Science.gov

Sample records for electric field driven

  1. Hydrogel Actuation by Electric Field Driven Effects

    NASA Astrophysics Data System (ADS)

    Morales, Daniel Humphrey

    Hydrogels are networks of crosslinked, hydrophilic polymers capable of absorbing and releasing large amounts of water while maintaining their structural integrity. Polyelectrolyte hydrogels are a subset of hydrogels that contain ionizable moieties, which render the network sensitive to the pH and the ionic strength of the media and provide mobile counterions, which impart conductivity. These networks are part of a class of "smart" material systems that can sense and adjust their shape in response to the external environment. Hence, the ability to program and modulate hydrogel shape change has great potential for novel biomaterial and soft robotics applications. We utilized electric field driven effects to manipulate the interaction of ions within polyelectrolyte hydrogels in order to induce controlled deformation and patterning. Additionally, electric fields can be used to promote the interactions of separate gel networks, as modular components, and particle assemblies within gel networks to develop new types of soft composite systems. First, we present and analyze a walking gel actuator comprised of cationic and anionic gel legs attached by electric field-promoted polyion complexation. We characterize the electro-osmotic response of the hydrogels as a function of charge density and external salt concentration. The gel walkers achieve unidirectional motion on flat elastomer substrates and exemplify a simple way to move and manipulate soft matter devices in aqueous solutions. An 'ionoprinting' technique is presented with the capability to topographically structure and actuate hydrated gels in two and three dimensions by locally patterning ions induced by electric fields. The bound charges change the local mechanical properties of the gel to induce relief patterns and evoke localized stress, causing rapid folding in air. The ionically patterned hydrogels exhibit programmable temporal and spatial shape transitions which can be tuned by the duration and/or strength of

  2. Electric field-free gas breakdown in explosively driven generators

    SciTech Connect

    Shkuratov, Sergey I.; Baird, Jason; Talantsev, Evgueni F.; Altgilbers, Larry L.

    2010-07-15

    All known types of gas discharges require an electric field to initiate them. We are reporting on a unique type of gas breakdown in explosively driven generators that does not require an electric field.

  3. Electric Field Driven Torque in ATP Synthase

    PubMed Central

    Miller, John H.; Rajapakshe, Kimal I.; Infante, Hans L.; Claycomb, James R.

    2013-01-01

    FO-ATP synthase (FO) is a rotary motor that converts potential energy from ions, usually protons, moving from high- to low-potential sides of a membrane into torque and rotary motion. Here we propose a mechanism whereby electric fields emanating from the proton entry and exit channels act on asymmetric charge distributions in the c-ring, due to protonated and deprotonated sites, and drive it to rotate. The model predicts a scaling between time-averaged torque and proton motive force, which can be hindered by mutations that adversely affect the channels. The torque created by the c-ring of FO drives the γ-subunit to rotate within the ATP-producing complex (F1) overcoming, with the aid of thermal fluctuations, an opposing torque that rises and falls with angular position. Using the analogy with thermal Brownian motion of a particle in a tilted washboard potential, we compute ATP production rates vs. proton motive force. The latter shows a minimum, needed to drive ATP production, which scales inversely with the number of proton binding sites on the c-ring. PMID:24040370

  4. Electric field driven torque in ATP synthase.

    PubMed

    Miller, John H; Rajapakshe, Kimal I; Infante, Hans L; Claycomb, James R

    2013-01-01

    FO-ATP synthase (FO) is a rotary motor that converts potential energy from ions, usually protons, moving from high- to low-potential sides of a membrane into torque and rotary motion. Here we propose a mechanism whereby electric fields emanating from the proton entry and exit channels act on asymmetric charge distributions in the c-ring, due to protonated and deprotonated sites, and drive it to rotate. The model predicts a scaling between time-averaged torque and proton motive force, which can be hindered by mutations that adversely affect the channels. The torque created by the c-ring of FO drives the γ-subunit to rotate within the ATP-producing complex (F1) overcoming, with the aid of thermal fluctuations, an opposing torque that rises and falls with angular position. Using the analogy with thermal Brownian motion of a particle in a tilted washboard potential, we compute ATP production rates vs. proton motive force. The latter shows a minimum, needed to drive ATP production, which scales inversely with the number of proton binding sites on the c-ring.

  5. Electric Field-Driven Assembly of Sulfonated Polystyrene Microspheres

    PubMed Central

    Mikkelsen, Alexander; Wojciechowski, Jarosław; Rajňák, Michal; Kurimský, Juraj; Khobaib, Khobaib; Kertmen, Ahmet; Rozynek, Zbigniew

    2017-01-01

    A designed assembly of particles at liquid interfaces offers many advantages for development of materials, and can be performed by various means. Electric fields provide a flexible method for structuring particles on drops, utilizing electrohydrodynamic circulation flows, and dielectrophoretic and electrophoretic interactions. In addition to the properties of the applied electric field, the manipulation of particles often depends on the intrinsic properties of the particles to be assembled. Here, we present an easy approach for producing polystyrene microparticles with different electrical properties. These particles are used for investigations into electric field-guided particle assembly in the bulk and on surfaces of oil droplets. By sulfonating polystyrene particles, we produce a set of particles with a range of dielectric constants and electrical conductivities, related to the sulfonation reaction time. The paper presents diverse particle behavior driven by electric fields, including particle assembly at different droplet locations, particle chaining, and the formation of ribbon-like structures with anisotropic properties. PMID:28772690

  6. Electric field-driven currents in the ionosphere of Mars

    NASA Astrophysics Data System (ADS)

    Fillingim, M. O.; Lillis, R. J.; Ma, Y.

    2011-10-01

    Mars has a complex magnetic topology. Crustal magnetic fields can interact with the solar wind magnetic field to form magnetic cusps. On the nightside, solar wind electron precipitation can produce regions of enhanced ionization at cusps while closed field regions adjacent to cusps can be devoid of significant ionization. Previously, using an electron transport model, we calculated the electron density and spatial structure of the nightside ionosphere of Mars using Mars Global Surveyor electron measurements as input. Localized regions of enhanced ionospheric density were found to occur at magnetic cusps adjacent to low density voids [1]. Additionally, we calculated the horizontal ionospheric currents driven by strong plasma gradients and by thermospheric neutral winds. In the dynamo region of the ionosphere, the collisional ions move in the direction of the applied force (the plasma gradient or neutral wind) while the magnetized electrons move perpendicular to both the applied force and ambient magnetic field. This difference in motion drives horizontal currents. Subsequently, we considered the existence of wind-driven cusp electrojets created by secondary currents arising from polarization electric fields which form in the presence of strong conductivity gradients [2]. At Earth, ionospheric currents at high latitudes are driven predominantly by externally imposed (magnetospheric) electric fields. Here, we compute the horizontal ionospheric currents in the vicinity of magnetic cusps resulting from external electric fields. In the absence of electric field observations, we use the electric field calculated from a global model of the Mars-solar wind interaction as input. We compare the magnitude of these currents with those driven by neutral winds and plasma gradients. Additionally, we estimate the magnitude of the electric field-driven electrojets, analogous to Earth's auroral electrojets. These enhanced currents can lead to localized, enhanced Joule heating

  7. Electric-field-driven resistive switching in dissipative Hubbard model

    NASA Astrophysics Data System (ADS)

    Li, Jiajun; Aron, Camille; Kotliar, Gabriel; Han, Jong

    Understanding of solids driven out of equilibrium by external fields has been one of the central goals in condensed matter physics for the past century and is relevant to nanotechnology applications such as resistive transitions. We study how strongly correlated electrons on a dissipative lattice evolve from equilibrium when driven by a constant electric field, focusing on the extent of the linear regime and hysteretic non-linear effects at higher fields. We access the non-equilibrium steady states, non-perturbatively in both the field and the electronic interactions, by means of a non-equilibrium dynamical mean-field theory in the Coulomb gauge. The linear response regime is limited by Joule heating effects and breaks down at fields orders of magnitude smaller than the quasi-particle energy scale. For large electronic interactions, strong but experimentally accessible electric fields can induce a resistive switching by driving the strongly correlated metal into a Mott insulator. Hysteretic I- V curves suggest that the non-equilibrium current is carried through a spatially inhomogeneous metal-insulator mixed state.

  8. Electric-field-driven resistive switching in dissipative Hubbard model

    NASA Astrophysics Data System (ADS)

    Li, Jiajun; Aron, Camille; Kotliar, Gabriel; Han, Jong

    2015-03-01

    Understanding of solids driven out of equilibrium by external fields has been one of the central goals in condensed matter physics for the past century and is relevant to nanotechnology applications such as resistive transitions. We study how strongly correlated electrons on a dissipative lattice evolve from equilibrium when driven by a constant electric field, focusing on the extent of the linear regime and hysteretic non-linear effects at higher fields. We access the non-equilibrium steady states, non-perturbatively in both the field and the electronic interactions, by means of a non-equilibrium dynamical mean-field theory in the Coulomb gauge. The linear response regime is limited by Joule heating effects and breaks down at fields orders of magnitude smaller than the quasi-particle energy scale. For large electronic interactions, strong but experimentally accessible electric fields can induce a resistive switching by driving the strongly correlated metal into a Mott insulator. Hysteretic I- V curves suggest that the non-equilibrium current is carried through a spatially inhomogeneous metal-insulator mixed state. Supported by NSF DMR-0907150, NSF DMR-1308141.

  9. Electric-field-driven polymer entry into asymmetric nanoscale channels.

    PubMed

    Nikoofard, Narges; Fazli, Hossein

    2012-02-01

    The electric-field-driven entry process of flexible charged polymers such as single-stranded DNA (ssDNA) into asymmetric nanoscale channels such as the α-hemolysin protein channel is studied theoretically and using molecular dynamics simulations. Dependence of the height of the free-energy barrier on the polymer length, the strength of the applied electric field, and the channel entrance geometry is investigated. It is shown that the squeezing effect of the driving field on the polymer and the lateral confinement of the polymer before its entry to the channel crucially affect the barrier height and its dependence on the system parameters. The attempt frequency of the polymer for passing the channel is also discussed. Our theoretical and simulation results support each other and describe related data sets of polymer translocation experiments through the α-hemolysin protein channel reasonably well.

  10. Electric field-driven water dipoles: nanoscale architecture of electroporation.

    PubMed

    Tokman, Mayya; Lee, Jane HyoJin; Levine, Zachary A; Ho, Ming-Chak; Colvin, Michael E; Vernier, P Thomas

    2013-01-01

    Electroporation is the formation of permeabilizing structures in the cell membrane under the influence of an externally imposed electric field. The resulting increased permeability of the membrane enables a wide range of biological applications, including the delivery of normally excluded substances into cells. While electroporation is used extensively in biology, biotechnology, and medicine, its molecular mechanism is not well understood. This lack of knowledge limits the ability to control and fine-tune the process. In this article we propose a novel molecular mechanism for the electroporation of a lipid bilayer based on energetics analysis. Using molecular dynamics simulations we demonstrate that pore formation is driven by the reorganization of the interfacial water molecules. Our energetics analysis and comparisons of simulations with and without the lipid bilayer show that the process of poration is driven by field-induced reorganization of water dipoles at the water-lipid or water-vacuum interfaces into more energetically favorable configurations, with their molecular dipoles oriented in the external field. Although the contributing role of water in electroporation has been noted previously, here we propose that interfacial water molecules are the main players in the process, its initiators and drivers. The role of the lipid layer, to a first-order approximation, is then reduced to a relatively passive barrier. This new view of electroporation simplifies the study of the problem, and opens up new opportunities in both theoretical modeling of the process and experimental research to better control or to use it in new, innovative ways.

  11. Flow-driven cell migration under external electric fields

    PubMed Central

    Li, Yizeng; Mori, Yoichiro; Sun, Sean X.

    2016-01-01

    Electric fields influence many aspects of cell physiology, including various forms of cell migration. Many cells are sensitive to electric fields, and can migrate toward a cathode or an anode, depending on the cell type. In this paper, we examine an actomyosin-independent mode of cell migration under electrical fields. Our theory considers a one-dimensional cell with water and ionic fluxes at the cell boundary. Water fluxes through the membrane are governed by the osmotic pressure difference across the cell membrane. Fluxes of cations and anions across the cell membrane are determined by the properties of the ion channels as well as the external electric field. Results show that without actin polymerization and myosin contraction, electric fields can also drive cell migration, even when the cell is not polarized. The direction of migration with respect to the electric field direction is influenced by the properties of ion channels, and are cell-type dependent. PMID:26765031

  12. Flow-Driven Cell Migration under External Electric Fields

    NASA Astrophysics Data System (ADS)

    Li, Yizeng; Mori, Yoichiro; Sun, Sean X.

    2015-12-01

    Electric fields influence many aspects of cell physiology, including various forms of cell migration. Many cells are sensitive to electric fields, and they can migrate toward a cathode or an anode, depending on the cell type. In this Letter, we examine an actomyosin-independent mode of cell migration under electrical fields. Our theory considers a one-dimensional cell with water and ionic fluxes at the cell boundary. Water fluxes through the membrane are governed by the osmotic pressure difference across the cell membrane. Fluxes of cations and anions across the cell membrane are determined by the properties of the ion channels as well as the external electric field. Results show that without actin polymerization and myosin contraction, electric fields can also drive cell migration, even when the cell is not polarized. The direction of migration with respect to the electric field direction is influenced by the properties of ion channels, and are cell-type dependent.

  13. Electric-field-driven switching of individual magnetic skyrmions

    NASA Astrophysics Data System (ADS)

    Hsu, Pin-Jui; Kubetzka, André; Finco, Aurore; Romming, Niklas; von Bergmann, Kirsten; Wiesendanger, Roland

    2017-02-01

    Controlling magnetism with electric fields is a key challenge to develop future energy-efficient devices. The present magnetic information technology is mainly based on writing processes requiring either local magnetic fields or spin torques, but it has also been demonstrated that magnetic properties can be altered on the application of electric fields. This has been ascribed to changes in magnetocrystalline anisotropy caused by spin-dependent screening and modifications of the band structure, changes in atom positions or differences in hybridization with an adjacent oxide layer. However, the switching between states related by time reversal, for example magnetization up and down as used in the present technology, is not straightforward because the electric field does not break time-reversal symmetry. Several workarounds have been applied to toggle between bistable magnetic states with electric fields, including changes of material composition as a result of electric fields. Here we demonstrate that local electric fields can be used to switch reversibly between a magnetic skyrmion and the ferromagnetic state. These two states are topologically inequivalent, and we find that the direction of the electric field directly determines the final state. This observation establishes the possibility to combine electric-field writing with the recently envisaged skyrmion racetrack-type memories.

  14. Electric field driven switching of individual magnetic skyrmions (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Hsu, Pin-Jui

    2016-10-01

    An interesting class of interface-driven non-collinear spin structures, i.e., chiral domain walls, cycloidal spin spirals and Néel-type skyrmions, have been observed in ultrathin transition metal films grown on heavy-element substrates making use of spin-polarized scanning tunneling microscopy (SP-STM) [1]. Due to a lack of structural inversion symmetry at interfaces, they exhibit a unique rotational sense as a consequence of interfacial Dzyaloshinskii-Moriya (DM) interactions. In this talk, I will present our results based on the investigations of such chiral spin textures under the influence of strain relief and the effect of local electric fields. While a nanoskyrmion lattice was revealed for Fe monolayers (ML) grown on Ir(111), a cycloidal spin spiral ground state has been resolved on Fe double-layers (DL) by employing SP-STM with vectorial magnetic field. As a result of a large lattice mismatch between the epitaxially grown Fe-DL film and the underlying Ir(111) substrate, local uniaxial strain relief occurs, leading to dislocation line patterns. Interestingly, the wavevector of spin spirals is strictly guided along the dislocation lines, while the spin spiral's wavefront exhibits a zigzag deformation [2]. By further increasing the Fe coverage to triple-layers (TL), the zigzag spin spiral remains the magnetic ground state, but with an enhanced periodicity as compared to that of Fe-DL. A magnetic phase transition from the spin spiral to a skyrmionic state, and finally to a saturated ferromagnetic state occurs for Fe-TL by applying an external magnetic field. STM-induced writing and deleting of individual skyrmions is demonstrated with a pronounced bias-polarity dependence, suggesting the decisive role of the local electric field between STM tip and Fe film for the switching mechanism [3]. [1] K. von Bergmann, A. Kubetzka, O. Pietzsch, and R. Wiesendanger, J. Phys.: Condens. Matter 26, 394002 (2014) [2] P.-J. Hsu, A. Finco, L. Schmidt, A. Kubetzka, K. von

  15. Current oscillation and chaotic dynamics in superlattices driven by crossed electric and magnetic fields.

    PubMed

    Wang, C; Cao, J C

    2005-03-01

    We have theoretically studied current oscillation and chaotic dynamics in doped GaAsAlAs superlattices driven by crossed electric and magnetic fields. When the superlattice system is driven by a dc voltage, a stationary or dynamic electric-field domain can be obtained. We carefully studied the electric-field-domain dynamics and current self-oscillation which both display different modes with the change of magnetic field. When an ac electric field is also applied to the superlattice, a typical nonlinear dynamic system is constructed with the ac amplitude, ac frequency, and magnetic field as the control parameters. Different nonlinear behaviors show up when we tune the control parameters.

  16. Electric Field Driven Self-Assembly of Colloidal Rods

    NASA Astrophysics Data System (ADS)

    Juarez, Jaime; Chaudhary, Kundan; Chen, Qian; Granick, Steve; Lewis, Jennifer

    2012-02-01

    The ability to assemble anisotropic colloidal building blocks into ordered configurations is of both scientific and technological importance. We are studying how electric field-induced interactions guide the self-assembly of these blocks into well aligned microstructures. Specifically, we present observations of the assembly of colloidal silica rods (L/D ˜ 4) within planar electrode cells as a function of different electric field parameters. Results from video microscopy and image analysis demonstrate that aligned microstructures form due to the competition between equilibrium interactions of induced dipoles and non-equilibrium processes (i.e., electro-osmosis). Under the appropriate electric field conditions (˜ kHZ AC fields), aligned colloidal rod fluids form over large areas on the electrode surface. The superposition of a DC electric field to this aligned colloidal rod fluid initiates their condensation into a vertically oriented crystalline phase. Ongoing work is now focused on exploring how temporal changes to electric fields influence colloidal rod dynamics and, hence, the assembly kinetics of aligned colloidal monolayers.

  17. Relationship between sprite streamer behavior and lightning-driven electric fields

    NASA Astrophysics Data System (ADS)

    Li, Jingbo; Cummer, Steven

    2012-01-01

    The lightning-driven electric fields not only initiate sprite streamers at high altitudes but also control their propagation to lower altitudes until termination. Thus, the relationship between sprite streamer behavior and their causative lightning-driven ambient electric field can reveal the internal microphysics during sprite development. In this work, we combined the measurements of broadband electromagnetic radiation from sprite-producing lightning, high-speed video of sprite optical emissions acquired at 5,000-10,000 frames per second, and numerical simulations to infer the background lightning-driven electric fields during the full extent of downward streamer propagation. For four sprites analyzed, all with positive polarity downward streamers, the observed streamers all terminate at locations where the ambient electric field is approximately 0.05 Ek, independent of the altitude where this field is reached. For two sprites with significant horizontal extent, the points of streamer termination closely follow the spatial contour of the E = 0.05 Ek surface, further confirming the consistency of this termination background field for positive sprite streamers. The positive streamers also begin their significant deceleration where the background field drops below 0.12-0.24 Ek. These measured termination field (Eter) and deceleration field (Edec) are consistent with previous laboratory experiments of positive streamer stopping field and critical field to sustain stable propagation. These results connect sprite streamer behavior with the lightning-driven background electric fields and can be a step to further constrain the existing model of streamer propagation in the mesosphere.

  18. Electric field driven mesoscale phase transition in polarized colloids

    NASA Astrophysics Data System (ADS)

    Khusid, Boris; Elele, Ezinwa; Lei, Qian

    2016-11-01

    A mesoscale phase transition in a polarized suspension was reported by Kumar, Khusid, Acrivos, PRL95, 2005 and Agarwal, Yethiraj, PRL102, 2009. Following the application of a strong AC field, particles aggregated head-to-tail into chains that bridged the interelectrode gap and then formed a cellular pattern, in which large particle-free domains were enclosed by particle-rich thin walls. Cellular structures were not observed in numerous simulations of field induced phase transitions in a polarized suspension. A requirement for matching the particle and fluid densities to avoid particle settling limits terrestrial experiments to negatively polarized particles. We present data on the phase diagram and kinetics of the phase transition in a neutrally buoyant, negatively polarized suspension subjected to a combination of AC and DC. Surprisingly, a weak DC component drastically speeds up the formation of a cellular pattern but does not affect its key characteristic. However, the application of a strong DC field destroys the cellular pattern, but it restores as the DC field strength is reduced. We also discuss the design of experiments to study phase transitions in a suspension of positively polarized, non-buoyancy-matched particles in the International Space Station. Supported by NASA's Physical Science Research Program, NNX13AQ53G.

  19. Electric-field-driven electron-transfer in mixed-valence molecules

    NASA Astrophysics Data System (ADS)

    Blair, Enrique P.; Corcelli, Steven A.; Lent, Craig S.

    2016-07-01

    Molecular quantum-dot cellular automata is a computing paradigm in which digital information is encoded by the charge configuration of a mixed-valence molecule. General-purpose computing can be achieved by arranging these compounds on a substrate and exploiting intermolecular Coulombic coupling. The operation of such a device relies on nonequilibrium electron transfer (ET), whereby the time-varying electric field of one molecule induces an ET event in a neighboring molecule. The magnitude of the electric fields can be quite large because of close spatial proximity, and the induced ET rate is a measure of the nonequilibrium response of the molecule. We calculate the electric-field-driven ET rate for a model mixed-valence compound. The mixed-valence molecule is regarded as a two-state electronic system coupled to a molecular vibrational mode, which is, in turn, coupled to a thermal environment. Both the electronic and vibrational degrees-of-freedom are treated quantum mechanically, and the dissipative vibrational-bath interaction is modeled with the Lindblad equation. This approach captures both tunneling and nonadiabatic dynamics. Relationships between microscopic molecular properties and the driven ET rate are explored for two time-dependent applied fields: an abruptly switched field and a linearly ramped field. In both cases, the driven ET rate is only weakly temperature dependent. When the model is applied using parameters appropriate to a specific mixed-valence molecule, diferrocenylacetylene, terahertz-range ET transfer rates are predicted.

  20. Electric-field-driven electron-transfer in mixed-valence molecules.

    PubMed

    Blair, Enrique P; Corcelli, Steven A; Lent, Craig S

    2016-07-07

    Molecular quantum-dot cellular automata is a computing paradigm in which digital information is encoded by the charge configuration of a mixed-valence molecule. General-purpose computing can be achieved by arranging these compounds on a substrate and exploiting intermolecular Coulombic coupling. The operation of such a device relies on nonequilibrium electron transfer (ET), whereby the time-varying electric field of one molecule induces an ET event in a neighboring molecule. The magnitude of the electric fields can be quite large because of close spatial proximity, and the induced ET rate is a measure of the nonequilibrium response of the molecule. We calculate the electric-field-driven ET rate for a model mixed-valence compound. The mixed-valence molecule is regarded as a two-state electronic system coupled to a molecular vibrational mode, which is, in turn, coupled to a thermal environment. Both the electronic and vibrational degrees-of-freedom are treated quantum mechanically, and the dissipative vibrational-bath interaction is modeled with the Lindblad equation. This approach captures both tunneling and nonadiabatic dynamics. Relationships between microscopic molecular properties and the driven ET rate are explored for two time-dependent applied fields: an abruptly switched field and a linearly ramped field. In both cases, the driven ET rate is only weakly temperature dependent. When the model is applied using parameters appropriate to a specific mixed-valence molecule, diferrocenylacetylene, terahertz-range ET transfer rates are predicted.

  1. En route to surface-bound electric field-driven molecular motors.

    PubMed

    Jian, Huahua; Tour, James M

    2003-06-27

    Four caltrop-shaped molecules that might be useful as surface-bound electric field-driven molecular motors have been synthesized. The caltrops are comprised of a pair of electron donor-acceptor arms and a tripod base. The molecular arms are based on a carbazole or oligo(phenylene ethynylene) core with a strong net dipole. The tripod base uses a silicon atom as its core. The legs of the tripod bear sulfur-tipped bonding units, as acetyl-protected benzylic thiols, for bonding to a gold surface. The geometry of the tripod base allows the caltrop to project upward from a metallic surface after self-assembly. Ellipsometric studies show that self-assembled monolayers of the caltrops are formed on Au surfaces with molecular thicknesses consistent with the desired upright-shaft arrangement. As a result, the zwitterionic molecular arms might be controllable when electric fields are applied around the caltrops, thereby constituting field-driven motors.

  2. Lightning-driven electric fields measured in the lower ionosphere: Implications for transient luminous events

    NASA Astrophysics Data System (ADS)

    Thomas, Jeremy N.; Barnum, Benjamin H.; Lay, Erin; Holzworth, Robert H.; Cho, Mengu; Kelley, Michael C.

    2008-12-01

    Transient luminous events above thunderstorms such as sprites, halos, and elves require large electric fields in the lower ionosphere. Yet very few in situ measurements in this region have been successfully accomplished, since it is typically too low in altitude for rockets and satellites and too high for balloons. In this article, we present some rare examples of lightning-driven electric field changes obtained at 75-130 km altitude during a sounding rocket flight from Wallops Island, Virginia, in 1995. We summarize these electric field changes and present a few detailed case studies. Our measurements are compared directly to a 2D numerical model of lightning-driven electromagnetic fields in the middle and upper atmosphere. We find that the in situ electric field changes are smaller than predicted by the model, and the amplitudes of these fields are insufficient for elve production when extrapolated to a 100 kA peak current stroke. This disagreement could be due to lightning-induced ionospheric conductivity enhancement, or it might be evidence of flaws in the electromagnetic pulse mechanism for elves.

  3. Propelling and spinning of microsheets in nematic liquid crystals driven by ac electric field

    NASA Astrophysics Data System (ADS)

    Rasna, M. V.; Ramudu, U. V.; Chandrasekar, R.; Dhara, Surajit

    2017-01-01

    Dynamics of microparticles in isotropic liquids by transducing the energy of an applied electric field have been studied for decades. Recently, such studies in anisotropic media like liquid crystals have opened up new perspectives in colloid science. Here, we report studies on ac-electric-field-driven dynamics of microsheets in nematic liquid crystals. In planar aligned liquid crystals, with negative dielectric anisotropy, the microsheets are propelled parallel to the director. A steady spinning of the microsheets is observed in homeotropic cells with positive dielectric anisotropy liquid crystals. The velocity of propelling and the angular frequency of spinning depends on the amplitude and the frequency of the applied electric field. The electrokinetic studies of anisotropic microparticles are important as they are potential for applications in microfluidics and in areas where the controlled transport or rotation is required.

  4. Electric-field-driven Phenomena for Manipulating Particles in Micro-Devices

    NASA Technical Reports Server (NTRS)

    Khusid, Boris; Acrivos, Andreas

    2004-01-01

    Compared to other available methods, ac dielectrophoresis is particularly well-suited for the manipulation of minute particles in micro- and nano-fluidics. The essential advantage of this technique is that an ac field at a sufficiently high frequency suppresses unwanted electric effects in a liquid. To date very little has been achieved towards understanding the micro-scale field-and shear driven behavior of a suspension in that, the concepts currently favored for the design and operation of dielectrophoretic micro-devices adopt the approach used for macro-scale electric filters. This strategy considers the trend of the field-induced particle motions by computing the spatial distribution of the field strength over a channel as if it were filled only with a liquid and then evaluating the direction of the dielectrophoretic force, exerted on a single particle placed in the liquid. However, the exposure of suspended particles to a field generates not only the dielectrophoretic force acting on each of these particles, but also the dipolar interactions of the particles due to their polarization. Furthermore, the field-driven motion of the particles is accompanied by their hydrodynamic interactions. We present the results of our experimental and theoretical studies which indicate that, under certain conditions, these long-range electrical and hydrodynamic interparticle interactions drastically affect the suspension behavior in a micro-channel due to its small dimensions.

  5. Molecular dynamics study of nanoconfined water flow driven by rotating electric fields under realistic experimental conditions.

    PubMed

    De Luca, Sergio; Todd, B D; Hansen, J S; Daivis, Peter J

    2014-03-25

    In our recent work, J. Chem. Phys. 2013, 138, 154712, we demonstrated the feasibility of unidirectional pumping of water, exploiting translational-rotational momentum coupling using nonequilibrium molecular dynamics simulations. Flow can be sustained when the fluid is driven out of equilibrium by an external spatially uniform rotating electric field and confined between two planar surfaces exposing different degrees of hydrophobicity. The permanent dipole moment of water follows the rotating field, thus inducing the molecules to spin, and the torque exerted by the field is continuously injected into the fluid, enabling a steady conversion of spin angular momentum into linear momentum. The translational-rotational coupling is a sensitive function of the rotating electric field parameters. In this work, we have found that there exists a small energy dissipation region attainable when the frequency of the rotating electric field matches the inverse of the dielectric relaxation time of water and when its amplitude lies in a range just before dielectric saturation effects take place. In this region, that is, when the frequency lies in a small window of the microwave region around ∼20 GHz and amplitude ∼0.03 V Å(-1), the translational-rotational coupling is most effective, yielding fluid velocities of magnitudes of ∼2 ms(-1) with only moderate fluid heating. In this work, we also confine water to a realistic nanochannel made of graphene giving a hydrophobic surface on one side and β-cristobalite giving a hydrophilic surface on the other, reproducing slip-and-stick velocity boundary conditions, respectively. This enables us to demonstrate that in a realistic environment, the coupling can be effectively exploited to achieve noncontact pumping of water at the nanoscale. A quantitative comparison between nonequilibrium molecular dynamics and analytical solutions of the extended Navier-Stokes equations, including an external rotating electric field has been performed

  6. Electric-field-driven domain wall dynamics in perpendicularly magnetized multilayers

    NASA Astrophysics Data System (ADS)

    López González, Diego; Shirahata, Yasuhiro; Van de Wiele, Ben; Franke, Kévin J. A.; Casiraghi, Arianna; Taniyama, Tomoyasu; van Dijken, Sebastiaan

    2017-03-01

    We report on reversible electric-field-driven magnetic domain wall motion in a Cu/Ni multilayer on a ferroelectric BaTiO3 substrate. In our heterostructure, strain-coupling to ferroelastic domains with in-plane and perpendicular polarization in the BaTiO3 substrate causes the formation of domains with perpendicular and in-plane magnetic anisotropy, respectively, in the Cu/Ni multilayer. Walls that separate magnetic domains are elastically pinned onto ferroelectric domain walls. Using magneto-optical Kerr effect microscopy, we demonstrate that out-of-plane electric field pulses across the BaTiO3 substrate move the magnetic and ferroelectric domain walls in unison. Our experiments indicate an exponential increase of domain wall velocity with electric field strength and opposite domain wall motion for positive and negative field pulses. The application of a magnetic field does not affect the velocity of magnetic domain walls, but independently tailors their internal spin structure, causing a change in domain wall dynamics at high velocities.

  7. Optical properties of a quantum well driven by a THz electric field

    NASA Astrophysics Data System (ADS)

    Maslov, Alexey V.

    2001-07-01

    A systematic study of linear optical properties of a quantum well driven by a periodic electric field with period in the THz frequency range is performed. The THz field is oriented in the growth direction of the quantum well. We present a general approach to characterize the optical properties of a modulated medium and discuss the use of short optical pulses (shorter than the modulation period) to obtain the optical properties in the frequency domain. Mixing of the quantum well subbands (both in the conduction and valence band) for strong THz fields is treated in terms of the states dressed by the THz field. Relations between the dressed states and the optical properties of the quantum well are given. In particular, our approach allowed us to find simple relations for the efficiency of the energy conversion of the incident light into the sidebands and generalize the rate of the exciton radiative decay for the case of THz-dressed exciton. We also predict the effect of mutual transparency of several coherent laser beams which are resonant with different Fourier components of the dressed exciton state. Finally, results of realistic calculations of the absorption spectra of THz-field driven quantum wells using multisubband semiconductor Bloch equations in the linear regime are presented.

  8. Electric-field-driven magnetization reversal in square-shaped nanomagnet-based multiferroic heterostructure

    SciTech Connect

    Peng, Ren-Ci; Nan, Ce-Wen E-mail: cwnan@tsinghua.edu.cn; Wang, J. J. E-mail: cwnan@tsinghua.edu.cn; Chen, Long-Qing; Hu, Jia-Mian

    2015-04-06

    Based on phase field modeling and thermodynamic analysis, purely electric-field-driven magnetization reversal was shown to be possible in a multiferroic heterostructure of a square-shaped amorphous Co{sub 40}Fe{sub 40}B{sub 20} nanomagnet on top of a ferroelectric layer through electrostrain. The reversal is made possible by engineering the mutual interactions among the built-in uniaxial magnetic anisotropy, the geometry-dependent magnetic configuration anisotropy, and the magnetoelastic anisotropy. Particularly, the incorporation of the built-in uniaxial anisotropy made it possible to reverse magnetization with one single unipolar electrostrain pulse, which is simpler than previous designs involving the use of bipolar electrostrains and may alleviate ferroelectric fatigue. Critical conditions for triggering the magnetization reversal are identified.

  9. Laser-driven electron acceleration in a plasma channel with an additional electric field

    SciTech Connect

    Cheng, Li-Hong; Xue, Ju-Kui; Liu, Jie

    2016-05-15

    We examine the electron acceleration in a two-dimensional plasma channel under the action of a laser field and an additional static electric field. We propose to design an appropriate additional electric field (its direction and location), in order to launch the electron onto an energetic trajectory. We find that the electron acceleration strongly depends on the coupled effects of the laser polarization, the direction, and location of the additional electric field. The additional electric field affects the electron dynamics by changing the dephasing rate. Particularly, a suitably designed additional electric field leads to a considerable energy gain from the laser pulse after the interaction with the additional electric field. The electron energy gain from the laser with the additional electric field can be much higher than that without the additional electric field. This engineering provides a possible means for producing high energetic electrons.

  10. Maximal Rabi frequency of an electrically driven spin in a disordered magnetic field

    NASA Astrophysics Data System (ADS)

    Palyi, Andras; Szechenyi, Gabor

    2014-03-01

    We present a theoretical study of the spin dynamics of a single electron confined in a quantum dot. Spin dynamics is induced by the interplay of electrical driving and the presence of a spatially disordered magnetic field, the latter being transverse to a homogeneous magnetic field. We focus on the case of strong driving, i.e., when the oscillation amplitude A of the electron's wave packet is comparable to the quantum dot length L. We show that electrically driven spin resonance can be induced in this system by subharmonic driving, i.e., if the excitation frequency is an integer fraction (1/2, 1/3, etc) of the Larmor frequency. At strong driving we find that (i) the Rabi frequencies at the subharmonic resonances are comparable to that at the fundamental resonance, and (ii) at each subharmonic resonance, the Rabi frequency can be maximized by setting the drive strength to an optimal, finite value. Our simple model is applied to describe electrical control of a spin-valley qubit in a weakly disordered carbon nanotube. Reference: http://arxiv.org/abs/1310.7350 Support from the Marie Curie CIG-293834, OTKA grant PD-100373 and the Janos Bolyai Scholarship of the Hungarian Academy of Sciences is acknowledged.

  11. Dynamics of Chemi-Ion Driven Flows in an Applied Electric Field

    NASA Astrophysics Data System (ADS)

    Tinajero, Jesse A.

    Chemi-ions are produced during combustion of a hydrocarbon fuel. If an external electric field is present, a charge separation occurs due to the electrical force acting on the positively and negatively charged species. These ions traverse in the direction of the electrode of opposite potential. Along their path, they continuously collide with neutral molecules within the surrounding bulk gas until they are able to recombine and neutralize at the downstream electrode. During each collision, the charged species give up their acquired momentum to the neutral molecules. Macroscopically, this transfer of momentum has been best described mathematically as a body force acting on the bulk gas. The effect is commonly referred to as an ion wind effect. Gravity effects make the electric field effects on combustion difficult to study with earth- based experiments. This is because the gravity-driven buoyancy effects behave as a body force also acting on the bulk gas. Buoyancy and electrical body forces act on the same order of magnitude. The two forces are coupled through temperature since the production of ions is temperature dependent. Between the two, the contribution to the net momentum of the gas is then difficult to distinguish. On the other hand, micro-gravity experiments allow for the direct study of electric field effects in the absence of gravity. Micro-gravity experiments on-board the International Space Station through NASA's Advanced Combustion via Micro- gravity Experiments program, or ACME, are planned for 2016--17. Nevertheless, preliminary studies are needed in preparation for the ISS experiments. These studies are described in this thesis. A replica of the ISS experiment for the electric field effects on laminar diffusion flames (EFIELD Flames) that is part of ACME was recreated in a ground based laboratory. A schlieren system was built to visualize the effect an applied electric field has on the flame's buoyant thermal plume when the electric field is given a

  12. Driven chemical kinetics: Optimalization of catalytic action of membrane proteins by rectangular alternating electric field

    NASA Astrophysics Data System (ADS)

    Fuliński, Andrzej

    1992-03-01

    The chemical kinetics driven by external force in the form of a train of alternating rectangular impulses is discussed. The model of the conformational transition of a membrane protein exposed to an ac electric field, proposed by R. D. Astumian and B. Robertson [J. Chem. Phys. 91, 4891 (1989)], is reconsidered. On the example of this model we show that the use of the driving field in the form of rectangular impulses has two distinct advantages over the usual sinusoidal driving. The first one is that the use of a rectangular driving field makes it possible to obtain the exact solution of the basic kinetic equation of the system. This in turn enables one to write down the simple and very good approximate solution for any form of the driving field, better than the harmonic expansion used by Astumian and Robertson. A more important advantage is the greater flexibility of the rectangular driving, which makes possible the better optimalization of the process of interest. Astumian and Robertson demonstrated that the movement of charge within the catalytic cycle provides a mechanism for the enzyme to absorb energy from an ac electric field and to use that energy to enhance the catalyzed process. In this paper we show that the use of the driving ac field in the form of alternating rectangular impulses of variable duration and amplitude (instead of the usual sinusoidal modulation) leads to further optimalization of the process. The efficiency of the energy transduction, for example, can be increased from about 25% for sinusoidal driving to about 37% for suitably chosen alternating rectangular pulses.

  13. Dynamical features and electric field strengths of double layers driven by currents. [in auroras

    NASA Technical Reports Server (NTRS)

    Singh, N.; Thiemann, H.; Schunk, R. W.

    1985-01-01

    In recent years, a number of papers have been concerned with 'ion-acoustic' double layers. In the present investigation, results from numerical simulations are presented to show that the shapes and forms of current-driven double layers evolve dynamically with the fluctuations in the current through the plasma. It is shown that double layers with a potential dip can form even without the excitation of ion-acoustic modes. Double layers in two-and one-half-dimensional simulations are discussed, taking into account the simulation technique, the spatial and temporal features of plasma, and the dynamical behavior of the parallel potential distribution. Attention is also given to double layers in one-dimensional simulations, and electrical field strengths predicted by two-and one-half-dimensional simulations.

  14. Nanoscale, electric field-driven water bridges in vacuum gaps and lipid bilayers.

    PubMed

    Ho, Ming-Chak; Levine, Zachary A; Vernier, P Thomas

    2013-11-01

    Formation of a water bridge across the lipid bilayer is the first stage of pore formation in molecular dynamic (MD) simulations of electroporation, suggesting that the intrusion of individual water molecules into the membrane interior is the initiation event in a sequence that leads to the formation of a conductive membrane pore. To delineate more clearly the role of water in membrane permeabilization, we conducted extensive MD simulations of water bridge formation, stabilization, and collapse in palmitoyloleoylphosphatidylcholine bilayers and in water-vacuum-water systems, in which two groups of water molecules are separated by a 2.8 nm vacuum gap, a simple analog of a phospholipid bilayer. Certain features, such as the exponential decrease in water bridge initiation time with increased external electric field, are similar in both systems. Other features, such as the relationship between water bridge lifetime and the diameter of the water bridge, are quite different between the two systems. Data such as these contribute to a better and more quantitative understanding of the relative roles of water and lipid in membrane electropore creation and annihilation, facilitating a mechanism-driven development of electroporation protocols. These methods can be extended to more complex, heterogeneous systems that include membrane proteins and intracellular and extracellular membrane attachments, leading to more accurate models of living cells in electric fields.

  15. Velocity field control of a class of electrically-driven manipulators

    NASA Astrophysics Data System (ADS)

    Moreno-Valenzuela, Javier; Campa, Ricardo; Santibáñez, Víctor

    2014-03-01

    This article addresses the control of robotic manipulators under the assumption that the desired motion in the operational space is encoded through a velocity field. In other words, a vectorial function assigns a velocity vector to each point in the robot workspace. Thus, the control objective is to design a control input such that the actual operational space velocity of the robot end-effector asymptotically tracks the desired velocity from the velocity field. This control formulation is known in the literature as velocity field control. A new velocity field controller together with a rigorous stability analysis is introduced in this article. The controller is developed for a class of electrically-driven manipulators. In this class of manipulators, the passivity property from the servo-amplifier voltage input to the joint velocity is not satisfied. However, global exponential stability of the state space origin of the closed-loop system is proven. Furthermore, the closed-loop system is proven to be and output strictly passive map from an auxiliary input to a filtered error signal. To confirm the theoretical conclusions, a detailed experimental study in a two degrees-of-freedom direct-drive manipulator is provided. Particularly, experiments consist of comparing the performance of a simple PI controller and a high-gain PI controller with respect to the new control scheme.

  16. Role of hydrodynamic interactions in the migration of polyelectrolytes driven by a pressure gradient and an electric field.

    PubMed

    Kekre, Rahul; Butler, Jason E; Ladd, Anthony J C

    2010-11-01

    Experiments have shown that DNA molecules in capillary electrophoresis migrate across field lines if a pressure gradient is applied simultaneously. We suggest that this migration results from an electrically driven flow field around the polyelectrolyte, which generates additional contributions to the center-of-mass velocity if the overall polymer conformation is asymmetric. This hypothesis leads to a coarse-grained polymer model, without explicit charges, that quantitatively explains the experimentally observed migration. The simulations contradict the widely held notion that charge neutrality eliminates the effects of hydrodynamic interactions in electrically driven flows of polyelectrolytes. We predict a measurable increase in the electrophoretic velocity of a sheared polyelectrolyte that depends on chain length.

  17. Global Evolving Models of Photospheric Flux as Driven by Electric Fields

    NASA Astrophysics Data System (ADS)

    DeRosa, Marc L.; Cheung, Mark; Kazachenko, Maria D.; Fisher, George H.

    2017-08-01

    We present a novel method for modeling the global radial magnetic field that is based on the incorporation of time series of photospheric electric fields. The determination of the electric fields is the result of a recently developed method that uses as input various data products from SDO/HMI, namely vector magnetic fields and line-of-sight Doppler images. For locations on the sphere where electric field data are unavailable, we instead use electric fields that are consistent with measurements of the mean differential rotation, meridional flow, and flux dispersal profiles. By combining these electric fields, a full-Sun model of the photospheric radial magnetic field can be advanced forward in time via Faraday's Law.

  18. Phase transition of nanotube-confined water driven by electric field.

    PubMed

    Fu, Zhaoming; Luo, Yin; Ma, Jianpeng; Wei, Guanghong

    2011-04-21

    The effects of electric field on the phase behaviors of water encapsulated in a thick single-walled carbon nanotube (SWCNT) (diameter = 1.2 nm) have been studied by performing extensive molecular dynamics simulations at atmospheric pressure. We found that liquid water can freeze continuously into either pentagonal or helical solidlike ice nanotube in SWCNT, depending on the strengths of the external electric field applied along the tube axis. Remarkably, the helical one is new ice phase which was not observed previously in the same size of SWCNT in the absence of electric field. Furthermore, a discontinuous solid-solid phase transition is observed between pentagonal and helical ice nanotubes as the strengths of the external electric field changes. The mechanism of electric-field-induced phase transition is discussed. The dependence of ice structures on the chiralities of SWCNTs is also investigated. Finally, we present a phase diagram of confined water in the electric field-temperature plane.

  19. Electrically driven optical antennas

    NASA Astrophysics Data System (ADS)

    Kern, Johannes; Kullock, René; Prangsma, Jord; Emmerling, Monika; Kamp, Martin; Hecht, Bert

    2015-09-01

    Unlike radiowave antennas, so far optical nanoantennas cannot be fed by electrical generators. Instead, they are driven by light or indirectly via excited discrete states in active materials in their vicinity. Here we demonstrate the direct electrical driving of an in-plane optical antenna by the broadband quantum-shot noise of electrons tunnelling across its feed gap. The spectrum of the emitted photons is determined by the antenna geometry and can be tuned via the applied voltage. Moreover, the direction and polarization of the light emission are controlled by the antenna resonance, which also improves the external quantum efficiency by up to two orders of magnitude. The one-material planar design offers facile integration of electrical and optical circuits and thus represents a new paradigm for interfacing electrons and photons at the nanometre scale, for example for on-chip wireless communication and highly configurable electrically driven subwavelength photon sources.

  20. Rigorous analysis of an electric-field-driven liquid crystal lens for 3D displays

    NASA Astrophysics Data System (ADS)

    Kim, Bong-Sik; Lee, Seung-Chul; Park, Woo-Sang

    2014-08-01

    We numerically analyzed the optical performance of an electric field driven liquid crystal (ELC) lens adopted for 3-dimensional liquid crystal displays (3D-LCDs) through rigorous ray tracing. For the calculation, we first obtain the director distribution profile of the liquid crystals by using the Erickson-Leslie motional equation; then, we calculate the transmission of light through the ELC lens by using the extended Jones matrix method. The simulation was carried out for a 9view 3D-LCD with a diagonal of 17.1 inches, where the ELC lens was slanted to achieve natural stereoscopic images. The results show that each view exists separately according to the viewing position at an optimum viewing distance of 80 cm. In addition, our simulation results provide a quantitative explanation for the ghost or blurred images between views observed from a 3D-LCD with an ELC lens. The numerical simulations are also shown to be in good agreement with the experimental results. The present simulation method is expected to provide optimum design conditions for obtaining natural 3D images by rigorously analyzing the optical functionalities of an ELC lens.

  1. Electric field-driven extraction of lipophilic anions across a carrier-mediated polymer inclusion membrane.

    PubMed

    See, Hong Heng; Hauser, Peter C

    2011-10-01

    The use of a cationic carrier-mediated polymer inclusion membrane (PIM) for extraction and preconcentration of anionic model analytes driven by an electric field directly into an aqueous acceptor solution is demonstrated. The optimized membrane was 20 μm thick and consisted of 60% cellulose triacetate as base polymer, 20% o-nitrophenyl octyl ether as plasticizer, and 20% Aliquat 336 as cationic carrier in the perchlorate form. By applying voltages of up to 700 V across the membrane, the lipophilic model analytes propanesulfonate, octanesulfonate, and decanesulfonate could be transported from the aqueous donor solution to the aqueous acceptor solution with efficiences >90% within 5 to 20 min. A preconcentration factor of 26, defined by the volume ratio between donor and acceptor compartments of the current cell design, could be achieved. The utility of the method for analytical applications is demonstrated by extraction of the herbicide glyphosate and its breakdown product aminomethylphosphonic acid from spiked river water, followed by quantification with capillary electrophoresis using contactless conductivity detection. Limits of detection of 0.8 and 1.5 ng/mL were obtained for glyphosate and aminomethylphosphonic acid, respectively.

  2. Conjugated ionomers for photovoltaic applications: electric field driven charge separation in organic photovoltaics. Final Technical report

    SciTech Connect

    Lonergan, Mark

    2015-05-29

    Final technical report for Conjugated ionomers for photovoltaic applications, electric field driven charge separation in organic photovoltaics. The central goal of the work we completed was been to understand the photochemical and photovoltaic properties of ionically functionalized conjugated polymers (conjugated ionomers or polyelectrolytes) and energy conversion systems based on them. We primarily studied two classes of conjugated polymer interfaces that we developed based either upon undoped conjugated polymers with an asymmetry in ionic composition (the ionic junction) or doped conjugated polymers with an asymmetry in doping type (the p-n junction). The materials used for these studies have primarily been the polyacetylene ionomers. We completed a detailed study of p-n junctions with systematically varying dopant density, photochemical creation of doped junctions, and experimental and theoretical work on charge transport and injection in polyacetylene ionomers. We have also completed related work on the use of conjugated ionomers as interlayers that improve the efficiency or organic photovoltaic systems and studied several important aspects of the chemistry of ionically functionalized semiconductors, including mechanisms of so-called "anion-doping", the formation of charge transfer complexes with oxygen, and the synthesis of new polyfluorene polyelectrolytes. We also worked worked with the Haley group at the University of Oregon on new indenofluorene-based organic acceptors.

  3. Electric field driven protonation/deprotonation of self-assembled monolayers of acid-terminated thiols.

    PubMed

    Burgess, Ian; Seivewright, Brian; Lennox, R Bruce

    2006-04-25

    Using electrochemical impedance spectroscopy (EIS), we provide an explanation for the pH dependence of the voltammetric peak height for the electric-field-driven protonation and deprotonation of carboxylic acid-terminated thiol self-assembled monolayers (SAMs). The current flowing through the interface can be divided into a purely capacitive current and a protonation/deprotonation current that is directly related to the rate of change of the SAM's protonation (or deprotonation). We demonstrate that at applied potentials close to those corresponding to half-ionization of the SAM and pHs near the pK(1/2), the equivalent circuit describing the interface consists of a Helmholtz film capacity in parallel with a "protonation/deprotonation" impedance which is further shown to be a series combination of a resistor, Rp, and capacitor Cp. Explicit expressions for Rp and Cp are derived in terms of the rate constants for the forward (protonation) and reverse (deprotonation) reactions. Simulated EIS data demonstrate the agreement between our model of the interface and experimental impedance and voltammetric data.

  4. Electrically Driven Prosthetic Elbow.

    DTIC Science & Technology

    The invention relates to an improved electrically driven prosthetic elbow wherein the elbow is capable of being rigidly locked into place in any...desired position, and upon driving the arm to the fully extended position, the elbow is automatically unlocked.

  5. Electric field measurements in a kHz-driven He jet—the influence of the gas flow speed

    NASA Astrophysics Data System (ADS)

    Sobota, A.; Guaitella, O.; Sretenović, G. B.; Krstić, I. B.; Kovačević, V. V.; Obrusník, A.; Nguyen, Y. N.; Zajíčková, L.; Obradović, B. M.; Kuraica, M. M.

    2016-12-01

    This report focuses on the dependence of electric field strength in the effluent of a vertically downwards-operated plasma jet freely expanding into room air as a function of the gas flow speed. A 30 kHz AC-driven He jet was used in a coaxial geometry, with an amplitude of 2 kV and gas flow between 700 sccm and 2000 SCCM. The electric field was measured by means of Stark polarization spectroscopy of the He line at 492.19 nm. While the minimum and the maximum measured electric fields remained unchanged, the effect of the gas flow speed is to cause stretching of the measured profile in space—the higher the flow, the longer and less steep the electric field profile. The portion of the effluent in which the electric field was measured showed an increase of electric field with increasing distance from the capillary, for which the probable cause is the contraction of the plasma bullet as it travels through space away from the capillary. There are strong indications that the stretching of the electric field profile with increase in the flow speed is caused by differences in gas mixing as a function of the gas flow speed. The simulated gas composition shows that the amount of air entrained into the gas flow behaves in a similar way to the observed behaviour of the electric field. In addition we have shown that the visible length of the plasma plume is associated with a 0.027 molar fraction of air in the He flow in this configuration, while the maximum electric field measured was associated with a 0.014 molar fraction of air at gas flow rates up to 1500 SCCM (4.9 m s-1). At higher flows vortices occur in the effluent of the jet, as seen in Schlieren visualization of the gas flow with and without the discharge.

  6. Lateral electric-field-driven non-volatile four-state memory in multiferroic heterostructures

    NASA Astrophysics Data System (ADS)

    Zhou, Cai; Zhang, Chao; Yao, Jinli; Jiang, Changjun

    2016-09-01

    A non-volatile four-state memory is formed using an in-plane side-polarization configuration in a Co/(011) Pb(Mg1/3Nb2/3)O3-PbTiO3 (Co/PMN-PT) heterostructure. The resistivity vs. electric field behavior shows a change from volatile butterfly to looplike to non-volatile butterfly characteristics when the temperature decreases from 290 K to 83 K under an electric field of 10 kV/cm and then increases back to 290 K; this behavior is attributed to the strain-mediated magnetoelectric effect. In addition, the in-plane resistivity of Co film, which was measured using the four-probe technique, can be controlled both electrically and magnetically. Specifically, a non-volatile resistivity is gained by the application of electric field pulses. Additionally, a four-state memory is obtained by co-mediation of the magnetic field and electric field pulses, compared with the two different states achieved under the application of the electric field only, which indicates that our results are highly important for multi-state memory and spintronic devices applications.

  7. Free-energy barrier for electric-field-driven polymer entry into nanoscale channels.

    PubMed

    Nikoofard, Narges; Fazli, Hossein

    2011-05-01

    Free-energy barrier for entry of a charged polymer into a nanoscale channel by a driving electric field is studied theoretically and using molecular dynamics simulations. Dependence of the barrier height on the polymer length, the driving field strength, and the channel entrance geometry is investigated. Squeezing effect of the electric field on the polymer before its entry to the channel is taken into account. It is shown that lateral confinement of the polymer prior to its entry changes the polymer length dependence of the barrier height noticeably. Our theory and simulation results are in good agreement and reasonably describe related experimental data.

  8. High sensitive space electric field sensing based on micro fiber interferometer with field force driven gold nanofilm.

    PubMed

    Zhu, Tao; Zhou, Liming; Liu, Min; Zhang, Jingdong; Shi, Leilei

    2015-10-28

    The traditional electrical field sensing can be realized by utilizing electro-optic materials or liquid crystals, and has limitations of easy breakdown, free assembly and difficult measurement of low-frequency. Here, we propose a new method to realize safe measurement of spatial dynamic electric field by using a micro fiber interferometer integrated with gold nanofilm. The energy of the electric charge received through antenna forms the intrinsic electric field with two micro electrodes, one of which is the 120 nm gold film vibration beam micromachined by femtosecond lasers and integrated with the micro fiber. The change of the intrinsic electric field force due to the spatial electric field will cause the vibration of the film beam. By demodulating the output signal of the micro fiber interferometer, the electric field can be measured. We demonstrate the detectable frequency ranges from tens of Hz to tens of KHz, and the minimum electric field intensity is ~200 V/m at 1 KHz. Our electric field measurement technology combining optical fiber interference with gold nanostructures shows the advantages of security, high sensitivity, compact size, and multiplexed multi-point and remote detection.

  9. High sensitive space electric field sensing based on micro fiber interferometer with field force driven gold nanofilm

    PubMed Central

    Zhu, Tao; Zhou, Liming; Liu, Min; Zhang, Jingdong; Shi, Leilei

    2015-01-01

    The traditional electrical field sensing can be realized by utilizing electro-optic materials or liquid crystals, and has limitations of easy breakdown, free assembly and difficult measurement of low-frequency. Here, we propose a new method to realize safe measurement of spatial dynamic electric field by using a micro fiber interferometer integrated with gold nanofilm. The energy of the electric charge received through antenna forms the intrinsic electric field with two micro electrodes, one of which is the 120 nm gold film vibration beam micromachined by femtosecond lasers and integrated with the micro fiber. The change of the intrinsic electric field force due to the spatial electric field will cause the vibration of the film beam. By demodulating the output signal of the micro fiber interferometer, the electric field can be measured. We demonstrate the detectable frequency ranges from tens of Hz to tens of KHz, and the minimum electric field intensity is ~200 V/m at 1 KHz. Our electric field measurement technology combining optical fiber interference with gold nanostructures shows the advantages of security, high sensitivity, compact size, and multiplexed multi-point and remote detection. PMID:26507680

  10. High sensitive space electric field sensing based on micro fiber interferometer with field force driven gold nanofilm

    NASA Astrophysics Data System (ADS)

    Zhu, Tao; Zhou, Liming; Liu, Min; Zhang, Jingdong; Shi, Leilei

    2015-10-01

    The traditional electrical field sensing can be realized by utilizing electro-optic materials or liquid crystals, and has limitations of easy breakdown, free assembly and difficult measurement of low-frequency. Here, we propose a new method to realize safe measurement of spatial dynamic electric field by using a micro fiber interferometer integrated with gold nanofilm. The energy of the electric charge received through antenna forms the intrinsic electric field with two micro electrodes, one of which is the 120 nm gold film vibration beam micromachined by femtosecond lasers and integrated with the micro fiber. The change of the intrinsic electric field force due to the spatial electric field will cause the vibration of the film beam. By demodulating the output signal of the micro fiber interferometer, the electric field can be measured. We demonstrate the detectable frequency ranges from tens of Hz to tens of KHz, and the minimum electric field intensity is ~200 V/m at 1 KHz. Our electric field measurement technology combining optical fiber interference with gold nanostructures shows the advantages of security, high sensitivity, compact size, and multiplexed multi-point and remote detection.

  11. Simulation and mathematical analyses of AC electric field driven apoptosis via microtubule disintegration

    NASA Astrophysics Data System (ADS)

    Tiwari, Pawan K.

    2015-09-01

    The moderate intensity alternating current electric fields with frequencies ranging between a few tens of kilohertz and a few tens of megahertz, also known as tumor treating fields (TTFs) are utilized as a modality in the electrotherapeutic treatment of the cancer cells. The application of sub-MHz TTF on the cancer cell results in the inducement of higher electric field at the furrow between the daughter cells, and such apoptosis stimulating phenomenon is investigated through the Maxwell two-dimensional (2D) finite element simulations. A furrow distance of the order of size of the nucleus accounts for the intense electric field inducement disintegrating the microtubule via the processes of its surface disruption and tubulin dimer detachment. A simulation and mathematical analyses of the microtubule disintegration mechanism is formulated to ascertain one of the factors causing an apoptosis of the cancer cells, and consequently checking their proliferation.

  12. Water film motor driven by alternating electric fields: its dynamical characteristics.

    PubMed

    Liu, Zhong-Qiang; Zhang, Guang-Cai; Li, Ying-Jun; Jiang, Su-Rong

    2012-03-01

    The "liquid film motor," a novel device with important implications for basic research and technology, is analyzed. It works perfectly with both direct current (dc) and alternating current (ac) fields. We develop a mathematical model describing electrohydrodynamical (EHD) motions induced by ac fields, which are more complex and have wider technological applications than those produced by dc fields. The main characteristics of these motions, derived in our paper and in full agreement with the experimental ones, are as follows: (i) Rotation of the film requires that the frequencies of the ac fields are exactly the same and their magnitudes surpass a threshold, which depends on their phase difference. (ii) Vibrations may be induced by fields with different frequencies. (iii) The EHD motions strongly depend on the polarization induced by the external electric field. However, these motions are little affected by the liquid's electrical conductivity, viscosity, dielectric constant, and density. Our model also predicts several features, which have yet to be experimentally verified.

  13. Spontaneous transition of core radial electric field driven by magnetic islands in the H-1NF heliac

    SciTech Connect

    Kumar, S. T. A.; Blackwell, B. D.; Howard, J.; Harris, J. H.

    2011-01-01

    This paper reports an experimental observation of spontaneous transition of the core radial electric field to a large positive value (E(r) similar to 5 kV m(-1)), with a strong electric-field shear (similar to 700 kV m(-2)) in a low temperature (T(e) similar to 10 eV) radio frequency generated argon plasma in the H-1NF heliac stellarator. The transition, which seems to be driven by a spontaneous excitation of m = 2 magnetic islands near the core, is associated with a localized increase in the plasma density and excitation of coherent low frequency (similar to 3 kHz) oscillations possibly due to unstable E(r) shear driven modes. Evidence suggests development of the core electron-root scenario, which previously has been observed only at high temperature electron cyclotron heated plasmas.

  14. Experimental Verification of Isotropic Radiation from a Coherent Dipole Source via Electric-Field-Driven LC Resonator Metamaterials

    NASA Astrophysics Data System (ADS)

    Tichit, Paul-Henri; Burokur, Shah Nawaz; Qiu, Cheng-Wei; de Lustrac, André

    2013-09-01

    It has long been conjectured that isotropic radiation by a simple coherent source is impossible due to changes in polarization. Though hypothetical, the isotropic source is usually taken as the reference for determining a radiator’s gain and directivity. Here, we demonstrate both theoretically and experimentally that an isotropic radiator can be made of a simple and finite source surrounded by electric-field-driven LC resonator metamaterials designed by space manipulation. As a proof-of-concept demonstration, we show the first isotropic source with omnidirectional radiation from a dipole source (applicable to all distributed sources), which can open up several possibilities in axion electrodynamics, optical illusion, novel transformation-optic devices, wireless communication, and antenna engineering. Owing to the electric- field-driven LC resonator realization scheme, this principle can be readily applied to higher frequency regimes where magnetism is usually not present.

  15. Experimental verification of isotropic radiation from a coherent dipole source via electric-field-driven LC resonator metamaterials.

    PubMed

    Tichit, Paul-Henri; Burokur, Shah Nawaz; Qiu, Cheng-Wei; de Lustrac, André

    2013-09-27

    It has long been conjectured that isotropic radiation by a simple coherent source is impossible due to changes in polarization. Though hypothetical, the isotropic source is usually taken as the reference for determining a radiator's gain and directivity. Here, we demonstrate both theoretically and experimentally that an isotropic radiator can be made of a simple and finite source surrounded by electric-field-driven LC resonator metamaterials designed by space manipulation. As a proof-of-concept demonstration, we show the first isotropic source with omnidirectional radiation from a dipole source (applicable to all distributed sources), which can open up several possibilities in axion electrodynamics, optical illusion, novel transformation-optic devices, wireless communication, and antenna engineering. Owing to the electric- field-driven LC resonator realization scheme, this principle can be readily applied to higher frequency regimes where magnetism is usually not present.

  16. Electric field driven magnetic domain wall motion in ferromagnetic-ferroelectric heterostructures

    SciTech Connect

    Van de Wiele, Ben; Laurson, Lasse; Franke, Kévin J. A.; Dijken, Sebastiaan van

    2014-01-06

    We investigate magnetic domain wall (MDW) dynamics induced by applied electric fields in ferromagnetic-ferroelectric thin-film heterostructures. In contrast to conventional driving mechanisms where MDW motion is induced directly by magnetic fields or electric currents, MDW motion arises here as a result of strong pinning of MDWs onto ferroelectric domain walls (FDWs) via local strain coupling. By performing extensive micromagnetic simulations, we find several dynamical regimes, including instabilities such as spin wave emission and complex transformations of the MDW structure. In all cases, the time-averaged MDW velocity equals that of the FDW, indicating the absence of Walker breakdown.

  17. Large stable deformation of dielectric elastomers driven on mode of steady electric field

    NASA Astrophysics Data System (ADS)

    Zhang, Junshi; Zhao, Jianwen; Wang, Shu; Chen, Hualing; Li, Dichen

    2017-05-01

    Dielectric elastomers (DEs) are capable of large deformation under the actuation of applied voltage and sprayed charge. Actuation of DE under voltage control is prone to electromechanical instabilities, while the DE under charge control always survives from instabilities with sacrificing a large deformation. In this article, a novel actuation mode of steady electric field is proposed. By tuning applied voltage and sprayed charge during viscoelastic creep, an invariable electric field is generated. Such an actuation method can both avoid the occurrence of electromechanical instabilities and guarantee a large deformation in DE actuation.

  18. Optical signatures of electric-field-driven magnetic phase transitions in graphene quantum dots

    NASA Astrophysics Data System (ADS)

    Basak, Tista; Shukla, Alok

    2016-06-01

    Experimental challenges in identifying various types of magnetic ordering in graphene quantum dots (QDs) pose a major hurdle in the application of these nanostructures for spintronic devices. Based upon phase diagrams obtained by employing the π -electron Pariser-Parr-Pople (PPP) model Hamiltonian, we demonstrate that the magnetic states undergo phase transition under the influence of an external electric field. Our calculations of the electroabsorption spectra of these QDs indicate that the spectrum in question carries strong signatures of their magnetic state (FM vs AFM), thus suggesting the possibility of an all-optical characterization of their magnetic nature. Further, the gaps for the up and the down spins are the same in the absence of an external electric field, both for the antiferromagnetic (AFM) and the ferromagnetic (FM) states of QDs. But, once the QDs are exposed to a suitably directed external electric field, gaps for different spins split and exhibit distinct variations with respect to the strength of the field. The nature of variation exhibited by the energy gaps corresponding to the up and down spins is different for the AFM and FM configurations of QDs. This selective manipulation of the spin-polarized gap splitting by an electric field in finite graphene nanostructures can open up new frontiers in the design of graphene-based spintronic devices.

  19. Electro-optic characteristics of 90° twisted nematic liquid crystal display driven by fringe-electric field

    NASA Astrophysics Data System (ADS)

    Song, I. S.; Shin, S. S.; Kim, H. Y.; Song, S. H.; Lee, S. H.

    2004-02-01

    We investigated the electro-optic characteristics of a fringe-field driven twisted nematic (TN) display. In the absence of an electric field, the liquid crystals (LCs) are initially twisted 90° from the top to the bottom substrate under parallel polarizers so that the cell appears to be black. In the presence of a fringe-electric field, the LCs with negative dielectric anisotropy are rotated toward a plane that is almost perpendicular to the horizontal component of the fringe field, above the entire electrode surface. The cell then appears to be white, and shows high transmittance. In addition, the cell displays a wide viewing angle and has excellent color characteristics over a wide viewing range due to almost in-plane switching, unlike a conventional TN device where the LC director tilts upward in only one direction and results in a narrow viewing angle.

