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Sample records for spin valve behavior

  1. Enhanced magnetoresistance in graphene spin valve

    Energy Technology Data Exchange (ETDEWEB)

    Iqbal, Muhammad Zahir, E-mail: zahir.upc@gmail.com [Faculty of Engineering Sciences, GIK Institute of Engineering Sciences and Technology, Topi 23640, Khyber Pakhtunkhwa (Pakistan); Hussain, Ghulam [Faculty of Engineering Sciences, GIK Institute of Engineering Sciences and Technology, Topi 23640, Khyber Pakhtunkhwa (Pakistan); Siddique, Salma [Department of Bioscience & Biotechnology, Sejong University, Seoul 143-747 (Korea, Republic of); Iqbal, Muhammad Waqas [Department of Physics, Riphah Institute of Computing and Applied Sciences (RICAS), Riphah International University, Lahore (Pakistan)

    2017-05-01

    Graphene has been explored as a promising candidate for spintronics due to its atomically flat structure and novel properties. Here we fabricate two spin valve junctions, one from directly grown graphene on Ni electrode (DG) and other from transferred graphene (TG). The magnetoresistance (MR) ratio for DG device is found to be higher than TG device i.e. ~0.73% and 0.14%, respectively. Also the spin polarization of Ni electrode is determined to be 6.03% at room temperature in case of DG device, however it reduces to 2.1% for TG device. From this analysis, we infer how environmental exposure of the sample degrades the spin properties of the magnetic junctions. Moreover, the transport measurements reveal linear behavior for current-voltage (I-V) characteristics, indicating ohmic behavior of the junctions. Our findings unveil the efficiency of direct growth of graphene for spin filtering mechanism in spin valve devices.

  2. Pseudo spin-valve behavior in oxide ferromagnet/superconductor/ferromagnet trilayers

    Energy Technology Data Exchange (ETDEWEB)

    Pang, B.S.H. [Device Materials Group, Department of Materials Science and Metallurgy, University of Cambridge, New Museum Site, Pembroke Street, Cambridge CB2 3QZ (United Kingdom)]. E-mail: brianpang@cantab.net; Bell, C. [Device Materials Group, Department of Materials Science and Metallurgy, University of Cambridge, New Museum Site, Pembroke Street, Cambridge CB2 3QZ (United Kingdom); Tomov, R.I. [Device Materials Group, Department of Materials Science and Metallurgy, University of Cambridge, New Museum Site, Pembroke Street, Cambridge CB2 3QZ (United Kingdom); Durrell, J.H. [Device Materials Group, Department of Materials Science and Metallurgy, University of Cambridge, New Museum Site, Pembroke Street, Cambridge CB2 3QZ (United Kingdom); Blamire, M.G. [Device Materials Group, Department of Materials Science and Metallurgy, University of Cambridge, New Museum Site, Pembroke Street, Cambridge CB2 3QZ (United Kingdom)

    2005-06-20

    La{sub 0.7}Ca{sub 0.3}MnO{sub 3}/YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}/La{sub 0.67}Sr{sub 0.33}MnO{sub 3} heterostructural devices with double coercivity have been fabricated. The superconducting critical current (I{sub c}) and critical temperature in both parallel (P) and antiparallel (AP) magnetic configurations remained unchanged within our measurement limits. This observation is contrary to results obtained elsewhere using similar metallic systems. A pseudo spin-valve magnetoresistive (MR) characteristic was observed at bias current (I{sub bias}){approx}I{sub c} at temperatures below the onset of superconductivity. The effect increased with decreasing temperature and I{sub bias} and can be explained using the assumption of the electron spin-charge separation.

  3. Spin Switching via Quantum Dot Spin Valves

    Science.gov (United States)

    Gergs, N. M.; Bender, S. A.; Duine, R. A.; Schuricht, D.

    2018-01-01

    We develop a theory for spin transport and magnetization dynamics in a quantum dot spin valve, i.e., two magnetic reservoirs coupled to a quantum dot. Our theory is able to take into account effects of strong correlations. We demonstrate that, as a result of these strong correlations, the dot gate voltage enables control over the current-induced torques on the magnets and, in particular, enables voltage-controlled magnetic switching. The electrical resistance of the structure can be used to read out the magnetic state. Our model may be realized by a number of experimental systems, including magnetic scanning-tunneling microscope tips and artificial quantum dot systems.

  4. Two-dimensional spin diffusion in multiterminal lateral spin valves

    Science.gov (United States)

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

    2008-01-01

    The effects of two-dimensional spin diffusion on spin extraction in lateral semiconductor spin valves have been investigated experimentally and theoretically. A ferromagnetic collector terminal of variable size is placed between the ferromagnetic electron spin injector and detector of a conventional lateral spin valve for spin extraction. It is observed that transverse spin diffusion beneath the collector terminal plays an important role along with the conventional longitudinal spin diffusion in describing the overall transport of spin carriers. Two-dimensional spin diffusion reduces the perturbation of the channel electrochemical potentials and improves spin extraction.

  5. Film edge nonlocal spin valves.

    Science.gov (United States)

    McCallum, Andrew T; Johnson, Mark

    2009-06-01

    Spintronics is a new paradigm for integrated digital electronics. Recently established as a niche for nonvolatile magnetic random access memory (MRAM), it offers new functionality while demonstrating low-power and high-speed performance. However, to reach high density spintronic technology must make a transition to the nanometer scale. Prototype devices are presently made using a planar geometry and have an area determined by the lithographic feature size, currently about 100 nm. Here we present a new nonplanar geometry in which one lateral dimension is given by a film thickness, on the order of 10 nm. With this new approach, cell sizes can shrink by an order of magnitude. The geometry is demonstrated with a nonlocal spin valve, where we study devices with an injector/detector separation much less than the spin diffusion length.

  6. Influence of DC-biasing on the performance of graphene spin valve

    Science.gov (United States)

    Iqbal, Muhammad Zahir; Hussain, Ghulam; Siddique, Salma; Hussain, Tassadaq; Iqbal, Muhammad Javaid

    2018-04-01

    Generating and controlling the spin valve signal are key factors in 'spintronics', which aims to utilize the spin degree of electrons. For this purpose, spintronic devices are constructed that can detect the spin signal. Here we investigate the effect of direct current (DC) on the magnetoresistance (MR) of graphene spin valve. The DC input not only decreases the magnitude of MR but also distorts the spin valve signal at higher DC inputs. Also, low temperature measurements revealed higher MR for the device, while the magnitude is noticed to decrease at higher temperatures. Furthermore, the spin polarization associated with NiFe electrodes is continuously increased at low DC bias and low temperatures. We also demonstrate the ohmic behavior of graphene spin valve by showing linear current-voltage (I-V) characteristics of the junction. Our findings may contribute significantly in modulating and controlling the spin transport properties of vertical spin valve structures.

  7. High frequency spin torque oscillators with composite free layer spin valve

    International Nuclear Information System (INIS)

    Natarajan, Kanimozhi; Arumugam, Brinda; Rajamani, Amuda

    2016-01-01

    We report the oscillations of magnetic spin components in a composite free layer spin valve. The associated Landau–Lifshitz–Gilbert–Slonczewski (LLGS) equation is studied by stereographically projecting the spin on to a complex plane and the spin components were found. A fourth order Runge–Kutta numerical integration on LLGS equation also confirms the similar trajectories of the spin components. This study establishes the possibility of a Spin Torque Oscillator in a composite free layer spin valve, where the exchange coupling is ferromagnetic in nature. In-plane and out-of-plane precessional modes of magnetization oscillations were found in zero applied magnetic field and the frequencies of the oscillations were calculated from Fast Fourier Transform of the components of magnetization. Behavior of Power Spectral Density for a range of current density is studied. Finally our analysis shows the occurrence of highest frequency 150 GHz, which is in the second harmonics for the specific choice of system parameters.

  8. Training and recovery behaviors of exchange bias in FeNi/Cu/Co/FeMn spin valves at high field sweep rates

    Energy Technology Data Exchange (ETDEWEB)

    Yang, D.Z. [Institutt for fysikk, NTNU, NO-7491 Trondheim (Norway); Key Laboratory for Magnetism and Magnetic Materials of Ministry of Education, Lanzhou University, Lanzhou 730000 (China); Kapelrud, A.; Saxegaard, M. [Institutt for fysikk, NTNU, NO-7491 Trondheim (Norway); Wahlstroem, E., E-mail: erik.wahlstrom@ntnu.no [Institutt for fysikk, NTNU, NO-7491 Trondheim (Norway)

    2012-09-15

    Training and recovery of exchange bias in FeNi/Cu/Co/FeMn spin valves have been studied by magnetoresistance curves with field sweep rates from 1000 to 4800 Oe/s. It is found that training and recovery of exchange field are proportional to the logarithm of the training cycles and recovery time, respectively. These behaviors are explained within the model based on thermal activation. For the field sweep rates of 1000, 2000 and 4000 Oe/s, the relaxation time of antiferromagnet spins are 61.4, 27.6, and 11.5 in the unit of ms, respectively, much shorter than the long relaxation time ({approx}10{sup 2}s) in conventional magnetometry measurements. - Highlights: Black-Right-Pointing-Pointer We measure antiferromagnet (AFM) spin dynamic behaviors at high field sweep rates. Black-Right-Pointing-Pointer Increasing the field sweep rates will reduce the AFM recovery and relaxation time. Black-Right-Pointing-Pointer AFM spin is in millisecond timescale, shorter the conventional report ({approx}10{sup 2}-10{sup 4}).

  9. Spin-resolved electron waiting times in a quantum-dot spin valve

    Science.gov (United States)

    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.

  10. Spin Valve Systems for Angle Sensor Applications

    OpenAIRE

    Johnson, Andrew

    2004-01-01

    A contact-less sensor with the ability to measure over a 360° range has been long sought after in the automotive industry. Such a sensor could be realized by utilizing the angle dependence of the Giant Magneto Resistance (GMR) Effect in a special type of magnetic multilayer called a spin valve arranged in a wheatstone bridge circuit [Spo96]. A spin valve consists of two ferromagnetic layers separated by nonmagnetic spacer layer where the magnetization of one of the ferromagnetic layers is pin...

  11. Inverse Magnetoresistance in Polymer Spin Valves.

    Science.gov (United States)

    Ding, Shuaishuai; Tian, Yuan; Li, Yang; Mi, Wenbo; Dong, Huanli; Zhang, Xiaotao; Hu, Wenping; Zhu, Daoben

    2017-05-10

    In this work, both negative and positive magnetoresistance (MR) in solution-processed regioregular poly(3-hexylthiophene) (RR-P3HT) is observed in organic spin valves (OSVs) with vertical La 2/3 Sr 1/3 MnO 3 (LSMO)/P3HT/AlO x /Co configuration. The ferromagnetic (FM) LSMO electrode with near-atomic flatness is fabricated by a DC facing-target magnetron sputtering method. This research is focused on the origin of the MR inversion. Two types of devices are investigated in details: One with Co penetration shows a negative MR of 0.2%, while the other well-defined device with a nonlinear behavior has a positive MR of 15.6%. The MR measurements in LSMO/AlO x /Co and LSMO/Co junctions are carried to exclude the interference of insulating layer and two FM electrodes themselves. By examining the Co thicknesses and their corresponding magnetic hysteresis loops, a spin-dependent hybrid-interface-state model by Co penetration is induced to explain the MR sign inversion. These results proven by density functional theory (DFT) calculations may shed light on the controllable interfacial properties in designing novel OSV devices.

  12. Large spin-valve effect in a lateral spin-valve device based on ferromagnetic semiconductor GaMnAs

    Science.gov (United States)

    Asahara, Hirokatsu; Kanaki, Toshiki; Ohya, Shinobu; Tanaka, Masaaki

    2018-03-01

    We investigate the spin-dependent transport properties of a lateral spin-valve device based on the ferromagnetic semiconductor GaMnAs. This device is composed of a GaMnAs channel layer grown on GaAs with a narrow trench across the channel. Its current-voltage characteristics show tunneling behavior. Large magnetoresistance (MR) ratios of more than ˜10% are obtained. These values are much larger than those (˜0.1%) reported for lateral-type spin metal-oxide-semiconductor field-effect transistors. The magnetic field direction dependence of the MR curve differs from that of the anisotropic magnetoresistance of GaMnAs, which confirms that the MR signal originates from the spin-valve effect between the GaMnAs electrodes.

  13. Graphene spin valve: An angle sensor

    Energy Technology Data Exchange (ETDEWEB)

    Iqbal, Muhammad Zahir, E-mail: zahir.upc@gmail.com [Faculty of Engineering Sciences, GIK Institute of Engineering Sciences and Technology, Topi 23640, Khyber Pakhtunkhwa (Pakistan); Hussain, Ghulam [Faculty of Engineering Sciences, GIK Institute of Engineering Sciences and Technology, Topi 23640, Khyber Pakhtunkhwa (Pakistan); Siddique, Salma [Department of Bioscience & Biotechnology, Sejong University, Seoul 143-747 (Korea, Republic of); Iqbal, Muhammad Waqas [Department of Physics, Riphah Institute of Computing and Applied Sciences (RICAS), Riphah International University, Lahore (Pakistan)

    2017-06-15

    Graphene spin valves can be optimized for various spintronic applications by tuning the associated experimental parameters. In this work, we report the angle dependent magnetoresistance (MR) in graphene spin valve for different orientations of applied magnetic field (B). The switching points of spin valve signals show a clear shift towards higher B for each increasing angle of the applied field, thus sensing the response for respective orientation of the magnetic field. The angular variation of B shifts the switching points from ±95 G to ±925 G as the angle is varied from 0° to 90° at 300 K. The observed shifts in switching points become more pronounced (±165 G to ±1450 G) at 4.2 K for similar orientation. A monotonic increase in MR ratio is observed as the angle of magnetic field is varied in the vertical direction at 300 K and 4.2 K temperatures. This variation of B (from 0° to 90°) increases the magnitude of MR ratio from ∼0.08% to ∼0.14% at 300 K, while at 4.2 K it progresses to ∼0.39% from ∼0.14%. The sensitivity related to angular variation of such spin valve structure can be employed for angle sensing applications.

  14. Interlayer quality dependent graphene spin valve

    Energy Technology Data Exchange (ETDEWEB)

    Iqbal, Muhammad Zahir, E-mail: zahir.upc@gmail.com [Faculty of Engineering Sciences, GIK Institute of Engineering Sciences and Technology, Topi, Khyber Pakhtunkhwa, 23640 Pakistan (Pakistan); Hussain, Ghulam [Faculty of Engineering Sciences, GIK Institute of Engineering Sciences and Technology, Topi, Khyber Pakhtunkhwa, 23640 Pakistan (Pakistan); Siddique, Salma [Department of Bioscience & Biotechnology, Sejong University, Seoul, 143-747 (Korea, Republic of); Iqbal, Muhammad Waqas [Department of Physics, Riphah Institute of Computing and Applied Sciences (RICAS), Riphah International University, Lahore (Pakistan); Murtaza, Ghulam [Centre for Advanced Studies in Physics, Government College University, Lahore 54000 (Pakistan); Ramay, Shahid Mahmood [Physics & Astronomy Department, College of Science, King Saud University, Riyadh 11451 (Saudi Arabia)

    2017-01-15

    It is possible to utilize the new class of materials for emerging two-dimensional (2D) spintronic applications. Here, the role of defects in the graphene interlayer and its influence on the spin valve signal is reported. The emergence of D peak in Raman spectrum reveals defects in the graphene layer. The linear I-V curve for defective and non-defective graphene samples indicate the ohmic nature of NiFe and graphene contact. A non-uniform magnetoresistive effect with a bump is persistently observed for defective graphene device at various temperatures, while a smooth and symmetric signal is detected for non-defective graphene spin valve. Parallel and antiparallel alignments of magnetization of magnetic materials shows low and high resistance states, respectively. The magnetoresistance (MR) ratio for defective graphene NiFe/graphene/NiFe spin valve is measured to be ~0.16% at 300 K which progresses to ~0.39% for non-defective graphene device at the same temperature. Similarly at 4.2 K the MR ratios are reported to be ~0.41% and ~0.78% for defective and non-defective graphene devices, respectively. Our investigation provides an evidence for relatively better response of the spin valve signal with high quality graphene interlayer.

  15. Spin current through quantum-dot spin valves

    International Nuclear Information System (INIS)

    Wang, J; Xing, D Y

    2006-01-01

    We report a theoretical study of the influence of the Coulomb interaction on the equilibrium spin current in a quantum-dot spin valve, in which the quantum dot described by the Anderson impurity model is coupled to two ferromagnetic leads with noncollinear magnetizations. In the Kondo regime, electrons transmit through the quantum dot via higher-order virtual processes, in which the spin of either lead electrons or a localized electron on the quantum dot may reverse. It is found that the magnitude of the spin current decreases with increasing Coulomb interactions due to spin flip effects on the dot. However, the spatial direction of the spin current remains unchanged; it is determined only by the exchange coupling between two noncollinear magnetizations

  16. Spin transport in benzofurane bithiophene based organic spin valves

    Energy Technology Data Exchange (ETDEWEB)

    Palosse, Mathieu; Séguy, Isabelle; Bedel-Pereira, Élena [CNRS, LAAS, 7 avenue du Colonel Roche, F-31400 Toulouse (France); Université de Toulouse (France); UPS, INSA, INP, ISAE (France); LAAS (France); CEMES, F-31077 Toulouse (France); Villeneuve-Faure, Christina [Université de Toulouse (France); UPS, INSA, INP, ISAE (France); LAAS (France); CEMES, F-31077 Toulouse (France); LAPLACE, Université Paul Sabatier, 118, route de Narbonne 31062 Toulouse Cedex 9 (France); Mallet, Charlotte; Frère, Pierre [MOLTECH-Anjou, UMR CNRS 6200, Université d’Angers, 2 Bd Lavoisier 49045 ANGERS Cedex (France); Warot-Fonrose, Bénédicte; Biziere, Nicolas [Université de Toulouse (France); UPS, INSA, INP, ISAE (France); LAAS (France); CEMES, F-31077 Toulouse (France); CNRS, CEMES-CNRS UPR 8011, 29 rue Jeanne Marvig, BP 94347, FR-31055 Toulouse Cedex 4 (France); Bobo, Jean-François, E-mail: jfbobo@cemes.fr [Université de Toulouse (France); UPS, INSA, INP, ISAE (France); LAAS (France); CEMES, F-31077 Toulouse (France); CNRS, CEMES-ONERA, NMH, 2 avenue Edouard Belin, FR-31055 Toulouse Cedex 4 (France)

    2014-01-15

    In this paper we present spin transport in organic spin-valves using benzofurane bithiophene (BF3) as spacer layer between NiFe and Co ferromagnetic electrodes. The use of an AlO{sub x} buffer layer between the top electrode and the organic layer is discussed in terms of improvements of stacking topology, electrical transport and oxygen contamination of the BF3 layer. A study of magnetic hysteresis cycles evidences spin-valve behaviour. Transport properties are indicative of unshorted devices with non-linear I-V characteristics. Finally we report a magnetoresistance of 3% at 40 K and 10 mV in a sample with a 50 nm thick spacer layer, using an AlO{sub x} buffer layer.

  17. Magnetic structure of the spin valve interface

    International Nuclear Information System (INIS)

    Nicholson, D.M.C.; Butler, W.H.; Zhang, X.; MacLaren, J.M.; Gurney, B.A.; Speriosu, V.S.

    1994-01-01

    Nonferromagnetic atoms present at Ni/Cu and Permalloy/Cu interfaces in sputtered spin valve magnetoresistive layered structures have been shown to cause reduced magnetoresistance. Here we show that a model in which the moments on the Ni atoms in the interfacial region of Ni/Cu are reduced substantially by interdiffusion with Cu is consistent with the experimental results. In contrast, we believe that moments persist at the permalloy/Cu interface, which first principle total energy calculations suggest will be disordered at finite temperatures. These reduced or disordered moments are expected to significantly reduce the GMR

  18. Spin diffusion length of Permalloy using spin absorption in lateral spin valves

    Science.gov (United States)

    Sagasta, Edurne; Omori, Yasutomo; Isasa, Miren; Otani, YoshiChika; Hueso, Luis E.; Casanova, Fèlix

    2017-08-01

    We employ the spin absorption technique in lateral spin valves to extract the spin diffusion length of Permalloy (Py) as a function of temperature and resistivity. A linear dependence of the spin diffusion length with the conductivity of Py is observed, evidencing that the Elliott-Yafet mechanism is the dominant spin relaxation mechanism in Permalloy. Completing the dataset with additional data found in the literature, we obtain λPy = (0.91 ± 0.04) (fΩm2)/ρPy.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2017-10-25

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

  20. Local spin valve effect in lateral (Ga,MnAs/GaAs spin Esaki diode devices

    Directory of Open Access Journals (Sweden)

    M. Ciorga

    2011-06-01

    Full Text Available We report here on a local spin valve effect observed unambiguously in lateral all-semiconductor all-electrical spin injection devices, employing p+ −(Ga,MnAs/n+ −GaAs Esaki diode structures as spin aligning contacts. We discuss the observed local spin-valve signal as a result of the interplay between spin-transport-related contribution and the tunneling anisotropic magnetoresistance of the magnetic contacts. The magnitude of the spin-related magnetoresistance change is equal to 30 Ω which is twice the magnitude of the measured non-local signal.

  1. Spin valve sensor for biomolecular identification: Design, fabrication, and characterization

    Science.gov (United States)

    Li, Guanxiong

    Biomolecular identification, e.g., DNA recognition, has broad applications in biology and medicine such as gene expression analysis, disease diagnosis, and DNA fingerprinting. Therefore, we have been developing a magnetic biodetection technology based on giant magnetoresistive spin valve sensors and magnetic nanoparticle (developed for the magnetic nanoparticle detection, assuming the equivalent average field of magnetic nanoparticles and the coherent rotation of spin valve free layer magnetization. Micromagnetic simulations have also been performed for the spin valve sensors. The analytical model and micromagnetic simulations are found consistent with each other and are in good agreement with experiments. The prototype spin valve sensors have been fabricated at both micron and submicron scales. We demonstrated the detection of a single 2.8-mum magnetic microbead by micron-sized spin valve sensors. Based on polymer-mediated self-assembly and fine lithography, a bilayer lift-off process was developed to deposit magnetic nanoparticles onto the sensor surface in a controlled manner. With the lift-off deposition method, we have successfully demonstrated the room temperature detection of monodisperse 16-nm Fe3O 4 nanoparticles in a quantity from a few tens to several hundreds by submicron spin valve sensors, proving the feasibility of the nanoparticle detection. As desired for quantitative biodetection, a fairly linear dependence of sensor signal on the number of nanoparticles has been confirmed. The initial detection of DNA hybridization events labeled by magnetic nanoparticles further proved the magnetic biodetection concept.

  2. Spin filter effect of hBN/Co detector electrodes in a 3D topological insulator spin valve

    Science.gov (United States)

    Vaklinova, Kristina; Polyudov, Katharina; Burghard, Marko; Kern, Klaus

    2018-03-01

    Topological insulators emerge as promising components of spintronic devices, in particular for applications where all-electrical spin control is essential. While the capability of these materials to generate spin-polarized currents is well established, only very little is known about the spin injection/extraction into/out of them. Here, we explore the switching behavior of lateral spin valves comprising the 3D topological insulator Bi2Te2Se as channel, which is separated from ferromagnetic Cobalt detector contacts by an ultrathin hexagonal boron nitride (hBN) tunnel barrier. The corresponding contact resistance displays a notable variation, which is correlated with a change of the switching characteristics of the spin valve. For contact resistances below ~5 kΩ, the hysteresis in the switching curve reverses upon reversing the applied current, as expected for spin-polarized currents carried by the helical surface states. By contrast, for higher contact resistances an opposite polarity of the hysteresis loop is observed, which is independent of the current direction, a behavior signifying negative spin detection efficiency of the multilayer hBN/Co contacts combined with bias-induced spin signal inversion. Our findings suggest the possibility to tune the spin exchange across the interface between a ferromagnetic metal and a topological insulator through the number of intervening hBN layers.

  3. Dynamics of spin torque switching in all-perpendicular spin valve nanopillars

    International Nuclear Information System (INIS)

    Liu, H.; Bedau, D.; Sun, J.Z.; Mangin, S.; Fullerton, E.E.; Katine, J.A.; Kent, A.D.

    2014-01-01

    We present a systematic experimental study of the spin-torque-induced magnetic switching statistics at room temperature, using all-perpendicularly magnetized spin-valves as a model system. Three physical regimes are distinguished: a short-time ballistic limit below a few nanoseconds, where spin-torque dominates the reversal dynamics from a thermal distribution of initial conditions; a long time limit, where the magnetization reversal probability is determined by spin-torque-amplified thermal activation; and a cross-over regime, where the spin-torque and thermal agitation both contribute. For a basic quantitative understanding of the physical processes involved, an analytical macrospin model is presented which contains both spin-torque dynamics and finite temperature effects. The latter was treated rigorously using a Fokker–Plank formalism, and solved numerically for specific sets of parameters relevant to the experiments to determine the switching probability behavior in the short-time and cross-over regimes. This analysis shows that thermal fluctuations during magnetization reversal greatly affect the switching probability over all the time scales studied, even in the short-time limit

  4. The spin-valve transistor: a preview and outlook

    NARCIS (Netherlands)

    Jansen, R.

    2003-01-01

    Combining ferromagnetic and semiconductor materials is a challenging route to create new options for electronic devices in which the spin of the electron is employed. The spin-valve transistor (SVT) is the first of such hybrid devices shown to work successfully. This review describes the basic

  5. Spin transfer torque in antiferromagnetic spin valves: From clean to disordered regimes

    KAUST Repository

    Saidaoui, Hamed Ben Mohamed

    2014-05-28

    Current-driven spin torques in metallic spin valves composed of antiferromagnets are theoretically studied using the nonequilibrium Green\\'s function method implemented on a tight-binding model. We focus our attention on G-type and L-type antiferromagnets in both clean and disordered regimes. In such structures, spin torques can either rotate the magnetic order parameter coherently (coherent torque) or compete with the internal antiferromagnetic exchange (exchange torque). We show that, depending on the symmetry of the spin valve, the coherent and exchange torques can either be in the plane, ∝n×(q×n) or out of the plane ∝n×q, where q and n are the directions of the order parameter of the polarizer and the free antiferromagnetic layers, respectively. Although disorder conserves the symmetry of the torques, it strongly reduces the torque magnitude, pointing out the need for momentum conservation to ensure strong spin torque in antiferromagnetic spin valves.

  6. Gate-tunable black phosphorus spin valve with nanosecond spin lifetimes

    Science.gov (United States)

    Avsar, Ahmet; Tan, Jun Y.; Kurpas, Marcin; Gmitra, Martin; Watanabe, Kenji; Taniguchi, Takashi; Fabian, Jaroslav; Özyilmaz, Barbaros

    2017-09-01

    Two-dimensional materials offer new opportunities for both fundamental science and technological applications, by exploiting the electron's spin. Although graphene is very promising for spin communication due to its extraordinary electron mobility, the lack of a bandgap restricts its prospects for semiconducting spin devices such as spin diodes and bipolar spin transistors. The recent emergence of two-dimensional semiconductors could help overcome this basic challenge. In this letter we report an important step towards making two-dimensional semiconductor spin devices. We have fabricated a spin valve based on ultrathin (~5 nm) semiconducting black phosphorus (bP), and established fundamental spin properties of this spin channel material, which supports all electrical spin injection, transport, precession and detection up to room temperature. In the non-local spin valve geometry we measure Hanle spin precession and observe spin relaxation times as high as 4 ns, with spin relaxation lengths exceeding 6 μm. Our experimental results are in a very good agreement with first-principles calculations and demonstrate that the Elliott-Yafet spin relaxation mechanism is dominant. We also show that spin transport in ultrathin bP depends strongly on the charge carrier concentration, and can be manipulated by the electric field effect.

  7. Enhanced magnetoresistance in lateral spin-valves

    Science.gov (United States)

    Adari, R.; Patil, T.; Murthy, M.; Maheshwari, R.; Vaidya, G.; Ganguly, S.; Saha, D.

    2010-09-01

    The effect of feature sizes on the characteristics of lateral spintronic devices have been investigated experimentally and theoretically. It is demonstrated that confining spin-transport in the active region of a device enhances magnitude of the spin-dependent response substantially. Numerical simulation of spin-transport corroborates the experimental observations. Device characteristics are found to be a strong function of spin-polarizer and analyzer dimensions. The response is observed to attain a peak value for an optimum device feature size, and this is seen to be a function of temperature. Spin dependent effects become weaker for very small and very large devices.

  8. Inverse spin valve effect in multilayer graphene device

    International Nuclear Information System (INIS)

    Goto, H; Tanaka, S; Tomori, H; Ootuka, Y; Kanda, A; Tsukagoshi, K

    2010-01-01

    We report the gate-voltage dependence of the spin transport in multilayer graphene (MLG) studied experimentally by the local measurement. The sample consists of a Ni/MLG/Ni junction, where the thickness of the MLG is 9 nm and the spacing of two Ni electrodes is 300 nm. At zero gate voltage, we observed the normal spin valve effect, in which the resistance for the antiparallel alignment of magnetization in ferromagnetic electrodes is larger than that for the parallel alignment. By applying a large gate voltage, on the other hand, the spin valve effect is reversed: the resistance for the antiparallel alignment becomes smaller than that for the parallel alignment. The result is qualitatively interpreted as a quantum interference effect, indicating that the mean free path and the spin relaxation length of the MLG are longer than the electrode spacing (300 nm).

  9. Spin valve effect in single-atom contacts

    International Nuclear Information System (INIS)

    Ziegler, M; Neel, N; Berndt, R; Lazo, C; Ferriani, P; Heinze, S; Kroeger, J

    2011-01-01

    Magnetic single-atom contacts have been controllably fabricated with a scanning tunnelling microscope. A voltage-dependent spin valve effect with conductance variations of ∼40% is reproducibly observed from contacts comprising a Cr-covered tip and Co and Cr atoms on ferromagnetic nanoscale islands on W(110) with opposite magnetization. The spin-dependent conductances are interpreted from first-principles calculations in terms of the orbital character of the relevant electronic states of the junction.

  10. Magnetostrictive GMR spin valves with composite FeGa/FeCo free layers

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Luping [Key Laboratory of Magnetic Materials and Devices & Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Institute of Materials Science, School of Materials Science and Engineering, Shanghai University, Shanghai 200072 (China); Zhan, Qingfeng, E-mail: zhanqf@nimte.ac.cn, E-mail: runweili@nimte.ac.cn; Yang, Huali; Li, Huihui; Zhang, Shuanglan; Liu, Yiwei; Wang, Baomin; Li, Run-Wei, E-mail: zhanqf@nimte.ac.cn, E-mail: runweili@nimte.ac.cn [Key Laboratory of Magnetic Materials and Devices & Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Tan, Xiaohua [Institute of Materials Science, School of Materials Science and Engineering, Shanghai University, Shanghai 200072 (China)

    2016-03-15

    We have fabricated strain-sensitive spin valves on flexible substrates by utilizing the large magnetostrictive FeGa alloy to promote the strain sensitivity and the composite free layer of FeGa/FeCo to avoid the drastic reduction of giant magnetoresistance (GMR) ratio. This kind of spin valve (SV-FeGa/FeCo) displays a MR ratio about 5.9%, which is comparable to that of the conventional spin valve (SV-FeCo) with a single FeCo free layer. Different from the previously reported works on magnetostrictive spin valves, the SV-FeGa/FeCo displays an asymmetric strain dependent GMR behavior. Upon increasing the lateral strain, the MR ratio for the ascending branch decreases more quickly than that for the descending branch, which is ascribed to the formation of a spiraling spin structure around the FeGa/FeCo interface under the combined influences of both magnetic field and mechanical strain. A strain sensitivity of GF = 7.2 was achieved at a magnetic bias field of -30 Oe in flexible SV-FeGa/FeCo, which is significantly larger than that of SV-FeCo.

  11. Magnetostrictive GMR spin valves with composite FeGa/FeCo free layers

    International Nuclear Information System (INIS)

    Liu, Luping; Zhan, Qingfeng; Yang, Huali; Li, Huihui; Zhang, Shuanglan; Liu, Yiwei; Wang, Baomin; Li, Run-Wei; Tan, Xiaohua

    2016-01-01

    We have fabricated strain-sensitive spin valves on flexible substrates by utilizing the large magnetostrictive FeGa alloy to promote the strain sensitivity and the composite free layer of FeGa/FeCo to avoid the drastic reduction of giant magnetoresistance (GMR) ratio. This kind of spin valve (SV-FeGa/FeCo) displays a MR ratio about 5.9%, which is comparable to that of the conventional spin valve (SV-FeCo) with a single FeCo free layer. Different from the previously reported works on magnetostrictive spin valves, the SV-FeGa/FeCo displays an asymmetric strain dependent GMR behavior. Upon increasing the lateral strain, the MR ratio for the ascending branch decreases more quickly than that for the descending branch, which is ascribed to the formation of a spiraling spin structure around the FeGa/FeCo interface under the combined influences of both magnetic field and mechanical strain. A strain sensitivity of GF = 7.2 was achieved at a magnetic bias field of -30 Oe in flexible SV-FeGa/FeCo, which is significantly larger than that of SV-FeCo.

  12. Magnetostrictive GMR spin valves with composite FeGa/FeCo free layers

    Science.gov (United States)

    Liu, Luping; Zhan, Qingfeng; Yang, Huali; Li, Huihui; Zhang, Shuanglan; Liu, Yiwei; Wang, Baomin; Tan, Xiaohua; Li, Run-Wei

    2016-03-01

    We have fabricated strain-sensitive spin valves on flexible substrates by utilizing the large magnetostrictive FeGa alloy to promote the strain sensitivity and the composite free layer of FeGa/FeCo to avoid the drastic reduction of giant magnetoresistance (GMR) ratio. This kind of spin valve (SV-FeGa/FeCo) displays a MR ratio about 5.9%, which is comparable to that of the conventional spin valve (SV-FeCo) with a single FeCo free layer. Different from the previously reported works on magnetostrictive spin valves, the SV-FeGa/FeCo displays an asymmetric strain dependent GMR behavior. Upon increasing the lateral strain, the MR ratio for the ascending branch decreases more quickly than that for the descending branch, which is ascribed to the formation of a spiraling spin structure around the FeGa/FeCo interface under the combined influences of both magnetic field and mechanical strain. A strain sensitivity of GF = 7.2 was achieved at a magnetic bias field of -30 Oe in flexible SV-FeGa/FeCo, which is significantly larger than that of SV-FeCo.

  13. Quasiclassical theory of spin-valve magnetoresistance: role of spin-flip scattering

    International Nuclear Information System (INIS)

    Baksalary, O.M.; Barnas, J.

    1997-01-01

    The Boltzmann kinetic equation is used to analyse the in-plane electronic transport in magnetic multilayers. Both diffuse and electron-momentum-conserving spin-flip scattering processes are included. Numerical results show that the momentum-conserving scattering processes reduce the spin-valve magnetoresistance. (author)

  14. Spin-dependent Seebeck coefficients of Ni80Fe20 and Co in nanopillar spin valves

    NARCIS (Netherlands)

    Dejene, F. K.; Flipse, J.; van Wees, B. J.

    2012-01-01

    We have experimentally determined the spin-dependent Seebeck coefficient of permalloy (Ni80Fe20) and cobalt (Co) using nanopillar spin valve devices, a stack of two ferromagnetic layers separated by a nonmagnetic layer. The devices were specifically designed to separate heat-related effects from

  15. The spin-valve transistor: Fabrication, characterization and physics

    NARCIS (Netherlands)

    Jansen, R.; van 't Erve, O.M.J.; Kim, S.D.; Vlutters, R.; Anil Kumar, P.S.; Lodder, J.C.

    2001-01-01

    An overview is given of the fabrication, basic properties, and physics of the spin-valve transistor. We describe the layout of this three-terminal ferromagnet/semiconductor hybrid device, as well as the operating principle. Fabrication technologies are discussed, including vacuum metal bonding. We

  16. Development of the spin valve transistor (invited paper)

    NARCIS (Netherlands)

    Monsma, D.J.; Vlutters, R.; Shimatsu, T.; Shimatsu, T.; Keim, Enrico G.; Mollema, R.H.; Lodder, J.C.

    1997-01-01

    As the easiest experimental approach, GMR (giant magnetoresistance) is usually measured using the current in plane (CIP)-GMR. The spin-valve transistor has previously been presented as a spectroscopic tool to measure current perpendicular to the planes (CPP)-GMR. Hot electrons cross the magnetic

  17. Control of spin injection by direct current in lateral spin valves

    OpenAIRE

    Casanova, Fèlix; Sharoni, Amos; Erekhinsky, Mikhail; Schuller, Ivan K.

    2008-01-01

    The spin injection and accumulation in metallic lateral spin valves with transparent interfaces is studied using d.c. injection current. Unlike a.c.-based techniques, this allows investigating the effects of the direction and magnitude of the injected current. We find that the spin accumulation is reversed by changing the direction of the injected current, whereas its magnitude does not change. The injection mechanism for both current directions is thus perfectly symmetric, leading to the sam...

  18. Spin-dependent thermoelectric effects in graphene-based spin valves.

    Science.gov (United States)

    Zeng, Minggang; Huang, Wen; Liang, Gengchiau

    2013-01-07

    Using first-principles calculations combined with non-equilibrium Green's function (NEGF), we investigate spin-dependent thermoelectric effects in a spin valve which consists of zigzag graphene nanoribbon (ZGNR) electrodes with different magnetic configurations. We find that electron transport properties in the ZGNR-based spin valve are strongly dependent on the magnetic configurations. As a result, with a temperature bias, thermally-induced currents can be controlled by switching the magnetic configurations, indicating a thermal magnetoresistance (MR) effect. Moreover, based on the linear response assumption, our study shows that the remarkably different Seebeck coefficients in the various magnetic configurations lead to a very large and controllable magneto Seebeck ratio. In addition, we evaluate thermoelectric properties, such as the power factor, electron thermal conductance and figure of merit (ZT), of the ZGNR-based spin valve. Our results indicate that the power factor and the electron thermal conductance are strongly related to the transmission gap and electron-hole symmetry of the transmission spectrum. Moreover, the value of ZT can reach 0.15 at room temperature without considering phonon scattering. In addition, we investigate the thermally-controlled magnetic distributions in the ZGNR-based spin valve and find that the magnetic distribution, especially the local magnetic moment around the Ni atom, is strongly related to the thermal bias. The very large, multi-valued and controllable thermal magnetoresistance and Seebeck effects indicate the strong potential of ZGNR-based spin valves for extremely low-power consuming spin caloritronics applications. The thermally-controlled magnetic moment in the ZGNR-based spin valve indicates its possible applications for information storage.

  19. Magneto-resistive and spin valve heads fundamentals and applications

    CERN Document Server

    Mallinson, John C

    2002-01-01

    This book is aims to be a comprehensive source on the physics and engineering of magneto-resistive heads. Most of the material is presented in a nonmathematical manner to make it more digestible for researchers, students, developers, and engineers.In addition to revising and updating material available in the first edition, Mallinson has added nine new chapters dealing with various aspects concerning spin valves, the electron spin tunneling effect, the electrostatic discharge effects, read amplifiers, and signal-to-noise ratios, making this a completely up-to-date reference.Th

  20. Magnetoresistance in hybrid organic spin valves at the onset of multiple-step tunneling.

    Science.gov (United States)

    Schoonus, J J H M; Lumens, P G E; Wagemans, W; Kohlhepp, J T; Bobbert, P A; Swagten, H J M; Koopmans, B

    2009-10-02

    By combining experiments with simple model calculations, we obtain new insight in spin transport through hybrid, CoFeB/Al2O3(1.5 nm)/tris(8-hydroxyquinoline)aluminium (Alq3)/Co spin valves. We have measured the characteristic changes in the I-V behavior as well as the intrinsic loss of magnetoresistance at the onset of multiple-step tunneling. In the regime of multiple-step tunneling, under the condition of low hopping rates, spin precession in the presence of hyperfine coupling is conjectured to be the relevant source of spin relaxation. A quantitative analysis leads to the prediction of a symmetric magnetoresistance around zero magnetic field in addition to the hysteretic magnetoresistance curves, which are indeed observed in our experiments.

  1. Effects of oxygen concentration in Co/CoO exchange-coupled spin valves

    International Nuclear Information System (INIS)

    Eckert, J.C.; Stern, N.P.; Snowden, D.S.; Checkelsky, J.G.; Sparks, P.D.; Carey, M.J.

    2004-01-01

    The properties of Co/CoO x exchange-coupled spin valves are explored at temperatures to 5 K. The spin valve structure is: 100 A CoO x /30 A Co/30 A Cu/10 A Co/50 A NiFe/50 A Ti. Our discovery is the considerable differences between the properties of the spin valves for which the CoO x layer is prepared in different O 2 concentrations

  2. Independent gate control of injected and detected spin currents in CVD graphene nonlocal spin valves

    Science.gov (United States)

    Anugrah, Yoska; Hu, Jiaxi; Stecklein, Gordon; Crowell, Paul A.; Koester, Steven J.

    2018-01-01

    Graphene is an ideal material for spintronic devices due to its low spin-orbit coupling and high mobility. One of the most important potential applications of graphene spintronics is for use in neuromorphic computing systems, where the tunable spin resistance of graphene can be used to apply analog weighting factors. A key capability needed to achieve spin-based neuromorphic computing systems is to achieve distinct regions of control, where injected and detected spin currents can be tuned independently. Here, we demonstrate the ability to achieve such independent control using a graphene spin valve geometry where the injector and detector regions are modulated by two separate bottom gate electrodes. The spin transport parameters and their dependence on each gate voltage are extracted from Hanle precession measurements. From this analysis, local spin transport parameters and their dependence on the local gate voltage are found, which provide a basis for a spatially-resolved spin resistance network that simulates the device. The data and model are used to calculate the spin currents flowing into, through, and out of the graphene channel. We show that the spin current flowing through the graphene channel can be modulated by 30% using one gate and that the spin current absorbed by the detector can be modulated by 50% using the other gate. This result demonstrates that spin currents can be controlled by locally tuning the spin resistance of graphene. The integration of chemical vapor deposition (CVD) grown graphene with local gates allows for the implementation of large-scale integrated spin-based circuits.

  3. Vortex Flipping in Superconductor-Ferromagnet Spin Valve Structures

    Science.gov (United States)

    Patino, Edgar J.; Aprili, Marco; Blamire, Mark; Maeno, Yoshiteru

    2014-03-01

    We report in plane magnetization measurements on Ni/Nb/Ni/CoO and Co/Nb/Co/CoO spin valve structures with one of the ferromagnetic layers pinned by an antiferromagnetic layer. In samples with Ni, below the superconducting transition Tc, our results show strong evidence of vortex flipping driven by the ferromagnets magnetization. This is a direct consequence of proximity effect that leads to vortex supercurrents leakage into the ferromagnets. Here the polarized electron spins are subject to vortices magnetic field occasioning vortex flipping. Such novel mechanism has been made possible for the first time by fabrication of the F/S/F/AF multilayered spin valves with a thin-enough S layer to barely confine vortices inside as well as thin-enough F layers to align and control the magnetization within the plane. When Co is used there is no observation of vortex flipping effect. This is attributed to Co shorter coherence length. Interestingly instead a reduction in pinning field of about 400 Oe is observed when the Nb layer is in superconducting state. This effect cannot be explained in terms of vortex fields. In view of these facts any explanation must be directly related to proximity effect and thus a remarkable phenomenon that deserves further investigation. Programa Nacional de Ciencias Basicas COLCIENCIAS (No. 120452128168).

  4. Strain effects on anisotropic magnetoresistance in a nanowire spin valve

    Science.gov (United States)

    Hossain, Md I.; Maksud, M.; Subramanian, A.; Atulasimha, J.; Bandyopadhyay, S.

    2016-11-01

    The longitudinal magnetoresistance of a copper nanowire contacted by two cobalt contacts shows broad spin-valve peaks at room temperature. However, when the contacts are slightly heated, the peaks change into troughs which are signature of anisotropic magnetoresistance (AMR). Under heating, the differential thermal expansion of the contacts and the substrate generates a small strain in the cobalt contacts which enhances the AMR effect sufficiently to change the peak into a trough. This shows the extreme sensitivity of AMR to strain. The change in the AMR resistivity coefficient due to strain is estimated to be a few m Ω -m/microstrain.

  5. Effective suppression of thermoelectric voltage in nonlocal spin-valve measurement

    Science.gov (United States)

    Ariki, Taisei; Nomura, Tatsuya; Ohnishi, Kohei; Kimura, Takashi

    2017-06-01

    We demonstrate that the background signal in the nonlocal spin-valve measurement can be sufficiently suppressed by optimizing the electrode design of the lateral spin valve. A relatively long length scale of heat propagation produces spin-independent thermoelectric signals under the combination of the Peltier and Seebeck effects. These unfavorable signals can be reduced by mixing the Peltier effects in two transparent ferromagnetic/nonmagnetic junctions. Proper understanding of the contribution from the heat current in no spin-current area is a key for effective reduction of the spin-independent background signal.

  6. Influence of mechanical strain on magnetic characteristics of spin valves

    Science.gov (United States)

    Áč, V.; Anwarzai, B.; Luby, S.; Majkova, E.

    2008-03-01

    Giant magnetoresistance (GMR) of Co and Fe-Co based e-beam evaporated spin valves with Cu and Au spacers was studied. The effect of strain on samples, which is detrimental in standard GMR sensors, was measured in a bending configuration. The different dependences of coercivity Hc and magnetic field Hip in the point of inflection of MR loops vs. strain were found. For sample with Co/Au/Co core, Hc, Hip increase with increasing compressive stress, whereas for sample with FeCo/Cu/Co core they increase with tensile stress. The highest relative change of MR ratio vs. bending in the strain interval ± 300 × 10-6 is 1-2 % of the basic magnetoresistance and, practically, it does not influence the SV output.

  7. Influence of mechanical strain on magnetic characteristics of spin valves

    International Nuclear Information System (INIS)

    Ac, V; Anwarzai, B; Luby, S; Majkova, E

    2008-01-01

    Giant magnetoresistance (GMR) of Co and Fe-Co based e-beam evaporated spin valves with Cu and Au spacers was studied. The effect of strain on samples, which is detrimental in standard GMR sensors, was measured in a bending configuration. The different dependences of coercivity H c and magnetic field H ip in the point of inflection of MR loops vs. strain were found. For sample with Co/Au/Co core, H c , H ip increase with increasing compressive stress, whereas for sample with FeCo/Cu/Co core they increase with tensile stress. The highest relative change of MR ratio vs. bending in the strain interval ± 300 x 10 -6 is 1-2 % of the basic magnetoresistance and, practically, it does not influence the SV output

  8. Aging effect of spin accumulation in non-local spin valves

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Bing; Zhang, Ziyu; Chen, Xiaobing; Zhang, Xiaohan; Pan, Jiahui; Ma, Jiajun; Li, Juan; Wang, Zhicheng [State Key Laboratory for Advanced Metals and Materials, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Wang, Le, E-mail: wangle@ruc.edu.cn [Department of Physics, Renmin University of China, Beijing 100872 (China); Xu, Xiaoguang, E-mail: xgxu@ustb.edu.cn [State Key Laboratory for Advanced Metals and Materials, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Jiang, Yong [State Key Laboratory for Advanced Metals and Materials, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China)

    2017-06-15

    Highlights: • First time to reveal the whole temporal evolution life of spintronics devices. • The gradual oxidation of the junctions’ areas and that of the channel are confirmed to be the predominant factors to determine the temporal evolution. • Physically, the temporal evolution can be evaluated by theories of S. Takahashi and A. Fert. • This study may offer some useful advice for the design and protection of future industrial spintronics devices. - Abstract: A temporal evolution of spin accumulation of Co/MgO/Ag spin valves have been studied by using the nonlocal spin detection technique over almost a 3-month period in the ambient environment after the fabrication of the devices. Three different stages of the spin accumulation are first observed due to aging effect. The aging effect comes from two contributions–the gradual oxidation of the Ag/MgO and MgO/Co interfaces at the junctions’ areas which arises from the annealing process and the oxidation of the side surfaces of the Ag channels. The theories of S. Takahashi and A. Fert are introduced to evaluate the different evolution stages of spin accumulation.

  9. Aging effect of spin accumulation in non-local spin valves

    International Nuclear Information System (INIS)

    Zhao, Bing; Zhang, Ziyu; Chen, Xiaobing; Zhang, Xiaohan; Pan, Jiahui; Ma, Jiajun; Li, Juan; Wang, Zhicheng; Wang, Le; Xu, Xiaoguang; Jiang, Yong

    2017-01-01

    Highlights: • First time to reveal the whole temporal evolution life of spintronics devices. • The gradual oxidation of the junctions’ areas and that of the channel are confirmed to be the predominant factors to determine the temporal evolution. • Physically, the temporal evolution can be evaluated by theories of S. Takahashi and A. Fert. • This study may offer some useful advice for the design and protection of future industrial spintronics devices. - Abstract: A temporal evolution of spin accumulation of Co/MgO/Ag spin valves have been studied by using the nonlocal spin detection technique over almost a 3-month period in the ambient environment after the fabrication of the devices. Three different stages of the spin accumulation are first observed due to aging effect. The aging effect comes from two contributions–the gradual oxidation of the Ag/MgO and MgO/Co interfaces at the junctions’ areas which arises from the annealing process and the oxidation of the side surfaces of the Ag channels. The theories of S. Takahashi and A. Fert are introduced to evaluate the different evolution stages of spin accumulation.

  10. Contact induced spin relaxation in graphene spin valves with Al2O3 and MgO tunnel barriers

    Directory of Open Access Journals (Sweden)

    Walid Amamou

    2016-03-01

    Full Text Available We investigate spin relaxation in graphene by systematically comparing the roles of spin absorption, other contact-induced effects (e.g., fringe fields, and bulk spin relaxation for graphene spin valves with MgO barriers, Al2O3 barriers, and transparent contacts. We obtain effective spin lifetimes by fitting the Hanle spin precession data with two models that include or exclude the effect of spin absorption. Results indicate that additional contact-induced spin relaxation other than spin absorption dominates the contact effect. For tunneling contacts, we find reasonable agreement between the two models with median discrepancy of ∼20% for MgO and ∼10% for Al2O3.

  11. Magnetic transport property of NiFe/WSe2/NiFe spin valve structure

    International Nuclear Information System (INIS)

    Zhao, Kangkang; Xing, Yanhui; Han, Jun; Feng, Jiafeng; Shi, Wenhua; Zhang, Baoshun; Zeng, Zhongming

    2017-01-01

    Highlight: • Two-dimensional (2D) materials have been proposed as promising candidate for spintronic applications due to their atomic crystal structure and physical properties. • In this article, we introduce exfoliated few-layer tungsten diselenide (WSe 2 ) as spacer in a Py/WSe 2 /Py vertical spin valve. • In this junction, the WSe 2 spacer exhibits metallic behavior. • We observed negative magnetoresistance (MR) with a ratio of −1.1% at 4 K and −0.21% at 300 K. • A general phenomenological analysis of the negative MR property is discussed. • Our result is anticipated to be beneficial for future spintronic applications. - Abstract: Two-dimensional (2D) materials have been proposed as promising candidate for spintronic applications due to their atomic crystal structure and physical properties. Here, we introduce exfoliated few-layer tungsten diselenide (WSe 2 ) as spacer in a Py/WSe 2 /Py vertical spin valve. In this junction, the WSe 2 spacer exhibits metallic behavior. We observed negative magnetoresistance (MR) with a ratio of −1.1% at 4 K and −0.21% at 300 K. A general phenomenological analysis of the negative MR property is discussed. Our result is anticipated to be beneficial for future spintronic applications.

  12. Magnetic transport property of NiFe/WSe{sub 2}/NiFe spin valve structure

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Kangkang [Key Lab of Opto-electronics Technology, Ministry of Education, College of Electronic Information and Control Engineering, Beijing University of Technology, Beijing 100124 (China); Key Lab of Nanodevices and Applications, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences (CAS), Suzhou 215123 (China); Xing, Yanhui, E-mail: xingyanhui@bjut.edu.cn [Key Lab of Opto-electronics Technology, Ministry of Education, College of Electronic Information and Control Engineering, Beijing University of Technology, Beijing 100124 (China); Han, Jun [Key Lab of Opto-electronics Technology, Ministry of Education, College of Electronic Information and Control Engineering, Beijing University of Technology, Beijing 100124 (China); Feng, Jiafeng [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences (CAS), Beijing 100190 (China); Shi, Wenhua; Zhang, Baoshun [Key Lab of Nanodevices and Applications, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences (CAS), Suzhou 215123 (China); Zeng, Zhongming, E-mail: zmzeng2012@sinano.ac.cn [Key Lab of Nanodevices and Applications, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences (CAS), Suzhou 215123 (China)

    2017-06-15

    Highlight: • Two-dimensional (2D) materials have been proposed as promising candidate for spintronic applications due to their atomic crystal structure and physical properties. • In this article, we introduce exfoliated few-layer tungsten diselenide (WSe{sub 2}) as spacer in a Py/WSe{sub 2}/Py vertical spin valve. • In this junction, the WSe{sub 2} spacer exhibits metallic behavior. • We observed negative magnetoresistance (MR) with a ratio of −1.1% at 4 K and −0.21% at 300 K. • A general phenomenological analysis of the negative MR property is discussed. • Our result is anticipated to be beneficial for future spintronic applications. - Abstract: Two-dimensional (2D) materials have been proposed as promising candidate for spintronic applications due to their atomic crystal structure and physical properties. Here, we introduce exfoliated few-layer tungsten diselenide (WSe{sub 2}) as spacer in a Py/WSe{sub 2}/Py vertical spin valve. In this junction, the WSe{sub 2} spacer exhibits metallic behavior. We observed negative magnetoresistance (MR) with a ratio of −1.1% at 4 K and −0.21% at 300 K. A general phenomenological analysis of the negative MR property is discussed. Our result is anticipated to be beneficial for future spintronic applications.

  13. Experimental study of the feasibility of a spin valve based on superconductor/ferromagnet proximity effect

    International Nuclear Information System (INIS)

    Garifullin, I. A.; Garif'yanov, N. N.; Salikhov, R. I.; Westerholt, K.; Sprungmann, D.; Zabel, H.; Brucas, R.; Hjoervarsson, B.

    2007-01-01

    The feasibility of a superconducting spin valve based on superconductor/ferromagnet proximity effect is discussed. Experimental results obtained by the authors to date in studies of this problem are presented

  14. Epitaxially grown MnAs /GaAs lateral spin valves

    Science.gov (United States)

    Saha, D.; Holub, M.; Bhattacharya, P.; Liao, Y. C.

    2006-10-01

    The authors report magnetoresistance of lateral spin valves fabricated from an epitaxially grown MnAs /GaAs heterostructure and utilizing a Schottky tunnel barrier for efficient spin injection. A coercive field difference between the two ferromagnetic MnAs contacts is obtained by a difference in aspect ratio. Peak magnetoresistances of 3.6% at 10K and 1.1% at 125K are measured for a 0.5μm channel length spin valve. The authors observe an exponential decay of the peak magnetoresistance with increasing channel length, which is indicative of diffusive spin transport. The magnetoresistance increases with increasing bias and with decreasing temperature. Control experiments have been carried out to confirm the spin-valve effect.

  15. Role of the magnetic anisotropy in organic spin valves

    Directory of Open Access Journals (Sweden)

    V. Kalappattil

    2017-09-01

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

  16. The multi-step tunneling analogue of conductivity mismatch in organic spin valves

    NARCIS (Netherlands)

    Tran, T. Lan Ahn; Le, T.Q.; Sanderink, Johannes G.M.; van der Wiel, Wilfred Gerard; de Jong, Machiel Pieter

    Carbon-based, molecular semiconductors offer several attractive attributes for spintronics, such as exceptionally weak spin-orbit coupling and compatibility with bottom-up nanofabrication. In spite of the promising properties of organic spin valves, however, the physical mechanisms governing

  17. The effect of electrodes on 11 acene molecular spin valve: Semi-empirical study

    Science.gov (United States)

    Aadhityan, A.; Preferencial Kala, C.; John Thiruvadigal, D.

    2017-10-01

    A new revolution in electronics is molecular spintronics, with the contemporary evolution of the two novel disciplines of spintronics and molecular electronics. The key point is the creation of molecular spin valve which consists of a diamagnetic molecule in between two magnetic leads. In this paper, non-equilibrium Green's function (NEGF) combined with Extended Huckel Theory (EHT); a semi-empirical approach is used to analyse the electron transport characteristics of 11 acene molecular spin valve. We examine the spin-dependence transport on 11 acene molecular junction with various semi-infinite electrodes as Iron, Cobalt and Nickel. To analyse the spin-dependence transport properties the left and right electrodes are joined to the central region in parallel and anti-parallel configurations. We computed spin polarised device density of states, projected device density of states of carbon and the electrode element, and transmission of these devices. The results demonstrate that the effect of electrodes modifying the spin-dependence behaviours of these systems in a controlled way. In Parallel and anti-parallel configuration the separation of spin up and spin down is lager in the case of iron electrode than nickel and cobalt electrodes. It shows that iron is the best electrode for 11 acene spin valve device. Our theoretical results are reasonably impressive and trigger our motivation for comprehending the transport properties of these molecular-sized contacts.

  18. Electrical and magnetic properties of nano-oxide added spin valves

    International Nuclear Information System (INIS)

    Li Kebin; Wu Yihong; Han Guchang; Qiu Jinjun; Zheng Yuankai; Guo Zaibing; An Lihua; Luo Ping

    2006-01-01

    The nano-oxide layer (NOL) inside the spin valve can smooth the surface topography, which results in two effects: suppressing the ferromagnetic Neel magnetostatic coupling and enhancing the RKKY exchange coupling between the free layer and the pinned layer. As a consequence, MR ratio is increased in the spin valve with NOL layer inside the pinned layer or on top of the free layer. Because of the enhancement of the specular reflectivity in the NOL added spin valves, the oscillation of the interlayer coupling field with respect to the thickness of the spacer layer and even the thickness of the cap layer has been observed. In terms of the performance of both electrical and magnetic properties of the spin valves, CoFe-O turns out to be the best materials inside the pinned layer. But, as a cap layer, ZnO is the best choice because of its crystalline growth on top of the free layer CoFe, which causes the enhancement of the MR ratio. About 4.5% of MR ratio has been achieved in a NOL added spin valve in the current-perpendicular-to-plane configuration. Large MR ratio observed in the NOL added CPP sensor is due to the increment of the interface scattering and current confined path in the NOL added pinned layer

  19. Dual function armchair graphene nanoribbon-based spin-photodetector: Optical spin-valve and light helicity detector

    Energy Technology Data Exchange (ETDEWEB)

    Ostovari, Fatemeh [Department of Physics, Tarbiat Modares University, P.O. Box 14115-335, Tehran 1411713116 (Iran, Islamic Republic of); Moravvej-Farshi, Mohammad Kazem, E-mail: Farshi-k@modares.ac.ir [Department of Physics, Tarbiat Modares University, P.O. Box 14115-335, Tehran 1411713116 (Iran, Islamic Republic of); Faculty of Electrical and Computer Engineering, Advanced Devices Simulation Lab (ADSL), Tarbiat Modares University, P.O. Box 14115-194, Tehran 1411713116 (Iran, Islamic Republic of)

    2014-08-18

    We show an armchair graphene nanoribbon channel connected between asymmetric ferromagnetic source-drain structure—i.e., p-type Co/Au/graphene source and n-type Co/Cu/graphene drain—can operate as dual function spin-photodetector, under zero external biases at room temperature. It can function as an optical spin-valve with magnetoresistance of greater than 60% and responsivity as high as 25.12 A/mW, when irradiated by an un-polarized light of energy ∼3.03 eV. Under a circularly polarized illumination, this optical spin-valve can also operate as a light helicity detector. The calculated magnetoresistances for right and left circularly polarized lights are both greater than 60%.

  20. Magnetoresistance Effect in NiFe/BP/NiFe Vertical Spin Valve Devices

    Directory of Open Access Journals (Sweden)

    Leilei Xu

    2017-01-01

    Full Text Available Two-dimensional (2D layered materials such as graphene and transition metal dichalcogenides are emerging candidates for spintronic applications. Here, we report magnetoresistance (MR properties of a black phosphorus (BP spin valve devices consisting of thin BP flakes contacted by NiFe ferromagnetic (FM electrodes. The spin valve effect has been observed from room temperature to 4 K, with MR magnitudes of 0.57% at 4 K and 0.23% at 300 K. In addition, the spin valve resistance is found to decrease monotonically as temperature is decreased, indicating that the BP thin film works as a conductive interlayer between the NiFe electrodes.

