular polycrystalline samples furnace-cooled from 1250 ° C , the solubility ranges of Ca, La, and Fe were found to be 0.45 ≤ x ≤ 0.70 , 0.39 ≤ y ≤ 0.66 , and 11.82 ≤ z ≤ 11.92 , respectively, assuming x + y + z = 13 . Despite that the samples were synthesized from various starting compositions, the values of z / (x + y) of the matrix M phase are smaller than the M-type regular value, 12, for all the samples and comes in a very limited range at ∼ 11 , suggesting most probably Ca occupation at particular Fe sites or Fe deficiency due to insertion of stacking fault to Ca/La/O packing. Single crystals of CaxLayFezO19 with various x / y ratios were synthesized successfully by the self-flux method, followed by the characterization of their magnetic properties. The saturation magnetization and the Curie temperature were found to be almost independent of the cation composition. In contrast, the hard-axis magnetization process at low temperature depended significantly on the Ca/La ratio, and showed a sharp jump at ≲ 10 kOe, which can be attributed to a spin reorientation transition associated with the appearance of Fe2+.

Hydride reorientation and its impact on ambient temperature mechanical properties of high burn-up irradiated and unirradiated recrystallized Zircaloy-2 nuclear fuel cladding with an inner liner

NASA Astrophysics Data System (ADS)

Auzoux, Q.; Bouffioux, P.; Machiels, A.; Yagnik, S.; Bourdiliau, B.; Mallet, C.; Mozzani, N.; Colas, K.

2017-10-01

Precipitation of radial hydrides in zirconium-based alloy cladding concomitant with the cooling of spent nuclear fuel during dry storage can potentially compromise cladding integrity during its subsequent handling and transportation. This paper investigates hydride reorientation and its impact on ductility in unirradiated and irradiated recrystallized Zircaloy-2 cladding with an inner liner (cladding for boiling water reactors) subjected to hydride reorientation treatments. Cooling from 400 °C, hydride reorientation occurs in recrystallized Zircaloy-2 with liner at a lower effective stress in irradiated samples (below 40 MPa) than in unirradiated specimens (between 40 and 80 MPa). Despite significant hydride reorientation, unirradiated recrystallized Zircaloy-2 with liner cladding containing ∼200 wppm hydrogen shows a high diametral strain at fracture (>15%) during burst tests at ambient temperature. This ductile behavior is due to (1) the lower yield stress of the recrystallized cladding materials in comparison to hydride fracture strength (corrected by the compression stress arising from the precipitation) and (2) the hydride or hydrogen-depleted zone as a result of segregation of hydrogen into the liner layer. In irradiated Zircaloy-2 with liner cladding containing ∼340 wppm hydrogen, the conservation of some ductility during ring tensile tests at ambient temperature after reorientation treatment at 400 °C with cooling rates of ∼60 °C/h is also attributed to the existence of a hydride-depleted zone. Treatments at lower cooling rates (∼6 °C/h and 0.6 °C/h) promote greater levels of hydrogen segregation into the liner and allow for increased irradiation defect annealing, both of which result in a significant increase in ductility. Based on this investigation, given the very low cooling rates typical of dry storage systems, it can be concluded that the thermal transients associated with dry storage should not degrade, and more likely should actually improve, ductility of recrystallized Zircaloy-2 cladding with inner liner with such hydrogen content.

Ultrafast optical control of individual quantum dot spin qubits.

PubMed

De Greve, Kristiaan; Press, David; McMahon, Peter L; Yamamoto, Yoshihisa

2013-09-01

Single spins in semiconductor quantum dots form a promising platform for solid-state quantum information processing. The spin-up and spin-down states of a single electron or hole, trapped inside a quantum dot, can represent a single qubit with a reasonably long decoherence time. The spin qubit can be optically coupled to excited (charged exciton) states that are also trapped in the quantum dot, which provides a mechanism to quickly initialize, manipulate and measure the spin state with optical pulses, and to interface between a stationary matter qubit and a 'flying' photonic qubit for quantum communication and distributed quantum information processing. The interaction of the spin qubit with light may be enhanced by placing the quantum dot inside a monolithic microcavity. An entire system, consisting of a two-dimensional array of quantum dots and a planar microcavity, may plausibly be constructed by modern semiconductor nano-fabrication technology and could offer a path toward chip-sized scalable quantum repeaters and quantum computers. This article reviews the recent experimental developments in optical control of single quantum dot spins for quantum information processing. We highlight demonstrations of a complete set of all-optical single-qubit operations on a single quantum dot spin: initialization, an arbitrary SU(2) gate, and measurement. We review the decoherence and dephasing mechanisms due to hyperfine interaction with the nuclear-spin bath, and show how the single-qubit operations can be combined to perform spin echo sequences that extend the qubit decoherence from a few nanoseconds to several microseconds, more than 5 orders of magnitude longer than the single-qubit gate time. Two-qubit coupling is discussed, both within a single chip by means of exchange coupling of nearby spins and optically induced geometric phases, as well as over longer-distances. Long-distance spin-spin entanglement can be generated if each spin can emit a photon that is entangled with the spin, and these photons are then interfered. We review recent work demonstrating entanglement between a stationary spin qubit and a flying photonic qubit. These experiments utilize the polarization- and frequency-dependent spontaneous emission from the lowest charged exciton state to single spin Zeeman sublevels.

Design of process parameters for the incremental tube forming (ITF) by FEM to control product properties

NASA Astrophysics Data System (ADS)

Nazari, Esmaeil; Löbbe, Christian; Gallus, Stefan; Izadyar, S. Ahmad; Tekkaya, A. Erman

2018-05-01

The incremental tube forming (ITF) is a process combination of the kinematic tube bending and spinning to shape high strength and tailored tubes with variable diameters and thicknesses. In contrast to conventional bending methods, the compressive stress superposition by the spinning process facilitates low bending stresses, so that geometrical errors are avoided and the shape accuracy is improved. The study reveals the interaction of plastic strains of the rolling and bending process through an explicit FEM investigation. For this purpose, the three-dimensional machine set-up is discretized and modeled in terms of the fully disclosed spinning process during the gradual deflection of the tube end for bending. The analysis shows that, depending on the forming tool shape, the stress superposition is accompanied by high plastic strains. Furthermore, this phenomenon is explained by the three dimensional normal and shear strains during the incremental spinning. Analyzing the strains history also shows a nonlinearity between the strains by bending and spinning. It is also shown that process parameters like rotational velocity of the spinning rolls have a huge influence on the deformation pattern. Finally, the method is used for the manufacturing of an example product, which reveals the high process flexibility. In one clamp a component with a graded wall thickness and outside diameter along the longitudinal axis is produced.

Exogenous (automatic) attention to emotional stimuli: a review.

PubMed

Carretié, Luis

2014-12-01

Current knowledge on the architecture of exogenous attention (also called automatic, bottom-up, or stimulus-driven attention, among other terms) has been mainly obtained from studies employing neutral, anodyne stimuli. Since, from an evolutionary perspective, exogenous attention can be understood as an adaptive tool for rapidly detecting salient events, reorienting processing resources to them, and enhancing processing mechanisms, emotional events (which are, by definition, salient for the individual) would seem crucial to a comprehensive understanding of this process. This review, focusing on the visual modality, describes 55 experiments in which both emotional and neutral irrelevant distractors are presented at the same time as ongoing task targets. Qualitative and, when possible, meta-analytic descriptions of results are provided. The most conspicuous result is that, as confirmed by behavioral and/or neural indices, emotional distractors capture exogenous attention to a significantly greater extent than do neutral distractors. The modulatory effects of the nature of distractors capturing attention, of the ongoing task characteristics, and of individual differences, previously proposed as mediating factors, are also described. Additionally, studies reviewed here provide temporal and spatial information-partially absent in traditional cognitive models-on the neural basis of preattention/evaluation, reorienting, and sensory amplification, the main subprocesses involved in exogenous attention. A model integrating these different levels of information is proposed. The present review, which reveals that there are several key issues for which experimental data are surprisingly scarce, confirms the relevance of including emotional distractors in studies on exogenous attention.

Molecular relaxation processes in dimethyldichlorosilane studied by vibrational spectroscopy

NASA Astrophysics Data System (ADS)

Bratu, I.; Grecu, Rodica; Iliescu, T.

1995-04-01

The paper presents the experimentally determined correlation functions ( CF) of the bands due to IR and Raman active vibrations ν asSiCl 2 and ν sSiCl 2 of dimethyldichlorosilane ( DMDCS) in pure liquid and in solutions. Both reorientational and vibrational relaxations (the last one being dominant) contribute to the profiles of these vibrational modes. Kubo-Rothschild's and Oxtoby's models compared with the experimental CF indicate an intermediate modulation regime.

Change of focus: from intensive care towards organ donation.

PubMed

Meyer, Käthe; Bjørk, Ida T

2008-02-01

To progress from identifying a potential organ donor to implementing the actual organ donation effectively is a challenging process for all involved. The nurses might find the change of focus difficult, as the donor organ acquisition process often starts before the relatives had been informed and have had the time to reorient themselves about the severe situation of the patient and have been briefed on the option of organ donation. The purpose was to investigate the hospital-based education in organ donation at the 28 Norwegian donor hospitals, and elicit the needs of the intensive care nurses for imparting of required knowledge and support in shifting their focus from intensive care towards the process of organ procurement. Hospital-based education and guidelines in organ donation were analyzed by scrutinizing the documents available. Eleven units were found to have their own guidelines and only three hospitals had organ donation in their educational programme. Intensive care nurses at three hospitals participated in focus groups. The main finding was the need for collaboration and mutual understanding within the treatment team. Nurses expounded the multiple responsibilities that they discharged during the course of intensive care. In reorienting their focus from intensive care to donor organ procurement, the time of death was explained as the crucial turning point. The knowledge of intensive care staff and professional competence were crucial in winning the relatives' trust and were central in the communication processes. Donor hospitals should implement systematic training and debriefing, where both nurses and physicians contribute to this process. Well-prepared protocols for organ donation at hospitals can define responsibilities assigned to different members of the donor organ acquisition team.

Post-electroconvulsive therapy recovery and reorientation time with methohexital and ketamine: a randomized, longitudinal cross-over design trial

PubMed Central

Yen, Tony; Khafaja, Mohamad; Lam, Nicholas; Crumbacher, James; Schrader, Ronald; Rask, John; Billstrand, Mary; Rothfork, Jacob; Abbott, Christopher C.

2014-01-01

Objectives Methohexital, a barbiturate anesthetic commonly used for electroconvulsive therapy (ECT), possesses dose-dependent anticonvulsant properties, and its use can interfere with effective seizure therapy in patients with high seizure thresholds. Ketamine, a NMDA-antagonist with epileptogenic properties not broadly used for ECT inductions, is a commonly used induction agent for general anesthesia. Recent studies suggest that the use of ketamine is effective in allowing successful ECT treatment in patients with high seizure thresholds without an increase in side-effects. In this preliminary study, we directly compared the recovery and re-orientation times of subjects receiving ketamine and methohexital for ECTs. Methods Twenty patients were randomized in a cross-over design to receive methohexital and ketamine for ECT inductions in alternating fashion for six trials. Primary outcome measures were recovery time (voluntary movement, respiratory effort, blood pressure, consciousness, and O2 saturation) and re-orientation time. Secondary outcome measures were individual recovery variables, side-effect occurrence, and seizure duration. Results: Overall recovery time was not significantly different between the two treatment arms (F(1,17) = 0.72, P = 0.41). Re-orientation time was faster in the methohexital arm (F(1,17) = 9.23, P = 0.007). Conclusion Ketamine inductions resulted in higher number of side-effects, higher subject dropout rates, and a longer reorientation time with respect to methohexital inductions. No significant difference in post-anesthesia recovery time was found between the ketamine and methohexital arms. Intolerability to ketamine affected a significant proportion of subjects, and suggests that ketamine should remain as an alternative or adjunctive agent for patients with high seizure thresholds. PMID:24755722

Comparison of Anion Reorientational Dynamics in MCB 9 H 10 and M 2 B 10 H 10 (M = Li, Na) via Nuclear Magnetic Resonance and Quasielastic Neutron Scattering Studies

DOE PAGES

Soloninin, Alexei V.; Dimitrievska, Mirjana; Skoryunov, Roman V.; ...

2016-12-13

The disordered phases of the 1-carba-closo-decaborates LiCB9H10 and NaCB9H10 exhibit the best solid-state ionic conductivities to date among all known polycrystalline competitors, likely facilitated in part by the highly orientationally mobile CB9H10- anions. We have undertaken both NMR and quasielastic neutron scattering (QENS) measurements to help characterize the monovalent anion reorientational mobilities and mechanisms associated with these two compounds and to compare their anion reorientational behaviors with those for the divalent B10H102- anions in the related Li2B10H10 and Na2B10H10 compounds. NMR data show that the transition from the low-T ordered to the high-T disordered phase for both LiCB9H10 and NaCB9H10more » is accompanied by a nearly two-orders-of-magnitude increase in the reorientational jump rate of CB9H10- anions. QENS measurements of the various disordered compounds indicate anion jump correlation frequencies on the order of 1010-1011 s-1 and confirm that NaCB9H10 displays jump frequencies about 60% to 120% higher than those for LiCB9H10 and Na2B10H10 at comparable temperatures. The Q-dependent quasielastic scattering suggests similar small-angular-jump reorientational mechanisms for the different disordered anions, changing from more uniaxial in character at lower temperatures to more multidimensional at higher temperatures, although still falling short of full three-dimensional rotational diffusion below 500 K within the nanosecond neutron window.« less

Spin Hall and Spin Swapping Torques in Diffusive Ferromagnets

NASA Astrophysics Data System (ADS)

Pauyac, Christian Ortiz; Chshiev, Mairbek; Manchon, Aurelien; Nikolaev, Sergey A.

2018-04-01

A complete set of the generalized drift-diffusion equations for a coupled charge and spin dynamics in ferromagnets in the presence of extrinsic spin-orbit coupling is derived from the quantum kinetic approach, covering major transport phenomena, such as the spin and anomalous Hall effects, spin swapping, spin precession, and relaxation processes. We argue that the spin swapping effect in ferromagnets is enhanced due to spin polarization, while the overall spin texture induced by the interplay of spin-orbital and spin precession effects displays a complex spatial dependence that can be exploited to generate torques and nucleate or propagate domain walls in centrosymmetric geometries without the use of external polarizers, as opposed to the conventional understanding of spin-orbit mediated torques.

Quantum Information Processing with Large Nuclear Spins in GaAs Semiconductors

NASA Astrophysics Data System (ADS)

Leuenberger, Michael N.; Loss, Daniel; Poggio, M.; Awschalom, D. D.

2003-03-01

We propose an implementation for quantum information processing based on coherent manipulations of nuclear spins I=3/2 in GaAs semiconductors. We describe theoretically an NMR method which involves multiphoton transitions and which exploits the nonequidistance of nuclear spin levels due to quadrupolar splittings. Starting from known spin anisotropies we derive effective Hamiltonians in a generalized rotating frame, valid for arbitrary I, which allow us to describe the nonperturbative time evolution of spin states generated by magnetic rf fields. We identify an experimentally observable regime for multiphoton Rabi oscillations. In the nonlinear regime, we find Berry phase interference. Ref: PRL 89, 207601 (2002).

Momentum Transfer in a Spinning Fuel Tank Filled with Xenon

NASA Technical Reports Server (NTRS)

Peugeot, John W.; Dorney, Daniel J.

2006-01-01

Transient spin-up and spin-down flows inside of spacecraft fuel tanks need to be analyzed in order to properly design spacecraft control systems. Knowledge of the characteristics of angular momentum transfer to and from the fuel is used to size the de-spin mechanism that places the spacecraft in a controllable in-orbit state. In previous studies, several analytical models of the spin-up process were developed. However, none have accurately predicted all of the flow dynamics. Several studies have also been conducted using Navier-Stokes based methods. These approaches have been much more successful at simulating the dynamic processes in a cylindrical container, but have not addressed the issue of momentum transfer. In the current study, the spin-up and spin-down of a fuel tank filled with gaseous xenon has been investigated using a three-dimensional unsteady Navier-Stokes code. Primary interests have been concentrated on the spin-up/spin-down time constants and the initial torque imparted on the system. Additional focus was given to the relationship between the dominant flow dynamics and the trends in momentum transfer. Through the simulation of both a cylindrical and a spherical tank, it was revealed that the transfer of angular momentum is nonlinear at early times and tends toward a linear pattern at later times. Further investigation suggests that the nonlinear spin up is controlled by the turbulent transport of momentum, while the linear phase is controlled by a Coriolis driven (Ekman) flow along the outer wall. These results indicate that the spinup and spin-down processes occur more quickly in tanks with curved surfaces than those with defined top, bottom, and side walls. The results also provide insights for the design of spacecraft de-spin mechanisms.

Correction of mid-spatial-frequency errors by smoothing in spin motion for CCOS

NASA Astrophysics Data System (ADS)

Zhang, Yizhong; Wei, Chaoyang; Shao, Jianda; Xu, Xueke; Liu, Shijie; Hu, Chen; Zhang, Haichao; Gu, Haojin

2015-08-01

Smoothing is a convenient and efficient way to correct mid-spatial-frequency errors. Quantifying the smoothing effect allows improvements in efficiency for finishing precision optics. A series experiments in spin motion are performed to study the smoothing effects about correcting mid-spatial-frequency errors. Some of them use a same pitch tool at different spinning speed, and others at a same spinning speed with different tools. Introduced and improved Shu's model to describe and compare the smoothing efficiency with different spinning speed and different tools. From the experimental results, the mid-spatial-frequency errors on the initial surface were nearly smoothed out after the process in spin motion and the number of smoothing times can be estimated by the model before the process. Meanwhile this method was also applied to smooth the aspherical component, which has an obvious mid-spatial-frequency error after Magnetorheological Finishing processing. As a result, a high precision aspheric optical component was obtained with PV=0.1λ and RMS=0.01λ.

Variable structure control of spacecraft reorientation maneuvers

NASA Technical Reports Server (NTRS)

Sira-Ramirez, H.; Dwyer, T. A. W., III

1986-01-01

A Variable Structure Control (VSC) approach is presented for multi-axial spacecraft reorientation maneuvers. A nonlinear sliding surface is proposed which results in an asymptotically stable, ideal linear sliding motion of Cayley-Rodriques attitude parameters. By imposing a desired equivalent dynamics on the attitude parameters, the approach is devoid of optimal control considerations. The single axis case provides a design scheme for the multiple axes design problem. Illustrative examples are presented.

Plastid sedimentation kinetics in roots of wild-type and starch-deficient mutants of Arabidopsis

NASA Technical Reports Server (NTRS)

MacCleery, S. A.; Kiss, J. Z.

1999-01-01

Sedimentation and movement of plastids in columella cells of the root cap were measured in seedlings of wild-type, a reduced starch mutant, and a starchless mutant of Arabidopsis. To assay for sedimentation, we used both linear measurements and the change of angle from the cell center as indices in vertical and reoriented plants with the aid of computer-assisted image analysis. Seedlings were fixed at short periods after reorientation, and plastid sedimentation correlated with starch content in the three strains of Arabidopsis. Amyloplasts of wild-type seedlings showed the greatest sedimentation, whereas plastids of the starchless mutant showed no significant sedimentation in the vertically grown and reoriented seedlings. Because previous research has shown that a full complement of starch is needed for full gravitropic sensitivity, this study correlates increased sensitivity with plastid sedimentation. However, although plastid sedimentation contributed to gravisensitivity, it was not required, because the gravitropic starchless mutant had plastids that did not sediment. This is the first study, to our knowledge, to measure plastid sedimentation in Arabidopsis roots after reorientation of seedlings. Taken together, the results of this study are consistent with the classic plastid-based and protoplast-based models of graviperception and suggest that multiple systems of perception exist in plant cells.

Differences between appetitive and aversive reinforcement on reorientation in a spatial working memory task.

PubMed

Golob, Edward J; Taube, Jeffrey S

2002-10-17

Tasks using appetitive reinforcers show that following disorientation rats use the shape of an arena to reorient, and cannot distinguish two geometrically similar corners to obtain a reward, despite the presence of a prominent visual cue that provides information to differentiate the two corners. Other studies show that disorientation impairs performance on certain appetitive, but not aversive, tasks. This study evaluated whether rats would make similar geometric errors in a working memory task that used aversive reinforcement. We hypothesized that in a task that used aversive reinforcement rats that were initially disoriented would not reorient by arena shape and thus make similar geometric errors. Tests were performed in a rectangular arena having one polarizing cue. In the appetitive condition water consumption was the reward. The aversive condition was a water maze task with reinforcement provided by escape to a hidden platform. In the aversive condition rats returned to the reinforced corner significantly more often than in the dry condition, and did not favor the diagonally opposite corner. Results show that rats can use cues besides arena shape to reorient in an aversive reinforcement condition. These findings may also reflect different strategies, with an escape/homing strategy in the wet condition and a foraging strategy in the dry condition.

Neural correlates of the spatial and expectancy components of endogenous and stimulus-driven orienting of attention in the Posner task.

PubMed

Doricchi, Fabrizio; Macci, Enrica; Silvetti, Massimo; Macaluso, Emiliano

2010-07-01

Voluntary orienting of visual attention is conventionally measured in tasks with predictive central cues followed by frequent valid targets at the cued location and by infrequent invalid targets at the uncued location. This implies that invalid targets entail both spatial reorienting of attention and breaching of the expected spatial congruency between cues and targets. Here, we used event-related functional magnetic resonance imaging (fMRI) to separate the neural correlates of the spatial and expectancy components of both endogenous orienting and stimulus-driven reorienting of attention. We found that during endogenous orienting with predictive cues, there was a significant deactivation of the right Temporal-Parietal Junction (TPJ). We also discovered that the lack of an equivalent deactivation with nonpredictive cues was matched to drop in attentional costs and preservation of attentional benefits. The right TPJ showed equivalent responses to invalid targets following predictive and nonpredictive cues. On the contrary, infrequent-unexpected invalid targets following predictive cues specifically activated the right Middle and Inferior Frontal Gyrus (MFG-IFG). Additional comparisons with spatially neutral trials demonstrated that, independently of cue predictiveness, valid targets activate the left TPJ, whereas invalid targets activate both the left and right TPJs. These findings show that the selective right TPJ activation that is found in the comparison between invalid and valid trials results from the reciprocal cancelling of the different activations that in the left TPJ are related to the processing of valid and invalid targets. We propose that left and right TPJs provide "matching and mismatching to attentional template" signals. These signals enable reorienting of attention and play a crucial role in the updating of the statistical contingency between cues and targets.

