Science.gov

Sample records for spin dependent pick-up

  1. Picking up the pieces.

    PubMed

    Metcalfe, Sarah

    2014-11-01

    The idea of managing patients who have experienced unimaginable horror or suffering can be very daunting. As general practitioners (GPs) we are often the first port of call for people after a significant event or, alternatively, become involved when the patient emerges from the tertiary care system. Part of our role is to help 'pick up the pieces', whether the effects have been predominantly physical, psychological or a combination of both. Sometimes the person before you is fragmented, the pieces so fragile and far flung, that putting them back together seems an impossible task. PMID:25551866

  2. Pick-up ions at Pluto

    NASA Astrophysics Data System (ADS)

    Kecskemety, K.; Cravens, T. E.

    1993-04-01

    Methane molecules escaping from Pluto's atmosphere are ionized, and the resulting ions are picked up by the solar wind. The mass loading associated with this ion pick-up can produce a cometlike interaction of the solar wind with Pluto. Heavy ion gyroradii are as large as a half million km in the weak interplanetary magnetic field that exists at 30 AU, which is about an order of magnitude larger than the size of the 'interaction region'. We have calculated velocity space distributions of pick-up ions using numerically determined ion trajectories. The predicted pick-up ion fluxes are high enough to be detectable by standard charged particle detectors as far upstream of Pluto as 10 exp 6 km.

  3. Pick-up ions at Pluto

    NASA Technical Reports Server (NTRS)

    Kecskemety, K.; Cravens, T. E.

    1993-01-01

    Methane molecules escaping from Pluto's atmosphere are ionized, and the resulting ions are picked up by the solar wind. The mass loading associated with this ion pick-up can produce a cometlike interaction of the solar wind with Pluto. Heavy ion gyroradii are as large as a half million km in the weak interplanetary magnetic field that exists at 30 AU, which is about an order of magnitude larger than the size of the 'interaction region'. We have calculated velocity space distributions of pick-up ions using numerically determined ion trajectories. The predicted pick-up ion fluxes are high enough to be detectable by standard charged particle detectors as far upstream of Pluto as 10 exp 6 km.

  4. Pick-Up and Kicker Electrodes for the CR

    SciTech Connect

    Peschke, C.; Nolden, F.; Thorndahl, L.

    2006-03-20

    The collector ring (CR) of the proposed GSI project FAIR includes a fast stochastic cooling system for exotic nuclei and antiprotons. To reach a good signal to noise ratio of the pick-up even with a low number of particles, a novel pick-up and kicker electrode system based on slotlines is presented. The sensitivity and noise properties of electrode models are calculated. These are compared with other types of electrodes. Different options for signal processing and layout of a pick-up or kicker with many electrodes for different beam velocities are discussed.

  5. Slow-wave synchronous pick-up and kicker

    SciTech Connect

    DiMassa, G.

    1988-01-01

    Slow-wave synchronous pick-up (PU) and Kicker (K) are proposed for the stochastic cooling of bunched beams in RHIC. A corrugated waveguide is used to support a slow wave that is synchronous with the beam.

  6. Pick-up and drop transfer of diamond nanosheets.

    PubMed

    Seshan, V; Island, J O; van Leeuwen, R; Venstra, W J; Schneider, B H; Janssens, S D; Haenen, K; Sudhölter, E J R; de Smet, L C P M; van der Zant, H S J; Steele, G A; Castellanos-Gomez, A

    2015-03-27

    Nanocrystalline diamond (NCD) is a promising material for electronic and mechanical micro- and nanodevices. Here we introduce a versatile pick-up and drop technique that makes it possible to investigate the electrical, optical and mechanical properties of as-grown NCD films. Using this technique, NCD nanosheets, as thin as 55 nm, can be picked-up from a growth substrate and positioned on another substrate. As a proof of concept, electronic devices and mechanical resonators are fabricated and their properties are characterized. In addition, the versatility of the method is further explored by transferring NCD nanosheets onto an optical fiber, which allows measuring its optical absorption. Finally, we show that NCD nanosheets can also be transferred onto two-dimensional crystals, such as MoS2, to fabricate heterostructures. Pick-up and drop transfer enables the fabrication of a variety of NCD-based devices without requiring lithography or wet processing. PMID:25742057

  7. "Micro-robots" pick up a glass bead

    SciTech Connect

    2011-01-01

    "Micro-robots", which are really collections of particles animated by magnetic fields, pick up a glass bead and move it around the screen. Each movement is precisely controlled. The "asters" were designed by Alexey Snezkho and Igor Aronson at Argonne National Laboratory. Video courtesy Nature Materials. Read the full story at http://go.usa.gov/KAT

  8. Strong Seasonal Variation of Martian Pick-up Ions and Reflected Ions

    NASA Astrophysics Data System (ADS)

    Yamauchi, Masatoshi; Hara, Takuya; Lundin, Rickard; Dubinin, Edik; Fedorov, Andrei; Frahm, Rudy; Futaana, Yoshifumi; Holmstrom, Mats; Barabash, Stas

    2015-04-01

    Mars Express (MEX) has operated for more than 10 years in the environment of Mars, providing solar wind ion observations by the Analyzer of Space Plasmas and Energetic Atoms (ASPERA-3) experiment's ion mass analyzer (IMA). In the region just outside the bow shock of Mars, IMA frequently observes ring-like distributed ions that include both pick-up ions of exospheric origin and reflected solar wind by the bow shock (Yamauchi et al., 2012). Although there are some restrictions imposed when using the IMA measurements, the length and quality of the IMA data is sufficient to statistically diagnose the seasonal and solar cycle variation. According to this long-term observation, the observation probability of the ring-like distributed ions outside the bow shock with certain intensity strongly depends on the season, i.e., the flux of these ions varies by nearly one order of magnitude every two years. A careful examination reveals that the variation of pick-up ions is locked to the distance from the Sun rather than the tilt angle of the rotation axis. This indicates that the planetary scale variation of solar UV has a drastic effect on the formation of the pick-up ions. Solar cycle effects are not distinguishable partly because they are masked by the seasonal effects and partly because MEX and IMA are optimum for such observations due to the instrumental limitations (FOV and energy range) and the lack of the magnetometer experiment on the Mars Express spacecraft

  9. Mixed messages from benthic microbial communities exposed to nanoparticulate and ionic silver: 3D structure picks up nano-specific effects, while EPS and traditional endpoints indicate a concentration-dependent impact of silver ions.

    PubMed

    Kroll, Alexandra; Matzke, Marianne; Rybicki, Marcus; Obert-Rauser, Patrick; Burkart, Corinna; Jurkschat, Kerstin; Verweij, Rudo; Sgier, Linn; Jungmann, Dirk; Backhaus, Thomas; Svendsen, Claus

    2016-03-01

    Silver nanoparticles (AgNP) are currently defined as emerging pollutants in surface water ecosystems. Whether the toxic effects of AgNP towards freshwater organisms are fully explainable by the release of ionic silver (Ag(+)) has not been conclusively elucidated. Long-term effects to benthic microbial communities (periphyton) that provide essential functions in stream ecosystems are unknown. The effects of exposure of periphyton to 2 and 20 μg/L Ag(+) (AgNO3) and AgNP (polyvinylpyrrolidone stabilised) were investigated in artificial indoor streams. The extracellular polymeric substances (EPS) and 3D biofilm structure, biomass, algae species, Ag concentrations in the water phase and bioassociated Ag were analysed. A strong decrease in total Ag was observed within 4 days. Bioassociated Ag was proportional to dissolved Ag indicating a rate limitation by diffusion across the diffusive boundary layer. Two micrograms per liter of AgNO3 or AgNP did not induce significant effects despite detectable bioassociation of Ag. The 20-μg/L AgNO3 affected green algae and diatom communities, biomass and the ratio of polysaccharides to proteins in EPS. The 20-μg/L AgNO3 and AgNP decreased biofilm volume to about 50 %, while the decrease of biomass was lower in 20 μg/L AgNP samples than the 20-μg/L AgNO3 indicating a compaction of the NP-exposed biofilms. Roughness coefficients were lower in 20 μg/L AgNP-treated samples. The more traditional endpoints (biomass and diversity) indicated silver ion concentration-dependent effects, while the newly introduced parameters (3D structure and EPS) indicated both silver ion concentration-dependent effects and effects related to the silver species applied. PMID:26122573

  10. Collision free pick up and movement of large objects

    SciTech Connect

    Drotning, W.D.; McKee, G.R.

    1998-08-01

    An automated system is described for the sensor-based precision docking and manipulation of large objects. Past work in the remote handling of large nuclear waste containers is extensible to the problems associated with the handling of large objects such as coils of flat steel in industry. Computer vision and ultrasonic proximity sensing as described here are used to control the precision docking of large objects, and swing damped motion control of overhead cranes is used to control the position of the pick up device and suspended payload during movement. Real-time sensor processing and model-based control are used to accurately position payloads.

  11. Lymph node pick up by separate stations: Option or necessity

    PubMed Central

    Morgagni, Paolo; Nanni, Oriana; Carretta, Elisa; Altini, Mattia; Saragoni, Luca; Falcini, Fabio; Garcea, Domenico

    2015-01-01

    AIM: To evaluate whether lymph node pick up by separate stations could be an indicator of patients submitted to appropriate surgical treatment. METHODS: One thousand two hundred and three consecutive gastric cancer patients submitted to radical resection in 7 general hospitals and for whom no information was available on the extension of lymphatic dissection were included in this retrospective study. RESULTS: Patients were divided into 2 groups: group A, where the stomach specimen was directly formalin-fixed and sent to the pathologist, and group B, where lymph nodes were picked up after surgery and fixed for separate stations. Sixty-two point three percent of group A patients showed < 16 retrieved lymph nodes compared to 19.4% of group B (P < 0.0001). Group B (separate stations) patients had significantly higher survival rates than those in group A [46.1 mo (95%CI: 36.5-56.0) vs 27.7 mo (95%CI: 21.3-31.9); P = 0.0001], independently of T or N stage. In multivariate analysis, group A also showed a higher risk of death than group B (HR = 1.24; 95%CI: 1.05-1.46). CONCLUSION: Separate lymphatic station dissection increases the number of retrieved nodes, leads to better tumor staging, and permits verification of the surgical dissection. The number of dissected stations could potentially be used as an index to evaluate the quality of treatment received. PMID:26015852

  12. Electric field by pick-up ions and electrons

    NASA Astrophysics Data System (ADS)

    Yamauchi, Masatoshi; Behar, Etienne; Nilsson, Hans; Holmstrom, Mats

    2016-04-01

    Observations by the Rosetta Plasma Consortium (RPC) showed increasing distortion of the solar wind flow as Rosetta approached the Sun, i.e., as the density of the newly born ions increased. This indicates azimuthal momentum transfer from the solar wind to the newly born ions because they are displaced by the solar wind electric field up to the ion gyroradius this the solar wind velocity, and conservation of the momentum (center of the mass) makes the solar wind to azimuthally shift by "counter action" of these pick-up ion motions. To understand this azimuthal momentum transfer, it is inevitable to model the electric field by the displacement of these pick-up ions and electrons. Although the E×B drift does not make charge separation when the scale size is larger than the ion gyroradius, ions and electrons move in the opposite direction to each other within the short distance up to a gyroradius, and therefore, the charge separation occurs. Thus, the newly-ionized neutrals (ion-electron pairs) create the electric field in the opposite (shielding) direction to the solar wind electric field (like the ionopause of Venus and Mars). However, such a newly induced "shielding" electric field will simultaneously be weakened by the solar wind electrons because the solar wind is also moved by this shielding electric field to reduce it, in the same way as the plasma oscillation (time scale of about 10‑4 s). In other words, the solar wind tries to maintain the solar wind electric field as far as the momentum allows. These two opposite effects must be combined when modelling the azimuthal electric field, and resultant ion/electron motions within a gyroradius, like the case for ROSETTA. Furthermore, the effect of the induced electric field by the pick-up ions and electrons will be different when the newly born ions are created as the result of photo-ionization and of the charge exchange because the electron effect is different between them. In the presentation, we model the

  13. Comparison of picked-up protons and water group ions upstream of Comet Halley's bow shock

    NASA Technical Reports Server (NTRS)

    Neugebauer, M.; Coates, A. J.; Neubauer, F. M.

    1990-01-01

    The similarities and differences between the picked-up cometary protons and water-group (WG) ions upstream of the bow shock of Comet Halley are examined using measurements obtained by the ion mass spectrometer and plasma analyzer experiments on board Giotto. It was found that the dependencies of the pitch angle and the energy diffusion rates of the cometary protons and WG ions on the ion densities and on the angle alpha between the interplanetary field and the solar wind velocity vector were very different. This finding could not be explained in terms of presently available theories and models.

  14. Stellar wind interaction and pick-up ion escape of the Kepler-11 "super-Earths"

    NASA Astrophysics Data System (ADS)

    Kislyakova, K. G.; Johnstone, C. P.; Odert, P.; Erkaev, N. V.; Lammer, H.; Lüftinger, T.; Holmström, M.; Khodachenko, M. L.; Güdel, M.

    2014-02-01

    Aims: We study the interactions between stellar winds and the extended hydrogen-dominated upper atmospheres of planets. We estimate the resulting escape of planetary pick-up ions from the five "super-Earths" in the compact Kepler-11 system and compare the escape rates with the efficiency of the thermal escape of neutral hydrogen atoms. Methods: Assuming the stellar wind of Kepler-11 is similar to the solar wind, we use a polytropic 1D hydrodynamic wind model to estimate the wind properties at the planetary orbits. We apply a direct simulation Monte Carlo model to model the hydrogen coronae and the stellar wind plasma interaction around Kepler-11b-f within a realistic expected heating efficiency range of 15-40%. The same model is used to estimate the ion pick-up escape from the XUV heated and hydrodynamically extended upper atmospheres of Kepler-11b-f. From the interaction model, we study the influence of possible magnetic moments, calculate the charge exchange and photoionization production rates of planetary ions, and estimate the loss rates of pick-up H+ ions for all five planets. We compare the results between the five "super-Earths" and the thermal escape rates of the neutral planetary hydrogen atoms. Results: Our results show that a huge neutral hydrogen corona is formed around the planet for all Kepler-11b-f exoplanets. The non-symmetric form of the corona changes from planet to planet and is defined mostly by radiation pressure and gravitational effects. Non-thermal escape rates of pick-up ionized hydrogen atoms for Kepler-11 "super-Earths" vary between ~6.4 × 1030 s-1 and ~4.1 × 1031 s-1, depending on the planet's orbital location and assumed heating efficiency. These values correspond to non-thermal mass loss rates of ~1.07 × 107 g s-1 and ~6.8 × 107 g s-1 respectively, which is a few percent of the thermal escape rates.

  15. Stellar wind interaction and pick-up ion escape of the Kepler-11 "super-Earths"

    NASA Astrophysics Data System (ADS)

    Kislyakova, Kristina; Johnstone, Colin; Odert, Petra; Erkaev, Nikolai; Lammer, Helmut; Lüftinger, Theresa; Holmstöm, Mats; Khodachenko, Maxim; Güdel, Manuel

    2014-05-01

    We present the results of modeling of the interactions between stellar wind and the extended hydrogen-dominated upper atmospheres of planets and estimate the resulting escape of planetary pick-up ions from the 5 «super-Earths» in the compact Kepler-11 system. We compare the escape rates with the efficiency of the thermal escape of neutral hydrogen atoms. Assuming the stellar wind of Kepler-11 is similar to the solar wind, we used a polytropic 1D hydrodynamic wind model to estimate the wind properties at the planetary orbits. We applied a Direct Simulation Monte Carlo Model to model the hydrogen coronae and the stellar wind plasma interaction around Kepler-11b-f planets within a realistic expected heating efficiency range of 15-40%. The same model was used to estimate the ion pick-up escape from the XUV heated and hydrodynamically extended upper atmospheres of Kepler-11b-f. Modeling clarifies the influence of possible magnetic moments on escape processes and allows to estimate the charge exchange and photoionization production rates of planetary ions as well as the loss rates of pick-up H+ ions for all five planets. This study presents also the comparison of the results between the five 'super-Earths' and in a more general sense also with the thermal escape rates of the neutral planetary hydrogen atoms. Our results show that for all Kepler-11b-f exoplanets, a huge neutral hydrogen corona is formed around the planet. The non-symmetric form of the corona changes from planet to planet and is defined mostly by radiation pressure, charge-exchange and gravitational effects. According to our estimates, nonthermal escape rates of pick-up ionized hydrogen atoms for Kepler-11 «super-Earths» vary between ~ 6.4 × 1030 s-1 and ~ 4.1 × 1031 s-1 depending on the planet's orbital location and assumed heating efficiency. These values correspond to non-thermal mass loss rates of ~ 1.07 × 107 g·s-1 and ~ 6.8 × 107 g·s-1 respectively, which is a few percent of the thermal

  16. Pick-Up Oxygen Ion Loss at Mars

    NASA Astrophysics Data System (ADS)

    Curry, S.; Liemohn, M. W.; Fang, X.; Ma, Y.

    2010-12-01

    The Mars pick-up ion transport model has been developed to study the relative role of kinetic processes on ion transport through near-Mars space. Mars does not have a strong, intrinsic dipole magnetic field and consequently the solar wind directly interacts with the dayside upper atmosphere causing particles to be stripped away from the atmosphere. The Mars Pickup Ion Model model calculates the detailed ion velocity space distribution (VSD) through a background magnetic and electric field model at specific locations. The main objective of this work is to robustly probe the sources of planetary ion escape from Mars' upper atmosphere. We explore three sources of ions: photoionization, charge exchange collisions, and impact ionization. Our results illustrate distinct differences in the velocity space distributions from the different source mechanisms, which can be used to decipher Mars ion observations according to their source population. Because the VSDs are non-Maxwellian and reveal asymmetirc, non-gyrotropic features, our simulation can uniquely investigate these distributions without using the Maxwellian assumptions of current MHD models. Our results help to further examine quantify the physical processes and source locations for specific VSD fine-structure features, and to put this into the context of real and virtual observations of escaping planetary ions.

  17. Axial Vibration Characteristics Considering a Moving Pick-Up Unit for the Flexible Optical Disk System

    NASA Astrophysics Data System (ADS)

    Jo, Jun Hyeon; Rhim, Yoon Chul

    2011-09-01

    The axial vibration characteristics of the flexible optical disk are investigated experimentally considering the pick-up window and the geometry of a moving pick-up. The axial runout of the disk is measured by using a laser displacement sensor along the four perpendicular radial directions. Measurements are conducted with respect to the shapes of pick-up faces, which have different radius of curvatures, as well as to the positions of the moving pick-up. A flat stabilizer with damping orifices is used in the experiment and the disk is rotated at 8,000, 10,000, and 12,000 rpm. The axial runouts and the displacements of the disk are measured for 6 different shaped pick-ups. The smallest axial runout of 10 µm, which is well manageable for the current optical disk drive technology, is obtained when we use the curved pick-up with curvatures of 400 mm in the direction of disk rotation.

  18. Anticipatory Adjustments to Being Picked Up in Infancy

    PubMed Central

    Reddy, Vasudevi; Markova, Gabriela; Wallot, Sebastian

    2013-01-01

    Anticipation of the actions of others is often used as a measure of action understanding in infancy. In contrast to studies of action understanding which set infants up as observers of actions directed elsewhere, in the present study we explored anticipatory postural adjustments made by infants to one of the most common adult actions directed to them – picking them up. We observed infant behavioural changes and recorded their postural shifts on a pressure mat in three phases: (i) a prior Chat phase, (ii) from the onset of Approach of the mother’s arms, and (iii) from the onset of Contact. In Study 1, eighteen 3-month-old infants showed systematic global postural changes during Approach and Contact, but not during Chat. There was an increase in specific adjustments of the arms (widening or raising) and legs (stiffening and extending or tucking up) during Approach and a decrease in thrashing/general movements during Contact. Shifts in postural stability were evident immediately after onset of Approach and more slowly after Contact, with no regular shifts during Chat. In Study 2 we followed ten infants at 2, 3 and 4 months of age. Anticipatory behavioural adjustments during Approach were present at all ages, but with greater differentiation from a prior Chat phase only at 3 and 4 months. Global postural shifts were also more phase differentiated in older infants. Moreover, there was significantly greater gaze to the mother’s hands during Approach at 4 months. Early anticipatory adjustments to being picked up suggest that infants’ awareness of actions directed to the self may occur earlier than of those directed elsewhere, and thus enable infants’ active participation in joint actions from early in life. PMID:23840324

  19. PAL-XFEL cavity beam position monitor pick-up design and beam test

    NASA Astrophysics Data System (ADS)

    Lee, Sojeong; Park, Young Jung; Kim, Changbum; Kim, Seung Hwan; Shin, Dong Cheol; Han, Jang-Hui; Ko, In Soo

    2016-08-01

    As an X-ray Free Electron Laser, PAL-XFEL is about to start beam commissioning. X-band cavity beam position monitor (BPM) is used in the PAL-XFEL undulator beam line. Prototypes of cavity BPM pick-up were designed and fabricated to test the RF characteristics. Also, the beam test of a cavity BPM pick-up was done in the Injector Test Facility (ITF). In the beam test, the raw signal properties of the cavity BPM pick-up were measured at a 200 pC bunch charge. According to the RF test and beam test results, the prototype cavity BPM pick-up design was confirmed to meet the requirements of the PAL-XFEL cavity BPM system.

  20. Not Just Being Lifted: Infants are Sensitive to Delay During a Pick-Up Routine.

    PubMed

    Fantasia, Valentina; Markova, Gabriela; Fasulo, Alessandra; Costall, Alan; Reddy, Vasudevi

    2015-01-01

    In the present study we observed whether infants show online adjustments to the mother's incipient action by looking at their sensitivity to changes as the pick-up unfolded. Twenty-three 3-month-old infants and their mothers were observed in the lab, where mothers were instructed (1) to pick-up their infants as they usually did (normal pick-up), and then (2) to delay the pick-up for 6 s after placing their hands on the infants' waist (delayed pick-up). In both Normal and Delayed conditions infant's body tension, affective displays and gaze shifts were coded during three phases: Approach, Contact, and Lift. Additionally, a measure of infants' head support in terms of head lag at the beginning and end of Lift was computed. Results showed that during normal pick-up infants tensed up their body during the Approach phase and increased their tension during contact, maintaining it through Lift; their head was also supported and in line with their body during Lift. When the pick-up was delayed, infants also tensed their body during Approach, yet this tension did not increase during the Contact phase and was significantly lower at Lift. Their head support was also lower in the Delayed condition and they shifted their gazes away from their mothers' face more often than in the Normal condition. These results suggest that infants are sensitive to changes of the timing of the pick-up sequence, which in turn may have affected their contribution to the interaction. PMID:26834674

  1. Not Just Being Lifted: Infants are Sensitive to Delay During a Pick-Up Routine

    PubMed Central

    Fantasia, Valentina; Markova, Gabriela; Fasulo, Alessandra; Costall, Alan; Reddy, Vasudevi

    2016-01-01

    In the present study we observed whether infants show online adjustments to the mother’s incipient action by looking at their sensitivity to changes as the pick-up unfolded. Twenty-three 3-month-old infants and their mothers were observed in the lab, where mothers were instructed (1) to pick-up their infants as they usually did (normal pick-up), and then (2) to delay the pick-up for 6 s after placing their hands on the infants’ waist (delayed pick-up). In both Normal and Delayed conditions infant’s body tension, affective displays and gaze shifts were coded during three phases: Approach, Contact, and Lift. Additionally, a measure of infants’ head support in terms of head lag at the beginning and end of Lift was computed. Results showed that during normal pick-up infants tensed up their body during the Approach phase and increased their tension during contact, maintaining it through Lift; their head was also supported and in line with their body during Lift. When the pick-up was delayed, infants also tensed their body during Approach, yet this tension did not increase during the Contact phase and was significantly lower at Lift. Their head support was also lower in the Delayed condition and they shifted their gazes away from their mothers’ face more often than in the Normal condition. These results suggest that infants are sensitive to changes of the timing of the pick-up sequence, which in turn may have affected their contribution to the interaction. PMID:26834674

  2. Seasonal Variation of Martian Pick-up Ions

    NASA Astrophysics Data System (ADS)

    Yamauchi, M.; Hara, T.; Lundin, R.; Dubinin, E.; Fedorov, A.; Sauvaud, J.-A.; Frahm, R.; Ramstad, R.; Futaana, Y.; Holmstrom, M.; Barabash, S.

    2015-10-01

    Statistics of Mars Express (MEX) ion mass analyser(IMA) data shows that ion production from exospheric hydrogen depends more on the Sun-Mars distance than the solar cycle phase or winter-summer hemispheric difference. This indicates that the EUV is not the only driver of the production of cold, exospheric-origin ions, and that the extension of the exosphere is strongly influenced by total irradiance that carries the majority of the solar energy to the Martian atmosphere.

  3. OBSERVATIONS OF ISOTROPIC INTERSTELLAR PICK-UP IONS AT 11 AND 17 AU FROM NEW HORIZONS

    SciTech Connect

    Randol, B. M.; McComas, D. J.; Elliott, H. A.; Gosling, J. T.; Schwadron, N. A.

    2012-08-10

    We report new observations by the Solar Wind Around Pluto (SWAP) instrument on the New Horizons spacecraft of an energy-per-charge (E/q) spectrum of interstellar pick-up ions (PUIs) from an unprecedented heliocentric distance of 17 AU. This E/q spectrum is fit well by an isotropic PUI distribution function combined with the detailed response of the SWAP instrument. In contrast to earlier work, we are also able to fit an isotropic PUI model to an E/q spectrum measured by SWAP at 11.3 AU by explicitly including two additional effects. These are (1) the E/q-dependent geometric factor of SWAP, which increases with decreasing E/q owing to effects associated with the post-acceleration of particles exiting the electrostatic analyzer portion of the instrument; and (2) a solar wind distribution, the model spectrum of which contributes significantly to the low-E/q part of the overall model owing, presumably, to secondary particles produced within the instrument.

  4. Skills and offensive tactics used in pick-up basketball games.

    PubMed

    Wang, Jianyu; Liu, Wenhao; Moffit, Jeffrey

    2009-10-01

    The purpose of this study was to describe skills and offensive tactics frequently used in pick-up basketball games. 65 participants were recruited from public basketball courts. An observational instrument was developed to analyze the performances of pick-up games. Participants' performances were videotaped and coded. Results indicated that the passing skills most frequently observed in the games were chest pass, overhead pass, and bounce pass. For dribbling, crossover dribble and change-of-pace dribble were frequently observed. Jump shot, set shot, and layup were also frequently used. The offensive tactics frequently used included drive, cut, and set screen. The study may be beneficial for helping young people prepare to play pick-up basketball games. PMID:20038001

  5. Detection of singly ionized energetic lunar pick-up ions upstream of earth's bow shock

    NASA Technical Reports Server (NTRS)

    Hilchenbach, M.; Hovestadt, D.; Klecker, B.; Moebius, E.

    1992-01-01

    Singly ionized suprathermal ions upstream of the earth's bow shock have been detected by using the time-of-flight spectrometer SULEICA on the AMPTE/IRM satellite. The data were collected between August and December 1985. The flux of the ions in the mass range between 23 and 37 amu is highly anisotropic towards the earth. The ions are observed with a period of about 29 days around new moon (+/- 3 days). The correlation of the energy of the ions with the solar wind speed and the interplanetary magnetic field orientation indicates the relation to the pick-up process. We conclude that the source of these pick-up ions is the moon. We argue that due to the impinging solar wind, atoms are sputtered off the lunar surface, ionized in the sputtering process or by ensuing photoionization and picked up by the solar wind.

  6. Detection of interstellar pick-up hydrogen in the solar system

    NASA Technical Reports Server (NTRS)

    Gloeckler, G.; Geiss, J.; Balsiger, H.; Fisk, L. A.; Galvin, A. B.; Ipavich, F. M.; Ogilvie, K. W.; Von Steiger, R.; Wilken, B.

    1993-01-01

    Interstellar hydrogen ionized primarily by the solar wind has been detected by the Solar Wind Ion Composition Spectrometer instrument on the Ulysses spacecraft at a distance of 4.8 AUs from the sun. This 'pick-up' hydrogen is identified by its distinct velocity distribution function, which drops abruptly at twice the local solar wind speed. From the measured fluxes of pick-up protons and singly charged helium, the number densities of neutral hydrogen and helium in the distant regions of the solar system are estimated to be 0.077 +/- 0.015 and 0.013 +/- 0.003 per cu cm, respectively.

  7. What Skills and Tactics Are Needed to Play Adult Pick-Up Basketball Games?

    ERIC Educational Resources Information Center

    Wang, Jianyu; Liu, Wenhao; Moffit, Jeffrey

    2010-01-01

    The purpose of this study was to examine skill levels and performance patterns of regular players of pick-up basketball games. By a survey, 65 participants were identified as regular players and participated in the study. An observational instrument used to analyze game performance of the participants was developed and both content and construct…

  8. 41 CFR 102-41.230 - May SASPs pick up or store donated drug paraphernalia in their distribution centers?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 41 Public Contracts and Property Management 3 2010-07-01 2010-07-01 false May SASPs pick up or store donated drug paraphernalia in their distribution centers? 102-41.230 Section 102-41.230 Public... SASPs pick up or store donated drug paraphernalia in their distribution centers? No, you must...

  9. 41 CFR 102-41.230 - May SASPs pick up or store donated drug paraphernalia in their distribution centers?

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 41 Public Contracts and Property Management 3 2013-07-01 2013-07-01 false May SASPs pick up or store donated drug paraphernalia in their distribution centers? 102-41.230 Section 102-41.230 Public... SASPs pick up or store donated drug paraphernalia in their distribution centers? No, you must...

  10. 41 CFR 102-41.230 - May SASPs pick up or store donated drug paraphernalia in their distribution centers?

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 41 Public Contracts and Property Management 3 2012-01-01 2012-01-01 false May SASPs pick up or store donated drug paraphernalia in their distribution centers? 102-41.230 Section 102-41.230 Public... SASPs pick up or store donated drug paraphernalia in their distribution centers? No, you must...

  11. 41 CFR 102-41.230 - May SASPs pick up or store donated drug paraphernalia in their distribution centers?

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 41 Public Contracts and Property Management 3 2011-01-01 2011-01-01 false May SASPs pick up or store donated drug paraphernalia in their distribution centers? 102-41.230 Section 102-41.230 Public... SASPs pick up or store donated drug paraphernalia in their distribution centers? No, you must...

  12. 41 CFR 102-41.230 - May SASPs pick up or store donated drug paraphernalia in their distribution centers?

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 41 Public Contracts and Property Management 3 2014-01-01 2014-01-01 false May SASPs pick up or store donated drug paraphernalia in their distribution centers? 102-41.230 Section 102-41.230 Public... SASPs pick up or store donated drug paraphernalia in their distribution centers? No, you must...

  13. Origin of the O(+) pick-up ions in the hehiosphere

    NASA Technical Reports Server (NTRS)

    Geiss, J.; Gloeckler, G.; Mall, U.

    1994-01-01

    The main sources for the ions in the interplanetary medium are the solar wind and the interstellar gas intruding into the heliosphere. Other sources, i.e. comets and planets can, however, contribute significantly locally. We present approximate expressions for deriving fluxes of pick-up ions originating from local neutral gas sources. Since the Io-torus is thought to be a relatively strong emitter of fast atoms, particular O and S, we used the O(+) data obtained by SWICS-Ulysses as a function of distance from Jupiter, both in and out-off the ecliptic plane in order to recognize a possible contribution of the Ionian source to the measured O(+). We find that - except for a very limited zone near the Jovian magnetosphere - the contribution of the Io-torus to the O(+) fluxes is minor, thus confirming our previous results on the pick-up H(+), He(+), N(+), O(+), and Ne(+) fluxes of interstellar origin.

  14. Design of a slim-type optical pick-up actuator using PMN-PT bimorphs

    NASA Astrophysics Data System (ADS)

    Ko, Byeongsik; Jung, Jung-Sub; Lee, Seung-Yop

    2006-12-01

    In this paper, a new optical pick-up actuator is proposed using PMN-PT (lead magnesium niobate-lead titanate) bimorphs for slim and small form factor optical disk drives. We suggest a novel structure enabling both tracking and focusing motions by changing the moving directions of the two parallel bimorphs. A cymbal-type flextensional structure is used as a displacement amplifier in order to meet the stroke requirement for optical pick-up actuators. We have performed the theoretical analyses for the bimorph actuator and displacement amplifier to predict the resultant force and displacement. The proposed actuator based on PMN-PT bimorphs and displacement amplifier has been manufactured, and the experimental results are compared to the analytical predictions. Experimental results agree well with the analytical predictions, showing that the cymbal structure amplifies the displacement twice and the focusing stroke is 52 µm at 10 V.

  15. Development of a tri-axial optical accelerometer using two DVD pick-up heads

    NASA Astrophysics Data System (ADS)

    Chu, Chih-Liang; Liao, Hong-Wei

    2008-12-01

    This study develops a low-cost, highly-sensitive, three-dimensional optical accelerometer in which the seismic mass comprises four rectangular blocks attached to the ends of a cross-form aluminum structure suspended on four thin steel strips. It is shown through ANSYS finite element (FE) simulations that the thin-strip suspension system restricts the seismic mass to just three degrees of motional freedom, namely one translational motion in the vertical direction and two rotational motions. These displacements are detected using two novel optical sensors based on commercial DVD optical pick-up heads. When the accelerometer experiences a vibrational force, the relative motion between the seismic mass and the base results in a change in the distribution of the reflected light spots on the surfaces of the four-quadrant photodetectors within the two pick-up heads. The resulting changes in the output voltage signals of the two pick-up heads are then used to calculate the corresponding acceleration of the base. The experimental results indicate that the resonance frequencies of the accelerometer in the X, Y and Z-axis directions are 130.51 Hz, 130.63 Hz and 130.90 Hz, respectively. Meanwhile, the sensitivities of the accelerometer in the X, Y and Z-axis directions are 21.28 V/g, 22.94 V/g and 22.75 V/g, respectively.

  16. Phase space diffusion and anisotropic pick-up ion distributions in the solar wind: an injection study

    NASA Astrophysics Data System (ADS)

    Chalov, S. V.; Fahr, H. J.

    1998-07-01

    Pick-up ions are produced all over the interplanetary space by ionization of neutral interstellar atoms. Over the last decade it was generally expected that after pick-up these ions quickly are isotropized in the velocity space comoving with the solar wind by strong pitch-angle scattering, though not assimilating to the thermodynamic state of solar wind ions. Recent studies of pick-up ion data obtained with plasma analyzers on AMPTE and ULYSSES have, however, revealed that during extended time periods substantially anisotropic distributions prevail. In this paper we want to improve the understanding of the evolutionary behaviour of pick-up ions in interplanetary phase space by an pick-up ion injection study taking into account all relevant diffusion terms describing pitch angle scattering, adiabatic cooling, drifts and energy diffusion. For particles injected at 1 AU the resulting distribution function stays substantially anisotropic up to distances of the order of 6 AU, unless increased isotropic turbulence levels and non-dissipative wave spectra are considered. The average bulk velocity of pick-up ions within this distance range is smaller than the solar wind velocity by factors of between 0.6 and 1.0. Pick-ups are shown to substantially become spread out from that solar wind parcel into which they were originally injected. Derivations of interstellar gas parameters using pick-up ion flux data can only be dared with additional care in the interpretation. As a consequence the location of the LISM helium cone axis and the LISM helium temperature are faked in the associated He(+) pick-up ion flux pattern.