  1. Evidence for triplet superconductivity in a superconductor-ferromagnet spin valve.

    Science.gov (United States)

    Leksin, P V; Garif'yanov, N N; Garifullin, I A; Fominov, Ya V; Schumann, J; Krupskaya, Y; Kataev, V; Schmidt, O G; Büchner, B

    2012-08-03

    We have studied the dependence of the superconducting (SC) transition temperature on the mutual orientation of magnetizations of Fe1 and Fe2 layers in the spin valve system CoO(x)/Fe1/Cu/Fe2/Pb. We find that this dependence is nonmonotonic when passing from the parallel to the antiparallel case and reveals a distinct minimum near the orthogonal configuration. The analysis of the data in the framework of the SC triplet spin valve theory gives direct evidence for the long-range triplet superconductivity arising due to noncollinearity of the two magnetizations.

  2. A review on organic spintronic materials and devices: II. Magnetoresistance in organic spin valves and spin organic light emitting diodes

    Directory of Open Access Journals (Sweden)

    Rugang Geng

    2016-09-01

    Full Text Available In the preceding review paper, Paper I [Journal of Science: Advanced Materials and Devices 1 (2016 128–140], we showed the major experimental and theoretical studies on the first organic spintronic subject, namely organic magnetoresistance (OMAR in organic light emitting diodes (OLEDs. The topic has recently been of renewed interest as a result of a demonstration of the magneto-conductance (MC that exceeds 1000% at room temperature using a certain type of organic compounds and device operating condition. In this report, we will review two additional organic spintronic devices, namely organic spin valves (OSVs where only spin polarized holes exist to cause magnetoresistance (MR, and spin organic light emitting diodes (spin-OLEDs where both spin polarized holes and electrons are injected into the organic emissive layer to form a magneto-electroluminescence (MEL hysteretic loop. First, we outline the major advances in OSV studies for understanding the underlying physics of the spin transport mechanism in organic semiconductors (OSCs and the spin injection/detection at the organic/ferromagnet interface (spinterface. We also highlight some of outstanding challenges in this promising research field. Second, the first successful demonstration of spin-OLEDs is reviewed. We also discuss challenges to achieve the high performance devices. Finally, we suggest an outlook on the future of organic spintronics by using organic single crystals and aligned polymers for the spin transport layer, and a self-assembled monolayer to achieve more controllability for the spinterface.

  3. High efficiency spin-valve and spin-filter in a doped rhombic graphene quantum dot device

    Science.gov (United States)

    Silva, P. V.; Saraiva-Souza, A.; Maia, D. W.; Souza, F. M.; Filho, A. G. Souza; Meunier, V.; Girão, E. C.

    2018-04-01

    Spin-polarized transport through a rhombic graphene quantum dot (rGQD) attached to armchair graphene nanoribbon (AGNR) electrodes is investigated by means of the Green's function technique combined with single-band tight-binding (TB) approach including a Hubbard-like term. The Hubbard repulsion was included within the mean-field approximation. Compared to anti-ferromagnetic (AFM), we show that the ferromagnetic (FM) ordering of the rGQD corresponds to a smaller bandgap, thus resulting in an efficient spin injector. As a consequence, the electron transport spectrum reveals a spin valve effect, which is controlled by doping with B/N atoms creating a p-n-type junction. The calculations point out that such systems can be used as spin-filter devices with efficiency close to a 100 % .

  4. Interplay of Peltier and Seebeck Effects in Nanoscale Nonlocal Spin Valves

    NARCIS (Netherlands)

    Bakker, F. L.; Slachter, A.; Adam, J-P; van Wees, B. J.

    2010-01-01

    We have experimentally studied the role of thermoelectric effects in nanoscale nonlocal spin valve devices. A finite element thermoelectric model is developed to calculate the generated Seebeck voltages due to Peltier and Joule heating in the devices. By measuring the first, second, and third

  5. Anomalous Nernst and anisotropic magnetoresistive heating in a lateral spin valve

    NARCIS (Netherlands)

    Slachter, Abraham; Bakker, Frank Lennart; van Wees, Bart Jan

    2011-01-01

    We measured the anomalous Nernst effect and anisotropic magnetoresistive heating in a lateral multiterminal permalloy/copper spin valve using all-electrical lock-in measurements. To interpret the results, a threedimensional thermoelectric finite-element model is developed. Using this model, we

  6. FY1995 study of high density near-contact magnetic recording using spin valve head; 1995 nendo spin valve head ni yoru chokomitsudo near contact jiki kiroku no kenkyu

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-03-01

    Development of high performance spin valves formed by amorphous magnetic layer and head-medium interface with nano-thickness molecular film for realizing an ultra-high density of 20 Gbit/in{sup 2} using contact recording. The giant magnetoresistance effect was investigated for spin valves using very thin amorphous magnetic layer. In amorphous-CoFeB/Cu/ Co spin valves, the maximum MR ratio of 6% was achieved at the thickness of the amorphous layer of 2 nm. The spin valves with the amorphous layer exhibit very good thermal stability. Design guideline for molecularly thin lubricant was established using newly derived lubrication equation considering lubricant porosity. Novel method for accurately measuring surface force due to molecularly thin lubricant was developed by using Michelson interferometry to detect cantilever displacement, which enabled two-dimensional transient force measurement. (NEDO)

  7. On the temperature dependence of spin pumping in ferromagnet–topological insulator–ferromagnet spin valves

    Directory of Open Access Journals (Sweden)

    A.A. Baker

    Full Text Available Topological insulators (TIs have a large potential for spintronic devices owing to their spin-polarized, counter-propagating surface states. Recently, we have investigated spin pumping in a ferromagnet–TI–ferromagnet structure at room temperature. Here, we present the temperature-dependent measurement of spin pumping down to 10 K, which shows no variation with temperature. Keywords: Topological insulator, Spin pumping, Spintronics, Ferromagnetic resonance

  8. Nanoscale magnetic characterization of tunneling magnetoresistance spin valve head by electron holography.

    Science.gov (United States)

    Park, Hyun Soon; Hirata, Kei; Yanagisawa, Keiichi; Ishida, Yoichi; Matsuda, Tsuyoshi; Shindo, Daisuke; Tonomura, Akira

    2012-12-07

    Nanostructured magnetic materials play an important role in increasing miniaturized devices. For the studies of their magnetic properties and behaviors, nanoscale imaging of magnetic field is indispensible. Here, using electron holography, the magnetization distribution of a TMR spin valve head of commercial design is investigated without and with a magnetic field applied. Characterized is the magnetic flux distribution in complex hetero-nanostructures by averaging the phase images and separating their component magnetic vectors and electric potentials. The magnetic flux densities of the NiFe (shield and 5 nm-free layers) and the CoPt (20 nm-bias layer) are estimated to be 1.0 T and 0.9 T, respectively. The changes in the magnetization distribution of the shield, bias, and free layers are visualized in situ for an applied field of 14 kOe. This study demonstrates the promise of electron holography for characterizing the magnetic properties of hetero-interfaces, nanostructures, and catalysts. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Gate-tunable large magnetoresistance in an all-semiconductor spin valve device.

    Science.gov (United States)

    Oltscher, M; Eberle, F; Kuczmik, T; Bayer, A; Schuh, D; Bougeard, D; Ciorga, M; Weiss, D

    2017-11-27

    A large spin-dependent and electric field-tunable magnetoresistance of a two-dimensional electron system is a key ingredient for the realization of many novel concepts for spin-based electronic devices. The low magnetoresistance observed during the last few decades in devices with lateral semiconducting transport channels between ferromagnetic source and drain contacts has been the main obstacle for realizing spin field effect transistor proposals. Here, we show both a large two-terminal magnetoresistance in a lateral spin valve device with a two-dimensional channel, with up to 80% resistance change, and tunability of the magnetoresistance by an electric gate. The enhanced magnetoresistance is due to finite electric field effects at the contact interface, which boost spin-to-charge conversion. The gating scheme that we use is based on switching between uni- and bidirectional spin diffusion, without resorting to spin-orbit coupling. Therefore, it can also be employed in materials with low spin-orbit coupling.

  10. Giant tunneling electroresistance effect driven by an electrically controlled spin valve at a complex oxide interface.

    Science.gov (United States)

    Burton, J D; Tsymbal, E Y

    2011-04-15

    A giant tunneling electroresistance effect may be achieved in a ferroelectric tunnel junction by exploiting the magnetoelectric effect at the interface between the ferroelectric barrier and a magnetic La(1-x)Sr(x)MnO3 electrode. Using first-principles density-functional theory we demonstrate that a few magnetic monolayers of La(1-x)Sr(x)MnO3 near the interface act, in response to ferroelectric polarization reversal, as an atomic-scale spin valve by filtering spin-dependent current. This produces more than an order of magnitude change in conductance, and thus constitutes a giant resistive switching effect.

  11. Stretchable Spin Valve with Stable Magnetic Field Sensitivity by Ribbon-Patterned Periodic Wrinkles.

    Science.gov (United States)

    Li, Huihui; Zhan, Qingfeng; Liu, Yiwei; Liu, Luping; Yang, Huali; Zuo, Zhenghu; Shang, Tian; Wang, Baomin; Li, Run-Wei

    2016-04-26

    A strain-relief structure by combining the strain-engineered periodic wrinkles and the parallel ribbons was employed to fabricate flexible dual spin valves onto PDMS substrates in a direct sputtering method. The strain-relief structure can accommodate the biaxial strain accompanying with stretching operation (the uniaxial applied tensile strain and the induced transverse compressive strain due to the Poisson effect), thus significantly reducing the influence of the residual strain on the giant magnetoresistance (GMR) performance. The fabricated GMR dual spin-valve sensor exhibits the nearly unchanged MR ratio of 9.9%, magnetic field sensitivity up to 0.69%/Oe, and zero-field resistance in a wide range of stretching strain, making it promising for applications on a conformal shape or a movement part.

  12. Temperature dependence of magnetoresistive properties in bottom spin valve films employing very thin Cu spacers

    Energy Technology Data Exchange (ETDEWEB)

    Jo, Soonchul [School of Electronic Engineering, Soongsil University, Seoul 156-743 (Korea, Republic of)]. E-mail: jschul@ssu.ac.kr; Seigler, Michael A. [Seagate Research, Pittsburgh, PA 15222 (United States)

    2007-09-15

    Temperature dependence of magnetoresistive properties in bottom spin valve films having very thin Cu spacers are reported. NiFeCr55 A/NiFe10 A/IrMn70 A/CoFetA/Ru4 A/CoFe(t+3)A/Cu/CoFe tA/NiFe10 A/Ta50 A bottom spin valve films were deposited using a DC magnetron sputter deposition system. Magnetoresistance (MR) ratio reached a maximum of 13.5% and 11.9% at the Cu thickness of 10.4 A, when the thickness of the CoFe layers t was 20 and 10 A, respectively. Unlike the top spin valves reported earlier, the dip in the MR ratio was not observed when the interlayer coupling between the free layer and reference layer became zero. Sheet resistance change (DR{sub s}) reached a maximum of 4.22 {omega}/{open_square} at the Cu spacer thickness of 10 A when the CoFe thickness t was 10 A. Temperature dependences of MR ratio, DR{sub s}, interlayer coupling field (H {sub i}), and sensitivity showed mostly monotonic decrease as the temperature was increased up to 200 deg. C. It turns out that DR{sub s} for the film having 10.4 A of Cu spacer thickness at 200 deg. C was larger than the DR{sub s} for the film having 20 A of Cu spacer thickness at 40 deg. C. This suggests a high output voltage of the spin valve sensor made of the thin Cu spacer even at high operating temperature. These very thin Cu spacers could be utilized for very small devices where the interlayer coupling field is dominated by high demagnetizing fields.

  13. Subdynamic Asymptotic Behavior of Microfluidic Valves

    Czech Academy of Sciences Publication Activity Database

    Tesař, Václav; Tippets, J.R.; Allen, R.W.K.; Low, Y.Y.

    2005-01-01

    Roč. 14, č. 2 (2005), s. 335-347 ISSN 1057-7157 Institutional research plan: CEZ:AV0Z20760514 Keywords : low Reynolds number * microfluidics * no-moving-part valves Subject RIV: BK - Fluid Dynamics Impact factor: 3.005, year: 2005

  14. Feedback control of noise in spin valves by the spin-transfer torque

    NARCIS (Netherlands)

    Bandopadyay, S.; Brataas, A.; Bauer, G.E.W.

    2011-01-01

    The miniaturization of magnetic read heads and random access memory elements makes them vulnerable to thermal fluctuations. We demonstrate how current-induced spin-transfer torques can be used to suppress the effects of thermal fluctuations. This enhances the fidelity of perpendicular magnetic spin

  15. Thickness dependence of the triplet spin-valve effect in superconductor–ferromagnet–ferromagnet heterostructures

    Directory of Open Access Journals (Sweden)

    Daniel Lenk

    2016-07-01

    Full Text Available Background: In nanoscale layered S/F1/N/F2/AF heterostructures, the generation of a long-range, odd-in-frequency spin-projection one triplet component of superconductivity, arising at non-collinear alignment of the magnetizations of F1 and F2, exhausts the singlet state. This yields the possibility of a global minimum of the superconducting transition temperature Tc, i.e., a superconducting triplet spin-valve effect, around mutually perpendicular alignment.Results: The superconducting triplet spin valve is realized with S = Nb a singlet superconductor, F1 = Cu41Ni59 and F2 = Co ferromagnetic metals, AF = CoOx an antiferromagnetic oxide, and N = nc-Nb a normal conducting (nc non-magnetic metal, which serves to decouple F1 and F2. The non-collinear alignment of the magnetizations is obtained by applying an external magnetic field parallel to the layers of the heterostructure and exploiting the intrinsic perpendicular easy-axis of the magnetization of the Cu41Ni59 thin film in conjunction with the exchange bias between CoOx and Co. The magnetic configurations are confirmed by superconducting quantum interference device (SQUID magnetic moment measurements. The triplet spin-valve effect has been investigated for different layer thicknesses, dF1, of F1 and was found to decay with increasing dF1. The data is described by an empirical model and, moreover, by calculations using the microscopic theory.Conclusion: The long-range triplet component of superconducting pairing is generated from the singlet component mainly at the N/F2 interface, where the amplitude of the singlet component is suppressed exponentially with increasing distance dF1. The decay length of the empirical model is found to be comparable to twice the electron mean free path of F1 and, thus, to the decay length of the singlet component in F1. Moreover, the obtained data is in qualitative agreement with the microscopic theory, which, however, predicts a (not investigated breakdown of the

  16. Thickness dependence of the triplet spin-valve effect in superconductor-ferromagnet-ferromagnet heterostructures.

    Science.gov (United States)

    Lenk, Daniel; Zdravkov, Vladimir I; Kehrle, Jan-Michael; Obermeier, Günter; Ullrich, Aladin; Morari, Roman; Krug von Nidda, Hans-Albrecht; Müller, Claus; Kupriyanov, Mikhail Yu; Sidorenko, Anatolie S; Horn, Siegfried; Deminov, Rafael G; Tagirov, Lenar R; Tidecks, Reinhard

    2016-01-01

    In nanoscale layered S/F1/N/F2/AF heterostructures, the generation of a long-range, odd-in-frequency spin-projection one triplet component of superconductivity, arising at non-collinear alignment of the magnetizations of F1 and F2, exhausts the singlet state. This yields the possibility of a global minimum of the superconducting transition temperature T c, i.e., a superconducting triplet spin-valve effect, around mutually perpendicular alignment. The superconducting triplet spin valve is realized with S = Nb a singlet superconductor, F1 = Cu41Ni59 and F2 = Co ferromagnetic metals, AF = CoO x an antiferromagnetic oxide, and N = nc-Nb a normal conducting (nc) non-magnetic metal, which serves to decouple F1 and F2. The non-collinear alignment of the magnetizations is obtained by applying an external magnetic field parallel to the layers of the heterostructure and exploiting the intrinsic perpendicular easy-axis of the magnetization of the Cu41Ni59 thin film in conjunction with the exchange bias between CoO x and Co. The magnetic configurations are confirmed by superconducting quantum interference device (SQUID) magnetic moment measurements. The triplet spin-valve effect has been investigated for different layer thicknesses, d F1, of F1 and was found to decay with increasing d F1. The data is described by an empirical model and, moreover, by calculations using the microscopic theory. The long-range triplet component of superconducting pairing is generated from the singlet component mainly at the N/F2 interface, where the amplitude of the singlet component is suppressed exponentially with increasing distance d F1. The decay length of the empirical model is found to be comparable to twice the electron mean free path of F1 and, thus, to the decay length of the singlet component in F1. Moreover, the obtained data is in qualitative agreement with the microscopic theory, which, however, predicts a (not investigated) breakdown of the triplet spin-valve effect for d F1 smaller

  17. Role of the antiferromagnetic pinning layer on spin wave properties in IrMn/NiFe based spin-valves

    Energy Technology Data Exchange (ETDEWEB)

    Gubbiotti, G., E-mail: gubbiotti@fisica.unipg.it; Tacchi, S. [Istituto Officina dei Materiali del CNR (IOM-CNR), Unità di Perugia, I-06123 Perugia (Italy); Del Bianco, L. [Department of Physics and Astronomy, University of Bologna, I-40127 Bologna (Italy); Department of Physics and Earth Sciences and CNISM, University of Ferrara, I-44122 Ferrara (Italy); Bonfiglioli, E.; Giovannini, L.; Spizzo, F.; Zivieri, R. [Department of Physics and Earth Sciences and CNISM, University of Ferrara, I-44122 Ferrara (Italy); Tamisari, M. [Department of Physics and Earth Sciences and CNISM, University of Ferrara, I-44122 Ferrara (Italy); Dipartimento di Fisica e Geologia, Università di Perugia, I-06123 Perugia (Italy)

    2015-05-07

    Brillouin light scattering (BLS) was exploited to study the spin wave properties of spin-valve (SV) type samples basically consisting of two 5 nm-thick NiFe layers (separated by a Cu spacer of 5 nm), differently biased through the interface exchange coupling with an antiferromagnetic IrMn layer. Three samples were investigated: a reference SV sample, without IrMn (reference); one sample with an IrMn underlayer (10 nm thick) coupled to the bottom NiFe film; one sample with IrMn underlayer and overlayer of different thickness (10 nm and 6 nm), coupled to the bottom and top NiFe film, respectively. The exchange coupling with the IrMn, causing the insurgence of the exchange bias effect, allowed the relative orientation of the NiFe magnetization vectors to be controlled by an external magnetic field, as assessed through hysteresis loop measurements by magneto-optic magnetometry. Thus, BLS spectra were acquired by sweeping the magnetic field so as to encompass both the parallel and antiparallel alignment of the NiFe layers. The BLS results, well reproduced by the presented theoretical model, clearly revealed the combined effects on the spin dynamic properties of the dipolar interaction between the two NiFe films and of the interface IrMn/NiFe exchange coupling.

  18. Magnetic scanning gate microscopy of CoFeB lateral spin valve

    Directory of Open Access Journals (Sweden)

    Héctor Corte-León

    2017-05-01

    Full Text Available Devices comprised of CoFeB nanostructures with perpendicular magnetic anisotropy and non-magnetic Ta channel were operated in thermal lateral spin valve (LSV mode and studied by magnetotransport measurements and magnetic scanning gate microscopy (SGM. Due to the short spin diffusion length of Ta, the spin diffusion signal was suppressed, allowing the study of the contribution from the anomalous Nernst (ANE and anomalous Hall effects (AHE. The magnetotransport measurements identified the switching fields of the CoFeB nanostructures and demonstrated a combination of AHE and ANE when the devices were operated in thermally-driven spin-injection mode. Modified scanning probe microscopy probes were fabricated by placing a NdFeB magnetic bead (MB on the apex of a commercial Si probe. The dipole magnetic field distribution around the MB was characterized by using differential phase contrast technique and direct measurement of the switching field induced by the bead in the CoFeB nanodevices. Using SGM we demonstrate the influence of localized magnetic field on the CoFeB nanostructures near the non-magnetic channel. This approach provides a promising route towards the study of thermal and spin diffusion effects using local magnetic fields.

  19. Magnetic scanning gate microscopy of CoFeB lateral spin valve

    Science.gov (United States)

    Corte-León, Héctor; Scarioni, Alexander Fernandez; Mansell, Rhodri; Krzysteczko, Patryk; Cox, David; McGrouther, Damien; McVitie, Stephen; Cowburn, Russell; Schumacher, Hans W.; Antonov, Vladimir; Kazakova, Olga

    2017-05-01

    Devices comprised of CoFeB nanostructures with perpendicular magnetic anisotropy and non-magnetic Ta channel were operated in thermal lateral spin valve (LSV) mode and studied by magnetotransport measurements and magnetic scanning gate microscopy (SGM). Due to the short spin diffusion length of Ta, the spin diffusion signal was suppressed, allowing the study of the contribution from the anomalous Nernst (ANE) and anomalous Hall effects (AHE). The magnetotransport measurements identified the switching fields of the CoFeB nanostructures and demonstrated a combination of AHE and ANE when the devices were operated in thermally-driven spin-injection mode. Modified scanning probe microscopy probes were fabricated by placing a NdFeB magnetic bead (MB) on the apex of a commercial Si probe. The dipole magnetic field distribution around the MB was characterized by using differential phase contrast technique and direct measurement of the switching field induced by the bead in the CoFeB nanodevices. Using SGM we demonstrate the influence of localized magnetic field on the CoFeB nanostructures near the non-magnetic channel. This approach provides a promising route towards the study of thermal and spin diffusion effects using local magnetic fields.

  20. Tunneling Planar Hall Effect in Topological Insulators: Spin Valves and Amplifiers.

    Science.gov (United States)

    Scharf, Benedikt; Matos-Abiague, Alex; Han, Jong E; Hankiewicz, Ewelina M; Žutić, Igor

    2016-10-14

    We investigate tunneling across a single ferromagnetic barrier on the surface of a three-dimensional topological insulator. In the presence of a magnetization component along the bias direction, a tunneling planar Hall conductance (TPHC), transverse to the applied bias, develops. Electrostatic control of the barrier enables a giant Hall angle, with the TPHC exceeding the longitudinal tunneling conductance. By changing the in-plane magnetization direction, it is possible to change the sign of both the longitudinal and transverse differential conductance without opening a gap in the topological surface state. The transport in a topological-insulator-ferromagnet junction can, thus, be drastically altered from a simple spin valve to an amplifier.

  1. Electron-electron interaction, weak localization and spin valve effect in vertical-transport graphene devices

    Energy Technology Data Exchange (ETDEWEB)

    Long, Mingsheng; Gong, Youpin; Wei, Xiangfei; Zhu, Chao; Xu, Jianbao; Liu, Ping; Guo, Yufen; Li, Weiwei; Liu, Liwei, E-mail: lwliu2007@sinano.ac.cn [Key Laboratory of Nanodevices and Applications-CAS and Collaborative Innovation Center of Suzhou Nano Science and Technology, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences (CAS), Suzhou 215123 (China); Liu, Guangtong [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

    2014-04-14

    We fabricated a vertical structure device, in which graphene is sandwiched between two asymmetric ferromagnetic electrodes. The measurements of electron and spin transport were performed across the combined channels containing the vertical and horizontal components. The presence of electron-electron interaction (EEI) was found not only at low temperatures but also at moderate temperatures up to ∼120 K, and EEI dominates over weak localization (WL) with and without applying magnetic fields perpendicular to the sample plane. Moreover, spin valve effect was observed when magnetic filed is swept at the direction parallel to the sample surface. We attribute the EEI and WL surviving at a relatively high temperature to the effective suppress of phonon scattering in the vertical device structure. The findings open a way for studying quantum correlation at relatively high temperature.

  2. Multi-terminal spin valve in a strong Rashba channel exhibiting three resistance states.

    Science.gov (United States)

    Lee, Joo-Hyeon; Kim, Hyung-Jun; Chang, Joonyeon; Han, Suk Hee; Koo, Hyun Cheol; Sayed, Shehrin; Hong, Seokmin; Datta, Supriyo

    2018-02-21

    In a strong spin-orbit interaction system, the existence of three resistance states were observed when two ferromagnetic (FM) contacts were used as current terminals while a separate normal metal contact pair was used as voltage terminals. This result is strikingly different from ordinary spin valve or magnetic tunnel junction devices, which have only two resistance states corresponding to parallel (R P ) and antiparallel (R AP ) alignments of the FM contacts. Our experimental results on a quantum well layer with a strong Rashba effect clearly exhibit unequal antiparallel states, i.e., R AP(1) > R P  > R AP(2) , up to room temperature. The three-states are observed without any degradation when the distance between the non-magnetic voltage probe and the ferromagnetic current probe was increased up to 1.6 mm.

  3. Spin-crossover behavior of polymeric iron(III) complexes

    International Nuclear Information System (INIS)

    Maeda, Yonezo; Miyamoto, Makoto; Takashima, Yoshimasa; Oshio, Hiroaki

    1989-01-01

    Polymeric spin-crossover iron(III) complexes possessing poly(4-vinylpyridine), poly(N-vinylimidazole) or poly(octylmethacrylate-co-4-vinylpyridine) as ligand are prepared. In this experience enriched 57 Fe was used to get strong Moessbauer absorption. The enriched behavior of the complexes were examined by magnetic susceptibilities measurement, and Moessbauer and esr spectroscopies. Some of them show spin-state behavior over a wide range of temperature. Some of them show rapid spin-state interexchange compared to the Moessbauer time scale and others not. Spin-crossover behavior of polymeric complexes is characterized of wide spin-state transition temperature range

  4. Influence of growth conditions on exchange bias of NiMn-based spin valves

    Energy Technology Data Exchange (ETDEWEB)

    Wienecke, Anja; Kruppe, Rahel; Rissing, Lutz [Institute for Microproduction Technology, Leibniz Universität Hannover, 30823 Garbsen (Germany)

    2015-05-07

    As shown in previous investigations, a correlation between a NiMn-based spin valve's thermal stability and its inherent exchange bias exists, even if the blocking temperature of the antiferromagnet is clearly above the heating temperature and the reason for thermal degradation is mainly diffusion and not the loss of exchange bias. Samples with high exchange bias are thermally more stable than samples with low exchange bias. Those structures promoting a high exchange bias are seemingly the same suppressing thermally induced diffusion processes (A. Wienecke and L. Rissing, “Relationship between thermal stability and layer-stack/structure of NiMn-based GMR systems,” in IEEE Transaction on Magnetic Conference (EMSA 2014)). Many investigations were carried out on the influence of the sputtering parameters as well as the layer thickness on the magnetoresistive effect. The influence of these parameters on the exchange bias and the sample's thermal stability, respectively, was hardly taken into account. The investigation described here concentrates on the last named issue. The focus lies on the influence of the sputtering parameters and layer thickness of the “starting layers” in the stack and the layers forming the (synthetic) antiferromagnet. This paper includes a guideline for the evaluated sputtering conditions and layer thicknesses to realize a high exchange bias and presumably good thermal stability for NiMn-based spin valves with a synthetic antiferromagnet.

  5. Ultra-low-pressure sputtering to improve exchange bias and tune linear ranges in spin valves

    Energy Technology Data Exchange (ETDEWEB)

    Tang, XiaoLi, E-mail: tangtang1227@163.com; Yu, You; Liu, Ru; Su, Hua; Zhang, HuaiWu; Zhong, ZhiYong; Jing, YuLan

    2017-05-01

    A series of CoFe/IrMn exchange bilayers was grown by DC-sputtering at different ultra-low argon pressures ranging from 0.008 to 0.1 Pa. This pressure range was one to two orders lower than the normal sputtering pressure. Results revealed that the exchange bias increased from 140 to 250 Oe in CoFe(10 nm)/IrMn (15 nm) bilayers of fixed thickness because of the improved crystalline structure and morphological uniformity of films. Since ferromagnetic /antiferromagnetic (FM/AF) bilayers are always used in linear magnetic sensors as detection layers, the varying exchange bias can successfully achieve tunable linear range in a crossed pinning spin valve. The linear range could be adjustable from −80 Oe – +80 Oe to −150 Oe – +150 Oe on the basis of giant magnetoresistance responses. Therefore, this method provides a simple method to tune the operating range of magnetic field sensors. - Highlights: • Increasing exchange bias was achieved in bilayer at ultra-low-pressure sputtering. • The low void density and smooth surface were achieved in low pressure. • Varying exchange bias achieved tunable linear range in spin valve.

  6. Resistive switching and voltage induced modulation of tunneling magnetoresistance in nanosized perpendicular organic spin valves

    Directory of Open Access Journals (Sweden)

    Robert Göckeritz

    2016-04-01

    Full Text Available Nanoscale multifunctional perpendicular organic spin valves have been fabricated. The devices based on an La0.7Sr0.3MnO3/Alq3/Co trilayer show resistive switching of up to 4-5 orders of magnitude and magnetoresistance as high as -70% the latter even changing sign when voltage pulses are applied. This combination of phenomena is typically observed in multiferroic tunnel junctions where it is attributed to magnetoelectric coupling between a ferromagnet and a ferroelectric material. Modeling indicates that here the switching originates from a modification of the La0.7Sr0.3MnO3 surface. This modification influences the tunneling of charge carriers and thus both the electrical resistance and the tunneling magnetoresistance which occurs at pinholes in the organic layer.

  7. Microbeads detection using Planar Hall effect in spin-valve structure

    International Nuclear Information System (INIS)

    Thanh, N.T.; Kim, K.W.; Kim, C.O.; Shin, K.H.; Kim, C.G.

    2007-01-01

    The Planar Hall effect in a spin-valve structure of Ta/NiFe/CoFe/Cu/CoFe/IrMn/Ta has been applied as a biosensor being capable of detecting Dynabeads ( R) M-280. The patterns with a size of 50x100μm 2 were prepared by lithography methods, and the biosensor performance was tested under the application of a DC magnetic field where the output signals were obtained from a nanovoltmeter. The sensor signal has produced high sensitivity results; especially, the real-time profiles revealed stable and significant signals at external applied magnetic field of around 7.0Oe with the resolution of 0.04 beads per μm 2 . With these results, it could be feasible to detect some commercial Dynabeads ( R) M-280 which can be used for recognition force and biomolecular interaction measurements

  8. Resistive switching and voltage induced modulation of tunneling magnetoresistance in nanosized perpendicular organic spin valves

    Energy Technology Data Exchange (ETDEWEB)

    Göckeritz, Robert; Homonnay, Nico; Müller, Alexander [Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, 06099 Halle (Saale) (Germany); Fuhrmann, Bodo [Interdisziplinäres Zentrum für Materialwissenschaften, Martin-Luther-Universität Halle-Wittenberg, 06099 Halle (Saale) (Germany); Schmidt, Georg, E-mail: georg.schmidt@physik.uni-halle.de [Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, 06099 Halle (Saale) (Germany); Interdisziplinäres Zentrum für Materialwissenschaften, Martin-Luther-Universität Halle-Wittenberg, 06099 Halle (Saale) (Germany)

    2016-04-15

    Nanoscale multifunctional perpendicular organic spin valves have been fabricated. The devices based on an La{sub 0.7}Sr{sub 0.3}MnO{sub 3}/Alq3/Co trilayer show resistive switching of up to 4-5 orders of magnitude and magnetoresistance as high as -70% the latter even changing sign when voltage pulses are applied. This combination of phenomena is typically observed in multiferroic tunnel junctions where it is attributed to magnetoelectric coupling between a ferromagnet and a ferroelectric material. Modeling indicates that here the switching originates from a modification of the La{sub 0.7}Sr{sub 0.3}MnO{sub 3} surface. This modification influences the tunneling of charge carriers and thus both the electrical resistance and the tunneling magnetoresistance which occurs at pinholes in the organic layer.

  9. Measurement of variable magnetic reversal paths in electrically contacted pseudo-spin-valve rings

    International Nuclear Information System (INIS)

    Hayward, T J; Llandro, J; Schackert, F D O; Morecroft, D; Balsod, R B; Bland, J A C; Castano, F J; Ross, C A

    2007-01-01

    In this work we show that the measurement of single magnetic reversal events is of critical importance in order to correctly characterize the switching of magnetic microstructures. Magnetoresistance measurements are performed on two pseudo-spin-valve ring structures with high enough signal to noise to allow the probing of single reversal events. Using this technique we acquire 'switching spectra' which demonstrate that the rings exhibit a range of variable reversal paths, including a bistable reversal mechanism of the hard layer, where the two switching routes have substantially different switching fields. The signature of the variable reversal paths would have been obscured in field cycle averaged data and in the bistable case would cause a fundamental misinterpretation of the reversal behaviour

  10. Effect of the strong coupling on the exchange bias field in IrMn/Py/Ru/Co spin valves

    Science.gov (United States)

    Tarazona, H. S.; Alayo, W.; Landauro, C. V.; Quispe-Marcatoma, J.

    2018-01-01

    The IrMn/Py/Ru/Co (Py = Ni81Fe19) spin valves have been produced by sputtering deposition and analyzed by magnetization measurements and a theoretical modelling of their exchange interactions, based on the macro-spin model. The Ru thickness was grown between 6 and 22 Å, which is small enough to promote strong indirect coupling between Py and Co. Results of measurements showed a large and gradual change in the shape of hysteresis loops when the Ru thickness was varied. The theoretical analysis, using numerical calculations based on the gradient conjugate method, provides the exchange coupling constants (bilinear and biquadratic), the exchange anisotropy fields and the magnetic anisotropy fields (uniaxial and rotatable). The exchange bias fields of spin valves were compared to that of a IrMn/Py bilayer. We found that the difference between these fields oscillates with Ru thickness in the same manner as the bilinear coupling constants.

  11. Spin-valves with modified synthetic antiferromagnets exhibiting an enhanced bias point control capability at submicrometer dimensions

    International Nuclear Information System (INIS)

    Park, J.-S.; Lee, S.-R.; Kim, Y.K.

    2004-01-01

    Bias point control is of practical importance for operating read sensors for magnetic recording and magnetic random access memory devices. To attain bias point control capability, in particular, at submicrometer cell size, a modified synthetic antiferromagnet-based spin-valve (MSSV) structure was devised. A series of calculations were carried out to investigate the effect of size variation on their MR transfer behaviors. The cell dimension was varied from 10 to 0.05 μm. The typical MSSV comprises IrMn (9.0)/CoFe (P1, 1.5)/Ru (0.7)/CoFe (P2, 3.0)/Ru (0.7)/CoFe (P3, 1.5)/Cu (2.8)/CoFe (1.6)/NiFe (3.2) (in nm). As the cell size decreased, the bias point in the MSSV maintained nearly zero regardless of the cell size. The bias point was further tuned by varying the P3 layer thickness. Moreover, the effective exchange field (H ex.eff ) of the MSSV was much larger than that of the conventional SSV. The field sensitivity of the MSSV was very high indicating that the free layer can rotate more sharply

  12. Spin-valves with modified synthetic antiferromagnets exhibiting an enhanced bias point control capability at submicrometer dimensions

    Science.gov (United States)

    Park, Jeong-Suk; Lee, Seong-Rae; Kim, Young Keun

    2004-08-01

    Bias point control is of practical importance for operating read sensors for magnetic recording and magnetic random access memory devices. To attain bias point control capability, in particular, at submicrometer cell size, a modified synthetic antiferromagnet-based spin-valve (MSSV) structure was devised. A series of calculations were carried out to investigate the effect of size variation on their MR transfer behaviors. The cell dimension was varied from 10 to 0.05 μm. The typical MSSV comprises IrMn (9.0)/CoFe (P1, 1.5)/Ru (0.7)/CoFe (P2, 3.0)/Ru (0.7)/CoFe (P3, 1.5)/Cu (2.8)/CoFe (1.6)/NiFe (3.2) (in nm). As the cell size decreased, the bias point in the MSSV maintained nearly zero regardless of the cell size. The bias point was further tuned by varying the P3 layer thickness. Moreover, the effective exchange field ( Hex.eff) of the MSSV was much larger than that of the conventional SSV. The field sensitivity of the MSSV was very high indicating that the free layer can rotate more sharply.

  13. Electric field-induced magnetoresistance in spin-valve/piezoelectric multiferroic laminates for low-power spintronics

    International Nuclear Information System (INIS)

    Huong Giang, D.T.; Thuc, V.N.; Duc, N.H.

    2012-01-01

    Electric field-induced magnetic anisotropy has been realized in the spin-valve-based {Ni 80 Fe 20 /Cu/Fe 50 Co 50 /IrMn}/piezoelectric multiferroic laminates. In this system, electric-field control of magnetization is accomplished by strain mediated magnetoelectric coupling. Practically, the magnetization in the magnetostrictive FeCo layer of the spin-valve structure rotates under an effective compressive stress caused by the inverse piezoelectric effect in external electrical fields. This phenomenon is evidenced by the magnetization and magnetoresistance changes under the electrical field applied across the piezoelectric layer. The result shows great potential for advanced low-power spintronic devices. - Highlights: ► Investigate electric field-induced magnetic anisotropy in spin-valve/piezoelectric. ► Magnetization, magnetoresistance changes under electric field across piezoelectric. ► Magnetization in magnetostrictive FeCo-layer rotates under a compressive stress. ► This advance shows great implications for low-power electronics and spintronics.

  14. Nanostructures based on superconducting Nb and ferromagnetic CuNi alloy for elaboration of spin-valve core

    International Nuclear Information System (INIS)

    Morari, Roman

    2013-01-01

    The main goal of our research group is the elaboration of superconducting spin-switch (valve) based on Ferromagnetic/Superconductor/Ferromagnetic core. We could realize all building blocks necessary for the fabrication of the core structure of the superconducting spin valve, consisting of two mirror symmetric bilayers. In other words, the spin valve consists of a F/S * /F trilayer, which can be regarded as a package of a F/S and S/F bilayer so that S * =2S in the trilayer. For such a trilayer, the theory predicts that the critical temperature depends on the relative orientation of the magnetization of the ferromagnetic layers. To enable a reversal of one of the magnetizations of the layers with respect to the other by an external magnetic field, the coercive forces of the F layers have to be different due to either intrinsic properties or to an antiferromagnetic pinning layer delivering an exchange bias. The main points of our study are presented here. (author)

  15. Thickness dependence of the triplet spin-valve effect in superconductor-ferromagnet heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Lenk, Daniel; Zdravkov, Vladimir I.; Kehrle, Jan; Obermeier, Guenther; Krug von Nidda, Hans-Albrecht; Mueller, Claus; Horn, Siegfried; Tidecks, Reinhard [Institut fuer Physik, Universitaet Augsburg (Germany); Morari, Roman [Institut fuer Physik, Universitaet Augsburg (Germany); D. Ghitsu Institute of Electronic Engineering and Nanotechnologies ASM, Kishinev (Moldova, Republic of); Sidorenko, Anatolie S. [D. Ghitsu Institute of Electronic Engineering and Nanotechnologies ASM, Kishinev (Moldova, Republic of); Tagirov, Lenar [Solid State Physics Department, Kazan Federal University (Russian Federation)

    2015-07-01

    We investigated the triplet spin-valve effect in nanoscale layered S/F{sub 1}/N/F{sub 2}/AF heterostructures with varying F{sub 1}-layer thickness (where S=Nb is a singlet superconducting, F{sub 1}=Cu{sub 41}Ni{sub 59} and F{sub 2}=Co a ferromagnetic, and N a normal-conducting, non-magnetic layer). The theory predicts a long-range, odd-in-frequency triplet component of superconductivity at non-collinear alignment of the magnetizations of F{sub 1} and F{sub 2}. This triplet component exhausts the singlet state and, thus, lowers the superconducting transition temperature, T{sub c}, yielding a global minimum of T{sub c} close to the perpendicular mutual orientations of the magnetizations. We found an oscillating decay of T{sub c} suppression, due to the generation of the triplet component, with increasing F{sub 1} layer thickness, which we discuss in the framework of recent theories.

  16. Investigations of the polymer/magnetic interface of organic spin-valves

    Energy Technology Data Exchange (ETDEWEB)

    Morley, N.A., E-mail: n.a.morley@sheffield.ac.uk [Department of Materials Science and Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD (United Kingdom); Dost, R.; Lingam, A.S.V. [Department of Materials Science and Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD (United Kingdom); Barlow, A.J. [National EPSRC XPS Users’ Service, School of Mechanical and Systems Engineering, Newcastle University, Newcastle upon Tyne NE1 7RU (United Kingdom)

    2015-12-30

    Graphical abstract: - Highlights: • Metal carbide and sulphide species are detected at a polymer–magnetic interface. • Top magnetic electrodes on P3HT have uniaxial anisotropy. • Top magnetic electrodes on PBTTT are isotropic. - Abstract: This work investigates the top interface of an organic spin-valve, to determine the interactions between the polymer and top magnetic electrode. The polymers studied are regio-regular poly(3-hexylthiophene) (RR-P3HT) and poly(2,5-bis(3-hexadecylthiophen-2-yl)thieno[3,2-b]thiophene (PBTTT) and the magnetic top electrodes are NiFe and Fe. X-ray photoelectron spectroscopy (XPS) is used to determine the bonding at the interface, along with the extent of how oxidised the magnetic layers are, while atomic force microscopy (AFM) is used to determine the surface roughness. A magneto-optic Kerr effect (MOKE) magnetometer is used to study the magnetic properties of the top electrode. It is shown that at the organic–magnetic interface the magnetic atoms interact with the polymer, as metallic–sulphide and metallic-carbide species are present at the interface. It is also shown that the structure of the polymer influences the anisotropy of the magnetic electrode, such that the magnetic electrodes grown on RR-P3HT have uniaxial anisotropy, while those grown on PBTTT are isotropic.

  17. Coupling behavior between adhesive and abrasive wear mechanism of aero-hydraulic spool valves

    OpenAIRE

    Chen Yunxia; Gong Wenjun; Kang Rui

    2016-01-01

    Leakage due to wear is one of the main failure modes of aero-hydraulic spool valves. This paper established a practical coupling wear model for aero-hydraulic spool valves based on dynamic system modelling theory. Firstly, the experiment for wear mechanism verification proved that adhesive wear and abrasive wear did coexist during the working process of spool valves. Secondly coupling behavior of each wear mechanism was characterized by analyzing actual time-variation of model parameters duri...

  18. Reversal mode instability and magnetoresistance in perpendicular (Co/Pd)/Cu/(Co/Ni) pseudo-spin-valves

    Science.gov (United States)

    Davies, J. E.; Gilbert, D. A.; Mohseni, S. M.; Dumas, R. K.; Åkerman, J.; Liu, Kai

    2013-07-01

    We have observed distinct temperature-dependent magnetization reversal modes in a perpendicular (Co/Pd)4/Co/Cu/(Co/Ni)4/Co pseudo-spin-valve, which are correlated with spin-transport properties. At 300 K, magnetization reversal occurs by vertically correlated domains. Below 200 K the hysteresis loop becomes bifurcated due to laterally correlated reversal of the individual stacks. The magnetic configuration change also leads to higher spin disorders and a significant increase in the giant magnetoresistance effect. First order reversal curve measurements reveal that the coupled state can be re-established through field cycling and allow direct determination of the interlayer coupling strength as a function of temperature.

  19. Strong spin-filtering and spin-valve effects in a molecular V–C60–V contact

    Directory of Open Access Journals (Sweden)

    Mohammad Koleini

    2012-08-01

    Full Text Available Motivated by the recent achievements in the manipulation of C60 molecules in STM experiments, we study theoretically the structure and electronic properties of a C60 molecule in an STM tunneljunction with a magnetic tip and magnetic adatom on a Cu(111 surface using first-principles calculations. For the case of a vanadium tip/adatom, we demonstrate how spin coupling between the magnetic V atoms, mediated by the C60, can be observed in the electronic transport, which display a strong spin-filtering effect, allowing mainly majority-spin electrons to pass (>95%. Moreover, we find a significant change in the conductance between parallel and anti-parallel spin polarizations in the junction (86% which suggests that STM experiments should be able to characterize the magnetism and spin coupling for these systems.

  20. Strong spin-filtering and spin-valve effects in a molecular V-C-60-V contact

    DEFF Research Database (Denmark)

    Koleini, Mohammad; Brandbyge, Mads

    2012-01-01

    Motivated by the recent achievements in the manipulation of C-60 molecules in STM experiments, we study theoretically the structure and electronic properties of a C-60 molecule in an STM tunneljunction with a magnetic tip and magnetic adatom on a Cu(111) surface using first-principles calculations....... For the case of a vanadium tip/adatom, we demonstrate how spin coupling between the magnetic V atoms, mediated by the C-60, can be observed in the electronic transport, which display a strong spin-filtering effect, allowing mainly majority-spin electrons to pass (>95%). Moreover, we find a significant change...... in the conductance between parallel and anti-parallel spin polarizations in the junction (86%) which suggests that STM experiments should be able to characterize the magnetism and spin coupling for these systems....

  1. Stoner vs. spin-mixing behavior in the bulk magnetism of Gd: A spin ...

    Indian Academy of Sciences (India)

    The temperature dependence of the rare-earth 2-bulk band has been regarded as an exemplary case which realizes the simple Stoner behavior. We examined the evolution of Gd2 bulk bands with temperature in the range 0.5 ≤ /C ≤ 1 with spin-resolved, photoemission spectroscopy. The direct observation of the ...

  2. Effect of uniaxial strain on the tunnel magnetoresistance of T-shaped graphene nanoribbon based spin-valve

    Science.gov (United States)

    Fouladi, A. Ahmadi

    2016-07-01

    We theoretically investigated the spin-dependent transport through a T-shaped graphene nanoribbon (TsGNR) based spin-valve consisting of armchair graphene sandwiched between two semi-infinite ferromagnetic armchair graphene nanoribbon leads in the presence of an applied uniaxial strain. Based on a tight-binding model and standard nonequilibrium Green's function technique, it is demonstrated that the tunnel magnetoresistance (TMR) for the system can be increased about 98% by tuning the uniaxial strain. Our results show that the absolute values of TMR around the zero bias voltage for compressive strain are larger than tensile strain. In addition, the TMR of the system can be nicely controlled by GNR width.

  3. Device properties of the spin-valve transistor and the magnetic tunnel transistor

    NARCIS (Netherlands)

    van 't Erve, O.M.J.

    Spin electronics is a new research area, which not only uses the electron’s charge but also its spin. By using the electron spin dependent properties of magnetic materials one can make devices with a new functionality. This has lead to magnetoresistive devices that can change their resistance by 10

  4. Soft magnetic characteristics of an ultrathin CoFeNi free layer in spin-valve films

    International Nuclear Information System (INIS)

    Fukuzawa, Hideaki; Iwasaki, Hitoshi; Koi, Katsuhiko; Sahashi, Masashi

    2006-01-01

    We have investigated the soft magnetic characteristics of an ultrathin Co-rich CoFeNi free layer in spin-valve films. By addition of Ni to a Co-rich CoFe free layer, magnetostriction (λ) of the films increased positively with Ni concentration, in contrast to which a Co 90 Fe 10 free layer showed a negatively large λ. However, Ni addition also caused an increase in coercivity of the easy axis direction (H c e.a. ). To avoid this problem, a slight decrease in the Co contents of a CoFeNi free layer was found to be effective for decreasing H c e.a. . In order to satisfy both the small λ and H c e.a. , a free layer of (Co 86 Fe 14 ) 88-94 Ni 12-6 proved to be an optimum composition in spin-valve films. Moreover, the zero λ composition of the CoFeNi free layer was changed by a high-conductance Cu layer deposited on the free layer, which was considered to come from the lattice strain of a free layer

  5. Correlations between atomic structure and giant magnetoresistance ratio in Co2(Fe,Mn)Si spin valves

    International Nuclear Information System (INIS)

    Lari, L; Sizeland, J; Gilks, D; Uddin, G M; Nedelkoski, Z; Hasnip, P J; Lazarov, V K; Yoshida, K; Galindo, P L; Sato, J; Oogane, M; Ando, Y; Hirohata, A

    2014-01-01

    We show that the magnetoresistance of Co 2 Fe x Mn 1−x Si-based spin valves, over 70% at low temperature, is directly related to the structural ordering in the electrodes and at the electrodes/spacer (Co 2 Fe x Mn 1−x Si/Ag) interfaces. Aberration-corrected atomic resolution Z-contrast scanning transmission electron microscopy of device structures reveals that annealing at 350 °C and 500 °C creates partial B2/L2 1 and fully L2 1 ordering of electrodes, respectively. Interface structural studies show that the Ag/Co 2 Fe x Mn 1−x Si interface is more ordered compared to the Co 2 Fe x Mn 1−x Si/Ag interface. The release of interface strain is mediated by misfit dislocations that localize the strain around the dislocation cores, and the effect of this strain is assessed by first principles electronic structure calculations. This study suggests that by improving the atomic ordering and strain at the interfaces, further enhancement of the magnetoresistance of CFMS-based current-perpendicular-to-plane spin valves is possible. (fast track communication)

  6. Comment on ''Giant magnetocurrent exceeding 3400% in magnetic tunnel transistors with spin-valve base layers'' [Appl. Phys. Lett. 83, 951

    NARCIS (Netherlands)

    Jansen, R.; van 't Erve, O.M.J.; Postma, F.M.; Lodder, J.C.

    2004-01-01

    In a recent letter,1 it was reported that a magnetic tunnel transistor ~MTT! with a spin-valve base can exhibit high magnetocurrent ~MC! as well as output collector current in the microampere regime. While the presented experimental results are sound and unambiguous, the comparison with the

  7. Superconducting spin valves based on epitaxial Fe/V-hybrid thin film heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Nowak, Gregor

    2010-12-10

    This study presents a systematic investigation of the SSV effect in FM/SC/FM and FM/N/FM/SC heterostructures. Before investigating the actual SSV effect, we first pre-analyzed structural, magnetic and superconducting properties of the Fe/V system. In these preliminary studies we demonstrated, that epitaxial Fe/V heterostructures of superior crystalline quality can be grown by DC sputter deposition. With a Fe/V interface thickness of only one monolayer, the chemical separation of the Fe and V layers is extremely sharp. Moreover, the magnetic investigation showed that from thicknesses of two Fe(001) monolayers on the Fe layers in the superlattice possess a magnetic moment. Furthermore, we demonstrated the interlayer exchange coupling as oscillatory function of the V interlayer thickness. The investigations of the superconducting parameters of the Fe/V system revealed a non-monotonic T{sub S} vs. d{sub Fe} dependence in sample series (1). This observation proves the presence of the FM/SC proximity effect. The studies of various heterostructures of the design AFM/FM/SC/FM revealed a strong counteracting influence on the SSV effect, the stray field effect. The sample containing Fe{sub 25}V{sub 75} alloy layers, has the highest ratio of Cooper pair coherence length and superconductor thickness (ξ{sub S})/(d{sub S}), and its superconducting transition temperature is comparable to the sample with Fe{sub 35}V{sub 65} alloy layers. Nevertheless, the SSV effect in sample Fe{sub 25}V{sub 75} with alloy layers is much smaller than in sample with Fe{sub 35}V{sub 65} alloy layers. For a high-performance superconducting spin valve based on a FM1/SC/FM2 heterostructure at least four parameters have to be optimized simultaneously. 1. The magnetic domain size in FM1 and FM2 has to be as large as possible in order to reduce the stray field effect resulting from magnetization components in the FM domain walls perpendicular to the SC layer. 2. When using ferromagnetic alloys as

  8. A non-invasive thermal drift compensation technique applied to a spin-valve magnetoresistive current sensor.

    Science.gov (United States)

    Sánchez Moreno, Jaime; Ramírez Muñoz, Diego; Cardoso, Susana; Casans Berga, Silvia; Navarro Antón, Asunción Edith; Peixeiro de Freitas, Paulo Jorge

    2011-01-01

    A compensation method for the sensitivity drift of a magnetoresistive (MR) Wheatstone bridge current sensor is proposed. The technique was carried out by placing a ruthenium temperature sensor and the MR sensor to be compensated inside a generalized impedance converter circuit (GIC). No internal modification of the sensor bridge arms is required so that the circuit is capable of compensating practical industrial sensors. The method is based on the temperature modulation of the current supplied to the bridge, which improves previous solutions based on constant current compensation. Experimental results are shown using a microfabricated spin-valve MR current sensor. The temperature compensation has been solved in the interval from 0 °C to 70 °C measuring currents from -10 A to +10 A.

  9. Formation of CCP-NOL in CPP-GMR spin valve structure for the enhancement of magnetoresistance

    International Nuclear Information System (INIS)

    Kang, Y.M.; Isogami, S.; Tsunoda, M.; Takahashi, M.; Yoo, S.I.

    2007-01-01

    For the MR enhancement in current perpendicular to plane-giant magetoresistance spin valve (CPP-GMR SV), a current-confined path-nano-oxide layer (CCP-NOL)-AlO x was formed on the Cu spacer of half SV structure. In order to form effective current-confining paths, an ultra-thin AlO x layer was deposited on a Cu spacer layer by O 2 reactive sputtering of Al with infra-red (IR) heat treatment on the substrate, and that enable to form an island-structured insulating AlO x layer having holes between AlO x islands. By controlling PO 2 and substrate temperature in the NOL deposition, AlO x layer formation without an oxidizing bottom layer could be achieved

  10. A Non-Invasive Thermal Drift Compensation Technique Applied to a Spin-Valve Magnetoresistive Current Sensor

    Directory of Open Access Journals (Sweden)

    Paulo Jorge Peixeiro de Freitas

    2011-02-01

    Full Text Available A compensation method for the sensitivity drift of a magnetoresistive (MR Wheatstone bridge current sensor is proposed. The technique was carried out by placing a ruthenium temperature sensor and the MR sensor to be compensated inside a generalized impedance converter circuit (GIC. No internal modification of the sensor bridge arms is required so that the circuit is capable of compensating practical industrial sensors. The method is based on the temperature modulation of the current supplied to the bridge, which improves previous solutions based on constant current compensation. Experimental results are shown using a microfabricated spin-valve MR current sensor. The temperature compensation has been solved in the interval from 0 °C to 70 °C measuring currents from −10 A to +10 A.

  11. Quantum interference effect in electron tunneling through a quantum-dot-ring spin valve.

    Science.gov (United States)

    Ma, Jing-Min; Zhao, Jia; Zhang, Kai-Cheng; Peng, Ya-Jing; Chi, Feng

    2011-03-28

    Spin-dependent transport through a quantum-dot (QD) ring coupled to ferromagnetic leads with noncollinear magnetizations is studied theoretically. Tunneling current, current spin polarization and tunnel magnetoresistance (TMR) as functions of the bias voltage and the direct coupling strength between the two leads are analyzed by the nonequilibrium Green's function technique. It is shown that the magnitudes of these quantities are sensitive to the relative angle between the leads' magnetic moments and the quantum interference effect originated from the inter-lead coupling. We pay particular attention on the Coulomb blockade regime and find the relative current magnitudes of different magnetization angles can be reversed by tuning the inter-lead coupling strength, resulting in sign change of the TMR. For large enough inter-lead coupling strength, the current spin polarizations for parallel and antiparallel magnetic configurations will approach to unit and zero, respectively.PACS numbers:

  12. Quantum interference effect in electron tunneling through a quantum-dot-ring spin valve

    Directory of Open Access Journals (Sweden)

    Ma Jing-Min

    2011-01-01

    Full Text Available Abstract Spin-dependent transport through a quantum-dot (QD ring coupled to ferromagnetic leads with noncollinear magnetizations is studied theoretically. Tunneling current, current spin polarization and tunnel magnetoresistance (TMR as functions of the bias voltage and the direct coupling strength between the two leads are analyzed by the nonequilibrium Green's function technique. It is shown that the magnitudes of these quantities are sensitive to the relative angle between the leads' magnetic moments and the quantum interference effect originated from the inter-lead coupling. We pay particular attention on the Coulomb blockade regime and find the relative current magnitudes of different magnetization angles can be reversed by tuning the inter-lead coupling strength, resulting in sign change of the TMR. For large enough inter-lead coupling strength, the current spin polarizations for parallel and antiparallel magnetic configurations will approach to unit and zero, respectively. PACS numbers:

  13. Behavior of lyophilized biological valves in a chronic animal model.

    Science.gov (United States)

    Maizato, Marina J S; Taniguchi, Fabio P; Ambar, Rafael F; Pitombo, Ronaldo N M; Leirner, Adolfo A; Cestari, Idágene A; Stolf, Noedir A G

    2013-11-01

    Glutaraldehyde is used in order to improve the mechanical and immunogenic properties of biological tissues, such as bovine pericardium membranes, used to manufacture heart valve bioprostheses. Lyophilization, also known as freeze-drying, preserves biological material without damage by freezing the water content and removing ice by sublimation. Through this process, dehydrated products of high quality may be obtained; also, the material may be easily handled. The lyophilization process reduces aldehyde residues in biological tissue previously treated with glutaraldehyde, thus promoting reduction of cytotoxicity, increasing resistance to inflammation, and possibly decreasing the potential for tissue calcification. The objective of this study was to chronically evaluate the calcification of bovine pericardium heart valve prostheses, previously lyophilized or not, in an animal model. Six-month-old sheep received implants of lyophilized and unlyophilized heart valve prostheses in the pulmonary position with right bypass. The study followed 16 animals for a period of 90 days. Right ventricle-pulmonary artery (RV/PA) transvalvular pressure gradient was evaluated before and immediately after implantation and before explantation, as were tissue calcium, inflammation intensity, and thrombosis and pannus formation. The t-test was used for statistical analysis. Twelve animals survived to the end of the experiment, but one of the animals in the control group had endocarditis and was excluded from the data. Four animals died early. The mean RV/PA gradient on implantation was 2.0 ± 1.6 mm Hg in the control group and 6.2 ± 4.1 mm Hg in the lyophilized group (P = 0.064). This mean gradient increased at explantation to 7.7 ± 3.9 mm Hg and 8.6 ± 5.8 mm Hg, respectively (P = 0.777). The average calcium content in the tissue leaflets after 3 months was 21.6 ± 39.1 mg Ca(2+)/g dry weight in the control group, compared with an average content of 41.2 ± 46.9 mg Ca(2+)/g dry weight

  14. Universal Behavior of Spin Dipolar Relaxation in Atomic Condensates

    Science.gov (United States)

    Deng, Yuangang; Zhou, Yiquan; Deng, Min; Liu, Qi; Tey, Mengkhoon; Gao, Bo; You, Li

    2017-04-01

    The dipolar relaxation of atomic spinor condensates is studied in terms of the semi-analytical scattering wave functions by utilizing the quantum-defect theory. At nonzero magnetic fields, inelastic dipolar relaxation of exothermic reaction leads to loss of the atomic population. By tuning the bias field, we find that the dipolar relaxation rate exhibits a universal behavior involving a unique dip and peak structure, different from the commonly referenced result based on the Born or the distortedwave Born approximations. The positions for the dip and the peak are shown to be determined dominantly by the short-range s-wave scattering length and the Van der Waals radius, independent of the dipolar interaction strength of ultracold atoms. This is confirmed by the precision measured dipolar relaxation decay rate for both spin-polarized atomic coherent spin states and twin-Fock states of F = 1 87 Rb BoseEinstein condensates. We observe the dipolar relaxation suppression as predicted by our theory for the large bias field, a feature not previously studied experimentally. Our results implicate the possibility of extracting the short-range scattering length and the Van der Waals dispersion coefficient from spin dipolar decay measurements.

  15. Spin valve-like magnetic tunnel diode exhibiting giant positive junction magnetoresistance at low temperature in Co2MnSi/SiO2/p-Si heterostructure

    Science.gov (United States)

    Maji, Nilay; Kar, Uddipta; Nath, T. K.

    2018-02-01

    The rectifying magnetic tunnel diode has been fabricated by growing Co2MnSi (CMS) Heusler alloy film carefully on a properly cleaned p-Si (100) substrate with the help of electron beam physical vapor deposition technique and its structural, electrical and magnetic properties have been experimentally investigated in details. The electronic- and magneto-transport properties at various isothermal conditions have been studied in the temperature regime of 78-300 K. The current-voltage ( I- V) characteristics of the junction show an excellent rectifying magnetic tunnel diode-like behavior throughout that temperature regime. The current ( I) across the junction has been found to decrease with the application of a magnetic field parallel to the plane of the CMS film clearly indicating positive junction magnetoresistance (JMR) of the heterostructure. When forward dc bias is applied to the heterostructure, the I- V characteristics are highly influenced on turning on the field B = 0.5 T at 78 K, and the forward current reduces abruptly (99.2% current reduction at 3 V) which is nearly equal to the order of the magnitude of the current observed in the reverse bias. Hence, our Co2MnSi/SiO2/p-Si heterostructure can perform in off ( I off)/on ( I on) states with the application of non-zero/zero magnetic field like a spin valve at low temperature (78 K).