Differential white matter involvement associated with distinct visuospatial deficits after right hemisphere stroke.

PubMed

Carter, Alex R; McAvoy, Mark P; Siegel, Joshua S; Hong, Xin; Astafiev, Serguei V; Rengachary, Jennifer; Zinn, Kristi; Metcalf, Nicholas V; Shulman, Gordon L; Corbetta, Maurizio

2017-03-01

Visuospatial attention depends on the integration of multiple processes, and people with right hemisphere lesions after a stroke may exhibit severe or no visuospatial deficits. The anatomy of core components of visuospatial attention is an area of intense interest. Here we examine the relationship between the disruption of core components of attention and lesion distribution in a heterogeneous group (N = 70) of patients with right hemisphere strokes regardless of the presence of clinical neglect. Deficits of lateralized spatial orienting, measured as the difference in reaction times for responding to visual targets in the contralesional or ipsilesional visual field, and deficits in re-orienting attention, as measured by the difference in reaction times for invalidly versus validly cued targets, were measured using a computerized spatial orienting task. Both measures were related through logistic regression and a novel ridge regression method to anatomical damage measured with magnetic resonance imaging. While many regions were common to both deficit maps, a deficit in lateralized spatial orienting was more associated with lesions in the white matter underlying the posterior parietal cortex, and middle and inferior frontal gyri. A deficit in re-orienting of attention toward unattended locations was associated with lesions in the white matter of the posterior parietal cortex, insular cortex and less so with white matter involvement of the anterior frontal lobe. An hodological analysis also supports this partial dissociation between the white matter tracts that are damaged in lateralized spatial biases versus impaired re-orienting. Our results underscore that the integrity of fronto-parietal white matter tracts is crucial for visuospatial attention and that different attention components are mediated by partially distinct neuronal substrates. Copyright © 2016 Elsevier Ltd. All rights reserved.

The role of the right temporoparietal junction in attention and social interaction as revealed by ALE meta-analysis

PubMed Central

Rottschy, C.; Oberwelland, E.; Bzdok, D.; Fox, P. T.; Eickhoff, S. B.; Fink, G. R.; Konrad, K.

2016-01-01

The right temporoparietal junction (rTPJ) is frequently associated with different capacities that to shift attention to unexpected stimuli (reorienting of attention) and to understand others’ (false) mental state [theory of mind (ToM), typically represented by false belief tasks]. Competing hypotheses either suggest the rTPJ representing a unitary region involved in separate cognitive functions or consisting of subregions subserving distinct processes. We conducted activation likelihood estimation (ALE) meta-analyses to test these hypotheses. A conjunction analysis across ALE meta-analyses delineating regions consistently recruited by reorienting of attention and false belief studies revealed the anterior rTPJ, suggesting an overarching role of this specific region. Moreover, the anatomical difference analysis unravelled the posterior rTPJ as higher converging in false belief compared with reorienting of attention tasks. This supports the concept of an exclusive role of the posterior rTPJ in the social domain. These results were complemented by meta-analytic connectivity mapping (MACM) and resting-state functional connectivity (RSFC) analysis to investigate whole-brain connectivity patterns in task-constrained and task-free brain states. This allowed for detailing the functional separation of the anterior and posterior rTPJ. The combination of MACM and RSFC mapping showed that the posterior rTPJ has connectivity patterns with typical ToM regions, whereas the anterior part of rTPJ co-activates with the attentional network. Taken together, our data suggest that rTPJ contains two functionally fractionated subregions: while posterior rTPJ seems exclusively involved in the social domain, anterior rTPJ is involved in both, attention and ToM, conceivably indicating an attentional shifting role of this region. PMID:24915964

Practicalities and challenges in re-orienting the health system in Zambia for treating chronic conditions.

PubMed

Aantjes, Carolien J; Quinlan, Tim K C; Bunders, Joske F G

2014-07-08

The rapid evolution in disease burdens in low- and middle income countries is forcing policy makers to re-orient their health system towards a system which has the capability to simultaneously address infectious and non-communicable diseases. This paper draws on two different but overlapping studies which examined how actors in the Zambian health system are re-directing their policies, strategies and service structures to include the provision of health care for people with chronic conditions. Study methods in both studies included semi-structured interviews with government health officials at national level, and governmental and non-governmental health practitioners operating from community-, primary health care to hospital facility level. Focus group discussions were conducted with staff, stakeholders and caregivers of programmes providing care and support at community- and household levels. Study settings included urban and rural sites. A series of adaptations transformed the HIV programme from an emergency response into the first large chronic care programme in the country. There are clear indications that the Zambian government is intending to expand this reach to patients with non-communicable diseases. Challenges to do this effectively include a lack of proper NCD prevalence data for planning, a concentration of technology and skills to detect and treat NCDs at secondary and tertiary levels in the health system and limited interest by donor agencies to support this transition. The reorientation of Zambia's health system is in full swing and uses the foundation of a decentralised health system and presence of local models for HIV chronic care which actively involve community partners, patients and their families. There are early warning signs which could cause this transition to stall, one of which is the financial capability to resource this process.

Spatiotemporal relationships between growth and microtubule orientation as revealed in living root cells of Arabidopsis thaliana transformed with green-fluorescent-protein gene construct GFP-MBD

NASA Technical Reports Server (NTRS)

Granger, C. L.; Cyr, R. J.

2001-01-01

Arabidopsis thaliana plants were transformed with GFP-MBD (J. Marc et al., Plant Cell 10: 1927-1939, 1998) under the control of a constitutive (35S) or copper-inducible promoter. GFP-specific fluorescence distributions, levels, and persistence were determined and found to vary with age, tissue type, transgenic line, and individual plant. With the exception of an increased frequency of abnormal roots of 35S GFP-MBD plants grown on kanamycin-containing media, expression of GFP-MBD does not appear to affect plant phenotype. The number of leaves, branches, bolts, and siliques as well as overall height, leaf size, and seed set are similar between wild-type and transgenic plants as is the rate of root growth. Thus, we conclude that the transgenic plants can serve as a living model system in which the dynamic behavior of microtubules can be visualized. Confocal microscopy was used to simultaneously monitor growth and microtubule behavior within individual cells as they passed through the elongation zone of the Arabidopsis root. Generally, microtubules reoriented from transverse to oblique or longitudinal orientations as growth declined. Microtubule reorientation initiated at the ends of the cell did not necessarily occur simultaneously in adjacent neighboring cells and did not involve complete disintegration and repolymerization of microtubule arrays. Although growth rates correlated with microtubule reorientation, the two processes were not tightly coupled in terms of their temporal relationships, suggesting that other factor(s) may be involved in regulating both events. Additionally, microtubule orientation was more defined in cells whose growth was accelerating and less stringent in cells whose growth was decelerating, indicating that microtubule-orienting factor(s) may be sensitive to growth acceleration, rather than growth per se.

Spin Evolution of Stellar Progenitors in Compact Binaries

NASA Astrophysics Data System (ADS)

Steinle, Nathan; Kesden, Michael

2018-01-01

Understanding the effects of various processes on the spins of stellar progenitors in compact binary systems is important for modeling the binary’s evolution and thus for interpreting the gravitational radiation emitted during inspiral and merger. Tides, winds, and natal kicks can drastically modify the binary parameters: tidal interactions increase the spin magnitudes, align the spins with the orbital angular momentum, and circularize the orbit; stellar winds decrease the spin magnitudes and cause mass loss; and natal kicks can misalign the spins and orbital angular momentum or even disrupt the binary. Also, during Roche lobe overflow, the binary may experience either stable mass transfer or common envelope evolution. The former can lead to a mass ratio reversal and alter the component spins, while the latter can dramatically shrink the binary separation. For a wide range of physically reasonable stellar-evolution scenarios, we compare the timescales of these processes to assess their relative contributions in determining the initial spins of compact binary systems.

Spin-orbit signatures in the dynamics of singlet-triplet qubits in double quantum dots

NASA Astrophysics Data System (ADS)

Rolon, Juan E.; Cota, Ernesto; Ulloa, Sergio E.

2017-05-01

We characterize numerically and analytically the signatures of the spin-orbit interaction in a two-electron GaAs double quantum dot in the presence of an external magnetic field. In particular, we obtain the return probability of the singlet state by simulating Landau-Zener voltage detuning sweeps which traverse the singlet-triplet (S -T+ ) resonance. Our results indicate that non-spin-conserving interdot tunneling processes arising from the spin-orbit interaction have well defined signatures. These allow direct access to the spin-orbit interaction scales and are characterized by a frequency shift and Fourier amplitude modulation of the Rabi flopping dynamics of the singlet-triplet qubits S -T0 and S -T+ . By applying the Bloch-Feshbach projection formalism, we demonstrate analytically that the aforementioned effects originate from the interplay between spin-orbit interaction and processes driven by the hyperfine interaction between the electron spins and those of the GaAs nuclei.

Surprises from the spins: astrophysics and relativity with detections of spinning black-hole mergers

NASA Astrophysics Data System (ADS)

Gerosa, Davide

2018-03-01

Measurements of black-hole spins are of crucial importance to fulfill the promise of gravitational-wave astronomy. On the astrophysics side, spins are perhaps the cleanest indicator of black-hole evolutionary processes, thus providing a preferred way to discriminate how LIGO's black holes form. On the relativity side, spins are responsible for peculiar dynamical phenomena (from precessional modulations in the long inspiral to gravitational-wave recoils at merger) which encode precious information on the underlying astrophysical processes. I present some examples to explore this deep and fascinating interplay between spin dynamics (relativity) and environmental effects (astrophysics). Black-hole spins indeed hide remarkable surprises on both fronts: morphologies, resonances, constraints on supernova kicks, multiple merger generations and more... These findings were presented at 12th Edoardo Amaldi Conference on Gravitational Waves, held on July 9-14, 2017 in Pasadena, CA, USA.

Mechanism of nuclear spin initiated para-H2 to ortho-H2 conversion.

PubMed

Buntkowsky, G; Walaszek, B; Adamczyk, A; Xu, Y; Limbach, H-H; Chaudret, B

2006-04-28

In this paper a quantitative explanation for a diamagnetic ortho/para H2 conversion is given. The description is based on the quantum-mechanical density matrix formalism originally developed by Alexander and Binsch for studies of exchange processes in NMR spectra. Only the nuclear spin system is treated quantum-mechanically. Employing the model of a three spin system, the reactions of the hydrogen gas with the catalysts are treated as a phenomenological rate process, described by a rate constant. Numerical calculations reveal that for nearly all possible geometrical arrangements of the three spin system an efficient spin conversion is obtained. Only in the chemically improbable case of a linear group H-X-H no spin conversion is obtained. The efficiency of the spin conversion depends strongly on the lifetime of the H-X-H complex and on the presence of exchange interactions between the two hydrogens. Even moderate exchange couplings cause a quench of the spin conversion. Thus a sufficiently strong binding of the dihydrogen to the S spin is necessary to render the quenching by the exchange interaction ineffective.

Incorporating cultural competence content into graduate nursing curricula through community-university collaboration.

PubMed

Axtell, Sara A; Avery, Melissa; Westra, Bonnie

2010-04-01

Health professionals are reorienting workforce education to better prepare students for working with increasingly diverse populations. The authors describe a community-based curriculum deliberation process in which community leaders and health workers deliberated with faculty and students to make recommendations about a graduate nursing curriculum. There were five areas of competencies recommended for graduate nursing to improve care of diverse populations: self-awareness, basic knowledge of culture and identity, attitudes that promote cross-cultural communication, cross-cultural clinical skills, and advocacy skills. The school now is in the process of phasing in recommendations gained from the deliberation.

Coherent spin control of a nanocavity-enhanced qubit in diamond

DOE PAGES

Li, Luozhou; Lu, Ming; Schroder, Tim; ...

2015-01-28

A central aim of quantum information processing is the efficient entanglement of multiple stationary quantum memories via photons. Among solid-state systems, the nitrogen-vacancy centre in diamond has emerged as an excellent optically addressable memory with second-scale electron spin coherence times. Recently, quantum entanglement and teleportation have been shown between two nitrogen-vacancy memories, but scaling to larger networks requires more efficient spin-photon interfaces such as optical resonators. Here we report such nitrogen-vacancy nanocavity systems in strong Purcell regime with optical quality factors approaching 10,000 and electron spin coherence times exceeding 200 µs using a silicon hard-mask fabrication process. This spin-photon interfacemore » is integrated with on-chip microwave striplines for coherent spin control, providing an efficient quantum memory for quantum networks.« less

Photoresist thin-film effects on alignment process capability

NASA Astrophysics Data System (ADS)

Flores, Gary E.; Flack, Warren W.

1993-08-01

Two photoresists were selected for alignment characterization based on their dissimilar coating properties and observed differences on alignment capability. The materials are Dynachem OFPR-800 and Shipley System 8. Both photoresists were examined on two challenging alignment levels in a submicron CMOS process, a nitride level and a planarized second level metal. An Ultratech Stepper model 1500 which features a darkfield alignment system with a broadband green light for alignment signal detection was used for this project. Initially, statistically designed linear screening experiments were performed to examine six process factors for each photoresist: viscosity, spin acceleration, spin speed, spin time, softbake time, and softbake temperature. Using the results derived from the screening experiments, a more thorough examination of the statistically significant process factors was performed. A full quadratic experimental design was conducted to examine viscosity, spin speed, and spin time coating properties on alignment. This included a characterization of both intra and inter wafer alignment control and alignment process capability. Insight to the different alignment behavior is analyzed in terms of photoresist material properties and the physical nature of the alignment detection system.

Synthetic spider silk production on a laboratory scale.

PubMed

Hsia, Yang; Gnesa, Eric; Pacheco, Ryan; Kohler, Kristin; Jeffery, Felicia; Vierra, Craig

2012-07-18

As society progresses and resources become scarcer, it is becoming increasingly important to cultivate new technologies that engineer next generation biomaterials with high performance properties. The development of these new structural materials must be rapid, cost-efficient and involve processing methodologies and products that are environmentally friendly and sustainable. Spiders spin a multitude of different fiber types with diverse mechanical properties, offering a rich source of next generation engineering materials for biomimicry that rival the best manmade and natural materials. Since the collection of large quantities of natural spider silk is impractical, synthetic silk production has the ability to provide scientists with access to an unlimited supply of threads. Therefore, if the spinning process can be streamlined and perfected, artificial spider fibers have the potential use for a broad range of applications ranging from body armor, surgical sutures, ropes and cables, tires, strings for musical instruments, and composites for aviation and aerospace technology. In order to advance the synthetic silk production process and to yield fibers that display low variance in their material properties from spin to spin, we developed a wet-spinning protocol that integrates expression of recombinant spider silk proteins in bacteria, purification and concentration of the proteins, followed by fiber extrusion and a mechanical post-spin treatment. This is the first visual representation that reveals a step-by-step process to spin and analyze artificial silk fibers on a laboratory scale. It also provides details to minimize the introduction of variability among fibers spun from the same spinning dope. Collectively, these methods will propel the process of artificial silk production, leading to higher quality fibers that surpass natural spider silks.

Synthetic Spider Silk Production on a Laboratory Scale

PubMed Central

Hsia, Yang; Gnesa, Eric; Pacheco, Ryan; Kohler, Kristin; Jeffery, Felicia; Vierra, Craig

2012-01-01

As society progresses and resources become scarcer, it is becoming increasingly important to cultivate new technologies that engineer next generation biomaterials with high performance properties. The development of these new structural materials must be rapid, cost-efficient and involve processing methodologies and products that are environmentally friendly and sustainable. Spiders spin a multitude of different fiber types with diverse mechanical properties, offering a rich source of next generation engineering materials for biomimicry that rival the best manmade and natural materials. Since the collection of large quantities of natural spider silk is impractical, synthetic silk production has the ability to provide scientists with access to an unlimited supply of threads. Therefore, if the spinning process can be streamlined and perfected, artificial spider fibers have the potential use for a broad range of applications ranging from body armor, surgical sutures, ropes and cables, tires, strings for musical instruments, and composites for aviation and aerospace technology. In order to advance the synthetic silk production process and to yield fibers that display low variance in their material properties from spin to spin, we developed a wet-spinning protocol that integrates expression of recombinant spider silk proteins in bacteria, purification and concentration of the proteins, followed by fiber extrusion and a mechanical post-spin treatment. This is the first visual representation that reveals a step-by-step process to spin and analyze artificial silk fibers on a laboratory scale. It also provides details to minimize the introduction of variability among fibers spun from the same spinning dope. Collectively, these methods will propel the process of artificial silk production, leading to higher quality fibers that surpass natural spider silks. PMID:22847722

Electron-Nuclear Quantum Information Processing

DTIC Science & Technology

2008-11-13

quantum information processing that exploits the anisotropic hyperfine coupling. This scheme enables universal control over a 1-electron, N-nuclear spin...exploits the anisotropic hyperfine coupling. This scheme enables universal control over a 1-electron, N-nuclear spin system, addressing only a...sample of irradiated malonic acid. (a) Papers published in peer-reviewed journals (N/A for none) Universal control of nuclear spins via anisotropic

A Multivariate Quality Loss Function Approach for Optimization of Spinning Processes

NASA Astrophysics Data System (ADS)

Chakraborty, Shankar; Mitra, Ankan

2018-05-01

Recent advancements in textile industry have given rise to several spinning techniques, such as ring spinning, rotor spinning etc., which can be used to produce a wide variety of textile apparels so as to fulfil the end requirements of the customers. To achieve the best out of these processes, they should be utilized at their optimal parametric settings. However, in presence of multiple yarn characteristics which are often conflicting in nature, it becomes a challenging task for the spinning industry personnel to identify the best parametric mix which would simultaneously optimize all the responses. Hence, in this paper, the applicability of a new systematic approach in the form of multivariate quality loss function technique is explored for optimizing multiple quality characteristics of yarns while identifying the ideal settings of two spinning processes. It is observed that this approach performs well against the other multi-objective optimization techniques, such as desirability function, distance function and mean squared error methods. With slight modifications in the upper and lower specification limits of the considered quality characteristics, and constraints of the non-linear optimization problem, it can be successfully applied to other processes in textile industry to determine their optimal parametric settings.

Manned space flight in transition

NASA Technical Reports Server (NTRS)

Drucker, E. E.; Pooler, W. S.; Wilemon, D. L.; Wood, B. D.

1973-01-01

A study was conducted to analyze the reorientation of NASA programs in the post-Apollo period. The study is an external view of NASA by unbiased observers as an input to and aid in the decision making process concerning near and long term planning. The subjects discussed are: (1) the near-term NASA scenario; (2) organization of field centers; (3) planning activities; and (4) operational activities. A summary of the recommendations arising as a result of the study is presented.

Solid-state electron spin lifetime limited by phononic vacuum modes.

PubMed

Astner, T; Gugler, J; Angerer, A; Wald, S; Putz, S; Mauser, N J; Trupke, M; Sumiya, H; Onoda, S; Isoya, J; Schmiedmayer, J; Mohn, P; Majer, J

2018-04-01

Longitudinal relaxation is the process by which an excited spin ensemble decays into its thermal equilibrium with the environment. In solid-state spin systems, relaxation into the phonon bath usually dominates over the coupling to the electromagnetic vacuum 1-9 . In the quantum limit, the spin lifetime is determined by phononic vacuum fluctuations 10 . However, this limit was not observed in previous studies due to thermal phonon contributions 11-13 or phonon-bottleneck processes 10, 14,15 . Here we use a dispersive detection scheme 16,17 based on cavity quantum electrodynamics 18-21 to observe this quantum limit of spin relaxation of the negatively charged nitrogen vacancy (NV - ) centre 22 in diamond. Diamond possesses high thermal conductivity even at low temperatures 23 , which eliminates phonon-bottleneck processes. We observe exceptionally long longitudinal relaxation times T 1 of up to 8 h. To understand the fundamental mechanism of spin-phonon coupling in this system we develop a theoretical model and calculate the relaxation time ab initio. The calculations confirm that the low phononic density of states at the NV - transition frequency enables the spin polarization to survive over macroscopic timescales.

High-sensitivity GMR with low coercivity in top-IrMn spin-valves

NASA Astrophysics Data System (ADS)

Liu, H. R.; Qu, B. J.; Ren, T. L.; Liu, L. T.; Xie, H. L.; Li, C. X.; Ku, W. J.

2003-12-01

Top-IrMn spin-valves with a structure of Ta/NiFe/CoFe/Cu/CoFe/IrMn/Ta have been investigated. The spin-valves were deposited by high vacuum DC magnetron sputtering at room temperature. The magnetoresistance ratio reaches 9.12% at room temperature. The coercivity of the free layer and the exchange bias field is 1.04 and 180 Oe, respectively. The maximum sensitivity of the spin-valves is 8.36%/Oe. A reduction of 33.2% of the coercivity was obtained after a 2-min RIE process. Utilizing standard integrated circuit (IC) process, mass production of robust giant magnetoresistance sensors can be achieved with these spin-valve thin films.

Characterization of Al 2219 material for the application of the spin-forming-process

NASA Astrophysics Data System (ADS)

Mueller-Wiesner, D.; Sieger, E.; Ernsberger, K.

1991-10-01

The shells of the propellant tanks of the Ariane 5 EPS stage are to be manufactured by the spin forming process. The material for the shells (hemispheres) is the aluminum alloy 2219. By a material characterization program optimized parameters for the application of the forming process starting from different material conditions (T31 temper and '0' condition) are determined. Based on the results of this program it was decided to start spin forming in the '0' condition for flight hardware.

Non-polymeric asymmetric binary glass-formers. II. Secondary relaxation studied by dielectric, 2H NMR, and 31P NMR spectroscopy

NASA Astrophysics Data System (ADS)

Pötzschner, B.; Mohamed, F.; Bächer, C.; Wagner, E.; Lichtinger, A.; Bock, D.; Kreger, K.; Schmidt, H.-W.; Rössler, E. A.