  17. Energetic cometary ion flows in the pick-up region of Comet Giacobini-Zinner

    NASA Astrophysics Data System (ADS)

    Richardson, I. G.; Cowley, S. W. H.; Hynds, R. J.; Daly, P. W.; Sanderson, T. R.; Wenzel, K.-P.

    The properties of energetic water-group ions in the extended pick-up region surrounding comet Giacobini-Zinner are examined using three-dimensional 65-95-keV ion observations from the EPAS instrument on the ICE spacecraft. The ion distribution is inferred to retain a significant ring-beam anisotropy beyond about 400,000 km from the comet though effects of partial scattering are also present. Closer to the comet, the ions are found to be isotropic, or nearly so, in the solar wind frame due to increased scattering by MHD waves.

  18. Seasonal variation of Martian pick-up ions: Evidence of breathing exosphere

    NASA Astrophysics Data System (ADS)

    Yamauchi, M.; Hara, T.; Lundin, R.; Dubinin, E.; Fedorov, A.; Sauvaud, J.-A.; Frahm, R. A.; Ramstad, R.; Futaana, Y.; Holmstrom, M.; Barabash, S.

    2015-12-01

    The Mars Express (MEX) Ion Mass Analyser (IMA) found that the detection rate of the ring-like distribution of protons in the solar wind outside of the bow shock to be quite different between Mars orbital summer (around perihelion) and orbital winter (around aphelion) for four Martian years, while the north-south asymmetry is much smaller than the perihelion-aphelion difference. Further analyses using eight years of MEX/IMA solar wind data between 2005 and 2012 has revealed that the detection frequency of the pick-up ions originating from newly ionized exospheric hydrogen with certain flux strongly correlates with the Sun-Mars distance, which changes approximately every two years. Variation due to the solar cycle phase is not distinguishable partly because this effect is masked by the seasonal variation under the MEX capability of plasma measurements. This finding indicates that the variation in solar UV has a major effect on the formation of the pick-up ions, but this is not the only controlling factor.

  19. Loss of Water from Saturn's E-Ring Through Ion Pick-Up

    NASA Technical Reports Server (NTRS)

    Leisner, J. S.; Russell, C. T.; Dougherty, M. K.; Blanco-Cano, X.; Smith, E. J.; Tsurutani, B. T.

    2005-01-01

    One of the possible loss processes for Saturn s E-ring is ionization followed by acceleration by the electric field associated with the corotating magnetized plasma. It is possible to determine if this process is occurring by detecting electromagnetic waves at the gyrofrequency of water group ions. If the energy the particle gains in this pick-up process is sufficiently great, the picked up ions will generate ion cyclotron waves. Pioneer 11 and Voyager 1 both observed intervals of such waves associated with water group ions during their passes through Saturn s E-ring. Presently the magnetometer onboard the Cassini spacecraft is also seeing water group ion cyclotron oscillations. The Cassini data allow the spatial and temporal behavior of the waves to be mapped in ways not possible during the previous flybys. Analyses of these waves allow us to study the rate of mass loading and its latitudinal and local time variation. In conjunction with previous data, we can then determine the variation as the inclination of the ring to the Sun changes, in accordance with Saturn's seasons. These waves may be the clue to how Saturn powers its magnetosphere as the newly born ions could be the driver for the radial motion of the plasma and to how the E-ring may play the equivalent role to that of Io in the jovian magnetosphere.

  20. A contactless methodology of picking up micro-particles from rigid surfaces by acoustic radiation force

    NASA Astrophysics Data System (ADS)

    Jia, Kun; Yang, Keji; Fan, Zongwei; Ju, Bing-Feng

    2012-01-01

    Controlled movement and pick up of small object from a rigid surface is a primary challenge in many applications. In this paper, a contactless methodology of picking up micro-particles within deionized water from rigid surfaces by acoustic radiation force is presented. In order to achieve this, an acoustic radiation force was generated by 1.75 MHz transducers. A custom built setup facilitates the optimization of the sound field by varying the parameters such as sound source size and source position. The three-dimensional pressure distributions are measured and its relative sound field is also characterized accordingly. The standing wave field has been formed and it is mainly composed of two obliquely incident plane waves and their reflectors. We demonstrated the gripping and positioning of silica beads, SiO2, and aluminum micro-particles of 100 μm to 500 μm in size with this method using acoustic radiation force. The acoustic radiation force generated is well controlled, contactless, and in the tens of nano-Newton range which allowed us to manipulate relative big micro objects such as MEMS components as well as moving objects such as living cells. The proposed method provided an alternative form of contactless operating environment with scalable dimensions suitable for the manipulating of small objects. This permits high-throughput processing and reduction in time required for MEMS assembling, cell biomechanics, and biotechnology applications.

  1. Comparison of high altitude pick-up ions at Mars and Venus

    NASA Astrophysics Data System (ADS)

    Curry, S.; Luhmann, J. G.; Liemohn, M. W.; McEnulty, T.; Wang, Y.; Johnson, B. C.; Fang, X.; Ma, Y.

    2013-12-01

    In the absence of a dipole magnetic field, the atmospheres of Mars and Venus are especially susceptible to scavenging, but each planet has unique physical processes controlling their planetary ion distributions and atmospheric escape. We present a comparison of virtual detections of atmospheric pick-up ions at Mars and Venus using the combined results from magnetohydrodynamic and test particle simulations. Pick-up ions form when the solar wind directly interacts with the neutral atmosphere, causing the newly created ions to be accelerated by the background convective electric field. In these weakly magnetized environments, heavy ion species can have gyroradii on the planetary scale size. In order to address the role of individual ion motion, this study will provide velocity space distributions and individual particle traces for different species at each planet in multiple locations. It will also quantify the influence of the remnant crustal magnetic fields at Mars and stronger gravitational field at Venus. Additionally, results for different solar conditions will be presented and compared with data observations in order to better describe the evolution of atmospheric volatiles at Mars and Venus.

  2. Sealed vacuum canister and method for pick-up and containment of material

    DOEpatents

    Stoutenburgh, R.R.

    1996-02-13

    A vacuum canister is described including a housing with a sealed vacuum chamber having a predetermined vacuum pressure therein and a valve having a first port for fluid communication with the vacuum chamber and a second port for receiving at least one of a fluid and a particulate material. The valve is operable between a first position to seal the vacuum chamber and retain the predetermined vacuum within the vacuum chamber, and a second position to access the vacuum chamber to permit vacuum fluid flow through the valve from the second port into the vacuum chamber. The vacuum canister, in the operation to pick up material with the valve in the second position, when the second port is located adjacent at least one of a fluid and a particulate material, is effective to displace through the valve at least one of a fluid and a particulate material into the housing. The vacuum canister is desirably suitable for picking up and containing hazardous material such as radioactive material, in which the vacuum canister includes a protective layer of lead having a predetermined thickness that is effective to shield radiation emitted from the radioactive material contained within the housing. Advantageously, the vacuum canister includes a vacuum means for establishing a predetermined vacuum pressure within the vacuum chamber. 6 figs.

  3. Sealed vacuum canister and method for pick-up and containment of material

    DOEpatents

    Stoutenburgh, Roger R.

    1996-01-01

    A vacuum canister including a housing with a sealed vacuum chamber having a predetermined vacuum pressure therein and a valve having a first port for fluid communication with the vacuum chamber and a second port for receiving at least one of a fluid and a particulate material. The valve is operable between a first position to seal the vacuum chamber and retain the predetermined vacuum within the vacuum chamber, and a second position to access the vacuum chamber to permit vacuum fluid flow through the valve from the second port into the vacuum chamber. In operation of the vacuum canister to pick up material with the valve in the second position, when the second port is located adjacent at least one of a fluid and a particulate material, is effective to displace through the valve at least one of a fluid and a particulate material into the housing. The vacuum canister is desirably suitable for picking up and containing hazardous material such as radioactive material, in which the vacuum canister includes a protective layer of lead having a predetermined thickness that is effective to shield radiation emitted from the radioactive material contained within the housing. Advantageously, the vacuum canister includes a vacuum means for establishing a predetermined vacuum pressure within the vacuum chamber.

  4. Spin Hall and spin Nernst effects: temperature dependence

    NASA Astrophysics Data System (ADS)

    Dyrdal, Anna; Barnas, Jozef; Dugaev, Vitalii

    We have considered temperature dependence of spin Hall and spin Nernst effect in two-dimensional electron gas with spin-orbit interaction of Rashba type [arXiv:1510.03080]. In our considerations we have employed the approach based on the Matsubara Green functions. The formalism used in the case of electric field as a driving force was subsequently adopted to the situation of a spin current driven by a temperature gradient. To achieve this, we have used the concept of an auxiliary vector field. Such a description gives the possibility to consider all mechanisms leading to the spin Hall and spin Nernst effect on equal footing and also their behavior at finite temperatures. Both spin Hall and spin Nernst conductivities were calculated in the approximation including the vertex correction. The total spin Hall conductivity, including vertex correction, has been shown to vanish exactly in the whole temperature range. Thus, our results extend the earlier ones to an arbitrary temperatures. In turn, the total spin Nernst conductivity remains finite when the vertex corrections are included. Using the Ioffe-Regel localization criterion, we have also estimated the range of parameters where the calculated results for the spin Hall and spin Nernst conductivities are applicable.

  5. 41 CFR 102-36.135 - How much time do we have to pick up excess personal property that has been approved for transfer?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... to pick up excess personal property that has been approved for transfer? 102-36.135 Section 102-36... pick up excess personal property that has been approved for transfer? Normally, you have 15 calendar days from the date of GSA allocation to pick up the excess personal property for transfer, and you...

  6. Titan's atmospheric sputtering and neutral torus produced by magnetospheric and pick-up ions

    NASA Astrophysics Data System (ADS)

    Michael, M.; Smith, H. T.; Johnson, R. E.; Shematovich, V.; Leblanc, F.; Ledvina, S.; Luhmann, J. H.

    As Titan does not possess an intrinsic magnetic field, Kronian magnetospheric ions can penetrate Titan's exobase as can locally produced pick-up ions (e.g. Shematovich et al. 2003). This can cause atmospheric loss and heating of the exobase region. Penetration by slowed and deflected magnetospheric ions and by the pick-up ions is described here using a 3-D Monte Carlo model (Michael et al. 2004). The incident ions can lead to the production of fast neutrals that collide with other atmospheric neutrals producing the ejection of both atomic and molecular nitrogen and heating. The recently calculated dissociation cross sections of N2 are used in the present model (Tully and Johnson 2002). The incident flux of slowed magnetospheric N+ ions and pick-up C2H5+ ions is estimated from the work of Brecht et al. (2000). These ions, which have energies less than 1.2 keV, were shown to be more efficient in ejecting material from Titan's atmosphere than the non-deflected co-rotating ions used earlier (Lammer et al. 1993). The loss rates are comparable or larger than those produced by photo-dissociation. Exobse heating rates are given and the loss rates of N and N2 are then used as a source of nitrogen for the Titan neutral torus. If atmospheric sputtering is important this torus will contain both atomic and molecular nitrogen and, therefore, will provide a distributed source of both atomic and molecular nitrogen ions that will be readily detected by Cassini (Smith et al. 2004) Acknowledgment: This work is supported by NASA's Planetary Atmospheres Program and by the CAPS-Cassini Instrument. Brecht, S.H., J.G. Luhmann, and D.J. Larson, J. Geophys. Res., 105, 13119, 2000. Lammer, H., and S.J. Bauer,. Planet. Space Sci., 41, 657, 1993. Shematovich, V.I.,et al, J. Geophys. Res., 108, 5086, 10.1029/2003JE002096, 2003. Michael, M. et al., submitted, Icarus, 2004. Smith, H.T., et al., Titan Aeronomy Workshop, Paris, January 7-9, 2004. Tully, C., R.E. Johnson, J. Chem. Phys. 117, 6556

  7. On the inlet vortex system. [preventing jet engine damage caused by debris pick-up

    NASA Technical Reports Server (NTRS)

    Bissinger, N. C.; Braun, G. W.

    1974-01-01

    The flow field of a jet engine with an inlet vortex, which can pick up heavy debris from the ground and damage the engine, was simulated in a small water tunnel by means of the hydrogen bubble technique. It was found that the known engine inlet vortex is accompained by a vortex system, consisting of two inlet vortices (the ground based and the trailing one), secondary vortices, and ground vortices. Simulation of the ground effect by an inlet image proved that the inlet vortex feeds on free stream vorticity and can exist without the presence of a ground boundary layer. The structural form of the inlet vortex system was explained by a simple potential flow model, which showed the number, location, and the importance of the stagnation points. A retractable horizontal screen or an up-tilt of the engine is suggested as countermeasure against debris ingestion.

  8. A Monolithic Confocal Laser Coupler For an Optical Pick-up

    NASA Astrophysics Data System (ADS)

    Mizuno, Takeshi; Doi, Masato; YoshinobuHiguchi, YoshinobuHiguchi; Taniguchi, Takehiro; NobukataOkano, NobukataOkano; Nakao, Takashi; Narui, Hironobu; Matsuda, Osamu

    1999-04-01

    We propose a novel optical pick-up using a confocal lasercoupler for an optical disk player. The laser coupler consists of aglass window and a monolithic optical element which includes a laserdiode, 8 photodiodes, and a pyramid-shaped prism mirror positionednear the confocal plane which acts as a knife edge and aphoto-coupler. The focusing-error signal is detected using theconfocal knife edge (CKE) method and the tracking-error signal isdetected using the CKE push-pull method. The jitter of Compact Disc(CD) readout was 6.7 ns at a line velocity of 1.2 m/s, and the DCoffsets of the tracking-error signal were sppressed to less than 1/3for a radial lens displacement of ±400 µm compared to theconventional push-pull method.

  9. Fast pick up technique for high quality heterostructures of bilayer graphene and hexagonal boron nitride

    SciTech Connect

    Zomer, P. J. Guimarães, M. H. D.; Brant, J. C.; Tombros, N.; Wees, B. J. van

    2014-07-07

    We present a fast method to fabricate high quality heterostructure devices by picking up crystals of arbitrary sizes. Bilayer graphene is encapsulated with hexagonal boron nitride to demonstrate this approach, showing good electronic quality with mobilities ranging from 17 000 cm{sup 2} V{sup −1} s{sup −1} at room temperature to 49 000 cm{sup 2} V{sup −1} s{sup −1} at 4.2 K, and entering the quantum Hall regime below 0.5 T. This method provides a strong and useful tool for the fabrication of future high quality layered crystal devices.

  10. Escape of Nitrogen from Titan's atmosphere driven by magnetospheric and pick-up ions

    NASA Astrophysics Data System (ADS)

    Michael, M.; Liu, M.; Johnson, R. E.; Luhmann, J. G.; Shematovich, V. I.

    2003-05-01

    The nitrogen rich atmosphere of Titan is a significant source of the neutrals in Saturn's magnetosphere. As Titan does not posses an intrinsic magnetic field, energetic Kronian magnetospheric ions penetrate Titan's atmospheric exobase as can local pick-up ions (e.g. Shematovich et al. 2003). Penetration by energetic ions is described here using a 3-D Monte Carlo model. The incident ions can lead directly or indirectly to the production of fast neutrals that collide with other atmospheric neutrals. This leads to dissociation and the ejection of both atomic and molecular nitrogen. The recently calculated dissociation cross sections of N2 are used in the present model (Tully and Johnson 2002). The incident flux of slowed magentospheric N+ ions and pick-up C2H_5+ ions is estimated from the work of Brecht et al. (2000). These ions of energy less than 1.2 keV are shown to be more efficient in ejecting material from Titan's atmosphere than the higher energy corotating ions described in early estimates (Lammer et al. 1998). This incident flux of ions are used in the model and the results are used as a source of nitrogen for the Saturnian plasma torus. Acknowledgment: This work is supported by NASA:s Planetary Atmospheres Program. References Brecht, S.H., J.G. Luhmann, and D.J. Larson, J. Geophys. Res., 105, 13119, 2000. Lammer, H. W. Stumptner, and S.J. Bauer, Planet. Space Sci., 46, 1207, 1998. Shematovich, V.I., R.E. Johnson, M. Michael and J.G. Luhmann, J. Geophys. Res., in press, 2003. Tully, C., R.E. Johnson, J. Chem. Phys. 117, 6556-6561, 2002.

  11. Generalized Jeans' Escape of Pick-Up Ions in Quasi-Linear Relaxation

    NASA Technical Reports Server (NTRS)

    Moore, T. E.; Khazanov, G. V.

    2011-01-01

    Jeans escape is a well-validated formulation of upper atmospheric escape that we have generalized to estimate plasma escape from ionospheres. It involves the computation of the parts of particle velocity space that are unbound by the gravitational potential at the exobase, followed by a calculation of the flux carried by such unbound particles as they escape from the potential well. To generalize this approach for ions, we superposed an electrostatic ambipolar potential and a centrifugal potential, for motions across and along a divergent magnetic field. We then considered how the presence of superthermal electrons, produced by precipitating auroral primary electrons, controls the ambipolar potential. We also showed that the centrifugal potential plays a small role in controlling the mass escape flux from the terrestrial ionosphere. We then applied the transverse ion velocity distribution produced when ions, picked up by supersonic (i.e., auroral) ionospheric convection, relax via quasi-linear diffusion, as estimated for cometary comas [1]. The results provide a theoretical basis for observed ion escape response to electromagnetic and kinetic energy sources. They also suggest that super-sonic but sub-Alfvenic flow, with ion pick-up, is a unique and important regime of ion-neutral coupling, in which plasma wave-particle interactions are driven by ion-neutral collisions at densities for which the collision frequency falls near or below the gyro-frequency. As another possible illustration of this process, the heliopause ribbon discovered by the IBEX mission involves interactions between the solar wind ions and the interstellar neutral gas, in a regime that may be analogous [2].

  12. Endocrinological profile and follicular development in cyclic ewes subjected to repeated ovum pick-up.

    PubMed

    Valasi, I; Theodosiadou, E; Fthenakis, G C; Papanikolaou, T; Deligiannis, C; Kalogiannis, D; Chadio, S; Amiridis, G S

    2013-05-01

    Blood concentrations of progesterone, FSH and oestradiol in Karagouniko ewes subjected to laparoscopic ovum pick-up (OPU) at specific stages of induced oestrous cycle, were measured. Twenty-four cyclic ewes were randomly allocated into four equal groups (A, B, C and D). Oestrus was synchronized with progestagen intravaginal sponges and detected by teaser rams (oestrus: day 0). In group A, during the induced oestrous cycle, OPU was performed on days 4, 9 and 14 (sessions A1, A2 and A3, respectively). In group B and group D, OPU was performed once, on day 9 and 14, respectively. In group C (controls), endoscopic observation of follicular population was performed three times, as in group A. Starting at sponge removal, progesterone was measured in blood samples collected on 22 daily occasions and oestradiol in samples collected on 27 occasions collected at various time-points starting 2h before to 24h after OPU. Follicular populations did not differ among A1, A2, A3 or between C1, C2, C3 and A1, A2, A3 or A1, B, D, respectively. Oocytes of better quality (category '1' or '2') were collected at A3 session compared with A1 (P<0.05). Progesterone concentration and oestrous cycle length did not differ among groups. Decreased oestradiol concentrations followed by FSH increase were recorded 3-5h after OPU. The results confirm the regulatory role of oestradiol on FSH secretion. The quality of collected oocytes was improved in subsequent pick-up sessions in the oestrous cycle. Moreover, OPU at specific stages of the luteal phase of the cycle, even when applied repeatedly, do not affect the normal oestrous cycle length of ewes. PMID:23523233

  13. Influence of applied magnetic field strength and frequency response of pick-up coil on the magnetic barkhausen noise profile

    NASA Astrophysics Data System (ADS)

    Vashista, M.; Moorthy, V.

    2013-11-01

    The influence of applied magnetic field strength and frequency response of the pick-up coil on the shape of Magnetic Barkhausen Noise (MBN) profile have been studied. The low frequency MBN measurements have been carried out using 5 different MBN pick-up coils at two different ranges of applied magnetic field strengths on quenched and tempered (QT) and case-carburised and tempered (CT) 18CrNiMo7 steel bar samples. The MBN pick-up coils have been designed to obtain different frequency response such that the peak frequency response varies from ˜4 kHz to ˜32 kHz and the amplitude of low frequency signals decreases gradually. At lower applied magnetic field strength of ±14,000 A/m, all the pick-up coils produced a single peak MBN profile for both QT and CT sample. However, at higher applied magnetic field strength of ±22,000 A/m, the MBN profile showed two peaks for both QT and CT samples for pick-up coils with peak frequency response up to ˜17 kHz. Also, there is systematic reduction in peak 2 for QT sample and asymmetric reduction in the heights of peak 1 and peak 2 for CT sample with increase in peak frequency response of the pick-up coils. The decreasing sensitivity of pick-up coils with increasing peak frequency response to MBN signal generation is indicated by the gradual reduction in width of MBN profile and height of peak 2 in the QT sample. The drastic reduction in peak 1 as compared to peak 2 in the CT sample shows the effect of decreasing low frequency response of the pick-up coils on lowering skin-depth of MBN signal detection. This study clearly suggests that it is essential to optimise both maximum applied magnetic field strength and frequency response of the MBN pick-up coil for maximising the shape of the MBN profile for appropriate correlation with the magnetisation process and hence the material properties.

  14. Solar cycle variation of interstellar neutral He, Ne, O density and pick-up ions along the Earth's orbit

    NASA Astrophysics Data System (ADS)

    Sokół, Justyna M.; Bzowski, Maciej; Kubiak, Marzena A.; Möbius, Eberhard

    2016-06-01

    We simulated the modulation of the interstellar neutral (ISN) He, Ne, and O density and pick-up ion (PUI) production rate and count rate along the Earth's orbit over the solar cycle (SC) from 2002 to 2013 to verify if SC-related effects may modify the inferred ecliptic longitude of the ISN inflow direction. We adopted the classical PUI model with isotropic distribution function and adiabatic cooling, modified by time- and heliolatitude-dependent ionization rates and non-zero injection speed of PUIs. We found that the ionization losses have a noticeable effect on the derivation of the ISN inflow longitude based on the Gaussian fit to the crescent and cone peak locations. We conclude that the non-zero radial velocity of the ISN flow and the energy range of the PUI distribution function that is accumulated are of importance for a precise reproduction of the PUI count rate along the Earth orbit. However, the temporal and latitudinal variations of the ionization in the heliosphere, and particularly their variation on the SC time-scale, may significantly modify the shape of PUI cone and crescent and also their peak positions from year to year and thus bias by a few degrees the derived longitude of the ISN gas inflow direction.

  15. The use of gas chromatography for the quantitative determination of micro-amounts of insecticide picked up by mosquitos*

    PubMed Central

    Pennell, J. T.; Miskus, R.; Craig, R.

    1964-01-01

    The test method recommended by the WHO Expert Committee on Insecticides for determining the susceptibility or resistance of adult mosquitos to insecticides has been evaluated quantitatively by the use of gas chromatography to measure the amount of dieldrin picked up by adult Culex quinquefasciatus Say (= C. pipiens fatigans Wiedemann). A strain homozygous for dieldrin-resistance was used to determine the pick-up as a function of time and concentration of dieldrin. The results of experiments using electron-capture detection with gas chromatography suggest that the pick-up is a linear function of the concentration on the paper and also of the time of exposure, even of the 24-hour exposure to the 4.0% dieldrin paper. PMID:14122446

  16. Plasma wave, magnetic field and energetic ion observations in the ion pick-up region of Comet Giacobini-Zinner

    NASA Astrophysics Data System (ADS)

    Richardson, I. G.; Cowley, S. W. H.; Wenzel, K.-P.; Scarf, F. L.; Smith, E. J.; Tsurutani, B. T.; Sanderson, T. R.; Hynds, R. J.

    Simultaneous plasma wave, magnetic field, and energetic ion observations made by the ICE spacecraft in the extended ion pick-up region surrounding comet Giacobini-Zinner are examined to determine the conditions under which two characteristic wave emissions, electrostatic waves at a few kHz, and electromagnetic waves at a few tens of Hz, are generated. The data are consistent with the view that the kHz electrostatic emissions result from an instability of the pick-up photoelectron 'beam' produced when the angle alpha between the magnetic field and the solar wind velocity vector is less than about 60 deg, while the behavior of the tens of Hz electromagnetic waves suggests that they are generated by the pick-up ion 'ring' which is present when alpha exceeds about 60 deg.

  17. On the stability of pick-up ion ring distributions in the outer heliosheath

    SciTech Connect

    Summerlin, Errol J.; Viñas, Adolfo F.; Moore, Thomas E.; Christian, Eric R.; Cooper, John F. E-mail: adolfo.figueroa-vinas-1@nasa.gov E-mail: eric.r.christian@nasa.gov

    2014-10-01

    The 'secondary energetic neutral atom (ENA)' hypothesis for the ribbon feature observed by the Interstellar Boundary Explorer (IBEX) posits that the neutral component of the solar wind continues beyond the heliopause and charge exchanges with interstellar ions in the Outer Heliosheath (OHS). This creates pick-up ions that gyrate about the draped interstellar magnetic field (ISMF) lines at pitch angles near 90° on the locus where the ISMF lies tangential to the heliopause and perpendicular to the heliocentric radial direction. This location closely coincides with the location of the ribbon feature according to the prevailing inferences of the ISMF orientation and draping. The locally gyrating ions undergo additional charge exchange and escape as free-flying neutral atoms, many of which travel back toward the inner solar system and are imaged by IBEX as a ribbon tracing out the locus described above. For this mechanism to succeed, the pick-up ions must diffuse in pitch angle slowly enough to permit secondary charge exchange before their pitch angle distribution substantially broadens away from 90°. Previous work using linear Vlasov dispersion analysis of parallel propagating waves has suggested that the ring distribution in the OHS is highly unstable, which, if true, would make the secondary ENA hypothesis incapable of rendering the observed ribbon. In this paper, we extend this earlier work to more realistic ring distribution functions. We find that, at the low densities necessary to produce the observed IBEX ribbon via the secondary ENA hypothesis, growth rates are highly sensitive to the temperature of the beam and that even very modest temperatures of the ring beam corresponding to beam widths of <1° are sufficient to damp the self-generated waves associated with the ring beam. Thus, at least from the perspective of linear Vlasov dispersion analysis of parallel propagating waves, there is no reason to expect that the ring distributions necessary to produce the

  18. INTERSTELLAR PICK-UP IONS OBSERVED BETWEEN 11 AND 22 AU BY NEW HORIZONS

    SciTech Connect

    Randol, B. M.; McComas, D. J.; Schwadron, N. A.

    2013-05-10

    We report new observations by the Solar Wind Around Pluto instrument on the New Horizons spacecraft, which measures energy per charge (E/q) spectra of solar wind and interstellar pick-up ions (PUIs) between 11 AU and 22 AU from the Sun. The data provide an unprecedented look at PUIs as there have been very few measurements of PUIs beyond 10 AU. We analyzed the PUI part of the spectra by comparing them to the classic Vasyliunas and Siscoe PUI model. Our analysis indicates that PUIs are usually well-described by this distribution. We derive parameters relevant to PUI studies, such as the ionization rate normalized to 1 AU. Our result for the average ionization rate between 11 and 12 AU agrees with an independently derived average value found during the same time. Later, we find a general increase in the ionization rate, which is consistent with the increase in solar activity. We also calculate the PUI thermal pressure, which appears to be roughly consistent with previous results. Through fitting of the solar wind proton peaks in our spectra, we derive solar wind thermal pressures. Based on our analysis, we predict a ratio of PUI thermal pressure to solar wind thermal pressure just inside the termination shock to be between 100 and >1000.

  19. Experience with the 1.7 GHz Schottky Pick-ups in the Tevatron

    SciTech Connect

    Jansson, A.; Lebrun, P.; Pasquinelli, R.; /Fermilab

    2004-07-01

    During a 2003 shutdown, new high-frequency Schottky pick-ups were installed in the Tevatron. These devices operate at 1.7 GHz (harmonic 36000 of the revolution frequency) and can in principle be used to measure tunes, chromaticities, momentum spread and transverse emittances of individual bunches. Only the transverse signal is used, as the longitudinal is dominated by coherent signal. The default mode of operation during a store is to sequentially acquire and analyze frequency data from different sets of bunches in the machine. This function is performed by an Open Access Client (OAC) written in Java/C++, running in the background. The resulting fit parameters are datalogged and can also be plotted in ''real time'' during the store. With an alternative setup, data from select bunches can be acquired continuously during the entire ramp (and squeeze), for analysis off-line. This paper describes the evolution, current status and performance of the acquisition and analysis software, and presents measurements with comparison to predictions and other measurement techniques. One example of such a measurement is the variation of beam-beam tune shift as a function of intensity and bunch position within a train.

  20. Mars atmospheric loss and isotopic fractionation by pick-up-ion sputtering and photochemical escape

    NASA Technical Reports Server (NTRS)

    Jakosky, B. M.; Pepin, R. O.; Johnson, R. E.; Fox, J. L.

    1994-01-01

    We examine the effects of loss of constituents of the Martian atmosphere due to sputtering by solar-wind pick-up ions and photochemical escape during the last 3.8 billion years. Sputtering is capable of efficiently removing species from the upper atmosphere to space, including the light noble gases; nitrogen and oxygen are removed by both sputtering ad photochemical processes. Due to diffusive separation (by mass) above the homopause, removal from the top of the atmosphere will fractionate the isotopes of each species, with the lighter isotope being preferentially lost. This allows current measurements of the isotopic ratios to be used as a measure of the atmospheric evolution as integrated over geologic time. For carbon and oxygen, isotopic fractionation is buffered by exchange of atmospheric species with non-atmospheric reservoirs of CO2 and H2O. This allows us to determine the size of the non-atmospheric reservoirs which are capable of mixing with the atmosphere; these reservoirs can be CO2 absorbed in the regolith and/or H2O in the polar ice caps. Such an exchangeable reservoir is required in order to keep the fractionation of the atmospheric gases as low as is observed.

  1. Hands-free device control using sound picked up in the ear canal

    NASA Astrophysics Data System (ADS)

    Chhatpar, Siddharth R.; Ngia, Lester; Vlach, Chris; Lin, Dong; Birkhimer, Craig; Juneja, Amit; Pruthi, Tarun; Hoffman, Orin; Lewis, Tristan

    2008-04-01

    Hands-free control of unmanned ground vehicles is essential for soldiers, bomb disposal squads, and first responders. Having their hands free for other equipment and tasks allows them to be safer and more mobile. Currently, the most successful hands-free control devices are speech-command based. However, these devices use external microphones, and in field environments, e.g., war zones and fire sites, their performance suffers because of loud ambient noise: typically above 90dBA. This paper describes the development of technology using the ear as an output source that can provide excellent command recognition accuracy even in noisy environments. Instead of picking up speech radiating from the mouth, this technology detects speech transmitted internally through the ear canal. Discreet tongue movements also create air pressure changes within the ear canal, and can be used for stealth control. A patented earpiece was developed with a microphone pointed into the ear canal that captures these signals generated by tongue movements and speech. The signals are transmitted from the earpiece to an Ultra-Mobile Personal Computer (UMPC) through a wired connection. The UMPC processes the signals and utilizes them for device control. The processing can include command recognition, ambient noise cancellation, acoustic echo cancellation, and speech equalization. Successful control of an iRobot PackBot has been demonstrated with both speech (13 discrete commands) and tongue (5 discrete commands) signals. In preliminary tests, command recognition accuracy was 95% with speech control and 85% with tongue control.

  2. Picking Up the Mantle of "Expert": Assigned Roles, Assertion of Identity, and Peer Recognition within a Programming Class

    ERIC Educational Resources Information Center

    Fields, Deborah; Enyedy, Noel

    2013-01-01

    Changing an established role in a classroom is difficult. It involves constructing a new set of relations within a community. In this article we investigate how students with newly developed interest and experience in programming developed outside the classroom pick up and establish their roles as experts in programming within the classroom…

  3. 77 FR 40385 - Withdrawal of Regulatory Guide 7.3; Procedures for Picking Up and Receiving Packages of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-09

    ... Packaging Requirements for Shipment and Receipt of Radioactive Material,'' which was issued in March 28... Radioactive Material AGENCY: Nuclear Regulatory Commission. ACTION: Notice of withdrawal; correction. SUMMARY... Commission) is withdrawing RG 7.3, ``Procedures for Picking Up and Receiving Packages of Radioactive...