  16. Magnetotransport in spin-valve systems with amorphous magnetic and superconducting partial layers; Magnetotransport in Spinventil-Systemen mit amorphen magnetischen und supraleitenden Teilschichten

    Energy Technology Data Exchange (ETDEWEB)

    Steiner, Roland Johannes

    2006-04-27

    The first part of this work deals with the fabrication and characterisation of spin valves with an amorphous FeB layer acting as a weak ferromagnet embedded into the structure. In the second part of this work ferromagnet/superconductor hybrid structures are fabricated and the relevant magnetic field dependent transport phenomena are analyzed. The interlayer of a conventional spin valve was replaced by a superconducting niobium layer. Small applied fields close to the coercivity field of the involved ferromagnets - and thus far below the critical magnetic field of the superconductor - affected the critical temperature of the niobium layer. Measurements of the field dependent resistance and the critical temperature of a FM/SC/FMsystem showed a local maximum in the T{sub c}(H)- and the R(H)-curve. (orig.)

  17. Spin valve heterostructures built using the shadowing effect: Setting NiFe and Co magnetization directions for non-collinear couplings

    Science.gov (United States)

    Krohling, A. C.; Bueno, T. E. P.; Nascimento, V. P.; Larica, C.; Krambrock, K.; Menzel, D.; Litterst, F. J.; Passamani, E. C.

    2017-12-01

    An experimental method was developed to set the magnetization direction in ferromagnetic layers of Si(100)/Cu/NiFe/Cu/Co/IrMn/Cu morphologically modified spin valves. Large uniaxial anisotropies emerged in the NiFe and Co layers due to modifications of their morphologies induced by the shadowing effect that arises from oblique depositions. Therefore, we set the uniaxial anisotropy axes in pre-set directions by controlling the sputtered beam direction relative to the sample reference. We were able to tune the angle between the magnetization directions of the NiFe and Co layers in a continuous interval from 0° to 90° due to the interplay between the Co and NiFe uniaxial anisotropies and the unidirectional anisotropy at the Co/IrMn interface. This type of non-collinear coupling cannot be found in conventional spin valve devices with passive spacers through which the coupling is governed by bilinear and biquadratic couplings. The methodology of preparation proposed here allows an extra control over the magnetism of the spin valves, which can be promising for technological applications.

  18. Significant manipulation of output performance of a bridge-structured spin valve magnetoresistance sensor via an electric field

    Science.gov (United States)

    Zhang, Yue; Yan, Baiqian; Ou-Yang, Jun; Wang, Xianghao; Zhu, Benpeng; Chen, Shi; Yang, Xiaofei

    2016-01-01

    Through principles of spin-valve giant magnetoresistance (SV-GMR) effect and its application in magnetic sensors, we have investigated electric-field control of the output performance of a bridge-structured Co/Cu/NiFe/IrMn SV-GMR sensor on a PZN-PT piezoelectric substrate using the micro-magnetic simulation. We centered on the influence of the variation of uniaxial magnetic anisotropy constant (K) of Co on the output of the bridge, and K was manipulated via the stress of Co, which is generated from the strain of a piezoelectric substrate under an electric field. The results indicate that when K varies between 2 × 104 J/m3 and 10 × 104 J/m3, the output performance can be significantly manipulated: The linear range alters from between -330 Oe and 330 Oe to between -650 Oe and 650 Oe, and the sensitivity is tuned by almost 7 times, making it possible to measure magnetic fields with very different ranges. According to the converse piezoelectric effect, we have found that this variation of K can be realized by applying an electric field with the magnitude of about 2-20 kV/cm on a PZN-PT piezoelectric substrate, which is realistic in application. This result means that electric-control of SV-GMR effect has potential application in developing SV-GMR sensors with improved performance.

  19. A spin-valve-like magnetoresistance of an antiferromagnet-based tunnel junction

    Czech Academy of Sciences Publication Activity Database

    Park, B.G.; Wunderlich, Joerg; Martí, X.; Holý, V.; Kurosaki, Y.; Yamada, M.; Yamamoto, H.; Nishide, A.; Hayakawa, J.; Takahashi, H.; Shick, Alexander; Jungwirth, Tomáš

    2011-01-01

    Roč. 10, č. 5 (2011), s. 347-351 ISSN 1476-1122 R&D Projects: GA AV ČR KAN400100652; GA MŠk LC510; GA MŠk(CZ) 7E08087 EU Projects: European Commission(XE) 268066 - 0MSPIN; European Commission(XE) 214499 - NAMASTE; European Commission(XE) 215368 - SemiSpinNet Grant - others:AV ČR(CZ) AP0801 Program:Akademická prémie - Praemium Academiae Institutional research plan: CEZ:AV0Z10100521; CEZ:AV0Z10100520 Keywords : spintronics * antiferromagnets Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 32.841, year: 2011

  20. Biomechanical Behavior of Bioprosthetic Heart Valve Heterograft Tissues: Characterization, Simulation, and Performance

    Science.gov (United States)

    Soares, Joao S.; Feaver, Kristen R.; Zhang, Will; Kamensky, David; Aggarwal, Ankush; Sacks, Michael S.

    2017-01-01

    The use of replacement heart valves continues to grow due to the increased prevalence of valvular heart disease resulting from an ageing population. Since bioprosthetic heart valves (BHVs) continue to be the preferred replacement valve, there continues to be a strong need to develop better and more reliable BHVs through and improved the general understanding of BHV failure mechanisms. The major technological hurdle for the lifespan of the BHV implant continues to be the durability of the constituent leaflet biomaterials, which if improved can lead to substantial clinical impact. In order to develop improved solutions for BHV biomaterials, it is critical to have a better understanding of the inherent biomechanical behaviors of the leaflet biomaterials, including chemical treatment technologies, the impact of repetitive mechanical loading, and the inherent failure modes. This review seeks to provide a comprehensive overview of these issues, with a focus on developing insight on the mechanisms of BHV function and failure. Additionally, this review provides a detailed summary of the computational biomechanical simulations that have been used to inform and develop a higher level of understanding of BHV tissues and their failure modes. Collectively, this information should serve as a tool not only to infer reliable and dependable prosthesis function, but also to instigate and facilitate the design of future bioprosthetic valves and clinically impact cardiology. PMID:27507280

  1. Valve-like behavior of the magnetoimpedance in the GHz range

    International Nuclear Information System (INIS)

    Sandacci, S.I.; Makhnovskiy, D.P.; Panina, L.V.

    2004-01-01

    High-frequency modification in magneto-impedance (MI) characteristics in the frequency range of 0.5-3 GHz has been investigated in 10 μm diameter amorphous microwires with a circumferential anisotropy. As frequency is increased, the peaks in the MI behavior observed at the anisotropy field reduce and become less sharp, disappearing completely at frequencies higher than 1.6 GHz. This 'valve-like' behavior can be explained by considering the dispersion properties of the effective permeability of the AC linear response combined with the rotational DC magnetization

  2. Chemical properties and GMR improvement of specular spin valves with nano-oxide layers, formed in ambient mixed gases

    International Nuclear Information System (INIS)

    Quang, H D; Hien, N T; Oh, S K; Sinh, N H; Yu, S C

    2004-01-01

    Specular spin valves (SVs) containing nano-oxide layers (NOLs) structured as substrate/seed/AF/P 1 /NOL/P 2 /Cu/F/NOL, have been fabricated. The NOLs were formed by natural oxidation in different ambient atmospheres of pure oxygen, oxygen/nitrogen and oxygen/argon gas mixtures. The fabrication conditions were optimized to enhance the magnetoresistance (MR) ratio, to suppress the interlayer coupling fields (H f ) between the free and pinned layers, to suppress the high interface density of the NOL, to ease the control of the NOL thickness and to form a smooth NOL/P 2 interface for promoting specular electron scattering. The characteristics of our specular SVs are the MR ratio of 14.1%, the exchange bias field of 44-45 mT, and H f weaker than 1.0 mT. The optimal conditions for oxidation time, total oxidation pressure and the annealing temperature were found to be 300 s, 0.14 Pa (oxygen/argon = 80/20) and 250 deg. C, respectively. Also, the origin of thermal stability of MMn-based (M = Fe, Pt, Ir, etc) specular SVs has been explained in detail by chemical properties of NOL using secondary-ion mass spectroscopy and x-ray photoelectron spectroscopy depth profile analyses. Thermal stability turns out to be caused by a decrease in MR ratios at high temperatures (>250 deg. C), which is a serious problem for device applications using the SV structure as a high density read head device

  3. Significant manipulation of output performance of a bridge-structured spin valve magnetoresistance sensor via an electric field

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yue; Yan, Baiqian; Ou-Yang, Jun; Zhu, Benpeng; Chen, Shi; Yang, Xiaofei, E-mail: hust-yangxiaofei@163.com [School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074 (China); Wang, Xianghao [School of Information Engineering, Wuhan University of Technology, Wuhan 430070 (China)

    2016-01-28

    Through principles of spin-valve giant magnetoresistance (SV-GMR) effect and its application in magnetic sensors, we have investigated electric-field control of the output performance of a bridge-structured Co/Cu/NiFe/IrMn SV-GMR sensor on a PZN-PT piezoelectric substrate using the micro-magnetic simulation. We centered on the influence of the variation of uniaxial magnetic anisotropy constant (K) of Co on the output of the bridge, and K was manipulated via the stress of Co, which is generated from the strain of a piezoelectric substrate under an electric field. The results indicate that when K varies between 2 × 10{sup 4 }J/m{sup 3} and 10 × 10{sup 4 }J/m{sup 3}, the output performance can be significantly manipulated: The linear range alters from between −330 Oe and 330 Oe to between −650 Oe and 650 Oe, and the sensitivity is tuned by almost 7 times, making it possible to measure magnetic fields with very different ranges. According to the converse piezoelectric effect, we have found that this variation of K can be realized by applying an electric field with the magnitude of about 2–20 kV/cm on a PZN-PT piezoelectric substrate, which is realistic in application. This result means that electric-control of SV-GMR effect has potential application in developing SV-GMR sensors with improved performance.

  4. Significant manipulation of output performance of a bridge-structured spin valve magnetoresistance sensor via an electric field

    International Nuclear Information System (INIS)

    Zhang, Yue; Yan, Baiqian; Ou-Yang, Jun; Zhu, Benpeng; Chen, Shi; Yang, Xiaofei; Wang, Xianghao

    2016-01-01

    Through principles of spin-valve giant magnetoresistance (SV-GMR) effect and its application in magnetic sensors, we have investigated electric-field control of the output performance of a bridge-structured Co/Cu/NiFe/IrMn SV-GMR sensor on a PZN-PT piezoelectric substrate using the micro-magnetic simulation. We centered on the influence of the variation of uniaxial magnetic anisotropy constant (K) of Co on the output of the bridge, and K was manipulated via the stress of Co, which is generated from the strain of a piezoelectric substrate under an electric field. The results indicate that when K varies between 2 × 10 4  J/m 3 and 10 × 10 4  J/m 3 , the output performance can be significantly manipulated: The linear range alters from between −330 Oe and 330 Oe to between −650 Oe and 650 Oe, and the sensitivity is tuned by almost 7 times, making it possible to measure magnetic fields with very different ranges. According to the converse piezoelectric effect, we have found that this variation of K can be realized by applying an electric field with the magnitude of about 2–20 kV/cm on a PZN-PT piezoelectric substrate, which is realistic in application. This result means that electric-control of SV-GMR effect has potential application in developing SV-GMR sensors with improved performance

  5. Tissue engineered aortic valve

    OpenAIRE

    Dohmen, P M

    2012-01-01

    Several prostheses are available to replace degenerative diseased aortic valves with unique advantages and disadvantages. Bioprotheses show excellent hemodynamic behavior and low risk of thromboembolic complications, but are limited by tissue deterioration. Mechanical heart valves have extended durability, but permanent anticoagulation is mandatory. Tissue engineering created a new generation heart valve, which overcome limitations of biological and mechanical heart valves due to remodelling,...

  6. Engineered spin-valve type magnetoresistance in Fe$_3$O$_4$-CoFe$_2$O$_4$ core-shell nanoparticles

    OpenAIRE

    Kumar, P. Anil; Ray, Sugata; Chakraverty, S.; Sarma, D. D.

    2013-01-01

    Naturally occurring spin-valve-type magnetoresistance (SVMR), recently observed in Sr2FeMoO6 samples, suggests the possibility of decoupling the maximal resistance from the coercivity of the sample. Here we present the evidence that SVMR can be engineered in specifically designed and fabricated core-shell nanoparticle systems, realized here in terms of soft magnetic Fe3O4 as the core and hard magnetic insulator CoFe2O4 as the shell materials. We show that this provides a magnetically switchab...

  7. Giant magnetoresistance effect in CoZr/Cu/Co spin-valve films (abstract)

    Energy Technology Data Exchange (ETDEWEB)

    Ben-Youssef, J. [CNRS-LMIMS, 92195 Meudon-Bellevue (France)]|[LPM Universite Mohammed V, Rabat (Morocco); Koshkina, O.; Le Gall, H. [CNRS-LMIMS, 92195 Meudon-Bellevue (France); Harfaoui, M.E. [LPMC Universite Ibn Tofail Kenitra (Morocco); Bouziane, K. [CNRS-LMIMS, 92195 Meudon-Bellevue (France); Yamani, M.E. [LPM Universite Mohammed V, Rabat (Morocco); Desvignes, J.M. [CNRS-LMIMS, 92195 Meudon-Bellevue (France)

    1997-04-01

    A high sensitivity of giant magnetoresistance (GMR) has been observed recently from soft magnetic layers such as NiFe, NiFeCo, and FeCoB. Amorphous CoZr alloys present ultrasoft properties compared to NiFe. GMR has been investigated for amorphous CoZr/Cu/Co thin films grown by rf diode sputtering using a target consisting of a Co disk partially covered with a Zr foil. The influence of the argon pressure on Cu layer deposition, Cu thickness, and Zr content on magnetic and transport properties was analyzed. The highest value of transverse GMR obtained along the easy axis is 3.6{percent} and the MR curve was saturated in a magnetic field of 100 Oe at room temperature. GMR shows scaling behavior with the sample composition. Very high sensitivity, around 1{endash}2{percent}/Oe was observed in a CoZr (3 nm)/Cu (3 nm)/Co (2 nm) sandwich. This study shows a large dependence of GMR on Cu thickness and the maximum of magnetoresistance strongly depending on the Ar pressure which modifies the interface roughness. The Zr content also influences the magnetotransport properties ({Delta}R/R and {Delta}R/R{Delta}H). The difference in coercivity between soft magnetic CoZr and hard magnetic Co layers induces antiferromagnetic alignment. Therefore a high MR ratio and field sensitivity are achieved by improving the magnetic properties of the CoZr layer.{copyright} {ital 1997 American Institute of Physics.}

  8. Valve-gaping behavior of raft-cultivated mussels in the Ría de Arousa, Spain

    Directory of Open Access Journals (Sweden)

    Luc A. Comeau

    2018-02-01

    Full Text Available We describe the valve-opening behavior of raft-cultivated mussels (Mytilus galloprovincialis in the Ría de Arousa (Arousa estuary, Spain. Eight rope-grown mussels [mean ± standard error (SEM, shell length 61.6 ± 2.1 mm] were connected to a non-invasive valvometry apparatus that monitored (one measurement min−1 the magnitude of valve openness systematically over a 10 day period. It was found that valves were open 97.5 ± 1.3% percent of the time. Valve closures were not synchronized among the eight monitored mussels, suggesting that feeding cessation was physiologically-regulated rather than environmentally-mediated. The opening amplitudes that were most frequently observed were in the range of 60–90%, indicating that, when open, valves are usually opened relatively close to their maximum possible extent. The majority (7/8 of mussels displayed a circadian rhythm (τ = 24.0 h in valve opening amplitude. They tended to exhibit maximum valve opening during nighttime and minimum opening during daytime. It is possible that the light:dark cycle represents an environmental zeitgeber entraining an endogenous gaping rhythm in this bivalve.

  9. In vivo behavior of epoxy-crosslinked porcine heart valve cusps and walls

    NARCIS (Netherlands)

    van Wachem, Pauline B.; Brouwer, Linda A.; Zeeman, R.; Dijkstra, Pieter J.; Feijen, Jan; Hendriks, Marc; Cahalan, Patrick T.; van Luyn, Marja J.A.

    2000-01-01

    Calcification limits the long-term durability of xenograft glutaraldehyde-crosslinked heart valves. In this study, epoxy-crosslinked porcine aortic valve tissue was evaluated after subcutaneous implantation in weanling rats. Non-crosslinked valves and valves crosslinked with glutaraldehyde or

  10. In vivo behavior of epoxy-crosslinked porcine heart valve cusps and walls

    NARCIS (Netherlands)

    van Wachem, PB; Brouwer, LA; Zeeman, R; Dijkstra, PJ; Feijen, J; Hendriks, M; Cahalan, PT; van Luyn, MJA

    Calcification limits the long-term durability of xenograft glutaraldehyde-crosslinked heart valves. In this study, epoxy-crosslinked porcine aortic valve tissue was evaluated after subcutaneous implantation in weanling rats, Non-crosslinked valves and valves crosslinked with glutaraldehyde or

  11. Influence of awareness of the Japanese Food Guide Spinning Top on eating behavior and obesity.

    Science.gov (United States)

    Takaizumi, Kanae; Harada, Kazuhiro; Shibata, Ai; Nakamura, Yoshio

    2011-01-01

    The purpose of the present study was to investigate the influence of awareness of the Japanese Food Guide Spinning Top on eating behavior and obesity in Japan. Participants were 1,558 Japanese male and female adults (40.2±12.2 years) who had been registered with a social research company. The cross-sectional questionnaire survey was conducted via the Internet in November 2007. Potential respondents were invited to complete the survey via e-mail, which contained a link to the survey Uniform Resource Locator (URL). The measures were awareness of the Japanese Food Guide Spinning Top, eating knowledge scores, eating attitude scores, and eating behaviors scores, according to the recommendations of the Health Japan 21 and the Food Balance Guide Spinning Top. Obesity was assessed by self-reported body mass index (BMI) and waist circumference. The relationships between awareness of the Japanese Food Guide Spinning Top, eating knowledge scores, eating attitude scores, eating behavior scores, and obesity were analyzed using path analysis. Path analysis revealed that awareness of the Japanese Food Guide Spinning Top was associated with BMI and waist circumference via eating behavior scores. In addition, eating knowledge scores and eating attitude scores were mediators of the association between awareness of the Japanese Food Guide Spinning Top and eating behavior scores. These results suggest that promotion of the Japanese Food Guide Spinning Top would be a useful strategy to encourage healthy eating and prevent obesity in the Japanese population.

  12. SPIN90 Modulates Long-Term Depression and Behavioral Flexibility in the Hippocampus

    Directory of Open Access Journals (Sweden)

    Dae Hwan Kim

    2017-09-01

    Full Text Available The importance of actin-binding proteins (ABPs in the regulation of synapse morphology and plasticity has been well established. SH3 protein interacting with Nck, 90 kDa (SPIN90, an Nck-interacting protein highly expressed in synapses, is essential for actin remodeling and dendritic spine morphology. Synaptic targeting of SPIN90 to spine heads or dendritic shafts depends on its phosphorylation state, leading to blockage of cofilin-mediated actin depolymerization and spine shrinkage. However, the physiological role of SPIN90 in long-term plasticity, learning and memory are largely unknown. In this study, we demonstrate that Spin90-knockout (KO mice exhibit substantial deficits in synaptic plasticity and behavioral flexibility. We found that loss of SPIN90 disrupted dendritic spine density in CA1 neurons of the hippocampus and significantly impaired long-term depression (LTD, leaving basal synaptic transmission and long-term potentiation (LTP intact. These impairments were due in part to deficits in AMPA receptor endocytosis and its pre-requisites, GluA1 dephosphorylation and postsynaptic density (PSD 95 phosphorylation, but also by an intrinsic activation of Akt-GSK3β signaling as a result of Spin90-KO. In accordance with these defects, mice lacking SPIN90 were found to carry significant deficits in object-recognition and behavioral flexibility, while learning ability was largely unaffected. Collectively, these findings demonstrate a novel modulatory role for SPIN90 in hippocampal LTD and behavioral flexibility.

  13. The Effectiveness of Cognitive-Behavioral Therapy (CBT in Reducing Worry, Anxiety and Panic Attacks Mitral Valve Prolapse Patients

    Directory of Open Access Journals (Sweden)

    AR Jamshidzehi ShahBakhsh

    2016-07-01

    Full Text Available Introduction: The mitral valve prolapse is a heart syndrome that is characterized by considerable physical and psychological consequences for affected patients. This study aimed to assess the efficacy of cognitive-behavioral therapy in reducing worrying, generalized anxiety and panic attacks in patients with mitral valve prolapse. Methods: This study is quasi-experimental research with pretest-posttest and control group. 16 patients with mitral valve prolapse divided into to two groups: experimental (n = 8 and control (n = 8 groups. CBT was used during 10 sessions twice a week with a focus on cognitive restructuring, modification of cognitive distortions and training of behavioral techniques for the experimental group. For participants health  concerns spot and doush (HCQ, Generalized anxiety disorder (GAD- 7 and Albania panic scales as pre-test, post-test. Results: Data were analyzed by covariance analysis. The results showed that worrying, anxiety, and panic attacks significantly reduced in the experimental group. Discussion: Cognitive behavioral therapy is remarkably effective for reducing fear, anxiety and panic patients with mitral valve prolapse. Therefore, it is recommended for the patients with mitral valve prolapse that cognitive behavioral therapy can be used as a complementary therapy.

  14. Spin mediated magneto-electro-thermal transport behavior in Ni80Fe20/MgO/p-Si thin films

    Science.gov (United States)

    Lou, P. C.; Beyermann, W. P.; Kumar, S.

    2017-09-01

    In Si, the spin-phonon interaction is the primary spin relaxation mechanism. At low temperatures, the absence of spin-phonon relaxation will lead to enhanced spin accumulation. Spin accumulation may change the electro-thermal transport within the material, and thus may serve as an investigative tool for characterizing spin-mediated behavior. Here, we present the first experimental proof of spin accumulation induced electro-thermal transport behavior in a Pd (1 nm)/Ni80Fe20 (25 nm)/MgO (1 nm)/p-Si (2 μm) specimen. The spin accumulation originates from the spin-Hall effect. The spin accumulation changes the phononic thermal transport in p-Si causing the observed magneto-electro-thermal transport behavior. We also observe the inverted switching behavior in magnetoresistance measurement at low temperatures in contrast to magnetic characterization, which is attributed to the canted spin states in p-Si due to spin accumulation. The spin accumulation is elucidated by current dependent anomalous Hall resistance measurement, which shows a decrease as the electric current is increased. This result may open a new paradigm in the field of spin-mediated transport behavior in semiconductor and semiconductor spintronics.

  15. Ferromagnetic resonance study of the half-Heusler alloy NiMnSb. The benefit of using NiMnSb as a ferromagnetic layer in pseudo-spin-valve based spin-torque oscillators

    Energy Technology Data Exchange (ETDEWEB)

    Riegler, Andreas

    2011-11-25

    Since the discovery of spin torque in 1996, independently by Berger and Slonczewski, and given its potential impact on information storage and communication technologies, (e.g. through the possibility of switching the magnetic configuration of a bit by current instead of a magnetic field, or the realization of high frequency spin torque oscillators (STO)), this effect has been an important field of spintronics research. One aspect of this research focuses on ferromagnets with low damping. The lower the damping in a ferromagnet, the lower the critical current that is needed to induce switching of a spin valve or induce precession of its magnetization. In this thesis ferromagnetic resonance (FMR) studies of NiMnSb layers are presented along with experimental studies on various spin-torque (ST) devices using NiMnSb. NiMnSb, when crystallized in the half-Heusler structure, is a half-metal which is predicted to have 100% spin polarization, a consideration which further increases its potential as a candidate for memory devices based on the giant magnetoresistance (GMR) effect. The FMR measurements show an outstandingly low damping factor for NiMnSb, in low 10{sup -3} range. This is about a factor of two lower than permalloy and well comparable to lowest damping for iron grown by molecular beam epitaxy (MBE). According to theory the 100% spin polarization properties of the bulk disappear at interfaces where the break in translational symmetry causes the gap in the minority spin band to collapse but can remain in other crystal symmetries such as (111). Consequently NiMnSb layers on (111)(In,Ga)As buffer are characterized in respect of anisotropies and damping. The FMR measurements on these samples indicates a higher damping that for the 001 samples, and a thickness dependent uniaxial in-plane anisotropy. Investigations of the material for device use is pursued by considering sub-micrometer sized elements of NiMnSb on 001 substrates, which were fabricated by electron

  16. Josephson magnetic rotary valve

    NARCIS (Netherlands)

    Soloviev, I.I.; Klenov, N.V.; Bakurskiy, S.V.; Bol’ginov, V.V.; Ryazanov, V.V.; Kupriyanov, M..Y.; Golubov, Alexandre Avraamovitch

    2014-01-01

    We propose a control element for a Josephson spin valve. It is a complex Josephson device containing ferromagnetic (F) layer in the weak-link area consisting of two regions, representing 0 and π Josephson junctions, respectively. The valve's state is defined by mutual orientations of the F-layer

  17. Studies of magnetization reversals about two kinds of MR curves observed in the spin valve using the (110) magnetite pinning layer

    Energy Technology Data Exchange (ETDEWEB)

    Matsuda, H., E-mail: matsuda.hiroshi01@ms.naist.jp [Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama-cho, Ikoma, Nara 630-0101 (Japan); Sakakima, H. [Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama-cho, Ikoma, Nara 630-0101 (Japan)

    2012-05-15

    In the spin valves composed of Co/Cu/Co on the epitaxial (110) Fe{sub 3}O{sub 4} as the pinning layer, we found out that shapes of magnetoresistance (MR) curves depended on thickness of the cobalt pinned layer (PL) with the field applied in the Left-Pointing-Angle-Bracket 110 Right-Pointing-Angle-Bracket direction of Fe{sub 3}O{sub 4}: (1) the flat-shaped MR curve showed low MR ratio under 2 nm thickness of cobalt pinned layer (PL): (2) the unusually shaped MR curve showed high MR ratio over 5 nm thickness of PL in spite of the hard direction of Co layers. We assumed that the synchronous magnetization reversal (SR) of PL and Fe{sub 3}O{sub 4} would occur at the MR switching field due to 90 Degree-Sign coupling between PL and Fe{sub 3}O{sub 4} layers. Then, only occurrence of SR of PL cause the drastic change of the magnetization relative angle between FL and PL, indicating the observation of the unusually shaped MR curve having high MR ratio. On the other hand, the SR of cobalt free layer (FL) together with the PL flip also occur due to the large contribution of Neel-type ferromagnetic coupling between FL and PL, which lead to less changing the relative angle of FL and PL during magnetization processes, indicating the observation of a flat-shaped MR curve having low MR ratio. This dependence of PL thickness on MR curves might come from the balance of Neel (ferromagnetic) and stray field (antiferromagnetic) coupling due to magnetic free pole at edge of PL. - Highlights: Black-Right-Pointing-Pointer 90 Degree-Sign Coupling between two magnetic layers giving rise to interested magnetization reversals in magnetic multi-layers. Black-Right-Pointing-Pointer Synchronous magnetization reversals during magnetization processes of spin valves. Black-Right-Pointing-Pointer Competing effects of Neel (orange peel), stray field coupling between ferromagnetic pinned and free layers in Fe{sub 3}O{sub 4} spin valves. Black-Right-Pointing-Pointer Interested magnetoresistance (MR

  18. Stoner vs. spin-mixing behavior in the bulk magnetism of Gd: A spin ...

    Indian Academy of Sciences (India)

    bulk magnetism of Gd: A spin-resolved photoemission study. K MAITI1,2,∗. , M C MALAGOLI2, A DALLMEYER2 and C CARBONE2,3. 1Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400 005, India. 2Institut für Festkörperforschung, Forschungszentrum Jülich, D-52428 Jülich, Germany. 3Consiglio ...

  19. Spin currents and filtering behavior in zigzag graphene nanoribbons with adsorbed molybdenum chains

    International Nuclear Information System (INIS)

    García-Fuente, A; Gallego, L J; Vega, A

    2015-01-01

    By means of density-functional-theoretic calculations, we investigated the structural, electronic and transport properties of hydrogen-passivated zigzag graphene nanoribbons (ZGNRs) on which a one-atom-thick Mo chain was adsorbed (with or without one or two missing atoms), or in which the passivating hydrogen atoms were replaced by Mo atoms. Mo-passivated ZGNRs proved to be nonmagnetic. ZGNRs with an adsorbed defect-free Mo chain were most stable with the Mo atoms forming dimers above edge bay sites, which suppressed the magnetic moments of the C atoms in that half of the ribbon; around the Fermi level of these systems, each spin component had a transmission channel via the Mo sp z band and one had an additional channel created by polarization of the ZGNR π * band, leading to a net spin current. The absence of an Mo dimer from an Mo chain adsorbed at the ZGNR edge made the system a perfect spin filter at low voltage bias by suppressing the Mo sp z band channels. Thus this last kind of hybrid system is a potential spin valve. (paper)

  20. Engineered spin-valve type magnetoresistance in Fe3O4-CoFe2O4 core-shell nanoparticles

    Science.gov (United States)

    Anil Kumar, P.; Ray, Sugata; Chakraverty, S.; Sarma, D. D.

    2013-09-01

    Naturally occurring spin-valve-type magnetoresistance (SVMR), recently observed in Sr2FeMoO6 samples, suggests the possibility of decoupling the maximal resistance from the coercivity of the sample. Here we present the evidence that SVMR can be engineered in specifically designed and fabricated core-shell nanoparticle systems, realized here in terms of soft magnetic Fe3O4 as the core and hard magnetic insulator CoFe2O4 as the shell materials. We show that this provides a magnetically switchable tunnel barrier that controls the magnetoresistance of the system, instead of the magnetic properties of the magnetic grain material, Fe3O4, and thus establishing the feasibility of engineered SVMR structures.

  1. Novel room-temperature spin-valve-like magnetoresistance in magnetically coupled nano-column Fe3O4/Ni heterostructure.

    Science.gov (United States)

    Xiao, Wen; Song, Wendong; Herng, Tun Seng; Qin, Qing; Yang, Yong; Zheng, Ming; Hong, Xiaoliang; Feng, Yuan Ping; Ding, Jun

    2016-08-25

    Herein, we design a room-temperature spin-valve-like magnetoresistance in a nano-column Fe3O4/Ni heterostructure without using a non-magnetic spacer or pinning layer. An Fe3O4 nano-column film is self-assembled on a Ni underlayer by the thermal decomposition method. The wet-chemical self-assembly is facile, economical and scalable. The magnetoresistance (MR) response of the Ni underlayer in the heterostructure under positive and negative out-of-plane magnetic fields differ by ∼0.25 at room temperature and ∼0.43 at 100 K. We attribute the spin-valve-like magnetoresistance to the unidirectional magnetic anisotropy of the Ni underlayer when being magnetically coupled by the Fe3O4 nano-column film. The out-of-plane negative-field magnetization is higher than the positive-field magnetization, affirming the unidirectional magnetic anisotropy of the Fe3O4/Ni heterostructure. Temperature-dependent magnetic and resistivity studies illustrate a close correlation between the magnetization transition of Fe3O4 and resistivity transition of Ni and prove a magnetic coupling between the Fe3O4 and Ni. First-principles calculations reveal that the Fe3O4/Ni model under a negative magnetic field is energetically more stable than that under a positive magnetic field. Furthermore, partial density of states (PDOS) analysis demonstrates the unidirectional magnetic anisotropy of the Ni 3d orbital. This is induced by the strong ferromagnetic coupling between Fe3O4 and Ni via oxygen-mediated Fe 3d-O 2p-Ni 3d hybridizations.

  2. The effects of load-sensitive behavior on the operability margins of motor-operated gate valves

    International Nuclear Information System (INIS)

    Steele, R. Jr.; Russell, M.J.; DeWall, K.G.; Watkins, J.C.

    1993-01-01

    Testing of motor-operated gate valves at various loads has produced a phenomenon we call load-sensitive behavior. This phenomenon has a significant effect on the accuracy of the methods used (and proposed) in the nuclear industry for determining that these valves can perform their design basis function. A valve subjected to tests with low flow and pressure loadings may achieve a stem thrust (at seating) analytically determined to be adequate for design basis flows and pressures, but this is no guarantee that the valve will achieve the same stem thrust when actually subjected to those design basis loads. This is because the friction at the interface between the stem and the stem nut is higher in tests with higher flow and pressure loadings, and this loss to friction is outside the control of the motor-operator's torque switch. This paper identifies a tentative method for determining, a stable, useful value for the stem/stem-nut coefficient of friction, one that can possibly be extrapolated and used in calculations to accurately estimate the design basis thrust requirements of these valves

  3. Hysteresis and compensation behaviors of mixed spin-2 and spin-1 hexagonal Ising nanowire core–shell structure

    International Nuclear Information System (INIS)

    Masrour, R.; Jabar, A.; Benyoussef, A.; Hamedoun, M.; Bahmad, L.

    2015-01-01

    The magnetic behaviors of a mixed spins (2-1) hexagonal Ising nanowire with core–shell structure are investigated by using the Monte Carlo simulations. The thermal magnetizations, the magnetic susceptibilities and the transition temperatures of core–shell are studied for different values of crystal field and exchange interactions. The thermal and magnetic hysteresis cycles are given for different values of the crystal field. - Highlights: • Critical temperature increase when exchange interaction increasing in core-shell. • Hysteresis loop areas decrease at above transition temperature. • Magnetic coercive field decrease when crystal field increasing. • Magnetic coercive field increase when exchange interaction increasing

  4. Predicting acute copper toxicity to valve closure behavior in the freshwater clam Corbicula fluminea supports the biotic ligand model.

    Science.gov (United States)

    Liao, Chung-Min; Jou, Li-John; Lin, Chieh-Ming; Chiang, Kuo-Chin; Yeh, Ching-Hung; Chou, Berry Yun-Hua

    2007-06-01

    The objective of this paper is to employ biotic ligand model (BLM) to link between acute copper (Cu) toxicity and its effect on valve closure behavior of freshwater clam Corbicula fluminea in order to further support for the BLM that potentially offers a rapid and cost-effective method to conduct the acute toxicity tests for freshwater clam exposed to waterborne Cu. Reanalysis of published experimental data of C. fluminea closure daily rhythm and dose-response profiles based on the laboratory-acclimated clams showed that a BLM-based Hill model best described the free Cu(2+)-activity-valve closure response relationships. Our proposed Cu-BLM-Corbicula model shows that free ionic form of waterborne Cu binds specifically to a biotic ligand (i.e., clam gills) and impairs normal valve closure behavior, indicating that a fixed-level of metal accumulation at a biotic ligand is required to elicit specific biological effects. With derived mechanistic-based Cu-BLM-Corbicula model, we show that the site-specific EC50(t) and valve closure behavior at any integrated time can be well predicted, indicating that our model has the potential to develop a biomonitoring system as a bioassay tool to on-line measure waterborne Cu levels in aquatic systems. Our results confirm that BLM can be improved to analytically and rigorously describe the bioavailable fraction of metal causing toxicity to valve closure behavior in freshwater C. fluminea. We suggest that the Cu-BLM-Corbicula model can be used to assist in developing technically defensible site-specific water quality criteria and performing ecological risk assessment and to promote more focused and efficient uses of resources in the regulation and control of metals and the protection of the aquatic ecosystems.

  5. Universal Behavior of Quantum Spin Liquid and Optical Conductivity in the Insulator Herbertsmithite

    Science.gov (United States)

    Shaginyan, V. R.; Msezane, A. Z.; Stephanovich, V. A.; Popov, K. G.; Japaridze, G. S.

    2018-04-01

    We analyze optical conductivity with the goal to demonstrate experimental manifestation of a new state of matter, the so-called fermion condensate. Fermion condensates are realized in quantum spin liquids, exhibiting typical behavior of heavy-fermion metals. Measurements of the low-frequency optical conductivity collected on the geometrically frustrated insulator herbertsmithite provide important experimental evidence of the nature of its quantum spin liquid composed of spinons. To analyze recent measurements of the herbertsmithite optical conductivity at different temperatures, we employ a model of strongly correlated quantum spin liquid located near the fermion condensation phase transition. Our theoretical analysis of the optical conductivity allows us to expose the physical mechanism of its temperature dependence. We also predict a dependence of the optical conductivity on a magnetic field. We consider an experimental manifestation (optical conductivity) of a new state of matter (so-called fermion condensate) realized in quantum spin liquids, for, in many ways, they exhibit typical behavior of heavy-fermion metals. Measurements of the low-frequency optical conductivity collected on the geometrically frustrated insulator herbertsmithite produce important experimental evidence of the nature of its quantum spin liquid composed of spinons. To analyze recent measurements of the herbertsmithite optical conductivity at different temperatures, we employ a model of a strongly correlated quantum spin liquid located near the fermion condensation phase transition. Our theoretical analysis of the optical conductivity allows us to reveal the physical mechanism of its temperature dependence. We also predict a dependence of the optical conductivity on a magnetic field.

  6. Spin quenching assisted by a strongly anisotropic compression behavior in MnP

    Energy Technology Data Exchange (ETDEWEB)

    Han, Fei; Wang, Di; Wang, Yonggang; Li, Nana; Bao, Jin-Ke; Li, Bing; Botana, Antia S.; Xiao, Yuming; Chow, Paul; Chung, Duck Young; Chen, Jiuhua; Wan, Xiangang; Kanatzidis, Mercouri G.; Yang, Wenge; Mao, Ho-Kwang

    2018-02-01

    We studied the crystal structure and spin state of MnP under high pressure with synchrotron X-ray diffraction and X-ray emission spectroscopy. MnP has an exceedingly strong anisotropy in compressibility, with the primary compressible direction along the b axis of the Pnma structure. X-ray emission spectroscopy reveals a pressure-driven quenching of the spin state in MnP. First-principles calculations suggest that the strongly anisotropic compression behavior significantly enhances the dispersion of the Mn d-orbitals and the splitting of the d-orbital levels compared to the hypothetical isotropic compression behavior. Thus, we propose spin quenching results mainly from the significant enhancement of the itinerancy of d electrons and partly from spin rearrangement occurring in the split d-orbital levels near the Fermi level. This explains the fast suppression of magnetic ordering in MnP under high pressure. The spin quenching lags behind the occurrence of superconductivity at ~8 GPa implying that spin fluctuations govern the electron pairing for superconductivity.

  7. Linking valve closure behavior and sodium transport mechanism in freshwater clam Corbicula fluminea in response to copper

    Energy Technology Data Exchange (ETDEWEB)

    Liao, C.-M. [Department of Bioenvironmental Systems Engineering, National Taiwan University, 1, Sec. 4, Roosevelt Road, Taipei, Taiwan 10617 (China)]. E-mail: cmliao@ntu.edu.tw; Lin, C.-M. [Department of Bioenvironmental Systems Engineering, National Taiwan University, 1, Sec. 4, Roosevelt Road, Taipei, Taiwan 10617 (China); Jou, L.-J. [Department of Bioenvironmental Systems Engineering, National Taiwan University, 1, Sec. 4, Roosevelt Road, Taipei, Taiwan 10617 (China); Department of Biomechatronic Engineering, National Ilan University, Ilan, Taiwan 260 (China); Chiang, K.-C. [Department of Bioenvironmental Systems Engineering, National Taiwan University, 1, Sec. 4, Roosevelt Road, Taipei, Taiwan 10617 (China)

    2007-06-15

    The purpose of this study is to develop a mechanistic model to describe a conceptually new 'flux-biological response' approach based on biotic ligand model (BLM) and Michaelis-Menten (M-M) kinetics to allow the linkage between valve closure behavior and sodium (Na) transport mechanism in freshwater clam Corbicula fluminea in response to waterborne copper (Cu). We test the proposed model against published data regarding Na uptake kinetics in rainbow trout and Na uptake profile in C. fluminea, confirming that the predictive model is robust. Here, we show that the predicted M-M maximum Cu internalization flux in C. fluminea is 0.369 {mu}mol g{sup -1} h{sup -1} with a half-saturation affinity constant of 7.87 x 10{sup -3} {mu}M. Dynamics of Na uptake and valve closure daily rhythm driven by external Cu can also be predicted simultaneously. We suggest that this 'Na transport-valve closure behavior' approach might provide the basis of a future design of biomonitoring tool. - A new flux-biological response model can link valve closure and sodium transport mechanisms in freshwater clam in response to copper.

  8. A feasibility study of developing toroidal tanks for a spinning spacecraft. Part 2: Evaluation of fluid behavior in spinning toroidal tanks

    Science.gov (United States)

    Anderson, J. E.

    1974-01-01

    An experimental program was conducted for the purpose of evaluating propellant behavior characteristics in spinning toroidal tanks. The effects of typical mission requirements, and related phenomena upon propellant slosh and settling, and orientation and stability of the ullage were investigated in a subscale model tank under both one-g and low-g acceleration environments. Specific conditions included were axial acceleration, spin rate, spinrate change, and spacecraft wobble, both singly and in combination. Methanol and water in combination with appropriate spin-rates and accelerations of the scale model system were used to simulate the behavior of fluorine, nitrogen tetroxide, monomethylhydrazine, and hydrazine. The experimental results indicate that no major fluid behavior problems would be encountered with the use of toroidal tanks containing any of the four propellants in a proposed spin-stabilized orbiter spacecraft.

  9. Spin transport and relaxation in graphene

    International Nuclear Information System (INIS)

    Han Wei; McCreary, K.M.; Pi, K.; Wang, W.H.; Li Yan; Wen, H.; Chen, J.R.; Kawakami, R.K.

    2012-01-01

    We review our recent work on spin injection, transport and relaxation in graphene. The spin injection and transport in single layer graphene (SLG) were investigated using nonlocal magnetoresistance (MR) measurements. Spin injection was performed using either transparent contacts (Co/SLG) or tunneling contacts (Co/MgO/SLG). With tunneling contacts, the nonlocal MR was increased by a factor of ∼1000 and the spin injection/detection efficiency was greatly enhanced from ∼1% (transparent contacts) to ∼30%. Spin relaxation was investigated on graphene spin valves using nonlocal Hanle measurements. For transparent contacts, the spin lifetime was in the range of 50-100 ps. The effects of surface chemical doping showed that for spin lifetimes in the order of 100 ps, charged impurity scattering (Au) was not the dominant mechanism for spin relaxation. While using tunneling contacts to suppress the contact-induced spin relaxation, we observed the spin lifetimes as long as 771 ps at room temperature, 1.2 ns at 4 K in SLG, and 6.2 ns at 20 K in bilayer graphene (BLG). Furthermore, contrasting spin relaxation behaviors were observed in SLG and BLG. We found that Elliot-Yafet spin relaxation dominated in SLG at low temperatures whereas Dyakonov-Perel spin relaxation dominated in BLG at low temperatures. Gate tunable spin transport was studied using the SLG property of gate tunable conductivity and incorporating different types of contacts (transparent and tunneling contacts). Consistent with theoretical predictions, the nonlocal MR was proportional to the SLG conductivity for transparent contacts and varied inversely with the SLG conductivity for tunneling contacts. Finally, bipolar spin transport in SLG was studied and an electron-hole asymmetry was observed for SLG spin valves with transparent contacts, in which nonlocal MR was roughly independent of DC bias current for electrons, but varied significantly with DC bias current for holes. These results are very important for

  10. A parametric study of the behavior of the angular momentum vector during spin rate changes of rigid body spacecraft

    Science.gov (United States)

    Longuski, J. M.

    1982-01-01

    During a spin-up or spin-down maneuver of a spinning spacecraft, it is usual to have not only a constant body-fixed torque about the desired spin axis, but also small undesired constant torques about the transverse axes. This causes the orientation of the angular momentum vector to change in inertial space. Since an analytic solution is available for the angular momentum vector as a function of time, this behavior can be studied for large variations of the dynamic parameters, such as the initial spin rate, the inertial properties and the torques. As an example, the spin-up and spin-down maneuvers of the Galileo spacecraft was studied and as a result, very simple heuristic solutions were discovered which provide very good approximations to the parametric behavior of the angular momentum vector orientation.

  11. Dynamic behavior of prosthetic aortic tissue valves as viewed by high-speed cinematography.

    Science.gov (United States)

    Rainer, W G; Christopher, R A; Sadler, T R; Hilgenberg, A D

    1979-09-01

    Using a valve testing apparatus of our own design and with a high-speed (600 to 800 frames per second) 16 mm movie camera, films were made of Hancock porcine, Carpentier-Edwards porcine, and Ionescu-Shiley bovine pericardial valves mounted in the aortic position and cycled under physiological conditions at 72 to 100 beats per minute. Fresh and explanted valves were observed using saline or 36.5% glycerol as the pumping solution. When fresh valves were studied using saline solution as the pumpint fluid, the Hancock and Carpentier-Edwards porcine valves showed high-frequency leaflet vibration, which increased in frequency with higher cycling rates. Abnormal leaflet motion was decreased when glycerol was used as the blood analogue. The Ionescu-Shiley bovine pericardial valve did not show abnormal leaflet motion under these conditions. Conclusions drawn from tissue valve testing studies that use excessively high pulsing rates and pressures (accelerated testing) and saline or water as pumping solutions cannot be transposed to predict the fate of tissue valves in a clinical setting.

  12. Finite-temperature behavior of an impurity in the spin-1/2 XXZ chain

    International Nuclear Information System (INIS)

    Yahagi, Ryoko; Deguchi, Tetsuo; Sato, Jun

    2014-01-01

    We study the zero- and the finite-temperature behavior of the integrable spin-1/2 XXZ periodic chain with an impurity by the algebraic and thermal Bethe ansatz methods. We evaluate the local magnetization on the impurity site at zero temperature analytically and derive the impurity susceptibility exactly from it. In the graphs of the impurity specific heat versus temperature, we show how the impurity spin becomes more liberated from the bulk many-body effect as the exchange coupling between the impurity spin and other spins decreases and that at low temperature it couples strongly to them such as in the Kondo effect. Thus, we observe not only the crossover behavior from the high- to the low-temperature regime, but another from the N-site chain to the (N − 1)-site chain with a free impurity spin. We also show that the estimate of the Wilson ratio at a given low temperature is independent of the impurity parameter if its absolute value is small enough with respect to the temperature and the universality class is described by the XXZ anisotropy in terms of the dressed charge. (paper)

  13. Critical behavior of the quantum spin- {1}/{2} anisotropic Heisenberg model

    Science.gov (United States)

    Sousa, J. Ricardo de

    A two-step renormalization group approach - a decimation followed by an effective field renormalization group (EFRG) - is proposed in this work to study the critical behavior of the quantum spin- {1}/{2} anisotropic Heisenberg model. The new method is illustrated by employing approximations in which clusters with one, two and three spins are used. The values of the critical parameter and critical exponent, in two- and three-dimensional lattices, for the Ising and isotropic Heisenberg limits are calculated and compared with other renormalization group approaches and exact (or series) results.

  14. Reduction of ballistic spin scattering in a spin-FET using stray electric fields

    International Nuclear Information System (INIS)

    Nemnes, G A; Manolescu, A; Gudmundsson, V

    2012-01-01

    The quasi-bound states which appear as a consequence of the Rashba spin-orbit (SO) coupling, introduce a strongly irregular behavior of the spin-FET conductance at large Rashba parameter. Moreover, the presence of the bulk inversion asymmetry, i.e. the Dresselhaus SO coupling, may compromise the spin-valve effect even at small values of the Rashba parameter. However, by introducing stray electric fields in addition to the SO couplings, we show that the effect of the SO induced quasi-bound states can be tuned. The oscillations of the spin-resolved conductance become smoother and the control of the spin-FET characteristics becomes possible. For the calculations we employ a multi-channel scattering formalism, based on the R-matrix method extended to spin transport, in the presence of Rashba and Dresselhaus SO couplings.

  15. Tricritical behavior in the diluted transverse spin-1 Ising model with a longitudinal crystal field

    International Nuclear Information System (INIS)

    Htoutou, K.; Oubelkacem, A.; Ainane, A.; Saber, M.

    2005-01-01

    The transverse spin-1 Ising model with a longitudinal crystal field exhibits a tricritical behavior. Within the effective field theory with a probability distribution technique that accounts for the self-spin correlations, we have studied the influence of site dilution on this behavior and have calculated the temperature-transverse field-longitudinal crystal field-concentration phase diagrams and determined, in particular, the influence of the concentration of magnetic atoms c on the tricritical behavior. We have found that the tricritical point appears for large values of the concentration c of magnetic atoms and disappears with the increase in dilution (small values of c). Results for square lattice are calculated numerically and some interesting results are obtained. In certain ranges of values of the strength of the longitudinal crystal field D/J when it becomes sufficiently negative, we found re-entrant phenomenon, which disappears with increase in the value of the strength of the transverse field

  16. Modulating the spin transport behaviors in ZBNCNRs by edge hydrogenation and position of BN chain

    Directory of Open Access Journals (Sweden)

    Jun Ouyang

    2016-03-01

    Full Text Available Using the density functional theory and the nonequilibrium Green’s function method, we study the spin transport behaviors in zigzag boron-nitrogen-carbon nanoribbons (ZBNCNRs by modulating the edge hydrogenation and the position of B-N nanoribbons (BNNRs chain. The different edge hydrogenations of the ZBNCNRs and the different position relationships of the BNNRs have been considered systematically. Our results show that the metallic, semimetallic and semiconductive properties of the ZBNCNRs can be modulated by the different edge hydrogenations and different position relationships of BN chains. And our proposaled ZBNCNRs devices act as perfect spin-filters with nearly 100% spin polarization. These effects would have potential applications for boron-nitrogen-carbon-based nanomaterials in spintronics nano-devices.

  17. Linking valve closure behavior and sodium transport mechanism in freshwater clam Corbicula fluminea in response to copper.

    Science.gov (United States)

    Liao, Chung-Min; Lin, Chieh-Ming; Jou, Li-John; Chiang, Kuo-Chin

    2007-06-01

    The purpose of this study is to develop a mechanistic model to describe a conceptually new "flux-biological response" approach based on biotic ligand model (BLM) and Michaelis-Menten (M-M) kinetics to allow the linkage between valve closure behavior and sodium (Na) transport mechanism in freshwater clam Corbicula fluminea in response to waterborne copper (Cu). We test the proposed model against published data regarding Na uptake kinetics in rainbow trout and Na uptake profile in C. fluminea, confirming that the predictive model is robust. Here, we show that the predicted M-M maximum Cu internalization flux in C. fluminea is 0.369 micromolg(-1)h(-1) with a half-saturation affinity constant of 7.87x10(-3) microM. Dynamics of Na uptake and valve closure daily rhythm driven by external Cu can also be predicted simultaneously. We suggest that this "Na transport-valve closure behavior" approach might provide the basis of a future design of biomonitoring tool.

  18. Spin-torque transistor

    NARCIS (Netherlands)

    Bauer, G.E.W.; Brataas, A.; Tserkovnyak, Y.; Van Wees, B.J.

    2003-01-01

    A magnetoelectronic thin-film transistor is proposed that can display negative differential resistance and gain. The working principle is the modulation of the soure–drain current in a spin valve by the magnetization of a third electrode, which is rotated by the spin-torque created by a control spin

  19. Resonance induced spin-selective transport behavior in carbon nanoribbon/nanotube/nanoribbon heterojunctions

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xiang-Hua [School of Physics and Microelectronics Science, Hunan University, Changsha 410082 (China); Department of Electrical and Information Engineering, Hunan Institute of Engineering, Xiangtan 411101 (China); Wang, Ling-Ling, E-mail: llwang@hnu.edu.cn [School of Physics and Microelectronics Science, Hunan University, Changsha 410082 (China); Li, Xiao-Fei, E-mail: xf.li@uestc.edu.cn [School of Physics and Microelectronics Science, Hunan University, Changsha 410082 (China); School of Optoelectronic Information, University of Electronic Science and Technology of China, Chengdu, Sichuan 610054 (China); Chen, Tong; Li, Quan [School of Physics and Microelectronics Science, Hunan University, Changsha 410082 (China)

    2015-09-04

    Carbon nanotubes (CNTs) and graphene nanoribbons (GNRs) are attractive in spintronics. Here, we propose GNR/CNT/GNR heterojunctions constructed by attaching zigzag-GNRs at the side-wall of CNT for spintronic devices. The thermal stability and electronic transport properties were explored using ab initio molecular dynamics simulations and nonequilibrium Green's function methods, respectively. Results demonstrate that the sp{sup 3}-hybridized contacts formed at the interface assure a good thermal stability of the system and make the CNT to be regarded as resonator. Only the electron of one spin-orientation and resonant energy is allowed to transport, resulting in the remarkable spin-selective transport behavior at the ferromagnetic state. - Highlights: • The new mechanism for spin-selective transport in molecular junction is proposed. • The two sp{sup 3} contacts formed between CNT and GNR can be regarded as electronic isolators. • The two isolators make the CNT act as a resonator. • Only the electron of one spin-orientation and resonant energy can form standing wave and transport through the whole junction.

  20. Resonance induced spin-selective transport behavior in carbon nanoribbon/nanotube/nanoribbon heterojunctions

    International Nuclear Information System (INIS)

    Zhang, Xiang-Hua; Wang, Ling-Ling; Li, Xiao-Fei; Chen, Tong; Li, Quan

    2015-01-01

    Carbon nanotubes (CNTs) and graphene nanoribbons (GNRs) are attractive in spintronics. Here, we propose GNR/CNT/GNR heterojunctions constructed by attaching zigzag-GNRs at the side-wall of CNT for spintronic devices. The thermal stability and electronic transport properties were explored using ab initio molecular dynamics simulations and nonequilibrium Green's function methods, respectively. Results demonstrate that the sp 3 -hybridized contacts formed at the interface assure a good thermal stability of the system and make the CNT to be regarded as resonator. Only the electron of one spin-orientation and resonant energy is allowed to transport, resulting in the remarkable spin-selective transport behavior at the ferromagnetic state. - Highlights: • The new mechanism for spin-selective transport in molecular junction is proposed. • The two sp 3 contacts formed between CNT and GNR can be regarded as electronic isolators. • The two isolators make the CNT act as a resonator. • Only the electron of one spin-orientation and resonant energy can form standing wave and transport through the whole junction

  1. Hysteresis and compensation behaviors of spin-3/2 cylindrical Ising nanotube system

    International Nuclear Information System (INIS)

    Kocakaplan, Yusuf; Keskin, Mustafa

    2014-01-01

    The hysteresis and compensation behaviors of the spin-3/2 cylindrical Ising nanotube system are studied within the framework of the effective-field theory with correlations. The effects of the Hamiltonian parameters are investigated on the magnetic and thermodynamic quantities, such as the total magnetization, hysteresis curves, and compensation behaviors of the system. Depending on the Hamiltonian parameters, some characteristic hysteresis behaviors are found, such as the existence of double and triple hysteresis loops. According to Néel classification nomenclature, the system displays Q-, R-, P-, N-, M-, and S- types of compensation behaviors for the appropriate values of the system parameters. We also compare our results with some recently published theoretical and experimental works and find a qualitatively good agreement

  2. Hysteresis and compensation behaviors of spin-3/2 cylindrical Ising nanotube system

    Energy Technology Data Exchange (ETDEWEB)

    Kocakaplan, Yusuf [Graduate School of Natural and Applied Sciences, Erciyes University, 38039 Kayseri (Turkey); Keskin, Mustafa, E-mail: keskin@erciyes.edu.tr [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)

    2014-09-07

    The hysteresis and compensation behaviors of the spin-3/2 cylindrical Ising nanotube system are studied within the framework of the effective-field theory with correlations. The effects of the Hamiltonian parameters are investigated on the magnetic and thermodynamic quantities, such as the total magnetization, hysteresis curves, and compensation behaviors of the system. Depending on the Hamiltonian parameters, some characteristic hysteresis behaviors are found, such as the existence of double and triple hysteresis loops. According to Néel classification nomenclature, the system displays Q-, R-, P-, N-, M-, and S- types of compensation behaviors for the appropriate values of the system parameters. We also compare our results with some recently published theoretical and experimental works and find a qualitatively good agreement.

  3. The spin glass behavior in the Heusler alloy Cu{sub 2}VAl

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Wei, E-mail: zw_2002@126.com [School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130 (China); Center for the Condensed-Matter Science and Technology, Department of Physics, Harbin Institute of Technology, Harbin 150001 (China); Sun, Yajuan [Department of Physics, School of Science, Tianjin Polytechnic University, Tianjin 300130 (China); Wang, Hongxia [Key Laboratory for Photonic and Electronic Bandgap Materials, Ministry of Education, College of Chemistry and Chemical Engineering, Harbin Normal University, Harbin 150025 (China); Li, Yu [College of Science, Northeast Forestry University, Harbin 150040 (China); Zhang, Xiao [School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130 (China); Sui, Yu [Center for the Condensed-Matter Science and Technology, Department of Physics, Harbin Institute of Technology, Harbin 150001 (China); Luo, Hongzhi; Meng, Fanbin [School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130 (China); Qian, Zhengnan [Center for the Condensed-Matter Science and Technology, Department of Physics, Harbin Institute of Technology, Harbin 150001 (China); Wu, Guangheng [State Key Laboratory for Magnetism, Institute of Physics, Chinese Academy of Sciences, Beijing 100080 (China)

    2014-03-15

    Highlights: • The static and dynamic magnetic properties of the Heusler alloy Cu{sub 2}VAl are investigated. • The linear AC susceptibilities are analyzed by using the Vogel–Fulcher model and the critical slowing down power law. • It has been established that a spin glass behavior exists in this material at low temperature. -- Abstract: The magnetic properties of the Heulser alloy Cu{sub 2}VAl were comprehensively investigated. A broad maximum at low temperature in both zero-field-cooled magnetization and the real part of the linear ac susceptibilities as well as a clear irreversibility between the zero-field-cooled and field-cooled magnetization curves were detected. The absence of the second harmonic ac susceptibility and a negative peak observed in the third harmonic ac susceptibility indicate its spin glass ground state. Fitting of the temperature dependences of the linear ac susceptibilities with different frequencies to the Vogel–Fulcher model and the critical slowing down power law confirms the spin glass nature of the detected magnetic behavior at low temperature in the Heusler alloy Cu{sub 2}VAl.

  4. Observation of Octupole Structures in Radon and Radium Isotopes and Their Contrasting Behavior at High Spin

    International Nuclear Information System (INIS)

    Cocks, J.; Butler, P.; Cann, K.; Greenlees, P.; Jones, G.; Asztalos, S.; Clark, R.; Deleplanque, M.; Diamond, R.; Fallon, P.; Lee, I.; Macchiavelli, A.; MacLeod, R.; Stephens, F.; Bhattacharyya, P.; Zhang, C.; Broda, R.; Fornal, B.; Jones, P.; Julin, R.; Lauritsen, T.; Smith, J.

    1997-01-01

    Multinucleon transfer reactions have been used, for the first time, to populate high-spin bands of alternating parity states in 218,220,222 Rn and 222,224,226 Ra. The behavior of the angular momentum alignment with rotational frequency for the Rn isotopes is very different when compared with Ra and Th isotopes with N∼134, indicating a transition from octupole vibrational to stable octupole deformation. Throughout the measured spin range the values of |D 0 /Q 0 | remain constant for 222 Ra and 226 Ra and have a very small value for 224 Ra, suggesting that the charge and mass distributions are not affected appreciably by rotations. copyright 1997 The American Physical Society

  5. Application of RELAP5/MOD3.3 to Calculate Thermal Hydraulic Behavior of the Pressurizer Safety Valve Performance Test Facility

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Chang Hyun; Kim, Young Ae; Oh, Seung Jong; Park, Jong Woon [Korea Hydro and Nuclear Power Co., Ltd., Daejeon (Korea, Republic of)

    2007-10-15

    The increase of the acceptance tolerance of Pressurizer Safety Valve (PSV) test is vital for the safe operation of nuclear power plants because the frequent tests may make the valves decrepit and become a cause of leak. Recently, Korea Hydro and Nuclear Power Company (KHNP) is building a PSV performance test facility to provide the technical background data for the relaxation of the acceptance tolerance of PSV including the valve pop-up characteristics and the loop seal dynamics (if the plant has the loop seal in the upstream of PSV). The discharge piping and supports must be designed to withstand severe transient hydrodynamic loads when the safety valve actuates. The evaluation of hydrodynamic loads is a two-step process: first the thermal hydraulic behavior in the piping must be defined, and then the hydrodynamic loads are calculated from the thermal hydraulic parameters such as pressure and mass flow. The hydrodynamic loads are used as input to the structural analysis.

  6. Double MgO-based Perpendicular Magnetic-Tunnel-Junction Spin-valve Structure with a Top Co2Fe6B2Free Layer using a Single SyAF [Co/Pt]nLayer.