2017-04-01

We investigate the secondary (β-) relaxations of an asymmetric binary glass former consisting of a spirobichroman derivative (SBC; Tg = 356 K) as the high-Tg component and the low-Tg component tripropyl phosphate (TPP; Tg = 134 K). The main relaxations are studied in Paper I [B. Pötzschner et al., J. Chem. Phys. 146, 164503 (2017)]. A high Tg contrast of ΔTg = 222 K is put into effect in a non-polymeric system. Component-selective studies are carried out by combining results from dielectric spectroscopy (DS) for mass concentrations cTPP ≥ 60% and those from different methods of 2H and 31P NMR spectroscopy. In the case of NMR, the full concentration range (10% ≤ cTPP ≤ 100%) is covered. The neat components exhibit a β-relaxation (β1 (SBC) and β2 (TPP)). The latter is rediscovered by DS in the mixtures for all concentrations with unchanged time constants. NMR spectroscopy identifies the β-relaxations as being alike to those in neat glasses. A spatially highly restricted motion with angular displacement below ±10° encompassing all molecules is involved. In the low temperature range, where TPP shows the typical 31P NMR echo spectra of the β2-process, very similar spectral features are observed for the (deuterated) SBC component by 2H NMR, in addition to its "own" β1-process observed at high temperatures. Apparently, the small TPP molecules enslave the large SBC molecules to perform a common hindered reorientation. The temperature dependence of the spin-lattice relaxation time of both components is the same and reveals an angular displacement of the SBC molecules somewhat smaller than that of TPP, though the time constants τβ2 are the same. Furthermore, T1(T) of TPP in the temperature region of the β2-process is absolutely the same as in the mixture TPP/polystyrene investigated previously. It appears that the manifestations of the β-process introduced by one component are essentially independent of the second component. Finally, at cTPP ≤ 20% one finds indications that the β2-process starts to disintegrate. More and more TPP molecules get immobilized upon decreasing cTPP. We conclude that the β-process is a cooperative process.

Efficient Reorientation Maneuvers for Spacecraft with Multiple Articulated Payloads

NASA Technical Reports Server (NTRS)

Mcclamroch, N. Harris

1993-01-01

A final report is provided which describes the research program during the period 3 Mar. 1992 to 3 Jun. 1993. A summary of the technical research questions that were studied and of the main results that were obtained is given. The specific outcomes of the research program, including both educational impacts as well as research publications, are listed. The research is concerned with efficient reorientation maneuvers for spacecraft with multiple articulated payloads.

ISS Expedition 18 Synchronized Position Hold,Engage,Reorient,Experimental Satellites (SPHERES)

NASA Image and Video Library

2008-10-26

ISS018-E-005214 (26 Oct. 2008) --- This close-up view shows three bowling-ball-sized free-flying satellites called Synchronized Position Hold, Engage, Reorient, Experimental Satellites (SPHERES) in the Destiny laboratory of the International Space Station. SPHERES were designed to test control algorithms for spacecraft by performing autonomous rendezvous and docking maneuvers inside the station. The results are important for multi-body control and in designing constellation and array spacecraft configurations.

Planar reorientation of a free-free beam in space using embedded electromechanical actuators

NASA Technical Reports Server (NTRS)

Kolmanovsky, Ilya V.; Mcclamroch, N. Harris

1993-01-01

It is demonstrated that the planar reorientation of a free-free beam in zero gravity space can be accomplished by periodically changing the shape of the beam using embedded electromechanical actuators. The dynamics which determine the shape of the free-free beam is assumed to be characterized by the Euler-Bernoulli equation, including material damping, with appropriate boundary conditions. The coupling between the rigid body motion and the flexible motion is explained using the angular momentum expression which includes rotatory inertia and kinematically exact effects. A control scheme is proposed where the embedded actuators excite the flexible motion of the beam so that it rotates in the desired sense with respect to a fixed inertial reference. Relations are derived which relate the average rotation rate to the amplitudes and the frequencies of the periodic actuation signal and the properties of the beam. These reorientation maneuvers can be implemented by using feedback control.

Initiation of geyser during the resettlement of cryogenic liquid under impulsive reverse gravity acceleration in microgravity environment

NASA Technical Reports Server (NTRS)

Hung, R. J.; Shyu, K. L.

1991-01-01

The requirement to settle or to position liquid fluid over the outlet end of spacecraft propellant tank prior to main engine restart poses a microgravity fluid behavior problem. Resettlement or reorientation of liquid propellant can be accomplished by providing optimal acceleration to the spacecraft such that the propellant is reoriented over the tank outlet without any vapor entrainment, any excessive geysering, or any other undesirable fluid motion for the space fluid management under microgravity environment. The purpose of present study is to investigate most efficient technique for propellant resettling through the minimization of propellant usage and weight penalties. Comparison between the constant reverse gravity acceleration and impulsive reverse gravity acceleration to be used for the activation of propellant resettlement, it shows that impulsive reverse gravity thrust is superior to constant reverse gravity thrust for liquid reorientation in a reduced gravity environment.

Attitude stabilization of a rigid spacecraft using two momentum wheel actuators

NASA Technical Reports Server (NTRS)

Krishnan, Hariharan; Mcclamroch, N. Harris; Reyhanoglu, Mahmut

1993-01-01

It is well known that three momentum wheel actuators can be used to control the attitude of a rigid spacecraft and that arbitrary reorientation maneuvers of the spacecraft can be accomplished using smooth feedback. If failure of one of the momentum wheel actuators occurs, it is demonstrated that two momentum wheel actuators can be used to control the attitude of a rigid spacecraft and that arbitrary reorientation maneuvers of the spacecraft can be accomplished. Although the complete spacecraft equations are not controllable, the spacecraft equations are small time locally controllable in a reduced nonlinear sense. The reduced spacecraft dynamics cannot be asymptotically stabilized to any equilibrium attitude using a time-variant continuous feedback control law, but discontinuous feedback control strategies are constructed which stabilize any equilibrium attitude of the spacecraft in finite time. Consequently, reorientation of the spacecraft can be accomplished using discontinuous feedback control.

Periacetabular osteotomy: a review of swiss experience.

PubMed

Büchler, Lorenz; Beck, Martin

2014-12-01

Symptomatic dysplasia of the hip and acetabular retroversion are possible causes of osteoarthritis in the young adult. Surgical management with reorientation of the acetabulum allows causal therapy of the deformity and preservation of the native hip joint. The Ganz' periacetabular osteotomy permits a free 3-dimensional reorientation of the acetabulum and respects the blood supply of the acetabular fragment. The posterior column remains intact with a stable fixation of the acetabular fragment and a preserved shape of the true pelvis. There is a significant learning curve with severe complications in up to 30 % of cases. Good results can be expected in the long-term follow-up if performed with correct indication at young age in hips with preserved joint cartilage and proper reorientation of the acetabular fragment. Overall survivorship is superior to the natural course of hip dysplasia with a preserved hip joint in 61 % after 20 years.

Hydraulic fracture orientation and production/injection induced reservoir stress changes in diatomite waterfloods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wright, C.A.; Conant, R.A.; Golich, G.M.

1995-12-31

This paper summarizes the (preliminary) findings from extensive field studies of hydraulic fracture orientation in diatomite waterfloods and related efforts to monitor the induced surface subsidence. Included are case studies from the Belridge and Lost Hills diatomite reservoirs. The primary purpose of the paper is to document a large volume of tiltmeter hydraulic fracture orientation data that demonstrates waterflood-induced fracture reorientation--a phenomenon not previously considered in waterflood development planning. Also included is a brief overview of three possible mechanisms for the observed waterflood fracture reorientation. A discussion section details efforts to isolate the operative mechanism(s) from the most extensive casemore » study, as well as suggesting a possible strategy for detecting and possibly mitigating some of the adverse effects of production/injection induced reservoir stress changes--reservoir compaction and surface subsidence as well as fracture reorientation.« less

Paleomagnetic reorientation of San Andreas Fault Observatory at Depth (SAFOD) core

USGS Publications Warehouse

Pares, J.M.; Schleicher, A.M.; van der Pluijm, B.A.; Hickman, S.

2008-01-01

We present a protocol for using paleomagnetic analysis to determine the absolute orientation of core recovered from the SAFOD borehole. Our approach is based on determining the direction of the primary remanent magnetization of a spot core recovered from the Great Valley Sequence during SAFOD Phase 2 and comparing its direction to the expected reference field direction for the Late Cretaceous in North America. Both thermal and alternating field demagnetization provide equally resolved magnetization, possibly residing in magnetite, that allow reorientation. Because compositionally similar siltstones and fine-grained sandstones were encountered in the San Andreas Fault Zone during Stage 2 rotary drilling, we expect that paleomagnetic reorientation will yield reliable core orientations for continuous core acquired from directly within and adjacent to the San Andreas Fault during SAFOD Phase 3, which will be key to interpretation of spatial properties of these rocks. Copyright 2008 by the American Geophysical Union.

Experimental Study on the Anisotropic Stress-Strain Behavior of Polycrystalline Ni-Mn-Ga in Directional Solidification

NASA Astrophysics Data System (ADS)

Teng, Yao; Shi, Tao; Zhu, Yuping; Li, Zongbin; Deng, Tao; Bai, Guonan

2016-03-01

A polycrystalline Ni-Mn-Ga ferromagnetic shape memory alloy produced by directional solidification is the subject of this research paper. The compressive stress-strain curves of the material for different cutting angles to the solidification direction are tested. The martensite Young's modulus, macroscopic reorientation strain, and phase transition critical stress are analyzed experimentally. The results show that mechanical behaviors in the loading-unloading cycle of the material present nonlinear and anisotropic characteristics, which are all closely related to the material's orientation to the solidification direction. The martensite Young's modulus, macroscopic reorientation strain, and phase transition critical stress achieve maximum values in the solidification direction. A 50° orientation to the solidification direction is the cut-off direction of the mechanical properties, where the martensite Young's modulus and reorientation start critical stress reach minimum values. The present study is expected to provide sound guidance for practical applications.

Scan Rate Dependent Spin Crossover Iron(II) Complex with Two Different Relaxations and Thermal Hysteresis fac-[Fe(II)(HL(n-Pr))3]Cl·PF6 (HL(n-Pr) = 2-Methylimidazol-4-yl-methylideneamino-n-propyl).

PubMed

Fujinami, Takeshi; Nishi, Koshiro; Hamada, Daisuke; Murakami, Keishiro; Matsumoto, Naohide; Iijima, Seiichiro; Kojima, Masaaki; Sunatsuki, Yukinari

2015-08-03

Solvent-free spin crossover Fe(II) complex fac-[Fe(II)(HL(n-Pr))3]Cl·PF6 was prepared, where HL(n-Pr) denotes 2-methylimidazol-4-yl-methylideneamino-n-propyl. The magnetic susceptibility measurements at scan rate of 0.5 K min(-1) showed two successive spin transition processes consisting of the first spin transition T1 centered at 122 K (T1↑ = 127.1 K, T1↓ = 115.8 K) and the second spin transition T2 centered at ca. 105 K (T2↑ = 115.8 K, T2↓ = 97.2 K). The magnetic susceptibility measurements at the scan rate of 2.0, 1.0, 0.5, 0.25, and 0.1 K min(-1) showed two scan speed dependent spin transitions, while the Mössbauer spectra detected only the first spin transition T1. The crystal structures were determined at 160, 143, 120, 110, 95 K in the cooling mode, and 110, 120, and 130 K in the warming mode so as to follow the spin transition process of high-spin HS → HS(T1) → HS(T2) → low-spin LS → LS(T2) → LS(T1) → HS. The crystal structures at all temperatures have a triclinic space group P1̅ with Z = 2. The complex-cation has an octahedral N6 coordination geometry with three bidentate ligands and assume a facial-isomer with Δ- and Λ-enantimorphs. Three imidazole groups of fac-[Fe(II)(HL(n-Pr))3](2+) are hydrogen-bonded to three Cl(-) ions. The 3:3 NH(imidazole)···Cl(-) hydrogen-bonds form a stepwise ladder assembly structure, which is maintained during the spin transition process. The spin transition process is related to the structural changes of the FeN6 coordination environment, the order-disorder of PF6(-) anion, and the conformation change of n-propyl groups. The Fe-N bond distance in the HS state is longer by 0.2 Å than that in the LS state. Disorder of PF6(-) anion is not observed in the LS state but in the HS state. The conformational changes of n-propyl groups are found in the spin transition processes except for HS → HS(T1) → HS(T2).

Paleomagnetic Reorientation of Structural Elements in Drill Cores: an example from Tolhuaca Geothermal Field

NASA Astrophysics Data System (ADS)

Perez-Flores, P.; Veloso, E. E.; Cembrano, J. M.; Sánchez, P.; Iriarte, S.; Lohmar, S.

2013-12-01

Reorientation of mesoscopic faults, veins and fractures recovered from drilling is critical to construct reliable structural models that can account for their architecture and deformation regime. However, oriented cores are expensive and time consuming to drill. Some techniques achieve reorientation by introducing tools into the borehole. Problems arise when boreholes are unstable or collapse. One alternative technique allowing reorientation is to obtain reliable paleomagnetic vectors to reorient each core piece after drilling. Here, we present stable and reliable remnant magnetic vectors calculated from the Tol-1 core to analyze the geometry of the fracture network and its relationship to regional tectonic. Tol-1 core is a vertical, 1073 m deep geothermal well, drilled at the Tolhuaca Geothermal Field in the Southern Volcanic Zone of the Andes by MRP Geothermal Chile Ltda (formerly GGE Chile SpA) in 2009. The core consists of basaltic/andesitic volcanic rocks with subordinate pyroclastic/volcaniclastic units, with probable Pleistocene age. Fault planes with slickenlines and mineral fiber kinematic indicators are common in the upper 700 m of the core. Calcite, quartz and calcite-quartz veins are recognized along of entire core, whereas epidote-quartz and calcite-epidote veins occur in the last 350 m, minor chlorite, anhydrite and clay-minerals are present. Orientations of structural features in the core were measured with a goniometer using the core's axis and a false north for each piece; hence, orientation data has a false strike but a real dip. To achieve total reorientation of the pieces, we collected 200 standard-size paleomagnetic specimens, ensuring that at least four of them were recovered from continuous pieces. Thermal (up to 700°C) and alternating field demagnetization (up to 90mT on steps of 2mT) methods were used to isolate a stable remnant magnetization (RM) vector, and each technique yielded similar results. RM vectors were recovered between 0 to 25mT, and between 0 to 625°C. The declination of RM vectors was used to bring pieces to a common anchor orientation calculated through the Geocentric Axial Dipole Model (GAD). The paleomagnetic technique proved to be reliable to reorient the Tol-1 core. Structural analyses along the core show N50-60E-striking preferential vein orientation. In addition, N40-50E- and N60-70W-striking preferential fault orientations were identified. Kinematic analysis of fault-slip data shows a N60E-striking bulk fault plane solution with normal strain regime. The veins and faults orientation show strain axes compatible with published regional stress field (σmax N238E).

ORNL Interim Progress Report on Hydride Reorientation CIRFT Tests

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Jy-An John; Yan, Yong; Wang, Hong

A systematic study of H. B. Robinson (HBR) high burnup spent nuclear fuel (SNF) vibration integrity was performed in Phase I project under simulated transportation environments, using the Cyclic Integrated Reversible-Bending Fatigue Tester (CIRFT) hot cell testing technology developed at Oak Ridge National Laboratory in 2013–14. The data analysis on the as-irradiated HBR SNF rods demonstrated that the load amplitude is the dominant factor that controls the fatigue life of bending rods. However, previous studies have shown that the hydrogen content and hydride morphology has an important effect on zirconium alloy mechanical properties. To address the effect of radial hydridesmore » in SNF rods, in Phase II a test procedure was developed to simulate the effects of elevated temperatures, pressures, and stresses during transfer-drying operations. Pressurized and sealed fuel segments were heated to the target temperature for a preset hold time and slow-cooled at a controlled rate. The procedure was applied to both non-irradiated/prehydrided and high-burnup Zircaloy-4 fueled cladding segments using the Nuclear Regulatory Commission-recommended 400°C maximum temperature limit at various cooling rates. Before testing high-burnup cladding, four out-of-cell tests were conducted to optimize the hydride reorientation (R) test condition with pre-hydride Zircaloy-4 cladding, which has the same geometry as the high burnup fuel samples. Test HR-HBR#1 was conducted at the maximum hoop stress of 145 MPa, at a 400°C maximum temperature and a 5°C/h cooling rate. On the other hand, thermal cycling was performed for tests HR-HBR#2, HR-HBR#3, and HR-HBR#4 to generate more radial hydrides. It is clear that thermal cycling increases the ratio of the radial hydride to circumferential hydrides. The internal pressure also has a significant effect on the radial hydride morphology. This report describes a procedure and experimental results of the four out-of-cell hydride reorientation tests of hydrided Zircaloy-4 cladding, which served as a guideline to prepare in-cell hydride reorientation samples with high burnup HBR fuel segments. This report also provides the Phase II CIRFT test data for the hydride reorientation irradiated samples. The variations in fatigue life are provided in terms of moment, equivalent stress, curvature, and equivalent strain for the tested SNFs. The CIRFT results appear to indicate that hydride reoriented treatment (HRT) have a negative effect on fatigue life, in addition to hydride reorientation effect. For HR4 specimen that had no pressurization procedure applied, the thermal annealing treatment alone showed a negative impact on the fatigue life compared to the HBR rod.« less

SPIN CORRELATIONS OF THE FINAL LEPTONS IN THE TWO-PHOTON PROCESSES γγ → e+e-, μ+μ-, τ+τ-

NASA Astrophysics Data System (ADS)

Lyuboshitz, Valery V.; Lyuboshitz, Vladimir L.

2014-12-01

The spin structure of the process γγ → e+e- is theoretically investigated. It is shown that, if the primary photons are unpolarized, the final electron and positron are unpolarized as well but their spins are strongly correlated. For the final (e+e-) system, explicit expressions for the components of the correlation tensor are derived, and the relative fractions of singlet and triplet states are found. It is demonstrated that in the process γγ → e+e- one of the Bell-type incoherence inequalities for the correlation tensor components is always violated and, thus, spin correlations of the electron and positron in this process have the strongly pronounced quantum character. Analogous consideration can be wholly applied as well to the two-photon processes γγ → μ+μ- and γγ → τ+τ-, which become possible at considerably higher energies.

Effects of salt and nanoparticles on the segmental motion of poly(ethylene oxide) in its crystalline and amorphous phases: 2H and 7Li NMR studies.

PubMed

Vogel, M; Herbers, C; Koch, B

2008-09-11

We use (2)H NMR to investigate the segmental motion of poly(ethylene oxide) (PEO) in neat and nanocomposite materials that do and do not contain salt. Specifically, in addition to a neat low-molecular-weight PEO, we study mixtures of this polymer with TiO 2 nanoparticles and LiClO 4. To characterize the polymer dynamics over a wide range of time scales, we combine (2)H NMR spin-lattice relaxation, line-shape, and stimulated-echo analyses. The results consistently show that the presence of nanoparticles hardly affects the behavior of the polymer, while addition of salt leads to substantial changes; e.g., it reduces the crystallinity. For neat PEO and a PEO-TiO 2 mixture, stimulated-echo spectroscopy enables measurement of rotational correlation functions for the crystalline phase. Analysis of the decays allows us to determine correlation times, to demonstrate the existence of a nonexponential relaxation, which implies a high complexity of the polymer dynamics in the crystal, and to show that the reorientation can be described as a large-angle jump. For a PEO-TiO 2-LiClO 4 mixture, we use (2)H and (7)Li NMR to study the polymer and the lithium dynamics, respectively. Analysis of the (7)Li spin-lattice relaxation reveals a high lithium ionic mobility in this nanocomposite polymer electrolyte. The (7)Li stimulated-echo decay is well described by a stretched exponential extending over about 6 orders of magnitude, indicating that a broad and continuous distribution of correlation times characterizes the fluctuations of the local lithium ionic environments.

Late Tharsis formation and implications for early Mars

NASA Astrophysics Data System (ADS)

Bouley, Sylvain; Baratoux, David; Matsuyama, Isamu; Forget, Francois; Séjourné, Antoine; Turbet, Martin; Costard, Francois

2016-03-01

The Tharsis region is the largest volcanic complex on Mars and in the Solar System. Young lava flows cover its surface (from the Amazonian period, less than 3 billion years ago) but its growth started during the Noachian era (more than 3.7 billion years ago). Its position has induced a reorientation of the planet with respect to its spin axis (true polar wander, TPW), which is responsible for the present equatorial position of the volcanic province. It has been suggested that the Tharsis load on the lithosphere influenced the orientation of the Noachian/Early Hesperian (more than 3.5 billion years ago) valley networks and therefore that most of the topography of Tharsis was completed before fluvial incision. Here we calculate the rotational figure of Mars (that is, its equilibrium shape) and its surface topography before Tharsis formed, when the spin axis of the planet was controlled by the difference in elevation between the northern and southern hemispheres (hemispheric dichotomy). We show that the observed directions of valley networks are also consistent with topographic gradients in this configuration and thus do not require the presence of the Tharsis load. Furthermore, the distribution of the valleys along a small circle tilted with respect to the equator is found to correspond to a southern-hemisphere latitudinal band in the pre-TPW geographical frame. Preferential accumulation of ice or water in a south tropical band is predicted by climate model simulations of early Mars applied to the pre-TPW topography. A late growth of Tharsis, contemporaneous with valley incision, has several implications for the early geological history of Mars, including the existence of glacial environments near the locations of the pre-TPW poles of rotation, and a possible link between volcanic outgassing from Tharsis and the stability of liquid water at the surface of Mars.

Late Tharsis formation and implications for early Mars.