  4. Oocyte recovery by ovum pick up and embryo production in river buffaloes (Bubalus bubalis).

    PubMed

    Manjunatha, B M; Ravindra, J P; Gupta, P S P; Devaraj, M; Nandi, S

    2008-08-01

    Ovum pick up (OPU) was conducted twice a week for 12 weeks in six cycling, non-descriptive (local breed), Indian buffaloes to study the efficiency of OPU on recovery of oocytes for embryo production. OPU was performed using an ultrasound equipment with a 5-MHz transvaginal transducer, a single-lumen, 18-gauge, 55-cm-long needle and a constant vacuum pressure of 110 mmHg. The number and size of follicles were determined before puncture. The recovered oocytes were graded, washed, matured for 24 h and then fertilized with frozen-thawed semen, followed by embryo culture on the oviductal monolayer. The mean number of follicles observed per animal per session did not differ between animals or between puncture sessions. A mean number of 3.62 +/- 0.32 mm follicles were observed, 2.90 +/- 0.15 mm follicles were punctured and 1.21 +/- 0.07 oocytes were recovered per animal per session, with an average recovery rate of 42%. Of the total oocytes recovered, 64% were suitable for in vitro embryo production (grade A + B) whereas 36% were classified to be of grades C + D. A mean number of 0.25 +/- 0.2 transferable embryos was produced in vitro per buffalo per session with a transferable embryo production rate of 32%. In conclusion, this study demonstrated that twice-a-week OPU could be applied repeatedly, without any adverse effects on the follicular growth and oocyte recovery and that recovered oocytes could be used for in vitro embryo production in buffaloes. PMID:18282214

  5. Comparison of ultrasound-guided vs laparoscopic transvaginal ovum pick-up (OPU) in simmental heifers.

    PubMed

    Santl, B; Wenigerkind, H; Schernthaner, W; Mödl, J; Stojkovic, M; Prelle, K; Holtz, W; Brem, G; Wolf, E

    1998-07-01

    Transvaginal ovum pick-up (OPU) offers several advantages over standard embryo transfer procedures. For a systematic comparison of the ultrasound-guided (U-OPU) and the laparoscopic OPU (L-OPU) method, groups of Simmental heifers were subjected to 1 of the 2 OPU-methods for 8 wk (15 sessions) followed by a treatment-free interval of 11 wk and then another 8-wk period of OPU using the alternative method. Parameters that were evaluated included the number of follicles aspirated, number and morphology of recovered cumulus-oocyte complexes (COCs), and developmental capacity of oocytes after in vitro maturation (IVM) and fertilization (IVF). Blood samples were also taken from the donors twice a wk for progesterone measurement. To evaluate effects of long-term OPU on subsequent fertility of donors, all heifers (n = 14) were inseminated during the first natural estrus after the OPU experiment. The proportion of Class I oocytes was significantly (P < 0.001) higher after U-OPU than after L-OPU (38.7% vs 21.0%). Following IVM/IVF, this difference in oocyte quality was reflected by the cleavage rate (U-OPU: 58.1%; L-OPU: 52.1%; P < 0.05) and the rate of development to morulae and blastocysts (U-OPU: 27.1%; L-OPU: 13.9%; P < 0.001). Among other factors, the greater changes in vacuum pressure during L-OPU vs U-OPU might be responsible for the difference in oocyte quality. This problem may be overcome by a more flexible system for regulating the vacuum. Progesterone levels were higher during the L-OPU than the U-OPU periods. Seven donors (50%) were diagnosed pregnant by ultrasonography on Day 28 and by palpation per rectum on Day 42. PMID:10734477

  6. Comparative pick-up ion distributions at Mars and Venus: Consequences for atmospheric deposition and escape

    NASA Astrophysics Data System (ADS)

    Curry, Shannon M.; Luhmann, Janet; Ma, Yingjuan; Liemohn, Michael; Dong, Chuanfei; Hara, Takuya

    2015-09-01

    Without the shielding of a substantial intrinsic dipole magnetic field, the atmospheres of Mars and Venus are particularly susceptible to similar atmospheric ion energization and scavenging processes. However, each planet has different attributes and external conditions controlling its high altitude planetary ion spatial and energy distributions. This paper describes analogous test particle simulations in background MHD fields that allow us to compare the properties and fates, precipitation or escape, of the mainly O+ atmospheric pick-up ions at Mars and Venus. The goal is to illustrate how atmospheric and planetary scales affect the upper atmospheres and space environments of our terrestrial planet neighbors. The results show the expected convection electric field-related hemispheric asymmetries in both precipitation and escape, where the degree of asymmetry at each planet is determined by the planetary scale and local interplanetary field strength. At Venus, the kinetic treatment of O+ reveals a strong nightside source of precipitation while Mars' crustal fields complicate the simple asymmetry in ion precipitation and drive a dayside source of precipitation. The pickup O+ escape pattern at both Venus and Mars exhibits low energy tailward escape, but Mars exhibits a prominent, high energy 'polar plume' feature in the hemisphere of the upward convection electric field while the Venus ion wake shows only a modest poleward concentration. The overall escape is larger at Venus than Mars (2.1 ×1025 and 4.3 ×1024 at solar maximum, respectively), but the efficiency (likelihood) of O+ escaping is 2-3 times higher at Mars. The consequences of these comparisons for pickup ion related atmospheric energy deposition, loss rates, and detection on spacecraft including PVO, VEX, MEX and MAVEN are considered. In particular, both O+ precipitation and escape show electric field controlled asymmetries that grow with energy, while the O+ fluxes and energy spectra at selected spatial

  7. Integral dependent spin couplings in CI calculations

    NASA Astrophysics Data System (ADS)

    Iberle, K.; Davidson, E. R.

    1982-06-01

    Although the number of ways to combine Slater determinants to form spin eigenfunctions increases rapidly with the number of open shells, most of these spin couplings will make only a small contribution to a given state, provided the spin coupling is chosen judiciously. The technique of limiting calculations to the interacting subspace pioneered by Bunge (1970) was employed by Munch and Davidson (1975) to the vanadium atom. The use of an interacting space looses its advantage in more complex cases. However, the problem can always be reduced to only one interacting spin coupling by making the coefficients integral dependent. The present investigation is concerned with the performance of integral dependent interacting couplings, taking into account the results of three test calculations.

  8. Integral dependent spin couplings in CI calculations

    NASA Technical Reports Server (NTRS)

    Iberle, K.; Davidson, E. R.

    1982-01-01

    Although the number of ways to combine Slater determinants to form spin eigenfunctions increases rapidly with the number of open shells, most of these spin couplings will make only a small contribution to a given state, provided the spin coupling is chosen judiciously. The technique of limiting calculations to the interacting subspace pioneered by Bunge (1970) was employed by Munch and Davidson (1975) to the vanadium atom. The use of an interacting space looses its advantage in more complex cases. However, the problem can always be reduced to only one interacting spin coupling by making the coefficients integral dependent. The present investigation is concerned with the performance of integral dependent interacting couplings, taking into account the results of three test calculations.

  9. Kinetic modeling of Europa's neutral atmosphere and pick-up ions

    NASA Astrophysics Data System (ADS)

    Tenishev, V.; Rubin, M.; Borovikov, D.; Jia, X.; Combi, M. R.; Gombosi, T. I.

    2013-12-01

    Europa was the highest priority outer planet exploration target in the 2007 NASA Science Plan, the 2006 Solar System Exploration Roadmap, and the 2003 planetary sciences Decadal Survey. The in-depth exploration of the plasma environment of Jupiter's moon Europa and investigation of its interaction with moon's surface and atmosphere remains a central objective of any proposed Europa Jupiter System Mission. The neutral species in Europa's atmosphere are mostly provided by ion sputtering of the water ice surface. Energetic ions and electrons from the Jovian magnetosphere produce molecular oxygen O2, the dominant species in Europa's atmosphere. Very close to the moon's surface the probability for collisional interaction between the species is close to the limit for a surface bound exosphere. The main loss mechanisms for neutrals are electron impact ionization, photoionization, as well as escape when neutral particles leave Europa's Hill sphere at roughly 8.7 Europa radii. The neutral and plasma environment of Europa are a tightly coupled system. A detailed study of this system requires coupled models of both the plasma and neutral environment. In this study we use coupled state-of-the-art computer models developed at the University of Michigan. In particular we include the BATSRUS MHD code of the Space Weather Modeling Framework (SWMF) and the Adaptive Mesh Particle Simulator (AMPS) model based on the DSMC method that both have well proven heritage in numerous space applications. In this investigation we calculate the plasma distribution in the vicinity of Europa at different locations along its orbit. The energetic ion flux derived from these calculations is used for simulation of the neutral particle sputtering that form Europa's atmosphere. The subsequent ionization of these neutral particles is the source of the pick-up ions. Populations of the neutrals and ions are calculated by tracing trajectories of the individual particles with accounting for both Europa

  10. Long term effect of Ovum Pick-up in buffalo species.

    PubMed

    Neglia, Gianluca; Gasparrini, Bianca; Vecchio, Domenico; Boccia, Lucia; Varricchio, Ettore; Di Palo, Rossella; Zicarelli, Luigi; Campanile, Giuseppe

    2011-02-01

    The aim of this study was to evaluate the effect of an Ovum Pick-up (OPU) treatment carried out for 9 months in buffalo (Bubalus bubalis) species. Eight pluriparous non-lactating buffalo cows underwent OPU for 9 months. Recovered cumulus enclosed oocytes (COCs) were classified and COCs suitable for in vitro embryo production (IVEP) were in vitro matured (IVM), fertilized (IVF) and cultured (IVC) to the blastocyst (Bl) stage. Animals were monitored for a total period of 270 days, but at the summer solstice, follicular turnover decreased and at the 68-day of the trial, we decided to increase the OPU sampling interval from 3-4 to 7 days. It was therefore possible to distinguish two phases: a first phase (18 sessions), during which OPU was carried out twice weekly and a second phase (16 sessions) during which OPU sessions were performed weekly. This reduction did not modify the percentage of good quality COCs, while the incidence of grade D COCs decreased (P<0.01). Furthermore, embryo production was higher in the second phase, either if embryos were calculated on the total recovered COCs (8.3% vs. 21.4%; P<0.01) and on grade A+B COCs (13.0% vs. 32.1%; P<0.01), that supposedly should have given similar blastocyst yield. During the total period of the trial it was possible to distinguish a first period of 6 months (34 sessions) characterized by blastocyst production (0.36 blastocyst/buffalo/session), followed by an unproductive period of 3 months (12 sessions), during which embryos were not produced. During the first 6 months a higher (P<0.01) number of follicles (5.06 vs. 3.71), small follicles (3.38 vs. 2.07), total COCs (2.58 vs. 1.56) and good quality (A+B) COCs (1.51 vs. 0.94) per subject/session were recorded compared to the last 3 months. No Blastocyst were produced during the second period, even if the percentage of grade A+B COCs was similar to that recorded during the first period. In conclusion, buffalo cows submitted to repeated OPU sampling for a 9-month

  11. 41 CFR 102-37.60 - How much time does a transferee have to pick up or remove surplus property from holding agency...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 41 Public Contracts and Property Management 3 2010-07-01 2010-07-01 false How much time does a transferee have to pick up or remove surplus property from holding agency premises? 102-37.60 Section 102-37... Provisions Donation Overview § 102-37.60 How much time does a transferee have to pick up or remove...

  12. Application of FIB with micro pick-up to microstructural study of irradiated SiC/SiC composites.

    PubMed

    Ozawa, Kazumi; Kondo, Sosuke; Kishimoto, Hirotatsu; Kohyama, Akira

    2004-01-01

    The combination of focused ion beam (FIB) micro-processing and the lift-out technique using the micro pick-up system was applied to the preparation of TEM specimens of irradiated SiC/SiC composites. The deformation caused by microstructural evolution was observed in the pyrolitic carbon interphase, and several helium bubbles and cavities were detected in the CVI matrix. PMID:15582959

  13. Type-I superconductor pick-up coil in superconducting quantum interference device-based ultra-low field nuclear magnetic resonance

    SciTech Connect

    Hwang, Seong-min Kim, Kiwoong; Kyu Yu, Kwon; Lee, Seong-Joo; Hyun Shim, Jeong; Körber, Rainer; Burghoff, Martin

    2014-02-10

    In ultra-low field nuclear magnetic resonance (ULF-NMR) with strong prepolarization field (B{sub p}), type-II superconducting pick-up coils may be vulnerable to flux pinning from the strong B{sub p}. Pick-up coils made of NbTi, Nb, and Pb were evaluated in terms of acquired NMR signal quality. The type-II pick-up coils showed degraded signals above 61 mT maximum exposure, while the Pb pick-up coil exhibited no such degradation. Furthermore, a negative counter pulse following a strong B{sub p} was shown to follow magnetic hysteresis loop to unpin the trapped flux in the type-II pick-up coil and restore the NMR signal.

  14. Temperature dependent spin structures in Hexaferrite crystal

    NASA Astrophysics Data System (ADS)

    Chao, Y. C.; Lin, J. G.; Chun, S. H.; Kim, K. H.

    2016-01-01

    In this work, the Hexaferrite Ba0.5Sr1.5Zn2Fe12O22 (BSZFO) is studied due to its interesting characteristics of long-wavelength spin structure. Ferromagnetic resonance (FMR) is used to probe the magnetic states of BSZFO single crystal and its temperature dependence behavior is analyzed by decomposing the multiple lines of FMR spectra into various phases. Distinguished phase transition is observed at 110 K for one line, which is assigned to the ferro(ferri)-magnetic transition from non-collinear to collinear spin state.

  15. Coulomb blockade of spin-dependent shuttling

    NASA Astrophysics Data System (ADS)

    Park, Hee Chul; Kadigrobov, Anatoli M.; Shekhter, Robert I.; Jonson, M.

    2013-12-01

    We show that nanomechanical shuttling of single electrons may enable qualitatively new functionality if spin-polarized electrons are injected into a nanoelectromechanical single-electron tunneling (NEM-SET) device. This is due to the combined effects of spin-dependent electron tunneling and Coulomb blockade of tunneling, which are phenomena that occur in certain magnetic NEM-SET devices. Two effects are predicted to occur in such structures. The first is a reentrant shuttle instability, by which we mean the sequential appearance, disappearance and again the appearance of a shuttle instability as the driving voltage is increased (or the mechanical dissipation is diminished). The second effect is an enhanced spin polarization of the nanomechanically assisted current flow.

  16. Cometary kilometric radio waves and plasma waves correlated with ion pick-up effect at Comet Halley

    NASA Technical Reports Server (NTRS)

    Oya, H.; Morioka, A.; Miyake, W.; Smith, E. J.; Tsurutani, B. T.

    1985-01-01

    Bow-shock movements at Comet Halley are inferred from the discrete spectra of the cometary kilometric radiation (30-195 kHz); the observed emissions can be interpreted as being generated and propagating from the moving shock. The shock motion is possibly associated with the time variation of the solar wind and cometary outgassing. It is concluded that these plasma wave phenomena are manifestations of ion pick-up processes, which occur even in a remote region 7 million to 10 million km from the cometary nucleus.

  17. Cometary kilometric radio waves and plasma waves correlated with ion pick-up effect at Comet Halley

    NASA Astrophysics Data System (ADS)

    Oya, H.; Morioka, A.; Miyake, W.; Smith, E. J.; Tsurutani, B. T.

    Bow-shock movements at Comet Halley are inferred from the discrete spectra of the cometary kilometric radiation (30-195 kHz); the observed emissions can be interpreted as being generated and propagating from the moving shock. The shock motion is possibly associated with the time variation of the solar wind and cometary outgassing. It is concluded that these plasma wave phenomena are manifestations of ion pick-up processes, which occur even in a remote region 7 million to 10 million km from the cometary nucleus.

  18. Design and evaluation of pick-up truck mounted boom for elevation of a multiband radiometer system

    NASA Technical Reports Server (NTRS)

    Bauer, M. E. (Principal Investigator); Tsuchida, R.

    1981-01-01

    Three concepts were considered for the boom design: a one-piece boom with a trolley, a folding boom, and a telescoping boom. The telescoping boom was selected over the other two concepts because of its easy manual operation. The boom is designed to mount on the bed of a pick-up truck and elevate the radiometer system 8 meters above the ground and 4 meters away from the truck. The selection of the boom components is discussed with justification of the final choice. Results of performance tests and one season's operation of the completed boom are reported.

  19. Spin-dependent terahertz oscillator based on hybrid graphene superlattices

    SciTech Connect

    Díaz, E.; Miralles, K.; Domínguez-Adame, F.; Gaul, C.

    2014-09-08

    We theoretically study the occurrence of Bloch oscillations in biased hybrid graphene systems with spin-dependent superlattices. The spin-dependent potential is realized by a set of ferromagnetic insulator strips deposited on top of a gapped graphene nanoribbon, which induce a proximity exchange splitting of the electronic states in the graphene monolayer. We numerically solve the Dirac equation and study Bloch oscillations in the lowest conduction band of the spin-dependent superlattice. While the Bloch frequency is the same for both spins, we find the Bloch amplitude to be spin dependent. This difference results in a spin-polarized ac electric current in the THz range.

  20. The spin dependent odderon in the diquark model

    NASA Astrophysics Data System (ADS)

    Szymanowski, Lech; Zhou, Jian

    2016-09-01

    In this short note, we report a di-quark model calculation for the spin dependent odderon and demonstrate that the asymmetrical color source distribution in the transverse plane of a transversely polarized hadron plays an essential role in yielding the spin dependent odderon. This calculation confirms the earlier finding that the spin dependent odderon is closely related to the parton orbital angular momentum.

  1. 41 CFR 102-37.60 - How much time does a transferee have to pick up or remove surplus property from holding agency...

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ...) FEDERAL MANAGEMENT REGULATION PERSONAL PROPERTY 37-DONATION OF SURPLUS PERSONAL PROPERTY General Provisions Donation Overview § 102-37.60 How much time does a transferee have to pick up or remove...

  2. 41 CFR 102-37.60 - How much time does a transferee have to pick up or remove surplus property from holding agency...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...) FEDERAL MANAGEMENT REGULATION PERSONAL PROPERTY 37-DONATION OF SURPLUS PERSONAL PROPERTY General Provisions Donation Overview § 102-37.60 How much time does a transferee have to pick up or remove...

  3. 41 CFR 102-37.60 - How much time does a transferee have to pick up or remove surplus property from holding agency...

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ...) FEDERAL MANAGEMENT REGULATION PERSONAL PROPERTY 37-DONATION OF SURPLUS PERSONAL PROPERTY General Provisions Donation Overview § 102-37.60 How much time does a transferee have to pick up or remove...

  4. 41 CFR 102-37.60 - How much time does a transferee have to pick up or remove surplus property from holding agency...

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...) FEDERAL MANAGEMENT REGULATION PERSONAL PROPERTY 37-DONATION OF SURPLUS PERSONAL PROPERTY General Provisions Donation Overview § 102-37.60 How much time does a transferee have to pick up or remove...

  5. Pick-up, transport and release of a molecular cargo using a small-molecule robotic arm

    NASA Astrophysics Data System (ADS)

    Kassem, Salma; Lee, Alan T. L.; Leigh, David A.; Markevicius, Augustinas; Solà, Jordi

    2016-02-01

    Modern-day factory assembly lines often feature robots that pick up, reposition and connect components in a programmed manner. The idea of manipulating molecular fragments in a similar way has to date only been explored using biological building blocks (specifically DNA). Here, we report on a wholly artificial small-molecule robotic arm capable of selectively transporting a molecular cargo in either direction between two spatially distinct, chemically similar, sites on a molecular platform. The arm picks up/releases a 3-mercaptopropanehydrazide cargo by formation/breakage of a disulfide bond, while dynamic hydrazone chemistry controls the cargo binding to the platform. Transport is controlled by selectively inducing conformational and configurational changes within an embedded hydrazone rotary switch that steers the robotic arm. In a three-stage operation, 79-85% of 3-mercaptopropanehydrazide molecules are transported in either (chosen) direction between the two platform sites, without the cargo at any time fully dissociating from the machine nor exchanging with other molecules in the bulk.

  6. Electronic Transport of Encapsulated WSe2 Fabricated by Pick-up of Pre-patterned hBN

    NASA Astrophysics Data System (ADS)

    Yang, Yafang; Watanabe, Kenji; Taniguchi, Takashi; Jarillo-Herrero, Pablo; MIT Team

    We report high quality WSe2 devices encapsulated between two hexagonal boron nitride (hBN) flakes using a pick-up method with etched hBN flakes. Previous work on graphene has shown that sample disorder can be greatly reduced via isolation from charge impurities in the substrate by means of encapsulation. However, the effect of encapsulation still remains unknown for dichalcogenides devices. Besides, the quality of contact to TMDs is also a critical factor limiting the transport performance of such devices. To measure the transport properties of dichalcogenide devices as a function of temperature, low resistance electrical contacts must be made to the material. To achieve this, we encapsulate few-layer WSe2 in hexagonal boron nitride that has been patterned to allow ionic liquid doping of the contact region. This technique simultaneously protects the WSe2 surface above and below, resulting in the highest mobility few-layer WSe2 devices reported to date.

  7. A non-dominated sorting genetic algorithm for a bi-objective pick-up and delivery problem

    NASA Astrophysics Data System (ADS)

    Velasco, N.; Dejax, P.; Guéret, C.; Prins, C.

    2012-03-01

    Some companies must transport their personnel within facilities. This is especially the case for oil companies that use helicopters to transport engineers, technicians and assistant personnel from platform to platform. This operation has the potential to become expensive if the transportation routes are not correctly planned and provide a bad quality of service. Here this issue is modelled as a pick-up and delivery problem where a set of transportation requests should be scheduled in routes, minimizing the total transportation cost while the most urgent requests are satisfied by priority. To solve the problem, a method based on a Non-dominated Sorting Genetic Algorithm (NSGA-II) is proposed. This algorithm is tested on both randomly generated and real instances provided by a petroleum company. The results show that the proposed algorithm improves the best-known solutions.

  8. Field dependent spin transport of anisotropic Heisenberg chain

    NASA Astrophysics Data System (ADS)

    Rezania, H.

    2016-04-01

    We have addressed the static spin conductivity and spin Drude weight of one-dimensional spin-1/2 anisotropic antiferromagnetic Heisenberg chain in the finite magnetic field. We have investigated the behavior of transport properties by means of excitation spectrum in terms of a hard core bosonic representation. The effect of in-plane anisotropy on the spin transport properties has also been studied via the bosonic model by Green's function approach. This anisotropy is considered for exchange constants that couple spin components perpendicular to magnetic field direction. We have found the temperature dependence of the spin conductivity and spin Drude weight in the gapped field induced spin-polarized phase for various magnetic field and anisotropy parameters. Furthermore we have studied the magnetic field dependence of static spin conductivity and Drude weight for various anisotropy parameters. Our results show the regular part of spin conductivity vanishes in isotropic case however Drude weight has a finite non-zero value and the system exhibits ballistic transport properties. We also find the peak in the static spin conductivity factor moves to higher temperature upon increasing the magnetic field at fixed anisotropy. The static spin conductivity is found to be monotonically decreasing with magnetic field due to increase of energy gap in the excitation spectrum. Furthermore we have studied the temperature dependence of spin Drude weight for different magnetic field and various anisotropy parameters.

  9. Realization of tunable spin-dependent splitting in intrinsic photonic spin Hall effect

    SciTech Connect

    Ling, Xiaohui; Yi, Xunong; Zhou, Xinxing; Liu, Yachao; Shu, Weixing; Wen, Shuangchun; Luo, Hailu

    2014-10-13

    We report the realization of tunable spin-dependent splitting in intrinsic photonic spin Hall effect. By breaking the rotational symmetry of a cylindrical vector beam, the intrinsic vortex phases that the two spin components of the vector beam carries, which is similar to the geometric Pancharatnam-Berry phase, are no longer continuous in the azimuthal direction, and leads to observation of spin accumulation at the opposite edge of the beam. Due to the inherent nature of the phase and independency of light-matter interaction, the observed photonic spin Hall effect is intrinsic. Modulating the topological charge of the vector beam, the spin-dependent splitting can be enhanced and the direction of spin accumulation is switchable. Our findings may provide a possible route for generation and manipulation of spin-polarized photons, and enables spin-based photonics applications.

  10. Unveiling the photonic spin Hall effect with asymmetric spin-dependent splitting.

    PubMed

    Zhou, Xinxing; Ling, Xiaohui

    2016-02-01

    The photonic spin Hall effect (SHE) manifests itself as the spin-dependent splitting of light beam. Usually, it shows a symmetric spin-dependent splitting, i.e., the left- and right-handed circularly polarized components are equally separated in position and intensity for linear polarization incidence. In this paper, we theoretically propose an asymmetric spin-dependent splitting at an air-glass interface under the illumination of elliptical polarization beam and experimentally demonstrate it with the weak measurement method. The left- and right-handed circularly polarized components show expectedly unequal intensity distributions and unexpectedly different spin-dependent shifts. Remarkably, the asymmetric spin-dependent splitting can be modulated by adjusting the handedness of incident polarization. The inherent physics behind this interesting phenomenon is attributed to the additional spatial Imbert-Fedorov shift. These findings offer us potential methods for developing new spin-based nanophotonic applications. PMID:26906868

  11. Embodied intersubjective engagement in mother–infant tactile communication: a cross-cultural study of Japanese and Scottish mother–infant behaviors during infant pick-up

    PubMed Central

    Negayama, Koichi; Delafield-Butt, Jonathan T.; Momose, Keiko; Ishijima, Konomi; Kawahara, Noriko; Lux, Erin J.; Murphy, Andrew; Kaliarntas, Konstantinos

    2015-01-01

    This study examines the early development of cultural differences in a simple, embodied, and intersubjective engagement between mothers putting down, picking up, and carrying their infants between Japan and Scotland. Eleven Japanese and ten Scottish mothers with their 6- and then 9-month-old infants participated. Video and motion analyses were employed to measure motor patterns of the mothers’ approach to their infants, as well as their infants’ collaborative responses during put-down, pick-up, and carry phases. Japanese and Scottish mothers approached their infants with different styles and their infants responded differently to the short duration of separation during the trial. A greeting-like behavior of the arms and hands was prevalent in the Scottish mothers’ approach, but not in the Japanese mothers’ approach. Japanese mothers typically kneeled before making the final reach to pick-up their children, giving a closer, apparently gentler final approach of the torso than Scottish mothers, who bent at the waist with larger movements of the torso. Measures of the gap closure between the mothers’ hands to their infants’ heads revealed variably longer duration and distance gap closures with greater velocity by the Scottish mothers than by the Japanese mothers. Further, the sequence of Japanese mothers’ body actions on approach, contact, pick-up, and hold was more coordinated at 6 months than at 9 months. Scottish mothers were generally more variable on approach. Measures of infant participation and expressivity indicate more active participation in the negotiation during the separation and pick-up phases by Scottish infants. Thus, this paper demonstrates a culturally different onset of development of joint attention in pick-up. These differences reflect cultures of everyday interaction. PMID:25774139

  12. Chirality dependent spin polarization of carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Wang, Jia; Jiang, Wanrun; Wang, Bo; Gao, Yang; Wang, Zhigang; Zhang, Rui-Qin

    2016-02-01

    The spin polarization of carbon nanotubes (CNTs) offers a tunable building block for spintronic devices and is also crucial for realizing carbon-based electronics. However, the effect of chiral CNTs is still unclear. In this paper, we use the density functional theory (DFT) method to investigate the spin polarization of a series of typical finite-length chiral CNTs (9, m). The results show that the spin density of chiral CNTs (9, m) decreases gradually with the increase in m and vanishes altogether when m is larger than or equal to 6. The armchair edge units on both ends of the (9, m) CNTs exhibit a clear inhibition of spin polarization, allowing control of the spin density of (9, m) CNTs by adjusting the number of armchair edge units on the tube end. Furthermore, analysis of the orbitals shows that the spin of the ground state for (9, m) CNTs mainly comes from the contributions of the frontier molecular orbitals (MOs), and the energy gap decreases gradually with the spin density for chiral CNTs. Our work further develops the study of the spin polarization of CNTs and provides a strategy for controlling the spin polarization of functional molecular devices through chiral vector adjustment.

  13. Pumped Spin-Current in Single Quantum Dot with Spin-Dependent Electron Temperature

    NASA Astrophysics Data System (ADS)

    Liu, Jia; Wang, Song; Du, Xiaohong

    2016-05-01

    Spin-dependent electron temperature effect on the spin pump in a single quantum dot connected to Normal and/or Ferromagnetic leads are investigated with the help of master equation method. Results show that spin heat accumulation breaks the tunneling rates balance at the thermal equilibrium state thus the charge current and the spin current are affected to some extent. Pure spin current can be obtained by adjusting pumping intensity or chemical potential of the lead. Spin heat accumulation of certain material can be detected by measuring the charge current strength in symmetric leads architectures. In practical devices, spin-dependent electron temperature effect is quite significant and our results should be useful in quantum information processing and spin Caloritronics.

  14. Pumped Spin-Current in Single Quantum Dot with Spin-Dependent Electron Temperature

    NASA Astrophysics Data System (ADS)

    Liu, Jia; Wang, Song; Du, Xiaohong

    2016-09-01

    Spin-dependent electron temperature effect on the spin pump in a single quantum dot connected to Normal and/or Ferromagnetic leads are investigated with the help of master equation method. Results show that spin heat accumulation breaks the tunneling rates balance at the thermal equilibrium state thus the charge current and the spin current are affected to some extent. Pure spin current can be obtained by adjusting pumping intensity or chemical potential of the lead. Spin heat accumulation of certain material can be detected by measuring the charge current strength in symmetric leads architectures. In practical devices, spin-dependent electron temperature effect is quite significant and our results should be useful in quantum information processing and spin Caloritronics.

  15. STEM Picks Up Speed

    ERIC Educational Resources Information Center

    Demski, Jennifer

    2009-01-01

    Algebra, geometry, earth science, physics--these require patience and perseverance to master. That kind of academic stamina is hard to advertise to kids nurtured on the instant engagement and gratification of modern digital technology. And there's little hope they'll be sustained by an intrinsic interest in math and science; they have to be shown…

  16. Picking Up the Pieces

    ERIC Educational Resources Information Center

    Robelen, Erik W.

    2005-01-01

    A school devastated by Hurricane Katrina, which struck southeastern Louisiana on August 29, reopens--but for teachers, the real work is just beginning. First, there was the storm. Roofing was ripped off some of the beige, block like buildings that make up Bonnabel High's nondescript campus nestled in a suburban neighborhood near the New Orleans…

  17. Temperature dependent spin transport properties of platinum inferred from spin Hall magnetoresistance measurements

    SciTech Connect

    Meyer, Sibylle Althammer, Matthias; Geprägs, Stephan; Opel, Matthias; Goennenwein, Sebastian T. B.; Gross, Rudolf

    2014-06-16

    We study the temperature dependence of the spin Hall magnetoresistance (SMR) in yttrium iron garnet/platinum hybrid structures via magnetization orientation dependent magnetoresistance measurements. Our experiments show a decrease of the SMR magnitude with decreasing temperature. Using the sensitivity of the SMR to the spin transport properties of the normal metal, we interpret our data in terms of a decrease of the spin Hall angle in platinum from 0.11 at room temperature to 0.075 at 10 K, while the spin diffusion length and the spin mixing conductance of the ferrimagnetic insulator/normal metal interface remain almost constant.

  18. Position dependent spin wave spectrum in nanostrip magnonic waveguides

    SciTech Connect

    Wang, Qi; Zhang, Huaiwu; Ma, Guokun; Liao, Yulong; Zhong, Zhiyong; Zheng, Yun

    2014-04-07

    The dispersion curves of propagating spin wave along different positions in nanostrip magnonic waveguides were studied by micromagnetic simulation. The results show that the modes of spin wave in the nanostrip magnonic waveguide are dependent on the position and the weak even modes of spin wave are excited even by symmetric excitation fields in a nanostrip magnonic waveguide. The reasons of the position dependent dispersion curve are explained by associating with geometrical confinement in the nanostrip magnonic waveguide.

  19. Search for exotic spin-dependent interactions with a spin-exchange relaxation-free magnetometer

    NASA Astrophysics Data System (ADS)

    Chu, P.-H.; Kim, Y. J.; Savukov, I.

    2016-08-01

    We propose a novel experimental approach to explore exotic spin-dependent interactions using a spin-exchange relaxation-free (SERF) magnetometer, the most sensitive noncryogenic magnetic-field sensor. This approach studies the interactions between optically polarized electron spins located inside a vapor cell of the SERF magnetometer and unpolarized or polarized particles of external solid-state objects. The coupling of spin-dependent interactions to the polarized electron spins of the magnetometer induces the tilt of the electron spins, which can be detected with high sensitivity by a probe laser beam similarly as an external magnetic field. We estimate that by moving unpolarized or polarized objects next to the SERF Rb vapor cell, the experimental limit to the spin-dependent interactions can be significantly improved over existing experiments, and new limits on the coupling strengths can be set in the interaction range below 10-2 m .

  20. Spin-dependent recombination and hyperfine interaction at deep defects

    NASA Astrophysics Data System (ADS)

    Ivchenko, E. L.; Bakaleinikov, L. A.; Kalevich, V. K.

    2015-05-01

    We present a theoretical study of optical electron-spin orientation and spin-dependent Shockley-Read-Hall recombination in the longitudinal magnetic field, taking into account the hyperfine coupling between the bound-electron spin and the nuclear spin of a deep paramagnetic center. The master rate equations for the coupled system are extended to describe the nuclear spin relaxation by using two distinct relaxation times, τn 1 and τn 2, respectively, for defect states with one and two (singlet) bound electrons. The general theory is developed for an arbitrary value of the nuclear spin I . The magnetic-field and excitation-power dependencies of the electron and nuclear spin polarizations are calculated for the value of I =1 /2 . In this particular case the nuclear effects can be taken into account by a simple replacement of the bound-electron spin relaxation time by an effective time dependent on free-electron and hole densities and free-electron spin polarization. The role of nuclear spin relaxation is visualized by isolines of the electron spin polarization on a two-dimensional graph with the axes log2(τn 1) and log2(τn 2) .

  1. Spin-dependent deprotonation induced giant magnetocurrent in electrochemical cells.

    PubMed

    Pan, Haiping; Shen, Yan; Duan, Jiashun; Lu, Kai; Hu, Bin

    2016-04-21

    A giant magnetocurrent (>100%) is observed in the electrochemical system based on tertiary amines at room temperature. This giant magnetocurrent is ascribed to spin-dependent deprotonation during the oxidation of tertiary amines. This presents a new approach of using spin-dependent deprotonation to generate giant magnetocurrent in electrochemical reactions. PMID:27009519

  2. Electronic Transport of Encapsulated WSe2 Fabricated by Pick-up of Pre-patterned hBN

    NASA Astrophysics Data System (ADS)

    Yang, Yafang; Churchill, Hugh; Watanabe, Kenji; Taniguchi, Takashi; Jarillo-Herrero, Pablo

    2015-03-01

    We report high quality WSe2 devices encapsulated between two hexagonal boron nitride (hBN) flakes using a pick-up method with etched hBN flakes. Previous work on graphene has shown that sample disorder can be greatly reduced via isolation from charge impurities in the substrate by means of encapsulation. However, the effect of encapsulation still remains unknown for dichalcogenides devices. Besides, the quality of contact to TMDs is also a critical factor limiting the transport performance of such devices. To measure the transport properties of dichalcogenide devices as a function of temperature, low resistance electrical contacts must be made to the material. To achieve this, we encapsulate few-layer WSe2 in hexagonal boron nitride that has been patterned to allow ionic liquid doping of the contact region. This technique simultaneously protects the WSe2 surface above and below, resulting in the highest mobility few-layer WSe2 devices reported to date. We acknowledge support from ONR Young Investigator Award N00014-13-1-0610.