    Science.gov (United States)

    Choi, Jin-Young; Lee, Dong-Gi; Baek, Jong-Ung; Park, Jea-Gun

    2018-02-01

    A new perpendicular spin-transfer-torque magnetic-tunnel-junction (p-MTJ) spin-valve was developed to achieve a high tunneling magnetoresistance (TMR) ratio. It had a double MgO-based spin-valve structure with a top Co 2 Fe 6 B 2 free layer and incorporated a single SyAF [Co(0.4 nm)/Pt(0.3 nm)] 3 layer and a new buffer layer of Co(0.6)/Pt(0.3)/Co(0.4). It had a TMR ratio of 180% and anisotropy exchange field (H ex ) of 3.44 kOe after ex-situ annealing of 350 °C for 30 min under a vacuum below 10 -6 torr and a perpendicular magnetic field of 3 tesla, thereby ensuring a memory margin and avoiding read disturbance failures. Its high level of performance was due to the face-center-cubic crystallinity of the MgO tunneling barrier being significantly improved by decreasing its surface roughness (i.e., peak-to-valley length of 1.4 nm).

  7. Aortic Valve Regurgitation

    Science.gov (United States)

    ... correct direction. These valves include the mitral valve, tricuspid valve, pulmonary valve and aortic valve. Each valve has ... Causes of aortic valve regurgitation include: Congenital heart valve disease. You may have been born with an aortic ...

  8. Sodium Gill Potential as a Tool to Monitor Valve Closure Behavior in Freshwater Clam Corbicula fluminea in Response to Copper

    Directory of Open Access Journals (Sweden)

    Wei-Yu Chen

    2008-09-01

    Full Text Available Valve closure behavior in freshwater clam Corbicula fluminea is a biologically sensitive endpoint. The purpose of this paper was to derive an electrophysiological response model of C. fluminea to assess copper (Cu-sodium (Na interactions in gill membrane, whereby valve closure behavior and Cu toxicity could be monitored. The proposed model was based on the integration of Cu bioavailability, Na and Cu internalizations, and electrochemically-based gill potentials. Based on Na active transport under non-equilibrium conditions, predicted gill potential of -8.2 mV agreed reasonably well with published the measured transepithelial potential of -7 mV in C. fluminea. Our proposed framework captured the general features observed in model applications including: (i 50% inhibitory Cu2+ activities for Na membrane potential (ENa and uptake rate (JNa were estimated to be 0.072 and 0.043 mM, respectively, with a stoichiometry of 3Cu2+: 1ENa and 1JNa; (ii the external Cu2+-dependent internal Na concentration could be parsimoniously estimated, and (iii the site-specific clam gill potentials could be monitored. Here we provided a new approach to monitor waterborne metal toxicity to reduce the nationwide economic losses due to bans on harvesting of contaminated clam and the potential risks to the health of clams.

  9. Sodium Gill Potential as a Tool to Monitor Valve Closure Behavior in Freshwater Clam Corbicula fluminea in Response to Copper

    Science.gov (United States)

    Liao, Chung-Min; Lin, Chieh-Ming; Jou, Li-John; Chen, Wei-Yu

    2008-01-01

    Valve closure behavior in freshwater clam Corbicula fluminea is a biologically sensitive endpoint. The purpose of this paper was to derive an electrophysiological response model of C. fluminea to assess copper (Cu)–sodium (Na) interactions in gill membrane, whereby valve closure behavior and Cu toxicity could be monitored. The proposed model was based on the integration of Cu bioavailability, Na and Cu internalizations, and electrochemically-based gill potentials. Based on Na active transport under non-equilibrium conditions, predicted gill potential of −8.2 mV agreed reasonably well with published the measured transepithelial potential of −7 mV in C. fluminea. Our proposed framework captured the general features observed in model applications including: (i) 50% inhibitory Cu2+ activities for Na membrane potential (ENa) and uptake rate (JNa) were estimated to be 0.072 and 0.043 μM, respectively, with a stoichiometry of 3Cu2+: 1ENa and 1JNa; (ii) the external Cu2+–dependent internal Na concentration could be parsimoniously estimated, and (iii) the site-specific clam gill potentials could be monitored. Here we provided a new approach to monitor waterborne metal toxicity to reduce the nationwide economic losses due to bans on harvesting of contaminated clam and the potential risks to the health of clams. PMID:27873813

  10. Magnetic Nanostructures Spin Dynamics and Spin Transport

    CERN Document Server

    Farle, Michael

    2013-01-01

    Nanomagnetism and spintronics is a rapidly expanding and increasingly important field of research with many applications already on the market and many more to be expected in the near future. This field started in the mid-1980s with the discovery of the GMR effect, recently awarded with the Nobel prize to Albert Fert and Peter Grünberg. The present volume covers the most important and most timely aspects of magnetic heterostructures, including spin torque effects, spin injection, spin transport, spin fluctuations, proximity effects, and electrical control of spin valves. The chapters are written by internationally recognized experts in their respective fields and provide an overview of the latest status.

  11. Random crystal field effect on the magnetic and hysteresis behaviors of a spin-1 cylindrical nanowire

    Energy Technology Data Exchange (ETDEWEB)

    Zaim, N.; Zaim, A., E-mail: ah_zaim@yahoo.fr; Kerouad, M., E-mail: kerouad@fs-umi.ac.ma

    2017-02-15

    In this work, the magnetic behavior of the cylindrical nanowire, consisting of a ferromagnetic core of spin-1 atoms surrounded by a ferromagnetic shell of spin-1 atoms is studied in the presence of a random crystal field interaction. Based on Metropolis algorithm, the Monte Carlo simulation has been used to investigate the effects of the concentration of the random crystal field p, the crystal field D and the shell exchange interaction J{sub s} on the phase diagrams and the hysteresis behavior of the system. Some characteristic behaviors have been found, such as the first and second-order phase transitions joined by tricritical point for appropriate values of the system parameters, triple and isolated critical points can be also found. Depending on the Hamiltonian parameters, single, double and para hysteresis regions are explicitly determined. - Highlights: • Phase diagrams of a ferromagnetic nanowire are examined by the Monte Carlo simulation. • Different types of the phase diagrams are obtained. • The effect of the random crystal field on the hysteresis loops is studied. • Single, double and para hysteresis regions are explicitly determined.

  12. Formation and partial melting of two types of spin-cluster glass behavior in vanadate spinel

    International Nuclear Information System (INIS)

    Huang Yuanjie; Pi Li; Tan Shun; Zhang Yuheng; Yang Zhaorong

    2012-01-01

    We report the doping effect on the various properties of spinels Co 1-x Zn x V 2 O 4 (0 ≤ x ≤ 0.2). For the parent compounds, the rise in magnetization, the valley in thermal conductance, the transition from the ferromagnetic arrangement to non-collinear alignment indicated by the specific heat for the V sublattice, especially the frequency dependence of AC susceptibility around T 1 = 59 K, verify the occurrence of the transition at T 1 besides the ferrimagnetic transition at T C . The ferrimagnetic transition at T C induces the spin-cluster glass behavior and the transition at T 1 yields the new spin-cluster glass (NSCG) behavior. As the Zn 2+ -doped content increases, the above phenomena are gradually weakening to vanishing, but the glassy behavior at T C still exists for all samples. Through the fourth-order perturbation theory, we discuss the reasons for the gradual vanishing of the transition at T 1 . (paper)

  13. The effect of reactor vessel vent valves (RVVV's) on SBLOCA behavior of the UMCP 2 x 4 B and W simulation loop

    International Nuclear Information System (INIS)

    Pertmer, G.A.; Almenas, K.; DiMarzo, M.; Bailery, S.

    1989-01-01

    This paper presents results of a series of Small Break LOCA tests performed at the University of Maryland 2 x 4 Loop, which is a 1/500 volume scaled model of a B and W PWR system. A feature of the B and W system which has a major impact on SBLOCA behavior is the Reactor Vessel Vent Valves, which provide a flow path between the upper plenum and downcomer in the vessel. This paper compares system behavior during a SBLOCA for two tests - one in which the valves are allowed to open, and one in which the valves are held closed. Similarities and differences between the system flow modes that occur during the transient are presented and discussed for the two tests

  14. The role of collagen cross-links in biomechanical behavior of human aortic heart valve leaflets - Relevance for tissue engineering

    NARCIS (Netherlands)

    Balguid, A.; Rubbens, M.P.; Mol, A.; Bank, R.A.; Bogers, A.J.J.C.; Kats, J.P. van; Mol, B.A.J.M. de; Baaijens, F.P.T.; Bouten, C.V.C.

    2007-01-01

    A major challenge in tissue engineering of functional heart valves is to determine and mimic the dominant tissue structures that regulate heart valve function and in vivo survival. In native heart valves, the anisotropic matrix architecture assures sustained and adequate functioning under

  15. Surprising Behavior of Spinning Tops and Eggs on an Inclined Plane

    Science.gov (United States)

    Cross, Rod

    2016-01-01

    A spinning top or a spinning hard-boiled egg is fascinating to observe since both objects can remain upright for a relatively long time without falling over. If spun at sufficient speed on a horizontal surface, the spin axis rises to a vertical position and the bottom end tends to remain fixed in position on the surface. If the initial spin is…

  16. Tunneling-Magnetoresistance Ratio Comparison of MgO-Based Perpendicular-Magnetic-Tunneling-Junction Spin Valve Between Top and Bottom Co2Fe6B2 Free Layer Structure.

    Science.gov (United States)

    Lee, Du-Yeong; Lee, Seung-Eun; Shim, Tae-Hun; Park, Jea-Gun

    2016-12-01

    For the perpendicular-magnetic-tunneling-junction (p-MTJ) spin valve with a nanoscale-thick bottom Co2Fe6B2 free layer ex situ annealed at 400 °C, which has been used as a common p-MTJ structure, the Pt atoms of the Pt buffer layer diffused into the MgO tunneling barrier. This transformed the MgO tunneling barrier from a body-centered cubic (b.c.c) crystallized layer into a mixture of b.c.c, face-centered cubic, and amorphous layers and rapidly decreased the tunneling-magnetoresistance (TMR) ratio. The p-MTJ spin valve with a nanoscale-thick top Co2Fe6B2 free layer could prevent the Pt atoms diffusing into the MgO tunneling barrier during ex situ annealing at 400 °C because of non-necessity of a Pt buffer layer, demonstrating the TMR ratio of ~143 %.

  17. Spin Speed and Duration Dependence of TiO2 Thin Films pH Sensing Behavior

    Directory of Open Access Journals (Sweden)

    Muhammad AlHadi Zulkefle

    2016-01-01

    Full Text Available Titanium dioxide (TiO2 thin films were applied as the sensing membrane of an extended-gate field-effect transistor (EGFET pH sensor. TiO2 thin films were deposited by spin coating method and the influences of the spin speed and spin duration on the pH sensing behavior of TiO2 thin films were investigated. The spin coated TiO2 thin films were connected to commercial metal-oxide-semiconductor field-effect transistor (MOSFET to form the extended gates and the MOSFET was integrated in a readout interfacing circuit to complete the EGFET pH sensor system. For the spin speed parameter investigation, the highest sensitivity was obtained for the sample spun at 3000 rpm at a fixed spinning time of 60 s, which was 60.3 mV/pH. The sensitivity was further improved to achieve 68 mV/pH with good linearity of 0.9943 when the spin time was 75 s at the speed of 3000 rpm.

  18. Dynamic magnetic hysteresis behavior and dynamic phase transition in the spin-1 Blume-Capel model

    Energy Technology Data Exchange (ETDEWEB)

    Deviren, Bayram, E-mail: bayram.deviren@nevsehir.edu.tr [Department of Physics, Nevsehir University, 50300 Nevsehir (Turkey); Keskin, Mustafa [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)

    2012-03-15

    The nature (time variation) of response magnetization m(wt) of the spin-1 Blume-Capel model in the presence of a periodically varying external magnetic field h(wt) is studied by employing the effective-field theory (EFT) with correlations as well as the Glauber-type stochastic dynamics. We determine the time variations of m(wt) and h(wt) for various temperatures, and investigate the dynamic magnetic hysteresis behavior. We also investigate the temperature dependence of the dynamic magnetization, hysteresis loop area and correlation near the transition point in order to characterize the nature (first- or second-order) of the dynamic transitions as well as obtain the dynamic phase transition temperatures. The hysteresis loops are obtained for different reduced temperatures and we find that the areas of the loops are decreasing with the increasing of the reduced temperatures. We also present the dynamic phase diagrams and compare the results of the EFT with the results of the dynamic mean-field approximation. The phase diagrams exhibit many dynamic critical points, such as tricritical ( Bullet ), zero-temperature critical (Z), triple (TP) and multicritical (A) points. According to values of Hamiltonian parameters, besides the paramagnetic (P), ferromagnetic (F) fundamental phases, one coexistence or mixed phase region, (F+P) and the reentrant behavior exist in the system. The results are in good agreement with some experimental and theoretical results. - Highlights: Black-Right-Pointing-Pointer Kinetic spin-1 Blume-Capel model is studied using the effective-field theory. Black-Right-Pointing-Pointer We investigated the dynamic magnetic hysteresis behavior. Black-Right-Pointing-Pointer Dynamic magnetization, hysteresis loop area and correlation are investigated. Black-Right-Pointing-Pointer System exhibits tricritical, zero-temperature, triple and multicritical points. Black-Right-Pointing-Pointer We present the dynamic phase diagrams and compare the results of the EFT

  19. Effects of vacancies on spin-dependent behavior of monolayer and bilayer graphene nanoribbons

    Science.gov (United States)

    Safari, E. Keshavarz; Shokri, A. A.; BabaeiPour, M.

    2017-11-01

    In this work, the effect of vacancies on magnetic properties and spin-dependent behaviors of monolayer and bilayer armchair and zigzag graphene nanoribbons is investigated using first principles calculations based on density functional theory (DFT). The armchair and zigzag graphene nanoribbons are composed of 6 rows and 4 rows of carbon atoms with the edges closed by the hydrogen atoms, respectively. Our results show that vacancies affect the magnetic properties and spin polarization of the graphene nanoribbons. It is seen that the monolayer armchair graphene nanoribbon with one vacancy in its supercell (24 carbon sites + 8 hydrogen sites) gives the magnetic moment of 0.79 μB , while magnetic moment in the monolayer zigzag graphene nanoribbon with one vacancy in its supercell (24 carbon sites + 6 hydrogen sites) is 1.72 μB (for site α) and 1.84 μB (for site β). The highest and lowest values of magnetic moment in different configurations of the bilayer armchair (zigzag) graphene nanoribbons with one vacancy in each layer of the supercell give 1.54 μB and 1.29 μB (3.51 μB and 2.72 μB), respectively. Numerical values of the magnetic moment in different configurations depended on the distance of vacancies from each other and from nanoribbon's edge as well as their orientations.

  20. Magnon Valve Effect between Two Magnetic Insulators

    Science.gov (United States)

    Wu, H.; Huang, L.; Fang, C.; Yang, B. S.; Wan, C. H.; Yu, G. Q.; Feng, J. F.; Wei, H. X.; Han, X. F.

    2018-03-01

    The key physics of the spin valve involves spin-polarized conduction electrons propagating between two magnetic layers such that the device conductance is controlled by the relative magnetization orientation of two magnetic layers. Here, we report the effect of a magnon valve which is made of two ferromagnetic insulators (YIG) separated by a nonmagnetic spacer layer (Au). When a thermal gradient is applied perpendicular to the layers, the inverse spin Hall voltage output detected by a Pt bar placed on top of the magnon valve depends on the relative orientation of the magnetization of two YIG layers, indicating the magnon current induced by the spin Seebeck effect at one layer affects the magnon current in the other layer separated by Au. We interpret the magnon valve effect by the angular momentum conversion and propagation between magnons in two YIG layers and conduction electrons in the Au layer. The temperature dependence of the magnon valve ratio shows approximately a power law, supporting the above magnon-electron spin conversion mechanism. This work opens a new class of valve structures beyond the conventional spin valves.

  1. Valve Disease

    Science.gov (United States)

    ... phen and Redux, which were removed from the market after being linked to heart valve disease. An ... have a prosthetic valve made of synthetic material. Beta-blockers control your heart rate and lower your ...

  2. Control Valve

    Energy Technology Data Exchange (ETDEWEB)

    Moore, Wayne R.

    2018-03-20

    A control valve includes a first conduit having a first inlet and a first outlet and defining a first passage; a second conduit having a second inlet and a second outlet and defining a second passage, the second conduit extending into the first passage such that the second inlet is located within the first passage; and a valve plate disposed pivotably within the first passage, the valve plate defining a valve plate surface. Pivoting of the valve plate within the first passage varies flow from the first inlet to the first outlet and the valve plate is pivotal between a first position and a second position such that in the first position the valve plate substantially prevents fluid communication between the first passage and the second passage and such that in the second position the valve plate permits fluid communication between the first passage and the second passage.

  3. Valve assembly

    International Nuclear Information System (INIS)

    Sandling, M.

    1981-01-01

    An improved valve assembly, used for controlling the flow of radioactive slurry, is described. Radioactive contamination of the air during removal or replacement of the valve is prevented by sucking air from the atmosphere through a portion of the structure above the valve housing. (U.K.)

  4. Problem: Heart Valve Stenosis

    Science.gov (United States)

    ... Understanding Problems and Causes Heart Murmurs and Valve Disease "Innocent" Heart Murmur Problem: Valve Stenosis - Problem: Aortic Valve Stenosis - Problem: Mitral Valve Stenosis - Problem: Tricuspid Valve Stenosis - Problem: Pulmonary Valve Stenosis Problem: Mitral ...

  5. On the effects of leaflet microstructure and constitutive model on the closing behavior of the mitral valve.

    Science.gov (United States)

    Lee, Chung-Hao; Rabbah, Jean-Pierre; Yoganathan, Ajit P; Gorman, Robert C; Gorman, Joseph H; Sacks, Michael S

    2015-11-01

    Recent long-term studies showed an unsatisfactory recurrence rate of severe mitral regurgitation 3-5 years after surgical repair, suggesting that excessive tissue stresses and the resulting strain-induced tissue failure are potential etiological factors controlling the success of surgical repair for treating mitral valve (MV) diseases. We hypothesized that restoring normal MV tissue stresses in MV repair techniques would ultimately lead to improved repair durability through the restoration of MV normal homeostatic state. Therefore, we developed a micro- and macro- anatomically accurate MV finite element model by incorporating actual fiber microstructural architecture and a realistic structure-based constitutive model. We investigated MV closing behaviors, with extensive in vitro data used for validating the proposed model. Comparative and parametric studies were conducted to identify essential model fidelity and information for achieving desirable accuracy. More importantly, for the first time, the interrelationship between the local fiber ensemble behavior and the organ-level MV closing behavior was investigated using a computational simulation. These novel results indicated not only the appropriate parameter ranges, but also the importance of the microstructural tuning (i.e., straightening and re-orientation) of the collagen/elastin fiber networks at the macroscopic tissue level for facilitating the proper coaptation and natural functioning of the MV apparatus under physiological loading at the organ level. The proposed computational model would serve as a logical first step toward our long-term modeling goal-facilitating simulation-guided design of optimal surgical repair strategies for treating diseased MVs with significantly enhanced durability.

  6. Mitral Valve Prolapse

    Science.gov (United States)

    ... Aortic Valve Regurgitation - Problem: Mitral Valve Regurgitation - Problem: Tricuspid Valve Regurgitation - Problem: Pulmonary ... Heart Valve Disease Symptoms Dr. Robert Bonow describes the symptoms that ...

  7. The phase diagrams and compensation behaviors of mixed spin Blume-Capel model in a trimodal magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Y.F. [Department of Physics, Suzhou University, Suzhou 215006 (China); Yan, S.L. [Department of Physics, Suzhou University, Suzhou 215006 (China); Jiangsu Key Loboratory of Film Materials, Suzhou University, Suzhou 215006 (China); CCAST (World Laboratory), PO Box 8730, Beijing 100080 (China)], E-mail: slyan@suda.edu.cn

    2008-04-07

    The phase diagrams and compensation behaviors of mixed spin-1/2 and spin-1 Blume-Capel model in a trimodal magnetic field are investigated in the framework of the effective field theory on simple cubic lattice. The change of negative crystal field and trimodal concentration can affect the TCP, the second-order phase and the magnetic field degeneration at ground state in T-H space. In T-D space, the trajectory of the TCP takes on the acre curve and there exist the two TCPs under certain condition. In addition to giving one or two compensation temperature points in M-T space, the mixed spin Blume-Capel model also provides one or two novel compensation magnetic field points in M-H space. Some results are not revealed in previous works.

  8. Experimental evidence of spin glass and exchange bias behavior in sputtered grown α-MnO{sub 2} nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Ashwani; Sanger, Amit; Singh, Amit Kumar; Kumar, Arvind [Nanoscience Laboratory, Institute Instrumentation Centre, Indian Institute of Technology Roorkee, Roorkee 247667 (India); Kumar, Mohit [Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100 (Israel); Chandra, Ramesh [Nanoscience Laboratory, Institute Instrumentation Centre, Indian Institute of Technology Roorkee, Roorkee 247667 (India)

    2017-07-01

    Highlights: • We have synthesized the α-MnO{sub 2} nanorods by using DC reactive sputtering. • We observed Spin glass and exchange bias behavior at low temperature in sputtered grown α-MnO{sub 2} nanorods. • Exchange bias arises due to exchange coupling of uncompensated FM spins and AFM spins at FM/AFM interface. - Abstract: Here, we present a single-step process to synthesize the α-MnO{sub 2} nanorods forest using reactive DC magnetron sputtering for the application of magnetic memories. The structural and morphological properties of the α-MnO{sub 2} nanorods were systematically studied using numerous analytical techniques, including X-ray diffraction, Raman spectroscopy, field-emission scanning electron microscopy and transmission electron microscopy. The magnetic measurements suggest that the α-MnO{sub 2} nanorods exhibit spin glass and exchange bias behaviour at low temperature. Such low temperature behaviour is explained by the core-shell type structure of nanorods. Antiferromagnetic core and shell of uncompensated ferromagnetic spins leads to the formation of antiferromagnetic/ferromagnetic (AFM/FM) interfaces, which originates exchange bias in the sample.

  9. Spin assignment and behavior of superdeformed bands in A∼150 mass region

    International Nuclear Information System (INIS)

    Khalaf, A.; Sirag, M.; Taha, M.

    2012-01-01

    The smoothed experimental dynamical moment of inertia J (2) values were fitted with a theoretical version depend on Harris three parameter formula in even power of angular frequency ω, derived for results from cranking model. The expansion parameters were adjusted by using a computer simulated search program. The best expansion parameters from the fit were used to assign the spins of the superdeformed ( SD ) rotational bands (RB ) by integrating the calculated J (2) . The data set include 23 RB's in 11 SD nuclei, which show no evidence of either irregular behavior near the bottom of the bands or abrupt angular momentum at low rotational frequency in the mass region ranging from A= 142 to A = 154. we used the differences of angular momenta at constant frequency as effective alignment. The relative properties of superdeformed rotational bands (SDRB's) are analyzed in terms of the effective alignment of the valence nucleons. The effective alignment is a powerful tool to assign the configurations, to select the identical bands as well as to predict new SD bands from other combination of the orbitals. The ΔI = 2 energy staggering observed in 3 of our selected SDRB's are also described from a smooth reference representing the finite difference approximation to the fourth derivative of the γ-ray transition energies.

  10. Circuit Simulation of All-Spin Logic

    KAUST Repository

    Alawein, Meshal

    2016-05-01

    With the aggressive scaling of complementary metal-oxide semiconductor (CMOS) nearing an inevitable physical limit and its well-known power crisis, the quest for an alternative/augmenting technology that surpasses the current semiconductor electronics is needed for further technological progress. Spintronic devices emerge as prime candidates for Beyond CMOS era by utilizing the electron spin as an extra degree of freedom to decrease the power consumption and overcome the velocity limit connected with the charge. By using the nonvolatility nature of magnetization along with its direction to represent a bit of information and then manipulating it by spin-polarized currents, routes are opened for combined memory and logic. This would not have been possible without the recent discoveries in the physics of nanomagnetism such as spin-transfer torque (STT) whereby a spin-polarized current can excite magnetization dynamics through the transfer of spin angular momentum. STT have expanded the available means of switching the magnetization of magnetic layers beyond old classical techniques, promising to fulfill the need for a new generation of dense, fast, and nonvolatile logic and storage devices. All-spin logic (ASL) is among the most promising spintronic logic switches due to its low power consumption, logic-in-memory structure, and operation on pure spin currents. The device is based on a lateral nonlocal spin valve and STT switching. It utilizes two nanomagnets (whereby information is stored) that communicate with pure spin currents through a spin-coherent nonmagnetic channel. By using the well-known spin physics and the recently proposed four-component spin circuit formalism, ASL can be thoroughly studied and simulated. Previous attempts to model ASL in the linear and diffusive regime either neglect the dynamic characteristics of transport or do not provide a scalable and robust platform for full micromagnetic simulations and inclusion of other effects like spin Hall

  11. Crystallization and Martensitic Transformation Behavior of Ti-Ni-Si Alloy Ribbons Prepared via Melt Spinning.

    Science.gov (United States)

    Park, Ju-Wan; Kim, Yeon-Wook; Nam, Tae-Hyun

    2018-09-01

    Ti-(50-x)Ni-xSi (at%) (x = 0.5, 1.0, 3.0, 5.0) alloy ribbons were prepared via melt spinning and their crystallization procedure and transformation behavior were investigated using differential scanning calorimtry, X-ray diffraction, and transmission electron microscopy. Ti-Ni-Si alloy ribbons with Si content less than 1.0 at% were crystalline, whereas those with Si content more than 3.0 at% were amorphous. Crystallization occurred in the sequence of amorphous →B2 → B2 → Ti5Si4 + TiNi3 → B2 + Ti5Si4 + TiNi3 + TiSi in the Ti-47.0Ni-3.0Si alloy and amorphous →R → R + Ti5Si4 + TiNi3 → R + Ti5Si4 + TiNi3 + TiSi in the Ti-45.0Ni-5.0Si alloy. The activation energy for crystallization was 189 ±8.6 kJ/mol for the Ti-47Ni-3Si alloy and 212±8.6 kJ/mol for the Ti-45Ni-5Si alloy. One-stage B2-R transformation behavior was observed in Ti-49.5Ni-0.5Si, Ti-49.0Ni-1.0Si, and Ti-47.0Ni- 3.0Si alloy ribbons after heating to various temperatures in the range of 873 K to 1073 K. In the Ti-45.0Ni-5.0Si alloy, one-stage B2-R transformation occurred after heating to 893 K, two-stage B2-R-B19' occurred after heating to 973 K, and two-stage B2-R-B19' occurred on cooling and one-stage B19'-B2 occurred on heating, after heating to 1073 K.

  12. Robust spin transfer torque in antiferromagnetic tunnel junctions

    KAUST Repository

    Saidaoui, Hamed Ben Mohamed

    2017-04-18

    We theoretically study the current-induced spin torque in antiferromagnetic tunnel junctions, composed of two semi-infinite antiferromagnetic layers separated by a tunnel barrier, in both clean and disordered regimes. We find that the torque enabling electrical manipulation of the Néel antiferromagnetic order parameter is out of plane, ∼n×p, while the torque competing with the antiferromagnetic exchange is in plane, ∼n×(p×n). Here, p and n are the Néel order parameter direction of the reference and free layers, respectively. Their bias dependence shows behavior similar to that in ferromagnetic tunnel junctions, the in-plane torque being mostly linear in bias, while the out-of-plane torque is quadratic. Most importantly, we find that the spin transfer torque in antiferromagnetic tunnel junctions is much more robust against disorder than that in antiferromagnetic metallic spin valves due to the tunneling nature of spin transport.

  13. Small sodium valve design and operating experience

    International Nuclear Information System (INIS)

    Abramson, R.; Elie, X.; Vercasson, M.; Nedelec, J.

    1974-01-01

    Conventionally, valves for sodium pipes smaller than 125 mm in diameter are called ''small sodium valves''. However, this limit should rather be considered as the lower limit o ''large sodium valves''. In fact, both the largest sizes of small valves and the smallest of large valves can be found in the range of 125-300 mm in diameter. Thus what is said about small valves also applies, for a few valve types, above the 125 mm limit. Sodium valves are described here in a general manner, with no manufacturing details except when necessary for understanding valve behavior. Operating experience is pointed out wherever possible. Finally, some information is given about ongoing or proposed development plans. (U.S.)

  14. Cyclic stress-strain behavior of polymeric nonwoven structures for the use as artificial leaflet material for transcatheter heart valve prostheses

    Directory of Open Access Journals (Sweden)

    Arbeiter Daniela

    2017-09-01

    Full Text Available Xenogenic leaflet material, bovine and porcine pericardium, is widely used for the fabrication of surgically implanted and transcatheter heart valve prostheses. As a biological material, long term durability of pericardium is limited due to calcification, degeneration and homogeneity. Therefore, polymeric materials represent a promising approach for a next generation of artificial heart valve leaflets with improved durability. Within the current study we analyzed the mechanical performance of polymeric structures based on elastomeric materials. Polymeric cast films were prepared and nonwovens were manufactured in an electrospinning process. Analysis of cyclic stress-strain behavior was performed, using a universal testing machine. The uniaxial cyclic tensile experiments of the elastomeric samples yielded a non-linear elastic response due to viscoelastic behavior with hysteresis. Equilibrium of stress-strain curves was found after a specific number of cycles, for cast films and nonwovens, respectively. In conclusion, preconditioning was found obligatory for the evaluation of the mechanical performance of polymeric materials for the use as artificial leaflet material for heart valve prostheses.

  15. Valve Corporation: Strategy Tipping Points and Thresholds

    Directory of Open Access Journals (Sweden)

    Teppo Felin

    2015-06-01

    Full Text Available Valve Corporation represents an intriguing case study of flat structure and self organization (Puranam & Håkonsson, 2015; Valve, 2012.  The structures and practices of Valve of course are not new. But the company provides an interesting experiment and illustration that powerfully highlights how organizational design can impact individual and collective behavior, strategy and performance.

  16. Valve Repair or Replacement

    Science.gov (United States)

    ... Replacement Menu Topics Topics FAQs Valve Repair or Replacement Heart valves play a key role in this ... leaflets with a tissue patch. What is valve replacement? Severe valve damage means the valve must be ...

  17. Amplification of spin-current polarization

    Science.gov (United States)

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

    2007-08-01

    A ferromagnet/semiconductor based electrically controlled spin-current amplifier using a dual-drain nonlocal lateral spin valve is demonstrated. The spin polarization injected by the source into the channel is amplified at the second drain contact. An amplified current spin polarization of 100% is measured. The controlled variation of amplifier gain with bias is also demonstrated. The observations are explained in the framework of the spin drift-diffusion model.

  18. Electrically Driven Spin Dynamics of Paramagnetic Impurities

    Science.gov (United States)

    Saha, D.; Siddiqui, L.; Bhattacharya, P.; Datta, S.; Basu, D.; Holub, M.

    2008-05-01

    The spin dynamics of dilute paramagnetic impurities embedded in a semiconductor GaAs channel of a conventional lateral spin valve has been investigated. It is observed that the electron spin of paramagnetic Mn atoms can be polarized electrically when driven by a spin valve in the antiparallel configuration. The transient current through the MnAs/GaAs/MnAs spin valve bears the signature of the underlying spin dynamics driven by the exchange interaction between the conduction band electrons in GaAs and the localized Mn electron spins. The time constant for this interaction is observed to be dependent on temperature and is estimated to be 80 ns at 15 K.

  19. Collective Behavior of a Spin-Aligned Gas of Interwell Excitons in Double Quantum Wells

    DEFF Research Database (Denmark)

    Larionov, A. V.; Bayer, M.; Hvam, Jørn Märcher

    2005-01-01

    The kinetics of a spin-aligned gas of interwell excitons in GaAs/AlGaAs double quantum wells (n–i–n heterostructure) is studied. The temperature dependence of the spin relaxation time for excitons, in which a photoexcited electron and hole are spatially separated between two adjacent quantum well...... is associated with indirect evidence of the coherence of the collective phase of interwell excitons at temperatures below the critical value....

  20. Antiferromagnetic spin-orbitronics

    KAUST Repository

    Manchon, Aurelien

    2015-05-01

    Antiferromagnets have long remained an intriguing and exotic state of matter, whose application has been restricted to enabling interfacial exchange bias in metallic and tunneling spin-valves [1]. Their role in the expanding field of applied spintronics has been mostly passive and the in-depth investigation of their basic properties mostly considered from a fundamental perspective.

  1. Spinning gland transcriptomics from two main clades of spiders (order: Araneae--insights on their molecular, anatomical and behavioral evolution.

    Directory of Open Access Journals (Sweden)

    Francisco Prosdocimi

    Full Text Available Characterized by distinctive evolutionary adaptations, spiders provide a comprehensive system for evolutionary and developmental studies of anatomical organs, including silk and venom production. Here we performed cDNA sequencing using massively parallel sequencers (454 GS-FLX Titanium to generate ∼80,000 reads from the spinning gland of Actinopus spp. (infraorder: Mygalomorphae and Gasteracantha cancriformis (infraorder: Araneomorphae, Orbiculariae clade. Actinopus spp. retains primitive characteristics on web usage and presents a single undifferentiated spinning gland while the orbiculariae spiders have seven differentiated spinning glands and complex patterns of web usage. MIRA, Celera Assembler and CAP3 software were used to cluster NGS reads for each spider. CAP3 unigenes passed through a pipeline for automatic annotation, classification by biological function, and comparative transcriptomics. Genes related to spider silks were manually curated and analyzed. Although a single spidroin gene family was found in Actinopus spp., a vast repertoire of specialized spider silk proteins was encountered in orbiculariae. Astacin-like metalloproteases (meprin subfamily were shown to be some of the most sampled unigenes and duplicated gene families in G. cancriformis since its evolutionary split from mygalomorphs. Our results confirm that the evolution of the molecular repertoire of silk proteins was accompanied by the (i anatomical differentiation of spinning glands and (ii behavioral complexification in the web usage. Finally, a phylogenetic tree was constructed to cluster most of the known spidroins in gene clades. This is the first large-scale, multi-organism transcriptome for spider spinning glands and a first step into a broad understanding of spider web systems biology and evolution.

  2. Antiferromagnetic versus spin-glass like behavior in MnIn{sub 2}S{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Sagredo, V. [Laboratorio de Magnetismo, Departamento de Fisica, Facultad de Ciencias, Universidad de los Andes, Merida (Venezuela)]. E-mail: sagredo@ula.ve; Moron, M.C. [Instituto de Ciencia de Materiales de Aragon, C.S.I.C.-Universidad de Zaragoza, E-50009, Zaragoza (Spain); Betancourt, L. [Laboratorio de Magnetismo, Departamento de Fisica, Facultad de Ciencias, Universidad de los Andes, Merida (Venezuela); Delgado, G.E. [Laboratorio de Cristalografia, Departamento de Quimica, Facultad de Ciencias, Universidad de los Andes, Merida (Venezuela)

    2007-05-15

    The low-temperature magnetic properties of MnIn{sub 2}S{sub 4} have been studied using AC magnetic susceptibility and magnetization experiments. High-temperature susceptibility fits indicate the presence of antiferromagnetic interactions. Low-field magnetization data show a peak at 5.6{+-}0.1 K, below which strong irreversibility is observed between zero-field-cooled (ZFC) and field-cooled (FC) cycles suggesting that the observed peak corresponds to a spin-glass-like transition instead of the antiferromagnetic one previously reported. Further evidence of this magnetic state comes from AC susceptibility data at different frequencies. The in-phase component {chi}'(T) exhibits the behavior expected of spin glasses, i.e. a shift of the cusp to higher temperatures for higher frequencies.

  3. Behavior of a spin-1/2 massive charged particle in Schwarzschild immersed in an electromagnetic universe

    Science.gov (United States)

    Al-Badawi, A.

    2018-02-01

    The Dirac equation is considered in a spacetime that represents a Schwarzschild metric coupled to a uniform external electromagnetic field. Due to the presence of electromagnetic field from the surroundings, the interaction with the spin-1/2 massive charged particle is considered. The equations of the spin-1/2 massive charged particle are separated into radial and angular equations by adopting the Newman-Penrose formalism. The angular equations obtained are similar to the Schwarzschild geometry. For the radial equations we manage to obtain the one dimensional Schrödinger-type wave equations with effective potentials. Finally, we study the behavior of the potentials by plotting them as a function of radial distance and expose the effect of the external parameter, charge and the frequency of the particle on them.

  4. Nuclear radiation actuated valve

    Science.gov (United States)

    Christiansen, David W.; Schively, Dixon P.

    1985-01-01

    A nuclear radiation actuated valve for a nuclear reactor. The valve has a valve first part (such as a valve rod with piston) and a valve second part (such as a valve tube surrounding the valve rod, with the valve tube having side slots surrounding the piston). Both valve parts have known nuclear radiation swelling characteristics. The valve's first part is positioned to receive nuclear radiation from the nuclear reactor's fuel region. The valve's second part is positioned so that its nuclear radiation induced swelling is different from that of the valve's first part. The valve's second part also is positioned so that the valve's first and second parts create a valve orifice which changes in size due to the different nuclear radiation caused swelling of the valve's first part compared to the valve's second part. The valve may be used in a nuclear reactor's core coolant system.

  5. Analysis of Complex Valve and Feed Systems

    Science.gov (United States)

    Ahuja, Vineet; Hosangadi, Ashvin; Shipman, Jeremy; Cavallo, Peter; Dash, Sanford

    2007-01-01

    A numerical framework for analysis of complex valve systems supports testing of propulsive systems by simulating key valve and control system components in the test loop. In particular, it is designed to enhance the analysis capability in terms of identifying system transients and quantifying the valve response to these transients. This system has analysis capability for simulating valve motion in complex systems operating in diverse flow regimes ranging from compressible gases to cryogenic liquids. A key feature is the hybrid, unstructured framework with sub-models for grid movement and phase change including cryogenic cavitations. The multi-element unstructured framework offers improved predictions of valve performance characteristics under steady conditions for structurally complex valves such as pressure regulator valve. Unsteady simulations of valve motion using this computational approach have been carried out for various valves in operation at Stennis Space Center such as the split-body valve and the 10-in. (approx.25.4-cm) LOX (liquid oxygen) valve and the 4-in. (approx.10 cm) Y-pattern valve (liquid nitrogen). Such simulations make use of variable grid topologies, thereby permitting solution accuracy and resolving important flow physics in the seat region of the moving valve. An advantage to this software includes possible reduction in testing costs incurred due to disruptions relating to unexpected flow transients or functioning of valve/flow control systems. Prediction of the flow anomalies leading to system vibrations, flow resonance, and valve stall can help in valve scheduling and significantly reduce the need for activation tests. This framework has been evaluated for its ability to predict performance metrics like flow coefficient for cavitating venturis and valve coefficient curves, and could be a valuable tool in predicting and understanding anomalous behavior of system components at rocket propulsion testing and design sites.

  6. Evidence for reentrant spin glass behavior in transition metal substituted Co-Ga alloys near critical concentration

    Science.gov (United States)

    Yasin, Sk. Mohammad; Srinivas, V.; Kasiviswanathan, S.; Vagadia, Megha; Nigam, A. K.

    2018-04-01

    In the present study magnetic and electrical transport properties of transition metal substituted Co-Ga alloys (near critical cobalt concentration) have been investigated. Analysis of temperature and field dependence of dc magnetization and ac susceptibility (ACS) data suggests an evidence of reentrant spin glass (RSG) phase in Co55.5TM3Ga41.5 (TM = Co, Cr, Fe, Cu). The magnetic transition temperatures (TC and Tf) are found to depend on the nature of TM element substitution with the exchange coupling strength Co-Fe > Co-Co > Co-Cu > Co-Cr. From magnetization dynamics precise transition temperatures for the glassy phases are estimated. It is found that characteristic relaxation times are higher than that of spin glasses with minimal spin-cluster formation. The RSG behavior has been further supported by the temperature dependence of magnetotransport studies. From the magnetic field and substitution effects it has been established that the magnetic and electrical transport properties are correlated in this system.

  7. Linear scaling between momentum and spin scattering in graphene

    NARCIS (Netherlands)

    Jozsa, C.; Maassen, T.; Popinciuc, M.; Zomer, P. J.; Veligura, A.; Jonkman, H. T.; van Wees, B. J.

    2009-01-01

    Spin transport in graphene carries the potential of a long spin-diffusion length at room temperature. However, extrinsic relaxation processes limit the current experimental values to 1-2 mu m. We present Hanle spin precession measurements in gated lateral spin valve devices in the low to high (up to

  8. Competing magnetic and spin-gapless semiconducting behavior in fully compensated ferrimagnetic CrVTiAl: Theory and experiment

    Science.gov (United States)

    Venkateswara, Y.; Gupta, Sachin; Samatham, S. Shanmukharao; Varma, Manoj Raama; Enamullah, Suresh, K. G.; Alam, Aftab

    2018-02-01

    We report the structural, magnetic, and transport properties of the polycrystalline CrVTiAl alloy along with first-principles calculations. The alloy crystallizes in a LiMgPdSn-type structure with a lattice parameter of 6.14 Å at room temperature. The absence of the (111) peak along with the presence of a weak (200) peak indicates the antisite disorder of Al with Cr and V atoms, which is different from the pure DO3 type. Magnetization measurements reveal a magnetic transition near 710 K, a coercive field of ˜100 Oe at 3 K, and a moment of ˜10-3μB/f .u . These observations are indicative of fully compensated ferrimagnetism in the alloy, which is confirmed by theoretical modeling. The temperature coefficient of resistivity is found to be negative, signaling the semiconducting nature. However, the absence of exponential dependence indicates the semiconducting nature with gapless/spin-gapless behavior. Electronic and magnetic properties of CrVTiAl for all three possible crystallographic configurations are studied theoretically. All the configurations are found to be different forms of semiconductors. The ground-state configuration is a fully compensated ferrimagnet with band gaps of 0.58 and 0.30 eV for the spin-up and -down bands, respectively. The next-higher-energy configuration is also fully compensated ferrimagnetic but has a spin-gapless semiconducting nature. The highest-energy configuration corresponds to a nonmagnetic, gapless semiconductor. The energy differences among these configurations are quite small (account the theoretical and experimental findings, we conclude that CrVTiAl is a fully compensated ferrimagnet with a predominantly spin-gapless semiconducting nature.

  9. Thermoelectric spin voltage in graphene.

    Science.gov (United States)

    Sierra, Juan F; Neumann, Ingmar; Cuppens, Jo; Raes, Bart; Costache, Marius V; Valenzuela, Sergio O

    2018-02-01

    In recent years, new spin-dependent thermal effects have been discovered in ferromagnets, stimulating a growing interest in spin caloritronics, a field that exploits the interaction between spin and heat currents 1,2 . Amongst the most intriguing phenomena is the spin Seebeck effect 3-5 , in which a thermal gradient gives rise to spin currents that are detected through the inverse spin Hall effect 6-8 . Non-magnetic materials such as graphene are also relevant for spin caloritronics, thanks to efficient spin transport 9-11 , energy-dependent carrier mobility and unique density of states 12,13 . Here, we propose and demonstrate that a carrier thermal gradient in a graphene lateral spin valve can lead to a large increase of the spin voltage near to the graphene charge neutrality point. Such an increase results from a thermoelectric spin voltage, which is analogous to the voltage in a thermocouple and that can be enhanced by the presence of hot carriers generated by an applied current 14-17 . These results could prove crucial to drive graphene spintronic devices and, in particular, to sustain pure spin signals with thermal gradients and to tune the remote spin accumulation by varying the spin-injection bias.

  10. Pseudogap Behavior of the Nuclear Spin-Lattice Relaxation Rate in FeSe Probed by 77Se-NMR

    Science.gov (United States)

    Shi, Anlu; Arai, Takeshi; Kitagawa, Shunsaku; Yamanaka, Takayoshi; Ishida, Kenji; Böhmer, Anna E.; Meingast, Christoph; Wolf, Thomas; Hirata, Michihiro; Sasaki, Takahiko

    2018-01-01

    We conducted 77Se-nuclear magnetic resonance studies of the iron-based superconductor FeSe in magnetic fields of 0.6 to 19 T to investigate the superconducting and normal-state properties. The nuclear spin-lattice relaxation rate divided by the temperature (T1T)-1 increases below the structural transition temperature Ts but starts to be suppressed below T*, well above the superconducting transition temperature Tc(H), resulting in a broad maximum of (T1T)-1 at Tp(H). This is similar to the pseudogap behavior in optimally doped cuprate superconductors. Because T* and Tp(H) decrease in the same manner as Tc(H) with increasing H, the pseudogap behavior in FeSe is ascribed to superconducting fluctuations, which presumably originate from the theoretically predicted preformed pair above Tc(H).

  11. First-order transition and tricritical behavior of the transverse crystal field spin-1 Ising model

    Science.gov (United States)

    Costabile, Emanuel; Viana, J. Roberto; de Sousa, J. Ricardo; de Arruda, Alberto S.

    2015-06-01

    The phase diagram of the spin-1 Ising model in the presence of a transverse crystal-field anisotropy (Dx) is studied within the framework of an effective-field theory with correlation. The effect of the coordination number (z) on the phase diagram in the T -Dx plane is investigated. We observe only second-order transitions for coordination number z Ricardo de Sousa and Branco, Phys. Rev. E 77 (2008) 012104] with a single tricritical point in the phase diagram.

  12. Spin Transfer Torque in Graphene

    Science.gov (United States)

    Lin, Chia-Ching; Chen, Zhihong

    2014-03-01

    Graphene is an idea channel material for spin transport due to its long spin diffusion length. To develop graphene based spin logic, it is important to demonstrate spin transfer torque in graphene. Here, we report the experimental measurement of spin transfer torque in graphene nonlocal spin valve devices. Assisted by a small external in-plane magnetic field, the magnetization reversal of the receiving magnet is induced by pure spin diffusion currents from the injector magnet. The magnetization switching is reversible between parallel and antiparallel configurations by controlling the polarity of the applied charged currents. Current induced heating and Oersted field from the nonlocal charge flow have also been excluded in this study. Next, we further enhance the spin angular momentum absorption at the interface of the receiving magnet and graphene channel by removing the tunneling barrier in the receiving magnet. The device with a tunneling barrier only at the injector magnet shows a comparable nonlocal spin valve signal but lower electrical noise. Moreover, in the same preset condition, the critical charge current density for spin torque in the single tunneling barrier device shows a substantial reduction if compared to the double tunneling barrier device.

  13. Spin-glass behavior of warwickite MgFeBO{sub 4} and CoFeBO{sub 4} crystals observed by Mössbauer spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Lyubutin, I.S.; Korotkov, N. Yu.; Frolov, K.V. [Shubnikov Institute of Crystallography, RAS, 119333 Moscow (Russian Federation); Kazak, N.V.; Platunov, M.S. [Kirensky Institute of Physics, SB of RAS, 660036 Krasnoyarsk (Russian Federation); Knyazev, Yu. V. [Siberian Federal University, 660074 Krasnoyarsk (Russian Federation); Bezmaternykh, L.N. [Kirensky Institute of Physics, SB of RAS, 660036 Krasnoyarsk (Russian Federation); Ovchinnikov, S.G. [Kirensky Institute of Physics, SB of RAS, 660036 Krasnoyarsk (Russian Federation); Siberian Federal University, 660074 Krasnoyarsk (Russian Federation); Siberian State Aerospace University, 660014 Krasnoyarsk (Russian Federation); Arauzo, A. [Servicio de Medidas Físicas, Universidad de Zaragoza, Pedro Cerbuna 12, 50009 Zaragoza (Spain); Bartolomé, J. [Instituto de Ciencia de Materiales de Aragón, CSIC-Universidad de Zaragoza and Departamento de Física de la Materia Condensada, 50009 Zaragoza (Spain)

    2015-09-05

    Highlights: • Spin-glass behavior of MgFeBO{sub 4} and CoFeBO{sub 4} observed by Mössbauer spectroscopy. • Transition temperature T{sub SG} increases strongly with Co substitution. • Dynamical scaling theory near T{sub SG} is fulfilled. • Spin-glass behavior is explained as due to short range correlations. • Inclusion of Co increases exchange interaction and magnetocrystalline anisotropy. - Abstract: Single crystals of MgFeBO{sub 4} and CoFeBO{sub 4} warwickites were obtained. The effects of charge ordering and magnetic properties were investigated by Mössbauer spectroscopy. Cation distribution over M1 and M2 nonequivalent sites and the average charge at the metal positions were established. Low temperature Mössbauer spectra reveal spin-glass behavior, with spin-freezing temperatures T{sub SG} of 15.2 and 33.2 K for Mg- and Co-warwickites, respectively, higher than that observed from the d.c. and a.c. magnetic susceptibility measurements. The difference is explained in terms of dynamical scaling theory. The specific shape of the Mössbauer spectra in the vicinity of the magnetic transition at T{sub SG} shows the difference between spin-glass and superparamagnetic behavior and demonstrates an overwhelming role of the exchange anisotropy in the properties of Mg-warwickite. In Co-warwickite the increase of magnetocrystalline anisotropy provokes an increase in magnetic viscosity.

  14. Diseases of the Tricuspid Valve

    Science.gov (United States)

    ... Valve Menu Topics Topics FAQs Diseases of the Tricuspid Valve Diseases of the heart valves are grouped according to ... heart valves , tricuspid incompetence , tricuspid insufficiency , tricuspid regurgitation , tricuspid ... Links MedlinePlus | Tricuspid Regurgitation Valve Disease Valve ...

  15. Room temperature relaxor ferroelectricity and spin glass behavior in Sr2FeTiO6 double perovskite

    International Nuclear Information System (INIS)

    Neenu Lekshmi, P.; Savitha Pillai, S.; Suresh, K.G.; Santhosh, P.N.; Varma, Manoj Raama

    2012-01-01

    Highlights: ► Studied the structure, dielectric and magnetic properties of Sr 2 FeTiO 6 complex double perovskite. ► The thermal evolution of the lattice parameter and volume shows no structural phase transition. ► Dielectric data analysis shows a diffuse phase transition characteristics. ► The diffusion-assisted small-polaron hopping conduction evidences an intermediate-valence state and semiconductor like behaviour. ► The magnetic characterisation exhibits a non-metallic spin-glass-like state below 16 K. - Abstract: The structure, dielectric and magnetic properties of complex Sr 2 FeTiO 6 double perovskite have been investigated. Reitveld analysis of X-ray powder diffraction pattern reveals that the material is stabilized in a cubic perovskite phase with Pm3 ¯ m space group without the B-site cations ordering. The temperature evolution of crystal structural studies indicates the absence of structural changes with temperature. The scanning electron micrograph exhibits heterogeneous grain distribution with average grain size of 1–7.5 μm. The bond valence sum calculations and diffusion-assisted small-polaron hopping conduction mechanism confirm the mixed valence state of Fe/Ti ions. Dielectric spectra show a broad dielectric anomaly coupled with a shift in dielectric maxima towards higher temperature with frequency, exhibiting a typical relaxor ferroelectric behavior. The relaxor behavior has been quantitatively characterized based on the phenomenological parameters (T m , T B , γ, ΔT relax ). The agreement of dielectric relaxation with non-linear Vogel Fulcher relation indicates that the system is indeed a relaxor exhibiting glassy characteristics. The transport studies show a semiconductor like behavior and a negligible magnetoresistance. Furthermore, the magnetic characterisation exhibits a non-metallic spin-glass-like state below 16 K, driven by competing interactions between the antiferromagnetic and the ferromagnetic states.

  16. Universal critical behavior of the two-dimensional Ising spin glass

    Science.gov (United States)

    Fernandez, L. A.; Marinari, E.; Martin-Mayor, V.; Parisi, G.; Ruiz-Lorenzo, J. J.

    2016-07-01

    We use finite size scaling to study Ising spin glasses in two spatial dimensions. The issue of universality is addressed by comparing discrete and continuous probability distributions for the quenched random couplings. The sophisticated temperature dependency of the scaling fields is identified as the major obstacle that has impeded a complete analysis. Once temperature is relinquished in favor of the correlation length as the basic variable, we obtain a reliable estimation of the anomalous dimension and of the thermal critical exponent. Universality among binary and Gaussian couplings is confirmed to a high numerical accuracy.

  17. Valve's Way

    DEFF Research Database (Denmark)

    Foss, Nicolai Juul; Dobrajska, Magdalena

    2015-01-01

    Puranam and Håkonsson (2015) challenge us to ponder what we as organization design theorists make of Valve’s way (see also Jeppesen, 2008). We believe that Valve, in spite of its radical vision, does not represent a challenge to fundamental organization design theory and that it is questionable...

  18. Vacuum Valve

    CERN Multimedia

    1974-01-01

    This valve was used in the Intersecting Storage Rings (ISR) to protect against the shock waves that would be caused if air were to enter the vacuum tube. Some of the ISR chambers were very fragile, with very thin walls - a design required by physicists on the lookout for new particles.

  19. Reentrant spin glass behavior in polycrystalline La0.7Sr0.3Mn1-XFeXO 3

    Directory of Open Access Journals (Sweden)

    Xavier Jr. M.M.

    2004-01-01

    Full Text Available The magnetic and transport properties of the compound La0.7Sr0.3Mn1-xFe xO 3 (0.1 < x <0.4 have been studied by means of electrical resistivity, AC magnetic susceptibility, and DC magnetization. At low concentrations (x <0.1, the system displays essentially para-to-ferromagnetic transitions as the temperature is decreased, although a decrease in the magnetic moment has been observed in previous studies at temperatures a little below T C. This ferromagnetism is explained by double exchange theory in terms of the formation of Mn+3/Mn+4 ions pairs in the system. At concentrations in the range 0.1 < x <0.4 the system is more complex. Increased Fe doping not only weakens the ferromagnetic (FM order and augments the resistivity of the samples, but also induces the appearance of a reentrant spin glass phase at low temperatures (T < 60 K. Irreversibility of the magnetization measured with zero field cooling and with field cooling has been observed. In addition, the AC susceptibility peak position varies with frequency. All these effects are characteristic of spin glass behavior. The results have been interpreted based in an increase of frustration due to increasing competition between FM Mn+3/Mn+4 interactions and antiferromagnetic interactions between ions at the boundaries of Fe clusters.

  20. Perpendicular Magnetic Anisotropy and Spin Glass-like Behavior in Molecular Beam Epitaxy Grown Chromium Telluride Thin Films.

    Science.gov (United States)

    Roy, Anupam; Guchhait, Samaresh; Dey, Rik; Pramanik, Tanmoy; Hsieh, Cheng-Chih; Rai, Amritesh; Banerjee, Sanjay K

    2015-04-28

    Reflection high-energy electron diffraction (RHEED), scanning tunneling microscopy (STM), vibrating sample magnetometry, and other physical property measurements are used to investigate the structure, morphology, magnetic, and magnetotransport properties of (001)-oriented Cr2Te3 thin films grown on Al2O3(0001) and Si(111)-(7×7) surfaces by molecular beam epitaxy. Streaky RHEED patterns indicate flat smooth film growth on both substrates. STM studies show the hexagonal arrangements of surface atoms. Determination of the lattice parameter from the atomically resolved STM image is consistent with the bulk crystal structures. Magnetic measurements show the film is ferromagnetic, having a Curie temperature of about 180 K, and a spin glass-like behavior was observed below 35 K. Magnetotransport measurements show the metallic nature of the film with a perpendicular magnetic anisotropy along the c-axis.

  1. ESR (electron spin resonance)-determined osmotic behavior of bull spermatozoa

    Energy Technology Data Exchange (ETDEWEB)

    Du, J.; Kleinhans, F.W.; Spitzer, V.J.; Critser, J.K. (Methodist Hospital, Indianapolis, IN (USA). Dept. of Medical Research); Horstman, L. (Purdue Univ., Lafayette, IN (USA). School of Veterinary Medicine); Mazur, P. (Oak Ridge National Lab., TN (USA))

    1990-01-01

    Our laboratories are pursuing a fundamental approach to the problems of semen cryopreservation. For many cell types (human red cells, yeast, HeLa) it has been demonstrated that there is an optimum cooling rate for cryopreservation. Faster rates allow insufficient time for cell dehydration and result in intracellular ice formation and cell death. It is possible to predict this optimal rate provided that the cell acts as an ideal osmometer and several other cell parameters are known such as the membrane hydraulic conductivity. It is the purpose of this work to examine the osmotic response of bull sperm to sucrose and NaCl utilizing electron spin resonance (ESR) to measure cell volume. For calibration purposes we also measured the ESR response of human red cells (RBC), the osmotic response of which is well documented with other methods. 15 refs., 1 fig.

  2. Temperature Dependence of the Elongation Behavior of Polyphenylene Sulfide using Melt Spinning Technique

    Science.gov (United States)

    Tan, Changbin; Yang, Yan; Gao, Jun; Li, Shenghu; Qing, Long

    2017-12-01

    The elongational properties of polyphenylene sulfide (PPS) melt were measured using a melt spinning technique. The relationship between extrusion temperature and melt strength (MS) as well as between elongational viscosity and drawability were investigated with respect to the effects of extrusion temperature and extensional strain rate on the melt extensional stress and elongational viscosity. The results showed that the stretching force for the PPS melt decreased with a rise of extrusion temperature while increased roughly with an increase of extensional rate. The MS decreased with an increase of temperature, and the ln MS was a linear function of 1/T when the extrusion velocity was constant. Both the melt extensional stress and elongational viscosity decreased with the increase of the extrusion temperature. With increase of the extensional strain rate, the extensional stress increased while the melt elongational viscosity first decreases and then increases gradually. A low melt elongational viscosity might be beneficial to improve the melt drawability.

  3. Critical behavior of mean-field spin glasses on a dilute random graph

    Energy Technology Data Exchange (ETDEWEB)

    De Sanctis, Luca [Dipartimento di Matematica e di Psicologia, Universita di Bologna, P.zza di Porta San Donato 5, 40126 Bologna (Italy); Barra, Adriano; Folli, Viola [Dipartimento di Fisica, Universita La Sapienza, P.le Aldo Moro 5, 00185 Roma (Italy)], E-mail: desanctis@dm.unibo.it, E-mail: adriano.barra@roma1.infn.it, E-mail: viola.folli@roma1.infn.it

    2008-05-30

    We provide a rigorous strategy to find the critical exponents of the overlaps for dilute spin glasses, in the absence of an external field. Such a strategy is based on the expansion of a suitably perturbed average of the overlaps, which is used in the formulation of the free energy as the difference between a cavity part and the derivative of the free energy itself, considered as a function of the connectivity of the model. We assume the validity of certain reasonable approximations, equivalent to assuming a second-order transition, e.g. that higher powers of overlap monomials are of smaller magnitude near the critical point, of which we do not provide a rigorous proof.

  4. Critical behavior of mean-field spin glasses on a dilute random graph

    International Nuclear Information System (INIS)

    De Sanctis, Luca; Barra, Adriano; Folli, Viola

    2008-01-01

    We provide a rigorous strategy to find the critical exponents of the overlaps for dilute spin glasses, in the absence of an external field. Such a strategy is based on the expansion of a suitably perturbed average of the overlaps, which is used in the formulation of the free energy as the difference between a cavity part and the derivative of the free energy itself, considered as a function of the connectivity of the model. We assume the validity of certain reasonable approximations, equivalent to assuming a second-order transition, e.g. that higher powers of overlap monomials are of smaller magnitude near the critical point, of which we do not provide a rigorous proof

  5. Aortic valve bypass

    DEFF Research Database (Denmark)

    Lund, Jens T; Jensen, Maiken Brit; Arendrup, Henrik

    2013-01-01

    In aortic valve bypass (AVB) a valve-containing conduit is connecting the apex of the left ventricle to the descending aorta. Candidates are patients with symptomatic aortic valve stenosis rejected for conventional aortic valve replacement (AVR) or transcatheter aortic valve implantation (TAVI). ...

  6. PREFACE: Spin Electronics

    Science.gov (United States)

    Dieny, B.; Sousa, R.; Prejbeanu, L.

    2007-04-01

    Conventional electronics has in the past ignored the spin on the electron, however things began to change in 1988 with the discovery of giant magnetoresistance in metallic thin film stacks which led to the development of a new research area, so called spin-electronics. In the last 10 years, spin-electronics has achieved a number of breakthroughs from the point of view of both basic science and application. Materials research has led to several major discoveries: very large tunnel magnetoresistance effects in tunnel junctions with crystalline barriers due to a new spin-filtering mechanism associated with the spin-dependent symmetry of the electron wave functions new magnetic tunnelling barriers leading to spin-dependent tunnelling barrier heights and acting as spin-filters magnetic semiconductors with increasingly high ordering temperature. New phenomena have been predicted and observed: the possibility of acting on the magnetization of a magnetic nanostructure with a spin-polarized current. This effect, due to a transfer of angular momentum between the spin polarized conduction electrons and the local magnetization, can be viewed as the reciprocal of giant or tunnel magnetoresistance. It can be used to switch the magnetization of a magnetic nanostructure or to generate steady magnetic excitations in the system. the possibility of generating and manipulating spin current without charge current by creating non-equilibrium local accumulation of spin up or spin down electrons. The range of applications of spin electronics materials and phenomena is expanding: the first devices based on giant magnetoresistance were the magnetoresistive read-heads for computer disk drives. These heads, introduced in 1998 with current-in plane spin-valves, have evolved towards low resistance tunnel magnetoresistice heads in 2005. Besides magnetic recording technology, these very sensitive magnetoresistive sensors are finding applications in other areas, in particular in biology. magnetic

  7. Fluid dynamic characterization of a polymeric heart valve prototype (Poli-Valve) tested under continuous and pulsatile flow conditions.