  20. Negative capacitance switching via VO{sub 2} band gap engineering driven by electric field

    SciTech Connect

    He, Xinfeng; Xu, Jing; Xu, Xiaofeng Gu, Congcong; Chen, Fei; Wu, Binhe Wang, Chunrui Xing, Huaizhong; Chen, Xiaoshuang; Chu, Junhao

    2015-03-02

    We report the negative capacitance behavior of an energy band gap modulation quantum well with a sandwich VO{sub 2} layer structure. The phase transition is probed by measuring its capacitance. With the help of theoretical calculations, it shows that the negative capacitance changes of the quantum well device come from VO{sub 2} band gap by continuously tuning the temperature or voltage. Experiments reveal that as the current remains small enough, joule heating can be ignored, and the insulator-metal transition of VO{sub 2} can be induced by the electric field. Our results open up possibilities for functional devices with phase transitions induced by external electric fields other than the heating or electricity-heat transition.

  1. Negative capacitance switching via VO2 band gap engineering driven by electric field

    NASA Astrophysics Data System (ADS)

    He, Xinfeng; Xu, Jing; Xu, Xiaofeng; Gu, Congcong; Chen, Fei; Wu, Binhe; Wang, Chunrui; Xing, Huaizhong; Chen, Xiaoshuang; Chu, Junhao

    2015-03-01

    We report the negative capacitance behavior of an energy band gap modulation quantum well with a sandwich VO2 layer structure. The phase transition is probed by measuring its capacitance. With the help of theoretical calculations, it shows that the negative capacitance changes of the quantum well device come from VO2 band gap by continuously tuning the temperature or voltage. Experiments reveal that as the current remains small enough, joule heating can be ignored, and the insulator-metal transition of VO2 can be induced by the electric field. Our results open up possibilities for functional devices with phase transitions induced by external electric fields other than the heating or electricity-heat transition.

  2. Reverse plasma motion driven by moderately screened rotating electric field in an electrodeless plasma thruster

    NASA Astrophysics Data System (ADS)

    Ohnishi, Naofumi; Nomura, Ryosuke; Nakamura, Takahiro; Nishida, Hiroyuki

    2016-01-01

    A reversely-induced azimuthal current has been found in two-dimensional particle simulations with moderately screened rotating electric field (REF) though an ideally penetrating REF drives a “positive” azimuthal current following rotating E × B drifts. This brings us an alternative acceleration concept, called a negative-moving response (NMR) acceleration, of the helicon plasma under practical conditions using a converging magnetic field because the internal electric potential, formed by the plasma response against the external field, drives the “negative” azimuthal current. Under realistic experimental conditions, e.g., a magnetic field of 0.2 T, AC frequency of <100 MHz, and AC voltage of <1000 V, the resultant thrust can be estimated at an observable level of >0.1 mN with the NMR acceleration. Moreover, the reverse REF is more favorable to the NMR acceleration than the conventional forward one because the reverse field produces a Lissajous acceleration in the converging magnetic field.

  3. Three-dimensional imaging of vortex structure in a ferroelectric nanoparticle driven by an electric field.

    PubMed

    Karpov, D; Liu, Z; Rolo, T Dos Santos; Harder, R; Balachandran, P V; Xue, D; Lookman, T; Fohtung, E

    2017-08-17

    Topological defects of spontaneous polarization are extensively studied as templates for unique physical phenomena and in the design of reconfigurable electronic devices. Experimental investigations of the complex topologies of polarization have been limited to surface phenomena, which has restricted the probing of the dynamic volumetric domain morphology in operando. Here, we utilize Bragg coherent diffractive imaging of a single BaTiO3 nanoparticle in a composite polymer/ferroelectric capacitor to study the behavior of a three-dimensional vortex formed due to competing interactions involving ferroelectric domains. Our investigation of the structural phase transitions under the influence of an external electric field shows a mobile vortex core exhibiting a reversible hysteretic transformation path. We also study the toroidal moment of the vortex under the action of the field. Our results open avenues for the study of the structure and evolution of polar vortices and other topological structures in operando in functional materials under cross field configurations.Imaging of topological states of matter such as vortex configurations has generally been limited to 2D surface effects. Here Karpov et al. study the volumetric structure and dynamics of a vortex core mediated by electric-field induced structural phase transition in a ferroelectric BaTiO3 nanoparticle.

  4. An evidence for prompt electric field disturbance driven by changes in the solar wind density under northward IMF Bz condition

    NASA Astrophysics Data System (ADS)

    Rout, Diptiranjan; Chakrabarty, D.; Sekar, R.; Reeves, G. D.; Ruohoniemi, J. M.; Pant, Tarun K.; Veenadhari, B.; Shiokawa, K.

    2016-05-01

    Before the onset of a geomagnetic storm on 22 January 2012 (Ap = 24), an enhancement in solar wind number density from 10/cm3 to 22/cm3 during 0440-0510 UT under northward interplanetary magnetic field (IMF Bz) condition is shown to have enhanced the high-latitude ionospheric convection and also caused variations in the geomagnetic field globally. Conspicuous changes in ΔX are observed not only at longitudinally separated low-latitude stations over Indian (prenoon), South American (midnight), Japanese (afternoon), Pacific (afternoon) and African (morning) sectors but also at latitudinally separated stations located over high and middle latitudes. The latitudinal variation of the amplitude of the ΔX during 0440-0510 UT is shown to be consistent with the characteristics of prompt penetration electric field disturbances. Most importantly, the density pulse event caused enhancements in the equatorial electrojet strength and the peak height of the F layer (hmF2) over the Indian dip equatorial sector. Further, the concomitant enhancements in electrojet current and F layer movement over the dip equator observed during this space weather event suggest a common driver of prompt electric field disturbance at this time. Such simultaneous variations are found to be absent during magnetically quiet days. In absence of significant change in solar wind velocity and magnetospheric substorm activity, these observations point toward perceptible prompt electric field disturbance over the dip equator driven by the overcompression of the magnetosphere by solar wind density enhancement.

  5. Lightning-Driven Electric Fields in the Stratosphere: Comparisons Between In-Situ Measurements and a Quasi-Electrostatic Field Model

    NASA Astrophysics Data System (ADS)

    Thomas, J. N.; Holzworth, R. H.; McCarthy, M. P.; Roy, N. G.; Solorzano, N. N.; Pinto, O.; Sato, M.

    2004-12-01

    During the Sprite Balloon Campaign in southeastern Brazil (December 6-7, 2002), 38 electric field changes greater than 10~V/m, correlated with cloud-to-ground and intra-cloud lightning, were measured above 30~km in altitude in the stratosphere. These electric field signatures are compared directly to an axi-symmetric quasi-electrostatic field (QSF) model developed by the authors and based on the model of Pasko et al. '97. Both the amplitude and the relaxation time of the lightning-driven electric fields are compared to this QSF model at the exact location of the in-situ balloon-borne measurements. The Brazilian Integrated Network (BIN), a regional ground-based lightning detection network that covers the southeast of Brazil, provides lightning location and peak current values for cloud-to-ground strokes, while remote extremely low frequency (ELF) magnetic field measurements from Japan and Antarctica provide charge moment estimates. These network and remote measurements, along with in-situ measurements of the conductivity by the Sprite flight 1 balloon payload, provide realistic input parameters to this QSF model. The in-situ electric field measurements are compared to the output of the QSF model for various cloud charge distributions and atmospheric conductivity profiles. When the electric field measurements agree well with the QSF model, the model can predict the electric field signature everywhere in the stratosphere and mesosphere, including sprite initiation altitudes. Thus, by utilizing in-situ electric field and conductivity measurements, local lightning network data, remote ELF measurements, and a QSF model of the lightning discharge, we are able to predict the amplitude and relaxation time of the electric field at sprite altitudes.

  6. Electric field-driven, magnetically-stabilized ferro-emulsion phase contactor

    DOEpatents

    Scott, T.C.

    1990-07-17

    Methods and systems are disclosed for interfacial surface area contact between a dispersed phase liquid and a continuous phase liquid in counter-current flow for purposes such as solvent extraction. Initial droplets of a dispersed phase liquid material containing ferromagnetic particles functioning as a packing'' are introduced to a counter-current flow of the continuous phase. A high intensity pulsed electric field is applied so as to shatter the initial droplets into a ferromagnetic emulsion comprising many smaller daughter droplets having a greater combined total surface area than that of the initial droplets in contact with the continuous phase material. A magnetic field is applied to control the position of the ferromagnetic emulsion for enhanced coalescence of the daughter droplets into larger reformed droplets. 2 figs.

  7. Electric field-driven, magnetically-stabilized ferro-emulsion phase contactor

    DOEpatents

    Scott, Timothy C.

    1990-01-01

    Methods and systems for interfacial surface area contact between a dispersed phase liquid and a continuous phase liquid in counter-current flow for purposes such as solvent extraction. Initial droplets of a dispersed phase liquid material containing ferromagnetic particles functioning as a "packing" are introduced to a counter-current flow of the continuous phase. A high intensity pulsed electric field is applied so as to shatter the initial droplets into a ferromagnetic emulsion comprising many smaller daughter droplets having a greater combined total surface area than that of the initial droplets in contact with the continuous phase material. A magnetic field is applied to control the position of the ferromagnetic emulsion for enhanced coalescence of the daughter droplets into larger reformed droplets.

  8. Terahertz plasmon-polariton modes in graphene driven by electric field inside a Fabry-Pérot cavity

    SciTech Connect

    Zhao, C. X.; Li, L. L.; Zhang, C.; Xu, W.; Peeters, F. M.

    2015-06-14

    We present a theoretical study on plasmon-polariton modes in graphene placed inside an optical cavity and driven by a source-to-drain electric field. The electron velocity and electron temperature are determined by solving self-consistently the momentum- and energy-balance equations in which electron interactions with impurities, acoustic-, and optic-phonons are included. Based on many-body self-consistent field theory, we develop a tractable approach to study plasmon-polariton in an electron gas system. We find that when graphene is placed inside a Fabry-Pérot cavity, two branches of the plasmon-polariton modes can be observed and these modes are very much optic- or plasmon-like. The frequencies of these modes depend markedly on driving electric field especially at higher resonant frequency regime. Moreover, the plasmon-polariton frequency in graphene is in terahertz (THz) bandwidth and can be tuned by changing the cavity length, gate voltage, and driving electric field. This work is pertinent to the application of graphene-based structures as tunable THz plasmonic devices.

  9. Electric-field-driven dynamics of magnetic domain walls in magnetic nanowires patterned on ferroelectric domains

    NASA Astrophysics Data System (ADS)

    Van de Wiele, Ben; Leliaert, Jonathan; Franke, Kévin J. A.; van Dijken, Sebastiaan

    2016-03-01

    Strong coupling of magnetic domain walls onto straight ferroelastic boundaries of a ferroelectric layer enables full and reversible electric-field control of magnetic domain wall motion. In this paper, the dynamics of this new driving mechanism is analyzed using micromagnetic simulations. We show that transverse domain walls with a near-180° spin structure are stabilized in magnetic nanowires and that electric fields can move these walls with high velocities. Above a critical velocity, which depends on material parameters, nanowire geometry and the direction of domain wall motion, the magnetic domain walls depin abruptly from the ferroelastic boundaries. Depinning evolves either smoothly or via the emission and annihilation of a vortex or antivortex core (Walker breakdown). In both cases, the magnetic domain wall slows down after depinning in an oscillatory fashion and eventually comes to a halt. The simulations provide design rules for hybrid ferromagnetic-ferroelectric domain-wall-based devices and indicate that material disorder and structural imperfections only influence Walker-breakdown-like depinning at high domain wall velocities.

  10. Mobility of nanometer-size solutes in water driven by electric field

    NASA Astrophysics Data System (ADS)

    Dinpajooh, Mohammadhasan; Matyushov, Dmitry V.

    2016-12-01

    We investigate the mobility of nanometer-size solutes in water in a uniform external electric field. General arguments are presented to show that a closed surface cutting a volume from a polar liquid will carry an effective non-zero surface charge density when preferential orientation of dipoles exists in the interface. This effective charge will experience a non-vanishing drag in an external electric field even in the absence of free charge carriers. Numerical simulations of model solutes are used to estimate the magnitude of the surface charge density. We find it to be comparable to the values typically reported from the mobility measurements. Hydrated ions can potentially carry a significant excess of the effective charge due to over-polarization of the interface. As a result, the electrokinetic charge can significantly deviate from the physical charge of free charge carriers. We propose to test the model by manipulating the polarizability of hydrated semiconductor nanoparticles with light. The inversion of the mobility direction can be achieved by photoexcitation, which increases the nanoparticle polarizability and leads to an inversion of the dipolar orientations of water molecules in the interface.

  11. Electrically driven optical metamaterials.

    PubMed

    Le-Van, Quynh; Le Roux, Xavier; Aassime, Abdelhanin; Degiron, Aloyse

    2016-06-22

    The advent of metamaterials more than 15 years ago has offered extraordinary new ways of manipulating electromagnetic waves. Yet, progress in this field has been unequal across the electromagnetic spectrum, especially when it comes to finding applications for such artificial media. Optical metamaterials, in particular, are less compatible with active functionalities than their counterparts developed at lower frequencies. One crucial roadblock in the path to devices is the fact that active optical metamaterials are so far controlled by light rather than electricity, preventing them from being integrated in larger electronic systems. Here we introduce electroluminescent metamaterials based on metal nano-inclusions hybridized with colloidal quantum dots. We show that each of these miniature blocks can be individually tuned to exhibit independent optoelectronic properties (both in terms of electrical characteristics, polarization, colour and brightness), illustrate their capabilities by weaving complex light-emitting surfaces and finally discuss their potential for displays and sensors.

  12. Electrically driven optical metamaterials

    NASA Astrophysics Data System (ADS)

    Le-van, Quynh; Le Roux, Xavier; Aassime, Abdelhanin; Degiron, Aloyse

    2016-06-01

    The advent of metamaterials more than 15 years ago has offered extraordinary new ways of manipulating electromagnetic waves. Yet, progress in this field has been unequal across the electromagnetic spectrum, especially when it comes to finding applications for such artificial media. Optical metamaterials, in particular, are less compatible with active functionalities than their counterparts developed at lower frequencies. One crucial roadblock in the path to devices is the fact that active optical metamaterials are so far controlled by light rather than electricity, preventing them from being integrated in larger electronic systems. Here we introduce electroluminescent metamaterials based on metal nano-inclusions hybridized with colloidal quantum dots. We show that each of these miniature blocks can be individually tuned to exhibit independent optoelectronic properties (both in terms of electrical characteristics, polarization, colour and brightness), illustrate their capabilities by weaving complex light-emitting surfaces and finally discuss their potential for displays and sensors.

  13. Electrically driven optical metamaterials

    PubMed Central

    Le-Van, Quynh; Le Roux, Xavier; Aassime, Abdelhanin; Degiron, Aloyse

    2016-01-01

    The advent of metamaterials more than 15 years ago has offered extraordinary new ways of manipulating electromagnetic waves. Yet, progress in this field has been unequal across the electromagnetic spectrum, especially when it comes to finding applications for such artificial media. Optical metamaterials, in particular, are less compatible with active functionalities than their counterparts developed at lower frequencies. One crucial roadblock in the path to devices is the fact that active optical metamaterials are so far controlled by light rather than electricity, preventing them from being integrated in larger electronic systems. Here we introduce electroluminescent metamaterials based on metal nano-inclusions hybridized with colloidal quantum dots. We show that each of these miniature blocks can be individually tuned to exhibit independent optoelectronic properties (both in terms of electrical characteristics, polarization, colour and brightness), illustrate their capabilities by weaving complex light-emitting surfaces and finally discuss their potential for displays and sensors. PMID:27328976

  14. Electric field-driven magnetocrystalline anisotropy switching of Fe/MgO: Towards full understanding from first principles

    NASA Astrophysics Data System (ADS)

    Nakamura, K.; Akiyama, T.; Ito, T.; Weinert, M.; Freeman, A. J.

    2010-03-01

    Controlling magnetic properties by an external electric field (E-field) is a key challenge in modern magnetic physics. Here, we investigate the magnetocrystalline anisotropy (MCA) modification by an E-field for thin films of Fe on a MgO substrate from first principles. Calculations were carried out by using the film FLAPW methodfootnotetextWimmer, Krakauer, Weinert, and Freeman, PRB 24, 864 (1981). with full optimization by atomic force calculations in which an E-field effect is incorporated.footnotetextNakamura et al., PRL 102, 18702 (2009); Weinert et al., J. Phys.: Condens. Matter 21, 084201 (2009). Results predict that the Fe/MgO interface gives rise to a large out-of-plane MCA due to an Fe-O hybridization at the interface and a MCA modification is induced by a change in the d-band structures at the Fermi level when an E-field is introduced. Importantly, however, the existence of an interfacial iron- oxide layer between the Fe layer and the MgO substrate is found to play a key role in demonstrating an electric field-driven MCA switching, i.e., from out-of-plane MCA to in-plane MCA --- as observed in experiments.footnotetextShiota et al., Appl. Phys. Express 2, 063001 (2009).

  15. Electric-field-driven magnetization switching and nonlinear magnetoelasticity in Au/FeCo/MgO heterostructures

    NASA Astrophysics Data System (ADS)

    Ong, P. V.; Kioussis, Nicholas; Amiri, P. Khalili; Wang, K. L.

    2016-07-01

    Voltage-induced switching of magnetization, as opposed to current-driven spin transfer torque switching, can lead to a new paradigm enabling ultralow-power and high density instant-on nonvolatile magnetoelectric random access memory (MeRAM). To date, however, a major bottleneck in optimizing the performance of MeRAM devices is the low voltage-controlled magnetic anisotropy (VCMA) efficiency (change of interfacial magnetic anisotropy energy per unit electric field) leading in turn to high switching energy and write voltage. In this work, employing ab initio electronic structure calculations, we show that epitaxial strain, which is ubiquitous in MeRAM heterostructures, gives rise to a rich variety of VCMA behavior with giant VCMA coefficient (~1800 fJ V-1m-1) in Au/FeCo/MgO junction. The heterostructure also exhibits a strain-induced spin-reorientation induced by a nonlinear magnetoelastic coupling. The results demonstrate that the VCMA behavior is universal and robust in magnetic junctions with heavy metal caps across the 5d transition metals and that an electric-field-driven magnetic switching at low voltage is achievable by design. These findings open interesting prospects for exploiting strain engineering to harvest higher efficiency VCMA for the next generation MeRAM devices.

  16. Electric-field-driven magnetization switching and nonlinear magnetoelasticity in Au/FeCo/MgO heterostructures

    PubMed Central

    Ong, P. V.; Kioussis, Nicholas; Amiri, P. Khalili; Wang, K. L.

    2016-01-01

    Voltage-induced switching of magnetization, as opposed to current-driven spin transfer torque switching, can lead to a new paradigm enabling ultralow-power and high density instant-on nonvolatile magnetoelectric random access memory (MeRAM). To date, however, a major bottleneck in optimizing the performance of MeRAM devices is the low voltage-controlled magnetic anisotropy (VCMA) efficiency (change of interfacial magnetic anisotropy energy per unit electric field) leading in turn to high switching energy and write voltage. In this work, employing ab initio electronic structure calculations, we show that epitaxial strain, which is ubiquitous in MeRAM heterostructures, gives rise to a rich variety of VCMA behavior with giant VCMA coefficient (~1800 fJ V−1m−1) in Au/FeCo/MgO junction. The heterostructure also exhibits a strain-induced spin-reorientation induced by a nonlinear magnetoelastic coupling. The results demonstrate that the VCMA behavior is universal and robust in magnetic junctions with heavy metal caps across the 5d transition metals and that an electric-field-driven magnetic switching at low voltage is achievable by design. These findings open interesting prospects for exploiting strain engineering to harvest higher efficiency VCMA for the next generation MeRAM devices. PMID:27424885

  17. Electric-field-driven magnetization switching and nonlinear magnetoelasticity in Au/FeCo/MgO heterostructures.

    PubMed

    Ong, P V; Kioussis, Nicholas; Amiri, P Khalili; Wang, K L

    2016-07-18

    Voltage-induced switching of magnetization, as opposed to current-driven spin transfer torque switching, can lead to a new paradigm enabling ultralow-power and high density instant-on nonvolatile magnetoelectric random access memory (MeRAM). To date, however, a major bottleneck in optimizing the performance of MeRAM devices is the low voltage-controlled magnetic anisotropy (VCMA) efficiency (change of interfacial magnetic anisotropy energy per unit electric field) leading in turn to high switching energy and write voltage. In this work, employing ab initio electronic structure calculations, we show that epitaxial strain, which is ubiquitous in MeRAM heterostructures, gives rise to a rich variety of VCMA behavior with giant VCMA coefficient (~1800 fJ V(-1)m(-1)) in Au/FeCo/MgO junction. The heterostructure also exhibits a strain-induced spin-reorientation induced by a nonlinear magnetoelastic coupling. The results demonstrate that the VCMA behavior is universal and robust in magnetic junctions with heavy metal caps across the 5d transition metals and that an electric-field-driven magnetic switching at low voltage is achievable by design. These findings open interesting prospects for exploiting strain engineering to harvest higher efficiency VCMA for the next generation MeRAM devices.

  18. Modeling of movement of liquid metal droplets driven by an electric field.

    PubMed

    Wang, M F; Jin, M J; Jin, X J; Zuo, S G

    2017-07-19

    The motion of liquid metal has potential applications ranging from micro-pumps and self-fueled motors to rapid cooling and drug delivery. In this study, we systematically investigate the effects of the radius of LMDs (liquid metal droplets), the concentration of electrolyte solution and the applied electric field on the movement behavior of LMDs experimentally. The research also explains the experimental phenomenon with an innovative modeling analysis, which combines pertinent forces (i.e., the driving force induced by the gradient of surface tension, the viscous friction between the droplet and its surrounding electrolyte, and the friction between the droplet and the substrate). The model is highly consistent with the rule that LMDs with a larger radius need smaller actuation voltage, and we can predict the critical voltages of LMDs with r = 2-4 mm through Velectrode = 30.62/r(2) - 0.998, which is obtained by fitting the parameters. We also obtain the model V = [-66.2Vr(2)/(259.7-17.7) + 1.253]r(2), which can predict the average velocity-voltage lines of LMDs with r = 3, 3.5 mm and V = 1-13 V. In addition, the velocity increases upon increasing the concentration of the electrolyte solution from 0.1 mol L(-1) to 0.3 mol L(-1), and tends to be stable at more than 0.3 mol L(-1) owing to the saturation of the EDL (electrical double layer) charge density. Additionally, we discuss the phenomenon of elongation during movement that occurs upon increasing the size of the LMDs. If the size of the LMDs continues to increase, the reverse movement from the anode to the cathode can occur, and the phenomenon can also be explained by the model.

  19. Transition of vertically aligned liquid crystal driven by fan-shaped electric field

    NASA Astrophysics Data System (ADS)

    Tsung, J. W.; Ting, T. L.; Chen, C. Y.; Liang, W. L.; Lai, C. W.; Lin, T. H.; Hsu, W. H.

    2017-09-01

    Interdigital electrodes are implemented in many commercial and novel liquid crystal devices to align molecules. Although many empirical principles and patents apply to electrode design, only a few numerical simulations of alignment have been conducted. Why and how the molecules align in an ordered manner has never been adequately explained. Hence, this investigation addresses the Fréedericksz transition of vertically aligned liquid crystal that is driven by fishbone electrodes, and thereafter identifies the mechanism of liquid crystal alignment. Theoretical calculations suggest that the periodic deformation that is caused by the fan-shaped fringe field minimizes the free energy in the liquid crystal cell, and the optimal alignment can be obtained when the cell parameters satisfy the relation p /2 d =√{k11/k33 } , where p is the spatial period of the strips of the electrode; d denotes the cell gap; and k11 and k33 are the splay and bend elastic constants of the liquid crystal, respectively. Polymer-stabilized vertical alignment test cells with various p values and spacings between the electrodes were fabricated, and the process of liquid crystal alignment was observed under an optical microscope. The degree of alignment was evaluated by measuring the transmittance of the test cell. The experimental results were consistent with the theoretical predictions. The principle of design, p /2 d =√{k11/k33 } , greatly improves the uniformity and stability of the aligned liquid crystal. The methods that are presented here can be further applied to cholesteric liquid crystal and other self-assembled soft materials.

  20. Microfluidic Device for Electric Field-Driven Single-Cell Captureand Activation

    SciTech Connect

    Toriello, Nicholas M.; Douglas, Erik S.; Mathies, Richard A.

    2005-09-20

    A microchip that performs directed capture and chemical activation of surface-modified single-cells has been developed. The cell-capture system is comprised of interdigitated gold electrodes microfabricated on a glass substrate within PDMS channels. The cell surface is labeled with thiol functional groups using endogenous RGD receptors and adhesion to exposed gold pads on the electrodes is directed by applying a driving electric potential. Multiple cell types can thus be sequentially and selectively captured on desired electrodes. Single-cell capture efficiency is optimized by varying the duration of field application. Maximum single-cell capture is attained for the 10 min trial, with 63+-9 percent (n=30) of the electrode pad rows having a single cell. In activation studies, single M1WT3 CHO cells loaded with the calcium-sensitive dye fluo-4 AM were captured; exposure to the muscarinic agonist carbachol increased the fluorescence to 220+-74percent (n=79) of the original intensity. These results demonstrate the ability to direct the adhesion of selected living single cells on electrodes in a microfluidic device and to analyze their response to chemical stimuli.

  1. Local energy and power in many-particle quantum systems driven by an external electrical field

    NASA Astrophysics Data System (ADS)

    Albareda, Guillermo; Traversa, Fabio Lorenzo; Oriols, Xavier

    2016-05-01

    We derive expressions for the expectation values of the local energy and the local power for a many-particle system of (scalar) charged particles interacting with an external electrical field. In analogy with the definition of the (local) current probability density, we construct a local energy operator such that the time-rate of change of its expectation value provides information on the spatial distribution of power. Results are presented as functions of an arbitrarily small volume Ω , and physical insights are discussed by means of the quantum hydrodynamical representation of the wavefunction, which is proven to allow for a clear-cut separation into contributions with and without classical correspondence. Quantum features of the local power are mainly manifested through the presence of non-local sources/sinks of power and through the action of forces with no classical counterpart. Many-particle classical-like effects arise in the form of current-force correlations and through the inflow/outflow of energy across the boundaries of the volume Ω . Interestingly, all these intriguing features are only reflected in the expression of the local power when the volume Ω is finite. Otherwise, for closed systems with Ω \\to ∞ , we recover a classical-like single-particle expression.

  2. Design and modeling of magnetically driven electric-field sensor for non-contact DC voltage measurement in electric power systems

    NASA Astrophysics Data System (ADS)

    Wang, Decai; Li, Ping; Wen, Yumei

    2016-10-01

    In this paper, the design and modeling of a magnetically driven electric-field sensor for non-contact DC voltage measurement are presented. The magnetic drive structure of the sensor is composed of a small solenoid and a cantilever beam with a cylindrical magnet mounted on it. The interaction of the magnet and the solenoid provides the magnetic driving force for the sensor. Employing magnetic drive structure brings the benefits of low driving voltage and large vibrating displacement, which consequently results in less interference from the drive signal. In the theoretical analyses, the capacitance calculation model between the wire and the sensing electrode is built. The expression of the magnetic driving force is derived by the method of linear fitting. The dynamical model of the magnetic-driven cantilever beam actuator is built by using Euler-Bernoulli theory and distributed parameter method. Taking advantage of the theoretical model, the output voltage of proposed sensor can be predicted. The experimental results are in good agreement with the theoretical results. The proposed sensor shows a favorable linear response characteristic. The proposed sensor has a measuring sensitivity of 9.87 μV/(V/m) at an excitation current of 37.5 mA. The electric field intensity resolution can reach 10.13 V/m.

  3. Lightning-driven electric fields measured in the upper mesosphere and lower ionosphere during the Thunderstorm-III rocket campaign: Implications for transient luminous events

    NASA Astrophysics Data System (ADS)

    Thomas, J. N.; Barnum, B. H.; Holzworth, R. H.; Lay, E. H.; Cho, M.

    2006-12-01

    On September 1, 1995, the Thunderstorm-III sounding rocket was launched from Wallops Island, VA, USA to measure the effects of lightning on the ionosphere. Thunderstorm-III measured hundreds of electric and magnetic field changes from an active storm near Wallops Island and a few other more distant storms. Although the majority of these measurements occurred at altitudes above 130 km, there were 60 lightning- driven electric field changes measured at 75-130 km altitude during the rocket descent. Most of these lightning occurred at horizontal distances of 250-300 km from the rocket as located by the National Lightning Detection Network. At these distances, weak quasi-static electric field components and strong electromagnetic components were measured. These are some of the only lightning-driven electric fields measured in the upper mesosphere / lower ionosphere ever to be reported, since this region is typically too low in altitude for rockets and satellites and too high for balloons. In this presentation, these electric field changes are summarized and a few detailed case studies are presented. Moreover, these measurements are compared directly to a 2-D numerical model of lightning-driven electromagnetic fields in the middle and upper atmosphere. Finally, the implications of these results for transient luminous events, such as sprites, elves, and halos that have been observed at these altitudes are discussed.

  4. Electrically Driven Supersonic Combustor

    NASA Astrophysics Data System (ADS)

    Leonov, S.; Sabelnikov, V.

    2009-01-01

    The paper considers a new method of supersonic combustor steering under non-optimal conditions, specifically, at low gas temperature. The method is based on near-surface electrical discharge application for flow management and flameholding. The experimental results on flameholding at gas temperature T0=300-760K are presented. The hydrogen and ethylene were injected directly into the M=2 flow from the wall at overall ER<0.2. The electrical discharge of filamentary type between flush mounted electrodes on the wall is used for a flame promotion. The power deposited is Wpl/Htot<2-5% of flow total enthalpy. The fuel ignition, and flameholding are demonstrated experimentally at combustion completeness η>0.9. The pressure elevation due to combustion is measured in accordance with operation mode. The fact is specially pointed that the discharge switching off leads to immediate extinction of the hydrogen/ethylene flame. The power threshold of fuels ignition over the plane wall was measured by variation of power deposition and the fuel mass flow rate. Based on the experimental data a new scheme of supersonic combustor is proposed. Local zones of combustion in multiple directly wall-fueled sections are supported by electrical discharges. Cross- section's expansions are adjusted with those zones of intensive reactions. This scheme is supposed to be quite prospective for practical apparatuses.

  5. Coupled electric fields in photorefractive driven liquid crystal hybrid cells - theory and numerical simulation

    NASA Astrophysics Data System (ADS)

    Moszczyński, P.; Walczak, A.; Marciniak, P.

    2016-12-01

    In cyclic articles previously published we described and analysed self-organized light fibres inside a liquid crystalline (LC) cell contained photosensitive polymer (PP) layer. Such asymmetric LC cell we call a hybrid LC cell. Light fibre arises along a laser beam path directed in plane of an LC cell. It means that a laser beam is parallel to photosensitive layer. We observed the asymmetric LC cell response on an external driving field polarization. Observation has been done for an AC field first. It is the reason we decided to carry out a detailed research for a DC driving field to obtain an LC cell response step by step. The properly prepared LC cell has been built with an isolating layer and garbage ions deletion. We proved by means of a physical model, as well as a numerical simulation that LC asymmetric response strongly depends on junction barriers between PP and LC layers. New parametric model for a junction barrier on PP/LC boundary has been proposed. Such model is very useful because of lack of proper conductivity and charge carriers of band structure data on LC material.

  6. An electric field-driven MIT in strongly-correlated thin-film superlattices: an inhomogeneous dynamical mean-field theory study

    NASA Astrophysics Data System (ADS)

    Bakalov, Petar; Locquet, Jean-Pierre

    Using an inhomogeneous dynamical mean-field theory (IDMFT) approach to the single-band Hubbard model we investigate the properties of thin-film superlattices made up of alternating strongly (U1) and weakly (U2 electric field on the correlation driven Mott-Hubbard metal-to-insulator transition. We find that when the periodicity of the superlattice is such that the strongly correlated regions are below a certain thickness, the MIT is suppressed due to proximity effects. This work was partially funded by the Flemish Fund for Scientific Research (FWO - Vlaanderen) under FWO Grant G.0520.10 and by the SITOGA FP7 project. Most of the calculations were performed on KU Leuven's ThinKing HPC cluster.

  7. Friction in carborane-based molecular rotors driven by gas flow or electric field: classical molecular dynamics.

    PubMed

    Prokop, Alexandr; Vacek, Jaroslav; Michl, Josef

    2012-03-27

    Friction in molecular rotors is examined by classical molecular dynamics simulations for grid-mounted azimuthal dipolar molecular rotors, whose rotation is either allowed to decay freely or is driven at GHz frequencies by a flow of rare gas or by a rotating electric field. The rotating parts (rotators) are propeller-shaped. Their two to six blades consist of condensed aromatic rings and are attached to a deltahedral carborane hub, whose antipodal carbons carry [n]staffane axles mounted on a square molecular grid. The dynamic friction constant η has been derived in several independent ways with similar results. Analysis of free rotation decay yields η as a continuous exponentially decreasing function of rotor frequency. The calculated dependence of friction torque on frequency resembles the classical macroscopic Stribeck curve. Its relation to rotational potential energy barriers and the key role of the rate of intramolecular vibrational redistribution (IVR) of energy and angular momentum from rotator rotation to other modes are considered in two limiting regimes. (i) In the strongly overdamped regime, rotation is much slower than IVR, and effective friction can be expressed through potential barriers to rotation. (ii) In the strongly underdamped regime, rotation is much faster than IVR, whose rate then determines friction.

  8. Multiplexed Electrochemical Immunoassay of Phosphorylated Proteins Based on Enzyme-Functionalized Gold Nanorod Labels and Electric Field-Driven Acceleration

    SciTech Connect

    Du, Dan; Wang, Jun; Lu, Donglai; Dohnalkova, Alice; Lin, Yuehe

    2011-09-09

    A multiplexed electrochemical immunoassay integrating enzyme amplification and electric field-driven strategy was developed for fast and sensitive quantification of phosphorylated p53 at Ser392 (phospho-p53 392), Ser15 (phospho-p53 15), Ser46 (phospho-p53 46) and total p53 simultaneously. The disposable sensor array has four spatially separated working electrodes and each of them is modified with different capture antibody, which enables simultaneous immunoassay to be conducted without cross-talk between adjacent electrodes. The enhanced sensitivity was achieved by multi-enzymes amplification strategy using gold nanorods (AuNRs) as nanocarrier for co-immobilization of horseradish peroxidase (HRP) and detection antibody (Ab2) at high ratio of HRP/Ab2, which produced an amplified electrocatalytic response by the reduction of HRP oxidized thionine in the presence of hydrogen peroxide. The immunoreaction processes were accelerated by applying +0.4 V for 3 min and then -0.2 V for 1.5 min, thus the whole sandwich immunoreactions could be completed in less than 5 min. The disposable immunosensor array shows excellent promise for clinical screening of phosphorylated proteins and convenient point-of-care diagnostics.

  9. Multiplexed electrochemical immunoassay of phosphorylated proteins based on enzyme-functionalized gold nanorod labels and electric field-driven acceleration.

    PubMed

    Du, Dan; Wang, Jun; Lu, Donglai; Dohnalkova, Alice; Lin, Yuehe

    2011-09-01

    A multiplexed electrochemical immunoassay integrating enzyme amplification and electric field-driven strategy was developed for fast and sensitive quantification of phosphorylated p53 at Ser392 (phospho-p53(392)), Ser15 (phospho-p53(15)), Ser46 (phospho-p53(46)), and total p53 simultaneously. The disposable sensor array has four spatially separated working electrodes, and each of them is modified with different capture antibody, which enables simultaneous immunoassay to be conducted without cross-talk between adjacent electrodes. The enhanced sensitivity was achieved by a multienzyme amplification strategy using gold nanorods (AuNRs) as nanocarrier for coimmobilization of horseradish peroxidase (HRP) and detection antibody (Ab(2)) at a high ratio of HRP/Ab(2), which produced an amplified electrocatalytic response by the reduction of HRP oxidized thionine in the presence of hydrogen peroxide. The immunoreaction processes were accelerated by applying +0.4 V for 3 min and then -0.2 V for 1.5 min; thus, the whole sandwich immunoreactions could be completed in less than 5 min. Under optimal conditions, this method could simultaneously detect phospho-p53(392), phospho-p53(15), phospho-p53(46), and total p53 ranging from 0.01 to 20 nM, 0.05 to 20 nM, 0.1 to 50 nM, and 0.05 to 20 nM with detection limits of 5 pM, 20 pM, 30 pM, and 10 pM, respectively. Accurate determinations of these proteins in human plasma samples were demonstrated by comparison to the standard ELISA method. The disposable immunosensor array shows excellent promise for clinical screening of phosphorylated proteins and convenient point-of-care diagnostics.

  10. Electrically Driven Liquid Film Boiling Experiment

    NASA Technical Reports Server (NTRS)

    Didion, Jeffrey R.

    2016-01-01

    This presentation presents the science background and ground based results that form the basis of the Electrically Driven Liquid Film Boiling Experiment. This is an ISS experiment that is manifested for 2021. Objective: Characterize the effects of gravity on the interaction of electric and flow fields in the presence of phase change specifically pertaining to: a) The effects of microgravity on the electrically generated two-phase flow. b) The effects of microgravity on electrically driven liquid film boiling (includes extreme heat fluxes). Electro-wetting of the boiling section will repel the bubbles away from the heated surface in microgravity environment. Relevance/Impact: Provides phenomenological foundation for the development of electric field based two-phase thermal management systems leveraging EHD, permitting optimization of heat transfer surface area to volume ratios as well as achievement of high heat transfer coefficients thus resulting in system mass and volume savings. EHD replaces buoyancy or flow driven bubble removal from heated surface. Development Approach: Conduct preliminary experiments in low gravity and ground-based facilities to refine technique and obtain preliminary data for model development. ISS environment required to characterize electro-wetting effect on nucleate boiling and CHF in the absence of gravity. Will operate in the FIR - designed for autonomous operation.

  11. Lower Electric Field-Driven Magnetic Phase Transition and Perfect Spin Filtering in Graphene Nanoribbons by Edge Functionalization.

    PubMed

    Rezapour, M Reza; Yun, Jeonghun; Lee, Geunsik; Kim, Kwang S

    2016-12-15

    Perfect spin filtering is an important issue in spintronics. Although such spin filtering showing giant magnetoresistance was suggested using graphene nanoribbons (GNRs) on both ends of which strong magnetic fields were applied, electric field controlled spin filtering is more interesting due to much easier precise control with much less energy consumption. Here we study the magnetic/nonmagnetic behaviors of zigzag GNRs (zGNRs) under a transverse electric field and by edge functionalization. Employing density functional theory (DFT), we show that the threshold electric field to attain either a half-metallic or nonmagnetic feature is drastically reduced by introducing proper functional groups to the edges of the zGNR. From the current-voltage characteristics of the edge-modified zGNR under an in-plane transverse electric field, we find a remarkable perfect spin filtering feature, which can be utilized for a molecular spintronic device. Alteration of magnetic properties by tuning the transverse electric field would be a promising way to construct magnetic/nonmagnetic switches.

  12. Pfirsch-Schlüter current-driven edge electric fields and their effect on the L-H transition power threshold

    NASA Astrophysics Data System (ADS)

    Aydemir, A. Y.

    2012-06-01

    An important contribution to the magnetohydrodynamic equilibrium at the tokamak edge comes from the Pfirsch-Schlüter current. The parallel electric field that can be associated with these currents is necessarily poloidally asymmetric and makes a similarly nonuniform contribution to the radial electric field on a flux surface. Here the role of the poloidal variation of this radial electric field in the L-H transition power threshold is investigated. Dependence of the resulting electric fields on magnetic topology, geometric factors such as the upper/lower triangularity and elongation, and the relative position of the X-point(s) in the poloidal plane are examined in detail. Starting with the assumption that an initially more negative radial electric field at the edge helps lower the transition power threshold, we find that our results are in agreement with a variety of experimental observations. In particular, for a ‘normal’ configuration of the plasma current and toroidal field we show the following. (i) The net radial electric field contribution by the Pfirsch-Schlüter currents at the plasma edge is negative for a lower single null and positive for a corresponding upper single null geometry. (ii) It becomes more negative as the X-point height is reduced. (iii) It also becomes more negative as the X-point radius is increased. These observations are consistent with the observed changes in the L-H transition power threshold PLH under similar changes in the experimental conditions. In addition we find that (iv) in USN with an unfavourable ion ∇B drift direction, the net radial electric field contribution is positive but decreases as the X-point radius decreases. This is consistent with the C-Mod observation that an L-I mode transition can be triggered by increasing the upper triangularity in this configuration. (v) Locally the radial electric field is positive above the outer mid-plane and reverses sign with reversal of the toroidal field, consistent with DIII

  13. Electric Field Imaging Project

    NASA Technical Reports Server (NTRS)

    Wilcutt, Terrence; Hughitt, Brian; Burke, Eric; Generazio, Edward

    2016-01-01

    NDE historically has focused technology development in propagating wave phenomena with little attention to the field of electrostatics and emanating electric fields. This work is intended to bring electrostatic imaging to the forefront of new inspection technologies, and new technologies in general. The specific goals are to specify the electric potential and electric field including the electric field spatial components emanating from, to, and throughout volumes containing objects or in free space.

  14. Electric field and plasma density measurements in the strongly driven daytime equatorial electrojet. I - The unstable layer and gradient drift waves. II - Two-stream waves

    NASA Technical Reports Server (NTRS)

    Pfaff, R. F.; Kelley, M. C.; Kudeki, E.; Fejer, B. G.; Baker, K. D.

    1987-01-01

    The results of electric field and plasma density measurements in the strongly driven daytime equatorial electrojet over Peru, made during the March 1983 Condor electrojet experiment from Punta Lobos, Peru, are discussed together with the rocket instrumentation used for the measurements and the pertinent payload dynamics. The overall characteristics of the irregularity layer observed in situ in the electrojet are described. Special consideration is given to the waves generated by the gradient drift instability (observed between 90 and 106.5 km) and to primary and secondary two-stream waves detected by the two probes on the topside between 103 and 111 km, where the electron current was considered to be strongest.

  15. Relativistic Electrons Produced by Reconnecting Electric Fields in a Laser-driven Bench-top Solar Flare

    NASA Astrophysics Data System (ADS)

    Zhong, J. Y.; Lin, J.; Li, Y. T.; Wang, X.; Li, Y.; Zhang, K.; Yuan, D. W.; Ping, Y. L.; Wei, H. G.; Wang, J. Q.; Su, L. N.; Li, F.; Han, B.; Liao, G. Q.; Yin, C. L.; Fang, Y.; Yuan, X.; Wang, C.; Sun, J. R.; Liang, G. Y.; Wang, F. L.; Ding, Y. K.; He, X. T.; Zhu, J. Q.; Sheng, Z. M.; Li, G.; Zhao, G.; Zhang, J.

    2016-08-01

    Laboratory experiments have been carried out to model the magnetic reconnection process in a solar flare with powerful lasers. Relativistic electrons with energy up to megaelectronvolts are detected along the magnetic separatrices bounding the reconnection outflow, which exhibit a kappa-like distribution with an effective temperature of ˜109 K. The acceleration of non-thermal electrons is found to be more efficient in the case with a guide magnetic field (a component of a magnetic field along the reconnection-induced electric field) than in the case without a guide field. Hardening of the spectrum at energies ≥500 keV is observed in both cases, which remarkably resembles the hardening of hard X-ray and γ-ray spectra observed in many solar flares. This supports a recent proposal that the hardening in the hard X-ray and γ-ray emissions of solar flares is due to a hardening of the source-electron spectrum. We also performed numerical simulations that help examine behaviors of electrons in the reconnection process with the electromagnetic field configurations occurring in the experiments. The trajectories of non-thermal electrons observed in the experiments were well duplicated in the simulations. Our numerical simulations generally reproduce the electron energy spectrum as well, except for the hardening of the electron spectrum. This suggests that other mechanisms such as shock or turbulence may play an important role in the production of the observed energetic electrons.

  16. Numerical simulations of electric field driven hierarchical self-assembly of monolayers of binary mixtures of particles

    NASA Astrophysics Data System (ADS)

    Amah, Edison; Musunuri, Naga; Hossain, Shahadat; Fischer, Ian; Singh, Pushpendra

    2016-11-01

    We numerically study the process of self-assembly of particle mixtures on fluid-liquid interfaces when an electric field is applied in the direction normal to the interface. Lateral forces cause particles to self-assemble into molecular-like hierarchical arrangements consisting of composite particles arranged in a pattern. As in experiments, if the particles sizes differ by a factor of two or more, the composite particle has a larger particle at its core with several smaller particles forming a ring around it. Approximately same sized particles form chains (analogous to polymeric molecules) in which positively and negatively polarized particles alternate when their concentrations are approximately equal, but when their concentrations differ substantially the particles whose concentration is larger form rings around the particles whose concentration is smaller. In some instances, particle chains with a positively polarized particle at one end and a negatively particle at the other folded to form circular chains. For submicron particles, only when the electric field intensity is larger than a critical value required for overcoming Brownian forces, a hierarchical pattern consisting of composite particles will form. The work was supported by National Science Foundation.

  17. Two-way self-consistent simulation of the inner magnetosphere driven by realistic electric and magnetic fields

    NASA Astrophysics Data System (ADS)

    Ilie, Raluca; Liemohn, Michael; Toth, Gabor

    2014-05-01

    The geomagnetic storm of August 6, 2011 is examined using the two-way self consistent coupling between the kinetic Hot Electron and Ion Drift Integrator (HEIDI) model, the Block Adaptive Tree Solar Wind Roes-Type Scheme (BATS-R-US) MHD model and the Ridley Ionospheric Model (RIM) through the Space Weather Modeling Framework (SWMF). HEIDI solves the time dependent, gyration and bounce-averaged kinetic equation for the phase space density of different ring current species and computes full pitch angle distributions for all local times and radial distances. This model was generalized to accommodate arbitrary magnetic fields and through the coupling with the SWMF it obtains magnetic field description along with plasma distribution at the model boundaries from the BATS-R-US model within the SWMF. Electric field self-consistency is assured by the passing of convection potentials from the Ridley Ionosphere Model (RIM) within SWMF. Our study tests the various levels of coupling between the three models, highlighting the role the magnetic field, plasma sheet conditions and the cross polar cap potential play in the formation and evolution of the ring current. We use the results of the coupled HEIDI, BATSRUS and RIM models during disturbed conditions to study the importance of a kinetic self-consistent approach to the description of geospace.

  18. Electric-Field-Driven Dual Vacancies Evolution in Ultrathin Nanosheets Realizing Reversible Semiconductor to Half-Metal Transition.

    PubMed

    Lyu, Mengjie; Liu, Youwen; Zhi, Yuduo; Xiao, Chong; Gu, Bingchuan; Hua, Xuemin; Fan, Shaojuan; Lin, Yue; Bai, Wei; Tong, Wei; Zou, Youming; Pan, Bicai; Ye, Bangjiao; Xie, Yi

    2015-12-02

    Fabricating a flexible room-temperature ferromagnetic resistive-switching random access memory (RRAM) device is of fundamental importance to integrate nonvolatile memory and spintronics both in theory and practice for modern information technology and has the potential to bring about revolutionary new foldable information-storage devices. Here, we show that a relatively low operating voltage (+1.4 V/-1.5 V, the corresponding electric field is around 20,000 V/cm) drives the dual vacancies evolution in ultrathin SnO2 nanosheets at room temperature, which causes the reversible transition between semiconductor and half-metal, accompanyied by an abrupt conductivity change up to 10(3) times, exhibiting room-temperature ferromagnetism in two resistance states. Positron annihilation spectroscopy and electron spin resonance results show that the Sn/O dual vacancies in the ultrathin SnO2 nanosheets evolve to isolated Sn vacancy under electric field, accounting for the switching behavior of SnO2 ultrathin nanosheets; on the other hand, the different defect types correspond to different conduction natures, realizing the transition between semiconductor and half-metal. Our result represents a crucial step to create new a information-storage device realizing the reversible transition between semiconductor and half-metal with flexibility and room-temperature ferromagnetism at low energy consumption. The as-obtained half-metal in the low-resistance state broadens the application of the device in spintronics and the semiconductor to half-metal transition on the basis of defects evolution and also opens up a new avenue for exploring random access memory mechanisms and finding new half-metals for spintronics.

  19. Electrically driven phase transition in magnetite nanostructures.

    PubMed

    Lee, Sungbae; Fursina, Alexandra; Mayo, John T; Yavuz, Cafer T; Colvin, Vicki L; Sofin, R G Sumesh; Shvets, Igor V; Natelson, Douglas

    2008-02-01

    Magnetite (Fe3O4), an archetypal transition-metal oxide, has been used for thousands of years, from lodestones in primitive compasses to a candidate material for magnetoelectronic devices. In 1939, Verwey found that bulk magnetite undergoes a transition at TV approximately 120 K from a high-temperature 'bad metal' conducting phase to a low-temperature insulating phase. He suggested that high-temperature conduction is through the fluctuating and correlated valences of the octahedral iron atoms, and that the transition is the onset of charge ordering on cooling. The Verwey transition mechanism and the question of charge ordering remain highly controversial. Here, we show that magnetite nanocrystals and single-crystal thin films exhibit an electrically driven phase transition below the Verwey temperature. The signature of this transition is the onset of sharp conductance switching in high electric fields, hysteretic in voltage. We demonstrate that this transition is not due to local heating, but instead is due to the breakdown of the correlated insulating state when driven out of equilibrium by electrical bias. We anticipate that further studies of this newly observed transition and its low-temperature conducting phase will shed light on how charge ordering and vibrational degrees of freedom determine the ground state of this important compound.

  20. Electrically driven phase transition in magnetite nanostructures

    NASA Astrophysics Data System (ADS)

    Lee, Sungbae; Fursina, Alexandra; Mayo, John T.; Yavuz, Cafer T.; Colvin, Vicki L.; Sumesh Sofin, R. G.; Shvets, Igor V.; Natelson, Douglas

    2008-02-01

    Magnetite (Fe3O4), an archetypal transition-metal oxide, has been used for thousands of years, from lodestones in primitive compasses to a candidate material for magnetoelectronic devices. In 1939, Verwey found that bulk magnetite undergoes a transition at TV~120K from a high-temperature `bad metal' conducting phase to a low-temperature insulating phase. He suggested that high-temperature conduction is through the fluctuating and correlated valences of the octahedral iron atoms, and that the transition is the onset of charge ordering on cooling. The Verwey transition mechanism and the question of charge ordering remain highly controversial. Here, we show that magnetite nanocrystals and single-crystal thin films exhibit an electrically driven phase transition below the Verwey temperature. The signature of this transition is the onset of sharp conductance switching in high electric fields, hysteretic in voltage. We demonstrate that this transition is not due to local heating, but instead is due to the breakdown of the correlated insulating state when driven out of equilibrium by electrical bias. We anticipate that further studies of this newly observed transition and its low-temperature conducting phase will shed light on how charge ordering and vibrational degrees of freedom determine the ground state of this important compound.

  1. Resonances and energy trapping in AT-cut quartz resonators operating with fast shear modes driven by lateral electric fields produced by surface electrodes.

    PubMed

    Ma, Tingfeng; Wang, Ji; Du, Jianke; Yang, Jiashi

    2015-05-01

    We analyze coupled thickness-shear and extensional vibrations of a piezoelectric resonator of AT-cut quartz. Different from most of the AT-cut quartz resonators studied in the literature which are based on the slow shear mode excited by a thickness electric field, the resonator in this paper operates with the fast shear mode driven by a lateral electric field produced by a pair of electrodes on the top surface of the resonator. Mindlin's first-order theory of piezoelectric plates is used. Dispersion relations of the relevant waves in unelectroded and electroded plates are presented and compared. The motional capacitance, resonant frequencies and mode shapes near resonances are obtained from an electrically forced vibration analysis. Trapped modes without vibration near the resonator edges are identified. The effects of various structural parameters on energy trapping are examined and the mechanisms are discussed. The results can provide important bases for the parameters design of new resonators operating with the fast shear mode with new excitation schemes. Copyright © 2015 Elsevier B.V. All rights reserved.

  2. Experimental evidence of edge intrinsic momentum source driven by kinetic ion loss and edge radial electric fields in tokamaks

    NASA Astrophysics Data System (ADS)

    Boedo, J. A.; deGrassie, J. S.; Grierson, B.; Stoltzfus-Dueck, T.; Battaglia, D. J.; Rudakov, D. L.; Belli, E. A.; Groebner, R. J.; Hollmann, E.; Lasnier, C.; Solomon, W. M.; Unterberg, E. A.; Watkins, J.

    2016-09-01

    Bulk ion toroidal velocity profiles, V| | D + , peaking at 40-60 km/s are observed with Mach probes in a narrow edge region of DIII-D discharges without external momentum input. This intrinsic rotation can be well reproduced by a first principle, collisionless kinetic loss model of thermal ion loss that predicts the existence of a loss-cone distribution in velocity space resulting in a co-Ip directed velocity. We consider two kinetic models, one of which includes turbulence-enhanced momentum transport, as well as the Pfirsch-Schluter (P-S) fluid mechanism. We measure a fine structure of the boundary radial electric field, Er, insofar ignored, featuring large (10-20 kV/m) positive peaks in the scrape off layer (SOL) at, or slightly inside, the last closed flux surface of these low power L- and H-mode discharges in DIII-D. The Er structure significantly affects the ion-loss model, extended to account for a non-uniform electric field. We also find that V| | D + is reduced when the magnetic topology is changed from lower single null to upper single null. The kinetic ion loss model containing turbulence-enhanced momentum transport can explain the reduction, as we find that the potential fluctuations decay with radius, while we need to invoke a topology-enhanced collisionality on the simpler kinetic model. The P-S mechanism fails to reproduce the damping. We show a clear correlation between the near core V| | C 6 + velocity and the peak edge V| | D + in discharges with no external torque, further supporting the hypothesis that ion loss is the source for intrinsic torque in the present tokamaks. However, we also show that when external torque is injected in the core, it can complete with, and eventually overwhelm, the edge source, thus determining the near SOL flows. Finally, we show some additional evidence that the ion/electron distribution in the SOL is non-Maxwellian.

  3. Experimental evidence of edge intrinsic momentum source driven by kinetic ion loss and edge radial electric fields in tokamaks

    SciTech Connect

    Boedo, J. A.; deGrassie, J. S.; Grierson, B.; Stoltzfus-Dueck, T.; Battaglia, D. J.; Rudakov, D. L.; Belli, E. A.; Groebner, R. J.; Hollmann, E.; Lasnier, C.; Solomon, W. M.; Unterberg, E. A.; Watkins, J.

    2016-09-21

    Here, bulk ion toroidal velocity profiles, VD+||, peaking at 40–60 km/s are observed with Mach probes in a narrow edge region of DIII-D discharges without external momentum input. This intrinsic rotation can be well reproduced by a first principle, collisionless kinetic loss model of thermal ion loss that predicts the existence of a loss-cone distribution in velocity space resulting in a co-Ip directed velocity. We consider two kinetic models, one of which includes turbulence-enhanced momentum transport, as well as the Pfirsch-Schluter (P-S) fluid mechanism. We measure a fine structure of the boundary radial electric field, Er, insofar ignored, featuring large (10–20 kV/m) positive peaks in the scrape off layer (SOL) at, or slightly inside, the last closed flux surface of these low power L- and H-mode discharges in DIII-D. The Er structure significantly affects the ion-loss model, extended to account for a non-uniform electric field. We also find that VD+|| is reduced when the magnetic topology is changed from lower single null to upper single null. The kinetic ion loss model containing turbulence-enhanced momentum transport can explain the reduction, as we find that the potential fluctuations decay with radius, while we need to invoke a topology-enhanced collisionality on the simpler kinetic model. The P-S mechanism fails to reproduce the damping. We show a clear correlation between the near core VC6+|| velocity and the peak edge VD+|| in discharges with no external torque, further supporting the hypothesis that ion loss is the source for intrinsic torque in the present tokamaks. However, we also show that when external torque is injected in the core, it can complete with, and eventually overwhelm, the edge source, thus determining the near SOL flows. Finally, we show some additional evidence that the ion/electron distribution in the SOL is non-Maxwellian.

  4. Experimental evidence of edge intrinsic momentum source driven by kinetic ion loss and edge radial electric fields in tokamaks

    DOE PAGES

    Boedo, J. A.; deGrassie, J. S.; Grierson, B.; ...

    2016-09-21

    Here, bulk ion toroidal velocity profiles, VD+||, peaking at 40–60 km/s are observed with Mach probes in a narrow edge region of DIII-D discharges without external momentum input. This intrinsic rotation can be well reproduced by a first principle, collisionless kinetic loss model of thermal ion loss that predicts the existence of a loss-cone distribution in velocity space resulting in a co-Ip directed velocity. We consider two kinetic models, one of which includes turbulence-enhanced momentum transport, as well as the Pfirsch-Schluter (P-S) fluid mechanism. We measure a fine structure of the boundary radial electric field, Er, insofar ignored, featuring largemore » (10–20 kV/m) positive peaks in the scrape off layer (SOL) at, or slightly inside, the last closed flux surface of these low power L- and H-mode discharges in DIII-D. The Er structure significantly affects the ion-loss model, extended to account for a non-uniform electric field. We also find that VD+|| is reduced when the magnetic topology is changed from lower single null to upper single null. The kinetic ion loss model containing turbulence-enhanced momentum transport can explain the reduction, as we find that the potential fluctuations decay with radius, while we need to invoke a topology-enhanced collisionality on the simpler kinetic model. The P-S mechanism fails to reproduce the damping. We show a clear correlation between the near core VC6+|| velocity and the peak edge VD+|| in discharges with no external torque, further supporting the hypothesis that ion loss is the source for intrinsic torque in the present tokamaks. However, we also show that when external torque is injected in the core, it can complete with, and eventually overwhelm, the edge source, thus determining the near SOL flows. Finally, we show some additional evidence that the ion/electron distribution in the SOL is non-Maxwellian.« less

  5. Experimental evidence of edge intrinsic momentum source driven by kinetic ion loss and edge radial electric fields in tokamaks

    SciTech Connect

    Boedo, J. A.; deGrassie, J. S.; Grierson, B.; Stoltzfus-Dueck, T.; Battaglia, D. J.; Rudakov, D. L.; Belli, E. A.; Groebner, R. J.; Hollmann, E.; Lasnier, C.; Solomon, W. M.; Unterberg, E. A.; Watkins, J.

    2016-09-01

    Bulk ion toroidal velocity profiles, V|| D+ , peaking at 40-60 km/s are observed with Mach probes in a narrow edge region of DIII-D discharges without external momentum input. This intrinsic rotation can be well reproduced by a first principle, collisionless kinetic loss model of thermal ion loss that predicts the existence of a loss-cone distribution in velocity space resulting in a co-Ip directed velocity. We consider two kinetic models, one of which includes turbulence-enhanced momentum transport, as well as a third, the Pfirsch-Schluter (P-S) fluid mechanism. We measure a fine structure of the boundary radial electric field, Er, previously ignored, featuring large (10–20 kV/m) positive peaks in the scrape off layer (SOL) at, or slightly inside, the last closed flux 2 surface (LCFS) of these low power L- and H-mode discharges in DIII-D. The Er structure significantly affects the ion-loss model, extended to account for a non-uniform electric field. We also find that V|| D+ is reduced when the magnetic topology is changed from lower single null (LSN) to upper single null (USN). The kinetic ion loss model containing turbulence-enhanced momentum transport can explain the reduction, as we find that the potential fluctuation profile differs between USN and LSN discharges, while we need to invoke a topology-enhanced collisionality on the simpler kinetic model. The P-S mechanism fails to reproduce the damping. We show a clear correlation between the near core V|| C6+ velocity and the peak edge V|| D+ in discharges with no external torque, further supporting the hypothesis that ion loss is the source for intrinsic torque in present tokamaks. However, we also show that when external torque is injected in the core, it can compete with, and eventually overwhelm, the edge source. Finally, we show some additional evidence that the ion/electron distribution in the SOL is non-Maxwellian.

  6. Experimental evidence of edge intrinsic momentum source driven by kinetic ion loss and edge radial electric fields in tokamaks

    SciTech Connect

    Boedo, J. A.; deGrassie, J. S.; Grierson, B.; Stoltzfus-Dueck, T.; Battaglia, D. J.; Rudakov, D. L.; Belli, E. A.; Groebner, R. J.; Hollmann, E.; Lasnier, C.; Solomon, W. M.; Unterberg, E. A.; Watkins, J.

    2016-09-21

    Here, bulk ion toroidal velocity profiles, VD+||, peaking at 40–60 km/s are observed with Mach probes in a narrow edge region of DIII-D discharges without external momentum input. This intrinsic rotation can be well reproduced by a first principle, collisionless kinetic loss model of thermal ion loss that predicts the existence of a loss-cone distribution in velocity space resulting in a co-Ip directed velocity. We consider two kinetic models, one of which includes turbulence-enhanced momentum transport, as well as the Pfirsch-Schluter (P-S) fluid mechanism. We measure a fine structure of the boundary radial electric field, Er, insofar ignored, featuring large (10–20 kV/m) positive peaks in the scrape off layer (SOL) at, or slightly inside, the last closed flux surface of these low power L- and H-mode discharges in DIII-D. The Er structure significantly affects the ion-loss model, extended to account for a non-uniform electric field. We also find that VD+|| is reduced when the magnetic topology is changed from lower single null to upper single null. The kinetic ion loss model containing turbulence-enhanced momentum transport can explain the reduction, as we find that the potential fluctuations decay with radius, while we need to invoke a topology-enhanced collisionality on the simpler kinetic model. The P-S mechanism fails to reproduce the damping. We show a clear correlation between the near core VC6+|| velocity and the peak edge VD+|| in discharges with no external torque, further supporting the hypothesis that ion loss is the source for intrinsic torque in the present tokamaks. However, we also show that when external torque is injected in the core, it can complete with, and eventually overwhelm, the edge source, thus determining the near SOL flows. Finally, we show some additional evidence that the ion/electron distribution in the SOL is non-Maxwellian.

  7. Experimental evidence of edge intrinsic momentum source driven by kinetic ion loss and edge radial electric fields in tokamaks

    DOE PAGES

    Boedo, J. A.; deGrassie, J. S.; Grierson, B.; ...

    2016-09-21

    Here, bulk ion toroidal velocity profiles, VD+||, peaking at 40–60 km/s are observed with Mach probes in a narrow edge region of DIII-D discharges without external momentum input. This intrinsic rotation can be well reproduced by a first principle, collisionless kinetic loss model of thermal ion loss that predicts the existence of a loss-cone distribution in velocity space resulting in a co-Ip directed velocity. We consider two kinetic models, one of which includes turbulence-enhanced momentum transport, as well as the Pfirsch-Schluter (P-S) fluid mechanism. We measure a fine structure of the boundary radial electric field, Er, insofar ignored, featuring largemore » (10–20 kV/m) positive peaks in the scrape off layer (SOL) at, or slightly inside, the last closed flux surface of these low power L- and H-mode discharges in DIII-D. The Er structure significantly affects the ion-loss model, extended to account for a non-uniform electric field. We also find that VD+|| is reduced when the magnetic topology is changed from lower single null to upper single null. The kinetic ion loss model containing turbulence-enhanced momentum transport can explain the reduction, as we find that the potential fluctuations decay with radius, while we need to invoke a topology-enhanced collisionality on the simpler kinetic model. The P-S mechanism fails to reproduce the damping. We show a clear correlation between the near core VC6+|| velocity and the peak edge VD+|| in discharges with no external torque, further supporting the hypothesis that ion loss is the source for intrinsic torque in the present tokamaks. However, we also show that when external torque is injected in the core, it can complete with, and eventually overwhelm, the edge source, thus determining the near SOL flows. Finally, we show some additional evidence that the ion/electron distribution in the SOL is non-Maxwellian.« less

  8. Experimental evidence of edge intrinsic momentum source driven by kinetic ion loss and edge radial electric fields in tokamaks

    DOE PAGES

    Boedo, J. A.; deGrassie, J. S.; Grierson, B.; ...

    2016-09-01

    Bulk ion toroidal velocity profiles, V|| D+ , peaking at 40-60 km/s are observed with Mach probes in a narrow edge region of DIII-D discharges without external momentum input. This intrinsic rotation can be well reproduced by a first principle, collisionless kinetic loss model of thermal ion loss that predicts the existence of a loss-cone distribution in velocity space resulting in a co-Ip directed velocity. We consider two kinetic models, one of which includes turbulence-enhanced momentum transport, as well as a third, the Pfirsch-Schluter (P-S) fluid mechanism. We measure a fine structure of the boundary radial electric field, Er, previouslymore » ignored, featuring large (10–20 kV/m) positive peaks in the scrape off layer (SOL) at, or slightly inside, the last closed flux 2 surface (LCFS) of these low power L- and H-mode discharges in DIII-D. The Er structure significantly affects the ion-loss model, extended to account for a non-uniform electric field. We also find that V|| D+ is reduced when the magnetic topology is changed from lower single null (LSN) to upper single null (USN). The kinetic ion loss model containing turbulence-enhanced momentum transport can explain the reduction, as we find that the potential fluctuation profile differs between USN and LSN discharges, while we need to invoke a topology-enhanced collisionality on the simpler kinetic model. The P-S mechanism fails to reproduce the damping. We show a clear correlation between the near core V|| C6+ velocity and the peak edge V|| D+ in discharges with no external torque, further supporting the hypothesis that ion loss is the source for intrinsic torque in present tokamaks. However, we also show that when external torque is injected in the core, it can compete with, and eventually overwhelm, the edge source. Finally, we show some additional evidence that the ion/electron distribution in the SOL is non-Maxwellian.« less

  9. Pulsed electric fields

    USDA-ARS?s Scientific Manuscript database

    The concept of pulsed electric fields (PEF) was first proposed in 1967 to change the behavior or microorganisms. The electric field phenomenon was identified as membrane rupture theory in the 1980s. Increasing the membrane permeability led to the application of PEF assisted extraction of cellular co...