  3. Phenotypic correlations between ovum pick-up in vitro production traits and pregnancy rates in Zebu cows.

    PubMed

    Vega, W H O; Quirino, C R; Serapião, R V; Oliveira, C S; Pacheco, A

    2015-01-01

    The growth of the Gyr breed in Brazil in terms of genetic gain for milk, along with conditions for market, has led to the use of ovum pick-up in vitro production (OPU-IVP) as a leader in biotechnology for the multiplication of genetic material. The aim of this study was to investigate phenotypic correlations between OPU-IVP-linked characteristics and pregnancy rates registered in an embryo transfer program using Gyr cows as oocyte donors. Data collected from 211 OPU sessions and 298 embryo transfers during the years 2012 and 2013 were analyzed and statistical analysis was performed. Estimates of simple Pearson correlations were calculated for NVcoc and PVcoc (number and proportion of viable cumulus-oocyte complexes, respectively); NcleavD4 and PcleavD4 (number and proportion of cleaved embryos on day 4 of culture, respectively); NTembD7 and PTembD7 (number and proportion of transferable embryos on day 7 of culture, respectively); NPrD30 and PPrD30 (number and proportion of pregnancies 30 days after transfer, respectively); and NPrD60 and PPrD60 (number and proportion of pregnancies 60 days after transfer, respectively). Moderate to moderately high correlations were found for all numerical characteristics, suggesting these as the most suitable parameters for selection of oocyte donors in Gyr programs. NVcoc is proposed as a selection trait due to positive correlations with percentage traits and pregnancy rates 30 and 60 days after transfer. PMID:26214412

  4. Pico Lantern: Surface reconstruction and augmented reality in laparoscopic surgery using a pick-up laser projector.

    PubMed

    Edgcumbe, Philip; Pratt, Philip; Yang, Guang-Zhong; Nguan, Christopher; Rohling, Robert

    2015-10-01

    The Pico Lantern is a miniature projector developed for structured light surface reconstruction, augmented reality and guidance in laparoscopic surgery. During surgery it will be dropped into the patient and picked up by a laparoscopic tool. While inside the patient it projects a known coded pattern and images onto the surface of the tissue. The Pico Lantern is visually tracked in the laparoscope's field of view for the purpose of stereo triangulation between it and the laparoscope. In this paper, the first application is surface reconstruction. Using a stereo laparoscope and an untracked Pico Lantern, the absolute error for surface reconstruction for a plane, cylinder and ex vivo kidney, is 2.0 mm, 3.0 mm and 5.6 mm, respectively. Using a mono laparoscope and a tracked Pico Lantern for the same plane, cylinder and kidney the absolute error is 1.4 mm, 1.5 mm and 1.5 mm, respectively. These results confirm the benefit of the wider baseline produced by tracking the Pico Lantern. Virtual viewpoint images are generated from the kidney surface data and an in vivo proof-of-concept porcine trial is reported. Surface reconstruction of the neck of a volunteer shows that the pulsatile motion of the tissue overlying a major blood vessel can be detected and displayed in vivo. Future work will integrate the Pico Lantern into standard and robot-assisted laparoscopic surgery. PMID:26024818

  5. Spin-dependent diffraction of evanescent waves by subwavelength gratings.

    PubMed

    Wu, Kedi; Wang, Guo Ping

    2015-08-15

    We present a way to observe the spin-to-orbital conversion phenomenon. A spinning evanescent wave can be asymmetrically transformed into propagation waves through one certain diffraction order by a periodical subwavelength grating. By detecting diffraction field distribution behind the grating, we observed spin-dependent diffraction patterns. Furthermore, replacing the periodical grating by a Fibonacci grating, we can simultaneously observe multiple order diffractions of a spin evanescent wave. In this case, the multiple diffraction beams can interfere with each other behind the quasi-periodical grating to form asymmetric interference patterns. Our work provides another way toward the realization of spin-to-orbital conversion of light. PMID:26274640

  6. Picking up the pieces”—Meanings of receiving home nursing care when being old and living with advanced cancer in a rural area

    PubMed Central

    Devik, Siri Andreassen; Hellzen, Ove; Enmarker, Ingela

    2015-01-01

    Rural home nursing care is a neglected area in the research of palliative care offered to older cancer patients. Because access to specialized services is hampered by long distances and fragmented infrastructure, palliative care is often provided through standard home nursing services and delivered by general district nurses. This study aimed to illuminate the lived experience and to interpret the meaning of receiving home nursing care when being old and living with advanced cancer in a rural area in Norway. Narrative interviews were conducted with nine older persons, and a phenomenological hermeneutic approach was used to interpret the meaning of the lived experience. The analysis revealed three themes, each with subthemes: being content with what one gets, falling into place, and losing one's place. The phrase picking up the pieces was found useful to sum up the meaning of this lived experience. The three respective themes refer to how the pieces symbolize the remaining parts of life or available services in their environment, and how the older persons may see themselves as pieces or bricks in a puzzle. A strong place attachment (physical insideness, social insideness, and autobiographical insideness) is demonstrated by the informants in this study and suggests that the rural context may provide an advantageous healthcare environment. Its potential to be a source of comfort, security, and identity concurs with cancer patients’ strong desire for being seen as unique persons. The study shows that district nurses play an essential role in the provision of palliative care for older rural patients. However, the therapeutic value of being in one's familiar landscape seems to depend on how homecare nurses manage to locate it and use it in a more or less person-centred manner. Communication skills and attentiveness to psychosocial aspects of patient care stand out as important attributes for nursing in this context. PMID:26362533

  7. "Picking up the pieces" - Meanings of receiving home nursing care when being old and living with advanced cancer in a rural area.

    PubMed

    Devik, Siri Andreassen; Hellzen, Ove; Enmarker, Ingela

    2015-01-01

    Rural home nursing care is a neglected area in the research of palliative care offered to older cancer patients. Because access to specialized services is hampered by long distances and fragmented infrastructure, palliative care is often provided through standard home nursing services and delivered by general district nurses. This study aimed to illuminate the lived experience and to interpret the meaning of receiving home nursing care when being old and living with advanced cancer in a rural area in Norway. Narrative interviews were conducted with nine older persons, and a phenomenological hermeneutic approach was used to interpret the meaning of the lived experience. The analysis revealed three themes, each with subthemes: being content with what one gets, falling into place, and losing one's place. The phrase picking up the pieces was found useful to sum up the meaning of this lived experience. The three respective themes refer to how the pieces symbolize the remaining parts of life or available services in their environment, and how the older persons may see themselves as pieces or bricks in a puzzle. A strong place attachment (physical insideness, social insideness, and autobiographical insideness) is demonstrated by the informants in this study and suggests that the rural context may provide an advantageous healthcare environment. Its potential to be a source of comfort, security, and identity concurs with cancer patients' strong desire for being seen as unique persons. The study shows that district nurses play an essential role in the provision of palliative care for older rural patients. However, the therapeutic value of being in one's familiar landscape seems to depend on how homecare nurses manage to locate it and use it in a more or less person-centred manner. Communication skills and attentiveness to psychosocial aspects of patient care stand out as important attributes for nursing in this context. PMID:26362533

  8. Catalytic Propulsion and Magnetic Steering of Soft, Patchy Microcapsules: Ability to Pick-Up and Drop-Off Microscale Cargo.

    PubMed

    Lu, Annie Xi; Liu, Yijing; Oh, Hyuntaek; Gargava, Ankit; Kendall, Eric; Nie, Zhihong; DeVoe, Don L; Raghavan, Srinivasa R

    2016-06-22

    We describe the creation of polymeric microcapsules that can exhibit autonomous motion along defined trajectories. The capsules are made by cross-linking aqueous microdroplets of the biopolymer chitosan using glutaraldehyde. A coflow microfluidic tubing device is used to generate chitosan droplets containing nanoparticles (NPs) with an iron (Fe) core and a platinum (Pt) shell. The droplets are then incubated in a Petri dish with the cross-linking solution, and an external magnet is placed below the Petri dish to pull the NPs together as a collective "patch" on one end of each droplet. This results in cross-linked capsules (∼150 μm in diameter) with an anisotropic (patchy) structure. When these capsules are placed in a solution of H2O2, the Pt shell of the NPs catalyzes the decomposition of H2O2 into O2 gas, which is ejected from the patchy end in the form of bubbles. As a result, the capsules (which are termed micromotors) move in a direction opposite to the bubbles. Furthermore, the micromotors can be steered along specific paths by an external magnet (the magnetic response arises due to the Fe in the core of the NPs). A given micromotor can thus be directed to meet with and adhere to an inert capsule, i.e., a model cargo. Adhesion occurs due to the soft nature of the two structures. Once the cargo is picked up, the micromotor-cargo pair can be moved along a specific path to a destination, whereupon the cargo can be released from the micromotor. We believe these soft micromotors offer significant benefits over their existing hard counterparts because of their biocompatibility, biodegradability, and ability to encapsulate a variety of payloads. PMID:27295420

  9. Ovarian follicular dynamics, follicle deviation, and oocyte yield in Gyr breed (Bos indicus) cows undergoing repeated ovum pick-up.

    PubMed

    Viana, J H M; Palhao, M P; Siqueira, L G B; Fonseca, J F; Camargo, L S A

    2010-04-15

    The objective of this study was to evaluate ovarian follicular dynamics during intervals between successive ovum pick-up (OPU) and determine its effects on the number and quality of recovered cumulus-oocyte complexes (COCs) in Zebu cows (Bos indicus). Pluriparous nonlactating Gyr cows (Bos indicus; n=10) underwent four consecutive OPU sessions at 96-h intervals. The dynamics of ovarian follicular growth between OPU sessions was monitored by twice-daily ultrasonographic examinations. A single dominant follicle (DF) or two codominant (CDF) follicles (>9mm) were present in 63.3% (19 of 30) of intervals studied, with follicle deviation beginning when the future dominant follicle (F1) achieved a diameter of 6.2+/-0.3mm. The phenomenon of codominance was observed in four (13.3%) of the inter-OPU intervals. The remaining intervals (36.6%, 11 of 30) were characterized by a greater follicular population, lower rate of follicular growth, and a smaller diameter F1 (P<0.0001). There was a tendency (P=0.08) toward an increase in the number of recovered COCs when dominant follicles were not present (NDF). The quality of COCs was not affected by the presence of a single dominant follicle, but codominant follicles resulted in recovery of a lower proportion of viable embryos (40.0%, 62.1%, and 63.6%; P<0.05) and higher proportions of degenerate COCs (56.0%, 30.3%, and 28.6%; P<0.05) for CDF, NDF, and DF respectively. We concluded that, in Zebu cows, (a) repeated follicle aspirations altered ovarian follicular dynamics, perhaps by increasing follicular growth rate; (b) follicular dominance could be established in cows undergoing twice-a-week OPU; and (c) the presence of a dominant follicle during short inter-OPU intervals may not affect COC quality, except when a codominant follicle was present. PMID:20071017

  10. Manipulating the spin-dependent splitting by geometric Doppler effect.

    PubMed

    Liu, Yachao; Ke, Yougang; Zhou, Junxiao; Luo, Hailu; Wen, Shuangchun

    2015-06-29

    We report the manipulation of spin-dependent splitting by geometric Doppler effect based on dielectric metasurfaces. The extrapolation of rotational Doppler effect from temporal to spatial coordinate gives the phase change when the local optical axes of dielectric metasurfaces are rotating in space. Therefore, the continuous variation of local optical axes in a certain direction will introduce a phase gradient in the same direction at the beam cross section. This is additive to the phase gradient appeared when breaking the rotational symmetry of linearly polarized cylindrical vector beams, which leads to the deflections of different spin components of light, i.e., photonic spin Hall effect. Hence, it is possible to manipulate the spin-dependent splitting by introducing the geometric Doppler effect. Theoretically and experimentally, we show that the magnitude and orientation of the spin-dependent splitting are both tunable when changing the spatial rotation rate of local optical axes and incident polarization. PMID:26191680

  11. Spin-dependent shot noise in semiconductor and graphene nanostructures

    NASA Astrophysics Data System (ADS)

    Dragomirova, Ralitsa L.

    Shot noise is the name given to the time-dependent non-equilibrium current (or voltage) fluctuations which persist down to zero temperature and are fundamentally related to the discrete nature of the electron charge. Over the past two decades it has become a major tool for gathering information about microscopic mechanisms of transport and correlations between charges which cannot be extracted from traditional conductance measurements. Recently a handful of theoretical and experimental studies have suggested that shot noise in systems with spin-dependent interactions provides a sensitive probe to differentiate between scattering from magnetic impurities, spin-flip scattering, and continuous spin precession effects on semiclassical or quantum transport of injected spin-polarized currents. This is due to the fact that any spin flip converts spin-↑ subsystem particle into a spin-↓ subsystem particle, where the two subsystems differ when spin degeneracy is lifted. Thus, the nonconservation of the number of particles in each subsystem generates additional source of current fluctuations. Here we generalize the scattering theory of quantum shot noise to include the full spin-density matrix of electrons. This formalism yields the spin-resolved shot noise power applicable for a generic spintronic device where partially polarized charge current or even pure spin current is injected from a spin-filtering or ferromagnetic electrode into a quantum-coherent nanostructure governed by arbitrary spin-dependent interactions. The developed formalism [2, 5] is applied in Chapter 5 to diffusive multichannel quantum wires with the Rashba spin-orbit (SO) coupling sandwiched between ferromagnetic source and ferromagnetic or normal drain electrodes. The crucial role played by the SO interactions in all-electrical control of spin in semiconductor nanostructures has ignited recent studies of their signatures on the shot noise. We investigate what is the effect of the Rahsba SO coupling

  12. Spin-dependent inelastic collisions in spin-2 Bose-Einstein condensates

    SciTech Connect

    Tojo, Satoshi; Hayashi, Taro; Tanabe, Tatsuyoshi; Hirano, Takuya; Kawaguchi, Yuki; Saito, Hiroki; Ueda, Masahito

    2009-10-15

    We studied spin-dependent two-body inelastic collisions in F=2 {sup 87}Rb Bose-Einstein condensates both experimentally and theoretically. The {sup 87}Rb condensates were confined in an optical trap and selectively prepared in various spin states in the F=2 manifold at a magnetic field of 3.0 G. The measured atom loss rates depend on the spin states of colliding atoms. We measured two fundamental loss coefficients for two-body inelastic collisions with total spins of 0 and 2. The loss coefficients determine the loss rates of all the spin pairs. The experimental results for mixtures of all spin combinations are in good agreement with numerical solutions of the Gross-Pitaevskii equations that include the effect of a magnetic field gradient.

  13. Strain-modulation of spin-dependent transport in graphene

    SciTech Connect

    Cao, Zhen-Zhou Hou, Jin; Cheng, Yan-Fu; Li, Guan-Qiang

    2014-10-27

    We investigate strain modulation of the spin-dependent electron transport in a graphene junction using the transfer matrix method. As an analogy to optics, we define the modulation depth in the electron optics domain. Additionally, we discuss the transport properties and show that the modulation depth and the conductance depend on the spin-orbit coupling strength, the strain magnitude, the width of the strained area, and the energy of the incident electron. The conductances of the spin-down and spin-up electrons have opposite and symmetrical variations, which results in the analogous features of their modulation depths. The maximum conditions for both the modulation depth and the electron spin upset rate are also analyzed.

  14. Angular dependent study on spin transport in magnetic semiconductor heterostructures with Dresselhaus spin-orbit interaction

    NASA Astrophysics Data System (ADS)

    Mirzanian, S. M.; Shokri, A. A.; Mikaili Agah, K.; Elahi, S. M.

    2015-09-01

    We investigate theoretically the effects of Dresselhaus spin-orbit coupling (DSOC) on the spin-dependent current and shot noise through II-VI diluted magnetic semiconductor/nonmagnetic semiconductor (DMS/NMS) barrier structures. The calculation of transmission probability is based on an effective mass quantum-mechanical approach in the presence of an external magnetic field applied along the growth direction of the junction and also applied voltage. We also study the dependence of spin-dependent properties on external magnetic field and relative angle between the magnetizations of two DMS layers in CdTe/CdMnTe heterostructures by including the DSOC effect. The results show that the DSOC has great different influence on transport properties of electrons with spin up and spin down in the considered system and this aspect may be utilized in designing new spintronics devices.

  15. Moments of nucleon spin-dependent generalized parton distributions

    SciTech Connect

    Wolfram Schroers; Richard Brower; Patrick Dreher; Robert Edwards; George Fleming; P. Hagler; Urs Heller; Thomas Lippert; John Negele; Andrew Pochinsky; Dru Renner; David Richards; Klaus Schilling

    2004-03-01

    We present a lattice measurement of the first two moments of the spin-dependent GPD H-tilde(x,xi,t). From these we obtain the axial coupling constant and the second moment of the spin-dependent forward parton distribution. The measurements are done in full QCD using Wilson fermions. In addition, we also present results from a first exploratory study of full QCD using Asqtad sea and domain-wall valence fermions.

  16. Ovum pick up in swine: the influence of aspiration vacuum pressure on oocyte recovery from preovulatory follicles.

    PubMed

    Brüssow, K P; Torner, H; Rátky, J; Hunter, M G; Nürnberg, G

    1997-01-01

    Endoscopical ovum pick up (OPU) in swine is a minimal invasive and reliable technique to aspirate oocytes from preovulatory follicles for studying intrafollicular development and oocyte maturation as well as for IVM/IVF-programs. The aim of the present study was to determine the effect of different aspiration vacuum pressures on oocyte recovery and on the morphology of cumulus oocyte complexes (COCs). Oestrus of crossbred Landrace gilts (n = 33) was synchronized by feeding altrenogest and follicular growth was stimulated with 1,000 IU PMSG 24 h after the last altrenogest application. On day 4 after PMSG application preovulatory healthy follicles of > 5 mm diameter were aspirated laparoscopically. Aspiration was carried out using a two-way cannula and an electronic aspiration pump. Five different vacuum pressures were used: 10, 17, 32, 47 and 66 ml water/min, corresponding to 30, 60, 125, 250 and 375 mm Hg, respectively. Fluids from different follicles were pooled per ovary and the morphology of cumulus oocyte complexes (COCs) was determined microscopically immediately after aspiration. COCs were classified into oocytes with intact cumulus (i.e. compact or slightly expanded COC), oocytes with corona radiata and denuded oocytes. A total of 695 follicles were aspirated and 501 COCs recovered. Increasing the aspiration pressure stepwise from 10 ml water/min up to 66 ml water/min resulted in a decrease in oocyte recovery rate. A significant higher (P < 0.05) rate of oocyte recovery (77.4% v.s. 59.8%) was achieved using a vacuum pressure of 17 ml water/min compared to 66 ml water/min, respectively. There was a tendency to reduce the portion of COCs with intact cumulus from 82 to 88% to 77% if the vacuum pressure increased to more than 47 ml water/min. A higher aspiration pressure provoked an increase (P < 0.05) in the number of denuded oocytes: 0 to 3% at 10 to 32 ml water/min, respectively, compared to 10% at 47 ml water/min to 17% at 66 ml water/min. These results

  17. Developmental competence of different quality bovine oocytes retrieved through ovum pick-up following in vitro maturation and fertilization.

    PubMed

    Saini, N; Singh, M K; Shah, S M; Singh, K P; Kaushik, R; Manik, R S; Singla, S K; Palta, P; Chauhan, M S

    2015-12-01

    In the present study, oocytes retrieved from cross bred Karan Fries cows by ovum pick-up technique were graded into Group 1 and Group 2, based on the morphological appearance of the individual cumulus-oocyte complexes (COCs). To analyze whether the developmental potential of the COCs bears a relation to morphological appearance, relative expression of a panel of genes associated with; (a) cumulus-oocyte interaction (Cx43, Cx37, GDF9 and BMP15), (b) fertilization (ZP2 and ZP3), (c) embryonic development (HSF1, ZAR1 and bFGF) and (d) apoptosis and survival (BAX, BID and BCL-XL, MCL-1, respectively) was studied at two stages: germinal vesicle (GV) stage and after in vitro maturation. The competence was further corroborated by evaluating the embryonic progression of the presumed zygotes obtained from fertilization of the graded COCs. The gene expression profile and development rate in pooled A and B grade (Group 1) COCs and pooled C and D grade (Group 2) COCs were determined and compared according to the original grades. The results of the study demonstrated that the morphologically characterized Group 2 COCs showed significantly (P<0.05) lower expression for most of the genes related to cumulus-oocyte interplay, fertilization and embryonic development, both at GV stage as well as after maturation. Group 1 COCs also showed greater expression of anti-apoptotic genes (BCL-XL and MCL1) both at GV stage and after maturation, while pro-apoptotic genes (BAX and BID) showed significantly (P<0.05) elevated expression in poor quality COCs at both the stages. The cleavage rate in Group 1 COCs was significantly higher than that of Group 2 (74.46±7.06 v. 31.57±5.32%). The development of the presumed zygotes in Group 2 oocytes proceeded up to 8- to 16-cell stages only, while in Group 1 it progressed up to morulae (35.38±7.11%) and blastocyst stages (9.70±3.15%), indicating their better developmental potential. PMID:26165355

  18. Laparoscopic ovum pick-up and in vitro production of sika deer embryos: effect of season and culture conditions.

    PubMed

    Locatelli, Y; Vallet, J C; Huyghe, F P; Cognié, Y; Legendre, X; Mermillod, P

    2006-09-15

    Amongst the 200 deer subspecies worldwide, more than 40 are considered as endangered. In vitro embryo production may represent an efficient way to produce and disseminate offspring from sparse remaining individuals in these species. With a view to establishing a method of in vitro embryo production, we assessed the ovarian response after hormonal stimulation (oFSH), oocyte yield following laporoscopic ovum pick-up (LOPU) and oocyte developmental competence according to seasonal reproductive status in sika deer (Cervus nippon nippon). Twelve adult sika deer hinds were allocated between two groups and submitted weekly to oFSH follicular growth stimulation followed by LOPU. Hinds in Group A (n=6) were treated first during the breeding season (5 weeks), and then during the non-breeding season (3 weeks). Hinds in Group B (n=6) were submitted to similar procedures but in the reverse order (treated first during the non-breeding season). Cumulus-oocytes complexes (COC) recovered from Group B were allowed to mature in vitro for 24 h in TCM-199 medium supplemented with oFSH, goat follicular fluid and 100 microM cysteamine. In vitro fertilization was performed with frozen/thawed semen in SOFaa medium supplemented with 20% estrous sheep serum and presumptive zygotes were cultured in the presence or absence of ovine oviductal epithelial cell monolayer (oOEC) in SOFaa-BSA medium. Mean number of follicles aspirated per hind per session decreased significantly between breeding and non-breeding season in Group A (9.8+/-0.7 versus 3.2+/-0.7, mean+/-S.E.M., respectively, P<0.001) but did not change between the non-breeding and the subsequent breeding season in Group B (5.3+/-0.7 and 5.7+/-0.7, respectively, P>0.05). Irrespective of the season, good quality COC with complete and compact cumulus investments were recovered allowing a high cleavage rate after in vitro maturation and fertilization. Whereas development to the blastocyst stage did not occur in SOF medium alone, high

  19. Spin-dependent Klein tunneling in polariton graphene with photonic spin-orbit interaction

    NASA Astrophysics Data System (ADS)

    Solnyshkov, Dmitry; Nalitov, Anton; Teklu, Berihu; Franck, Louis; Malpuech, Guillaume

    2016-02-01

    We study Klein tunneling in polariton graphene. We show that the photonic spin-orbit coupling associated with the energy splitting between TE and TM photonic modes can be described as an emergent gauge field. It suppresses the Klein tunneling in a small energy range close to the Dirac points. Thanks to polariton spin-anisotropic interactions, polarized optical pumping allows one to create potential barriers acting on a single polariton spin. We show that the resulting spin-dependent Klein tunneling can be used to create a perfectly transmitting polarization rotator operating at microscopic scale.

  20. Spin-dependent Seebeck effect and spin caloritronics in magnetic graphene

    NASA Astrophysics Data System (ADS)

    Rameshti, Babak Zare; Moghaddam, Ali G.

    2015-04-01

    We investigate the spin-dependent thermoelectric effects in magnetic graphene in both diffusive and ballistic regimes. Employing the Boltzmann and Landauer formalisms we calculate the spin and charge Seebeck coefficients (thermopower) in magnetic graphene varying the spin splitting, temperature, and doping of the junction. It is found that while in normal graphene the temperature gradient drives a charge current, in the case of magnetic graphene a significant spin current is also established. In particular we show that in the undoped magnetic graphene in which different spin carriers belong to conduction and valence bands, a pure spin current is driven by the temperature gradient. In addition it is revealed that profound thermoelectric effects can be achieved at intermediate easily accessible temperatures when the thermal energy is comparable with Fermi energy kBT ≲μ . By further investigation of the spin-dependent Seebeck effect and a significantly large figure of merit for spin thermopower ZspT , we suggest magnetic graphene as a promising material for spin-caloritronics studies and applications.

  1. Spin-dependent recombination probed through the dielectric polarizability

    PubMed Central

    Bayliss, Sam L.; Greenham, Neil C.; Friend, Richard H.; Bouchiat, Hélène; Chepelianskii, Alexei D

    2015-01-01

    Despite residing in an energetically and structurally disordered landscape, the spin degree of freedom remains a robust quantity in organic semiconductor materials due to the weak coupling of spin and orbital states. This enforces spin-selectivity in recombination processes which plays a crucial role in optoelectronic devices, for example, in the spin-dependent recombination of weakly bound electron-hole pairs, or charge-transfer states, which form in a photovoltaic blend. Here, we implement a detection scheme to probe the spin-selective recombination of these states through changes in their dielectric polarizability under magnetic resonance. Using this technique, we access a regime in which the usual mixing of spin-singlet and spin-triplet states due to hyperfine fields is suppressed by microwave driving. We present a quantitative model for this behaviour which allows us to estimate the spin-dependent recombination rate, and draw parallels with the Majorana–Brossel resonances observed in atomic physics experiments. PMID:26439933

  2. Spin-dependent recombination probed through the dielectric polarizability.

    PubMed

    Bayliss, Sam L; Greenham, Neil C; Friend, Richard H; Bouchiat, Hélène; Chepelianskii, Alexei D

    2015-01-01

    Despite residing in an energetically and structurally disordered landscape, the spin degree of freedom remains a robust quantity in organic semiconductor materials due to the weak coupling of spin and orbital states. This enforces spin-selectivity in recombination processes which plays a crucial role in optoelectronic devices, for example, in the spin-dependent recombination of weakly bound electron-hole pairs, or charge-transfer states, which form in a photovoltaic blend. Here, we implement a detection scheme to probe the spin-selective recombination of these states through changes in their dielectric polarizability under magnetic resonance. Using this technique, we access a regime in which the usual mixing of spin-singlet and spin-triplet states due to hyperfine fields is suppressed by microwave driving. We present a quantitative model for this behaviour which allows us to estimate the spin-dependent recombination rate, and draw parallels with the Majorana-Brossel resonances observed in atomic physics experiments. PMID:26439933

  3. Pick-up ions at Comet P/Halley's bow shock - Observations with the IIS spectrometer on Giotto. [Implanted In Spectrometer

    NASA Technical Reports Server (NTRS)

    Wilken, B.; Johnstone, A.; Coates, A.; Amata, E.; Borg, H.

    1987-01-01

    Gaseous material expanding from the nucleus of Comet Halley into space forms the neutral coma around the comet. Ionization in the solar UV radiation removes particles from the coma and injects them into the solar wind plasma. These freshly created ions are accelerated by the interplanetary electric field on cycloidal trajectories with gyrocenters moving with the speed of the magnetic field lines. In the solar wind frame of reference these particles move along the magnetic field lines with a fixed pitch angle. Pitch-angle scattering and energy diffusion reduce quickly the initial energy anisotropy which is associated with the narrow pick-up structures. First observations of heavy cometary pick-up ions (water group ions) at the bow shock are presented. The evolution of the distribution function in the vicinity of the shock and radial density profiles are discussed.

  4. Anomalous organic magnetoresistance from competing carrier-spin-dependent interactions with localized electronic and nuclear spins

    NASA Astrophysics Data System (ADS)

    Flatté, Michael E.

    Transport of carriers through disordered electronic energy landscapes occurs via hopping or tunneling through various sites, and can enhance the effects of carrier spin dynamics on the transport. When incoherent hopping preserves the spin orientation of carriers, the magnetic-field-dependent correlations between pairs of spins influence the charge conductivity of the material. Examples of these phenomena have been identified in hopping transport in organic semiconductors and colloidal quantum dots, as well as tunneling through oxide barriers in complex oxide devices, among other materials. The resulting room-temperature magnetic field effects on the conductivity or electroluminescence require external fields of only a few milliTesla. These magnetic field effects can be dramatically modified by changes in the local spin environment. Recent theoretical and experimental work has identified a regime for low-field magnetoresistance in organic semiconductors in which the spin-relaxing effects of localized nuclear spins and electronic spins interfere1. The regime is studied experimentally by the controlled addition of localized electronic spins, through the addition of a stable free radical (galvinoxyl) to a material (MEH-PPV) that exhibits substantial room-temperature magnetoresistance (20 initially suppressed by the doping, as the localized electronic spin mixes one of the two spins whose correlation controls the transport. At intermediate doping, when one spin is fully decohered but the other is not, there is a regime where the magnetoresistance is insensitive to the doping level. For much greater doping concentrations the magnetoresistance is fully suppressed as both spins that control the charge conductivity of the material are mixed. The behavior is described within a theoretical model describing the effect of carrier spin dynamics on the current. Generalizations to amorphous and other disordered crystalline semiconductors will also be described. This work was

  5. Chirality-Dependent Transmission of Spin Waves through Domain Walls

    NASA Astrophysics Data System (ADS)

    Buijnsters, F. J.; Ferreiros, Y.; Fasolino, A.; Katsnelson, M. I.

    2016-04-01

    Spin-wave technology (magnonics) has the potential to further reduce the size and energy consumption of information-processing devices. In the submicrometer regime (exchange spin waves), topological defects such as domain walls may constitute active elements to manipulate spin waves and perform logic operations. We predict that spin waves that pass through a domain wall in an ultrathin perpendicular-anisotropy film experience a phase shift that depends on the orientation of the domain wall (chirality). The effect, which is absent in bulk materials, originates from the interfacial Dzyaloshinskii-Moriya interaction and can be interpreted as a geometric phase. We demonstrate analytically and by means of micromagnetic simulations that the phase shift is strong enough to switch between constructive and destructive interference. The two chirality states of the domain wall may serve as a memory bit or spin-wave switch in magnonic devices.

  6. Chirality-Dependent Transmission of Spin Waves through Domain Walls.

    PubMed

    Buijnsters, F J; Ferreiros, Y; Fasolino, A; Katsnelson, M I

    2016-04-01

    Spin-wave technology (magnonics) has the potential to further reduce the size and energy consumption of information-processing devices. In the submicrometer regime (exchange spin waves), topological defects such as domain walls may constitute active elements to manipulate spin waves and perform logic operations. We predict that spin waves that pass through a domain wall in an ultrathin perpendicular-anisotropy film experience a phase shift that depends on the orientation of the domain wall (chirality). The effect, which is absent in bulk materials, originates from the interfacial Dzyaloshinskii-Moriya interaction and can be interpreted as a geometric phase. We demonstrate analytically and by means of micromagnetic simulations that the phase shift is strong enough to switch between constructive and destructive interference. The two chirality states of the domain wall may serve as a memory bit or spin-wave switch in magnonic devices. PMID:27104725

  7. Spin-dependent shot noise in magnetic graphene superlattice

    NASA Astrophysics Data System (ADS)

    Sattari, Farhad

    2015-10-01

    We study the spin-dependent shot noise properties in magnetic graphene superlattice with Rashba spin-orbit interaction (RSOI). The magnetic field generated by N parallel ferromagnets (FM) deposited on a dielectric layer. We consider two types of magnetic profiles: the FM stripes with magnetization parallel (P) or antiparallel (AP) perpendicular to the graphene. It is found that the shot noise of a spin state can be efficiently controlled by the number of barrier, RSOI strength and magnetic field. In the first case the Fano factor shows a peak with value approximately F = 1/3 for the both spin-up and spin-down electrons at new Dirac-like point. The position of the new Dirac point is robust against the magnetic field and RSOI. In the second case the Fano factor increases by increasing the number of barriers, and plateau of the Fano factor is formed. The results indicate that there is a strong relationship between spin-dependent shot noise and the magnitude of the spin polarization.

  8. Longitudinal spin separation of light and its performance in three-dimensionally controllable spin-dependent focal shift

    PubMed Central

    Liu, Sheng; Li, Peng; Zhang, Yi; Gan, Xuetao; Wang, Meirong; Zhao, Jianlin

    2016-01-01

    Spin Hall effect of light, which is normally explored as a transverse spin-dependent separation of a light beam, has attracted enormous research interests. However, it seems there is no indication for the existence of the longitudinal spin separation of light. In this paper, we propose and experimentally realize the spin separation along the propagation direction by modulating the Pancharatnam-Berry (PB) phase. Due to the spin-dependent divergence and convergence determined by the PB phase, a focused Gaussian beam could split into two opposite spin states, and focuses at different distances, representing the longitudinal spin separation. By combining this longitudinal spin separation with the transverse one, we experimentally achieve the controllable spin-dependent focal shift in three dimensional space. This work provides new insight on steering the spin photons, and is expected to explore novel applications of optical trapping, manipulating, and micromachining with higher degree of freedom. PMID:26882995

  9. Longitudinal spin separation of light and its performance in three-dimensionally controllable spin-dependent focal shift.

    PubMed

    Liu, Sheng; Li, Peng; Zhang, Yi; Gan, Xuetao; Wang, Meirong; Zhao, Jianlin

    2016-01-01

    Spin Hall effect of light, which is normally explored as a transverse spin-dependent separation of a light beam, has attracted enormous research interests. However, it seems there is no indication for the existence of the longitudinal spin separation of light. In this paper, we propose and experimentally realize the spin separation along the propagation direction by modulating the Pancharatnam-Berry (PB) phase. Due to the spin-dependent divergence and convergence determined by the PB phase, a focused Gaussian beam could split into two opposite spin states, and focuses at different distances, representing the longitudinal spin separation. By combining this longitudinal spin separation with the transverse one, we experimentally achieve the controllable spin-dependent focal shift in three dimensional space. This work provides new insight on steering the spin photons, and is expected to explore novel applications of optical trapping, manipulating, and micromachining with higher degree of freedom. PMID:26882995

  10. Magnetization dynamics driven by angle-dependent spin-orbit spin-transfer torque

    NASA Astrophysics Data System (ADS)

    Lee, Seo-Won; Lee, Kyung-Jin

    2015-11-01

    Spin-orbit torque allows efficient control of the magnetization by using the in-plane current. Recent experiments found a strong angular dependence of spin-orbit torque. We theoretically investigate magnetization switching and domain wall motion induced by an angle-dependent spinorbit torque in perpendicularly magnetized layers. We obtain analytic expressions for the switching current and the domain wall velocity, which are in agreement with numerical results. Based on the expressions, we find that a spin-orbit torque that increases with increasing polar angle of the magnetization is beneficial for both switching and domain wall motion. Our result will serve as a guideline to design and interpret switching and domain wall experiments based on the spin-orbit torque.

  11. [Spin dependent phenomena in medium energy physics]. Technical progress report

    SciTech Connect

    Souder, P.A.

    1992-11-01

    The Syracuse University Medium Energy Physics Group was actively engaged in several research projects. A laser was used to polarize muonic atoms with the goal of measuring fundamental spin-dependent parameters in the reaction {mu}{sup {minus}} + {sup 3}He {yields} {sup 3}H + {nu}. Time-averaged polarizations of 26.8{plus_minus}2.3% were achieved for the muon in muonic {sup 3}He. The new approach uses atomic spin-dependent reactions between laser polarized Rb vapor and muonic helium. To exploit these high polarizations in a muon capture experiment an ion chamber which will detect the recoil tritons and also serve as a polarizing cell. Final data-taking will begin for an experiment to measure the spin-dependent structure functions of the neutron. A 288-element hodoscope system which features good timing and precise mechanical tolerances was constructed and evaluated.

  12. Spin-Dependent Transport in Fe/GaAs(100)/Fe Vertical Spin-Valves

    NASA Astrophysics Data System (ADS)

    Wong, P. K. Johnny; Zhang, Wen; Wu, Jing; Will, Iain G.; Xu, Yongbing; Xia, Ke; Holmes, Stuart N.; Farrer, Ian; Beere, Harvey E.; Ritchie, Dave A.

    2016-07-01

    The integration of magnetic materials with semiconductors will lead to the development of the next spintronics devices such as spin field effect transistor (SFET), which is capable of both data storage and processing. While the fabrication and transport studies of lateral SFET have attracted greatly attentions, there are only few studies of vertical devices, which may offer the opportunity for the future three-dimensional integration. Here, we provide evidence of two-terminal electrical spin injection and detection in Fe/GaAs/Fe vertical spin-valves (SVs) with the GaAs layer of 50 nanometers thick and top and bottom Fe electrodes deposited by molecular beam epitaxy. The spin-valve effect, which corresponds to the individual switching of the top and bottom Fe layers, is bias dependent and observed up to 20 K. We propose that the strongly bias- and temperature-dependent MR is associated with spin transport at the interfacial Fe/GaAs Schottky contacts and in the GaAs membranes, where balance between the barrier profiles as well as the dwell time to spin lifetime ratio are crucial factors for determining the device operations. The demonstration of the fabrication and spin injection in the vertical SV with a semiconductor interlayer is expected to open a new avenue in exploring the SFET.