PubMed

Bouley, Sylvain; Baratoux, David; Matsuyama, Isamu; Forget, Francois; Séjourné, Antoine; Turbet, Martin; Costard, Francois

2016-03-17

The Tharsis region is the largest volcanic complex on Mars and in the Solar System. Young lava flows cover its surface (from the Amazonian period, less than 3 billion years ago) but its growth started during the Noachian era (more than 3.7 billion years ago). Its position has induced a reorientation of the planet with respect to its spin axis (true polar wander, TPW), which is responsible for the present equatorial position of the volcanic province. It has been suggested that the Tharsis load on the lithosphere influenced the orientation of the Noachian/Early Hesperian (more than 3.5 billion years ago) valley networks and therefore that most of the topography of Tharsis was completed before fluvial incision. Here we calculate the rotational figure of Mars (that is, its equilibrium shape) and its surface topography before Tharsis formed, when the spin axis of the planet was controlled by the difference in elevation between the northern and southern hemispheres (hemispheric dichotomy). We show that the observed directions of valley networks are also consistent with topographic gradients in this configuration and thus do not require the presence of the Tharsis load. Furthermore, the distribution of the valleys along a small circle tilted with respect to the equator is found to correspond to a southern-hemisphere latitudinal band in the pre-TPW geographical frame. Preferential accumulation of ice or water in a south tropical band is predicted by climate model simulations of early Mars applied to the pre-TPW topography. A late growth of Tharsis, contemporaneous with valley incision, has several implications for the early geological history of Mars, including the existence of glacial environments near the locations of the pre-TPW poles of rotation, and a possible link between volcanic outgassing from Tharsis and the stability of liquid water at the surface of Mars.

Laser-Induced Ultrafast Demagnetization: Femtomagnetism, a New Frontier?

NASA Astrophysics Data System (ADS)

Zhang, Guoping; Huebner, Wolfgang; Beaurepaire, Eric; Bigot, Jean-Yves

The conventional demagnetization process (spin precession, magnetic domain motion and rotation) is governed mainly by spin-lattice, magnetic dipole and Zeeman, and spin-spin interactions. It occurs on a timescale of nanoseconds. Technologically, much faster magnetization changes are always in great demand to improve data processing speed. Unfortunately, the present speed of magnetic devices is already at the limit of the conventional mechanism with little room left. Fortunately and unprecedentedly, recent experimental investigations have evidenced much faster magnetization dynamics which occurs on a femtosecond time scale: femtomagnetism. This novel spin dynamics has not been well-understood until now. This article reviews the current status of ultrafast spin dynamics and presents a perspective for future experimental and theoretical investigations.Present address: Department of Physics and Astronomy, The University of Tennessee at Knoxville, TN 37996-1200, USA; gpzhang@utk.edu

Reorienting health services in the Northern Territory of Australia: a conceptual model for building health promotion capacity in the workforce.

PubMed

Judd, Jenni; Keleher, Helen

2013-06-01

Reorienting work practices to include health promotion and prevention is complex and requires specific strategies and interventions. This paper presents original research that used 'real-world' practice to demonstrate that knowledge gathered from practice is relevant for the development of practice-based evidence. The paper shows how practitioners can inform and influence improvements in health promotion practice. Practitioner-informed evidence necessarily incorporates qualitative research to capture the richness of their reflective experiences. Using a participatory action research (PAR) approach, the research question asked 'what are the core dimensions of building health promotion capacity in a primary health care workforce in a real-world setting?' PAR is a method in which the researcher operates in full collaboration with members of the organisation being studied for the purposes of achieving some kind of change, in this case to increase the amount of health promotion and prevention practice within this community health setting. The PAR process involved six reflection and action cycles over two years. Data collection processes included: survey; in-depth interviews; a training intervention; observations of practice; workplace diaries; and two nominal groups. The listen/reflect/act process enabled lessons from practice to inform future capacity-building processes. This research strengthened and supported the development of health promotion to inform 'better health' practices through respectful change processes based on research, practitioner-informed evidence, and capacity-building strategies. A conceptual model for building health promotion capacity in the primary health care workforce was informed by the PAR processes and recognised the importance of the determinants approach. Practitioner-informed evidence is the missing link in the evidence debate and provides the links between evidence and its translation to practice. New models of health promotion service delivery can be developed in community settings recognising the importance of involving practitioners themselves in these processes.

Study of Spin through Gluon Poles

NASA Astrophysics Data System (ADS)

Anikin, I. V.; Szymanowski, L.; Teryaev, O. V.; Volchanskiy, N.

2017-12-01

Based on the use of contour gauge and collinear factorization, we propose a new set of single spin asymmetry which can be measured in polarized Drell-Yan process by SPD@NICA. We stress that all of discussed single spin asymmetries exist owing to the gluon poles manifesting in the twist-3 or twist-2⊗twist-3 parton distributions related to the transverse-polarized Drell-Yan process.

Evaluating the Fabreville Heart Health Program in Laval, Canada: a dialogue between two paradigms, positivism and constructivism.

PubMed

Nguyen, Minh Nguyet; Otis, Joanne

2003-06-01

As part of the Canadian Federal-Provincial Initiative in Heart Health, the goal of the Fabreville Heart Health Program was to sensitize a district of Laval, Quebec's second most populous city, to heart-healthy behaviours. The program was planned and implemented by a committee composed of Fabreville community leaders and professionals from the Public Health Department. Between 1992 and 1994, intervention objectives were defined by the department in terms of changing individual behaviours associated with cardiovascular risk factors, namely diet, sedentariness and smoking, as well as adapting physical and social environments to facilitate these changes. However, from 1994 to its conclusion in 1997, the program was re-oriented to engage the population in mobilizing their own community and taking charge of interventions themselves. Actions then became dependent on the interests and motivation of Fabreville residents to transform their lifestyles and aspects of their physical environment. The initial evaluation process, based on the positivist paradigm, was designed to measure changes in individual behaviours and certain physical environments, such as an increase in designated non-smoking areas. However, following the re-orientation towards community mobilization, it was decided that evaluation should go beyond the professional production of data to include a process of the collective construction of knowledge. Evaluation methodology then became based on the constructivist paradigm. Yet field constraints such as lack of community involvement in both leadership and process evaluation, and the need to ensure evaluation standards and fulfil sponsor obligations, compelled the Public Health Department to return to using a certain number of positivist methods. The ensuing inter-paradigm dialogue helped broaden the scope of evaluation and contributed to gaining a more in-depth understanding of the processes and outcomes of community mobilization.

Bioactivity of cellulose acetate/hydroxyapatite nanoparticle composite fiber by an electro-spinning process.

PubMed

Kwak, Dae Hyun; Lee, Eun Ju; Kim, Deug Joong

2014-11-01

Hydroxyapatite/cellulose acetate composite webs were fabricated by an electro-spinning process. This electro-spinning process makes it possible to fabricate complex three-dimensional shapes. Nano fibrous web consisting of cellulose acetate and hydroxyapatite was produced from their mixture solution by using an electro-spinning process under high voltage. The surface of the electro-spun fiber was modified by a plasma and alkaline solution in order to increase its bioactivity. The structure, morphology and properties of the electro-spun fibers were investigated and an in-vitro bioactivity test was evaluated in simulated body fluid (SBF). Bioactivity of the electro-spun web was enhanced with the filler concentration and surface treatment. The surface changes of electro-spun fibers modified by plasma and alkaline solution were investigated by FT-IR (Fourier Transform Infrared Spectroscopy) and XPS (X-ray Photoelectron Spectroscopy).

Reorientation Timescales and Pattern Dynamics for Titan's Dunes: Does the Tail Wag the Dog or the Dragon?

NASA Astrophysics Data System (ADS)

Hayes, A. G.; Ewing, R. C.; Cassini Radar Science Team, T.

2011-12-01

Fields of bedform patterns persist across many orders of magnitude, from cm-scale sub-aqueous current ripples to km-scale aeolian dunes, and form with surprisingly little difference in expression despite a range of formative environments. Because of the remarkable similarity between and among patterns, extracting information about climate and environment from these patterns is a challenge. For example, crest orientation is not diagnostic of a particular flow regime; similar patterns form under many different flow configurations. On Titan, these challenges have played out with many attempts to reconcile dune-field patterns with modeled and expected wind regimes. We propose that thinking about the change in dune orientation, rather than the orientation itself, can provide new insights on the long-term stability of the dune-field patterns and the formative wind regime. In this work, we apply the re-orientation model presented by Werner and Kocurek [Geology, 1997] to the equatorial dune fields of Titan. We measure variations in pattern parameters (crest spacing, crest length and defect density, which is the number of defect pairs per total crest length) both within and between Titan's dune fields to describe pattern maturity and identify areas where changes in dune orientation are likely to occur (or may already be occurring). Measured defect densities are similar to Earth's largest linear dune fields, such as the Namib Sand Sea and the Simpson Desert. We use measured defect densities in the Werner and Kocurek model to estimate crestline reorientation rates. We find reorientation timescales varying from ten to a hundred thousand times the average migration timescale (time to migrate a bedform one meter, ~1 Titan year according to Tokano (Aeolian Research, 2010)). Well organized patterns have the longest reorientation time scales (~10^5 migration timescales), while the topographically or spatially isolated patches of dunes show the shortest reorientation times (~10^3 migration timescales). In addition, comparisons between spacing and defect density of Titan's dunes and some of the largest fields observed on Earth and Mars reveal that dune patterns on all three planets are geometrically similar, suggesting that growth and organization share common pattern dynamics. Our results suggest that Titan's dunes may react to gross bedform transport averaged over orbital timescales, relaxing the requirement that a single modern wind regime is required to produce the observed pattern.

Spin structure of the 'Forward' nucleon charge-exchange reaction n + p {yields} p + n and the deuteron charge-exchange breakup

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lyuboshitz, V. L., E-mail: Valery.Lyuboshitz@jinr.ru; Lyuboshitz, V. V.

2011-02-15

The structure of the nucleon charge-exchange process n + p {yields} p + n is investigated basing on the isotopic invariance of the nucleon-nucleon scattering. Using the operator of permutation of the spin projections of the neutron and proton, the connection between the spin matrices, describing the amplitude of the nucleon charge-exchange process at zero angle and the amplitude of the elastic scattering of the neutron on the proton in the 'backward' direction, has been considered. Due to the optical theorem, the spin-independent part of the differential cross section of the process n + p {yields} p + n atmore » zero angle for unpolarized particles is expressed through the difference of total cross sections of unpolarized proton-proton and neutron-proton scattering. Meantime, the spin-dependent part of this cross section is proportional to the differential cross section of the deuteron charge-exchange breakup d + p {yields} (pp) + n at zero angle at the deuteron momentum k{sub d} = 2 k{sub n} (k{sub n} is the initial neutron momentum). Analysis shows that, assuming the real part of the spin-independent term of the 'forward' amplitude of the process n + p {yields} p + n to be smaller or of the same order as compared with the imaginary part, in the wide range of neutron laboratory momenta k{sub n} > 700 MeV/c the main contribution into the differential cross section of the process n + p {yields} p + n at zero angle is provided namely by the spin-dependent term.« less

Anomalous spin-dependent tunneling statistics in Fe/MgO/Fe junctions induced by disorder at the interface

NASA Astrophysics Data System (ADS)

Yan, Jiawei; Wang, Shizhuo; Xia, Ke; Ke, Youqi

2018-01-01

We present first-principles analysis of interfacial disorder effects on spin-dependent tunneling statistics in thin Fe/MgO/Fe magnetic tunnel junctions. We find that interfacial disorder scattering can significantly modulate the tunneling statistics in the minority spin of the parallel configuration (PC) while all other spin channels remain dominated by the Poissonian process. For the minority-spin channel of PC, interfacial disorder scattering favors the formation of resonant tunneling channels by lifting the limitation of symmetry conservation at low concentration, presenting an important sub-Poissonian process in PC, but is destructive to the open channels at high concentration. We find that the important modulation of tunneling statistics is independent of the type of interfacial disorder. A bimodal distribution function of transmission with disorder dependence is introduced and fits very well our first-principles results. The increase of MgO thickness can quickly change the tunneling from a sub-Poissonian to Poissonian dominated process in the minority spin of PC with disorder. Our results provide a sensitive detection method of an ultralow concentration of interfacial defects.

Tunable room-temperature spin-selective optical Stark effect in solution-processed layered halide perovskites.

PubMed

Giovanni, David; Chong, Wee Kiang; Dewi, Herlina Arianita; Thirumal, Krishnamoorthy; Neogi, Ishita; Ramesh, Ramamoorthy; Mhaisalkar, Subodh; Mathews, Nripan; Sum, Tze Chien

2016-06-01

Ultrafast spin manipulation for opto-spin logic applications requires material systems that have strong spin-selective light-matter interaction. Conventional inorganic semiconductor nanostructures [for example, epitaxial II to VI quantum dots and III to V multiple quantum wells (MQWs)] are considered forerunners but encounter challenges such as lattice matching and cryogenic cooling requirements. Two-dimensional halide perovskite semiconductors, combining intrinsic tunable MQW structures and large oscillator strengths with facile solution processability, can offer breakthroughs in this area. We demonstrate novel room-temperature, strong ultrafast spin-selective optical Stark effect in solution-processed (C6H4FC2H4NH3)2PbI4 perovskite thin films. Exciton spin states are selectively tuned by ~6.3 meV using circularly polarized optical pulses without any external photonic cavity (that is, corresponding to a Rabi energy of ~55 meV and equivalent to applying a 70 T magnetic field), which is much larger than any conventional system. The facile halide and organic replacement in these perovskites affords control of the dielectric confinement and thus presents a straightforward strategy for tuning light-matter coupling strength.

Spin-lattice relaxation of individual solid-state spins

NASA Astrophysics Data System (ADS)

Norambuena, A.; Muñoz, E.; Dinani, H. T.; Jarmola, A.; Maletinsky, P.; Budker, D.; Maze, J. R.

2018-03-01

Understanding the effect of vibrations on the relaxation process of individual spins is crucial for implementing nanosystems for quantum information and quantum metrology applications. In this work, we present a theoretical microscopic model to describe the spin-lattice relaxation of individual electronic spins associated to negatively charged nitrogen-vacancy centers in diamond, although our results can be extended to other spin-boson systems. Starting from a general spin-lattice interaction Hamiltonian, we provide a detailed description and solution of the quantum master equation of an electronic spin-one system coupled to a phononic bath in thermal equilibrium. Special attention is given to the dynamics of one-phonon processes below 1 K where our results agree with recent experimental findings and analytically describe the temperature and magnetic-field scaling. At higher temperatures, linear and second-order terms in the interaction Hamiltonian are considered and the temperature scaling is discussed for acoustic and quasilocalized phonons when appropriate. Our results, in addition to confirming a T5 temperature dependence of the longitudinal relaxation rate at higher temperatures, in agreement with experimental observations, provide a theoretical background for modeling the spin-lattice relaxation at a wide range of temperatures where different temperature scalings might be expected.

Antiferromagnetic domain wall as spin wave polarizer and retarder.

PubMed

Lan, Jin; Yu, Weichao; Xiao, Jiang

2017-08-02

As a collective quasiparticle excitation of the magnetic order in magnetic materials, spin wave, or magnon when quantized, can propagate in both conducting and insulating materials. Like the manipulation of its optical counterpart, the ability to manipulate spin wave polarization is not only important but also fundamental for magnonics. With only one type of magnetic lattice, ferromagnets can only accommodate the right-handed circularly polarized spin wave modes, which leaves no freedom for polarization manipulation. In contrast, antiferromagnets, with two opposite magnetic sublattices, have both left and right-circular polarizations, and all linear and elliptical polarizations. Here we demonstrate theoretically and confirm by micromagnetic simulations that, in the presence of Dzyaloshinskii-Moriya interaction, an antiferromagnetic domain wall acts naturally as a spin wave polarizer or a spin wave retarder (waveplate). Our findings provide extremely simple yet flexible routes toward magnonic information processing by harnessing the polarization degree of freedom of spin wave.Spin waves are promising candidates as carriers for energy-efficient information processing, but they have not yet been fully explored application wise. Here the authors theoretically demonstrate that antiferromagnetic domain walls are naturally spin wave polarizers and retarders, two key components of magnonic devices.

Controlling the quantum dynamics of a mesoscopic spin bath in diamond

PubMed Central

de Lange, Gijs; van der Sar, Toeno; Blok, Machiel; Wang, Zhi-Hui; Dobrovitski, Viatcheslav; Hanson, Ronald

2012-01-01

Understanding and mitigating decoherence is a key challenge for quantum science and technology. The main source of decoherence for solid-state spin systems is the uncontrolled spin bath environment. Here, we demonstrate quantum control of a mesoscopic spin bath in diamond at room temperature that is composed of electron spins of substitutional nitrogen impurities. The resulting spin bath dynamics are probed using a single nitrogen-vacancy (NV) centre electron spin as a magnetic field sensor. We exploit the spin bath control to dynamically suppress dephasing of the NV spin by the spin bath. Furthermore, by combining spin bath control with dynamical decoupling, we directly measure the coherence and temporal correlations of different groups of bath spins. These results uncover a new arena for fundamental studies on decoherence and enable novel avenues for spin-based magnetometry and quantum information processing. PMID:22536480

Ultrafast magnon generation in an Fe film on Cu(100).

PubMed

Schmidt, A B; Pickel, M; Donath, M; Buczek, P; Ernst, A; Zhukov, V P; Echenique, P M; Sandratskii, L M; Chulkov, E V; Weinelt, M

2010-11-05

We report on a combined experimental and theoretical study of the spin-dependent relaxation processes in the electron system of an iron film on Cu(100). Spin-, time-, energy- and angle-resolved two-photon photoemission shows a strong characteristic dependence of the lifetime of photoexcited electrons on their spin and energy. Ab initio calculations as well as a many-body treatment corroborate that the observed properties are determined by relaxation processes involving magnon emission. Thereby we demonstrate that magnon emission by hot electrons occurs on the femtosecond time scale and thus provides a significant source of ultrafast spin-flip processes. Furthermore, engineering of the magnon spectrum paves the way for tuning the dynamic properties of magnetic materials.

Spin Current through a Quantum Dot in the Presence of an Oscillating Magnetic Field

NASA Astrophysics Data System (ADS)

Zhang, Ping; Xue, Qi-Kun; Xie, X. C.

2003-11-01

Nonequilibrium spin transport through an interacting quantum dot is analyzed. The coherent spin oscillations in the dot provide a generating source for spin current. In the interacting regime, the Kondo effect is influenced in a significant way by the presence of the processing magnetic field. In particular, when the precession frequency is tuned to resonance between spin-up and spin-down states of the dot, Kondo singularity for each spin splits into a superposition of two resonance peaks. The Kondo-type cotunneling contribution is manifested by a large enhancement of the pumped spin current in the strong coupling low temperature regime.

Heat engine by exorcism of Maxwell Demon using spin angular momentum reservoir

NASA Astrophysics Data System (ADS)

Bedkihal, Salil; Wright, Jackson; Vaccaro, Joan; Gould, Tim

Landauer's erasure principle is a hallmark in thermodynamics and information theory. According to this principle, erasing one bit of information incurs a minimum energy cost. Recently, Vaccaro and Barnett (VB) have explored the role of multiple conserved quantities in memory erasure. They further illustrated that for the energy degenerate spin reservoirs, the cost of erasure can be solely in terms of spin angular momentum and no energy. Motivated by the VB erasure, in this work we propose a novel optical heat engine that operates under a single thermal reservoir and a spin angular momentum reservoir. The novel heat engine exploits ultrafast processes of phonon absorption to convert thermal phonon energy to coherent light. The entropy generated in this process then corresponds to a mixture of spin up and spin down populations of energy degenerate electronic ground states which acts as demon's memory. This information is then erased using a polarised spin reservoir that acts as an entropy sink. The proposed heat engines goes beyond the traditional Carnot engine.

Quasi-elastic (QENS) and inelastic neutron scattering (INS) on hexamethylbenzene

NASA Astrophysics Data System (ADS)

Krawczyk, J.; Mayer, J.; Natkaniec, I.; Nowina Konopka, M.; Pawlukojć; Steinsvoll, O.; Janik, J. A.

2005-05-01

The Quasi-elastic Neutron scattering (QENS) spectra of polycrystalline hexamethylbenzene (HMB) were measured for temperatures from 10 K to room temperature (phase III and phase II) for momentum transfer 1.9 Å -1. The Inelastic Neutron scattering (INS) and QENS spectra for momentum transfer 0.5-2.9 Å -1 were measured at T=20, 100 and 130 K for energy transfer up to 200 meV. The low-resolution diffraction patterns, used as the phase indicator, were also obtained. In the phase III (below 117 K), we see practically no quasi-elastic broadening. In phase II, the broadening changes with the temperature are in good agreement with the Arrhenius law. The estimated activation barrier to reorientation is 6 kJ/mol. The fitted mean time between instantaneous 120° jumps of CH 3 groups changes from 10 -11 s at T=130 K to 2×10 -13 s at room temperature. On the basis of EISF versus momentum transfer dependency it is hardly possible to decide what is the geometry of the reorientation. Both reorientation of the CH 3 groups around the three-fold symmetry axis and reorientation of the whole molecule around the six-fold symmetry axis of the benzene ring could describe our results, the former being more probable. The measured INS spectra are compared with the quantum chemical ab initio calculations performed for an isolated HMB molecule.

Statics and dynamics of free and hydrogen-bonded OH groups at the air/water interface.