    Science.gov (United States)

    De Gaetano, Francesco; Serrani, Marta; Bagnoli, Paola; Brubert, Jacob; Stasiak, Joanna; Moggridge, Geoff D; Costantino, Maria Laura

    2015-11-01

    Only mechanical and biological heart valve prostheses are currently commercially available. The former show longer durability but require anticoagulant therapy; the latter display better fluid dynamic behavior but do not have adequate durability. New Polymeric Heart Valves (PHVs) could potentially combine the hemodynamic properties of biological valves with the durability of mechanical valves. This work presents a hydrodynamic evaluation of 2 groups of newly developed supra-annular, trileaflet prosthetic heart valves made from styrenic block copolymers (SBC): Poli-Valves. 2 types of Poli-Valves made of SBC and differing in polystyrene fraction content were tested under continuous and pulsatile flow conditions as prescribed by ISO 5840 Standard. A pulse duplicator designed ad hoc allowed the valve prototypes to be tested at different flow rates and frequencies. Pressure and flow were recorded; pressure drops, effective orifice area (EOA), and regurgitant volume were computed to assess the behavior of the valve. Both types of Poli-Valves met the minimum requirements in terms of regurgitation and EOA as specified by the ISO 5840 Standard. Results were compared with 5 mechanical heart valves (MHVs) and 5 tissue heart valves (THVs), currently available on the market. Based on these results, PHVs based on styrenic block copolymers, as are Poli-Valves, can be considered a promising alternative for heart valve replacement in the near future.

  8. Influence of face-centered-cubic texturing of Co2Fe6B2 pinned layer on tunneling magnetoresistance ratio decrease in Co2Fe6B2/MgO-based p-MTJ spin valves stacked with a [Co/Pd](n)-SyAF layer.

    Science.gov (United States)

    Takemura, Yasutaka; Lee, Du-Yeong; Lee, Seung-Eun; Chae, Kyo-Suk; Shim, Tae-Hun; Lian, Guoda; Kim, Moon; Park, Jea-Gun

    2015-05-15

    The TMR ratio of Co2Fe6B2/MgO-based p-MTJ spin valves stacked with a [Co/Pd]n-SyAF layer decreased rapidly when the ex situ magnetic annealing temperature (Tex) was increased from 275 to 325 °C, and this decrease was associated with degradation of the Co2Fe6B2 pinned layer rather than the Co2Fe6B2 free layer. At a Tex above 325 °C the amorphous Co2Fe6B2 pinned layer was transformed into a face-centered-cubic (fcc) crystalline layer textured from [Co/Pd]n-SyAF, abruptly reducing the Δ1 coherence tunneling of perpendicular-spin-torque electrons between the (100) MgO tunneling barrier and the fcc Co2Fe6B2 pinned layer.

  9. Pulse Duplicator Hydrodynamic Testing of Bioengineered Biological Heart Valves.

    Science.gov (United States)

    Buse, Eric E; Hilbert, Stephen L; Hopkins, Richard A; Converse, Gabriel L

    2016-12-01

    There are many heart valve replacements currently available on the market; however, these devices are not ideal for pediatric patients with congenital heart valve defects. Decellularized valve substitutes offer potential for improved clinical outcomes and require pre-clinical testing guidelines and testing systems suitable for non-crosslinked, biological heart valves. The objective of this study was to assess the hydrodynamic performance of intact, bioengineered pulmonary valves using a custom pulse duplicator capable of testing intact biological valved conduits. The mechanical behavior of valve associated sinus and arterial tissue was also evaluated under biaxial loading. Cryopreserved, decellularized, extracellular matrix (ECM) conditioned and glutaraldehyde fixed valves showed reduced pressure gradients and increased effective orifice area for decellularized and ECM conditioned valves. ECM conditioning resulted in increased elastic modulus but decreased stretch in circumferential and longitudinal directions under biaxial loading. Overall, decellularization and ECM conditioning did not compromise the scaffolds, which exhibited satisfactory bench top performance.

  10. Automated control of the laser welding process of heart valve scaffolds

    OpenAIRE

    Weber Moritz; Hoheisel Anna L.; Glasmacher Birgit

    2016-01-01

    Using the electrospinning process the geometry of a heart valve is not replicable by just one manufacturing process. To produce heart valve scaffolds the heart valve leaflets and the vessel have to be produced in separated spinning processes. For the final product of a heart valve they have to be mated afterwards. In this work an already existing three-axes laser was enhanced to laser weld those scaffolds. The automation control software is based on the robot operating system (ROS). The mecha...

  11. Spin glass behavior of the antiferromagnetic Heisenberg model on scale free network

    International Nuclear Information System (INIS)

    Surungan, Tasrief; Zen, Freddy P; Williams, Anthony G

    2015-01-01

    Randomness and frustration are considered to be the key ingredients for the existence of spin glass (SG) phase. In a canonical system, these ingredients are realized by the random mixture of ferromagnetic (FM) and antiferromagnetic (AF) couplings. The study by Bartolozzi et al. [Phys. Rev. B73, 224419 (2006)] who observed the presence of SG phase on the AF Ising model on scale free network (SFN) is stimulating. It is a new type of SG system where randomness and frustration are not caused by the presence of FM and AF couplings. To further elaborate this type of system, here we study Heisenberg model on AF SFN and search for the SG phase. The canonical SG Heisenberg model is not observed in d-dimensional regular lattices for (d ≤ 3). We can make an analogy for the connectivity density (m) of SFN with the dimensionality of the regular lattice. It should be plausible to find the critical value of m for the existence of SG behaviour, analogous to the lower critical dimension (d l ) for the canonical SG systems. Here we study system with m = 2, 3, 4 and 5. We used Replica Exchange algorithm of Monte Carlo Method and calculated the SG order parameter. We observed SG phase for each value of m and estimated its corersponding critical temperature. (paper)

  12. Transcatheter aortic valve replacement

    Science.gov (United States)

    ... gov/ency/article/007684.htm Transcatheter aortic valve replacement To use the sharing features on this page, please enable JavaScript. Transcatheter aortic valve replacement (TAVR) is surgery to replace the aortic valve. ...

  13. Aortic Valve Disease

    Science.gov (United States)

    ... It is then replaced with an artificial valve (prosthesis). There are two valve options for aortic valve ... place, the catheter will be withdrawn from your body through the original access point. Because not all ...

  14. Spin-glass, antiferromagnetism and Kondo behavior in Ce2Au1 ...

    Indian Academy of Sciences (India)

    report high pressure electrical resistivity of Ce2AuSi3, ac susceptibility (χ) and magnetoresistance of various alloys of this solid solution in order to gain better knowledge of the magnetism of these alloys. High pressure resistivity behavior is consistent with the proposal that Ce2AuSi3 lies at the left-hand side of the maximum ...

  15. Spin-glass, antiferromagnetism and Kondo behavior in Ce 2 Au Co ...

    Indian Academy of Sciences (India)

    ) and magnetoresistance of various alloys of this solid solution in order to gain better knowledge of the magnetism of these alloys. High pressure resistivity behavior is consistent with the proposal that Ce2AuSi3 lies at the left-hand side of the ...

  16. Spin-glass, antiferromagnetism and Kondo behavior in Ce 2 Au 1- ...

    Indian Academy of Sciences (India)

    ) and magnetoresistance of various alloys of this solid solution in order to gain better knowledge of the magnetism of these alloys. High pressure resistivity behavior is consistent with the proposal that Ce2AuSi3 lies at the left-hand side of the ...

  17. What Is Heart Valve Disease?

    Science.gov (United States)

    ... Heart Valves Sometimes heart valves can’t be repaired and must be replaced. This surgery involves removing the faulty valve and replacing it with a man-made or biological valve. Biological valves are made ...

  18. Magnetic resonance imaging of prosthetic heart valves.

    Science.gov (United States)

    Soulen, R L; Budinger, T F; Higgins, C B

    1985-03-01

    To evaluate the safety of magnetic resonance (MR) imaging of prosthetic heart valves, nine different synthetic and tissue valves were studied ex vivo. Deflection was measured in 0.35-tesla (T) and 1.5-T superconducting magnets and at the edge of the bore of a 2.35-T electromagnet in field gradients of 5, 1.1, and 6.3 mT/cm, respectively. No valve deflected in the 0.35-T magnet; six synthetic valves deflected 0.25 degrees-3 degrees in the 1.5-T magnet; all valves deflected 1 degree-27 degrees at the edge of the 2.35-T magnet. Each valve was then submerged in a vial of water and the temperature was measured immediately before and after each of two spin-echo imaging sequences in the two superconducting magnets. No significant temperature rise followed exposure in either magnet. Image distortion varied from negligible to severe in both imagers; magnitude of distortion paralleled magnitude of deflection. These data suggest that patients with present-day prosthetic heart valves can be safely imaged in present-day MR imagers and that prosthesis-induced artifacts will not interfere with interpretation in most instances.

  19. Four-state ferroelectric spin-valve

    Czech Academy of Sciences Publication Activity Database

    Quindeau, A.; Fina, I.; Martí, Xavier; Apachitei, G.; Ferrer, P.; Nicklin, C.; Pippel, E.; Hesse, D.; Alexe, M.

    2015-01-01

    Roč. 5, May (2015), 09749 ISSN 2045-2322 Institutional support: RVO:68378271 Keywords : electronic and spintronic devices * ferroelectrics and multiferroics Subject RIV: BE - Theoretical Physics Impact factor: 5.228, year: 2015

  20. Mechanical behavior of silk during the evolution of orb-web spinning spiders.

    Science.gov (United States)

    Elices, Manuel; Plaza, Gustavo R; Arnedo, Miquel A; Pérez-Rigueiro, José; Torres, Fernando G; Guinea, Gustavo V

    2009-07-13

    The development of an accurate and reproducible approach to measuring the tensile behavior of spider silk has allowed characterizing and comparing the range of mechanical properties exhibited by different spider species with unprecedented detail. The comparison of silks spun by spiders belonging to different phylogenetic groups has revealed that evolution locked in many of the important properties of spider silks very early in the history of orb-web weaving spiders, despite the fact that the silk gland system is relatively isolated in physiological terms from the rest of the organism and should thus mutate quickly. The variations observed between species may be grouped in at least two patterns that are shown not to be related to phylogeny. Beyond the relevance of these results for the evolutionary biology of spiders and silks, the conservation of the basic traits observed in the mechanical behavior of spider silks is likely to set a limit to the range of properties that can be expected from artificial fibers bioinspired in natural silks.

  1. Preparation and tribological behavior of Cu-nanoparticle polyelectrolyte multilayers obtained by spin-assisted layer-by-layer assembly

    Energy Technology Data Exchange (ETDEWEB)

    Yang Guangbin [Key Laboratory for Special Functional Materials of Ministry of Education, Henan University, Kaifeng 475004 (China); Geng Zhengang [Shanxi Academy of Building Research, Taiyuan 030001 (China); Ma Hongxia; Wu Zhishen [Key Laboratory for Special Functional Materials of Ministry of Education, Henan University, Kaifeng 475004 (China); Zhang Pingyu [Key Laboratory for Special Functional Materials of Ministry of Education, Henan University, Kaifeng 475004 (China)], E-mail: pingyu@henu.edu.cn

    2009-01-01

    Polyelectrolyte multilayers (PEMs) fabricated by spin-assisted layer-by-layer assembly technique were used as nanoreactors for in-situ synthesis Cu nanoparticles. Chemical reaction within the PEMs was initiated by a reaction cycle in which Cu{sup 2+} was absorbed into the polymer-coated substrate and then reduced in NaBH{sub 4} solutions. Repeating the above process resulted in an increase in density of the nanoparticles and further growth in the dimension of the particles initially formed. So, different Cu-nanoparticle polyelectrolyte multilayers were formed in the process. The friction and wear properties of Cu-nanoparticle PEMs formed by different reaction cycles were investigated on a microtribometer against a stainless steel ball. The PEMs reinforced with Cu nanoparticles, prepared under the best preparation conditions, possess good tribological behavior, because of the weakened adhesion between the PEMs and the substrate and decreased mobility of the polymeric chains in the presence of excessive Cu nanoparticles generated at larger reaction cycles.

  2. Spin diffusion and torques in disordered antiferromagnets

    KAUST Repository

    Manchon, Aurelien

    2017-02-01

    We have developed a drift-diffusion equation of spin transport in collinear bipartite metallic antiferromagnets. Starting from a model tight-binding Hamiltonian, we obtain the quantum kinetic equation within Keldysh formalism and expand it to the lowest order in spatial gradient using Wigner expansion method. In the diffusive limit, these equations track the spatio-temporal evolution of the spin accumulations and spin currents on each sublattice of the antiferromagnet. We use these equations to address the nature of the spin transfer torque in (i) a spin-valve composed of a ferromagnet and an antiferromagnet, (ii) a metallic bilayer consisting of an antiferromagnet adjacent to a heavy metal possessing spin Hall effect, and in (iii) a single antiferromagnet possessing spin Hall effect. We show that the latter can experience a self-torque thanks to the non-vanishing spin Hall effect in the antiferromagnet.

  3. Microfluidic sieve valves

    Science.gov (United States)

    Quake, Stephen R; Marcus, Joshua S; Hansen, Carl L

    2015-01-13

    Sieve valves for use in microfluidic device are provided. The valves are useful for impeding the flow of particles, such as chromatography beads or cells, in a microfluidic channel while allowing liquid solution to pass through the valve. The valves find particular use in making microfluidic chromatography modules.

  4. Remote actuated valve implant

    Energy Technology Data Exchange (ETDEWEB)

    McKnight, Timothy E.; Johnson, Anthony; Moise, Kenneth J.; Ericson, Milton Nance; Baba, Justin S.; Wilgen, John B.; Evans, Boyd Mccutchen

    2016-05-10

    Valve implant systems positionable within a flow passage, the systems having an inlet, an outlet, and a remotely activatable valve between the inlet and outlet, with the valves being operable to provide intermittent occlusion of the flow path. A remote field is applied to provide thermal or magnetic activation of the valves.

  5. Remote actuated valve implant

    Science.gov (United States)

    McKnight, Timothy E; Johnson, Anthony; Moise, Jr., Kenneth J; Ericson, Milton Nance; Baba, Justin S; Wilgen, John B; Evans, III, Boyd McCutchen

    2014-02-25

    Valve implant systems positionable within a flow passage, the systems having an inlet, an outlet, and a remotely activatable valve between the inlet and outlet, with the valves being operable to provide intermittent occlusion of the flow path. A remote field is applied to provide thermal or magnetic activation of the valves.

  6. Microscopic studies of nonlocal spin dynamics and spin transport (invited)

    Energy Technology Data Exchange (ETDEWEB)

    Adur, Rohan; Du, Chunhui; Cardellino, Jeremy; Scozzaro, Nicolas; Wolfe, Christopher S.; Wang, Hailong; Herman, Michael; Bhallamudi, Vidya P.; Pelekhov, Denis V.; Yang, Fengyuan; Hammel, P. Chris, E-mail: hammel@physics.osu.edu [Department of Physics, The Ohio State University, Columbus, Ohio 43210 (United States)

    2015-05-07

    Understanding the behavior of spins coupling across interfaces in the study of spin current generation and transport is a fundamental challenge that is important for spintronics applications. The transfer of spin angular momentum from a ferromagnet into an adjacent normal material as a consequence of the precession of the magnetization of the ferromagnet is a process known as spin pumping. We find that, in certain circumstances, the insertion of an intervening normal metal can enhance spin pumping between an excited ferromagnetic magnetization and a normal metal layer as a consequence of improved spin conductance matching. We have studied this using inverse spin Hall effect and enhanced damping measurements. Scanned probe magnetic resonance techniques are a complementary tool in this context offering high resolution magnetic resonance imaging, localized spin excitation, and direct measurement of spin lifetimes or damping. Localized magnetic resonance studies of size-dependent spin dynamics in the absence of lithographic confinement in both ferromagnets and paramagnets reveal the close relationship between spin transport and spin lifetime at microscopic length scales. Finally, detection of ferromagnetic resonance of a ferromagnetic film using the photoluminescence of nitrogen vacancy spins in neighboring nanodiamonds demonstrates long-range spin transport between insulating materials, indicating the complexity and generality of spin transport in diverse, spatially separated, material systems.

  7. Spin transport in graphene nanostructures

    NARCIS (Netherlands)

    Guimaraes, M. H. D.; van den Berg, J. J.; Vera-Marun, I. J.; Zomer, P. J.; van Wees, B. J.

    2014-01-01

    Graphene is an interesting material for spintronics, showing long spin relaxation lengths even at room temperature. For future spintronic devices it is important to understand the behavior of the spins and the limitations for spin transport in structures where the dimensions are smaller than the

  8. Rigorous control of logarithmic corrections in four-dimensional phi4 spin systems. II. Critical behavior of susceptibility and correlation length

    International Nuclear Information System (INIS)

    Hara, T.; Tasaki, H.

    1987-01-01

    Continuing the analysis started in Part I of this work, they investigate critical phenomena in weakly coupled phi 4 spin systems in four dimensions. Concerning the critical behavior of the susceptibility and the correlation length (in the high-temperature phase), the existence of logarithmic corrections to their mean field type behavior is rigorously shown (i.e., they prove chi(t) ∼ t -1 absolute value 1n t/sup 1/3/, zeta(t) ∼ t/sup -1/2/ absolute value of ln t/sup 1/6/)

  9. Non-fermi liquid and spin-glass behavior of the Sc{sub 1-x}U{sub x}Pd{sub 3} system

    Energy Technology Data Exchange (ETDEWEB)

    Gajewski, D.A.; Allenspach, P.; Seaman, C.L. [California Univ., San Diego, La Jolla, CA (United States). Inst. of Pure and Applied Physical Sciences; Maple, M.B. [California Univ., San Diego, La Jolla, CA (United States). Inst. of Pure and Applied Physical Sciences]|[Los Alamos National Lab., NM (United States)

    1993-09-01

    Previous electrical resistivity {rho}T, magnetic susceptibility {chi}T, and specific heat C(T) measurements on the Y{sub 1-x}U{sub x}Pd{sub 3} system have revealed Kondo behavior for 0 < {times} < 0.2 and spin-glass-like behavior for 0.3 < {times} < 0.5. The Kondo behavior is unusual and characterized by non-Fermi liquid behavior at low temperatures T {much_lt} T{sub K}, where T{sub K} is the Kondo temperature: {rho}T/{rho}(0) {approximately} 1 {minus} T/(aT{sub K}), and C(T)/T {approximately} 1 {minus} (1/T{sub K})1nT with evidence for a finite T = 0 residual entropy S(0) = (R/2)1n(2). We report measurements of {rho}T, {chi}T, and C(T) on the Sc{sub 1-x}U{sub x}Pd{sub 3} system which reveal similar Kondo, non-Fermi liquid, and spin-glass behaviors.

  10. Which valve is which?

    Directory of Open Access Journals (Sweden)

    Pravin Saxena

    2015-01-01

    Full Text Available A 25-year-old man presented with a history of breathlessness for the past 2 years. He had a history of operation for Tetralogy of Fallot at the age of 5 years and history suggestive of Rheumatic fever at the age of 7 years. On echocardiographic examination, all his heart valves were severely regurgitating. Morphologically, all the valves were irreparable. The ejection fraction was 35%. He underwent quadruple valve replacement. The aortic and mitral valves were replaced by metallic valve and the tricuspid and pulmonary by tissue valve.

  11. Spin current

    CERN Document Server

    Valenzuela, Sergio O; Saitoh, Eiji; Kimura, Takashi

    2012-01-01

    In a new branch of physics and technology called spin-electronics or spintronics, the flow of electrical charge (usual current) as well as the flow of electron spin, the so-called 'spin current', are manipulated and controlled together. This book provides an introduction and guide to the new physics and application of spin current.

  12. Tunneling effect of the spin-2 Bose condensate driven by external magnetic fields

    International Nuclear Information System (INIS)

    Yu Zhaoxian; Jiao Zhiyong

    2004-01-01

    In this Letter, we have studied tunneling effect of the spin-2 Bose condensate driven by external magnetic field. We find that the population transfers among spin-0 and spin-±1, spin-0 and spin-±2 exhibit the step structure under the external cosinusoidal magnetic field, respectively, but there do not exist step structure among spin-±1 and spin-±2. The tunneling current among spin-±1 and spin-±2 may exhibit periodically oscillation behavior, but among spin-0 and spin-±1, spin-0 and spin-±2, the tunneling currents exhibit irregular oscillation behavior

  13. Dependency of tunneling magnetoresistance ratio on Pt seed-layer thickness for double MgO perpendicular magnetic tunneling junction spin-valves with a top Co2Fe6B2 free layer ex-situ annealed at 400 °C.

    Science.gov (United States)

    Takemura, Yasutaka; Lee, Du-Yeong; Lee, Seung-Eun; Park, Jea-Gun

    2016-12-02

    For the double MgO based perpendicular magnetic tunneling junction (p-MTJ) spin-valves with a top Co 2 Fe 6 B 2 free layer ex situ annealed at 400 °C, the tunneling-magnetoresistance ratio (TMR) strongly depended on the platinum (Pt) seed layer thickness (t Pt ): it peaked (∼134%) at a specific t Pt (3.3 nm). The TMR ratio was initially and slightly increased from 113%-134% by the enhancement of the magnetic moment of the Co 2 Fe 6 B 2 pinned layer when t Pt increased from 2.0-3.3 nm, and then rapidly decreased from 134%-38.6% by the degrading face-centered-cubic crystallinity of the MgO tunneling barrier when t Pt increased from 3.3-14.3 nm.

  14. Spin-Precession Organic Magnetic Sensor

    Science.gov (United States)

    2012-09-26

    with the voltage and we get a value of ~200 per tesla for the quantity [V -1 (dV/dB)], which roughly translates into a sensitivity of 14 nT/Hz 1/2...Ideally, the response should be similar to the spin- valve measurements—the resistance changes as the magnetization of each of the contacts flips as we...strips. Typical spin- valve measurements employ strip widths of ~10-20 nm. However, the smallest width achievable in our FIB process is 500 nm, and the

  15. Dynamic hysteresis behaviors for the two-dimensional mixed spin (2, 5/2) ferrimagnetic Ising model in an oscillating magnetic field

    Science.gov (United States)

    Ertaş, Mehmet

    2015-09-01

    Keskin and Ertaş (2009) presented a study of the magnetic properties of a mixed spin (2, 5/2) ferrimagnetic Ising model within an oscillating magnetic field. They employed dynamic mean-field calculations to find the dynamic phase transition temperatures, the dynamic compensation points of the model and to present the dynamic phase diagrams. In this work, we extend the study and investigate the dynamic hysteresis behaviors for the two-dimensional (2D) mixed spin (2, 5/2) ferrimagnetic Ising model on a hexagonal lattice in an oscillating magnetic field within the framework of dynamic mean-field calculations. The dynamic hysteresis curves are obtained for both the ferromagnetic and antiferromagnetic interactions and the effects of the Hamiltonian parameters on the dynamic hysteresis behaviors are discussed in detail. The thermal behaviors of the coercivity and remanent magnetizations are also investigated. The results are compared with some theoretical and experimental works and a qualitatively good agreement is found. Finally, the dynamic phase diagrams depending on the frequency of an oscillating magnetic field in the plane of the reduced temperature versus magnetic field amplitude is examined and it is found that the dynamic phase diagrams display richer dynamic critical behavior for higher values of frequency than for lower values.

  16. What Is Heart Valve Surgery?

    Science.gov (United States)

    ... working correctly. Most valve replacements involve the aortic Tricuspid valve and mitral valves. The aortic valve separates the ... in life and cause problems. •Aging can make valves weaken or harden. • Certain diseases can scar or destroy a valve. What can ...

  17. Corrosion of valve metals

    International Nuclear Information System (INIS)

    Draley, J.E.

    1976-01-01

    A general survey related to the corrosion of valve metals or film-forming metals. The way these metals corrode with some general examples is described. Valve metals form relatively perfect oxide films with little breakdown or leakage when anodized

  18. Half-metallic superconducting triplet spin multivalves

    Science.gov (United States)

    Alidoust, Mohammad; Halterman, Klaus

    2018-02-01

    We study spin switching effects in finite-size superconducting multivalve structures. We examine F1F2SF3 and F1F2SF3F4 hybrids where a singlet superconductor (S) layer is sandwiched among ferromagnet (F) layers with differing thicknesses and magnetization orientations. Our results reveal a considerable number of experimentally viable spin-valve configurations that lead to on-off switching of the superconducting state. For S widths on the order of the superconducting coherence length ξ0, noncollinear magnetization orientations in adjacent F layers with multiple spin axes leads to a rich variety of triplet spin-valve effects. Motivated by recent experiments, we focus on samples where the magnetizations in the F1 and F4 layers exist in a fully spin-polarized half-metallic phase, and calculate the superconducting transition temperature, spatially and energy resolved density of states, and the spin-singlet and spin-triplet superconducting correlations. Our findings demonstrate that superconductivity in these devices can be completely switched on or off over a wide range of magnetization misalignment angles due to the generation of equal-spin and opposite-spin triplet pairings.

  19. A case of SAPIEN XT valve fallen into left ventricle during valve-in-valve transcatheter aortic valve implantation.

    Science.gov (United States)

    Koizumi, Shigeki; Ehara, Natsuhiko; Nishiya, Kenta; Koyama, Tadaaki

    2017-06-24

    Late transcatheter heart valve embolization is a rare but life-threatening complication of transcatheter aortic valve implantation. Surgical intervention is performed for most cases, but some cases were treated by valve-in-valve transcatheter aortic valve implantation. We describe a patient in whom a 29-mm Edwards SAPIEN XT valve migrated into the left ventricular outflow tract 41 days after the initial implantation. We tried to perform valve-in-valve transcatheter aortic valve implantation using a transfemoral approach. As soon as the second transcatheter heart valve touched the first implanted valve, it fell into the left ventricle. Immediate surgical intervention was required. The first valve was removed, and surgical aortic valve replacement was successfully performed. In conclusion, we should choose surgical aortic valve replacement for late transcatheter heart valve embolization. Even if we need to treat by catheter intervention, transapical approach may be better.

  20. Spin Waves in Terbium

    DEFF Research Database (Denmark)

    Jensen, J.; Houmann, Jens Christian Gylden; Bjerrum Møller, Hans

    1975-01-01

    with increasing temperatures implies that the two-ion coupling is effectively isotropic above ∼ 150 K. We present arguments for concluding that, among the mechanisms which may introduce anisotropic two-ion couplings in the rare-earth metals, the modification of the indirect exchange interaction by the spin......The energies of spin waves propagating in the c direction of Tb have been studied by inelastic neutron scattering, as a function of a magnetic field applied along the easy and hard directions in the basal plane, and as a function of temperature. From a general spin Hamiltonian, consistent...... with the symmetry, we deduce the dispersion relation for the spin waves in a basal-plane ferromagnet. This phenomenological spin-wave theory accounts for the observed behavior of the magnon energies in Tb. The two q⃗-dependent Bogoliubov components of the magnon energies are derived from the experimental results...

  1. Spin relaxation in quantum dots: Role of the phonon modulated spin-orbit interaction

    Science.gov (United States)

    Alcalde, A. M.; Romano, C. L.; Sanz, L.; Marques, G. E.

    2010-01-01

    We calculate the spin relaxation rates in a parabolic InSb quantum dots due to the spin interaction with acoustical phonons. We considered the deformation potential mechanism as the dominant electron-phonon coupling in the Pavlov-Firsov spin-phonon Hamiltonian. We analyze the behavior of the spin relaxation rates as a function of an external magnetic field and mean quantum dot radius. Effects of the spin admixture due to Dresselhaus contribution to spin-orbit interaction are also discussed.

  2. Aortic valve surgery - open

    Science.gov (United States)

    ... while you are connected to this machine. This machine does the work of your heart while your heart is stopped. If your aortic valve is too damaged, you will need a new valve. This is called replacement surgery. Your surgeon will remove your aortic valve ...

  3. Bicuspid Aortic Valve

    Science.gov (United States)

    2006-08-01

    with tricuspid aortic valves matched for age, gender and grade of valvular disease . These studies suggest that the predisposition for aortic...enlargement in healthy patients with normally functioning BAV when compared to healthy subjects with normally functioning tricuspid aortic valves ...ascending aorta but also in the pulmonary arteries of patients with BAV, compared to that of patients with tricuspid aortic valves . These studies

  4. Heart Valve Diseases

    Science.gov (United States)

    Your heart has four valves. Normally, these valves open to let blood flow through or out of your heart, and then shut to keep it from flowing ... close tightly. It's one of the most common heart valve conditions. Sometimes it causes regurgitation. Stenosis - when ...

  5. When a Heart Murmur Signals Valve Disease

    Science.gov (United States)

    ... Understanding Problems and Causes Heart Murmurs and Valve Disease "Innocent" Heart Murmur Problem: Valve Stenosis - Problem: Aortic Valve Stenosis - Problem: Mitral Valve Stenosis - Problem: Tricuspid Valve Stenosis - Problem: Pulmonary Valve Stenosis Problem: Mitral ...

  6. Autologous human tissue-engineered heart valves: prospects for systemic application.

    Science.gov (United States)

    Mol, Anita; Rutten, Marcel C M; Driessen, Niels J B; Bouten, Carlijn V C; Zünd, Gregor; Baaijens, Frank P T; Hoerstrup, Simon P

    2006-07-04

    Tissue engineering represents a promising approach for the development of living heart valve replacements. In vivo animal studies of tissue-engineered autologous heart valves have focused on pulmonary valve replacements, leaving the challenge to tissue engineer heart valves suitable for systemic application using human cells. Tissue-engineered human heart valves were analyzed up to 4 weeks and conditioning using bioreactors was compared with static culturing. Tissue formation and mechanical properties increased with time and when using conditioning. Organization of the tissue, in terms of anisotropic properties, increased when conditioning was dynamic in nature. Exposure of the valves to physiological aortic valve flow demonstrated proper opening motion. Closure dynamics were suboptimal, most likely caused by the lower degree of anisotropy when compared with native aortic valve leaflets. This study presents autologous tissue-engineered heart valves based on human saphenous vein cells and a rapid degrading synthetic scaffold. Tissue properties and mechanical behavior might allow for use as living aortic valve replacements.

  7. Reentrant spin glass behavior and magnetodielectric coupling of an Ir-based double perovskite compound, La2CoIrO6.

    Science.gov (United States)

    Song, Jiyue; Zhao, Bangchuan; Yin, Lihua; Qin, Yanfeng; Zhou, Jiafeng; Wang, Dong; Song, Wenhai; Sun, Yuping

    2017-09-12

    The structural, magnetic, electrical and dielectric properties of an Ir-based double perovskite compound, La 2 CoIrO 6 , have been investigated. The sample undergoes a paramagnetic-ferromagnetic transition at T C , followed by a reentrant spin-glass transition at lower temperatures. The reentrant spin glass state in La 2 CoIrO 6 is associated with the competitions of the antiferromagnetic coupling between Ir 4+ and Co 2+ ions and the ferromagnetic clusters. La 2 CoIrO 6 shows a semiconducting transport behavior in the temperature range 65 to 360 K and the transport behavior can be well described by the three-dimensional Mott variable range hopping conduction mechanism. Moreover, a strong frequency dependence of dielectric constant behavior for La 2 CoIrO 6 is observed and the dielectric relaxation can be ascribed to the electron hopping between different transition metal ions. In addition, the isothermal magnetic field dependent dielectric constant measurements show that a clear magnetodielectric coupling effect exists in La 2 CoIrO 6 at low temperatures.

  8. Spin tracking in RHIC

    Energy Technology Data Exchange (ETDEWEB)

    Luccio, A.U. [Brookhaven National Lab., Upton, NY (United States); Katayama, T. [Univ. of Tokyo (Japan); Wu, H. [Riken Inst., Tokyo (Japan)

    1997-07-01

    In the acceleration of polarized protons in RHIC many spin depolarizing resonances are encountered. Helical Siberian snakes will be used to overcome depolarizing effects. The behavior of polarization can be studied by numerical tracking in a model accelerator. That allows one to check the strength of the resonances, to study the effect of snakes, to find safe lattice tune regions, and finally to study the operation of special devices like spin flippers. In this paper the authors describe numerical spin tracking. Results show that, for the design corrected distorted orbit and the design beam emittance, the polarization of the beam will be preserved in the whole range of proton energies in RHIC.

  9. Spin-dependent transport and current-induced spin transfer torque in a disordered zigzag silicene nanoribbon

    International Nuclear Information System (INIS)

    Zhou, Benliang; Zhou, Benhu; Liu, Guang; Guo, Dan; Zhou, Guanghui

    2016-01-01

    We study theoretically the spin-dependent transport and the current-induced spin transfer torque (STT) for a zigzag silicene nanoribbon (ZSiNR) with Anderson-type disorders between two ferromagnetic electrodes. By using the nonequilibrium Green's function method, it is predicted that the transport property and STT through the junction depend sensitively on the disorder, especially around the Dirac point. As a result, the conductance decreases and increases for two electrode in parallel and antiparallel configurations, respectively. Due to the disorder, the magnetoresistance (MR) decreases accordingly even within the energy regime for the perfect plateau without disorders. In addition, the conductance versus the relative angle of the magnetization shows a cosine-like behavior. The STT per unit of the bias voltage versus the angle of the magnetization exhibits a sine-like behavior, and versus the Fermi energy is antisymmetrical to the Dirac point and exhibits sharp peaks. Furthermore, the peaks of the STT are suppressed much as the disorder strength increases, especially around the Dirac point. The results obtained here may provide a valuable suggestion to experimentally design spin valve devices based on ZSiNR.

  10. The External Nasal Valve.

    Science.gov (United States)

    Hamilton, Grant S

    2017-05-01

    The external nasal valve is a complex entity comprised of multiple structures and tissue types. As such, there is no single operation that can address all problems of the external valve. This article reviews the relevant anatomy, pathologic conditions, and treatments for external nasal valve dysfunction, including a detailed review of the nasal muscles and their contribution to external nasal valve patency. Surgical and nonsurgical options for treatment and the evidence supporting the importance of proper external nasal valve function on quality-of-life measures are discussed. Copyright © 2016 Elsevier Inc. All rights reserved.

  11. Spin dynamics with inertia in metallic ferromagnets

    Science.gov (United States)

    Kikuchi, Toru; Tatara, Gen

    2015-11-01

    The nonadiabatic contribution of environmental degrees of freedom yields an effective inertia of spin in the effective spin dynamics. In this paper, we study several aspects of the inertia of spin in metallic ferromagnets: (i) a concrete expression of the spin inertia ms: ms=ℏ Sc/(2 gsd) , where Sc is the spin polarization of conduction electrons and gsd is the s d coupling constant; (ii) a dynamical behavior of spin with inertia, discussed from the viewpoints of a spinning top and of a particle on a sphere; (iii) the behavior of spin waves and domain walls in the presence of inertia and the behavior of spin with inertia under a time-dependent magnetic field.

  12. SOLA-LOOP analysis of a back pressure check valve

    International Nuclear Information System (INIS)

    Travis, J.R.

    1984-01-01

    The SOLA-LOOP computer code for transient, nonequilibrium, two-phase flows in networks has been coupled with a simple valve model to analyze a feedwater pipe breakage with a back-pressure check valve. Three tests from the Superheated Steam Reactor Safety Program Project (PHDR) at Kahl, West Germany, are analyzed, and the calculated transient back-pressure check valve behavior and fluid dynamics effects are found to be in excellent agreement with the experimentally measured data

  13. Spin relaxation through lateral spin transport in heavily doped n -type silicon

    Science.gov (United States)

    Ishikawa, M.; Oka, T.; Fujita, Y.; Sugiyama, H.; Saito, Y.; Hamaya, K.

    2017-03-01

    We experimentally study temperature-dependent spin relaxation including lateral spin diffusion in heavily doped n -type silicon (n+-Si ) layers by measuring nonlocal magnetoresistance in small-sized CoFe/MgO/Si lateral spin-valve (LSV) devices. Even at room temperature, we observe large spin signals, 50-fold the magnitude of those in previous works on n+-Si . By measuring spin signals in LSVs with various center-to-center distances between contacts, we reliably evaluate the temperature-dependent spin diffusion length (λSi) and spin lifetime (τSi). We find that the temperature dependence of τSi is affected by that of the diffusion constant in the n+-Si layers, meaning that it is important to understand the temperature dependence of the channel mobility. A possible origin of the temperature dependence of τSi is discussed in terms of the recent theories by Dery and co-workers.

  14. Emergence of non-Fermi liquid behaviors in 5d perovskite SrIrO3 thin films: Interplay between correlation, disorder, and spin-orbit coupling

    Science.gov (United States)

    Biswas, Abhijit; Kim, Ki-Seok; Jeong, Yoon H.

    2016-02-01

    We investigate the effects of compressive strain on the electrical resistivity of 5d iridium based perovskite SrIrO3 by depositing epitaxial films of thickness 35 nm on various substrates such as GdScO3 (110), DyScO3 (110), and SrTiO3 (001). Surprisingly, we find anomalous transport behaviors as expressed by ρ∝Tε in the temperature dependent resistivity, where the temperature exponent ε evolves continuously from 4/5 to 1 and to 3/2 with an increase of compressive strain. Furthermore, magnetoresistance always remains positive irrespective of resistivity upturns at low temperatures. These observations imply that the delicate interplay between correlation and disorder in the presence of strong spin-orbit coupling is responsible for the emergence of the non-Fermi liquid behaviors in 5d perovskite SrIrO3 thin films. We offer a theoretical framework for the interpretation of the experimental results.

  15. Aortic or Mitral Valve Replacement With the Biocor and Biocor Supra

    Science.gov (United States)

    2017-04-26

    Aortic Valve Insufficiency; Aortic Valve Regurgitation; Aortic Valve Stenosis; Aortic Valve Incompetence; Mitral Valve Insufficiency; Mitral Valve Regurgitation; Mitral Valve Stenosis; Mitral Valve Incompetence

  16. Spin glass behavior in nanogranular La0.25Ca0.75MnO3 manganites

    International Nuclear Information System (INIS)

    2UB, Universitat de Barcelona, Martí i Franquès 1, planta 3, edifici nou, 08028 Barcelona (Spain))" data-affiliation=" (Grup de Magnetisme, Dept. Física Fonamental, Facultat de Física, Universitat de Barcelona, Martí i Franquès 1, planta 4, edifici nou, 08028 Barcelona (Spain); Institut de Nanociència i Nanotecnologia IN2UB, Universitat de Barcelona, Martí i Franquès 1, planta 3, edifici nou, 08028 Barcelona (Spain))" >Fernández-Martínez, Antoni; 2UB, Universitat de Barcelona, Martí i Franquès 1, planta 3, edifici nou, 08028 Barcelona (Spain))" data-affiliation=" (Grup de Magnetisme, Dept. Física Fonamental, Facultat de Física, Universitat de Barcelona, Martí i Franquès 1, planta 4, edifici nou, 08028 Barcelona (Spain); Institut de Nanociència i Nanotecnologia IN2UB, Universitat de Barcelona, Martí i Franquès 1, planta 3, edifici nou, 08028 Barcelona (Spain))" >García-Santiago, Antoni; 2UB, Universitat de Barcelona, Martí i Franquès 1, planta 3, edifici nou, 08028 Barcelona (Spain))" data-affiliation=" (Grup de Magnetisme, Dept. Física Fonamental, Facultat de Física, Universitat de Barcelona, Martí i Franquès 1, planta 4, edifici nou, 08028 Barcelona (Spain); Institut de Nanociència i Nanotecnologia IN2UB, Universitat de Barcelona, Martí i Franquès 1, planta 3, edifici nou, 08028 Barcelona (Spain))" >Hernàndez, Joan Manel; Zhang, Tao

    2014-01-01

    The magnetic properties of two nanogranular La 0.25 Ca 0.75 MnO 3 manganites with different average grain sizes have been studied. Besides the well-known exchange bias effect and the appearance of ferromagnetic clusters in the grains of both samples, the results show the occurrence of an antiferromagnetic transition and spin-glass properties. Both samples are described as core–shell magnetic systems, whose main difference is found in the interface between the outer ferromagnetic and the inner antiferromagnetic phases of the grains. - Highlights: • Nanogranular manganites show antiferromagnetism in magnetic measurements. • Exchange bias effect was observed in magnetic hysteresis cycles. • Spin-glass properties were detected at low temperatures. • A core-shell model was applied to describe the results in both samples. • These features have nothing to do with usual properties of nanoparticle manganites

  17. Verification of the Thomson-Onsager reciprocity relation for spin caloritronics

    NARCIS (Netherlands)

    Dejene, F. K.; Flipse, J.; van Wees, B. J.

    2014-01-01

    We investigate the Thomson-Onsager relation between the spin-dependent Seebeck and spin-dependent Peltier effect. To maintain identical device and measurement conditions we measure both effects in a single Ni80Fe20/Cu/Ni80Fe20 nanopillar spin valve device subjected to either an electrical or a

  18. Frustration and long-range behavior of the exchange interactions in AuFe spin-glass alloys

    Czech Academy of Sciences Publication Activity Database

    Khmelevskyi, S.; Kudrnovský, Josef; Gyorffy, B. L.; Mohn, P.; Drchal, Václav; Weinberger, P.

    2004-01-01

    Roč. 70, č. 22 (2004), 224432/1-224432/6 ISSN 1098-0121 R&D Projects: GA ČR GA202/04/0583 Grant - others:RTN(XX) HPRN-CT-2000-00143 Institutional research plan: CEZ:AV0Z1010914 Keywords : effective exchange interaction * spin-glass AuFe alloy * first-principles study * disorder and frustration Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.075, year: 2004

  19. Transcatheter Tricuspid Valve-in-Valve Intervention for Degenerative Bioprosthetic Tricuspid Valve Disease.

    Science.gov (United States)

    Praz, Fabien; George, Isaac; Kodali, Susheel; Koulogiannis, Konstantinos P; Gillam, Linda D; Bechis, Mary Z; Rubenson, David; Li, Wei; Duncan, Alison

    2017-08-23

    Isolated reoperative tricuspid valve replacement is one of the highest risk operations classified in the Society of Thoracic Surgeons registry, particularly in the setting of preexisting right ventricular dysfunction. Transcatheter tricuspid valve-in-valve implantation represents an attractive alternative to redo surgery in patients with tricuspid bioprosthetic valve degeneration who are considered high-risk or unsuitable surgical candidates. In this review article, the authors discuss the emergence of transcatheter tricuspid valve-in-valve therapy, preprocedural echocardiographic assessment of tricuspid bioprosthetic valve dysfunction, periprocedural imaging required for tricuspid valve-in-valve implantation, and postprocedural assessment of tricuspid transcatheter device function. Copyright © 2017 American Society of Echocardiography. All rights reserved.

  20. Intelligent Flow Control Valve

    Science.gov (United States)

    Kelley, Anthony R (Inventor)

    2015-01-01

    The present invention is an intelligent flow control valve which may be inserted into the flow coming out of a pipe and activated to provide a method to stop, measure, and meter flow coming from the open or possibly broken pipe. The intelligent flow control valve may be used to stop the flow while repairs are made. Once repairs have been made, the valve may be removed or used as a control valve to meter the amount of flow from inside the pipe. With the addition of instrumentation, the valve may also be used as a variable area flow meter and flow controller programmed based upon flowing conditions. With robotic additions, the valve may be configured to crawl into a desired pipe location, anchor itself, and activate flow control or metering remotely.

  1. Transcatheter Tricuspid Valve Replacement.

    Science.gov (United States)

    Krishnaswamy, Amar; Navia, Jose; Kapadia, Samir R

    2018-01-01

    Tricuspid regurgitation (TR) is a common entity, most commonly functional in nature due to right-sided dysfunction in the setting of concomitant cardiac disease or pulmonary hypertension. Patients living with TR often experience numerous limitations as a result of right-sided heart failure symptoms, including functional decline, frequent hospitalizations, liver failure, and kidney failure. Furthermore, patients with significant TR demonstrate worse survival, although a cause-and-effect relationship has not been proven. For patients with a degenerated surgical bioprosthesis or valve ring, placement of a transcatheter aortic valve prosthesis in a valve-in-valve or valve-in-ring fashion may provide symptomatic benefit. For patients with native valve regurgitation, novel devices for treatment are currently under development. Copyright © 2017 Elsevier Inc. All rights reserved.

  2. Low noise control valve

    International Nuclear Information System (INIS)

    Christie, R.S.

    1975-01-01

    Noise is one of the problems associated with the use of any type of control valve in systems involving the flow of fluids. The advent of OSHA standards has prompted control valve manufacturers to design valves with special trim to lower the sound pressure level to meet these standards. However, these levels are in some cases too high, particularly when a valve must be located in or near an area where people are working at tasks requiring a high degree of concentration. Such locations are found around and near research devices and in laboratory-office areas. This paper describes a type of fluid control device presently being used at PPL as a bypass control valve in deionized water systems and designed to reduce sound pressure levels considerably below OSHA standards. Details of the design and construction of this constant pressure drop variable flow control valve are contained in the text and are shown in photographs and drawings. Test data taken are included

  3. Quantum size effects on spin-transfer torque in a double barrier magnetic tunnel junction with a nonmagnetic-metal (semiconductor) spacer

    International Nuclear Information System (INIS)

    Daqiq, Reza; Ghobadi, Nader

    2016-01-01

    We study the quantum size effects of an MgO-based double barrier magnetic tunnel junction with a nonmagnetic-metal (DBMTJ-NM) (semiconductor (DBMTJ-SC)) spacer on the charge current and the spin-transfer torque (STT) components using non-equilibrium Green's function (NEGF) formalism. The results show oscillatory behavior due to the resonant tunneling effect depending on the structure parameters. We find that the charge current and the STT components in the DBMTJ-SC demonstrate the magnitude enhancement in comparison with the DBMTJ-NM. The bias dependence of the STT components in a DBMTJ-NM shows different behavior in comparison with spin valves and conventional MTJs. Therefore, by choosing a specific SC spacer with suitable thickness in a DBMTJ the charge current and the STT components significantly increase so that one can design a device with high STT and faster magnetization switching. - Highlights: • The quantum size effects are studied in double barrier magnetic tunnel junctions. • Spin torque (ST) components oscillate for increasing of middle spacer thicknesses. • Due to the resonant tunneling in the quantum well, oscillations have appeared. • By replacement a metal spacer with a semiconductor (ZnO) ST has increased. • The ST components vs. bias show gradually decreasing unlike spin valves or MTJs.

  4. Modeling the Mitral Valve

    Science.gov (United States)

    Kaiser, Alexander

    2016-11-01

    The mitral valve is one of four valves in the human heart. The valve opens to allow oxygenated blood from the lungs to fill the left ventricle, and closes when the ventricle contracts to prevent backflow. The valve is composed of two fibrous leaflets which hang from a ring. These leaflets are supported like a parachute by a system of strings called chordae tendineae. In this talk, I will describe a new computational model of the mitral valve. To generate geometry, general information comes from classical anatomy texts and the author's dissection of porcine hearts. An MRI image of a human heart is used to locate the tips of the papillary muscles, which anchor the chordae tendineae, in relation to the mitral ring. The initial configurations of the valve leaflets and chordae tendineae are found by solving solving an equilibrium elasticity problem. The valve is then simulated in fluid (blood) using the immersed boundary method over multiple heart cycles in a model valve tester. We aim to identify features and mechanisms that influence or control valve function. Support from National Science Foundation, Graduate Research Fellowship Program, Grant DGE 1342536.

  5. Prosthetic heart valves.

    Science.gov (United States)

    Chambers, J

    2014-10-01

    Heart valve replacements improve symptoms and life expectancy but may have potential problems. Biological replacements have limited durability but do not require anticoagulation and are usually used for the relatively elderly. Mechanical valves have a virtually zero primary failure rate but require anticoagulation and are usually used for the relatively younger patient. Transcatheter valves are used for patients in whom conventional surgery is not technically feasible or who have significant comorbidities. This article discusses the management of patients after valve replacement and discusses future developments. © 2014 John Wiley & Sons Ltd.

  6. Biological heart valves.

    Science.gov (United States)

    Ciubotaru, Anatol; Cebotari, Serghei; Tudorache, Igor; Beckmann, Erik; Hilfiker, Andres; Haverich, Axel

    2013-10-01

    Cardiac valvular pathologies are often caused by rheumatic fever in young adults, atherosclerosis in elderly patients, or by congenital malformation of the heart in children, in effect affecting almost all population ages. Almost 300,000 heart valve operations are performed worldwide annually. Tissue valve prostheses have certain advantages over mechanical valves such as biocompatibility, more physiological hemodynamics, and no need for life-long systemic anticoagulation. However, the major disadvantage of biological valves is related to their durability. Nevertheless, during the last decade, the number of patients undergoing biological, rather than mechanical, valve replacement has increased from half to more than three-quarters for biological implants. Continuous improvement in valve fabrication includes development of new models and shapes, novel methods of tissue treatment, and preservation and implantation techniques. These efforts are focused not only on the improvement of morbidity and mortality of the patients but also on the improvement of their quality of life. Heart valve tissue engineering aims to provide durable, "autologous" valve prostheses. These valves demonstrate adaptive growth, which may avoid the need of repeated operations in growing patients.

  7. St Jude Epic heart valve bioprostheses versus native human and porcine aortic valves - comparison of mechanical properties.

    Science.gov (United States)

    Kalejs, Martins; Stradins, Peteris; Lacis, Romans; Ozolanta, Iveta; Pavars, Janis; Kasyanov, Vladimir

    2009-05-01

    The major problem with heart valve bioprostheses made from chemically treated porcine aortic valves is their limited longevity caused by gradual deterioration, which has a causal link with valve tissue mechanical properties. To our best knowledge, there are no published studies on the mechanical properties of modern, commercially available bioprostheses comparing them to native human valves. The objective of this study is to determine the mechanical properties of St Jude Epic bioprostheses and to compare them with native human and porcine aortic valves. Leaflets from eight porcine aortic valves and six Epic bioprostheses were analyzed using uni-axial tensile tests in radial and circumferential directions. Mechanical properties of human valves have been previously published by our group. Results are represented as mean values+/-S.D. Circumferential direction. Modulus of elasticity of Epic bioprostheses in circumferential direction at the level of stress 1.0 MPa is 101.99+/-58.24 MPa, 42.3+/-4.96 MPa for native porcine and 15.34+/-3.84 MPa for human aortic valves. Ultimate stress is highest for Epic bioprostheses 5.77+/-1.94 MPa, human valves have ultimate stress of 1.74+/-0.29 MPa and porcine 1.58+/-0.26 MPa. Ultimate strain in circumferential direction is highest for human valves 18.35+/-7.61% followed by 7.26+/-0.69% for porcine valves and 5.95+/-1.54% for Epic bioprostheses. Radial direction. Modulus of elasticity in radial direction is 9.18+/-1.81 MPa for Epic bioprostheses, 5.33+/-0.61 MPa for native porcine, and 1.98+/-0.15 MPa for human aortic valve leaflets. In the radial direction ultimate stress is highest for Epic bioprostheses 0.7+/-0.21 MPa followed by native porcine valves 0.55+/-0.11 MPa and 0.32+/-0.04 MPa for human valves. For human valves ultimate strain is 23.92+/-4.87%, for native porcine valves 8.57+/-0.8% and 7.92+/-1.74% for Epic bioprostheses. Epic bioprostheses have non-linear stress-strain behavior similar to native valve tissue, but they

  8. Options for Heart Valve Replacement

    Science.gov (United States)

    ... are the most commonly replaced valves. Pulmonary and tricuspid valve replacements are fairly uncommon in adults. Replacing a ... Problems and Causes • Risks, Signs and Symptoms • Accurate Diagnosis • Treatment Options ... Repair Valve Replacement - Ross Procedure - Newer Surgery Options - ...

  9. Automated control of the laser welding process of heart valve scaffolds

    Directory of Open Access Journals (Sweden)

    Weber Moritz

    2016-09-01

    Full Text Available Using the electrospinning process the geometry of a heart valve is not replicable by just one manufacturing process. To produce heart valve scaffolds the heart valve leaflets and the vessel have to be produced in separated spinning processes. For the final product of a heart valve they have to be mated afterwards. In this work an already existing three-axes laser was enhanced to laser weld those scaffolds. The automation control software is based on the robot operating system (ROS. The mechatronically control is done by an Arduino Mega. A graphical user interface (GUI is written with Python and Kivy.

  10. Effects of valve geometry and tissue anisotropy on the radial stretch and coaptation area of tissue-engineered heart valves.

    Science.gov (United States)

    Loerakker, S; Argento, G; Oomens, C W J; Baaijens, F P T

    2013-07-26

    Tissue engineering represents a promising technique to overcome the limitations of the current valve replacements, since it allows for creating living autologous heart valves that have the potential to grow and remodel. However, also this approach still faces a number of challenges. One particular problem is regurgitation, caused by cell-mediated tissue retraction or the mismatch in geometrical and material properties between tissue-engineered heart valves (TEHVs) and their native counterparts. The goal of the present study was to assess the influence of valve geometry and tissue anisotropy on the deformation profile and closed configuration of TEHVs. To achieve this aim, a range of finite element models incorporating different valve shapes was developed, and the constitutive behavior of the tissue was modeled using an established computational framework, where the degree of anisotropy was varied between values representative of TEHVs and native valves. The results of this study suggest that valve geometry and tissue anisotropy are both important to maximize the radial strains and thereby the coaptation area. Additionally, the minimum degree of anisotropy that is required to obtain positive radial strains was shown to depend on the valve shape and the pressure to which the valves are exposed. Exposure to pulmonary diastolic pressure only yielded positive radial strains if the anisotropy was comparable to the native situation, whereas considerably less anisotropy was required if the valves were exposed to aortic diastolic pressure. Copyright © 2013 Elsevier Ltd. All rights reserved.

  11. Spin current

    CERN Document Server

    Valenzuela, Sergio O; Saitoh, Eiji; Kimura, Takashi

    2017-01-01

    Since the discovery of the giant magnetoresistance effect in magnetic multilayers in 1988, a new branch of physics and technology, called spin-electronics or spintronics, has emerged, where the flow of electrical charge as well as the flow of electron spin, the so-called “spin current,” are manipulated and controlled together. The physics of magnetism and the application of spin current have progressed in tandem with the nanofabrication technology of magnets and the engineering of interfaces and thin films. This book aims to provide an introduction and guide to the new physics and applications of spin current, with an emphasis on the interaction between spin and charge currents in magnetic nanostructures.

  12. Emergence of non-Fermi liquid behaviors in 5d perovskite SrIrO{sub 3} thin films: Interplay between correlation, disorder, and spin-orbit coupling

    Energy Technology Data Exchange (ETDEWEB)

    Biswas, Abhijit [Department of Physics, POSTECH, Pohang 790-784 (Korea, Republic of); Kim, Ki-Seok [Department of Physics, POSTECH, Pohang 790-784 (Korea, Republic of); Institute of Edge of Theoretical Science (IES), POSTECH, Pohang 790-784 (Korea, Republic of); Jeong, Yoon H., E-mail: yhj@postech.ac.kr [Department of Physics, POSTECH, Pohang 790-784 (Korea, Republic of)

    2016-02-15

    We investigate the effects of compressive strain on the electrical resistivity of 5d iridium based perovskite SrIrO{sub 3} by depositing epitaxial films of thickness 35 nm on various substrates such as GdScO{sub 3} (110), DyScO{sub 3} (110), and SrTiO{sub 3} (001). Surprisingly, we find anomalous transport behaviors as expressed by ρ∝T{sup ε} in the temperature dependent resistivity, where the temperature exponent ε evolves continuously from 4/5 to 1 and to 3/2 with an increase of compressive strain. Furthermore, magnetoresistance always remains positive irrespective of resistivity upturns at low temperatures. These observations imply that the delicate interplay between correlation and disorder in the presence of strong spin-orbit coupling is responsible for the emergence of the non-Fermi liquid behaviors in 5d perovskite SrIrO{sub 3} thin films. We offer a theoretical framework for the interpretation of the experimental results. - Highlights: • We studied the effect of compressive strain on the perovskite SrIrO{sub 3} thin films. • We revealed non-Fermi liquid behaviors in the transport properties. • Irrespective of weak localization effects, magnetoresistance remains positive. • Mott-Anderson-Griffiths scenario is proposed to account for the NFL behaviors.

  13. Spin Electronics

    Science.gov (United States)

    2003-08-01

    applications, a ferromagnetic metal may be used as a source of spin-polarized electronics to be injected into a semiconductor, a superconductor or a...physical phenomena in II-VI and III-V semiconductors. In II-VI systems, the Mn2+ ions act to boost the electron spin precession up to terahertz ...conductors, proximity effect between ferromagnets and superconductors , and the effects of spin injection on the physical properties of the

  14. Spin doctoring

    OpenAIRE

    Vozková, Markéta

    2011-01-01

    1 ABSTRACT The aim of this text is to provide an analysis of the phenomenon of spin doctoring in the Euro-Atlantic area. Spin doctors are educated people in the fields of semiotics, cultural studies, public relations, political communication and especially familiar with the infrastructure and the functioning of the media industry. Critical reflection of manipulative communication techniques puts spin phenomenon in historical perspective and traces its practical use in today's social communica...

  15. Interfacial spin-orbit splitting and current-driven spin torque in anisotropic tunnel junctions

    KAUST Repository

    Manchon, Aurelien

    2011-05-17

    Spin transport in magnetic tunnel junctions comprising a single magnetic layer in the presence of interfacial spin-orbit interaction (SOI) is investigated theoretically. Due to the presence of interfacial SOI, a current-driven spin torque can be generated at the second order in SOI, even in the absence of an external spin polarizer. This torque possesses two components, one in plane and one perpendicular to the plane of rotation, that can induce either current-driven magnetization switching from an in-plane to out-of-plane configuration or magnetization precessions, similar to spin transfer torque in spin valves. Consequently, it appears that it is possible to control the magnetization steady state and dynamics by either varying the bias voltage or electrically modifying the SOI at the interface.

  16. Muon spin rotation and other microscopic probes of spin-glass dynamics

    International Nuclear Information System (INIS)

    MacLaughlin, D.E.

    1980-01-01

    A number of different microscopic probe techniques have been employed to investigate the onset of the spin-glass state in dilute magnetic alloys. Among these are Moessbauer-effect spectroscopy, neutron scattering, ESR of the impurity spins, host NMR and, most recently, muon spin rotation and depolarization. Spin probes yield information on the microscopic static and dynamic behavior of the impurity spins, and give insight into both the spin freezing process and the nature of low-lying excitations in the ordered state. Microscopic probe experiments in spin glasses are surveyed, and the unique advantages of muon studies are emphasized

  17. Mitral Valve Disease

    Science.gov (United States)

    ... clots, but they also are less durable than mechanical valves and may need to be replaced in the future. Like mitral valve repair, replacement can be done minimally invasively or with traditional open heart surgery. Your medical team will discuss the advantages ...

  18. Microscopic understanding of spin current probed by shot noise

    Science.gov (United States)

    Arakawa, Tomonori

    The spin currents is one of key issue in the spintronics field and the generation and detection of those have been intensively studied by using various materials. The analysis of experiments, however, relies on phenomenological parameters such as spin relaxation length and spin flip time. The microscopic nature of the spin current such as energy distribution and energy relaxation mechanism, has not yet well understood. To establish a better microscopic understanding of spin currents, I focused on the shot noise measurement which is well established technique in the field of mesoscopic physics [Y. M. Blanter and M. B üttiker, Phys. Rep. 336, 1 (2000).]. Although there are many theoretically works about shot noise in the presence of spin currents, for example detection of spin accumulation [J. Meair, P. Stano, and P. Jacquod, Phys. Rev. B 84 (2011).], estimation of spin flip currents, and so on, these predictions have never been experimentally confirmed. In this context, we reported the first experimental detention of shot noise in the presence of the spin accumulation in a (Ga,Mn)As/tunnel barrier/n-GaAs based lateral spin valve device [T. Arakawa et al., Phys. Rev. Lett. 114, 016601 (2015).]. Together with this result, we found however that the effective temperature of the spin current drastically increases due to the spin injection process. This heating of electron system could be a big problem to realize future spin current devices by using quantum coherence, because the effective temperature rise directly related to the destruction of the coherence of the spin current. Therefore, then we focused on the mechanism of this heating and the energy relaxation in a diffusive channel. By measuring current noise and the DC offset voltage in the usual non-local spin valve signal as a function of the spin diffusion channel length, we clarified that the electron-electron interaction length, which is the characteristic length for the relaxation of the electron system, is

  19. ULTRA HIGH VACUUM VALVE

    Science.gov (United States)

    Fry, W.A.