  13. Spin-Dependent Transport in Fe/GaAs(100)/Fe Vertical Spin-Valves.

    PubMed

    Wong, P K Johnny; Zhang, Wen; Wu, Jing; Will, Iain G; Xu, Yongbing; Xia, Ke; Holmes, Stuart N; Farrer, Ian; Beere, Harvey E; Ritchie, Dave A

    2016-01-01

    The integration of magnetic materials with semiconductors will lead to the development of the next spintronics devices such as spin field effect transistor (SFET), which is capable of both data storage and processing. While the fabrication and transport studies of lateral SFET have attracted greatly attentions, there are only few studies of vertical devices, which may offer the opportunity for the future three-dimensional integration. Here, we provide evidence of two-terminal electrical spin injection and detection in Fe/GaAs/Fe vertical spin-valves (SVs) with the GaAs layer of 50 nanometers thick and top and bottom Fe electrodes deposited by molecular beam epitaxy. The spin-valve effect, which corresponds to the individual switching of the top and bottom Fe layers, is bias dependent and observed up to 20 K. We propose that the strongly bias- and temperature-dependent MR is associated with spin transport at the interfacial Fe/GaAs Schottky contacts and in the GaAs membranes, where balance between the barrier profiles as well as the dwell time to spin lifetime ratio are crucial factors for determining the device operations. The demonstration of the fabrication and spin injection in the vertical SV with a semiconductor interlayer is expected to open a new avenue in exploring the SFET. PMID:27432047

  14. Spin-Dependent Transport in Fe/GaAs(100)/Fe Vertical Spin-Valves

    PubMed Central

    Wong, P. K. Johnny; Zhang, Wen; Wu, Jing; Will, Iain G.; Xu, Yongbing; Xia, Ke; Holmes, Stuart N.; Farrer, Ian; Beere, Harvey E.; Ritchie, Dave A.

    2016-01-01

    The integration of magnetic materials with semiconductors will lead to the development of the next spintronics devices such as spin field effect transistor (SFET), which is capable of both data storage and processing. While the fabrication and transport studies of lateral SFET have attracted greatly attentions, there are only few studies of vertical devices, which may offer the opportunity for the future three-dimensional integration. Here, we provide evidence of two-terminal electrical spin injection and detection in Fe/GaAs/Fe vertical spin-valves (SVs) with the GaAs layer of 50 nanometers thick and top and bottom Fe electrodes deposited by molecular beam epitaxy. The spin-valve effect, which corresponds to the individual switching of the top and bottom Fe layers, is bias dependent and observed up to 20 K. We propose that the strongly bias- and temperature-dependent MR is associated with spin transport at the interfacial Fe/GaAs Schottky contacts and in the GaAs membranes, where balance between the barrier profiles as well as the dwell time to spin lifetime ratio are crucial factors for determining the device operations. The demonstration of the fabrication and spin injection in the vertical SV with a semiconductor interlayer is expected to open a new avenue in exploring the SFET. PMID:27432047

  15. A Search for Exotic Spin-Dependent Interactions of the Neutron using Neutron Spin Rotation

    NASA Astrophysics Data System (ADS)

    Haddock, Chris; Nsr Collaboration

    2016-03-01

    Many theories beyond the Standard Model lead at low energy to spin-dependent, weakly-coupled interactions of mesoscopic range. Laboratory constraints on such interactions are quite poor. We describe an experiment in progress at the LANSCE spallation neutron source at Los Alamos to search for exotic axial couplings of neutrons to matter from light vector boson exchange. The experiment makes use of a slow neutron polarimeter and a target with an oscillating mass density. Neutron Spin Rotation.

  16. Spin tune dependence on closed orbit in RHIC

    SciTech Connect

    Ptitsyn, V.; Bai, M.; Roser, T.

    2010-05-23

    Polarized proton beams are accelerated in RHIC to 250 GeV energy with the help of Siberian Snakes. The pair of Siberian Snakes in each RHIC ring holds the design spin tune at 1/2 to avoid polarization loss during acceleration. However, in the presence of closed orbit errors, the actual spin tune can be shifted away from the exact 1/2 value. It leads to a corresponding shift of locations of higher-order ('snake') resonances and limits the available betatron tune space. The largest closed orbit effect on the spin tune comes from the horizontal orbit angle between the two snakes. During RHIC Run in 2009 dedicated measurements with polarized proton beams were taken to verify the dependence of the spin tune on the local orbits at the Snakes. The experimental results are presented along with the comparison with analytical predictions.

  17. Spin-Dependent Transport Phenomena in Ferromagnet/Semiconductor Heterostructures

    NASA Astrophysics Data System (ADS)

    Geppert, Chad Christopher

    This dissertation examines several aspects of spin-dependent transport phenomena in epitaxially grown ferromagnet/n-GaAs heterostructures. Further maturation of the field of semiconductor-based spintronics is hindered by difficulties in evaluating device performance across materials systems. Using Fe/n-GaAs and Co2MnSi/n-GaAs heterostructures as a test case, the main goal of this work is to demonstrate how such difficulties may be overcome by (1) specifying a more quantitative framework for evaluating transport parameters and (2) the introduction of a new spin-to-charge conversion phenomenon which may be parameterized by bulk semiconductor parameters. In the introductory chapter, this work is placed in the broader context of developing improved methods for the generation, modulation, and detection of spins. The lateral spin-valve geometry is presented as a concrete example of the typical measurement procedures employed. Chapter 2 presents the charge-based transport properties of these samples and establishes the notation and calculation techniques to be employed in subsequent chapters. In particular, we examine in detail the calculation of the electrochemical potential for a given carrier concentration. Chapter 3 provides a full derivation of the equations governing spin-dependent transport in the large polarization regime. This is applied to the case of extracting spin lifetimes and diffusion rates, demonstrating how quantitative agreement with theoretical predictions may be obtained upon properly accounting for both device geometry and material parameters. Further examination of the boundary conditions applicable to the heterojunctions of these samples demonstrates to what extent device performance may be parameterized across materials systems. Chapter 4 presents experimental observations of a new spin-to-charge conversion phenomenon using a non-magnetic probe. In the presence of a large non-equilibrium spin accumulation, the combination of a non-constant density

  18. Spin-dependent electron transport in nanoscale samples

    NASA Astrophysics Data System (ADS)

    Wei, Yaguang

    In this thesis, we describe the research in which we use metallic nanoparticles to explore spin-dependent electron transport at nanometer scale. Nanoscale samples were fabricated by using a state of the art electron beam lithography and shadow evaporation technique. We have investigated spin relaxation and decoherence in metallic grains as a function of bias voltage and magnetic field at low temperatures (down to ˜30mK). At low temperatures, the discrete energy levels within a metallic nanoparticle provides a new means to study the physics of the spin-polarized electron tunneling. We describe measurements of spin-polarized tunneling via discrete energy levels of single Aluminum grain. Spin polarized current saturates quickly as a function of bias voltage, which demonstrates that the ground state and the lowest excited states carry spin polarized current. The ratio of electron-spin relaxation time (T1) to the electron-phonon relaxation rate is in quantitative agreement with the Elliot-Yafet scaling, an evidence that spin-relaxation in Al grains is driven by the spin-orbit interaction. The spin-relaxation time of the low-lying excited states is T1 ≈ 0.7 mus and 0.1 mus in two samples, showing that electron spin in a metallic grain could be a potential candidate for quantum information research. We also present measurements of mesoscopic resistance fluctuations in cobalt nanoparticles at low temperature and study how the fluctuations with bias voltage, bias fingerprints, respond to magnetization-reversal processes. Bias fingerprints rearrange when domains are nucleated or annihilated. The domain wall causes an electron wave function-phase shift of ˜5 pi. The phase shift is not caused by the Aharonov-Bohm effect; we explain how it arises from the mistracking effect, where electron spins lag in orientation with respect to the moments inside the domain wall. The dephasing length at low temperatures is only 30 nm, which is attributed to the large magnetocrystalline

  19. All-Optical Helicity Dependent Spin Switching in a Many-Spin System

    NASA Astrophysics Data System (ADS)

    Latta, Tanner; Zhang, G. P.

    All-optical helicity dependent magnetic switching (AOS) is achieved through using an ultrafast laser pulse to manipulate and switch the spin of an electron from one direction to another. This process happens in a short amount of femtoseconds after the laser pulse is introduced. All-optical helicity dependent magnetic switching (AOS) does not fall to the assistance of any external magnetic field. Linearly polarized light, as well as right and left circularly polarized light are used to manipulate the spin of the electrons. Ferrimagnetic, rather than ferromagnetic, materials are more suitable to create conditions in which AOS are viable due to the orientation of the spins within this material. In the following study we show and conclude that AOS is possible with the use of left and right circularly polarized laser pulses. All-optical helicity dependent magnetic switching has many applications in magnetic recording technology or magnetic memory devices. DE-FG02-06ER46304.

  20. Spin-dependent Seebeck effect in Aharonov-Bohm rings with Rashba and Dresselhaus spin-orbit interactions

    NASA Astrophysics Data System (ADS)

    Liu, Bin; Li, Yunyun; Zhou, Jun; Nakayama, Tsuneyoshi; Li, Baowen

    2016-06-01

    We theoretically investigate the spin-dependent Seebeck effect in an Aharonov-Bohm mesoscopic ring in the presence of both Rashba and Dresselhaus spin-orbit interactions under magnetic flux perpendicular to the ring. We apply the Green's function method to calculate the spin Seebeck coefficient employing the tight-binding Hamiltonian. It is found that the spin Seebeck coefficient is proportional to the slope of the energy-dependent transmission coefficients. We study the strong dependence of spin Seebeck coefficient on the Fermi energy, magnetic flux, strength of spin-orbit coupling, and temperature. Maximum spin Seebeck coefficients can be obtained when the strengths of Rashba and Dresselhaus spin-orbit couplings are slightly different. The spin Seebeck coefficient can be reduced by increasing temperature and disorder.

  1. Crystalline Direction Dependence of Spin Precession Angle and Its Application to Complementary Spin Logic Devices.

    PubMed

    Park, Youn Ho; Kim, Hyung-Jun; Chang, Joonyeon; Choi, Heon-Jin; Koo, Hyun Cheol

    2015-10-01

    In a semiconductor channel, spin-orbit interaction is divided into two terms, Rashba and Dresselhaus effects, which are key phenomena for modulating spin precession angles. The direction of Rashba field is always perpendicular to the wavevector but that of Dresselhaus field depends on the crystal orientation. Based on the individual Rashba and Dresselhaus strengths, we calculate spin precession angles for various crystal orientations in an InAs quantum well structure. When the channel length is 1 μm, the precession angle is 550° for the [110] direction and 460° for the [1-10] direction, respectively. Using the two spin transistors with different crystal directions, which play roles of n- and p-type transistors in conventional charge transistors, we propose a complementary logic device. PMID:26726362

  2. Spin-dependent transport of spin-orbit coupled holes in GaAs nanostructures

    NASA Astrophysics Data System (ADS)

    Hamilton, Alex

    2012-02-01

    In undergraduate physics, we are often taught that holes in the valence band are just positively charged heavy electrons. But valence band holes are spin-3/2 particles, and this gives them very different properties to spin-1/2 electrons, particularly when confined to low dimensions. These differences show up as highly anisotropic spin properties, which can be directly probed with conventional transport measurements. We have fabricated high quality hole quantum wires that show clean and stable quantized conductance plateaus [1]. In contrast to 1D electron quantum systems, the spin-splitting in these hole wires is highly anisotropic [2], and depends only on the orientation of the in-plane magnetic field relative to the quantum wire [3]. However the orientation and k-dependence of the spin-splitting cannot be reconciled with existing theories, suggesting that more theoretical work is needed before we understand the physics of spin-3/2 holes, even on ``simple'' (100) surfaces. We have also studied spin-3/2 holes in quantum dots, which show characteristic signatures of Kondo physics. A clear zero-bias peak is observed in the differential conductance, which splits with an applied in-plane magnetic field. The splitting is twice as large as the splitting for the lowest one-dimensional subband, consistent with Kondo physics. Unlike electrons this splitting is highly anisotropic with magnetic field, due to the strong spin-orbit coupling [4]. [4pt] [1] O. Klochan et al., Appl. Phys. Lett. 89, 092105 (2006).[0pt] [2] R. Danneau et al., Phys. Rev. Lett. 97, 026403 (2006).[0pt] [3] J C H Chen et al, New Journal of Physics 12, 033043 (2010).[0pt] [4] O. Klochan et al, Phys. Rev. Lett. 107, 076805 (2011).

  3. Spin-dependent transport phenomena in organic semiconductors

    NASA Astrophysics Data System (ADS)

    Bergeson, Jeremy D.

    Thin-film organic semiconductors transport can have an anomalously high sensitivity to low magnetic fields. Such a response is unexpected considering that thermal fluctuation energies are greater than the energy associated with the intrinsic spin of charge carriers at a modest magnetic field of 100 Oe by a factor of more than 104 at room temperature and is still greater by 102 even at liquid helium temperatures. Nevertheless, we report experimental characterization of (1) spin-dependent injection, detection and transport of spin-polarized current through organic semiconductors and (2) the influence of a magnetic field on the spin dynamics of recombination-limited transport. The first focus of this work was accomplished by fabricating basic spin-valve devices consisting of two magnetic layers spatially separated by a nonmagnetic organic semiconductor. The spin-valve effect is a change in electrical resistance due to the magnetizations of the magnetic layers changing from parallel to antiparallel alignment, or vice versa. The conductivities of the metallic contacts and that of the semiconductor differed by many orders of magnitude, which inhibited the injection of a spin-polarized current from the magnet into the nonmagnet. We successfully overcame the problem of conductivity mismatch by inserting ultra-thin tunnel barriers at the metal/semiconductor interfaces which aided in yielding a ˜20% spin-valve effect at liquid helium temperatures and the effect persisted up to 150 K. We built on this achievement by constructing spin valves where one of the metallic contacts was replaced by the organic-based magnetic semiconductor vanadium tetracyanoethylene (V[TCNE]2). At 10 K these devices produced the switching behavior of the spin-valve effect. The second focus of this work was the bulk magnetoresistance (MR) of small molecule, oligomer and polymer organic semiconductors in thin-film structures. At room temperature the resistance can change up to 8% at 100 Oe and 15% at

  4. 3He Spin-Dependent Cross Sections and Sum Rules

    SciTech Connect

    Slifer, Karl; Amaryan, Moscov; Amaryan, Moskov; Auerbach, Leonard; Averett, Todd; Berthot, J.; Bertin, Pierre; Bertozzi, William; Black, Tim; Brash, Edward; Brown, D.; Burtin, Etienne; Calarco, John; Cates, Gordon; Chai, Zhengwei; Chen, Jian-Ping; Choi, Seonho; Chudakov, Eugene; Ciofi, Claudio; Cisbani, Evaristo; De Jager, Cornelis; Deur, Alexandre; DiSalvo, R.; Dieterich, Sonja; Djawotho, Pibero; Finn, John; Fissum, Kevin; Fonvieille, Helene; Frullani, Salvatore; Gao, Haiyan; Gao, Juncai; Garibaldi, Franco; Gasparian, Ashot; Gilad, Shalev; Gilman, Ronald; Glamazdin, Oleksandr; Glashausser, Charles; Glockle, W.; Golak, J.; Goldberg, Emma; Gomez, Javier; Gorbenko, Viktor; Hansen, Jens-Ole; Hersman, F.; Holmes, Richard; Huber, Garth; Hughes, Emlyn; Humensky, Thomas; Incerti, Sebastien; Iodice, Mauro; Jensen, S.; Jiang, Xiaodong; Jones, C.; Jones, G.; Jones, Mark; Jutier, Christophe; Kamada, H.; Ketikyan, Armen; Kominis, Ioannis; Korsch, Wolfgang; Kramer, Kevin; Kumar, Krishna; Kumbartzki, Gerfried; Kuss, Michael; Lakuriqi, Enkeleida; Laveissiere, Geraud; LeRose, John; Liang, Meihua; Liyanage, Nilanga; Lolos, George; Malov, Sergey; Marroncle, Jacques; McCormick, Kathy; McKeown, Robert; Meziani, Zein-Eddine; Michaels, Robert; Mitchell, Joseph; Nogga, Andreas; Pace, Emanuele; Papandreou, Zisis; Pavlin, Tina; Petratos, Gerassimos; Pripstein, David; Prout, David; Ransome, Ronald; Roblin, Yves; Rowntree, David; Rvachev, Marat; Sabatie, Franck; Saha, Arunava; Salme, Giovanni; SCOPETTA, S.; Skibinski, R.; Souder, Paul; Saito, Teijiro; Strauch, Steffen; Suleiman, Riad; Takahashi, Kazunori; Todor, Luminita; Tsubota, Hiroaki; Ueno, Hiroaki; Urciuoli, Guido; van der Meer, Rob; Vernin, Pascal; Voskanyan, Hakob; Witala, Henryk; Wojtsekhowski, Bogdan; Xiong, Feng; Xu, Wang; Yang, Jae-Choon; Zhang, Bin; Zolnierczuk, Piotr

    2008-07-01

    We present a measurement of the spin-dependent cross sections for the \\vec{^3He}(\\vec{e},e')X} reaction in the quasielastic and resonance regions at four-momentum transfer 0.1 < Q^2< 0.9 GeV^2. The spin-structure functions have been extracted and used to evaluate the nuclear Burkhardt--Cottingham and extended GDH sum rules for the first time. Impulse approximation and exact three-body Faddeev calculations are also compared to the data in the quasielastic region.

  5. Spin asymmetries for elastic proton scattering and the spin-dependent couplings of the Pomeron

    SciTech Connect

    Trueman, T. L.

    2008-03-01

    This paper serves as a report on the large amount of analysis done in conjunction with the polarized proton program at the Relavitistic Heavy Ion Collider at Brookhaven National Laboratory. This comprises elastic scattering data of protons on protons in colliding beam or fixed target mode and proton beams on carbon targets. In addition to providing a model for the energy dependence of the analyzing power of elastic scattering needed for proton polarimetry, it also provides some significant information about the spin dependence of dominant Regge poles. Most notably, the data indicate that the Pomeron has a significant spin-flip coupling. This allows the exploration of the double-spin flip asymmetry A{sub NN} for which some data over a wide energy range are now available, along with a concrete realization of a proposed Odderon search.

  6. Interfacial Structure Dependent Spin Mixing Conductance in Cobalt Thin Films.

    PubMed

    Tokaç, M; Bunyaev, S A; Kakazei, G N; Schmool, D S; Atkinson, D; Hindmarch, A T

    2015-07-31

    Enhancement of Gilbert damping in polycrystalline cobalt thin-film multilayers of various thicknesses, overlayered with copper or iridium, was studied in order to understand the role of local interface structure in spin pumping. X-ray diffraction indicates that cobalt films less than 6 nm thick have strong fcc(111) texture while thicker films are dominated by hcp(0001) structure. The intrinsic damping for cobalt thicknesses above 6 nm is weakly dependent on cobalt thickness for both overlayer materials, and below 6 nm the iridium overlayers show higher damping enhancement compared to copper overlayers, as expected due to spin pumping. The interfacial spin mixing conductance is significantly enhanced in structures where both cobalt and iridium have fcc(111) structure in comparison to those where the cobalt layer has subtly different hcp(0001) texture at the interface. PMID:26274431

  7. Do umbilical outpouchings affect the behaviour or clinical condition of pigs during 6 h housing in a pre-transport pick-up facility?

    PubMed

    Schild, Sarah-Lina Aa; Rousing, Tine; Jensen, Henrik E; Barington, Kristiane; Herskin, Mette S

    2015-08-01

    This study focused on behavioural and clinical effects of umbilical outpouchings (UOs) in pigs. Matched pairs of pigs with UOs (diameter 12 cm; range 4-20; diagnosed p.m. as hernia or non-hernia) and controls (N=28) were compared during a 6-h stay in a pick-up facility. Overall, skin lesion scores were increased after the 6-h stay. Behaviour of the UO-pigs differed from the controls (a shorter latency to lie down (P<0.05) and decreased aggression (P<0.05)). Pigs with umbilical hernia showed e.g. increased sitting (P<0.05) and decreased lying (P<0.05) compared to pigs with non-hernia UOs. No effects of the size of the OUs were found. These results are among the first to establish knowledge about UO-pigs and suggest that a stay in a pick-up facility can be challenging for pig welfare. The behavioural findings suggest that UO-pigs, and especially pigs with hernia, may be less fit for mixing and housing in barren environments. PMID:26267102

  8. In-situ observations of cometary pick-up ions greater than 0.2 AU upstream of Comet Halley - ICE observations

    NASA Astrophysics Data System (ADS)

    Wenzel, K.-P.; Sanderson, T. R.; Richardson, I. G.; Cowley, S. W. H.; Hynds, R. J.; Bame, S. J.; Zwickl, R. D.; Smith, E. J.; Tsurutani, B. T.

    1986-08-01

    Burst-like enhancements of energetic ions were observed by the EPAS instrument on the International Cometary Explorer (ICE) during its closest approach to (28 x 10 to the 6th km upstream of) Comet P/Halley, in late March 1986. The ion intensity was modulated by the varying solar wind speed (the latter reaching maxima of around 600 km/s), as was found to be the case for heavy cometary ions accelerated by pick-up in the solar wind flow, during the ICE encounter with Comet P/Giacobini-Zinner (G-Z). Therefore it is concluded that the observed pick-up ions (most probably greater than or equal to 65 keV oxygen ions) are produced by heavy neutrals from Comet Halley. The observations of energetic ions at such large distances suggest the presence, in the neutral atmosphere surrounding the nucleus, of a component with an ionization scale length of 5-10 million km, resulting from a relatively high expansion speed of a few km/s and/or an ionization time scale of a few times 10 to the 6ths.

  9. Measuring spin-dependent structure functions at CEBAF

    SciTech Connect

    Schaefer, A.

    1994-04-01

    The author analyses whether CEBAF with a 10 GeV beam could contribute significantly to the understanding of spin-dependent deep-inelastic scattering as well as semi-inclusive reactions. The main advantage of CEBAF is the much better attainable statistics, its great disadvantage its comparably low energy, which limits the accessible x-range to about 0.15 to 0.7. Within these constraints CEBAF could provide (1) high precision data which would be very valuable to understand the Q{sup 2} dependence of the spin-dependent structure functions g{sub 1}(x) and G{sub 2}(x) and (2) the by far most precise determination of the third moments of g{sub 1}(x) and g{sub 2}(x) the latter of which the author argues to be related to a fundamental property of the nucleon.

  10. Vector spin modeling for magnetic tunnel junctions with voltage dependent effects

    SciTech Connect

    Manipatruni, Sasikanth Nikonov, Dmitri E.; Young, Ian A.

    2014-05-07

    Integration and co-design of CMOS and spin transfer devices requires accurate vector spin conduction modeling of magnetic tunnel junction (MTJ) devices. A physically realistic model of the MTJ should comprehend the spin torque dynamics of nanomagnet interacting with an injected vector spin current and the voltage dependent spin torque. Vector spin modeling allows for calculation of 3 component spin currents and potentials along with the charge currents/potentials in non-collinear magnetic systems. Here, we show 4-component vector spin conduction modeling of magnetic tunnel junction devices coupled with spin transfer torque in the nanomagnet. Nanomagnet dynamics, voltage dependent spin transport, and thermal noise are comprehended in a self-consistent fashion. We show comparison of the model with experimental magnetoresistance (MR) of MTJs and voltage degradation of MR with voltage. Proposed model enables MTJ circuit design that comprehends voltage dependent spin torque effects, switching error rates, spin degradation, and back hopping effects.

  11. Vector spin modeling for magnetic tunnel junctions with voltage dependent effects

    NASA Astrophysics Data System (ADS)

    Manipatruni, Sasikanth; Nikonov, Dmitri E.; Young, Ian A.

    2014-05-01

    Integration and co-design of CMOS and spin transfer devices requires accurate vector spin conduction modeling of magnetic tunnel junction (MTJ) devices. A physically realistic model of the MTJ should comprehend the spin torque dynamics of nanomagnet interacting with an injected vector spin current and the voltage dependent spin torque. Vector spin modeling allows for calculation of 3 component spin currents and potentials along with the charge currents/potentials in non-collinear magnetic systems. Here, we show 4-component vector spin conduction modeling of magnetic tunnel junction devices coupled with spin transfer torque in the nanomagnet. Nanomagnet dynamics, voltage dependent spin transport, and thermal noise are comprehended in a self-consistent fashion. We show comparison of the model with experimental magnetoresistance (MR) of MTJs and voltage degradation of MR with voltage. Proposed model enables MTJ circuit design that comprehends voltage dependent spin torque effects, switching error rates, spin degradation, and back hopping effects.

  12. Angular Dependence of Superconductivity in Superconductor / Spin Valve Heterostructures

    NASA Astrophysics Data System (ADS)

    Jara, Alejandro; Safranski, Christopher; Krivorotov, Ilya; Wu, Chien-Te; Valls, Oriol

    2014-03-01

    The superconducting condensate in superconductor / ferromagnet (S/F) multilayers consists of singlet and triplet components. For a non-collinear state of magnetization of the multilayer, all three spin components Sz =(0 , +/- 1) of the triplet condensate are generally non-zero, which can result in a long range proximity effect in S/F multilayers. Indeed, the Sz = +/- 1 triplet components of the condensate are immune to pair breaking by the exchange field and, unlike the singlet and the Sz = 0 triplet components, they can penetrate deep into the ferromagnetic layers. Here we report measurements demonstrating magnetic control of the triplet component amplitude in Nb/Co/Cu/Co/CoOx superconducting spin valves. We find that for all values of the layer thicknesses employed in the experiment, Tc shows non-monotonic angular dependence with a minimum near perpendicular orientation of the Co layers. This drop in Tc is evidence of the enhanced long-range triplet amplitude in the maximally non-collinear configuration of the spin valve. We will present detailed measurements of the magnitude of this effect as a function of thicknesses of both Co and Cu layers of the spin valve. We will also compare our data to theoretical predictions of the angular dependence of Tc for this system.

  13. Nonlinear Spin Polarization Dependence of Spin Susceptibility in Interacting Two-Dimensional Electron Systems

    NASA Astrophysics Data System (ADS)

    Yang, K. F.; Liu, H. W.; Nagase, K.; Amakata, K.; Mishima, T. D.; Santos, M. B.; Hirayama, Y.

    2011-12-01

    We measure the spin polarization (P) of two-dimensional electron gases confined to an InSb quantum well using parallel and tilted magnetic fields. The nonlinear field dependence of P is prominent, leading to a direct deduction of the spin susceptibility (χs) over a wide range of P from 0.07 to 1. χs is found to increase nonlinearly with P and exceed χgm ∝ m*g* (where m* and g* are the effective mass and g factor) as commonly used in experiments. We show that χs and χgm obey a square law χs/χ0 = (χgm/χ0)2, where χ0 is the paramagnetic spin susceptibility.

  14. Bottom quark contribution to spin-dependent dark matter detection

    NASA Astrophysics Data System (ADS)

    Li, Jinmian; Thomas, Anthony W.

    2016-05-01

    We investigate a previously overlooked bottom quark contribution to the spin-dependent cross section for Dark Matter (DM) scattering from the nucleon. While the mechanism is relevant to any supersymmetric extension of the Standard Model, for illustrative purposes we explore the consequences within the framework of the Minimal Supersymmetric Standard Model (MSSM). We study two cases, namely those where the DM is predominantly Gaugino or Higgsino. In both cases, there is a substantial, viable region in parameter space (mb˜ -mχ ≲ O (100) GeV) in which the bottom contribution becomes important. We show that a relatively large contribution from the bottom quark is consistent with constraints from spin-independent DM searches, as well as some incidental model dependent constraints.

  15. TOPICAL REVIEW: Applications of spin dependent transport materials

    NASA Astrophysics Data System (ADS)

    Daughton, J. M.; Pohm, A. V.; Fayfield, R. T.; Smith, C. H.

    1999-11-01

    Newly developed materials that exhibit large changes in effective resistance with applied fields are being put to practical use. Magnetic multilayers with giant magnetoresistance (GMR) and spin dependent tunnelling (SDT) structures are being used in magnetic field sensors. Spin valves are being sold in read heads for hard drives and galvanic isolators. Both spin valves and SDT structures are being used in non-volatile random access memory development. After a brief introduction to these materials, the development of their uses in sensors, read heads, isolators and non-volatile memory are summarized. GMR magnetic field sensors represent a small, but growing market. SDT sensors have the potential to sense very small fields (to 1 pT). Spin valve read heads have enabled very high aerial packing densities for hard drives, up to 24 Gbits per square inch. GMR isolators can be used to duplicate the function of opto-isolators, but at much higher speeds and packing densities. Application of these materials to non-volatile random access memory could result in speeds and densities of semiconductor memory with the non-volatility of hard disk drives. Future directions in this field indicate a merging of semiconductor and these new magnetic materials.

  16. Single-particle strength in neutron-rich 69Cu from the 70Zn(d ,3He)69Cu proton pick-up reaction

    NASA Astrophysics Data System (ADS)

    Morfouace, P.; Franchoo, S.; Sieja, K.; Stefan, I.; de Séréville, N.; Hammache, F.; Assié, M.; Azaiez, F.; Borcea, C.; Borcea, R.; Grassi, L.; Guillot, J.; Le Crom, B.; Lefebvre, L.; Matea, I.; Mengoni, D.; Napoli, D.; Petrone, C.; Stanoiu, M.; Suzuki, D.; Testov, D.

    2016-06-01

    We have performed the 70Zn(d ,3He)69Cu proton pick-up reaction in direct kinematics using a deuteron beam at 27 MeV. The outgoing 3He particles were detected at the focal-plane detection system of an Enge split-pole spectrometer. The excitation-energy spectrum was reconstructed up to 7 MeV and spectroscopic factors were obtained after analysis of the angular distributions in the finite-range distorted-wave Born approximation. The results show three new angular distributions for which the π f7 /2 strength was measured and a lower limit of the centroid is established. State-of-the-art shell-model calculations are performed and predict a π f7 /2 strength that lies too high in energy in comparison to our experimental results.

  17. Case of ovarian hyperstimulation and oocyte pick-up during very early period of unnoticed pregnancy followed by ongoing normal pregnancy.

    PubMed

    Takenaka, Hiroshi; Nakao, Kazuki; Horikawa, Michiharu; Negishi, Hiroaki

    2016-04-01

    We report a case of unnoticed pregnancy that was maintained during low estrogen and progesterone circumstances, that showed menses-like bleeding, and was then discovered after ovarian hyperstimulation during the next period. The patient was 39 years old and primigravid. She underwent intrauterine insemination, followed by luteal support with human chorionic gonadotrophin and progestin; however, she experienced menstruation-like bleeding 15 days later. As low estradiol and progesterone levels were confirmed on the 2nd day of bleeding, ovarian hyperstimulation of short protocol for in vitro fertilization was commenced. Although 13 mature follicles were observed, only six oocytes were retrieved and one developed into a blastocyst. Four days after oocyte pick-up, a gestational sac was seen in utero. The fetus is currently growing uneventfully. This case suggests that pregnancy can be maintained during ovarian hyperstimulation, even if menstruation-like bleeding is shown in low-progesterone circumstances. PMID:26869522

  18. HHMS-PI modeling of the solar wind with pick-up protons from the Sun to Voyager 2

    NASA Astrophysics Data System (ADS)

    Detman, T. R.; Intriligator, D. S.; Dryer, M.; Sun, W.; Deehr, C. S.; Intriligator, J.

    2011-12-01

    Our 3D time-dependent magnetohydrodynamic (MHD) solar wind model, the Hybrid Heliospheric Modeling System with Pickup Protons (HHMS-PI) (Detman et al., 2011) has been extended to Voyager 2. HHMS-PI uses a time-dependent lower boundary condition at 0.1 AU driven indirectly by solar observations via the Wang-Sheeley-Arge source surface current sheet model (Arge and Pizzo, 2000). We show results for the Halloween 2003 solar events for the solar wind and pickup protons throughout the heliosphere extending beyond Voyager 2 (at 73 AU) to 75 AU. We also show the latitudinal and longitudinal extent of the interplanetary propagation of these events. This work was funded by NASA Grant NNX08AE40G and by Carmel Research Center, Inc.

  19. Precision measurement of the neutron spin dependent structure functions

    SciTech Connect

    Kolomensky, Y.G.

    1997-02-01

    In experiment E154 at the Stanford Linear Accelerator Center the spin dependent structure function g{sub 1}{sup n} (x, Q{sup 2}) of the neutron was measured by scattering longitudinally polarized 48.3 GeV electrons off a longitudinally polarized {sup 3}He target. The high beam energy allowed the author to extend the kinematic coverage compared to the previous SLAC experiments to 0.014 {le} x {le} 0.7 with an average Q{sup 2} of 5 GeV{sup 2}. The author reports the integral of the spin dependent structure function in the measured range to be {integral}{sub 0.014}{sup 0.7} dx g{sub 1}{sup n}(x, 5 GeV{sup 2}) = {minus}0.036 {+-} 0.004(stat.) {+-} 0.005(syst.). The author observes relatively large values of g{sub 1}{sup n} at low x that call into question the reliability of data extrapolation to x {r_arrow} 0. Such divergent behavior disagrees with predictions of the conventional Regge theory, but is qualitatively explained by perturbative QCD. The author performs a Next-to-Leading Order perturbative QCD analysis of the world data on the nucleon spin dependent structure functions g{sub 1}{sup p} and g{sub 1}{sup n} paying careful attention to the experimental and theoretical uncertainties. Using the parameterizations of the helicity-dependent parton distributions obtained in the analysis, the author evolves the data to Q{sup 2} = 5 GeV{sup 2}, determines the first moments of the polarized structure functions of the proton and neutron, and finds agreement with the Bjorken sum rule.

  20. Spin-dependent refraction at the atomic step of transition-metal dichalcogenides

    NASA Astrophysics Data System (ADS)

    Koshino, Mikito; Habe, Tetsuro

    2015-03-01

    We theoretically propose a spin-dependent electronic transport mechanism in the transition metal dichalcogenide, in which the spin-unpolarized electron beam is split into different directions depending on spins at an atomic domain boundary. Specifically, we calculate the electronic transmission across a boundary between monolayer and bilayer of the transition metal dichalcogenide, and demonstrate that up-spin and down-spin electrons entering the boundary are refracted and collimated to opposite directions. The phenomenon is attributed to the strong spin-orbit interaction, the trigonally-warped Fermi surface, and the different crystal symmetries between the monolayer and bilayer systems. The spin-dependent refraction suggests a potential application for a spin splitter, which spatially separates up-spin and down-spin electrons simply by passing the electric current through the boundary.