PubMed

Vila Verde, Ana; Bolhuis, Peter G; Campen, R Kramer

2012-08-09

We use classical atomistic molecular dynamics simulations of two water models (SPC/E and TIP4P/2005) to investigate the orientation and reorientation dynamics of two subpopulations of OH groups belonging to water molecules at the air/water interface at 300 K: those OH groups that donate a hydrogen bond (called "bonded") and those that do not (called "free"). Free interfacial OH groups reorient in two distinct regimes: a fast regime from 0 to 1 ps and a slow regime thereafter. Qualitatively similar behavior was reported by others for free OH groups near extended hydrophobic surfaces. In contrast, the net reorientation of bonded OH groups occurs at a rate similar to that of bulk water. This similarity in reorientation rate results from compensation of two effects: decreasing frequency of hydrogen-bond breaking/formation (i.e., hydrogen-bond exchange) and faster rotation of intact hydrogen bonds. Both changes result from the decrease in density at the air/water interface relative to the bulk. Interestingly, because of the presence of capillary waves, the slowdown of hydrogen-bond exchange is significantly smaller than that reported for water near extended hydrophobic surfaces, but it is almost identical to that reported for water near small hydrophobic solutes. In this sense water at the air/water interface has characteristics of water of hydration of both small and extended hydrophobic solutes.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Yizhou, E-mail: yliu062@ucr.edu; Yin, Gen; Lake, Roger K., E-mail: rlake@ece.ucr.edu

Single skyrmion creation and annihilation by spin waves in a crossbar geometry are theoretically analyzed. A critical spin-wave frequency is required both for the creation and the annihilation of a skyrmion. The minimum frequencies for creation and annihilation are similar, but the optimum frequency for creation is below the critical frequency for skyrmion annihilation. If a skyrmion already exists in the cross bar region, a spin wave below the critical frequency causes the skyrmion to circulate within the central region. A heat assisted creation process reduces the spin-wave frequency and amplitude required for creating a skyrmion. The effective field resultingmore » from the Dzyaloshinskii-Moriya interaction and the emergent field of the skyrmion acting on the spin wave drive the creation and annihilation processes.« less

Spin-up studies of the Space Shuttle Orbiter main gear tire

NASA Technical Reports Server (NTRS)

Daugherty, Robert H.; Stubbs, Sandy M.

1988-01-01

One of the factors needed to describe the wear behavior of the Space Shuttle Orbiter main gear tires is their behavior during the spin-up process. An experimental investigation of tire spin-up processes was conducted at the NASA Langley Research Center's Aircraft Landing Dynamics Facility. During the investigation, the influence of various parameters such as forward speed and sink speed on tire spin-up forces were evaluated. A mathematical model was developed to estimate drag forces and spin-up times and is presented. The effect of prerotation was explored and is discussed. Also included is a means of determining the sink speed of the orbiter at touchdown based upon the appearance of the rubber deposits left on the runway during spinup.

Antiferromagnetic Spin Wave Field-Effect Transistor

DOE PAGES

Cheng, Ran; Daniels, Matthew W.; Zhu, Jian-Gang; ...

2016-04-06

In a collinear antiferromagnet with easy-axis anisotropy, symmetry dictates that the spin wave modes must be doubly degenerate. Theses two modes, distinguished by their opposite polarization and available only in antiferromagnets, give rise to a novel degree of freedom to encode and process information. We show that the spin wave polarization can be manipulated by an electric field induced Dzyaloshinskii-Moriya interaction and magnetic anisotropy. We propose a prototype spin wave field effect transistor which realizes a gate-tunable magnonic analog of the Faraday effect, and demonstrate its application in THz signal modulation. In conclusion, our findings open up the exciting possibilitymore » of digital data processing utilizing antiferromagnetic spin waves and enable the direct projection of optical computing concepts onto the mesoscopic scale.« less

Hidden transition in multiferroic and magnetodielectric CuCrO2 evidenced by ac-susceptibility

NASA Astrophysics Data System (ADS)

Shukla, Kaushak K.; Pal, Arkadeb; Singh, Abhishek; Singh, Rahul; Saha, J.; Sinha, A. K.; Ghosh, A. K.; Patnaik, S.; Awasthi, A. M.; Chatterjee, Sandip

2017-04-01

Ferroelectric polarization, magnetic-field dependence of the dielectric constant and ac and dc magnetizations of frustrated CuCrO2 have been measured. A new spin freezing transition below 32 K is observed which is thermally driven. The nature of the spin freezing is to be a single-ion process. Dilution by the replacements of Cr ions by magnetic Mn ions showed suppression of the spin freezing transition suggesting it to be fundamentally a single-ion freezing process. The observed freezing, which is seemingly associated to geometrical spin frustration, represents a novel form of magnetic glassy behavior.

Software Library for Bruker TopSpin NMR Data Files

DOE Office of Scientific and Technical Information (OSTI.GOV)

A software library for parsing and manipulating frequency-domain data files that have been processed using the Bruker TopSpin NMR software package. In the context of NMR, the term "processed" indicates that the end-user of the Bruker TopSpin NMR software package has (a) Fourier transformed the raw, time-domain data (the Free Induction Decay) into the frequency-domain and (b) has extracted the list of NMR peaks.

Fine structure and optical pumping of spins in individual semiconductor quantum dots

NASA Astrophysics Data System (ADS)

Bracker, Allan S.; Gammon, Daniel; Korenev, Vladimir L.

2008-11-01

We review spin properties of semiconductor quantum dots and their effect on optical spectra. Photoluminescence and other types of spectroscopy are used to probe neutral and charged excitons in individual quantum dots with high spectral and spatial resolution. Spectral fine structure and polarization reveal how quantum dot spins interact with each other and with their environment. By taking advantage of the selectivity of optical selection rules and spin relaxation, optical spin pumping of the ground state electron and nuclear spins is achieved. Through such mechanisms, light can be used to process spins for use as a carrier of information.

High-fidelity readout and control of a nuclear spin qubit in silicon.

PubMed

Pla, Jarryd J; Tan, Kuan Y; Dehollain, Juan P; Lim, Wee H; Morton, John J L; Zwanenburg, Floris A; Jamieson, David N; Dzurak, Andrew S; Morello, Andrea

2013-04-18

Detection of nuclear spin precession is critical for a wide range of scientific techniques that have applications in diverse fields including analytical chemistry, materials science, medicine and biology. Fundamentally, it is possible because of the extreme isolation of nuclear spins from their environment. This isolation also makes single nuclear spins desirable for quantum-information processing, as shown by pioneering studies on nitrogen-vacancy centres in diamond. The nuclear spin of a (31)P donor in silicon is very promising as a quantum bit: bulk measurements indicate that it has excellent coherence times and silicon is the dominant material in the microelectronics industry. Here we demonstrate electrical detection and coherent manipulation of a single (31)P nuclear spin qubit with sufficiently high fidelities for fault-tolerant quantum computing. By integrating single-shot readout of the electron spin with on-chip electron spin resonance, we demonstrate quantum non-demolition and electrical single-shot readout of the nuclear spin with a readout fidelity higher than 99.8 percent-the highest so far reported for any solid-state qubit. The single nuclear spin is then operated as a qubit by applying coherent radio-frequency pulses. For an ionized (31)P donor, we find a nuclear spin coherence time of 60 milliseconds and a one-qubit gate control fidelity exceeding 98 percent. These results demonstrate that the dominant technology of modern electronics can be adapted to host a complete electrical measurement and control platform for nuclear-spin-based quantum-information processing.

Spin Filtering in Storage Rings

NASA Astrophysics Data System (ADS)

Nikolaev, N. N.; Pavlov, F. F.

The spin filtering in storage rings is based on a multiple passage of a stored beam through a polarized internal gas target. Apart from the polarization by the spin-dependent transmission, a unique geometrical feature of interaction with the target in such a filtering process, pointed out by H.O. Meyer,1 is a scattering of stored particles within the beam. A rotation of the spin in the scattering process affects the polarization buildup. We derive here a quantum-mechanical evolution equation for the spin-density matrix of a stored beam which incorporates the scattering within the beam. We show how the interplay of the transmission and scattering within the beam changes from polarized electrons to polarized protons in the atomic target. After discussions of the FILTEX results on the filtering of stored protons,2 we comment on the strategy of spin filtering of antiprotons for the PAX experiment at GSI FAIR.3.

Service delivery, community development, and disability.

PubMed

Murphy, John W

2010-01-01

Service delivery has traditionally been based on market forces. When this is the case, the community becomes a silent partner in this process. Services, accordingly, are directed mostly to correcting personal ills and have little to do with community uplift. Another model, based on the work of Amartya Sen, is available that conceptualizes interventions in a very different way. If understood in the context of community development, the focus of services is social change, rather than merely personal rehabilitation. This reorientation is discussed in this article.

Development and operation of a Pr 2 Fe 14 B based cryogenic permanent magnet undulator for a high spatial resolution x-ray beam line

DOE PAGES

Benabderrahmane, C.; Valleau, M.; Ghaith, A.; ...

2017-03-02

Short period, high field undulators are used to produce hard x-rays on synchrotron radiation based storage ring facilities of intermediate energy and enable short wavelength free electron laser. Cryogenic permanent magnet undulators take benefit from improved magnetic properties of RE 2Fe 14B (Rare Earth based magnets) at low temperatures for achieving short period, high magnetic field and high coercivity. Using Pr 2Fe 14B instead of Nd 2Fe 14B, which is generally employed for undulators, avoids the limitation caused by the spin reorientation transition phenomenon, and simplifies the cooling system by allowing the working temperature of the undulator to be directlymore » at the liquid nitrogen one (77 K). We describe here the development of a full scale (2 m), 18 mm period Pr 2Fe 14B cryogenic permanent magnet undulator (U18). The design, construction and optimization, as well as magnetic measurements and shimming at low temperature are presented. In conclusion, the commissioning and operation of the undulator with the electron beam and spectrum measurement using the Nanoscopmium beamline at SOLEIL are also reported.« less

Large magnetic entropy change in multiferroic HoFeO3 single crystal

NASA Astrophysics Data System (ADS)

Das, Moumita; Mandal, Prabhat

2018-04-01

In this article magnetic and magnetocaloric properties of HoFeO3 single crystal have been investigated by magnetization measurement in the temperature range 6-30K and near spin reorientation transition (TSR) region 45-61K. Remarkably large and reversible magnetic entropy change (-ΔSm) = 27J/kg K, has been observed for a field change of 0-6T near 9.5K due to metamagnetic transition. The value of ΔSm is 6J/kg K at 6T near TSR. This magnetocaloric parameter is larger than previously reported value along [100] crystallographic axis due to its anisotropic nature along different axis. This value is larger than some of the potential magnetic refrigerants in the same temperature range which is not reported previously. The ΔSm is also quite large for a small and moderate field change. For an example the values of ΔSmax are 7 and 12 J/kg K for field change of 2 and 3T. The large value of this magnetocaloric parameter suggests that HoFeO3 could be considered as a potential refrigerant material for low-temperature magnetic refrigeration technology to liquefaction the hydrogen and helium in fuel industry.

Effect of Organic Blocking Layer on the Energy Storage Characteristics of High-Permittivity Sol-Gel Thin Film Based on Neat 2-Cyanoethyltrimethoxysilane

NASA Astrophysics Data System (ADS)

Kim, Yunsang; Kathaperumal, Mohanalingam; Pan, Ming-Jen; Perry, Joseph

2014-03-01

Organic-inorganic hybrid sol-gel materials with polar groups that can undergo reorientational polarization provide a potential route to dielectric materials for energy storage. We have investigated the influence of nanoscale polymeric layer on dielectric and energy storage properties of 2-cyanoethyltrimethoxysilane (CNETMS) films. Two polymeric materials, fluoropolymer (CYTOP) and poly(p-phenylene oxide, PPO), are examined as potential materials to control charge injection from electrical contacts into CNETMS films by means of a potential barrier, whose width and height are defined by thickness and permittivity. Blocking layers ranging from 20 nm to 200 nm were deposited on CNETMS films by spin casting and subjected to thermal treatment. Polarization-electric field measurements show 30% increase in extractable energy density with PPO/CNETMS bilayers, relative to CNETMS alone, due to improved breakdown strength. Conduction current of the bilayers indicate that onset of charge conduction at high field is much delayed, which can be translated into effective suppression of charge injection and probability of breakdown events. The results will be discussed in regards to film morphology, field partitioning, width and height of potential barrier, charge trapping and loss of bilayers.

Development and operation of a Pr 2 Fe 14 B based cryogenic permanent magnet undulator for a high spatial resolution x-ray beam line

DOE Office of Scientific and Technical Information (OSTI.GOV)

Benabderrahmane, C.; Valleau, M.; Ghaith, A.

Short period, high field undulators are used to produce hard x-rays on synchrotron radiation based storage ring facilities of intermediate energy and enable short wavelength free electron laser. Cryogenic permanent magnet undulators take benefit from improved magnetic properties of RE 2Fe 14B (Rare Earth based magnets) at low temperatures for achieving short period, high magnetic field and high coercivity. Using Pr 2Fe 14B instead of Nd 2Fe 14B, which is generally employed for undulators, avoids the limitation caused by the spin reorientation transition phenomenon, and simplifies the cooling system by allowing the working temperature of the undulator to be directlymore » at the liquid nitrogen one (77 K). We describe here the development of a full scale (2 m), 18 mm period Pr 2Fe 14B cryogenic permanent magnet undulator (U18). The design, construction and optimization, as well as magnetic measurements and shimming at low temperature are presented. In conclusion, the commissioning and operation of the undulator with the electron beam and spectrum measurement using the Nanoscopmium beamline at SOLEIL are also reported.« less

Development and operation of a Pr2 Fe14 B based cryogenic permanent magnet undulator for a high spatial resolution x-ray beam line

NASA Astrophysics Data System (ADS)

Benabderrahmane, C.; Valléau, M.; Ghaith, A.; Berteaud, P.; Chapuis, L.; Marteau, F.; Briquez, F.; Marcouillé, O.; Marlats, J.-L.; Tavakoli, K.; Mary, A.; Zerbib, D.; Lestrade, A.; Louvet, M.; Brunelle, P.; Medjoubi, K.; Herbeaux, C.; Béchu, N.; Rommeluere, P.; Somogyi, A.; Chubar, O.; Kitegi, C.; Couprie, M.-E.

2017-03-01

Short period, high field undulators are used to produce hard x-rays on synchrotron radiation based storage ring facilities of intermediate energy and enable short wavelength free electron laser. Cryogenic permanent magnet undulators take benefit from improved magnetic properties of RE2 Fe14B (Rare Earth based magnets) at low temperatures for achieving short period, high magnetic field and high coercivity. Using Pr2 Fe14B instead of Nd2 Fe14B , which is generally employed for undulators, avoids the limitation caused by the spin reorientation transition phenomenon, and simplifies the cooling system by allowing the working temperature of the undulator to be directly at the liquid nitrogen one (77 K). We describe here the development of a full scale (2 m), 18 mm period Pr2 Fe14B cryogenic permanent magnet undulator (U18). The design, construction and optimization, as well as magnetic measurements and shimming at low temperature are presented. The commissioning and operation of the undulator with the electron beam and spectrum measurement using the Nanoscopmium beamline at SOLEIL are also reported.

Anomalous Hall effect in the van der Waals bonded ferromagnet Fe3 -xGeTe2

NASA Astrophysics Data System (ADS)

Liu, Yu; Stavitski, Eli; Attenkofer, Klaus; Petrovic, C.

2018-04-01

We report the anomalous Hall effect (AHE) in single crystals of a quasi-two-dimensional Fe3 -xGeTe2 (x ≈0.36 ) ferromagnet grown by the flux method which induces defects on the Fe site and bad metallic resistivity. Fe K-edge x-ray absorption spectroscopy was measured to provide information on the local atomic environment in such crystals. The dc and ac magnetic susceptibility measurements indicate a second-stage transition below 119 K in addition to the paramagnetic to ferromagnetic transition at 153 K. A linear scaling behavior between the modified anomalous Hall resistivity ρx y/μ0Heff and longitudinal resistivity ρxx 2M /μ0Heff implies that the AHE in Fe3 -xGeTe2 should be dominated by the intrinsic Karplus-Luttinger mechanism rather than the extrinsic skew-scattering and side-jump mechanisms. The observed deviation in the linear-M Hall conductivity σxy A below 30 K is in line with its transport characteristic at low temperatures, implying the scattering of conduction electrons due to magnetic disorder and the evolution of the Fermi surface induced by a possible spin-reorientation transition.

Energy extraction of a spinning particle via the super Penrose process from an extremal Kerr black hole

NASA Astrophysics Data System (ADS)

Liu, Yan; Liu, Wen-Biao

2018-03-01

The energy extraction of the collisional Penrose process has been investigated in recent years. Previous researchers mainly concentrated on the case of nonspin massive or massless particles, and they discovered that when the collision occurs near the horizon of extremal rotating black holes, the arbitrary large efficiency can be achieved with the particle's angular momentum below the critical value as L1<2 . In this paper, the energy extraction of spinning massive particles is calculated via the super Penrose process. We obtain the dependence of the impact factor and the turning points on the particle's spin s . The super Penrose process can occur only when s ≤1 and J1<2 , where J1 is the spinning particle's angular momentum. It is found that the efficiency of the energy extraction is monotonously increasing with the particle's spin s increasing for s <1 , and it can become arbitrarily high when the collision occurs close to the horizon. We compare the maximum extracted energy of spinning particles with that of the nonspin case and find a significant increase of the extracted energy. When s →1 , the maximum extracted energy can be orders of magnitude larger than that of the nonspin case. For the astrophysical black holes, the large efficiency is also obtained. Naturally, when the particle's spin s ≪1 , we can degenerate the result back to the nonspin case.

Quasiparticle spin resonance and coherence in superconducting aluminium

NASA Astrophysics Data System (ADS)

Quay, C. H. L.; Weideneder, M.; Chiffaudel, Y.; Strunk, C.; Aprili, M.

2015-10-01

Conventional superconductors were long thought to be spin inert; however, there is now increasing interest in both (the manipulation of) the internal spin structure of the ground-state condensate, as well as recently observed long-lived, spin-polarized excitations (quasiparticles). We demonstrate spin resonance in the quasiparticle population of a mesoscopic superconductor (aluminium) using novel on-chip microwave detection techniques. The spin decoherence time obtained (~100 ps), and its dependence on the sample thickness are consistent with Elliott-Yafet spin-orbit scattering as the main decoherence mechanism. The striking divergence between the spin coherence time and the previously measured spin imbalance relaxation time (~10 ns) suggests that the latter is limited instead by inelastic processes. This work stakes out new ground for the nascent field of spin-based electronics with superconductors or superconducting spintronics.

Enabling health systems transformation: what progress has been made in re-orienting health services?

PubMed

Wise, Marilyn; Nutbeam, Don

2007-01-01

The Ottawa Charter has been remarkably influential in guiding the development of the goals and concepts of health promotion, and in shaping global public health practice in the past 20 years. However, of the five action areas identified in the Ottawa Charter, it appears that there has been little systematic attention to the challenge of re-orienting health services, and less than optimal progress in practice. The purposes of re-orienting health services as proposed in the Ottawa Charter were to achieve a better balance in investment between prevention and treatment, and to include a focus on population health outcomes alongside the focus on individual health outcomes. However, there is little evidence that a re-orientation of health services in these terms has occurred systematically anywhere in the world. This is in spite of the fact that direct evidence of the need to re-orient health services and of the potential benefits of doing so has grown substantially since 1986. Patient education, preventive care (screening, immunisation), and organisational and environmental changes by health organisations have all been found to have positive health and environmental outcomes. However, evidence of effectiveness has not been sufficient, on its own, to sway community preferences and political decisions. The lack of progress points to the need for significant re-thinking of the approaches we have adopted to date. The paper proposes a number of ways forward. These include working effectively in partnership with the communities we want to serve to mobilise support for change, and to reinforce this by working more effectively at influencing broader public opinion through the media. The active engagement of clinical health professionals is also identified as crucial to achieving sustainable change. Finally we recognize that by working in partnership with like-minded advocacy organizations, the IUHPE could put its significant knowledge and experience to work in leading action to transform health care systems to make a major contribution to the improvement of public health.

Field-induced negative differential spin lifetime in silicon.

PubMed

Li, Jing; Qing, Lan; Dery, Hanan; Appelbaum, Ian

2012-04-13

We show that the electric-field-induced thermal asymmetry between the electron and lattice systems in pure silicon substantially impacts the identity of the dominant spin relaxation mechanism. Comparison of empirical results from long-distance spin transport devices with detailed Monte Carlo simulations confirms a strong spin depolarization beyond what is expected from the standard Elliott-Yafet theory even at low temperatures. The enhanced spin-flip mechanism is attributed to phonon emission processes during which electrons are scattered between conduction band valleys that reside on different crystal axes. This leads to anomalous behavior, where (beyond a critical field) reduction of the transit time between spin-injector and spin-detector is accompanied by a counterintuitive reduction in spin polarization and an apparent negative spin lifetime.

In search of elementary spin 0 particles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krasny, Mieczyslaw Witold, E-mail: krasny@lpnhep.in2p3.fr; Płaczek, Wiesław

2015-01-15

The Standard Model of strong and electroweak interactions uses point-like spin 1/2 particles as the building bricks of matter and point-like spin 1 particles as the force carriers. One of the most important questions to be answered by the present and future particle physics experiments is whether the elementary spin 0 particles exist, and if they do, what are their interactions with the spin 1/2 and spin 1 particles. Spin 0 particles have been searched extensively over the last decades. Several initial claims of their discoveries were finally disproved in the final experimental scrutiny process. The recent observation of themore » excess of events at the LHC in the final states involving a pair of vector bosons, or photons, is commonly interpreted as the discovery of the first elementary scalar particle, the Higgs boson. In this paper we recall examples of claims and subsequent disillusions in precedent searches spin 0 particles. We address the question if the LHC Higgs discovery can already be taken for granted, or, as it turned out important in the past, whether it requires a further experimental scrutiny before the existence of the first ever found elementary scalar particle is proven beyond any doubt. An example of the Double Drell–Yan process for which such a scrutiny is indispensable is discussed in some detail. - Highlights: • We present a short history of searches of spin 0 particles. • We construct a model of the Double Drell–Yan Process (DDYP) at the LHC. • We investigate the contribution of the DDYP to the Higgs searches background.« less

Enhanced spin pumping into superconductors provides evidence for superconducting pure spin currents

NASA Astrophysics Data System (ADS)

Jeon, Kun-Rok; Ciccarelli, Chiara; Ferguson, Andrew J.; Kurebayashi, Hidekazu; Cohen, Lesley F.; Montiel, Xavier; Eschrig, Matthias; Robinson, Jason W. A.; Blamire, Mark G.