    1962-05-29

    A valve for high vacuum applications such as the CStellarator where chamber pressures as low as 2 x 10/sup -10/ mm Hg are necessary is designed with a line-of-sight path through the valve for visual inspection of the contents of reactants in such chambers. The valve comprises a turnable resilient metal ball having an aperture therethrough, means for selectively turning the ball to rotate the axis of its line-of-sight path, and soft, deformable opposing orifices that are movable relatively toward said ball to seal with opposite ball surfaces upon said movement of said axis of said line-of-sight path. The valve also includes a bellows seal connected between said orifices and internal actuating means that eliminates the requirement for gasketed turnable valve closing stems. (AEC)

  20. Multiple-port valve

    International Nuclear Information System (INIS)

    Doody, T.J.

    1978-01-01

    A multiple-port valve assembly is designed to direct flow from a primary conduit into any one of a plurality of secondary conduits as well as to direct a reverse flow. The valve includes two mating hemispherical sockets that rotatably receive a spherical valve plug. The valve plug is attached to the primary conduit and includes diverging passageways from that conduit to a plurality of ports. Each of the ports is alignable with one or more of a plurality of secondary conduits fitting into one of the hemispherical sockets. The other hemispherical socket includes a slot for the primary conduit such that the conduit's motion along that slot with rotation of the spherical plug about various axes will position the valve-plug ports in respect to the secondary conduits

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

    Science.gov (United States)

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

    2017-06-27

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

  2. Dynamic magnetic behavior of the mixed spin (2, 5/2) Ising system with antiferromagnetic/antiferromagnetic interactions on a bilayer square lattice

    International Nuclear Information System (INIS)

    Ertaş Mehmet; Keskin Mustafa

    2013-01-01

    Using the mean-field theory and Glauber-type stochastic dynamics, we study the dynamic magnetic properties of the mixed spin (2, 5/2) Ising system for the antiferromagnetic/antiferromagnetic (AFM/AFM) interactions on the bilayer square lattice under a time varying (sinusoidal) magnetic field. The time dependence of average magnetizations and the thermal variation of the dynamic magnetizations are examined to calculate the dynamic phase diagrams. The dynamic phase diagrams are presented in the reduced temperature and magnetic field amplitude plane and the effects of interlayer coupling interaction on the critical behavior of the system are investigated. We also investigate the influence of the frequency and find that the system displays richer dynamic critical behavior for higher values of frequency than that of the lower values of it. We perform a comparison with the ferromagnetic/ferromagnetic (FM/FM) and AFM/FM interactions in order to see the effects of AFM/AFM interaction and observe that the system displays richer and more interesting dynamic critical behaviors for the AFM/AFM interaction than those for the FM/FM and AFM/FM interactions. (general)

  3. Spin glasses

    CERN Document Server

    Bovier, Anton

    2007-01-01

    Spin glass theory is going through a stunning period of progress while finding exciting new applications in areas beyond theoretical physics, in particular in combinatorics and computer science. This collection of state-of-the-art review papers written by leading experts in the field covers the topic from a wide variety of angles. The topics covered are mean field spin glasses, including a pedagogical account of Talagrand's proof of the Parisi solution, short range spin glasses, emphasizing the open problem of the relevance of the mean-field theory for lattice models, and the dynamics of spin glasses, in particular the problem of ageing in mean field models. The book will serve as a concise introduction to the state of the art of spin glass theory, usefull to both graduate students and young researchers, as well as to anyone curious to know what is going on in this exciting area of mathematical physics.

  4. Technology Reinvestment Program/Advanced ``Zero Emission'' Control Valve (Phase II)

    Energy Technology Data Exchange (ETDEWEB)

    J. Napoleon

    1998-12-01

    The objectives of this effort are to determine, develop and demonstrate the feasibility of significantly reducing the cost and expanding the applications for a family of Advanced Zero Emissions Control Valves that meets the fugitive emissions requirements of the 1990 Amendments to the Clean Air Act. This program is a direct technology spin-off from the valve technology that is critical to the US Navy's Nuclear Powered Fleet. These zero emissions valves will allow the Hydrocarbon and Chemical Processing Industries, etc., to maintain their competitiveness and still meet environmental and safety requirements. Phase 2 is directed at refining the basic technologies developed during Phase 1 so that they can be more readily selected and utilized by the target market. In addition to various necessary certifications, the project will develop a full featured digital controller with ``smart valve'' growth capability, expanding valve sizes/applications and identifying valve materials to permit applications in severe operational environments.

  5. Gate valve performance prediction

    International Nuclear Information System (INIS)

    Harrison, D.H.; Damerell, P.S.; Wang, J.K.; Kalsi, M.S.; Wolfe, K.J.

    1994-01-01

    The Electric Power Research Institute is carrying out a program to improve the performance prediction methods for motor-operated valves. As part of this program, an analytical method to predict the stem thrust required to stroke a gate valve has been developed and has been assessed against data from gate valve tests. The method accounts for the loads applied to the disc by fluid flow and for the detailed mechanical interaction of the stem, disc, guides, and seats. To support development of the method, two separate-effects test programs were carried out. One test program determined friction coefficients for contacts between gate valve parts by using material specimens in controlled environments. The other test program investigated the interaction of the stem, disc, guides, and seat using a special fixture with full-sized gate valve parts. The method has been assessed against flow-loop and in-plant test data. These tests include valve sizes from 3 to 18 in. and cover a considerable range of flow, temperature, and differential pressure. Stem thrust predictions for the method bound measured results. In some cases, the bounding predictions are substantially higher than the stem loads required for valve operation, as a result of the bounding nature of the friction coefficients in the method

  6. GIANT PROSTHETIC VALVE THROMBUS

    Directory of Open Access Journals (Sweden)

    Prashanth Kumar

    2015-04-01

    Full Text Available Mechanical prosthetic valves are predisposed to bleeding, thrombosis & thromboembolic complications. Overall incidence of thromboembolic complications is 1% per year who are on oral anticoagulants, whereas bleeding complications incidence is 0.5% to 6.6% per year. 1, 2 Minimization of Scylla of thromboembolic & Charybdis of bleeding complication needs a balancing act of optimal antithrombotic therapy. We are reporting a case of middle aged male patient with prosthetic mitral valve presenting in heart failure. Patient had discontinued anticoagulants, as he had subdural hematoma in the past. He presented to our institute with a giant prosthetic valve thrombus.

  7. FLUID MECHANICS OF ARTIFICIAL HEART VALVES

    OpenAIRE

    Dasi, Lakshmi P; Simon, Helene A; Sucosky, Philippe; Yoganathan, Ajit P

    2009-01-01

    1. Artificial heart valves have been in use for over five decades to replace diseased heart valves. Since the first heart valve replacement performed with a caged-ball valve, more than 50 valve designs have been developed, differing principally in valve geometry, number of leaflets and material. To date, all artificial heart valves are plagued with complications associated with haemolysis, coagulation for mechanical heart valves and leaflet tearing for tissue-based valve prosthesis. For mecha...

  8. Valve monitoring ITI-MOVATS

    International Nuclear Information System (INIS)

    Moureau, S.

    1993-01-01

    ITI-MOVATS provides a wide range of test devices to monitor the performance of valves: motor operated gate or globe valve, butterfly valve, air operated valve, and check valve. The ITI-MOVATS testing equipment is used in the following three areas: actuator setup/baseline testing, periodic/post-maintenance testing, and differential pressure testing. The parameters typically measured with the MOVATS diagnostic system as well as the devices used to measure them are described. (Z.S.)

  9. Transcatheter valve-in-valve implantation for failed bioprosthetic heart valves.

    Science.gov (United States)

    Webb, John G; Wood, David A; Ye, Jian; Gurvitch, Ronen; Masson, Jean-Bernard; Rodés-Cabau, Josep; Osten, Mark; Horlick, Eric; Wendler, O; Dumont, Eric; Carere, Ronald G; Wijesinghe, Namal; Nietlispach, Fabian; Johnson, Mark; Thompson, Chrisopher R; Moss, Robert; Leipsic, Jonathon; Munt, Brad; Lichtenstein, Samuel V; Cheung, Anson

    2010-04-27

    The majority of prosthetic heart valves currently implanted are tissue valves that can be expected to degenerate with time and eventually fail. Repeat cardiac surgery to replace these valves is associated with significant morbidity and mortality. Transcatheter heart valve implantation within a failed bioprosthesis, a "valve-in-valve" procedure, may offer a less invasive alternative. Valve-in-valve implantations were performed in 24 high-risk patients. Failed valves were aortic (n=10), mitral (n=7), pulmonary (n=6), or tricuspid (n=1) bioprostheses. Implantation was successful with immediate restoration of satisfactory valve function in all but 1 patient. No patient had more than mild regurgitation after implantation. No patients died during the procedure. Thirty-day mortality was 4.2%. Mortality was related primarily to learning-curve issues early in this high-risk experience. At baseline, 88% of patients were in New York Heart Association functional class III or IV; at the last follow-up, 88% of patients were in class I or II. At a median follow-up of 135 days (interquartile range, 46 to 254 days) and a maximum follow-up of 1045 days, 91.7% of patients remained alive with satisfactory valve function. Transcatheter valve-in-valve implantation is a reproducible option for the management of bioprosthetic valve failure. Aortic, pulmonary, mitral, and tricuspid tissue valves were amenable to this approach. This finding may have important implications with regard to valve replacement in high-risk patients.

  10. Anomalous 125Te Nuclear Spin Relaxation Coincident with Charge Kondo Behavior in Superconducting Pb1-xTlxTe

    Science.gov (United States)

    Mukuda, Hidekazu; Matsumura, Takashi; Maki, Shota; Yashima, Mitsuharu; Kitaoka, Yoshio; Miyake, Kazumasa; Murakami, Hironaru; Giraldo-Gallo, Paula; Geball, Theodore H.; Fisher, Ian R.

    2018-02-01

    We report the results of a 125Te NMR study of single crystalline Pb1-xTlxTe (x = 0, 0.35, 1.0%) as a window on the novel electronic states associated with the thallium impurities in PbTe. The Knight shift is enhanced as x increases, corresponding to an increase in the average density of states (DOS) coupled to a strong spatial variation in the local DOS surrounding each Tl dopant. Remarkably, for the superconducting composition (x = 1.0%), the 125Te nuclear spin relaxation rate (1/T1T) for Te ions that are close to the Tl dopants is unexpectedly enhanced in the normal state below a characteristic temperature of ˜10 K, below which the resistivity experiences an upturn. Such a simultaneous upturn in both the resistivity and (1/T1T) was not suppressed in the high magnetic field. We suggest that these observations are consistently accounted for by dynamical charge fluctuations in the absence of paramagnetism, which is anticipated by the charge Kondo scenario associated with the Tl dopants. In contrast, such anomalies were not detected in the non-superconducting samples (x = 0 and 0.35%), suggesting a connection between dynamical valence fluctuations and the occurrence of superconductivity in Pb1-xTlxTe.

  11. Microfibrous Solid Dispersions of Poorly Water-Soluble Drugs Produced via Centrifugal Spinning: Unexpected Dissolution Behavior on Recrystallization.

    Science.gov (United States)

    Marano, Stefania; Barker, Susan A; Raimi-Abraham, Bahijja T; Missaghi, Shahrzad; Rajabi-Siahboomi, Ali; Aliev, Abil E; Craig, Duncan Q M

    2017-05-01

    Temperature-controlled, solvent-free centrifugal spinning may be used as a means of rapid production of amorphous solid dispersions in the form of drug-loaded sucrose microfibers. However, due to the high content of amorphous sucrose in the formulations, such microfibers may be highly hygroscopic and unstable on storage. In this study, we explore both the effects of water uptake of the microfibers and the consequences of deliberate recrystallization for the associated dissolution profiles. The stability of sucrose microfibers loaded with three selected BCS class II model drugs (itraconazole (ITZ), olanzapine (OLZ), and piroxicam (PRX)) was investigated under four different relative humidity conditions (11, 33, 53, and 75% RH) at 25 °C for 8 months, particularly focusing on the effect of the highest level of moisture (75% RH) on the morphology, size, drug distribution, physical state, and dissolution performance of microfibers. While all samples were stable at 11% RH, at 33% RH the ITZ-sucrose system showed greater resistance against devitrification compared to the OLZ- and PRX-sucrose systems. For all three samples, the freshly prepared microfibers showed enhanced dissolution and supersaturation compared to the drug alone and physical mixes; surprisingly, the dissolution advantage was largely maintained or even enhanced (in the case of ITZ) following the moisture-induced recrystallization under 75% RH. Therefore, this study suggests that the moisture-induced recrystallization process may result in considerable dissolution enhancement compared to the drug alone, while overcoming the physical stability risks associated with the amorphous state.

  12. Thermal behavior of organic free radicals in γ-ray irradiated pepper studied by electron spin resonance spectroscopy

    International Nuclear Information System (INIS)

    Ichii, Akane; Abe, Aika; Ukai, Mitsuko

    2003-01-01

    Using electron spin resonance (ESR) spectroscopy, we revealed heating effects on irradiated pepper. The representative ESR spectrum of the irradiated pepper is consisted of four components a sextet centered at g=2.0, a singlet at the same g-value, a singlet at g=4.0 and side peaks near g=2.0. The first one is attributable to a signal with hyperfine (hf) interactions of Mn 2+ (hf constant=7.4 mT). The second one is due to an organic free radical that is induced by the γ-ray irradiation. The third one may originated from Fe 3+ in the nonhem proteins. The fourth signal was found at the symmetric positions of the organic free radical, i.e., the second signal. Upon heating, the forth signals decreased monotonicaly. The ESR signal of the pepper heated for more than 10 min was essentially the same as that before the irradiation. On the other hand, the second signal increased and then leveled off at a constant value by further heating. This is indicative the occurrence of some biochemical reactions such as Maillard reaction during heating procedures. (author)

  13. TOPICAL REVIEW: Spin current, spin accumulation and spin Hall effect

    Directory of Open Access Journals (Sweden)

    Saburo Takahashi and Sadamichi Maekawa

    2008-01-01

    Full Text Available Nonlocal spin transport in nanostructured devices with ferromagnetic injector (F1 and detector (F2 electrodes connected to a normal conductor (N is studied. We reveal how the spin transport depends on interface resistance, electrode resistance, spin polarization and spin diffusion length, and obtain the conditions for efficient spin injection, spin accumulation and spin current in the device. It is demonstrated that the spin Hall effect is caused by spin–orbit scattering in nonmagnetic conductors and gives rise to the conversion between spin and charge currents in a nonlocal device. A method of evaluating spin–orbit coupling in nonmagnetic metals is proposed.

  14. Spin Waves in Terbium

    DEFF Research Database (Denmark)

    Jensen, J.; Houmann, Jens Christian Gylden

    1975-01-01

    The selection rules for the linear couplings between magnons and phonons propagating in the c direction of a simple basal-plane hcp ferromagnet are determined by general symmetry considerations. The acoustic-optical magnon-phonon interactions observed in the heavy-rare-earth metals have been...... explained by Liu as originating from the mixing of the spin states of the conduction electrons due to the spin-orbit coupling. We find that this coupling mechanism introduces interactions which violate the selection rules for a simple ferromagnet. The interactions between the magnons and phonons propagating...... in the c direction of Tb have been studied experimentally by means of inelastic neutron scattering. The magnons are coupled to both the acoustic- and optical-transverse phonons. By studying the behavior of the acoustic-optical coupling, we conclude that it is a spin-mixed-induced coupling as proposed...

  15. Modulation of pure spin currents with a ferromagnetic insulator

    Science.gov (United States)

    Villamor, Estitxu; Isasa, Miren; Vélez, Saül; Bedoya-Pinto, Amilcar; Vavassori, Paolo; Hueso, Luis E.; Bergeret, F. Sebastián; Casanova, Fèlix

    2015-01-01

    We propose and demonstrate spin manipulation by magnetically controlled modulation of pure spin currents in cobalt/copper lateral spin valves, fabricated on top of the magnetic insulator Y3F e5O12 (YIG). The direction of the YIG magnetization can be controlled by a small magnetic field. We observe a clear modulation of the nonlocal resistance as a function of the orientation of the YIG magnetization with respect to the polarization of the spin current. Such a modulation can only be explained by assuming a finite spin-mixing conductance at the Cu/YIG interface, as it follows from the solution of the spin-diffusion equation. These results open a path towards the development of spin logics.

  16. Spin electronics

    CERN Document Server

    Buhrman, Robert; Daughton, James; Molnár, Stephan; Roukes, Michael

    2004-01-01

    This report is a comparative review of spin electronics ("spintronics") research and development activities in the United States, Japan, and Western Europe conducted by a panel of leading U.S. experts in the field. It covers materials, fabrication and characterization of magnetic nanostructures, magnetism and spin control in magnetic nanostructures, magneto-optical properties of semiconductors, and magnetoelectronics and devices. The panel's conclusions are based on a literature review and a series of site visits to leading spin electronics research centers in Japan and Western Europe. The panel found that Japan is clearly the world leader in new material synthesis and characterization; it is also a leader in magneto-optical properties of semiconductor devices. Europe is strong in theory pertaining to spin electronics, including injection device structures such as tunneling devices, and band structure predictions of materials properties, and in development of magnetic semiconductors and semiconductor heterost...

  17. Spin glasses

    International Nuclear Information System (INIS)

    Fischer, K.H.; Hertz, J.A.

    1993-01-01

    Spin glasses, simply defined by the authors as a collection of spins (i.e., magnetic moments) whose low-temperature state is a frozen disordered one, represent one of the fascinating new fields of study in condensed matter physics, and this book is the first to offer a comprehensive account of the subject. Included are discussions of the most important developments in theory, experimental work, and computer modeling of spin glasses, all of which have taken place essentially within the last two decades. The first part of the book gives a general introduction to the basic concepts and a discussion of mean field theory, while the second half concentrates on experimental results, scaling theory, and computer simulation of the structure of spin glasses

  18. Tunneling effect of the spin-2 Bose condensate driven by external magnetic fields

    OpenAIRE

    Yu, Zhao-xian; Jiao, Zhi-yong

    2003-01-01

    In this paper, we have studied tunneling effect of the spin-2 Bose condensate driven by external magnetic field. We find that the population transfers among spin-0 and spin-$\\pm1$, spin-0 and spin-$\\pm2$ exhibit the step structure under the external cosinusoidal magnetic field respectively, but there do not exist step structure among spin-$\\pm1$ and spin-$\\pm2$. The tunneling current among spin-$\\pm1$ and spin-$\\pm2$ may exhibit periodically oscillation behavior, but among spin-0 and spin-$\\p...

  19. Fluid-faulting interactions: Fracture-mesh and fault-valve behavior in the February 2014 Mammoth Mountain, California, earthquake swarm

    Science.gov (United States)

    Shelly, David R.; Taira, Taka’aki; Prejean, Stephanie; Hill, David P.; Dreger, Douglas S.

    2015-01-01

    Faulting and fluid transport in the subsurface are highly coupled processes, which may manifest seismically as earthquake swarms. A swarm in February 2014 beneath densely monitored Mammoth Mountain, California, provides an opportunity to witness these interactions in high resolution. Toward this goal, we employ massive waveform-correlation-based event detection and relative relocation, which quadruples the swarm catalog to more than 6000 earthquakes and produces high-precision locations even for very small events. The swarm's main seismic zone forms a distributed fracture mesh, with individual faults activated in short earthquake bursts. The largest event of the sequence, M 3.1, apparently acted as a fault valve and was followed by a distinct wave of earthquakes propagating ~1 km westward from the updip edge of rupture, 1–2 h later. Late in the swarm, multiple small, shallower subsidiary faults activated with pronounced hypocenter migration, suggesting that a broader fluid pressure pulse propagated through the subsurface.

  20. Blocked Urethral Valves

    Science.gov (United States)

    ... the penis. Rarely, small membranes form across the urethra in boys early in pregnancy, and they can block the flow of urine out of the bladder. These membranes are called posterior urethral valves and can have life-threatening consequences ...

  1. Dry product valve

    International Nuclear Information System (INIS)

    Greaves, James D.

    1984-01-01

    This invention provides a system for delivering particulate radioactive or other toxic wastes to a container in which they can be solidified. The system includes a set of valves that prevent the escape of dusty materials to the atmosphere

  2. Ball check valve

    International Nuclear Information System (INIS)

    Bevilacqua, F.

    1978-01-01

    A pressurized nuclear reactor having an instrument assembly sheathed in a metallic tube which is extended vertically upward into the reactor core by traversing a metallic guide tube which is welded to the wall of the vessel is described. Sensors in each instrument assembly are connected to instruments outside the vessel to manifest the conditions within the core. Each instrument assembly probe is moved into position within a metallic guide channel. The guide channel penetrates the wall of the vessel and forms part of the barrier to the environment within the pressure vessel. Each channel includes a ball check valve which is opened by the instrument assembly probe when the probe passes through the valve. A ball valve element is moved from its seat by the probe to a position lateral of the bore of the channel and is guided to its seat along a sloped path within the valve body when the probe is removed. 5 claims, 3 figures

  3. Dynamic magnetic behavior of the mixed-spin bilayer system in an oscillating field within the mean-field theory

    International Nuclear Information System (INIS)

    Ertaş, Mehmet; Keskin, Mustafa

    2012-01-01

    The dynamic magnetic behavior of the mixed Ising bilayer system (σ=2 and S=5/2), with a crystal-field interaction in an oscillating field are studied, within the mean-field approach, by using the Glauber-type stochastic dynamics for both ferromagnetic/ferromagnetic and antiferromagnetic/ferromagnetic interactions. The time variations of average magnetizations and the temperature dependence of the dynamic magnetizations are investigated. The dynamic phase diagrams are presented in the reduced temperature and magnetic field amplitude plane and they exhibit several ordered phases, coexistence phase regions and critical points as well as a re-entrant behavior depending on interaction parameters. -- Highlights: ► Dynamic magnetic behavior of the mixed Ising bilayer system is investigated within the Glauber-type stochastic dynamics. ► The time variations of average magnetizations are studied to find the phases. ► The temperature dependence of the dynamic magnetizations is investigated to obtain the dynamic phase transition points. ► The dynamic phase diagrams are presented and they exhibit several ordered phases, coexistence phase regions and critical points as well as a re-entrant behavior.

  4. Dynamic magnetic behavior of the mixed-spin bilayer system in an oscillating field within the mean-field theory

    Energy Technology Data Exchange (ETDEWEB)

    Ertaş, Mehmet [Department of Physics, Erciyes University, 38039 Kayseri (Turkey); Keskin, Mustafa, E-mail: keskin@erciyes.edu.tr [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)

    2012-07-23

    The dynamic magnetic behavior of the mixed Ising bilayer system (σ=2 and S=5/2), with a crystal-field interaction in an oscillating field are studied, within the mean-field approach, by using the Glauber-type stochastic dynamics for both ferromagnetic/ferromagnetic and antiferromagnetic/ferromagnetic interactions. The time variations of average magnetizations and the temperature dependence of the dynamic magnetizations are investigated. The dynamic phase diagrams are presented in the reduced temperature and magnetic field amplitude plane and they exhibit several ordered phases, coexistence phase regions and critical points as well as a re-entrant behavior depending on interaction parameters. -- Highlights: ► Dynamic magnetic behavior of the mixed Ising bilayer system is investigated within the Glauber-type stochastic dynamics. ► The time variations of average magnetizations are studied to find the phases. ► The temperature dependence of the dynamic magnetizations is investigated to obtain the dynamic phase transition points. ► The dynamic phase diagrams are presented and they exhibit several ordered phases, coexistence phase regions and critical points as well as a re-entrant behavior.

  5. Aortic valve replacement

    DEFF Research Database (Denmark)

    Kapetanakis, Emmanouil I; Athanasiou, Thanos; Mestres, Carlos A

    2008-01-01

    BACKGROUND AND AIMS OF THE STUDY: Prompted by anecdotal evidence and observations by surgeons, an investigation was undertaken into the potential differences in implanted aortic valve prosthesis sizes, during aortic valve replacement (AVR) procedures, between northern and southern European...... assigned to the 'small' aortic size subset. Effective orifice area indices were calculated for all patients to assess the geographic distribution of patient-prosthesis mismatch. Univariable and multivariable logistic regression analyses adjusting for possible confounding variables were performed. RESULTS...

  6. Coanda effect in valves

    Directory of Open Access Journals (Sweden)

    Uruba Václav

    2017-01-01

    Full Text Available Coanda effect takes place in flow within valves diffuser for certain conditions. The valve plug in half-closed position forms wall-jet, which could be stable or instable, depending on geometry and other conditions. This phenomenon was subject of experimental study using time-resolved PIV technique. For the acquired data analysis the special spatio-temporal methods have been used.

  7. pH-Sensitive Hydrogel for Micro-Fluidic Valve

    Directory of Open Access Journals (Sweden)

    Zhengzhi Yang

    2012-07-01

    Full Text Available The deformation behavior of a pH-sensitive hydrogel micro-fluidic valve system is investigated using inhomogeneous gel deformation theory, in which the fluid-structure interaction (FSI of the gel solid and fluid flow in the pipe is considered. We use a finite element method with a well adopted hydrogel constitutive equation, which is coded in commercial software, ABAQUS, to simulate the hydrogel valve swelling deformation, while FLUENT is adopted to model the fluid flow in the pipe of the hydrogel valve system. The study demonstrates that FSI significantly affects the gel swelling deformed shapes, fluid flow pressure and velocity patterns. FSI has to be considered in the study on fluid flow regulated by hydrogel microfluidic valve. The study provides a more accurate and adoptable model for future design of new pH-sensitive hydrogel valves, and also gives a useful guideline for further studies on hydrogel fluidic applications.

  8. Superconducting spin-triplet-MRAM with infinite magnetoresistance ratio

    Energy Technology Data Exchange (ETDEWEB)

    Lenk, Daniel; Ullrich, Aladin; Obermeier, Guenter; Mueller, Claus; Krug von Nidda, Hans-Albrecht; Horn, Siegfried; Tidecks, Reinhard [Institut fuer Physik, Universitaet Augsburg, D-86159 Augsburg (Germany); Morari, Roman [Institut fuer Physik, Universitaet Augsburg, D-86159 Augsburg (Germany); D. Ghitsu Institute of Electronic Engineering and Nanotechnologies ASM, Academiei Str. 3/3, MD2028 Kishinev (Moldova, Republic of); Solid State Physics Department, Kazan Federal University, 420008 Kazan (Russian Federation); Zdravkov, Vladimir I. [Institut fuer Physik, Universitaet Augsburg, D-86159 Augsburg (Germany); D. Ghitsu Institute of Electronic Engineering and Nanotechnologies ASM, Academiei Str. 3/3, MD2028 Kishinev (Moldova, Republic of); Institute of Applied Physics and Interdisciplinary Nanoscience Center, Universitaet Hamburg, Jungiusstrasse 9A, D-20355 Hamburg (Germany); Sidorenko, Anatoli S. [D. Ghitsu Institute of Electronic Engineering and Nanotechnologies ASM, Academiei Str. 3/3, MD2028 Kishinev (Moldova, Republic of); Tagirov, Lenar R. [Institut fuer Physik, Universitaet Augsburg, D-86159 Augsburg (Germany); Solid State Physics Department, Kazan Federal University, 420008 Kazan (Russian Federation)

    2016-07-01

    We fabricated a nanolayered hybrid superconductor-ferromagnet spin-valve structure, i.e. the superconducting transition temperature of this structure depends on its magnetic history. The observed spin-valve effect is based on the generation of the long range odd in frequency triplet component, arising from a non-collinear relative orientation of the constituent ferromagnetic layers. We investigated the effect both as a function of the sweep amplitude of the magnetic field, determining the magnetic history, and the applied transport current. Moreover, we demonstrate the possibility of switching the system from the normal o the superconducting state by applying field pulses, yielding an infinite magnetoresistance ratio.

  9. Edwards valve-in-valve implantation in tricuspid position.

    Science.gov (United States)

    Álvarez-Fuente, Maria; Haas, Nikolaus A; Del Cerro, Maria Jesus

    2017-10-01

    We present two cases of percutaneous Sapien XT valve-in-valve implantation in the tricuspid position: a 20-year-old man with severe congenital pulmonary stenosis and percutaneous valvuloplasty, who required surgical implantation of two protheses, pulmonary and tricuspid, and a 12-year-old boy with CHD and a degenerated tricuspid prosthesis. We implanted three Sapien XT valve-in-valves, two in the tricuspid position and one in the pulmonic position. Sapien XT valve-in-valve implantation in the tricuspid position is feasible and can decrease the number of surgeries in CHD patients.

  10. Spin Waves in the FCC Kagome Lattice

    Science.gov (United States)

    Leblanc, Martin; Southern, Byron; Plumer, Martin; Whitehead, John

    2014-03-01

    The impact of an effective local cubic anisotropy on the spin wave excitations and inelastic neutron scattering intensity peaks of the Heisenberg model on the 3D fcc kagome lattice are examined through a linear spin wave theory. Previous Monte Carlo simulations revealed that the addition of anisotropy to the fcc kagome lattice changes the order of the phase transition from weakly first order to continuous and restricts the T = 0 spin configuration to a number of discrete ground states, removing the continuous degeneracy. It is shown that the addition of anisotropy removes the number of zero energy modes in the excitation spectrum associated with the removed degeneracies. These results are relevant to Ir-Mn alloys which have been widely used by the magnetic storage industry in thin-film form as the antiferromagnetic pinning layer in GMR and TMR spin valves. Supported by NSERC of Canada.

  11. Transcatheter tissue engineered heart valves.

    Science.gov (United States)

    Emmert, Maximilian Y; Weber, Benedikt; Falk, Volkmar; Hoerstrup, Simon P

    2014-01-01

    Valvular heart disease represents a leading cause of mortality worldwide. Transcatheter heart valve replacement techniques have been recently introduced into the clinical routine expanding the treatment options for affected patients. However, despite this technical progress toward minimally invasive, transcatheter strategies, the available heart valve prostheses for these techniques are bioprosthetic and associated with progressive degeneration. To overcome such limitations, the concept of heart valve tissue engineering has been repeatedly suggested for future therapy concepts. Ideally, a clinically relevant heart valve tissue engineering concept would combine minimally invasive strategies for both, living autologous valve generation as well as valve implantation. Therefore, merging transcatheter techniques with living tissue engineered heart valves into a trascatheter tissue engineered heart valve concept could significantly improve current treatment options for patients suffering from valvular heart disease. This report provides an overview on transcatheter tissue engineered heart valves and summarizes available pre-clinical data.

  12. Thermodynamic behavior and enhanced magnetocaloric effect in a frustrated spin-1/2 Ising-Heisenberg triangular tube

    Science.gov (United States)

    Alécio, Raphael Cavalcante; Strečka, Jozef; Lyra, Marcelo L.

    2018-04-01

    The thermodynamic behavior of an Ising-Heisenberg triangular tube with Heisenberg intra-rung and Ising inter-rung interactions is exactly obtained in an external magnetic field within the framework of the transfer-matrix method. We report rigorous results for the temperature dependence of the magnetization, entropy, pair correlations and specific heat, as well as typical iso-entropic curves. The discontinuous field-driven ground-state phase transitions are reflected in some anomalous thermodynamic behavior as for instance a striking low-temperature peak of the specific heat and an enhanced magnetocaloric effect. It is demonstrated that the intermediate magnetization plateaus shrink in and the relevant sharp edges associated with the magnetization jump round off upon increasing temperature.

  13. Spin correlations in Ho2Ti2O7: A dipolar spin ice system

    DEFF Research Database (Denmark)

    Bramwell, S.T.; Harris, M.J.; Hertog, B.C. den

    2001-01-01

    described by a nearest neighbor spin ice model and very accurately described by a dipolar spin ice model. The heat capacity is well accounted for by the sum of a dipolar spin ice contribution and an expected nuclear spin contribution, known to exist in other Ho(3+) salts. These results settle the question......The pyrochlore material Ho(2)Ti(2)O(7) has been suggested to show "spin ice" behavior. We present neutron scattering and specific heat results that establish unambiguously that Ho(2)Ti(2)O(7) exhibits spin ice correlations at low temperature. Diffuse magnetic neutron scattering is quite well...

  14. Exploratory study of the effects of wing-leading-edge modifications on the stall/spin behavior of a light general aviation airplane

    Science.gov (United States)

    1979-01-01

    Configurations with full-span and segmented leading-edge flaps and full-span and segmented leading-edge droop were tested. Studies were conducted with wind-tunnel models, with an outdoor radio-controlled model, and with a full-scale airplane. Results show that wing-leading-edge modifications can produce large effects on stall/spin characteristics, particularly on spin resistance. One outboard wing-leading-edge modification tested significantly improved lateral stability at stall, spin resistance, and developed spin characteristics.

  15. Transcatheter Aortic Valve Replacement for Degenerative Bioprosthetic Surgical Valves

    DEFF Research Database (Denmark)

    Dvir, Danny; Webb, John; Brecker, Stephen

    2012-01-01

    Transcatheter aortic valve-in-valve implantation is an emerging therapeutic alternative for patients with a failed surgical bioprosthesis and may obviate the need for reoperation. We evaluated the clinical results of this technique using a large, worldwide registry....

  16. NRC valve performance test program - check valve testing

    International Nuclear Information System (INIS)

    Jeanmougin, N.M.

    1987-01-01

    The Valve Performance Test Program addresses the current requirements for testing of pressure isolation valves (PIVs) in light water reactors. Leak rate monitoring is the current method used by operating commercial power plants to survey the condition of their PIVs. ETEC testing of three check valves (4-inch, 6-inch, and 12-inch nominal diameters) indicates that leak rate testing is not a reliable method for detecting impending valve failure. Acoustic emission monitoring of check valves shows promise as a method of detecting loosened internals damage. Future efforts will focus on evaluation of acoustic emission monitoring as a technique for determining check valve condition. Three gate valves also will be tested to evaluate whether the check valve results are applicable to gate type PIVs

  17. Phase transition and critical behaviors of spin-orbital coupling spinel compound CdV2O4

    Science.gov (United States)

    Wang, Li; Sun, Duohua; Wang, Rongjuan; Zhu, Yuanyuan; Lu, Zhihong; Xiong, Rui; Liu, Yong; Shi, Jing

    2016-03-01

    The temperature dependent susceptibility and specific heat of spinel compound CdV2O4 were investigated. The structural transition accompanied with orbital order appearing at 89.6 K is confirmed to be a first order transition, while the magnetic transitions at 30.2 K is revealed to be a second order one. For the paramagnetism-antiferromagnetic transition, the width of critical region was estimated to be about 1.5 K by differentiating with Gaussian fluctuation. In critical region, the critical behavior of specific heat was compared with renormalization-group theory. Critical exponent α and critical amplitude ratio (A+/A-) fitting to the data was found to be -0.017 and 1.26, respectively. The value of A+/A- shows the critical behavior of CdV2O4's deviates from 3D-Heisenberg and shifts to 3D-XY. The analysis of specific heat in low temperature range gives out that Debye temperature ΘD for CdV2O4 is estimated to be 190 K.

  18. Spin transport in epitaxial graphene

    Science.gov (United States)

    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.

  19. [Usefulness of magnetic resonance imaging for managing patients with prosthetic carbon valve in the mitral position].

    Science.gov (United States)

    Koito, H; Imai, Y; Suzuki, J; Ohkubo, N; Nakamura, C; Takahashi, H; Iwasaka, T; Inada, M

    1997-11-01

    The safety, findings and clinical usefulness of magnetic resonance (MR) imaging were assessed in patients with a prosthetic carbon valve in the mitral position. In vitro deflection, heating and image distortion due to the magnetic field of a 1.5 tesla MR machine were examined in three carbon valves (CarboMedics, St. Jude Medical and Björk-Shiley valves). In vivo MR imaging of the left ventricular horizontal long-axis, vertical long-axis and short-axis views was performed by electrocardiographically synchronized spin echo and field (gradient) echo techniques in eight patients with prosthetic mitral carbon valves, consisting of six CarboMedics valves, one St. Jude Medical valve and one Björk-Shiley valve. No deflection and significant heating was seen in all three valves in vitro. Although little image distortion was shown in the CarboMedics and St. Jude Medical valves, a small distortion toward the frequency encoded direction was seen in the Björk-Shiley valve but caused no difficulty in assessing the surrounding images. Four of the eight patients had normal sinus rhythm and the other four had atrial fibrillation. The prosthetic valves were depicted as signal voids in the images taken by both spin echo and field echo techniques in vivo. Clear structural information with little image distortion of the adjacent tissues of the prosthetic valves were obtained in all patients, although the image of the Björk-Shiley valve which contained stainless steel in the frame had a slightly stronger distortion than those of the CarboMedics and St. Jude Medical valves which contained titanium. The stainless wire suture material used to close the sternal incision was depicted as a signal void, and the areas of the signal loss were larger in the images taken by the field echo technique than those by the spin echo technique. The images taken by the spin echo technique in patients with atrial fibrillation had reduced quality due to the irregularity of repetition time. Cine MR

  20. Dynamic behaviors of spin-1/2 bilayer system within Glauber-type stochastic dynamics based on the effective-field theory

    International Nuclear Information System (INIS)

    Ertaş, Mehmet; Kantar, Ersin; Keskin, Mustafa

    2014-01-01

    The dynamic phase transitions (DPTs) and dynamic phase diagrams of the kinetic spin-1/2 bilayer system in the presence of a time-dependent oscillating external magnetic field are studied by using Glauber-type stochastic dynamics based on the effective-field theory with correlations for the ferromagnetic/ferromagnetic (FM/FM), antiferromagnetic/ferromagnetic (AFM/FM) and antiferromagnetic/antiferromagnetic (AFM/AFM) interactions. The time variations of average magnetizations and the temperature dependence of the dynamic magnetizations are investigated. The dynamic phase diagrams for the amplitude of the oscillating field versus temperature were presented. The results are compared with the results of the same system within Glauber-type stochastic dynamics based on the mean-field theory. - Highlights: • The Ising bilayer system is investigated within the Glauber dynamics based on EFT. • The time variations of average order parameters to find phases are studied. • The dynamic phase diagrams are found for the different interaction parameters. • The system displays the critical points as well as a re-entrant behavior

  1. Dynamic behaviors of spin-1/2 bilayer system within Glauber-type stochastic dynamics based on the effective-field theory

    Energy Technology Data Exchange (ETDEWEB)

    Ertaş, Mehmet; Kantar, Ersin, E-mail: ersinkantar@erciyes.edu.tr; Keskin, Mustafa

    2014-05-01

    The dynamic phase transitions (DPTs) and dynamic phase diagrams of the kinetic spin-1/2 bilayer system in the presence of a time-dependent oscillating external magnetic field are studied by using Glauber-type stochastic dynamics based on the effective-field theory with correlations for the ferromagnetic/ferromagnetic (FM/FM), antiferromagnetic/ferromagnetic (AFM/FM) and antiferromagnetic/antiferromagnetic (AFM/AFM) interactions. The time variations of average magnetizations and the temperature dependence of the dynamic magnetizations are investigated. The dynamic phase diagrams for the amplitude of the oscillating field versus temperature were presented. The results are compared with the results of the same system within Glauber-type stochastic dynamics based on the mean-field theory. - Highlights: • The Ising bilayer system is investigated within the Glauber dynamics based on EFT. • The time variations of average order parameters to find phases are studied. • The dynamic phase diagrams are found for the different interaction parameters. • The system displays the critical points as well as a re-entrant behavior.

  2. Diffusional behavior of n-paraffins with various chain lengths in urea adduct channels by pulsed field-gradient spin-echo NMR spectroscopy

    International Nuclear Information System (INIS)

    Kim, Sunmi; Kuroki, Shigeki; Ando, Isao

    2006-01-01

    The diffusion coefficients (D) of n-paraffin molecules (n-C n H 2n+2 ) with various chain-lengths (n = 8, 12, 21, 26, 28 and 32) in the long channels of a deuterated urea-d 4 adduct have been measured at 25 deg. C by means of pulsed field-gradient spin-echo 1 H NMR method. The aim is to clarify diffusional behavior of the n-paraffin molecules in the urea adduct channels. From the experimental results, it is found that n-paraffin molecules are diffusing in the long channels and have two kinds of diffusion components, namely a fast (D ∼ 10 -10 m 2 /s) and a slow diffusion component (D ∼ 10 -11 m 2 /s). The diffusing-time (Δ) dependence of the diffusion coefficients of the n-paraffins shows some likely evidence of restricted diffusion since the n-paraffin molecules are confined in the urea channel. The diffusion coefficients (D) decrease as the carbon number increases from 8 to 28, and very slowly decreases as the carbon number increases from 28 to 32

  3. Anaesthesia for transvenous transcatheter tricuspid valve-in-valve ...

    African Journals Online (AJOL)

    2011-02-27

    Feb 27, 2011 ... Keywords: transvenous, transcatheter, tricuspid prosthesis, valve-in-valve implantation. Abstract. The authors report and discuss the anaesthetic management of a transvenous transcatheter tricuspid valve replacement. The conduct of anaesthesia, the challenges encountered and the specific risks ...

  4. Mitral Valve Aneurysm: A Rare Complication of Aortic Valve Endocarditis

    Directory of Open Access Journals (Sweden)

    A Moaref

    2008-11-01

    Full Text Available A 20-year-old intravenous drug abuser man, refered to our hospital with dyspnea and orthopnea. Tranesophagealechocardiography revealed severe aortic regurgitation, healed vegetation of aortic valve and an aneurysm of theanterior leaflet of the mitral valve. The patient was discharged after aortic valve replacement and mitral valverepair.

  5. Radial Force: An Underestimated Parameter in Oversizing Transcatheter Aortic Valve Replacement Prostheses: In Vitro Analysis with Five Commercialized Valves.

    Science.gov (United States)

    Egron, Sandrine; Fujita, Buntaro; Gullón, Lucía; Désirée, Pott; Schmitz-Rode, Thomas; Ensminger, Stephan; Steinseifer, Ulrich

    2017-09-05

    The goal is to inform in depth on transcatheter aortic valve replacement (TAVR) prosthesis mechanical behavior, depending on frame type, design, and size, and how it crucially impacts the oversizing issue in clinical use, and ultimately the procedure outcome. Transcatheter aortic valve replacement is an established therapy for high-risk patients suffering from aortic stenosis, and the indication for TAVR is progressively expanding to intermediate-risk patients. Choosing the optimal oversizing degree is crucial to safely anchor the TAVR valve-which involves limiting the risks for embolism, aortic regurgitation, conductance disturbance, or annulus rupture-and to increase the valve prosthesis performance. The radial force (RF) profiles of five TAVR prostheses were measured in vitro: the CoreValve 23 and 26 (Medtronic, MN), the Acurate neo S (Symetis, Switzerland), and the SAPIEN XT 23 and 26 (Edwards Lifesciences, CA). Measurements were run with the RX Machine equipment (Machine Solutions Inc., AZ), which is used in ISO standard tests for intravascular stents. Test protocols were adapted for TAVR prostheses. With the prostheses RF profiles' results, mechanical behavior differences could be described and discussed in terms of oversizing strategy and clinical impact for all five valves. Besides, crossing the prostheses' RF profiles with their recommended size windows made the assessment of borderline size cases possible and helped analyze the risks when accurate measurement of patient aortic annulus proves difficult. The prostheses' RF profiles bring new support in clinical decision-making for valve type and size in patients.

  6. What Is Heart Valve Disease?

    Science.gov (United States)

    ... is called a valve-in-valve procedure. Heart-Healthy Lifestyle Changes to Treat Other Related Heart Conditions To ... your doctor may advise you to make heart-healthy lifestyle changes, such as: Heart-healthy eating Aiming for ...

  7. Pneumococcal pulmonary valve endocarditis

    Directory of Open Access Journals (Sweden)

    Apostolos Vrettos

    2017-07-01

    Full Text Available Pulmonary valve endocarditis is a rare type of infective endocarditis (IE. Streptococcus pneumoniae is a pathogen that is uncommonly associated with IE. A 50 year-old male was referred to us after an incidental echocardiographic finding of a pulmonary valve vegetation. The patient had a recent admission for drainage of a scrotal abscess from which S. pneumoniae was isolated, complicated by hospital acquired pneumonia and pulmonary embolism. Analysis using polymerase chain reaction of the surgically resected mass revealed signs of 16S ribosomal DNA consistent with S. pneumoniae infection. This was an extremely rare case of pneumococcal pulmonary valve IE presenting entirely asymptomatically in the absence of any known risk factors.

  8. Variable Valve Actuation

    Energy Technology Data Exchange (ETDEWEB)

    Jeffrey Gutterman; A. J. Lasley

    2008-08-31

    Many approaches exist to enable advanced mode, low temperature combustion systems for diesel engines - such as premixed charge compression ignition (PCCI), Homogeneous Charge Compression Ignition (HCCI) or other HCCI-like combustion modes. The fuel properties and the quantity, distribution and temperature profile of air, fuel and residual fraction in the cylinder can have a marked effect on the heat release rate and combustion phasing. Figure 1 shows that a systems approach is required for HCCI-like combustion. While the exact requirements remain unclear (and will vary depending on fuel, engine size and application), some form of substantially variable valve actuation is a likely element in such a system. Variable valve actuation, for both intake and exhaust valve events, is a potent tool for controlling the parameters that are critical to HCCI-like combustion and expanding its operational range. Additionally, VVA can be used to optimize the combustion process as well as exhaust temperatures and impact the after treatment system requirements and its associated cost. Delphi Corporation has major manufacturing and product development and applied R&D expertise in the valve train area. Historical R&D experience includes the development of fully variable electro-hydraulic valve train on research engines as well as several generations of mechanical VVA for gasoline systems. This experience has enabled us to evaluate various implementations and determine the strengths and weaknesses of each. While a fully variable electro-hydraulic valve train system might be the 'ideal' solution technically for maximum flexibility in the timing and control of the valve events, its complexity, associated costs, and high power consumption make its implementation on low cost high volume applications unlikely. Conversely, a simple mechanical system might be a low cost solution but not deliver the flexibility required for HCCI operation. After modeling more than 200 variations of

  9. High-order study of the quantum critical behavior of a frustrated spin-1/2 antiferromagnet on a stacked honeycomb bilayer

    Science.gov (United States)

    Bishop, R. F.; Li, P. H. Y.

    2017-12-01

    We study a frustrated spin-1/2 J1-J2-J3-J1⊥ Heisenberg antiferromagnet on an A A -stacked bilayer honeycomb lattice. In each layer we consider nearest-neighbor (NN), next-nearest-neighbor, and next-next-nearest-neighbor antiferromagnetic (AFM) exchange couplings J1,J2 , and J3, respectively. The two layers are coupled with an AFM NN exchange coupling J1⊥≡δ J1 . The model is studied for arbitrary values of δ along the line J3=J2≡α J1 that includes the most highly frustrated point at α =1/2 , where the classical ground state is macroscopically degenerate. The coupled cluster method is used at high orders of approximation to calculate the magnetic order parameter and the triplet spin gap. We are thereby able to give an accurate description of the quantum phase diagram of the model in the α δ plane in the window 0 ≤α ≤1 ,0 ≤δ ≤1 . This includes two AFM phases with Néel and striped order, and an intermediate gapped paramagnetic phase that exhibits various forms of valence-bond crystalline order. We obtain accurate estimations of the two phase boundaries, δ =δci(α) , or equivalently, α =αc i(δ ) , with i =1 (Néel) and 2 (striped). The two boundaries exhibit an "avoided crossing" behavior with both curves being re-entrant. Thus, in this α δ window, Néel order exists only for values of δ in the range δc1 (α ) , with δc1 0 for αc 1(0 ) ≈0.49 (1 ) , and striped order similarly exists only for values of δ in the range δc2 (α ) , with δc2 αc2(0) ≈0.600 (5 ) and δc2 0 for αc 2(0 ) >α >α2<≈0.56 (1 ) .

  10. Mitigating check valve slamming and subsequentwater hammer events for PPFS using MOC

    International Nuclear Information System (INIS)

    Tian Wenxi; Su Guanghui; Wang Gaopeng; Qiu Suizheng; Xiao Zejun

    2009-01-01

    The method of characteristic (MOC) was adopted to analyze the check valve-induced water hammer behaviors for a Parallel Pumps Feedwater System (PPFS) during the alternate startup process. The motion of check valve disc was simulated using inertial valve model. Transient parameters including the pressure oscillation, local flow velocity and slamming of the check valve disc etc. have been obtained. The results showed that severe slamming between the valve disc and valve seat occurred during the alternate startup of parallel pumps. The induced maximum pressure vibration amplitude is up to 5.0 MPa. The scheme of appending a damping torque to slow down the check valve closing speed was also performed to mitigate of water hammer. It has been numerically approved to be an effective approach. (authors)

  11. Designing magnetic droplet soliton nucleation employing spin polarizer

    Science.gov (United States)

    Mohseni, Morteza; Mohseni, Majid

    2018-04-01

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

  12. Electrical spin injection into high mobility 2D systems.

    Science.gov (United States)

    Oltscher, M; Ciorga, M; Utz, M; Schuh, D; Bougeard, D; Weiss, D

    2014-12-05

    We report on spin injection into a high mobility 2D electron system confined at an (Al,Ga)As/GaAs interface, using (Ga,Mn)As Esaki diode contacts as spin aligners. We measured a clear nonlocal spin valve signal, which varies nonmonotonically with the applied bias voltage. The magnitude of the signal cannot be described by the standard spin drift-diffusion model, because at maximum this would require the spin polarization of the injected current to be much larger than 100%, which is unphysical. A strong correlation of the spin signal with contact width and electron mean free path suggests that ballistic transport in the 2D region below ferromagnetic contacts should be taken into account to fully describe the results.

  13. Robust and Selective Switching of an FeIII Spin-Crossover Compound on Cu2N/Cu(100) with Memristance Behavior.

    Science.gov (United States)

    Jasper-Toennies, Torben; Gruber, Manuel; Karan, Sujoy; Jacob, Hanne; Tuczek, Felix; Berndt, Richard

    2017-11-08

    The switching between two spin states makes spin-crossover molecules on surfaces very attractive for potential applications in molecular spintronics. Using scanning tunneling microscopy, the successful deposition of [Fe(pap) 2 ] + (pap = N-2-pyridylmethylidene-2-hydroxyphenylaminato) molecules on Cu 2 N/Cu(100) surface is evidenced. The deposited Fe III spin-crossover compound is controllably switched between three different states, each of them exhibiting a characteristic tunneling conductance. The conductance is therefore employed to readily read the state of the molecules. A comparison of the experimental data with the results of density functional theory calculations reveals that all Fe(pap) 2 molecules are initially in their high-spin state. The two other states are compatible with the low-spin state of the molecule but differ with respect to their coupling to the substrate. As a proof of concept, the reversible and selective nature of the switching is used to build a two-molecule memory.

  14. Biomechanical properties of native and tissue engineered heart valve constructs.

    Science.gov (United States)

    Hasan, Anwarul; Ragaert, Kim; Swieszkowski, Wojciech; Selimović, Seila; Paul, Arghya; Camci-Unal, Gulden; Mofrad, Mohammad R K; Khademhosseini, Ali

    2014-06-27

    Due to the increasing number of heart valve diseases, there is an urgent clinical need for off-the-shelf tissue engineered heart valves. While significant progress has been made toward improving the design and performance of both mechanical and tissue engineered heart valves (TEHVs), a human implantable, functional, and viable TEHV has remained elusive. In animal studies so far, the implanted TEHVs have failed to survive more than a few months after transplantation due to insufficient mechanical properties. Therefore, the success of future heart valve tissue engineering approaches depends on the ability of the TEHV to mimic and maintain the functional and mechanical properties of the native heart valves. However, aside from some tensile quasistatic data and flexural or bending properties, detailed mechanical properties such as dynamic fatigue, creep behavior, and viscoelastic properties of heart valves are still poorly understood. The need for better understanding and more detailed characterization of mechanical properties of tissue engineered, as well as native heart valve constructs is thus evident. In the current review we aim to present an overview of the current understanding of the mechanical properties of human and common animal model heart valves. The relevant data on both native and tissue engineered heart valve constructs have been compiled and analyzed to help in defining the target ranges for mechanical properties of TEHV constructs, particularly for the aortic and the pulmonary valves. We conclude with a summary of perspectives on the future work on better understanding of the mechanical properties of TEHV constructs. © 2013 Published by Elsevier Ltd.

  15. Interference Spins

    DEFF Research Database (Denmark)

    Popovski, Petar; Simeone, Osvaldo; Nielsen, Jimmy Jessen

    2015-01-01

    on traffic load and interference condition leads to performance gains. In this letter, a general network of multiple interfering two-way links is studied under the assumption of a balanced load in the two directions for each link. Using the notion of interference spin, we introduce an algebraic framework...

  16. Spinning worlds

    NARCIS (Netherlands)

    Schwarz, H.

    2017-01-01

    The thesis "Spinning Worlds" is about the characterisation of two types of gas-giant exoplanets: Hot Jupiters, with orbital periods of fewer than five days, and young, wide-orbit gas giants, with orbital periods as long as thousands of years. The thesis is based on near-infrared observations of 1

  17. Cavitation problems in sodium valves

    International Nuclear Information System (INIS)

    Elie, X.

    1976-01-01

    Cavitation poses few problems for sodium valves, in spite of the fact that the loops are not pressurized. This is no doubt due to the low flow velocities in the pipes. For auxiliary loop valves we are attempting to standardize performances with respect to cavitation. For economic reasons cavitation thresholds are approached with large diameter valves. (author)

  18. Optothermally actuated capillary burst valve

    DEFF Research Database (Denmark)

    Eriksen, Johan; Bilenberg, Brian; Kristensen, Anders

    2017-01-01

    We demonstrate the optothermal actuation of individual capillary burst valves in an all-polymer microfluidic device. The capillary burst valves are realised in a planar design by introducing a fluidic constriction in a microfluidic channel of constant depth. We show that a capillary burst valve can...

  19. Telocytes in human heart valves.

    Science.gov (United States)

    Yang, Yang; Sun, Wei; Wu, Sean M; Xiao, Junjie; Kong, Xiangqing

    2014-05-01

    Valve interstitial cells (VICs) are responsible for maintaining the structural integrity and dynamic behaviour of the valve. Telocytes (TCs), a peculiar type of interstitial cells, have been recently identified by Popescu's group in epicardium, myocardium and endocardium (visit www.telocytes.com). The presence of TCs has been identified in atria, ventricles and many other tissues and organ, but not yet in heart valves. We used transmission electron microscopy and immunofluorescence methods (double labelling for CD34 and c-kit, or vimentin, or PDGF Receptor-β) to provide evidence for the existence of TCs in human heart valves, including mitral valve, tricuspid valve and aortic valve. TCs are found in both apex and base of heart valves, with a similar density of 27-28 cells/mm(2) in mitral valve, tricuspid valve and aortic valve. Since TCs are known for the participation in regeneration or repair biological processes, it remains to be determined how TCs contributes to the valve attempts to re-establish normal structure and function following injury, especially a complex junction was found between TCs and a putative stem (progenitor) cell. © 2014 The Authors. Journal of Cellular and Molecular Medicine published by John Wiley & Sons Ltd and Foundation for Cellular and Molecular Medicine.

  20. Building valve amplifiers

    CERN Document Server

    Jones, Morgan

    2013-01-01

    Building Valve Amplifiers is a unique hands-on guide for anyone working with tube audio equipment--as an electronics hobbyist, audiophile or audio engineer. This 2nd Edition builds on the success of the first with technology and technique revisions throughout and, significantly, a major new self-build project, worked through step-by-step, which puts into practice the principles and techniques introduced throughout the book. Particular attention has been paid to answering questions commonly asked by newcomers to the world of the valve, whether audio enthusiasts tackling their first build or

  1. Tricuspid valve and percutaneous approach: No longer the forgotten valve!

    Science.gov (United States)

    Bouleti, Claire; Juliard, Jean-Michel; Himbert, Dominique; Iung, Bernard; Brochet, Eric; Urena, Marina; Dilly, Marie-Pierre; Ou, Phalla; Nataf, Patrick; Vahanian, Alec

    2016-01-01

    Tricuspid valve disease is mainly represented by tricuspid regurgitation (TR), which is a predictor of poor outcome. TR is usually secondary, caused by right ventricle pressure or volume overload, the leading cause being left-sided heart valve diseases. Tricuspid surgery for severe TR is recommended during left valve surgery, and consists of either a valve replacement or, most often, a tricuspid repair with or without prosthetic annuloplasty. When TR persists or worsens after left valvular surgery, redo isolated tricuspid surgery is associated with high mortality. In addition, a sizeable proportion of patients present with tricuspid surgery deterioration over time, and need a reintervention, which is associated with high morbi-mortality rates. In this context, and given the recent major breakthrough in the percutaneous treatment of aortic and mitral valve diseases, the tricuspid valve appears an appealing challenge, although it raises specific issues. The first applications of transcatheter techniques for tricuspid valve disease were valve-in-valve and valve-in-ring implantation for degenerated bioprosthesis or ring annuloplasty. Some concerns remain regarding prosthesis sizing, rapid ventricular pacing and the best approach, but these procedures appear to be safe and effective. More recently, bicuspidization using a transcatheter approach for the treatment of native tricuspid valve has been published, in two patients. Finally, other devices are in preclinical development. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

  2. Nuclear Spin Lattice Relaxation and Conductivity Studies of the Non-Arrhenius Conductivity Behavior in Lithium Fast Ion Conducting Sulfide Glasses

    Energy Technology Data Exchange (ETDEWEB)

    Meyer, Benjamin Michael [Iowa State Univ., Ames, IA (United States)

    2003-01-01

    As time progresses, the world is using up more of the planet's natural resources. Without technological advances, the day will eventually arrive when these natural resources will no longer be sufficient to supply all of the energy needs. As a result, society is seeing a push for the development of alternative fuel sources such as wind power, solar power, fuel cells, and etc. These pursuits are even occurring in the state of Iowa with increasing social pressure to incorporate larger percentages of ethanol in gasoline. Consumers are increasingly demanding that energy sources be more powerful, more durable, and, ultimately, more cost efficient. Fast Ionic Conducting (FIC) glasses are a material that offers great potential for the development of new batteries and/or fuel cells to help inspire the energy density of battery power supplies. This dissertation probes the mechanisms by which ions conduct in these glasses. A variety of different experimental techniques give a better understanding of the interesting materials science taking place within these systems. This dissertation discusses Nuclear Magnetic Resonance (NMR) techniques performed on FIC glasses over the past few years. These NMR results have been complimented with other measurement techniques, primarily impedance spectroscopy, to develop models that describe the mechanisms by which ionic conduction takes place and the dependence of the ion dynamics on the local structure of the glass. The aim of these measurements was to probe the cause of a non-Arrhenius behavior of the conductivity which has been seen at high temperatures in the silver thio-borosilicate glasses. One aspect that will be addressed is if this behavior is unique to silver containing fast ion conducting glasses. more specifically, this study will determine if a non-Arrhenius correlation time, τ, can be observed in the Nuclear Spin Lattice Relaxation (NSLR) measurements. If so, then can this behavior be modeled with a new single

  3. Effect of resistance feedback on spin torque-induced switching of nanomagnets

    International Nuclear Information System (INIS)

    Garzon, Samir; Webb, Richard A.; Covington, Mark; Kaka, Shehzaad; Crawford, Thomas M.

    2009-01-01

    In large magnetoresistance devices spin torque-induced changes in resistance can produce GHz current and voltage oscillations which can affect magnetization reversal. In addition, capacitive shunting in large resistance devices can further reduce the current, adversely affecting spin torque switching. Here, we simultaneously solve the Landau-Lifshitz-Gilbert equation with spin torque and the transmission line telegrapher's equations to study the effects of resistance feedback and capacitance on magnetization reversal of both spin valves and magnetic tunnel junctions. While for spin valves parallel (P) to anti-parallel (AP) switching is adversely affected by the resistance feedback due to saturation of the spin torque, in low resistance magnetic tunnel junctions P-AP switching is enhanced. We study the effect of resistance feedback on the switching time of magnetic tunnel junctions, and show that magnetization switching is only affected by capacitive shunting in the pF range.