  1. Spin-dependent refraction at the atomic step of transition-metal dichalcogenides

    NASA Astrophysics Data System (ADS)

    Habe, Tetsuro; Koshino, Mikito

    2015-05-01

    We theoretically propose a spin-dependent electronic transport mechanism in which the spin-unpolarized electron beam is split into different directions depending on spins at an atomic domain boundary in nonmagnetic material. Specifically, we calculate the electronic transmission across a boundary between the monolayer and bilayer of the transition-metal dichalcogenide, and demonstrate that up-spin and down-spin electrons entering the boundary are refracted and collimated to opposite directions. The phenomenon is attributed to the strong spin-orbit interaction, the trigonally warped Fermi surface, and the different crystal symmetries between the monolayer and bilayer systems. The spin-dependent refraction suggests a potential application for a spin splitter, which spatially separates up-spin and down-spin electrons simply by passing the electric current through the boundary.

  2. Organic light-emitting devices using spin-dependent processes

    DOEpatents

    Vardeny, Z. Valy; Wohlgenannt, Markus

    2010-03-23

    The maximum luminous efficiency of organic light-emitting materials is increased through spin-dependent processing. The technique is applicable to all electro-luminescent processes in which light is produced by singlet exciton decay, and all devices which use such effects, including LEDs, super-radiant devices, amplified stimulated emission devices, lasers, other optical microcavity devices, electrically pumped optical amplifiers, and phosphorescence (Ph) based light emitting devices. In preferred embodiments, the emissive material is doped with an impurity, or otherwise modified, to increase the spin-lattice relaxation rate (i.e., decrease the spin-lattice time), and hence raise the efficiency of the device. The material may be a polymer, oligomer, small molecule, single crystal, molecular crystal, or fullerene. The impurity is preferably a magnetic or paramagnetic substance. The invention is applicable to IR, UV, and other electromagnetic radiation generation and is thus not limited to the visible region of the spectrum. The methods of the invention may also be combined with other techniques used to improve device performance.

  3. Exotic Paired States with Anisotropic Spin-Dependent Fermi Surfaces

    SciTech Connect

    Feiguin, Adrian E.; Fisher, Matthew P. A.

    2009-07-10

    We propose a model for realizing exotic paired states in cold Fermi gases by using a spin-dependent optical lattice to engineer mismatched Fermi surfaces for each hyperfine species. The BCS phase diagram shows a stable paired superfluid state with coexisting pockets of momentum space with gapless unpaired carriers, similar to the Sarma state in polarized mixtures, but in our case the system is unpolarized. We propose the possible existence of an exotic 'Cooper-pair Bose-metal' phase, which has a gap for single fermion excitations but gapless and uncondensed 'Cooper-pair' excitations residing on a 'Bose surface' in momentum space.

  4. Spin-dependent thermal and electrical transport in a spin-valve system

    SciTech Connect

    Wang, Zheng-Chuan; Su, Gang; Gao, Song

    2001-06-01

    Within the framework of Bu{close_quotes}ttiker{close_quote}s gauge invariant and charge conservation dc transport theory, the spin-dependent thermal and electrical transport in a ferromagnet-insulator-ferromagnet tunnel junction is investigated at finite bias voltage and finite temperature. It is observed that the relative orientations of magnetizations in the two ferromagnetic (FM) electrodes as well as temperature have remarkable effects on the differential conductance, thermopower, Peltier effect, and thermal conductivity. At low temperature the quantum resonant tunneling is predominant, leading to the deviation of classical transport theory, while the transport of electrons are crucially governed by thermal processes at high temperature. The so-called spin-valve phenomenon is clearly uncovered for both the differential conductance and the thermal conductivity at low temperature. The Wiedemann-Franz law is examined, and the inelastic tunneling spectroscopy is also discussed. Our findings are expected to be measured in the near future.

  5. Stacking order dependence of inverse spin Hall effect and anomalous Hall effect in spin pumping experiments

    NASA Astrophysics Data System (ADS)

    Kim, Sang-Il; Kim, Dong-Jun; Seo, Min-Su; Park, Byong-Guk; Park, Seung-Young

    2015-05-01

    The dependence of the measured DC voltage on the non-magnetic material (NM) in NM/CoFeB and CoFeB/NM bilayers is studied under ferromagnetic resonance conditions in a TE011 resonant cavity. The directional change of the inverse spin Hall effect (ISHE) voltage VISHE for the stacking order of the bilayer can separate the pure VISHE and the anomalous Hall effect (AHE) voltage VAHE utilizing the method of addition and subtraction. The Ta and Ti NMs show a broad deviation of the spin Hall angle θISH, which originates from the AHE in accordance with the high resistivity of NMs. However, the Pt and Pd NMs show that the kinds of NMs with low resistivity are consistent with the previously reported θISH values. Therefore, the characteristics that NM should simultaneously satisfy to obtain a reasonable VISHE value in bilayer systems are large θISH and low resistivity.

  6. Spin-dependent tunneling effects in magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Gao, Li

    2009-03-01

    It has long been known that current extracted from magnetic electrodes through ultra thin oxide tunnel barriers is spin polarized. This current gives rise to two important properties: tunneling magnetoresistance (TMR) when the tunnel barrier is sandwiched between two thin magnetic electrodes and, spin momentum transfer, which can be used to manipulate the magnetic state of the magnetic electrodes. In the first part of my talk I show how the structure of thin CoFe layers can be made amorphous by simply sandwiching them between two amorphous layers, one of them the tunnel barrier. No glass forming elements are needed. By slightly changing the thickness of these layers or by heating them above their glass transition temperature they become crystalline. Surprisingly, the TMR of the amorphous structure is significantly higher than of its crystalline counterpart. The tunneling anisotropic magnetoresistance, which has complex voltage dependence, is also discussed. In the second part of my talk I discuss the microwave emission spectrum from magnetic tunnel junctions induced by spin torque from spin polarized dc current passed through the device. We show that the spectrum is very sensitive to small variations in device structures, even in those devices which exhibit similarly high TMR (˜120%) and which have similar resistance-area products (˜4-10 φμm^2). We speculate that these variations are due to non-uniform spatial magnetic excitation arising from inhomogeneous current flow through the tunnel barrier. [In collaboration with Xin Jiang, M. Hayashi, Rai Moriya, Brian Hughes, Teya Topuria, Phil Rice, and Stuart S.P. Parkin

  7. The Promise and the Challenge of Space Solar Power in the 21st Century: Picking up the Gauntlet

    NASA Astrophysics Data System (ADS)

    Mankins, John C.

    2002-01-01

    The history of human civilization is a history of great infrastructure. Chief among these developments have been advances in power, transport, and communications. Without dramatic and steady advances in these critical systems during the past two hundred years-- especially in the available sources of power--the world would be a drastically poorer and harsher home for humanity. At the same time, through the global use of existing energy technologies humanity is rapidly consuming irreplaceable fossil resources as well as changing the environment and the climate for the world itself. Both must raise concerns about the long-term sustainability of the infrastructures that have enabled our world. The importance of abundant and affordable energy in space exploration and development is equally clear. Current missions of exploration and scientific discovery are narrowly constrained by a lack of energy. Future, even more ambitious missions will never be realized without new, reliable and less expensive sources of energy. Even more, the potential emergence of new space industries such as space tourism, manufacturing in space, solar power satellites (SPS) and others, will depend on advances in space power systems just as much as they will on progress in space transportation. Recent studies and technological advances suggest that large-scale space solar power (SSP) systems may enable progress in both arenas during the next several decades. Of course, there are tremendous engineering and technological barriers that must be surmounted to someday make large SSP systems possible. Diverse areas of technology must be advanced. Some of these include space transportation, solar power generation, wireless power transmission, robotics, structural concepts and materials, and others. Nevertheless, there are potential benefits in the offing that seem to many to make challenging even these daunting technical barriers worthwhile--and perhaps essential. Unfortunately, the political and

  8. Spin-independent interferences and spin-dependent interactions with scalar dark matter

    NASA Astrophysics Data System (ADS)

    Martinez, R.; Ochoa, F.

    2016-05-01

    We explore mechanisms of interferences under which the spin-independent interaction in the scattering of scalar dark matter with nucleus is suppressed in relation to the spin-dependent one. We offer a detailed derivation of the nuclear amplitudes based on the interactions with quarks in the framework of a nonuniversal U(1)' extension of the standard model. By assuming a range of parameters compatible with collider searches, electroweak observables and dark matter abundance, we find scenarios for destructive interferences with and without isospin symmetry. The model reveals solutions with mutually interfering scalar particles, canceling the effective spin-independent coupling with only scalar interactions, which requires an extra Higgs boson with mass M H > 125 GeV. The model also possesses scenarios with only vector interactions through two neutral gauge bosons, Z and Z', which do not exhibit interference effects. Due to the nonuniversality of the U(1)' symmetry, we distinguish two family structures of the quark sector with different numerical predictions. In one case, we obtain cross sections that pass all the Xenon-based detector experiments. In the other case, limits from LUX experiment enclose an exclusion region for dark matter between 9 and 800 GeV. We examine a third scenario with isospin-violating couplings where interferences between scalar and vector boson exchanges cancel the scattering. We provide solutions where interactions with Xenon-based detectors is suppressed for light dark matter, below 6 GeV, while interactions with Germanium- and Silicon-based detectors exhibit solutions up to the regions of interest for positive signals reported by CoGeNT and CDMS-Si experiments, and compatible with the observed DM relic density for DM mass in the range 8 .3-10 GeV. Spin-dependent interactions become the dominant source of scattering around the interference regions, where Maxwellian speed distribution is considered.

  9. Device Concepts Based on Spin-dependent Transmission in Semiconductor Heterostructures

    NASA Technical Reports Server (NTRS)

    Ting, David Z. - Y.; Cartoixa, X.

    2004-01-01

    We examine zero-magnetic-field spin-dependent transmission in nonmagnetic semiconductor heterostructures with structural inversion asymmetry (SIA) and bulk inversion asymmetry (BIA), and report spin devices concepts that exploit their properties. Our modeling results show that several design strategies could be used to achieve high spin filtering efficiencies. The current spin polarization of these devices is electrically controllable, and potentially amenable to highspeed spin modulation, and could be integrated in optoelectronic devices for added functionality.

  10. Angular-dependent magnetization reversal processes in artificial spin ice

    NASA Astrophysics Data System (ADS)

    Burn, D. M.; Chadha, M.; Branford, W. R.

    2015-12-01

    The angular dependence of the magnetization reversal in interconnected kagome artificial spin ice structures has been studied through experimental MOKE measurements and micromagnetic simulations. This reversal is mediated by the propagation of magnetic domain walls along the interconnecting bars, which either nucleate at the vertex or arrive following an interaction in a neighboring vertex. The physical differences in these processes show a distinct angular dependence allowing the different contributions to be identified. The configuration of the initial magnetization state, either locally or on a full sublattice of the system, controls the reversal characteristics of the array within a certain field window. This shows how the available magnetization reversal routes can be manipulated and the system can be trained.

  11. Magnetic Spin Relaxation Probed with Sweep Speed Dependent Coercivity

    NASA Astrophysics Data System (ADS)

    Gredig, Thomas; Byrne, Matthew

    The magnetic spin relaxation of finite-length iron chains has been investigated in iron phthalocyanine thin films by means of sweep speed dependence on magnetic coercivity. The Fe(II) ions are embedded in a carbon matrix and molecules self-assemble during vacuum sublimation, so that the Fe(II) cores form well-separated chains of 1.3 nm and tunable chain lengths within the polycrystalline thin film. The average length of the chains is controlled through deposition variables and ranges from 30 nm to 300 nm. The coercivity strongly increases with chain length in this regime. This may be an interesting experimental realization of a low-dimensional finite-sized Ising model. The coercivity dependence on chain length and sweep speed is described with an Ising model based on Glauber dynamics. Research support from NSF under Grant DMR 0847552.

  12. Clinic Attendance for Antiretroviral Pills Pick-Up among HIV-Positive People in Nepal: Roles of Perceived Family Support and Associated Factors

    PubMed Central

    Kikuchi, Kimiyo; Ghimire, Mamata; Shibanuma, Akira; Pant, Madhab Raj; Poudel, Krishna C.; Jimba, Masamine

    2016-01-01

    Introduction HIV-positive people’s clinic attendance for medication pick-up is critical for successful HIV treatment. However, limited evidence exists on it especially in low-income settings such as Nepal. Moreover, the role of family support in clinic attendance remains under-explored. Therefore, this study was conducted to examine the association between perceived family support and regular clinic attendance and to assess factors associated with regular clinic attendance for antiretroviral pills pick-up among HIV-positive individuals in Nepal. Methods A cross-sectional study was conducted among 423 HIV-positive people in three districts of Nepal. Clinic attendance was assessed retrospectively for the period of 12 months. To assess the factors associated, an interview survey was conducted using a semi-structured questionnaire from July to August, 2015. Multiple logistic regression models were used to assess the factors associated with regular clinic attendance. Results Of 423 HIV-positive people, only 32.6% attended the clinics regularly. They were more likely to attend them regularly when they received high family support (AOR = 3.98, 95% CI = 2.29, 6.92), participated in support programs (AOR = 1.68, 95% CI = 1.00, 2.82), and had knowledge on the benefits of antiretroviral therapy (AOR = 2.62, 95% CI = 1.15, 5.99). In contrast, they were less likely to attend them regularly when they commuted more than 60 minutes to the clinics (AOR = 0.53, 95% CI = 0.30, 0.93), when they self-rated their health status as being very good (AOR = 0.13, 95% CI = 0.04, 0.44), good (AOR = 0.14, 95% CI = 0.04, 0.46), and fair (AOR = 0.21, 95% CI = 0.06, 0.70). Conclusion HIV-positive individuals are more likely to attend the clinics regularly when they receive high family support, know the benefits of antiretroviral therapy, and participate in support programs. To improve clinic attendance, family support should be incorporated with HIV care programs in resource limited settings

  13. Spin-dependent delay time in ferromagnet/insulator/ferromagnet heterostructures

    SciTech Connect

    Xie, ZhengWei; Zheng Shi, De; Lv, HouXiang

    2014-07-07

    We study theoretically spin-dependent group delay and dwell time in ferromagnet/insulator/ferromagnet (FM/I/FM) heterostructure. The results indicate that, when the electrons with different spin orientations tunnel through the FM/I/FM junction, the spin-up process and the spin-down process are separated on the time scales. As the self-interference delay has the spin-dependent features, the variations of spin-dependent dwell-time and spin-dependent group-delay time with the structure parameters appear different features, especially, in low incident energy range. These different features show up as that the group delay times for the spin-up electrons are always longer than those for spin-down electrons when the barrier height or incident energy increase. In contrast, the dwell times for the spin-up electrons are longer (shorter) than those for spin-down electrons when the barrier heights (the incident energy) are under a certain value. When the barrier heights (the incident energy) exceed a certain value, the dwell times for the spin-up electrons turn out to be shorter (longer) than those for spin-down electrons. In addition, the group delay time and the dwell time for spin-up and down electrons also relies on the comparative direction of magnetization in two FM layers and tends to saturation with the thickness of the barrier.

  14. Spin force and the generation of sustained spin current in time-dependent Rashba and Dresselhaus systems

    SciTech Connect

    Ho, Cong Son Tan, Seng Ghee; Jalil, Mansoor B. A.

    2014-05-14

    The generation of spin current and spin polarization in a two-dimensional electron gas structure is studied in the presence of Dresselhaus and Rashba spin-orbit couplings (SOC), the strength of the latter being modulated in time by an ac gate voltage. By means of the non-Abelian gauge field approach, we established the relation between the Lorentz spin force and the spin current in the SOC system, and showed that the longitudinal component of the spin force induces a transverse spin current. For a constant (time-invariant) Rashba system, we recover the universal spin Hall conductivity of e/(8π) , derived previously via the Berry phase and semi-classical methods. In the case of a time-dependent SOC system, the spin current is sustained even under strong impurity scattering. We evaluated the ac spin current generated by a time-modulated Rashba SOC in the absence of any dc electric field. The magnitude of the spin current reaches a maximum when the modulation frequency matches the Larmor frequency of the electrons.

  15. Realization of spin-dependent splitting with arbitrary intensity patterns based on all-dielectric metasurfaces

    SciTech Connect

    Ke, Yougang; Liu, Yachao; He, Yongli; Zhou, Junxiao; Luo, Hailu Wen, Shuangchun

    2015-07-27

    We report the realization of spin-dependent splitting with arbitrary intensity patterns based on all-dielectric metasurfaces. Compared with the plasmonic metasurfaces, the all-dielectric metasurface exhibits more high transmission efficiency and conversion efficiency, which makes it possible to achieve the spin-dependent splitting with arbitrary intensity patterns. Our findings suggest a way for generation and manipulation of spin photons, and thereby offer the possibility of developing spin-based nanophotonic applications.

  16. Spinning-frequency-dependent linewidths in 1H-decoupled 13C magic-angle spinning NMR spectra

    NASA Astrophysics Data System (ADS)

    Nakai, Toshihito; McDowell, Charles A.

    1994-09-01

    The broadenings observed in 13C MAS NMR spectra, which depend on the sample-spinning speed, were studied, using polycrystalline adamantane. Not only was a monotonic increase of the linewidths with the increase of the spinning frequency observed, but also a novel resonant feature was found. The phenomena were interpreted as originating from rotary-resonance 13C 1H recoupling.

  17. Spin-dependent thermoelectronic transport of a single molecule magnet Mn(dmit){sub 2}

    SciTech Connect

    Su, Zhongbo; Wei, Xinyuan; Yang, Zhongqin; An, Yipeng

    2014-05-28

    We investigate spin-dependent thermoelectronic transport properties of a single molecule magnet Mn(dmit){sub 2} sandwiched between two Au electrodes using first-principles density functional theory combined with nonequilibrium Green's function method. By applying a temperature difference between the two Au electrodes, spin-up and spin-down currents flowing in opposite directions can be induced due to asymmetric distribution of the spin-up and spin-down transmission spectra around the Fermi level. A pure spin current and 100% spin polarization are achieved by tuning back-gate voltage to the system. The spin caloritronics of the molecule with a perpendicular conformation is also explored, where the spin-down current is blocked strongly. These results suggest that Mn(dmit){sub 2} is a promising material for spin caloritronic applications.

  18. Improved embryo development in Japanese black cattle by in vitro fertilization using ovum pick-up plus intracytoplasmic sperm injection with dithiothreitol.

    PubMed

    Oikawa, Toshinori; Itahashi, Tomoko; Numabe, Takashi

    2016-01-01

    The purpose of this study was to determine whether dithiothreitol (DTT) treatment of sperm and ethanol activation improve embryo production by intracytoplasmic sperm injection (ICSI). Further, we compared ICSI with standard in vitro fertilization (IVF) in oocytes obtained from cattle. We demonstrated that DTT reduced the disulfide bond in the bovine sperm head. Using oocytes obtained from a slaughterhouse, ICSI-DTT treatment without ethanol showed the highest rate of blastocyst formation. We applied these results to fertilization using ovum pick-up (OPU). Eleven Japanese black cattle served as donors for OPU plus standard IVF (OPU-IVF). Of them, four donors with low embryo development rates were selected to determine whether embryo development was enhanced by OPU plus ICSI (OPU-ICSI). We assessed effects on embryo development following IVF and ICSI in oocytes obtained using OPU. Blastocyst rates were significantly higher for OPU-ICSI than for OPU-IVF. Our results suggest that OPU-ICSI improves the blastocyst development rate in donors with low embryo production compared with the standard OPU-IVF. PMID:26460690

  19. Anti-Muellerian hormone levels in plasma of Holstein-Friesian heifers as a predictive parameter for ovum pick-up and embryo production outcomes

    PubMed Central

    VERNUNFT, Andreas; SCHWERHOFF, Mona; VIERGUTZ, Torsten; DIEDERICH, Mike; KUWER, Andreas

    2014-01-01

    The aim of this study was to investigate whether plasma anti-Muellerian hormone (AMH) levels of Holstein-Friesian heifers could be used to predict ovum pick-up (OPU) and embryo production outcomes. Plasma samples and data were collected from 64 heifers, which underwent repeated OPU with subsequent in vitro embryo production followed by embryo flushing after superovulation. AMH levels were significantly positively correlated with the number of follicles aspirated per OPU session (r = 0.45), recovered oocytes per OPU (r =0.43) and in vitro produced embryos per OPU (r = 0.28). No significant correlations between AMH and in vivo produced embryos were ascertained. Our results suggest that correlations between AMH and outcomes of an OPU-IVF program are too low to use AMH as a precise predictive parameter for the success of a particular OPU procedure in Holstein-Friesian heifers. However, AMH can help to identify groups of very good or very poor oocyte donors. PMID:25482112

  20. The effects of twisting and type of aspiration needle on the efficiency of transvaginal ultrasound-guided ovum pick-up in cattle.

    PubMed

    Sasamoto, Yoshihiko; Sakaguchi, Minoru; Katagiri, Seiji; Yamada, Yutaka; Takahashi, Yoshiyuki

    2003-10-01

    The effects of twisting and type (single- or double-lumen) of aspiration needle on the efficiency of transvaginal ultrasound-guided ovum pick-up (US-guided OPU) were investigated in cattle. The first study using slaughterhouse ovaries revealed that twisting of the needle during follicle aspiration improved the oocyte recovery rate without deleterious effects on the attachment of cumulus layers. Vacuum pressure affected the oocyte recovery and cumulus attachment, regardless of the needle type. The needle type did not affect the oocyte recovery or cumulus attachment with an optimized vacuum pressure. In the second study, US-guided OPU was performed in live cows using two types of needles with a vacuum pressure of 75 mmHg. The needle type did not affect the oocyte recovery or cumulus attachment of the recovered oocytes. The results revealed that twisting of the needle is effective in follicle aspiration, and suggested that a single-lumen needle is as useful as a double-lumen needle for US-guided OPU in cattle. PMID:14600345

  1. Cytoskeletal and mitochondrial properties of bovine oocytes obtained by Ovum Pick-Up: the effects of follicle stimulation and in vitro maturation.

    PubMed

    Somfai, Tamás; Matoba, Satoko; Inaba, Yasushi; Nakai, Michiko; Imai, Kei; Nagai, Takashi; Geshi, Masaya

    2015-12-01

    Follicle stimulation by follicular stimulating hormone (FSH) is known to improve developmental competence of bovine oocytes obtained by Ovum Pick-Up (OPU); however, the exact factors in oocytes affected by this treatment have remained unclear. We compared in vitro matured (IVM) oocytes obtained at the immature stage from cows by OPU either without or with stimulation with FSH (non-stimulated and stimulated OPU, respectively) to those obtained by superstimulation and in vivo maturation in terms of cytoskeleton morphology, mitochondrial distribution, intracellular adenosine triphosphate (ATP) content and H2 O2 levels at the metaphase-II stage and intracellular Ca(2+) levels after in vitro fertilization (IVF). Confocal microscopy after immunostaining revealed reduced size of the meiotic spindle, associated with increased tendencies of microfilament degradation and insufficient mitochondrial re-distribution in non-stimulated OPU-derived IVM oocytes compared with those collected by stimulated OPU, which in turn resembled in vivo matured oocytes. However, there was no difference in mitochondrial functions between oocytes obtained by stimulated or non-stimulated OPU in terms of ATP content, cytoplasmic H2 O2 levels, base Ca(2+) levels and the frequencies and amplitudes of Ca(2+) oscillations after IVF. Larger size of metaphase spindles in oocytes obtained by stimulated OPU may reflect and potentially contribute to their high developmental competence. PMID:26154026

  2. Improved embryo development in Japanese black cattle by in vitro fertilization using ovum pick-up plus intracytoplasmic sperm injection with dithiothreitol

    PubMed Central

    OIKAWA, Toshinori; ITAHASHI, Tomoko; NUMABE, Takashi

    2015-01-01

    The purpose of this study was to determine whether dithiothreitol (DTT) treatment of sperm and ethanol activation improve embryo production by intracytoplasmic sperm injection (ICSI). Further, we compared ICSI with standard in vitro fertilization (IVF) in oocytes obtained from cattle. We demonstrated that DTT reduced the disulfide bond in the bovine sperm head. Using oocytes obtained from a slaughterhouse, ICSI-DTT treatment without ethanol showed the highest rate of blastocyst formation. We applied these results to fertilization using ovum pick-up (OPU). Eleven Japanese black cattle served as donors for OPU plus standard IVF (OPU-IVF). Of them, four donors with low embryo development rates were selected to determine whether embryo development was enhanced by OPU plus ICSI (OPU-ICSI). We assessed effects on embryo development following IVF and ICSI in oocytes obtained using OPU. Blastocyst rates were significantly higher for OPU-ICSI than for OPU-IVF. Our results suggest that OPU-ICSI improves the blastocyst development rate in donors with low embryo production compared with the standard OPU-IVF. PMID:26460690

  3. What is the most relevant standard of success in assisted reproduction?: The cumulated singleton/twin delivery rates per oocyte pick-up: the CUSIDERA and CUTWIDERA.

    PubMed

    Germond, Marc; Urner, Françoise; Chanson, Alain; Primi, Marie-Pierre; Wirthner, Daniel; Senn, Alfred

    2004-11-01

    National and international registries are essential tools for establishing new standards and comparing success rates, but they do not take into account the total pregnancy/delivery rate per oocyte recovery. In Switzerland and Germany, because of legal constraints, a maximum of three two-pronuclear zygotes are allocated for transfer whereas all the supernumerary pronuclear zygotes are immediately cryopreserved, preventing selection of the transferred embryos. We report on a 10 years' experience (1993-2002) of our centre which performs transfers of unselected embryos and cryopreservation at the two-pronuclear zygote stage. As approximately 30% of all deliveries are from cryo cycles, it is essential to take into account the contribution of the cryo transfers, and we propose therefore to evaluate, as a measure of IVF performance, the cumulated delivery rate per oocyte pick-up. This delivery rate is broken down further into the cumulated singleton delivery rate (CUSIDERA) and the cumulated twin delivery rate (CUTWIDERA). The sum (S) of these two rates is a measure of efficacy while the ratio CUTWIDERA/S as a percentage is a measure of safety of IVF treatments. Using these new indexes, the average 10 year efficacy and safety of our IVF programme were 26 and 19%, respectively. Both CUSIDERA and CUTWIDERA can be calculated easily in any clinical situation and yield useful parameters for patient counselling and internal/external benchmarking purposes. PMID:15358719

  4. Spin-dependent modes in nuclei and nuclear forces

    NASA Astrophysics Data System (ADS)

    Suzuki, Toshio; Otsuka, Takaharu; Honma, Michio

    2012-10-01

    Spin-dependent modes in nuclei are studied and important roles of tensor and three-body forces on nuclear structure are discussed. New shell model Hamiltonians, which have proper tensor components, are shown to explain spin properties of both stable and exotic nuclei. Gamow-Teller (GT) strengths in Ni isotopes, especially in 56Ni, are found to be well described by pf-shell Hamiltonian GXPF1J, which leads to a remarkable improvement in the evaluation of electron capture rates in stellar environmnets. GT strength in 40Ar obtained with VMU (monopole-based universal interaction) is found to be consistent with the experimental strength, and neutrino capture reaction cross sections for solar neutrinos from 8B are found to be enhanced compared with previous calculations. The repulsive monopole corrections to the microscopic two-body interactions in isospin T=1 channel are important for the proper shell evolutions in neutron-rich isotopes. The three-body force, in particular the Fujita-Miyazawa force induced by δ excitations, is pointed out to be responsible for the repulsive corrections among the valence neutrons. The important roles of the three-body force on the energies of exotic calcium isotopes as well as on the closed-shell nature of 48Ca and M1 transition in 48Ca are demonstrated.

  5. Magnetic field-dependent spin structures of nanocrystalline holmium

    PubMed Central

    Szary, Philipp; Kaiser, Daniel; Bick, Jens-Peter; Lott, Dieter; Heinemann, André; Dewhurst, Charles; Birringer, Rainer; Michels, Andreas

    2016-01-01

    The results are reported of magnetic field-dependent neutron diffraction experiments on polycrystalline inert-gas condensed holmium with a nanometre crystallite size (D = 33 nm). At T = 50 K, no evidence is found for the existence of helifan(3/2) or helifan(2) structures for the nanocrystalline sample, in contrast with results reported in the literature for the single crystal. Instead, when the applied field H is increased, the helix pattern transforms progressively, most likely into a fan structure. It is the component of H which acts on the basal-plane spins of a given nanocrystallite that drives the disappearance of the helix; for nanocrystalline Ho, this field is about 1.3 T, and it is related to a characteristic kink in the virgin magnetization curve. For a coarse-grained Ho sample, concomitant with the destruction of the helix phase, the emergence of an unusual angular anisotropy (streak pattern) and the appearance of novel spin structures are observed. PMID:27047307

  6. Spin-dependent Seebeck effects in graphene-based molecular junctions

    NASA Astrophysics Data System (ADS)

    Li, Jianwei; Wang, Bin; Xu, Fuming; Wei, Yadong; Wang, Jian

    2016-05-01

    We report a first-principles investigation of spin-dependent transport properties in two different graphene-based molecular junctions. By applying different temperatures between two leads without bias voltage, spin-dependent currents are driven which depend on reference temperature T , temperature gradient Δ T , and gate voltage Vg. Moreover, pure spin currents without charge currents can be obtained by adjusting T ,Δ T , and Vg for both molecular junctions. The directions of pure spin currents in these two molecular junctions are opposite, which can be understood by analyzing the transmission coefficients under equilibrium states. Spin thermopower, thermal conductance, and the figure of merit as functions of T ,Vg, and chemical potential μ were also investigated in the linear response regime. Large spin thermopower and spin figure of merit can be obtained by adjusting Vg and μ for each junction, which indicates proper application of spin caloritronic devices of our graphene-based molecular junctions.

  7. Spin-orbit torque induced spike-timing dependent plasticity

    SciTech Connect

    Sengupta, Abhronil Al Azim, Zubair; Fong, Xuanyao; Roy, Kaushik

    2015-03-02

    Nanoelectronic devices that mimic the functionality of synapses are a crucial requirement for performing cortical simulations of the brain. In this work, we propose a ferromagnet-heavy metal heterostructure that employs spin-orbit torque to implement spike-timing dependent plasticity. The proposed device offers the advantage of decoupled spike transmission and programming current paths, thereby leading to reliable operation during online learning. Possible arrangement of such devices in a crosspoint architecture can pave the way for ultra-dense neural networks. Simulation studies indicate that the device has the potential of achieving pico-Joule level energy consumption (maximum 2 pJ per synaptic event) which is comparable to the energy consumption for synaptic events in biological synapses.

  8. Spin-orbit torque induced spike-timing dependent plasticity

    NASA Astrophysics Data System (ADS)

    Sengupta, Abhronil; Al Azim, Zubair; Fong, Xuanyao; Roy, Kaushik

    2015-03-01

    Nanoelectronic devices that mimic the functionality of synapses are a crucial requirement for performing cortical simulations of the brain. In this work, we propose a ferromagnet-heavy metal heterostructure that employs spin-orbit torque to implement spike-timing dependent plasticity. The proposed device offers the advantage of decoupled spike transmission and programming current paths, thereby leading to reliable operation during online learning. Possible arrangement of such devices in a crosspoint architecture can pave the way for ultra-dense neural networks. Simulation studies indicate that the device has the potential of achieving pico-Joule level energy consumption (maximum 2 pJ per synaptic event) which is comparable to the energy consumption for synaptic events in biological synapses.

  9. Advanced Petroleum-Based Fuels - Diesel Emissions Project (APBF-DEC): 2,000-Hour Performance of a NOx Adsorber Catalyst and Diesel Particle Filter System for a Medium-Duty, Pick-Up Diesel Engine Platform; Final Report

    SciTech Connect

    Not Available

    2007-03-01

    Presents the results of a 2,000-hour test of an emissions control system consisting of a nitrogen oxides adsorber catalyst in combination with a diesel particle filter, advanced fuels, and advanced engine controls in an SUV/pick-up truck vehicle platform.

  10. Charged particle behavior in low-frequency geomagnetic pulsations. 3. Spin phase dependence

    SciTech Connect

    Kivelson, M.G.; Southwood, D.J.

    1983-01-01

    Low-frequency modulations of the fluxes of magnetospheric charged particles are often observed in conjunction with geomagnetic pulsations. In some cases, the flux modulations depend on detector look direction even after effects arising from pitch angle anisotropy have been removed. For a detector on a spinning spacecraft, the look direction dependence creates flux modulations ordered by the spin phase angle, so the term 'spin phase dependence' provides a convenient description of the phenomenon considered in this paper. Spin phase dependence occurs only when the gyroradius of the detected particles (charge q; energy, W) is comparable with some other characteristic length of the problem. In particular, spin phase dependence occurs when the particle gyroradius a/sub L/ is comparable with lambda/sub perpendicular/, the wavelength transverse to B. ATS 6 and GEOS have provided examples of this type of 'finite gyroradius' effect. Wave-related spin phase dependence may also arise with a/sub L/<

  11. Stacking order dependence of inverse spin Hall effect and anomalous Hall effect in spin pumping experiments

    SciTech Connect

    Kim, Sang-Il; Seo, Min-Su; Park, Seung-Young; Kim, Dong-Jun; Park, Byong-Guk

    2015-05-07

    The dependence of the measured DC voltage on the non-magnetic material (NM) in NM/CoFeB and CoFeB/NM bilayers is studied under ferromagnetic resonance conditions in a TE{sub 011} resonant cavity. The directional change of the inverse spin Hall effect (ISHE) voltage V{sub ISHE} for the stacking order of the bilayer can separate the pure V{sub ISHE} and the anomalous Hall effect (AHE) voltage V{sub AHE} utilizing the method of addition and subtraction. The Ta and Ti NMs show a broad deviation of the spin Hall angle θ{sub ISH}, which originates from the AHE in accordance with the high resistivity of NMs. However, the Pt and Pd NMs show that the kinds of NMs with low resistivity are consistent with the previously reported θ{sub ISH} values. Therefore, the characteristics that NM should simultaneously satisfy to obtain a reasonable V{sub ISHE} value in bilayer systems are large θ{sub ISH} and low resistivity.

  12. Temperature dependence of spin Hall magnetoresistance in W/CoFeB bilayer

    NASA Astrophysics Data System (ADS)

    Okuno, Takaya; Taniguchi, Takuya; Kim, Sanghoon; Baek, Seung-heon Chris; Park, Byong-Guk; Moriyama, Takahiro; Kim, Kab-Jin; Ono, Teruo

    2016-08-01

    We investigate the temperature dependence of the spin Hall magnetoresistance (SMR) in a W/CoFeB bilayer. The SMR is found to increase with decreasing temperature. An analysis based on the SMR theory suggests that the spin Hall angle of W and/or the spin polarization of CoFeB can be the origin of the temperature dependence of the SMR. We also find that the spin diffusion length and the resistivity of W do not significantly vary with temperature, which indicates the necessity of further study on the electron transport mechanism in W films to reveal the origin of the spin Hall effect in W.