2018-06-01

Unlike conventional spin-singlet Cooper pairs, spin-triplet pairs can carry spin1,2. Triplet supercurrents were discovered in Josephson junctions with metallic ferromagnet spacers, where spin transport can occur only within the ferromagnet and in conjunction with a charge current. Ferromagnetic resonance injects a pure spin current from a precessing ferromagnet into adjacent non-magnetic materials3,4. For spin-singlet pairing, the ferromagnetic resonance spin pumping efficiency decreases below the critical temperature (Tc) of a coupled superconductor5,6. Here we present ferromagnetic resonance experiments in which spin sink layers with strong spin-orbit coupling are added to the superconductor. Our results show that the induced spin currents, rather than being suppressed, are substantially larger in the superconducting state compared with the normal state; although further work is required to establish the details of the spin transport process, we show that this cannot be mediated by quasiparticles and is most likely a triplet pure spin supercurrent.

Single-spin observables and orbital structures in hadronic distributions

NASA Astrophysics Data System (ADS)

Sivers, Dennis

2006-11-01

Single-spin observables in scattering processes (either analyzing powers or polarizations) are highly constrained by rotational invariance and finite symmetries. For example, it is possible to demonstrate that all single-spin observables are odd under the finite transformation O=PAτ where P is parity and Aτ is a finite symmetry that can be designated “artificial time reversal”. The operators P, O and Aτ all have eigenvalues ±1 so that all single-spin observables can be classified into two distinct categories: (1) P-odd and Aτ-even, (2) P-even and Aτ-odd. Within the light-quark sector of the standard model, P-odd observables are generated from pointlike electroweak processes while Aτ-odd observables (neglecting quark mass parameters) come from dynamic spin-orbit correlations within hadrons or within larger composite systems, such as nuclei. The effects of Aτ-odd dynamics can be inserted into transverse-momentum dependent constituent distribution functions and, in this paper, we construct the contribution from an orbital quark to the Aτ-odd quark parton distribution ΔNGq/p↑front(x,kTN;μ2). Using this distribution, we examine the crucial role of initial- and final-state interactions in the observation of the scattering asymmetries in different hard-scattering processes. This construction provides a geometrical and dynamical interpretation of the Collins conjugation relation between single-spin asymmetries in semi-inclusive deep inelastic scattering and the asymmetries in Drell-Yan production. Finally, our construction allows us to display a significant difference between the calculation of a spin asymmetry generated by a hard-scattering mechanism involving color-singlet exchange (such as a photon) and a calculation of an asymmetry with a hard-scattering exchange involving gluons. This leads to an appreciation of the process-dependence inherent in measurements of single-spin observables.

Synthesis and Characterization of Ferromagnetic/Antiferromagnetic Perovskite Oxide Superlattices

NASA Astrophysics Data System (ADS)

Jia, Yue

Perovskite oxides span a diverse range of functional properties such as ferromagnetism, superconductivity, and ferroelectricity, which makes them promising candidate materials for applications such as sensors, energy conversion and data storage devices. With recent advances in thin film deposition techniques, the precise manipulation of atomic layers on the unit cell level make it possible to synthesize epitaxial thin film heterostructures consisting of layers with different properties. The structural compatibility of perovskite oxides allows them to be epitaxially grown in complex heterostructures such as superlattices with a large density of interfaces where the interplay between spin, charge, orbital, and lattice degrees of freedom gives rise to new behaviors. The ferromagnetic (FM)/antiferromagnetic (AF) interface is particularly interesting due to exchange coupling which is not only of interest for fundamental research but also is of great significance for industrial applications. Unlike metallic systems that have been studied for decades with wide ranges of applications in devices such as hard disk drives, thin films of complex metal oxides is a relatively new field. Perovskite oxides show much more diverse functional properties than metals and open new pathways for tailoring propertiestowards specific device applications. Epitaxial La0.7Sr0.3MnO3 (LSMO)/La 0.7Sr0.3FeO3 (LSFO) superlattices serve as model systems to explore the magnetic structure and exchange coupling at perovskite oxide interfaces. Earlier work suggested that (001)-oriented LSMO/LSFO superlattices with compensated AF spins at the interface display spin-flop coupling characterized by perpendicular alignment between the AF spin axes and the FM moments at a sublayer thickness of 6 unit cells (u.c.). Changing the crystallographic orientation of the interface from (001) to (111) introduces changes to factors such as the charge density of each stacking layer, the magnetic iiistructure of the AF layer at the interface, the symmetry of the lattice, and the orbital degeneracy. Therefore, different properties and exchange coupling mechanisms are expected. (111)-oriented LSMO/LSFO superlattices with sublayer thicknesses ranging from 3 to 60 u.c. were synthesized and characterized. Detailed analysis of their structural, electronic, and magnetic properties were performed using synchrotron radiation based resonant x-ray reflectivity, soft x-ray magnetic spectroscopy, and photoemission electron microscopy to explore the effect of sublayer thickness on the magnetic structure and exchange coupling at (111)-oriented perovskite oxide interfaces. Interfacial effects and ultrathin superlattice sublayers can stabilize orientations of the LSFO AF spin axis which differ from that of LSFO films and LSMO/LSFO bilayers. In the ultrathin limit (3 to 6 u.c.), it was found that the AF properties of the LSFO sublayers are preserved with an out-of-plane canting of the AF spin axis, while the FM properties of the LSMO sublayers are significantly depressed. For thicker LSFO layers (> 9 u.c.), the out-of-plane canting of the AF spin axis is only present in superlattices with thick LSMO sublayers. As a result, exchange coupling in the form of spin-flop coupling exists only in superlattices which display both robust ferromagnetism and out-of-plane canting of the AF spin axis. A portion of the AF moments can be reoriented by a moderate external magnetic field through spin-flop coupling with the FM LSMO sublayers that have low magnetocrystalline anisotropy in the (111) plane. The AF order in the spin-flop coupled superlattices was studied using angle-dependent x-ray magnetic linear dichroism. The AF order can be categorized into two types: majority of the AF moments cant out-of-the-plane of the film along the or directions depending on the LSFO layer thickness, while a minority portion lies within the (111) plane in different AF domains. The energy difference between domains with their spin axes along the in-plane or out-of-plane directions is small, and the magnetic order of AF thin films is far ivmore complex than in bulk LSFO. The complex AF structure in these (111)-oriented LSMO/LSFO superlattices illustrates that complex metal oxide heterostructures can serve as fertile ground for discovery of new magnetic phases, which have potential applications in next generation information technology devices.

Clinical reasoning and population health: decision making for an emerging paradigm of health care.

PubMed

Edwards, Ian; Richardson, Barbara

2008-01-01

Chronic conditions now provide the major disease and disability burden facing humanity. This development has necessitated a reorientation in the practice skills of health care professions away from hospital-based inpatient and outpatient care toward community-based management of patients with chronic conditions. Part of this reorientation toward community-based management of chronic conditions involves practitioners' understanding and adoption of a concept of population health management based on appropriate theoretical models of health care. Drawing on recent studies of expertise in physiotherapy, this article proposes a clinical reasoning and decision-making framework to meet these challenges. The challenge of population and community-based management of chronic conditions also provides an opportunity for physiotherapists to further clarify a professional epistemology of practice that embraces the kinds of knowledge and clinical reasoning processes used in physiotherapy practice. Three case studies related to the management of chronic musculoskeletal pain in different populations are used to exemplify the range of epistemological perspectives that underpin community-based practice. They illustrate the link between conceptualizations of practice problems and knowledge sources that are used as a basis for clinical reasoning and decision making as practitioners are increasingly required to move between the clinic and the community.

Active suppression after involuntary capture of attention.

PubMed

Sawaki, Risa; Luck, Steven J

2013-04-01

After attention has been involuntarily captured by a distractor, how is it reoriented toward a target? One possibility is that attention to the distractor passively fades over time, allowing the target to become attended. Another possibility is that the captured location is actively suppressed so that attention can be directed toward the target location. The present study investigated this issue with event-related potentials (ERPs), focusing on the N2pc component (a neural measure of attentional deployment) and the Pd component (a neural measure of attentional suppression). Observers identified a color-defined target in a search array, which was preceded by a task-irrelevant cue array. When the cue array contained an item that matched the target color, this item captured attention (as measured both behaviorally and with the N2pc component). This capture of attention was followed by active suppression (indexed by the Pd component), and this was then followed by a reorienting of attention toward the target in the search array (indexed by the N2pc component). These findings indicate that the involuntary capture of attention by a distractor is followed by an active suppression process that presumably facilitates the subsequent voluntary orienting of attention to the target.

Off-center lithium in the fluoroperovskite KZnF3

NASA Astrophysics Data System (ADS)

Toulouse, J.; Wang, X. Q.; Rousseau, M.

1991-10-01

In studying the effect of point defects on structural phase transitions in fluoroperovskites, we have characterized the Li defect in KZnF3. The dielectric-loss measurements on KZnF3:Li have revealed that the lithium defect possesses an electric dipole moment and therefore sits in an off-center position approximately 0.15 Å from a normal K site. Complementary ultrasonic measurements of the sound velocity indicate that Li constitutes a <100> orthorhombic defect. The δv/v results indicate that, similar to the KBr-KCN system, the strain ellipsoid is not an ellipsoid of revolution. The shape factors of the ellipsoid are found to be λa-λb~0.013 and λb-λc~0.006. This translates into two distinct relaxation processes at high and low temperatures, respectively, primarily associated with the reorientation of the major and minor axes of the ellipsoid. The dielectric-loss peak is then associated with the relaxation of the lithium defect between the three cube axes, i.e., the major-axis reorientation. The above interpretation is consistent with the large anharmonicity and anisotropy that have been found in the motion of the fluorine ions in KZnF3 and other related fluoroperovskites exhibiting a soft mode.

The heroines of their own stories: Insights from the use of life history drawings in research with a transnational migrant community

PubMed Central

Hirsch, Jennifer S.; Philbin, Morgan M.

2016-01-01

In this paper, we discuss how Life History Drawings can serve as a valuable method for global health research. The introduction discusses qualitative approaches to concepts such as reliability, validity and triangulation, and situates the use of participatory visual methods within the broader field of participatory research. The paper reports on an experience using life history drawings as part of extended ethnographic research in rural Mexico and among Mexican migrants living in Atlanta. The primary method for that parent project was comparative ethnographic research, which included life histories collected from 13 pairs of women over 15 months of participant observation. Early in the research, the drawings contributed to a major reorientation in the direction of the research project. The insights generated through analysis of the life history drawings exemplify how this participatory research technique can direct attention to social processes that feel salient to community members. In this case, they called attention to the enormity of social change in this community over one generation, reorienting the study from one focused on change causes by migration to one that focused on two trajectories of change: generational and migration-related. PMID:27109003

Shear alters motility of Escherichia coli

NASA Astrophysics Data System (ADS)

Molaei, Mehdi; Jalali, Maryam; Sheng, Jian

2013-11-01

Understanding of locomotion of microorganisms in shear flows drew a wide range of interests in microbial related topics such as biological process including pathogenic infection and biophysical interactions like biofilm formation on engineering surfaces. We employed microfluidics and digital holography microscopy to study motility of E. coli in shear flows. We controlled the shear flow in three different shear rates: 0.28 s-1, 2.8 s-1, and 28 s-1 in a straight channel with the depth of 200 μm. Magnified holograms, recorded at 15 fps with a CCD camera over more than 20 minutes, are analyzed to obtain 3D swimming trajectories and subsequently used to extract shear responses of E.coli. Thousands of 3-D bacterial trajectories are tracked. The change of bacteria swimming characteristics including swimming velocity, reorientation, and dispersion coefficient are computed directly for individual trajectory and ensemble averaged over thousands of realizations. The results show that shear suppresses the bacterial dispersions in bulk but promote dispersions near the surface contrary to those in quiescent flow condition. Ongoing analyses are focusing to quantify effect of shear rates on tumbling frequency and reorientation of cell body, and its implication in locating the hydrodynamic mechanisms for shear enhanced angular scattering. NIH, NSF, GoMRI.

Neural correlates of adolescents' viewing of parents' and peers' emotions: Associations with risk-taking behavior and risky peer affiliations.

PubMed

Saxbe, Darby; Del Piero, Larissa; Immordino-Yang, Mary Helen; Kaplan, Jonas; Margolin, Gayla

2015-01-01

Social reorientation from parents to same-age peers is normative in adolescence, but the neural correlates of youths' socioemotional processing of parents and peers have not been explored. In the current study, 22 adolescents (average age 16.98) underwent neuroimaging (functional magnetic resonance imaging) while viewing and rating emotions shown in brief video clips featuring themselves, their parents, or an unfamiliar peer. Viewing self vs. other and parents vs. the peer activated regions in the medial prefrontal cortex, replicating prior findings that this area responds to self-relevant stimuli, including familiar and not just similar others. Viewing the peer compared with parents elicited activation in posterior 'mentalizing' structures, the precuneus, posterior cingulate cortex (PCC), bilateral posterior superior temporal sulcus and right temporoparietal junction, as well as the ventral striatum and bilateral amygdala and hippocampus. Relative activations in the PCC and precuneus to the peer vs. the parent were related both to reported risk-taking behavior and to affiliations with more risk-taking peers. The results suggest neural correlates of the adolescent social reorientation toward peers and away from parents that may be associated with adolescents' real-life risk-taking behaviors and social relationships.

Graphene as transmissive electrodes and aligning layers for liquid-crystal-based electro-optic devices.

PubMed

Basu, Rajratan; Shalov, Samuel A

2017-07-01

In a conventional liquid crystal (LC) cell, polyimide layers are used to align the LC homogeneously in the cell, and transmissive indium tin oxide (ITO) electrodes are used to apply the electric field to reorient the LC along the field. It is experimentally presented here that monolayer graphene films on the two glass substrates can function concurrently as the LC aligning layers and the transparent electrodes to fabricate an LC cell, without using the conventional polyimide and ITO substrates. This replacement can effectively decrease the thickness of all the alignment layers and electrodes from about 100 nm to less than 1 nm. The interaction between LC and graphene through π-π electron stacking imposes a planar alignment on the LC in the graphene-based cell-which is verified using a crossed polarized microscope. The graphene-based LC cell exhibits an excellent nematic director reorientation process from planar to homeotropic configuration through the application of an electric field-which is probed by dielectric and electro-optic measurements. Finally, it is shown that the electro-optic switching is significantly faster in the graphene-based LC cell than in a conventional ITO-polyimide LC cell.

In Situ Observation of Chymotrypsin Catalytic Activity Change Actuated by Nonheating Low-Frequency Magnetic Field.

PubMed

Efremova, Maria V; Veselov, Maxim M; Barulin, Alexander V; Gribanovsky, Sergey L; Le-Deygen, Irina M; Uporov, Igor V; Kudryashova, Elena V; Sokolsky-Papkov, Marina; Majouga, Alexander G; Golovin, Yuri I; Kabanov, Alexander V; Klyachko, Natalia L

2018-04-24

Magnetomechanical modulation of biochemical processes is a promising instrument for bioengineering and nanomedicine. This work demonstrates two approaches to control activity of an enzyme, α-chymotrypsin immobilized on the surface of gold-coated magnetite magnetic nanoparticles (GM-MNPs) using a nonheating low-frequency magnetic field (LF MF). The measurement of the enzyme reaction rate was carried out in situ during exposure to the magnetic field. The first approach involves α-chymotrypsin-GM-MNPs conjugates, in which the enzyme undergoes mechanical deformations with the reorientation of the MNPs under LF MF (16-410 Hz frequency, 88 mT flux density). Such mechanical deformations result in conformational changes in α-chymotrypsin structure, as confirmed by infrared spectroscopy and molecular modeling, and lead to a 63% decrease of enzyme initial activity. The second approach involves an α-chymotrypsin-GM-MNPs/trypsin inhibitor-GM-MNPs complex, in which the activity of the enzyme is partially inhibited. In this case the reorientation of MNPs in the field leads to disruption of the enzyme-inhibitor complex and an almost 2-fold increase of enzyme activity. The results further demonstrate the utility of magnetomechanical actuation at the nanoscale for the remote modulation of biochemical reactions.

Analytic expression for the giant fieldlike spin torque in spin-filter magnetic tunnel junctions

NASA Astrophysics Data System (ADS)

Tang, Y.-H.; Huang, Z.-W.; Huang, B.-H.

2017-08-01

We propose analytic expressions for fieldlike, T⊥, and spin-transfer, T∥, spin torque components in the spin-filter-based magnetic tunnel junction (SFMTJ), by using the single-band tight-binding model with the nonequilibrium Keldysh formalism. In consideration of multireflection processes between noncollinear magnetization of the spin-filter (SF) barrier and the ferromagnetic (FM) electrode, the central spin-selective SF barrier plays an active role in the striking discovery T⊥≫T∥ , which can be further identified by the unusual barrier thickness dependence of giant T⊥. Our general expressions reveal the sinusoidal angular dependence of both spin torque components, even in the presence of the SF barrier.

Efficient reorientation of a deformable body in space: A free-free beam example

NASA Technical Reports Server (NTRS)

Kolmanovsky, Ilya V.; Mcclamroch, N. Harris

1993-01-01

It is demonstrated that the planar reorientation of a free-free beam in zero gravity space can be accomplished by periodically changing the shape of the beam using internal actuators. A control scheme is proposed in which electromechanical actuators excite the flexible motion of the beam so that it rotates in the desired manner with respect to a fixed inertial reference. The results can be viewed as an extension of previous work to a distributed parameter case.

Achieving giant magnetically induced reorientation of martensitic variants in magnetic shape-memory Ni-Mn-Ga Films by microstructure engineering.

PubMed

Ranzieri, Paolo; Campanini, Marco; Fabbrici, Simone; Nasi, Lucia; Casoli, Francesca; Cabassi, Riccardo; Buffagni, Elisa; Grillo, Vincenzo; Magén, Cesar; Celegato, Federica; Barrera, Gabriele; Tiberto, Paola; Albertini, Franca

2015-08-26

Giant magnetically induced twin variant reorientation, comparable in intensity with bulk single crystals, is obtained in epitaxial magnetic shape-memory thin films. It is found to be tunable in intensity and spatial response by the fine control of microstructural patterns at the nanoscopic and microscopic scales. A thorough experimental study (including electron holography) allows a multiscale comprehension of the phenomenon. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Angular momentum of phonons and its application to single-spin relaxation

NASA Astrophysics Data System (ADS)

Nakane, Jotaro J.; Kohno, Hiroshi

2018-05-01

We reexamine the relaxation process of a single spin embedded in an elastic medium, a problem studied recently by Garanin and Chudnovsky (GC) [Phys. Rev. B 92, 024421 (2015), 10.1103/PhysRevB.92.024421] from the viewpoint of angular-momentum transfer. Using Noether's theorem, we identify two distinct angular momenta of the medium, one Newtonian discussed by GC and the other field-theoretical, both of which consist of an orbital part and a spin part. For both angular momenta, we found that the orbital part is as essential as the spin part in the relaxation process. In particular, the angular-momentum transfer from the (real) spin to the Newtonian orbital part may be considered as an incipient rotation that leads to the Einstein-de Haas effect.

Net Shape Spin Formed Cryogenic Aluminum Lithium Cryogenic Tank Domes for Lower Cost Higher Performance Launch Vehicles

NASA Technical Reports Server (NTRS)

Curreri, Peter A.; Hoffman, Eric; Domack, Marcia; Brewster, Jeb; Russell, Carolyn

2013-01-01

With the goal of lower cost (simplified manufacturing and lower part count) and higher performance (higher strength to weight alloys) the NASA Technical Maturation Program in 2006 funded a proposal to investigate spin forming of space launch vehicle cryogenic tank domes. The project funding continued under the NASA Exploration Technology Development Program through completion in FY12. The first phase of the project involved spin forming of eight, 1 meter diameter "path finder" domes. Half of these were processed using a concave spin form process (MT Aerospace, Augsburg Germany) and the other half using a convex process (Spincraft, Boston MA). The convex process has been used to produce the Ares Common Bulkhead and the concave process has been used to produce dome caps for the Space Shuttle light weight external tank and domes for the NASDA H2. Aluminum Lithium material was chosen because of its higher strength to weight ratio than the Aluminum 2219 baseline. Aluminum lithium, in order to obtain the desired temper (T8), requires a cold stretch after the solution heat treatment and quench. This requirement favors the concave spin form process which was selected for scale up. This paper describes the results of processing four, 5.5 meter diameter (upper stage scale) net shaped spin formed Aluminum Lithium domes. In order to allow scalability beyond the limits of foundry and rolling mills (about 12 foot width) the circular blank contained one friction stir weld (heavy lifter scales require a flat blank containing two welds). Mechanical properties data (tensile, fracture toughness, stress corrosion, and simulated service testing) for the parent metal and weld will also be discussed.

Morphology effects on spin-dependent transport and recombination in polyfluorene thin films

NASA Astrophysics Data System (ADS)

Miller, Richards; van Schooten, K. J.; Malissa, H.; Joshi, G.; Jamali, S.; Lupton, J. M.; Boehme, C.

2016-12-01

We have studied the role of spin-dependent processes on conductivity in polyfluorene (PFO) thin films by preforming continuous wave (cw) electrically detected magnetic resonance (EDMR) spectroscopy at temperatures between 10 K and room temperature using microwave frequencies between about 1 GHz and 20 GHz, as well as pulsed EDMR at the X band (10 GHz). Variable frequency EDMR allows us to establish the role of spin-orbit coupling in spin-dependent processes whereas pulsed EDMR allows for the observation of coherent spin motion effects. We used PFO for this study in order to allow for the investigation of the effects of microscopic morphological ordering since this material can adopt two distinct intrachain morphologies: an amorphous (glassy) phase, in which monomer units are twisted with respect to each other, and an ordered (β) phase, where all monomers lie within one plane. In thin films of organic light-emitting diodes, the appearance of a particular phase can be controlled by deposition parameters and solvent vapor annealing, and is verified by electroluminescence spectroscopy. Under bipolar charge-carrier injection conditions, we conducted multifrequency cw EDMR, electrically detected Rabi spin-beat experiments, and Hahn echo and inversion-recovery measurements. Coherent echo spectroscopy reveals electrically detected electron-spin-echo envelope modulation due to the coupling of the carrier spins to nearby nuclear spins. Our results demonstrate that, while conformational disorder can influence the observed EDMR signals, including the sign of the current changes on resonance as well as the magnitudes of local hyperfine fields and charge-carrier spin-orbit interactions, it does not qualitatively affect the nature of spin-dependent transitions in this material. In both morphologies, we observe the presence of at least two different spin-dependent recombination processes. At room temperature and 10 K, polaron-pair recombination through weakly spin-spin coupled intermediate charge-carrier pair states is dominant, while at low temperatures, additional signatures of spin-dependent charge transport through the interaction of polarons with triplet excitons are seen in the half-field resonance of a triplet spin-1 species. This additional contribution arises since triplet lifetimes are increased at lower temperatures. We tentatively conclude that spectral broadening induced by hyperfine coupling is slightly weaker in the more ordered β-phase than in the glassy phase since protons are more evenly spaced, whereas broadening effects due to spin-orbit coupling, which impacts the distribution of g -factors, appear to be somewhat more significant in the β-phase.