  10. Electrically Driven Polariton Light Emitting Devices

    NASA Astrophysics Data System (ADS)

    Tsintzos, Simeon I.; Pelekanos, Nikolaos T.; Savvidis, Pavlos G.

    The aim of this chapter is to highlight the recent progress in the rapidly developing field of electrically driven polariton devices. The unprecedented potential of polariton-based devices owes its origin mainly to the bosonic property of polaritons to condense in the same final state, thus requiring no population inversion to achieve lasing. Consequently, it is widely believed that the threshold of a polariton laser is at least two orders of magnitude lower than that of a conventional semiconductor photon laser operating in the weak-coupling regime [C. Weisbuch, M. Nishioka, A. Ishikawa, Y. Arakawa, Phys. Rev. Lett. 69, 3314-3317 (1992)]. This makes polariton lasers extremely promising as ultralow threshold lasers or as low-power sources of coherent and nonclassical light. Electrical injection of these entangled light-matter states is a key step toward the realisation of practical, compact devices. Recent demonstrations of electrically pumped polariton LEDs in organic as well as inorganic material systems operating up to room temperature have highlighted the potential of such devices for real-world polariton-based applications in optoelectronics.

  11. Distillation under electric fields

    SciTech Connect

    Shah, V.M.; Blankenship, K.D.; Tsouris, C.

    1997-11-01

    Distillation Is the most common separation process used in the chemical and petroleum industry. Major limitations in the applicability and efficiency of distillation come from thermodynamic equilibria, that is, vapor-liquid equilibria (VLE), and heat and mass transfer rates. In this work, electric fields are used to manipulate the VLE of mixtures. VLE experiments are performed for various binary mixtures in the presence of electric fields on the order of a few kilovolts per centimeter. The results show that the VLE is changed by electric fields, with changes in the separation factor as high as 10% being observed. Batch distillation experiments are also carried out for binary mixtures of 2-propanol and water with and without an applied electric field. Results show enhanced distillation rates and separation efficiency in the presence of an electric field but decreased separation enhancement when the electric current is increased. The latter phenomenon is caused by the formation at the surface of the liquid mixture of microdroplets that are entrained by the vapor. These observations suggest that there should be an electric field strength for each system for which the separation enhancement is maximum.

  12. Advances in Electrically Driven Thermal Management

    NASA Technical Reports Server (NTRS)

    Didion, Jeffrey R.

    2017-01-01

    Electrically Driven Thermal Management is a vibrant technology development initiative incorporating ISS based technology demonstrations, development of innovative fluid management techniques and fundamental research efforts. The program emphasizes high temperature high heat flux thermal management required for future generations of RF electronics and power electronic devices. This presentation reviews i.) preliminary results from the Electrohydrodynamic (EHD) Long Term Flight Demonstration launched on STP-H5 payload in February 2017 ii.) advances in liquid phase flow distribution control iii.) development of the Electrically Driven Liquid Film Boiling Experiment under the NASA Microgravity Fluid Physics Program.

  13. Light-field-driven currents in graphene.

    PubMed

    Higuchi, Takuya; Heide, Christian; Ullmann, Konrad; Weber, Heiko B; Hommelhoff, Peter

    2017-09-25

    The ability to steer electrons using the strong electromagnetic field of light has opened up the possibility of controlling electron dynamics on the sub-femtosecond (less than 10(-15) seconds) timescale. In dielectrics and semiconductors, various light-field-driven effects have been explored, including high-harmonic generation, sub-optical-cycle interband population transfer and the non-perturbative change of the transient polarizability. In contrast, much less is known about light-field-driven electron dynamics in narrow-bandgap systems or in conductors, in which screening due to free carriers or light absorption hinders the application of strong optical fields. Graphene is a promising platform with which to achieve light-field-driven control of electrons in a conducting material, because of its broadband and ultrafast optical response, weak screening and high damage threshold. Here we show that a current induced in monolayer graphene by two-cycle laser pulses is sensitive to the electric-field waveform, that is, to the exact shape of the optical carrier field of the pulse, which is controlled by the carrier-envelope phase, with a precision on the attosecond (10(-18) seconds) timescale. Such a current, dependent on the carrier-envelope phase, shows a striking reversal of the direction of the current as a function of the driving field amplitude at about two volts per nanometre. This reversal indicates a transition of light-matter interaction from the weak-field (photon-driven) regime to the strong-field (light-field-driven) regime, where the intraband dynamics influence interband transitions. We show that in this strong-field regime the electron dynamics are governed by sub-optical-cycle Landau-Zener-Stückelberg interference, composed of coherent repeated Landau-Zener transitions on the femtosecond timescale. Furthermore, the influence of this sub-optical-cycle interference can be controlled with the laser polarization state. These coherent electron dynamics in

  14. Electric field divertor plasma pump

    DOEpatents

    Schaffer, M.J.

    1994-10-04

    An electric field plasma pump includes a toroidal ring bias electrode positioned near the divertor strike point of a poloidal divertor of a tokamak, or similar plasma-confining apparatus. For optimum plasma pumping, the separatrix of the poloidal divertor contacts the ring electrode, which then also acts as a divertor plate. A plenum or other duct near the electrode includes an entrance aperture open to receive electrically-driven plasma. The electrode is insulated laterally with insulators, one of which is positioned opposite the electrode at the entrance aperture. An electric field E is established between the ring electrode and a vacuum vessel wall, with the polarity of the bias applied to the electrode being relative to the vessel wall selected such that the resultant electric field E interacts with the magnetic field B already existing in the tokamak to create an E [times] B/B[sup 2] drift velocity that drives plasma into the entrance aperture. The pumped plasma flow into the entrance aperture is insensitive to variations, intentional or otherwise, of the pump and divertor geometry. Pressure buildups in the plenum or duct connected to the entrance aperture in excess of 10 mtorr are achievable. 11 figs.

  15. Electric field divertor plasma pump

    DOEpatents

    Schaffer, Michael J.

    1994-01-01

    An electric field plasma pump includes a toroidal ring bias electrode (56) positioned near the divertor strike point of a poloidal divertor of a tokamak (20), or similar plasma-confining apparatus. For optimum plasma pumping, the separatrix (40) of the poloidal divertor contacts the ring electrode (56), which then also acts as a divertor plate. A plenum (54) or other duct near the electrode (56) includes an entrance aperture open to receive electrically-driven plasma. The electrode (56) is insulated laterally with insulators (63,64), one of which (64) is positioned opposite the electrode at the entrance aperture. An electric field E is established between the ring electrode (56) and a vacuum vessel wall (22), with the polarity of the bias applied to the electrode being relative to the vessel wall selected such that the resultant electric field E interacts with the magnetic field B already existing in the tokamak to create an E.times.B/B.sup.2 drift velocity that drives plasma into the entrance aperture. The pumped plasma flow into the entrance aperture is insensitive to variations, intentional or otherwise, of the pump and divertor geometry. Pressure buildups in the plenum or duct connected to the entrance aperture in excess of 10 mtorr are achievable.

  16. Field-aligned currents and large scale magnetospheric electric fields

    NASA Technical Reports Server (NTRS)

    Dangelo, N.

    1980-01-01

    D'Angelo's model of polar cap electric fields (1977) was used to visualize how high-latitude field-aligned currents are driven by the solar wind generator. The region 1 and region 2 currents of Iijima and Potemra (1976) and the cusp field-aligned currents of Wilhjelm et al. (1978) and McDiarmid et al. (1978) are apparently driven by different generators, although in both cases the solar wind is their ultimate source.

  17. Electrically driven and electrically tunable quantum light sources

    NASA Astrophysics Data System (ADS)

    Lee, J. P.; Murray, E.; Bennett, A. J.; Ellis, D. J. P.; Dangel, C.; Farrer, I.; Spencer, P.; Ritchie, D. A.; Shields, A. J.

    2017-02-01

    Compact and electrically controllable on-chip sources of indistinguishable photons are desirable for the development of integrated quantum technologies. We demonstrate that two quantum dot light emitting diodes (LEDs) in close proximity on a single chip can function as a tunable, all-electric quantum light source. Light emitted by an electrically excited driving LED is used to excite quantum dots in the neighbouring diode. The wavelength of the quantum dot emission from the neighbouring driven diode is tuned via the quantum confined Stark effect. We also show that we can electrically tune the fine structure splitting.

  18. FIREX project and effects of self-generated electric and magnetic fields on electron-driven fast ignition

    NASA Astrophysics Data System (ADS)

    Mima, Kunioki; Sunahara, A.; Shiraga, Hiroyuki; Nishimura, H.; Azechi, H.; Nakamura, T.; Johzaki, T.; Nagatomo, H.; Garcia, C.; Velarde, P.

    2010-12-01

    Fast ignition is a new scheme in laser fusion, in which higher energy gain with a smaller laser pulse energy is expected. A cone target has been introduced for realizing higher coupling efficiency. At ILE, Osaka University, a laser with four beams and a total output of 10 kJ ps-1, laser for fast ignition experiment (LFEX), has been constructed and we have carried out an integrated experiment with one beam of the LFEX. Through experiments it was found that the coupling efficiency is degraded when the laser pre-pulse is not sufficiently small. Namely, the main pulse is absorbed in the long-scale pre-plasma produced by the pre-pulse and the hot electron energy is higher than that for a clean pulse. Furthermore, the distance between the hot electron source and the core plasma is large. Hence, we are exploring how to overcome the pre-pulse effects on the cone target. In this paper it is proposed that a thin foil covers the laser entrance of the cone to mitigate the pre-plasma and a double cone reduces the loss of high-energy electrons from the side wall of the cone. The simulations indicate that a higher coupling efficiency is expected for the double cone target with a thin foil at the laser entrance. Namely, the pre-pulse will be absorbed by the foil and the electromagnetic fields generated on the surface of the inner cone will confine high-energy electrons.

  19. Enhanced laser-radiation-pressure-driven proton acceleration by moving focusing electric-fields in a foil-in-cone target

    SciTech Connect

    Zou, D. B.; Zhuo, H. B. Yu, T. P.; Yang, X. H.; Shao, F. Q.; Ma, Y. Y.; Yin, Y.; Ge, Z. Y.; Wu, H. C.

    2015-02-15

    A foil-in-cone target is proposed to enhance stable laser-radiation-pressure-driven proton acceleration by avoiding the beam degradation in whole stage of acceleration. Two and three-dimensional particle-in-cell simulations demonstrate that the guiding cone can substantially improve the spectral and spatial properties of the ion beam and lead to better preservation of the beam quality. This can be attributed to the focusing effect of the radial sheath electric fields formed on the inner walls of the cone, which co-move with the accelerated foil and effectively suppress the undesirable transverse explosion of the foil. It is shown that, by using a transversely Gaussian laser pulse with intensity of ∼2.74 × 10{sup 22 }W∕cm{sup 2}, a quasi-monoenergetic proton beam with a peak energy of ∼1.5 GeV/u, density ∼10n{sub c}, and transverse size ∼1λ{sub 0} can be obtained.

  20. FIREX Project and Effects of Self-generated Electric and Magnetic Fields on Electron Driven Fast Ignition

    NASA Astrophysics Data System (ADS)

    Mima, Kunioki; Sunahara, A.; Shiraga, Hiroyuki; Nishimura, H.; Azechi, H.; Johzaki, T.; Nagatomo, H.; Garcia, C.; Veralde, P.

    2010-11-01

    The fast ignition is a new scheme in laser fusion, in which higher energy gain is expected with smaller laser pulse energy. The cone target has been introduced for realizing higher coupling efficiency. At ILE, Osaka University, the laser with 4 beams and the total output of 10kJ/ps: LFEX has been built and we have started the integrated experiments. The experiments showed that the coupling efficiency is degraded because of the laser pre-pulse. Namely, the main pulse is absorbed in a long scale pre-plasma produced by the pre-pulse and hot electron energy is higher than that for a clean pulse. Furthermore, the distance between the hot electron source and the core plasma is long. So, we are exploring how to overcome the pre-pulse effects on the cone target. The next series of experiments is planned for this fall. In these experiments, the LFEX pre-pulse level will be reduced and advanced targets for mitigating the pre-pulse effects will be introduced. In this paper, it is proposed that a thin foil cover the laser entrance of a cone to mitigate the pre-plasma and a double cone reduce loss of high energy electrons from the side wall of the cone. The simulations indicate that higher coupling efficiency is expected for the double cone target with a thin foil on the laser entrance. Namely, the pre-pulse will be absorbed by the foil and the electro-magnetic fields generated on the surface of the inner cone will confine high energy electrons. The goal of the next series of experiments will be high coupling efficiency to heat a compressed plasma to temperatures higher than 2 keV.

  1. Electric and magnetic fields

    NASA Technical Reports Server (NTRS)

    Kaufman, H. R.; Robinson, R. S.; Etters, R. D.

    1982-01-01

    A number of energy momentum anomalies are described that result from the use of Abraham-Lorentz electromagnetic theory. These anomalies have in common the motion of charged bodies or current carrying conductors relative to the observer. The anomalies can be avoided by using the nonflow approach, based on internal energy of the electromagnetic field. The anomalies can also be avoided by using the flow approach, if all contributions to flow work are included. The general objective of this research is a fundamental physical understanding of electric and magnetic fields which, in turn, might promote the development of new concepts in electric space propulsion. The approach taken is to investigate quantum representations of these fields.

  2. Electronic properties of nanoentities revealed by electrically driven rotation

    PubMed Central

    Fan, D. L.; Zhu, Frank Q.; Xu, Xiaobin; Cammarata, Robert C.; Chien, C. L.

    2012-01-01

    Direct electric measurement via small contacting pads on individual quasi-one-dimensional nanoentities, such as nanowires and carbon nanotubes, are usually required to access its electronic properties. We show in this work that 1D nanoentities in suspension can be driven to rotation by AC electric fields. The chirality of the resultantrotation unambiguously reveals whether the nanoentities are metal, semiconductor, or insulator due to the dependence of the Clausius–Mossotti factor on the material conductivity and frequency. This contactless method provides rapid and parallel identification of the electrical characteristics of 1D nanoentities. PMID:22645373

  3. Electric field imaging

    NASA Astrophysics Data System (ADS)

    Smith, Joshua Reynolds

    The physical user interface is an increasingly significant factor limiting the effectiveness of our interactions with and through technology. This thesis introduces Electric Field Imaging, a new physical channel and inference framework for machine perception of human action. Though electric field sensing is an important sensory modality for several species of fish, it has not been seriously explored as a channel for machine perception. Technological applications of field sensing, from the Theremin to the capacitive elevator button, have been limited to simple proximity detection tasks. This thesis presents a solution to the inverse problem of inferring geometrical information about the configuration and motion of the human body from electric field measurements. It also presents simple, inexpensive hardware and signal processing techniques for makin the field measurements, and several new applications of electric field sensing. The signal processing contribution includes synchronous undersampling, a narrowband, phase sensitive detection technique that is well matched to the capabilities of contemporary microcontrollers. In hardware, the primary contributions are the School of Fish, a scalable network of microcontroller-based transceive electrodes, and the LazyFish, a small footprint integrated sensing board. Connecting n School of Fish electrodes results in an array capable of making heterodyne measurements of any or all n(n - 1) off-diagonal entries in the capacitance matrix. The LazyFish uses synchronous undersampling to provide up to 8 high signal- to-noise homodyne measurements in a very small package. The inverse electrostatics portion of the thesis presents a fast, general method for extracting geometrical information about the configuration and motion of the human body from field measurements. The method is based on the Sphere Expansion, a novel fast method for generating approximate solutions to the Laplace equation. Finally, the thesis describes a variety

  4. Electrically Driven Technologies for Radioactive Aerosol Abatement

    SciTech Connect

    David W. DePaoli; Ofodike A. Ezekoye; Costas Tsouris; Valmor F. de Almeida

    2003-01-28

    The purpose of this research project was to develop an improved understanding of how electriexecy driven processes, including electrocoalescence, acoustic agglomeration, and electric filtration, may be employed to efficiently treat problems caused by the formation of aerosols during DOE waste treatment operations. The production of aerosols during treatment and retrieval operations in radioactive waste tanks and during thermal treatment operations such as calcination presents a significant problem of cost, worker exposure, potential for release, and increased waste volume.

  5. Skyrmion motion driven by oscillating magnetic field

    PubMed Central

    Moon, Kyoung-Woong; Kim, Duck-Ho; Je, Soong-Geun; Chun, Byong Sun; Kim, Wondong; Qiu, Z.Q.; Choe, Sug-Bong; Hwang, Chanyong

    2016-01-01

    The one-dimensional magnetic skyrmion motion induced by an electric current has attracted much interest because of its application potential in next-generation magnetic memory devices. Recently, the unidirectional motion of large (20 μm in diameter) magnetic bubbles with two-dimensional skyrmion topology, driven by an oscillating magnetic field, has also been demonstrated. For application in high-density memory devices, it is preferable to reduce the size of skyrmion. Here we show by numerical simulation that a skyrmion of a few tens of nanometres can also be driven by high-frequency field oscillations, but with a different direction of motion from the in-plane component of the tilted oscillating field. We found that a high-frequency field for small skyrmions can excite skyrmion resonant modes and that a combination of different modes results in a final skyrmion motion with a helical trajectory. Because this helical motion depends on the frequency of the field, we can control both the speed and the direction of the skyrmion motion, which is a distinguishable characteristic compared with other methods. PMID:26847334

  6. Electric potential and electric field imaging

    NASA Astrophysics Data System (ADS)

    Generazio, E. R.

    2017-02-01

    The technology and methods for remote quantitative imaging of electrostatic potentials and electrostatic fields in and around objects and in free space is presented. Electric field imaging (EFI) technology may be applied to characterize intrinsic or existing electric potentials and electric fields, or an externally generated electrostatic field made be used for "illuminating" volumes to be inspected with EFI. The baseline sensor technology (e-Sensor) and its construction, optional electric field generation (quasi-static generator), and current e-Sensor enhancements (ephemeral e-Sensor) are discussed. Demonstrations for structural, electronic, human, and memory applications are shown. This new EFI capability is demonstrated to reveal characterization of electric charge distribution creating a new field of study embracing areas of interest including electrostatic discharge (ESD) mitigation, crime scene forensics, design and materials selection for advanced sensors, dielectric morphology of structures, tether integrity, organic molecular memory, and medical diagnostic and treatment efficacy applications such as cardiac polarization wave propagation and electromyography imaging.

  7. Development of an electrically driven molecular motor.

    PubMed

    Murphy, Colin J; Sykes, E Charles H

    2014-10-01

    For molecules to be used as components in molecular machinery, methods are required that couple individual molecules to external energy sources in order to selectively excite motion in a given direction. While significant progress has been made in the construction of synthetic molecular motors powered by light and by chemical reactions, there are few experimental examples of electrically driven molecular motors. To this end, we pioneered the use of a new, stable and tunable molecular rotor system based on surface-bound thioethers to comprehensively study many aspects of molecular rotation. As biological molecular motors often operate at interfaces, our synthetic system is especially amenable to microscopic interrogation as compared to solution-based systems. Using scanning tunneling microscopy (STM) and density functional theory, we studied the rotation of surface-bound thioethers, which can be induced either thermally or by electrons from the STM tip in a two-terminal setup. Moreover, the temperature and electron flux can be adjusted to allow each rotational event to be monitored at the molecular scale in real time. This work culminated in the first experimental demonstration of a single-molecule electric motor, where the electrically driven rotation of a butyl methyl sulfide molecule adsorbed on a copper surface could be directionally biased. The direction and rate of the rotation are related to the chirality of both the molecule and the STM tip (which serves as the electrode), illustrating the importance of the symmetry of the metal contacts in atomic-scale electrical devices.

  8. Electrically driven spin qubit based on valley mixing

    NASA Astrophysics Data System (ADS)

    Huang, Wister; Veldhorst, Menno; Zimmerman, Neil M.; Dzurak, Andrew S.; Culcer, Dimitrie

    2017-02-01

    The electrical control of single spin qubits based on semiconductor quantum dots is of great interest for scalable quantum computing since electric fields provide an alternative mechanism for qubit control compared with magnetic fields and can also be easier to produce. Here we outline the mechanism for a drastic enhancement in the electrically-driven spin rotation frequency for silicon quantum dot qubits in the presence of a step at a heterointerface. The enhancement is due to the strong coupling between the ground and excited states which occurs when the electron wave function overcomes the potential barrier induced by the interface step. We theoretically calculate single qubit gate times tπ of 170 ns for a quantum dot confined at a silicon/silicon-dioxide interface. The engineering of such steps could be used to achieve fast electrical rotation and entanglement of spin qubits despite the weak spin-orbit coupling in silicon.

  9. Thermalization of field driven quantum systems

    PubMed Central

    Fotso, H.; Mikelsons, K.; Freericks, J. K.

    2014-01-01

    There is much interest in how quantum systems thermalize after a sudden change, because unitary evolution should preclude thermalization. The eigenstate thermalization hypothesis resolves this because all observables for quantum states in a small energy window have essentially the same value; it is violated for integrable systems due to the infinite number of conserved quantities. Here, we show that when a system is driven by a DC electric field there are five generic behaviors: (i) monotonic or (ii) oscillatory approach to an infinite-temperature steady state; (iii) monotonic or (iv) oscillatory approach to a nonthermal steady state; or (v) evolution to an oscillatory state. Examining the Hubbard model (which thermalizes under a quench) and the Falicov-Kimball model (which does not), we find both exhibit scenarios (i–iv), while only Hubbard shows scenario (v). This shows richer behavior than in interaction quenches and integrability in the absence of a field plays no role. PMID:24736404

  10. Thermalization of field driven quantum systems

    NASA Astrophysics Data System (ADS)

    Fotso, H.; Mikelsons, K.; Freericks, J. K.

    2014-04-01

    There is much interest in how quantum systems thermalize after a sudden change, because unitary evolution should preclude thermalization. The eigenstate thermalization hypothesis resolves this because all observables for quantum states in a small energy window have essentially the same value; it is violated for integrable systems due to the infinite number of conserved quantities. Here, we show that when a system is driven by a DC electric field there are five generic behaviors: (i) monotonic or (ii) oscillatory approach to an infinite-temperature steady state; (iii) monotonic or (iv) oscillatory approach to a nonthermal steady state; or (v) evolution to an oscillatory state. Examining the Hubbard model (which thermalizes under a quench) and the Falicov-Kimball model (which does not), we find both exhibit scenarios (i-iv), while only Hubbard shows scenario (v). This shows richer behavior than in interaction quenches and integrability in the absence of a field plays no role.

  11. Graphene-contact electrically driven microdisk lasers

    PubMed Central

    Kim, Yoon-Ho; Kwon, Soon-Hong; Lee, Jung Min; Hwang, Min-Soo; Kang, Ju-Hyung; Park, Won Il; Park, Hong-Gyu

    2012-01-01

    Active nanophotonic devices are attractive due to their low-power consumption, ultrafast modulation speed and high-density integration. Although electrical operation is required for practical implementation of these devices, it is not straightforward to introduce a proper current path into such a wavelength-scale nanostructure without affecting the optical properties. For example, to demonstrate electrically driven nanolasers, complicated fabrication techniques have been used thus far. Here we report an electrically driven microdisk laser using a transparent graphene electrode. Current is injected efficiently through the graphene sheet covering the top surface of the microdisk cavity, and, for the first time, lasing operation was achieved with a low-threshold current of ~300 μA at room temperature. In addition, we measured significant electroluminescence from a graphene-contact subwavelength-scale single nanopillar structure. This work represents a new paradigm for the practical applications of integrated photonic systems, by conformally mounting graphene on the complex surfaces of non-planar three-dimensional nanostructures. PMID:23047681

  12. Overview - Electric fields. [in magnetosphere

    NASA Technical Reports Server (NTRS)

    Cauffman, D. P.

    1979-01-01

    The electric fields session is designed to review progress in observation, theory, and modeling of magnetospheric electric fields, and to expose important new results. The present report comments on the state and prospects of electric field research, with particular emphasis on relevance to quantitative modeling of the magnetospheric processes. Attention is given to underlying theories and models. Modeling philosophy is discussed relative to explanatory models and representative models. Modeling of magnetospheric electric fields, while in its infancy, is developing rapidly on many fronts employing a variety of approaches. The general topic of magnetospheric electric fields is becoming of prime importance in understanding space plasmas.

  13. Magnetospheric electric fields and currents

    NASA Technical Reports Server (NTRS)

    Mauk, B. H.; Zanetti, L. J.

    1987-01-01

    The progress made in the years 1983-1986 in understanding the character and operation of magnetospheric electric fields and electric currents is discussed, with emphasis placed on the connection with the interior regions. Special attention is given to determinations of global electric-field configurations, measurements of the response of magnetospheric particle populations to the electric-field configurations, and observations of the magnetospheric currents at high altitude and during northward IMF. Global simulations of current distributions are discussed, and the sources of global electric fields and currents are examined. The topics discussed in the area of impulsive and small-scale phenomena include substorm current systems, impulsive electric fields and associated currents, and field-aligned electrodynamics. A key finding of these studies is that the electric fields and currents are interrelated and cannot be viewed as separate entities.

  14. Repetitive control of electrically driven robot manipulators

    NASA Astrophysics Data System (ADS)

    Fateh, Mohammad Mehdi; Ahsani Tehrani, Hojjat; Karbassi, Seyed Mehdi

    2013-04-01

    This article presents a novel robust discrete repetitive control of electrically driven robot manipulators for tracking of a periodic trajectory. We propose a novel model, which presents the highly non-linear dynamics of robot manipulator in the form of linear discrete-time time-varying system. Based on the proposed model, we develop a two-term control law. The first term is an ordinary time-optimal and minimum-norm (TOMN) control by employing parametric controllers to guarantee stability. The second term is a novel robust control to improve the control performance in the face of uncertainties. The robust control estimates and compensates uncertainties including the parametric uncertainty, unmodelled dynamics and external disturbances. Performance of the proposed method is compared with two discrete methods, namely the TOMN control and an adaptive iterative learning (AIL) control. Simulation results confirm superiority of the proposed method in terms of the convergence speed and precision.

  15. Field-driven dynamics of nematic microcapillaries

    NASA Astrophysics Data System (ADS)

    Khayyatzadeh, Pouya; Fu, Fred; Abukhdeir, Nasser Mohieddin

    2015-12-01

    Polymer-dispersed liquid-crystal (PDLC) composites long have been a focus of study for their unique electro-optical properties which have resulted in various applications such as switchable (transparent or translucent) windows. These composites are manufactured using desirable "bottom-up" techniques, such as phase separation of a liquid-crystal-polymer mixture, which enable production of PDLC films at very large scales. LC domains within PDLCs are typically spheroidal, as opposed to rectangular for an LCD panel, and thus exhibit substantially different behavior in the presence of an external field. The fundamental difference between spheroidal and rectangular nematic domains is that the former results in the presence of nanoscale orientational defects in LC order while the latter does not. Progress in the development and optimization of PDLC electro-optical properties has progressed at a relatively slow pace due to this increased complexity. In this work, continuum simulations are performed in order to capture the complex formation and electric field-driven switching dynamics of approximations of PDLC domains. Using a simplified elliptic cylinder (microcapillary) geometry as an approximation of spheroidal PDLC domains, the effects of geometry (aspect ratio), surface anchoring, and external field strength are studied through the use of the Landau-de Gennes model of the nematic LC phase.

  16. Cryosurgery with Pulsed Electric Fields

    PubMed Central

    Daniels, Charlotte S.; Rubinsky, Boris

    2011-01-01

    This study explores the hypothesis that combining the minimally invasive surgical techniques of cryosurgery and pulsed electric fields will eliminate some of the major disadvantages of these techniques while retaining their advantages. Cryosurgery, tissue ablation by freezing, is a well-established minimally invasive surgical technique. One disadvantage of cryosurgery concerns the mechanism of cell death; cells at high subzero temperature on the outer rim of the frozen lesion can survive. Pulsed electric fields (PEF) are another minimally invasive surgical technique in which high strength and very rapid electric pulses are delivered across cells to permeabilize the cell membrane for applications such as gene delivery, electrochemotherapy and irreversible electroporation. The very short time scale of the electric pulses is disadvantageous because it does not facilitate real time control over the procedure. We hypothesize that applying the electric pulses during the cryosurgical procedure in such a way that the electric field vector is parallel to the heat flux vector will have the effect of confining the electric fields to the frozen/cold region of tissue, thereby ablating the cells that survive freezing while facilitating controlled use of the PEF in the cold confined region. A finite element analysis of the electric field and heat conduction equations during simultaneous tissue treatment with cryosurgery and PEF (cryosurgery/PEF) was used to study the effect of tissue freezing on electric fields. The study yielded motivating results. Because of decreased electrical conductivity in the frozen/cooled tissue, it experienced temperature induced magnified electric fields in comparison to PEF delivered to the unfrozen tissue control. This suggests that freezing/cooling confines and magnifies the electric fields to those regions; a targeting capability unattainable in traditional PEF. This analysis shows how temperature induced magnified and focused PEFs could be used to

  17. Quasi-Static Electric Field Generator

    NASA Technical Reports Server (NTRS)

    Generazio, Edward R. (Inventor)

    2017-01-01

    A generator for producing an electric field for with an inspection technology system is provided. The generator provides the required variable magnitude quasi-static electric fields for the "illumination" of objects, areas and volumes to be inspected by the system, and produces human-safe electric fields that are only visible to the system. The generator includes a casing, a driven, non-conducting and triboelectrically neutral rotation shaft mounted therein, an ungrounded electrostatic dipole element which works in the quasi-static range, and a non-conducting support for mounting the dipole element to the shaft. The dipole element has a wireless motor system and a charging system which are wholly contained within the dipole element and the support that uses an electrostatic approach to charge the dipole element.

  18. Chiral symmetry breaking dictated by electric-field-driven shape transitions of nucleating conglomerate domains in a bent-core liquid crystal

    NASA Astrophysics Data System (ADS)

    Deepa, G. B.; Pratibha, R.

    2014-04-01

    Generating and controlling chiral symmetry breaking and enantiomeric excess is not only interesting from a fundamental perspective but can also lead to novel functional materials. In this work, we show how the dark conglomerate (DC) liquid crystalline phase characterized by macroscopic chiral domains offers such a possibility if formed under an electric field. In addition the chiral domains are electro-optically switchable. The chiral segregation in the DC phase can be tuned by using dc or ac fields at different frequencies. Consequently, the enantioselectivity, dielectric parameters and switching polarization in the DC phase become tunable. Another interesting aspect is that the nucleating conglomerate domains formed under ac fields exhibit frequency dependent shape transitions which have a striking resemblance to domain shape changes observed in two-dimensional monolayers. This can therefore be used as a model experimental system to get a physical insight into the effects of chiral and electrostatic interactions, under external fields, on domain growth and interface structures. The domain shape transitions can also be used to investigate the role of growth morphology in coarsening and scaling hypotheses. From a technological point of view this opens up the possibility of obtaining chiral thin films with preferential sense of chirality which can be useful in chiroptical and nonlinear optical applications.

  19. Electric Field Containerless Processing Technology

    NASA Technical Reports Server (NTRS)

    Elleman, D. D.; Rhim, W. K.

    1985-01-01

    The objective of this task is to develop the science and technology base required to design and construct a high temperature electric field positioning module that could be used by materials scientists to conduct containerless science experiments in a low gravity environment. Containerless science modules that employ electric fields to position and manipulate samples offer several advantages over acoustic or electromagnetic systems. The electric field system will operate not only at atmospheric pressures but also in a vacuum, in contrast to the acoustic modules which can only operate in atmosphere where the acoustic forces are sufficient. The electric field technique puts minimum energy into the sample, whereas the electromagnetic system can deposit energy into the sample through eddy current heat as well as physical mixing in the sample. Two types of electric field modules have been constructed and tested to date. One employs a charged sample and uses electrostatic forces to position and control the sample. The second type of module induces electrical polarization of the sample and electric field gradients to position and control the sample.

  20. Low electric-field driven ultrahigh electrostrains in Sb-substituted (Na,K)NbO{sub 3} lead-free ferroelectric ceramics

    SciTech Connect

    Fu, Jian; Zuo, Ruzhong E-mail: rzzuo@hotmail.com; Qi, He; Zhang, Chen; Li, Jingfeng; Li, Longtu

    2014-12-15

    Lead-free (Na{sub 0.52}K{sub 0.48})(Nb{sub 1−y}Sb{sub y})O{sub 3} (NKNS{sub y}) ferroelectric ceramics were reported to exhibit an ultrahigh electrostrain (dynamic d{sub 33}* (=S/E) of 800–1100 pm/V) in a relatively low driving electric field range (1–4 kV/mm). As evidenced by in-situ synchrotron x-ray diffraction and dielectric measurements, the mechanism of generating large strains was ascribed to both the low-field induced reversible rhombohedral-monoclinic phase transition (1–2 kV/mm) and the enhanced domain switching (2–4 kV/mm) owing to the normal to relaxor phase transformation, which contribute to ∼62% and ∼38% of the total strain, respectively. The results indicate that the NKNS{sub y} compositions would have excellent potentials for applications of lead-free actuator ceramics.

  1. Electric field in neutron stars

    SciTech Connect

    Adam, R. I. Sulaksono, A.

    2016-04-19

    In a compact star, an electric field is generated by the charge polarization effect. We investigate the charge polarization effect due to a significant difference of core and crust densities in the form of a combination of two Gaussian functions. The results indicate that the electric field only occurs significantly on the crust of the compact star. As a consequence, the mass-radius relationship only affects compact stars with mass ≤ 1.0 M{sub ⊙}.

  2. Introducing electric fields

    NASA Astrophysics Data System (ADS)

    Roche, John

    2016-09-01

    The clear introduction of basic concepts and definitions is crucial for teaching any topic in physics. I have always found it difficult to teach fields. While searching for better explanations I hit on an approach of reading foundational texts and electromagnetic textbooks in ten year lots, ranging from 1840 to the present. By combining this with modern techniques of textual interpretation I attempt to clarify three introductory concepts: how the field is defined; the principle of superposition and the role of the electrostatic field in a circuit.

  3. Revisiting the Corotation Electric Field

    NASA Astrophysics Data System (ADS)

    Rothwell, P. L.

    2001-05-01

    The rotation of the Earth's dipole magnetic field produces a corotation electric field in the nonrotating frame of reference. A quick calculation implies that this field might arise from the relative motion of an observer in the nonrotating frame and the motion of rotating magnetic field lines. However, upon applying Faraday's Law one finds that total time rate of change of the magnetic field as seen in the nonrotating frame is zero due to the azimuthal symmetry of the dipole. Therefore, classical EM theory(1) predicts a zero corotation electric field in the nonrotating frame for a vacuum. This conundrum has been traditionally treated in the following manner(2,3). 1) Start with a vacuum state with no conductors and plasma present. The transformation between E (the electric field in the nonrotating frame) and E' (the electric field in the rotating frame)implies that in the rotating frame E' is nonzero while E = 0. 2) In the presence of a thin conducting spherical shell (the ionosphere) polarization charges form in the shell due to the magnetic force on the electrons. A polarization electric field Ep is created such that in the idealized case the shell has a uniform electric potential. This Ep has a component along the magnetic field lines outside the shell. 3) Plasma will polarize along B, thus canceling the parallel component of Ep which allows the potential on the shell to be mapped along the magnetic field lines setting E' = 0. From the transformation equation E is now nonzero. This is the electric field required in the nonrotating frame for the plasma to corotate with the dipole. The presence of the corotation electric field is not a local result, but a nonlocal effect that requires the presence of an ionosphere and a conducting plasma. (1) W.K.H. Panofsky and M. Phillips, Classical Electricity and Magnetism, Addison-Wesley, 1956. (2) H. Alfven and C.-G. Falthammar, Cosmical Electrodynamics, 2nd ed., Oxford Press, 1963. (3) E.W.Hones and J.E.Bergeson, J. Geophys

  4. Neoclassical Radial Electric Field and Transport with Finite Orbits

    SciTech Connect

    Wang, W. X.; Hinton, F. L.; Wong, S. K.

    2001-07-30

    Neoclassical transport in a toroidal plasma with finite ion orbits is studied, including for the first time the self-consistent radial electric field. Using a low-noise {delta}f particle simulation, we demonstrate that a deep electric-field well develops in a region with a steep density gradient, because of the self-collision--driven ion flux. We find that the electric field agrees with the standard neoclassical expression, when the toroidal rotation is zero, even for a steep density gradient. Ion thermal transport is modified by the electric-field well in a way which is consistent with the orbit squeezing effect, but smoothed by the finite orbits.

  5. Alkali-vapor magnetic resonance driven by fictitious radiofrequency fields

    SciTech Connect

    Zhivun, Elena; Wickenbrock, Arne; Patton, Brian; Budker, Dmitry

    2014-11-10

    We demonstrate an all-optical {sup 133}Cs scalar magnetometer, operating in nonzero magnetic field, in which the magnetic resonance is driven by an effective oscillating magnetic field provided by the AC Stark shift of an intensity-modulated laser beam. We achieve a projected shot-noise-limited sensitivity of 1.7fT/√(Hz) and measure a technical noise floor of 40fT/√(Hz). These results are essentially identical to a coil-driven scalar magnetometer using the same setup. This all-optical scheme offers advantages over traditional coil-driven magnetometers for use in arrays and in magnetically sensitive fundamental physics experiments, e.g., searches for a permanent electric dipole moment of the neutron.

  6. THOR Electric Field Instrument - EFI

    NASA Astrophysics Data System (ADS)

    Khotyaintsev, Yuri; Bale, Stuart D.; Bonnell, John W.; Lindqvist, Per-Arne; Phal, Yamuna; Rothkaehl, Hanna; Soucek, Jan; Vaivads, Andris; Åhlen, Lennart

    2016-04-01

    Turbulence Heating ObserveR (THOR) is the first mission ever flown in space dedicated to plasma turbulence. The Electric Field Instrument (EFI) will measure the vector electric field from 0 to 200 kHz. EFI consists of two sets of sensors: Spin-plane Double Probes (EFI-SDP) providing high sensitivity DC electric field in the spacecraft spin plane (2D), and the High-Frequency Antenna (EFI-HFA) providing 3D electric field at frequencies above ~1 kHz. EFI-SDP consists of 4 biased spherical probes extended on 50 m long wire booms, 90 degrees apart in the spin plane, giving a 100 m baseline for each of the two spin-plane electric field components. EFI-HFA consists of 6 x 1.25 m long monopoles, forming 3 dipolar antennas crossed at 90 degrees to each other. In addition to the sensors, EFI contains HFA and SDP pre-amplifiers, as well as bias electronics boards (BEBs) hosted in the man electronics box of the Field and Wave processor (FWP). As THOR spacecraft has a sun-pointing spin axis, EFI-SDP measures the electric field in the plane approximately orthogonal to the sun using long wire booms. The sun-pointing attitude greatly reduces errors due to wake effects and asymmetric photoelectron clouds, enabling the highly accurate in comparison to earlier missions ±0.1 mV/m near-DC electric field measurements. Interferometry using the electric field probes can be used to infer wavelengths and scale sizes at the smallest scales in the plasma. EFI also measures the floating potential of the satellite, which can be used to estimate the plasma density at very high time resolution (up to a few hundred Hz). The sun-pointing attitude greatly reduces changes in the illuminated area, and hence the associated spin-dependent errors. In combination with densities derived from the observed plasma frequency emission line, EFI monitors the plasma density from DC to a few hundred Hz. EFI measurements characterize electric field and density variations associated with kinetic scale plasma

  7. THOR Electric Field Instrument - EFI

    NASA Astrophysics Data System (ADS)

    Khotyaintsev, Yuri; Bale, Stuart D.; Rothkaehl, Hanna; Bonnell, John; Åhlen, Lennart; Vaivads, Andris; Lindqvist, Per-Arne; Ivchenko, Nickolay; Soucek, Jan

    2017-04-01

    Turbulence Heating ObserveR (THOR) is the first mission ever flown in space dedicated to plasma turbulence. The Electric Field Instrument (EFI) is to measure the electric field vector in the frequency range 0-200 kHz. EFI consists of two sets of sensors: Spin-plane Double Probes (EFI-SDP) providing high sensitivity DC electric field in the spacecraft spin plane (2D), and the High-Frequency Antenna (EFI-HFA) providing 3D electric field at frequencies above 1 kHz. EFI-SDP consists of 4 biased spherical probes extended on 50 m long wire booms, 90 degrees apart in the spin plane, giving a 100 m baseline for each of the two spin-plane electric field components. EFI-HFA consists of 6 x 1.25 m long monopoles, forming 3 dipolar antennas crossed at 90 degrees to each other. In addition to the sensors, EFI contains HFA and SDP pre-amplifiers, as well as bias electronics boards (BEBs) hosted in the man electronics box of the Field and Wave processor (FWP). As THOR spacecraft has a sun-pointing spin axis, EFI-SDP measures the electric field in the plane approximately orthogonal to the sun using long wire booms. The sun-pointing attitude greatly reduces errors due to wake effects and asymmetric photoelectron clouds, enabling the highly accurate in comparison to earlier missions ±0.1 mV/m near-DC electric field measurements. Interferometry using the electric field probes can be used to infer wavelengths and scale sizes at the smallest scales in the plasma. EFI also measures the floating potential of the satellite, which can be used to estimate the plasma density at very high time resolution (up to a few hundred Hz). The sun-pointing attitude greatly reduces changes in the illuminated area, and hence the associated spin-dependent errors. In combination with densities derived from the observed plasma frequency emission line, EFI monitors the plasma density from DC to a few hundred Hz. EFI measurements characterize electric field and density variations associated with kinetic

  8. Electric fields and quantum wormholes

    NASA Astrophysics Data System (ADS)

    Engelhardt, Dalit; Freivogel, Ben; Iqbal, Nabil

    2015-09-01

    Electric fields can thread a classical Einstein-Rosen bridge. Maldacena and Susskind have recently suggested that in a theory of dynamical gravity the entanglement of ordinary perturbative quanta should be viewed as creating a quantum version of an Einstein-Rosen bridge between the particles, or a "quantum wormhole." We demonstrate within low-energy effective field theory that there is a precise sense in which electric fields can also thread such quantum wormholes. We define a nonperturbative "wormhole susceptibility" that measures the ease of passing an electric field through any sort of wormhole. The susceptibility of a quantum wormhole is suppressed by powers of the U (1 ) gauge coupling relative to that for a classical wormhole but can be made numerically equal with a sufficiently large amount of entangled matter.

  9. Effects of guide field in driven magnetic reconnection

    NASA Astrophysics Data System (ADS)

    Cheng, C. Z.; Inoue, S.; Horiuchi, R.; Ono, Y.; Guo, X.

    2016-10-01

    Decoupling of electron and ion dynamics is the key physical process in the magnetic reconnection layer. It leads to the generation of parallel E-field and in-plane electrostatic E-field, and determines how particles gain energy. For antiparallel magnetic reconnection (zero guide field case), the electron and ion dynamics decoupling is due to meandering particle (unmagnetized) orbits in the field reversal region and particle acceleration by parallel electric field in the separatrix region. The parallel E-field is produced mainly from the driven inductive E-field due to the quadrupole out-of-plane magnetic field generation. The decoupling of electron and ion dynamics causes charge separation which produces the in-plane electrostatic E-field. If the guide field is stronger than the reconnecting magnetic field, both electrons and ions are magnetized in the entire magnetic reconnection domain, and the electron-ion dynamics decoupling process changes from the zero guide field case. Then, the structure of parallel and electrostatic E-fields, and thus how electrons/ions gain energy also changes. We will explain the physical mechanisms of electron-ion dynamics decoupling on the E-field generation, and how electron and ion are heated/accelerated based on the driven reconnection simulation results.

  10. Synaptic Effects of Electric Fields

    NASA Astrophysics Data System (ADS)

    Rahman, Asif

    Learning and sensory processing in the brain relies on the effective transmission of information across synapses. The strength and efficacy of synaptic transmission is modifiable through training and can be modulated with noninvasive electrical brain stimulation. Transcranial electrical stimulation (TES), specifically, induces weak intensity and spatially diffuse electric fields in the brain. Despite being weak, electric fields modulate spiking probability and the efficacy of synaptic transmission. These effects critically depend on the direction of the electric field relative to the orientation of the neuron and on the level of endogenous synaptic activity. TES has been used to modulate a wide range of neuropsychiatric indications, for various rehabilitation applications, and cognitive performance in diverse tasks. How can a weak and diffuse electric field, which simultaneously polarizes neurons across the brain, have precise changes in brain function? Designing therapies to maximize desired outcomes and minimize undesired effects presents a challenging problem. A series of experiments and computational models are used to define the anatomical and functional factors leading to specificity of TES. Anatomical specificity derives from guiding current to targeted brain structures and taking advantage of the direction-sensitivity of neurons with respect to the electric field. Functional specificity originates from preferential modulation of neuronal networks that are already active. Diffuse electric fields may recruit connected brain networks involved in a training task and promote plasticity along active synaptic pathways. In vitro, electric fields boost endogenous synaptic plasticity and raise the ceiling for synaptic learning with repeated stimulation sessions. Synapses undergoing strong plasticity are preferentially modulated over weak synapses. Therefore, active circuits that are involved in a task could be more susceptible to stimulation than inactive circuits

  11. Theory of multiphoton single and double ionization of two-electron atomic systems driven by short-wavelength electric fields: An ab initio treatment

    SciTech Connect

    Foumouo, Emmanuel; Piraux, Bernard; Kamta, Gerard Lagmago; Edah, Gaston

    2006-12-15

    We give a detailed account of an ab initio computational treatment of multiphoton single ionization (with or without excitation) as well as double ionization of two-electron atoms exposed to short-wavelength electric fields. This treatment is time dependent and based on a spectral method of configuration interaction type combined with Jacobi or J-matrix calculations. It involves a complete treatment of electron-electron correlation in the initial and final states as well as during the time propagation. The atom eigenvalue problem is first solved by means of the spectral method. It consists of expanding the atom wave function in a basis of products of complex Coulomb-Sturmian functions of the electron radial coordinates and bipolar harmonics of the angular coordinates. This method allows a high-resolution study of many atomic states, in particular high-lying singly excited states as well as many doubly excited states. Results for He are presented and discussed in detail. The time-dependent Schroedinger equation is then solved by means of an explicit scheme of Runge-Kutta type. An accurate calculation of the probability of single and double ionization is carried out by projecting the ionizing wave packet on fully correlated multichannel scattering wave functions generated by means of the J-matrix method. After a detailed analysis of the accuracy of this method, we show that our results for the total cross section of one-photon single and double ionization of He and H{sup -} are in very good agreement with those obtained by the most sophisticated approaches. Two-photon double ionization of He is then considered, and results are presented in a frequency regime where substantial discrepancies subsist between all existing calculations. Our results demonstrate that electron correlations in the final state play a significant role.

  12. Electrically driven PEDOT/PSS actuators

    NASA Astrophysics Data System (ADS)

    Okuzaki, H.; Hosaka, K.; Suzuki, H.; Ito, T.

    2010-04-01

    Free-standing films made of poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (PEDOT/PSS) were prepared by casting water dispersion of its colloidal particles. Specific surface area, water vapor sorption, and electroactive polymer actuating behavior of the resulting films were investigated by means of sorption isotherm, and electromechanical analysis. It was found that the non-porous PEDOT/PSS film, having a specific surface area of 0.13 m2 g-1, sorbed water vapor of 1080 cm3(STP) g-1, corresponding to 87 wt%, at relative water vapor pressure of 0.95. A temperature rise from 25 to 40 °C lowered sorption degree, indicative of an exothermic process, where isosteric heat of sorption decreased with increasing water vapor sorption and the value reached 43.9 kJ mol-1, being consistent with the heat of water condensation (44 kJ mol-1). Upon application of 10 V, the film underwent contraction of 2.4% in air at 50% relative humidity (RH) which significantly increased to 4.5% at 90% RH. The principle lay in desorption of water vapor sorbed in the film due to Joule heating, where electric field was capable of controlling the equilibrium of water vapor sorption.

  13. Electric fields in the magnetosphere

    NASA Technical Reports Server (NTRS)

    Heppner, J. P.

    1972-01-01

    Two techniques, tracking the motions of Ba(+) clouds and measuring the differences in floating potential between symmetric double probes, were successful in: (1) demonstrating the basic convective nature of magnetospheric electric fields, (2) mapping global patterns of convection at upper ionosphere levels, and (3) revealing the physics of electric currents in the ionosphere and the importance of magnetosphere-ionosphere feedback in altering the imposed convection.

  14. Simultaneous measurement of nanoscale electric and magnetic optical fields

    NASA Astrophysics Data System (ADS)

    Le Feber, B.; Rotenberg, N.; Beggs, D. M.; Kuipers, L.

    2014-01-01

    Control of light-matter interactions at the nanoscale has advanced fields such as quantum optics, photovoltaics and telecommunications. These advances are driven by an improved understanding of the nanoscale behaviour of light, enabled by direct observations of the local electric fields near photonic nanostructures. With the advent of metamaterials that respond to the magnetic component of light, schemes have been developed to measure the nanoscale magnetic field. However, these structures interact not only with the magnetic field, but also with the electric field of light. Here, we demonstrate the essential simultaneous detection of both electric and magnetic fields with subwavelength resolution. By explaining our measurements through reciprocal considerations, we create a route towards designing probes sensitive to specific desired combinations of electric and magnetic field components. Simultaneous access to nanoscale electric and magnetic fields will pave the way for new designs of optical nanostructures and metamaterials.

  15. The Dynamics of Ultrasonically Levitated Drops in an Electric Field

    NASA Technical Reports Server (NTRS)

    Trinh, E. H.; Holt, R. G.; Thiessen, D. B.

    1996-01-01

    Ultrasonic and electrostatic levitation techniques have allowed the experimental investigation of the nonlinear oscillatory dynamics of free droplets with diameter between 0.1 and 0.4 cm. The measurement of the resonance frequencies of the first three normal modes of large amplitude shape oscillations in an electric field of varying magnitude has been carried out with and without surface charges for weakly conducting liquids in air. These oscillations of nonspherical levitated drops have been driven by either modulating the ultrasonic field or by using a time-varying electric field, and the free decay from the oscillatory state has been recorded. A decrease in the resonance frequency of the driven fundamental quadrupole mode has been measured for increasing oblate deformation in the absence of an electric field. Similarly, a decrease in this frequency has also been found for increasing DC electric field magnitude. A soft nonlinearity exists in the amplitude dependence of the resonant mode frequencies for freely decaying as well as ultrasonically and electrically driven uncharged drops. This decrease in resonance frequency is accentuated by the presence of free surface charge on the drop. Subharmonic resonance excitation has been observed for drops in a time-varying electric field, and hysteresis exists for resonant modes driven to large amplitude. Mode coupling from lower-order resonances to higher-order modes has been found to be very weak, even for fairly large amplitude shape oscillations. Most of these results are in general agreement with predictions from recent analytical and numerical investigations.

  16. Measuring Energy Scaling of Laser Driven Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Williams, Jackson; Goyon, Clement; Mariscal, Derek; Pollock, Brad; Patankar, Siddharth; Moody, John

    2016-10-01

    Laser-driven magnetic fields are of interest in particle confinement, fast ignition, and ICF platforms as an alternative to pulsed power systems to achieve many times higher fields. A comprehensive model describing the mechanism responsible for creating and maintaining magnetic fields from laser-driven coils has not yet been established. Understanding the scaling of key experimental parameters such as spatial and temporal uniformity and duration are necessary to implement coil targets in practical applications yet these measurements prove difficult due to the highly transient nature of the fields. We report on direct voltage measurements of laser-driven coil targets in which the laser energy spans more than four orders of magnitude. Results suggest that at low energies, laser-driven coils can be modeled as an electric circuit; however, at higher energies plasma effects dominate and a simple circuit treatment is insufficient to describe all observed phenomenon. The favorable scaling with laser power and pulse duration, observed in the present study and others at kilojoule energies, has positive implications for sustained, large magnetic fields for applications on the NIF. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  17. Microstickies agglomeration by electric field.

    PubMed

    Du, Xiaotang Tony; Hsieh, Jeffery S

    2016-01-01

    Microstickies deposits on both paper machine and paper products when it agglomerates under step change in ionic strength, pH, temperature and chemical additives. These stickies increase the down time of the paper mill and decrease the quality of paper. The key property of microstickies is its smaller size, which leads to low removal efficiency and difficulties in measurement. Thus the increase of microstickies size help improve both removal efficiency and reduce measurement difficulty. In this paper, a new agglomeration technology based on electric field was investigated. The electric treatment could also increase the size of stickies particles by around 100 times. The synergetic effect between electric field treatment and detacky chemicals/dispersants, including polyvinyl alcohol, poly(diallylmethylammonium chloride) and lignosulfonate, was also studied.

  18. Apparatuses and methods for generating electric fields

    DOEpatents

    Scott, Jill R; McJunkin, Timothy R; Tremblay, Paul L

    2013-08-06

    Apparatuses and methods relating to generating an electric field are disclosed. An electric field generator may include a semiconductive material configured in a physical shape substantially different from a shape of an electric field to be generated thereby. The electric field is generated when a voltage drop exists across the semiconductive material. A method for generating an electric field may include applying a voltage to a shaped semiconductive material to generate a complex, substantially nonlinear electric field. The shape of the complex, substantially nonlinear electric field may be configured for directing charged particles to a desired location. Other apparatuses and methods are disclosed.

  19. Electrophoresis in strong electric fields.

    PubMed

    Barany, Sandor

    2009-01-01

    Two kinds of non-linear electrophoresis (ef) that can be detected in strong electric fields (several hundred V/cm) are considered. The first ("classical" non-linear ef) is due to the interaction of the outer field with field-induced ionic charges in the electric double layer (EDL) under conditions, when field-induced variations of electrolyte concentration remain to be small comparatively to its equilibrium value. According to the Shilov theory, the non-linear component of the electrophoretic velocity for dielectric particles is proportional to the cubic power of the applied field strength (cubic electrophoresis) and to the second power of the particles radius; it is independent of the zeta-potential but is determined by the surface conductivity of particles. The second one, the so-called "superfast electrophoresis" is connected with the interaction of a strong outer field with a secondary diffuse layer of counterions (space charge) that is induced outside the primary (classical) diffuse EDL by the external field itself because of concentration polarization. The Dukhin-Mishchuk theory of "superfast electrophoresis" predicts quadratic dependence of the electrophoretic velocity of unipolar (ionically or electronically) conducting particles on the external field gradient and linear dependence on the particle's size in strong electric fields. These are in sharp contrast to the laws of classical electrophoresis (no dependence of V(ef) on the particle's size and linear dependence on the electric field gradient). A new method to measure the ef velocity of particles in strong electric fields is developed that is based on separation of the effects of sedimentation and electrophoresis using videoimaging and a new flowcell and use of short electric pulses. To test the "classical" non-linear electrophoresis, we have measured the ef velocity of non-conducting polystyrene, aluminium-oxide and (semiconductor) graphite particles as well as Saccharomice cerevisiae yeast cells as a

  20. Linear electric field mass spectrometry

    DOEpatents

    McComas, David J.; Nordholt, Jane E.

    1992-01-01

    A mass spectrometer and methods for mass spectrometry. The apparatus is compact and of low weight and has a low power requirement, making it suitable for use on a space satellite and as a portable detector for the presence of substances. High mass resolution measurements are made by timing ions moving through a gridless cylindrically symmetric linear electric field.

  1. Linear electric field mass spectrometry

    DOEpatents

    McComas, D.J.; Nordholt, J.E.

    1992-12-01

    A mass spectrometer and methods for mass spectrometry are described. The apparatus is compact and of low weight and has a low power requirement, making it suitable for use on a space satellite and as a portable detector for the presence of substances. High mass resolution measurements are made by timing ions moving through a gridless cylindrically symmetric linear electric field. 8 figs.

  2. Ionizing gas breakdown waves in strong electric fields.

    NASA Technical Reports Server (NTRS)

    Klingbeil, R.; Tidman, D. A.; Fernsler, R. F.

    1972-01-01

    A previous analysis by Albright and Tidman (1972) of the structure of an ionizing potential wave driven through a dense gas by a strong electric field is extended to include atomic structure details of the background atoms and radiative effects, especially, photoionization. It is found that photoionization plays an important role in avalanche propagation. Velocities, electron densities, and temperatures are presented as a function of electric field for both negative and positive breakdown waves in nitrogen.

  3. 30 CFR 18.91 - Electric equipment for which field approvals will be issued.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... OF LABOR TESTING, EVALUATION, AND APPROVAL OF MINING PRODUCTS ELECTRIC MOTOR-DRIVEN MINE EQUIPMENT AND ACCESSORIES Field Approval of Electrically Operated Mining Equipment § 18.91 Electric equipment... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Electric equipment for which field approvals...

  4. 30 CFR 18.91 - Electric equipment for which field approvals will be issued.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... OF LABOR TESTING, EVALUATION, AND APPROVAL OF MINING PRODUCTS ELECTRIC MOTOR-DRIVEN MINE EQUIPMENT AND ACCESSORIES Field Approval of Electrically Operated Mining Equipment § 18.91 Electric equipment... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Electric equipment for which field approvals...

  5. Optical measurement of electric fields

    NASA Astrophysics Data System (ADS)

    Steiger, Andreas; de la Rosa, M. I.; Perez, Conception; Gemisic, Minja; Gruetzmacher, Klaus; Seidel, Joachim

    2003-05-01

    Local electric field strengths in low density plasmas can be measured directly by Doppler-free two-photon spectroscopy of atomic hydrogen mostly present in such discharges. This method is based on the Stark-splitting of the atomic resonance lines and causes no significant perturbation to the discharge. For this purpose, we take advantage of our advanced pulsed UV-laser spectrometers which provide not only the peak power needed for two-photon excitation but also the high spectral resolution to resolve the atomic hyperfine splitting. In a first experiment with opto-galvanic detection, atomic hydrogen was produced by thermal dissociation in a small cell filled with hydrogen gas and the Stark-splitting of the 1S-2S and the 1S-3S/D transition was measured. Electric fields as low as 200 V/cm and 30 V/cm respectively could be determined in accordance with theory. In addition, we have performed measurements in a hollow cathode discharge which provides higher electric fields in its cathode fall region and the 1S-2S spectrum was detected spatially resolved by means of opto-galvanic and polarization spectroscopy as well. Selected experimental results will be presented which clearly demonstrate the high potential of this optical method.

  6. Electrically Driven General Systems for UAV’s

    DTIC Science & Technology

    2007-11-01

    systems are discussed in this paper. First the Barracuda M-05 UAV Demonstrator and second the 270 VDC More Electric Aircraft project launched by the...German Federal Office of Defense Technology and Procurement (BWB). 3.1 Barracuda M-05 The Barracuda M-05 is a company founded unmanned...test flight. Figure 4 showed a picture of the first flight. Figure 4: Barracuda M-05 First Flight With respect to electrically driven

  7. GROUNDWATER AND SOIL REMEDIATION USING ELECTRICAL FIELD

    EPA Science Inventory

    Enhancements of contaminants removal and degradation in low permeability soils by electrical fields are achieved by the processes of electrical heating, electrokinetics, and electrochemical reactions. Electrical heating increases soil temperature resulting in the increase of cont...

  8. GROUNDWATER AND SOIL REMEDIATION USING ELECTRICAL FIELD

    EPA Science Inventory

    Enhancements of contaminants removal and degradation in low permeability soils by electrical fields are achieved by the processes of electrical heating, electrokinetics, and electrochemical reactions. Electrical heating increases soil temperature resulting in the increase of cont...

  9. Domain wall motion driven by an oscillating magnetic field

    NASA Astrophysics Data System (ADS)

    Moon, Kyoung-Woong; Kim, Duck-Ho; Kim, Changsoo; Kim, Dae-Yun; Choe, Sug-Bong; Hwang, Chanyong

    2017-03-01

    The coherent unidirectional motion of magnetic domain walls (DWs) is a key technology used in memory and logic device applications, as demonstrated in magnetic strips by electric current flow as well as in films by oscillation of a tilted magnetic field. Here we introduce a coherent unidirectional motion of DWs in the strip, utilizing an oscillating field, which is described within a previous 1D model. The essential criterion for DW motion in this approach is the oscillating-field-induced modulation of the DW width, which has not been previously considered. This DW motion driven by width modulation sheds light on high frequency domain manipulation in spin devices. A comprehensive inspection of field angle dependence reveals that unidirectional DW motion in this model requires chiral DWs, followed by asymmetric deformation of the domain shape.

  10. 18. Electrically driven pumps in Armory Street Pump House. Pumps ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    18. Electrically driven pumps in Armory Street Pump House. Pumps in background formerly drew water from the clear well. They went out of service when use of the beds was discontinued. Pumps in the foreground provide high pressure water to Hamden. - Lake Whitney Water Filtration Plant, Armory Street Pumphouse, North side of Armory Street between Edgehill Road & Whitney Avenue, Hamden, New Haven County, CT

  11. Fatigue crack growth in ferroelectrics driven by cyclic electric loading

    NASA Astrophysics Data System (ADS)

    Zhu, Ting; Yang, Wei

    1998-12-01

    Fatigue crack growth has been observed recently in ferroelectrics under cyclic electric loading. Does the crack grow by electric breakdown, or by the stress field near the crack tip? The present paper provides a mechanistic explanation for the electric-field-induced fatigue crack growth. The non-uniform electric field near an insulated crack tip might cause domain switching which in turn produces a concentrated stress field characterized by a stress intensity factor. For ferroelectrics poled along a direction perpendicular to the crack, we are able to show quantitatively that: (1) the stress intensity factor under a negative electric field is nine times as large as the stress intensity factor under a positive electric field; (2) the crack starts to grow if the stress intensity factor is higher than the fracture toughness of the material, but the stress intensity factor decreases as the crack extends and eventually results in crack arrest; (3) by reversing the electric field, the stress intensity factor is increased and crack growth resumes; and (4) this model can predict the extent of fatigue crack growth. In contrast to the conventional perception of (mechanical) fatigue, the fatigue crack growth in ferroelectrics under cyclic electric loading is a step by step cleavage process caused by a domain switching sequence that generates a cyclic driving stress field near the crack tip.

  12. Pulsed electric field increases reproduction.

    PubMed

    Panagopoulos, Dimitris J

    2016-01-01

    Purpose To study the effect of pulsed electric field - applied in corona discharge photography - on Drosophila melanogaster reproduction, possible induction of DNA fragmentation, and morphological alterations in the gonads. Materials and methods Animals were exposed to different field intensities (100, 200, 300, and 400 kV/m) during the first 2-5 days of their adult lives, and the effect on reproductive capacity was assessed. DNA fragmentation during early- and mid-oogenesis was investigated by application of the TUNEL (Terminal deoxynucleotide transferase dUTP Nick End Labeling) assay. Sections of follicles after fixation and embedding in resins were observed for possible morphological/developmental abnormalities. Results The field increased reproduction by up to 30% by increasing reproductive capacity in both sexes. The effect increased with increasing field intensities. The rate of increase diminished at the strongest intensities. Slight induction of DNA fragmentation was observed exclusively in the nurse (predominantly) and follicle cells, and exclusively at the two most sensitive developmental stages, i.e., germarium and predominantly stage 7-8. Sections of follicles from exposed females at stages of early and mid-oogennesis other than germarium and stages 7-8 did not reveal abnormalities. Conclusions (1) The specific type of electric field may represent a mild stress factor, inducing DNA fragmentation and cell death in a small percentage of gametes, triggering the reaction of the animal's reproductive system to increase the rate of gametogenesis in order to compensate the loss of a small number of gametes. (2) The nurse cells are the most sensitive from all three types of egg chamber cells. (3) The mid-oogenesis checkpoint (stage 7-8) is more sensitive to this field than the early oogenesis one (germarium) in contrast to microwave exposure. (4) Possible therapeutic applications, or applications in increasing fertility, should be investigated.

  13. Relaxor ferroelectricity and electric-field-driven structural transformation in the giant lead-free piezoelectric (Ba ,Ca ) (Ti ,Zr ) O3

    NASA Astrophysics Data System (ADS)

    Brajesh, Kumar; Tanwar, Khagesh; Abebe, Mulualem; Ranjan, Rajeev

    2015-12-01

    There is great interest in lead-free (B a0.85C a0.15 ) (T i0.90Z r0.10 ) O3 (15/10BCTZ) because of its exceptionally large piezoelectric response [Liu and Ren, Phys. Rev. Lett. 103, 257602 (2009), 10.1103/PhysRevLett.103.257602]. In this paper, we have analyzed the nature of: (i) crystallographic phase coexistence at room temperature, (ii) temperature- and field-induced phase transformation to throw light on the atomistic mechanisms associated with the large piezoelectric response of this system. A detailed temperature-dependent dielectric and lattice thermal expansion study proved that the system exhibits a weak dielectric relaxation, characteristic of a relaxor ferroelectric material on the verge of exhibiting a normal ferroelectric-paraelectric transformation. Careful structural analysis revealed that a ferroelectric state at room temperature is composed of three phase coexistences, tetragonal (P 4 m m )+ orthorhombic(Amm 2 )+rhombohedral(R 3 m ) . We also demonstrate that the giant piezoresponse is associated with a significant fraction of the tetragonal phase transforming to rhombohedral. It is argued that the polar nanoregions associated with relaxor ferroelectricity amplify the piezoresponse by providing an additional degree of intrinsic structural inhomogeneity to the system.