  13. Spin-Dependent Molecule Symmetry at a Pentacene-Co Spinterface.

    PubMed

    Chu, Yu-Hsun; Hsu, Chuang-Han; Lu, Chun-I; Yang, Hung-Hsiang; Yang, Tsung-Han; Luo, Chi-Hung; Yang, Kai-Jheng; Hsu, Shih-Hao; Hoffmann, Germar; Kaun, Chao-Cheng; Lin, Minn-Tsong

    2015-07-28

    Incorporating spin-polarized scanning tunneling microscopy (SP-STM) measurements and first-principles calculations, we resolve spin-polarized states and consequent features in a pentacene(PEN)-Co hybrid system. Symmetry reduction of PEN clarifies the PEN adsorption site and the Co stacking methods. Near the Fermi energy, the molecular symmetry is spin-dependently recovered and an inversion of spin-polarization in PEN with respect to Co is observed. The experimental findings and calculation results are interpreted by a pz-d hybridization model, in which spin-dependent bonding-antibonding splitting of molecular orbitals happens at metal-organic spinterfaces. PMID:26083646

  14. Temperature Dependent Spin Transport in Silicon Controlled by an Electrostatic Gate

    NASA Astrophysics Data System (ADS)

    Li, Jing; Appelbaum, Ian

    2011-03-01

    Long-distance (~ 500 μ m) lateral spin polarized electron transport in undoped silicon under the control of an electrostatic gate is studied from 40K to 120K. The temperature dependence of average spin polarization, transport time, and spin dephasing during coherent precession can be largely attributed to reduction of finite spin lifetime at higher temperatures. Measurements on devices with different transport lengths are shown to modify the effect of electrostatic gating. Support from ONR is acknowledged.

  15. Spin-polarization and spin-dependent logic gates in a double quantum ring based on Rashba spin-orbit effect: Non-equilibrium Green's function approach

    SciTech Connect

    Eslami, Leila Esmaeilzadeh, Mahdi

    2014-02-28

    Spin-dependent electron transport in an open double quantum ring, when each ring is made up of four quantum dots and threaded by a magnetic flux, is studied. Two independent and tunable gate voltages are applied to induce Rashba spin-orbit effect in the quantum rings. Using non-equilibrium Green's function formalism, we study the effects of electron-electron interaction on spin-dependent electron transport and show that although the electron-electron interaction induces an energy gap, it has no considerable effect when the bias voltage is sufficiently high. We also show that the double quantum ring can operate as a spin-filter for both spin up and spin down electrons. The spin-polarization of transmitted electrons can be tuned from −1 (pure spin-down current) to +1 (pure spin-up current) by changing the magnetic flux and/or the gates voltage. Also, the double quantum ring can act as AND and NOR gates when the system parameters such as Rashba coefficient are properly adjusted.

  16. Ovum pick up, in vitro embryo production, and pregnancy rates from a large-scale commercial program using Nelore cattle (Bos indicus) donors.

    PubMed

    Pontes, J H F; Melo Sterza, F A; Basso, A C; Ferreira, C R; Sanches, B V; Rubin, K C P; Seneda, M M

    2011-06-01

    The objective was to clarify in vitro production of bovine embryos in Brazil. Data from 656 ovum pick-up/in vitro production (OPU/IVP) procedures, performed on 317 Nelore (Bos indicus) donors, without hormone stimulation or control of ovarian follicular waves, were analysed. Donors were subjected to OPU from one to nine times (no specific schedule), with < 15 d between consecutive procedures. There were 20,848 oocytes, of which 15,747 (75.53%) were considered viable, 5,446 embryos were obtained, 5,398 embryos were immediately transferred, resulting in 1,974 pregnancies (36.57%) at Day 30 and 1,788 (33.12%) pregnancies at Day 60. The average number of total and viable oocytes produced per OPU session was (mean ± SEM) 30.84 ± 0.88 and 23.35 ± 0.7 (average of 8.1 ± 0.3 embryos and 3.0 ± 0.1 pregnancies per OPU-IVP procedure). Since oocyte production varied widely among donor, they were designated as very high, high, intermediate, and low, with 58.94 ± 2.04, 32.61 ± 0.50, 22.13 ± 0.50, and 10.26 ± 0.57 oocytes, respectively, produced by 78, 80, 79, and 80 donors. The number of viable oocytes recovered ranged from 0 to 128; since donors with numerous viable oocytes produced many viable embryos and pregnancies, oocyte production was useful for donor selection. However, there was no significant effect of the number of OPU sessions per donor on mean numbers of oocytes produced. In conclusion, we confirmed field reports of high oocyte production by some Nelore donors and demonstrated individual variation in oocyte yield, which was associated with embryo production and pregnancy rates. PMID:21334055

  17. Effects of ovum pick-up frequency and FSH stimulation: a retrospective study on seven years of beef cattle in vitro embryo production.

    PubMed

    De Roover, R; Feugang, J M N; Bols, P E J; Genicot, G; Hanzen, Ch

    2008-04-01

    The aim of this retrospective study was to compare the number of follicles, cumulus oocyte complexes (COCs) and cultured In Vitro Produced (IVP) embryos obtained from 1396 non-stimulated Ovum Pick-up (OPU) sessions on 81 donor animals in a twice weekly OPU scheme. Results were obtained from 640 sessions following FSH-LH superstimulation, on 112 donors subjected to OPU once every 2 weeks. The stimulation protocol started with the insertion of an ear implant containing 3 mg norgestomet (Crestar, Intervet, Belgium) 8 days before puncture (day -8). The dominant follicle was ablated by ultrasound-guided follicle puncture on day -6. On day -3 and day -2, cows were injected with FSH (Ovagen, ICP) twice daily (8 am to 8 pm), i.e. a total dose of 160 mug FSH and 40 mug LG per donor per stimulation cycle. Animals were punctured 48 h after the last FSH injection (day 0). Progesterone implants were removed the next day. Stimulated donor cows were treated with this protocol at 14-day intervals. Follicles were visualized with a Dynamic Imaging ultrasound scanner, equipped with a 6.5 MHz sectorial probe. Follicles were punctured with 55 cm long, 18 gauge needles at an aspiration pressure corresponding to a flow rate of 15 ml/min. Cumulus oocyte complexes were recovered and processed in a routine IVF set-up. Results demonstrate that, expressed per session, FSH stimulation prior to OPU increases production efficiency with significantly more follicles punctured and oocytes retrieved. However, when overall results during comparable 2-week periods are considered (four non-stimulated sessions vs one stimulated), more follicles are punctured and more oocytes are retrieved using the non-stimulated protocol. No significant differences in the number of cultured embryos could be detected, indicating that FSH/LH stimulation prior to OPU might have a positive effect on in vitro oocyte developmental competence as more embryos are cultured with less, presumably better-quality, oocytes. PMID

  18. Effects of eCG and FSH on ovarian response, recovery rate and number and quality of oocytes obtained by ovum pick-up in Holstein cows.

    PubMed

    Sendag, Sait; Cetin, Yunus; Alan, Muhammet; Hadeler, Klaus-Gerd; Niemann, Heiner

    2008-06-01

    The goal of the present study was to compare the ovarian response, oocyte yields per animal, and the morphological quality of oocytes collected by ultrasound guided follicular aspiration from Holstein cows treated either with FSH or eCG. Twenty four normal cyclic, German Holstein cows were randomly divided into two groups. Fourteen cows received 3000 IU eCG on day-4 prior to ovum pick-up (OPU) (day 0), 2 days later (day-2), 625 microg cloprostenol was administered. On day-1 GnRH was administered i.m. and 24h later OPU (day 0) was performed. In ten cows a total dose of 500 IU follicle stimulating hormone (Pluset) was administered intramuscularly in a constant dosage for 4 days with intervals of 12h, starting on day-5. Luteolysis was induced by application of 625 microg cloprostenol on day-2. On day-1 (24h after the last FSH treatment) GnRH was administered i.m. and 24h later OPU (day 0) was performed. Ovarian follicles were visualized on the ultrasound monitor, counted and recorded. All visible antral follicles were punctured. Recovered oocytes were graded morphologically based on the cumulus investment. Average follicle number in ovaries was higher in FSH group than eCG group (p<0.05). Oocyte yields per animal did not differ between FSH and eCG groups. The proportion of grade A oocytes was higher in the FSH group in the than eCG group (p<0.05). Likewise, rate of grade C oocytes in FSH group were lower than eCG group (p<0.05). In conclusion, these results suggest that ovarian response, follicle number in ovaries and oocyte quality are affected by the type of gonadotropin and FSH is better alternative than eCG for OPU treatment. PMID:18294785

  19. Differential gene expression in cumulus oocyte complexes collected by ovum pick up from repeat breeder and normally fertile Holstein Friesian heifers.

    PubMed

    Puglisi, Roberto; Cambuli, Caterina; Capoferri, Rossana; Giannino, Laura; Lukaj, Aleksander; Duchi, Roberto; Lazzari, Giovanna; Galli, Cesare; Feligini, Maria; Galli, Andrea; Bongioni, Graziella

    2013-09-01

    The aim of this study was to establish whether perturbed gene expression during cumulus oocyte development causes repeat breeding in cattle. In this study, a repeat breeder was defined as a normal estrous cycling animal that did not become pregnant after three inseminations despite the absence of clinically detectable reproductive disorders. Transcripts of genes extracted from cumulus oocyte complexes (COC) that were collected from three repeat breeder and three normally fertile Holstein Friesian heifers were compared. Up to 40 COC were collected from each heifer by means of repeated sessions of ovum pick up in the absence of hormonal stimulation; immediately plunged into liquid nitrogen; and stored at -80°C until analysis. For each heifer, RNA was extracted from the pooled COC and hybridized on GeneChip(®) Bovine Gene Array (Affymetrix). Analysis of gene expression profiles of repeat breeder and control COC showed that 178 genes were differentially expressed (log2 fold change>1.5). Of these genes, 43 (24%) were up-regulated and 135 (76%) were down-regulated in repeat breeder relative to control heifers. This altered pattern of expression occurred in genes involved in several cellular biological processes and cellular components such as metabolism, angiogenesis, substrate/ion transport, regulation/signaling, cell adhesion and cytoskeleton. From these, 13 genes potentially involved in cumulus oocyte growth were subjected to validation by qRT-PCR and nine genes (annexin A1, ANXA1; lactoferrin, LTF; interferon stimulated exonuclease 20kDa, ISG20/HEM45; oxidized low density lipoprotein receptor 1, OLR1; fatty acid desaturase 2, FADS2; glutathione S-transferase A2 and A4, GSTA2 and GSTA4; glutathione peroxidase 1, GPX1; endothelin receptor type A, EDNRA) were confirmed to be differentially expressed. This study identified potential marker genes for fertility in dairy cattle. PMID:23911014

  20. Voltage dependence properties of ballistic spin currents and spin transfer torques in magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Chshiev, Mairbek

    2009-03-01

    Interest in spintronics [1] has been strongly accentuated by the discovery of current induced magnetization switching caused by spin transfer torque (STT) [2]. Among the most favorable candidate systems for the realization of STT-based spintronic devices are epitaxial magnetic tunnel junctions (MTJ) [3]. Here we present a systematic study of voltage-induced STT in MTJs and provide an insight into the nature of its voltage behavior by investigating the properties of ballistic spin currents [4,5]. We demonstrate that the band filling has a dramatic impact on voltage dependence properties of both STT components, tunnel magnetoresistance (TMR) as well as on equilibrium interlayer exchange coupling [5]. Both in-plane (Slonczewski) and perpendicular-to-the-plane (field-like) STT components demonstrate a wide range of nontrivial behavior as a function of applied voltage [4,5]. The explanation is given in terms of the spin and charge current dependence on the interplay between evanescent states in the insulator and the Fermi surfaces of the ferromagnetic electrodes comprising the MTJ [5]. In particular we show that in ballistic regime the field-like torque is an even parity function of applied voltage while the parallel torque may exhibit a wide range of behavior [4,5]. Recent experiments [6] are in agreement with these predictions. Calculations are based on the non-equilibrium Green functions technique.[4pt] [1] A. Fert et al, Mat. Sci. Eng. B, 84, 1 (2001); S. A. Wolf, Science, 294, 1488 (2001)[0pt] [2] J. C. Slonczewski, J. Magn. Magn. Mat. 159, L1 (1996); L. Berger, Phys. Rev. B 54, 9353 (1996[0pt] [3] W. H. Butler et al, Phys. Rev. B, 63, 054416 (2001); J. Mathon and A. Umerski, Phys. Rev. B, 63, 220403(R) (2001)[0pt] [4] I. Theodonis et al, Phys. Rev. Lett. 97, 237205 (2006)[0pt] [5] M. Chshiev et al. IEEE Trans. Mag. 44 (11) (2008); A. Kalitsov et al., submitted[0pt] [6] H. Kubota et al, Nature Physics 4, 37 (2008); J. C. Sankey et al, ibid. 4, 67 (2008); A. Deac et

  1. Spin Dependent Transport Properties of Metallic and Semiconducting Nanostructures

    NASA Astrophysics Data System (ADS)

    Sapkota, Keshab R.

    Present computing and communication devices rely on two different classes of technologies; information processing devices are based on electrical charge transport in semiconducting materials while information storage devices are based on orientation of electron spins in magnetic materials. A realization of a hybrid-type device that is based on charge as well as spin properties of electrons would perform both of these actions thereby enhancing computation power to many folds and reducing power consumptions. This dissertation focuses on the fabrication of such spin-devices based on metallic and semiconducting nanostructures which can utilize spin as well as charge properties of electrons. A simplified design of the spin-device consists of a spin injector, a semiconducting or metallic channel, and a spin detector. The channel is the carrier of the spin signal from the injector to the detector and therefore plays a crucial role in the manipulation of spin properties in the device. In this work, nanostructures like nanowires and nanostripes are used to function the channel in the spin-device. Methods like electrospinning, hydrothermal, and wet chemical were used to synthesize nanowires while physical vapor deposition followed by heat treatment in controlled environment was used to synthesis nanostripes. Spin-devices fabrication of the synthesized nanostructures were carried out by electron beam lithography process. The details of synthesis of nanostructures, device fabrication procedures and measurement techniques will be discussed in the thesis. We have successfully fabricated the spin-devices of tellurium nanowire, indium nanostripe, and indium oxide nanostripe and studied their spin transport properties for the first time. These spin-devices show large spin relaxation length compared to normal metals like copper and offer potentials for the future technologies. Further, Heusler alloys nanowires like nanowires of Co 2FeAl were synthesized and studied for electrical

  2. Nuclear Spin Orientation Dependence of Magnetoconductance: A New Method for Measuring the Spin of Charged Excitations in the QHE

    SciTech Connect

    Bowers, C.R.; Reno, J.L.; Simmons, J.A.; Vitkalov, S.A.

    1998-12-01

    A new method for measuring the spin of the electrically charged ground state excitations m the Q$j~j quantum Hall effect ia proposed and demonstmted for the tirst time in GaAs/AIGaAs nndtiquantum wells. The method is &sed on the nuclear spin orientation dependence of" the 2D dc conductivity y in the quantum Hall regime due to the nuclear hyperfine interaction. As a demonstration of this method the spin of the electrically charged excitations of the ground state is determined at filling factor v = 1.

  3. Shape Biased Low Power Spin Dependent Tunneling Magnetic Field Sensors

    NASA Astrophysics Data System (ADS)

    Tondra, Mark; Qian, Zhenghong; Wang, Dexin; Nordman, Cathy; Anderson, John

    2001-10-01

    Spin Dependent Tunneling (SDT) devices are leading candidates for inclusion in a number of Unattended Ground Sensor applications. Continued progress at NVE has pushed their performance to 1OOs of pT I rt. Hz 1 Hz. However, these sensors were designed to use an applied field from an on-chip coil to create an appropriate magnetic sensing configuration. The power required to generate this field (^100mW) is significantly greater than the power budget (^lmW) for a magnetic sensor in an Unattended Ground Sensor (UGS) application. Consequently, a new approach to creating an ideal sensing environment is required. One approach being used at NVE is "shape biasing." This means that the physical layout of the SDT sensing elements is such that the magnetization of the sensing film is correct even when no biasing field is applied. Sensors have been fabricated using this technique and show reasonable promise for UGS applications. Some performance trade-offs exist. The power is easily tinder 1 MW, but the sensitivity is typically lower by a factor of 10. This talk will discuss some of the design details of these sensors as well as their expected ultimate performance.

  4. Nuclear Spin Dependent Parity Violation in Diatomic Molecules

    NASA Astrophysics Data System (ADS)

    Altuntas, Emine; Cahn, Sidney; Demille, David; Kozlov, Mikhail

    2016-05-01

    Nuclear spin-dependent parity violation (NSD-PV) effects arise from exchange of the Z0 boson between electrons and the nucleus, and from interaction of electrons with the nuclear anapole moment, a parity-odd magnetic moment. The latter scales with nucleon number of the nucleus A as A 2 / 3 , whereas the Z0 coupling is independent of A. Thus the former is the dominant source of NSD-PV for nuclei with A >= 20. We study NSD-PV effects using diatomic molecules, where signals are dramatically amplified by bringing rotational levels of opposite parity close to degeneracy in a strong magnetic field. The NSD-PV interaction matrix element is measured using a Stark-interference technique. We present results that demonstrate statistical sensitivity to NSD-PV effects surpassing that of any previous atomic parity violation measurement, using the test system 138 Ba19 F. We report our progress on measuring and cancelling systematic effects due to combination of non-reversing stray E-fields, Enr with B-field inhomogeneities. Short-term prospects for measuring the nuclear anapole moment of 137 Ba19 F are discussed. In the long term, our technique is sufficiently general and sensitive to enable measurements across a broad range of nuclei.

  5. Ferrimagnetic ordering and spin entropy of field-dependent intermediate spins in Na0.82CoO2

    NASA Astrophysics Data System (ADS)

    Shu, G. J.; Chou, F. C.

    2016-04-01

    The peculiar field-dependent magnetism of Na0.82CoO2 has been investigated through an analysis of its dc and ac spin susceptibilities. To account for the easily activated narrow b2 g-a1 g gap of the crystal field for Co in the cobalt oxide layer, the spin-state transition of Co3 + (3 d6 ) between the low-spin (LS) state b2g 2a1g 0 of S =0 and the intermediate-spin (IS) state b2g 1a1g 1 of S =1 is thus seen as thermally activated and exhibits a Boltzmann distribution. The IS state of Co3 + within each √{13 }a hexagonal superlattice formed by the S =1 /2 state of the Co4 + ions appears randomly within each supercell and shows significant temperature and field dependence. The magnetic field is found to assist in pinning down the thermally activated state of Co3 + and swings the Boltzmann distribution weight toward a higher fraction of the IS state. The field dependence of the in-plane magnetic moment from the added number of S =1 spins is used to explain the origin of A -type antiferromagnetic (AF) ordering, particularly that the ferromagnetic (FM)-like behavior below TN at low field is actually a ferrimagnetic IS spin ordering of Co3 +.

  6. Paradoxical effects of bovine somatotropin treatment on the ovarian follicular population and in vitro embryo production of lactating buffalo donors submitted to ovum pick-up.

    PubMed

    Ferraz, M L; Sá Filho, M F; Batista, E O S; Watanabe, Y F; Watanabe, M R; Dayan, A; Joaquim, D C; Accorsi, M R; Gimenes, L U; Vieira, L M; Baruselli, P S

    2015-03-01

    The aim of the present study was to evaluate the effect of bovine somatotropin (bST; 500mg) administration on lactating buffalo donors submitted to two different ovum pick-up (OPU) and in vitro embryo production schemes with a 7 or 14d intersession OPU interval. A total of 16 lactating buffalo cows were randomly assigned into one of four experimental groups according to the bST treatment (bST or No-bST) and the OPU intersession interval (7 or 14d) in a 2×2 factorial design (16 weeks of OPU sessions). The females submitted to OPU every 14d had a larger (P<0.001) number of ovarian follicles suitable for puncture (15.6±0.7 vs. 12.8±0.4) and an increased (P=0.004) number of cumulus-oocyte complexes (COCs) recovered (10.0±0.5 vs. 8.5±0.3) compared to the 7d interval group. However, a 7 or 14d interval between OPU sessions had no effect (P=0.34) on the number of blastocysts produced per OPU (1.0±0.1 vs. 1.3±0.2, respectively). In addition, bST treatment increased (P<0.001) the number of ovarian follicles suitable for puncture (15.3±0.5 vs. 12.1±0.4) but reduced the percentage (18.9% vs. 10.9%; P=0.009) and the number (1.4±0.2 vs. 0.8±0.1; P=0.003) of blastocysts produced per OPU session compared with the non-bST-treated buffaloes. In conclusion, the 14d interval between OPU sessions and bST treatment efficiently increased the number of ovarian follicles suitable for puncture. However, the OPU session interval had no effect on embryo production, and bST treatment reduced the in vitro blastocyst outcomes in lactating buffalo donors. PMID:25623138

  7. Prolonging the interval from ovarian hyperstimulation to laparoscopic ovum pick-up improves oocyte yield, quality, and developmental competence in goats.

    PubMed

    Abdullah, R B; Liow, S L; Rahman, A N M A; Chan, W K; Wan-Khadijah, W E; Ng, S C

    2008-09-15

    The objective was to evaluate the effect of the interval between ovarian hyperstimulation and laparoscopic ovum pick-up (LOPU) on quality and developmental competence of goat oocytes before and after in vitro maturation (IVM) and intracytoplasmic sperm injection (ICSI). Estrus was synchronized with an intravaginal insert containing 0.3g progesterone (CIDR) for 10d, combined with a luteolytic treatment of 125 microg cloprostenol 36 h prior to CIDR removal. Ovaries were hyperstimulated with 70 mg FSH and 500 IU hCG given im 36, 60, or 72 h prior to LOPU (n=15, 16, and 7 does, respectively). For these groups, oocyte retrieval rates (mean+/-S.E.M.) were 24.7+/-2.9, 54.5+/-4.7, and 82.8+/-4.6% (P<0.001), and the proportions of cumulus-oocyte complexes (COC) with more than five layers of cumulus cells were 29.7+/-8.3, 37.6+/-6.9, and 37.3+/-7.0% (P<0.001). The proportion of IVM oocytes was highest at 72 h (82.1+/-2.8%; P<0.05), with no significant difference between 36 and 60 h (57.3+/-8.9% and 69.0+/-8.4%). Cleavage rates of ICSI embryos were 4.2+/-4.2, 70.9+/-8.4, and 78.9+/-8.2% with LOPU 36, 60, and 72 h post FSH/hCG (P<0.01), with a lower proportion of Grade-A embryos (P<0.05) following LOPU at 36 h compared to 60 and 72 h (29.7+/-8.3%, 37.6+/-6.9%, and 37.3+/-7.0%). In summary, a prolonged interval from FSH/hCG to LOPU improved oocyte retrieval rate and oocyte quality. Therefore, under the present conditions, LOPU 60 or 72 h after FSH/hCG optimized yields of good-quality oocytes for IVM and embryo production in goats. PMID:18579196

  8. Ovarian Follicular Dynamics, Ovarian Follicular Growth, Oocyte Yield, In vitro Embryo Production and Repeated Oocyte Pick Up in Thai Native Heifers Undergoing Superstimulation

    PubMed Central

    Chasombat, J.; Nagai, T.; Parnpai, R.; Vongpralub, T.

    2013-01-01

    The objective of this study was to compare the effectiveness of the protocols for superstimulation of follicular growth in Thai native heifers. Heifers (n = 20) were randomly divided into four groups of five heifers/group. Heifers were given a single dose by i.m. administration of 100 mg Follicle Stimulating Hormone dissolved in polyvinylpyrrolidone (FSHp) at 24 h. Ovum pick up (OPU) occurred at 72 h (F24O72 protocol; Group 1) or 96 h (F24O96 protocol; Group 2), and at 36 h and OPU at 72 h (F36O72 protocol; Group 3) or 96 h (F36O96 protocol; Group 4) after follicular ablation. The dynamics of ovarian follicular growth were monitored by twice-daily ultrasonographic examinations. Blood sample collections were performed every 12 h after initiation of treatment for assessment of FSH, E2 and P4 profiles. All heifers were subjected to eight repeated sequential sessions of OPU. The follicular deviation commenced 24±5.32 h after follicular ablation in all groups. The circulatory FSH surged quickly from 24 to 36 h (>0.8 ng/ml) after follicular ablation and circulatory estrogen levels steadily increased from 36 h until OPU in all groups. At the end of the OPU sessions, the mean number of aspirated follicles/heifer/session in F36O72 protocol (Group 3) and F36O96 protocol (Group 4) were higher than in the two other groups (p<0.05). The number of cumulus-oocyte complexes (COCs), cleaved and day 8 blastocysts rates in the F36O72 protocol (Group 3) were higher than in the other groups (p<0.05). It can be concluded that a single dose i.m. administration of 100 mg FSHp at 36 h and OPU at 72 h after follicular ablation (F36O72 protocol; Group 3) was the most effective protocol for superstimulation of follicular growth for repeated OPU and subsequent in vitro embryo production in Thai native heifers. PMID:25049814

  9. Two different schemes of twice-weekly ovum pick-up in dairy heifers: effect on oocyte recovery and ovarian function.

    PubMed

    Petyim, S; Båge, R; Hallap, T; Bergqvist, A-S; Rodríguez-Martínez, H; Larsson, B

    2003-06-01

    The aim of the present study was to compare two different schemes of twice-weekly ovum pick-up (OPU), continuous (C) and discontinuous (DC), with special emphasis on differences in oocyte yield and quality, estrous cyclicity, ovarian dynamics, and progesterone production. Subsequent to characterization of their normal estrous cycles (pre-OPU period), eight dairy heifers were subjected to 4 months of twice-weekly OPU under two different schemes: the DC (OPU restricted to Days 0-12 of the cycle) and the C schemes. Effects of the two different schemes on oocyte yield, quality, and in vitro competence, together with effects on ovarian dynamics and progesterone production, were monitored. The mean numbers of punctured follicles and recovered oocytes per session were slightly higher (not significant (n.s.)) using the DC scheme, but in total, similar numbers of oocytes were obtained. The quality of the oocytes as well as cleavage rate after in vitro fertilization of the oocytes did not differ between the two OPU schemes. There was no influence of a corpus luteum (CL) producing progesterone on the oocyte yield and quality, whereas the presence of dominant follicles appeared to decrease the number of recovered ooctyes. During the pre-OPU period, all heifers showed normal cyclicity. In the DC scheme, the heifers showed regular and normal cyclic activity throughout the puncture period, with one to two complete follicular waves during the interval from the last OPU to the next estrus. In the C scheme, the heifers occasionally revealed cyclicities with irregular interestrous intervals and weaker signs of estrus. No complete follicular waves were seen during the OPU period in this scheme. The CL developed from the ovulation of the preovulatory follicles in the DC scheme showed similar characteristics to the CLs of the pre-OPU period; however, the CL-like structures from the puncture of follicles, in both the DC and the C schemes, revealed a shorter life span and inferior

  10. An Exact Separation of the Spin-Free and Spin-Dependent Terms of the Dirac-Coulomb-Breit Hamiltonian

    NASA Technical Reports Server (NTRS)

    Dyall, Kenneth G.

    1994-01-01

    The Dirac Hamiltonian is transformed by extracting the operator (sigma x p)/2mc from the small component of the wave function and applying it to the operators of the original Hamiltonian. The resultant operators contain products of Paull matrices that can be rearranged to give spin-free and spin-dependent operators. These operators are the ones encountered in the Breit-Pauli Hamiltonian, as well as some of higher order in alpha(sup 2). However, since the transformation of the original Dirac Hamiltonian is exact, the new Hamiltonian can be used in variational calculations, with or without the spin-dependent terms. The new small component functions have the same symmetry properties as the large component. Use of only the spin-free terms of the new Hamiltonian permits the same factorization over spin variables as in nonrelativistic theory, and therefore all the post-Self-Consistent Field (SCF) machinery of nonrelativistic calculations can be applied. However, the single-particle functions are two-component orbitals having a large and small component, and the SCF methods must be modified accordingly. Numerical examples are presented, and comparisons are made with the spin-free second-order Douglas-Kroll transformed Hamiltonian of Hess.

  11. Giant spin-dependent thermoelectric effect in magnetic tunnel junctions.

    PubMed

    Lin, Weiwei; Hehn, Michel; Chaput, Laurent; Negulescu, Béatrice; Andrieu, Stéphane; Montaigne, François; Mangin, Stéphane

    2012-01-01

    Thermoelectric effects in magnetic nanostructures and the so-called spin caloritronics are attracting much interest. Indeed it provides a new way to control and manipulate spin currents, which are key elements of spin-based electronics. Here we report on a giant magnetothermoelectric effect in a magnetic tunnel junction. The thermovoltage in this geometry can reach 1 mV. Moreover a magnetothermovoltage effect could be measured with ratio similar to the tunnel magnetoresistance ratio. The Seebeck coefficient can then be tuned by changing the relative magnetization orientation of the two magnetic layers in the tunnel junction. Therefore, our experiments extend the range of spintronic devices application to thermoelectricity and provide a crucial piece of information for understanding the physics of thermal spin transport. PMID:22434187

  12. Spin-dependent Klein tunneling in graphene: Role of Rashba spin-orbit coupling

    NASA Astrophysics Data System (ADS)

    Liu, Ming-Hao; Bundesmann, Jan; Richter, Klaus

    2012-02-01

    Within an effective Dirac theory the low-energy dispersions of monolayer graphene in the presence of Rashba spin-orbit coupling and spin-degenerate bilayer graphene are described by formally identical expressions. We explore implications of this correspondence for transport by choosing chiral tunneling through pn and pnpjunctions as a concrete example. A real-space Green's function formalism based on a tight-binding model is adopted to perform the ballistic transport calculations, which cover and confirm previous theoretical results based on the Dirac theory. Chiral tunneling in monolayer graphene in the presence of Rashba coupling is shown to indeed behave like in bilayer graphene. Combined effects of a forbidden normal transmission and spin separation are observed within the single-band n↔p transmission regime. The former comes from real-spin conservation, in analogy with pseudospin conservation in bilayer graphene, while the latter arises from the intrinsic spin-Hall mechanism of the Rashba coupling.

  13. Spin-dependent electron transport in zinc- and manganese-doped adenine molecules

    SciTech Connect

    Simchi, Hamidreza; Esmaeilzadeh, Mahdi Mazidabadi, Hossein

    2014-01-28

    The spin-dependent electron transport properties of zinc- and manganese-doped adenine molecules connected to zigzag graphene leads are studied in the zero bias regime using the non-equilibrium Green's function method. The conductance of the adenine molecule increased and became spin-dependent when a zinc or manganese atom was doped into the molecules. The effects of a transverse electric field on the spin-polarization of the transmitted electrons were investigated and the spin-polarization was controlled by changing the transverse electric field. Under the presence of a transverse electric field, both the zinc- and manganese-doped adenine molecules acted as spin-filters. The maximum spin-polarization of the manganese-doped adenine molecule was greater than the molecule doped with zinc.

  14. Configurational dependence of the magnetization dynamics in spin valve systems: Influence of spin pumping and domain wall induced coupling

    NASA Astrophysics Data System (ADS)

    Salikhov, R.; Abrudan, R.; Brüssing, F.; Gross, K.; Luo, C.; Westerholt, K.; Zabel, H.; Radu, F.; Garifullin, I. A.

    2012-10-01

    Using time-resolved x-ray resonant magnetic scattering we report on the precessional dynamics of spin valve systems with parallel (P) and antiparallel (AP) orientation of the ferromagnetic layers separated by a nonmagnetic spacer layers. Previously we observed in Co/Cu/Ni81Fe19(Py) spin valve systems an increase of the magnetic damping parameter in Py with changing magnetization direction of Py and Co layers from P to AP orientation [Salikhov , Appl. Phys. Lett.APPLAB0003-695110.1063/1.3633115 99, 092509 (2011)]. We attributed this finding to the configurational dependence of the spin pumping effect [Kim and Chappert, J. Magn. Magn. Mater.JMMMDC0304-885310.1016/j.jmmm.2004.09.036 286, 56 (2005)]. Here we extend our earlier findings by investigating the temperature dependence of the spin pumping effect and possible other causes for the configurational dependence of the damping parameter, such as domain wall induced coupling or magnetic dipole coupling. The main focus is on Co/Cu/Py trilayers and on Co2MnGe/V/Py trilayers with spin valve properties.

  15. Improving Limits on Exotic Spin Dependent Long Range Forces using Double Boson Exchange

    NASA Astrophysics Data System (ADS)

    Aldaihan, Sheakha; Snow, William Michael; Krause, Dennis; Long, Joshua

    2016-03-01

    The existence of very light weakly interacting particles that mediate new long range forces has been suggested in many extensions of the Standard Model. Such particles span a length scale between a μm and a few meters and include axions, familons, Majorons,and arions. Parameterizations of forces in this range show that they are composite-dependent, have a Yukawa shape, and have both spin-dependent as well as spin independent components. Very stringent limits on spin-independent couplings exist. For long range spin dependent forces, limits are weaker by 20 orders of magnitude compared to their spin independent analogs. The disparity in the limits raises the question of whether interesting limits on spin dependent couplings can be inferred from spin independent searches for long range forces. We show that this is possible using higher order contributions corresponding to double boson exchange and report the limits placed on spin dependent couplings using this method. We gratefully acknowledge the support of Indiana University and the National Science Foundation. The first author also acknowdges King Abdullah scholarship program.

  16. Metal thickness dependence on spin wave propagation in magnonic crystal using yttrium iron garnet

    SciTech Connect

    Kanazawa, Naoki; Goto, Taichi Hoong, Jet Wei; Buyandalai, Altansargai; Takagi, Hiroyuki; Inoue, Mitsuteru

    2015-05-07

    Magnonic crystals (MCs) are key components for spin wave manipulation. MCs realized with periodically metallized surfaces have an advantage in ease of the fabrication, but the effect of the metal thickness has not been studied well. In this work, the metal thickness dependence on the transmission spectra of localized mode spin waves was investigated. The metal thickness over half of the skin depth was necessary to prevent strong attenuation of spin waves.

  17. Spin-dependent mechanism for diatomic ligand binding to heme

    PubMed Central

    Franzen, Stefan

    2002-01-01

    The nature of diatomic ligand recombination in heme proteins is elucidated by using a Landau–Zener model for the electronic coupling in the recombination rate constant. The model is developed by means of explicit potential energy surfaces calculated by using density functional theory (DFT). The interaction of all possible spin states of the three common diatomic ligands, CO, NO, and O2, and high-spin heme iron is compared. The electronic coupling, rebinding barrier, and Landau–Zener force terms can be obtained and used to demonstrate significant differences among the ligands. In particular the intermediate spin states of NO (S = 3/2) and O2 (S = 1) are shown to be bound states. Rapid recombination occurs from these bound states in agreement with experimental data. The slower phases of O2 recombination can be explained by the presence of two higher spin states, S = 2 and S = 3, which have a small and relatively large barrier to ligand recombination, respectively. By contrast, the intermediate spin state for CO is not a bound state, and the only recombination pathway for CO involves direct recombination from the S = 2 state. This process is significantly slower according to the Landau–Zener model. Quantitative estimates of the parameters used in the rate constants provide a complete description that explains rebinding rates that range from femtoseconds to milliseconds at ambient temperature. PMID:12477933

  18. A simple and effective theory for all-optical helicity-dependent spin switching

    NASA Astrophysics Data System (ADS)

    Zhang, Guoping; Bai, Yihua; George, Thomas F.