  4. EMT-inducing biomaterials for heart valve engineering: taking cues from developmental biology

    Science.gov (United States)

    Sewell-Loftin, M.K.; Chun, Young Wook; Khademhosseini, Ali; Merryman, W. David

    2012-01-01

    Although artificial prostheses for diseased heart valves have been around for several decades, viable heart valve replacements have yet to be developed due to their complicated nature. The majority of research in heart valve replacement technology seeks to improve decellularization techniques for porcine valves or bovine pericardium as an effort to improve current clinically used valves. The drawback of clinically used valves is that they are nonviable and thus do not grow or remodel once implanted inside patients. This is particularly detrimental for pediatric patients, who will likely need several reoperations over the course of their lifetimes to implant larger valves as the patient grows. Due to this limitation, additional biomaterials, both synthetic and natural in origin, are also being investigated as novel scaffolds for tissue engineered heart valves, specifically for the pediatric population. Here, we provide a brief overview of valves in clinical use as well as of the materials being investigated as novel tissue engineered heart valve scaffolds. Additionally, we focus on natural-based biomaterials for promoting cell behavior that is indicative of the developmental biology process that occurs in the formation of heart valves in utero, such as epithelial-to-mesenchymal transition or transformation (EMT). By engineering materials that promote native developmental biology cues and signaling, while also providing mechanical integrity once implanted, a viable tissue engineered heart valve may one day be realized. A viable tissue engineered heart valve, capable of growing and remodeling actively inside a patient, could reduce risks and complications associated with current valve replacement options and improve overall quality of life in the thousands of patients who received such valves each year, particularly for children. PMID:21751069

  5. EMT-inducing biomaterials for heart valve engineering: taking cues from developmental biology.

    Science.gov (United States)

    Sewell-Loftin, M K; Chun, Young Wook; Khademhosseini, Ali; Merryman, W David

    2011-10-01

    Although artificial prostheses for diseased heart valves have been around for several decades, viable heart valve replacements have yet to be developed due to their complicated nature. The majority of research in heart valve replacement technology seeks to improve decellularization techniques for porcine valves or bovine pericardium as an effort to improve current clinically used valves. The drawback of clinically used valves is that they are nonviable and thus do not grow or remodel once implanted inside patients. This is particularly detrimental for pediatric patients, who will likely need several reoperations over the course of their lifetimes to implant larger valves as the patient grows. Due to this limitation, additional biomaterials, both synthetic and natural in origin, are also being investigated as novel scaffolds for tissue-engineered heart valves, specifically for the pediatric population. Here, we provide a brief overview of valves in clinical use as well as of the materials being investigated as novel tissue-engineered heart valve scaffolds. Additionally, we focus on natural-based biomaterials for promoting cell behavior that is indicative of the developmental biology process that occurs in the formation of heart valves in utero, such as epithelial-to-mesenchymal transition or transformation. By engineering materials that promote native developmental biology cues and signaling, while also providing mechanical integrity once implanted, a viable tissue-engineered heart valve may one day be realized. A viable tissue-engineered heart valve, capable of growing and remodeling actively inside a patient, could reduce risks and complications associated with current valve replacement options and improve overall quality of life in the thousands of patients who received such valves each year, particularly for children.

  6. Direct observation of the spin-dependent Peltier effect.

    Science.gov (United States)

    Flipse, J; Bakker, F L; Slachter, A; Dejene, F K; van Wees, B J

    2012-02-05

    The Peltier coefficient describes the amount of heat that is carried by an electrical current when it passes through a material. When two materials with different Peltier coefficients are placed in contact with one another, the Peltier effect causes a net flow of heat either towards or away from the interface between them. Spintronics describes the transport of electric charge and spin angular momentum by separate spin-up and spin-down channels in a device. The observation that spin-up and spin-down charge transport channels are able to transport heat independently of each other has raised the possibility that spin currents could be used to heat or cool the interface between materials with different spin-dependent Peltier coefficients. Here, we report the direct observation of the heating and cooling of such an interface by a spin current. We demonstrate this spin-dependent Peltier effect in a spin-valve pillar structure that consists of two ferromagnetic layers separated by a non-ferromagnetic metal. Using a three-dimensional finite-element model, we extract spin-dependent Peltier coefficients in the range -0.9 to -1.3 mV for permalloy. The magnetic control of heat flow could prove useful for the cooling of nanoscale electronic components or devices.

  7. Spin transport in fully hexagonal boron nitride encapsulated graphene

    NARCIS (Netherlands)

    Gurram, M.; Omar, S.; Zihlmann, S.; Makk, P.; Schoenenberger, C.; van Wees, B. J.

    2016-01-01

    We study fully hexagonal boron nitride (hBN) encapsulated graphene spin valve devices at room temperature. The device consists of a graphene channel encapsulated between two crystalline hBN flakes: thick-hBN flake as a bottom gate dielectric substrate which masks the charge impurities from SiO2/Si

  8. Mitral Valve Prolapse

    Science.gov (United States)

    ... Body Mind Sexual Health Food & Fitness Diseases & Conditions Infections Drugs & Alcohol School & Jobs Sports Expert Answers (Q&A) Staying Safe Videos for Educators Search English Español Mitral Valve ... You Play? Print en español Prolapso de ...

  9. Thermostatic Radiator Valve Evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Dentz, Jordan [Advanced Residential Integrated Energy Solutions Collaborative, New York, NY (United States); Ansanelli, Eric [Advanced Residential Integrated Energy Solutions Collaborative, New York, NY (United States)

    2015-01-01

    A large stock of multifamily buildings in the Northeast and Midwest are heated by steam distribution systems. Losses from these systems are typically high and a significant number of apartments are overheated much of the time. Thermostatically controlled radiator valves (TRVs) are one potential strategy to combat this problem, but have not been widely accepted by the residential retrofit market.

  10. Bicuspid aortic valve

    Science.gov (United States)

    ... females. A BAV often exists in babies with coarctation of the aorta (narrowing of the aorta). BAV is also seen ... to view the blood vessels of the heart Treatment ... to the heart and into the narrow opening of the aortic valve. A balloon attached to the end of ...

  11. SAFETY SHUTOFF VALVE

    DEFF Research Database (Denmark)

    2010-01-01

    It is disclosed a shut-off valve which acts automatically and has a fully mechanical performance with respect to the loosing of the tower-shape part balance under the effect of the special acceleration Which is arisen from the quakes waves or serious vibrations, while such vibrations are mainly r...

  12. Nonequilibrium Spin Dynamics in a Trapped Fermi Gas with Effective Spin-Orbit Interactions

    International Nuclear Information System (INIS)

    Stanescu, Tudor D.; Zhang Chuanwei; Galitski, Victor

    2007-01-01

    We consider a trapped atomic system in the presence of spatially varying laser fields. The laser-atom interaction generates a pseudospin degree of freedom (referred to simply as spin) and leads to an effective spin-orbit coupling for the fermions in the trap. Reflections of the fermions from the trap boundaries provide a physical mechanism for effective momentum relaxation and nontrivial spin dynamics due to the emergent spin-orbit coupling. We explicitly consider evolution of an initially spin-polarized Fermi gas in a two-dimensional harmonic trap and derive nonequilibrium behavior of the spin polarization. It shows periodic echoes with a frequency equal to the harmonic trapping frequency. Perturbations, such as an asymmetry of the trap, lead to the suppression of the spin echo amplitudes. We discuss a possible experimental setup to observe spin dynamics and provide numerical estimates of relevant parameters

  13. Spin transport in lateral structures with semiconducting channel

    Science.gov (United States)

    Zainuddin, Abu Naser

    Spintronics is an emerging field of electronics with the potential to be used in future integrated circuits. Spintronic devices are already making their mark in storage technologies in recent times and there are proposals for using spintronic effects in logic technologies as well. So far, major improvement in spintronic effects, for example, the `spin-valve' effect, is being achieved in metals or insulators as channel materials. But not much progress is made in semiconductors owing to the difficulty in injecting spins into them, which has only very recently been overcome with the combined efforts of many research groups around the world. The key motivations for semiconductor spintronics are their ease in integration with the existing semiconductor technology along with the gate controllability. At present semiconductor based spintronic devices are mostly lateral and are showing a very poor performance compared to their metal or insulator based vertical counterparts. The objective of this thesis is to analyze these devices based on spin-transport models and simulations. At first a lateral spin-valve device is modeled with the spin-diffusion equation based semiclassical approach. Identifying the important issues regarding the device performance, a compact circuit equivalent model is presented which would help to improve the device design. It is found that the regions outside the current path also have a significant influence on the device performance under certain conditions, which is ordinarily neglected when only charge transport is considered. Next, a modified spin-valve structure is studied where the spin signal is controlled with a gate in between the injecting and detecting contacts. The gate is used to modulate the rashba spin-orbit coupling of the channel which, in turn, modulates the spin-valve signal. The idea of gate controlled spin manipulation was originally proposed by Datta and Das back in 1990 and is called 'Datta-Das' effect. In this thesis, we have

  14. Measurement of reed valve kinematics

    Directory of Open Access Journals (Sweden)

    Fenkl Michael

    2016-01-01

    Full Text Available The measurement of key kinematic parameters of a reed valve movement is necessary for the further development of the reed valve system. These parameters are dependent on the geometry and material properties of the valve. As they directly affect the quantity of air flowing around the valve, a simple and easy to implement measurement of various valve configuration based on the air flow has been devised and is described in this paper, along with its technical parameters and drawbacks when evaluating reed valves used in reciprocating air compressors. Results are presented for a specimen of a compressor under examination. All kinematic parameters, and timing of the opening and closing of the valve, obtained from the measurement are presented and discussed.

  15. Structural and photodegradation behaviors of Fe{sup 3+}-doping TiO{sub 2} thin films prepared by a sol–gel spin coating

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Huey-Jiuan; Yang, Tien-Syh [Department of Materials Science and Engineering, National United University, 1 Lien-Da, Kung-Ching Li, Miao-Li 36003, Taiwan (China); Wang, Moo-Chin, E-mail: mcwang@kmu.edu.tw [Department of Fragrance and Cosmetic Science, Kaohsiung Medical University, 100 Shih-Chuan 1st Road, Kaohsiung 80782, Taiwan (China); Hsi, Chi-Shiung, E-mail: chsi@nuu.edu.tw [Department of Materials Science and Engineering, National United University, 1 Lien-Da, Kung-Ching Li, Miao-Li 36003, Taiwan (China)

    2014-10-15

    Highlights: • Pure and various Fe{sup 3+}-doped TiO{sub 2} thin films have been successfully fabricated. • The phase of all thin films was single phase of anatase TiO{sub 2} when calcined at 823 K. • The crystallinity of TiO{sub 2} thin films decreased as Fe{sup 3+}-doping increased. • The photodegradation of each sample increased as the irradiation time increased. • The photodegradation increased as Fe{sup 3+}-doping increased at a fixed irradiation time. - Abstract: Pure and various Fe{sup 3+}-doping TiO{sub 2} thin films have been successfully fabricated on glass substrate prepared by a sol–gel spin coating route. The structural and photodegradation behavior of these films after calcined at various temperatures for 1 h were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) spectrum and degradation of 1.0 × 10{sup −5} M methylene blue solution. When all thin films after calcined at 823 K for 1 h, the crystalline phase are comprised only contained single phase of anatase TiO{sub 2}. The crystallinity of various Fe{sup 3+}-doping TiO{sub 2} thin films decreases with Fe{sup 3+}-doping concentration increased. The PL intensity of all thin films also decreases with Fe{sup 3+}-doping concentration increased. When all various Fe{sup 3+}-doping TiO{sub 2} thin films after calcined at 823 K for 1 h, the photodegradation of each sample increases with irradiation time increased. Moreover, the photodegradation also increases with Fe{sup 3+}-doping concentration increased when fixed at constant irradiation time.

  16. Heat-driven spin torques in antiferromagnets

    Science.gov (United States)

    Białek, Marcin; Bréchet, Sylvain; Ansermet, Jean-Philippe

    2018-04-01

    Heat-driven magnetization damping, which is a linear function of a temperature gradient, is predicted in antiferromagnets by considering the sublattice dynamics subjected to a heat-driven spin torque. This points to the possibility of achieving spin torque oscillator behavior. The model is based on the magnetic Seebeck effect acting on sublattices which are exchange coupled. The heat-driven spin torque is estimated and the feasibility of detecting this effect is discussed.

  17. Tricuspid valve endocarditis.

    Science.gov (United States)

    Hussain, Syed T; Witten, James; Shrestha, Nabin K; Blackstone, Eugene H; Pettersson, Gösta B

    2017-05-01

    Right-sided infective endocarditis (RSIE) is less common than left-sided infective endocarditis (IE), encompassing only 5-10% of cases of IE. Ninety percent of RSIE involves the tricuspid valve (TV). Given the relatively small numbers of TVIE cases operated on at most institutions, the purpose of this review is to highlight and discuss the current understanding of IE involving the TV. RSIE and TVIE are strongly associated with intravenous drug use (IVDU), although pacemaker leads, defibrillator leads and vascular access for dialysis are also major risk factors. Staphylococcus aureus is the predominant causative organism in TVIE. Most patients with TVIE are successfully treated with antibiotics, however, 5-16% of RSIE cases eventually require surgical intervention. Indications and timing for surgery are less clear than for left-sided IE; surgery is primarily considered for failed medical therapy, large vegetations and septic pulmonary embolism, and less often for TV regurgitation and heart failure. Most patients with an infected prosthetic TV will require surgery. Concomitant left-sided IE has its own surgical indications. Earlier surgical intervention may potentially prevent further destruction of leaflet tissue and increase the likelihood of TV repair. Fortunately, TV debridement and repair can be accomplished in most cases, even those with extensive valve destruction, using a variety of techniques. Valve repair is advocated over replacement, particularly in IVDUs patients who are young, non-compliant and have a higher risk of recurrent infection and reoperation with valve replacement. Excising the valve without replacing, it is not advocated; it has been reported previously, but these patients are likely to be symptomatic, particularly in cases with septic pulmonary embolism and increased pulmonary vascular resistance. Patients with concomitant left-sided involvement have worse prognosis than those with RSIE alone, due predominantly to greater likelihood of

  18. In a spin at Brookhaven spin physics

    CERN Document Server

    Makdisi, Y I

    2003-01-01

    The mysterious quantity that is spin took centre stage at Brookhaven for the SPIN2002 meeting last September. The 15th biennial International Spin Physics Symposium (SPIN2002) was held at Brookhaven National Laboratory on 9-14 September 2002. Some 250 spin enthusiasts attended, including experimenters and theorists in both nuclear and high-energy physics, as well as accelerator physicists and polarized target and polarized source experts. The six-day symposium included 23 plenary talks and 150 parallel talks. SPIN2002 was preceded by a one-day spin physics tutorial for students, postdocs, and anyone else who felt the need for a refresher course. (2 refs).

  19. Spin-Circuit Representation of Spin Pumping

    Science.gov (United States)

    Roy, Kuntal

    2017-07-01

    Circuit theory has been tremendously successful in translating physical equations into circuit elements in an organized form for further analysis and proposing creative designs for applications. With the advent of new materials and phenomena in the field of spintronics and nanomagnetics, it is imperative to construct the spin-circuit representations for different materials and phenomena. Spin pumping is a phenomenon by which a pure spin current can be injected into the adjacent layers. If the adjacent layer is a material with a high spin-orbit coupling, a considerable amount of charge voltage can be generated via the inverse spin Hall effect allowing spin detection. Here we develop the spin-circuit representation of spin pumping. We then combine it with the spin-circuit representation for the materials having spin Hall effect to show that it reproduces the standard results as in the literature. We further show how complex multilayers can be analyzed by simply writing a netlist.

  20. Spin Coherence in Semiconductor Nanostructures

    National Research Council Canada - National Science Library

    Flatte, Michael E

    2006-01-01

    ... dots, tuning of spin coherence times for electron spin, tuning of dipolar magnetic fields for nuclear spin, spontaneous spin polarization generation and new designs for spin-based teleportation and spin transistors...

  1. Electronic spin transport and spin precession in single graphene layers at room temperature.

    Science.gov (United States)

    Tombros, Nikolaos; Jozsa, Csaba; Popinciuc, Mihaita; Jonkman, Harry T; van Wees, Bart J

    2007-08-02

    Electronic transport in single or a few layers of graphene is the subject of intense interest at present. The specific band structure of graphene, with its unique valley structure and Dirac neutrality point separating hole states from electron states, has led to the observation of new electronic transport phenomena such as anomalously quantized Hall effects, absence of weak localization and the existence of a minimum conductivity. In addition to dissipative transport, supercurrent transport has also been observed. Graphene might also be a promising material for spintronics and related applications, such as the realization of spin qubits, owing to the low intrinsic spin orbit interaction, as well as the low hyperfine interaction of the electron spins with the carbon nuclei. Here we report the observation of spin transport, as well as Larmor spin precession, over micrometre-scale distances in single graphene layers. The 'non-local' spin valve geometry was used in these experiments, employing four-terminal contact geometries with ferromagnetic cobalt electrodes making contact with the graphene sheet through a thin oxide layer. We observe clear bipolar (changing from positive to negative sign) spin signals that reflect the magnetization direction of all four electrodes, indicating that spin coherence extends underneath all of the contacts. No significant changes in the spin signals occur between 4.2 K, 77 K and room temperature. We extract a spin relaxation length between 1.5 and 2 mum at room temperature, only weakly dependent on charge density. The spin polarization of the ferromagnetic contacts is calculated from the measurements to be around ten per cent.

  2. Anomalous Tunneling of Spin Wave in Polar State of Spin-1 BEC

    International Nuclear Information System (INIS)

    Watabe, Shohei; Ohashi, Yoji; Kato, Yusuke

    2012-01-01

    We investigate tunneling properties of collective spin-wave excitations in the polar state of a spin-1 spinor Bose-Einstein condensate. Within the mean-field theory at T = 0, we show that when the condensate is in the critical supercurrent state, the spin wave mode exhibits perfect transmission through a nonmagnetic potential barrier in the low energy limit, unless the strength of a spin-independent interaction c o equals that of a spin-dependent interaction c o Such an anomalous tunneling behavior is absent in the case of a magnetic barrier. We also clarify a scaling law of the transmission probability as a function of the mode energy.

  3. Anomalous Tunneling of Spin Wave in Polar State of Spin-1 BEC

    Science.gov (United States)

    Watabe, Shohei; Kato, Yusuke; Ohashi, Yoji

    2012-12-01

    We investigate tunneling properties of collective spin-wave excitations in the polar state of a spin-1 spinor Bose-Einstein condensate. Within the mean-field theory at T = 0, we show that when the condensate is in the critical supercurrent state, the spin wave mode exhibits perfect transmission through a nonmagnetic potential barrier in the low energy limit, unless the strength of a spin-independent interaction co equals that of a spin-dependent interaction co Such an anomalous tunneling behavior is absent in the case of a magnetic barrier. We also clarify a scaling law of the transmission probability as a function of the mode energy.

  4. Mechanical Valve Replacement: Early Results

    Directory of Open Access Journals (Sweden)

    Habib Cakir

    2012-02-01

    Full Text Available Aim: Valve diseases in developing countries like Turkey which often occur as a complication of rheumatic fever are a serious disease. Surgical treatment of valve diseases should be done before irreversible damage to the myocardium occurred. In this study, we aimed to present the early results of mechanical valve replacement operations. Method: A hundred patients with mechanical valve replacement surgery were retrospectively evaluated in Seyhan Application Center attached to our clinic between July 2007 and August 2011. Results: Fifty patients were male and 50 were women. The mean age of patients was 47.88 (18-78. Isolated aortic valve replacement (AVR was performed to 23 patients, isolated mitral valve replacement (MVR was 32, double valve replacement (AVR + MVR was 12, MVR + aortic valve valvuloplasty was 1, AVR + mitral kommissurotomi was 1, AVR + coronary artery bypass graft surgery (CABG was 17, MVR + CABG was 8, MVR + atrial septal defect closure was 2 and Bentall procedure.was 4 patients. In addition, ablation procedure was performed to 5 patients intraoperatively because of preoperative atrial fibrillation. Two patients (2 % died in early postoperative period. Conclusion: Mechanical prosthetic valves are used for surgical treatment of valve disease with low mortality and morbidity in a large group of patients like women that not to think to get pregnant, non advanced age group and patients have less risky for anticoagulation drug in our clinic. [Cukurova Med J 2012; 37(1.000: 49-54

  5. Cyclonic valve test: preliminary results

    Energy Technology Data Exchange (ETDEWEB)

    Monteiro, Andre Sampaio; Moraes, Carlos Alberto C.; Marins, Luiz Philipe M.; Soares, Fabricio; Oliveira, Dennis; Lima, Fabio Soares de; Airao, Vinicius [Petroleo Brasileiro S.A. (PETROBRAS), Rio de Janeiro, RJ (Brazil); Ton, Tijmen [Twister BV, Rijswijk (Netherlands)

    2012-07-01

    For many years, the petroleum industry has been developing a valve that input less shear to the flow for a given required pressure drop and this can be done using the cyclonic concept. This paper presents a comparison between the performances of a cyclonic valve (low shear) and a conventional globe valve. The aim of this work is to show the advantages of using a cyclonic low shear valve instead of the commonly used in the primary separation process by PETROBRAS. Tests were performed at PETROBRAS Experimental Center (NUEX) in Aracaju/SE varying some parameters: water cut; pressure loss (from 4 kgf/cm2 to 10 kgf/cm2); flow rates (30 m3/h and 45 m3/h). Results indicates a better performance of the cyclonic valve, if compared with a conventional one, and also that the difference of the performance, is a function of several parameters (emulsion stability, water content free, and oil properties). The cyclonic valve tested can be applied as a choke valve, as a valve between separation stages (for pressure drop), or for controlling the level of vessels. We must emphasize the importance to avoid the high shear imposed by conventional valves, because once the emulsion is created, it becomes more difficult to break it. New tests are being planned to occur in 2012, but PETROBRAS is also analyzing real cases where the applications could increase the primary process efficiency. In the same way, the future installations are also being designed considering the cyclonic valve usage. (author)

  6. Transcatheter aortic valve implantation in failed bioprosthetic surgical valves

    DEFF Research Database (Denmark)

    Dvir, Danny; Webb, John G; Bleiziffer, Sabine

    2014-01-01

    IMPORTANCE: Owing to a considerable shift toward bioprosthesis implantation rather than mechanical valves, it is expected that patients will increasingly present with degenerated bioprostheses in the next few years. Transcatheter aortic valve-in-valve implantation is a less invasive approach......, stroke, and New York Heart Association functional class. RESULTS: Modes of bioprosthesis failure were stenosis (n = 181 [39.4%]), regurgitation (n = 139 [30.3%]), and combined (n = 139 [30.3%]). The stenosis group had a higher percentage of small valves (37% vs 20.9% and 26.6% in the regurgitation...... and combined groups, respectively; P = .005). Within 1 month following valve-in-valve implantation, 35 (7.6%) patients died, 8 (1.7%) had major stroke, and 313 (92.6%) of surviving patients had good functional status (New York Heart Association class I/II). The overall 1-year Kaplan-Meier survival rate was 83...

  7. Electron Spins in Semiconductor Quantum Dots

    NARCIS (Netherlands)

    Hanson, R.

    2005-01-01

    This thesis describes a series of experiments aimed at understanding and controlling the behavior of the spin degree of freedom of single electrons, confined in semiconductor quantum dots. This research work is motivated by the prospects of using the electron spin as a quantum bit (qubit), the basic

  8. Tricuspid Valve Replacement, Mechnical vs. Biological Valve, Which Is Better?

    Directory of Open Access Journals (Sweden)

    Haitham Akram Altaani

    2013-06-01

    Full Text Available Background: The initial trial in tricuspid surgery is repair; however, replacement is done whenever the valve is badly diseased. Tricuspid valve replacement comprises 1.7% of all tricuspid valve surgeries. Materials and Methods: The present retrospective study was performed using the medical records of 21 cases who underwent tricuspid valve replacement from January 2002 until the end of December 2010. The mean age of the participants was 52.3±8.8 years and 66.7% were females. In addition, tricuspid valve replacement was associated with mitral valve surgery, aortic valve surgery, and both in 14.3%, 4.8%, and 33.3% of the cases, respectively. Yet, isolated tricuspid valve replacement and redo surgery were performed in 10 cases (47.6% and 8 cases (38.1%, respectively. Besides, trial of repair was done in 14 cases (66.7%. Moreover, biological and mechanical valves were used in 76.2% and 23.8% of the patients, respectively. Results: According to the results, early mortality was 23.8% and one year survival was 66.7%. Moreover, early mortality was caused by right ventricular failure, multiorgan failure, medistinitis, and intracerbral bleeding in 42%, 28.6%, 14.3%, and 14.3% of the cases, respectively. In addition, 57.1% of the deaths had occurred in the cases where the biological valve was used, while 42.9% of the deaths had taken place where the mechanical one was utilized. Conclusions: The patients who require tricuspid valve replacement are usually high risk surgical candidates with early and long term mortality. The findings of the current study showed no significant hemodynamic difference between mechanical and biological valves.

  9. Charge and spin transport in nanoscale junction from first principles

    Science.gov (United States)

    Mandal, Subhasish

    Recently nanoscale junctions consisting of 0-D nanostructures (single molecule) or 1-D nanostructures (semiconducting nanowire) sandwiched between two metal electrodes are successfully fabricated and characterized. What lacks in the recent developments is the understanding of the mechanism behind the observed phenomena at the level of atoms and electrons. For example, the origin of observed switching effect in a semiconducting nanowire due to the influence of an external gate bias is not yet understood at the electronic structure level. On the same context, different experimental groups have reported different signs in tunneling magneto-resistance for the same organic spin valve structure, which has baffled researchers working in this field. In this thesis, we present the answers to some of these subtle questions by investigating the charge and spin transport in different nanoscale junctions. A parameter-free, single particle Green's function approach in conjunction with a posteriori density functional theory (DFT) involving a hybrid orbital dependent functional is used to calculate the tunneling current in the coherent transport limit. The effect of spin polarization is explicitly incorporated to investigate spin transport in a nanoscale junction. Through the electron transport studies in PbS nanowire junction, a new orbital controlled mechanism behind the switching of the current is proposed. It can explain the switching behavior, not only in PbS nanowire, but in other lead-chalcogenide nanowires as well. Beside this, the electronic structure properties of this nanowire are studied using periodic DFT. The quantum confinement effect was investigated by calculating the bandgap of PbS nanowires with different diameters. Subsequently, we explain an observed semiconducting to metallic phase transition of this nanowire by calculating the bandgap of the nanowire under uniform radial strain. The compressive radial strain on the nanowire was found to be responsible for

  10. Patents and heart valve surgery--I: mechanical valves.

    Science.gov (United States)

    Cheema, Faisal H; Hussain, Nasir; Kossar, Alexander P; Polvani, Gianluca

    2013-04-01

    Valvular heart disease, inherited or acquired, affects more than 5 million Americans yearly. Whereas medical treatment is beneficial in the initial stages of valvular heart disease, surgical correction provides symptomatic relief and long-term survival benefits. Surgical options include either repair or replacement using mechanical or bio-prosthetic valves. Patient age and the post-operative need for anticoagulation therapy are major determinants of the choice between use of mechanical or bio-prosthetic valves. Since the first mechanical valves were made available several decades ago, the incorporation of increasingly sophisticated materials and methodologies has led to substantial improvements in the valve design, and has catalyzed a parallel increase in the amount of patents issued for these emerging technologies. In this paper, we have chronologically reviewed such patents, briefly discussed various challenges that mechanical heart valve implementation is faced with and finally reviewed some of the strategies employed to overcome such obstacles. An ideal prosthetic heart valve would comprehensively mimic the natural hemodynamics and physiology of the native heart valve. Additionally, such a valve would be easily implantable, associated with a minimal risk of thrombosis and thus need for anti-coagulation, and with a proven long-term durability. With cutting edge technological advancements in the recent times, the ongoing innovative and collaborative efforts of physicians, scientists, and engineers will not seize until an ideal mechanical heart valve becomes a reality.

  11. Induced spin polarization effect in graphene by ferromagnetic nanocontact

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-03-07

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

  12. Tunneling spin injection into single layer graphene.

    Science.gov (United States)

    Han, Wei; Pi, K; McCreary, K M; Li, Yan; Wong, Jared J I; Swartz, A G; Kawakami, R K

    2010-10-15

    We achieve tunneling spin injection from Co into single layer graphene (SLG) using TiO₂ seeded MgO barriers. A nonlocal magnetoresistance (ΔR(NL)) of 130  Ω is observed at room temperature, which is the largest value observed in any material. Investigating ΔR(NL) vs SLG conductivity from the transparent to the tunneling contact regimes demonstrates the contrasting behaviors predicted by the drift-diffusion theory of spin transport. Furthermore, tunnel barriers reduce the contact-induced spin relaxation and are therefore important for future investigations of spin relaxation in graphene.

  13. In vitro investigation of prosthetic heart valves in magnetic resonance imaging: evaluation of potential hazards.

    Science.gov (United States)

    Pruefer, D; Kalden, P; Schreiber, W; Dahm, M; Buerke, M; Thelen, M; Oelert, H

    2001-05-01

    Magnetic resonance (MR) imaging is used in an increasing number of patients, and not only after cardiac valve replacement. However, ferromagnetic biomedical implants are often considered a contraindication for MR imaging because of the potential hazards with respect to their movement, dislodgement, or heating effects during the procedure. The purpose of this study was to assess ferromagnetism, attraction forces, heating effects, and artifacts associated with prosthetic heart valve implants. Seventeen common heart valve prostheses (12 mechanical, five biological) were examined in vitro using a high-field-strength 1.5 Tesla (T) MR system. Attractive forces, temperature changes and the amount of artifacts were assessed by applying turbo-spin and gradient-echo sequences. The maximal calculated corresponding ferromagnetic force was (0.22 x 10(-3) N) in the static magnetic field. The temperature changes ranged from 0 to 0.5 degrees C maximum. Artifacts produced by the presence of the heart valve prostheses were less evident using a spin-echo sequence than a gradient-echo sequence. MR imaging exerted no significant force on the examined heart valve prostheses, and did not result in significant biological relevant temperature increase. None of the associated artifacts is considered to pose a substantial risk on MR imaging. MR procedures performed with a 1.5 T MR system can be applied safely in patients with heart valve prostheses evaluated in this study.

  14. Anterior Urethral Valves

    Directory of Open Access Journals (Sweden)

    Vidyadhar P. Mali

    2006-07-01

    Full Text Available We studied the clinical presentation and management of four patients with anterior urethral valves; a rare cause of urethral obstruction in male children. One patient presented antenatally with oligohydramnios, bilateral hydronephrosis and bladder thickening suggestive of an infravesical obstruction. Two other patients presented postnatally at 1 and 2 years of age, respectively, with poor stream of urine since birth. The fourth patient presented at 9 years with frequency and dysuria. Diagnosis was established on either micturating cystourethrogram (MCU (in 2 or on cystoscopy (in 2. All patients had cystoscopic ablation of the valves. One patient developed a postablation stricture that was resected with an end-to-end urethroplasty. He had an associated bilateral vesicoureteric junction (VUJ obstruction for which a bilateral ureteric reimplantation was done at the same time. On long-term follow-up, all patients demonstrated a good stream of urine. The renal function is normal. Patients are continent and free of urinary infections. Anterior urethral valves are rare obstructive lesions in male children. The degree of obstruction is variable, and so they may present with mild micturition difficulty or severe obstruction with hydroureteronephrosis and renal impairment. Hence, it is important to evaluate the anterior urethra in any male child with suspected infravesical obstruction. The diagnosis is established by MCU or cystoscopy and the treatment is always surgical, either a transurethral ablation or an open resection. The long-term prognosis is good.

  15. Posterior Urethral Valves

    Directory of Open Access Journals (Sweden)

    Steve J. Hodges

    2009-01-01

    Full Text Available The most common cause of lower urinary tract obstruction in male infants is posterior urethral valves. Although the incidence has remained stable, the neonatal mortality for this disorder has improved due to early diagnosis and intensive neonatal care, thanks in part to the widespread use of prenatal ultrasound evaluations. In fact, the most common reason for the diagnosis of posterior urethral valves presently is the evaluation of infants for prenatal hydronephrosis. Since these children are often diagnosed early, the urethral obstruction can be alleviated rapidly through catheter insertion and eventual surgery, and their metabolic derangements can be normalized without delay, avoiding preventable infant mortality. Of the children that survive, however, early diagnosis has not had much effect on their long-term prognosis, as 30% still develop renal insufficiency before adolescence. A better understanding of the exact cause of the congenital obstruction of the male posterior urethra, prevention of postnatal bladder and renal injury, and the development of safe methods to treat urethral obstruction prenatally (and thereby avoiding the bladder and renal damage due to obstructive uropathy are the goals for the care of children with posterior urethral valves[1].

  16. Automatic fire hydrant valve development

    International Nuclear Information System (INIS)

    Drumheller, K.

    1976-01-01

    The development of a remotely-controlled valve to operate a fire hydrant is described. Assembled from off-the-shelf components, the prototype illustrates that a valve light enough to be handled by one man is possible. However, it does not have the ruggedness or reliability needed for actual fire-fighting operations. Preliminary testing by City of Tacoma fire department personnel indicates that the valve may indeed contribute significantly to fire-fighting efficiency

  17. High-spin nuclear spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Diamond, R.M.

    1986-07-01

    High-spin spectroscopy is the study of the changes in nuclear structure, properties, and behavior with increasing angular momentum. It involves the complex interplay between collective and single-particle motion, between shape and deformation changes, particle alignments, and changes in the pairing correlations. A review of progress in theory, experimentation, and instrumentation in this field is given. (DWL)

  18. Mechanisms of function and disease of natural and replacement heart valves.

    Science.gov (United States)

    Schoen, Frederick J

    2012-01-01

    Over the past several decades, there has been substantial progress toward understanding the mechanisms of heart valve function and dysfunction. This review summarizes an evolving conceptual framework of heart valve functional structure, developmental biology, and pathobiology and explores the implications of key insights. I emphasize: (a) valve cell and extracellular matrix biology and the impact of biomechanical factors on function, homeostasis, environmental adaptation, and key pathological processes; (b) the role of developmental processes, valvular cell behavior, and extracellular matrix remodeling in congenital and acquired valve abnormalities; and (c) the cell/matrix biology of degeneration in replacement tissue valves. I also summarize how these considerations may ultimately inform the potential for prevention and treatment of major diseases and potentially therapeutic regeneration of the cardiac valves. Recent advances and opportunities for research and clinical translation are highlighted.

  19. Mitral Valve Prolapse in Pregnancy

    Directory of Open Access Journals (Sweden)

    Shi-Min Yuan

    Full Text Available Abstract Mitral valve prolapse is a benign condition. Mitral regurgitation is only complicated in patients with severe mitral valve prolapse. Women with mitral valve prolapse in the absence of other cardiovascular disorders tolerate pregnancy well and do not develop remarkable cardiac complications. Nevertheless, serious complications of mitral valve prolapse, including arrhythmia, infective endocarditis and cerebral ischemic events, can be present in pregnancy. Debates remain with regard to the use of prophylactic antibiotics and β-blockers in the pregnant women with mitral valve prolapse. The prognosis of the pregnant patients might be closely related to the pathological and (or functional changes of the mitral valve. Non-myxomatous mitral valve prolapse poses no or little obstetric risks in terms of pregnancy, labor and neonatal complications; whereas myxomatous mitral valve prolapse is a major etiology of valvular heart disease in women of childbearing age. In the pregnant patients with mitral valve prolapse progressing into major complications, surgical interventions are considered. Medicinal treatment of such patients with β-blockers should be a concern for the fetal safety.

  20. Latest design of gate valves

    Energy Technology Data Exchange (ETDEWEB)

    Kurzhofer, U.; Stolte, J.; Weyand, M.

    1996-12-01

    Babcock Sempell, one of the most important valve manufacturers in Europe, has delivered valves for the nuclear power industry since the beginning of the peaceful application of nuclear power in the 1960s. The latest innovation by Babcock Sempell is a gate valve that meets all recent technical requirements of the nuclear power technology. At the moment in the United States, Germany, Sweden, and many other countries, motor-operated gate and globe valves are judged very critically. Besides the absolute control of the so-called {open_quotes}trip failure,{close_quotes} the integrity of all valve parts submitted to operational forces must be maintained. In case of failure of the limit and torque switches, all valve designs have been tested with respect to the quality of guidance of the gate. The guidances (i.e., guides) shall avoid a tilting of the gate during the closing procedure. The gate valve newly designed by Babcock Sempell fulfills all these characteristic criteria. In addition, the valve has cobalt-free seat hardfacing, the suitability of which has been proven by friction tests as well as full-scale blowdown tests at the GAP of Siemens in Karlstein, West Germany. Babcock Sempell was to deliver more than 30 gate valves of this type for 5 Swedish nuclear power stations by autumn 1995. In the presentation, the author will report on the testing performed, qualifications, and sizing criteria which led to the new technical design.

  1. Ultrathin gate valve for high vacuum operation

    Science.gov (United States)

    Ugiansky, R. J.

    1971-01-01

    Thin, compact, high-vacuum gate valve used to join two vacuum systems together demonstrates multiple operation reliability. Valve measurements and non-protruding handle make valve usable in confined areas.

  2. 49 CFR 192.145 - Valves.

    Science.gov (United States)

    2010-10-01

    ... BY PIPELINE: MINIMUM FEDERAL SAFETY STANDARDS Design of Pipeline Components § 192.145 Valves. (a) Except for cast iron and plastic valves, each valve must meet the minimum requirements of API 6D...

  3. Heat and spin interconversion

    International Nuclear Information System (INIS)

    Ohnuma, Yuichi; Matsuo, Mamoru; Maekawa, Sadamichi; Saitoh, Eeiji

    2017-01-01

    Spin Seebeck and spin Peltier effects, which are mutual conversion phenomena of heat and spin, are discussed on the basis of the microscopic theory. First, the spin Seebeck effect, which is the spin-current generation due to heat current, is discussed. The recent progress in research on the spin Seebeck effect are introduced. We explain the origin of the observed sign changes of the spin Seebeck effect in compensated ferromagnets. Next, the spin Peltier effect, which is the heat-current generation due to spin current, is discussed. Finally, we show that the spin Seebeck and spin Peltier effects are summarized by Onsager's reciprocal relation and derive Kelvin's relation for the spin and heat transports. (author)

  4. Spin Hall effects in metallic antiferromagnets – perspectives for future spin-orbitronics

    Directory of Open Access Journals (Sweden)

    Joseph Sklenar

    2016-05-01

    Full Text Available We investigate angular dependent spin-orbit torques from the spin Hall effect in a metallic antiferromagnet using the spin-torque ferromagnetic resonance technique. The large spin Hall effect exists in PtMn, a prototypical CuAu-I-type metallic antiferromagnet. By applying epitaxial growth, we previously reported an appreciable difference in spin-orbit torques for c- and a-axis orientated samples, implying anisotropic effects in magnetically ordered materials. In this work we demonstrate through bipolar-magnetic-field experiments a small but noticeable asymmetric behavior in the spin-transfer-torque that appears as a hysteresis effect. We also suggest that metallic antiferromagnets may be good candidates for the investigation of various unidirectional effects related to novel spin-orbitronics phenomena.

  5. Usefulness of magnetic resonance imaging for managing patients with prosthetic carbon valve in the mitral position

    Energy Technology Data Exchange (ETDEWEB)

    Koito, Hitoshi; Imai, Yuko; Suzuki, Junichi; Ohkubo, Naohiko; Nakamura, Chikako; Takahashi, Hideki; Iwasaka, Toshiji; Inada, Mitsuo [Kansai Medical School, Moriguchi, Osaka (Japan)

    1997-11-01

    The safety, findings and clinical usefulness of MR imaging were assessed in patients with a prosthetic carbon valve (CarboMedics: A, St. Jude Medical: B and Bjoerk-Shiley: C valves) in the mitral position. Little image distortion was shown in A and B, a small distortion toward the frequency encoded direction was seen in C, but caused no difficulty in assessing the surrounding images. Four of the 8 patients had normal sinus rhythm and the other four had atrial fibrillation. The prosthetic valves were depicted as signal voids in the images taken by both spin echo and field echo techniques in vivo. Clear structural information with little image distortion of the adjacent tissues of the prosthetic valves were obtained in all patients, although the image of C which contained stainless steel in the frame had a slightly stronger distortion than those of the A and B which contained titanium. The stainless wire suture material used to close the sternal incision was depicted as a signal void, and the areas of the signal loss were larger in the images taken by the field echo technique than those by the spin echo technique. The images (spin echo) in patients with atrial fibrillation had reduced quality due to the irregularity of repetition time. Cine MR imaging (field echo) showed physiological mitral regurgitant jets as signal loss within the flowing blood, which appeared as high signal intensity, bidirectionally in the bileaflet mechanical valve and unidirectionally in the monoleaflet mechanical valve. The wall of the abnormal cavity was disrupted abruptly and the rest of the wall consisted of pericardium and adjacent tissue in the images (spin echo). The images (field echo) showed an abnormal jet flow from the basal part of the left ventricular cavity into the abnormal cavity, which was compatible with left ventricular pseudoaneurysm. (K.H.)

  6. Impact of Disorder on Spin Dependent Transport Phenomena

    KAUST Repository

    Saidaoui, Hamed

    2016-07-03

    The impact of the spin degree of freedom on the transport properties of electrons traveling through magnetic materials has been known since the pioneer work of Mott [1]. Since then it has been demonstrated that the spin angular momentum plays a key role in the scattering process of electrons in magnetic multilayers. This role has been emphasized by the discovery of the Giant Magnetoresistance in 1988 by Fert and Grunberg [2, 3]. Among the numerous applications and effects that emerged in mesoscopic devices two mechanisms have attracted our attention during the course of this thesis: the spin transfer torque and the spin Hall effects. The former consists in the transfer of the spin angular momentum from itinerant carriers to local magnetic moments [4]. This mechanism results in the current-driven magnetization switching and excitations, which has potential application in terms of magnetic data storage and non-volatile memories. The latter, spin Hall effect, is considered as well to be one of the most fascinating mechanisms in condensed matter physics due to its ability of generating non-equilibrium spin currents without the need for any magnetic materials. In fact the spin Hall effect relies only on the presence of the spin-orbit interaction in order to create an imbalance between the majority and minority spins. The objective of this thesis is to investigate the impact of disorder on spin dependent transport phenomena. To do so, we identified three classes of systems on which such disorder may have a dramatic influence: (i) antiferromagnetic materials, (ii) impurity-driven spin-orbit coupled systems and (iii) two dimensional semiconducting electron gases with Rashba spin-orbit coupling. Antiferromagnetic materials - We showed that in antiferromagnetic spin-valves, spin transfer torque is highly sensitive to disorder, which prevents its experimental observation. To solve this issue, we proposed to use either a tunnel barrier as a spacer or a local spin torque using

  7. Transcatheter Tricuspid Valve-in-Valve Replacement with an Edwards Sapien 3 Valve

    Science.gov (United States)

    Loyalka, Pranav; Nascimbene, Angelo; Metz, Benjamin; Gregoric, Igor D.; Raman, Ajay Sundara

    2017-01-01

    A few case reports and case series have documented the outcomes in patients with tricuspid bioprosthetic valvular degeneration who underwent transcatheter implantation of the Medtronic Melody and the Edwards Sapien XT and Sapien 3 valves. In this report, we describe the case of a 49-year-old woman with severe bioprosthetic tricuspid valvular stenosis and multiple comorbidities who underwent transcatheter tricuspid valve replacement with a Sapien 3 valve. PMID:28761403

  8. Transcatheter Aortic Valve Replacement for Perceval Sutureless Aortic Valve Failure.

    Science.gov (United States)

    Kalra, Ankur; Reyes, Manuel; Yang, Eric Y; Little, Stephen H; Nabi, Faisal; Barker, Colin M; Ramchandani, Mahesh; Reul, Ross M; Reardon, Michael J; Kleiman, Neal S

    2017-06-01

    As experience with Perceval aortic prosthesis and valve-in-valve TAVR grows, it will be crucial to meticulously document short- and long-term follow-up for establishment of real-world safety and durability of these new technologies.

  9. Structural valve deterioration in the Mitroflow biological heart valve prosthesis

    DEFF Research Database (Denmark)

    Issa, Issa Farah; Poulsen, Steen Hvitfeldt; Waziri, Farhad

    2018-01-01

    OBJECTIVES: Concern has been raised regarding the long-term durability of the Mitroflow biological heart valve prosthesis. Our aim was to assess the incidence of structural valve degeneration (SVD) for the Mitroflow bioprosthesis in a nationwide study in Denmark including all patients alive in De...

  10. Substituent effect in spin-crossover behavior of iron(II)-Ar-pybox complexes (Ar-pybox = 4-aryl-2,6-bis(oxazolin-2-yl)pyridine)

    Science.gov (United States)

    Kimura, Akifumi; Ishida, Takayuki

    2018-01-01

    Spin-crossover (SCO) is a reversible transition between low-spin (LS) and high-spin (HS) states by external stimuli like heat. The SCO behavior of [Fe(Ar-pybox)2](ClO4)2 was investigated, where Ar-pybox stands for 4-aryl-2,6-bis(oxazolin-2-yl)pyridine with Ar = 4-pyridyl (4Py), 3-thienyl (3Th), and phenyl (Ph). They were characterized by means of single-crystal X-ray diffraction study, being consistent with the results of the magnetic measurements. The SCO temperatures (T1/2) in the polycrystalline state were determined to be 360 and 230 K for Ar = 4Py and Ph, respectively. The 3Th derivative possessed a HS state in all the temperature range. The solution susceptometry was also performed to purge intermolecular interaction and rigid crystal lattice effects, affording T1/2 = 310, 240, and 240 K for Ar = 4Py, 3Th, and Ph, respectively, in acetone. The substituent effect analysis using the Hammett substituent constant (σp) clarified that electron-withdrawing groups raise T1/2. A plausible model describing the substituent effect on T1/2 is proposed based on d-π interaction. The present result is regarded as a successful example of crystal field engineering.

  11. High Reliability Cryogenic Piezoelectric Valve Actuator Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Cryogenic fluid valves are subject to harsh exposure and actuators to drive these valves require robust performance and high reliability. DSM's piezoelectric...

  12. Birefringence (spin rotation and spin dichroism) of high-energy deuterons

    International Nuclear Information System (INIS)

    Baryshevskij, V.G.; Rovba, A.A.

    2016-01-01

    The phenomenon of birefringence (spin rotation and spin dichroism) of high-energy deuterons, currently observed in experiments, is the macroscopic quantum effect similar to the birefringence effect known in optics. This paper considers the contribution coming to the spin dichroism effect from the interaction of deuteron electric quadrupole moment and nuclear electric field. The effect proves to be responsive to the behavior of deuteron ground state wave functions at a small distance. [ru

  13. Nuclear spin pumping and electron spin susceptibilities

    NARCIS (Netherlands)

    Danon, J.; Nazarov, Y.V.

    2011-01-01

    In this work we present a new formalism to evaluate the nuclear spin dynamics driven by hyperfine interaction with nonequilibrium electron spins. To describe the dynamics up to second order in the hyperfine coupling it suffices to evaluate the susceptibility and fluctuations of the electron spin.

  14. Electron spin resonance and nuclear magnetic resonance of sodium macrostructures in strongly irradiated NaCl-K crystals: Manifestation of quasi-one-dimensional behavior of electrons

    NARCIS (Netherlands)

    Cherkasov, FG; Mustafin, RG; L'vov, SG; Denisenko, GA; den Hartog, HW; Vainshtein, D. I.

    1998-01-01

    Data from an investigation of electron spin resonance and nuclear magnetic resonance of NaCl-K (similar to 1 mole%) crystals strongly irradiated with electrons imply the observation of a metal-insulator transition with decreasing temperature and the manifestation of quasi-one-dimensional electron

  15. Homoepitaxial graphene tunnel barriers for spin transport

    Directory of Open Access Journals (Sweden)

    Adam L. Friedman

    2016-05-01

    Full Text Available Tunnel barriers are key elements for both charge-and spin-based electronics, offering devices with reduced power consumption and new paradigms for information processing. Such devices require mating dissimilar materials, raising issues of heteroepitaxy, interface stability, and electronic states that severely complicate fabrication and compromise performance. Graphene is the perfect tunnel barrier. It is an insulator out-of-plane, possesses a defect-free, linear habit, and is impervious to interdiffusion. Nonetheless, true tunneling between two stacked graphene layers is not possible in environmental conditions usable for electronics applications. However, two stacked graphene layers can be decoupled using chemical functionalization. Here, we demonstrate that hydrogenation or fluorination of graphene can be used to create a tunnel barrier. We demonstrate successful tunneling by measuring non-linear IV curves and a weakly temperature dependent zero-bias resistance. We demonstrate lateral transport of spin currents in non-local spin-valve structures, and determine spin lifetimes with the non-local Hanle effect. We compare the results for hydrogenated and fluorinated tunnel and we discuss the possibility that ferromagnetic moments in the hydrogenated graphene tunnel barrier affect the spin transport of our devices.

  16. Mechanical Valve Replacement: Early Results

    Directory of Open Access Journals (Sweden)

    Habib Cakir

    2012-03-01

    Conclusion: Mechanical prosthetic valves are used for surgical treatment of valve disease with low mortality and morbidity in a large group of patients like women that not to think to get pregnant, non advanced age group and patients have less risky for anticoagulation drug in our clinic. [Cukurova Med J 2012; 37(1: 49-54

  17. Artificial aortic valves: an overview.

    Science.gov (United States)

    Morsi, Y S; Birchall, I E; Rosenfeldt, F L

    2004-06-01

    This review discusses strategies that may address some of the limitations associated with replacing diseased or dysfunctional aortic valves with mechanical or tissue valves. These limitations range from structural failure and thromboembolic complications associated with mechanical valves to a limited durability and calcification with tissue valves. In pediatric patients there is an issue with the inability of substitutes to grow with the recipient. The emerging science of tissue engineering potentially provides an attractive alternative by creating viable tissue structures based on a resorbable scaffold. Morphometrically precise, biodegradable polymer scaffolds may be fabricated from data obtained from scans of natural valves by rapid prototyping technologies such as fused deposition modelling. The scaffold provides a mechanical profile until seeded cells produce their own extra cellular matrix. The microstructure of the forming tissue may be aligned into predetermined spatial orientations via fluid transduction in a bioreactor. Although there are many technical obstacles that must be overcome before tissue engineered heart valves are introduced into routine surgical practice these valves have the potential to overcome many of the shortcomings of current heart valve substitutes.

  18. Determination of oxidation state of iron in normal and pathologically altered human aortic valves

    Energy Technology Data Exchange (ETDEWEB)

    Czapla-Masztafiak, J. [Institute of Nuclear Physics PAN, Radzikowskiego 152, 31-342 Kraków (Poland); Lis, G.J.; Gajda, M.; Jasek, E. [Department of Histology, Jagiellonian University Medical College, Kopernika 7, 31-034 Kraków (Poland); Czubek, U. [Department of Coronary Disease, Jagiellonian University Medical College, John Paul II Hospital, Prądnicka 80, 31-202 Kraków (Poland); Bolechała, F. [Department of Forensic Medicine, Jagiellonian University Medical College, Grzegórzecka 16, 31-531 Kraków (Poland); Borca, C. [Swiss Light Source, Paul Scherrer Institute, 5232 Villigen PSI (Switzerland); Kwiatek, W.M. [Institute of Nuclear Physics PAN, Radzikowskiego 152, 31-342 Kraków (Poland)

    2015-12-01

    In order to investigate changes in chemical state of iron in normal and pathologically altered human aortic valves X-ray absorption spectroscopy was applied. Since Fe is suspected to play detrimental role in aortic valve stenosis pathogenesis the oxidation state of this element has been determined. The experimental material consisted of 10 μm sections of valves excised during routine surgery and from autopsies. The experiment was performed at the MicroXAS beamline of the SLS synchrotron facility in Villigen (Switzerland). The Fe K-edge XANES spectra obtained from tissue samples were carefully analyzed and compared with the spectra of reference compounds containing iron in various chemical structures. The analysis of absorption edge position and shape of the spectra revealed that both chemical forms of iron are presented in valve tissue but Fe{sup 3+} is the predominant form. Small shift of the absorption edge toward higher energy in the spectra from stenotic valve samples indicates higher content of the Fe{sup 3+} form in pathological tissue. Such a phenomenon suggests the role of Fenton reaction and reactive oxygen species in the etiology of aortic valve stenosis. The comparison of pre-edge regions of XANES spectra for control and stenotic valve tissue confirmed no differences in local symmetry or spin state of iron in analyzed samples.

  19. Experience with valves for PHWR reactors

    International Nuclear Information System (INIS)

    Narayan, K.; Mhetre, S.G.

    1977-01-01

    Material specifications and inspection and testing requirements of the valves meant for use in nuclear reactors are mentioned. In the heavy water systems (both primary and moderator) of a PHWR type reactor, the valves used are gate valves, globe valves, diaphragm valves, butterfly valves, check valves and relief valves. Their locations and functions they perform in the Rajasthan Atomic Power Station Unit-1 are described. Experience with them is given. The major problems encountered with them have been : (1) leakage from the stem seals and body bonnet joint, (2) leakage due to failure of diaphragm and/or washout of the packing and (3) malfunctioning. Measures taken to solve these are discussed. Finally a mention has been made of improved versions of valves, namely, metal diaphragm valve and inverted relief valve. (M.G.B.)

  20. [Traumatic aortic valve insufficiency].

    Science.gov (United States)

    Nascimento, J; Lemos, C; Marques, A M; Antunes, M J; Gonsalves, A

    1996-02-01

    The traumatic aortic valvular insufficiency (TAVI), through less frequent after a non-penetrating thoracic traumatism, is a serious entity with a very reserved prognosis. So it must be suspected in every patients with signs or symptoms of de novo heart failure post-traumatism. The transthoracic echocardiography and eventually transesophageal echocardiography have a fundamental role in the confirmation of the diagnosis. The clinical picture of traumatic aortic regurgitation is quickly evolutionary and the non efficacy of medical therapy has placed the valvular substitution surgery as the best succeeded treatment. With the advent of the aortic valve repairing surgery some TAVI cases has been submitted to this procedure. Nevertheless, the development of residual aortic regurgitation in these situations, usually requiring later valvular replacement surgery, make the aortic valvuloplasty a controversial surgical technique. The AA describe a recent clinical case of aortic regurgitation after a non-penetrant thoracic traumatism, discussing the aspects connected with physiopathology, diagnosis and therapy. The singularity of this case was based on the fact that the initial clinical diagnosis had been prejudiced by the context of a polytraumatism and there had been a time free of symptoms between the traumatism and the beginning of the symptomatology of left ventricular failure. Even though the identification of the problem allowed an intensive treatment of this serious situation that ended with the replacement of the aortic valve by mechanical aortic prosthesis, with the patient's total recovery.

  1. Patents and heart valve surgery - II: tissue valves.

    Science.gov (United States)

    Cheema, Faisal H; Kossar, Alexander P; Rehman, Atiq; Younas, Fahad; Polvani, Gianluca

    2013-08-01

    Valvular heart disease affects millions of Americans yearly and currently requires surgical intervention to repair or replace the defective valves. Through a close-knit collaboration between physicians, scientists and biomedical engineers, a vast degree of research and development has been aimed towards the optimization of prosthetic heart valves. Although various methods have made fantastic strides in producing durable prostheses, the therapeutic efficacy of prosthetic valves is inherently limited by a dependency upon lifelong anticoagulant regimens for recipients - a difficult challenge for many in clinical setting. Thus, biological tissue valves have been developed to circumvent vascular and immunemediated complications by incorporating biological materials to mimic native valves while still maintaining a necessary level of structural integrity. Over the past decade, a multitude of patents pertaining to the refinement of designs as well as the advancement in methodologies and technologies associated with biological tissue valves have been issued. This review seeks to chronicle and characterize such patents in an effort to track the past, present, and future progress as well as project the trajectory of tissue valves in the years to come.

  2. Design of Over Center Valves Based on Predictable Performance

    DEFF Research Database (Denmark)

    Hansen, M.R.; Andersen, T.O.; Pedersen, P.

    2004-01-01

    A typical oil hydraulic over center valve system and a time domain simulation model is introduced together with a hypothesis that flow force compensation should reduce the inherent oscillatory behavior of such hydraulic systems. A few results are shown from a parameter study that confirms...

  3. Robotic mitral valve surgery.

    Science.gov (United States)

    Kypson, Alan P; Nifong, L Wiley; Chitwood, W Randolph

    2003-12-01

    A renaissance in cardiac surgery has begun. The early clinical experience with computer-enhanced telemanipulation systems outlines the limitations of this approach despite some procedural success. Technologic advancements, such as the use of nitinol U-clips (Coalescent Surgical Inc., Sunnyvale, CA) instead of sutures requiring manual knot tying, have been shown to decrease operative times significantly. It is expected that with further refinements and development of adjunct technologies, the technique of computer-enhanced endoscopic cardiac surgery will evolve and may prove to be beneficial for many patients. Robotic technology has provided benefits to cardiac surgery. With improved optics and instrumentation, incisions are smaller. The ergometric movements and simulated three-dimensional optics project hand-eye coordination for the surgeon. The placement of the wristlike articulations at the end of the instruments moves the pivoting action to the plane of the mitral annulus. This improves dexterity in tight spaces and allows for ambidextrous suture placement. Sutures can be placed more accurately because of tremor filtration and high-resolution video magnification. Furthermore, the robotic system may have potential as an educational tool. In the near future, surgical vision and training systems might be able to model most surgical procedures through immersive technology. Thus, a "flight simulator" concept emerges where surgeons may be able to practice and perform the operation without a patient. Already, effective curricula for training teams in robotic surgery exist. Nevertheless, certain constraints continue to limit the advancement to a totally endoscopic computer-enhanced mitral valve operation. The current size of the instruments, intrathoracic instrument collisions, and extrathoracic "elbow" conflicts still can limit dexterity. When smaller instruments are developed, these restraints may be resolved. Furthermore, a working port incision is still required for

  4. A computational model of aging and calcification in the aortic heart valve.

    Directory of Open Access Journals (Sweden)

    Eli J Weinberg

    Full Text Available The aortic heart valve undergoes geometric and mechanical changes over time. The cusps of a normal, healthy valve thicken and become less extensible over time. In the disease calcific aortic stenosis (CAS, calcified nodules progressively stiffen the cusps. The local mechanical changes in the cusps, due to either normal aging or pathological processes, affect overall function of the valve. In this paper, we propose a computational model for the aging aortic valve that connects local changes to overall valve function. We extend a previous model for the healthy valve to describe aging. To model normal/uncomplicated aging, leaflet thickness and extensibility are varied versus age according to experimental data. To model calcification, initial sites are defined and a simple growth law is assumed. The nodules then grow over time, so that the area of calcification increases from one model to the next model representing greater age. Overall valve function is recorded for each individual model to yield a single simulation of valve function over time. This simulation is the first theoretical tool to describe the temporal behavior of aortic valve calcification. The ability to better understand and predict disease progression will aid in design and timing of patient treatments for CAS.

  5. Quantification and Analysis of Leaflet Flutter on Biological Prosthetic Cardiac Valves.

    Science.gov (United States)

    Avelar, Artur H de F; Canestri, Jean A; Bim, Camila; Silva, Maíra G M; Huebner, Rudolf; Pinotti, Marcos

    2017-09-01

    The use of porcine or bovine pericardium biological cardiac valves has as its main disadvantage a relatively short lifespan, with failures due to calcification and fatigue. Increasing these valves' durability constitutes a great challenge. An understudied phenomenon is the effect of flutter, an oscillation of the leaflets that can cause regurgitation and accelerate calcification and fatigue. As a starting point to study how to reduce or prevent these oscillations, a method was developed to quantify the flutter frequencies occurring at the point of the valve's full opening. On a test bench that simulates the heart flow, the cusp behaviors of eight biological valves were filmed with a high speed camera at 2000 frames per second at different flow rates and motion capture software obtained the frequencies and amplitudes of the vibrations of each leaflet. Oscillations in the range of 200 Hz with average amplitudes of 0.4 mm were found; larger nominal diameter valves obtained lower values, and bovine pericardial valves had superior performance compared to porcine valves. A dimensionless analysis was performed to find a relationship between the geometric and mechanical properties of the valves with the critical speed of the onset of fluttering. This relationship inspired a method to predict whether flutter will occur in the bioprosthesis. This method is a new tool for the consideration of maximizing the life of prosthetic valves. © 2016 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

  6. Spin glass behavior in nanogranular La{sub 0.25}Ca{sub 0.75}MnO{sub 3} manganites

    Energy Technology Data Exchange (ETDEWEB)

    Fernández-Martínez, Antoni [Grup de Magnetisme, Dept. Física Fonamental, Facultat de Física, Universitat de Barcelona, Martí i Franquès 1, planta 4, edifici nou, 08028 Barcelona (Spain); Institut de Nanociència i Nanotecnologia IN" 2UB, Universitat de Barcelona, Martí i Franquès 1, planta 3, edifici nou, 08028 Barcelona (Spain); García-Santiago, Antoni, E-mail: agarciasan@ub.edu [Grup de Magnetisme, Dept. Física Fonamental, Facultat de Física, Universitat de Barcelona, Martí i Franquès 1, planta 4, edifici nou, 08028 Barcelona (Spain); Institut de Nanociència i Nanotecnologia IN" 2UB, Universitat de Barcelona, Martí i Franquès 1, planta 3, edifici nou, 08028 Barcelona (Spain); Hernàndez, Joan Manel [Grup de Magnetisme, Dept. Física Fonamental, Facultat de Física, Universitat de Barcelona, Martí i Franquès 1, planta 4, edifici nou, 08028 Barcelona (Spain); Institut de Nanociència i Nanotecnologia IN" 2UB, Universitat de Barcelona, Martí i Franquès 1, planta 3, edifici nou, 08028 Barcelona (Spain); Zhang, Tao [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China)

    2014-06-01

    The magnetic properties of two nanogranular La{sub 0.25}Ca{sub 0.75}MnO{sub 3} manganites with different average grain sizes have been studied. Besides the well-known exchange bias effect and the appearance of ferromagnetic clusters in the grains of both samples, the results show the occurrence of an antiferromagnetic transition and spin-glass properties. Both samples are described as core–shell magnetic systems, whose main difference is found in the interface between the outer ferromagnetic and the inner antiferromagnetic phases of the grains. - Highlights: • Nanogranular manganites show antiferromagnetism in magnetic measurements. • Exchange bias effect was observed in magnetic hysteresis cycles. • Spin-glass properties were detected at low temperatures. • A core-shell model was applied to describe the results in both samples. • These features have nothing to do with usual properties of nanoparticle manganites.