  14. Electric Field Induced Interfacial Instabilities

    NASA Technical Reports Server (NTRS)

    Kusner, Robert E.; Min, Kyung Yang; Wu, Xiao-lun; Onuki, Akira

    1999-01-01

    The study of the interface in a charge-free, critical and near-critical binary fluid in the presence of an externally applied electric field is presented. At sufficiently large fields, the interface between the two phases of the binary fluid should become unstable and exhibit an undulation with a predefined wavelength on the order of the capillary length. As the critical point is approached, this wavelength is reduced, potentially approaching length-scales such as the correlation length or critical nucleation radius. At this point the critical properties of the system may be affected. In this paper, the flat interface of a marginally polar binary fluid mixture is stressed by a perpendicular alternating electric field and the resulting instability is characterized by the critical electric field E(sub c) and the pattern observed. The character of the surface dynamics at the onset of instability is found to be strongly dependent on the frequency f of the field applied. The plot of E(sub c) vs. f for a fixed temperature shows a sigmoidal shape, whose low and high frequency limits are well described by a power-law relationship, E(sub c) = epsilon(exp zeta) with zeta = 0.35 and zeta = 0.08, respectively. The low-limit exponent compares well with the value zeta = 4 for a system of conducting and non-conducting fluids. On the other hand, the high-limit exponent coincides with what was first predicted by Onuki. The instability manifests itself as the conducting phase penetrates the non-conducting phase. As the frequency increases, the shape of the pattern changes from an array of bifurcating strings to an array of column-like (or rod-like) protrusions, each of which spans the space between the plane interface and one of the electrodes. For an extremely high frequency, the disturbance quickly grows into a parabolic cone pointing toward the upper plate. As a result, the interface itself changes its shape from that of a plane to that of a high sloping pyramid.

  15. Cell separation using electric fields

    NASA Technical Reports Server (NTRS)

    Mangano, Joseph (Inventor); Eppich, Henry (Inventor)

    2009-01-01

    The present invention involves methods and devices which enable discrete objects having a conducting inner core, surrounded by a dielectric membrane to be selectively inactivated by electric fields via irreversible breakdown of their dielectric membrane. One important application of the invention is in the selection, purification, and/or purging of desired or undesired biological cells from cell suspensions. According to the invention, electric fields can be utilized to selectively inactivate and render non-viable particular subpopulations of cells in a suspension, while not adversely affecting other desired subpopulations. According to the inventive methods, the cells can be selected on the basis of intrinsic or induced differences in a characteristic electroporation threshold, which can depend, for example, on a difference in cell size and/or critical dielectric membrane breakdown voltage. The invention enables effective cell separation without the need to employ undesirable exogenous agents, such as toxins or antibodies. The inventive method also enables relatively rapid cell separation involving a relatively low degree of trauma or modification to the selected, desired cells. The inventive method has a variety of potential applications in clinical medicine, research, etc., with two of the more important foreseeable applications being stem cell enrichment/isolation, and cancer cell purging.

  16. Cell separation using electric fields

    NASA Technical Reports Server (NTRS)

    Mangano, Joseph A. (Inventor); Eppich, Henry M. (Inventor)

    2003-01-01

    The present invention involves methods and devices which enable discrete objects having a conducting inner core, surrounded by a dielectric membrane to be selectively inactivated by electric fields via irreversible breakdown of their dielectric membrane. One important application of the invention is in the selection, purification, and/or purging of desired or undesired biological cells from cell suspensions. According to the invention, electric fields can be utilized to selectively inactivate and render non-viable particular subpopulations of cells in a suspension, while not adversely affecting other desired subpopulations. According to the inventive methods, the cells can be selected on the basis of intrinsic or induced differences in a characteristic electroporation threshold, which can depend, for example, on a difference in cell size and/or critical dielectric membrane breakdown voltage. The invention enables effective cell separation without the need to employ undesirable exogenous agents, such as toxins or antibodies. The inventive method also enables relatively rapid cell separation involving a relatively low degree of trauma or modification to the selected, desired cells. The inventive method has a variety of potential applications in clinical medicine, research, etc., with two of the more important foreseeable applications being stem cell enrichment/isolation, and cancer cell purging.

  17. IEMDC - In-Line Electric Motor Driven Compressor

    SciTech Connect

    Michael J. Crowley

    2004-03-31

    This report covers the fifth quarter (01/01/04 to 03/31/04) of the In-Line Electric Motor Driven Compressor (IEMDC) project. Design efforts on the IEMDC continued with compressor efforts focused on performing aerodynamic analyses. These analyses were conducted using computational fluid dynamics. Compressor efforts also entailed developing mechanical designs of components through the use of solid models and working on project deliverables. Electric motor efforts focused on the design of the magnetic bearing system, motor pressure housing, and the motor-compressor interface. The mechanical evaluation of the main interface from both the perspective of the compressor manufacturer and electric motor manufacturer indicates that an acceptable design has been achieved. All mechanical and aerodynamic design efforts have resulted in considerable progress being made towards the completion of the compressor and electric motor design and towards the successful completion of the IEMDC unit.

  18. Electrically driven magnetic antenna based on multiferroic composites

    NASA Astrophysics Data System (ADS)

    Wang, X.-G.; Sukhov, A.; Chotorlishvili, L.; Jia, C.-L.; Guo, G.-H.; Berakdar, J.

    2017-03-01

    We suggest and demonstrate via large scale numerical simulations an electrically operated spin-wave inducer based on composite multiferroic junctions. Specifically, we consider an interfacially coupled ferromagnetic/ferroelectric structure that emits controllably spin waves in the ferromagnets if the ferroelectric polarization is poled by an external electric field. The roles of geometry and material properties are discussed.

  19. Electrically driven magnetic antenna based on multiferroic composites.

    PubMed

    Wang, X-G; Sukhov, A; Chotorlishvili, L; Jia, C-L; Guo, G-H; Berakdar, J

    2017-03-08

    We suggest and demonstrate via large scale numerical simulations an electrically operated spin-wave inducer based on composite multiferroic junctions. Specifically, we consider an interfacially coupled ferromagnetic/ferroelectric structure that emits controllably spin waves in the ferromagnets if the ferroelectric polarization is poled by an external electric field. The roles of geometry and material properties are discussed.

  20. Electric Field Induced Interfacial Instabilities

    NASA Technical Reports Server (NTRS)

    Kusner, Robert E.; Min, Kyung Yang; Wu, Xiao-Lun; Onuki, Akira

    1996-01-01

    The study of the interface in a charge-free, nonpolar, critical and near-critical binary fluid in the presence of an externally applied electric field is presented. At sufficiently large fields, the interface between the two phases of the binary fluid should become unstable and exhibit an undulation with a predefined wavelength on the order of the capillary length. As the critical point is approached, this wavelength is reduced, potentially approaching length-scales such as the correlation length or critical nucleation radius. At this point the critical properties of the system may be affected. In zero gravity, the interface is unstable at all long wavelengths in the presence of a field applied across it. It is conjectured that this will cause the binary fluid to break up into domains small enough to be outside the instability condition. The resulting pattern formation, and the effects on the critical properties as the domains approach the correlation length are of acute interest. With direct observation, laser light scattering, and interferometry, the phenomena can be probed to gain further understanding of interfacial instabilities and the pattern formation which results, and dimensional crossover in critical systems as the critical fluctuations in a particular direction are suppressed by external forces.

  1. Electric Dipole Moment Experiment Systematic from Electric Field Discharge Current

    NASA Astrophysics Data System (ADS)

    Feinberg, B.; Gould, Harvey

    2014-09-01

    A magnetic field, in the direction of the electric field and synchronous with the electric field reversal, will mimic an EDM signal. One might expect a discharge across the electric field plates to produce magnetic fields with only small or vanishing components parallel to the electric field, minimizing its systematic effect. Our experimental model, using simulated discharge currents, found otherwise: the discharge current may be at an angle to the normal, and thus generate a normal magnetic field. Comparison of data from the experimental model with the results from calculations will be presented, along with estimates of the time-averaged normal magnetic field seen by atoms in an electron EDM experiment using a fountain of laser-cooled francium, as a function of discharge current.

  2. Electric Mars: The first survey of Martian parallel electric fields.

    NASA Astrophysics Data System (ADS)

    Collinson, G.; Mitchell, D. L.; Glocer, A.; Grebowsky, J. M.; Peterson, W. K.; Connerney, J. E. P.; Andersson, L.; Espley, J. R.; Mazelle, C. X.; Savaud, J. A.; Fedorov, A.; Ma, Y.; Bougher, S. W.; Lillis, R. J.; Ergun, R. E.; Jakosky, B. M.

    2015-12-01

    We present the results of the first survey of parallel electric fields at Mars, using electron measurements from the MAVEN Solar Wind Electron Analyzer (SWEA), and the Magnetometer (MAG). We discuss three fields: (1) The first upper limit on the strength of the "Polar Wind" ambipolar electric field; (2) The "trans-terminator" field, a newly discovered electric force accelerating ions on closed field lines from day to nightside, and (3) possible signatures of very high strength electrostatic mirroring during the passage of a Coronal Mass Ejection.

  3. Pair-production in inhomogeneous electric fields

    NASA Astrophysics Data System (ADS)

    Xue, She-Sheng

    2008-01-01

    This is a preliminary study on the rate of electron-positron pair production in spatially inhomogeneous electric fields. We study the rate in the Sauter field and compare it to the rate in the homogeneous field.

  4. Charged Hadron Properties in Background Electric Fields

    SciTech Connect

    William Detmold, Brian C. Tiburzi, Andre Walker-Loud

    2010-02-01

    We report on a lattice calculation demonstrating a novel new method to extract the electric polarizability of charged pseudo-scalar mesons by analyzing two point correlation functions computed in classical background electric fields.

  5. An electrically driven gas-liquid-liquid contactor for bioreactor and other applications

    SciTech Connect

    Tsouris, C.; Borole, A.P.; Kaufman, E.N.; DePaoli, D.W.

    1999-05-01

    An electrically driven gas-liquid-liquid bioreactor is described here, in which an aqueous medium containing a biocatalyst is introduced as a discontinuous phase into an organic-continuous liquid phase containing a substrate to be converted by the biocatalyst. A gas discontinuous phase, which may be needed to provide oxygen or a gaseous substrate to the biocatalyst, is also introduced into the bioreactor. In contrast to previous work on electrically driven contactors, it was found that the electroconvection generated by the electric field between parallel-plate electrodes may be employed to increase the volume fraction of the discontinuous gas phase in the bioreactor, providing the means for enhanced mass transfer. The electrically driven bioreactor was utilized for oil desulfurization experiments with Rhodococcus sp. IGTS8 bacteria as the biocatalyst. The organic phase used in the experiments was hexadecane containing dibenzothiophene, a model sulfur compound, that is oxidatively desulfurized to 2-hydroxybiphenyl (2-HBP) by the bacteria in the presence of air or oxygen. The gas volume fraction was increased by 60% by the application of a pulsed electric field, thus providing a means for increased transport of oxygen needed for oxidative desulfurization. The velocity of droplets and bubbles was measured by a phase Doppler velocimeter. The average rising velocity of bubbles was decreased from 13 to less than 3 cm/s and the average horizontal velocity was increased from 0 to 5 cm/s as the field strength was increased from 0 to 4 kV/cm. Desulfurization rates ranged from 1.0 to 5.50 mg of 2-HBP/g of dry cells/h. The desulfurization rate with aeration was doubled under the electric field as compared to the zero-field desulfurization under the same conditions.

  6. Reversible electric-field control of magnetization at oxide interfaces

    NASA Astrophysics Data System (ADS)

    Cuellar, F. A.; Liu, Y. H.; Salafranca, J.; Nemes, N.; Iborra, E.; Sanchez-Santolino, G.; Varela, M.; Hernandez, M. Garcia; Freeland, J. W.; Zhernenkov, M.; Fitzsimmons, M. R.; Okamoto, S.; Pennycook, S. J.; Bibes, M.; Barthélémy, A.; Te Velthuis, S. G. E.; Sefrioui, Z.; Leon, C.; Santamaria, J.

    2014-06-01

    Electric-field control of magnetism has remained a major challenge which would greatly impact data storage technology. Although progress in this direction has been recently achieved, reversible magnetization switching by an electric field requires the assistance of a bias magnetic field. Here we take advantage of the novel electronic phenomena emerging at interfaces between correlated oxides and demonstrate reversible, voltage-driven magnetization switching without magnetic field. Sandwiching a non-superconducting cuprate between two manganese oxide layers, we find a novel form of magnetoelectric coupling arising from the orbital reconstruction at the interface between interfacial Mn spins and localized states in the CuO2 planes. This results in a ferromagnetic coupling between the manganite layers that can be controlled by a voltage. Consequently, magnetic tunnel junctions can be electrically toggled between two magnetization states, and the corresponding spin-dependent resistance states, in the absence of a magnetic field.

  7. Reversible electric-field control of magnetization at oxide interfaces.

    PubMed

    Cuellar, F A; Liu, Y H; Salafranca, J; Nemes, N; Iborra, E; Sanchez-Santolino, G; Varela, M; Garcia Hernandez, M; Freeland, J W; Zhernenkov, M; Fitzsimmons, M R; Okamoto, S; Pennycook, S J; Bibes, M; Barthélémy, A; te Velthuis, S G E; Sefrioui, Z; Leon, C; Santamaria, J

    2014-06-23

    Electric-field control of magnetism has remained a major challenge which would greatly impact data storage technology. Although progress in this direction has been recently achieved, reversible magnetization switching by an electric field requires the assistance of a bias magnetic field. Here we take advantage of the novel electronic phenomena emerging at interfaces between correlated oxides and demonstrate reversible, voltage-driven magnetization switching without magnetic field. Sandwiching a non-superconducting cuprate between two manganese oxide layers, we find a novel form of magnetoelectric coupling arising from the orbital reconstruction at the interface between interfacial Mn spins and localized states in the CuO2 planes. This results in a ferromagnetic coupling between the manganite layers that can be controlled by a voltage. Consequently, magnetic tunnel junctions can be electrically toggled between two magnetization states, and the corresponding spin-dependent resistance states, in the absence of a magnetic field.

  8. Electric-field guiding of magnetic skyrmions

    NASA Astrophysics Data System (ADS)

    Upadhyaya, Pramey; Yu, Guoqiang; Amiri, Pedram Khalili; Wang, Kang L.

    2015-10-01

    We theoretically study equilibrium and dynamic properties of nanosized magnetic skyrmions in thin magnetic films with broken inversion symmetry, where an electric field couples to magnetization via spin-orbit coupling. Based on a symmetry-based phenomenology and micromagnetic simulations we show that this electric-field coupling, via renormalizing the micromagnetic energy, modifies the equilibrium properties of the skyrmion. This change, in turn, results in a significant alteration of the current-induced skyrmion motion. Particularly, the speed and direction of the skyrmion can be manipulated by designing a desired energy landscape electrically, which we describe within Thiele's analytical model and demonstrate in micromagnetic simulations including electric-field-controlled magnetic anisotropy. We additionally use this electric-field control to construct gates for controlling skyrmion motion exhibiting a transistorlike and multiplexerlike function. The proposed electric-field effect can thus provide a low-energy electrical knob to extend the reach of information processing with skyrmions.

  9. Synchronizing fast electrically driven phenomena with synchrotron x-ray probes

    SciTech Connect

    Grigoriev, Alexei; Do, D.-H.; Evans, Paul G.; Adams, Bernhard; Landahl, Eric; Dufresne, Eric M.

    2007-02-15

    Time scales of long-range physical processes in solids are typically in the range of picoseconds to nanoseconds. These times are commensurate with the time resolution of structural probes based on modern synchrotron x-ray sources. Several processes of technological and scientific interest can be driven by applied electric fields, but synchronizing electrically driven phenomena with an x-ray probe poses a technical challenge. We describe the synchronization of a well-defined number of fast electrical pulses with the time structure of synchrotron x rays to probe the dynamics of thin films and nanostructures. This synchronization technique yields x-ray transient signals with 600 ps transitions in ferroelectric thin films, with a contribution of approximately 320 ps due to timing jitter in the synchronization.

  10. Compact Electric- And Magnetic-Field Sensor

    NASA Technical Reports Server (NTRS)

    Winterhalter, Daniel; Smith, Edward

    1994-01-01

    Compact sensor measures both electric and magnetic fields. Includes both short electric-field dipole and search-coil magnetometer. Three mounted orthogonally providing triaxial measurements of electromagnetic field at frequencies ranging from near 0 to about 10 kHz.

  11. Imaging electric field dynamics with graphene optoelectronics

    PubMed Central

    Horng, Jason; Balch, Halleh B.; McGuire, Allister F.; Tsai, Hsin-Zon; Forrester, Patrick R.; Crommie, Michael F.; Cui, Bianxiao; Wang, Feng

    2016-01-01

    The use of electric fields for signalling and control in liquids is widespread, spanning bioelectric activity in cells to electrical manipulation of microstructures in lab-on-a-chip devices. However, an appropriate tool to resolve the spatio-temporal distribution of electric fields over a large dynamic range has yet to be developed. Here we present a label-free method to image local electric fields in real time and under ambient conditions. Our technique combines the unique gate-variable optical transitions of graphene with a critically coupled planar waveguide platform that enables highly sensitive detection of local electric fields with a voltage sensitivity of a few microvolts, a spatial resolution of tens of micrometres and a frequency response over tens of kilohertz. Our imaging platform enables parallel detection of electric fields over a large field of view and can be tailored to broad applications spanning lab-on-a-chip device engineering to analysis of bioelectric phenomena. PMID:27982125

  12. Imaging electric field dynamics with graphene optoelectronics

    NASA Astrophysics Data System (ADS)

    Horng, Jason; Balch, Halleh B.; McGuire, Allister F.; Tsai, Hsin-Zon; Forrester, Patrick R.; Crommie, Michael F.; Cui, Bianxiao; Wang, Feng

    2016-12-01

    The use of electric fields for signalling and control in liquids is widespread, spanning bioelectric activity in cells to electrical manipulation of microstructures in lab-on-a-chip devices. However, an appropriate tool to resolve the spatio-temporal distribution of electric fields over a large dynamic range has yet to be developed. Here we present a label-free method to image local electric fields in real time and under ambient conditions. Our technique combines the unique gate-variable optical transitions of graphene with a critically coupled planar waveguide platform that enables highly sensitive detection of local electric fields with a voltage sensitivity of a few microvolts, a spatial resolution of tens of micrometres and a frequency response over tens of kilohertz. Our imaging platform enables parallel detection of electric fields over a large field of view and can be tailored to broad applications spanning lab-on-a-chip device engineering to analysis of bioelectric phenomena.

  13. Entanglement generation by electric field background

    SciTech Connect

    Ebadi, Zahra Mirza, Behrouz

    2014-12-15

    The quantum vacuum is unstable under the influence of an external electric field and decays into pairs of charged particles, a process which is known as the Schwinger pair production. We propose and demonstrate that this electric field can generate entanglement. Using the Schwinger pair production for constant and pulsed electric fields, we study entanglement for scalar particles with zero spins and Dirac fermions. One can observe the variation of the entanglement produced for bosonic and fermionic modes with respect to different parameters.

  14. The electron signature of parallel electric fields

    NASA Astrophysics Data System (ADS)

    Burch, J. L.; Gurgiolo, C.; Menietti, J. D.

    1990-12-01

    Dynamics Explorer I High-Altitude Plasma Instrument electron data are presented. The electron distribution functions have characteristics expected of a region of parallel electric fields. The data are consistent with previous test-particle simulations for observations within parallel electric field regions which indicate that typical hole, bump, and loss-cone electron distributions, which contain evidence for parallel potential differences both above and below the point of observation, are not expected to occur in regions containing actual parallel electric fields.

  15. Advances in Optimizing Weather Driven Electric Power Systems.

    NASA Astrophysics Data System (ADS)

    Clack, C.; MacDonald, A. E.; Alexander, A.; Dunbar, A. D.; Xie, Y.; Wilczak, J. M.

    2014-12-01

    The importance of weather-driven renewable energies for the United States (and global) energy portfolio is growing. The main perceived problems with weather-driven renewable energies are their intermittent nature, low power density, and high costs. The National Energy with Weather System Simulator (NEWS) is a mathematical optimization tool that allows the construction of weather-driven energy sources that will work in harmony with the needs of the system. For example, it will match the electric load, reduce variability, decrease costs, and abate carbon emissions. One important test run included existing US carbon-free power sources, natural gas power when needed, and a High Voltage Direct Current power transmission network. This study shows that the costs and carbon emissions from an optimally designed national system decrease with geographic size. It shows that with achievable estimates of wind and solar generation costs, that the US could decrease its carbon emissions by up to 80% by the early 2030s, without an increase in electric costs. The key requirement would be a 48 state network of HVDC transmission, creating a national market for electricity not possible in the current AC grid. These results were found without the need for storage. Further, we tested the effect of changing natural gas fuel prices on the optimal configuration of the national electric power system. Another test that was carried out was an extension to global regions. The extension study shows that the same properties found in the US study extend to the most populous regions of the planet. The extra test is a simplified version of the US study, and is where much more research can be carried out. We compare our results to other model results.

  16. EMSP Final Report: Electrically Driven Technologies for Radioactive Aerosol Abatement

    SciTech Connect

    DePaoli, D.W.

    2003-01-22

    The purpose of this research project was to develop an improved understanding of how electrically driven processes, including electrocoalescence, acoustic agglomeration, and electric filtration, may be employed to efficiently treat problems caused by the formation of aerosols during DOE waste treatment operations. The production of aerosols during treatment and retrieval operations in radioactive waste tanks and during thermal treatment operations such as calcination presents a significant problem of cost, worker exposure, potential for release, and increased waste volume. There was anecdotal evidence in the literature that acoustic agglomeration and electrical coalescence could be used together to change the size distribution of aerosol particles in such a way as to promote easier filtration and less frequent maintenance of filtration systems. As such, those electrically driven technologies could potentially be used as remote technologies for improved treatment; however, existing theoretical models are not suitable for prediction and design. To investigate the physics of such systems, and also to prototype a system for such processes, a collaborative project was undertaken between Oak Ridge National Laboratory (ORNL) and the University of Texas at Austin (UT). ORNL was responsible for the larger-scale prototyping portion of the project, while UT was primarily responsible for the detailed physics in smaller scale unit reactors. It was found that both electrical coalescence and acoustic agglomeration do in fact increase the rate of aggregation of aerosols. Electrical coalescence requires significantly less input power than acoustic agglomeration, but it is much less effective in its ability to aggregate/coalesce aerosols. The larger-scale prototype showed qualitatively similar results as the unit reactor tests, but presented more difficulty in interpretation of the results because of the complex multi-physics coupling that necessarily occur in all larger

  17. Plasma heating by electric field compression.

    PubMed

    Avinash, K; Kaw, P K

    2014-05-09

    Plasma heating by compression of electric fields is proposed. It is shown that periodic cycles of external compression followed by the free expansion of electric fields in the plasma cause irreversible, collisionless plasma heating and corresponding entropy generation. As a demonstration of general ideas and scalings, the heating is shown in the case of a dusty plasma, where electric fields are created due to the presence of charged dust. The method is expected to work in the cases of compression of low frequency or dc electric fields created by other methods. Applications to high power laser heating of plasmas using this scheme are discussed.

  18. Electrically small, complementary electric-field-coupled resonator antennas

    NASA Astrophysics Data System (ADS)

    Odabasi, H.; Teixeira, F. L.; Guney, D. O.

    2013-02-01

    We study the radiation properties of electrically small resonant antennas (ka <1) composed of electric-field-coupled (ELC) and complementary electric-field-coupled (CELC) resonators and a monopole antenna. We use such parasitic ELC and CELC "metaresonators" to design various electrically small antennas. In particular, monopole-excited and bent-monopole-excited CELC resonator antennas are proposed that provide very low profiles on the order of λ0/20. We compare the performance of the proposed ELC and CELC antennas against more conventional designs based upon split-ring resonators.

  19. The Electric Field of a Weakly Electric Fish

    NASA Astrophysics Data System (ADS)

    Rasnow, Brian K.

    Freshwater fish of the genus Apteronotus (family Gymnotidae) generate a weak, high frequency electric field (<100 mV/cm, 0.5-10 kHz) which permeates their local environment. These nocturnal fish are acutely sensitive to perturbations in their electric field caused by other electric fish, and nearby objects whose impedance is different from the surrounding water. This thesis presents high temporal and spatial resolution maps of the electric potential and field on and near Apteronotus. The fish's electric field is a complicated and highly stable function of space and time. Its characteristics, such as spectral composition, timing, and rate of attenuation, are examined in terms of physical constraints, and their possible functional roles in electroreception. Temporal jitter of the periodic field is less than 1 musec. However, electrocyte activity is not globally synchronous along the fish's electric organ. The propagation of electrocyte activation down the fish's body produces a rotation of the electric field vector in the caudal part of the fish. This may assist the fish in identifying nonsymmetrical objects, and could also confuse electrosensory predators that try to locate Apteronotus by following its fieldlines. The propagation also results in a complex spatiotemporal pattern of the EOD potential near the fish. Visualizing the potential on the same and different fish over timescales of several months suggests that it is stable and could serve as a unique signature for individual fish. Measurements of the electric field were used to calculate the effects of simple objects on the fish's electric field. The shape of the perturbation or "electric image" on the fish's skin is relatively independent of a simple object's size, conductivity, and rostrocaudal location, and therefore could unambiguously determine object distance. The range of electrolocation may depend on both the size of objects and their rostrocaudal location. Only objects with very large dielectric

  20. Regional United States electric field and GIC hazard impacts (Invited)

    NASA Astrophysics Data System (ADS)

    Gannon, J. L.; Balch, C. C.; Trichtchenko, L.

    2013-12-01

    Geomagnetically Induced Currents (GICs) are primarily driven by impulsive geomagnetic disturbances created by the interaction between the Earth's magnetosphere and sharp velocity, density, and magnetic field enhancements in the solar wind. However, the magnitude of the induced electric field response at the ground level, and therefore the resulting hazard to the bulk power system, is determined not only by magnetic drivers, but also by the underlying geology. Convolution techniques are used to calculate surface electric fields beginning from the spectral characteristics of magnetic field drivers and the frequency response of the local geology. Using these techniques, we describe historical scenarios for regions across the United States, and the potential impact of large events on electric power infrastructure.

  1. Electric field soundings through thunderstorms

    NASA Technical Reports Server (NTRS)

    Marshall, Thomas C.; Rust, W. D.

    1991-01-01

    Twelve balloon soundings of the electric field in thunderstorms are reported. The maximum magnitude of E in the storms averaged 96 +/-28 kV/m, with the largest being 146 kV/m. The maximum was usually observed between vertically adjacent regions of opposite charge. Using a 1D approximation to Gauss' law, four to ten charge regions in the storms are inferred. The magnitude of the density in the charge regions varied between 0.2 and 13 nC/cu m. The vertical extent of the charge regions ranged from 130 to 2100 m. None of the present 12 storms had charge distributions that fit the long-accepted model of Simpson et al. (1937, 1941) of a lower positive charge, a main negative charge, and an upper positive charge. In addition to regions similar to the Simpson model, the present storms had screening layers at the upper and lower cloud boundaries and extra charge regions, usually in the lower part of the cloud.

  2. Electric fields in the ionosphere

    NASA Technical Reports Server (NTRS)

    Kirchhoff, V. W. J. H.

    1975-01-01

    F-region drift velocities, measured by incoherent-scatter radar were analyzed in terms of diurnal, seasonal, magnetic activity, and solar cycle effects. A comprehensive electric field model was developed that includes the effects of the E and F-region dynamos, magnetospheric sources, and ionospheric conductivities, for both the local and conjugate regions. The E-region dynamo dominates during the day but at night the F-region and convection are more important. This model provides much better agreement with observations of the F-region drifts than previous models. Results indicate that larger magnitudes occur at night, and that daily variation is dominated by the diurnal mode. Seasonal variations in conductivities and thermospheric winds indicate a reversal in direction in the early morning during winter from south to northward. On magnetic perturbed days and the drifts deviate rather strongly from the quiet days average, especially around 13 L.T. for the northward and 18 L.T. for the westward component.

  3. Electric field soundings through thunderstorms

    NASA Technical Reports Server (NTRS)

    Marshall, Thomas C.; Rust, W. D.

    1991-01-01

    Twelve balloon soundings of the electric field in thunderstorms are reported. The maximum magnitude of E in the storms averaged 96 +/-28 kV/m, with the largest being 146 kV/m. The maximum was usually observed between vertically adjacent regions of opposite charge. Using a 1D approximation to Gauss' law, four to ten charge regions in the storms are inferred. The magnitude of the density in the charge regions varied between 0.2 and 13 nC/cu m. The vertical extent of the charge regions ranged from 130 to 2100 m. None of the present 12 storms had charge distributions that fit the long-accepted model of Simpson et al. (1937, 1941) of a lower positive charge, a main negative charge, and an upper positive charge. In addition to regions similar to the Simpson model, the present storms had screening layers at the upper and lower cloud boundaries and extra charge regions, usually in the lower part of the cloud.

  4. Modeling the electric field of weakly electric fish.

    PubMed

    Babineau, David; Longtin, André; Lewis, John E

    2006-09-01

    Weakly electric fish characterize the environment in which they live by sensing distortions in their self-generated electric field. These distortions result in electric images forming across their skin. In order to better understand electric field generation and image formation in one particular species of electric fish, Apteronotus leptorhynchus, we have developed three different numerical models of a two-dimensional cross-section of the fish's body and its surroundings. One of these models mimics the real contour of the fish; two other geometrically simple models allow for an independent study of the effects of the fish's body geometry and conductivity on electric field and image formation. Using these models, we show that the fish's tapered body shape is mainly responsible for the smooth, uniform field in the rostral region, where most electroreceptors are located. The fish's narrowing body geometry is also responsible for the relatively large electric potential in the caudal region. Numerical tests also confirm the previous hypothesis that the electric fish body acts approximately like an ideal voltage divider; this is true especially for the tail region. Next, we calculate electric images produced by simple objects and find they vary according to the current density profile assigned to the fish's electric organ. This explains some of the qualitative differences previously reported for different modeling approaches. The variation of the electric image's shape as a function of different object locations is explained in terms of the fish's geometrical and electrical parameters. Lastly, we discuss novel cues for determining an object's rostro-caudal location and lateral distance using these electric images.

  5. Estimating Electric Fields from Vector Magnetogram Sequences

    NASA Astrophysics Data System (ADS)

    Fisher, George H.; Welsch, B. T.; Abbett, W. P.; Bercik, D. J.

    2009-05-01

    We describe a new technique for estimating the three-dimensional vector electric field in the solar atmosphere by using a time-sequence of vector magnetograms to find an electric field distribution that obeys all 3 components of Faraday's law. The technique uses a ``poloidal-toroidal'' decomposition (PTD) to describe the electric field in terms of two scalar functions. The ``inductive'' PTD solutions to Faraday's Law are not unique, however, since additional contributions to the electric field from a potential function have no effect on Faraday's law. We then describe how estimates for the total electric field including both the inductive and potential components can be made by using variational techniques. The variational approach we develop is similar to Longcope's ``Minimum Energy Fit'' technique, in that the electric field obeys the vertical component of the magnetic induction equation, while also minimizing a positive definite functional. The purely potential part of the electric field can then be recovered by subtracting the PTD electric field from the total field.

  6. Electric-field and magnetic-field sensors

    NASA Astrophysics Data System (ADS)

    Wieckowski, T. W.

    1993-05-01

    Analysis of double-loaded loop antennas and their properties has led to the design of new measuring sensors which enable has led to determination of both electric field strength and magnetic field strength. Sensors of the design proposed are applicable to a quasipoint measurement providing independent determination of the electric and magnetic component of the field.

  7. Spectral studies of the sources of ionospheric electric fields

    SciTech Connect

    Earle, G.D.; Kelley, M.C. )

    1987-01-01

    Spectral analyses have been performed upon a number of incoherent scatter radar data sets obtained at Jicamarca, Peru; Chatanika, Alaska; and Arecibo, Puerto Rico, with the goal of understanding the sources of electric fields with periods in the range of 1-10 hours. Two distinct sources are identified and studied in some detail. In quiet times, atmospheric gravity waves seem the most likely source of the ionospheric electric field. In fact, both in an average sense and in the single case study available the mesospheric winds measured at Poker Flat, Alaska, in this frequency range are remarkably similar in magnitude to the quiet time thermospheric plasma drifts measured overhead by the nearby Chatanika radar. Such drifts are driven by electric fields which, the authors argue, could easily be generated by the observed wind fields. Comparison with the spectra of electric field measurements at other latitudes suggests that such a source is worldwide and determines the geophysical noise level of low- and mid-latitude electric field measurements. Turning to active times, the authors present a measure of the transfer function for electric field measurements. Turning to active times, they present a measure of the transfer function for electric field penetration between high- and low-altitude L shells. At the very lowest frequencies (periods of {ge} 10 hours) the low-altitude sites are well shielded, presumably by an Alfven layer at the inner edge of the ring current. Higher frequency fluctuations penetrate very easily to low latitudes. A response peak seems to occur in the 3- to 5-hour range of periods, with a lower response occurring at 1 cycle/hour, although this result must be viewed as preliminary for now. Between L = 5.5 and L = 1.4 the zonal electric field component as projected to the equatorial plane of the magnetosphere penetrates with little or no attenuation.

  8. Interaction and Aggregation of Colloidal Biological Particles and Droplets in Electrically-Driven Flows

    NASA Technical Reports Server (NTRS)

    Davis, Robert H.; Loewenberg, Michael

    1997-01-01

    The primary objective of this research was to develop a fundamental understanding of aggregation and coalescence processes during electrically-driven migration of cells, particles and droplets. The process by which charged cells, particles, molecules, or drops migrate in a weak electric field is known as electrophoresis. If the migrating species have different charges or surface potentials, they will migrate at different speeds and thus may collide and aggregate or coalesce. Aggregation and coalescence are undesirable, if the goal is to separate the different species on the basis of their different electrophoretic mobilities.

  9. Electric Potential and Electric Field Imaging with Applications

    NASA Technical Reports Server (NTRS)

    Generazio, Ed

    2016-01-01

    The technology and techniques for remote quantitative imaging of electrostatic potentials and electrostatic fields in and around objects and in free space is presented. Electric field imaging (EFI) technology may be applied to characterize intrinsic or existing electric potentials and electric fields, or an externally generated electrostatic field may be used for (illuminating) volumes to be inspected with EFI. The baseline sensor technology, electric field sensor (e-sensor), and its construction, optional electric field generation (quasistatic generator), and current e-sensor enhancements (ephemeral e-sensor) are discussed. Demonstrations for structural, electronic, human, and memory applications are shown. This new EFI capability is demonstrated to reveal characterization of electric charge distribution, creating a new field of study that embraces areas of interest including electrostatic discharge mitigation, crime scene forensics, design and materials selection for advanced sensors, dielectric morphology of structures, inspection of containers, inspection for hidden objects, tether integrity, organic molecular memory, and medical diagnostic and treatment efficacy applications such as cardiac polarization wave propagation and electromyography imaging.

  10. Distributed monitoring system for electric-motor-driven compressors

    SciTech Connect

    Castleberry, K.N.

    1996-01-01

    Personnel in the Instrumentation and Controls Division at the Oak Ridge National Laboratory, in association with the United States Enrichment corporation (USEC), the Navy, and various Department of Energy sponsors, have been involved in the development and application of motor-current signature analysis (CSA) for several years. In that time CSA has proven to not only be useful for manually applied periodic monitoring of electrically driven equipment but it has also been demonstrated to be well suited for dedicated monitoring systems in industrial settings. Recent work has resulted in the development and installation of a system that can monitor up to 640 motor and compressor stages for various aerodynamic conditions in the gas compressors and electrical problems in the drive motors. This report describes a demonstration of that technology installed on 80 stages at each of the two USEC uranium enrichment plants.

  11. Electric Field Generation in Martian Dust Devils

    NASA Technical Reports Server (NTRS)

    Barth, Erika L.; Farrell, William M.; Rafkin, Scot C. R.

    2015-01-01

    Terrestrial dust devils are known to generate electric fields from the vertical separation of charged dust particles. The particles present within the dust devils on Mars may also be subject to similar charging processes and so likely contribute to electric field generation there as well. However, to date, no Marsin situ instrumentation has been deployed to measure electric field strength. In order to explore the electric environment of dust devils on Mars, the triboelectric dust charging physics from the MacroscopicTriboelectric Simulation (MTS) code has been coupled to the Mars Regional Atmospheric ModelingSystem (MRAMS). Using this model, we examine how macroscopic electric fields are generated within martian dust disturbances and attempt to quantify the time evolution of the electrodynamical system.Electric fields peak for several minutes within the dust devil simulations. The magnitude of the electric field is a strong function of the size of the particles present, the average charge on the particles and the number of particles lifted. Varying these parameters results in peak electric fields between tens of millivolts per meter and tens of kilovolts per meter.

  12. Electric Field Generation in Martian Dust Devils

    NASA Technical Reports Server (NTRS)

    Barth, Erika L.; Farrell, William M.; Rafkin, Scot C. R.

    2015-01-01

    Terrestrial dust devils are known to generate electric fields from the vertical separation of charged dust particles. The particles present within the dust devils on Mars may also be subject to similar charging processes and so likely contribute to electric field generation there as well. However, to date, no Marsin situ instrumentation has been deployed to measure electric field strength. In order to explore the electric environment of dust devils on Mars, the triboelectric dust charging physics from the MacroscopicTriboelectric Simulation (MTS) code has been coupled to the Mars Regional Atmospheric ModelingSystem (MRAMS). Using this model, we examine how macroscopic electric fields are generated within martian dust disturbances and attempt to quantify the time evolution of the electrodynamical system.Electric fields peak for several minutes within the dust devil simulations. The magnitude of the electric field is a strong function of the size of the particles present, the average charge on the particles and the number of particles lifted. Varying these parameters results in peak electric fields between tens of millivolts per meter and tens of kilovolts per meter.

  13. Electric field generation in martian dust devils

    NASA Astrophysics Data System (ADS)

    Barth, Erika L.; Farrell, William M.; Rafkin, Scot C. R.

    2016-04-01

    Terrestrial dust devils are known to generate electric fields from the vertical separation of charged dust particles. The particles present within the dust devils on Mars may also be subject to similar charging processes and so likely contribute to electric field generation there as well. However, to date, no Mars in situ instrumentation has been deployed to measure electric field strength. In order to explore the electric environment of dust devils on Mars, the triboelectric dust charging physics from the Macroscopic Triboelectric Simulation (MTS) code has been coupled to the Mars Regional Atmospheric Modeling System (MRAMS). Using this model, we examine how macroscopic electric fields are generated within martian dust disturbances and attempt to quantify the time evolution of the electrodynamical system. Electric fields peak for several minutes within the dust devil simulations. The magnitude of the electric field is a strong function of the size of the particles present, the average charge on the particles and the number of particles lifted. Varying these parameters results in peak electric fields between tens of millivolts per meter and tens of kilovolts per meter.

  14. A physical theory of the instabilities of electrically driven jets

    NASA Astrophysics Data System (ADS)

    Hohman, Moses Macduff

    Electrospinning and electrospraying produce nanoscale fibers and drops from liquid pushed through a millimeter-scale nozzle. This thesis argues that both phenomena can be understood by analyzing the instability of electrically forced fluid jets with increasing field strength. We present a systematic study of the development of the instability to derive the essential mechanisms from first principles. An asymptotic approximation of the equations of electrohydrodynamics is developed so that quantitative comparisons with experiment can be carried out. The approximation governs long wavelength axisymmetric distortions of the jet as well as long wavelength oscillations of the jet centerline. Three different instabilities are identified: the classical (axisymmetric) Rayleigh instability, and electric field induced varicose and whipping instabilities. At increasing field strengths, the electrical instabilities are enhanced while the Rayleigh instability is suppressed. Which electric instability wins depends strongly on the surface charge density and radius of the jet. Through a combination of theory and experiments the surface charge density on the jet as it thins from the nozzle is determined. Quantitative agreement between theory and experiment requires taking into account both the fringe fields of the nozzle and the local charge distribution in the vicinity of the nozzle. Combining the jet shapes and charge densities with the stability analysis yields predictions for the instabilities that agree with experiments. In total, the work suggests that the most useful paradigm for understanding electrospraying and electrospinning is not a Taylor cone, but instead that of a rapidly whipping jet.

  15. Nanomechanical electric and electromagnetic field sensor

    DOEpatents

    Datskos, Panagiotis George; Lavrik, Nickolay

    2015-03-24

    The present invention provides a system for detecting and analyzing at least one of an electric field and an electromagnetic field. The system includes a micro/nanomechanical oscillator which oscillates in the presence of at least one of the electric field and the electromagnetic field. The micro/nanomechanical oscillator includes a dense array of cantilevers mounted to a substrate. A charge localized on a tip of each cantilever interacts with and oscillates in the presence of the electric and/or electromagnetic field. The system further includes a subsystem for recording the movement of the cantilever to extract information from the electric and/or electromagnetic field. The system further includes a means of adjusting a stiffness of the cantilever to heterodyne tune an operating frequency of the system over a frequency range.

  16. Horizontal electric fields from lightning return strokes

    NASA Technical Reports Server (NTRS)

    Thomson, E. M.; Medelius, P. J.; Rubinstein, M.; Uman, M. A.; Johnson, J.

    1988-01-01

    An experiment to measure simultaneously the wideband horizontal and vertical electric fields from lightning return strokes is described. Typical wave shapes of the measured horizontal and vertical fields are presented, and the horizontal fields are characterized. The measured horizontal fields are compared with calculated horizontal fields obtained by applying the wavetilt formula to the vertical fields. The limitations and sources of error in the measurement technique are discussed.

  17. Interaction Between Flames and Electric Fields Studied

    NASA Technical Reports Server (NTRS)

    Yuan, Zeng-Guang; Hegde, Uday

    2003-01-01

    The interaction between flames and electric fields has long been an interesting research subject that has theoretical importance as well as practical significance. Many of the reactions in a flame follow an ionic pathway: that is, positive and negative ions are formed during the intermediate steps of the reaction. When an external electric field is applied, the ions move according to the electric force (the Coulomb force) exerted on them. The motion of the ions modifies the chemistry because the reacting species are altered, it changes the velocity field of the flame, and it alters the electric field distribution. As a result, the flame will change its shape and location to meet all thermal, chemical, and electrical constraints. In normal gravity, the strong buoyant effect often makes the flame multidimensional and, thus, hinders the detailed study of the problem.

  18. Fiber-Optic Electric-Field Meter

    NASA Technical Reports Server (NTRS)

    Johnston, A. R.

    1986-01-01

    Sensor for measuring electric-field strength does not greatly alter field in which placed. Sensor used to map fields in electric power substation or under high-voltage transmission line. Also used for laboratory measurements. Fused-silica fibers guide light from source to photometer. Light emerges from tip of source fiber, passes through curved coupler, and enters tip of photometer fiber. Attenuation of coupler changes with distance between fiber tips.

  19. ELECTRIC AND MAGNETIC FIELDS <100 KHZ IN ELECTRIC AND GASOLINE-POWERED VEHICLES.

    PubMed

    Tell, Richard A; Kavet, Robert

    2016-12-01

    Measurements were conducted to investigate electric and magnetic fields (EMFs) from 120 Hz to 10 kHz and 1.2 to 100 kHz in 9 electric or hybrid vehicles and 4 gasoline vehicles, all while being driven. The range of fields in the electric vehicles enclosed the range observed in the gasoline vehicles. Mean magnetic fields ranged from nominally 0.6 to 3.5 µT for electric/hybrids depending on the measurement band compared with nominally 0.4 to 0.6 µT for gasoline vehicles. Mean values of electric fields ranged from nominally 2 to 3 V m(-1) for electric/hybrid vehicles depending on the band, compared with 0.9 to 3 V m(-1) for gasoline vehicles. In all cases, the fields were well within published exposure limits for the general population. The measurements were performed with Narda model EHP-50C/EHP-50D EMF analysers that revealed the presence of spurious signals in the EHP-50C unit, which were resolved with the EHP-50D model.

  20. Molecular dynamics in high electric fields

    NASA Astrophysics Data System (ADS)

    Apostol, M.; Cune, L. C.

    2016-06-01

    Molecular rotation spectra, generated by the coupling of the molecular electric-dipole moments to an external time-dependent electric field, are discussed in a few particular conditions which can be of some experimental interest. First, the spherical-pendulum molecular model is reviewed, with the aim of introducing an approximate method which consists in the separation of the azimuthal and zenithal motions. Second, rotation spectra are considered in the presence of a static electric field. Two particular cases are analyzed, corresponding to strong and weak fields. In both cases the classical motion of the dipoles consists of rotations and vibrations about equilibrium positions; this motion may exhibit parametric resonances. For strong fields a large macroscopic electric polarization may appear. This situation may be relevant for polar matter (like pyroelectrics, ferroelectrics), or for heavy impurities embedded in a polar solid. The dipolar interaction is analyzed in polar condensed matter, where it is shown that new polarization modes appear for a spontaneous macroscopic electric polarization (these modes are tentatively called "dipolons"); one of the polarization modes is related to parametric resonances. The extension of these considerations to magnetic dipoles is briefly discussed. The treatment is extended to strong electric fields which oscillate with a high frequency, as those provided by high-power lasers. It is shown that the effect of such fields on molecular dynamics is governed by a much weaker, effective, renormalized, static electric field.

  1. Electric field replaces gravity in laboratory

    NASA Astrophysics Data System (ADS)

    Gorgolewski, S.

    For several years experiments in physical laboratories and in the fitotron have shown that one can replace gravitational field with electrical fields for plants. First obvious experiments in strong electrical fields in the MV/m regi on show that any materials and living plants respond immediately to Coulomb forces. Such fields are found in nature during thunderstorms. One has to be very careful in handling such strong fields for safety reasons. The fair weather global electrical field is about 20,000 times weaker. The coulomb forces are proportional to the square of the field strength and are thus 400 milion times weaker for a field of the order of 100 V/m.Yet it was found that some plants respond to such "weak" fields. We must remember that the electrical field is a factor of 10 38 times stronger than gravitational interaction. In plants we have dissociated in water mineral salts and the ions are subject to such ernormous forces. It was shown and published that the positive charges in the air in fields of the order of 3kV/m enhance lettuce growth by a factor of four relative to fields about 30 times weaker (100V/m). Reversal of the field polarity reverses the direction of plant growth and retards the plant's growth. Such fields overpower the gravitropism in the laboratory. More so horizontal electrical field is othogonal to gravity, now the fields do not see each other. Lettuce now growth horizontally ignoring the gravitational field. We can thus select the plants whose electrotropism even in the laboratory overwhelms gravity. This is important for the long space flights that we must grow vegetarian food for the crew. The successful harvesting of wheat in orbit does not contradict our experimental findings because wheat is not electrotropic like all plants from the grass family. The results of fitotron experiments with kV/m electrical fields are richly illustrated with colour digital photographs. We also subjected the candle flame to very strong horizontal

  2. Enzyme catalyzed electricity-driven water softening system.

    PubMed

    Arugula, Mary A; Brastad, Kristen S; Minteer, Shelley D; He, Zhen

    2012-12-10

    Hardness in water, which is caused by divalent cations such as calcium and magnesium ions, presents a major water quality problem. Because hard water must be softened before use in residential applications, there is great interest in the saltless water softening process because, unlike ion exchange softeners, it does not introduce additional ions into water. In this study, a saltless hardness removal driven by bioelectrochemical energy produced through enzymatic oxidation of glucose was proposed and investigated. Glucose dehydrogenase was coated on a carbon electrode to catalyze glucose oxidation in the presence of NAD⁺ as a cofactor/mediator and methylene green as an electrocatalyst. The results showed that electricity generation stimulated hardness removal compared with non-electricity conditions. The enzymatic water softener worked upon a 6h batch operation per day for eight days, and achieved an average hardness removal of 46% at a high initial concentration of 800 mg/L as CaCO₃. More hardness was removed at a lower initial concentration. For instance, at 200mg/L as CaCO₃ the enzymatic water softener removed 76.4±4.6% of total hardness. The presence of magnesium ions decreased hardness removal because of its larger hydrated radius than calcium ions. The enzymatic water softener removed 70-80% of total hardness from three actual hard water samples. These results demonstrated a proof-of-concept that enzyme catalyzed electricity generation can be used to soften hard water. Copyright © 2012 Elsevier Inc. All rights reserved.

  3. Magnetic field dependence of threshold electric field for magnetoelectric switching of exchange-bias polarity

    NASA Astrophysics Data System (ADS)

    Nguyen, Thi Van Anh; Shiratsuchi, Yu; Kobane, Atsushi; Yoshida, Saori; Nakatani, Ryoichi

    2017-08-01

    We report the magnetic field dependence of the threshold electric field Eth for the magnetoelectric switching of the perpendicular exchange bias in Pt/Co/Au/Cr2O3/Pt stacked films using a reversible isothermal electric tuning approach. The Eth values for the positive-to-negative and negative-to-positive switching are different because of the unidirectional nature of the interfacial exchange coupling. The Eth values are inversely proportional to the magnetic-field strength, and the quantitative analysis of this relationship suggests that the switching is driven by the nucleation and growth of the antiferromagnetic domain. We also find that the magnetic-field dependence of Eth exhibits an offset electric field that might be related to the uncompensated antiferromagnetic moments located mainly at the interface.

  4. Electric field assisted switching in magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Wang, Weigang; Li, Mingen; Hagemen, Stephen; Chien, C. L.

    2012-02-01

    It is of great interest to acquire large effects of electric field on magnetic properties, partly driven by the premise that voltage-controlled magnetization reversal would be far more energy efficient and be compatible with the ubiquitous voltage-controlled semiconductor devices. Normally the effect of electric field in metallic systems is negligible because the electric field can only penetrate into the materials by a few monolayers due to screening by the free electrons. Here we report the pronounced effects of electric field in magnetic tunnel junctions (MTJs) with very thin CoFeB electrodes, where the magnetic anisotropy originates solely from the CoFeB/MgO interfaces. The MTJs have the key structure of Co40Fe40B20(1.2-1.3nm)/MgO(1.2-2nm)/Co40Fe40B20(1.6nm) and the tunneling magnetoresistance in all junctions is in excess of 100%. Due to the redistribution of electrons among the different 3d orbitals of Fe and Co, the perpendicular magnetic anisotropy of the CoFeB electrodes can be significantly modified by an applied electric field. As a result, the coercivity, the magnetic configuration, and the tunneling magnetoresistance of the MTJs can be manipulated by voltage pulses, such that the high and low resistance states of the MTJ can be reversibly controlled by voltages less than 1.5 V in magnitude and with much smaller current densities.

  5. Control of magnetism by electric fields.

    PubMed

    Matsukura, Fumihiro; Tokura, Yoshinori; Ohno, Hideo

    2015-03-01

    The electrical manipulation of magnetism and magnetic properties has been achieved across a number of different material systems. For example, applying an electric field to a ferromagnetic material through an insulator alters its charge-carrier population. In the case of thin films of ferromagnetic semiconductors, this change in carrier density in turn affects the magnetic exchange interaction and magnetic anisotropy; in ferromagnetic metals, it instead changes the Fermi level position at the interface that governs the magnetic anisotropy of the metal. In multiferroics, an applied electric field couples with the magnetization through electrical polarization. This Review summarizes the experimental progress made in the electrical manipulation of magnetization in such materials, discusses our current understanding of the mechanisms, and finally presents the future prospects of the field.

  6. Physics and Chemistry in High Electric Fields

    DTIC Science & Technology

    1992-10-06

    in heterogeneous catalysis and in chemical vapor deposition, may be established. To discuss field effects qualitatively, we look, in Fig. 1, at a...fields thus opening up new reaction pathways in heterogeneous catalysis . Most work so far has been concentrating on static electric fields; how- ever

  7. Michaelis-Menten equation for an enzyme in an oscillating electric field.

    PubMed Central

    Robertson, B; Astumian, R D

    1990-01-01

    The electric charges on an enzyme may move concomitantly with a conformational change. Such an enzyme will absorb energy from an oscillating electric field. If in addition the enzyme has a larger association constant for substrate than for product, as is often true, it can use this energy to drive the catalyzed reaction away from equilibrium. Approximate analytical expressions are given for the field-driven flux, electrical power absorbed, free-energy produced per unit time, thermodynamic efficiency, and zero-flux concentrations. The field-driven flux is written as a generalized Michaelis-Menten equation. PMID:2248999

  8. Control of Hall angle of Skyrmion driven by electric current

    NASA Astrophysics Data System (ADS)

    Gao-Bin, Liu; Da, Li; de Chatel, P. F.; Jian, Wang; Wei, Liu; Zhi-Dong, Zhang

    2016-06-01

    Skyrmions are very promising for applications in spintronics and magnetic memory. It is desired to manipulate and operate a single skyrmion. Here we report on the thermal effect on the motion of current-driven magnetic Skyrmions in magnetic metal. The results show that the magnon current induced by the thermal gradient acts on Skyrmions via magnonic spin-transfer torque, an effect of the transverse and longitudinal Skyrmions drift velocities, thus leading to the effective manipulation of the Hall angle through the ratio of thermal gradient to electric current density, which can be used as a Skyrmion valve. Project supported by the National Natural Science Foundation of China (Grant No. 51331006) and the Fund from the Chinese Academy of Sciences (Grant No. KJZD-EW-M05).

  9. Electric field imaging of single atoms

    NASA Astrophysics Data System (ADS)

    Shibata, Naoya; Seki, Takehito; Sánchez-Santolino, Gabriel; Findlay, Scott D.; Kohno, Yuji; Matsumoto, Takao; Ishikawa, Ryo; Ikuhara, Yuichi

    2017-05-01

    In scanning transmission electron microscopy (STEM), single atoms can be imaged by detecting electrons scattered through high angles using post-specimen, annular-type detectors. Recently, it has been shown that the atomic-scale electric field of both the positive atomic nuclei and the surrounding negative electrons within crystalline materials can be probed by atomic-resolution differential phase contrast STEM. Here we demonstrate the real-space imaging of the (projected) atomic electric field distribution inside single Au atoms, using sub-Å spatial resolution STEM combined with a high-speed segmented detector. We directly visualize that the electric field distribution (blurred by the sub-Å size electron probe) drastically changes within the single Au atom in a shape that relates to the spatial variation of total charge density within the atom. Atomic-resolution electric field mapping with single-atom sensitivity enables us to examine their detailed internal and boundary structures.

  10. Electric field imaging of single atoms

    PubMed Central

    Shibata, Naoya; Seki, Takehito; Sánchez-Santolino, Gabriel; Findlay, Scott D.; Kohno, Yuji; Matsumoto, Takao; Ishikawa, Ryo; Ikuhara, Yuichi

    2017-01-01

    In scanning transmission electron microscopy (STEM), single atoms can be imaged by detecting electrons scattered through high angles using post-specimen, annular-type detectors. Recently, it has been shown that the atomic-scale electric field of both the positive atomic nuclei and the surrounding negative electrons within crystalline materials can be probed by atomic-resolution differential phase contrast STEM. Here we demonstrate the real-space imaging of the (projected) atomic electric field distribution inside single Au atoms, using sub-Å spatial resolution STEM combined with a high-speed segmented detector. We directly visualize that the electric field distribution (blurred by the sub-Å size electron probe) drastically changes within the single Au atom in a shape that relates to the spatial variation of total charge density within the atom. Atomic-resolution electric field mapping with single-atom sensitivity enables us to examine their detailed internal and boundary structures. PMID:28555629

  11. Electric field imaging of single atoms.

    PubMed

    Shibata, Naoya; Seki, Takehito; Sánchez-Santolino, Gabriel; Findlay, Scott D; Kohno, Yuji; Matsumoto, Takao; Ishikawa, Ryo; Ikuhara, Yuichi

    2017-05-30

    In scanning transmission electron microscopy (STEM), single atoms can be imaged by detecting electrons scattered through high angles using post-specimen, annular-type detectors. Recently, it has been shown that the atomic-scale electric field of both the positive atomic nuclei and the surrounding negative electrons within crystalline materials can be probed by atomic-resolution differential phase contrast STEM. Here we demonstrate the real-space imaging of the (projected) atomic electric field distribution inside single Au atoms, using sub-Å spatial resolution STEM combined with a high-speed segmented detector. We directly visualize that the electric field distribution (blurred by the sub-Å size electron probe) drastically changes within the single Au atom in a shape that relates to the spatial variation of total charge density within the atom. Atomic-resolution electric field mapping with single-atom sensitivity enables us to examine their detailed internal and boundary structures.

  12. Electric field control of the magnetocaloric effect.

    PubMed

    Gong, Yuan-Yuan; Wang, Dun-Hui; Cao, Qing-Qi; Liu, En-Ke; Liu, Jian; Du, You-Wei

    2015-02-04

    Through strain-mediated magnetoelectric coupling, it is demonstrated that the magnetocaloric effect of a ferromagnetic shape-memory alloy can be controlled by an electric field. Large hysteresis and the limited operating temperature region are effectively overcome by applying an electric field on a laminate comprising a piezoelectric and the alloy. Accordingly, a model for an active magnetic refrigerator with high efficiency is proposed in principle.

  13. Pulsed Electric Fields for Biological Weapons Defense

    DTIC Science & Technology

    2002-01-01

    studies of Bacillus atrophaeus (formerly Bacillus subtilis var. niger). 15. SUBJECT TERMS nanosecond high-field electric pulse, electroperturbation...sterility monitoring kit, which utilizes spores of Bacillus atrophaeus (formerly Bacillus subtilis var. niger) deposited on paper in glassine envelopes, has...report a study of the application of ultra- short high-field electric pulses (5 MV/m, 100-ns pulse width, 4-ns rise time) to Bacillus atrophaeus spores

  14. Microwave ovens: mapping the electrical field distribution.

    PubMed

    Ng, K H

    1991-07-01

    Uniformity of electric field intensity of microwaves within the microwave oven cavity is necessary to ensure even load-heating, and is particularly important in pathology procedures where small volume irradiation is carried out. A simple and rapid method for mapping electric field distribution, using reversible thermographic paint, is described. Spatial heating patterns for various positions, and the effects of introducing dummy loads to modify heating distributions, have been obtained for a dedicated microwave processor, and comparison made with a domestic microwave oven.

  15. Tendon Fibroplasia Induction by Exogenous Electrical Fields.

    DTIC Science & Technology

    1986-08-10

    AD-A172 279 TENDON FIEROPLASIA INDUCTION BY EXOGENOUS ELECTRICAL 1/𔃻 FIELDS(U) MEDICAL COLL OF VIRGINIA RICHMOND DEPT OF PHYSIOLOGY AND BIOPHYSICS S...Security Classification) Tendon Fibroplasia Induction by Exogenous Electrical Fields l2dAL 9I F.; Liu, Li-Ming. 134. TYPE PF REPORT 13b. TIME COVERED 14... tendon explant fibroplasia, collagen synthesis and oriented migration. Independent variables are: pulse repetition rate, pulse duration, peak current

  16. Electrical-driven transport of endohedral fullerene encapsulating a single water molecule.

    PubMed

    Xu, Baoxing; Chen, Xi

    2013-04-12

    Encapsulating a single water molecule inside an endohedral fullerene provides an opportunity for manipulating the H2O@C60 through the encapsulated polar H2O molecule. Using molecular dynamic simulations, we propose a strategy of electrical-driven transport of H2O@C60 inside a channel, underpinned by the unique behavior of a water molecule free from a hydrogen-bonding environment. When an external electrical field is applied along the channel's axial direction, steady-state transport of H2O@C60 can be reached. The transport direction and rate depend on the applied electrical intensity as well as the polar orientation of the encapsulated H2O molecule.

  17. Electric/magnetic field sensor

    SciTech Connect

    Schill, Jr., Robert A.; Popek, Marc

    2009-01-27

    A UNLV novel electric/magnetic dot sensor includes a loop of conductor having two ends to the loop, a first end and a second end; the first end of the conductor seamlessly secured to a first conductor within a first sheath; the second end of the conductor seamlessly secured to a second conductor within a second sheath; and the first sheath and the second sheath positioned adjacent each other. The UNLV novel sensor can be made by removing outer layers in a segment of coaxial cable, leaving a continuous link of essentially uncovered conductor between two coaxial cable legs.

  18. Electric field measurements with stratospheric balloons

    NASA Technical Reports Server (NTRS)

    Iversen, I. B.

    1989-01-01

    Electric fields and currents in the middle atmosphere are important elements of the modern picture of this region. Balloon instruments, reaching the level of the stratosphere, were used extensively for the experimental work. The research has shown good progress, both in the MAP period and in the years before and after. The knowledge was increased about, e.g., the upper atmosphere potential, the electric properties of the medium itself and about the coupling with magnetospheric (ionospheric) fields and currents. Also various measurements have brought about a discussion of the possible existence of hitherto unknown sources. Throughout the MAP period the work on a possible definition of an electric index has continued.

  19. Crystal growth under external electric fields

    SciTech Connect

    Uda, Satoshi; Koizumi, Haruhiko; Nozawa, Jun; Fujiwara, Kozo

    2014-10-06

    This is a review article concerning the crystal growth under external electric fields that has been studied in our lab for the past 10 years. An external field is applied electrostatically either through an electrically insulating phase or a direct injection of an electric current to the solid-interface-liquid. The former changes the chemical potential of both solid and liquid and controls the phase relationship while the latter modifies the transport and partitioning of ionic solutes in the oxide melt during crystallization and changes the solute distribution in the crystal.

  20. Electrically-driven optical antennas enabled by mesoscopic contacts

    NASA Astrophysics Data System (ADS)

    Uskov, Alexander V.; Khurgin, Jacob B.; Bouhelier, Alexandre; Buret, Mikael; Protsenko, Igor E.; Smetanin, Igor V.

    2017-02-01

    Electrically driven optical antennas are attracting much attention, in particular, due to necessity to develop integrated electrical source of surface plasmons for future plasmonic nanocircuitries. By default, this term denotes a metal nanostructure, in which electromagnetic oscillations at optical frequencies are excited by electrons, tunneling between metallic parts of the structure when a bias voltage is applied between them. Instead of relying on an inefficient inelastic light emission in a tunnel gap, we are suggesting to use ballistic nanoconstrictions as the feed element of an optical antennas in order to excite electromagnetic plasmonic modes. Similarly to tunneling structures, the voltage applied at the constriction falls over the contact of nanoscale length. Electron passing through the contact ballistically can gain the energy provided by the bias 1eV and exchange it into an mode of the optical antenna. We discussed the underlying mechanisms responsible for the optical emission, and show that with nanoscale contact, one can reach quantum efficiency orders of magnitude larger than with standard tunneling structures.

  1. Adaptive electric field control of epileptic seizures.

    PubMed

    Gluckman, B J; Nguyen, H; Weinstein, S L; Schiff, S J

    2001-01-15

    We describe a novel method of adaptively controlling epileptic seizure-like events in hippocampal brain slices using electric fields. Extracellular neuronal activity is continuously recorded during field application through differential extracellular recording techniques, and the applied electric field strength is continuously updated using a computer-controlled proportional feedback algorithm. This approach appears capable of sustained amelioration of seizure events in this preparation when used with negative feedback. Seizures can be induced or enhanced by using fields of opposite polarity through positive feedback. In negative feedback mode, such findings may offer a novel technology for seizure control. In positive feedback mode, adaptively applied electric fields may offer a more physiological means of neural modulation for prosthetic purposes than previously possible.

  2. Rotating Capacitor Measures Steady Electric Fields

    NASA Technical Reports Server (NTRS)

    Johnston, A. R.; Kirkham, H.; Eng, B.

    1986-01-01

    Portable sensor measures electric fields created by dc powerlines or other dc-high-voltage sources. Measures fields from 70 to 50,000 V/m with linearity of 2 percent. Sensor used at any height above ground. Measures both magnitude and direction of field and provides signals representing these measurements to remote readout device. Sensor functions with minimal disturbance of field it is measuring.

  3. Midday reversal of equatorial ionospheric electric field

    NASA Astrophysics Data System (ADS)

    Rastogi, R. G.

    1997-10-01

    A comparative study of the geomagnetic and ionospheric data at equatorial and low-latitude stations in India over the 20 year period 1956-1975 is described. The reversal of the electric field in the ionosphere over the magnetic equator during the midday hours indicated by the disappearance of the equatorial sporadic E region echoes on the ionograms is a rare phenomenon occurring on about 1% of time. Most of these events are associated with geomagnetically active periods. By comparing the simultaneous geomagnetic H field at Kodaikanal and at Alibag during the geomagnetic storms it is shown that ring current decreases are observed at both stations. However, an additional westward electric field is superimposed in the ionosphere during the main phase of the storm which can be strong enough to temporarily reverse the normally eastward electric field in the dayside ionosphere. It is suggested that these electric fields associated with the V×Bz electric fields originate at the magnetopause due to the interaction of the solar wind and the interplanetary magnetic field.

  4. Magnetospheric electric fields and auroral oval

    NASA Technical Reports Server (NTRS)

    Laakso, Harri; Pedersen, Arne; Craven, John D.; Frank, L. A.