Spin-current probe for phase transition in an insulator

DOE PAGES

Qiu, Zhiyong; Li, Jia; Hou, Dazhi; ...

2016-08-30

Spin fluctuation and transition have always been one of the central topics of magnetism and condensed matter science. Experimentally, the spin fluctuation is found transcribed onto scattering intensity in the neutron-scattering process, which is represented by dynamical magnetic susceptibility and maximized at phase transitions. Importantly, a neutron carries spin without electric charge, and therefore it can bring spin into a sample without being disturbed by electric energy. However, large facilities such as a nuclear reactor are necessary. Here we present that spin pumping, frequently used in nanoscale spintronic devices, provides a desktop microprobe for spin transition; spin current is amore » flux of spin without an electric charge and its transport reflects spin excitation. Additionally, we demonstrate detection of antiferromagnetic transition in ultra-thin CoO films via frequency-dependent spin-current transmission measurements, which provides a versatile probe for phase transition in an electric manner in minute devices.« less

Anisotropic interactions of a single spin and dark-spin spectroscopy in diamond

NASA Astrophysics Data System (ADS)

Epstein, R. J.; Mendoza, F. M.; Kato, Y. K.; Awschalom, D. D.

2005-11-01

Experiments on single nitrogen-vacancy (N-V) centres in diamond, which include electron spin resonance, Rabi oscillations, single-shot spin readout and two-qubit operations with a nearby13C nuclear spin, show the potential of this spin system for solid-state quantum information processing. Moreover, N-V centre ensembles can have spin-coherence times exceeding 50 μs at room temperature. We have developed an angle-resolved magneto-photoluminescence microscope apparatus to investigate the anisotropic electron-spin interactions of single N-V centres at room temperature. We observe negative peaks in the photoluminescence as a function of both magnetic-field magnitude and angle that are explained by coherent spin precession and anisotropic relaxation at spin-level anti-crossings. In addition, precise field alignment unmasks the resonant coupling to neighbouring `dark' nitrogen spins, otherwise undetected by photoluminescence. These results demonstrate the capability of our spectroscopic technique for measuring small numbers of dark spins by means of a single bright spin under ambient conditions.

Coherent electron-spin-resonance manipulation of three individual spins in a triple quantum dot

DOE Office of Scientific and Technical Information (OSTI.GOV)

Noiri, A.; Yoneda, J.; Nakajima, T.

2016-04-11

Quantum dot arrays provide a promising platform for quantum information processing. For universal quantum simulation and computation, one central issue is to demonstrate the exhaustive controllability of quantum states. Here, we report the addressable manipulation of three single electron spins in a triple quantum dot using a technique combining electron-spin-resonance and a micro-magnet. The micro-magnet makes the local Zeeman field difference between neighboring spins much larger than the nuclear field fluctuation, which ensures the addressable driving of electron-spin-resonance by shifting the resonance condition for each spin. We observe distinct coherent Rabi oscillations for three spins in a semiconductor triple quantummore » dot with up to 25 MHz spin rotation frequencies. This individual manipulation over three spins enables us to arbitrarily change the magnetic spin quantum number of the three spin system, and thus to operate a triple-dot device as a three-qubit system in combination with the existing technique of exchange operations among three spins.« less

Spin effects induced by thermal perturbation in a normal metal/magnetic insulator system

NASA Astrophysics Data System (ADS)

Lyapilin, I. I.; Okorokov, M. S.; Ustinov, V. V.

2015-05-01

Using one of the methods of quantum nonequilibrium statistical physics, we have investigated the spin transport transverse to the normal metal/ferromagnetic insulator interface in hybrid nanostructures. An approximation of the effective parameters, when each of the interacting subsystems (electron spin, magnon, and phonon) is characterized by its own effective temperature, has been considered. The generalized Bloch equations which describe the spin-wave current propagation in the dielectric have been derived. Finally, two sides of the spin transport "coin" have been revealed: the diffusive nature of the magnon motion and magnon relaxation processes, responsible for the spin pumping, and the spin-torque effect.

Evolution of Italian Universities' Rules for Spin-Offs: The Usefulness of Formal Regulations

ERIC Educational Resources Information Center

Salvador, Elisa

2009-01-01

Spin-off firms may be seen as a key mechanism for the external transmission of knowledge developed at universities. The proliferation of academic spin-offs in recent years has led universities to develop specific rules for the regulation and management of the spin-off process. This paper draws on the Italian experience. More than fifty Italian…

Spin transport in epitaxial graphene

NASA Astrophysics Data System (ADS)

Tbd, -

2014-03-01

Spintronics is a paradigm focusing on spin as the information vector in fast and ultra-low-power non volatile devices such as the new STT-MRAM. Beyond its widely distributed application in data storage it aims at providing more complex architectures and a powerful beyond CMOS solution for information processing. The recent discovery of graphene has opened novel exciting opportunities in terms of functionalities and performances for spintronics devices. We will present experimental results allowing us to assess the potential of graphene for spintronics. We will show that unprecedented highly efficient spin information transport can occur in epitaxial graphene leading to large spin signals and macroscopic spin diffusion lengths (~ 100 microns), a key enabler for the advent of envisioned beyond-CMOS spin-based logic architectures. We will also show that how the device behavior is well explained within the framework of the Valet-Fert drift-diffusion equations. Furthermore, we will show that a thin graphene passivation layer can prevent the oxidation of a ferromagnet, enabling its use in novel humide/ambient low-cost processes for spintronics devices, while keeping its highly surface sensitive spin current polarizer/analyzer behavior and adding new enhanced spin filtering property. These different experiments unveil promising uses of graphene for spintronics.

Spin Forming of an Aluminum 2219-T6 Aft Bulkhead for the Orion Multi-Purpose Crew Vehicle: Phase II Supplemental Report

NASA Technical Reports Server (NTRS)

Piascik, Robert S.; Squire, Michael D.; Domack, Marcia S.; Hoffman, Eric K.

2015-01-01

The principal focus of this project was to assist the Orion Multi-Purpose Crew Vehicle (MPCV) Program in developing a spin forming fabrication process for manufacture of the aft bulkhead of the pressure vessel. The spin forming process will enable a single piece aluminum (Al) 2219 aft bulkhead which will eliminate the current multiple piece welded construction, simplify fabrication, and lead to an enhanced design that will reduce vehicle weight by eliminating welds. Phase I of this assessment explored spin forming the single-piece forward pressure vessel bulkhead from aluminum-lithium 2195.

Effect of Dangling Bond Spins on the Dark Exciton Recombination and Spin Polarization in CdSe Colloidal Nanostructures

NASA Astrophysics Data System (ADS)

Rodina, A. V.; Golovatenko, A. A.; Shornikova, E. V.; Yakovlev, D. R.; Efros, Al. L.

2018-04-01

We present theoretical aspects of the exchange interaction between the ground optically-forbidden "dark" exciton state and surface dangling bonds in colloidal CdSe spherical nanocrystals and nanoplatelets. The influence of the dangling bond spins on the radiative recombination and spin splitting of the dark exciton is shown. Processes of optically-driven and external magnetic field-driven formation of the dangling bond magnetic polaron (DBMP) are considered. Thermodynamic and dynamic polarization mechanisms of the DBMP formation within these two processes and corresponding critical temperatures are compared. Experimental manifestations of the DBMP formation in CdSe nanocrystals and nanoplatelets are discussed.

Towards the Knittability of Graphene Oxide Fibres

PubMed Central

Seyedin, Shayan; Romano, Mark S.; Minett, Andrew I.; Razal, Joselito M.

2015-01-01

Recent developments in graphene oxide fibre (GO) processing include exciting demonstrations of hand woven textile structures. However, it is uncertain whether the fibres produced can meet the processing requirements of conventional textile manufacturing. This work reports for the first time the production of highly flexible and tough GO fibres that can be knitted using textile machinery. The GO fibres are made by using a dry-jet wet-spinning method, which allows drawing of the spinning solution (the GO dispersion) in several stages of the fibre spinning process. The coagulation composition and spinning conditions are evaluated in detail, which led to the production of densely packed fibres with near-circular cross-sections and highly ordered GO domains. The results are knittable GO fibres with Young’s modulus of ~7.9 GPa, tensile strength of ~135.8 MPa, breaking strain of ~5.9%, and toughness of ~5.7 MJ m−3. The combination of suitable spinning method, coagulation composition, and spinning conditions led to GO fibres with remarkable toughness; the key factor in their successful knitting. This work highlights important progress in realising the full potential of GO fibres as a new class of textile. PMID:26459866

Tunable room-temperature spin-selective optical Stark effect in solution-processed layered halide perovskites

PubMed Central

Giovanni, David; Chong, Wee Kiang; Dewi, Herlina Arianita; Thirumal, Krishnamoorthy; Neogi, Ishita; Ramesh, Ramamoorthy; Mhaisalkar, Subodh; Mathews, Nripan; Sum, Tze Chien

2016-01-01

Ultrafast spin manipulation for opto–spin logic applications requires material systems that have strong spin-selective light-matter interaction. Conventional inorganic semiconductor nanostructures [for example, epitaxial II to VI quantum dots and III to V multiple quantum wells (MQWs)] are considered forerunners but encounter challenges such as lattice matching and cryogenic cooling requirements. Two-dimensional halide perovskite semiconductors, combining intrinsic tunable MQW structures and large oscillator strengths with facile solution processability, can offer breakthroughs in this area. We demonstrate novel room-temperature, strong ultrafast spin-selective optical Stark effect in solution-processed (C6H4FC2H4NH3)2PbI4 perovskite thin films. Exciton spin states are selectively tuned by ~6.3 meV using circularly polarized optical pulses without any external photonic cavity (that is, corresponding to a Rabi energy of ~55 meV and equivalent to applying a 70 T magnetic field), which is much larger than any conventional system. The facile halide and organic replacement in these perovskites affords control of the dielectric confinement and thus presents a straightforward strategy for tuning light-matter coupling strength. PMID:27386583

Quasiparticle spin resonance and coherence in superconducting aluminium.

PubMed

Quay, C H L; Weideneder, M; Chiffaudel, Y; Strunk, C; Aprili, M

2015-10-26

Conventional superconductors were long thought to be spin inert; however, there is now increasing interest in both (the manipulation of) the internal spin structure of the ground-state condensate, as well as recently observed long-lived, spin-polarized excitations (quasiparticles). We demonstrate spin resonance in the quasiparticle population of a mesoscopic superconductor (aluminium) using novel on-chip microwave detection techniques. The spin decoherence time obtained (∼100 ps), and its dependence on the sample thickness are consistent with Elliott-Yafet spin-orbit scattering as the main decoherence mechanism. The striking divergence between the spin coherence time and the previously measured spin imbalance relaxation time (∼10 ns) suggests that the latter is limited instead by inelastic processes. This work stakes out new ground for the nascent field of spin-based electronics with superconductors or superconducting spintronics.

Spin-lattice relaxation of coupled metal-radical spin-dimers in proteins: application to Fe(2+)-cofactor (Q(A)(-.), Q(B)(-.), phi(-.)) dimers in reaction centers from photosynthetic bacteria.

PubMed Central

Calvo, Rafael; Isaacson, Roger A; Abresch, Edward C; Okamura, Melvin Y; Feher, George

2002-01-01

The spin-lattice relaxation times (T(1)) for the reduced quinone acceptors Q(A)(-.) and Q(B)(-.), and the intermediate pheophytin acceptor phi(-.), were measured in native photosynthetic reaction centers (RC) containing a high spin Fe(2+) (S = 2) and in RCs in which Fe(2+) was replaced by diamagnetic Zn(2+). From these data, the contribution of the Fe(2+) to the spin-lattice relaxation of the cofactors was determined. To relate the spin-lattice relaxation rate to the spin-spin interaction between the Fe(2+) and the cofactors, we developed a spin-dimer model that takes into account the zero field splitting and the rhombicity of the Fe(2+) ion. The relaxation mechanism of the spin-dimer involves a two-phonon process that couples the fast relaxing Fe(2+) spin to the cofactor spin. The process is analogous to the one proposed by R. Orbach (Proc. R. Soc. A. (Lond.). 264:458-484) for rare earth ions. The spin-spin interactions are, in general, composed of exchange and dipolar contributions. For the spin dimers studied in this work the exchange interaction, J(o), is predominant. The values of J(o) for Q(A)(-.)Fe(2+), Q(B)(-.)Fe(2+), and phi(-.)Fe(2+) were determined to be (in kelvin) -0.58, -0.92, and -1.3 x 10(-3), respectively. The |J(o)| of the various cofactors (obtained in this work and those of others) could be fitted with the relation exp(-beta(J)d), where d is the distance between cofactor spins and beta(J) had a value of (0.66-0.86) A(-1). The relation between J(o) and the matrix element |V(ij)|(2) involved in electron transfer rates is discussed. PMID:12414679

Modulation of attentional networks by food-related disinhibition.

PubMed

Hege, Maike A; Stingl, Krunoslav T; Veit, Ralf; Preissl, Hubert

2017-07-01

The risk of weight gain is especially related to disinhibition, which indicates the responsiveness to external food stimuli with associated disruptions in eating control. We adapted a food-related version of the attention network task and used functional magnetic resonance imaging to study the effects of disinhibition on attentional networks in 19 normal-weight participants. High disinhibition scores were associated with a rapid reorienting response to food pictures after invalid cueing and with an enhanced alerting effect of a warning cue signalizing the upcoming appearance of a food picture. Imaging data revealed activation of a right-lateralized ventral attention network during reorienting. The faster the reorienting and the higher the disinhibition score, the less activation of this network was observed. The alerting contrast showed activation in visual, temporo-parietal and anterior sites. These modulations of attentional networks by food-related disinhibition might be related to an attentional bias to energy dense and palatable food and increased intake of food in disinhibited individuals. Copyright © 2017 Elsevier Inc. All rights reserved.

Reorientation of Sputnik Planitia implies a subsurface ocean on Pluto.

PubMed

Nimmo, F; Hamilton, D P; McKinnon, W B; Schenk, P M; Binzel, R P; Bierson, C J; Beyer, R A; Moore, J M; Stern, S A; Weaver, H A; Olkin, C B; Young, L A; Smith, K E

2016-12-01

The deep nitrogen-covered basin on Pluto, informally named Sputnik Planitia, is located very close to the longitude of Pluto's tidal axis and may be an impact feature, by analogy with other large basins in the Solar System. Reorientation of Sputnik Planitia arising from tidal and rotational torques can explain the basin's present-day location, but requires the feature to be a positive gravity anomaly, despite its negative topography. Here we argue that if Sputnik Planitia did indeed form as a result of an impact and if Pluto possesses a subsurface ocean, the required positive gravity anomaly would naturally result because of shell thinning and ocean uplift, followed by later modest nitrogen deposition. Without a subsurface ocean, a positive gravity anomaly requires an implausibly thick nitrogen layer (exceeding 40 kilometres). To prolong the lifetime of such a subsurface ocean to the present day and to maintain ocean uplift, a rigid, conductive water-ice shell is required. Because nitrogen deposition is latitude-dependent, nitrogen loading and reorientation may have exhibited complex feedbacks.

Reorientation of Sputnik Planitia implies a subsurface ocean on Pluto

NASA Astrophysics Data System (ADS)

Nimmo, F.; Hamilton, D. P.; McKinnon, W. B.; Schenk, P. M.; Binzel, R. P.; Bierson, C. J.; Beyer, R. A.; Moore, J. M.; Stern, S. A.; Weaver, H. A.; Olkin, C. B.; Young, L. A.; Smith, K. E.; Moore, J. M.; McKinnon, W. B.; Spencer, J. R.; Beyer, R.; Binzel, R. P.; Buie, M.; Buratti, B.; Cheng, A.; Cruikshank, D.; Ore, C. Dalle; Earle, A.; Gladstone, R.; Grundy, W.; Howard, A. D.; Lauer, T.; Linscott, I.; Nimmo, F.; Parker, J.; Porter, S.; Reitsema, H.; Reuter, D.; Roberts, J. H.; Robbins, S.; Schenk, P. M.; Showalter, M.; Singer, K.; Strobel, D.; Summers, M.; Tyler, L.; White, O. L.; Umurhan, O. M.; Banks, M.; Barnouin, O.; Bray, V.; Carcich, B.; Chaikin, A.; Chavez, C.; Conrad, C.; Hamilton, D. P.; Howett, C.; Hofgartner, J.; Kammer, J.; Lisse, C.; Marcotte, A.; Parker, A.; Retherford, K.; Saina, M.; Runyon, K.; Schindhelm, E.; Stansberry, J.; Steffl, A.; Stryk, T.; Throop, H.; Tsang, C.; Verbiscer, A.; Winters, H.; Zangari, A.; Stern, S. A.; Weaver, H. A.; Olkin, C. B.; Young, L. A.; Smith, K. E.

2016-12-01

The deep nitrogen-covered basin on Pluto, informally named Sputnik Planitia, is located very close to the longitude of Pluto’s tidal axis and may be an impact feature, by analogy with other large basins in the Solar System. Reorientation of Sputnik Planitia arising from tidal and rotational torques can explain the basin’s present-day location, but requires the feature to be a positive gravity anomaly, despite its negative topography. Here we argue that if Sputnik Planitia did indeed form as a result of an impact and if Pluto possesses a subsurface ocean, the required positive gravity anomaly would naturally result because of shell thinning and ocean uplift, followed by later modest nitrogen deposition. Without a subsurface ocean, a positive gravity anomaly requires an implausibly thick nitrogen layer (exceeding 40 kilometres). To prolong the lifetime of such a subsurface ocean to the present day and to maintain ocean uplift, a rigid, conductive water-ice shell is required. Because nitrogen deposition is latitude-dependent, nitrogen loading and reorientation may have exhibited complex feedbacks.

Transient increase in the levels of gamma-tubulin complex in reorientation of cortical microtubules by gravity in azuki bean epicotyls

NASA Astrophysics Data System (ADS)

Soga, Kouichi; Kotake, Toshihisa; Wakabayashi, Kazuyuki; Kamisaka, Seiichiro; Hoson, Takayuki

Azuki bean (Vigna angularis Ohwi et Ohashi) seedlings were exposed to centrifugal hypergravity, and the changes in the orientation of cortical microtubules and the expression of genes cording γ-tubulin complex (VaTUBG and VaSpc98p) were examined. By 300 g treatment, the percentage of cells with transverse microtubules was decreased, while that with longitudinal microtubules was increased in epicotyls. Hypergravity increased the expression of VaTUBG and VaSpc98p transiently. Also, the expression of both genes was increased transiently by removal of hypergravity stimulus. Lanthanum and gadolinium ions, potential blockers of mechanosensitive calcium ion-permeable channels (mechanoreceptors), nullified reorientation of microtubules as well as up-regulation of expression of VaTUBG and VaSpc98p by hypergravity. These results suggest that mechanoreceptors on the plasma membrane may perceive the gravity signal, which leads to reorientation of cortical microtubules by transiently stimulating the formation of γ-tubulin complex.

A theoretical investigation of soliton induced supercontinuum generation in liquid core photonic crystal fiber and dual core optical fiber

NASA Astrophysics Data System (ADS)

Porsezian, K.; Nithyanandan, K.; Vasantha Jayakantha Raja, R.; Ganapathy, R.

2013-07-01

The supercontinuum generation (SCG) in liquid core photonic crystal fiber (LCPCF) with versatile nonlinear response and the spectral broadening in dual core optical fiber is presented. The analysis is presented in two phase, phase I deals with the SCG in LCPCF with the effect of saturable nonlinearity and re-orientational nonlinearity. We identify and discuss the generic nature of the saturable nonlinearity and reorientational nonlinearity in the SCG, using suitable model. For the physical explanation, modulational instability and soliton fission techniques is implemented to investigate the impact of saturable nonlinear response and slow nonlinear response, respectively. It is observed that the saturable nonlinearity inevitably suppresses the MI and the subsequent SCG. On the other hand, the re-orientational nonlinearity contributes to the slow nonlinear response in addition to the conventional fast response due to the electronic contribution. The phase II features the exclusive investigation of the spectral broadening in the dual core optical fiber.

Spontaneous reorientations of meta-atoms and electromagnetic spatial solitons in a liquid metacrystal.

PubMed

Zharov, Alexander A; Zharov, Alexander A; Zharova, Nina A

2014-08-01

We show that transverse electromagnetic waves propagating along an external static electric field in liquid metacrystal (LMC) can provoke spontaneous rearrangement of elongated meta-atoms that changes the direction of the anisotropy axis of the LMC. This kind of instability may reorient the meta-atoms from the equilibrium state parallel to a static field to the state along a high-frequency field and back at the different threshold intensities of electromagnetic waves in such a way that bistability in the system takes place. Reorientation of meta-atoms causes a change in the effective refraction index of LMC that creates, in turn, the conditions for the formation of bright spatial solitons. Such spatial solitons are the self-consistent domains of redirected meta-atoms with trapped photons. We find that the instability thresholds as well as energy flux captured by the spatial soliton can be easily managed by variation of the static electric field applied to the LMC. We study the effects of soliton excitation and collisions via numerical simulations.

Influence of hydride orientation on fracture toughness of CWSR Zr-2.5%Nb pressure tube material between RT and 300 °C

NASA Astrophysics Data System (ADS)

Sharma, Rishi K.; Sunil, Saurav; Kumawat, B. K.; Singh, R. N.; Tewari, Asim; Kashyap, B. P.