  7. Critical and reentrant behavior of the spin quantum 1/2 anisotropic Heisenberg antiferromagnet model with Dzyaloshinskii–Moriya interaction in a longitudinal magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Parente, Walter E.F.; Pacobahyba, J.T.M.; Araújo, Ijanílio G. [Departamento de Física, Universidade Federal de Roraima, BR 174, Km 12. Bairro Monte Cristo. CEP: 69300-000 Boa Vista, Roraima (Brazil); Neto, Minos A., E-mail: minos@pq.cnpq.br [Universidade Federal do Amazonas, Departamento de Física, 3000, Japiim, 69077-000, Manaus-AM (Brazil); Ricardo de Sousa, J. [Universidade Federal do Amazonas, Departamento de Física, 3000, Japiim, 69077-000, Manaus-AM (Brazil); National Institute of Science and Technology for Complex Systems, 3000, Japiim, 69077-000, Manaus-AM (Brazil); Akinci, Ümit [Department of Physics, Dokuz Eylül University, Tr-35160 Izmir (Turkey)

    2014-04-15

    In this paper we study the quantum spin-1/2 anisotropic Heisenberg antiferromagnet model in the presence of a Dzyaloshinskii–Moriya interaction (D) and a uniform longitudinal (H) magnetic field. Using the effective-field theory with a finite cluster N=2 spin (EFT-2) we calculate the phase diagrams in the H−T and D−T planes on a simple cubic lattice (z=6). We have only observed second order phase transitions for values between Δ∈[0,1], where the cases were analysed: Ising (Δ=1), anisotropic Heisenberg (Δ=0.6) and isotropic Heisenberg (Δ=0). - Highlights: • Anisotropic Heisenberg antiferromagnet on a simple cubic lattice. • Effective-field theory. • Dzyaloshinskii–Moriya interaction.

  8. Prosthetic valve endocarditis after transcatheter aortic valve implantation

    DEFF Research Database (Denmark)

    Olsen, Niels Thue; De Backer, Ole; Thyregod, Hans G H

    2015-01-01

    or worse postprocedural paravalvular regurgitation (hazard ratio, 4.0 [1.5-11]), implantation of >1 prosthesis (hazard ratio, 5.2 [1.5-18]), and any vascular complication (hazard ratio, 3.8 [1.5-9.8]). CONCLUSIONS: TAVI-PVE occurred at a slightly higher rate than reported for surgically implanted valves...... risk factors. METHODS AND RESULTS: Observational single-center study of 509 consecutive patients treated with a transcatheter implanted self-expandable aortic valve prosthesis (Medtronic CoreValve). We identified 18 patients diagnosed with TAVI-PVE during a median follow-up period of 1.4 years...

  9. Aortic Valve Leaflet Perforation after Mitral Valve Repair

    Directory of Open Access Journals (Sweden)

    M. Aboelnasr

    2013-01-01

    Full Text Available  A 32-year-old patient with symptomatic severe aortic regurge, 6 weeks after mitral valve repair, was admitted for aortic valve surgery. No preoperative clinical data consistent with infective endocarditis could be detected. Preoperative transthoracic echocardiography showed aortic leaflet perforation affecting non coronary cusp. During operation, leaflet perforation was detected and closed completely with autologous pericardial patch. No vegetations or abscess could be seen during operation. Iatrogenic aetiology of leaflet perforation after mitral repair was suspected in  this case. Recognition of this complication will help in  avoiding it during mitral valve surgery and expecting it as a possible complication during intraoperative transesophageal echocardiography.

  10. Decoherence dynamics of a single spin versus spin ensemble

    NARCIS (Netherlands)

    Dobrovitski, V.V.; Feiguin, A.E.; Awschalom, D.D.; Hanson, R.

    2008-01-01

    We study decoherence of central spins by a spin bath, focusing on the difference between measurement of a single central spin and measurement of a large number of central spins (as found in typical spin-resonance experiments). For a dilute spin bath, the single spin demonstrates Gaussian

  11. Spin state switching in iron coordination compounds

    Directory of Open Access Journals (Sweden)

    Philipp Gütlich

    2013-02-01

    Full Text Available The article deals with coordination compounds of iron(II that may exhibit thermally induced spin transition, known as spin crossover, depending on the nature of the coordinating ligand sphere. Spin transition in such compounds also occurs under pressure and irradiation with light. The spin states involved have different magnetic and optical properties suitable for their detection and characterization. Spin crossover compounds, though known for more than eight decades, have become most attractive in recent years and are extensively studied by chemists and physicists. The switching properties make such materials potential candidates for practical applications in thermal and pressure sensors as well as optical devices.The article begins with a brief description of the principle of molecular spin state switching using simple concepts of ligand field theory. Conditions to be fulfilled in order to observe spin crossover will be explained and general remarks regarding the chemical nature that is important for the occurrence of spin crossover will be made. A subsequent section describes the molecular consequences of spin crossover and the variety of physical techniques usually applied for their characterization. The effects of light irradiation (LIESST and application of pressure are subjects of two separate sections. The major part of this account concentrates on selected spin crossover compounds of iron(II, with particular emphasis on the chemical and physical influences on the spin crossover behavior. The vast variety of compounds exhibiting this fascinating switching phenomenon encompasses mono-, oligo- and polynuclear iron(II complexes and cages, polymeric 1D, 2D and 3D systems, nanomaterials, and polyfunctional materials that combine spin crossover with another physical or chemical property.

  12. Developments in mechanical heart valve prosthesis

    Indian Academy of Sciences (India)

    Most commonly used for replacement are mechanical heart valves and biological valves. This paper briefly outlines the evolution, designs employed, materials being used,. and important factors that affect the performance of mechanical heart valves. The clinical performance of mechanical heart valves is also addressed.

  13. Shuttle valves and system for fluid control

    Energy Technology Data Exchange (ETDEWEB)

    Caralli, M. J.; Friedline, G. W.

    1985-04-23

    An apparatus system for drying gases to provide a reverse flow to and from a pair of absorbent beds is automatically solely controlled by a unitary inlet logic shuttle valve unit and by a unitary outlet logic shuttle valve unit. Each valve unit employs positive acting slide valve elements that operate in a smooth and effective manner.

  14. Developments in mechanical heart valve prosthesis

    Indian Academy of Sciences (India)

    Artificial heart valves are engineered devices used for replacing diseased or damaged natural valves of the heart. Most commonly used for replacement are mechanical heart valves and biological valves. This paper briefly outlines the evolution, designs employed, materials being used,. and important factors that affect the ...

  15. Developments in mechanical heart valve prosthesis

    Indian Academy of Sciences (India)

    M. Senthilkumar (Newgen Imaging) 1461 1996 Oct 15 13:05:22

    Mechanical heart valves; biological valves; valve design; valve performance. 1. Introduction. The human heart can be considered a twin positive displacement pump working in tandem for supporting the systemic and pulmonary circulation of blood. Each pump comprises of a receiving chamber called atrium and a pumping ...

  16. Shuttle valves and system for fluid control

    International Nuclear Information System (INIS)

    Caralli, M. J.; Friedline, G. W.

    1985-01-01

    An apparatus system for drying gases to provide a reverse flow to and from a pair of absorbent beds is automatically solely controlled by a unitary inlet logic shuttle valve unit and by a unitary outlet logic shuttle valve unit. Each valve unit employs positive acting slide valve elements that operate in a smooth and effective manner

  17. Spin-polarized spin excitation spectroscopy

    International Nuclear Information System (INIS)

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

    2010-01-01

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

  18. Magnons, Spin Current and Spin Seebeck Effect

    Science.gov (United States)

    Maekawa, Sadamichi

    2012-02-01

    When metals and semiconductors are placed in a temperature gradient, the electric voltage is generated. This mechanism to convert heat into electricity, the so-called Seebeck effect, has attracted much attention recently as the mechanism for utilizing wasted heat energy. [1]. Ferromagnetic insulators are good conductors of spin current, i.e., the flow of electron spins [2]. When they are placed in a temperature gradient, generated are magnons, spin current and the spin voltage [3], i.e., spin accumulation. Once the spin voltage is converted into the electric voltage by inverse spin Hall effect in attached metal films such as Pt, the electric voltage is obtained from heat energy [4-5]. This is called the spin Seebeck effect. Here, we present the linear-response theory of spin Seebeck effect based on the fluctuation-dissipation theorem [6-8] and discuss a variety of the devices. [4pt] [1] S. Maekawa et al, Physics of Transition Metal Oxides (Springer, 2004). [0pt] [2] S. Maekawa: Nature Materials 8, 777 (2009). [0pt] [3] Concept in Spin Electronics, eds. S. Maekawa (Oxford University Press, 2006). [0pt] [4] K. Uchida et al., Nature 455, 778 (2008). [0pt] [5] K. Uchida et al., Nature Materials 9, 894 (2010) [0pt] [6] H. Adachi et al., APL 97, 252506 (2010) and Phys. Rev. B 83, 094410 (2011). [0pt] [7] J. Ohe et al., Phys. Rev. B (2011) [0pt] [8] K. Uchida et al., Appl. Phys. Lett. 97, 104419 (2010).

  19. Cavitation guide for control valves

    International Nuclear Information System (INIS)

    Tullis, J.P.

    1993-04-01

    This guide teaches the basic fundamentals of cavitation to provide the reader with an understanding of what causes cavitation, when it occurs, and the potential problems cavitation can cause to a valve and piping system. The document provides guidelines for understanding how to reduce the cavitation and/or select control valves for a cavitating system. The guide provides a method for predicting the cavitation intensity of control valves, and how the effect of cavitation on a system will vary with valve type, valve function, valve size, operating pressure, duration of operation and details of the piping installation. The guide defines six cavitation limits identifying cavitation intensities ranging from inception to the maximum intensity possible. The intensity of the cavitation at each limit Is described, including a brief discussion of how each level of cavitation influences the valve and system. Examples are included to demonstrate how to apply the method, including making both size and pressure scale effects corrections. Methods of controlling cavitation are discussed providing information on various techniques which can be used to design a new system or modify an existing one so it can operate at a desired level of cavitation

  20. Cavitation guide for control valves

    Energy Technology Data Exchange (ETDEWEB)

    Tullis, J.P. [Tullis Engineering Consultants, Logan, UT (United States)

    1993-04-01

    This guide teaches the basic fundamentals of cavitation to provide the reader with an understanding of what causes cavitation, when it occurs, and the potential problems cavitation can cause to a valve and piping system. The document provides guidelines for understanding how to reduce the cavitation and/or select control valves for a cavitating system. The guide provides a method for predicting the cavitation intensity of control valves, and how the effect of cavitation on a system will vary with valve type, valve function, valve size, operating pressure, duration of operation and details of the piping installation. The guide defines six cavitation limits identifying cavitation intensities ranging from inception to the maximum intensity possible. The intensity of the cavitation at each limit Is described, including a brief discussion of how each level of cavitation influences the valve and system. Examples are included to demonstrate how to apply the method, including making both size and pressure scale effects corrections. Methods of controlling cavitation are discussed providing information on various techniques which can be used to design a new system or modify an existing one so it can operate at a desired level of cavitation.

  1. Characteristic analysis of servo valve

    International Nuclear Information System (INIS)

    Ko, J. H.; Ryu, D. R.; Lee, J. H.; Kim, Y. S.; Na, J. C.; Kim, D. S.

    2008-01-01

    Electro-pneumatic servo valve is an electro-mechanical device which converts electric signals into a proper pneumatic flow rate or pressure. In order to improve the overall performance of pneumatic servo systems, electro-pneumatic servo valves are required, which have fast dynamic characteristics, no air leakage at a null point, and can be fabricated at a low-cost. The first objective of this research is to design and to fabricate a new electro-pneumatic servo valve which satisfies the above-mentioned requirements. In order to design the mechanism of the servo valve optimally, the flow inside the valve depending upon the position of spool was analyzed variously, and on the basis of such analysis results, the valve mechanism, which was formed by combination of the spool and the sleeve, was designed and manufactured. And a tester for conducting an overall performance test was designed and manufactured, and as a result of conducting the flow rate test, the pressure test and the frequency test on the developed pneumatic servo valve

  2. Innovations in tricuspid valve intervention.

    Science.gov (United States)

    El-Eshmawi, Ahmed; Tang, Gilbert H L; Verma, Subodh; Yanagawa, Bobby; Ruel, Marc; Adams, David H

    2017-03-01

    Tricuspid valve disease has received much less attention in terms of intervention. The main reason for this is the widely held belief that treatment of left-sided valve disease leads to resolution of functional tricuspid regurgitation. Recent data show that tricuspid regurgitation is not benign and that many patients will benefit from intervention at the time of left-sided valve surgery, or in isolated tricuspid disease. This review describes the latest surgical and interventional options and strategies. Latest valve guidelines now recommend a more aggressive surgical approach to the treatment of moderate or severe tricuspid regurgitation, with annuloplasty being the preferred technique. Guidelines now also promote treatment of isolated significant tricuspid dilatation even without significant regurgitation, as a prophylactic strategy to prevent disease progression. This renewed interest in surgical repair has been accompanied by development of newer tricuspid annuloplasty rings. For patients in whom surgery would be high risk, transcatheter therapies are emerging as a promising alternative. Various repair devices have reported early experience. Recent surgical and transcatheter innovations in the treatment of tricuspid valve disease are promising and have the potential of removing the stigma of the tricuspid valve as the 'forgotten valve'.

  3. Butterfly valve torque prediction methodology

    International Nuclear Information System (INIS)

    Eldiwany, B.H.; Sharma, V.; Kalsi, M.S.; Wolfe, K.

    1994-01-01

    As part of the Motor-Operated Valve (MOV) Performance Prediction Program, the Electric Power Research Institute has sponsored the development of methodologies for predicting thrust and torque requirements of gate, globe, and butterfly MOVs. This paper presents the methodology that will be used by utilities to calculate the dynamic torque requirements for butterfly valves. The total dynamic torque at any disc position is the sum of the hydrodynamic torque, bearing torque (which is induced by the hydrodynamic force), as well as other small torque components (such as packing torque). The hydrodynamic torque on the valve disc, caused by the fluid flow through the valve, depends on the disc angle, flow velocity, upstream flow disturbances, disc shape, and the disc aspect ratio. The butterfly valve model provides sets of nondimensional flow and torque coefficients that can be used to predict flow rate and hydrodynamic torque throughout the disc stroke and to calculate the required actuation torque and the maximum transmitted torque throughout the opening and closing stroke. The scope of the model includes symmetric and nonsymmetric discs of different shapes and aspects ratios in compressible and incompressible fluid applications under both choked and nonchoked flow conditions. The model features were validated against test data from a comprehensive flowloop and in situ test program. These tests were designed to systematically address the effect of the following parameters on the required torque: valve size, disc shapes and disc aspect ratios, upstream elbow orientation and its proximity, and flow conditions. The applicability of the nondimensional coefficients to valves of different sizes was validated by performing tests on 42-in. valve and a precisely scaled 6-in. model. The butterfly valve model torque predictions were found to bound test data from the flow-loop and in situ testing, as shown in the examples provided in this paper

  4. Ferroelectric Fluid Flow Control Valve

    Science.gov (United States)

    Jalink, Antony, Jr. (Inventor); Hellbaum, Richard F. (Inventor); Rohrbach, Wayne W. (Inventor)

    1999-01-01

    An active valve is controlled and driven by external electrical actuation of a ferroelectric actuator to provide for improved passage of the fluid during certain time periods and to provide positive closure of the valve during other time periods. The valve provides improved passage in the direction of flow and positive closure in the direction against the flow. The actuator is a dome shaped internally prestressed ferroelectric actuator having a curvature, said dome shaped actuator having a rim and an apex. and a dome height measured from a plane through said rim said apex that varies with an electric voltage applied between an inside and an outside surface of said dome shaped actuator.

  5. Thermostatic Radiator Valve Evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Dentz, J. [Advanced Residential Integrated Energy Solutions Collaborative (ARIES), New York, NY (United States); Ansanelli, E. [Advanced Residential Integrated Energy Solutions Collaborative (ARIES), New York, NY (United States)

    2015-01-01

    A large stock of multifamily buildings in the Northeast and Midwest are heated by steam distribution systems. Losses from these systems are typically high and a significant number of apartments are overheated much of the time. Thermostatically controlled radiator valves (TRVs) are one potential strategy to combat this problem, but have not been widely accepted by the residential retrofit market. In this project, the ARIES team sought to better understand the current usage of TRVs by key market players in steam and hot water heating and to conduct limited experiments on the effectiveness of new and old TRVs as a means of controlling space temperatures and reducing heating fuel consumption. The project included a survey of industry professionals, a field experiment comparing old and new TRVs, and cost-benefit modeling analysis using BEopt™ (Building Energy Optimization software).

  6. Safety Testing of Left Ventricular Vent Valves

    OpenAIRE

    Gavin, Caroline; Coblentz, John; Acsell, Jeffrey R.; Shackelford, Anthony G.; Sistino, Joseph J.

    2015-01-01

    Vent vacuum relief valves (VRVs) are used to limit the negative pressure at the ventricular vent catheter tip as well as prevent reversal of blood flow and prevention of air embolism. The purpose of this study was to evaluate the performance of three commercially available ventricular vent valves. The negative pressure at which the vent valve opened was measured at the valve inlet using high-fidelity pressure transducers. Also, the flow rate at which air entrainment occurred due to valve open...

  7. Disordered kagomé spin ice

    Science.gov (United States)

    Greenberg, Noah; Kunz, Andrew

    2018-05-01

    Artificial spin ice is made from a large array of patterned magnetic nanoislands designed to mimic naturally occurring spin ice materials. The geometrical arrangement of the kagomé lattice guarantees a frustrated arrangement of the islands' magnetic moments at each vertex where the three magnetic nanoislands meet. This frustration leads to a highly degenerate ground state which gives rise to a finite (residual) entropy at zero temperature. In this work we use the Monte Carlo simulation to explore the effects of disorder in kagomé spin ice. Disorder is introduced to the system by randomly removing a known percentage of magnetic islands from the lattice. The behavior of the spin ice changes as the disorder increases; evident by changes to the shape and locations of the peaks in heat capacity and the residual entropy. The results are consistent with observations made in diluted physical spin ice materials.

  8. Current-based detection of nonlocal spin transport in graphene for spin-based logic applications

    Science.gov (United States)

    Wen, Hua; Zhu, Tiancong; Luo, Yunqiu Kelly; Amamou, Walid; Kawakami, Roland K.

    2014-05-01

    Graphene has been proposed for novel spintronic devices due to its robust and efficient spin transport properties at room temperature. Some of the most promising proposals require current-based readout for integration purposes, but the current-based detection of spin accumulation has not yet been developed. In this work, we demonstrate current-based detection of spin transport in graphene using a modified nonlocal geometry. By adding a variable shunt resistor in parallel to the nonlocal voltmeter, we are able to systematically cross over from the conventional voltage-based detection to current-based detection. As the shunt resistor is reduced, the output current from the spin accumulation increases as the shunt resistance drops below a characteristic value R*. We analyze this behavior using a one-dimensional drift-diffusion model, which accounts well for the observed behavior. These results provide the experimental and theoretical foundation for current-based detection of nonlocal spin transport.

  9. Snakes and spin rotators

    International Nuclear Information System (INIS)

    Lee, S.Y.

    1990-01-01

    The generalized snake configuration offers advantages of either shorter total snake length and smaller orbit displacement in the compact configuration or the multi-functions in the split configuration. We found that the compact configuration can save about 10% of the total length of a snake. On other hand, the spilt snake configuration can be used both as a snake and as a spin rotator for the helicity state. Using the orbit compensation dipoles, the spilt snake configuration can be located at any distance on both sides of the interaction point of a collider provided that there is no net dipole rotation between two halves of the snake. The generalized configuration is then applied to the partial snake excitation. Simple formula have been obtained to understand the behavior of the partial snake. Similar principle can also be applied to the spin rotators. We also estimate the possible snake imperfections are due to various construction errors of the dipole magnets. Accuracy of field error of better than 10 -4 will be significant. 2 refs., 5 figs

  10. Human tissue valves in aortic position: determinants of reoperation and valve regurgitation

    NARCIS (Netherlands)

    T.P. Willems (Tineke); E.W. Steyerberg (Ewout); V.E. Kleyburg-Linkers; E. Bos (Egbert); L.A. van Herwerden (Lex); J.R.T.C. Roelandt (Jos); J.J.M. Takkenberg (Hanneke)

    2001-01-01

    textabstractBACKGROUND: Human tissue valves for aortic valve replacement have a limited durability that is influenced by interrelated determinants. Hierarchical linear modeling was used to analyze the relation between these determinants of durability and valve

  11. Non-equilibrium study of spin wave interference in systems with both Rashba and Dresselhaus (001) spin-orbit coupling

    International Nuclear Information System (INIS)

    Chen, Kuo-Chin; Su, Yu-Hsin; Chang, Ching-Ray; Chen, Son-Hsien

    2014-01-01

    We study the electron spin transport in two dimensional electron gas (2DEG) system with both Rashba and Dresselhaus (001) spin-orbital coupling (SOC). We assume spatial behavior of spin precession in the non-equilibrium transport regime, and study also quantum interference induced by non-Abelian spin-orbit gauge field. The method we adopt in this article is the non-equilibrium Green's function within a tight binding framework. We consider one ferromagnetic lead which injects spin polarized electron to a system with equal strength of Rashba and Dresselhaus (001) SOC, and we observe the persistent spin helix property. We also consider two ferromagnetic leads injecting spin polarized electrons into a pure Dresselhaus SOC system, and we observe the resultant spin wave interference pattern

  12. Spin excitations in systems with hopping electron transport and strong position disorder in a large magnetic field

    Science.gov (United States)

    Shumilin, A. V.

    2016-10-01

    We discuss the spin excitations in systems with hopping electron conduction and strong position disorder. We focus on the problem in a strong magnetic field when the spin Hamiltonian can be reduced to the effective single-particle Hamiltonian and treated with conventional numerical technics. It is shown that in a 3D system with Heisenberg exchange interaction the spin excitations have a delocalized part of the spectrum even in the limit of strong disorder, thus leading to the possibility of the coherent spin transport. The spin transport provided by the delocalized excitations can be described by a diffusion coefficient. Non-homogenous magnetic fields lead to the Anderson localization of spin excitations while anisotropy of the exchange interaction results in the Lifshitz localization of excitations. We discuss the possible effect of the additional exchange-driven spin diffusion on the organic spin-valve devices.

  13. Minimally invasive aortic valve replacement

    DEFF Research Database (Denmark)

    Foghsgaard, Signe; Schmidt, Thomas Andersen; Kjaergard, Henrik K

    2009-01-01

    In this descriptive prospective study, we evaluate the outcomes of surgery in 98 patients who were scheduled to undergo minimally invasive aortic valve replacement. These patients were compared with a group of 50 patients who underwent scheduled aortic valve replacement through a full sternotomy...... operations were completed as mini-sternotomies, 4 died later of noncardiac causes. The aortic cross-clamp and perfusion times were significantly different across all groups (P replacement...... is an excellent operation in selected patients, but its true advantages over conventional aortic valve replacement (other than a smaller scar) await evaluation by means of randomized clinical trial. The "extended mini-aortic valve replacement" operation, on the other hand, is a risky procedure that should...

  14. Aortic valve surgery - minimally invasive

    Science.gov (United States)

    ... valve surgery. Techniques include min-thoracotomy, min-sternotomy, robot-assisted surgery, and percutaneous surgery. To perform the ... M. is also a founding member of Hi-Ethics and subscribes to the principles of the Health ...

  15. Mitral Valve Prolapse (For Parents)

    Science.gov (United States)

    ... that affect the body's connective tissues, such as Marfan syndrome . Some research has shown that kids with MVP ... EKG (Video) Your Heart & Circulatory System Heart Murmurs Marfan Syndrome Mitral Valve Prolapse EKG (Video) Arrhythmias Marfan Syndrome ...

  16. Spin-Mechatronics

    Science.gov (United States)

    Matsuo, Mamoru; Saitoh, Eiji; Maekawa, Sadamichi

    2017-01-01

    We investigate the interconversion phenomena between spin and mechanical angular momentum in moving objects. In particular, the recent results on spin manipulation and spin-current generation by mechanical motion are examined. In accelerating systems, spin-dependent gauge fields emerge, which enable the conversion from mechanical angular momentum into spins. Such a spin-mechanical effect is predicted by quantum theory in a non-inertial frame. Experiments which confirm the effect, i.e., the resonance frequency shift in nuclear magnetic resonance, the stray field measurement of rotating metals, and electric voltage generation in liquid metals, are discussed.

  17. Temperature dependent behavior of localized and delocalized electrons in nitrogen-doped 6H SiC crystals as studied by electron spin resonance

    Czech Academy of Sciences Publication Activity Database

    Savchenko, Dariia; Kalabukhova, E.; Shanina, B.; Cichoň, Stanislav; Honolka, Jan; Kiselov, V.; Mokhov, E.

    2016-01-01

    Roč. 119, č. 4 (2016), 1-7, č. článku 045701. ISSN 0021-8979 R&D Projects: GA ČR GP13-06697P; GA MŠk LO1409; GA MŠk(CZ) LM2011029 Grant - others:SAFMAT(XE) CZ.2.16/3.1.00/22132; AV ČR(CZ) Fellowship J. E. Purkyně Institutional support: RVO:68378271 Keywords : electron spin resonance * SiC * nitrogen donors * conduction electrons Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.068, year: 2016

  18. Kawasaki Dynamics on Bidimensional Spin Systems

    Science.gov (United States)

    Resende, Denilson C.; Cacüador, Felipe C.; Dantas, Sócrates O.

    Under the influence of an external field many systems exhibit slow relaxations processes. In that sense, we study the Physics of this behavior/process in the early stages of its evolution on bidimensional Ising systems using Monte Carlo simulations at a broad range of temperature and spins up concentration. The Monte Carlo simulations were done up to second neighbors interactions shown a more stable dynamic regime than first neighbors interactions, when the systems energy is considered. The behavior of relative energy/spin and the relative perimeter (the line between spin up and spin down regions) are monitored against Monte Carlo steps. Also, our findings show that the stretching index (a2) exhibit values below the borderline (1) in a broad range of concentration below 50% and temperature from 0.5 ≤T ≤ 4.5 (in units of J/kB , where J is the ferromagnetic constant and kB is the Boltzmann constant).

  19. Spin-Hall nano-oscillator: A micromagnetic study

    Energy Technology Data Exchange (ETDEWEB)

    Giordano, A.; Azzerboni, B.; Finocchio, G. [Department of Electronic Engineering, Industrial Chemistry and Engineering, University of Messina, C.da di Dio, I-98166 Messina (Italy); Carpentieri, M. [Department of Electrical and Information Engineering, Politecnico of Bari, via E. Orabona 4, I-70125 Bari (Italy); Laudani, A. [Department of Engineering, University of Roma Tre, via V. Volterra 62, I-00146 Roma (Italy); Gubbiotti, G. [Istituto Officina dei Materiali del CNR (CNR-IOM), Unità di Perugia c/o Dipartimento di Fisica e Geologia, Via A. Pascoli, 06123 Perugia (Italy)

    2014-07-28

    This Letter studies the dynamical behavior of spin-Hall nanoscillators from a micromagnetic point of view. The model parameters have been identified by reproducing recent experimental data quantitatively. Our results indicate that a strongly localized mode is observed for in-plane bias fields such as in the experiments, while predict the excitation of an asymmetric propagating mode for large enough out-of plane bias field similarly to what observed in spin-torque nanocontact oscillators. Our findings show that spin-Hall nanoscillators can find application as spin-wave emitters for magnonic applications where spin waves are used for transmission and processing information on nanoscale.

  20. Tissue-engineered heart valves

    Czech Academy of Sciences Publication Activity Database

    Filová, Elena; Straka, František; Miřejovský, T.; Mašín, J.; Bačáková, Lucie

    2009-01-01

    Roč. 58, Suppl.2 (2009), S141-S158 ISSN 0862-8408 R&D Projects: GA MŠk(CZ) 1M0510; GA AV ČR(CZ) 1QS500110564 Institutional research plan: CEZ:AV0Z50110509 Keywords : bioarteficial heart valve * valve interstitial cells * pulse flow bioreactor Subject RIV: EI - Biotechnology ; Bionics Impact factor: 1.430, year: 2009

  1. Kytococcus schroeteri prosthetic valve endocarditis

    OpenAIRE

    Yousri, Taher; Hawari, Mohammad; Saad, Rasheed; Langley, Steve

    2010-01-01

    We report the case of a 64-year-old male patient with a prosthetic aortic valve who presented with clinical features of endocarditis confirmed by transoesophageal echocardiography. His blood cultures were positive for a very rare and newly described organism—Kytococcus schroeteri. The patient underwent aortic valve replacement and a 6-week course of intravenous antibiotics. This is the fifth reported case of endocarditis associated with this organism.

  2. Kytococcus schroeteri prosthetic valve endocarditis.

    Science.gov (United States)

    Yousri, Taher; Hawari, Mohammad; Saad, Rasheed; Langley, Steve

    2010-09-29

    We report the case of a 64-year-old male patient with a prosthetic aortic valve who presented with clinical features of endocarditis confirmed by transoesophageal echocardiography. His blood cultures were positive for a very rare and newly described organism-Kytococcus schroeteri. The patient underwent aortic valve replacement and a 6-week course of intravenous antibiotics. This is the fifth reported case of endocarditis associated with this organism.

  3. Performance of distributing valves in hydroelectric speed governors: analysis of the influence of the internal geometry

    Energy Technology Data Exchange (ETDEWEB)

    Retzlaff, L.; Pacheco, M.I.; Ferronatto, D.; Negri, V.J. de [Federal University of Santa Catarina (LASHIP/EMC/UFSC), Florianopolis, SC (Brazil). Mechanical Engineering Dept. Lab. of Hydraulic and Pneumatic Systems], E-mail: victor@emc.ufsc.br; Belan, H.C. [Federal Institute of Santa Catarina (IFSC), Chapeco, SC (Brazil). Mechanical Engineering Dept.; Soares, J.M.C. [REIVAX Automacao e Controle, Florianopolis, SC (Brazil)

    2009-07-01

    This paper discusses an analysis of the influence of internal geometric parameters on the performance of distributing valves including the theoretical and experimental analysis of a 3000 Lpm valve which is used in the speed control of a 350 MVA turbine. Using a model that represents the fluid flow through the valve, it is possible to study the influence of the internal geometry, such the orifice area, radial clearances and internal channels, on the behavior of flow rate and pressure. With the validated model, different valve configurations can be evaluated either in the design phase or during the operation and qualification tests. These results could aid both professionals involved in the operation and maintenance of hydroelectric power plants in identifying and tracking any changes in the valves performance and design engineers in the definition of the geometric and dimensional tolerances. (author)

  4. A New Spin on Photoemission Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Jozwiak, Chris [Univ. of California, Berkeley, CA (United States)

    2008-12-01

    The electronic spin degree of freedom is of general fundamental importance to all matter. Understanding its complex roles and behavior in the solid state, particularly in highly correlated and magnetic materials, has grown increasingly desirable as technology demands advanced devices and materials based on ever stricter comprehension and control of the electron spin. However, direct and efficient spin dependent probes of electronic structure are currently lacking. Angle Resolved Photoemission Spectroscopy (ARPES) has become one of the most successful experimental tools for elucidating solid state electronic structures, bolstered by-continual breakthroughs in efficient instrumentation. In contrast, spin-resolved photoemission spectroscopy has lagged behind due to a lack of similar instrumental advances. The power of photoemission spectroscopy and the pertinence of electronic spin in the current research climate combine to make breakthroughs in Spin and Angle Resolved Photoemission Spectroscopy (SARPES) a high priority . This thesis details the development of a unique instrument for efficient SARPES and represents a radical departure from conventional methods. A custom designed spin polarimeter based on low energy exchange scattering is developed, with projected efficiency gains of two orders of magnitude over current state-of-the-art polarimeters. For energy analysis, the popular hemispherical analyzer is eschewed for a custom Time-of-Flight (TOF) analyzer offering an additional order of magnitude gain in efficiency. The combined instrument signifies the breakthrough needed to perform the high resolution SARPES experiments necessary for untangling the complex spin-dependent electronic structures central to today's condensed matter physics.

  5. A spin-resolved photoemission study

    Indian Academy of Sciences (India)

    Stoner vs. spin-mixing behavior in the bulk magnetism of Gd: A spin-resolved photoemission study. K MAITI1,2,∗. , M C MALAGOLI2, A DALLMEYER2 and C CARBONE2,3. 1Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400 005, India. 2Institut für Festkörperforschung, Forschungszentrum Jülich, ...

  6. The Role of Coulomb Interactions for Spin Crossover Behaviors and Crystal Structural Transformation in Novel Anionic Fe(III Complexes from a π-Extended ONO Ligand

    Directory of Open Access Journals (Sweden)

    Suguru Murata

    2016-05-01

    Full Text Available To investigate the π-extension effect on an unusual negative-charged spin crossover (SCO FeIII complex with a weak N2O4 first coordination sphere, we designed and synthesized a series of anionic FeIII complexes from a π-extended naphthalene derivative ligand. Acetonitrile-solvate tetramethylammonium (TMA salt 1 exhibited an SCO conversion, while acetone-solvate TMA salt 2 was in a high-spin state. The crystal structural analysis for 2 revealed that two-leg ladder-like cation-anion arrays derived from π-stacking interactions between π-ligands of the FeIII complex anion and Coulomb interactions were found and the solvated acetone molecules were in one-dimensional channels between the cation-anion arrays. A desolvation-induced single-crystal-to-single-crystal transformation to desolvate compound 2’ may be driven by Coulomb energy gain. Furthermore, the structural comparison between quasi-polymorphic compounds 1 and 2 revealed that the synergy between Coulomb and π-stacking interactions induces a significant distortion of coordination structure of 2.

  7. Noninvasive valve monitor using alternating electromagnetic field

    Science.gov (United States)

    Eissenberg, David M.; Haynes, Howard D.; Casada, Donald A.

    1993-01-01

    One or more electrical coils are carefully located on the outside of a valve body. An alternating current passing through the coil(s) results in an alternating electromagnetic field being transmitted into the valve body and valve internals. The electromagnetic field varies in intensity and polarity in the valve. As the position of a valve internal part is changed, the electromagnetic field throughout the valve body and its internals is altered. A passive receiver coil carefully located on the outside of the valve body detects the intensity of the electromagnetic field at that location as an induced electrical voltage in the coil. With the change in position of the valve internal part, there is a corresponding change in the induced voltage as a result of the alteration in the alternating electromagnetic field at that location. Changes in the voltage provide an indication of the position and motion of valve internals.

  8. Development of an effective valve packing program

    Energy Technology Data Exchange (ETDEWEB)

    Hart, K.A.

    1996-12-01

    Current data now shows that graphite valve packing installed within the guidance of a controlled program produces not only reliable stem sealing but predictable running loads. By utilizing recent technological developments in valve performance monitoring for both MOV`s and AOV`s, valve packing performance can be enhanced while reducing maintenance costs. Once known, values are established for acceptable valve packing loads, the measurement of actual valve running loads via the current MOV/AOV diagnostic techniques can provide indication of future valve stem sealing problems, improper valve packing installation or identify the opportunity for valve packing program improvements. At times the full benefit of these advances in material and predictive technology remain under utilized due to simple past misconceptions associated with valve packing. This paper will explore the basis for these misconceptions, provide general insight into the current understanding of valve packing and demonstrate how with this new understanding and current valve diagnostic equipment the key aspects required to develop an effective, quality valve packing program fit together. The cost and operational benefits provided by this approach can be significant impact by the: elimination of periodic valve repacking, reduction of maintenance costs, benefits of leak-free valve operation, justification for reduced Post Maintenance Test Requirements, reduced radiation exposure, improved plant appearance.

  9. Development of an effective valve packing program

    International Nuclear Information System (INIS)

    Hart, K.A.

    1996-01-01

    Current data now shows that graphite valve packing installed within the guidance of a controlled program produces not only reliable stem sealing but predictable running loads. By utilizing recent technological developments in valve performance monitoring for both MOV's and AOV's, valve packing performance can be enhanced while reducing maintenance costs. Once known, values are established for acceptable valve packing loads, the measurement of actual valve running loads via the current MOV/AOV diagnostic techniques can provide indication of future valve stem sealing problems, improper valve packing installation or identify the opportunity for valve packing program improvements. At times the full benefit of these advances in material and predictive technology remain under utilized due to simple past misconceptions associated with valve packing. This paper will explore the basis for these misconceptions, provide general insight into the current understanding of valve packing and demonstrate how with this new understanding and current valve diagnostic equipment the key aspects required to develop an effective, quality valve packing program fit together. The cost and operational benefits provided by this approach can be significant impact by the: elimination of periodic valve repacking, reduction of maintenance costs, benefits of leak-free valve operation, justification for reduced Post Maintenance Test Requirements, reduced radiation exposure, improved plant appearance

  10. Heart valve viscoelastic properties - a pilot study

    Directory of Open Access Journals (Sweden)

    Kochová P.

    2007-10-01

    Full Text Available The effects of cryopreservation on the biological tissue mechanics are still largely unknown. Generalized Maxwell model was applied to characterize quantitatively the viscoelastic behavior of sheep mitral heart valve tissue. Three different groups of specimens are supposed to be tested: fresh tissue specimens (control group, cryopreserved allografts from tissue bank and allografts already used as tissue replacements taken from the animals approximately one year after the surgery. Specific aim of this study is to determine whether or not the treatment used for storage in tissue bank influences significantly the mechanical properties and behavior of the tissue. At the moment, only the first group of specimens was examined. The methodology presented in this paper proved suitable to complete the study.

  11. Spin-transport-phenomena in metals, semiconductors, and insulators

    Energy Technology Data Exchange (ETDEWEB)

    Althammer, Matthias Klaus

    2012-07-19

    Assuming that one could deterministically inject, transport, manipulate, store and detect spin information in solid state devices, the well-established concepts of charge-based electronics could be transferred to the spin realm. This thesis explores the injection, transport, manipulation and storage of spin information in metallic conductors, semiconductors, as well as electrical insulators. On the one hand, we explore the spin-dependent properties of semiconducting zinc oxide thin films deposited via laser-molecular beam epitaxy (laser-MBE). After demonstrating that the zinc oxide films fabricated during this thesis have excellent structural, electrical, and optical properties, we investigate the spin-related properties by optical pump/probe, electrical injection/optical detection, and all electrical spin valve-based experiments. The two key results from these experiments are: (i) Long-lived spin states with spin dephasing times of 10 ns at 10 K related to donor bound excitons can be optically addressed. (ii) The spin dephasing times relevant for electrical transport-based experiments are {<=} 2 ns at 10 K and are correlated with structural quality. On the other hand we focus on two topics of current scientific interest: the comparison of the magnetoresistance to the magnetothermopower of conducting ferromagnets, and the investigation of pure spin currents generated in ferromagnetic insulator/normal metal hybrid structures. We investigate the magnetoresistance and magnetothermopower of gallium manganese arsenide and Heusler thin films as a function of external magnetic field orientation. Using a series expansion of the resistivity and Seebeck tensors and the inherent symmetry of the sample's crystal structure, we show that a full quantitative extraction of the transport tensors from such experiments is possible. Regarding the spin currents in ferromagnetic insulator/normal metal hybrid structures we studied the spin mixing conductance in yttrium iron garnet

  12. Dynamic nuclear spin polarization

    Energy Technology Data Exchange (ETDEWEB)

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

    1996-11-01

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

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

    Science.gov (United States)

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

    2017-10-01

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

  14. LOFT pressurizer safety: relief valve reliability

    Energy Technology Data Exchange (ETDEWEB)

    Brown, E.S.

    1978-01-18

    The LOFT pressurizer self-actuating safety-relief valves are constructed to the present state-of-the-art and should have reliability equivalent to the valves in use on PWR plants in the U.S. There have been no NRC incident reports on valve failures to lift that would challenge the Technical Specification Safety Limit. Fourteen valves have been reported as lifting a few percentage points outside the +-1% Tech. Spec. surveillance tolerance (9 valves tested over and 5 valves tested under specification). There have been no incident reports on failures to reseat. The LOFT surveillance program for assuring reliability is equivalent to nuclear industry practice.

  15. LOFT pressurizer safety: relief valve reliability

    International Nuclear Information System (INIS)

    Brown, E.S.

    1978-01-01

    The LOFT pressurizer self-actuating safety-relief valves are constructed to the present state-of-the-art and should have reliability equivalent to the valves in use on PWR plants in the U.S. There have been no NRC incident reports on valve failures to lift that would challenge the Technical Specification Safety Limit. Fourteen valves have been reported as lifting a few percentage points outside the +-1% Tech. Spec. surveillance tolerance (9 valves tested over and 5 valves tested under specification). There have been no incident reports on failures to reseat. The LOFT surveillance program for assuring reliability is equivalent to nuclear industry practice

  16. Emergency Valve-in-Valve Transcatheter Aortic Valve Implantation for the Treatment of Acute Stentless Bioprosthetic Aortic Insufficiency and Cardiogenic Shock

    Directory of Open Access Journals (Sweden)

    Ivan D. Hanson

    2018-01-01

    Full Text Available Bioprosthetic aortic valve degeneration may present as acute, severe aortic regurgitation and cardiogenic shock. Such patients may be unsuitable for emergency valve replacement surgery due to excessive risk of operative mortality but could be treatable with transfemoral valve-in-valve transcatheter aortic valve implantation (TAVI. There is a paucity of data regarding the feasibility of valve-in-valve TAVI in patients presenting with cardiogenic shock due to acute aortic insufficiency from stentless bioprosthetic valve degeneration. We present one such case, highlighting the unique aspects of valve-in-valve TAVI for this challenging patient subset.

  17. Spin at Lausanne

    International Nuclear Information System (INIS)

    Anon.

    1980-01-01

    From 25 September to 1 October, some 150 spin enthusiasts gathered in Lausanne for the 1980 International Symposium on High Energy Physics with Polarized Beams and Polarized Targets. The programme was densely packed, covering physics interests with spin as well as the accelerator and target techniques which make spin physics possible

  18. Transport theory for femtosecond laser-induced spin-transfer torques

    Science.gov (United States)

    Baláž, Pavel; Žonda, Martin; Carva, Karel; Maldonado, Pablo; Oppeneer, Peter M.

    2018-03-01

    Ultrafast demagnetization of magnetic layers pumped by a femtosecond laser pulse is accompanied by a nonthermal spin-polarized current of hot electrons. These spin currents are studied here theoretically in a spin valve with noncollinear magnetizations. To this end, we introduce an extended model of superdiffusive spin transport that enables the treatment of noncollinear magnetic configurations, and apply it to the perpendicular spin valve geometry. We show how spin-transfer torques arise due to this mechanism and calculate their action on the magnetization present, as well as how the latter depends on the thicknesses of the layers and other transport parameters. We demonstrate that there exists a certain optimum thickness of the out-of-plane magnetized spin-current polarizer such that the torque acting on the second magnetic layer is maximal. Moreover, we study the magnetization dynamics excited by the superdiffusive spin-transfer torque due to the flow of hot electrons employing the Landau–Lifshitz–Gilbert equation. Thereby we show that a femtosecond laser pulse applied to one magnetic layer can excite small-angle precessions of the magnetization in the second magnetic layer. We compare our calculations with recent experimental results.

  19. Transport theory for femtosecond laser-induced spin-transfer torques.

    Science.gov (United States)

    Baláž, Pavel; Žonda, Martin; Carva, Karel; Maldonado, Pablo; Oppeneer, Peter M

    2018-03-21

    Ultrafast demagnetization of magnetic layers pumped by a femtosecond laser pulse is accompanied by a nonthermal spin-polarized current of hot electrons. These spin currents are studied here theoretically in a spin valve with noncollinear magnetizations. To this end, we introduce an extended model of superdiffusive spin transport that enables the treatment of noncollinear magnetic configurations, and apply it to the perpendicular spin valve geometry. We show how spin-transfer torques arise due to this mechanism and calculate their action on the magnetization present, as well as how the latter depends on the thicknesses of the layers and other transport parameters. We demonstrate that there exists a certain optimum thickness of the out-of-plane magnetized spin-current polarizer such that the torque acting on the second magnetic layer is maximal. Moreover, we study the magnetization dynamics excited by the superdiffusive spin-transfer torque due to the flow of hot electrons employing the Landau-Lifshitz-Gilbert equation. Thereby we show that a femtosecond laser pulse applied to one magnetic layer can excite small-angle precessions of the magnetization in the second magnetic layer. We compare our calculations with recent experimental results.

  20. Valve-less microdispenser

    Science.gov (United States)

    Tan, Ming Kwang; Xin, Wang; Lee, Weng Kent

    2015-11-01

    We demonstrate the concept of valve-less microdispenser to control of the liquid flow through the nozzle, by incorporating Leidenfrost effect into the nozzle design. When the nozzle is heated above the Leidenfrost point, a thin vapor layer is formed between the heated substrate and the liquid above it. The vapor pressure due to the presence of the vapor layer, together with the effect of surface tension of the liquid, exerted on the liquid-vapor interface, preventing the flow of the liquid through the nozzle. The experimental results shown that nozzles of diameter 400 micrometer and below, the nozzle temperature of 150 degree Celsius is sufficient to prevent the continuous flowing of the liquid, whereas for nozzles of diameter between 400 to 500 micrometer, the nozzle temperature needs to increase to 160 degree Celsius in order to prevent the continuous flowing of the liquid. When nozzle temperature below 160 degree Celsius, intermittent ejection of microdroplets, whose size is a function of nozzle temperature, is observed.

  1. Spin-glass behavior and incommensurate modulation in high-pressure perovskite BiCr0.5Ni0.5O3.

    Science.gov (United States)

    Arévalo-López, Ángel M; Dos Santos-García, Antonio J; Levin, Jessica R; Attfield, J Paul; Alario-Franco, Miguel A

    2015-02-02

    The BiCr(0.5)Ni(0.5)O(3) perovskite has been obtained at high pressure. Neutron and synchrotron diffraction data show a Pnma orthorhombic structure with a = 5.5947(1) Å, b = 7.7613(1) Å, and c = 5.3882(1) Å at 300 K and random B-site Cr/Ni distribution. Electron diffraction reveals an incommensurate modulation parallel to the b axis. The combination of either Cr-O-Ni (J > 0) or Cr-O-Cr/Ni-O-Ni (J neutron diffraction, and muon-spin-relaxation measurements demonstrate that variations in the local bonding and charge states contribute to the magnetic frustration.

  2. Long-time behavior of the momentum distribution during the sudden expansion of a spin-imbalanced Fermi gas in one dimension.

    Science.gov (United States)

    Bolech, C J; Heidrich-Meisner, F; Langer, S; McCulloch, I P; Orso, G; Rigol, M

    2012-09-14

    We study the sudden expansion of spin-imbalanced ultracold lattice fermions with attractive interactions in one dimension after turning off the longitudinal confining potential. We show that the momentum distribution functions of majority and minority fermions quickly approach stationary values due to a quantum distillation mechanism that results in a spatial separation of pairs and majority fermions. As a consequence, Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) correlations are lost during the expansion. Furthermore, we argue that the shape of the stationary momentum distribution functions can be understood by relating them to the integrals of motion in this integrable quantum system. We discuss our results in the context of proposals to observe FFLO correlations, related to recent experiments by Liao et al., Nature (London) 467, 567 (2010).

  3. Spin physics in semiconductors

    CERN Document Server

    2017-01-01

    This book offers an extensive introduction to the extremely rich and intriguing field of spin-related phenomena in semiconductors. In this second edition, all chapters have been updated to include the latest experimental and theoretical research. Furthermore, it covers the entire field: bulk semiconductors, two-dimensional semiconductor structures, quantum dots, optical and electric effects, spin-related effects, electron-nuclei spin interactions, Spin Hall effect, spin torques, etc. Thanks to its self-contained style, the book is ideally suited for graduate students and researchers new to the field.

  4. Mechanical heart valve cavitation in patients with bileaflet valves.

    Science.gov (United States)

    Johansen, Peter; Andersen, Tina S; Hasenkam, J Michael; Nygaard, Hans; Paulsen, Peter K

    2014-01-01

    Today, the quality of mechanical heart valves is quite high, and implantation has become a routine clinical procedure with a low operative mortality (mechanism found to be a possible contributor to these adverse effects is cavitation. In vitro, cavitation has been directly demonstrated by visualization and indirectly in vivo by registering of high frequency pressure fluctuations (HFPF). Tilting disc valves are thought of having higher cavitation potential than bileaflet valves due to higher closing velocities. However, the thromboembolic potential seems to be the same. Further studies are therefore needed to investigate the cavitation potential of bileaflet valves in vivo. The post processing of HFPF have shown difficulties when applied on bileaflet vavles due to asynchronous closure of the two leaflets. The aim of this study was therefore to isolate the pressure signature from each leaflet closure and perform cavitation analyses on each component. Six patients were included in the study (St. Jude Medical (n=3) and CarboMedics (n=3); all aortic bileaflet mechanical heart valves). HFPFs were recorded intraoperatively through a hydrophone at the aortic root. The pressure signature relating to the first and second leaflet closure was isolated and cavitation parameters were calculated (RMS after 50 kHz highpass filtering and signal energy). Data were averaged over 30 heart cycles. For all patients both the RMS value and signal energy of the second leaflet closure were higher than for the first leaflet closure. This indicates that the second leaflet closure is most prone to cause cavitation. Therefore, quantifying cavitation based on the HFPF related to the second leaflet closure may suggest that the cavitation potential for bileaflet valves in vivo may be higher than previous studies have suggested.

  5. Heisenberg spin glass experiments and the chiral ordering scenario

    International Nuclear Information System (INIS)

    Campbell, Ian A.; Petit, Dorothee C.M.C.

    2010-01-01

    An overview is given of experimental data on Heisenberg spin glass materials so as to make detailed comparisons with numerical results on model Heisenberg spin glasses, with particular reference to the chiral driven ordering transition scenario due to Kawamura and collaborators. On weak anisotropy systems, experiments show critical exponents which are very similar to those estimated numerically for the model Heisenberg chiral ordering transition but which are quite different from those at Ising spin glass transitions. Again on weak anisotropy Heisenberg spin glasses, experimental torque data show well defined in-field transverse ordering transitions up to strong applied fields, in contrast to Ising spin glasses where fields destroy ordering. When samples with stronger anisotropies are studied, critical and in-field behavior tend progressively towards the Ising limit. It can be concluded that the essential physics of laboratory Heisenberg spin glasses mirrors that of model Heisenberg spin glasses, where chiral ordering has been demonstrated numerically. (author)

  6. Development of mechanical heart valves - an inspiring tale

    Directory of Open Access Journals (Sweden)

    P Rajashekar

    2015-01-01

    Full Text Available The historical evolution of the prosthetic heart valves from the first attempts with the Hufnagel′s valve in the treatment of the aortic insufficiency to the Starr-Edwards′ ball valve and later the tilting disc valves (Bjork-Shiley etc., and finally the bileaflet valves (St. Jude are discussed. The Indian contribution with Chitra valve is also described.

  7. Current Challenges in Translating Tissue-Engineered Heart Valves

    NARCIS (Netherlands)

    Stassen, O M J A; Muylaert, D E P; Bouten, Carlijn V. C.; Hjortnaes, J; Hjortnaes, J

    OPINION STATEMENT: Heart valve disease is a major health burden, treated by either valve repair or valve replacement, depending on the affected valve. Nearly 300,000 valve replacements are performed worldwide per year. Valve replacement is lifesaving, but not without complications. The in situ

  8. A retrospective analysis of mitral valve pathology in the setting of bicuspid aortic valves

    Science.gov (United States)

    van Rensburg, Annari; Doubell, Anton

    2017-01-01

    The therapeutic implications of bicuspid aortic valve associations have come under scrutiny in the transcatheter aortic valve implantation era. We evaluate the spectrum of mitral valve disease in patients with bicuspid aortic valves to determine the need for closer echocardiographic scrutiny/follow-up of the mitral valve. A retrospective analysis of echocardiograms done at a referral hospital over five years was conducted in patients with bicuspid aortic valves with special attention to congenital abnormalities of the mitral valve. One hundred and forty patients with a bicuspid aortic valve were included. A congenital mitral valve abnormality was present in eight (5.7%, P = 0.01) with a parachute mitral valve in four (2.8%), an accessory mitral valve leaflet in one (0.7%), mitral valve prolapse in one, a cleft in one and the novel finding of a trileaflet mitral valve in one. Minor abnormalities included an elongated anterior mitral valve leaflet (P abnormal papillary muscles (P = 0.002) and an additional chord or tendon in the left ventricle cavity (P = 0.007). Mitral valve abnormalities occur more commonly in patients with bicuspid aortic valves than matched healthy individuals. The study confirms that abnormalities in these patients extend beyond the aorta. These abnormalities did not have a significant functional effect. PMID:28515127

  9. Intro to Valve Guide Reconditioning. Automotive Mechanics. Valves. Instructor's Guide [and] Student Guide.

    Science.gov (United States)

    Horner, W.

    This instructional package, one in a series of individualized instructional units on tools and techniques for repairing worn valve guides in motor vehicles, provides practical experience for students in working on cylinder heads. Covered in the module are reaming valve guides that are oversized to match a new oversized valve, reaming valve guides…

  10. Transcatheter valve-in-valve implantation due to severe aortic regurgitation in a degenerated aortic homograft

    DEFF Research Database (Denmark)

    Olsen, Lene Kjaer; Engstrøm, Thomas; Søndergaard, Lars

    2009-01-01

    a successful valve-in-valve implantation of a CoreValve aortic valve prosthesis through the right subclavian artery in a case of severe aortic regurgitation within a degenerated aortic homograft. The case exemplifies the possibilities of expanding the indications for TAVI, as well as other vascular access...

  11. The nordic aortic valve intervention (NOTION) trial comparing transcatheter versus surgical valve implantation

    DEFF Research Database (Denmark)

    Thyregod, Hans Gustav; Søndergaard, Lars; Ihlemann, Nikolaj

    2013-01-01

    Degenerative aortic valve (AV) stenosis is the most prevalent heart valve disease in the western world. Surgical aortic valve replacement (SAVR) has until recently been the standard of treatment for patients with severe AV stenosis. Whether transcatheter aortic valve implantation (TAVI) can...

  12. Early clinical outcome of aortic transcatheter valve-in-valve implantation in the Nordic countries

    DEFF Research Database (Denmark)

    Ihlberg, Leo; Nissen, Henrik Hoffmann; Nielsen, Niels Erik

    2013-01-01

    Transcatheter valve-in-valve implantation has emerged as an option, in addition to reoperative surgical aortic valve replacement, to treat failed biologic heart valve substitutes. However, the clinical experience with this approach is still limited. We report the comprehensive experience...

  13. Infective Endocarditis of the Aortic Valve with Anterior Mitral Valve Leaflet Aneurysm

    NARCIS (Netherlands)

    Tomsic, Anton; Li, Wilson W. L.; van Paridon, Marieke; Bindraban, Navin R.; de Mol, Bas A. J. M.

    2016-01-01

    Mitral valve leaflet aneurysm is a rare and potentially devastating complication of aortic valve endocarditis. We report the case of a 48-year-old man who had endocarditis of the native aortic valve and a concomitant aneurysm of the anterior mitral valve leaflet. Severe mitral regurgitation occurred

  14. Bistable fluidic valve is electrically switched

    Science.gov (United States)

    Fiet, O.; Salvinski, R. J.

    1970-01-01

    Bistable control valve is selectively switched by direct application of an electrical field to divert fluid from one output channel to another. Valve is inexpensive, has no moving parts, and operates on fluids which are relatively poor electrical conductors.

  15. 49 CFR 195.260 - Valves: Location.

    Science.gov (United States)

    2010-10-01

    ... PIPELINE Construction § 195.260 Valves: Location. A valve must be installed at each of the following... that is more than 100 feet (30 meters) wide from high-water mark to high-water mark unless the...

  16. Passive Airbag Vent Control Valve Study

    National Research Council Canada - National Science Library

    Rosato, Nicholas

    1999-01-01

    .... The venting candidates studied consisted of two different linear spring check valve designs, a magnetostatic check valve design, along with two precision release blowout vents configured using a four...

  17. Stem clutch for motor driven valve

    Science.gov (United States)

    Blum, D. E.; Wiltens, J. F.

    1972-01-01

    Development of mechanical device to reduce possibility of damage to motor driven needle valve is discussed. Mechanical clutch is employed to allow slippage when needle valve reaches limit of travel. Operation of system for various conditions is described.

  18. Cells for tissue engineering of cardiac valves.

    Science.gov (United States)

    Jana, Soumen; Tranquillo, Robert T; Lerman, Amir

    2016-10-01

    Heart valve tissue engineering is a promising alternative to prostheses for the replacement of diseased or damaged heart valves, because tissue-engineered valves have the ability to remodel, regenerate and grow. To engineer heart valves, cells are harvested, seeded onto or into a three-dimensional (3D) matrix platform to generate a tissue-engineered construct in vitro, and then implanted into a patient's body. Successful engineering of heart valves requires a thorough understanding of the different types of cells that can be used to obtain the essential phenotypes that are expressed in native heart valves. This article reviews different cell types that have been used in heart valve engineering, cell sources for harvesting, phenotypic expression in constructs and suitability in heart valve tissue engineering. Natural and synthetic biomaterials that have been applied as scaffold systems or cell-delivery platforms are discussed with each cell type. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

  19. Comparative study between CardiaMed valves (freely floating valve leaflets versus St. Jude Medical (fixed valve leaflets in mitral valve replacement surgery

    Directory of Open Access Journals (Sweden)

    Mostafa Ahmed

    2017-09-01

    Conclusions: CardiaMed freely floating leaflet prostheses showed good hemodynamic characteristics. The prosthesis adequately corrects hemodynamics and is safe and no worse than the St. Jude Medical valve in the mitral valve position.

  20. Honeycomb artificial spin ice at low temperatures

    Science.gov (United States)

    Zeissler, Katharina; Chadha, Megha; Cohen, Lesley; Branford, Will

    2015-03-01

    Artificial spin ice is a macroscopic playground for magnetically frustrated systems. It consists of a geometrically ordered but magnetically frustrated arrangement of ferromagnetic macros spins, e.g. an arrangement of single domain ferromagnetic nanowires on a honeycomb lattice. Permalloy and cobalt which have critical temperature scales far above 290 K, are commonly used in the construction of such systems. Previous measurements have shown unusual features in the magnetotransport signature of cobalt honeycomb artificial spin ice at temperatures below 50 K which are due to changes in the artificial spin ice's magnetic reversal. In that case, the artificial spin ice bars were 1 micron long, 100 nm wide and 20 nm thick. Here we explore the low temperature magnetic behavior of honeycomb artificial spin ice structures with a variety of bar dimensions, indirectly via electrical transport, as well as, directly using low temperature magnetic imaging techniques. We discuss the extent to which this change in the magnetic reversal at low temperatures is generic to the honeycomb artificial spin ice geometry and whether the bar dimensions have an influence on its onset temperature. The EPSRC (Grant No. EP/G004765/1; Grant No. EP/L504786/1) and the Leverhulme Trust (Grant No. RPG 2012-692) funded this scientific work.