    1992-01-01

    DC electric field variations in a synchronous orbit (GEOS 2) during four substorms in the time sector 19 to 01 LT were investigated. Simultaneously, the imaging photometer on board DE 1 provided auroral images that are also utilized. Substorm onset is defined here as a sudden appearance of large electric fields. During the growth phase, the orientation of the electric field begins to oscillate some 30 min prior to onset. About 10 min before the onset GEOS 2 starts moving into a more tenuous plasma, probably due to a thinning of the current sheet. The onset is followed by a period of 10 to 15 min during which large electric fields occur. This interval can be divided into two intervals. During the first interval, which lasts 4 to 8 min, very large fields of 8 to 20 mV/m are observed, while the second interval contains relatively large fields (2 to 5 mV/m). A few min after the onset, the spacecraft returns to a plasma region of higher electron fluxes which are usually larger than before substorm. Some 30 min after onset, enhanced activity, lasting about 10 min, appears in the electric field. One of the events selected offers a good opportunity to study the formation and development of the Westward Traveling Surge (WST). During the traversal of the leading edge of the WTS (approximately 8 min) a stable wave mode at 5.7 mHz is detected.

  5. Electric current-driven migration of electrically neutral particles in liquids

    SciTech Connect

    Zhang, Xinfang E-mail: r.qin@imperial.ac.uk; Qin, Rongshan E-mail: r.qin@imperial.ac.uk

    2014-03-17

    We design and experimentally demonstrate a migration of electrically neutral particles in liquids driven by electric current according to the discrepancies of their electrical conductivities. A force from electric current to electrically neutral particles has been identified to drive the particles toward the lateral surface from the centre of suspension via three distinguishable zones, namely, pushing, trapping, and expelling zones. The driving force can overtake gravity in practical cases. The property of the force is found neither similar to that of the force in electromagnetophoresis nor similar to that of the electromigration force in terms of direction and magnitude. An expression for the force at the pushing zone has been developed based on the numerical calculation of the thermodynamics of suspension fluids. The excellent agreement between numerical calculations and experimental data demonstrates that our calculation provides fundamental and predictive insight into particles separation from the liquids. Therefore, it is possible to use the force in many engineering applications such as separation of particles according to the differences of their electrical conductivities.

  6. Biological effects of electric fields: EPRI's role

    SciTech Connect

    Kavet, R.

    1982-07-01

    Since 1973 the Electric Power Research Institute (EPRI) has supported research to evaluate the biological effects which may result from exposure to electric fields produced by AC overhead transmission lines; more recently, EPRI has also begun DC research. Through 1981 EPRI will have expended $8.7M on these efforts. Ongoing AC projects are studying a variety of lifeforms exposed to electric fields; these include humans, miniature swine, rats, honeybees, chick embryos, and crops. The status of these projects is discussed. The DC program has not as yet produced data. These studies will add to the current data base so as to enable a more complete assessment of health risks which may be associated with exposure to electric fields at power frequencies.

  7. Electric field induced spin-polarized current

    DOEpatents

    Murakami, Shuichi; Nagaosa, Naoto; Zhang, Shoucheng

    2006-05-02

    A device and a method for generating an electric-field-induced spin current are disclosed. A highly spin-polarized electric current is generated using a semiconductor structure and an applied electric field across the semiconductor structure. The semiconductor structure can be a hole-doped semiconductor having finite or zero bandgap or an undoped semiconductor of zero bandgap. In one embodiment, a device for injecting spin-polarized current into a current output terminal includes a semiconductor structure including first and second electrodes, along a first axis, receiving an applied electric field and a third electrode, along a direction perpendicular to the first axis, providing the spin-polarized current. The semiconductor structure includes a semiconductor material whose spin orbit coupling energy is greater than room temperature (300 Kelvin) times the Boltzmann constant. In one embodiment, the semiconductor structure is a hole-doped semiconductor structure, such as a p-type GaAs semiconductor layer.

  8. Stability of Spherical Vesicles in Electric Fields

    PubMed Central

    2010-01-01

    The stability of spherical vesicles in alternating (ac) electric fields is studied theoretically for asymmetric conductivity conditions across their membranes. The vesicle deformation is obtained from a balance between the curvature elastic energies and the work done by the Maxwell stresses. The present theory describes and clarifies the mechanisms for the four types of morphological transitions observed experimentally on vesicles exposed to ac fields in the frequency range from 500 to 2 × 107 Hz. The displacement currents across the membranes redirect the electric fields toward the membrane normal to accumulate electric charges by the Maxwell−Wagner mechanism. These accumulated electric charges provide the underlying molecular mechanism for the morphological transitions of vesicles as observed on the micrometer scale. PMID:20575588

  9. Evolution of tachyon kink with electric field

    NASA Astrophysics Data System (ADS)

    Cho, Inyong; Kwon, O.-Kab; Lee, Chong Oh

    2007-04-01

    We investigate the decay of an inhomogeneous D1-brane wrapped on a S1 with an electric field. The model that we consider consists of an array of tachyon kink and anti-kink with a constant electric flux. Beginning with an initially static configuration, we numerically evolve the tachyon field with some perturbations under a fixed boundary condition at diametrically opposite points on the circle S1. When the electric flux is smaller than the critical value, the tachyon kink becomes unstable; the tachyon field rolls down the potential, and the lower dimensional D0- and bar D0-brane become thin, which resembles the caustic formation known for this type of the system in the literature. For the supercritical values of the electric flux, the tachyon kink remains stable.

  10. IEMDC IN-LINE ELECTRIC MOTOR DRIVEN COMPRESSOR

    SciTech Connect

    Michael J. Crowley; Prem N. Bansal

    2004-10-01

    This report contains the final project summary and deliverables required by the award for the development of an In-line Electric Motor Driven Compressor (IEMDC). Extensive work was undertaken during the course of the project to develop the motor and the compressor section of the IEMDC unit. Multiple design iterations were performed to design an electric motor for operation in a natural gas environment and to successfully integrate the motor with a compressor. During the project execution, many challenges were successfully overcome in order to achieve the project goals and to maintain the system design integrity. Some of the challenges included limiting the magnitude of the compressor aerodynamic loading for appropriate sizing of the magnetic bearings, achieving a compact motor rotor size to meet the rotor dynamic requirements of API standards, devising a motor cooling scheme using high pressure natural gas, minimizing the impact of cooling on system efficiency, and balancing the system thrust loads for the magnetic thrust bearing. Design methods that were used on the project included validated state-of-the-art techniques such as finite element analysis and computational fluid dynamics along with the combined expertise of both Curtiss-Wright Electro-Mechanical Corporation and Dresser-Rand Company. One of the most significant areas of work undertaken on the project was the development of the unit configuration for the system. Determining the configuration of the unit was a significant step in achieving integration of the electric motor into a totally enclosed compression system. Product review of the IEMDC unit configuration was performed during the course of the development process; this led to an alternate design configuration. The alternate configuration is a modular design with the electric motor and compressor section each being primarily contained in its own pressure containing case. This new concept resolved the previous conflict between the aerodynamic flow

  11. Rotationally Vibrating Electric-Field Mill

    NASA Technical Reports Server (NTRS)

    Kirkham, Harold

    2008-01-01

    A proposed instrument for measuring a static electric field would be based partly on a conventional rotating-split-cylinder or rotating-split-sphere electric-field mill. However, the design of the proposed instrument would overcome the difficulty, encountered in conventional rotational field mills, of transferring measurement signals and power via either electrical or fiber-optic rotary couplings that must be aligned and installed in conjunction with rotary bearings. Instead of being made to rotate in one direction at a steady speed as in a conventional rotational field mill, a split-cylinder or split-sphere electrode assembly in the proposed instrument would be set into rotational vibration like that of a metronome. The rotational vibration, synchronized with appropriate rapid electronic switching of electrical connections between electric-current-measuring circuitry and the split-cylinder or split-sphere electrodes, would result in an electrical measurement effect equivalent to that of a conventional rotational field mill. A version of the proposed instrument is described.

  12. Electric Field Controlled Self-Assembly of Hierarchically Ordered Membranes

    PubMed Central

    Velichko, Yuri S.; Mantei, Jason R.; Bitton, Ronit; Carvajal, Daniel; Shull, Kenneth R.; Stupp, Samuel I.

    2012-01-01

    Self-assembly in the presence of external forces is an adaptive, directed organization of molecular components under nonequilibrium conditions. While forces may be generated as a result of spontaneous interactions among components of a system, intervention with external forces can significantly alter the final outcome of self-assembly. Superimposing these intrinsic and extrinsic forces provides greater degrees of freedom to control the structure and function of self-assembling materials. In this work we investigate the role of electric fields during the dynamic self-assembly of a negatively charged polyelectrolyte and a positively charged peptide amphiphile in water leading to the formation of an ordered membrane. In the absence of electric fields, contact between the two solutions of oppositely charged molecules triggers the growth of closed membranes with vertically oriented fibrils that encapsulate the polyelectrolyte solution. This process of self-assembly is intrinsically driven by excess osmotic pressure of counterions, and the electric field is found to modify the kinetics of membrane formation, and also its morphology and properties. Depending on the strength and orientation of the field we observe a significant increase or decrease of up to nearly 100% in membrane thickness, as well as the controlled rotation of nanofiber growth direction by 90 degrees, resulting in a significant increase in mechanical stiffness. These results suggest the possibility of using electric fields to control structure in self-assembly processes involving diffusion of oppositely charged molecules. PMID:23166533

  13. Extreme Harmonic Generation in Electrically Driven Spin Resonance

    NASA Astrophysics Data System (ADS)

    Stehlik, Jiri

    2015-03-01

    InAs nanowire double quantum dots offer a rich platform for studying single spin physics in a material with large spin-orbit (SO) coupling. The large SO coupling allows all electrical control of the electron spin through electric dipole spin resonance (EDSR). Here an oscillating electric field of frequency f displaces the electron wave function, while a magnetic field with strength B is applied. Spin rotations occur when the resonance condition hf = gμB B is met. Here g is the electron g-factor, h is Planck's constant, and μB is the Bohr magneton. We find that near zero interdot detuning efficient spin rotations also occur when hf = ngμB B , with n being an integer as large as 8 in our system. The harmonics feature a striking odd/even dependence. While the odd harmonics show an enhancement of the leakage current, the even harmonics show a reduction. In contrast, we do not observe any measurable harmonics at large detuning. We link the presence of harmonics with additional anti-crossings present in the level diagram. This implies that harmonics are the result of Landau-Zener transitions occurring at multiple anti-crossings. Recent theoretical work supports this conclusion. Research performed in collaboration with M. D. Schroer, M. Z. Maialle, M. H. Degani, and J. R. Petta. Research was supported by the Sloan and Packard Foundations, Army Research Office, DARPA QuEST and the NSF.

  14. Magnetospheric electric field measurements during sudden commencements

    NASA Technical Reports Server (NTRS)

    Aggson, T. L.; Skillman, T. L.

    1973-01-01

    Direction measurements of electric fields were made in the outer magnetosphere during two sudden commencements in 1972. These measurements were observed with the double floating probe experiment carried aboard the IMP 6 satellite. The initial variations of the measured electric field consisted of an increase from a background of about 1 mv/meter to some 10 mv/meter at about 7 rE (earth radi) and to some 4 mv/meter at 3 rE. These initial electric field disturbances were longitudinal, oriented counter clockwise about an axis pointed north. A solution of Maxwell's third equation is derived for these measurements using a quasi-static version of Mead's model of the magnetosphere B (t). This solution seems to describe well the magnitude and direction of the initial perturbation of the electric field vectors observed during these two sudden commencements. After the initial increase, the measured electric field rings several times with periods of the order of minutes. This observed oscillatory behavior correlates with magnetic observatory records taken near the foot of the magetic field line passing through the satellite.

  15. Electric field measurements from Halley, Antarctica

    NASA Astrophysics Data System (ADS)

    Nicoll, Keri; Harrison, R. Giles

    2016-04-01

    Antarctica is a unique location for the study of atmospheric electricity. Not only is it one of the most pollutant free places on Earth, but its proximity to the south magnetic pole means that it is an ideal location to study the effects of solar variability on the atmospheric electric field. This is due to the reduced shielding effect of the geomagnetic field at the poles which leads to a greater flux of incoming Galactic Cosmic Rays (GCRs) as well as an increased probability of energetic particle precipitation from SEPs and relativistic electrons. To investigate such effects, two electric field mills of different design were installed at the British Antarctic Survey Halley base in February 2015 (75. 58 degrees south, 26.66 degrees west). Halley is situated on the Brunt Ice Shelf in the south east of the Weddell Sea and has snow cover all year round. Preliminary analysis has focused on selection of fair weather criteria using wind speed and visibility measurements which are vital to assess the effects of falling snow, blowing snow and freezing fog on the electric field measurements. When the effects of such adverse weather conditions are removed clear evidence of the characteristic Carnegie Curve diurnal cycle exists in the Halley electric field measurements (with a mean value of 50V/m and showing a 40% peak to peak variation in comparison to the 34% variation in the Carnegie data). Since the Carnegie Curve represents the variation in thunderstorm activity across the Earth, its presence in the Halley data confirms the presence of the global atmospheric electric circuit signal at Halley. The work presented here will discuss the details of the Halley electric field dataset, including the variability in the fair weather measurements, with a particular focus on magnetic field fluctuations.

  16. Magnetoexciton in nanotube under external electric field

    NASA Astrophysics Data System (ADS)

    Garcia Russi, L. F.; Paredes Gutiérrez, H.; Santos, Y. F.; Mikhailov, I. D.

    2016-08-01

    We study the Aharonov-Bohm oscillation of the energy levels of an electron-hole pair confined in a narrow nanotube in the presence of the magnetic field applied along the symmetry axis. We show that the electric field applied at the same direction makes the oscillation more pronounced.

  17. On interplanetary electric and magnetic fields

    NASA Astrophysics Data System (ADS)

    Alekseev, I. I.; Kropotkin, A. P.; Veselovskii, I. S.

    1982-08-01

    A kinematic model of the stationary electromagnetic fields in interplanetary space with finite conductivity is considered. The electrodynamic problem is solved for a medium with uniform conductivity and radial plasma outflow from a spherical source. Simple analytical formulae are obtained for electric and magnetic fields, currents and charges in the case of a uniformly-magnetized rotating sphere.

  18. Stratospheric electric field measurements with transmediterranean balloons

    NASA Astrophysics Data System (ADS)

    de La Morena, B. A.; Alberca, L. F.; Curto, J. J.; Holzworth, R. H.

    1993-01-01

    The horizontal component of the stratospheric electric field was measured using a balloon in the ODISEA Campaign of Transmediterranean Balloon Program. The balloon flew between Trapani (Sicily) and El Arenosillo (Huelva, Spain) along the 39 deg N parallel at a height between 34 and 24 km. The high values found for the field on fair-weather and its quasi-turbulent variation, both in amplitude and direction, are difficult to explain with the classical electric field source. A new source, first described by Holzworth (1989), is considered as possibly causing them.

  19. A model for polar cap electric fields

    NASA Technical Reports Server (NTRS)

    Dangelo, N.

    1976-01-01

    A model is proposed relating polar cap ionospheric electric fields to the parameters of the solar wind near the orbit of the earth. The model ignores the notion of field line merging. An essential feature is the role played by velocity shear instabilities in regions of the outer magnetosphere, in which mapping of the magnetosheath electric field would produce sunward convection. The anomalous resistivity which arises from velocity shear turbulence, suffices to essentially disconnect the magnetosphere from the magnetosheath, at any place where that resistivity is large enough. The magnetosheath-magnetosphere system, as a consequence, acts as a kind of diode or rectifier for the magnetosheath electric fields. Predictions of the model are compared with several observations related to polar cap convection.

  20. Electric fields associated with dipolarization fronts

    NASA Astrophysics Data System (ADS)

    Sun, Wei-Jie; Fu, Suiyan; Parks, George K.; Pu, Zuyin; Zong, Qiu-Gang; Liu, Jiang; Yao, Zhonghua; Fu, Huishan; Shi, Quanqi

    2014-07-01

    Electric fields associated with dipolarization fronts (DFs) have been investigated in the magnetotail plasma sheet using Cluster observations. We have studied each term in the generalized Ohm's law using data obtained from the multispacecraft Cluster. Our results show that in the plasma flow frame, electric fields are directed normal to the DF in the magnetic dip region ahead of the DF as well as in the DF layer but in opposite directions. Case and statistical studies show that the Hall electric field is important while the electron pressure gradient term is much smaller. The ions decouple from the magnetic field in the DF layer and dip region (E + Vi×B ≠ 0), whereas electrons remain frozen-in (E + Ve×B=∇pe/nee).

  1. Studying electric fields in dipolarization fronts

    NASA Astrophysics Data System (ADS)

    Balcerak, Ernie

    2014-11-01

    In Earth's magnetotail, sharp increases in the magnetic field known as dipolarization fronts are associated with high-speed plasma flows that connect Earth's ionosphere via electric currents. Some aspects of these dipolarization fronts have puzzled scientists; in particular, the dip in magnetic field that occurs just ahead of the dipolarization front layer is not well understood. Sun et al. analyze observations made using the Cluster satellites to elucidate the details of electric fields associated with dipolarization fronts. The study shows that a type of electric current known as a Hall current dominates in the dipolarization front region and in the region where the magnetic field dips, but this current flows in opposite directions in these two regions.

  2. Coherent polarization driven by external electromagnetic fields

    NASA Astrophysics Data System (ADS)

    Apostol, M.; Ganciu, M.

    2010-11-01

    The coherent interaction of the electromagnetic radiation with an ensemble of polarizable, identical particles with two energy levels is investigated in the presence of external electromagnetic fields. The coupled non-linear equations of motion are solved in the stationary regime and in the limit of small coupling constants. It is shown that an external electromagnetic field may induce a macroscopic occupation of both the energy levels of the particles and the corresponding photon states, governed by a long-range order of the quantum phases of the internal motion (polarization) of the particles. A lasing effect is thereby obtained, controlled by the external field. Its main characteristics are estimated for typical atomic matter and atomic nuclei. For atomic matter the effect may be considerable (for usual external fields), while for atomic nuclei the effect is extremely small (practically insignificant), due to the great disparity in the coupling constants. In the absence of the external field, the solution, which is non-analytic in the coupling constant, corresponds to a second-order phase transition (super-radiance), which was previously investigated.

  3. Electric field induced activation of H2--can DFT do the job?

    PubMed

    Schirmer, Birgitta; Grimme, Stefan

    2010-11-14

    The activation of dihydrogen by frustrated Lewis pairs (FLP) is initially driven by the electric field created inside a molecular cavity [Angew. Chem., Int. Ed., 2010, 49, 1402]. Here we test the accuracy of different density functional methods to describe H(2) dissociation in an external electric field in comparison to almost exact results. For larger field strengths (>0.06 a.u.), the dissociation mechanism changes from bi-radical like to zwitter-ionic.

  4. Nature of an electric-field-induced colloidal martensitic transition.

    PubMed

    Yethiraj, Anand; Wouterse, Alan; Groh, Benito; van Blaaderen, Alfons

    2004-02-06

    We study the properties of a solid-solid close-packed to body-centered tetragonal transition in a colloidal suspension via fluorescence confocal laser scanning microscopy, in three dimensions and in real space. This structural transformation is driven by a subtle competition between gravitational and electric dipolar field energy, the latter being systematically varied via an external electric field. The transition threshold depends on the local depth in the colloidal sediment. Structures with order intermediate between close-packed and body-centered tetragonal were observed, with these intermediate structures also being stable and long lived. This is essentially a colloidal analogue of an "atomic-level" interfacial structure. We find qualitative agreement with theory (based purely on energetics). Quantitative differences can be attributed to the importance of entropic effects.

  5. Large Field Visualization with Demand-Driven Calculation

    NASA Technical Reports Server (NTRS)

    Moran, Patrick J.; Henze, Chris

    1999-01-01

    We present a system designed for the interactive definition and visualization of fields derived from large data sets: the Demand-Driven Visualizer (DDV). The system allows the user to write arbitrary expressions to define new fields, and then apply a variety of visualization techniques to the result. Expressions can include differential operators and numerous other built-in functions, ail of which are evaluated at specific field locations completely on demand. The payoff of following a demand-driven design philosophy throughout becomes particularly evident when working with large time-series data, where the costs of eager evaluation alternatives can be prohibitive.

  6. Microwave electric field sensing with Rydberg atoms

    NASA Astrophysics Data System (ADS)

    Stack, Daniel T.; Kunz, Paul D.; Meyer, David H.; Solmeyer, Neal

    2016-05-01

    Atoms form the basis of precise measurement for many quantities (time, acceleration, rotation, magnetic field, etc.). Measurements of microwave frequency electric fields by traditional methods (i.e. engineered antennas) have limited sensitivity and can be difficult to calibrate properly. Highly-excited (Rydberg) neutral atoms have very large electric-dipole moments and many dipole allowed transitions in the range of 1 - 500 GHz. It is possible to sensitively probe the electric field in this range using the combination of two quantum interference phenomena: electromagnetically induced transparency and the Autler-Townes effect. This technique allows for very sensitive field amplitude, polarization, and sub-wavelength imaging measurements. These quantities can be extracted by measuring properties of a probe laser beam as it passes through a warm rubidium vapor cell. Thus far, Rydberg microwave electrometry has relied upon the absorption of the probe laser. We report on our use of polarization rotation, which corresponds to the real part of the susceptibility, for measuring the properties of microwave frequency electric fields. Our simulations show that when a magnetic field is present and directed along the optical propagation direction a polarization rotation signal exists and can be used for microwave electrometry. One central advantage in using the polarization rotation signal rather than the absorption signal is that common mode laser noise is naturally eliminated leading to a potentially dramatic increase in signal-to-noise ratio.

  7. Electric-field-stimulated protein mechanics.

    PubMed

    Hekstra, Doeke R; White, K Ian; Socolich, Michael A; Henning, Robert W; Šrajer, Vukica; Ranganathan, Rama

    2016-12-15

    The internal mechanics of proteins-the coordinated motions of amino acids and the pattern of forces constraining these motions-connects protein structure to function. Here we describe a new method combining the application of strong electric field pulses to protein crystals with time-resolved X-ray crystallography to observe conformational changes in spatial and temporal detail. Using a human PDZ domain (LNX2(PDZ2)) as a model system, we show that protein crystals tolerate electric field pulses strong enough to drive concerted motions on the sub-microsecond timescale. The induced motions are subtle, involve diverse physical mechanisms, and occur throughout the protein structure. The global pattern of electric-field-induced motions is consistent with both local and allosteric conformational changes naturally induced by ligand binding, including at conserved functional sites in the PDZ domain family. This work lays the foundation for comprehensive experimental study of the mechanical basis of protein function.

  8. Electric field controlled emulsion phase contactor

    DOEpatents

    Scott, T.C.

    1995-01-31

    A system is described for contacting liquid phases comprising a column for transporting a liquid phase contacting system, the column having upper and lower regions. The upper region has a nozzle for introducing a dispersed phase and means for applying thereto a vertically oriented high intensity pulsed electric field. This electric field allows improved flow rates while shattering the dispersed phase into many micro-droplets upon exiting the nozzle to form a dispersion within a continuous phase. The lower region employs means for applying to the dispersed phase a horizontally oriented high intensity pulsed electric field so that the dispersed phase undergoes continuous coalescence and redispersion while being urged from side to side as it progresses through the system, increasing greatly the mass transfer opportunity. 5 figs.

  9. Electric field controlled emulsion phase contactor

    DOEpatents

    Scott, Timothy C.

    1995-01-01

    A system for contacting liquid phases comprising a column for transporting a liquid phase contacting system, the column having upper and lower regions. The upper region has a nozzle for introducing a dispersed phase and means for applying thereto a vertically oriented high intensity pulsed electric field. This electric field allows improved flow rates while shattering the dispersed phase into many micro-droplets upon exiting the nozzle to form a dispersion within a continuous phase. The lower region employs means for applying to the dispersed phase a horizontally oriented high intensity pulsed electric field so that the dispersed phase undergoes continuous coalescence and redispersion while being urged from side to side as it progresses through the system, increasing greatly the mass transfer opportunity.

  10. Electric field induced deformation of sessile drops

    NASA Astrophysics Data System (ADS)

    Corson, Lindsey; Tsakonas, Costas; Duffy, Brian; Mottram, Nigel; Brown, Carl; Wilson, Stephen

    2014-11-01

    The ability to control the shape of a drop with the application of an electric field has been exploited for many technological applications including measuring surface tension, producing an optical display device, and optimising the optical properties of microlenses. In this work we consider, both theoretically and experimentally, the deformation of pinned sessile drops with contact angles close to either 0° or 90° resting on the lower substrate inside a parallel plate capacitor due to an A.C. electric field. Using both asymptotic and numerical approaches we obtain predictive equations for the static and dynamic drop shape deformations as functions of the key experimental parameters (drop size, capacitor plate separation, electric field magnitude and contact angle). The asymptotic results agree well with the experimental results for a range of liquids. We gratefully acknowledge the financial support of EPSRC via research Grants EP/J009865 and EP/J009873.

  11. Microfluidic Screening of Electric Fields for Electroporation

    NASA Astrophysics Data System (ADS)

    Garcia, Paulo A.; Ge, Zhifei; Moran, Jeffrey L.; Buie, Cullen R.

    2016-02-01

    Electroporation is commonly used to deliver molecules such as drugs, proteins, and/or DNA into cells, but the mechanism remains poorly understood. In this work a rapid microfluidic assay was developed to determine the critical electric field threshold required for inducing bacterial electroporation. The microfluidic device was designed to have a bilaterally converging channel to amplify the electric field to magnitudes sufficient to induce electroporation. The bacterial cells are introduced into the channel in the presence of SYTOX®, which fluorescently labels cells with compromised membranes. Upon delivery of an electric pulse, the cells fluoresce due to transmembrane influx of SYTOX® after disruption of the cell membranes. We calculate the critical electric field by capturing the location within the channel of the increase in fluorescence intensity after electroporation. Bacterial strains with industrial and therapeutic relevance such as Escherichia coli BL21 (3.65 ± 0.09 kV/cm), Corynebacterium glutamicum (5.20 ± 0.20 kV/cm), and Mycobacterium smegmatis (5.56 ± 0.08 kV/cm) have been successfully characterized. Determining the critical electric field for electroporation facilitates the development of electroporation protocols that minimize Joule heating and maximize cell viability. This assay will ultimately enable the genetic transformation of bacteria and archaea considered intractable and difficult-to-transfect, while facilitating fundamental genetic studies on numerous diverse microbes.

  12. Microfluidic Screening of Electric Fields for Electroporation

    PubMed Central

    Garcia, Paulo A.; Ge, Zhifei; Moran, Jeffrey L.; Buie, Cullen R.

    2016-01-01

    Electroporation is commonly used to deliver molecules such as drugs, proteins, and/or DNA into cells, but the mechanism remains poorly understood. In this work a rapid microfluidic assay was developed to determine the critical electric field threshold required for inducing bacterial electroporation. The microfluidic device was designed to have a bilaterally converging channel to amplify the electric field to magnitudes sufficient to induce electroporation. The bacterial cells are introduced into the channel in the presence of SYTOX®, which fluorescently labels cells with compromised membranes. Upon delivery of an electric pulse, the cells fluoresce due to transmembrane influx of SYTOX® after disruption of the cell membranes. We calculate the critical electric field by capturing the location within the channel of the increase in fluorescence intensity after electroporation. Bacterial strains with industrial and therapeutic relevance such as Escherichia coli BL21 (3.65 ± 0.09 kV/cm), Corynebacterium glutamicum (5.20 ± 0.20 kV/cm), and Mycobacterium smegmatis (5.56 ± 0.08 kV/cm) have been successfully characterized. Determining the critical electric field for electroporation facilitates the development of electroporation protocols that minimize Joule heating and maximize cell viability. This assay will ultimately enable the genetic transformation of bacteria and archaea considered intractable and difficult-to-transfect, while facilitating fundamental genetic studies on numerous diverse microbes. PMID:26893024

  13. Microfluidic Screening of Electric Fields for Electroporation.

    PubMed

    Garcia, Paulo A; Ge, Zhifei; Moran, Jeffrey L; Buie, Cullen R

    2016-02-19

    Electroporation is commonly used to deliver molecules such as drugs, proteins, and/or DNA into cells, but the mechanism remains poorly understood. In this work a rapid microfluidic assay was developed to determine the critical electric field threshold required for inducing bacterial electroporation. The microfluidic device was designed to have a bilaterally converging channel to amplify the electric field to magnitudes sufficient to induce electroporation. The bacterial cells are introduced into the channel in the presence of SYTOX(®), which fluorescently labels cells with compromised membranes. Upon delivery of an electric pulse, the cells fluoresce due to transmembrane influx of SYTOX(®) after disruption of the cell membranes. We calculate the critical electric field by capturing the location within the channel of the increase in fluorescence intensity after electroporation. Bacterial strains with industrial and therapeutic relevance such as Escherichia coli BL21 (3.65 ± 0.09 kV/cm), Corynebacterium glutamicum (5.20 ± 0.20 kV/cm), and Mycobacterium smegmatis (5.56 ± 0.08 kV/cm) have been successfully characterized. Determining the critical electric field for electroporation facilitates the development of electroporation protocols that minimize Joule heating and maximize cell viability. This assay will ultimately enable the genetic transformation of bacteria and archaea considered intractable and difficult-to-transfect, while facilitating fundamental genetic studies on numerous diverse microbes.

  14. Velocity modulation of microtubules in electric fields.

    PubMed

    Dujovne, Irene; van den Heuvel, Martin; Shen, Yi; de Graaff, Martijn; Dekker, Cees

    2008-12-01

    We show that the speed of microtubules gliding over a kinesin-coated surface can be controlled over a wide range of values by the application of an electric field. The speed can be increased by up to a factor of 5 compared to the speed at zero field when assisting forces are applied and slowed down to zero velocity for opposing fields. Sideways applied fields also induce significant motion. The kinesin surface density impacts the rate of velocity change, whereas the ATP concentration does not seem to play a major role, provided that it is nonzero. A simple grab-and-release model is presented that explains the velocity change with applied electric fields.

  15. Regularization of chaos by noise in electrically driven nanowire systems

    NASA Astrophysics Data System (ADS)

    Hessari, Peyman; Do, Younghae; Lai, Ying-Cheng; Chae, Junseok; Park, Cheol Woo; Lee, GyuWon

    2014-04-01

    The electrically driven nanowire systems are of great importance to nanoscience and engineering. Due to strong nonlinearity, chaos can arise, but in many applications it is desirable to suppress chaos. The intrinsically high-dimensional nature of the system prevents application of the conventional method of controlling chaos. Remarkably, we find that the phenomenon of coherence resonance, which has been well documented but for low-dimensional chaotic systems, can occur in the nanowire system that mathematically is described by two coupled nonlinear partial differential equations, subject to periodic driving and noise. Especially, we find that, when the nanowire is in either the weakly chaotic or the extensively chaotic regime, an optimal level of noise can significantly enhance the regularity of the oscillations. This result is robust because it holds regardless of whether noise is white or colored, and of whether the stochastic drivings in the two independent directions transverse to the nanowire are correlated or independent of each other. Noise can thus regularize chaotic oscillations through the mechanism of coherence resonance in the nanowire system. More generally, we posit that noise can provide a practical way to harness chaos in nanoscale systems.

  16. Electric Field Quantitative Measurement System and Method

    NASA Technical Reports Server (NTRS)

    Generazio, Edward R. (Inventor)

    2016-01-01

    A method and system are provided for making a quantitative measurement of an electric field. A plurality of antennas separated from one another by known distances are arrayed in a region that extends in at least one dimension. A voltage difference between at least one selected pair of antennas is measured. Each voltage difference is divided by the known distance associated with the selected pair of antennas corresponding thereto to generate a resulting quantity. The plurality of resulting quantities defined over the region quantitatively describe an electric field therein.

  17. Drug Release from Electric Field Responsive Nanoparticles

    PubMed Central

    Ge, Jun; Neofytou, Evgenios; Cahill, Thomas J.; Beygui, Ramin E.; Zare, Richard N.

    2012-01-01

    We describe a new temperature and electric field dual-stimulus responsive nanoparticle system for programmed drug delivery. Nanoparticles of a conducting polymer (polypyrrole) are loaded with therapeutic pharmaceuticals and are subcutaneously localized in vivo with the assistance of a temperature-sensitive hydrogel (PLGA-PEG-PLGA). We have shown that drug release from the conductive nanoparticles is controlled by the application of a weak, external DC electric field. This approach represents a novel interactive drug delivery system that can show an externally tailored release profile with an excellent spatial, temporal, and dosage control. PMID:22111891

  18. ELF magnetic fields in electric and gasoline-powered vehicles.

    PubMed

    Tell, R A; Sias, G; Smith, J; Sahl, J; Kavet, R

    2013-02-01

    We conducted a pilot study to assess magnetic field levels in electric compared to gasoline-powered vehicles, and established a methodology that would provide valid data for further assessments. The sample consisted of 14 vehicles, all manufactured between January 2000 and April 2009; 6 were gasoline-powered vehicles and 8 were electric vehicles of various types. Of the eight models available, three were represented by a gasoline-powered vehicle and at least one electric vehicle, enabling intra-model comparisons. Vehicles were driven over a 16.3 km test route. Each vehicle was equipped with six EMDEX Lite broadband meters with a 40-1,000 Hz bandwidth programmed to sample every 4 s. Standard statistical testing was based on the fact that the autocorrelation statistic damped quickly with time. For seven electric cars, the geometric mean (GM) of all measurements (N = 18,318) was 0.095 µT with a geometric standard deviation (GSD) of 2.66, compared to 0.051 µT (N = 9,301; GSD = 2.11) for four gasoline-powered cars (P < 0.0001). Using the data from a previous exposure assessment of residential exposure in eight geographic regions in the United States as a basis for comparison (N = 218), the broadband magnetic fields in electric vehicles covered the same range as personal exposure levels recorded in that study. All fields measured in all vehicles were much less than the exposure limits published by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) and the Institute of Electrical and Electronics Engineers (IEEE). Future studies should include larger sample sizes representative of a greater cross-section of electric-type vehicles.

  19. Electric Field Effects in RUS Measurements

    SciTech Connect

    Darling, Timothy W; Ten Cate, James A; Allured, Bradley; Carpenter, Michael A

    2009-09-21

    Much of the power of the Resonant Ultrasound Spectroscopy (RUS) technique is the ability to make mechanical resonance measurements while the environment of the sample is changed. Temperature and magnetic field are important examples. Due to the common use of piezoelectric transducers near the sample, applied electric fields introduce complications, but many materials have technologically interesting responses to applied static and RF electric fields. Non-contact optical, buffered, or shielded transducers permit the application of charge and externally applied electric fields while making RUS measurements. For conducting samples, in vacuum, charging produces a small negative pressure in the volume of the material - a state rarely explored. At very high charges we influence the electron density near the surface so the propagation of surface waves and their resonances may give us a handle on the relationship of electron density to bond strength and elasticity. Our preliminary results indicate a charge sign dependent effect, but we are studying a number of possible other effects induced by charging. In dielectric materials, external electric fields influence the strain response, particularly in ferroelectrics. Experiments to study this connection at phase transformations are planned. The fact that many geological samples contain single crystal quartz suggests a possible use of the piezoelectric response to drive vibrations using applied RF fields. In polycrystals, averaging of strains in randomly oriented crystals implies using the 'statistical residual' strain as the drive. The ability to excite vibrations in quartzite polycrystals and arenites is explored. We present results of experimental and theoretical approaches to electric field effects using RUS methods.

  20. Electric field effects in RUS measurements.

    PubMed

    Darling, Timothy W; Allured, Bradley; Tencate, James A; Carpenter, Michael A

    2010-02-01

    Much of the power of the Resonant Ultrasound Spectroscopy (RUS) technique is the ability to make mechanical resonance measurements while the environment of the sample is changed. Temperature and magnetic field are important examples. Due to the common use of piezoelectric transducers near the sample, applied electric fields introduce complications, but many materials have technologically interesting responses to applied static and RF electric fields. Non-contact optical, buffered, or shielded transducers permit the application of charge and externally applied electric fields while making RUS measurements. For conducting samples, in vacuum, charging produces a small negative pressure in the volume of the material--a state rarely explored. At very high charges we influence the electron density near the surface so the propagation of surface waves and their resonances may give us a handle on the relationship of electron density to bond strength and elasticity. Our preliminary results indicate a charge sign dependent effect, but we are studying a number of possible other effects induced by charging. In dielectric materials, external electric fields influence the strain response, particularly in ferroelectrics. Experiments to study this connection at phase transformations are planned. The fact that many geological samples contain single crystal quartz suggests a possible use of the piezoelectric response to drive vibrations using applied RF fields. In polycrystals, averaging of strains in randomly oriented crystals implies using the "statistical residual" strain as the drive. The ability to excite vibrations in quartzite polycrystals and arenites is explored. We present results of experimental and theoretical approaches to electric field effects using RUS methods.

  1. Polarization extension mechanism revealed through dynamic ferroelectric hysteresis and electric field driven structural distortions in lead free Na0.5Bi0.5TiO3 ceramic

    NASA Astrophysics Data System (ADS)

    Karthik, T.; Asthana, Saket

    2017-09-01

    The electric field amplitude (E o) dependent dynamic ferroelectric hysteresis and polarization current density curves measured at room temperature for Na0.5Bi0.5TiO3 (NBT), showed three different stages of polarization reversal mechanism. The scaling relationship confirmed the dominance of domain wall motion at Stage I (i.e. upto E o  <  35 kV cm-1), followed by domain switching at Stage II (35 kV cm-1  <  E o  <  60 kV cm-1). Interestingly, a unique behaviour with two sub stages was observed in Stage III (60 kV cm-1  <  E o  <  90 kV cm-1), with two distinct switching mechanisms viz., polarization rotation at Stage III-A and polarization extension at Stage III-B. X-ray diffraction analysis based on the Rietveld refined atomic positional co-ordinates, in electrically poled system strongly favors the polarization extension mechanism proposed at Stage III-B. The measured E o-dependent longitudinal piezoelectric response (d 33 and g33) values match closely with our proposed polarization reversal mechanism.

  2. Electric field stimulated growth of Zn whiskers

    SciTech Connect

    Niraula, D.; McCulloch, J.; Irving, R.; Karpov, V. G.; Warrell, G. R.; Shvydka, Diana

    2016-07-15

    We have investigated the impact of strong (∼10{sup 4} V/cm) electric fields on the development of Zn whiskers. The original samples, with considerable whisker infestation were cut from Zn-coated steel floors and then exposed to electric fields stresses for 10-20 hours at room temperature. We used various electric field sources, from charges accumulated in samples irradiated by: (1) the electron beam of a scanning electron microscope (SEM), (2) the electron beam of a medical linear accelerator, and (3) the ion beam of a linear accelerator; we also used (4) the electric field produced by a Van der Graaf generator. In all cases, the exposed samples exhibited a considerable (tens of percent) increase in whiskers concentration compared to the control sample. The acceleration factor defined as the ratio of the measured whisker growth rate over that in zero field, was estimated to approach several hundred. The statistics of lengths of e-beam induced whiskers was found to follow the log-normal distribution known previously for metal whiskers. The observed accelerated whisker growth is attributed to electrostatic effects. These results offer promise for establishing whisker-related accelerated life testing protocols.

  3. Electric fields and double layers in plasmas

    NASA Technical Reports Server (NTRS)

    Singh, Nagendra; Thiemann, H.; Schunk, R. W.

    1987-01-01

    Various mechanisms for driving double layers in plasmas are briefly described, including applied potential drops, currents, contact potentials, and plasma expansions. Some dynamical features of the double layers are discussed. These features, as seen in simulations, laboratory experiments, and theory, indicate that double layers and the currents through them undergo slow oscillations which are determined by the ion transit time across an effective length of the system in which double layers form. It is shown that a localized potential dip forms at the low potential end of a double layer, which interrupts the electron current through it according to the Langmuir criterion, whenever the ion flux into the double is disrupted. The generation of electric fields perpendicular to the ambient magnetic field by contact potentials is also discussed. Two different situations were considered; in one, a low-density hot plasma is sandwiched between high-density cold plasmas, while in the other a high-density current sheet permeates a low-density background plasma. Perpendicular electric fields develop near the contact surfaces. In the case of the current sheet, the creation of parallel electric fields and the formation of double layers are also discussed when the current sheet thickness is varied. Finally, the generation of electric fields and double layers in an expanding plasma is discussed.

  4. Electric field stimulated growth of Zn whiskers

    NASA Astrophysics Data System (ADS)

    Niraula, D.; McCulloch, J.; Warrell, G. R.; Irving, R.; Karpov, V. G.; Shvydka, Diana

    2016-07-01

    We have investigated the impact of strong (˜104 V/cm) electric fields on the development of Zn whiskers. The original samples, with considerable whisker infestation were cut from Zn-coated steel floors and then exposed to electric fields stresses for 10-20 hours at room temperature. We used various electric field sources, from charges accumulated in samples irradiated by: (1) the electron beam of a scanning electron microscope (SEM), (2) the electron beam of a medical linear accelerator, and (3) the ion beam of a linear accelerator; we also used (4) the electric field produced by a Van der Graaf generator. In all cases, the exposed samples exhibited a considerable (tens of percent) increase in whiskers concentration compared to the control sample. The acceleration factor defined as the ratio of the measured whisker growth rate over that in zero field, was estimated to approach several hundred. The statistics of lengths of e-beam induced whiskers was found to follow the log-normal distribution known previously for metal whiskers. The observed accelerated whisker growth is attributed to electrostatic effects. These results offer promise for establishing whisker-related accelerated life testing protocols.

  5. Electric fields and double layers in plasmas

    NASA Astrophysics Data System (ADS)

    Singh, Nagendra; Thiemann, H.; Schunk, R. W.

    1987-05-01

    Various mechanisms for driving double layers in plasmas are briefly described, including applied potential drops, currents, contact potentials, and plasma expansions. Some dynamical features of the double layers are discussed. These features, as seen in simulations, laboratory experiments, and theory, indicate that double layers and the currents through them undergo slow oscillations which are determined by the ion transit time across an effective length of the system in which double layers form. It is shown that a localized potential dip forms at the low potential end of a double layer, which interrupts the electron current through it according to the Langmuir criterion, whenever the ion flux into the double is disrupted. The generation of electric fields perpendicular to the ambient magnetic field by contact potentials is also discussed. Two different situations were considered; in one, a low-density hot plasma is sandwiched between high-density cold plasmas, while in the other a high-density current sheet permeates a low-density background plasma. Perpendicular electric fields develop near the contact surfaces. In the case of the current sheet, the creation of parallel electric fields and the formation of double layers are also discussed when the current sheet thickness is varied. Finally, the generation of electric fields and double layers in an expanding plasma is discussed.

  6. Airborne biological particles and electric fields

    NASA Astrophysics Data System (ADS)

    Benninghoff, William S.; Benninghoff, Anne S.

    1982-01-01

    In November and December 1977 at McMurdo Station in Antarctica we investigated the kinds, numbers, and deposition of airborne particles larger than 2 μm while measuring electric field gradient at 2.5 m above the ground. Elementary collecting devices were used: Staplex Hi-Volume and Roto-rod samplers, Tauber (static sedimentation) traps, petrolatum-coated microscope slides, and snow (melted and filtered). The electric fields were measured by a rotating dipole (Stanford Radioscience Laboratory field mill number 2). During periods of blowing snow and dust the electric field gradient was + 500 to + 2500 V/m, and Tauber traps with grounded covers collected 2 or more times as much snow and dust as the ones with ungrounded covers. During falling snow the electric field gradient was -1000 to -1500 V/m, and the ungrounded traps collected almost twice as much snow and dust as those grounded. These observations suggest that under the prevailing weather conditions in polar regions the probable net effect is deposition of greater quantities of dust, including diaspores and minute organisms, on wet, grounded surfaces. This hypothesis needs examination for its use in explanation of biological distribution patterns.

  7. Electric fields yield chaos in microflows

    PubMed Central

    Posner, Jonathan D.; Pérez, Carlos L.; Santiago, Juan G.

    2012-01-01

    We present an investigation of chaotic dynamics of a low Reynolds number electrokinetic flow. Electrokinetic flows arise due to couplings of electric fields and electric double layers. In these flows, applied (steady) electric fields can couple with ionic conductivity gradients outside electric double layers to produce flow instabilities. The threshold of these instabilities is controlled by an electric Rayleigh number, Rae. As Rae increases monotonically, we show here flow dynamics can transition from steady state to a time-dependent periodic state and then to an aperiodic, chaotic state. Interestingly, further monotonic increase of Rae shows a transition back to a well-ordered state, followed by a second transition to a chaotic state. Temporal power spectra and time-delay phase maps of low dimensional attractors graphically depict the sequence between periodic and chaotic states. To our knowledge, this is a unique report of a low Reynolds number flow with such a sequence of periodic-to-aperiodic transitions. Also unique is a report of strange attractors triggered and sustained through electric fluid body forces. PMID:22908251

  8. Critical electric field strengths of onion tissues treated by pulsed electric fields.

    PubMed

    Asavasanti, Suvaluk; Ersus, Seda; Ristenpart, William; Stroeve, Pieter; Barrett, Diane M

    2010-09-01

    The impact of pulsed electric fields (PEF) on cellular integrity and texture of Ranchero and Sabroso onions (Allium cepa L.) was investigated. Electrical properties, ion leakage rate, texture, and amount of enzymatically formed pyruvate were measured before and after PEF treatment for a range of applied field strengths and number of pulses. Critical electric field strengths or thresholds (E(c)) necessary to initiate membrane rupture were different because dissimilar properties were measured. Measurement of electrical characteristics was the most sensitive method and was used to detect the early stage of plasma membrane breakdown, while pyruvate formation by the enzyme alliinase was used to identify tonoplast membrane breakdown. Our results for 100-μs pulses indicate that breakdown of the plasma membrane occurs above E(c)= 67 V/cm for 10 pulses, but breakdown of the tonoplast membrane is above either E(c)= 200 V/cm for 10 pulses or 133 V/cm for 100 pulses. This disparity in field strength suggests there may be 2 critical electrical field strengths: a lower field strength for plasma membrane breakdown and a higher field strength for tonoplast membrane breakdown. Both critical electric field strengths depended on the number of pulses applied. Application of a single pulse at an electric field up to 333 V/cm had no observable effect on any measured properties, while significant differences were observed for n≥10. The minimum electric field strength required to cause a measurable property change decreased with the number of pulses. The results also suggest that PEF treatment may be more efficient if a higher electric field strength is applied for a fewer pulses.

  9. Direct observation of electric field induced pattern formation and particle aggregation in ferrofluids

    NASA Astrophysics Data System (ADS)

    Rajnak, Michal; Petrenko, Viktor I.; Avdeev, Mikhail V.; Ivankov, Olexandr I.; Feoktystov, Artem; Dolnik, Bystrik; Kurimsky, Juraj; Kopcansky, Peter; Timko, Milan

    2015-08-01

    Ferrofluids typically respond to magnetic fields and can be manipulated by external magnetic fields. Here, we report on formation of visually observable patterns in a diluted low-polarity ferrofluid exposed to external electric fields. This presents a specific type of ferrofluid structure driven by a combined effect of electrohydrodynamics and electrical body forces. The free charge and permittivity variation are considered to play a key role in the observed phenomenon. The corresponding changes in the ferrofluid structure have been found at nanoscale as well. By small-angle neutron scattering (SANS), we show that the magnetic nanoparticles aggregate in direct current (dc) electric field with a strong dependence on the field intensity. The anisotropic aggregates preferably orient in the direction of the applied electric field. Conducting SANS experiments with alternating current (ac) electric fields of various frequencies, we found a critical frequency triggering the aggregation process. Our experimental study could open future applications of ferrofluids based on insulating liquids.

  10. Direct observation of electric field induced pattern formation and particle aggregation in ferrofluids

    SciTech Connect

    Rajnak, Michal; Kopcansky, Peter; Timko, Milan; Petrenko, Viktor I.; Avdeev, Mikhail V.; Ivankov, Olexandr I.; Feoktystov, Artem; Dolnik, Bystrik; Kurimsky, Juraj

    2015-08-17

    Ferrofluids typically respond to magnetic fields and can be manipulated by external magnetic fields. Here, we report on formation of visually observable patterns in a diluted low-polarity ferrofluid exposed to external electric fields. This presents a specific type of ferrofluid structure driven by a combined effect of electrohydrodynamics and electrical body forces. The free charge and permittivity variation are considered to play a key role in the observed phenomenon. The corresponding changes in the ferrofluid structure have been found at nanoscale as well. By small-angle neutron scattering (SANS), we show that the magnetic nanoparticles aggregate in direct current (dc) electric field with a strong dependence on the field intensity. The anisotropic aggregates preferably orient in the direction of the applied electric field. Conducting SANS experiments with alternating current (ac) electric fields of various frequencies, we found a critical frequency triggering the aggregation process. Our experimental study could open future applications of ferrofluids based on insulating liquids.

  11. Electric and magnetic fields in cryopreservation.

    PubMed

    Wowk, Brian

    2012-06-01

    Electromagnetic warming has a long history in cryobiology as a preferred method for recovering large tissue masses from cryopreservation, especially from cryopreservation by vitrification. It is less well-known that electromagnetic fields may be able to influence ice formation during cryopreservation by non-thermal mechanisms. Both theory and published data suggest that static and oscillating electric fields can respectively promote or inhibit ice formation under certain conditions. Evidence is less persuasive for magnetic fields. Recent claims that static magnetic fields smaller than 1 mT can improve cryopreservation by freezing are specifically questioned.

  12. Photoionization of atomic hydrogen in electric field

    SciTech Connect

    Gorlov, Timofey V; Danilov, Viatcheslav V

    2010-01-01

    Laser assisted ionization of high energy hydrogen beams in magnetic fields opens wide application possibilities in accelerator physics and other fields. The key theoretical problem of the method is the calculation of the ionization probability of a hydrogen atom affected by laser and static electric fields in the particle rest frame. A method of solving this problem with the temporal Schr dinger equation including a continuum spectrum is presented in this paper in accurate form for the first time. This method allows finding the temporal evolution of the wave function of the hydrogen atom as a function of laser and static electric fields. Solving the problem of photoionization reveals quantum effects that cannot be described by the cross sectional approach. The effects play a key role in the problems of photoionization of H0 beams with the large angular or energy spread.

  13. Electric current quadratic in an applied electric field

    NASA Astrophysics Data System (ADS)

    Deyo, Eric

    The theory of the photogalvanic effect in a low frequency electric field is developed. We complete the semiclassical theory of the effect in bulk samples lacking inversion symmetry, taking into account contributions from the asymmetry of scattering, the shift current, and the effect of Berry's phase. We consider the effect in such samples both in the presence and absence of a constant magnetic field. It is found that by experimentally measuring this effect, that Berry's curvature and the average shift of the center of mass of an electron during a scattering event can be extracted. We also investigate the magnetic field dependence of the part of the electrical current which is quadratic in voltage in mesoscopic conductors. We find that the part of the current which is quadratic in bias voltage, and linear in an applied magnetic field can be related to the effective electron-electron interaction strength. We also find that in the case when the magnetic field is oriented parallel to the plane of a two dimensional sample, that the spin-orbit scattering rate can be measured.

  14. Full Electric Field Control of Exchange Bias

    NASA Astrophysics Data System (ADS)

    Wu, Stephen

    2014-03-01

    Exchange bias is the shift of a magnetic hysteresis curve due to interfacial magnetic coupling between a ferromagnet (FM) and an antiferromagnet (AFM). This ubiquitous effect has long been used in the electronics industry to bias the magnetization of FM layers in magnetic devices. Its continued understanding is of critical importance to advance the development of future high-density magnetic storage media and other novel magnetic devices. However, due to the technological limitations of manipulating and observing an atomically thin interface, exchange bias is not well understood. In this talk we present a multiferroic field effect device with BiFeO3 (BFO) (antiferromagnetic-ferroelectric) as the gate dielectric and La0.7Sr0.3MnO3 (LSMO) (ferromagnetic) as the conducting channel, which exhibits the direct, bipolar electric control of exchange bias. Here the magnetic states at the AFM/FM interface can be directly manipulated with electric fields and the results can be observed as a change in exchange bias polarity and magnitude. Control of exchange bias at this level has significant implications because it represents a form of electric field control of magnetism and may potentially offer a route toward the eventual full electric field control of magnetization. In this device, exchange bias is reversibly switched between two stable states with opposite exchange bias polarities upon ferroelectric poling of the BFO. No field cooling, temperature cycling, or additional applied magnetic or electric field beyond BFO poling is needed for this bipolar modulation effect. Detailed temperature dependent measurements and a model will be presented which will attribute this effect to the coupled antiferromagnetic-ferroelectric order in BFO along with the modulation of interfacial exchange interactions due to ionic displacement of Fe3+ in BFO relative to Mn3 + / 4 + in LSMO.

  15. Longitudinal ultrasonic waves in DC electric field

    NASA Astrophysics Data System (ADS)

    Sobotka, Jerzy

    2009-06-01

    The results of experimental studies of the propagation of longitudinal waves in saturated rock samples in which there is a flow of electric charges are presented. It is shown that the electric field affects elastic parameters in heterophase media by changing their dynamic characteristics. The aim of the study of the effect of electric field on the propagation of elastic waves in saturated porous media was to determine the optimum conditions for this effect, and to construct a set of effective parameters which could be used to increase the effectiveness of seismoacoustic prospecting methods, particularly acoustic logging, and be helpful for developing new methods of increasing the effectiveness of oil extraction from productive wells.

  16. Health of workers exposed to electric fields.

    PubMed Central

    Broadbent, D E; Broadbent, M H; Male, J C; Jones, M R

    1985-01-01

    The results of health questionnaire interviews with 390 electrical power transmission and distribution workers, together with long term estimates of their exposure to 50 Hz electric fields, and short term measurements of the actual exposure for 287 of them are reported. Twenty eight workers received measurable exposures, averaging about 30 kVm-1h over the two week measurement period. Estimated exposure rates were considerably greater, but showed fair correlation with the measurements. Although the general level of health was higher than we have found in manual workers in other industries, there were significant differences in the health measures between different categories of job, different parts of the country, and in association with factors such as overtime, working alone, or frequently changing shift. After allowing for the effects of job and location, however, we found no significant correlations of health with either measured or estimated exposure to electric fields. PMID:3970875

  17. Intermediate inflation driven by DBI scalar field

    NASA Astrophysics Data System (ADS)

    Nazavari, N.; Mohammadi, A.; Ossoulian, Z.; Saaidi, Kh.

    2016-06-01

    Picking out a DBI scalar field as inflation, the slow-rolling inflationary scenario is studied by attributing an exponential time function to scale factor, known as intermediate inflation. The perturbation parameters of the model are estimated numerically for two different cases, and the final result is compared with Planck data. The diagram of tensor-to-scalar ratio r versus scalar spectra index ns is illustrated, and it is found that they are within an acceptable range as suggested by Planck. In addition, the acquired values for amplitude of scalar perturbation reveal the ability of the model to depict a good picture of the Universe in one of its earliest stages. As a further argument, the non-Gaussianity is investigated, displaying that the model prediction stands in a 68% C.L. regime according to the latest Planck data.

  18. Motion Driven by Strain Gradient Fields

    PubMed Central

    Wang, Chao; Chen, Shaohua

    2015-01-01

    A new driving mechanism for direction-controlled motion of nano-scale objects is proposed, based on a model of stretching a graphene strip linked to a rigid base with linear springs of identical stiffness. We find that the potential energy difference induced by the strain gradient field in the graphene strip substrate can generate sufficient force to overcome the static and kinetic friction forces between the nano-flake and the strip substrate, resulting in the nanoscale flake motion in the direction of gradient reduction. The dynamics of the nano-flake can be manipulated by tuning the stiffness of linear springs, stretching velocity and the flake size. This fundamental law of directional motion induced by strain gradient could be very useful for promising designs of nanoscale manipulation, transportation and smart surfaces. PMID:26323603

  19. Non-intrusive electric field sensing

    NASA Astrophysics Data System (ADS)

    Schultz, S. M.; Selfridge, R.; Chadderdon, S.; Perry, D.; Stan, N.

    2014-04-01

    This paper presents an overview of non-intrusive electric field sensing. The non-intrusive nature is attained by creating a sensor that is entirely dielectric, has a small cross-sectional area, and has the interrogation electronics a long distance away from the system under test. One non-intrusive electric field sensing technology is the slab coupled optical fiber sensor (SCOS). The SCOS consists of an electro-optic crystal attached to the surface of a D-shaped optical fiber. It is entirely dielectric and has a cross-sectional area down to 0.3mm by 0.3mm. The SCOS device functions as an electric field sensor through use of resonant mode coupling between the crystal waveguide and the core of a D-shaped optical fiber. The resonant mode coupling of a SCOS device occurs at specific wavelengths whose spectral locations are determined in part by the effective refractive index of the modes in the slab. An electric field changes the refractive index of the slab causing a shift in the spectral position of the resonant modes. This paper describes an overview of the SCOS technology including the theory, fabrication, and operation. The effect of crystal orientation and crystal type are explained with respect to directional sensitivity and frequency response.

  20. Nonthermal processing by radio frequency electric fields

    USDA-ARS?s Scientific Manuscript database

    Radio frequency electric fields (RFEF) processing is relatively new and has been shown to inactivate bacteria in apple juice, orange juice and apple cider at moderately low temperatures. Key equipment components of the process include a radio frequency power supply and a treatment chamber that is ca...

  1. Static electric fields modify the locomotory behaviour of cockroaches.

    PubMed

    Jackson, Christopher W; Hunt, Edmund; Sharkh, Suleiman; Newland, Philip L

    2011-06-15

    Static electric fields are found throughout the environment and there is growing interest in how electric fields influence insect behaviour. Here we have analysed the locomotory behaviour of cockroaches (Periplaneta americana) in response to static electric fields at levels equal to and above those found in the natural environment. Walking behaviour (including velocity, distance moved, turn angle and time spent walking) were analysed as cockroaches approached an electric field boundary in an open arena, and also when continuously exposed to an electric field. On approaching an electric field boundary, the greater the electric field strength the more likely a cockroach would be to turn away from, or be repulsed by, the electric field. Cockroaches completely exposed to electric fields showed significant changes in locomotion by covering less distance, walking slowly and turning more often. This study highlights the importance of electric fields on the normal locomotory behaviour of insects.

  2. Vacuum interface flashover with bipolar electric fields

    SciTech Connect

    Tucker, W.K.; Anderson, R.A.; Hasti, D.E.; Jones, E.E.; Bennett, L.F.

    1985-05-01

    High energy, compact, particle accelerators require accelerating cavities that have large gradients and operate with high efficiency. The bipolar electric fields required in these efficient accelerating cavities place severe requirements on the vacuum interface. Experimentally, we have found that the bipolar flashover field varies as t/sup -1/2/ for times out to 300 ns and then remains essentially constant at 33 kV/cm for longer duration waveforms, whereas materials subjected to unipolar electric fields follow a t/sup -1/6/ relationship. Furthermore, specific accelerating cavities offer enhancements that may be employed to achieve highly uniform electric fields across the vacuum interface. Using these results and the results of a previously developed theory of unipolar flashover, a new interface has been designed and 50 kV/cm bipolar flashover field achieved for a waveform train that lasted 1 ..mu..s. This paper will discuss the design of this vacuum interface and the evaluation of various materials that led to achieving bipolar flashover fields 50% greater than we had previously obtained for long duration waveforms. 10 refs., 6 figs.

  3. Silicon Photomultiplier Performance in High ELectric Field

    NASA Astrophysics Data System (ADS)

    Montoya, J.; Morad, J.

    2016-12-01

    Roughly 27% of the universe is thought to be composed of dark matter. The Large Underground Xenon (LUX) relies on the emission of light from xenon atoms after a collision with a dark matter particle. After a particle interaction in the detector, two things can happen: the xenon will emit light and charge. The charge (electrons), in the liquid xenon needs to be pulled into the gas section so that it can interact with gas and emit light. This allows LUX to convert a single electron into many photons. This is done by applying a high voltage across the liquid and gas regions, effectively ripping electrons out of the liquid xenon and into the gas. The current device used to detect photons is the photomultiplier tube (PMT). These devices are large and costly. In recent years, a new technology that is capable of detecting single photons has emerged, the silicon photomultiplier (SiPM). These devices are cheaper and smaller than PMTs. Their performance in a high electric fields, such as those found in LUX, are unknown. It is possible that a large electric field could introduce noise on the SiPM signal, drowning the single photon detection capability. My hypothesis is that SiPMs will not observe a significant increase is noise at an electric field of roughly 10kV/cm (an electric field within the range used in detectors like LUX). I plan to test this hypothesis by first rotating the SiPMs with no applied electric field between two metal plates roughly 2 cm apart, providing a control data set. Then using the same angles test the dark counts with the constant electric field applied. Possibly the most important aspect of LUX, is the photon detector because it's what detects the signals. Dark matter is detected in the experiment by looking at the ratio of photons to electrons emitted for a given interaction in the detector. Interactions with a low electron to photon ratio are more like to be dark matter events than those with a high electron to photon ratio. The ability to

  4. C/NOFS Satellite Electric Field and Plasma Density Observations of Plasma Instabilities Below the Equatorial F-Peak -- Evidence for Approximately 500 km-Scale Spread-F "Precursor" Waves Driven by Zonal Shear Flow and km-Scale, Narrow-Banded Irregularities

    NASA Technical Reports Server (NTRS)

    Pfaff, R.; Freudenreich, H.; Klenzing, J.; Liebrecht, C.; Valladares, C.

    2011-01-01

    As solar activity has increased, the ionosphere F-peak has been elevated on numerous occasions above the C/NOFS satellite perigee of 400km. In particular, during the month of April, 2011, the satellite consistently journeyed below the F-peak whenever the orbit was in the region of the South Atlantic anomaly after sunset. During these passes, data from the electric field and plasma density probes on the satellite have revealed two types of instabilities which had not previously been observed in the C/NOFS data set (to our knowledge): The first is evidence for 400-500km-scale bottomside "undulations" that appear in the density and electric field data. In one case, these large scale waves are associated with a strong shear in the zonal E x B flow, as evidenced by variations in the meridional (outward) electric fields observed above and below the F-peak. These undulations are devoid of smaller scale structures in the early evening, yet appear at later local times along the same orbit associated with fully-developed spread-F with smaller scale structures. This suggests that they may be precursor waves for spread-F, driven by a collisional shear instability, following ideas advanced previously by researchers using data from the Jicamarca radar. A second new result (for C/NOFS) is the appearance of km-scale irregularities that are a common feature in the electric field and plasma density data that also appear when the satellite is below the F -peak at night. The vector electric field instrument on C/NOFS clearly shows that the electric field component of these waves is strongest in the zonal direction. These waves are strongly correlated with simultaneous observations of plasma density oscillations and appear both with, and without, evidence of larger-scale spread-F depletions. These km-scale, quasi-coherent waves strongly resemble the bottomside, sinusoidal irregularities reported in the Atmosphere Explorer satellite data set by Valladares et al. [JGR, 88, 8025, 1983

  5. Composite lateral electric field excited piezoelectric resonator.

    PubMed

    Zaitsev, B D; Shikhabudinov, A M; Borodina, I A; Teplykh, A A; Kuznetsova, I E

    2017-01-01

    The novel method of suppression of parasitic oscillations in lateral electric field excited piezoelectric resonator is suggested. Traditionally such resonator represents the piezoelectric plate with two electrodes on one side of the plate. The crystallographic orientation of the plate is selected so that the tangential components of electric field excite bulk acoustic wave with given polarization travelling along the normal to the plate sides. However at that the normal components of field excite the parasitic Lamb waves and bulk waves of other polarization which deteriorate the resonant properties of the resonator. In this work we suggest to separate the source of the HF electric field and resounded piezoelectric plate by air gap. In this case the tangential components of the field in piezoelectric plate do not practically weaken but normal components significantly decrease. This method is realized on the composite resonator having the structure "glass plate with rectangular electrodes - air gap - plate of 128 Y-X lithium niobate." It has been shown that there exist the optimal value of the width gap which ensure the good quality of series and parallel resonances in frequency range 3-4MHz with record values of Q-factor of ∼15,000 in both cases.

  6. Tikekar superdense stars in electric fields

    NASA Astrophysics Data System (ADS)

    Komathiraj, K.; Maharaj, S. D.

    2007-04-01

    We present exact solutions to the Einstein-Maxwell system of equations with a specified form of the electric field intensity by assuming that the hypersurface {t=constant} are spheroidal. The solution of the Einstein-Maxwell system is reduced to a recurrence relation with variable rational coefficients which can be solved in general using mathematical induction. New classes of solutions of linearly independent functions are obtained by restricting the spheroidal parameter K and the electric field intensity parameter α. Consequently, it is possible to find exact solutions in terms of elementary functions, namely, polynomials and algebraic functions. Our result contains models found previously including the superdense Tikekar neutron star model [J. Math. Phys. 31, 2454 (1990)] when K=-7 and α=0. Our class of charged spheroidal models generalize the uncharged isotropic Maharaj and Leach solutions [J. Math. Phys. 37, 430 (1996)]. In particular, we find an explicit relationship directly relating the spheroidal parameter K to the electromagnetic field.

  7. Electric fields in Scanning Electron Microscopy simulations

    NASA Astrophysics Data System (ADS)

    Arat, K. T.; Bolten, J.; Klimpel, T.; Unal, N.

    2016-03-01

    The electric field distribution and charging effects in Scanning Electron Microscopy (SEM) were studied by extending a Monte-Carlo based SEM simulator by a fast and accurate multigrid (MG) based 3D electric field solver. The main focus is on enabling short simulation times with maintaining sufficient accuracy, so that SEM simulation can be used in practical applications. The implementation demonstrates a gain in computation speed, when compared to a Gauss-Seidel based reference solver is roughly factor of 40, with negligible differences in the result (~10-6 𝑉). In addition, the simulations were compared with experimental SEM measurements using also complex 3D sample, showing that i) the modelling of e-fields improves the simulation accuracy, and ii) multigrid method provide a significant benefit in terms of simulation time.