    All-optical helicity-dependent spin switching (AOS) represents a new frontier in magnetic recording technology, where a single ultrafast laser pulse, without any assistance from an external magnetic field, can permanently switch spin within a few hundred femtoseconds. By contrast, the existing theory does rely on an artificial magnetic field to switch spins. Here we develop a microscopic spin switch theory, free of any artificial field, and demonstrate unambiguously that both circularly and linearly polarized lights can switch spins faithfully. Our theory is based on the Hookean theory, but includes two new elements: spin-orbit coupling and exchange interaction. We predict that left (right) circularly polarized light only flips (flops) spin, a symmetry constraint that strongly favors ferrimagnetic orderings over ferromagnetic ones, with the allowable exchange interaction within 10 meV, consistent with all prior theories. The effect of the laser amplitude is highly nonlinear: If it is too weak, AOS does not occur, but if too strong, the spin cants; a compromise between them produces a narrow spin reversal window as observed experimentally. We envision that our model can be easily extended to describe spin frustrated systems and multiferroics, where the light-spin interaction Supported by the U.S. Department of Energy under Contract No. DE-FG02-06ER46304 and the National Energy Research Scientific Computing Center.

  19. Dependence of the Spin Hall Torque Efficiency on the Transparency of Pt-Ferromagnetic Layer Interfaces

    NASA Astrophysics Data System (ADS)

    Pai, Chi-Feng; Ou, Yongxi; Ralph, Daniel C.; Buhrman, Robert A.

    2015-03-01

    We report that spin current transport across Pt-ferromagnet (FM) interfaces is strongly dependent on the type and the thickness of the FM layer and on post-deposition processing protocols. By employing both harmonic voltage response measurements and spin-torque ferromagnetic resonance measurements on various Pt-Co and Pt-CoFe magnetic heterostructures, we find that the efficiency of the Pt spin Hall effect in exerting a damping-like spin torque on the FM ranges from < 0.05 to > 0.10 under different interfacial conditions. We also show that the temperature dependence of the spin torque efficiencies for both the damping-like torque and field-like torque is dependent upon the details of the Pt-FM interface. The ``internal'' spin Hall angle of the Pt thin films used in this study, after taking the interfacial spin transmission factor that is derived from the spin mixing conductance into account, is estimated to be ~0.20. This suggests that a careful engineering of Pt-FM interfaces can improve the spin-Hall-torque efficiency of Pt-based spintronic devices. Now at Massachusetts Institute of Technology.

  20. Inversion of spin dependent photocurrent at Fe3O4/modulation doped GaAs heterointerfaces

    NASA Astrophysics Data System (ADS)

    Shirahata, Y.; Wada, E.; Itoh, M.; Taniyama, T.

    2011-04-01

    We demonstrate inversion of the spin dependent photocurrent across an Fe3O4/modulation doped GaAs interface under optical spin orientation condition. The spin dependent photocurrent for fully epitaxial Fe3O4/GaAs and Fe/GaAs interfaces clearly show the opposite magnetic field dependence, where the spin filtering efficiency for the Fe3O4/GaAs decreases with increasing magnetic field. The results clearly indicate that the spin polarization of the Fe3O4 layer has the opposite sign to that of Fe at the Fermi energy, consistent with theoretical predictions, and the result is a consequence of the atomically flat Fe3O4/GaAs interface we obtained.

  1. Dependence of nuclear spin singlet lifetimes on RF spin-locking power

    NASA Astrophysics Data System (ADS)

    DeVience, Stephen J.; Walsworth, Ronald L.; Rosen, Matthew S.

    2012-05-01

    We measure the lifetime of long-lived nuclear spin singlet states as a function of the strength of the RF spin-locking field and present a simple theoretical model that agrees well with our measurements, including the low-RF-power regime. We also measure the lifetime of a long-lived coherence between singlet and triplet states that does not require a spin-locking field for preservation. Our results indicate that for many molecules, singlet states can be created using weak RF spin-locking fields: more than two orders of magnitude lower RF power than in previous studies. Our findings suggest that for many endogenous biomolecules, singlets and related states with enhanced lifetimes might be achievable in vivo with safe levels of RF power.

  2. Effect of repeated eCG treatments and ovum pick-up on ovarian response and oocyte recovery during early pregnancy in suckling beef cows.

    PubMed

    Aller, J F; Mucci, N C; Kaiser, G G; Callejas, S S; Alberio, R H

    2012-07-01

    This study was designed to evaluate in suckling early pregnant beef cows with and without eCG-pre-stimulation: (i) the influence of day gestation (from 40 to 101 days) and the consecutive eCG treatments on the follicular growth induced by means of ultrasound-guided transvaginal follicle ablation (FA; all follicles ≥ 5 mm) and the number and quality oocytes recovered by ovum pick-up (OPU) and (ii) the possible effects of repeated hormonal stimulation and FA/OPU on pregnancy outcome. Twelve suckling early pregnant Angus cows (40 days post fixed-time artificial insemination) were randomly assigned to each of two groups (n=6 group(-1)). Group 1 treatments included: FA (Day 0), eCG (1600 IU; Day 1) and OPU (Day 5). Group 2: as cited Group 1 with no eCG treatment. In both groups, OPU was repeated five times (Days 45, 59, 73, 87 and 101 of gestation). The numbers (mean ± SEM) of class II (5-9 mm; 4.3 ± 0.9) and class III (≥10 mm; 2.5 ± 0.4) follicles visualized per cow per OPU session in eCG-treated cows were greater (P<0.05) than for non-treated cows (0.9 ± 0.1 and 0.9 ± 0.1, respectively). In contrast, the number (mean ± SEM) of class I (<5mm) follicles per cow per OPU session was lower for cows with eCG treatment (2.8 ± 0.4) than for non-treated cows (5.7 ± 0.5). The mean number of aspirated follicles was not significantly different (P<0.05) between eCG-treated cows and non-treated cows at 45 and 59 days of pregnancy. However, the mean number of aspirated follicles was greater (P=0.03) in eCG-treated cows than non-treated cows from 73 day of pregnancy onwards. The numbers (mean ± SEM) of recovered oocytes and viable oocytes/cow/session were greater (P<0.05) for eCG-treated cows (2.2 ± 0.2 and 1.6 ± 0.4, respectively) than for non-treated cows (1.0 ± 0.2 and 0.9 ± 0.2, respectively). No donor pregnancies were lost either during or following OPU procedure. We can conclude that (1) eCG-treated pregnant suckled cows can be a source of oocytes for IVF at

  3. In vivo collection of follicular fluid and granulosa cells from individual follicles of different diameters in cattle by an adapted ovum pick-up system

    PubMed Central

    2013-01-01

    Background Most studies on granulosa cell (GC) function in cattle have been performed using GC and follicular fluid (FF) samples collected from slaughterhouse ovaries. Using this approach, the follicular developmental stage and functional status are unknown and indirectly inferred, limiting data interpretation. Ultrasound-guided follicle aspiration has previously been used to recover GC or FF samples, but this was mostly carried out in large follicles or pools of small follicles, without recording the efficiency of recovery. The present study was aimed at adapting and evaluating an ovum pick-up (OPU) system for the in vivo recovery of FF and GC from individual follicles of different diameters. Methods In the first trial, the losses of fluid inside the tubing system were calculated using a conventional or an adapted-OPU system. Blood plasma volumes equivalent to the amount of FF in follicles of different diameters were aspirated using a conventional OPU Teflon circuit. The OPU system was then adapted by connecting 0.25 mL straws to the circuit. A second trial evaluated the efficiency of FF recovery in vivo. Follicles ranging from 4.0 to 16.8 mm in diameter were aspirated individually using the conventional or adapted-OPU systems. A third trial assessed the in vivo recovery of GC and the subsequent amount of RNA obtained from the follicles of different diameters from Holstein and Gir cattle. Results In Trial I, the plasma recovery efficiency was similar (P > 0.05) for the volumes expected for 12 and 10 mm follicles, but decreased (P < 0.05) for smaller follicles (45.7+/−4.0%, 12.4+/−4.3% and 0.0+/−0.0% for 8, 6, and 4 mm follicles, respectively). Using the adaptation, the losses intrinsic to the aspiration system were similar for all follicle diameters. In Trial II, the expected and recovered volumes of FF were correlated (r = 0.89) and the efficiency of recovery was similar among follicles <12 mm, while larger follicles had a progressive increase

  4. Optically induced spin-dependent diffusive transport in the presence of spin-orbit interaction for all-optical magnetization reversal

    NASA Astrophysics Data System (ADS)

    Elyasi, Mehrdad; Yang, Hyunsoo

    2016-07-01

    We have considered the effect of different spin-orbit interaction mechanisms on the process of demagnetization under the influence of short-pulse lasers. All-optical magnetization reversal of perpendicularly magnetized thin films can occur if there are sufficient strong spin-Hall, skew scattering, and Rashba interactions. In the presence of spin-orbit interactions, the transient charge currents provide the generation of transverse-spin currents and accumulations, which eventually exert spin-transfer torque on the magnetization. By combining the optically excited spin-dependent diffusive transport with the spin and charge currents due to skew scattering, spin-Hall, inverse spin-Hall, and Rashba interactions into a numerical model, we demonstrate a possibility of ultrafast all-optical magnetization reversal. This understanding provokes intriguing, more in-depth experimental studies on the role of spin-orbit interaction mechanisms in optimizing structures for all-optical magnetization reversal.

  5. Optimized weak measurement for spatial spin-dependent shifts at Brewster angle

    NASA Astrophysics Data System (ADS)

    Zhang, Yi; Li, Peng; Liu, Sheng; Han, Lei; Cheng, Huachao; Zhao, Jianlin

    2016-07-01

    As Brewster law goes, the polarization selectivity when a light beam reflected at Brewster angle is feasible. We find that this polarization selectivity is still effective incorporated with weak measurement. So we realize an optimized weak measurement technique without preselection polarizer. This scheme is exploited to observe the spatial spin-dependent shifts when a linearly polarized beam is reflected at Brewster angle. The theoretical and experimental results show that by changing the polarization orientation of incident beam, the in-plane spin-dependent shift direction can be reversed, while the out-of-plane spin-dependent shift direction keeps unchanged. Our results may enrich the application of weak measurement.

  6. Limits on spin-dependent wimp-nucleon interactions from the cryogenic dark matter search

    SciTech Connect

    Akerib, D.S.; Armel-Funkhouser, M.S.; Attisha, M.J.; Bailey, C.N.; Baudis, L.; Bauer, Daniel A.; Brink, P.L.; Brusov, P.P.; Bunker, R.; Cabrera, B.; Caldwell, D.O.; Chang, C.L.; Cooley, J.; Crisler, M.B.; Cushman, P.; Daal, M.; DeJongh, F.; Dixon, R.; Dragowsky, M.R.; Driscoll, D.D.; Duong, L.; /Case Western Reserve U. /UC, Berkeley /Brown U. /Florida U. /Fermilab /Stanford U., Phys. Dept. /UC, Santa Barbara /Minnesota U. /Caltech /Colorado U., Denver /LBL, Berkeley /Santa Clara U.

    2005-09-01

    The Cryogenic Dark Matter Search (CDMS) is an experiment to detect weakly interacting massive particles (WIMPs) based on their interactions with Ge and Si nuclei. We report the results of an analysis of data from the first two runs of CDMS at the Soudan Underground Laboratory in terms of spin-dependent WIMP-nucleon interactions on {sup 73}Ge and {sup 29}Si. These data exclude new regions of spin-dependent WIMP-nucleon interaction parameter space, including regions relevant to spin-dependent interpretations of the annual modulation signal reported by the DAMA/NaI experiment.

  7. Dependence of Kambersky damping on Fermi level and spin orientation

    SciTech Connect

    Qu, T.; Victora, R. H.

    2014-05-07

    Kambersky damping represents the loss of magnetic energy from the electrons to the lattice through the spin orbit interaction. It is demonstrated that, for bcc Fe-based transition metal alloys, the logarithm of the energy loss is proportional to the density of states at the Fermi level. Both inter and intraband damping are calculated for spins at arbitrary angle to the previously examined [001] direction. Although the easy axis 〈100〉 shows isotropic relaxation and achieves the minimum damping value of 0.002, other directions, such as 〈110〉, show substantial anisotropic damping.

  8. Controlling spin-dependent localization and directed transport in a bipartite lattice

    NASA Astrophysics Data System (ADS)

    Luo, Yunrong; Lu, Gengbiao; Kong, Chao; Hai, Wenhua

    2016-04-01

    We study coherent control of spin-dependent dynamical localization (DL) and directed transport (DT) of a spin-orbit-coupled single atom held in a driven optical bipartite lattice. Under the high-frequency limit and nearest-neighbor tight-binding approximation, we find a new decoupling mechanism between states with the same (different) spins, which leads to two sets of analytical solutions describing DL and DT with (without) spin flipping. The analytical results are numerically confirmed, and perfect agreements are found. Extending the research to a system of spin-orbit-coupled single atoms, the spin current and quantum information transport with controllable propagation speed and distance are investigated. The results can be experimentally tested in the current setups and may be useful in quantum information processing.

  9. Hysteresis loops of spin-dependent electronic current in a paramagnetic resonant tunnelling diode

    NASA Astrophysics Data System (ADS)

    Wójcik, P.; Spisak, B. J.; Wołoszyn, M.; Adamowski, J.

    2012-11-01

    Nonlinear properties of the spin-dependent electronic transport through a semiconductor resonant tunnelling diode with a paramagnetic quantum well are considered. The spin-dependent Wigner-Poisson model of the electronic transport and the two-current Mott’s formula for the independent spin channels are applied to determine the current-voltage curves of the nanodevice. Two types of the electronic current hysteresis loops are found in the current-voltage characteristics for both the spin components of the electronic current. The physical interpretation of these two types of the electronic current hysteresis loops is given based on the analysis of the spin-dependent electron densities and the potential energy profiles. The differences between the current-voltage characteristics for both the spin components of the electronic current allow us to explore the changes of the spin polarization of the current for different electric fields and determine the influence of the electronic current hysteresis on the spin polarization of the current flowing through the paramagnetic resonant tunnelling diode.

  10. [Spin dependent phenomena in medium energy physics]. [Syracuse Univ. , Syracuse, New York

    SciTech Connect

    Souder, P.A.

    1992-11-01

    The Syracuse University Medium Energy Physics Group was actively engaged in several research projects. A laser was used to polarize muonic atoms with the goal of measuring fundamental spin-dependent parameters in the reaction [mu][sup [minus

  11. Spin dependent momentum density and Fermi surface of ferromagnetic Ni obtained by positron annihilation experiments

    NASA Astrophysics Data System (ADS)

    Hamid, A. S.; Uedono, A.

    2004-11-01

    The spin-dependent momentum density and Fermi surface of ferromagnetic Ni have been obtained through positron annihilation experiments. The measurements were carried out through 2D angular correlation of annihilation radiation (ACAR) using longitudinally polarized positrons. The magnetic field direction was reversed in order to study the effect of the spin-dependent positron-electron momentum space density on the Fermi surface of Ni. The results showed that ferromagnetic Ni had different Fermi surfaces for the majority-spin and minority-spin states. The differences due to the spin-states were studied in the momentum space and in the wave vector space. In general, the experimental results showed good agreement with previous theoretical calculations.

  12. The spin-dependent transport properties of zigzag α-graphyne nanoribbons and new device design

    PubMed Central

    Ni, Yun; Wang, Xia; Tao, Wei; Zhu, Si-Cong; Yao, Kai-Lun

    2016-01-01

    By performing first-principle quantum transport calculations, we studied the electronic and transport properties of zigzag α-graphyne nanoribbons in different magnetic configurations. We designed the device based on zigzag α-graphyne nanoribbon and studied the spin-dependent transport properties, whose current-voltage curves show obvious spin-polarization and conductance plateaus. The interesting transport behaviours can be explained by the transport spectra under different magnetic configurations, which basically depends on the symmetry matching of the electrodes’ bandstructures. Simultaneously, spin Seebeck effect is also found in the device. Thus, according to the transport behaviours, zigzag α-graphyne nanoribbons can be used as a dual spin filter diode, a molecule signal converter and a spin caloritronics device, which indicates that α-graphyne is a promising candidate for the future application in spintronics. PMID:27180808

  13. The spin-dependent transport properties of zigzag α-graphyne nanoribbons and new device design.

    PubMed

    Ni, Yun; Wang, Xia; Tao, Wei; Zhu, Si-Cong; Yao, Kai-Lun

    2016-01-01

    By performing first-principle quantum transport calculations, we studied the electronic and transport properties of zigzag α-graphyne nanoribbons in different magnetic configurations. We designed the device based on zigzag α-graphyne nanoribbon and studied the spin-dependent transport properties, whose current-voltage curves show obvious spin-polarization and conductance plateaus. The interesting transport behaviours can be explained by the transport spectra under different magnetic configurations, which basically depends on the symmetry matching of the electrodes' bandstructures. Simultaneously, spin Seebeck effect is also found in the device. Thus, according to the transport behaviours, zigzag α-graphyne nanoribbons can be used as a dual spin filter diode, a molecule signal converter and a spin caloritronics device, which indicates that α-graphyne is a promising candidate for the future application in spintronics. PMID:27180808

  14. The spin-dependent transport properties of zigzag α-graphyne nanoribbons and new device design

    NASA Astrophysics Data System (ADS)

    Ni, Yun; Wang, Xia; Tao, Wei; Zhu, Si-Cong; Yao, Kai-Lun

    2016-05-01

    By performing first-principle quantum transport calculations, we studied the electronic and transport properties of zigzag α-graphyne nanoribbons in different magnetic configurations. We designed the device based on zigzag α-graphyne nanoribbon and studied the spin-dependent transport properties, whose current-voltage curves show obvious spin-polarization and conductance plateaus. The interesting transport behaviours can be explained by the transport spectra under different magnetic configurations, which basically depends on the symmetry matching of the electrodes’ bandstructures. Simultaneously, spin Seebeck effect is also found in the device. Thus, according to the transport behaviours, zigzag α-graphyne nanoribbons can be used as a dual spin filter diode, a molecule signal converter and a spin caloritronics device, which indicates that α-graphyne is a promising candidate for the future application in spintronics.

  15. Detection and Measurement of Spin-Dependent Dynamics in Random Telegraph Signals

    NASA Astrophysics Data System (ADS)

    House, M. G.; Xiao, Ming; Guo, GuoPing; Li, HaiOu; Cao, Gang; Rosenthal, M. M.; Jiang, HongWen

    2013-09-01

    A quantum point contact was used to observe single-electron fluctuations of a quantum dot in a GaAs heterostructure. The resulting random telegraph signals (RTS) contain statistical information about the electron spin state if the tunneling dynamics are spin dependent. We develop a statistical method to extract information about spin-dependent dynamics from RTS and use it to demonstrate that these dynamics can be studied in the thermal energy regime. The tunneling rates of each spin state are independently measured in a finite external magnetic field. We confirm previous findings of a decrease in overall tunneling rates for the spin excited state compared to the ground state as an external magnetic field is increased.

  16. Spin-dependent transport in a magnetic two-dimensional electron gas

    NASA Astrophysics Data System (ADS)

    Smorchkova, I. P.; Kikkawa, J. M.; Samarth, N.; Awschalom, D. D.

    1998-07-01

    Magneto-transport and magneto-optical probes are used to interrogate spin-dependent transport in magnetic heterostructures wherein a two dimensional electron gas (2DEG) is exchange-coupled to local moments. At low temperatures, the significant s-d exchange-enhanced spin splitting in these “magnetic” 2DEGs is responsible for the observation of unusual transport properties such as a complete spin polarization of the gas at large Landau level filling factors and a pronounced, non-monotonic background magneto-resistance. Magneto-transport measurements of gated samples performed in a parallel field geometry are used to systematically study the variation of the magneto-resistance with sheet concentration, yielding new insights into the dependence of spin transport on the Fermi energy of the majority spin carriers.

  17. Spin-dependent two-body interactions from gravitational self-force computations

    NASA Astrophysics Data System (ADS)

    Bini, Donato; Damour, Thibault; Geralico, Andrea

    2015-12-01

    We analytically compute, through the eight-and-a-half post-Newtonian order and the fourth-order in spin, the gravitational self-force correction to Detweiler's gauge invariant redshift function for a small mass in circular orbit around a Kerr black hole. Using the first law of mechanics for black hole binaries with spin [L. Blanchet, A. Buonanno and A. Le Tiec, Phys. Rev. D 87, 024030 (2013)] we transcribe our results into a knowledge of various spin-dependent couplings, as encoded within the spinning effective-one-body model of T. Damour and A. Nagar [Phys. Rev. D 90, 044018 (2014)]. We also compare our analytical results to the (corrected) numerical self-force results of A. G. Shah, J. L. Friedman and T. S. Keidl [Phys. Rev. D 86, 084059 (2012)], from which we show how to directly extract physically relevant spin-dependent couplings.

  18. Sum rule measurements of the spin-dependent compton amplitude (nucleon spin structure at Q{sup 2} = 0)

    SciTech Connect

    Babusci, D.; Giordano, G.; Baghaei, H.; Cichocki, A.; Blecher, M.; Breuer, M.; Commeaux, C.; Didelez, J.P.; Caracappa, A.; Fan, Q.

    1995-12-31

    Energy weighted integrals of the difference in helicity-dependent photo-production cross sections ({sigma}{sub {1/2}} - {sigma}{sub 3/2}) provide information on the nucleon`s Spin-dependent Polarizability ({gamma}), and on the spin-dependent part of the asymptotic forward Compton amplitude through the Drell-Hearn-Gerasimov (DHG) sum rule. (The latter forms the Q{sup 2}=0 limit of recent spin-asymmetry experiments in deep-inelastic lepton-scattering.) There are no direct measurements of {sigma}{sub {1/2}} or {sigma}{sub 3/2}, for either the proton or the neutron. Estimates from current {pi}-photo-production multipole analyses, particularly for the proton-neutron difference, are in good agreement with relativistic-l-loop Chiral calculations ({chi}PT) for {gamma} but predict large deviations from the DHG sum rule. Either (a) both the 2-loop corrections to the Spin-Polarizability are large and the existing multipoles are wrong, or (b) modifications to the Drell-Hearn-Gerasimov sum rule are required to fully describe the isospin structure of the nucleon. The helicity-dependent photo-reaction amplitudes, for both the proton and the neutron, will be measured at LEGS from pion-threshold to 470 MeV. In these double-polarization experiments, circularly polarized photons from LEGS will be used with SPHICE, a new frozen-spin target consisting of {rvec H} {center_dot} {rvec D} in the solid phase. Reaction channels will be identified in SASY, a large detector array covering about 80% of 4{pi}. A high degree of symmetry in both target and detector will be used to minimize systematic uncertainties.

  19. Approximate spin projected spin-unrestricted density functional theory method: Application to diradical character dependences of second hyperpolarizabilities

    SciTech Connect

    Nakano, Masayoshi Minami, Takuya Fukui, Hitoshi Yoneda, Kyohei Shigeta, Yasuteru Kishi, Ryohei; Champagne, Benoît; Botek, Edith

    2015-01-22

    We develop a novel method for the calculation and the analysis of the one-electron reduced densities in open-shell molecular systems using the natural orbitals and approximate spin projected occupation numbers obtained from broken symmetry (BS), i.e., spin-unrestricted (U), density functional theory (DFT) calculations. The performance of this approximate spin projection (ASP) scheme is examined for the diradical character dependence of the second hyperpolarizability (γ) using several exchange-correlation functionals, i.e., hybrid and long-range corrected UDFT schemes. It is found that the ASP-LC-UBLYP method with a range separating parameter μ = 0.47 reproduces semi-quantitatively the strongly-correlated [UCCSD(T)] result for p-quinodimethane, i.e., the γ variation as a function of the diradical character.

  20. Approximate spin projected spin-unrestricted density functional theory method: Application to diradical character dependences of second hyperpolarizabilities

    NASA Astrophysics Data System (ADS)

    Nakano, Masayoshi; Minami, Takuya; Fukui, Hitoshi; Yoneda, Kyohei; Shigeta, Yasuteru; Kishi, Ryohei; Champagne, Benoıît; Botek, Edith

    2015-01-01

    We develop a novel method for the calculation and the analysis of the one-electron reduced densities in open-shell molecular systems using the natural orbitals and approximate spin projected occupation numbers obtained from broken symmetry (BS), i.e., spin-unrestricted (U), density functional theory (DFT) calculations. The performance of this approximate spin projection (ASP) scheme is examined for the diradical character dependence of the second hyperpolarizability (γ) using several exchange-correlation functionals, i.e., hybrid and long-range corrected UDFT schemes. It is found that the ASP-LC-UBLYP method with a range separating parameter μ = 0.47 reproduces semi-quantitatively the strongly-correlated [UCCSD(T)] result for p-quinodimethane, i.e., the γ variation as a function of the diradical character.

  1. Student understanding of the time dependence of spin-1/2 systems

    NASA Astrophysics Data System (ADS)

    Passante, Gina

    2016-03-01

    Time dependence is one of the most difficult concepts in quantum mechanics and one that is relevant throughout instruction. In this talk I will explore student responses to written questions regarding the time dependence for spin-1/2 systems after lecture instruction and again after a tutorial on the topic. These questions were asked in a junior-level quantum mechanics course that is taught using a spins-first curriculum.

  2. Equations of motion of test particles for solving the spin-dependent Boltzmann-Vlasov equation

    NASA Astrophysics Data System (ADS)

    Xia, Yin; Xu, Jun; Li, Bao-An; Shen, Wen-Qing

    2016-08-01

    A consistent derivation of the equations of motion (EOMs) of test particles for solving the spin-dependent Boltzmann-Vlasov equation is presented. The resulting EOMs in phase space are similar to the canonical equations in Hamiltonian dynamics, and the EOM of spin is the same as that in the Heisenburg picture of quantum mechanics. Considering further the quantum nature of spin and choosing the direction of total angular momentum in heavy-ion reactions as a reference of measuring nucleon spin, the EOMs of spin-up and spin-down nucleons are given separately. The key elements affecting the spin dynamics in heavy-ion collisions are identified. The resulting EOMs provide a solid foundation for using the test-particle approach in studying spin dynamics in heavy-ion collisions at intermediate energies. Future comparisons of model simulations with experimental data will help to constrain the poorly known in-medium nucleon spin-orbit coupling relevant for understanding properties of rare isotopes and their astrophysical impacts.

  3. Spin-dependent Seebeck effects in a graphene nanoribbon coupled to two square lattice ferromagnetic leads

    SciTech Connect

    Zhou, Benhu Zeng, Yangsu; Zhou, Benliang; Zhou, Guanghui; Ouyang, Tao

    2015-03-14

    We theoretically investigate spin-dependent Seebeck effects for a system consisting of a narrow graphene nanoribbon (GNR) contacted to square lattice ferromagnetic (FM) electrodes with noncollinear magnetic moments. Both zigzag-edge graphene nanoribbons (ZGNRs) and armchair-edge graphene nanoribbons (AGNRs) were considered. Compared with our previous work with two-dimensional honeycomb-lattice FM leads, a more realistic model of two-dimensional square-lattice FM electrodes is adopted here. Using the nonequilibrium Green's function method combining with the tight-binding Hamiltonian, it is demonstrated that both the charge Seebeck coefficient S{sub C} and the spin-dependent Seebeck coefficient S{sub S} strongly depend on the geometrical contact between the GNR and the leads. In our previous work, S{sub C} for a semiconducting 15-AGNR system near the Dirac point is two orders of magnitude larger than that of a metallic 17-AGNR system. However, S{sub C} is the same order of magnitude for both metallic 17-AGNR and semiconducting 15-AGNR systems in the present paper because of the lack of a transmission energy gap for the 15-AGNR system. Furthermore, the spin-dependent Seebeck coefficient S{sub S} for the systems with 20-ZGNR, 17-AGNR, and 15-AGNR is of the same order of magnitude and its maximum absolute value can reach 8 μV/K. The spin-dependent Seebeck effects are not very pronounced because the transmission coefficient weakly depends on spin orientation. Moreover, the spin-dependent Seebeck coefficient is further suppressed with increasing angle between the relative alignments of magnetization directions of the two leads. Additionally, the spin-dependent Seebeck coefficient can be strongly suppressed for larger disorder strength. The results obtained here may provide valuable theoretical guidance in the experimental design of heat spintronic devices.

  4. Spin-dependent shot noise in diluted magnetic semiconductor/semiconductor heterostructures with a nonmagnetic barrier

    NASA Astrophysics Data System (ADS)

    Wu, Shuang; Guo, Yong

    2014-05-01

    We investigate quantum size effect on the spin-dependent shot noise in the diluted magnetic semiconductor (DMS)/semiconductor heterostructure with a nonmagnetic semiconductor (NMS) barrier in the presence of external magnetic and electric fields. The results demonstrate that the NMS barrier plays a quite different role from the DMS layer in the electron transport process. It is found that spin-down shot noise shows relatively regular oscillations as the width of DMS layer increases, while the spin-up shot noise deceases monotonically. However, as the width of NMS layer increases, the spin-down shot noise displays irregular oscillations at first and then decreases while the spin-up shot noise decreases at a quite different rate. The results indicate that the shot noise can be used as a sensitive probe in detecting material type and its size.

  5. Spin-dependent screening and Auger neutralization of He{sup +} ions in metals

    SciTech Connect

    Alducin, M.; Diez Muino, R.; Juaristi, J.I.

    2004-07-01

    The screening of a He{sup +} ion embedded in a paramagnetic electron gas is studied using density functional theory within the local spin density approximation. We calculate the induced electron density and the induced density of states for each spin orientation, parallel and antiparallel to that of the electron bound to the He{sup +} ion. Our results show that the screening is preferably due to parallel spin electrons, especially for low electron densities of the medium. In a second step, the rates for Auger neutralization of a He{sup +} ion in an electron gas are calculated, paying special attention to their dependence on the spin of the electron excited in the Auger process. The results obtained are used to interpret experiments in which the spin polarization of the emitted yield is measured when a He{sup +} projectile is neutralized in front of a metal surface.

  6. Spin-dependent electron emission from metals in the neutralization of He{sup +} ions

    SciTech Connect

    Alducin, M.; Roesler, M.; Juaristi, J.I.

    2005-08-15

    We calculate the spin-polarization of electrons emitted in the neutralization of He{sup +} ions interacting with metals. All stages of the emission process are included: the spin-dependent perturbation induced by the projectile, the excitation of electrons in Auger neutralization processes, the creation of a cascade of secondaries, and the escape of the electrons through the surface potential barrier. The model allows us to explain in quantitative terms the measured spin-polarization of the yield in the interaction of spin-polarized He{sup +} ions with paramagnetic surfaces, and to disentangle the role played by each of the involved mechanisms. We show that electron-electron scattering processes at the surface determine the spin-polarization of the total yield. High energy emitted electrons are the ones providing direct information on the He{sup +} ion neutralization process and on the electronic properties of the surface.

  7. Compact vacuum tubes with GaAs(Cs,O) photocathodes for studying spin-dependent phenomena

    NASA Astrophysics Data System (ADS)

    Alperovich, V. L.; Orlov, D. A.; Grishaev, V. G.; Kosolobov, S. N.; Jaroshevich, A. S.; Scheibler, H. E.; Terekhov, A. S.

    2009-08-01

    Compact proximity focused vacuum tubes with GaAs(Cs,O) photocathodes are used for experimental studying spindependent phenomena. Firstly, spin-dependent emission of optically oriented electrons from p-GaAs(Cs,O) into vacuum in a magnetic field normal to the surface was observed in a nonmagnetic vacuum diode. This phenomenon is explained by the jump in the electron g-factor at the semiconductor-vacuum interface. Due to this jump, the effective electron affinity on the semiconductor surface depends on the mutual direction of optically oriented electron spins and the magnetic field, resulting in the spin-dependent photoemission. It is demonstrated that the observed effect can be used for the determination of spin diffusion length in semiconductors. Secondly, we developed a prototype of a new spin filter, which consists of a vacuum tube with GaAs(Cs,O) photocathode and a nickel-covered venetian blind dynode. Preliminary results on spin-dependent reflection of electrons from the oxidized polycrystal nickel layer are presented.

  8. Time Dependence of the freezing temperature for thin film spin glasses

    NASA Astrophysics Data System (ADS)

    Orbach, Raymond

    There have been many measurements of the dependence of the ``freezing temperature'', Tf, on the thickness o of thin film spin glasses. Tf decreases with decreasing o, but never vanishes. This contribution suggests that the dependence of Tf on o is a time dependent relationship. Because the lower critical dimension of a spin glass, dl ~ 2 . 5 , when the spin glass correlation length ξ (t , T) grows to o, the spin glass dimensionality crosses over from d = 3 to d = 2 . What remains are spin glass correlations for length scales <= o . The time dependence of the magnetization dynamics are then activated, with activation energy equal to a largest barrier Δmax (o) , and an associated activation time τ. For measurements at time scales such that ξ (t , T) < o , the effective dimension d = 3 , and the characteristic cusp and knee of a spin glass is observed. For experimental time scales greater than τ, with ξ (t , T) ~ o , the zero-field cooled magnetization has grown to the field-cooled value of the magnetization, leading to the identification of Tf. Quantitative agreement with experiment is exhibited. Supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Science and Engineering under Award DE-SC0013599.

  9. Karplus dependence of spin-spin coupling constants revisited theoretically. Part 1: second-order double perturbation theory.

    PubMed

    Rusakova, Irina L; Krivdin, Leonid B

    2013-11-01

    A double perturbation theory (DPT) at the second order level of approximation formalism has been applied to examine the dihedral angle dependence of the Fermi-contact (FC) contribution to nuclear spin-spin coupling constants. The unperturbed wave function of the ground state in DPT was approximated by the Hartree-Fock Slater determinant, while the excited states were treated as the single excited determinants. An analytical expression relating the FC term of vicinal proton-proton spin-spin coupling constants across the aliphatic single carbon-carbon bond to the dihedral angle describing inner rotation around the C-C bond in the ten-electron ten-orbital moiety H-C-C-H has been derived and analyzed. In particular, it has been shown that extrema of (3)J(H,H) are observed at φ = πn, n = 0, ±1, ±2,…, which provides a theoretical background of a well-known semiempirical Karplus equation. PMID:24071769

  10. The magnetic field dependence of cross-effect dynamic nuclear polarization under magic angle spinning

    SciTech Connect

    Mance, Deni; Baldus, Marc; Gast, Peter; Huber, Martina; Ivanov, Konstantin L.

    2015-06-21

    We develop a theoretical description of Dynamic Nuclear Polarization (DNP) in solids under Magic Angle Spinning (MAS) to describe the magnetic field dependence of the DNP effect. The treatment is based on an efficient scheme for numerical solution of the Liouville-von Neumann equation, which explicitly takes into account the variation of magnetic interactions during the sample spinning. The dependence of the cross-effect MAS-DNP on various parameters, such as the hyperfine interaction, electron-electron dipolar interaction, microwave field strength, and electron spin relaxation rates, is analyzed. Electron spin relaxation rates are determined by electron paramagnetic resonance measurements, and calculations are compared to experimental data. Our results suggest that the observed nuclear magnetic resonance signal enhancements provided by MAS-DNP can be explained by discriminating between “bulk” and “core” nuclei and by taking into account the slow DNP build-up rate for the bulk nuclei.