2017-05-01

An experimental setup was designed, fabricated and used to form radial hydrides in Zr-2.5%Nb alloy pressure tube spool. The design of setup was based on ensuring a hoop stress in the spool greater than threshold stress for reorientation of hydrides in this alloy, which was achieved by manipulating the thermal expansion coefficient of the plunger and pressure tube material and diametral interference between them. The experimental setup was loaded on a universal testing machine (UTM) fitted with an environmental chamber and subjected to a temperature cycle for the stress reorientation treatment. The metallographic examination of the hydrogen charged spools subjected to stress re-orientation treatment using this set up revealed formation of predominantly radial hydrides. The variation of fracture toughness of material containing radial hydride with test temperature showed typical 'S' curve behavior with transition temperatures more than that of the material containing circumferential hydride.

Look up: Human adults use vertical height cues in reorientation.

PubMed

Du, Yu; Spetch, Marcia L; Mou, Weimin

2016-11-01

Numerous studies have shown that people and other animals readily use horizontal geometry (distance and directional information) to reorient, and these cues sometimes dominate over other cues when reorienting in navigable environments. Our study investigated whether horizontal cues (distance/angle) dominate over vertical cues (wall height) when they are in conflict. Adult participants learned two locations (opposite corners) in either a rectangular room (with distance information) or a rhombus room (with angle information). Both training rooms had 2 opposite high walls as height cues. On each trial, participants were disoriented and then asked to locate the correct corners. In testing, the rooms were modified to provide (a) distance or angle cues only, (b) height cues only, and (c) both height and horizontal cues in conflict. Participants located the correct corners successfully with horizontal (distance/angle) or height cues alone. On conflict tests, participants did not show preference for the horizontal information (distance/angle) over the height cues. The results are discussed in terms of the geometric module theory and the adaptive combination theory.

Electron spin relaxation in carbon nanotubes: Dyakonov-Perel mechanism

NASA Astrophysics Data System (ADS)

Semenov, Yuriy; Zavada, John; Kim, Ki Wook

2010-03-01

The long standing problem of unaccountable short spin relaxation in carbon nanotubes (CNT) meets a disclosure in terms of curvature-mediated spin-orbital interaction that leads to spin fluctuating precession analogous to Dyakonov-Perel mechanism. Strong anisotropy imposed by arbitrary directed magnetic field has been taken into account in terms of extended Bloch equations. Especially, stationary spin current through CNT can be controlled by spin-flip processes with relaxation time as less as 150 ps, the rate of transversal polarization (i.e. decoherence) runs up to 1/(70 ps) at room temperature while spin interference of the electrons related to different valleys can be responsible for shorter spin dephasing. Dependencies of spin-relaxation parameters on magnetic field strength and orientation, CNT curvature and chirality have been analyzed.

A Review of the MLAS Parachute Systems

NASA Technical Reports Server (NTRS)

Taylor, Anthony P.; Kelley, Christopher; Magner, Eldred; Peterson, David; Hahn, Jeffrey; Yuchnovicz, Daniel E.

2009-01-01

The NASA Engineering and Safety Center (NESC) is developing the Max Launch Abort System (MLAS) as a risk-mitigation design should problems arise with the baseline Orion spacecraft launch abort design. The Max in MLAS is dedicated to Max Faget, the renowned NASA spacecraft designer. The MLAS flight test vehicle consists of boost skirt, coast skirt and the MLAS fairing which houses a full scale boilerplate Orion Crew Module (CM). The objective of the flight test is to prove that the CM can be released from the MLAS fairing during pad abort conditions without detrimental recontact between the CM and fairing, achieving performance similar to the Orion launch abort system. The boost and coast skirts provide the necessary thrust and stability to achieve the flight test conditions and are released prior to the test -- much like the Little Joe booster was used in the Apollo Launch Escape System tests. To achieve the test objective, two parachutes are deployed from the fairing to reorient the CM/fairing to a heatshield first orientation. The parachutes then provide the force necessary to reduce the total angle of attack and body angular rates required for safe release of the CM from the fairing. A secondary test objective after CM release from the fairing is to investigate the removal of the CM forward bay cover (FBC) with CM drogue parachutes for the purpose of attempting to synchronously deploying a set of CM main parachutes. Although multiple parachute deployments are used in the MLAS flight test vehicle to complete its objective, there are only two parachute types employed in the flight test. Five of the nine parachutes used for MLAS are 27.6 ft D(sub 0) ribbon parachutes, and the remaining four are standard G-12 cargo parachutes. This paper presents an overview of the 27.6 ft D(sub 0) ribbon parachute system employed on the MLAS flight test vehicle for coast skirt separation, fairing reorientation, and as drogue parachutes for the CM after separation from the fairing. Discussion will include: the process used to select this design, previously proven as a spin/stall recovery parachute; descriptions of all components of the parachute system; the minor modifications necessary to adapt the parachute to the MLAS program; the techniques used to analyze the parachute for the multiple roles it performs; a discussion of the rigging techniques used to interface the parachute system to the vehicle; and a brief description of how the evolution of the program affected parachute usage and analysis. An overview of the Objective system, rationale for the MLAS approach and the future of the program will also be presented. We hope to have flight test results to report at the time of the Conference Presentation.

Corrigendum to "Multiple-quantum spin counting in magic-angle-spinning NMR via low-power symmetry-based dipolar recoupling" [J. Magn. Reson. 236 (2013) 31-40

NASA Astrophysics Data System (ADS)

Teymoori, Gholamhasan; Pahari, Bholanath; Viswanathan, Elumalai; Edén, Mattias

2017-03-01

The authors regret that an inappropriate NMR data processing, not known to all authors at the time of publication, was used to produce the multiple-quantum coherence (MQC) spin counting data presented in our article: this lead to artificially enhanced results, particularly concerning those obtained at long MQC excitation intervals (τexc). Here we reproduce Figs. 4-7 with correctly processed data.

Process optimization electrospinning fibrous material based on polyhydroxybutyrate

NASA Astrophysics Data System (ADS)

Olkhov, A. A.; Tyubaeva, P. M.; Staroverova, O. V.; Mastalygina, E. E.; Popov, A. A.; Ischenko, A. A.; Iordanskii, A. L.

2016-05-01

The article analyzes the influence of the main technological parameters of electrostatic spinning on the morphology and properties of ultrathin fibers on the basis of polyhydroxybutyrate. It is found that the electric conductivity and viscosity of the spinning solution affects the process of forming fibers macrostructure. The fiber-based materials PHB lets control geometry and optimize the viscosity and conductivity of a spinning solution. The resulting fibers have found use in medicine, particularly in the construction elements musculoskeletal.

Spin Forming Aluminum Crew Module (CM) Metallic Aft Pressure Vessel Bulkhead (APVBH) - Phase II

NASA Technical Reports Server (NTRS)

Hoffman, Eric K.; Domack, Marcia S.; Torres, Pablo D.; McGill, Preston B.; Tayon, Wesley A.; Bennett, Jay E.; Murphy, Joseph T.

2015-01-01

The principal focus of this project was to assist the Multi-Purpose Crew Vehicle (MPCV) Program in developing a spin forming fabrication process for manufacture of the Orion crew module (CM) aft pressure vessel bulkhead. The spin forming process will enable a single piece aluminum (Al) alloy 2219 aft bulkhead resulting in the elimination of the current multiple piece welded construction, simplify CM fabrication, and lead to an enhanced design. Phase I (NASA TM-2014-218163 (1)) of this assessment explored spin forming the single-piece CM forward pressure vessel bulkhead. The Orion MPCV Program and Lockheed Martin (LM) recently made two critical decisions relative to the NESC Phase I work scope: (1) LM selected the spin forming process to manufacture a single-piece aft bulkhead for the Orion CM, and (2) the aft bulkhead will be manufactured from Al 2219. Based on the Program's new emphasis related to the spin forming process, the NESC was asked to conduct a Phase II assessment to assist in the LM manufacture of the aft bulkhead and to conduct a feasibility study into spin forming the Orion CM cone. This activity was approved on June 19, 2013. Dr. Robert Piascik, NASA Technical Fellow for Materials at the Langley Research Center (LaRC), was selected to lead this assessment. The project plan was approved by the NASA Engineering and Safety Center (NESC) Review Board (NRB) on July 18, 2013. The primary stakeholders for this assessment were the NASA and LM MPCV Program offices. Additional benefactors are commercial launch providers developing CM concepts.

Spin Forming Aluminum Crew Module (CM) Metallic Aft Pressure Vessel Bulkhead (APVBH) - Phase II

NASA Technical Reports Server (NTRS)

Hoffman, Eric K.; Domack, Marcia S.; Torres, Pablo D.; McGill, Preston B.; Tayon, Wesley A.; Bennett, Jay E.; Murphy, Joseph T.

2015-01-01

The principal focus of this project was to assist the Multi-Purpose Crew Vehicle (MPCV) program in developing a spin forming fabrication process for manufacture of the Orion crew module (CM) aft pressure vessel bulkhead. The spin forming process will enable a single piece aluminum (Al) alloy 2219 aft bulkhead resulting in the elimination of the current multiple piece welded construction, simplify CM fabrication, and lead to an enhanced design. Phase I (NASA TM-2014-218163, (1)) of this assessment explored spin forming the single-piece CM forward pressure vessel bulkhead. The MPCV Program and Lockheed Martin (LM) recently made two critical decisions relative to the NESC Phase I work scope: (1) LM selected the spin forming process to manufacture a singlepiece aft bulkhead for the Orion CM, and (2) the aft bulkhead will be manufactured from Al 2219. Based on the Program's new emphasis related to the spin forming process, the NESC was asked to conduct a Phase II assessment to assist in the LM manufacture of the aft bulkhead and to conduct a feasibility study into spin forming the Orion CM cone. This activity was approved on June 19, 2013. Dr. Robert Piascik, NASA Technical Fellow for Materials at the Langley Research Center (LaRC), was selected to lead this assessment. The project plan was approved by the NASA Engineering and Safety Center (NESC) Review Board (NRB) on July 18, 2013. The primary stakeholders for this assessment are the NASA and LM MPCV Program offices. Additional benefactors are commercial launch providers developing CM concepts.

Fabrication of large area woodpile structure in polymer

NASA Astrophysics Data System (ADS)

Gupta, Jaya Prakash; Dutta, Neilanjan; Yao, Peng; Sharkawy, Ahmed S.; Prather, Dennis W.

2009-02-01

A fabrication process of three-dimensional Woodpile photonic crystals based on multilayer photolithography from commercially available photo resist SU8 have been demonstrated. A 6-layer, 2 mm × 2mm woodpile has been fabricated. Different factors that influence the spin thickness on multiple resist application have been studied. The fabrication method used removes, the problem of intermixing, and is more repeatable and robust than the multilayer fabrication techniques for three dimensional photonic crystal structures that have been previously reported. Each layer is developed before next layer photo resist spin, instead of developing the whole structure in the final step as used in multilayer process. The desired thickness for each layer is achieved by the calibration of spin speed and use of different photo resist compositions. Deep UV exposure confinement has been the defining parameter in this process. Layer uniformity for every layer is independent of the previous developed layers and depends on the photo resist planarizing capability, spin parameters and baking conditions. The intermixing problem, which results from the previous layers left uncrossed linked photo resist, is completely removed in this process as the previous layers are fully developed, avoiding any intermixing between the newly spun and previous layers. Also this process gives the freedom to redo every spin any number of times without affecting the previously made structure, which is not possible in other multilayer process where intermediate developing is not performed.

Probing the ATP-induced conformational flexibility of the PcrA helicase protein using molecular dynamics simulation.

PubMed

Mhashal, Anil R; Choudhury, Chandan Kumar; Roy, Sudip

2016-03-01

Helicases are enzymes that unwind double-stranded DNA (dsDNA) into its single-stranded components. It is important to understand the binding and unbinding of ATP from the active sites of helicases, as this knowledge can be used to elucidate the functionality of helicases during the unwinding of dsDNA. In this work, we investigated the unbinding of ATP and its effect on the active-site residues of the helicase PcrA using molecular dynamic simulations. To mimic the unbinding process of ATP from the active site of the helicase, we simulated the application of an external force that pulls ATP from the active site and computed the free-energy change during this process. We estimated an energy cost of ~85 kJ/mol for the transformation of the helicase from the ATP-bound state (1QHH) to the ATP-free state (1PJR). Unbinding led to conformational changes in the residues of the protein at the active site. Some of the residues at the ATP-binding site were significantly reoriented when the ATP was pulled. We observed a clear competition between reorientation of the residues and energy stabilization by hydrogen bonds between the ATP and active-site residues. We also checked the flexibility of the PcrA protein using a principal component analysis of domain motion. We found that the ATP-free state of the helicase is more flexible than the ATP-bound state.

Mechanical Stress Induces Remodeling of Vascular Networks in Growing Leaves

PubMed Central

Bar-Sinai, Yohai; Julien, Jean-Daniel; Sharon, Eran; Armon, Shahaf; Nakayama, Naomi; Adda-Bedia, Mokhtar; Boudaoud, Arezki

2016-01-01

Differentiation into well-defined patterns and tissue growth are recognized as key processes in organismal development. However, it is unclear whether patterns are passively, homogeneously dilated by growth or whether they remodel during tissue expansion. Leaf vascular networks are well-fitted to investigate this issue, since leaves are approximately two-dimensional and grow manyfold in size. Here we study experimentally and computationally how vein patterns affect growth. We first model the growing vasculature as a network of viscoelastic rods and consider its response to external mechanical stress. We use the so-called texture tensor to quantify the local network geometry and reveal that growth is heterogeneous, resembling non-affine deformations in composite materials. We then apply mechanical forces to growing leaves after veins have differentiated, which respond by anisotropic growth and reorientation of the network in the direction of external stress. External mechanical stress appears to make growth more homogeneous, in contrast with the model with viscoelastic rods. However, we reconcile the model with experimental data by incorporating randomness in rod thickness and a threshold in the rod growth law, making the rods viscoelastoplastic. Altogether, we show that the higher stiffness of veins leads to their reorientation along external forces, along with a reduction in growth heterogeneity. This process may lead to the reinforcement of leaves against mechanical stress. More generally, our work contributes to a framework whereby growth and patterns are coordinated through the differences in mechanical properties between cell types. PMID:27074136

Transcriptional and computational study of expansins differentially expressed in response to inclination in radiata pine.

PubMed

Mateluna, Patricio; Valenzuela-Riffo, Felipe; Morales-Quintana, Luis; Herrera, Raúl; Ramos, Patricio

2017-06-01

Plants have the ability to reorient their vertical growth when exposed to inclination. This response can be as quick as 2 h in inclined young pine (Pinus radiata D. Don) seedlings, with over accumulation of lignin observed after 9 days s. Several studies have identified expansins involved in cell expansion among other developmental processes in plants. Six putative expansin genes were identified in cDNA libraries isolated from inclined pine stems. A differential transcript abundance was observed by qPCR analysis over a time course of inclination. Five genes changed their transcript accumulation in both stem sides in a spatial and temporal manner compared with non-inclined stem. To compare these expansin genes, and to suggest a possible mechanism of action at molecular level, the structures of the predicted proteins were built by comparative modeling methodology. An open groove on the surface of the proteins composed of conserved zresidues was observed. Using a cellulose polymer as ligand the protein-ligand interaction was evaluated, with the results showing differences in the protein-ligand interaction mode. Differences in the binding energy interaction can be explained by changes in some residues that generate differences in electrostatic surface in the open groove region, supporting the participation of six members of multifamily proteins in this specific process. The data suggests participation of different expansin proteins in the dissembling and remodeling of the complex cell wall matrix during the reorientation response to inclination. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

The development of involuntary and voluntary attention from childhood to adulthood: a combined behavioral and event-related potential study.

PubMed

Wetzel, Nicole; Widmann, Andreas; Berti, Stefan; Schröger, Erich

2006-10-01

This study investigated auditory involuntary and voluntary attention in children aged 6-8, 10-12 and young adults. The strength of distracting stimuli (20% and 5% pitch changes) and the amount of allocation of attention were varied. In an auditory distraction paradigm event-related potentials (ERPs) and behavioral data were measured from subjects either performing a sound duration discrimination task or watching a silent video. Pitch changed sounds caused prolonged reaction times and decreased hit rates in all age groups. Larger distractors (20%) caused stronger distraction in children, but not in adults. The amplitudes of mismatch negativity (MMN), P3a, and reorienting negativity (RON) were modulated by age and by voluntary attention. P3a was additionally affected by distractor strength. Maturational changes were also observed in the amplitudes of P1 (decreasing with age) and N1 (increasing with age). P2-modulation by voluntary attention was opposite in young children and adults. Results suggest quantitative and qualitative changes in auditory voluntary and involuntary attention and distraction during development. The processing steps involved in distraction (pre-attentive change detection, attention switch, reorienting) are functional in children aged 6-8 but reveal characteristic differences to those of young adults. In general, distractibility as indicated by behavioral and ERP measures decreases from childhood to adulthood. Behavioral and ERP markers for different processing stages involved in voluntary and involuntary attention reveal characteristic developmental changes from childhood to young adulthood.

Dual reorientation relaxation routes of water molecules in oxyanion’s hydration shell: A molecular geometry perspective

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, Wen Jun; Yang, Yi Isaac; Gao, Yi Qin, E-mail: gaoyq@pku.edu.cn

2015-12-14

In this study, we examine how complex ions such as oxyanions influence the dynamic properties of water and whether differences exist between simple halide anions and oxyanions. Nitrate anion is taken as an example to investigate the hydration properties of oxyanions. Reorientation relaxation of its hydration water can occur through two different routes: water can either break its hydrogen bond with the nitrate to form one with another water or switch between two oxygen atoms of the same nitrate. The latter molecular mechanism increases the residence time of oxyanion’s hydration water and thus nitrate anion slows down the translational motionmore » of neighbouring water. But it is also a “structure breaker” in that it accelerates the reorientation relaxation of hydration water. Such a result illustrates that differences do exist between the hydration of oxyanions and simple halide anions as a result of different molecular geometries. Furthermore, the rotation of the nitrate solute is coupled with the hydrogen bond rearrangement of its hydration water. The nitrate anion can either tilt along the axis perpendicularly to the plane or rotate in the plane. We find that the two reorientation relaxation routes of the hydration water lead to different relaxation dynamics in each of the two above movements of the nitrate solute. The current study suggests that molecular geometry could play an important role in solute hydration and dynamics.« less

Reorientation and faulting of Pluto due to volatile loading within Sputnik Planitia.

PubMed

Keane, James T; Matsuyama, Isamu; Kamata, Shunichi; Steckloff, Jordan K

2016-12-01

Pluto is an astoundingly diverse, geologically dynamic world. The dominant feature is Sputnik Planitia-a tear-drop-shaped topographic depression approximately 1,000 kilometres in diameter possibly representing an ancient impact basin. The interior of Sputnik Planitia is characterized by a smooth, craterless plain three to four kilometres beneath the surrounding rugged uplands, and represents the surface of a massive unit of actively convecting volatile ices (N 2 , CH 4 and CO) several kilometres thick. This large feature is very near the Pluto-Charon tidal axis. Here we report that the location of Sputnik Planitia is the natural consequence of the sequestration of volatile ices within the basin and the resulting reorientation (true polar wander) of Pluto. Loading of volatile ices within a basin the size of Sputnik Planitia can substantially alter Pluto's inertia tensor, resulting in a reorientation of the dwarf planet of around 60 degrees with respect to the rotational and tidal axes. The combination of this reorientation, loading and global expansion due to the freezing of a possible subsurface ocean generates stresses within the planet's lithosphere, resulting in a global network of extensional faults that closely replicate the observed fault networks on Pluto. Sputnik Planitia probably formed northwest of its present location, and was loaded with volatiles over million-year timescales as a result of volatile transport cycles on Pluto. Pluto's past, present and future orientation is controlled by feedbacks between volatile sublimation and condensation, changing insolation conditions and Pluto's interior structure.

Reorientation and faulting of Pluto due to volatile loading within Sputnik Planitia

NASA Astrophysics Data System (ADS)

Keane, James T.; Matsuyama, Isamu; Kamata, Shunichi; Steckloff, Jordan K.

2016-12-01

Pluto is an astoundingly diverse, geologically dynamic world. The dominant feature is Sputnik Planitia—a tear-drop-shaped topographic depression approximately 1,000 kilometres in diameter possibly representing an ancient impact basin. The interior of Sputnik Planitia is characterized by a smooth, craterless plain three to four kilometres beneath the surrounding rugged uplands, and represents the surface of a massive unit of actively convecting volatile ices (N2, CH4 and CO) several kilometres thick. This large feature is very near the Pluto-Charon tidal axis. Here we report that the location of Sputnik Planitia is the natural consequence of the sequestration of volatile ices within the basin and the resulting reorientation (true polar wander) of Pluto. Loading of volatile ices within a basin the size of Sputnik Planitia can substantially alter Pluto’s inertia tensor, resulting in a reorientation of the dwarf planet of around 60 degrees with respect to the rotational and tidal axes. The combination of this reorientation, loading and global expansion due to the freezing of a possible subsurface ocean generates stresses within the planet’s lithosphere, resulting in a global network of extensional faults that closely replicate the observed fault networks on Pluto. Sputnik Planitia probably formed northwest of its present location, and was loaded with volatiles over million-year timescales as a result of volatile transport cycles on Pluto. Pluto’s past, present and future orientation is controlled by feedbacks between volatile sublimation and condensation, changing insolation conditions and Pluto’s interior structure.

Spin wave nonreciprocity for logic device applications

NASA Astrophysics Data System (ADS)

Jamali, Mahdi; Kwon, Jae Hyun; Seo, Soo-Man; Lee, Kyung-Jin; Yang, Hyunsoo

2013-11-01

The utilization of spin waves as eigenmodes of the magnetization dynamics for information processing and communication has been widely explored recently due to its high operational speed with low power consumption and possible applications for quantum computations. Previous proposals of spin wave Mach-Zehnder devices were based on the spin wave phase, a delicate entity which can be easily disrupted. Here, we propose a complete logic system based on the spin wave amplitude utilizing the nonreciprocal spin wave behavior excited by microstrip antennas. The experimental data reveal that the nonreciprocity of magnetostatic surface spin wave can be tuned by the bias magnetic field. Furthermore, engineering of the device structure could result in a high nonreciprocity factor for spin wave logic applications.