  8. Influence of electric field on cellular migration

    NASA Astrophysics Data System (ADS)

    Guido, Isabella; Bodenschatz, Eberhard

    Cells have the ability to detect continuous current electric fields (EFs) and respond to them with a directed migratory movement. Dictyostelium discoideum (D.d.) cells, a key model organism for the study of eukaryotic chemotaxis, orient and migrate toward the cathode under the influence of an EF. The underlying sensing mechanism and whether it is shared by the chemotactic response pathway remains unknown. Whereas genes and proteins that mediate the electric sensing as well as that define the migration direction have been previously investigated in D.d. cells, a deeper knowledge about the cellular kinematic effects caused by the EF is still lacking. Here we show that besides triggering a directional bias the electric field influences the cellular kinematics by accelerating the movement of cells along their path. We found that the migratory velocity of the cells in an EF increases linearly with the exposure time. Through the analysis of the PI3K and Phg2 distribution in the cytosol and of the cellular adherence to the substrate we aim at elucidating whereas this speed up effect in the electric field is due to either a molecular signalling or the interaction with the substrate. This work is part of the MaxSynBio Consortium which is jointly funded by the Federal Ministry of Education and Research of Germany and the Max Planck Society.

  9. Generation, transmission, and detection of terahertz photons on an electrically driven single chip

    SciTech Connect

    Ikushima, Kenji; Ito, Atsushi; Okano, Shun

    2014-02-03

    We demonstrate single photon counting of terahertz (THz) waves transmitted from a local THz point source through a coplanar two-wire waveguide on a GaAs/AlGaAs single heterostructure crystal. In the electrically driven all-in-one chip, quantum Hall edge transport is used to achieve a noiseless injection current for a monochromatic point source of THz fields. The local THz fields are coupled to a coplanar two-wire metal waveguide and transmitted over a macroscopic scale greater than the wavelength (38 μm in GaAs). THz waves propagating on the waveguide are counted as individual photons by a quantum-dot single-electron transistor on the same chip. Photon counting on integrated high-frequency circuits will open the possibilities for on-chip quantum optical experiments.

  10. Field-aligned currents and large-scale magnetospheric electric fields

    NASA Technical Reports Server (NTRS)

    Dangelo, N.

    1979-01-01

    The existence of field-aligned currents (FAC) at northern and southern high latitudes was confirmed by a number of observations, most clearly by experiments on the TRIAD and ISIS 2 satellites. The high-latitude FAC system is used to relate what is presently known about the large-scale pattern of high-latitude ionospheric electric fields and their relation to solar wind parameters. Recently a simplified model was presented for polar cap electric fields. The model is of considerable help in visualizing the large-scale features of FAC systems. A summary of the FAC observations is given. The simplified model is used to visualize how the FAC systems are driven by their generators.

  11. Behavioral effects of electric and magnetic fields

    SciTech Connect

    Laties, V.G.

    1992-04-01

    Two set of behavioral studies were conducted. (1) Electric field: Three procedures were used to determine how aversive a 100 kV/m 60-Hz electric field is for the rat. Each of the procedures enabled rats to respond in order to reduce exposure to the field. The rats did reduce exposure slightly with one, but not with the other two, whereas they reduced their exposure to moderate illumination in all three procedures. The results show that while the procedures were appropriate for assessing stimulus aversiveness, 100 kV/m is not a generally aversive stimulus for the rat. (2) Magnetic Field: Thomas, Schrot and Liboff (Bioelectromagnetics: 7: 349--357 (1986)) reported that immediately after exposure for 30 min to a horizontal 60-Hz, 5 {times} 10{sup {minus}5}T field combined with a total static field of 2.61 {times} 10{sup {minus}5}T, the rate of lever pressing by rats increased during the DRL component of a multiple fixed ratio, DRL schedule of food reinforcement. This project failed to confirm those observations in an experiment that duplicated the behavioral baseline and the magnetic field exposure conditions, with the exception that the total DC vector was greater in these Rochester experiments than it was in Thomas et al, which was done in Bethesda, MD.

  12. Field-aligned currents and ionospheric electric fields

    NASA Technical Reports Server (NTRS)

    Yasuhara, F.; Akasofu, S.-I.

    1977-01-01

    It is shown that the observed distribution of the ionospheric electric field can be deduced from an equation combining Ohm's law with the current continuity equation by using the 'observed' distribution of field-aligned currents as the boundary condition for two models of the ionosphere. The first model has one conductive annular ring representing the quiet-time auroral precipitation belt; the second has two conductive annular rings that simulate the discrete and diffuse auroral regions. An analysis is performed to determine how well the electric-field distribution can be reproduced. The results indicate that the first model reproduces the Sq(p)-type distribution, the second model reproduces reasonably well a substorm-type potential and ionospheric current patterns together with the Harang discontinuity, and that the distribution of field-aligned currents is the same for both models.

  13. Nonequilibrium condensation and coarsening of field-driven dipolar colloids.

    PubMed

    Jäger, Sebastian; Schmidle, Heiko; Klapp, Sabine H L

    2012-07-01

    In colloidal suspensions, self-organization processes can be easily fueled by external fields. Here we consider monolayers of particles with permanent dipole moments that are driven by rotating external fields. In recent experiments, it has been shown that the particles in such systems self-organize into two-dimensional clusters. Here we report results from a computer simulation study of these pattern forming systems. Specifically, we employ Langevin dynamics simulations, Brownian dynamics simulations that include hydrodynamic interactions, and Wang-Landau Monte Carlo simulations of soft spheres interacting via dipolar potentials. We investigate at which field strengths and frequencies clusters form and explore the influence of hydrodynamic interactions. We also examine the phase behavior of the equilibrium system resulting from a time average of the colloidal interactions in the rotating field. In this way we demonstrate that the clustering described in the driven system arises from a first-order phase transition between a vapor and a condensed phase.

  14. Nonequilibrium condensation and coarsening of field-driven dipolar colloids

    NASA Astrophysics Data System (ADS)

    Jäger, Sebastian; Schmidle, Heiko; Klapp, Sabine H. L.

    2012-07-01

    In colloidal suspensions, self-organization processes can be easily fueled by external fields. Here we consider monolayers of particles with permanent dipole moments that are driven by rotating external fields. In recent experiments, it has been shown that the particles in such systems self-organize into two-dimensional clusters. Here we report results from a computer simulation study of these pattern forming systems. Specifically, we employ Langevin dynamics simulations, Brownian dynamics simulations that include hydrodynamic interactions, and Wang-Landau Monte Carlo simulations of soft spheres interacting via dipolar potentials. We investigate at which field strengths and frequencies clusters form and explore the influence of hydrodynamic interactions. We also examine the phase behavior of the equilibrium system resulting from a time average of the colloidal interactions in the rotating field. In this way we demonstrate that the clustering described in the driven system arises from a first-order phase transition between a vapor and a condensed phase.

  15. Fundamental properties of field emission-driven direct current microdischarges

    NASA Astrophysics Data System (ADS)

    Rumbach, Paul; Go, David B.

    2012-11-01

    For half a century, it has been known that the onset of field emission in direct current microdischarges with gap sizes less than 10 μm can lead to breakdown at applied voltages far less than predicted by Paschen's law. It is still unclear how field emission affects other fundamental plasma properties at this scale. In this work, a one-dimensional fluid model is used to predict basic scaling laws for fundamental properties including ion density, electric field due to space charge, and current-voltage relations in the pre-breakdown regime. Computational results are compared with approximate analytic solutions. It is shown that field emission provides an abundance of cathode electrons, which in turn create large ion concentrations through ionizing collisions well before Paschen's criterion for breakdown is met. Breakdown due to ion-enhanced field emission occurs when the electric field due to space charge becomes comparable to the applied electric field. Simple scaling analysis of the 1D Poisson equation demonstrates that an ion density of n+ ≈ 0.1VAɛ0/qd2 is necessary to significantly distort the electric field. Defining breakdown in terms of this critical ion density leads analytically to a simple, effective secondary emission coefficient γ' of the same mathematical form initially suggested by Boyle and Kisliuk [Phys. Rev. 97, 255 (1955)].

  16. Field Operations Program Neighborhood Electric Vehicles - Fleet Survey

    SciTech Connect

    Francfort, James Edward; Carroll, M.

    2001-07-01

    This report summarizes a study of 15 automotive fleets that operate neighborhood electric vehicles(NEVs) in the United States. The information was obtained to help Field Operations Program personnel understand how NEVs are being used, how many miles they are being driven, and if they are being used to replace other types of fleet vehicles or as additions to fleets. (The Field Operations Program is a U.S. Department of Energy Program within the DOE Office of Energy Efficiency and Renewable Energy, Transportation Technologies). The NEVs contribution to petroleum avoidance and cleaner air can be estimated based on the miles driven and by assuming gasoline use and air emissions values for the vehicles being replaced. Gasoline and emissions data for a Honda Civic are used as the Civic has the best fuel use for a gasoline-powered vehicle and very clean emissions. Based on these conservation assumptions, the 348 NEVs are being driven a total of about 1.2 million miles per year. This equates to an average of 3,409 miles per NEV annually or 9 miles per day. It is estimated that 29,195 gallons of petroleum use is avoided annually by the 348 NEVs. This equates to 87 gallons of petroleum use avoided per NEV, per year. Using the 348 NEVs avoids the generation of at least 775 pounds of smog- forming emissions annually.

  17. Field Operations Program - Neighborhood Electric Vehicle Fleet Use

    SciTech Connect

    Francfort, J. E.; Carroll, M. R.

    2001-07-02

    This report summarizes a study of 15 automotive fleets that operate neighborhood electric vehicles (NEVs) in the United States. The information was obtained to help Field Operations Program personnel understand how NEVs are being used, how many miles they are being driven, and if they are being used to replace other types of fleet vehicles or as additions to fleets. (The Field Operations Program is a U.S. Department of Energy Program within the DOE Office of Energy Efficiency and Renewable Energy, Transportation Technologies). The NEVs contribution to petroleum avoidance and cleaner air can be estimated based on the miles driven and by assuming gasoline use and air emissions values for the vehicles being replaced. Gasoline and emissions data for a Honda Civic are used as the Civic has the best fuel use for a gasoline-powered vehicle and very clean emissions. Based on these conservation assumptions, the 348 NEVs are being driven a total of about 1.2 million miles per year. This equates to an average of 3,409 miles per NEV annually or 9 miles per day. It is estimated that 29,195 gallons of petroleum use is avoided annually by the 348 NEVs. This equates to 87 gallons of petroleum use avoided per NEV, per year. Using the 348 NEVs avoids the generation of at least 775 pounds of smog-forming emissions annually.

  18. Thermospheric Response to Solar Wind Electric Field Fluctuations

    NASA Astrophysics Data System (ADS)

    Perlongo, N. J.; Ridley, A. J.

    2013-12-01

    The electron density of the thermosphere is of paramount importance for radio communications and drag on low altitude satellites, particularly during geomagnetic storms. Transient enhancements of ion velocities and subsequent density and temperature increases frequently occur as a result of storm-driven solar wind electric field fluctuations. Since the Earth's dipole magnetic field is tilted and offset from the center of the planet, significant asymmetries arise that alter the thermospheric response to energy input based upon the time of day of the disturbance. This study utilizes the Global Ionosphere-Thermosphere Model (GITM) to investigate this phenomenon by enhancing the convective electric field for one hour of the day in 22 different simulations. An additional baseline run was conducted with no IMF perturbation. Furthermore, four configurations of Earth's magnetic field were considered, Internal Geomagnetic Reference Field (IGRF), a perfect dipole, a dipole tilted by 10 degrees, and a tilted and offset dipole. These runs were conducted at equinox when the amount of sunlight falling on the different hemispheres is the same. Two additional runs were conducted at the solstices for comparison. It was found that the most geo-effective times are when the poles are pointed towards the sun. The electron density, neutral density and temperature as well as the winds are explored.

  19. Flow Field Measurement of Mixing Driven by Buoyancy

    NASA Technical Reports Server (NTRS)

    Batur, C.; Zhong, H.

    2003-01-01

    Mixing driven by buoyancy-induced flows inside a cavity consists of stretching and folding of an interface. Measurement of the flow field using particle imaging velocimetry shows that during stretching the flow field has a single elliptic point, thus dominated by a single vortex. However, global bifurcation that results in folding introduces a hyperbolic point whereby the flow field degenerates to multiple vortex interactions. The short-lived coherent structure observed during mixing which results in the Rayleigh- Taylor morphology is attributed to vortex interactions. The mixing characteristics of non-homogeneous fluids driven by buoyancy are important towards understanding transport phenomenon in a microgravity environment. Mixing consists of stretching and folding of an interface due to a flow field whose intensity depends on the body force. For miscible liquids, the characteristic of the flow field determines whether mass transport is governed by diffusion or bulk stirring which induces mixing. For technologically important processes, transport of mass is governed by the coupling of the body force to scalar gradients such as concentration and or temperature' 2 3 . In order to lend insight into these classes of problems we consider a model experimental system to study mixing driven by buoyancy-induced flows. The characteristics of mixing is addressed from detail measurements of the flow field using particle imaging velocimetry (PIV), and its corresponding interface dynamics using image processing techniques.

  20. Method of electric field flow fractionation wherein the polarity of the electric field is periodically reversed

    DOEpatents

    Stevens, Fred J.

    1992-01-01

    A novel method of electric field flow fractionation for separating solute molecules from a carrier solution is disclosed. The method of the invention utilizes an electric field that is periodically reversed in polarity, in a time-dependent, wave-like manner. The parameters of the waveform, including amplitude, frequency and wave shape may be varied to optimize separation of solute species. The waveform may further include discontinuities to enhance separation.

  1. Fluctuations of Electrical Conductivity: A New Source for Astrophysical Magnetic Fields.

    PubMed

    Pétrélis, F; Alexakis, A; Gissinger, C

    2016-04-22

    We consider the generation of a magnetic field by the flow of a fluid for which the electrical conductivity is nonuniform. A new amplification mechanism is found which leads to dynamo action for flows much simpler than those considered so far. In particular, the fluctuations of the electrical conductivity provide a way to bypass antidynamo theorems. For astrophysical objects, we show through three-dimensional global numerical simulations that the temperature-driven fluctuations of the electrical conductivity can amplify an otherwise decaying large scale equatorial dipolar field. This effect could play a role for the generation of the unusually tilted magnetic field of the iced giants Neptune and Uranus.

  2. Fluctuations of Electrical Conductivity: A New Source for Astrophysical Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Pétrélis, F.; Alexakis, A.; Gissinger, C.

    2016-04-01

    We consider the generation of a magnetic field by the flow of a fluid for which the electrical conductivity is nonuniform. A new amplification mechanism is found which leads to dynamo action for flows much simpler than those considered so far. In particular, the fluctuations of the electrical conductivity provide a way to bypass antidynamo theorems. For astrophysical objects, we show through three-dimensional global numerical simulations that the temperature-driven fluctuations of the electrical conductivity can amplify an otherwise decaying large scale equatorial dipolar field. This effect could play a role for the generation of the unusually tilted magnetic field of the iced giants Neptune and Uranus.

  3. Magnetostimulated inhomogeneity of electric field in aluminum

    SciTech Connect

    Sobol, V.R.; Mazurenko, O.N.; Drozd, A.A.

    1997-06-01

    The peculiarities of potential and current distribution in metals under inhomogeneous action of magnetic field is studied experimentally and analytically. Magnetic field inhomogeneity is modeled with a method of curving the electric current lines in rectangular conductors through the use of preset profiles of samples. Observed inhomogeneous distribution of electric potential is analyzed on the base of charge continuity. It is shown that current density redistribution takes place. Near one side current density is high and near another it is small. This is a reason of decrease of an effective cross-section of conductor with respective enhancement of magnetoresistance. Some analytical relations and modes of applications of observed phenomena in cryogenic electronic devices are proposed.

  4. Amplification of magnetic fields by supernova-driven turbulence

    NASA Astrophysics Data System (ADS)

    Kim, J.; Balsara, D. S.

    2006-06-01

    Observations of μG magnetic fields in radio galaxies at cosmological epochs as early as around z=2 have shortened the available time for dynamo action. This fact suggests that the mean-field dynamo mechanism in a global galactic scale either is too slow to amplify a seed field generated by the Biermann battery effect to the level of the observed field strength at z˜2 or needs much stronger seed fields of an order of 10-10 G. A ``contamination'' picture that amplified magnetic fields in smaller objects, such as stars or AGNs, within a relatively shorter timescale spread out through supernova ejecta, stellar winds, and AGN jets to nearby environments is gaining momentum. In line with this picture, we demonstrate, through three-dimensional numerical experiments, that magnetic fields can be amplified by supernova-driven turbulence with two orders of magnitude smaller e-folding timescale than that of the mean-field dynamo mechanism. Therefore, supernova-driven turbulence may play an important role in amplifying small-scale B-fields in any astrophysical systems that have harbored massive stars.

  5. Dynamics of Spinor Condensates Driven by an Inhomogeneous Magnetic Field

    NASA Astrophysics Data System (ADS)

    Zheng, Gong-Ping; Chang, Gao-Zhan; Li, Pin; Li, Ting; Wei, L. F.

    2017-06-01

    A variational wavefunction including the breather, dipole and scissor modes simultaneously is constructed to investigate the collective-excitation dynamics of spin-1 ^{87}Rb condensates driven by a space- and time-dependent magnetic field. When the Dirac point never enters the condensate, it is shown that the dipole, breather and scissor modes will be all excited driven by the sinusoidal oscillation of the Dirac point, due to the coupling of different collective modes from the inhomogeneity of the magnetic field. A resonance-driving phenomenon is observed. If the Dirac point passes through the condensate, our numerical results agree with most experimental observations (Ray et al. in Nature 505:657, 2014) and find that the center of mass of the condensate does not follow the zero point of the magnetic field. Hopefully, our method can be extended to study the similar dynamics for the other spinor condensates.

  6. An effective magnetic field from optically driven phonons

    NASA Astrophysics Data System (ADS)

    Nova, T. F.; Cartella, A.; Cantaluppi, A.; Först, M.; Bossini, D.; Mikhaylovskiy, R. V.; Kimel, A. V.; Merlin, R.; Cavalleri, A.

    2016-10-01

    Light fields at terahertz and mid-infrared frequencies allow for the direct excitation of collective modes in condensed matter, which can be driven to large amplitudes. For example, excitation of the crystal lattice has been shown to stimulate insulator-metal transitions, melt magnetic order or enhance superconductivity. Here, we generalize these ideas and explore the simultaneous excitation of more than one lattice mode, which are driven with controlled relative phases. This nonlinear mode mixing drives rotations as well as displacements of the crystal-field atoms, mimicking the application of a magnetic field and resulting in the excitation of spin precession in the rare-earth orthoferrite ErFeO3. Coherent control of lattice rotations may become applicable to other interesting problems in materials research--for example, as a way to affect the topology of electronic phases.

  7. Dynamics of Spinor Condensates Driven by an Inhomogeneous Magnetic Field

    NASA Astrophysics Data System (ADS)

    Zheng, Gong-Ping; Chang, Gao-Zhan; Li, Pin; Li, Ting; Wei, L. F.

    2017-10-01

    A variational wavefunction including the breather, dipole and scissor modes simultaneously is constructed to investigate the collective-excitation dynamics of spin-1 ^{87}Rb condensates driven by a space- and time-dependent magnetic field. When the Dirac point never enters the condensate, it is shown that the dipole, breather and scissor modes will be all excited driven by the sinusoidal oscillation of the Dirac point, due to the coupling of different collective modes from the inhomogeneity of the magnetic field. A resonance-driving phenomenon is observed. If the Dirac point passes through the condensate, our numerical results agree with most experimental observations (Ray et al. in Nature 505:657, 2014) and find that the center of mass of the condensate does not follow the zero point of the magnetic field. Hopefully, our method can be extended to study the similar dynamics for the other spinor condensates.

  8. Spin generation by strong inhomogeneous electric fields

    NASA Astrophysics Data System (ADS)

    Finkler, Ilya; Engel, Hans-Andreas; Rashba, Emmanuel; Halperin, Bertrand

    2007-03-01

    Motivated by recent experiments [1], we propose a model with extrinsic spin-orbit interaction, where an inhomogeneous electric field E in the x-y plane can give rise, through nonlinear effects, to a spin polarization with non-zero sz, away from the sample boundaries. The field E induces a spin current js^z= z x(αjc+βE), where jc=σE is the charge current, and the two terms represent,respectively, the skew scattering and side-jump contributions. [2]. The coefficients α and β are assumed to be E- independent, but conductivity σ is field dependent. We find the spin density sz by solving the equation for spin diffusion and relaxation with a source term ∇.js^z. For sufficiently low fields, jc is linear in E, and the source term vanishes, implying that sz=0 away from the edges. However, for large fields, σ varies with E. Solving the diffusion equation in a T-shaped geometry, where the electric current propagates along the main channel, we find spin accumulation near the entrance of the side channel, similar to experimental findings [1]. Also, we present a toy model where spin accumulation away from the boundary results from a nonlinear and anisotropic conductivity. [1] V. Sih, et al, Phys. Rev. Lett. 97, 096605 (2006). [2] H.-A. Engel, B.I. Halperin, E.I.Rashba, Phys. Rev. Lett. 95, 166605 (2005).

  9. Electric fields produced by Florida thunderstorms

    NASA Technical Reports Server (NTRS)

    Livingston, J. M.; Krider, E. P.

    1978-01-01

    Twenty-five field mill sites provided data on the electric fields produced during both the intense and the final, less active periods of summer air mass thunderstorms in east central Florida. During the periods of intense lightning activity, time- and area-averaged fields were usually -0.8 to -2.1 kV/m, while for the less active periods, the field values were typically in the range of -2.3 to -4.3 kV/m. Furthermore, during the active storm periods, which represented about 27% of the total storm durations, about 71% of all lightning discharges occurred. Also, fewer lightning discharges in the final storm period than in the active period reached the ground.

  10. Extremely low frequency electric fields and cancer: assessing the evidence.

    PubMed

    Kheifets, Leeka; Renew, David; Sias, Glenn; Swanson, John

    2010-02-01

    Much of the research and reviews on extremely low frequency (ELF) electric and magnetic fields (EMFs) have focused on magnetic rather than electric fields. Some have considered such focus to be inappropriate and have argued that electric fields should be part of both epidemiologic and laboratory work. This paper fills the gap by systematically and critically reviewing electric-fields literature and by comparing overall strength of evidence for electric versus magnetic fields. The review of possible mechanisms does not provide any specific basis for focusing on electric fields. While laboratory studies of electric fields are few, they do not indicate that electric fields should be the exposure of interest. The existing epidemiology on residential electric-field exposures and appliance use does not support the conclusion of adverse health effects from electric-field exposure. Workers in close proximity to high-voltage transmission lines or substation equipment can be exposed to high electric fields. While there are sporadic reports of increase in cancer in some occupational studies, these are inconsistent and fraught with methodologic problems. Overall, there seems little basis to suppose there might be a risk for electric fields, and, in contrast to magnetic fields, and with a possible exception of occupational epidemiology, there seems little basis for continued research into electric fields. (c) 2009 Wiley-Liss, Inc.

  11. Microchannel protein separation by electric field gradient focusing.

    PubMed

    Petsev, Dimiter N; Lopez, Gabriel P; Ivory, Cornelius F; Sibbett, Scott S

    2005-06-01

    A microchannel device is presented which separates and focuses charged proteins based on electric field gradient focusing. Separation is achieved by setting a constant electroosmotic flow velocity against step changes in electrophoretic velocity. Where these two velocities are balanced for a given analyte, the analyte focuses at that point because it is driven to it from all points within the channel. We demonstrate the separation and focusing of a binary mixture of bovine serum albumin and phycoerythrin. The device is constructed of intersecting microchannels in poly(dimethylsiloxane)(PDMS) inlaid with hollow dialysis fibers. The device uses no exotic chemicals such as antibodies or synthetic ampholytes, but operates instead by purely physical means involving the independent manipulation of electrophoretic and electroosmotic velocities. One important difference between this apparatus and most other devices designed for field-gradient focusing is the injection of current at discrete intersections in the channel rather than continuously along the length of a membrane-bound separation channel.

  12. Electric and magnetic fields at power frequencies.

    PubMed

    Miller, Anthony B; Green, Lois M

    2010-01-01

    Exposures to electric and magnetic fields are among the most ubiquitous exposures that the Canadian population experiences. Sources of electric and magnetic field exposures may be occupational or residential and include proximity to certain types of electrical equipment, transmission and distribution power lines as well as appliance use. The early studies of children tended toward a consistent association between risks for leukemia and brain cancer and residential proximity to power lines having high wire configuration. More recent studies-and studies which have attempted to improve upon the measurement of exposure by using calculated fields, point-in-time or personal monitoring-have been inconsistent, with some suggesting increased risk and others not. Occupational exposures have suggested an increase in risk for leukemia, and to a lesser extent brain cancer and Non-Hodgkin lymphoma. However, studies of residential exposures and cancer in adults generally have suggested no effect. Laboratory work has been unable to demonstrate a biological mechanism which might explain the epidemiological findings. In spite of extensive efforts over the past 20 years and many expert reviews, it has been difficult to reach consensus regarding the carcinogenic effects of electric and magnetic fields. Exposure assessment has proven to be complex, and agreement on the relevant exposure metric has not yet been obtained. There is justification to question whether point-in-time measures in homes are appropriate indices of the relevant etiological exposure, as they fail to account for changes over time, peak exposures or time-varying fields. Nevertheless, it is probably desirable to err on the side of caution in not placing too much weight on the inconsistencies. The IARC has classified EMF as a "possible carcinogen" which refers to the circumstances where there is limited evidence of carcinogenicity in humans and inadequate evidence in experimental animals. The IARC review indicated

  13. Fabrication 3D buried channel optical waveguide modulators on field-driven ion exchange process

    NASA Astrophysics Data System (ADS)

    Zhou, Zigang; Chen, Wenqiang; Zhu, Li; Li, Jing; Luo, Xiaoying

    2010-10-01

    A high electric field technique was developed to fabricate buried optical waveguide modulator on K9 optical glass. The 80V voltage was applied on the glass to accelerate the field-driven ion exchange process by expeditiously replacing host sodium ions in the glass with silver ions. As a result, the optical loss for optical waveguide modulator was measured using the edge coupling technique with a 0.6328μm He-Ne laser. Loss of 0.20 dB/cm was obtained for channel waveguides of 25μm in depth, relatively low for waveguides of such depth at red wavelength.

  14. Electrical Grounding - a Field for Geophysicists and Electrical Engineers Partnership

    NASA Astrophysics Data System (ADS)

    Freire, P. F.; Pane, E.; Guaraldo, N.

    2012-12-01

    , layered stratified or showing lateral variations, ranging down to several tens of kilometers deep, reaching the crust-mantle interface (typically with the order of 30-40 km). This work aims to analyze the constraints of the current soil models being used for grounding electrodes design, and suggests the need of a soil modeling methodology compatible with large grounding systems. Concerning the aspects related to soil modeling, electrical engineers need to get aware of geophysics resources, such as: - geophysical techniques for soil electrical resistivity prospection (down to about 15 kilometers deep); and - techniques for converting field measured data, from many different geophysical techniques, into adequate soil models for grounding grid simulation. It is also important to equalize the basic knowledge for the professionals that are working together for the specific purpose of soil modeling for electrical grounding studies. The authors have experienced the situation of electrical engineers working with geophysicists, but it was not clear for the latter the effective need of the electrical engineers, and for the engineers it was unknown the available geophysical resources, and also, what to do convert the large amount of soil resistivity data into a reliable soil model.

  15. Field-driven magnetization dynamics of nanoparticles and nanowires

    NASA Astrophysics Data System (ADS)

    Lu, Jie

    This thesis is about micromagnetism in confined magnetic microstructures. The field-driven magnetization dynamics of nanoparticles and nanowires is systematically discussed following a clear thread of thought: from "macrospin" to "microspin". At the same time, four topics are raised and investigated. First, inspired by the traditional ferromagnetic resonance technique, two strategies for measuring the Gilbert damping coefficient using the magnetic circular dichroism effect are presented and discussed. The investigation is performed within a framework of the linear response of the macrospin in 2-D magnetic films to external time-dependent fields. The object of the study then turns to Stoner particles, which are single-domain magnetic nanoparticles, that are quasi 0-D systems and still assumed to be macrospins. The field-driven magnetization reversal in multi-axial Stoner particles is investigated and the corresponding Eular equations are presented. The Eular equations provide a unified framework for research of this kind. After that, the macrospin assumption itself is examined. The study of when and how it fails results in the famous "nucleation problem" in micromagnetism, thus the discussion then moves into the microspin category. The nucleation problem of single-domain cuboid permalloy nanowires, which are quasi 1-D systems, is investigated and a magnetization reversal mode named "domain formation and domain wall propagation" is revealed. Field-driven magnetic domain wall propagation is an excellent example of microspin behavior, and has been a hot issue in recent spintronic research. The effects of transverse magnetic anisotropies on field-driven transverse wall propagation in narrow magnetic nanowires are systematically investigated. These results should not only deepen the understanding of the domain wall dynamics in magnetic nanowires, but also offer inspiration for further developments of ultrafast nano-devices with higher integration levels.

  16. Transient electrical field across cellular membranes: pulsed electric field treatment of microbial cells

    NASA Astrophysics Data System (ADS)

    Timoshkin, I. V.; MacGregor, S. J.; Fouracre, R. A.; Crichton, B. H.; Anderson, J. G.

    2006-02-01

    The pulsed electric field (PEF) treatment of liquid and pumpable products contaminated with microorganisms has attracted significant interest from the pulsed power and bioscience research communities particularly because the inactivation mechanism is non-thermal, thereby allowing retention of the original nutritional and flavour characteristics of the product. Although the biological effects of PEF have been studied for several decades, the physical mechanisms of the interaction of the fields with microorganisms is still not fully understood. The present work is a study of the dynamics of the electrical field both in a PEF treatment chamber with dielectric barriers and in the plasma (cell) membrane of a microbial cell. It is shown that the transient process can be divided into three physical phases, and models for these phases are proposed and briefly discussed. The complete dynamics of the time development of the electric field in a spherical dielectric shell representing the cellular membrane is then obtained using an analytical solution of the Ohmic conduction problem. It was found that the field in the membrane reaches a maximum value that could be two orders of magnitude higher than the original Laplacian electrical field in the chamber, and this value was attained in a time comparable to the field relaxation time in the chamber. Thus, the optimal duration of the field during PEF treatment should be equal to such a time.

  17. Electric Field Induced Surface Modification of Au

    SciTech Connect

    Erchak, A.A.; Franklin, G.F.; Houston, J.E.; Mayer, T.M.; Michalske, T.A.

    1999-02-15

    We discuss the role of localized high electric fields in the modification of Au surfaces with a W probe using the Interfacial Force Microscope. Upon bringing a probe close to a Au surface, we measure both the interfacial force and the field emission current as a function of separation with a constant potential of 100 V between tip and sample. The current initially increases exponentially as the separation decreases. However, at a distance of less than {approximately} 500{angstrom} the current rises sharply as the surface begins to distort and rapidly close the gap. Retraction of the tip before contact is made reveals the formation of a mound on the surface. We propose a simple model, in which the localized high electric field under the tip assists the production of mobile Au adatoms by detachment from surface steps, and a radial field gradient causes a net flux of atoms toward the tip by surface diffusion. These processes give rise to an unstable surface deformation which, if left unchecked, results in a destructive mechanical contact. We discuss our findings with respect to earlier work using voltage pulses in the STM as a means of nanofabrication.

  18. Electron transport in argon in crossed electric and magnetic fields

    PubMed

    Ness; Makabe

    2000-09-01

    An investigation of electron transport in argon in the presence of crossed electric and magnetic fields is carried out over a wide range of values of electric and magnetic field strengths. Values of mean energy, ionization rate, drift velocity, and diffusion tensor are reported here. Two unexpected phenomena arise; for certain values of electric and magnetic field we find regions where the swarm mean energy decreases with increasing electric fields for a fixed magnetic field and regions where swarm mean energy increases with increasing magnetic field for a fixed electric field.

  19. Aircraft electric field measurements: Calibration and ambient field retrieval

    NASA Technical Reports Server (NTRS)

    Koshak, William J.; Bailey, Jeff; Christian, Hugh J.; Mach, Douglas M.

    1994-01-01

    An aircraft locally distorts the ambient thundercloud electric field. In order to determine the field in the absence of the aircraft, an aircraft calibration is required. In this work a matrix inversion method is introduced for calibrating an aircraft equipped with four or more electric field sensors and a high-voltage corona point that is capable of charging the aircraft. An analytic, closed form solution for the estimate of a (3 x 3) aircraft calibration matrix is derived, and an absolute calibration experiment is used to improve the relative magnitudes of the elements of this matrix. To demonstrate the calibration procedure, we analyze actual calibration date derived from a Lear jet 28/29 that was equipped with five shutter-type field mill sensors (each with sensitivities of better than 1 V/m) located on the top, bottom, port, starboard, and aft positions. As a test of the calibration method, we analyze computer-simulated calibration data (derived from known aircraft and ambient fields) and explicitly determine the errors involved in deriving the variety of calibration matrices. We extend our formalism to arrive at an analytic solution for the ambient field, and again carry all errors explicitly.

  20. Colloidal Switches by Electric and Magnetic Fields.

    PubMed

    Demirörs, Ahmet Faik; Beltramo, Peter J; Vutukuri, Hanumantha Rao

    2017-05-24

    External electric and magnetic fields have already been proven to be a versatile tool to control the particle assembly; however, the degree of control of the dynamics and versatility of the produced structures is expected to increase if both can be implemented simultaneously. For example, while micromagnets can rapidly assemble superparamagnetic particles, repeated, rapid disassembly or reassembly is not trivial because of the remanence and coercivity of metals used in such applications. Here, an interdigitated design of micromagnet and microfabricated electrodes enables rapid switching of colloids between their magnetic and electric potential minima. Active control over colloids between two such adjacent potential minima enables a fast on/off mechanism, which is potentially important for optical switches or display technologies. Moreover, we demonstrate that the response time of the colloids between these states is on the order of tens of milliseconds, which is tunable by electric field strength. By carefully designing the electrode pattern, our strategy enables the switchable assembly of single particles down to few microns and also hierarchical assemblies containing many particles. Our work on precise dynamic control over the particle position would open new avenues to find potential applications in optical switches and display technologies.

  1. Electric-field control of magnetic domain wall motion and local magnetization reversal

    PubMed Central

    Lahtinen, Tuomas H. E.; Franke, Kévin J. A.; van Dijken, Sebastiaan

    2012-01-01

    Spintronic devices currently rely on magnetic switching or controlled motion of domain walls by an external magnetic field or spin-polarized current. Achieving the same degree of magnetic controllability using an electric field has potential advantages including enhanced functionality and low power consumption. Here we report on an approach to electrically control local magnetic properties, including the writing and erasure of regular ferromagnetic domain patterns and the motion of magnetic domain walls, in CoFe-BaTiO3 heterostructures. Our method is based on recurrent strain transfer from ferroelastic domains in ferroelectric media to continuous magnetostrictive films with negligible magnetocrystalline anisotropy. Optical polarization microscopy of both ferromagnetic and ferroelectric domain structures reveals that domain correlations and strong inter-ferroic domain wall pinning persist in an applied electric field. This leads to an unprecedented electric controllability over the ferromagnetic microstructure, an accomplishment that produces giant magnetoelectric coupling effects and opens the way to electric-field driven spintronics. PMID:22355770

  2. Receptive field properties of rod-driven horizontal cells in the skate retina

    PubMed Central

    1992-01-01

    The large receptive fields of retinal horizontal cells result primarily from extensive intercellular coupling via gap (electrical) junctions; thus, the extent of the receptive field provides an index of the degree to which the cells are electrically coupled. For rod-driven horizontal cells in the dark-adapted skate retina, a space constant of 1.18 +/- 0.15 mm (SD) was obtained from measurements with a moving slit stimulus, and a comparable value (1.43 +/- 0.55 mm) was obtained with variation in spot diameter. These values, and the extensive spread of a fluorescent dye (Lucifer Yellow) from the site of injection to neighboring cells, indicate that the horizontal cells of the all-rod retina of skate are well coupled electrically. Neither the receptive field properties nor the gap-junctional features of skate horizontal cells were influenced by the adaptive state of the retina: (a) the receptive field organization was unaffected by light adaptation, (b) similar dye coupling was seen in both dark- and light-adapted retinae, and (c) no significant differences were found in the gap-junctional particle densities measured in dark- and light-adapted retinas, i.e., 3,184 +/- 286/microns 2 (n = 8) and 3,073 +/- 494/microns 2 (n = 11), respectively. Moreover, the receptive fields of skate horizontal cells were not altered by either dopamine, glycine, GABA, or the GABAA receptor antagonists bicuculline and picrotoxin. We conclude that the rod-driven horizontal cells of the skate retina are tightly coupled to one another, and that the coupling is not affected by photic and pharmacological conditions that are known to modulate intercellular coupling between cone-driven horizontal cells in other species. PMID:1359000

  3. Cathode driven high gain crossed-field amplifier

    NASA Astrophysics Data System (ADS)

    1983-07-01

    The objective of this three-phase program is to achieve the design of a cathode driven high gain re-entrant Crossed Field Amplifier capable of meeting the parameters of Raytheon Company specification No. 968838 dated 10 May 1978. The effort includes the fabrication and test of three developmental and four final configuration tubes. One final configuration tube will be life tested and two will be delivered to the Navy. The tasks discussed during this report period relate to the cold tests performed on various subassemblies of model no. 4 and on the sealed-in model no. 4 of the S-band high gain cathode driven crossed field amplifier. Based on the performance of model no. 3 certain remedial measures have been implemented in model no. 4 that have resulted in the elimination of key resonances within the tube and an improvement in the isolation between the cathode and anode circuits.

  4. Stable solutions of inflation driven by vector fields

    NASA Astrophysics Data System (ADS)

    Emami, Razieh; Mukohyama, Shinji; Namba, Ryo; Zhang, Ying-li

    2017-03-01

    Many models of inflation driven by vector fields alone have been known to be plagued by pathological behaviors, namely ghost and/or gradient instabilities. In this work, we seek a new class of vector-driven inflationary models that evade all of the mentioned instabilities. We build our analysis on the Generalized Proca Theory with an extension to three vector fields to realize isotropic expansion. We obtain the conditions required for quasi de-Sitter solutions to be an attractor analogous to the standard slow-roll one and those for their stability at the level of linearized perturbations. Identifying the remedy to the existing unstable models, we provide a simple example and explicitly show its stability. This significantly broadens our knowledge on vector inflationary scenarios, reviving potential phenomenological interests for this class of models.

  5. Low frequency electric and magnetic fields

    NASA Technical Reports Server (NTRS)

    Spaniol, Craig

    1989-01-01

    Following preliminary investigations of the low frequency electric and magnetic fields that may exists in the Earth-ionospheric cavity, measurements were taken with state-of-the art spectrum analyzers. As a follow up to this activity, an investigation was initiated to determine sources and values for possible low frequency signal that would appear in the cavity. The lowest cavity resonance is estimated at about 8 Hz, but lower frequencies may be an important component of our electromagnetic environment. The potential field frequencies produced by the electron were investigated by a classical model that included possible cross coupling of the electric and gravitation fields. During this work, an interesting relationship was found that related the high frequency charge field with the extremely low frequency of the gravitation field. The results of numerical calculations were surprisingly accurate and this area of investigation is continuing. The work toward continued development of a standardized monitoring facility is continuing with the potential of installing the prototype at West Virginia State College early in 1990. This installation would be capable of real time monitoring of ELF signals in the Earth-ionoshpere cavity and would provide some directional information. A high gain, low noise, 1/f frequency corrected preamplifier was designed and tested for the ferrite core magnetic sensor. The potential application of a super conducting sensor for the ELF magnetic field detection is under investigation. It is hoped that a fully operational monitoring network could pinpoint the location of ELF signal sources and provide new information on where these signals originate and what causes them, assuming that they are natural in origin.

  6. Manipulation of a neutral and nonpolar nanoparticle in water using a nonuniform electric field

    NASA Astrophysics Data System (ADS)

    Xu, Zhen; Wang, Chunlei; Sheng, Nan; Hu, Guohui; Zhou, Zhewei; Fang, Haiping

    2016-01-01

    The manipulation of nanoparticles in water is of essential importance in chemical physics, nanotechnology, medical technology, and biotechnology applications. Generally, a particle with net charges or charge polarity can be driven by an electric field. However, many practical particles only have weak and even negligible charge and polarity, which hinders the electric field to exert a force large enough to drive these nanoparticles directly. Here, we use molecular dynamics simulations to show that a neutral and nonpolar nanoparticle in liquid water can be driven directionally by an external electric field. The directed motion benefits from a nonuniform water environment produced by a nonuniform external electric field, since lower water energies exist under a higher intensity electric field. The nanoparticle spontaneously moves toward locations with a weaker electric field intensity to minimize the energy of the whole system. Considering that the distance between adjacent regions of nonuniform field intensity can reach the micrometer scale, this finding provides a new mechanism of manipulating nanoparticles from the nanoscale to the microscale.

  7. Nanoscale structural evolution of electrically driven insulator to metal transition in vanadium dioxide

    SciTech Connect

    Freeman, Eugene Shukla, Nikhil; Datta, Suman; Stone, Greg; Engel-Herbert, Roman; Gopalan, Venkatraman; Paik, Hanjong; Moyer, Jarrett A.; Cai, Zhonghou; Wen, Haidan; Schlom, Darrell G.

    2013-12-23

    The structural evolution of tensile strained vanadium dioxide thin films was examined across the electrically driven insulator-to-metal transition by nanoscale hard X-ray diffraction. A metallic filament with rutile (R) structure was found to be the dominant conduction pathway for an electrically driven transition, while the majority of the channel area remained in the monoclinic M1 phase. The filament dimensions were estimated using simultaneous electrical probing and nanoscale X-ray diffraction. Analysis revealed that the width of the conducting channel can be tuned externally using resistive loads in series, enabling the M1/R phase ratio in the phase coexistence regime to be tuned.

  8. Electric-field-induced domain intersection in BaTiO3 single crystal

    NASA Astrophysics Data System (ADS)

    He, Ming; Wang, Mengxia; Zhang, Zhihua

    2017-03-01

    Large-angle convergent beam electron diffraction was used to determine the directions of polarization vectors in a BaTiO3 single crystal. Domain intersections driven by an electric field were investigated by in situ transmission electron microscopy. The dark triangles observed in the domain intersection region can be accounted for by dislocations and the strain field. Domains nucleate at the domain tip depending on the dislocations and strain field to relieve the accumulated stress. Schematic representations of the intersecting domains and the microscopic structure are given, clarifying the special electric-field-induced domain structure.

  9. Spin-valley dynamics of electrically driven ambipolar carbon-nanotube quantum dots

    NASA Astrophysics Data System (ADS)

    Osika, E. N.; Chacón, A.; Lewenstein, M.; Szafran, B.

    2017-07-01

    An ambipolar n-p double quantum dot defined by potential variation along a semiconducting carbon-nanotube is considered. We focus on the (1e,1h) charge configuration with a single excess electron of the conduction band confined in the n-type dot and a single missing electron in the valence band state of the p-type dot for which lifting of the Pauli blockade of the current was observed in the electric-dipole spin resonance (Laird et al 2013 Nat. Nanotechnol. 8 565). The dynamics of the system driven by periodic electric field is studied with the Floquet theory and the time-dependent configuration interaction method with the single-electron spin-valley-orbitals determined for atomistic tight-binding Hamiltonian. We find that the transitions lifting the Pauli blockade are strongly influenced by coupling to a vacuum state with an empty n dot and a fully filled p dot. The coupling shifts the transition energies and strongly modifies the effective g factors for axial magnetic field. The coupling is modulated by the bias between the dots but it appears effective for surprisingly large energy splitting between the (1e,1h) ground state and the vacuum (0e, 0h) state. Multiphoton transitions and high harmonic generation effects are also discussed.

  10. Electric and Magnetic Field control of Exchange Bias

    NASA Astrophysics Data System (ADS)

    Binek, Christian

    2007-03-01

    Exchange bias (EB) and its accompanying training effect are fundamental interface phenomena in coupled magnetic thin films with significant impact in spintronic applications. Here we report on the electric field control of the EB in innovative antiferromagnetic (AF)/ferromagnetic (FM) heterostructures and the magnetic field control of the EB training effect in exchange coupled all FM bilayer systems. Electric control of the EB is realized in Cr2O3 (111)/(Co/Pt)3 heterostructures by taking advantage of the magnetoelectric (ME) properties of the AF pinning layer [1]. An electric field induces excess magnetization in the ME Cr2O3 film. Exchange coupling between the induced magnetization and the CoPt thin film gives rise to electrically controlled perpendicular EB. Bias fields are measured by means of AGFM, SQUID-magnetometry and polar Kerr-rotation. Electrically controlled EB is proposed for novel spintronic applications such as pure voltage control of magnetic configurations in spin valve-type architectures. The latter provide an attractive alternative to current-induced switching of the magnetization [2]. In addition, training of the EB effect is studied in novel all FM heterostructures of exchange coupled soft and hard FM thin films [3]. FM bilayers show remarkable analogies to the conventional AF/FM EB systems. Not only do they exhibit a tunable EB effect, they also show a distinct training behavior upon cycling the soft layer through consecutive hysteresis loops. In contrast to conventional EB systems, all FM bilayers allow the observation of training induced changes in the bias-setting hard layer by means of simple magnetometry. Initialization of the EB is achieved at constant temperature exclusively by means of magnetic fields. Our experiments show unambiguously that EB training is driven by deviations from the equilibrium spin configuration of the pinning layer. The experimental data show excellent agreement with our theoretical predictions including the

  11. 2D profile of poloidal magnetic field diagnosed by a laser-driven ion-beam trace probe (LITP)

    SciTech Connect

    Yang, Xiaoyi; Xiao, Chijie Chen, Yihang; Xu, Tianchao; Lin, Chen; Wang, Long; Xu, Min; Yu, Yi

    2016-11-15

    Based on large energy spread of laser-driven ion beam (LIB), a new method, the Laser-driven Ion-beam Trace Probe (LITP), was suggested recently to diagnose the poloidal magnetic field (B{sub p}) and radial electric field (E{sub r}) in toroidal devices. Based on another property of LIB, a wide angular distribution, here we suggested that LITP could be extended to get 2D B{sub p} profile or 1D profile of both poloidal and radial magnetic fields at the same time. In this paper, we show the basic principle, some preliminary simulation results, and experimental preparation to test the basic principle of LITP.

  12. Electric tuning of magnetization dynamics and electric field-induced negative magnetic permeability in nanoscale composite multiferroics

    PubMed Central

    Jia, Chenglong; Wang, Fenglong; Jiang, Changjun; Berakdar, Jamal; Xue, Desheng

    2015-01-01

    Steering magnetism by electric fields upon interfacing ferromagnetic (FM) and ferroelectric (FE) materials to achieve an emergent multiferroic response bears a great potential for nano-scale devices with novel functionalities. FM/FE heterostructures allow, for instance, the electrical manipulation of magnetic anisotropy via interfacial magnetoelectric (ME) couplings. A charge-mediated ME effect is believed to be generally weak and active in only a few angstroms. Here we present an experimental evidence uncovering a new magnon-driven, strong ME effect acting on the nanometer range. For Co92Zr8 (20 nm) film deposited on ferroelectric PMN-PT we show via ferromagnetic resonance (FMR) that this type of linear ME allows for electrical control of simultaneously the magnetization precession and its damping, both of which are key elements for magnetic switching and spintronics. The experiments unravel further an electric-field-induced negative magnetic permeability effect. PMID:26058060

  13. Electric tuning of magnetization dynamics and electric field-induced negative magnetic permeability in nanoscale composite multiferroics

    NASA Astrophysics Data System (ADS)

    Jia, Chenglong; Wang, Fenglong; Jiang, Changjun; Berakdar, Jamal; Xue, Desheng

    2015-06-01

    Steering magnetism by electric fields upon interfacing ferromagnetic (FM) and ferroelectric (FE) materials to achieve an emergent multiferroic response bears a great potential for nano-scale devices with novel functionalities. FM/FE heterostructures allow, for instance, the electrical manipulation of magnetic anisotropy via interfacial magnetoelectric (ME) couplings. A charge-mediated ME effect is believed to be generally weak and active in only a few angstroms. Here we present an experimental evidence uncovering a new magnon-driven, strong ME effect acting on the nanometer range. For Co92Zr8 (20 nm) film deposited on ferroelectric PMN-PT we show via ferromagnetic resonance (FMR) that this type of linear ME allows for electrical control of simultaneously the magnetization precession and its damping, both of which are key elements for magnetic switching and spintronics. The experiments unravel further an electric-field-induced negative magnetic permeability effect.

  14. Electric tuning of magnetization dynamics and electric field-induced negative magnetic permeability in nanoscale composite multiferroics.

    PubMed

    Jia, Chenglong; Wang, Fenglong; Jiang, Changjun; Berakdar, Jamal; Xue, Desheng

    2015-06-09

    Steering magnetism by electric fields upon interfacing ferromagnetic (FM) and ferroelectric (FE) materials to achieve an emergent multiferroic response bears a great potential for nano-scale devices with novel functionalities. FM/FE heterostructures allow, for instance, the electrical manipulation of magnetic anisotropy via interfacial magnetoelectric (ME) couplings. A charge-mediated ME effect is believed to be generally weak and active in only a few angstroms. Here we present an experimental evidence uncovering a new magnon-driven, strong ME effect acting on the nanometer range. For Co92Zr8 (20 nm) film deposited on ferroelectric PMN-PT we show via ferromagnetic resonance (FMR) that this type of linear ME allows for electrical control of simultaneously the magnetization precession and its damping, both of which are key elements for magnetic switching and spintronics. The experiments unravel further an electric-field-induced negative magnetic permeability effect.

  15. Motional sideband excitation using rotating electric fields

    NASA Astrophysics Data System (ADS)

    Isaac, C. A.

    2013-04-01

    A form of motional sideband excitation is described in which a rotating dipole electric field is applied asymmetrically onto a Penning-type trap in the presence of a mechanism for cooling the axial motion of the trapped particles. In contrast to the traditional motional sideband excitation, which uses an oscillating electric field, the rotating field results in only one active sideband in each sense of rotation and so avoids accidental excitation of the other sideband making it applicable to Penning-type traps with a large degree of anharmonicity. Expressions are derived for the magnetron radius expansion and compression rates attainable, and approximations are made for the case of strong and weak drives. A comparison is made with data, taken using a two-stage positron accumulator presented by Isaac [C. A. Isaac, C. J. Baker, T. Mortensen, D. P. van der Werf, and M. Charlton, Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.107.033201 107, 033201 (2011)], showing good agreement between the model and experiment.

  16. Extracting Nucleon Magnetic Moments and Electric Polarizabilities from Lattice QCD in Background Electric Fields

    SciTech Connect

    William Detmold; Tiburzi, Brian C.; Walker-Loud, Andre

    2010-03-01

    Nucleon properties are investigated in background electric fields. As the magnetic moments of baryons affect their relativistic propagation in constant electric fields, electric polarizabilities cannot be determined without knowledge of magnetic moments. We devise combinations of baryon two-point functions in external electric fields to isolate both observables. Using an ensemble of anisotropic gauge configurations with dynamical clover fermions, we demonstrate how magnetic moments and electric polarizabilities can be determined from lattice QCD simulations in background electric fields. We obtain results for both the neutron and proton. Our study is currently limited to electrically neutral sea quarks.

  17. Radial-Electric-Field Piezoelectric Diaphragm Pumps

    NASA Technical Reports Server (NTRS)

    Bryant, Robert G.; Working, Dennis C.; Mossi, Karla; Castro, Nicholas D.; Mane, Pooma

    2009-01-01

    In a recently invented class of piezoelectric diaphragm pumps, the electrode patterns on the piezoelectric diaphragms are configured so that the electric fields in the diaphragms have symmetrical radial (along-the-surface) components in addition to through-the-thickness components. Previously, it was accepted in the piezoelectric-transducer art that in order to produce the out-of-plane bending displacement of a diaphragm needed for pumping, one must make the electric field asymmetrical through the thickness, typically by means of electrodes placed on only one side of the piezoelectric material. In the present invention, electrodes are placed on both sides and patterned so as to produce substantial radial as well as through-the-thickness components. Moreover, unlike in the prior art, the electric field can be symmetrical through the thickness. Tests have shown in a given diaphragm that an electrode configuration according to this invention produces more displacement than does a conventional one-sided electrode pattern. The invention admits of numerous variations characterized by various degrees of complexity. Figure 1 is a simplified depiction of a basic version. As in other piezoelectric diaphragm pumps of similar basic design, the prime mover is a piezoelectric diaphragm. Application of a suitable voltage to the electrodes on the diaphragm causes it to undergo out-of-plane bending. The bending displacement pushes a fluid out of, or pulls the fluid into, a chamber bounded partly by the diaphragm. Also as in other diaphragm pumps in general, check valves ensure that the fluid flows only in through one port and only out through another port.

  18. Importance of electric fields from ionized nanoparticles for radiation therapy

    NASA Astrophysics Data System (ADS)

    Shmatov, M. L.

    2017-05-01

    A model is presented in which electric fields from ionized particles in a biological tissue enhance the biological effect of ionizing radiation. The model is based on the data on enhancing the gamma radiation effect on biological cells by static electric fields and on estimates of the typical intensities of electric fields from ionized nanoparticles in a biological tissue.

  19. Ultrafast electrical control of a resonantly driven single photon source

    SciTech Connect

    Cao, Y.; Bennett, A. J. Ellis, D. J. P.; Shields, A. J.; Farrer, I.; Ritchie, D. A.

    2014-08-04

    We demonstrate generation of a pulsed stream of electrically triggered single photons in resonance fluorescence, by applying high frequency electrical pulses to a single quantum dot in a p-i-n diode under resonant laser excitation. Single photon emission was verified, with the probability of multiple photon emission reduced to 2.8%. We show that despite the presence of charge noise in the emission spectrum of the dot, resonant excitation acts as a “filter” to generate narrow bandwidth photons.

  20. Electric Field Dependence of Photo-Induced Field Emission Current.

    NASA Astrophysics Data System (ADS)

    Egert, Charles Michael

    We have measured the photo-induced field emission current from a tungsten field emitter as a function of electric field. These experiments were performed with a retardation energy analyzer to measure total current and a 127(DEGREES) cylindrical differential energy analyzer to measure the energy resolved PFE current. The results of these experiments are compared with a simple theory of PFE, developed by Schwartz and Schaich, which is an extension of field emission theory including the surface photoeffect, but assuming constant photoexcitation matrix elements. Our experimental results disagree with this theory in two ways: First, for high fields and photon energy (electrons emitted above the field emission barrier maximum) theory predicts a larger increase in PFE current than is observed experimentally. Second, we have also confirmed the existence of a field dependent oscillatory component of the PFE current emitted from the W(110) surface with photon energies of 2.7 eV and 3.5 eV. The simple theory described here, as well as more sophisticated calculations, have been unable to explain this oscillatory feature. We have also reported, for the first time, the field dependence of the energy resolved PFE current measured with a 127(DEGREES) cylindrical energy analyzer. These preliminary results show evidence of the oscillatory component previously only observed in the total PFE current.

  1. Electrostatic air filters generated by electric fields

    SciTech Connect

    Bergman, W.; Biermann, A.H.; Hebard, H.D.; Lum, B.Y.; Kuhl, W.D.

    1981-01-27

    This paper presents theoretical and experimental findings on fibrous filters converted to electrostatic operation by a nonionizing electric field. Compared to a conventional fibrous filter, the electrostatic filter has a higher efficiency and a longer, useful life. The increased efficiency is attributed to a time independent attraction between polarized fibers and charged, polarized particles and a time dependent attraction between charged fibers and charged, polarized particles. The charge on the fibers results from a dynamic process of charge accumulation due to the particle deposits and a charge dissipation due to the fiber conductivity.

  2. Perturbative renormalization of the electric field correlator

    NASA Astrophysics Data System (ADS)

    Christensen, C.; Laine, M.

    2016-04-01

    The momentum diffusion coefficient of a heavy quark in a hot QCD plasma can be extracted as a transport coefficient related to the correlator of two colour-electric fields dressing a Polyakov loop. We determine the perturbative renormalization factor for a particular lattice discretization of this correlator within Wilson's SU(3) gauge theory, finding a ∼ 12% NLO correction for values of the bare coupling used in the current generation of simulations. The impact of this result on existing lattice determinations is commented upon, and a possibility for non-perturbative renormalization through the gradient flow is pointed out.

  3. Magnetic resonance electrical impedance tomography for determining electric field distribution during electroporation

    NASA Astrophysics Data System (ADS)

    Kranjc, Matej; Bajd, Franci; Serša, Igor; Miklavčič, Damijan

    2013-04-01

    Electroporation is a phenomenon caused by externally applied electric field to cells that results in an increase of cell membrane permeability to various molecules. Accurate coverage of the tissue with a sufficiently large electric field presents one of the most important conditions for successful membrane permeabilization. Applications based on electroporation would greatly benefit with a method for monitoring the electric field, especially if it could be done in situ. As the membrane electroporation is a consequence of an induced transmembrane potential, which is directly proportional to the local electric field, we have been investigating current density imaging and magnetic resonance electrical impedance tomography techniques to determine the electric field distribution during electroporation. In this paper, we present comparison of current density and electric field distribution in an agar phantom and in a liver tissue exposed to electroporation pulses. As expected, a region of increased electrical conductivity was observed in the liver tissue exposed to sufficiently high electric field but not in agar phantom.

  4. Impact of electric fields on honey bees

    SciTech Connect

    Bindokas, V.P.

    1985-01-01

    Biological effects in honey bee colonies under a 765-kV, 60-Hz transmission line (electric (E) field = 7 kV/m) were confirmed using controlled dosimetry and treatment reversal to replicate findings within the same season. Hives in the same environment but shielded from E field are normal, suggesting effects are caused by interaction of E field with the hive. Bees flying through the ambient E field are not demonstrably affected. Different thresholds and severity of effects were found in colonies exposed to 7, 5.5, 4.1, 1.8, and 0.65 to 0.85 kV/m at incremental distances from the line. Most colonies exposed at 7 kV/m failed in 8 weeks and failed to overwinter at greater than or equal to4.1 kV/m. Data suggest the limit of a biological effects corridor lies between 15 and 27 m (4.1 and 1.8 kV/m) beyond the outer phase of the transmission line. Mechanisms to explain colony disturbance fall into two categories, direct perception of enhanced in-hive E fields, and perception of shock from induced currents. The same effects induced in colonies with total-hive E-field exposure can be reproduced with shock or E-field exposure of worker bees in extended hive entranceways (= porches). Full-scale experiments demonstrate bee exposure to E fields including 100 kV/m under moisture-free conditions within a non-conductive porch causes no detectable effect on colony behavior. Exposure of bees on a conductive (e.g. wet) substrate produces been disturbance, increased mortality, abnormal propolization, and possible impairment of colony growth. Thresholds for effects caused by step-potential-induced currents are: 275-350 nA - disturbance of single bees; 600 nA - onset of abnormal propolization; and 900 nA - sting.

  5. Soil Identification using Field Electrical Resistivity Method

    NASA Astrophysics Data System (ADS)

    Hazreek, Z. A. M.; Rosli, S.; Chitral, W. D.; Fauziah, A.; Azhar, A. T. S.; Aziman, M.; Ismail, B.

    2015-06-01

    Geotechnical site investigation with particular reference to soil identification was important in civil engineering works since it reports the soil condition in order to relate the design and construction of the proposed works. In the past, electrical resistivity method (ERM) has widely being used in soil characterization but experienced several black boxes which related to its results and interpretations. Hence, this study performed a field electrical resistivity method (ERM) using ABEM SAS (4000) at two different types of soils (Gravelly SAND and Silty SAND) in order to discover the behavior of electrical resistivity values (ERV) with type of soils studied. Soil basic physical properties was determine thru density (p), moisture content (w) and particle size distribution (d) in order to verify the ERV obtained from each type of soil investigated. It was found that the ERV of Gravelly SAND (278 Ωm & 285 Ωm) was slightly higher than SiltySAND (223 Ωm & 199 Ωm) due to the uncertainties nature of soils. This finding has showed that the results obtained from ERM need to be interpreted based on strong supported findings such as using direct test from soil laboratory data. Furthermore, this study was able to prove that the ERM can be established as an alternative tool in soil identification provided it was being verified thru other relevance information such as using geotechnical properties.

  6. Instability-driven electromagnetic fields in coronal plasmas

    SciTech Connect

    Manuel, M. J.-E.; Li, C. K.; Seguin, F. H.; Sinenian, N.; Frenje, J. A.; Casey, D. T.; Petrasso, R. D.; Hager, J. D.; Betti, R.; Hu, S. X.; Delettrez, J.; Meyerhofer, D. D.

    2013-04-15

    Filamentary electromagnetic fields previously observed in the coronae of laser-driven spherical targets [F. H. S eguin et al., Phys. Plasma. 19, 012701 (2012)] have been further investigated in laser irradiated plastic foils. Face-on proton-radiography provides an axial view of these filaments and shows coherent cellular structure regardless of initial foil-surface conditions. The observed cellular fields are shown to have an approximately constant scale size of 210 lm throughout the plasma evolution. A discussion of possible field-generation mechanisms is provided and it is demonstrated that the likely source of the cellular field structure is the magnetothermal instability. Using predicted temperature and density profiles, the fastest growing modes of this instability were found to be slowly varying in time and consistent with the observed cellular size.

  7. Instability-driven electromagnetic fields in coronal plasmas

    DOE PAGES

    Manuel, M. J.-E.; Li, C. K.; Seguin, F. H.; ...

    2013-04-15

    Filamentary electromagnetic fields previously observed in the coronae of laser-driven spherical targets [F. H. S eguin et al., Phys. Plasma. 19, 012701 (2012)] have been further investigated in laser irradiated plastic foils. Face-on proton-radiography provides an axial view of these filaments and shows coherent cellular structure regardless of initial foil-surface conditions. The observed cellular fields are shown to have an approximately constant scale size of 210 lm throughout the plasma evolution. A discussion of possible field-generation mechanisms is provided and it is demonstrated that the likely source of the cellular field structure is the magnetothermal instability. Using predicted temperature andmore » density profiles, the fastest growing modes of this instability were found to be slowly varying in time and consistent with the observed cellular size.« less

  8. Electric and magnetic field exposure, chemical exposure, and leukemia risk in electrical'' occupations

    SciTech Connect

    Bowman, J.D.; Sobel, E.; London, S.J.; Thomas, D.C.; Garabrant, D.H.; Pearce, N.; Peters, J.M. . Dept. of Preventive Medicine)

    1992-12-01

    This project was conducted to address what are the extremely low frequency (ELF) magnetic and electric field exposures of workers in electrical'' occupations and do they exceed exposures encountered in non-electrical'' occupations and what are the chemical and physical exposures in the electrical'' occupations and do they exceed exposures encountered in non-electrical'' occupations Two subsidiary issues were does characterization and quantification of ELF magnetic field exposure in the electrical'' occupations provide data to support a dose response relationship between leukemia risk and electric or magnetic field exposure and do dffferences in chemical exposure between the occupations help explain the previously observed leukemia risk associated with these electrical'' occupations Data were collected in 3 regions in which electrical workers had been reported to have an excess of leukemia - New Zealand, Los Angeles and Seattle Measurements of magnetic fields were made on 493 electrical workers and 163 non-electrical workers.

  9. Electric and magnetic field exposure, chemical exposure, and leukemia risk in ``electrical`` occupations. Final report

    SciTech Connect

    Bowman, J.D.; Sobel, E.; London, S.J.; Thomas, D.C.; Garabrant, D.H.; Pearce, N.; Peters, J.M.

    1992-12-01

    This project was conducted to address what are the extremely low frequency (ELF) magnetic and electric field exposures of workers in ``electrical`` occupations and do they exceed exposures encountered in ``non-electrical`` occupations? and what are the chemical and physical exposures in the ``electrical`` occupations and do they exceed exposures encountered in ``non-electrical`` occupations? Two subsidiary issues were does characterization and quantification of ELF magnetic field exposure in the ``electrical`` occupations provide data to support a dose response relationship between leukemia risk and electric or magnetic field exposure? and do dffferences in chemical exposure between the occupations help explain the previously observed leukemia risk associated with these ``electrical`` occupations? Data were collected in 3 regions in which electrical workers had been reported to have an excess of leukemia - New Zealand, Los Angeles and Seattle Measurements of magnetic fields were made on 493 electrical workers and 163 non-electrical workers.

  10. Assembly of LIGA using Electric Fields

    SciTech Connect

    FEDDEMA, JOHN T.; WARNE, LARRY K.; JOHNSON, WILLIAM A.; OGDEN, ALLISON J.; ARMOUR, DAVID L.

    2002-04-01

    The goal of this project was to develop a device that uses electric fields to grasp and possibly levitate LIGA parts. This non-contact form of grasping would solve many of the problems associated with grasping parts that are only a few microns in dimensions. Scaling laws show that for parts this size, electrostatic and electromagnetic forces are dominant over gravitational forces. This is why micro-parts often stick to mechanical tweezers. If these forces can be controlled under feedback control, the parts could be levitated, possibly even rotated in air. In this project, we designed, fabricated, and tested several grippers that use electrostatic and electromagnetic fields to grasp and release metal LIGA parts. The eventual use of this tool will be to assemble metal and non-metal LIGA parts into small electromechanical systems.

  11. Random electric field instabilities of relaxor ferroelectrics

    DOE PAGES

    Arce-Gamboa, Jose R.; Guzman-Verri, Gian G.

    2017-06-13

    Relaxor ferroelectrics are complex oxide materials which are rather unique to study the effects of compositional disorder on phase transitions. Here, we study the effects of quenched cubic random electric fields on the lattice instabilities that lead to a ferroelectric transition and show that, within a microscopic model and a statistical mechanical solution, even weak compositional disorder can prohibit the development of long-range order and that a random field state with anisotropic and power-law correlations of polarization emerges from the combined effect of their characteristic dipole forces and their inherent charge disorder. As a result, we compare and reproduce severalmore » key experimental observations in the well-studied relaxor PbMg1/3Nb2/3O3–PbTiO3.« less

  12. Assembly of LIGA Using Electric Fields

    NASA Astrophysics Data System (ADS)

    Feddema, J. T.; Warne, L. K.; Johnson, W. A.; Ogden, A. J.; Armour, D. L.

    2002-04-01

    The goal of this project was to develop a device that uses electric fields to grasp and possibly levitate LlGA parts. This non-contact form of grasping would solve many of the problems associated with grasping parts that are only a few microns in dimensions. Scaling laws show that for parts this size, electrostatic and electromagnetic forces are dominant over gravitational forces. This is why micro-parts often stick to mechanical tweezers. If these forces can be controlled under feedback control, the parts could be levitated, possibly even rotated in air. In this project, we designed, fabricated, and tested several grippers that use electrostatic and electromagnetic fields to grasp and release metal LlGA parts. The eventual use of this tool will be to assemble metal and non-metal LlGA parts into small electromechanical systems.

  13. Electric fields and double layers in plasmas

    NASA Astrophysics Data System (ADS)

    Singh, Nagendra; Thiemann, H.; Schunk, R. W.

    1987-05-01

    Various mechanisms for driving double layers (DLs) in plasmas are described, including applied potential drops, currents, contact potentials, and plasma expansions. Somne dynamic features of the DLs are discussed; and it is demonstrated that DLs and the currents through them undergo slow oscillations, determined by the ion transit time across an effective length of the system in which the DLs form. It is shown that a localized potential dip forms at the low potential end of a DL, which interrupts the electron current through it according to the Langmuir criterion whenever the ion flux into the DL is disrupted. Also considered is the generation of electric fields perpendicular to the ambient magnetic field by contact potentials.

  14. A Gravitational Experiment Involving Inhomogeneous Electric Fields

    NASA Astrophysics Data System (ADS)

    Datta, T.; Yin, Ming; Vargas, Jose

    2004-02-01

    Unification of gravitation with other forms of interactions, particularly with electromagnetism, will have tremendous impacts on technology and our understanding of nature. The economic impact of such an achievement will also be unprecedented and far more extensive than the impact experienced in the past century due to the unification of electricity with magnetism and optics. Theoretical unification of gravitation with electromagnetism using classical differential geometry has been pursued since the late nineteen twenties, when Einstein and Cartan used teleparallelism for the task. Recently, Vargas and Torr have followed the same line of research with more powerful mathematics in a more general geometric framework, which allows for the presence of other interactions. Their approach also uses Kähler generalization of Cartan's exterior calculus, which constitutes a language appropriate for both classical and quantum physics. Given the compelling nature of teleparallelism (path-independent equality of vectors at a distance) and the problems still existing with energy-momentum in general relativity, it is important to seek experimental evidence for such expectations. Such experimental programs are likely to provide quantitative guidance to the further development of current and future theories. We too, have undertaken an experimental search for potential electrically induced gravitational (EIG) effects. This presentation describes some of the practical concerns that relates to our investigation of electrical influences on laboratory size test masses. Preliminary results, appear to indicate a correlation between the application of a spatially inhomogeneous electric field and the appearance of an additional force on the test mass. If confirmed, the presence of such a force will be consistent with the predictions of Vargas-Torr. More importantly, proven results will shed new light and clearer understanding of the interactions between gravitational and electromagnetic

  15. Finite-size effects on the magnetoelectric response of field-driven ferroelectric/ferromagnetic chains

    NASA Astrophysics Data System (ADS)

    Jia, Chenglong; Sukhov, Alexander; Horley, Paul P.; Berakdar, Jamal

    2011-07-01

    We study theoretically the coupled multiferroic dynamics of a finite one-dimensional ferroelectric/ferromagnet chain driven by harmonic magnetic and electric fields as a function of the chain length. We consider the case of a linear magnetoelectric coupling that results from the spin-polarized screening charge at the interface. We performed Monte-Carlo simulations and calculations based on the coupled Landau-Lifshitz-Gilbert and Landau-Khalatnikov equations showing that the net magnetization and the total polarization of thin heterostructures, i.e. with up to ten ferroelectric and ferromagnetic sites counted from the interface, can be completely reversed by external electric and magnetic fields, respectively. However, for larger systems merely a limited magnetoelectrical control is achievable.

  16. Influence of relative humidity on analyzing electric field exposure using ELF electric field measurements.

    PubMed

    Korpinen, Leena H; Kuisti, Harri A; Tarao, Hiroo; Elovaara, Jarmo A

    2013-07-01

    The objective of the study was to investigate the influence of humidity on analyzing electric field exposure using extremely low frequency (ELF) electric field measurements. The study included 322 measurements in a climate room. We used two commercial three-axis meters, EFA-3 and EFA-300, and employed two measurement techniques in the climate room where we varied the temperature from 15 to 25 °C, the relative humidity from 55% to 95%, and the electric field from 1 to 25 kV/m. We calculated Pearson correlations between humidity and percentage errors for all data and for data at different levels of humidity. When the relative humidity was below 70%, the results obtained by the different measurement methods in terms of percentage errors were of the same order of magnitude for the considered temperatures and field strength, but the results were less reliable when the relative humidity was higher than 80%. In the future, it is important to take humidity into account when electric field measurement results will be compared to the values given in different exposure guidelines. Copyright © 2013 Wiley Periodicals, Inc.

  17. Planned waveguide electric field breakdown studies

    SciTech Connect

    Wang Faya; Li Zenghai

    2012-12-21

    This paper presents an experimental setup for X-band rf breakdown studies. The setup is composed of a section of WR90 waveguide with a tapered pin located at the middle of the waveguide E-plane. Another pin is used to rf match the waveguide so it operates in a travelling wave mode. By adjusting the penetration depth of the tapered pin, different surface electric field enhancements can be obtained. The setup will be used to study the rf breakdown rate dependence on power flow in the waveguide for a constant maximum surface electric field on the pin. Two groups of pins have been designed. The Q of one group is different and very low. The other has a similar Q. With the test of the two groups of pins, we should be able to discern how the net power flow and Q affect the breakdown. Furthermore, we will apply an electron beam treatment to the pins to study its effect on breakdown. Overall, these experiments should be very helpful in understanding rf breakdown phenomena and could significantly benefit the design of high gradient accelerator structures.

  18. Inhibition of brain tumor cell proliferation by alternating electric fields

    SciTech Connect

    Jeong, Hyesun; Oh, Seung-ick; Hong, Sunghoi E-mail: radioyoon@korea.ac.kr; Sung, Jiwon; Jeong, Seonghoon; Yoon, Myonggeun E-mail: radioyoon@korea.ac.kr; Koh, Eui Kwan

    2014-11-17

    This study was designed to investigate the mechanism by which electric fields affect cell function, and to determine the optimal conditions for electric field inhibition of cancer cell proliferation. Low-intensity (<2 V/cm) and intermediate-frequency (100–300 kHz) alternating electric fields were applied to glioblastoma cell lines. These electric fields inhibited cell proliferation by inducing cell cycle arrest and abnormal mitosis due to the malformation of microtubules. These effects were significantly dependent on the intensity and frequency of applied electric fields.

  19. Transport in organic semiconductors in large electric fields: From thermal activation to field emission

    NASA Astrophysics Data System (ADS)

    Worne, J. H.; Anthony, J. E.; Natelson, D.

    2010-02-01

    Understanding charge transport in organic semiconductors in large electric fields is relevant to many applications. We present transport measurements in organic field-effect transistors based on poly(3-hexylthiophene) and 6,13-bis(triisopropyl-silylethynyl) (TIPS) pentacene with short channels, from room temperature down to 4.2 K. Near 300 K transport in both systems is well described by thermally assisted hopping with Poole-Frenkel-type enhancement of the mobility. At low temperatures and large gate voltages, transport in both materials becomes nearly temperature independent, crossing over into field-driven tunneling. These data, particularly in TIPS-pentacene, show that great caution must be exercised when considering more exotic (e.g., Tomonaga-Luttinger liquid) interpretations of transport.

  20. Saturation of the Electric Field Transmitted to the Magnetosphere

    NASA Technical Reports Server (NTRS)

    Lyatsky, Wladislaw; Khazanov, George V.; Slavin, James A.

    2010-01-01

    We reexamined the processes leading to saturation of the electric field, transmitted into the Earth's ionosphere from the solar wind, incorporating features of the coupled system previously ignored. We took into account that the electric field is transmitted into the ionosphere through a region of open field lines, and that the ionospheric conductivity in the polar cap and auroral zone may be different. Penetration of the electric field into the magnetosphere is linked with the generation of the Alfven wave, going out from the ionosphere into the solar wind and being coupled with the field-aligned currents at the boundary of the open field limes. The electric field of the outgoing Alfven wave reduces the original electric field and provides the saturation effect in the electric field and currents during strong geomagnetic disturbances, associated with increasing ionospheric conductivity. The electric field and field-aligned currents of this Alfven wave are dependent on the ionospheric and solar wind parameters and may significantly affect the electric field and field-aligned currents, generated in the polar ionosphere. Estimating the magnitude of the saturation effect in the electric field and field-aligned currents allows us to improve the correlation between solar wind parameters and resulting disturbances in the Earth's magnetosphere.

  1. Saturation of the Electric Field Transmitted to the Magnetosphere

    NASA Technical Reports Server (NTRS)

    Lyatsky, Wladislaw; Khazanov, George V.; Slavin, James A.

    2010-01-01

    We reexamined the processes leading to saturation of the electric field, transmitted into the Earth's ionosphere from the solar wind, incorporating features of the coupled system previously ignored. We took into account that the electric field is transmitted into the ionosphere through a region of open field lines, and that the ionospheric conductivity in the polar cap and auroral zone may be different. Penetration of the electric field into the magnetosphere is linked with the generation of the Alfven wave, going out from the ionosphere into the solar wind and being coupled with the field-aligned currents at the boundary of the open field limes. The electric field of the outgoing Alfven wave reduces the original electric field and provides the saturation effect in the electric field and currents during strong geomagnetic disturbances, associated with increasing ionospheric conductivity. The electric field and field-aligned currents of this Alfven wave are dependent on the ionospheric and solar wind parameters and may significantly affect the electric field and field-aligned currents, generated in the polar ionosphere. Estimating the magnitude of the saturation effect in the electric field and field-aligned currents allows us to improve the correlation between solar wind parameters and resulting disturbances in the Earth's magnetosphere.

  2. Nonlinear response of electric fields at a neutral point

    NASA Astrophysics Data System (ADS)

    Berkovsky, Mikhail; Dufty, James W.; Calisti, Annette; Stamm, Roland; Talin, Bernard

    1995-05-01

    The complex dynamics of electric fields at a neutral point in a plasma is studied via a model of noninteracting ``quasiparticles.'' The simplicity of the model allows the reduction of the many-body problem to an effective single-particle analysis-all properties of interest can be reduced to quadratures. Still, the final calculations to extract a quantitative or even qualitative understanding of the field dynamics can be difficult. Attention here is focused on the dynamics of the conditional electric field: the field value at time t for a given initial value of the field. In addition to the relevant linear response function (electric field time correlation function), this property provides the complete nonlinear response of the electric field to arbitrary initial field perturbations. The static properties (distribution of electric fields and field time derivatives) and the electric field time correlation function have been known for some time for this model. We compare these results and the present result for the conditional electric field with molecular dynamics simulations including interactions. The comparisons suggest that the model provides a quantitative representation of electric field dynamics in real plasmas, except at strong coupling. The exact theoretical results are compared also with those obtained by modeling the electric field as a stochastic variable obeying a kangaroo process. The latter can be constructed to yield both the exact stationary distribution and the exact electric field time correlation function. However, we find that the conditional field is never well approximated by this process. An alternative representation of the joint distribution for electric fields, consistent with the exact stationary distribution, field correlation function, and conditional electric field, is suggested.

  3. Introduction to power-frequency electric and magnetic fields.

    PubMed Central

    Kaune, W T

    1993-01-01

    This paper introduces the reader to electric and magnetic fields, particularly those fields produced by electric power systems and other sources using frequencies in the power-frequency range. Electric fields are produced by electric charges; a magnetic field also is produced if these charges are in motion. Electric fields exert forces on other charges; if in motion, these charges will experience magnetic forces. Power-frequency electric and magnetic fields induce electric currents in conducting bodies such as living organisms. The current density vector is used to describe the distribution of current within a body. The surface of the human body is an excellent shield for power-frequency electric fields, but power-frequency magnetic fields penetrate without significant attenuation; the electric fields induced inside the body by either exposure are comparable in magnitude. Electric fields induced inside a human by most environmental electric and magnetic fields appear to be small in magnitude compared to levels naturally occurring in living tissues. Detection of such fields thus would seem to require the existence of unknown biological mechanisms. Complete characterization of a power-frequency field requires measurement of the magnitudes and electrical phases of the fundamental and harmonic amplitudes of its three vector components. Most available instrumentation measures only a small subset, or some weighted average, of these quantities. Hand-held survey meters have been used widely to measure power-frequency electric and magnetic fields. Automated data-acquisition systems have come into use more recently to make electric- and magnetic-field recordings, covering periods of hours to days, in residences and other environments.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8206045

  4. Dynamics of an electric dipole moment in a stochastic electric field.

    PubMed

    Band, Y B

    2013-08-01

    The mean-field dynamics of an electric dipole moment in a deterministic and a fluctuating electric field is solved to obtain the average over fluctuations of the dipole moment and the angular momentum as a function of time for a Gaussian white-noise stochastic electric field. The components of the average electric dipole moment and the average angular momentum along the deterministic electric-field direction do not decay to zero, despite fluctuations in all three components of the electric field. This is in contrast to the decay of the average over fluctuations of a magnetic moment in a stochastic magnetic field with Gaussian white noise in all three components. The components of the average electric dipole moment and the average angular momentum perpendicular to the deterministic electric-field direction oscillate with time but decay to zero, and their variance grows with time.

  5. Manipulating colloids with charges and electric fields

    NASA Astrophysics Data System (ADS)

    Leunissen, M. E.

    2007-02-01

    This thesis presents the results of experimental investigations on a variety of colloidal suspensions. Colloidal particles are at least a hundred times larger than atoms or molecules, but suspended in a liquid they display the same phase behavior, including fluid and crystalline phases. Due to their relatively large size, colloids are much easier to investigate and manipulate, though. This makes them excellent condensed matter model systems. With this in mind, we studied micrometer-sized perspex (‘PMMA’) spheres, labeled with a fluorescent dye for high-resolution confocal microscopy imaging, and suspended in a low-polar mixture of the organic solvents cyclohexyl bromide and cis-decalin. This system offered us the flexibility to change the interactions between the particles from ‘hard-sphere-like’ to long-ranged repulsive (between like-charged particles), long-ranged attractive (between oppositely charged particles) and dipolar (in an electric field). We investigated the phase behavior of our suspensions as a function of the particle concentration, the ionic strength of the solvent and the particles’ charges. In this way, we obtained new insight in the freezing and melting behavior of like-charged and oppositely charged colloids. Interestingly, we found that the latter can readily form large crystals, thus defying the common belief that plus-minus interactions inevitably lead to aggregation. Moreover, we demonstrated that these systems can serve as a reliable model system for classical ionic matter (‘salts’), and that opposite-charge interactions can greatly facilitate the self-assembly of new structures with special properties for applications. On a slightly different note, we also studied electrostatic effects in mixtures of the cyclohexyl bromide solvent and water, both with and without colloidal particles present. This provided new insight in the stabilization mechanisms of oil-water emulsions and gave us control over the self-assembly of various

  6. Aircraft measurement of electric field - Self-calibration

    NASA Technical Reports Server (NTRS)

    Winn, W. P.

    1993-01-01

    Aircraft measurement of electric fields is difficult as the electrically conducting surface of the aircraft distorts the electric field. Calibration requires determining the relations between the undistorted electric field in the absence of the vehicle and the signals from electric field meters that sense the local distorted fields in their immediate vicinity. This paper describes a generalization of a calibration method which uses pitch and roll maneuvers. The technique determines both the calibration coefficients and the direction of the electric vector. The calibration of individual electric field meters and the elimination of the aircraft's self-charge are described. Linear combinations of field mill signals are examined and absolute calibration and error analysis are discussed. The calibration method was applied to data obtained during a flight near thunderstorms.

  7. Manipulation of nano-entities in suspension by electric fields

    NASA Astrophysics Data System (ADS)

    Fan, Donglei

    Nanoscale entities, including nanospheres, nanodisks, nanorings, nanowires and nanotubes are potential building blocks for nanoscale devices. Among them, nanowires is an important type of nanoparticles, due to the potential application in microelectronics and bio-diagnosis. Manipulation of nanowires in suspension has been a formidable problem. As described in this thesis, using AC electric fields applied to strategically designed microelectrodes, nanowires in suspension can be driven to align, to chain, to accelerate in directions parallel and perpendicular to its orientation, to concentrate onto designated places, and to disperse in a controlled manner with high efficiency despite an extremely low Reynolds number at the level of 10-5. Randomly oriented nanowires in suspension can be rapidly assembled into extended nonlinear structures within seconds. We show that both the electric field and its gradient play the essential roles of aligning and transporting the nanowires into scaffolds according to the electric field distributions inherent to the geometry of the microelectrodes. The assembling efficiency depends strongly on the frequency of the applied AC voltages and varies as square of the voltage. Furthermore, nanowires have been rotated by AC electric fields applied to strategically designed electrodes. The rotation of the nanowires can be instantly switched on or off with precisely controlled rotation speed (to at least 25000 rpm), definite chirality, and total angle of rotation. This new method has been used to controllably rotate magnetic and non-magnetic nanowires as well as multi-wall carbon nanotubes. We have also produced a micromotor using a rotating nanowire that can drive particles into circular motion. This has application to microfluidic devices, micro-stirrers, and micro electromechanical systems (MEMS). To move and place nanowires onto designated locations with high precision, electrophoretic force has been combined with dielectrophoretic force to

  8. Electric-field-induced response of a droplet embedded in a polyelectrolyte gel

    NASA Astrophysics Data System (ADS)

    Mohammadi, Aliasghar

    2013-08-01

    The electric-field induced response of a droplet embedded in a quenched polyelectrolyte gel is calculated theoretically. The response comprises the droplet translation and the electric-field induced flow fields within the droplet. The gel is modeled as a soft, and electrically charged porous solid saturated with a salted Newtonian fluid. The droplet is considered an incompressible Newtonian fluid with no free charge. An analytical solution, using the perturbation methodology and linear superposition, is obtained for the leading-order steady response to a DC electric-field. The fluid within the droplet is driven due to hydrodynamic coupling with the electroosmotic flow. The fluid velocity within the droplet is linearly proportional to the electroosmotic flow. Moreover, the microrheological response function of a droplet within a polyelectrolyte gel is also provided, highlighting the importance of boundary conditions at the droplet-gel interface on microrheological measurements.

  9. Electrical integrity of oxides in a radiation field

    SciTech Connect

    Zinkle, S.J.; Kinoshita, C.

    1996-04-01

    In the absence of an applied electric field, irradiation generally produces a decrease in the permanent (beam-off) electrical conductivity of ceramic insulators. However, in the past 6 years several research groups have reported a phenomenon known as radiation induced electrical degradation (RIED), which produces significant permanent increases in the electrical conductivity of ceramic insulators irradiated with an applied electric field. RIED has been reported to occur at temperatures between 420 and 800 K with applied electric fields as low as 20 V/mm.

  10. Lattice Assisted Nuclear Reactions From Nanostructured Metamaterials Electrically Driven at Their Optimal Operating Point

    NASA Astrophysics Data System (ADS)

    Swartz, Mitchell R.

    2011-03-01

    In lattice assisted nuclear reactions, hydrogen-loaded alloys enable near room temperature deuterium fusion and other nuclear reactions (1). The structural metamaterial shape of some D-loaded Pd nanostructures and deuterium flux (2) through them, driven by an applied electric field, appear to play decisive roles. The spiral Phusor -type cathode with open helical cylindrical geometry in a high electrical resistance solution is a LANR metamaterial design creating intrapalladial deuteron flow. Optimal operating point technology allows improved and more reproducible operation (3). LANR power gain can be considerable. In situ imaging has revealed that the excess power gain is linked to non-thermal near-IR emission when the LANR devices are operated at their OOP. LANR devices have shown power gains more than 200%, and short term power gains to ~ 8000 % . 1. Swartz, M, J. Sci. Exploration, 23, 4, 419-436 (2009). 2. Swartz, M, Fusion Technology, 22, 2, 296-300 (1992); 26, 4T, 74-77 (1994); 32, 126-130 (1997). 3. Swartz. M, Fusion Technology, 31, 63-74 (1997).

  11. Electrically and magnetically dual-driven Janus particles for handwriting-enabled electronic paper

    SciTech Connect

    Komazaki, Y. Hirama, H.; Torii, T.

    2015-04-21

    In this work, we describe the synthesis of novel electrically and magnetically dual-driven Janus particles for a handwriting-enabled twisting ball display via the microfluidic technique. One hemisphere of the Janus particles contains a charge control agent, which allows the display color to be controlled by applying a voltage and superparamagnetic nanoparticles, allows handwriting by applying a magnetic field to the display. We fabricated a twisting ball display utilizing these Janus particles and tested the electric color control and handwriting using a magnet. As a result, the display was capable of permitting handwriting with a small magnet in addition to conventional color control using an applied voltage (80 V). Handwriting performance was improved by increasing the concentration of superparamagnetic nanoparticles and was determined to be possible even when 80 V was applied across the electrodes for 4 wt. % superparamagnetic nanoparticles in one hemisphere. This improvement was impossible when the concentration was reduced to 2 wt. % superparamagnetic nanoparticles. The technology presented in our work can be applied to low-cost, lightweight, highly visible, and energy-saving electronic message boards and large whiteboards because the large-size display can be fabricated easily due to its simple structure.

  12. Increasing the interlayer distance in layered microribbons enhances the electrically driven twisting response

    NASA Astrophysics Data System (ADS)

    Zhang, Yifan; Zhou, Zichao; Peng, Cheng; Duan, Ran; Che, Yanke; Zhao, Jincai

    2017-08-01

    We designed a class of layered microribbons self-assembled from perylene diimide (PDI) molecules that exhibited a fast electrically driven twisting response. By increasing the length of the side chains of the PDIs, the microribbons maintained the same intralayer molecular orientation but exhibited enlarged interlayer distances, and the elasticity moduli of the resulting layered microribbons were effectively reduced from ˜1.5 GPa to ˜75 MPa . The electrically driven twisting response of the microribbons was inversely proportional to the elasticity modulus, indicating that the electroresponse of the resulting materials can be controlled through the interlayer distance. Furthermore, we demonstrated that the influence of the elastic modulus of the microribbons on the electrically driven twisting follows a screw dislocation mechanism. Our work provides a way to design and develop soft materials with a fast mechanical response to external stimuli.

  13. Generating Electricity during Walking with a Lower Limb-Driven Energy Harvester: Targeting a Minimum User Effort

    PubMed Central

    Shepertycky, Michael; Li, Qingguo

    2015-01-01

    Background Much research in the field of energy harvesting has sought to develop devices capable of generating electricity during daily activities with minimum user effort. No previous study has considered the metabolic cost of carrying the harvester when determining the energetic effects it has on the user. When considering device carrying costs, no energy harvester to date has demonstrated the ability to generate a substantial amount of electricity (> 5W) while maintaining a user effort at the same level or lower than conventional power generation methods (e.g. hand crank generator). Methodology/Principal Findings We developed a lower limb-driven energy harvester that is able to generate approximately 9W of electricity. To quantify the performance of the harvester, we introduced a new performance measure, total cost of harvesting (TCOH), which evaluates a harvester’s overall efficiency in generating electricity including the device carrying cost. The new harvester captured the motion from both lower limbs and operated in the generative braking mode to assist the knee flexor muscles in slowing the lower limbs. From a testing on 10 participants under different walking conditions, the harvester achieved an average TCOH of 6.1, which is comparable to the estimated TCOH for a conventional power generation method of 6.2. When generating 5.2W of electricity, the TCOH of the lower limb-driven energy harvester (4.0) is lower than that of conventional power generation methods. Conclusions/Significance These results demonstrated that the lower limb-driven energy harvester is an energetically effective option for generating electricity during daily activities. PMID:26039493

  14. Generating Electricity during Walking with a Lower Limb-Driven Energy Harvester: Targeting a Minimum User Effort.

    PubMed

    Shepertycky, Michael; Li, Qingguo

    2015-01-01

    Much research in the field of energy harvesting has sought to develop devices capable of generating electricity during daily activities with minimum user effort. No previous study has considered the metabolic cost of carrying the harvester when determining the energetic effects it has on the user. When considering device carrying costs, no energy harvester to date has demonstrated the ability to generate a substantial amount of electricity (> 5W) while maintaining a user effort at the same level or lower than conventional power generation methods (e.g. hand crank generator). We developed a lower limb-driven energy harvester that is able to generate approximately 9W of electricity. To quantify the performance of the harvester, we introduced a new performance measure, total cost of harvesting (TCOH), which evaluates a harvester's overall efficiency in generating electricity including the device carrying cost. The new harvester captured the motion from both lower limbs and operated in the generative braking mode to assist the knee flexor muscles in slowing the lower limbs. From a testing on 10 participants under different walking conditions, the harvester achieved an average TCOH of 6.1, which is comparable to the estimated TCOH for a conventional power generation method of 6.2. When generating 5.2W of electricity, the TCOH of the lower limb-driven energy harvester (4.0) is lower than that of conventional power generation methods. These results demonstrated that the lower limb-driven energy harvester is an energetically effective option for generating electricity during daily activities.

  15. Comparison of electrically driven lasers for space power transmission

    NASA Technical Reports Server (NTRS)

    Deyoung, R. J.; Lee, J. H.; Williams, M. D.; Schuster, G.; Conway, E. J.

    1988-01-01

    High-power lasers in space could provide power for a variety of future missions such as spacecraft electric power requirements and laser propulsion. This study investigates four electrically pumped laser systems, all scaled to 1-MW laser output, that could provide power to spacecraft. The four laser systems are krypton fluoride, copper vapor, laser diode array, and carbon dioxide. Each system was powered by a large solar photovoltaic array which, in turn, provided power for the appropriate laser power conditioning subsystem. Each system was block-diagrammed, and the power and efficiency were found for each subsystem block component. The copper vapor system had the lowest system efficiency (6 percent). The CO2 laser was found to be the most readily scalable but has the disadvantage of long laser wavelength.

  16. Keldysh field theory for driven open quantum systems.

    PubMed

    Sieberer, L M; Buchhold, M; Diehl, S

    2016-09-01

    Recent experimental developments in diverse areas-ranging from cold atomic gases to light-driven semiconductors to microcavity arrays-move systems into the focus which are located on the interface of quantum optics, many-body physics and statistical mechanics. They share in common that coherent and driven-dissipative quantum dynamics occur on an equal footing, creating genuine non-equilibrium scenarios without immediate counterpart in equilibrium condensed matter physics. This concerns both their non-thermal stationary states and their many-body time evolution. It is a challenge to theory to identify novel instances of universal emergent macroscopic phenomena, which are tied unambiguously and in an observable way to the microscopic drive conditions. In this review, we discuss some recent results in this direction. Moreover, we provide a systematic introduction to the open system Keldysh functional integral approach, which is the proper technical tool to accomplish a merger of quantum optics and many-body physics, and leverages the power of modern quantum field theory to driven open quantum systems.

  17. Keldysh field theory for driven open quantum systems

    NASA Astrophysics Data System (ADS)

    Sieberer, L. M.; Buchhold, M.; Diehl, S.

    2016-09-01

    Recent experimental developments in diverse areas—ranging from cold atomic gases to light-driven semiconductors to microcavity arrays—move systems into the focus which are located on the interface of quantum optics, many-body physics and statistical mechanics. They share in common that coherent and driven-dissipative quantum dynamics occur on an equal footing, creating genuine non-equilibrium scenarios without immediate counterpart in equilibrium condensed matter physics. This concerns both their non-thermal stationary states and their many-body time evolution. It is a challenge to theory to identify novel instances of universal emergent macroscopic phenomena, which are tied unambiguously and in an observable way to the microscopic drive conditions. In this review, we discuss some recent results in this direction. Moreover, we provide a systematic introduction to the open system Keldysh functional integral approach, which is the proper technical tool to accomplish a merger of quantum optics and many-body physics, and leverages the power of modern quantum field theory to driven open quantum systems.

  18. Difficulties in Learning the Concept of Electric Field.

    ERIC Educational Resources Information Center

    Furio, C.; Guisasola, J.

    1998-01-01

    Analyzes students' main difficulties in learning the concept of electric field. Briefly describes the main conceptual profiles within which electric interactions can be interpreted and concludes that most students have difficulty using the idea of electric field. Contains 28 references. (DDR)

  19. Spectroscopic investigation of electric field fluctuations in a steady plasma

    NASA Technical Reports Server (NTRS)

    Druetta, M. P.

    1971-01-01

    The electric fluctuations caused by plasma oscillations of a steady plasma were investigated. In order to observe this phenomenon electric field fluctuations are created in a helium plasma by an electron beam. Spectroscopic analysis reveals satellite lines disposed symmetrically in pairs about a forbidden atomic line and separated from it by the frequency of the electric field oscillations.

  20. Variations in the atmospheric electric field at mountainous observation points

    NASA Astrophysics Data System (ADS)

    Adzhiev, A. Kh.; Kupovykh, G. V.

    2015-05-01

    Study of unitary variation in the electric field of the near-surface atmosphere is a topical tasks of atmospheric electricity. This work substantiates the possible registration of global variations in the electric field intensity of the near-surface atmospheric layer at mountainous stations and discusses the results of observations in the Elbrus region.

  1. Empirical models of high latitude electric fields

    NASA Technical Reports Server (NTRS)

    Heppner, J. P.

    1976-01-01

    Model cross sections of the high latitude dawn-dusk electric field based on OGO-6 data are presented for the signature profiles, most frequently encountered for both + and -Y orientations of the interplanetary magnetic field. Line integrals give a total potential of 76 keV in each case. To illustrate extremes, examples of model cross-sections with total potentials of 23 keV and 140 keV are also given. Model convection patterns are also presented utilizing OGO-6 data on boundary locations at other magnetic local times. When this information is combined with characteristic field geometries in the region of the Harang discontinuity, and is supplemented by data from Ba+ cloud motions in the polar cap, it becomes possible to construct realistic convection patterns on the nightside which deviate from the usual sun-aligned patterns. The observational models presented are of limited applicability as a consequence of the variability of observed distributions. These limitations are emphasized with particular attention given to several types of recurrent deviations which have not previously been discussed.

  2. Liquid methanol under a static electric field

    SciTech Connect

    Cassone, Giuseppe; Giaquinta, Paolo V.; Saija, Franz; Saitta, A. Marco

    2015-02-07

    We report on an ab initio molecular dynamics study of liquid methanol under the effect of a static electric field. We found that the hydrogen-bond structure of methanol is more robust and persistent for field intensities below the molecular dissociation threshold whose value (≈0.31 V/Å) turns out to be moderately larger than the corresponding estimate obtained for liquid water. A sustained ionic current, with ohmic current-voltage behavior, flows in this material for field intensities above 0.36 V/Å, as is also the case of water, but the resulting ionic conductivity (≈0.40 S cm{sup −1}) is at least one order of magnitude lower than that of water, a circumstance that evidences a lower efficiency of proton transfer processes. We surmise that this study may be relevant for the understanding of the properties and functioning of technological materials which exploit ionic conduction, such as direct-methanol fuel cells and Nafion membranes.

  3. Electric field response in bilayer graphene: Ab initio investigation

    NASA Astrophysics Data System (ADS)

    Mori, Yutaro; Minamitani, Emi; Ando, Yasunobu; Kasamatsu, Shusuke; Watanabe, Satoshi

    2016-11-01

    Stimulated by quantum capacitance measurements, we have investigated the electric properties of bilayer graphene (BLG) with carrier doping under an external electric field using ab initio calculations. We found that the relative permittivity of BLG depends weakly on the applied electric field, and that the BLG can be regarded as a dielectric material rather than a pair of metallic films. We also found that carrier doping affects the band gap of BLG under electric fields, although carrier doping has a much smaller effect on the band gap and density of states than the application of electric fields.

  4. Simulation of radio emission from air showers in atmospheric electric fields

    SciTech Connect

    Buitink, S.; Huege, T.; Falcke, H; Kuijpers, J.

    2010-02-25

    We study the effect of atmospheric electric fields on the radio pulse emitted by cos- mic ray air showers. Under fair weather conditions the dominant part of the radio emission is driven by the geomagnetic field. When the shower charges are accelerated and deflected in an electric field additional radiation is emitted. We simulate this effect with the Monte Carlo code REAS2, using CORSIKA-simulated showers as input. In both codes a routine has been implemented that treats the effect of the electric field on the shower particles. We find that the radio pulse is significantly altered in background fields of the order of ~100 V/cm and higher. Practically, this means that air showers passing through thunderstorms emit radio pulses that are not a reliable measure for the shower energy. Under other weather circumstances significant electric field effects are expected to occur rarely, but nimbostratus clouds can harbor fields that are large enough. In general, the contribution of the electric field to the radio pulse has polarization properties that are different from the geomagnetic pulse. In order to filter out radio pulses that have been affected by electric field effects, radio air shower experiments should keep weatherinformation and perform full polarization measurements of the radio signal.

  5. Electropumping of water with rotating electric fields

    NASA Astrophysics Data System (ADS)

    De Luca, Sergio; Todd, B. D.; Hansen, J. S.; Daivis, Peter J.

    2013-04-01

    Pumping of fluids confined to nanometer dimension spaces is a technically challenging yet vitally important technological application with far reaching consequences for lab-on-a-chip devices, biomimetic nanoscale reactors, nanoscale filtration devices and the like. All current pumping mechanisms require some sort of direct intrusion into the nanofluidic system, and involve mechanical or electronic components. In this paper, we present the first nonequilibrium molecular dynamics results to demonstrate that non-intrusive electropumping of liquid water on the nanoscale can be performed by subtly exploiting the coupling of spin angular momentum to linear streaming momentum. A spatially uniform rotating electric field is applied to water molecules, which couples to their permanent electric dipole moments. The resulting molecular rotational momentum is converted into linear streaming momentum of the fluid. By selectively tuning the degree of hydrophobicity of the solid walls one can generate a net unidirectional flow. Our results for the linear streaming and angular velocities of the confined water are in general agreement with the extended hydrodynamical theory for this process, though also suggest refinements to the theory are required. These numerical experiments confirm that this new concept for pumping of polar nanofluids can be employed under laboratory conditions, opening up significant new technological possibilities.

  6. Electropumping of water with rotating electric fields.

    PubMed

    De Luca, Sergio; Todd, B D; Hansen, J S; Daivis, Peter J

    2013-04-21

    Pumping of fluids confined to nanometer dimension spaces is a technically challenging yet vitally important technological application with far reaching consequences for lab-on-a-chip devices, biomimetic nanoscale reactors, nanoscale filtration devices and the like. All current pumping mechanisms require some sort of direct intrusion into the nanofluidic system, and involve mechanical or electronic components. In this paper, we present the first nonequilibrium molecular dynamics results to demonstrate that non-intrusive electropumping of liquid water on the nanoscale can be performed by subtly exploiting the coupling of spin angular momentum to linear streaming momentum. A spatially uniform rotating electric field is applied to water molecules, which couples to their permanent electric dipole moments. The resulting molecular rotational momentum is converted into linear streaming momentum of the fluid. By selectively tuning the degree of hydrophobicity of the solid walls one can generate a net unidirectional flow. Our results for the linear streaming and angular velocities of the confined water are in general agreement with the extended hydrodynamical theory for this process, though also suggest refinements to the theory are required. These numerical experiments confirm that this new concept for pumping of polar nanofluids can be employed under laboratory conditions, opening up significant new technological possibilities.

  7. Review Of Fiber-Optic Electric-Field Sensors

    NASA Technical Reports Server (NTRS)

    De Paula, Ramon P.; Jarzynski, Jacek

    1989-01-01

    Tutorial paper reviews state of art in fiber-optic sensors of alternating electric fields. Because such sensors are made entirely of dielectric materials, they are relatively transparent to incident electric fields; they do not distort fields significantly. Paper presents equations that express relationships among stress, strain, and electric field in piezoactive plastic and equations for phase shift in terms of photoelastic coefficients and strains in optical fiber.

  8. Effects of Nonconvective Electric Fields on Magnetospheric Plasma Dynamics.

    DTIC Science & Technology

    1983-01-31

    of Plasma and Electric Fields in the Magnetosphere, Yosemite , CA, 1982. 5. Silevitch, M.B., Excitation of Transient Double Layers and their Coupling to...Fields in Particle Data, Chapman Conference on High Latitude Electric Fields, Yosemite , CA, 1980, Paper 50. 20. M.B. Silevitch, E.C. Whipple Jr., and M.E...Greenspan, Temporal Behavior of Particle Fluxes Associated with Auroral Arcs, Chapman Conference on High Latitude Electric Fields, Yosemite , CA, 1980

  9. Electric field observations of equatorial bubbles

    NASA Technical Reports Server (NTRS)

    Aggson, T. L.; Maynard, N. C.; Hanson, W. B.; Saba, Jack L.

    1992-01-01

    Results from the double floating probe experiment performed on the San Marco D satellite are presented, with emphasis on the observation of large incremental changes in the convective electric field vector at the boundary of equatorial plasma bubbles. Attention is given to isolated bubble structures in the upper ionospheric F regions; these observed bubble encounters are divided into two types - type I (live bubbles) and type II (dead bubbles). Type I bubbles show varying degrees of plasma depletion and large upward velocities range up to 1000 km/s. The geometry of these bubbles is such that the spacecraft orbit may cut them where they are tilting either eastward or (more often) westward. Type II bubbles exhibit plasma density depletion but no appreciable upward convection. Both types of events are usually surrounded by a halo of plasma turbulence, which can extend considerably beyond the region of plasma depletion.

  10. Electric field observations of equatorial bubbles

    NASA Astrophysics Data System (ADS)

    Aggson, T. L.; Maynard, N. C.; Hanson, W. B.; Saba, Jack L.

    1992-03-01

    Results from the double floating probe experiment performed on the San Marco D satellite are presented, with emphasis on the observation of large incremental changes in the convective electric field vector at the boundary of equatorial plasma bubbles. Attention is given to isolated bubble structures in the upper ionospheric F regions; these observed bubble encounters are divided into two types - type I (live bubbles) and type II (dead bubbles). Type I bubbles show varying degrees of plasma depletion and large upward velocities range up to 1000 km/s. The geometry of these bubbles is such that the spacecraft orbit may cut them where they are tilting either eastward or (more often) westward. Type II bubbles exhibit plasma density depletion but no appreciable upward convection. Both types of events are usually surrounded by a halo of plasma turbulence, which can extend considerably beyond the region of plasma depletion.

  11. Disturbance dynamo electric fields in response to geomagnetic storms occurring at different universal times

    NASA Astrophysics Data System (ADS)

    Huang, C.

    2013-12-01

    Perturbed electric fields in the earth's ionosphere, resulting from the penetration electric fields from high latitudes and/or from the dynamo mechanism driven by the neutral disturbances, occurr in the storm periods. In general, the identification of the penetration electric fields is easier than that of the dynamo electric fields. At times, the latter becomes unperceivable or difficult to identify. This is an interesting problem which motivates a model study to investigate the possible reasons. Model runs made with the National Center for Atmospheric Research Thermosphere Ionosphere Electrodynamics General Circulation Model (NCAR/TIEGCM) will be presented. Theoretical studies of ionospheric responses to geomagnetic storms with model simulations indicate that the intensities of disturbance dynamo electric fields are highly dependent on various parameters such as solar activities, seasonal effects and universal times, etc. When geomagnetic storms commence at 01~07 UT in summer solstices with low solar fluxes, the disturbance dynamo electric fields become very small. As compared with the general daily variations, they seem to be unperceivable. This phenomenon can be explained by the model results which show that the positive charge accumulation at low latitudes will be weakened when the equatward neutral disturbances penetrate into the opposite hemisphere in the storm time. For other cases, the magnitudes of the dynamo electric fields are relatively larger under the same geomagnetic activity.

  12. Catastrophic drop breakup in electric field.

    PubMed

    Raut, Janhavi S; Akella, Sathish; Singh, Amitkumar; Naik, Vijay M

    2009-05-05

    We report novel observations revealing the catastrophic breakup of water drops containing surfactant molecules, which are suspended in oil and subjected to an electric field of strength approximately 10(5) V/m. The observed breakup was distinctly different from the gradual end pinch-off or tip-streaming modes reported earlier in the literature. There was no observable characteristic deformation of the drop prior to breakup. The time scales involved in the breakup and the resultant droplet sizes were much smaller in the phenomenon observed by us. We hypothesize that this mode of drop breakup is obtained by the combined effect of an external electric field that imposes tensile stresses on the surface of the drop, and characteristic stress-strain behavior for tensile deformation exhibited by the liquid drop in the presence of a suitable surfactant, which not only lowers the interfacial tension (and hence the cohesive strength) of the drop but also simultaneously renders the interface nonductile or brittle at high enough concentration. We have identified the relevant thermodynamic parameter, viz., the sum of interfacial tension, sigma, and the Gibbs elasticity, epsilon, which plays a decisive role in determining the mode of drop breakup. The parameter (epsilon + sigma) represents the internal restoration stress of a liquid drop opposing rapid, short-time-scale perturbations or local deformations in the drop shape under the influence of external impulses or stresses. A thermodynamic "state" diagram of (epsilon + sigma) versus interfacial area per surfactant molecule adsorbed at the drop interface shows a "maximum" at a critical transition concentration (ctc). Below this concentration of the surfactant, the drop undergoes tip streaming or pinch off. Above this concentration, the drop may undergo catastrophic disintegration if the external stress is high enough to overcome the ultimate cohesive strength of the drop's interface.

  13. DC Electric Fields and Associated Plasma Drifts Observed with the C/NOFS Satellite

    NASA Technical Reports Server (NTRS)

    Pfaff, R.; Freudenreich, H.; Bromund, K.; Rowland, D.

    2009-01-01

    Initial DC electric field observations and associated plasma drifts are presented from the Vector Electric Field Investigation (VEFI) on the Air Force Communication/Navigation Outage Forecasting System (C/NOFS) satellite. We present statistical averages of the vector fields for the first year of operations that include both the zonal and radial components of the resulting E x B plasma flows at low latitudes. Magnetic field data from the VEFI science magnetometer are used to compute the plasma flows. The DC electric field detector reveals zonal and radial electric fields that undergo strong diurnal variations, typically displaying eastward and outward-directed fields during the day and westward and downward-directed fields at night. There is considerable variation in the large scale DC electric field data, in both the daytime and nighttime cases, with enhanced structures typically observed at night. In general, the measured zonal DC electric field amplitudes include excursions that extend within the 0.4 - 2 m V/m range, corresponding to E x B drifts of the order of 30-150 m/s. The average vertical or radial electric fields may exceed the zonal fields in amplitude by a factor of 1.5 to 2. Although the data compare well, in a general sense, with previous satellite observations and statistical patterns of vertical ion drifts, the E x B drifts we report from C/NOFS rarely show a pronounced pre-reversal enhancement after sunset. We attribute this to a combination of extreme solar minimum conditions and the fact that the C/NOFS orbit of 401 by 867 km carries the probes essentially above the lower altitude regions where the wind-driven dynamo might be expected to create enhanced upwards drifts in the early evening. Evidence for wavenumber 4 tidal effects and other longitudinal signatures have been detected and will be presented. We also discuss off-equatorial electric fields and their relation to the ambient plasma density.

  14. Field-Driven Mott Gap Collapse and Resistive Switch in Correlated Insulators

    NASA Astrophysics Data System (ADS)

    Mazza, G.; Amaricci, A.; Capone, M.; Fabrizio, M.

    2016-10-01

    Mott insulators are "unsuccessful metals" in which Coulomb repulsion prevents charge conduction despite a metal-like concentration of conduction electrons. The possibility to unlock the frozen carriers with an electric field offers tantalizing prospects of realizing new Mott-based microelectronic devices. Here we unveil how such unlocking happens in a simple model that shows the coexistence of a stable Mott insulator and a metastable metal. Considering a slab subject to a linear potential drop, we find, by means of the dynamical mean-field theory, that the electric breakdown of the Mott insulator occurs via a first-order insulator-to-metal transition characterized by an abrupt gap collapse in sharp contrast to the standard Zener breakdown. The switch on of conduction is due to the field-driven stabilization of the metastable metallic phase. Outside the region of insulator-metal coexistence, the electric breakdown occurs through a more conventional quantum tunneling across the Hubbard bands tilted by the field. Our findings rationalize recent experimental observations and may offer a guideline for future technological research.

  15. On intense diverging electric field associated with black aurora

    SciTech Connect

    Marklund, G.; Blomberg, L.; Faelthammar, C.G.; Lindqvist, P.A.

    1994-08-15

    The authors present measurements made from the double-probe electric field instrument on the Freja satellite of a very intense electric field event seen in the auroral oval. The electric field measurements are correlated with potential, charged particle, and wave activity measurements. They see two very narrow electric field events separated by approximately 5 km, having field strengths near 1 V/m. These structures are seen to be associated with an excess of positive charge, to be associated with no electron precipitation, with slight plasma depletions, and with wave activity. The authors suggest these structures are black aurorae, with a total absence of auroral emissions.

  16. Detection and learning of floral electric fields by bumblebees.

    PubMed

    Clarke, Dominic; Whitney, Heather; Sutton, Gregory; Robert, Daniel

    2013-04-05

    Insects use several senses to forage, detecting floral cues such as color, shape, pattern, and volatiles. We report a formerly unappreciated sensory modality in bumblebees (Bombus terrestris), detection of floral electric fields. These fields act as floral cues, which are affected by the visit of naturally charged bees. Like visual cues, floral electric fields exhibit variations in pattern and structure, which can be discriminated by bumblebees. We also show that such electric field information contributes to the complex array of floral cues that together improve a pollinator's memory of floral rewards. Because floral electric fields can change within seconds, this sensory modality may facilitate rapid and dynamic communication between flowers and their pollinators.

  17. Electricity Demand Evolution Driven by Storm Motivated Population Movement

    SciTech Connect

    Allen, Melissa R; Fernandez, Steven J; Fu, Joshua S; Walker, Kimberly A

    2014-01-01

    Managing the risks posed by climate change to energy production and delivery is a challenge for communities worldwide. Sea Level rise and increased frequency and intensity of natural disasters due to sea surface temperature rise force populations to move locations, resulting in changing patterns of demand for infrastructure services. Thus, Infrastructures will evolve to accommodate new load centers while some parts of the network are underused, and these changes will create emerging vulnerabilities. Combining climate predictions and agent based population movement models shows promise for exploring the universe of these future population distributions and changes in coastal infrastructure configurations. In this work, we created a prototype agent based population distribution model and developed a methodology to establish utility functions that provide insight about new infrastructure vulnerabilities that might result from these patterns. Combining climate and weather data, engineering algorithms and social theory, we use the new Department of Energy (DOE) Connected Infrastructure Dynamics Models (CIDM) to examine electricity demand response to increased temperatures, population relocation in response to extreme cyclonic events, consequent net population changes and new regional patterns in electricity demand. This work suggests that the importance of established evacuation routes that move large populations repeatedly through convergence points as an indicator may be under recognized.

  18. The influence of electric field and confinement on cell motility.

    PubMed

    Huang, Yu-Ja; Samorajski, Justin; Kreimer, Rachel; Searson, Peter C

    2013-01-01

    The ability of cells to sense and respond to endogenous electric fields is important in processes such as wound healing, development, and nerve regeneration. In cell culture, many epithelial and endothelial cell types respond to an electric field of magnitude similar to endogenous electric fields by moving preferentially either parallel or antiparallel to the field vector, a process known as galvanotaxis. Here we report on the influence of dc electric field and confinement on the motility of fibroblast cells using a chip-based platform. From analysis of cell paths we show that the influence of electric field on motility is much more complex than simply imposing a directional bias towards the cathode or anode. The cell velocity, directedness, as well as the parallel and perpendicular components of the segments along the cell path are dependent on the magnitude of the electric field. Forces in the directions perpendicular and parallel to the electric field are in competition with one another in a voltage-dependent manner, which ultimately govern the trajectories of the cells in the presence of an electric field. To further investigate the effects of cell reorientation in the presence of a field, cells are confined within microchannels to physically prohibit the alignment seen in 2D environment. Interestingly, we found that confinement results in an increase in cell velocity both in the absence and presence of an electric field compared to migration in 2D.

  19. The Influence of Electric Field and Confinement on Cell Motility

    PubMed Central

    Huang, Yu-Ja; Samorajski, Justin; Kreimer, Rachel; Searson, Peter C.

    2013-01-01

    The ability of cells to sense and respond to endogenous electric fields is important in processes such as wound healing, development, and nerve regeneration. In cell culture, many epithelial and endothelial cell types respond to an electric field of magnitude similar to endogenous electric fields by moving preferentially either parallel or antiparallel to the field vector, a process known as galvanotaxis. Here we report on the influence of dc electric field and confinement on the motility of fibroblast cells using a chip-based platform. From analysis of cell paths we show that the influence of electric field on motility is much more complex than simply imposing a directional bias towards the cathode or anode. The cell velocity, directedness, as well as the parallel and perpendicular components of the segments along the cell path are dependent on the magnitude of the electric field. Forces in the directions perpendicular and parallel to the electric field are in competition with one another in a voltage-dependent manner, which ultimately govern the trajectories of the cells in the presence of an electric field. To further investigate the effects of cell reorientation in the presence of a field, cells are confined within microchannels to physically prohibit the alignment seen in 2D environment. Interestingly, we found that confinement results in an increase in cell velocity both in the absence and presence of an electric field compared to migration in 2D. PMID:23555674

  20. Experimental and numerical study of electrically driven magnetohydrodynamic flow in a modified cylindrical annulus. II. Instabilities

    NASA Astrophysics Data System (ADS)

    Stelzer, Zacharias; Miralles, Sophie; Cébron, David; Noir, Jérôme; Vantieghem, Stijn; Jackson, Andrew

    2015-08-01

    We present an investigation of the stability of liquid metal flow under the influence of an imposed magnetic field by means of a laboratory experiment as well as a linear stability analysis of the setup using the finite element method. The experimental device ZUrich Cylindrical CHannel INstability Investigation is a modified cylindrical annulus with electrically driven flow of liquid GaInSn operating at Hartmann and Reynolds numbers up to M = 2022 and Re = 2.6 ṡ 105, respectively. The magnetic field gives rise to a free shear layer at the prominent inner electrode. We identify several flow regimes characterized by the nature of the instabilities. Above a critical current I c = O ( 0 . 1 A ) , the steady flow is destabilized by a Kelvin-Helmholtz mechanism at the free shear layer. The instability consists of counterrotating vortices traveling with the mean flow. For low forcing, the vortices are restricted to the free shear layer. Their azimuthal wave number m grows with M and decreases with Re. At Re/M ≈ 25, the instability becomes container-filling and energetically significant. It enhances the radial momentum transport which manifests itself in a broadening of the free shear layer width δS. We propose that this transition may be related to an unstable Hartmann layer. At R e / M 2 = O ( 1 ) , an abrupt change is observed in the mean azimuthal velocity < u ϕ ¯ > and the friction factor F, which we interpret as the transition between an inertialess and an inertial regime.

  1. A simple model for estimating a magnetic field in laser-driven coils

    SciTech Connect

    Fiksel, Gennady; Fox, William; Gao, Lan; Ji, Hantao

    2016-09-26

    Magnetic field generation by laser-driven coils is a promising way of magnetizing plasma in laboratory high-energy-density plasma experiments. A typical configuration consists of two electrodes—one electrode is irradiated with a high-intensity laser beam and another electrode collects charged particles from the expanding plasma. The two electrodes are separated by a narrow gap forming a capacitor-like configuration and are connected with a conducting wire-coil. The charge-separation in the expanding plasma builds up a potential difference between the electrodes that drives the electrical current in the coil. A magnetic field of tens to hundreds of Teslas generated inside the coil has been reported. This paper presents a simple model that estimates the magnetic field using simple assumptions. Lastly, the results are compared with the published experimental data.

  2. A simple model for estimating a magnetic field in laser-driven coils

    SciTech Connect

    Fiksel, Gennady; Fox, William; Gao, Lan; Ji, Hantao

    2016-09-26

    Magnetic field generation by laser-driven coils is a promising way of magnetizing plasma in laboratory high-energy-density plasma experiments. A typical configuration consists of two electrodes—one electrode is irradiated with a high-intensity laser beam and another electrode collects charged particles from the expanding plasma. The two electrodes are separated by a narrow gap forming a capacitor-like configuration and are connected with a conducting wire-coil. The charge-separation in the expanding plasma builds up a potential difference between the electrodes that drives the electrical current in the coil. A magnetic field of tens to hundreds of Teslas generated inside the coil has been reported. This paper presents a simple model that estimates the magnetic field using simple assumptions. Lastly, the results are compared with the published experimental data.

  3. A simple model for estimating a magnetic field in laser-driven coils

    NASA Astrophysics Data System (ADS)

    Fiksel, Gennady; Fox, William; Gao, Lan; Ji, Hantao

    2016-09-01

    Magnetic field generation by laser-driven coils is a promising way of magnetizing plasma in laboratory high-energy-density plasma experiments. A typical configuration consists of two electrodes—one electrode is irradiated with a high-intensity laser beam and another electrode collects charged particles from the expanding plasma. The two electrodes are separated by a narrow gap forming a capacitor-like configuration and are connected with a conducting wire-coil. The charge-separation in the expanding plasma builds up a potential difference between the electrodes that drives the electrical current in the coil. A magnetic field of tens to hundreds of Teslas generated inside the coil has been reported. This paper presents a simple model that estimates the magnetic field using simple assumptions. The results are compared with the published experimental data.

  4. A simple model for estimating a magnetic field in laser-driven coils

    DOE PAGES

    Fiksel, Gennady; Fox, William; Gao, Lan; ...

    2016-09-26

    Magnetic field generation by laser-driven coils is a promising way of magnetizing plasma in laboratory high-energy-density plasma experiments. A typical configuration consists of two electrodes—one electrode is irradiated with a high-intensity laser beam and another electrode collects charged particles from the expanding plasma. The two electrodes are separated by a narrow gap forming a capacitor-like configuration and are connected with a conducting wire-coil. The charge-separation in the expanding plasma builds up a potential difference between the electrodes that drives the electrical current in the coil. A magnetic field of tens to hundreds of Teslas generated inside the coil has beenmore » reported. This paper presents a simple model that estimates the magnetic field using simple assumptions. Lastly, the results are compared with the published experimental data.« less

  5. CFT driven cosmology and conformal higher spin fields

    NASA Astrophysics Data System (ADS)

    Barvinsky, A. O.

    2016-05-01

    Conformal higher spin (CHS) field theory, which is a solid part of recent advanced checks of AdS/CFT correspondence, finds applications in cosmology. The hidden sector of weakly interacting CHS fields suggests a resolution of the hierarchy problem in the model of initial conditions for inflationary cosmology driven by a conformal field theory. These initial conditions are set by thermal garland-type cosmological instantons in the sub-Planckian energy range for the model of CHS fields with a large positive coefficient β of the Gauss-Bonnet term in their total conformal anomaly and a large number of their polarizations N . The upper bound of this range MP/√{β } is shown to be much lower than the gravitational cutoff MP/√{N } which is defined by the requirement of smallness of the perturbatively nonrenormalizable graviton loop contributions. In this way we justify the approximation scheme in which the nonrenormalizable graviton sector is subject to effective field theory under this cutoff, whereas the renormalizable sector of multiple CHS fields is treated beyond perturbation theory and dynamically generates the bound on the inflation scale of the CFT cosmology MP/√{β }≪MP/√{N }. This confirms recent predictions for the origin of the Starobinsky R2 and Higgs inflation models from the CHS cosmology, which occurs at the energy scale 3 or 4 orders of magnitude below the gravitational cutoff, √{N /β }˜10-3- 10-4 . We also consider cosmological models dominated by fermionic CHS fields with a negative β and anomaly free models of infinite towers of CHS fields with β =0 and briefly discuss the status of unitarity in CHS models.

  6. Uplift and Outflow of Bacterial Spores via Electric Field

    NASA Astrophysics Data System (ADS)

    Dehel, T.

    The questions of how did life arise and is there life on other planets are some of the most profound questions that humanity asks Although there has been controversial signs of past bacterial life in meteorites which originated on Mars and there are current claims of bacterial life high in the atmosphere the issues of origin by chemical process or contamination make these types of results arguable and they will likely remain that way until a comprehensive theory is developed to explain why the claims might be true This paper proposes a complete theory for the spread of bacterial life throughout the galaxy by combining current knowledge from the fields of bacteriology stellar evolution and space weather Here we show the possibility that the forces of uplift on a charged bacteria particle are sufficient bring at least some lighter types of bacteria high into the ionosphere and subsequently move the charged spore onto magnetic field lines The bacteria spore is then driven down the magnetotail where during a solar storm a structure known as a plasmoid is propelled radially outward into space at velocities exceeding solar system escape velocity From that point the plasmoids are capable of reaching Mars the outer planets and even others systems eventually depositing the bacterial spores either via comets or direct interaction with the receiving planet The solid observational evidence for the strength of the electric fields and the speeds that the plasmoids leave the magnetotail during geomagnetic storms provide a firm

  7. Measurements of the vertical atmospheric electric field and of the electrical conductivity with stratospheric balloons

    NASA Technical Reports Server (NTRS)

    Iversen, I. B.; Madsen, M. M.; Dangelo, N.

    1985-01-01

    Measurements of the atmospheric (vertical) electric field with balloons in the stratosphere are reported. The atmospheric electrical conductivity is also measured and the current density inferred. The average vertical current shows the expected variation with universal time and is also seen to be influenced by external (magnetospheric) electric fields.

  8. Static electric field detection and behavioural avoidance in cockroaches.

    PubMed

    Newland, Philip L; Hunt, Edmund; Sharkh, Suleiman M; Hama, Noriyuki; Takahata, Masakazu; Jackson, Christopher W

    2008-12-01

    Electric fields are pervasively present in the environment and occur both as a result of man-made activities and through natural occurrence. We have analysed the behaviour of cockroaches to static electric fields and determined the physiological mechanisms that underlie their behavioural responses. The behaviour of animals in response to electric fields was tested using a Y-choice chamber with an electric field generated in one arm of the chamber. Locomotory behaviour and avoidance were affected by the magnitude of the electric fields with up to 85% of individuals avoiding the charged arm when the static electric field at the entrance to the arm was above 8-10 kV m(-1). Electric fields were found to cause a deflection of the antennae but when the antennae were surgically ablated, the ability of cockroaches to avoid electric fields was abolished. Fixation of various joints of the antennae indicated that hair plate sensory receptors at the base of the scape were primarily responsible for the detection of electric fields, and when antennal movements about the head-scape joint were prevented cockroaches failed to avoid electric fields. To overcome the technical problem of not being able to carry out electrophysiological analysis in the presence of electric fields, we developed a procedure using magnetic fields combined with the application of iron particles to the antennae to deflect the antennae and analyse the role of thoracic interneurones in signalling this deflection. The avoidance of electric fields in the context of high voltage power lines is discussed.

  9. IEMDC-IN-LINE ELECTRIC MOTOR DRIVEN COMPRESSOR

    SciTech Connect

    Michael J. Crowley; Prem N. Bansal; John E. Tessaro

    2003-06-01

    During this reporting period, significant progress has been made towards the development of the IEMDC System design. Considerable effort was put forth by Curtiss-Wright EMD in the resolution of the technical issue of aerodynamically induced radial forces. This has provided a design basis with which to establish the radial magnetic bearing load capacity and the rotordynamic design. Dresser-Rand has made considerable progress on the flowpath design for the compressor section particularly on the volute and inlet aerodynamic design. All efforts show progression towards the successful integration of a centrifugal compressor and variable speed electric motor ventilated by the process gas. These efforts continue to confirm the feasibility of the IEMDC system design.

  10. Submerged electricity generation plane with marine current-driven motors

    DOEpatents

    Dehlsen, James G.P.; Dehlsen, James B.; Fleming, Alexander

    2014-07-01

    An underwater apparatus for generating electric power from ocean currents and deep water tides. A submersible platform including two or more power pods, each having a rotor with fixed-pitch blades, with drivetrains housed in pressure vessels that are connected by a transverse structure providing buoyancy, which can be a wing depressor, hydrofoil, truss, or faired tube. The platform is connected to anchors on the seafloor by forward mooring lines and a vertical mooring line that restricts the depth of the device in the water column. The platform operates using passive, rather than active, depth control. The wing depressor, along with rotor drag loads, ensures the platform seeks the desired operational current velocity. The rotors are directly coupled to a hydraulic pump that drives at least one constant-speed hydraulic-motor generator set and enables hydraulic braking. A fluidic bearing decouples non-torque rotor loads to the main shaft driving the hydraulic pumps.

  11. Electrically driven light emission from individual CdSe nanowires.

    PubMed

    Doh, Yong-Joo; Maher, Kristin N; Ouyang, Lian; Yu, Chun L; Park, Hongkun; Park, Jiwoong

    2008-12-01

    We report electroluminescence (EL) measurements carried out on three-terminal devices incorporating individual n-type CdSe nanowires. Simultaneous optical and electrical measurements reveal that EL occurs near the contact between the nanowire and a positively biased electrode or drain. The surface potential profile, obtained by using Kelvin probe microscopy, shows an abrupt potential drop near the position of the EL spot, while the band profile obtained from scanning photocurrent microscopy indicates the existence of an n-type Schottky barrier at the interface. These observations indicate that light emission occurs through a hole leakage or an inelastic scattering induced by the rapid potential drop at the nanowire-electrode interface.

  12. A new probe for measuring small electric fields in plasmas

    NASA Technical Reports Server (NTRS)

    Stenzel, R. L.

    1991-01-01

    A dipolar double probe has been developed for in situ measurements of small electric fields in laboratory plasmas. The probe measures dc to ac electric fields (f values between 0 and 20 MHz) with high sensitivity (Emin about 10 microV/cm) and responds to both space charge electric fields and inductive electric fields. Using voltage-to-frequency conversion, the probe signal is obtained free of errors and loading effects by a transmission line. Various examples of useful applications for the new probe are presented, such as measurements of dc ambipolar fields, ac space-charge fields of ion acoustic waves, ac inductive fields of whistler waves, and mixed inductive and space-charge electric fields in current-carrying magnetoplasmas.

  13. Studying electric field enhancement factor of the nanostructured emission surface

    NASA Astrophysics Data System (ADS)

    Zartdinov, A. N.; Nikiforov, K. A.

    2016-08-01

    Mathematical model of nanostructured field emission surface is proposed. In order to determine geometrical parameters of the surface structure digital processing of scanning electron microscopy images was used. Effective value of local electrical field enhancement factor is defined and calculated within the Fowler-Nordheim theory. It was found effective enhancement factor decreases as the applied electrical field increases for a fixed geometry.

  14. Spiking patterns of a hippocampus model in electric fields

    NASA Astrophysics Data System (ADS)

    Men, Cong; Wang, Jiang; Qin, Ying-Mei; Wei, Xi-Le; Che, Yan-Qiu; Deng, Bin

    2011-12-01

    We develop a model of CA3 neurons embedded in a resistive array to mimic the effects of electric fields from a new perspective. Effects of DC and sinusoidal electric fields on firing patterns in CA3 neurons are investigated in this study. The firing patterns can be switched from no firing pattern to burst or from burst to fast periodic firing pattern with the increase of DC electric field intensity. It is also found that the firing activities are sensitive to the frequency and amplitude of the sinusoidal electric field. Different phase-locking states and chaotic firing regions are observed in the parameter space of frequency and amplitude. These findings are qualitatively in accordance with the results of relevant experimental and numerical studies. It is implied that the external or endogenous electric field can modulate the neural code in the brain. Furthermore, it is helpful to develop control strategies based on electric fields to control neural diseases such as epilepsy.

  15. Lattice vacancies in silicon film exposed to external electric field

    NASA Astrophysics Data System (ADS)

    Mao, Yuliang; Caliste, Damien; Pochet, Pascal

    2013-07-01

    Density functional calculations based on wavelet basis set are performed to investigate the structure, internal electric-charge distribution, and formation energy of lattice vacancies in silicon film under electric fields. It was found that the formation energies of vacancies both in JT⊥ (Jahn-Teller distortion orthogonal to electric field) and JT‖ (Jahn-Teller distortion parallel to electric field) distortions are decreased with the increasing of field strength, due to the charge polarization in the whole space of silicon film. For the split vacancy, it can lower its energy by moving further away from the split space to form a tetragonal JT⊥ vacancy under electric field. Our results also demonstrate the importance of the potential fluctuations induced by the electric fields on the charge redistribution within the vacancy defects.

  16. Electrically driven biofouling release of a poly(tetrafluoroethylene) membrane modified with an electrically induced reversibly cross-linked polymer.

    PubMed

    Chuo, Tsai-Wei; Wei, Ta-Chin; Chang, Yung; Liu, Ying-Ling

    2013-10-23

    Electrically induced reversible reactions between ferrocene (Fc) and β-cyclodextrin (β-CD) groups have been utilized for preparation of poly(tetrafluoroethylene) (PTFE) membranes exhibiting electrically driven biofouling release properties. PTFE membrane is surface-modified with polymer chains possessing Fc pendant groups. The surface layer is then cross-linked with a difunctional β-CD compound by means of the Fc/β-CD complexation reaction. The electrically induced reversibly cross-linking and de-cross-linking behaviors of the surface layer of the modified PTFE membrane have been characterized with Fourier transform Infrared, X-ray photoelectron spectroscopy, and scanning electron microscopy. The surface-modified PTFE membrane has been fouled with protein absorption. Electrical treatment of the fouled membrane results in a protein detachment from the membrane surface driven by the surface structure change accompanied with the electrically induced de-cross-linking reaction of the Fc/β-CD linkages. A smart membrane exhibiting a novel cleaning technology for membrane fouling has been developed.

  17. Introduction to extremely-low-frequency electric and magnetic fields

    SciTech Connect

    Tenforde, T.S.

    1989-07-01

    The interaction with living systems of electromagnetic fields in the extremely-low-frequency (ELF) range below 300 Hz will be summarized briefly in this paper. In materials with the electrical and magnetic properties of living tissues, these fields have a long wavelength (5000 m) and skin depth (150 m). As a consequence, in their interactions with humans and other living organisms ELF fields behave as though they are composed of independent electric and magnetic components of an ELF field is commonly referred to as the quasi-static approximation,'' which permits the radiating properties of the field to be neglected in describing its interaction with living organisms. The electric and magnetic components of an ELF field have several distinctly different features in their interactions with humans and other living organisms. First, the electrical conductivity of tissue is approximately 14 to 15 orders of magnitude greater than that of air at ELF electric fields. Consequently, the body behaves like a good electrical conductor in ELF electric fields. As a result, an electrical charge is developed on the surface of a living object in an external ELF field, but the electric field penetrates into the body only to a very limited extent.

  18. Comparison Of Lightning Data From Electric Field Change And Electric Field Derivative Antennas

    NASA Astrophysics Data System (ADS)

    Bandara, S. A.; Marshall, T. C.; Karunarathne, S.; Karunarathne, N. D.; Siedlecki, R.; Stolzenburg, M.

    2016-12-01

    During the summer of 2016, we deployed an array of E-change sensors and electric field derivative sensors (dE/dt) in and around Oxford, Mississippi, USA. We use both E-change and dE/dt waveforms to determine the time-of-arrival locations of fast lightning events like initial breakdown pulses, narrow bipolar pulses, stepped leader pulses, and return strokes. The locations from two systems will be compared for each pulse category. Further, the pulses from dE/dt antennas will be digitally integrated and compared with the data from E-change sensors. We will discuss capabilities, advantages, and disadvantages of dE/dt waveforms over electric field change waveforms.

  19. Strong Peak Electric Field in Streamer Discharges Caused by Rapid Changes in the External Electric Field

    NASA Astrophysics Data System (ADS)

    Ihaddadene, K. M. A.; Celestin, S. J.

    2015-12-01

    Laboratory spark discharges in air and lightning stepped leaders produce X-rays [e.g., Dwyer et al., GRL, 32, L20809, 2005; Nguyen et al., J. Phys. D: Appl. Phys., 41, 234012, 2008; Rahman et al., GRL, 35, L06805, 2008; March and Montanyà, GRL, 37, L19801, 2010; 38, L04803, 2011; Kochkin et al., J. Phys. D: Appl., 45, 425202, 2012; 48, 025205, 2015]. However, the processes behind the production of these X-rays are still not fully understood. Recently, the encounter between negative and positive streamers has been suggested as a plausible mechanism for the production of X-rays by spark discharges [Cooray et al., JASTP, 71, 1890, 2009; Kochkin et al., J. Phys. D: Appl. Phys., 45, 425202, 2012], but the increase of the electric field involved in this process is accompanied by a strong increase of the conductivity, which in turn makes this electric field collapse over a few tens of picoseconds, preventing the production of significant X-ray emissions [Ihaddadene and Celestin, GRL, 45, 5644, 2015]. Moreover, it has been reported that X-ray emission in laboratory spark discharges is influenced by the time derivative of the applied voltage [March and Montanya, GRL, 37, L19801, 2010]. Additionally, Celestin and Pasko [JGR, 116, A03315, 2011, Section 3.3] have indicated that quickly increasing applied voltages had an impact on peak electric fields in streamer numerical models. In this work, we simulate numerically the effect of impulsive applied electric fields on the dynamics of streamer discharges in air at ground level and investigate conditions under which production of thermal runaway electrons and the associated X-rays is possible.

  20. Microscopic mechanism on coalescence of the nano-droplets in present non-uniform electric field by molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Chen, Qicheng; Ma, Jie; Wang, Bingbing; Zhang, Yingjin

    2016-11-01

    Molecular dynamics simulations are performed to investigate the nano-droplets coalescence process in a non-uniform electric field. Coalescence of droplets driven by dielectrophoresis (DEP) could be observed clearly in a strong electric field. The efficiency of coalescence is remarkably improved about 2 times for non-uniform electric field as much as the efficiency for the uniform electric field. Increasing the gradient of the field, it is found that the DEP force will accelerate the droplets motion of coalescence. But when the gradient of the field increases to a certain degree, the DEP force acting on the droplets presents strongly and rapidly nonlinear increasing and induces the droplets forming the chain structure due to intensively elongating. Moreover, the average operating voltages is much lower in non-uniform electric field.

  1. Higgs mode in electric-field-induced superconductors

    NASA Astrophysics Data System (ADS)

    Koyama, Tomio

    2014-08-01

    We develop a theory for the Higgs (gap-amplitude) mode excitation in electric-field-induced (EFI) superconductors. The Higgs mode can be excited directly by an oscillating electric field in EFI superconductors since the gap value depends sensitively on the external electric field that induces superconducting carriers. The mass of the Higgs mode in EFI superconductors does not coincide with the threshold energy of pair-breaking two-particle excitations.

  2. Polarization tensor of a photon in an electric field

    NASA Astrophysics Data System (ADS)

    Katkov, V. M.

    2017-07-01

    The polarization operator is investigated at arbitrary photon energy in a constant and homogeneous electric field of the strength E. When the photon energy is less than the vacuum energy = eEℏ / mc , the found probability describes the absorption of a soft photon by virtual electron and positron in an electric field. At this energy, the main contribution to the probability gives the process of the absorption of a soft photon by real electron and positron produced by an electric field.

  3. Electric field induced bacterial flocculation of Enteroaggregative Escherichia coli 042

    SciTech Connect

    Kumar, Aloke; Mortensen, Ninell P; Mukherjee, Partha P; Retterer, Scott T; Doktycz, Mitchel John

    2011-01-01

    A response of the aggregation dynamics of enteroaggregative Escherichia coli under low magnitude steady and oscillating electric fields is presented. The presence of uniform electric fields hampered microbial adhesion and biofilm formation on a transverse glass surface, but instead promoted the formation of flocs. Extremely heterogeneous distribution of live and dead cells was observed among the flocs. Moreover, floc formation was largely observed to be independent of the frequency of alternating electric fields.

  4. Ultrafast terahertz-field-driven ionic response in ferroelectric BaTiO3

    DOE PAGES

    Chen, F.; Zhu, Y.; Liu, S.; ...

    2016-11-22

    The dynamical processes associated with electric field manipulation of the polarization in a ferroelectric remain largely unknown but fundamentally determine the speed and functionality of ferroelectric materials and devices. Here in this paper we apply subpicosecond duration, single-cycle terahertz pulses as an ultrafast electric field bias to prototypical BaTiO3 ferroelectric thin films with the atomic-scale response probed by femtosecond x-ray-scattering techniques. We show that electric fields applied perpendicular to the ferroelectric polarization drive large-amplitude displacements of the titanium atoms along the ferroelectric polarization axis, comparable to that of the built-in displacements associated with the intrinsic polarization and incoherent across unitmore » cells. This effect is associated with a dynamic rotation of the ferroelectric polarization switching on and then off on picosecond time scales. These transient polarization modulations are followed by long-lived vibrational heating effects driven by resonant excitation of the ferroelectric soft mode, as reflected in changes in the c-axis tetragonality. The ultrafast structural characterization described here enables a direct comparison with first-principles-based molecular-dynamics simulations, with good agreement obtained.« less

  5. Ordering in linear multipolar colloids driven by an external field.

    PubMed

    Alarcón-Waess, O

    2006-08-14

    An approach to describe a linear multipolar colloid driven by an external field is developed by considering a colloid which in absence of the field is low structured and its coupling potential is axially symmetric. The equilibrium correlation of one component of the orientation tensor, self and collective, is computed up to linear order in density, which can be measured in an appropriate light scattering experiment. The self-correlation is written in terms of the second and fourth order parameters. All the equilibrium quantities are computed up to two-body level. This is done by assuming that the two-body equilibrium density function is given by the Boltzmann distribution, whereas the one-body density function is computed as solution of the equilibrium N-body Smoluchowski equation in the absence of hydrodynamic interactions. These observables, self and collective, as well as the second and fourth order parameters are able to describe when the colloid would evolve to an orientationally ordered phase. Explicit results for the dipole and quadrupole moments are reported. These results predict a different alignment with the external field for each moment. A relationship is provided between second and fourth order parameters, predicting the critical value of the external field in which the colloid goes into an axially symmetric phase.

  6. Electric field-controlled rippling of graphene

    NASA Astrophysics Data System (ADS)

    Osváth, Zoltán; Lefloch, François; Bouchiat, Vincent; Chapelier, Claude

    2013-10-01

    Metal-graphene interfaces generated by electrode deposition induce barriers or potential modulations influencing the electronic transport properties of graphene based devices. However, their impact on the local mechanical properties of graphene is much less studied. Here we show that graphene near a metallic interface can exhibit a set of ripples self-organized into domains whose topographic roughness is controlled by the tip bias of a scanning tunneling microscope. The reconstruction from topographic images of graphene bending energy maps sheds light on the local electro-mechanical response of graphene under STM imaging and unveils the role of the stress induced by the vicinity of the graphene-metal interface in the formation and the manipulation of these ripples. Since microscopic rippling is one of the important factors that limit charge carrier mobility in graphene, the control of rippling with a gate voltage may have important consequences in the conductance of graphene devices where transverse electric fields are created by contactless suspended gate electrodes. This opens up also the possibility to dynamically control the local morphology of graphene nanomembranes.Metal-graphene interfaces generated by electrode deposition induce barriers or potential modulations influencing the electronic transport properties of graphene based devices. However, their impact on the local mechanical properties of graphene is much less studied. Here we show that graphene near a metallic interface can exhibit a set of ripples self-organized into domains whose topographic roughness is controlled by the tip bias of a scanning tunneling microscope. The reconstruction from topographic images of graphene bending energy maps sheds light on the local electro-mechanical response of graphene under STM imaging and unveils the role of the stress induced by the vicinity of the graphene-metal interface in the formation and the manipulation of these ripples. Since microscopic rippling is one

  7. Linear electric field time-of-flight ion mass spectrometer

    DOEpatents

    Funsten, Herbert O.; Feldman, William C.

    2008-06-10

    A linear electric field ion mass spectrometer having an evacuated enclosure with means for generating a linear electric field located in the evacuated enclosure and means for injecting a sample material into the linear electric field. A source of pulsed ionizing radiation injects ionizing radiation into the linear electric field to ionize atoms or molecules of the sample material, and timing means determine the time elapsed between ionization of atoms or molecules and arrival of an ion out of the ionized atoms or molecules at a predetermined position.

  8. Electric field effects on electronic characteristics of arsenene nanoribbons

    NASA Astrophysics Data System (ADS)

    Luo, Yanwei; Li, Yuxiao; Wang, Fei; Guo, Peng; Jia, Yu

    2017-10-01

    By using the first-principles calculations, we investigate the effects of electric field on electronic structures of armchair and zigzag arsenene nanoribbons (AsNRs) with different widths. The results show that for each case, quantum size effects induce a smaller band gap in larger AsNRs. Moreover, electric field can reduce effectively the band gap of AsNRs. In addition, the electric field can induce only the transition of band structures in the A-AsNRs or Z-AsNRs with narrow size. The band gap decrease more rapidly and the threshold electric field induced metal becomes smaller in the wider AsNRs.

  9. Double-sensor method for detection of oscillating electric field.

    PubMed

    Ohkuma, Yasunori; Ikeyama, Taeko; Nogi, Yasuyuki

    2011-04-01

    An electric-field sensor consisting of thin copper plates is designed to measure an oscillating electric field produced by charge separations on a plasma column. The sensor installed in a vacuum region around plasma detects charges induced by the electric field on the copper plates. The value of the induced charges depends not only on the strength of the electric field, but also on the design of the sensor. To obtain the correct strength of the electric field, a correction factor arising from the design of the sensor must be known. The factor is calculated numerically using Laplace's equation and compared with a value measured using a uniform electric field in the frequency range of 10-500 kHz. When an external circuit is connected to the sensor to measure the induced charges, the electric field around the sensor is disturbed. Therefore, a double-sensor method for excluding a disturbed component in the measured electric field is proposed. The reliability of the double-sensor method is confirmed by measuring dipole-like and quadrupole-like electric fields. © 2011 American Institute of Physics

  10. Spectral studies of the sources of ionospheric electric fields

    NASA Technical Reports Server (NTRS)

    Earle, G. D.; Kelley, M. C.

    1987-01-01

    Spectral analyses (applying the Fourier analysis methods) were performed on three incoherent scatter radar data sets (obtained at Jicamarca, Peru; Chatanika, Alaska; and Arecibo, Puerto Rico) with the aim of investigating the origin of ionospheric electric fields in the frequency range of 0.01-2 cycles/h. In quiet times, atmospheric gravity waves appeared to be the most likely source of the ionospheric electric field. This hypothesis was tested by a direct simultaneous comparison of measurements of gravity waves in the mesosphere and of electric fields in the thermosphere during very quiet conditions. The results indicated that a gravity wave source is a plausible candidate for the electric field fluctuations.

  11. Measuring electric fields from surface contaminants with neutral atoms

    SciTech Connect

    Obrecht, J. M.; Wild, R. J.; Cornell, E. A.

    2007-06-15

    In this paper we demonstrate a technique of utilizing magnetically trapped neutral {sup 87}Rb atoms to measure the magnitude and direction of stray electric fields emanating from surface contaminants. We apply an alternating external electric field that adds to (or subtracts from) the stray field in such a way as to resonantly drive the trapped atoms into a mechanical dipole oscillation. The growth rate of the oscillation's amplitude provides information about the magnitude and sign of the stray field gradient. Using this measurement technique, we are able to reconstruct the vector electric field produced by surface contaminants. In addition, we can accurately measure the electric fields generated from adsorbed atoms purposely placed onto the surface and account for their systematic effects, which can plague a precision surface-force measurement. We show that baking the substrate can reduce the electric fields emanating from adsorbate and that the mechanism for reduction is likely surface diffusion, not desorption.

  12. Extracting nucleon magnetic moments and electric polarizabilities from lattice QCD in background electric fields

    SciTech Connect

    Detmold, W.; Tiburzi, B. C.; Walker-Loud, A.

    2010-03-01

    Nucleon properties are investigated in background electric fields. As the magnetic moments of baryons affect their relativistic propagation in constant electric fields, electric polarizabilities cannot be determined without knowledge of magnetic moments. This is analogous to the experimental situation, for which determination of polarizabilities from the Compton amplitude requires subtraction of Born terms. With the background field method, we devise combinations of nucleon correlation functions in constant electric fields that isolate magnetic moments and electric polarizabilities. Using an ensemble of anisotropic gauge configurations with dynamical clover fermions, we demonstrate how both observables can be determined from lattice QCD simulations in background electric fields. We obtain results for the neutron and proton, however, our study is currently limited to electrically neutral sea quarks. The value we extract for the nucleon isovector magnetic moment is comparable to those obtained from measuring lattice three-point functions at similar pion masses.

  13. Focus on the electrical field-induced strain of electroactive polymers and the observed saturation

    NASA Astrophysics Data System (ADS)

    Guyomar, D.; Yuse, K.; Cottinet, P.-J.; Kanda, M.; Lebrun, L.

    2010-12-01

    Thanks to their large electrical field-induced strains, electroactive polymers can be used in various applications; as electroactive materials for artificial muscles or as active materials of membranes, due to their flexibility. One drawback concerning their use involves the saturation of the electrical field-induced strain which occurs at around 20% for a polymer film with a thickness of 80 μm. Few studies have been devoted to the understanding of this saturation. To this end, the present paper describes mechanical measurements of the extensive strain versus stress and the determination of the current flowing through an electroactive polymer driven by an electrical field. These experiments have clearly demonstrated that the observed saturation of the electrical induced strain was not due to a mechanical saturation within the sample but to the saturation of the electrically induced polarization. By carrying out a suitable modeling of the polarization versus electrical field, it was possible to calculate the strain and current versus electrical field. These values were then compared to experimental data, and were found to show a very good agreement.

  14. Electrically driven magnetization dynamics in yttrium iron garnet

    NASA Astrophysics Data System (ADS)

    Jungfleisch, Matthias Benjamin

    Creation and manipulation of magnetization states by spin-orbital torques are important for novel spintronics applications. Magnetic insulators were mostly ignored for this particular purpose, despite their low Gilbert damping, which makes them outstanding materials for magnonic applications and investigation of nonlinear spin-wave phenomena. Here, we demonstrate the propagation of spin-wave modes in micro-structured yttrium iron garnet (Y3Fe5O12,YIG) stripes. Spin waves propagating along the long side of the stripe are detected by means of spatially-resolved Brillouin light scattering (BLS) microscopy. The propagation distance of spin waves is determined in the linear regime, where an exponential decay of 10 μm is observed. We also explored the possibility of driving magnetization dynamics with spin Hall effects (SHE) in bilayers of YIG/Pt microstructures. For this purpose we adopted a spin-transfer torque ferromagnetic resonance (ST-FMR) approach. Here a rf charge current is passed through the Pt layer, which generates a spin-transfer torque at the interface from an oscillating spin current via the SHE. This gives rise to a resonant excitation of the magnetization dynamics. In all metallic systems the magnetization dynamics is detected via the homodyne anisotropic magnetoresistance of the ferromagnetic layer. However, since there is no charge flowing through ferromagnetic insulators there is no anisotropic magnetoresistance. Instead, we show that for the case of YIG/Pt the spin Hall magnetoresistance can be used. Our measured voltage spectra can be well fitted to an analytical model evidencing that the ST-FMR concept can be extended to insulating systems. Furthermore, we employ spatially-resolved BLS spectroscopy to map the ST-FMR driven spin dynamics. We observe the formation of a strong, self-localized spin-wave intensity in the center of the sample. This spin-wave `bullet' is created due to nonlinear cross coupling of eigenmodes existing in the magnetic

  15. Initial Determinations of Ionospheric Electric Fields and Joule Heating from MAVEN Observations

    NASA Astrophysics Data System (ADS)

    Fillingim, M. O.; Fogle, A. L.; Aleryani, O.; Dunn, P.; Lillis, R. J.; McFadden, J. P.; Connerney, J. E. P.; Mahaffy, P. R.; Andersson, L.; Ergun, R.

    2015-12-01

    MAVEN provides in-situ measurements of the neutral and ion species as well as the magnetic field throughout the ionosphere of Mars. By combining these measurements, we are able to calculate both the ionospheric currents and the ionospheric conductivity. It is then straightforward to determine the electric field in the collisional ionosphere from a simplified Ohm's law. In addition, we can also estimate the amount of Joule heating in the ionosphere from j · E. Here, we show initial determinations of both ionospheric electric fields and Joule heating using MAVEN data. The electric fields are highly variable from orbit-to-orbit suggesting that the ionospheric electrodynamics can change on timescales of several hours. These changes may be driven by changes in the upstream solar wind and IMF or may result from dynamical variations of thermospheric neutral winds.

  16. Pulsed electric field assisted assembly of polyaniline

    NASA Astrophysics Data System (ADS)

    Kumar, Arun; Kazmer, David O.; Barry, Carol M. F.; Mead, Joey L.

    2012-08-01

    Assembling conducting polyaniline (PANi) on pre-patterned nano-structures by a high rate, commercially viable route offers an opportunity for manufacturing devices with nanoscale features. In this work we report for the first time the use of pulsed electric field to assist electrophoresis for the assembly of conducting polyaniline on gold nanowire interdigitated templates. This technique offers dynamic control over heat build-up, which has been a main drawback in the DC electrophoresis and AC dielectrophoresis as well as the main cause of nanowire template damage. The use of this technique allowed higher voltages to be applied, resulting in shorter assembly times (e.g., 17.4 s, assembly resolution of 100 nm). Moreover, the area coverage increases with the increase in number of pulses. A similar trend was observed with the deposition height and the increase in deposition height followed a linear trend with a correlation coefficient of 0.95. When the experimental mass deposited was compared with Hamaker’s theoretical model, the two were found to be very close. The pre-patterned templates with PANi deposition were subsequently used to transfer the nanoscale assembled PANi from the rigid templates to thermoplastic polyurethane using the thermoforming process.

  17. Pulsed electric field assisted assembly of polyaniline.

    PubMed

    Kumar, Arun; Kazmer, David O; Barry, Carol M F; Mead, Joey L

    2012-08-24

    Assembling conducting polyaniline (PANi) on pre-patterned nano-structures by a high rate, commercially viable route offers an opportunity for manufacturing devices with nanoscale features. In this work we report for the first time the use of pulsed electric field to assist electrophoresis for the assembly of conducting polyaniline on gold nanowire interdigitated templates. This technique offers dynamic control over heat build-up, which has been a main drawback in the DC electrophoresis and AC dielectrophoresis as well as the main cause of nanowire template damage. The use of this technique allowed higher voltages to be applied, resulting in shorter assembly times (e.g., 17.4 s, assembly resolution of 100 nm). Moreover, the area coverage increases with the increase in number of pulses. A similar trend was observed with the deposition height and the increase in deposition height followed a linear trend with a correlation coefficient of 0.95. When the experimental mass deposited was compared with Hamaker's theoretical model, the two were found to be very close. The pre-patterned templates with PANi deposition were subsequently used to transfer the nanoscale assembled PANi from the rigid templates to thermoplastic polyurethane using the thermoforming process.

  18. Electric field-controlled rippling of graphene.

    PubMed

    Osváth, Zoltán; Lefloch, François; Bouchiat, Vincent; Chapelier, Claude

    2013-11-21

    Metal-graphene interfaces generated by electrode deposition induce barriers or potential modulations influencing the electronic transport properties of graphene based devices. However, their impact on the local mechanical properties of graphene is much less studied. Here we show that graphene near a metallic interface can exhibit a set of ripples self-organized into domains whose topographic roughness is controlled by the tip bias of a scanning tunneling microscope. The reconstruction from topographic images of graphene bending energy maps sheds light on the local electro-mechanical response of graphene under STM imaging and unveils the role of the stress induced by the vicinity of the graphene-metal interface in the formation and the manipulation of these ripples. Since microscopic rippling is one of the important factors that limit charge carrier mobility in graphene, the control of rippling with a gate voltage may have important consequences in the conductance of graphene devices where transverse electric fields are created by contactless suspended gate electrodes. This opens up also the possibility to dynamically control the local morphology of graphene nanomembranes.

  19. Electric Field and Density Measurements with STEREO-SWaves.

    NASA Astrophysics Data System (ADS)

    Kellogg, P. J.; Goetz, K.; Monson, S. J.; Bale, S. D.; Maksimovic, M.

    2007-12-01

    The STEREO experiment SWaves has a low frequency part which is designed to make measurements of low frequency electric fields and rapid measurements of density fluctuations, using the three 6 meter stacer monopole antennas. The short antennas of STEREO respond both to density fluctuations and to electric fields. Therefore, it is desired to obtain four quantities, density and 3 components of electric field, from three measurements, the potentials on the three orthogonal antennas relative to the spacecraft, which requires some additional information. One possibility is to add a fourth equation implied by the large plasma conductivity, so large that electric field parallel to the magnetic field is zero, a condition which has often been used in electric field measurements. Under selected conditions, this seems to work. There are also conditions, for example ion acoustic waves, where the responses to density fluctuations and to electric fields are available from dispersion relations, and this provides another possible solution. A situation where it is not likely that the parallel electric field is zero is the case of solitary, intense bursts of Langmuir waves. For this case, it is expected that there is an electron density depression due to the ponderomotive pressure, and a resulting low frequency electric field from the non-neutrality which would be expected to have components parallel to the magnetic field. Examples will be discussed.

  20. Surface electric fields for North America during historical geomagnetic storms

    USGS Publications Warehouse

    Wei, Lisa H.; Homeier, Nichole; Gannon, Jennifer L.

    2013-01-01

    To better understand the impact of geomagnetic disturbances on the electric grid, we recreate surface electric fields from two historical geomagnetic storms—the 1989 “Quebec” storm and the 2003 “Halloween” storms. Using the Spherical Elementary Current Systems method, we interpolate sparsely distributed magnetometer data across North America. We find good agreement between the measured and interpolated data, with larger RMS deviations at higher latitudes corresponding to larger magnetic field variations. The interpolated magnetic field data are combined with surface impedances for 25 unique physiographic regions from the United States Geological Survey and literature to estimate the horizontal, orthogonal surface electric fields in 1 min time steps. The induced horizontal electric field strongly depends on the local surface impedance, resulting in surprisingly strong electric field amplitudes along the Atlantic and Gulf Coast. The relative peak electric field amplitude of each physiographic region, normalized to the value in the Interior Plains region, varies by a factor of 2 for different input magnetic field time series. The order of peak electric field amplitudes (largest to smallest), however, does not depend much on the input. These results suggest that regions at lower magnetic latitudes with high ground resistivities are also at risk from the effect of geomagnetically induced currents. The historical electric field time series are useful for estimating the flow of the induced currents through long transmission lines to study power flow and grid stability during geomagnetic disturbances.

  1. Surface electric fields for North America during historical geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Wei, Lisa H.; Homeier, Nicole; Gannon, Jennifer L.

    2013-08-01

    To better understand the impact of geomagnetic disturbances on the electric grid, we recreate surface electric fields from two historical geomagnetic storms—the 1989 "Quebec" storm and the 2003 "Halloween" storms. Using the Spherical Elementary Current Systems method, we interpolate sparsely distributed magnetometer data across North America. We find good agreement between the measured and interpolated data, with larger RMS deviations at higher latitudes corresponding to larger magnetic field variations. The interpolated magnetic field data are combined with surface impedances for 25 unique physiographic regions from the United States Geological Survey and literature to estimate the horizontal, orthogonal surface electric fields in 1 min time steps. The induced horizontal electric field strongly depends on the local surface impedance, resulting in surprisingly strong electric field amplitudes along the Atlantic and Gulf Coast. The relative peak electric field amplitude of each physiographic region, normalized to the value in the Interior Plains region, varies by a factor of 2 for different input magnetic field time series. The order of peak electric field amplitudes (largest to smallest), however, does not depend much on the input. These results suggest that regions at lower magnetic latitudes with high ground resistivities are also at risk from the effect of geomagnetically induced currents. The historical electric field time series are useful for estimating the flow of the induced currents through long transmission lines to study power flow and grid stability during geomagnetic disturbances.

  2. Microbial ecology meets electrochemistry: electricity-driven and driving communities.

    PubMed

    Rabaey, Korneel; Rodríguez, Jorge; Blackall, Linda L; Keller, Jurg; Gross, Pamela; Batstone, Damien; Verstraete, Willy; Nealson, Kenneth H

    2007-05-01

    Bio-electrochemical systems (BESs) have recently emerged as an exciting technology. In a BES, bacteria interact with electrodes using electrons, which are either removed or supplied through an electrical circuit. The most-described type of BES is microbial fuel cells (MFCs), in which useful power is generated from electron donors as, for example, present in wastewater. This form of charge transport, known as extracellular electron transfer, was previously extensively described with respect to metals such as iron and manganese. The importance of these interactions in global biogeochemical cycles is essentially undisputed. A wide variety of bacteria can participate in extracellular electron transfer, and this phenomenon is far more widespread than previously thought. The use of BESs in diverse research projects is helping elucidate the mechanism by which bacteria shuttle electrons externally. New forms of interactions between bacteria have been discovered demonstrating how multiple populations within microbial communities can co-operate to achieve energy generation. New environmental processes that were difficult to observe or study previously can now be simulated and improved via BESs. Whereas pure culture studies make up the majority of the studies performed thus far, even greater contributions of BESs are expected to occur in natural environments and with mixed microbial communities. Owing to their versatility, unmatched level of control and capacity to sustain novel processes, BESs might well serve as the foundation of a new environmental biotechnology. While highlighting some of the major breakthroughs and addressing only recently obtained data, this review points out that despite rapid progress, many questions remain unanswered.

  3. Standard and nonstandard nematic electrohydrodynamic convection in the presence of asymmetric ac electric fields.

    PubMed

    Low, Jonathan; Hogan, S John

    2008-10-01

    In planar nematic electrohydrodynamic convection (EHC), a microscopic liquid crystal cell is driven by a homogeneous ac electric field, which, if strong enough, causes the fluid to destabilize into a regular pattern-forming state. We consider asymmetric electric fields E(t)=E(t+T) not equal-E(t+T2) , which leads to the possibility of three different types of instabilities at onset: conductive, dielectric, and subharmonic. The first two are already well known as they are easily produced when the system is driven by symmetric electric fields; the third can only occur when the electric field symmetry is broken. We present theoretical results on EHC using linear stability analysis and Floquet theory. We consider rigid and free boundary conditions, extending the model to two Fourier modes in the vertical plane, the inclusion of flexoelectricity, and using standard (nematic electric conductivity sigma_{a}>0 and dielectric anisotorpy _{a}<0 ) and nonstandard (sigma_{a}<0) material parameters. We make full use of a three-dimensional linear model where two mutually perpendicular planar wave numbers q and p can be varied. Our results show that there is a qualitative difference between the boundary conditions used, which is also dependent on how many vertical Fourier modes were used in the model. We have obtained threshold values favoring oblique rolls in subharmonic and dielectric regimes in parameter space. For the nonstandard EHC parameter values, both conduction and subharmonic regimes disappear and only the dielectric threshold exists.

  4. Properties of a field emission-driven Townsend discharge

    NASA Astrophysics Data System (ADS)

    Rumbach, Paul; Go, David

    2012-10-01

    For half a century, it has been known that the onset of field emission in direct current (DC) microplasmas with gap sizes less than 10 μm can lead to breakdown at applied voltages far less than predicted by Paschen's law. It is still unclear how field emission affects other fundamental plasma properties at this scale. In this work, a one-dimensional fluid model is used to predict basic scaling laws for fundamental properties such as ion density, electric field due to space charge, and current voltage relations in the pre-breakdown regime. Computational results are compared with approximate analytic solutions. It is shown that ionizing collisions by field-emitted electrons produce significant ion densities well before Paschen's criteria for breakdown is met. When positive space charge densities become sufficiently large, the effect of ion-enhanced field emission leads to breakdown. Defining breakdown mathematically using a solvability condition leads to a full modified Paschen's curve, while defining it physically in terms of a critical ion density leads analytically to an effective secondary emission coefficient, γ', of the form initially suggested by Boyle and Kisliuk.footnotetextBoyle, W.S. and Kisliuk, P., Phys. Rev. 97, 255 (1955).

  5. Laboratory observation of magnetic field growth driven by shear flow

    NASA Astrophysics Data System (ADS)

    Intrator, T. P.; Dorf, L.; Sun, X.; Feng, Y.; Sears, J.; Weber, T.

    2014-04-01

    Two magnetic flux ropes that collide and bounce have been characterized in the laboratory. We find screw pinch profiles that include ion flow vi, magnetic field B, current density J, and plasma pressure. The electron flow ve can be inferred, allowing the evaluation of the Hall J ×B term in a two fluid magnetohydrodynamic Ohm's Law. Flux ropes that are initially cylindrical are mutually attracted and compress each other, which distorts the cylindrical symmetry. Magnetic field is created via the ∇×ve×B induction term in Ohm's Law where in-plane (perpendicular) shear of parallel flow (along the flux rope) is the dominant feature, along with some dissipation and magnetic reconnection. We predict and measure the growth of a quadrupole out-of-plane magnetic field δBz. This is a simple and coherent example of a shear flow driven dynamo. There is some similarity with two dimensional reconnection scenarios, which induce a current sheet and thus out-of-plane flow in the third dimension, despite the customary picture that considers flows only in the reconnection plane. These data illustrate a general and deterministic mechanism for large scale sheared flows to acquire smaller scale magnetic features, disordered structure, and possibly turbulence.

  6. Laboratory observation of magnetic field growth driven by shear flow

    SciTech Connect

    Intrator, T. P. Feng, Y.; Sears, J.; Weber, T.; Dorf, L.; Sun, X.

    2014-04-15

    Two magnetic flux ropes that collide and bounce have been characterized in the laboratory. We find screw pinch profiles that include ion flow v{sub i}, magnetic field B, current density J, and plasma pressure. The electron flow v{sub e} can be inferred, allowing the evaluation of the Hall J×B term in a two fluid magnetohydrodynamic Ohm's Law. Flux ropes that are initially cylindrical are mutually attracted and compress each other, which distorts the cylindrical symmetry. Magnetic field is created via the ∇×v{sub e}×B induction term in Ohm's Law where in-plane (perpendicular) shear of parallel flow (along the flux rope) is the dominant feature, along with some dissipation and magnetic reconnection. We predict and measure the growth of a quadrupole out-of-plane magnetic field δB{sub z}. This is a simple and coherent example of a shear flow driven dynamo. There is some similarity with two dimensional reconnection scenarios, which induce a current sheet and thus out-of-plane flow in the third dimension, despite the customary picture that considers flows only in the reconnection plane. These data illustrate a general and deterministic mechanism for large scale sheared flows to acquire smaller scale magnetic features, disordered structure, and possibly turbulence.

  7. Plasma rotation driven by static nonresonant magnetic fields

    SciTech Connect

    Garofalo, A. M.; Burrell, K. H.; DeBoo, J. C.; DeGrassie, J. S.; Jackson, G. L.; Schaffer, M. J.; Strait, E. J.; Solomon, W. M.; Park, J.-K.; Lanctot, M.; Reimerdes, H.

    2009-05-15

    Recent experiments in high temperature DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 64 (2002)] plasmas reported the first observation of plasma acceleration driven by the application of static nonresonant magnetic fields (NRMFs), with resulting improvement in the global energy confinement time. Although the braking effect of static magnetic field asymmetries is well known, recent theory [A. J. Cole et al., Phys. Rev. Lett. 99, 065001 (2007)] predicts that in some circumstances they lead instead to an increase in rotation frequency toward a 'neoclassical offset' rate in a direction opposed to the plasma current. We report the first experimental confirmation of this surprising result. The measured NRMF torque shows a strong dependence on both plasma density and temperature, above expectations from neoclassical theory. The consistency between theory and experiment improves with modifications to the expression of the NRMF torque accounting for a significant role of the plasma response to the external field and for the beta dependence of the plasma response, although some discrepancy remains. The magnitude and direction of the observed offset rotation associated with the NRMF torque are consistent with neoclassical theory predictions. The offset rotation rate is about 1% of the Alfven frequency or more than double the rotation needed for stable operation at high {beta}{sub N} above the n=1 no-wall kink limit in DIII-D.

  8. IEMDC -IN-LINE ELECTRIC MOTOR DRIVEN COMPRESSOR

    SciTech Connect

    Michael J. Crowley; Prem N. Bansal; John E. Tessaro

    2004-01-01

    Dresser-Rand completed the preliminary aerodynamic flowpath of the volute and inlet design for the compressor section. This has resulted in considerable progress being made on the development of the compressor section and ultimately towards the successful integration of the IEMDC System design. Significant effort was put forth in the design of aerodynamic components which resulted in a design that meets the limits of aerodynamically induced radial forces previously established. Substantial effort has begun on the mechanical design of the compressor pressure containing case and other internal components. These efforts show progression towards the successful integration of a centrifugal compressor and variable speed electric motor ventilated by the process gas. All efforts continue to confirm the feasibility of the IEMDC system design. During the third quarter reporting period, the focus was to further refine the motor design and to ensure that the IEMDC rotor system supported on magnetic bearing is in compliance with the critical speed and vibration requirements of the API standards 617 and 541. Consequently specification to design magnetic bearings was developed and an RFQ to three magnetic bearing suppliers was issued. Considerable work was also performed to complete preliminary reports on some of the deliverable tasks under phase 1.0. These include specification for the VFD, RFQ for the magnetic bearings, and preliminary write-up for motor instrumentation and control schematic. In order to estimate motor efficiency at various operating points, plots of calculated motor losses, and motor cooling gas flow rates were also prepared. Preliminary evaluations of motor support concepts were performed via FEA to determine modal frequencies. Presentation was made at DOE Morgantown on August 12, 2003 to provide project status update. Preparations for the IEMDC motor-compressor presentation, at the GMRC conference in Salt Lake City to be held on October 5, 2003, were also

  9. Time dependent response of equatorial ionospheric electric fields to magnetospheric disturbances

    SciTech Connect

    Fejer, B.G.; Scherliess, L.

    1995-04-01

    The authors use extensive radar measurements of F region vertical plasma drifts and auroral electrojet indices to determine the storm time dependence of equatorial zonal electric fields. These disturbance drifts result from the prompt penetration of high latitude electric fields and from the dynamo action of storm time winds which produce the largest perturbations a few hours after the onset of magnetic activity. The signatures of the equatorial disturbance electric fields change significantly depending on the relative contributions of these two components. The prompt electric field responses, with lifetimes of about one hour, are in excellent agreement with results from global convection models. The electric fields generated by storm time winds have longer lifetimes, amplitudes proportional to the energy input into the high latitude ionosphere, and a daily variation which follows closely the disturbance dynamo pattern of Blanc and Richmond. The storm wind driven electric fields are responsible for the larger amplitudes and longer lifetimes of the drift perturbations following sudden decreases in convection compared to those associated with sudden convection enhancements. 14 refs., 6 figs., 1 tab.

  10. Temperature Modulation of Electric Fields in Biological Matter

    PubMed Central

    Daniels, Charlotte S.; Rubinsky, Boris

    2011-01-01

    Pulsed electric fields (PEF) have become an important minimally invasive surgical technology for various applications including genetic engineering, electrochemotherapy and tissue ablation. This study explores the hypothesis that temperature dependent electrical parameters of tissue can be used to modulate the outcome of PEF protocols, providing a new means for controlling and optimizing this minimally invasive surgical procedure. This study investigates two different applications of cooling temperatures applied during PEF. The first case utilizes an electrode which simultaneously delivers pulsed electric fields and cooling temperatures. The subsequent results demonstrate that changes in electrical properties due to temperature produced by this configuration can substantially magnify and confine the electric fields in the cooled regions while almost eliminating electric fields in surrounding regions. This method can be used to increase precision in the PEF procedure, and eliminate muscle contractions and damage to adjacent tissues. The second configuration considered introduces a third probe that is not electrically active and only applies cooling boundary conditions. This second study demonstrates that in this probe configuration the temperature induced changes in electrical properties of tissue substantially reduce the electric fields in the cooled regions. This novel treatment can potentially be used to protect sensitive tissues from the effect of the PEF. Perhaps the most important conclusion of this investigation is that temperature is a powerful and accessible mechanism to modulate and control electric fields in biological tissues and can therefore be used to optimize and control PEF treatments. PMID:21695144

  11. High-frequency electric field measurement using a toroidal antenna

    DOEpatents

    Lee, Ki Ha

    2002-01-01

    A simple and compact method and apparatus for detecting high frequency electric fields, particularly in the frequency range of 1 MHz to 100 MHz, uses a compact toroidal antenna. For typical geophysical applications the sensor will be used to detect electric fields for a wide range of spectrum starting from about 1 MHz, in particular in the frequency range between 1 to 100 MHz, to detect small objects in the upper few meters of the ground. Time-varying magnetic fields associated with time-varying electric fields induce an emf (voltage) in a toroidal coil. The electric field at the center of (and perpendicular to the plane of) the toroid is shown to be linearly related to this induced voltage. By measuring the voltage across a toroidal coil one can easily and accurately determine the electric field.

  12. Storage of an electric field for photocurrent generation in ferroelectric-functionalized organic devices.

    PubMed

    Hu, Laigui; Dalgleish, Simon; Matsushita, Michio M; Yoshikawa, Hirofumi; Awaga, Kunio

    2014-01-01

    Organic optoelectronic devices are usually driven by the electric field generated from an electrode potential difference or bias voltage. Although poled ferroelectric domains may produce oriented stray fields, few efforts have been made to utilize them for photocurrent generation in organic devices. Here we show that large net fields caused by incomplete screening during ferroelectric polarization, and which can be 'restored' by short voltage pulses, can facilitate exciton dissociation in organic semiconductors. The oriented fields, comparable with that produced by an electrode potential difference (1~10 MV m(-1)), here are found to be responsible for the photocurrent in our devices. A prototype for an organic photodetector driven by such stray fields is demonstrated. The photoresponsivity, without any optimization, can achieve ~0.1 mA W(-1). This study provides a different operation principle for the generation of photocurrent in organic optoelectronic devices. Furthermore, the polarity-tunable photoresponse may lead to new photoresponsive memory devices.

  13. Inner Magnetospheric Electric Fields Derived from IMAGE EUV

    NASA Technical Reports Server (NTRS)

    Gallagher, D. L.; Adrian, M. L.

    2007-01-01

    The local and global patterns of plasmaspheric plasma transport reflect the influence of electric fields imposed by all sources in the inner magnetosphere. Image sequences of thermal plasma G:istribution obtained from the IMAGE Mission Extreme Ultraviolet Imager can be used to derive plasma motions and, using a magnetic field model, the corresponding electric fields. These motions and fields directly reflect the dynamic coupling of injected plasmasheet plasma and the ionosphere, in addition to solar wind and atmospheric drivers. What is being learned about the morphology of inner magnetospheric electric fields during storm and quite conditions from this new empirical tool will be presented and discussed.

  14. Nanoscale Electric Field Sensor-Development and Testing

    NASA Astrophysics Data System (ADS)

    Brame, Jon; Woods, Nathan

    2008-10-01

    The goal of this project is to test a carbon nanotube based electric field sensing device. The device consists of a miniature gold needle suspended on a mat of carbon nanotubes over a trench on a Si/Si02 substrate. Field tests were made by recording the electric field inside dust devils in a Nevada desert, and those electric fields were simulated in a lab environment. Further tests to determine the device sensitivity were performed by manually manipulating the gold needle with an Atomic Force Microscope (AFM) tip. We report on fabrication techniques, field and lab test results and AFM testing results.

  15. Simultaneous electric-field measurements on nearby balloons.

    NASA Technical Reports Server (NTRS)

    Mozer, F. S.

    1972-01-01

    Electric-field payloads were flown simultaneously on two balloons from Great Whale River, Canada, on September 21, 1971, to provide data at two points in the upper atmosphere that differed in altitude by more than one atmospheric density scale height and in horizontal position by 30-140 km. The altitude dependences in the two sets of data prove conclusively that the vertical electric field at balloon altitudes stems from fair-weather atmospheric electricity sources and that the horizontal fields are mapped down ionospheric fields, since the weather-associated horizontal fields were smaller than 2 mV/m.

  16. A thermo-electric-driven flowing liquid lithium limiter/divertor for magnetic confined fusion

    NASA Astrophysics Data System (ADS)

    Ruzic, D. N.; Xu, Wenyu; Curreli, Davide; Andruczyk, Daniel; Mui, Travis

    2012-10-01

    The concept of using a liquid metal, especially liquid lithium, as the plasma facing surface may provide the best path forward toward reactor designs. A liquid PFC can effectively eliminate the erosion and thermal stress problems compared to the solid PFC while transferring heat and prolong the lifetime limit of the PFCs. A liquid lithium surface can also suppress the hydrogen isotopes recycling and getter the impurities in fusion reactor. The Lithium/metal infused trench (LiMIT) concept successfully proved that the thermoelectric effect can induce electric currents inside liquid lithium and an external magnetic field can drive liquid lithium to flow within metallic open trenches. IR camera and thermocouple measurements prove the strong heat transfer ability of this concept. A new flowing lithium system with active control of the temperature gradient inside the lithium trenches and back flow channels has been designed. TEMHD driven liquid lithium run steady state and pulsed for a few seconds of high heat flux (˜15MW/m^2) has been used to investigate the transient reaction of the flowing lithium. A similar tray is scheduled to be tested in HT-7, Hefei, China as a limiter in Sept. 2012. Related movies and analysis will be shown.

  17. Electrically-driven spectrally-broadened random lasing based on disordered photonic crystal structures

    NASA Astrophysics Data System (ADS)

    Guo, X. J.; Wang, Y. F.; Jia, Y. F.; Zheng, W. H.

    2017-07-01

    We present the effect of radius randomness on the resonant spectrum and modal characteristics of a photonic crystal. With the introduction of randomness, different localizations were analyzed. The random pattern was then fabricated onto our lateral cavity surface emitting laser. Electrically driven random lasing was obtained with the localization and broadened spectrum, and the decrease of threshold and the increase of output power were also observed. The decreased threshold was due to the appearance of additional modes and the degree of localization. The output power reached a maximum with a random variance of 20 nm. It meant that there was a transition case in a regime ranging from Anderson localization to the local band edge resonance, and a balance between the Fabry-Perot-like effect and the random modulation effect. When the random variance reached 50 nm, the transition case in a regime ranging from localized to diffusive became remarkable. The experimental results are consistent with our theoretical analysis. One of the properties that make a random laser special with respect to regular lasers is its complex features in emission spectra, which means low spectral coherence. Our investigation on this kind of laser has referential and instructional significances for full-field imaging at visible wavelengths and other wavelengths.

  18. Reception and learning of electric fields in bees

    PubMed Central

    Greggers, Uwe; Koch, Gesche; Schmidt, Viola; Dürr, Aron; Floriou-Servou, Amalia; Piepenbrock, David; Göpfert, Martin C.; Menzel, Randolf

    2013-01-01

    Honeybees, like other insects, accumulate electric charge in flight, and when their body parts are moved or rubbed together. We report that bees emit constant and modulated electric fields when flying, landing, walking and during the waggle dance. The electric fields emitted by dancing bees consist of low- and high-frequency components. Both components induce passive antennal movements in stationary bees according to Coulomb's law. Bees learn both the constant and the modulated electric field components in the context of appetitive proboscis extension response conditioning. Using this paradigm, we identify mechanoreceptors in both joints of the antennae as sensors. Other mechanoreceptors on the bee body are potentially involved but are less sensitive. Using laser vibrometry, we show that the electrically charged flagellum is moved by constant and modulated electric fields and more strongly so if sound and electric fields interact. Recordings from axons of the Johnston organ document its sensitivity to electric field stimuli. Our analyses identify electric fields emanating from the surface charge of bees as stimuli for mechanoreceptors, and as biologically relevant stimuli, which may play a role in social communication. PMID:23536603

  19. FLARES IN THE CRAB NEBULA DRIVEN BY UNTWISTING MAGNETIC FIELDS

    SciTech Connect

    Sturrock, Peter; Aschwanden, Markus J. E-mail: aschwanden@lmsal.com

    2012-06-01

    The recent discovery of PeV electrons from the Crab Nebula, produced on rapid timescales of one day or less with a sharply peaked gamma-ray spectrum without hard X-rays, challenges traditional models of diffusive shock acceleration followed by synchrotron radiation. Here, we outline an acceleration model involving a DC electric field parallel to the magnetic field in a twisted toroidal field around the pulsar. Sudden developments of resistivity in localized regions of the twisted field are thought to drive the particle acceleration, up to PeV energies, resulting in flares. This model can reproduce the observed timescales of T Almost-Equal-To 1 day, the peak photon energies of U{sub {Phi},rr} Almost-Equal-To 1 MeV, maximum electron energies of U{sub e,rr} Almost-Equal-To 1 PeV, and luminosities of L Almost-Equal-To 10{sup 36} erg s{sup -1}.

  20. Rocket borne instrument to measure electric fields inside electrified clouds

    NASA Technical Reports Server (NTRS)

    Ruhnke, L. H. (Inventor)

    1973-01-01

    An apparatus for measuring the electric field in the atmosphere which includes a pair of sensors carried on a rocket for sensing the voltages in the atmosphere being measured is described. One of the sensors is an elongated probe with a fine point which causes a corona current to be produced as it passes through the electric field. An electric circuit is coupled between the probe and the other sensor and includes a high ohm resistor which linearizes the relationship between the corona current and the electric field being measured. A relaxation oscillator and transmitter are provided for generating and transmitting an electric signal having a frequency corresponding to the magnitude of the electric field.

  1. Electrical Field Effects in Phthalocyanine Film Growth by Vapor Deposition

    NASA Technical Reports Server (NTRS)

    Banks, Curtis E.; Zhu, Shen; Frazier, Donald O.; Penn, Benjamin; Abdeldayem, Hossin; Hicks, Roslin; Sarkisov, Sergey

    1999-01-01

    Phthalocyanine, an organic material, is a very good candidate for non-linear optical application, such as high-speed switching and optical storage devices. Phthalocyanine films have been synthesized by vapor deposition on quartz substrates. Some substrates were coated with a very thin gold film for introducing electrical field. These films have been characterized by surface morphology, material structure, chemical and thermal stability, non-linear optical parameters, and electrical behaviors. The films have excellent chemical and optical stability. However, the surface of these films grown without electrical field shows flower-like morphology. When films are deposited under an electrical field ( an aligned structure is revealed on the surface. A comparison of the optical and electrical properties and the growth mechanism for these films grown with and without an electrical field will be discussed.

  2. Disrupting long-range polar order with an electric field

    NASA Astrophysics Data System (ADS)

    Guo, Hanzheng; Liu, Xiaoming; Xue, Fei; Chen, Long-Qing; Hong, Wei; Tan, Xiaoli

    2016-05-01

    Electric fields are known to favor long-range polar order through the aligning of electric dipoles in relation to Coulomb's force. Therefore, it would be surprising to observe a disordered polar state induced from an ordered state by electric fields. Here we show such an unusual phenomenon in a polycrystalline oxide where electric fields induce a ferroelectric-to-relaxor phase transition. The nonergodic relaxor phase with disordered dipoles appears as an intermediate state under electric fields during polarization reversal of the ferroelectric phase. Using the phenomenological theory, the underlying mechanism for this unexpected behavior can be attributed to the slow kinetics of the ferroelectric-to-relaxor phase transition, as well as its competition against domain switching during electric reversal. The demonstrated material could also serve as a model system to study the transient stages in first-order phase transitions; the slow kinetics does not require the use of sophisticated ultrafast tools.

  3. Fetal exposure to low frequency electric and magnetic fields

    NASA Astrophysics Data System (ADS)

    Cech, R.; Leitgeb, N.; Pediaditis, M.

    2007-02-01

    To investigate the interaction of low frequency electric and magnetic fields with pregnant women and in particular with the fetus, an anatomical voxel model of an 89 kg woman at week 30 of pregnancy was developed. Intracorporal electric current density distributions due to exposure to homogeneous 50 Hz electric and magnetic fields were calculated and results were compared with basic restrictions recommended by ICNIRP guidelines. It could be shown that the basic restriction is met within the central nervous system (CNS) of the mother at exposure to reference level of either electric or magnetic fields. However, within the fetus the basic restriction is considerably exceeded. Revision of reference levels might be necessary.

  4. Dipole Relaxation in an Electric Field.

    ERIC Educational Resources Information Center

    Neumann, Richard M.

    1980-01-01

    Derives an expression for the orientational entropy of a rigid rod (electric dipole) from Boltzmann's equation. Subsequent application of Newton's second law of motion produces Debye's classical expression for the relaxation of an electric dipole in a viscous medium. (Author/GS)

  5. Dipole Relaxation in an Electric Field.

    ERIC Educational Resources Information Center

    Neumann, Richard M.

    1980-01-01

    Derives an expression for the orientational entropy of a rigid rod (electric dipole) from Boltzmann's equation. Subsequent application of Newton's second law of motion produces Debye's classical expression for the relaxation of an electric dipole in a viscous medium. (Author/GS)

  6. Middle atmospheric electric fields over thunderstorms

    NASA Technical Reports Server (NTRS)

    Holzworth, Robert H.

    1992-01-01

    This grant has supported a variety of investigations all having to do with the external electrodynamics of thunderstorms. The grant was a continuation of work begun while the PI was at the Aerospace Corporation (under NASA Grant NAS6-3109) and the general line of investigation continues today under NASA Grants NAG5-685 and NAG6-111. This report will briefly identify the subject areas of the research and associated results. The period actually covered by the grant NAG5-604 included the following analysis and flights: (1) analysis of five successful balloon flights in 1980 and 1981 (under the predecessor NASA grant) in the stratosphere over thunderstorms; (2) development and flight of the Hy-wire tethered balloon system for direct measurement of the atmospheric potential to 250 kV (this involved multiple tethered balloon flight periods from 1981 through 1986 from several locations including Wallops Island, VA, Poker Flat and Ft. Greely, AK and Holloman AFB, NM.); (3) balloon flights in the stratosphere over thunderstorms to measure vector electric fields and associated parameters in 1986 (2 flights), 1987 (4 flights), and 1988 (2 flights); and (4) rocket-borne optical lightning flash detectors on two rocket flights (1987 and 1988) (the same detector design that was used for the balloon flights listed under #3). In summary this grant supported 8 stratospheric zero-pressure balloon flights, tethered aerostat flights every year between 1982-1985, instruments on 2 rockets, and analysis of data from 6 stratospheric flights in 1980/81.

  7. Parallel electric field in flux restoration during ultrafiltration

    SciTech Connect

    Silva, M.; Zaniquelli, M.E.D. ); Galembeck, F. )

    1991-01-01

    Ultrafiltration membrane permeability may be restored by applying an electric field parallel to the plane of the membrane in the feed compartment of ultrafiltration cells. Two different electrode arrangements are described. Under some conditions, flux restoration is complete. An electric field parallel to the membrane can thus be used to eliminate membrane polarization and fouling.

  8. Electric and Magnetic Fields | RadTown USA | US EPA

    EPA Pesticide Factsheets

    2016-05-31

    Electromagnetic fields (EMF) are a combination of electric and magnetic fields of energy that surround any electrical device when it is plugged in and turned on. Scientific experiments have not clearly shown whether or not exposure to EMF increases cancer risk. Scientists continue to study the issue.

  9. High School Students' Representations and Understandings of Electric Fields

    ERIC Educational Resources Information Center

    Cao, Ying; Brizuela, Bárbara M.

    2016-01-01

    This study investigates the representations and understandings of electric fields expressed by Chinese high school students 15 to 16 years old who have not received high school level physics instruction. The physics education research literature has reported students' conceptions of electric fields post-instruction as indicated by students'…

  10. High School Students' Representations and Understandings of Electric Fields

    ERIC Educational Resources Information Center

    Cao, Ying; Brizuela, Bárbara M.

    2016-01-01

    This study investigates the representations and understandings of electric fields expressed by Chinese high school students 15 to 16 years old who have not received high school level physics instruction. The physics education research literature has reported students' conceptions of electric fields post-instruction as indicated by students'…

  11. Photodetachment dynamics in a time-dependent oscillating electric field

    NASA Astrophysics Data System (ADS)

    Wang, De-hua; Xu, Qin-feng; Du, Jie

    2017-03-01

    Using the time-dependent form of closed orbit theory, as developed by Haggerty and Delos [M.R. Haggerty, J.B. Delos, Phys. Rev. A 61, 053406 (2000)], and by Yang and Robicheaux [B.C. Yang, F. Robicheaux, Phys. Rev. A 93, 053413 (2016)], we study the photodetachment dynamics of a hydrogen negative ion in a time-dependent oscillating electric field. Compared to the photodetachment in a static electric field, the photodetachment dynamics of a negative ion in the time-dependent oscillating electric field become much more complicated but more interesting. Since the applied electric field is oscillating with time, the photodetachment cross section of the negative ion in the oscillating electric field is time-dependent. In a time-dependent framework, we put forward an analytical formula for calculating the instantaneous photodetachment cross section of this system. Our study suggests that the instantaneous photodetachment cross section exhibits oscillatory structure, which depends sensitively on the frequency of the oscillating electric field. With increasing frequency of the oscillating electric field, the number of closed orbits increases and the oscillatory structure in the photodetachment cross section becomes much more complicated. The connection between the detached electron's closed orbit with the oscillating cross section is analyzed quantitatively. This study provides a clear and intuitive picture for the photodetachment processes of a negative ion in the presence of an oscillating electric field. We hope that our work will be useful in guiding future experimental research.

  12. Electric and Magnetic Field Detection in Elasmobranch Fishes

    NASA Astrophysics Data System (ADS)

    Kalmijn, Ad. J.

    1982-11-01

    Sharks, skates, and rays receive electrical information about the positions of their prey, the drift of ocean currents, and their magnetic compass headings. At sea, dogfish and blue sharks were observed to execute apparent feeding responses to dipole electric fields designed to mimic prey. In training experiments, stingrays showed the ability to orient relative to uniform electric fields similar to those produced by ocean currents. Voltage gradients of only 5 nanovolts per centimeter would elicit either behavior.

  13. Exploiting Electric and Magnetic Fields for Underwater Characterization

    DTIC Science & Technology

    2011-03-01

    numerical models in order to quantify the practical limits on standoff excitation for induction coil (magnetic dipole) and electrode (electric dipole...commercially available electric (Ag/AgCl electrodes) and magnetic (wideband induction coil B-field sensors) receivers formed an initial testbed for...improved performance using an electric field source rather than marinized versions of terrestrial induction coil sources (e.g., EM-61S).  Interaction with

  14. Design of pressure-driven microfluidic networks using electric circuit analogy.

    PubMed

    Oh, Kwang W; Lee, Kangsun; Ahn, Byungwook; Furlani, Edward P

    2012-02-07

    This article reviews the application of electric circuit methods for the analysis of pressure-driven microfluidic networks with an emphasis on concentration- and flow-dependent systems. The application of circuit methods to microfluidics is based on the analogous behaviour of hydraulic and electric circuits with correlations of pressure to voltage, volumetric flow rate to current, and hydraulic to electric resistance. Circuit analysis enables rapid predictions of pressure-driven laminar flow in microchannels and is very useful for designing complex microfluidic networks in advance of fabrication. This article provides a comprehensive overview of the physics of pressure-driven laminar flow, the formal analogy between electric and hydraulic circuits, applications of circuit theory to microfluidic network-based devices, recent development and applications of concentration- and flow-dependent microfluidic networks, and promising future applications. The lab-on-a-chip (LOC) and microfluidics community will gain insightful ideas and practical design strategies for developing unique microfluidic network-based devices to address a broad range of biological, chemical, pharmaceutical, and other scientific and technical challenges.

  15. An experimental study on the motion, deformation and electrical charging of water drops falling in oil in the presence of high voltage D.C. electric field

    SciTech Connect

    Jalaal, M.; Khorshidi, B.; Esmaeilzadeh, E.

    2010-11-15

    The motion, deformation and electrical charging of conducting water drops falling in an insulating liquid subjected to various electric fields strength were studied experimentally. The drop motion was recorded contentiously by high speed camera and their responses to deformation under the influence of electric field were digitally extracted by image processing of the sequential frames. Two parameters were defined for describing the deviation and deformation of the drops under the electric forces. Outcomes depicted that the deviation of the drops from the vertical line would be increased by adding to the applied electrical potential as well as reduction of drop size. Moreover, regarding to deformation diagram, the results revealed a dissimilar deformation manner between large and small drops, which can be helpful in describing the drop-drop electro coalescence phenomena and in design of electrically driven droplet-based systems. (author)

  16. Reversible electrically-driven magnetic domain wall rotation in multiferroic heterostructures to manipulate suspended on-chip magnetic particles

    NASA Astrophysics Data System (ADS)

    Nowakowski, Mark; Sohn, Hyunmin; Liang, Cheng-Yen; Hockel, Joshua; Wetzlar, Kyle; Keller, Scott; McLellan, Brenda; Marcus, Matthew; Doran, Andrew; Young, Anthony; Kläui, Mathias; Carman, Gregory; Bokor, Jeffrey; Candler, Robert

    2015-03-01

    We experimentally demonstrate reversible electrically-driven, strain-mediated domain wall (DW) rotation in Ni rings fabricated on piezoelectric [Pb(Mg1/3Nb2/3) O3]0.66-[PbTiO3]0.34 (PMN-PT) substrates. An electric field applied across the PMN-PT substrate induces a strain in the Ni rings producing DW rotation around the ring toward the dominant PMN-PT strain axis by inverse magnetostriction. We observe DWs reversibly cycled between their initial and rotated state as a function of the applied electric field with x-ray magnetic circular dichroism photo-emission electron microscopy. The DW rotation is analytically predicted using a fully coupled micromagnetic/elastodyanmic multi-physics simulation to verify that the experimental behavior is caused by the electrically-generated strain in this multiferroic system. Finally, this DW rotation is used to capture and manipulate magnetic particles in a fluidic environment to demonstrate a proof-of-concept energy-efficient pathway for multiferroic-based lab-on-a-chip applications. Supported by TANMS (NSF 11-537), E3S, US Dept of Energy (DE-AC02-05CH11231), EU, and DFG.

  17. Two-level systems driven by large-amplitude fields

    NASA Astrophysics Data System (ADS)

    Nori, F.; Ashhab, S.; Johansson, J. R.; Zagoskin, A. M.

    2009-03-01

    We analyze the dynamics of a two-level system subject to driving by large-amplitude external fields, focusing on the resonance properties in the case of driving around the region of avoided level crossing. In particular, we consider three main questions that characterize resonance dynamics: (1) the resonance condition, (2) the frequency of the resulting oscillations on resonance, and (3) the width of the resonance. We identify the regions of validity of different approximations. In a large region of the parameter space, we use a geometric picture in order to obtain both a simple understanding of the dynamics and quantitative results. The geometric approach is obtained by dividing the evolution into discrete time steps, with each time step described by either a phase shift on the basis states or a coherent mixing process corresponding to a Landau-Zener crossing. We compare the results of the geometric picture with those of a rotating wave approximation. We also comment briefly on the prospects of employing strong driving as a useful tool to manipulate two-level systems. S. Ashhab, J.R. Johansson, A.M. Zagoskin, F. Nori, Two-level systems driven by large-amplitude fields, Phys. Rev. A 75, 063414 (2007). S. Ashhab et al, unpublished.

  18. Nonlinear piezoelectricity in epitaxial ferroelectrics at high electric fields

    SciTech Connect

    Grigoriev, Alexei; Sichel, Rebecca; Lee, Ho Nyung; Landahl, Eric C.; Adams, Bernhard; Dufresne, Eric M.; Evans, Paul G.

    2008-01-01

    Non-linear effects in the coupling of polarization with elastic strain have been predicted to occur in ferroelectric materials subjected to high electric fields. Such predictions are tested here for a Pb(Zr0.2,Ti0.8)O3 ferroelectric thin film at electric fields in the range of several MV/cm. Thermal runaway and subsequent low-frequency dielectric breakdown are overcome by using nanosecond electrical pulses to apply high electric fields, which made the probing of the film's structure possible at piezoelectric strains reaching up to 2.7%. The piezoelectric strain exceeds predictions based on constant piezoelectric coefficients at electric fields from 2 to 4 MV/cm, which is consistent with a non-linear effect predicted to occur at concomitant piezoelectric distortions. At higher fields, the piezoelectric response decreases, suggesting that elastic interactions between atoms enter a new regime.

  19. Sources of Low-latitude Ionospheric Electric-field Disturbances

    NASA Astrophysics Data System (ADS)

    Richmond, A. D.; Peymirat, C.

    2001-12-01

    Storm-time ionospheric electric-field disturbances at middle and low latitudes are generated both by direct magnetosphere-ionosphere interactions at high latitudes and by secondary effects of disturbance thermospheric winds. These disturbance electric fields can have a strong influence on the equatorial ionosphere. Using the NCAR Magnetosphere-Thermosphere-Ionosphere-Electrodynamics General Circulation Model (MTIEGCM), we simulate low-latitude electric-field disturbances associated with direct penetration from high latitudes and with secondary generation by disturbed thermospheric winds. The simulations display a number of features observed in equatorial electric fields on time scales of minutes to hours. Models like the MTIEGCM, together with simultaneous global observations of ionospheric electric fields and thermospheric winds, can help clarify the relative importance of the different mechanisms that produce ionospheric disturbances.

  20. Lamb-shift and electric field measurements in plasmas

    NASA Astrophysics Data System (ADS)

    Doveil, F.; Chérigier-Kovacic, L.; Ström, P.

    2017-01-01

    The electric field is a quantity of particular relevance in plasma physics. Indeed, its fluctuations are responsible for different macroscopic phenomena such as anomalous transport in fusion plasmas. Answering a long-standing challenge, we offer a new method to locally and non-intrusively measure weak electric fields and their fluctuations in plasmas, by means of a beam of hydrogen ions or atoms. We present measurements of the electric field in vacuum and in a plasma where Debye shielding is measured. For the first time, we have used the Lamb-shift resonance to measure oscillating electric fields around 1 GHz and observed the strong enhancement of the Lyman-α signal. The measurement is both direct and non-intrusive. This method provides sensitivity (mV cm-1) and temporal resolution (ns) that are three orders higher compared to current diagnostics. It thus allows measuring fluctuations of the electric field at scales not previously reached experimentally.